JP2005325736A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the combustion efficiency by stabilizing a tumble flow in an internal combustion engine. <P>SOLUTION: The tumble flow and a squish flow can be generated in a combustion chamber 16. A middle squish area 33 is installed in an outer peripheral wall surface of the combustion chamber 16, to which a suction port 17 and an exhaust port 18 at a lower surface of a cylinder head 12 are adjacent. In the middle squish area 33, a guide 35 is formed by eliminating the inside area of an approximately 1.5 times a radius R (=1.5r) of a radius r of a valve body 19a with center at the axis O of a suction valve 19. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an internal combustion engine that enables stratified combustion by directly injecting fuel into a combustion chamber.

  2. Description of the Related Art Conventionally, an in-cylinder spark ignition internal combustion engine that directly injects fuel into a combustion chamber instead of an intake port is known. In this in-cylinder spark-ignition internal combustion engine, when the intake valve is opened and closed, air is drawn into the combustion chamber from the intake port to generate a tumble flow, and fuel directly from the fuel injection valve faces the tumble flow. Spray. Then, the tumble flow and fuel spray are mixed in the combustion chamber, and this mixture is led to the ignition plug by the piston cavity, ignites and explodes to obtain engine torque, and when the exhaust valve is opened and closed, The combustion gas is discharged from the exhaust port and processed.

  In addition, in this in-cylinder spark ignition internal combustion engine, the fuel spray injected into the tumble flow is atomized and vaporized early, so that the air-fuel mixture is efficiently guided to the spark plug. A squish area for the piston surface is provided on the ceiling. For this reason, the squish flow from the squish area toward the center of the combustion chamber can reliably lead the air-fuel mixture to the spark plug as a tumble flow.

  FIG. 8 is a horizontal sectional view of a combustion chamber in a conventional internal combustion engine. In the conventional internal combustion engine, as shown in FIG. 8, the combustion chamber 001 is composed of a cylinder block (cylinder bore), a lower surface of the cylinder head, and a top surface of the piston, and two intake ports 002 and exhaust ports are provided at the upper portion. 003 communicates and can be opened and closed by an intake valve and an exhaust valve, respectively. The cylinder head is provided with an injector for injecting gasoline fuel directly into the combustion chamber 001 and an ignition plug on the ceiling of the combustion chamber 001. Has been. In addition, an intake squish area 004 and an exhaust squish area 005 are formed in the cylinder head constituting the ceiling portion of the combustion chamber 001, and an intermediate squish area 006 is formed therebetween.

  Therefore, when air is drawn into the combustion chamber 001 from the intake port 002 to generate a tumble flow, and fuel is injected into the tumble flow to generate an air-fuel mixture, an intermediate squish with respect to the tumble flow of the air-fuel mixture is generated. Diffusion is suppressed by the squish flow from the area 006, and a high-quality air-fuel mixture is guided to the spark plug as a tumble flow.

  In addition, there exists what was described in the following patent document 1 as what aims at combustion improvement using a tumble flow and a squish flow. In the “combustion chamber structure of a spark ignition direct injection engine” described in Patent Document 1, an intermediate squish area is provided between the intake squish area and the exhaust squish area, and the width of the intermediate squish area is set to the diameter of the cylinder. By defining from the fuel spray width and the like, it is possible to generate a squish flow that suppresses fuel adhesion to the side wall surface of the concave portion of the piston top surface and suppresses the diffusion of the air-fuel mixture to the side.

JP 2003-227339 A

  However, in the above-described conventional internal combustion engine, although it is possible to improve the combustion by suppressing the diffusion of the tumble flow by the intermediate squish area, the flow of the air flowing from the intake port 002 into the combustion chamber 001 is inhibited. As a result, the strength and flow rate of the tumble flow are reduced. FIG. 9 is a graph showing the tumble flow (tumble ratio) with respect to the lift amount of the intake valve. As shown in the graph of FIG. 9, when the squish area is not provided, the tumble flow increases substantially proportionally with the increase in the valve lift amount. On the other hand, when the squish area is provided, the tumble flow increases almost in proportion to the predetermined position as the valve lift increases, but the degree of increase decreases in the middle.

  In addition, in the “combustion chamber structure of a spark ignition direct injection engine” described in Patent Document 1, the size of the intermediate squish area is optimized to suppress fuel adhesion to the concave portion of the piston top surface. However, the tumble flow and the point of stabilizing the flow rate are not particularly described.

  The present invention solves such problems, and an object of the present invention is to provide an internal combustion engine that improves the combustion efficiency by stabilizing the tumble flow.

  In order to solve the above-described problems and achieve the object, an internal combustion engine of the present invention can open and close a combustion chamber, an intake port and an exhaust port communicating with the combustion chamber, and the intake port and the exhaust port, respectively. Intake valve and exhaust valve, tumble flow generating means for generating a tumble flow in the combustion chamber, squish flow generating means for generating a squish flow toward the center of the combustion chamber, and fuel injection for injecting fuel into the combustion chamber In an internal combustion engine comprising a valve and a spark plug provided on a ceiling portion of the combustion chamber, at least an axial center of the intake valve is provided on a side wall surface adjacent to the intake port and the exhaust port in the combustion chamber. A guide portion is formed by removing an inner region having a radius 1.2 to 1.7 times the valve portion radius as a center.

  In the internal combustion engine of the present invention, the squish flow generating means is constituted by a piston top surface and a lower surface of the cylinder head exposed to the combustion chamber, and the guide portion is formed on the lower surface of the cylinder head. It is said.

  In the internal combustion engine of the present invention, the squish flow generating means includes an exhaust squish area formed corresponding to the outer periphery of the combustion chamber, an intake squish area, and an intermediate squish area between the exhaust and intake sides. The intermediate squish area is characterized in that the guide portion is formed by removing an inner region having a radius approximately 1.5 times the radius of the valve portion with the axial center of the intake valve as a center. .

  In the internal combustion engine of the present invention, the guide portion is formed by removing a region from an angle of a straight line connecting at least the shaft centers of the two intake valves arranged side by side to an angle advanced approximately 45 degrees toward the exhaust valve. It is characterized by that.

  In the internal combustion engine of the present invention, the guide portion has an inclined surface that smoothly connects the ceiling surface of the combustion chamber and the lower surface of the cylinder head.

  According to the internal combustion engine of the present invention, the tumble flow generating means for generating the tumble flow in the combustion chamber and the squish flow generating means for generating the squish flow toward the center of the combustion chamber are provided, and the intake port in the combustion chamber is provided. The guide portion is formed on the side wall surface adjacent to the exhaust port by removing the inner region having a radius 1.2 to 1.7 times the radius of the valve body around the axial center of the intake valve. The air flow sucked into the combustion chamber is converted into a tumble flow by the tumble flow generation means, the diffusion is suppressed by the squish flow generation means, and a predetermined air flow rate is burned by the guide portion without lowering the tumble flow. Combustion efficiency can be improved by stabilizing the tumble flow.

  Embodiments of an internal combustion engine according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 is a horizontal sectional view (II cross section of FIG. 4) of a combustion chamber in an internal combustion engine according to one embodiment of the present invention, FIG. 2-1 is a cross sectional view of 2A-2A in FIG. 1 is a cross-sectional view taken along 2B-2B in FIG. 1, FIG. 2C is a cross-sectional view taken along 2C-2C in FIG. 1, FIG. 3 is a schematic view showing a ceiling portion of a combustion chamber in the internal combustion engine of the present embodiment, and FIG. FIG. 5A to FIG. 5D are schematic views showing the air flow into the combustion chamber when the intake valve is opened, and FIG. 6 is the embodiment. FIG. 7 is a graph showing the flow rate with respect to the tumble flow in the internal combustion engine of the present embodiment.

  The internal combustion engine of the present embodiment is a cylinder injection type spark ignition engine, and as shown in FIGS. 1 to 4, a cylinder head 12 is fastened on a cylinder block 11, and a plurality of cylinder bores are connected to the cylinder block 12. 13 are formed in series, and a piston 14 is fitted to each cylinder bore 13 so as to be movable up and down. A crankshaft (not shown) is rotatably supported at the lower portion of the cylinder block 11, and each piston 14 is connected to the crankshaft via a connecting rod 15.

  Each combustion chamber 16 is constituted by a cylinder bore 13 formed in the cylinder block 11, a lower surface of the cylinder head 12, and a top surface of the piston 14, and a central portion of the ceiling portion (lower surface of the cylinder head 12) is increased. The pent roof shape is inclined like this. Two intake ports 17 and an exhaust port 18 are formed on the upper portion of the combustion chamber 16, that is, on the lower surface of the cylinder head 12, respectively, and the intake valve 19 is opposed to the intake port 17 and the exhaust port 18. And the valve bodies 19a and 20a of the exhaust valve 20 are located respectively. Therefore, when the intake valve 19 and the exhaust valve 20 move up and down at a predetermined timing, the intake port 17 and the exhaust port 18 are opened and closed, and the intake port 17 and the combustion chamber 16, and the combustion chamber 16 and the exhaust port 18 are respectively connected. You can communicate. Although not shown, an intake pipe is connected to the intake port 17 via an intake manifold, while an exhaust pipe is connected to the exhaust port 18 via an exhaust manifold.

  A fuel injection valve 21 that directly injects fuel into the combustion chamber 16 is mounted on the side of the combustion chamber 16, that is, on the lower surface of the cylinder head 12 on the intake port 17 side. The fuel injection valve 21 is provided between the two intake ports 17 in a state inclined at a predetermined angle with respect to the vertical direction, and can inject fuel toward a substantially central portion in the combustion chamber 16. A spark plug 22 is attached to the center of the ceiling of the combustion chamber 16, that is, the lower surface of the cylinder head 12 between each intake port 17 and each exhaust port 18. The spark plug 22 can ignite a mixture of air sucked into the combustion chamber 16 and fuel spray injected into the combustion chamber 16 by generating a spark at a predetermined time.

  Further, tumble flow generating means for generating a tumble flow in the combustion chamber 16 and squish flow generating means for generating a squish flow toward the center of the combustion chamber 16 are provided. In the case of the present embodiment, the tumble flow generating means is configured by the shape of the intake port 17, and as shown in detail in FIG. 4, the air flow introduced from the intake port 17 into the combustion chamber 16 is changed to FIG. 4. A tumble flow T can be generated by applying a longitudinal turning force in the counterclockwise direction, and fuel is injected from the fuel injection valve 21 toward the tumble flow T of air. The squish flow generating means is constituted by squish areas 31, 32, and 33 described later formed on the top surface of the piston 14 and the cavity 14 a and the lower surface of the cylinder head 12. As shown in detail in FIG. 4, during the compression stroke in which the piston 14 rises, a squish flow S toward the center of the combustion chamber 16 is generated between the top surface of the piston 14 and the squish areas 31, 32, 33. In addition, the air-fuel mixture can be guided to the vicinity of the spark plug 22.

  In the present embodiment, the squish area 31, facing the top surface of the piston 14 on the lower surface of the combustion chamber 16 on the cylinder head 12 side so that the operational effects of the tumble flow T and squish flow S are effectively exhibited. 32 and 33 are formed. That is, as described above, the lower surface of the cylinder head exposed to the combustion chamber 16 is an inclined surface 34 having a raised central portion, and two intake ports 17 and two exhaust ports 18 are formed in parallel. Has been. An intake side squish area 31 is formed between the two intake ports 17 so as to avoid the ports 17 and 18 outside the intake port 17 and the two exhaust ports 18. An exhaust-side squish area 32 is formed therebetween. An intermediate squish area 33 is formed between the intake port 17 and the exhaust port 18.

  Each intermediate squish area 33 has a line-symmetric shape, and is smoothly connected to the inclined surface 34 via the guide portion 35. Each guide portion 35 has a shape in which an inner region having a radius R that is 1.2 to 1.7 times the radius r of the valve portion 19a around at least the axis O of each intake valve 19 is removed. ing. The guide portion 35 is provided in a region from an angle of a straight line L connecting the axis O of the two intake valves 19 to an angle advanced by a predetermined angle θ = 30 degrees toward the exhaust valve 20 side. It is to be noted that the guide portion 35 is optimally configured so that a region having a radius R (= 1.5r) approximately 1.5 times the radius of the valve body 19a centering on the axis O of the intake valve 19 is an angle of the straight line L. It is desirable to remove the region from the angle θ to the angle advanced to 45 ° from the exhaust valve 20 side.

  Here, the influence of the intermediate squish area 33 on the air flow (tumble flow) introduced from the intake port 17 into the combustion chamber 16 will be described. The arrows shown in FIGS. 5-1 to 5-4 indicate the flow of air flowing into the combustion chamber 16 from the intake port when the intake valve is opened, and FIGS. 5-1 and 5-2 have no intermediate squish area. 5-3 and 5-4 show a conventional intermediate squish area. FIGS. 5A and 5C show the flow of air at an angular position where θ = 45 degrees advances from the angle of the straight line L connecting the axis O of the intake valve 19 to the exhaust valve 20 side. 5-2 and FIG. 5-4 show the air flow at the angle position where θ = 60 degrees has advanced from the angle of the straight line L to the exhaust valve 20 side.

  As shown in FIGS. 5A and 5B, if there is no intermediate squish area in the cylinder head, the exhaust valve 20 side of the combustion chamber 16 from the intake port 19 (left side in the figure) at any angle. Air is flowing smoothly. On the other hand, as shown in FIGS. 5-3 and 5-4, when the cylinder head has the conventional intermediate squish area 010, at the position of θ = 60 degrees (FIG. 5-4), from the intake port 19 to the combustion chamber 16 Although air smoothly flows into the exhaust valve 20 side of the engine, air does not smoothly flow from the intake port 19 to the exhaust valve 20 side of the combustion chamber 16 at the position θ = 45 degrees (FIG. 5-3). , Where turbulence occurs.

  Thus, if the cylinder head does not have the intermediate squish area 33, air smoothly flows from the intake port 19 into the combustion chamber 16, but if the intermediate squish area 010 is present, the intake port 19 has a position θ = 45 degrees. It can be seen that air does not smoothly flow into the combustion chamber 16. Therefore, in this embodiment, although the intermediate squish area 33 is provided in order to generate the squish flow that suppresses the diffusion of the tumble flow and guides the air-fuel mixture to the spark plug, the above-described position of θ = 0 to 45 degrees is provided. The guide 35 is formed by removing. In this case, as shown in FIG. 5A, the air flow flowing into the combustion chamber 16 from the intake port 17 has a radius approximately 1.5 times the radius r of the valve portion 19 a centering on the axis O of the intake valve 19. Since it is concentrated in the inner region of R (= 1.5r), the guide portion 35 is formed by removing this region.

  When the guide portion 35 is formed by removing the above-described region in the intermediate squish area 33, the axial center O of the intake valve 19 is set to be inclined at a predetermined angle, and the lower surface of the cylinder head 12 is radiused from the inclined axial center O. It will be scraped off into a cylindrical shape by R. As shown in FIG. 1, the guide portion 35 is made to match the surrounding wall surface so as to be smoothly continuous along the circumferential direction of the combustion chamber 16. 1 is a cross-sectional view at the lower end portion of the cylinder head, and the guide portion 35 is indicated by a solid line, but the guide portion 35 indicated by a two-dot difference line indicates the shape of the uppermost portion of the combustion chamber 16. ing. Further, the guide portion 35 has a substantially vertical surface in the vicinity of the intake port 17 shown in FIG. 2A and inclines as it goes to the exhaust port 18 side as shown in FIGS. 2-2 and 2-3. Is set to

  The vehicle is provided with an electronic control unit (ECU) for controlling the engine and the like, and the ECU performs overall control of the engine. That is, the ECU determines the fuel injection amount, injection timing, ignition timing, etc. based on the detected engine speed, intake air amount, throttle opening, accelerator opening, engine cooling water temperature, and other engine operating conditions. The valve 21 and the spark plug 22 can be controlled. Specifically, the fuel injection amount is set based on the engine speed and the intake air amount, and is corrected based on changes in operating conditions such as the throttle opening, the accelerator opening, and the engine coolant temperature.

  In the internal combustion engine of this embodiment configured as described above, when a predetermined amount of air is introduced into the combustion chamber 16 through the intake port 17 when the intake valve 19 is opened, this air flow is tumbled in the combustion chamber 16. A fuel amount corresponding to the air amount is injected from the fuel injection valve 21 toward the tumble flow T. Then, the air / fuel mixture is compressed as the piston 14 moves upward, and is guided to the vicinity of the spark plug 22 by the squish flow S from the top surface of the piston 14 and the squish areas 31, 32, 33. The air-fuel mixture is ignited and combusted by the spark plug 22, and the combustion gas is discharged to the outside from the exhaust port 18 as exhaust gas when the exhaust valve 20 is opened.

  In this case, in the present embodiment, in the two intermediate squish areas 33, the side walls adjacent to the intake ports 17 are scraped to form the guide portions 35, and the intermediate squish areas 33 are formed from the intake ports 17 to the combustion chamber 16. A smooth flow can be ensured without adversely affecting the air flow flowing into the. For this reason, the airflows flowing into the combustion chambers 16 from the intake ports 17 are merged at the optimum positions of the combustion chambers 16 to generate a strong tumble flow T, and fuel is injected here. Further, each squish area 31, 32, 33 can suppress the diffusion of the tumble flow T, and a high-quality air-fuel mixture is guided to the spark plug 22.

  FIG. 6 is a graph showing the strength of the tumble flow in the combustion chamber. Region 1 is a region of θ = 45 to 90 degrees, and region 2 is a region of θ = 0 to 45 degrees. As can be seen from the graph of FIG. 6, in the combustion chamber having no squish area, a strong tumble flow can be generated in both regions 1 and 2, but in the combustion chamber having a conventional squish area, the tumble flow is generated in region 2. The strength is decreasing. On the other hand, in the combustion chamber having the squish area of this embodiment, a strong tumble flow can be generated in both regions 1 and 2 in substantially the same manner as the combustion chamber having no squish area.

  FIG. 7 is a graph showing the flow rate with respect to the tumble flow. White circles represent conventional combustion chambers, and hatched circles represent combustion chambers of the present embodiment. As can be seen from the graph of FIG. 7, generally, the flow rate tends to decrease as the tumble flow becomes stronger. In the conventional combustion chamber, the intermediate region is applied. In the present embodiment, the tumble flow T can be strengthened without reducing the flow rate by setting the intermediate squish area 33 to the optimum shape.

  As described above, in the internal combustion engine of the present embodiment, the combustion chamber 16 can generate the tumble flow T and the squish flow S, and the intake port 17 and the exhaust port 18 on the lower surface of the cylinder head 12 are adjacent to each other. An intermediate squish area 33 is provided on the outer peripheral wall surface of the outer rim, and in the intermediate squish area 33, a radius R (= 1....) Approximately 1.5 times the radius r of the valve body 19a with the axis O of the intake valve 19 as the center. The guide portion 35 is formed by removing the inner region 5r).

  Therefore, the air flow flowing into the combustion chamber 16 from the intake port 17 becomes a tumble flow T due to this port shape, and this tumble flow T has a predetermined air flow rate without being lowered by the guide portion 34 of the intermediate squish area 33. The squish areas 31, 32, and 33 suppress the diffusion of the tumble flow T, and the air-fuel mixture is appropriately guided to the vicinity of the spark plug 22. As a result, by stabilizing the tumble flow T, mixing of air and fuel becomes good, combustion efficiency can be improved, fuel consumption can be improved, and engine performance can be improved.

  As described above, the internal combustion engine according to the present invention is intended to improve combustion by optimizing the shape of the squish area, and is useful when applied to any internal combustion engine to which tumble flow or squish flow is applied. is there.

It is a horizontal sectional view (II section of Drawing 4) of a combustion chamber in an internal-combustion engine concerning one example of the present invention. It is 2A-2A sectional drawing of FIG. It is 2B-2B sectional drawing of FIG. It is 2C-2C sectional drawing of FIG. It is the schematic showing the ceiling part of the combustion chamber in the internal combustion engine of a present Example. It is a longitudinal cross-section of the combustion chamber in the internal combustion engine of a present Example. It is the schematic showing the air flow to a combustion chamber at the time of opening of an intake valve. It is the schematic showing the air flow to a combustion chamber at the time of opening of an intake valve. It is the schematic showing the air flow to a combustion chamber at the time of opening of an intake valve. It is the schematic showing the air flow to a combustion chamber at the time of opening of an intake valve. It is a graph showing the intensity | strength of the tumble flow in the internal combustion engine of a present Example. It is a graph showing the flow volume with respect to the tumble flow in the internal combustion engine of a present Example. It is a horizontal sectional view of the combustion chamber in the conventional internal combustion engine. It is a graph showing the tumble flow (tumble ratio) with respect to the lift amount of the intake valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Cylinder block 12 Cylinder head 14 Piston 16 Combustion chamber 17 Intake port 18 Exhaust port 19 Intake valve 20 Exhaust valve 21 Fuel injection valve 22 Spark plug 31 Intake side squish area 32 Exhaust side squish area 33 Intermediate squish area 34 Inclined surface 35 Guide part

Claims (5)

  A combustion chamber, an intake port and an exhaust port communicating with the combustion chamber, an intake valve and an exhaust valve capable of opening and closing the intake port and the exhaust port, respectively, and a tumble flow generating means for generating a tumble flow in the combustion chamber An internal combustion engine comprising: a squish flow generating means for generating a squish flow toward the center of the combustion chamber; a fuel injection valve for injecting fuel into the combustion chamber; and an ignition plug provided at a ceiling portion of the combustion chamber In the combustion chamber, on the side wall surface where the intake port and the exhaust port are adjacent to each other, an inner region having a radius of 1.2 to 1.7 times the radius of the valve portion around at least the axial center of the intake valve is formed. An internal combustion engine that is removed to form a guide portion.   2. The internal combustion engine according to claim 1, wherein the squish flow generating means includes a piston top surface and a lower surface of a cylinder head exposed to the combustion chamber, and the guide portion is formed on a lower surface of the cylinder head. An internal combustion engine.   3. The internal combustion engine according to claim 2, wherein the squish flow generating means includes an exhaust squish area formed corresponding to an outer peripheral portion of the combustion chamber, an intake squish area, and an intermediate squish between the exhaust side and the intake side. And the guide portion is formed in the intermediate squish area with an inner region having a radius approximately 1.5 times the radius of the valve portion removed from the axial center of the intake valve. An internal combustion engine.   2. The internal combustion engine according to claim 1, wherein a region of the guide portion is removed from an angle of a straight line that connects at least the shaft centers of the two intake valves arranged in parallel to an angle that travels approximately 45 degrees toward the exhaust valve. An internal combustion engine characterized by being formed.   5. The internal combustion engine according to claim 1, wherein the guide portion has an inclined surface that smoothly connects a ceiling surface of the combustion chamber and a lower surface of the cylinder head.

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