Combustion chamber structure

Abstract

This technology provides an effective method for forming tumble flow within the cylinders of an internal combustion engine. [Solution] In a combustion chamber structure of an internal combustion engine configured to form a tumble flow within the cylinder, a first opening is provided in the center of the ceiling wall, which is the wall surface of the cylinder head forming the ceiling portion of the combustion chamber, so that the tip of the spark plug is exposed into the combustion chamber. In the combustion chamber structure of the internal combustion engine, a second opening is provided at a position on the intake side of the first opening in the ceiling wall, so that the nozzle of the in-cylinder injection valve is exposed into the combustion chamber. In the combustion chamber structure of the internal combustion engine, a concave spray escape section is formed around the second opening in the ceiling wall. A slit is then formed in the ceiling wall, extending from the spray escape section toward the first opening.

Description

Technical Field

[0001] The present disclosure relates to a combustion chamber structure of an internal combustion engine.

Background Art

[0002] In the combustion chamber of an internal combustion engine, a technique is known in which a recess called a spray escape portion is provided in the cylinder head around the injection hole of an in-cylinder injection valve to suppress the collision and adhesion of fuel (spray) injected from the injection hole to the wall surface of the cylinder head or the like (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to provide a technique effective in forming a tumble flow in the cylinder of an internal combustion engine.

Means for Solving the Problems

[0005] Aspects of the present disclosure are a combustion chamber structure of an internal combustion engine configured to form a tumble flow in the cylinder, a first opening provided at the center of the ceiling wall surface portion, which is the wall surface of the cylinder head forming the ceiling portion of the combustion chamber, and formed such that the tip of the spark plug is exposed into the combustion chamber; a second opening provided at a position on the intake side of the first opening in the ceiling wall surface portion and formed such that the injection hole portion of the in-cylinder injection valve is exposed into the combustion chamber; a spray escape portion provided around the second opening in the ceiling wall surface portion and formed in a concave shape; and A slit is formed in the ceiling wall portion, extending from the spray escape portion toward the first opening. It has a combustion chamber structure. [Effects of the Invention]

[0006] This disclosure provides an effective technique for forming tumble flow within the cylinders of an internal combustion engine. [Brief explanation of the drawing]

[0007] [Figure 1] This is a cross-sectional view showing an example of the schematic configuration of an internal combustion engine in an embodiment. [Figure 2] This is a cross-sectional view showing an example of the configuration of the ceiling wall portion of the cylinder head in the embodiment. [Figure 3] Figure 2 shows the ceiling and wall surface viewed from below. [Figure 4] This diagram schematically shows the fuel and intake air flow in the combustion chamber structure of a comparative example. [Figure 5] This diagram schematically shows the flow of fuel and intake air in the combustion chamber structure of the embodiment. [Modes for carrying out the invention]

[0008] A known type of internal combustion engine is one in which the cylinder is configured to form a tumble flow (longitudinal vortex flow). In the combustion chamber of such an internal combustion engine, the nozzle portion of the in-cylinder injection valve is exposed into the combustion chamber. In some cases, a concave spray relief section is formed around the opening for the injection valve. This spray relief section is designed to prevent obstruction of the flow of fuel (spray) injected from the nozzle of the in-cylinder injection valve. In other words, the spray relief section is designed to prevent the fuel (spray) injected from the nozzle of the in-cylinder injection valve from hitting the ceiling of the combustion chamber.

[0009] However, when a spray vent section as described above is provided in the combustion chamber, some of the fuel and intake air flowing on the tumble flow may flow into the spray vent section and accumulate inside it. In such cases, the tumble flow may be attenuated, potentially affecting the formation and combustion of the air-fuel mixture. Furthermore, the fuel accumulated inside the spray vent section may adhere to the area around the nozzle of the in-cylinder injection valve, potentially causing deposit formation. This disclosure solves these problems.

[0010] This disclosure relates to a combustion chamber structure for an internal combustion engine configured to form a tumble flow within the cylinder. This combustion chamber structure is applied to a combustion chamber comprising a first opening, a second opening, and a spray relief section. The first opening is provided in the center of the cylinder head wall (ceiling wall portion) that forms the ceiling portion of the combustion chamber, and is formed so that the tip of the spark plug is exposed into the combustion chamber. The second opening is provided on the ceiling wall portion at a position closer to the intake than the first opening, and is formed so that the nozzle portion of the in-cylinder injection valve is exposed into the combustion chamber. The spray relief section is provided around the second opening on the ceiling wall portion and is formed in a concave shape. In the combustion chamber structure according to this disclosure, a slit extending from the spray relief section toward the first opening is provided on the ceiling wall portion.

[0011] In the combustion chamber structure according to this disclosure, when some of the fuel and intake air flowing on the tumble flow enter the spray vent section, that fuel and intake air flows out of the spray vent section through the slits. The fuel and intake air that flow out of the spray vent section merge with the main flow of the tumble flow and flow together. This makes it possible to suppress the stagnation of fuel and intake air in the spray vent section. As a result, the attenuation of the tumble flow can be kept to a minimum. In addition, since the scavenging performance of the spray vent section is improved, the formation and accumulation of deposits around the nozzle of the in-cylinder injection valve can also be suppressed.

[0012] The following describes specific embodiments of this disclosure with reference to the drawings. The dimensions, materials, shapes, relative arrangements, etc., of the components described in the following embodiments are not intended to limit the technical scope of the invention to those unless otherwise specified.

[0013] <Embodiment> Figure 1 is a cross-sectional view showing an example of a schematic configuration of an internal combustion engine 1 to which this disclosure applies. In Figure 1, only the configuration around the combustion chamber Cc1 of the internal combustion engine 1 is shown. The internal combustion engine 1 in this embodiment is a spark-ignition internal combustion engine (e.g., a gasoline engine) having one or more cylinders 101.

[0014] The internal combustion engine 1 in this embodiment comprises a cylinder block 10 and a cylinder head 11. The cylinder block 10 is provided with a cylindrical cylinder 101. A piston 102 is mounted in the cylinder 101 so as to be able to reciprocate along the axial direction of the cylinder 101. In the following description, the top dead center side of the piston 102 (the upper side in Figure 1) will be referred to as the upper side, and the bottom dead center side of the piston 102 will be referred to as the lower side.

[0015] A cylinder head 11 is mounted on the upper side of the cylinder block 10 so as to close the upper opening of the cylinder 101. Figure 1 shows the state in which the piston 102 is at top dead center, and in this state, the top surface of the piston 102, the lower wall surface of the cylinder head 11, and the inner wall surface of the cylinder 101 of the cylinder block 10 define the combustion chamber Cc1. In this embodiment, the lower wall surface of the cylinder head 11 forms the ceiling portion of the combustion chamber Cc1. The portion 11a is referred to as the ceiling wall portion 11a. In the example shown in Figure 1, the ceiling wall portion 11a is formed in the shape of a pent roof, but other shapes may be adopted.

[0016] In the cylinder head 11, an intake port 111, an exhaust port 112, an intake valve 113, an exhaust valve 114, a spark plug 116, and an in-cylinder injection valve 117 are arranged. The intake port 111 is a passage for guiding intake air (air) into the cylinder 101. The exhaust port 112 is a passage for guiding the burned gas from inside the cylinder 101 to the outside of the cylinder 101 (for example, an exhaust passage). The intake valve 113 is a poppet valve that opens and closes the opening end of the intake port 111 on the ceiling wall surface portion 11a (111a in FIG. 3 to be described later). The exhaust valve 114 is a poppet valve that opens and closes the opening end of the exhaust port 112 on the ceiling wall surface portion 11a (112a in FIG. 3 to be described later). The intake valve 113 and the exhaust valve 114 are respectively opened and closed by an intake-side camshaft and an exhaust-side camshaft not shown in the figure.

[0017] In the internal combustion engine 1 of the present embodiment, as shown in FIG. 3 to be described later, two intake ports 111 and two exhaust ports 112 are provided respectively. Accordingly, two intake valves 113 and two exhaust valves 114 are also provided respectively. Further, in the internal combustion engine 1 of the present embodiment, it is assumed that the shape of the intake port 111 and the shape of the top surface of the piston 102 are designed such that a tumble flow of intake air is formed inside the cylinder 101.

[0018] The spark plug 116 is a spark plug for igniting the air-fuel mixture formed inside the combustion chamber Cc1. In the example shown in FIG. 1, the spark plug 116 is inserted and screwed into a plug hole 115 extending upward from the central portion of the ceiling wall surface portion 11a. At that time, the plug hole 115 is configured such that the tip portion (electrode portion) of the spark plug 116 is exposed inside the combustion chamber Cc1.

[0019] The in-cylinder injector 117 is a fuel injector that directly injects fuel into the cylinder 101. In this embodiment, as shown in Figure 3 described later, the in-cylinder injector 117 is mounted near the peripheral edge of the ceiling wall portion 11a, between the open ends 111a of the two intake ports 111. At that time, the in-cylinder injector 117 is mounted on the cylinder head 11 such that the tip portion including the injection hole is exposed inside the combustion chamber Cc1. Details of the mounting of the in-cylinder injector 117 will be described later.

[0020] (Structure of the combustion chamber) Here, the structure of the combustion chamber Cc1 of the internal combustion engine 1 in this embodiment will be described in detail with reference to Figures 2 and 3. Figure 2 is a cross-sectional view showing an example of the configuration of the ceiling wall portion 11a of the cylinder head 11 in this embodiment. Figure 3 is a view of the ceiling wall portion 11a shown in Figure 2 from below.

[0021] In this embodiment, the open ends 111a of the two intake ports 111 and the open ends 112a of the two exhaust ports 112 are arranged to surround the open end 115a of the plug hole 115 (corresponding to the "first opening" in this disclosure), as shown in Figure 3. An opening 118 is provided near the periphery of the ceiling wall portion 11a, between the open ends 111a of the two intake ports 111, for inserting the tip portion of the in-cylinder injection valve 117 into the combustion chamber Cc1. At that time, a spray escape portion 118a is provided around the opening 118, as illustrated in Figures 2 and 3. In one example, the spray escape portion 118a may be a substantially cylindrical recess (depression) extending from the periphery side of the ceiling wall portion 11a toward the center. The opening 118 may be located inside the spray escape portion 118a. With the opening 118 and spray relief section 118a configured in this way, the fuel (spray) injected from the nozzle of the in-cylinder injection valve 117 can flow inside the combustion chamber Cc1 without hitting the ceiling wall section 11a. The shape of the spray relief section 118a is such that the fuel (spray) from the nozzle of the in-cylinder injection valve 117 does not hit the ceiling Any shape other than a roughly cylindrical shape is acceptable as long as it does not collide with the wall surface 11a.

[0022] Furthermore, in this embodiment, a slit 119 is provided in the ceiling wall portion 11a of the cylinder head 11, as shown in Figures 2 and 3. In one example, the slit 119 may be a substantially semi-cylindrical groove. In that case, the slit 119 should be formed such that one end communicates with the spray escape portion 118a, and the other end is located between the spray escape portion 118a and the opening end 115a of the spark plug hole 115. Note that the shape of the slit 119 is not limited to a substantially semi-cylindrical shape and may be appropriately changed according to the shape of the combustion chamber Cc1, etc. The length of the slit 119 may be determined according to the results of experiments, simulations, etc.

[0023] (Effects and workings of the embodiment) Next, the operation and effects of the combustion chamber structure in this embodiment will be explained based on Figures 4 and 5. Figure 4 is a schematic diagram showing the flow of fuel and intake air in the combustion chamber structure of a comparative example. Figure 5 is a schematic diagram showing the flow of fuel and intake air in the combustion chamber structure of this embodiment. The difference between the comparative example and this embodiment is the presence or absence of the slit 119. That is, Figure 4 shows the flow of fuel and intake air in a combustion chamber structure without the slit 119, and Figure 5 shows the flow of fuel and intake air in a combustion chamber structure with the slit 119.

[0024] The intake air flowing into the cylinder 101 from the intake port 111 flows along the ceiling wall 11a from the intake side (the side where the opening end 111a of the intake port 111 is located) to the exhaust side (the side where the opening end 112a of the exhaust port 112 is located), and then flows downward along the wall of the cylinder 101 on the exhaust side. The intake air that has flowed downward along the wall of the cylinder 101 on the exhaust side then flows along the top surface (crown surface) of the piston 102 from the exhaust side to the intake side. The intake air that has flowed along the top surface (crown surface) of the piston 102 then flows along the wall of the cylinder 101 on the intake side towards the ceiling wall 11a. As a result, a tumble flow is formed inside the combustion chamber Cc1, as shown by the solid arrows in Figures 4 and 5. When fuel is injected from the in-cylinder injection valve 117 into the combustion chamber Cc1 where such a tumble flow is formed, the injected fuel spray is mixed with the intake air while swirling on the tumble flow.

[0025] In a combustion chamber structure without a slit 119, as shown in the comparative example in Figure 4, if some of the fuel and intake air flowing on the tumble flow enter the spray escape section 118a, the fuel and intake air may accumulate inside the spray escape section 118a, as indicated by the dashed arrow in Figure 4. When such a phenomenon occurs, the tumble flow may be attenuated, or combustion deposits may be generated around the nozzle of the in-cylinder injection valve 117.

[0026] In contrast, in the combustion structure of this embodiment, when a portion of the fuel and intake air flowing on the tumble flow enters the spray escape section 118a, the fuel and intake air flow out of the spray escape section 118a through the slit 119, as shown by the dashed arrow in Figure 5. The fuel and intake air that flow out of the spray escape section 118a merge with the main flow of the tumble flow and flow together. This suppresses the stagnation of fuel and intake air in the spray escape section 118a. As a result, the attenuation of the tumble flow can be kept to a minimum. Furthermore, because the scavenging performance of the spray escape section 118a is improved, it is also possible to suppress fuel adhesion and deposit formation around the injection holes of the in-cylinder injection valve 117. [Explanation of Symbols]

[0027] 1...Internal combustion engine, 10...Cylinder block, 101...Cylinder, 11...Cylinder head, 111...Intake port, 112...Exhaust port, 113...Intake valve, 114...Exhaust valve, 115...Spark plug hole, 115a...Opening end (first opening), 116...Spark plug, 117...In-cylinder injection valve, 118...Opening ( Second opening), 118a...spray escape section, 119...slit

Claims

[Claim 1] A combustion chamber structure for an internal combustion engine configured such that a tumble flow is formed inside the cylinder, A first opening is provided in the center of the ceiling wall portion, which is the wall surface of the cylinder head that forms the ceiling portion of the combustion chamber, and is formed so that the tip of the spark plug is exposed into the combustion chamber, A second opening is provided in the ceiling wall portion at a position closer to the intake side than the first opening, and is formed such that the nozzle portion of the in-cylinder injection valve is exposed into the combustion chamber, A spray escape section is provided around the second opening in the ceiling wall portion and is formed in a concave shape, Equipped with, A slit is formed in the ceiling wall portion, extending from the spray escape portion toward the first opening. Combustion chamber structure.

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