Combustion chamber structure of internal combustion engine

Abstract

To provide a combustion chamber structure of an internal combustion engine maintaining a tumble flow even in the vicinity of a compression top dead point to stabilize combustion.SOLUTION: A combustion chamber structure of an internal combustion engine 10 includes a piston 40 where a recessed part 42 receiving a tumble flow T is formed on a piston top surface 41. In the combustion chamber structure of an internal combustion engine 10, the recessed part 42 is eccentrically arranged so that the position of the upper end of the recessed part 42 of the piston top surface 41 shown as a point P2 is located outward with respect to the cylinder center relative to a position (point P1) where the tumble flow T swirling along a cylinder head inner wall surface 32 flows to the side of the piston top surface 41 in the vicinity of a top dead point in a cross section where the swirling diameter of the tumble flow T in the combustion chamber 20 becomes maximum.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This invention relates to the combustion chamber structure of an internal combustion engine.

Background Art

[0002] Patent Document 1 discloses an internal combustion engine. This internal combustion engine guides a tumble flow in the combustion chamber to suppress a decrease in the intensity of the tumble flow. This internal combustion engine causes the tumble flow to collapse before top dead center of compression to generate a strong airflow turbulence in the combustion chamber. This internal combustion engine improves the output performance by expanding the lean combustion region due to this airflow turbulence.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a super lean burn engine that performs combustion in a lean state, since the air-fuel ratio λ is large, it is difficult to stabilize combustion compared to conventional stoichiometric combustion. Therefore, an internal combustion engine that can maintain a tumble flow even near top dead center of compression to stabilize combustion is desired.

Means for Solving the Problems

[0005] Hereinafter, the means for solving the above problems and their effects will be described. The combustion chamber structure of an internal combustion engine for solving the above problems has a piston with a recess formed in the piston top surface for receiving a tumble flow. In the cross section where the turning diameter of the tumble flow in the combustion chamber is maximum, the upper end position of the recess on the piston top surface is located more outward with respect to the cylinder center than the position where the tumble flow that has turned along the inner wall surface of the cylinder head near top dead center flows into the piston top surface side, and the recess is eccentrically arranged.

Advantages of the Invention

[0006] The combustion chamber structure of the internal combustion engine can maintain the tumble flow even near the compression top dead center and stabilize combustion.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0008] Hereinafter, the combustion chamber structure of the internal combustion engine 10 will be described with reference to FIGS. 1 and 2. FIGS. 1 and 2 are cross-sectional views of the combustion chamber structure of the internal combustion engine 10, and are cross-sectional views showing a cross section passing through the center of the cylinder 37 among the cross sections orthogonal to the central axis of the swirling flow by the tumble flow T. The turning diameter of the tumble flow T in the combustion chamber 20 is maximum in this cross section. FIG. 2 is a cross-sectional view of the combustion chamber structure of the internal combustion engine 10 of the same embodiment near top dead center.

[0009] As shown in FIGS. 1 and 2, the combustion chamber structure of the internal combustion engine 10 includes a cylinder block 30, a cylinder head 31, and a piston 40. The cylinder block 30 includes a cylinder 37. The cylinder head 31 includes a cylinder head inner wall surface 32. The piston 40 includes a piston top surface 41. A recess 42 is formed in the piston top surface 41. The combustion chamber 20 is defined by the cylinder 37, the cylinder head inner wall surface 32, and the piston top surface 41.

[0010] As shown in FIGS. 1 and 2, the cylinder head 31 is provided with an intake port 33 through which intake air flows into the combustion chamber 20, and an exhaust port 35 through which the burned gas generated by the combustion of the air-fuel mixture in the combustion chamber 20 is discharged. Further, the internal combustion engine 10 includes an intake valve 34 that opens and closes the intake port 33 with respect to the combustion chamber 20, and an exhaust valve 36 that opens and closes the exhaust port 35 with respect to the combustion chamber 20. When intake air flows into the combustion chamber 20 from the intake port 33, the intake air swirls along the cylinder head inner wall surface 32, generating a tumble flow T as indicated by the arrows in FIGS. 1 and 2.

[0011] As shown in FIG. 2, in the recess 42 of the piston 40, at a cross section where the turning diameter of the tumble flow T in the combustion chamber 20 is maximum, the upper end position of the recess 42 on the piston top surface 41 is eccentrically arranged so as to be located outward with respect to the cylinder center, rather than the position where the tumble flow T swirling along the cylinder head inner wall surface 32 flows into the piston top surface 41 side near the top dead center. In FIG. 2, the position where the tumble flow T swirling along the cylinder head inner wall surface 32 flows into the piston top surface 41 side is indicated by point P1. In FIG. 2, the upper end position of the recess 42 on the piston top surface 41 is indicated by point P2.

[0012] Hereinafter, as a comparative example, the combustion chamber structure of a conventional internal combustion engine 110 will be described with reference to FIG. 3. FIG. 3 is a cross-sectional view of the combustion chamber structure of the conventional internal combustion engine 110, and shows a cross-section passing through the center of the cylinder 37 among the cross-sections orthogonal to the central axis of the swirl flow by the tumble flow T. The turning diameter of the tumble flow T in the combustion chamber 120 is the largest in this cross-section. FIG. 3 is a cross-sectional view of the combustion chamber structure of the conventional internal combustion engine 110 near top dead center.

[0013] As shown in FIG. 3, the combustion chamber structure of the conventional internal combustion engine 110 includes a cylinder block 30, a cylinder head 31, and a piston 140. The cylinder block 30 includes a cylinder 37. The cylinder head 31 includes a cylinder head inner wall surface 32. The piston 140 includes a piston top surface 141. A recess 142 is formed in the piston top surface 141. The combustion chamber 120 is defined by the cylinder 37, the cylinder head inner wall surface 32, and the piston top surface 141.

[0014] As shown in FIG. 3, the cylinder head 31 is provided with an intake port 33 through which intake air flows into the combustion chamber 120, and an exhaust port 35 through which the burned gas generated by the combustion of the air-fuel mixture in the combustion chamber 120 is discharged. Further, the internal combustion engine 110 includes an intake valve 34 that opens and closes the intake port 33 with respect to the combustion chamber 120, and an exhaust valve 36 that opens and closes the exhaust port 35 with respect to the combustion chamber 120. When intake air flows into the combustion chamber 120 from the intake port 33, the intake air swirls along the cylinder head inner wall surface 32, and a tumble flow T as shown by the arrow in FIG. 3 is generated.

[0015] As shown in FIG. 3, in the combustion chamber structure of the conventional internal combustion engine 110, the upper end position of the recess 142 of the piston top surface 141 is not eccentrically arranged with respect to the cylinder center. In FIG. 3, the upper end position of the recess 142 of the piston top surface 141 is indicated by a point P3.

[0016] As shown in FIG. 3, in the combustion chamber structure of the conventional internal combustion engine 110, since the upper end position of the recess 142 on the piston top surface 141 is not eccentrically arranged, the tumble flow T is attenuated due to the collision between the tumble flow T and the upper end position of the recess 142. The attenuation of the tumble flow T caused thereby makes it difficult to stabilize combustion.

[0017] <Operation of the present embodiment> The recess 42 of the piston 40 is eccentrically arranged such that the upper end position of the recess 42 on the piston top surface 41 is located outward with respect to the cylinder center, rather than the position where the tumble flow T swirling along the inner wall surface 32 of the cylinder head at the vicinity of the top dead center and flowing into the piston top surface 41 side, in the cross section where the turning diameter of the tumble flow T in the combustion chamber 20 is maximum. Therefore, in the combustion chamber structure of the internal combustion engine 10 described above, when the tumble flow T goes from the cylinder head 31 into the recess 42 along the inner wall surface 32 of the cylinder head, it is difficult to collide with the upper end position of the piston top surface 41.

[0018] <Effect of the present embodiment> (1) Since the attenuation of the tumble flow T due to the collision with the upper end position of the piston top surface 41 can be suppressed, the tumble flow T can be maintained even near the compression top dead center to stabilize combustion.

Explanation of reference numerals

[0019] 10... Internal combustion engine, 20... Combustion chamber, 30... Cylinder block, 31... Cylinder head, 32... Inner wall surface of cylinder head, 33... Intake port, 34... Intake valve, 35... Exhaust port, 36... Exhaust valve, 37... Cylinder, 40... Piston, 41... Piston top surface, 42... Recess, P2... Upper end position, T... Tumble flow

Claims

[Claim 1] A combustion chamber structure of an internal combustion engine having a piston having a recess formed on a piston top surface to receive a tumble flow, At a cross section where the swirl diameter of the tumble flow in the combustion chamber is maximum, The upper end position of the recess in the piston top surface is located outward with respect to the center of the cylinder from the position where the tumble flow that has swirled along the inner wall surface of the cylinder head near the top dead center flows into the piston top surface side. The recess is eccentrically disposed Combustion chamber structure of an internal combustion engine.

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