JP6365611B2 - Engine combustion chamber structure - Google Patents

Description

  The present invention relates to a combustion chamber structure of an engine, and more particularly to a combustion chamber structure having a pent roof type cylinder head surface.

  2. Description of the Related Art Conventionally, a combustion chamber engine having a pent roof type cylinder head surface has been adopted as a vehicle engine. The pent roof type cylinder head surface has an intake port side inclined surface and an exhaust port side inclined surface inclined to both sides from a top portion provided with a hole portion to which a spark plug is attached. In the pent roof type cylinder head surface, two intake port openings are provided on the intake port side inclined surface, and two exhaust port openings are provided on the exhaust port side inclined surface. In such an engine having a pent roof type combustion chamber on the cylinder head surface, a spark plug can be arranged on the top of the cylinder head surface, so that the spark propagation efficiency can be increased and a high compression ratio can be realized. Is also easy.

  With respect to the combustion chamber structure having such a pent roof type cylinder head surface, attempts have been made to improve the generation of intake flow (tumble flow) and obtain high combustion characteristics (Patent Documents 1 and 2).

JP 2011-256730 A JP 2012-127218 A

  However, in the design of the cylinder head, there are cases where the inclination angle of the inclined surface on the exhaust port side must be changed from the conventional angle. In such a case, the conventional combustion chamber structure has an adverse effect on the tumble flow. Exerts a deterioration in combustion characteristics. For example, when a cylinder stop system (switchable hydraulic lash adjuster) is accommodated in the cylinder head, the inclination angle formed by the exhaust valve shaft core with respect to the cylinder shaft core must be reduced. In such a case, the inclination angle of the inclined surface on the exhaust port side must also be changed, resulting in a bad influence on the tumble flow.

  The present invention has been made to solve the above-described problems, and can generate a tumble flow that circulates greatly in the combustion chamber regardless of the inclination angle of the inclined surface on the exhaust port side, and has excellent combustion. It is an object of the present invention to provide an engine combustion chamber structure capable of realizing the characteristics.

  In the combustion chamber structure of the engine according to one aspect of the present invention, the ceiling of the combustion chamber is configured by a pent roof type cylinder head surface having an intake port side inclined surface and an exhaust port side inclined surface inclined to both sides from the top. This is a structure. And the combustion chamber structure of the engine which concerns on this aspect is equipped with two exhaust port opening and a bulging part.

In the region between the opening edges of the two exhaust port openings, the bulging portion has the cylinder head surface protruding from the virtual plane including the opening surfaces of the two exhaust port openings toward the combustion chamber.
The bulging portion extends in a direction intersecting with a line segment connecting the centers of the two exhaust port openings, and is connected to an inner peripheral surface of a cylinder bore surrounding a side periphery of the combustion chamber. The bulging amount from the virtual plane gradually increases from the top side toward the cylinder bore inner peripheral surface side.

In the combustion chamber structure of the engine according to this aspect, a tumble flow that circulates greatly in the combustion chamber can be generated by providing a bulging portion in a region between the opening edges of the two exhaust port openings. Therefore, even if the inclination angle of the inclined surface on the exhaust port side is changed, a high tumble ratio and turbulent energy can be realized. In particular, even if the inclination angle of the inclined surface of the exhaust port side with respect to the axis of the combustion chamber is smaller than the conventional angle, the inclination angle of the inclined surface on the exhaust port side becomes gentler than that of the exhaust port opening. It is possible to suppress stagnation of the tumble flow on the side away from the top.
Moreover, in the combustion chamber structure of the engine which concerns on this aspect, it is set as the structure where the bulging part is extended in the direction which cross | intersects with the line segment which connects between the centers of two exhaust port opening. Furthermore, the bulging portion is configured to be connected to the inner peripheral surface of the cylinder bore that surrounds the side periphery of the combustion chamber. Therefore, in the combustion chamber structure of the engine according to this aspect, the tumble flow can be smoothly guided by the bulging portion, and the tumble flow can be largely circulated to the inner peripheral surface side of the cylinder bore.
In the engine combustion chamber structure according to this aspect, the bulging amount of the bulging portion is gradually increased from the top side toward the cylinder bore inner peripheral surface side, so that the tumble flow can be smoothly guided. can do. Therefore, it is further effective to generate a tumble flow that circulates greatly in the combustion chamber.

  Therefore, in the combustion chamber structure of the engine according to this aspect, it is possible to generate a tumble flow that circulates greatly in the combustion chamber regardless of the inclination angle of the inclined surface on the exhaust port side, and to realize excellent combustion characteristics.

In the combustion chamber structure of the engine according to one aspect of the present invention, the ceiling of the combustion chamber is configured by a pent roof type cylinder head surface having an intake port side inclined surface and an exhaust port side inclined surface inclined to both sides from the top. In the combustion chamber structure of the engine, the exhaust port side inclined surface has two exhaust port openings provided in a state of being spaced apart from each other, and a region between the opening edges of the two exhaust port openings, A bulging portion formed by projecting the cylinder head surface closer to the combustion chamber than the virtual plane including the opening surfaces of the two exhaust port openings, and the bulging portion has a bulging amount from the virtual plane. However, in the direction connecting the centers of the two exhaust port openings, the opening of the two exhaust port openings is formed with the middle portion in the region between the opening edges of the two exhaust port openings as the top. Gradually decreases towards the edge.

In the combustion chamber structure of the engine according to this aspect, a tumble flow that circulates greatly in the combustion chamber can be generated by providing a bulging portion in a region between the opening edges of the two exhaust port openings. Therefore, even if the inclination angle of the inclined surface on the exhaust port side is changed, a high tumble ratio and turbulent energy can be realized. In particular, even if the inclination angle of the inclined surface of the exhaust port side with respect to the axis of the combustion chamber is smaller than the conventional angle, the inclination angle of the inclined surface on the exhaust port side becomes gentler than that of the exhaust port opening. It is possible to suppress stagnation of the tumble flow on the side away from the top.
In the engine combustion chamber structure according to this aspect, the shape of the bulging portion in the direction connecting the centers of the two exhaust port openings is gradually reduced toward both sides with the intermediate portion at the top. . Therefore, the tumble flow can be guided smoothly, and a large tumble flow can be generated toward the inner peripheral surface of the cylinder bore in the combustion chamber.

Therefore, in the combustion chamber structure of the engine according to this aspect, it is possible to generate a tumble flow that circulates greatly in the combustion chamber regardless of the inclination angle of the inclined surface on the exhaust port side, and to realize excellent combustion characteristics.

  In the engine combustion chamber structure according to another aspect of the present invention, in the above configuration, when the virtual circumscribing line with respect to the opening edges of the two exhaust port openings is drawn on the top portion side, the bulging portion is the virtual circumscribing portion. It has a starting point on the opposite side of the top from the line.

  In the combustion chamber structure of the engine according to this aspect, the starting point of the bulging part is arranged on the side opposite to the top part from the virtual circumscribing line, which is further effective for realizing a high tumble ratio and turbulent energy. is there.

  The combustion chamber structure of the engine according to another aspect of the present invention is the above-described configuration, wherein the bulging portion has the bulging amount from the imaginary plane in a direction connecting between the centers of the two exhaust port openings. It gradually decreases toward the opening edge of the two exhaust port openings, with the middle portion in the region between the opening edges of the two exhaust port openings as the top.

  In the combustion chamber structure of the engine according to this aspect, the shape of the bulging portion in the direction connecting between the centers of the two exhaust port openings is gradually reduced toward both sides with the intermediate portion as the top. Therefore, the tumble flow can be guided smoothly, and a large tumble flow can be generated toward the inner peripheral surface of the cylinder bore in the combustion chamber.

  An engine combustion chamber structure according to another aspect of the present invention includes an exhaust valve that opens and closes the exhaust port opening, an exhaust port that continues from the exhaust port opening, an exhaust port, and a shaft portion of the exhaust valve. And a hydraulic lash adjuster disposed between the two.

  In the combustion chamber structure of the engine according to this aspect, since a hydraulic lash adjuster (HLA) is provided between the exhaust port and the shaft portion of the exhaust valve, the shaft of the exhaust valve with respect to the shaft core of the combustion chamber. The inclination angle formed by the core may be smaller than when the HLA is not provided. As a result, the inclination angle of the inclined surface on the exhaust port side becomes gentle, but as described above, a large tumble flow can be generated by providing the bulging portion. Therefore, even in such a case, excellent combustion characteristics can be realized.

  In the engine combustion chamber structure according to another aspect of the present invention, in the above configuration, the hydraulic lash adjuster is a switchable hydraulic lash adjuster.

  The switchable hydraulic lash adjuster (S-HLA) provided in the combustion structure of the engine according to this aspect occupies a larger area in the cylinder head than a normal HLA. Even in such a case, in this aspect, a large tumble flow can be generated, and deterioration of combustion characteristics can be suppressed.

  The combustion chamber structure of the engine according to another aspect of the present invention further includes an intake valve that opens and closes the intake port opening in the above configuration, and an inclination angle formed by the axis of the exhaust valve with respect to the axis of the combustion chamber is The inclination angle formed by the axis of the intake valve with respect to the axis of the combustion chamber is smaller.

  As in this embodiment, when the inclination angle formed by the exhaust valve axis with respect to the combustion chamber axis is smaller than the inclination angle formed by the intake valve axis with respect to the combustion chamber axis, the tumble flow may occur. Although an adverse effect can be considered, as described above, by providing the bulging portion, the adverse effect can be avoided, and a large tumble flow can be generated. Therefore, excellent combustion characteristics can also be realized in the combustion chamber structure of the engine according to this aspect.

  In the combustion chamber structure of an engine according to another aspect of the present invention, in the above configuration, the inclination angle formed by the axis of the exhaust valve with respect to the axis of the combustion chamber is specifically within a range of 15 ° to 20 °. is there.

  Even when the exhaust valve is provided with such an angle of the axis, as described above, a large tumble flow can be generated, and excellent combustion characteristics can be realized.

  In the combustion chamber structure of the engine according to each of the above aspects, it is possible to generate a tumble flow that circulates greatly in the combustion chamber regardless of the inclination angle of the inclined surface on the exhaust port side, and to realize excellent combustion characteristics.

1 is a schematic cross-sectional view showing a partial configuration of an engine 100 according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing a partial configuration of a cylinder head 1 according to an embodiment of the present invention. 2 is a schematic plan view showing a configuration of a cylinder head surface in the cylinder head 1. FIG. It is a model perspective view which shows the structure of a cylinder head surface. FIG. 3 is a schematic diagram showing an arrangement relationship between exhaust port openings 3a and 6a and a bulging portion 11 on a cylinder head surface. FIG. 4 is a cross-sectional view taken along the line VI-VI in FIG. 3, illustrating a configuration of a combustion chamber 100 a in the engine 100. (A) is a schematic diagram which shows the structure of the combustion chamber in the cylinder head 80 which concerns on a reference example, (b) is a schematic diagram which shows the structure of the combustion chamber in the cylinder head 90 which concerns on a comparative example. It is a characteristic view which shows the tumble ratio in the comparative example with respect to a reference example, and an Example. It is a characteristic view which shows the turbulent energy in the comparative example with respect to a reference example, and an Example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The form described below is one embodiment of the present invention, and the present invention is not limited to the following form except for the essential configuration.

1. Structure of Combustion Chamber 100a in Engine 100 The structure of the combustion chamber 100a in the engine 100 according to the embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing a partial configuration of an engine 100 according to the embodiment.

  As shown in FIG. 1, engine 100 includes a cylinder head 1, a cylinder block 15, and a piston 20. In FIG. 1, only one piston 20 and a portion corresponding thereto are extracted and illustrated, but the engine 100 according to the present embodiment is a multi-cylinder engine.

  The cylinder head 1 has a cylinder head surface that forms the ceiling of the combustion chamber 100a. The cylinder head surface has a top portion 12, and an intake port side inclined surface 9 and an exhaust port side inclined surface 10 that are inclined and extend from the top surface 12 to both sides. The cylinder head surface of the cylinder head 1 in the engine 100 according to the present embodiment is a so-called pent roof type cylinder head surface.

  The cylinder block 15 has a cylinder bore inner circumferential surface 16 that faces a cylinder bore in which the piston 20 is reciprocally accommodated. The cylinder bore inner peripheral surface 16 is continuous with the lower edges of the intake port side inclined surface 9 and the exhaust port side inclined surface 10.

  The piston 20 has a piston top surface 21 that faces the cylinder head surface of the cylinder head 1.

  A combustion chamber 100a of the engine 100 is surrounded by a pent roof-type cylinder head surface including an intake port side inclined surface 9 and an exhaust port side inclined surface 10 in the cylinder head 1, a cylinder bore inner peripheral surface 16, and a piston top surface 21. Space.

2. Cylinder Head Surface in Cylinder Head 1 The configuration of the cylinder head surface in the cylinder head 1 will be described with reference to FIGS. 2 is a schematic cross-sectional view showing a partial configuration of the cylinder head 1, FIG. 3 is a schematic plan view showing the configuration of the cylinder head surface, and FIG. 4 is a schematic perspective view showing the configuration of the cylinder head surface. It is.

  As shown in FIGS. 2 and 3, intake port openings 2 a and 5 a of the two intake ports 2 and 5 are opened on the intake port side inclined surface 9 constituting the cylinder head surface. Here, the intake port opening 2a and the intake port opening 5a are provided on the intake port side inclined surface 9 in a state of being spaced apart from each other in a direction intersecting the maximum inclined surface direction of the intake port side inclined surface 9. ing.

  In FIG. 2, only the intake port 2 and the intake port opening 2a are shown for the convenience of illustration.

  Exhaust port openings 3a and 6a of the two exhaust ports 3 and 6 are formed in the exhaust port side inclined surface 10 constituting the cylinder head surface. Here, the exhaust port opening 3a and the exhaust port opening 6a are provided in the exhaust port side inclined surface 10 in a state of being spaced apart from each other in a direction intersecting the maximum inclined surface direction of the exhaust port side inclined surface 10. ing.

  As in the above, FIG. 2 shows only the exhaust port 3 and the exhaust port opening 3a for convenience of illustration.

As shown in FIG. 2, in the cylinder head 1, with respect to Ax ₁ (the axis of the combustion chamber 100a) the cylinder axis, the angle θ1 which the exhaust valve axis Ax ₃ eggplant, within the range of 15 ° to 20 ° It is. In the present embodiment, the angle θ1 is 17 °.

Although details are not shown, with respect to the cylinder axis Ax _1, the angle formed by the intake valve axis is in the range of 22 ° ~ 23 °. In the present embodiment, the angle is 23 °. That is, in the engine 100 according to this embodiment, the angle θ1 of the cylinder axis Ax _1, formed by the exhaust valve axis Ax _3, relative to the cylinder axis Ax _1, than the angle formed by the intake valve axis Is also small.

In cylinder head 1 according to this embodiment, as described above, with respect to the cylinder axis Ax _1, the angle θ1 which the exhaust valve axis Ax ₃ eggplant, smaller than the conventional angle 22 ° ~23 °, 17 ° This is because a switchable type hydraulic lash adjuster (HLA) 4 is provided between the exhaust ports 3 and 6 and the shaft portion of the exhaust valve.

  As shown in FIG. 3, a spark plug mounting hole 8 is formed in the top 12 of the cylinder head surface. In the present embodiment, the spark plug mounting hole 8 is opened on the axial center of the combustion chamber 100a. In the engine 1, by realizing the center plug, the propagation efficiency of the spark can be increased and a high compression ratio can be realized.

  Further, as shown in FIG. 3, fuel injection holes 7 are provided on the outer edge side of the intake port openings 2a and 5a.

  Here, the exhaust port side inclined surface 10 is provided with a bulging portion 11 in a region between the opening edges of the exhaust port opening 3a and the exhaust port opening 6a (a region indicated by an arrow A). As indicated by the arrow B in FIG. 4, the bulging portion 11 in the exhaust port side inclined surface 10 is a portion that protrudes to the combustion chamber 100a side from a virtual plane including the exhaust port opening 3a and the exhaust port opening 6a. .

3. Configuration of the bulging portion 11 The configuration of the bulging portion 11 on the exhaust port side inclined surface 10 will be described with reference to FIGS. 5 and 6. FIG. 5 is a schematic diagram showing an arrangement relationship between the exhaust port openings 3a and 6a and the bulging portion 11, and FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. It is a schematic cross section shown.

As shown in FIG. 5, when the cylinder head surface is viewed in plan from the piston 20 side, the bulging portion 11 has a substantially triangular shape. Specifically, the area between the opening edge of the exhaust port openings 3a and the exhaust port 6a as a starting point P _1, the spark plug mounting hole 8 becomes triangular width is gradually increased toward the outer periphery of the opposite Yes.

Here, at the top portion 12 side, it pulls the exhaust port openings 3a, the external tangents L ₂ of each opening edge of 6a virtually. At this time, the starting point P ₁ of the bulging portion 11 is positioned on the opposite side of the top portion 12 than the circumscribed line L _2. That is, as the starting point _{P 1,} when pulling the virtual line _{L 1} parallel to the bounding line _{L 2,} the phantom line _{L 1} is an exhaust port opening 3a, the center line _Ax 3a of 6a, and _{Ax 6a} and circumscribing lines _{L 2} Located between.

In the present embodiment, the center line Ax _3a of the exhaust port opening _3a and the center line Ax _6a of the exhaust port opening 6a are on one straight line.

Further, the starting point _{P 1} of the bulging portion 11 is located on the middle line _{Ax 11} between the exhaust port openings 3a and the exhaust port opening 6a. The bulging portion 11, around the middle line Ax _11, it is formed symmetrically in the width direction. Specifically, the bulge portion 11 in the width direction, toward the opening edge portion of the exhaust port openings 6a in the middle line Ax _11, overhanging amount gradually increases and exceeds the median line Ax _11, an exhaust port openings 3a The amount of overhang gradually decreases toward the opening edge portion.

On the other hand, the opposite side of the portion to the start point P ₁ in the bulging portion 11 is smoothly connected to the cylinder bore inner peripheral surface 16 (see Figure 1.). Here, “smoothly” means that there is no large step.

  Next, as shown in FIG. 6, the bulging amount of the bulging portion 11 gradually increases from the top 12 side toward the cylinder bore inner peripheral surface 16 side. Specifically, the height from the virtual plane (exhaust port opening surface 10a) including the exhaust port openings 3a and 6a to the bulging portion surface 11a is G1 on the top 12 side, and G1 on the cylinder bore inner peripheral surface 16 side. A larger G2 is obtained.

  As shown in FIG. 6, the bulging portion surface 11 a is not a straight line, and there is a portion where the inclination changes in the extending direction of the bulging portion 11 from the top 12 side to the cylinder bore inner peripheral surface 16 side. .

  Moreover, the bulging part surface 11a is a smooth surface.

4). Characteristic Evaluation Result The characteristic evaluation result of the structure of the combustion chamber 100a according to the above configuration will be described with reference to FIGS. FIG. 7A is a schematic diagram showing the configuration of the combustion chamber in the cylinder head 80 according to the reference example, and FIG. 7B is a schematic diagram showing the configuration of the combustion chamber in the cylinder head 90 according to the comparative example. is there. FIG. 8 is a characteristic diagram showing tumble ratios in the comparative example and the example with respect to the reference example, and FIG. 9 is a characteristic diagram showing turbulent energy in the comparative example and the example with respect to the reference example.

(Reference example)
First, a combustion chamber structure according to a reference example will be described with reference to FIG.

  As shown in FIG. 7A, in the cylinder head 80 according to the reference example, the angle θ2 formed by the exhaust valve shaft core with respect to the cylinder shaft core is 23 °. For this reason, the exhaust port side inclined surface 80a is inclined more than the exhaust port side inclined surface 10 of the example (the above embodiment).

  In addition, the bulging part is not formed in the exhaust port side inclined surface 80a which concerns on a reference example.

(Comparative example)
Next, the combustion chamber structure according to the comparative example will be described with reference to FIG.

  As shown in FIG. 7B, in the cylinder head 90 according to the comparative example, the angle θ3 formed by the exhaust valve shaft core with respect to the cylinder shaft core is 17 °, similar to the above θ1. For this reason, the exhaust port side inclined surface 90a is inclined at the same angle as the exhaust port side inclined surface 10 of the example (the above embodiment).

  However, in the cylinder head 90 according to the comparative example, the bulging portion is not formed on the exhaust port side inclined surface 90a.

《Tumble ratio》
The evaluation result of the tumble ratio in the comparative example and the example with respect to the reference example will be described with reference to FIG. In FIG. 8, the tumble ratio in the reference example is “100”, and the comparative example and the example are relatively represented.

  As shown in FIG. 8, when the inclination angle of the exhaust port side changes with the change in the inclination angle of the exhaust valve shaft as in the comparative example, the tumble ratio decreases by about 9% compared to the reference example. ing.

  On the other hand, in the example in which the bulging portion 11 is provided on the exhaust port side inclined surface 10, the decrease in the tumble ratio is only about 3% compared to the reference example.

《Turbulent energy》
The evaluation results of the turbulent energy in the comparative example and the example with respect to the reference example will be described with reference to FIG. In FIG. 9, the turbulent energy in the reference example is “100”, and the comparative example and the example are relatively represented.

  As shown in FIG. 9, the turbulent energy of the comparative example is reduced by about 6% compared to the reference example.

  On the other hand, the turbulent energy of the example is about 2% higher than that of the reference example.

<< Summary of evaluation >>
From the above two evaluation results, in the combustion chamber structure according to the embodiment, by providing the bulging portion 11 on the inclined surface 10 on the exhaust port side, a tumble flow that circulates greatly in the combustion chamber similar to the reference example is generated. It can be estimated that

  On the other hand, in the comparative example in which the bulging portion is not provided on the exhaust port side inclined surface, as shown in FIG. 7B, the portion on the cylinder bore inner peripheral surface side of the exhaust port side inclined surface 90a (the portion indicated by the arrow C). A “wall” is formed. Accordingly, it is presumed that the tumble flow cannot circulate greatly in the combustion chamber, and the dead volume D is formed. Therefore, it is considered that the evaluation results of the tumble ratio and turbulent energy were bad.

5. Effect In the structure of the combustion chamber 100a in the engine 100 according to the present embodiment, the two exhaust port openings 3a. By providing the bulging portion 11 in the region between the opening edges of 6a, it is possible to generate a tumble flow that circulates greatly in the combustion chamber 100a. Therefore, even when the inclination angle of the exhaust port side inclined surface 10 is changed with the change of the inclination angle of the exhaust valve shaft core, it is possible to realize a high tumble ratio and turbulent energy. In the present embodiment, to reduce the inclination angle θ1 of the exhaust valve axis Ax ₃ with respect to the cylinder axis Ax ₁ in a conventional ratio, the inclination angle of the exhaust port side inclined surface 10 is a gentle accordingly. Even in such a structure, stagnation of the tumble flow on the side farther from the top than the exhaust port opening can be suppressed.

  Therefore, in the structure of the combustion chamber 100a in the engine 100 according to the present embodiment, generation of a tumble flow that circulates greatly in the combustion chamber 100a even if the inclination angle of the exhaust port side inclined surface 10 is gentler than the conventional one. It is possible to achieve excellent combustion characteristics.

  Further, the bulging portion 11 is configured to extend in a direction intersecting with a line segment connecting the centers of the two exhaust port openings 3a and 6a. Further, the bulging portion 11 is configured to be connected to a cylinder bore inner peripheral surface 16 surrounding the side periphery of the combustion chamber 100a. Therefore, in the structure of the combustion chamber 100a in the engine 100 according to the present embodiment, the tumbling portion 11 can smoothly guide the tumble flow, and the tumble flow can be circulated greatly to the cylinder bore inner peripheral surface 16 side. it can.

  Further, in the structure of the combustion chamber 100a in the engine 100 according to the present embodiment, the bulging amount of the bulging portion 11 is gradually increased from the top portion 12 side toward the cylinder bore inner peripheral surface 16 side. The flow of the flow can be guided smoothly.

Further, in the combustion chamber 100amp structure of the engine 100 according to this embodiment, the starting point P ₁ of the bulging portion 11, as shown in FIG. 5, by arranging on the side opposite to the top portion 12 than the external tangents L ₂ High tumble ratio and turbulent energy can be realized.

Further, in the structure of the combustion chamber 100a in the engine 100 according to the present embodiment, the protruding height of the bulging portion 11 in the direction connecting the centers of the two exhaust port openings 3a and 6a (the width direction of the bulging portion 11). but a portion of the median line Ax ₁₁ to the top, so that gradually decreases toward both sides. Therefore, the tumble flow can be guided smoothly, and a large tumble flow can be generated toward the cylinder bore inner peripheral surface 16 side in the combustion chamber 100a.

In the cylinder head 1 according to this embodiment, the exhaust port 3 and 6 has a configuration including the switchable type hydraulic lash adjuster (HLA) between the exhaust valve shank, the exhaust valve axis relative to the cylinder axis Ax ₁ The inclination angle θ ₁ formed by Ax ₃ is smaller than that of the reference example that does not include the HLA. In association with this, the inclination angle of the exhaust port side inclined surface 10 becomes gentle, but a large tumble flow can be generated by providing the bulging portion 11 as described above. Therefore, even in such a case, excellent combustion characteristics can be realized.

[Modification]
As shown in FIG. 5, the shape of the bulging portion 11 when the cylinder head surface is viewed in plan from the piston top surface 21 side is substantially triangular in the above embodiment, but the present invention is not limited to this. It is not something to receive. For example, it may be a fin shape or a line shape. However, from the viewpoint of generating a tumble flow that circulates largely in the combustion chamber 100a, it is desirable to have a shape as shown in FIG.

Also, the position of the starting point P ₁ of the bulging portion 11, the present invention is not intended to be limited to the position shown in FIG. For example, the starting point may be positioned at the hole edge of the spark plug mounting hole 8, or may be configured on or near the line connecting the center of the exhaust port opening 3a and the center of the exhaust port 6a.

  Moreover, in the structure of the combustion chamber 100a in the engine 100 according to the above embodiment, the bulge portion 11 having an integral structure is provided, but a bulge portion divided into a plurality of portions may be provided.

  Furthermore, in the structure of the combustion chamber 100a in the engine 100 according to the above-described embodiment, only the bulging portion 11 projecting toward the combustion chamber 100a with respect to a virtual plane including the two exhaust port openings 3a and 6a is provided. However, the present invention is not limited to this. For example, a groove for guiding intake air can be formed on the top portion 12 or the exhaust port side inclined surface 10 and the groove can be combined with the bulging portion.

In the above-described embodiment, the switchable HLA 4 is attached to some cylinders of the multi-cylinder engine and the cylinder is deactivated, and the above configuration is applied to a cylinder in which the inclination angle of the exhaust valve shaft core Ax ₃ is conventionally changed. However, the present invention is not limited to this. The same configuration may be adopted for the cylinders to which the HLA is not attached so that the tumble flow is the same for all the cylinders. That is, the attachment of the switchable HLA 4 and the formation of the bulging portion 11 are not necessarily linked, and can contribute to the generation of a tumble flow that circulates in the combustion chamber 100a.

DESCRIPTION OF SYMBOLS 1 Cylinder head 2,5 Intake port 2a, 5a Intake port opening 3,6 Exhaust port 3a, 6a Exhaust port opening 9 Intake port side inclined surface 10 Exhaust port side inclined surface 11 Expansion part 12 Top surface 15 Cylinder block 16 In cylinder bore Circumferential surface 20 Piston 21 Piston top surface 100 Engine 100a Combustion chamber

Claims (8)

In the combustion chamber structure of the engine in which the ceiling of the combustion chamber is constituted by a pent roof type cylinder head surface having an intake port side inclined surface and an exhaust port side inclined surface inclined to both sides from the top part,
Two exhaust port openings provided on the exhaust port side inclined surface at a distance from each other;
In the region between the opening edges of the two exhaust port openings, a bulging portion in which the cylinder head surface projects to the combustion chamber side from a virtual plane including the opening surfaces of the two exhaust port openings;
Equipped with a,
The bulging portion extends in a direction intersecting a line segment connecting the centers of the two exhaust port openings, and is connected to an inner circumferential surface of a cylinder bore surrounding a side circumference of the combustion chamber. The amount of bulge from the virtual plane gradually increases from the top side toward the cylinder bore inner peripheral surface side,
Engine combustion chamber structure. In the combustion chamber structure of the engine in which the ceiling of the combustion chamber is constituted by a pent roof type cylinder head surface having an intake port side inclined surface and an exhaust port side inclined surface inclined to both sides from the top part,
Two exhaust port openings provided on the exhaust port side inclined surface at a distance from each other;
In the region between the opening edges of the two exhaust port openings, a bulging portion in which the cylinder head surface projects to the combustion chamber side from a virtual plane including the opening surfaces of the two exhaust port openings;
With
In the direction in which the bulging amount from the virtual plane connects between the centers of the two exhaust port openings, the bulging portion has the intermediate portion in the region between the opening edges of the two exhaust port openings as a top. Decreasing toward the opening edge of the two exhaust port openings,
Engine combustion chamber structure. The engine combustion chamber structure according to claim 1 ,
When drawing a virtual tangent to the opening edge of the two exhaust port openings on the top side,
The bulge has a starting point on the opposite side of the top from the virtual circumscribing line,
Engine combustion chamber structure. The engine combustion chamber structure according to claim 1 or 3 ,
In the direction in which the bulging amount from the virtual plane connects between the centers of the two exhaust port openings, the bulging portion has the intermediate portion in the region between the opening edges of the two exhaust port openings as a top. Decreasing toward the opening edge of the two exhaust port openings,
Engine combustion chamber structure. A combustion chamber structure for an engine according to any one of claims 1 to 4 ,
An exhaust valve for opening and closing the exhaust port opening;
An exhaust port continuing from the exhaust port opening;
A hydraulic lash adjuster disposed between the exhaust port and the shaft of the exhaust valve;
Further comprising
Engine combustion chamber structure. The engine combustion chamber structure according to claim 5 ,
The hydraulic lash adjuster is a switchable hydraulic lash adjuster,
Engine combustion chamber structure. A combustion chamber structure for an engine according to claim 5 or 6 ,
An intake valve that opens and closes the intake port opening;
The inclination angle formed by the axis of the exhaust valve with respect to the axis of the combustion chamber is smaller than the inclination angle formed by the axis of the intake valve with respect to the axis of the combustion chamber.
Engine combustion chamber structure. The engine combustion chamber structure according to claim 7 ,
An inclination angle formed by the axis of the exhaust valve with respect to the axis of the combustion chamber is within a range of 15 ° to 20 °.
Engine combustion chamber structure.

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