Internal combustion engine

Abstract

The present invention provides an internal combustion engine that can suppress the attenuation of tumble flow generated within the cylinder. [Solution] An internal combustion engine 1 is provided with a cylinder head 5 attached to a cylinder block 2, a combustion chamber 6 formed inside, an intake port 8 and an exhaust port 10 formed on the ceiling wall surface 7 which is the inner surface of the combustion chamber 6, and an intake valve 12 that opens and closes the intake port 8 on the combustion chamber 6 side, wherein the intake valve 12 has a mask portion 12c that protrudes toward the combustion chamber 6 side from the rear end edge of its outer circumference that faces away from the exhaust port 10, and the cylinder head 5 has a wall portion 5a that faces the mask portion 12c when the intake valve 12 closes the intake port 8.

Description

Technical Field

[0001] The present invention relates to an internal combustion engine provided with an intake port that opens into a combustion chamber formed inside a cylinder head, and an intake valve that opens and closes the intake port.

Background Art

[0002] Patent Document 1 describes an internal combustion engine configured such that the flow of intake air flowing from the intake port into the combustion chamber becomes a tumble flow that swirls vertically in the axial direction in the cylinder bore. The internal combustion engine described in this Patent Document 1 is configured to form a strong tumble flow at low loads and to ensure the amount of intake air flowing into the cylinder at high loads. Specifically, a tumble flow forming device capable of changing the cross-sectional area of the flow path in the intake passage is provided, and at low loads, the cross-sectional area of the flow path is decreased by the tumble flow forming device, and at high loads, the cross-sectional area of the flow path is increased by the tumble flow forming device. Further, on the back side of the umbrella portion of the intake valve that opens and closes the intake port, a slope surface is formed against which the intake air constricted by the tumble flow forming device hits. This slope surface is formed in a streamline shape, and the angle formed by the back plane of the valve and the umbrella surface of the valve is configured to be smaller than the angles in other regions.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described in Patent Document 1, by reducing the flow path cross-sectional area of ​​the intake passage at low load and increasing the flow path cross-sectional area of ​​the intake passage at high load, it is possible to generate a strong tumble flow at low load and ensure intake airflow at high load. On the other hand, at the timing when the intake valve closes the intake port, a reverse tumble flow opposite to the tumble flow is generated near the intake valve. Since this reverse tumble flow is generated at a position half a turn away from the position where the tumble flow is generated in the circumferential direction of the intake valve, even if a slope surface is formed on the intake valve, as in the intake valve described in Patent Document 1, to generate a strong tumble flow, the tumble flow in the cylinder may be attenuated by the reverse tumble flow opposite to that tumble flow.

[0005] This invention was made in view of the above-mentioned technical problems, and aims to provide an internal combustion engine that can suppress the attenuation of tumble flow generated in the cylinder. [Means for solving the problem]

[0006] To achieve the above objective, this invention provides an internal combustion engine in which a combustion chamber is formed inside a cylinder head attached to a cylinder block, an intake port and an exhaust port are formed on the ceiling wall surface which is the inner surface of the combustion chamber, and an intake valve is provided to open and close the intake port on the combustion chamber side, wherein the intake valve has a mask portion that protrudes toward the combustion chamber side from the rear end edge of its outer circumference that faces away from the exhaust port, and the cylinder head has a wall portion that faces the mask portion when the intake valve is closed to close the intake port. [Effects of the Invention]

[0007] According to this invention, the intake valve is provided with a mask portion that protrudes toward the combustion chamber from the rear edge of its outer circumference that faces away from the exhaust port. Furthermore, the ceiling wall surface, which forms the combustion chamber, has a wall portion that faces the mask portion when the intake valve is closed to the intake port. Therefore, the flow resistance of the intake air flowing into the combustion chamber from the gap between the area where the mask portion is formed on the intake valve and the ceiling wall portion is greater than at other locations. In addition, by forming the mask portion, the length of the area with high flow resistance can be increased, further increasing the flow resistance of the intake air. As a result, the generation of reverse tumble flow caused by the intake air flowing into the combustion chamber from the area where the mask portion is formed can be suppressed, and the weakening of the tumble flow by the reverse tumble flow can be suppressed, thus enabling rapid combustion in the combustion chamber. [Brief explanation of the drawing]

[0008] [Figure 1] This is an enlarged cross-sectional view illustrating an example of an internal combustion engine in an embodiment of this invention. [Figure 2] This is a perspective view illustrating an example of an intake valve. [Figure 3] This is a perspective view of an intake valve from the underside to illustrate another example of an intake valve. [Figure 4] This is a perspective view illustrating an example of an intake valve in which the mask portion protrudes beyond the outer edge of the valve portion. [Modes for carrying out the invention]

[0009] The present invention will be described below based on the embodiments shown in the figures. The embodiments described below are merely examples of how the present invention can be implemented and do not limit the invention.

[0010] Figure 1 shows a cross-sectional view illustrating an example of an internal combustion engine according to an embodiment of the present invention. As shown in Figure 1, the internal combustion engine 1 comprises a cylinder block 2, and a bore 3 is formed in the cylinder block 2. Inside the bore 3 is a piston 4 that moves up and down while maintaining an airtight seal inside the bore 3 in accordance with the rotation of a crankshaft (not shown). A cylinder head 5 is attached to the upper side of the cylinder block 2 (the side of the opening of the bore 3, which is the upper side in Figure 1). The lower surface of the cylinder head 5 is recessed upwards at a position corresponding to the bore 3, and this recessed position is the combustion chamber 6.

[0011] The combustion chamber 6 is formed in a pent-roof shape, with its ceiling wall 7 gradually rising from both the left and right sides. A spark plug (not shown) is provided in its central portion (i.e., at the intersection with the central axis of the bore 3). An intake port 8 is formed on one side of the ridge of the ceiling wall 7, and an intake pipe 9 is connected to this intake port 8.

[0012] Similarly, an exhaust port 10 is formed on the other side of the ridge of the ceiling wall surface 7, and an exhaust pipe 11 is connected to the exhaust port 10. Specifically, the intake port 8 and the exhaust port 10 are formed such that the line connecting the centers of the intake port 8 and the exhaust port 10 is perpendicular to the ridge.

[0013] In the following description, the direction in which the intake port 8 and exhaust port 10 face each other will be described as the left-right direction, and the direction of the ridge line will be described as the front-rear direction. The internal combustion engine 1 may be a multi-cylinder engine, and multiple cylinders are provided in which the bore 3 and ports 8, 10 etc. configured as described above are formed, and an intake manifold (not shown) is connected to each intake port 8, and a throttle valve (not shown) for adjusting the opening area is provided in the flow path upstream of the intake manifold.

[0014] An intake valve 12 is provided, configured to close the intake port 8 from the combustion chamber 6 side. This intake valve 12 is configured similarly to a conventional intake valve and consists of a rod 12a that is movable up and down in a direction perpendicular to the intake port 8, and a conical portion 12b connected to the lower end of the rod 12a, which is formed to have a larger diameter than the opening area of ​​the intake port 8.

[0015] Similarly, an exhaust valve 13 is provided, configured to close the exhaust port 10 from the combustion chamber 6 side. This exhaust valve 13 is configured in the same way as a conventional exhaust valve, and consists of a rod 13a that is provided to be movable up and down in a direction perpendicular to the exhaust port 10, and a conical portion 13b connected to the lower end of the rod 13a, which is formed to have a larger diameter than the opening area of ​​the exhaust port 10.

[0016] Each of the valves 12 and 13 described above is configured to open and close the intake port 8 and exhaust port 10 in accordance with the rotation of the crankshaft (not shown). In other words, they open and close in accordance with the up and down movement of the piston 4. Specifically, during the intake stroke, which supplies air and fuel into the bore 3, the intake valve 12 opens and closes once as the piston 4 descends from top dead center to bottom dead center, and during the exhaust stroke, which discharges exhaust gases from the bore 3, the exhaust valve 13 opens and closes once as the piston 4 rises from bottom dead center to top dead center.

[0017] As shown in Figure 2, a mask portion 12c is formed on the intake valve 12 described above. This mask portion 12c is configured to suppress the inflow of intake air (outside air) into the combustion chamber 6 through the gap with the cylinder head 5. Specifically, the mask portion 12c is formed to protrude vertically towards the combustion chamber 6 from a range corresponding to half the circumference of the lower end of the valve portion 12b, centered on the rear end of the outer edge of the valve portion 12b opposite to the exhaust valve 13 (or exhaust port 10). The mask portion 12c may be molded integrally with the intake valve 12, or it may be molded separately and then fixed to the intake valve 12.

[0018] Further, an outer edge of a lower end portion (opening end portion) of the cylinder head 5 is formed so as to surround a mask portion 12c formed on the intake valve 12. Specifically, a wall portion 5a facing the mask portion 12c is formed on the cylinder head 5 in a state where the intake valve 12 has retreated to close the intake port 8. That is, the wall portion 5a is formed in a substantially semi-circular shape similar to the mask portion 12c. Further, the wall portion 5a is formed parallel to the central axis of the intake valve 12 so that the gap between the mask portion 12c and the wall portion 5a does not change during the process in which the intake valve 12 retreats. This mask portion 12c is for suppressing the inflow of outside air from the gap with the wall portion 5a during the process of closing the intake valve 12. Therefore, the gap between the mask portion 12c and the wall portion 5a is determined to be the smallest within a dimension range where they do not contact each other even when the mask portion 12c and the wall portion 5a are closest to each other due to, for example, manufacturing errors or assembly errors.

[0019] In the intake process of taking in outside air into the combustion chamber 6, the internal combustion engine 1 configured as described above, the intake valve 12 is driven toward the combustion chamber 6 side, and the piston 4 descends. As the piston 4 descends in this way, the volume of the combustion chamber 6 increases and the pressure decreases, so that outside air is taken into the combustion chamber 6. In addition to the outside air, fuel is injected into the combustion chamber 6. This fuel may be injected toward the intake port 8 or directly into the combustion chamber 6.

[0020] Since the intake port 8 is formed in the pent-roof type ceiling wall surface 7 as described above, the outside air flowing in from the intake port 8 becomes a tumble flow TS as indicated by an arrow in FIG. 1. That is, a counterclockwise vortex on the paper surface along the central axis direction of the bore 3 is formed.

[0021] Then, the intake valve 12 closes at the timing when the speed of the piston 4 is the fastest. That is, the intake valve 12 retreats, and the valve portion 12b abuts against the intake port 8. In the process of closing the intake port 8 in this way, the area through which the outside air flows in the intake port 8 becomes narrower, etc., so that the outside air easily flows from the rear end portion on the side opposite to the exhaust port 10 (IN side) in the valve portion 12b toward the combustion chamber 6 side.

[0022] On the other hand, as described above, the rear end portion of the valve portion 12b is surrounded by the wall portion 5a, and the gap is formed narrower than other portions. Therefore, the flow resistance of the outside air flowing from the rear end portion toward the combustion chamber 6 side becomes larger than other portions. As a result, it is possible to suppress the generation of a reverse tumble flow opposing the tumble flow TS.

[0023] In addition, since the intake valve 12 described above is formed with a mask portion 12c protruding toward the combustion chamber 6 side, the length of the portion with a large flow resistance can be increased, and furthermore, the flow resistance of the intake air can be increased. As a result, it is possible to suppress the generation of a reverse tumble flow due to the intake air flowing from the portion where the mask portion 12c is formed toward the combustion chamber 6 side, and it is possible to suppress the weakening of the tumble flow TS by the reverse tumble flow. Therefore, combustion in the combustion chamber 6 can be performed quickly. Furthermore, since the mask portion 12c is additionally provided on the valve portion 12b, the rigidity of the valve portion 12b can be improved, and it is possible to suppress the generation of a reverse tumble flow due to the outside air flowing into the combustion chamber 6 from the rear end portion side of the valve 12b when the valve 12b is deflected, etc.

[0024] In the embodiment of this invention, two intake ports 8, two exhaust ports 10, two intake valves 12, and two exhaust valves 13 may be provided respectively. That is, two intake ports may be formed side by side on one side of the ridge line of the ceiling wall surface 7, an intake valve may be provided corresponding to each intake port, and two exhaust ports may be formed side by side on the other side, and an exhaust valve may be provided corresponding to each exhaust port.

[0025] In such cases, if intake air flowing into the combustion chamber 6 from adjacent intake ports interferes with each other, the intake airflow within the bore 3 may become turbulent, potentially weakening the tumble flow TS. An example of an intake valve 12 that can suppress such interference between intake air is shown in Figure 3. Figure 3 shows a perspective view of the intake valve 12 as seen from the bottom side.

[0026] The intake valve 12 shown in Figure 3, like the intake valve 12 shown in Figure 2, is equipped with a mask portion 12c that protrudes vertically from its rear end. On the other hand, this mask portion 12c is configured such that the gap between it and the wall portion 5a on the exhaust port 10 side (EX side) gradually increases. That is, the radius of curvature of the mask portion 12c is configured to gradually decrease with respect to the rear end of the intake valve 12.

[0027] By configuring the gap between the mask portion 12c and the wall portion 5a to gradually increase on the exhaust port 10 side (EX side), the intake airflow flowing into the combustion chamber 6 from near the front end of the mask portion 12c (the end on the exhaust port 10 side) curves towards the exhaust port 10 side as it enters the combustion chamber 6, thereby suppressing interference with the intake airflow flowing into the combustion chamber 6 from adjacent intake ports. As a result, the mask portion 12c can not only suppress the generation of reverse tumble flow but also enhance the tumble flow TS.

[0028] Furthermore, as described above, by providing the intake valve 12 with a mask portion 12c configured to have a gradually changing radius of curvature, the manufacturing precision requirements can be relaxed compared to when the mask portion 12c is provided on the cylinder head 5. This is because the clearance between the intake valve 12 and the wall portion 5a of the cylinder head 5 is narrow, requiring high precision coaxiality, while the valve seat (the seating surface that contacts the valve portion 12b) is perfectly round and the mask portion 12c is elliptical, making it impossible to perform simultaneous machining with the same tool and thus preventing high coaxiality from being achieved.

[0029] In this embodiment of the invention, the mask portion 12c may be formed to protrude outward from the outer edge of the intake valve 12, as shown in Figure 4. That is, similar to a conventional intake valve, the valve portion 12b may be formed in a circular shape, and the mask portion 12c, which is configured to have an extremely small gap with the wall portion 5a provided on the cylinder head 5, may be integrally attached or integrally molded to the lower end of the rear end side (IN side) of the valve portion 12b. Note that the mask portion 12c shown in Figure 4 is configured, similar to the mask portion 12c shown in Figure 3, such that the radius of curvature of the mask portion 12c gradually decreases with respect to the rear end of the intake valve 12. [Explanation of symbols]

[0030] 1. Internal combustion engine 2 Cylinder Blocks 3 Bore 5 Cylinder head 5a Wall 6 Combustion chamber 7 Ceiling and wall surfaces 8 intake ports 10 exhaust ports 12 Intake valves 12a, 13a rods 12b, 13b Valve section 12c Mask section TS Tumble Style

Claims

[Claim 1] An internal combustion engine comprising a cylinder head attached to a cylinder block, a combustion chamber formed inside the cylinder head, an intake port and an exhaust port formed on the ceiling wall surface which forms the inner surface of the combustion chamber, and an intake valve that opens and closes the intake port on the combustion chamber side, The intake valve is provided with a mask portion that protrudes toward the combustion chamber from the rear end edge of its outer circumference that faces away from the exhaust port, The cylinder head has a wall portion facing the mask portion when the intake valve is closed off the intake port. An internal combustion engine characterized by the following features.

Images