Valve structure of engine

Abstract

To generate a swirl flow for combustion air in an intake valve 8 of an engine 1 to reduce various losses generated when charging the combustion air from an intake passage 6 to a combustion chamber 2 by a swirl effect, and then to generate a swirl flow for exhaust gas in an exhaust valve 9 of the engine 1 to smoothly improve a scavenging effect from the combustion chamber 2 to an exhaust passage 7.SOLUTION: With a starting point at a boundary between a valve stem 21 and an umbrella part 22, and an end point just before a boundary between the umbrella part 22 and a valve face 23, the umbrella part 22 of an intake valve 8 has a plurality of swirling vanes arranged in a spiral shape from the starting point on the valve stem side to the end point on the valve face side. With a starting point at a boundary between a valve stem 31 and an umbrella part 32, and an end point just before a boundary between the umbrella part 32 and a valve face 33, the umbrella part 32 of an exhaust valve 9 has a plurality of swirling vanes arranged in a spiral shape from the starting point on the valve stem side to the end point on the valve face side.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to gasoline engines and diesel engines, and more particularly to improvements in the intake valve structure of an intake system that introduces combustion air or a mixture of combustion air and fuel from an intake passage into a combustion chamber, and the exhaust valve structure of an exhaust system that exhausts air from the combustion chamber into an exhaust passage, in gasoline engines and diesel engines. [Background technology]

[0002] Conventionally, so-called reciprocating engines are known, which obtain power by converting the reciprocating motion of a piston into the rotary motion of a crankshaft via a connecting rod. In this type of engine, it is considered effective to generate a strong flow of the mixture in the combustion chamber from the viewpoint of improving the fuel consumption rate and purifying the combustion gas.

[0003] In order to generate a strong flow of the mixture in the combustion chamber, the shape of the intake port is a spiral inlet type or a tangential inlet type. By providing the intake port with a spiral inlet type or a tangential inlet type, the combustion air or the mixture of the combustion air and the fuel that flows into the combustion chamber generates a swirling flow called a swirl in the combustion chamber. This swirl increases the turbulence of the mixture, and the flame spreads faster. The combustion period of the mixture in the combustion chamber is shortened, and the combustion is stable. In addition to improving the fuel consumption rate, similar measures are also used to improve the output and purify the combustion gas. In addition, when multiple intake ports are installed in one combustion chamber, a method of making a variable swirl structure in which a butterfly valve is installed in the intake passage of one of the intake ports to adjust the inflow amount depending on the operating conditions of the combustion chamber is also used.

[0004] In order to generate a swirl in the combustion air or the mixture of the combustion air and the fuel flowing into the combustion chamber, there are several ideas for generating a swirling flow on the surface of the intake valve of the intake system. For example, Patent Document 1 devised an intake device in which a plurality of vanes are provided on the surface of the inlet valve to cause a swirl in the intake flow. Patent Document 2 devised an intake port structure of an intake system in which swirl flow is generated in the combustion air or the mixture of the combustion air and the fuel by providing swirl vanes protruding radially inward in a spiral shape along the inner wall of the intake passage at the intake port of the intake passage formed in a tubular shape to guide the combustion air or the mixture of the combustion air and the fuel that is sucked and filled into the combustion chamber through the intake valve.

[0005] However, in Patent Document 1, the shape of the blade is rectangular in cross section as shown in FIG. 4 of Patent Document 1, and the shape of the blade from the stem side to the face side is also rectangular as shown in FIGS. 2 and 3. The blade described in Patent Document 1 acts as a barrier to the air that flows into the combustion chamber at high speed when the intake valve opens, and it is assumed that the inflowing air becomes stagnant here, resulting in a greater pumping loss due to the stagnation of the inflow of combustion air than the generation of a swirl flow in the inflowing air. In Patent Document 2, the swirling vanes are limited to being provided along the inner wall of the intake passage at the inlet port of the intake passage. There is no mention of the intake valve and the exhaust valve. In general, when the intake valve opens to the combustion chamber during the intake stroke, the combustion air that enters the combustion chamber flows along the shape of the intake valve's umbrella and is diffused 360 degrees before entering. In order to generate a swirling flow in the combustion air that enters the combustion chamber, it is more efficient and effective to provide a swirling flow by the umbrella part of the intake valve. And when the exhaust valve opens toward the combustion chamber during the exhaust stroke and exhausts the exhaust gas after combustion in the combustion chamber into the exhaust passage, the exhaust gas is discharged into the exhaust passage along the shape of the exhaust valve's umbrella. In order to generate a swirling flow in the exhaust gas after combustion in the combustion chamber and quickly discharge the exhaust gas in the combustion chamber, it is more efficient and effective to provide a swirling flow by the umbrella part of the exhaust valve that the exhaust gas first comes into contact with when the exhaust valve opens toward the combustion chamber during the exhaust stroke, and the exhaust gas can be efficiently guided into the exhaust passage. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Utility Model Application Publication No. 6-4303

[0007] [Patent Document 2] JP 2003-27949 A Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, the present invention has an object to provide a valve structure for an engine's intake system in which swirl vanes are provided in the intake valve head portion to generate a swirling flow (swirl) at the intake valve head portion of the combustion air or a mixture of combustion air and fuel just before it is sucked into the combustion chamber via the intake valve, in order to reduce various losses that occur when the combustion air or a mixture of combustion air and fuel flows into and fills the combustion chamber via the intake valve, and an exhaust valve structure for an engine's exhaust system in which swirl vanes are provided in the exhaust valve head portion to generate a swirling flow (swirl) of exhaust gas at the exhaust valve head portion in order to smoothly discharge exhaust gas after combustion in the combustion chamber during the exhaust stroke when the exhaust valve opens and the exhaust gas is discharged. [Means for solving the problem]

[0009] 1. An intake valve that is provided at the combustion chamber inlet port, which is the end of an intake passage formed in a tubular shape to guide the combustion air or a mixture of combustion air and fuel from the intake passage to the combustion chamber, and opens and closes the valve by driving a cam. There is The intake valve head portion of the intake valve is formed by rotating the swirl vanes in a spiral shape from the starting point on the valve stem side to the ending point on the valve face side, with the boundary between the valve stem of the intake valve and the intake valve head portion at the center of the intake valve head portion of the intake valve as the starting point, and the boundary between the intake valve head portion and the valve face of the intake valve as the ending point. In the intake valve provided at a plurality of locations, the height of the tip of the swirl vane provided on the intake valve head portion is formed so as to gradually increase from the position of the starting point of the swirl vane on the valve stem side toward the valve face, the height of the tip of the swirl vane reaches a peak point at a position midway along the shortest straight line distance between the valve stem and the valve face on the intake valve head portion, and the height of the tip of the swirl vane is formed so as to gradually decrease from the peak point of the swirl vane toward the end point of the swirl vane on the valve face side, and the twist angle α of the swirl vane on the intake valve head portion is the valve stem position at which the swirl vane starts. The cross-sectional shape of the swirl vanes provided on the intake valve head portion is gradually wider and gently inclined from the tip of the swirl vanes toward the surface of the intake valve head portion, and the swirl vanes have inner and outer sides formed so as to form an arc that is concave inwardly of the swirl vanes themselves, so that the combustion air or a mixture of combustion air and fuel drawn into the combustion chamber from the intake passage is swirled by the swirl vanes provided on the intake valve head portion and flows into the combustion chamber. 2. An exhaust valve that opens and closes by driving a cam provided at the exhaust port of the combustion chamber, which is the end of the exhaust passage formed in a tubular shape to guide exhaust gas after combustion in the combustion chamber from the combustion chamber to the exhaust passage. There is The exhaust valve head portion of the exhaust valve is formed by rotating the swirl blades in a spiral shape from the starting point on the valve stem side to the end point on the valve face side, with the boundary between the valve stem of the exhaust valve and the exhaust valve head portion at the center of the exhaust valve head portion of the exhaust valve as the starting point, and the boundary between the exhaust valve head portion and the valve face of the exhaust valve as the end point. In the exhaust valve provided at a plurality of locations, the height of the tip of the swirl vane provided on the exhaust valve head portion is formed to gradually increase from the position which is the starting point of the swirl vane on the valve stem side toward the valve face, the height of the tip of the swirl vane reaches a peak point at a position which is the midpoint of the shortest straight line distance between the valve stem and the valve face on the exhaust valve head portion, and the height of the tip of the swirl vane is formed to gradually decrease from the peak point of the swirl vane toward the end point of the swirl vane on the valve face side, and the twist angle α of the swirl vane on the exhaust valve head portion is The exhaust valve is characterized in that the exhaust gas discharged from the combustion chamber to the exhaust passage is swirled by the swirling vanes provided on the exhaust valve head portion, and the cross-sectional shape of the swirling vanes provided on the exhaust valve head portion gradually becomes wider and gently slopes from the tip of the swirling vanes to the surface of the exhaust valve head portion, and the exhaust gas discharged from the combustion chamber to the exhaust passage is discharged from the combustion chamber to the exhaust passage while being swirled by the swirling vanes provided on the exhaust valve head portion. Effect of the Invention

[0010] First invention According to the method, the swirl vanes provided on the intake valve umbrella portion generate a swirling flow in the combustion air or the mixture of combustion air and fuel that passes through the intake passage into the combustion chamber and is drawn in through the intake valve, so that the combustion air or the mixture of combustion air and fuel can flow efficiently when the intake valve is opened to the combustion chamber, and the combustion air or the mixture of combustion air and fuel can be filled into the combustion chamber while reducing various losses that occur when the air flows in. Furthermore, the effect of the gently shaped swirl vanes provided on the intake valve umbrella portion is that they can effectively generate a swirling flow near the entrance of the combustion chamber while minimizing loss in flow rate, and they can effectively generate a swirling flow even on the surface of the intake valve umbrella portion where the swirl vanes do not directly act, and guide the boundary layer gas with a slow flow rate on the umbrella portion surface to the center where the flow rate is faster, smoothing the flow of the combustion air or the mixture of combustion air and fuel, so that the combustion air or the mixture of combustion air and fuel can flow efficiently into the combustion chamber when the intake valve is opened to the combustion chamber.

[0011] The second invention According to the above, the effect of the swirl vanes provided on the exhaust valve umbrella portion is to generate a swirling flow in the exhaust gas discharged from the combustion chamber into the exhaust passage through the exhaust valve during the exhaust stroke of the combustion cycle, and when the exhaust valve opens, the exhaust gas discharged from the combustion chamber into the exhaust passage itself forms a vortex, allowing it to flow efficiently into the exhaust passage, and the exhaust gas can be discharged from the combustion chamber into the exhaust passage while reducing various losses that occur when the exhaust valve opens. Furthermore, the effect of the gently shaped swirl vanes provided on the exhaust valve umbrella portion is to effectively generate a swirling flow near the entrance of the combustion chamber while minimizing loss in flow velocity, and even on the exhaust valve umbrella surface where the swirl vanes do not directly act, a swirling flow is effectively generated as a vortex by induction, and the gas in the boundary layer with a slow flow velocity on the umbrella surface is guided to the center where the flow velocity is faster, thereby smoothing the flow of the exhaust gas and improving the scavenging effect of efficiently discharging the exhaust gas from the combustion chamber into the exhaust passage when the exhaust valve opens. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is an external view of an intake valve having a swirling vane mechanism on the valve head. [Diagram 2] This is an external view of an intake valve with a swirl vane mechanism installed on the valve head, as viewed from above. [Diagram 3] FIG. 3 is a schematic diagram showing one of the swirl vane mechanisms in the head portion of the intake valve, taken along line A-B in FIG. 2. [Figure 4] 2 is a cross-sectional view showing one of the swirl vane mechanisms in the head portion of the intake valve, taken along line C-D in FIG. 1. [Diagram 5] FIG. 1 is an external view of an exhaust valve having a swirling blade mechanism on the head of the exhaust valve. [Figure 6] This is an external view of an exhaust valve with a swirling vane mechanism on the head of the exhaust valve, as seen from above. [Figure 7] FIG. 7 is a schematic diagram showing one of the swirl vane mechanisms in the head portion of the exhaust valve, taken between M-N in FIG. 6. [Figure 8] 2 is a cross-sectional view showing one of the swirl vane mechanisms in the head portion of the intake valve, taken along the line J-K in FIG. 1. [Figure 9] 1 is a cross-sectional view of a combustion chamber and its surroundings, showing a schematic configuration of a typical direct injection engine. [Figure 10] FIG. 1 is a cross-sectional view of a mechanism for driving a direct acting valve that drives a general exhaust valve that opens and closes a combustion chamber. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The intake valve 8 and exhaust valve 9 of the present invention will be described below. Generally, automobile engines include gasoline engines that use gasoline as fuel and diesel engines that use diesel as fuel. Here, a four-stroke cycle gasoline engine will be described as an embodiment. In addition, in a four-wheeled automobile and a two-wheeled motorcycle equipped with a gasoline engine, in this embodiment, an engine 1 mounted on a four-wheeled automobile will be described as an embodiment. Currently, gasoline engines mounted on four-wheeled automobiles are mainly direct injection engines that inject gasoline into the cylinder, so in this embodiment, the direct injection engine 1 will be described as an embodiment. Figures 1 to 4 are explanatory diagrams regarding the intake valve 8, and Figures 5 to 8 are explanatory diagrams regarding the exhaust valve 9. Figure 9 is a cross-sectional view showing the main parts of a general direct injection type engine 1 in which combustion air is sucked into the combustion chamber of a gasoline engine and fuel is directly injected into the combustion chamber 16. Note that since Figure 9 is a diagram showing the positional relationship between the intake valve 8 and the exhaust valve 9 of a general engine 1, the swirl vane mechanism in the valve head portion of this embodiment is intentionally removed from the drawing of Figure 9 and is not shown. Cam mechanisms for driving the valves that open and close the intake valve 8 and the exhaust valve 9 toward the combustion chamber 2 are generally of a direct-acting type, a swing arm type, or a rocker arm type. FIG. 10 is a cross-sectional view of a typical direct-acting type valve driving mechanism. As in FIG. 9, the swirl vane mechanism in the valve head of this embodiment is purposely omitted from the drawing of FIG. 10 and is not shown. In this invention, the same effect can be obtained with any cam driving mechanism, so the description of the cam mechanism is omitted in this embodiment. An embodiment related to the intake valve 8 of the intake system will be described as Example 1, and an embodiment related to the exhaust valve 9 of the exhaust system will be described as Example 2. In this embodiment, the intermediate position of the shortest linear distance between the valve stem and the valve face on the surface of the valve head of each of the intake valve and exhaust valve is commonly referred to as the intermediate position S.

[0014] As shown in FIG. 9, the engine 1 of this embodiment includes a cylinder in which a piston 3 is accommodated so as to be capable of reciprocating, a combustion chamber 2 provided in at least one of the cylinder and the piston 3, and an intake passage 6 and an exhaust passage 7 connected to the combustion chamber 2. The intake passage 6 connected to the combustion chamber 2 at the top of the cylinder is open at the top of the combustion chamber 2. An intake valve 8 is provided at the opening, and the opening is normally closed by the intake valve 8. When the intake valve 8 is pushed by the drive of a cam 10 provided at the top end of the intake valve 8, the intake valve 8 opens toward the combustion chamber 2, and combustion air flows from the intake passage 6 into the combustion chamber 2. Similarly, an exhaust passage 7 connected to the combustion chamber 2 at the top of the cylinder is open at the top of the combustion chamber 2. An exhaust valve 9 is provided at the opening, and the opening is normally closed by the exhaust valve 9. When the exhaust valve 9 is pushed by the drive of a cam 10 provided at the top end of the exhaust valve 9, the exhaust valve 9 opens toward the combustion chamber 2, and exhaust gas is discharged from the combustion chamber 2 to the exhaust passage 7. Figure 10 explains a direct acting valve system using an exhaust valve as an example. Taking the exhaust valve as an example, the valve drive system opens and closes the valve by a structure in which the movement of an elliptical cam 10 pushes the exhaust valve 9 towards the combustion chamber to open it, or retracts it to close it. When the movement of the elliptical cam 10 pushes the exhaust valve 9 towards the combustion chamber 2 to open it, the exhaust gas after combustion is exhausted from the combustion chamber 2 into the exhaust passage 7. Similarly, the intake valve 8 is also a valve drive system.

[0015] A four-stroke cycle engine is a combustion engine that completes one cycle by four strokes: intake stroke, compression stroke, expansion stroke, and exhaust stroke. The intake valve 8 opens at the same time as the piston 3 moves from top dead center to bottom dead center during the intake stroke of the combustion cycle, and the intake valve 8 closes when the piston 3 reaches bottom dead center after the intake air is sucked into the combustion chamber 2 from the intake passage 6. The intake valve 8 then closes when the piston 3 moves from bottom dead center to top dead center during the compression stroke. During the compression stroke, fuel is injected into the cylinder from the fuel injection nozzle 4 just before the piston 3 reaches top dead center, and is ignited and burned by the spark plug 5 just before the piston 3 reaches top dead center. During the expansion stroke, the combustion pressure of the combustion gas pushes the piston 3 toward bottom dead center. The force of the combustion pressure of the combustion gas pushing the piston 3 toward bottom dead center during the expansion stroke becomes the power (output) of the engine 1. During the exhaust stroke, the piston 3 reaches the bottom dead center and moves toward the top dead center, at the same time the exhaust valve 9 opens, discharging the exhaust gas after combustion in the combustion chamber 2 into the exhaust passage 7. This is the series of strokes in a four-stroke cycle engine. EXAMPLES

[0016] As shown in Fig. 1, the structure of the intake valve 8 is roughly divided into a collet at the upper end, a rod-shaped valve stem 21, a head portion 22, and a valve face 23 on the outer periphery of the head portion 22. The part of the valve stem 21 that connects to the head portion 22 is slightly narrowed to reduce the air resistance of the combustion air flowing into the combustion chamber. The head portion 22 of the intake valve 8 is provided with swirl vanes 24 for the purpose of generating a swirl flow in the combustion air flowing into the combustion chamber 2. The starting point of the swirl vanes 24 starts at the boundary between the valve stem 21 and the head portion 22, and ends just before the boundary between the head portion 22 and the valve face 23.

[0017] Next, the configuration of the swirl vanes 24 provided on the head portion 22 of the intake valve 8, which is a characteristic feature of the present invention, will be described in detail. Fig. 2 is a view of the intake valve 8 seen from above the valve stem 21, Fig. 3 is an explanatory diagram showing one of the swirl vanes 24 provided on the intake valve head portion 22, showing the area between A and B in Fig. 2, and Fig. 4 is a cross-sectional view of the swirl vane 24 provided on the intake valve head portion 22 in Fig. 1, taken along the line C and D.

[0018] As shown in Fig. 9, the intake passage 6 is formed in a tubular shape to guide the combustion air to the combustion chamber 2, and one end is connected to the combustion chamber inlet port. An intake valve 8 is attached to the combustion chamber inlet port at the end of the intake passage 6, and the combustion air is supplied to the combustion chamber 2 by opening and closing the intake valve 8. As shown in Figs. 1 and 2, a plurality of swirl vanes 24 (three in Fig. 2) are provided at regular intervals on the umbrella portion 22 of the intake valve 8. As shown in Figs. 1 to 3, each swirl vane 24 is bent in the swirl direction R to form a spiral shape so as to swirl the combustion air flowing along the surface of the intake valve umbrella portion 22 in the direction of arrow F.

[0019] 1 to 3, the swirl vane 24 is formed in a twisted blade shape in the swirl direction R. The swirl vane 24 is formed so that the height from the intake valve head portion 22 to the tip 28 gradually increases in the direction of arrow F, i.e., from the boundary between the valve stem 21 of the intake valve 8 and the intake valve head portion 22, which is the starting point of the swirl vane 24, to a peak point 27, which is the midpoint S of the shortest straight-line distance between the valve stem 21 and the valve face 23 on the intake valve head portion 22. The height from the intake valve head portion 22 to the tip 28 is set to the peak point 27, where the height of the tip 28 of the swirl vane 24 is maximum, at the midpoint S of the shortest straight-line distance between the valve stem 21 and the valve face 23 on the intake valve head portion 22. In the intake valve head portion 22, the height of the swirl vanes 24 from the intake valve head portion 22 to the tip portion 28 is maximum at the midpoint S of the shortest straight-line distance between the valve stem 21 and the valve face 23, and the height becomes gradually lower as it approaches from the midpoint S of the shortest straight-line distance between the valve stem 21 and the valve face 23 to the end point, which is just before the boundary between the head portion 22 of the intake valve 8 and the valve face 23.

[0020] The twist angle α of the swirl vane 24 is set so that it gradually increases in the direction of arrow F, that is, from the boundary between the valve stem 21 of the intake valve 8 and the intake valve head 22, which is the start point of the swirl vane 24, to just before the boundary between the head 22 of the intake valve 8 and the valve face 23, which is the end point. Furthermore, the inner side surface 25 of the swirl vane 24 is gently inclined from the tip 28 to the inner base point 29 of the swirl vane 24, and the inner side surface 25 is provided so as to form an arc that is recessed inwardly of the swirl vane 24 itself. On the other hand, the outer side surface of the swirl vane 24 is gently inclined from the tip 28 to the outer base point 30 of the swirl vane, and the side surface 26 is provided so as to form an arc that is recessed inwardly of the swirl vane itself.

[0021] Next, the operation and effect of the intake valve configured as above will be described.

[0022] In order to convert as much of the expansion energy generated by combustion as possible into the force pushing the piston 3, it is better for the combustion speed to be as fast as possible. To do this, it is important that the gasoline particles, which are the fuel, and the combustion air are mixed thoroughly. For this reason, it is important to get the combustion air into the cylinder as efficiently as possible. The faster the mixture burns and the faster the flame speed, the more heat energy is converted into kinetic energy and the greater the expansion energy. To speed up combustion, it is desirable to first mix the gasoline particles, which are the fuel, well with the combustion air, so that the hydrocarbon molecules can react chemically with oxygen molecules immediately. Furthermore, to speed up the flame speed, it is effective to make the flow of the combustion gas strong and large. The flow of the mixture in the combustion chamber is particularly problematic when the engine 1 is running at low speed. When the engine is running at high speed, the combustion air that fills the combustion chamber 2 flows quite fast, so the mixture is sufficiently stirred and the flame speed is also fast. However, at low to medium speeds, the piston descends slowly, so the speed of the combustion air that fills the combustion chamber 2 also slows down, and the gasoline particles in the cylinder tend to be less likely to vaporize. Therefore, it becomes necessary to create vortex flows such as dumbles, which are vertical vortices, and swirls, which are horizontal vortices, in the combustion air inside the cylinder. In the present invention, the emphasis is on strengthening the swirl in the combustion chamber 2. The important thing about swirl is that the vortex created during the intake stroke remains without attenuation during the compression stroke, and the vortex flow becomes even stronger, smoothly transitioning from ignition to the expansion stroke, and effectively converting it into expansion energy that pushes the piston 3.

[0023] In the intake stroke of a four-stroke engine, the combustion air is drawn in by the opening and closing of the intake valve 8 and is guided to the upper surface of the intake valve 8 through the intake passage 6. When the intake valve 8 opens toward the combustion chamber 2, the combustion air flows through the intake passage 6 and comes into contact with the intake valve head 22, and comes into contact with the inner surface 25 of the swirling vane 24 provided on the intake valve head 22, and the combustion air flows along the inner surface 25 of the spirally provided swirling vane 24. As a result, the combustion air is given a flow component in the circumferential direction R, and gradually begins to swirl in the circumferential direction R. Then, the combustion air flows into the combustion chamber 2 while maintaining the swirling flow. In a normal engine 1, the combustion air flowing through the intake passage 6 is rarely in a rectified state. When the combustion air flows into the combustion chamber 2, a loss of the swirl (swirling flow) effect occurs due to the influence of the pressure in the combustion chamber 2, etc. However, if a swirling flow is imparted to the combustion air immediately before it flows into the combustion chamber 2 as in this embodiment, such losses can be reduced to some extent.

[0024] By configuring the swirl vane 24 as described above, a swirl flow can be effectively generated. When the intake valve 8 opens toward the combustion chamber 2 during the intake stroke, the combustion air in the intake passage 6 starts to flow into the combustion chamber 2 at a high flow rate. The swirl vane 24 must not interfere with the combustion air flowing toward the combustion chamber 2 at this high flow rate. In the umbrella portion 22 of the intake valve 8, the starting point of the swirl vane 24 starts from the boundary position between the valve stem 21 of the intake valve 8 and the intake valve umbrella portion 22, which has a slow flow rate and is a position that does not interfere with the combustion air flowing into the combustion chamber 2 at a high flow rate, and reaches a peak point 27 where the height of the tip of the swirl vane is maximum at the intermediate position S of the intake valve umbrella portion 22, which is the shortest straight line distance between the valve stem 21 and the valve face 23 on the intake valve umbrella portion 22, which is the intermediate position of the intake valve umbrella portion 22. In other words, by gradually increasing the height of the swirl vanes from the starting point of the swirl vanes toward the peak point 27, which is the intermediate position S, a swirl flow is generated from the combustion air in the boundary layer of the umbrella portion 22 of the intake valve 8, where the flow velocity is slower than the combustion air flowing toward the combustion chamber 2 at a high flow velocity in the umbrella portion 22 of the intake valve 8. Conversely, in order to maintain and grow the swirl flow generated by the swirl vanes 24, the height of the swirl vanes 24 from the intake valve head 22 to the tip 28 is maximized at the midpoint S of the shortest straight-line distance between the valve stem 21 and the valve face so as not to interfere with the opening and closing of the intake valve 8 near the valve face 23 of the intake valve 8, and the swirl vanes 24 are formed so as to gradually decrease in height as they approach the end point, just before the boundary between the head 22 and the valve face 23 of the intake valve 8, from the midpoint S of the shortest straight-line distance between the valve stem 21 and the valve face 23, until the swirl vanes 24 ends at the boundary between the head 22 and the valve face 23 of the intake valve 8, at which point the height is zero. In order to increase the amount of combustion air flowing into the combustion chamber 2, the vicinity of the valve face 23, which is the end of the intake valve 8, must be made wide so that the opening is 360 degrees wider when the intake valve 8 opens. This structure avoids interfering with the opening and closing of the intake valve 8 during the intake stroke, which is one of the series of strokes in a four-stroke engine.

[0025] In order to grow the swirling vortex obtained by the swirl vanes 24 provided on the umbrella portion 22 of the intake valve 8 and guide it into the combustion air itself so that it spreads throughout the entire combustion air, the twist angle α of the swirl vanes 24 of the intake valve 8 is set so that it gradually increases in the direction of arrow F, that is, from the boundary between the valve stem 21 and the intake valve umbrella portion 22 of the intake valve 8, which is the starting point of the swirl vanes 24, to just before the boundary between the umbrella portion 22 and the valve face 23 of the intake valve 8, which is the end point. This structure allows the combustion air passing over the surface of the intake valve umbrella portion 22 to come into contact with any part of the swirl vanes 24 as much as possible, and guides the swirl flow generated on the surface of the swirl vanes 24 into the entire combustion air.

[0026] The direction of the airflow flowing at high speed cannot be changed suddenly. If the direction is changed, the airflow will be resisted at the point where the direction is changed, resulting in a loss of flow velocity. In the present invention, the combustion air flowing on the surface of the valve umbrella portion 22 is not suddenly and forcibly swirled, but the height of the swirling vane is gradually increased from the starting point of the swirling vane to the peak point 27 at the intermediate position S, and the combustion air in the boundary layer on the surface of the umbrella portion 22, which has a slower flow velocity than the combustion air flowing toward the combustion chamber 2 at a high flow velocity, is swirled on the surface of the umbrella portion 22, while the twist angle α of the swirling vane 24 is gradually increased (increased) to grow the swirling flow. In the intake stroke, the intake valve 8 opens, and in order to diffuse the combustion air from the narrow intake passage 6 to the wide combustion chamber 2, it is more efficient and effective to slowly and gradually change the direction at first to generate a swirling flow (swirl) for the combustion air.

[0027] Furthermore, in order to scoop up the combustion air flowing from the valve stem 21 side toward the valve face 23 side on the surface of the umbrella portion 22 of the intake valve 8, the inner side of the swirl vane 24 is gently inclined from the tip 28 to the inner base point 29 of the swirl vane 24, and the inner side 25 is formed in an arc that is concave inward of the swirl vane 24 itself, so that a swirling vortex can be smoothly obtained by the swirl vane 24 as if scooping up the combustion air. When the intake valve 8 opens toward the combustion chamber 2 during the intake stroke, the location where the flow velocity of the combustion air flowing into the combustion chamber 2 is fastest is near the center of the section between the valve face 23 at the end of the intake valve 8 and the intake passage 6, which is least affected by the wall of the intake passage 6 and the intake valve 8 and has the fastest flow velocity. By making the inside side surface 25 of the swirl vane 24 form an arc that is concave inward of the swirl vane 24 itself, when the intake valve 8 opens toward the combustion chamber 2 during the intake stroke, the combustion air flows at high speed from the valve stem 21 side toward the valve face 23 side on the surface of the umbrella portion 22 of the intake valve 8, enters the arc section of the inside side surface 25 of the swirl vane 24, rotates as if scooped up, and is accelerated and guided toward the center of the fast flow velocity. If the swirling vortexes generated in the arc section of the inside side surface 25 of the swirl vane 24 become numerous and strong, they will spread to the entire combustion air flowing into the combustion chamber 2, and a swirl, which is a large and strong horizontal vortex, can be formed in the entire combustion air.

[0028] On the other hand, the outer side 26 of the swirl vane 24 is gently inclined from the tip 28 to the outer base point 30 of the swirl vane 24, similar to the inner side 25, and the outer side 26 is provided so as to form an arc concave inward of the swirl vane 24 itself. The difference from the inner side 25 is that the swirl vane 24 itself does not create a blind spot where the combustion air stagnates. The emphasis is placed on preventing the combustion air from stagnation on the outer side 26 of the swirl vane 24 of the umbrella part 22 of the intake valve 8. When the valve face 23 side of the intake valve 8 is viewed from the valve stem 21 side, the outer side 26 of the swirl vane 24 is in shadow. When the intake valve 8 opens toward the combustion chamber 2 during the intake stroke, the combustion air flows in a flash from the valve stem 21 side toward the valve face 23 side on the surface of the umbrella part 22 of the intake valve 8. If any part of the swirl vane 24 is shaded, the flow rate of the intake combustion air may be weakened only in that part. Also, when the intake valve 8 opens toward the combustion chamber 2 during the intake stroke, the combustion air flows toward the combustion chamber at high speed. The high-speed combustion air tends to flow from the area of ​​high pressure to the area of ​​low pressure. In the present invention, focusing on this point, the structure is designed to prevent the air from accumulating on the outer side surface 26 of the swirl vane 24, which is shaded when viewed from the valve stem 21 side of the intake valve 8 to the valve face 23 side. The outer side surface 26 is designed to be in an arc that is concave inward of the swirl vane 24 itself, so that the combustion air that tries to accumulate on the outer side surface of the swirl vane rotates in a state where it is scooped up in the section that is concave inward, and is guided to the area with a high flow rate.

[0029] As described above, according to the intake valve 8 structure of the engine 1 of the first embodiment of the present invention, just before the combustion air flows into the combustion chamber 2 due to the opening operation of the intake valve 8 during the intake stroke, a swirling flow is generated in the combustion air flowing over the surface of the intake valve head portion 22, thereby reducing various losses that occur at that time and improving the filling efficiency of the combustion air flowing into the combustion chamber 2. EXAMPLES

[0030] 5, the structure of the exhaust valve 9 is roughly divided into a collet at the upper end, a rod-shaped valve stem 31, a head portion 32, and a valve face 33 on the outer periphery of the head portion 32. The head portion 32 of the exhaust valve 9 is provided with swirl vanes 34 for the purpose of generating a swirl flow in the exhaust gas that is discharged into the exhaust passage 7 after combustion in the combustion chamber 2 when the exhaust valve 9 opens toward the combustion chamber 2 during the exhaust stroke. The starting point of the swirl vanes 34 is the boundary between the valve stem 31 and the head portion 32, and ends just before the boundary between the head portion 32 and the valve face 33.

[0031] Next, the configuration of the swirl vanes 34 provided on the head portion 32 of the exhaust valve 9, which is a characteristic feature of the present invention, will be described in detail. Figure 6 is a diagram of the exhaust valve 9 viewed from above the valve stem 31, Figure 7 is an explanatory diagram showing one of the swirl vanes 34 provided on the exhaust valve head portion 32, generally taken along the line M-N in Figure 6, and Figure 8 is a cross-sectional view of the swirl vanes 34 provided on the exhaust valve head portion 32, taken along the line J-K in Figure 5.

[0032] As shown in FIG. 9, the exhaust passage 7 is formed in a tubular shape so as to guide the exhaust gas after combustion in the combustion chamber 2 during the expansion stroke to the exhaust passage 7, and the end of the exhaust passage 7 is connected to the combustion chamber exhaust port. An exhaust valve 9 is attached to the combustion chamber exhaust port, and exhaust gas is discharged from the inside of the combustion chamber 2 to the exhaust passage 7 by opening and closing the exhaust valve 9. As shown in FIG. 6, a plurality of swirl vanes 34 (three in FIG. 2) are provided at regular intervals on the umbrella portion 32 of the exhaust valve 9. As shown in FIG. 5 to FIG. 8, each swirl vane 34 is bent in the swirl direction R to form a spiral shape so that the exhaust gas flowing on the surface of the exhaust valve umbrella portion 32 in the direction of arrow F rotates in the R direction along the surface of the exhaust valve umbrella portion 32.

[0033] As shown in Figures 5 to 7, the swirl vane 34 is formed in a twisted vane shape. The swirl vane 34 is formed so that the height from the exhaust valve head 32 to the tip 38 gradually increases from the boundary between the valve stem 31 of the exhaust valve 9 and the exhaust valve head 32, which is the starting point of the swirl vane 34, to the midpoint S of the shortest straight line distance between the valve stem 31 and the valve face 33 on the exhaust valve head 32. The height from the exhaust valve head 32 to the tip 38 is set to a peak point 37 where the height of the tip 38 of the swirl vane is maximum at the midpoint S of the shortest straight line distance between the valve stem 31 and the valve face 33 on the exhaust valve head 32. In the exhaust valve head portion 32, the height of the swirl vanes 34 from the exhaust valve head portion 32 to the tip portion 38 is maximum at the midpoint S of the shortest straight-line distance between the valve stem 31 and the valve face 33, and the height gradually decreases as it approaches the end point, that is, just before the boundary between the head portion 32 of the exhaust valve 9 and the valve face 33, from the midpoint S of the shortest straight-line distance between the valve stem 31 and the valve face 33.

[0034] The swirl vane 34 is provided such that the twist angle α of the exhaust valve 9 gradually increases from the boundary between the valve stem 31 and the exhaust valve head 32 of the exhaust valve 9, which is the start point of the swirl vane, to the boundary between the head 32 and the valve face 33 of the exhaust valve 9, which is the end point of the swirl vane. The inner side surface 35 of the swirl vane 34 is gently inclined from the tip 38 to the inner base point 39 of the swirl vane 34, and the inner side surface 35 is provided so as to form an arc recessed inwardly of the swirl vane 34 itself. On the other hand, the outer side surface 36 of the swirl vane 34 is gently inclined from the tip 38 to the outer base point 40 of the swirl vane 34, and the outer side surface 36 is provided so as to form an arc recessed inwardly of the swirl vane 34 itself.

[0035] Next, the operation and effect of the exhaust valve 9 configured as above will be described.

[0036] Usually, the effect of a high expansion ratio can also be obtained by increasing compression. However, increasing compression in a gasoline engine causes the problem of knocking. Knocking is caused by the high temperature in the combustion chamber 2 during compression. Scavenging is effective in solving this temperature problem. By sufficiently discharging the hot exhaust gas after combustion into the exhaust passage 7, the temperature before compression can be lowered, and it is possible to suppress the temperature rise during compression. Even in Miller cycle engines, which suppress the effective value of the compression ratio by reducing the amount of combustion air taken in, improving the scavenging effect makes it possible to achieve high efficiency without sacrificing output.

[0037] In a series of strokes of a four-stroke cycle engine, the exhaust gas discharged from the combustion chamber 2 by the opening and closing of the exhaust valve 9 in the exhaust stroke is guided to the exhaust passage 7 along the surface of the head portion 32, which is the upper surface of the exhaust valve 9. When the exhaust valve 9 opens toward the combustion chamber 2, the exhaust gas coming into contact with the exhaust valve head portion 32 from the combustion chamber 2 comes into contact with the outer side surface 36 of the swirling vane 34 provided on the exhaust valve head portion 32, and the exhaust gas flows along the outer side surface 36 of the swirling vane 34 provided in a spiral shape. As a result, the exhaust gas is given a flow component in the circumferential direction R, and gradually begins to swirl in the circumferential direction R. Then, the exhaust gas flows into the exhaust passage 7 while maintaining the swirling flow. In a normal engine 1, the exhaust gas that flows into the exhaust passage 7 when the exhaust valve 9 opens in the exhaust stroke is not in a rectified state. When the exhaust valve 9 opens and the exhaust gas flows into the exhaust passage 7, which is much narrower than the combustion chamber 2, the exhaust gas violently collides with each other, making it difficult to be discharged, thereby reducing the scavenging effect. However, as in the second embodiment of the present invention, a swirling flow is imparted to the surface of the exhaust valve head 32 just before the exhaust valve 9 opens and the air flows into the exhaust passage 7, forming a vortex that flows from the combustion chamber 2 into the exhaust passage 7, thereby improving the scavenging effect.

[0038] By configuring the swirl vanes 34 as described above, it is possible to effectively generate a swirl flow. That is, when the exhaust valve 9 opens toward the combustion chamber 2 during the exhaust stroke, the exhaust gas is pushed by the rising of the piston 3 and starts to be discharged from the combustion chamber 2 to the exhaust passage 7 at a high flow rate. Even though the swirl vanes 34 are used, they must not obstruct the exhaust gas discharged into the exhaust passage 7 at this high flow rate. In the exhaust valve 9 of the present invention, the height of the tip 38 of the swirl vanes 34 is maximized at the midpoint S of the shortest straight line distance between the valve stem 32 of the exhaust valve 9 and the exhaust valve head 32, which is the midpoint between the valve stem 31 and the valve face 33. In the umbrella portion 32 of the exhaust valve 9, the exhaust gas is discharged into the exhaust passage 7 at a high flow rate and in a turbulent state, and a swirl flow is generated from the exhaust gas in the boundary layer on the surface of the umbrella portion 32 of the exhaust valve 9 near the boundary between the umbrella portion 32 of the exhaust valve 9 and the valve face 33 where the exhaust gas first inoculates the umbrella portion 32. The swirl vanes 34, whose height from the exhaust valve umbrella portion 32 to the tip 38 is maximum at the intermediate position S of the shortest straight line distance between the valve stem 31 and the valve face 33 so as not to interfere with the opening and closing of the exhaust valve 9 near the valve face 33 of the exhaust valve 9, are formed so as to gradually become lower as they approach the boundary between the umbrella portion 32 of the exhaust valve 9 and the valve face 33, which is the end point, from the intermediate position S of the shortest straight line distance between the valve stem 31 and the valve face 33, and the swirl vanes 34 end at the boundary between the umbrella portion 32 of the exhaust valve 9 and the valve face 33, and their height is zero. In order to increase the amount of exhaust gas discharged from the combustion chamber 2 to the exhaust passage 7, the area near the valve face 33 at the end of the exhaust valve 9 must be made wide so that the opening becomes 360 degrees wider when the exhaust valve 9 opens. This avoids interfering with the opening and closing action of the exhaust valve during the exhaust stroke, which is one of the series of processes in a four-stroke engine.

[0039] In order to grow the swirling vortex generated by the swirling vanes 34 provided on the head portion 32 of the exhaust valve 9 and guide it to the exhaust gas itself so that it spreads throughout the exhaust gas, the twist angle α of the swirling vanes 34 of the exhaust valve 9 is set to gradually increase from the boundary between the valve stem 31 and the head portion 32 of the exhaust valve 9, which is the starting point of the swirling vanes 34, to just before the boundary between the head portion 32 and the valve face 33 of the exhaust valve 9, which is the end point, so that the exhaust gas passing over the upper part of the exhaust valve head portion 32 can come into contact with any part of the swirling vanes 34 as much as possible, thereby guiding the swirling vortex generated on the surface of the swirling vanes 34 to the entire exhaust gas. In addition, since most of the exhaust gas itself flows into the exhaust passage 7 near the boundary between the valve stem 31 and the head portion 22 of the exhaust valve 9, which is the starting point of the swirling vanes 34, the twist angle α of the swirling vanes becomes smaller toward the starting point of the swirling vanes 34.

[0040] When the exhaust valve 9 opens during the exhaust stroke and exhaust gas is discharged from the combustion chamber 2 to the exhaust passage 7, the exhaust gas flows from the combustion chamber 2 to the exhaust valve head 32 with great force from all directions of 360 degrees. At this time, the exhaust gases collide violently from the exhaust valve head 32 to the valve stem 31, resulting in a large loss in the flow rate of the exhaust gas. The loss in flow rate reduces the exhaust efficiency and does not improve the scavenging effect. In general, in order to efficiently flow a fluid from a wide area to a narrow area, it is more efficient to form a vortex in the flowing fluid itself. Even if the exhaust gas flows from the combustion chamber 2 to the exhaust valve head 32 from all directions of 360 degrees, the flow rate and pressure of the exhaust gas in all directions of 360 degrees are never uniform and are in a turbulent state. If the exhaust gas itself, which is in a turbulent state at the exhaust valve head 32, is brought into a state in which it is easy to form a vortex, the exhaust gases collide with each other, and the loss in the flow rate of the exhaust gas can be reduced. In the present invention, by providing swirl vanes 34 that generate a swirling flow from the exhaust gas in the boundary layer on the surface of the exhaust valve head 32 near the boundary between the exhaust valve 9, which first comes into contact with the exhaust valve head 32, and the valve face 33, the swirl vanes 34 of the exhaust valve head 32 generate a swirling flow in the exhaust gas itself flowing over the surface of the head 32 before the exhaust valve 9 opens during the exhaust stroke and the exhaust gases collide with each other, bringing the exhaust gases into a state where they are likely to form vortices and causing the exhaust gases to collide with each other, reducing the loss of exhaust gas flow velocity and allowing the exhaust gas to be discharged smoothly into the exhaust passage 7. Reducing the loss of exhaust gas flow velocity during the exhaust stroke improves the scavenging effect, reduces the load on the exhaust stroke, and leads to improved engine output.

[0041] Furthermore, in order to scoop up the exhaust gas flowing from the valve face 33 side toward the valve stem 31 side on the surface of the head portion 32 of the exhaust valve 9, the swirl vane 34 smoothly creates a swirling vortex, with the outer side 36 of the swirl vane 34 gently inclined from the tip 38 position to the outer base point 40 of the swirl vane, and the outer side 36 is arranged in an arc that is concave inward of the swirl vane 34 itself. When the exhaust valve 9 opens toward the combustion chamber 2 during the exhaust stroke, the location where the flow speed of the exhaust gas discharged from the combustion chamber 2 is fastest is near the center of the section between the valve face 33 at the end of the exhaust valve 9 and the exhaust passage 7, where the flow speed is the fastest and is least affected by the wall of the exhaust passage 7 and the exhaust valve 9. By forming the outer side surface 36 of the swirl vane 34 in an arc concave toward the inside of the swirl vane 34 itself, when the exhaust valve 9 opens toward the combustion chamber 2 during the exhaust stroke, exhaust gas flows at high speed from the valve face 33 side toward the valve stem 31 side on the surface of the umbrella part 32 of the exhaust valve 9. The exhaust gas flowing on the surface of the umbrella part 32 of the exhaust valve 9 enters the arc section of the outer side surface 36 of the swirl vane 34, where the exhaust gas rotates as if scooped up, and is accelerated and guided toward the center of the flow velocity where the flow velocity is high. If the swirling vortexes generated in the arc section of the outer side surface 36 of the swirl vane 34 become large and strong, they will spread to the entire exhaust gas discharged from the combustion chamber to the exhaust passage 7, forming large and strong vortices in the entire exhaust gas with the umbrella part 32 of the exhaust valve 9 as the base point, and the exhaust gas flowing into the exhaust passage 7 can be smoothly flowed at a high flow velocity, improving the scavenging effect.

[0042] On the other hand, the inner side 35 of the swirl vane 34 is gently inclined from the tip 38 to the inner base point 39 of the swirl vane 34, similar to the outer side 36, and the inner side 36 is provided so as to form an arc concave inward of the swirl vane 34 itself. The difference from the outer side 36 is that the swirl vane 34 itself is in the shadow, so that no blind spot is created in the umbrella part 32 where exhaust gas stagnates. The emphasis is placed on ensuring that exhaust gas does not stagnate on the inner side 35 of the swirl vane 34 of the umbrella part 32 of the exhaust valve 9. In the exhaust valve 9, when viewed from the exhaust gas discharged into the exhaust passage 7, the inner side 35 of the swirl vane 34 is in the shadow when viewed from the valve face 33 side of the exhaust valve 9 to the valve stem 31 side, which is the opposite to the intake valve 8 of the first embodiment. When the exhaust valve 9 opens toward the combustion chamber 2 during the exhaust stroke, the exhaust gas flows from the valve face 33 side toward the valve stem 31 side at once on the surface of the head portion 32 of the exhaust valve 9. If there is a portion where the gas is stagnant on any of the swirl vanes 34, the flow rate of the exhaust gas exhausted from that portion may be weakened. Also, when the exhaust valve 9 opens toward the combustion chamber 2 during the exhaust stroke, the exhaust gas flows toward the exhaust passage 7 at high speed. High-speed exhaust gas tends to flow from an area of ​​high pressure to an area of ​​low pressure. This is the focus of the present invention. The exhaust valve 9 is designed to prevent exhaust gas from stagnating on the inner side surface 35 of the swirl vanes, which is in shadow when looking from the valve face 33 side of the exhaust valve 9 toward the valve stem 31 side. The inner side 35 is structured to form an arc that concaves inward of the swirl vane 34 itself, so that exhaust gas that tends to accumulate on the inner side 35 of the swirl vane 34 is rotated in such a way that it is scooped up in the section that concaves inward and is guided to an area with a high flow rate.

[0043] Therefore, according to the structure of the exhaust valve 9 of the engine 1 of the second embodiment of the present invention, when the exhaust valve 9 opens during the exhaust stroke and causes exhaust gas to flow from the combustion chamber 2 into the exhaust passage 7, a swirling flow is generated in the exhaust gas flowing over the surface of the exhaust valve head portion 32, thereby reducing various losses that occur at that time. This reduces the loss in flow velocity when the exhaust gas flows from the combustion chamber 2 into the exhaust passage 7 and improves scavenging efficiency.

[0044] Therefore, with the structure of the exhaust valve 9 of the engine 1 of the second embodiment, the same effects and advantages as those of the first embodiment described above can be obtained. By generating a swirling flow in the exhaust gas when it flows from the combustion chamber 2 into the exhaust passage 7 due to the opening operation of the exhaust valve 9, various losses that occur at that time can be reduced, and the efficiency of the scavenging effect of the combustion chamber 2 can be improved.

[0045] The structure of the intake valve 8 and the structure of the exhaust valve 9 of the engine 1 of the present invention are not limited to the above-mentioned embodiment 1 and embodiment 2, and may be modified within the scope of the claims. For example, the following configuration may be adopted.

[0046] The number of swirl vanes 34 to be attached can be changed as appropriate, and may be designed to obtain an optimal flow (swirl flow) depending on the type of engine 1, the inner diameter of the intake passage 6 and exhaust passage 7, the shape and size of the intake valve 8 and exhaust valve 9, the shape of the combustion chamber, the swirl flow strength, etc. [Industrial Applicability]

[0047] The present invention is utilized in the industry of manufacturing automobiles equipped with gasoline and diesel engines. [Explanation of symbols]

[0048] 1. Engine 2. Combustion chamber 3. Piston 6. Intake passage 7. Exhaust passage 8. Intake valve 9. Exhaust valve 10. Cam 11. Lifter 12. Valve spring 13. Upper retainer 14. Lower retainer 15. Valve guide 21. Intake valve stem 22. Umbrella 23. Intake valve face 24. Swirling vane 25. Inner side of swirl vane 26. Outer side of swirl vane 27. Swirl vane peak point 28. Swirl vane tip 29. Inner side base point of swirl vane 30. Outer side base point of swirl vane 31. Exhaust valve stem 32. Umbrella 33. Exhaust valve face 34. Swirl vane 35. Inner side of swirl vane 36. Outer side of swirl vane 37. Swirl vane peak point 38. Swirl vane tip 39. Inner side base point of swirl vane 40. Outer side base point of swirl vane R. Swirling direction F. Flow direction

Claims

1. 1. An intake valve which is provided at a combustion chamber inlet which is the end of a tubular intake passage which guides combustion air or a mixture of combustion air and fuel to be drawn into a combustion chamber from the intake passage to the combustion chamber, and which opens and closes by driving a cam, characterized in that: a boundary between the valve stem of the intake valve and the intake valve head portion which is at the center of the intake valve head portion of the intake valve and a boundary between the intake valve head portion and the valve face of the intake valve are set as a starting point, and swirling vanes are provided at a plurality of points on the intake valve head portion in a spiral shape from a starting point on the valve stem side to an end point on the valve face side, and the combustion air or the mixture of combustion air and fuel drawn into the combustion chamber is caused to flow into the combustion chamber while being swirled by the swirling vanes provided on the intake valve head portion.

2. 2. The engine valve structure as described in claim 1, characterized in that the height of the tip of the swirl vane provided on the intake valve head portion is gradually increased from a position which is the starting point of the swirl vane on the valve stem side toward the intake valve face, the height of the tip of the swirl vane reaching a peak point at a position on the intake valve head portion which is the shortest straight-line distance between the valve stem and the valve face, and the height of the tip of the swirl vane gradually decreasing from the peak point of the swirl vane toward the end point of the swirl vane on the valve face side.

3. 2. The engine valve structure according to claim 1, wherein the swirl vanes are arranged so that a twist angle α of the swirl vanes of the intake valve head portion gradually increases from the valve stem side, which is the starting point of the swirl vanes, to the valve face side, which is the end point of the swirl vanes.

4. 2. The engine valve structure as described in claim 1, characterized in that the cross-sectional shape of the swirl vane provided on the intake valve head portion is gradually wider and gently inclined as it approaches the surface of the intake valve head portion from the tip of the swirl vane, and the swirl vane has inner and outer sides formed so as to form an arc that is concave inward of the swirl vane itself.

5. 1. An exhaust valve in which the valve is opened and closed by driving a cam provided at a combustion chamber exhaust port which is an end of a tubular exhaust passage which guides exhaust gas after combustion in the combustion chamber from the combustion chamber to an exhaust passage, the exhaust valve having a valve opening and closing mechanism, the exhaust valve having a valve opening and closing mechanism, the exhaust valve having a valve opening and closing mechanism, and a valve face having a valve opening and closing mechanism, the exhaust valve having a valve opening and closing mechanism, the exhaust valve having a valve opening and closing mechanism, and a valve face having a valve opening and closing mechanism, the exhaust valve having a valve opening and closing mechanism,

6. 6. An engine valve structure as described in claim 5, characterized in that the height of the tip of the swirl vane provided on the exhaust valve head portion is gradually increased from a position which is the starting point of the swirl vane on the valve stem side to the exhaust valve face side which is the end point of the swirl vane, the height of the tip of the swirl vane reaches its maximum at a peak point at a position midway along the shortest straight-line distance between the valve stem and the valve face on the exhaust valve head portion, and the height of the tip of the swirl vane gradually decreases from the peak point of the swirl vane towards the end point of the swirl vane on the valve face side.

7. 6. An engine valve structure as described in claim 5, characterized in that the swirl vanes are arranged so that a twist angle α of the swirl vanes of the exhaust valve head portion gradually increases from the valve stem side, which is the starting point of the swirl vanes, to the valve face, which is the end point of the swirl vanes.

8. 6. An engine valve structure as described in claim 5, characterized in that the cross-sectional shape of the swirl vane provided on the exhaust valve head portion is gradually wider and gently inclined as it approaches the surface of the exhaust valve head portion from the tip of the swirl vane, and the swirl vane has inner and outer sides formed so as to form an arc that is concave inward of the swirl vane itself.

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