JP2015214924A - Intake valve and intake and exhaust system including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intake valve capable of suppressing degradation in intake air charging efficiency.SOLUTION: In an intake valve 10 including a stem 10a and an umbrella portion 10b and opening or closing an intake opening 7a open to a combustion chamber 6 of an internal combustion engine E, the umbrella portion 10b includes a valve face 10c formed to expose a base material 26b to an outer peripheral portion and abutting on a valve seat 13 defining the intake opening 7a; and an umbrella front surface concave portion 37 formed in at least part of an umbrella front surface 10f closer to the combustion chamber 6 than the valve face 10c by recessing the base material 26b with respect to an adjacent outer peripheral surface 10g or the valve face 10c, and a heat insulating coating layer 25 is formed on a surface of the base material 26b in the umbrella front surface concave portion 37 so as to define a smooth outline. With this configuration, an increase in surface area is suppressed and a heating value input from combustion gas into the umbrella portion 10b is reduced.

Description

  The present invention relates to an intake valve that has a stem and an umbrella and opens and closes an intake opening of a combustion chamber of an internal combustion engine, and an intake / exhaust device including the intake valve.

  As an intake / exhaust valve for an internal combustion engine, a poppet valve having an umbrella portion that is a valve body and a stem that is a shaft body that moves the umbrella portion is generally used so as to withstand high pressure from the combustion chamber side. Yes. The intake / exhaust valve is likely to become high temperature because it receives heat from the combustion surface (also referred to as the head surface or the umbrella surface) on the combustion chamber side exposed to the combustion gas. However, the high temperature of the intake / exhaust valve means the outflow of the thermal energy of the fuel gas, which reduces the thermal efficiency of the internal combustion engine. Under such a background, a heat insulating coating layer formed on the combustion surface of an intake / exhaust valve is known (for example, Patent Document 1).

  In the intake valve, while the combustion surface side is heated by the combustion gas, the umbrella radius surface (also referred to as the umbrella back) opposite to the combustion surface is cooled by the intake air, and between the heat insulating coating layer and the base material. In addition to the temperature difference becoming larger and the heating on the combustion surface side and the cooling on the umbrella round surface side being repeated, the coating layer is likely to crack or peel off due to mechanical stress at the time of valve seating. Therefore, in Patent Document 1, heat insulation coating is also applied to the umbrella round surface and the stem of the intake valve.

Japanese Utility Model Publication No.59-141108

  By the way, the heat transfer amount is obtained by multiplying the heat transfer coefficient, area, time, and temperature difference, and the heat transfer coefficient can be reduced by providing a heat insulating coating layer, but when the area is increased, the heat transfer quantity is increased accordingly. Become. However, in the intake valve described in Patent Document 1, heat insulation coating is simply applied to the surfaces of the umbrella front, back and stem. Therefore, the surface area increases at the edge portion of the heat insulating coating according to the thickness of the heat insulating coating, and the amount of heat input from the combustion gas and the amount of heat released to the intake air increase by the amount corresponding to the amount of increase in the surface area. As a result, the intake air is thermally expanded, and the charging efficiency of the intake air is reduced. Also, the effective opening area of the intake opening decreases by the thickness of the thermal insulation coating on the back of the umbrella, and the stem diameter increases by the thickness of the thermal insulation coating of the stem, and the proportion of the stem area in the cross section of the intake port increases. By doing so, the charging efficiency of the intake air also decreases.

  In view of such a background, it is an object of the present invention to provide an intake valve and an intake / exhaust device including the intake valve that can suppress a decrease in intake charging efficiency.

  In order to solve such a problem, the present invention includes an intake air opening having an opening (7a) of a combustion chamber (6) of an internal combustion engine (E) having a stem (10a) and an umbrella (10b). A valve face (10c), wherein the umbrella portion is formed so as to expose a base material (26b) at an outer peripheral portion, and is in contact with a valve seat (13) defining the intake opening; And at least part of the umbrella surface (10f) closer to the combustion chamber than the valve face, an umbrella surface recess (37) in which a base material is recessed with respect to adjacent portions (10g, 10c), It is set as the structure by which the heat insulation coating layer (25) is formed in the surface of the preform | base_material in the said umbrella surface recessed part so that a smooth outer contour may be defined.

  According to this configuration, the umbrella surface recess is formed in the umbrella surface, and the thermal insulation coating layer is formed so as to define a smooth outer contour in the umbrella surface recess, thereby suppressing an increase in surface area. A heat insulating coating layer can be formed. As a result, the amount of heat input from the combustion gas to the umbrella portion can be reduced, the amount of heat released from the intake valve to the intake air can be reduced, and a decrease in intake charging efficiency can be suppressed.

  In the above invention, the stem is disposed on the side of the umbrella portion (10b) with respect to the sliding shaft portion (31) guided by the valve guide (12) so as to slide. The cross-sectional area of the base material can be configured to have a thin shaft portion (32) smaller than the sliding shaft portion.

  According to this configuration, the amount of heat transmitted from the umbrella portion to the sliding shaft portion by heat conduction is reduced, and the umbrella surface can be kept at a high temperature, so the amount of heat input from the combustion gas to the umbrella portion is reduced. In addition, the amount of heat released from the intake valve to the intake air can be reduced, and a decrease in intake charging efficiency can be suppressed. In particular, the amount of heat released from the intake valve to the intake air is greatly reduced by the synergistic effect of the heat insulating coating layer and the thin shaft portion in the concave portion of the umbrella.

  In the above invention, the umbrella portion (10b) is at least part of the back of the umbrella (10e) closer to the stem (10a) than the valve face (10c) with respect to the adjacent portion (10c). A heat insulating coating layer (25) is formed on the surface of the base material (26b) in the umbrella back recess so as to have an umbrella back recess (36) in which the base material is recessed and to define a smooth outer contour. It can be set as a structure.

  According to this configuration, the umbrella back recess is formed on the back of the umbrella, and the thermal insulation coating layer is formed so as to define a smooth outer contour in the umbrella back recess, thereby suppressing an increase in surface area. A heat insulating coating layer can be formed. Thereby, since the amount of heat radiation from the umbrella part to the intake air can be reduced and the umbrella table can be kept at a high temperature, the amount of heat input from the combustion gas to the umbrella part can also be reduced, and a decrease in intake charging efficiency can be suppressed.

  Moreover, in said invention, it can be set as the structure by which the heat insulation coating layer (25) is formed in the surface of the base material (26a) of the said thin shaft part (32) so that a smooth outer contour may be defined. .

  According to this configuration, since the heat insulating coating layer is formed so as to define a smooth outer contour in the thin shaft portion, it takes time for the heat to reach the surface of the stem in the thin shaft portion. The change in the amount of heat becomes slow, and a sudden rise in intake air temperature due to a temporary increase in engine speed or load can be suppressed. It is also possible to reduce the amount of heat released from the stem to the intake air.

  In the above invention, the base material (26a) of the thin shaft portion (32) exhibits a circular cross-sectional shape having a diameter (D) smaller than the diameter (D1) of the sliding shaft portion (31). The heat insulating coating layer (25) is disposed on the same axis as the sliding shaft portion, and has a substantially uniform thickness (t1) over the entire circumference of the base material of the thin shaft portion, and the stem (10a) in the thin shaft portion is formed. ) Has a diameter (D2) equal to or smaller than the diameter of the sliding shaft portion (D2 ≦ D1).

  According to this configuration, it is possible to prevent an increase in the stem diameter in the thin shaft portion in comparison with the sliding shaft portion, thereby reducing the effective charging area and reducing the intake charging efficiency due to the increase in the area occupied by the stem in the intake port section. Can be suppressed. Further, even when the thin shaft portion is configured to enter the inside of the valve guide when the valve is closed, the heat insulating coating layer can be prevented from interfering with the valve guide.

  Moreover, in said invention, the said thin shaft part (32) and the said heat insulation coating layer (25) are rather than the edge part (12a) by the side of the said umbrella part (10b) of the said valve guide (12) at the time of valve closing. It can be set as the structure currently formed in the said umbrella part side.

  According to this configuration, even when the intake valve is closed, the thin shaft portion does not enter the inside of the valve guide, thereby preventing the heat insulating coating layer formed on the outer peripheral surface of the thin shaft portion from interfering with the valve guide. it can.

  In the above invention, the thin shaft portion (32) and the umbrella back recess (36) are formed to be continuous with each other, and the heat insulating coating layer (25) is continuous from the umbrella back recess to the thin shaft portion. It can be set as the structure formed.

  According to this configuration, it is possible to more effectively suppress a sudden rise in intake air temperature due to a temporary increase in engine speed or load.

  In order to solve the above problems, the present invention provides the intake valve (10), the intake valve guide (12) for slidably supporting the stem (10a) of the intake valve, and the stem (11a). ) And an umbrella portion (11b), and an exhaust valve (11) for opening and closing the exhaust opening (8a) of the combustion chamber (6) of the internal combustion engine (E), and the stem of the exhaust valve being slidable An intake / exhaust device (16) having an exhaust valve guide (12) to be supported, wherein the intake valve guide and the exhaust valve guide are made of a common member.

  According to this configuration, since the intake valve guide and the exhaust valve guide are made of a common member while suppressing a decrease in the intake charging efficiency, the component cost can be reduced. Further, since it is not necessary to distinguish between the intake valve guide and the exhaust valve guide, the assembly work is facilitated and the assembly cost can be reduced.

  Thus, according to the present invention, it is possible to provide an intake valve and an intake / exhaust device including the intake valve that can suppress a reduction in intake charging efficiency.

Sectional drawing of the principal part of the internal combustion engine which concerns on embodiment Front view of the intake valve shown in FIG. FIG. 2 is a cross-sectional view of the main part of the intake valve shown in FIG. The graph for demonstrating the effect of the intake valve which concerns on embodiment The graph for demonstrating the effect of the intake valve which concerns on embodiment Sectional drawing of the principal part of the intake valve which concerns on other embodiment Sectional drawing of the principal part of the intake valve which concerns on other embodiment

  Hereinafter, an embodiment in which an intake valve 10 and an intake / exhaust device 16 according to the present invention are applied to an internal combustion engine E for an automobile will be described in detail with reference to the drawings. Below, it demonstrates according to the up-down direction shown in FIG. 1 on the basis of the state in which the internal combustion engine E was mounted in the motor vehicle.

  As shown in FIG. 1, the internal combustion engine E is an in-line multi-cylinder automobile gasoline engine, and includes a cylinder block 2 having a plurality of cylinders 1 in which pistons (not shown) are accommodated, and an upper end surface 2 a of the cylinder block 2. A cylinder head 3 fastened to the cylinder block 2 with a lower end surface 3 a to be joined and a head cover 4 fastened to the upper part of the cylinder head 3 are provided.

  The cylinders 1 are formed in the cylinder block 2 so as to extend substantially in the vertical direction and to be parallel to each other and in a row. Hereinafter, the arrangement direction of the plurality of cylinders 1 arranged in a row is referred to as a cylinder row direction. Each cylinder 1 has an upper end opened to the upper end surface 2 a of the cylinder block 2, and a lower end opened to a crank chamber (not shown) formed in the lower part of the cylinder block 2. A block cooling water passage (water jacket) 5 is formed on the side of the cylinder 1 of the cylinder block 2 so as to integrally surround the side periphery of each cylinder 1. A portion extending in the cylinder row direction of the block cooling water passage 5 is curved so as to follow the side peripheral portion of each cylinder 1, and the upper end of the block cooling water passage 5 is opened to the upper end surface 2 a of the cylinder block 2. doing.

  A combustion chamber recess 3b, which is a curved depression, is formed in a portion of the lower end surface 3a of the cylinder head 3 that faces each cylinder 1. Each combustion chamber recess 3 b defines a combustion chamber 6 together with a portion above the piston of each cylinder 1. Further, inside the cylinder head 3, one end is opened on one side surface along the cylinder row direction, while two other ends branched into two branches are connected to each combustion chamber recess 3 b, and one end is An exhaust port 8 is formed which opens to the other side surface along the cylinder row direction of the cylinder head 3 and has two branched other ends connected to the respective combustion chamber recesses 3b. The side on which the intake port 7 is provided with reference to the combustion chamber recess 3b is the intake side, and the side on which the exhaust port 8 is provided is the exhaust side. The cylinder head 3 is formed with an ignition plug insertion hole (not shown) so as to open on the wall surface of the combustion chamber recess 3b and the upper surface of the cylinder head 3, and the ignition plug is inserted into the ignition plug insertion hole.

  Inside the cylinder head 3, a head cooling water passage 9 (in the vicinity of the combustion chamber recess 3 b and the exhaust port 8 is provided in order to suppress a temperature rise due to heat propagation from the combustion gas in the combustion chamber 6 and the exhaust port 8. 9a, 9b, 9c, 9d). The head cooling water passage 9 sandwiches the main cooling water passage 9a extending in the cylinder row direction (longitudinal direction) of the cylinder head 3 and the exhaust port 8 from above and below so as to pass near the upper part of the plurality of combustion chamber recesses 3b. Upper exhaust side cooling water passage 9b and lower exhaust side cooling water passage 9c, main cooling water passage 9a, upper exhaust side cooling water passage 9b and lower exhaust side, which are arranged so as to extend in the longitudinal direction of cylinder head 3, respectively. An unillustrated exhaust side connecting passage communicating with the cooling water passage 9c, an intake side cooling water passage 9d extending in the cylinder row direction of the cylinder head 3, and the main cooling water passage 9a and the intake side It has an unillustrated intake side connecting passage that communicates with the cooling water passage 9d.

  The cylinder head 3 is provided with an intake valve 10 and an exhaust valve 11 that open and close the intake openings 7a and the exhaust openings 8a. The cylinder head 3 is fitted with cylindrical valve guides 12 and 12 in two holes formed so as to communicate with the intake port 7 and the exhaust port 8 from the upper surface. An intake opening 7 a and an exhaust opening 8 a that open toward the combustion chamber 6 are defined by annular valve seats 13 and 13 at a connection portion between the combustion chamber recess 8 and the combustion chamber recess 3 b. The intake valve 10 and the exhaust valve 11 are slidably supported by valve guides 12 and 12, respectively, and rod-like stems 10a and 11a disposed across the intake port 7 and the exhaust port 8, and the stems 10a and 11a. It is a poppet valve which is formed integrally with the lower end of the valve and has umbrella portions 10b and 11b which are valve bodies seated on the valve seats 13 and 13. Frustum-shaped valve faces 10c and 11c (seal surfaces) that come into contact with the valve seats 13 and 13 are formed on the outer peripheral portions of the umbrella portions 10b and 11b.

  Disc-shaped retainers 14 and 14 are fixed near the upper ends of the intake valve 10 and the exhaust valve 11, and a compression coil spring 15 is interposed between each retainer 14 and the upper surface of the cylinder head 3. . As a result, the intake valve 10 and the exhaust valve 11 are always urged upward (the valve closing direction), the umbrella portions 10b and 11b are seated on the valve seats 13 and 13, and the intake opening 7a and the exhaust opening 8a are closed. The valve guide 12, the retainer 14, and the compression coil spring 15 provided for the intake valve 10 and the exhaust valve 11 are common members. The intake port 7, the exhaust port 8, the intake valve 10, the exhaust valve 11, the valve guides 12 and 12, the valve seats 13 and 13, the retainers 14 and 14, and the compression coil springs 15 and 15, An intake / exhaust device 16 capable of exhausting from the combustion chamber 6 is configured.

  A valve operating chamber 17 defined between the cylinder head 3 and the head cover 4 accommodates a valve operating mechanism 18 that opens and drives the intake valve 10 and the exhaust valve 11. The valve mechanism 18 has a known configuration including a camshaft 19 and a rocker shaft 20 supported by the cylinder head 3, an intake rocker arm 21 and an exhaust rocker arm 22 that are swingably supported by the rocker shaft 20. Yes. The intake rocker arm 21 and the exhaust rocker arm 22 each have one end that contacts the cam and the other end that contacts the stem ends of the intake valve 10 and the exhaust valve 11.

  When the camshaft 19 is rotationally driven at a rotational speed half that of the crankshaft via a power transmission mechanism (not shown), the intake rocker arm 21 and the exhaust rocker arm 22 that are in contact with the cam via a roller are respectively moved at predetermined timings. Swing. As a result, the intake valve 10 and the exhaust valve 11 are driven downward (opening direction) against the biasing force of the compression coil spring 15, and the umbrella portions 10b and 11b are separated from the valve seats 13 and 13, thereby The opening 7 a and the exhaust opening 8 a are opened, and the intake port 7 and the exhaust port 8 communicate with the combustion chamber 6.

  Next, the intake valve 10 will be described in detail with reference to FIGS. 2 and 3. As described above, the intake valve 10 includes the stem 10a and the umbrella portion 10b. In this specification, the umbrella portion 10b is a portion below the change start point (change point P) of the cross-sectional shape that continuously expands from the upper side (the stem 10a side) downward until reaching the valve face 10c. And the stem 10a refers to all the portions above the change point P (above the umbrella portion 10b). That is, the change point P becomes a boundary between the stem 10a and the umbrella portion 10b.

  The stem 10a is slidably supported by the valve guide 12 as described above. 2 and 3, the valve guide 12 when the intake valve 10 is in the closed position is indicated by an imaginary line. An annular groove 10d is formed in the vicinity of the upper end of the stem 10a, and a cotter (not shown) divided into two is fitted into the annular groove 10d. The aforementioned retainer 14 is fixed in the vicinity of the upper end of the stem 10a through a cotter. On the other hand, on the surface of the stem 10a below the valve guide 12 (below the lower end 12a of the valve guide 12 when in the closed position) and the surface of the umbrella portion 10b, a heat insulating coating is formed on the entire surface excluding the annular valve face 10c. Layer 25 is formed.

  In the present embodiment, the base material 26 (portion excluding the heat insulating coating layer 25) of the intake valve 10 composed of the base material 26a of the stem 10a and the base material 26b of the umbrella portion 10b has a thermal conductivity of 30 W / m · K. It is made of solid stainless steel. The base material 26 is not limited to a form formed only of stainless steel. For example, the surface of the stainless steel is subjected to surface treatment such as chromium plating or nitriding in order to improve wear resistance in the sliding shaft portion 31. It may be what you did. The exhaust valve 11 may also be formed of heat resistant stainless steel, like the intake valve 10.

On the other hand, the heat insulating coating layer 25 is formed of a material having a lower thermal conductivity than the base material 26. In this embodiment, zirconia (ZrO ₂ ) -based ceramics having a thermal conductivity of about 1.5 W / m · K is used as the heat insulating coating layer 25. The heat insulation coating layer 25 can be formed using techniques such as gas flame or arc spraying, plasma spraying, explosion spraying, sputtering, ion plating and the like.

  The cylinder block 2 and the cylinder head 3 are formed of an aluminum alloy, and the valve guide 12 is formed of a sintered material having excellent lubricity including graphite.

  The base material 26a of the stem 10a is formed in a circular cross-sectional shape, and is slidably guided by the valve guide 12 so as to slide (a portion surrounded by the valve guide 12 shown in FIG. A portion having a length corresponding to the continuous valve lift amount) and a cross-sectional area smaller than the cross-sectional area of the sliding shaft portion 31 on the umbrella portion 10b side than the sliding shaft portion 31 (the cross-sectional view is omitted, the diameter in FIG. 3) D)), and a thin shaft portion 32. In the present embodiment, the thin shaft portion 32 is formed in a circular cross-sectional shape having a smaller diameter than the sliding shaft portion 31 and is arranged coaxially with the sliding shaft portion 31, and an upper end portion connected to the sliding shaft portion 31. Then, the cross-sectional area of the sliding shaft portion 31 is formed so as to be oblique (tapered) in cross section with respect to the outer contour of the stem 10a so that the cross-sectional area of the sliding shaft portion 31 gradually decreases as it proceeds downward. The portion above the slide shaft portion 31 (see FIG. 2) in the stem 10a is not guided by the valve guide 12 and slides except the portion where the annular groove 10d is formed and the chamfered portion at the upper end. The general shaft portion 33 has the same diameter as the shaft portion 31.

  The thin shaft portion 32 is formed so as to reach the umbrella portion 10b from a position corresponding to the lower end 12a of the valve guide 12 when the intake valve 10 is in the valve closing position. That is, the thin shaft portion 32 is connected to the lower end (end portion on the umbrella portion 10b side) of the sliding shaft portion 31 and the upper end of the umbrella portion 10b, and between the sliding shaft portion 31 and the thin shaft portion 32 and the sliding portion. The general shaft portion 33 is not formed between the moving shaft portion 31 and the umbrella portion 10b. In other words, the thin shaft portion 32 configured in this manner is such that a recess in which the base material 26a is recessed all around the stem 10a with respect to the adjacent slide shaft portion 31 reaches the lower end of the stem 10a. It is formed by being formed.

  In the stem 10a, the heat insulating coating layer 25 is formed over the entire circumference and the entire length of the thin shaft portion 32 (that is, over the entire concave portion) with a substantially constant thickness. The thickness t1 of the heat insulating coating layer 25 formed on the outer peripheral surface of the thin shaft portion 32 is such that the diameter D2 of the stem 10a in the thin shaft portion 32 (the diameter D + 2t1 of the thin shaft portion 32) is the diameter D1 of the sliding shaft portion 31. It is set to be as follows (D2 = D + 2t1 ≦ D1). As described above, the heat insulating coating layer 25 is formed only on the surface of the thin shaft portion 32 (only the concave portion) of the stem 10a, so that the heat insulating coating layer 25 is not formed on the thin shaft portion 32. The outer contour is smooth. In the present embodiment, the diameter D2 of the stem 10a in the thin shaft portion 32 and the diameter D1 of the sliding shaft portion 31 are the same (D2 = D1), and the outer contour of the stem 10a is further smoothed.

  When the diameter D2 of the stem 10a in the portion where the heat insulating coating layer 25 is formed is the same as or close to the diameter D1 of the sliding shaft portion 31 as in this embodiment, the insertion allowance of the valve guide 12 with respect to the cylinder head 3 If there are variations in the valve length, the distance between the valve seat 23 and the valve guide 12, etc., the heat insulating coating layer 25 may interfere with the valve guide 12 when the valve is closed. The position of the heat insulating coating layer 25 and the position of the thin shaft portion 32 may be set so that the upper end of the heat insulating coating layer 25 is slightly below the lower end 12a.

  In this case, when the valve is closed, a portion of the stem 10a where the base material 26 that is not covered with the heat insulating coating layer 25 is exposed is formed below the valve guide 12, and this portion may be exposed to the intake air. Even when such a portion does not occur, the sliding shaft portion 31 that is not covered with the heat insulating coating layer 25 is exposed to the intake air when the valve is opened. However, since the temperature of such a portion is lower than the temperature in the vicinity of the lower end of the umbrella portion 10b or the stem 10a, the amount of heat transferred to the intake air is very small, and its influence is small.

  On the other hand, the upper end position of the heat insulation coating layer 25 is set below the lower end 12a of the valve guide 12 when the valve is closed, and the diameter D2 of the stem 10a in the thin shaft portion 32 is the diameter D1 of the sliding shaft portion 31. By setting the thickness t1 of the heat insulating coating layer 25 so as to be smaller than that, high accuracy is not required for manufacturing and assembling of the intake valve 10, so that the effect is great in terms of cost and work efficiency.

  As described above, the umbrella portion 10b includes the valve face 10c that exposes the base material 26b, the umbrella back 10e on the stem 10a side with respect to the valve face 10c, and the umbrella surface 10f on the combustion chamber 6 side with respect to the valve face 10c. Is done. The outer contour of the umbrella back 10e has a trumpet shape in which the cross-sectional shape continuously expands from the top to the bottom. On the other hand, the outer contour of the umbrella face 10f is constituted by a substantially cylindrical outer peripheral surface 10g extending downward from the outer edge of the valve face 10c and a bottom surface 10h generally facing the combustion chamber 6. The bottom surface 10h is a truncated cone-shaped convex surface portion 10i bulging toward the combustion chamber 6 from the lower edge of the outer peripheral surface 10g toward the center, and is substantially orthogonal to the axis of the stem 10a from the inner edge of the convex surface portion 10i toward the center. It is composed of a donut-shaped flat surface portion 10j extending in the direction and a curved concave surface portion 10k that gradually becomes deeper from the inner edge of the flat surface portion 10j toward the center, thereby ensuring strength and weight reduction of the umbrella portion 10b. It has been.

  The base material 26b of the umbrella portion 10b includes a concave wall surface 26c that is recessed obliquely (tapered) from the inner edge (upper edge) of the valve face 10c with respect to the outer contour of the umbrella back 10e, and a concave wall surface. After bending with respect to the concave wall surface 26c at the bottom edge of 26c, it extends in a trumpet shape along the outer contour of the umbrella back 10e to reach the boundary (change point P) with the stem 10a, and the thin shaft portion 32 (stem 10a) and a concave bottom surface 26d continuous without a step. In other words, the umbrella back recess 36 is formed over the entire umbrella back 10e in which the base material 26b is recessed with respect to the adjacent valve face 10c.

  On the other hand, in the umbrella surface 10f, the base material 26b of the umbrella portion 10b includes a concave wall surface 26e that is recessed obliquely (tapered) from the outer edge (lower edge) of the valve face 10c with respect to the outer contour of the umbrella surface 10f. And a concave bottom surface 26f extending along the outer contour of the umbrella surface 10f after being bent with respect to the concave wall surface 26e at the bottom edge of the concave wall surface 26e. The concave bottom surface 26f has, in order from the concave wall surface 26e side, a convex concave bottom surface 26g, a flat concave bottom surface 26h, and a curved concave concave bottom surface 26i that are smoothly connected to each other without bending. In other words, an umbrella surface recess 37 in which the base material 26b is recessed with respect to the adjacent outer peripheral surface 10g and the valve face 10c is formed over the entire bottom surface 10h of the umbrella table 10f.

  In the present embodiment, the umbrella back recess 36 is formed over the entire umbrella back 10e, and the entire bottom surface 26d serving as the bottom surface of the recess is positioned above the upper edge of the valve face 10c. It is difficult to determine whether 36 can be said to be a recess. Therefore, in this specification, the intersection p1 of the line that has the above-mentioned bent portion in the cross-sectional outline and is orthogonal to the two surfaces (the outer peripheral portion of the concave wall surface 26c and the concave bottom surface 26d) constituting the bent portion is bent. It is located above the point p2, that is, the bent part protrudes downward, or has a curved part instead of the bent part, and the center points of the two curvature radii on the curved line are The concave portion of the umbrella back 10e is defined as including a curved portion that is above the midpoint of the curved line between the two points, that is, including a curved portion that protrudes downward.

  Similarly, in the present embodiment, since the umbrella front concave portion 37 is formed over the entire bottom surface 10h of the umbrella front surface 10f, the convex concave bottom surface 26g and the flat concave bottom surface 26h among the concave bottom surfaces 26f serving as the bottom surfaces of the concave portions. And the outer peripheral portion of the curved concave concave bottom surface 26i are located below the lower end of the outer peripheral surface 10g of the umbrella face 10f, so it is difficult to determine whether or not it is a concave portion. Therefore, in the present specification, the intersection p3 of the line having the bent portion described above in the cross-sectional outline and perpendicular to the two surfaces (the outer peripheral portion of the concave wall surface 26e and the concave bottom surface 26f) constituting the bent portion is bent. The one located above the point p4, that is, the bent portion protrudes upward, or has a curved portion instead of the bent, and the center point of the two curvature radii on the curved line is The concave portion of the umbrella table 10f is defined to include a curved portion that is above the midpoint of the curved line between the two points, that is, a curved portion that protrudes upward. Therefore, it can be said that the curved concave bottom surface 26 i is a concave portion further formed at the center of the umbrella front concave portion 37.

  And in the umbrella back 10e, the heat insulation coating layer 25 is formed over the whole umbrella back recessed part 36 with the substantially constant thickness. That is, the heat insulating coating layer 25 is formed so as to be continuous from the outer peripheral surface of the thin shaft portion 32 to the umbrella back 10e of the umbrella portion 10b. The thickness t2 of the heat insulating coating layer 25 formed in the umbrella back recess 36 is the same as the thickness t1 of the heat insulating coating layer 25 formed on the thin shaft portion 32, and the outer contour of the stem 10a and the umbrella portion 10b The outer contour is smooth and continuous. Further, the thickness t2 has the same value as the depth of the outer peripheral portion of the umbrella back concave portion 36, more precisely, the depth at the outer edge of the concave bottom surface 26f. In this way, the outer contour of the umbrella back 10e is formed by forming the heat insulating coating layer 25 only on the surface of the base material 26a in the umbrella back concave portion 36 in the umbrella back 10e, as compared with the case where the heat insulating coating layer 25 is not formed. Is smooth.

  On the other hand, in the umbrella surface 10f, the heat insulating coating layer 25 has a relatively thin thickness t3 on the convex concave bottom surface 26g and the flat concave bottom surface 26h, and this thickness t3 is the depth of the outer peripheral portion of the umbrella front concave portion 37. More precisely, it is the same value as the depth at the outer edge of the convex concave bottom surface 26g. On the other hand, the heat insulating coating layer 25 is formed relatively thick on the curved concave bottom surface 26i. Thus, the outer contour of the umbrella surface 10f is formed in the umbrella surface 10f as compared with the case where the heat insulation film layer 25 is not formed by forming the heat insulation film layer 25 only on the surface of the base material 26a in the umbrella surface recess 37. Is smooth.

  Next, the effect of the intake valve 10 configured as described above will be described.

  4 and 5 are graphs showing the effects of the intake valve 10 according to the embodiment in comparison with other examples. In the graph of FIG. 4, the horizontal axis represents the surface area of the umbrella table 10f, and the vertical axis represents the amount of heat input from the umbrella table 10f. In the graph of FIG. 5, the horizontal axis represents the surface area of the umbrella back 10e + shaft portion (stem 10a), (A) the vertical axis represents the average temperature of the umbrella back 10e + shaft portion (stem 10a), and (B) the vertical axis. The amount of heat radiation from the umbrella back 10e + shaft (stem 10a) is taken.

  In each graph, the white diamond indicates the base (when the thin shaft portion 32 is not formed on the base material 26a of the stem 10a and the heat insulating coating layer 25 is not formed). The white circle represents base + simple umbrella front and back heat insulation + shaft part heat insulation (when the heat insulation film layer 25 is formed on the umbrella surface 10f and the umbrella back 10e in the base shape and the heat insulation film layer 25 is also formed on the shaft part). Show. White triangles indicate thinning (when the thin shaft portion 32 is formed in the base shape). The white-painted square is made of thin shaft + simple umbrella front / back heat insulation + thin shaft part heat insulation (thinned, simply forming the heat insulation coating layer 25 on the umbrella front / back 10f and umbrella back 10e, and also forming the heat insulation coating layer 25 on the thin shaft portion 32. Is formed).

  Also, the black rhombus indicates umbrella surface heat insulation (when the heat insulation coating layer 25 is formed in the umbrella surface recess 37 after the umbrella surface recess 37 is formed in the umbrella surface 10f). Black triangles indicate thinning + umbrella surface heat insulation (when thinning is performed and the heat insulating coating layer 25 is formed only in the umbrella front concave portion 37 after forming the umbrella front concave portion 37 on the umbrella surface 10f). . The black circles are thinned + heat-insulated on the front and back of the umbrella (thinned, and the umbrella front and rear recesses 37 and 36 are formed on the umbrella front and back 10f and the umbrella back 10e. (When the heat insulation coating layer 25 is formed). The black squares correspond to the intake valve 10 of the present embodiment. Thin shaft + umbrella front and back heat insulation + shaft portion heat insulation (thin shaft, umbrella front concave portion 37 and umbrella back concave portion 36 are provided on the umbrella front 10f and umbrella back 10e. In this case, the heat insulating coating layer 25 is formed in the umbrella front concave portion 37 and the umbrella back concave portion 36 and the heat insulating coating layer 25 is also formed on the thin shaft portion 32).

Here, the heat input Q1 from the combustion gas shown in FIG. 4 to the umbrella table 10f is expressed by the following equation (1).
_{Q 1 = h 1 × A 1} × (Tg 1 -Tw 1) ··· (1)
Here, h ₁ : heat transfer coefficient, A ₁ : surface area of the umbrella table, Tg ₁ : combustion gas temperature, Tw ₁ : wall surface temperature of the umbrella table.

In the graph of FIG. 4, from the viewpoint of heat efficiency of the internal combustion engine E, the amount of heat input Q ₁ is preferably small. Assuming that the combustion gas temperature Tg ₁ is constant, the smaller the heat transfer coefficient h ₁ and the surface area A _{1 of the} umbrella surface and the higher the wall surface temperature Tw _{1 of the} umbrella surface, the smaller the heat input Q ₁ .

On the other hand, the heat release amount Q2 from the umbrella back + shaft portion to the intake air shown in FIG. 5B is expressed by the following equation (2).
_{Q 2 = h 2 × A 2} × (Tw 2 -Tg 2) ··· (2)
However, _{h 2:} thermal conductivity, _{A 2:} Kasaura + surface area of the shaft portion, Tw _2: Kasaura + shank of wall temperature, Tg _2: is the intake air temperature.

In the graph of FIG. 5 (B), from the viewpoint of heat efficiency of the internal combustion engine E, the heat radiation amount Q ₂ is preferably small. When the intake air temperature Tg ₂ is constant, the lower the wall temperature Tw ₂ of the heat transfer coefficient h ₂ and Kasaura + small surface area A ₂ of the shaft portion and Kasaura + shank, the heat radiation amount Q ₂ is small. That is, in the graph of FIG. 5 (A), towards and Kasaura average temperature less surface area A ₂ of Kasaura + shank is low is preferred.

  First, the amount of heat input from the umbrella table will be described with reference to FIG. In the base + simple umbrella front and back heat insulation + shaft heat insulation (white circle), the heat transfer coefficient is reduced by forming the heat insulation coating layer 25 on the umbrella face 10f with respect to the base (white rhombus), but the surface area of the umbrella front is reduced. Since the effect of increasing the surface area exceeds the heat insulating effect by reducing the heat transfer coefficient, the amount of heat input from the umbrella surface is increasing. On the other hand, in the narrow axis (white triangle), the amount of heat input from the umbrella table is slightly smaller than the base (white rhombus). This is because the amount of heat transmitted through the thin shaft portion 32 from the umbrella portion 10b to the sliding shaft portion 31 by heat conduction is reduced, and the umbrella surface 10f is kept at a relatively high temperature. However, with thin-shaft + simple umbrella front / back insulation + thin-shaft thermal insulation (white square), the surface area of the umbrella surface increases compared to narrow shaft (white triangle), so the amount of heat input from the umbrella front also increases. doing.

  In contrast, in the umbrella surface insulation (black rhombus), the heat insulating coefficient layer 25 is formed on the umbrella surface 10f and the heat transfer coefficient is reduced without causing an increase in the surface area of the umbrella surface relative to the base (white rhombus). As a result, the heat input from the umbrella table has decreased significantly. In addition, in the thin shaft + umbrella surface insulation (black triangle), the heat input from the umbrella table is greatly reduced for the base (white rhombus), and slightly for the umbrella insulation (black diamond). However, the amount of heat input from the umbrella table is reduced because the umbrella table 10f is kept at a relatively high temperature as described above. Furthermore, the heat input from the front of the umbrella is almost the same for the thin shaft + umbrella front and back insulation (black circle) and thin shaft + umbrella front and back insulation + shaft heat insulation (black square). Has decreased.

  Next, with reference to FIG. 5 (A) and (B), the thermal radiation amount from an umbrella back + axial part is demonstrated. In the base + simple umbrella front and back insulation + shaft insulation (white circle), the average temperature of the umbrella back + shaft is lower than the base (white rhombus) as shown in (A), but the umbrella back + shaft As a result of the fact that the surface area increases and the effect of increasing the surface area exceeds the heat insulating effect by reducing the heat transfer coefficient, the amount of heat released from the back of the umbrella and the shaft is increased as shown in (B). On the other hand, in the narrow axis (white triangle), both the average temperature of the umbrella back + shaft part and the surface area of the umbrella back + shaft part are reduced as shown in (A), compared to the base (white rhombus). As shown in (B), the amount of heat released from the umbrella back + shaft is also reduced. However, with thin-shaft + simple umbrella front and back heat insulation + thin-shaft heat insulation (white square), the average temperature of the back of the umbrella + shaft decreases as shown in (A) in contrast to thin-shaft (white triangle). However, the surface area of the back of the umbrella and the shaft has increased, and as a result of the effect of the increased surface area exceeding the heat insulation effect by reducing the heat transfer coefficient, the amount of heat released from the back of the umbrella and the shaft as shown in (B) Is increasing.

  On the other hand, in the umbrella surface insulation (black rhombus), as shown in (A) with respect to the base (white rhombus), the thermal insulation coating layer is formed on the umbrella back 10e without causing an increase in the surface area of the umbrella back + shaft portion. Since the heat transfer coefficient is reduced by forming 25, the average temperature of the umbrella back and the shaft portion is greatly reduced. As a result, as shown in (B), in the umbrella surface heat insulation (black rhombus), the heat radiation from the umbrella back and the shaft portion is reduced with respect to the base (white rhombus).

  In addition, as shown in (A), in the thin shaft + umbrella surface insulation (black triangle), for the base (white rhombus), the surface area of the umbrella back + shaft and the average temperature of the umbrella back + shaft Both are significantly reduced, and for thin shafts (white triangles), the surface area of the back of the umbrella and the shaft does not change, the average temperature of the back of the umbrella and the shaft decreases significantly, and the umbrella surface is insulated (black) For the rhombus, the surface area of the umbrella back and the shaft is greatly reduced, and the average temperature of the umbrella back and the shaft is also reduced. As a result, as shown in (B), with thin shaft + umbrella front insulation (black triangle), the amount of heat released from the umbrella back + shaft is significantly reduced compared to the base (white rhombus). It has also decreased against shafting (white triangles) and umbrella surface insulation (black diamonds). In particular, in the amount of heat released from the back of the umbrella and the shaft in (B), the reduction from the base (white rhombus) to the thin shaft + umbrella surface insulation (black triangle) is reduced from the base (white rhombus) to the umbrella surface insulation ( It is larger than the sum of the reduction amount to the black diamond shape and the reduction amount from the base (white diamond shape) to the narrow axis (white triangle). This is considered to be due to the synergistic effect of the umbrella surface insulation and the narrow shaft.

  Furthermore, in the thin shaft + umbrella front and back heat insulation (black circle), as shown in (A), the average temperature of the umbrella back and the shaft portion is lower than the thin shaft + umbrella front heat insulation (black triangle). It should be noted that the surface area of the umbrella back + shaft portion is slightly increased with respect to the thinning of the shaft + the umbrella surface insulation (black triangle) despite the formation of the umbrella back recess 36 in the umbrella back 10e. This is because the minimum wall thickness between the front and back of the valve at the center of the bulb, which becomes a high temperature, is made constant in order to adjust the comparison conditions. As a result of this effect, as shown in (B), in the thin shaft + umbrella front and back insulation (black circle), the amount of heat released from the umbrella back + shaft is slightly smaller than the thin shaft + umbrella front insulation (black triangle). Has increased. However, when the thermal conductivity of the heat insulation coating layer 25 is smaller, or when the strength burden can be expected on the heat insulation coating layer 25 and the increase in the surface area of the back of the umbrella + shaft can be reduced to 0, the thinning of the shaft + the umbrella It is possible to reduce the amount of heat released from the back of the umbrella and the shaft with respect to the front heat insulation (black triangle).

  Finally, as shown in (A), thin shaft + umbrella front / back insulation + shaft heat insulation (black square), fine shaft + umbrella front insulation (black triangle) and thin shaft + umbrella front / back insulation (black circle) On the other hand, the average temperature of the back of the umbrella and the shaft is decreasing. On the other hand, since the heat insulating coating layer 25 is formed on the thin shaft portion 32, the surface area of the umbrella back + shaft portion is reduced to thin shaft + umbrella front insulation (black triangle) or thin shaft + umbrella front and back insulation (black circle). On the other hand, it is increasing. Due to this effect, as shown in (B), in the case of thin shaft + umbrella front and back heat insulation + shaft heat insulation (black square), the amount of heat released from the back of the umbrella + shaft portion becomes thin shaft + umbrella front heat insulation (black triangle). ) And thin shaft + umbrella heat insulation (black circle) slightly increased. However, when the thermal conductivity of the heat insulating coating layer 25 is smaller, or when the strength burden can be expected on the heat insulating coating layer 25 and the thin shaft portion 32 can be made thinner, the thin shaft + umbrella surface insulation (black triangle) ) Or thin shaft + umbrella front and back insulation (black circle), it is possible to reduce the amount of heat released from the umbrella back + shaft.

  Thus, in the intake valve 10 according to the embodiment, the umbrella portion 10b is formed so as to expose the base material 26b on the outer peripheral portion, and the valve face 10c that contacts the valve seat 13 that defines the intake opening 7a; At least a part of the umbrella surface 10f on the combustion chamber 6 side of the valve face 10c has an adjacent outer peripheral surface 10g and an umbrella surface concave portion 37 in which the base material 26b is recessed with respect to the valve face 10c. A heat insulating coating layer 25 is formed on the surface of the base material 26b in the umbrella front concave portion 37 so as to define the contour. Therefore, the heat insulation coating layer 25 can be formed on the umbrella surface 10f while suppressing an increase in surface area, and the amount of heat input from the combustion gas to the umbrella portion 10b is reduced, and the amount of heat released from the intake valve 10 to the intake air is reduced. This reduces the reduction in intake charging efficiency.

  In addition, the stem 10a is arranged to be guided by the valve guide 12 so as to slide, and the umbrella portion 10b side of the sliding shaft portion 31 is arranged, and the cross-sectional area of the base material 26a is the sliding shaft. The thin shaft portion 32 is smaller than the portion 31. Therefore, the amount of heat transmitted through the thin shaft portion 32 from the umbrella portion 10b to the sliding shaft portion 31 by heat conduction is reduced, and the umbrella surface 10f is kept at a high temperature, so that the combustion gas enters the umbrella portion 10b. While the amount of heat is reduced, the amount of heat released from the intake valve 10 to the intake air is reduced, and the reduction in intake charge efficiency is suppressed.

  In this embodiment, the umbrella part 10b has an umbrella back recess 36 in which the base material 26b is recessed with respect to the adjacent valve face 10c in at least a part of the umbrella back 10e closer to the stem 10a than the valve face 10c. The heat insulation coating layer 25 is formed on the surface of the base material 26b in the umbrella back recess 36 so as to define a smooth outer contour. Therefore, it is possible to form the heat insulating coating layer 25 on the umbrella back 10e while suppressing an increase in the surface area, reducing the heat radiation amount from the umbrella portion 10b to the intake air, and maintaining the umbrella surface 10f at a high temperature. The amount of heat input from the combustion gas to the umbrella portion 10b can also be reduced, and a decrease in intake charging efficiency can be suppressed. In addition, a decrease in the intake charging efficiency is also suppressed by suppressing a decrease in the effective opening area of the intake opening 7a.

  Further, since the heat insulating coating layer 25 is formed on the surface of the base material 26a of the thin shaft portion 32 so as to define a smooth outer contour on the stem 10a, the umbrella back 10e and the surface of the stem 10a are interposed. The amount of heat transferred from the intake valve 10 to the intake air is slightly increased. However, in the thin shaft portion 32, the heat conducted through the base material 26a of the stem 10a having a higher thermal conductivity than the case where the heat insulating coating layer 25 is not formed is thermally insulated. Since it takes time to conduct the coating layer 25 radially outward and reach the surface of the stem 10a, the change in the heat dissipation becomes slow, and the intake temperature suddenly increases due to a temporary increase in engine speed or load. It is suppressed. It is also possible to reduce the amount of heat released from the stem to the intake air, and to suppress a decrease in the charging efficiency of the intake air.

  In the present embodiment, the base material 26 a of the thin shaft portion 32 has a circular cross-sectional shape having a diameter D smaller than the diameter D1 of the sliding shaft portion 31 and is arranged coaxially with the sliding shaft portion 31, and the heat insulating coating layer 25. Is formed to have a substantially uniform thickness t1 over the entire circumference of the base material 26a of the thin shaft portion 32, and the diameter D2 of the stem 10a in the thin shaft portion 32 is equal to or smaller than the diameter of the sliding shaft portion 31 (D2 ≦ D1). Yes. Therefore, the diameter D2 of the stem 10a in the thin shaft portion 32 is prevented from increasing in comparison with the sliding shaft portion 31, and the effective opening area of the intake opening 7a is reduced and the area occupied by the stem 10a in the intake port section is increased. A reduction in intake charge efficiency is suppressed. Even when the thin shaft portion 32 is configured to enter the inside of the valve guide 12 when the valve is closed, interference of the heat insulating coating layer 25 with the valve guide 12 is prevented.

  However, in the present embodiment, the thin shaft portion 32 and the heat insulating coating layer 25 are formed closer to the umbrella portion 10b than the lower end 12a on the umbrella portion 10b side of the valve guide 12 when in the valve closing position. Therefore, the thin shaft portion 32 does not enter the inside of the valve guide 12, and the heat insulating coating layer 25 formed on the outer peripheral surface of the thin shaft portion 32 does not interfere with the valve guide 12. When the diameter D2 of the stem 10a in the portion 32 is set to be equal to or larger than the diameter D1 of the sliding shaft portion 31, or when the diameter D2 of the stem 10a in the thin shaft portion 32 is set to be equal to or smaller than the diameter D1 of the sliding shaft portion 31 Precise management of the thickness t of the coating layer 25 can be omitted.

  In the present embodiment, the thin shaft portion 32 and the umbrella back concave portion 36 are formed so as to be continuous with each other, and the heat insulating coating layer 25 is formed continuously from the umbrella back concave portion 36 to the thin shaft portion 32, thereby temporarily A sudden rise in intake air temperature due to an increase in engine speed or load is further effectively suppressed.

  On the other hand, the exhaust valve 11 is exposed to the combustion gas in the combustion chamber 6 on the front surface of the umbrella portion 11b, and the surface of the back of the umbrella and the stem 11a is exposed to the exhaust gas in the exhaust port 8. Compared to high temperatures. Since the intake valve 10 and the exhaust valve 11 are subjected to a spring force of the compression coil spring 15 acting in the valve closing direction, an impact load (axial tensile force) due to the inertia force at the valve closing time, and a bending force from the cam, The strength with respect to the directional tensile force and the bending force is required, and the material and dimensions are determined so as to satisfy the required strength. The diameter of the stem 10a of the exhaust valve 11 is a dimension that satisfies the required strength even at high temperatures.

  As described above, the valve guide 12 that slidably supports the intake valve 10 and the valve guide 12 that slidably supports the exhaust valve 11 are a common member. The diameter D1 of the stem 10a is the same as the diameter of the stem 11a of the exhaust valve 11. Therefore, the stem 10a of the intake valve 10 having a relatively low temperature has a margin for the required strength, and the thin shaft portion 32 can be formed on the base material 26a of the stem 10a. On the other hand, since the valve guide 12, the retainer 14, and the compression coil spring 15 are common members for intake and exhaust, it is possible to reduce the cost of parts. Further, since it is not necessary to distinguish between the parts for intake and exhaust, assembly work is facilitated, and the assembly cost is reduced.

The zirconia-based ceramics that are the material of the heat insulating coating layer 25 has a specific gravity of 560-590 kg / m ³ and is lighter than the stainless steel that is the base material 26 of the intake valve 10. Therefore, even if the diameter D2 of the intake valve 10 in the thin shaft portion 32 is the same as the diameter D1 of the sliding shaft portion 31, the stem 10a has the diameter D1 of the sliding shaft portion 31 over the entire length only by the base material 26a. The intake valve 10 is reduced in weight as compared with the case where it is formed.

  Although the description of the specific embodiment is finished as described above, the present invention is not limited to the above embodiment and can be widely modified. For example, in the above-described embodiment, the intake valve 10 and the intake / exhaust device 16 have been described as being applied to an internal combustion engine E for automobiles as an example, but may be widely applied to railway vehicles, ships, aircraft, and the like. it can.

  In the above embodiment, the heat insulating coating layer 25 is also formed on the thin shaft portion 32 of the intake valve 10, but the heat insulating coating layer 25 may not be formed on the thin shaft portion 32 as shown in FIG. 6. Alternatively, the heat insulating coating layer 25 is not formed on the thin shaft portion 32, and the umbrella back recess 36 and the heat insulating coating layer 25 are not formed on the umbrella back 10e, or the umbrella back recess 36 and the heat insulating coating layer 25 are formed on the umbrella back 10e. In a form in which the heat insulating coating layer 25 is not formed on the thin shaft portion 32 and in which the umbrella surface concave portion 37 and the heat insulating coating layer 25 are not formed on the umbrella surface 10f, the umbrella surface concave portion 37 and the heat insulating coating layer 25 are formed on the umbrella surface 10f. It is good also as a form which is not formed. Furthermore, the thin shaft portion 32 may not be formed and the heat insulating coating layer 25 may not be formed on the stem 10a, or a combination of this configuration and the above-described configuration may be used. If a heat sink coating 25 is formed on the surface of the base material 26 in the recess so as to define a smooth outer contour in part, a recess recessed in the adjacent portion is provided. An increase in heat input or heat release can be suppressed.

  In the above embodiment, the diameter D2 of the stem 10a in the thin shaft portion 32 is set to the same thickness (D2 = D1) as the diameter D1 of the sliding shaft portion 31, but as shown in FIG. The diameter D2 of the stem 10a in the portion 32 may be set to be smaller than the diameter D1 of the sliding shaft portion 31 (D2 = D + 2t <D1).

  In the above embodiment, the base material 26 of the intake valve 10 is formed of stainless steel. However, the base material 26a of the stem 10a or a form formed of other materials such as austenitic heat-resistant steel and nickel-based heat-resistant alloy is used. The base material 26b of the umbrella part 10b may be formed from different materials, and the base material 26 of the intake valve 10 may be formed by joining the two. Further, in the above embodiment, the base material 26 of the intake valve 10 has a solid structure, but may have a hollow structure.

In the said embodiment, although the heat insulation coating layer 25 is formed with the zirconia type ceramic, oxide type ceramics, such as an alumina, cordierite, zircon, and titanium, and carbide type ceramics, such as a silicon carbide, as the heat insulation coating layer 25 other than that. Nitride ceramics such as silicon nitride, aluminum silicate, chromium oxide, WC + Co alloy, WC + Ni + W + Cr ₃ C ₂ alloy and Cr ₃ C ₂ + Ni—Cr alloy may be used.

  In addition, the specific configuration, arrangement, quantity, angle, material, and the like of each member and part can be changed as long as they do not depart from the spirit of the present invention. On the other hand, not all the constituent elements shown in the above embodiment are necessarily essential, and can be appropriately selected.

6 Combustion chamber 7a Intake opening 8a Exhaust opening 10 Intake valve 10a Stem 10b Umbrella 10c Valve face 10e Umbrella 10f Umbrella 10g Outer peripheral surface 11 Exhaust valve 11a Stem 11b Umbrella 12 Valve guide 12a Lower end (end on the umbrella side)
16 Intake / exhaust device 25 Insulation coating layer 26 Base material 26a Base material of stem 10a 26b Base material of umbrella portion 10b 31 Sliding shaft portion 32 Thin shaft portion 36 Umbrella back recess 37 Umbrella front recess t1 Thin shaft portion 32 Thickness of the heat insulating coating layer 25 D1 Diameter of the sliding shaft portion 31 D2 Diameter of the stem 10a in the thin shaft portion E E Internal combustion engine

Claims (8)

An intake valve having a stem and an umbrella and opening and closing an intake opening of a combustion chamber of an internal combustion engine,
The umbrella portion is formed so that a base material (26b) is exposed on an outer peripheral portion, and a valve face that abuts on a valve seat that defines the intake opening; and an umbrella surface closer to the combustion chamber than the valve face At least in part, having an umbrella front recess with the base material recessed relative to the adjacent part,
An intake valve, wherein a heat insulating coating layer is formed on a surface of a base material in the umbrella recess so as to define a smooth outer contour.   The stem is arranged so as to be slid by a valve guide, and is arranged closer to the umbrella portion than the sliding shaft portion, and the cross-sectional area of the base material is smaller than the sliding shaft portion. The intake valve according to claim 1, further comprising a thin shaft portion. The umbrella part has an umbrella back recess in which a base material is recessed with respect to an adjacent part in at least a part of the umbrella back on the stem side than the valve face;
The intake valve according to claim 1 or 2, wherein a heat insulating coating layer is formed on a surface of the base material in the concave portion of the umbrella back so as to define a smooth outer contour.   The intake valve according to claim 3, wherein a heat insulating coating layer is formed on a surface of the base material of the thin shaft portion so as to define a smooth outer contour. The base material of the thin shaft portion is arranged coaxially with the sliding shaft portion with a circular cross-sectional shape having a diameter smaller than the diameter of the sliding shaft portion,
The heat insulating coating layer is formed in a substantially uniform thickness over the entire circumference of the base material of the thin shaft portion,
The intake valve according to claim 4, wherein a diameter of the stem in the thin shaft portion is equal to or less than a diameter of the sliding shaft portion.   The said thin shaft part and the said heat insulation coating layer are formed in the said umbrella part side rather than the edge part by the side of the said umbrella part of the said valve guide at the time of valve closing, The Claim 4 or Claim 5 characterized by the above-mentioned. The described intake valve. The thin shaft portion and the umbrella back recess are formed to be continuous with each other,
The intake valve according to any one of claims 4 to 6, wherein the heat insulating coating layer is formed continuously from the umbrella back recess to the thin shaft portion. The intake valve according to any one of claims 1 to 7,
An intake valve guide that slidably supports the stem of the intake valve;
An exhaust valve having a stem and an umbrella, and opening and closing an exhaust port that opens to a combustion chamber of the internal combustion engine;
An exhaust valve guide that slidably supports the stem of the exhaust valve;
The intake / exhaust device, wherein the intake valve guide and the exhaust valve guide are made of a common member.

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