CN111801488A

CN111801488A - Valve for internal combustion engine

Info

Publication number: CN111801488A
Application number: CN201880090447.9A
Authority: CN
Inventors: 吉野良一; 国武浩史; 佐藤大树
Original assignee: Nittan Valve Co Ltd
Current assignee: Nittan Corp
Priority date: 2018-03-02
Filing date: 2018-03-02
Publication date: 2020-10-20
Also published as: JPWO2019167260A1; WO2019167260A1; JP7064250B2; KR20200124248A

Abstract

Provided is a valve for an internal combustion engine, which can suppress the possibility of peeling of the outer peripheral part of a heat insulating layer fixed to the valve bottom surface as much as possible. The valve bottom surface (5) faces the combustion chamber (S), a heat insulating layer (11) is fixed to the valve bottom surface (5), a peripheral wall portion (16) is integrally provided on the valve bottom surface (5) in a state of surrounding the heat insulating layer (11), and an inner peripheral surface (16i) of the peripheral wall portion (16) abuts against the entire peripheral surface (11p) of the heat insulating layer (11) over the entire thickness range from the valve bottom surface (5) to the surface of the heat insulating layer (11).

Description

Valve for internal combustion engine

Technical Field

The present invention relates to a valve for an internal combustion engine (engine) used as an intake valve and an exhaust valve in an internal combustion engine of an automobile or the like.

Background

In an internal combustion engine (engine) of an automobile or the like, an internal combustion engine valve is provided as an intake valve and an exhaust valve in an intake port and an exhaust port that open into a combustion chamber, respectively. The valve for an internal combustion engine is provided with a shaft part and a Head part (Head) which is integrated with one end of the shaft part in a state of expanding the diameter, and the Head part is structured as follows: the head portion has a distal end surface formed as a wide valve bottom surface (Face), and is reduced in diameter as it approaches the shaft portion from the valve bottom surface, and a Seat surface (Seat) is provided on the outer peripheral portion of the head portion on the back side of the valve bottom surface. The valve for an internal combustion engine is arranged in a combustion chamber such that a back surface of a head portion faces openings of an intake port and an exhaust port, and is operated by a valve operating mechanism, and a Seat surface (Seat) of the head portion of the valve for an internal combustion engine is separately seated on a Seat insert provided at a peripheral edge portion of the openings of the intake port and the exhaust port, thereby opening and closing the intake port and the exhaust port, respectively.

Further, as shown in patent document 1, an internal combustion engine in which a heat insulating layer is provided on a wall surface defining a combustion chamber has been proposed for the purpose of improving heat efficiency. In this case, since the valve bottom surface of the valve (intake valve, exhaust valve) for the internal combustion engine also partitions the combustion chamber, the valve bottom surface also serves as a wall surface partitioning the combustion chamber, and if a heat insulating layer is provided on the valve bottom surface, thermal efficiency can be improved.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 5629463

Disclosure of Invention

Problems to be solved by the invention

However, the present inventors have found that when the valve (head) for an internal combustion engine is used in a combustion chamber, the heat insulating layer tends to peel from the outer peripheral portion of the valve bottom surface and to peel from the outer peripheral portion toward a radially inner portion (radially central portion) with the peeling point as a starting point. If such an internal combustion engine valve is used, the thermal efficiency of the internal combustion engine cannot be sufficiently improved.

The present invention has been made in view of the above circumstances, and an object thereof is to suppress as much as possible the possibility that the outer peripheral portion of the heat insulating layer peels off from the valve bottom surface in the valve for an internal combustion engine having the heat insulating layer fixed to the valve bottom surface.

Means for solving the problems

In order to achieve the above object, the following configurations (1) to (19) are employed.

(1) In the valve for internal combustion engine with heat insulating layer fixed to the bottom of valve facing combustion chamber,

a peripheral wall integrally provided on the valve bottom surface so as to surround the heat insulating layer,

the inner peripheral surface of the peripheral wall abuts against the entire peripheral surface of the heat insulating layer over the entire thickness range from the valve bottom surface to the surface of the heat insulating layer.

According to this configuration, since the peripheral wall covers the entire peripheral surface of the heat insulating layer over the entire thickness range from the valve bottom surface to the surface of the heat insulating layer, a boundary (line) formed by the valve bottom surface (joint surface) and the heat insulating layer (joint surface) is not exposed to the outside due to the peripheral wall, and it is possible to suppress the combustion gas (pressure, temperature, and the like) from acting on the boundary between the valve bottom surface and the heat insulating layer and causing the outer peripheral portion of the heat insulating layer to peel off (turn up) from the valve bottom surface. Even if a force tending to peel off the valve bottom surface acts on the outer peripheral portion of the heat insulating layer and the peeling-off, warping, or the like of the outer peripheral portion of the heat insulating layer occurs, a frictional force is generated between the outer peripheral portion of the heat insulating layer and the inner peripheral surface of the peripheral wall, and the operation of the outer peripheral portion of the heat insulating layer tending to peel off can be suppressed by this frictional force. Therefore, the possibility of the outer peripheral portion of the heat insulating layer peeling off from the valve bottom surface can be suppressed as much as possible.

(2) In the structure of the above (1), the structure is such that,

the heat insulating layer is disposed on the valve bottom surface in a reduced diameter state that is radially inwardly retracted from an outer peripheral edge of the valve bottom surface.

According to this configuration, it is needless to say that the same operational effects as those of the above-mentioned (1) (suppression of the combustion gas from the outside by the peripheral wall at the boundary (line) between the valve bottom surface and the heat insulating layer and suppression of the operation of the outer peripheral portion of the heat insulating layer to be peeled off from the valve bottom surface by the frictional force based on the contact relationship between the inner peripheral surface of the peripheral wall and the entire peripheral surface of the heat insulating layer) can be obtained, even if the thermal expansion coefficient of the heat insulating layer is different from that of the valve bottom surface, the diameter of the heat insulating layer is made smaller than that of the valve bottom surface, compared to the case where the heat insulating layer is fixed to the entire valve bottom surface, the difference between the amount of contraction of the heat insulating layer on the inner side in the radial direction and the amount of contraction of the heat insulating layer on the inner side in the radial direction of the valve bottom surface during thermal contraction or the difference between the amount of expansion of the heat insulating layer on the outer side in the radial direction and the amount of expansion of the heat insulating layer on the outer side in the radial direction of the valve bottom surface during thermal expansion can be suppressed, and the force in the direction of separation from.

(3) In the structure of (2), the structure is such that,

the thermal insulation layer has a coefficient of thermal expansion less than the coefficient of thermal expansion of the valve bottom surface,

the inner peripheral surface of the peripheral wall is joined to the entire peripheral surface of the heat insulating layer, and one end surface of the peripheral wall is joined to the valve bottom surface on the outer peripheral side of the heat insulating layer.

According to this configuration, the peripheral wall stretches (tightens) the entire periphery of the heat insulating layer radially outward in accordance with thermal expansion of the valve bottom surface and presses (tightens) the entire periphery of the heat insulating layer radially inward in accordance with thermal contraction of the valve bottom surface, based on the fact that the peripheral wall is coupled to the valve bottom surface and the entire periphery of the heat insulating layer. Therefore, at the time of thermal expansion and thermal contraction, the peripheral wall causes a force in a direction that reduces the difference in the amount of expansion and the difference in the amount of contraction between the heat insulating layer and the valve bottom surface to act on the heat insulating layer, and the possibility of the heat insulating layer peeling from the valve bottom surface can be further suppressed.

(4) In the above-mentioned structure (3), the structure is such that,

the outer edge of the heat insulating layer is set closer to the outer edge of the valve bottom surface than the radial center of the valve bottom surface.

According to this configuration, even if a configuration is adopted in which peeling due to thermal expansion or thermal contraction acting on the outer peripheral portion of the heat insulating layer is suppressed, the heat insulating function can be basically ensured by the heat insulating layer.

(5) In the above-mentioned structure (3), the structure is such that,

the peripheral wall is formed of a covering material that covers the entire heat insulating layer including not only the entire peripheral surface of the heat insulating layer but also the surface of the heat insulating layer.

According to this configuration, since the surface of the heat insulating layer is also covered with the covering material in a state of being bonded to the valve bottom surface and the surface side of the heat insulating layer is pressed toward the valve bottom surface, the operation in which the outer peripheral portion of the heat insulating layer is intended to be peeled off from the valve bottom surface can be effectively suppressed as compared with a case where the covering material covers only the entire peripheral surface of the heat insulating layer.

(6) In the above-described configuration of (5),

the covering material is set to cover the entire portion of the outer peripheral side of the heat insulating layer in the valve bottom surface,

the coating material contains a heat insulating component.

According to this configuration, even when the diameter of the heat insulating layer is made smaller than the diameter of the valve bottom surface in order to suppress peeling of the heat insulating layer due to thermal expansion or thermal contraction, the heat insulating property of the valve bottom surface can be improved as compared with a case where the entire outer peripheral portion of the heat insulating layer in the valve bottom surface is not covered with the covering material.

(7) In the above-mentioned structure (3), the structure is such that,

the thermal expansion coefficient of the peripheral wall is set to be larger than that of the heat insulating layer.

According to this configuration, the ability of the peripheral wall to follow the valve bottom surface can be improved more than that of the heat insulating layer during thermal expansion and thermal contraction, and a radial force can be applied to the entire peripheral surface of the heat insulating layer via (the inner peripheral surface of) the peripheral wall as the valve bottom surface thermally expands and contracts. Therefore, the possibility of the heat insulating layer peeling off from the valve bottom surface can be further suppressed.

(8) In the above-described configuration of (5),

an extension portion is provided in the cover member, the extension portion extending to an edge portion from the valve bottom surface to a valve seat surface,

the edge portion is provided with an engaging portion,

the extension portion of the covering material is mechanically engaged with the engagement portion.

According to this configuration, the mechanical engagement between the extension portion of the covering material and the edge portion can improve the bonding strength between the covering material and the valve bottom surface, and the ability of the covering material to resist the operation such as peeling or warping of the outer peripheral portion of the heat insulating layer can be improved.

(9) In the structure of the above (1), the structure is such that,

a recess extending radially outward from a radially central portion of the valve bottom surface,

the heat insulating layer is fixed to the bottom wall of the recess, and the entire peripheral surface of the heat insulating layer is covered by the inner peripheral wall of the recess as the peripheral wall.

According to this configuration, the entire peripheral surface of the heat insulating layer is covered with the recess inner peripheral wall of the valve bottom surface, and the same operational effect as (1) above can be obtained.

(10) In the above-described structure of (9), the structure is such that,

the entire peripheral surface of the heat insulating layer is also fixed to the inner peripheral wall of the recess.

According to this configuration, the inner peripheral wall of the pocket is also expanded and contracted by the same thermal expansion coefficient as that of the valve bottom surface as the valve bottom surface is expanded and contracted, and a radial force can be applied to the entire peripheral surface of the heat insulating layer by the thermal expansion and thermal contraction (displacement movement in the radial direction) of the inner peripheral wall of the pocket, thereby significantly reducing the difference in expansion amount or contraction amount between the heat insulating layer and the valve bottom surface. Therefore, the possibility of the heat insulating layer peeling off from the valve bottom surface can be extremely effectively suppressed.

(11) In the above-described structure of (9), the structure is such that,

a coating material is bonded to the surface of the heat insulating layer in the recess and the valve bottom surface so as to coat the entire surface of the heat insulating layer and the valve bottom surface.

According to this configuration, not only the relationship between the heat insulating layer and the recess inner peripheral wall but also the action such as peeling or warping of the outer peripheral portion of the heat insulating layer is resisted by the coating material bonded to the surface of the heat insulating layer and the valve bottom surface, and the possibility of the outer peripheral portion of the heat insulating layer peeling from the valve bottom surface can be further suppressed. In this case, of course, the actual length of the valve bottom surface in contact with the coating material in the radial direction of the valve bottom surface is limited by the presence of the recess, and therefore, the influence of thermal expansion and thermal contraction can be reduced, and the bonding strength of the coating material to the valve bottom surface can be sufficiently ensured.

(12) In the structure of the above (1), the structure is such that,

the heat insulating layer is formed by integrating a plurality of respective structural layers in a laminated state.

According to this structure, the heat insulating layer has a laminated structure including a plurality of structural layers, and even if a boundary exists between adjacent structural layers, the same operational effect as in (1) above can be obtained.

(13) In the structure of the above (1), the structure is such that,

the thermal insulation layer has a coefficient of thermal expansion different from that of the valve bottom surface,

the thickness of the outer peripheral portion of the heat insulating layer is thinner than the thickness of a portion radially inward of the outer peripheral portion of the heat insulating layer.

According to this structure, it is possible to suppress occurrence of cracks due to bending stress acting on the outer peripheral portion of the heat insulating layer during thermal expansion or thermal contraction.

That is, the heat insulating layer and the valve bottom surface (valve bottom surface portion) are integrally flexed at the time of thermal expansion and thermal contraction based on the difference in thermal expansion coefficient between the heat insulating layer and the valve bottom surface, and bending stress acts on them. The maximum bending stress with respect to the heat insulating layer is generated as an edge stress on the outer surface of the heat insulating layer in the wall thickness direction, and the value of the maximum bending stress is larger as the distance from the neutral surface to the outer surface in the wall thickness direction is longer. Therefore, the longer the distance from the vertical surface to the outer surface in the thickness direction, the higher the possibility of cracks occurring in the outer peripheral portion of the heat insulating layer, and when cracks occur, the thicker the thickness of the heat insulating layer, the deeper the depth of the cracks. Further, when the heat insulating layer and the valve bottom surface (valve bottom surface portion) are integrally bent, the outer peripheral portion of the heat insulating layer tends to be smaller (the curvature tends to be larger) than the portion radially inward of the outer peripheral portion with respect to the radius of curvature of the heat insulating layer. Therefore, in claim 13, the thickness of the outer peripheral portion of the heat insulating layer is made thinner than the thickness of the portion radially inward of the outer peripheral portion thereof, so that the distance from the neutral surface to the outer surface in the thickness direction in the heat insulating layer is reduced, thereby reducing the maximum bending stress during thermal expansion and thermal contraction. As a result, as described above, the occurrence of cracks due to bending stress acting on the outer peripheral portion of the heat insulating layer can be suppressed, and the outer peripheral portion of the heat insulating layer can be suppressed from peeling off from the valve bottom surface due to cracks.

(14) In the above-described configuration of (13),

the thickness of the outer peripheral portion of the heat insulating layer is set to be thinner toward the radially outer side of the heat insulating layer.

According to this configuration, the thinner the wall thickness of the radially outer portion, which is more likely to cause cracking, of the wall thickness of the outer peripheral portion of the heat insulating layer, the more reliably the occurrence of cracking can be suppressed, and accordingly, the peeling of the outer peripheral portion of the heat insulating layer from the valve bottom surface due to cracking can be reliably suppressed. On the other hand, in this case, since the thickness of only the outer peripheral portion of the heat insulating layer is smaller than the thickness of the radially inner portion of the heat insulating layer and the thickness thereof becomes thinner toward the radially outer side, the thickness of the outer peripheral portion of the heat insulating layer is not made as thin as possible, and the heat insulating property of the heat insulating layer on the valve bottom surface can be suppressed from being lowered as much as possible. Therefore, the peeling of the outer peripheral portion of the heat insulating layer due to the crack can be reliably suppressed while suppressing the decrease in the heat insulating property of the heat insulating layer on the valve bottom surface as much as possible.

(15) In the above-described structure (14), the structure is such that,

the inner circumferential wall of the recess is inclined toward a radially outer side of the recess as facing the opening side of the recess,

the heat insulation layer is fixed on the bottom wall of the concave part,

the entire peripheral surface of the heat insulating layer is inclined so as to expand radially outward of the heat insulating layer as it goes toward the thickness direction surface side of the heat insulating layer, and the surface of the heat insulating layer is set flush with the portion of the valve bottom surface other than the recess.

According to this configuration, the entire peripheral surface of the heat insulating layer can be made thinner toward the radially outer side of the heat insulating layer while being in contact with the inner peripheral wall of the recess. Therefore, the heat insulating layer can be prevented from peeling off from the valve bottom surface due to the action of the combustion gas and the occurrence of cracks while suppressing the decrease in the heat insulating function of the heat insulating layer as much as possible.

In this case, since the surface of the heat insulating layer is set flush with the portion of the valve bottom surface other than the recess, the entire valve bottom surface can be flattened, and the basic structure and basic performance of a general valve having a flattened valve bottom surface can be ensured.

(16) In the above-described structure of (15), the structure is such that,

a coating material is bonded to the surface of the thermal insulation layer and the valve bottom surface in the recess in such a manner as to coat the surface of the thermal insulation layer and the valve bottom surface as a whole.

According to this configuration, not only the effect of the abutment of the recess inner peripheral wall with the entire peripheral surface of the heat insulating layer can be obtained, but also the covering material bonded to the surface of the heat insulating layer and the valve bottom surface can further suppress the possibility that the outer peripheral portion of the heat insulating layer peels off from the valve bottom surface against the peeling, warping, and the like of the outer peripheral portion of the heat insulating layer. In this case, of course, the actual length of the valve bottom surface in contact with the coating material in the radial direction of the valve bottom surface is limited by the presence of the recess, and therefore, the influence of thermal expansion and thermal contraction can be reduced, and the bonding strength of the coating material to the valve bottom surface can be sufficiently ensured.

(17) In the above-described structure (14), the structure is such that,

the heat insulation layer is fixed on the bottom wall of the concave part,

the entire peripheral surface of the heat insulating layer is in contact with the inner peripheral wall of the recess in a state of being inclined so as to expand radially outward of the heat insulating layer as facing the thickness direction surface side of the heat insulating layer,

the surface of the heat insulating layer is formed in a state of bulging outside of the recess opening.

According to this configuration, the entire peripheral surface of the heat insulating layer can be brought into contact with the inner peripheral wall of the recess, the outer peripheral portion of the heat insulating layer can be made thinner on the radially outer side thereof, the amount of protrusion of the heat insulating layer from the valve bottom surface can be suppressed, and the thickness of the portion of the heat insulating layer on the radially inner side of the outer peripheral portion can be made thicker. Therefore, the heat insulation performance of the valve bottom surface can be improved while the peeling-off suppressing effect of the heat insulating layer and the flattening of the entire valve bottom surface are improved as much as possible.

(18) In the above-described configuration of (13),

According to this configuration, since the covering member covers the surface of the heat insulating layer even in a state of being bonded to the valve bottom surface and presses the surface side of the heat insulating layer toward the valve bottom surface, an operation (including a case where a crack occurs in the outer peripheral portion of the heat insulating layer) in which the outer peripheral portion of the heat insulating layer is separated from the valve bottom surface can be effectively suppressed, as compared with a case where the covering member covers only the entire peripheral surface of the heat insulating layer.

(19) In the above-described configuration of (13),

the thermal expansion coefficient of the thermal insulation layer is smaller than that of the valve bottom surface.

According to this configuration, even when the thermal expansion coefficient difference is based on the thermal expansion coefficient of the heat insulating layer being smaller than the thermal expansion coefficient of the valve bottom surface, the same operational effects as those of claim 13 can be obtained.

Effects of the invention

As is apparent from the above description, according to the present invention, in the valve for an internal combustion engine having the heat insulating layer fixed to the valve bottom surface, the possibility of the outer peripheral portion of the heat insulating layer peeling off from the valve bottom surface can be suppressed as much as possible. As a result, the thermal insulation layer can be prevented from peeling off and spreading over the entire valve bottom surface from the peeling point of the thermal insulation layer outer peripheral portion with respect to the valve bottom surface.

Drawings

Fig. 1 is an explanatory view showing an intake valve or an exhaust valve of an internal combustion engine valve according to a first embodiment used for an internal combustion engine.

Fig. 2 is an explanatory view for explaining a head portion of the valve according to the first embodiment.

Fig. 3 is an explanatory diagram simply showing a vertical cross-sectional structure of fig. 2.

Fig. 4 is a plan view of fig. 3 as viewed from above.

Fig. 5 is an explanatory diagram illustrating thermal expansion occurring between the valve bottom surface (head portion) and the heat insulating layer.

Fig. 6 is an explanatory diagram illustrating thermal contraction generated between the valve bottom surface (head portion) and the heat insulating layer.

Fig. 7 is an explanatory diagram for simply illustrating the operation of the combustion gas with respect to the valve of the first embodiment.

Fig. 8 is an explanatory diagram for simply illustrating the operation of the combustion gas with respect to a valve provided with a general heat insulating layer.

Fig. 9 is a graph showing the structures of the laminates of experimental examples 1 to 3 and the peeling ratios of the outer peripheral portions of the laminates as the results of the respective experiments.

Fig. 10 is an explanatory view explaining a state of an experiment of an experimental example performed using a durability tester.

FIG. 11 is a photograph showing the peeled state of the outer periphery of the laminate before and after the experiment in Experimental example 1 (magnification: 5 times overall and 50 times magnification of each part).

FIG. 12 is a photograph showing the peeled state of the outer periphery of the laminate before and after the experiment in Experimental example 2 (magnification: 5 times overall and 50 times magnification of each part).

FIG. 13 is a photograph showing the peeled state of the outer periphery of the laminate before and after the experiment in Experimental example 3 (magnification: 5 times overall and 50 times magnification of each part).

Fig. 14 is an explanatory view conceptually illustrating a state in which the peripheral wall portion stretches the entire peripheral surface of the heat insulating layer radially outward during thermal expansion as an action of the peripheral wall portion of the valve of the first embodiment.

Fig. 15 is an explanatory view conceptually illustrating a state in which the peripheral wall portion tightens the entire peripheral surface of the heat insulating layer radially inward at the time of heat shrinkage as a function of the peripheral wall portion of the valve of the first embodiment.

Fig. 16 is a graph showing the structure of experimental example 4 and the peeling rate of the heat insulating layer as a result of the experiment.

FIG. 17 is a photograph showing the peeled state of the outer periphery of the laminate before and after the experiment in Experimental example 4 (magnification: 5 times overall and 50 times magnification of each part).

Fig. 18 is an explanatory view for explaining a head portion of the valve according to the second embodiment.

Fig. 19 is a longitudinal sectional view showing a head portion of a valve according to a third embodiment.

Fig. 20 is a plan view of fig. 19 as viewed from above.

Fig. 21 is an enlarged view of fig. 19.

Fig. 22 is a longitudinal sectional view showing a head portion of the valve according to the fourth embodiment.

Fig. 23 is an explanatory diagram for explaining a state in which the head portion of the valve is changed to a deflected state by thermal contraction.

Fig. 24 is an enlarged explanatory view for explaining generation of bending stress by enlarging a portion W of fig. 23.

Fig. 25 is a longitudinal sectional view showing a head portion of the valve according to the fifth embodiment.

Fig. 26 is a longitudinal sectional view showing a head portion of the valve according to the sixth embodiment.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In fig. 1, reference numeral 1 denotes an intake valve or an exhaust valve (hereinafter, referred to as a valve) as a valve for an internal combustion engine mounted on a cylinder head 2.

A part of the wall surface of the cylinder head 2 defines a combustion chamber S. An intake port and an exhaust port (hereinafter, referred to as a port) P are formed in the cylinder head 2 so as to open into the combustion chamber S, and a valve seat insert 9 is provided at an opening peripheral edge portion of the port P.

The valve 1 includes a shaft portion (Stem)3 and a Head portion (Head)4 integrated with one end of the shaft portion 3 in a diameter-expanded state as a valve main body 1A. The head 4 has the following structure: the head portion 4 has a front end Face formed as a valve bottom Face (Face)5 having a width and a circular shape in front view, and is formed with a Seat Face (Seat)7 on the back side of the valve bottom Face 5 in the outer peripheral portion of the head portion 4 via an edge portion (Margin)6 as the diameter decreases from the valve bottom Face 5 toward the shaft portion 3. The valve 1 is disposed in the combustion chamber S such that the back surface of the head 4 faces the opening of the port P, and by operating the valve 1 by the valve operating mechanism 10, the Seat surface (Seat)7 of the head 4 in the valve 1 is seated separately from the Seat insert 9 at the opening peripheral edge portion of the port P. Thus, the valve 1 (head 4) opens and closes the port P while directing the valve bottom surface 5 of the valve main body 1A toward the combustion chamber S.

In the present embodiment, SUH11 is used as a material of the valve main body 1A. Therefore, the thermal conductivity of the valve body (SUH11) is about 20.5W/mK (at room temperature), and the thermal expansion coefficient is about 11.0X 10^-6/° c (at room temperature).

In the valve 1, as shown in fig. 2 and 3, a heat insulating layer 11 is fixed (bonded) to the valve bottom surface 5 of the valve main body 1A. In the present embodiment, the heat insulating layer 11 is formed by stacking a first heat insulating layer 12 and a second heat insulating layer 13 having the same diameter as the first heat insulating layer 12 in this order in a direction away from the valve bottom surface 5 (upward direction in fig. 3), and the valve bottom surface 5 and the first heat insulating layer 12, and the first heat insulating layer 12 and the second heat insulating layer 13 are bonded (sintered) by firing, respectively. Therefore, the heat insulating layer 11 forms a boundary B1 between the valve bottom surface 5 and the first heat insulating layer 12, and a boundary B2 between the first heat insulating layer 12 and the second heat insulating layer 13. In fig. 2 and 3, the thickness of the heat insulating layer 11 (the first heat insulating layer 12 and the second heat insulating layer 13) is exaggerated because it is not easy to actually illustrate the thickness (the same applies to the drawings below in fig. 4).

The first insulating layer 12 and the second insulating layer 13 have a fine porous structure to exhibit an insulating function. Therefore, in the present embodiment, the first heat insulating layer 12 and the second heat insulating layer 13 contain, as components, hollow ceramic beads or hollow glass beads as inorganic pigments and a binder having excellent heat resistance. More specifically, first thermal insulation layer 12 contains hollow ceramic beads or hollow glass beads: about 40 to 80 wt%, a binder (e.g., a silicon-based binder or a zirconia-based binder): about 20 to 60 wt%, and the second heat insulating layer 13 contains hollow ceramic beads or hollow glass beads: about 50 to 90 wt%, a binder (e.g., a silicon-based binder or a zirconia-based binder): about 10 to 50 wt%.

In this case, as for the content of the hollow ceramic beads or the hollow glass beads, as described above, the second thermal insulation layer 13 is more than the first thermal insulation layer 12. This is because the thermal insulation performance is effectively improved by adjusting the amount of existence of the fine hollows (hollows of ceramic beads or glass beads), and the thermal conductivity of the second thermal insulation layer 13 is made lower than the thermal conductivity of the first thermal insulation layer 12, and the thermal expansion coefficient of the first thermal insulation layer 12 is made an intermediate value between the thermal expansion coefficient of the second thermal insulation layer 13 and the thermal expansion coefficient of the valve bottom surface 5 by adjusting the amount of existence of the hollow ceramic beads or the hollow glass beads, and the influence (peeling or the like) due to the difference in thermal expansion and the difference in thermal contraction with respect to the first thermal insulation layer 12 and the second thermal insulation layer 13 is reduced. In this case, of course, the thermal expansion coefficients of the first and second insulating

layers

12 and 13 are both smaller than the thermal expansion coefficient of the valve bottom surface 5.

More specifically, the first heat insulating layer 12 has a thermal conductivity of 0.4 to 1.2W/mK (at room temperature) in a layer thickness of about 20 to 100 μm on the valve bottom surface 5, and the second heat insulating layer 13 has a thermal conductivity of 0.2 to 1.0W/mK (at room temperature) in a layer thickness of about 20 to 250 μm on the first heat insulating layer 12.

In addition, regarding the thermal expansion coefficient of the thermal insulation layers 11 (the first thermal insulation layer 12 and the second thermal insulation layer 13), in a basic structure in which the thermal expansion coefficient of the thermal insulation layer 11 is smaller than that of the valve bottom surface 5 and the thermal expansion coefficient of the second thermal insulation layer 13 is smaller than that of the first thermal insulation layer 12, the difference in thermal expansion coefficient between the first thermal insulation layer 12 and the second thermal insulation layer 13 is smaller than that between the valve main body 1A and the first thermal insulation layer 12. This is because the thermal influence (peeling or the like) between the first heat insulating layer 12 and the second heat insulating layer 13 is lower than the thermal influence between the valve bottom surface 5 and the first heat insulating layer 12.

As shown in fig. 3 and 4, the heat insulating layers 11 (the first heat insulating layer 12 and the second heat insulating layer 13) are narrower than the outer edge of the valve bottom surface 5. Specifically, the outer edge of the heat insulating layer 11 is set closer to the outer edge of the valve bottom surface 5 than the radially central portion O of the valve bottom surface 5. This is to reduce the thermal expansion difference and the thermal contraction difference due to the difference in thermal expansion coefficient between the valve main body 1A (the valve bottom surface 5) and the heat insulating layer 11 by shortening the length to be thermally expanded and thermally contracted while securing the heat insulating function with respect to the valve bottom surface 5 by the heat insulating layer 11, and thereby to suppress the heat insulating layer 11 from peeling off from the valve bottom surface 5.

The peeling of the heat insulating layer 11 from the valve bottom surface 5 and the diameter reduction of the heat insulating layer 11 as a measure for suppressing the peeling are specifically described based on fig. 5 and 6, taking as an example the case where the heat insulating layer 11 is sintered (bonded) to the entire valve bottom surface 5.

In the valve 1, the valve bottom surface 5 (valve body 1A) and the heat insulating layer 11 are actually sintered and integrated, but when the valve bottom surface 5 and the heat insulating layer 11 are thermally expanded and thermally contracted separately, since the thermal expansion coefficient of the valve bottom surface 5 is larger than that of the heat insulating layer 11, the reference state shown in fig. 5(a) is a state in which the diameter of the valve bottom surface 5 is expanded by the diameter of the heat insulating layer 11 as shown in fig. 5(b) at the time of thermal expansion, and an expansion amount difference Δ Le based on the thermal expansion coefficient difference occurs. The expansion amount difference Δ Le is obtained by the following equation.

ΔLe＝ΔLe1-ΔLe2＝(α1-α2)×D×ΔTe

In this case, Δ Le 1: amount of expansion of valve bottom surface 5, Δ Le 2: expansion amount of the heat insulating layer, α 1: coefficient of thermal expansion of valve bottom surface 5, α 2: thermal expansion coefficient of the heat insulating layer, D: diameter (target length) of the heat insulating layer 11 and the valve bottom surface 5 before thermal expansion, Δ Te: temperature change upon thermal expansion.

On the other hand, in the case of thermal contraction, the reference state shown in fig. 6(a) is a state in which the diameter of the valve bottom surface 5 is reduced to a smaller diameter than the heat insulating layer 11 as shown in fig. 6(b), and a contraction amount difference Δ Lc is generated due to a difference in thermal expansion coefficient. The shrinkage difference Δ Lc is obtained by the following equation.

ΔLc＝ΔLc1-ΔLc2＝(α1-α2)×D×ΔTc

In this case, Δ Lc 1: shrinkage of valve bottom surface 5, Δ Lc 2: shrinkage of the heat insulating layer, α 1: coefficient of thermal expansion of valve bottom surface 5, α 2: thermal expansion coefficient of the heat insulating layer, D: diameter (target length) of the heat insulating layer 11 and the valve bottom surface 5 before heat shrinkage, Δ Tc: temperature change upon thermal shrinkage.

Actually, as described above, in the valve 1, the expansion amount difference Δ Le and the contraction amount difference Δ Lc are intended to be generated based on the difference in the thermal expansion coefficients in a state where the valve bottom surface 5 and the heat insulating layer 11 are sintered and integrated. Therefore, it is assumed that the phenomenon at this time is that, during thermal expansion, the valve bottom surface 5 expands in diameter as the reference state shown in fig. 5(a) changes to fig. 5(c), and the portion of the outer peripheral edge portion of the heat insulating layer 11 at this time closer to the joint surface with the valve bottom surface 5 is stretched radially outward. Therefore, it is considered that the thermal insulation layer 11 is more likely to peel off from the valve bottom surface 5 as the expansion amount difference Δ Le at this time increases.

On the other hand, it is estimated that the phenomenon at the time of thermal contraction changes from the reference state shown in fig. 6(a) (the same state as the reference state shown in fig. 5 (a)) to fig. 6(c), the valve bottom surface 5 is reduced in diameter, and a portion of the outer peripheral edge portion of the heat insulating layer 11 at this time closer to the joining surface with the valve bottom surface 5 is stretched more inward in the radial direction. Therefore, it is considered that the greater the shrinkage amount difference Δ Le at this time, the more likely the heat insulating layer 11 is peeled off from the valve bottom surface 5.

Therefore, the present inventors paid attention to the point that when the target length D to be influenced by thermal expansion and thermal contraction is shortened in the above equation for obtaining the expansion amount difference Δ Le and the contraction amount difference Δ Lc, the expansion amount difference Δ Le and the contraction amount difference Δ Lc become smaller, and the target length D to be influenced by thermal expansion and thermal contraction is determined as the length of a portion where the heat insulating layer 11 and the valve bottom surface 5 are sintered (bonded), and bonded the heat insulating layer 11 to the valve bottom surface 5 in a state where the diameter thereof is reduced from the diameter of the valve bottom surface 5.

As shown in fig. 2 to 4, the valve bottom surface 5 and the heat insulating layer 11 on the valve bottom surface 5 are covered with a coating material 15. The covering material 15 is formed into a substantially cylindrical shape with a bottom portion disposed away from the valve bottom surface 5, and the covering material 15 is provided with a peripheral wall portion 16 serving as a peripheral wall and a bottom wall portion 17 integrally provided with the peripheral wall portion 16 to form a bottom portion. The coating material 15 (the peripheral wall portion 16 and the bottom wall portion 17) contains ceramics such as zirconia, alumina, silica, and silicate as a main component, and hollow ceramic beads and hollow glass beads as components of the heat insulating layer 11 are not contained in the coating material 15. Thus, the thermal conductivity of the coating material 15 is ensured to be as close as possible to that of the heat insulating layer 11 by the main component (thermal conductivity of the valve bottom surface 5 (valve main body 1A) > thermal conductivity of the coating material 15 > thermal conductivity of the heat insulating layer 11) even though the coating material 15 is not as close as possible to that of the heat insulating layer 11, and the thermal expansion coefficient of the coating material 15 is as close as possible to that of the valve bottom surface 5 (thermal expansion coefficient of the valve bottom surface 5 > thermal expansion coefficient of the coating material 15 > thermal expansion coefficient of the heat insulating layer 11). In the present embodiment, the coating material 15 has a thermal conductivity of 0.2 to 4W/m.K (at room temperature) and a thermal expansion coefficient equal to or less than that of the valve body 1A. In fig. 2 to 4, the thickness of the covering material 15 (the peripheral wall portion 16 and the bottom wall portion 17) is exaggerated because it is not easy to actually illustrate it (the same applies to the drawings below in fig. 5).

As shown in fig. 3, one end surface (lower end surface in fig. 3) of the peripheral wall portion 16 is bonded (sintered) to the valve bottom surface 5 on the outer peripheral side of the heat insulating layer 11. The inner peripheral surface 16i of the peripheral wall portion 16 covers (surrounds) the entire peripheral surface 11p of the heat insulating layer 11 in a state of being in contact with the entire peripheral surface 11p of the heat insulating layer 11 over the entire thickness range from the valve bottom surface 5 to the surface 13s of the second heat insulating layer 13, and a boundary B1 between the valve bottom surface 5 and the first heat insulating layer 12 and a boundary B2 between the first heat insulating layer 12 and the second heat insulating layer 13 are not exposed to the outside. In the present embodiment, the inner peripheral surface 16i of the peripheral wall portion 16 is bonded (sintered) to the entire peripheral surface of the heat insulating layer 11.

In the present embodiment, the outer peripheral surface of the peripheral wall portion 16 is expanded in the radial direction of the valve bottom surface 5 to the outer peripheral edge of the valve bottom surface 5. Thus, the entire portion of the valve bottom surface 5 on the outer peripheral side of the heat insulating layer 11 is covered with one end surface (thick wall surface) of the peripheral wall portion 16, and the peripheral wall portion 16 does not have the same material (component) as the heat insulating layer 11, but ensures heat insulation at the portion of the valve bottom surface 5 where the heat insulating layer 11 does not exist. In this case, the thickness of the peripheral wall portion 16 is determined depending on the degree of the diameter of the heat insulating layer 11, but when importance is placed on the heat insulation property with respect to the valve bottom surface 5 and the peeling of the outer peripheral portion of the heat insulating layer 11 is suppressed, the diameter of the heat insulating layer 11 tends to be increased, on the other hand, the thickness of the peripheral wall portion 16 is decreased, and when importance is placed on the suppression of the peeling of the outer peripheral portion of the heat insulating layer 11 and the heat insulation property of the valve bottom surface 5 is ensured, the diameter of the heat insulating layer 11 tends to be decreased, and on the other hand, the thickness of the peripheral wall portion 16. In the present embodiment, the wall thickness of the peripheral wall portion 16 is 1 μm to 30 μm, and the heat insulating layer 11 is present radially inside the inner peripheral surface 16i of the peripheral wall portion 16.

As shown in fig. 3 and 4, the bottom wall 17 abuts against the surface 11s (13s) of the heat insulating layer 11 (second heat insulating layer 13) and covers the surface 11s (13 s). The bottom wall portion 17 is integrally provided on the other end surface of the peripheral wall portion 16 so as to close the other end opening, and the bottom wall portion 17 resists a force in a direction (upward direction in fig. 3) away from the other end of the peripheral wall portion 16 due to the outer peripheral portion of the second heat insulating layer 13 when the bottom wall portion 17 is acted on by the force in the case where the peripheral wall portion 16 is joined to the valve bottom surface 5. In the present embodiment, the bottom wall 17 is also bonded (sintered) to the surface 13s of the second heat insulating layer 13, and the thickness of the bottom wall 17 is 1 μm to 30 μm.

Therefore, such a valve 1 produces the following effects.

(1) In the valve 1, the peeling of the outer peripheral portion of the heat insulating layer 11 due to the action of the combustion gas is suppressed while ensuring the heat insulating property of the valve bottom surface 5 as much as possible.

Even when the head portion 4 of the valve 1 is used in a state of being disposed in the combustion chamber S, since the one end surface of the peripheral wall portion 16 of the covering material 15 is joined to the valve bottom surface 5 and the inner peripheral surface 16i of the peripheral wall portion 16 of the covering material 15 is joined to the entire peripheral surface 11p of the heat insulating layer 11 (the first heat insulating layer 12, the second heat insulating layer 13) over the entire thickness range thereof, as shown in fig. 7, the combustion gas does not act on the boundary B1 between the valve bottom surface 5 and the first heat insulating layer 12 and the boundary B2 between the first heat insulating layer 12 and the second heat insulating layer 13. Therefore, the peeling of the outer peripheral portion of the first heat insulating layer 12 from the valve bottom surface 5 or the peeling of the second heat insulating layer 13 from the first heat insulating layer 12 is suppressed.

In the present embodiment, since the bottom wall portion 17 is provided at the other end of the peripheral wall portion 16 of the covering material 15, and the bottom wall portion 17 covers the surface 13s of the second heat insulating layer 13 in a state of being bonded to the surface 13s of the second heat insulating layer 13, the peripheral wall portion 16 and the bottom wall portion 17 enclose the entire heat insulating layer 11, and the combustion gas does not act (enter) at the boundary between the peripheral surface 11p of the heat insulating layer 11 and the inner peripheral surface 16i of the peripheral wall portion 16 of the covering material 15 (see fig. 7), and the peeling of the outer peripheral portion of the heat insulating layer 11 due to the action of the combustion gas is suppressed with high reliability.

On the other hand, not only basic heat insulation with respect to the valve bottom surface 5 is ensured by the heat insulation layer 11, but also heat insulation with respect to a portion of the valve bottom surface 5 where the heat insulation layer 11 is not disposed can be ensured since the peripheral wall portion 16 of the covering material 15 having a heat conductivity as close to that of the heat insulation layer 11 as possible covers the portion.

Therefore, the peripheral wall portion 16 of the heat insulating layer 11 and the covering material 15 can ensure heat insulation against the valve bottom surface 5 as much as possible, and can suppress peeling of the outer peripheral portions of the first heat insulating layer 12 and the second heat insulating layer 13 due to the action of the combustion gas with high reliability.

In this case, regarding thermal expansion and thermal contraction, the thickness of the peripheral wall portion 16 in the covering material 15 is extremely smaller than the radius of the valve bottom surface 5 (the length to be affected by thermal expansion and thermal contraction is small), and the thermal expansion coefficient of the peripheral wall portion 16 (covering material 15) is close to the thermal expansion coefficient of the valve bottom surface 5 (valve main body 1A) to improve the followability, so that the peripheral wall portion 16 is suppressed from peeling off from the valve bottom surface 5 due to thermal expansion or thermal contraction.

On the other hand, as shown in fig. 8, when the peripheral wall portion 16 of the covering material 15 does not cover the entire peripheral surface 11p of the heat insulating layer 11 (the first heat insulating layer 12 and the second heat insulating layer 13), the combustion gas directly acts on the boundary B1 and the boundary B2, and the outer peripheral portion 11a of the heat insulating layer 11 tends to easily peel off from the valve bottom surface 5.

(2) In the valve 1, peeling of the outer peripheral portion 11a of the heat insulating layer 11 due to a difference in thermal expansion or thermal contraction is suppressed.

The present inventors have found that the heat insulating layer outer peripheral portion 11a tends to easily peel off from the valve bottom surface 5, but in the present embodiment, peeling off of the heat insulating layer outer peripheral portion 11a due to a difference in thermal expansion or thermal contraction is suppressed from two different viewpoints.

(2-1) first, as described above, the heat insulating layer 11 is bonded to the valve bottom surface 5 in a state of being reduced in diameter from the valve bottom surface 5. This is specifically reflected in that when the target length D, which is influenced by thermal expansion and thermal contraction, is shortened in the equation for determining the expansion amount difference Δ Le and the contraction amount difference Δ Lc based on the above-described thermal expansion coefficient difference, the expansion amount difference Δ Le and the contraction amount difference Δ Lc become smaller, and the target length D, which is influenced by the expansion amount difference Δ Le and the contraction amount difference Δ Lc, is determined as the length of the joint portion between the heat insulating layer 11 and the valve bottom surface 5.

Thus, as described above, the diameter of the heat insulating layer 11 decreases with respect to the diameter of the valve bottom surface 5, and the peeling of the heat insulating layer outer peripheral portion 11a from the valve bottom surface 5 is suppressed.

FIG. 9 shows the experimental modes and the evaluation of the respective experimental results of experimental examples 1 to 3 for proving the above. Experimental examples 1 to 3 durability tests were performed on valves having structures specific to the experimental examples under common experimental conditions, and the results of the tests were evaluated by a common evaluation method.

(a) Common experimental conditions

Test object

A poppet valve in which a heat insulating layer 11 (first heat insulating layer 12, second heat insulating layer 13) and a coating layer 17 (corresponding to the bottom wall 17 of the coating material 15, and therefore the same reference numeral 17 as that of the bottom wall 17 is used hereinafter) are laminated on the valve bottom surface 5

The heat insulation layer 11: the first heat insulating layer 12 and the second heat insulating layer 13 shown in the first embodiment are stacked

Coating layer 17: only the bottom wall portion 17 of the covering material 15 shown in the first embodiment

Overall layer thickness of the heat insulating layer and the coating layer (hereinafter, referred to as a laminate 26): 120 μm

Combination of valve bottom face 5 with first insulation layer 12, combination of first insulation layer 12 with second insulation layer 13, combination of second insulation layer 13 with cladding 17: sintering

A valve: diameter of valve bottom surface 5: 32mm material: SUH11

Content of the experiment

The valve 1E of each of experimental examples 1 to 3 was subjected to a durability test using a durability tester 20 (valve-seat abrasion tester). As shown in fig. 10, the durability test was: after the valve 1E of each experimental example was placed on the durability tester 20, the valve 1E was moved up and down by the rocker arm 22 while rotating on its axis by the rotor 25, and in this state, the flame from the gas burner 21 was applied to the valve bottom surface 5. In fig. 10 showing the experimental contents, 23 is a thermometer for measuring the temperature of the

valve bottom surface

5, and 24 is a water jacket for cooling the durability tester.

Conditions of durability test

Up-down speed of valve 1E: 3000rpm (corresponding to 6000rpm in engine speed)

Rotation speed (rotation speed) of the valve 1E: 20rpm

Temperature of valve 1E (valve bottom surface temperature): 400 deg.C

Gas used in the gas burner: LPG (liquefied Petroleum gas)

Duration of the durability test: 50hr

Intermediate inspection time of experimental results: 10, 20, 30, 40, 50hr

(b) The test method specific to each test example (the structure of the specific laminate 26 (heat-insulating layer 11 and coating layer 17))

Experimental example 1: a manner in which the valve bottom surface 5 (diameter 32mm) was entirely covered with the laminate 26 (diameter 32mm) (see the structural view of Experimental example 1 in FIG. 9)

Experimental example 2: a manner in which the valve bottom surface 5 (diameter 32mm) was covered with a laminate 26 (diameter 29mm) having a diameter smaller than that of the valve bottom surface 5 (see the structural view of Experimental example 2 in FIG. 9)

Experimental example 3: a diameter of the laminate 26 was reduced (diameter 26mm) further than that in Experimental example 2 (see the structural drawing of Experimental example 3 in FIG. 9)

(c) Common evaluation method

After the experiment of each experimental example, image information of the state of the laminated body 26 on the valve bottom surface 5 (the state viewed from the axial direction of the shaft portion 3 in the valve 1E) was obtained, the peeling area of the laminated body 26 was derived from the image information, and the peeling ratio was obtained by dividing the peeling area by the area of the laminated body 26 covering the valve bottom surface 5 (hereinafter referred to as the total area). Then, the greater the peeling rate, the greater the degree of peeling of the laminate (heat insulating layer 11 and coating layer 17)26 from the valve bottom surface 5.

(d) Results and evaluation of each experiment

In experimental example 1, peeling of the laminate 26 started to occur at the outer peripheral portion of the valve bottom surface 5 10 hours after the start of the experiment, and the state shown in fig. 11 was obtained 20 hours after the start of the experiment, and the peeling rate at 50 hours after the start of the experiment was 11.8%.

In experimental example 2, the state shown in fig. 12 was obtained 50 hours after the start of the experiment, and the peeling rate at this time point was 4.5%.

In experimental example 3, the state shown in fig. 13 was obtained 50 hours after the start of the experiment, and the peeling rate at this time point was 2.8%.

As can be understood from the above, the peeling of the stacked body 26 on the valve bottom surface 5 can be suppressed as the diameter of the stacked body 26 is reduced.

(2-2) secondly, the inner peripheral surface 16i of the peripheral wall portion 16 of the coating material 15 is bonded to the entire peripheral surface of the heat insulating layer 11 in a reduced diameter state over the entire thickness range from the valve bottom surface 5 to the surface 11s of the heat insulating layer 11, and one end surface of the peripheral wall portion 16 is bonded to a portion of the valve bottom surface 5 where the heat insulating layer 11 is not present, and the thermal expansion coefficient of the coating material 15 is as close as possible to the thermal expansion coefficient of the valve bottom surface 5 (head portion 4) and is larger than the thermal expansion coefficient of the heat insulating layer 11.

Thus, during thermal expansion, as shown in fig. 14, the thermal expansion (diameter expansion) of the peripheral wall portion 16 itself, and further the thermal expansion (diameter expansion) of the peripheral wall portion 16 and the valve bottom surface 5 cooperate with each other to stretch the entire peripheral surface 11p of the heat insulating layer 11 outward in the radial direction (see the arrow in fig. 14), and the portion of the heat insulating layer 11 farther from the valve bottom surface 5 is subjected to a large tensile force. Therefore, the thermal expansion amount difference Δ Le due to the difference in thermal expansion coefficient between the valve bottom surface 5 and the heat insulating layer 11 is reduced, and the heat insulating layer 11 is prevented from peeling off due to thermal expansion.

In this case, since the bottom wall 17 of the covering material 15 is also intended to thermally expand (expand) radially outward in the present embodiment, the thermal expansion force thereof acts as a force intended to expand the diameter of the peripheral wall 16, and the tensile force that stretches the entire peripheral surface 11p of the heat insulating layer 11 radially outward is increased, as in the case of the valve bottom surface 5. The wall thickness ratio of the peripheral wall portion 16 is large and the strength thereof is improved, which contributes to reliably applying the tensile force to the entire peripheral surface 11p of the heat insulating layer 11. At this time, even if the outer peripheral portion of the heat insulating layer 11 is intended to warp, a frictional force is generated between the outer peripheral portion of the heat insulating layer 11 and the inner peripheral surface 16i of the peripheral wall portion 16, and even if a force (a force toward the bottom wall portion 17) is generated due to the warp of the outer peripheral portion of the heat insulating layer 11, the bottom wall portion 17 resists the force. Therefore, in the present embodiment, the peeling-off suppressing effect of the heat insulating layer 11 is also improved in accordance with these cases.

On the other hand, during thermal contraction, as shown in fig. 15, the peripheral wall portion 16 itself thermally contracts (shrinks) and further presses (tightens) the entire peripheral surface of the heat insulating layer 11 radially inward in cooperation with the thermal contraction (diameter reduction) of the valve bottom surface 5 (see the arrow in fig. 15), and the portion of the heat insulating layer 11 that is farther from the valve bottom surface 5 receives a larger pressing force. Therefore, the above-described shrinkage amount difference Δ Lc due to the difference in thermal expansion coefficient between the valve bottom surface 5 and the heat insulating layer 11 is reduced, and peeling of the heat insulating layer 11 due to thermal shrinkage is suppressed.

At this time, since the bottom wall portion 17 of the covering material 15 is also intended to be thermally contracted (reduced in diameter) radially outward, the thermal contraction force thereof acts as a force intended to reduce the diameter of the peripheral wall portion 16, and the pressing force for pressing the entire peripheral surface of the heat insulating layer 11 radially inward is increased, as in the case of the valve bottom surface 5. Therefore, the peeling-off suppressing effect of the heat insulating layer 11 is improved in the thermal shrinkage as well as in the thermal expansion.

Fig. 16 shows the experimental mode specific to experimental example 4 for proving the above and evaluation of each experimental result. Experimental example 4 is an example in which the valve 1E having the unique structure was subjected to an endurance test under the common experimental conditions described above, and the experimental results thereof were evaluated by the same common evaluation method as described above.

Experimental example 4 specific Experimental mode

In experimental example 4, the valve bottom surface 5 (diameter 32mm) was covered with the heat insulating layer 11 (diameter 29mm) having a diameter smaller than that of the valve bottom surface, and the heat insulating layer 11 and the portion of the valve bottom surface 5 where the heat insulating layer 11 is not present were covered with the coating material 15 (see the structural diagram of experimental example 4 in fig. 16).

Experimental example 4 Experimental results

In experimental example 4, the state shown in fig. 17 was obtained 50 hours after the start of the experiment, and the peeling rate at this time point was 0%. From this and the experimental results of experimental example 2 described above, it can be understood that the covering material 15, particularly the peripheral wall portion 16 contributes to suppressing the peeling of the heat insulating layer 11 due to the difference in thermal expansion coefficient.

Fig. 18 shows a second embodiment, fig. 19 to 21 show a third embodiment, fig. 22 to 24 show a fourth embodiment, fig. 25 shows a fifth embodiment, and fig. 26 shows a sixth embodiment. In each of the embodiments, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

The second embodiment shown in fig. 18 shows a modification of the first embodiment.

In the second embodiment, the edge portion 6 of the outer peripheral portion of the head portion 4 is formed with a projection 28 as an engaging portion over the entire periphery of the head portion 4.

On the other hand, an extension portion 29 is integrally provided on the peripheral wall portion 16 of the covering material 15, the extension portion 29 extends to the edge portion 6, and the extension portion 29 is mechanically engaged with the protrusion 28 by being bonded (sintered) to the edge portion 6.

This can improve the bonding strength between the coating material 15 and the valve bottom surface 5, and can improve the ability of the bottom wall portion 17 of the coating material 15 to resist the operation such as peeling or warping of the heat insulating layer outer peripheral portion 11 a.

The third embodiment shown in fig. 19 to 21 shows a modification of the first embodiment.

In the third embodiment, the valve bottom surface 5 is formed with a recess 31 that extends radially outward around the radial center of the valve bottom surface 5. The heat insulating layer 11 (the first heat insulating layer 12 and the second heat insulating layer 13 laminated and integrated with the first heat insulating layer 12) is accommodated in the recess 31, the heat insulating layer 11 (the bottom surface of the first heat insulating layer 12) is bonded (for example, sintered) to the bottom wall 31b of the recess 31, and the entire peripheral surface 11p of the heat insulating layer 11 is bonded (for example, sintered) in a state of being in contact with the inner peripheral wall 31wi of the recess 31 as the peripheral wall.

The entire surface 11s (13s) of the heat insulating layer 11 (second heat insulating layer 13) and the valve bottom surface 5 (except for the recess 31) in the recess 31 are coated with the coating material 15, and the coating material 15 is bonded (for example, sintered) to the surface 11s of the heat insulating layer 11 and the valve bottom surface 5 in the recess 31.

Thus, the entire peripheral surface 11p of the heat insulating layer 11 is covered with the pocket inner peripheral wall 31wi of the valve bottom surface 5, and the combustion gas does not directly act on the boundary B1 between the valve bottom surface 5 and the first heat insulating layer 12 and the boundary B2 between the first heat insulating layer 12 and the second heat insulating layer 13. On the other hand, in the third embodiment, not only can basic heat insulation with respect to the valve bottom surface 5 be ensured by the heat insulating layer 11, but also heat insulation with respect to a portion of the valve bottom surface 5 where the heat insulating layer 11 is not disposed can be ensured since the portion is covered with the covering material 15 having a thermal conductivity as close to that of the heat insulating layer 11 as possible.

During thermal expansion, the pocket inner circumferential wall 31wi expands in diameter to stretch the entire circumferential surface 11p of the heat insulating layer 11 outward in the radial direction, and the portion of the heat insulating layer 11 farther from the bottom wall 31b of the pocket 31 receives a large tensile force. On the other hand, during heat shrinkage, the recess inner circumferential wall 31wi is reduced in diameter to press (tighten) the entire circumferential surface 11p of the heat insulating layer 11 radially inward, and the portion of the heat insulating layer 11 farther from the bottom wall 31b of the recess 31 is subjected to a larger pressing force. Therefore, during thermal expansion, the difference in thermal expansion amount due to the difference in thermal expansion coefficient between the pocket bottom wall 31b and the first heat insulating layer 12 and the difference in thermal expansion coefficient between the first heat insulating layer 12 and the second heat insulating layer 13 is reduced, and during thermal contraction, the difference in contraction amount due to the difference in thermal expansion coefficient between the pocket bottom wall 31b and the first heat insulating layer 12 and the difference in thermal expansion coefficient between the first heat insulating layer 12 and the second heat insulating layer 13 is reduced, and peeling of the outer peripheral portion of the heat insulating layer 11 due to the difference in thermal expansion coefficient caused by thermal expansion or thermal contraction is suppressed.

In this case, since the peripheral wall having sufficient strength is used as the peripheral wall by the concave inner peripheral wall 31wi, a tensile force at the time of thermal expansion or a pressing force at the time of thermal contraction can be reliably applied to the peripheral surface of the heat insulating layer 11, and the heat insulating layer 11 can be prevented from peeling off with high reliability due to a difference in thermal expansion coefficient caused by thermal expansion or thermal contraction.

Even if the outer peripheral portion of the heat insulating layer 11 is intended to warp, a frictional force is generated between the outer peripheral portion of the heat insulating layer 11 and the concave inner peripheral wall 31wi, and the covering material 15 resists the force generated by the warp of the outer peripheral portion 11a of the heat insulating layer 11 or the like (force toward the covering material 15). At this time, of course, the actual length of the valve bottom surface 5 in contact with the coating material 15 in the radial direction of the valve bottom surface 5 is limited by the presence of the recess 31, and therefore, the influence of thermal expansion and thermal contraction is reduced, and the bonding strength of the coating material 15 to the valve bottom surface 5 is sufficiently ensured.

The fourth embodiment shown in fig. 22 to 24 shows a modification of the first embodiment.

In the fourth embodiment, it is shown that the heat insulating layer 11 is prevented from cracking due to bending stress based on the difference in thermal expansion coefficient caused by thermal expansion or thermal contraction, and thus it is desired to prevent the heat insulating layer 11 from peeling off from the valve bottom surface 5 due to the cracking. Therefore, in the fourth embodiment, the thickness (the vertical length in fig. 22) of the outer peripheral portion 11a of the heat insulating layer 11 fixed to the valve bottom surface 5, which is flat as a whole, is thinner than the thickness of the portion 11b radially inward of the outer peripheral portion 11a of the heat insulating layer 11.

Specifically, the case of thermal contraction of the valve 1 will be described as an example. In a situation where the thermal expansion coefficient of the heat insulating layer 11 is smaller than the thermal expansion coefficient of the valve bottom surface 5, as shown in fig. 23, when the valve 1 thermally contracts (lower diagram of fig. 23) from the reference state (upper diagram of fig. 23), the heat insulating layer 11 and the valve bottom surface 5 (valve bottom surface portion) integrally flex, and bending stress acts on them. Fig. 24 is an enlarged view of a portion W (outer peripheral portion) shown in fig. 23. As can be seen from fig. 24, when the heat insulating layer 11 on the valve bottom surface 5 is bent by thermal contraction, the bending stress is caused by

σ＝(y/ρ)E

To indicate. Here, ρ: radius of curvature of neutral surface N in outer peripheral portion 11a, y: distance from the neutral plane N, y/ρ: strain, E: modulus of elasticity in the longitudinal direction.

Therefore, the bending stress σ with respect to the heat insulating layer 11 reaches a maximum value when the distance y from the neutral surface N reaches a maximum value, that is, when the distance ymax from the neutral surface N to the outer surface of the heat insulating layer 11 in the wall thickness direction (at the time of edge stress), and the maximum value (maximum bending stress) σ max increases as the distance ymax from the neutral surface N to the outer surface in the wall thickness direction increases. As a result, the maximum bending stress σ max increases as the thickness of the heat insulating layer 11 increases, and in such a case, the possibility of occurrence of cracks in the heat insulating layer 11 increases, and in the case of occurrence of cracks, the depth of the cracks increases as the thickness of the heat insulating layer 11 increases. In particular, in addition to the above-described action of the combustion gas and the action of the difference in thermal expansion coefficient between the heat insulating layer 11 and the valve bottom surface 5, the outer peripheral portion 11a of the heat insulating layer 11 has a tendency that the radius ρ of curvature of the outer peripheral portion 11a of the heat insulating layer caused by thermal expansion or thermal contraction becomes smaller (the tendency that the curvature becomes larger) than the radius ρ' of curvature of the portion 11b radially inward of the outer peripheral portion 11a, and the possibility that cracks occur in the outer peripheral portion 11a becomes larger than the portion 11b radially inward of the outer peripheral portion 11a, as can be seen from the expression for obtaining the above-described bending stress.

Thus, as shown in fig. 22, by making the thickness of the outer peripheral portion 11a of the heat insulating layer 11 thinner than the thickness of the portion 11b radially inward of the outer peripheral portion 11a, the distance y from the neutral surface N to the outer surface in the thickness direction in the heat insulating layer 11 decreases, and the maximum bending stress σ max during thermal expansion and thermal contraction decreases.

Specifically, the thickness of the portion 11b radially inward of the outer peripheral portion 11a of the heat insulating layer 11 is maintained at a constant thickness, while the thickness of the outer peripheral portion 11a is set to be thinner toward the radially outward side of the heat insulating layer 11, and the outer peripheral edge 11aa of the heat insulating layer 11 reaches the vicinity of the outer peripheral edge of the valve bottom surface 5 in a state where the peripheral surface of the heat insulating layer 11 having a minute thickness is formed at the outer peripheral edge 11 aa.

This can reliably prevent the occurrence of cracks in the heat insulating layer outer peripheral portion 11a, and accordingly, the heat insulating layer outer peripheral portion 11a can be prevented from peeling off from the valve bottom surface 5 due to cracks. On the other hand, in this case, since the thickness of only the outer peripheral portion 11a of the heat insulating layer 11 is thinner than the thickness of the radially inner portion 11b of the heat insulating layer 11 and becomes thinner toward the radially outer side, the thickness of the outer peripheral portion 11a of the heat insulating layer 11 is not made as thin as possible, and a decrease in the heat insulating property of the heat insulating layer 11 on the valve bottom surface 5 can be suppressed as much as possible.

In the present embodiment, the coating material 15 covers not only the peripheral surface of the heat insulating layer having a small thickness at the outer peripheral edge 11aa but also the surface 11s of the heat insulating layer 11, and is bonded to the heat insulating layer 11 and the valve bottom surface 5. Therefore, the same action as that of the first embodiment and the like is ensured with respect to the clad material 15.

In the present embodiment, the peripheral surface 11p of the heat insulating layer 11 is defined as a minute thickness portion of the outer peripheral edge 11aa of the heat insulating layer 11, and the other exposed portion is defined as the surface 11s, but a portion including the outer peripheral portion 11a of the heat insulating layer 11 may be defined as the peripheral surface 11p of the heat insulating layer 11.

A fifth embodiment shown in fig. 25 shows a modification of the third and fourth embodiments. In the fifth embodiment, the same components as those in the third and fourth embodiments are denoted by the same reference numerals and their descriptions are omitted except for the first embodiment.

The fifth embodiment shows that the thickness of the outer peripheral portion 11a of the heat insulating layer 11 is reduced in a state where the inner peripheral wall 31wi of the recess 31 is used as the peripheral wall.

In the fifth embodiment, as in the fourth embodiment, a recess 31 that extends radially outward from the radially central portion of the valve bottom surface 5 is formed in the valve bottom surface 5, and the recess inner circumferential wall 31wi is inclined so as to face radially outward of the recess 31 as it faces the opening 31o side of the recess 31. The heat insulating layer 11 is fixed (sintered) to the bottom wall 31b of the recess 31, and the surface 11s of the heat insulating layer 11 is formed as a flat surface, and the peripheral surface 11p thereof is radially outwardly expanded toward the thickness direction surface side of the heat insulating layer 11. The entire peripheral surface 11p of the heat insulating layer 11 is bonded (sintered) in contact with the recess inner peripheral wall 31wi, and the surface of the heat insulating layer 11 is set flush with the portion of the valve bottom surface 5 other than the recess 31.

The coating material 15 is bonded to the surface 11s of the heat insulating layer 11 and the valve bottom surface 5 in the recess 31 so as to coat the entire surface 11s of the heat insulating layer 11 and the valve bottom surface 5, and the surface of the coating material 15 formed on the valve bottom surface 5 is a flat surface.

Therefore, in the fifth embodiment, the entire peripheral surface 11p of the heat insulating layer 11 can be brought into contact with the pocket inner peripheral wall 31wi, and the outer peripheral portion 11a of the heat insulating layer 11 can be made thinner toward the radially outer side thereof, whereby the heat insulating layer 11 can be prevented from peeling off from the valve bottom surface 5 due to the action of the combustion gas and the occurrence of cracks while suppressing the decrease in the heat insulating function of the heat insulating layer 11 as much as possible. Of course, in the present embodiment, since the heat insulating layer 11 is joined to the valve bottom surface 5 in a state of being reduced in diameter compared to the valve bottom surface 5, the peeling-off suppressing effect by the reduced diameter of the heat insulating layer 11 can be obtained.

Further, since the surface 11s of the heat insulating layer 11 is set flush with the portion of the valve bottom surface 5 other than the recess 31 and the surface of the covering material 15 formed on the valve bottom surface 5 is accordingly a flat surface, even when the heat insulating layer 11 is provided on the valve bottom surface 5, the entire valve bottom surface side can be flattened (planarized), and the basic structure and basic performance of a general valve having a flattened valve bottom surface can be ensured.

Further, the coating material 15 bonded to the surface of the heat insulating layer 11 and the valve bottom surface 5 can further suppress the possibility that the heat insulating layer outer peripheral portion 11a peels off from the valve bottom surface 5 against the peeling, warping, and the like of the outer peripheral portion of the heat insulating layer 11. In this case, of course, the actual length of the valve bottom surface 5 in contact with the coating material 15 in the radial direction of the valve bottom surface 5 is limited by the presence of the recess 31, and therefore, the influence of thermal expansion and thermal contraction can be reduced, and the bonding strength of the coating material 15 to the valve bottom surface 5 can be sufficiently ensured.

The sixth embodiment shown in fig. 26 shows a modification of the fourth and fifth embodiments. In the sixth embodiment, the same components as those in the fourth and fifth embodiments are denoted by the same reference numerals and their descriptions are omitted except for the first embodiment.

This sixth embodiment shows an embodiment in which the peeling of the heat insulating layer outer peripheral portion 11a and the flattening of the entire valve bottom surface 5 side are achieved as much as possible, and the heat insulating property of the heat insulating layer 11 is improved as compared with the fifth embodiment.

In the sixth embodiment, the heat insulating layer 11 is joined to the inner peripheral wall 31wi and the bottom wall 31b of the recess 31 in a state of being filled in the recess 31 (the structure in the fifth embodiment), and the surface 11s of the heat insulating layer 11 is formed in a state of being slightly raised outside the opening 31o of the recess 31. Specifically, the surface 11s of the radially inner portion 11b of the heat insulating layer 11 is parallel to the valve bottom surface 5 (recess bottom wall 31b) at a position slightly outside the recess 31 opening 31o, while the surface 11s of the outer peripheral portion 11a of the heat insulating layer 11 is formed so as to expand radially outward toward the inside in the thickness direction of the heat insulating layer 11 (downward in fig. 26), and the outer edge of the surface 11s is connected to the peripheral surface 11p of the heat insulating layer 11 at the position of the recess opening edge 31 oo. Therefore, the entire thickness of the heat insulating layer 11 is made thicker than that of the fifth embodiment while making the heat insulating layer surface 11s as flat as possible.

In the present embodiment, the coating material 15 is bonded to the surface 11s of the heat insulating layer 11 and the valve bottom surface 5 so as to coat the entire surface 11s of the heat insulating layer 11 and the valve bottom surface 5.

Therefore, in the sixth embodiment, the peeling-off suppressing effect of the heat insulating layer outer peripheral portion 11a and the flattening of the entire valve bottom surface 5 side can be achieved as much as possible, and the heat insulating property of the heat insulating layer 11 can be improved as compared with the fifth embodiment.

In the present embodiment, the recess inner circumferential wall 31wi is defined as a circumferential wall, and the surface of the heat insulating layer 11 that abuts against the recess inner circumferential wall 31wi is defined as a circumferential surface 11p, but not only the surface of the heat insulating layer 11 that abuts against the recess inner circumferential wall 31wi but also the surface that abuts against the outer circumferential portion of the covering material 15 may be defined as a circumferential surface 11p, and in this case, the recess inner circumferential wall 31wi and the outer circumferential portion of the covering material 15 form a circumferential wall.

The embodiments have been described above, but the present invention includes the following embodiments.

(1) In each embodiment, as the peripheral wall, a peripheral wall which is formed only by the peripheral wall portion 16 without the bottom wall portion 17 is used.

(2) The thickness of the peripheral wall portion 16 is set so as not to cover the entire portion of the valve bottom surface 5 where the heat insulating layer 11 is not present.

(3) As the engaging portion of the edge portion 6, various engaging portions such as a concave portion are used.

(4) As a material of the valve body 1A, SUH35 (thermal conductivity: about 12.6W/mK (at room temperature)) and thermal expansion coefficient: about 1.5X 10 was used^-6/° c (at room temperature), and the like.

(5) As the heat insulating layer 11, a single layer heat insulating layer and three or more layers heat insulating layers are used.

(6) In the third embodiment (see fig. 21), the pocket inner circumferential wall 31wi is inclined radially inward or radially outward of the pocket 31 as it opens into the pocket 31.

Description of the reference numerals

1 valve

Valve bottom surface

6 edge part

11 insulating layer

11a outer peripheral part of the heat insulating layer

11b radial inner part of the insulation layer

Peripheral surface of 11p heat-insulating layer

Surface of 11s insulating layer

12 first heat insulation layer

13 secondary insulating layer

13s surface of the second thermal insulation layer 13

15 coating material

16 peripheral wall part (peripheral wall)

16i inner peripheral surface of the peripheral wall 16 (inner peripheral surface of peripheral wall)

17 bottom wall part

29 extension

31 recess

31b bottom wall of recess

31wi concave inner peripheral wall (peripheral wall, inner peripheral surface of peripheral wall)

31o recess opening

Radial center of O-valve bottom surface 5

And S, a combustion chamber.

Claims

1. A valve for an internal combustion engine, in which a heat insulating layer is fixed to a valve bottom surface facing a combustion chamber,

2. The valve for an internal combustion engine according to claim 1,

3. The valve for an internal combustion engine according to claim 2,

4. A valve for an internal combustion engine according to claim 3,

the outer edge of the heat insulating layer is set closer to the outer edge of the valve bottom surface than the radially central portion of the valve bottom surface.

5. A valve for an internal combustion engine according to claim 3,

6. A valve for an internal combustion engine according to claim 5,

the coating material contains a heat insulating component.

7. A valve for an internal combustion engine according to claim 3,

8. A valve for an internal combustion engine according to claim 5,

the edge portion is provided with an engaging portion,

9. The valve for an internal combustion engine according to claim 1,

10. The valve for an internal combustion engine according to claim 9,

11. The valve for an internal combustion engine according to claim 9,

12. The valve for an internal combustion engine according to claim 1,

13. The valve for an internal combustion engine according to claim 1,

14. The valve for an internal combustion engine according to claim 13,

15. The valve for an internal combustion engine according to claim 14,

the heat insulation layer is fixed on the bottom wall of the concave part,

16. The valve for an internal combustion engine according to claim 15,

17. The valve for an internal combustion engine according to claim 14,

the heat insulation layer is fixed on the bottom wall of the concave part,

18. The valve for an internal combustion engine according to claim 13,

19. The valve for an internal combustion engine according to claim 13,