Patent Description:
In order to achieve a low fuel consumption rate for an engine, it is important to reduce the amount of heat loss in a combustion chamber of the engine. It is known that forming a thermal barrier coating on the inner wall surface of a cylinder liner which defines the combustion chamber of the engine suppresses the release of heat generated by the combustion of air-fuel mixture to the outside of the combustion chamber through the inner wall surface and thus reduces the heat loss in the combustion chamber (for example, Patent Document <NUM>). The cylinder liner described in Patent Document <NUM> has a first thermal barrier coating formed on the inner wall surface at a portion (a portion mainly constituting the combustion chamber) on the upper side in the cylinder axis direction, and a second thermal barrier coating formed on the inner wall surface at a portion on the lower side in the cylinder axis direction. Each of the first thermal barrier coating and the second thermal barrier coating is formed over the entire circumference on the inner wall surface of the cylinder liner. Further, the second thermal barrier coating has a thermal conductivity smaller than that of the first thermal barrier coating.

If the engine is operated for a long time, the thermal barrier coating may be damaged or worn. For example, in the cylinder liner described in Patent Document <NUM>, as the piston moves vertically along the cylinder axis direction in the cylinder liner, the piston ring mounted on the piston comes into slide contact with the thermal barrier coating, so that the thermal barrier coating may be peeled off from the cylinder liner, or the surface of the thermal barrier coating may be eroded to reduce the thickness of the thermal barrier coating. In addition, the surface of the thermal barrier coating may be eroded due to erosion during engine operation to reduce the thickness of the thermal barrier coating.

Further, if the engine is operated for a long time, deposits such as carbon (soot) generated by the combustion of air-fuel mixture may adhere to the wall surface of the combustion chamber and reduce the fuel efficiency of the engine. In order to avoid the reduction in the fuel efficiency of the engine, maintenance work may be performed to scrape off the deposits from the wall surface of the combustion chamber with a metal brush, for example, but the thermal barrier coating may be damaged during the maintenance work. Therefore, in order to maintain the thermal barrier performance of the thermal barrier coating, it is necessary to replace parts such as the cylinder liner on which the thermal barrier coating is formed. Since the entire part on which the thermal barrier coating is formed, such as the cylinder liner, is replaced, the cost for maintaining the thermal barrier performance of the thermal barrier layer may increase.

In view of the above circumstances, an object of at least one embodiment of the present disclosure is to provide a thermal barrier coating member that can suppress damage to the thermal barrier coating and suppress an increase in the cost for maintaining the thermal barrier performance of the thermal barrier layer.

A thermal barrier coating member according to the present disclosure is at least one thermal barrier coating member mounted on an inner wall surface, facing a combustion chamber of an engine, of a cylinder liner accommodating a piston slidably along the axial direction. The thermal barrier coating member is provided with: a base layer configured to be detachably fitted into a recess formed in the inner wall surface of the cylinder liner; and a thermal barrier coating layer formed on the opposite side of the base layer from the inner wall surface of the cylinder liner. The thermal barrier coating layer is disposed above a piston ring which is positioned at the uppermost position in the axial direction of the cylinder liner when the piston reaches top dead center.

At least one embodiment of the present disclosure provides a thermal barrier coating member that can suppress damage to the thermal barrier coating and suppress an increase in the cost for maintaining the thermal barrier performance of the thermal barrier layer.

Embodiments of the present disclosure will be described below with reference to the accompanying drawings. It is intended, however, that unless particularly identified, dimensions, materials, shapes, relative positions, and the like of components described in the embodiments shall be interpreted as illustrative only and not intended to limit the scope of the present disclosure.

The same features can be indicated by the same reference numerals and not described in detail.

<FIG> is a schematic cross-sectional view of an engine having a combustion chamber according to an embodiment of the present disclosure. <FIG> is a schematic enlarged cross-sectional view of the vicinity of the combustion chamber of the engine shown in <FIG>. As shown in <FIG> and <FIG>, a thermal barrier coating member <NUM> according to some embodiments is mounted on an inner wall surface <NUM> of a cylinder liner <NUM> facing a combustion chamber <NUM> of an engine <NUM>. First, the combustion chamber <NUM> of the engine <NUM> will be described.

As shown in <FIG>, the engine <NUM> includes a cylinder block <NUM>, a cylinder head <NUM>, a piston <NUM>, and a cylinder liner <NUM>. Hereinafter, the extension direction of the center axis CA of the cylinder liner <NUM> (vertical direction in <FIG>) is defined as the axial direction. In the axial direction, the side where the cylinder head <NUM> is located with respect to the piston <NUM> (upper side in <FIG>) is defined as the upper side, and the side opposite to the upper side is defined as the lower side. Further, the direction perpendicular to the axial direction of the cylinder liner <NUM> is defined as the radial direction. In the radial direction, the side toward the center axis CA of the cylinder liner <NUM> is defined as the inner side or inside, and the side away from the center axis CA is defined as the outer side or outside.

The cylinder block <NUM> has a cylindrical space <NUM> extending along the axial direction. In the cylindrical space <NUM>, the cylinder liner <NUM> of cylindrical shape extending along the axial direction is fitted from above in the axial direction. The cylinder liner <NUM> is configured to accommodate the piston <NUM> slidably along the axial direction.

The piston <NUM> is accommodated in an interior space <NUM> defined by an inner wall surface <NUM> of the cylinder liner <NUM>. The piston <NUM> is formed in a bottomed tubular shape including a head portion <NUM> having a circular contour shape when viewed from above in the axial direction and a cylindrical skirt portion <NUM> extending downward along the axial direction from a lower outer peripheral edge of the head portion <NUM> in the axial direction. The piston <NUM> has a top surface <NUM> disposed at the upper side of the head portion <NUM> in the axial direction. In the embodiment shown in <FIG>, the top surface <NUM> has a concave curved surface <NUM> recessed downward in the axial direction toward the inside in the radial direction.

The piston <NUM> is mechanically connected to one end portion <NUM> of a connecting rod <NUM> via a piston pin <NUM>. The connecting rod <NUM> includes the above-described one end portion <NUM> and the other end portion <NUM> disposed on the opposite side from the one end portion <NUM>. The other end portion <NUM> of the connecting rod <NUM> is mechanically connected to a crankshaft <NUM>.

The cylinder head <NUM> is attached to the cylinder block <NUM> so that a lower end portion <NUM> disposed on the lower side in the axial direction abuts on an upper end portion <NUM> of the cylinder block <NUM> disposed on the upper side in the axial direction. A gasket (not shown) may be interposed between the upper end portion <NUM> and the lower end portion <NUM>.

As shown in <FIG>, when the piston <NUM> is at top dead center, the combustion chamber <NUM> is defined between the piston <NUM> and the cylinder head <NUM> in the axial direction. The combustion chamber <NUM> is defined by the top surface <NUM> of the piston <NUM>, a lower surface <NUM> of the cylinder head <NUM> disposed opposite to the top surface <NUM> of the piston <NUM>, and the inner wall surface <NUM> of the cylinder liner <NUM>.

At least one annular piston ring groove <NUM> to which a piston ring <NUM> is mounted is formed on the outer peripheral portion of the head portion <NUM> of the piston <NUM>. In the embodiment shown in <FIG>, three annular piston ring grooves <NUM> are formed on the outer peripheral portion of the head portion <NUM> at separate positions in the axial direction. The piston ring <NUM> mounted in the piston ring groove <NUM> has an outer peripheral surface <NUM> which protrudes outward in the radial direction from the outer peripheral surface <NUM> of the head portion <NUM> and abuts on the inner wall surface <NUM> of the cylinder liner <NUM>. The outer peripheral surface <NUM> slides on the inner wall surface <NUM> of the cylinder liner <NUM> when the piston <NUM> slides in the cylinder liner <NUM> along the axial direction. The gap between the inner wall surface <NUM> of the cylinder liner <NUM> and the outer peripheral surface <NUM> of the piston <NUM> is closed by the piston ring <NUM>.

As shown in <FIG>, inside the cylinder head <NUM>, an intake passage <NUM> for supplying combustion gas to the combustion chamber <NUM> and an exhaust passage <NUM> for discharging exhaust gas from the combustion chamber <NUM> are formed. The intake passage <NUM> allows gas (combustion gas) to flow to the combustion chamber <NUM> through an intake port 16A formed in the lower surface <NUM> of the cylinder head <NUM>. The exhaust passage <NUM> allows gas (exhaust gas) to flow from the combustion chamber <NUM> through an exhaust port 17A formed in the lower surface <NUM> of the cylinder head <NUM>.

As shown in <FIG>, the engine <NUM> includes an intake valve <NUM> configured to open and close the intake port 16A, and an exhaust valve <NUM> configured to open and close the exhaust port 17A. When the intake port 16A is fully closed by the intake valve <NUM>, the supply of intake air from the intake passage <NUM> to the combustion chamber <NUM> is cut off. Further, when the exhaust port 17A is fully closed by the exhaust valve <NUM>, the discharge of exhaust gas from the combustion chamber <NUM> to the exhaust passage <NUM> is cut off.

As shown in <FIG>, the engine <NUM> includes an ignition device <NUM>. In the embodiment shown in <FIG>, the ignition device <NUM> is composed of an ignition plug <NUM> capable of igniting air-fuel mixture. Further, in the embodiment shown in <FIG>, the engine <NUM> is composed of a precombustion chamber engine 1A including a combustion chamber forming portion <NUM> which forms the combustion chamber <NUM> and a precombustion chamber forming portion <NUM> which forms a precombustion chamber <NUM>. In the engine 1A, the ignition device <NUM> is disposed in the precombustion chamber <NUM>. The combustion chamber forming portion <NUM> includes the cylinder head <NUM>, the piston <NUM>, and the cylinder liner <NUM>, which are members defining the combustion chamber <NUM>. In this disclosure, the precombustion chamber engine 1A will be described as an example, but the thermal barrier coating member <NUM> according to some embodiments of the present disclosure can also be applied to an engine of a direct injection type in which the ignition device <NUM> is provided in the combustion chamber <NUM>. The thermal barrier coating member <NUM> according to some embodiments of the present disclosure can be applied to any of a diesel engine, a gas engine, and a gasoline engine.

In the embodiment shown in <FIG>, the precombustion chamber forming portion <NUM> includes a precombustion chamber mouthpiece <NUM> disposed on the cylinder head <NUM> so as to be positioned above the combustion chamber <NUM> (opposite to the piston <NUM> in the axial direction). The precombustion chamber <NUM> is formed in the precombustion chamber mouthpiece <NUM>. The precombustion chamber forming portion <NUM> has a plurality of injection holes <NUM> connecting the precombustion chamber <NUM> formed therein to the outside. The combustion chamber <NUM> communicates with the precombustion chamber <NUM> via the plurality of injection holes <NUM>.

In the embodiment shown in <FIG>, the engine <NUM> includes a fuel supply device <NUM> for directly supplying a fuel gas to the precombustion chamber <NUM> not via the combustion chamber <NUM>. As shown in <FIG>, the fuel supply device <NUM> is configured to supply a fuel gas to the precombustion chamber <NUM>, and the supply amount of the fuel gas to the precombustion chamber <NUM> is controlled by the opening degree of a fuel supply valve <NUM>.

In the engine <NUM> (1A), when the piston <NUM> moves downward in the intake stroke, the intake valve <NUM> opens the intake port 16A, and the exhaust valve <NUM> closes the exhaust port 17A. When the intake port 16A is opened, a lean premixed gas mixing the fuel gas and air is introduced into the combustion chamber <NUM> through the intake passage <NUM>. Further, as the fuel supply valve <NUM> opens, the fuel gas is introduced into the precombustion chamber <NUM>. Meanwhile, in the compression stroke, when the piston <NUM> moves upward, the fuel supply valve <NUM> closes. Further, the lean premixed gas introduced into the combustion chamber <NUM> through the intake port 16A is compressed as the piston <NUM> moves upward, and a part of the lean premixed gas is introduced into the precombustion chamber <NUM> through each of the injection holes <NUM> of the precombustion chamber <NUM>.

In the combustion stroke, the lean premixed gas introduced from the combustion chamber <NUM> to the precombustion chamber <NUM> is mixed with the fuel gas to produce an air-fuel mixture having a concentration suitable for ignition in the precombustion chamber <NUM>. The air-fuel mixture in the precombustion chamber <NUM> is ignited by the ignition device <NUM> at a predetermined timing when the piston <NUM> arrives at the vicinity of the compression top dead center, which leads to combustion of the air-fuel mixture in the precombustion chamber <NUM>. The combustion flame generated by the combustion in the precombustion chamber <NUM> is injected into the combustion chamber <NUM> through each of the injection holes <NUM>, and ignites the lean premixed gas in the combustion chamber <NUM>. This leads to combustion of the lean premixed gas in the combustion chamber <NUM>. The piston <NUM> which receives the combustion pressure of the lean premixed gas in the combustion chamber <NUM> reciprocates (moves vertically) in the cylinder liner <NUM> along the axial direction. The reciprocating motion of the piston <NUM> is converted to a rotational motion by the connecting rod <NUM> and the crankshaft <NUM>.

<FIG> is an explanatory diagram for describing the thermal barrier coating member according to an embodiment of the present disclosure and schematically shows a cross-section along the center axis of the cylinder liner. <FIG> is an explanatory diagram for describing the thermal barrier coating member according to an embodiment of the present disclosure and schematically shows a plan view when the combustion chamber is viewed from below in the axial direction.

As shown in <FIG>, for example, the thermal barrier coating member <NUM> according to some embodiments includes a base layer <NUM> configured to be detachably fitted into a recess <NUM> formed in the inner wall surface <NUM> of the cylinder liner <NUM>, and a thermal barrier coating layer <NUM> formed on the opposite side (inside surface) <NUM> of the base layer <NUM> from the inner wall surface <NUM> of the cylinder liner <NUM>. As shown in <FIG>, the thermal barrier coating layer <NUM> is disposed above the piston ring <NUM> (combustion chamber-side piston ring 12A) which is at the uppermost position of the cylinder liner <NUM> in the axial direction when the piston <NUM> reaches top dead center.

In the illustrated embodiment, as shown in <FIG>, the inner wall surface <NUM> of the cylinder liner <NUM> includes an inner wall surface <NUM> which extends along the axial direction and comes into contact with the outer peripheral surface <NUM> of the piston ring <NUM>, and a step wall surface <NUM> which is disposed above and radially outward of the inner wall surface <NUM> and extends along the axial direction. The upper end of the step wall surface <NUM> is connected to an upper surface <NUM> of the cylinder liner <NUM>. Further, a step surface <NUM> is formed between the lower end of the step wall surface <NUM> and the upper end of the inner wall surface <NUM> to connect them. The step surface <NUM> extends along a direction intersecting (e.g., perpendicular to) the axial direction. The recess <NUM> includes the step wall surface <NUM> and the step surface <NUM>. In the embodiment shown in <FIG>, the recess <NUM> (step wall surface <NUM> and step surface <NUM>) is formed in an annular shape extending along the circumferential direction of the cylinder liner <NUM>.

In the illustrated embodiment, as shown in <FIG>, the base layer <NUM> is formed in a cylindrical shape extending along the axial direction. The base layer <NUM> has an outside surface <NUM> disposed on the outer side in the radial direction, and an inside surface <NUM> disposed on the opposite side from the outside surface <NUM>, that is, on the inner side in the radial direction. The thermal barrier coating layer <NUM> has one surface <NUM> formed on the inside surface <NUM> of the base layer <NUM>, and the other surface <NUM> disposed on the opposite side from the one surface <NUM> and facing the combustion chamber <NUM>. In the embodiment shown in <FIG>, the thermal barrier coating layer <NUM> is formed on the inside surface <NUM> from the upper end to the lower end of the inside surface <NUM>. When the thermal barrier coating member <NUM> is attached to the recess <NUM> of the cylinder liner <NUM>, the outside surface <NUM> of the base layer <NUM> faces the step wall surface <NUM>, and a lower end portion <NUM> of the base layer <NUM> abuts on the step surface <NUM>. The step surface <NUM> and the lower end portion <NUM> of the base layer <NUM> are positioned below the upper end <NUM> of the piston <NUM> when the piston <NUM> reaches top dead center. Further, as shown in <FIG>, the thermal barrier coating layer <NUM> is formed on the inside surface <NUM> over the entire circumference of the cylinder liner <NUM> in the circumferential direction.

The thermal barrier coating layer <NUM> is configured to have a lower thermal conductivity than the base layer <NUM> and the cylinder liner <NUM>. For example, the thermal barrier coating layer <NUM> may be formed by supporting a ceramic made of zirconia, titanium oxide, or aluminum oxide on the inside surface <NUM> of the base layer <NUM> by surface treatment such as thermal spraying, plating, or vacuum vapor deposition. Further, the thermal barrier coating layer <NUM> may be an anodic oxide film formed on the inside surface <NUM> of the base layer <NUM> by anodic oxidation. Further, it may be formed by applying a thermal barrier coating or a heat insulation coating to the inside surface <NUM> of the base layer <NUM>. The thermal barrier coating layer <NUM> is desirably configured to have a high conformability to the temperature of the gas in the combustion chamber <NUM>. For example, when the thermal barrier coating layer <NUM> has a small heat capacity and a high conformability, the temperature difference between the thermal barrier coating layer <NUM> and the gas in the combustion chamber <NUM> can be reduced, so that the heat loss can be reduced.

The base layer <NUM> is configured to have a thermal conductivity equivalent to or lower than the cylinder liner <NUM>. In the illustrated embodiment, the base layer <NUM> is made of aluminum of the same type as the cylinder liner <NUM>. The base layer <NUM> and the cylinder liner <NUM> may be made of steel, titanium, nickel, copper, or an alloy thereof instead of aluminum. The base layer <NUM> may be made of a different material from the cylinder liner <NUM>. For example, in an embodiment, the base layer <NUM> has a smaller linear expansion coefficient than the cylinder liner <NUM> and a higher linear expansion coefficient than the thermal barrier coating layer <NUM>. In this case, since the difference in the linear expansion coefficient between the base layer <NUM> and the thermal barrier coating layer <NUM> is small, when the base layer <NUM> and the thermal barrier coating layer <NUM> expand due to heat transferred from the combustion chamber <NUM>, it is possible to prevent the thermal barrier coating layer <NUM> from separating from the base layer <NUM>.

The replacement of the thermal barrier coating member <NUM> will be described with reference to <FIG>. First, the cylinder head <NUM> is detached from the cylinder block <NUM>. Then, the thermal barrier coating member <NUM> is pulled out upward in the axial direction, removed from the cylinder liner <NUM>, and replaced with a new thermal barrier coating member <NUM>. After the thermal barrier coating member <NUM> is replaced, the cylinder head <NUM> is attached to the cylinder block <NUM>. The replacement of the thermal barrier coating member <NUM> can be performed more easily and quickly than the replacement of the cylinder liner <NUM> on which the thermal barrier coating is directly formed.

In the illustrated embodiment, as shown in <FIG>, each of the step surface <NUM> of the recess <NUM> and the lower end portion <NUM> of the base layer <NUM> is disposed above a combustion chamber-side piston ring 12A when the piston <NUM> reaches top dead center. In this case, since the thermal barrier coating member <NUM> can be removed from the cylinder liner <NUM> regardless of the position of the piston <NUM> incorporated in the engine <NUM>, the thermal barrier coating member <NUM> can be easily replaced. Further, when each of the step surface <NUM> of the recess <NUM> and the lower end portion <NUM> of the base layer <NUM> is disposed above the combustion chamber-side piston ring 12A when the piston <NUM> reaches top dead center, it is unnecessary to smoothly connect the cylinder liner <NUM> and the thermal barrier coating member <NUM>. Thus, strict dimensional control is not required for the thermal barrier coating member <NUM>. However, in some embodiments, each of the step surface <NUM> of the recess <NUM> and the lower end portion <NUM> of the base layer <NUM> may be disposed below the combustion chamber-side piston ring 12A when the piston <NUM> reaches top dead center.

If the thermal barrier coating is directly formed on the cylinder liner <NUM>, when the piston <NUM> is assembled from above the cylinder liner <NUM> at the time of manufacturing or replacement of parts, the thermal barrier coating of the cylinder liner <NUM> may be damaged due to the piston <NUM>. Assembling the piston <NUM> from below the cylinder liner <NUM> in order to avoid damage to the thermal barrier coating of the cylinder liner <NUM> requires the assembling of the cylinder liner <NUM> incorporated with the piston <NUM> to the engine <NUM>, which takes a lot of effort. In contrast, when the thermal barrier coating layer <NUM> is provided on the thermal barrier coating member <NUM> that is detachable from the cylinder liner <NUM>, it is easy to assemble the piston <NUM>. Specifically, by removing the thermal barrier coating member <NUM> from the cylinder liner <NUM> when the piston <NUM> is assembled to the engine <NUM>, the piston <NUM> can be assembled from above the cylinder liner <NUM> without damaging the thermal barrier coating layer <NUM>. After the piston <NUM> is assembled to the engine <NUM>, by attaching the thermal barrier coating member <NUM> to the cylinder liner <NUM>, damage to the thermal barrier coating layer <NUM> can be reduced.

As described above, for example as shown in <FIG>, the thermal barrier coating member <NUM> according to some embodiments includes the base layer <NUM> configured to be detachably fitted into the recess <NUM> formed in the inner wall surface <NUM> of the cylinder liner <NUM>, and the thermal barrier coating layer <NUM> formed on the opposite side (inside surface) <NUM> of the base layer <NUM> from the inner wall surface <NUM> of the cylinder liner <NUM>. As shown in <FIG>, the thermal barrier coating layer <NUM> is disposed above the combustion chamber-side piston ring 12A when the piston <NUM> reaches top dead center.

According to the above configuration, the thermal barrier coating member <NUM> includes the base layer <NUM> and the thermal barrier coating layer <NUM> formed on the opposite side (inside surface) <NUM> of the base layer <NUM> from the inner wall surface <NUM> of the cylinder liner <NUM>. Further, the base layer <NUM> of the thermal barrier coating member <NUM> is configured to be detachably fitted into the recess <NUM> of the cylinder liner <NUM>. Accordingly, by replacing the thermal barrier coating member <NUM>, the thermal barrier coating layer <NUM> can be replaced without replacing the cylinder liner <NUM>. In contrast, when the thermal barrier coating layer <NUM> is directly formed on the cylinder liner <NUM>, the cylinder liner <NUM> needs to be replaced in order to replace the thermal barrier coating layer <NUM>. Thus, with the above-described thermal barrier coating member <NUM>, since the thermal barrier coating layer <NUM> can be replaced without replacing the cylinder liner <NUM>, as compared to the case where the thermal barrier coating layer <NUM> is directly formed on the cylinder liner <NUM>, it is possible to suppress an increase in the cost for maintaining the thermal barrier performance of the thermal barrier coating layer <NUM>.

Specifically, according to the above configuration, the replacement of the thermal barrier coating member <NUM> can be performed easily and quickly. Further, since deposits adhering to the thermal barrier coating layer <NUM> can be removed with the thermal barrier coating member <NUM> detached from the cylinder liner <NUM>, as compared to the case where the thermal barrier coating layer <NUM> is directly formed on the cylinder liner <NUM>, the maintenance of the thermal barrier coating layer <NUM> can be performed easily and quickly. Thus, with the above-described thermal barrier coating member <NUM>, since the replacement and maintenance of the thermal barrier coating layer <NUM> can be performed easily and quickly, it is possible to suppress an increase in the cost for maintaining the thermal barrier performance of the thermal barrier coating layer <NUM>. Further, if a high-performance thermal barrier coating layer <NUM> will be developed, it is easy to change to the high-performance thermal barrier coating layer <NUM>.

If the thermal barrier coating layer <NUM> is disposed vertically across the piston ring (combustion chamber-side piston ring 12A) which is positioned at the uppermost position of the cylinder liner <NUM> in the axial direction when the piston <NUM> reaches top dead center, when the piston <NUM> moves vertically along the axial direction, the piston ring <NUM> comes into slide contact with the thermal barrier coating layer <NUM>, so that the thermal barrier coating layer <NUM> is damaged by the contact with the piston ring <NUM>, and the thermal barrier performance of the thermal barrier coating layer <NUM> may decrease. In contrast, according to the above configuration, the thermal barrier coating layer <NUM> is disposed above the combustion chamber-side piston ring 12A when the piston <NUM> reaches top dead center. Accordingly, even when the piston <NUM> moves vertically along the axial direction, the piston ring <NUM> does not come into contact with the thermal barrier coating layer <NUM>. Therefore, with the above-described thermal barrier coating member <NUM>, it is possible to prevent the thermal barrier performance of the thermal barrier coating layer <NUM> from decreasing due to the contact with the piston ring <NUM>, and it is possible to maintain the thermal barrier performance of the thermal barrier coating layer <NUM> for a long time. Thus, since the replacement frequency of the thermal barrier coating member <NUM> can be reduced, it is possible to suppress an increase in the cost for maintaining the thermal barrier performance of the thermal barrier coating layer <NUM>.

In addition, the heat loss (heat input) from the combustion chamber <NUM> to the cylinder liner <NUM> is larger at an upper portion of the cylinder liner <NUM> (for example, the portion above the upper end <NUM> of the piston <NUM>), which is exposed to heat for a long time in the combustion chamber <NUM>, than at a lower portion of the cylinder liner <NUM>. Therefore, sufficient thermal barrier effect can be obtained by the thermal barrier coating member <NUM> which insulates heat at the upper portion of the cylinder liner <NUM>.

Hereinafter, with reference to <FIG>, some modification examples of the thermal barrier coating member <NUM> (7A) will be described. The thermal barrier coating member <NUM> described below has basically the same configuration as the thermal barrier coating member <NUM> (7A) described above. In the following modifications, the same features as those of the thermal barrier coating member <NUM>(7A) are denoted by the same reference sings, and description thereof will be omitted. The characteristic features of each modification will be mainly described below.

Generally, when the piston <NUM> moves vertically along the axial direction in the cylinder liner <NUM>, the piston <NUM> swings in the rotational direction about the axis CB of the piston pin <NUM> which rotatably supports the piston <NUM>. If the upper portion of the piston <NUM> collides with the thermal barrier coating layer <NUM> due to the swinging motion of the piston <NUM>, the thermal barrier coating layer <NUM> may be damaged.

<FIG> are each an explanatory diagram for describing the first to fourth modification examples of the thermal barrier coating member according to an embodiment of the present disclosure. <FIG> schematically show a cross-section of the engine <NUM> taken along the center axis CA of the cylinder liner <NUM>.

In some embodiments, as shown in <FIG>, the base layer <NUM> includes a coated portion <NUM> on which the thermal barrier coating layer <NUM> is formed, and an exposed portion <NUM> on which the thermal barrier coating layer <NUM> is not formed. At least a part of the exposed portion <NUM> has a protrusion <NUM> which protrudes to the opposite side from the inner wall surface <NUM> with respect to the coated portion <NUM>. Of the protrusions <NUM>, the protrusion <NUM> formed at the lower end portion <NUM> of the base layer <NUM> in the axial direction is referred to as a lower protrusion <NUM>.

In the embodiment shown in <FIG>, the inside surface <NUM> of the base layer <NUM> has an upper inside surface <NUM> extending downward along the axial direction from the upper end of the base layer <NUM>, a lower inside surface <NUM> disposed below the upper inside surface <NUM> and radially inward of the upper inside surface <NUM> and extending along the axial direction, and a step surface <NUM> connecting the lower end of the upper inside surface <NUM> and the upper end of the lower inside surface <NUM>. The step surface <NUM> extends along a direction intersecting (e.g., perpendicular to) the axial direction. The thermal barrier coating layer <NUM> is formed from the upper end to the lower end of the upper inside surface <NUM> and is not formed on the lower inside surface <NUM>. The lower inside surface <NUM> is disposed radially inward of the other surface <NUM> of the thermal barrier coating layer <NUM> facing the combustion chamber <NUM>. In other words, the coated portion <NUM> includes the upper inside surface <NUM>, and the protrusion <NUM> (lower protrusion <NUM>) includes the lower inside surface <NUM>.

In the embodiment shown in <FIG>, the inside surface <NUM> of the base layer <NUM> has an upper inside surface <NUM> extending downward along the axial direction from the upper end of the base layer <NUM>, and a lower inclined surface <NUM> inclined radially inward toward the lower side in the axial direction from the lower end of the upper inside surface <NUM>. The thermal barrier coating layer <NUM> is formed from the upper end of the upper inside surface <NUM> to an upper portion 824A of the lower inclined surface <NUM> and is not formed on a lower portion of the lower inclined surface <NUM>. The lower portion of the lower inclined surface <NUM> is disposed radially inward of the other surface <NUM> of the thermal barrier coating layer <NUM> facing the combustion chamber <NUM>. In other words, the coated portion <NUM> includes the upper inside surface <NUM> and the upper portion 824A of the lower inclined surface <NUM>, and the lower protrusion <NUM> (protrusion <NUM>) includes the lower portion of the lower inclined surface <NUM>.

In the embodiment shown in <FIG>, the inside surface <NUM> of the base layer <NUM> has an inclined surface <NUM> formed from the upper end to the lower end of the base layer <NUM>. The inclined surface <NUM> is inclined radially inward toward the lower side in the axial direction. The thermal barrier coating layer <NUM> is formed on an upper portion 825A of the inclined surface <NUM> and is not formed on a lower portion 825B of the inclined surface <NUM>. In the illustrated embodiment, the thermal barrier coating layer <NUM> is formed on the inclined surface <NUM> from the upper end of the inclined surface <NUM> to the lower side of the center of the inclined surface <NUM>. The lower portion 825B of the inclined surface <NUM> is disposed radially inward of the other surface <NUM> of the thermal barrier coating layer <NUM> facing the combustion chamber <NUM>. In other words, the coated portion <NUM> includes the upper portion 825A of the inclined surface <NUM>, and the lower protrusion <NUM> (protrusion <NUM>) includes the lower portion 825B of the inclined surface <NUM>.

In the embodiment shown in <FIG>, the inside surface <NUM> of the base layer <NUM> has an upper inside surface <NUM> extending downward along the axial direction from the upper end of the base layer <NUM>, a lower inside surface <NUM> disposed below the upper inside surface <NUM> and extending along the axial direction, a lower inclined surface <NUM> inclined radially inward toward the lower side in the axial direction from the lower end of the lower inside surface <NUM>, and a protruding surface portion <NUM> disposed between the upper inside surface <NUM> and the lower inside surface <NUM> and protruding radially inward with respect to the upper inside surface <NUM> and the lower inside surface <NUM>. In the illustrated embodiment, the protruding surface portion <NUM> has an upward inclined surface 828A inclined radially inward toward the lower side from the lower end of the upper inside surface <NUM>, and a downward inclined surface 828B inclined radially inward toward the upper side from the upper end of the lower inside surface <NUM>.

In the embodiment shown in <FIG>, the thermal barrier coating layer <NUM> has a first thermal barrier coating layer 9A formed on at least the upper inside surface <NUM> and a second thermal barrier coating layer 9B formed on at least the lower inside surface <NUM>. In the illustrated embodiment, the first thermal barrier coating layer 9A is further formed on an upper portion of the upward inclined surface 828A. Further, the second thermal barrier coating layer 9B is further formed on a lower portion of the downward inclined surface 828B and an upper portion 827A of the lower inclined surface <NUM>. A lower portion of the upward inclined surface 828A and an upper portion of the downward inclined surface 828B of the protruding surface portion <NUM> and the lower portion of the lower inclined surface <NUM> are disposed radially inward of the other surfaces <NUM> of the first thermal barrier coating layer 9A and the second thermal barrier coating layer 9B. In other words, the coated portion <NUM> includes the upper inside surface <NUM>, the upper portion of the upward inclined surface 828A, and the lower portion of the downward inclined surface 828B, the lower inside surface <NUM>, and the upper portion 827A of the lower inclined surface <NUM>. The lower protrusion <NUM> includes the lower portion of the lower inclined surface <NUM>, and the protrusion <NUM> further includes an upper protrusion <NUM> disposed above the lower protrusion <NUM> in the axial direction. In the illustrated embodiment, the upper protrusion <NUM> includes a tip portion of the protruding surface portion <NUM>, that is, the lower portion of the upward inclined surface 828A and the upper portion of the downward inclined surface 828B.

According to the above configuration, the base layer <NUM> of the thermal barrier coating member <NUM> has the protrusion <NUM> which protrudes to the opposite side from the inner wall surface <NUM> with respect to the coated portion <NUM>. In this case, when the piston <NUM> swings, the upper portion of the piston <NUM> collides with the protrusion <NUM> not coated with the thermal barrier coating layer <NUM>, so that it is possible to prevent the upper portion of the piston <NUM> from colliding with the thermal barrier coating layer <NUM>. By preventing the upper portion of the piston <NUM> from colliding with the thermal barrier coating layer <NUM>, it is possible to maintain the thermal barrier performance of the thermal barrier coating layer <NUM> for a long time.

In some embodiments, as shown in <FIG>, the protrusion <NUM> includes the lower protrusion <NUM> formed at the lower end portion <NUM> of the base layer <NUM> in the axial direction, and the coated portion <NUM> is disposed above the lower protrusion <NUM> in the axial direction. According to the above configuration, the lower protrusion <NUM> is disposed below the coated portion <NUM> (thermal barrier coating layer <NUM>) in the axial direction. In this case, when the piston <NUM> moves upward while swinging, the upper portion of the piston <NUM> collides with the lower protrusion <NUM> at an early stage. This restricts the swinging motion of the piston <NUM> and corrects the position of the piston <NUM>. Thus, it is possible to effectively prevent the collision between the thermal barrier coating layer <NUM> disposed above the lower protrusion <NUM> and the upper portion of the piston <NUM>.

In some embodiments, as shown in <FIG>, <FIG>, and <FIG>, the coated portion <NUM> has a first inner surface <NUM> extending along the axial direction. The upper inside surface <NUM> in <FIG> and <FIG> corresponds to the first inner surface <NUM>. Further, each of the upper inside surface <NUM> and the lower inside surface <NUM> in <FIG> corresponds to the first inner surface <NUM>.

According to the above configuration, the coated portion <NUM> has the first inner surface <NUM> extending along the axial direction. The thickness of the thermal barrier coating layer <NUM> formed on the first inner surface <NUM> can be easily made uniform at the time of film formation. By making the thickness of the thermal barrier coating layer <NUM> uniform, it is possible to prevent the thermal barrier performance from varying with the position of the thermal barrier coating layer <NUM>, so that it is possible to effectively exhibit the thermal barrier effect of the thermal barrier coating layer <NUM>.

In some embodiments, as shown in <FIG>, the coated portion <NUM> has a second inner surface <NUM> inclined such that a distance from the center axis CA of the cylinder liner <NUM> increases toward the upper side in the axial direction. Each of the upper portion 824A of the lower inclined surface <NUM> in <FIG> and the upper portion 825A of the inclined surface <NUM> in <FIG> corresponds to the second inner surface <NUM>. Further, each of the upper portion of the upward inclined surface 828A and the upper portion 827A of the lower inclined surface <NUM> in <FIG> corresponds to the second inner surface <NUM>.

According to the above configuration, the coated portion <NUM> has the second inner surface <NUM> inclined such that a distance from the center axis CA of the cylinder liner <NUM> increases toward the upper side in the axial direction. The thermal barrier coating layer <NUM> formed on the second inner surface <NUM> can be easily tapered toward the lower end at the time of film formation of the lower edge <NUM>. By forming the lower edge <NUM> of the thermal barrier coating layer <NUM> in a tapered shape, it is possible to prevent the thermal barrier coating layer <NUM> from separating from the base layer <NUM>. By preventing the separation of the thermal barrier coating layer <NUM> from the base layer <NUM>, it is possible to maintain the thermal barrier performance of the thermal barrier coating layer <NUM> for a long time. Thus, since the replacement frequency of the thermal barrier coating member <NUM> can be reduced, it is possible to suppress an increase in the cost for maintaining the thermal barrier performance of the thermal barrier coating layer <NUM>.

In the embodiments shown in <FIG>, the coated portion <NUM> has the second inner surface <NUM>, and the lower edge <NUM> of the thermal barrier coating layer <NUM> has a tapered shape. In this case, as compared to the case where the thermal barrier coating layer <NUM> has a uniform thickness, the thermal barrier coating layer <NUM> can be formed to the lower side of the base layer <NUM> while suppressing an increase in the gap between the outer peripheral surface <NUM> of the piston <NUM> and the inside surface <NUM> of the base layer <NUM>. By reducing the gap, the heat loss in the combustion chamber <NUM> due to the gap can be reduced.

In some embodiments, as shown in <FIG>, the coated portion <NUM> has a third inner surface <NUM> inclined such that a distance from the center axis CA of the cylinder liner <NUM> increases toward the lower side in the axial direction. The lower portion of the downward inclined surface 828B in <FIG> corresponds to the third inner surface <NUM>.

According to the above configuration, the coated portion <NUM> has the third inner surface <NUM> inclined such that a distance from the center axis CA of the cylinder liner <NUM> increases toward the lower side in the axial direction. The thermal barrier coating layer <NUM> formed on the third inner surface <NUM> can be easily tapered toward the upper end at the time of film formation of the upper edge <NUM>. By forming the upper edge <NUM> of the thermal barrier coating layer <NUM> in a tapered shape, it is possible to prevent the thermal barrier coating layer <NUM> from separating from the base layer <NUM>. By preventing the separation of the thermal barrier coating layer <NUM> from the base layer <NUM>, it is possible to maintain the thermal barrier performance of the thermal barrier coating layer <NUM> for a long time. Thus, since the replacement frequency of the thermal barrier coating member <NUM> can be reduced, it is possible to suppress an increase in the cost for maintaining the thermal barrier performance of the thermal barrier coating layer <NUM>.

In some embodiments, as shown in <FIG>, the protrusion <NUM> includes the lower protrusion <NUM>, and the upper protrusion <NUM> disposed above the lower protrusion <NUM> in the axial direction. As shown in <FIG>, at least a part (the whole in the illustrated example) of the upper protrusion <NUM> is positioned below the upper end <NUM> of the piston <NUM> when the piston <NUM> reaches top dead center. According to the above configuration, the protrusion <NUM> includes the lower protrusion <NUM> and the upper protrusion <NUM> disposed above the lower protrusion <NUM> in the axial direction. In this case, by making the upper portion of the piston <NUM> to collide with either of the upper protrusion <NUM> or the lower protrusion <NUM>, which are at different axial positions, it is possible to effectively prevent the collision between the thermal barrier coating layer <NUM> and the upper portion of the piston <NUM>.

In some embodiments, as shown in <FIG>, the thermal barrier coating layer <NUM> is configured such that at least one of the upper edge <NUM> or the lower edge <NUM> is tapered toward the tip side. According to the above configuration, since the thermal barrier coating layer <NUM> is configured such that at least one of the upper edge <NUM> or the lower edge <NUM> is tapered toward the tip side, it is possible to prevent the upper edge <NUM> or the lower edge <NUM> from separating from the base layer <NUM>. By preventing the separation of the thermal barrier coating layer <NUM> from the base layer <NUM>, it is possible to maintain the thermal barrier performance of the thermal barrier coating layer <NUM> for a long time. Thus, since the replacement frequency of the thermal barrier coating member <NUM> can be reduced, it is possible to suppress an increase in the cost for maintaining the thermal barrier performance of the thermal barrier coating layer <NUM>.

<FIG> are each an explanatory diagram for describing the fifth to eighth modification examples of the thermal barrier coating member according to an embodiment of the present disclosure. <FIG> schematically show a plan view of the engine <NUM> when the combustion chamber <NUM> is viewed from below in the axial direction. In <FIG>, the hatching of the cylinder liner <NUM> is omitted.

In some embodiments, as shown in <FIG>, in a plan view of the combustion chamber <NUM> viewed from below in the axial direction, the protrusion <NUM> is formed in a predetermined range R1, R2 (a range of at least ±<NUM>°) in the circumferential direction of the cylinder liner <NUM> with respect to a first straight line SL1 extending from the center axis CA of the cylinder liner <NUM> in the direction perpendicular to the axis CB of the piston pin <NUM>. In the illustrated embodiment, the base layer <NUM> does not have the protrusion <NUM> in the pair of ranges between the predetermined range R1 and the predetermined range R2 in the circumferential direction of the cylinder liner <NUM>.

In <FIG>, in the above-described plan view, of the intersections P1 and P2 between the first straight line SL1 and the inside surface <NUM> of the base layer <NUM>, the position of one intersection P1 is defined as the <NUM>° position, the clockwise direction about the center axis CA is defined as the forward direction, and the circumferential angle in the forward direction with respect to the <NUM>° position is defined as θ.

In the embodiment shown in <FIG>, the protrusion <NUM> includes a one-side protrusion 86A formed in the predetermined range R1 based on the <NUM>° position and an other-side protrusion 86B formed in the predetermined range R2 based on the <NUM>° position. As each of the predetermined ranges R1, R2 is enlarged, the possibility that the protrusion <NUM> collides with the upper portion of the piston <NUM> is increased, but the area where the thermal barrier coating layer <NUM> is formed on the base layer <NUM> is reduced, so that the thermal barrier effect of the thermal barrier coating layer <NUM> is reduced.

In the illustrated embodiment, the one-side protrusion 86A is formed at least in the range of -<NUM>°≤θ≤<NUM>°. The other-side protrusion 86B is formed at least in the range of <NUM>°≤θ≤<NUM>°. The predetermined range R1, R2 may be, for example, a range of ±<NUM>° or a range of ±<NUM>°.

Since the piston <NUM> swings in the direction perpendicular to the axis CB of the piston pin <NUM>, there is a high possibility that the upper portion of the piston <NUM> collides with the thermal barrier coating member <NUM> in the predetermined range R1, R2 (for example, ±<NUM>°) in the circumferential direction of the cylinder liner <NUM> with respect to the first straight line SL1 extending in the direction perpendicular to the axis CB of the piston pin <NUM>. According to the above configuration, since the protrusion <NUM> (one-side protrusion 86A and other-side protrusion 86B) is formed in the predetermined range R1, R2 where the upper portion of the piston <NUM> is likely to collide with the thermal barrier coating member <NUM> to make the upper portion of the piston <NUM> to collide with the protrusion <NUM>, it is possible to effectively prevent the collision between the thermal barrier coating layer <NUM> and the upper portion of the piston <NUM>.

Further, in the above-described thermal barrier coating member <NUM>, since the protrusion <NUM> is formed in a limited range in the circumferential direction of the cylinder liner <NUM>, as compared to the case where the protrusion <NUM> is formed over the entire circumference in the circumferential direction of the cylinder liner <NUM>, the area where the thermal barrier coating layer <NUM> is formed on the base layer <NUM> can be enlarged, so that the thermal barrier effect of the thermal barrier coating layer <NUM> can be improved.

In some embodiments, as shown in <FIG>, the base layer <NUM> includes a coated portion <NUM> on which the thermal barrier coating layer <NUM> is formed, and an exposed portion <NUM> on which the thermal barrier coating layer <NUM> is not formed. As shown in <FIG>, in a plan view of the combustion chamber <NUM> viewed from below in the axial direction, the coated portion <NUM> is formed out of a predetermined range R3, R4 (e.g., a range of ±<NUM>°) in the circumferential direction of the cylinder liner <NUM> with respect to a first straight line SL1 extending from the center axis CA of the cylinder liner <NUM> in the direction perpendicular to the axis CB of the piston pin <NUM>. In the illustrated embodiment, the base layer <NUM> does not have the coated portion <NUM> in the predetermined range R3 and the predetermined range R4 in the circumferential direction of the cylinder liner <NUM>.

In <FIG>, as in <FIG>, in the above-described plan view, of the intersections P1 and P2 between the first straight line SL1 and the inside surface <NUM> of the base layer <NUM>, the position of one intersection P1 is defined as the <NUM>° position, the clockwise direction about the center axis CA is defined as the forward direction, and the circumferential angle in the forward direction with respect to the <NUM>° position is defined as θ.

In the embodiment shown in <FIG>, the coated portion <NUM> includes a one-side coated portion 84A formed in one range R5 of a pair of ranges R5, R6 between the predetermined range R3 based on the <NUM>° position and the predetermined range R4 based on the <NUM>° position in the circumferential direction of the cylinder liner <NUM>, and an other-side coated portion 84B formed in the other range R6. As each of the predetermined ranges R3, R4 where the coated portion <NUM> is not formed is enlarged, the possibility that the upper portion of the piston <NUM> collides with the thermal barrier coating layer <NUM> is decreased, but the area where the thermal barrier coating layer <NUM> is formed on the base layer <NUM> is reduced, so that the thermal barrier effect of the thermal barrier coating layer <NUM> is reduced.

In the illustrated embodiment, the one-side coated portion 84A is formed at least in the range of <NUM>°≤θ≤<NUM>°. The other-side coated portion 84B is formed at least in the range of <NUM>°≤θ≤<NUM>°. The predetermined range R3, R4 may be, for example, a range of ±<NUM>° or a range of ±<NUM>°.

Since the piston <NUM> swings in the direction perpendicular to the axis CB of the piston pin <NUM>, there is a high possibility that the upper portion of the piston <NUM> collides with the thermal barrier coating member <NUM> in the predetermined range R3, R4 (for example, ±<NUM>°) in the circumferential direction of the cylinder liner <NUM> with respect to the first straight line SL1 extending in the direction perpendicular to the axis CB of the piston pin <NUM>. If the thermal barrier coating layer <NUM> is separated from the base layer <NUM> due to the collision between the upper portion of the piston <NUM> and the thermal barrier coating layer <NUM> of the thermal barrier coating member <NUM>, the vicinity of the separated portion becomes easy to separate, so that the separation of the thermal barrier coating layer <NUM> from the base layer <NUM> may progress, and the thermal barrier performance of the thermal barrier coating layer <NUM> may deteriorate at an early stage. According to the above configuration, since the coated portion <NUM> is not formed in the predetermined range R3, R4 (for example, ±<NUM>°) where the upper portion of the piston <NUM> is likely to collide with the thermal barrier coating member <NUM>, it is possible to effectively prevent the collision between the thermal barrier coating layer <NUM> and the upper portion of the piston <NUM>. By preventing the collision between the thermal barrier coating layer <NUM> and the upper portion of the piston <NUM>, it is possible to prevent the thermal barrier coating layer <NUM> from separating from the base layer <NUM>, so that it is possible to maintain the thermal barrier performance of the thermal barrier coating layer <NUM> for a long time.

In some embodiments, as shown in <FIG>, the base layer <NUM> includes a coated portion <NUM> on which the thermal barrier coating layer <NUM> is formed, and an exposed portion <NUM> on which the thermal barrier coating layer <NUM> is not formed. As shown in <FIG>, in a plan view of the combustion chamber <NUM> viewed from below in the axial direction, the coated portion <NUM> is formed out of a predetermined range R7, R8 (e.g., a range of ±<NUM>°) in the circumferential direction of the cylinder liner <NUM> with respect to a second straight line SL2 extending from the center axis CA of the cylinder liner <NUM> and passing through the center CP of the intake port 16A.

In <FIG>, in the above-described plan view, the position of the intersection P3 between the second straight line SL2 and the inside surface <NUM> of the base layer <NUM> is defined as the <NUM>° position, the clockwise direction about the center axis CA is defined as the forward direction, and the circumferential angle in the forward direction with respect to the <NUM>° position is defined as θ.

In the embodiment shown in <FIG>, two intake ports 16A are formed on the lower surface <NUM> of the cylinder head <NUM> at separate positions in the circumferential direction of the cylinder liner <NUM>. The coated portion <NUM> is not formed in a predetermined range R7 in the circumferential direction of the cylinder liner <NUM> with respect to the second straight line SL2 passing through the center CP of one of the intake ports 16A and a predetermined ranges R8 in the circumferential direction of the cylinder liner <NUM> with respect to the second straight line SL2 passing through the center CP of the other intake port 16A.

In the embodiment shown in <FIG>, the coated portion <NUM> includes a one-side coated portion 84C formed in a narrower range R9 of a pair of ranges R9, R10 between the predetermined range R7 and the predetermined range R8 in the circumferential direction of the cylinder liner <NUM>, and an other-side coated portion 84D formed in the other wider range R10. As each of the predetermined ranges R7, R8 where the coated portion <NUM> is not formed is enlarged, the transfer of heat stored in the thermal barrier coating layer <NUM> to the combustion gas is suppressed, but the area where the thermal barrier coating layer <NUM> is formed on the base layer <NUM> is reduced, so that the thermal barrier effect of the thermal barrier coating layer <NUM> is reduced. The predetermined range R7, R8 may be, for example, a range of ±<NUM>° or a range of ±<NUM>°.

If the thermal barrier coating layer <NUM> is disposed in the vicinity of the intake port 16A, the combustion gas (e.g., combustion air) introduced into the combustion chamber <NUM> through the intake port 16A may be heated and expanded by heat stored in the thermal barrier coating layer <NUM> before combustion, resulting in a decrease in combustion efficiency. According to the above configuration, the thermal barrier coating layer <NUM> does not have the coated portion <NUM> in the vicinity of the intake port 16A, i.e., in a plan view of the combustion chamber <NUM> viewed from below in the axial direction, in the predetermined range R7, R8 (e.g., a range of ±<NUM>°) in the circumferential direction of the cylinder liner <NUM> with respect to the second straight line SL2 extending from the center axis CA of the cylinder liner <NUM> and passing through the center CP of the intake port 16A, but has the coated portion <NUM> in the range R9, R10 other than the predetermined range R7, R8. Thus, since the coated portion <NUM> is not formed in the vicinity of the intake port 16A, the combustion gas introduced into the combustion chamber <NUM> through the intake port 16A is prevented from being heated by heat stored in the thermal barrier coating layer <NUM> before combustion, suppressing a decrease in combustion efficiency.

In the above-described embodiments, for example as shown in <FIG>, the base layer <NUM> of the thermal barrier coating member <NUM> is formed in an annular shape extending along the circumferential direction of the cylinder liner <NUM>. However, as shown in <FIG>, it may be formed in an arc shape (semicircular shape in the illustrated example) extending along the circumferential direction of the cylinder liner <NUM>. As shown in <FIG>, a plurality of (two in the illustrated example) thermal barrier coating members <NUM> may be detachably fitted into the recess <NUM> of the cylinder liner <NUM>. Further, the recess <NUM> of the cylinder liner <NUM> may be an arcshaped groove extending along the circumferential direction of the cylinder liner <NUM>.

The present disclosure is not limited to the embodiments described above, but includes modifications to the embodiments described above, and embodiments composed of combinations of those embodiments. For example, the engine <NUM> on which the thermal barrier coating member <NUM> is mounted may be used for any of a marine engine, a power generation engine, and an automobile engine. When the engine <NUM> is a marine engine or a power generation engine, since the engine is operated for a long period of time, replacement work and maintenance work are required more frequently than in an automobile engine, and the replacement work and the maintenance work need to be performed quickly. Therefore, the present invention is particularly useful for a marine engine and a power generation engine.

The contents described in the above embodiments would be understood as follows, for instance.

<NUM>) A thermal barrier coating member (<NUM>) according to at least one embodiment of the present disclosure is at least one thermal barrier coating member (<NUM>) mounted on an inner wall surface (<NUM>), facing a combustion chamber (<NUM>) of an engine (<NUM>), of a cylinder liner (<NUM>) accommodating a piston (<NUM>) slidably along an axial direction. The thermal barrier coating member (<NUM>) comprises: a base layer (<NUM>) configured to be detachably fitted into a recess (<NUM>) formed in the inner wall surface (<NUM>) of the cylinder liner (<NUM>); and a thermal barrier coating layer (<NUM>) formed on an opposite side (inside surface <NUM>) of the base layer (<NUM>) from the inner wall surface (<NUM>) of the cylinder liner (<NUM>). The thermal barrier coating layer (<NUM>) is disposed above a piston ring (combustion chamber-side piston ring 12A) which is positioned at an uppermost position in the axial direction of the cylinder liner (<NUM>) when the piston (<NUM>) reaches top dead center.

According to the above configuration <NUM>), the thermal barrier coating member (<NUM>) includes the base layer (<NUM>) and the thermal barrier coating layer (<NUM>) formed on the opposite side (inside surface <NUM>) of the base layer (<NUM>) from the inner wall surface (<NUM>) of the cylinder liner (<NUM>). Further, the base layer (<NUM>) of the thermal barrier coating member (<NUM>) is configured to be detachably fitted into the recess (<NUM>) of the cylinder liner (<NUM>). Accordingly, by replacing the thermal barrier coating member (<NUM>), the thermal barrier coating layer (<NUM>) can be replaced without replacing the cylinder liner (<NUM>). In contrast, when the thermal barrier coating layer (<NUM>) is directly formed on the cylinder liner (<NUM>), the cylinder liner (<NUM>) needs to be replaced in order to replace the thermal barrier coating layer (<NUM>). Thus, with the above-described thermal barrier coating member (<NUM>), since the thermal barrier coating layer (<NUM>) can be replaced without replacing the cylinder liner (<NUM>), as compared to the case where the thermal barrier coating layer (<NUM>) is directly formed on the cylinder liner (<NUM>), it is possible to suppress an increase in the cost for maintaining the thermal barrier performance of the thermal barrier coating layer (<NUM>).

If the thermal barrier coating layer (<NUM>) is disposed vertically across the piston ring (combustion chamber-side piston ring 12A) which is positioned at the uppermost position of the cylinder liner (<NUM>) in the axial direction when the piston (<NUM>) reaches top dead center, when the piston (<NUM>) moves vertically along the axial direction, the piston ring (<NUM>) comes into slide contact with the thermal barrier coating layer (<NUM>), so that the thermal barrier coating layer (<NUM>) is damaged by the contact with the piston ring (<NUM>), and the thermal barrier performance of the thermal barrier coating layer (<NUM>) may decrease. In contrast, according to the above configuration <NUM>), the thermal barrier coating layer (<NUM>) is disposed above the combustion chamber-side piston ring (12A) when the piston (<NUM>) reaches top dead center. Accordingly, even when the piston (<NUM>) moves vertically along the axial direction, the piston ring (<NUM>) does not come into contact with the thermal barrier coating layer (<NUM>). Therefore, with the above-described thermal barrier coating member (<NUM>), it is possible to prevent the thermal barrier performance of the thermal barrier coating layer (<NUM>) from decreasing due to the contact with the piston ring (<NUM>), and it is possible to maintain the thermal barrier performance of the thermal barrier coating layer (<NUM>) for a long time. Thus, since the replacement frequency of the thermal barrier coating member (<NUM>) can be reduced, it is possible to suppress an increase in the cost for maintaining the thermal barrier performance of the thermal barrier coating layer (<NUM>).

<NUM>) In some embodiments, in the thermal barrier coating member (<NUM>) described in <NUM>), the base layer (<NUM>) includes: a coated portion (<NUM>) on which the thermal barrier coating layer (<NUM>) is formed; and an exposed portion (<NUM>) on which the thermal barrier coating layer (<NUM>) is not formed. At least a part of the exposed portion (<NUM>) has a protrusion (<NUM>) which protrudes to the opposite side from the inner wall surface (<NUM>) with respect to the coated portion (<NUM>).

Generally, when the piston (<NUM>) moves vertically along the axial direction in the cylinder liner (<NUM>), the piston (<NUM>) swings in the rotational direction about the axis of the piston pin (<NUM>). If the upper portion of the piston (<NUM>) collides with the thermal barrier coating layer (<NUM>) due to the swinging motion of the piston (<NUM>), the thermal barrier coating layer (<NUM>) may be damaged. According to the above configuration <NUM>), the base layer (<NUM>) of the thermal barrier coating member (<NUM>) has the protrusion (<NUM>) which protrudes to the opposite side from the inner wall surface (<NUM>) with respect to the coated portion (<NUM>). In this case, when the piston (<NUM>) swings, the upper portion of the piston (<NUM>) collides with the protrusion (<NUM>) not coated with the thermal barrier coating layer (<NUM>), so that it is possible to prevent the upper portion of the piston (<NUM>) from colliding with the thermal barrier coating layer (<NUM>). By preventing the upper portion of the piston (<NUM>) from colliding with the thermal barrier coating layer (<NUM>), it is possible to maintain the thermal barrier performance of the thermal barrier coating layer (<NUM>) for a long time.

<NUM>) In some embodiments, in the thermal barrier coating member (<NUM>) described in <NUM>), the protrusion (<NUM>) includes a lower protrusion (<NUM>) formed at a lower end portion of the base layer (<NUM>) in the axial direction. The coated portion (<NUM>) is disposed above the lower protrusion (<NUM>) in the axial direction.

According to the above configuration <NUM>), the lower protrusion (<NUM>) is disposed below the coated portion (<NUM>) in the axial direction. In this case, when the piston (<NUM>) moves upward while swinging, the upper portion of the piston (<NUM>) collides with the lower protrusion (<NUM>) at an early stage. This restricts the swinging motion of the piston (<NUM>) and corrects the position of the piston (<NUM>). Thus, it is possible to effectively prevent the collision between the thermal barrier coating layer (<NUM>) and the upper portion of the piston (<NUM>).

<NUM>) In some embodiments, in the thermal barrier coating member (<NUM>) described in <NUM>), the coated portion (<NUM>) has a first inner surface (<NUM>) extending along the axial direction.

According to the above configuration <NUM>), the coated portion (<NUM>) has the first inner surface (<NUM>) extending along the axial direction. The thickness of the thermal barrier coating layer (<NUM>) formed on the first inner surface (<NUM>) can be easily made uniform at the time of film formation. By making the thickness of the thermal barrier coating layer (<NUM>) uniform, it is possible to prevent the thermal barrier performance from varying with the position of the thermal barrier coating layer (<NUM>), so that it is possible to effectively exhibit the thermal barrier effect of the thermal barrier coating layer (<NUM>).

<NUM>) In some embodiments, in the thermal barrier coating member (<NUM>) described in <NUM>) or <NUM>), the coated portion (<NUM>) has a second inner surface (<NUM>) inclined such that a distance from a center axis (CA) of the cylinder liner (<NUM>) increases toward an upper side in the axial direction.

According to the above configuration <NUM>), the coated portion (<NUM>) has the second inner surface (<NUM>) inclined such that a distance from the center axis (CA) of the cylinder liner (<NUM>) increases toward the upper side in the axial direction. The thermal barrier coating layer (<NUM>) formed on the second inner surface (<NUM>) can be easily tapered toward the lower end at the time of film formation of the lower edge (<NUM>). By forming the lower edge (<NUM>) of the thermal barrier coating layer (<NUM>) in a tapered shape, it is possible to prevent the thermal barrier coating layer (<NUM>) from separating from the base layer (<NUM>). By preventing the separation of the thermal barrier coating layer (<NUM>) from the base layer (<NUM>), it is possible to maintain the thermal barrier performance of the thermal barrier coating layer (<NUM>) for a long time. Thus, since the replacement frequency of the thermal barrier coating member (<NUM>) can be reduced, it is possible to suppress an increase in the cost for maintaining the thermal barrier performance of the thermal barrier coating layer (<NUM>).

<NUM>) In some embodiments, in the thermal barrier coating member (<NUM>) described in any one of <NUM>) to <NUM>), the protrusion (<NUM>) further includes an upper protrusion (<NUM>) disposed above the lower protrusion (<NUM>) in the axial direction.

According to the above configuration <NUM>), the protrusion (<NUM>) includes the lower protrusion (<NUM>) and the upper protrusion (<NUM>) disposed above the lower protrusion (<NUM>) in the axial direction. In this case, by making the upper portion of the piston (<NUM>) to collide with either of the upper protrusion (<NUM>) or the lower protrusion (<NUM>), which are at different axial positions, it is possible to effectively prevent the collision between the thermal barrier coating layer (<NUM>) and the upper portion of the piston (<NUM>).

<NUM>) In some embodiments, in the thermal barrier coating member (<NUM>) described in any one of <NUM>) to <NUM>), in a plan view of the combustion chamber (<NUM>) viewed from below in the axial direction, the protrusion (<NUM>) is formed within a range of at least ±<NUM>° in a circumferential direction of the cylinder liner (<NUM>) with respect to a first straight line (SL1) extending from a center axis (CA) of the cylinder liner (<NUM>) in a direction perpendicular to an axis (CB) of a piston pin (<NUM>) which rotatably supports the piston (<NUM>).

Since the piston (<NUM>) swings in the direction perpendicular to the axis (CB) of the piston pin (<NUM>), there is a high possibility that the upper portion of the piston (<NUM>) collides with the thermal barrier coating member (<NUM>) in the predetermined range (R1, R2 (for example, ±<NUM>°)) in the circumferential direction of the cylinder liner (<NUM>) with respect to the first straight line (SL1) extending in the direction perpendicular to the axis (CB) of the piston pin (<NUM>). According to the above configuration <NUM>), since the protrusion (<NUM>) is formed in the predetermined range (R1, R2) where the upper portion of the piston (<NUM>) is likely to collide with the thermal barrier coating member (<NUM>) to make the upper portion of the piston (<NUM>) to collide with the protrusion (<NUM>), it is possible to effectively prevent the collision between the thermal barrier coating layer (<NUM>) and the upper portion of the piston (<NUM>).

<NUM>) In some embodiments, in the thermal barrier coating member (<NUM>) described in any one of <NUM>) to <NUM>), at least one of an upper edge (<NUM>) or a lower edge (<NUM>) of the thermal barrier coating layer (<NUM>) is tapered toward a tip side.

According to the above configuration <NUM>), since the thermal barrier coating layer (<NUM>) is configured such that at least one of the upper edge (<NUM>) or the lower edge (<NUM>) is tapered toward the tip side, it is possible to prevent the upper edge (<NUM>) or the lower edge (<NUM>) from separating from the base layer (<NUM>). By preventing the separation of the thermal barrier coating layer (<NUM>) from the base layer (<NUM>), it is possible to maintain the thermal barrier performance of the thermal barrier coating layer (<NUM>) for a long time. Thus, since the replacement frequency of the thermal barrier coating member (<NUM>) can be reduced, it is possible to suppress an increase in the cost for maintaining the thermal barrier performance of the thermal barrier coating layer (<NUM>).

<NUM>) In some embodiments, in the thermal barrier coating member (<NUM>) described in any one of <NUM>) to <NUM>), the base layer (<NUM>) includes: a coated portion (<NUM>) on which the thermal barrier coating layer (<NUM>) is formed; and an exposed portion (<NUM>) on which the thermal barrier coating layer (<NUM>) is not formed. In a plan view of the combustion chamber (<NUM>) viewed from below in the axial direction, the coated portion (<NUM>) is formed in a range other than ±<NUM>° in a circumferential direction of the cylinder liner (<NUM>) with respect to a first straight line (SL1) extending from a center axis (CA) of the cylinder liner (<NUM>) in a direction perpendicular to an axis (CB) of a piston pin (<NUM>) which rotatably supports the piston (<NUM>).

Since the piston (<NUM>) swings in the direction perpendicular to the axis (CB) of the piston pin (<NUM>), there is a high possibility that the upper portion of the piston (<NUM>) collides with the thermal barrier coating member (<NUM>) in the predetermined range (R3, R4) (for example, ±<NUM>°) in the circumferential direction of the cylinder liner (<NUM>) with respect to the first straight line (SL1) extending in the direction perpendicular to the axis (CB) of the piston pin (<NUM>). If the thermal barrier coating layer (<NUM>) is separated from the base layer (<NUM>) due to the collision between the upper portion of the piston (<NUM>) and the thermal barrier coating layer (<NUM>) of the thermal barrier coating member (<NUM>), the vicinity of the separated portion becomes easy to separate, so that the separation of the thermal barrier coating layer (<NUM>) from the base layer (<NUM>) may progress, and the thermal barrier performance of the thermal barrier coating layer (<NUM>) may deteriorate at an early stage. According to the above configuration <NUM>), since the coated portion (<NUM>) is not formed in the predetermined range (R3, R4 (for example, ±<NUM>°)) where the upper portion of the piston (<NUM>) is likely to collide with the thermal barrier coating member (<NUM>), it is possible to effectively prevent the collision between the thermal barrier coating layer (<NUM>) and the upper portion of the piston (<NUM>). By preventing the collision between the thermal barrier coating layer (<NUM>) and the upper portion of the piston (<NUM>), it is possible to prevent the thermal barrier coating layer (<NUM>) from separating from the base layer (<NUM>), so that it is possible to maintain the thermal barrier performance of the thermal barrier coating layer (<NUM>) for a long time.

<NUM>) In some embodiments, in the thermal barrier coating member (<NUM>) described in any one of <NUM>) to <NUM>), the base layer (<NUM>) includes: a coated portion (<NUM>) on which the thermal barrier coating layer (<NUM>) is formed; and an exposed portion (<NUM>) on which the thermal barrier coating layer (<NUM>) is not formed. In a plan view of the combustion chamber (<NUM>) viewed from below in the axial direction, the coated portion (<NUM>) is formed in a range other than ±<NUM>° in a circumferential direction of the cylinder liner (<NUM>) with respect to a second straight line (SL2) extending from a center axis (CA) of the cylinder liner (<NUM>) and passing through center (CP) of an intake port (16A).

Claim 1:
A thermal barrier coating member (<NUM>), at least one of which is configured to be mounted on an inner wall surface (<NUM>,<NUM>) of a cylinder liner (<NUM>) accommodating a piston (<NUM>) slidably along an axial direction, the inner wall surface (<NUM>,<NUM>) facing a combustion chamber (<NUM>) of an engine, the thermal barrier coating member (<NUM>) comprising:
a base layer (<NUM>) configured to be detachably fitted into a recess (<NUM>) formed in the inner wall surface (<NUM>,<NUM>) of the cylinder liner (<NUM>); and
a thermal barrier coating layer (<NUM>) formed on an opposite side (<NUM>) of the base layer (<NUM>) from the inner wall surface (<NUM>,<NUM>) of the cylinder liner (<NUM>),
wherein the thermal barrier coating layer (<NUM>) is configured to be disposed above a piston ring (<NUM>) which is positioned at an uppermost position in the axial direction of the cylinder liner (<NUM>) when the piston (<NUM>) reaches top dead center;
wherein the base layer (<NUM>) includes:
a coated portion (<NUM>) on which the thermal barrier coating layer (<NUM>) is formed; and
an exposed portion (<NUM>) on which the thermal barrier coating layer (<NUM>) is not formed, and
wherein at least a part of the exposed portion (<NUM>) has a protrusion (<NUM>) which protrudes to the opposite side from the inner wall surface (<NUM>,<NUM>) with respect to the coated portion (<NUM>);
wherein the protrusion (<NUM>) includes a lower protrusion formed at a lower end portion of the base layer (<NUM>) in the axial direction, and
wherein the coated portion (<NUM>) is disposed above the lower protrusion in the axial direction;
wherein the thermal barrier coating layer (<NUM>) has one surface (<NUM>) formed on the inside surface of the base layer (<NUM>) and the other surface (<NUM>) disposed on the opposite side from the one surface (<NUM>), and
characterized in that
the lower protrusion is disposed radially inward of the other (<NUM>) surface of the thermal barrier coating layer