Thermal insulation film component

Abstract

The present application provides a heat-insulating film member. The heat-insulating film member of the present application is at least one heat-insulating film member installed on an inner wall surface of a combustion chamber of an engine in a cylinder liner in which a piston is slidably accommodated in an axial direction, and has: a base layer configured to be detachably fitted to a recess formed on the inner wall surface of the cylinder liner; and a heat-insulating film layer formed on a surface of the base layer opposite to the inner wall surface of the cylinder liner, the heat-insulating film layer being disposed above a piston ring located at an uppermost side in the axial direction of the cylinder liner when the piston reaches a top dead center.

Description

Heat insulation film components

[0001] This application is a divisional application of the invention patent application filed on June 25, 2020, with application number 202080093128.0 and title "Heat Insulation Film Component". Technical Field

[0002] The present invention relates to a heat insulation film component mounted on a cylinder liner that slidably houses a piston along the axial direction. Background Technology

[0003] To achieve low fuel consumption in engines, reducing heat loss within the engine combustion chamber is crucial. It is known that a structure reduces heat loss within the combustion chamber by forming a heat-insulating film on the inner wall surface of the cylinder liner that divides the engine combustion chamber, thereby suppressing the release of heat generated from the combustion of the fuel-air mixture through the inner wall surface towards the outside of the combustion chamber (e.g., Patent Document 1). The cylinder liner described in Patent Document 1 has: a first heat-insulating film formed on the inner wall surface of a portion located above the cylinder axis (primarily constituting the combustion chamber); and a second heat-insulating film formed on the inner wall surface of a portion located below the cylinder axis. Both the first and second heat-insulating films are formed over the entire circumferential direction of the inner wall surface of the cylinder liner. Furthermore, the second heat-insulating film has a lower thermal conductivity than the first heat-insulating film.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-21537 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] If the engine is run for an extended period, there is a possibility of damage or wear to the heat insulation film. For example, in the cylinder liner described in Patent Document 1, as the piston moves vertically within the cylinder liner along the cylinder axis, the piston rings mounted on the piston come into contact with the heat insulation film, sliding and moving simultaneously. Therefore, it is possible for the heat insulation film to peel off from the cylinder liner, or for its surface to be sheared away, reducing its thickness. Additionally, corrosion during engine operation may further reduce the surface area of ​​the heat insulation film, decreasing its thickness.

[0009] Furthermore, if the engine is run for extended periods, deposits such as carbon (coal) produced by the combustion of the air-fuel mixture will adhere to the combustion chamber walls, potentially reducing the engine's fuel efficiency. To prevent this reduction, maintenance work is sometimes performed, such as scraping off the deposits with a metal brush and removing them from the combustion chamber walls. However, this maintenance work may damage the heat insulation film. Therefore, to maintain the heat insulation performance of the film, it is necessary to replace components with the heat insulation film, such as cylinder liners. Replacing the entire component with the heat insulation film, such as cylinder liners, can potentially increase the cost of maintaining the heat insulation performance of the insulation layer.

[0010] In view of the above, at least one embodiment of the present invention aims to provide a heat insulation film component that can suppress damage to the heat insulation film and suppress the increased cost caused by maintaining the heat insulation performance of the heat insulation layer.

[0011] Technical solutions for solving the problem

[0012] The heat insulation film component of the present invention is at least one heat insulation film component installed on the inner wall surface of the combustion chamber facing the engine of a cylinder liner that slidably houses a piston along the axial direction, wherein it has: a base layer configured to be detachably fitted relative to a recess formed on the inner wall surface of the cylinder liner; and a heat insulation film layer formed on the surface of the base layer opposite to the inner wall surface of the cylinder liner, the heat insulation film layer being disposed above the piston ring on the uppermost axial side of the cylinder liner when the piston reaches top dead center.

[0013] Invention Effects

[0014] According to at least one embodiment of the present invention, a heat insulation film component is provided, which can suppress damage to the heat insulation film and suppress the increase in cost resulting from maintaining the heat insulation performance of the heat insulation layer. Attached Figure Description

[0015] Figure 1 is a schematic cross-sectional view of an engine with a combustion chamber according to an embodiment of the present invention.

[0016] Figure 2 is an enlarged schematic cross-sectional view showing the area near the combustion chamber of the engine in Figure 1.

[0017] Figure 3 is an explanatory diagram illustrating a heat insulation film component according to an embodiment of the present invention, and is an explanatory diagram schematically showing a cross section along the central axis of the cylinder liner.

[0018] Figure 4 is an explanatory diagram illustrating the heat insulation film component in one embodiment of the present invention, and is a schematic diagram showing the plane of the combustion chamber as viewed from an axially downward perspective.

[0019] Figure 5 is an explanatory diagram illustrating a first modified example of the heat insulation film component in one embodiment of the present invention.

[0020] Figure 6 is an explanatory diagram illustrating a second modified example of the heat insulation film component in one embodiment of the present invention.

[0021] Figure 7 is an explanatory diagram illustrating a third modified example of the heat insulation film component according to an embodiment of the present invention.

[0022] Figure 8 is an explanatory diagram illustrating a fourth modified example of the heat insulation film component according to an embodiment of the present invention.

[0023] Figure 9 is an explanatory diagram illustrating a fifth modified example of the heat insulation film component in one embodiment of the present invention.

[0024] Figure 10 is an explanatory diagram illustrating a sixth modified example of the heat insulation film component according to an embodiment of the present invention.

[0025] Figure 11 is an explanatory diagram illustrating a seventh modified example of the heat insulation film component according to an embodiment of the present invention.

[0026] Figure 12 is an explanatory diagram illustrating an eighth modified example of the heat insulation film component according to an embodiment of the present invention. Detailed Implementation

[0027] Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the constituent components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples.

[0028] For example, expressions such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" that indicate relative or absolute configuration not only strictly indicate such configuration, but also indicate the state of relative displacement by angle or distance with tolerance or to the extent that the same function can be obtained.

[0029] For example, expressions indicating the equality of things such as "same", "equal" and "homogeneous" not only indicate a state of strict equality, but also indicate a state of difference where there is a tolerance or a difference that can achieve the same degree of functionality.

[0030] For example, expressions representing shapes such as quadrilaterals or cylinders not only refer to shapes in a strictly geometric sense, but also to shapes that include concave or convex parts or chamfered parts within the range where the same effect can be obtained.

[0031] On the other hand, expressions that "include," "contain," or "have" a constituent element are not exclusive expressions that exclude the existence of other constituent elements.

[0032] In addition, the same markings are sometimes used for the same structures and the descriptions are omitted.

[0033] (engine)

[0034] Figure 1 is a schematic cross-sectional view of an engine with a combustion chamber according to an embodiment of the present invention. Figure 2 is a schematic cross-sectional view showing an enlarged view of the vicinity of the combustion chamber of the engine in Figure 1. As shown in Figures 1 and 2, in some embodiments, a heat insulation film component 7 is mounted on the inner wall surface 61 of the cylinder liner 6 facing the combustion chamber 10 of the engine 1. First, the combustion chamber 10 of the engine 1 will be described.

[0035] As shown in Figure 1, the engine 1 has a cylinder block 3, a cylinder head 4, a piston 5, and a cylinder liner 6. Hereinafter, the direction of extension of the central axis CA of the cylinder liner 6 (the vertical direction in Figure 1) is defined as the axial direction; the side of the cylinder head 4 relative to the piston 5 in the axial direction (the upper side in Figure 1) is defined as the upper side; and the side opposite to this upper side is defined as the lower side. Furthermore, the direction orthogonal to the axial direction of the cylinder liner 6 is defined as the radial direction; the side radially towards the central axis CA of the cylinder liner 6 is defined as the inner side; and the side away from the central axis CA is defined as the outer side.

[0036] A cylindrical space 30 extending axially is formed on the cylinder block 3. A cylindrical cylinder liner 6 extending axially is inserted into this cylindrical space 30 from the upper axial side. The cylinder liner 6 is configured to slidably accommodate the piston 5 along the axial direction.

[0037] The piston 5 is housed within an internal space 60 defined by the inner wall surface 61 of the cylinder liner 6. The piston 5 is formed as a bottomed cylindrical shape, having a cap 51 with a circular profile when viewed from the upper axial side and a cylindrical skirt 52 extending axially downward from the lower outer periphery of the cap 51. The piston 5 has a top surface 53 disposed on the upper axial side of the cap 51. In the embodiment shown in FIG. 1, the top surface 53 has a concave curved surface 531 that is recessed axially downward as it moves radially inward.

[0038] The piston 5 is mechanically connected to one end 141 of the connecting rod 14 via a piston pin 13. The connecting rod 14 includes the one end 141 and another end 142 located on the opposite side of the one end 141. The other end 142 of the connecting rod 14 is mechanically connected to the crankshaft 15.

[0039] The cylinder head 4 is mounted on the cylinder body 3 such that its lower end 41, located on the axially lower side, abuts against the upper end 31, located on the axially upper side. Alternatively, a gasket (not shown) may be sandwiched between the upper end 31 and the lower end 41.

[0040] As shown in Figure 2, when the piston 5 is at top dead center, the combustion chamber 10 is divided between the piston 5 and the cylinder head 4 in the axial direction. The combustion chamber 10 is divided by the top surface 53 of the piston 5, the lower surface 42 of the cylinder head 4 located opposite to the top surface 53 of the piston 5, and the inner wall surface 61 of the cylinder liner 6.

[0041] At least one annular piston ring groove 54 for mounting piston ring 12 is formed on the outer periphery of the cap portion 51 of piston 5. In the embodiment shown in FIG. 2, three piston ring grooves 54 are formed on the outer periphery of the cap portion 51 at axially spaced positions. The piston ring 12 mounted on the piston ring groove 54 has an outer peripheral surface 121 that protrudes radially outward from the outer peripheral surface 55 of the cap portion 51 and abuts against the inner wall surface 61 of the cylinder liner 6. When piston 5 slides axially within cylinder liner 6, the outer peripheral surface 121 slides on the inner wall surface 61 of cylinder liner 6. The gap between the inner wall surface 61 of cylinder liner 6 and the outer peripheral surface 55 of piston 5 is closed by piston ring 12.

[0042] As shown in Figure 2, an intake flow path 16 for delivering combustion gases to the combustion chamber 10 and an exhaust flow path 17 for discharging exhaust gases from the combustion chamber 10 are formed inside the cylinder head 4. The intake flow path 16, through an intake port 16A formed on the lower surface 42 of the cylinder head 4, allows gas (combustion gases) to flow between itself and the combustion chamber 10. The exhaust flow path 17, through an exhaust port 17A formed on the lower surface 42 of the cylinder head 4, allows gas (exhaust gases) to flow between itself and the combustion chamber 10.

[0043] As shown in Figure 2, the engine 1 includes: an intake valve 18 configured to open and close an intake port 16A; and an exhaust valve 19 configured to open and close an exhaust port 17A. When the intake port 16A is fully closed by the intake valve 18, the intake air supply from the intake flow path 16 to the combustion chamber 10 is cut off. Furthermore, when the exhaust port 17A is fully closed by the exhaust valve 19, the exhaust from the combustion chamber 10 to the exhaust flow path 17 is cut off.

[0044] As shown in Figure 2, the engine 1 has an ignition device 24. In the embodiment shown in Figure 2, the ignition device 24 includes a spark plug 241 capable of igniting (igniting) a gas-fuel mixture. Furthermore, in the embodiment shown in Figure 2, the engine 1 is configured as a secondary combustion chamber engine 1A having a combustion chamber forming portion 11 forming the aforementioned combustion chamber 10 and a secondary combustion chamber forming portion 21 forming a secondary combustion chamber 20. In engine 1A, the ignition device 24 is disposed in the secondary combustion chamber 20. The combustion chamber forming portion 11 includes a cylinder head 4, a piston 5, and a cylinder liner 6, which define the combustion chamber 10. In this invention, the secondary combustion chamber engine 1A is described as an example, but the heat insulation film component 7 of several embodiments of the present invention can also be applied to direct injection engines where the ignition device 24 is disposed in the combustion chamber 10. The heat insulation film component 7 of some embodiments of the present invention can also be applied to any of diesel engines, gas engines, and gasoline engines.

[0045] In the embodiment shown in FIG2, the auxiliary combustion chamber forming portion 21 is located at the upper part of the combustion chamber 10 (opposite to the piston 5 in the axial direction) and is constituted by an auxiliary chamber port metal part 22 provided on the cylinder head 4. The auxiliary combustion chamber 20 is formed inside the auxiliary chamber port metal part 22. The auxiliary combustion chamber forming portion 21 is formed with a plurality of nozzles 23 that communicate with the auxiliary combustion chamber 20 formed therein to the outside, and the combustion chamber 10 and the auxiliary combustion chamber 20 are connected through these plurality of nozzles 23.

[0046] In the embodiment shown in FIG2, the engine 1 has a fuel supply device 25 that supplies fuel gas directly to the auxiliary combustion chamber 20 without passing through the combustion chamber 10. As shown in FIG2, the fuel supply device 25 is configured to supply fuel gas to the auxiliary combustion chamber 20, and the amount of fuel gas supplied to the auxiliary combustion chamber 20 is controlled by the opening of the fuel supply valve 26.

[0047] During the intake stroke of engine 1 (1A), as piston 5 descends, intake valve 18 opens intake port 16A, and exhaust valve 19 closes exhaust port 17A. When intake port 16A is open, a lean premixed air-fuel mixture is introduced into combustion chamber 10 from intake airflow path 16. Additionally, fuel gas is introduced into secondary combustion chamber 20 by opening fuel supply valve 26. On the other hand, during the compression stroke, as piston 5 ascends, fuel supply valve 26 closes. The lean premixed air introduced into combustion chamber 10 via intake port 16A is then compressed as piston 5 ascends, and a portion of it is introduced into secondary combustion chamber 20 through each of the plurality of nozzles 23.

[0048] During the combustion stroke, the lean premixed air introduced from the combustion chamber 10 into the auxiliary combustion chamber 20 mixes with the fuel gas, generating a mixture of suitable concentration for ignition in the auxiliary combustion chamber 20. Furthermore, when the piston 5 is near the top dead center of the compression stroke, the mixture in the auxiliary combustion chamber 20 is ignited by the ignition device 24 at a predetermined time, causing combustion. The combustion flame generated in the auxiliary combustion chamber 20 is ejected from each of the plurality of nozzles 23 into the combustion chamber 10, igniting the lean premixed air within the combustion chamber 10. Thus, combustion of the lean premixed air in the combustion chamber 10 is achieved. The piston 5, subjected to the combustion pressure of the lean premixed air within the combustion chamber 10, reciprocates axially (up and down) within the cylinder liner 6. The reciprocating motion of the piston 5 is converted into rotational motion via the connecting rod 14 and the crankshaft 15.

[0049] Figure 3 is an explanatory diagram illustrating the heat insulation film component according to one embodiment of the present invention, and is a schematic diagram showing a cross-section along the central axis of the cylinder liner. Figure 4 is an explanatory diagram illustrating the heat insulation film component according to one embodiment of the present invention, and is a schematic diagram showing a plane seen from an axially downward view of the combustion chamber.

[0050] For example, as shown in Figure 2, in some embodiments, the heat insulation film component 7 includes a base layer 8 and a heat insulation film layer 9. The base layer 8 is configured to be detachably fitted into a recess 62 formed on the inner wall surface 61 of the cylinder liner 6. The heat insulation film layer 9 is formed on the inner surface 82 of the base layer 8 opposite to the inner wall surface 61 of the cylinder liner 6. As shown in Figure 2, the heat insulation film layer 9 is disposed above the piston ring 12 (combustion chamber side piston ring 12A), which is located at the uppermost axial side of the cylinder liner 6 when the piston 5 reaches top dead center.

[0051] As shown in Figure 3, in the illustrated embodiment, the inner wall surface 61 of the cylinder liner 6 includes: an axially extending inner wall surface 65 abutting the outer peripheral surface 121 of the piston ring 12; and a stepped wall surface 63 extending axially above and radially outward of the inner wall surface 65. The upper end of the stepped wall surface 63 is connected to the upper surface 66 of the cylinder liner 6. Additionally, a stepped surface 64 connecting the lower end of the stepped wall surface 63 and the upper end of the inner wall surface 65 is formed. This stepped surface 64 extends in a direction intersecting (e.g., orthogonal) to the axial direction. The aforementioned recess 62 includes the stepped wall surface 63 and the stepped surface 64. In the embodiment shown in Figure 4, the recess 62 (the stepped wall surface 63 and the stepped surface 64) is formed as an annular shape extending circumferentially along the cylinder liner 6.

[0052] In the illustrated embodiment, as shown in FIG3, the base layer 8 is formed as a cylindrical shape extending axially. The base layer 8 has an outer surface 81 located radially outward and an inner surface 82 located on the opposite side of the outer surface 81, i.e., radially inward. The heat insulation film layer 9 has a side 91 formed on the inner surface 82 of the base layer 8 and another side 92 located on the opposite side of the side 91 and facing the combustion chamber 10. In the embodiment shown in FIG3, the heat insulation film layer 9 is formed on the inner surface 82 from the upper end to the lower end. When the heat insulation film component 7 is installed on the recess 62 of the cylinder liner 6, the outer surface 81 of the base layer 8 faces the stepped wall surface 63, and the lower end 83 of the base layer 8 abuts against the stepped surface 64. The stepped surface 64 and the lower end 83 of the base layer 8 are located below the upper end 56 of the piston 5 when the piston 5 reaches top dead center. Furthermore, as shown in FIG4, the heat insulation film layer 9 is formed over the entire circumference of the cylinder liner 6 relative to the inner surface 82.

[0053] The heat insulation film layer 9 is configured to have a lower thermal conductivity than the base layer 8 or the cylinder liner 6. For example, the heat insulation film layer 9 can also be formed by applying a ceramic substrate made of materials such as zirconium oxide, titanium oxide, or alumina to the surface of the inner side surface 82 of the base layer 8 using surface treatments such as spraying, electroplating, or vacuum evaporation. Alternatively, the heat insulation film layer 9 can also be formed by anodizing the inner side surface 82 of the base layer 8. Alternatively, it can be formed by applying a heat-insulating or heat-resistant coating to the surface of the inner side surface 82 of the base layer 8. The heat insulation film layer 9 is preferably configured to have high temperature tracking ability to the gas temperature within the combustion chamber 10. For example, if the heat capacity of the heat insulation film layer 9 is small and its tracking ability is high, the temperature difference between the heat insulation film layer 9 and the gas within the combustion chamber 10 can be reduced, thereby reducing heat loss in the combustion chamber 10.

[0054] The base layer 8 is configured to have the same thermal conductivity as or lower than that of the cylinder liner 6. In the illustrated embodiment, the base layer 8 is made of the same type of aluminum as the cylinder liner 6. Alternatively, the base layer 8 and the cylinder liner 6 may not be made of aluminum, but rather of steel, titanium, nickel, copper, or their alloys, and the base layer 8 may also be made of a different type of material than the cylinder liner 6. For example, in some embodiments, the coefficient of linear expansion of the base layer 8 is smaller than that of the cylinder liner 6, and its coefficient of linear expansion is higher than that of the heat insulation film layer 9. In this case, because the difference in the coefficients of linear expansion between the base layer 8 and the heat insulation film layer 9 is small, when heat is transferred within the combustion chamber 10 and the base layer 8 or the heat insulation film layer 9 expands, the peeling of the heat insulation film layer 9 from the base layer 8 can be suppressed.

[0055] The replacement procedure for the heat insulation film component 7 will be described based on Figure 1. First, the cylinder head 4 is removed from the cylinder block 3. Then, the heat insulation film component 7 is pulled upwards axially and removed from the cylinder liner 6, and replaced with a new heat insulation film component 7. After replacing the heat insulation film component 7, the cylinder head 4 is installed on the cylinder block 3. The replacement procedure for the heat insulation film component 7 is simpler and faster than the replacement procedure for the cylinder liner 6, which has a directly formed heat insulation film.

[0056] In the illustrated embodiment, the stepped surface 64 of the recess 62 and the lower end portion 83 of the base layer 8, as shown in FIG3, are positioned above the combustion chamber side piston ring 12A when the piston 5 reaches top dead center. In this case, the heat insulation film component 7 can be removed from the cylinder liner 6 regardless of the position of the piston 5 assembled in the engine 1, thus facilitating the replacement of the heat insulation film component 7. Furthermore, if the stepped surface 64 of the recess 62 and the lower end portion 83 of the base layer 8 are positioned above the combustion chamber side piston ring 12A when the piston 5 reaches top dead center, a smooth connection between the cylinder liner 6 and the heat insulation film component 7 is not required, thus eliminating the need for strict dimensional control of the heat insulation film component 7. Additionally, in several other embodiments, the stepped surface 64 of the recess 62 and the lower end portion 83 of the base layer 8 may be positioned below the combustion chamber side piston ring 12A when the piston 5 reaches top dead center.

[0057] Furthermore, assuming a heat-insulating film is directly formed on the cylinder liner 6, if the piston 5 is assembled from above the cylinder liner 6 during manufacturing or component replacement, the heat-insulating film on the cylinder liner 6 may be damaged by the piston 5. To avoid damage to the heat-insulating film on the cylinder liner 6, when assembling the piston 5 from below the cylinder liner 6, the cylinder liner 6 with the piston 5 pre-assembled needs to be assembled onto the engine 1, which requires considerable labor. To address this, by providing a heat-insulating film layer 9 on the heat-insulating film component 7 that is detachable from the cylinder liner 6, the assembly operation of the piston 5 becomes easier. Specifically, when assembling the piston 5 onto the engine 1, by removing the heat-insulating film component 7 from the cylinder liner 6, the piston 5 can be assembled from above the cylinder liner 6 without damaging the heat-insulating film layer 9. After the piston 5 is assembled onto the engine 1, by installing the heat-insulating film component 7 onto the cylinder liner 6, damage to the heat-insulating film layer 9 can be prevented.

[0058] As described above, some embodiments of the heat insulation film component 7, for example as shown in FIG2, have the aforementioned base layer 8 and heat insulation film layer 9. The base layer 8 is configured to be detachably fitted with a recess 62 formed relative to the inner wall surface 61 of the cylinder liner 6. The heat insulation film layer 9 is formed on the inner surface 82 of the base layer 8 opposite to the inner wall surface 61 of the cylinder liner 6. As shown in FIG2, this heat insulation film layer 9 is disposed above the combustion chamber side piston ring 12A when the piston 5 reaches top dead center.

[0059] According to the above structure, the heat insulation film component 7 includes a base layer 8 and a heat insulation film layer 9 formed on the surface (inner surface) 82 of the base layer 8 opposite to the inner wall surface 61 of the cylinder liner 6. Furthermore, the heat insulation film component 7 is configured such that the base layer 8 is detachably fitted into the recess 62 of the cylinder liner 6. Therefore, by replacing the heat insulation film component 7, the heat insulation film layer 9 can be replaced even without replacing the cylinder liner 6. In contrast, if the heat insulation film layer 9 is directly formed on the cylinder liner 6, the cylinder liner 6 needs to be replaced when replacing the heat insulation film layer 9. Therefore, according to the heat insulation film component 7, the heat insulation film layer 9 can be replaced even without replacing the cylinder liner 6, thus suppressing the increase in cost associated with maintaining the heat insulation performance of the heat insulation film layer 9 compared to the case where the heat insulation film layer 9 is directly formed on the cylinder liner 6.

[0060] Specifically, based on the above configuration, the replacement of the heat insulation film component 7 can be performed simply and quickly. Furthermore, when the heat insulation film component 7 is removed from the cylinder liner 6, deposits adhering to the heat insulation film layer 9 can be removed. Therefore, compared to the case where the heat insulation film is directly formed on the cylinder liner 6, maintenance of the heat insulation film layer 9 can be performed simply and quickly. Thus, based on the heat insulation film component 7 described above, the replacement and maintenance of the heat insulation film layer 9 can be performed simply and quickly, thereby suppressing the increase in cost associated with maintaining the heat insulation performance of the heat insulation film layer 9. In addition, if a high-performance heat insulation film layer 9 is developed, it can be easily replaced with the aforementioned high-performance heat insulation film layer 9.

[0061] Assuming the heat insulation film 9 is positioned from top to bottom relative to the piston ring (combustion chamber side piston ring 12A) on the uppermost axial side of the cylinder liner 6 when the piston 5 reaches top dead center, the heat insulation film 9 may break due to contact with the piston ring 12 as the piston 5 moves up and down axially, potentially reducing its heat insulation performance. Therefore, according to the above configuration, the heat insulation film 9 is positioned above the combustion chamber side piston ring 12A when the piston 5 reaches top dead center. Thus, even if the piston 5 moves up and down axially, the piston ring 12 does not contact the heat insulation film 9. Therefore, according to the above-described heat insulation film component 7, the reduction in heat insulation performance of the heat insulation film 9 caused by contact with the piston ring 12 can be prevented, and the heat insulation performance of the heat insulation film 9 can be maintained for a long time. This reduces the replacement frequency of the heat insulation film component 7, thus suppressing the increase in cost associated with maintaining the heat insulation performance of the heat insulation film 9.

[0062] Furthermore, the heat loss (heat inflow) from the combustion chamber 10 to the cylinder liner 6 is greater at the upper part of the cylinder liner 6 (e.g., the part located above the upper end 56 of the piston 5) than at the lower part of the cylinder liner 6, where the cylinder liner 6 is exposed to heat for a longer period within the combustion chamber 10. Therefore, by using the aforementioned heat insulation film component 7 to insulate the upper part of the cylinder liner 6, a sufficient heat insulation effect can be obtained.

[0063] Hereinafter, several variations of the above-described heat insulation film component 7 (7A) will be described using Figures 5 to 12. The heat insulation film component 7 described below has the same basic structure as the heat insulation film component 7 (7A) described above. In the following variations, structures that are the same as those in the heat insulation film component 7 (7A) will be marked with the same labels and their descriptions will be omitted. The description will focus on the characteristic structures of each variation.

[0064] Normally, when the piston 5 moves up and down axially within the cylinder liner 6, it performs a swaying motion in the direction of rotation with the axis CB of the piston pin 13 that rotatably supports the piston 5 as the center of rotation. Due to the swaying motion of the piston 5, the heat insulation film 9 may be damaged when the upper part of the piston 5 collides with it.

[0065] Figures 5 through 8 are explanatory diagrams illustrating each of the first to fourth variations of the heat insulation film component according to an embodiment of the present invention. In Figures 5 through 8, a cross-section of the engine 1 along the central axis CA of the cylinder liner 6 is schematically shown.

[0066] In some embodiments, as shown in Figures 5 to 8, the substrate layer 8 includes a film-coated portion 84 to which a heat-insulating film layer 9 is formed and an exposed portion 85 to which the heat-insulating film layer 9 is not formed. At least a portion of the exposed portion 85 has a protrusion 86 that protrudes further toward the opposite side of the inner wall surface 61 than the film-coated portion 84. Among the protrusions 86, the protrusion 86 formed at the axial lower end portion 83 of the substrate layer 8 is designated as a lower-side protrusion 87.

[0067] In the embodiment shown in FIG5, the inner surface 82 of the substrate layer 8 includes: an upper inner surface 821 extending axially downward from the upper end of the substrate layer 8; a lower inner surface 822 extending axially at a position lower than and radially inward of the upper inner surface 821; and a stepped surface 823 connecting the lower end of the upper inner surface 821 and the upper end of the lower inner surface 822. The stepped surface 823 extends in a direction intersecting (e.g., orthogonal) to the axial direction. The heat insulation film layer 9 is formed from the upper end to the lower end of the upper inner surface 821, but not on the lower inner surface 822. Moreover, the lower inner surface 822 is located radially inward than the other side 92 of the heat insulation film layer 9 facing the combustion chamber 10. That is, the film-formed portion 84 includes the upper inner surface 821, and the protrusion 86 (lower protrusion 87) includes the lower inner surface 822.

[0068] In the embodiment shown in FIG6, the inner surface 82 of the substrate layer 8 includes: an upper inner surface 821 extending axially downward from the upper end of the substrate layer 8; and a lower inclined surface 824 that slopes radially inward from the lower end of the upper inner surface 821 downward in the axial direction. The heat insulation film layer 9 is formed from the upper end of the upper inner surface 821 to the upper portion 824A of the lower inclined surface 824, but not at the lower portion of the lower inclined surface 824. Moreover, the lower portion of the lower inclined surface 824 is located radially inward than the other side 92 of the heat insulation film layer 9 facing the combustion chamber 10. That is, the film-formed portion 84 includes the upper inner surface 821 and the upper portion 824A of the lower inclined surface 824, and the lower protrusion 87 (protrusion 86) includes the lower portion of the lower inclined surface 824.

[0069] In the embodiment shown in FIG. 7, the inner surface 82 of the substrate layer 8 includes an inclined surface 825 formed from the upper end to the lower end of the substrate layer 8. This inclined surface 825 is radially inward as it slopes downward axially. The heat insulation film layer 9 is formed on the upper portion 825A of the inclined surface 825, but not on the lower portion 825B. In the illustrated embodiment, the heat insulation film layer 9 forms the inclined surface 825 from the upper end of the inclined surface 825 to the lower side of the center position of the inclined surface 825. Furthermore, the lower portion 825B of the inclined surface 825 is located radially inward than the other side 92 of the heat insulation film layer 9 facing the combustion chamber 10. That is, the film-formed portion 84 includes the upper portion 825A of the inclined surface 825, and the lower side protrusion 87 (protrusion 86) includes the lower portion 825B of the inclined surface 825.

[0070] In the embodiment shown in FIG8, the inner surface 82 of the substrate layer 8 includes: an upper inner surface 821 extending axially downward from the upper end of the substrate layer 8; a lower inner surface 826 extending axially below the upper inner surface 821; a lower inclined surface 827 inclined radially inward from the lower end of the lower inner surface 826 towards the axial direction; and a protruding portion 828 protruding radially inward between the upper inner surface 821 and the lower inner surface 826. In the illustrated embodiment, the protruding portion 828 includes an upper inclined surface 828A and a lower inclined surface 828B, the upper inclined surface 828A inclined radially inward from the lower end of the upper inner surface 821 towards the direction downward, and the lower inclined surface 828B inclined radially inward from the upper end of the lower inner surface 826 towards the direction upward.

[0071] In the embodiment shown in FIG8, the aforementioned heat insulation film layer 9 includes a first heat insulation film layer 9A with at least an upper inner surface 821 and a second heat insulation film layer 9B with at least a lower inner surface 826. In the illustrated embodiment, the first heat insulation film layer 9A further has an upper portion of an upper inclined surface 828A. Additionally, the second heat insulation film layer 9B further has a lower portion of a lower inclined surface 828B and an upper portion 827A of a lower inclined surface 827. The lower portion of the upper inclined surface 828A, the upper portion of the lower inclined surface 828B, and the lower portion of the lower inclined surface 827 of the protruding portion 828 are located radially inwardly than the other side 92 of each of the first heat insulation film layer 9A and the second heat insulation film layer 9B. That is, the film-forming portion 84 includes an upper inner surface 821, an upper portion of an upper inclined surface 828A, a lower portion of a lower inclined surface 828B, a lower inner surface 826, and an upper portion 827A of a lower inclined surface 827. The lower protrusion 87 includes a lower portion of a lower inclined surface 827, and the protrusion 86 also includes an upper protrusion 88 located axially upward than the lower protrusion 87. In the illustrated embodiment, the upper protrusion 88 includes the front end of the protrusion portion 828, i.e., the lower portion of the upper inclined surface 828A and the upper portion of the lower inclined surface 828B.

[0072] According to the above configuration, the base layer 8 of the heat insulation film component 7 has a protrusion 86 that protrudes further to the opposite side of the inner wall surface 61 than the film-forming portion 84. In this case, when the piston 5 performs a shaking motion, by causing the upper part of the piston 5 to collide with the protrusion 86 where the heat insulation film layer 9 is not formed, the collision between the upper part of the piston 5 and the heat insulation film layer 9 can be suppressed. By suppressing the collision between the upper part of the piston 5 and the heat insulation film layer 9, the heat insulation performance of the heat insulation film layer 9 can be maintained for a long time.

[0073] In some embodiments, as shown in Figures 5 to 8, the protrusion 86 includes the aforementioned lower-side protrusion 87 formed on the axially lower end portion 83 of the base layer 8, and the film-forming portion 84 is configured to be located axially higher than the lower-side protrusion 87. According to this configuration, the lower-side protrusion 87 is located axially lower than the film-forming portion 84 (heat insulation film layer 9). In this case, when the piston 5 rises while oscillating, the upper part of the piston 5 can collide with the lower-side protrusion 87 earlier. Therefore, the oscillating motion of the piston 5 can be suppressed, the position of the piston 5 can be corrected, and thus the collision between the heat insulation film layer 9, located higher than the lower-side protrusion 87, and the upper part of the piston 5 can be effectively suppressed.

[0074] In some embodiments, as shown in Figures 5, 6, and 8, the film-forming portion 84 has a first inner surface 841 extending axially. The upper inner surface 821 in Figures 5 and 6 corresponds to the first inner surface 841. Furthermore, the upper inner surface 821 and the lower inner surface 826 in Figure 8 each correspond to the first inner surface 841.

[0075] According to the above configuration, the film-forming portion 84 has a first inner surface 841 extending axially. The heat insulation film 9 formed on the first inner surface 841 is easy to make uniform in thickness during its film formation. By making the thickness of the heat insulation film 9 uniform, the deviation of the heat insulation performance of each part of the heat insulation film 9 can be suppressed, and thus the heat insulation effect of the heat insulation film 9 can be effectively utilized.

[0076] In some embodiments, as shown in Figures 6 to 8, the film-forming portion 84 has a second inner surface 842, which is inclined such that the distance between the cylinder liner 6 and the central axis CA increases as it moves upward in the axial direction. The upper portion 824A of the lower inclined surface 824 in Figure 6 and the upper portion 825A of the inclined surface 825 in Figure 7 correspond to the second inner surface 842, respectively. Furthermore, the upper portion of the upper inclined surface 828A and the upper portion 827A of the lower inclined surface 827 in Figure 8 correspond to the second inner surface 842, respectively.

[0077] According to the above configuration, the film-forming portion 84 has a second inner surface 842, which is inclined as it faces upward in the axial direction and the distance from the central axis CA of the cylinder liner 6 increases. When the heat insulation film 9 formed on this second inner surface 842 has its lower edge 93 formed, its wall thickness easily becomes thinner as it faces downward. By making the lower edge 93 of the heat insulation film 9 into a pointed shape, it is possible to suppress the heat insulation film 9 from peeling off from the base layer 8. By suppressing the heat insulation film 9 from peeling off from the base layer 8, the heat insulation performance of the heat insulation film 9 can be maintained for a long time. As a result, the replacement frequency of the heat insulation film component 7 can be reduced, and thus the increase in cost caused by maintaining the heat insulation performance of the heat insulation film 9 can be suppressed.

[0078] In the embodiments shown in Figures 6 to 8, the film-forming portion 84 has the aforementioned second inner surface 842, and the lower edge 93 of the heat insulation film layer 9 has a pointed shape. In this case, compared to a heat insulation film layer 9 with a uniform thickness, it is possible to suppress the increase of the gap between the outer peripheral surface 55 of the piston 5 and the inner surface 82 of the base layer 8, and it is possible to form the heat insulation film layer 9 on the lower side of the base layer 8. By reducing the aforementioned gap, heat loss in the combustion chamber 10 caused by this gap can be suppressed.

[0079] In some embodiments, as shown in FIG8, the film-forming portion 84 has a third inner surface 843, which is inclined as the distance from the central axis CA of the cylinder liner 6 increases towards the axially downward side. The lower part of the lower inclined surface 828B in FIG8 corresponds to the third inner surface 843.

[0080] According to the above configuration, the film-forming portion 84 has a third inner surface 843, which is inclined as it faces downward in the axial direction, increasing in distance from the central axis CA of the cylinder liner 6. When the heat insulation film 9 formed on this third inner surface 843 has its upper edge 94 coated, its wall thickness tends to decrease as it faces upward. By making the upper edge 94 of the heat insulation film 9 tapered, peeling of the heat insulation film 9 from the base layer 8 can be suppressed. By suppressing peeling of the heat insulation film 9 from the base layer 8, the heat insulation performance of the heat insulation film 9 can be maintained for a long time. This reduces the frequency of replacement of the heat insulation film component 7, thus suppressing the increase in cost associated with maintaining the heat insulation performance of the heat insulation film 9.

[0081] In some embodiments, as shown in FIG8, the protrusion 86 includes a lower side protrusion 87 and an upper side protrusion 88 located axially upwards from the lower side protrusion 87. As shown in FIG8, at least a portion (all of it in the example) of the upper side protrusion 88 is located below the upper end 56 of the piston 5 when the piston 5 reaches top dead center. According to the above configuration, the protrusion 86 includes a lower side protrusion 87 and an upper side protrusion 88 located axially upwards from the lower side protrusion 87. In this case, by causing the upper part of the piston 5 to collide with either the upper side protrusion 88 or the lower side protrusion 87, which are axially different from each other, the collision between the upper part of the piston 5 and the heat insulation film layer 9 can be effectively suppressed.

[0082] In some embodiments, as shown in Figures 6 to 8, the heat insulation film layer 9 is configured such that at least one of its upper edge 94 or lower edge 93 becomes thinner towards the front end. According to this configuration, since at least one of the upper edge 94 or lower edge 93 of the heat insulation film layer 9 is thinner towards the front end, peeling of its upper edge 94 or lower edge 93 from the base layer 8 can be suppressed. By suppressing peeling of the heat insulation film layer 9 from the base layer 8, the heat insulation performance of the heat insulation film layer 9 can be maintained for a long period. This reduces the frequency of replacement of the heat insulation film component 7, thus suppressing the increase in cost associated with maintaining the heat insulation performance of the heat insulation film layer 9.

[0083] Figures 9 to 12 are explanatory diagrams illustrating the fifth to eighth modifications of the heat insulation film component according to one embodiment of the present invention. In Figures 9 to 12, the plane seen from below in the axial direction of the combustion chamber 10 of the engine 1 is schematically represented. In addition, in Figures 9 to 11, the cross-sectional lines representing the cylinder liner 6 are omitted.

[0084] In some embodiments, as shown in FIG9, the aforementioned protrusion 86, when viewed from below in the axial direction of the combustion chamber 10, is formed within a predetermined range R1, R2 (at least ±30°) in the circumferential direction of the cylinder liner 6, with reference to a first straight line SL1 extending from the central axis CA of the cylinder liner 6 in a direction orthogonal to the axis CB of the piston pin 13. In the illustrated embodiment, the base layer 8 does not have the protrusion 86 formed on each of the pair of ranges between the predetermined range R1 and the predetermined range R2 in the circumferential direction of the cylinder liner 6.

[0085] In Figure 9, in the above planar observation, the position of one of the intersection points P1 and P2 of the first straight line SL1 and the inner side surface 82 of the base layer 8 is defined as the 0° position, the clockwise direction centered on the central axis CA is defined as the positive direction, and the circumferential angle relative to the 0° position in the positive direction is defined as θ.

[0086] In the embodiment shown in FIG9, the protrusion 86 includes a protrusion 86A formed on one side within a predetermined range R1 based on the 0° position and a protrusion 86B formed on the other side within a predetermined range R2 based on the 180° position. If each of the predetermined ranges R1 and R2 is increased, the probability of the protrusion 86 colliding with the upper part of the piston 5 increases accordingly, but since the area in the base layer 8 where the heat insulation film layer 9 is formed is correspondingly reduced, the heat insulation effect of the heat insulation film layer 9 is reduced.

[0087] In the illustrated embodiment, the protrusion 86A on one side is formed in a range of at least -30° ≤ θ ≤ 30°. The protrusion 86B on the other side is formed in a range of at least 150° ≤ θ ≤ 210°. The aforementioned ranges R1 and R2 can be, for example, ±30° or ±45°.

[0088] Because the piston 5 moves in a direction orthogonal to the axis CB of the piston pin 13, the upper part of the piston 5 is highly likely to collide with the heat insulation film component 7 within a specified range R1 and R2 (e.g., ±30°) in the circumferential direction of the cylinder liner 6, based on the first straight line SL1 extending in a direction orthogonal to the axis CB of the piston pin 13. According to the above configuration, protrusions 86 (one-sided protrusion 86A and the other-sided protrusion 86B) are provided within the specified range R1 and R2 where the upper part of the piston 5 is highly likely to collide. By causing the upper part of the piston 5 to collide with these protrusions 86, the collision between the upper part of the piston 5 and the heat insulation film layer 9 can be effectively suppressed.

[0089] Furthermore, by defining the range of the protrusion 86 in the circumferential direction of the cylinder liner 6, the heat insulation film component 7 can increase the area in the base layer 8 where the heat insulation film layer 9 is formed, compared to the case where the protrusion 86 is formed in the entire circumferential direction of the cylinder liner 6, thereby improving the heat insulation effect brought about by the heat insulation film layer 9.

[0090] In some embodiments, as shown in FIG10, the base layer 8 includes a film-coated portion 84 with a heat-insulating film 9 and an exposed portion 85 without a heat-insulating film 9. As shown in FIG10, the film-coated portion 84, when viewed from a plane observing the combustion chamber 10 axially downward, is formed in a range outside a predetermined range R3 and R4 (e.g., ±30°) in the circumferential direction of the cylinder liner 6, with reference to a first straight line SL1 extending from the central axis CA of the cylinder liner 6 in a direction orthogonal to the axis CB of the piston pin 13. In the illustrated embodiment, the base layer 8 does not have a film-coated portion 84 formed in the predetermined ranges R3 and R4 in the circumferential direction of the cylinder liner 6.

[0091] In Figure 10, similar to Figure 9, in the above planar observation, the position of one of the intersection points P1 and P2 of the first straight line SL1 and the inner side surface 82 of the base layer 8 is defined as the 0° position, the clockwise direction centered on the central axis CA is defined as the positive direction, and the circumferential angle relative to the positive direction of the 0° position is defined as θ.

[0092] In the embodiment shown in FIG10, the film-forming portion 84 has a film-forming portion 84A on one side of a pair of ranges R5 and R6 located between a predetermined range R3 based on the 0° position and a predetermined range R4 based on the 180° position, and a film-forming portion 84B on the other side of the other range R6, which are located in the circumferential direction of the cylinder liner 6. If the predetermined ranges R3 and R4 where the film-forming portion 84 is not formed are increased, the possibility of the upper part of the piston 5 colliding with the heat insulation film layer 9 is correspondingly reduced, but since the area where the heat insulation film layer 9 is formed in the base layer 8 is correspondingly reduced, the heat insulation effect of the heat insulation film layer 9 is reduced.

[0093] In the illustrated embodiment, the film-forming portion 84A is formed on one side within a range of at least 60° ≤ θ ≤ 120°. The film-forming portion 84B on the other side is formed within a range of at least 240° ≤ θ ≤ 300°. The aforementioned ranges R3 and R4 can be, for example, ±30° or ±45°.

[0094] Because the piston 5 moves in a direction orthogonal to the axis CB of the piston pin 13, the upper part of the piston 5 is highly likely to collide with the heat insulation film component 7 within a specified range R3 and R4 (e.g., ±30°) in the circumferential direction of the cylinder liner 6, based on a first straight line SL1 extending in a direction orthogonal to the axis CB of the piston pin 13. If the upper part of the piston 5 collides with the heat insulation film layer 9 of the heat insulation film component 7, causing the heat insulation film layer 9 to peel off from the base layer 8, the area near the peeled part is prone to peeling. Therefore, as the peeling of the heat insulation film layer 9 from the base layer 8 progresses, the heat insulation performance of the heat insulation film layer 9 may decrease prematurely. According to the above configuration, by not forming a film-forming portion 84 within the specified range R3 and R4 (e.g., ±30°) where the probability of collision with the upper part of the piston 5 of the heat insulation film component 7 is high, the collision between the upper part of the piston 5 and the heat insulation film layer 9 can be effectively suppressed. By suppressing the collision between the upper part of the piston 5 and the heat insulation film layer 9, the peeling of the heat insulation film layer 9 from the base layer 8 can be suppressed, thus maintaining the heat insulation performance of the heat insulation film layer 9 for a long time.

[0095] In some embodiments, as shown in FIG11, the aforementioned base layer 8 includes a film-coated portion 84 with a heat-insulating film 9 and an exposed portion 85 without a heat-insulating film 9. As shown in FIG11, in a planar view of the combustion chamber 10 viewed from an axially downward perspective, the film-coated portion 84 is formed in a range outside a predetermined range R7, R8 (e.g., a range of ±15°) in the circumferential direction of the cylinder liner 6, with reference to a second straight line SL2 extending from the central axis CA of the cylinder liner 6 and passing through the center CP of the intake port 16A.

[0096] In Figure 11, in the above planar view, the position of the intersection point P3 of the second straight line SL2 and the inner side surface 82 of the base layer 8 is defined as the 0° position, the clockwise direction centered on the central axis CA is defined as the positive direction, and the circumferential angle relative to the positive direction of the 0° position is defined as θ.

[0097] In the embodiment shown in FIG11, two air inlets 16A are formed on the lower surface 42 of the cylinder head 4 at positions that are far apart from each other in the circumferential direction of the cylinder liner 6. Within a defined range R7 in the circumferential direction of the cylinder liner 6 based on a second straight line SL2 passing through the center CP of one of the two air inlets 16A, and within a defined range R8 in the circumferential direction of the cylinder liner 6 based on the second straight line SL2 passing through the center CP of the other air inlet 16A, no film-forming portion 84 is formed.

[0098] In the embodiment shown in FIG11, the film-forming portion 84 includes: a film-forming portion 84C formed on one side of a pair of ranges R9 and R10 located in the circumferential direction of the cylinder liner 6 between the specified ranges R7 and R8, wherein the narrower range R9 is formed; and a film-forming portion 84D formed on the other side of the larger range R10. If each of the specified ranges R7 and R8 where the film-forming portion 84 is not formed is increased, the transfer of heat accumulated in the heat insulation film layer 9 to the combustion gas can be suppressed, but the area in the base layer 8 where the heat insulation film layer 9 is formed becomes correspondingly smaller, thus reducing the heat insulation effect of the heat insulation film layer 9. The specified ranges R7 and R8 may be, for example, a range of ±30° or a range of ±45°.

[0099] Assuming a heat-insulating film layer 9 is disposed near the intake port 16A, the combustion gas (e.g., combustion air) introduced into the combustion chamber 10 from the intake port 16A will be heated and expanded before combustion due to the heat accumulated in the heat-insulating film layer 9, potentially reducing combustion efficiency. According to the above configuration, when viewed from below in the axial direction near the intake port 16A, i.e., in the plane of the combustion chamber 10, the heat-insulating film layer 9 does not form a film-forming portion 84 within a predetermined range R7, R8 (e.g., ±15°) in the circumferential direction of the cylinder liner 6, based on a second straight line SL2 extending from the central axis CA of the cylinder liner 6 and passing through the center CP of the intake port 16A. Film-forming portions 84 are formed in the range R9, R10 outside the aforementioned predetermined range R7, R8. Thus, by not forming film-forming portions 84 near the intake port 16A, it is possible to suppress the heating of the combustion gas introduced into the combustion chamber 10 from the intake port 16A before combustion due to the heat accumulated in the heat-insulating film layer 9, thereby suppressing the reduction in combustion efficiency.

[0100] In some of the embodiments described above, the base layer 8 of the heat insulation film component 7 is formed as an annular shape extending circumferentially along the cylinder liner 6, as shown in FIG. 4, but it can also be formed as an arc shape extending circumferentially along the cylinder liner 6 (semi-circular in the example shown in FIG. 12). As shown in FIG. 12, multiple (two in the example shown) heat insulation film components 7 can also be detachably fitted into the recess 62 of the cylinder liner 6. Alternatively, the recess 62 of the cylinder liner 6 can also be an arc-shaped groove extending circumferentially along the cylinder liner 6.

[0101] This invention is not limited to the embodiments described above, but also includes modifications to the embodiments and appropriate combinations thereof. For example, the engine 1 equipped with the heat insulation film component 7 can be used for any purpose, such as a marine engine, a power generation engine, or an automotive engine. Furthermore, when the engine 1 is a marine engine or a power generation engine, due to its long-term operation, more replacement and maintenance operations are required compared to automotive engines, and these operations need to be performed quickly. Therefore, this invention is particularly useful for marine engines and power generation engines.

[0102] The contents described in the above-mentioned embodiments are as follows.

[0103] 1) The heat insulation film component 7 of at least one embodiment of the present invention is at least one heat insulation film component 7 installed on the inner wall surface 61 of the combustion chamber 10 facing the engine 1 in the cylinder liner 6, the cylinder liner 6 slidably receiving the piston 5 in the axial direction, wherein it has: a base layer 8 configured to be detachably fitted relative to the recess 62 formed on the inner wall surface 61 of the cylinder liner 6; a heat insulation film layer 9 formed on the surface (inner surface 82) of the base layer 8 opposite to the inner wall surface 61 of the cylinder liner 6, the heat insulation film layer 9 being disposed above the piston ring (combustion chamber side piston ring 12A) on the uppermost side of the cylinder liner 6 in the axial direction when the piston 5 reaches top dead center.

[0104] According to the configuration described in 1) above, the heat insulation film component 7 includes a base layer 8 and a heat insulation film layer 9 formed on the surface of the base layer 8 opposite to the inner wall surface 61 of the cylinder liner 6 (inner surface 82). Furthermore, the heat insulation film component 7 is configured such that the base layer 8 is detachably fitted into the recess 62 of the cylinder liner 6. Therefore, by replacing the heat insulation film component 7, the heat insulation film layer 9 can be replaced even without replacing the cylinder liner 6. In contrast, when the heat insulation film layer 9 is directly formed on the cylinder liner 6, the cylinder liner 6 needs to be replaced when replacing the heat insulation film layer 9. Therefore, according to the heat insulation film component 7 described above, the heat insulation film layer 9 can be replaced even without replacing the cylinder liner 6, thus suppressing the increase in cost associated with maintaining the heat insulation performance of the heat insulation film layer 9 compared to the case where the heat insulation film layer 9 is directly formed on the cylinder liner 6.

[0105] Assuming the heat insulation film 9 is positioned from top to bottom relative to the piston ring (combustion chamber side piston ring 12A) on the uppermost axial side of the cylinder liner 6 at the moment the piston 5 reaches top dead center, when the piston 5 moves up and down axially, the heat insulation film 9 may be damaged due to contact with the piston ring 12 as it slides and moves. This would reduce the heat insulation performance of the heat insulation film 9. Therefore, according to the configuration described in 1), the heat insulation film 9 is positioned above the combustion chamber side piston ring 12A when the piston 5 reaches top dead center. Thus, even if the piston 5 moves up and down axially, the piston ring 12 will not contact the heat insulation film 9. Therefore, according to the heat insulation film component 7 described above, the reduction in heat insulation performance of the heat insulation film 9 caused by contact with the piston ring 12 can be prevented, and the heat insulation performance of the heat insulation film 9 can be maintained for a long time. This reduces the replacement frequency of the heat insulation film component 7, thus suppressing the increase in cost associated with maintaining the heat insulation performance of the heat insulation film 9.

[0106] 2) In some embodiments, in the heat insulation film component 7 described in 1) above, the base layer 8 has a film-formed portion 84 on which the heat insulation film layer 9 is formed, and an exposed portion 85 on which the heat insulation film layer 9 is not formed, and at least a portion of the exposed portion 85 has a protrusion 86 that protrudes further toward the opposite side of the inner wall surface 61 than the film-formed portion 84.

[0107] Normally, when the piston 5 moves axially up and down within the cylinder liner 6, it also performs a swaying motion in the rotational direction centered on the piston pin 13. Due to this swaying motion, the upper part of the piston 5 may collide with the heat insulation film layer 9, potentially damaging the heat insulation film layer 9. According to the configuration described in 2) above, the base layer 8 of the aforementioned heat insulation film component 7 has a protrusion 86 that protrudes further to the opposite side of the inner wall surface 61 than the film-forming portion 84. In this case, when the piston 5 sways, by causing the upper part of the piston 5 to collide with the protrusion 86 where the heat insulation film layer 9 is not formed, the collision between the upper part of the piston 5 and the heat insulation film layer 9 can be suppressed. By suppressing the collision between the upper part of the piston 5 and the heat insulation film layer 9, the heat insulation performance of the heat insulation film layer 9 can be maintained for a long period.

[0108] 3) In some embodiments, in the heat insulation film component 7 described in 2) above, the protrusion 86 includes a lower side protrusion 87 formed at the lower axial end of the base layer 8, and the film-forming portion 84 is configured to be located on the upper side of the axial direction, which is closer to the lower side protrusion 87.

[0109] According to the configuration described in 3) above, the lower side protrusion 87 is located further axially downward than the film-forming portion 84. In this case, when the piston 5 rises while performing a swaying motion, the upper part of the piston 5 can collide with the lower side protrusion 87 earlier. As a result, the swaying motion of the piston 5 can be suppressed, the position of the piston 5 can be corrected, and thus the collision between the upper part of the piston 5 and the heat insulation film layer 9 can be effectively suppressed.

[0110] 4) In some embodiments, in the heat insulation film component 7 described in 3) above, the film-forming portion 84 has a first inner surface 841 extending along the axial direction.

[0111] According to the configuration described in 4) above, the film-forming portion 84 has a first inner surface 841 extending axially. The heat insulation film 9 formed on the first inner surface 841 is easy to make uniform in thickness during its film formation. By making the thickness of the heat insulation film 9 uniform, deviations in the heat insulation performance of each part of the heat insulation film 9 can be suppressed, thus effectively exerting the heat insulation effect of the heat insulation film 9.

[0112] 5) In some embodiments, in the heat insulation film component 7 described in 3) or 4) above,

[0113] The film-forming portion 84 has a second inner surface 842 that is inclined such that the distance from the central axis CA of the cylinder liner 6 increases as it moves toward the upper side of the axial direction.

[0114] According to the configuration described in 5) above, the film-forming portion 84 has a second inner surface 842, which is inclined such that the distance between the second inner surface 842 and the central axis CA of the cylinder liner 6 increases as it moves upward toward the axial direction. When the heat insulation film 9 formed on this second inner surface 842 has its lower edge 93 formed, its wall thickness easily becomes thinner as it moves toward the lower end. By making the lower edge 93 of the heat insulation film 9 into a pointed shape, peeling of the heat insulation film 9 from the base layer 8 can be suppressed. By suppressing peeling of the heat insulation film 9 from the base layer 8, the heat insulation performance of the heat insulation film 9 can be maintained for a long time. As a result, the replacement frequency of the heat insulation film component 7 can be reduced, thus suppressing the increase in cost associated with maintaining the heat insulation performance of the heat insulation film 9.

[0115] 6) In some embodiments, in the heat insulation film component 7 of any one of 3) to 5) above, the protrusion 86 further includes an upper protrusion 88 located on the axially upper side than the lower protrusion 87.

[0116] According to the configuration described in 6) above, the protrusion 86 includes a lower side protrusion 87 and an upper side protrusion 88 located axially upwards from the lower side protrusion 87. In this case, by causing the upper part of the piston 5 to collide with either the upper side protrusion 87 or the lower side protrusion 87, which are axially different from each other, the collision between the upper part of the piston 5 and the heat insulation film layer 9 can be effectively suppressed.

[0117] 7) In some embodiments, in the heat insulation film component 7 of any one of 2) to 6) above, the protrusion 86 forms a range of ±30° in the circumferential direction of the cylinder liner 6 with reference to a first straight line SL1, which extends from the central axis CA of the cylinder liner 6 in a direction orthogonal to the axis CB of the piston pin 13 that rotatably supports the piston 5.

[0118] Because the piston 5 moves in a direction orthogonal to the axis CB of the piston pin 13, the upper part of the piston 5 is highly likely to collide with the heat insulation film component 7 within a specified range R1, R2 (e.g., ±30°) in the circumferential direction of the cylinder liner 6, based on the first straight line SL1 extending in a direction orthogonal to the axis CB of the piston pin 13. According to the configuration described in 7), a protrusion 86 is provided within the specified range R1, R2 where the upper part of the piston 5 of the heat insulation film component 7 is highly likely to collide. By causing the upper part of the piston 5 to collide with this protrusion 86, the collision between the upper part of the piston 5 and the heat insulation film layer 9 can be effectively suppressed.

[0119] 8) In some embodiments, in the heat insulation film component 7 of any one of 1) to 7) above, the heat insulation film layer 9 is configured such that at least one of its upper edge 94 or lower edge 93 becomes thinner as it moves toward the front end side.

[0120] According to the configuration described in 8) above, at least one of the upper edge 94 or the lower edge 93 of the heat insulation film layer 9 is configured to thin as it moves toward the front end sidewall, thus preventing its upper edge 94 or lower edge 93 from peeling off from the base layer 8. By preventing the heat insulation film layer 9 from peeling off from the base layer 8, the heat insulation performance of the heat insulation film layer 9 can be maintained for a long time. As a result, the replacement frequency of the heat insulation film component 7 can be reduced, thereby suppressing the increase in cost associated with maintaining the heat insulation performance of the heat insulation film layer 9.

[0121] 9) In some embodiments, in the heat insulation film component 7 of any one of 1) to 8) above, the base layer 8 has a film-coated portion 84 on which the heat insulation film layer 9 is formed and an exposed portion 85 on which the heat insulation film layer 9 is not formed. The film-coated portion 84, when viewed from below the combustion chamber 10 in a plane view, is formed in a range other than ±30° in the circumferential direction of the cylinder liner 6, with reference to a first straight line SL1 extending from the central axis CA of the cylinder liner 6 in a direction orthogonal to the axis CB of the piston pin 13 that rotatably supports the piston 5.

[0122] Because the piston 5 moves in a direction orthogonal to the axis CB of the piston pin 13, the upper part of the piston 5 is highly likely to collide with the heat insulation film component 7 within a specified range R3, R4 (e.g., ±30°) in the circumferential direction of the cylinder liner 6, based on the first straight line SL1 extending in a direction orthogonal to the axis CB of the piston pin 13. If the upper part of the piston 5 collides with the heat insulation film layer 9 of the heat insulation film component 7, causing the heat insulation film layer 9 to peel off from the base layer 8, the area near the peeling point is prone to peeling. Therefore, as the peeling of the heat insulation film layer 9 from the base layer 8 progresses, the heat insulation performance of the heat insulation film layer 9 may decrease prematurely. According to the configuration described above (9), by not forming a film-forming portion 84 within the specified range R3, R4 (e.g., ±30°) where the upper part of the piston 5 in the heat insulation film component 7 is highly likely to collide, the collision between the upper part of the piston 5 and the heat insulation film layer 9 can be effectively suppressed. By suppressing the collision between the upper part of the piston 5 and the heat insulation film layer 9, the heat insulation film layer 9 can be prevented from peeling off from the base layer 8, thus maintaining the heat insulation performance of the heat insulation film layer 9 for a long time.

[0123] 10) In some embodiments, in the heat insulation film component 7 of any one of 1) to 9) above, the base layer 8 has a film-coated portion 84 on which the heat insulation film layer 9 is formed and an exposed portion 85 on which the heat insulation film layer 9 is not formed. The film-coated portion 84, when viewed from the plane of the combustion chamber 10 from the axial direction downward, is formed in a range other than ±15° in the circumferential direction of the cylinder liner 6, with reference to a second straight line SL2 extending from the central axis CA of the cylinder liner 6 and passing through the center CP of the intake port 16A.

[0124] Assuming that the heat insulation film layer 9 is disposed near the air intake 16A, the combustion gas (e.g., combustion air) introduced into the combustion chamber 10 from the air intake 16A is heated and expands before combustion due to the heat accumulated in the heat insulation film layer 9, which may reduce the combustion efficiency. According to the above configuration of 10), when viewed from below in the axial direction near the air intake 16A, i.e., in the plane of the combustion chamber 10, the heat insulation film layer 9 does not form a film-forming portion 84 within a predetermined range R7, R8 (e.g., ±15°) in the circumferential direction of the cylinder liner 6, based on the second straight line SL2 extending from the central axis CA of the cylinder liner 6 and passing through the center CP of the air intake 16A, but forms a film-forming portion 84 in the range R9, R10 outside the predetermined range R7, R8. In this way, by not forming a film portion 84 near the air inlet 16A, it is possible to suppress the combustion gas introduced into the combustion chamber 10 from the air inlet 16A from being heated before combustion due to the heat accumulated in the heat insulation film layer 9, thereby suppressing the reduction in combustion efficiency.

[0125] Explanation of reference numerals in the attached figures

[0126] 1. 1A: Engine

[0127] 3: Cylinder block

[0128] 4: Cylinder head

[0129] 5: Piston

[0130] 6: Cylinder Liner

[0131] 7: Heat insulation film components

[0132] 8: Basal layer

[0133] 9: Heat insulation film layer

[0134] 9A: First heat insulation film layer

[0135] 9B: Second heat insulation film layer

[0136] 10: Combustion Chamber

[0137] 11: Combustion chamber forming section

[0138] 12: Piston rings

[0139] 12A: Combustion chamber side piston ring

[0140] 13: Piston pin

[0141] 14: Linkage

[0142] 15: Crankshaft

[0143] 16: Intake airflow path

[0144] 16A: Air Inlet

[0145] 17: Exhaust Flow Path

[0146] 17A: Exhaust port

[0147] 18: Intake valve

[0148] 19: Exhaust valve

[0149] 20: Secondary Combustion Chamber

[0150] 21: Auxiliary combustion chamber forming section

[0151] 22: Metal parts for the auxiliary chamber's opening

[0152] 23: Spray nozzle

[0153] 24: Ignition device

[0154] 25: Fuel supply device

[0155] 26: Fuel supply valve

[0156] 30: Space

[0157] 42: Lower surface

[0158] 51: Head

[0159] 52: Skirt

[0160] 53: Top surface

[0161] 54: Piston ring groove

[0162] 55: Outer perimeter

[0163] 56: Top

[0164] 60: Interior space

[0165] 61, 65: Inner wall surface

[0166] 62: Concave

[0167] 63: Stepped wall

[0168] 64: Stepped surface

[0169] 66: Upper surface

[0170] 81: Outer side

[0171] 82: Inner side

[0172] 83: Lower end

[0173] 84, 84A~84D: Film-forming portion

[0174] 85: Exposed area

[0175] 86, 86A, 86B: Protruding parts

[0176] 87: Lower side protrusion

[0177] 88: Upper side protrusion

[0178] 91: One side

[0179] 92: The Other Side

[0180] 93: Lower edge

[0181] 94: Upper edge

[0182] 821: Upper inner side

[0183] 822, 826: Lower inner side

[0184] 823: Stepped surface

[0185] 824, 827: Lower lateral inclined surface

[0186] 825: Inclined surface

[0187] 828: Emphasize the face

[0188] 828A: Upper inclined surface

[0189] 828B: Lower inclined surface

[0190] 841: First Inner Face

[0191] 842: Second inner face

[0192] 843: Third Inner Face

[0193] CA: Central Axis

[0194] CB: Axis

[0195] CP: Center

[0196] P1~P3: Intersection Points

[0197] R1~R10: Range

[0198] SL1: First straight line

[0199] SL2: Second straight line

Claims

1. A heat insulation film component, comprising at least one heat insulation film component mounted on the inner wall surface of the combustion chamber facing the engine within a cylinder liner in which a piston is axially slidably housed, wherein, It comprises: a base layer configured to be detachably fitted relative to a recess formed on the inner wall surface of the cylinder liner; and a heat-insulating film layer formed on the surface of the base layer opposite to the inner wall surface of the cylinder liner, the heat-insulating film layer being disposed above the piston ring on the uppermost side of the cylinder liner in the axial direction when the piston reaches top dead center. The base layer has: a portion with the heat-insulating film formed thereon and an exposed portion without the heat-insulating film formed thereon. In a planar view of the combustion chamber from below in the axial direction, the portion with the film formed is formed in a range other than ±15° in the circumferential direction of the cylinder liner, with a reference to a second straight line extending from the central axis of the cylinder liner and passing through the center of the intake port.

2. The heat insulation film component as claimed in claim 1, wherein, At least a portion of the exposed portion has a protrusion that protrudes further toward the opposite side of the inner wall surface than the film-forming portion.

3. The heat insulation film component as described in claim 2, wherein, The protrusion has a lower side protrusion formed at the lower axial end of the substrate layer, and the film-forming portion is configured to be located further up axially than the lower side protrusion.

4. The heat insulation film component as claimed in claim 3, wherein, The film-forming portion has a first inner surface extending along the axial direction.

5. The heat insulation film component as claimed in claim 3 or 4, wherein, The film-forming portion has a second inner surface that is inclined in such a way that the distance from the central axis of the cylinder liner increases as it moves toward the upper side of the axial direction.

6. The heat insulation film component as claimed in claim 3 or 4, wherein, The protrusion also includes an upper side protrusion located on the upper side of the axial direction, which is higher than the lower side protrusion.

7. The heat insulation film component as described in any one of claims 2 to 4, wherein, In a planar view of the combustion chamber from below the axial direction, the protrusion is formed within a range of at least ±30° in the circumferential direction of the cylinder liner, with reference to a first straight line extending from the central axial direction of the cylinder liner orthogonal to the axis of the piston pin that rotatably supports the piston.

8. The heat insulation film component as described in any one of claims 1 to 4, wherein, The heat insulation film layer is configured such that at least one of its upper or lower edge becomes thinner as it moves toward the front end.

9. The heat insulation film component as claimed in claim 1, wherein, In a planar view of the combustion chamber from below the axial direction, the film-forming portion is formed within a range of ±30° in the circumferential direction of the cylinder liner, with reference to a first straight line extending from the central axial direction of the cylinder liner orthogonal to the axis of the piston pin that rotatably supports the piston.

Images