JP2017110501A - Engine structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To finely transport heat to a cooling portion while improving the thermal efficiency of an engine.SOLUTION: An engine structure is equipped with a cylinder liner 51 and a water jacket 26 (a cooling portion). The cylinder liner 51 includes a first liner member 62, and a second liner member 63 abutting on one end in an axial direction thereof and disposed at a position corresponding to a water jacket 26. The first liner member 62 has thermal conductivity anisotropy in which thermal conductivity in an axial direction is larger than thermal conductivity in a diametrical direction. The second liner member 63 includes an outer cylinder portion 64a and an inner cylinder portion 64b adjacent to each other through a boundary surface 65 inclining close to a core from a lower side to an upper side. The outer cylinder portion 64a has a thermal conductivity anisotropy in which thermal conductivity in the diametrical direction is larger than thermal conductivity in the axial direction, and the inner cylinder portion 64b has thermal conductivity anisotropy in which thermal conductivity in the axial direction is larger than the thermal conductivity in the diametrical direction.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an engine structure.

  In recent years, a technique for improving the fuel efficiency by reducing the cooling loss by insulating the combustion chamber and thereby improving the thermal efficiency of the engine has been studied. For example, Patent Document 1 discloses an engine structure including a cylinder liner in which a plating layer containing a plate-like zeolite is formed on the inner peripheral surface of a cylinder base material made of aluminum or an aluminum alloy. The plating layer contains plate-like zeolite in a state in which the longitudinal direction is perpendicular to the thickness direction of the plating layer, and thereby the thermal conductivity in the thickness direction of the plating layer is kept low. That is, the plating layer suppresses heat radiation from the cylinder liner to the cylinder block, and as a result, contributes to a reduction in cooling loss of the engine and, in turn, an improvement in thermal efficiency.

Japanese Patent Laying-Open No. 2015-40482

  However, the engine structure of Patent Document 1 prevents the temperature rise of cooling water and oil flowing outside the cylinder liner by suppressing heat dissipation to the cylinder block. For this reason, for example, in a cold district, there is a possibility that the heating function using the thermal energy of the cooling water may be adversely affected.

  The present invention has been made in view of the circumstances as described above, and has an engine structure capable of satisfactorily transporting heat to a cooling unit through which cooling water, oil, and the like circulate while increasing the thermal efficiency of the engine. The purpose is to provide.

  In view of the problems as described above, the applicant of the present application comprises a cylinder liner composed of a cylindrical first liner member that occupies most of the cylinder liner and a second liner member that abuts one end thereof, and the first liner member. The second liner member is made of a resin material having a thermal conductivity anisotropy having a thermal conductivity in the axial direction (first direction) larger than that in the radial direction (second direction). It is made of a material such as high aluminum, and a water jacket or the like is disposed outside the second liner member. The combustion heat received by the cylinder liner is moved to the second liner member exclusively while being moved in the axial direction by the first liner member. It was considered to transmit to the cooling water from this second liner member (Japanese Patent Application No. 2014-223037). However, as described above, the combustion liner can be smoothly conducted in the axial direction only by configuring the cylinder liner with the first liner member and the second liner member. However, heat transfer from the first liner member to the second liner member can be achieved. The second liner member is not necessarily sufficient to conduct heat to the cooling part satisfactorily, and further improvement is considered necessary for better heat transfer to the cooling part.

  Such a problem is solved by the present invention as follows.

  That is, the present invention is an engine structure including a cylinder liner that forms a combustion chamber, and a cooling unit that is located on the outer side in the radial direction and through which a cooling medium flows. The cylinder liner is a cylindrical first member. A liner member, and a cylindrical second liner member disposed at a position corresponding to the cooling portion in contact with one end in the axial direction, the first liner member having an axial thermal conductivity in the radial direction. The second liner member has a boundary surface that inclines so as to approach the axial center from the first liner member side toward the anti-first liner member side. The outer cylinder part includes an outer cylinder part and an inner cylinder part adjacent to each other, and the outer cylinder part has a thermal conductivity anisotropy having a radial thermal conductivity larger than an axial thermal conductivity, and the inner cylinder Part has a thermal conductivity anisotropy whose axial thermal conductivity is larger than the radial thermal conductivity. And those are.

  According to this engine structure, combustion heat is conducted in the axial direction along the first liner member, transmitted from the first liner member to the inner cylinder portion of the second liner member, and further from the inner cylinder portion to the outer cylinder portion. It is transmitted, moved (conducted) radially outward and transmitted to the cooling unit. At this time, since the first liner member and the inner cylinder portion of the second liner member have the same thermal conductivity anisotropy, heat transfer from the first liner member to the inner cylinder portion is performed smoothly. Moreover, although the thermal conductivity anisotropy differs between the inner cylinder part and the outer cylinder part of the second liner member, the heat from the inner cylinder part to the outer cylinder part is caused by being adjacent to the inner and outer sides through an inclined boundary surface. Transmission is performed smoothly. And since the outer cylinder part has thermal conductivity anisotropy whose radial direction thermal conductivity is larger than the axial direction thermal conductivity, the heat transferred from the inner cylinder part to the outer cylinder part is cooled at a low temperature. It will move smoothly toward the part. Therefore, it is possible to efficiently perform heat transport to the cooling unit while suppressing heat radiation from the cylinder liner to the outside (cylinder block).

  In this case, for example, the second liner member has a rectangular cross-sectional shape along the center line, and the boundary surface is located on a diagonal line of the rectangular cross section.

  According to this engine structure, a large area of the boundary surface can be secured with a simple structure, and heat transfer from the first liner member to the cooling unit can be performed more smoothly.

  In the engine structure described above, the position of the boundary line formed on the inner peripheral surface of the second liner member by the boundary surface is located on the inner side of both axial ends of the second liner member. Is preferred.

  According to this engine structure, since a part of the outer cylinder part of the second liner member faces the combustion chamber, that is, a part of the outer cylinder part forms the combustion chamber, so the heat generated in the combustion chamber Can be guided directly to the cooling part while being received by the outer cylinder part. Therefore, heat transport can be performed more efficiently to the cooling unit.

  According to another aspect of the present invention, there is provided an engine structure including a cylinder liner that forms a combustion chamber, and a cooling unit that is located radially outside and through which a cooling medium flows. A cylindrical first liner member having a thermal conductivity anisotropy greater in the axial direction than that in the radial direction and a position corresponding to the cooling part in contact with one end in the axial direction And a cylindrical second liner member having a thermal conductivity anisotropy greater in radial direction than in the axial direction, and among the cylinder liners, the first liner member in the axial direction When the end on the side is defined as the first end and the end on the second liner member side is defined as the second end, the first liner member and the second liner member are separated from the first end, respectively. 2 Boundary surface including a surface that inclines so as to approach the axis as it goes to the end Those that are in contact with each other through.

  According to this engine structure, the combustion heat is transmitted in the axial direction along the first liner member, and is transmitted from the first liner member to the second liner member. At this time, the first liner member and the second liner member have different heat conduction anisotropies, but the first liner member and the second liner member are in contact with each other via the inclined surface, so the first liner member is in contact with the first liner member and the second liner member. Heat transfer from the member to the second liner member is performed smoothly. And since the 2nd liner member has thermal conductivity anisotropy whose radial direction thermal conductivity is larger than the axial direction thermal conductivity, the heat transmitted from the 1st liner member to the 2nd liner member is temperature It moves smoothly toward the low cooling part. Therefore, it is possible to efficiently perform heat transport to the cooling unit while suppressing heat radiation from the cylinder liner to the outside (cylinder block).

  In the engine structure as described above, it is preferable that the cooling unit is provided at a position around the combustion chamber corresponding to the end of the compression process.

  According to this configuration, heat generated in the combustion chamber can be efficiently transmitted to the cooling unit.

  According to the engine structure of the present invention as described above, it is possible to satisfactorily transport heat to the cooling unit while increasing the thermal efficiency of the engine.

1 is a cross-sectional view of a multi-cylinder engine to which an engine structure of the present invention is applied. It is principal part sectional drawing of the cylinder block which shows the said engine structure. It is principal part sectional drawing of a cylinder block which shows the modification of the engine structure of this invention. It is a graph which shows the evaluation test result of heat transfer performance. It is sectional drawing of a cylinder block which shows the reference example of an engine structure. It is principal part sectional drawing of a cylinder block which shows the modification of the engine structure of this invention. It is principal part sectional drawing of a cylinder block which shows the modification of the engine structure of this invention. It is principal part sectional drawing of a cylinder block which shows the modification of the engine structure of this invention.

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

(Overall engine structure)
FIG. 1 is a cross-sectional view of a multi-cylinder engine 1 (hereinafter abbreviated as engine 1) to which the present invention is applied. The engine 1 is an engine for a vehicle such as an automobile, and is an in-line 4-cylinder gasoline engine in which four cylinders are arranged in a direction perpendicular to the paper surface of FIG.

  The engine 1 includes an engine body 2 and auxiliary equipment such as an unillustrated intake / exhaust manifold and various pumps assembled thereto.

  The engine body 2 includes a cam cap 3, a cylinder head 4, a cylinder block 5, a crankcase (not shown), and an oil pan (not shown) that are connected in the vertical direction.

  Four cylinder bores 7 are formed in the cylinder block 5, and pistons 8 are slidably accommodated in the respective cylinder bores 7, and are combusted by these pistons 8, cylinder bores 7, cylinder heads 4, and intake / exhaust valves 14 and 15 described later. A chamber 10 is formed for each cylinder. Each piston 8 is connected via a connecting rod 9 to a crankshaft (not shown) that is rotatably supported by the crankcase.

  The cylinder head 4 is provided with the same number of recesses 4 a as the cylinder bore 7 for forming the combustion chamber 10. The cylinder head 4 is provided with an intake port 12 and an exhaust port 13 that open to the combustion chamber 10 at the position of each recess 4a for each cylinder, and an intake valve 14 and an exhaust valve that open and close the intake port 12 and the exhaust port 13, respectively. 15 is installed in each of the ports 12 and 13, respectively.

  The intake valve 14 and the exhaust valve 15 are urged in the direction of closing the ports 12 and 13 (upward in FIG. 1) by return springs 16 and 17, respectively, and are provided on the outer periphery of the camshafts 18 and 19. Each port 12 and 13 is configured to be opened by being pressed by the cam portions 18a and 19a. Specifically, as the cam shafts 18 and 19 rotate, the cam portions 18a and 19a push down the cam followers 20a and 21a provided at the center of the swing arms 20 and 21, so that the swing arms 20 and 21 are turned on. The top of the pivot mechanism of the hydraulic lash adjusters 24, 25 provided on one end side is swung around a fulcrum, and the other end of the swing arms 20, 21 is subjected to the biasing force of the return springs 16, 17 along with this swinging. The intake valve 14 and the exhaust valve 15 are pressed down against it. As a result, the ports 12 and 13 are opened.

  The cylinder head 4 and the cylinder block 5 are provided with a water jacket. Specifically, the cylinder block 5 is provided with a water jacket 26 (corresponding to a cooling unit of the present invention) so as to integrally surround the four cylinder bores 7. Further, the cylinder head 4 is provided with a water jacket 27 at a position on the intake side (right side in FIG. 1) of the combustion chamber 10 and below the intake port 12, and also on the exhaust side (in FIG. 1). A water jacket 28 is provided at a position below the exhaust port 13 on the left side), and a water jacket 29 is provided immediately above the combustion chamber 10 and between the ports 12 and 13. .

  Although not shown in detail, the water jacket 26 of the cylinder block 5 and the water jackets 27 and 28 of the cylinder head 4 are not shown in the drawing, and are connected to the gasket holes not shown in the figure. Are communicated with each other.

  Each of the water jackets 26 to 29 is connected to a water pump (not shown). Thereby, the cooling water (cooling fluid) circulates between the engine main body 2 and the radiator (not shown), so that each water jacket 26 to 29 is provided. Are distributed in a predetermined order.

  Reference numerals 30 to 32 in FIG. 1 are oil gallery formed in the cylinder block 5 and the cylinder head 4. These oil galleries are connected to an oil pump (not shown), whereby hydraulic pressure for operation is supplied to hydraulic operating devices such as the hydraulic lash adjusters 24 and 25, and oil for cooling and cooling (cooling). Fluid) is supplied to each part of the engine body 2.

(Detailed structure of cylinder block 5)
As shown in FIGS. 1 and 2, the cylinder block 5 includes a block body 50 that is a cast product of an aluminum alloy, and a cylindrical cylinder liner 51 that is cast or press-fitted into the block body 50. The cylinder bore 7 is formed by the cylinder liner 51.

  The block body 50 includes four cylinder portions 55, a skirt portion 56 that is connected to the lower side of the cylinder portion 55 to form a crank chamber, and a crankshaft bearing portion 57 that is formed inside the skirt portion 56. ing. The cylinder liner 51 is disposed in each cylinder portion 55.

  The cylinder liner 51 includes a first liner member 62 that forms a portion other than the upper end portion of the cylinder bore 7, and a second liner member 63 that abuts on the upper end and forms the upper end portion of the cylinder bore 7. . In this example, the second liner member 63 forms a part of the combustion chamber at the end of the compression process, for example.

  The first liner member 62 has a cylindrical shape having a certain thickness over the axial direction. The first liner member 62 is made of a high thermal conductivity carbon fiber reinforced resin composite material (CFRP) and has thermal conductivity anisotropy. More specifically, the first liner member 62 is made of, for example, a carbon fiber reinforced resin composite material obtained by impregnating and laminating pitch-based carbon fibers in an epoxy resin or the like, and the carbon fibers of the cylinder liner 51 (first liner member 62). It is formed in a cylindrical shape so as to be parallel to the center line. As a result, the first liner member 62 has a thermal conductivity equal to or higher than that of the metal material, and has a thermal conductivity greater in the vertical direction (axial direction) than in the thickness direction (radial direction). That is, it has a structure having thermal conductivity anisotropy. In the following description, this heat conduction anisotropy is referred to as a first heat conduction anisotropy for convenience.

  As shown in FIG. 2, the second liner member 63 has a cylindrical shape having the same outer diameter and the same inner diameter as the first liner member 62. The second liner member 63 and the first liner member 62 are in contact with each other on a plane orthogonal to the center line (axial center) of the cylinder liner 51.

  The second liner member 63 is a tapered boundary surface 65 inclined with respect to the center line of the cylinder liner 51. Specifically, from the lower side (first liner member 62 side) to the upper side (anti-first liner member 62 side). It has an outer cylinder part 64a and an inner cylinder part 64b that are adjacent to each other inside and outside through a boundary surface 65 that is inclined so as to approach the axis as it goes.

  As shown in FIG. 2, in this example, the cross-sectional shape (the cross-sectional shape of the solid part) along the axis of the second liner member 63 is a rectangle, and the cylindrical portions 64a and 64b are diagonal lines of the rectangular cross-section. The boundary surface 65 is formed on the upper side. Therefore, only the inner cylinder portion 64 b of the second liner member 63 is in contact with the first liner member 62.

  Similarly to the first liner member 62, the second liner member 63 also has thermal conductivity anisotropy by being formed of a high thermal conductivity carbon fiber reinforced resin composite material (CFRP). 64a and the inner cylinder part 64b have mutually different heat conduction anisotropies. Specifically, unlike the first liner member 62, the outer cylinder portion 64a has a heat conductivity characteristic (for convenience, the heat conductivity in the thickness direction (radial direction) is larger than the heat conductivity in the vertical direction (axial direction). Similarly to the first liner member 62, the inner cylindrical portion 64 b has the first heat conduction anisotropy.

  The water jacket 26 is provided at the radially outer side (outer periphery) of the second liner member 63, that is, at a position around the combustion chamber corresponding to the end of the compression process. The water jacket 26 is formed by the outer peripheral surface of the second liner member 63, the wall surface of the stepped portion 50a formed in the block main body 50, and the gasket. That is, the outer peripheral surface of the second liner member 63 in the cylinder liner 51 is in direct contact with the cooling water.

(Operational effects of the engine structure above)
According to the engine structure as described above, since the first liner member 62 of the cylinder liner 51 has the first heat conduction anisotropy, the heat received by the cylinder liner 51 is exclusively indicated by the arrows in FIG. As indicated by A <b> 1, it moves along the first liner member 62 toward the water jacket 26 having the low temperature, that is, toward the second liner member 63. Then, the heat that has reached the upper end of the first liner member 62 moves the second liner member 63 outward in the radial direction as indicated by an arrow A2 in FIG. Is transmitted to. That is, since both the inner cylindrical portion 64 b of the second liner member 63 and the first liner member 62 have the first thermal conductivity anisotropy, the heat reaching the upper end of the first liner member 62 is the first liner member 62. To the second liner member 63 (inner cylinder portion 64b). Further, the outer cylinder portion 64a and the inner cylinder portion 64b of the second liner member 63 have different heat conduction anisotropies, but these are adjacent to each other inside and outside via the inclined boundary surface 65 as described above. Therefore, the heat transmitted to the inner cylinder part 64b is smoothly transmitted from the inner cylinder part 64b to the outer cylinder part 64a. And since the outer cylinder part 64a has 2nd heat conduction anisotropy, the heat transmitted to the said outer cylinder part 64a is the diameter of the 2nd liner member 63 toward the water jacket 26 side with low temperature. It will move smoothly outward in the direction.

  Thus, according to the engine structure described above, the heat received by the cylinder liner 51 moves toward the upper end of the cylinder liner 51 as indicated by arrows A1 and A2 in FIG. The upper end portion is transmitted to the cooling water in the water jacket 26 while smoothly moving outward in the radial direction.

  Therefore, according to this engine structure, heat radiation from the cylinder liner 51 to the cylinder portion 55 can be suppressed and the combustion chamber 10 can be maintained at a high temperature to increase the thermal efficiency of the engine, while the heat received by the cylinder liner 51 is increased. Can be efficiently transmitted to the cooling water in the water jacket 26 to raise the temperature of the cooling water. In particular, according to this engine structure, the wall surface of the water jacket 26 is formed by the second liner member 63, and the cooling water directly contacts the second liner member 63, so that the second liner member 63 changes to the cooling water. Heat transfer is performed efficiently. Therefore, according to the engine structure described above, the heat of combustion can be efficiently transmitted to the cooling water via the cylinder liner 51 (the first liner member 62 and the second liner member 63) to raise the temperature of the cooling water. it can.

  FIG. 3 shows a modification of the engine structure. The figure is a sectional view of the cylinder block 5 and corresponds to FIG.

  The modification shown in FIG. 3 is common to the structure of FIG. 2 in that the second liner member 63 has an outer cylinder part 64a and an inner cylinder part 64b. However, the boundary surface 65 is different from the structure shown in FIG. The area is small. That is, the position of the boundary line formed on the inner peripheral surface of the second liner member 63 by the boundary surface 65 is located inside the axial both ends of the second liner member 63 and the second liner member 63 The outer cylinder part 64 a and the inner cylinder part 64 b are formed so that the position of the boundary line formed on the lower end surface is located inside the outer peripheral surface of the second liner member 63. With this configuration, a part of the outer cylindrical portion 64a of the second liner member 63 faces the combustion chamber. That is, a part of the inner peripheral surface of the outer cylinder part 64a forms a combustion chamber.

  According to the engine structure shown in FIG. 3, the heat received by the cylinder liner 51 moves toward the upper end of the cylinder liner 51 as indicated by arrows A1 and A2 in FIG. Further, it is transmitted to the cooling water in the water jacket 26 while smoothly moving radially outward at the upper end of the cylinder liner 51. In addition, according to this engine structure, a part of the outer cylindrical portion 64a faces the combustion chamber as described above, so that the heat generated in the combustion chamber directly flows as shown by the arrow A3 in FIG. It is transmitted to the cooling water in the water jacket 26 through the outer cylinder part 64a. Therefore, it is possible to efficiently raise the temperature of the cooling water.

FIG. 4 shows the results of measuring the temporal change in the heat flux (W / mm ² ) of the second liner member 63 for the engine structure of FIGS. 2 and 3 and the engine structure of the reference example shown in FIG. The engine structure shown in FIG. 5 is the same as that shown in FIGS. 2 and 3 except that the entire second liner member 63 is formed of a carbon fiber reinforced resin composite material (CFRP) having the second thermal conductivity anisotropy. Is the same.

  As shown in FIG. 4, the engine structure of FIGS. 2 and 3 generally has a higher heat flux value than the engine structure of FIG. 5, and the water jacket 26 is more efficient in combustion heat than the engine structure of FIG. 5. It can be considered that it is transmitted to the cooling water inside. That is, in the engine structure of FIG. 5, the thermal conductivity anisotropy of the liner members 62 and 63 is orthogonal to each other, and there is a tendency that heat transfer from the first liner member 62 to the second liner member 63 is difficult. 2 and 3, this point is improved.

  In particular, as shown in FIG. 4, according to the engine structure of FIG. 3, the rise of the heat flux value with the passage of time is faster than that of the engine structure of FIG. This is because, in the engine structure of FIG. 2, the combustion heat received by the first liner member 62 is transmitted to the cooling water (see arrows A1 and A2 in FIG. 2), whereas in the engine structure of FIG. In addition to the heat received by the first liner member 62 being transferred to the cooling water, the combustion heat is directly transferred from the second liner member 63 (outer cylinder portion 64a) to the cooling water (arrow A3 in FIG. 3). For reference). From this, according to the engine structure shown in FIG. 3, the temperature of the cooling water can be raised more efficiently immediately after the engine is started, and thus the heating function using the thermal energy of the cooling water can be activated earlier. Can be considered.

  2 and 3 are exemplifications of a preferred embodiment of the engine structure according to the present invention, and the specific configuration thereof can be appropriately changed without departing from the gist of the present invention.

  For example, in the engine structure of the above embodiment, the boundary surface 65 between the outer cylinder portion 64a and the inner cylinder portion 64b is, as shown in FIGS. 2 and 3, the boundary surface 65 in the cross section of the second liner member 63. Although the boundary line to be formed is a surface that is a straight line, the boundary surface 65 may be a surface in which the boundary line is a curved line (curved line) as shown in FIG. In short, the boundary surface 65 may be a surface that is inclined so as to approach the axial center of the cylinder liner 51 from the lower side (first liner member 62 side) to the upper side (anti-first liner member 62 side).

  In the cylinder liner 51, a portion corresponding to the inner cylindrical portion 64b of the second liner member 63 shown in FIGS. 2 and 3 is formed by the first liner member 62 as shown in FIGS. It may be what was done. In FIG. 7, a taper portion is formed at the upper end portion of the first liner member 62, so that a portion corresponding to the inner cylinder portion 64 b of FIG. 2 is formed integrally with the first liner member 62. On the other hand, in FIG. 8, a truncated cone-shaped protrusion corresponding to the inner cylindrical portion 64b of FIG. 3 is integrally formed on the upper end surface of the first liner member 62. That is, in the cylinder liner 51, the first liner member 62 and the second liner member 63 are directed from the lower end portion (first end portion of the present invention) to the upper end portion (second end portion of the present invention) of the cylinder liner 51. Accordingly, a configuration may be adopted in which they are in contact with each other via a boundary surface 66 including an inclined surface 66a that is inclined so as to approach the axial center. According to such a configuration, since the boundary as shown in FIGS. 2 and 3 is not formed between the inner cylindrical portion 64 b of the second liner member 63 and the first liner member 62, the first liner member 62 is separated from the first liner member 62. Heat transfer to the second liner member 63 is performed more smoothly.

  Moreover, in the said embodiment, although the 1st liner member 62 and the 2nd liner member 63 are both formed with the high thermal conductivity carbon fiber reinforced resin composite material (CFRP) as a material which has thermal conductivity anisotropy. Of course, it may be formed of a material having thermal conductivity anisotropy other than this. For example, composite materials of graphite and metal (aluminum, etc.), that is, composite materials in which graphite is oriented in the metal so that there is a difference in the heat transfer coefficient in the orthogonal direction, and heat conduction anisotropic using multi-walled carbon nanotubes You may be comprised with the material which has property.

DESCRIPTION OF SYMBOLS 1 Engine 5 Cylinder block 7 Cylinder bore 26 Water jacket 51 Cylinder liner 62 1st liner member 63 2nd liner member 64a Outer cylinder part 64b Inner cylinder part 65, 66 Boundary surface 66a Inclined surface

Claims (5)

An engine structure including a cylinder liner that forms a combustion chamber, and a cooling unit that is located radially outside and through which a cooling medium flows,
The cylinder liner includes a cylindrical first liner member, and a cylindrical second liner member disposed in a position corresponding to the cooling portion in contact with one axial end thereof,
The first liner member has a thermal conductivity anisotropy in which an axial thermal conductivity is larger than a radial thermal conductivity,
The second liner member includes an outer cylindrical portion and an inner cylindrical portion that are adjacent to each other inside and outside through a boundary surface that is inclined so as to approach the axial center from the first liner member side toward the anti-first liner member side,
The outer cylinder portion has a thermal conductivity anisotropy whose radial thermal conductivity is larger than the axial thermal conductivity, and the inner cylindrical portion has an axial thermal conductivity of radial thermal conductivity. An engine structure characterized by having a larger thermal conductivity anisotropy. The engine structure according to claim 1,
The engine structure, wherein the second liner member has a rectangular cross-sectional shape along a center line, and the boundary surface is located on a diagonal line of the rectangular cross section. The engine structure according to claim 1,
An engine structure characterized in that a position of a boundary line formed on an inner peripheral surface of the second liner member by the boundary surface is located on an inner side than both axial ends of the second liner member. An engine structure including a cylinder liner that forms a combustion chamber, and a cooling unit that is located radially outside and through which a cooling medium flows,
The cylinder liner has a cylindrical first liner member having a thermal conductivity anisotropy that has a larger thermal conductivity in the axial direction than the thermal conductivity in the radial direction, and contacts the one end in the axial direction to correspond to the cooling unit. And a cylindrical second liner member having a thermal conductivity anisotropy that is disposed at a position where the thermal conductivity in the radial direction is larger than the thermal conductivity in the axial direction,
Among the cylinder liners, when the end on the first liner member side in the axial direction is defined as the first end, and the end on the second liner member side is defined as the second end,
The first liner member and the second liner member are in contact with each other via a boundary surface including an inclined surface that is inclined so as to approach the axial center as it goes from the first end portion to the second end portion. , Engine structure characterized by that. The engine structure according to any one of claims 1 to 4,
The engine structure according to claim 1, wherein the cooling section is provided at a position around the combustion chamber corresponding to the last stage of the compression process.

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