Insert element and its manufacturing process

Abstract

An insert member that effectively disperses shear stress generated at the interface of composite casting is provided. Such a member comprises, on a surface (11s) to which cast metal is to be bonded by composite casting: a projecting portion (3) of mesh shape; bottom surfaces (F) surrounded by the projecting portion (3); and a separate protruding portion (5a, 5b) preferably in a pin shape. The projecting portion (3) comprises a top portion and a vertical wall portion extending from the bottom surface. The width at the top portion is greater than the width of the vertical wall portion. At least some of the bottom surfaces (F) are approximately planar. When the projecting portion (3) is projected onto a plane, it forms linear portions (31) and a joining portion (32) where linear portions merge.

Description

Technical Field The present invention relates to an insert member and a method for manufacturing the same. More particularly, the present invention relates to an insert member having a vibration damping effect and a method for manufacturing the same. Technological background A cylinder block (hereinafter also referred to as B / C), which is a core part of an automobile, is cast using a high-productivity die-casting process, and sleeves in which pistons slide are inserted into the aluminum at the same time as die-casting. Such a sleeve inserted into cast metal by die casting conventionally has separate protrusions with narrowed distal ends on the outer peripheral surface of the sleeve (see, for example, Patent Documents JP 4429025 B2 and JP 4210468 B2). These protrusions increase the adhesion and bonding force (adhesion force) between a cylinder and the sleeve, reduce the residual stress between the bores, avoid the reduction of the adhesion force to aluminum in the radial direction, and furthermore, improve heat dissipation during combustion, and thus, these protrusions contribute to excellent engine performance. Recently, to improve the operating comfort of the vehicle, the need to reduce noise and vibration generated by rotating parts has increased, not only for a B / C, but also for a brake drum, a shaft portion of a transmission case, and an aluminum wheel hub. Some examples in which a cast iron insert member is inserted into an aluminum body by composite casting have been reported (for example, see JP H05-187466 A). Problem of Invention Nowadays, engine downsizing involving sleeve thinning is highly desired. In this situation, conventional techniques, for example, presented in Documents JP 4429025 B2 and JP 4210468 B2., pose a major problem in that sleeve thinning deteriorates rigidity. This is due to the fact that the sleeves are exposed to high injection pressure of aluminum molten metal during die casting molding, and furthermore, when a cylinder head is attached to the B / C, high bolt fastening loads are likely to generate high compression distortion in the sleeves. In a rotating aluminum part comprising an insert member as described in JP H05-187466 A, there is a large difference in Young's modulus between the inserted cast member and the aluminum. Due to this difference, there is concern that a high rotational torque exerted during braking will generate a high shear stress locally at the composite casting interface, and that plastic deformation of the aluminum may occur in the local regions around the interface. Thus, the development of a new sleeve structure that further increases rigidity and disperses stresses generated by external force would be desirable to help prevent deterioration of noise, vibration, and harshness (BVD) characteristics around bores. Solution The inventors have conducted extensive studies and designed an insert member having mesh-like protruding portions on the surface to which the cast metal is to be bonded by composite casting and also having an effective structure for reducing distortion and stress, and its manufacturing method for solving the above problems. [1] One embodiment provides an insert member comprising, on a surface to which the cast metal is to be bonded by composite casting: a protruding portion of mesh shape; bottom surfaces surrounded by the projecting portion; and a separate protruding portion, in which the projecting portion comprises an upper portion and a vertical wall portion extending from a bottom level of the bottom surfaces, the width of the upper part is greater than the width of the vertical wall portion, at least some of the bottom surfaces are approximately flat, the separated protruding portion has a pin shape extending from at least some of the bottom surfaces, and when the mesh-shaped protruding portion is assumed to be projected onto a plane, the protruding portion forms linear portions and a joining portion in which at least two of the linear portions merge. [2] Another embodiment relates to an insert element comprising, on a surface to which the cast metal is to be bonded by composite casting: a protruding portion of mesh shape; and bottom surfaces surrounded by the protruding part, in which the projecting portion comprises an upper portion and a vertical wall portion extending from a bottom level of the bottom surfaces, the width of the upper part is greater than the width of the vertical wall portion, at least some of the bottom surfaces are convex surfaces bulged in an outer peripheral direction of the surface to which the cast metal is to be bonded by composite casting, and when the mesh-shaped protruding portion is assumed to be projected onto a plane, the protruding portion forms linear portions and a joining portion in which at least two of the linear portions merge. [3] Yet another embodiment relates to an insert member comprising, on a surface to which the cast metal is to be bonded by composite casting: a protruding portion of mesh shape; bottom surfaces surrounded by the projecting portion; and a separate protruding portion, in which the projecting portion comprises a vertical wall portion extending from the bottom level of the bottom surfaces and having randomly different heights, at least some of the bottom surfaces are approximately flat, the separated protruding portion has a pin shape extending from at least some of the bottom surfaces, and when the mesh-shaped protruding portion is assumed to be projected onto a plane, the protruding portion forms linear portions and a joining portion in which at least two of the linear portions merge. [4] Yet another embodiment relates to an insert member comprising, on a surface to which the cast metal is to be bonded by composite casting: a protruding portion of mesh shape; and bottom surfaces surrounded by the protruding part, in which the projecting portion comprises a vertical wall portion extending from the level (bottom level) of the bottom surfaces and having different heights of randomly, at least some of the bottom surfaces are convex surfaces arched in an outer peripheral direction of the surface to which the cast metal is to be bonded by composite casting, and when the mesh-shaped protruding portion is assumed to be projected onto a flat plane, the protruding portion forms linear portions and a joining portion in which at least two of the linear portions merge. [5] In the insert element according to the above in point [2] or point [4], it is preferable that a bottom surface which constitutes / forms a convex surface includes a separate protruding pin-shaped portion extending from the bottom level (bottom surface level). [6] In the element to be inserted according to any of [1], [3], and [5] above, it is preferable that the protruding pin-shaped portion be (a) a tapered pin-shaped protruding portion in which the diameter of a distal end of the protruding portion is less than the diameter of the base of the protruding portion and has a height of 0.1 mm or more and 0.5 mm or less, and / or (b) a protruding portion having a half-dome shape. [7] In the member to be inserted according to any of [1], [3], [5], and [6] above, it is preferable to form one to ten of the separate protruding portions in each bottom surface surrounded by the protruding portion. [8] In the element to be inserted according to any of [1] to [7] above, it is preferable that when the mesh-shaped protruding portion is assumed to be projected onto a plane, the projected area of ​​the protruding portion is 5% or more and 70% or less relative to the total projected area. [9] In the element to be inserted according to any of points [1] to [8] above, it is preferable that when the mesh-shaped protruding portion is assumed to be projected onto a plane, the diameter of a circle inscribed in an outline of a portion enclosed by the linear portions and the joining portion is 0.5 mm or more and 30 mm or less.

[10] In the element to be inserted according to any of [1] to [9] above, it is preferable that the height of the mesh-shaped protruding portion is 0.1 mm or more and 5.0 mm or less.

[11] In the element to be inserted according to any of [1] to

[10] above, it is preferable that the length of the linear portions in the width direction be 0.1 mm or more and 8.0 mm or less.

[12] In the insert member according to any one of [1 ] to [11 ] above, it is preferable that the insert member is a cylinder sleeve, a brake sliding member, a support member, and a hub for a motorcycle wheel.

[13] According to another aspect, there is provided a method of manufacturing an insert element comprising at least the steps of: applying a mold coating agent to a surface, onto which molten metal is to be poured, of a mold; forming a mold coating layer into a shape with cracks and depressions on a surface of the mold coating layer by drying the applied mold coating agent; and perform a casting by pouring the molten metal onto the mold coating layer while rotating the mold, wherein cracks include multiple gaps extending from the surface of the mold coating layer and reaching a surface of the mold, the gap widths decrease from the surface of the coating layer mold towards the mold surface, at least some of the gaps extend along the mold surface, and the hollows have a pin shape that does not reach the surface of the mold.

[14] According to yet another aspect, there is provided a method of manufacturing an insert element comprising at least the steps of: applying a mold coating agent to a surface, onto which molten metal is to be poured, of a mold; forming a mold coating layer into a shape with cracks on a surface of the mold coating layer by drying the applied mold coating agent; and perform a casting by pouring the molten metal onto the mold coating layer while rotating the mold, wherein cracks include multiple gaps extending from the surface of the mold coating layer to a surface of the mold, the gap widths decrease from the surface of the mold coating layer towards the mold surface, some of the gaps extend along the mold surface, and central portions of at least some of the portions defined by the cracks in the mold coating layer are recessed relative to the surroundings of the central portions (surroundings surrounding those central portions).

[15] According to yet another aspect, there is provided a method of manufacturing an insert element comprising at least the steps of: applying a mold coating agent to a surface, onto which molten metal is to be poured, of a mold; forming a mold coating layer into a shape with cracks and pits on a surface of the mold coating layer by drying the curing agent mold coating applied; and perform a casting by pouring the molten metal onto the mold coating layer while rotating the mold, wherein the cracks include multiple gaps extending from the surface of the mold coating layer toward a surface of the mold, the gap widths decrease from the surface of the mold coating layer towards the mold surface, the depths of the gaps differ randomly (so that the cracks have a random variation in depth), and the hollows have a pin shape that does not reach the surface of the mold.

[16] According to another aspect, there is provided a method of manufacturing an insert element comprising at least the steps of: applying a mold coating agent to a surface, onto which molten metal is to be poured, of a mold; forming a mold coating layer into a shape with cracks on a surface of the mold coating layer by drying the applied mold coating agent; and perform a casting by pouring the molten metal onto the mold coating layer while rotating the mold, wherein the cracks include multiple gaps extending from the surface of the mold coating layer toward a surface of the mold, the gap widths decrease from the surface of the mold coating layer towards the mold surface, the depths of the gaps differ randomly, and central parts of at least some of the parts defined by the cracks in the mold coating layer are recessed relative to the surroundings of the central parts (surroundings surrounding these central parts).

[17] In the method of manufacturing an insert member according to any of

[13] to

[16] above, it is preferable that the cracks have a mesh shape.

[18] In the method of manufacturing an insert member according to any one of

[13] to

[17] above, it is preferable that the mold coating agent contains at least a flame retardant material, a binder and a solvent.

[19] In the method for manufacturing an insert member according to any one of

[13] to

[18] above, it is preferable that the step of forming the mold coating layer comprises heating the mold coating agent to a temperature between an evaporation temperature of a solvent and a temperature higher than the evaporation temperature of 110°C, inclusive, and drying the solvent to form the mold coating layer with the shape of the cracks. Beneficial effects An insert member according to the present invention reduces shear and compressive stresses at the composite casting interface and improves vibration damping characteristics in a product obtained by inserting the insert member into aluminum or the like by composite casting, and thus prevents deterioration of BVD characteristics. In addition, the insert member has specific shapes on the surface to which the cast metal is to be bonded by composite casting, which increases the contact area with the aluminum used for composite casting and improves the thermal conductivity that affects the heat transfer and thermal diffusivity of the insert member into the aluminum. Brief description of the figures Figure 1 is a conceptual perspective view of an exemplary cylinder sleeve. Figure 2 is a schematic enlarged view of area d1 in Figure 1 and a conceptual perspective view of a surface, to which the cast metal is to be bonded by composite casting, of an insert member according to a first embodiment of the present invention. Figure 3 is an enlarged schematic view of the surface, to which the cast metal is to be bonded by composite casting, of a cylinder sleeve similar to that of Figure 1 and a conceptual perspective view of a surface, to which the cast metal is to be bonded by composite casting, of an insert according to a second embodiment of the present invention. Figure 4 is a schematic sectional view of an exemplary cylinder block. Figure 5 is a top view of a portion of the surface, to which a cast metal is to be bonded by composite casting, of an insert member according to the first embodiment of the present invention when viewed in two dimensions. Figure 6 is a sectional view taken along line AA' of Figure 5. Figure 7 is an enlarged sectional view of a separate tapered pin-shaped protruding portion in Figure 6. Figure 8 is an enlarged sectional view of a separate half-dome-shaped protruding portion in Figure 6. Figure 9 is a schematic cross-sectional view of projecting portions having tapered shapes. Figure 10 is a sectional view taken along line BB' of Figure 5 and a schematic view of projecting portions composed of vertical wall portions. Figure 11 is an electron microscope photograph at a magnification of 12 times of a portion of the surface, to which the cast metal is to be bonded by composite casting, of an insert member according to the first embodiment of the present invention. Figure 12 is a top view of a portion of the surface, to which a cast metal is to be bonded by composite casting, of an insert member according to the second embodiment of the present invention when viewed in two dimensions. Figure 13 is a sectional view taken along line DD' in Figure 12. Figure 14 is an electron microscope photograph at a magnification of a factor of 20 of a portion of the surface, to which the cast metal is to be bonded by composite casting, of an insert member according to the second embodiment of the present invention. Figures 15A, 15B, 15C, 15D, 15E, 15F, 15G, 15H, corresponding to successive moments during manufacturing, together form a diagram for explaining a method of manufacturing an insert element according to the present invention. Figures 16A, 16B, 16C, 16D, corresponding to different stages in the processing, form a diagram for explaining the mechanism of forming a mold coating layer in the method of manufacturing an insert member according to the present invention. Figure 17 is a diagram schematically illustrating an insert element obtained using the mold coating layer described in Figure 16D. Figures 18A and 18B, 18C, 18D are used to schematically explain the stresses generated at a composite casting interface and the stress-reducing effect in the case where an insert member is a cylinder sleeve to be inserted into an engine cylinder block by composite casting. Figures 19A and 19B, 19C, 19D is a diagram for explaining the stresses generated at a composite casting interface and the stress-reducing effect in the case where an insert member is a sliding member configured to contact brake shoes, inserted into an aluminum drum brake by composite casting. Figure 20 is an electron microscope photograph of an insert element, illustrating an example of external reliefs of the insert element. Figure 21 is an electron microscope photograph of a cross-section of an insert element. Details of Embodiments Illustrating the Invention Hereinafter, embodiments will be described in detail, without the scope of the present invention being limited to these embodiments. One embodiment provides an insert member. Examples of materials for the insert member include cast iron, a copper alloy, tin, or a zinc alloy, which are metals having large specific gravities, self-sliding properties, and a large vibration damping coefficient. In particular, cast iron is suitable because cast iron is a ternary alloy commonly containing iron, carbon, and silicon, is an alloy in which graphite having an excellent self-sliding property is crystallized, and has an excellent vibration damping property. For example, cast iron may contain, in addition to Fe, between 3.1 and 3.8% by mass of T.C (total carbon), 1.9 to 2.5% by mass of Si, 0.5 to 1.0% by mass of Mn, 0.01 to 0.5% by mass of P, and 0.02 to 0.1% by mass of S relative to the total mass of the cast iron. The shape of the body of an insert member is not particularly limited but may be appropriately selected depending on the application. Examples of the shape of the insert member include a cylindrical shape, a semi-cylindrical shape, a U-shape or an inverted T-shape viewed in cross-section, and a curved shape or an approximately planar plate shape. Examples for the insert member include those to be inserted into a certain type of die-casting parts by composite casting, such as a cylinder sleeve to be inserted into an engine cylinder block; a an annular sliding member, which contacts brake shoes, to be inserted into an aluminum drum brake of a regenerative brake of an electric vehicle, a hybrid vehicle, or the like; a die-cast wheel hub boss for a motorcycle and special machines; further, a crankshaft journal part in a cylinder block or a lower crankcase; and a support part in a transmission case or a crankcase of an electric motor or the like. Hereinafter, the present invention will be described by illustrating a cylinder sleeve of cylindrical shape; however, the present invention is not limited to inserts having specific shapes or to specific products. Figure 1 is a conceptual perspective view of a cylinder sleeve 11, which is an example of an insert. The cylinder sleeve 11 has a tubular structure defined by an inner surface 11is and an outer surface 11s, and the outer surface 11s is the surface to which the cast metal, such as aluminum, is to be bonded by composite casting. Figure 2 is an example of an enlarged schematic perspective view of the area indicated by d1 in Figure 1 and is a schematic perspective view of an insert according to a first embodiment of the present application. The cylinder sleeve includes mesh-like protruding portions 3, a lower surface or bottom surface F, and separate protruding portions 5a and 5b on the surface 11s to which the cast metal is to be bonded by composite casting.The mesh-shaped protruding portions 3 protrude from the bottom surface F and continuously exist on the entire surface to which the cast metal is to be bonded by composite casting. Figure 3 is an enlarged schematic perspective view of an area of the surface to which the cast metal is to be bonded by composite casting of a cylinder sleeve similar to that of Figure 1 and is a schematic perspective view of an insert element according to a second embodiment of the present application. The... The configuration of the mesh-shaped protruding portion 3 is almost identical to that of Figure 2. However, in Figure 3, a lower surface or bottom surface C, surrounded by the mesh-shaped protruding portion 3, has a convex surface structure in which the center forms a boss relative to its surroundings (here relative to the area surrounding the bulged area). In the following, a cylinder sleeve will be briefly described. Figure 4 is a conceptual diagram illustrating an example of a cylinder block comprising a cylinder sleeve as a component. The cylinder block 10 is cast by bonding aluminum 12 to the outer peripheral surface of the cylinder sleeve 11, by composite casting. First embodiment relating to an insertion element The first embodiment of the present invention relates to an insert member. The insert member according to the present embodiment comprises, on a surface to which cast metal is to be bonded by composite casting: a mesh-shaped protruding portion 3; bottom surfaces surrounded by the protruding portion; and at least one separate protruding portion 5a and / or 5b, wherein at least some of the bottom surfaces F constitute an approximately planar surface, the separate protruding portion may be a pin-shaped protruding portion 5a extending from at least some of the bottom surfaces F, and when the mesh-shaped protruding portion 3 is assumed to be projected onto a plane, the protruding portion forms linear portions and a joining portion in which at least two of the linear portions merge.In a first mode of the first embodiment, the projecting portion 3 comprises an upper portion and a vertical wall portion extending from the lower surface, and the width L4 of the upper portion 4 is greater than the width L7 of the vertical wall portion 7. In a second mode of the first embodiment, the projecting portion 3 comprises a vertical wall portion 7 extending from the lower surface and having heights . randomly different. Figure 5 is a top view of the surface 11s, to which a cast metal is to be bonded by composite casting, of an insert member according to the first embodiment viewed in a two-dimensional form from a direction perpendicular to the surface. Figure 6 is a sectional view taken along the line AA' of Figure 5. The surface 11s, to which the cast metal is to be bonded by composite casting, of the insert member corresponds to the outer peripheral surface of the cylinder sleeve 11 of Figure 1. When the surface 11s to which the cast metal is to be bonded by composite casting is viewed two-dimensionally from the outer peripheral direction, the protruding portion 3 has a mesh-like structure comprising linear portions (31; 31a, 31b, 31c, 31d, 31d, 31e) and joining portions (32; 32a, 32b, 32c, 32d). The linear portions 31 and 31a, 31b, 31c, 31d, 31d, 31e are portions in which the protruding portions 3 can be recognized in linear or strip-like shapes having widths. The linear portions may be either linear or curved, and may not be uniform in width, length, or height and have indefinite shapes. The longitudinal length La of the linear portion 31 is not particularly limited.The lateral length of the linear portion 31, in other words, the length Lb of the upper part of the linear portion in the width direction is preferably 0.1 mm or more and 8.0 mm or less, more preferably 0.1 mm or more and 5.0 mm or less, and most preferably about 0.2 mm or more and 3.0 mm or less. The extension or lateral length Lb of the linear portion 31 corresponds to the width of the linear portion 31 projected onto a plane. A lateral length Lb of less than 0.1 mm may result in insufficient anchoring effect on the aluminum used for composite casting and insufficient effect of the linear portions 31 in reducing deformation of the aluminum. A lateral length Lb of more than 8.0 mm may result in insufficient weight reduction. Setting the lengths of the upper portions of the linear portions 31 within the above range increases the number of hub portions, which constitute the joining portion 32 into which the linear portions 31 merge. It is noted that the length of the upper surface of the upper portion of the linear portion 31 in the width direction can be measured using, for example, a digital microscope. For example, the measurement is performed between 1 and 50 points, and the length can be determined as a range including measured values ​​based on the average value or the minimum and maximum values, or preferably a range including all the measured values.It should be noted that the length Lb of the upper part of the linear portion in the width direction may differ in certain cases between a first mode in which the projecting portions 3 have cross sections of narrowed shapes and a second mode in which the projecting portions are composed of vertical wall portions. The details will be described below. In Fig. 5, the joining portion 32a is formed by the joining area of ​​three linear portions 31a, 31b, and 31c that join together. The number of linear portions 31 merging into a joining portion 32 is not particularly limited but is at least 2, and preferably 2 to 6 inclusive. It is preferable that a mesh-shaped protruding portion 3 comprises at least two joining portions 32. In the case where a mesh-shaped protruding portion 3 comprises two or more joining portions 32, the number of linear portions 31 merging at each joining portion 32 may be the same or different. The mesh-shaped protruding portions 3 formed on the outer peripheral surface of the insert member provide a reinforcing rib effect that improves the rigidity of the insert member.In addition, it is preferable that the linear portions 31 merge into a joining portion 32 from random directions, from the viewpoint of dispersing stresses generated by an external force after the element to be inserted. be inserted by casting. Merging linear portions 31 from random directions means, for example, that two linear portions 31 merge into a joining portion 32 from different directions instead of being parallel to each other. The bottom surface or bottom surface F is a portion surrounded by linear portions 31a, 31b, 31d, and 31e and joining portions 32a, 32b, 32c, and 32d of the protruding portions 3 when viewed in two dimensions. Meanwhile, with reference to FIG. 6, the bottom surface F is a portion defined as an approximately planar surface nearly parallel to the inner surface 11is of the member to be inserted. In the present description, the expression "an approximately planar surface" means a surface in which there is practically no difference in thickness between the center and the surroundings of the bottom surface F, or the difference is less than about 100 μm, unlike the convex surface. The surroundings of the bottom surface F denote portions at which the protruding portions 3 extend, and the center denotes a portion at least far from the surroundings.In the partial structure illustrated in Figures 5 and 6 of the element to be inserted according to the present embodiment, the protruding portions 3 form a continuous mesh without interruption, and it is then permissible to form an area surrounded by the protruding portions 3 and also by the lower surface F (for example when the lower surface F has an annular geometry or surrounding islands of greater thickness). This area is called a cell in the present description. It should be noted that a cell is not limited to an area (island) completely surrounded by continuous protruding portions 3 but can be an area surrounded by protruding portions 3 with an interruption, which can also be considered as a cell in the same way, for example, by compensating the interrupted part with an imaginary extension line on the top view. In Figures 5 and 6, separate protruding portions 5a and 5b are formed in a cell.The separate protruding portions 5a and 5b are projecting portions. each having a pin shape having an approximately circular shape when viewed in two dimensions, in contrast to the continuous protruding portion 3. It is preferable that one to ten separate protruding portions 5a and 5b are formed per cell, and it is further preferable that one to six separate protruding portions are formed per cell. However, not all multiple cells existing on the inserter need to have separate protruding portions. Multiple separate protruding portions 5a and / or 5b included in a cell may have the same shape or different shapes. The separate protruding portions are roughly divided into a set of protruding portions 5a in tapered pin shapes and a set of protruding portions 5b in half-dome shapes. Figure 7 is an enlarged view of the separate protruding portion 5a of Figure 6, which shows a cross-section of the separate protruding portion 5a in tapered pin shape. The separate protruding portion 5a in tapered pin shape is a portion in which the diameter R5a of the base of the protruding portion at which the protruding portion extends from the bottom surface F is greater than the diameter of the distal end portion of the pin, and the height h5a of the protruding portion is about twice or more the diameter R5a of the base of the protruding portion. The height h5a of the separate protruding portion 5a in the form of a tapered pin is, for example, between 0.1 mm and 0.5 mm, and preferably between 0.2 mm and 0.4 mm.Separate protruding portions with h5a heights less than the above range may result in insufficient shear stress dispersion effect and insufficient heat radiation effect at the composite casting interface. Separate protruding portions with h5a heights greater than the above range may reduce the aluminum filling property in the cells when manufacturing an insert and make the formation of gaps at the . level of the interface of the protruding portions 3, which reduces the performance of the insertion element 11 itself. Figure 8 is an enlarged view of the separate protruding portion 5b of Figure 6, which shows a cross-section of the separate protruding portion 5b in a half-dome shape. The separate protruding portion 5b in a half-dome shape is a portion in which the height h5b of the protruding portion is less than about twice the diameter R5b of the base of the protruding portion and the distal end is substantially curved. The height h5b of the separate protruding portion 5b in a half-dome shape is, for example, about 0.1 mm to 0.5 mm, and preferably about 0.2 mm to 0.4 mm. Referring to Figure 5, when the surface 11s to which the cast metal is to be bonded by composite casting is viewed two-dimensionally from a direction perpendicular to the surface, an inscribed circle 1e may be drawn on the bottom surface or bottom surface F surrounded by the protruding portions 3. The diameter of this inscribed circle 1e is preferably between 0.5 mm and 30 mm inclusive, more preferably between 1.0 and 15 mm, and most preferably between 1.5 mm and 5.0 mm. Diameters smaller than 0.5 mm may result in insufficient effective contact area with aluminum during composite casting. Therefore, it may be difficult to maintain an effective anchoring effect on the aluminum used for composite casting. Thermal conductivity may also be insufficient. Diameters larger than 30 mm may result in insufficient effective contact area with aluminum after insertion of the insert.This may further lead to a case where effective mesh-like structures cannot be obtained, which would otherwise contribute to the dispersion of stresses generated by an external force. By setting the diameters of the inscribed circles within the above range, the effective contact area with aluminum during composite casting can be sufficient, thereby achieving favorable thermal conductivity when used as . insert member. Furthermore, the mesh-like structure can disperse stresses. It is noted that, in the case where the member to be inserted has, for example, a cylindrical shape, the diameter of the inscribed circle can be determined as an average value by correcting a captured image of protruding portions 3 on a curved surface into an image on a flat surface using a digital microscope, creating, for example, 1 to 50 inscribed circles on the bottom surfaces F according to the corrected image, and obtaining the average value from these inscribed circles. Furthermore, the diameter of the inscribed circle 1e can be determined as a range including measured values ​​according to the minimum diameter and the maximum diameter, or preferably a range including all the measured values. It is noted that the present invention is not limited to a mode in which all the flat parts are enclosed by the linear portions.In this case, inscribed circles can be drawn along certain linear portions 31, and their diameters can be treated in the same way as above. Assuming that the surface 11s, to which the cast metal is to be bonded by composite casting, of the member to be inserted is projected onto a plane from a direction perpendicular to the surface, the projected area of ​​the mesh-shaped protruding portions 3 projected onto the plane is preferably 5% to 70% inclusive, more preferably 10% to 60% inclusive, and most preferably 16% to 43% inclusive of the total projected area. If the projected area of ​​the mesh-shaped protruding portions is less than 5%, the effective contact area with aluminum during composite casting may be insufficient. Furthermore, the effect as reinforcing ribs reducing stresses generated by an external force may decrease. If the projected area of ​​the mesh-shaped protruding portions exceeds 70%, a weight-reducing effect may not be achieved.Setting the projected area of ​​the mesh-shaped protruding portions 3 within the above range of the total projected area. improves rigidity while achieving the necessary adhesive strength, heat transfer, and heat dissipation on the cast metal used for composite casting, after composite casting. In addition, this setting can also improve the thermal conductivity and specific modulus as an insert element after composite casting. It is noted that the projected area can be calculated by trivialization processing based on an image captured, for example, with a microscope and subjected to plane correction. The projected area can be determined as the average ratio of the projected area of ​​the protruding portions from the measurement results, for example, from 1 to 50 points. Alternatively, the projected area can be determined as a range including measured values ​​according to the minimum value and the maximum value of the area ratio, or preferably a range including all measured values.The mesh-like protruding portions 3 are continuously formed on the surface of the insert member 11. The expression "continuously" is not limited to modes in which all the linear portions are connected but includes modes in which only some of the linear portions 31 are connected. In the present embodiment, the cross-sectional shapes of the protruding portions 3 are generally classified into two modes. The cross-sectional shape mentioned here is a cross-sectional shape perpendicular to the surface to which the cast metal is to be bonded by composite casting and perpendicular to the longitudinal direction of a linear portion 31. In the embodiment illustrated in FIGS. 5 and 6, the protruding portion 3a in the first mode includes a cross-section in a narrowed shape and the protruding portion 3b in the second mode includes a vertical wall portion, in a mixed manner. However, the insert member according to the present invention may include only the protruding portions 3a in the first mode, may include only the protruding portions 3b in the second mode, or may comprise the two types of protruding portions in a mixed manner. In the case where the two types exist in a mixed manner, the protruding portions 3a in the first mode and the protruding portions 3b in the second mode may be present in the protruding portions 3 that make up the same cell. The protruding portion 3a in the first mode will be described. Fig. 9 is an enlarged schematic view of cross-sections of protruding portions (linear portions) with shapes having narrowed portions. Referring to Fig. 9, the protruding portion 3a includes an upper portion 4 and a vertical wall portion 7, which rises and extends almost perpendicularly from the lower surface F. The vertical wall portion 7 has an almost constant width L7 from the lower surface F to the vicinity of the upper portion 4 in the illustrated cross-section, and the upper portion 4 has a width L4 greater than the width L7 of the vertical wall portion 7. Such shapes can be said to be shapes having narrowed portions. However, the shape having a narrowed portion is not limited to that shown in Fig. 9. The width L7 of the vertical wall portion 7 need not be constant.In addition, the protruding portion 3a may have a mode illustrated in FIG. 6 in which the width increases continuously from the vertical wall portion to the upper portion, or the protruding portion 3a may have a mode as illustrated in FIG. 9 in which the vertical wall portion 7 and the upper portion 4 form a corner E with which the vertical wall portion 7 and the upper portion 4 are in contact at a certain angle. The width L4 of the upper portion 4 corresponds to the width Lb of the linear portion explained with reference to FIG. 5. When the structure has the above shape on the surface of the insert member, while the insert member is inserted into the insert molding, molten metal flows out and for example wraps around the shape having a narrowed portion, in particular, here the corner E formed by the vertical wall portion 7 and the upper part 4 and having an undercut shape. This improves the anchoring effect and prevents gaps from occurring between the aluminum 12 and the element to be inserted 11 even when an external force is exerted. The cross-sectional shapes illustrated in Figure 9 may also be referred to as an approximate T-shape for one and an approximate inverted L-shape for the other. In a protruding portion 3a having an approximately T-shaped cross-section, the vertical wall portion 7 may contact the upper portion 4 of the protruding portion at a position that evenly separates / distributes the upper portion 4. However, the vertical wall portion 7 may contact the upper portion 4 by joining it at a position that unevenly separates the upper portion. The shape of the upper portion 4 of the protruding portion 3a may be tapered toward one end or may have a constant thickness substantially throughout the entire upper portion 4 of the protruding portion.The vertical wall portion 7 may have an almost constant width L7 in a cross-sectional view from the vicinity of the lower surface or bottom surface F to the vicinity of the upper portion 4 and may have irregularities on the side surfaces. In addition, the vertical wall portion 7 may extend approximately perpendicular to the approximately planar surface constituting the lower surface F or may extend at an angle to the line perpendicular to the approximately planar surface. The height h3 of the projecting portion 3a can be expressed by the sum of the height h4 of the upper part 4 and the height h7 of the vertical wall portion 7. The height h3 of the projecting portion 3a can be substantially constant along the longitudinal direction La of the linear portion 31 or can be partially different in certain case. The height h3 of the protruding portion 3a is preferably between 0.1 mm and 5.0 mm, inclusive, more preferably between 0.1 mm and 3 mm, and most preferably between 0.5 and 1.5 mm, inclusive. Heights less than or equal to 0.1 mm may result in insufficient anchoring effect on the aluminum used for composite casting and may reduce the effect as stiffness-enhancing reinforcing ribs. In addition, this setting may reduce the contact area with the aluminum 12, which is necessary for diffusing heat. If the height h3 of the protruding portion 3a exceeds 5.0 mm, centrifugal casting formation may be difficult in some cases. Setting the heights h3 of the protruding portions 3a within the above range increases the effective contact area with the metal used for composite casting and may improve heat dissipation.It is noted that the height h3 of the protruding portions 3a can be determined as an average value by performing a line analysis on an arbitrary surface of the element to be inserted, for example, by using a measurement function of a digital microscope and the image analysis software WinROOF2013. Furthermore / alternatively, by using a digital microscope to observe a cross-section, the height h3 of the protruding portions 3a can be determined as a range including measured values ​​based on the minimum height and the maximum height of the protruding portions 3a relative to the bottom surface or bottom surface F in an arbitrary measurement area, or preferably a range including all the measured values. Now, the protruding portion 3b in the second mode will be described. The protruding portion 3b in the second mode includes a vertical wall portion whose height is randomly different along the longitudinal direction of the linear portion 31. The protruding portion 3b in the second mode includes a vertical wall portion but does not have a top portion with a large width. As illustrated in the protruding portion 3b of FIG. 6, the cross-sectional shape may have, for example, example, the width decreasing from the bottom / bottom surface F towards the distal end. Alternatively or otherwise, the width may be constant or may have an indefinite shape, from the bottom surface F to the distal end. The height h3 of the protruding portion 3b is randomly different along the longitudinal direction of the linear portion. Figure 10 is a cross-sectional view of the linear portion 31a in Figure 5 taken along the line B-B'. The linear portion 31a in Figure 5 is a protruding portion 3b in the second mode and has the height h3 varying along the longitudinal direction of the linear portion 31a, in which portions in which the protruding portions h3 are low and portions in which the protruding portions h3 are high are randomly present.In the protruding portion 3b of the second mode, when the surface to which the cast metal is to be bonded by composite casting is viewed two-dimensionally from the outer peripheral direction, the length Lb of the linear portion in the width direction is shorter than the length Lb of the linear portion in the width direction in the protruding portion 3a in the first mode and is preferably between 0.1 mm and 3.0 mm, and more preferably between 0.2 mm and 2 mm. It is noted that the insert member according to the present embodiment has protruding portions of various shapes producible in a manufacturing method, described later, on the surface to which the cast metal is to be bonded by composite casting, and therefore, the insert member according to the present embodiment may have protruding portions having sectional shapes other than the sectional shapes described in the first and second embodiments. For the general outer shape of an insert member, the protruding portions 3 have mesh shapes that are similar to a surface pattern of a musk melon and include separate protruding portions in a space surrounded by the protruding portions 3. In addition or otherwise, in the insert member, at least some of the bottom surfaces are convex surfaces bulged in the outer peripheral direction of the surface to which the cast metal is to be bonded by composite casting. Referring to Figure 1, the thickness 11b of the insert member is preferably 2 to 20 mm. The thickness of the insert member, for example in Figure 6, is the sum of the thickness h9 from the inner peripheral surface of the insert member to the bottom surface or bottom surface F, and the height h3 of the mesh-like protruding portions h3. The height h3 of the protruding portions is preferably 1 to 70%, and more preferably 10 to 50%, of the thickness of the insert member. Figure 11 is an electron microscope photograph capturing the surface, to which the cast metal is to be bonded by composite casting, of an insert member according to the first embodiment at a magnification of 12 times. In Figure 11, mesh-like protruding portions 3 and separate protruding portions 5a can be clearly observed. A second embodiment relates to an insert member. An insert member according to the present embodiment comprises, on a surface to which cast metal is to be bonded by composite casting: a mesh-shaped protruding portion 3; and bottom surfaces surrounded by the protruding portion, among which at least some of the bottom surfaces are convex surfaces bulged in an outer peripheral direction of the surface to which the cast metal is to be bonded by composite casting, and when the mesh-shaped protruding portion is assumed to be projected onto a plane, the protruding portion forms linear portions and a joining portion in which at least two of the linear portions merge. In a first mode of the second embodiment, the protruding portion 3 comprises an upper portion and a vertical wall portion extending from the lower / bottom surface, and the width of the upper portion is greater than the width of the vertical wall portion. In a second mode of the second embodiment, the protruding portion 3 comprises a vertical wall portion extending from the lower / bottom surface and having randomly different heights. Figure 12 is a top view of the surface, to which a cast metal is to be bonded by composite casting, of an insert member according to the second embodiment viewed in a two-dimensional form from a direction perpendicular to the surface. Figure 13 is a sectional view taken along the line DD' in Figure 12. The surface 11s, to which the cast metal is to be bonded by composite casting, of the insert member 11 includes a bottom surface or bottom surface C and projecting portions 3. The projecting portion 3 has a structure extending from the bottom surface C in the outer peripheral direction O of the surface to which the cast metal is to be bonded by composite casting. The projecting portions 3 have a mesh-like structure including linear portions 31 and joining portions 32, when viewed in two dimensions. In the present embodiment, the planar shape and cross-sectional shape of the protruding portion 3 are the same as those of the first embodiment and may also include all the modifications described in the first embodiment. Thus, their description is omitted here. With reference to Figures 12 and 13, the bottom surface or bottom surface C is an approximately planar surface but has a convex surface, the center of which is convex relative to its surroundings in the outer peripheral direction of the surface to which the cast metal is to be bonded by composite casting. Here, the expression "the center is convex relative to its surroundings in the outer peripheral direction" means that in a cell, the maximum thickness hc1 of the insert 11 from the inner peripheral surface 11is to the center of the bottom surface C is greater than the minimum thickness hc2 of the insert measured also from the inner peripheral surface 11is to the vicinity of the bottom surface C, the difference hc1 -hc2 is greater than or equal to 0.1 mm, and the center is bulged (here in a generally concave area due to the protruding portions 3) in the outer peripheral direction of the surface to which the cast metal is to be bonded by composite casting. It should be noted that the vicinity of the bottom surface C denotes base portions of the protruding portions 3, and the center denotes a portion at least distant from such vicinity.The bottom surface C defined as above, comprising a convex surface bulged in the outer peripheral direction of the surface to which the cast metal is to be bonded by composite casting, is also referred to as the convex bottom surface C in this specification. At least only some of the multiple cells included in the insert must include C-convex bottom surfaces. It is preferable, for example, that 10% or more, or preferably 30% more of the cells include C-convex bottom surfaces. Thus, in some cells of the insert of the second embodiment, the bottom surfaces of the cells may be approximately planar surfaces in the same manner as in the first embodiment. According to a modification of the second embodiment, an insert member may have separate protruding portions extending from a convex bottom surface C. The separate protruding portions may be tapered pin-shaped separate protruding portions 5a, may be half-dome-shaped separate protruding portions 5b, or may be a mixture of both types. Further, also in a modification of the second embodiment, an insert member 11 may have separate protruding portions 5a and 5b extending from the approximately planar surface in cells whose bottom surfaces are approximately planar. In the case where separate protruding portions are present, the preferable shapes and sizes, and the number of the separate protruding portions may be the same as in the first embodiment. It is noted that although in the first embodiment, the heights of a protruding portion 3 and the separate protruding portions 5a and 5b are defined as the height from the approximately planar bottom surface F. The height of a protruding portion 3 in the present embodiment is defined with reference to the base of the protruding portion 3, and the heights of the separate protruding portions 5a and 5b are defined with reference to the bottom level of the concave bottom surface C where such a protruding portion is formed. Figure 14 is an electron microscope photograph capturing the surface, to which the cast metal is to be bonded by composite casting, of an insert member according to the second embodiment at a magnification of a factor of 20. In Figure 14, a mesh-shaped protruding portion 3 and a convex bottom surface C are clearly visible. In addition, it can also be observed that the height of the protruding portion 3 varies randomly along the longitudinal direction of the linear portion. Furthermore, it can also be observed that many small recessed holes are formed on the side surfaces of the vertical walls of the mesh-shaped protruding portion 3. Since the aluminum molten metal used in the composite casting also penetrates into these small recessed holes, the adhesion interface between the insert member 11 and the aluminum 12 becomes multidimensional.Thus, even if a shear force, a compressive force or the like caused by an external force acts on the adhesion interface, debonding practically does not occur. This helps to increase the strength of the insert itself. The element to be inserted according to the first and second embodiments of the The present invention is inserted into aluminum 12, an aluminum alloy, or another non-ferrous alloy during composite casting. An element obtained by inserting the element to be inserted into these metals and alloys by composite casting is called an insert element. As described above, the insert element has favorable adhesion between the element to be inserted and a metal or alloy used for composite casting, such as aluminum, and also has favorable thermal conductivity as an insert element. It should be noted that the thermal conductivity can be measured by a laser flash method.For example, when the insert member 11 is a cylinder sleeve to be inserted into an engine cylinder block by composite casting, the cylinder sleeve must uniformly dissipate heat into the surrounding aluminum cylinder body and must have high rigidity because the cylinder sleeve is likely to receive combustion pressure and compression load while the cylinder head is attached thereto. Applying the present invention to a cylinder sleeve and inserting the cylinder sleeve, for example, of aluminum by composite casting, provides an engine cylinder block 10 having more excellent thermal conductivity and diffusivity. In addition, even with a high compression ratio of the engine, heat can be efficiently dissipated from the cylinder sleeve to the aluminum cylinder body.This reduces the rise in combustion temperature accompanying the increase in compression ratio. Furthermore, since the specific modulus of the cylinder sleeve can be improved; even if the weight is the same, bore deformation, in other words, a change in circularity of the inserted cylinder sleeve can be avoided during the maneuvering or fixing described above. This reduces mechanical losses and blow-by gases of the engine, further reducing the occurrence of noise, vibration, and the like. If the cylinder sleeve has the same rigidity, its thickness and weight can be reduced. As a result, the engine . can be lightened. Also provided is a method of manufacturing an insert member according to one embodiment, in accordance with the invention. The method may comprise at least the steps of applying a mold coating agent to the surface 60 of a mold 61 into which molten metal 43 is to be poured, forming a mold coating layer 62 having a shape with cracks 65 on the surface by drying the applied mold coating agent, and pouring molten metal 43 onto the mold coating layer 62 and casting, while rotating the mold 61. The material and shape of the mold 61 for molding the insert member are not particularly limited but may be selected depending on the preform or application of the insert member. For example, in the case of molding a cylinder sleeve to be inserted into an engine cylinder block by composite casting as the insert member, the mold is preferably a metal mold and preferably has a cylindrical shape. In this case, it is preferable to use a centrifugal casting method using centrifugal force. It should be noted that the surfaces of the mold used for molding the insert member may be, for example, machined surfaces, which are approximately flat. Figures 15A to 15H briefly explain a method for manufacturing the insert member according to one aspect of the present invention. Figure 15A schematically illustrates the liquid mold coating agent 62 prepared in a container 6. The mold coating agent 62 may contain at least a flame retardant material, a binder, and a solvent. The mold coating agent 62 may contain aggregates in some cases. As a flame retardant material, diatomite powder is preferable, especially to prevent white solidification of molten metal and to ensure sufficient demolding properties, as well as to protect the mold surface. The lower limit of the The amount of the flame retardant material to be mixed is preferably 2% by mass or more, and more preferably 8% by mass or more of the total mass of the mold coating agent. The upper limit is preferably 40% by mass or less, more preferably 27% by mass or less, and most preferably 15% by mass or less of the total mass of the mold coating agent. Examples of the binder include bentonite, montmorillonite, kaolinite, sepiolite, attapulgite, and fireclay. In particular, bentonite is preferable since bentonite absorbs solvent, swells, and gels, so that when bentonite is mixed in a solvent with a flame retardant material and an aggregate, the bentonite can have a viscosity that prevents separation and enables the mold coating agent to be fixed on the mold surface. The lower limit of the amount of binder to be mixed is preferably 2 mass% or more, more preferably 5 mass% or more, and most preferably 8 mass% or more of the total mass of the mold coating agent. The upper limit is preferably 20 mass% or less, and more preferably 12 mass% or less of the total mass of the mold coating agent.If the amount of binder is less than 2% by mass, separation of the binder from the flame retardant material is likely to occur, and the strength of the mold coating layer may be insufficient in some cases. If the amount of binder exceeds 20% by mass, the suspension viscosity of the mold coating agent is too high, which may make coating difficult. The solvent may be water. The lower limit of the amount of solvent to be mixed is preferably 60% by mass or more of the total mass of the mold coating agent. The upper limit is preferably 85% by mass or less of the total mass of the mold coating agent. The mold coating agent may also contain, in addition to the materials described above, an organic solvent having a boiling point higher than that of water, such as butanol. In this case, such an organic solvent can be mixed with water for use. The mold coating agent may also contain aggregates in addition to the materials described above. Examples of aggregates that may be used include mineral powder or artificial ceramic sand composed of aluminum oxide and silicon dioxide, such as mullite and cerabeads sand, and casting sand, such as zirconium sand, chromite sand, silica sand, olivine sand, and spinel sand. In particular, mullite and cerabeads sand are preferable in that they have sufficiently small densities to prevent separation from the flame retardant material and the binder, and do not absorb the solvent and facilitate contraction of the mold coating layer to increase the number of cracks in the mold coating layer when the mold coating layer is dried and solidified.The lower limit of the amount of aggregate to be mixed is preferably 1.0 mass% or more, more preferably 1.5 mass% or more, and most preferably 3 mass% or more of the total mass of the mold coating agent. The upper limit is not particularly limited but is preferably 25 mass% or less, and more preferably 10 mass% or less. The mold coating agent may be prepared in the form of a slurry by mixing at least the fire retardant material, the binder, and the solvent, and further adding to the mixture the aggregate in some cases. 15B is a conceptual drawing illustrating a step of applying a mold coating agent 62 to the inner peripheral surface 60 of a mold 61, into which molten metal is to be poured. In this embodiment, the surface onto which the molten metal is to be poured (hereinafter also referred to as the molten metal contact surface) corresponds to the inner peripheral surface 60 of the mold 61, and it is preferable that the inner peripheral surface 60 before forming a mold coating layer 62 is almost flat. In the application step, the mold coating agent 62 is applied to the inner peripheral surface 60 of the mold using a nozzle 41 while rotating the cylindrical mold 61 in a constant direction r. It is preferable that the inner peripheral surface 60 of the mold at the time of applying the mold coating agent to the mold is heated to be at a temperature that does not cause a sudden rise in the temperature of the mold coating agent. The heating temperature is preferably 110 to 210°C, and more preferably 120 to 180°C. Figure 15C is a conceptual diagram illustrating a step of forming a mold coating layer having a shape with cracks by drying the applied mold coating agent. It is preferable that the mold 61 is rotated in the constant direction r until the mold coating agent is dried. The mold coating agent may be dried while the mold rotation continues after application. The mold coating agent may be dried and solidified by the heat of the mold 61 that has been heated or by the heat of the mold 61 as it is further heated. Furthermore, the time required to dry and solidify the mold coating agent may be reduced by heating the mold 61 from outside the mold as needed after the mold rotation has stopped. When the mold coating agent is dried by additional heating after application, the heating is preferably carried out at a temperature higher than or equal to the evaporation temperature of the solvent and lower than or equal to a temperature (high threshold temperature) which is higher than the evaporation temperature of 110°C. This prevents a sudden rise in the temperature of the solvent from inside the mold coating agent 62 and also prevents excessive generation of air bubbles (vapor of water), and thus, in this state, the mold coating layer having a shape with cracks can be formed by the contraction caused by the drying and solidification of the mold coating agent 62. The lower limit of the heating temperature is preferably equal to or higher than the solvent evaporation temperature, more preferably equal to or higher than the temperature 10°C higher than the solvent evaporation temperature, and most preferably equal to or higher than the temperature 20°C higher than the solvent evaporation temperature. The upper limit of the heating temperature is preferably equal to or lower than the temperature (high threshold temperature) 110°C higher than the solvent evaporation temperature, and more preferably equal to or lower than an high threshold temperature that exceeds the solvent evaporation temperature by 80°C. The thickness of the mold coating layer 62 after drying can be determined according to a desired maximum height of the protruding portions 3 or other factors in the insert member 11 and is not particularly limited, but its average thickness is preferably 0.1 mm to 5.0 mm, and more preferably 0.5 mm to 2.0 mm. Next, the formation mechanism of the mold coating layer 62 will be described, with reference to FIGS. 16A to 16D. FIG. 16A schematically illustrates a stage in which a portion of a volatile component 63 evaporates from the mold coating agent 62 applied to the heated mold 61. FIG. 16B illustrates an early state of the mold coating layer 62 during drying and solidification. At this stage, a large amount of the volatile component 63 evaporates from the mold coating layer 62, and contraction 64 begins to occur at random intervals on the surface of the mold coating layer 62, thereby generating cracks 65. FIG. 16C illustrates an intermediate state during drying and solidification. The contraction 64 of the mold coating layer 62 mold coating 62 progresses further, and the cracks 65 that have occurred from the surface of the mold coating layer 62 enlarge toward the surface of the mold 61. As a result, the cross-sections of the gaps in the thickness direction of the mold coating layer become wedge-shaped. In some cases, the mold coating layer 62 may be completely dried and solidified in this cracked state. Figure 16D illustrates a terminal state during drying and solidification. Cracks 65 having passed through the mold lining layer 62 occur, and blocks defined / bounded by the cracks 65 appear. A block is a mold lining layer which is not substantially in contact with another adjacent block in some cases, and in other cases, a portion of which is in contact with another adjacent block. Furthermore, contraction of the mold lining layer, particularly contraction of each block, advances the cracks 65. The continuous cracks extending from the surface of the mold lining layer 62 toward the surface of the mold 61 serve as a mold (cavity) for forming the mesh-like protruding portions 3. In the case where cracks 65 are formed in which gaps / dips further extend approximately perpendicular to the cracks formed at an early stage from the surface of the mold coating layer 62 toward the mold, and along the mold surface 61, the protruding portions 3 formed using this mold coating layer 62 will constitute the protruding portions 3a in the first mode having narrowed structures including vertical wall portions 7 and upper portions 4. To form cracks 65 serving as a mold for the protruding portions 3a in the first mode, the drying and solidification time is set relatively long. On the other hand, in the case where cracks 65 are formed which extend from the surface of the mold coating layer 62 but do not reach the surface of the mold 61, the cracks mainly serve as a mold (imprint) for forming protruding portions 3b in the second mode. The protruding portions 3b in the second mode include the vertical wall portions, the heights of which are randomly different. To form cracks 65 serving as a mold for the protruding portions 3b in the second mode, the drying and solidification time is set relatively short. However, since various factors affect the formation of cracks in either mode, specific conditions can be determined by preliminary experiments or the like. In one embodiment, moisture evaporation from the surface of the mold coating layer 62 forms depressions 67. Among the depressions 67, relatively deep depressions serve as molds (cavities) for forming separate protruding portions 5a into the tapered pin shapes described in the first embodiment. Among the depressions 67, relatively shallow ones serve as molds for forming separate protruding portions 5b into the half-dome shapes described in the first embodiment. To form depressions 67 that can serve as molds for separate protruding portions, it is preferable under the above conditions to set the mold temperature relatively high, the thickness of the mold coating layer 62 relatively small, and the amount of bentonite a little less.However, the formation of hollows 67 also depends on other various conditions, the temperature of the mold 61, the thickness of the mold coating layer 62, the amount of bentonite cannot be specifically defined. Thus, to obtain hollows 67 in the desired shapes, with the desired dimensions, and in the desired number, the temperature of the mold, the thickness of the mold coating layer, and the amount of bentonite can be determined by preliminary experiment or the like. In one embodiment, due to the evaporation of moisture from the surface of the mold coating layer 62, the contraction of the entire block forms large depressions 66 (see an example in FIG. 16D) on the surface (outer surface) of the mold coating layer 62. These serve as molds for forming convex bottom surfaces C according to the second embodiment. To form large depressions 66, it is preferable under the above conditions to set a relatively low mold temperature, a relatively large thickness of the mold coating layer, and a slightly larger amount of bentonite. However, the formation of large depressions 66 also depends on other various conditions, the temperature of the mold 61, the thickness of the mold coating layer 62, the amount of bentonite cannot be specifically defined.Thus, to obtain large depressions 66, the mold temperature, the thickness of the mold coating layer, and the amount of bentonite can be determined by preliminary experiment or the like. It is noted that in the case where there are practically no depressions on a mold coating layer 62 after drying, the surface of the mold coating layer 62 can serve as a bottom surface F having an approximately flat surface. The mold coating layer 62 thus obtained may have a surface comprising mesh-shaped cracks 65. This makes it possible to manufacture an insert element having mesh-shaped protruding portions 3. Referring to Figure 15D, there is shown a conceptual diagram of the step in which the molten metal 43 of cast iron is poured into the mold 61 over the mold coating layer 62, and centrifugal casting is performed while rotating the mold 61 in the constant direction r. As in Figure 15B, the molten metal 43 may be poured into the cylinder using a molten metal feeder, such as a nozzle, while rotating the mold 61. By rotating the mold 61, the centrifugal force causes the molten metal 43 to also flow into the cracks 65 of the mold coating layer 62. Thus, desired mesh-like protruding portions 3 can be formed on the surface of the insert member 11 or 48. Figure 15E is a conceptual diagram of the solidification step of the cast iron molten metal. The cast iron molten metal 43 is cooled from outside the mold 61 and solidified to obtain a casting 44 having the shape of the member to be inserted. The molten metal is poured into the mold and molded by casting, and the cast metal can be cooled and solidified naturally. After the molten metal solidifies, the rotation of the mold is stopped. Figure 15F is a conceptual diagram illustrating the step of removing the molded part 44 in the form of the insert from the mold 61. The method of removing the molded part from the mold 61 is not particularly limited but is selected depending on the shape of the mold. For example, in the case of a cylindrical mold, the molded part 44 can be removed from the mold 61 by attaching a mandrel to a portion of the inner peripheral surface of the molded part 44 and pulling it in the direction of the arrow 45 in Figure 15F. Figure 15G is a conceptual diagram illustrating a step in which the mold coating layer 62 is to be removed from the molded part 44 extracted from the mold 61. The mold coating layer 62 may be attached to the surface of the molded part 44 extracted from the mold. The method of extracting the mold coating layer 62 from the molded part 44 is not particularly limited. Examples of this method include shot blasting, water jet cleaning, and dry ice cleaning. Figure 15H illustrates an insert member 48 after the mold coating layer 62 has been removed from the molded part 44. The solidified mold coating layer is removed from the molded part 44 so as to obtain the insert member 48 having mesh-like protruding portions 3 on the surface. Figure 17 is a diagram illustrating an insert element 11 or 48 formed with the mold coating layer 62 shown in Figure 16D. Projecting portions 3, a distinct protruding portion 5a, and a convex bottom surface C are formed in correspondence with the shapes of the cracks 65 and a depression 67. The present invention makes it possible to form protruding portions in specified shapes with heights that cannot be obtained by conventional manufacturing methods, on the surface 11s, to which the cast metal is to be bonded, of an insert member. This makes it possible to obtain high adhesive strength on the aluminum 12 used for composite casting. The insert member 11, 48 according to the present invention is also applicable to members other than sliding parts, having high rigidity and excellent heat transfer, heat dissipation, and thermal conductivity, for example, an insert member in a part on which a rotational torque acts, such as an aluminum brake drum, a die-cast aluminum wheel hub for motorcycles, and a journal in a transmission system having an electric motor. The insert member thus obtained can be inserted, for example, into aluminum or another material, for example, by a die casting process to provide an insert member. The conditions for injecting aluminum or other materials are not particularly limited, but for example, for ADC12, ADC10, or ADC3, the molten metal can be poured at 620 to 670°C, and the molding can be carried out with an injection pressure of 50 to 100 MPa at an injection speed of 1.5 to 4.0 m / second. Since the insert member according to the present invention has the protruding portions 3 including the linear portions 31 and the joining portions 32 on the surface 11s to which the cast metal is to be bonded by composite casting, the insert member has a larger surface area for contacting the cast metal used for casting. composite than those in conventional cases, which effectively improves heat transfer and heat dissipation. In the case where the insert member has protruding portions 3a in the cross-sectional shapes of the first mode, the metal used for composite casting penetrates into these portions, thereby improving the adhesive force, reducing the possibility of gaps between the insert member and the cast metal, and improving the thermal conductivity to the cast metal. In addition, for example, in the case where the protruding portions have an isotropic mesh-like structure, the protruding portions exert a reinforcing rib effect, thereby contributing to the dispersion and reduction of stresses generated by the external force from various directions.For example, when the insert member is a cylinder sleeve, the specific modulus in the radial direction of the bore or in the axial direction can be improved, and thus, deformation of the insert member can be prevented. This makes it possible to reduce the thickness and weight of the cylinder sleeve while maintaining the same rigidity. Furthermore, in the case where the shapes of the protruding portions 3b are present in the second mode, when molten aluminum is filled between the bores, such as when die casting a multi-cylinder cylinder block; since the heights of the protruding portions are randomly different, there are inevitably portions at which low protruding portions face each other. This facilitates the passage of molten metal between the protruding portions or between the bores, thereby improving the filling properties of the molten metal.This effect is remarkable compared to conventional techniques in which the heights of the protruding portions are uniform. In addition, it allows to reduce the bore pitch compared to conventional techniques and thus, to reduce the size of the engine. A description is then provided for the effect of dispersing and reducing the stress generated at the interface of the composite casting, in an element insertion in which an insert member 11 according to the present embodiment is inserted into aluminum or the like by composite casting. Figures 18A to 18D are used to explain stresses generated at the interface between a sleeve and cast metal in a cylinder block in the case where an insert member 11 is the cylinder sleeve which is inserted into the cylinder block of the engine by composite casting. Figure 18A is a diagram schematically illustrating a cylinder sleeve 11 having protruding portions 3 on the surface and aluminum 12 used for composite casting. Figure 18B is an enlarged view of part X in Figure 18A. In the mode illustrated in Figure 18B, a separate pin-shaped protruding portion or a concave bottom surface does not exist in a cell composed of protruding portions 3.This symbol ti indicates the shear stress generated when the cylinder head is fixed to the cylinder sleeve 11, at the interface (composite casting interface) between the element to be inserted and the metal, such as aluminium. The symbol indicates the compressive stress generated when the cylinder sleeve 11 is inserted into aluminium 12 by composite casting. Figure 18C is a diagram illustrating a composite casting interface of another cylinder sleeve inserted into an engine cylinder block as in Figure 18A, having a surface structure according to the first embodiment of the present invention. In one embodiment illustrated in Figure 18C, separate protruding portions 5a shaped like tapered pins and separate protruding portions 5b shaped like half domes are present in cells composed of / bounded by protruding portions 3. The symbol t2 indicates the shear stress generated at the composite casting interface when a cylinder head is fixed on the cylinder sleeve 11. Comparing the shear stress value t2 with the shear stress value t1 in Figure 18B, t2 < Tb The existence of separate protruding portions reduces the shear stress generated at the composite casting interface. Figure 18D is a diagram illustrating a composite casting interface of yet another cylinder sleeve inserted into an engine cylinder block as in Figure 18A, having a surface structure according to the second embodiment of the present invention. In one mode illustrated in Figure 18D, the cells composed of / delimited by protruding portions 3 have a convex surface structure in which the lower surface bulges toward the outer peripheral surface side of the cylinder sleeve 11. The symbol o2 indicates the compressive stress generated when the cylinder sleeve 11 is inserted into aluminum 12 by composite casting. Comparing the compressive stress value o2 with the compressive stress value in Figure 18B, o2 < 0^ The lower surface (bottom surface) shaped as a convex surface reduces compressive stresses. As described above, in the case of using an insert member comprising separate pin-shaped protrusions 5a, 5b according to one embodiment of the present invention, in an engine cylinder block, the protrusions serve as barriers against a shear or compressive load exerted on the composite casting interface and disperse and reduce shear stresses generated at the interface area of ​​the composite casting. This reduces the amount of distortion in the insert member and thus reduces shape deformation. In addition, in the case of using an insert member having a bottom surface with a convex surface structure, the surface rigidity of the bottom surface of the cell improves. This improves the overall rigidity of the insert member, reducing bore deformation if it is a sleeve and enabling the thickness of the sleeve to be further reduced.Additionally, it improves vibration damping properties and provides more silence / quietness (in operation). Next, the series of Figures 19A, 19B, 19C, 19d makes it possible to explain the stresses generated at the composite casting interface of a sleeve, in the case where the insert member 11 is a sleeve which is a sliding member inserted into a drum brake by composite casting and configured to be in contact with the brake shoes 14. Figure 19A is a cross-sectional diagram schematically illustrating a sleeve 11 including protruding portions 3 on its surface, aluminum 12 used for composite casting, and brake shoes 14 located inside these parts. In Figure 19A, N indicates a braking load, and r indicates the direction of rotation of the wheel. Figure 19B is an enlarged view of the part Y in Figure 19A. In a mode illustrated in Figure 19B, a separate pin-shaped protruding portion or a bulged / domed bottom surface C does not exist in cells composed of protruding portions 3.The symbol ti indicates the shear stress generated in the composite casting interface of the sleeve 11 at the time when the braking load N acts on the drum brake rotating in the direction r. The symbol Oi indicates the compressive stress generated when the sleeve 11 is inserted into aluminum 12 by composite casting. The arrow indicated by O indicates the direction of the outer peripheral surface of the sleeve 11; the arrow indicated by t indicates the direction of the rotational torque. Figure 19C is a diagram illustrating a composite casting interface of another sleeve inserted into a drum brake similar to that of Figure 19A and having a surface structure according to the first embodiment of the present invention. In one embodiment illustrated in Figure 19C, separate protruding portions 5a in the shape of tapered pins and separate protruding portions 5b in the shape of half domes are present in cells composed of protruding portions 3. The symbol 12 indicates the shear stress generated in the composite casting interface of the sleeve 11 at the time when the braking load N acts on the drum brake rotating in the r direction. Comparing the shear stress value t2 with shear stress value ti in Figure 19B, t2 < Tp The existence of separate protruding portions 5a, 5b reduces the shear stress generated at the composite casting interface.Figure 19D is a diagram illustrating a composite casting interface of yet another sleeve inserted into a drum brake similar to that of Figure 19A and having a surface structure according to the second embodiment of the present invention. In one mode illustrated in Figure 19D, the cells composed of / delimited by the protruding portions 3 have convex surface structures in which the bottom surface of the sleeve bulges toward the outer peripheral surface side. The symbol o2 indicates the compressive stress generated when the cylinder sleeve 11 is inserted into aluminum 12 by composite casting. Comparing the compressive stress value o2 with the compressive stress value in Figure 19B, o2 < a,. The bottom surface in the form of a convex surface C (or bulged surface) reduces the compressive stresses.This reduces local deformations of the sleeve 11, stabilizes the p value (friction coefficient) and reduces brake squeal. As described above, the use of an insert member 11 according to the embodiments of the present invention for a drum brake makes it possible to reduce vibration of a rotating insert member and stabilize the friction coefficient and braking characteristics, in addition to the effect described with reference to FIGS. 18A-18D above. Practical examples Hereinafter, the present invention will be described in more detail with the aid of examples (practical cases). However, the following examples are not intended to limit the present invention. The elements to be inserted according to the first and second embodiments of the present invention were manufactured by a method described in the third embodiment. In Examples 1 and 2, inserts 11 according to the first embodiment were manufactured, and in Examples 3 and 4, inserts 11 according to the second embodiment were manufactured. The manufacturing conditions are shown in Table 1. Table 1 Mold temperature / °C Mold coating layer thickness / mm Bentonite mixing ratio / mass % Example 1 155 1 ​​10 Example 2 160 1 10 Example 3 135 1.5 11 Example 4 130 2 9.5 Figure 11 shows an electron microscope photograph of an insert element obtained in Example 1. It can be visually recognized that portions 10 separate protrusions 5a in the shape of tapered pins were formed in cells in addition to the mesh-like protruding portions 3. Figure 20 shows an electron microscope photograph of an insert obtained in Example 2. The scale in the figure indicates 500 μm. It can be visually recognized that separate protrusions 5b in the shape of half domes were formed in cells. It is noted that all the 15 arrows indicate separate protruding portions 5b in half-dome shapes. Figure 14 shows an electron microscope photograph of an insert member 11 obtained in Example 3. It can be visually recognized from Figure 14 that a bottom surface C is a convex surface bulged in the outer peripheral direction of the surface to which the cast metal is to be bonded by composite casting. Figure 21 shows an electron microscope photograph of a cross-section of an insert 11 obtained in Example 4. The scale in the figure indicates 500 pm. Furthermore, in Figure 21, it is clearly visually recognized from the cross-sectional view that the lower surface or bottom surface C is a convex surface. 5 The characteristics of the elements to be inserted in Examples 1 to 4 have been evaluated, and it was confirmed that all the elements 11 had the same effect as that described with reference to FIGS. 18A-18D, that is, the effect of dispersing and reducing the shear stress generated at the interface area of ​​the composite casting. In addition, the rigidity of each insert element 11 as a whole was improved, and the 10 deformation of the bore was reduced. Industrial application The insert members 11, 48 according to the present invention can be particularly suitably applied to cylinder sleeves to be inserted into a cylinder block (B / C) by die-casting in aluminum, a sliding member for an aluminum drum brake, support members for an electric motor, a lower case, and a transmission case, furthermore, hubs for motorcycle wheels, and the like, which are all insert members that must have characteristics BVD, as in vibration damping property.

Claims

Claims 1. Insert element (11; 48) comprising, on a surface (11s) to which the cast metal (43) is to be bonded by composite casting: a protruding portion (3) of mesh shape; bottom surfaces (C, F) surrounded by the projecting portion (3); and a separate protruding portion (5a, 5b); wherein the projecting portion (3) comprises an upper part (4) and a vertical wall portion (7) extending from the level of the bottom surfaces (F), the width (L4) of the upper part (4) is greater than the width (L7) of the vertical wall portion (7), at least some of the bottom surfaces (F) are approximately flat, the separate protruding portion (5a, 5b) has a pin shape extending from at least some of the bottom surfaces (F), and when the mesh-shaped protruding portion (3) is assumed to be projected onto a plane, the protruding portion forms linear portions (31a, 31b, 31c, 31d, 31e) and a joining portion (32a, 32b, 32c, 32d) in which at least two of the linear portions merge.

2. Insert element (11; 48) comprising, on a surface (11s) to which the cast metal (43) is to be bonded by composite casting: a protruding portion of mesh shape; and bottom surfaces (C, F) surrounded by the protruding portion, wherein the projecting portion comprises an upper part (4) and a vertical wall portion (7) extending from the level of the bottom surfaces (F), the width (L4) of the upper part (4) is greater than the width (L7) of the vertical wall portion (7), at least some of the bottom surfaces are convex (C) cambered surfaces in an outer peripheral direction of the surface (11s) to which the cast metal (43) is to be bonded by composite casting, and when the mesh-shaped protruding portion (3) is assumed to be projected onto a plane, the protruding portion forms linear portions (31a, 31b, 31c, 31d, 31e) and a joining portion (32a, 32b, 32c, 32d) in which at least two of the linear portions merge.

3. Insert element (11; 48) comprising, on a surface (11s) to which the cast metal (43) is to be bonded by composite casting: a protruding portion (3) of mesh shape; bottom surfaces (C, F) surrounded by the projecting portion (3); and a separate protruding portion (5a, 5b); wherein the projecting portion (3) comprises a vertical wall portion (7) extending from the level of the bottom surfaces (F) and having randomly different heights, at least some of the bottom surfaces (F) are approximately flat, the separate protruding portion (5a, 5b) has a pin shape extending from at least some of the bottom surfaces (F), and when the mesh-shaped protruding portion (3) is assumed to be projected onto a plane, the protruding portion forms linear portions (31a, 31b, 31c, 31d, 31e) and a joining portion (32a, 32b, 32c, 32d) in which at least two of the linear portions merge.

4. Insert element (11; 48) comprising, on a surface (11s) to which the cast metal (43) is to be bonded by composite casting: a protruding portion (3) of mesh shape; and bottom surfaces (C, F) surrounded by the projecting portion (3); wherein the projecting portion (3) comprises a vertical wall portion (7) extending from the level of the bottom surfaces (F) and having different heights randomly, at least some of the bottom surfaces are convex surfaces (C) curved in an outer peripheral direction of the surface (11s) to which the cast metal (43) is to be bonded by composite casting, and when the mesh-shaped protruding portion (3) is assumed to be projected onto a flat plane, the protruding portion forms linear portions (31a, 31b, 31c, 31d, 31e) and a joining portion (32a, 32b, 32c, 32d) in which at least two of the linear portions merge.

5. An insert element according to claim 2 or claim 4, wherein a determined bottom surface which constitutes a convex surface (C) comprises a separate protruding portion (5a, 5b) in the form of a pin extending from said determined bottom surface.

6. An insert element according to any one of claims 1, 3 and 5, wherein the separate protruding pin-shaped portion (5a, 5b) is (a) a tapered pin-shaped protruding portion (5a) in which the diameter of a distal end of the protruding portion is less than the diameter (R5a) of a base of the protruding portion and has a height (h5a) of between 0.1 mm and 0.5 mm, and / or (b) a protruding portion (5b) having a half-dome shape.

7. Method for manufacturing an insert element (11; 48), comprising the steps of: applying a mold coating agent to a surface (60) of a mold (61), from the side of which molten metal (43) is to be poured; forming a mold coating layer (62) into a shape with cracks (65) and depressions (67) on a surface of the mold coating layer (62) while drying the applied mold coating agent; and performing a casting by pouring the molten metal (43) onto the mold coating layer (62) while rotating the mold (61), wherein the cracks (65) comprise multiple gaps extending from the surface of the mold coating layer and reaching a surface (60) of the mold (61), the widths of the gaps decrease from the surface of the mold coating layer (62) towards the surface (60) of the mold (61), at least some of the gaps extend along the surface (60) of the mold (61), and the hollows (67) have a pin shape which does not reach the surface (60) of the mold (61).

8. Method for manufacturing an insert element (11; 48), comprising the steps of: applying a mold coating agent to a surface (60) of a mold (61), from the side of which molten metal (43) is to be poured; forming a mold coating layer (62) into a shape with cracks (65) on a surface of the mold coating layer by drying the applied mold coating agent; and performing a casting by pouring the molten metal (43) onto the mold coating layer (62) while rotating the mold (61), wherein the cracks (65) comprise multiple gaps extending from the surface of the mold coating layer (62) to a surface (60) of the mold (61), the widths of the gaps decrease from the surface of the mold coating layer (62) towards the surface (60) of the mold (61), some of the gaps extend along the surface (60) of the mold (61), and in the mold coating layer (62) are recessed relative to the surroundings surrounding these central portions.

9. Method for manufacturing an insert element (11; 48), comprising the steps of: applying a mold coating agent to a surface (60) of a mold (61), from the side of which molten metal (43) is to be poured; forming a mold coating layer (62) into a shape with cracks (65) and pits (67) on a surface of the mold coating layer by drying the applied mold coating agent; and performing a casting by pouring the molten metal (43) onto the mold coating layer (62) while rotating the mold (61), wherein the cracks (65) comprise multiple gaps extending from the surface of the mold coating layer toward a surface (60) of the mold (61), the widths of the gaps decrease from the surface of the mold coating layer towards the surface (60) of the mold (61), the depths of the gaps differ randomly, and the hollows (67) have a pin shape which does not reach the surface (60) of the mold (61).

10. Method of manufacturing an insert element (11; 48), comprising the steps of: applying a mold coating agent to a surface (60) of a mold (61), from the side of which molten metal (43) is to be poured; forming a mold coating layer (62) into a shape with cracks (65) on a surface of the mold coating layer by drying the applied mold coating agent; and performing a casting by pouring the molten metal (43) onto the mold coating layer (62) while rotating the mold (61), wherein the cracks (65) comprise multiple gaps extending from the surface of the mold coating layer toward a surface (60) of the mold (61), 5 the gap widths decrease from the surface of the coating layer of mold towards the surface (60) of the mold (61), the depths of the gaps differ randomly, and central parts of at least some of the parts defined by the cracks (65) in the mold coating layer (62) are recessed relative to the surroundings 10 surrounding these central parts.

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