Cylinder liner, block manufacturing method and cylinder liner manufacturing method

Abstract

A cylinder liner that is casted in a block and defines a cylinder bore for one cylinder includes: a cylindrical liner body; a projection part including a plurality of projections on an outer peripheral surface of a part of the liner body; and a bore adjacent part inclined at a predetermined angle to an axial direction of the body and extending in the inclination direction, at a predetermined part between an upper side end and a lower side end of the body, of the outer peripheral surface of the body, which faces another cylinder bore to be adjacent when casted in the block. The outer peripheral surface of the bore adjacent part is positioned more on an inner side of the body than the outer peripheral surface above and below, and is formed such that the projections are absent on at least a part of the outer peripheral surface.

Claims

1. A cylinder liner that is casted in an aluminum alloy block and defines a cylinder bore corresponding to one cylinder, comprising: a cylindrical liner body; a projection part provided so as to include a plurality of projections on an outer peripheral surface of a part of the liner body; and a bore adjacent part provided so as to be inclined at a predetermined angle to an axial direction of the liner body and to extend in the inclination direction, at a predetermined part between an upper side end and a lower side end of the liner body, of the outer peripheral surface of the liner body, which faces another cylinder bore to be adjacent when casted in the block, wherein the bore adjacent part is a groove formed such that the outer peripheral surface is positioned more on an inner side of the liner body than the outer peripheral surface above and below the bore adjacent part, and the projections are absent on at least a part of the outer peripheral surface, and in the projection part, a height of the projections is 0.2 mm to 0.7 mm, the number of projections is 10 pieces/cm.sup.2 to 100 pieces/cm.sup.2, and a projection area ratio calculated as a ratio occupied in a unit area by a total area of cross-sectional areas of the projections at the position of 0.2 mm from the base of the projections in the projections present within the unit area is 10% to 50%.

2. A cylinder liner according to claim 1, further comprising: a positioning part provided so as to be at a predetermined relative position to the bore adjacent part such that the bore adjacent part is positioned at a predetermined position facing the other adjacent cylinder bore when casted in the block.

3. The cylinder liner according to claim 2, wherein the bore adjacent part is provided in a pair at one side face part and the other side face part positioned on an opposite side of the one side face part across a center axis of the liner body, at the predetermined part between the upper side end and the lower side end of the liner body, and the positioning part is provided on a part corresponding to at least one of the one side face part and the other side face part at the lower side end of the liner body.

4. The cylinder liner according to claim 3, wherein the positioning part is provided in a pair at respective lower parts of the one side face part and the other side face part at the lower side end of the liner body, and the bore adjacent parts and the positioning parts are provided such that a virtual line defined by connecting the bore adjacent parts provided in the pair and a virtual line defined by connecting the positioning parts provided in the pair cross at an angle of 0 degrees to 90 degrees in an upper view of the liner body.

5. The cylinder liner according to claim 4, wherein the virtual line defined by connecting the bore adjacent parts provided in the pair and the virtual line defined by connecting the positioning parts provided in the pair overlap in the upper view of the liner body.

6. The cylinder liner according to claim 1, wherein the bore adjacent part is two grooves to be line symmetrical to each other when a center line of the liner body is a reference in a side view of the liner body, and is formed in a shape of crossing the two grooves in a cross-hatch shape in a side view of the liner body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A is a top view of a bore block configured including a cylinder liner of the present invention.

(2) FIG. 1B is an enlarged view regarding a part (part A) of an upper surface of the bore block illustrated in FIG. 1A.

(3) FIG. 1C is a B-B′ sectional view of the bore block illustrated in FIG. 1A.

(4) FIG. 1D is a C-C′ sectional view of the bore block illustrated in FIG. 1A.

(5) FIG. 2A is a view illustrating a side face of the cylinder liner of the present invention.

(6) FIG. 2B is a view illustrating an upper surface of the cylinder liner of the present invention.

(7) FIG. 2C is an enlarged view of an outer peripheral surface of the cylinder liner of the present invention.

(8) FIG. 3 is an enlarged view of a part (part D) of a bore block cross section illustrated in FIG. 1D.

(9) FIG. 4 is a diagram illustrating a flow of manufacture of the cylinder liner of the present invention.

(10) FIG. 5 is a diagram illustrating a flow of manufacture of the bore block configured including the cylinder liner of the present invention.

(11) FIG. 6 is a view illustrating another configuration example of a groove part.

(12) FIG. 7 is a view illustrating a side face of the cylinder liner provided with a high-heat conductive film.

(13) FIG. 8 is a diagram illustrating a flow of manufacture of the cylinder liner provided with the high-heat conductive film.

(14) FIG. 9 is a view illustrating a side face of the cylinder liner provided with the high-heat conductive film and a low-heat conductive film.

DESCRIPTION OF EMBODIMENTS

(15) Hereinafter, specific embodiments of the present invention will be described based on the drawings. Configurations described in the present embodiments do not mean to limit a technical range of the invention thereto unless described in particular.

First Embodiment

(16) In FIG. 1A to FIG. 1D, a bore block 1 with a cylinder liner 10 of the present embodiment mounted thereon is illustrated. For details, FIG. 1A is a top view of the bore block 1, and FIG. 1B is an enlarged view in which a part (part A illustrated in FIG. 1A) between cylinder bores 2 that are adjacent in the bore block 1 is enlarged. In addition, FIG. 1C is a sectional view of the bore block 1 on a B-B′ cross section illustrated in FIG. 1A, and FIG. 1D is a sectional view of the bore block 1 on a C-C′ cross section illustrated in FIG. 1A. The bore block 1 is the configuration of a part of a cylinder block of an internal combustion engine, and the cylinder bore 2 corresponding to a cylinder of the internal combustion engine is defined by each cylinder liner 10. Note that, while the bore block 1 illustrated in the present embodiment has a form that three cylinder bores are arrayed in series, the cylinder liner 10 of the present embodiment can be applied also to the bore block 1 having other cylinder bore array forms.

(17) A manufacturing method of the bore block 1 will be described later, and a structure of the bore block 1 will be described first. The bore block 1 is formed by casting three cylinder liners 10 by an aluminum alloy. The casted aluminum alloy forms a block body 3 of the bore block 1. Then, in the bore block 1, an inter-bore passage 4 is formed between the three cylinder bores 2 arrayed in series each other. An array direction (a crosswise direction in FIG. 1A and a direction of the C-C′ cross section) of the cylinder bores is defined as a longitudinal direction of the bore block 1, and a direction orthogonal to it (that is, a vertical direction in FIG. 1A and a direction of the B-B′ cross section) is defined as a front-back direction of the bore block 1. Then, the inter-bore passage 4 has a roughly columnar shape, extending in the front-back direction of the bore block 1 while being inclined downwards in an axial direction (height direction) of the cylinder bore 2 from an opening end provided on the upper surface (deck surface) of the bore block 1, as illustrated in FIG. 1B and FIG. 1C. The inter-bore passage 4 is formed by predetermined machining after the bore block 1 is casted and formed as described later. Then, though detailed illustrations are omitted, in the case where the bore block 1 is incorporated and a so-called cylinder block of an internal combustion engine is formed, a water jacket inside the cylinder block and the inter-bore passage 4 are connected to attain a passage where a cooling medium (cooling water or the like) can be distributed in the internal combustion engine after completion.

(18) Note that, as a material of the block body 3 of the bore block 1, in consideration of weight reduction and costs, the aluminum alloy such as JIS ADC10 (reference standard: US ASTM A380.0) or JIS ADC12 (reference standard: US ASTM A383.0) can be adopted.

(19) Next, the cylinder liner 10 mounted on the bore block 1 will be described based on FIG. 2. FIG. 2A illustrates a side face of the cylinder liner 10, and FIG. 2B illustrates an upper surface of the cylinder liner 10. Further, FIG. 2C is an enlarged view of an outer peripheral surface S1 of the cylinder liner 10. The cylinder liner 10 has a cylindrical shape and is mounted on the bore block 1, and an inner peripheral surface S2 of the cylinder liner 10 forms a wall surface of the cylinder bore 2. Note that, as a material of the cylinder liner 10, in consideration of wear resistance, seize resistance and workability, cast iron such as JIS FC230 is used. One example of a composition of the cast iron is T. C: 2.9 to 3.7 (mass %, the same shall apply hereinafter), Si: 1.6 to 2.8, Mn: 0.5 to 1.0, P: 0.05 to 0.4 and the rest is Fe. As needed, Cr: 0.05 to 0.4 (mass %, the same shall apply hereinafter), B: 0.03 to 0.08, and Cu: 0.3 to 0.5 may be added.

(20) Here, a plurality of projections 13 are formed on a large part of the outer peripheral surface S1 of the cylinder liner 10. Since the cylinder liner 10 is casted by the cast iron, the outer peripheral surface S1 is a casted surface. Since the projections 13 are formed on the outer peripheral surface S1, adhesion of the block body 3 and the cylinder liner 10 can be improved when casted by the aluminum alloy during manufacture of the bore block 1. FIG. 2C illustrates projections in a shape that a distal end has a larger diameter than a base as the projections 13 provided on the outer peripheral surface S1, however, the shape of the projections 13 is not limited thereto. For example, the shape such as a trapezoid or a quadrangle can be adopted.

(21) In addition, a dimension and a distribution of the projections 13 on the outer peripheral surface S1 can be set in consideration of the adhesion of the block body 3 and the cylinder liner 10 in the bore block 1. For example, a height of the projections 13 is 0.2 to 0.7 mm, and the number of the projections is 10 to 100 pieces per cm.sup.2. Also, it is desirable that a projection area ratio is 10 to 50%. The projection area ratio is calculated as a ratio occupied in a unit area by a total area of cross sectional areas of the projections 13 at the position of 0.2 mm from the base of the projections 13 in the projections 13 present within the unit area. When the projection area ratio is lower than 10%, bond strength of the block body 3 and the cylinder liner 10 declines. On the other hand, when the projection area ratio exceeds 50%, since decline of castability due to joining of the projections is invited, a gap is formed, the adhesion declines, and heat conductivity declines. Note that a distribution of the projections 13 described above is a numerical value on the outer peripheral surface S1 of the cylinder liner 10 excluding a groove part 11 to be described later.

(22) Here, the groove part 11 will be described. For the groove part 11, differently from the outer peripheral surface S1 of the cylinder liner 10 excluding the groove part 11, the projections 13 described above are not formed on the surface. Further, the groove part 11 is provided on a position facing the other cylinder bore 2 to be adjacent to the cylinder bore 2 with the cylinder liner 10 mounted thereon when the cylinder liner 10 is casted in the bore block 1. Specifically, the groove part 11 is provided on a predetermined part between an upper side end and a lower side end of the cylinder liner 10, of the outer peripheral surface which faces the other cylinder bore 2 to be adjacent to the cylinder bore 2 with the cylinder liner 10 mounted thereon when the cylinder liner 10 is casted in the bore block 1. The “predetermined part” here is the position on the outer peripheral surface separated downwards by a predetermined distance D1 from the upper side end of the cylinder liner 10. Then, the groove part 11 in the present example has a shape of crossing two roughly rectangular grooves in a cross-hatch shape, in a side view of the cylinder liner 10 (as illustrated in FIG. 2A). Of the two grooves configuring the groove part 11, one groove is formed such that the axial direction of the groove in the side view of the cylinder liner 10 is inclined by a predetermined angle A1 to the axial direction of the cylinder liner 10. In addition, of the two roughly rectangular grooves, the other groove is formed so as to be line symmetrical with the one groove when a center line Lc of the cylinder liner 10 is a reference, in the side view of the cylinder liner 10. The groove part 11 having the above-described shape is provided at two parts on the outer peripheral surface of the cylinder liner 10 so as to be a pair across the center axis of the cylinder liner 10. That is, in an upper view of the cylinder liner 10 as illustrated in FIG. 2B, the groove part 11 is provided at two parts on the outer peripheral surface of the cylinder liner 10 so as to be the pair across a center of the cylinder liner 10. Then, since the groove part 11 is formed by cutting, from a basic member of the cylinder liner 10 originally in a cylindrical shape, the outer peripheral surface of the basic member corresponding to the part where the groove part 11 is to be formed as described later, the outer peripheral surface of the groove part 11 is positioned more on an inner side of the cylinder liner 10 than the outer peripheral surface S1 of the cylinder liner 10 positioned above and below the groove part 11. That is, a surface of the groove part 11 is at a position one stage lower than the outer peripheral surface S1 of the cylinder liner 10 in a radial direction of the cylinder liner 10 in the upper view. From the above, the groove part 11 corresponds to a bore adjacent part of the present invention, and the outer peripheral surface S1 of the cylinder liner 10 other than the groove part 11 corresponds to a projection part of the present invention. Note that, while the groove part 11 is in the state where the projections 13 are generally removed and are absent on the surface by being formed by cutting the basic member of the cylinder liner 10 as described above, a condition where some projections 13 are partially removed and only the base part remains, for example, is possible depending on the machining state. That is, for the groove part 11, it is sufficient when the projections 13 are completely removed in at least a part thereof, and it is not necessary that the projections 13 are completely removed in the whole.

(23) Since the groove part 11 is provided in the cylinder liner 10 in this way, in the case where the cylinder liner 10 is casted in the bore block 1, the configuration between the adjacent cylinder bores is as illustrated in FIG. 3. FIG. 3 is an enlarged view of part D (the part held between the adjacent cylinder bores 2) on the cross section of the bore block 1 illustrated in FIG. 1D. The part D is also the part including the inter-bore passage 4.

(24) As described above, the groove part 11 is arranged so as to face the adjacent cylinder bore 2. Thus, the inter-bore passage 4 arranged between the adjacent cylinder bores 2 is in the state of being held between the groove part 11 of the cylinder liner 10 on the side of one cylinder bore 2 and the groove part 11 of the cylinder liner 10 on the side of the other cylinder bore 2. Here, since the surface of the groove part 11 is at the position lower than the outer peripheral surface S1 above and below, that is, distal ends of the projections 13, between the groove parts 11 facing each other, space for forming the inter-bore passage 4 is easily secured. In other words, interference of the inter-bore passage 4 and the cylinder liner 10 can be avoided, and the state where the block body 3 is interposed more between the cylinder liner 10 and the inter-bore passage 4 is easily established. This makes it possible to increase a passage diameter (passage cross-sectional area) of the inter-bore passage 4 even while reducing a pitch between the cylinder bores 2, and suitably cool the cylinder liner 10 inside each cylinder bore 2. Note that, in the example illustrated in FIG. 3, the surface of the groove part 11 is formed by the surface parallel to an inner wall surface of the cylinder liner 10, however, the surface of the groove part 11 does not need to be parallel to the inner wall surface of the cylinder liner 10, and the shape of the surface of the groove part 11 can be appropriately set as long as the interference of the inter-bore passage 4 and the cylinder liner 10 can be avoided.

(25) Here, a dimension of the groove part 11 will be mentioned. First, the predetermined distance D1 for specifying the position of the groove part 11 in the axial direction of the cylinder liner 10 is determined such that the groove part 11 is arranged at the position closest to the inter-bore passage 4, of the outer peripheral surface of the cylinder liner 10 facing the adjacent cylinder bore 2. In addition, the inclination angle A1 of the two grooves configuring the groove part 11 is set to be equal to the inclination angle of the inter-bore passage 4. Note that the position and the inclination angle of the inter-bore passage 4 are determined in consideration of the position of a combustion chamber to be formed when a piston inside the cylinder bore is positioned at a top dead center, when the cylinder block is formed including the bore block 1 and the engine is configured further. That is, the position and the inclination angle of the inter-bore passage 4 are determined corresponding to the part which is exposed to an environment of a relatively high temperature and especially needs cooling by the cooling medium in the cylinder liner 10. In addition, as illustrated in FIG. 3, corresponding to the passage diameter of the inter-bore passage 4 for cooling the cylinder bore 2, that is, to suitably transmit heat to the inter-bore passage 4, a width and depth of each groove configuring the groove part 11 are determined. If the width of each groove is determined to be unnecessarily large to the passage diameter of the inter-bore passage 4, since an area where the projections 13 are formed on the outer peripheral surface S1 of the cylinder liner 10 becomes small, the adhesion of the cylinder liner 10 and the block body 3 can be undesirably affected. Therefore, it is preferable that the width of each groove configuring the groove part 11 is determined from viewpoints of avoiding the interference with the inter-bore passage 4 and securing the adhesion.

(26) In addition, it is preferable that the depth of each groove configuring the groove part 11 is determined from the viewpoints of avoiding the interference with the inter-bore passage 4 and securing the strength of the cylinder liner 10. If the depth of each groove is set unnecessarily large, since a thickness of the cylinder liner 10 at the part corresponding to the groove part 11 is reduced, the strength of the cylinder liner 10 declines. Also, when the depth of each groove is set unnecessarily small, a distance by which the groove part 11 is positioned more on the inner side of the cylinder liner 10 than the outer peripheral surface S1 above and below is reduced as a result, and it becomes difficult to sufficiently avoid the interference with the inter-bore passage 4. Thus, problems regarding avoidance of the interference with the inter-bore passage 4 and securing of the strength of the cylinder liner 10 are taken into consideration and the depth of each groove configuring the groove part 11 is determined.

(27) Next, a positioning groove 12 (corresponding to a positioning part of the present invention) used to make the groove part 11 face the other adjacent cylinder bore 2 will be described. The positioning groove 12 is formed at the lower side end of the cylinder liner 10, right below a center part of the groove part 11, as illustrated in FIG. 2A. Then, for a relative positional relation of the groove part 11 and the positioning groove 12, the respective positions of both are determined such that a virtual line L1 defined by mutually connecting the center parts of the paired groove parts 11 provided at two parts on the outer peripheral surface of the cylinder liner 10 and a virtual line L2 defined by mutually connecting the center parts of the paired positioning grooves 12 provided on the lower side end overlap in the upper view of the cylinder liner 10. By such a configuration, when the position of the cylinder liner 10 in the bore block 1 is determined based on the positioning groove 12, the position of the groove part 11 is also determined at the predetermined position with the positioning groove 12 as the reference. More specifically, since the virtual lines L1 and L2 overlap as described above, when the position of the cylinder liner 10 is determined using the paired positioning grooves 12, the positions of the paired groove parts 11 are also determined so as to be lined with the paired positioning grooves 12.

(28) In addition, as a different method, instead of the form that the virtual line L1 and the virtual line L2 overlap, the respective positions of the paired groove parts 11 and the paired positioning grooves 12 may be determined such that the virtual line L1 and the virtual line L2 cross at an angle of 0 degrees to 90 degrees in the upper view. It is important that the relative positional relation of the virtual line L1 and the virtual line L2 is determined to be a predetermined relation. Also by such a configuration, when the position of the cylinder liner 10 in the bore block 1 is determined based on the positioning groove 12, the position of the groove part 11 is also determined to be the predetermined position, that is, the position suitably facing the adjacent cylinder bore.

(29) <Manufacturing Method of Cylinder Liner 10>

(30) The cylinder liner 10 is manufactured by a centrifugal casting method. According to the centrifugal casting method, the cylinder liner 10 including the plurality of uniform projections 13 on the outer peripheral surface S1 can be manufactured with excellent productivity. Hereinafter, the manufacturing method of the cylinder liner 10 will be described based on FIG. 4.

(31) First, in S101, the basic member of the cylinder liner 10 is casted. The basic member is a cylindrical structure including the outer peripheral surface S1 where the projections 13 are formed. As one example, a coating agent is prepared by mixing diatomaceous earth having an average grain diameter of 0.002 to 0.02 mm, bentonite (binder), water and a surfactant by a predetermined ratio. The coating agent is sprayed and applied to an inner surface of a mold (die) which is heated to 200 to 400° C. and rotated, and a coating layer is formed on the inner surface of the mold. The thickness of the coating layer is 0.5 to 1.1 mm. By an effect of the surfactant, a plurality of recessed holes are formed in the coating layer by bubbles of steams generated from inside of the coating layer. After the coating layer is dried, molten cast iron is casted inside the rotated mold. At the time, the molten metal is filled in the recessed holes of the coating layer, and the plurality of uniform projections are formed. After the molten metal is solidified and the cylinder liner 10 is formed, the cylinder liner 10 is taken out from the mold together with the coating layer. The coating agent is removed by blasting, and the basic member of the cylinder liner 10 including the plurality of uniform projections 13 on the outer peripheral surface is manufactured.

(32) Next, in S102, to the basic member of the cylinder liner 10, the machining reference surface is provided. Specifically, an end face at the lower side end of the cylinder liner 10, where the positioning groove 12 is to be formed, is cut and formed as the machining reference surface. Subsequently, in S103, cutting parts where the groove parts 11 and the positioning grooves 12 are to be formed are determined. For the positioning grooves 12, the two positions across the center axis of the cylinder liner 10 at the lower side end of the cylinder liner 10 are determined as the cutting parts (corresponding to a second part of the present invention) of the positioning grooves 12. A straight line connecting the cutting parts of the two positioning grooves 12 corresponds to the virtual line L2, and crosses with the center axis of the cylinder liner 10. In addition, while the groove part 11 is formed to be the pair at two parts on the outer peripheral surface separated downwards by the predetermined distance D1 from the upper side end of the cylinder liner 10, for the paired groove parts 11, the two positions on the outer peripheral surface across the center axis of the cylinder liner 10 are determined as the cutting parts of the groove parts 11 (corresponding to the first part of the present invention). Further, a straight line connecting the cutting parts of the two groove parts 11 corresponds to the virtual line L1, and as described above, the cutting parts of the groove parts 11 are determined so as to overlap with the virtual line L2 in the upper view of the cylinder liner 10.

(33) Then, in S104, the groove parts 11 are formed by cutting the surface of the basic member of the cylinder liner 10 so as to form the grooves for which the two grooves that have the width and depth determined as described above and are inclined by the predetermined angle A1 to the axial direction of the basic member of the cylinder liner 10 are crossed in the cross-hatch shape at the cutting parts on the outer peripheral surface determined in S103. Then, in S105, the positioning grooves 12 are formed by cutting the basic member of the cylinder liner 10 in the radial direction (the direction from the outer peripheral surface S1 to the inner peripheral surface S2) at the cutting parts at the lower side end determined in S103. The shape of the positioning groove 12 is not limited to a specific shape as long as the cylinder liner 10 can be positioned in a manufacturing process of the bore block 1. For example, the positioning groove 12 may be an appropriately rounded recess as illustrated in FIG. 2A so that a positioning jig is fitted.

(34) Note that the manufacturing method of the cylinder liner 10 is not limited to the method illustrated in FIG. 4. For example, the positioning groove 12 may be formed in advance and the groove part 11 may be formed thereafter. Also in this case, the relative positional relation between the positioning groove 12 and the groove part 11 described above, that is, overlap of the virtual lines L1 and L2 in the upper view, is taken into consideration.

(35) <Manufacturing Method of Bore Block 1>

(36) The manufacturing method of the bore block 1 illustrated in FIG. 1A or the like using the cylinder liner 10 manufactured according to the above-described method will be described based on FIG. 5. First, in S201, inside the mold for the bore block 1, the cylinder liners 10 for the number according to the number of the cylinder bores to be formed there are positioned (in the present embodiment, the three cylinder liners 10 are positioned). Specifically, using the positioning groove 12 provided on the lower side end of each cylinder liner 10, the three cylinder liners 10 are positioned. A jig for positioning is a straight positioning shaft. By fitting the respective positioning grooves 12 of the three cylinder liners 10 to the positioning shaft, the three cylinder liners 10 can be positioned on a straight line. At the time, the groove parts 11 of the respective cylinder liners 10 are also lined on a straight line along the positioning shaft. Then, since the positioning shaft is positioned to the mold along the longitudinal direction of the bore block 1, when the cylinder liners 10 are positioned by the positioning shaft, the respective groove parts 11 are placed in the state of facing the adjacent cylinder bores.

(37) Now, when the respective cylinder liners 10 are positioned just by fitting the positioning grooves 12 of the respective cylinder liners 10 to the positioning shaft, that is, when the positions of the two groove parts 11 in the respective cylinder liners 10 are determined without taking the inclination direction of the inter-bore passage 4 into consideration, it is concerned that the relative positions of the inter-bore passage 4 and the groove parts 11 are not the relative positions effective for solving the problems regarding the avoidance of the interference with the inter-bore passage 4, the securing of the adhesion with the bore block 1 and the securing of the strength of the cylinder liners 10 as described above. However, the groove part 11 in the present embodiment is configured by crossing the two roughly rectangular grooves to be line symmetrical to each other with the center line Lc of the cylinder liner 10 as the reference in the cross-hatch shape in the side view of the cylinder liner 10, as described in the description of FIG. 2A above. Therefore, even in the case where the respective cylinder liners 10 are positioned without taking the positions of the two groove parts 11 in the respective cylinder liners 10 into consideration, that is, even in the case where the positions of the two groove parts 11 in the cylinder liner 10 are inverted, the relative positions of the inter-bore passage 4 and the groove parts 11 can be the relative positions effective for solving the problems regarding the avoidance of the interference with the inter-bore passage 4, the securing of the adhesion with the bore block 1 and the securing of the strength of the cylinder liners 10 as illustrated in FIG. 3 described above.

(38) Next, when the three cylinder liners 10 are positioned inside the mold in S201, in S202, by a molten aluminum alloy to form the block body 3 being filled inside the mold, the cylinder liners 10 are casted and a basic structure of the bore block 1 is formed. Then, in S203, to the basic structure, boring for forming the inter-bore passage 4 is performed. The boring at the time is performed along the front-back direction of the basic structure at the angle inclined downward by the predetermined angle A1 in the axial direction of the cylinder bore 2 from the position of the opening end set on the upper surface of the basic structure. Thus, as illustrated in FIG. 3 described above, the inter-bore passage 4 is formed in the form of passing through the part held between the groove part 11 of the cylinder liner 10 on the side of one cylinder bore 2 and the groove part 11 of the cylinder liner 10 on the side of the other cylinder bore 2, of a wall part of the bore block 1 formed between the adjacent cylinder bores 2. In addition, in S203, finishing of the inner peripheral surface S2 of the cylinder liner 10 is also performed. After machining is ended, the thickness of the cylinder liner 10 is 1.0 to 2.5 mm, for example.

(39) In such a manufacturing method of the bore block 1, even in the case where the inter-bore passage 4 is bored after casting, as illustrated in FIG. 3, the groove parts 11 of the cylinder liners 10 are arranged so as to face each other at the part where the bored part and the outer peripheral surface of the cylinder liner 10 are the closest, the interference of the inter-bore passage 4 and the cylinder liner 10 can be suitably avoided. Such a configuration of the cylinder liner 10 is particularly useful in the case of reducing the inter-bore pitch of the bore block 1. In addition, since the formation part of the groove part 11 in the cylinder liner 10 is limited to the range of facing the other adjacent cylinder bore 2, unnecessary decline of the adhesion of the cylinder liner 10 and the block body 3 after casting can be avoided.

(40) <Modification 1>

(41) In the above-described cylinder liner 10, the groove part 11 is provided in the pair at two parts on the outer peripheral surface of the cylinder liner 10, however, the groove part 11 may be provided at only one part on the outer peripheral surface instead of the form. For example, of the three cylinder bores 2 formed in the bore block 1 illustrated in FIG. 1A or the like, for the cylinder bore 2 positioned at an end on a right side or a left side, the other adjacent cylinder bore is positioned only on the left or right. For the cylinder liner 10 included in such a cylinder bore 2, even when only one groove part 11 is provided, there is no problem when the groove part 11 is arranged so as to face the other adjacent cylinder bore 2.

(42) In addition, it is not necessary to provide the positioning groove 12 in the pair at the lower side end of the cylinder liner 10, and when the cylinder liner 10 can be positioned at the predetermined position where the groove part 11 faces the other adjacent cylinder bore 2 inside the mold in an interaction with the jig for positioning, the number and the shape of the positioning grooves 12 are not limited specifically. Further, the arrangement at the lower side end of the positioning groove 12 does not need to be right below the groove part 11, and is not limited to a specific position when the cylinder liner 10 can be positioned at the predetermined position inside the mold as described above.

(43) Further, the groove part 11 does not need to be the shape of crossing the two roughly rectangular grooves in the cross-hatch shape, and even in the case where the positions of the two groove parts 11 in the cylinder liner 10 are mutually inverted, the shape of the groove part 11 is not limited specifically when it is such a shape that the inter-bore passage 4 can pass between the groove parts 11 facing each other. Note that, when work of determining the positions of the two groove parts in the cylinder liner 10 in consideration of the inclination direction of the inter-bore passage 4 is additionally performed when positioning the cylinder liner 10 inside the mold for the bore block 1, the shape of the groove part may be configured only by one roughly rectangular groove parts 11′ having the same inclination angle as the inter-bore passage 4 as illustrated in FIG. 6.

(44) <Modification 2>

(45) Of the outer peripheral surface of the cylinder liner 10, at least on the groove part 11 and the peripheral part, a high-heat conductive film 14 may be provided. For example, as illustrated in FIG. 7, the high-heat conductive film 14 may be provided in the range from the upper side end to an intermediate part in the axial direction of the cylinder liner 10, of the outer peripheral surface of the cylinder liner 10. The high-heat conductive film 14 is provided over an entire circumferential direction of the cylinder liner, including the surface of the groove part 11 and the projections 13. Note that, in the example illustrated in FIG. 7, a lower end of the high-heat conductive film 14 in the axial direction of the cylinder liner 10 is positioned below the lower end of the groove part 11, however, the lower end of the high-heat conductive film 14 may be determined so as to be at the position equal to the lower end of the groove part 11. In short, it is sufficient when the high-heat conductive film 14 is formed at the part including the groove part 11 and the periphery and the part that easily receives heat generated inside the cylinder bore 2 when the internal combustion engine is operated, of the outer peripheral surface of the cylinder liner 10.

(46) Here, the high-heat conductive film 14 is formed by a material capable of improving heat conductivity between the cylinder liner 10 and the block body 3 compared to the state where the high-heat conductive film 14 is not formed. Specifically, the high-heat conductive film 14 is configured by a sprayed layer of aluminum, the aluminum alloy (an Al—Si alloy, an Al—Si—Cu alloy, an Al—Cu alloy or the like), copper or a copper alloy. Note that as the material of the sprayed layer, the material other than the ones described above can be used when it is the material satisfying at least one of conditions (A) and (B) below.

(47) (A) The material having a melting point at or below a molten metal temperature of a casting material of the block body 3, or the material containing such a material. The “molten metal temperature” here is the temperature of the molten metal of the casting material to be filled inside the mold when casting the cylinder liner 10 by the casting material of the block body 3.

(48) (B) The material to be metallurgically bonded with the casting material of the block body 3, or the material containing such a material.

(49) When the cylinder liner 10 is casted in the block body 3 in the state where the high-heat conductive film 14 is formed on the outer peripheral surface at an upper part of the cylinder liner 10, the upper part of the cylinder liner 10 and the block body 3 are bonded through the high-heat conductive film 14. The bond strength and the adhesion at the time become higher than that in the case where the upper part of the cylinder liner 10 and the block body 3 are bonded without interposing the high-heat conductive film 14. When the adhesion of the upper part of the cylinder liner 10 and the block body 3 is improved in such a manner, the heat conductivity between the upper part of the cylinder liner 10 and the block body 3 is improved. In particular, in the configuration that the groove part 11 is provided on the upper part of the cylinder liner 10, it is possible that the bond strength, the adhesion and the heat conductivity between the cylinder liner 10 and the block body 3 at the groove part 11 and the periphery decline since the projections 13 are not formed at the groove part 11, however, the decline of the bond strength, the adhesion and the heat conductivity between the cylinder liner 10 and the block body 3 due to provision of the groove part 11 can be suppressed by bonding the groove part 11 and the peripheral part with the block body 3 through the high-heat conductive film 14.

(50) <Manufacturing Method of Cylinder Liner 10>

(51) Hereinafter, based on FIG. 8, the manufacturing method of the cylinder liner 10 in the present modification will be described. In FIG. 8, same symbols are attached to processes similar to the ones in FIG. 4 above.

(52) In the example illustrated in FIG. 8, after the process of S105 is ended, the process of S1001 is performed. In the process of S1001, the high-heat conductive film 14 is formed by plasma spraying, arc spraying or HVOF spraying of the aluminum, the aluminum alloy, the copper, the copper alloy or the like in the range from the upper side end to the intermediate part in the axial direction, of the outer peripheral surface of the cylinder liner 10. The “intermediate part” at the time is determined, as described above, as the position equal to the lower end of the groove part 11 in the axial direction of the cylinder liner 10 or the position below the lower end and the position capable of covering the outer peripheral surface at the part that easily receives the heat generated inside the cylinder bore 2 when the internal combustion engine is operated with the high-heat conductive film 14. In addition, the thickness of the high-heat conductive film 14 is determined such that a recess formed between the adjacent projections 13 is not filled by the high-heat conductive film 14. That is, the thickness of the high-heat conductive film 14 is determined so as to obtain an anchor effect by the projections 13 by the casting material of the block body 3 flowing into the recess when the cylinder liner 10 is casted by the casting material of the block body 3.

(53) Note that, while the example that the high-heat conductive film 14 is formed by spraying is described in the present modification, the high-heat conductive film 14 may be formed by shot coating or plating. In the case of forming the high-heat conductive film 14 by shot coating, as the material of the high-heat conductive film 14, zinc, tin, aluminum, an alloy containing at least one of the zinc and the tin or the like can be used. In shot coating, since the high-heat conductive film 14 can be formed without melting the coating material, the oxide is not easily contained inside the high-heat conductive film 14. Thus, the decline of the heat conductivity of the high-heat conductive film 14 due to the oxide being contained can be suppressed. In the case of forming the high-heat conductive film 14 by plating, as the material of the high-heat conductive film 14, the aluminum, the aluminum alloy, the copper, the copper alloy or the like can be used.

(54) In addition, while the example that only the high-heat conductive film 14 is provided on the outer peripheral surface of the cylinder liner 10 is described in the present modification, a low-heat conductive film 15 may be provided in addition to the high-heat conductive film 14. Specifically, the low-heat conductive film 15 may be provided in the entire circumferential direction of the outer peripheral surface of the cylinder liner 10 from the intermediate part in the axial direction of the cylinder liner 10 to the lower side end. The “low-heat conductive film 15” here is formed by the material capable of lowering the heat conductivity between the cylinder liner 10 and the block body 3 compared to the state where the low-heat conductive film 15 is not formed. Specifically, the low-heat conductive film 15 is configured by the sprayed layer of a ceramic material (alumina, zirconia or the like), the sprayed layer of the oxide and a ferrous material containing many pores, a layer of a mold release agent (the mold release agent for which vermiculite, hitasol and water glass are mixed, the mold release agent for which a liquid material with silicon as a main component and the water glass are mixed or the like) for die casting formed through coating, the layer of the coating agent (the coating agent in which diatomaceous earth is mixed as the main component, the coating agent in which graphite is mixed as the main component or the like) for die centrifugal casting formed through coating, the layer of a metallic coating formed through coating, the layer of a low adherence agent (the low adherence agent in which the graphite, the water glass and water are mixed, the low adherence agent in which boron nitride and the water glass are mixed or the like) formed through coating, the layer of a heat resistance resin formed through resin coating, a chemical conversion treatment layer (the chemical conversion treatment layer of phosphate, the chemical conversion treatment layer of magnetite or the like) formed through chemical conversion treatment or the like. When the high-heat conductive film 14 and the low-heat conductive film 15 are provided on the outer peripheral surface of the cylinder liner 10, while the heat at the part that easily receives the heat generated inside the cylinder bore 2 of the cylinder liner 10 (the part on the upper side of the intermediate part in the axial direction of the cylinder liner 10) is easily radiated through the high-heat conductive film 14 to the block body 3, heat radiation to the block body 3 from the part that does not easily receive the heat generated inside the cylinder bore 2 (the part below the intermediate part in the axial direction of the cylinder liner 10) is suppressed by the low-heat conductive film 15. Thus, a temperature distribution in the axial direction of the cylinder liner 10 can be brought closer to be uniform.

REFERENCE NUMERAL LIST

(55) 1: bore block 2: cylinder bore 3: block body 4: inter-bore passage 10: cylinder liner 11: groove part 11′: groove part 12: positioning groove 13: projection 14: high-heat conductive film 15: low-heat conductive film L1: virtual line L2: virtual line S1: outer peripheral surface S2: inner peripheral surface