Composite cylinder block

Abstract

A cylinder block (1) comprises a metal main block (2), and a resin outer member (3) which is welded to the main block (2). The main block (2) has a cylinder wall (13) forming a cylinder bore (16), and a second columnar portion (14B) spaced apart from the cylinder wall (13). The outer member (3) has a second columnar portion insertion hole (53), and forms a water jacket between the cylinder wall (13) and the outer member (3). The second columnar portion (14B) is accommodated in the second columnar portion insertion hole (53) in a state of being isolated from the water jacket, with a predetermined gap between the second columnar portion and the second columnar portion insertion hole (53), and reaches a cylinder head.

Description

[Technical field]

[0001] The present invention relates to a composite cylinder block for an internal combustion engine which is constructed by combining metal members and synthetic resin members. [Background technology]

[0002] For example, Patent Document 1 discloses an engine block in which a resin block is attached to the outer peripheral surface of a metal cylinder liner.

[0003] The engine block of Patent Document 1 includes, in addition to a cylinder liner and a resin block, a metal block member and a metal protrusion.

[0004] The block member in Patent Document 1 is made of metal and functions as a base to support the resin block.

[0005] The protrusion in Patent Document 1 has an opening into which a bolt for fixing the cylinder head is inserted, and protrudes from the block member toward the cylinder head.

[0006] In Patent Document 1, damage to the resin block caused by heat from the cylinder liner is reduced by a water jacket formed within the resin block.

[0007] However, the engine block of Patent Document 1 does not disclose anything about warming up the protrusions located on the outside of the water jacket, or even about warming up the engine block.

[0008] That is, when an engine block is constructed from metal parts and resin parts, there is room for further improvement in terms of taking into consideration the warming up of the metal parts. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2020-112147 A Summary of the Invention

[0010] The composite cylinder block of the present invention comprises a metal main block and a resin outer member welded to the main block. The main block has a cylinder wall forming a cylinder bore and a columnar portion formed at a position spaced apart from the cylinder wall. The outer member forms a water jacket between itself and the cylinder wall. The columnar portion is housed within the outer member isolated from the water jacket and with a predetermined gap between it and the outer member, and extends to the cylinder head.

[0011] In the composite cylinder block of the present invention, the gap between the columnar portion of the main block and the outer member forms an air layer (thermal insulation layer), so that the columnar portion is less likely to be cooled by cooling water during engine warm-up (internal combustion engine warm-up), thereby improving warm-up performance. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a perspective view of a composite cylinder block according to an embodiment of the present invention; [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] FIG. [Figure 7] FIG. 4 is a perspective view of the outer member in a upside-down state. [Figure 8] An enlarged view of a portion of Figure 7. [Figure 9] FIG. [Figure 10] FIG. [Figure 11] FIG. 3 is a perspective view of a cross section taken along line AA in FIG. 2 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] An embodiment of the present invention will now be described in detail with reference to the drawings.

[0014] First, the overall structure of a composite cylinder block 1 of one embodiment will be described. The composite cylinder block 1 is composed of two members: a metal main block 2 and an outer member 3 made of synthetic resin. Figures 1 to 3 and 11 show the composite cylinder block 1 with the main block 2 and outer member 3 integrated together, while Figures 4 and 5 show the main block 2 alone, and Figures 6 to 10 show the outer member 3 alone. The main block 2 and the outer member 3 are manufactured separately and welded together using a heat welding technique described below.

[0015] The illustrated example is a cylinder block 1 for an in-line three-cylinder engine, and for convenience of explanation, as indicated by "#1" in FIG. 1, the cylinders will be called #1, #2, and #3, starting from the right front side of FIG. 1. The direction parallel to the line on which the centers of these three cylinders are aligned will be called the "cylinder row direction", the direction parallel to the central axis of each cylinder will be called the "cylinder axis direction", and the direction perpendicular to the cylinder row direction will be called the "width direction". In addition, following the general directions of top dead center and bottom dead center, the terms "upper", "upper", "lower", and "lower" will be used. Note that the present invention is not limited to an in-line three-cylinder engine. Furthermore, the "front" of the cylinder block 1 means the #1 cylinder side in the cylinder row direction, and the "rear" means the #3 cylinder side.

[0016] The metallic main block 2 is a unit that integrates the parts that support the load or reaction force caused by the combustion and explosion of the internal combustion engine, and each part is cast integrally using an appropriate metallic material. In a preferred embodiment, it is cast integrally by die casting using an aluminum alloy. As shown in Figs. 4 and 5, the main block 2 includes a lower deck 11 that is plate-shaped along a plane perpendicular to the cylinder axis direction, a base portion 12 that rises upward from the upper surface of the lower deck 11, three cylindrical cylinder walls 13 that extend further upward from the base portion 12, a total of eight columnar portions 14 that also rise upward from the base portion 12, and four main bearing portions 15 provided on the lower surface of the lower deck 11. Each cylinder wall 13 forms a cylinder bore 16, and these cylinder bores 16 extend through the base portion 12 to the lower surface of the lower deck 11.

[0017] The lower deck 11 expands in a generally symmetrical manner in the width direction around the cylinder row, with the width dimension being relatively large on the #3 cylinder side and relatively small on the #1 cylinder side (see FIG. 3). The plate-like lower deck 11 has an appropriate thickness to provide the necessary rigidity. The cylinder bores 16 terminate at the lower surface of the lower deck 11. In other words, the cylinder wall 13 does not protrude downward beyond the lower deck 11. When the engine is finally assembled, a crankcase component (e.g., an oil pan) (not shown) is attached to the lower surface of the lower deck 11.

[0018] The main bearings 15 are provided at four locations, including the front and rear ends in the cylinder row direction and between the cylinders, in order to rotatably support the crankshaft (not shown). Each of the main bearings 15 is formed as a relatively thick rectangular plate that protrudes downward from the lower surface of the lower deck 11, and has a semicircular bearing recess 15a at the center of the lower surface. Bearing caps (not shown) are finally attached to these main bearings 15, and the journal portion of the crankshaft is rotatably supported via a bearing metal (not shown). The lower surface of the lower deck 11, except for the main bearings 15, is a flat surface along a plane perpendicular to the cylinder axial direction.

[0019] The cylinder wall 13 has a cylindrical shape with a substantially constant thickness (radial dimension). In the illustrated example, three cylindrical cylinder walls 13 are connected to each other at the inter-cylinder portions to form a so-called Siamese structure. In other words, the bore pitch is shorter than the outer diameter of the cylinder walls 13. In the illustrated example, the main block 2 is made of an aluminum alloy, so that a cast iron cylinder liner (not shown) is inserted or a wear-resistant metal is sprayed on the inner peripheral surface of the cylinder bore 16.

[0020] The base portion 12 has a side surface 21 rising substantially at a right angle from the upper surface of the lower deck 11, and a top surface 22 parallel to the upper and lower surfaces of the lower deck 11. The columnar portions 14 each rise upward from the top surface 22 of the base portion 12 substantially at a right angle (in other words, along the cylinder axial direction).

[0021] The pillar-shaped portions 14 are provided at eight locations in total, including both front and rear ends in the cylinder row direction and between the cylinders, so as to surround the cylinder row in which the three cylinder walls 13 are connected. In the following, when it is necessary to distinguish between them, they are called the first pillar-shaped portion 14A, the second pillar-shaped portion 14B, the third pillar-shaped portion 14C, the fourth pillar-shaped portion 14D, the fifth pillar-shaped portion 14E, the sixth pillar-shaped portion 14F, the seventh pillar-shaped portion 14G, and the eighth pillar-shaped portion 14H, in order from the #1 cylinder side, as shown in FIG. 4, and when it is not necessary to distinguish between them, they are collectively called the pillar-shaped portion 14. Each pillar-shaped portion 14 is independent and is also separated from the cylinder wall 13. These pillar-shaped portions 14 function as bolt boss portions into which cylinder head bolts (not shown) for fixing a cylinder head (not shown) arranged on the cylinder block 1 are screwed.

[0022] The six columnar sections 14 excluding the first columnar section 14A and the second columnar section 14B, that is, the third columnar section 14C to the eighth columnar section 14H, each have a simple cylindrical shape with a circular cross section, and a bolt hole 24 into which a cylinder head bolt is screwed is formed at the center of the upper end. Basically, the diameters of the third columnar section 14C to the eighth columnar section 14H are set to be equal to each other. Here, in the illustrated example, since the main block 2 is cast by a die casting method, a so-called draft is given to the surface of each section along the cylinder axial direction as necessary, and therefore, strictly speaking, the third columnar section 14C to the eighth columnar section 14H, which are cylindrical, have a tapered shape with a slightly smaller diameter at the upper end.

[0023] Unlike the third columnar portion 14C to the eighth columnar portion 14H, the first columnar portion 14A has a shape as if two parallel cylinders were joined at a part of the outer circumferential surface. In other words, in a plan view as shown in FIG. 5 and a cross-sectional view perpendicular to the cylinder axis direction, the first columnar portion 14A has a shape of the letter "8". Specifically, a main columnar portion 14Aa having a diameter similar to that of the third columnar portion 14C to the eighth columnar portion 14H and a sub-columnar portion 14Ab having a smaller diameter are integrated. The main columnar portion 14Aa is a portion that functions as a bolt boss portion for a cylinder head bolt like the third columnar portion 14C to the eighth columnar portion 14H, and has a bolt hole 24 at the center of the upper end portion. This main columnar portion 14Aa is provided at a position symmetrical to the fourth columnar portion 14D across the center of the #1 cylinder, that is, at a position where a total of eight cylinder head bolts are evenly arranged. The sub-cylindrical portion 14Ab is located diagonally outside the main cylindrical portion 14Aa, that is, on the opposite side to the cylinder wall 13 of the #1 cylinder. An oil passage 25 is formed in the center of the sub-cylindrical portion 14Ab along the cylinder axial direction for supplying oil pressurized by an oil pump (not shown) to the cylinder head. In other words, the sub-cylindrical portion 14Ab corresponds to a tube constituting the oil passage 25 having a circular cross section. In this way, the first columnar portion 14A is formed by connecting the main cylindrical portion 14Aa, which serves as the bolt boss portion, and the sub-cylindrical portion 14Ab, which serves as the tube of the oil passage 25, at part of the circumferential surface, and a pair of recessed grooves 14Ac remain on the outer circumferential surface between them.

[0024] The second columnar portion 14B is similar to the first columnar portion 14A and has a shape as if two parallel cylinders were joined at a part of the outer circumferential surface. In other words, in the plan view and the cross-sectional view perpendicular to the cylinder axis direction as shown in FIG. 5, it has a shape of the letter "8". Specifically, the main columnar portion 14Ba, which has a smaller diameter than the third columnar portion 14C to the eighth columnar portion 14H, and the sub-columnar portion 14Bb, which has a slightly smaller diameter than the main columnar portion 14Ba, are integrated together. The main columnar portion 14Ba is a portion that functions as a bolt boss portion for the cylinder head bolts, similar to the third columnar portion 14C to the eighth columnar portion 14H, and has a bolt hole 24 at the center of the upper end portion. This main columnar portion 14Ba is provided at a position symmetrical to the third columnar portion 14C across the center of the #1 cylinder, that is, at a position where the arrangement of the total eight cylinder head bolts is uniform. The sub-cylindrical portion 14Bb is located in front of and inward of the main cylindrical portion 14Ba in the width direction, that is, next to the main cylindrical portion 14Ba on an arc centered on the center of the cylinder #1. In the center of this sub-cylindrical portion 14Bb, an oil passage 26 is formed along the cylinder axial direction to supply oil pressurized by an oil pump (not shown) to the cylinder head, similar to the sub-cylindrical portion 14Ab of the first columnar portion 14A. In other words, the sub-cylindrical portion 14Bb corresponds to a tube constituting the oil passage 26 having a circular cross section. In this way, the second columnar portion 14B is formed by connecting the main cylindrical portion 14Ba, which is the bolt boss portion, and the sub-cylindrical portion 14Bb, which is the tube of the oil passage 26, at a part of the circumferential surface, and a pair of recessed grooves 14Bc remain on the outer circumferential surface between them.

[0025] In the illustrated example, the second columnar section 14B is configured such that its lower portion is integrated with the side surface 21 of the base section 12, whereas the other columnar sections 14 (first columnar section 14A, third columnar section 14C to eighth columnar section 14H) are not continuous with the side surface 21 of the base section 12 and protrude from the top surface 22 of the base section 12. In other words, of the outer circumferential surface of the second columnar section 14B having an "8"-shaped cross section, its inner portion (portion toward the cylinder wall 13) rises up from the top surface 22 of the base section 12, whereas its outer portion (portion opposite the cylinder wall 13) extends below the top surface 22 and continues to the lower deck 11.

[0026] The lower end of the oil passage 25 passing through the first columnar portion 14A and the lower end of the oil passage 26 passing through the second columnar portion 14B are each connected to a sub-oil gallery (not shown) extending in the width direction of the main block 2 formed near the front end of the lower deck 11. The sub-oil gallery along the width direction is connected to a main oil gallery 27 (see Figs. 11 and 4) extending along the cylinder row direction formed on the lower side of the row of cylinder walls 13. High-pressure oil (lubricating oil) pressurized by an oil pump (not shown) is supplied to the main oil gallery 27. A part of this high-pressure oil is supplied to the cylinder head side through two oil passages 25 and 26. Also, as shown in Fig. 11, a part of the high-pressure oil is supplied to the bearing recess 15a through an oil passage 28 passing through the main bearing portion 15.

[0027] The base portion 12 is formed so as to protrude outward by a substantially constant width from the outer contours of the three cylinder walls 13 arranged in series, and is also formed so as to protrude outward by a substantially constant width from the outer contours of the columnar portions 14 excluding the second columnar portion 14B. In other words, the shape of the side surface 21 of the base portion 12 is determined so as to follow the outer contours of the cylinder walls 13 and the columnar portions 14 and surround the outside thereof. Basically, the side surface 21 is a combination of a cylindrical surface concentric with the cylinder walls 13 and a cylindrical surface concentric with the columnar portions 14.

[0028] In other words, as shown in Fig. 5, the top surface 22 exists with a substantially constant width (see reference symbol D1 in Fig. 5) around the cylinder wall 13 except for the portion adjacent to the columnar portion 14, and the top surface 22 exists with a relatively narrow substantially constant width (see reference symbol D2 in Fig. 5) around the columnar portion 14. Around the first columnar portion 14A, the top surface 22 exists with a width similar to that around the other columnar portions 14, following the "8"-shaped cross-sectional shape of the first columnar portion 14A. In addition, the top surface 22 exists with a relatively narrow width between each columnar portion 14 except the second columnar portion 14B and the adjacent cylinder wall 13.

[0029] As for the second columnar portion 14B, since both the main columnar portion 14Ba and the sub columnar portion 14Bb have smaller diameters than the other columnar portions 14, a top surface 22 having a width approximately equal to the width (see D1 in FIG. 5) of the portion other than the portion adjacent to the other columnar portion 14 exists between the second columnar portion 14B and the cylinder wall 13. On the other hand, no top surface 22 exists on the outside of the second columnar portion 14B.

[0030] Furthermore, the base portion 12 has three oil drop hole forming portions 31 each having a rectangular shape in a plan view. The first oil drop hole forming portion 31A is located between the #1 cylinder and the #2 cylinder and is located outside the third columnar portion 14C, and the second oil drop hole forming portion 31B is located between the #2 cylinder and the #3 cylinder and is located outside the fifth columnar portion 14E. The third oil drop hole forming portion 31C is located on the opposite side of the cylinder row from these two oil drop hole forming portions 31A and 31B, and is located between the fourth columnar portion 14D and the sixth columnar portion 14F, that is, on the side of the #2 cylinder. In the center of each of these oil drop hole forming portions 31, a lower half of the oil drop hole 32 extending in the cylinder axial direction is formed. As described later, the lower half of the oil drop hole 32 forms a part of the oil drop hole for returning oil used on the cylinder head side to the crankcase by its own weight. The lower half of the oil drop hole 32 has a generally rectangular cross-sectional shape that is elongated in the cylinder row direction, as shown in FIG. 5, but on the underside of the lower deck 11, which is the final oil outlet, the shape is narrowed to a circular hole, as shown in FIG. 3.

[0031] As shown in Figures 4 and 5, the oil drop hole forming portion 31 is part of the base portion 12 and has the same height as the periphery of the cylinder wall 13, etc., and a part of the top surface 22 of the base portion 12, which forms the same plane, surrounds the periphery of the lower half of the oil drop hole 32.

[0032] The top surface 22 of the base portion 12, including the portion surrounding the cylinder wall 13, the portion surrounding the columnar portion 14, and the portion surrounding the lower half of the oil drop hole 32, is aligned along a single plane perpendicular to the cylinder axial direction. As will be described later, this top surface 22 is the surface that becomes the joint surface with the synthetic resin outer member 3, and forms a plane perpendicular to the cylinder axial direction and therefore is a plane parallel to the lower surface of the lower deck 11.

[0033] Next, the synthetic resin outer member 3 is not a member that supports the load or reaction force accompanying the combustion and explosion of the internal combustion engine, but mainly constitutes a water jacket through which cooling water flows between the main block 2 and the upper deck portion that serves as the joint surface with the cylinder head, and each part is integrally formed using an appropriate synthetic resin material. In one embodiment, it is integrally injection molded using a thermoplastic resin, for example, a fiber-reinforced resin made by blending glass fiber with a polyamide resin.

[0034] As shown in Fig. 6 to Fig. 10, the outer member 3 is generally in the shape of a rectangular frame or cylinder. The main parts of the outer member 3 include an upper deck portion 41 which is a joint or boundary surface with the cylinder head, a water jacket wall 42 which surrounds the cylinder wall 13 of the main block 2 and the columnar portion 14 other than the second columnar portion 14B to form a water jacket, a joint flange portion 43 which protrudes from the lower end of the water jacket wall 42 to the inner periphery, a front flange portion 44 and a rear flange portion 45 which are the front end face and the rear end face of the composite cylinder block 1, an oil drop hole forming portion 46 which respectively correspond to the oil drop hole forming portion 31 on the main block 2 side, and a lower side wall portion 47 which covers the periphery of the base portion 12 on the main block 2 side. As described later, the outer member 3 is combined with the main block 2 so as to cover the main block 2 while accommodating the cylinder wall 13 of the main block 2 on the inner periphery side of the water jacket wall 42.

[0035] The upper deck portion 41 is connected to the upper end of the outer member 3 in a substantially rectangular frame shape, and its upper surface is a flat surface along a plane perpendicular to the cylinder axial direction. The upper deck portion 41 includes left and right side edges 41a, 41b that are linear, a front edge 41c, and a rear edge 41d. The side edges 41a, 41b are connected to the upper part of the water jacket component wall 42 located on the inside via several ribs 41e that extend in the width direction. The upper end surface of the water jacket component wall 42 constitutes a part of the upper deck portion 41, and is along a single plane together with the side edges 41a, 41b, the front edge 41c, and the rear edge 41d. The cylinder head (not shown) is mounted on the upper deck portion 41 via a cylinder head gasket (not shown). As a cylinder head gasket, for example, a composite gasket is used in which the portion in contact with the metal main block 2, such as the top surface of the cylinder wall 13, is a metal seal, and the portion in contact with the synthetic resin upper deck portion 41 is a rubber seal.

[0036] The water jacket constituent wall 42 has a shape that generally follows the outer contour of the cylinder wall 13 and the columnar portion 14 (excluding the second columnar portion 14B) of the main block 2 in a plan view, and has a wall surface that is substantially parallel to the cylinder axis direction. More specifically, the water jacket constituent wall 42 is configured by combining a total of eight cylinder facing surfaces 51, three on each of the left and right sides and three on the front and rear ends, which are relatively gently curved and face the outer circumferential surface of the cylinder wall 13 without overlapping with the columnar portion 14, and a total of seven columnar portion facing surfaces 52 that surround the columnar portion 14 other than the second columnar portion 14B. As shown in FIG. 9, when it is necessary to distinguish the eight cylinder facing surfaces 51 individually, they are called the first cylinder facing surface 51A, the second cylinder facing surface 51B, to the eighth cylinder facing surface 51H in the clockwise order from the front end. The seven columnar portion facing surfaces 52 are individually distinguished as a first columnar portion facing surface 52A, a third columnar portion facing surface 52C,..., an eighth columnar portion facing surface 52H, in accordance with the names of the columnar portions 14 inserted therein. Each columnar portion facing surface 52 is located between two adjacent cylinder facing surfaces 51, and has a concave shape as a concave groove surface with a relatively small radius of curvature.

[0037] 1, the position of the cylinder facing surface 51 is set so that an appropriate gap (in other words, a water jacket) of, for example, about several millimeters is formed between the cylinder wall 13 and the cylinder facing surface 51 when the cylinder facing surface 51 is combined with the main block 2. In contrast, the columnar portion facing surface 52 is configured to be an arc surface with a diameter slightly larger than that of each columnar portion 14 so that a relatively small gap is formed between the columnar portion 14 and the outer circumferential surface of each columnar portion 14, and to be generally concentric with each columnar portion 14 when the cylinder facing surface 51 is combined with the main block 2. More specifically, the third columnar portion facing surface 52C to the sixth columnar portion 14F corresponding to the third columnar portion 14C to the sixth columnar portion 14F each form a cylindrical surface with a substantially semicircular cross section. The seventh columnar portion facing surface 52G and the eighth columnar portion facing surface 52H corresponding to the seventh columnar portion 14G and the eighth columnar portion 14H are located at positions corresponding to the corners of the ends of the continuous water jacket, and therefore form cylindrical surfaces with a cross section of about 3 / 4 of a circle, which is larger than a semicircle. In other words, about 3 / 4 of the circumference of the seventh columnar portion 14G and the eighth columnar portion facing surface 52H is surrounded by the seventh columnar portion facing surface 52G and the eighth columnar portion facing surface 52H. The first columnar portion facing surface 52A corresponding to the first columnar portion 14A has a cross section that follows the outline of the character "8" so that a small gap remains all around, corresponding to the first columnar portion 14A that has a cross section shaped like the character "8". As a result, as shown in FIG. 1, the first columnar portion 14A fits into the first columnar portion facing surface 52A with a small gap remaining all around.

[0038] The second columnar portion 14B does not have a corresponding groove (columnar portion facing surface) in the water jacket constituent wall 42. The second columnar portion insertion hole 53 is formed in a pipe shape extending in the cylinder axial direction on the outside of the water jacket constituent wall 42 (specifically, the first cylinder facing surface 51A to the eighth cylinder facing surface 51H) for the second columnar portion 14B so as to be independent from the water jacket (see Figs. 6 and 10). The second columnar portion insertion hole 53 has a cross-sectional shape that follows the outline of the figure "8" so that a small gap remains around the entire circumference in correspondence with the second columnar portion 14B having an "8"-shaped cross section. The second columnar portion insertion hole 53 having a cross-sectional shape that follows the outline of the figure "8" opens at the upper end on the upper surface of the upper deck portion 41 and extends downward from there. As a result, as shown in Figs. 1 and 2, the second columnar section 14B fits into the second columnar section insertion hole 53 with a slight gap remaining all around.

[0039] The joint flange portion 43, which protrudes from the lower end of the water jacket wall 42 toward the inner periphery, is formed along a plane perpendicular to the cylinder axial direction together with the lower end surface of the water jacket wall 42, and constitutes the outer member side joint surface 57. This outer member side joint surface 57 is basically shaped to correspond to the area of ​​the top surface 22 of the base portion 12 of the main block 2. That is, the joint flange portion 43 protrudes like an eave so as to follow the contour of the periphery of the three cylinder walls 13 connected in series on the top surface 22 of the base portion 12, and has seven openings 54 corresponding to the seven columnar portions 14 except the second columnar portion 14B, and the outer member side joint surface 57 is continuously formed on the lower surfaces of these openings. The six openings 54 for the third columnar portion 14C to the eighth columnar portion 14H are circular, and the opening 54 for the first columnar portion 14A is approximately shaped like the letter "8" similar to the first columnar portion facing surface 52A. The outer opening edge of each opening 54 is continuous with the corresponding columnar portion facing surface 52 in the cylinder axial direction without any step.

[0040] 7, 8 and 10, a welding rib 56 is formed on the outer member side joining surface 57, including the lower surface of the water jacket constituent wall 42 and the lower surface of the joining flange portion 43, so as to heat-weld the synthetic resin material and protrude downward in a bead shape of a certain width from the outer member side joining surface 57. The welding rib 56 has a main welding rib 56a that is continuous around the entire circumference so as to pass around the outsides of the three cylinder walls 13 and the seven columnar portions 14, similar to the contour of the water jacket constituent wall 42, and a columnar portion welding rib 56b that is in the shape of an arc and that individually fits along the inner portions (portions that enter between the cylinders) of the seven openings 54, and the columnar portion welding rib 56b is continuous with the main welding rib 56a.

[0041] 10 and 8 show the welding ribs 56 on the outer member 3 before welding. When the outer member 3 is joined to the main block 2 through the welding process, the welding ribs 56 are heated and melted, reducing their height (amount of protrusion) until only a small portion remains.

[0042] The oil drop hole forming portion 46 of the outer member 3 is provided at three locations on the outer member 3 so as to correspond to the oil drop hole forming portion 31 on the main block 2 side. Each oil drop hole forming portion 46 protrudes downward from the upper deck portion 41 in a duct shape, and an oil drop hole upper half portion 58 extending in the cylinder axial direction is formed on the inner peripheral side. This oil drop hole upper half portion 58 is continuous with the oil drop hole lower half portion 32 on the main block 2 side to form an oil drop hole extending from the cylinder head to the crankcase. The upper end of the oil drop hole upper half portion 58 opens between the side edge portions 41a, 41b of the upper deck portion 41 and the water jacket component wall 42. The lower end of the oil drop hole upper half portion 58 opens in an elongated shape along the cylinder row direction on the same plane as the joint flange portion 43 and the lower surface of the water jacket component wall 42, as shown in Figures 7 and 10. In other words, the lower end surface of the oil drop hole forming portion 46 forms part of the outer member side joint surface 57, and the lower ends of the oil drop hole upper halves 58 open into this outer member side joint surface 57. Also, a welding rib 56 (welding rib 56c for oil drop hole) similar to that described above is formed on the outer member side joint surface 57 so as to surround the periphery of each oil drop hole upper halves 58.

[0043] The front flange portion 44 has an upper end portion continuous with the front edge portion 41c of the upper deck portion 41, and forms a flange surface 44a (see FIG. 6) having relatively high rigidity. Similarly, the rear flange portion 45 has an upper end portion continuous with the rear edge portion 41d of the upper deck portion 41, and forms a flange surface 45a (see FIG. 7) having relatively high rigidity. The flange surfaces 44a, 45a are aligned along a plane perpendicular to the cylinder row direction.

[0044] The lower sidewall portion 47 extends downward in the cylinder axial direction from a position on the outer periphery of the outer member joint surface 57 so as to cover the periphery of the base portion 12 on the main block 2 side. The lower end of the lower sidewall portion 47 is configured to reach near the upper surface of the upper deck portion 41 when combined with the main block 2. Furthermore, the lower sidewall portion 47 is cut out at the oil drop hole forming portion 46 to avoid interference with the oil drop hole forming portion 31 on the main block 2 side.

[0045] A cooling water inlet 59 (see FIG. 6) extending from the outer surface of the outer member 3 to the water jacket is provided on the eighth cylinder opposing surface 51H on the side of the #1 cylinder.

[0046] Next, the joining of the main block 2 and the outer member 3 and the composite cylinder block 1 finally constructed by this joining will be described.

[0047] As described above, the metallic main block 2 and the synthetic resin outer member 3 are manufactured separately and then joined using a heat welding technique (a type of hot plate welding). The joining is performed between the top surface 22 of the base 12 and the outer member side joining surface 57. In the joining process, a heater is disposed on the underside of the lower deck 11 of the metallic main block 2, and the base 12 is heated from below while the main block 2 and the outer member 3 are separated from each other. The heater is, for example, in a plate-like configuration with four rectangular openings through which the main bearings 15 pass, and is provided in an area that covers at least the projection surface of the base 12 and is disposed so as to be substantially in close contact with the underside of the lower deck 11. When the temperature near the top surface 22 of the base portion 12, which is the joint surface on the main block 2 side, rises to an appropriate temperature (for example, about 200 to 300°C) at which the welding rib 56 of the synthetic resin outer member 3 can melt and soften, the outer member side joint surface 57 is brought into close contact with the top surface 22 of the base portion 12, and the outer member 3 is pressed toward the main block 2. This melts the welding rib 56, and the main block 2 and the outer member 3 are joined together. Therefore, the welding rib 56 essentially becomes a seal line between them. In order to increase the joining strength, an appropriate primer treatment may be applied in advance to the top surface 22 of the base portion 12, which is the joint surface, as necessary.

[0048] When they are joined together, a water jacket serving as a flow path for cooling water is formed between the cylinder wall 13 of the main block 2 and the water jacket forming wall 42 of the outer member 3. This water jacket is sealed by the joining between the top surface 22 of the base portion 12 provided so as to surround the periphery of the cylinder wall 13 and the joining surface 57 of the outer member side. That is, the water jacket is sealed at the welding rib 56 serving as the seal line shown in FIG. 10. Note that, when the welding rib 56 is welded, the upper end surface of the cylinder wall 13 of the main block 2 and the upper surface of the upper deck portion 41 of the outer member 3 are aligned on approximately the same plane. Note that, considering that the seal between the upper deck portion 41 of the outer member 3 and the cylinder head is a rubber seal, the upper surface of the upper deck portion 41 may be slightly lower than the upper end surface of the cylinder wall 13 of the main block 2.

[0049] All of the other seven columnar portions 14 except for the second columnar portion 14B are inside the water jacket, and cooling water surrounds the outer circumferential surfaces of the columnar portions 14. A seal line consisting of the welding rib 56 passes outside the seven columnar portions 14, that is, outside the opening 54 (on the water jacket constituent wall 42 side), and seals the water jacket in a manner including the seven columnar portions 14. Therefore, as shown in FIG. 11, for example, a relatively narrow water jacket exists between the outer circumferential surfaces of the columnar portions 14 and the water jacket constituent wall 42 (columnar portion opposing surface 52).

[0050] In contrast, the second columnar section 14B is housed in the second columnar section insertion hole 53 of the outer member 3 and is isolated from the water jacket. In other words, the second columnar section 14B is surrounded by a wall around the second columnar section insertion hole 53 made of synthetic resin and does not come into contact with the cooling water. A small gap that serves as an air layer exists between the inner wall surface of the second columnar section insertion hole 53 and the outer peripheral surface of the second columnar section 14B.

[0051] The cylinder head (not shown) is placed on the upper surface of the upper deck portion 41 and fixed via cylinder head bolts. The cylinder head bolts are screwed into the bolt holes 24 of the columnar portions 14. The columnar portions 14, which serve as bolt bosses, each continue in a straight line along the cylinder axial direction up to the base portion 12, and linearly transmit the load along the bolt axial direction to the base portion 12. The base portion 12 is thick and solidly constructed, and reliably supports the load acting from the cylinder head. Similarly, the main bearing portion 15 is integrated with the solid base portion 12, and can reliably support the crankshaft.

[0052] As shown in Fig. 1 and Fig. 11, the oil drop hole forming portion 31 of the main block 2 and the oil drop hole forming portion 46 of the outer member 3 are joined by butting against each other. As with the water jacket, the welding rib 56 (56c) provided on the outer member 3 melts and softens, and is joined to the joining surface (top surface 22) on the main block 2 side. As a result, the oil drop hole lower half 32 and the oil drop hole upper half 58 are connected as a single passage, forming the oil drop hole. The upper end of the oil drop hole is further connected to the oil drop hole on the cylinder head side.

[0053] In this manner, the composite cylinder block 1 of the above embodiment is constructed so that the metal main block 2 that receives the load and reaction force has a minimum volume, and many parts such as the water jacket component wall 42 are made of synthetic resin as the outer member 3, thereby achieving a significant weight reduction.

[0054] As described above, the cylinder block 1 of the embodiment includes a metal main block 2 and a resin outer member 3 welded to the main block 2. The main block 2 includes a cylinder wall 13 that defines a cylinder bore 16, and a columnar portion 14 formed at a position spaced apart from the cylinder wall 13. The outer member 3 includes a water jacket component wall 42 that defines a water jacket between the main block 2 and the cylinder wall 13, and a second columnar portion insertion hole 53. The second columnar portion 14B is accommodated in the second columnar portion insertion hole 53 in the outer member 3 in a state isolated from the water jacket and with a predetermined gap between the second columnar portion insertion hole 53 in the outer member 3 and the second columnar portion insertion hole 53 in the outer member 3 over the entire circumference, and reaches the cylinder head.

[0055] Therefore, when the main block 2 is heated to weld the outer member 3, the thermally expanded second columnar portion 14B does not interfere with the second columnar portion insertion hole 53 in the outer member 3, so that the outer member 3 can be easily positioned in the desired position of the main block 2.

[0056] After the outer member 3 is welded to the main block 2, the gap between the inner wall surface of the second columnar portion insertion hole 53 and the outer peripheral surface of the second columnar portion 14B forms an air layer (thermal insulation layer), so that the second columnar portion 14B and the oil in the oil passage 26 are less likely to be cooled by the cooling water during engine warm-up (internal combustion engine warm-up), and overall warm-up performance can be improved.

[0057] Furthermore, pressure from the oil acts on the oil passages 25 and 26. However, the oil passage 25 is formed in the first columnar section 14A made of metal. The oil passage 26 is formed in the second columnar section 14B made of metal. Therefore, the cylinder block 1 can ensure pressure resistance.

[0058] The second columnar portion 14B is integral with a main cylindrical portion 14Ba as the main columnar portion into which the cylinder head bolts for fixing the cylinder head are screwed, and a secondary cylindrical portion 14Bb as a secondary columnar portion having oil passages 26 therein that supply oil pressurized by the oil pump to the cylinder head.

[0059] Therefore, deformation of the cylinder block 1 during casting can be suppressed.

[0060] The second columnar section 14B has a pair of grooves 14Bc on the outer circumferential surface between the main cylindrical section 14Ba and the secondary cylindrical section 14Bb. By having the pair of grooves 14Bc, the second columnar section 14B is more hollowed out than if the second columnar section 14B does not have the pair of grooves 14Bc and the outer shape of the cross section is an oval shape.

[0061] Therefore, the cylinder block 1 can be made lighter by providing the second columnar section 14B with the pair of recessed grooves 14Bc.

[0062] Although one embodiment of the present invention has been described above in detail, the present invention is not limited to the above embodiment and various modifications are possible. For example, the second columnar portion 14B in the above embodiment is formed with at least the bolt holes 24, but the second columnar portion 14B may not have the bolt holes 24. That is, the second columnar portion 14B may be formed with only an oil passage for supplying oil pressurized by the oil pump to the cylinder head. In other words, the second columnar portion 14B may be formed with only something like the above-mentioned secondary cylindrical portion 14Ab.

[0063] In the above embodiment, only the second columnar portion 14B of the columnar portions 14 is housed in the outer member 3 isolated from the water jacket, but the cylinder block 1 may be configured so that all the columnar portions 14 are housed in the outer member 3 isolated from the water jacket. In this case, the cylinder block may be configured so that all the columnar portions 14 are housed in the outer member 3 isolated from the water jacket with a predetermined gap between them all around the circumference, and reach the cylinder head.

Claims

1. The rotor includes a metal main block and a resin outer member welded to the main block. The main block has a cylinder wall that defines a cylinder bore, and a columnar portion that is formed at a position spaced from the cylinder wall, The outer member forms a water jacket between itself and the cylinder wall, The columnar portion has a bolt hole or an oil passage therein, is housed within the outer member isolated from the water jacket with a specified gap between it and the outer member, and extends to the cylinder head to form a composite cylinder block.

2. 2. The composite cylinder block according to claim 1, wherein the pillar portion functions as a bolt boss into which a cylinder head bolt for fixing the cylinder head is screwed.

3. 3. The composite cylinder block according to claim 1, wherein the columnar portion has an oil passage therein for supplying pressurized oil to the cylinder head.

4. 2. The composite cylinder block according to claim 1, wherein the pillar-shaped portion is integral with a main pillar-shaped portion serving as a bolt boss into which a cylinder head bolt for fixing the cylinder head is screwed, and a sub-pillar portion having an oil passage therein for supplying pressurized oil to the cylinder head.

5. 5. The composite cylinder block according to claim 4, wherein said columnar portion has a pair of grooves on an outer circumferential surface between said main columnar portion and said sub columnar portion.

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