Composite cylinder block

Abstract

To consider cooling of each part of a metallic main block 2.SOLUTION: A cylinder block 1 has a metallic main block 2, and a resinous outer member 3 welded to the main block 2. The main block 2 has a cylinder wall 13 configuring a cylinder bore 16, and a columnar portion 14 formed at a position separated from the cylinder wall 13. The outer member 3 configures a water jacket between the outer member 3 and the cylinder wall 13. The columnar portion 14 is located in the water jacket and reaches a cylinder head.SELECTED DRAWING: Figure 1

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 a metal block member and a metal protrusion in addition to a cylinder liner and a resin block.

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

[0005] 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. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2020-112147 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the engine block of Patent Document 1 does not disclose anything about cooling the protrusions located outside the water jacket.

[0008] That is, when an engine block is constructed from metal parts and resin parts, there is room for further improvement in terms of cooling the metal parts. [Means for solving the problem]

[0009] 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 defining a cylinder bore and a pillar-shaped portion formed at a position spaced apart from the cylinder wall. The outer member defines a water jacket between itself and the cylinder wall, and the pillar-shaped portion is located within the water jacket and extends to the cylinder head. At the same time, it has an oil passage inside that supplies pressurized oil to the cylinder head. It is characterized by the following. [Effects of the Invention]

[0010] The composite cylinder block of the present invention can suppress a temperature rise in the columnar portion. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view of a composite cylinder block according to an embodiment of the present invention. [Figure 2] FIG. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] Plan view of the main block. [Figure 6] FIG. [Figure 7] FIG. 4 is a perspective view of the outer member in a state where it is turned upside down. [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 INVENTION

[0012] An embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[0013] First, the overall structure of a composite cylinder block 1 according to one embodiment will be described. The composite cylinder block 1 is composed of two members: a metal main block 2 and a synthetic resin outer member 3. 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 outer member 3 are manufactured separately and then welded together using a heat welding technique described below.

[0014] The illustrated example is a cylinder block 1 for an in-line three-cylinder engine. For ease of explanation, as indicated by the designations "#1" and so on in FIG. 1, the cylinders will be referred to as #1, #2, and #3, starting from the front right side of FIG. 1. The direction parallel to the line through which the centers of these three cylinders are aligned will be referred to as the "cylinder row direction," the direction parallel to the central axis of each cylinder will be referred to as the "cylinder axis direction," and the direction perpendicular to the cylinder row direction will be referred to as the "cylinder width direction." Terms such as "top," "upper," "lower," and "belower" will be used to refer to typical directions of top dead center and bottom dead center. Note that the present invention is not limited to in-line three-cylinder engines. Furthermore, the "front" of the cylinder block 1 refers to the #1 cylinder side in the cylinder row direction, and the "rear" refers to the #3 cylinder side.

[0015] The metal main block 2 integrates components that support the loads and reaction forces associated with combustion and explosion in an internal combustion engine. Each component is integrally cast using an appropriate metal material. In a preferred embodiment, the block is integrally cast using an aluminum alloy by die-casting. As shown in FIGS. 4 and 5 , the main block 2 includes a plate-shaped lower deck 11 extending along a plane perpendicular to the cylinder axis, a base 12 extending upward from the upper surface of the lower deck 11, three cylindrical cylinder walls 13 extending upward from the base 12, a total of eight columnar portions 14 also extending upward from the base 12, and four main bearing portions 15 provided on the underside of the lower deck 11. Each cylinder wall 13 defines a cylinder bore 16, which extends through the base 12 to the underside of the lower deck 11.

[0016] The lower deck 11 extends approximately symmetrically 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-shaped lower deck 11 has an appropriate thickness to ensure the necessary rigidity. The cylinder bores 16 terminate at the lower surface of the lower deck 11. In other words, the cylinder walls 13 do not protrude below the lower deck 11. When the internal combustion engine is finally assembled, crankcase components (e.g., an oil pan, not shown) are attached to the lower surface of the lower deck 11.

[0017] The main bearings 15 are provided at four locations in the cylinder row direction, at both the front and rear ends and between the cylinders, to rotatably support the crankshaft (not shown). Each main bearing 15 is formed as a relatively thick rectangular plate that protrudes downward from the underside of the lower deck 11, and each main bearing 15 has a semicircular bearing recess 15a in the center of its underside. Bearing caps (not shown) are ultimately attached to these main bearings 15, and the crankshaft journals are rotatably supported via bearing metals (not shown). The underside of the lower deck 11, excluding the main bearings 15, is flat along a plane perpendicular to the cylinder axial direction.

[0018] The cylinder walls 13 are cylindrical and have 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 into the inner peripheral surface of the cylinder bore 16, or a wear-resistant metal is thermally sprayed onto the inner peripheral surface.

[0019] The base portion 12 has side surfaces 21 that rise substantially perpendicularly from the upper surface of the lower deck 11, and a top surface 22 that is 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 at a substantially perpendicular angle (in other words, along the cylinder axial direction).

[0020] The pillar-shaped portions 14 are provided at eight locations, including the front and rear ends of the cylinder row and between the cylinders, so that the three cylinder walls 13 surround the continuous cylinder row. Hereinafter, when it is necessary to distinguish between them, they will be referred to as 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, starting from the #1 cylinder side, as shown in FIG. 4 . When no distinction is necessary, they will be collectively referred to as pillar-shaped portions 14. Each pillar-shaped portion 14 is independent and separate from the cylinder walls 13. These pillar-shaped portions 14 function as bolt bosses onto which cylinder head bolts (not shown) are threaded for fixing a cylinder head (not shown) disposed on the cylinder block 1.

[0021] The six columnar sections 14 excluding the first columnar section 14A and the second columnar section 14B, i.e., 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 threaded is formed at the center of the upper end. Basically, the third columnar section 14C to the eighth columnar section 14H have the same diameter. Here, in the illustrated example, because the main block 2 is cast by die-casting, a so-called draft is provided as necessary on the surface of each section along the cylinder axial direction. 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.

[0022] Unlike the third to eighth columnar sections 14C to 14H, the first columnar section 14A has a shape resembling two parallel cylinders joined at a portion of their outer peripheries. In other words, in a plan view and a cross-sectional view perpendicular to the cylinder axis direction, as shown in FIG. 5, the first columnar section 14A has an "8" shape. Specifically, a main columnar section 14Aa having a diameter similar to that of the third to eighth columnar sections 14C to 14H is integrated with a sub-columnar section 14Ab having a smaller diameter. Like the third to eighth columnar sections 14C to 14H, the main columnar section 14Aa functions as a bolt boss for a cylinder head bolt and has a bolt hole 24 at the center of its upper end. This main columnar section 14Aa is located symmetrically to the fourth columnar section 14D across the center of the #1 cylinder, i.e., where a total of eight cylinder head bolts are evenly spaced. The sub-cylindrical portion 14Ab is located diagonally outside the main cylindrical portion 14Aa, that is, on the opposite side from the cylinder wall 13 of the #1 cylinder. An oil passage 25 is formed in the center of this 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 pipe that forms the oil passage 25, which has 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 pipe for the oil passage 25, at parts of their circumferential surfaces, with a pair of recessed grooves 14Ac remaining on the outer circumferential surface between them.

[0023] The second columnar portion 14B is similar to the first columnar portion 14A and has a shape resembling two parallel cylinders joined at a portion of their outer peripheries. In other words, in a plan view and a cross-sectional view perpendicular to the cylinder axis direction, as shown in FIG. 5, it has an "8" shape. Specifically, a main columnar portion 14Ba, which has a smaller diameter than the third to eighth columnar portions 14C to 14H, is integrated with a sub-columnar portion 14Bb, which has a slightly smaller diameter than the main columnar portion 14Ba. Like the third to eighth columnar portions 14C to 14H, the main columnar portion 14Ba functions as a bolt boss for the cylinder head bolts and has a bolt hole 24 at the center of its upper end. This main columnar portion 14Ba is located symmetrically to the third columnar portion 14C across the center of the #1 cylinder, i.e., where a total of eight cylinder head bolts are evenly spaced. The sub-cylindrical portion 14Bb is located in front of and inward of the main cylindrical portion 14Ba in the width direction, i.e., adjacent to the main cylindrical portion 14Ba on an arc centered at the center of the #1 cylinder. Similar to the sub-cylindrical portion 14Ab of the first columnar portion 14A, an oil passage 26 is formed at the center of this sub-cylindrical portion 14Bb along the cylinder axial direction to supply oil pressurized by an oil pump (not shown) to the cylinder head. In other words, the sub-cylindrical portion 14Bb corresponds to a pipe constituting the oil passage 26, which has a circular cross section. Thus, the second columnar portion 14B is formed by connecting the main cylindrical portion 14Ba, which serves as the bolt boss portion, and the sub-cylindrical portion 14Bb, which serves as the pipe for the oil passage 26, at portions of their circumferential surfaces, with a pair of recessed grooves 14Bc remaining on the outer circumferential surface between them.

[0024] In the illustrated example, the second columnar section 14B is configured such that the lower portion thereof 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 peripheral surface of the second columnar section 14B having an "8"-shaped cross section, the inner portion (the portion facing the cylinder wall 13) rises up from the top surface 22 of the base section 12, whereas the outer portion (the portion opposite the cylinder wall 13) extends below the top surface 22 and continues to the lower deck 11.

[0025] 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 each communicate with a sub-oil gallery (not shown) extending in the width direction of the main block 2 and formed near the front end of the lower deck 11. This sub-oil gallery along the width direction communicates with a main oil gallery 27 (see FIGS. 11 and 4) formed on the lower side of the row of cylinder walls 13 and extending in the cylinder row direction. High-pressure oil (lubricating oil) pressurized by an oil pump (not shown) is supplied to the main oil gallery 27. A portion of this high-pressure oil is supplied to the cylinder head side via two oil passages 25 and 26. As shown in FIG. 11, a portion of the high-pressure oil is also supplied to the bearing recess 15a via an oil passage 28 passing through the main bearing portion 15.

[0026] 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 of them. Essentially, 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.

[0027] In other words, as shown in Fig. 5, the top surface 22 exists with a substantially constant width (see 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 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 of the other columnar portions 14, following the "8"-shaped cross section of the first columnar portion 14A. In addition, a top surface 22 with a relatively narrow width also exists between each columnar portion 14 except for the second columnar portion 14B and the adjacent cylinder wall 13.

[0028] As for the second columnar portion 14B, both the main columnar portion 14Ba and the sub columnar portion 14Bb have smaller diameters than the other columnar portions 14, and so a top surface 22 having a width similar to the width (see D1 in FIG. 5) of the portion other than the portion adjacent to the other columnar portions 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.

[0029] Furthermore, the base portion 12 has three oil drop hole formation portions 31, each of which is rectangular in plan view. The first oil drop hole formation portion 31A is located between the #1 and #2 cylinders and is outside the third columnar portion 14C. The second oil drop hole formation portion 31B is located between the #2 and #3 cylinders and is outside the fifth columnar portion 14E. The third oil drop hole formation portion 31C is located on the opposite side of the cylinder row from the two oil drop hole formation portions 31A and 31B, between the fourth columnar portion 14D and the sixth columnar portion 14F, i.e., to the side of the #2 cylinder. Each of these oil drop hole formation portions 31 has a lower oil drop hole half 32 extending in the cylinder axial direction formed in its center. As described below, this lower oil drop hole half 32 forms a part of the oil drop hole that returns oil used in the cylinder head to the crankcase by gravity. 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 Figure 5, but on the underside of the lower deck 11, which is the final oil outlet, it is narrowed to a circular hole as shown in Figure 3.

[0030] 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.

[0031] The entire 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 along a single plane perpendicular to the cylinder axial direction. As will be described later, this top surface 22 is the surface that will be joined to the synthetic resin outer member 3, and forms a plane perpendicular to the cylinder axial direction, and therefore is a plane parallel to the underside of the lower deck 11.

[0032] Next, the synthetic resin outer member 3 is not a component that supports the load or reaction force associated with combustion and explosion in the internal combustion engine, but mainly constitutes a water jacket through which cooling water flows between it and the main block 2, and also constitutes the upper deck portion that is the joint surface with the cylinder head, and is integrally formed in each part 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 polyamide resin.

[0033] 6 to 10, the outer member 3 has a generally rectangular frame or cylindrical shape overall. The outer member 3 primarily includes an upper deck portion 41 that serves as a joint or boundary surface with the cylinder head, a water jacket-constituting wall 42 that surrounds the cylinder wall 13 of the main block 2 and the columnar portions 14 other than the second columnar portion 14B to form a water jacket, a joint flange portion 43 that extends inward from the lower end of the water jacket-constituting wall 42, a front flange portion 44 and a rear flange portion 45 that form the front and rear end faces of the combined cylinder block 1, oil drop hole-forming portions 46 that correspond to the oil drop hole-forming portions 31 on the main block 2, and a lower side wall portion 47 that surrounds the periphery of the base portion 12 on the main block 2. As described below, the outer member 3 is assembled with the main block 2 by placing the cylinder wall 13 of the main block 2 inside the water jacket-constituting wall 42 and covering the main block 2.

[0034] The upper deck portion 41 extends from the upper end of the outer member 3 in a generally rectangular frame shape, and its upper surface is flat and aligned along a plane perpendicular to the cylinder axial direction. The upper deck portion 41 includes linear left and right side edges 41a, 41b, a front edge 41c, and a rear edge 41d. The side edges 41a, 41b are connected to the upper portion of the water jacket wall 42 located inside via several ribs 41e extending in the width direction. The upper end surface of the water jacket wall 42 forms part of the upper deck portion 41 and is aligned along a single plane together with the side edges 41a, 41b, the front edge 41c, and the rear edge 41d. A cylinder head (not shown) is mounted on the upper deck portion 41 via a cylinder head gasket (not shown). As the cylinder head gasket, for example, a composite gasket is used in which the part that comes into contact with the metal main block 2, such as the top surface of the cylinder wall 13, is a metal seal, and the part that comes into contact with the synthetic resin upper deck part 41 is a rubber seal.

[0035] In a plan view, the water jacket wall 42 has a shape that generally follows the outer contours of the cylinder wall 13 and the columnar portions 14 (excluding the second columnar portion 14B) of the main block 2, and has wall surfaces that are substantially parallel to the cylinder axial direction. More specifically, the water jacket wall 42 is configured by combining a total of eight cylinder-facing surfaces 51, three on each side of the cylinder wall 13 and three on the front and rear ends, that are relatively gently curved and face the outer circumferential surface of the cylinder wall 13 without overlapping with the columnar portions 14, and a total of seven columnar portion-facing surfaces 52 that surround the columnar portions 14 other than the second columnar portion 14B. As shown in FIG. 9 , when it is necessary to individually distinguish the eight cylinder-facing surfaces 51, they are referred to as the first cylinder-facing surface 51A, the second cylinder-facing surface 51B, to the eighth cylinder-facing surface 51H, in 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, to 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.

[0036] 1, the position of the cylinder-opposing surface 51 is set so that, when combined with the main block 2, an appropriate gap (in other words, a water jacket) of, for example, about several millimeters is formed between the cylinder-opposing surface 51 and the cylinder wall 13. In contrast, the columnar-portion-opposing surface 52 forms an arcuate 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-opposing surface 52 and the outer circumferential surface of each columnar portion 14, and is configured to be approximately concentric with each columnar portion 14 when combined with the main block 2. More specifically, the third columnar-portion-opposing surfaces 52C to 52F 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-section facing surfaces 52G and 52H corresponding to the seventh columnar section 14G and the eighth columnar section 14H are located at corners of the continuous water jacket, forming cylindrical surfaces with cross sections measuring approximately three-quarters of a circle, which is larger than a semicircle. In other words, approximately three-quarters of the circumference of the seventh columnar section 14G and the eighth columnar section 14H is surrounded by the seventh columnar-section facing surfaces 52G and 8th columnar-section facing surfaces 52H. The first columnar-section facing surface 52A corresponding to the first columnar section 14A has a cross-sectional shape that follows the outline of the figure "8" so that a small gap remains around the entire circumference, corresponding to the first columnar section 14A whose cross section is shaped like an "8." This allows the first columnar section 14A to fit within the first columnar-section facing surface 52A with a small gap remaining around the entire circumference, as shown in FIG. 1 .

[0037] The second columnar portion 14B does not have a corresponding recessed groove portion (columnar portion-facing surface) in the water jacket constituent wall 42. For the second columnar portion 14B, a second columnar portion insertion hole 53 is formed in the shape of a conduit extending in the cylinder axial direction on the outside of the water jacket constituent wall 42 (more specifically, the first cylinder-facing surface 51A to the eighth cylinder-facing surface 51H) 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, corresponding to the second columnar portion 14B, which has an "8"-shaped cross section. The second columnar portion insertion hole 53, which has a cross-sectional shape that follows the outline of the figure "8," opens at its upper end to the top 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, leaving a small gap all around the circumference.

[0038] The joining flange portion 43, which protrudes inward from the lower end of the water jacket constituent wall 42, is formed along a plane perpendicular to the cylinder axial direction together with the lower end surface of the water jacket constituent wall 42, and constitutes an outer member-side joining surface 57. This outer member-side joining surface 57 basically has a shape corresponding to the area of ​​the top surface 22 of the base portion 12 of the main block 2. That is, the joining flange portion 43 protrudes like an eave so as to follow the contours of the three cylinder walls 13 connected in series on the top surface 22 of the base portion 12, and is provided with seven openings 54 corresponding to the seven columnar portions 14 excluding the second columnar portion 14B, and the outer member-side joining surface 57 is formed continuously 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 generally shaped like an "8," similar to the first columnar portion-facing surface 52A. The outer edge of each opening 54 is continuous with the corresponding columnar portion facing surface 52 in the axial direction of the cylinder without any step.

[0039] 7, 8, and 10, a bead-like welding rib 56 of a certain width protruding downward from the outer member-side joining surface 57 is formed on the outer member-side joining surface 57, which includes the lower surface of the water jacket constituent wall 42 and the lower surface of the joining flange portion 43, for heat welding of a synthetic resin material. The welding rib 56 includes a main welding rib 56a that is continuous around the entire circumference, passing around the outside of the three cylinder walls 13 and the seven columnar portions 14, similar to the outline of the water jacket constituent wall 42, and arc-shaped columnar portion welding ribs 56b that respectively fit along the inside portions of the seven openings 54 (portions that fit between the cylinders), and the columnar portion welding ribs 56b are continuous with the main welding rib 56a.

[0040] 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) and leaving only a small portion remaining.

[0041] The oil drop hole forming portions 46 of the outer member 3 are provided at three locations on the outer member 3 to correspond to the oil drop hole forming portions 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-like shape, and an upper oil drop hole half portion 58 extending in the cylinder axial direction is formed on the inner periphery. This upper oil drop hole half portion 58 is continuous with the lower oil drop hole 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 ends of the upper oil drop hole half portions 58 open between the side edge portions 41a, 41b of the upper deck portion 41 and the water jacket wall 42. As shown in FIGS. 7 and 10 , the lower ends of the upper oil drop hole half portions 58 open in an elongated shape along the cylinder row direction, on the same plane as the lower surfaces of the joining flange portion 43 and the water jacket wall 42. That is, the lower end surface of the oil drop hole forming portion 46 forms part of the outer member side joining surface 57, and the lower ends of the oil drop hole upper halves 58 open into this outer member side joining surface 57. Then, a welding rib 56 (oil drop hole welding rib 56c) similar to the one described above is formed on the outer member side joining surface 57 so as to surround the periphery of each oil drop hole upper half 58.

[0042] The front flange portion 44 has an upper end that is continuous with the front edge portion 41c of the upper deck portion 41, forming a flange surface 44a (see FIG. 6) with relatively high rigidity. Similarly, the rear flange portion 45 has an upper end that is continuous with the rear edge portion 41d of the upper deck portion 41, forming a flange surface 45a (see FIG. 7) with relatively high rigidity. The flange surfaces 44a, 45a are aligned along a plane perpendicular to the cylinder row direction.

[0043] The lower sidewall 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 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 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.

[0044] 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.

[0045] 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.

[0046] As described above, the metal 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 joining surface 57. In the joining process, a heater is disposed on the underside of the lower deck 11 of the metal main block 2, and the base 12 is heated from below while the main block 2 and the outer member 3 are separated. The heater is, for example, a plate-like configuration with four rectangular openings through which the main bearings 15 pass. The heater is provided in an area that covers at least the projected surface of the base 12 and is disposed so as to be in substantial contact with the underside of the lower deck 11. When the temperature near the top surface 22 of the base portion 12, which serves as the joining surface on the main block 2 side, rises to an appropriate temperature (e.g., 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 joining 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, joining the main block 2 and the outer member 3 together. Therefore, the welding rib 56 essentially serves as a seal line between them. If necessary, to increase the joining strength, the top surface 22 of the base portion 12, which serves as the joining surface, may be treated with a suitable primer in advance.

[0047] When they are joined together, a water jacket, which serves as a cooling water flow path, 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 joint between the top surface 22 of the base portion 12, which is provided to surround the periphery of the cylinder wall 13, and the outer member-side joint surface 57. In other words, the water jacket is sealed at the welding rib 56, which serves 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 a rubber seal is used to form the seal between the upper deck portion 41 of the outer member 3 and the cylinder head, 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.

[0048] All of the other seven columnar portions 14 except for the second columnar portion 14B are located 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 that includes 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).

[0049] 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 coolant. 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.

[0050] The cylinder head (not shown) is placed on the upper surface of the upper deck portion 41 and fixed in place via cylinder head bolts. The cylinder head bolts are threaded 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 all the way to the base portion 12, linearly transmitting the load along the bolt axial direction to the base portion 12. The base portion 12 is thick and sturdy, and reliably supports the load acting from the cylinder head. Similarly, the main bearing portion 15 is integrated with the sturdy base portion 12, enabling it to reliably support the crankshaft.

[0051] 1 and 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 in a butt-together manner. 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, thereby 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.

[0052] In this way, the composite cylinder block 1 of the above embodiment is configured 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.

[0053] As described above, the cylinder block 1 of the above embodiment has a metal main block 2 and a resin outer member 3 welded to the main block 2. The main block 2 has 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. A water jacket is formed between the outer member 3 and the cylinder wall 13. The columnar portions 14, excluding the second columnar portion 14B, are located within the water jacket and extend to the cylinder head.

[0054] Therefore, the water jacket in the cylinder block 1 can suppress a temperature rise in the columnar portion 14 except for the second columnar portion 14B.

[0055] The pillar portion 14 functions as a bolt boss onto which a cylinder head bolt for fixing the cylinder head is screwed.

[0056] Therefore, the cylinder block 1 can suppress temperature rise in the female thread portion of the cylinder head bolt inside the columnar portion 14 excluding the second columnar portion 14B, suppressing a decrease in axial force and improving durability.

[0057] The first columnar portion 14A of the columnar portion 14 has an oil passage 25 therein that supplies oil pressurized by the oil pump to the cylinder head.

[0058] Therefore, in the cylinder block 1, the oil flowing through the oil passage 25 of the first columnar section 14A can be cooled by the cooling water.

[0059] 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.

[0060] Of the columnar portion 14, the first columnar portion 14A and the second columnar portion 14B are integral with main cylindrical portions 14Aa, 14Ba as main columnar portions onto which cylinder head bolts that fix the cylinder head are respectively threaded, and secondary cylindrical portions 14Ab, 14Bb as secondary columnar portions that respectively have oil passages 25, 26 therein that supply oil pressurized by the oil pump to the cylinder head.

[0061] Therefore, deformation of the cylinder block 1 during casting can be suppressed.

[0062] The first columnar section 14A has a pair of recessed grooves 14Ac on the outer circumferential surface between the main cylindrical section 14Aa and the sub-cylindrical section 14Ab.

[0063] Therefore, the cylinder block 1 can increase the surface area of ​​the outer periphery of the first columnar section 14A, and can efficiently cool the first columnar section 14A.

[0064] Furthermore, since the first columnar portion 14A has a pair of groove portions 14Ac and the second columnar portion 14B has a pair of groove portions 14Bc, the cylinder block 1 is lighter than when the first columnar portion 14A and the second columnar portion 14B do not have a pair of groove portions 14Ac, Bc and the cross-sectional outer shapes of the first columnar portion 14A and the second columnar portion 14B are oval.

[0065] Therefore, the cylinder block 1 can be made lighter by having the first columnar section 14A with the pair of recessed grooves 14Ac and the second columnar section 14B with the pair of recessed grooves 14Bc.

[0066] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment and various modifications are possible. For example, although the columnar portion 14 in the above embodiment is formed with at least the bolt holes 24, the columnar portion 14 may not have the bolt holes 24. In other words, the columnar portion may only have an oil passage formed therein for supplying oil pressurized by an oil pump to the cylinder head. In other words, the columnar portion may be formed with only the above-mentioned secondary cylindrical portions 14Ab and 14Bb, for example. [Explanation of symbols]

[0067] 1...Cylinder block 2...Main block 3...Outer member 11...Lower deck 12...Base 13...Cylinder wall 14...Columnar part 14A…1st columnar part 14Aa...Main cylinder section 14Ab... Sub-cylindrical part 14Ac…Concave groove part 14B…Second columnar part 14Ba...Main cylinder section 14Bb...Sub-cylindrical section 14Bc…Concave groove part 14C...Third columnar part 14D…4th columnar part 14E...5th columnar part 14F…6th columnar part 14G…7th columnar part 14H…8th columnar part 15...Main bearing part 15...Bearing recess 16...Cylinder bore 21...Side 22…Top surface 24...Bolt hole 25...Oil passage 26...Oil passage

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 pillar portion formed at a position spaced from the cylinder wall, The outer member forms a water jacket between itself and the cylinder wall, a cylinder head that is connected to the water jacket and has an oil passage therein for supplying pressurized oil to the cylinder head;

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

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

4. 4. The composite cylinder block according to claim 3, wherein the pillar portion has a pair of grooves on the outer circumferential surface between the main pillar portion and the sub pillar portion.

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