Composite cylinder block

Abstract

To ensure pressure resistance of an oil passage formed in a cylinder block.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 first columnar portion 14A and a second columnar portion 14B formed so as to reach a cylinder head. The first columnar portion 14A and the second columnar portion 14B internally have oil passages 25 and 26 supplying pressurized oil to the cylinder head, respectively.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a composite cylinder block of an internal combustion engine configured by combining a metal member and a synthetic resin member.

Background Art

[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 the cylinder liner and the resin block.

[0004] The block member of Patent Document 1 is made of metal and functions as a base for supporting the resin block. The protrusion of 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 this Patent Document 1, damage to the resin block due to heat from the cylinder liner is reduced by a water jacket formed in the resin block.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, the engine block of Patent Document 1 does not disclose anything regarding the oil passage in the engine block.

[0008] That is, when the engine block is composed of metal parts and resin parts, there is room for further improvement in setting the oil passage in the engine block.

Means for Solving the Problems

[0009] The composite cylinder block of the present invention has a metal main block and a resin outer member welded to the main block. The main block has a columnar portion formed to reach the cylinder head, and the columnar portion has an oil passage inside for supplying pressurized oil to the cylinder head.

Effects of the Invention

[0010] In the composite cylinder block of the present invention, since the oil passage is formed inside the metal columnar portion, pressure resistance can be ensured.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Modes for Carrying Out the Invention

[0012] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0013] First, the overall configuration of the 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 a synthetic resin outer member 3. FIGS. 1 to 3 and FIG. 11 show the composite cylinder block 1 in a state where the main block 2 and the outer member 3 are integrated. FIGS. 4 and 5 show the main block 2 alone, and FIGS. 6 to 10 show the outer member 3 alone. The main block 2 and the outer member 3 are each manufactured individually and are welded together using a heat welding technique described later.

[0014] The illustrated example is a cylinder block 1 for an in-line three-cylinder engine. For convenience of explanation, as attached with "♯1" etc. in FIG. 1, from the right front side of FIG. 1 in order, it will be called the ♯1 cylinder, the ♯2 cylinder, and the ♯3 cylinder. And the direction parallel to the straight line on which the centers of these three cylinders are arranged 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 orthogonal to the cylinder row direction will be called the "width direction", respectively. Also, following the general directions of top dead center and bottom dead center, terms such as "up", "above", "down", "below" are used. Note that the present invention is not limited to an in-line three-cylinder engine. Further, the "front" of the cylinder block 1 means the ♯1 cylinder side with respect to the cylinder row direction, and the "rear" means the ♯3 cylinder side.

[0015] The metal main block 2 integrates in one body the parts that support the loads or reaction forces associated with the combustion and explosion of the internal combustion engine, and is integrally cast using an appropriate metal material for each part. In a preferred embodiment, it is integrally cast by die casting using an aluminum alloy. As shown in FIGS. 4 and 5, the main block 2 includes a lower deck 11 having a plate shape along a plane orthogonal to the cylinder axis direction, a pedestal portion 12 rising upward from the upper surface of the lower deck 11, three cylindrical cylinder walls 13 extending further upward from the pedestal portion 12, a total of eight columnar portions 14 rising upward from the pedestal portion 12 as well, 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 penetrate the pedestal portion 12 and extend to the lower surface of the lower deck 11.

[0016] The lower deck 11 expands so as to be substantially symmetric in the width direction around the cylinder bank. The width dimension is relatively large in the portion on the #3 cylinder side and relatively small in the portion on the #1 cylinder side (see FIG. 3). The plate-shaped lower deck 11 has an appropriate thickness so as to have the required rigidity. Note that the cylinder bore 16 terminates at the lower surface of the lower deck 11. That is, the cylinder wall 13 does not protrude below the lower deck 11. In the state finally assembled as an internal combustion engine, a crankcase constituent member (for example, an oil pan) (not shown) is attached to the lower surface of the lower deck 11.

[0017] The main bearing portions 15 are provided at a total of four locations, namely, both front and rear ends in the cylinder row direction and positions between cylinders, in order to rotatably support a crankshaft (not shown). The main bearing portions 15 are each formed to project downward from the lower surface of the lower deck 11 so as to have a relatively thick plate shape of a rectangle, and each has a semi-circular bearing recess 15a at the center of the lower surface. Finally, bearing caps (not shown) are attached to these main bearing portions 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 forms a flat surface along one plane orthogonal to the cylinder axis direction, excluding the main bearing portions 15.

[0018] The cylinder wall 13 has a substantially constant thickness (radial dimension) and is cylindrical. In the illustrated example, three cylindrical cylinder walls 13 form a so-called siamese structure in which they are connected to each other at the portion between cylinders. That is, the bore pitch is shorter than the outer diameter of the cylinder wall 13. Since the main block 2 is formed of an aluminum alloy in the illustrated example, 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 sprayed thereon.

[0019] The pedestal portion 12 has a side surface 21 that rises 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 substantially perpendicularly upward (in other words, along the cylinder axis direction) from the top surface 22 of the pedestal portion 12.

[0020] The columnar portions 14 are provided at a total of eight locations, namely, at both the front and rear ends in the cylinder row direction and at positions between cylinders, so as to surround a cylinder row in which three cylinder walls 13 are in series. Hereinafter, when it is necessary to distinguish each of them, as shown in FIG. 4, starting from the #1 cylinder side in order, they are called the first columnar portion 14A, the second columnar portion 14B, the third columnar portion 14C, the fourth columnar portion 14D, the fifth columnar portion 14E, the sixth columnar portion 14F, the seventh columnar portion 14G, and the eighth columnar portion 14H, and when there is no need for distinction, they are collectively referred to as the columnar portion 14. Each of the columnar portions 14 is independent and separated from the cylinder wall 13. These columnar portions 14 function as bolt boss portions into which cylinder head bolts (not shown) for fixing a cylinder head (not shown) disposed on the cylinder block 1 are respectively screwed.

[0021] Six columnar portions 14 excluding the first columnar portion 14A and the second columnar portion 14B, that is, the third columnar portion 14C to the eighth columnar portion 14H, each form a simple cylindrical shape with a circular cross-section, and bolt holes 24 into which cylinder head bolts are screwed are formed at the centers of the upper end portions. Basically, the diameters of the third columnar portion 14C to the eighth columnar portion 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, so-called draft gradients are given to the surfaces of the respective portions along the cylinder axis direction as required. Therefore, the third columnar portion 14C to the eighth columnar portion 14H, which are cylindrical, strictly speaking, have a tapered shape in which the upper end portion is slightly smaller in diameter.

[0022] Unlike the third to eighth columnar portions 14C to 14H, the first columnar portion 14A has a shape as if two parallel cylinders are joined at a part of the outer peripheral surface. In other words, in a plan view as shown in FIG. 5 and a cross-sectional view orthogonal to the cylinder axis direction, it has a figure-eight shape. Specifically, a main cylinder portion 14Aa having the same diameter as the third to eighth columnar portions 14C to 14H and a sub-cylinder portion 14Ab having a smaller diameter than this are integrated. The main cylinder portion 14Aa is a portion that functions as a bolt boss portion for the cylinder head bolts in the same manner as the third to eighth columnar portions 14C to 14H, and has a bolt hole 24 at the center of the upper end portion. This main cylinder portion 14Aa is provided at a position symmetric with the fourth columnar portion 14D across the cylinder center of the #1 cylinder, that is, at a position where the arrangement of a total of eight cylinder head bolts is uniform. The sub-cylinder portion 14Ab is located on the obliquely outer side of the main cylinder portion 14Aa, that is, on the side opposite to the cylinder wall 13 of the #1 cylinder. An oil passage 25 along the cylinder axis direction for supplying oil pressurized by an oil pump (not shown) to the cylinder head is formed at the center of this sub-cylinder portion 14Ab. In other words, the sub-cylinder portion 14Ab corresponds to a pipe constituting the oil passage 25 having a circular cross-section. As described above, the first columnar portion 14A is formed by connecting the main cylinder portion 14Aa serving as a bolt boss portion and the sub-cylinder portion 14Ab serving as a pipe of the oil passage 25 at a part of the peripheral surface, and a pair of concave groove portions 14Ac remain on the outer peripheral surface between the two.

[0023] The second columnar portion 14B is similar to the first columnar portion 14A and has a shape as if two parallel cylinders are joined at a part of their outer peripheral surfaces. In other words, in a plan view as shown in FIG. 5 and a cross-sectional view orthogonal to the cylinder axis direction, it has a figure-eight shape. Specifically, a main cylindrical portion 14Ba having a smaller diameter than the third to eighth columnar portions 14C to 14H and a sub-cylindrical portion 14Bb having a slightly smaller diameter than the main cylindrical portion 14Ba are integrated. The main cylindrical portion 14Ba is a portion that functions as a bolt boss portion for the cylinder head bolts, similar to the third to eighth columnar portions 14C to 14H, and has a bolt hole 24 at the center of its upper end portion. This main cylindrical portion 14Ba is provided at a position symmetric to the third columnar portion 14C with the cylinder center of the #1 cylinder in between, that is, at a position where the arrangement of a total of eight cylinder head bolts is uniform. The sub-cylindrical portion 14Bb is located in front of the main cylindrical portion 14Ba and inside in the width direction, that is, adjacent to the main cylindrical portion 14Ba on an arc centered on the cylinder center of the #1 cylinder. At the center of this sub-cylindrical portion 14Bb, an oil passage 26 along the cylinder axis direction for supplying oil pressurized by an oil pump (not shown) to the cylinder head is formed, similar to the sub-cylindrical portion 14Ab of the first columnar portion 14A. In other words, the sub-cylindrical portion 14Bb corresponds to a pipe constituting the oil passage 26 having a circular cross-section. Thus, the second columnar portion 14B is formed by connecting the main cylindrical portion 14Ba serving as a bolt boss portion and the sub-cylindrical portion 14Bb serving as a pipe of the oil passage 26 at a part of their peripheral surfaces, and a pair of concave groove portions 14Bc remain on the outer peripheral surface between the two.

[0024] Also, in the illustrated example, while the other columnar portions 14 (the first columnar portion 14A, the third to eighth columnar portions 14C to 14H) protrude from the top surface 22 of the pedestal portion 12 without being continuous with the side surface 21 of the pedestal portion 12, the lower portion of the second columnar portion 14B is configured to be integrated with the side surface 21 of the pedestal portion 12. That is, among the outer peripheral surfaces of the second columnar portion 14B having a figure-eight cross-sectional shape, the inner portion (the portion toward the cylinder wall 13) rises from the top surface 22 of the pedestal portion 12, while the outer portion (the portion on the side opposite to the cylinder wall 13) extends downward from the top surface 22 and is continuous to the lower deck 11.

[0025] The lower end portions of the oil passages 25 passing through the first columnar portion 14A and the lower end portions of the oil passages 26 passing through the second columnar portion 14B communicate with a sub-oil gallery (not shown) extending in the width direction of the main block 2 formed near the front end portion of the lower deck 11, respectively. And this sub-oil gallery along the width direction communicates with a main oil gallery 27 (see FIGS. 11 and 4) extending along the cylinder row direction formed on the lower side of the column of the cylinder wall 13. High-pressure oil (lubricating oil) pressurized from 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 the 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 the oil passage 28 passing through the main bearing portion 15.

[0026] The pedestal portion 12 is formed so as to project outward with a substantially constant width from the outer contour of the three cylinder walls 13 arranged in series, and is also formed so as to project outward with a substantially constant width from the outer contour of the columnar portions 14 excluding the second columnar portion 14B. That is, the shape of the side surface 21 of the pedestal portion 12 is determined so as to surround the outside while following the outer contours of the cylinder wall 13 and the columnar portions 14. Basically, the side surface 21 is a combination of a cylindrical surface concentric with the cylinder wall 13 and a cylindrical surface concentric with the columnar portion 14.

[0027] In other words, as shown in FIG. 5, a top surface 22 exists around the cylinder wall 13 excluding the adjacent portion to the columnar portion 14 with a substantially constant width (see reference numeral D1 in FIG. 5), and a top surface 22 exists around the columnar portion 14 with a relatively narrow substantially constant width (see reference numeral D2 in FIG. 5). Around the first columnar portion 14A, a top surface 22 exists with the same width as around the other columnar portions 14 along the figure-eight cross-sectional shape of the first columnar portion 14A. Also, a top surface 22 exists with a relatively narrow width between each columnar portion 14 excluding the second columnar portion 14B and the adjacent cylinder wall 13.

[0028] Regarding the second columnar portion 14B, since both the main cylindrical portion 14Ba and the sub-cylindrical portion 14Bb have a smaller diameter than the other columnar portions 14, a top surface 22 having a width approximately the same as the width (see D1 in FIG. 5) other than the adjacent portions with the other columnar portions 14 exists between the cylinder wall 13. On the other hand, on the outside of the second columnar portion 14B, there is no top surface 22.

[0029] Furthermore, the pedestal portion 12 is provided with three oil drain hole forming portions 31 having a quadrangular shape in plan view. The first oil drain hole forming portion 31A is located outside the third columnar portion 14C between the #1 cylinder and the #2 cylinder, and the second oil drain hole forming portion 31B is located outside the fifth columnar portion 14E between the #2 cylinder and the #3 cylinder. The third oil drain hole forming portion 31C is on the opposite side of these two oil drain hole forming portions 31A and 31B across the cylinder row, and is between the fourth columnar portion 14D and the sixth columnar portion 14F, that is, on the side of the #2 cylinder. In the central portion of these oil drain hole forming portions 31, oil drain hole lower halves 32 extending in the cylinder axis direction are respectively formed. As will be described later, this oil drain hole lower half 32 constitutes a part of an oil drain hole for returning the oil used on the cylinder head side to the crankcase by its own weight. As shown in the opening shape in FIG. 5, the oil drain hole lower half 32 has a substantially rectangular cross-sectional shape that is elongated in the cylinder row direction, but at the lower surface of the lower deck 11 that is the final oil outlet, as shown in FIG. 3, it is constricted into a circular hole.

[0030] As shown in FIGS. 4 and 5, the oil drain hole forming portion 31 has the same height as around the cylinder wall 13 as a part of the pedestal portion 12, and a part of the top surface 22 of the pedestal portion 12 forming the same plane surrounds the periphery of the oil drain hole lower half 32.

[0031] The top surface 22 of the pedestal portion 12 is along one plane orthogonal to the cylinder axis direction, including the portion surrounding the cylinder wall 13, the portion surrounding the columnar portion 14, and the portion surrounding the lower half portion 32 of the oil drain hole. As will be described later, this top surface 22 is a surface that serves as a joint surface with the synthetic resin outer member 3, forms a plane orthogonal to the cylinder axis direction, and thus is a plane parallel to the lower surface of the lower deck 11.

[0032] Next, the synthetic resin outer member 3 is not a member that supports the load or reaction force associated with the combustion and explosion of the internal combustion engine. Instead, it mainly forms a water jacket through which cooling water flows between the main block 2 and constitutes an upper deck portion that serves as a joint surface with the cylinder head. It is integrally formed with 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 in which glass fibers are blended with a polyamide resin.

[0033] As shown in FIGS. 6 to 10, the outer member 3 generally has a substantially rectangular frame shape or cylindrical shape as a whole. The outer member 3 mainly includes an upper deck portion 41 that serves as a joint surface or boundary surface with the cylinder head, a water jacket forming wall 42 that surrounds the columnar portions 14 other than the cylinder wall 13 and the second columnar portion 14B of the main block 2 to form a water jacket, a joint flange portion 43 that projects inward from the lower end of the water jacket forming wall 42, a front flange portion 44 and a rear flange portion 45 that serve as the front end surface and the rear end surface of the composite cylinder block 1, an oil drain hole forming portion 46 corresponding to the oil drain hole forming portion 31 on the main block 2 side, and a lower side wall portion 47 that covers the periphery of the pedestal portion 12 on the main block 2 side. As will be described later, the outer member 3 is combined with the main block 2 by covering the main block 2 while accommodating the cylinder wall 13 of the main block 2 inside the inner peripheral side of the water jacket forming wall 42.

[0034] The upper deck portion 41 is continuous in a substantially rectangular frame shape at the upper end of the outer member 3, and its upper surface forms a flat surface along one plane orthogonal to the cylinder axis direction. The upper deck portion 41 includes linear left and right side edge portions 41a, 41b, a front edge portion 41c, and a rear edge portion 41d. The side edge portions 41a, 41b are connected to the upper part of the water jacket forming wall 42 located inside via several ribs 41e extending in the width direction. The upper end surface of the water jacket forming wall 42 constitutes a part of the upper deck portion 41 and is along one plane together with the side edge portions 41a, 41b, the front edge portion 41c, and the rear edge portion 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 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.

[0035] In plan view, the water jacket forming wall 42 has a shape generally following the outer contour of the cylinder wall 13 and the columnar portions 14 (excluding the second columnar portion 14B) of the main block 2, and has a wall surface substantially parallel to the cylinder axis direction. More specifically, the water jacket forming wall 42 is composed of a total of eight cylinder facing surfaces 51, three on each of the left and right sides and at both the front and rear ends, which are relatively gently curved and face the outer peripheral surface of the cylinder wall 13 without overlapping the columnar portions 14, and a total of seven columnar portion facing surfaces 52 surrounding the columnar portions 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 designated as the first cylinder facing surface 51A, the second cylinder facing surface 51B... the eighth cylinder facing surface 51H in the clockwise direction from the front end. Regarding the seven columnar portion facing surfaces 52, they are individually distinguished as the first columnar portion facing surface 52A, the third columnar portion facing surface 52C... the eighth columnar portion facing surface 52H according to the name of the columnar portion 14 inserted therein. The columnar portion facing surfaces 52 are each located between two adjacent cylinder facing surfaces 51 and are recessed in the form of a concave groove surface with a relatively small radius of curvature.

[0036] When combined with the main block 2, the cylinder opposing surface 51 is positioned such that, as shown in FIG. 1, an appropriate gap (in other words, a water jacket), for example, on the order of several millimeters, is formed between the cylinder wall 13. On the other hand, the columnar portion opposing surface 52 forms an arc surface with a diameter slightly larger than the diameter of each columnar portion 14 so that a relatively small gap is formed between the columnar portion opposing surface 52 and the outer peripheral surface of each columnar portion 14, and is configured to be substantially concentric with each columnar portion 14 when combined with the main block 2. More specifically, the third columnar portion opposing surface 52C to the sixth columnar portion opposing surface 52F corresponding to the third columnar portion 14C to the sixth columnar portion 14F each form a cylindrical surface with a substantially semi-circular cross-section. The seventh columnar portion opposing surface 52G and the eighth columnar portion opposing surface 52H corresponding to the seventh columnar portion 14G and the eighth columnar portion 14H are located at positions corresponding to the corner portions of the end of the continuous water jacket, and thus form a cylindrical surface with a cross-section of about 3 / 4 of a circle, which is larger than a semi-circle. That is, about 3 / 4 of the circumference of the seventh columnar portion 14G and the eighth columnar portion 14H is surrounded by the seventh columnar portion opposing surface 52G and the eighth columnar portion opposing surface 52H. The first columnar portion opposing surface 52A corresponding to the first columnar portion 14A has a cross-sectional shape along the outer shape of the figure-eight corresponding to the first columnar portion 14A with a figure-eight cross-section, so that a slight gap remains throughout the circumference. As a result, as shown in FIG. 1, the first columnar portion 14A fits into the first columnar portion opposing surface 52A with a slight gap remaining throughout the circumference.

[0037] Regarding the second columnar part 14B, the water jacket constituting wall 42 does not have a corresponding concave groove part (columnar part facing surface). For the second columnar part 14B, a second columnar part insertion hole 53 is formed in a pipe shape extending in the cylinder axis direction outside the water jacket constituting wall 42 (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 part insertion hole 53 has a cross-sectional shape along the outer shape of the "8" so that a slight gap remains all around corresponding to the second columnar part 14B having a cross-sectional shape of "8". The second columnar part insertion hole 53 having a cross-sectional shape along the outer shape of the "8" has an upper end opening to the upper surface of the upper deck part 41 and extends downward therefrom. Thereby, as shown in FIGS. 1 and 2, the second columnar part 14B fits into the second columnar part insertion hole 53 leaving a slight gap all around.

[0038] The joint flange part 43 projecting inward from the lower end of the water jacket constituting wall 42 is formed along a single plane orthogonal to the cylinder axis direction together with the lower end surface of the water jacket constituting wall 42 and constitutes the outer member side joint surface 57. This outer member side joint surface 57 basically has a shape corresponding to the region of the top surface 22 of the pedestal part 12 of the main block 2. That is, the joint flange part 43 projects in a eaves shape along the contour around the three cylinder walls 13 continuously connected in a series on the top surface 22 of the pedestal part 12, and has seven opening parts 54 corresponding to the seven columnar parts 14 excluding the second columnar part 14B. The outer member side joint surface 57 is continuously configured on their lower surfaces. The six opening parts 54 for the third columnar part 14C to the eighth columnar part 14H are circular, and the opening part 54 for the first columnar part 14A has a substantially "8" shape similar to the first columnar part facing surface 52A. The outer opening edges of each opening part 54 are continuous in the cylinder axis direction without a step with the corresponding columnar part facing surface 52.

[0039] Here, on the outer member side joint surface 57 including the lower surface of the water jacket constituting wall 42 and the lower surface of the joint flange portion 43, as shown in FIGS. 7, 8, and 10, for heat welding of the synthetic resin material, welding ribs 56 protruding downward in a bead shape with a certain width are formed from the outer member side joint surface 57. The welding rib 56 has a main welding rib 56a that is continuous over the entire circumference so as to pass outside the three cylinder walls 13 and the seven columnar portions 14 in the same manner as the contour of the water jacket constituting wall 42, and arc-shaped welding ribs 56b for columnar portions along the inner portions (portions entering between the cylinders) of the seven openings 54, and the welding ribs 56b for columnar portions are continuous with the main welding rib 56a.

[0040] Note that FIGS. 10 and 8 show the welding ribs 56 on the outer member 3 before the welding process. In the state where the outer member 3 is joined to the main block 2 through the welding process, the welding ribs 56 are heated and melted, so that their height (projection amount) decreases and only a slight amount remains.

[0041] The oil drain 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 drain hole forming portions 31 on the main block 2 side, respectively. Each oil drain hole forming portion 46 protrudes downward in a pipe shape from the upper deck portion 41, and an upper half portion 58 of the oil drain hole extending in the cylinder axis direction is formed on the inner peripheral side. The upper half portion 58 of this oil drain hole forms an oil drain hole leading from the cylinder head to the crankcase by being continuous with the lower half portion 32 of the oil drain hole on the main block 2 side. Note that the upper end of the upper half portion 58 of the oil drain hole opens between the side edge portions 41a and 41b of the upper deck portion 41 and the water jacket forming wall 42. The lower end of the upper half portion 58 of the oil drain hole opens in an elongated shape along the cylinder row direction in the same plane as the lower surfaces of the joint flange portion 43 and the water jacket forming wall 42, as shown in FIGS. 7 and 10. That is, the lower end surface of the oil drain hole forming portion 46 constitutes a part of the outer member side joint surface 57, and the lower end of the upper half portion 58 of the oil drain hole opens in the outer member side joint surface 57. Then, welding ribs 56 (welding ribs 56c for oil drain holes) similar to those described above are formed on the outer member side joint surface 57 so as to surround the periphery of each upper half portion 58 of the oil drain hole.

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

[0043] The lower side wall portion 47 extends downward along the cylinder axis direction from a position on the outer peripheral side of the outer member side joint surface 57 so as to cover the periphery of the pedestal portion 12 on the main block 2 side. The lower end of the lower side wall portion 47 is configured to reach near the upper surface of the upper deck portion 41 when combined with the main block 2. Further, at the location of the oil drain hole forming portion 46, the lower side wall portion 47 is notched to avoid interference with the oil drain hole forming portion 31 on the main block 2 side.

[0044] In addition, a cooling water inlet 59 (see FIG. 6) leading from the outer surface of the outer member 3 to the water jacket is provided in the eighth cylinder facing 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 formed by this joining will be described.

[0046] As described above, the metal main block 2 and the synthetic resin outer member 3 are each manufactured 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 pedestal portion 12 and the outer member side joining surface 57. In the joining process, a heater for heating is disposed on the lower surface of the lower deck 11 of the metal main block 2, and the pedestal portion 12 is heated from below while the main block 2 and the outer member 3 are separated. The heater has, for example, a plate-like configuration with four rectangular openings through which the main bearing portions 15 respectively pass, and is provided in a range at least covering the projection surface of the pedestal portion 12 and is arranged so as to be substantially in close contact with the lower surface of the lower deck 11. By heating using this heater, when the temperature near the top surface 22 of the pedestal portion 12, which becomes the joining surface on the main block 2 side, rises to an appropriate temperature (for example, about 200 to 300 °C) at which the welding ribs 56 of the synthetic resin outer member 3 can be melted and softened, the outer member side joining surface 57 is brought into close contact with the top surface 22 of the pedestal portion 12, and the outer member 3 is pressed toward the main block 2. Thereby, the welding ribs 56 are melted and the main block 2 and the outer member 3 are integrally joined. Therefore, the welding ribs 56 become a substantial sealing line between the two. In addition, in order to increase the joining force, if necessary, an appropriate primer treatment may be performed in advance on the top surface 22 of the pedestal portion 12 that becomes the joining surface.

[0047] In the integrally joined state, 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 pedestal portion 12 provided so as to surround the periphery of the cylinder wall 13 and the outer member side joining surface 57. That is, the water jacket is sealed at the welding ribs 56 that become the sealing line shown in FIG. 10. In addition, in the state where the welding ribs 56 are 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 substantially on the same plane. In consideration of the fact 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 made slightly lower than the upper end surface of the cylinder wall 13 of the main block 2.

[0048] Of the other seven columnar portions 14 excluding the second columnar portion 14B, all are within the water jacket, and the cooling water surrounds the outer peripheral surface of the columnar portion 14. The sealing line formed by the welding rib 56 passes outside the seven columnar portions 14, that is, outside the opening 54 (on the side of the water jacket forming wall 42), and seals the water jacket in a form including the seven columnar portions 14. Therefore, for example, as shown in FIG. 11, there is a relatively narrow water jacket between the outer peripheral surface of the columnar portion 14 and the water jacket forming wall 42 (the columnar portion facing surface 52).

[0049] In contrast, the second columnar portion 14B is accommodated in the second columnar portion insertion hole 53 of the outer member 3 and is isolated from the water jacket. That is, the second columnar portion 14B is surrounded by the wall around the second columnar portion insertion hole 53 made of synthetic resin and does not come into contact with the cooling water. There is a slight gap serving as an air layer between the inner wall surface of the second columnar portion insertion hole 53 and the outer peripheral surface of the second columnar portion 14B.

[0050] The cylinder head (not shown) is arranged on the upper surface of the upper deck portion 41 and is fixed via cylinder head bolts. The cylinder head bolts are respectively screwed into the bolt holes 24 of the columnar portions 14. The columnar portions 14 serving as bolt boss portions are all continuously in a straight line along the cylinder axis direction until reaching the pedestal portion 12, and linearly transmit the load along the bolt axis direction to the pedestal portion 12. And the pedestal portion 12 is thick and firmly configured, and the pedestal portion 12 surely supports the load acting from the cylinder head. Similarly, the main bearing portion 15 is integrated with the firm pedestal portion 12 and can surely support the crankshaft.

[0051] In addition, as shown in FIGS. 1 and 11, the oil drain hole forming portion 31 of the main block 2 and the oil drain hole forming portion 46 of the outer member 3 are joined in a manner that they abut against each other. Similar to the water jacket, the welding ribs 56 (56c) provided on the outer member 3 side melt and soften and are joined to the joint surface (top surface 22) on the main block 2 side. As a result, the lower half portion 32 of the oil drain hole and the upper half portion 58 of the oil drain hole are continuous as a single passage, and the oil drain hole is formed. The upper end of the oil drain hole is further connected to the oil drain hole on the cylinder head side.

[0052] As described above, the composite cylinder block 1 of the above embodiment is configured such that the metal main block 2 that receives loads and reaction forces has a minimum volume, and many parts such as the water jacket constituent wall 42 are made of synthetic resin as the outer member 3, so a significant weight reduction can be achieved.

[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 first columnar portion 14A and a second columnar portion 14B formed to reach the cylinder head. The first columnar portion 14A and the second columnar portion 14B each have an oil passage 25, 26 inside for supplying pressurized oil to the cylinder head.

[0054] Pressure from the oil acts on the oil passages 25, 26. However, the oil passage 25 is formed inside the metal first columnar portion 14A. The oil passage 26 is formed inside the metal second columnar portion 14B. Therefore, the cylinder block 1 can ensure pressure resistance.

[0055] Note that the first columnar portion 14A and the second columnar portion 14B are formed at positions separated from the cylinder wall 13.

[0056] The cylinder block 1 has a cylinder wall 13 where the main block 2 forms a cylinder bore 16, an outer member 3 forms a water jacket between the cylinder wall 13, and a first columnar portion 14A is located in the water jacket and reaches the cylinder head.

[0057] Therefore, the cylinder block 1 can cool the oil flowing through the oil passage 25 of the first columnar portion 14A with cooling water.

[0058] The second columnar portion 14B is housed in a state of being isolated from the water jacket in the second columnar portion insertion hole 53 in the outer member 3 and having a predetermined gap over the entire circumference between the second columnar portion insertion hole 53, and reaches the cylinder head.

[0059] Therefore, after the outer member 3 is welded to the main block 2 in the cylinder block 1, 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 becomes an air layer (heat insulation layer), so that the heat of the cooling water hardly escapes to the second columnar portion 14B during engine warm-up (during warm-up of the internal combustion engine), and the warm-up performance is generally improved.

[0060] In addition, when the main block 2 is heated and the outer member 3 is welded in the cylinder block 1, the second columnar portion 14B that has thermally expanded 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 arranged at the intended position of the main block 2.

[0061] The first columnar portion 14A has a pair of concave groove portions 14Ac on the outer peripheral surface between the main columnar portion 14Aa and the sub-columnar portion 14Ab. By having the pair of concave groove portions 14Ac, the first columnar portion 14A is hollowed out compared to the case where the outer shape of the cross section is an oval shape without the pair of concave groove portions 14Ac.

[0062] The second columnar portion 14B has a pair of concave groove portions 14Bc on the outer peripheral surface between the main columnar portion 14Ba and the sub-columnar portion 14Bb. By having the pair of concave groove portions 14Bc, the second columnar portion 14B is hollowed out compared to the case where the outer shape of the cross-section is oval without the pair of concave groove portions 14Bc.

[0063] Therefore, the cylinder block 1 can be made lighter by the first columnar portion 14A having the pair of concave groove portions 14Ac. The cylinder block 1 can be made lighter by the second columnar portion 14B having the pair of concave groove portions 14Bc.

[0064] 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.

[0065] For example, in the above-described embodiment, only the second columnar portion 14B of the columnar portions 14 is housed in the outer member 3 in a state of being isolated from the water jacket. However, the cylinder block 1 may be configured such that all the columnar portions 14 are housed in the outer member 3 in a state of being isolated from the water jacket. In this case, all the columnar portions 14 are housed in a state of being isolated from the water jacket in the outer member 3 and having a predetermined gap over the entire circumference between them, and the cylinder block may be configured to reach the cylinder head.

Explanation of reference numerals

[0066] 1... Cylinder block 2... Main block 3... Outer member 11... Lower deck 13... Cylinder wall 14... Columnar portion 14A... First columnar portion 14Aa... Main columnar portion 14Ab... Sub-columnar portion 14Ac... Concave groove portion 14B... Second columnar portion 14Ba... Main columnar portion 14Bb... Sub-columnar portion 14Bc… Concave groove part 24… Bolt hole 25… Oil passage 26… Oil passage

Claims

1. A composite cylinder block comprising a metal main block and a resin outer member welded to the main block, wherein the main block has a columnar portion formed to reach a cylinder head, and the columnar portion has an oil passage inside for supplying pressurized oil to the cylinder head.

2. The main block has a cylinder wall constituting a cylinder bore, the outer member forms a water jacket between the outer member and the cylinder wall, and the columnar portion is located in the water jacket and reaches the cylinder head. The composite cylinder block according to claim 1, characterized in that.

3. The main block has a cylinder wall constituting a cylinder bore, the outer member forms a water jacket between the outer member and the cylinder wall, and the columnar portion is housed in the outer member in a state of being isolated from the water jacket and having a predetermined gap between the columnar portion and the outer member, and reaches the cylinder head. The composite cylinder block according to claim 1, characterized in that.

4. The composite cylinder block according to any one of claims 1 to 3, characterized in that the columnar portion is integral with a bolt boss portion into which a cylinder head bolt for fixing the cylinder head is screwed.

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