Cylinder block of internal combustion engine

Abstract

To provide a cylinder block of an internal combustion engine capable of restraining generation of a blow hole in a positioning hole of the cylinder block.SOLUTION: In the cylinder block 1 of the internal combustion engine according to the present invention, the cast portion 61 facing the upper end portion of the positioning hole 42 is provided in the first flange portion 4 overlapping the bulging connection portion 6 in the height direction. In other words, since the core portion 61 is provided, it is possible to reduce the thickness of the positioning hole forming portion 40 of the bulging connection portion 6 in which the positioning hole 42 is formed. As a result, the occurrence of blowholes in the positioning hole 42 of the cylinder block 1 can be suppressed.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a cast internal combustion engine cylinder block. [Background technology]

[0002] A known example of a conventional cast cylinder block for an internal combustion engine is that described in Patent Document 1 below.

[0003] In conventional cast cylinder blocks for internal combustion engines, a first flange portion provided along a first side edge portion of the lower end of the cylinder block and a second flange portion provided along a second side edge portion of the cylinder block adjacent to the first flange portion have a bulging connection portion that gradually expands toward the lower end of the cylinder block, and this bulging connection portion ensures the rigidity of the cylinder block.

[0004] In addition, the cylinder block was provided with a positioning hole forming portion in a first flange portion that overlapped with the bulging connection portion in the height direction of the cylinder block, in which a positioning hole opening on the lower end side of the first flange portion was formed by machining after the casting for positioning during finishing processing of the cylinder block. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 09-042046 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the cylinder block of the conventional internal combustion engine, the bulging connection portion is provided only for the purpose of ensuring the rigidity of the cylinder block, and therefore the positioning hole forming portion overlapping with the bulging connection portion is thick, which may cause blowholes in the positioning hole, leaving room for improvement.

[0007] Therefore, the present invention has been devised in consideration of the technical problems of the conventional cylinder blocks of internal combustion engines, and aims to provide a cylinder block of an internal combustion engine that can suppress the occurrence of blowholes in positioning holes. [Means for solving the problem]

[0008] In one aspect, the present invention provides a cylinder block for an internal combustion engine formed by casting, which integrally has a cylinder portion that accommodates a piston and a crankcase portion that accommodates a crankshaft, the cylinder block comprising: a first flange portion that is provided along a first side edge portion of the cylinder block and protrudes laterally from the cylinder block; a second flange portion that is adjacent to the first side edge portion and extends along a second side edge portion of the cylinder block that is perpendicular to the protruding direction of the first flange portion and protrudes in the protruding direction of the first flange portion; a bulging connection portion that is provided so as to straddle the first flange portion and the second flange portion and connects the first flange portion and the second flange portion in a protruding build-up manner in the protruding direction of both flange portions; a positioning hole that is provided along the second side edge portion of the first flange portion at a position that overlaps with the bulging connection portion in the extending direction of the second flange portion, the positioning hole having one end that opens to the opposite side from the bulging connection portion; and a cast-out portion that is recessed laterally relative to the bulging connection portion during casting, and faces the other end of the positioning hole. [Effects of the Invention]

[0009] According to the present invention, the first flange portion adjacent to the bulging connection portion has a cast-out portion facing the upper end of the positioning hole, which makes it possible to reduce the thickness of the positioning hole forming portion of the bulging connection portion where the positioning hole is formed, thereby suppressing the occurrence of blowholes in the positioning hole of the cylinder block. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view of a cylinder block of an internal combustion engine according to the present invention, viewed from a first side surface side. [Figure 2] 1 is a perspective view of a cylinder block of an internal combustion engine according to the present invention, viewed from the rear side. [Figure 3] FIG. 3 is a view taken in the direction of the arrow A in FIG. 2. [Figure 4] FIG. 4 is a cross-sectional view taken along line BB in FIG. 3. [Figure 5] FIG. 4 is a cross-sectional view taken along line CC in FIG. [Figure 6] FIG. 4 is a cross-sectional view taken along line DD in FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of a cylinder block for an internal combustion engine according to the present invention will be described in detail with reference to the drawings. In this embodiment, as in the conventional case, the cylinder block for an internal combustion engine is applied to an automobile engine (spark ignition internal combustion engine).

[0012] (Cylinder block configuration) FIG. 1 shows a perspective view of the cylinder block 1 of the internal combustion engine according to this embodiment, viewed obliquely from above on the first side surface 13 side. FIG. 2 shows a perspective view of the cylinder block 1 of FIG. 1, viewed obliquely from above on the rear side (rear end surface 12 side) of the cylinder block 1. FIG. 3 shows a side view of the cylinder block 1, viewed from the direction A in FIG. 2 (the first side surface 13 side). FIG. 4 shows a cross-sectional view of the cylinder block 1 taken along line BB in FIG. 3. FIG. 5 shows a cross-sectional view of the cylinder block 1 taken along line CC in FIG. 3. FIG. 6 shows a cross-sectional view of the cylinder block 1 taken along line DD in FIG. 3. In the explanation of each figure, the direction parallel to the line connecting the centers of the three cylinders is defined as the "cylinder row direction," the direction parallel to the central axis of each cylinder is defined as the "height direction," and the direction perpendicular to the cylinder row direction and the height direction is defined as the "width direction." In addition, the top dead center side is defined as "top" and the bottom dead center side as "bottom."

[0013] As shown in Figures 1 to 4, the cylinder block 1 of the internal combustion engine according to this embodiment is formed by casting a metal such as an aluminum alloy or cast iron, and integrally includes a cylinder section 2 in which a piston (not shown) is slidably housed, and a crankcase section 3 provided below the cylinder section 2 and in which the upper half of a crankshaft (not shown) is rotatably housed. The cylinder section 2 has a plurality of cylinders 20 (three in this embodiment) arranged in series. The crankcase section 3 has a so-called half-skirt structure, and a plurality of bearings 31 that support the upper half (upper half circumference) of the crankshaft (not shown) are provided in the cylinder row direction, which is the axial direction of the crankshaft (not shown).

[0014] A ladder frame (not shown) is attached to the lower part of the crankcase 3 as a bearing member having a plurality of integral bearings that support the lower half (lower half circumference) of the crankshaft (not shown). That is, the crankcase 3 and the ladder frame (not shown) form a single crankcase, and cooperate with the ladder frame (not shown) to rotatably support the crankshaft (not shown). Furthermore, an oil pan (not shown) that stores lubricating oil (engine oil) is attached to the lower part of the ladder frame (not shown).

[0015] A front cover (not shown) that houses, for example, a cam and chain or a pulley and belt (not shown) is attached to a front end surface 11 of the cylinder block 1. On the other hand, a gear case (not shown) that integrally houses, for example, multiple gear elements (not shown) that reduce the speed and transmit the output of the engine is attached to a rear end surface 12 of the cylinder block 1.

[0016] A cylinder head (not shown) is placed on top of the cylinder block 1. An intake manifold (not shown) is connected to the cylinder head (not shown) on a first side surface 13 of the cylinder block 1 shown in Fig. 2, and an exhaust pipe (not shown) is connected to a second side surface 14 of the cylinder block 1 opposite the first side surface 13.

[0017] A first flange 4, which is a brim-shaped flange that protrudes outward in the width direction (to the side), is provided on a first side edge 131, which is the lower end of the first side surface 13 of the cylinder block 1, and extends in the cylinder row direction along the first side edge 131. A first screw insertion hole 41 that penetrates the first flange 4 perpendicularly is provided in the first flange 4, and a screw (not shown) inserted into the first screw insertion hole 41 is fastened to a female threaded hole (not shown) provided in the ladder frame (not shown), thereby fixing the ladder frame (not shown) to the cylinder block 1. Note that in a configuration in which the crankshaft (not shown) is supported by a plurality of bearing members, for example a plurality of bearing caps, the screw (not shown) inserted into the first screw insertion hole 41 is fastened to a female threaded hole provided in the oil pan (not shown), thereby fixing the oil pan (not shown) to the cylinder block 1.

[0018] A second flange 5 is provided at a second side edge 132 of the cylinder block 1, which is a side edge on the rear end surface 12 side of the first side surface 13 of the cylinder block 1 and is adjacent to the first side edge 131 and perpendicular to the protruding direction of the first flange 4. The second flange 5 extends along the height direction of the cylinder block 1 and protrudes in the protruding direction of the first flange 4. The second flange 5 is formed so that the amount of protrusion gradually increases toward the bottom, and is formed in a triangular shape when viewed in the cylinder row direction. The second flange 5 is provided with a second screw insertion hole 51 that penetrates perpendicularly to the second flange 5. A screw (not shown) inserted into the second screw insertion hole 51 is fastened to a female threaded hole (not shown) provided in a gear case (not shown), thereby fixing the gear case (not shown) to the cylinder block 1.

[0019] In addition, a bulging connection portion 6 is provided at the corner formed between the first flange portion 4 and the second flange portion 5. The bulging connection portion 6 connects the first and second flange portions 4, 5 and the first side surface 13 in a padded manner, spanning the first flange portion 4 and the second flange portion 5. The bulging connection portion 6 is configured as a so-called cone-shaped portion that is formed in a generally triangular prism shape that bulges outward in the width direction of the cylinder block 1, which is the protruding direction of both flange portions 4, 5, and gradually widens toward the lower end of the cylinder block 1, thereby increasing the rigidity of the cylinder block 1.

[0020] Furthermore, a positioning hole 42, which serves as a reference position for machining the finished surface FS of the cylinder block 1, is formed in the cylinder block 1 by machining after casting so that the positioning hole 42 opens into the lower end surface of the first flange portion 4. The positioning hole 42 is provided in the first flange portion 4 at a position in the height direction of the cylinder block 1 that overlaps with the bulging connection portion 6, and is provided in a location that is thicker than the general portion of the first flange portion 4. A positioning pin (not shown) is inserted into the positioning hole 42, and the finished surface FS of the cylinder block 1 is machined while the cylinder block 1 is positioned by the positioning pin (not shown), thereby ensuring dimensional accuracy of the finished surface FS of the cylinder block 1.

[0021] Furthermore, a cast-out portion 61 is formed at the lower end of the bulging connection portion 6. The cast-out portion 61 is recessed from the side (outside in the width direction) of the bulging connection portion 6 along the width direction of the cylinder block 1 and faces the upper end of the positioning hole 42. In other words, the cast-out portion 61 is recessed to a position deeper than the inner end of the positioning hole 42 in the width direction of the cylinder block 1. Specifically, as shown in FIG. 5 , the inner end of the cast-out portion 61 has a cross section perpendicular to the recess direction that is formed by an arc-shaped surface 610 that is concentric with the center P of the positioning hole 42, and this arc-shaped surface 610 is formed with a radius of curvature larger than the radius of the positioning hole 42. In this way, by providing the cast-out portion 61 at the lower end of the bulging connection portion 6, the upper end of the positioning hole 42 is exposed to the outside through the cast-out portion 61. Therefore, the positioning hole 42 is not a blind hole, but rather a through-hole that penetrates along the height direction of the cylinder block 1 through the flange-shaped positioning hole forming portion 40, which has a predetermined thickness that is thicker than the first flange portion 4.

[0022] Furthermore, the upper surface 611 and the lower surface 612 that define the core portion 61 are formed to be generally parallel to each other. As a result, the core portion 61 is formed by protrusions that extend generally parallel to each other in the mold opening direction from the inner surface of a casting mold (not shown) that is divided in the width direction of the cylinder block 1, without using a so-called collapsible core.

[0023] 4, a hollow portion 62 having a reduced thickness is provided inside the bulging connection portion 6. The hollow portion 62 is defined by a bottom wall 63 that separates the hollow portion 62 from the cut-out portion 61, and an outer wall 64 that connects the bottom wall 63 to an upper end of the bulging connection portion 6 that is connected to the first side surface 13, thereby forming the outer surface of the bulging connection portion 6. The bottom wall 63 extends linearly in the recess direction of the cut-out portion 61, i.e., along the width direction of the cylinder block 1, and is configured as a rib that connects the outer wall 64 to the crankcase inner wall 30 that is the first side surface 13 and defines the crankcase portion 3.

[0024] 4, the bottom wall 63 of the bulging connection portion 6 is provided such that an outer end 630 of the bottom wall 63 protrudes more than the outer end 420 of the positioning hole 42 in the width direction of the cylinder block 1. In this embodiment, the outer end 630 of the bottom wall 63 protrudes relatively more than the outer end 400 of the positioning hole forming portion 40 in which the positioning hole 42 is formed. As a result, the upper end of the positioning hole 42 is covered by the bottom wall 63 of the bulging connection portion 6. Furthermore, the bulging connection portion 6 is provided with a rib 65 above the cast portion 61 that protrudes from the outer wall 64 of the cylinder block 1 outward in the width direction and generally parallel to the cast portion 61.

[0025] (Effects of this embodiment) As described above, the cylinder block 1 of the internal combustion engine according to this embodiment has the cast-out portion 61 facing the upper end of the positioning hole 42 in the first flange portion 4 that overlaps with the bulging connection portion 6 in the height direction. In other words, the provision of the cast-out portion 61 makes it possible to reduce the thickness of the positioning hole forming portion 40 of the bulging connection portion 6 where the positioning hole 42 is formed. This makes it possible to suppress the occurrence of blowholes in the positioning hole 42 of the cylinder block 1.

[0026] In this embodiment, a hollow portion 62 is provided inside the bulging connection portion 6, and a rib-like bottom wall 63 is provided at the bottom of the hollow portion 62, connecting an outer wall 64 of the bulging connection portion 6 and the crankcase inner wall 30 that defines the crankcase portion 3. In other words, the rib-like bottom wall 63 formed by the formation of the cut-out portion 61 connects the outer wall 64 of the bulging connection portion 6 and the crankcase inner wall 30. This makes it possible to reduce stress acting on the area around the cut-out portion 61 while ensuring the rigidity of the cylinder block 1.

[0027] In this embodiment, the core 61 is opened along the mold opening direction, which is the dividing direction of the casting mold (not shown) used to cast the cylinder block 1, and is formed by a protrusion provided on the casting mold (not shown). This makes it possible to form the core 61 by the protrusion provided on the casting mold (not shown) without using a collapsible core. As a result, the core 61 can be formed relatively easily, and the productivity of the cylinder block 1 can be improved.

[0028] In this embodiment, a ladder frame (not shown) that supports the lower end of the crankshaft (not shown) is connected to the first flange portion 4, and a gear case (not shown) that houses a reducer is connected to the second flange portion 5, and the positioning holes 42 communicate with the outside via the cast-out portions 61. Since the positioning holes 42 are configured to communicate with the outside via the cast-out portions 61 in this way, it is possible to discharge contaminants from inside the ladder frame (not shown) to the outside via the positioning holes 42, compared to when the positioning holes 42 open into the inside of the gear case (not shown). This makes it possible to prevent contaminants that are discharged from the inside of the ladder frame (not shown) via the positioning holes 42 from entering the inside of the gear case (not shown).

[0029] Furthermore, in this embodiment, the bottom wall 63 of the bulging connection portion 6 protrudes outward beyond the positioning hole forming portion 40 in the width direction of the cylinder block 1, and a rib 65 that protrudes outward in the width direction of the cylinder block 1 is provided at the top of the cast-out portion 61 in the bulging connection portion 6. This effectively prevents water or contaminants from outside the cylinder block 1 from entering the inside of the ladder frame (not shown) through the positioning hole 42 or the inside of an oil pan (not shown) that communicates with the inside of the ladder frame (not shown).

[0030] The present invention is not limited to the configurations exemplified in the above-described embodiments, but can be freely modified according to, for example, the specifications of the internal combustion engine to which the present invention is applied.

[0031] For example, in the present invention, the first side edge 131 of the cylinder block 1 is not limited to the lower edge of the first side surface 13 of the cylinder block 1, and the first flange 4 is not limited to a connecting piece with a ladder frame (not shown) or an oil pan (not shown). In other words, the first flange 4 can be set on any side edge of the cylinder block 1.

[0032] Similarly, in the present invention, the second side edge 132 of the cylinder block 1 is not limited to the side edge on the rear end surface 12 side of the first side surface 13 of the cylinder block 1, and the second flange 5 is not limited to the connecting piece with the gear case (not shown). In other words, the second flange 5 can be set to any side edge of the cylinder block 1 that is connected perpendicular to the first flange 4.

[0033] In addition, in the above embodiment, an example is given in which the cast-out portion 61 is formed by a protrusion that protrudes from the inner surface of the casting mold (not shown) along the mold opening direction, but the cast-out portion 61 may be formed using a collapsible core such as a sand mold, and may open in a direction different from the dividing direction of the casting mold (not shown). [Explanation of symbols]

[0034] 1...Cylinder block 131...First side edge 132…Second side edge 2...Cylinder section 3...Crankcase section 30...Inner wall of crankcase 4...First flange 40...Positioning hole forming section 42...Positioning hole 5...Second flange 6...Bulging connection part 61...Castout section 62...Cavity part 63...Bottom wall (rib) 64...Outer wall

Claims

1. A cylinder block for an internal combustion engine, which is formed by casting and integrally has a cylinder portion that houses a piston and a crankcase portion that houses a crankshaft, a first flange portion provided along a first side edge portion of the cylinder block and protruding laterally from the cylinder block; a second flange portion adjacent to the first side edge portion, extending along a second side edge portion of the cylinder block perpendicular to the protruding direction of the first flange portion, and protruding in the protruding direction of the first flange portion; a bulging connection portion that is provided so as to straddle the first flange portion and the second flange portion and connects the first flange portion and the second flange portion in a protruding shape that bulges in the protruding direction of both flange portions; a positioning hole provided along the second side edge portion at a position in the first flange portion that overlaps with the bulging connection portion in the extending direction of the second flange portion, the positioning hole having one end opening to the opposite side from the bulging connection portion; a cast-out portion that is recessed laterally relative to the bulging connection portion during casting and faces the other end of the positioning hole; A cylinder block of an internal combustion engine.

2. 2. A cylinder block for an internal combustion engine according to claim 1, The bulging connection portion has a hollow portion therein, a rib is provided at a lower end of the bulging connection portion and at a lower portion of the cavity portion, the rib connecting an outer wall of the bulging connection portion and an inner crankcase wall that defines the crankcase portion. Cylinder block of an internal combustion engine.

3. 3. A cylinder block for an internal combustion engine according to claim 2, The hollow portion is opened along a dividing direction of the casting mold used for casting and is formed by a protrusion provided on the casting mold. Cylinder block of an internal combustion engine.

4. 4. A cylinder block for an internal combustion engine according to claim 3, the first flange portion is connected to a ladder-shaped bearing member that bears the lower end side of the crankshaft or to an oil pan, The second flange portion is connected to a gear case that houses a reducer, The positioning hole communicates with the outside through the cast-out portion. Cylinder block of an internal combustion engine.

5. 5. A cylinder block for an internal combustion engine according to claim 4, the rib extends farther than the outer end of the positioning hole in a recess direction of the cast-out portion, The other end of the positioning hole is covered by the rib. Cylinder block of an internal combustion engine.

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