JP5588904B2 - Cylinder block and cylinder block manufacturing method - Google Patents

Description

  The present invention relates to a cylinder block and a manufacturing method thereof.

  As disclosed in Patent Document 1 below, it is known to manufacture a cylinder block integrally provided with a crankcase by a die casting method or gravity casting.

  Patent Document 1 will be described with reference to FIGS. 6 is a perspective view of the cylinder block 102 including the crankcase 101, FIG. 7 is a longitudinal sectional view schematically showing the crankcase 101 and the casting mold 110 of FIG. 6, and FIG. 8 is shown in FIG. 2 is a cross-sectional view schematically showing a crankcase 101 and a core (cylinder side core 111 and crank side core 112) in a vertical cross section in a direction orthogonal to the cross section of the crankcase 101. FIG. The cylinder block 102 including the crankcase 101 is manufactured by gravity casting with a casting mold 110. As shown in FIG. 8, the cylinder-side core 111 and the crank-side core 112 are such that the draft angle 130 of the crank-side core 112 is near the bearing deepest portion 121 of the journal bearing portion 120 from the mating surface 150 on the crank side C. The draft angle 131 of the cylinder side core 111 is formed from the vicinity of the bearing deepest portion 121 of the journal bearing portion 120, which is the split surface 160 with the crankshaft core 112, toward the cylinder side H. It is formed to be wide. Therefore, in a state where the cylinder side core 111 and the crank side core 112 are combined, the part of the split surface 160 is thick, and from the split surface 160 toward the deepest bearing 121 on the cylinder side H and the mating surface 150. A partition wall 122 having a reduced thickness is formed. And according to this crankcase 101, since the distance between the crank web rotating between the journal bearing portions 120 and the partition wall 122 can be secured, the stirring resistance of the crank web can be reduced, and the engine output can be improved. Have been described.

JP 2008-69749 A

  By the way, the explosive force and thermal stress generated when the engine is operated are transmitted to the partition wall (bearing wall) of the crank chamber. Further, when the piston moves up and down during engine operation, a large pressure change generated between the partition walls is transmitted to the partition walls. Then, the explosive force, thermal stress, and pressure change concentrate on the corners of the partition walls (corner corners), and cracks may occur at the corners of the partition walls. However, in the conventional crankcase as disclosed in Patent Document 1, there is a possibility that cracks cannot be sufficiently prevented from occurring at the corners of the partition wall of the crank chamber.

  Therefore, the present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a cylinder block and a method of manufacturing the cylinder block that can prevent cracks from occurring at the corners of the bearing wall.

        The present invention has been made to solve the above problems, and a cylinder block according to the present invention has a bearing wall 3 formed with a semicircular support surface 10 for rotatably supporting a crankshaft of an internal combustion engine. The cylinder block 1 is formed by a die casting method, and an upper surface 3a which is a surface opposite to the semicircular support surface 10 and side surfaces 3b and 3b of the bearing wall 3 are formed. It is characterized by being continuous through curved surfaces 3c and 3c having a chill layer.

  The cylinder block manufacturing method according to the present invention includes a cylinder block 1 including a bearing wall 3 formed with a semicircular support surface 10 for rotatably supporting a crankshaft of an internal combustion engine. The cylinder block 1 is formed such that corners between the upper surface 3a, which is the surface opposite to the semicircular support surface 10, and the side surfaces 3b, 3b of the bearing wall 3 are curved surfaces 3c, 3c. A die casting step and a machining step for machining the bearing wall 3 so that the upper surface 3a and the side surfaces 3b, 3b of the bearing wall 3 are continuous via curved surfaces 3c, 3c having a chill layer. Features.

  According to the cylinder block of the present invention, it is possible to prevent cracks from occurring at the corners of the bearing wall of the crank chamber. Moreover, according to the cylinder block manufacturing method of the present invention, it is possible to manufacture a cylinder block that can prevent cracks from occurring at the corners of the bearing wall of the crank chamber.

It is a principal part front view of the cylinder block in one Embodiment of this invention. It is the sectional view on the AA line of FIG. FIG. 3 is a sectional view taken along line BB in FIG. 1. It is sectional drawing which shows a bearing wall and a die-casting die typically. It is the BB sectional drawing of FIG. 1 in the state before performing a machining process. It is a perspective view of the cylinder block containing the crankcase in a prior art. It is a longitudinal cross-sectional view which shows typically the crankcase and casting mold of FIG. It is sectional drawing which shows typically the crankcase and core in the longitudinal cross-section of the direction orthogonal to the cross section of the crankcase shown in FIG.

  Hereinafter, a cylinder block according to an embodiment of the present invention will be described with reference to the drawings. The cylinder block of this embodiment is a cylinder block of a horizontally opposed engine. FIG. 1 shows one of a pair of left and right cylinder blocks as viewed from the mating surface side of both cylinder blocks. Since this cylinder block 1 is made of an aluminum alloy and is for a horizontally opposed four-cylinder engine, two cylinder bores 2 are formed. The cylinder block 1 includes a plurality of bearing walls 3 (bearing portions) for rotatably supporting a journal portion of a crankshaft (not shown). The bearing wall 3 has a plate shape whose thickness direction is the axial direction of the crankshaft, and a plurality of the bearing walls 3 are arranged at intervals along the axial direction of the crankshaft. In the present embodiment, the bearing walls 3 are formed at a total of five locations, but four of the five locations are formed at positions facing the cylinder bore 2, and the remaining one of the bearing walls 3 is It is formed at a position away from the cylinder bore 2. As shown in FIG. 2, the bearing walls 3 are each formed with a semicircular support surface 10 for rotatably supporting the journal portion of the crankshaft. Further, on both sides of the semicircular support surface 10 of the bearing wall 3, an overlapping surface 11 that overlaps with the other cylinder block is formed, and a screw hole 12 is formed in the overlapping surface 11. FIG. 2 shows one of the bearing walls 3 formed at a position facing the cylinder bore 2. As shown in FIG. 2, a cylinder liner 13 made of cast iron or the like is cast on the wall surface of the cylinder bore 2.

  As shown in FIG. 3, the bearing wall 3 is provided with an upper surface 3 a that is substantially parallel to the axis of the crankshaft on the cylinder bore 2 side and is a surface opposite to the semicircular support surface 10. . The bearing wall 3 includes two side surfaces 3b and 3b extending in a direction orthogonal to the upper surface 3a (the axial direction of the cylinder bore 2). The upper surface 3a and the two side surfaces 3b and 3b are continuous via the curved surfaces 3c and 3c. The upper surface 3a and the two side surfaces 3b, 3b of the bearing wall 3 are formed by performing machining processing such as cutting after molding by the die casting method. However, machining processing is applied to the curved surfaces 3c, 3c. It has not been. Accordingly, the curved surfaces 3c and 3c are provided with a chill layer (solidified layer) formed as a refined structure on the surface of the die-cast product during molding by the die casting method. Since the upper surface 3a and the two side surfaces 3b, 3b of the bearing wall 3 are continuous with the curved surfaces 3c, 3c of R3-10 as the corners, explosive force, thermal stress and pressure changes are curved when the engine is operating. It is possible to prevent the occurrence of cracks at these locations by concentrating on the locations 3c and 3c. In addition, the curved surfaces 3c and 3c are provided with the chill layer formed when the die-casting method is used as they are, and since the strength is excellent, the occurrence of cracks at the curved surfaces 3c and 3c is further prevented. Yes.

  Next, the manufacturing method of the cylinder block 1 of this embodiment is demonstrated. First, a die casting process for forming the cylinder block 1 by a die casting method is performed. As shown in FIG. 4, the die casting mold 30 includes a fixed mold 31 and a movable mold 32. A cavity is defined by the fixed mold 31 and the movable mold 32, and the cylinder block 1 is formed by filling the cavity with a molten metal such as a molten aluminum alloy with a plunger tip. Here, the bearing wall 3 of the cylinder block 1 gradually increases in thickness from the crankshaft side C toward the cylinder bore side H. However, the bearing wall 3 on the cylinder bore side H is separated from the split surface 33 of the fixed mold 31 and the movable mold 32. It is shaped to gradually reduce its thickness. Further, the portion of the bearing wall 3 whose thickness is gradually reduced is formed so as to have curved surfaces 3c and 3c of R3 to 10 depending on the shape of the movable mold 32.

  After the cylinder block 1 molded in the die casting process is taken out from the die casting mold 30, a machining process step is performed in which the cylinder block 1 is subjected to a machining process such as a cutting process. In this machining process, the machining allowance S shown in black in FIG. 5 is removed from the bearing wall 3 to form the upper surface 3a and the side surface 3b of the bearing wall 3 (see FIG. 3). Then, the bearing wall 3 is formed by interposing the curved surfaces 3c and 3c having the chill layer formed when the die casting method is performed without performing the machining process between the upper surface 3a and the side surface 3b of the bearing wall 3. Are set to be curved surfaces of R3 to 10. Thus, the cylinder block 1 of this embodiment is manufactured.

  In the present embodiment, the horizontally opposed cylinder block has been described, but the present invention can also be applied to each type of cylinder block such as a series layout or a V type.

DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Cylinder bore 3 Bearing wall 3a Upper surface 3b Side surface 3c Curved surface 10 Semicircular support surface 11 Overlapping surface 12 Screw hole 13 Cylinder liner 30 Die-casting die 31 Fixed die 32 Movable die 33 Split surface
C Crankshaft side H Cylinder bore side S Machining allowance

Claims (2)

In a cylinder block including a bearing wall formed with a semicircular support surface for rotatably supporting a crankshaft of an internal combustion engine,
The cylinder block is formed by a die casting method,
The cylinder block characterized by the upper surface which is a surface on the opposite side to this semicircular support surface, and the side surface of this bearing wall continuing through the curved surface provided with a chill layer. In a method of manufacturing a cylinder block having a bearing wall formed with a semicircular support surface for rotatably supporting a crankshaft of an internal combustion engine,
A die casting step of forming a cylinder block so that a corner between the upper surface which is the surface opposite to the semicircular support surface and the side surface of the bearing wall is a curved surface;
Machining step for machining the bearing wall such that the upper surface and the side surface of the bearing wall are continuous via a curved surface having a chill layer;
A method for manufacturing a cylinder block, comprising:

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