JP4441762B2 - 2-cycle engine cylinder manufacturing method and manufacturing apparatus - Google Patents

Description

  The present invention relates to a manufacturing method and apparatus for improving productivity of a cylinder used in a two-cycle engine.

Conventionally, there is a die casting method as a method for manufacturing a cylinder for a two-cycle engine. As an example of this method, a split mold that forms the outer shape of the cylinder, a base that is disposed under the split mold and has a passage mold piece for forming a scavenging passage, and a cylinder bore that is inserted into the split mold. A core body for forming a scavenging port, a slider inserted inside the core body so as to be movable in the axial direction, and a core piece for forming a scavenging port attached to the tip of the core body and moving forward and backward in the radial direction of the core body There is one using a manufacturing apparatus provided with (Patent Document 1). In this manufacturing apparatus, the core body is inserted into the split mold, and a slider provided on the core body is moved in the axial direction of the core body so that the core piece extends outward in the radial direction of the core body. Then, the tip of the core piece is brought into contact with the passage type piece of the base. After that, by injecting a molten metal such as aluminum from the spout provided in the split mold, the outer shape of the cylinder and the scavenging passage are formed between the split mold and the core body and the base, and at the same time by the core body. The inner periphery of the cylinder bore is formed, and a scavenging port for opening the scavenging passage to the cylinder bore is formed by a core piece advanced outward in the radial direction of the core body.
Japanese Patent Publication No.58-31461

  However, the above manufacturing method has a complicated apparatus. The core piece forming the scavenging port moves in the radial direction by contact with the inclined surface provided on the slider in conjunction with the movement of the slider in the axial direction. Since the contact force to the mold piece cannot be increased, the injection pressure of the molten metal injected into the split mold gate cannot be increased. When this injection pressure is increased, the core piece moves due to the pressure, and a gap is formed between the core piece and the passage-type piece, and burrs are generated. On the other hand, when the injection pressure is reduced, the molten metal is difficult to rotate around the entire cylinder having a complicated shape. In addition, the core piece and the supporting portion thereof are easily deformed by heat and adjustment thereof is difficult, so that productivity is lowered.

  Then, an object of this invention is to provide the manufacturing method and apparatus which can manufacture efficiently a favorable cylinder without a burr | flash.

  In order to achieve the above object, the present invention molds a cylinder having a partition wall between a cylinder bore whose one end in the axial direction is open and a scavenging passage having a scavenging port opened to the cylinder bore. A scavenging core that forms the scavenging passage, a plurality of port cores that form part of the scavenging port and cylinder bore, and a plurality of port cores inserted between the plurality of port cores A bore core forming the other part of the cylinder bore is prepared, and after the bore core is retracted in one of the axial directions of the cylinder bore, the plurality of port cores are retracted toward the axis of the cylinder bore. Open the mold.

  When molding a cylinder, a port core is inserted into the scavenging core, and a bore core is inserted into the port core and fixed. In this state, molten metal is injected around each of the cores to form an outer shape of the cylinder and a cylinder bore, and at the same time, a scavenging passage and a scavenging port that opens the cylinder bore are formed. Then, after the bore core is retracted in the axial direction of the cylinder bore, each port core is retracted closer to the axial center of the cylinder bore and the mold is opened to mold the cylinder. In this way, the port core is firmly positioned by pressing the port core against the scavenging core by inserting the bore core, so a good cylinder free from burrs caused by the gap between the cores can be obtained. It can be produced efficiently.

  In a preferred embodiment of the present invention, at least a part of a contact surface of the bore core with the port core is formed in a tapered shape that becomes narrower toward the other side in the axial direction of the cylinder bore, and the bore core is formed. By advancing to the other of the cylinder bores, the plurality of port cores can be smoothly moved and positioned radially outward of the cylinder bores. Thereby, at the time of pouring the molten metal, it is possible to prevent the port core from being inclined in the radial direction of the cylinder due to the pouring pressure, or to form a gap between these cores. As a result, a good cylinder without burrs can be obtained, and the molten metal injection pressure, that is, the molding pressure can be increased to increase the production efficiency.

  The present invention also relates to a manufacturing apparatus for molding a cylinder provided with a partition wall between a cylinder bore having one end in the axial direction opened and a scavenging passage having a scavenging port opened to the cylinder bore. A scavenging core forming the scavenging passage, a plurality of port cores forming part of the scavenging port and the cylinder bore, and the other part of the cylinder bore inserted between the plurality of port cores And the plurality of port cores are set so as to be able to move forward and backward in directions toward and away from the axis of the cylinder bore, and the bore cores can be moved back and forth in the direction of the axis of the cylinder bore. Is set to

  According to this apparatus, the manufacturing method of the present invention can be implemented, and a good cylinder without burrs is efficiently produced. Further, the structure is simplified as compared with a complicated conventional molding apparatus using a slider and a core piece.

  In a preferred embodiment of the present invention, at least a part of the contact surface of the bore core with the port core is formed in a tapered shape that becomes narrower toward the other side in the axial direction of the cylinder bore. According to this configuration, the port core can be positioned by advancing the bore core above the cylinder and moving the port core radially outward of the cylinder bore. It is possible to prevent the child from tilting in the radial direction of the cylinder and from forming a gap between these cores. As a result, a good cylinder without burrs can be obtained, and the molten metal injection pressure, that is, the molding pressure can be increased to increase production efficiency.

  In a preferred embodiment of the present invention, a locking portion for locking the port core to the bore core by insertion of the bore core is provided. According to this configuration, the port core is more reliably positioned.

  Further, in a preferred embodiment of the present invention, the scavenging port opens to the cylinder bore in a direction deviated to one side from the axial center of the cylinder bore, and a contact surface between the bore core and the port core is a scavenging port. The one side edge of the port is set to be included. According to this configuration, when the port core is moved closer to the axial center of the cylinder bore and the scavenging port forming portion of the port core is extracted from the scavenging port of the scavenging passage, a part of the port core is not caught by the cylinder bore. Can be extracted reliably and smoothly.

  According to the present invention, a good cylinder without burrs can be efficiently manufactured.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an apparatus for manufacturing a cylinder for a two-cycle engine according to an embodiment of the present invention. This manufacturing apparatus is for casting a cylinder 1 connected to an upper portion of a crankcase (not shown). The cylinder 1 has a cylinder bore 10 with one end (lower part in FIG. 1) in a direction along the axis C (hereinafter referred to as the axis direction) opened, and a scavenging passage having a scavenging port 11 opened to the cylinder bore. A partition wall 13 is provided between the two. The apparatus includes fixed and movable main molds 2 and 2 which are divided into two left and right sides forming the outer shape of the cylinder 1, and a gate 20 is provided at the junction. In FIG. 1, the one in the axial direction is downward and the other is upward, but this manufacturing apparatus is disposed upside down from FIG. 1, and the one is upward and the other is downward. In some cases.

  The apparatus is further provided with a passage-type piece 31 which is disposed below the main molds 2 and 2 and protrudes inward of each main mold 2 (upward in FIG. 1) to form the scavenging passage 12 in the cylinder 1. One scavenging core 3, a plurality of port cores 4, 4 inserted into the main molds 2, 2 to form part of the scavenging port 11 and the cylinder bore 10, and these port cores 4, 4 4 and a single bore core 5 which is inserted into the cylinder 4 so as to be movable forward and backward and forms the other part of the cylinder bore 10.

  The cylinder 1 is opposed to a part of its peripheral wall by a suction port 14 for sucking an air-fuel mixture into the cylinder bore 10, and around the axis C of the suction port 14 and the cylinder bore 10. And an exhaust port 15 for exhausting the combustion gas combusted in the above, and a large number of cooling fins 16 for air cooling are formed on the outer surface. One or more scavenging passages 12 are provided across a line connecting the suction port 14 and the exhaust port 15.

  2 to 4 are cross-sectional views of the main part of the manufacturing apparatus showing the steps for manufacturing the cylinder 1. As shown in FIG. 2, the scavenging core 3 has four passage-type pieces 31 that form two pairs of scavenging passages 12 on the left and right sides of the cylinder 1 so as to face each other. The bore core 5 is formed in a wedge shape in cross section. That is, a long arc surface 51 and a short arc surface 52 are formed on the outer peripheral surface of the bore core 5 so as to face each other, and both side surfaces connecting corresponding ends of the arc surfaces 51 and 52 are in contact with the port core 4. Non-parallel contact surfaces 53 and 53 are formed. The long arc surface 51 faces the intake port 14, and the short arc surface 52 faces the exhaust port 15.

  The port core 4 is divided into left and right parts, and these divided cores 4 and 4 are driven by a mold driving device (not shown) so as to approach and separate from the axis C of the cylinder bore 10 in the radial direction. Moving. Arc portions 42 and 42 that form a part of the inner peripheral surface of the cylinder bore 10 are provided above the divided cores 4, and the bore core 5 is formed on the inner surface opposite to the arc surface 42. A linear contact surface 43 that contacts the contact surface 53 is provided, and each of the divided cores 4 has a crescent-shaped cross section. The arcuate surfaces 42 and 42 of the port core 4 form an inner peripheral surface of the cylinder bore 10 together with the arcuate surfaces 51 and 52 of the bore core 5 that forms the other part of the cylinder bore 10. Further, the port core 4 divided into two projects outwardly in the radial direction, comes into contact with the upper part of the passage mold piece 31 forming the scavenging core 3, and the scavenging port is located at the upper end of the scavenging passage 12. An arc-shaped port mold 41 that forms 11 is formed.

  Further, as shown in FIG. 1, the contact surface 53 of the bore core 5 with the port core 4 has a width W2 on the upper side serving as the top of the cylinder smaller than a width W1 on the lower side serving as the cylinder base, It is formed in a taper shape that becomes narrower toward the top of the cylinder 1. Accordingly, the bore cores 5 are inserted into the divided port cores 4 and advanced upward so that the respective port cores 4 are pressed radially outwardly in the radial direction of the port die 41. Each port core 4 is positioned by bringing the protruding tip surface into contact with the passage mold piece 31.

  Further, the insertion of the bore core 5 between the bore core 5 and the port core 4 causes the port core 4 to be locked, so that the port core 5 is separated from the axis of the cylinder bore 10. A locking portion 6 is provided to prevent the tilting in the direction of the movement. The locking portion 6 includes an annular groove 61 formed on the upper portion of the bore core 5 and an annular protrusion 62 formed on the upper inner surface of the port core 4 and engaged with the groove 61. When the bore core 5 is inserted into the port core 4, the protrusion 62 and the groove 61 are engaged with each other.

  Further, the scavenging port 11 of the scavenging passage 12 is configured so that the combustion gas in the cylinder bore 10 is smoothly discharged from the exhaust port 15 to the outside during the scavenging stroke of the cylinder 1 as shown in FIG. In this case, the opening is directed from the axis C toward the direction A deviated to one side S1 opposite to the side where the exhaust port 15 is formed. In order to form such a scavenging port 11, the contact surfaces 53 and 43 of the bore core 5 and the port core 4 are set so as to include one side edge 11a of the one side S1 of the scavenging port 11. Yes. That is, one side edge of the contact surfaces 43 and 53 between the port core 4 and the bore core 5 is made to coincide with the edge of one side S1 of the scavenging port 11. As a result, when the bore core 5 of FIG. 1 is pulled out below the cylinder 1 and each port core 4 is pulled out along the directing direction A of the scavenging port 11, as shown in FIG. Can be extracted smoothly. That is, when the port core 4 is extended toward the center side from the one side edge 11a of the scavenging port 11, as indicated by a two-dot chain line 4a, the port core 4 is aligned along the directing direction A of the scavenging port 11. In this embodiment, it is difficult to extract the port core 4 because the outer peripheral surface of the extended portion 4a may be caught by the vicinity 10a of the scavenging port 11 in the cylinder bore 10 when it is extracted. Since the portion 4a is eliminated, the port core 4 can always be smoothly extracted in the A direction.

  Next, a method for forming a cylinder using the above manufacturing apparatus will be described. First, in the first step, a single scavenging core 3 is disposed inside the main molds 2 and 2 that are faced to each other as shown in FIG. Subsequently, the port cores 4 and 4 are inserted into the main mold 2 from below the scavenging core 3, and the port cores 4 and 4 are moved radially outward by the mold driving device. The front end surface of the port die 41 for forming a scavenging port formed on each core 4 is brought close to or in contact with the upper part of each pair of left and right passage type pieces 31 provided on the scavenging core 3. Further, the bore core 5 is inserted upward from below the port core 4. At this time, each port core 4 is pressed radially outward by the tapered contact surface 53 formed in the upper portion of the bore core 5, so that the tip surface of the port die 41 is moved as shown in FIG. 2. It strongly contacts the passage-type piece 31 of the scavenging core 3. Further, the engagement of the groove 61 and the protrusion 62 of the locking portion 6 provided in the bore core 5 and the port core 4 shown in FIG. 1 causes the port core 4 to tilt away from the axis C of the cylinder bore 10. Is prevented. As a result, the positioning of the port cores 4 and 4 is made strong, and as a result, a good cylinder free from burrs caused by the gaps between the cores can be efficiently produced.

  After assembling the cores 3, 4, 5 in this way, the molten metal is injected from the gate 20 of the main mold 2 into the cavity of the main mold 2. Thus, the outer shape of the cylinder 1 is formed by the inner surface of the main mold 2, and the cylinder bore 10 is formed in the cylinder 1 by the port core 4 and the bore core 5. Further, a scavenging passage 12 is formed in the cylinder 1 by the passage type piece 31 of the scavenging core 3, and a scavenging port 11 is formed by the port die 41 at the upper part of the port core 4. A partition wall 13 of the cylinder 1 is formed between them.

  At the time of pouring the molten metal, each port core 4 is positioned by being pressed radially outward by the tapered contact surface 53 of the bore core 5, and the bore core 5 and the port core 4 are positioned. Since the port core 5 is prevented from tilting in the direction away from the axis C of the cylinder bore 10 by the locking portion 6 provided in the molten metal, the pressure of the molten metal acts on the upper portion of the bore core 4 when the molten metal is injected. Thus, the so-called opening of the mouth, in which a gap is formed between the cores 4 and 5 by tilting the upper portion of the port core 4 away from the upper portion of the bore core 5 in the radial direction, is prevented. Accordingly, it is possible to improve the production efficiency by increasing the pouring pressure of the molten metal, that is, the molding pressure, while eliminating the burr generated at the opening portion.

  After forming the cylinder 1 in this manner, in the second step, the bore core 5 is retracted below the cylinder 1 and extracted. This state is shown in FIG. Subsequently, in the third step shown in FIG. 4, each port core 4 is moved closer to the axial center C of the cylinder bore 10 by the mold driving device and extracted from the scavenging port 11. At this time, as described above, the contact surfaces 53 and 43 of the bore core 5 and the port core 4 are set so as to include the one side edge 11a of the one side S1 of the scavenging port 11. When the core 4 is extracted along the directing direction A of the scavenging port 11, each port core 4 can be smoothly extracted without being caught by a part 10 a of the cylinder bore 10. Thereafter, the scavenging core 3 is retracted downward, the main molds 2 and 2 are opened to the left and right, and the molded cylinder 1 is taken out. In this way, a high-quality cylinder without burrs can be efficiently produced using a manufacturing apparatus with a simple structure.

  In addition, although the contact surfaces 53 and 53 of the bore core 5 shown in FIG. 1 are entirely tapered, only a part, for example, only the upper half may be tapered. Furthermore, configurations can be added, deleted, and changed without departing from the spirit of the present invention, and such configurations are also included in the scope of the present invention.

It is a longitudinal cross-sectional view which shows the manufacturing apparatus of the cylinder for 2 cycle engines concerning one Embodiment of this invention. FIG. 5 is a cross-sectional view of the main part of the apparatus showing the first step when manufacturing a cylinder. It is a cross-sectional view of the principal part of the apparatus showing the second step. It is a transverse cross section of an important section of a device showing the 3rd process similarly.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder 3 Scavenging core 4 Port core 5 Bore core 6 Locking part 10 Cylinder bore 11 Scavenging port 12 Scavenging passage 13 Partition wall 43,53 Contact surface C Center axis of cylinder bore

Claims (6)

A method of molding a cylinder provided with a partition wall between a cylinder bore having one end in the axial direction opened and a scavenging passage having a scavenging port opened to the cylinder bore,
A scavenging core that forms the scavenging passage, a plurality of divided port cores that form part of the scavenging port and the cylinder bore, and another portion of the cylinder bore that is inserted between the plurality of port cores. Prepare the bore core to be formed,
A method for manufacturing a cylinder for a two-stroke engine, wherein the bore core is retracted in one of the axial directions of the cylinder bore, and then the plurality of port cores are retracted closer to the axial center of the cylinder bore to open the mold.   2. The bore according to claim 1, wherein at least a part of a contact surface of the bore core with the port core is formed in a tapered shape that becomes narrower toward the other side in the axial direction of the cylinder bore, and the bore core is formed on the cylinder bore. A method for manufacturing a cylinder for a two-cycle engine, wherein the plurality of port cores are moved radially outward of a cylinder bore by being advanced to the other side. A manufacturing apparatus that molds a cylinder provided with a partition wall between a cylinder bore whose one end in the axial direction is open and a scavenging passage having a scavenging port that opens to the cylinder bore,
A scavenging core that forms the scavenging passage, a plurality of divided port cores that form part of the scavenging port and the cylinder bore, and another portion of the cylinder bore that is inserted between the plurality of port cores. With a bore core to form,
The plurality of port cores are set so as to be able to advance and retreat in directions approaching and separating from the axis of the cylinder bore,
The bore core is an apparatus for manufacturing a cylinder for a two-cycle engine, which is set so as to freely advance and retract in the axial direction of the cylinder bore.   4. The manufacture of a cylinder for a two-stroke engine according to claim 3, wherein at least a part of a contact surface of the bore core with the port core is formed in a tapered shape that becomes narrower toward the other axial direction of the cylinder bore. apparatus.   5. The two-cycle engine cylinder manufacturing apparatus according to claim 3 or 4, wherein a locking portion for locking the port core to the bore core by insertion of the bore core is provided.   6. The scavenging port according to claim 3, wherein the scavenging port opens to the cylinder bore in a direction deviated to one side from the axis of the cylinder bore, and a contact surface between the bore core and the port core is a scavenging port. An apparatus for manufacturing a cylinder for a two-cycle engine, which is set so as to include the side edge on the one side.

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