JP5658188B2 - Mold for manufacturing piston and piston manufacturing method - Google Patents

Description

The present invention relates to a piston manufacturing mold and the piston production method.

  Conventionally, as a 2-cycle engine, for example, a 2-cycle engine described in Patent Document 1 below is known. This two-cycle engine employs a structure that aims to reduce hydrocarbons (HC; Hydro Carbon) in the exhaust discharged from the combustion chamber of the cylinder block through the exhaust port in the scavenging process. Yes.

  Specifically, in the two-cycle engine of Patent Document 1, the exhaust port is located at a position where the center of the opening is displaced by approximately 90 ° from the piston pin (output shaft) to the cylinder block in the circumferential direction of the piston. It is provided to be arranged. Further, the suction port is provided with respect to the cylinder block at a position shifted by approximately 90 ° from the piston pin to the other side (a position facing the exhaust port) in the circumferential direction.

  Further, a pair of first scavenging ports communicating with the combustion chamber with respect to the cylinder block are provided at substantially the same positions as the exhaust ports in the axial direction of the piston. One of the pair of first scavenging ports is disposed at a position shifted from the piston pin to the exhaust port side in the circumferential direction, and the other of the pair of first scavenging ports is an axis of the piston and an opening center of the exhaust port. And a line connecting the two (hereinafter, referred to as a first straight line) with respect to one of the first scavenging ports as a symmetry axis.

  In addition, a pair of second scavenging ports communicating with the combustion chamber are provided at positions closer to the bottom dead center from the first scavenging port in the axial direction with respect to the cylinder block. One of the pair of second scavenging ports is arranged at a position shifted from the piston pin to the suction port side in the circumferential direction, and the other of the pair of second scavenging ports has the first straight line as the target axis. It arrange | positions substantially symmetrically with one side of the 2nd scavenging opening. The second scavenging port communicates with a crank chamber different from the combustion chamber, and allows a fuel-containing gas (hereinafter referred to as gas A) in the crank chamber to flow into the fuel chamber from the second scavenging port. ing.

  A pair of exhaust circulation grooves (grooves) that connect the exhaust port and each of the first scavenging ports to each other near the top dead center with respect to the sliding surface of the piston that slides inside the combustion chamber is a first straight line. Is substantially symmetrical with respect to the target axis. Thus, in the vicinity of the top dead center, a gas having a fuel weight concentration smaller than that of the gas A (hereinafter referred to as gas B) is introduced from the exhaust port through the exhaust circulation groove to the first scavenging port and filled. Is possible.

  In such a two-cycle engine of Patent Document 1, first, when the piston is positioned near the top dead center, the exhaust port and the first scavenging port are communicated with each other by the exhaust circulation groove, and the exhaust gas B Is introduced into the first scavenging port which is at a low pressure. Subsequently, when the piston moves from the top dead center to the bottom dead center, the gas having a small fuel weight concentration filled in the first scavenging port before the gas A flows into the combustion chamber from the second scavenging port. By flowing B into the combustion chamber and exhausting it from the exhaust port, it is possible to reduce HC in the exhaust.

JP 2001-140651 A

  By the way, in the two-cycle engine as described above, layout flexibility is required, for example, when it is necessary to arrange the opening center of the exhaust port at a position other than a position shifted by 90 ° from the piston pin because of layout. There is.

The present invention has been made to solve such problems, and an object thereof is to provide a manufacturing mold and the piston production method of Lupi piston can increase the flexibility of layout.

The piston (1) obtained by the piston manufacturing die and the piston manufacturing method according to the present invention has an exhaust port (103) communicating with the combustion chamber (102) and the combustion chamber (102) with respect to the cylinder block (101). ) And a pair of first scavenging ports (104, 104) spaced apart from each other in the circumferential direction and a pair of first scavenging ports (104, 104) communicating with the combustion chamber (102) and spaced apart from each other in the circumferential direction. The second scavenging port (105, 105) is applied to a two-cycle engine (100) provided with a pair of pin bosses (2a, 2b) that protrude radially inward from the inner peripheral surface (12) and into which a piston pin is inserted. 2b) and a pair of grooves (3a, 3b) provided on the sliding contact surface (11) in sliding contact with the cylinder block (101) and communicating the exhaust port (103) and the first scavenging ports (104, 104). And The pair of grooves (3a, 3b) are arranged asymmetrically with an imaginary line (C) perpendicular to the axis (A) of the piston (1) and perpendicular to the axis (B) of the piston pin. .

In the piston (1), a pair of grooves (3a, 3b) communicating the exhaust port (103) and the first scavenging port (104, 104) are orthogonal to the axis (A) of the piston (1) and They are arranged asymmetrically with an imaginary line (C) orthogonal to the axis (B) of the piston pin as an axis. Therefore, for example, two cycles in which the opening center of the exhaust port (103) is arranged at a position other than the position shifted by 90 ° from the piston pin and the opening center of the exhaust port (103) is not positioned on the virtual line (C). In the case of the engine (100), the exhaust port (103) and the first scavenging port (104, 104) communicate with each other by a pair of grooves (3a, 3b) arranged asymmetrically about the virtual line (C). It becomes possible to do. Accordingly, the flexibility of layout can be increased.

  By the way, when molding the piston described in Patent Document 1, for example, the following method can be considered. That is, a split outer mold (main mold) for forming the sliding contact surface of the piston and a core mold for forming the inner peripheral surface of the piston are prepared. The outer mold is provided with a convex portion for forming a groove portion, and the core mold is provided with a concave portion for forming a protruding portion that protrudes inward from the inner peripheral surface of the piston corresponding to the groove portion. In addition, the core mold forms an inner peripheral surface on one pin boss side, and when viewed from the axial direction of the piston, the first core mold has a substantially bow shape and an inner peripheral surface on the other pin boss side And a second core mold having a substantially bow shape when viewed from the axial direction of the piston, and a central core mold sandwiched between the first core mold and the second core mold, To divide. After the material is poured between the molds and cured, first, the central core mold is extracted along the axial direction of the piston, and then the first core mold does not interfere with the pin boss and the protruding portion. Next, the first core mold is moved to the space after the central core mold is extracted, and then extracted along the axial direction of the piston. Subsequently, the second core mold interferes with the pin boss and the protrusion. In order to avoid this, the second central mold is shifted to the space after the central core mold and the first core mold are extracted, and then extracted along the axial direction of the piston and released.

However, such a method causes the following problems particularly when the above-described piston is manufactured. That is, in the above-described piston, since the pair of groove portions are arranged asymmetrically with respect to the imaginary line, one groove portion is always arranged closer to the imaginary line than the other groove portion. Then, when the core mold for forming the inner peripheral surface on the other groove side is shifted, the core mold easily interferes with the protruding portion corresponding to the one groove, so that it is difficult to release the mold. There is a risk. On the other hand, it is also conceivable to avoid interference with the protrusion by providing a notch by notching the corner of the arcuate shape of the core mold that forms the inner peripheral surface on the other groove side. In this case, waste meat is produced on the inner peripheral surface of the manufactured piston. When the sagging occurs, there are problems that the weight of the piston increases, the vibration of the engine increases, and a cavity (sink nest) tends to occur on the inner peripheral surface of the piston during molding. Therefore, as a result of intensive studies, the present inventor has come up with a piston manufacturing die and a piston manufacturing method suitable for manufacturing the above-described piston.

The piston manufacturing die according to the present invention (50) is a piston manufacturing mold for manufacturing a piston (1) described above (50), in the piston (1), a pair of grooves (3a, 3b), the first outer mold (61) that forms the sliding contact surface (11) on the one groove (3a) side close to the virtual line (C), and the other groove (3b) side in the piston (1) The second outer mold (62) forming the sliding contact surface (11) and the first outer mold (61) are arranged opposite to each other, and the inner peripheral surface (12) on the one groove (3a) side in the piston (1). ) Forming the first core mold (71) and the second outer mold (62), and spaced apart from the first core mold (71), the piston (1) , The second core mold (72) forming the inner peripheral surface (12) on the other groove (3b) side, the first core mold (71) and the second A central core mold (73) sandwiched between the core mold (72), and the second core mold (72) has one groove (3a) at the time of mold release. Corresponding to the first projecting portion (4a) projecting inward from the inner peripheral surface (12) of the piston (1) is provided with a relief portion (72b), and the relief portion (72b ) Is a surface in contact with the central core mold (73) in the second core mold (72).

Further, the piston production method according to the present invention, there is provided a piston production method for producing a piston (1) above, to prepare the above-mentioned piston manufacturing mold (50), a first outer mold (61 ) And the second outer mold (62) and the first core mold (71), the second core mold (72), and the central core mold (73), the molten material is poured, After the material has hardened, the central core mold (73) is extracted along the axis (A) of the piston (1), and the first core mold (71) is oriented in the axis (A) direction of the piston (1). When viewed from above, the first core mold (71) is placed in the central core so that it does not overlap with the pin boss (2a) on the one groove (3a) side and the first protrusion (4a). After the mold (73) is moved to the space after being extracted, the first core mold (71) is moved along the axis (A) of the piston (1). When the second core mold (72) is viewed from the direction of the axis (A) of the piston (1), the pin boss (2a) on the other groove (3b) side and the other groove (3b) are removed. Correspondingly, the second projecting portion (4b) projecting inward from the inner peripheral surface (12) of the piston (1) does not overlap with the first projecting portion (4a) in the escape portion (72b). After the second core mold (72) is moved to the space after the central core mold (73) and the first core mold (71) are extracted so as not to overlap, The core mold (72) is extracted along the axis (A) of the piston (1).

  In these present inventions, the core mold includes a first core mold (71) that forms an inner peripheral surface (12) on the one groove (3a) side in the piston (1), and a piston (1). Between the second core mold (72) forming the inner peripheral surface (12) on the other groove (3b) side, between the first core mold (71) and the second core mold (72) A center core mold (73) sandwiched between the first projecting portion (4a) corresponding to one groove portion (3a) close to the imaginary line (C). (72b) is a surface that comes into contact with the central core mold (73) in the second core mold (72), and thus escapes from the inner peripheral surface (12) of the manufactured piston (1). The portion (72b) does not come into contact with the piston (1) to be manufactured, and no waste occurs. Therefore, the flexibility of the layout can be increased, and the mold can be easily released without causing any waste.

According to the present invention, it is possible to provide a manufacturing mold and the piston production method of a piston which can enhance the flexibility of layout.

It is sectional drawing which shows one Embodiment which concerns on the piston obtained by the metal mold | die for piston manufacture of this invention, and a piston manufacturing method with a cylinder block. It is a front view of the piston in FIG. It is a right view of the piston in FIG. It is a bottom view of the piston in FIG. FIG. 5 is a VV arrow view in FIG. 3. FIG. 6 is a view taken in the direction of arrows VI-VI in FIG. 2. It is sectional drawing which shows one Embodiment which concerns on the metal mold | die for piston manufacture of this invention. It is a VIII-VIII arrow line view in FIG. It is the IX-IX arrow directional view in FIG. It is a XX arrow line view in FIG. It is a XI-XI arrow line view in FIG. It is sectional drawing which shows the flow of one Embodiment which concerns on the piston manufacturing method of this invention. It is sectional drawing which shows the flow following FIG.

It will now be described in detail embodiments of the piston manufacturing mold and the piston production method of the present invention with reference to accompanying drawings.

[2-cycle engine]
First, a two-cycle engine to which the piston according to this embodiment is applied will be described. FIG. 1 is a cross-sectional view showing an embodiment of a piston obtained by a piston manufacturing die and a piston manufacturing method according to the present invention together with a cylinder block.

  As shown in FIG. 1, in the two-cycle engine 100, the piston 1 reciprocates in the combustion chamber 102 of the cylinder block 101 along the axis A direction (the direction perpendicular to the paper surface in FIG. 1). In the two-cycle engine 100, an exhaust port 103, a pair of first scavenging ports 104 and 104, and a pair of second scavenging ports 105 and 105 that communicate with the combustion chamber 102 are provided for the cylinder block 101. ing.

  The exhaust port 103 is an opening for exhausting gas, and for the convenience of the layout of the two-cycle engine 100, the center 103a of the opening is disposed at a position other than the position shifted by 90 ° from the axis B of the piston pin. . More specifically, when a line perpendicular to the axis A of the piston 1 and perpendicular to the axis B of a piston pin (not shown) inserted into the piston 1 is defined as a virtual line C, A straight line E connecting the axis A and the opening center 103a of the exhaust port 103 forms a predetermined angle α (α ≠ 0) with the virtual line C.

  The first scavenging port 104 is for scavenging by introducing gas into the combustion chamber 102, and is provided at a position substantially similar to the exhaust port 103 in the direction of the axis A of the piston 1. The pair of first scavenging ports 104, 104 are arranged at substantially line symmetrical positions with the straight line E as the axis of symmetry in the circumferential direction of the piston 1.

  The second scavenging port 105 is for scavenging by introducing gas into the combustion chamber 102, and is located slightly closer to the bottom dead center than the first scavenging port 104 in the direction of the axis A of the piston 1. Is provided. The pair of second scavenging ports 105 are provided at positions farther from the exhaust port 103 than the pair of first scavenging ports 104 and 104 in the circumferential direction of the piston 1, and are arranged substantially line-symmetrically with the straight line E as the symmetry axis. Has been. Each second scavenging port 105 communicates with a crank chamber (not shown) separate from the combustion chamber 102, and allows a fuel-containing gas (hereinafter referred to as gas A) in the crank chamber to flow into the fuel chamber. ing.

  In such a two-cycle engine 100, in the crank angle range close to top dead center, the exhaust port 103 and the first scavenging ports 104 are communicated with each other by exhaust circulation grooves 3a and 3b of the piston 1 described later, As a result, a gas having a fuel weight concentration lower than that of the gas A (hereinafter referred to as gas B) is filled into the first scavenging ports 104 from the exhaust port 103 via the exhaust circulation grooves 3a and 3b. When the piston moves from the top dead center to the bottom dead center, the fuel weight concentration charged in the first scavenging port 104 before the gas A flows into the combustion chamber 102 from the second scavenging port 105. The small gas B flows into the combustion chamber 102 and is discharged from the exhaust port 103, so that HC in the exhaust gas is reduced.

[piston]
Next, the piston 1 according to this embodiment applied to the two-cycle engine 100 configured as described above will be described. 2 is a front view of the piston in FIG. 1, FIG. 3 is a right side view of the piston in FIG. 1, FIG. 4 is a bottom view of the piston in FIG. 1, and FIG. 6 is a view taken along arrow VI-VI in FIG.

  As shown in FIGS. 2 to 5, the piston 1 has a substantially cylindrical shape with a bottom on the piston head side. On the sliding contact surface 11 of the piston 1, piston ring grooves 13 and 13 are provided in the circumferential direction in the portion on the piston head side. As shown in FIG. 5, the inner peripheral surface 12 of the piston 1 has a smaller diameter in the piston head side portion 12 a than in the skirt side portion 12 b. As shown in FIG. 4, the piston 1 includes a pair of pin bosses 2a and 2b and a pair of exhaust circulation grooves (groove portions) 3a and 3b.

  The pin bosses 2a and 2b support the piston pin so as to be rotatable, and project radially inward from the inner peripheral surface 12 of the piston 1. The pin bosses 2a and 2b are provided 180 degrees apart so as to face each other in the circumferential direction of the piston 1. The pin boss 2a is provided on an inner peripheral surface on the side of one exhaust circulation groove 3a, which will be described in detail later, on the inner peripheral surface 12 divided by the virtual line C, and the pin boss 2b is an inner periphery divided by the virtual line C. Of the surface 12, it is provided on the inner peripheral surface on the other exhaust circulation groove 3b side which will be described in detail later. The pin bosses 2a and 2b are respectively provided with piston pin holes 21a and 21b into which piston pins are inserted.

  As described above, the exhaust circulation grooves 3a and 3b communicate the exhaust port 103 and the first scavenging port 104 in the two-cycle engine 100 (see FIG. 1). The skirt side is recessed (see FIG. 3). The exhaust circulation grooves 3a and 3b are arranged asymmetrically around the virtual line C in the circumferential direction of the piston 1 (see FIG. 4), and one exhaust circulation groove 3a is more than the other exhaust circulation groove 3b. It is arranged at a position close to the virtual line C. Thus, as in the above-described two-cycle engine 100, when the opening center 103a of the exhaust port 103 is disposed at a position other than the position shifted by 90 ° from the axis B of the piston pin (that is, the straight line E and the virtual line) The exhaust port 103 and each of the first scavenging ports 104 can communicate with each other (see FIG. 1).

  The inner peripheral surface 12 of the piston 1 is provided with a first projecting portion 4a projecting radially inward corresponding to one exhaust circulation groove 3a, and in the radial direction corresponding to the other exhaust circulation groove 3b. The 2nd protrusion part 4b which protrudes inside is provided. Note that, as shown in FIG. 6, the thickness between the exhaust circulation groove 3a and the first protrusion 4a is made thicker than the thickness of the upper portion thereof. The same applies to the thickness between the exhaust circulation groove 3b and the second protrusion 4b.

  Here, as shown in FIG. 4, in the direction of the axis B of the piston pin, the distance from the piston head side portion 12a of the inner peripheral surface 12 to the tip of the pin boss 2b is a distance da. In the direction of the axis B of the piston pin, the distance from the tip of the pin boss 2b to the end of the first protrusion 4a near the virtual line C is a distance db. In the piston 1 according to the present embodiment, as described above, one exhaust circulation groove 3a is disposed at a position closer to the imaginary line C than the other exhaust circulation groove 3b. The one protruding portion 4a and the pin boss 2b on the exhaust circulation groove 3b side are disposed relatively close to each other. For this reason, in the piston 1, the distance db <the distance da.

[Mold for piston production]
Next, a piston manufacturing die for manufacturing the above-described piston 1 will be described. 7 is a cross-sectional view showing an embodiment of the piston manufacturing mold according to the present invention, FIG. 8 is a view taken along arrows VIII-VIII in FIG. 7, and FIG. 9 is a view taken along arrows IX-IX in FIG. FIG. 10 is a cross-sectional view of the portion where the exhaust circulation grooves 3a and 3b are formed, FIG. 10 is a cross-sectional view of the portion where the pin bosses 2a and 2b are formed, and FIG. It is a XI arrow line view and sectional drawing by the side of a piston head.

  As shown in FIGS. 7 and 8, the piston manufacturing mold 50 includes a main mold (outer mold) 60 that forms the sliding contact surface 11 of the piston 1 and a core mold that forms the inner peripheral surface 12 of the piston 1. 70.

  Inside the main mold 60, there are provided a forming portion 60a in which the piston 1 is formed, a gate 60b into which a material such as molten metal is injected, and an overflow 60c in which the material at the initial stage of injection is stored. . The main mold 60 is divided into a first main mold (first outer mold) 61 and a second main mold (second outer mold) 62 along the direction of the axis B of the piston pin (see FIG. 8). ).

  As shown in FIG. 9, the first main mold 61 has a sliding contact surface 11 on the exhaust circulation groove 3 a side close to the virtual line C among the sliding contact surfaces 11 divided by the virtual line C in the piston 1. Form. The second main mold 62 forms a sliding contact surface 11 on the other exhaust circulation groove 3 b side in the sliding contact surface 11 divided by the imaginary line C in the piston 1.

  The first main mold 61 is provided with a protruding first protrusion 63 for forming the exhaust circulation groove 3a, and the second main mold 62 has a protrusion for forming the exhaust circulation groove 3b. The second protrusion 64 is provided. As shown in FIG. 10, the first main mold 61 is provided with a protrusion for forming a piston pin hole 21a (see FIG. 4), and the second main mold 62 has a piston pin hole. Protrusions for forming 21b (see FIG. 4) are provided.

  As shown in FIG. 8, the core mold 70 includes a first core mold 71, a second core mold 72, and a central core mold 73 along the direction of the axis B of the piston pin. It is divided into As shown in FIG. 9, the first core mold 71 is arranged to face the first main mold 61, and in the piston 1, the exhaust circulation groove 3 a in the inner peripheral surface 12 divided by the virtual line C. The inner peripheral surface 12 on the side is formed. The second core mold 72 is disposed opposite to the second main mold 62 and is spaced apart from the first core mold 71, and the inner peripheral surface divided by the virtual line C in the piston 1. 12, an inner peripheral surface 12 on the other exhaust circulation groove 3 b side is formed. The center core mold 73 is sandwiched between the first core mold 71 and the second core mold 72, and the first core mold 71 and the second core mold 12 on the inner peripheral surface 12 of the piston 1. A portion (portion near the imaginary line C) other than the portion formed in the core mold 72 is formed. The center core mold 73 is further divided along the direction of the imaginary line C into a third core mold 73a, a fourth core mold 73b, and a fifth core mold 73c. .

  The third core mold 73 a is located in the center portion of the center core mold 73 in the direction of the imaginary line C. The fourth core mold 73b is located on the side where the exhaust circulation grooves 3a and 3b are formed in the direction of the imaginary line C in the central core mold 73. The fifth core mold 73 c is located on the opposite side of the fourth core mold 73 b in the direction of the imaginary line C in the central core mold 73. As shown in FIG. 10, the first core mold 71 and the second core mold 72 are provided with recesses for forming the pin bosses 2a and 2b, respectively. As shown in FIG. 11, a core comprising a first core mold 71, a second core mold 72, a third core mold 73a, a fourth core mold 73b, and a fifth core mold 73c. In the mold 70, the outer diameter of the portion of the inner peripheral surface 12 of the piston 1 where the portion 12a on the fixer head side is formed is smaller than that of the portion where the skirt side portion 12b is formed (see FIG. 9). .

  As shown in FIG. 9, the first core die 71 and the fourth core die 73 b have a first recess 74 for forming the first protrusion 4 a (see FIG. 4) across the first core die 71 and the fourth core die 73 b. Is provided. The second core mold 72 and the fourth core mold 73b are provided with a second recess 75 for forming the second projecting portion 4b (see FIG. 4) across the two.

  As shown in FIGS. 9 to 11, exhaust circulation grooves 3 a and 3 b are formed on the contact surface 72 a of the second core mold 72 with the third core mold 73 a and the fourth core mold 73 b. A concave portion is provided on the side portion, and the concave portion prevents interference with the first protruding portion 4a (see FIG. 4) protruding inward from the inner peripheral surface 12 of the piston 1 at the time of mold release. For this reason, it is an escape portion 72b (details will be described later). On the other hand, on the contact surface of the third core mold 73a with the second core mold 72, there is provided a protrusion that matches the escape portion 72b. The fourth core mold 73b has a width in the direction of the axis B of the piston pin (see FIG. 10) larger than that of the fifth core mold 73c. With such a configuration, the escape portion 72b is a surface that comes into contact with the third core mold 73a and the fourth core mold 73b, and as a result, the inner peripheral surface 12 of the piston 1 to be manufactured and the second core mold 73b. It is made for the escape part 72b of the core metal mold | die 72 not to contact | abut.

[Piston manufacturing method]
Next, a piston manufacturing method for manufacturing the piston 1 using the above-described piston manufacturing mold 50 will be described.

  12 is a cross-sectional view showing a flow of one embodiment according to the piston manufacturing method of the present invention, FIG. 12 (a) is a cross-sectional view when the material is solidified, and FIG. 12 (b) is a third core mold. FIG. 12C is a cross-sectional view after extracting the fifth core mold 73c, and FIG. 12D is a cross-sectional view after extracting the fourth core mold 73b. It is. First, the piston manufacturing die 50 is prepared, and the space between the first main die 61 and the second main die 62, the first core die 71, the second core die 72, and the central core die 73 is obtained. Pour molten metal or other material into the

  When the melted material is solidified as shown in FIG. 12 (a), then, from the molded piston 1 along the axis A of the piston 1, as shown in FIGS. 12 (b) and 12 (c). These are extracted in the order of the three core mold 73a and the fifth core mold 73c. Subsequently, as shown in FIG. 12 (d), when the fourth core mold 73 b is viewed from the direction of the axis A of the piston 1, the first protrusion 4 a and the second protrusion 4 b do not overlap. Next, after the fourth core mold 73b is moved to the space after the third core mold 73a is extracted, the fourth core mold 73b is moved from the piston 1 along the axis A of the piston 1. Pull out.

  13 is a cross-sectional view showing a flow subsequent to FIG. 12, where FIG. 13 (a) is a cross-sectional view showing a state in which the first core mold 71 is displaced, and FIG. 13 (b) is a view showing the first core mold 71. FIG. 13C is a cross-sectional view after the second core mold 72 is displaced, and FIG. 13D is a cross-sectional view after the second core mold 72 is extracted. . As shown in FIG. 13A, when the first core mold 71 is viewed from the direction of the axis A of the piston 1, the first core is prevented from overlapping with the pin boss 2a and the first protrusion 4a. The mold 71 is moved to the space after the third core mold 73a, the fourth core mold 73b, and the fifth core mold 73c are extracted. Thereafter, as shown in FIG. 13B, the first core mold 71 is extracted from the piston 1 along the axis A of the piston 1.

  Subsequently, as shown in FIG. 13 (c), when the second core mold 72 is viewed from the direction of the axis A of the piston 1, the pin boss 2b and the second protrusion 4b do not overlap with each other, and The second core mold 72 is replaced with the third core mold 73a, the fourth core mold 73b, the fifth core mold 73c and the like so that the first projecting portion 4a does not overlap with the escape portion 72b. The first core mold 71 is moved to the space after being extracted.

  Here, when the escape portion 72b is not provided in the second core mold 72 (when the second core mold 72 is provided up to the corner F in FIG. 13C), the second core mold 72 is provided. In order to prevent the mold 72 and the first protrusion 4a from interfering with each other, the relationship between the width dc of the second core mold 72 along the axis B of the piston pin and the above-mentioned distance db is the distance db. > Width dc needs to be satisfied. However, in the piston 1 according to the present embodiment, the distance db <distance da and the relationship between the distance da and the width dc satisfy the distance da <width dc as described above, and therefore the distance db <width dc. It becomes. In view of such a structure, the piston manufacturing die 50 according to the present embodiment is provided with a relief portion 72b in order to prevent interference between the second core die 72 and the first protruding portion 4a. .

  Thereafter, as shown in FIG. 13 (d), the second core mold 72 is extracted from the piston 1 along the axis A of the piston 1. Furthermore, the mold release operation is completed by releasing the main mold 60 after the core mold 70 is released.

  As described above, in the piston 1 according to the present embodiment, the pair of exhaust circulation grooves 3a and 3b communicating the exhaust port 103 and the first scavenging ports 104 are orthogonal to the axis A of the piston 1 and the axis B of the piston pin. Since the opening center 103a of the exhaust port 103 is disposed at a position other than the position shifted by 90 ° from the piston pin, the exhaust line 103 is located on the virtual line C. In the case of the two-cycle engine 100 in which the opening center 103a is not located, the exhaust port 103 and each of the first scavenging ports 104 are connected by a pair of exhaust circulation grooves 3a and 3b arranged asymmetrically about the imaginary line C. It becomes possible to communicate. Accordingly, the flexibility of layout can be increased.

  In the piston manufacturing mold 50 and the piston manufacturing method using the same according to the present embodiment, the core mold 70 forms the inner peripheral surface 12 on the one exhaust circulation groove 3a side in the piston 1. A first core mold 71, a second core mold 72 that forms the inner peripheral surface 12 on the other exhaust circulation groove 3 b side in the piston 1, and a first core mold and a second core mold An escape portion 72b for preventing interference with the first projecting portion 4a corresponding to one of the exhaust circulation grooves 3a that is divided into a central core mold 73 sandwiched therebetween and that is close to the imaginary line C, The surface of the core die 72 that is in contact with the central core die 73 prevents the inner peripheral surface 12 of the manufactured piston 1 from coming into contact with the escape portion 72b. There will be no waste in the piston 1 that is made. Therefore, the flexibility of the layout can be increased, and the mold can be easily released without causing any waste.

Having described the embodiment of the piston production mold and the piston production method of the present invention, the present invention is not limited to the above embodiment. For example, in the above embodiment, the central core mold 73 is divided into the third core mold 73a, the fourth core mold 73b, and the fifth core mold 73c, but the exhaust circulation grooves 3a, The first recess 74 and the second recess 75 for forming 3b are not provided across the fourth core mold 73b, and the fourth core mold 73b is extracted as it is along the axis A of the piston 1. If possible, the central core mold 73 may not be divided.

  DESCRIPTION OF SYMBOLS 1 ... Piston, 2a, 2b ... Pin boss | hub, 3a, 3b ... Exhaust circulation groove (groove part), 4a ... 1st protrusion part, 4b ... 2nd protrusion part, 11 ... Sliding contact surface, 12 ... Inner peripheral surface, 50 ... Piston Manufacturing mold 61: First main mold (first outer mold) 62: Second main mold (second outer mold) 71: First core mold 72: Second core mold 72a ... Abutting surface, 72b ... Escape part, 73 ... Central core mold, 100 ... Two-cycle engine, 101 ... Cylinder block, 102 ... Combustion chamber, 103 ... Exhaust port, 104 ... First scavenging port, 105 ... No. Two scavenging ports, A ... axis of piston, B ... axis of piston pin, C ... virtual line.

Claims (2)

An exhaust port (103) communicating with the combustion chamber (102) with respect to the cylinder block (101) and a pair of first scavenging ports (104) communicating with the combustion chamber (102) and spaced apart from each other in the circumferential direction. , 104) and a pair of second scavenging ports (105, 105) communicating with the combustion chamber (102) and spaced apart from each other in the circumferential direction through the crank chamber (100) ) it is applied to,
A pair of pin bosses (2a, 2b) that protrude radially inward from the inner peripheral surface (12) and into which a piston pin is inserted;
A pair of grooves (3a, 3b) provided on a sliding contact surface (11) in sliding contact with the cylinder block (101) and communicating the exhaust port (103) and the first scavenging port (104, 104); With
The pair of grooves (3a, 3b) are arranged asymmetrically with an imaginary line (C) perpendicular to the axis (A) of the piston (1) and perpendicular to the axis (B) of the piston pin. A piston manufacturing mold (50) for manufacturing the piston (1) ,
A first outer mold (61) that forms a sliding contact surface (11) on the side of one groove (3a) close to the virtual line (C) of the pair of grooves (3a, 3b) in the piston (1); ,
A second outer mold (62) that forms a sliding contact surface (11) on the other groove (3b) side in the piston (1);
A first core mold (71) disposed opposite to the first outer mold (61) and forming an inner peripheral surface (12) on the one groove (3a) side in the piston (1);
Arranged opposite the second outer mold (62) and spaced apart from the first core mold (71), the inner circumference of the piston (1) on the other groove (3b) side A second core mold (72) forming a surface (12);
A central core mold (73) sandwiched between the first core mold (71) and the second core mold (72);
The second core mold (72) has a first protrusion that protrudes inwardly from the inner peripheral surface (12) of the piston (1) corresponding to the one groove (3a) at the time of mold release. An escape portion (72b) for preventing interference with the portion (4a) is provided,
In the second core mold (72), the escape portion (72b) is a surface for making contact with the central core mold (73), and a piston manufacturing mold (50). Prepare piston manufacturing mold (50) according to 請 Motomeko 1,
The first outer mold (61) and the second outer mold (62), the first core mold (71), the second core mold (72), and the central core mold (73). Pour molten material between and
After the material has hardened, the central core mold (73) is extracted along the axis (A) of the piston (1),
When the first core mold (71) is viewed from the direction of the axis (A) of the piston (1), the pin boss (2a) on the one groove (3a) side, and the first protrusion ( 4a), the first core mold (71) is moved to the space after the central core mold (73) is removed, so that the first core mold (71) does not overlap. (71) is extracted along the axis (A) of the piston (1),
When the second core mold (72) is viewed from the direction of the axis (A) of the piston (1), the pin boss (2a) on the other groove (3b) side and the other groove (3b) ) And the second protrusion (4b) protruding inwardly from the inner peripheral surface (12) of the piston (1) so as not to overlap with each other and the first protrusion at the escape portion (72b). The space after the central core mold (73) and the first core mold (71) are extracted from the second core mold (72) so as not to overlap with the portion (4a). And moving the second core mold (72) along the axis (A) of the piston (1).

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