JP5025153B2 - Mold apparatus, cast product, and mold manufacturing method - Google Patents

Description

  The present invention includes a cylindrical inner mold that defines an inner periphery of an annular cavity, and a pair of outer molds that each have an outer periphery defining surface that defines the outer periphery of the cavity in a closed state in half in the circumferential direction. , Mold apparatus adopting a side gate system at a position opposed to the circumferential direction of the cavity by 180 °, a cast product cast by the mold apparatus, a method of manufacturing a pair of outer molds provided in the mold apparatus, and the mold The present invention relates to a casting method using the apparatus.

  An example of a mold apparatus having an annular cavity is a mold apparatus used for casting a vehicle wheel having a cylindrical rim. Hereinafter, a mold apparatus used for casting a vehicle wheel will be described as an example. As a mold apparatus used for casting a vehicle wheel, a cylindrical inner mold (upper mold) for defining the inner periphery of the rim forming space of the cavity, and an outer periphery defining surface for defining the outer periphery of the rim forming space in a closed state There is known a mold apparatus including a pair of outer molds (horizontal molds) each having a half in the circumferential direction (see, for example, Patent Documents 1 and 2). The mold apparatus described in Patent Documents 1 and 2 adopts a side gate method, and is provided on a pair of horizontal type dividing surfaces, and the pair of horizontal types is closed in the circumferential direction of the rim forming space. There are two weir forming spaces respectively connected to the rim forming space from a position opposed to 180 °.

Here, accurate roundness is required for the rim of the vehicle wheel. Although the exact roundness of the rim is finally obtained by cutting after casting, the outer periphery of the rim forming space is round when casting in order to obtain a rim with as high roundness as possible at the casting stage. In fact, a mold apparatus having a perfect circle on the inner circumference is used.
Japanese Patent Laid-Open No. 3-142056 Japanese Patent Laid-Open No. 2-41761

  By the way, in the mold apparatus, various devices have been made to realize directional solidification in which the molten metal gradually solidifies from a position far from the weir toward the weir. However, using the mold apparatus described in the above-mentioned Patent Documents 1 and 2 that employs a side gate method and has a weir formation space that faces 180 °, an attempt is made to obtain a vehicle wheel with as high roundness as possible at the casting stage. , Directional solidification is difficult to achieve. In particular, with the recent increase in the diameter of vehicle wheels, the circumference of the rim forming space has become longer, and it has become increasingly difficult to achieve directional solidification.

  In view of the above circumstances, the present invention is equipped with a mold apparatus that easily realizes directional solidification in which the molten metal gradually solidifies from a position far from the weir toward the weir, a cast product cast by the mold apparatus, and the mold apparatus. It is an object of the present invention to provide a pair of outer mold manufacturing methods and a casting method using the mold apparatus.

In the first mold apparatus of the present invention that solves the above-described object, mold closing and mold opening are performed along a cylindrical inner mold that defines the inner periphery of an annular cavity and a slide surface that is orthogonal to the dividing surface. In a mold apparatus comprising a pair of outer molds each having an outer periphery demarcating surface that defines the outer periphery of the cavity in a state where the mold is closed in half in the circumferential direction.
The pair of outer molds are provided on the dividing surface and have two weir forming spaces respectively connected to the cavities from a position opposed to the circumferential direction of the cavities by 180 ° when the mold is closed. The outline of the outer periphery defining surface is an ellipse having a major axis in the radial direction along the dividing surface of the cavity.

  In order to actually use the produced mold on the production line at the casting site, it is necessary to perform trial casting (so-called test blowing) several tens of times to set and confirm casting conditions. It is common for molds that have finished test blowing to cool to room temperature before being placed on the production line, but when the pair of external molds that have finished test blowing have cooled to room temperature, the residual stress produced during mold production. As a result, the outline of the outer periphery defining surface becomes a perfect circle. However, when the first mold apparatus of the present invention is actually used on the production line, the pair of outer molds are heated again and thermally expanded, so that the contour of the outer periphery defining surface returns to an ellipse.

The mold manufacturing method of the present invention that solves the above-described object includes a cylindrical inner mold that defines the inner periphery of an annular cavity, and mold closing and mold opening along a slide surface that is orthogonal to the dividing surface. And a pair of outer molds each having a half of an outer periphery defining surface in the circumferential direction for defining the outer periphery of the mold in a closed state, provided on the split surface, and the cavity in a state in which the pair of outer molds are closed In the mold manufacturing method for a pair of outer molds provided in a mold apparatus having two weir formation spaces respectively connected to the cavity from a position opposed to the circumferential direction by 180 °,
A mold production process for producing a pair of outer molds in which the contour of the outer periphery defining surface is a perfect circle;
A heating step of heating the pair of produced outer molds;
The outer peripheral demarcation surface deformed into an ellipse having a major axis in a direction perpendicular to the slide surface with respect to the radial direction along the dividing surface of the cavity by cooling the pair of heated outer molds to room temperature. And a processing step of processing the contour into a perfect circle.

  According to the mold manufacturing method of the present invention, when the pair of heated outer molds are cooled to room temperature, the outline of the outer peripheral demarcation surface is changed from a perfect circle to the ellipse due to residual stress generated when the mold manufacturing process is performed. However, in the processing step, the contour of the deformed outer periphery defining surface is returned to a perfect circle. When the pair of outer molds subjected to this processing step are actually used on a production line, the pair of outer molds are heated again and thermally expanded, so that the contour of the outer peripheral demarcation surface is subjected to residual stress. It becomes an ellipse having a major axis in the radial direction, which is different from the ellipse. In addition, in the mold manufacturing process, since a pair of outer molds whose outer peripheral demarcation surfaces have a perfect circle need only be manufactured, a mold is manufactured as compared with a pair of outer molds whose contour is an ellipse. Is easy.

In the second mold apparatus of the present invention for solving the above-described object, mold closing and mold opening are performed along a cylindrical inner mold that defines the inner periphery of an annular cavity and a slide surface that is orthogonal to the dividing surface. In a mold apparatus comprising a pair of outer molds each having an outer periphery demarcating surface that defines the outer periphery of the cavity in a state where the mold is closed in half in the circumferential direction.
The inner mold defines the inner circumference of the cavity, and the contour defines an inner circumference that is an ellipse having a major axis in a direction orthogonal to the radial direction along the dividing surface of the cavity on the slide surface. Has a surface,
The pair of outer molds are provided on the dividing surface and have two weir forming spaces respectively connected to the cavity from a position opposed to the circumferential direction of the cavity by 180 ° when the mold is closed. The outline is a perfect circle or an ellipse having a major axis in the radial direction in a state of thermal expansion during casting.

  Since the inner mold is cylindrical, it is less affected by deformation due to residual stress or thermal expansion generated during mold fabrication than the pair of outer molds.

A cast product cast using the first and second mold apparatuses of the present invention, and a cast product cast using a mold apparatus including a pair of outer molds manufactured by the mold manufacturing method of the present invention, It corresponds to a casting of the present invention that solves the above-mentioned object. That is, the casting of the present invention includes an annular body,
A pair of weirs connected to the annular body at positions facing 180 °,
The annular body is characterized in that the wall thickness gradually decreases from a portion where each of the pair of weirs is connected toward a portion shifted by 90 ° from the portion in the circumferential direction of the annular body. To do.

  The cast product of the present invention has a shape that facilitates directional solidification in which the molten metal gradually solidifies from a position far from the pair of weirs toward the pair of weirs due to a thickness gradient in the circumferential direction of the annular body. It can be said that this is a cast product. That is, according to the first and second mold apparatuses of the present invention and the mold apparatus including a pair of outer molds manufactured by the mold manufacturing method of the present invention, the pair of outer molds thermally expanded during casting and the above-mentioned The cavity formed by the inner mold has a dam front portion between the dam front portion where the two dam formation spaces are connected to each other and a portion shifted by 90 ° from the dam front portion in the circumferential direction of the cavity. Is provided with a thickness gradient that becomes the thickest space, and the directional solidification is easily realized. In addition, what is necessary is just to cut in a post process, in order to obtain the exact roundness of the said cyclic | annular body.

In the third mold apparatus of the present invention that solves the above-described object, mold closing and mold opening are performed along a cylindrical inner mold that defines the inner periphery of an annular cavity and a slide surface that is orthogonal to the dividing surface. A pair of outer molds each having an outer periphery demarcating surface that divides the cavity outer periphery in a state in which the mold is closed in half in the circumferential direction. In a mold apparatus having two weir formation spaces respectively connected to the cavity from a position opposed to the circumferential direction of the cavity by 180 °,
An air cooling means for air-cooling the front part of the dam where each of the dam formation spaces of the cavity is connected;
Mist cooling means for mist cooling a portion of the cavity that is shifted by 90 ° in the circumferential direction of the cavity from the front portion of the weir is provided.

  The first and second mold apparatuses according to the present invention make it easy to realize the directional solidification by the thickness gradient of the cavity. This third mold apparatus is different in the cooling capacity of the cooling means for cooling the cavity. Thus, the directional solidification can be easily realized. That is, the mist cooling means is a cooling means for spraying a liquid as a cooling medium, and has a cooling capacity higher than that of the air cooling means for cooling by air, and also a cooling pipe for cooling by circulating the liquid. The cooling capacity is higher than that. Accordingly, the portion of the cavity that is shifted by 90 ° from the front portion of the weir is strongly cooled, and the portion can be solidified earliest. On the other hand, the front part of the weir remains relatively weakly cooled, and the front part of the weir can be finally solidified.

In the casting method of the present invention that solves the above-described object, mold closing and mold opening are performed along a cylindrical inner mold that defines the inner periphery of an annular cavity and a slide surface that is orthogonal to the dividing surface. A pair of outer molds each having an outer periphery demarcating surface that divides the outer periphery in a state in which the mold is closed in half in the circumferential direction. In a casting method in which casting is performed using a mold apparatus having two weir formation spaces respectively connected to the cavity from a position facing 180 ° in the circumferential direction,
A pouring process for filling the cavity with molten metal;
A first cooling start step for starting cooling the portion of the cavity that is shifted by 90 ° in the circumferential direction of the cavity from the front portion of the dam where the dam formation spaces are connected, after completion of the pouring step;
And a second cooling start step for starting cooling of the front portion of the weir after the first cooling start step.

  In the casting method of the present invention, the directional solidification is easily realized by varying the cooling start timing. Further, by performing the casting method of the present invention using the third mold apparatus of the present invention, the directional solidification is further easily realized.

  In the third mold apparatus of the present invention, it is preferable that the mist cooling means starts mist cooling at a start timing earlier than the air cooling start timing by the air cooling means.

  According to the present invention, a mold apparatus that can easily realize directional solidification in which a molten metal gradually solidifies from a position far from the weir toward the weir, a cast product cast by the mold apparatus, and a pair provided in the mold apparatus It is possible to provide an outer mold manufacturing method and a casting method using the mold apparatus.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view showing the internal structure of a low-pressure casting mold apparatus according to an embodiment of the present invention.

  A mold apparatus 1 for low-pressure casting shown in FIG. 1 adopts a side gate method used when casting a dish type vehicle wheel, and includes a lower mold 11, an upper mold 12, and a pair of horizontal molds 13. And. These molds 11 to 13 are all molds. A vehicle wheel cast using this mold apparatus 1 has a cylindrical rim and a disk provided with a window connected to the inner peripheral surface of the rim.

  FIG. 1 shows a mold apparatus 1 that is closed. In FIG. 1, a lower mold 11, an upper mold 12, and a pair of horizontal molds 13 are not shown in FIG. For the sake of clarity, the lower mold 11 is subjected to left-down hatching, the upper mold 12 is subjected to right-down hatching, and the pair of horizontal molds 13 are subjected to cross hatching.

  The lower mold 11 shown in FIG. 1 is fixedly arranged on the lower mold platen 140. On the other hand, the upper mold 12 is movable up and down. The upper mold 12 is fixed to an upper mold platen 150 that is attached to a piston rod 151 of a cylinder (not shown) and moves up and down, and moves up and down as the upper mold platen 150 moves up and down. Note that an accommodation space 141 in which piping (not shown) serving as a cooling medium conveyance path is accommodated inside the lower mold platen 140.

  The pair of horizontal molds 13 are such that the mold opens when they are separated from each other and closes when they approach each other until they come into contact. The horizontal mold 13 shown in FIG. 1 slides on the horizontal surface 140a of the lower mold platen 140 in a direction perpendicular to the paper surface of FIG. That is, in the pair of horizontal molds 13, the horizontal surface 140 a of the lower mold platen 140 orthogonal to the dividing surface (parting surface) 13 a becomes a slide surface, and mold closing and mold opening are performed along the horizontal plane 140 a. FIG. 1 shows only one horizontal mold 13 of the pair of horizontal molds 13, and the one horizontal mold 13 is closed by sliding toward the front side of the paper, and slides toward the back side of the paper. To open the mold.

  In the mold apparatus 1 shown in FIG. 1, the upper mold 12 descends on the fixedly arranged lower mold 11 and closes to each other until the pair of horizontal molds 13 come into contact with each other, so that the cavity C is formed. It is formed. The horizontal mold 13 forms the outer peripheral surface of the rim of the vehicle wheel, and the lower mold 11 forms the front surface (design surface) of the disk of the vehicle wheel. Further, the upper mold 12 forms the inner peripheral surface of the rim and also forms the back surface of the disk.

  On the other hand, in the mold apparatus 1 that is closed, the pair of horizontal molds 13 are separated from each other and the upper mold 12 is raised so that the mold is opened. The cast product of the vehicle hole obtained by filling the cavity C with the molten metal is not separated from the rising upper mold 12, and the flange tip (so-called inner rim flange) of the rim opposite to the disk is not shown. By being pushed downward by the pushing plate, the upper die 12 is removed.

  Further, in the mold apparatus 1 shown in FIG. 1, a gate collar 161 provided with a recess 1611 is provided on the horizontal surface 140 a of the lower mold platen 140 that becomes the slide surface of the horizontal mold 13. A stalk 170 is connected to the recess 1611, and a strainer (not shown) is set in the recess 1611. The gate collar 161 is attached to the upper end of the stalk 170 by a presser plate 162. The stalk 170 is inserted into a closed holding furnace (not shown), and the stalk 170 is provided with a heat insulating material 171. A molten aluminum is held in the holding furnace. By applying a pressure of 2 MPa or more and 10 MPa or less to the molten metal, the molten metal in the holding furnace reaches the recess 1611 through the stalk 170. Therefore, the opening of the recess 1611 becomes the gate 160 of the mold apparatus 1 shown in FIG. In the mold apparatus 1 shown in FIG. 1, a pouring bracket 163 is provided in order to prevent the molten metal reaching the pouring gate 160 from leaking between the horizontal mold 13 and the lower mold platen 140.

A pair of horizontal 13, the cavity C in the mold closed state, the cylindrical rim forming space C _R in the circumferential direction into two leading respectively from 180 ° opposite positions on the rim molding space C _R weir forming space 131 Have. These two dam formation spaces 131 are formed in the split surfaces 13 a of the pair of horizontal molds 13. FIG. 1 shows a state in which the right half of the mold apparatus 1 is cut along a split surface 13a of a pair of horizontal molds 13, and a state in which the left half is cut along a plane different from the split surface 13a. Therefore, the weir forming space 131 is shown only on the right side of FIG. Note that the gate 160 is also provided at a position opposed to 180 °, but only the gate 160 on the right side is shown in FIG.

  The pair of horizontal molds 13 also has a runner formation space 132 that connects the gate 160 and the weir formation space 131 in a closed state. This runner formation space 132 is also formed on the split surface 13a of the pair of horizontal molds 13. At the time of filling the cavity C with the molten metal, the molten metal that has reached the gate 160 from a holding furnace (not shown) is filled into the cavity C from the weir forming space 131 through the runner forming space 132. The runner formation space 132 shown in FIG. 1 extends toward the dam formation space 131 by bending about 90 ° after the portion connected to the gate 160 rises. That is, the runner formation space 132 is provided with a portion 1321 that extends substantially parallel to the horizontal surface 140 a of the lower mold platen 140. The thickness of the runner formation space 132 in the vicinity of the weir formation space 1322 is thicker than the thickness of the runner formation space 132 in the vicinity of the gate 160.

  The pair of horizontal molds 13 also has a belly rib forming space 133 and a ventral bulge forming space 134. The belly rib forming space 133 is a space that extends from the runner formation space 132 toward the horizontal plane 140a along the dividing surface 13a and is thinner than the thickness of the runner formation space 132. The ventral bulging portion molding space 134 bulges to the tip 1331 of the belly rib molding space 133, and one end is connected to the edge 160 a of the gate 160 and the other end is connected to the dam formation space vicinity portion 1322 of the runner forming space 132. Space. Further, the pair of horizontal molds 13 also have a back rib forming space 135 and a back bulging portion forming space 136. The back rib forming space 135 is a space that extends from the runner forming space 132 toward the opposite side of the horizontal surface 140a along the dividing surface 13a and is separated from the cavity C and is thinner than the thickness of the runner forming space 132. The back side bulging portion forming space 136 is a space that swells at the tip 1351 of the back rib forming space 135, one end connected to the edge 160 a of the gate 160 and the other end connected to the weir forming space 131. When the molten metal flows in the runner formation space 132, the molten metal inevitably enters the dividing surface 13a. In the mold apparatus 1 shown in FIG. 1, by utilizing this tendency, an abdominal rib molding space 133 and a back rib molding space 135 are provided, and the molten metal is actively guided to the spaces 133 and 135, and the molten metal is fed to the ventral side bulging portion. It inserts in the shaping | molding space 134 or the back side bulging part shaping | molding space 136. When the molten metal that has passed through the abdominal rib molding space 133 and the back rib molding space 135 enters the abdominal bulging portion molding space 134 and the back bulging portion molding space 136, the space suddenly expands, and those spaces 134 are also expanded. , 136 is in a negative pressure state, the molten metal stays in the spaces 134, 136, and while it stays, the horizontal mold 13 is deprived of heat and solidifies. Therefore, the molten metal does not enter the split surface 13a until it exceeds the ventral bulge portion forming space 134 and the back bulge portion forming space 136. Further, the molten metal in the belly rib forming space 133 and the molten metal in the back rib forming space 135 solidify faster than the molten metal in the runner forming space 132, and the solidified melt plays the role of fins, so that the molten metal in the runner forming space 132 is melted. Cooling is promoted. Further, the runner is reinforced by the molten metal solidified in the belly rib molding space 133 and the back rib molding space 135 and the molten metal solidified in the belly side bulging portion molding space 134 and the back side bulging portion molding space 136.

The portion of the runner formation space 132 near the weir formation space 1322 is thicker on the side where the belly rib forming space 133 is provided than on the side where the back rib forming space 135 is provided. In FIG. 1, the upper mold 12, the base space are expressed surface 120 to form a portion where there is the most thickness of the disk forming space C _D by the dotted lines, in which the rim forming space C _R, leading to a disk forming space C _D C _RD is a fairly thick space. Further, the weir forming space 131 is a thinner space than the runner forming space 132. In addition to increasing the thickness of the portion 1322 near the dam formation space of the runner formation space 132, further increasing the thickness on the side of the dam formation space vicinity portion 1322 where the belly rib forming space 133 is provided. Thus, a temperature gradient is secured between the portion 1322 near the dam formation space and the root space C _RD with the thin dam formation space 131 interposed therebetween, and before the molten metal in the root space C _RD solidifies, The molten metal is prevented from solidifying.

  Furthermore, a vent hole 138 is provided in the portion of the horizontal mold 13 that forms the inner rim flange of the vehicle wheel rim. The vent hole 138 communicates with the cavity 13 b in the horizontal mold 13.

  The lower mold | type 11 has the nest | insert 112 which forms the front surface of the boss | hub part provided in the disk of a vehicle wheel in the center part. The insert 112 has a two-piece structure including a base 1120 and a hub hole forming body 1121. The hub hole forming body 1121 protrudes toward the upper mold and forms a hub hole of the vehicle wheel. The hub hole forming body 1121 is hollow, and an air cooling pipe (not shown) is disposed in the hub hole forming body 1121. A water cooling pipe 1122 is also embedded in the base 1120. Further, a water cooling pipe 1111 is embedded in the lower mold so as to surround the base body 1120 of the insert 112.

Inside the upper mold 12, a cavity 12 a having a central portion opening toward the lower mold 11 is provided. The upper mold 12 also has a nesting 20, and the nesting 20 of the upper mold 12 is disposed in the cavity 12a so as to close the opening 12b in the central portion of the cavity 12a. Nested 20 of the upper mold 12, to form a rear surface of the boss portion of the vehicle wheel, but also to form riser forming space R leading to the boss forming space portion C _B of the cavity C as shown in FIG. A storage chamber 21 is provided in the central portion of the insert 20 of the upper mold 12. In the accommodation chamber 21, the demarcating member 220 having the inner peripheral edge 221 is stacked with a gap connected to the hot water forming space R between adjacent demarcating members 220. The hot water forming space R is defined by the inner peripheral edge 221 of each of the defining members 220 stacked in the accommodation chamber 21. The storage chamber 21 has a peripheral wall 211 and an upper lid 212. The upper lid 212 is fixed to the peripheral wall 211 by a wheel 213 and is in contact with the uppermost defining member 220. A pressing bolt 214 is provided on the upper lid 212, and the defining member 220 is pressed downward by the pressing bolt 214. For this reason, it is prevented that the demarcating member 220 floats up when the molten metal is filled into the cavity C. Further, the uppermost demarcating member 220 has a space S between an outer peripheral portion from a position outside the inner peripheral edge 221 to the outer peripheral edge 222 and the upper lid 212. The space S and the gap provided between the demarcating members 220 adjacent in the accommodation chamber 21 are connected by a not-shown vertical groove provided on the outer peripheral edge 222 of each demarcating member 220. An air flow path pipe 31 is connected to the space S in the storage chamber 21. When the molten metal is filled into the cavity C, the air in the cavity C reaches the space S in the storage chamber 21 through the gap provided between the adjacent defining members 220 and passes through the air flow path pipe 31. Discharged outside. The air in the cavity C also escapes from the vent hole 138 provided in the horizontal mold 13. On the other hand, immediately after the filling of the molten metal into the cavity C is completed, pressurized air is supplied from the air passage pipe 31. The molten metal filled in the hot water forming space R is pushed by the pressurized air supplied by the air flow path pipe 31 from the gaps different in the height direction provided between the adjacent demarcating members 220, and sufficient A feeder effect is obtained.

In addition, two types of cooling means including an air cooling pipe 121 and a mist cooling means 122 are provided in the cavity 12 a of the upper mold 12. The air cooling pipe 121 performs cooling by blowing air from a plurality of locations different in the height direction corresponding to the rim width direction of the vehicle wheel. The mist cooling means 122 performs cooling by spraying water. The mist cooling means 122 shown in FIG. 1 sprays water toward the portion of the rim of the vehicle wheel that forms the hump provided on the side opposite to the disk (so-called inner side). spread, the entire part corresponding to the inner side of the rim forming space C _R is strongly cooled.

  FIG. 2 is a diagram schematically showing the internal structure of the upper die when the upper die during casting is viewed from above.

The Figure 2 is shown a pair of horizontal 13 with two halves outer peripheral defining surface 137 that defines a state in which closed the mold the outer periphery of the annular rim forming space C _R in the circumferential direction, one point in FIG. A chain line is a line indicating the split surface 13 a of the pair of horizontal molds 13. Further, in FIG. 2, the provided dividing surface 13a, respectively, from 180 ° opposite positions in the circumferential direction of the rim forming space C _R in a state where the pair of outer mold 13 is closed mold to the rim forming space C _R Two connected weir forming spaces 131 are also shown.

Cooling pipe 121 shown in FIG. 2, the rim forming space C _R, in which each weir forming space 131 to cool the dam front portion G led is. On the other hand, the mist cooling means 122, the rim forming space C _R, the moiety A shifted 90 ° in the circumferential direction of the rim forming space C _R from the dam front portion G is for mist cooling. There is a large difference in cooling capacity between the air cooling pipe 121 and the mist cooling means 122. The mist cooling means 122 not only has a higher cooling capacity than the air cooling pipe 121 but also circulates liquid to perform cooling. The cooling capacity is higher than that of the cooling pipe (for example, the water cooling pipes 1111 and 1122 arranged in the lower mold shown in FIG. 1). Thus, the mold apparatus 1 shown in FIG. 1, the rim forming space C _R, the portion A which is shifted 90 ° from the dam front portion G is strongly cooled, can be most quickly solidify the portion A. On the other hand, the pre-weir portion G remains relatively weakly cooled, and the pre-weir portion G can be finally solidified. Therefore, the mold apparatus shown in FIG. 1 facilitates the directional solidification in which the molten metal gradually solidifies from a position far from the pair of weirs toward the pair of weirs due to the difference in cooling capacity of the cooling means. This corresponds to an embodiment of the third mold apparatus of the present invention.

As shown in FIG. 2, the upper mold 12 is a cylindrical mold, and is less affected by deformation due to residual stress generated during mold fabrication and deformation due to thermal expansion during casting. The upper mold 12 during the casting shown in Figure 2, the contour of the inner peripheral defining surface 123 that defines the inner circumference of the rim forming space C _R is a perfect circle. On the other hand, the respective horizontal molds constituting the pair of horizontal molds 13 are easily affected by deformation due to residual stress generated during mold production or deformation due to thermal expansion during casting. A pair of horizontal 13 shown in FIG. 2 is deformed by thermal expansion during casting, the contoured rim forming space C _R of the outer peripheral defining surface 137, the length in the radial direction (see arrow Y) along the dividing surface 13a An ellipse with an axis. Thus, the rim forming space C _R shown in FIG. 2, the thickness gradient in which the dam front portion G becomes a space the most thick between the weir front portion G, and from the dam front portion G 90 ° displaced portions A becomes what is provided, the rim forming space C _R, directional solidification is easily achieved towards the weir.

  Then, the casting process which casts using the casting_mold | template apparatus shown in FIG. 1 is demonstrated.

  FIG. 3 is a flowchart showing a casting process in which casting is performed using the mold apparatus shown in FIG.

  First, foreign substances such as dust are removed from the molds 11 to 13 in the mold open state, and a strainer is set in the recess 1611 provided in the gate collar 161 to close the mold of the mold apparatus 1 (step S1). . In addition, before performing this mold closing, if necessary, in order to improve the heat retaining property of the mold and the mold releasability of the cast product, a mold forming agent mainly composed of silica is sprayed on the molds 11 to 13. At this time, the coating agent is sprayed and pressurized air is supplied from the air channel pipe 31 into the accommodating chamber 21 so that the coating agent does not enter the gap of the demarcating member 220 that defines the hot water forming space R. It is preferable to blow out pressurized air from the gap.

  Subsequently, the molten metal in the holding furnace (not shown in FIG. 1) is filled with the molten metal into the cavity C of the mold apparatus 1 which has been closed by applying a pressure of 2 MPa to 10 MPa (step S2). At this time, the air in the cavity C escapes through the gap of the demarcating member 220 that demarcates the hot water forming space R and also escapes from the vent hole 138 of the horizontal mold 13. Immediately after the filling of the molten metal into the cavity C is completed, pressurized air is supplied from the air channel pipe 31 into the housing chamber 21, and the molten metal filled in the hot water forming space R is pushed from the gap of the defining member 220. In this way, a sufficient hot-spring effect is obtained.

Then, mist cooling by the mist cooling means 122 starts, the rim forming space C _R shown in FIG. 2, 90 ° displaced portions A in the circumferential direction of the rim forming space C _R weir front portion G is strongly cooled (step S3). Then, the air cooling by air cooling pipe 121 starts, the rim forming space C _R, dam front portion G is weakly cooled (step S4). The previous step S3 corresponds to an example of a first cooling start process in the casting method of the present invention, and this step S4 corresponds to an example of a second cooling start process in the casting method of the present invention. In this way, by accelerating the cooling start timing by the mist cooling means 122 from the cooling start timing by the air cooling pipe 121, the directivity that the molten metal gradually solidifies from a position far from the pair of weirs toward the pair of weirs. Solidification is easier to achieve. In addition, as described with reference to FIG. 2, the rim forming space _CR has the thickest dam formation portion G between the dam front portion G and the portion A that is shifted by 90 ° from the dam front portion G. since the thickness gradient that causes the space in which is provided, the rim forming space C _R, directional solidification becomes more more easily achieved towards the weir. Incidentally, even if no such thickness gradient is provided on the rim forming space C _R, performing the step S4 to the step S3 after the implementation, the rim forming space C _R, directional solidification towards the weir It becomes an effective means for realizing.

  When a predetermined cooling time has elapsed, mold opening is performed (step S5). Subsequently, the cast product of the vehicle hole is extracted from the mold apparatus 1 (step S6), and the series of casting processes is completed.

  FIG. 4 is a view showing a cast product of a vehicle wheel cast by performing the casting process shown in FIG.

  The cast product W of the vehicle wheel shown in FIG. 4 corresponds to an embodiment of the cast product of the present invention. This cast product W is in a state before casting, a cylindrical (annular) rim 91, a disk (not shown) connected to the inner peripheral surface of the rim 91 and provided with a window portion, and the rim 91. , And a pair of weirs 92 connected to positions opposed to each other by 180 °. The thickness of the rim 91 gradually decreases from a portion 911 where the pair of weirs 92 are connected to a portion 912 that is shifted by 90 ° from the portion 911 in the circumferential direction of the rim 91. A runner 93 is connected to the weir 92 shown in FIG. In the cast product W of the vehicle wheel shown in FIG. 4, the exact roundness of the rim 91 is obtained by cutting performed in a subsequent process.

  Next, a pair of horizontal mold manufacturing methods shown in FIG. 2 will be described.

  FIG. 5 is a diagram showing step by step how the pair of horizontal molds shown in FIG. 2 is manufactured.

  Fig.5 (a) is a figure which shows a pair of horizontal type | mold immediately after finishing metal mold | die preparation.

The contour of the outer peripheral defining surface 137 of the pair of lateral 13 shown in FIG. 5 (a), the rim forming space C _R shown in FIG. 2, an ellipse having a major axis in the radial direction Y along the split surface 13a. In short, the outline of the outer periphery defining surface 137 is an ellipse that is long on the weir side.

  FIG. 5B is a view showing a pair of horizontal molds that have been cooled to room temperature after being subjected to experimental casting (so-called test blowing) several tens of times.

  Trial casting is performed in order to set and confirm casting conditions before actually using the produced mold on the production line on the casting site. The pair of horizontal molds 13 which have been cooled to room temperature after being subjected to a test casting of several tens of times are deformed so as to enter the inner side due to residual stress generated during the mold production (see arrows in the figure), and The contour becomes a perfect circle.

  FIG.5 (c) is a figure which shows a pair of horizontal mold | type which deform | transformed by thermal expansion by attaching a pair of horizontal mold | type shown in FIG.5 (b) to a casting_mold | template apparatus, and actually using it on the manufacturing line of a casting field.

  The pair of horizontal molds 13 whose outer periphery defining surface 137 has a perfect circle shape when cooled to room temperature are deformed so as to open outward by thermal expansion during casting in the field (see arrows in the figure). The outline of returns to a long ellipse on the weir side. That is, the contour substantially coincides with the contour of the outer periphery defining surface 137 of the pair of horizontal molds 13 immediately after the mold production is finished, as shown in FIG. In the mold manufacturing method described here, the contour of the outer periphery defining surface 137 is made elliptical in advance in the mold manufacturing stage in anticipation of thermal expansion of the pair of horizontal molds 13. A mold apparatus 1 shown in FIG. 1 includes a pair of horizontal molds 1 manufactured in this manner, and corresponds to an embodiment of the first mold apparatus of the present invention.

  Next, an embodiment of the mold manufacturing method of the present invention will be described.

  FIG. 6 is a diagram showing step by step how a pair of horizontal molds are manufactured by the mold manufacturing method according to an embodiment of the mold manufacturing method of the present invention.

  Fig.6 (a) is a figure which shows a pair of horizontal type | mold immediately after finishing metal mold | die preparation.

  The outline of the outer periphery defining surface 137 of the pair of horizontal molds 13 shown in FIG. 6A is a perfect circle. That is, in the mold manufacturing method of the present embodiment, first, a pair of horizontal molds 137 in which the contour of the outer periphery defining surface 137 is a perfect circle is manufactured (mold manufacturing process). The pair of horizontal dies 13 are molds, and in order to process the contour of the outer periphery defining surface 137 into a perfect circle, it may be simply processed by a lathe, and the processing is easier than when processing the contour into an ellipse.

  FIG. 6B is a diagram showing a pair of horizontal molds which have been cooled to room temperature after performing trial casting about several tens of times.

The produced pair of horizontal molds 13 is heated by performing trial casting about several tens of times (heating process). Then, the pair of horizontal molds 13 which have been cooled to room temperature after completing several tens of trial castings are deformed so as to enter the inside again due to residual stress generated during mold production (see the arrows in the figure). contour defining plane 137, the rim forming space C _R shown in FIG. 2, the ellipse having a major axis in the direction X orthogonal in the horizontal plane 140a of the lower platen 140 in the radial direction Y along the dividing surface 13a Become. Therefore, the outer periphery defining surface 137 whose contour is deformed into an ellipse is shaved with a grinder or the like, and the contour is processed into a perfect circle (machining process). That is, only a portion deformed from the outline at the time of mold production is scraped off by a grinder or the like. In FIG. 6B, the outer periphery defining surface 137 whose contour is processed into a perfect circle is indicated by a dotted line.

  FIG. 6C is a view showing a pair of horizontal molds that are deformed by thermal expansion by attaching the pair of horizontal molds shown in FIG. 6B to a mold apparatus and actually using them on a production line at a casting site.

  The pair of horizontal molds 13 that have been processed to return to a perfect circle are deformed so as to open to the outside again by thermal expansion during casting in the field (see arrows in the figure), and the contour of the outer periphery defining surface 137 is the weir side It transforms into a long ellipse. Thus, the pair of horizontal molds 13 manufactured by the mold manufacturing method of the present embodiment can be paired with a pair of horizontal molds similar to the pair of horizontal molds 13 shown in FIG. 13

  Finally, an embodiment of the second mold apparatus of the present invention will be described. In the following description, descriptions overlapping with those described so far will be omitted, and components having the same names as the names of the components described so far will be described with the same reference numerals used. The mold apparatus described here also employs a side gate method used when casting a vehicle wheel, like the mold apparatus shown in FIG. An upper mold 12 and a pair of horizontal molds 13 are provided. The difference between this mold apparatus and the mold apparatus shown in FIG. 1 is the contour of the inner periphery defining surface 123 of the upper mold and the contour of the outer periphery defining surfaces 137 of the pair of outer molds.

  FIG. 7 is a schematic plan view of an upper mold and a pair of horizontal molds provided in the mold apparatus which is an embodiment of the second mold apparatus of the present invention as viewed from above.

  In FIG. 7, the pair of horizontal molds 13 is closed and opened by sliding in the horizontal direction in the figure on the horizontal surface 140a of the lower mold platen. FIG. 7 shows a pair of horizontal molds 13 in an opened state. Although not shown here, the dividing surfaces 13a of the pair of horizontal dies 13 are also provided on the periphery of an annular rim forming space that is a part of the cavity when the mold is closed, as in the mold apparatus 1 shown in FIG. Two weir forming spaces are provided respectively connected to the rim forming space from a position opposed to the direction by 180 °. When the pair of horizontal molds 13 shown in FIG. 7 are closed, the outline of the outer periphery defining surface 137 is a direction X orthogonal to the radial direction Y along the dividing surface 13a of the annular rim forming space on the horizontal plane 140a. Becomes an ellipse having a major axis. That is, simply speaking, the outline of the outer periphery defining surface 137 is an ellipse that is long in the sliding direction of the horizontal mold 13.

  Also, the contour of the inner periphery defining surface 123 of the upper mold 12 shown in FIG.

  FIG. 8 is a schematic plan view of the upper die during casting as seen from above.

8, a pair of lateral 13 having two halves outer peripheral defining surface 137 that defines a state in which closed the mold the outer periphery of the annular rim forming space C _R in the circumferential direction is also shown, one-dot chain line in FIG. These are the lines indicating the split surfaces 13a of the pair of horizontal molds 13. The pair of horizontal molds 13 shown in FIG. 8 also perform mold closing and mold opening by sliding in the horizontal direction in the figure. Further, in this figure 8, the rim forming space C _R 2 two leading each of the weir forming space 131 is also shown.

The upper mold 12 is a cylindrical mold, and is less affected by deformation due to residual stress generated during mold manufacture or due to thermal expansion during casting. Susceptible to deformation due to thermal expansion during casting. The contour of the inner periphery defining surface 123 of the upper mold 12 shown in FIG. 8 is substantially the same as the contour of the inner periphery defining surface 123 of the upper mold 12 shown in FIG. It is. On the other hand, the pair of horizontal molds 13 shown in FIG. 8 is deformed by thermal expansion during casting, and the contour of the outer periphery defining surface 137 is a perfect circle. Accordingly, the rim forming space C _R shown in FIG. 8 is also in front of the dam between the dam front portion G and the portion A shifted by 90 ° from the dam front portion G, similarly to the rim forming space C _R shown in FIG. becomes what thickness gradient portion G becomes a space where the most thick is provided, the rim forming space C _R, directional solidification is easily achieved towards the weir.

  Further, when casting is performed using the mold apparatus of the present embodiment, a vehicle wheel cast product W shown in FIG. 4 is obtained. Here, when the molten metal filled in the cavity C is solidified and the mold is opened, the upper mold 12 is raised, and the cast product W of the vehicle hole is not separated from the rising upper mold 12 and will rise with the upper mold 12. And At this time, twisting occurs at the gate 160 (see FIG. 1), and the base portions of the pair of dams 92 of the rim 91 are pulled away from each other, which may cause distortion in the cast product of the vehicle wheel. That is, the rim 91 may extend in the radial direction Y along the dividing surface 13a. Even if the rim 91 does not extend in the radial direction Y when the mold is opened, the rim 91 may extend in the radial direction Y due to distortion at this time in a heat treatment step performed in a later step. . However, since the inner peripheral shape of the rim 91 cast by the mold apparatus of the present embodiment is an ellipse having a major axis in the direction X orthogonal to the radial direction Y, the rim 91 extends in the radial direction Y. Then, the inner peripheral shape of the rim 91 is just a perfect circle.

  In the mold apparatus of the present embodiment, the pair of horizontal molds 13 in which the contour of the outer periphery defining surface 137 becomes a perfect circle at the time of casting is used. However, due to the balance with the contour of the inner periphery defining surface 123, the outer periphery defining surface 137 at the time of casting is used. A pair of horizontal molds may be used in which the outline is an ellipse having a major axis in the radial direction Y.

  In the above description, the low pressure casting mold apparatus used when casting the vehicle wheel has been described as an example. However, the present invention provides a mold apparatus used when casting an article other than the vehicle wheel. Can also be applied. The present invention can also be applied to a mold apparatus for pressure casting other than low pressure casting.

It is sectional drawing which shows the internal structure of the casting_mold | template apparatus for low pressure casting which is one Embodiment of this invention. It is a figure which shows typically the internal structure of the upper type | mold when the upper type | mold at the time of casting is seen from upper direction. It is a flowchart which shows the casting process which casts using the casting_mold | template apparatus shown in FIG. It is a figure which shows the cast product of the wheel for vehicles cast | casted by implementing the casting process shown in FIG. It is the figure which showed a mode that a pair of horizontal type | mold shown in FIG. 2 was manufactured in steps. It is the figure which showed a mode that a pair of horizontal mold | die was manufactured by the mold manufacturing method which is one Embodiment of the mold manufacturing method of this invention in steps. It is the typical top view which looked at the upper mold and a pair of horizontal molds which were arranged in the mold apparatus which is one embodiment of the 2nd mold apparatus of the present invention from the upper part. It is the typical top view which looked at the upper model at the time of casting from the upper part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold apparatus 11 Lower mold 12 Upper mold 121 Air cooling pipe 122 Mist cooling means 123 Inner periphery demarcation surface 13 Horizontal type 13a Dividing surface 131 Weir formation space 132 Runway formation space 137 Outer periphery demarcation surface 160 Pouring gate C Cavity C _R rim forming space G Weir Front part

Claims (5)

A cylindrical inner mold that defines the inner periphery of the annular cavity, and an outer periphery definition that defines the outer periphery of the cavity with the mold closed while the mold is closed and opened along a slide surface orthogonal to the dividing surface. In a mold apparatus comprising a pair of outer molds each having a half surface in the circumferential direction,
The inner mold defines an inner periphery of the cavity, and has an inner periphery defining surface that is a perfect circle in a state where the contour is thermally expanded during casting;
The pair of outer molds are provided on the dividing surface and have two weir formation spaces respectively connected to the cavities from positions opposed to the circumferential direction of the cavities by 180 ° when the mold is closed. The contour of the outer periphery defining surface in the state and the state of thermal expansion during casting is an ellipse having a major axis in the radial direction along the dividing surface of the cavity ,
The cavity formed by the pair of outer molds thermally expanded at the time of casting and the inner mold thermally expanded at the time of casting includes a front part of the weir connected to each of the two weir forming spaces, and the circumferential direction of the cavity. A mold apparatus , wherein a thickness gradient is provided between the front portion of the weir and a portion shifted by 90 ° from which the front portion of the weir is thickest. A cylindrical inner mold that defines the inner periphery of the annular cavity, and an outer periphery definition that defines the outer periphery of the cavity with the mold closed while the mold is closed and opened along a slide surface orthogonal to the dividing surface. In a mold apparatus comprising a pair of outer molds each having a half surface in the circumferential direction,
The inner mold defines an inner circumference of the cavity, and a long axis extends in a direction perpendicular to the slide surface with respect to a radial direction along the dividing surface of the cavity in a state where the contour is thermally expanded during casting. Having an inner periphery defining surface that is an ellipse having,
The pair of outer molds are provided on the dividing surface, and have two weir forming spaces respectively connected to the cavity from positions opposed to the circumferential direction of the cavity by 180 ° when the mold is closed. The outline of is an ellipse having a long axis in the radial direction in a state of being a perfect circle in a state of being thermally expanded at the time of casting or in a state of being thermally expanded at the time of casting ,
The cavity formed by the pair of outer molds thermally expanded at the time of casting and the inner mold thermally expanded at the time of casting includes a front part of the weir connected to each of the two weir forming spaces, and the circumferential direction of the cavity. A mold apparatus , wherein a thickness gradient is provided between the front portion of the weir and a portion shifted by 90 ° from which the front portion of the weir is thickest. The mold apparatus according to claim 1 or 2,
And cooling means for cooling of the cavity, the weir front portion,
A mold apparatus comprising: a mist cooling means for mist cooling a portion of the cavity that is shifted by 90 ° from the front portion of the weir in the circumferential direction of the cavity. An annular body manufactured using the mold apparatus according to claim 1,
A pair of weirs connected at 180 ° opposite positions of the annular body,
The annular body has a thickness that gradually decreases from a portion where each of the pair of weirs is connected to a portion shifted by 90 ° from the portion in the circumferential direction of the annular body. Casting products. A cylindrical inner mold that defines the inner periphery of the annular cavity, and an outer periphery definition that defines the outer periphery of the cavity with the mold closed while the mold is closed and opened along a slide surface orthogonal to the dividing surface. A pair of outer molds each having a half surface in the circumferential direction, provided on the split surface, and facing the cavity from a position facing the circumferential direction of the cavity by 180 ° with the pair of outer molds closed. In the method of manufacturing a pair of outer molds provided in a mold apparatus having two weir forming spaces connected to each other,
A mold making process for producing a pair of outer molds whose contour of the outer periphery defining surface is a perfect circle;
A heating step of heating the pair of produced outer molds;
The outer periphery defining surface deformed into an ellipse having a long axis in a direction orthogonal to the radial direction along the dividing surface of the cavity on the slide surface by cooling the pair of heated outer molds to room temperature. A mold manufacturing method comprising: a processing step of processing the outline of the mold into a perfect circle.

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