JP2016131988A - Method and apparatus for casting hollow cylindrical rotary member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for casting a hollow cylindrical rotary member, enabling the whole wall thickness of the hollow cylindrical rotary member to be uniformized.SOLUTION: The method for casting a hollow cylindrical rotary member 1 comprises the step of: filling molten metal M into a cavity 12 having a shape conforming with a contour of the hollow cylindrical rotary member 1, of a metallic mold 11 which has the cavity 12, and at an upper end in an axis L direction, an opening 13 communicated with the cavity 12; causing the metallic mold 11 to autorotate in a direction corresponding to a circumferential direction of the hollow cylindrical rotary member 1 before solidification of the molten metal M in the cavity 12 is completed; and discharging a solidified molten metal M in the cavity 12 from the opening 13 at the time of formation of a solidified layer C having a predetermined thickness on a metallic mold surface forming the cavity 12.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a casting method for a hollow cylindrical rotating member and a casting apparatus for performing the casting method.

  As a casting method of a cylindrical rotating member such as a camshaft, a method of obtaining a solid body by filling a mold cavity with a molten metal has been conventionally known (see, for example, Patent Document 1).

  On the other hand, in recent years, in order to reduce the weight, the cylindrical rotating member is desired to be a hollow body instead of a solid body.

  As a method for casting a hollow member, conventionally, a method in which a core is placed in a cavity and cast is generally used. Further, as a method not using a core, a mold having a cavity formed in a shape corresponding to a shoe mold as a hollow member is filled with molten metal from a gate provided at the position of the ankle of the shoe mold, and the mold is formed to form the cavity A method is known in which, after forming a solidified layer along the surface, the mold is inverted and the unsolidified molten metal in the cavity is discharged from the gate (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 07-080628 Japanese Patent Laid-Open No. 03-008553

  By the way, in a hollow cylindrical rotating member such as a camshaft, it is desirable that the entire wall thickness is uniform in order to ensure uniform strength in the entire hollow cylindrical rotating member.

  However, the conventional method for casting a hollow member that does not use a core has the disadvantage that the thickness cannot be made uniform.

  Then, an object of this invention is to provide the casting apparatus which enforces the casting method of the hollow cylindrical rotating member which can make the whole wall thickness uniform, and the said casting method.

  The inventors of the present invention have examined the cause of the inability to make the thickness of the entire hollow member uniform in the conventional hollow member casting method. As a result, the present inventors filled the molten metal from the side farther from the gate in the cavity toward the side closer to the side closer to the side closer to the gate, so that solidification is started earlier than the side near the gate. As a result, it has been found that the thickness of the hollow member increases on the side farther from the gate in the cavity and the thickness of the hollow member decreases on the near side.

  In view of the above knowledge, the method for casting a hollow cylindrical rotating member of the present invention has a cavity having a shape that follows the outer shape of the hollow cylindrical rotating member, and has an opening that communicates with the cavity at the upper end in the axial direction. Filling the cavity with the molten metal, rotating the mold in the circumferential direction of the hollow cylindrical rotating member before the solidification of the molten metal in the cavity is completed, and forming the cavity And a step of discharging the unsolidified molten metal in the cavity from the opening when a solidified layer having a predetermined thickness is formed on the mold surface.

  In the casting method of the present invention, after the molten metal is filled in the cavity of the mold, the mold is rotated in the direction corresponding to the circumferential direction of the hollow cylindrical rotating member before the solidification of the molten metal in the cavity is completed. Let As a result, the solidification speed on the entire mold surface is made uniform, and the thickness of the obtained solidified layer can be made uniform, so that a hollow cylindrical rotating member with uniform overall thickness can be obtained. .

  In the casting method of the present invention, it is preferable that the step of filling the cavity with the molten metal is performed while rotating the mold in the circumferential direction of the hollow cylindrical rotating member. By the centrifugal force generated as the mold rotates, the molten metal supplied into the cavity flows down on the mold surface while spreading in the circumferential direction, so that the solidification rate on the entire mold surface can be made more uniform. The thickness of the entire hollow cylindrical rotating member can be made more uniform.

  In the casting method of the present invention, it is preferable that the method further comprises a step of revolving the mold along a predetermined path before the solidification of the molten metal in the cavity is completed. By revolving the mold in addition to the rotation, the centrifugal force can be increased, the solidification rate on the entire mold surface can be made more uniform, and the overall thickness of the hollow cylindrical rotating member can be made more uniform. Can be

  In the casting method of the present invention, it is preferable that the step of filling the cavity with the molten metal is performed by inclining the mold with respect to the vertical direction. Due to the inclination of the mold, the supplied molten metal has a slower speed from the side closer to the opening to the side farther from the opening than in the case where the mold is not inclined. Therefore, the solidification rate on the entire mold surface can be made more uniform, and the overall thickness of the hollow cylindrical rotating member can be made more uniform.

  Further, in the casting method of the present invention, the step of discharging the unsolidified molten metal is preferably performed with the opening directed downward in the vertical direction. By doing so, the unsolidified molten metal in the cavity is performed. The solidified layer can be formed to a desired thickness.

  Further, the casting method of the present invention includes a mold having a cavity having a shape that follows the outer shape of the hollow cylindrical rotating member, and having an opening communicating with the cavity at the upper end in the axial direction, and a grip for gripping the mold. Casting of a hollow cylindrical rotating member comprising: means; a rotating means for rotating the mold in a direction corresponding to a circumferential direction of the hollow cylindrical rotating member; and a tilting means for tilting the mold with respect to a vertical direction. It can be implemented by a device.

  In the casting apparatus of the present invention, the mold includes a fine recess formed by dimple processing on the mold surface forming the cavity, and the fine recess has a dimple area ratio as the distance from the opening increases. It is preferable to increase. Since the solidification rate can be slowed in the region of the mold surface where the fine recesses are provided, it occurs between the side far from the opening filled with the molten metal and the side close to the opening. The difference in thickness of the solidified layer can be further reduced, and the overall thickness of the hollow cylindrical rotating member can be further uniformed.

  In the casting apparatus of the present invention, it is preferable that the mold is formed such that the mold surface forming the cavity has a lower thermal conductivity as it is separated from the opening. By slowing down the solidification rate by slowing the cooling rate of the molten metal on the side far from the opening on the mold surface, and by increasing the solidification rate by increasing the cooling rate of the molten metal on the side near the opening. The difference in the thickness of the solidified layer generated between the side far from the opening and the side close to the opening can be further reduced, and the overall thickness of the hollow cylindrical rotating member can be made more uniform.

  In the casting apparatus of the present invention, the mold is divided by a dividing surface including an axis corresponding to the rotation axis of the hollow cylindrical rotating member, and one end is opened to the cavity on the dividing surface and the other end is It is preferable to provide a gas vent passage communicating with the outside of the mold. The degassing passage can be easily formed by providing the dividing surface.

It is explanatory drawing which shows the hollow cylindrical rotating member cast with the casting method of this embodiment, and the metal mold | die used for casting, FIG. 1A shows a hollow cylindrical rotating member, and FIG. 1B shows a metal mold | die. It is explanatory drawing which shows the casting apparatus which enforces the casting method of this embodiment, FIG. 2A shows the time of molten metal filling, and FIG. 2B shows the time of molten metal discharge | emission. It is explanatory drawing which shows the casting method of this embodiment, FIG. 3A shows the initial state of molten metal filling, and FIG. 3B shows the middle state of molten metal filling. It is explanatory drawing which shows the casting method of this embodiment, FIG. 4A shows the middle state of molten metal filling, and FIG. 4B shows the completion state of molten metal filling. It is explanatory drawing which shows the casting method of this embodiment, and shows a molten metal discharge | emission state.

  Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

  A hollow cylindrical rotating member 1 shown in FIG. 1A is, for example, a camshaft as an automotive part, and is cast by a mold 11 shown in FIG. 1B. The hollow cylindrical rotating member 1 includes a shaft portion 2 having a predetermined diameter, one end closed and the other end opened, and a cam portion 3 projecting outward from the shaft portion 2 and eccentric from the shaft L. Rotated as center.

  The mold 11 includes a cavity 12 having a shape along the outer diameter of the hollow cylindrical rotating member 1, and serves as an opening at the upper end located on the extension line of the axis L corresponding to the axis L ′ of the hollow cylindrical rotating member 1. A gate 13 is provided and supported by a jig 14 provided outside. Further, the mold 11 is divided into two on the surface including the axis L, and the outer peripheral edge on the side opposite to the pouring gate 13 side and the outer peripheral edge of the portion corresponding to the cam portion 3 on the pouring gate 13 side. Is provided with a gas vent passage 15 having one end opened and the other end communicating with the outside. 1B shows a cross section when the mold 11 is divided by the dividing surface. The gas vent passage 15 can be easily formed by being provided on the dividing surface.

  The mold 11 is held by a mold holding robot 21 shown in FIG. 2A. The mold holding robot 21 corresponds to the casting apparatus of the present invention.

  The mold gripping robot 21 includes a first link mechanism 24 coupled to the base body 22 via a first joint 23, a second link mechanism 26 coupled to the first link mechanism 24 via a second joint 25, A handle 28 is coupled to the second link mechanism 26 via a third joint 27, and the bottom of the mold 11 is gripped by the handle 28. The handle 28 corresponds to the gripping means of the present invention.

  The third joint 27 is provided with a servo motor (not shown), and the mold holding robot 21 rotates the handle 28 with respect to the second link mechanism 26 by the third joint 27, so that the mold 11 is moved around the axis L. The rotating shaft can be rotated in a direction corresponding to the circumferential direction of the hollow cylindrical rotating member 1 (hereinafter referred to as a circumferential direction). The third joint corresponds to the rotation means of the present invention.

  The mold holding robot 21 tilts the first link mechanism 24 with respect to the base body 22 and tilts the second link mechanism 26 with respect to the first link mechanism 24, thereby changing the tilt of the mold 11. (See FIGS. 2A and 2B). The first joint 23, the first link mechanism 24, the second joint 25, and the second link mechanism 26 correspond to the tilting means of the present invention.

  In addition, the mold holding robot 21 can revolve the mold 11 around the second joint 25 by rotating the second link mechanism 26 with respect to the first link mechanism 24. The 1st link mechanism 24, the 2nd joint 25, and the 2nd link mechanism 26 are equivalent to the revolution means of this invention.

  A molten metal supply robot 31 is provided on the side of the mold holding robot 21. The molten metal supply robot 31 includes a first link mechanism 24 coupled to the base body 22 via a first joint 23 and a second link mechanism 26 coupled to the first link mechanism 24 via a second joint 25. . A pouring pot 32 in which the molten metal M is accommodated is provided at the tip of the second link mechanism 26.

  The molten metal supply robot 31 changes the supply amount of the molten metal M supplied from the pouring pot 32 by tilting the second link mechanism 26 relative to the first link mechanism 24 to change the inclination of the pouring pot 32. Can do.

  Next, the casting method of this embodiment is demonstrated with reference to FIGS.

  First, as shown in FIG. 2A, the mold holding robot 21 rotates the mold 11 in the circumferential direction while holding the mold 11 so that the gate 11 is positioned above and tilted with respect to the vertical direction. On the other hand, the molten metal M is supplied into the cavity from the pouring pot 32 through the gate 13 by the molten metal supply robot 31. At this time, as shown in FIGS. 3A and 3B, the mold holding robot 21 and the molten metal supply robot 31 gradually increase the inclination angle of the mold 11 with respect to the vertical direction as the amount of molten metal supplied into the cavity 12 increases. The supply amount of the molten metal M supplied from the pouring pot 32 is gradually reduced.

  The molten metal M supplied into the cavity 12 is rotated while the mold 11 is inclined, and the mold 11 is rotated while flowing down the mold surface from the side closer to the gate 13 to the side farther from the side. Thus, the mold surface flows down in the circumferential direction by the centrifugal force generated in association with the rotation.

  Thereafter, the molten metal M flowing down the mold surface is filled in the cavity 12 from the side far from the gate 13 toward the side closer to the side. As the molten metal M is filled, as shown in FIG. 4A, the air A in the cavity 12 accumulates on the outer peripheral edge of the portion corresponding to the cam portion 3, but the air A is exhausted to the outside of the mold by the gas vent passage 15. The When the filling of the molten metal M into the cavity 12 is completed, as shown in FIG. 4B, the cavity 12 is in a state where the gate 13 is positioned upward and the axis L is directed upward in the vertical direction.

  The molten metal M flowing down from the mold surface and filling from the side farther from the pouring gate 13 is cooled by contact with the mold surface and gradually solidifies to form a solidified layer C. The thickness gradually increases with time.

  When the solidified layer C having a predetermined thickness is formed in the cavity 12 after the filling of the molten metal is completed, the mold 11 is turned upside down by the mold gripping robot 21 as shown in FIG. 2B. As shown in FIG. 5, the unsolidified molten metal M in the cavity 12 is discharged from the gate 13 while the mold 11 is rotated. At this time, since the mold 11 rotates with the pouring gate 13 facing downward in the vertical direction, the unsolidified molten metal M can be quickly discharged.

  Then, the hollow cylindrical rotating member 1 shown in FIG. 1 can be obtained by dividing the mold 11 at the dividing surface and taking out a cast body made of the solidified layer C having a predetermined thickness.

  According to the casting method of the present embodiment, when the molten metal M is filled into the cavity 12, the molten metal M that is supplied rotates close to the mold 11 so that the supplied molten metal M is close to the gate 13 on the mold surface. It flows down while spreading in the circumferential direction from the side to the far side, and then cooled on the mold surface to form a solidified layer C. For this reason, the solidification rate of the molten metal is made uniform between a region far from the gate 13 in the cavity 12 where the molten metal M is initially filled and a region near the gate 13 in the cavity 12 where the molten metal M is filled last. The difference in thickness of the solidified layer C generated between the region far from the gate 13 and the region close to the gate 13 can be reduced, and the hollow cylindrical rotating member 1 having the uniform thickness can be obtained.

  Further, when the molten metal M is filled into the cavity 12, the air A accumulated in the cavity 12 is exhausted to the outside of the mold through the gas vent passage 15, so that the hollow cylinder is formed by the air A accumulated in the cavity 12. It is possible to prevent blowholes from occurring on the surface of the rotary member 1.

  In this embodiment, the molten metal M is filled in the cavity 12 while rotating the mold 11. However, the molten metal M is filled in the cavity 12 without rotating the mold 11, and immediately after the filling, the cavity 12 is filled. The mold 11 may be rotated before solidification of the molten metal M is completed.

  Further, the molten metal M is filled in the cavity 12 while rotating the mold 11, but the molten metal M may be filled while revolving the mold 11 while rotating. By the revolution, the spread of the molten metal M flowing down on the mold surface is further promoted, and the difference in the thickness of the solidified layer C generated between the region far from the gate 13 and the region near the gate 13 in the cavity 12 is further increased. Can be small.

  Although not shown, the mold 11 includes fine recesses formed on the mold surface by dimple processing, and the fine recesses are dimple area ratio (ratio of the fine recesses in the mold surface) as the distance from the gate 13 increases. May be formed to be large.

  In the region where the fine recesses are provided on the mold surface, when the melt M flows down the mold surface, the melt M does not enter the bottom of the fine recesses, and there is a gap between the melt M and the bottom of the fine recesses. The thermal conductivity of the mold surface is lowered by the heat insulating effect due to the gap, and the solidification rate of the molten metal M is slowed. The mold 11 is formed so that the dimple area ratio increases as the fine concave portion on the mold surface moves away from the gate 13, so that the thermal conductivity of the mold surface decreases as the distance from the gate 13 increases. The solidification rate of M becomes slow. As a result, the difference in the thickness of the solidified layer C generated between the region far from the gate 13 where the molten metal M is previously filled and the region near the gate 13 can be further reduced.

  Moreover, it is preferable that the metal mold | die 11 is formed so that the heat conductivity may become low as the metal mold | die surface which forms the cavity 12 moves away from the gate 13. For example, the mold 11 is formed of a first mold material (for example, a copper alloy) having a first thermal conductivity in a region close to the gate 13, and in a region far from the gate 13 than the first mold material. Alternatively, the second mold material (for example, SKD material) having a low conductivity may be used. By doing so, the molten metal is slowly cooled in the region far from the gate 13 on the mold surface to slow the solidification rate, and in the region near the gate 13 the molten metal is immediately cooled to increase the solidification rate. The difference in the thickness of the solidified layer C generated between the region far from the gate 13 in the cavity 12 and the region near the gate 13 can be further reduced.

  In this embodiment, the casting method of the hollow cylindrical rotating member 1 including the shaft portion 2 having one end closed and the other end opened is described. However, the hollow cylindrical rotating member casting including the shaft portion having both ends opened is described. It is also applicable to the method. In this case, a shutter that can be opened and closed is provided at a position corresponding to the one end, the molten metal M is poured into the cavity with the shutter closed, and solidification of the molten metal M at the position corresponding to the one end is completed. You may make it open the said end by opening the said shutter previously, discharging the molten metal M of the part.

DESCRIPTION OF SYMBOLS 1 ... Hollow cylindrical rotating member, 2 ... Shaft part, 3 ... Cam part, 11 ... Mold, 12 ... Cavity, 13 ... Sprue, 15 ... Degassing path, 21 ... Casting apparatus, 24 ... 1st link mechanism, 25 ... 2nd joint, 26 ... 2nd link mechanism, 27 ... 3rd joint, 28 ... Handle, C ... Solidified layer L ... Rotating shaft, M ... Molten metal.

Claims (9)

Filling the molten metal into the cavity of the mold having a cavity having a shape along the outer shape of the hollow cylindrical rotating member, and having an opening communicating with the cavity at the upper end in the axial direction;
A step of rotating the mold in a direction corresponding to a circumferential direction of the hollow cylindrical rotating member before the solidification of the molten metal in the cavity is completed;
And a step of discharging the unsolidified molten metal in the cavity from the opening when a solidified layer having a predetermined thickness is formed on the mold surface forming the cavity. Method of casting a rotating member. In the casting method of the hollow cylindrical rotating member according to claim 1,
The step of filling the cavity with the molten metal is performed while rotating the mold in the circumferential direction of the hollow cylindrical rotating member. In the casting method of the hollow cylindrical rotating member according to claim 1 or 2,
Furthermore, before the solidification of the molten metal in the cavity is completed, there is provided a step of revolving the mold along a predetermined track. In the casting method of the hollow cylindrical rotating member according to any one of claims 1 to 3,
The step of filling the cavity with the molten metal is performed by inclining the mold with respect to the vertical direction. In the casting method of the hollow cylindrical rotating member according to any one of claims 1 to 4,
The step of discharging the unsolidified molten metal is performed by directing the opening downward in the vertical direction. A mold having a cavity shaped along the outer shape of the hollow cylindrical rotating member, and having an opening communicating with the cavity at the upper end in the axial direction;
Gripping means for gripping the mold;
Rotation means for rotating the mold in a direction corresponding to the circumferential direction of the hollow cylindrical rotating member;
An apparatus for casting a hollow cylindrical rotating member, comprising: tilting means for tilting the mold with respect to the vertical direction. In the casting apparatus of the hollow cylindrical rotating member according to claim 6,
The mold includes a fine recess formed by dimple processing on a mold surface forming the cavity,
The hollow cylindrical rotating member casting apparatus, wherein the fine concave portion has a dimple area ratio that increases as the distance from the opening portion increases. In the casting apparatus of the hollow cylindrical rotating member according to claim 6 or 7,
The casting apparatus for a hollow cylindrical rotating member, wherein the mold is formed such that a mold surface forming the cavity has a lower thermal conductivity as the cavity is separated from the opening. In the casting apparatus of the hollow cylindrical rotating member according to any one of claims 6 to 8,
The mold is divided by a dividing surface including an axis corresponding to the rotation axis of the hollow cylindrical rotating member, and a gas vent passage having one end opened to the cavity and the other end communicating with the outside of the mold is provided on the dividing surface. An apparatus for casting a hollow cylindrical rotating member.