This is a National stage Application under 35 U.S.C. ยง371 of PCT/JP2006/303062 with an International Filing Date of Feb. 21, 2006, and claims priority from Japanese Patent Application No. JP 2005-045157 filed Feb. 22, 2005; the entire disclosure of which are incorporated by reference.
The present invention relates to an impeller for a supercharger, which makes use of exhaust gas from an internal combustion engine to feed a compressed air, and a method of manufacturing the same.
In a supercharger incorporated in an engine of an automobile or the like, an impeller at an exhaust side is caused to rotate with utilization of exhaust gas from an internal combustion engine thereby rotating a impeller coaxially at an intake side to feed a compressed air to the engine to increase an engine output. Since the exhaust side impeller is exposed to the high temperature exhaust gas discharged from the engine, in general it has been made from a heat resistant Ni-based super alloy, and it is not so much complex in shape, so that it is manufactured by the lost wax casting process. On the other hand, since the intake side impeller is not exposed to a high temperature, usually it is made from an aluminum alloy. In order to achieve an increase in compressibility of compressed air, the intake side impeller has often a complex blade configuration, in which two types of full and splitter blades having different shapes are arranged alternately adjacent to each other in plural.
Recently, higher speed rotation is requested of an intake side impeller for an increase in combustion efficiency and application of titanium alloys having a higher strength than that of aluminum alloys and disclosed in JP-A-2003-94148 (Patent Publication 1) has been examined. Also, for conventional impellers made of an aluminum alloy, a blade configuration of an impeller and an improvement in dimensional accuracy have been examined with a view to an improvement in aerodynamic performance. Further, application of magnesium alloys having higher strength than aluminum alloys and smaller weight than titanium alloys has been examined.
In case of applying a lost wax casting process to manufacture of an intake side impeller, it is necessary to fabricate an sacrificial pattern having the same form as a final product of an impeller as a die casting method. For example, Patent Publication 1 proposes to redesign a blade configuration so that a die insert (slide die) can be taken out of a blade part of a sacrificial pattern, and Patent Publication 1 proposes an impeller manufactured by a lost wax casting process, which is referred to as investment casting. Such proposal is excellent in enabling mass production of impellers made of a titanium alloy at a relatively low cost.
In manufacture of a casting made of aluminum or magnesium alloys, a die casting method is frequently used, according to which casting defects are hard to generate, a favorable dimensional accuracy is obtained, and a casting having a smooth casting surface can be mass-produced in high cycle. In the die casting method, a molten metal or semi-molten metal is filled directly into dies to form and shape a casting. According to a pressure at which a molten metal is fed into dies, for example, the die casting method is classified into a low-pressure casting method, a gravity casting method, and a pressurization casting method. Also, according to a feeding way for a molten metal, the die casting method is classified into an absorption casting method, a decompression casting method and an injection casting method. In particular, the pressurization casting method, in which a pressurized molten metal is filled into dies, is generally referred to call die-casting and frequently used since it is favorable in run quality and hard to generate nonuniformity in cooling. Also, the injection casting method, in which a molten metal in a semi-molten state is fed to dies, is called a thixomold casting method, suffers less solidification defect such as shrinkage, crack of a casting, and presents a high, dimensional accuracy since a semi-molten metal being lower in molten metal temperature than a conventional die casting method is injection-molded into dies.
With regard to an impeller produced by casting in dies includes, JP-A-2000-213493 (Patent Publication 2) discloses one example thereof which is produced by jointing separately formed blade parts to a hub part, and which the impeller is simple in shape without undercuts at blade parts. Also, for example, JP-A-2004-291032 (Patent Publication 3) discloses a molding machine for molding of various molded products such as ornaments made of an aluminum alloy or a magnesium alloy, various containers, housings for precision parts, camera, computer, etc., automotive parts, business machine parts, etc. but a applied shape is limited to a simple shape, which facilitates release of a housing from dies.
As set forth above, the intake side impeller has often a complex blade configuration in which two types of full and splitter blades are arranged. Especially, in the case where such an impeller has no undercut at blade parts, it has been produced by a plaster mold process instead of the conventional die casting method, according to which plaster mold process, a casting mold is fabricated by pouring plaster in a flexible rubber pattern. The rubber pattern is fabricated by forming a master model of an impeller, a silicon rubber into the master model to form a rubber mold, and further pouring a silicon rubber into the rubber mold, and so it is possible to reproduce a complex shape, but involves a problem that its dimensional accuracy is inferior to the die casting method.
The present inventors considered to use a die casting method having advantages of excellent dimensional accuracy than a plaster mold process, forming of a smooth and fine casting surface, reducing machining, and to form an impeller by directly pouring a molten metal into a forming die for a sacrificial pattern while paying attention to a fact that a sacrificial pattern used in a lost wax casting method has substantially the same shape as that of the impeller. In the case of an impeller, in which undercuts are provided radially of a center axle in a space surrounded by a blade, in which full and splitter blades are alternately formed adjacent to each other, however, the die opening is difficult after casting. Also, even in the case of using a forming die for an sacrificial pattern used in the method of, for example, Patent Publication 1, it leads to redesigning a blade configuration so that a slide die adapted for two-dimensional movement can be taken out of an impeller as cast, so that the blade configuration is extremely limited and it becomes difficult to manufacture an impeller having a high aerodynamic performance and being complex in shape.
An object of the invention is to solve the problems and to provide an impeller for a supercharger, in which a high aerodynamic performance can be expected, and a method of manufacturing the same.
The present inventors tried to form an impeller having a shape, in which an undercut is formed radially, by casting a molten metal directly in a die and have examined application of a slide die having a specific structure in a mold for casting and optimization of a release operation thereof whereby attaining the invention.
That is, the manufacturing method according to the invention is of manufacturing an impeller for a supercharger by die casting, which impeller comprises a disk-shaped hub extending radially of a center axle, a plurality of blades extending from the hub and consisting of full blades and splitter blades arranged alternately and in adjacent relationship, each of which blades has an aerodynamically curved surface, spaces defined by the blades forming undercuts extending radially of the center axle,
wherein the process of die casting comprises the step of:
casting a molten metal into a space, which is defined by arranging a plurality of slide dies, each of which has a bottomed groove portion in the form of a splitter blade and a spatial configuration between a pair of adjacent full blades, radially toward the center axle, to form the impeller, and
subsequently moving and releasing the slide dies radially of the center axle while rotating those slide dies.
In the invention, a die device used in the process of die casting comprises a moving die capable of opening and closing movements in a direction along a center axle, a stationary die, a plurality of slide dies capable of moving radially of the center axle, and a slide support provided on the respective slide die to support the same, and the respective each of the slide supports is driven to enable interlocking of the plurality of slide dies.
Also, the slide die can be formed by integrally bonding a plurality of cores (that is, a plurality of components) with one another slide die. Also, a motional line, along which each of the slide dies is released from a cast impeller, preferably consisting of a motional line at XY coordinates on a two-dimensional plane, to which the center axle of the impeller is perpendicular, and a motional line including a rotational component about the motional line at the XY coordinates.
According to the above manufacturing method, it is possible to form parting-line corresponding parts only on a trailing edge face, a fillet face, and a leading edge face, which form an outer peripheral of a full blade, in a space surrounded by blades. Thereby, it is possible to obtain an impeller for a supercharger, which is new and excellent in aerodynamic performance, and in which any parting-line corresponding part is not present both on a hub surface and blade surfaces in a space surrounded by blades.
That is, an impeller for a supercharger, according to the invention, which is of a die casting and has a center axle, and which comprises a disk-shaped hub extending radially of the center axle, a plurality of blades extending from the hub and consisting of full blades and splitter blades arranged alternately and in adjacent relationship, each of which blades has an aerodynamically curved surface, spaces defined by the blades forming undercuts extending radially of the center axle,
wherein respective spaces defined by pairs of the adjacent full blades comprise parting-line corresponding parts only on a trailing edge face, a fillet face, and a leading edge face, which form an outer peripheral of the full blade.
In the invention, an aluminum alloy is cast in dies to provide an impeller for a supercharger, made of an aluminum alloy. In addition, other general casting materials such as magnesium alloys, etc. than aluminum alloys can be also used in the invention.
The impeller according to the invention can be used as an impeller at an intake side of a supercharger. In this case, lightweight casting materials such as aluminum alloys and magnesium alloys are especially preferred. Also, magnesium alloys are especially suitable to application of the invention in terms of being more light and larger in specific strength than aluminum alloys.
According to the invention, it is possible to provide an impeller for a supercharger, which is excellent in aerodynamic performance and in which any parting-line corresponding part is not present on a hub surface and blade surfaces in a space surrounded by blades, which is very industrially effective.
As described above, an important feature of the invention resides in that application of a slide die, which has a specified construction, to dies for casting of a molten metal and a release operation of the dies are optimized by trying to apply a die casting method, in which a molten metal is filled directly in dies to provide for forming to manufacture a configuration having an undercut formed radially of a center axle.
Specifically, the die casting process comprises:
casting a molten metal into a space, which is defined by arranging a plurality of slide dies, each of which has a bottomed groove portion in the form of a splitter blade and a spatial configuration between a pair of adjacent full blades, radially toward the center axle, to form the impeller, and
subsequently moving and releasing the slide dies radially of the center axle while rotating those slide dies.
A slide die, which constitutes one of important features of the invention, comprises a bottomed groove portion in the form of a splitter blade and a spatial configuration between a pair of adjacent full blades, and a space between full blades, which includes a splitter blade, that is, a space corresponding to two full blades in simple representation can be formed by a single slide die. That is, a bottomed groove portion in the form of a splitter blade defines a cavity, in which a splitter blade is formed, and a space defined by arranging a plurality of slide dies radially toward a center axle defines a cavity to determine shapes of full blades and a center axle. Thereby, it is possible to form a cavity having substantially the same configuration as that of the impeller for a supercharger.
In this manner, a single slide die defines a space corresponding to two full blades whereby the dies can be made simple and parting-line corresponding parts can be provided only on a trailing edge face, a fillet face, and a leading edge face, which form an outer peripheral of a full blade. Thereby, no parting-line is present in the space and no parting-line corresponding part is present on a hub surface and blade surfaces in a space surrounded by blades, in a cast impeller thus obtained.
In the invention, while a molten metal is cast into a slide die arranged in this manner to provide for forming a configuration, in which an undercut is formed radially, is aimed at, so that even when it is tried to move and release a slide die on a two-dimensional space defined radially of a center axle, the cast impeller cannot be released.
Hereupon, according to the invention, the slide die is moved and released radially of a center axle while being rotated. That is, a motional line, in which the slide die is released from a cast impeller, comprises a rotational component about the motional line moving at the XY coordinates in addition to a motional line at XY coordinates on a two-dimensional plane, to which the center axle of the impeller is perpendicular and which extends radially, whereby even a configuration, in which an undercut is formed radially, can be released. Also, further movement of the slide die in a Z direction being a direction toward the center axle may be added depending upon a blade configuration.
The impeller for a supercharger, obtained by the manufacturing method described above, makes an aerodynamically excellent impeller for a supercharger since no parting-line corresponding part is present both on a hub surface and blade surfaces.
Subsequently, a specific example of an impeller for a supercharger is cited and described with reference to the drawings. First, a shape of an impeller for a supercharger is described by way of example.
In
In addition, the blade surface referred to in the invention means a curved surface not including the trailing edge surface 21 and the fillet surface 22, which define outer peripheral sides of the full blade 3, and the leading edge surface 23, which defines a topmost portion of the full blade, for example, in the impeller 1 for the supercharger shown in
Also, a parting-line referred to in the invention means a difference in level formed on parting faces of a die device and a linear trace generated by insetting of a molten metal into a parted section of the die device.
Also, a slide die applied in the invention and having a bottomed groove in the form of a splitter blade and a spatial configuration between a pair of adjacent full blades suffices to enable moving integrally when being released from an impeller thus cast. Also, while the slide die may be fabricated integrally, it may be provided by fabricating a plurality of cores and then bonding them by means of bolting, brazing, etc. to be made integral. For example, with a slide die 8 shown in
Casting, in which a molten metal is cast directly in dies to provide for molding, is applied to manufacture an impeller 1 for a supercharger, shown in
Also,
Also,
With such construction, the slide die 8 is made readily rotatable about the rotational axis 14 with less resistance. Also, as shown in
In the invention, it is important to determine an rotational axis of a slide die. As specific measures, a three-dimensional model, in which CAD/CAM is used, can be used to beforehand retrieve a radial undercut in the space 10 shown in
In the invention, it is not necessarily required that the rotational axis 14 described above be perpendicular to the center axle 20 of an impeller depending upon an orientation of an undercut and intersect the center axle 20 of an impeller. For example, it does not matter whether the slide die 8 is withdrawn and moved at an angle of several degrees to the center axle 20 of an impeller.
The slide dies 8 corresponding in number to the spaces 10 on an impeller are arranged annularly as shown in
Subsequently, an explanation will be given to a specific operation when the slide dies 8 are withdrawn and moved radially from a molding 18 as cast and formed at the time of die release. After casting and forming, the moving die 6 is separated from the stationary die 7 as shown in
Since the slide die 8 is connected through the bearing 15 mounted on the rotational axis 14 to the slide support 9 by the stationary pin 16 as shown in
In addition, a method of manually withdrawing and moving individual slide supports, preferably, a method, in which the slide supports 9 are integrated in an interlocking construction and the slide dies 8 are pulled out of an impeller at a time, can be adopted as measures for movement of the slide supports 9. For example, as shown in
As described above, an impeller for a supercharger, according to the invention, can be obtained by removing an unnecessary runner channel, sprue gate, flash, etc. from a molding 18 after casting and forming. Also, it is possible to perform surface treatment, such as plating, coating, etc., on an impeller thus obtained.
Thereby, it is possible to obtain an impeller for a supercharger, not having any parting-line corresponding part present on both a hub surface and blade surfaces in a space surrounded by blades.
According to the invention, while a molten metal may be manufactured by any method as far as an alloy as used is appropriate, it suffices in case of using, for example, an aluminum alloy and a magnesium alloy to melt the same with the use of a direct heating furnace such as gas type one, etc., an indirect heating furnace such as electric type one, etc., a melting crucible provided on a casting machine, or the like. It suffices to treat a molten metal in the atmosphere or in an atmosphere of inert gas. Subsequently, it suffices to supply a molten metal to a casting machine to cast the same in dies at a temperature suited to casting and in a molten or semi-molten state with flowability. At this time, it suffices that conditions of casting and forming, such as temperature, pressure, speed in casting, a cooling pattern after casting, etc. be selected so as to be conformed to a molten metal, a configuration of an impeller, a casting machine, etc. In addition, application of the vacuum casting method, the decompression casting method, or the pressurization casting method in casting a molten metal in dies is preferable since a favorable run quality is obtained even for a thin-walled portion of an impeller. Also, the thixomold casting method is preferable since a molding suffers less solidification defect such as shrinkage, crack, etc.
The impeller according to the invention is used in a supercharger, which makes use of exhaust gas from an internal combustion engine to feed a compressed air.
Number | Date | Country | Kind |
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2005-045157 | Feb 2005 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2006/003062 | 2/21/2006 | WO | 00 | 8/1/2007 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2006/090701 | 8/31/2006 | WO | A |
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2004-291032 | Oct 2004 | JP |
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Number | Date | Country | |
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20090252609 A1 | Oct 2009 | US |