Metal deforming – By use of closed-die and coacting work-forcer – Forcing work into or within closed die; e.g. – forging
Reexamination Certificate
2002-07-16
2004-02-10
Larson, Lowell (Department: 3725)
Metal deforming
By use of closed-die and coacting work-forcer
Forcing work into or within closed die; e.g., forging
C072S352000, C072S478000
Reexamination Certificate
active
06688154
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a die for forging a cylindrical rotor having thin, vane-accommodating grooves which extend inward from the periphery of the rotor, to a forging production system for producing the rotor, to a method for forging the rotor, and to the rotor.
BACKGROUND OF THE INVENTION
Rotors have been employed in rotary compressors and vane pumps. Conventionally, rotors have been formed through the following method: aluminum alloy powder, an aluminum alloy cast material, or an extrusion material thereof is subjected to extrusion by use of an extrusion die as shown in
FIG. 15
having portions that form vane-accommodating grooves (hereinafter referred to as “vane-accommodating-groove-forming portions” or simply “groove-forming portions”) (
151
), and the thus-extruded preform is subjected to cutting; or a method as disclosed in Japanese Patent Application Laid-Open (kokai) No. 3-165948 in which an aluminum alloy material is subjected to forging by use of a die shown in
FIG. 16
, to thereby form a side wall of a cylindrical rotor and vane-accommodating grooves. When vane-accommodating grooves are formed through forging, in many cases, as shown in
FIG. 17
, a cylindrical portion (
171
) is provided at a position of a vane-accommodating-groove-forming portion which corresponds to the bottom of a vane-accommodating groove, in order to reduce stress concentration factor, form a relief of a working tool to thereby improve workability, and apply back pressure to a vane to thereby improve sealing performance.
When the aforementioned method in which an extruded preform is subjected to cutting is employed, since a material for a rotor to be extruded is easily twisted to thereby generate bending and warpage, possibly leading to failure to obtain dimensional accuracy in terms of straightness of a vane-accommodating groove which extends toward the axis of a rotor, excess working is required in order to obtain such dimensional accuracy, resulting in an increase in production costs. In addition, due to poor lubrication between the extrusion die and an aluminum alloy material, sticking and galling occur on the surface of the extrusion die, resulting in poor surface precision. Therefore, since excess working is required in order to attain high surface precision, production costs increase. When the extrusion die is employed, due to stress applied to the die, cracking is generated from sticking or galling occurring on the bottom of the groove-forming portions, thereby lowering durability of the die. In addition, since the shape of a chamfer (
152
), which is shown in greater detail in FIG.
1
(B) and which is provided on the base of the groove-forming portion in order to prevent bending or breakage of the groove-forming portion, is reflected on the extruded rotor, machining for removing the resultant chamfer of the rotor is required in the subsequent step.
Meanwhile, when the aforementioned forging method is employed, the shape of a chamfer (
172
), which is provided on the base of a groove-forming portion of a forging die in order to prevent bending or breakage of the groove forming portion as in the case of the aforementioned extrusion die, is reflected on a forged product, and thus machining for removing the resultant chamfer of the forged product is required. Therefore, the resultant forged product (i.e., rotor) must be subjected to machining, resulting in high production costs. Since excess material (
181
) as shown in
FIG. 18
, which is required for working of the resultant chamfer, is removed, yield on the basis of the raw material is lowered, and production costs increase.
When a conventional forging die shown in
FIG. 19
having no chamfer at a base (
191
) of a groove-forming portion is employed, during molding of a material, stress is applied to the base of the groove-forming portion, the groove-forming portion is bent, and dimensional accuracy in terms of straightness of a vane-accommodating groove is impaired. As a result, machining for obtaining such dimensional accuracy is required, and production costs increase. In addition, since the base of the groove-forming portion may be broken during forging in accordance with the degree of stress applied thereto, costs required for the die increase; i.e., production costs increase.
In order to solve dimensional-accuracy-related problems encountered by the aforementioned forging method, Japanese Patent No. 3127587 discloses a forging die including a die portion for forming a side wall of a cylindrical rotor and vane-accommodating-groove-forming portions, the groove-forming portions being formed separately from the die portion, and being shrunk on the die portion. However, since each of the groove-forming portions is supported merely by its base, considerable deviation of the groove-forming portion occurs during molding, thereby lowering dimensional accuracy of a vane-accommodating groove of the resultant forged product.
Meanwhile, in order to solve the mentioned accuracy-related problems, Japanese Patent Application Laid-Open (kokai) No. 2000-220588 discloses a mechanism in which vane-accommodating-groove-forming portions are provided on a punch, and deviation of the groove-forming portions is prevented by means of grooves for mating the groove-forming portions, the mating grooves being provided on a die. However, since a material intrudes into the mating grooves under application of pressure, and flash-shaped excess material which is formed through punching remains in vane-accommodating grooves of the resultant rotor, high production costs are required for removing the excess material.
SUMMARY OF THE INVENTION
In view of the foregoing, the present invention has been accomplished for solving the following problems: problems involved in an extrusion method; i.e., high production costs attributed to excess working required for producing vane-accommodating grooves of high accuracy; and problems involved in a forging method; i.e., high production costs attributed to excess working for removing excess material corresponding to the chamfer of vane-accommodating grooves, low dimensional accuracy of the vane-accommodating grooves, and generation of flash-shaped, excess material on the side wall of a rotor.
The present invention provides a forging die for producing a rotor of high dimensional accuracy at low cost, which die enables production of vane-accommodating grooves of high accuracy, and enables prevention or reduction of working required for removing chamfers of the vane-accommodating grooves. The present invention also provides a forging production system for producing the rotor; a method for producing the rotor; and the rotor.
The present inventors have performed extensive studies on the relation between a forging die and working accuracy of vane-accommodating grooves of a forged rotor product, thus leading to completion of the invention on the basis of their findings.
1) A first embodiment of the present invention for solving the aforementioned problems provides a forging die for forging a cylindrical rotor having a plurality of vane-accommodating grooves which extend toward an axis of the rotor, comprising an upper die; a lower die having a mold cavity in a center portion, and a plurality of vane-accommodating-groove-forming portions which protrude inward from an inner wall which defines the mold cavity; and a spacer having a plurality of shell segments for defining a shape of a side wall of the cylindrical rotor which is segmented by the vane-accommodating grooves, and a flange for joining the shell segments, the spacer being provided in the interior of the mold cavity of the lower die.
2) A second embodiment of the present invention for solving the aforementioned problems provides a forging die according to 1), wherein each of the shell segments of the spacer has an axial length equal to or greater than the axial length of the rotor and twice or less than twice the axial length of the rotor.
3) A third embodiment of the present invention for solving the aforementioned problems provides a forging
Anazawa Yoshiyuki
Yamada Hidemi
Yokoi Keiichi
Larson Lowell
Showa Denko Kabushiki Kaisha
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