This application is based on Japanese Patent Application No. 2003-394166 filed on Nov. 25, 2003, the disclosure of which is incorporated herein by reference.
This invention relates to a manufacturing method for a cylindrical part, which has a thin-walled portion at least at one longitudinal end.
As a method for manufacturing a cylindrical part having a thin-walled portion, such as, for example, a cylindrical part 300 with a thin-walled portion 302 at its one end, as shown in
As another method for manufacturing the cylindrical part with the thin-walled portion 302, an extrusion process can be applied, as disclosed in the following publications:
For example, as shown in
It is, however, necessary in such a method that a large pushing force must be applied to the punch 330 so that the punch 330 is plunged into the base metal 340, because the thin-walled portion 302 is formed in a manner that a part of the material for the base metal 340 flows backwardly (namely, in an opposite direction of the punch 330) being pressed. Furthermore, in such a backward extrusion process, the material of the base metal 340 flows, as indicated by an arrow in
As a result, a life time of working jigs, that is the die 310 and the punch 330, will become shorter, the base metal 340 may change its shape. Furthermore, the base metal 340 and the die 310, as well as the base metal 340 and the punch 330 may be adhered to each other, and therefore it may happen that the cylindrical part 300 can not be detached from the die 310. In
The inventors of the present invention studied another method for manufacturing a cylindrical part having a thin-walled portion at its one end, by an ironing process. In this manufacturing process, a base metal of a cylindrical shape with a closed end is formed, an inner wall of the closed end of the base metal is pushed by a punch, so that the base metal is extended by the ironing process during the punch is plunged into the base metal, a thin-walled portion is formed adjacent to the closed end, and the closed end is punched out, to finally form a cylindrical part having the thin-walled portion at one end. Since the base metal is extended in the ironing process, the ironing process can be performed by a smaller pressing force than that for the backward extrusion process. Accordingly, the adhesion between the base metal and the working jigs (the die and punch) may not occur. And since the base metal is processed by a smaller pressing force, the life time of the working jigs can be elongated.
In the above method for manufacturing the thin-walled portion adjacent to the closed end of the cylindrical base metal by the ironing process, however, it is not possible to form an inner side step portion at a boundary between the thin-walled portion and a heavy-walled portion. In the case that an outer side step portion is formed on a cylindrical part, an inner wall of a closed end of a base metal 400 is plunged by a punch 410, and an outer peripheral portion of the base metal 400 having the closed end is extended by the ironing process by a step portion 422 formed at an inner surface of a die 420. According to this method, the thin-walled portion 402 is formed adjacent to the closed end and the outer side step portion 404 due to a difference of thickness is formed on the outer periphery of the base metal 400.
In the above method, however, a material volume flowing from the thin-walled portion 402 to the heavy-walled portion 403 varies depending on a thickness of a base metal 400, when the base metals with a closed end has variation in its thickness before the base metal is processed, and thereby dimensional accuracy for a length of the heavy-walled portion is varied.
The present invention is made in view of the above problems, and it is an object of the present invention to provide a manufacturing method for a cylindrical part, for example, a housing for a fuel pump, which has a thin-walled portion at least at one longitudinal end of the cylindrical part and an inner-side step portion between the thin-walled portion and the other (heavy-walled) portion.
It is a further object of the present invention to provide a method of manufacturing the cylindrical part with the thin-walled portion at a lower cost, and according to the manufacturing method of the present invention, a base metal formed with thin-walled portion adjacent to its closed end can be easily detached from working jigs, such as a die, a punch and so on.
It is a further object of the present invention to provide a manufacturing method, according to which a thin-walled portion as well as a heavy-walled portion for a cylindrical part can be manufactured with a higher accuracy, even if there exist variations in thickness of a base metal.
According to a feature of the present invention, a cup-shaped base metal is at first formed, which has a cylindrical wall, a closed end and an open end at both sides of the cylindrical wall. A thin-walled portion is then formed by an ironing process on a portion of the cylindrical wall adjacent to the closed end, so that an outer-side step portion is formed between the thin-walled portion and the remaining (heavy-walled) portion of the cylindrical wall due to a difference of thickness of the walls of two portions. The closed end of the base metal is punched out, so that the thin-walled portion remains at the base metal. Then, the thin-walled portion is outwardly enlarged in its radial direction. As above, the cylindrical part having the thin-walled portion as well as an inner-side step portion can be manufactured by the ironing process, so that the manufacturing cost becomes lower than a method of a cutting process. Furthermore, a plunging force to the base metal by the working jigs (a die, a punch, an so on) can be made smaller than that in a backward extrusion process, so that an adhesion of the base metal to the working jigs can be prevented and thereby the base metal can be easily detached from the working jigs. Furthermore, a working force for the working jigs can be made smaller compared with the backward extrusion process, so that the lifetime of the working jigs can be elongated and the change of shape for the base metal can be prevented.
During the ironing process of the cylindrical wall adjacent to the closed end to form a thin-walled portion and a heavy-walled portion, a portion of the cylindrical wall is longitudinally extended so that a material of those portion flows from the thin-walled portion to the heavy-walled portion. When there are variations in thickness of the base metal for the cylindrical wall, a material volume flowing from the thin-walled portion to the heavy-walled portion varies depending on the variations of the thickness of the base metal, even when a length of longitudinal extension is controlled at a constant value. As a result, a dimensional accuracy at the heavy-walled portion may be decreased. Accordingly, in another feature of the present invention, a longitudinal length of the thin-walled portion, which will be formed by the ironing process at the cylindrical portion adjacent to the closed end, is adjusted depending on the thickness of the base metal.
According to a further feature of the present invention, when a thin-walled portion is formed by the ironing process at the cylindrical wall adjacent to the closed end, a longitudinal length of the thin-walled portion is made longer than a longitudinal length of the final product of the cylindrical part. And a positioning step portion is formed by the ironing process on the thin-walled portion at such a position, which corresponds to the longitudinal length required for the final product of the cylindrical part, and then the closed end is punched out. Accordingly, a dimensional accuracy for the longitudinal length of the thin-walled portion can be enhanced.
According to a further feature of the present invention, a thin-walled portion is formed by the ironing process on the cylindrical wall adjacent to its open end, and an inner-side step portion is thereby formed at a boundary between the thin-walled portion and the remaining cylindrical wall (heavy-walled portion) because of the difference of the thickness of the walls. Thereafter, the thin-walled portion is formed on the cylindrical wall according to the method mentioned above. As a result, the thin-walled portions are formed on both sides of the cylindrical wall, wherein inner-side step portions are respectively formed in the inner peripheral surface of the cylindrical wall.
When the cylindrical part having a thin-walled portion less than 3 mm is formed by the backward extrusion process, a larger punching force is applied to the base metal and thereby a larger force is applied to the base metal in a radial and outward direction. As a result, an adhesion of the base metal to a die or to a punch may occur and the base metal can not be easily detached from the die and the punch.
However, as mentioned above, the thin-walled portions are formed by the ironing process according to the present invention, the adhesion of the base metal to the die or the punch can be prevented and can be easily detached from the die and the punch, even when the thickness of the thin-walled portions is less than 3 mm.
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawing.
In the drawing:
An embodiment of the present invention will be explained with reference to the drawings, wherein an inner diameter and an outer diameter respectively designate a radius.
A fuel pump according to an embodiment of the present invention is shown in
A pump casing 17 is interposed between the inlet side cover 16 and the housing 12. A pump channel 80 of a C-shape is formed between the inlet side cover 16 and the pump casing 17. An impeller 20 is rotationally housed in a space defined by the inlet side cover 16 and the pump casing 17, wherein the impeller 20, the inlet side cover 16 and the pump casing 17 form a pump portion. The pump casing 17 holds a bearing at its central portion.
A plurality of blade grooves are formed at an outer periphery of the impeller 20, which has a disk shape. When the impeller 20 is rotated with a shaft 41 of an armature 40, a pressure difference is generated in the vicinity of the blade grooves of the impeller 20 by fluid friction, and fuel in the pump channel 80 is pressurized by repeating the generation of the above pressure difference by the plurality of the blade grooves. The fuel, which is sucked into the pump channel 80 from a fuel tank (not shown) through a fuel inlet port (not shown) formed in the inlet side cover 16, is discharged into a motor space formed through a communicating port 82 formed in the pump casing 17. The motor space is formed by the pump casing 17, discharge side cover 18 and the housing 12, and the armature 40 is rotationally housed in this motor space. A reference numeral 84 is an armature cover, and a reference numeral 70 designates a commutator. The fuel discharged into the motor space flows through a gap between the armature 40 and magnets 30 toward the commutator 70, and then discharged from the fuel pump 10 to an engine through a discharge port (not shown) formed in the discharge side cover 18.
The four permanent magnets 30 having an arc shape of one-fourth are fixed to the inner peripheral surface of the housing 12. The magnets 30 are polarized so that different poles are alternately arranged in a rotating direction of the armature 40. The permanent magnets 30 are held by a resin element 32.
The commutator 70 is assembled to an axial end of the armature 40, and the cover 84 is arranged at the opposite end of the armature 40. The permanent magnets 30, the armature 40, the commutator 70 and a brush device (not shown) form a direct current electric motor. The shaft 41 of the armature 40 is rotationally supported by bearings 26, 27, which are respectively held by the pump casing 17 and the discharge side cover 18.
The armature 40 comprises a coil core, which is divided into six poles. Multiple armature coils, each having a bobbin 60 and a winding 62 wound on the bobbin, are respectively fixed to the poles.
The commutator 70 has six segments 72 for supplying electric power to the armature coils. The segments 72 are formed of conductive material, such as cupper, carbon and the like, and the adjacent segments are electrically insulated from each other.
A manufacturing process for the housing 12 will be hereinafter explained.
(1) Pressing Process:
A base metal 100 of a cup shape is made from a plate material 90 having the same thickness by a pressing process, as shown in
(2) Squeezing Work:
A thin-walled portion is formed at the open end of the base metal 100. As shown in
(3) Ironing Process at the Open End:
As shown in
(4) Ironing Process at the Closed End:
A thin-walled portion will be formed at the cylindrical wall of the base metal 140 adjacent to its closed end by the ironing process. As shown in
In the above ironing process shown in
(5) Process for Forming the Step Portion:
As shown in
As shown in
(6) Punching Out Process:
In this process, as shown in
(7) Diameter Enlarging Process:
The thin-walled portion 232 of the base metal 230 is radially and outwardly enlarged, as shown in
Accordingly, a base metal 260 is formed, as shown in
(8) Punching Out Process:
A flange portion 145 adjacent to the thin-walled portion 143 is punched out from the base metal 260 to form the final product of the housing 12, as shown in
(Other Embodiments)
In the above embodiment, thin-walled portions are formed on both sides of the cylindrical part. The present invention can be also applied to a method of manufacturing a cylindrical part having a thin-walled portion at one side thereof.
According to such a modified method, a thin-walled portion is at first formed by the ironing process on a cylindrical wall adjacent to a closed end, so that an outer-side step portion is formed on an outer peripheral surface of the cylindrical wall. Then the closed end is punched out and the thin-walled portion is enlarged in a radial and outward direction to form an inner-side step portion on an inner peripheral surface of the cylindrical wall.
In the embodiments above, the word “closed end” does not mean an end completely closed, but includes such an end partly closed by an end portion of the cylindrical wall.
Number | Date | Country | Kind |
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2003-394166 | Nov 2003 | JP | national |