Method of Manufacturing Sheet Metal Back Face Pulley
In the invention, a sheet metal-made cup-shaped material (4) comprising: a circular base plate portion (2); and a cylindrical portion (3) which extends from an outer peripheral edge portion of the base plate portion (2) in one direction along the axis of the base plate portion (2) is prepared, an annular expansion (40) that is radially outward expanded is formed in the cylindrical portion (3), and the annular expansion (40) and the cylindrical portion (3) are clampingly pressed by a rotary lower mold (5) and a flat-face forming rolling roller (16) to a degree at which the annular expansion (40) disappears, whereby the outer circumferential face (30) of the cylindrical portion (3) is flatly formed. Therefore, the axial length (h4) of a sheet metal-made back face pulley (11) is increased, and the increased axial length (h4) can be used as the effective length.
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The present invention relates to a method of producing a back face pulley made of a sheet metal, and more particularly to a method of producing a sheet metal-made back face pulley in which the effective length of a cylindrical portion that is to be in contact with the back face of a belt to support the back face of the belt can be increased.
BACKGROUND ARTConventionally, a sheet metal-made back face pulley which causes a cylindrical portion to be in contact with the back face of a belt to function as, for example, a tensioner is known. The applicant of the present application has disclosed a production method in which the length of the cylindrical portion is increased (elongated) (Patent Literature 1).
In the production method in which the length of the cylindrical portion is increased (elongated), as shown in the left half of
Then, the rotary upper mold 6 is lowered as indicated by the arrow e in the right half of
As shown in the left half of
Then, the rotary upper mold 6a is lowered as indicated by the arrow g in the right half of
Namely, by the cup-shaped material 4 in which the thickness t1 of the cylindrical portion 3 shown in
Patent Literature 1: WO98/05447
DISCLOSURE OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTIONHowever, the conventional method of enlarging a cylindrical portion merely provides a method of simply clampingly pressing a portion corresponding to an approximately lower half of the cylindrical portion 3 which extends in one direction along the axis C1 of the base plate portion 2, thereby downward extending the portion while being thinned. In a first step of downward extending while thinning, work hardening is caused in the portion which has been thinned and downward extended. In a second step, however, the thick portion 3a corresponding to the approximately upper half of the cylindrical portion 3 must be extended toward the portion where work hardening is caused in the first step, while being thinned. Therefore, molding in which the thick portion 3a is extended is relatively troublesome.
Furthermore, an effective length h3 of the cylindrical portion 3 with which the back face of a belt can be in contact is limited to a value which is obtained by subtracting the axial length Δh of the upper-end curved portion 11b of the cylindrical portion 3 from the axial length h2 of the cylindrical portion 3.
The invention solves these problems. It is an object of the invention to provide a method of producing a sheet metal-made back face pulley in which the effective length of a cylindrical portion that can be contacted with the back face of a belt can be increased, molding is easily conducted, and accurate flatness and dimensionality can be obtained by a reduced number of steps.
MEANS FOR SOLVING THE PROBLEMSThe method of producing a sheet metal-made back face pulley according to the invention is characterized in that a sheet metal-made cup-shaped material comprising: a circular base plate portion; and a cylindrical portion which extends from an outer peripheral edge portion of the base plate portion in one direction along an axis of the base plate portion is prepared, an annular expansion is formed in the cylindrical portion, and the annular expansion is clampingly pressed by a rotary inner mold and a flat-face forming rolling roller to a degree at which at least the annular expansion disappears, whereby an outer circumferential face of the cylindrical portion is flatly formed.
EFFECTS OF THE INVENTIONAccording to the production method, the annular expansion is clampingly pressed by the rotary inner mold and the flat-face forming rolling roller to a degree at which at least the annular expansion disappears, whereby the expanding volume amount of the annular expansion is converted into the extended distance by which the cylindrical portion is axially extended. Therefore, the axial length of the sheet metal-made cup-shaped material is larger than the original length (original dimension) correspondingly with the expanding volume amount, and it is possible to provide a sheet metal-made back face pulley in which the increased axial length can be used as the effective length.
Furthermore, since the annular expansion is clampingly pressed by the rotary inner mold and the flat-face forming rolling roller to a degree at which the annular expansion disappears, to flatten the outer circumferential face of the cylindrical portion, molding can be conducted by a clamping press force which is smaller as compared with the case where the whole outer circumferential face of the cylindrical portion is clampingly pressed to be flatly formed. Therefore, molding is facilitated, and accurate flatness and dimensionality can be obtained by a reduced number of steps.
Moreover, the cylindrical portion is not work-hardened or is low in degree of work hardening. Therefore, the conversion of the expanding volume amount of the annular expansion into the axial extended distance of the cylindrical portion is smoothly performed, and the production efficiency can be enhanced.
Since the whole of the increased axial length can be used as the effective length, for example, it is possible to attain an effect that a small positional displacement in the width direction of a belt is absorbed, and a stable contact state with the back face of the belt can be maintained.
In the production method of the invention, preferably, the annular expansion is formed by expansion in a radially outward direction of the cylindrical portion.
When the annular expansion is formed by expansion in a radially outward direction of the cylindrical portion in this way, only the annular expansion can be pressed by the flat-face forming rolling roller, and the annular expansion can be efficiently extended for a short time period to disappear.
In the production method of the invention, preferably, an upper end portion of the cylindrical portion is pressed by a groove-forming protrusion disposed in a roll-forming roller, to form an annular groove in the upper end portion of the cylindrical portion, and an annular projection that projects in a direction opposite to a direction along which the cylindrical portion extends is formed above the annular groove.
When an upper end portion of the cylindrical portion is pressed by the groove-forming protrusion disposed in the roll-forming roller, to form the annular groove as described above, the annular projection that projects in the direction opposite to the direction along which the cylindrical portion extends is formed in the cylindrical portion. Therefore, the axial length of the sheet metal-made cup-shaped material can be further increased correspondingly with the projection distance of the annular projection.
BRIEF DESCRIPTION OF THE DRAWINGS [
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- 2 circular base plate portion
- 3 cylindrical portion
- 4 sheet metal-made cup-shaped material,
- 15 projection
- 15a outer circumferential face of projection 15
- 40 expansion
Hereinafter, a preferred embodiment of the method of producing a sheet metal-made back face pulley according to the invention will be described with reference to the drawings. In the embodiment, the components which are identical with those of the conventional example that has been described with reference to
As shown in the left half of
As shown in the left half of
Then, the rotary upper mold 6a is lowered as indicated by the arrow e in the right half of
While rotating the cup-shaped material 4 in this way, a first roll-forming roller 70 is moved in the direction of the arrow f, so that a first groove-forming protrusion 72 having a mountain-like section shape which is protruded radially outward in the vicinity of an upper end portion of the first roll-forming roller 70 is pressed radially inward into an upper end portion of the cylindrical portion 3, and the cylindrical-portion pressing face 71 of the first roll-forming roller 70 is caused to butt against the outer circumferential face 30 of the cylindrical portion 3. While the first roll-forming roller 70 reversely rotates with following the rotation of the cup-shaped material 4, therefore, an annular first groove 12 that is opened in a valley-like shape is formed in an outer peripheral edge of the upper end portion of the cylindrical portion 3.
By a pushing-up action of an upper inclined face of the first groove-forming protrusion 72 which is generated when the annular first groove 12 that is opened in a valley-like shape is formed in the outer peripheral edge of the upper end portion of the cylindrical portion 3 as described above, the upper side of the annular first groove 12 in the cylindrical portion 3 is upward pushed up, so that an annular projection 14 that projects in a direction opposite to a direction along which the cylindrical portion 3 extends is formed in an upper end portion of the cylindrical portion 3. By a pushing-down action of an lower inclined face of the first groove-forming protrusion 72, the lower side of the annular first groove 12 in the cylindrical portion 3 is downward pushed down, so that a cup-shaped material 4A in which the cylindrical portion 3 is extended slightly and downward is molded.
As shown in the left half of
A second roll-forming roller 90 is moved in the direction of the arrow h with respect to the cup-shaped material 4A which rotates about the axis C1 together with the rotary lower mold 5c and the rotary upper mold 6b as described above, whereby a second groove-forming protrusion 92 which is protruded radially outward in the vicinity of an upper end portion of the second roll-forming roller 90 is fitted into the annular first groove 12 (see the right half of
While the second roll-forming roller 90 reversely rotates with following the rotation of the cup-shaped material 4A, therefore, the annular first groove 12 that has been already formed is pressed open by the second groove-forming protrusion 92 to form an annular second groove 13 that is largely opened in a valley-like shape. By a pushing-up action of an upper inclined face of the second groove-forming protrusion 92 which is generated when the annular second groove 13 that is largely opened in a valley-like shape is formed in the upper end portion of the cylindrical portion 3 as described above, an annular projection 15 that projects more largely than the annular projection 14 in a direction opposite to a direction along which the cylindrical portion 3 extends is formed in the cylindrical portion 3.
By a pushing-down action of an lower inclined face of the second groove-forming protrusion 92, the lower side of the annular second groove 13 in the cylindrical portion 3 is downward pushed down, so that the lower end of the cylindrical portion 3 butts against a restriction face 58 of the rotary lower mold 5b, thereby restricting the downward extension of the cylindrical portion 3. Therefore, the lower side of the annular second groove 13 of the cylindrical portion 3 is pushed into an annular recess 95 which is formed immediately below the second groove-forming protrusion 92 of the second roll-forming roller 90, thereby forming a cup-shaped material 4B in which an expansion 40 that is radially outward expanded is formed.
As shown in the right half of
After an outer circumferential face 16a of a flat-face forming rolling roller 16 is caused to butt against the outer circumferential face of the expansion 40, the flat-face forming rolling roller 16 is moved in the direction of the arrow i with respect to the cup-shaped material 4B which rotates about the axis C1 together with the rotary lower mold 5c and the rotary upper mold 6b as described above, so that the annular expansion 40 is clampingly pressed by the outer circumferential face 16a of the flat-face forming rolling roller 16, and the outer circumferential face 53 of the rotary lower mold 5d, and the expansion 40 is caused to disappear, thereby flattening the outer circumferential face 30 of the cylindrical portion 3 as shown in
As described above, the annular expansion 40 that is radially outward expanded is clampingly pressed by the rotary lower mold 5d and the flat-face forming rolling roller 16 to a degree at which the annular expansion 40 disappears, whereby the outer circumferential face 30 of the cylindrical portion 3 is flatly formed. As compared with the case where the whole outer circumferential face 30 of the cylindrical portion 3 is clampingly pressed to be flatly formed, therefore, molding can be conducted by a smaller clamping press force. Therefore, molding is facilitated, and accurate flatness and dimensionality can be obtained by a reduced number of steps. Since the cylindrical portion 3 is not work-hardened in the preceding stage in which the annular expansion 40 is clampingly pressed, the conversion of the expanding volume amount of the annular expansion 40 into the axial extended distance of the cylindrical portion 3 is smoothly performed, and the production efficiency can be enhanced.
Namely, the sheet metal-made back face pulley 11 in which, as shown in
When, as shown in the left half of
When, in the first roll-forming roller 70, the first groove-forming protrusion 72 having a mountain-like section shape is used as shown in the right half of
In the embodiment, the method in which the sheet metal-made back face pulley 11 shown in
As described above, the invention is the technique in which, in a sheet metal-made cup-shaped material comprising: a circular base plate portion; and a cylindrical portion which extends from an outer peripheral edge portion of the base plate portion in one direction along an axis of the base plate portion, an annular expansion which is expanded radially outward is formed in the cylindrical portion, and the annular expansion is clampingly pressed by a rotary inner mold and a flat-face forming rolling roller to a degree at which at least the annular expansion disappears, whereby an outer circumferential face of the cylindrical portion is flatly formed, so that the axial length of the cylindrical portion is increased, and the increased axial length can be used as the effective length, whereby a small positional displacement in the width direction of a belt is absorbed, and a stable contact state with the back face of the belt can be maintained.
Claims
1. A method of producing a sheet metal-made back face pulley wherein a sheet metal-made cup-shaped material com-prising: a circular base plate portion; and a cylindrical portion which extends from an outer peripheral edge portion of said base plate portion in one direction along an axis of said base plate portion is prepared, an annular expansion is formed in said cylindrical portion, and said annular expansion is clampingly pressed by a rotary inner mold and a flat-face forming rolling roller to a degree at which at least said annular expansion disappears, whereby an outer circumferential face of said cylindrical portion is flatly formed.
2. A method of producing a sheet metal-made back face pulley according to claim 1, wherein said annular expansion is formed by expansion in a radially outward direction of said cylindrical portion.
3. A method of producing a sheet metal-made back face pulley according to claim 1, wherein an upper end portion of said cylindrical portion is pressed by a groove-forming protrusion disposed in a roll-forming roller, to form an annular groove in an upper end portion of said cylindrical portion, and an annular projection that projects in a direction opposite to a direction along which said cylindrical portion extends is formed above said annular groove.
4. A method of producing a sheet metal-made back face pulley according to claim 2, wherein an upper end portion of said cylindrical portion is pressed by a groove-forming protrusion disposed in a roll-forming roller, to form an annular groove in an upper end portion of said cylindrical portion, and an annular projection that projects in a direction opposite to a direction along which said cylindrical portion extends is formed above said annular groove.
Type: Application
Filed: Dec 10, 2004
Publication Date: Nov 22, 2007
Applicant: Kanemitsu Corporation (Hyogo)
Inventors: Toshiaki Kanemitsu (Hyogo), Kunihiro Harada (Hyogo), Naoki Fujii (Hyogo)
Application Number: 11/791,709
International Classification: B21H 1/04 (20060101);