Rocker arm made of sheet metal and method of manufacturing the same
A rocker arm includes: a body that is made of sheet metal and includes a pair of side walls; and a pair of axial holes that are respectively formed through the pair of side walls and have a first diameter and through which an axis is inserted. The pair of axial holes include thickened portions formed partially or overall of circumference of the pair of axial holes, and the thickened portion is formed by expanding a hole that has a second diameter smaller than the first diameter and is formed in a pre-arranged range for forming the axial hole in a blank material so as to causing plastic flow in a metallic material of the circumference of the hole.
1. A rocker arm comprising:
a body that comprises sheet metal and includes a pair of side walls;
a pair of axial holes that are respectively formed through the pair of side walls and have a first diameter and through which an axis is inserted,
wherein the pair of axial holes include thickened portions formed partially or overall of a circumference of the pair of axial holes,
wherein the thickened portion is formed by expanding a hole that has a second diameter smaller than the first diameter and is formed in a pre-arranged range for forming the axial hole in a blank material so as to cause plastic flow in a metallic material of the circumference of the hole, and
wherein the second diameter is smaller than a diameter of the axis of said rocker arm.
2. The rocker arm according to claim 1 , wherein the thickened portion is formed at a portion of the circumference of the axial hole at sides of loading ranges.
3. The rocker arm according to claim 1 , wherein only the thickened portion is projected from the side wall in a direction in which the axis is extended.
4. A method of manufacturing a rocker arm that includes a body that includes a pair of side walls, and a pair of axial holes that are respectively formed through the pair of side walls and have a first diameter and through which an axis is inserted, the method comprising:
forming a hole having a second diameter smaller than the first diameter in pre-arranged ranges of a blank material, said second diameter being smaller than a diameter of the axis of said rocker arm; and
expanding the hole having the second diameter to form the axial hole having the first diameter so that a thickened portion is formed partially or overall of a circumference of the axial hole by causing plastic flow in a metallic material of the circumference.
5. A rocker arm that includes a body that includes a pair of side walls, and a pair of axial holes that are respectively formed through the pair of side walls and have a first diameter and through which an axis is inserted, produced by a method comprising:
forming a hole having a second diameter smaller than the first diameter in pre-arranged ranges of a blank material, said second diameter being smaller than a diameter of the axis of said rocker arm; and
expanding the hole having the second diameter to form the axial hole having the first diameter so that a thickened portion is formed partially or overall of a circumference of the axial hole by causing plastic flow in a metallic material of the circumference.
6. The rocker arm according to claim 1 , wherein the axis is bridged between said pair of side walls and non-rotatably attached to said side walls by fitting the axis to circumferential faces of said pair of axial holes.
7. The rocker arm according to claim 1 , wherein the axis comprises expanding opposite end faces that are fitted to said thickened portions such that the axis does not project from said sidewalls.
8. The rocker arm according to claim 1 , further comprising a lash adjuster formed at a second end of said body between said side walls.
9. The rocker arm according to claim 8 , further comprising a valve carrier formed at a first end of said body.
10. The rocker arm according to claim 9 , wherein said side walls, said lash adjuster carrier and said valve carrier comprise a single, integrated piece.
11. The rocker arm according to claim 1 , wherein the thickness of said thickened portions comprise a thickness approximately 1.5 times a thickness of said side walls.
12. The rocker arm according to claim 1 , further comprising a roller supported on the axis between said side walls.
13. The rocker arm according to claim 12 , wherein said roller comprises a plurality of needle rollers turnably disposed along an inside surface of said roller.
14. The rocker arm according to claim 1 , wherein said axial holes comprise an elliptical shape.
15. The rocker arm according to claim 1 , wherein said axial holes comprise a semicircular shape.
16. The method according to claim 4 , wherein said pre-arranged ranges are pre-arranged to ensure that the second diameter of said axial holes is smaller than a diameter of the axis.