Outer shell unit and method of manufacturing the unit

1. A method of manufacturing an outer shell unit provided with a cylindrical outer shell housing a damping force generating mechanism and a knuckle bracket mounted on the outer shell to connect a knuckle, the method comprising the steps of;

forming a bottom of the outer shell using a closing process which totally closes the bottom of the outer shell with a process using a cored bar disposed coaxially with the outer shell, the cored bar rotating with the outer shell, and a die pressing the bottom of the outer shell, the die rotating around a die axis having a predetermined offset from a rotation axis of the outer shell, and

welding the knuckle bracket to the outer shell after forming the bottom.

2. The method of manufacturing an outer shell unit as defined in claim 1 , wherein a vertical downward welding method is used to weld the lower end of the knuckle bracket to the outer shell.

3. The method of manufacturing an outer shell unit as defined in claim 1 , wherein a protrusion projecting from the bottom of the outer shell is formed by the closing process.

4. The method of manufacturing an outer shell unit as defined in claim 1 , further comprising the steps of,

mounting a spring guide on the outer shell to support a suspension spring,

forming a step by a bulge forming along the outer shell, and

mounting the spring guide by press-fitting on the step.

5. The method of producing an outer shell unit of claim 1 , wherein a spring guide is mounted on the outer shell to support a suspension spring, the method comprising the steps of;

providing a processing line for the outer shell to form an outer shell from a pipe member using a mechanical process, and

providing a welding line for the outer shell unit to mount a knuckle bracket and a spring guide on an outer shell,

wherein the cycle time for forming one outer shell in the processing line is made substantially equal to the cycle time for welding one outer shell unit in the welding line.

6. The method of producing an outer shell unit as defined in claim 5 , wherein a cylindrical double-plate knuckle bracket is mounted on the outer shell in the welding line and one end of the knuckle bracket is welded by a vertical downward welding method to the outer shell.

7. A method of welding an outer shell unit comprising a cylindrical outer shell housing a damping force generating mechanism and a suspension component welded to the outer shell, the method consisting of the steps of;

disposing a torch of an arc-welding unit in proximity to the welding position of a suspension component and the side of the outer shell, and

welding the suspension component to the outer shell by rotating the outer shell unit so that the welded position facing the torch rises.

8. The method of welding an outer shell unit as defined in claim 7 , wherein a horizontal plane including a central axis (O) of the outer shell is taken to be a horizontal reference plane (X),

the point at which a line extended from the torch intersects with the outer shell unit is taken to be a welding point (W), and

the welding point (W) is either on the horizontal reference plane (X) or offset to be above the horizontal reference plane by a vertical offset (Lx).

9. The method of welding an outer shell unit as defined in claim 8 , wherein

a vertical plane including the central axis (O) of the outer shell is taken to be a vertical reference plane (Y),

the welding point (W) is offset from the vertical reference plane (Y) by a horizontal offset (Ly), and

the vertical offset (Lx) is smaller than the horizontal offset amount (Ly).

10. The method of welding an outer shell unit as defined in claim 7 , wherein

a horizontal plane including the central axis (O) of the outer shell is taken to be the horizontal reference plane (X),

the torch has a torch angle (θx) inclined upwardly with respect to the horizontal reference plane (X), and

the torch angle (θx) is set in a range of 0–30 degrees.