Abstract: A metal composite and a metal joining method that are capable of suppressing an influence on joining strength of a friction stir welded section due to a tool hole formed when a tool is extracted, in the case in which two metals are joined through friction stir welding. In an overlapping section in an axial direction in which a first shaft and a second shaft overlap in the axial direction, an inscribed section in which the first shaft and the second shaft come in contact with each other and an non-inscribed section in which the first shaft and the second shaft do not come in contact with each other are formed. In the non-inscribed section, a plate thickness of the second shaft is decreased. Then, a starting point of a friction stir welded section is formed in the inscribed section, and an endpoint is formed in the non-inscribed section.

Abstract: A dissimilar metal joining method includes moving a tool on a first metal along a first track on an overlapped part where the first metal is overlapped on a second metal while the tool is rotated around an axis of the tool and is pressed along the axis against the first metal such that the tool penetrates the first metal and is inserted into the second metal by a first insertion depth. The tool is moved from the first track to a second track which is on the overlapped part and which is substantially parallel to the first track after the tool has moved along an entirety of the first track. The tool is moved on the first metal along the second track on the overlapped part while the tool is rotated around the axis and is pressed against the first metal along the axis.

Abstract: A transmission includes a first shaft and a second shaft. The first shaft is made of a first metal material. The first shaft has a hollow structure. The second shaft is made of a second metal material different from the first metal material. The second shaft is fitted into the hollow structure of the first shaft at an axial overlap section. The first shaft and the second shaft are coaxially connected at the axial overlap section with friction stir welding.

Abstract: A metal composite and a metal joining method that are capable of suppressing an influence on joining strength of a friction stir welded section due to a tool hole formed when a tool is extracted, in the case in which two metals are joined through friction stir welding. In an overlapping section in an axial direction in which a first shaft and a second shaft overlap in the axial direction, an inscribed section in which the first shaft and the second shaft come in contact with each other and an non-inscribed section in which the first shaft and the second shaft do not come in contact with each other are formed. In the non-inscribed section, a plate thickness of the second shaft is decreased. Then, a starting point of a friction stir welded section is formed in the inscribed section, and an endpoint is formed in the non-inscribed section.

Abstract: A dissimilar metal joining method includes moving a tool on a first metal along a first track on an overlapped part where the first metal is overlapped on a second metal while the tool is rotated around an axis of the tool and is pressed along the axis against the first metal such that the tool penetrates the first metal and is inserted into the second metal by a first insertion depth. The tool is moved from the first track to a second track which is on the overlapped part and which is substantially parallel to the first track after the tool has moved along an entirety of the first track. The tool is moved on the first metal along the second track on the overlapped part while the tool is rotated around the axis and is pressed against the first metal along the axis.

Abstract: A transmission includes a first shaft and a second shaft. The first shaft is made of a first metal material. The first shaft has a hollow structure. The second shaft is made of a second metal material different from the first metal material. The second shaft is fitted into the hollow structure of the first shaft at an axial overlap section. The first shaft and the second shaft are coaxially connected at the axial overlap section with friction stir welding.

Abstract: A conventional projector headlamp has low efficiency because an amount of light is shaded almost half by a shutter for a low-beam light distribution. In addition, only a projection lens is seen in the installed condition, inviting old-fashioned designs disadvantageously. In a projector headlamp (1) of the invention, a vertical section passing through the center of a projection lens (5) includes a convex front surface and a flat rear surface (5a). A line connecting the upper end to the lower end on the rear surface (5a) is tilted to the vertical. Thus, the projection lens (5) has a prismatic action for directing the entire light downward. This is effective to reduce an amount of light to be shaded by a shutter (4) and provide improved brightness and novel designed appearances.

Abstract: A conventional projector headlamp has low efficiency because an amount of light is shaded almost half by a shutter for a low-beam light distribution. In addition, only a projection lens is seen in the installed condition, inviting old-fashioned designs disadvantageously. In a projector headlamp (1) of the invention, a vertical section passing through the center of a projection lens (5) includes a convex front surface and a flat rear surface (5a). A line connecting the upper end to the lower end on the rear surface (5a) is tilted to the vertical. Thus, the projection lens (5) has a prismatic action for directing the entire light downward. This is effective to reduce an amount of light to be shaded by a shutter (4) and provide improved brightness and novel designed appearances.