Lamp and lighting apparatus

1. A lamp, comprising:

a translucent cover;

a mounting board on which a semiconductor light-emitting element is mounted;

a first housing comprising a metal plate and thermally coupled with the mounting board, the first housing including a first un-covered exterior surface, a second un-covered exterior surface and a third un-covered exterior surface; and

a second housing including a power receiving unit configured to receive power for causing the semiconductor light-emitting element to emit light,

wherein the first housing is disposed closer to an illuminated area than the second housing is, and

wherein the second housing has a thermal conductivity that is lower than a thermal conductivity of the first un-covered exterior surface,

wherein a metal bended part of the first housing connects the first un-covered exterior surface and the second un-covered exterior surface, and further connects the first un-covered exterior surface to the third un-covered exterior surface,

wherein the second un-covered exterior surface and the third un-covered exterior surface extend parallel to the radial symmetrical center axis of the lamp,

wherein the first un-covered exterior surface extends perpendicular to the radial symmetrical center axis of the lamp,

wherein the translucent cover is retained by the third un-covered exterior surface such that the translucent covered is closer to the mounting board than the first un-covered exterior surface.

2. The lamp according to claim 1 , further comprising a translucent cover disposed closer to the illuminated area than the mounting board is.

3. The lamp according to claim 1 , wherein the first housing includes a protruding portion which protrudes toward the illuminated area to be higher than the mounting board, and the protruding portion has, as the first un-covered exterior surface, a surface facing the illuminated area.

4. The lamp according to claim 3 ,

wherein the protruding portion is formed into an annular shape to enclose the mounting board.

5. The lamp according to claim 3 ,

wherein the protruding portion has a height which is measured from the mounting board and which is set such that the protruding portion is formed in a region outside a range of a ½ beam angle of light emitted from the semiconductor light-emitting element.

6. The lamp according to claim 3 ,

wherein h 3 <(D 3 −DL)/2×3 1/2 , where h 3 denotes a height of the protruding portion measured from the mounting board, D 3 denotes an inner diameter of the protruding portion at an end facing the illuminated area, and DL denotes a maximum diameter of a region in which a sealing member for covering the semiconductor light-emitting device is formed.

7. The lamp according to claim 1 , wherein the first housing has thermal conductivity higher than thermal conductivity of glass.

8. The lamp according to claim 1 , wherein the first housing has thermal emittance greater than or equal to 0.6.

9. A lighting apparatus comprising:

the lamp according to claim 1 ; and

lighting equipment to which the lamp is attached,

wherein the lighting equipment includes:

an equipment body formed to cover the lamp, and

a socket attached to the equipment body for supplying power to the lamp.

10. A lamp, comprising:

a mounting board on which a semiconductor light-emitting element is mounted;

a first housing thermally coupled with the mounting board, the first housing including a first un-covered exterior surface, a second un-covered exterior surface and a third un-covered exterior surface;

a second housing including a power receiving unit configured to receive power for causing the semiconductor light-emitting element to emit light,

wherein the first housing is disposed closer to an illuminated area than the second housing is, and

wherein the first un-covered exterior surface, the second un-covered exterior surface and the third un-covered exterior surface of the first housing defines a protruding portion which protrudes toward the illuminated area to be higher than the mounting board,

wherein the first un-covered surface is formed on an end of the protruding portion in a direction away from the mounting board,

and

a translucent cover that is disposed closer to the illuminated area than the mounting board is,

wherein the translucent cover is fixed to the third un-covered exterior surface,

wherein the protruding portion protrudes toward the illuminated area such that the first un-covered exterior surface, in a direction of a radial symmetrical center axis of the lamp, is spaced farther from the semiconductor light-emitting element than a forward-most surface of the translucent cover.

11. The lamp according to claim 1 , wherein the second housing comprises a resin material.

12. The lamp according to claim 1 ,

wherein the lamp is greater in width than in height.

13. The lamp according to claim 10 , wherein an entire outer periphery of the translucent cover is surrounded by the inner wall surface of the protruding portion.

14. The lamp according to claim 1 , wherein a portion of the cylindrical outer surface of the first housing, which defines the second un-covered exterior surface, abuts an inner cylindrical side surface of a base portion of the second housing.

15. A lamp, comprising:

a translucent cover;

a mounting board on which a semiconductor light-emitting element is mounted;

a first housing comprising a metal plate and thermally coupled with the mounting board, the first housing including a first un-covered exterior surface, a second un-covered exterior surface and a third un-covered exterior surface; and

a second housing including a power receiving unit configured to receive power for causing the semiconductor light-emitting element to emit light, the first housing is disposed closer to an illuminated area than the second housing is, and the first housing including the first un-covered exterior surface exposed at least to the illuminated area, and

the second housing has a thermal conductivity that is lower than a thermal conductivity of the first un-covered exterior surface,

the second un-covered exterior surface being defined by an outer cylindrical surface provided at a lateral side of the lamp and the third un-covered exterior surface being defined by an inner cylindrical surface surrounded by the second un-covered exterior surface, wherein an annular space is defined radially between the inner cylindrical surface and the outer cylindrical surface,

wherein the translucent cover is retained by the third un-covered exterior surface such that the translucent covered is closer to the mounting board than the first un-covered exterior surface.

16. A lamp, comprising:

a translucent cover;

a mounting board on which a semiconductor light-emitting element is mounted;

a first housing formed of a metal plate and thermally coupled with the mounting board, the first housing including a first un-covered exterior surface, a second un-covered exterior surface and a third un-covered exterior surface that together define a protruding portion; and

a second housing including a power receiving unit configured to receive power for causing the semiconductor light-emitting element to emit light,

wherein the first housing is disposed closer to an illuminated area than the second housing is, and the first un-covered exterior surface is exposed at least to the illuminated area, and

wherein the second housing has a thermal conductivity that is lower than a thermal conductivity of the first un-covered exterior surface,

wherein the second un-covered exterior surface is defined by an outer cylindrical surface exposed to a lateral side of the lamp,

wherein the protruding portion protrudes toward the illuminated area to be higher than the mounting board,

wherein the translucent cover is retained by the protruding portion, and

wherein the protruding portion protrudes toward the illuminated area such that, in a direction of a radial symmetrical center axis of the lamp, the first un-covered exterior surface is spaced farther from the semiconductor light-emitting element than a forward-most surface of the translucent cover.