1. Field of the Invention
The present invention relates to a vehicular headlamp, in which a light source unit for light distribution formation is accommodated inside a lamp chamber that is defined by a lamp body and a front cover, and the light source unit is provided with a metal heat transfer member.
2. Related Art
Various vehicular headlamps have been proposed in recent years with configurations that accommodate a light source unit for light distribution formation, which has a light-emitting element such as a light-emitting diode as a light source, within a lamp chamber in order to reduce power consumption. However, the amount of heat generated by the light-emitting element has become a concern over the course of developing a light-emitting element capable of achieving a high light flux that matches the light intensity required for headlamp light distribution. In other words, while a light-emitting element capable of high light flux can achieve a high light flux, correspondingly, a large amount of heat is generated. This leads to problems of reduced luminous efficiency and variations in the color of light emitted.
Patent Document 1 describes a structure (headlamp) in which a projecting portion is formed on a metal heat transfer member that serves as a light source unit structural member attached with a light-emitting element. A blast fan is provided at a predetermined position on the inner side of a lamp body. Air blowing from the blast fan hits the projecting portion of the metal heat transfer member and promotes the release of heat from the projecting portion. Thus, the light-emitting element is cooled.
Although this type of headlamp is equipped with a lighting circuit that controls lighting of the light-emitting element, Patent Document 1 makes no mention of a lighting circuit. Patent Document 2, similar to Patent Document 1, describes a structure (headlamp) in which a light-emitting element is attached to a metal heat transfer material that serves as a light source unit structural member, and a lighting circuit is provided outside a lamp chamber (on a lower surface of a lamp body) so that the lighting circuit (electronic components that structure the lighting circuit) is not affected by the heat of the light-emitting element.    [Patent Document 1] Japanese Patent Application Laid-Open (Kokai) No. 2006-294263    [Patent Document 2] Japanese Patent Application Laid-Open (Kokai) No. 2007-35547