Patent Application
20120140500
Not Applicable.
Not Applicable.
The present invention relates in general to headlamp assemblies for motor vehicles, and, more specifically, to housing structures for passively increasing air circulation.
Headlamp assemblies for motor vehicles typically include a housing and a lens cover creating a chamber that contains a light source, such as an incandescent lamp, a light emitting diode (LED), a high intensity discharge (HID) lamp, or a projection lamp, electrically connected to a power source. The chamber may also include a reflector surrounding the light source or the housing itself may be made reflective.
During operation of the light source (i.e., during illumination driven by the power source), heat is generated within the chamber which must be removed. In some designs, the chamber is hermetically sealed, while in other designs a vent is introduced in the housing. When a vent is used, a membrane or filter is typically required to remove contaminants and to reduce entry of moisture into the chamber which could cause condensation. Thermal management and condensation management are important design aspects for both sealed and vented lamps.
It is desirable to keep light sources cool during use and to maintain relatively constant temperature distribution throughout the chamber. Condensation is related to the partial pressure of water vapor in the air contained in the lamp. As the air is heated, the partial pressure of the water vapor increases. When the high pressure water vapor reaches a cold region, it expands and condensation occurs. In order to avoid hot or cold spots in the chamber, fans have sometimes been added to headlamp assemblies in order to circulate air within the chamber or within a passageway separated from the chamber by a wall. The fan results in added cost and reduced reliability of a headlamp system. Without a fan, however, circulation in conventional headlamp assemblies has been due only to density differences between hot and cold air. Insufficient mixing in conventional assemblies can increase condensation and prevent efficient heat removal from the headlamp.
In one aspect of the invention, a lighting system for an automotive vehicle comprises a housing adapted for mounting to the vehicle and having a generally outward facing backplate and at least one socket for an incandescent light source. A transparent lens cover is attached to the housing and forms an internal chamber between the lens cover and the housing. A staircase circulator on the housing comprises a plurality of steps and risers rising from the backplate toward the lens cover along a path that is spaced from the socket, wherein the path is generally along a natural convection flowpath of air within the chamber.
Referring now to
Housing 10 is adapted to be mounted to the body of a vehicle via attachment brackets 16. A boot cap 17 is provided as an attachment point for a main light source and/or reflector. Lamp sockets 11 and 12 may be associated with signal or accessory lighting. A socket 18 is provided in housing 10 for receiving a headlamp adjuster mechanism, i.e., for controlling the direction of the headlight beam. Pivot bosses 19 work in concert with the adjuster as known in the art.
A vent hole 20 is provided in housing 10 to allow equalization of pressure during temperature cycling of the headlamp assembly resulting from heat generated by the various light sources operating in the headlamp assembly.
Staircase circulator 15 is shown in greater detail in
As illustrated in
As shown in
The invention may include one or more distinct staircase circulators formed on the headlamp housing. After the general shape of a lamp housing and lens cover have been selected early in a design process, temperature generation and air circulation are simulated based on the selected shapes without the presence of a staircase circulator. The temperature distribution and airflow directions are observed in the simulation and then one or more staircase circulators are placed in appropriate is locations to draw airflow into regions that assist in equalizing overall temperatures.
Thus, in a preferred method of the invention, a shape of the housing is configured including at least one socket for a light source in a generally outward-facing backplate, wherein the backplate lacks a staircase circulator. A shape of the transparent lens cover is configured for attaching to the housing to form an internal chamber between the lens cover and the housing. A convective airflow pattern is simulated within the chamber resulting from operation of the light source. Regions of relatively stagnant flow are identified within the convective airflow pattern. A path and profile of a staircase circulator are configured for interacting with the simulated convective airflow pattern in order to reduce the region of stagnant flow. The path of the staircase circulator may be substantially aligned with the region of stagnant flow. The profile of the staircase circulator is comprised of a plurality of steps and risers rising from the backplate toward the lens cover along a path that is spaced from the socket. The path may be substantially straight, curved with a substantially constant radius of curvature, or otherwise curved or serpentine in any manner necessary to redirect the air circulation as desired.
The foregoing description utilizes a staircase circulator as an integral part of a headlamp housing operating passively, without moving parts, and without any significant added cost while distributing air within the chamber to reduce hot or cold spots and obtaining results previously obtained only by the added cost and reduced reliability associated with a fan.
