Patent Description:
Use of semiconductor-based lighting systems is increasingly common in the automotive industry. Design constraints of the vehicle environment and aesthetic considerations often make it desirable to use optical components to transport and/or diffuse light from the light emitting element to a remote point of illumination. Such optical components should be made of material with high optical efficiency and be carefully aligned with the light emitting element to minimize loss of the light output at the point of illumination. Further, optical performance should withstand mechanical stresses (e.g., vibration), thermal stresses and penetration of moisture to the greatest extent possible.

Areas for development include alignment and precision of the LED projection, thermal management, reliability and durability, ease and quality of manufacturing, and possibly reduced labor and material costs. Thus, continued innovation and refinement of materials and manufacturing processes are important contributors toward the introduction of improved LED-based lighting systems.

Document <CIT> relates to a vehicle lighting device which can decrease the proportion occupied by the non-light emitting region with respect to the light emitting region when viewed from the front. <CIT> discloses a similar lighting assembly of the prior art.

In the complete specification, "LED" is used as a simplification for any solid state light source including, among others, semi-conductor light sources or light emitting diodes (LED).

The present invention is directed to a lighting assembly according to appended claim <NUM> and a method for molding an integrated optical device and support structure assembly of a lighting assembly according to appended claim <NUM>.

In another aspect, the heat sink is formed from a thermally conductive material.

In another aspect, the thermally conductive material is at least one of aluminum and an aluminum alloy.

In another aspect, at least one of the first material and the second material is a thermoplastic.

In another aspect, the first material is a PMMA.

In another aspect, the second material is polycarbonate.

In another aspect, the second material is opaque in the visible and infrared light ranges.

For example, the second material may absorb near- infrared wavelength under <NUM> or under <NUM>.

In another aspect, the optical device is connected to the support structure by mechanical contact.

In another aspect, the optical device is connected to the support structure by a tongue-and-groove joint.

In another aspect, the optical device is connected to the support structure by an angled tongue-and-groove joint.

In another aspect, the lighting assembly forms part of a signaling device, an exterior lighting assembly, or an interior lighting assembly.

In another aspect, the step of injecting a second material further includes injecting the second material around the first material of the optical device portion of the assembly.

In another aspect of the method at least one of the first material and the second material is a thermoplastic.

In another aspect of the method, the first material is a PMMA.

In another aspect of the method, the second material is polycarbonate.

In another aspect of the method, the second material is opaque in the visible and infrared light ranges. For example, the second material may absorb near-infrared wavelength under <NUM> or under <NUM>.

In other aspects of the method, the optical device is connected to the support structure by at least one of a mechanical contact, a tongue-and-groove joint and an angled tongue-and-groove joint.

The foregoing general description of the illustrative implementations and the following detailed description thereof are merely exemplary aspects of the teachings of this disclosure, and are not restrictive.

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:.

Referring now to the drawings, , as used herein, the words "a", "an" and the like generally carry a meaning of "one or more", unless stated otherwise.

<FIG> is a diagram of a lighting assembly <NUM> having a mounting structure <NUM> connected to a fixation assembly <NUM>, according to one example. The mounting structure may be one or more of a printed circuit board (PCB), heat sink or any suitable structure on which an LED may be mounted. In one embodiment, the mounting structure includes a printed circuit board to which the LED is mounted, as well as a heat sink thermally coupled to the LED. The mounting structure <NUM> may serve as a base to which the fixation assembly <NUM> is mounted and upon which the fixation assembly <NUM> is positioned. The mounting structure <NUM> may provide the lighting assembly <NUM> with thermal capacity to store and dissipate excess heat generated by operation of the lighting assembly <NUM>, particularly from an LED <NUM>.

The fixation assembly <NUM> serves as a support structure and may be connected to an optical device represented as a light pipe <NUM> in the figure. The light pipe <NUM> may be positioned in a substantially perpendicular direction relative to the heat sink <NUM>. In other examples not falling under the scope of the appended claims, the fixation assembly <NUM> may include other componentry rather than the light pipe <NUM> such as a collimator lens, a collector lens, or other optical element. In conventional lighting assemblies, the fixation assembly <NUM> is made from the same material as the light pipe for ease of manufacturing, and may encapsulate the LED <NUM> to prevent moisture exposure thereto. However, the inventors recognized that such configuration often results in sub-optimal design and/or operation of the assembly to compensate for heat from the LED <NUM> (including convection and radiation), which may have an effect on the material properties of the fixation assembly <NUM> and the light pipe <NUM>.

In one example, the intensity of the heat from the LED <NUM> may be such that electrical current to the LED <NUM> may be de-rated to operate at below the maximum limit of the LED <NUM> to protect thermal limits of the light pipe <NUM> and/or the fixation assembly <NUM>, rather than the LED <NUM>. Further, the light pipe <NUM> may have to be positioned farther from the LED <NUM> than is ideal for light transmission purposes but, again, limiting material properties of the light pipe <NUM> may necessitate such positioning of the light pipe <NUM> with respect to the LED <NUM>. Heat from the LED <NUM> may also be absorbed and then conducted by the fixation assembly <NUM> to the heat sink <NUM> where it is dissipated.

In the interest of extending performance of such systems, including that of components such as optical devices and fixation assemblies, especially with respect to optical efficiency, thermal effectiveness, and increasing light output, careful design and material selection should be made. The inventors recognized that materials that may be optically efficient may have relatively low temperature thresholds, and are thus not well suited to meeting certain thermal requirements. Conversely, materials that may have suitable thermal properties may not be optically efficient. Further, durability and reliability of the lighting systems may depend on operating temperatures and assembly, so much so that electrical current directed to LED elements may be reduced or de-rated in order to reduce thermal loads that optical devices may be subject to, and therefore reducing the brightness and optical effectiveness of the lighting system.

In one example of the invention, the fixation assembly <NUM> may be made, at least in part, of a different material than the light pipe.

<FIG> is a schematic diagram of a lighting assembly 101a, according to one example of the invention. As seen, the fixation assembly 128a may include the light pipe <NUM>, and may be connected to a heat sink <NUM>. The LED <NUM> may also be mounted on the heat sink <NUM>, positioned below the light pipe <NUM> and optically coupled to a first end of the light pipe <NUM> such that at least some, and preferably all, light emitted by the LED <NUM> may be directed into the first end of the light pipe <NUM> and out a second end of the light pipe <NUM>.

The light pipe <NUM> may be connected to the fixation assembly 128a such that a longitudinal axis of the light pipe <NUM> is approximately located along a vertical z-axis. Further, the fixation assembly 128a may be connected to or surround the light pipe <NUM> enclosing a region between the first end of the light pipe <NUM> and the heat sink <NUM>, such that the fixation assembly 128a, the heat sink <NUM>, and the light pipe <NUM> enclose the LED <NUM> and light emitted by the LED <NUM>. The LED <NUM> is typically not sealed such that it can vent to atmosphere for pressure and humidity control. However, in some situations, the LED <NUM> may be hermetically sealed to minimize exposure of the LED <NUM> to moisture. The fixation assembly 128a supports the light pipe <NUM> above the LED <NUM> and the heat sink <NUM> such that the light pipe <NUM> does not directly contact the heat sink <NUM>. The light pipe <NUM> and the fixation assembly 128a are formed of different materials with different optical, thermal, and mechanical properties, allowing the lighting assembly 101a to achieve improved performance compared with the fixation assembly 128a and the light pipe <NUM> were formed from only one material. The light pipe110 and holder assembly 128a, 128b are typically not sealed to an LED PCB board due to thermal constraints.

The light pipe <NUM> may be formed from a material, for example, a thermoplastic such as acrylic, acrylic glass, or polymethyl methacrylate (PMMA), to optimize Total Internal Reflection (TIR) or other optical properties of the light pipe <NUM>. Further, material selection for, and/or design of, the light pipe <NUM> may then have less emphasis on thermal properties if the fixation assembly 128a is formed from a design and/or a material with superior thermal properties to absorb, conduct, or deflect sufficient heat such that less thermal energy is conducted to the light pipe <NUM>. The light pipe <NUM> may then be subjected to a thermal operating range, primarily thermal energy from the LED <NUM>, that is not more than can be handled by the light pipe <NUM> and the material properties of the light pipe <NUM>.

The fixation assembly 128a may be designed to optimize thermal and mechanical properties of the lighting system. For example, the fixation assembly may be designed to absorb, block or deflect heat (convection, conduction and radiation) from the LED and/or heat sink. Heat conducted from the LED to the support structure can cause plastic deformation and failure of the system due to poor optical alignment, for example. Thus, in some embodiments, the fixation assembly provides a mechanically robust fixation of the light pipe even in a hot environment.

In one example, a temperature difference between an operating temperature of the light pipe <NUM> and the fixation assembly 128a may be approximately in the range of <NUM> to <NUM> degrees Celsius, the fixation assembly 128a operating at a higher temperature than that of the light pipe <NUM>. The ability to decouple the material properties of the light pipe <NUM> from those of the fixation assembly 128a by using more than one material may allow for selection of material properties for each component for specific temperature ranges and other properties. This can extend the overall performance limits of the fixation assembly 128a to durably allow brighter and more efficient light output from the LED <NUM> (such as through increased electrical current) to be directed through to the second end of the light pipe <NUM>.

In one example, the TIR efficiency of the light pipe <NUM> may be increased by forming the light pipe <NUM> from a first material specific for that purpose, the first material needing thermal properties to durably meet a first temperature limit. Further, the fixation assembly 128a may be formed from a second material, the second material able to durably meet a second temperature limit that is higher than the first temperature limit and having a suitable thermal conductivity for conducting heat generated by the LED <NUM> through to the heat sink <NUM> at a rate that meets or exceeds performance requirements. The first material may have superior optical properties (e.g., TIR at a given wavelength) to that of the second material, and the second material may have superior thermal conductivity to that of the first material. While PMMA and PC are provided as exemplary materials for the light pipe <NUM> and the fixation assembly 128a, respectively, one skilled in the art would recognize that the light pipe <NUM> and the fixation assembly 128a may be formed from a wide variety of materials suitable to meet the optical, thermal and mechanical requirements of a particular application of the lighting assembly.

<FIG> is a schematic diagram of a lighting assembly 101b, according to one example. The fixation assembly 128b may include the light pipe <NUM> and a fixation assembly 128b connected to the heat sink104. The fixation assembly 128b may be identical to fixation assembly 128a with the exception that at least a portion of the fixation assembly 128b may be opaque in the visible and infrared light ranges, or black in color to avoid light leakage through the fixation assembly 128b. For example, the second material may absorb infrared wavelength under <NUM> or under <NUM>.

As a result, a greater proportion of light emitted by the LED <NUM> may then be directed through the light pipe <NUM> rather than diffused through the fixation assembly 128b as might occur through light leakage if at least a portion of the fixation assembly 128b was not opaque or black.

Further, in some embodiments, the area of contact between the fixing assembly <NUM> and the light pipe <NUM> may be selected to minimize optical losses of the light pipe <NUM>. In particular, the present inventors recognized that interruption of the cylindrical outer surface of the light pipe <NUM> can reduce the efficiency with which light can be transmitted to the output end of the light pipe by TIR. Thus, in one embodiment the contact area is selected to meet the minimum mechanical strength requirement and to preserve optical efficiency of the light pipe to the greatest extent. In some embodiments, the interface of the fixation assembly and the light pipe may be modified to improve mechanical coupling, which may improve the optical efficiency possible for a given application. <FIG> are diagrams of joints between the fixation assembly <NUM> and the light pipe <NUM>, according to one example. In <FIG>, the fixation assembly <NUM> may surround the light pipe <NUM> or other optical device to secure the light pipe <NUM> to the fixation assembly <NUM>, creating a joint between the light pipe <NUM> and the fixation assembly <NUM>. The joint may be formed from mechanical contact during a manufacturing process, such as overmolding where the fixation assembly <NUM> and the light pipe <NUM> may be molded from distinct materials in one process and in one mold, such as injection of a first material to form the light pipe <NUM> followed by injection of a second material to form the fixation assembly <NUM>. In such a case, it may be advantageous for the fixation assembly <NUM> to have a higher shrinkage rate than that of the light pipe <NUM>. With this configuration, the joint formed between the fixation assembly <NUM> and the light pipe <NUM> has an amount of mechanical interference that further strengthens the joint and locks the components together, preferably without introducing stresses that may otherwise negatively affect the durability or performance of the lighting assembly <NUM>.

<FIG> illustrates a butt joint where the light pipe <NUM> may be pressed into the fixation assembly <NUM>, and a nominal interference fit holds the two parts together. Transfer of thermal energy between the fixation assembly <NUM> and the light pipe <NUM> may be a function of surface area contact between the two. For optimal thermal efficiency between the two parts, surface area contact should be minimized. More surface area contact may be needed between the two parts to provide sufficient friction or interference than compared with examples of <FIG>. For example, a thickness T of the fixation assembly <NUM> may have to be greater than a thickness Tb of the 128b (<FIG>) or a thickness Tc of the 128c (<FIG>) to provide a comparable joint between the light pipe <NUM> and the fixation assembly <NUM> as between the light pipe 110b and the fixation assembly 128b, or between the light pipe 110c and the fixation assembly 128c.

<FIG> illustrate different joint configurations from that of <FIG> that may allow less surface area contact and may withstand more mechanical forces and vibration. In one example, the light pipe 110b and the fixation assembly 128b may be joined by an angled tongue-and-groove joint. In another example, the light pipe 110c and the fixation assembly 128c may be joined by a tongue-and-groove joint. The thermal efficiency of these examples may be higher than that illustrated by <FIG>. However, the optical efficiencies may be affected, possibly through lower TIR efficiency, by surface irregularities of the interiors of the light pipes 110b, 110c in the vicinity of where the fixation assemblies 128b, 128c contact the light pipes 110b, 110c, respectively.

Claim 1:
A lighting assembly (<NUM>) comprising:
a mounting structure (<NUM>);
a solid state light source (<NUM>) mounted on the mounting structure (<NUM>);
an optical device (<NUM>) formed by a light pipe (<NUM>) optically coupled to the solid state light source (<NUM>); and
a support structure (<NUM>) for connecting the optical device (<NUM>) to the mounting structure (<NUM>) surrounding the light pipe (<NUM>) and enclosing a region between the first end of the light pipe (<NUM>) and the mounting structure (<NUM>), wherein the solid state light source (<NUM>) is enclosed within a space formed by the mounting structure (<NUM>), the support structure (<NUM>), and the optical device (<NUM>), and the support structure (<NUM>) absorbs thermal energy to reduce an operating temperature of the optical device (<NUM>), and
the optical device (<NUM>) is formed from a first material and the support structure (<NUM>) is formed from a different, second material, the lighting assembly (<NUM>) being characterized in that
the support structure (<NUM>) supports the light pipe (<NUM>) above the solid state light source (<NUM>) and the mounting structure (<NUM>) such that the light pipe (<NUM>) does not directly contact the mounting structure (<NUM>) and the solid sate light source (<NUM>), and the solid state light source (<NUM>) can vent to atmosphere for pressure and humidity control.