The present invention relates generally to vehicles and, more particularly, to a vehicle manufacturing process that can be used to decrease fabrication time and cost when bonding assembly techniques are used in the vehicle fabrication process.
Vehicle manufacturers are continually looking for ways to lower overall vehicle cost while improving vehicle characteristics. One such way that has been identified in recent years is the use of structural adhesives. Bonding components and structures together during vehicle manufacturing offer a number of advantages over traditional vehicle fabrication techniques, identified advantages including:
While most car makers appreciate the advantages offered by structural adhesives and therefore have started to modify their manufacturing procedures in order to utilize structure adhesives to a greater extent, further improvements are still needed. The present invention provides a manufacturing process improvement that further simplifies the use of structural adhesives during the vehicle assembly process while minimizing the use of mechanical fasteners.
The present invention provides a method of assembling a vehicle structure, where the vehicle structure is comprised of at least a first component and a second component, the method comprising the steps of (i) applying a layer of a structural adhesive onto at least one surface of a pair of surfaces, where a first surface of the pair of surfaces corresponds to a first region of the first component, and where a second surface of the pair of surfaces corresponds to a second region of the second component; (ii) aligning the first region of the first component with the second region of the second component; (iii) applying pressure to the vehicle structure, the pressure joining the first region of the first component to the second region of the second component, where the layer of structural adhesive is interposed between the first region of the first component and the second region of the second component; (iv) maintaining a position of the first component relative to the second component with a curing fixture, where the position results from the step of applying pressure to the vehicle structure to join the first region of the first component to the second region of the second component; (v) directing a laser beam at a plurality of localized regions of the vehicle structure, where the laser beam irradiates and heats the plurality of localized regions to a temperature above an ambient temperature, where the laser beam expedites curing of a plurality of adhesive regions proximate to the plurality of localized regions, and where the plurality of adhesive regions comprise a portion of the layer of structural adhesive; and (vi) removing the vehicle structure from the curing fixture after the step of directing the laser beam at the plurality of localized regions, where the step of removing the vehicle structure from the curing fixture is performed prior to curing the layer of structural adhesive, and where the plurality of adhesive regions continues to maintain the position of the first component relative to the second component after the vehicle structure is removed from the curing fixture. The vehicle structure may be placed into a curing oven after it has been removed from the curing fixture, where the curing oven heats the vehicle structure in order to complete curing of the structural adhesive layer. Additional fabrication and assembly procedures may be performed on the vehicle structure after it has been removed from the curing fixture but before it is placed into the curing oven. The laser beam may be directed sequentially or simultaneously at the plurality of localized regions.
In another aspect of the method, the laser beam may be optically split into a first beam and a second beam, where the first laser beam is directed at the plurality of localized regions and the second laser beam is directed at a second plurality of localized regions, and where the first laser beam irradiates and heats the plurality of localized regions and the second laser beam irradiates and heats the second plurality of localized regions. The second plurality of localized regions may be proximate to the plurality of adhesive regions. The plurality of localized regions may be located on the front surface of the first component, where the front surface is distal from the first surface of the first component and the front surface is separated from the first surface by a first material width corresponding to the thickness of the first component, and the second plurality of localized regions may be located on the rear surface of the second component, where the rear surface is distal from the second surface of the second component and is separated from the second surface by a second material width corresponding to the thickness of the second component. Alternately, the plurality of localized regions may be located on the front surface of the first component, where the front surface is distal from the first surface of the first component and the front surface is separated from the first surface by a first material width corresponding to the thickness of the first component, and the second plurality of localized regions may be located on the second surface of the second component, where the second plurality of localized regions is adjacent to the second region of the second component.
In another aspect of the method, a second laser beam may be directed at a second plurality of localized regions, where the second laser beam irradiates and heats the second plurality of localized regions. The second plurality of localized regions may be proximate to the plurality of adhesive regions. The plurality of localized regions may be located on the front surface of the first component, where the front surface is distal from the first surface of the first component and the front surface is separated from the first surface by a first material width corresponding to the thickness of the first component, and the second plurality of localized regions may be located on the rear surface of the second component, where the rear surface is distal from the second surface of the second component and is separated from the second surface by a second material width corresponding to the thickness of the second component. Alternately, the plurality of localized regions may be located on the front surface of the first component, where the front surface is distal from the first surface of the first component and the front surface is separated from the first surface by a first material width corresponding to the thickness of the first component, and the second plurality of localized regions may be located on the second surface of the second component, where the second plurality of localized regions is adjacent to the second region of the second component.
In another aspect of the method, the laser beam may be directed through an aperture in a third component prior to irradiating and heating at least one of the plurality of localized regions of the vehicle structure, where the third component may be an additional component of the vehicle structure.
In another aspect of the method, at least one of the pair of surfaces may be pretreated prior to applying the layer of structural adhesive.
In another aspect of the method, the laser beam may be directed at the plurality of localized regions as the vehicle structure moves relative to the laser beam thereby causing the laser beam to sequentially irradiate and heat the plurality of localized regions; alternately, the laser beam may be directed at the plurality of localized regions as the laser beam moves relative to the vehicle structure thereby causing the laser beam to sequentially irradiate and heat the plurality of localized regions.
A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings.
It should be understood that the accompanying figures are only meant to illustrate, not limit, the scope of the invention and should not be considered to be to scale. Additionally, the same reference label on different figures should be understood to refer to the same component or a component of similar functionality.
As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises”, “comprising”, “includes”, and/or “including”, as used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” and the symbol “/” are meant to include any and all combinations of one or more of the associated listed items. Additionally, while the terms first, second, etc. may be used herein to describe various steps or calculations, these steps or calculations should not be limited by these terms, rather these terms are only used to distinguish one step or calculation from another. For example, a first calculation could be termed a second calculation, similarly, a first step could be termed a second step, similarly, a first component could be termed a second component, all without departing from the scope of this disclosure.
After completion of any required surface pretreatment procedures, adhesive is applied to one or both of the surfaces to be bonded (step 103). The adhesive may be a single part adhesive, such as a heat curable adhesive that cures at a temperature above room temperature, or a two part adhesive, such as a two part epoxy. The layer of adhesive may be comprised solely of adhesive, or may contain a plurality of granules (e.g., spherical or non-spherical beads) that set the separation distance between the two surfaces to be bonded. If the adhesive layer contains granules, the granules may be uniformly or non-uniformly distributed throughout the adhesive layer, and may be comprised of a material selected to control heat transfer across the bond layer/joint.
After application of the adhesive, the surfaces of the two components are aligned and brought together (step 105), after which the parts are placed within a fixture (step 107), also referred to as a jig, that is configured to maintain the bonded components in their desired relative positions until the adhesive has cured, or at least until the bonded structure can be removed from the fixture and handled as described below. In some embodiments the individual components are held by different fixtures. These individual fixtures are used both to align and position the components during initial contact and to maintain the relative positions of the components throughout the curing process. In other embodiments, a first fixture(s) is used to position the components during initial contact and a second fixture(s) is used to maintain the relative positions of the parts during curing. In yet other embodiments, during initial contact the components are positioned by hand, after which they are mounted within a fixture that maintains their relative positions throughout the curing process.
In a conventional bonding process, the bonded components are held in the curing fixture throughout the entire curing process, thus significantly impacting vehicle assembly time. For some conventional applications, rather than room temperature curing the bonded components and the curing fixture are all placed within a curing oven, thereby allowing the temperature to be raised and the curing time to be decreased.
In accordance with the invention, after the parts have been bonded together and are being held together by a curing fixture, localized regions of the bonded assembly are heated using lasers (step 109). Laser heating allows small regions of the assembly to be rapidly heated to a temperature that is sufficient to either (i) completely cure the adhesive in the heated regions or (ii) cure the adhesive in the heated regions to a sufficient degree to allow handling of the assembly without further need of the curing fixture. Once localized regions of the structure have been heated, thereby curing (or partially curing) localized regions of the adhesive, the curing fixture is removed (step 111). Removal of the curing fixture at this stage, rather than after completely curing the entire layer of adhesive as required in the conventional approach, expedites vehicle assembly. Additionally, if the assembly is subsequently placed in a curing oven, for example after completion of further vehicle assembly, elimination of the curing fixture allows a smaller curing oven to be used and decreases the time required to reach the desired temperature.
Although not a requirement of the invention, typically after removal of the curing fixture (step 111), the vehicle structure will undergo further processing (step 113). As step 113 is optional, it is shown in phantom. Further processing may include attaching other components to the vehicle structure or integrating the bonded structure into another vehicle structure, where the additional processing steps may include the use of additional adhesive layers or mechanical fasteners. Further processing may also include applying surface treatments to the bonded structure, for example painting the structure. After the curing fixture has been removed (step 111), or after the curing fixture has been removed (step 111) and additional processing has been completed (step 113), the structure undergoes a complete curing cycle (step 115). This final curing cycle may be performed at room temperature, or the structure may be placed in an oven in order to heat the entire structure and expedite curing.
In the embodiment illustrated in
As illustrated in
In the preferred and illustrated embodiment, the assembly system is automated, thereby further lowering manufacturing cost while improving quality control. In this embodiment a controller 217, typically comprised of a microprocessor or a programmable logic device, controls operation of laser 211 (i.e., laser operating characteristics such as output power, beam profile, pulse frequency, pulse duration, etc.). Preferably controller 217 also controls the locations of irradiated regions 301 by controlling the position of fixture 217, and thus components 201/203. Alternately, controller 217 may control the locations of irradiated regions 301 by controlling the location of the laser beam 209 on surface 219 of component 201. Preferably beam location is controlled by optics 213, for example using beam turning optics such as those that are well known by those of skill in the art (e.g., optical fibers, mirrors, etc.). Alternately, controller 217 may control the locations of irradiated regions 301 relative to the assembly by controlling both the location of laser beam 209 on surface 219, and the location of the assembly via fixture 207.
In order to control the heating of each region 301, thus insuring sufficient temperature and pulse duration to properly cure the adjacent adhesive region 303, controller 217 preferably monitors the output characteristics of laser 211, including output power and beam quality, as well as the thermal characteristics of each irradiated region 215. The thermal characteristics of the irradiated regions may be monitored using sensors 221 that are in thermal contact with one or both components 201 and 203. Alternately, or in combination with one or more contacting sensors, a non-contact thermal sensor(s) 223 may be used to monitor the thermal characteristics of region 215.
In general, the operating characteristics of laser 211 and laser beam 209 are selected based on the characteristics of the components to be irradiated (e.g., reflectivity, thermal conductivity, panel thickness, etc.) as well as the characteristics of the adhesive comprising layer 205 (e.g., acceptable curing temperature range, curing time versus temperature, etc.). Additionally, the initial cost, operational costs and equipment reliability are considered when selecting laser source 211. Operating characteristics that are selected based on the materials and adhesives to be bonded include the laser's wavelength, output power, pulse duration, number and frequency of pulses applied per region (e.g., region 215), beam spot size, and focal length.
In the preferred embodiment illustrated and described above, either the bonded structure or the laser beam or both are moving while laser 211 is pulsed, thereby sequentially irradiating localized regions 301. The pulses may be generated any of a variety of ways, for example by pulsing the laser on/off or optically shuttering beam 209. In an alternate configuration, either the bonded structure or the laser beam or both move while laser 211 is operated in a continuous or semi-continuous mode. As a result, the region irradiated and heated by laser 211 is elongated, as is the region of adhesive that undergoes expedited curing.
In addition to sequentially irradiating localized regions of the bonded structure, in at least one embodiment multiple localized regions are simultaneously irradiated. Simultaneous irradiation may be accomplished using multiple lasers or using a single laser in which the laser beam has been optically split into multiple beams.
As noted above, laser assisted curing in accordance with the invention is not limited to a single type of laser or a single set of laser operating characteristics. Additionally it should be understood that the invention is not limited to a single configuration for the beam delivery system.
In the beam delivery system configuration illustrated in
It will be appreciated that the use of multiple sources, or a single source split into multiple beams, allows other adhesive curing configurations as well. For example, in the embodiment shown in
Due to the small diameter of the laser beam(s) used to augment adhesive curing, the inventors envision that the flexibility of the present invention lends itself to a variety of curing arrangements, all of which benefit from the ability to tack structures together by rapidly curing localized regions within an adhesive layer. For example,
Systems and methods have been described in general terms as an aid to understanding details of the invention. In some instances, well-known structures, materials, and/or operations have not been specifically shown or described in detail to avoid obscuring aspects of the invention. In other instances, specific details have been given in order to provide a thorough understanding of the invention. One skilled in the relevant art will recognize that the invention may be embodied in other specific forms, for example to adapt to a particular system or apparatus or situation or material or component, without departing from the spirit or essential characteristics thereof. Therefore the disclosures and descriptions herein are intended to be illustrative, but not limiting, of the scope of the invention.