Abstract:
Laser welding of plastic involves a laser passing through laser translucent then laser absorbent material. A technical description as envisaged here is Laser Contour Welding. Universally, laser welding is done by Quasi simultaneous techniques and rarely by Contour techniques. Regular or symmetrical parts, under 5 inches are welded by Quasi simultaneous. Asymmetric and large parts are best welded by Contour Welding. Kinematics of robots permits a complex contour. Automotive plastic manifolds exceed 5 inches with asymmetry. The pairing of robot contour and laser welding facilitates a new Automotive manifold. It requires a new split line for laser access and manufacturing as described. Encompassing the above requirements and solutions can reduce the moldings for a V8 to 2 major operations.

Description:
[0001]     The application claims priority to U.S. Provisional Application No. 60/485,270 which was filed on Jul. 7, 2003. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention is generally related to an intake manifold and a method of assembling an intake manifold. More particularly, this invention relates to an intake manifold fabricated from an inner shell inserted and welded within an outer shell utilizing a laser welding process.  
         [0003]     Plastic intake manifolds have been developed for use in motor vehicles that provide reduced weight and cost. A plastic intake manifold is typically constructed from a plurality of parts that are molded separately and then joined to one another. Various methods are known for joining plastic parts including vibration welding. Joint configurations for these plastic parts typically include a complicated cross-section for providing sufficient melt down material as well as features for trapping flash. Such joint geometries contribute substantially to the cost of fabricating an intake manifold.  
         [0004]     Further, vibrational welding methods lead to the design of plastic manifolds that are designed to include a series of horizontal or vertical slices. Horizontal and vertical slices result in a plurality of parts that must be joined. Further the many parts each require a separate molding tools and assembly stations that complicate assembly and increase overall cost. Additionally, if any of the joints in such a process are defective the intake manifold assembly cannot be repaired.  
         [0005]     Laser welding has been used to join plastic parts with success. Laser welding of plastic is accomplished by directing a laser through a laser translucent material onto a laser absorbent material. Laser Transmission Contour Welding is known for use with large asymmetrical parts. Kinematics of robots has advanced to permit following a complex contour such as is typical of an intake manifold assembly. However, typically laser welding is simply applied to joints originally designed according to known conventions for producing a vibration-welded joint. There is still a plurality of parts that require many joints. Further, in some instances, parts are inaccessible once the manifold is complete. Such construction increases the likelihood that an improper joint may result in the entire intake manifold being unusable. Laser welding requires that the parts touch without substantial gaps and access to the joint for the laser-welding tool.  
         [0006]     Accordingly, it is desirable to design a plastic intake manifold to take advantage of laser welding processes to reduce the number of parts and to reduce the number of joints.  
       SUMMARY OF THE INVENTION  
       [0007]     This invention is a plastic intake manifold assembly including an inner shell and an outer shell including an improved joint interface for a laser transmission weld.  
         [0008]     The intake manifold assembly includes an outer shell and an inner shell. The outer shell defines a cavity having an inner surface. The inner shell includes a plenum type tube and a plurality of dividers that extend radially outward from the plenum tube. The plenum tube includes a mounting flange for a throttle body. The plenum and the tube may be integrated so as to appear as one part or the tube may remain separate and appear as a throttle zip tube which has the effect of increasing the length of the column of air passing through the throttle body or discharging the air into the plenum in a nominally central location of the manifold. Air entering through the plenum tube flows into the spaces between the dividers. The dividers are jointed at an outer periphery to the outer shell to form the runners or air passages.  
         [0009]     The outer shell includes the typical and necessary external features common to all intake manifolds for mounting to an engine. Such features include flanges for mounting to each intake opening of the engine, along with other openings for sensors and other devices that commonly are installed within an intake manifold assembly. The inner shell includes the dividers that provide for and define the runners or air passages that deliver air at a desired pressure and flow rate to each of the engine cylinders. Fully assembled, the inner shell is fully within the outer shell. The dividers are joined to the outer shell to define the separate air passages that delivers airflow to each cylinder.  
         [0010]     The outer periphery of the divider is joined to the outer shell by a laser-welded joint. The laser welded joint forms a substantially air tight seal between each divider and the inner surface of the cavity of the outer shell. The laser weld joint is accomplished by application of laser energy along an outside surface of the outer shell. The outer shell is preferably fabricated from a plastic material that is laser translucent to the laser. The inner shell, and specifically the dividers are fabricated from a plastic material that is substantially laser opaque. This preferential material configuration provides for the laser to penetrate the outer shell and reach the inner shell, where the energy from the laser creates a molten pool of plastic within the inner shell at the interface between the inner shell and the outer shell, that cause corresponding melting of the adjacent surface in the outer shell. The plastic then intermixes and forms the desired joint.  
         [0011]     The laser device is set a desired distance from the outer surface and moved along the path at a speed determined to provide the desired joint depth and strength. Further, a worker skilled in the art would understand the settings including beam strength, focal length, and feed rate that is required to produce the desired depth of the laser weld joint. A laser weld joint requires contact between parts to be joined and must be accessible to the laser device. The laser device is traversed about the outer surface of the outer shell, however the laser device may also be moved within the cavity to provide desired joints.  
         [0012]     The example intake manifold assembly includes the plurality of like shaped dividers that are inserted within a substantially circular outer shell. Processing consideration for assembly of the inner shell to the outer shell requires that each successive divider be of cross-sectional area sufficiently smaller than the preceding divider to aid assembly. The example cavity is stepped such that the smallest diameter or cross-sectional area is at an end distal to initial insertion of the inner shell. Each successive joint location is larger than the preceding such that each divider is easily passed through to the desired location. Each divider abuts a tapered area of the cavity. The tapered area corresponds to a taper on the periphery of the divider. This taper provides for good contact between the two parts to be joined. The laser weld joint is best performed on two parts that are in direct contact with each other.  
         [0013]     The intake manifold assembly of this invention provides for a clamping of the inner shell to provide the desirable contact at the joints. The clamping of the inner shell to the outer shell is accomplished by applying a clamping force that selectively collapses the inner shell against the outer shell. The inner shell includes a plurality of deformations provided at selective stages of the inner shell. Application of force compresses and collapses the inner shell at the deformations such that the tapered areas substantially abut the tapered periphery of the dividers. This contact provides a favorable joint for application of the laser.  
         [0014]     The intake manifold assembly of this invention includes an innovative joint that provides contact between the inner shell and outer shell and access to the joint area for the laser device. The resulting intake manifold assembly provides for a reduction of component parts and a reduction in part and assembly costs.  
         [0015]     These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a schematic view of an inner shell and an outer shell of an intake manifold according to this invention.  
         [0017]      FIG. 2  is a schematic view of the assembled intake manifold.  
         [0018]      FIG. 3  is a top schematic view of the assembled intake manifold.  
         [0019]      FIG. 4  is a schematic view of a collapsible inner shell within the outer shell.  
         [0020]      FIG. 5  is a schematic view of the outer shell collapsed onto the inner shell.  
         [0021]      FIG. 6  is an enlarged schematic view of an interface between the inner shell and the outer shell.  
         [0022]      FIG. 7  is another enlarged schematic view of the interface between the inner shell and the outer shell.  
         [0023]      FIG. 8  is a top view schematically illustrating a web segment directing airflow.  
         [0024]      FIG. 9  is a schematic sectional view illustrating blocking and directing of airflow with the web segment.  
         [0025]      FIG. 10  is a schematic sectional view illustrating a center inlet tube of the inner shell.  
         [0026]      FIG. 11  is a schematic view illustrating assembly of an example intake manifold according to this invention.  
         [0027]      FIG. 12  is a cross-sectional view of an example intake manifold according to this invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0028]     Referring to  FIG. 1 , an intake manifold assembly  10  includes an outer shell  12  and an inner shell  14 . The outer shell  12  and the inner shell  14  are disposed along a longitudinal axis  16 . The outer shell  12  defines a cavity  18  having an inner surface  20 .  FIG. 1  is a schematic illustration of the intake manifold assembly  10  of this invention and does not show such features common to all manifolds. The inner shell  14  includes a plenum tube  22  that extends substantially the entire length of the inner shell  14 . A plurality of dividers  24  extend radially outward from the plenum tube  22 . The plenum tube  22  includes a mount  30  for a throttle body  38 . Air entering through the plenum tube  22  flows into the spaces between the dividers  24 . The dividers  24  include an outer periphery  36  that is joined with outer shell  12  to form air passages  26  within the manifold assembly  10 .  
         [0029]     The inner shell  14  shown includes nine dividers  24  to form the eight air passages  26  required for an eight-cylinder engine. As appreciated, a worker with the benefit of this disclosure will recognize the applicability to other intake manifolds for other engine configurations. The intake manifold assembly  10  of this invention substantially includes only the two parts, the outer shell  12  and inner shell  14 . The outer shell  12  includes the typical and necessary external features common to all intake manifolds for mounting to an engine. Such features include flanges for mounting to each intake opening of the engine, along with other openings for sensors and other devices that commonly are installed within an intake manifold assembly. The inner shell  14  includes the dividers  24  that provide for and define the runners or air passages  26  that deliver air at a desired pressure and flow rate to each of the engine cylinders. The dividers  24  are disposed at angle  27  relative to a plane perpendicular to the longitudinal axis  16 . The angle  27  accommodates the spacing between cylinders of an engine as known.  
         [0030]     Referring to  FIG. 2 , the intake manifold assembly  10  is schematically shown in an assembled state. Fully assembled, the inner shell  14  is fully within the outer shell  12 . The dividers  24  are joined to the outer shell  12  to define the separate air passages  26  that deliver airflow to each cylinder. Further, besides defining air passages  26 , the dividers  24  provide the structure that defines a first end  23  and a second end  25  of the intake manifold assembly  10 . The dividers  24  provide the division between the air passages  26  for each of the cylinders.  
         [0031]     In the example embodiment illustrated in  FIG. 2  each of the dividers  24  provides a portion of each adjacent air passage  26 . That is, the dividers  24  provide a separation wall for two air passages  26 . As appreciated, the number of dividers  24  can be modified within the contemplation of this invention to provide for different air passage configuration. Each air passage  26  may be formed from there own set of dividers  24  such that no air passage  26  shares a divider  24 . Further, the various air passages  26  can be selectively configured through the use of more or less dividers  24 .  
         [0032]     The dividers  24  include the outer periphery  36  that is joined to the outer shell  12  by a laser welded joint shown schematically by arrows  46 . The laser welded joint  46  forms a substantially air tight seal between each divider  24  and the inner surface  20  of the cavity  18  of the outer shell  12 . The laser weld joint  46  is accomplished by application of laser energy along an outer surface  28  of the outer shell  12 . The outer shell  12  is preferably fabricated from a plastic material that is substantially laser transparent or translucent to the laser. That is the outer shell  12  is formed from a material that provides for some transmission of the laser through to the inner shell  14 . The inner shell  14 , and specifically the dividers  24  are fabricated from a plastic material that is substantially laser opaque. This preferential material configuration provides for the laser to penetrate the outer shell  12  and reach the inner shell  14 , where the energy from the laser creates a molten pool of plastic within the inner shell  14 , that causes corresponding melting of the adjacent surface in the outer shell  12 . The laser device  40  is subsequently moved or deactivated, providing for the re-solidification of the melted plastic. The melted plastic from the inner shell  14  intermixes with the melted plastic from the outer shell  12  to form the laser weld joint  46 . The laser weld joint  46  provides both the desired structural rigidity to the intake manifold assembly  10  along with the desired air seal between adjacent air passages  26 .  
         [0033]     Referring to  FIG. 3 , a top schematic view of the intake manifold assembly  10  is shown and illustrates how the laser weld joint  46  is formed. The example intake manifold assembly  10  is illustrated as substantially circular; however, other shapes as are desired and required for each application are within the contemplation of this invention. Further, example movement of the laser device  40  along the path  42  as circular. A robot as known can be used for moving the laser device  40  along the contours of the intake manifold assembly  10 . Movement of the laser device  40  follows a path that provides the desired joint and moves along the contours of the outer surface  28 . The example intake manifold assembly  10  is shown with several joints  46  that are substantially linear about the longitudinal axis  16 , however, the path and therefore the joint  46  can be any shape as is required to join the dividers  24  to the inner surface  20  of the outer shell  12 .  
         [0034]     The laser device  40  is set a desired distance from the outer surface  28  and moved along the path  42  at a speed determined to provide the desired joint depth and strength. The specific laser device  40  is as known. Further, a worker versed in the art would understand the settings including beam strength, focal length, and feed rate that is required to produce the desired depth of the laser weld joint. A laser weld joint requires contact between parts to be joined and must be accessible to the laser device  40 .  
         [0035]     In the example shown in  FIG. 3 , the laser device  40  is traversed about the outer surface of the outer shell  12 , however the laser device  40  may also be moved within the cavity  18  to provide desired joints.  
         [0036]     Referring to  FIG. 4 , the example intake manifold assembly  10  includes the plurality of like shaped dividers  24  that are inserted within a substantially circular outer shell  12 . The dividers  24  are shown as substantially identical, however it is not required that each divider be identical, only that the shape of the divider  24  corresponds to the cavity  18 . Processing consideration for assembly of the inner shell  14  to the outer shell  12  require that each successive divider  24  be of cross-sectional area sufficiently smaller than the preceding divider  24  to allow for ease of assembly. Assembly of the plurality of dividers  24  into a successive diameter of the same size would make assembly difficult, as each successive divider would require very precise alignment to allow the first divider  24  to be installed to the far end of the outer shell  12 .  
         [0037]     Accordingly, the example cavity  18  is stepped such that the smallest diameter or cross-sectional area is at an end distal to initial insertion of the inner shell. Each successive joint location is just a bit larger than the preceding such that each divider  24  is easily passed through to the desired location. The difference in relative cross-sectional areas is such that to the naked eye no difference will be perceived. The difference between cross-sectional areas is greatly exaggerated in  FIG. 4  to illustrate the specific example configuration.  
         [0038]     In the example intake manifold assembly  10  shown, each divider  24  abuts a tapered area  48  of the cavity  18 . The tapered area  48  corresponds to a taper on the periphery of the divider  24 . This taper provides for good contact between the two parts to be joined. The laser weld joint  46  is best performed on two parts that are in direct contact with each other. The intake manifold assembly of this invention provides for a clamping of the inner shell  14  to provide the desirable contact at the joints  46 . The clamping of the inner shell  14  to the outer shell  12  is provide by applying a clamping force  54  that selectively collapses the inner shell  14  against the outer shell  12 .  
         [0039]     The inner shell  14  includes a plurality of deformations  44  provided at selective stages of the inner shell  14 . Application of the force  54  compresses and collapses the inner shell  14  at the deformations  44  such that the tapered areas  48  substantially abut the tapered periphery of the dividers  24 . The number of deformations  44  for each collapsible portion along the plenum tube  22  is determined to progressively and selectively collapse the plenum tube  22 . The greater the number of deformations  44  the less force required to collapse that section of the plenum tube  22 . The deformations  44  can take different forms such as dimples or serrations within the plenum tube. Further, the deformations  44  can be a flexible portion of the plenum tube  22 .  
         [0040]     The process can proceed by collapsing one divider  24  into the tapered area  48 , performing the weld, and then further collapsing the inner shell for the next divider. Alternatively, the entire inner shell  14  may be collapsed at once such that each divider  24  abuts the inner surface  20  of the cavity  18 . In either process, the clamping, collapsing of the inner shell  14  produces the desired abutted contact between the dividers  24  and the inner surface  20  of the outer shell  12 .  
         [0041]     Referring to  FIG. 5 , another example intake manifold assembly  10  according to this invention includes deformations  52  in the outer shell  12  such that a clamping force  54  is applied to selectively collapse the outer shell  12  into contact with the inner shell  14 . The force  54  causes the outer shell  12  to compress enough to contact the periphery  36  of each divider  24 . The contact provides the desired joint geometry for the laser weld joint  46 .  
         [0042]     Additionally, the inner shell  14  can be formed from a plastic material that has less re-enforcing content to encourage local deformations that in turn result in improved contact for welding. The inner shell  14  and the outer shell  12  are formed from a plastic material including re-enforcing material. One of the inner shell  14  and the outer shell  12  is more compliant than the other to facilitate local deformations and improved contacts. The relative compliance between the inner shell  14  and the outer shell  12  is provided by a reduction in the amount of re-enforcing material provided in the more compliant one of the inner shell  14  and outer shell  12 . The re-enforcing material present within the inner shell  14  and the outer shell  12  is as known.  
         [0043]     Referring to  FIG. 6 , an enlarged view of the joint  46  is shown and includes the tapered area  48  in proximity to the periphery  36  of the divider. Preferably, the divider  24  contacts the tapered area  48  and the laser device  40  provides the desired energy to form the joint  46 . However, the joint  46  can also be formed with a gap  56  between the divider  24  and the outer shell  12 . Gaps  56  form due to tolerance stack ups and manufacturing deviations that inevitably are encountered in any assembly and manufacturing process.  
         [0044]     Accordingly, it is desirable to develop a process that can accommodate such variations. The joint  46  can be formed between the divider  24  and the outer shell  12  with gaps  56  of up to approximately 0.2 mm. Preferably, the divider  24  is in direct contact with the outer shell  12 , however a joint  46  as desired can be formed over gaps  56  of approximately 0.2 mm. Although, a gap of 0.2 mm is described, the specific joint geometry and material may result in more or less of a gap  56  being allowable while still providing a joint as desired.  
         [0045]     Referring to  FIG. 7 , a schematic view of the laser device  40  forming the joint is shown. The laser device  40  transmits energy that forms a molten plastic pool  55  between the inner shell  14  and the outer shell  12 . The molten plastic pool  55  intermixes and re-solidifies, resulting in the desired joint  46 .  
         [0046]     Referring to  FIG. 8 , a schematic view of the example air passage  26  is shown and includes a web section  58 . Typically, the length and size of the air passage  26  is carefully selected to provide desired engine performance characteristics. The length of the air passage  26  is closely controlled such that all air passages  26  are of the same length to provide equal airflow to each cylinder and provide equal acoustic lengths to minimize emissions of undesirable noise through the throttle body  38 . The web section  58  calibrates the length of the air passage  26  for the example intake manifold assembly  10  as desired.  
         [0047]     The web section  58  blocks airflow  60  entering the air passage  26  from the plenum tube  22 . Airflow  60  must circulate about the plenum tube  22  before reaching the intake opening  62  to the cylinder. The position of the web section  58  corresponds with opening  61  within the plenum tube  22  to provide the desired length of the air passage  26 .  
         [0048]     Referring to  FIG. 9 , a cross sectional view of adjacent air passages  26  includes the web sections  58  and illustrates how airflow  60  is diverted about the plenum tube  22 . The web sections  58  correspond with the openings  61  in the plenum tube  22  to provide the desired length of air passage  26 .  
         [0049]     Referring to  FIG. 10 , in another example intake manifold assembly  10  according to this invention, the mount  30  for the throttle body  38  is part of the outer shell  12 . The inner shell includes an intake tube  64  that extends transversely from the plenum tube  22 . The intake tube  64  provides a conduit for incoming airflow into the plenum tube  22  from a central location of the manifold assembly  10 . A laser weld joint  66  seals the interface between the intake tube  62  and the outer shell  12  to provide the desires air passage  26 . The mount  30  is illustrated in a central location, however other locations as would be required by application specific requirements are within the contemplation of this invention.  
         [0050]     Referring to  FIG. 11 , another example intake manifold assembly  70  is shown and includes an inner shell  72  that is inserted into an outer shell  74 . In previous example embodiments the dividers were illustrated as substantially circular members disposed about a central plenum tube. However, the inner shell  72  need not consist of circular members. The inner shell  72  includes dividers  75  that form air passages  84  through the intake manifold assembly  70 .  
         [0051]     The dividers  75  are J-shaped channels that include the desired configuration of the air passages. Further, the dividers  75  include an enclosed portion  86  and a walled portion  88 . The enclosed portion  86  provides a tube that extends into a cavity  76  of the outer shell  74 . The enclosed portion  86  does not require a laser weld joint. The walled portion  88  includes two sides that correspond to inner surfaces  90  of the cavity  76  to form the remainder of the air passage into intake runners  78  within the outer shell  74 .  
         [0052]     The outer shell  74  defines the cavity  76  and the runners  78  that extend and connect with the engine to communicate air to each engine cylinder. Assembly of the intake manifold assembly  70  includes molding the inner shell  72  and the outer shell  74 . The inner shell  72  is inserted into the outer shell  74 . The inner shell  72  is then clamped such that surfaces of the inner shell  72  that will form the weld joint with the outer shell  74  are in substantial contact with the inner surface  90  of the outer shell  74 . The contact between the inner shell  72  and the outer shell  74  is preferably within a desired gap range to provide the desired laser weld joint.  
         [0053]     The laser device  40  is traversed along the outer surface  91  of the outer shell  74  along a predetermined path  82 . The predetermined path  82  corresponds with the position of the inner shell  72  such that the desired laser weld joint is formed. The predetermined path  82  is illustrated as a simple rectangular path; however, the path of the laser device  40  can be of any shape required to provide the desired air passages and intake mold configuration. Once the laser weld joint is complete, the intake manifold assembly  70  is substantially complete except for assembly of external devices such as the throttle body  38 , sensors and other hardware supporting operation.  
         [0054]     Referring to  FIG. 12 , the assembled intake manifold assembly  70  is shown as a cross-section through the mount  30 . Airflow  80  through the mount  30  enters the cavity  76 . The cavity  76  is in communication with each of the air passages formed by the dividers  75 . In this example intake manifold assembly  70  the dividers  75  include the enclosed portion  86  that extends into the cavity  76 . Airflow  80  entering the enclosed portion  86  flows through the air passage to the walled portion  88 . The walled portion  88  cooperates with the inner surface  90  to define the remainder of the air passage.  
         [0055]     Forming of the laser weld joint along the weld path  82  provides the desired structural connection between the inner shell  72  and outer shell  74 . Further the laser weld joint provides the air sealing required to isolate airflow to each cylinder. The laser weld joint requires no special joint configuration, other than the need to provide sufficient weld area, and to provide access to the joint area.  
         [0056]     The example intake manifolds of this invention provide a substantial reduction in the number of parts, along with a substantial simplification in the joint between manifold parts. The example intake manifolds described include substantially two components, however, additional components as be required for a specific application would also benefit from the simplified joint configuration and laser weld process. Further, the example intake manifold substantially reduces assembly and manufacture time and expense.  
         [0057]     Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.