Abstract:
An intake manifold assembly ( 100  includes an inner shell ( 12 ) that is inserted into an outer shell ( 14 ), and a cover ( 25 ) that seals the open end ( 38 ) of the outer shell ( 14 ). The inner shell ( 12 ) includes dividers ( 16 ) that form air passages ( 18 ). A laser device ( 40 ) is traversed along the outer surface of the outer shell ( 14 ) along a predetermined path ( 44 ) that corresponds with the position of the inner shell ( 12 ) such that a desired laser weld joint ( 45 ) is formed The intake manifold assembly ( 10 ) of this invention includes features and methods of assembly that improve the laser weld joints utilized to assemble the plastic intake manifold assembly ( 10 ). Both design details and clamping detail are described, every known configuration of U type manifolds can be made by this technique. The technique provides high value and low cost. High reliability is a well known feature of laser welding.

Description:
[0001]     The application claims priority to U.S. Provisional Application Ser. Nos. 60/559,984 filed on Apr. 6, 2004, 60/566,560 filed on Apr. 29, 2004, and 60/602,356 filed on Aug. 18, 2004. 
     
    
     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. Each of the many parts requires a separate molding tool and assembly station that complicates assembly and increases overall cost. Additionally, at least some of the joints are not accessible for reprocessing once the completed part is assembled making impractical repair of a defective intake manifold assembly.  
         [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 requires aligned joints and contact between surfaces to be jointed. Disadvantageously, plastic parts are not typically fabricated to the tolerances required to provide desired alignment between joint contact surfaces. Further, part inconsistencies and imperfections can affect joint alignment causing undesirable weld performance.  
         [0006]     Accordingly, it is desirable to design a plastic intake manifold with assembly and joint features that improve and simplify joint structure for improved laser welded 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]     An example intake manifold assembly of this invention includes an inner shell that is inserted into an outer shell, and a cover that seals the open end of the outer shell. The inner shell includes dividers that form air passages. The dividers are J-shaped channels that include the desired configuration of the air passages. A laser device is traversed along the outer surface of the outer shell along a predetermined path that corresponds with the position of the inner shell such that a desired laser weld joint is formed.  
         [0009]     In weld joint locations, the thickness of the outer shell is of a lesser thickness than non-weld joint areas. The thinner sections allow for more laser energy to penetrate to the inner shell without increasing the energy output from the laser device or modifying the material composition of the outer shell. The increased energy provided at the inner shell increases the amount of molten plastic produced, that in turn increases the size of a gap that can be bridged and welded.  
         [0010]     The inner shell includes edge surfaces that are placed in contact with the inner surface of the cavity. The edge surface includes pads disposed in areas where it is desired to increase the strength of the laser weld joint. The pads provide a larger surface area for the laser weld joint in the discrete localized area. During the welding process the laser device will retrace the desired weld path that corresponds to the location of the pads such that an increased weld area is provided in the areas defined by the pads.  
         [0011]     The inner shell is clamped to the outer shell by a clamping device that cooperates with a clamping ridge fabricated into the outer shell and a clamping pad provided on the inner shell. The clamping device is an elongated bladed member inserted between the inner shell and the outer shell. Rotation of the clamping device forces the inner shell outward and downward against the inner surface of the outer shell. Rotation of the clamping device pushes the inner shell tightly against the outer shell to deform the inner shell in a manner that reduces or substantially eliminates gaps therebetween.  
         [0012]     The cover includes an axial joint, a radial joint portion and a transitional joint between the axial joint and the radial joint. Between the axial joint and the radial joint is the transitional joint were the interface between the cover and the outer shell curves from the flange to the edge interface. The cover is clamped and pressed onto the outer shell. The different joint configurations reduce the effects on fit caused by the generous tolerances required by the injection molding process.  
         [0013]     The example intake manifolds of this invention provide a substantial reduction in the number of manufacturing steps, along with a substantial simplification in the joint between manifold parts. Further, the features provided with the methods and configurations of the intake manifold improve laser weld joint performance and application. Accordingly, the methods and intake manifold feature of this invention improve and simplify assembly to provide improved laser welded joint structures.  
         [0014]     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  
       [0015]      FIG. 1  is a schematic view illustrating assembly of an example intake manifold according to this invention.  
         [0016]      FIG. 2  is a perspective view of an example intake manifold according to this invention.  
         [0017]      FIG. 3  is a cross-sectional view of a joint between an inner shell and an outer shell.  
         [0018]      FIG. 4  is a perspective view of an inner shell.  
         [0019]      FIG. 5  is a top view of the inner shell.  
         [0020]      FIG. 6  is a partial cross-sectional view of an example device for clamping and aligning the inner shell with the outer shell according to this invention.  
         [0021]      FIG. 7  is another partial cross-sectional view of another device for clamping and aligning the inner shell with the outer shell according to this invention.  
         [0022]      FIG. 8  is a plan view of a cover attached to the outer shell.  
         [0023]      FIG. 9  is a side view of the cover attached to the outer shell.  
         [0024]      FIG. 10  is an enlarged cross-sectional view of a radial joint between the cover and the outer shell.  
         [0025]      FIG. 11  is an enlarged cross-sectional view of an axial joint between the cover and the outer shell.  
         [0026]      FIG. 12  is an enlarged cross-sectional view of a transitional joint between the cover and the outer shell.  
         [0027]      FIG. 13  is a plan view of a cover including a throttle body mount according to this invention.  
         [0028]      FIG. 14  is a side view of the cover illustrated in  FIG. 13 .  
         [0029]      FIG. 15  is a schematic illustration of another throttle body mounting configuration according to this invention.  
         [0030]      FIG. 16  is a schematic illustration of a molding machine tool for fabricating an outer shell according to this invention.  
         [0031]      FIG. 17  is a plan view of an outer shell and inner shell interface according to this invention.  
         [0032]      FIG. 18  is a side view of an outer shell and inner shell according to this invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0033]     Referring to  FIG. 1 , an example intake manifold assembly  10  is shown and includes an inner shell  12  that is inserted into an outer shell  14 , and a cover  25  that seals the open end  38  of the outer shell  14 . The inner shell  12  includes dividers  16  that form air passages  18  through the intake manifold assembly  10 . The dividers  16  are J-shaped channels that include the desired configuration of the air passages. Further, the dividers  16  include enclosed portions  20  and walled portions  22 . The enclosed portions  20  provide a tube that extends into a cavity  24  of the outer shell  14 . The walled portions  22  include two sides that correspond to an inner surface  28  of the cavity  24  to form the remainder of an air passage  32  into intake runners  34  within the outer shell  14 .  
         [0034]     The outer shell  14  defines the cavity  24  and runners  34  that extend and connect with an engine (not shown) to communicate air to each engine cylinder. The intake manifold assembly  10  is assembled by inserting the inner shell  12  into the outer shell  14  as is shown. The inner shell  12  is then clamped such that surfaces of the inner shell  12  that will form a weld joint with the outer shell  14  are in substantial contact with the inner surface  28  of the outer shell  14 .  
         [0035]     A laser device  40  is traversed along the outer surface  42  of the outer shell  14  along a predetermined path  44 . The predetermined path  44  corresponds with the position of the inner shell  12  such that a desired laser weld joint is formed. The predetermined path  44  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 joints for joining the inner shell  12  to the outer shell  14 .  
         [0036]     Referring to  FIG. 2 , laser weld joints  45  are formed by applying a directed beam of laser energy through the outer shell  14  and onto the inner shell  12 . The outer shell  14  is formed from a laser transmissive or transparent material that allows a portion of laser energy to penetrate through the outer shell  14 . Typical laser transparent materials allow between 10% and 30% of the laser energy to penetrate through to the inner surface of the outer shell  14 . The specific amount of laser energy that penetrates through to the inner shell  12  is dependent on the material composition of the outer shell  14 , the thickness of the outer shell  14  and the power of the laser device  40 .  
         [0037]     Laser energy that penetrates the outer shell  14  impacts the inner shell  12 . The inner shell  12  is composed of a laser absorbent material such that laser energy is absorbed and transformed into heat energy that in turn generates a region of molten plastic material. The molten plastic material transfers a portion of heat to the outer shell  14 . The portion of the outer shell  14  adjacent the molten material of the inner shell  12  melts and intermixes with the molten material of the inner shell  12 . The molten material will then cool and form the desired bond and laser welded joint  45 .  
         [0038]     The power and type of laser device  40  used to perform the laser weld maybe of any known configuration. Further, it is within the contemplation of this invention to utilize any known laser device for generating and performing the laser weld operation.  
         [0039]     Once the laser weld joint  45  is complete, the intake manifold assembly  10  is substantially complete except for assembly of external devices such as a throttle body, sensors and other hardware supporting operation.  
         [0040]     The assembled intake manifold assembly  10  is shown as a cross-section through the mount  48 . Airflow  50  through the mount  48  enters the cavity  24 . The cavity  24  is in communication with each of the air passages formed by the dividers  16 . In this example, the dividers  16  include the enclosed portion  20  that extend into the cavity  24 . Airflow  50  entering the enclosed portion  20  flows through the air passage to the walled portion  22 . The walled portion  22  cooperates with the inner surface  28  to define the remainder of the air passage  18 .  
         [0041]     Formation of a laser weld joint requires that the inner shell  12  and the outer shell  14  be in substantial contact at the weld joint interface. Gaps between the inner shell  12  and the outer shell  14  can cause undesirable weld properties. The size of the gap that is allowable is related to the amount of laser energy that is transmitted to the joint interface. The greater the energy that penetrates the outer shell  14 , the larger the gap that can be accommodated by the laser weld joint. Accordingly, the inventive process described in this disclosure includes methods and configurations to optimize laser energy and minimize gaps between the inner shell  12  and the outer shell  14  at weld joint interfaces.  
         [0042]     Referring to  FIG. 3 , the amount of laser energy available is related to the laser energy power and the thickness of the laser transmissive or transparent material. The thicker the materials the less laser energy that will be available for a welding operation. However, the outer shell  14  must include a thickness that is capable of enduring durability and pressure testing. Accordingly a minimum thickness is required in all areas of the outer shell  14 .  
         [0043]     In weld joint locations, the thickness of the outer shell  14  is combined with the thickness of the inner shell  12  joined in that specific area. The outer shell  14  can therefore be a lesser thickness in weld areas  56 . The outer shell  14  includes a first thickness  60  and a second thickness  62  less than the first thickness  60 . The second thickness  62  is aligned with the portion of the inner shell  12  along the predetermined weld path  44 . As an example, the first thickness is approximately 4 mm and the second thickness is approximately 2 mm. The thinner section provided by the second thickness allows for more laser energy  58  to penetrate to the inner shell  12  without increasing the energy output from the laser device  40  or modifying the material composition of the outer shell  14 . The increased energy provided at the inner shell  12  increases the amount of molten plastic produced, that in turn increases the size of any the gap that can be bridged and welded.  
         [0044]     Another method for increasing the amount of molten plastic at the weld interface is to fabricate the inner shell  12  with a reduced amount of glass reinforcement material. Injection molded plastic parts include a portion of glass fiber for reinforcing and strengthening the material. The inner shell  12  is not a load bearing part and is not subject to pressure requirements as the outer shell  14  is; accordingly, the inner shell  12  may be of a reduced strength. Therefore the amount of glass reinforcement is reduced to approximately 15%. Typical glass reinforcement content is approximately 30%. The reduced amount of glass reinforcement results in an increase in percent resin content. The resin is the part of the plastic material that forms the molten plastic pool in the presence of heat from the laser device  40 . The increased amount of resin material results in an increase in the amount of molten material responsive to the same amount of laser energy. The increased size of the molten plastic pool results in an increased gap size that may be comfortably accommodated and still provide the desired laser weld joint.  
         [0045]     Another method according to this invention for increasing the size of the molten plastic pool is to include a foaming agent in one of the outer shell  14  or inner shell  12 . The foaming agent increases and expands the molten plastic pool by releasing gas from the material upon exposure to heat. The released gas provides an expansion or inflation of the molten plastic material. The foaming agent may comprise any agent that provides an out-gassing upon exposure to heat energy. As appreciated any foaming agent as is known in the art is within the contemplation of this invention.  
         [0046]     Referring to  FIGS. 4 and 5 , the inner shell  12  includes edge surfaces  70  that are placed in contact with the inner surface  28  of the cavity  24 . The edge surfaces  70  include a first width  72 . The first width  72  provides for tolerances in location during the assembly process. The laser device  40  aims the laser beam through the outer shell  14  such that the penetrating portion of the beam will impact on the inner shell  12 . The edge surfaces  70  provide the weld joint interface with the outer shell  14 . The first width  72  provides the desired tolerance and a desired contact area for the laser weld joint. The contact area provides the desired and resulting strength of the completed laser weld joint.  
         [0047]     The edge surface  70  include pads  76  disposed in area where it is desired to increase the strength of the laser weld joint. The pads  76  include a second width  74  that is greater than the first width  72  to provide a larger surface area for the laser weld joint in the discrete localized area. During the welding process the laser device  40  will retrace the desired weld path that corresponds to the location of the pads  76  such that an increased weld area is provided in the discrete localized areas defined by the pads  76 .  
         [0048]     Increasing the weld area and the amount of molten plastic material at a weld interface are ways to increase the amount of gap that can be accommodated by a laser welded joint. As appreciated, it is desirable to eliminate gaps at a weld interface. Accordingly, this invention includes a method of clamping the inner shell  12  to the outer shell  14 . Clamping is complicated because the inner shell  12  and outer shell  14  are substantially irregularly shaped, and because any clamping must be done in such a way so as to not obstruct access of the laser device  40 .  
         [0049]     Referring to  FIG. 6 , an example clamping device  80  is shown that corresponds to a clamping ridge  82  fabricated into the outer shell  14  and a clamping pad  84  provided in the inner shell  12 . The clamping device  80  is an elongated bladed member inserted between the inner shell  12  and the outer shell  14 . The clamping device  80  includes a first tab  86  that contacts the clamping pad  84  and a second tab  88  in contact with the clamping rib  82 . The clamping device  80  rotates in a direction indicated at  90  to force the inner shell  12  outward and downward against the inner surface  28  of the outer shell  14 . Rotation of the clamping device  80  pushes the inner shell  12  tightly against the outer shell  14  to deform the inner shell  12  in a manner that reduces or substantially eliminates gaps therebetween.  
         [0050]     Prior to application of rotary force by the clamping device  80 , an alignment tool  94  is inserted through the outer shell  14  and received with the inner shell  12  (indicated by dashed outline within the air passage  18 ). The alignment tool  94  assures alignment of the walled portions  22  with the air passages  34  such that there is no overlapping of the inner shell  12  over opening for the air passages  34 . The alignment tool  94  includes a cutout center section  96  to accommodate initial misalignment of the inner shell  12 . As appreciated although a single alignment tool  94  is shown, several alignment tools  94  may be used to accommodate multiple air passages and align each air passages with the inner shell  12 . Once the inner shell  12  is aligned as desired the clamping device  80  is rotated to force abutment of the inner shell  12  with the outer shell  14 . The laser device  40  traverses along the desired weld path and directs laser energy  58  through the outer shell  14  to generate the desired laser weld joint  45 .  
         [0051]     Referring to  FIG. 7  another clamping device  100  is shown and includes a housing  102  that is inserted along with the inner shell  12  into the outer shell  14  The housing  102  supports a plurality of pneumatically operated pistons  104  that contact and push the inner shell  12  against the outer shell  14 . Actuation of the pistons  104  pushes the housing  102  against the outer shell  14  and the inner shell  12  upward and outward against the inner surface  28  of the cavity  24 . The pistons  104  are located to provide increased pressure at desired points to eliminate gaps and provide a tight fit for the generation of the laser weld joint. As appreciated, the specific location of the pistons  104  are determined for the specific application to provide the desired pressure and force required to drive the inner shell  12  upward and outward against the inner surface  28  of the outer shell  14 . The clamping device  100  may temporarily deform portions of the inner shell  12  in order to eliminate gaps in the desired laser weld joint area.  
         [0052]     Referring to  FIGS. 8 and 9 , the cover  25  is welded over the open end  38  of the outer shell  14  to seal the cavity  24  once the inner shell  12  has been attached ( FIG. 1 ). Open end  38  in the outer shell  14  is irregularly shaped and therefore presents mating assembly problems with the cover  25 . Further, as both the cover  25  and the outer shell  14  are formed from injection molded plastic, tolerances are generally generous and therefore require an innovative method and design for assuring a desired fit and seal. Any, single type of joint such as an axial or radially oriented joint that extends about the entire interface between the cover  25  and outer shell  14  is problematic due to the tolerances provided each plastic part.  
         [0053]     Referring also to  FIGS. 10-12 , the cover  25  therefore includes an axial joint  108  portion and a radial joint portion  110  separated by a transitional joint  112  between the axial joint  108  and the radial joint  110 . As the outer shell  14  is formed from a laser transmissive or transparent material, the cover  25  is fabricated from a laser absorbent material. The cover  25  includes a flange  114  at a top and bottom end that corresponds to a lip  116  provided on the outer shell  14 . The laser device  40  directs laser energy  58  through the lip  116  of the outer shell  14  and into the flange  114  of the cover  25 .  
         [0054]     A middle portion  118  between the top and bottom axial joints  108  includes the radial joint  110  were the laser device  40  directs laser energy  58  normal to the surface of the outer shell  14 . Laser energy  58  is transmitted through the outer shell  14  and into the sides of the cover  25  to form the radial joint  110 . Between the axial joint  108  and the radial joint  110  is the transitional joint  112  were the interface between the cover  25  and the outer shell  14  curves from the flange  114  to the edge interface  120 . The cover  25  is clamped and pressed onto the outer shell  14 , and the different joint configurations reduces the effects on fit caused by the generous tolerances require by the injection molding process.  
         [0055]     Referring to  FIGS. 13 and 14 , another example cover  125  according to this invention is shown that includes a mount  120  for a throttle body  52 . The mount  120  defines an opening  122  for air to enter the intake manifold assembly  10 . In some intake manifold applications it is desirable to install the throttle body  52  at the end of the manifold instead of at a top portion. The example cover  125  includes the mount  120  for the throttle body  52  and includes the several various joint features as described above with reference to  FIGS. 10-12 . The cover  125  is attached by a laser weld joint through the axial joint  108 , transition joint  112  and radial joint  110 . The mount  120  is included with the cover  125  to eliminate any additional components otherwise required to attach a throttle body to the intake manifold.  
         [0056]     Referring to  FIG. 15 , another example manifold assembly  126  includes an extension tube  132  for extending an air inlet into the cavity  124 . It is desirable that an air passage from the opening of the intake manifold into the engine be of a substantially equal length for each engine cylinder. Mounting of a throttle body at the cover does not provide this desired feature and therefore the tube  132  is provide to extend the opening into the cavity  124  inwardly to a substantially centrally located position. In the example intake manifold assembly  126  a throttle body  130  is mounted to a tube  136  above the intake manifold  126  with an opening  135  that extends around and through the cover  140  and into the cavity  124  of a outer shell  128 . The tube  132  is attached to two curved sections  134 ,  136 . The curved sections  134 , 136  provide a desired curve to traverse a desired angle  138 . In the example shown each curved section  134 ,  136  provides approximately 80 degrees of curve that are joined by a laser welded joint  142  to provide the desired curve radius form the cover  140  to the throttle body  130 . The tube  132  is attached to one of the curved sections  134  or the cover  140  at a laser weld joint  144 . The throttle body  130  is disposed atop the outer shell  128  but at a slight upward angle relative to the outer shell  128 . As appreciated, the specific angle and position of the throttle body  130  is application specific. The curves sections  134  and tube  132  can be modified to provide the desired position of the throttle body  130 . Further, the length of the tube  132  can be adjusted to tune the intake manifold assembly  126  as desired.  
         [0057]     Referring to  FIG. 16 , a mold  150  for fabricating an outer shell  160  according to this invention is shown and includes a first half  152  and a second half  154 . The first half  152  and the second half  154  are separate along the parting line  158 . An insert  156  moves into a cavity  155  to complete the cavity for forming the outer shell  160 . The insert  156  includes an alignment feature  162  to provide alignment of the completed outer shell  160  and the insert  156  within the cavity  155 . The alignment feature  162  is a tab that fits within an opening  159  defined by the mold halves  152 ,  154 . The alignment feature  162  maintains position of the insert  156  during the molding process to assure a consistent desired material thickness of the outer shell  160 . The alignment feature  162  results in the formation of an opening  164  within the outer shell  160  that must be plugged to seal the manifold assembly.  
         [0058]     Referring to  FIGS. 17 and 18 , the inner shell  165  includes a plug  166  that fits within the opening  164  of the outer shell  160 . The inner shell  165  is inserted into the outer shell  160  such that a portion abuts an inner surface of the outer shell  160  adjacent the opening  164 . A laser device  40  directs laser energy  58  to weld the inner shell  165  to the outer shell  160  adjacent the opening  160 . The resulting laser weld joint  168  seals the manifold assembly. The plug  166  of the inner shell  165  not only provides the function of plugging the opening  164 , but also provides an alignment function to properly align the inner shell  165  relative to the outer shell  160 . This alignment function provides alignment at a substantially inaccessible location for the interface between the outer shell  160  and the inner shell  165  and therefore provides additional alignment that is not otherwise practical.  
         [0059]     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.  
         [0060]     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.