Patent Publication Number: US-8122866-B2

Title: Acoustic bumpers with engine front cover hidden mounting

Description:
TECHNICAL FIELD 
     This invention relates to acoustic bumpers and to reduction of radiated noise from an internal combustion engine cover, such as a front cover, the acoustic bumpers being mounted on hidden rear surfaces of the cover. 
     BACKGROUND OF THE INVENTION 
     It is known in the art to provide various means for reducing auditory noise radiated from operating internal combustion engines such as automotive vehicle engines. In the design of a new engine, various components and covers mounted to the exterior of an engine block and crankcase are evaluated for noise radiation at audible frequencies. Where possible, noise may be reduced by connecting a component or cover more securely to the engine block so they act more like a solid body. However, the application of additional bolts may be prevented by internal components under the cover and may result in alignment or leak problems if applied. Another solution may be to increase the stiffness of a cover to increase its stiffness and change the radiated noise frequencies. However, this generally increases mass and unnecessary mass is not desired as it may adversely affect fuel economy. Suitable alternative means for reducing radiated noise from a cover or component are desired. 
     SUMMARY OF THE INVENTION 
     The present invention provides novel acoustic bumpers that control noise transmission from an engine front cover, or other component, which may be formed as a single metal casting mounted on the engine block. In one embodiment, the cover carries a water pump and internal water distribution passages and covers an overhead camshaft drive mechanism and an oil pump mounted on the engine block. Because of the cam drive and the water pump with passages, noise control of the cover central portions is provided by acoustic bumpers carried on inside cover bosses and engaging surfaces in accessible locations on the engine block front face or on associated components. 
     The acoustic bumpers may be doughnut shaped annular rings having identical coaxial locating recesses on opposite sides for error-free installation. A central web between the recesses includes an axially located retainer hole. Each bumper may be mounted on a pillar or boss on the inside cover face that includes a fastener receiving blind hole centrally located on a raised circular locator to position the bumper on the boss. Any suitable fastener may be used, but a headed push pin retainer is preferred for ease of assembly and retention. The pillars are of selected height suitable for engagement of the bumper with a mating engine block or component surface at each location. 
     The bumpers are installed on the cover prior to installation of the cover on the engine block and may be installed by a supplier and shipped to the assembly site ready for cover installation. When the cover is installed, the bumpers engage the selected locations on the block or associated mechanism and exert a noise damping force on the cover to reduce transmission of noise vibrations from the cover exterior to the external surroundings. 
     The resilient bumpers are usable in locations where bolting or internal ribbing is not possible or is undesirable due to added weight, lack of clearance or possible leak problems. When installed, the bumpers are not visible, need no maintenance and are prevented from detaching by compression of the bumpers and the cover locators at each location. 
     These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a resilient acoustic bumper and fastener assembly attached to a mounting boss of an engine front cover; 
         FIG. 2  is a front view of an engine front cover having rear mounted acoustic bumpers; 
         FIG. 3  is a cross-sectional view from the line  3 - 3  of  FIG. 2  showing noise damping engagement of an acoustic bumper on the front cover with an associated engine block; 
         FIG. 4  is a cross-sectional view from the line  4 - 4  of  FIG. 2  showing noise damping engagement of another acoustic bumper on the front cover with an associated chain tensioner body attached to the engine block; and 
         FIG. 5  is a rear view of the engine front cover showing noise damping acoustic bumpers at various exemplary locations on the inside of the front cover for noise damping engagement of the bumpers with the engine block or associated components for damping noise vibrations of the engine cover all in accordance with the invention. 
     
    
    
     DESCRIPTION OF AN EXEMPLARY EMBODIMENT 
     Referring first to  FIG. 1  of the drawings in detail, numeral  10  generally indicates an assembly of an acoustic bumper  12  and retainer  14  attached to a boss  16  which may be on the inside of an engine front cover for damping noise vibrations of the cover in accordance with the invention. 
     Bumper  12  may be formed of any suitable resilient oil and temperature resistant elastomer material capable of maintaining resilient compression qualities in a hot engine oil lubricated environment within an engine cover. The acoustic bumper  12  is configured as an annular ring  18  (generally doughnut shaped) having identical coaxial locating recesses  20  on opposite sides of the ring  18  so that the bumper  12  may be installed with either side facing inward to avoid assembly errors. The recesses are separated by a central web  22  including an axially located through retainer hole  24 . The sides of the annular ring  18  and the locating recesses  20  may be sloped to accommodate withdrawal from a forming die or to improve ease of installation. 
     The retainer  14  may be of any suitable form, such as a headed screw if desired, but it may be a manual push pin  26  having a head  28  and a shank  30  including withdrawal deterring means, such as deformable ridges  32  around the shank for holding the shank in an opening  33 , such as a blind hole, after manual installation. 
     The cover boss  16  may include only a raised annular portion  34  of the cover configured to be received in either of the locating recesses  20  of the acoustic bumper  12  for maintaining the bumper in installed position on the boss. However a height extending pillar  36  may be added to position the height of the bumper to engage an associated engine block or component with a desired degree of compression. The retainer hole  33  may be a blind hole sized to receive the retainer shank  30  and hold the retainer in place until the bumper is installed in compression in an assembly, for example, where the bumper  12  is maintained in position by the raised portion  34  and the retainer  14  is no longer needed for retention, unless disassembled. 
       FIG. 2  illustrates an engine  38  showing the front side of an engine cover  40  formed as a metal casting, such as aluminum, and mounted on an engine block  42  (see  FIGS. 3 and 4 ). The cover  40  includes a peripheral portion  44  including numerous peripheral mounting bosses  46  for receiving mounting bolts, not shown, for attaching the cover  40  to the engine block  42 . A large central portion  48  of the cover  40  is unsupported and thus is subject to receive and respond to noise vibrations from the various block mounted accessories as well as other mechanisms or components which may be mounted on the cover  40 . 
     For example, the front cover  40  includes a mounting boss  50  for receiving a front mounted water pump, not shown, which connects with internal water passages  52  cast into the cover  40  for conducting water from the water pump boss  50  to engine block inlet passages, not shown, in the block front face. An air intake boss  54  supports an air intake throttle body, not shown, and connects with internal air passages  56  in the cover  40  for conducting intake air to manifold passages, not shown, in the engine block  42 . 
     The front of the block, not shown, generally mounts multiple mechanisms required for engine operation. These may include a camshaft drive mechanism including primary and secondary drive chains with associated chain tensioners. An oil pump  58  may be mounted to the block surrounding the end of the crankshaft, not shown. 
     Details of these features are not illustrated, it being understood that they may occupy considerable space behind the front cover and thereby interfere with direct mounting of the unsupported central portion  48  of the cover  40  to the block in order to reduce transmission of noise vibrations from the unsupported central portion. Additionally, direct mounting of the central portion to the block may be undesirable as it may introduce alignment problems for bolt openings and create additional oil leakage paths that need to be sealed. 
       FIG. 3  is a cross-sectional view of the engine  38  from the line  3 - 3  of  FIG. 2  in the direction of the arrows.  FIG. 3  shows the cast cover  40  including a water passage  52  and a pillar  36  extending inward from the outer face of the cover to an inner end  60  on which is mounted a boss  16 , forming part of an acoustic bumper assembly  10  as previously described. Assembly  10  includes a raised annular portion  34  on which an acoustic bumper  12  is received. A retainer  14 , holding the bumper  12  in position, has the head  28  engaging the web  22  of the bumper and a shank  30  extending through the retainer hole  24  into the blind hole  33  of the pillar  36  and retained therein by the deformable ridges  32  gripping the sides of the blind hole  33 . 
     Upon installation of the cover  40  as shown on the front of the engine block  42 , the acoustic bumper  12  is urged into compressive engagement with an opposing surface  62  of the block  42 , so that the bumper  12  applies a damping force on the cover to reduce noise vibrations of the cover  40  adjacent to the bumper  12 . Note that, after installation of the cover, the acoustic bumper  12  is retained in place radially by the raised annular portion  34  of the pillar  36  extending into the associated recess  20  of the bumper  12  so that the retainer  14  is no longer needed after the cover is installed. 
       FIG. 4  is a cross-sectional view of the engine  38  from the line  4 - 4  of  FIG. 2  in the direction of the arrows.  FIG. 4  is similar to  FIG. 3  in that an acoustic bumper  12  is mounted on a pillar  36  of the cover  40  in exactly the same way as described for the location shown in  FIG. 3 , so that like reference numerals are used for like parts. However, at this location, the bumper  12  engages a body of a camshaft chain tensioner  64  mounted to the front end of the engine block  42 . The length of the cover pillar  36  is adjusted to accommodate the raised surface of the tensioner body  64  so that the compressive force of the bumper  12  on the cover is controlled accordingly. Preferably, all of the acoustic bumpers  12  mounted on an engine cover are of the same design and size so that installation errors will be avoided. 
     Referring now to  FIG. 5  of the drawings, the inside face  66  of the engine front cover  40  is shown. The peripheral mounting bosses  46  are shown as in  FIG. 2  as is the large unsupported central portion  48  of the cover as viewed from the inside, including the outlets of water passages  52  and air passages  56  which connect with mating openings, not shown, in the engine block. The inside face  68  of the water pump recess is also shown, as are the cast-in water passages  52 . A recess  70  into which the oil pump extends is also shown. 
       FIG. 5  also shows the positions of the pillars  36  of  FIGS. 3 and 4  having the acoustic bumpers  12  mounted on them to form bumper assemblies  10 . It will be recognized that the left hand bumper assembly  10  of  FIG. 5  is located at Section  3 - 3  on the right side of the exterior of front cover  40  of  FIG. 2 . Similarly, the right hand bumper assembly  10  of  FIG. 5  is located at Section  4 - 4  on the left side of the exterior of front cover  40  of  FIG. 2 . 
     In order to illustrate the versatility of the noise dampening features of the present invention,  FIG. 5  also illustrates two exemplary additional locations suitable for the mounting of acoustic bumpers  12  on the inside of the engine front cover  40 . One additional location  72  is positioned on a water passage wall of the cover and the other additional location  74  is positioned on the internal face  68  of the water pump cavity. It should be understood that additional or alternative locations for acoustic bumpers  12  to be located may be positioned at any place where there is access from the inside of the front cover  40  to the front of the engine block, except where a moving component, such as a timing chain, is blocking the way. As was previously mentioned, all the acoustic bumpers should be of identical size and design. This provides many more locations for mounting of acoustic bumpers  12  than would be possible if the bumpers had to be located through the outside of the cover or on the block face where other devices could be compromised. 
     It should be understood that the acoustic bumper of this invention is capable of use in many applications where a resilient bumper is required and is not limited by the disclosure herein of a specific application to an engine front cover. Neither should the application to a front engine cover limit applications to other covers including engine covers or to machines other than engines wherein a need for damping noise vibrations or other damping applications exists. 
     While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.