Abstract:
A coolant valve mounting arrangement is provided for a vibrating environment with significant temperature fluctuations. The mounting arrangement includes a fastener, a housing, a compression limiter and a mounting base. The compression limiter is arranged to minimize the housing thickness in order to reduce subsequent thermal expansion effects, while maintaining packaging, stiffness and strength requirements. A spring washer can be implemented to ensure that an adequate force is applied to the housing to maintain the integrity of a leak-free interface with the mounting base.

Description:
BACKGROUND 
       [0001]    The present invention relates to a mounting arrangement, and more particularly, to the mounting arrangement of a coolant valve to a mounting base within a vibrating, variable temperature environment. 
         [0002]    As fuel economy becomes paramount in the transportation industry, efforts have increased to achieve higher internal combustion engine efficiencies and to seek alternative powertrains Coolant valve assemblies are well known and can be arranged to provide coolant flow control for temperature management of various powertrain components including internal combustion engines, transmissions and various components of hybrid electric and fuel cell vehicles. 
         [0003]    One prong of the quest for improved fuel economy includes lightweighting. Significant strides have been made in the material sector to provide metal alternatives that not only offer significant weight savings, but also potential improvements in performance and cost. Management of the inherent properties of these lightweight materials is especially vital in intense environments offered by the powertrains and drivetrains of current and future vehicles. 
         [0004]    The design of an engine component to function for many years and miles on the exterior of an internal combustion engine, while maintaining multiple leak-free seals offers several challenges, especially for electronic components. These challenges include vibrational loading, substantial temperature fluctuations, water invasion and immersion, engine fluid exposure, along with elbow loads from mechanics during times of maintenance. 
         [0005]    The aforementioned challenges are further exacerbated by the packaging requirements. With the onset of new technologies and trends such as turbocharging and noise abatement, to name a few, the available space on and around the engine is highly sought after in the powertrain world. In addition, tool clearances for fastening the component to the engine in a crowded environment can also affect the design. An engine component of considerable size that resides on the outside of the engine and needs to interface with multiple components is likely to undergo several modifications to package properly within the engine compartment. 
         [0006]    The aforementioned demands apply to an electronic coolant valve, typically a plastic component within a pressurized ethylene glycol coolant system, required to function without failure and maintain a leak-free seal with the engine or other vehicle mounting base over the lifetime of the vehicle. 
         [0007]    The use of a plastic material requires management of its inherent thermal properties. Most plastic materials contain higher coefficients of thermal expansion than metals, meaning that the size of a plastic component will change more than a metal component of equivalent size when subject to the same temperature change. The magnitude of linear thermal expansion is calculated from the following formula: 
         [0000]      Δ h=h   0   αΔT  
       where:
           Δh=change in height   h 0 =original height   α=coefficient of thermal expansion   ΔT=change in temperature   
               
 
         [0013]    The magnitude of the thickness or height of the housing is one of the factors that influences its change in height due to a change in temperature. This change in height is further pronounced with most plastic materials that possess a high coefficient of thermal expansion. It should be understood that the change in height can be positive or negative, for increasing or decreasing temperatures, respectively. 
         [0014]    Referring to  FIG. 1A , a cross-sectional view of a prior art coolant valve mounting arrangement  100  is shown that contains a fastener  102 , a housing  104 , a compression limiter  106 , and a mounting base  108 . In this arrangement, the housing  104  spans the entire length of compression limiter  106 , shown as distance h PO ±x 2  in  FIG. 1B . Packaging a coolant valve, often cylindrical in form, on the engine often requires it to be offset from the engine; in some instances, distance h PO  can be 100 mm or more. This large magnitude of housing height at the mounting location yields large fluctuations in size due to thermal expansion which result in stresses within the mounting structure of the coolant valve. A solution is required to reduce the housing height within the mounting arrangement, yet maintain the strength, stiffness and packaging requirements dictated by the engine application. 
         [0015]    An additional challenge resides in maintaining the coolant valve&#39;s leak-free seal with the engine. Referring again to  FIG. 1B , given the manufacturing variation in height h PO ±x 2  of the housing  104  and the manufacturing variation in height S±x 1  of the compression limiter  106 , a distance dL 1  represents the difference in these two heights. Typically, this distance dL 1  can be positive or negative. A positive distance represents a condition where the compression limiter height S is taller than the housing height h PO . This condition is shown in  FIG. 1B . A negative distance represents a condition where the compression limiter height S is shorter than the housing height h PO , such that the housing extends beyond the limiter. Distance dL 1  must be designed to prevent an excessive negative clearance which could result in either of two scenarios: a high stress condition could result due to excessive compression of the plastic housing required for the fastener to contact the top of the compression limiter during the torquing process; or, if the fastener only contacts the housing and not the limiter after the torquing process, plastic creep could occur over time, possibly resulting in a loosening of the joint. In addition to manufacturing tolerances, temperature of the respective mounting arrangement components also affects the distance dL 1 . Applying the aforementioned formula for thermal expansion, one can understand that as housing thickness increases, the effect on the distance dL 1  caused by the housing also increases. Furthermore, an excessive positive dL 1  clearance can potentially result in excessive movement of the housing within the mounting joint, especially at cold temperatures, which can be a detriment to maintaining a leak-free seal with the mounting base. In typical applications, the distance dL 1  is designed where the greatest negative clearance (housing protrusion beyond the limiter) will allow for compression of the housing within the stress limits of the material until the limiter is contacted by the torqued fastener. However, due to typical tolerances of the housing thickness and compression limiter, this design scenario usually requires that distance dL 1  is biased towards a positive clearance. A solution is required to eliminate or reduce the risk of coolant valve seal leakage during a positive distance dL 1  condition. 
       SUMMARY 
       [0016]    A coolant valve mounting arrangement for a vibrating environment with large temperature fluctuations is provided. The arrangement includes a housing, a mounting base, a compression limiter, and a fastener. The compression limiter contains a shelf along its length to support one side of the housing of a thickness that is less than the length of the limiter. The compression limiter can be formed from various processes such as machining, powder metallurgy, metal injection molding, drawing or forging. In another aspect, a washer can be installed on the compression limiter shelf to increase the amount of support area with the housing. The fastener extends through a through hole of the compression limiter and attaches the compression limiter to the mounting base. The fastener can include an integral flange or separate washer component for optimum clamping of the mounting arrangement. The housing is preferably made of plastic, which can be over-molded on the compression limiter, but can also be made of different metals. The mounting base can contain a recessed opening to receive the compression limiter. The shape of the compression limiter can be round for ease of manufacturing. In another aspect of the compression limiter, a male component can be inserted into a female component to form the shelf that supports the housing. The male component can contain a through slit along its length to provide for an elastic characteristic to aid in the assembly process of the two components. In yet another aspect of the compression limiter, one upper element can abut against a lower element to form the shelf that supports the housing. 
         [0017]    Either of the aforementioned coolant valve mounting arrangements can include a spring washer and support washer combination placed between the fastener and the housing. The presence of the spring washer can ensure that a sealing force is applied to the housing under all manufacturing tolerance and operating temperature conditions. It is possible that the fastener clamp load on the housing can be reduced due to sizing of the housing with respect to the compression limiter; this condition can be magnified at cold operating conditions when the housing, potentially made from a material with a high coefficient of thermal expansion such as plastic, reduces in height more than the compression limiter subjected to the same cold temperature. In a cold operating condition, the effective height of the spring washer would be greater than in a hot operating condition due to the resultant thickness variation of the housing. Different types of spring washers can be used including split type, Belleville type or wave type. The presence of the support washer ensures that the spring washer can function as intended without harming, deforming or inducing unwanted stresses in the housing. 
         [0018]    In another embodiment, a compression limiter shelf supports a second side of the housing. The fastener applies a clamp load to the compression limiter and couples it to the housing. A spring washer and supporting washer arrangement is possible between the compression limiter shelf and second side of the housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The foregoing Summary as well as the following Detailed Description will be best understood when read in conjunction with the appended drawings. In the drawings: 
           [0020]      FIG. 1A  is a cross-sectional view of a prior art coolant valve mounting arrangement. 
           [0021]      FIG. 1B  is a detailed view taken from  FIG. 1A . 
           [0022]      FIG. 2  is a cross-sectional view of a first embodiment of a coolant valve mounting arrangement. 
           [0023]      FIG. 3  is a cross-sectional view of a first variation of the coolant valve mounting arrangement of  FIG. 2 . 
           [0024]      FIG. 4  is a cross-sectional view of a second variation of the coolant valve mounting arrangement of  FIG. 2 . 
           [0025]      FIG. 5  is a cross-sectional view of a third variation of the coolant valve mounting arrangement of  FIG. 2 . 
           [0026]      FIGS. 5A and 5B  are a perspective view and a cross-sectional view of a compression limiter component of  FIG. 5 . 
           [0027]      FIG. 6  is a cross-sectional view of a fourth variation of the coolant valve mounting arrangement of  FIG. 2 . 
           [0028]      FIGS. 6A and 6B  are detailed views taken from  FIG. 6 . 
           [0029]      FIG. 7  is a cross-sectional view of a fifth variation of the coolant valve mounting arrangement of  FIG. 2 . 
           [0030]      FIG. 8  is a cross-sectional view of a second embodiment of a coolant valve mounting arrangement. 
           [0031]      FIG. 9  is a cross-sectional view of a first variation of the coolant valve mounting arrangement of  FIG. 8 . 
           [0032]      FIG. 10  is a cross-sectional view of a portion of a coolant valve housing and a mounting base. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0033]    Certain terminology is used in the following description for convenience only and is not limiting. The words “inner,” “outer,” “inwardly,” and “outwardly” refer to directions towards and away from the parts referenced in the drawings. A reference to a list of items that are cited as “at least one of a, b, or c” (where a, b, and c represent the items being listed) means any single one of the items a, b, c or combinations thereof. The terminology includes the words specifically noted above, derivatives thereof, and words of similar import. 
         [0034]    Referring to  FIG. 2 , a first embodiment of a coolant valve mounting arrangement  10  is shown that includes a fastener  12 , a housing  14  of the coolant valve with a height h h , a compression limiter  16  with a height h CL , a mounting base  18  and a central axis  13 . The compression limiter  16  has an upper or first portion with an outer surface that is disposed within a through aperture of the housing  14 . The housing  14  can retain the first portion of the compression limiter  16  by means of an interference fit, or, if a plastic is used for the material of the housing  14 , the housing  14  can be over-molded on the first portion of the compression limiter  16 . The compression limiter  16  contains a second portion with a first side in the form of a shelf  15  located at a medial position on the compression limiter  16  at a height h SH  to support the housing  14 . The through aperture of the housing  14  is axially aligned with a through aperture or hole of the compression limiter  16 . The fastener  12  extends through the through aperture of hole of the compression limiter  16  and attaches to the mounting base  18 . The form of the compression limiter  16  can be of any shape, with the option of it being round for ease of manufacturing. In order to minimize thermal expansion of the housing  14  and subsequent stresses, a height h h  of the housing  14  can be significantly smaller than the height h CL  of the compression limiter  16 , due to the presence of the shelf  15  or its height h SH . The preferred material of the compression limiter  16  is metal and its form, including the shelf  15 , can be achieved by any metal removal or metal forming processes such as machining, drawing, powder metallurgy, metal injection molding, or forging. The mounting base  18  optionally includes a recess  19  for guiding or seating the compression limiter  16 . A generous size of such a recess  19  would be required to account for positional and size tolerances. 
         [0035]    Now referencing  FIG. 1 &#39;s prior art coolant valve mounting arrangement  100  with a fastener  102 , a housing  104  with a height h PO , a compression limiter  106  with a height S, and a mounting base  108 , one can observe that the magnitude of housing  104  height h PO  is larger than the magnitude of the housing  14  height h h  of  FIG. 2 &#39;s coolant valve mounting arrangement  10 . Due to this difference in housing height magnitude, the thermal expansion of the housing  104  of the prior art coolant valve mounting arrangement  100  exceeds the thermal expansion of the housing  14  of  FIG. 2 &#39;s coolant valve mounting arrangement  10 . Therefore, the resultant thermal stresses in the housing  14  of the coolant valve mounting arrangement  10  are likely lower than the resultant thermal stresses in the housing  104  of the coolant valve mounting arrangement  100 . Furthermore, this improvement can be further illustrated by a shown distance dL 2  in  FIG. 2 , which represents the distance in height between the top of the housing  14  and the top of the compression limiter  16 . The distance dL 2  is affected by the manufacturing tolerances of the compression limiter  16  and the housing  14  in addition to temperature and resultant thermal expansion effects. Comparing  FIG. 2 &#39;s coolant valve mounting arrangement  10  to  FIG. 1 &#39;s prior art coolant valve mounting arrangement  100 , one can observe that the distance dL 2  is less sensitive to temperature of the coolant valve mounting arrangement than dL 1  due to the difference in housing  14 ,  104  heights h h , h PO . 
         [0036]    Referring now to  FIGS. 3-7 , multiple variations of the first embodiment of the mounting arrangement  10  provided in  FIG. 2  are shown that will also result in a lower thermal stress condition than the prior art coolant valve mounting arrangement  100  shown in  FIG. 1A . 
         [0037]      FIG. 3  shows a coolant valve mounting arrangement  20  with a washer  27  that can be installed on the compression limiter shelf  15  in order to increase the support area beyond that provided by the shelf  15  and reduce the contact stress and thus the potential for material deformation of the housing  14 . 
         [0038]      FIG. 4  shows a coolant valve mounting arrangement  30  with a compression limiter  36  that has an integral flange  37  to provide a shelf  35  for support of the housing  14 . The compression limiter  36  can be formed by various metal-forming processes such as machining, drawing, powder metallurgy, metal injection molding, and forging. 
         [0039]      FIG. 5  shows a coolant valve mounting arrangement  40  with a compression limiter  46  that contains a male element  41  that is inserted in a female element  47 . The female element  47  is shorter than the male element  41 , such that a first portion is formed from the extending male portion and a second portion is formed from the female portion. One end of the female element  47  is coplanar with one end of the male element  41  and abuts with the mounting base  18 , while the other end of the female element forms a shelf  45  that supports the housing  14 . Referring now to  FIGS. 5A and 5B , optionally a through slit  42  exists along the length of the male segment  41  to add an elastic characteristic which enables ease of installation of the female segment  47 . 
         [0040]      FIG. 6  shows a coolant valve mounting arrangement  50  that adds an optional spring washer  59  with a spring constant k that imparts a force F on the housing  14  through an optional support washer  53 . The addition of the spring washer  59  ensures that the force F is applied to the housing  14  for all housing and compression limiter size variations and coolant valve mounting arrangement operating temperatures. The spring washer  59  can be of various types including split type, Belleville type or wave type. 
         [0041]    The addition of the support washer  53  ensures that the spring washer  59  can function as intended without harming, deforming or inducing unwanted stresses in the housing  14 . Housing  14  height h h  and spring washer  59  height h s  are shown in  FIG. 6 . Housing  14  height h h  and spring washer  59  height h s  both vary with the coolant valve mounting arrangement operating temperature. As operating temperature increases, housing  14  height h h  increases due to thermal expansion, causing spring washer  59  height h s  to decrease. Due to the spring constant k of the spring washer  59 , the force imparted on the housing through support washer  53  increases as spring washer  59  height h s  decreases. As operating temperature decreases, housing  14  height h h  decreases due to thermal contraction, causing spring washer  59  height h s  to increase. Due to the spring constant k of the spring washer  59 , the force imparted on the housing through support washer  53  decreases as spring washer  59  height h s  increases. The design of the spring washer  59  must be such that the force F applied by the spring washer  59  to the housing  14  when the spring washer  59  is at its maximum height (minimum temperature condition), is adequate for sealing while not overstressing the housing  14  material when at its minimum height (maximum temperature condition). The support washer  53  is made from metal, and given its smaller height and lower coefficient of thermal expansion in comparison with the typically plastic housing  14 , it has been ignored in the above discussion, although it would also have some minimal effect.  FIGS. 6A and 6B  show detailed views of the coolant valve mounting arrangement of  FIG. 6  at the maximum and minimum operating temperature conditions. Referring to  FIG. 6A , which represents a maximum operating temperature condition, a maximum housing thickness due to thermal expansion is shown as h h,max , in addition to a resultant spring washer  59  height h s,min . Now referring to  FIG. 6B , which represents a minimum operating temperature condition, a minimum housing thickness due to thermal contraction is shown as h h,min , in addition to a resultant spring washer height h s,max . 
         [0042]    Referring to  FIG. 10 , which shows a portion  90  of the housing  14  and the mounting base  18  away from a fastening location, housing portion  90  contains an optional groove  96  for an optional seal  94 . The seal  94  can be of many forms, such as an O-ring or a press-in-place (PIP) gasket. The application of a load to the housing portion  90  causes compression of the seal  94  against the mounting base  18 , thus providing a leak-proof interface. Referring again to  FIG. 6B , the optional spring washer  59  is preferably designed to ensure that the force F applied to the housing  14  through support washer  53  is enough to facilitate a leak-proof interface between the housing  14  and the mounting base  18  during a minimum operating temperature condition when the spring washer  59  is at its greatest height h s,max . In addition, referring again to  FIG. 6A , for all size conditions, the maximum force imparted on the housing  14  by the spring washer  59  via support washer  53  at its minimum height condition h s,min  should not exceed the yield stress of the housing  14 . This relationship can be characterized by the following equation: 
         [0000]    
       
         
           
             
               
                 
                   F 
                   preload 
                 
                 + 
                 
                   k 
                    
                   
                     ( 
                     
                       
                         h 
                         
                           s 
                           , 
                           max 
                         
                       
                       - 
                       
                         h 
                         
                           s 
                           , 
                           min 
                         
                       
                     
                     ) 
                   
                 
               
               
                 A 
                 
                   2 
                    
                   
                       
                   
                    
                   nd 
                    
                   
                       
                   
                    
                   disc 
                 
               
             
             ≤ 
             
               σ 
               
                 y 
                 , 
                 housing 
               
             
           
         
       
     
         [0043]    where: 
         [0044]    F preload =force applied to the coolant valve housing  14  by the resilient disc (spring washer  59 ) at a minimum operating temperature and; 
         [0045]    k=spring constant of the first resilient disc (spring washer  59 ); 
         [0046]    h s,max =height of the first resilient disc (spring washer  59 ) at the minimum operating temperature of the mounting arrangement; 
         [0047]    h s,min =height of the first resilient disc (spring washer  59 ) at the maximum operating temperature of the mounting arrangement; 
         [0048]    A 2nd disc =minimum contact area of the second disc (support washer  53 ) with the housing; 
         [0049]    σ y,housing =yield strength of the housing  14 . 
         [0050]      FIG. 7  shows a coolant valve mounting arrangement  60  with a compression limiter  66  with a first or upper element  61  that abuts against a second or lower element  67 . A shelf  65  is formed at the abutment location of these two elements. 
         [0051]      FIG. 8  shows a second embodiment of a coolant valve mounting arrangement  70  with a fastener  72 , a housing  74  of the coolant valve, a compression limiter  76 , and a mounting base  78 . The compression limiter  76  contains a shelf  75  to support the housing  74 . However, compared to the first embodiment shown in  FIGS. 2-7 , the housing  74  is located at the opposite end of the compression limiter  76  and directly interfaces with the mounting base  78 . Depending on the design of the coolant valve attachment points, which greatly depends on the loading and packaging requirements, this embodiment could prove more favorable in some application environments. 
         [0052]      FIG. 9  shows a coolant valve mounting arrangement  80  that is a variant of the second embodiment shown in  FIG. 8 . This variant includes a fastener  82 , a housing  84  of the coolant valve, a compression limiter  86  and a mounting base  88 . The compression limiter  86  includes a shelf  85  that interfaces with a spring washer  89  that transmits a force to the housing through support washer  83 . The addition of spring washer  89  ensures that a force is maintained on the housing  84  for all size variations and operating temperatures in order to maintain a leak-free interface with the mounting base  88 . The presence of the support washer ensures proper function of the spring washer  89 , without harming, deforming or inducing stresses on the surface of the housing  84 . While here the housing  84  is arranged against the mounting base  88 , the same force relationship as previously described would also be applicable based on the changes of the housing height and spring washer height due to thermal expansion and contraction. 
         [0053]    As in the first embodiment and respective variations shown in  FIGS. 2-7 , both of the coolant valve mounting arrangements  70 ,  80  shown in  FIGS. 8 and 9  will likely result in a lower thermal stress condition than the coolant valve mounting arrangement  100  shown in  FIG. 1A  due to the reduced housing height. 
         [0054]    For a given coolant valve that contains multiple attachment points, typically three or more, there may be a mixture of mounting arrangements with some as shown in  FIGS. 2-7  and others as shown in  FIGS. 8-9 . 
         [0055]    Having thus described various embodiments of the present coolant valve mounting arrangement in detail, it is to be appreciated and will be apparent to those skilled in the art that many physical changes, only a few of which are exemplified in the detailed description above, could be made in the apparatus without altering the inventive concepts and principles embodied therein. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore to be embraced therein.