Abstract:
A damped windage tray for an engine including a windage tray formed from a laminate. The laminate operates to damp vibrations of the windage tray. The laminate includes a first constraining layer, a second constraining layer and a viscoelastic damping layer disposed between the first and second constraining layer. The viscoelastic damping layer spans substantially the entirety of the first and second constraining layers. Additionally, a method of forming the windage tray is provided.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to engine windage trays and a method of making the windage trays.  
       BACKGROUND OF THE INVENTION  
       [0002]     Internal combustion engines use oil pans disposed beneath the crankcase of an engine to collect and store oil as a source of oil for an oil pump that distributes it under pressure throughout the engine. The crankcase volume is at least partially defined by a cylinder block having a crankshaft rotatably mounted thereto. The crankshaft mechanically engages pistons, reciprocally movable within bores defined by the cylinder block, through a link such as a connecting rod. The rotational motion of the crankshaft coupled with the reciprocal motion of the pistons combine to cause turbulent airflow within the crankcase. This airflow is sometimes referred to as “windage” and may be pronounced at high engine speeds. The windage may also entrain oil thrown or ejected from journal bearings such as main bearings, which support the crankshaft within the cylinder block, and the rod bearings, which support the connecting rod on the crankshaft. Additionally, the windage may entrain oil already in the sump or collection volume of the oil pan. The windage along with the entrained oil in the crankcase volume operates to increase drag or rotational resistance of the rotating crankshaft thereby reducing the efficiency of the engine. This loss in efficiency may lead to reduced engine performance. Additionally, the oil within the crankcase volume may entrain an amount of air causing the oil within the sump to become aerated. The increased volume of the aerated oil may cause additional oil to become entrained by the windage thereby leading to a “runaway” condition under certain engine operating modes.  
         [0003]     Engineers have employed oil deflectors, often referred to as “windage trays”, to isolate the effects of the crankshaft and other rotating parts on the oil contained within the oil pan. The windage tray is disposed beneath the rotating parts of the engine and operates to create a barrier between these rotating parts and the oil collection volume of the oil pan. Windage trays are typically mounted to main caps supporting the crankshaft, between the oil pan and the cylinder block, or to the oil pan. Prior art windage trays are simply a panel of metal or molded plastic.  
         [0004]     More recently, efforts have been made to reduce the noise, vibration, and harshness, or NVH, of vehicles. One of the main sources of NVH is the internal combustion engine. Although the prior art windage tray may serve a valuable function in controlling engine efficiency loss due to windage, the windage tray and oil pan can be a source of radiated noise. The windage tray may radiate noise due to vibrations caused by the high-speed impact of oil thrown from the crankshaft as well as vibrations transmitted to the windage tray through the part of the engine to which the windage tray is mounted. While both solid metal and molded plastic windage trays may be effective at reducing windage losses within the crankcase, they may create a resonance due to interaction with other engine components thereby increasing the overall engine noise.  
       SUMMARY OF THE INVENTION  
       [0005]     A damped windage tray for an engine includes a windage tray formed from a laminate. The laminate is operable to damp vibrations of the windage tray and includes a first constraining layer, a second constraining layer, and a viscoelastic damping layer disposed between the first and second constraining layers and spanning substantially the entirety of the first and second constraining layers.  
         [0006]     The viscoelastic damping layer may include a first viscoelastic layer and a second viscoelastic layer bonded by a high tack polymer layer. Additionally, at least one of the first and second constraining layers may be formed from cold rolled steel or other suitable material. The windage tray may be configured to be mountable to a main cap, an oil pan, or between the oil pan and a cylinder block of the engine. Additionally, the composite loss factor for the laminate may be chosen to have a maximum at approximately the equilibrium oil temperature of the engine. Additionally, an internal combustion engine is disclosed incorporating the damped windage tray of the present invention.  
         [0007]     A method of forming a windage tray for an internal combustion engine includes forming a laminate having a first constraining layer, a second constraining layer and a viscoelastic damping layer disposed between the first and second constraining layer and spanning substantially the entirety of the first and second constraining layers. Subsequently, a windage tray is formed from the laminate.  
         [0008]     Forming the laminate may include coating the first constraining layer with a first viscoelastic layer and coating the second constraining layer with a second viscoelastic layer. Subsequently the first and second viscoelastic layer are bonded with a high tack polymer. The windage tray may be formed using at least one stamping operation. Additionally, the first constraining layer, the second constraining layer, and the viscoelastic damping layer may be selected such that the maximum composite loss factor of the laminate formed therefrom is substantially coincident with an equilibrium oil temperature of the internal combustion engine.  
         [0009]     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a schematic, cross sectional view of a laminated panel structure;  
         [0011]      FIG. 2  is a partial view of the lower portion of an internal combustion engine including the damped windage tray of the present invention;  
         [0012]      FIG. 3  is a schematic bottom view of the damped windage tray formed from the laminated panel structure of  FIG. 1 ;  
         [0013]      FIG. 3   a  is a sectional view of the windage tray of  FIG. 3  taken along line A-A and illustrating the laminated nature of the present invention; and  
         [0014]      FIG. 4  is a graph depicting the relationship between composite loss factor and temperature for an exemplary construction of the laminated panel structure of  FIG. 1 .  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]     Referring to the drawings wherein like reference numbers refer to like or similar components throughout the several figures, there is shown in  FIG. 1 a  cross section of a laminate  10 . The laminate  10  is a laminated sheet structure, which includes a first constraining layer  12  and a second constraining layer  14 . A first and second viscoelastic layer  16  and  18 , respectively, are disposed between and each spans, or is coextensive with, the entirety of the first constraining layer  12  and the second constraining layer  14 . In the preferred embodiment, the first viscoelastic layer  16  is applied to the first constraining layer  12  to form a laminate  20 , while the second viscoelastic layer  18  is applied to the second constraining layer  14  to form a laminate  22 . The laminates  20  and  22  are bonded by a high tack polymer layer  24  to form the laminate  10 . The high tack polymer layer  24  and first and second viscoelastic layer  16  and  18  taken together form a viscoelastic damping layer  25 . In the preferred embodiment, the first and second constraining layers  12  and  14  are formed from draw quality cold rolled steel, while the first and second viscoelastic layers  16  and  18  are formed from a high strength damping polymer. Such a laminate  10  is available from Material Sciences Corporation of Elk Grove Village, Ill. USA. Those skilled in the art will recognize that the viscoelastic damping layer  25  may include additional polymer layers in addition to the first and second viscoelastic layer  16  and  18  and the high tack polymer layer  24 . The thickness and composition of the viscoelastic damping layer  25  may be modified to tailor the composite loss factor, bond strength, overall stiffness of the laminate  10 , as well as additional properties dictated by the specific application.  
         [0016]     Referring now to  FIG. 2 , there is shown a portion of an internal combustion engine  26 . The engine  26  includes a cylinder case or block  28  having a crankshaft  30  rotatably mounted thereto. The crankshaft  30  is supported within the cylinder block  28  by a plurality of main caps  32 , one of which is shown in  FIG. 2 . An oil pan  34  is mounted to the lower portion of the cylinder block  28  and functions as a reservoir to supply oil  35  to a positive displacement pump  36  through a pickup tube  38 . The oil pan  34  and cylinder block  28  cooperate to form a crankcase volume  40 . The performance of the engine can be influenced by windage within the crankcase volume  40 , therefore an oil deflector or windage tray  42  is provided between the crankshaft  30  and the oil  35  within the oil pan  34 . By isolating the windage effects caused by moving parts within the crankcase  40 , such as the crankshaft  30 , engine performance and efficiency may increase. Additionally the amount of entrained air within the oil  35  delivered to the pump  36  may be reduced by the inclusion of the windage tray  42 .  
         [0017]     Referring to  FIG. 3 , and with further reference to  FIG. 2 , there is shown an exemplary windage tray  42  consistent with the present invention. The windage tray  42  is formed from the laminate  10  described with reference to  FIG. 1 . The windage tray  42  defines a plurality of holes  44  sufficiently configured to enable mounting of the windage tray  42  between the oil pan  34  and the cylinder block  28 . Additionally, a plurality of holes  46  are defined by the windage tray  42  and are sufficiently configured to enable mounting of the windage tray  42  to the main caps  32 . An opening  48  is defined by the windage tray  42  to enable the pickup tube  38  to pass therethrough as well as to allow oil drainage to the oil pan  34 . Additionally, slots  50  are defined by the windage tray  42  to enable increased control of the oil thrown from the rotating crankshaft  30  during engine operation. Other methods of oil control may include holes, fins, tabs, screens, and grooves. Those skilled in the art will recognize that other methods of mounting the windage tray  42  within the crankcase volume  40  of the engine  26  such as, for example, within the oil pan. However, the windage tray  42  should be mounted above the upper level of the oil  35  shown within the oil pan  34  and sufficiently remote from the crankshaft  30  to avoid interference with moving parts. Referring to  FIG. 3A , a cross sectional view of the windage tray  42 , taken along line A-A of  FIG. 3 , is shown further illustrating the laminated nature of the present invention. In the preferred embodiment the windage tray  42  is formed by stamping the laminate  10  to the net shape of the windage tray  42  in one or more stamping operations. Preferably, the viscoelastic damping layer  25  will span substantially the entirety of the first and second constraining layers  12  and  14 .  
         [0018]     Referring to  FIG. 4 , with further reference to  FIG. 1 , the relationship between the composite loss factor and temperature for an exemplary laminate  10  is shown. The exemplary laminate  10  includes a first and second constraining layer  12  and  14  formed from draw quality cold rolled steel. Each of the first and second constraining layers  12  and  14  are 0.019 inches in thickness. Additionally, the first and second viscoelastic layers  16  and  18  are formed from a high strength damping polymer. Each of the viscoelastic layers  16  and  18  are 0.0006 inches in thickness. While the high tack polymer layer  24  is 0.0004 inches in thickness. The graph shown in  FIG. 4  was developed through testing of the exemplary laminate  10  described hereinabove. For testing, a specimen beam of laminate  10  was formed having the spatial dimensions of 8.5 inches in length and 0.75 inches in width. This beam was then mechanically fastened to a high mass fixture such that the beam would function as a free beam of 7 inches in length and 0.75 inches in width having one end fixed. The beam was excited using a magnetic transducer, while an accelerometer recorded the response. Measurements were taken at 10 degrees F. intervals over a range of 50 degrees F. to 350 degrees F. for various modes (2, 3, 4, 5, and 6) of bending. Those skilled in the art should recognize that the dimensions described herein above are only exemplary in nature and are not meant to limit the scope of the present invention. It should also be apparent that the dimensions and composition of the laminate  10  are application specific.  
         [0019]     Curves shown in  FIG. 4  represent the results of the testing described hereinabove. Each of the curves was generated to represent a different one of the bending modes of the beam. As indicated in  FIG. 4 , the maximum composite loss factor for the beam is achieved at approximately 200 degrees F. for all modes of bending. This temperature corresponds to the typical equilibrium operating temperature for oil  35  within the internal combustion engine  26 . That is, maximum damping and noise attenuation of the windage tray  42  will occur at an oil temperature range within which the typical internal combustion engine  26  most frequently operates. Since the laminate  10 , shown in  FIG. 1 , is coextensive with the entire windage tray  42 , a measure of noise attenuation is provided at every point on the windage tray  42 . Additionally, the composite loss factor remains relatively high for temperature values above 200 degrees F. should a high oil temperature excursion occur due to factors such as a high ambient air temperature or a performance oriented driving schedule.  
         [0020]     Those skilled in the art will recognize that the equilibrium oil temperature is application specific; therefore, the materials and dimensional properties of the laminate  10 , shown in  FIG. 1 , should be tuned to each application. Additionally, it may be desirable to have different compositions for each of the first and second constraining layers  12  and  14 . For example, if aesthetics are a concern, one or both of the first and second constraining layers  12  and  14  may be formed from stainless steel or aluminum. Additionally, the respective thickness of the first and second constraining layers  12  and  14  may be different. It is also contemplated that the first and second constraining layers  12  and  14  may be a non-metallic composition such as a composite material possessing the requite properties to provide a desired stiffness to the viscoelastic damping layer  25 .  
         [0021]     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.