Patent Publication Number: US-8522925-B2

Title: Debris flush system for balance shaft bearings

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This non-provisional patent application claims the benefit of U.S. Provisional Patent Application No. 60/839,210, entitled “DEBRIS FLUSH CHANNEL FOR BALANCE SHAFT MODULE,” filed Aug. 22, 2006, which is hereby incorporated in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a fluid filtration system, and more particularly, to an engine oil filtration system for reciprocating internal combustion-type engines having at least one balance shaft. 
     BACKGROUND 
     In many internal combustion engines, the engine crankshaft typically drives a balance shaft assembly to reduce engine vibration and noise due to the mass forces associated with the cyclic accelerations of reciprocating pistons and their connecting rods. Balance shafts are required to maintain substantially fixed angular timing relationships with the engine&#39;s crankshaft in order to fulfill their force cancellation functionality. And while single balance shafts are sometimes used for such purposes, many engines utilize two balance shafts. Regardless of whether a single balance shaft or multiple balance shafts are utilized, proper and adequate lubrication of the balance shaft bearings is essential in light of the shafts&#39; rotational speed rates and associated centrifugal loadings. 
     Oil provides lubrication for the balance shaft bearings, as well as the other components of the engine. An oil pump may be driven by, or connected to, one of the balance shafts, the engine&#39;s crankshaft, or other drive mechanisms. During operation of the engine, the oil pump operates to provide pressurized oil to the various components of the engine by means of a network of pressurized oil passages. To ensure that clean oil is sent through the system, the oil is typically forced through an oil filter by the oil pump to remove contamination, debris, wear residue, and other foreign substances. 
     The network of pressurized oil passages within an engine&#39;s lubrication system typically extends to include the bearings of its balance shafts when present. If any contamination is resident in the oil passages between the oil filter and the balance shaft bearings when the engine is initially assembled, it will not be filtered out of the oil before reaching the bearings. Such build-phase contamination risks damage to balance shaft bearings, especially hydrostatic-type bearings at the extremities of current art lubrication passage networks where the oil passages terminate, leaving only bearing-to-journal running clearance as escape route for the oil and its possible contaminants to return back to the sump. If the oil contains contaminants larger than can readily escape the very small oil film clearance gap, they will be trapped at the lubrication network terminal bearings, where cyclic motion of the shaft&#39;s journal can work them into the clearance gap and produce bearing damage. Damage to balance shaft bearings can lead to engine failure, especially if oil pump functionality is impaired or lost. 
     Therefore, there exists a significant need for a balance shaft bearing lubrication system capable of readily and efficiently flushing debris and other such contaminants from the balance shaft bearings in order to desensitize the engine system to the risk of failure due to build-phase contamination of its lubrication circuit. 
     SUMMARY OF THE INVENTION 
     An embodiment of the present invention provides an engine lubrication system comprising a network of oil passages for the supply of captured pressurized oil to the engine&#39;s various key working clearances and components. The system includes a pump operable to provide pressurized oil to a filter in pressurized fluid communication with the engine&#39;s lubrication network, also referred to as an engine oil circuit, which includes an oil supply passage, also referred to as a bearing feed circuit, to feed one or more bearings for one or more balance shafts. The balance shaft bearing oil supply passage is in fluid communication with a flush channel, which provides a bypass route downstream of the balance shaft bearing oil supply passage. The flush channel is in pressurized fluid communication with the inlet passage of the oil pump so that contaminated pressurized oil may flow both to and past one or more balance shaft bearings and ultimately back to the pump for subsequent delivery to the filter for cleaning. 
     The opening of an additional lube passage flow area, such as that constituted by such a flush channel as means of allowing contaminants to bypass terminal balance shaft bearings, acts to lower the flow resistance of the engine&#39;s pressurized lubrication network, thus incrementally reducing the pressure available to force oil through the network and its components, particularly at low engine speeds. It is therefore desirable to control the flow resistance of the flush channel, preferably by at least one discharge passage in fluid communication with at least one debris-settling chamber, where larger, heavier debris as may be present in the oil may be accumulated without risk of damage to the oil pump. Alternatively, multiple settling chambers and discharge passages may be arranged in series to provide labyrinth seal-type functionality. 
     Although the above embodiment provides for the flush channel or channels to flush at least one balance shaft bearings by routing circulating oil and any entrained debris through a series of settling chambers and discharge passages on to the oil pump, it is to be understood that discharge directly to the sump, with or without a settling chamber and/or discharge passage, as well as the flushing of less than all terminal balance shaft bearings, are contemplated herein. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       Objects and advantages together with the operation of the invention may be better understood by reference to the following detailed description taken in connection with the following illustration, wherein: 
         FIG. 1  is a schematic view of one embodiment of an engine oil filtration system; 
         FIG. 2  illustrates a cross-sectional view of a balance shaft module having a bearing oil supply passage and flush channel; 
         FIG. 3  illustrates an enlarged partial view of the cross-sectional view of  FIG. 2  showing the flush channel with a series of debris-settling chambers in communication with discharge passages and leading to the oil pump inlet; 
         FIG. 4  is a schematic view of a second embodiment of an engine oil lubrication system; and 
         FIG. 5  is a schematic view of a third embodiment of an engine oil lubrication system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the present invention is described with reference to the embodiments described herein, it should be clear that the present invention should not be limited to such embodiments. Therefore, the description of the embodiments herein is illustrative of the present invention and should not limit the scope of the invention as claimed. 
     Reference will now be made in detail to the embodiments of the invention as illustrated in the accompanying figures. Referring now to  FIG. 1 , a schematic diagram of the oil filtration system  10  is shown. The system  10  may include a dirty oil sump  12  that feeds an oil pump  14 . The pump  14  includes a first inlet passage  13  for fluid communication with the sump  12  and is operable to provide pressurized oil to the engine&#39;s lubrication network  18  of oil supply passages which includes a balance shaft bearing supply passage  22 , also referred to as a bearing feed circuit. Additionally, as illustrated in  FIG. 1 , the pump  14  may be an integral component of a balance shaft module  20 . The pump  14  may pass pressurized oil to an oil filter  16  to remove debris, contaminants and other foreign substances from the oil. The pressurized, filtered oil may then pass to an engine lubrication network  18 , also referred to as an engine oil circuit, to lubricate and cool various components of the engine, including but not limited to the cylinders, valve train, etc. 
     The engine lubrication network  18  is in pressurized fluid communication with the balance shaft module  20 , whereby at least a portion of pressurized oil passing through the engine lubrication network  18  passes into the balance shaft module  20  via a balance shaft module inlet  60 . Also, as will be readily appreciated by one skilled in the art, a portion of the oil exiting the network  18  may be routed directly back to the dirty oil sump  12 , via an engine oil return passage  35 , or the like. 
     The balance shaft module  20  houses at least one balance shaft for offsetting vibrations generated by an inherently unbalanced engine. As best shown in  FIG. 2 , in one embodiment the balance shaft module  20  includes at least one bearing surface  50  for supporting a balance shaft. Also, the balance shaft module  20  may include a bearing supply passage  22  in pressurized fluid communication with the module inlet  60 . The bearing supply passage  22  may route pressurized oil from the module inlet  60  to each bearing surface  50  so as to provide lubrication between the balance shaft and corresponding bearing surfaces  50 . 
     As further shown in  FIG. 2 , the supply passage  22  may extend through one or more bearing surfaces  50  to a flush channel  24 . The supply passage  22  and flush channel  24  are in pressurized fluid communication whereby debris, contaminants and other foreign substances collected in the oil may be routed past the bearing surfaces  50  to the flush channel  24 . In this arrangement, the bearing surfaces  50  of the balance shaft module  20  are fed with pressurized oil such that they are less susceptible to damage from contaminants in the oil because the contaminants are flushed away therefrom. Further, the flow rate of the pressurized oil also serves to cool the bearing surfaces  50  more uniformly, thereby extending the life of the bearings. Therefore, the bearing surfaces  50  are less likely to retain a substantial amount of debris and other contaminants from the oil, thus resulting in a substantially decreased risk of bearing damage during operation. 
     The flush channel  24  may have any suitable configuration to provide an engineered flow resistance capable of producing an upstream, contaminant-mobilizing flow rate in oil passing through the bearing surfaces  50  such that the oil passing through the bearings  50  is maintained at sufficient pressure while also passing through the bearings  50  at a sufficient rate to effectively carry debris and other contaminants past and/or remove debris and other contaminants from the bearings  50  under all engine operating conditions. For example, the flush channel  24  may include a one or more debris settling chambers  26 ,  30 , and  34  in series fluid communication with one another via one or more discharge passages  28  and  32  extending therebetween. Each of the chambers  26 ,  30  and  34  and/or discharge passages  28  and  32  may have any suitable cross-sectional area, cross-sectional shape, length, finish or any other suitable feature or construction to produce the desired upstream, contaminant-mobilizing flow rate. Other methods and techniques as applied to the flush channel  24  to achieve the desired upstream flow rate and oil pressure at the bearings  50  will be readily apparent to one skilled in the art. In addition and advantageously, the debris settling chambers  26 ,  30 , and  34  may also serve to accumulate, and thus remove, larger and heavier debris from bypassing oil. Also, it will be appreciated that the forgoing description and depiction of a series of settling chambers is illustrative only, with either fewer or more of such chambers being capable of providing similar flow resistance and debris accumulation. Additionally, as best shown in  FIG. 3 , the second and third settling chambers  30  and  34 , may be cast as an integral portion of the module  20  to avoid unnecessary manufacturing costs. 
     Referring now to  FIGS. 2 and 3 , the flush channel  24  is also in pressurized fluid communication with an inlet  13  of the pump  14  via a balance shaft module outlet  36  such that contaminated oil may pass from the balance shaft module  20  to the pump  14  and ultimately be passed through the oil filter  16  for cleaning before being passed on through the system  10  again. Similar to the aforementioned chambers  26 ,  30  and  34  and discharge passages  28  and  32 , the module outlet  36  may be configured to assist the flush channel  24  in providing the aforementioned-engineered flow resistance within the module  20 . 
     Referring now to  FIG. 4 , an alternative embodiment of an engine oil lubrication system  40  is shown. This system  40  is similar to that shown in  FIG. 1  except the flush channel  24 , comprising a single settling chamber  26  and passage  28 , discharges into the sump. 
       FIG. 5  illustrates yet another embodiment of an engine oil lubrication system  60 . This system  60  is similar to that shown in  FIG. 4  except the flush channel  24  discharges into the sump without employing a settling chamber. Here, the flush channel  24  has any suitable cross-sectional area and length to produce the appropriate flow resistance to allow the desired flow rate through the bearings  50 . 
     While the invention has been described with reference to the preferred embodiment, other embodiments, modifications, and alternations may occur to one skilled in the art upon reading and understanding of this specification and are to be covered to the extent that they fall within the scope of the appended claims. Indeed, the invention as described by the claims is broader than and not limited by the preferred embodiment, and the terms in the claims have their full and ordinary meaning.