Abstract:
An aftermarket modification for diesel engines that operate in cold environments particularly those using a liquid-to-air oil cooler. Engine oil can be routed to a bypass module having a thermostatic element that directs the oil to bypass the oil cooler and return to the engine if the engine oil is below the desired temperature. Once the desired oil temperature is reached, the thermostatic element moves toward a closed position to direct oil through the oil cooler. A pressure bypass element can be incorporated into the bypass module. If the pressure differential between the inlet and outlet of the cooler exceeds a set point, the bypass element moves toward an open position to direct a portion of the oil to bypass the oil cooler.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 13/417,760. 
    
    
     TECHNICAL FIELD 
     This invention relates generally to internal combustion engines and more specifically to oil coolers for internal combustion engines. 
     BACKGROUND 
     Compression ignition (diesel) engines experience various operational difficulties in cold temperatures. Difficult starting in cold weather can be attributed to various causes: Cold weather reduces the available battery current, decreasing the electrical power available to the engine self-starter. Injected fuel condenses on the cold cylinder surfaces leading to improper atomization, which inhibits formation of a combustible mixture inside the cylinder. The engine lubricating oil tends to thicken, leading to increased friction resisting the starter motor, further taxing a battery that may be operating at a reduced output. Hard starting problems can occur with mobile engines such as those in large trucks, buses and even smaller trucks such as the 6.0L and 6.4L POWER STROKE® diesel engines sold by Ford Motor Company. Engines for fixed installations often also encounter similar difficulties starting in cold weather. 
     Various systems and devices may be utilized to improve starting in cold weather, including battery heaters (to produce higher battery output), engine block heaters (to reduce oil viscosity and reduce fuel condensation), glow-plugs (installed in the cylinder to assist with combustion) and the like. 
     Proper lubrication can also be a problem in cold weather operation. The cold diesel fuel injected into the cold cylinders can condense and pass along the cylinder walls, diluting the lubricating oil. Engine lubrication in cold weather can also be a problem. The engine lubricating oil becomes more viscous in cold temperatures reducing its effectiveness in lubricating engine components during startup and initial operation. Consequently, some operators elect to use an very thin oil such as an exemplary 0W-20 to allow for easier cold weather starting. However, once the engine is warmed, the viscosity and therefore the oil film thickness in the bearings and elsewhere may drop below that recommended by manufacturers, allowing metal-to-metal contact at bearing surfaces leading to accelerated wear. Thus, another problem operators of diesel engines encounter during cold weather operation is selecting an oil that will adequately lubricate yet will not contribute unnecessarily to starting difficulties. 
     Since diesel engines operate in all seasons, hot weather operation is also a consideration. To aid hot weather operation, diesel engines are often equipped with engine oil coolers, which reduce oil temperature during hot driving conditions so as to keep the oil at a proper viscosity level. However, engine oil coolers do not aid engine operation in cold environments where it is often desirable to warm the oil rather than cooling it. If engines having an oil cooler could be fitted with a device to aid cold weather starting and operation then the useful temperature range of a diesel engine and its performance might be improved. 
     SUMMARY 
     The following presents a simplified summary of the disclosure in order to provide a basic understanding to the reader. This summary is not an extensive overview of the disclosure and it does not identify key/critical elements of the invention or delineate the scope of the invention. Its sole purpose is to present some concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later. 
     Briefly, the present invention comprises a diesel engine oil system intended for cold weather operation. According to an illustrative embodiment, the system has a bypass module which includes both a pressure bypass element and a thermostatic bypass element which operate independently of one another. The system has several configurations. In one configuration, oil from the engine after passing through a filter can be directed to a tee fitting which has one branch coupled to an oil cooler and another branch coupled to the bypass module. If the oil temperature is below a preset temperature (about 180 F.), the thermostatic element will be open allowing high pressure oil to proportionately bypass the cooler, directing the oil to return to the engine. 
     In an alternative configuration, oil from the engine may also be introduced to the bypass module at another port if required by the installation environment. In this configuration. oil is either directed to the cooler or to the return oil engine circuit depending on the position of the thermostatic element in the bypass module. 
     In addition to a thermal bypass valve, the bypass module or block may include a pressure bypass element. This element opens at a predetermined pressure differential between the oil supply and the oil return oil to the engine. Should the return oil pressure drop or the supply pressure increase resulting in a pressure differential above a preset threshold level (indicative of a restricted or plugged oil cooler or oil cooler line), the pressure element will direct oil to flow to the return oil line to prevent oil starvation. When the pressure differential is below the threshold value (indicating that the engine oil demands are below that of the restriction) the pressure bypass element will close, directing oil to the oil cooler. 
     Many of the attendant features will be more readily appreciated as the same becomes better understood by reference to the following detailed description considered in connection with the accompanying drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The present invention will be better understood from a reading of the following detailed description, taken in conjunction with the accompanying drawing figures in which like references designate like elements and, in which: 
         FIG. 1  is a schematic diagram of the cold weather lubrication system of the present invention; 
         FIG. 2  is a cut-away perspective view of a bypass module showing the various ports and the temperatures and pressure bypass valve element; 
         FIG. 3  illustrates the oil flow through the bypass module in one operational configuration of the present system; 
         FIG. 4  illustrates the oil flow through the bypass module in another operational configuration; and 
         FIG. 5  shows a process for modifying a diesel engine for cold weather operation. 
     
    
    
     DETAILED DESCRIPTION 
     The drawing figures are intended to illustrate the general manner of construction and are not necessarily to scale. In the detailed description and in the drawing figures, specific illustrative examples are shown and herein described in detail. It should be understood, however, that the drawing figures and detailed description are not intended to limit the invention to the particular form disclosed, but are merely illustrative and intended to teach one of ordinary skill how to make and/or use the invention claimed herein and for setting forth the best mode for carrying out the invention. 
       FIG. 1  is a schematic diagram of an embodiment of a cold weather lubrication system incorporating features of the present invention as applied to an illustrative embodiment comprising a 6.0L or 6.4L Ford POWER STROKE diesel engine. The system of the present example is generally designated by the numeral  100  and may be a “stock” or Original Equipment Manufacturer (OEM) system but preferably comprises a retrofit aftermarket modification to an existing engine. The hose lengths provided and fittings shown are exemplary, and not meant to be limiting in any way. The engine is provided with an oil distribution manifold M, which in the illustrative embodiment is mounted to the top of the engine. The manifold M has an outlet  102  for oil which is pumped from the engine through the manifold by the engine low pressure oil pump (not shown). 
     In one embodiment, the oil is directed by line  104  to an oil filter mounting base  106  to which is attached an oil filter  110 . Oil filter  110  is shown as spin-on style filter, which screws on to the conventionally constructed mounting base  106  and which has its own internal anti-backflow valve. Oil passes through the media within the oil filter and the filtered oil is discharged through line  112 . The oil filter may be located in any convenient location in the engine compartment, or external to it. Alternatively, for example if the engine has an internal oil filter, or other filter that filters the oil before exiting manifold outlet port  102 , the oil filter may be omitted so that the engine oil discharge connects directly to the tee fitting as shown in the dashed line  104   a  in  FIG. 1 . Additionally, although oil filter  110  is shown in the illustrative embodiment as spin-on style filter, cartridge, canister or other types of oil filters, with or without integral anti-backflow valves, may be utilized and therefore depiction of a spin-on filter is not intended to limit the invention in any way. 
     Line  112  connects to inlet  116  of tee fitting  120 . Tee  120  has an outlet  122  coupled by line  124  to the inlet of oil cooler  130 . Tee  120  has a second outlet  126  which is coupled by line  132  to the bypass block or module  140  at a first port  166 . Oil cooler  130  has an outlet  146 , which is connected to a second port  168  of bypass module. A third port  170  of bypass module is connected to port  103  of the manifold M by line  175 . 
     The oil cooler  130  may be of a parallel plate construction optimized for liquid-to-liquid heat transfer, but preferably is of tube-and-fin construction optimized for liquid-to-air heat transfer. In a tube-and-fin configuration, hot oil passes through the tubes where it is cooled by the air passing over the tubes. Fins are attached to the tubes to increase the surface area and therefore the efficiency of the heat transfer between the oil and the air. The oil cooler  130  may be located in any suitable location where it can be subject to adequate airflow for cooling. A convenient location is to secure the cooler to the air conditioning condenser using suitable mounting brackets. 
       FIG. 2  is a cut-away perspective view of the bypass module showing the various ports and the temperature and pressure bypass valve elements. The bypass module  140  has a body  160  of aluminum or other suitable material. Lower passage  164  extends within the body and may be intercepted at its blind end by threaded port  166 . For simplicity, the threads are not shown. Alternatively, connections equivalent to threaded connections (e.g. quick disconnect, O-ring, hose clamp, etc.) may be provided. 
     Module  140  may include an auxiliary port  162  threaded to receive a fitting for connection for oil from the engine in one installation configuration as will be more fully explained hereinafter. If port  162  is present, but not used, it will be blocked by a threaded plug, or its equivalent. 
     An upper passage  169  extends in the upper portion of the bypass module, parallel to lower passage  164 . Passage  169  has a port  170  which may be threaded (or equivalent) for connection to oil return line ( 175  of  FIG. 1 ) for returning oil to the engine via the manifold (M of  FIG. 1 ). Oil from the cooler ( 130  of  FIG. 1 ) may be connected to the passage  169  at port  168 . The upper passage  169  and lower passage  164  are coupled via a pressure bypass valve  190  and a temperature bypass valve  180 . Temperature bypass valve  180  may be the type that is fully-open or fully-closed but is typically an analog valve that opens gradually from a closed position to its fully-open position. Conversely, the pressure bypass valve  190  may be an analog valve that opens gradually from a closed position to its fully-open position but is typically of the type that is fully-open or fully-closed. 
     A first transverse passage  172  extends between the upper and lower parallel passageways  164 ,  169 . The passage  172  may be threaded to receive a thermostatic element  180 . Thermostatic element operates to open a path from the upper passage  169  to lower passage  164  when a predetermined temperature is reached. The exemplary thermostatic valve element has a sealed chamber  182  that contains a material, such as a wax pellet, which will melt and expands as heated by the oil. Alternatively other thermostatic valve constructions may be provided. A rod  185  operates a valve member  186  in the passageway. Initially the thermostat is open, or is partially open, when the oil temperature in the module is below a preset threshold, as for example 180 degrees Fahrenheit, allowing some or all of the oil flow to bypass the cooler to return to the engine at port  170 . The thermostatic element stays open until the oil temperature reaches the nominal thermostat opening temperature. 
     Thereafter. the thermostat element will dynamically adjust to progressively close in response to changes in oil temperatures, increasing flow to the cooler  130  as the oil temperature rises above the optimum preset temperature. If the temperature of the oil again decreases below the preset limit. the thermostatic element will open proportionately to allow oil to bypass the cooler, thus maintaining a minimum operational oil temperature. 
     Pressure bypass element  190  occupies the passage  191  between the lower passage  164  which receives oil from the engine (supply oil) and upper passage  168 . If the return oil pressure in passage  170  drops or the supply pressure in passage  164  increases, the pressure element  190  will be subjected to an increased pressure differential, causing the valve flow control member  192  to open and direct high pressure oil to the return line via passage  191 . This ensures the engine will continue to receive oil even if the oil cooler is occluded or the engine oil demand is above the flow-rate of the oil cooler. This assures a constant flow of oil to the engine in extreme operating conditions such as racing or in sub-freezing conditions. When the pressure differential across the pressure element is below the threshold valve required to open the pressure element, for example if the engine oil demand has decreased, the element is closed, blocking flow between passages  164  and  168 . 
     The pressure bypass valve  190  has a flow control member  192  seated in the opening between the passages  164  and  168 . Spring  195  exerts a predetermined downward biasing force on the flow control member  192 , maintaining the element closed until a predetermined pressure differential occurs which may be sufficient to overcome the spring bias. In alternative examples electronic sensing components may be used to sense pressure and temperature and operate electronically controlled valves. 
       FIG. 3  illustrates the oil flow through the bypass module according to a first embodiment. The thermostatic pressure elements  180  and  190 , as described above, are also represented by the letters P and T. The cooler bypass port  166  may be coupled to branch  126  of tee  120 . The cooler outlet may be coupled to port  168  at one end of passage  169 . The opposite end of passage  169  has a port  170  for return oil to the engine. 
     In operation, oil from the engine, after filtration, enters the inlet  116  of tee  120 , upstream of the cooler  130 . If the temperature of the oil is below a preset level, thermostatic bypass element  180  will be open allowing oil to flow through passage  169 , bypassing the oil cooler, and exiting port  170  to return to the engine. Once the oil reaches a predetermined temperature, typically about 180 F., then temperature element  180  will close, blocking the bypass channel and forcing the oil through the cooler, into the bypass module  140  at port  168 , through passageway  169  to the return oil line  175 . 
       FIG. 4  illustrates the oil flow through the bypass module in another embodiment. As in the embodiment of  FIG. 3 , the bypass elements  180 ,  190  are indicated by the letters P and T. Inlet port  162  is coupled to receive oil from the engine. If both bypass elements  180  and  190  are closed, oil flows out through the port  166  and may be directed through line  132  to the inlet of cooler  130 . Cold oil returns via port  168  and travels through the module to the return engine oil circuit at port  170 . The Tee fitting  120  is omitted since the tee channel is essentially incorporated into the bypass module. 
     The bypass elements  180  and  190  are independent working, as described, and will proportionately close to block bypass flow or open proportionately to allow a certain flow of oil to bypass the cooler. 
     The modification or retrofit for installing the system generally involves removing the Air Conditioning condenser and installing the oil cooler to the condenser. The bypass module  140  may be attached to the oil cooler or elsewhere on the vehicle using suitable brackets if necessary. The oil lines are coupled and the condenser reinstalled, removing any interfering structure. 
       FIG. 5  shows a process for modifying a diesel engine for cold weather operation. At block  502  the tee fitting is connected to the engine oil outlet port. If an oil filter is present, then at block  504  the oil filter is interposed between the engine oil outlet port and the tee fitting. At block  506  connecting one branch of the tee to an oil cooler may be performed. At block  508  connecting the other branch of the tee to a bypass module at a first port may be performed. At block  510  connecting the outlet of the cooler to a second port of the bypass module, said second port communicating via a passageway with a return oil port may be performed. At block  512  connecting the return oil port to the engine return oil port may be performed. And at block  515  installing a thermostatic element which operates to direct oil to the return port of the oil temperature may be below a preset level and which, when closed, directs oil to the cooler before being directed to the return port may be performed. Note: As used herein “connected” does not mean attached directly, but means fluidically connected so that the oil flows from one element to another, and leaves open the possibility of intervening hoses, fitting or other elements, as opposed to the elements being physically connected directly to each other. 
     Although certain illustrative embodiments and methods have been disclosed herein, it will be apparent from the foregoing disclosure to those skilled in the art that variations and modifications of such embodiments and methods may be made without departing from the invention. For example, although in the illustrative embodiment of  FIG. 1  the oil flow direction is from the engine to the tee fitting then to the oil cooler and bypass module, the position of the tee fitting and bypass module may be reversed (essentially reversing the flow in  FIG. 1 ) so that the oil flows first to the bypass module then to the oil cooler and tee fitting. Similarly, although in the illustrative embodiment of  FIG. 1  the oil flows to the oil filter then to the oil cooler, the oil filter may be omitted or may be installed downstream of the oil cooler (e.g. in hose  175 ). The oil filter may also be incorporated into the manifold where a manifold is required. Finally, although in the illustrative embodiment a manifold is attached to the engine to provide the oil outlet and return ports, the manifold may be omitted for example, where the engine is already equipped with oil outlet and return ports. Accordingly, it is intended that the invention should be limited only to the extent required by the appended claims and the rules and principles of applicable law. Additionally, as used herein, references to direction such as “up” or “down” are intend to be exemplary and are not considered as limiting the invention and, unless otherwise specifically defined, the terms “generally,” “substantially,” or “approximately” when used with mathematical concepts or measurements mean within ±10 degrees of angle or within 10 percent of the measurement, whichever is greater, and as used herein, a step of “providing” a structural element recited in a method claim means and includes obtaining, fabricating, purchasing, acquiring or otherwise gaining access to the structural element for performing the steps of the method.