Patent Publication Number: US-9416696-B2

Title: Oil property management system and method for internal combustion engine fuel economy and minimum wear rates

Description:
TECHNICAL FIELD 
     The present device and methods relate to engine oil management for an internal combustion engine. Specifically, the device relates to a system for accurately controlling the viscosity of engine oil based on operating parameters of the engine, while the methods relate to operation of the management system. 
     BACKGROUND OF THE INVENTION 
     The performance of an internal combustion engine is closely tied to fuel economy and operation temperature, which is in part a function of friction caused by the numerous moving parts of an engine. Engine oils have been engineered to provide adequate lubrication to such parts over a wide range of viscosities. However, optimizing viscosity to increase engine performance can be accomplished by controlling the engine oil temperature. 
     Current systems use a thermostat to bypass an engine oil cooler when the oil temperature drops below a specified threshold. This allows the engine oil temperature to be raised until the threshold is met and the bypass is closed. Then the engine oil begins to be cooled once again by passing through the engine oil cooler. 
     There are several problems with the simple thermostat system. First, bypassing the engine oil cooler is a slow method for raising the engine oil temperature. Second, bypassing the engine oil cooler may be insufficient for raising the engine oil temperature to the specific threshold. Finally, the engine oil temperature is the only parameter considered in changing the engine oil viscosity. Accordingly, the simple thermostat system cannot be counted on for optimizing engine oil viscosity and engine performance. 
     The present system and methods solve these and other problems in providing an engine oil management system for an internal combustion engine. 
     SUMMARY OF THE INVENTION 
     A method for managing the characteristics of engine oil in a lubrication system for an internal combustion engine is disclosed. Generally speaking, the method comprises the steps of determining a target viscosity for the engine oil based on engine speed and engine load, comparing the target viscosity to an actual viscosity of the engine oil, deriving a target engine oil temperature, and diverting engine oil to one of either an oil cooler or an oil heater until the target engine oil temperature is achieved. In a preferred embodiment, the step of determining a target viscosity for the engine oil is comprised of receiving an engine speed input signal, receiving an engine load input signal, and then ascertaining the target viscosity from a lubrication model based on engine speed and engine load. 
     Similarly, the step of determining a target viscosity of the engine oil may comprise the steps of providing an engine speed input signal to an estimator, and providing an engine load input signal to the estimator. The estimator then controls one of two preferred engine oil diverting mechanisms: a three-way valve, or two bypass valves. Such valves operate to open and close alternate paths to divert engine oil from an oil cooler to a heating mechanism or to merely bypass the cooler, as necessary. Regular circulation of the engine oil is restored once engine oil temperature is within desired parameters. 
     Further, an oil viscosity management system for an internal combustion engine is also disclosed. Generally speaking, the oil management system comprises an engine lubrication system having a requisite volume of engine oil, an engine oil cooler coupled to the lubrication system, an engine oil heating mechanism also coupled to the lubrication system, a valving system for directing flow of the engine oil and coupled to each of the lubrication system, the engine oil cooler and the engine oil heating mechanism, a signal generator for generating a signal based on operational parameters of the internal combustion engine, and an estimator for controlling the valving system in response to a signal received from the signal generator. 
     As with the disclosed methods, the valving system may use one of either two bypass valves or a three-way valve, to be controlled by the estimator. Additional components, such as an engine oil viscosity meter to measure actual engine oil viscosity, an engine oil temperature gauge for measuring an actual engine oil temperature, and the like, may also be included in the system for optimizing the engine oil viscosity. 
     These and other embodiments and their advantages can be more readily understood from a review of the following detailed description and the corresponding appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustrating an embodiment of the present engine oil viscosity management system having an exhaust-based heater and a three-way valve; 
         FIG. 2  is a schematic illustrating an alternate embodiment of the present engine oil viscosity management system having an exhaust-based heater and two bypass valves; 
         FIG. 3  is a schematic illustrating an embodiment of the estimator used in the engine oil viscosity management systems of  FIG. 1  and  FIG. 2 ; and 
         FIG. 4  is a side view of an embodiment of an alternate engine oil heating mechanism using engine exhaust diverted through the oil sump. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIGS. 1-4 , various embodiments of an engine oil management system are shown and consistently referenced by the number “10” throughout. Like components in the different embodiments are similarly referenced throughout the drawing figures and the following descriptions. 
     In a first illustrated embodiment of  FIG. 1 , the system  10  is generally comprised of an engine oil temperature conditioning estimator  12 , a three-way valve  14 , an engine oil cooler  16 , and an engine oil heating mechanism  18 . 
     The estimator  12  accepts engine speed and engine load signals from sensors (not shown) typically used in internal combustion engines to monitor engine operation conditions. The values of these signals are input to a lubrication model  20  within the estimator  12 . The lubrication model  20  is generally a table which identifies a target engine oil viscosity based on parameters such as engine load and engine speed (RPMs). Once the signal values are input and a target oil viscosity is determined, the estimator  12  compares the target viscosity to a working engine oil viscosity. The working engine oil viscosity may be determined in at least one of two preferred ways: using an oil viscosity gauge or by using a predictive model based on oil temperature and oil type. Once the working engine oil viscosity is determined (empirically or theoretically), the information is sent to the estimator  12 , as well. The frequency for which these various measurements and determinations may be made, and the resulting signal output, is preferably on a continuous basis, though longer intervals may be adequate for some operations. 
     A viscosity-temperature model, also stored within the estimator  12 , is used to compare the target engine oil viscosity and the determined (empirical or theoretical) working engine oil viscosity to derive a target engine oil temperature. An engine oil temperature sensor (not shown) inputs an actual oil temperature to the estimator  12  to determine whether the engine oil needs to be cooled or warmed for optimum operation. 
     When the actual engine oil temperature is higher than the target oil temperature, the estimator  12  sends a signal to the three-way valve  14 . The output signal from the estimator  12  commands the valve  14  to maintain normal engine oil flow to an engine oil cooler  16  where the engine oil is cooled. 
     When the actual engine oil temperature is lower than the target oil temperature, the estimator  12  sends a different signal to the three-way valve  14 . This output signal commands the valve  14  to divert the engine oil through a heating mechanism  18 . The heating mechanism  18  may be comprised of a chamber  22  where the engine oil is heated. The heating chamber  22  may have an electric heating coil (not shown) or, as illustrated in  FIGS. 1 and 2 , engine exhaust may be passed through the chamber  22  on a closed path to heat the chamber contents, i.e., the engine oil. The valve  14  will continue to divert the engine oil to the heating mechanism  18  until subsequent readings determine the oil temperature to be within a desired temperature range. 
     Alternatively, the estimator  12  may divert engine exhaust gas through a closed path through the engine oil pan (sump)  24 , as illustrated in  FIG. 4 . This is the preferred method for heating the engine oil as the larger volume of oil in the sump  24  allows for a more gradual, safer increase of oil temperature. 
     Of course, when the actual oil temperature is within an acceptable range of the target oil temperature, then a different path for the engine oil may be commanded by the estimator  12 , bypassing both the cooler  16  and the heating mechanism  18 . Continued measurement of engine operations are performed, possibly including the measurement of oil temperature and/or the determination of oil viscosity based on the measured oil temperature or, in an alternate embodiment, by direct measurement. 
     With reference to  FIG. 2 , where two bypass valves  26  are used in place of the three-way valve  14 , operation is similar. The bypass valves  26  are controlled by the estimator  12 . When the actual oil temperature is too high, a first bypass valve  27  is closed to flow engine oil to the engine oil cooler  16 . When, and if, the target engine oil temperature is achieved, the bypass valve  27  may be opened to divert engine oil from the cooler  16  and into the second bypass valve  28 , which is typically closed as well, resuming regular engine oil circulation. 
     However, when the actual oil temperature is too low (for example, at engine start up), the first bypass valve  27  will be opened to divert engine oil to the second bypass valve  28  which is also opened to divert engine oil through a heating mechanism  18 , as described above. The second bypass valve may alternatively be used to divert engine exhaust through the oil sump  24 , also as described above. As soon as the target oil temperature is achieved, the bypass valve  28  is closed and regular circulation of the engine oil or exhaust is resumed. 
     It should be understood that in most instances, weather and load conditions will dictate that the engine oil will need to be cooled. Accordingly, as explained above, engine oil flow through the engine oil cooler will constitute “regular circulation” in most cases.