Patent Publication Number: US-9896979-B2

Title: System and method for controlling a temperature of oil in a power-plant of a vehicle

Description:
TECHNICAL FIELD 
     The present invention relates to a system and a method for controlling a temperature of oil in a power-plant of a vehicle. 
     BACKGROUND 
     As a by-product of generating power for propelling a motor vehicle, the vehicle&#39;s power-plant, such as an internal combustion engine, typically generates heat energy. Accordingly, after the power-plant is activated, it proceeds through a “warm-up” period during which the temperature of the power-plant is increased from an ambient temperature. Generally, following the warm-up period, the power-plant is cooled in order to maintain its operating temperature in a particular range and ensure the power-plant&#39;s efficient and reliable performance. 
     In a majority of motor vehicles, power-plants are cooled by a circulating fluid, such as a specially formulated chemical compound mixed with water. Additionally, vehicle power-plants are lubricated and cooled by oils that are generally derived from petroleum-based and non-petroleum synthesized chemical compounds. Such oils mainly use base oils composed of hydrocarbons that are blended with chemical additives to minimize a power-plant&#39;s internal friction and wear. 
     SUMMARY 
     A system is provided for controlling a temperature of oil in a power-plant operable to propel a vehicle. The system includes a heat-exchanger arranged relative to the power-plant. The heat-exchanger is configured to receive the oil from the power-plant, modify the temperature of the oil, and return the modified temperature oil to the power-plant. The system also includes a valve configured to direct the oil through the heat-exchanger during a warm-up operation of the power-plant such that the temperature of the oil is increased. The valve is also configured to direct the oil to bypass the heat-exchanger during a low load operation of the power-plant such that the temperature of the oil is increased. Additionally, the valve is configured to direct the oil through the heat-exchanger during a high load operation of the power-plant such that the temperature of the oil is decreased. 
     The valve may be additionally configured to direct the oil to bypass the heat-exchanger during a low ambient temperature start of the power-plant such that the temperature of the oil is not modified by the heat-exchanger. 
     The system may also include an actuator configured to operate the valve. The system may additionally include a spring configured to bias or load the valve against the actuator. The actuator may be one of a wax motor and a solenoid. The wax motor may be configured as a two-stage wax motor. Furthermore, the system may include a controller in electrical communication with the actuator. In such a case, the controller is configured to regulate the actuator according to one of the warm-up, low load, and high load operation of the power-plant. 
     Moreover, the system may additionally include a fluid pump configured to circulate a coolant through the heat-exchanger for modifying the temperature of the oil. 
     The power-plant may be an internal combustion engine. 
     A method of controlling a temperature of oil in a vehicle power-plant is also provided. 
     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 
         FIG. 1  is a schematic diagrammatic view of a vehicle system employing one type of an actuator and configured to control temperature of oil in a power-plant; 
         FIG. 2  is a schematic diagrammatic view of the vehicle system employing an alternate type of an actuator, illustrating a power-plant during a cold start operation; 
         FIG. 3  is a schematic diagrammatic view of the vehicle system shown in  FIG. 2 , illustrating the power-plant during a subsequent warm-up operation; 
         FIG. 4  is a schematic diagrammatic view of the vehicle system shown in  FIG. 2 , illustrating the power-plant during continued warm-up operation; 
         FIG. 5  is a schematic diagrammatic view of the vehicle system shown in  FIG. 2 , illustrating the power-plant during a low load operation; 
         FIG. 6  is a schematic diagrammatic view of the vehicle system shown in  FIG. 2 , illustrating the power-plant during a high load operation; and 
         FIG. 7  schematically illustrates, in flow chart format, a method of controlling a temperature of oil of the power-plant shown in  FIGS. 1-6 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, wherein like reference numbers refer to like components,  FIGS. 1-6  show a system  10  adapted for controlling a temperature of oil in a power-plant  12  of a motor vehicle. The power-plant  12  may be an internal combustion (IC) engine, such as a spark ignition or a compression ignition engine, a fuel cell, or an electric motor operable to propel the vehicle. As such, the subject vehicle may be a conventional, a hybrid, or an electric type. 
     The power-plant  12  produces heat energy as a by-product of generating power used to propel the vehicle. Such heat energy is removed by a circulating heat transfer fluid or coolant  14 , continuously cycling through multiple coolant conduits of the system  10  via a fluid or coolant pump  16 . The contemplated coolant is typically a solution of a suitable organic chemical (most often ethylene glycol, diethylene glycol, or propylene glycol) in water. The power-plant  12  is additionally cooled and lubricated by a body of oil  18 . The oil  18  is continuously circulated through multiple oil conduits of the system  10  and through specifically configured channels and lubrication ports (not shown) arranged inside the power-plant  12  via an oil pump  20 . The contemplated oil is generally derived from a petroleum or a non-petroleum based chemical compound synthesized to minimize the power-plant&#39;s internal friction and wear. 
     The system  10  also includes a heat-exchanger  22  in fluid communication with the power-plant  12 . The heat-exchanger  22  is arranged relative to the power-plant  12 , and is configured to receive the oil  18  from the power-plant, modify the temperature of the oil, and return the modified temperature oil to the power-plant. As shown in  FIG. 1 , the heat-exchanger  22  is contemplated as a coolant-to-oil radiator. The heat-exchanger  22  transfers heat energy between the coolant  14  and the oil  18 , depending on the relative temperatures of the bodies of coolant and oil. Accordingly, when the oil temperature is greater than that of the coolant, the heat-exchanger  22  employs the coolant  14  for absorbing heat energy from the oil  18  to thus cool the oil. Additionally, when the coolant temperature is greater than that of the oil, the heat-exchanger  22  employs the coolant  14  for transferring the heat energy to the oil  18  to thus heat the oil. The fluid pump  16  is, therefore, configured to circulate the coolant  14  through the heat-exchanger  22  in order to modify the temperature of the oil  18 . 
     The coolant  14  is delivered to the heat-exchanger  22  via a conduit  24  and exits the heat-exchanger via conduit  26 . The oil  18  is delivered to the heat-exchanger  22  via a conduit  29 . After the temperature of the oil  18  has been modified inside the heat-exchanger  22 , the oil exits the heat-exchanger via conduit  30  and proceeds via a conduit  31  back to the power-plant  12 . A conduit  32  is arranged between the conduit  28  and the conduit  31  to permit the oil to bypass the heat-exchanger  22  on demand. The system  10  also includes a spool valve  33 . The valve  33  includes an inner hollow (not shown) that is in fluid communication with the oil  18  and is also connected to the exterior surface of the valve via cross-drill or the like passages represented by apertures  34  and  36 . The valve  33  is shuttled back and forth inside the conduit  28  for selectively controlling the flow of oil  18  through the heat-exchanger  22 . The valve  33  is configured to direct the oil  18  through the heat-exchanger  22  during warm-up and during high load operation of the power-plant  12 . The valve  33  is also configured to block off access of the oil  18  to the conduit  29  to thereby bypass the heat-exchanger  22  during low load operation of the power-plant  12 . 
     The system  10  is configured such that directing the oil  18  through the heat-exchanger  22  during the warm-up operation of the power-plant  12  via the valve  33  acts to increase the temperature of the oil when the temperature of the coolant  14  is relatively higher than that of the oil. Additionally, directing the oil through the heat-exchanger  22  during the high load operation of the power-plant  12  via the valve  33  acts to reduce the temperature of the oil when the temperature of the coolant  14  is relatively lower than that of the oil. Furthermore, directing the oil  18  to bypass the heat-exchanger  22  during the low load operation of the power-plant  12  acts to increase the temperature of the oil above that of the coolant  14 . 
     The system  10  also includes an actuator  38  and a spring  40 . The spring  40  is configured in a spring set position to bias the valve  33  against the actuator  38 . The spring  40  is sized to overcome a set or predetermined difference in pressure of the oil  18  between the conduits  28  and  32 . The actuator  38  is configured to operate the valve  33  by displacing the valve in the direction of compressing the spring  40  during cold start conditions and subsequent warm-up operation of the power-plant  12 . The actuator  38  may be configured as an externally regulated magnetic solenoid (as shown in  FIG. 1 ) or as a wax motor (as shown in  FIGS. 2-6 ). As shown in each of  FIGS. 1-6 , the controller  46  is in electrical communication with the actuator  38 . The controller  46  is configured, i.e., programmed, to regulate the actuator according to one of the warm-up, low load, and high load operation of the power-plant  12 . The defining temperature and pressure parameters of the coolant  14  and the oil  18  for each of the warm-up, low load, and high load operation of the power-plant  12  may be established empirically during testing and development of the power-plant and the subject vehicle. 
     In the case that the actuator  38  is a wax motor, as illustrated by  FIGS. 2-6 , the wax motor functions as a linear actuator that is capable of providing an appropriately short range of linear motion via a plunger. Generally, the wax motor has three principal components, a block of wax, a plunger that bears on the wax, and an electric heater that heats the wax (not shown). The electric heater may be a positive temperature coefficient (PTC) thermistor, which, as known by those skilled in the art, is a type of an electronic component that is characterized by resistance that varies significantly with temperature. The wax motor operates when the electric heater is energized through the application of an electric current to heat the wax block. When the wax block is thus heated, the wax block will expand to drive the plunger to thereby displace the valve  33 . When the electric current is removed, the wax block will cool down and contract to thereby cause the plunger to be pushed in or withdrawn with the assist from the force of the spring  40 . The wax motor may additionally employ an internal spring (not shown) incorporated directly into the wax motor configured to assist the spring  40  in withdrawing the plunger. 
     As shown in  FIGS. 2-6 , the actuator  38  may also be configured as a two-stage wax motor where essentially two wax motors, each having a plunger, are arranged in series. In the case of the two-stage wax motor, a first wax motor  42  may be configured to be activated by the controller  46  at a first predetermined temperature of the oil  18  to displace the valve  33  via a plunger  43 , thereby exposing the aperture  36  to the conduit  32  and permitting the oil to bypass the heat-exchanger  22  (as shown in  FIG. 5 ). A second wax motor  44  may be activated by the controller  46  at a second predetermined temperature of the oil  18  to displace both the first wax motor and the valve  33  via a plunger  45  further toward the spring  40 , thereby exposing the aperture  34  to the conduit  29  and permitting the oil to flow to the heat-exchanger  22  (as shown in  FIG. 6 ). The first and the second predetermined temperatures at which the respective first and second wax motors  42 ,  44  are configured to be activated may be established empirically during testing and development of the power-plant  12  and the subject vehicle. Although  FIGS. 2-6  illustrate the controller  46  being employed to control the wax motors  42 ,  44 , the wax motors may also be configured to react directly to the temperature of the fluid flowing through the conduit  28  without any other external regulation. 
     Following is a detailed description of operation of the system  10  in connection with various operating modes of the power-plant  12  shown in  FIGS. 2-6 . A cold start of the power-plant  12  is shown in  FIG. 2 , where the temperatures of both the coolant  14  and the oil  18  are at an ambient temperature that is significantly below zero Celsius. During such a cold start of the power-plant  12  the pressure of the oil  18  in the conduit  28  is significantly higher than the pressure in conduit  31 . As a result, the pressure of the oil  18  is sufficient to displace the valve  33  away from the actuator  38  to fully compress the spring  40  and expose the aperture  34  to the conduit  32 . Additionally, an internal restriction through the heat-exchanger  22  is sufficient to generate a significant difference in oil pressure between the conduit  29  and the conduit  32  and force the majority of the oil  18  to bypass the heat-exchanger. Accordingly, during the low ambient temperature start of the power-plant  12  the valve  33  directs the oil  18  to bypass the heat-exchanger  22 , such that the temperature of the oil is not modified by the heat-exchanger, and is therefore permitted to increase independently of the temperature of the coolant  14 . 
       FIG. 3  illustrates continued operation of the power-plant  12  and the gradual warming up of the oil  18 . As the oil  18  warms up, the pressure of the oil  18  in the conduit  28  decreases, as does the internal restriction through the heat-exchanger  22 , which causes the valve  33  to be displaced back toward the actuator  38  in response to the force of the spring  40 . As the valve  33  is displaced by the spring  40  during the gradual warm up of the power-plant  12 , the aperture  36  becomes exposed to the conduit  32 . Such a change in the difference between oil pressure in the conduits  28  and  31  permits a gradually increasing portion of the oil  18  to go through the heat-exchanger  22  to be heated by the coolant  14 , while the remaining portion of the oil will still flow through the conduit  32 . Thus, during the gradual warming up of the oil  18 , as shown in  FIG. 3 , the heat-exchanger  22  performs as an oil heater. 
     As shown in  FIG. 4 , when the oil  18  continues to warm up, the difference in pressure between the conduits  28  and  31  will decrease below a threshold value, thus permitting the spring  40  to overcome the pressure difference and displace the valve  33  fully toward the actuator  38 . The threshold value of the difference in pressure of the oil  18  may be established empirically during testing and development of the power-plant  12  and the subject vehicle. For example, the threshold value of the difference in pressure of the oil  18  between the conduits  28  and  31  at which the valve  33  can be fully displaced may be set at 150 KPa, which typically occurs around zero degrees Celsius. At such a point, the valve  33  will be fully closed, thereby directing substantially all the flow of the oil  18  through the heat-exchanger  22  to be heated by the coolant  14  and permitting the heat-exchanger to continue performing as an oil heater. 
     As substantially all the oil  18  begins to flow through the heat-exchanger  22 , and the power-plant  12  continues to warm up, the temperature of the oil  18  will increase further. As the power-plant  12  continues to warm-up, each of the temperatures of the coolant  14  and the oil  18  will eventually reach the first predetermined temperature. The first predetermined temperature may be set at an equilibrium point where the temperatures of the coolant  14  and the oil  18  are substantially at par. Such an equilibrium point has been established to occur around 80 degrees Celsius for some applications of an IC engine operating at road load in a motor vehicle. 
       FIG. 5  illustrates the power-plant  12  in a substantially warm or steady-state operating state where the temperatures of the coolant  14  and of the oil  18  have reached the first predetermined temperature, for example 80 degrees Celsius. Such a steady-state operating state of the power-plant  12  will typically occur when the host vehicle is subjected to a relatively low road load, such as cruising at highway speeds. As shown in  FIG. 5 , after the temperature of the oil  18  reaches the first predetermined temperature, the first wax motor  42  of the actuator  38  will be activated by the controller  46  to displace the valve  33  via the plunger  43 . Such displacement of the valve  33  will expose the aperture  36  to the conduit  32  and permit the oil  18  to bypass the heat-exchanger  22 , thus permitting the temperature of the oil to increase above the temperature of the coolant  14 . 
       FIG. 6  illustrates the power-plant  12  operating as an increased load. During high load operation of the power-plant  12 , such as at higher vehicle speeds, when the vehicle is traveling up a grade, or is towing a load, the temperature of the oil  18  will increase to above that of the coolant  14 , for example up to 110 degrees Celsius. The temperature of the oil  18  has a particular tendency to exceed the temperature of the coolant  14  in IC engines employing piston squirters. A piston squirter is a device used to spray oil at the underside of a piston that reciprocates inside a cylinder to generate a cooling effect during high load operation of some IC engines. When the temperature of the oil  18  has thus exceeded the temperature of the coolant  14 , the second wax motor  44  of the actuator  38  will be activated by the controller  46 . The activation of the second wax motor  44  will displace the valve  33  via the plunger  45 . Such displacement of the valve  33  will expose the aperture  34  to the conduit  29  and permit the oil  18  to flow through the heat-exchanger  22  to be cooled to the temperature of the coolant  14 , thus allowing the heat-exchanger to perform as an oil cooler. 
       FIG. 7  depicts a method  50  of controlling the temperature of oil  18  in the power-plant  12  shown in  FIGS. 1-5 . The method  50  is described with reference to  FIGS. 1-5 , and the above description of the system  10 . The method commences at block  52 , and then proceeds to frame  54 . In frame  54 , the method includes directing the oil  18  through a heat-exchanger  22  during the warm-up operation of the power-plant  12  such that the temperature of the oil is increased. The method then advances to frame  56 . In frame  56 , the method includes directing the oil  18  to bypass the heat-exchanger  22  during the low load operation of the power-plant  12  such that the temperature of the oil is increased. From frame  56  the method proceeds to frame  58 , where it includes directing the oil  18  through the heat-exchanger  22  during the high load operation of the power-plant  12  such that the temperature of the oil is reduced. According to the method  50 , following frame  58 , the method may loop back to frame  56  and permit the oil to again bypass the heat-exchanger  22  when the power-plant  12  reverts to the low load operation. 
     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.