Abstract:
An active/passive system for managing the temperature of fluid within an automatic transmission includes two heat exchangers, an active solenoid valve and a passive wax motor valve. A first heat exchanger provides transmission fluid heating and receives a flow of engine coolant. A second heat exchanger provides transmission fluid cooling and is exposed to ambient air. The solenoid valve which is preferably driven by a signal from a transmission control module (TCM) and the wax motor valve cooperate to provide three states of operation: transmission fluid heating, that is, heat added, cooling, that is, heat removed and pass-through or bypass (without heating or cooling).

Description:
FIELD 
       [0001]    The present disclosure relates to a system for managing the temperature of an automatic transmission and more particularly to a two valve system for managing the temperature of fluid within an automatic transmission. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0003]    Modern automatic motor vehicle transmissions utilize a several quart or liter fill of transmission fluid (hydraulic oil). The transmission fluid serves several purposes. First and most obvious is the lubrication of the numerous rotating and moving parts within the transmission. Second is the transfer of heat out of the transmission to maintain an appropriate operating temperature and third is use in the pressurized hydraulic control system of the transmission. 
         [0004]    To achieve proper heat transfer to the ambient, a transmission oil cooler remote from the transmission is provided with a flow of transmission fluid. The oil cooler may be mounted within the vehicle radiator in which case heat is first transferred to engine coolant within the radiator and thence to the ambient or the oil cooler may be directly exposed to air flow, for example, through the engine compartment. 
         [0005]    Such a device addresses only one aspect of transmission fluid temperature control however: ensuring that the transmission fluid temperature and thus the internal components of the transmission do not exceed design operating limits. While such a purpose is of great importance, there are other operating considerations relating to transmission fluid temperature. For example, when a vehicle and its transmission are started in cold weather, the viscosity of the cold transmission fluid can cause significant parasitic frictional losses. Depending upon the temperature, it can be several minutes before the transmission fluid temperature rises into a range where frictional losses become negligible. This delay is primarily due to the fact that only frictional heating from the rotation of parts heats the transmission fluid. During this time, fuel economy can be significantly degraded. 
         [0006]    It is therefore apparent that improved control of automatic transmission fluid temperature is desirable. 
       SUMMARY 
       [0007]    The present invention provides an active/passive system for managing the temperature of fluid within an automatic transmission. The system receives a flow of transmission fluid from the transmission and includes a first heat exchanger for transferring heat from engine coolant to the transmission fluid, a second heat exchanger for transferring heat from the transmission fluid to the ambient, a first, two position, diverter spool valve for directing transmission fluid to a first path which includes the first heat exchanger or a second path which includes a second, bypass valve which directs fluid flow to either the second heat exchanger the or bypasses it and returns the fluid to the transmission. The first, two position valve is solenoid operated by a signal from a transmission control module (TCM) or engine control module (ECM) and the second, bypass valve is preferably controlled by a passive wax motor. 
         [0008]    When the transmission and transmission fluid is cold or below a threshold design temperature, the solenoid of the first, two position diverter valve is activated and fluid flow is directed to the first heat exchanger where heat in the engine coolant is transferred to the transmission fluid to assist its warming up. As the temperature of the transmission and transmission fluid rises and passes the same or a related threshold design temperature, the solenoid is deactivated and the first valve directs fluid flow to the second path. Typically at this time, the wax motor will be cold and the flow of transmission fluid will be returned to the transmission. As the temperature of the transmission and the transmission fluid continue to rise, the wax motor will sense this and translate the bypass valve to direct fluid flow to the second heat exchanger which will transfer heat to the ambient and lower the temperature of the transmission fluid. 
         [0009]    An alternate embodiment system for managing the temperature of fluid within an automatic transmission includes two solenoid operated valves that may be controlled by two outputs from a transmission control module and which provide the three states of operation: transmission fluid circulation without heat transfer, circulation with heat transfer in from the engine coolant and circulation with heat transfer out to the ambient. 
         [0010]    Thus it is an aspect of the present invention to provide a system for managing the temperature of fluid within an automatic transmission. 
         [0011]    It is a further aspect of the present invention to provide an active/passive system for managing the temperature of fluid within an automatic transmission. 
         [0012]    It is a still further aspect of the present invention to provide a system for managing the temperature of fluid within an automatic transmission having a first heat exchanger for transferring heat from engine coolant. 
         [0013]    It is a still further aspect of the present invention to provide a system for managing the temperature of fluid within an automatic transmission having a second heat exchanger for transferring heat to the ambient. 
         [0014]    It is a still further aspect of the present invention to provide a system for managing the temperature of fluid within an automatic transmission having a two position solenoid operated valve. 
         [0015]    It is a still further aspect of the present invention to provide a system for managing the temperature of fluid within an automatic transmission having a bypass valve operated by a wax motor. 
         [0016]    It is a still further aspect of the present invention to provide a system for managing the temperature of fluid within an automatic transmission having a pair of heat exchangers and a pair of valves each having a inlet and a pair of outlets. 
         [0017]    It is a still further aspect of the present invention to provide a system for managing the temperature of fluid within an automatic transmission having a pair of heat exchangers and a pair of solenoid valves. 
         [0018]    Further advantages, aspects and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0019]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0020]      FIG. 1  is a schematic view of a temperature management system according to the present invention associated with an automatic transmission; and 
           [0021]      FIG. 2  is an enlarged, cross sectional view of a logic or spool valve showing the non-overlapping operation of the pistons. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0023]    With reference now to  FIG. 1 , a temperature management system which is illustrated in association with an automatic transmission is generally designated by the reference number  10 . The temperature management system  10  is utilized in conjunction with an automatic transmission  12  which, in turn, is utilized in conjunction with a prime mover  14  such as an internal combustion gas, Diesel or flex fuel engine or other power plant, e.g., hybrid. 
         [0024]    The temperature management system  10  includes a hydraulic supply line  18  which receives a flow of hydraulic fluid (transmission oil) under pressure from the automatic transmission  12  and provides it to an inlet port  20 A of a first, three way, two position diverter spool valve  20 . The three way spool valve  20  includes a spool  22  having spaced apart lands or pistons  22 A and  22 B which translate within a circular bore  24  defined by a cylindrical housing  26 . The spool  22  is connected to and translated by a plunger  28  of a solenoid assembly  30  which is disposed and translates within a solenoid coil  32 . When the solenoid coil  32  is energized, the plunger  28  and the spool  22  translate to the left, to the position illustrated in  FIG. 1 . When the solenoid coil  32  is de-energized, the plunger  28 , the spool  22  and the lands or pistons  22 A and  22 B translate to the right, to the positions illustrated in dashed lines in  FIG. 1 . 
         [0025]    Note that in the energized (left) position of the spool  22 , the land or piston  22 B fully closes off the port  20 C and in the right (de-energized) position of the spool  22 , the land or piston  22 A fully closes off the port  20 B. A compression spring  34  is disposed between the end of the spool  22  opposite the solenoid assembly  30  and an end of the cylindrical housing  26  and biases the spool  22  and the plunger  28  to the right in  FIG. 1 . 
         [0026]    The cylindrical housing  26  also defines a first outlet port  20 B and a second outlet port  20 C as well as two exhaust or vent ports  20 D and  20 E. When the solenoid coil  32  is energized oil or fluid flows from the inlet port  20 A out through the first outlet port  20 B. The first outlet port  20 B communicates through a first oil or fluid line  36  to an oil inlet  38  of a first heat exchanger  40 . The first heat exchanger  40  includes a first plurality of tubes or passageways (not illustrated) that communicate between the oil inlet  38  and an oil outlet  42 . The oil outlet  42  of the first heat exchanger  40  communicates through a fluid return line  44  with the automatic transmission  12 . 
         [0027]    The first heat exchanger  40  also includes a second plurality of tubes or passageways (also not illustrated) which are interleaved and in thermal communication with, but provide flow isolated from, the first tubes or passageways. A coolant inlet  46  communicates through the second plurality of tubes or passageways with a coolant outlet  48 . The coolant inlet  46  and the coolant outlet  48  are connected by a coolant supply line  52  and a coolant return line  54 , respectively, to appropriate coolant passageways in the prime mover  14 . 
         [0028]    When the solenoid coil  32  in de-energized, a flow path from the inlet port  20 A to the second outlet port  20 C is established and a second oil or fluid line  56  to an inlet port  60 A of second, three way diverter or bypass valve assembly  60 . The second diverter valve assembly  60  includes a housing  62  which defines the inlet port  60 A as well as a first outlet port  60 B and a second outlet port  60 C. The second, bypass valve assembly  60  also includes a wax motor  64  that preferably senses the temperature of the transmission fluid or oil in the second fluid line  56  by, for example, exposing the housing of the wax motor  64  to flow in the second fluid line  56  or a similar method of heat transfer. The wax motor  64  drives a linearly translating valve member  66  that directs transmission fluid or oil flow through the second outlet port  60 C to a bypass or return line  44 A which may be an extension of the return line  44  when the transmission fluid is relatively cool. As the temperature rises in the second fluid line  56 , wax in the wax motor  64  heats, translates and repositions the valve member  66  to close off the second outlet port  60 C and the bypass or return line  44 A and open the first outlet port  60 B and an extension of the second fluid line  56 , designated  56 A. The extension of the second fluid line  56 A communicates with an oil inlet  68  of a second heat exchanger  70 . The second heat exchanger  70  includes a first plurality of tubes or passageways (not illustrated) that communicate between the oil inlet  68  and an oil outlet  72 . The oil outlet  72  of the second heat exchanger  70  communicates through the fluid return line  44  with the automatic transmission  12 . 
         [0029]    The second heat exchanger  70  also includes a second plurality of tubes or passageways (also not illustrated) which are interleaved and in thermal communication with, but flow isolated from, the first tubes or passageways. An air inlet  76  communicates through the second plurality of tubes or passageways with an air outlet  78 . Thus, when the wax motor  64  repositions the valve member  66  to direct transmission fluid flow through the extension of the second fluid or oil line  56 , the second heat exchanger  70  transfers heat from the transmission fluid to the ambient air, thereby cooling the transmission fluid. 
         [0030]    A transmission control module or TCM  80  which is typically associated with and which controls the automatic transmission  12  is provided with data, e.g., internal temperature, from the transmission  12  and provides an electrical signal to the solenoid coil  32  when the temperature of the transmission  12  is below a predetermined threshold valve. Alternatively, such control may be provided and commanded by an engine control unit (ECU) or a body control unit (BCU). 
         [0031]    As an additional alternative, the second valve assembly  60  and specifically the wax motor  64  may be replaced with a second, electrically driven solenoid valve having the same configuration, namely, one inlet  60 A and two outlets  60 B and  60 C which is under the control of the transmission control module, the engine control unit or the body control unit  80 . 
         [0032]    As illustrated in  FIG. 2 , the first, two position spool valve  20  includes the spool  22  having axially spaced apart lands or pistons  22 A and  22 B which translate within the circular bore  24  defined by the cylindrical housing  26 . The axial spacing “A” between the adjacent (inner) faces of the lands or pistons  22 A and  22 B is greater than the adjacent edge distance “B” between the first outlet port  20 B and the second outlet port  20 C in the cylindrical housing  26 . As such, the lands or pistons  22 A and  22 B cannot close off both of the outlet ports  20 B and  20 C at the same time. Stated somewhat differently, at least one of the outlet ports  20 B or  20 C will always be at least partially open, thereby providing a fail-safe feature by ensuring that there will always be a flow of transmission fluid through the valve  20  and one of the heat exchangers  40  or  70 . This same axial distance relationship may, and preferably will be, utilized in the second diverter valve  60 . 
         [0033]    The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.