Abstract:
An active fluid reservoir for transmission fluid of an automatic transmission, in a first embodiment, comprehends an elongate reservoir disposed adjacent and parallel to fluid lines leading from the automatic transmission to the transmission oil (fluid) cooler (TOC). Depending upon available space, the reservoir may be associated with either the supply or return line or two smaller reservoirs associated with both lines. Thermally actuated valves at each end of the reservoir(s) open to allow fluid flow through the reservoir as fluid temperature increases and a diverter valve in the cooler line(s) closes to divert flow into the reservoir. In a second embodiment, the fluid reservoir comprehends a container, tank or similar storage device in fluid communication with a transmission oil cooler (TOC) line. Again, the device includes thermally actuated valves which open to provide fluid flow from the oil cooler line to the reservoir and a diverter valve in the oil cooler line which closes upon a temperature increase to divert flow to the reservoir.

Description:
FIELD 
       [0001]    The present disclosure relates to automatic transmissions and more particularly to fluid expansion reservoirs for automatic transmissions. 
       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]    Motor vehicle automatic transmissions must and do provide both reliable torque multiplication and torque and speed matching over a wide range of both ambient and operating temperatures. The operating temperature of an automatic transmission may be considered to range from cold, i.e., a winter morning start, through warm, i.e., normal operation, to hot, i.e., maximum operating temperature. The fluid within a transmission, commonly referred to as “automatic transmission fluid” or ATF, contracts when it is cold and expands when it is hot. Thus, the noted temperature limits correspond to the minimum and maximum volumes of transmission fluid for a given mass of transmission fluid. 
         [0004]    The minimum design or start up temperature dictates the minimum mass of transmission fluid required in the transmission. Under this operating condition, the transmission fluid is most dense which reduces the volume of transmission fluid within the transmission sump and transmission and the viscosity of the fluid is at a maximum thereby further reducing sump and transmission fluid volume due to fluid coating or adhering to transmission components and surfaces. 
         [0005]    The maximum design or operating temperature dictates the maximum transmission sump fluid volume which maintains a fluid level below the rotating components of the transmission. If the transmission fluid contacts the rotating components, the fluid will become foamy with entrained air which increases frictional drag and adds heat to the transmission fluid. Eventually, the entrained air will interfere with the action of the transmission pump, transmission fluid pressure will drop, forcing a transmission shutdown and possibly causing damage to the transmission. 
         [0006]    It is therefore apparent that the automatic transmission and transmission fluid cooling system must accommodate the cold and, more significantly, the hot volume of transmission fluid, while maintaining intended and desired vehicle performance. This requirement, in addition to the requirements of various vehicle ride heights, suspension components and various engine configurations have proliferated the number of transmission oil (ATF) pans and filter/pump pickups for the same model of automatic transmission. 
         [0007]    The present invention is directed to an apparatus for accommodating the volume change of transmission fluid from cold to hot while maintaining proper transmission sump and operating levels. 
       SUMMARY 
       [0008]    The present invention provides an active fluid reservoir for the transmission fluid of an automatic transmission. In a first embodiment, the fluid reservoir comprehends an elongate reservoir disposed adjacent and parallel to fluid lines leading from the automatic transmission to the transmission oil (fluid) cooler (TOO). Depending upon available space, the reservoir may be a single, larger reservoir associated with either the supply or return line or two smaller reservoirs associated with both lines. Thermally actuated valves at each end of the reservoir(s) open to allow fluid flow through the reservoir as fluid temperature increases and a diverter valve in the cooler line(s) closes to divert flow into the reservoir. In a second embodiment, the fluid reservoir comprehends a container, tank or similar storage device in fluid communication with a transmission oil cooler (TOO) line. Again, the device includes thermally actuated valves which open to provide fluid flow from the oil cooler line to the reservoir and a diverter valve in the oil cooler line which closes upon a temperature increase to divert flow to the reservoir. In both embodiments, the reservoir must be located above the transmission sump to that the transmission fluid returns by gravity to the sump when the engine and transmission are not operating. 
         [0009]    It is thus an aspect of the present invention to provide an active transmission fluid reservoir for automatic transmissions. 
         [0010]    It is a further aspect of the present invention to provide a transmission fluid reservoir having a pair of thermally actuated flow valves and a thermally actuated diverter valve. 
         [0011]    It is a still further aspect of the present invention to provide a transmission fluid reservoir having at least one elongate reservoir disposed along a transmission oil cooler line. 
         [0012]    It is a still further aspect of the present invention to provide a transmission fluid reservoir having at least one elongate reservoir disposed along a transmission oil cooler line, a pair of flow controlling valves and a diverter valve. 
         [0013]    It is a still further aspect of the present invention to provide a transmission fluid reservoir having at least one elongate reservoir disposed along a transmission oil cooler line, a pair of thermally actuated flow controlling valves and a thermally actuated diverter valve. 
         [0014]    It is a still further aspect of the present invention to provide a transmission fluid reservoir having a pair of elongate reservoirs disposed along a respective pair of transmission oil cooler lines. 
         [0015]    It is a still further aspect of the present invention to provide a transmission fluid reservoir having a storage container. 
         [0016]    It is a still further aspect of the present invention to provide a transmission fluid reservoir having a storage container, a pair of flow controlling valves and a diverter valve. 
         [0017]    It is a still further aspect of the present invention to provide a transmission fluid reservoir having a storage container, a pair of thermally actuated flow controlling valves and a thermally actuated diverter valve. 
         [0018]    Further aspects, advantages 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 diagram of a portion of an exemplary motor vehicle powertrain having a radiator, an engine and a transmission and incorporating the present invention; 
           [0021]      FIG. 2  is a diagrammatic view of a first embodiment of a transmission fluid reservoir according to the present invention in a cold or low temperature operating state or condition; 
           [0022]      FIG. 3  is a diagrammatic view of a first embodiment of a transmission fluid reservoir according to the present invention in a hot or high temperature operating state or condition; 
           [0023]      FIG. 4  is a diagrammatic view of a second embodiment of a transmission fluid reservoir according to the present invention in a cold or low temperature operating state or condition; and 
           [0024]      FIG. 5  is a diagrammatic view of a second embodiment of a transmission fluid reservoir according to the present invention in a hot or high temperature operating state or condition; 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0026]    With reference to  FIG. 1 , a portion of a motor vehicle powertrain incorporating the present invention is illustrated and generally designated by the reference number  10 . The illustrated powertrain  10  includes a radiator  12  which is in fluid communication with an engine  14  which may be a gas, Diesel or flex fuel engine. The output of the engine  14  is coupled to the input of a transmission  16 . The transmission includes a fluid sump  18  into which transmission fluid flows under the influence of gravity and is collected. The transmission  16  also includes an output shaft  20  which drives a final drive assembly (FDA)  22  which may include, for example, a prop shaft, a differential, axles and tires and wheels (all not illustrated). 
         [0027]    The radiator  12  includes a transmission oil (fluid) cooler  24  disposed therewithin. The transmission oil cooler  24  is in fluid communication with the transmission  16  through a pair of fluid lines, pipes or hoses  26  and  28 , one of which ( 26 ) functions as a supply line of hotter fluid from the transmission  16  to the transmission oil cooler  24  in the radiator  12  and the other of which ( 28 ) functions as a return line of cooler fluid from the transmission oil cooler  24  to the transmission  16 . 
         [0028]    Disposed in one of the fluid lines, pipes or hoses, preferably the supply line  26 , is an active transmission fluid expansion reservoir assembly  30 . At the outset, it should be noted that the transmission fluid expansion reservoir assembly  30  must be disposed generally above the level of the sump  18  of the transmission  16  such that when the engine  14  and transmission  16  are not operating, fluid which has accumulated in the transmission fluid expansion reservoir assembly  30  will return to the sump  18  under the influence of gravity. 
         [0029]    Turning now to  FIGS. 2 and 3 , a first embodiment of an active transmission fluid expansion reservoir assembly  30  is illustrated in fluid communication with the transmission oil cooler supply line  26 . The transmission fluid expansion reservoir assembly  30  is an in-line, cylindrical assembly and typically occupies an axial distance of several inches along the length of and parallel to the cooler supply line  26 . If packaging and space limitations do not permit such a configuration, multiple, smaller reservoir assemblies may be utilized, for example, one on each of the supply and return lines  26  and  28 . 
         [0030]    Disposed within the cooler supply line  26  is a first or diverter valve  32  which is capable of substantially fully opening and fully closing the flow path through the cooler supply line  26 . The first or diverter valve  32  preferably comprehends a circular disc  34  or similar valve structure such as a ball valve that is opened and closed through 90 degrees of rotation. Other valve configurations such as a sliding valve, a poppet valve or an iris valve—the common feature of such valves being their full opening and closing with relatively limited input motion—may also be utilized here and at the other valve locations. The circular disc  34  is secured to a shaft or rod  36  that is supported by the wall of the cooler supply line  26  or other suitable structure and is coupled to a bi-metallic operator  38 . As the temperature of the transmission oil in the cooler supply line  26  increases, the bi-metallic operator  38  rotates the circular disc  34  from the position illustrated in  FIG. 2  which allows unrestricted fluid flow of transmission oil through the cooler supply line  26  to the position illustrated in  FIG. 3  which closes off the cooler supply line  26  and inhibits flow therethrough. Alternatively, the bi-metallic operator  38  may be replaced by an operator utilizing the thermal expansion of a fluid. Additionally, it should be appreciated that the circular disc  34  (or other valve configuration) may be coupled to and rotated by an electric, hydraulic or pneumatic actuator controlled by a signal from a temperature sensor such as a thermistor located, for example within the transmission  16 . 
         [0031]    The in-line transmission fluid expansion reservoir assembly  30  also includes a reservoir  40  that preferably extends axially along one side of the cooler supply line  26 . Alternatively, the reservoir  40  may be concentrically disposed about the cooler supply line  26  as indicated by the dashed reference line  42 . At the upstream end of the reservoir  40 , between the cooler supply line  26  and the reservoir  40 , is disposed a second or inlet valve  44 . The second or inlet valve  44  may be of construction similar to that of the first or diverter valve  32 . Thus, it may include a circular disc  46  that is attached to a shaft  48  that is rotated by a bi-metal operator  52 . At the downstream end of the reservoir  40 , between the cooler supply line  26  and the reservoir  40 , is disposed a third or outlet valve  54 . The third or outlet valve  54  may also be of construction similar to that of the first or diverter valve  32 . Thus it may include a circular disc  56  that is attached to a shaft  58  that is rotated by a bi-metal operator  62 . 
         [0032]    The second or inlet valve  44  and the third or outlet valve  54  operate in unison but in opposition to the first or diverter valve  32 . That is, as the temperature of the transmission fluid increases, the bi-metallic operators  52  and  62  rotate the second or inlet valve  44  and the third or outlet valve  54 , respectively, from the closed positions illustrated in  FIG. 2  to the open positions illustrated in  FIG. 3 . Thus, as the second or inlet valve  44  and the third or outlet valve  54  open, the first or diverter valve  32  closes. Once again, it should be appreciated that all three valves  32 ,  44  and  54  may be controlled by one or more electric, hydraulic or pneumatic operators controlled by a signal from temperature sensor located, for example, within the transmission  16 . 
         [0033]    Accordingly, during operation of the engine  14  and the transmission  16 , as the temperature of the transmission fluid increases, the diverter valve  32  closes and the inlet valve  44  and the outlet valve  54  open, providing the additional volume of the reservoir  40  to the fluid circuit which accommodates the temperature related expansion of the transmission fluid. When the engine  14  is shut off and the transmission fluid and the transmission  16  cool down, the diverter valve  32  re-opens and the inlet valve  44  and the outlet valve  54  close. As this is occurring, the transmission fluid is also contracting and, before the outlet valve  54  fully closes, the transmission fluid which has accumulated in the reservoir  40  flows into the sump  18  of the transmission  16  under the influence of gravity. 
         [0034]    Referring now to  FIGS. 4 and 5 , a second embodiment of an active transmission fluid expansion reservoir assembly  70  employing a container or tank as the fluid reservoir is illustrated in conjunction with the transmission oil cooler supply line  26 . The transmission fluid expansion reservoir assembly  70  includes a container or tank  72  which may be located at any convenient location above the level of the sump  18  of the transmission  16  and mounted to any convenient under-hood component such as the radiator  12 , the engine  14  or the transmission  16 . The container or tank  72  includes an inlet line or tube  74  in fluid communication with the transmission oil cooler supply line  26  and an outlet line or tube  76  also in fluid communication with the transmission oil cooler supply line  26 . 
         [0035]    Disposed within the transmission oil cooler supply line  26  is a first or diverter valve  82  which is capable of substantially fully opening and fully closing the flow path through the cooler supply line  26 . The first or diverter valve  82  preferably comprehends a circular disc  84  or similar valve structure that is opened and closed through 90 degrees of rotation. The circular disc  84  is secured to a shaft or rod  86  that is supported by the wall of the cooler supply line  26  or other suitable structure and is coupled to a bi-metallic operator  88 . As the temperature of the transmission oil in the cooler supply line  26  increases, the bi-metallic operator  88  rotates the circular disc  84  from the open position illustrated in  FIG. 4  which allows unrestricted fluid flow of transmission oil through the cooler supply line  26  to the closed position illustrated in  FIG. 5  which closes off the cooler supply line  26  and inhibits flow therethrough. Again, it should be appreciated that the circular disc  84  may be coupled to and rotated by an electric, hydraulic or pneumatic actuator controlled by a signal from a temperature sensor located, for example, within the transmission  16 . 
         [0036]    At the juncture of the inlet line or tube  74  and the transmission oil cooler supply line  26 , the tank type transmission fluid expansion reservoir assembly  70  includes a second or inlet valve  92 . The second or inlet valve  92  may be of construction similar to that of the first or diverter valve  82 . Thus it may include a circular disc  94  that is attached to a shaft  96  that is rotated by a bi-metal operator  98 . At the juncture of the outlet line or tube  76  and the cooler supply line  26 , is a third or outlet valve  102 . The third or outlet valve  102  may also be of construction similar to that of the first or diverter valve  82 . Thus it may include a circular disc  104  that is attached to a shaft  106  that is rotated by a bi-metal operator  108 . 
         [0037]    The second or inlet valve  92  and the third or outlet valve  102  operate in unison but in opposition to the first or diverter vale  82 . That is, as the temperature of the transmission fluid increases, the bi-metallic operators  88  and  108  respectively rotate the second or inlet valve  92  and the third or outlet valve  102  from the closed positions illustrated in  FIG. 4  to the open positions illustrated in  FIG. 5 . Thus, as the second or inlet valve  92  and the third or outlet valve  102  open, the first or diverter valve  82  closes. Once again, it should be appreciated that all three valves  82 ,  92  and  102  may be controlled by one or more electric, hydraulic or pneumatic operators controlled by a signal from temperature sensor located, for example within the transmission  16 . 
         [0038]    Accordingly, during operation of the engine  14  and the transmission  16 , as the temperature of the transmission fluid increases, the diverter valve  82  closes and the inlet valve  92  and the outlet valve  102  open, providing the additional volume of the container or tank  72  to the hydraulic circuit which accommodates the temperature related expansion of the transmission fluid. When the engine  14  is shut off and the transmission fluid and the transmission  16  cool down, the diverter valve  82  re-opens and the inlet valve  92  and the outlet valve  102  close. As this is occurring, the transmission fluid is also contracting and, before the outlet valve  102  fully closes, the transmission fluid which has accumulated in the container or tank  72  flows into the sump  18  of the transmission  16  under the influence of gravity. 
         [0039]    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.