Abstract:
A pressurized fluid supply system for a vehicle transmission is provided. The fluid supply system has a pump with at least high and low pressure outputs that supplies high and low pressure components via a directional valve. The pressurized fluid supply system minimizes the parasitic loss upon a vehicle engine.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to pressurized hydraulic fluid supply system for automatic transmissions. 
       BACKGROUND OF THE INVENTION 
       [0002]    Automatic transmissions for vehicles require a source of pressurized fluid. The source of pressurized fluid is typically a hydraulic pump powered by the vehicle engine. The pump is parasitic load on the vehicle engine. In a quest to improve vehicle mileage, it is desirable to minimize the parasitic load provided by the hydraulic pump of the transmission. 
       SUMMARY OF THE INVENTION 
       [0003]    To make manifest the above noted and other desires, a revelation of the present invention is brought forth. In a preferred embodiment, the present invention provides freedom of a hydraulic system for an automatic transmission having a pump with both low and high pressure outlets. One of the pressure outlets is connected with a directional valve having a first position delivering pressurized fluid from an outlet range matched pressurized fluid consuming components, a second position delivering pressurized fluid to non-range matched pressurized fluid components, and a third position delivering non-pressurized fluid to an inlet of the pump. 
         [0004]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0006]      FIG. 1  is schematic view of a pressurized fluid system for an automotive vehicle transmission according to the present invention; 
           [0007]      FIG. 2  is a schematic view of an alternate embodiment pressurized fluid supply system to that shown in  FIG. 1 ; 
           [0008]      FIG. 3  is a schematic view of a pump utilized in the pressurized fluid system of the present invention; and 
           [0009]      FIG. 4  is a schematic view of yet another embodiment of a pump utilized as a pressurized fluid source for a pressurized fluid system according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0010]    The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
         [0011]    Referring to  FIG. 1 , a multiple pressure hydraulic supply system for an automotive transmission is provided. The system  7  has a pressurized fluid source provided by a balanced vane pump  10 . Pump  10  has a high pressure outlet  12  and a low pressure outlet  14 . The inlet  16  of the pump  10  is connected with a sump  18  via a filter  20 . Inlet  16  is connected with a lower branch  22  and an upper branch  24  of the pump  10 . 
         [0012]    Outlet  12  is connected with a line  26 . The high pressure line  26  connects the high pressure outlet  12  with high pressure hydraulic fluid consuming components  30  which are various clutches, and gear actuators of the transmission. 
         [0013]    Pump low pressure outlet  14  and filter  34  is connected with a directional valve  36 , which is shown as a direct control, electrically actuated valve. Alternatively this can be a two-stage directional valve as well. The directional valve  36  has a first position  35  connecting the directional valve via a line  41  with low pressure consuming function components  40  which includes cooling and lubrication for the clutch, gears, and bearings. In a third position  37  directional valve  36  connects the low pressure outlet with the pump inlet line  16  via line  42 . In a second position directional valve  36  is connected the outlet  14  with lines  44  and  26  which connects with high pressure components  30 . The high pressure line  26  is also connected with a pressure regulator valve  48 . 
         [0014]    The pressure regulator valve  48  is used to properly control the line pressure in high pressure line  26 , and bleed the surplus flow to low pressure lube/cooling  40  as well as dump the excessive flow back to the inlet  16  of the pump  10 . The pressure regulator valve  48  has one end under the feedback pressure while the other ends with a bias spring  63  and a pilot pressure  65 , which connects with a proportional pressure control solenoid valve (not shown). The pressure regulator valve  48  includes two supply ports  67  connecting with the high pressure line  26 . A port  69  connects with a low pressure cooler/lube line  53  and a port  71  connects with the pump inlet  16 . 
         [0015]    In  FIG. 1 , the pressure regulator valve  48  is shown in the closed, non-regulating position  52 , at such position the engine either is off or running at idle speeds when there is no excess flow. When the hydraulic pressure supplied from the pump  10  increases and the flow is excessive, the pressure regulator valve  48  moves to a second regulating position  56 , where part of the flow is bled off to the low pressure cooler/lube line  53 . When the engine speed further increases to mid or high operating speed, the pressure regulator valve  48  is moved to a third position  54 . At this point, the valve flow bleeds both to the low pressure lube/cooling line  40  and to the pump inlet  16  line. Under all above three operating conditions, the regulated high pressure fluid is provided to the high pressure actuation such as gear shifting or clutch actuation indicated as  30  in  FIG. 1   
         [0016]    In operation when the engine speed is low, but there is a need to maintain the adequate line pressure, the directional valve  36  switches to position  36  and main pressure regulator will be at any intermediate position between  52  and  56  depending on the line pressure requirement. Under such condition, flow from both sides of the pump will go to main line  26 . 
         [0017]    When the engine speed is above certain point, the vehicle is at cruise speed but neither requires the high line pressure for actuation or the high cooling/lubrication flow for clutches and gears, the high pressure side of the pump will be capable to provide enough flow through line  10  to maintain the adequate line pressure. Under such condition, the directional valve  36  will move to the middle position  37 , the flow from the low pressure side of the pump  14  re-circulates back to the pump inlet  16 , which consumes the minimum power. The main regulator  48  at this moment, depending on the required line pressure, can be at any intermediate position. 
         [0018]    When the vehicle is at high energy launch, it requires both the moderate high line pressure for actuation and high cooling/lubrication flow. Under such condition, because of the reasonably high engine speed, the flow from the high pressure side of the pump is capable to maintain adequate line pressure through line  10  and  26 . The main pressure regulator is at any intermediate position of  52 ,  56 , or  54  depending on the required line pressure. The directional valve  36  will be switched to position  35 , which routes the flow from low pressure side of the pump to line  41 , and connects directly to the clutch and gear lube line. 
         [0019]    Referring to  FIG. 2  an alternate preferred embodiment hydraulic supply system of the present invention is provided with items performing functions identical or similar to that of  FIG. 1 , being given identical reference numbers. Vane pump  10  has a high pressure outlet  12  connected with a directional valve  72  via a filter  70  and provided in a high pressure line  26 . In a first position  74  the directional-valve  72  connects the high pressure outlet  12  with an accumulator  86 , which connects with the high pressure hydraulically powered components  30  which include gear actuation, and clutch actuation of the transmission. When directional valve  72  is moved from its first position  74  connecting with the accumulator and high pressure components  30 , to a third position  76 , fluid from outlet  12  recirculates into the inlet  16  of the pump  10 . When directional valve  72  is moved to its second position  78  the outlet  12  is fluidly connected with low pressure line  88  to be delivered to cooling/lube line of bearing or gear  90 , and clutch  92  via a flow control valve  91 . 
         [0020]    In operation high pressure outlet  12  charges accumulator  86  when the directional valve is in position  74 . Once the accumulator  86  is fully charged, solenoid valve  72  is switched to position  76  or  72  depending upon operating needs. If a high actuation load is needed for high pressure components  30 , especially when engine speed is low, then components  30  can receive pressurized fluid from both the high pressure outlet  12  and the accumulator  86 , or both if needed. When there is no high flow needed for actuation of the components  30 , directional valve  72  can proceed to position  76 . In such operating mode, the cooling/lubrication flow requirements can be met fully by low pressure output portion  14  while the output portion  12  recirculates back to pump inlet. When high lube flow is required and no longer met by the pump output  14  alone during high energy launching, directional valve  72  will be switched to position  78  and flow from the outlet  12  and outlet  14  will both go to the cooling/lube circuit. 
         [0021]      FIG. 3  illustrates a binary gear pump  100  having a high pressure output  12 , a low pressure output  14 , suction inlets  119  and  121 . Pump  110  can be a substitute for vane pump  10  shown in  FIGS. 1 and 2 . In another alternative pump arrangement  210  is provided having a high pressure pump  211  driven by the engine  207  via pulley, direct shaft or via a shaft powered by the transmission which in turn powers the low pressure outlet pump  215  via a clutch  213 . When low pressure output is undesirable clutch  213  will open disconnecting low pressure pump  215 . 
         [0022]    The description of the invention is merely exemplary in nature and, thus, 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.