Hydraulic circuit for oil supply of an automatic, particularly a stepped automatic transmission for motor vehicles

Abstract

The invention concerns a hydraulic circuit ( 3 ) for oil supply of an automatic transmission, in particular a stepped automatic transmission for motor vehicles, consisting of a low pressure circuit ( 4 ) for delivering a first volume stream V 1 at a first pressure level P 1 and a high pressure circuit ( 5 ) for delivering a second volume stream V 2 at a second, higher pressure P 2. It is proposed that when necessary the first pressure level P 1 of the first volume stream V 1 can be modulated to the higher pressure P 2 and the two volume streams V 1, V 2 can be summed at the same pressure level P 2.

1 . Hydraulic circuit ( 3 ,  12 ) for oil supply of an automatic transmission, in particular a stepped automatic transmission for motor vehicles, consisting of a low-pressure circuit ( 4 ) for delivering a first volume stream V 1  at a first pressure level P 1  and a high pressure circuit ( 5 ) for delivering a second volume stream V 2  at a second higher pressure P 2 , such that the first pressure level P 1  of the first volume stream V 1  can, when necessary, be modulated to the higher pressure level P 2  and the two volume streams V 1  and V 2  can be summed at the same pressure level P 2 .  
   
   
       2 . Hydraulic circuit according to  claim 1 , characterized in that the summing of the volume streams V 1 , V 2  takes place when a gearshift is initiated in the stepped automatic transmission.  
   
   
       3 . Hydraulic circuit according to claims  1  or  2 , characterized in that a pressure-relief valve ( 8 ) is associated with the high pressure circuit ( 5 ) to maintain the pressure level P 2 .  
   
   
       4 . Hydraulic circuit according to claims  1 ,  2  or  3 , characterized in that a pressure-relief valve ( 9 ) is associated with the low pressure circuit ( 4 ) to maintain the pressure level P 1 .  
   
   
       5 . Hydraulic circuit according to  claim 4 , characterized in that the pressure-relief valve ( 9 ) can be adjusted by a pressure regulator to change the pressure level P 1 , in particular to increase it to the pressure level P 2 .  
   
   
       6 . Hydraulic circuit according to any of  claims 1  to  5 , characterized in that a first delivery element ( 6 ) is associated with the low pressure circuit ( 4 ) to deliver the first volume stream V 1  and a second delivery element ( 7 ) is associated with the high pressure circuit to deliver the second volume stream V 2 .  
   
   
       7 . Hydraulic circuit ( 3 ) according to any of  claims 1  to  6 , characterized in that a one-way valve ( 11 ) opening towards the high pressure circuit ( 5 ) is arranged between the high pressure circuit ( 5 ) and the low pressure circuit ( 4 ).  
   
   
       8 . Hydraulic circuit ( 12 ) according to any of  claims 1  to  6 , characterized in that the two volume streams V 1 , V 2  can be summed by means of a switching variable-path valve ( 14 ).  
   
   
       9 . Hydraulic circuit ( 12 ) according to  claim 8 , characterized in that the variable-path valve ( 14 ) has two positions ( 14   a,    14   b ), namely a first position ( 14   a ) in which the two volume streams V 1 , V 2  are separated and a second position ( 14   b ) in which the two volume streams V 1 , V 2  are combined.  
   
   
       10 . Hydraulic circuit according to  claim 6 , characterized in that the two delivery elements ( 6 ,  7 ) form a tandem pump.  
   
   
       11 . Hydraulic circuit according to  claim 6 , characterized in that the first delivery element ( 6 ) is formed as an electrically driven pump and the second delivery element ( 7 ) is formed as a mechanically driven pump, in particular driven by the pump impeller of the stepped automatic transmission.  
   
   
       12 . Hydraulic circuit according to  claim 6 , characterized in that the two delivery elements ( 6 ,  7 ) are formed as a dual-circuit pump.  
   
   
       13 . Hydraulic circuit according to claims  6 ,  10  or  12 , characterized in that the delivery elements ( 6 ,  7 ) are formed as gear-type, radial piston or vane cell pumps.