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Ratio control system for an automatic transmission in a vehicle
   
Document Number
US Patent 7320654
Issued Date
January 22, 2008
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Abstract
A procedure for the control of ratio-change occurrences of an automatic transmission in a motor vehicle, which vehicle possesses a hydraulic system with at least two hydraulic pressure branches (3, 9) with different hydraulic pressures, wherein in a first hydraulic pressure branch (3) controllable pressure reducing valves (4, 5) can be found, by which the hydraulic users (S1, S2) can be supplied with an activation pressure, wherein in the first hydraulic pressure branch (3), a pressure regulation valve (6) is placed, the exit port of which is connected to a line of the second hydraulic pressure branch (9), and wherein by the activation of the pressure regulation valve (6) the pressure in the first hydraulic circuit (3) is adjustable, and whereby in the first hydraulic pressure branch (3) a hydraulic pressure is provided, which represents the highest, necessary operational pressure of the hydraulic users (S1, S2, 11) plus an offset pressure. Further, provision is made that in certain operational conditions of the motor vehicle, one of the pressure reducing valves (4, 5) of, respectively, one of the two ratio-changing organs (S1, S2) remains fully open and the offset-pressure becomes reduced to the value of zero, or to nearly zero, and upon the removal of said certain operational condition the off-set pressure is once again increased and the pressure reducing valve (5) resumes its function of pressure reduction.
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Number of Claims:
9
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Owner
ZF Friedrichshafen AG (88038 Friedrichshafen,DE)
Published
January 22, 2008
Application Number
10/930,016
Filed
August 30, 2004
US Classification
474/28   474/18
Int'l Classification
F16H   59/00   (20060101)  
Examiner
Attorney/Law Firm
Priority Data
Sep 11, 2003 [DE] 103 41 917
USPTO Field of Search
474/18   474/28   477/44   477/45   477/46   477/47   477/48   477/49   477/50   701/51  
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