Method for determining characteristics of an automatic transmission
AssigneeZF Friedrichshafen AG
InventorsThilo Schmidt, Valentine Herbeth, Klaus Steinhauser, Jorg Arnold
Life of this patent
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Abstract
A method of determining a fill current value of at least one frictionally engaging shift element of an automatic transmission. The automatic transmission includes a hydrodynamic converter at which a speed ratio arises and an output shaft. In a control sequence, with a stationary output shaft, the speed ratio is influenced by changing a control current, and the fill current value is determined from the progression of the speed ratio arising during the control sequence, in conjunction with the progression of the control current.
Claims12
A method for determining characteristic values (i_EDS_F) of frictionally engaging shift elements (E) of an automatic transmission (1), the automatic transmission comprising at least one frictionally engaging shift element (E), an output shaft (14), a hydrodynamic drive element (4) which comprises a pump impeller (5) that is connected, in a rotationally fixed manner, to a drive motor (2) and a turbine runner (6) that is connectable, either in a rotationally fixed manner or subject to slip, to an output shaft (14) by at least one frictionally engaging shift element (E), the pump impeller (5), rotating at an engine speed (n_M), and the turbine rotor (6), rotating at a turbine speed (n_T), being operatively connected hydrodynamically, and a quotient of the turbine speed (n_T) and the engine speed (n_M) forming a changeable speed ratio (n), a transfer capability of the at least one frictionally engaging shift element (E) being changeable by an electrical control current (i_EDS) via control of a gearshift device (18), a fill current value (i_EDS_F) existing for each of the at least one frictionally engaging shift element (E) at which the at least one frictionally engaging shift element starting from a disengaged state either transitions or returns into a state of torque transfer subject to slip, the method comprising the steps of:
- linearly adjusting, with a ramp shaped progression, the control current (i_EDS) of a respective one of the at least one frictionally engaging shift element (E) in a control sequence to influence the speed ratio (n), ramp shaped progression having a constant gradient from a control current value of zero to another control current value at which the at least one frictionally engaging shift element (E) is either fully engaged or fully disengaged, with the output shaft (14) being stationary, and
- determining the fill current value (i_EDS_F) of the respective one of the at least one frictionally engaging shift element (E) from a linear progression of the speed ratio (n), resulting during the control sequence, in conjunction with the ramp shaped progression of the control current (i_EDS).
Dependencies are inferred from the claim text.