Method for determining a reference value of an actuating current

Patent metadata

Field	Value
Publication number	US-9927024-B2
Application number	US-201514934266-A
Country	US
Kind code	B2
Filing date	Nov 6, 2015
Priority date	Nov 11, 2014
Publication date	Mar 27, 2018
Grant date	Mar 27, 2018

Abstract

A method is described for determining a reference value of an actuating current that corresponds to a defined operating point of an electro-hydraulically actuated frictional shifting element of a continuously variable power-branched transmission, at which the shifting element transmission capacity is zero, and starting from which an increase of actuating force immediately increases the transmission capacity. The actuating current reference value of the shifting element, when closed with a further shifting element decoupled from the transmission output and when a transmission input rotational speed is higher than a defined threshold, is reduced until a rotational speed difference between the rotational speeds of the shifting element halves exceeds a predefined limit value such that, at the time when the limit value is exceeded, the reference value of the actuating current is the reference value of the actuating current that corresponds to the defined operating point of the shifting element.

First claim

The invention claimed is:

1. A method of determining a reference value (i 9 soll (T 6 ), i 9 soll (T 8 )) of an actuating current (i 9 ) of an electro-hydraulically actuated frictional shifting element ( 9 , 10 ) of a continuously variable power-branched transmission ( 3 ), the method comprising:
defining an operating point of the electro-hydraulically actuated shifting element, at which a transmission capacity of the electro-hydraulically actuated shifting element ( 9 , 10 ) is substantially equal to zero;
increasing an actuating force resulting in an immediate increase of the transmission capacity of the electro-hydraulically actuated shifting element, wherein a first shifting element half of the electro-hydraulically actuated shifting element is connected to a transmission input ( 6 ) and a second shifting element half of the electro-hydraulically actuated shifting element ( 9 , 10 ) is coupled to a transmission output ( 4 );
decoupling the second shifting element half from the transmission output; and
reducing the reference value (i 9 soll ) of the actuating current (i 9 ) of the shifting element ( 9 , 10 ) in a substantially closed operating condition, until a rotational speed difference (Δn), between rotational speeds of the first shifting element half of the electro-hydraulically actuated shifting element and the second shifting element half of the electro-hydraulically actuated shifting element, exceeds a first predefined limit value (Δngrenz 1 ),
such that the reference value (i 9 soll (T 6 )) of the actuating current (i 9 ), at a time-point (T 6 ) when the first predefined limit value (Δngrenz 1 ) is exceeded, is the reference value (i 9 soll (T 6 )) of the actuating current (i 9 ) that corresponds to the defined operating point of the shifting element ( 9 , 10 ) used to adapt a first curve (ipdown) used for subsequent actuation of the shifting element ( 9 , 10 ) during operation of the transmission ( 3 ).

2. The method according to claim 1 , further comprising setting a reference value of a hydraulic actuating pressure (p 9 ) of the shifting element ( 9 , 10 ), in an area of a valve device ( 39 ), as a function of the reference value (i 9 soll ) of the actuating current (i 9 ) and which is applied in an area of a piston chamber of the shifting element ( 9 , 10 ).

3. The method according to claim 2 , further comprising initially changing the shifting element ( 9 , 10 ) from an open operating condition, in which the piston chamber is substantially, completely drained, to the closed operating condition, by acting upon the reference value (i 9 soll ) of the actuating current (i 9 ) and, as a result, applying a pressure pulse in the area of the piston chamber at a defined pressure level of the actuating pressure and for a defined operating time.

4. The method according to claim 3 , further comprising before reaching the closed operating condition of the shifting element ( 9 , 10 ), in which the rotational speed difference (Δn), between rotational speeds of the first shifting element half of the electro-hydraulically actuated shifting element and the second shifting element half of the electro-hydraulically actuated shifting element, is substantially equal to zero,
reducing the reference value (i 9 soll ) of the actuating current (i 9 ) along a ramp from a first level (i 9 soll (T 1 )) of the pressure pulse in a direction toward a second level (i 9 soll (T 3 )) at which the shifting element ( 9 , 10 ) is still in the closed operating condition; and
reducing the reference value (i 9 soll ), of the actuating current (i 9 ), along a ramp until the rotational speed difference (Δn), between rotational speeds of the first shifting element half of the electro-hydraulically actuated shifting element and the second shifting element half of the electro-hydraulically actuated shifting element, exceeds the first predefined limit value (Δngrenz 1 ).

5. The method according to claim 1 , further comprising, from the time-point (T 6 ) at which the rotational speed difference (Δn), between rotational speeds of the first shifting element half of the electro-hydraulically actuated shifting element and the second shifting element half of the electro-hydraulically actuated shifting element, exceeds the first predefined limit value (Δngrenz 1 ),
setting the reference value (i 9 soll ) of the actuating current (i 9 ) for a predefined time period to a level at which the rotational speed difference (Δn), between rotational speeds of the first shifting element half of the electro-hydraulically actuated shifting element and the second shifting element half of the electro-hydraulically actuated shifting element, is larger than an additional limit value, which is larger than the first predefined limit value (Δngrenz 1 ).

6. The method according to claim 5 , further comprising, after lapse of the predefined time period,
increasing the reference value (i 9 soll ) of the actuating current (i 9 ) along a ramp until the rotational speed difference (Δn), between rotational speeds of the first shifting element half of the electro-hydraulically actuated shifting element and the second shifting element half of the electro-hydraulically actuated shifting element, falls below a second predefined limit value (Δngrenz 2 ) such that the reference value (i 9 soll (T 8 )) corresponds to the defined operating point of the shifting element ( 9 , 10 ) used to adapt a second curve (ipup) used for subsequent actuation of the shifting element ( 9 , 10 ) during operation of the transmission ( 3 ).

7. The method according to claim 1 , further comprising, after determining the reference value (i 9 soll (T 8 )) of the actuating current (i 9 ) that corresponds to the defined operating point of the shifting element ( 9 , 10 ), reducing the reference value (i 9 soll ) of the actuating current (i 9 ) to a level (i 9 soll (T 0 )) at which the shifting element ( 9 , 10 ) changes to a completely open operating condition.

8. The method according to claim 1 , further comprising determining the rotational speeds of the first shifting element half of the electro-hydraulically actuated shifting element and the second shifting element half of the electro-hydraulically actuated shifting element by measurement.

9. The method according to claim 6 , further comprising empirically determining the first and second predefined limit values (Δngrenz 1 , Δngrenz 2 ).

10. The method according to claim 6 , further comprising actuating the shifting element with reference to a relationship between reference values of the actuating current, reference values of actuating pressure and a characteristic diagram that shows an operating temperature of the transmission.

11. The method according to claim 10 , further comprising actuating the shifting element ( 9 , 10 ) with reference to the first and second curves (ipup, ipdown) that diagram a relationship between reference values (i 9 soll ) of the actuating current (i 9 ) and reference values of actuating pressure (p 9 ), which are determined empirically.

12. The method according to claim 11 , further comprising adapting either the characteristic diagram or the first and second curves (ipup, ipdown) as a function of a deviation between the reference value (i 9 soll ) of the actuating current (i 9 ) corresponding to the defined operating point of the shifting element ( 9 , 10 ), and the reference value (i 9 soll ) of the actuating current (i 9 ) obtainable for the defined operating point of the shifting element from either the characteristic diagram or the first and second curves.

Assignees

• Zahnradfabrik Friedrichshafen

Inventors

• Bieber Sven
• Kuhn Jan-Frederik
• Hiemer Marcus
• Schinacher Stephan
• Brugger Mario
• Lukassek Markus

Classifications

• F16H2702/06

  Combinations of transmissions with parallel force splitting paths having same output · CPC title

• F16H2061/062

  for controlling filling of clutches or brake servos, e.g. fill time, fill level or pressure during filling · CPC title

• F16H61/061 Primary

  using electric control means · CPC title

• F16H2059/465

  Detecting slip, e.g. clutch slip ratio · CPC title

• F16H2061/6609

  Control of clutches or brakes in torque split transmissions · CPC title