Interrelated power delivery controls – including engine control – Transmission control – Continuously variable friction transmission
Patent
1994-04-21
1996-06-18
Ta, Khoi Q.
Interrelated power delivery controls, including engine control
Transmission control
Continuously variable friction transmission
477 47, 477 48, F16H 6100, B60K 4126
Patent
active
055272312
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to a method according for controlling a continuously variable transmission of a motor vehicle.
The usual automatic transmission controls with internal combustion engines generally respond to retraction of the gas pedal by reducing the transmission ratio. However, when driving on curves or when braking, this is not always desirable since such load changes can in some circumstances lead to unsafe driving conditions or, when the vehicle accelerates again by increased gas, the transmission ratio must be forcibly increased.
In this connection and in connection with automatically shifting multi-step transmissions, the German Patent document DE-33 41 652 C2 has disclosed that this reduction of the transmission ratio (upshiding) in curves can be avoided by sensing the transverse acceleration of the motor vehicle. However, this procedure can only avoid shifting in curves.
In order to be able specifically to prevent a reduction of the transmission ratio already when approaching a curve, the DE- 39 22 040 A1 corresponding to U.S. Pat. No. 5,025,689, discloses a method for controlling an automatically shifting transmission, according to which the rate of change of the gas pedal is sensed and, if this rate falls below the specified (negative) limit, a signal is generated to prevent upshifting, inasmuch as push-type operation is detected. Upshifting is then prevented, until pull-type operation resumes and a fixed amount of time has passed.
The German Patent document DE- 39 22 051 A1 corresonding to U.S. Pat. No. 5,157,609, additionally provides that this period of time be made dependent on another parameter (driving activity), from a combination of several operating or driving parameters, and which evaluates the driving style of a driver or the currently prevailing traffic situation.
Starting from this prior art, it is an object of the invention to create a method for controlling a continuously variable motor-vehicle transmission, preferably electro-hydraulically operated, which is further improved in particular as regards its behavior in adjusting its transmission ratio or the engine rpm during braking.
According to the invention, this object is achieved by a method for controlling a continuously variable transmission (2) , which is activated electro-hydraulically, of a motor vehicle driven with an internal combustion engine (4), which can be controlled by a power-control element, including one of a gas pedal and a throttle valve, such that the transmission ration (ue) of the transmission (2) is automatically adjusted through the intermediacy of at least one characteristic control curve (RKL.sub.j) in dependence on the position of the power control element (alpha (t)) and the engine rpm (nmot (t)), the method comprising the step of:
controlling the continuously variable transmission by increasing the transmission ratio (ue) at a fifth specific, finite, and slow rate (fifth time derivative of the transmission ratio cg5=due/dt=f(SK(t)), if
a) at least one of 1) a service brake of the motor vehicle is activated (brake signal b=1 and 2) the time derivative of the driving speed (dv(t)/dr) is less than a first negative longitudinal-acceleration limit value (albg (ue, nmot, t), albg(ue, nmot, t)<0 (dv(t)/dt<albg(ue, nmot, t)); and
b) a transverse acceleration (aq(t)), sensed by means of a transverse-acceleration sensor (16), falls below a first specific transverse-acceleration limit curve (aqgl(v(t))) (aq(t)<aqgl(v(t))); and
c) the time derivative of the driving speed (dv(t)/dt) is greater than a second negative longitudinal-acceleration limit value (albbg(nmot, ue, SK(t), t)=k(ue, SK(t)) * albg(ue, nmot, t)<0, (dv(t)/dr>dt albbg(nmott, ue, SK(t)=k(ue, SK(t)) * albg(ue, nmot, t)); and
d) the driving speed (v(t)) is less than a driving-speed limit value (vg(ue, SK(t))), (v(t)<vg(ue, SK(t))).
The advantages of the invention primarily are to be regarded as the circumstance that a method has been created to control a continuously variable motor-vehic
REFERENCES:
patent: 4590561 (1986-05-01), Abo et al.
patent: 4679145 (1987-07-01), Beeck et al.
patent: 4823267 (1989-04-01), Kumura
patent: 5166877 (1992-11-01), Ishikawa et al.
patent: 5319999 (1994-06-01), Morishige et al.
patent: 5390117 (1995-02-01), Graf et al.
Petersmann Joseph
Seidel Willi
Dr. Ing. h.c.F. Porsche AG
Ta Khoi Q.
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