Interrelated power delivery controls – including engine control – Clutch control – Condition responsive control
Reexamination Certificate
1999-12-14
2001-09-04
Wright, Dirk (Department: 3681)
Interrelated power delivery controls, including engine control
Clutch control
Condition responsive control
C701S087000, C474S011000
Reexamination Certificate
active
06283893
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method of controlling the operation of a friction-based torque-transmitting system such as, in particular, a transmission or a continuously variable transmission in the drive train of a motor vehicle.
Systems for transmitting torque in the drive train of a motor vehicle by means of a frictional engagement, e.g., clutches (including lock-up clutches in the torque converters of automatic transmissions), continuously variable transmissions operating with endless flexible torque-transmitting devices, friction-drive mechanisms, as well as brakes, are increasingly being automated, i.e., operated under the control of appropriate actuators. The control or regulation of the torque to be transmitted through frictional engagement by the respective torque-transmitting system in each given case should be performed with the smallest amount of contact force possible in order to minimize the load on the actuators, to keep energy consumption small, and to achieve a high level of control/regulation accuracy. However, the amount of contact force should be sufficient to avoid a condition of permanent slippage that would rapidly wear out or destroy the friction-based torque-transmitting system. To avoid the risk of wear-out or destruction, an excess amount of contact pressure is used in most cases between elements transmitting torque through frictional engagement. Generally, an excess amount of contact pressure is also employed for the purpose of preventing unintended slippage due to wear of individual parts, settling effects, temperature effects or viscosity-based parameter changes.
One possibility to recognize a slippage condition between elements transmitting torque through frictional engagement is known from DE 195 44 061 A1. To recognize the limit between adhesion and slippage, a pressure-operated actuator element that controls the compressive contact force between the two elements transmitting torque through frictional engagement is supplied with an actuating pressure that includes a superimposed modulated signal. The signal variation is correlated, e.g., to the rate of rotation of an output shaft of the transmission. The limit between adhesion and slippage is determined as the point where the level of correlation falls below or rises above a predetermined value. The process of adding a modulated signal to the actuating pressure requires additional control elements and is relatively expensive.
OBJECT OF THE INVENTION
The object of the present invention is to provide a method of the kind discussed above as well as an apparatus for performing the method whereby the operating state of a friction-based torque-transmitting system can be controlled simply and cost-effectively without the need to apply unnecessarily large amounts of actuating force to the parts of the system that are in frictional engagement but, on the other hand, with the assurance that the system will not be damaged by sudden fluctuations of the torque.
SUMMARY OF THE INVENTION
To meet this objective, the invention provides a method of controlling the operation of a system that transmits torque through a frictional engagement in the drive train of a motor vehicle. A currently preferred embodiment of the inventive method has the following steps:
a) Certain operating parameters of the drive train are continuously monitored, in particular the respective rates of rotation of an input element and an output element of the friction-based torque-transmitting system.
b) A correlation is established and analyzed between the respective rates of rotation of the input element and an output element.
c) A change is effected in the operating state of the system if the correlation is found to have crossed a given threshold value.
For example, in an advantageous embodiment of the invention, the torque-transmitting capacity of the system is increased when the correlation is found to have fallen below a predetermined value.
In a particular embodiment of the inventive concept, following a decrease in correlation, the transmission ratio of a continuously variable transmission is rapidly changed in such a way that a preset level of correlation is restored between the respective rates of rotation of the input element and the output element.
As a further solution, the object of the invention is met by the following method of controlling a friction-based torque-transmitting system in the drive train of a motor vehicle:
a) Certain operating parameters that are predictors of an imminent peak torque load are continuously monitored.
b) A change is initiated in the operating state of the system if the monitored operating parameters are found to predict an imminent peak torque load.
By registering and recognizing imminent peak torque loads at the onset, it is possible to control friction-based torque-transmitting systems so that operating conditions that could cause damage to the systems themselves or to other components are avoided or that even in case of a peak torque load, the state of adhesive friction between the frictionally engaged components of the system does not change to sliding friction.
In an advantageous application of the immediately preceding concept, a change of the rate of rotation of at least one driven wheel of the motor vehicle is measured and if it is found to exceed a predetermined value, a change is initiated in the operating state of the friction-based torque-transmitting system.
Instead of measuring the rate of rotation of at least one driven wheel, it is also possible to measure the difference between the respective rates of rotation of the at least one driven wheel and a further wheel of the motor vehicle and to initiate a change in the operating state of the friction-based torque-transmitting system if the difference exceeds a given threshold value.
In another advantageous embodiment of the inventive method, a change in the operating state of the torque-transmitting system is initiated upon activation of stabilizing systems that are provided for the purpose of stabilizing a driving behavior of the motor vehicle. In a variation of the same concept, certain threshold values occurring in algorithms used to activate the stabilizing systems are lowered, and the change in the operating state of the friction-based torque-transmitting system is initiated when the lowered threshold values are exceeded.
The generically named torque-transmitting system in any of the aforementioned embodiments of the inventive method can be a friction clutch. In this case, the change in the operating state comprises an increase or decrease of the torque-transmitting capacity of the friction clutch.
Further, in any of the aforementioned embodiments of the inventive method., the torque-transmitting system can be a continuously variable transmission, in which case the change in the operating state can comprise an increase or decrease of the torque-transmitting capacity of the continuously variable transmission.
Likewise, in the immediately preceding case where the torque-transmitting system is a continuously variable transmission, the change in the operating state could also comprise an increase or decrease of the transmission ratio of the continuously variable transmission.
Sudden changes in magnitude of the engine torque can cause a motor vehicle to jolt or shake and thereby cause discomfort to the occupants of the vehicle. Aimed in particular at preventing this undesirable jolting or shaking of the vehicle is an embodiment of the inventive method wherein at least one control parameter governing engine torque is monitored and, after a change of the control parameter has been found, a change of the transmission ratio of a continuously variable transmission is initiated. As an example of this concept, it can be advantageous to change the continuously variable transmission towards an underdrive condition when the torque is increased.
Finally, the scope of the present invention also covers any kind of apparatus functioning in accordance with any of the embodiments of the method described above.
The novel featu
Bitzer Franz
Fritzner Anton
Darby & Darby
LuK Getriebe-Systeme GmbH
Wright Dirk
LandOfFree
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