Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Reexamination Certificate
2001-04-18
2002-10-15
Nguyen, Tan (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
C701S062000, C477S098000, C477S065000
Reexamination Certificate
active
06466854
ABSTRACT:
The invention relates to a method for controlling a high-temperature operating mode of an electronically controlled automatic transmission.
Under certain operating conditions of the vehicle, high temperatures can be reached in the transmission. If specific temperatures limits are exceeded, parts can be damaged or undesired chemical changes of the transmission oil can take place. High temperatures appear when great amounts of hear are produced and/or only a small amount of heat is removed. Operating situations with low engine rotational speed in which liquid pumps in the cooling system are operated only at low rotational speeds so that the heat removal is limited are critical. High temperatures can also appear when a hydrodynamic converter, front-mounted on the transmission, is operated with open lock-up clutch. With an open lock-up clutch considerable, amounts of heat can be produced in the converter due to hydraulic losses. Unfavorable, in addition, is that the converter as a rule is operated with open lock-up clutch when low engine rotational speeds are present.
High temperatures can also occur on the friction surfaces of a lock-up clutch operating with a regulated slip.
Transmission controls are known in which a special temperature lowering high-temperature drive program is stored which is accessed at high temperatures of the transmission. Such a high-temperature drive program essentially modulates the heat economy of a transmission and is suited for lowering the temperature of the transmission. For a driver, it is, of course, clearly noticeable when such a high-temperature drive program is accessed: the lower gears are turned off extensively, a great consumption, the same as high noise and vibration load appear. The special high-temperature drive program comprises both a shift program for a gear change control and a converter shift program for controlling the lock-up clutch.
Due to the negative effects upon the driving operation it is desirable to access the special high-temperature drive program only when it is indispensably necessary. In EP 0 751 323 A2, it is, therefore, proposed to vary the limit temperature above which the special high-temperature shift program is accessed according to the temperature gradient. The value of the limit temperature is higher when the temperature increases only slowly. But if the limit temperature is exceeded, the driving comfort is noticeably reduced.
In DE 197 55 128 A1 it is proposed to reduce the engine torque when the transmission temperature exceeds a predetermined limited value. The consequence of this is, likewise, a very extensive limitation of the driving operation.
In addition DE 39 22 051 C2, for example, has disclosed a method for control of an automatic transmission in which in an electronic control unit for control of the gear changed several shift programs are stored which are accessed according to a driving activity characteristic. Depending on the value of the driving activity characteristic, a consumption-optimized shift program, or shift programs therebetween are accessed. However, this method cannot solve the problem of an inadmissible increase of the transmission or engine temperature.
The problem on which the invention is based is to provide a high-temperature operating mode for an electronically controlled automatic transmission in which the negative effects noticeable by the driver are reduced.
This problem is solved, according to the invention, with the features of the main claim. Sub-claims contain advantageous developments of the invention.
It is proposed, therefore, when an actual temperature value, e.g. a measured temperature of the transmission sump, is high that a first limit value, to provide an evaluation counter, which is normally provided with the driving activity characteristics, with a high-temperature operating value with which a shift program is associated in any case available which also has temperature-lowering properties
The invention is based on the knowledge that a formerly performance-optimized shift program which, because of a driver's sportive drive mode, is accessed normally, that is, below the first limit temperature, also has temperature-lowering properties.
The rotational speed level of a formerly performance-optimized shift program is increased so that the hear removal is favorable and also the hydrodynamic converter is predominantly operated with closed lock-up clutch.
The shift program, which is accessed, can be a concrete shift program. In many cases, it has been found that another temperature increase can be prevented by accessing such a more performance-optimized shift program, and the effects of this high-temperature operating mode noticeable by the driver are substantially less disadvantageous.
One other advantage of the invention is the use of an always available shift program whereby storing space in the electronic control unit is spared and application expenditure is reduced.
Nevertheless, in order to prevent overheating of the aggregate under extreme operating conditions, it is advantageous that a second, high temperature limited value be provided and that a special high-temperatures shift program be directly accessed for a gear charge control when the actual temperature is higher than the second limit value. This development of the invention makes available two steps of the high-temperature operating mode. The second, higher limit value is reached only very seldom here so that the uncomfortable to drive special high-temperature shift program only very rarely has to be activated.
In automatic transmissions, having a front-mounted hydrodynamic converter with a lock-up clutch, it can be advantageous that a special high-temperature converter shift program be accessed when the actual temperature value is higher than the first temperature limited value. Therefore, while after exceeding the first limit temperature for a gear change control, a shift program in any case available is accessed which is associated with a specific value of the driving activity characteristic, a first high-temperature converter shift program is accessed for controlling the lock-up clutch. Such a high-temperature converter shift program has, in comparison, with the converter shift program used normally, that is, below the first limit temperature, an enlarged range in which the lock-up clutch is closed. But it is also possible to access the converter shift program which is normally associated with the corresponding shift program for gear change control.
When a second high-temperature converter shift program is provided which is accessed when the actual temperature value is higher than the second limit value, the same as in the shift program for gear change control, it is, likewise, possible to react gradually to higher temperatures. In the first high-temperature converter shift program, there also can be admitted for the sake of better drive ability ranges with open or regulated slipping lock-up clutch when extreme conditions are covered by the second high-temperature converter shift program.
A simple exit from the function is possible when the actual temperature value is compared with a third limit value and the evaluation counter is again provided with the actual value of the driving activity characteristic of the actual temperature value is lower than the third limit value. The third limit value is below the first limit value. By means of this temperature hysteresis, a back and forth jumping between operating states is prevented.
The heat economy of the prime mover is also modulated by the transmission control. In many cases, the engine temperature can also be lowered by an increased rotational speed level. An advantageous development of the invention provides, therefore, that both an actual transmission temperature and an actual engine temperature are continuously measured. The engine temperature value is compared with a first engine temperature limit value and the transmission temperature value with a first transmission temperature limit value. The evaluation counter is then provided with a high-
Henneken Markus
Herbster Kai-Uwe
Jauch Friedemann
Mauz Thomas
Schuler Franz-Josef
Davis & Bujold P.L.L.C.
Nguyen Tan
Tran Dalena
ZF Friedrichshafen AG
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