Machine element or mechanism – Gearing – With fluid drive
Patent
1991-12-19
1994-09-06
Braun, Leslie A.
Machine element or mechanism
Gearing
With fluid drive
192 4A, 475 81, F16H 4704, F16H 6112
Patent
active
053437799
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a continuously variable driving unit for motor vehicles having the characteristics stated in the preamble of claim 1.
German Patent 35 12 523 has disclosed a continuously variable power-distribution combined powershift transmission with group gear changes. The transmission consists of two parts. One is a continuously variable power-distribution coupling transmission with several shafts. The other part is a selector transmission having a gear group and several group gears which act upon the main output shaft. Both coupling shafts alternatively drive the selector transmission. The gear selections take place at synchronization speeds free of load and without interrupting the tractive force. The transmission acts like a continuous transmission with large adjusting range and allows operation of the internal combustion machine in a vehicle along the curve for minimal consumption of fuel, thus making it possible to save fuel.
The continuously variable, power-distribution coupling transmission contains displacement machines which form a hydrostatic transmission. If the whole reduction ratio of the transmission is to be widened, either the hydrostatic transmission has to be enlarged or the number of gears in the selector transmission has to be increased. The first step leads to greater hydrostatic power flow and thus to poorer efficiency and more weight and required space due to the larger displacement machines. A fine graduation of the selector transmission due to the increased number of gears results in an accordingly higher number of clutches. The clutches can be, for instance, power shiftable, positive multi-disc clutches.
During a change of gear, the transmission output shaft is connected with another coupling shaft. Said change of gear takes place at a synchronous speed of the participating coupling shafts. The coupling shafts are connected via the multi-disc clutches with the output shaft of the transmission, an overlap in the clutch actuation appears during the change of gear in which a rigid reduction ratio exists between hydrostatic and mechanical transmission branches.
Relative speeds appear between the discs of power-transmitting clutches neither during regular operation within a selector range nor during a regular development of the change of gear. Even though a synchronous speed does not always very precisely exist during the change of gear, the speed differences between the clutches are so slight that almost no friction occurs when the clutches interlock.
The clutches are designed so that slippage of the clutch discs can be tolerated only very limitedly.
However, defective operation such as a drop in pressure in the actuating pistons of a clutch as result of wear, mechanical failure or lack of fluid can result in the engaging pressure of the clutch not being enough to transmit the torque to the transmission. The clutch then slips or--in case of lack of fluid--will no longer be engaged during a change of gear. Slippage would destroy the clutch discs within a short time such as about 2 min.
If a clutch cannot be engaged, the power train can be absolutely interrupted.
Defective operation of the clutches leads, therefore, to altogether very disadvantageous consequences for the drive of a motor vehicle.
The invention is based on the problem of providing an arrangement and a process which detect defective operation of a clutch, informs the driver, protects the clutch and ensures safe driving.
SUMMARY OF THE INVENTION
According to the invention this is obtained by the fact that a control device is connected with sensors for the speed of an input shaft of the coupling transmission and the speed of the output shaft of the transmission, and the control device actuates, in accordance with the ratio of said speeds, a monitoring device, multi-disc clutches and a brake.
With the arrangement according to the invention is obtained that the clutches be controlled by sensors which already exist for control of the transmission. Malfunction of one of the clutches will be indicated to the contro
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patent: 4989703 (1991-02-01), Forsyth et al.
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patent: 5135443 (1992-08-01), Paton et al.
patent: 5193416 (1993-03-01), Kanayama
patent: 5222921 (1993-06-01), Garcia
Nikolaus Heinrich
Paton Robert
Braun Leslie A.
Ta Khoi
Zahnradfabrik Friedrichshafen AG
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