Machine element or mechanism – Gearing – In series plural interchangeably locked nonplanetary units
Patent
1996-09-26
1998-10-13
Wright, Dirk
Machine element or mechanism
Gearing
In series plural interchangeably locked nonplanetary units
F16H 3704
Patent
active
058196013
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a transmission, especially for a motor vehicle.
A transmission is known to perform the function of adapting as thoroughly as possible to each other the operating conditions between a prime mover and a motor vehicle. The different conditions of use of a motor vehicle (loading, unloading, city, land, expressway and mountain driving) require a large range of traction and speed. To utilize as fully as possible the traction-speed diagram, a transmission having at least four or more gears is required or desirable. The power train of a motor vehicle is, in general, designed so as to achieve the highest speed in the level road with a maximum engine power. The final speed and mileages depend on the tractional resistance of the motor vehicle. To achieve a high road speed without making allowance for disadvantages in mileage in the lower and medium speed ranges, it has become customary to use hand-operated transmissions with five gears.
Also known (GB-A 657 228) are transmissions with added speed levels (overdrive).
The overdrive can be designed so as to make it possible to drive in a consumption-optimated range by lowering the engine speed. Whether to utilize the intrinsic advantage of an overdrive depends to a great extent on the type of driver concerned. A driver not very inclined to shift will not as a rule make use of an existing overdrive.
DE-A 28 42 390 has disclosed an electronic gearchange mechanism for actuating an overdrive, which allows changing a gearshift pattern. In this manner, depending on whether an economy-or power-oriented mode of driving is desired, the driver of a motor vehicle can adjust the shifting conditions of the overdrive. Here, the overdrive is actuated by the driver by an additional switch in the gearshift lever, a contact in the transmission ensuring that it be possible to engage the overdrive only if the highest gear has been previously introduced.
DE-A 30 26 742 has disclosed a process for an engine contact when changing the gears of a stepped transmission. The stepped transmission is designed as a hand-operable transmission with an added overdrive. The overdrive is engaged and disengaged by an automatic transmission control according to vehicle parameters. The known suggestion concerns the engine contact when engaging or disengaging the overdrive in order to obtain a gearshift operation which is as smooth as possible. Nothing more detailed is said about the design of the stepped transmission itself.
DE-A 29 21 169 has also disclosed a multiple gear synchronized manually operated transmission which has four gears and an overdrive for the third and fourth gears. The gear wheels for the third and fourth gears are coordinated with an additional pair of gear wheels. Said pair of gear wheels are engaged and disengaged preferably by a hydraulically actuated multi-disc clutch. When the clutch is engaged and a third or fourth gear is shifted, the longer ratio of the pair of gear wheels is active. If the clutch is disengaged (when the accelerator is lowered), it is shifted down from the overdrive to the direct short ratio of the shifted third or fourth gear, which practically corresponds to a down shift to a lower gear.
In the above explained concept of a transmission, it is a disadvantage that the driver, in the absence of clear situations, no longer knows after some time whether he is driving, for example, in third gear or in third gear with overdrive engaged. He does not know whether or not to shift in certain situations. If, for example, the driver is going to shift from the third gear to the fourth gear, the overdrive of the third gear can engage unexpectedly. The deficient overview can result in the driver driving in the wrong gear for a long period of time.
The problem on which the invention is based is to provide a transmission with a large total ratio in which the lower gears can be manually operated in a manner familiar to the driver with additional overdrive gears which adhere to the highest gear. This transmission must stand out specially by a light weight
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patent: 4831894 (1989-05-01), Braun
patent: 4856375 (1989-08-01), Beim
patent: 4966048 (1990-10-01), Braun
patent: 5125282 (1992-06-01), Bender et al.
Wright Dirk
ZF Friedrichshafen AG
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