Machine element or mechanism – Gearing – Interchangeably locked
Reexamination Certificate
2001-09-28
2003-07-22
Bonck, Rodney H. (Department: 3681)
Machine element or mechanism
Gearing
Interchangeably locked
C074S329000, C074S333000, C074S031000
Reexamination Certificate
active
06595077
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims the priority of PCT/EP99/10240 filed Dec. 21, 1999 and German patent document 198 60 2502, filed Dec. 24, 1998, the disclosures of which are expressly incorporated by reference herein.
The present invention relates to a change-speed gearbox with two component transmissions arranged parallel to one another in the power flow.
The manual gearboxes with a friction clutch that predominate in motor vehicles are simple and robust but have the disadvantage that an interruption in the tractive effort occurs during gear changes. Although conventional automatic transmissions with a hydrodynamic converter avoid an interruption in the tractive effort during gear changes, they are less efficient than manual gearboxes owing to the converter. Moreover, they are heavier and more costly.
In the case of change-speed gearboxes with two frictional power-shift clutches and two component transmissions arranged parallel to one another in the power flow, gear changes can be performed under load, and more specifically with overlapping control of the power-shift clutches. This makes it possible to achieve economical automatic transmissions with good efficiency. In general, the even-numbered gears are assigned to one component transmission and the uneven-numbered gears are assigned to the other component transmission, with the result that it is possible to perform sequential gear changes under load but it is not readily possible to skip individual gears, referred to as double upshifting or double downshifting.
U.S. Pat. No. 4,658,663 has disclosed a change-speed gearbox of the generic type. In this change-speed gearbox, an input shaft is connected to an output shaft by a first and a second component transmission, which are arranged parallel to one another in the power flow and each have a frictional power-shift clutch. Concentrically arranged intermediate shafts of the component transmissions can be connected to the input shaft by the power-shift clutches. The intermediate shafts can be operatively connected to the output shaft by means of gearbox constants, of a common layshaft arranged parallel to the input shaft and of gearwheel pairs. The gearwheel pairs for forward gears I, III, and IV and the gearwheel pair for the reverse gear belong to the first component transmission. The fourth gear is designed as a direct gear and can be selected by engaging a selector element between the output shaft and the intermediate shaft of the first component transmission.
The gearwheel pairs of forward gears II and V and an additional gearwheel pair, the transmission ratio of which is equal to the transmission ratio of third gear, the gearwheel pair of which belongs to the first component transmission, belong to the second component transmission. In the first component transmission, a gearwheel clutch for third gear and the direct clutch for fourth gear are combined to give a changing clutch with a common sliding selector sleeve, which can be coupled to a loose wheel of the gearwheel pair for third gear or to the output shaft.
Although all double downshifts and double upshifts are possible without an interruption in torque transmission in this change-speed gearbox, the gear changes from the direct fourth gear to first and third gear, the gearwheel pairs of which likewise belong to the first component transmission, require the temporary engagement of the additional gearwheel pair of third gear. To start off from first gear, the first power-shift clutch of the first component transmission is always used, as a result of which there is increased wear on the latter compared with the second power-shift clutch.
SUMMARY OF THE INVENTION
An object on which the invention is based is to develop a change-speed gearbox, in particular to reduce the effort involved in its construction, its costs and weight and increase efficiency. According to the invention, it is achieved by the features of the independent claims. Further refinements will become apparent from the subclaims.
The invention starts from a change-speed gearbox in which an input shaft is connected to an output shaft by at least one first and one second component transmission, which are arranged parallel to one another in the power flow. Each component transmission has a frictional power-shift clutch and an intermediate shaft, it being possible in each case for the intermediate shaft to be operatively connected to the input shaft by means of the power-shift clutch. The change-speed gearbox furthermore has at least one gearbox constant per component transmission, each gearbox constant having a gearwheel on one of the two intermediate shafts, at least one of which gears can be operatively connected to a first layshaft arranged parallel to the input shaft.
It is proposed that at least one gearbox constant can be brought into operative connection with the first and the second power-shift clutch. Power can advantageously be output to a layshaft by both power-shift clutches via at least one gearbox constant. With a certain number of gearwheel pairs, it is possible to achieve a particularly large number of power-shift options and, in particular, to achieve at least the most important double upshifts and double downshifts under load without additional gearwheel pairs. If at least one gearwheel of the gearbox constants on an intermediate shaft is embodied as a loose wheel and can be brought into operative connection with the first power-shift clutch by means of at least one selector element and with the second power-shift clutch by means of a selector element or, preferably, can be connected directly by means of a respective selector element to one intermediate shaft in each case, a gearbox constant can be brought into operative connection with the first and the second power-shift clutch in a manner that is particularly simple in terms of construction and economical in terms of space and with a high efficiency and low losses due to tooth engagements.
Further degrees of freedom with respect to various gear change options can furthermore be achieved if the gearwheel of the first gearbox constant on the first intermediate shaft and the gearwheel of the second gearbox constant on the second intermediate shaft are embodied as loose wheels. It is furthermore possible to achieve a situation where both power-shift clutches can be closed in all gears.
If at least the gearbox constant assigned to the lowest gear can be brought into operative connection with the first and the second power-shift clutch, either the first, the second or both power-shift clutches can advantageously be used for the purpose of starting off. The stresses resulting from the starting-off operation can be distributed between both power-shift clutches. Despite economical dimensioning, it is possible to avoid an excessive temperature, to reduce wear and extend service intervals. If one power-shift clutch fails, the second power-shift clutch can furthermore be used for starting off from first gear and reliability of mobility can be increased.
The power-shift clutches can also be designed differently for different starting-off operations and/or be used individually or jointly for starting off from a higher gear. The power-shift clutches are advantageously used individually or jointly for starting off as a function of at least one operating parameter, e.g. as a function of loading, friction, temperature and/or wear etc. detected at the power-shift clutches.
It is furthermore proposed that the power-shift clutch of the first component transmission can be brought into operative connection with a second layshaft parallel to the input shaft by means of the first gearbox constant, which shaft can be brought into operative connection with the output shaft by at least one gearwheel pair assigned to the first component transmission. An additional torque path can be created by means of the additionally engageable second layshaft. If, in particular, the output shaft can be connected to the intermediate shaft of the first component transmission by an engageable and disengageable se
Geiberger Axel
Heizel Markus
Kolb Andreas
Sperber Ralf
Straub Heinrich
Abdelnour Dennis
Bonck Rodney H.
Crowell & Moring LLP
Daimler-Chrysler AG
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