192 clutches and power-stop control – Clutches – Plural clutch-assemblage
Patent
1993-11-08
1996-01-02
Pitts, Andrea L.
192 clutches and power-stop control
Clutches
Plural clutch-assemblage
192 487, 192 871, 192 85AA, F16D 2100
Patent
active
054800145
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to clutches and in particular to clutches used to couple gear wheels to associated shafts in a vehicle transmission in order to engage selected drive ratios.
Such clutches are frequently arranged to be able to operate under load to provide a so-called "powershift" transmission in which ratio changes can be made without loss of driving torque through the transmission and without the operation of any associated main drive clutch. Frequently, such clutches are arranged in a double clutch arrangement positioned between two gear wheels with one clutch of the arrangement arranged to couple one gear to an associated shaft and the other clutch arranged alternatively to couple the other gear wheel to the same shaft.
Powershift transmissions are traditionally relatively bulky and expensive due to the relatively large size and complexity of existing ratio engaging clutches.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a double clutch arrangement which is suitable for use in a powershift transmission and which is particularly compact and economical to produce.
According to the present invention there is provided a double clutch arrangement including first and second clutches with an engaging means therebetween, the engaging means being movable in a first direction to engage the first clutch and disengage the second clutch and in a second direction opposite to said first direction to engage the second clutch and disengage the first clutch, and resilient means are positioned between the engaging means and each respective clutch such that all clutch engaging pressure is transmitted from the engaging means to each respective clutch via the resilient means so that during changes between the engaged states of the clutches the resilient means maintain sufficient clutch engagement pressure to ensure that the output torque of the arrangement never falls to zero.
In a preferred form the engaging means is moved in the first direction by spring means and in the second direction by fluid pressure.
Each resilient means preferably comprises one or more conical Belleville springs positioned between the engaging means and the associated clutch. The clearance between the engaging means, the Belleville springs and the clutches and the conical distortion of the Belleville springs ensuring that the output torque of the arrangement never falls to zero.
Preferably each clutch is of a multi-plate type.
The operation of the clutches may be further modulated by a modulating valve which controls the rate of increase and decrease of fluid pressure.
It is possible to provide a double clutch arrangement in accordance with the present invention whose width in an axial sense is no larger than the conventional axial width of a double mechanical gearbox synchroniser. Thus it would be possible to turn an existing gearbox provided with double mechanical synchronisers positioned between gear pairs into a powershift transmission by replacing each double synchroniser with a double clutch in accordance with the present invention.
One embodiment of the present invention, as applied to a tractor transmission, will now be described, by way of example only, with reference to the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a vertical section through part of a tractor gearbox which includes a double clutch in accordance with the present invention;
FIG. 2 is an enlarged view of part of FIG. 1, and
FIG. 3 shows the torque curve of the double clutch during changes in the state of engagement of the clutches.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, this shows part of a tractor gearbox in which gears 10 and 11 are rotatably mounted around an input shaft 12 and are arranged to be selectively coupled to the shaft 12 via a double clutch arrangement 13. Gears 10 and 11 mesh respectively with gears 14 and 15 which are splined at 14a and 15a onto a hollow shaft 16 which drives the adjacent stage of the gearbox. A hollow
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Barton John R.
Brace Christian J.
Massey Ferguson Manufacturing Limited
Pitts Andrea L.
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