192 clutches and power-stop control – Clutches – Progressive engagement
Patent
1999-02-05
2000-04-25
Bonck, Rodney H.
192 clutches and power-stop control
Clutches
Progressive engagement
192 5334, F16D 2306
Patent
active
060532947
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a synchronizer in a vehicle gearbox, comprising a guide sleeve intended to be non-rotatably joined to a shaft in the gearbox, an engaging sleeve which is non-rotatably, but axially displaceably, mounted on the guide sleeve, an engaging ring provided with exterior engaging teeth and which is intended to be solidly joined to a gear rotatably mounted on said shaft and is lockable relative to the guide sleeve by axial displacement of the engaging sleeve from a neutral position to an engagement position, in which interior engaging teeth on the engaging sleeve engage the exterior teeth on the engaging ring, and a synchronizing ring cooperating with the engaging sleeve and the engaging ring, said synchronizing ring having a conical frictional surface which is movable to engagement with a facing conical frictional surface on the engaging ring.
DESCRIPTION OF THE RELATED ART
In heavy vehicle gearboxes there is often a need to increase the synchronizing torque above what is normally obtained with a common simple synchronization, in order to reduce the shifting effort and eliminate the risk of wear injury to the back and shoulders of professional truck drivers. One method of increasing the synchronizing torque and thus reducing the shifting effort is to arrange a so-called double synchronization, i.e. a synchronizer with two concentric synchronizing rings for each releasable running gear. A double synchronization reduces the shifting effort on the shift lever by about 30% in comparison to a corresponding single synchronization, but it involves an increase in the manufacturing costs of the gearbox which is not insignificant. Another method is to increase the length of stroke of the shift lever to increase the mechanical advantage, but this presupposes that there is space available so that the driver will not risk hitting his knuckles on surrounding components in the cab. A long stroke also creates problems in trucks having the engine and gearbox placed under a tiltable cab.
A third method is to use a pneumatic or hydraulic servo unit but this is an expensive solution.
SUMMARY OF THE INVENTION
The purpose of the present invention is to achieve a synchronizer of the type described by way of introduction, by means of which it is possible, while retaining the short shift length for the gear lever, and without having to use a servo unit, to reduce the shifting force which is necessary to apply to the gear lever, to a fraction of that needed for shifting in hitherto known gearboxes with synchronizers of the type described by way of introduction.
This is achieved according to the invention by virtue of the fact that the synchronizing ring is fixed rotationally relative to a torque-transmitting element, has cam surfaces which cooperate with cam surfaces on the engaging sleeve and which upon relative rotation between the torque-transmitting element and the engaging sleeve--caused by frictional engagement between the frictional surfaces of the synchronizing ring and of the engaging ring--create a force acting on the engaging sleeve in the engaging direction.
The invention is based on the idea of transmitting a portion of the rotational energy of the gearbox itself to the shifting mechanism and in this manner creating a type of integrated servo system which assists the manually initiated and terminated shifting process. In principle, shifting, after manual initiation of the synchronizing process, can be effected entirely by the servo system created. This is, however, in certain cases not desirable since it might cause unintentional shifting.
In a further development of the synchronizer according to the invention, the torque-transmitting element is displaceable away from the synchronizing ring against the effect of a spring force, which in a preferred embodiment is generated by a spring washer package between a surface of the torque-transmitting element and a facing surface on the guide sleeve. By selecting the spring characteristic for the compressed spring pack
REFERENCES:
patent: 4185725 (1980-01-01), Maina
patent: 4299317 (1981-11-01), Katayama
patent: 5105927 (1992-04-01), Frost
patent: 5135087 (1992-08-01), Frost
patent: 5425437 (1995-06-01), Nellums
patent: 5507376 (1996-04-01), Skotnicki
patent: 5678670 (1997-10-01), Olsson
AB Volvo
Bonck Rodney H.
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