192 clutches and power-stop control – Clutches – Progressive engagement
Patent
1996-06-17
1997-10-21
Bonck, Rodney H.
192 clutches and power-stop control
Clutches
Progressive engagement
192 5334, 192 5331, 74339, F16D 2306
Patent
active
056786700
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a synchronizing device in a vehicle gearbox, comprising a guide sleeve, intended to be non-rotatably joined to a shaft in a gearbox, an engaging sleeve, which is non-rotatably but axially displaceably mounted on the guide sleeve, an engaging ring provided with external engaging teeth, said ring being designed to be non-rotatably joined to a gear rotatably mounted on said shaft and being lockable relative to the guide sleeve by axial displacement of the engaging sleeve from a neutral position to an engaging position, in which internal engaging teeth on the engaging sleeve engage with external teeth on the engaging ring, and with synchronizing means cooperating with the engaging sleeve and the engaging ring, in the form of at least two concentric synchronizing rings, each having an individual conical frictional surface, said synchronizing rings being displaceable in engagement with corresponding conical frictional surfaces on a sleeve element rotationally fixed relative to the engaging ring and lying between said synchronizing rings.
Synchronizing devices of the abovementioned type, so-called double synchronizers, are used i.a. in gearboxes for trucks to increase the synchronizing torque and thus reduce the shifting work and make possible relatively short shifting movements of the shift lever. A double synchronization provides an approximately 30% reduction in the shifting force on the shift lever compared with the corresponding single synchronization. In many cases the shifting force can exceed 200N on the shift lever in a gearbox with single synchronization and this means that even with a double synchronization the shifting force will be high. An additional reduction would therefore be desirable to eliminate the risk of wear-related injuries to the back and shoulders of truck drivers.
One method is to increase the shifting distance in the shift lever to provide a greater mechanical advantage, but this presupposes that space is available so that the driver will not risk hitting his knuckles against parts in the cab. A long shifting distance will also create problems in trucks with the engine and gearbox placed under a tippable cab. Another method is to use a compressed air servo unit, but this is an expensive solution.
The purpose of the present invention is to achieve a double synchronization of the type described by way of introduction, by means of which it is possible, while retaining a short shifting distance of the shift lever, to reduce, without a servo unit, the shifting force which must be applied to the shift lever, to a fraction of what is required for shifting in previously known gearboxes with double synchronization of the type described.
This is achieved according to the invention by virtue of the fact that that one synchronizing ring is fixed rotationally relative to the torque transmitting element which has cam surfaces cooperating with cam surfaces on the engaging sleeve, said cam surfaces, upon relative rotation between the torque transmitting element and the engaging sleeve,--caused by frictional engagement between the frictional surfaces of the synchronizing means--creates a force acting in the engaging direction of the engaging sleeve.
The invention is based on the idea of transferring 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 in the manually initiated and terminated shifting sequence. In principle, shifting, after manual initiation of the synchronizing sequence, can be effected entirely under the influence of the created servo system. However, in many cases it can be undesirable, since it can result in involuntary shifting.
In a further development of the synchronizing device according to the invention, the torque transmitting element is axially displaceably joined to said synchronizing ring and is moveable away from the synchronizing ring against the effect of the spring force, which in a preferred embodiment is created by a cup spring p
REFERENCES:
patent: 3548983 (1970-12-01), Hiraiwa
patent: 4289223 (1981-09-01), Strehler et al.
patent: 4732247 (1988-03-01), Frost
patent: 4805755 (1989-02-01), Fukumoto et al.
patent: 5135087 (1992-08-01), Frost
patent: 5544727 (1996-08-01), Braun
Bonck Rodney H.
Volvo Lastvagnar AB
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