Machine element or mechanism – Gearing – Interchangeably locked
Patent
1981-03-23
1983-10-18
Dorner, Kenneth
Machine element or mechanism
Gearing
Interchangeably locked
74359, 74360, 74357, F16H 506, F16H 308
Patent
active
044098588
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to transmission and particularly to vehicle transmissions.
There is an increasing market requirement, particularly in such vehicles as tractors and forklift trucks, to provide a transmission with a manual forward/reverse shuttle facility and more than one reverse drive ratio. Many previous attempts to provide such a transmissin have involved the use of a large number of gear wheels and/or complex and expensive planetary gear sets and have frequently therefore been expensive, bulky and heavy.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a transmission which can meet the above market requirement in a particularly simple and compact manner.
According to a first aspect of the present invention there is provided a vehicle transmission assembly having parallel input, output and idler shafts each provided with a first gear wheel and a second gear wheel, the first gear wheels on the input and output shafts being in constant mesh and the first gear wheel on the idler shaft being in constant mesh with the input shaft first gear wheel along, the second gear wheels on the input and output shafts also being in constant mesh and the second gear wheel on the ilder shaft being in constant mesh with output shaft second gear wheel along, first clutch means for alternatively coupling the input shaft first or second gear wheel to the input shaft, second clutch means for alternatively coupling the output shaft first or second gear wheel to the output shaft, and control means for engaging the first and second clutch means in order to obtain a number of different output shaft ratios, said assembly being characterised in that one of the first and second clutch means in a synchromesh clutch unit of the type specified and the other of said first and second clutch means is a non-synchromesh clutch unit, in that the first and second gear wheels of the idler shaft are fixedly rotatable therewith, and in that the control means is operable to ensure that the non-synchromesh clutch unit is engaged before the synchromesh clutch unit on the selection of each output shaft ratio.
Using a transmission assembly in accordance with the present invention it is possible to provide two output shaft ratios in one rotation sense by coupling both first gear wheels or both second gear wheels to the input and output shaft.
With the inlet shaft first gear wheel and output shaft second gear wheel coupled with their respective shafts, a first output shaft rtio in the other rotational sense is obtained via a series arrangement of the input shaft first gear, the idler shaft first and second gear wheels and the output shaft second gear wheel.
With the input shaft second gear wheel and output shaft first gear wheel coupled with their respective shafts, a second output shaft ratio in the other rotational sense is obtained via a series arrangement of the input and output shaft second gear wheels and idler shaft second and first gear wheels, and the input and output shaft first gear wheels.
It is to be understood that the idler shaft and its first and second gear wheels may be provided as parts of a gear cluster or, if the first and second idler gear wheels are arranged to have the same number of teeth, all three components may be constituted by parts of a single extra wide gear wheel.
It will be appreciated from the above that the transmission assembly of the present invention provides two forward ratios and two reverse ratios from six gears and is extremely compact and economical to produce. In particular, as discussed below, the use of one synchromesh clutch unit and one non-synchromesh clutch unit not only results in a cheaper construction but also enables the spacing between the input and output shafts to be made significantly less than that necessary if two synchromesh clutch units were employed. It has been found possible to adopt this arrangement by arranging the non-synchromesh clutch to operate first.
In a preferred arrangement the first clutch means is the synchromesh clutch
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Dorner Kenneth
Massey-Ferguson Services N.V.
Thompson John C.
Wright D.
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