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Axle Gear and Differential Housing Disclosure Number: IPCOM000249144D
Publication Date: 2017-Feb-08
Document File: 4 page(s) / 144K

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The Prior Art Database

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Axle Gear and Differential Housing


A driven axle of landbound vehicle, such as a truck, comprises an axle gear. A crown wheel

of the axle gear may be connected to a differential housing and a pinion engages with the 5

crown wheel. In the vehicle, the pinion is connected to a driven shaft such a propeller shaft.

In an axle gear a gear ratio is given by the number of teeth of the crown wheel divided by the

number of teeth on the pinion. A low gear ratio requires more teeth on the pinion (less

difference in number of teeth between pinion and crown wheel) than a high gear ratio (larger

difference in number of teeth between pinion and crown wheel). Thus, for the same size of 10

the crown wheel, a low gear ratio requires a larger diameter pinion than a high gear ratio.

In existing axle gears for vehicles, the pinion is kept at the same location in a housing of the

axle gear, e.g. in line with the driven shaft, irrespective of the gear ratio of the axle gear of

the relevant vehicle. Thus, the positon of the crown wheel has to be adapted to the diameter 15

of the relevant pinion. In Fig. 1 a comparison between the positions of crown wheels and pinions in a low gear ratio axle gear and a high gear ratio axle gear are shown.

There are several rules of thumb to follow when designing a crown wheel. The crown wheel

can’t be too thin, i.e. if there is too little material below the teeth, the crown wheel may 20

rupture under load, or may distort too much during hardening. On the other hand, a too thick

crown wheel will be costly, and the weight of the axle gear will be unnecessarily high.

Patent document EP1977144 discloses a differential gear assembly. A crown wheel and a

casing/housing of a differential gear assembly are adapted to be joined by welding. The 25

casing has a circular flange with an axially extending lip engaged in a circular groove which

is further relieved at the radially outer side to give clearance for a high energy welding beam.

The interface between the crown wheel and the flange is a frusto-conical surface which

presents an oblique angle to the welding beam.


Due to the differing sizes of the pinions, and since the crown wheel is connected to the

differential housing, there is typically a need for a manufacturer to provide a number of

different differential housings in order to adapt the axle gears to different vehicles, requiring

different axle gear ratios.




Fig. 1 schematically illustrates two axle gears 2 of previously known kind. Fig. 1 is presented for comparison of pinion gear 4, 4’ size and crown wheel 6, 6’ position. As is clearly shown in

Fig. 1, the high gear ratio axle gear, such as the exemplified 4:1 gear ratio, has a pinion 4 of smaller diameter than the pinion 4’ of the low gear ratio axle gear, such as the exemplified 5

2:1 gear ratio. This means that the crown wheel 6 of the high gear ratio axle gear is

positioned closer to the centre axis 10 of the pinion 4 than the crown wheel...