Disc brake arrangement for an individual wheel drive

The invention relates to a disc brake arrangement for an individual wheel drive with rear-mounted planetary gear (3) for motor vehicles. A brake (7) is designed as pneumatically or hydraulically actuated disc brake and acts as a service, parking, emergency and auxiliary brake. The brake caliper (8) is situated below the horizontal center line of the wheel. The brake actuating device (9) is a combined diaphragm and spring accumulator cylinder situated in the axial direction and when the wheel head is assembled lies protected in a hollow axle body (10). An emergency release device (11) of the parking brake, which in case of failure of the vehicles own pressurized air system, allows towing, and is accessible from below through a hole (12) of the axle body (10).

FIELD OF THE INVENTION 
The invention relates to a disc brake arrangement for an individual wheel 
drive with rear-mounted planetary gear for motor vehicles. Individual 
wheel drives with rear-mounted planetary gear are known already, one 
example of such wheel drives having been given in German Patent No. 26 30 
206. 
BACKGROUND OF THE INVENTION 
Such individual wheel drives with rear-mounted planetary gear can be used, 
for example, in local traffic buses. Since in this drive, the otherwise 
usual axle bridge housing for axle drive and differential are omitted and 
replaced by an axle body without interior shafts or an individual wheel 
suspension, it is possible to build buses having very low floor height. In 
the former driving arrangements for low floor buses with individual wheel 
drives, the arrangement of the actuating device for disc brakes proves 
disadvantageous, since it reduces the passage in the floor of the bus to 
the height of the wheels. 
SUMMARY OF THE INVENTION 
The problem, on which the invention is based, is to provide an individual 
wheel drive with disc brakes which are reduced in the axial direction so 
that the passage in the floor of a low-floor bus is not unduly restricted 
by the axial length of the wheel assembly. 
The brake caliper is here situated below the horizontal center line of the 
wheel. The brake-actuating device is situated in the axial direction in a 
hollow axle body. When the wheel head is assembled, it is protected 
against shocks by its position inside the hollow axle body. This disc 
brake arrangement can be advantageously used particularly in individual 
wheel drives for low-floor buses. 
In an advantageous embodiment of the invention, the brake caliper is 
situated below the horizontal center line of the wheel in a circular 
sector between 150.degree. and 210.degree. of the vertical. Here the 
normal vector of the circular disc points in direction to the wheel axle. 
The angle is measured by the radius vector pointing vertically upward, 
that is, in the direction of the vertical axis of the vehicle. 
The brake-actuating device is preferably designed as a combined diaphragm 
and spring accumulator cylinder. The brake is designed as a pneumatical or 
hydraulically actuated disc brake. It acts in the same manner as a 
service, parking, emergency and auxiliary brake. 
The parking brake advantageously has an emergency release device which is 
accessible from below through a hole in the axle body. In case of failure 
of the vehicle's own pressurized air system, the emergency release device 
may be used in order to make it possible to tow the vehicle. 
In this disc brake arrangement for an individual wheel drive, the input is 
preferably electric. A possible field of use of this disc brake 
arrangement is in electrically driven rear wheels combined with rigid axle 
systems for dual or single tires. 
In an advantageous embodiment of the invention, the input power of a large 
electromotor is provided by several smaller ones. Their respective input 
power is combined by a spur gear assembly. The individual, small 
electromotors have a small axial length so that the whole drive unit 
projects less in the direction to the interior of the bus. The passage 
width in the interior of the vehicle limited by the height of the wheels 
is thus increased without increasing total width of the vehicle. This 
drive is adapted to the required wheel torque and the wheel speed by a 
rear-mounted planetary gear. The distribution of the input power of the 
individual wheel drive over several electromotors of less power, which are 
shorter than the motors of more power, offers, together with the reduction 
of the total length of the individual wheel drive, still other advantages. 
In case of failure of a prime mover in the wheel head, operation with the 
remaining motors is still possible. Besides, advantages in cost result 
from the use of motors belonging to the efficiency class of passenger car 
prime movers and thus can be mass produced. 
The spur gear on the output side of the spur gear assembly is preferably 
connected by a shaft with the sun gear of the planetary gear. The wheel 
bearing which rotatably supports the wheel hub is situated axially between 
the spur gear assembly drive and the planetary gear. The rims are fastened 
on the wheel hub. 
In an advantageous embodiment of the invention, the electromotors can be 
separately regulated. This makes possible a higher efficiency in the part 
load area compared to a one-motor individual wheel drive. 
The prime mover(s) is (are) preferably cooled by air, water, oil or other 
means.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In one embodiment of the invention, two prime movers 1 drive a spur gear 
assembly 2 which is connected by a shaft with the sun gear of a planetary 
gear 3. The ring gear of the planetary gear 3 is stationary. The planet 
carrier drives two rims 6 via a wheel hub. The wheel bearing 4, which 
rotatably supports the wheel hub 5, is mounted axially between spur gear 
assembly 2 and planet gear 3. One brake 7, preferably a pneumatically 
actuated disc brake, performs the service, parking, emergency and 
auxiliary brake functions. The brake caliper 8 is situated below the 
horizontal center line of the wheel. It is in a circular sector between 
150.degree. and 210.degree. of the vertical vector passing through the 
wheel axis. The brake-actuating device 9 is a combined diaphragm and 
spring accumulator cylinder, which is disposed in the axial direction and 
the wheel hub, lies protected in a hollow axle body 10. In a technical 
variant of this, the brake 7 is hydraulically actuated. An emergency 
release device 11 of the parking brake, which in case of failure of the 
vehicle, makes possible towing of the vehicle, is accessible from below 
through a hole 12 of the axle body 10. 
REFERENCE NUMERALS 
1 prime mover 
2 spur gear assembly 
3 planetary gear 
4 wheel bearing 
5 wheel hub 
6 rim 
7 brake 
8 brake caliper 
9 brake-actuating device 
10 axle body 
11 emergency release device 
12 hole