Vehicle drive assembly with auxiliary engine

A drive assembly, particularly for driving a vehicle, comprises a driving engine and an auxiliary engine as well as auxiliary assemblies which can be selectively driven by one of the engines. In a clear frontal area of the vehicle engine, a single-bank radial engine constructed as an internal-combustion engine is arranged as the auxiliary engine to save space. For achieving a compact, high-powered arrangement, the single-bank radial engine is constructed as a 4-cylinder 2-stroke engine with a crank guide power unit.

BACKGROUND AND SUMMARY OF THE INVENTION 
The present invention relates to a drive assembly, particularly for driving 
a vehicle, having a driving engine and an auxiliary engine as well as 
auxiliary assemblies driven by way of a clutch selectively by one of the 
engines. 
French Patent Document FR-A-1 463 799 shows a drive assembly with a driving 
engine to which an auxiliary engine is assigned for the optional driving 
of auxiliary assemblies. The auxiliary engine which, if required, is used 
for driving the auxiliary assemblies is arranged laterally of the driving 
engine. The auxiliary assemblies are arranged at a distance from the clear 
frontal areas of both engines and constructionally are assigned 
essentially to the auxiliary engine. The considerable installation space 
is a disadvantage in this case. 
The present invention is based on the object of providing, for a drive 
assembly, an arrangement of an auxiliary engine with a lower requirement 
with respect to installation space. 
This object has been achieved according to the present invention in that a 
single-bank radial engine constructed as an internal-combustion engine is 
arranged as an auxiliary engine in a clear frontal area of the driving 
engine. Furthermore, a particularly space-saving arrangement is achieved 
by a single-bank radial engine which is constructed as a 4-cylinder 
2-stroke engine with a crank guide power unit. By virtue of this 
single-bank radial engine which is described in detail, for example, in 
the European Patent EP-A-0 187 930, a short, compact and powerful 
auxiliary engine is achieved for a space-saving arrangement. However, the 
present invention is advantageous not only with respect to the overall 
size of the auxiliary engine. It also represents a considerable advantage 
with respect to the overall arrangement because of the fact that auxiliary 
assemblies may remain which are provided in the front-side end area of the 
driving engine and are arranged in order to utilize the given installation 
space. Thus, a separate arrangement which requires additional installation 
space is unnecessary. 
The advantageous arrangement of the present invention is promoted in a 
simple manner in that the single-bank radial engine with the interposition 
of a shiftable clutch is arranged in alignment with a power unit shaft of 
the driving unit. 
A further feature of the present invention achieves short overall length of 
the drive assembly in that, on the outer circumference, the clutch is in a 
rotating connection with output pulleys of enveloping gears provided in 
several planes in the clear frontal area of the driving engine for driving 
the auxiliary assemblies. 
The above-described shiftable clutch may be configured such that by means 
of it, the auxiliary assemblies are optionally driven by the single-bank 
radial engine during stoppage, idling or possibly heavy loading of the 
driving engine. However, an operating method is also conceivable for the 
shiftable clutch in that, if required, only some of the auxiliary 
assemblies are driven by the single-bank radial engine. This applies 
particularly to the case in which one or several of these separately 
optionally driven auxiliary assemblies have to furnish an increased power 
which cannot be provided when the given rotational speed of the driving 
engine is maintained, such as an increased air-conditioning performance 
and/or an increased electric consumption from the wiring at a slow driving 
speed or a stop-and-go driving method of the vehicle. 
In addition, the single-bank radial engine and the shiftable clutch can 
form a retrofit unit.

DETAILED DESCRIPTION OF THE DRAWINGS 
An assembly 1 serving for driving a conventional vehicle (not shown) 
comprises a driving engine 2, which is used for driving the vehicle and 
has numerous auxiliary assemblies arranged in the front-side end area. The 
auxiliary assemblies are, for example, a coolant pump 3 with a driving 
pulley 4 and a power steering pump 5 with a driving pulley 6. Together 
with an output pulley 8 assigned to the power unit shaft or crankshaft 7 
of the driving engine 2, the driving pulleys 4 and 6 are disposed in a 
plane of flexible transmitting device 9 in the form of, for example, a 
conventional toothed belt, chain and the like. Additional auxiliary 
assemblies are a generator 10 with a driving pulley 11 and an 
air-conditioning compressor 12 with a driving pulley 13 Together with 
another output pulley 14 assigned to the power unit shaft 7, the driving 
pulleys 11 and 13 are situated in another plane of a second enveloping 
drive train 15. 
An auxiliary engine 17, which is used for the optional drive of the 
above-mentioned auxiliary assemblies 3, 5, 10, 12, is arranged in 
alignment with the power unit shaft 7 of the driving engine 2 with the 
interposition of a conventional clutch 16 which can be operator shifted 
or, in a known manner, shifted in response to selected ones of engine and 
vehicle parameters. 16. In order to achieve a short overall length of the 
drive assembly 1, the auxiliary engine 17, which is arranged in the clear 
frontal area of the driving engine 2, is constructed as a single-bank 
radial engine 18. In order to achieve, together with a space-saving 
arrangement, a short, compact and powerful auxiliary engine 17, the 
single-bank radial engine 18 is constructed as a 4-cylinder 2-stroke 
engine with a conventional scotch-yoke unit which converts reciprocating 
to rotary movement. 
For the optional driving of the above-mentioned auxiliary assemblies 3, 5, 
10, 12, the shiftable clutch 16, on the outer circumference, is 
non-rotatably connected with the output pulleys 8 and 14 of the enveloping 
power trains 9 and 15 of the auxiliary assemblies 3, 5 and 10, 12 divided 
into two groups. The clutch 16 can be shifted in that either both groups 
of auxiliary assemblies 3, 5 and 10, 12 or, as required, one of the groups 
3, 5 or 10, 12 can be driven by the single-bank radial engine 18. 
The single-bank radial engine 18 arranged on the driving engine 2 may also 
be equipped with the shiftable clutch 16 as a retrofit unit. 
Although the invention has been described and illustrated in detail, it is 
to be clearly understood that the same is by way of illustration and 
example, and is not to be taken by way of limitation. The spirit and scope 
of the present invention are to be limited only by the terms of the 
appended claims.