Sound insulated vehicle drive unit

A drive unit comprising a reciprocating-piston type internal combustion engine and a transmission and output shaft is disclosed in which the sound-generating parts of the internal combustion engine are combined to form one driving mechanism body which is supported via an element which transmits power and isolates structure-borne sound, at the engine casing constructed as a noise capsule. To prevent sound from being radiated from the transmission casing towards the outside and structure-borne sound from being transmitted to the noise capsule, the transmission casing is rigidly connected to the driving mechanism carrier and the noise capsule also encloses the entire transmission casing.

BACKGROUND AND SUMMARY OF THE INVENTION 
The invention relates to a vehicle drive unit of the type having a 
reciprocating piston engine, a transmission, and a transmission output 
shaft. The engine sound generating parts are enclosed in an engine casing. 
Such a drive unit is known from German published unexamined patent 
application (DOS) No. 2,612,182. Although the entire driving mechanism 
carrier is suspended in a structure-borne noise isolated manner in the 
noise capsule in this known drive unit, the disadvantage is that the 
transmission casing is rigidly connected to the noise capsule so that the 
transmission noises and the noises originating from the output shaft 
outside the transmission are transmitted to the noise capsule which can 
thus only incompletely fulfill its task of sound insulation. In addition, 
the sound insulation of the driving mechanism carrier requires the 
crankshaft and transmission input shaft to be separated in the known drive 
unit, which separation is achieved by an elastic coupling inserted between 
them. However, this requires considerable installation space especially in 
a location in which in most cases, such as, for example, in a motor 
vehicle, there are very restrictive space conditions. 
An object of the invention is to construct the known drive unit in such a 
manner that transmission of structure-borne noise to the noise capsule is 
presented even with a continuous metallic connection between the 
crankshaft and the transmission shaft. 
In a drive unit of the type initially mentioned, this object is achieved by 
providing that the sound insulating engine casing also encloses the 
transmission and transmission casing. 
Since any metallic connection between the transmission casing and the noise 
capsule is avoided in the drive unit constructed in accordance with the 
invention, the transmission of sound between these two and the radiation 
of sound from the transmission casing to the outside is avoided overall 
without requiring a flexible coupling between the crankshaft and the 
transmission shaft or an encapsulation which is remote from the engine. 
Constructing the drive unit, in especially preferred embodiments, with the 
transmission output shaft connected via a flexible shaft coupling to a 
further output shaft, suppresses the transmission of sound generated in 
the internal combustion engine or the transmission via the output shaft to 
the outside, the flexible coupling being arranged at a location which 
provides sufficient space. 
The construction of the drive unit in certain preferred embodiments with an 
elastic support assembly connecting the crankshaft and transmission output 
shaft at the engine casing noise capsule, offers the advantage of 
supporting the output shaft in the noise capsule which completely closes 
the latter off towards the outside but, at the same time, allows relative 
movements between the output shaft and the noise capsule. In especially 
preferred embodiments with a toothed elastic ring coupling, a better 
compound effect between the support rings and the elastic ring layer which 
provides the possibility of increased carrying capability of the support 
is obtained. 
Due to the construction of especially preferred embodiments of the drive 
unit, with a skeleton type transmission and the transmission casing 
constructed as a support frame, resultant increases in weight can be 
avoided by reducing the dimensions of the transmission casing to form a 
support frame carrying the transmission shafts since the tasks of the 
transmission casing as outside shielding and oil container can be taken 
over by the noise capsule in the drive unit according to the invention. 
Other objects, advantages and novel features of the present invention will 
become apparent from the following detailed description of the invention 
when considered in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
In the reciprocating-piston-type internal combustion engine 1 constructed 
as a skeleton engine, the driving mechanism carrier 7, essentially 
consisting of cylinder head 1, on which a cylinder head cover 4 separated 
by a noise-damping gasket 3 is placed, cylinder housing 5 and crank 
mechanism 6, is placed on the engine casing 8 with interposition of a 
frame-shaped elastic sealing strip 24. 
The engine casing 8, which at the same time is used as oil sump for the 
internal combustion engine 1, extends into the upper area of cylinder 
casing 5 and completely surrounds the lower area of crank mechanism 6 so 
that it serves, together with the elastic non-metallic connection to the 
driving mechanism carrier 7, as a noise capsule which damps all noises 
emanating from the latter. The engine casing 8 is suspended via engine 
carriers 9 and elastic engine bearings 10. 
On driving mechanism carrier 7, a transmission casing 11 comprising a 
manual or an automatic gear shift mechanism is mounted, if desired with 
interposition of a coupling housing. As can be seen from FIG. 1, the 
engine casing 8 is laterally extended so that it also completely encloses 
the transmission casing 11 and serves as a noise capsule and as oil sump 
for the transmission, which transmission is constructed in a skeleton type 
of construction. 
The elements penetrating through the noise capsule such as a gear lever 12 
are separated from the latter by elastic elements 13 so that the 
transmission of structure-borne noises from them from driving mechanism 
carrier 7 and transmission casing 11 to the noise capsule is prevented. 
The same applies to the penetration of crankshaft 14 and the transmission 
output shaft 15 as parts of the ouput shaft through the noise capsule in 
which they are supported with the aid of elastic support ring units 16. 
These ring units include an outer support ring 17 which is inserted into 
the noise capsule and an inner support ring 19 which is placed onto the 
crankshaft 14 and the transmission output shaft 15, respectively, with 
interposition of bearing shells 18, between which support rings an elastic 
ring layer 20 is located. The two support rings 17 and 19 are provided 
with projections 21 which point towards one another and which engage the 
ring layer 20 offset with respect to one another over the circumference. 
This achieves a greater connecting surface and thus a better 
interconnection between the ring layer 20 and the two support rings 17 and 
19, whereas the elasticity of the ring layer 20 is scarcely impaired both 
in the radial and in the circumferential direction. 
Between transmission output shaft 15 and the adjoining part of the output 
shaft 22, an elastic flexible shaft coupling 23 is inserted outside the 
noise capsule which eliminates a transmission of sound out of the noise 
capsule via output shaft 22. 
Although the present invention has been described and illustrated in 
detail, it is to be clearly understood that the same is by way of 
illustration and example only, 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.