Positive displacement supercharger using the exhaust gases of an internal combustion engine

The present invention discloses an exhaust gas supercharger. The supercharger is coupled with an internal combustion engine having a plurality of cylinders. The cylinders produce exhaust gas pulses which drive the supercharger. The supercharger includes a first and second housing each defining a chamber. A first and second partition are movable in the housing chambers. Inlets and outlets are associated with the housing chambers. Exhaust ducts transmit exhaust gases from a first and second set of cylinders to the first housing to drive the first partition. A first and second pair of air ducts are coupled with the second housing to transmit air from the second housing chamber to the first and second set of cylinders. A guide rod connects the first and second partitions together so that they move simultaneously. Also, a biasing element is coupled with the guide rod to move the partitions to a middle position in the housing chambers between exhaust pulses of the first and second set of cylinders.

BACKGROUND AND SUMMARY OF THE INVENTION 
The invention relates to a positive displacement supercharger for the 
compression of air using the exhaust gases of an internal combustion 
engine, and more specifically a piston engine. The supercharger according 
to this invention has at least one exhaust gas chamber and at least one 
air chamber, each of said chambers being able to be varied in its volume 
by way of a moving, chamber partition, said chambers each having an inlet 
and an outlet. 
Positive displacement superchargers driven by exhaust gas are known as a 
theoretical possibility. However the utilization of the exhaust gas energy 
periodically leaving one of the engine cylinders poses difficulties in 
many cases. 
In the case of four cylinder engines the exhaust gas pulses mutually hinder 
each other so that, with an increase in the number of cylinders, there is 
less and less available energy gradient for driving the partition by means 
of the natural exhaust gas pulses. A similar effect is to be noted at a 
high engine speed. 
For a number of different methods--more specifically those that have been 
recently developed--it is beneficial or even unavoidable to use a positive 
displacement supercharger. For this reason there is a need for general 
purpose positive displacement superchargers, which may be used for engines 
having a large number of cylinders or a high rated engine speed. 
The object of the present invention is to so develop a positive 
displacement supercharger of the type described above that may be used for 
a number of different applications, more specially with engines with a 
large number of cylinders or a high rated speed for producing novel 
methods and systems operating to save energy. 
In order to effect this purpose the supercharger according to this 
invention has partitions that are ganged together for joint motion. There 
is then the possibility of designing the supercharger with exhaust gas 
chambers that are to be acted upon by exhaust gas in opposite directions, 
the engine cylinders used for operation of the supercharger by supplying 
it with exhaust gas being associated in two groups with the two exhaust 
gas chambers. The outcome of this design is that the frequency of the 
pressure pulse taking effect in one exhaust gas chamber is halved and the 
available energy gradient is correspondingly improved, more specially as 
regards the utilization of the high energy natural exhaust pulses of IC 
engines. In keeping with one specially useful form of the invention, the 
supercharger has two exhaust gas chambers, that are placed on the two 
sides of a partition and two air chambers which are placed on two sides of 
another partition. Then it is possible to be certain of a very efficient 
separation of the exhaust gas sections from the air sections. 
In keeping with a further useful development of the invention, the 
partitions are fitted with a guide rod running out of the chambers to a 
point at which it is guided in the direction of motion of the partitions, 
the guide play and the guided length being of such a size that a partition 
designed in the form of a piston may be moved in its chamber without 
making contact with the chamber walls. Therefore, losses through friction 
may be kept down to a minimum, more specially seeing that the separation 
of the exhaust gas chambers from the air chamber or chamber cuts out any 
danger of a mixing together of the exhaust gas and the supercharged air, 
if the seal of the chambers on the two sides of the piston is produced by 
having a suitably narrow clearance between the piston and the chamber 
inner face next thereto. 
The partitions that are ganged together so that they are moved jointly may 
be linked by mechanical means or their motion may be caused to be in step 
by way of a synchronizing means. 
In keeping with a further useful design, the acting faces of the partition 
facing into the supercharging air chamber and into the exhaust gas chamber 
are different in area. If the acting face on the exhaust gas side is 
larger, then a high supercharging pressure may be produced; if the acting 
face on the supercharged air side is larger, then a large volumetric air 
pumping rate will be possible. 
In keeping with a further useful development of the invention, two 
partitions are ganged together for motion in unison by joining them 
together by way of a means which is adapted to transmit the motion of the 
one partition to the other one in the opposite direction so that there is 
a balancing of inertial forces. The device for transmission of motion may 
be mechanical or hydraulic in its operation. 
As part of a specially beneficial further development of the invention, the 
supercharger has two exhaust gas chambers and two supercharging air 
chambers, the outlet of the first supercharging air chamber being joined 
up via a cooler with the inlet of the second supercharging air chamber and 
having its outlet joined with the inlet of the engine cylinder that is to 
be supercharged. In this case the air that is firstly compressed may 
expand and perform work that is absorbed by the supercharger and at the 
same time the supercharging air cooled by cooling and expansion will 
improve the engine performance. 
In the event of two exhaust gas chambers not being enough for efficient 
supercharger operation, each exhaust gas outlet may be fitted with a 
choke, that if desired may be one that is adjustable with respect to the 
pressure and/or the time of the choking effect to optimize the exhaust gas 
pulses. For the same purpose it is furthermore possible for the exhaust 
gas inlet and/or outlet to be fitted with a controlled valve. 
A further development of the invention consists in that an exhaust gas 
collecting means is joined with the exhaust gas inlet on the upstream side 
thereof and the exhaust gas side of the supercharger is fitted with a 
pulse generator. This stroke control may be on the basis of an automatic 
controller, that for example takes into account the operating 
characteristics and data of the system as a whole. The stroke control on 
the exhaust gas side of the supercharger may however be triggered by the 
natural exhaust gas pulses of the engine or by a connection with the 
engine. 
Further useful developments of the invention will be seen from the 
dependent claims taken in conjunction with the account now to be given. 
Using the following account, working examples of the invention to be seen 
in the figures will now be explained.

DETAILED DESCRIPTION OF THE INVENTION 
In FIG. 1 the reader will see a four cylinder engine 11 functioning as a 
pulse generator for a positive displacement supercharger 10, the four 
cylinders 1, 2, 3, and 4 of the engine each having an outlet valve 12, 14, 
16 and 18 respectively. If the outlets were to open into a common exhaust 
pipe, the interaction of the pressure pulses produced thereby might become 
so pronounced that there would no longer be sufficient energy left over 
for the operation of the supercharger 10. Therefore the supercharger 10 is 
designed with two exhaust gas chambers 22 and 24, that are separated from 
each other by a moving partition 26. Each of the exhaust gas chambers 22 
and 24 has an exhaust gas inlet 28 and 30 respectively and an exhaust gas 
outlet 32 and 34. The outlet valves 12, 14, 16 and 18 are placed in pairs 
for use with the two exhaust gas chambers 22 and 24, namely in such a way 
that the outlet valves 12 and 18 are used with the exhaust gas chamber 22 
and outlet valves 14 and 16 are used with the exhaust gas chamber 24. The 
partition 26 is joined up with a second partition 38 by way of a piston 
rod 36 so that there is a sort of double piston, the two partitions moving 
in the same direction. The piston rod 36 is guided for axial motion. 
The supercharging section 44 has the second partition 38 placed in it which 
separates the supercharging air chambers 40 and 42 (of which there are two 
in the present working example) from each other. Each supercharging air 
chamber has a supercharging air inlet 48 and 50 and a supercharging air 
outlet 52 and 54. The supercharging air outlets so are distributed like 
the exhaust gas inlets 28 and 30 among the four engine cylinders such that 
supercharging operation corresponds to two twin cylinder engines, that are 
made up of the paired cylinders 1 and 4 on the one hand and 2 and 3 on the 
other. 
For reasons of balancing inertia and to equalize ignition intervals between 
the separate cylinders, in the prior art four stroke engines with four 
cylinders have been so designed that the pistons of the two outer 
cylinders 1 and 4 are moved at the same crank angle to the engine 
crankshaft, whereas the two inner cylinders 2 and 3 are both displaced by 
180 degrees from cylinders 1 and 4. For this reason, the outer pistons are 
moved in the same direction, whereas the inner pistons are moved in 
exactly the opposite directions. The ignition timing offset between the 
two inner cylinders 2 and 3, on the one hand, and the two outer cylinders 
1 and 4, on the other, amounts to 360 degrees about the cranksahft in each 
case. As a result, there is an even timing sequence of 180 degrees about 
the crank axis. If the two outer pistons for example are moving through 
their bottom dead center (bdc), then at the same time the inner pistons 
will run through their top dead center (tdc). At this point in time, 
because of so-called valve overlap, the inlet valve of the one outer 
cylinder will still be open while the outlet valve of the other outer 
cylinder has just been opened. 
The air displaced from the supercharging air chamber 42 by the momentum of 
exhaust gas from the cylinder 1 or 4 is supplied back to the cylinders 4 
and 1 by way of the inlet valves 62 and 56, whereas the air displaced from 
the supercharging air chamber 40 by the exhaust pulse from the cylinders 2 
or 3 makes its way, via the inlet valves 60 and 58, into the cylinders 3 
and 2. 
In keeping with these principles in a four cylinder engine, the cylinder 
whose outlet valve is opened, will pump air by virtue of the exhaust gas 
pulse into that cylinder whose inlet valve is opened at the same time 
without any special pulse generator being necessary for this. As a result, 
direct supercharging of the engine cylinders is possible from the 
supercharger, i.e. there is compression of the supercharging air during 
the supply into the engine, preferably towards the end of the suction 
stroke. In the case of the known so-called supercharging and so-called 
direct delayed supercharging, the compressed air is firstly displaced into 
a storage means and flows from it into the engine. 
FIG. 2 shows the two piston supercharger 10 somewhat more clearly, while at 
the same time making clear that by having acting faces of different area 
of the partitions 26a and 38a, special effects may be produced. In FIG. 2, 
the partition 26a on the exhaust gas side of the supercharger 10 is larger 
than the partition 38a on the supercharging air side. The outcome of this 
is that a high supercharging air pressure may be produced. If the area 
ratio were to be reversed so that the partition 38a would be larger than 
the partition 26a, a high volumetric air pumping rate might be produced. 
In addition, FIG. 2 shows the check valves 64, 66, on the one hand, and 68 
and 70, on the other, which are placed at the supercharging air inlets 48 
and 50 and the air outlets 52 and 54, respectively. The spring 35 acting 
on the guide rod 43 is for example able to be acted upon by tension and 
compression and in this case has the tendency of keeping the partitions 
26a and 38a that are ganged together, in their middle position between the 
two end positions of the reciprocating motion. The characteristic of the 
spring 35 is selected in keeping with the purpose in question. More 
specially, it may have a characteristic that is highly progressive when 
the two partitions are near their end positions so as to act as a buffer. 
The check valves 68 and 70 of the two supercharging air outlets 52 and 54 
are not mandatory. 
FIG. 3 shows a modification in which the two partitions 72 and 74 are not 
rigidly joined together for moving in step. In fact, the partitions 72 and 
74 are joined together by a means, generally referenced 76, for causing 
them to move in opposite directions to each other so that there is a 
balancing of inertial forces. The piston rod 78 of the partition 72 is 
formed with racks 80 and 82 at two opposite sides. Each of teh racks 80 
and 82 meshes with a stationary rotating pinion 84 and 86. The piston rod 
88 of the partition 74 has a forked end 90, the two facing or inne sides 
of the fork each having a rack structure 92 and 94, that meshed with the 
pinions 84 and 86. 
If the partition 72 is acted upon by exhaust gas coming through the exhaust 
inlet 96 of the exhaust gas chamber 98 and moved downwards in terms of 
FIG. 3, at the same time the partition 74 is moved upwards in the 
supercharging air chamber 100 to displace the supercharging air through 
the supercharging air outlet 102. Then acting through the exhaust gas 
inlet 104 the exhaust gas pulse moves the partition 72 upwards and the 
partition 74 downwards so that the supercharging air is displaced through 
the supercharging air outlet 106. 
The mechanical means 76 is only shown by way of example and it may as 
another example be replaced by a hydraulic means for the transmission of 
motion. 
The motion of the partitions that are ganged for motion in step may be 
influenced by spring elements 35 in FIG. 2 and/or by damping elements 
acting for example on the connection rod 43 and 36. 
This makes it possible for example to produce a preferred resting position 
in the two end positions of the partitions and/or damping of motion when 
the partitions get near these end positions. The spring element or 
elements may be so designed that they cause an automatic adaptation of the 
supercharging stroke or of the pumped air flow to the load of the engine 
as represented by the intensity of the exhaust gas pulse.