Note: Descriptions are shown in the official language in which they were submitted.
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I n t e r n a 1 C o m b u s t i o n E n g i n e ,
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Particularly, A Free-Piston Engine
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S p e c i f i c a t i o n
This invention relates to an internal combustion engine
and, more specifically, to a free-piston engine in ac-
cordance with the preambles of claims 1 and/or 34.
Internal combustion engines have pistons guided within
cylinders, which pistons, together with said cylinders,
define combustion chambers within which a fuel/air mix-
ture will be ignited. For driving purposes, the kinetic
energy of said pistons will be transfexred, e~g. by me
chanical means or, with free-piston engines, more speci-
fically by way of pneumatic, but preferably by way of
hydraulic media.
An internal combustion engine of said type is known from
German patent 286,806. With said known internal combus-
tion engine, both front faces of the piston projections
comprise compression chambers intended to compress the
charge air prior to combustion. Into said compression
chambers, air will flow through corresponding radial
ports through the cylinder wall in the area.of said pis-
~on projections at both cylinder ends, it being necessa-
ry to control said radial inlet ports via separate pis-
ton slide valves. Precompressed air will flow through
radial bores provided in, and controlled by, such piston
projections into the hollow piston, through ducts to-
wards the opposite piston projection and thence via the
corresponding radial bores provided in said piston pro-
jection into the~ appropriate combustion chamber. During
piston return travel, the direction of air flow through
the piston will change. Exhaust gases will leave, under
piston face control, the combustion chambers via outlet
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ports arranged in the radial symmetry plane of the cy-
linder. Said known internal combustion engine will
transfer its power mechanically, via a piston rod, to-
wards the outside; to such extent, it is not really a
free-piston engine.
Said known engine suffers, amon~ other things, from the
drawback that for inlet control purposes separate piston
slide valves will be required, over and above said radi-
al bores provided in the piston projections. Operation
and control of this engine is complicated and highly
unreliable, gas flow paths through the entire piston are
long, complicated and subject to high losses, the sub-
stantial expansion occurring within the hollow piston
i causing, to a large extent, the loss o~ the relatively
high, and highly power-consuming, degree of precompres-
sion achieved previously. Charge cycles associated with
any piston travel, combustion chamber filling, and fuel/
air mixing actions invariably are low-efficiency, elabo-
rate and complicated processes.
As opposed to this, the object of the invention is to
improve a similarly structured internal combustion en-
gine and, more specifically, a free-piston engine in
accordance with the characterizing clauses of claims 1
and/or 34 so that control and operation become less com-
plicated, more versatile, more efficient and more reli-
able, while power transfer will be achieved in a parti-
` cularly cost-efficient manner.
According to the invention, this object is achieved by
the features of the characterizing part o~ claim 1 and/
or 34.
Above all, such measures will cause the admission of
air, or of the air/fuel mixture, into the combustion
chambers as well as the removal of exhaust gases there-
from to proceed via short, low-turbulence paths in a
low-loss manner, controlled only by the position of the
piston and of its two cylindrical projections in a par-
ticularly reliable as well as simple way. Therefore, the
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piston and its two cylindrical projections are suitably
dimensioned, and ducts and bores are assigned, separate-
ly pursuant to claim 1 and jointly pursuant to claim 34,
to one half of the overall piston length as well as to
the inlet ports located only at the center of the cylin-
der, and to the cylinder outlet ports arranged on either
side of said inlet ports.
Depending upon piston position, said inlet ports toge-
ther with such bores and ducts will form, pursuant to
claim 34, a permanently open connection or, pursuant to
claim 1, will be linked to, or blocked as regards, one
half of said piston while the outlet ports assigned to
said half of such piston will be blocked or open. Thus,
air or a fuel/air mixture will flow in a low-loss manner
along a short path through said ducts and bores into the
combustion chambers and therein follow short paths along
the walls of said combustion chambers. In the process,
practically all of the exhaust gases present within the
combustion chamber will be pushed out of them so that
rapid, optimal filling/exhaust action will result for
the combustion chambers. In order to achieve a ~uel/air
mixture as homogeneous as possible within the combustion
chambers and to obtain a rapid and satisfactory filling/
exhaust cycle, a preferential development of the inven-
tion consists in arranging, according to the invention,
such ducts within said cylindrical projections so that
their orifices are located in a ring~ e arrangement on
the lateral surfaces of said cylindrical projections;
injection nozzles and/or spark electrodes, likewise pro-
vided in a ring-like arrangementj end in toroid-like
recesses coaxial with respect to said cylindrical pro-
jections and located within the faces of said combustion
chambers. ~hese measures will ensure optimum flushing of
exhaust gases out of the combustion chambers by the air
or the fuel/air mixture entering thereinto, and obtain
satisfactory charging, mixing and combustion, and cause
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piston movement in a particularly expedient and effi-
cient manner, thus enhancing the drive power achievable
from such engine.
Simultaneously, thanks to the toroid-like configuration
of said combustion chambers, it is now possible to de-
fine, by engineering means, to a higher degree of preci-
sion the minimum chamber volume (clearance volume~ and
the maximum compression ratio of the fuel/air mixture as
well as the course of its combustion and the useful ef-
fects obtainable therefrom. According to the invention,
displacement transducers sensing the precise position of
the piston so as to permit determining and controlling
optimum fuel injection and/or ignition timing are loca-
ted within the cylinder walls. This link between piston
position sensing, more particularly in free-piston en-
gines, and starting the combustion process will ensure
particularly reliable engine function and high engine
efficiency.
Said displacement transducers might for instance be mag-
netic-field sensors operating inductively and generat-
ing, thanks to piston movements, an inductive voltage
depending upon piston position.
German patent application 1,480,100, laid open for oppo-
sition, discloses a free-piston ignition engine. Said
engine has no ducts of any description within its pis-
ton; moreover, its inlet ports are outside the radial
symmetry plane of the cylinder and have to be control-
led, just as the outlet ducts, via the piston faces.
Since, in this known instance, gas inflows into, and
outflows from, the corresponding combustion chamber are
not directed concentrically and radially outwards from
the axis, and since the inflow has to be directed to-
wards, and the outflow away from, the cylinder axis, and
since, moreover, inflows and outflows will proceed at
opposite ends of any combustion chamber in the same ra-
dial plane, resulting flow conditions are highly unsa-
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tisfactory, just as the filling and exhaust cycles, allof which leads to unreliable, high-loss and thus ineffi-
cient operation.
Moreover, controlling both the inlet and outlet proces-
ses with a single, joint piston edge will lead, with
this configuration of inlet and outlet ports, to low-re-
liability control action and engine operation.
German patent application 1,480,100, laid open for oppo-
sition, provides for kinetic energy to be transferred
from the piston of the free-piston combustion engine to
a hydraulic fluid in order to drive hydraulic-power mo-
tors, for instance in vehicles; this design principle
will permit pumps to be configured for any type of act~
ating or delivery media.
Printed German patent specification 3,029,287 discloses
a piston rod bearing a piston on either face as well as
a third piston located centrally between said pistons on
such piston rod. With respect to the cylinder, the two
outer pistons deine one combustion chamber each, while
the central piston delimits, with respect to the cylin-
der, two chambers permitting a fuel/air mixture to be
precompressed prior to being fed into, and ignited with-
in, said combustion chambers via overflow ducts.
Another known arrangement (from US patent 4;449,488 and
published German patent specification 2,816,660) is to
provide, within a piston defining, together with the
cylinder, certain combustion chambers, a second piston
to form chambers for precompression of air.
In general, air or else a fuel/air mixture can be fed
into any such combustion chamber. In the first case,
fuel will be injected subsequently into said combustion
chambers. Generally speaking, spark electrodes may be
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located within said combustion chambers, or the compres-
sion ratio obtainable within them can be chosen high
enough to cause spontaneous ignition of a fuel/air mix-
ture.
Liquid, gaseous or even solid fuels may be used, such as
gasoline, diesel oil, heavy oil, light fractions, coal
dust, etc.
Further free-piston engines are known (from ~S patent
4,205,528) to have a piston guided within a cylinder,
said cylinder defining, together with the piston faces,
combustion chambers, while the piston faces comprise
projections and the comb~stion chambers nozzles permit-
ting fuel to be injected, the cylinder wall having air
inlet ports and exhaust gas outlet ports blocked or re-
leased by the piston depending upon its position. Said
projections located on the piston faces have the shape
of truncated cones; they guide the air being fed into
the combustion chambers so as to flush exhaust gases
from such combustion chambers whenever any compression
stroke is initiated.
With all engines mentioned, and more particularly with
said free-piston engines, substantial design and/or en-
gineering efforts are required if introducing air and
fuel into the combustion chambers is to be c~ntrolled as
a function of piston position. Said known control sys-
tems often suffer from low reliability. Flow paths lead-
ing to and from combustion chambers are frequently long,
cause turbulence and entail losses. This is why said
known engines are, in practice, subject to frequent
failures despite their sophisticated design, and place a
high maintenance load on their operators. Finally, the
efficiency of such engines tends to be insatisfactory in
practical use.
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One embodiment o~ the invention is characterized by hav-
ing the fuel injection nozzles and/or the spark elec-
trodes located in an arrangement similar to a ring with-
in the cylinder wall of the combustion chamber placed
opposite to and facing the piston end faces. This mea-
sure contributes to forming, within the combustion cham-
bers, a fuel/air mixture as homogeneous as possible and
to ignite and to burn it in a manner as expedient and as
efficient as possible.
In a further embodiment of the invention, the engine
according to the invention is fitted with a device de-
signed to compress air or a fuel/air mixture, which de-
vice is arranged either within the cylinder itself or
external to it. In the last-mentioned instance, a charge
air accumulator will be associated with said compression
device.
External compression of air can be performed according
to the turbocharger principle; however, common pump
types may likewise be used for compression purposes.
In another embodiment of the invention, the internal
combustion engine according to the invention is designed
to be used within a system operated by a pressure fluid
and switchable between engine and pump operation, such
as a hydraulic unit, and coupled with a dynamo used as a
motor while the internal combustion engine is being
started.
This will provide starting means for the internal com-
bustion engine. While starting is proceeding, the dynamo
will be supplied with power via an accumulator to drive
the system, for instance a hydraulic unit, now operating
as a pump so that the internal combustion engine which,
at the faces of its piston projections, is subject to
the action o~ said pressure fluid, will be started. As
soon as the internal combustion engine has been started,
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the system operated by a pressure fluid will act as an
engine driving, for instance, a hydraulic unit; among
other things, the dynamo will now be driven and charge,
in its turn, the battery. Moreover, the system operated
by the pressure fluid comprises an engine or motor dri-
ven by said pressure fluid, which engine or motor will
absorb the drive power developed by the internal combus~
tion engine via said pressure fluid and convert said
drive power into effective work.
With another embodiment of the invention, the inlet-port
axes of the internal combustion engine provided to admit
air or a fuel/air mixture are located ~ithin the cylin-
der wall so as to superimpose, upon the axial movement
of the piston, a rotary movement of said piston around
its longitudinal axis. Said measure will prevent, among
other things, the piston from producing excessive run-
ning-in marks.
Essential, non-obvious developments of the internal com-
bustion engine according to the invention relate to the
geometrical configuration of said cylindrical piston
projections, which configurations deviate from the con-
tinuously smooth cylindrical outer surface of projec-
tions having constant, uniform diameters.
We claim, for instance, piston projections featuring
adjoining cylindrical longitudinal sections, each having
a differing diameter, all guided movably within the cy-
linder by suitabIe axial bores of appropriate diameters,
the faces of the cylindrical longitudinal sections of
the piston projections causing them to become variable-
volume chambers owing to the alternating piston move-
ments occurring within the engine during combustion,
within wich chambers the pressure of some fluid may be
increased.
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Our claims extend, for instance, to embodiments of said
cylindrical projections which have on one side - and
pursuant to another development, on both sides - of a
larger-diameter longitudinal section acting as a disk-
shaped, at least one further cylindrical longitudinal
section the diameter of which is inferior to the diame-
ter of the pistonO
Both the free end faces of said projections and the fa-
ces of said longitudinal sections of such projections
will perform travelling movements during any stroke of
the piston while being radially sealed with respect to
the corresponding bores within the cylinder, all without
having the cylinder ends come into contact with the cor-
responding piston ends facing them within the cylinder.
Depending upon the embodiment claimed and the inlet and
outlet flow paths associated therewith, such travelling
movements of the end faces of said projections serve to
compress some fluid, such as a gas or a hydraulic fluid
actuating a system operated by a pressure fluid, and/or
the gas or the fuel/air mixture to be ignited within the
internal combustion engine.
Thus, the longitudinal sections of said piston proiec-
tions will create, for instance, a double-capacity or
two-stage compressor for the internal combustion engine,
which compressor will render a separate turbocharger
superfluous. Over and above that, a pressure fluid pump
will be formed, which pump will be configured as a reci-
procating pump (for instance a one-stage pump having two
alternatingly pressurized or delivering chambers, or a
two-stage one) to be linked to a d~wnstream system actu-
ated by a pressure fluid, for which system the internal
combustion engine will develop its power, particularly
if designed as a free-piston engine.
Within the inlet and outlet ducts of said variable-vo-
lume chambers, there will be suitable control valves -
such as non-return valves, or pressure-controlled slide
valves, or externally controlled regulating valves - to
ensure reliable operation of the piston~swept volumes.
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Between the chambers designed to compress the combustion
air or the fuel/air mixture, and the inlet ducts of the
internal combustion engine located within the radial
symmetry plane of the cylinder, open or closed-loop con-
trol valves may be provided, which valves will then con-
trol the filling ratio of the combustion chamber.
Pursuant to a non-obvious development of the invention,
the pressure medium of the system operated by it will be
used to cool the cylinder, preferably in the area of the
combustion engine, while being admitted through the suc-
tion duct to the variable-volume cylinder chamber acting
as a pump.
Finally, the internal combustion engine may be designed
( to be used a~ a free-piston engine, or else combined
with a mechanical drive articulated with respect to the
piston or its projections.
With the solution in accordance with claim 34, preferab-
ly precompressed inlet gas destined to be burned is kept
continuously available within the hollow piston invari-
ably refilled so that it can flow directly into the com-
bustion chambers whenever the bores provided within the
lateral surfaces of the projections are opened.
Two embodiments of the object of this invention as well
as a block diagram showing a system according to the
invention are shown on, and will now be explained with
reference to, the drawing wherein:
Fig. 1 shows a sectional view of an embodiment of the
internal combustion engine according to the in-
vention configured as a free-piston engine with-
out integrated compressor but with a pressure
fluid pump suitable for hydraulic media integra-
ted into one end of the engine, which medium is
used to cool the cylinder on the intake side of
~- the pump;
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Fig. 2 shows a cross-sectional view of the engine pur-
suant to Fig. 1, displaying the arrangement of
the pressure-medium intake ducts used to cool
the cylinder;
Fig. 3 shows a sectional view of another embodiment of
the internal combustion engine according to the
invention configured as a free-piston engine
having an integrated compressor providing twice
the filling volume, and an integrated pressure
fluid pump designed for hydraulic media and used
to transfer the power delivered by the engine;
Fig. 4 shows a block diagram of how to use an engine
according to the invention in connection with a
! system operated via a pressure fluid and fitted
with a starting device for the internal combus-
tion engine.
The internal combustion engine in accordance with the
embodiment of the invention as per Fig. 1 consists of a
cylinder 1 within which a piston 4 can reciprocate over
the distance defined by its stroke while being radially
sealed with respect to the axially extending cylinder
bore supporting it. Together with its end faces 26, 27,
said cylinder bore forms cylinder chamber 9. At each of
its ends, the piston is designed to have one face, de-
signated 5 and 6, respectively. At either side of piston
4, there extend, away from faces 5 and 6, a~nd coaxially
with respect to piston 4, cylindrical projections 7, 8
having uniform diameters inferior to the.one defining
piston 4~ The ends of said projections 7, 8 are guided
movably and in a radially sealed manner, within further
axial cylinder bores 12, 13, which bores extend away
from cylinder chamber 9, prolonging it, at a diameter
approximately equal to the one defining projections 7, 8
within cylinder l; at their ends, said bores are closed
by one lateral face each, designated 87 or 88 respec-
tively. Within radial symmetry plane Z of said cylinder,
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12
there are inlet ports 2 within longitudinal cylinder
wall 100, which ports lead radially into cylinder cham-
ber 9 and are used to supply air or the fuel/air mixture
required for ~urning within combustion chambers 10, 11
of said engine. At either side of such inlet ports ~,
outlet ports 3 passing through longitudinal cylinder
wall 100 are arranged at distances b and likewise within
either one radial plane Zl, z2 of said cylinder. The
axis of inlet ports 2 may be spaced with respect to the
longitudinal cylinder axis A-A such as to have piston 4
rotated by the inflowing gas around its longitu~inal
axis A-A. At its cylindrical (outer) surface 80, piston
4 is provided with radial orifices 90, 91 ending at
ducts 18, 19 within piston 4, said orifices 90, 91 being
arranged in radial planes Kl, K2 of piston 4 located at
distances at either side of radial plane K of said pis-
ton 4.
Within piston 4, ducts 18, 19 lead, preferably so as to
maintain a nearly constant Elow cross-section, as indi-
vidual ducts hollowing out piston 4, or as bundled
ducts, from orifices 90, 91 into projections 7, 8 of
piston 4, where they once more lead into bores 20, 21
preferably distributed in a ring-shaped arrangement
around the periphery of projection 7 or 8, respectively,
and, located in one radial plane each, paSS through the
cylindrical outer surfaces 101, 102 of such projections
7, 8 into said projections, for instance in a radial
direction. Thus, a flow path connection is attributed to
either of the two longitudinal halves 401, 402 of the
piston which connection leads fro~ orifices 90, 91 -
preferentially likewise located in a ring-shaped arran-
gement at the periphery of the body of piston 4
through ducts 18, 19 assigned separately to either lon-
gitudinal half 401, 402 and to either projection 7, 8,
which ducts are located within piston 4 and its projec-
tions 7, 8 and lead up to bores 20, 21, all of them in-
tended fox the admission and the passage of air or of a
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3L3~S~
13
fuel/air mixture for combustion purposes, starting at
ports 2 in longitudinal cylinder wall 100 and leading
into the combustion chambers 10, 11 located axially to
either side of piston 4 within cylinder chamber 9.
Piston 4 may, alonq its lateral surface and within radi-
al planes Kl and K2, and/or longitudinal cylinder wall
100 may, along the interior surface area of cylinder
chamber 9 and within radial symmetry plane Z, be peri-
pherally provided with a flow duct which may be confi-
gured, by way of example, as a, for instance all-around,
groove-like cavity permitting the establishment a flow
path connection distributed over the entire periphery
between individual inlet ports 2 located in a ring-
shaped arrangement and/or orifices 90, 91 located, in a
ring-shaped arrangement, on the lateral face of the pis-
ton, a feature that may be important if piston 4 is to
rotate around its axis ~-A, specifically if configured
as a free piston.
Piston 4 is sealed radially and preferably at its ends,
if necessary, however, also between planes ~1 and K2,
via sealing means such as piston rings and/or annular
seals located between its peripheral surface, i.e. its
lateral surface and the axial cylinder bores forming
cylinder chamber 9. At their ends, i.e. between the ra-
dial planes comprising bores 20, 21 and their free end
faces within said cylinder bores 12, 13, such cylindri-
cal projections 7, 8 are likewise sealed by means of
sealing means 14, 15 such as annular seals relative to
cylinder 1, so as to prevent any axial flow path from
being formed between the corresponding free end faces of
projections 7, 8 and combustion chambers 10, lI. Within
the ends of cylinder chamber 9 facing piston 4, i.e.
within the interior end faces 26, 27 of cylinder 1, to-
roid-like recesses 83, 84 are provided, both preferably
coaxial with respect to cylinder axis A-A, around pro-
jections 7, 8 and/or cylinder bores 12, 13, into which
toroid-like recesses 83, 84 injection nozzles 28, 29
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14
and/or spark electrodes 128, 129 project and/or act
which are located, preferably in a ring-shaped arrange-
ment on the periphery of cylinder 1, within said toroid-
like recesses 83, 84 determining approximately the clea-
rance volume of combustion chambers 10, 11 at their ma-
ximum compression ratios.
Dimensions as well as length and distance attributes are
chosen so as to have coincide the approximately radial
planes Z and Kl whenever piston 4 approaches, with face
6 of one of its piston halves 401, face 27 of cylinder 1
turned towards it, thus creating an open path between
the inlet ports and orifice 90 of the other piston half
! 401 so as to link, by way of an open flow duct, inlet
ports 2 with duct 18 associated with said other longitu-
dinal half 401, and via bores 20 in projection 7 direct-
ly with combustion chamber 10 so as to permit the gas to
be ignited to flow thereinto. For this purpose, bores 20
are spaced at a certain distance away from face S of the
piston (just as bores 21 with respect its face 6), and
the axial length of cylinder chamber 9, of piston 4, of
combustion chambers 10, 11, and of projections 7, 8 as
well as the maximum distance separating faces 5 and 26
or 6 and 27 are chosen so as to have bores 20, 21 open
within cylinder chamber 9 or within combustion chambers
10, 11 whenever piston 4 is near its opposite clearance
position, i.e. near face 27 or 26, as the case may be.
~wing to the largely symmetrical arrangement of surfa-
ces, chambers, ducts, bores, distances etc. with respect
to radial symmetry plane Z of cylinder 1 and to radial
symmetry plane K of piston 4, the above definition is
just as true for the dimensions characteri~ing the other
travelling directions of piston 4.
Likewise near the dead-center positions of piston ~ are
the open flow path connections between inlet ports 2 and
the corresponding combustion chamber 10 or 11, as well
as outlet ports 3 located in common radial planes Zl or
Z2. In these top or bottom dead~center positions of the
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piston, the outlet ports 3 corresponding to radial
planes 21 or 22 will be opened by one of the faces 5 or
6 of piston 4 with respect to the appropriate combustion
chamber 10 or 11 so as to permit exhaust gases to leave
combustion chamber 10 or 11, i.e. to be flushed out of
combustion chamber 10 or 11 by the fresh gas fed in via
inlet ports 2.
For the purpose of engine cortrol, particularly necessa-
ry if piston 4 is configured as a free piston, displace-
ment transducers 30, 31 will be arranged within the wall
of cylinder 1, for example near the ends of cylinder
chamber 9, so as to capture the various in-travel posi-
tions of piston 4; -the various piston position signals
may be used and will serve to activate, at the proper
time, injection nozzles 28, 29 or spark electrodes l2B,
129.
Further away from the two dead-center positions and to-
wards the intermediate piston position, i.e. in the di-
rection of diminishing distances between radial symmetry
planes Z and K, the flow path connection between inlet
ports 2 and orifices 90, 91 through piston 4 itself is
blocked, just as are the flow paths leading from bores
20, 21 to combustion chambers 10, 11, via the sealed
lateral surfaces of projections 7, 8 on the one hand and
cylinder bores 12, 13 on the other hand, as are the flow
paths leading from combustion chambers 10, 11 to outlet
ports 3 via end faces 5, 6 and the sealed lateral surfa-
ces of piston 4.
The cylinder ends are provided with faces 87, 88, which
faces close said axial cylinder bores 12, 13 within
which the free ends of projections 7, 8 move as the pis-
ton reciprocates so that, within said cylinder bores 12,
13, a variable-volume chamber is created between end
faces 87, 88 formed by cylinder 1 and the end faces of
the free ends of said projections 7, 8, which chambers
are used to pump a pressure fluid, any such variable-vo-
lume chamber acting~ as its volume decreases as a func-
3 31~?S~7l~
- 16
tion of piston advance, to increase the pressure exerted
on the medium located within said variable-volume cham-
ber.
Said end faces 87, 88 comprise pressure fluid ducts 81,
82, 85, 86 leading axially to cylinder bores 12, 13,
which ducts serve as inlets on the suction side and as
outlets on the delivery side; for the control of said
ducts, control valves 22, 23, 24, 25 are therein provi-
ded, configured, for instance, as non-return valves, or
as pressure-controlled slide valves, or as open or
closed-loop control valves triggered externally, for
instance electrically.
Finally, pressure fluid ducts 81, 82, respectively loca-
ted on the suction side, lead from the opposite end of
the cylinder and its end faces 87, 88 via pressure fluid
ducts 81l 82 provided within longitudinal cylinder wall
100 and designed to have as large a surface (cross-sec-
tional extent) as possible with respect to said cylinder
wall, for instance through separate ducts parallel to
pressure-fluid ducts 81, 82 on the suction side, towards
the then other face located at the other end of the cy-
linder, and thence via the suction-side control (i.e.
inlet) valve axially into the end faces of cylinder
bores 12, 13. This arrangement is intended to cool, by
means of the pressure fluid admitted on the suction
side, cylinder 1, preferentially in the area of longitu-
dinal cylinder wall 100 in the longitudinal` area sur-
rounding cylinder chamber 9, and thus the internal com-
bustion engine.
In summary, Fig. 1 shows an embodiment of a free-piston
engine according to the invention. The wall of cylinder
1 comprises air inlet ports 2 and exhaust-gas outlet
ports 3; moreover, it guides axially movable piston ~.
Said inlet ports 2 are arranged in one, and said outlet
ports in two, annular zones. Piston 4 has, on its end
faces 5, 6 one cylindrical projection each (7, 8), the
:13~S~
17
diameter of which is inferior to the diameter of piston
4. Said piston is guided within a cylinder chamber 9
subdivided by it into combustion chambers 10, 11. In all
their positions, said cylindrical projections 7, 8 are
within cylinder bores 12, 13 which may, as can be seen
from the block diagram shown in Fig. 4, lead to a hy-
draulic motor, for instance via hydraulic lines.
Via their end faces, said cylindrical projections 7,8
are in contact with any hydraulic fluid present within
said lines. Cylindrical projections 7, 8 are provided
with seals 14, 15 so as to be sealed off against any
such hydraulic fluid. Piston 4 may likewise be provided
with seals 16, 17 in order to seal off combustion cham-
bers 10, 11. Moreover, piston 4 features ducts 18, 19
starting at its side faces and ending at bores 20, 21 of
cylindrical projections 7, 8. Depending upon the type of
engine ~pursuant to claim 1 or to claim 34), said ducts
are separate, or open with respect to each other. Bores
20, 21 end at the lateral faces of said cylindrical pro-
jections 7, 8. The ends of ducts 18, 19 on the lateral
faces of piston 4, where they form orifices 90, 91, will
be located, according to one solution (claim 1) in two
zones Kl, K2, and according to the other solution tclaim
34) in one zone surrounding the axially central area of
piston 4 in an arrangement that is equidistant, i.e.
similar to a ring. Said ring~shaped arrangement has
likewise been chosen for the orifices of bores 20, 21,
located within annular zones of cylindrical projections
7,8.
Said combustion chambers 10, 11 are provided, coaxially
with respect to said cylindrical projections 7, 8 and
opposite to end faces 5, 6 of piston 4, with one toroid-
like recess in both end faces 26 and 27 of cylinder
chamber 9, within which recesses fuel injection nozzles
28, 29 are located, likewise in a ring-like arrangement.
By way of displacement transducers 30, 31, magnetic
field sensors are arranged within the wall of cylinder 1
~L3~
18
in the areas defined by combustion chambers 10, 11, the
function of ~hich transducers is to control the injec-
tion nozzles 28, 29 and/or the additional or alternative
ignition devices (spark electrodes 128, 12~) as a func-
tion of the position attained by piston 4.
The internal combustion engine according to the inven-
tion and, more specifically, the free-piston engine to
Fig. 1 function as follows:
Either air or a fuel/air mixture is fed into the combus-
tion chambers 10, 11 via ducts 18, 19 and bores 20, 21
of piston 4 and its cylindrical projections 7, 8. In the
first case, nozzles 28, 29 are used to inject fuel, re-
sulting in auto-ignitionl or else ignition is obtained
by means of spark electrodes. In the position of piston
4 shown by Fig~ 1, air or a fuel/air mixture is compres-
sed, within combustion chamber 11, to the volume corres-
ponding to said toroid-shaped recess 84 provided in face
27. The other combustion chamber, 10, contains exhaust
gases leaving via outlet ports 3 provided within the
wall of cylinder 1. Said ducts 18 of piston 4 form an
open flow path connected to inlet ports 2 of said cylin-
der so that, for instance, precompressed air or a com-
pressed fuel/air mixture may flow, via ducts 18 and
bores 20, into combustion chamber 10, flushing out, in
the process, the exhaust gases present within such com-
bustion chamber 10.
From its right-hand position shown in Fig. 1, piston 4
will be driven leftwards upon ignition.
This movement of piston 4 will block outlet ports 3 and,
according to the solution proposed by claim 1, e~en in-
let ports 2 within the wall of cylinder 1 by the lateral
surace of the piston, causing the precompressed air or
fuel/air mixture within combustion chamber 10 to be fur-
ther compressed. The orifices of ducts 18 and bores 20
will~likewise be blocked by this piston movement.
7~
As soon as the piston has reached a predetermined stroke
position, magnetic field sensor 30 will send a control
signal to the system controlling the injection nozzles
28, causing it to inject fuel, or to ignition system
128, causing it to ignite the fuelJair mixture.
As soon as piston 4 has reached its other limit posi-
tion, at left in Fig. 1, the conditions prevailing in
combustion chamber 10 correspond to the conditions shown
on Fig~ 1 for combustion chamber 11. The piston des-
cribes a reciprocating movement transferred to the hy-
draulic medium present within the variable-volume cham-
bers of cylinder bores 12, 13, thus permitting a hydrau-
lic motor or a turbine to be driven.
Fig. 4 shows a block diagram of a system operated by
some pressure fluid to be used with, and linked up to,
the internal combustion engine in accordance with the
invention, preferably configured as a free-piston en-
gine. In Fig. 4, said engine is designated 33. From said
engine, hydraulic lines 34 and 35 lead to hydraulic mo-
tor 36. Within hydraulic lines 34, 35, a cooling device
37 is arranged. Said hydraulic motor 36 acts upon shaft
39 of a system driving, say, a vehicle such as an auto-
mobile. Downstream from, or hierarchically inferior to,
hydraulic motor 36, there is a switchable accumulator
40. From hydraulic line 34, a hydraulic line 42 leads
from branch 41 to a starter unit 43 linked, via another
hydraulic line, to branch 44 o~ hydraulic line 35. Said
starter unit 43 consists of the hydraulic unit 46 that
can be switched from motor to pump operation, and of
dynamo 47 that can be switched to a generator mode and
is operable as a generator, and of battery 48.
~henever internal combustion engine 33 is being started,
dynamo 47 will operate as a motor supplied by battery
48, and drive hydraulic unit 46 switched to pump opera-
tlon, which unit ~ill crank the internal combustion en-
glne.
~pon starting internal combustion engine 33, preferably
as a free-piston engine, said hydraulic unit 46 will
switch to its motor mode and drive dynamo 47, which dy-
namo will, in its generator mode, charge battery 48. If,
by way of example, some vehicle such as an automobile is
braked down, hydraulic motor 36 will operate as a pump
and deliver hydraulic fluid to accumulator 40, thus
storing energy that can be resupplied to hydraulic motor
36 during acceleration. Moreover, internal combustion
engine 33 comprises a compressor 50 delivering fresh air
for combustion purposes, and an accumulator Sl storing
precompressed fresh air that can be supplied to combus-
tion chambers 10, 11.
!
Fig. 2 shows a sectional view of the internal combustion
engine, preferably a free-piston engine, to Fig. 1,
which view demonstrates one possible arrangement and
configuration of suction-sider maximized-surface pres-
sure fluid ducts 81, 82 through longitudinal cylinder
wall 100.
Fig. 3 shows another embodiment of the internal combus-
tion engine according to the invention, once more a
free-piston engine, which engine, as to its central area
of cylinder 1, and as to the pressure fluid pumps at the
ends of such cylinder, is in accordance with the embodi-
ment shown in Fig. 1 so that the corresponding descrip-
tion as to configuration and function given for Fig. 1
is similarly applicable to the section corresponding to
the internal combustion engine within cylinder chamber
9, the environment delimiting said chamber, and the
pressure-fluid pumps located in the terminal areas with-
in cylinder bores 135 and 136, instead of bores 12 and
13 as per Fig. 3. Only as regards seals 14, 15 and 16,
17, small differences are shown insofar as projections
7, 8 bear two annular seals located next to each other
and as piston 4 bears at least one annular seal in radi-
al plane K between bores 90 and ~1.
.
: ~,
13C~!~ii0~7l:1
21
Between the internal combustion engine in the central
area of cylinder 1 comprising piston 4, and the pressure
fluid pump located in the terminal areas of cylinder 1
comprising cylinder bores 135 and 136, the free ends of
the third longitudinal sections 125, 126 of projections
7, 8, the end faces 87, 88, and valves 22 through 25,
all of which correspond as to structure, configuration
and function to the embodiment represented in ~ig. 1,
the embodiment according to Fig. 3 comprises at either
side of said internal combustion engine within cylinder
chamber 9, a compressor integrated into cylinder 1 per-
mitting fresh gas as well as air ~or the internal com-
bustion engine to be precompressed as supplied by said
integrated compressor via inlet ports 2.
Said compressor is formed by compression stages arranged
symmetrically at either side of said cylinder's radial
symmetry plane Z and of said piston's radial symmetry
plane K. Each of said compressor stages is formed by
axial cylinder bores 133, 134 having a diameter superior
to the diameter of cylinder bores 12, 13 and 135, 136,
as well as an axial length superior to the stroke of
piston 4.
In each o said axial cylinder bores 133, 134, one disk-
shaped piston is guided so as to be axially displace-
able, to be sealed with respect to the wall of its bore
by sealing means 14, 15, and so as to be reciprocated
together with piston 4. Either of said disk7shaped pis-
tons comprises asecond, axially short longitudinal sec-
tion, 123 or 124, of said projections 7 or 8, the diame-
ter of which sections is superior to the first and third
longitudinal sections 121, 122 and 125, 126, which dia-
meter corresponds to the diameter of cylinder bores 133,
134 equal, for instance, to the diameter of piston 4 or
to the diameter of cylinder chamber 9.
Said second longitudinal sections 123, 124 of projec-
tions 7, 8, forming a flat, disk-shaped piston will now
automatically be displaced along with any stroke of pis-
~3~;ic17~
22
ton 4, following the same tra~ectory over identical dis-
tances and w.ithout ever touching the ends of cylinder
bores 133, 134 whenever the piston reaches a dead-center
position. The first and third longitudinal sections 121,
122 and 125, 126, axially adjacent to said second longi-
tudinal sections 123, 124 are all sealed within the cor-
responding cylinder bores 12, 13 or 135, 136. At either
end of said cylinder bores 133, 134, there terminate
inlet ports 152, 154, 156, 158, preferably valve-con-
trolled, and outlet ports 151, 153, 155, 157, all of
which ports lead radially through the cylinder wall and
permit pressureless fresh gas and air for combustion
purposes to be fed into said compressor, as well as the
delivery of precompressed fresh gas and air from said
compressor to inlet ports 2.
By way of example, inlet ports 132, 158 and 154, 156 may
be coupled for the purpose of fresh gas supply, just as
outlet ports 151, 157 and 153, 155 may be coupled,
through which precompressed fresh gas may be fed and
guided, possibly under valve control, jointly to said
inlet ports 2.
The function of said compressor equipment is as follows:
Fresh gas and air will be sucked, via possibly valve-
controlled inlet ports 152, 158, into one of the cham-
bers increasing in size within cylinder bores 133, 134
during any stroke of piston 4 until the piston reaches
one of its dead-center positions, while simultaneously
the fresh gas sucked in during the previous-stroke will
be compressed within the space decreasing in size within
cylinder bores 133, 134 for delivery to inlet ports 2
via possibly valve-controlled outlet ports 153, 155.
Once piston 4 has reached either of its dead-center po-
sitions, it will be driven back in the opposite direc-
tion within the engine under the action of expanding
combustion gases; simultaneously, increasing and de-
creasing spaces will alternate automatically within the
:!L3~ 70
23
compression system, just as inlet ports 152, 154, 156,
158 and outlet ports 151, 153, 155, 157 are correspon-
dingly and alternatingly activated, possibly together
with the valves associated with them.
In the case of the solution proposed according to claim
34, precompressed air or a precompressed fuel/air mix-
ture will be guided, directly and continuously, from
said compressor via inlet ports 2 and orifices 90, 91
thereto connected over the entire piston stroke, which
orifices preferably form axially oriented oblong holes,
and into hollow piston 4, where it can be accumulated
under pretensioning pressure for continuous refilling so
that it will invariably be available to flow, directly,
in precompressed form, and without any unnecessary loss
of tension into combustion chambers 10, 11 whenever
bores 20, 21 are opened or unblocked.
