CA1305070C - Internal combustion engine, particularly, a free-piston engine - Google Patents

Abstract

ABSTRACT
Internal combustion engine, more specifically a free-piston engine, having at least one cylinder and a piston arranged therein and guided to be movable and sealed. The piston performs axial stroke movements within cylinder chamber, and features cylindrical pro-jections extending axially spaced from the piston to either side and having at least over part of their length a diameter inferior to the diameter of the piston. The projections are guided at least over some part of their length within axial cylinder bores and therein partially sealed. Combustion chambers are pro-vided within the cylinder, which combustion chambers are formed and delimited by certain parts of the in-side cylinder wall defining cylinder chamber on the one hand and by certain surface parts of piston and its projections on the other hand. The surfaces defining the combustion chambers being formed more particularly by end faces. Inlet ports are arranged in the longitudinal wall to admit air or fuel/air mixtures, and outlet ports are arranged within the longitudinal cylinder wall so as to permit exhaust gases to be expelled. The inlet ports and outlet ports are opening and cleared or covered and closed depending upon the axial position of piston and its projections.

Description

13~t7~ ' I n t e r n a 1 C o m b u s t i o n E n g i n e , =============================~=-=======a=============
Particularly, A Free-Piston Engine =================_=====================
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 ~3~ 7~

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 ~L3~ 71~

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 ~l3~ 7~

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-~3~?5;070 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 ~L~3C~S~7~

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.

.

.
:

~3~p~0t7~

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, ~3C~507~

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.
~' ~3~ 7C~

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.

~L3(~S~:)7~

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;
.~

- .

~3~S0~7~

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, ~L3~S~7~

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 . .

3L3~S~

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 ~3(~07C~

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 .~

~3~5~

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~

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~

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~

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 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~

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 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.

Claims (35)

1. Internal combustion engine, more specifically a free-piston engine, having at least one cylinder (1) comprising one piston (4) therein arranged and guided to be movable and sealed, which piston may perform axial stroke movements within cylinder chamber (9), and fea-turing cylindrical projections (7, 8) extending axially away from said piston (4) to either side and having at least over part of their length a diameter inferior to the diameter of piston (4), said projections (7, 8) be-ing guided at least over some part of their length with-in axial cylinder bores (12, 13) and therein partially sealed; and having combustion chambers (10, 11) within cylinder (1), which combustion chambers are formed and delimited by certain parts of the inside cylinder wall defining cylinder chamber (9) on the one hand and by certain surface parts of piston (4) and its projections (7, 8) on the other hand, the surfaces defining said combustion chambers (10, 11) being formed more particu-larly by end faces (5 and 26, or 6 and 27); and having inlet ports (2) arranged in longitudinal wall (100) to admit air or fuel/air mixtures, and outlet ports (3) arranged withinin longitudinal cylinder wall (100) so as to permit exhaust gases to be expelled, said inlet ports (2) and outlet ports (3) being opened and cleared or covered and closed depending upon the axial position of piston (4) and its projections (7,.8); and having ducts (18, 19) within said piston (4) and its projections (7, 8), which ducts permit the controlled passage of-gases such as air or fuel/air mixtures by forming flow path connections linked to ports (20, 21) located in the la-teral surfaces (101, 102) of projections (7, 8), and which ducts may be brought into open flow connection with, or blocked with respect to, said inlet ports (2), on the one hand, depending upon the axial position of said piston (4) and its projections (7, 8) relative to cylinder (1) while, on the other hand, said ducts may be brought into open flow connection with said combustion chambers (10, 11) via bores (20, 21), or blocked by means of said axial cylinder bores (12, 13) at approxi-mately identical axial piston positions relative to cy-linder (1); and characterized in that said ducts (18 and 19) are arranged, without any flow path connection be-tween them and separately from each other, one each within one of the two longitudinal piston halves (401 and 402) and their projections (7 or 8), located to ei-ther side of a symmetry plane (K) arranged perpendicu-larly with respect to the longitudinal axis (A-A) of piston (4); in that each of said ducts (18 or 19) is connected with the corresponding orifice (90 or 91) lo-cated within the peripheral surface (80) of piston (4), said orifices (90 or 91) being arranged in the area of radial planes (R1 or K2) located parallel to and at dis-tance (a) from said symmetry plane (K) of piston (4); in that all inlet ports (2) located in longitudinal cylin-der wall (100) are arranged in the area of symmetry plane (2) of cylinder (1), which plane is perpendicular to longitudinal axis (A-A); in that said outlet ports (3) for one of the two combustion chambers (10 or 11) associated with one of the two longitudinal halves (401 or 402) of said piston are separate from each other, namely in areas located in radial planes (Z1 or Z2) in parallel to and at a distance (b) with respect to symme-try plane (Z) of cylinder (l); and in that distances (a) of orifices (90 or 91) at either side of symmetry plane (K) of piston (4) as well as distances (b) of said out-let ports (3) at either side of symmetry plane (Z) of cylinder (1) are defined so that all inlet ports (2) may be in open flow path connection with the orifices (90 or 91), ducts (18 or 19), bores (20 or 21), the combustion chamber (10 or 11) and outlet ports (3) associated with one of said longitudinal halves (401 or 402) of said piston whenever the face (6 or 5) of the other longitu-dinal half (402 or 401) is near the inside surface (27 or 26) turned towards it within cylinder chamber (9).

2. Internal combustion engine according to claim 1, wherein the end faces of said projections may act upon a fluid to increase its pressure, characterized in that said fluid consists of a gas or a hydraulic fluid actuating a system operated by a pressure fluid, which system is directly driven by said internal combus-tion engine.

3. Internal combustion engine according to claim 1, characterized in that said combustion chambers (10, 11) both feature toroid-like recesses (83, 84) in their end faces (5, 6 or 26, 27) arranged coaxially with respect to said projections (7, 8).

4. Internal combustion engine according to claim 3, characterized in that said toroid-like recesses (83, 84) are formed within the inside end faces (26, 27) of the cylinder walls defining cylinder chamber (9).

5. Internal combustion engine according to claim 4, characterized in that said toroid-like recesses (83, 84) are formed into the end faces (5, 6) of piston (4).

6. Internal combustion engine according to claim 1, having injection nozzles and/or spark electrodes acting into the combus-tion chambers and arranged within the cylinder end faces delimiting said combustion chambers, characterized in that said injection nozzles (28, 29) and/or spark elec-trodes (128, 129) are located in a ring-shaped arrange-ment surrounding longitudinal axis (A-A).

7. Internal combustion engine according to claim 3, characterized in that said injection nozzles (28, 29) and/or spark electrodes (128, 129) end at said toroid-ike recesses (82, 84).

8. Internal combustion engine according to claim 1, characterized in that said bores (20, 21) on the periphery of projections (7, 8), and/or the inlet ports (2) on the periphery of longitudinal cylinder wall (100), and/or the outlet ports (3) on the periphery of said longitudinal cylinder wall (100) are arranged in a ring-like pattern.

9. Internal combustion engine according to claim 1, characterized in that, in order to control injection and/or ignition tim-ing, displacement transducers (30, 31) located within said cylinder wall are arranged with cylinder (1) in order to capture the axial position of piston (4).

10. Internal combustion engine according to claim 9, characterized in that said displacement transducers (30, 31) are magnetic field sensors operating electrically and delivering a voltage depending upon piston position, which voltage, upon processing by electrically operated components, is used to correlate injection and/or igni-tion timing with the axial position of piston (4) within cylinder (1).

11. Internal combustion engine according to claim 1, characterized in that, within longitudinal cylinder wall (100), the axes of inlet ports (2) are spaced, relative to longitudinal axis (A-A), so that a rotational movement around longi-tudinal axis (A-A) will be superimposed upon the axial travel of piston (4) and its projections (7, 8).

12. Internal combustion engine according to claim 1, characterized in that said ducts 18, 193 are each configured as a single individual duct, or as a bundle of multiple ducts.

13. Internal combustion engine according to claim 12, characterized in that such ducts (18, 19) are formed to have substantially constant flow cross-sections.

14. Internal combustion engine according to claim 1, characterized in that said projections (7, 8) exhibit axially juxtaposed longitudi-nal sections (121 through 126) formed by cylindrical lateral surfaces, such longitudinal sections having dif-fering diameters relative to adjoining longitudinal sec-tions, so that end faces spaced axially and pointing towards, and away from, said piston (4) are formed along said projections (7, 8), such cylindrical lateral surfa-ces of differing diameters being movably and slidingly guided within corresponding axial cylinder bores (l2 and 13, 133 through 136) of appropriate diameters, and so that suitable sealing means (14, 15) are provided be-tween said cylindrical lateral surfaces of differing diameters and the appropriate axial cylinder bares (12 and 13, 133 through 136) therewith associated.

15. Internal combustion engine according to claim 14, characterized in that said projections (7, 8) each have, axially side by side and in a direction away from piston (4), a first longitudinal section (121, 122) having a cylindrical lateral surface and a diameter inferior to the diameter of piston (4), as well as a second longitu-dinal section (123, 124) having a cylindrical lateral surface the diameter of which is superior to the diame-ter of said first longitudinal section (121, 122).

16. Internal combustion engine according to claim 15, characterized in that said projections (7, 8) each have, axially side by side and in a direction away from said piston (4), three sequential longitudinal sections (121 through 126) having a cylindrical lateral surface, the diameter of either terminal longitudinal section (125, 126) formed at the free end of said projections (7, 8) and having a cylindrical lateral surface being again inferior to the diameter of each second longitudinal section (123, 124).

17. Internal combustion engine according to claim 1, wherein the free terminal ends of said projections are plunged, while radially sealed, into an axial cylinder bore delimited at. its terminal end by a face formed by the cylinder, the plunging depth depending upon axial piston positions without, however, having any such free terminal face of said projections reach the face terminating said axial cylinder bore so that, within said cylinder bore, a va-riable-volume chamber is formed between said end faces opposite to each other, within which chamber the termi-nally free face of the corresponding projection acts to increase the pressure of a given volume of fluid, char-acterized in that valve-controlled supply and removal, preferentially controlled via non-return valves or pres-sure-controlled slide valves, of the pressure fluid ac-tuating a system operated by such pressure fluid into and out of said variable-volume chamber within said ter-minal axial cylinder bores (12, 13, 135, 136) is per-formed in a manner so that, by the stroke movements of piston (4) and its projections (7, 8), a pressure fluid pump is formed which pump has two pressure generating chambers and is integrated, together with the internal combustion engine, into said cylinder (1) as a power source actuating a system operated by a pressure fluid.

18. Internal combustion engine according to claim 15 or claim 16, characterized in that said axial cylinder bores (133, 134) designed to receive the two second lon-gitudinal sections (123, 124) of projections (7, 8) have an axial length at least sufficient to permit either of said second longitudinal sections (123, 124) of projec-tions (7, 8) to perform, depending upon the stroke of piston (4), an axial stroke as a disk-shaped piston, which stroke is equal to the maximum possible stroke of piston (4) within cylinder chamber (9).

19. Internal combustion engine according to claim 18, characterized in that bores (151 through 158) piercing the wall of cylinder (1) at the ends of said axial cy-linder bores (133, 134) provided for the second longitu-dinal sections (123, 124) of projections (7, 8), which bores (151 through 158) have associated with, or as-signed to, them controlling valves, preferably non-re-turn valves, pressure-controlled slide valves or, in a particularly preferable embodiment, valves under exter-nal open or closed-loop control, said bores (151, 153, 155 and 157) serving as outlets and bores (152, 154, 156 and 158) as inlets for a fluid, and every pair of one inlet and one outlet bore (151, 152 or 153, 154 or 155, 156 or 157, 158), preferentially leading perpendicularly into the cylinder bores (133, 134) of said second longi-tudinal sections (123, 124), is assigned to one vari-able-volume chamber within cylinder bores (133, 134), which chamber is hermetically sealed with respect to the other chambers within cylinder (1), each of said cylin-der bores (133, 134) being subdivided into two axially adjacent chambers of negatively correlated, variable capacity by said second longitudinal sections (123, 124) forming separating, disk-shaped pistons.

20. Internal combustion engine according to any one of the other claims, characterized in that supply and remo-val of pressure fluid to and from said variable-volume chamber within either axially outermost and axially ter-minal cylinder bores (12, 13 or 135, 136) is caused by said terminal end faces (87, 88) formed by cylinder (1), the valves (22, 23, 24 and 25) controlling said supply and removal of pressure fluid being preferably integra-ted into said end faces (87, 88) of the cylinder wall.

21. Internal combustion engine according to claim 1, characterized in that the hydraulic or pneumatic pressure fluid has the subsidiary function of cooling cylinder (1), in a particularly preferential embodiment in the area of the combustion engine, i.e.
the walls around cylinder. chamber (9).

22. Internal combustion engine according to claim 21, characterized in that the hydraulic or pneumatic pres-sure fluid is fed, at low pressure, into cylinder (1) of said engine on its suction sides at both ends of said cylinder (1), in that such pressure fluid is led at ei-ther end face area of cylinder (1) to pressure fluid ducts (81, 82), said ducts preferably being large-sur-face ones, and axially run towards the opposite terminal end of the cylinder through longitudinal cylinder wall (100), at which opposite ends said pressure fluid may enter, under valve control, via bores and valves into the axially outermost variable-volume chambers within either terminal cylinder bore (12, 13 or 135, 136) while the pressure fluid may leave, at increased pressure (through pressure piping) the variable-volume chambers located within the terminal cylinder bores (12, 13 or 135, 136) via the corresponding outlet valve (22, 24) and exit from cylinder (1) in a directly axial direction at the same end face of the cylinder via one of outlets (85 or 86).

23. Internal combustion engine according to claim 22, characterized in that the end faces (87, 86) formed by the cylinder wall are made up out of at least two wall areas located parallel to each other and preferably con-sisting of sealed cylinder wall components arranged ad-jacent to each other, the exterior terminal wall area comprising the pressure fluid connections leading to the system operated by said pressure fluid, while the adja-cent wall area parallel to the first one but located axially further towards the interior transfers suction-side supplies into the pressure fluid ducts (81, 82) comprise the inlet (23, 25) and outlet (22, 24) valves and direct suction-side supplies arriving from the other end of the cylinder through pressure fluid ducts (81, 82) via the corresponding inlet valve (23, 25) into the axially exterior, variable-volume chamber of the corres-ponding cylinder bore (12, 13 or 135, 136).

24. Internal combustion engine according to claim 1, characterized in that precompressed air or a precompressed fuel/air mix-ture is supplied to said internal combustion engine via some other, separate compressor unit (50), preferably an accumulator (51), through said inlet ports (2).

25. Internal combustion engine according to claim 1, wherein the end faces of said projections alternatingly act to compress a temporarily enclosed volume of air before said air is supplied to the corresponding combustion chamber of said internal combustion engine, characterized in that any air or fuel/air mixture intended to fill the combustion chambers (10, 11) of said engine through inlet ports (152, 154, 156, 158) may be introduced into the corres-ponding axial cylinder bore (133 or 134) of the appro-priate second longitudinal section (123 or 124) of the corresponding projection (7 or 8) for precompression, within one of said cylinder bores (133 or 134), by the stroke of one of said second longitudinal sections (123 or 124) depending upon the movements of piston (4), and for transfer to inlet ports (2) via outlet ports (151, 153, 155, 157) and connecting ducts.

26. Internal combustion engine according to claim 1, the engine acting to precompress air or a fuel/air mixture via the front faces of its projections, the precompressed fluid being supplied to the combustion chambers via ducts within the piston, characterized in that, at least one, but prefer-ably two or four variable-volume chambers within cylin-der bores (133, 134) of said second longitudinal sec-tions (123, 124) of projections (7, 8) are used for pre-compression purposes, and that their outlet ports (151, 153, 155, 157) may be in connection with inlet ports (2) within longitudinal cylinder wall (100).

27. Internal combustion engine according to claim 26, characterized in that, during any stroke of piston (4) and said second longitudinal section (123 or 124) of projections (7, 8) the two outlet ports (151 and 157 or 153 and 155) located at either side of symmetry plane (Z) and assigned to the corresponding variable-volume chamber of cylinder bores (133 or 134) being reduced in size are jointly linked to the corresponding inlet ports (2).

28. Internal combustion engine according to one of claims 19, 25, 26, or 27, characterized in that valves are assigned to said bores (151 through 158), which valves are preferentially built into said bores (151 through 158) or into longitudinal cylinder wall (100), in that at least some of the valves assigned to bores (151 through 158) are used for manual or automatic open or closed-loop control of the volume of gas filling the corresponding combustion chamber and, for this pur-pose, said open or closed-loop control valves are fit-ted, if necessary, with an exhaust air connection as well as with manual or automatic control means.

29. Internal combustion engine according to one of claims 18 or 25, characterized in that said projections (7, 8) each feature two longitudinal sections (121 and 123, 122 and 124), the first of which sections (121 or 123) have a diameter inferior to the diameter of piston (4), while the corresponding second longitudinal section (122, 124) have a diameter superior to the diameter of said first longitudinal section (121 or 122), the cor-responding, axially outermost variable-volume chamber within the appropriate cylinder bore (133 or 134) being used to increase the pressure of a hydraulic or pneuma-tic pressure fluid actuating a system operated by such pressure fluid, said terminal chamber being linked up to pressure fluid connections (81, 82, 85, 86) and valves (22 through 25), and the axially outermost free terminal face of projections (7, 8), simultaneously constituting the large-size end face of said second longitudinal sec-tion (123 or 124), acting to increase the pressure of said fluid contained within the corresponding terminal chamber, while the smaller end of said second longitudi-nal section (123, or 124) facing piston (4) is used, within the adjacent, negatively-correlated variable-vo-lume chamber within said axial cylinder bore (133 or 134), to precompress the air or the fuel/air mixture to be fed into said combustion chambers (10, 11).

30. Internal combustion engine according to claim 18, its axially terminal cylinder bores being used to pre-compress air or fuel/air mixture intended to fill the combustion chambers of the engine, characterized in that said axial cylinder bore (133 or 134) is configured to be fitted with valve-controlled pressure-fluid inlets and outlets, and constitutes, together with said second, larger-diameter longitudinal section (123 or 124) of the corresponding projection (7, 8), an alternating piston pump for a system operated by a pressure fluid.

31. Internal combustion engine according to claim 2, characterized in that said internal combustion engine (33), specifically if configured as a free-piston engine, is used, within a system actuated by a hydraulic or pneumatic pressure fluid, together with a hydraulic or pneumatic drive unit (46) switchable from motor to pump operation and vice-versa, said drive unit (46) being coupled to an electrically driven unit (47) switchable from starter to dynamo operation and vice-versa, and including a battery (48) which unit, in order to crank internal combustion engine (33), may be switched to its starter mode, while other-wise it is in its dynamo mode, linked up to a hydraulic or pneumatic motor (36) and an accumulator (40).

32. Internal combustion engine according to claim 1, characterized in that said piston (4) is configured as a free piston.

33. Internal combustion engine according to claim 1, said engine having a direct mechanical drive connection acting axially via an articulated, directly linked mechanical transmission member, characterized in that said internal combustion engine has axial, mechanical driving lines at either side via articulated mechanical transmission mem-bers.

34. Internal combustion engine, more specifically a free-piston engine, having at least one cylinder (1) comprising one piston (4) therein arranged and guided to be movable and sealed, which piston may perform axial stroke movements within cylinder chamber (9), and fea-turing cylindrical projections (7, 8) extending axially away from said piston (4) to either side and having at least over part of their length a diameter inferior to the diameter of piston (4), said projections (7, 8) be-ing guided at least over some part of their length with-in axial cylinder bores (12, 13) and therein partially sealed; and having combustion chambers (10, 11) within cylinder (1), which combustion chambers are formed and delimited by certain parts of the inside cylinder wall defining cylinder chamber (9) on the one hand and by certain surface parts of piston (4) and its projections (7, 8) on the other hand, the surfaces defining said combustion chambers (10, 11) being formed more particu-larly by end faces (5 and 26, or 6 and 27); and having inlet ports (2) arranged in longitudinal wall (100) to admit air or fuel/air mixtures, and outlet ports (3) arranged withinin longitudinal cylinder wall (100) so as to permit exhaust gases to be expelled, said outlet ports (3) being opened and cleared or covered and closed depending upon the axial position of piston (4) and its projections (7, 8); and having ducts (18, 19) within said piston (4) and its projections (7, 8); which ducts permit the passage of gases such as air or fuel/air mix-tures by forming flow path connections linked to ports (20, 21) located within the lateral surfaces (101, 102) of projections (7, 8), said ducts (18, 19) occupying the space within said piston and within both projections (7, 8), being in continuously open flow connection with each other and capable of being linked by an open flow path connection with inlet ports (2), as well as capable of being linked, via bores (20, 21), by an open flow path connection with said combustion chambers (10, 11), or else of being blocked by axial cylinder bores (12, 13);
and characterized in that said ducts (18 and 19) are linked, in a permanently open flow path connection with said inlet ports (2); in that said ducts (18, 19) are in connection with orifices (90 or 91) located within the peripheral surface (80) of piston (4), said orifices being arranged in the central axial area of piston (4) and in a preferentially symmetrical arrangement relative to symmetry plane (K), said orifices (90, 91), or said inlet port (2), or at least a recess (such as a groove) located between peripheral piston surface and longitudi-nal cylinder wall (100), extending axially and in paral-lel to said cylinder axis (A-A) over an axial distance corresponding approximately to the length of piston (4), said symmetry plane (K) being preferentially located centrally relative to the longitudinal extension of ori-fices (90, 91) or of said recesses within the peripheral surface of piston (4), or else said symmetry plane (Z) being preferentially located centrally relative to the longitudinal extension of inlet ports (2) or of said recesses in the peripheral surface of cylinder chamber (9); in that all inlet ports (2) located in longitudinal cylinder wall (100) are arranged in the area of symmetry plane (Z) of cylinder (1), which plane is perpendicular to longitudinal axis (A-A); in that said outlet ports (3) for one of the two combustion chambers (10 or 11) associated with one of the two longitudinal halves (401 or 402) of said piston are separate from each other, namely in areas located in radial planes (Z1 or Z2) in parallel to and at a distance (b) with respect to symme-try plane (Z) of cylinder (l); and in that distances (a) of orifices (90 or 91) at either side of symmetry plane (K) of piston (4) as well as distances (b) of said out-let ports (3) at either side of symmetry plane (Z) of cylinder (1) are chosen so that all inlet ports (2) may be in open flow path connection with orifices (90 or 91) or ducts (18 or 19) as well as with the bores (20 or 21) associated with one of said longitudinal halves (401 or 402) of said piston, the combustion chambers (10 or 11) and outlet ports (3) whenever the face (6 or S) of the other longitudinal half (402 or 401) is near the inside surface (27 or 26) turned towards it within cylinder chamber (9).

35. Internal combustion engine according to claim 34, characterized in that said orifices (90, 91) are oblong holes arranged in parallel to each other and with res-pect to cylinder axis (A-A), the center lines of which oblong holes being arranged in parallel to axis (A-A) within symmetry plane (K) of said piston.

Legend Saugleitung = suction line Schnitt A-B = section A-B