DE102013106792A1 - Free piston device and method for operating a free piston device - Google Patents

Abstract

The invention relates to a free piston device, comprising at least one free piston engine, which comprises at least one linearly movable piston device and a piston receptacle. The piston receptacle has expansion chambers and expansion spaces formed by them, which are delimited by working pistons of the piston device. The free-piston engine comprises a spring-back device for providing a spring-back force for the piston device. A control and / or regulating device enables the control and / or regulation of work cycles of the working pistons. The working pistons are mechanically coupled to one another to provide a movement of a working piston as a function of a movement of the other working piston. With the control and / or regulating device, a four-stroke operation of both working pistons can be controlled and / or regulated, the working strokes of the working pistons being delayed by two working strokes of the four-stroke operation. The invention also relates to a method for operating a free piston device.

Description

The invention relates to a free-piston device, comprising at least one free-piston engine comprising at least one linearly movable piston device and a piston receptacle, the piston receptacle having a first expansion chamber forming a first expansion chamber and a second expansion space forming the second expansion chamber for respective expansion of a working medium, wherein the at least a piston device having a first expansion chamber limiting the first working piston and the second expansion space limiting second working piston, the free piston engine further comprises a return spring means for providing a return spring force for the at least one piston device and wherein the free piston device comprises a control and / or regulating device for controlling and / or rules of power strokes of the first working piston and the second working piston.

Moreover, the invention relates to a method for operating a free-piston device.

Free piston devices are for example from the DE 102 19 549 A1 , of the DE 102 42 141 A1 , of the DE 10 2006 029 532 A1 and the DE 10 2011 000 620 A1 known. Under the action of an expanding working medium, in particular a fuel-air mixture, a working piston can be moved and the occurring mechanical kinetic energy of the at least one piston device can be removed by an energy coupling device. The fuel is for example gasoline, diesel, hydrogen or methane, and instead of air, another oxidizer can be used. The energy coupling device is in the case of the above-mentioned documents in each case an electric linear drive, with which the mechanical energy can be converted into electrical energy.

Normally, free-piston devices are operated in a two-stroke process, but this entails disadvantages. For a reliable flushing of the expansion space with working medium, an overpressure of the incoming working medium is required, which is why in practice a compressor or a charging device is used. However, this requires a higher technical and energy costs. It also proves to be disadvantageous that the charge change in the second power stroke must take place within a short period of time, which is disturbing especially at high operating frequencies of the free piston device. This can undesirably remain high residual amounts of unburned working medium in the expansion space. This affects the performance of the free-piston engine whose operating point is not optimally adjustable.

To overcome the above disadvantages, it is also known to operate free-piston devices in a four-stroke process, as for example in the DE 10 2011 000 620 A1 is mentioned. Due to the design, however, disadvantages also occur. While in the third working cycle (working) of the working piston is moved under the action of the expanding working medium and in the second and fourth working cycle (compression, ejection) under the action of the return spring device, it requires an energy coupling device to move the working piston in the first power stroke (suction) , For this purpose, it is necessary to provide energy, for example, by embodiments of the energy coupling device as a linear electric drive. For example, this is done in that during the third working cycle of the piston device energy is removed and stored temporarily, which is fed back to the piston device during the intake stroke. However, this is disadvantageous since a multiple conversion of energy occurs, also shows in practice that such a linear actuator must be dimensioned so that during the third and fourth working cycle substantially all of the energy released during the expansion of the working medium can be converted , so the linear drive must be designed for high performance. However, the linear drive is underutilized in the remaining work cycles.

Object of the present invention is to provide a free-piston device of the type mentioned, with a higher efficiency can be achieved, and to provide a method for operating such a free-piston device.

This object is achieved in a generic free piston device according to the invention in that the first piston and the second working piston are mechanically coupled to each other to provide movement of a working piston in response to movement of the other working piston and that with the control and / or regulating device a four-stroke operation of first working piston and the second working piston can be controlled and / or regulated, wherein the working cycles of the first working piston and the second working piston are time-delayed by two power strokes of the four-stroke operation.

"Time-shifted by two work cycles" can in this case be understood in particular as meaning that the working cycle of one working piston follows the working cycle of the respective other working piston for two cycles or leads two cycles. As a result, the working cycles of the working piston can differ by two power strokes of the four-stroke operation. For example, a working piston, the first power stroke and the other working piston perform the third power stroke and vice versa, and a working piston, the second power stroke and the other working piston perform the fourth power stroke and vice versa. In the free-piston device according to the invention, it is provided that the working pistons are mechanically coupled to one another, the free-piston device, as it were, comprises a mechanical coupling device for coupling the working pistons to one another. By the movement of a working piston, a movement of the respective other working piston can be effected by the mechanical coupling. Since the control and / or regulating device can control and / or regulate the operation of each working piston in a four-stroke process, this gives rise to the possibility of operating the free-piston device as a whole energetically and advantageously with respect to the pollutant emissions in a four-stroke process. If a working piston executes the power stroke, the mechanical coupling causes the other working piston to move simultaneously in the intake stroke. In a corresponding manner, a coupled movement can take place, in which one working piston executes the ejection stroke and the other working piston carries out the compression stroke. In contrast to the prior art explained in the introduction, in particular it is not necessary to maintain the four-stroke process using an energy coupling device. This has an advantageous effect on the operating point of both working pistons and thus of the free piston device as a whole, with which a higher efficiency can be achieved in this way.

The working cycles of the two working pistons may in particular have the same respective duration.

It is advantageous if the control and / or regulating device for controlling and / or regulating the working cycles of the first working piston and the second working piston is in operative connection with a valve device arranged on the first expansion chamber and / or the second expansion chamber. The valve device comprises, for example, at least one inlet valve and at least one outlet valve at each expansion chamber, via which the working medium can be admitted into the expansion space or can be discharged therefrom.

The control and / or regulating device can advantageously be in operative connection with an ignition device arranged on the first expansion chamber and / or the second expansion chamber, with which the working medium can be ignited in the first expansion space or second expansion space.

The control and / or regulating device can also be in operative connection with an injection device arranged at the first expansion chamber and / or the second expansion chamber, via which the working medium is injected directly into the expansion space.

The control and / or regulating device can also be in operative connection with a mixing device for providing the working medium as a fuel-oxidizer mixture, so that the mixing ratio can be controlled and / or regulated.

The control and / or regulating device can also be in operative connection with a charging device, for example a turbocharger, for providing a volumetric flow of the working medium or its pressure increase.

It is advantageous if the stroke of the first working piston and the second working piston is the same and / or if the stroke of the first working piston and the second working piston is controllable and / or controllable. For example, a control and / or regulation of the stroke during operation of the free-piston device is possible. For this purpose, for example, an electric linear generator (linear drive) can be used.

In a structurally simple embodiment, the first working piston and the second working piston is movable from a respective top dead center to a respective bottom dead center, and the position of the respective top dead center and / or the respective bottom dead center is, preferably in operation of the free piston device, controllable and / or controllable. For this purpose, for example, an electric linear drive can be used.

It is advantageous if the at least one piston device comprises or forms a coupling device for coupling the first working piston to the second working piston. As a result, a structurally simple embodiment can be achieved in which the coupling device is part of the at least one piston device and can move together with it.

In an advantageous embodiment of the free-piston device according to the invention, it is advantageous if the expansion chambers and the working piston arranged therein are arranged side by side and the first working piston and the second working piston are preferably movable parallel to one another. With a structurally simple design, a compact design of the free-piston device can be achieved.

Preferably, the first piston and the second piston are rigidly coupled together. In the present case, this can be understood in particular to mean that the first and second working pistons are immovable relative to one another, independently of the working stroke of each working piston. The rigid coupling allows a structurally simple design and reliable operation of the free-piston device.

It is advantageous if piston support elements fixed to the first working piston and the second working piston are firmly connected to one another via a coupling element. The piston bearing elements are, for example, fixed to the piston working piston rods, which are fixedly connected at their opposite sides of the working piston via the coupling element, so that a firm connection of the working piston can be achieved with each other. The coupling element is, for example, aligned transversely to an axis of the free-piston device, along which the at least one piston device is movable. The working piston can move synchronously axially and thus parallel to each other under the coupling by the coupling element.

It is advantageous if the at least one piston device comprises a return spring piston which is fixed on a further piston supporting element on a side opposite the first working piston and the second working piston on the coupling element, wherein the return spring piston limits a resilience space of the return spring device. The return spring means, which will be discussed in more detail below, may comprise a springback bounded by a return spring piston. The return spring piston can be fixed on the coupling element via a further piston-carrying element, in particular in the form of a piston rod. This gives the possibility to exert a spring-back force on the first working piston and the second working piston at the same time. Furthermore, a compact design of the free-piston device can be achieved.

It is advantageous if the further piston-carrying element, based on an axis defined by the free-piston device, is arranged centrally between the first working piston and the second working piston. This allows the mass of moving components to be distributed more evenly. The requirements on the mechanical strength of the components of the free-piston device can be reduced. Ideally, a smoother and smoother running of the free piston device is made possible.

In a further advantageous embodiment of the free-piston device according to the invention, it is favorable if the first working piston and the second working piston are movably coupled to one another and are movable relative to one another.

For example, it is favorable if the at least one piston device comprises a first section having the first working piston and a second section having the second working piston, which are each movable along an axis of the free piston device, and if the sections are under the control and / or regulation of the working cycles of Working piston relative to each other are gegengleich movable. The first and the second section preferably each comprise a working piston and a piston carrier element fixed thereto, for example in the form of a piston rod. The sections are aligned coaxially with each other and can move axially counterparts (antiparallel) in controlling the working cycles of the working piston by means of the control and / or regulating device, wherein they are axially spaced from each other. The working pistons are movably coupled to each other in this embodiment, wherein by a movement of a working piston, a movement of the respective other working piston can be effected. In the present embodiment, it is also possible to distribute the mass of moving components as evenly as possible, thereby reducing the mechanical strength of the components and ideally to achieve a quieter and more uniform operation of the free-piston device.

It proves to be favorable when the first working piston and the second working piston are arranged on a side facing away from the other second or first portion of the first and the second portion. This makes it easier to mechanically couple the first portion and the second portion, for example on sides facing each other.

It proves to be advantageous if the at least one piston device comprises a distance changing mechanism for providing a different distance of the first portion and the second portion from each other depending on the working cycle of the working piston. By the distance changing mechanism, a movable coupling of the working piston and a relative movement of the piston can be ensured to each other.

For example, it may be provided that the first section and the second section occupy a minimum distance from each other when the working pistons occupy a respective bottom dead center and occupy a maximum distance from each other when the working pistons occupy a respective top dead center, in particular in the Previously mentioned advantageous embodiment of the free-piston device according to the invention.

In a structurally simple implementation of the free-piston device in practice, it proves to be advantageous if the distance change mechanism comprises a joint member which is rotatably mounted on the first portion and the second portion each about a transversely oriented axis of rotation axis, wherein the axes of rotation on opposite sides the axis are arranged. As used herein, "transverse to axis" means that the axes of rotation perpendicularly intersect a plane containing the axis of the free piston device. The hinge element is pivotally mounted on the first and second portions each about a rotation axis, wherein the rotation axes are arranged on different sides of the axis. The hinge member may thereby extend from one side of the axle to the opposite side of the axle and intersect a plane containing the axis of the free piston device and aligned parallel to the axes of rotation. In a movement of the first portion, caused by a movement of the corresponding working piston, the joint member can be pivoted about the respective axes of rotation, thereby causing a movement of the second portion and the second working piston, and vice versa.

It proves to be advantageous if the joint element is rotatably fixed to the at least one piston receptacle or to a housing of the free-piston engine about a rotational axis aligned transversely to the axis. By fixing to the piston receptacle or the housing, a more reliable operation of the free piston device can be achieved, in which the joint element is fixed to the device.

In another advantageous embodiment of the free-piston device according to the invention, it is favorable if the distance-changing mechanism comprises at least one pair of articulated elements, one of which is rotatably fixed to the first section and the second section and which are rotatably connected to each other, wherein the axes of rotation are aligned transversely to the axis , If the articulation elements pivot relative to the first or second section and relative to one another, the spacing of the sections can be changed from one another and thereby a relative movement of the working pistons can be achieved by mechanical coupling.

Preferably, two pairs of hinge elements are provided, with the pairs of hinge elements facing each other with respect to the axis. For example, the pairs of hinge elements are arranged symmetrically with respect to each other with respect to the axis.

The joint or joints, in which the joint elements are connected to each other, are preferably movable transversely to the direction of movement of the piston device in at least one guide of the free-piston device.

It proves to be favorable if the return spring device comprises or forms at least one gas spring device, wherein the piston receptacle has at least one return spring chamber, in which at least one resilience space is formed, and if the at least one piston device comprises at least one return spring piston which delimits the at least one resilience space is coupled to the first working piston and / or the second working piston via at least one piston bearing element. The gas spring device allows, for example, to adjust the operating point of the free-piston engine, wherein in particular an adjustment during operation of the free-piston device is possible. The adjustment of the operating point is effected in particular by adjusting the return spring force of the gas spring device, as for example in the DE 10 2011 000 620 A1 or DE 10 2006 029 532 A1 is described.

A gas taken up in the rebound chamber can be compressed under the action of the return spring piston. In the subsequent expansion, a return spring force can be exerted on the return spring piston and a piston-carrying element of the same, for example a piston rod. The piston rod may comprise a working piston at an end opposite the return spring piston. It is also conceivable, as explained above, that the piston-carrying element is connected to a coupling element which is mechanically coupled to one another by two working pistons.

Alternatively or in addition to a gas spring device, the return spring means may be mechanically formed, for example comprise a mechanical spring.

It is advantageous if the return spring device comprises a first return spring unit which is assigned to the first working piston and a second return spring unit which is assigned to the second working piston, wherein each return spring unit is connected to the piston by means of a return spring piston which is connected to one of the working pistons via a piston bearing element respective working piston acts. Each return spring unit may comprise a springback chamber, a resilience space, and a return spring piston disposed therein. Each return spring piston is connected to one of the working pistons via a piston-carrying element, in particular a piston rod. As a result, each return spring unit can provide a spring-back force for itself, which acts on the respective working piston.

In another advantageous embodiment, it can be provided that the return spring device is assigned to the first working piston and the second working piston together and acts via a return spring piston on a piston supporting element, which is coupled with two working pistons. As mentioned above, the restoring force can be exerted via a piston supporting element fixed to the return spring piston, in particular to the above-mentioned coupling element, which in turn is connected to the piston carrying elements of the working piston. In this embodiment, both working piston associated with a common return spring means, in which only a spring-back chamber and a resilience space can be used.

In a further advantageous embodiment of the free-piston device according to the invention, in which the return spring device comprises or forms at least one gas spring device, it can be provided that a resilience space is formed by the first expansion chamber and / or the second expansion chamber, wherein the expansion space of the expansion chamber and the resilience space with respect to a Volume change are inverse to each other. A volume change of the expansion space of the expansion chamber may be in synchronism with a volume change of the resilience space in the same expansion chamber, wherein an increase in volume of the expansion space causes a decrease in the volume of the resilience space, and vice versa.

The resilience space is preferably delimited by a return spring piston of the piston device, the return spring piston particularly preferably being formed by the working piston in the expansion chamber, in which the expansion space and the resilience space are formed. During a movement of the working piston, the volume of the expansion space and the volume of the resilience space can be changed synchronously and inversely to one another, and this in a structurally simple manner. The working piston can define the expansion space with a first side of the piston and the return spring space with a second side of the piston opposite the first side of the piston. In addition, a compact design of the free-piston engine can be achieved.

Particularly preferably, both expansion chambers are designed such that they form an expansion chamber and a resilience space, wherein the first expansion space, a first resilience space and the second expansion space, a second resilience space are assigned.

As already mentioned, it is favorable if the return spring force exerted by the return spring device can be controlled and / or regulated during operation of the free piston device, as described, for example, in US Pat DE 10 2011 000 620 A1 or the DE 10 2006 029 532 A1 is described.

It is advantageous if the at least one free-piston engine comprises an energy coupling device for discharging and / or coupling energy from or into the at least one piston device. The energy coupling device makes it possible to decouple mechanical kinetic energy of the at least one piston device by conversion. Alternatively or additionally, energy can be converted via the energy coupling device into mechanical kinetic energy into the at least one piston device. The energy coupling device can be designed in many ways, for example electrically, mechanically, pneumatically and / or hydraulically.

In a structurally simple embodiment, it is advantageous if the energy coupling device comprises at least one electric linear drive with a coil arrangement and a magnet arrangement movable relative thereto. The electric linear drive (linear generator) makes it possible to convert the mechanical energy into electrical energy, which can be easily stored in a constructive way. Conversely, electrical energy can be converted into mechanical energy via the linear drive, into which at least one piston device is coupled.

Preferably, the coil assembly is arranged stationary to the piston receiving, and the magnetic order is fixed to a piston supporting member of a working piston. As a result, a structurally simple embodiment of the linear drive can be achieved. The magnet arrangement may comprise magnets arranged alternately in a poleward direction along the axis, which magnets may cooperate with stationary coils arranged approximately on the piston receptacle or on a housing of the free-piston device.

It proves to be advantageous if the movement of the at least one piston device can be controlled and / or regulated by means of the energy coupling device during operation of the free piston device. This makes it possible to set an operating point of the at least one free-piston engine in its operation. For this purpose, the energy coupling device can be in operative connection with the control and / or regulating device.

It is favorable if the energy coupling device comprises a first energy coupling unit, which is assigned to the first working piston, and a second energy coupling unit, which is assigned to the second working piston, wherein each Energy coupling unit is arranged on a piston support member of the respective working piston and cooperates with this. For example, it is provided that a magnet arrangement is fixed to each piston piston associated with a working piston, which cooperates with a stationary coil arrangement. The movement of each working piston can be used by itself to decouple its mechanical kinetic energy, or energy can be coupled into the at least one piston device.

In another advantageous embodiment, it is favorable if the energy coupling device is assigned to the first working piston and the second working piston, wherein the energy coupling device is arranged on a piston supporting element for the first working piston and the second working piston.

It is advantageous if the free piston device comprises a first free piston engine and a second free piston engine, which are identical or substantially identical and which are arranged so that they are symmetrical or substantially symmetrical to each other with respect to a plane of symmetry, which plane of symmetry perpendicular to an axis of Free piston device is along which the respective at least one piston device is movable.

It is advantageous if the working cycles of the working piston are controllable and / or controllable via the control and / or regulating device such that the at least one piston device of the first free-piston engine and the at least one piston device of the second free-piston engine are movable in opposite directions. This makes it possible to ensure a mass and torque compensation in the free-piston device. The free-piston engines are arranged symmetrically relative to each other, that the respective piston devices can be moved against the same axial, each free-piston engine comprises two working pistons, which are mechanically coupled and the power strokes are time-offset by two power strokes of the four-stroke operation. In the present embodiment, in particular, the power strokes of the free-piston engines are identical, i. H. to each working piston of a free-piston engine, there is a working piston of the other free piston engine, which executes the same power stroke.

As mentioned above, the invention also relates to a method for operating a free-piston device. An inventive method, which solves the object set initially, is characterized in that a free-piston device of the type described above is operated so that the control and / or regulating device controls a four-stroke operation of the first working piston and the second working piston and / or regulated, wherein the working cycles of the first working piston and the second working piston are time-delayed by two working cycles of the four-stroke operation.

The advantages already described in connection with the explanation of the free-piston device according to the invention can be achieved using the method. In this regard, to avoid repetition, reference is made to the above explanations.

In particular, it can be provided that advantageous embodiments of the method according to the invention are used, the features of which have already been mentioned in connection with the explanation of advantageous embodiments of the free-piston device according to the invention. To avoid repetition, reference is also made in this respect to the above explanations.

• – eine an der ersten Expansionskammer und/oder der zweiten Expansionskammer angeordnete Ventileinrichtung;
• – eine an der ersten Expansionskammer und/oder der zweiten Expansionskammer angeordnete Zündeinrichtung;
• – der ersten Expansionskammer und/oder der zweiten Expansionskammer angeordnete Einspritzeinrichtung;
• – eine Mischeinrichtung zum Bereitstellen des Arbeitsmediums als Brennstoff-Oxidator-Gemisch;
• – eine Ladeeinrichtung zum Bereitstellen eines Volumenstroms des Arbeitsmediums.

In particular, it is expedient for the control and / or regulating device for controlling and / or regulating the working cycles of the first working piston and the second working piston to control and / or regulate at least one of the following:

• - A arranged on the first expansion chamber and / or the second expansion chamber valve means;
• - An arranged on the first expansion chamber and / or the second expansion chamber ignition device;
• - the first expansion chamber and / or the second expansion chamber arranged injection device;
• - A mixing device for providing the working medium as a fuel-oxidizer mixture;
• - A charging device for providing a volume flow of the working medium.

The following description of preferred embodiments of the invention is used in conjunction with the drawings for a more detailed explanation of the invention. Show it:

1 a schematic representation of a first preferred embodiment of a free-piston device according to the invention;

2 a schematic representation of a second preferred embodiment of a free-piston device according to the invention;

3 a schematic representation of a third preferred embodiment of a free-piston device according to the invention;

4 a schematic representation of a fourth preferred embodiment of a free-piston device according to the invention and

5 : A schematic representation of a fifth preferred embodiment of a free-piston device according to the invention.

1 shows a schematic representation of a total with the reference numeral 10 occupied advantageous embodiment of a free piston device according to the invention. It includes a free-piston engine 12 holding a piston 14 has, for example, by a not shown in the drawing housing the free piston device 10 is formed. In the piston receptacle 14 is a piston device 16 along an axis defined by it 18 arranged linearly movable.

In the free piston device 10 includes the piston device 16 a first working piston 20 and a second working piston 22 , The working pistons 20 and 22 are on piston bearing elements 24 respectively 26 set, which are designed in this case as piston rods. At her the working piston 20 . 22 opposite ends are the piston rods 26 through one of the piston means 16 comprising coupling element 28 firmly connected to each other, which is perpendicular to the axis 18 is aligned. In this way, the working pistons 20 and 22 rigidly coupled with each other.

The piston device 16 further comprises a return spring piston 30 that is attached to a piston carrier 32 is set, in this case also designed as a piston rod. The piston rod 32 is at her the recoil piston 30 opposite end fixed to the coupling element 28 connected. The piston rod 32 defines the axis 18 ,

The piston receiver 14 has two laterally juxtaposed expansion chambers 34 and 36 on, the expansion spaces 38 respectively 40 form. The working pistons 20 and 22 limit the expansion areas 38 respectively 40 each with a piston side. The expansion spaces 38 and 40 In the present case, in particular combustion chambers in which a working medium can burn, around the working pistons 20 and 22 to move and thus the piston device 16 drive. The working medium is a fuel with oxidizer (in particular air), wherein as fuel, for example, gasoline, diesel, hydrogen or methane can be used.

In the present case, every expansion chamber is on the front side 34 . 36 an inlet 42 and an outlet 44 arranged, to which a supply line 43 or a discharge line 45 are connected. There may be more than one inlet and one delivery line and more than one outlet and discharge line. About the inlet 42 can the working fluid in the respective expansion chamber 34 . 36 be coupled. About the outlet 44 can combustion products and unburned working medium from the respective expansion chamber 34 . 36 be dissipated.

At the respective inlet 42 is a valve 46 arranged, via a control line 47 with a control and / or regulating device 48 the free piston device 10 is in active connection. Under control by the control and / or regulating device 48 can the inlet 42 controlled open and locked. At the respective outlet 44 is a valve 50 arranged, via a control line 51 with control and / or regulating device 48 is in active connection. The outlet 44 can thereby be controlled open and lock.

Next is at each expansion chamber 34 . 36 , For example, the front side, an ignition device 52 arranged. The ignition device 52 is via a control line 53 with the control and / or regulating device 48 in active connection. By appropriate control of the control and / or regulating device 48 can the respective ignition device 52 the working medium in the respective expansion area 38 . 40 ignite, whereupon this burns and the power pistons 20 . 22 drives. In this case, the respective working piston 20 . 22 be moved from a top dead center OT to a bottom dead center UT.

In the free piston device 10 it is possible that the control and / or regulating device 48 the valves 46 . 50 and the ignition device 52 the expansion chambers 34 . 36 independently of each other. This allows a respective power stroke of the working piston 20 . 22 set separately. In particular, it is possible the working cycles of the working piston 20 . 22 to be controlled so that they each perform four work cycles, the free piston device 10 So operated in four-stroke process, each working piston 20 . 22 executes four-stroke cycles associated with it. This will be discussed below.

The free-piston engine 12 comprises a return spring device 54 , which is designed here as a gas spring device. The return spring device 54 has one of the piston receiving 14 formed springback chamber 56 on, in which a resilience space 58 is formed. The recoil piston 30 bounded with one side of the resilience space 58 , The resilience space 58 has a variable volume, and a compressible gas is received therein.

At the springback chamber 56 is an inlet and / or outlet 64 arranged. Through the inlet and / or outlet 64 can gas in the resilience space 58 coupled or drained from this. At the inlet and / or outlet 64 is a valve 66 arranged, via a control line 68 with the control and / or regulating device 48 is actively connected. The valve 66 can be controlled to the inlet and / or outlet 64 to open or lock.

The return spring device 54 can be double acting. For example, it may comprise, in addition to the gas, a mechanical elastic element, for example in the form of a spring, on the return spring piston 30 at whose the springback space 58 opposite side and at the rebound chamber 56 attacks. It may be from the springback chamber 56 Also, a compression space containing a compressible gas may be formed. The compression space may be at the rebound space 58 opposite side of the return spring piston 30 be arranged and limited by this.

The operation of the return spring means 54 is in detail in the DE 10 2011 000 620 A1 the same applicant, to which reference is made. In the present case, it is only important that compression of the gas in the resilience space 58 a spring-back force on the recoil piston 30 , the piston rod 32 , the coupling element 28 and over the piston rods 24 . 26 on the power pistons 20 respectively 22 can be exercised. Leads one of the working pistons 20 . 22 the power stroke, the piston device 16 for compressing the gas in resilience space 58 moved axially. The in the expansion of the gas in the resilience space 58 occurring return spring force moves the piston device 16 axially in the opposite direction.

The free-piston engine 12 further comprises an energy coupling device 70 , which in the present case is designed as an electrically effective energy coupling device. It includes a linear electric drive 72 , The linear drive 72 includes a magnet assembly 74 attached to the piston rod 32 fixed and movable with this. The magnet arrangement 74 has alternating poled magnets.

The linear drive 72 further includes a coil assembly 76 , which is designed fixed device. For example, the coil arrangement 76 at the piston receiver 14 or a housing, not shown in the drawing of the free-piston device 10 established. The coil arrangement 76 includes coils that the magnet assembly 74 surrounded by a ring.

The linear drive 72 is over a line 78 electrically with the control and / or regulating device 48 coupled. This allows, on the one hand, the linear drive 72 from the control and / or regulating device 48 to control the working point of the free-piston engine 12 (also in its operation) in a conventional manner. In this case, the linear drive 72 electrical energy is supplied, resulting in mechanical kinetic energy of the piston device 16 can be changed.

Conversely, mechanical kinetic energy of the piston device through the linear drive 72 be converted into electrical energy. This electrical energy can be stored in an energy storage, not shown in the drawing, or supplied to an electrical load.

As already mentioned, the working pistons 20 and 22 in the free piston device 10 under control of the valves 46 . 50 and the ignition devices 52 each operated in four-stroke mode. The control and / or regulating device 48 In particular, the work cycles can be controlled such that the power strokes are time-delayed by two power strokes of the four-stroke operation. This allows the working cycles of the working piston 20 . 22 to distinguish two working cycles.

While the working piston 20 performs an intake stroke, the working piston 22 perform a combustion cycle ( 1 ) and vice versa. While the working piston 20 performs a compression stroke, the working piston 22 perform an exhaust stroke (not shown) and vice versa. Because the working pistons 20 . 22 further rigid and immovable with each other via the coupling element 28 mechanically coupled, can be a movement of a working piston 20 . 22 cause a movement of the other working piston. The working pistons move in particular synchronously.

This allows it with the free piston device 10 to perform a preferred embodiment of a method according to the invention. For example, the control and / or regulating device controls 48 first a combustion cycle of the working piston 22 (shown in 1 , the working piston 22 has already moved to bottom dead center UT). By burning the working piston 22 and thus the piston device 16 under compression of the gas in the springback space 58 emotional. Due to the rigid mechanical coupling, this leads to the fact that the working piston 20 is moved. The movement of both working pistons 20 . 22 is synchronous, with the same stroke and parallel to each other. By controlling the valves 46 . 50 and the ignition device 52 whose first power stroke (suction of working medium) is controlled. During expansion of the gas in the springback space 58 becomes the piston device 16 under the action of the recoil force in opposite Direction moves, the working piston 20 a compression stroke and the working piston 22 performs an exhaust stroke. In a similar way, the valves 46 . 50 driven.

Subsequently, the working medium in the expansion space 38 under control of the ignition device 52 ignited, and the working piston 20 performs a power stroke, the working piston 22 an intake stroke, wherein the piston device 16 again under compression of the gas in the springback space 58 is moved. Again, the valves 46 . 50 and the ignition device 52 controlled accordingly.

Subsequently, by expansion of the gas in the resilience space 58 from the working piston 20 an exhaust stroke and from the power piston 22 a compression stroke to be performed, the valves 56 . 50 be controlled accordingly.

The above explanations show that with the free piston device 10 Overall, a four-stroke process can be performed without requiring electrical energy from the linear drive 72 must be cached. In each of the four work cycles, a movement of the piston device 16 be ensured, on the one hand with expansion of the working medium in one of the expansion areas 38 . 40 and as a result of the mechanical coupling of the working pistons 20 and 22 , On the other hand, the movement of the piston device takes place under the effect of expansion in the resilience space 58 ,

With the free piston device according to the invention, a higher efficiency than in conventional operated in four-stroke mode devices can be achieved, in which the linear drive 72 does not need to be used in the meantime to extract mechanical energy, temporarily store and reinsert. At the same time, a structurally simple design and compact design of the free-piston device 10 be achieved.

2 shows a schematic representation of a second preferred embodiment of a reference numeral 80 occupied free piston device according to the invention. The free piston device 80 comprises two identically designed free-piston engines 12 , their respective construction with that of the free-piston engine 12 the free piston device 10 matches. With respect to this construction or the advantages that can be achieved, reference is made to the above explanations. In addition, the free piston device 80 the control and regulating device 48 on. This is with the valves 46 . 50 and / or the ignition devices 52 , the linear drives 72 and / or the valves 66 in active connection. This is in 2 Not shown.

The free-piston engines 12 are axially spaced and coaxially aligned with each other and arranged relative to each other so that they are symmetrical with respect to a plane of symmetry 82 are. The symmetry plane 82 is perpendicular to the axis 18 aligned.

In the free piston device 80 can the respective piston devices 16 especially against the same along the axis 18 be moved, with each free-piston engine 12 operated in the four-stroke process. Each of the working pistons 20 . 22 both free-piston engines 12 is operated as explained above also in the four-stroke process. The opposite movement of the piston devices 16 can be achieved in particular by the fact that the control and regulating device 48 the valves 46 . 50 , the ignition devices 52 and the linear drives 72 both free-piston engines 12 so controls that the Arbeitstake of the working piston 20 . 22 run in phase. This makes it possible to achieve that at the same time the working pistons 20 . 22 a free-piston engine 12 perform a power stroke and an intake stroke as the working piston 20 . 22 the other free piston engine 12 , Correspondingly, at the same time in a free-piston engine 12 a compression stroke and an exhaust stroke performed as in the other free piston engine 12 ,

By the opposite movement of the piston devices 16 can compensate for the moving masses of the free-piston device 80 be achieved. The strength of the moving components can be reduced. In addition, a calmer and smoother operation of the free piston device 80 be achieved.

3 shows a schematic representation of a reference numeral 90 occupied preferred third embodiment of a free-piston device according to the invention. For the same and equivalent features and components of the free piston device 10 and 90 identical reference numerals are used. The with the free piston device 10 achievable advantages can in the free piston device 90 also be achieved.

In 3 (and also in 4 ) are not shown electrical lines that the control and / or regulating device 48 with the electrically active components of the free-piston device 90 combines.

In the free piston device 90 are the expansion chambers 34 and 36 not juxtaposed, but coaxially aligned with each other and opposite end sides of the free piston device 90 positioned. The piston device 16 has a first section 92 on the the working piston 20 and the piston rod 24 includes as well as a second section 94 holding the working piston 22 and the piston rod 26 includes. The piston rods 24 and 26 are aligned coaxially with each other, and the sections 92 and 94 are axially spaced from each other.

Instead of the recoil piston 30 come with the free piston device 90 two recoil pistons 96 and 98 the piston device 16 for use. The recoil pistons 96 . 98 are at the piston rods 24 . 26 the working piston 20 respectively 22 set opposite.

The return spring device 54 includes two recoil units 100 and 102 , each configured as a gas spring units and identical in structure and function to the return spring device 54 in the free piston device 10 , In this regard, reference is made to the above explanations. Every working piston 20 . 22 is at the free piston device 90 therefore a separate springback unit 100 . 102 assigned, via which a return spring force on the respective working piston 20 . 22 can be exercised.

The energy coupling device 70 in the free piston device 90 is also divided into two and includes a first power coupling unit 104 and a second power coupling unit 106 , Each energy coupling unit 104 . 106 includes a linear electric drive 72 , designed like the linear drive 72 the free piston device 10 , It is on the piston rods 24 and 26 in each case the magnet arrangement 74 set and device fixed that of the magnet assembly 74 associated coil arrangement 76 ,

The provision of two energy coupling units 104 and 106 allows it on the first section 92 and the second section 94 acting independently of each other to couple mechanical energy in the form of electrical energy or energy via the linear drive 72 couple. Each energy coupling unit 104 . 106 works like the linear drive 72 in the free piston device 10 , so that in this regard above explanations can be referenced.

In the free piston device 90 are the working pistons 20 . 22 also mechanically coupled with each other. However, they are movably coupled and movable relative to each other. For this purpose, the piston device comprises 16 a distance change mechanism 107 , This includes holding elements 108 and 110 and a joint element connecting them 112 , The holding elements 108 and 110 For example, they are transverse to the axis 18 aligned and firmly with the piston rods 24 respectively 26 connected. The connection between the retaining elements 108 . 110 and the piston rods 24 . 26 is rigid. The holding elements 108 . 110 show off the piston rods 24 and 26 away from each other with respect to the axis sides 18 ,

The joint element 112 is preferably each end of the holding elements 108 . 110 rotatably fixed via joints. The rotation can be about axes of rotation defined by the joints 114 on the holding element 108 and 116 on the holding element 110 respectively. In addition, the joint element 112 rotatably on a housing of the free-piston device 90 set, namely about a rotation axis 118 , The axes of rotation 114 . 116 and 118 are transverse to the axis 18 aligned, with the axis of rotation 118 the axis 18 cuts. The joint element 112 cuts one of the axes 18 and 118 spanned plane and extends from one side of the plane to the opposite side of the plane.

In the free piston device 90 become the valves 46 . 50 and the ignition devices 52 in a similar manner as in the free-piston device 10 so driven that the working pistons 20 . 22 each run a four-stroke cycle and thus the free piston device 90 also performs a four-stroke cycle. The working pistons 20 . 22 are mechanically coupled to each other mechanically. During a movement of the first section 92 in the axial direction pivots the joint element 112 relative to the holding element 108 around the axis of rotation 114 and relative to the housing about the axis of rotation 118 , This causes the joint element 110 also relative to the holding element 110 around the axis of rotation 116 pivoted and at the same time the second section 94 in the opposite direction of the first section 92 is moved axially. Take the power pistons 20 . 22 the respective bottom dead center, is the distance of the sections 92 . 94 minimal from each other. In the respective resilience space 58 the gas is compressed. Under expansion of the gas, the sections can 92 . 94 be moved axially in direction away from each other direction. Take the power pistons 20 . 22 the respective top dead center, is the distance of the sections 92 . 94 maximum of each other and the gas in each springback space 58 has expanded.

By the opposite antiparallel movement of the sections 92 and 94 in the free piston device 90 a balance of the moving masses can be achieved. As with the free piston device 80 This can reduce the mechanical strength of the moving components, and it becomes a quieter and more uniform operation of the free-piston device 90 achieved.

To further stabilize the piston device 16 and to further mass balance can holding elements 108 ' . 110 ' and another joint element 112 ' the sections 92 and 94 connect with each other (in 3 by dash-dotted lines shown), which are symmetrical to the holding elements 108 . 110 and to the hinge element 112 are.

4 shows a schematic representation of a fourth preferred embodiment of a free-piston device according to the invention, denoted by the reference numeral 120 is occupied. Same and equivalent features and components of the free-piston devices 10 and 120 respectively 90 and 120 are occupied by identical reference numerals. The with the free piston devices 10 and 90 achievable advantages can with the free piston device 120 also be achieved.

The construction of the free-piston devices 120 and 90 is apart from the movable coupling of the sections 92 and 94 equal to each other, so that only the differences are discussed below and, moreover, reference is made to the above explanations.

In the free piston device 120 are the sections 92 and 94 also movably coupled together via a distance changing mechanism 121 , This includes a first pair of hinge elements 122 . 124 and a second pair of hinge elements 126 . 128 , The joint elements 122 and 124 are at the piston rods 24 respectively 26 rotatably fixed about axes of rotation 130 respectively 132 , To each other are the joint elements 122 and 124 around a rotation axis 134 rotatably held. The joint elements 126 and 128 are at the piston rods 24 respectively 26 also around the axes of rotation 130 respectively 132 rotatably fixed. To each other are the joint elements 126 and 128 around a rotation axis 136 rotatably held. All rotary axes 130 to 136 are parallel to each other and perpendicular to the axis 18 aligned, with the axes of rotation 130 and 132 the axis 18 to cut.

The joint elements 122 and 124 on the one hand are symmetrical with respect to the axis 18 to the joint elements 126 and 128 on the other hand.

Under the effect of the joint elements 122 . 128 are the working pistons 20 . 22 mechanically and movably coupled relative to each other. The sections 92 and 94 can move axially relative to each other and opposite. Moves the section 92 like when the power piston 20 performs a combustion cycle, pivot the joint elements 122 . 126 around the axis of rotation 130 and relative to the hinge elements 124 . 128 around the axes of rotation 134 . 136 , The joint elements 124 . 128 pivot about the axis of rotation 132 , This causes the second section 94 opposite to the first section 92 can be moved. The joint elements 122 to 128 effectively form a spreader joint, the approach of the sections 92 . 94 is spread apart and its spread with increasing distance of the sections 92 . 94 is reduced from each other (symbolized by double arrows 138 in 4 ).

For the rotary axes 134 . 136 defining joints between the joint elements 122 . 124 respectively. 126 . 128 has the free piston engine 12 guides 140 on. Along the guides 140 The joints can be transverse to the axis 18 to move back and fourth. The guides 140 are for example of a housing of the free-piston device 120 educated.

Incidentally, the power strokes of the working piston 20 . 22 also with the free piston device 120 controlled according to a four-stroke process, so that the free-piston device 120 also performs a four-stroke process.

In the free piston device 120 can through the oppositely movable sections 92 and 94 also a balance of moving masses can be achieved.

5 schematically shows another, generally with the reference numeral 150 occupied advantageous embodiment of a free piston device according to the invention. The construction of the free piston device 150 is similar to the construction of the free piston device 10 in 1 , The main differences will be discussed below. The same or equivalent features and components are assigned the same reference numerals. The with the free piston device 10 achievable advantages can with the free piston device 150 also be achieved. In particular, it is possible, via the control device, the working cycles of the working piston 20 . 22 be controlled so that their working cycles differ by two power strokes of the four-stroke operation from each other.

In the free piston device 150 eliminates the separate springback chamber 56 on the working piston 20 . 22 opposite side of the free-piston engine 12 , However, it is also in the free piston device 150 the return spring means 54 a gas spring device, wherein this present case has at least one resilience space of one of the expansion chambers 34 . 36 is formed. In the present case, in particular, two springback spaces 152 . 154 intended.

The resilience space 152 is formed in the expansion chamber 34 , The expansion chamber 34 has on a front side, which is opposite to that end face on which the valves 46 . 50 and the ignition device 52 are arranged a wall 156 on. The resilience space 156 is between the wall 156 and the working piston 20 educated. In Circumferential direction is the resilience space 152 through the outer wall of the expansion chamber 34 limited, which also the expansion space 38 limited.

Correspondingly, the expansion chamber forms 36 the resilience space 154 between a wall 158 and the working piston 22 ,

On the walls 156 . 158 is each an inlet and / or outlet 160 arranged. In the same way as with the inlet and / or outlet 64 can gas in the respective resilience space 152 . 154 coupled or drained from this. At the respective inlet and / or outlet 160 is a valve 162 arranged with the control and / or regulating device 48 is operatively connected (not shown).

The volume change of the expansion space 38 and the resilience space 152 is synchronous and inverse to each other. Expands the working fluid in the expansion space 38 , or is absorbed working fluid, the gas in the resilience space 152 compressed. Conversely, with an expansion of the gas in the resilience space 152 a compression of the working medium or an expulsion of the combustion products.

The same applies to the expansion area 40 and the resilience space 154 , The free piston device 150 according to 5 Accordingly, has a return spring, which in the expansion chambers 34 . 36 is integrated. This allows a structurally simple design and a compact design of the free-piston device 150 be achieved. This is especially due to the fact that the working piston 20 . 22 each with opposite piston sides, the expansion spaces 38 . 40 or the resilience spaces 152 . 154 limit. Separate recoil pistons can be saved.

In further advantageous embodiments of the free-piston device according to the invention, constructions according to the 2 . 3 and 4 be provided, wherein also integrated return spring means are used, wherein the return spring chambers of a respective expansion chamber 34 . 36 are formed. Separate springback chambers, as with the free-piston devices 80 . 90 and 120 the case can be saved.

LIST OF REFERENCE NUMBERS

10

 Free-piston device

12

 Free piston engine

14

 piston receiving

16

 piston device

18

 axis

20

 first working piston

22

 second working piston

24

 Piston bearing element (piston rod)

26

 Piston bearing element (piston rod)

28

 coupling element

30

 Rear spring piston

32

 Piston bearing element (piston rod)

34

 expansion chamber

36

 expansion chamber

38

 expansion space

40

 expansion space

42

 inlet

43

 feed

44

 outlet

45

 discharge

46

 Valve

47

 control line

48

 Control and / or regulating device

50

 Valve

51

 control line

52

 ignition device

53

 control line

54

 Return spring means

56

 Rebound chamber

58

 Resilience space

64

 Inlet and / or outlet

66

 Valve

68

 control line

70

 Energy coupling device

72

 linear drive

74

 magnet assembly

76

 coil assembly

78

 management

80

 Free-piston device

82

 plane of symmetry

90

 Free-piston device

92

 first section

94

 second part

96

 Rear spring piston

98

 Rear spring piston

100

 Rear spring unit

102

 Rear spring unit

104

 Energy coupling unit

106

 Energy coupling unit

107

 Distance changing mechanism

108

 retaining element

110

 retaining element

112

 joint element

114

 axis of rotation

116

 axis of rotation

118

 axis of rotation

120

 Free-piston device

121

 Distance changing mechanism

122

 joint element

124

 joint element

126

 joint element

128

 joint element

130

 axis of rotation

132

 axis of rotation

134

 axis of rotation

136

 axis of rotation

138

 double arrow

140

 guide

150

 Free-piston device

152

 Resilience space

154

 Resilience space

156

 wall

158

 wall

160

 Inlet / outlet

162

 Valve

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10219549 A1 [0003]
• DE 10242141 A1 [0003]
• DE 102006029532 A1 [0003, 0033, 0041]
• DE 102011000620 A1 [0003, 0005, 0033, 0041, 0071]

Claims (33)

Free-piston device, comprising at least one free-piston engine ( 12 ), the at least one linearly movable piston device ( 16 ) and a piston receptacle ( 14 ), wherein the piston receptacle ( 14 ) a first expansion space ( 38 ) forming the first expansion chamber ( 34 ) and a second expansion space ( 40 ) forming the second expansion chamber ( 36 ) for the respective expansions of a working medium, wherein the at least one piston device ( 16 ) one the first expansion space ( 38 ) limiting first working piston ( 20 ) and a second expansion space ( 40 ) limiting second working piston ( 22 ), wherein the free-piston engine ( 12 ) further comprises a return spring device ( 54 ) for providing a return spring force for the at least one piston device ( 16 ) and wherein the free piston device ( 10 ; 80 ; 90 ; 120 ; 150 ) a control and / or regulating device ( 48 ) for controlling and / or regulating power strokes of the first working piston ( 20 ) and the second working piston ( 22 ), characterized in that the first working piston ( 20 ) and the second working piston ( 22 ) are mechanically coupled to each other to provide movement of a working piston ( 20 ) in response to a movement of the other working piston ( 22 ) and that with the control and / or regulating device ( 48 ) a four-stroke operation of the first working piston ( 20 ) and the second working piston ( 22 ) is controllable and / or controllable, wherein the power strokes of the first working piston ( 20 ) and the second working piston ( 22 ) are time-offset by two working cycles of the four-stroke operation. Free piston device according to claim 1, characterized in that the control and / or regulating device ( 48 ) for controlling and / or regulating the working cycles of the first working piston ( 20 ) and the second working piston ( 22 ) is in operative connection with at least one of the following: - one at the first expansion chamber ( 34 ) and / or the second expansion chamber ( 36 ) arranged valve device ( 46 . 50 ); - one at the first expansion chamber ( 34 ) and / or the second expansion chamber ( 36 ) arranged ignition device ( 52 ); - one at the first expansion chamber ( 34 ) and / or the second expansion chamber ( 36 ) arranged injection device; - A mixing device for providing the working medium as a fuel-oxidizer mixture; - A charging device for providing a volume flow of the working medium. Free-piston device according to claim 1 or 2, characterized in that the stroke of the first working piston ( 20 ) and the second working piston ( 22 ) is equal and / or that the stroke of the first working piston ( 20 ) and the second working piston ( 22 ) is controllable and / or controllable. Free-piston device according to one of the preceding claims, characterized in that the first working piston ( 20 ) and the second working piston ( 22 ) are movable from a respective top dead center (TDC) to a respective bottom dead center (TDC) and that the position of the respective top dead center (TDC) and / of the respective bottom dead center (TDC) is controllable and / or controllable. Free-piston device according to one of the preceding claims, characterized in that the at least one piston device ( 16 ) comprises or forms a coupling device for coupling the first working piston ( 20 ) with the second working piston ( 22 ). Free-piston device according to one of the preceding claims, characterized in that the expansion chambers ( 34 . 36 ) and the working pistons ( 20 . 22 ) are arranged side by side and that the first working piston ( 20 ) and the second working piston ( 22 ) are movable parallel to each other. Free-piston device according to one of the preceding claims, characterized in that the first working piston ( 20 ) and the second working piston ( 22 ) are rigidly coupled together. Free-piston device according to one of the preceding claims, characterized in that on the first working piston ( 20 ) and on the second working piston ( 22 ) piston members ( 24 . 26 ) via a coupling element ( 28 ) are firmly connected. Free-piston device according to claim 8, characterized in that the at least one piston device ( 16 ) a return spring piston ( 30 ), which via a further piston carrying member ( 32 ) on a first working piston ( 20 ) and the second working piston ( 22 ) opposite side on the coupling element ( 28 ), wherein the return spring piston ( 30 ) a resilience space ( 58 ) of the return spring device ( 54 ) limited. Free-piston device according to claim 9, characterized in that the further piston-carrying element ( 32 ), relative to one of the free piston device ( 10 ; 80 ) defined axis ( 18 ) in the middle between the first working piston ( 20 ) and the second working piston ( 22 ) is arranged. Free-piston device according to one of the preceding claims, characterized in that the first working piston ( 20 ) and the second Working piston ( 22 ) are movably coupled together and movable relative to each other. Free-piston device according to one of the preceding claims, characterized in that the at least one piston device ( 16 ) one in the first working piston ( 20 ), the first section ( 92 ) and one in the second working piston ( 22 ), the second section ( 94 ), each along an axis ( 18 ) of the free piston device ( 90 ; 120 ) are movable, and that the sections ( 92 . 94 ) under control and / or regulation of the working cycles of the working pistons ( 20 . 22 ) are movable relative to each other against the same. Free-piston device according to claim 12, characterized in that the first working piston ( 20 ) and the second working piston ( 22 ) at one of the other second and first sections ( 92 ) facing away from the first or second section ( 94 ) are arranged. Free-piston device according to claim 12 or 13, characterized in that the at least one piston device ( 16 ) a distance changing mechanism ( 107 . 121 ) for providing a different distance of the first section ( 92 ) and the second section ( 94 ) depending on the working cycle of the working piston ( 20 . 22 ). Free-piston device according to claim 14, characterized in that the first section ( 92 ) and the second section ( 94 ) occupy a minimum distance from each other when the working pistons ( 20 . 22 ) take a respective bottom dead center (UT) and take a maximum distance from each other when the working piston ( 20 . 22 ) assume a respective top dead center (TDC). Free piston device according to claim 14 or 15, characterized in that the distance changing mechanism ( 107 ) a joint element ( 112 ), the first section ( 92 ) and the second section ( 94 ) each about a transverse to the axis ( 18 ) oriented axis of rotation ( 114 . 116 ) is rotatably fixed, wherein the axes of rotation ( 114 . 116 ) on opposite sides of the axis ( 18 ) are arranged. Free-piston device according to claim 16, characterized in that the joint element ( 112 ) on the at least one piston receptacle ( 14 ) or a housing of the free-piston engine ( 12 ) about a transverse to the axis ( 18 ) oriented axis of rotation ( 118 ) is rotatably fixed. Free piston device according to claim 14 or 15, characterized in that the distance changing mechanism ( 121 ) at least one pair of joint elements ( 122 . 124 . 126 . 128 ), one of which on the first section ( 92 ) or on the second section ( 94 ) is rotatably fixed and which are rotatably connected to each other, wherein the axes of rotation ( 130 . 132 . 134 . 136 ) each transverse to the axis ( 18 ) are aligned. Free-piston device according to claim 18, characterized in that two pairs of joint elements ( 122 . 124 . 126 . 128 ) are provided, wherein the pairs of joint elements ( 122 . 124 . 126 . 128 ) each other with respect to the axis ( 18 ) are opposite. Free-piston device according to one of the preceding claims, characterized in that the return spring device ( 54 ) comprises or forms at least one gas spring device, wherein the piston receptacle ( 14 ) at least one rebound chamber ( 56 ), in which at least one resilience space ( 58 ) is formed, and that the at least one piston device ( 16 ) at least one return spring piston ( 30 ; 96 . 98 ) comprising the at least one resilience space ( 58 ) and with the first working piston ( 20 ) and / or the second working piston ( 22 ) via at least one piston carrier element ( 24 . 26 . 32 ) is coupled. Free-piston device according to claim 20, characterized in that the return spring device ( 54 ) a first recoil unit ( 100 ), which is the first working piston ( 20 ) and a second recoil unit ( 102 ), the second working piston ( 22 ), each return spring unit ( 100 . 102 ) via a return spring piston ( 96 . 98 ), which via a piston carrying element ( 24 . 26 ) with one of the working pistons ( 20 . 22 ) is connected to the respective working piston ( 20 . 22 ) acts. Free-piston device according to claim 20, characterized in that the return spring device ( 54 ) the first working piston ( 20 ) and the second working piston ( 22 ) is assigned together and via a return spring piston ( 30 ) on a piston carrier element ( 32 ) acting with both working pistons ( 20 . 22 ) is coupled. Free-piston device according to one of the preceding claims, characterized in that that of the return spring device ( 54 ) exerted spring force in the operation of the free-piston device ( 10 ; 80 ; 90 ; 120 ; 150 ) is controllable and / or controllable. Free-piston device according to one of the preceding claims, characterized in that the at least one free-piston engine ( 12 ) an energy coupling device ( 70 ) comprises for discharging and / or coupling energy from or into the at least one piston device ( 16 ). Free-piston device according to claim 24, characterized in that the energy coupling device ( 70 ) at least one electric linear drive ( 72 ), with a coil arrangement ( 76 ) and a relatively movable magnet assembly ( 74 ). Free-piston device according to claim 25, characterized in that the coil arrangement ( 76 ) fixed to the piston receptacle ( 14 ) is arranged and that the magnet arrangement ( 74 ) on a piston carrier element ( 24 . 26 . 32 ) of a working piston ( 20 . 22 ). Free-piston device according to one of claims 24 to 26, characterized in that the movement of the at least one piston device ( 16 ) by means of the energy coupling device ( 70 ) during operation of the free-piston device ( 10 ; 80 ; 90 ; 120 ; 150 ) is controllable and / or controllable. Free-piston device according to one of claims 24 to 27, characterized in that the energy coupling device ( 70 ) a first energy coupling unit ( 104 ), which is the first working piston ( 20 ), and a second energy coupling unit ( 106 ), the second working piston ( 22 ), each energy coupling unit ( 104 . 106 ) on a piston carrier element ( 24 . 26 ) of the respective working piston ( 20 . 22 ) is arranged and cooperates with this. Free-piston device according to one of claims 24 to 27, characterized in that the energy coupling device ( 70 ) the first working piston ( 22 ) and the second working piston ( 22 ), wherein the energy coupling device ( 70 ) on a piston carrier element ( 32 ) for the first working piston ( 20 ) and the second working piston ( 22 ) is arranged. Free-piston device according to one of the preceding claims, characterized in that the free-piston device ( 80 ) a first free-piston engine ( 12 ) and a second free piston engine ( 12 ) which are identical or substantially identical and which are arranged so as to be symmetrical with respect to a plane of symmetry ( 82 ) are symmetrical or substantially symmetrical with respect to each other, which plane of symmetry ( 82 ) perpendicular to an axis ( 18 ) of the free piston device ( 80 ), along which the respective at least one piston device ( 16 ) is movable. Free-piston device according to claim 30, characterized in that via the control and / or regulating device ( 48 ) the working cycles of the working pistons ( 20 . 22 ) are controllable and / or regulatable such that the at least one piston device ( 16 ) of the first free-piston engine ( 12 ) and the at least one piston device ( 16 ) of the second free-piston engine ( 12 ) are movable against the same. Method for operating a free piston device according to one of the preceding claims, wherein the control and / or regulating device controls and / or regulates a four-stroke operation of the first working piston and the second working piston, wherein the working cycles of the first working piston and the second working piston by two power strokes of the four-stroke operation are delayed. A method according to claim 32, characterized in that the control and / or regulating device for controlling and / or regulating the working cycles of the first working piston and the second working piston at least one of the following controls and / or controls: - one at the first expansion chamber and / or the second expansion chamber arranged valve means; - An arranged on the first expansion chamber and / or the second expansion chamber ignition device; - An arranged on the first expansion chamber and / or the second expansion chamber injection device; - A mixing device for providing the working medium as a fuel-oxidizer mixture; - A charging device for providing a volume flow of the working medium.

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