DE102016120354B4 - free piston device - Google Patents

Abstract

Free-piston device, comprising a free-piston engine (15) with a piston device (16) defining an axis (24) which under the action of the expansion of a medium in an expansion space (28) delimited by a piston (20) of the piston device (16). , and a return spring device (38) can be moved back and forth axially, and at least one energy coupling device (40, 42) which has a stator arrangement (48) and a rotor arrangement (46) connected to the piston device (16) via a holding element (58). , wherein the runner assembly (46) is plate-shaped and defines a plane (50), characterized by a positioning of the axis (24) at a transverse distance from the plane (50) of the runner assembly (46), wherein a reference plane (24) containing the axis (24) 54) is aligned transversely to the plane (50) of the rotor arrangement (46), the stator arrangement (48) comprising at least one stator section (56) which is plate-shaped and parallel to the rotor anor Dnung (46) is arranged, and wherein the rotor arrangement (46) in the plane (50) defined by it and transverse to the reference plane (54) protrudes with at least one end section (68, 70) beyond the at least one stator section (56), wherein the holding element (58) is connected to the end section (68, 70).

Description

The invention relates to a free-piston device, comprising a free-piston engine with a piston device that defines an axis and that can be moved back and forth axially under the effect of the expansion of a medium in an expansion space that is delimited by a piston of the piston device, and a return spring device, and at least one Energy coupling device which has a stator arrangement and a rotor arrangement connected to the piston device via a holding element, the rotor arrangement being designed in the shape of a plate or essentially in the shape of a plate and defining a plane.

In the free-piston device, the movement of the piston device takes place under the effect of the expansion of the medium in the expansion space on the one hand and the opposite effect of the resilience device on the other. The resilience device can, for example, be designed mechanically and/or have a gas spring which is compressed when the combustion piston moves from top dead center to bottom dead center and when it expands the combustion piston moves from bottom dead center to top dead center. Such a free-piston device is for example in DE 10 2006 029 532 A1 described. This free-piston device includes an energy coupling device, designed as a linear generator, with a rotor arrangement, which is designed as a magnet arrangement connecting the combustion piston to the gas spring piston. The stator arrangement, designed as a coil arrangement, surrounds the piston device.

In the DE 102 42 141 A1 discloses a free-piston device with an energy coupling device that is also configured electromagnetically. The magnet (runner) assembly is fixed to a spaced transversely to the axis tubular support member. The coil (stator) assembly surrounds the magnet assembly. In this way, a short design of the free-piston device can be achieved.

The non-prepublished patent application DE 10 2016 109 038 A1 The same applicant describes a generic free-piston device in which energy coupling devices in the form of linear generators arranged laterally next to the piston device are used. The electromagnetically designed energy coupling devices have a flat design, in which the rotor (magnet) arrangement is plate-shaped and designed to define a plane. The same applies to the stator (coil) arrangements arranged on both sides of the rotor arrangement. The axis is located in the plane of the slider assembly and forms a plane of motion therewith. With an overall very flat design of the free-piston device, a high power density can be achieved. Such free-piston devices with a flat design have proven themselves in practice. However, due to the flat design, the torsional rigidity and thus the moment of resistance of the piston device with the energy coupling device in the plane of the rotor arrangement is not all that great. Undesirable resonant vibrations can occur, even if only at higher operating frequencies.

the DE 10 2007 035 914 A1 discloses a free-piston device, comprising at least one piston receptacle, at least one piston device that is linearly movable in this corresponding piston receptacle and has a first piston surface and a second piston surface that faces away from the first piston surface, and an expansion space that is arranged in the piston receptacle and is delimited by the first piston surface, wherein the piston device can be driven under the action of a medium which expands in the expansion space. A resilience space is arranged in the at least one piston receptacle and is delimited by the second piston surface.

Other embodiments of free-piston devices are in the WO 00/77366 A1 and in the DE 10 2006 003 826 A1 described.

The object of the present invention is to further develop a generic free-piston device in such a way that a robust construction with, if possible, a high power density is possible while maintaining a compact design.

This object is achieved by a free-piston device according to the invention with the features of claim 1.

In the present invention, the axis, unlike the aforementioned free piston device DE 10 2016 109 038 A1 , not arranged in the plane of the rotor arrangement. Instead, the axle is spaced from the plane of the runner assembly so that a transverse spacing between the axle and the runner assembly can be achieved. A reference plane, which contains the axis, is aligned transversely to the plane of the runner arrangement, with "transverse" presently being understood as non-identical and non-parallel and in particular also including a right angle between the reference plane and the plane of the runner arrangement. In relation to the in the DE 10 2016 109 038 A1 described free-piston device, the rotor assembly is therefore inclined relative to a reference plane and in particular aligned perpendicular to this, whereby the Extension of the free-piston device can be reduced in the reference plane. This leads to a more robust construction, so that resonant vibrations only occur at frequencies significantly above the normal operating frequencies of free-piston devices. At the same time, with the usual dimensions of the components of the free-piston device, a compact design can be realized in all three spatial directions, in the axial direction, perpendicular to the axis in the reference plane, and perpendicular to the two directions mentioned.

In a sense, the runner assembly can be viewed as tilted or canted relative to the plane of motion in the conventional free piston device. In the present case, the reference plane can therefore also be regarded as the plane of movement of the free-piston device according to the invention.

The stator arrangement, in particular a coil arrangement of the stator arrangement, comprises at least one stator section which is plate-shaped or essentially plate-shaped and is arranged parallel to the rotor arrangement. This enables a flat construction of the energy coupling device, as a result of which a high power density can be achieved.

The power density can be increased further if the stator arrangement comprises two stator sections between which the rotor arrangement is positioned. Stator sections of the stator can be arranged on both sides of the rotor arrangement. Radially outwardly of the axis, an inner stator section is followed by the rotor assembly and then an outer stator section, the rotor assembly being movable axially between the stator sections by the piston means.

It has proven to be favorable, especially in the last-mentioned advantageous embodiment, that the rotor arrangement protrudes in the plane defined by it and transversely, especially perpendicularly, to the reference plane with at least one end section over a stator section and when the holding element is connected to the end section. The connection of the holding element to the end section that protrudes beyond the stator section allows a stator section to be positioned radially inside the rotor arrangement, with another stator section preferably being able to be positioned radially outside the rotor arrangement to increase the power density.

It is favorable if the reference plane is oriented perpendicularly or essentially perpendicularly to the plane of the rotor arrangement, in the present case “essentially perpendicular” can in particular be a slight deviation from a right angle, for example up to approx. 5°.

In an advantageous embodiment of the free-piston device, the reference plane intersects the rotor arrangement in the middle or essentially in the middle. In the present case, this can be understood to mean, for example, that a perpendicular from the axis to the plane of the rotor arrangement intersects the rotor arrangement in the middle or approximately in the middle.

In an advantageous embodiment, the rotor arrangement passes through the reference plane and, in the last-mentioned advantageous embodiment, is preferably positioned in equal parts above and below the reference plane.

It is favorable if the rotor arrangement is designed symmetrically or essentially symmetrically with respect to the reference plane.

It is advantageously provided that the rotor arrangement has its greatest extension parallel to the axis.

Furthermore, it is advantageously provided that the rotor arrangement has its smallest extent radially to the axis in the reference plane.

The at least one energy coupling device is preferably designed to be electromagnetic, with the rotor arrangement being or comprising a magnet arrangement and the stator arrangement being a coil arrangement. The energy coupling device forms in particular a linear generator. The magnet arrangement comprises, for example, magnet elements arranged axially one after the other, between which flux guide elements for bundling the magnetic flux can be positioned.

Advantageously, the rotor arrangement protrudes with two end sections on opposite sides over the stator section, the end sections being connected to the holding element. As a result, the rotor arrangement can be robustly connected to the piston device at mutually opposite end sections, for example above and below the reference plane.

The stator arrangement advantageously has its greatest extent parallel to the axis.

It is favorable if the stator arrangement has its smallest extent radially to the axis in the reference plane.

In a preferred embodiment, the free-piston device comprises two energy coupling devices, in particular linear generators ren, whereby the power density of the free-piston device can be increased.

It is advantageous if the energy coupling devices are arranged opposite one another with respect to a plane which is oriented transversely and in particular perpendicularly to the reference plane and contains the axis. The energy coupling devices can be positioned on opposite sides of the piston device, for example a piston rod of the piston device which connects a combustion piston with a resilience or gas spring piston.

Advantageously, the energy coupling means are symmetrical or substantially symmetrical with respect to the aforesaid plane containing the axis and oriented transversely to the reference plane. In an advantageous embodiment, this plane is aligned perpendicular to the reference plane and/or parallel to the plane of the rotor arrangements.

As will be discussed below, a common holding element can be provided which connects the piston device to the rotor arrangements.

It is favorable if the holding element has an axial extent that is less than the axial extent of the rotor arrangement. The mass of the free-piston device can be reduced in order to increase the efficiency.

The detailed configuration of the holding element is discussed below.

It proves to be advantageous if the holding element has at least one first section aligned radially or essentially radially to the axis, which is directly or indirectly connected to the piston device, and at least one second section aligned at an angle thereto, which is connected to the rotor arrangement . The connection of the piston assembly to the rotor assembly via an angled support member reduces the tendency of the support member to resonate.

It proves to be advantageous if the first section is aligned parallel to the plane of the rotor arrangement and if the second section is aligned parallel to the reference plane. In this way, the first and the second section can in particular enclose a right or substantially right angle.

In an advantageous embodiment, the holding element on the first section and second section is L-shaped in cross section relative to the axis, i.e. the first section and the second section form the shape of an L in cross section.

The holding element favorably has at least one third section, which connects the first section, a bushing of the holding element connected thereto, or the piston device and the second section to one another in the manner of a strut. The bushing can be connected, for example, to a piston rod of the piston device, which is passed through the axle. The construction of the holding element is made even more robust by the third section, in particular a holding element with a "truss-like" cross section is created.

It is favorable if two first sections and two second sections are provided, which connect mutually opposite end sections of the rotor arrangement to the piston device. It has already been mentioned that end sections which advantageously protrude beyond a stator section are connected to the holding element. In the present embodiment, in particular, the two second sections are fixed to the end sections of the rotor arrangement, the second sections being connected directly or indirectly to the piston device via respective first sections. For example, the cross section of the holding element has the shape of two L's formed as mirror images of each other at the first sections and second sections. A stator section of the stator arrangement is advantageously arranged between the second sections.

If two energy coupling devices are provided, it is advantageous if the holding element is designed symmetrically or essentially symmetrically with respect to the aforementioned plane, which is aligned transversely to the reference plane and contains the axis. In addition to a simple construction, this allows the introduction of force to be evened out and leads to smoother running of the free-piston device.

In an advantageous embodiment of the free-piston device, which comprises two energy coupling devices, the holding element is configured, at least in sections, in a double T-shape in cross section with respect to the axis. "Bars" of the T (-) are preferably formed by respective second portions for connecting the support member to a runner assembly. The "vertical bars" of the T (|) are preferably formed by respective first sections of the retaining element for direct or indirect connection to the piston device. The bars are preferably aligned parallel to the reference plane and perpendicular to the plane of the slider assembly. The vertical streaks surfaces are preferably aligned perpendicular to the reference plane.

The holding element can comprise or form two legs and a bridge connecting them. For example, the legs are the second sections mentioned above and the bridge is formed by the first sections mentioned above. The legs are preferably aligned parallel to one another.

If two energy coupling devices are present, four legs can be present, with two legs defining a common plane and being spaced apart from the other two legs via the bridge. A common bridge can be provided. In this way, for example, the above-mentioned double-T-shaped configuration of the holding element can be achieved.

It proves to be favorable if the free-piston device has a bearing device, via which the holding element and/or the rotor arrangement is displaceably mounted on a housing accommodating the free-piston motor and the at least one energy coupling device. As a result, a compact housing for the free-piston device can be provided, the moving components of which are mounted relative to the housing via the bearing device. The bearing device can be or include a slide bearing, roller bearing or ball bearing.

The holding element can be encompassed by the piston device.

Provision can be made for the holding element to be formed by a piston rod which connects a combustion piston to a resilience piston, for example a gas spring piston.

The connection between the holding element and the piston rod can be in one piece. In another advantageous embodiment, the holding element can be formed separately from the piston rod and can be connected to it.

For example, the holding element comprises or forms a bushing through which the piston rod extends.

• 1: eine schematische perspektivische Teildarstellung einer erfindungsgemäßen Freikolbenvorrichtung;
• 2: eine schematische Darstellung der Freikolbenvorrichtung in Schnittansicht längs der Linie 2-2 in 1; und
• 3: eine Darstellung entsprechend 2 bei einer weiteren vorteilhaften Ausführungsform der erfindungsgemäßen Freikolbenvorrichtung.

The following description of preferred embodiments of the invention, in conjunction with the drawing, serves to explain the invention in more detail. Show it:

• 1 : a schematic perspective partial illustration of a free-piston device according to the invention;
• 2 1 is a schematic representation of the free piston device in a sectional view along line 2-2 in FIG 1 ; and
• 3 : a representation accordingly 2 in a further advantageous embodiment of the free-piston device according to the invention.

the 1 and 2 show an advantageous embodiment of a free-piston device according to the invention, designated by the reference number 10 .

The free-piston device 10 comprises an only in 2 shown housing 12, which forms a receiving space 14. A free-piston engine 15 is accommodated in the accommodation space 14 . The free-piston engine 15 comprises a piston device 16 which comprises a piston rod 18 , a combustion piston 20 and a rebound piston 22 . The piston rod 18 defines an axis 24.

The free-piston device 10 includes a piston receptacle 26 which forms an expansion space 28 . The combustion piston 20 delimits the expansion space 28 on one side with a piston surface 30.

An ignitable mixture can be supplied to the expansion chamber 28 in a manner known per se via lines not shown in the drawing, and when it burns, the expanding medium exerts a displacement force on the piston surface 30 . The piston assembly 16 is moved from the top dead center to a bottom dead center as the combustion piston 20 moves.

A further piston receptacle 32 is arranged opposite the piston receptacle 26 and is associated with the spring-back piston 22 . The resilience piston 22 is, for example, a gas spring piston which, with a piston surface 34, delimits a resilience space 36 on one side, in which a compressible gas (or gas mixture) is accommodated. The movement of the piston device 16 compresses the gas, resulting in a springback force on the piston device 16 in order to move the combustion piston 20 again from bottom dead center to top dead center. In this way, the free-piston device 10 comprises a spring-back device 38.

In addition or as an alternative, it can be provided that a mechanical spring-back device is provided.

In addition, it can be provided that the pressure of the gas in the resilience space 36 is controlled and/or regulated in a manner known per se. For this purpose, on the piston mount 32, for example As in the drawing not shown supply lines and / or valves can be arranged.

The free-piston device 10 can also have a control device for controlling the combustion and/or the resilience device 38. In addition, the energy coupling devices of the free-piston device 10 mentioned below can be controlled by the control device in a manner known per se in order to control the movement of the piston device 16 during operation of the free-piston device 10 to control and/or regulate.

The free-piston device 10 comprises two energy coupling devices 40, 42, which are configured symmetrically to one another with respect to a plane of symmetry 44 containing the axis 24. Identical reference numbers are used for the components of the energy coupling devices 40, 42, and the energy coupling device 40 is essentially discussed below.

Energy coupling device 40 is designed as a linear generator 45 and includes a rotor arrangement 46, which is designed as a magnet arrangement, and a stator arrangement 48, designed as a coil arrangement.

The rotor arrangement 46 comprises magnet elements 52 arranged axially next to one another, between which flux guide elements can be arranged for bundling the magnetic flux.

The free-piston device 10 defines a reference plane 54. The reference plane 54 contains the axis 24 and in the present case is oriented transversely and in particular perpendicularly to the plane 50 of the rotor arrangement 46. The plane of symmetry 44 is also aligned transversely and in particular perpendicularly to the reference plane 54 .

The runner assembly 46 can be considered as relative to the plane of motion in which in FIG DE 10 2016 109 038 described free-piston device are tilted or tilted. The reference plane 54 can therefore also be referred to as the plane of movement in the present case.

Here, the axis 24 is positioned at a distance from the plane 50 of the rotor assembly 46, which in turn is at a transverse distance from the axis 24. The reference plane 54 intersects the rotor assembly 46 in the middle so that it has sections on both sides of the reference plane 54 . In particular, the rotor arrangement 46 and advantageously the energy coupling device 40 as a whole are designed symmetrically with respect to the reference plane 54 .

The rotor arrangement 46 has its greatest extension parallel to the axis 24 and its smallest extension radially to the axis 24 in the reference plane 54.

The stator assembly 48 includes two stator sections 56. The stator sections 56 are spaced from one another with the rotor assembly 46 disposed between the stator sections 56. As shown in FIG.

Both stator sections 56 are plate-shaped and define a plane parallel to the plane of the rotor assembly 46 . The stator sections 56 have the greatest extent parallel to the axis 24, and the smallest extent in the reference plane 54 radially to the axis 24. The reference plane 54 intersects the stator sections 56 in the middle.

The stator sections 56 comprise, in a manner known per se, coils which are not shown in the drawing and which interact with the magnetic elements 52 of the rotor arrangement 46 .

The rotor arrangement 46 is firmly connected to the piston device 16 by means of a holding element 58 of the free-piston device 10 . When the piston device 16 moves, the runner arrangement 46 is displaced between the stator sections 56 parallel to the axis 24 and likewise executes a reciprocating movement.

A bearing device 60 is provided, via which the rotor arrangement 46 is displaceably mounted on the inside of the housing 12 . The bearing device 60 includes, for example, plain bearings, roller bearings or ball bearings ( 2 ).

A high power density can be achieved with the energy coupling device 40 . The flat design of the rotor arrangement 46 and the stator sections 56 is beneficial for this, so that the energy coupling device 40 is designed overall in a flat design. This makes it possible to achieve a high power density with the free-piston device 10 with a compact design at the same time. The free-piston device 10 is of compact construction in all three spatial directions—axially, perpendicular thereto in the reference plane 54 and perpendicular to the axis 24 in the plane of symmetry 44 .

Furthermore, a robust construction is achieved by the configuration of the holding element 58 explained below.

The holding element 58 connects the rotor assembly 46 to the piston device 16 and in particular special its piston rod 18. The holding element 58 comprises a bushing 62, through which the piston rod 18 is guided. The bushing 62 is firmly connected to the piston rod 18 .

Furthermore, the holding element 58 comprises two first sections 64 on opposite sides of the reference plane 54, which are aligned radially with respect to the axis 24 and, in particular, lie in the plane of symmetry 44.

A respective first section 64 is connected to a respective second section 66, the sections 64, 66 being angled towards one another. In a cross-section about axis 24 ( 2 ) the sections 64, 66 collectively have the shape of an L. Sections 66 are aligned parallel to reference plane 54 and connect first sections 64 to end sections 68, 70 of rotor assembly 46.

The end portions 68, 70 are located opposite each other on the rotor assembly 46 and protrude beyond the stator sections 56, in the plane of the rotor assembly 46 and perpendicular to the reference plane 54.

In this manner, the runner assembly 46 is connected at the end portions 68, 70 to the second portions 66 which are spaced from one another. One of the stator sections 56 is arranged between the second sections 66 .

The first sections 64 are connected to the bushing 62 and, via this, indirectly to the piston rod 18 .

The holding element 58 is designed symmetrically with respect to the plane of symmetry 44 . Both energy coupling devices 40, 42 are connected to the holding element 58. As a result, the holding element 58 has a double-T-shaped configuration in cross section with respect to the axis 24 . The slashes (-) of the T are formed by the respective second portions 66 and the vertical bars (|) of the T are formed by the first portions 64. FIG.

The holding element 58 can also be regarded as comprising two legs 72 which are spaced apart from one another and which are connected to one another via a bridge 74 . The legs 72 are presently formed by the sections 66 parallel to the reference plane 54. The bridge 74 can be considered here to be formed by the first sections 64 and the bushing 62. A common bridge 74 is provided for the legs 72 which connect the runner assemblies 46 of both energy coupling devices 40, 42 to the piston rod 18.

In the axial direction, the holding element 58 only extends along a section of the extent of the energy coupling device 40 to save weight. For example, the axial extent of the holding element 58 is approximately one fifth to approximately one third of the extent of the rotor arrangement 46.

In the case of the free-piston device 10, a robust construction can be achieved through the arrangement of the energy coupling devices 40, 42 and the shape of the holding element 58. There is a high torsional rigidity in the reference plane 54, combined with an increased section modulus. Resonant vibrations do not occur up to well above the usual operating frequencies of the free-piston device 10 .

3 shows in one of the 2 Correspondingly, a schematic sectional view of an embodiment of a free-piston device according to the invention, denoted by reference numeral 80 . Identical reference symbols are used for the same or equivalent features and components of the free-piston devices 10 and 80 . The advantages that can be achieved with the free-piston device 10 are also achieved with the free-piston device 80 .

In the case of the free-piston device 80, the retaining element 58 has an even more robust construction.

In addition to the first sections 64 and the second sections 66, third sections 82 are provided. The third sections 82 are strut-shaped and connect the bushing 62 to the second sections 66. The third sections 82 preferably run in the radial direction with respect to the axis 24. In addition to the double-T shape, the holding element 58 is in cross section with respect to the axis 24 , formed in this way sections X-shaped.

Third sections could also be provided to connect the first sections 64 to the second sections 66 . For example, if the holding element 58 is manufactured integrally with the piston rod 18, third sections could connect the piston rod 18 to the second sections.

Reference List

10

free piston device

12

casing

14

recording room

15

free piston engine

16

piston device

18

piston rod

20

combustion piston

22

springback piston

24

axis

26

piston mount

28

expansion space

30

piston area

32

piston mount

34

piston area

36

rebound space

38

springback device

40

energy coupling device

42

energy coupling device

44

plane of symmetry

45

linear generator

46

runner arrangement

48

stator assembly

50

level

52

magnetic element

54

reference plane

56

stator section

58

holding element

60

storage facility

62

Rifle

64

first section

66

second part

68

end section

70

end section

72

leg

74

bridge

80

free piston device

82

third section

Claims (20)

Free-piston device, comprising a free-piston motor (15) with a piston device (16) defining an axis (24) which under the effect of the expansion of a medium in an expansion space (28) delimited by a piston (20) of the piston device (16). , and a return spring device (38) can be moved back and forth axially, and at least one energy coupling device (40, 42) which has a stator arrangement (48) and a rotor arrangement (46) connected to the piston device (16) via a holding element (58). , wherein the runner assembly (46) is plate-shaped and defines a plane (50), characterized by a positioning of the axis (24) at a transverse distance from the plane (50) of the runner assembly (46), wherein a reference plane (24) containing the axis (24) 54) is aligned transversely to the plane (50) of the rotor arrangement (46), the stator arrangement (48) comprising at least one stator section (56) which is plate-shaped and parallel to the rotor anor Dnung (46) is arranged, and wherein the rotor arrangement (46) in the plane (50) defined by it and transverse to the reference plane (54) protrudes with at least one end section (68, 70) beyond the at least one stator section (56), wherein the holding element (58) is connected to the end section (68, 70). Free piston device claim 1 , characterized in that the reference plane (54) is aligned perpendicular to the plane (50) of the rotor assembly (46). Free piston device claim 1 or 2 , characterized in that the reference plane (54) intersects the rotor assembly (46) in the middle. Free piston device claim 3 , characterized in that the rotor arrangement (46) is designed symmetrically with respect to the reference plane (54). Free-piston device according to one of the preceding claims, characterized in that the at least one energy coupling device (40, 42) is designed electromagnetically, the rotor arrangement (46) being or comprising a magnet arrangement and the stator arrangement (48) being or comprising a coil arrangement. Free-piston device according to one of the preceding claims, characterized in that the stator arrangement (48) comprises two stator sections (56), between which the rotor arrangement (46) is positioned. Free-piston device according to one of the preceding claims, characterized in that the rotor arrangement (46) with two end sections (68, 70) projects beyond the stator section (56) on opposite sides, the end sections (68, 70) being connected to the holding element (58) are connected. Free-piston device according to one of the preceding claims, characterized in that the free-piston device (10; 80) comprises two energy coupling devices (40, 42). Free piston device claim 8 , characterized in that the energy coupling devices (40, 42) are arranged opposite one another with respect to a plane (44) which is oriented transversely to the reference plane (54) and contains the axis (24). Free piston device claim 9 , characterized in that the energy coupling devices (40, 42) are designed symmetrically with respect to the first-mentioned plane (44). Free-piston device according to one of the preceding claims, characterized in that the holding element (58) has at least one first section (64) which is aligned radially with respect to the axis (24) and is connected to the piston device (16), and at least one section which is aligned at an angle thereto second section (66) connected to the rotor assembly (46). Free piston device claim 11 , characterized in that the first section (64) is oriented parallel to the plane (50) of the rotor assembly (46) and that the second section (66) is oriented parallel to the reference plane (54). Free piston device claim 12 , characterized in that the holding element (58) on the first portion (64) and second portion (66) is L-shaped in cross section. Free-piston device according to one of Claims 11 until 13 , characterized in that the holding element (58) has at least a third section (82) which connects the first section (64), a bushing (62) connected thereto or the piston device (16) and the second section (66) in the manner of a strut connects. Free-piston device according to one of Claims 11 until 14 , characterized in that there are two first sections (64) and two second sections (66) connecting opposite end sections (68, 70) of the rotor assembly (46) to the piston means (16). Free-piston device according to one of Claims 11 until 15 , as far as one of the Claims 1 until 7 related, in connection with claim 9 or 10 , characterized in that the holding element (58) is designed symmetrically with respect to the first-mentioned plane (44). Free-piston device according to one of the preceding claims, characterized in that the holding element (58) is configured, at least in sections, in cross-section as a double T. Free-piston device according to one of the preceding claims, characterized in that the free-piston device (10; 80) has a bearing device (60) via which the holding element (58) and/or the rotor arrangement (46) on one of the free-piston motor (15) and the at least a housing (12) accommodating an energy coupling device (40, 42) is displaceably mounted. Free-piston device according to one of the preceding claims, characterized in that the holding element (58) is connected to a piston rod (18) of the piston device (16). Free piston device claim 19 , characterized in that the holding element (58) comprises or forms a bushing (62) through which the piston rod (16) extends.

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