Free-piston linear generator and method for controlling a free-piston linear generator

Abstract

Free-piston linear generator for generating electrical energy, built according to the opposed-piston principle, with: a cylindrical space (12) which has a longitudinal axis (A), a piston (14) movable in the cylinder chamber (12) along the longitudinal axis (A) and a counter-piston (14') movable in the cylinder chamber (12) along the longitudinal axis (A), mechanically separate from the piston (14), wherein the piston (14) and counter-piston (14') define a combustion chamber (16) within the cylinder chamber (12) with their end faces facing each other, several rotors (20) and associated stators (34, 36) mechanically coupled to the piston (14) and the counter-piston (14'), in each of which electrical energy can be generated when the associated rotor (20) is moved, wherein at least one inlet channel (44) opens into the combustion chamber (16), through which combustion fluid and / or air is introduced into the combustion chamber (16), at least one exhaust channel (46) extends from the combustion chamber (16), through which combustion gas escapes from the combustion chamber (16), which at least one intake channel (44) or, in the case of several intake channels, all intake channels (44) open into the combustion chamber (16) via one or more intake openings (48) in the area of ​​the bottom dead center of the piston (14), and which at least one exhaust port (46) or, in the case of multiple exhaust ports, all exhaust ports (46) extend in the region of the bottom dead center of the counter-piston (14') into one or more exhaust ports (50) from the combustion chamber (16), characterized in that, via an electrical control (42) for the stators (34, 36) or a variable reset device, the resistance which is opposed to the associated rotor (20) when moving along its associated stator (34, 36) and thus the movement of piston (14) and counter-piston (14') is controlled or regulated in such a way that the piston (14) at least when moving towards the bottom dead center lags behind the counter-piston (14') in order to reach its bottom dead center later than the counter-piston (14').

Description

[0001] The invention relates to a free-piston linear generator for generating electrical energy and a method for controlling a free-piston linear generator.

[0002] Such a free-piston linear generator combines a so-called free-piston engine, i.e., an internal combustion engine, with a so-called electric linear generator for extracting electrical energy from the system. A free-piston engine is characterized by the fact that it directly couples a heat engine with internal or external combustion with a working machine for providing pneumatic, hydraulic, or electrical energy. The free piston can move freely between its dead centers without kinematic constraints.

[0003] There are free-piston linear generators in which the rotor is positioned as a ring-shaped or disc-shaped magnet in direct extension of the piston coaxially to the longitudinal axis and runs in a ring-shaped stator surrounding it.

[0004] However, there is also another system of rotors and stators in which the rotors and stators are not coaxial with the longitudinal axis and in direct extension of the piston, but are arranged in groups to the side of the longitudinal axis. Thus, when viewed longitudinally at such systems, rotor-stator groups are arranged next to each other as stacks to the left and right, or above or below (spatial direction is not restricted). The invention relates to a free-piston linear generator with both systems.

[0005] In free-piston linear generators, which are constructed according to the opposed-piston principle, a piston and a mechanically separated opposing piston lie opposite each other in the cylinder chamber and their end faces define a common combustion chamber. This combustion chamber is enlarged when combustion fluid is burned in the combustion chamber. The pistons move apart and are then pushed back together by a spring-back mechanism. The gas and fuel supply as well as the combustion gas removal must be controlled in the combustion chamber. For this purpose, essentially diametrically opposed inlet and exhaust ports open into the combustion chamber. The inlet and exhaust ports are open when the pistons are at bottom dead center. In the area of ​​bottom dead center, the exhaust ports are open so that the combustion gas can flow out of the combustion chamber when the pistons are subsequently moved towards each other.Such an arrangement of the inlet and outlet openings is called cross-flushing.

[0006] A longitudinal scavenging of the combustion chamber is described in the generic US 2006 / 0 124 083 A1, in which the stators are also controlled in such a way that the pistons are synchronized with an initially asynchronous movement.

[0007] Furthermore, opposed-piston internal combustion engines are known from DE 195 03 444 C1 and DE 39 00 800 A1.

[0008] DE 852 620 B shows a valveless two-stroke internal combustion engine.

[0009] Furthermore, US 2009 / 0 090 334 A1 discloses an internal combustion engine for generating electrical energy with two pistons running asynchronously to one another.

[0010] The invention provides a free-piston linear generator which exhibits improved running performance during operation.

[0011] This is achieved by a free-piston linear generator for generating electrical energy, which is constructed according to the opposed-piston principle and has the features of claim 1.

[0012] The piston is deliberately moved asynchronously to the opposing piston, for example it runs behind the opposing piston at least during the movement towards the bottom dead center, i.e. due to the higher speed of the opposing piston it reaches its bottom dead center and the exhaust port earlier than the piston reaches its dead center and its intake port.

[0013] This different speed of the two pistons can be achieved by an electrical control system for the stators. The term "control system" refers to both open-loop and closed-loop control, with the latter being preferred. This control system changes the resistance opposed by the associated rotor as it moves along its associated stator. This control system then controls or regulates the movement of the piston and counter-piston. The control system controls or regulates the current in the corresponding coils of the stators, thereby braking the corresponding piston by reducing the permitted current flow through the coil. Alternatively or additionally, the speed or, more generally, the movement of the pistons can be controlled / regulated using variable or inherently different gas springs.For example, the amount of gas in the reset chamber can be changed and / or the reset pistons can have different piston diameters.

[0014] Furthermore, it is also possible to adjust the resistance of the piston and counter-piston using a variable return device, for example an adjustable gas spring.

[0015] The free-piston linear generator according to the invention operates exclusively according to the longitudinal scavenging principle. This means that there are no inlet and outlet ports located diametrically opposite one another or within a common annular section. Instead, the inlet ports are assigned to the piston and positioned at its bottom dead center, while the outlet ports are located near the bottom dead center of the opposing piston. This longitudinal scavenging removes gas more completely from the combustion chamber. Due to the fact that a free-piston linear generator has a variable stroke, this solution has not been considered previously. However, tests have shown that it is highly practical and advantageous.

[0016] A variant of the invention provides that the at least one inlet opening and the at least one outlet opening are closed in predetermined positions by the piston or counter-piston during operation. The piston and counter-piston are therefore used to control the fluid supply and the fluid outlet, respectively, eliminating the need for separate valves.

[0017] It is particularly advantageous if, as the piston and opposing piston move away from each other, i.e., toward bottom dead center, at least one exhaust port, or if several are present, preferably all exhaust ports, are opened before at least one or even all exhaust ports. This means that the exhaust gas is discharged during the stroke toward bottom dead center, before the fresh gas is supplied, and not only after bottom dead center is reached.

[0018] Longitudinal flushing, especially flushing with an outlet opened first, improves the flushing efficiency and reduces short-circuit flushing.

[0019] There are several ways to open the exhaust port before the intake port. One possibility is for at least one exhaust port to be closer to the axial center of the combustion chamber, relative to the top dead center of the piston and opposing piston, than at least one intake port. The axial center is determined when the piston and opposing piston are at top dead center, i.e. when they are as close to each other as possible. The axial distance between the piston and opposing piston is halved. This then results in the axial center of the combustion chamber. Provided that the piston and opposing piston do not move to bottom dead center at extremely different speeds, the opposing piston reaches the exhaust port first, moves past it so that it is exposed and exhaust gas can flow out through it.

[0020] Optionally, the cross-sectional areas of the or all inlet openings may be identical to the cross-sectional area or areas of the or all outlet openings.

[0021] A variant of the invention provides that the aforementioned electrical control can control the stator of the counter-piston in such a way that it opposes a different, in particular lower, resistance to the counter-piston during the movement along the stroke in the direction of the bottom dead center than the stator of the piston opposes to the piston.

[0022] Alternatively or additionally, it is also possible for the stator to offer varying resistance to the opposing piston during the travel path, i.e., along the stroke, due to the control system. For example, the resistance may increase toward bottom dead center.

[0023] Multiple inlet ports can extend from the intake port and / or multiple outlet ports can merge into the exhaust port. This improves scavenging. Furthermore, the gas flow can be faster and more even.

[0024] In particular, inlet openings and / or outlet openings with different cross-sections can be provided. These different cross-sections of the inlet openings and / or different cross-sections of the outlet openings are due to the fact that the flow is deliberately divided into sub-flows, but the different openings are located at different distances from the not-yet-branched channel. This results in different flow pressures and gas quantities in the sub-channels. For example, the cross-section of the respective inlet opening or outlet opening can become increasingly smaller with increasing distance from the not-yet-branched section of the inlet channel or outlet channel.

[0025] As already mentioned, the intake duct can split into several sub-ducts near the intake ports. These sub-ducts then lead to the intake ports. The last section of each sub-duct, which then terminates at the intake port, is the so-called intake port end. The same applies to the exhaust ports. These can also have sub-ducts that begin at the exhaust ports with exhaust port ends, i.e., the first section of the sub-duct. The sub-ducts then merge into a common exhaust port.

[0026] The intake port ends and / or exhaust port ends enter the combustion chamber at different angles or exit from the combustion chamber at different angles. These angles are measured in a radial section view relative to the longitudinal axis. These different angles are intended to optimize the flow through the combustion chamber.

[0027] In this context, it may be advantageous if those intake duct ends that are furthest away from a branching point on the intake duct, where the duct splits into sub-ducts, extend at a larger angle to the intake duct section immediately upstream of this branching point than the intake duct ends that are closer to the branching point. The intake duct ends located close to the branching point typically extend essentially parallel to one another in a straight line into the combustion chamber, whereas the more distant intake duct ends open into the combustion chamber facing toward one another.

[0028] Viewed in radial section, there may be pairs of inlet openings opposite each other, which can optionally even be designed in such a way that the inlet openings are aligned symmetrically to an axis.

[0029] The different flows to the intake ports or from the exhaust ports can be easily achieved by creating a circumferentially closed or nearly circumferentially closed annular space extending from the intake port around the combustion chamber, and by fluidly connecting the intake ports to the annular space. The same can also be provided for the exhaust port.

[0030] The cross-section of the annular space can be reduced with increasing distance from the inlet duct, especially continuously. Since the gas available for inflow upstream of the annular space decreases with increasing distance from the inlet duct section, the cross-section of the annular space is adjusted to accommodate the reduced gas flow.

[0031] The intake port, the intake port ends, the exhaust port, and / or the exhaust port ends should, when viewed from the side, run at an angle to the longitudinal axis in the area of ​​the transition to the intake ports or exhaust ports, for example, inclined toward the center of the combustion chamber. This gives the incoming gas a motion component directed toward the exhaust ports, allowing for rapid, complete inflow of gas into the combustion chamber. The same applies to the exhaust flow. Here, too, the sub-ports should be as diverted as possible.

[0032] The invention also relates to a method for controlling the piston and / or the counter-piston of a free-piston linear generator according to the invention for generating electrical energy, which is designed according to the counter-piston principle and has an electrical control system for the stators. The method is characterized by the following step: Controlling the stators in such a way that the resistance which is opposed by the stator to at least one rotor when moving along its associated stator is changed so that when the piston and counter-piston move away from each other, the piston at least during the movement towards the bottom dead centre follows the counter-piston in order to reach its bottom dead centre later than the counter-piston, wherein at least one outlet opening is opened before the at least one inlet opening.

[0033] The control system can further control a stator, but in particular control all stators, in such a way that the stator or stators oppose a different resistance to the opposing piston during the movement along the stroke in the direction of the bottom dead center than the stator or stators assigned to the piston oppose the piston during its movement in the direction of the bottom dead center.

[0034] Further features and advantages of the invention will become apparent from the following description and the following drawings, to which reference is made.

[0035] The drawings show: - Fig. 1 a schematic longitudinal sectional view through an exemplary first embodiment of the free-piston linear generator according to the invention, wherein the piston and counter-piston are shown at bottom dead center, - Fig. 2 the free-piston linear generator according to Fig. 1 with piston and counter piston at top dead center, - Fig. 3 a sectional view in the form of a radial section through the free-piston linear generator according to Fig. 1, - Fig. 4 is a schematic longitudinal sectional view through an exemplary second embodiment of the free-piston linear generator according to the invention, wherein the piston and counter-piston are shown at bottom dead center, - Fig. 5 the free-piston linear generator according to Fig. 4 with piston and counter piston at top dead center, - Fig. 6 a radial section view through the combustion chamber along the line VI-VI in Fig. 1, and - Fig. 7 a radial section view through the combustion chamber along the line VI-VI in Fig. 1 with an alternative gas routing.

[0036] In Fig. 1 shows a free-piston linear generator which has an internal combustion engine in the form of a piston engine with variable stroke, through which electrical energy is generated by means of a linear generator.

[0037] The free-piston linear generator shown is designed as an opposed-piston system.

[0038] In Fig. 1, the outer casing of the generator has been omitted for clarity. Inside the casing is a cylinder 10, within which a cylinder chamber 12 is formed. A piston 14 and a counter-piston 14', which are not mechanically connected to each other, are accommodated in the cylinder chamber 12. The pistons 14, 14' are each movable back and forth along a longitudinal axis A of the cylinder chamber and the generator and define a common combustion chamber 16 between them, which constitutes a part of the cylinder chamber 12.

[0039] Between the pistons 14, 14', preferably in the axial center between the pistons 14, an imaginary radial plane R is shown, which runs perpendicular to the longitudinal axis A. The Fig. The generator shown in Figure 1 is essentially mirror-symmetrical to the radial plane R, resulting in a left and a right half with essentially identical structures. However, there are also variants in which the left and right halves differ slightly, which can sometimes have advantages. For simplicity, the left half is explained below; the corresponding explanations apply to the right half.

[0040] Not shown is an injection system that can inject fuel into the combustion chamber 16.

[0041] Each piston 14, 14' is mechanically coupled to its own return piston 18, arranged coaxially with it, as well as to rotors 20, here in the form of plate-shaped rotors. The rotors 20 comprise several adjacent permanent magnets 22, or a single permanent magnet, which collectively have a plate-shaped configuration. The permanent magnet(s) can be arranged on a carrier plate 24. This carrier plate 24 is part of the rotor 20.

[0042] The return piston 18 is part of a return device 26 and is accommodated longitudinally in a cylindrical space, in which it defines a so-called return chamber 28. This forms a gas spring intended for returning the piston 14.

[0043] The connection of the piston 14 with the return piston 18 and the two runners 20 is made via a mechanical connection system 30.

[0044] As in Fig. 1, the two runners 20 are located laterally of the longitudinal axis A, viewed in the direction of the longitudinal axis A, and form a pair of runners which are opposite one another with respect to the longitudinal axis A, preferably diametrically to the longitudinal axis A.

[0045] The rotors 20 do not extend axially beyond an area limited by radial planes in which the opposite end faces of the piston 14 and its return piston 18 are located (see Fig. 1). These end faces also define the combustion chamber 16 on the one hand and the return chamber 28 on the other. Thus, the rotors 20 and stators are located completely laterally away from the piston 14 and return piston 18 and do not increase the axial installation space, although they themselves have a considerable axial length.

[0046] The connection system 30 comprises a cross-shaped coupling part 31, which is articulated to the associated piston 14, 14', its return piston 18 and the rotors 20.

[0047] In Fig. 3 shows a schematic sectional view whose sectional plane in the region of the cylinder 10 is the radial plane R and is offset radially outside the cylinder 10, namely along a radial plane which intersects the two fastenings 32 of the coupling part and the rotors 20.

[0048] The fastenings 32 are located diametrically opposite to the longitudinal axis A and in a radial plane.

[0049] Fig. Figure 3 further shows that stators 34, 36 are provided for each of the plate-shaped rotors 20 lying in one plane, with stators 34 being upper stators and stators 36 being lower stators. Between each pair of stators 34, 36 there is a slight gap 38 into which the respective plate-shaped rotor 20 projects laterally or through. The stators 34, 36 are usually designed as induction coils, i.e. windings. A relative movement between the rotor 20 and the stators 34, 36 induces a voltage or current, creating a permanently excited synchronous machine. Of course, it is also conceivable for the rotor 20 to have the coil and the stators 34, 36 to have the permanent magnet(s).

[0050] In the Fig. In the embodiment shown in Figure 3, each rotor 20 is mounted on the housing 41 via at least one linear bearing 40 or several linear bearings, regardless of its attachment to the connection system 30. The linear bearing(s) 40 run parallel to the longitudinal axis A.

[0051] All stators are connected to an electrical control system 42. The corresponding cables are only indicated to improve clarity.

[0052] For supplying air and / or a mixture of combustible fluid and air, an inlet port 44 and an outlet port 46 are provided in the wall of the cylinder 10. This inlet port 44 opens into the combustion chamber 16 via several inlet openings 48 when the cylinder 10 is at bottom dead center (see Fig. 1) or near the bottom dead center. The inlet openings 48 are distributed on an annular surface close to or immediately adjacent to the end face of the piston 14 facing the combustion chamber 16 (see Fig. 1). This means that these intake ports 48 are open to the combustion chamber 16 when the piston 14 has reached bottom dead center.

[0053] At the opposite end of the combustion chamber 16, relative to the bottom dead center, several exhaust ports 50 are also arranged distributed over an annular surface. Here, too, the exhaust ports 50 preferably directly border on the end face of the opposing piston 14' facing the combustion chamber 16 or are arranged in its vicinity. In any case, the exhaust ports 50 are open when the opposing piston 14' is at bottom dead center (see Fig. 1).

[0054] The free-piston linear generator is operated in such a way as will be explained in more detail below that when piston 14 and counter-piston 14' are moved from the top dead center ( Fig. 2) to the bottom dead center ( Fig. 1) The exhaust ports must be opened first before the intake ports are exposed. As shown in the Fig. 1 and Fig. 2, all inlet openings are assigned to the piston 14 and arranged at its bottom dead center, whereas all outlet openings 50 are assigned to the opposing piston 14' and are located at its bottom dead center.

[0055] The possibilities of how it can be ensured that the exhaust ports 50 are opened first when the pistons 14, 14' are moved to the bottom dead center are presented below.

[0056] A first option is that the exhaust ports 50 are located closer to the axial center of the combustion chamber 16 than the inlet ports 48. The axial center of the combustion chamber is set to the position of piston 14 and counter-piston 14' at their top dead centers ( Fig. 2) in which the axial center is half the distance between the pistons 14, 14'. The axial center coincides, for example, with the Fig. 1 as the radial plane R. If both pistons 14, 14' experience approximately the same driving force and also the same counterforce, for example, through the return devices 26 with their return pistons 18, both pistons 14, 14' move at approximately the same speed from top dead center to bottom dead center. Thus, the opposing piston 14', which otherwise covers the exhaust ports 50, can then release them earlier, as Fig. 1 shows when the piston 14 the inlet openings 48.

[0057] The functionality of the free-piston linear generator shown can now be briefly explained below using the Fig. 1 to 3 are described.

[0058] In Fig. 2, the pistons 14, 14' are in the top dead center position, meaning they are as close together as possible. Fuel in the combustion chamber, which is either injected or previously introduced through the intake ports 48, is ignited by an igniter, causing the combustion chamber to expand and the pistons 14, 14' to move away from each other.

[0059] The rotors 20 are moved between their stators 34, 36 via the respective connection system 30, thereby inducing current. Furthermore, the return pistons 18 move such that the respective return chamber 28 becomes smaller and the gas contained therein is compressed. Shortly before reaching the respective bottom dead center, the outlet openings 50 are first exposed by the opposing piston 14', allowing exhaust gas to flow out. Subsequently, the inlet openings 48 are exposed by the piston 14 sliding past them, allowing fresh gas or a gas-fuel mixture to flow into the combustion chamber 16. The incoming gas or fuel-gas mixture then forces the combustion gases completely out of the combustion chamber 16. This is therefore a pure longitudinal scavenging process, without any cross- or reverse scavenging.

[0060] The compressed gas in the respective return chamber 28 causes the respective return piston 18 to be subjected to force, moving its piston 14, 14' toward top dead center. During the movement toward top dead center, the pistons 14, 14' then close the inlet openings 48 and the outlet openings 50 again.

[0061] Of course, the return chambers 28 can also be connected to a gas reservoir via switchable valves in order to be able to adapt the gas volume to the movements of the return piston 18.

[0062] While in the solution just described, the piston and opposing piston 14 or 14' move synchronously from and to the axial center of the combustion chamber 16, it may alternatively be advantageous if the piston 14 lags behind the movement of the opposing piston 14' at least up to bottom dead center, in order to reach its bottom dead center and thus the intake ports 48 later than the opposing piston 14' has reached and exposed the exhaust ports 50. The latter variant can be achieved, for example, and this is not to be understood as limiting, by the electrical control 42. The control 42 can be used to control or regulate the resistance that the stators 34, 36 oppose to the rotors 20 and thus to the pistons 14, 14' during movement along their stators 34, 36.It is of course possible that only the piston 14 is subjected to resistance, whereas the counter piston 14' may move without additional resistance caused by the control 42.

[0063] For example, a predetermined time-displacement curve can be stored for one or both pistons 14, 14', and the respective position of the piston 14, 14' is then permanently queried via corresponding sensors, and the resistance of the stator 34, 36 ensures that the respective piston is also moved within the predetermined time-displacement diagram.

[0064] Another option for variably moving the pistons 14, 14' over time is realized through the reset devices. For example, the resulting resistances can be adjusted and modified by changing the gas quantity in the reset chambers 28 using valves (inlet or outlet valves).

[0065] Of course, optimal combinations can also be created from all of the above-mentioned variants.

[0066] The embodiment according to the Fig. 4 and Fig. 5 essentially corresponds to the Fig. 1 to 3, wherein the groups of rotors / stators arranged laterally next to the longitudinal axis A, here rotors 20 and stators 34, are not arranged laterally next to the movable unit comprising pistons 14, 14', connecting system 30 and return device 26, but spatially between the cylinder 10 including pistons 14, 14' and the respective return device. The stators 34 here comprise annular or disc-shaped permanent magnets 22, which are arranged next to one another and are moved within a stator 34 in the form of a toroidal coil. For reasons of clarity, the toroidal coil is shown in Fig. 5 omitted.

[0067] Even in the embodiment according to the Fig. 4 and Fig. 5, the exhaust ports 50 are exposed before the inlet ports 48 when the pistons 14, 14' move toward the bottom dead center. This is identical to the previously determined Fig. 1 to 3 described measures or combinations of measures.

[0068] As the Fig. 1, Fig. 2, Fig. 3 and Fig. 4, several inlet openings 48 and several outlet openings 50 are provided. Fig. Figure 6 illustrates, in a cross-section in the area of ​​the intake ports 48, what the channel layout inside the cylinder 10 may look like. The intake port 44 splits into several sub-channels at a branching point 52, up to which it is still guided as a single channel. First, two sub-channels are formed, which complement each other to form an annular space 54. This annular space 54 completely surrounds the combustion chamber 16. From the annular space 54, further sub-channels then branch off radially inward towards the combustion chamber 16. These sub-channels are shown in radial section according to Fig. 6 are designed in pairs symmetrically to a plane of symmetry S. The associated inlet channel ends 56, 58, and 60 form the ends of the sub-channels, which then end in the inlet openings 48. In addition, a central sub-channel is provided with an inlet channel end 62, which lies on the axis of symmetry S.

[0069] As in Fig. 6, the cross-section of the annular space 54 decreases continuously with increasing distance from the branch point 52.

[0070] The inlet openings 48 can also have a different cross-section with increasing distance from the branch point 52.

[0071] As in Fig. However, as can be seen in Figure 6, the angle of flow, indicated by arrows, in the pairs of opposite inlet channel ends 56, 58, and 60 relative to the channel section upstream of the branch point 52 is significantly different. Thus, with increasing distance between the corresponding inlet channel end 56 to 60 and the branch point 52, the gas or fuel-gas mixture flows in at a larger angle relative to the direction of the inlet channel 44 immediately upstream of the branch point 52 and also relative to the axis of symmetry S. These different flow directions are intended to achieve optimal scavenging.

[0072] The length of each inlet opening 48 in the axial direction should be the same.

[0073] In the Fig. 1, Fig. 2, Fig. 3 and Fig. 4 also shows that the inlet channel ends and the outlet channel ends, viewed in side view and in the region of the transition to the inlet openings 48 and outlet openings 50, extend obliquely to the longitudinal axis A, namely obliquely inward and obliquely toward the axial center of the combustion chamber 16. This is intended to provide a direction for the inflowing gas or fuel-gas mixture as well as the outflowing combustion gas, whereby rapid scavenging can be achieved.

[0074] The embodiment according to Fig. 7 corresponds to the following difference Fig. 6. The annular space 54 does not extend circumferentially closed around the combustion chamber 16, but ends at the inlet channel ends 60. Here too, however, the cross section of the partial channels forming the not entirely circumferentially closed annular space 54 decreases with increasing distance from the branch point 52. The angles of the flow in the pairs of opposite inlet channel ends 56, 58 and 60 relative to the Fig. 6 and Fig. The canal section before junction 52 shown in Figure 7 is different.

Claims

[1] Free-piston linear generator for generating electrical energy, constructed according to the opposed-piston principle, with: a cylinder chamber (12) having a longitudinal axis (A), a piston (14) movable in the cylinder chamber (12) along the longitudinal axis (A) and a counter-piston (14') movable in the cylinder chamber (12) along the longitudinal axis (A) and mechanically separate from the piston (14), wherein the piston (14) and the counter-piston (14') delimit a combustion chamber (16) with their end faces facing each other within the cylinder chamber (12), a plurality of rotors (20) mechanically coupled to the piston (14) and the counter-piston (14') and associated stators (34, 36), in each of which electrical energy can be generated upon movement of the associated rotor (20), wherein at least one inlet channel (44) opens into the combustion chamber (16), via which combustion fluid and / or air is introduced into the combustion chamber (16), at least one outlet channel (46) extends from the combustion chamber (16), through which combustion gas escapes from the combustion chamber (16), the at least one inlet port (44) or, in the case of several inlet ports, all inlet ports (44) open into the combustion chamber (16) in the region of the bottom dead center of the piston (14) via one or more inlet openings (48), and the at least one exhaust port (46) or, in the case of several exhaust ports, all exhaust ports (46) extend from the combustion chamber (16) in one or more exhaust openings (50) in the region of the bottom dead center of the counter-piston (14'), characterized bythat via an electrical control (42) for the stators (34, 36) or a variable return device, the resistance which is opposed to the associated rotor (20) during movement along its associated stator (34, 36) and thus the movement of piston (14) and counter-piston (14') is controlled or regulated in such a way that the piston (14) follows the counter-piston (14') at least during the movement towards the bottom dead center in order to reach its bottom dead center later than the counter-piston (14'). [2] Free-piston linear generator according to claim 1, characterized by that the at least one inlet opening (48) and the at least one outlet opening (50) are closed in predetermined positions by the piston (14) and / or counter-piston (14') during operation in order to control the fluid supply and / or the fluid outlet. [3] Free-piston linear generator according to claim 1 or 2, which is designed such that when the piston (14) and counter-piston (14') move away from each other, the at least one outlet opening (50) is opened before the at least one inlet opening (48). [4] Free-piston linear generator according to claim 3, characterized by that the at least one outlet opening (50) is located closer to the axial center of the combustion chamber (16) relative to the top dead centers of the piston (14) and counter-piston (14') than the at least one inlet opening (48). [5] Free-piston linear generator according to one of the preceding claims, wherein the control (42) controls the at least one stator (34, 36) assigned to the counter-piston (14') in such a way that it opposes a different resistance to the counter-piston (14') during movement along the stroke in the direction of the bottom dead center than the at least one stator (34, 36) of the piston (14) opposes to the piston (14). [6] Free-piston linear generator according to one of the preceding claims, characterized by that a plurality of inlet openings (48) extend from the inlet channel (44) and / or a plurality of outlet openings (50) merge into the outlet channel (46), in particular wherein inlet openings (48) and / or outlet openings (50) with different cross-sections are provided. [7] Free-piston linear generator according to claim 6, characterized by that the inlet channel (44) has a plurality of sub-channels leading to the inlet openings (48), and each sub-channel has at least one inlet channel end which ends in an inlet opening (48), and / or that outlet channel ends extending from the outlet openings (50) have sub-channels of a common outlet channel (46), wherein the inlet channel ends and / or the outlet channel ends open into and / or extend from the combustion chamber (16) at different angles, as seen in a radial sectional view to the longitudinal axis (A). [8] Free-piston linear generator according to claim 7, characterized by that the inlet channel ends furthest away from the branching point (52) of the inlet channel (44) at which it branches into sub-channels extend at a greater angle relative to the channel section immediately upstream of the branching point (52) than the inlet channel ends closest to the branching point (52), in particular wherein the angle increases with increasing distance from the branching point (52). [9] Free-piston linear generator according to claim 7 or 8, characterized by that, seen in radial sectional view, there are inlet openings (48) arranged in pairs opposite one another, in particular wherein the inlet openings (48) are aligned symmetrically to an axis. [10] Free-piston linear generator according to one of claims 6-9, characterized bythat an annular space (54) extending from the inlet channel (44) leads around the combustion chamber (16) and the inlet openings (48) are fluidly connected to the annular space (54), in particular wherein the cross section of the annular space (54) decreases with increasing distance from the inlet channel (44), preferably continuously. [11] Free-piston linear generator according to one of claims 6-10, characterized by that the inlet channel (44), the inlet channel ends, the outlet channel (46) and / or the outlet channel ends, seen in side view and in the region of the transition to the inlet openings (48) and / or the outlet openings (50), run obliquely to the longitudinal axis (A), in particular are inclined obliquely towards the axial center of the combustion chamber (16). [12] Method for controlling the piston (14) and counter-piston (14') of a free-piston linear generator according to one of the preceding claims for generating electrical energy, which is designed according to the counter-piston principle and has an electrical control for the stators (34, 36), characterized by following step: Controlling the stators (34, 36) in such a way that the resistance which is opposed by the stator (34, 36) to at least one rotor (20) during movement along its associated stator (34, 36) is changed in such a way that when the piston (14) and the counter-piston (14') move away from one another, the piston (14) follows the counter-piston (14') at least during the movement towards the bottom dead centre in order to reach its bottom dead centre later than the counter-piston (14'), wherein the at least one outlet opening (50) is opened before the at least one inlet opening (48). [13] Method according to claim 12, characterized bythat the control system controls at least one stator (34, 36) in such a way that it opposes the counter-piston (14') with a different resistance during movement along the stroke in the direction of the bottom dead center than the stator or stators (34, 36) assigned to the piston (14) oppose the piston (14).

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