DE102011000620B4 - Free piston device and method for operating a free piston device - Google Patents

Abstract

There is provided a free-piston device with at least one free-piston engine, comprising at least one piston seat, in which at least one expansion space for the expansion of a working medium is formed and in which at least one resilience space is formed, and a linearly movable piston device with at least one piston, wherein a first piston side the piston device delimits the at least one expansion space and a second piston side of the piston device delimits the at least one resilience space and wherein in the at least one resilience space a return spring means for providing a restoring force for the piston device is arranged, wherein at least one compression space is provided, which of the at least one Expansion space and the at least one resilience space is separated, which is bounded by at least one piston of the piston device, and in which by means of the piston means a Federeinrich tion and / or a medium is compressible.

Description

The invention relates to a free-piston device with at least one free-piston engine, comprising at least one piston receptacle, in which at least one expansion space for the expansion of a working medium is formed and in which at least one resilience space is formed, and a linearly movable piston device with at least one piston, wherein a first piston side the piston device delimits at least one expansion space and a second piston side of the piston device delimits the at least one resilience space and wherein in the at least one resilience space a return spring device for providing a restoring force for the piston device is arranged.

The invention further relates to a method for operating a free-piston device.

Free piston devices are for example from the WO 03/091556 A1 and the EP 1 398 863 A1 known.

From the WO 2007/147789 A1 a method for operating a free-piston device is known in which the restoring force is controlled and / or regulated during operation of the free-piston device by the desired value of at least one state variable of a gas in the resilience space is specified, the actual value is detected and at deviation from the target value at least approximately to the same is adjusted.

Control and regulation techniques for free piston devices are described in the article "Free-Piston Diesel Engine Timing and Control - Towards Electronic Cam and Crankshaft" by TA Johansen et al., In IEEE Trans. Control Systems Technology, 10 (188-190), 2002 , and "Dynamics and Control of a Free-Piston Diesel Engine" by TA Johansen et al., in Proc. American Control Conference, Arlington, Va., 2001.

From the DE 43 44 915 A1 For example, a linear combustion engine generator is known in which two opposed pistons operating on a two-stroke principle bring a rotor with one or more coil-shaped pairs of magnetic poles into reciprocating linear motion and thereby generate electric current on the cylindrical stator in the windings.

From the DE 198 13 992 A1 is a free-piston internal combustion engine with electrical energy output known. It is a non-metallic, permanent magnetic piston provided in a cylinder, which is offset by combustion pressure in linear oscillatory movements. The energy extraction takes place inductively by arranged around the cylinder coils.

In the article "Comparison of gas spring variants with variable characteristic for a free-piston engine" by S.-E. Pohl and C. Ferrari, Forsch. Engineering (2007) 71: Pages 181 to 188, gas spring variants are described, which are suitable for use in a free-piston engine due to their adjustable spring characteristic.

From the WO 2009/156257 A1 a method for operating a free-piston device is known in which a force profile of a force-displacement curve for a piston device is specified.

From the WO 2007/147789 a free piston device is known comprising at least one piston receptacle in which at least one piston device is arranged to be linearly movable, wherein the at least one piston device is drivable under the action of a medium which expands in an expansion space, and wherein the at least one piston receptacle has a resilience space, in which a compressible gas is received for exerting a restoring force on the at least one piston device, and at least one actuator for controlling and / or regulating the restoring force, which is arranged on the resilience space, wherein the restoring force in the operation of the free-piston device is controllable and / or controllable ,

From the DE 10 2007 035914 A1 a free piston device is known, comprising at least one piston receptacle, at least one in the corresponding piston receptacle linearly movable piston device having a first piston surface and a second piston surface which faces away from the first piston surface, and an expansion chamber arranged in the piston receiving, which is bounded by the first piston surface wherein the piston means is drivable under the action of a medium which expands in the expansion space. In the at least one piston receiving a return spring space is arranged, which is limited by the second piston surface.

The invention has for its object to provide a free piston device of the type mentioned, which allows extended operating options.

This object is achieved in the aforementioned free piston device according to the invention in that at least one compression space is seen before, which is separated from the at least one expansion space and the at least one resilience space, which is bounded by at least one piston of the piston device, and in which by means of the piston device, a medium and / or a spring device is compressible.

The at least one piston chamber is a functional space, which can receive a spring device and / or a medium for its compression. The spring device can be used in different ways depending on the operation of the free-piston device.

The medium can be used, for example, in particular in a two-stroke operation of the free-piston device, to generate a pressure difference between an inlet port and an outlet port of the expansion space. The compressed medium can be used for pressure loading of the expansion space. It is possible to provide over the compression space a portion of the required for the pressure charge of the expansion space medium or the full amount of media.

This is also possible in a four-stroke operation of the free-piston device. It can thereby increase the efficiency. In a four-stroke operation, the spring device in the compression space can also be used to provide a driving force for the piston device opposite the return spring device of the resilience space.

Each of the at least one compression chamber is assigned (at least) one piston, which ensures the compression of medium which is received in the at least one piston chamber or the spring device. This corresponding piston is rigidly connected to the piston device or is a part of the piston device.

In one embodiment, the at least one expansion space is arranged in the piston receptacle, that is, is arranged in the cylinder in which the piston device is arranged. In principle, it is also possible for the at least one compression space to be arranged outside the piston receptacle for the piston device.

It is basically possible that the at least one expansion space and the at least one compression space are arranged on the same axis or are arranged at different distances with respect to this axis. The axis is in particular coaxial or parallel to a direction of movement for the linear movement of the piston device. It is also possible in principle that the resilience space and the compression space are arranged on the same axis or are arranged at a distance from the axis.

In principle, the spring device may comprise one or more mechanical springs, such as steel springs. It is also possible that the spring device is formed by a compressible medium. Furthermore, it is possible that the spring device comprises a compressible medium and, for example, additionally one or more mechanical springs are provided. In particular, in a four-stroke operation can be provided by the spring means a propelling force for the piston device which acts in the opposite direction to the restoring force of the return spring means in the resilience space.

It is favorable if a fluid connection device is provided, through which the at least one expansion space and the at least one compression space are fluidically connected or connectable. As a result, compressed medium and in particular compressed gas (for example air) can be made available to the at least one expansion space in order to generate, for example, a flushing pressure.

In particular, compressed medium (for example charge air) can be supplied via the fluid connection device to the at least one expansion space.

As a result, a pressure charger is formed by means of the at least one compression space.

It is favorable if the fluid connection device is connected in a fluid-effective manner to an inlet connection of the at least one expansion space. Through this inlet port can then be a subset or a total amount of charge medium, which is required for operation, provide.

It is also advantageous if the at least one compression space is fluidly connected on the output side to a pressure storage device. As a result, the pressure storage device can be provided with compressed medium which can be provided to the expansion space instantaneously or with a time delay.

In one embodiment, the at least one expansion space is fluidly connected on the input side to a pressure storage device. Thereby, compressed medium may be provided from the accumulator means to generate, for example, a purge pressure in the expansion space.

In particular, the pressure storage device is associated with a valve, by means of which temporally controlled the at least one expansion space compressed medium can be fed. That's it For example, it is possible to provide such compressed medium to the at least one expansion space with a time offset from a generation time of the compressed medium.

In principle, it is possible that the pressure storage device is formed by one or more lines for medium.

In an advantageous embodiment, the pressure storage device comprises at least one storage container for medium. This storage container can form a buffer for compressed medium. This also makes it possible, for example, to decouple a provision of compressed medium in an expansion space in terms of time from the production of the compressed medium into the at least one compression space.

Advantageously, at least one first port is assigned to the at least one compression space, can be inserted via the medium and, in particular, medium can be introduced from a medium-containing environment. For example, air can be sucked in from the environment into the compression space via the first connection. This makes it possible to load the compression chamber with medium to be compressed.

In particular, a controllable valve device (charging valve device) is seated at the first port. As a result, it is possible to timely control and in particular adapted to a corresponding cycle operation of the free-piston device to draw medium into the at least one compression space.

Furthermore, at least one second port is assigned to the at least one compression space, via which compressed medium can be discharged. Compressed medium can be made available for further use via the second connection (in particular in a four-stroke mode) or compressed medium can be discharged in order to "switch off", for example, a gas spring which is formed by compressed medium in the at least one compression space. ; this is particularly advantageous or necessary in a four-stroke operation of the free-piston device. The second terminal may be separate from a first terminal or integrally formed with the first terminal.

It is advantageous if a controllable valve device is arranged in the second connection. As a result, a corresponding timing is possible. In particular, a controllable valve device is assigned to the first connection and the second connection in order to enable timed control adapted to one another. It is fundamentally possible for the first connection and the second connection to be formed by means of the valve device.

The medium is in particular a gas such as air.

In an advantageous embodiment, the medium is an oxidizer for the combustion of fuel in the at least one expansion space and is in particular air.

In one embodiment, the at least one compression space is arranged inversely with respect to a volume change to the at least one resilience space, wherein a volume increase of the resilience space causes a synchronous volume reduction of the at least one compression space and a volume reduction of the at least one resilience space causes a synchronous increase in volume of the at least one compression space. As a result, for example, by means of the restoring force of the return spring device in the resilience space, compressed medium can be generated in the at least one compression space.

In one embodiment, the at least one compression space and the at least one resilience space are then arranged in a common housing, wherein a piston side opposite the second piston side, which is formed in particular on the piston with the second piston side, limits the at least one compression space. As a result, a compression space and the resilience space can be accommodated compactly in a housing.

It is also possible that the at least one compression space and the at least one resilience space are arranged in different housings. Depending on the application, an optimized design can then be realized.

It is also possible for the at least one expansion space and the at least one compression space to be inversely disposed with respect to a volume change, wherein a volume increase of the at least one expansion space causes a synchronous volume reduction of the at least one compression space and a volume reduction of the at least one expansion space causes a synchronous volume increase of the at least causes a compression space. As a result, for example, a power stroke in the expansion space can be used directly for the production of compressed medium.

In particular, then the at least one compression space and the at least one expansion space are arranged in a same housing or the same housing part, wherein one of the piston side opposite the first piston side delimits the at least one compression space, and in particular the first piston side and the piston side delimiting the at least one compression space are formed on the same piston. As a result, a compact design can be obtained.

In one embodiment, a first compression space is associated with the at least one expansion space, and the second compression space is associated with the at least one resilience space, wherein the first compression space and the second compression space are separate spaces. It is thereby possible to produce a larger amount of compressed medium and to lower pulsations.

In an advantageous embodiment, a linear drive is provided with a magnetic device arranged on the piston device and a coil device, wherein the magnetic device is movable relative to the coil device. By moving the piston device, the magnetic device, which in particular comprises permanent magnets, is moved on the coil device. This induces a voltage and generates a usable current. The free-piston device can thereby generate electricity. By means of a corresponding current application of the coil device, the movement of the piston device, in particular with regard to stroke, compression, etc., can also be influenced.

The invention is further based on the object to provide a method of the type mentioned, with which result in extended operating options.

This object is achieved in the said method according to the invention in that in the at least one compression space compressed medium is generated, which is provided to the at least one expansion space and / or arranged in the at least one compression space spring means for driving the piston device is used.

The inventive method is carried out in particular on the free-piston device according to the invention.

The at least one compression space causes a movement of the piston device from the top dead center (relative to the expansion space) in a four-stroke operation via a spring device arranged therein (such as a mechanical spring device or gas spring device) in relaxation (decompression) of the spring device bottom dead center. During the movement of the piston device in the opposite direction, the spring device is tensioned (compressed).

For example, in a two-stroke operation, the compressed medium may be used to generate a purge pressure differential in the at least one expansion space.

In a four-stroke operation, for example, a compressed medium can be used as a gas spring to provide a driving force for the piston device against a restoring force of the return spring device.

Alternatively or additionally, it is also possible to provide the driving force counter to the restoring force by a mechanical spring device which comprises one or more mechanical springs.

Further advantageous embodiments of the method according to the invention have already been explained in connection with the device according to the invention.

In particular, the free-piston device can be operated in a two-stroke operation or in a four-stroke operation. It is in principle possible that a two-stroke operation or four-stroke operation is possible on the same free piston device without structural changes.

In one embodiment of a two-stroke operation, a valve device, which is assigned to the at least one compression space, is controlled so that the at least one compression space is either fluidly connected to a medium-containing environment or connected to a pressure storage device. The at least one compression space thus has two modes of operation, namely, for the suction of medium for subsequent compression, and on the other hand, the compression process.

In particular, the operation then takes place in such a way that, when the piston device is in top dead center OT _ex with respect to the at least one expansion chamber, the valve device is actuated such that the at least one compression chamber is fluidically connected to the environment. As a result, medium from the environment (in particular air) can flow into the at least compression space.

When moving out of the piston device from the top dead center OT _ex then medium from the environment is sucked into the at least one compression chamber. This is filled with medium.

If the valve device is actuated in a top dead center OT _{r of} the piston device relative to the at least one resilience space such that the at least one compression space is fluidically connected to the pressure storage device, then the corresponding movement of the piston device can be compressed out of top dead center OT _r Generate medium and couple into the pressure storage device.

It is then compressed when moving out of the piston device from the top dead center OT _r medium and the pressure storage device provided for later use, in particular as a charging medium.

In particular, compressed medium from the pressure storage device is provided to the at least one expansion space for a flushing operation at the end of an expansion phase of the piston device in the at least one expansion space. It is achieved by a temporal offset between the formation of the compressed medium and coupling of the compressed medium in the expansion space. Compressed medium in the at least one compression chamber is generated only after the end of the expansion phase of the piston device (at the end of the expansion phase, the piston device at bottom dead center with respect to the expansion space) in the at least one compression chamber, it already needed immediately at the end of the expansion phase in the expansion space becomes.

In a four-stroke operation, it is advantageous if, in a power stroke in which the piston device moves out of a top dead center OT _ex with respect to the at least one expansion space, a valve device which is assigned to the at least one expansion space is activated, that medium from the environment is sucked into the at least one compression space, in particular if in a later cycle (Ausschiebetakt) the compressed medium forms a spring device which drives the piston device in a forward thrust with a force which is directed against the restoring force of the return spring in the resilience space , In this working cycle in which, for example, combustion takes place in the expansion space, the at least one compression space is then loaded with fresh medium.

In a following after a power stroke Ausschiebetakt for exhaust gases, which were generated in the power stroke and which follows the power stroke and in which the piston device in the direction of the top dead center OT _ex (from the bottom dead center UT _ex out) moves, is advantageously the valve means so controlled that the medium is compressed in the at least one compression space and / or the spring device is compressed in the at least one compression space. The spring device acts as an energy store, in which mechanical energy is stored to generate a driving force in a subsequent cycle. Furthermore, the spring device serves to cushion the return movement of the piston device. If a compressible medium is used, then this forms a gas spring.

It is advantageous if in a subsequent intake stroke, which follows the Ausschiebetakt and flows into the fresh gas in the at least one expansion space, the spring means the piston means from the top dead center (OT _ex ) based on the expansion space in the direction of bottom dead center (UT _ex ) moves and in particular medium in the at least one compression space forms a gas spring for the piston device. The relaxation of the spring device counteracts the restoring force of the return device and causes a displacement of the piston device starting from the top dead center OT _ex in the direction of the bottom dead center UT _ex via a corresponding spring force. If the compression chamber is filled with a compressed medium, then the relaxation of this medium causes a propulsion of the piston device against the restoring force of the return device. The compressible medium then forms a gas spring.

Furthermore, it is advantageous if in a subsequent compression stroke, which follows the intake stroke and in which gas is compressed in the at least one expansion space, the valve device is driven so that medium flows out of the at least one compression space. As a result, new fresh medium can subsequently flow into the at least one compression chamber for later use in the intake stroke. It is basically also possible that the outflowing medium is released to the environment.

In an advantageous embodiment, outflowing compressed medium is provided to an accumulator device in order, for example, to be able to provide the compressed medium to the expansion space. This can increase the efficiency.

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

1 a schematic representation of an embodiment of a free piston device according to the invention;

2 a schematic representation of a second embodiment of a free-piston device;

3 a schematic representation of a third embodiment of a free-piston device;

4 a schematic representation of a fourth embodiment of a free-piston device;

5 a schematic representation of a fifth embodiment of a free-piston device;

6 a schematic representation of a sixth embodiment of a free-piston device;

7 a schematic representation of a first embodiment of a valve device which is associated with a compression chamber;

8th a schematic representation of a second embodiment of a valve device; and

9 a schematic representation of a third embodiment of a valve device.

An embodiment of a free piston device according to the invention, which in 1 shown and there with 10 is designated, comprises (at least) a free-piston engine 12 , The free-piston engine 12 in turn, includes one as a whole 14 designated piston receptacle (cylinder). In the piston receptacle is a piston device 16 arranged linearly movable. In the embodiment shown, the piston device 16 a first piston 18 and a second piston 20 on. The first piston 18 and the second piston 20 are about a connecting element 22 such as a rod connected together.

The free-piston engine 12 has an expansion chamber 24 on, in which an expansion space 26 is formed. The expansion space 26 For example, is a combustion chamber in which a fuel with oxidant (especially air) can burn and thus the piston device 16 drives.

The expansion chamber 24 has a housing 28 in which the first piston 18 is arranged. The first piston 18 limited thereby with a first piston side 30 the expansion area 26 , The expansion space 26 has a variable volume.

In one embodiment is at an end face 32 the expansion chamber 24 is (at least) one inlet port 34 arranged over which oxidizer, fuel or an oxidizer-fuel mixture in the expansion space 26 can be coupled. At the inlet port sits (at least) a controllable valve 36 which signal-effectively with a control / regulation device 38 connected is. The inlet connection 34 can thereby be controlled open and lock.

At the front 32 is still (at least) an outlet port 40 arranged on which (at least) a controllable valve 42 sitting. This controllable valve is signal effective with the control / regulating device 38 connected. About the valve 42 let waste products of an expansion phase and in particular controlled discharge combustion gases.

At the front 32 also optionally sits an ignition device 44 , which signal effective with the control / regulating device 38 connected is. About the ignition device 44 can ignite an oxidizer-fuel mixture. It may also be provided an injection valve to fuel or a mixture directly into the expansion space 26 inject.

The expansion chamber 24 is in the area of the front side 32 designed such that in a top dead center OT _{ex of} the expansion space 26 the piston device 16 between the first piston side 30 and the front side 32 a room 46 remains. This is the expansion chamber 24 for example, on the front side 32 dome-shaped.

The piston device 16 refers to the expansion area 26 also a bottom dead center UT _ex . The linear movement of the piston device 16 takes place between top dead center OT _ex and bottom dead center UT _ex . These dead points may be fixed or variable. For example, these can be variably adjustable via a linear drive (see below) (possibly also during operation). Also, a variable restoring force of the resilience space (see below) can allow a variable adjustment of the dead centers.

The piston receiver 14 also has a chamber 48 on. In this chamber 48 is a resilience space 50 educated. The resilience space 50 represents a restoring force of the piston device 16 ready to move from the bottom dead center UT _ex toward the top dead center OT _ex .

In the resilience space 50 a return spring means is arranged. It can basically be a mechanical spring device. In a preferred embodiment, the return spring device is formed by a compressible medium and in particular compressible gas, so that a gas spring for providing the restoring force is present.

The second piston 20 has a second piston side 52 on which the resilience space 50 in the chamber 48 limited. The volume of the resilience space 50 is variable.

The resilience space 50 is the second piston side 52 opposite by a front side 54 the chamber 48 limited. At the front 54 can have one or more connections 56 be arranged over the springback medium in the resilience space 50 einkoppelbar is or can be removed from this.

The connection 56 is a valve 58 assigned, which is particularly controllable. The valve 58 is signal effective with the control / regulation device 38 connected.

In the chamber 48 is a compression room 60 arranged. The compression space is through one of the second piston side 52 of the second piston 20 opposite piston side 62 limited. He is also through an end wall 64 the chamber 48 limited. The volume of the compression space 60 is variable and inversely variable to the volume of the resilience space 50 : When the volume of the resilience space 50 is increased, correspondingly synchronously the volume of the compression space 60 abased; when the volume of the resilience space 50 is decreased synchronously, the volume of the compression space 60 elevated.

The chamber 48 has a housing 66 in which both the compression space 60 as well as the resilience space 50 are limited, and both are through different sides of the second piston 20 limited.

In the front wall 64 is an opening 68 formed, through which the connecting element 22 is guided. It is for a corresponding seal at the opening 68 taken care of.

Between the case 28 and the housing 66 the piston receiving 14 is a linear actuator 70 of the free-piston engine 12 arranged. This includes a magnetic device 72 , In one embodiment, the magnetic device has a plurality of alternately poled magnetic elements 74 on which at the connecting element 22 are arranged.

The magnetic device 72 moves with the piston device 16 ,

Stationary (that is immovable with respect to the piston receptacle 14 ) is a coil device 76 arranged, wherein the magnetic device 72 during the movement of the piston device 16 in the coil device 76 emotional.

In one embodiment, the linear movement of the piston device 16 used on the coil device 76 to generate electricity. This electrical current is usable.

It is also possible in principle, via the linear drive 70 the movement of the piston device 16 to control or regulate. This is in 1 by the signal connection of the control / regulation device 38 with the linear drive 70 indicated (reference numeral 78 ).

The piston device 16 with her second piston 20 refers to the resilience space 50 a bottom dead center UT _r on which the piston side 62 their smallest distance to the front wall 64 Has. Furthermore, it has a top dead center OT _r , in which the second piston side 52 their smallest distance to the front side 54 Has. At top dead center OT _ex (relative to the expansion space 26 ) is the piston device 16 related to the resilience space 50 in its bottom dead center UT _r . Accordingly, the piston device is located 16 in its bottom dead center UT _ex with respect to the expansion space 26 in its top dead center OT _r relative to the resilience space 50 ,

The compression room 60 can accommodate a compressible medium and especially a gaseous medium. In particular, the compression space decreases 60 Air on.

At the front wall 64 the chamber 48 a connection device is arranged, via which a coupling / decoupling of medium can take place.

Basically, the connection device comprises 80 a first connection 82 , via which medium from a medium-containing environment can be coupled. The environment contained in the medium is, for example, the ambient air, from the air into the compression space 16 is sucked.

Furthermore, the connection device comprises 80 a second connection 84 , via the medium and in particular compressed medium from the compression space 60 is deductible.

At the connection device 80 sits a valve device 86 , About this can be the Opening and closing the first connection 82 and the second port 84 timed. The valve device 86 is to signal effective with the control / regulation device 38 connected.

The connection device 80 is a fluid connection device 88 associated, via which medium and in particular compressed medium from the compression space 60 the expansion area 26 via its inlet connection 34 is available. It can thereby realize a pressure loader or a flush.

The fluid connection device 88 is to a pressure storage device 90 connected. The pressure storage device 90 can basically by one or more lines 92 be formed, via which medium (in particular compressed medium) of the compression space 60 the inlet connection 34 is supplied.

It is also possible that the pressure storage device 90 additionally one or more storage tanks 94 includes. As a result, a buffer pressure storage can be realized.

It is basically provided that the pressure storage device 90 and in particular the storage container 94 a controllable valve 96 is assigned, which signals effective with the control / regulating device 38 connected is. Through the valve 96 can be a provision of buffered compressed medium to the expansion space 26 timed.

The compression room 60 is one of the expansion room 26 and the resilience space 50 separate room in which medium is compressible. It is a functional space, wherein, for example, by compressed medium there, the pressure which at the inlet port 34 is present, can be increased; this is especially true in a two-stroke operation of the free-piston engine 12 meaningful.

Compressed medium in the compression room 60 For example, it can also be used in four-stroke operation to provide a gas spring. In principle, it is also possible in particular in a four-stroke operation that in the corresponding compression space 60 alternatively or additionally, a mechanical spring device 85 is arranged. This mechanical spring device 85 includes one or more mechanical springs, which are located on the second piston 20 and a wall of the compression space 60 (especially on the front wall 64 ) is supported.

In one embodiment, the valve device is 86 , which at the connection device 80 sits as a three / two-way valve 98 educated ( 7 ). There are basically two fluid paths, namely one the first port 82 associated injection path for medium from the environment and a second port 84 associated decoupling path for compressed medium from the compression space 60 ,

In a further embodiment of a valve device 86 , are, as in 8th indicated, a first check valve 100 for the first connection 82 and a second shut-off valve 102 for the second connection 84 intended. The check valves 100 . 102 are in particular threshold-controlled (for example by spring loading). For example, they only open when a certain threshold pressure is exceeded or undershot. In particular, then, for example, the first check valve 100 which is the first connection 82 is assigned, opened until a certain pressure threshold is exceeded. The second shut-off valve 102 opens when a certain pressure threshold is exceeded. The check valves 100 . 102 are in particular check valves without active control. They are so far "passive" controlled by the thresholds.

It is also possible that the valve device 86 , as in 9 indicated, for the first connection 82 and the second port 84 separate controllable valves 104 . 106 includes.

The valve device 86 for a compression chamber may be formed by means of different types of valves, such as poppet valves, switching valves, check valves, overflow valves, rotary valves, etc.

The free-piston engine 12 works as follows:
In a two-stroke operation is the valve device 86 (Charging valve device) switched so that either the first port 82 is open and the second connection 84 closed, or the first connection 82 is closed and the second connection 84 is open. In the first case is the compression space 60 fluidly connected to the environment, so that medium from the environment in the compression space 60 can be sucked. In the second case is the compression space 60 fluidly effective with the pressure storage device 90 connected so that compressed medium to the pressure storage device 90 for buffering or for direct supply to the inlet connection 34 is deliverable.

When the first piston 18 the piston device 16 in the top dead center OT _ex (relative to the expansion space 26 ), then the valve means 86 so driven that the first connection 82 is active, that is, that medium in the compression space 86 is sucked. When the first piston 18 then from top dead center OT _ex towards bottom dead center UT _ex moves, so increases the volume of the expansion space 26 and synchronously, the volume of the compression space increases 60 , The one in the compression room 60 resulting negative pressure causes medium (especially fresh air) from the environment through the first port 82 in the compression room 60 is sucked in.

In the resilience space 50 the corresponding spring device is compressed. When a gas spring is used as the return spring means, the springback space increases 50 the pressure. This will cause the piston device 16 braked and comes in top dead center OT _r (relative to the resilience space 50 ) to stand. It then turns the direction of movement.

When the piston device 16 is located at top dead center OT _r , the valve device 86 so driven that the first connection 82 is locked and the compression space 60 fluidly effective with the pressure storage device 90 is connected. If then the second piston 20 from the top dead center OT _r in the direction of the bottom dead center UT _r (relative to the resilience space 50 ) due to the restoring force of the return spring means of the resilience space 50 moves, then the medium in the compression chamber 60 compressed. As a result, the pressure storage device 90 "filled". It becomes the storage tank 94 filled or at the inlet port 34 stands for compressed medium.

When the direction of movement of the piston device 16 in turn turned over when the first piston 18 reached the top dead center OT _ex or the second piston 20 reaches the bottom dead center UT _r , then the valve device 86 again so controlled that the second connection 84 closed and the first connection 82 is opened. This allows the compression space 60 be reloaded with compressible medium.

As mentioned above, the pressure storage device 90 through one or more lines 92 be formed. In the case of providing a storage container 94 especially the valve 96 so controlled that a time offset between the supply of compressed medium at the inlet port 34 and the generation of the compressed medium in the compression space 60 is present.

The compressed medium becomes in the compression space 60 during the compression phase of the first piston 18 (during movement of the first piston 18 from its bottom dead center UT _ex to top dead center OT _ex ). A flush of the expansion room 26 (Coupling of oxidizer and fuel and discharge of exhaust gases) takes place but only at the end of an expansion phase of the piston device 16 (at the end of the phase of movement between top dead center OT _ex and bottom dead center UT _ex ). As a result, there is a time lag when compressed medium is needed for purging and when compressed medium in the compression space 60 is produced. Through the storage tank 94 and according to the control of the valve 96 this can be compensated, that is the storage container 94 acts as a buffer and compressed medium becomes the expansion space 26 then provided when needed, namely, in a short period of time to reach the bottom dead center UT _{ex of} the first piston 18 around.

In the two-stroke operation of the free-piston engine 12 becomes compressed medium and in particular charge air the expansion space 26 especially provided as a combustion chamber. The compression room 60 effectively forms a pump to provide compressed charge air.

It can then, for example, the entire for a combustion process in the expansion space 26 needed fresh air or only part of it in the compression space 60 be compressed.

In principle, it is then possible, for example, for an additional electrical pressure charger to be provided. This can optionally by the linear drive 70 are driven.

In 1 are the first piston 18 and the second piston 20 shown with the same diameter. It is also possible that the second piston 20 a different diameter than the first piston 18 having. By adjusting the diameter of the second piston 20 in relation to the first piston 18 For example, the mass of a compressed medium can be adjusted to that for flushing the expansion space 26 required mass corresponds.

In a four-stroke operation of the free-piston engine 12 There are basically four different measures, namely:
In one cycle, for example, the combustion of fuel takes place in the expansion space 26 , The piston device 16 with her first piston 18 moves thereby from the top dead center OT _ex in the direction of the bottom dead center UT _ex . During this movement, the return spring means in the resilience space 50 compressed. The valve device 86 is so controlled that the first connection 82 is open and medium from the environment in the compression space 60 is sucked in.

In a subsequent Ausschiebetakt drives the return spring in the resilience space 50 the piston device 16 in the opposite direction from the bottom dead center UT _ex to the top dead center OT _ex . The valve device 86 is controlled so that the compression space 60 is locked, which means that no medium can escape from this. One or more valves 42 at the outlet port (s) 40 are open, so exhaust fumes from the expansion area 26 can be repelled. The medium in the compression room 60 becomes inverse to the volume change of the resilience space 50 compressed. The pressure in the compression chamber 60 rises and the piston device 16 This will over the compression space 60 braked.

In a subsequent intake stroke, the valve or valves are 42 closed. The inlet port (s) 34 are open and oxidizer and fuel can be coupled. The piston device 16 moves from the top dead center OT _ex toward the bottom dead center UT _ex . This causes a suction of fresh gas in the expansion space 26 , The return spring device in the resilience space 50 is compressed and the compression space 60 will be expanded. This will cause the piston device 16 in the direction of top dead center OT _r (relative to the resilience space 50 ) speeds up.

Upon reaching the top dead center OT _r (relative to the resilience space 50 ) become the valve or valves 36 which the inlet connections or the 34 are assigned, closed. The expansion space 26 is now filled with a fuel-oxidizer mixture. The return spring means of the resilience space 50 provides a restoring force which the piston means 16 in the direction of top dead center OT _ex (relative to the expansion space 26 ) speeds up. The mixture in the expansion space 26 is compressed (compression stroke).

In one embodiment, the compression space is 60 fluidly connected to the environment. This will ensure that compressed media is not in the compression space 60 remains. By the movement of the piston device 16 becomes medium from the compression space 60 expelled.

In an alternative embodiment, the second port becomes 84 open. As a result, compressed medium of the pressure storage device 90 provided.

In the first case, the compression space 60 during the working cycle and the compression stroke no function. In the second case, it is used to provide compressed medium.

In a two-stroke process, the compressed medium is stored in the compression space 60 was generated, used a pressure differential between the inlet port 34 and the outlet port 40 provide.

In a four-stroke operation, the compressed medium becomes in the compression space 60 used to provide a gas spring to the piston device 16 to drive in the intake stroke.

Additionally, by providing compressed medium for the expansion space 26 An efficiency improvement in a four-stroke operation can be achieved.

By appropriate timing of the valve device 86 It is also possible in a four-stroke operation to influence the piston movement and, where appropriate, a compression or a stroke. Through the compression room 60 or a control time of the valve device 86 is then another manipulated variable for controlling / regulating the operation of the free-piston device 10 provided.

It may alternatively or additionally be provided that a mechanical spring device in the compression space 60 is arranged. In the power stroke and in the compression stroke, the spring device has no special function. In the Ausschiebetakt the spring device in the compression space 60 compressed. The mechanical spring device is tensioned. In the subsequent intake stroke, the spring device can relax. It generates a driving force against the restoring force of the return spring device and drives the movement of the piston device 16 from the top dead center OT _ex toward the bottom dead center UT _ex .

In a further embodiment of a free-piston engine, which in 2 shown schematically and there with 108 is designated, is a housing 110 provided in which the expansion space 26 is formed.

In the case 110 is another compression room 112 educated. This compression space is through a piston side 114 limited, which is the first piston side 30 of the first piston 18 opposite.

The housing 110 also has an end wall 116 on which the compression space 112 the first piston 18 limited opposite.

At the front wall 116 is a connection device 118 arranged on which a controllable valve device 120 sitting.

Otherwise, the free piston engine 108 (especially with regard to the resilience space 50 ) designed the same as the free-piston engine 12 ,

The compression room 112 is a compression space which is inverse to the expansion space 26 is: If the volume of the expansion space 26 increases, then the volume of the compression space decreases 112 synchronous and vice versa. The volume change of the compression space 112 is in turn synchronous with the volume change of the resilience space 50 ,

The valve device 120 is with the control / regulation device 38 connected. Through it can be controlled accordingly, that medium in the compression space 112 is sucked in or compressed medium is discharged.

The compression room 60 forms a first compression space and the compression space 112 forms a second compression space, these compression spaces are separated from each other. By providing multiple compression spaces increased control possible or increased control options arise. It is possible to provide a larger mass per working cycle of compressed medium.

By providing a plurality of compression chambers, a larger amount of medium can be compressed and, in addition, pulsations can be reduced, since medium compression takes place both in an up-movement and in an out-movement. Also the resilience space 50 is a compression space when a gas spring is used there.

In particular, the connection device 118 with the pressure storage device 90 connected.

Through the compression room 112 can provide compressed medium in a different clock compared to the compression space 60 ,

Otherwise, the free-piston engine works 108 as described.

In a further embodiment of a free-piston engine, which in 3 shown schematically and there with 122 is designated, is a housing 124 provided in which the first piston 18 is arranged. The first piston 18 limited thereby with its first piston side 30 the expansion area 26 , With a second piston side opposite the first piston side 126 he limits a resilience space 128 which is in the same housing 124 is formed.

The second piston 20 is in a housing 130 arranged in which a compression space 132 and no resilience space is formed.

The free-piston engine 122 basically works the same as the free-piston engine 12 , where the free piston engine 122 and the free-piston engine 12 only in the arrangement of the resilience space 50 differ.

In a fourth embodiment of a free-piston engine, which in 4 shown schematically and there with 134 is designated, are a housing corresponding to the housing 110 and a housing corresponding to the housing 66 intended. In the free-piston engine 108 lie the case 110 and 66 in a line and are particularly coaxial with each other. In the free-piston engine 134 is a piston device 136 provided (with the first piston 18 and the second piston 20 ), where the housing 110 and 66 not coaxial with each other, but in one direction 137 transverse to a direction of movement 138 the piston device 136 are spaced. At the first piston 18 sits a connecting element 140 for example in the form of a rod. This connecting element extends coaxially with the piston 18 in the direction of movement 138 , At the rod 138 sits the magnet device 72 which are in the coil device 76 emotional.

At the connecting element 140 sits a cross element 142 which is in the direction 137 is oriented. At the cross element 142 again sits another connection element 144 which is at least approximately parallel to the direction of movement 138 is aligned. At the connecting element 144 again, the second piston sits 20 in the case 66 ,

The connecting element 144 and the connecting element 140 are oriented approximately parallel to each other.

The first piston 18 and the second piston 20 they move parallel to each other, moving in the direction 137 spaced from each other.

The cross element 142 has a first page 148 on which the housing 110 is facing. It also has a second page 150 on which the housing 66 is facing. The first page 148 is turned away to the second page 150 that is the first piston 18 in the case 110 and the second piston 20 in the case 66 are on different sides relative to the cross element 142 arranged.

Otherwise, the free-piston engine works 134 as described above.

In a further embodiment of a free-piston engine, which in 5 shown schematically and there with 152 is designated, is the Structure basically the same as in the free-piston engine 134 , It is again a cross element 142 intended. The housing 110 and the case 66 However, they are on the same page 148 of the cross element 142 arranged. For example, they are arranged directly next to each other.

In a further embodiment of a free-piston engine, which in 6 shown schematically and there with 154 is designated, and which is a variant of the free-piston engine 122 is, are the case 124 and the case 130 in a transverse direction 137 to a direction of movement of a corresponding piston device 156 staggered to each other. They are on the same page 158 a cross element 160 arranged.

In principle, a compression space can be arranged as desired in order, for example, to optimally adapt the construction volume of the corresponding free-piston engine to an application. However, a piston for the compression of medium in the compression chamber is rigidly connected to the piston device of the free-piston engine.

For example, the linear drive is located 70 between the expansion area 26 and the resilience space 50 or between the expansion area 26 and the compression room 60 , For example, it is also possible for the compression space to be located between the expansion space and the linear drive.

It is also possible that a gas exchange takes place between the resilience space and a compression space. The gas exchange can also be within a housing such as the housing 66 take place and in particular on the piston 20 respectively.

About the diameter of the compression chamber, the pumped medium mass can be adjusted. The diameter can basically be chosen independently of the diameter of the expansion space.

For example, it is provided that a diameter of the resilience space is greater than a diameter of a compression space. As a result, for example, compressed medium can be delivered from the compression space to the resilience space for providing the restoring force. It can also be provided that the diameter of the compression space is greater than the diameter of the expansion space. This can increase the loading volume.

In a two-stroke operation, a pressure loader can be realized, wherein the at least one expansion space is provided by the at least one compression space pressurized, compressed medium. If appropriate, the corresponding pressure charging of the at least one expansion space can also be assisted by an electric charger and / or turbocharger.

A corresponding free-piston engine device can be used, for example, for driving a vehicle or as an auxiliary drive. It can be used to generate electricity, for example in combined heat and power plants or for mobile power generation.

LIST OF REFERENCE NUMBERS

10

Free-piston device

12

Free piston engine

14

piston receiving

16

piston device

18

First piston

20

Second piston

22

connecting element

24

expansion chamber

26

expansion space

28

casing

30

First piston side

32

front

34

inlet port

36

Valve

38

Control / regulating device

40

outlet

42

Valve

44

ignition device

46

room

48

chamber

50

Resilience space

52

Second piston side

54

front

56

connection

58

Valve

60

compression chamber

62

piston side

64

bulkhead

66

casing

68

opening

70

linear drive

72

magnetic device

74

magnetic elements

76

coil device

78

signal-effective connection

80

connecting device

82

First connection

84

Second connection

85

spring means

86

valve means

88

Fluid communication means

90

Pressure storage device

92

management

94

storage container

96

Valve

98

3/2-way valve

100

First check valve

102

Second check valve

104

Valve

106

Valve

108

Free piston engine

110

casing

112

compression chamber

114

piston side

116

bulkhead

118

connecting device

120

valve means

122

Free piston engine

124

casing

126

Second piston side

128

Resilience space

130

casing

132

compression chamber

134

Free piston engine

136

piston device

137

direction

138

mover

140

connecting element

142

crossmember

144

connecting element

148

First page

150

Second page

152

Free piston engine

154

Free piston engine

156

piston device

158

page

160

crossmember

Claims (37)

Free-piston device with at least one free-piston engine ( 12 ; 108 ; 122 ; 134 ; 152 ; 154 ), comprising at least one piston receptacle ( 14 ), in which at least one expansion space ( 26 ) is formed for the expansion of a working medium and in which at least one resilience space ( 50 ) is formed, and a linearly movable piston device ( 16 ) with at least one piston ( 18 ; 20 ), wherein a first piston side ( 30 ) of the piston device ( 16 ) the at least one expansion space ( 26 ) and a second piston side ( 52 ) of the piston device ( 16 ) the at least one resilience space ( 50 ) and wherein in the at least one resilience space ( 50 ) a return spring device for the provision of a restoring force for the piston device ( 16 ), characterized in that at least one compression space ( 60 ; 112 ) is provided, which of the at least one expansion space ( 26 ) and the at least one resilience space ( 50 ) separated by at least one piston ( 20 ; 18 ) of the piston device ( 16 ) is limited, and in which by means of the piston device ( 16 ) a spring device and / or a medium is compressible. Free-piston device according to claim 1, characterized in that the spring device comprises a compressible medium or is formed by a compressible medium. Free-piston device according to claim 1 or 2, characterized by a fluid connection device ( 88 ) through which the at least one expansion space ( 26 ) and the at least one compression space ( 60 ) are fluidically connected or connectable. Free-piston device according to claim 3, characterized in that via the fluid connection device ( 88 ) is supplied to the at least one expansion space compressed medium. Free-piston device according to claim 3 or 4, characterized in that the fluid connection device ( 88 ) to an inlet port ( 34 ) of the at least one expansion space is fluidly connected. Free-piston device according to one of the preceding claims, characterized in that the at least one compression space ( 60 ) on the output side with a pressure storage device ( 90 ) is fluidically connected. Free-piston device according to one of the preceding claims, characterized in that the at least one expansion space ( 26 ) on the input side with a pressure storage device ( 90 ) is fluidically connected. Free piston device according to claim 6 or 7, characterized in that the pressure storage device ( 90 ) a valve ( 96 ) is assigned, by means of which temporally controlled the at least one expansion space ( 26 ) compressed medium can be fed. Free-piston device according to one of claims 6 to 8, characterized in that the pressure storage device ( 90 ) by one or more lines ( 92 ) is formed for medium. Free piston device according to one of claims 6 to 9, characterized in that the pressure storage device ( 90 ) at least one storage container ( 94 ) for medium. Free-piston device according to one of the preceding claims, characterized in that the at least one compression space ( 60 ) at least one first port ( 82 ) is assigned, via the medium is insertable and in particular medium from an environment containing medium is insertable. Free-piston device according to claim 11, characterized in that at the first connection a controllable valve device ( 86 ) sits. Free-piston device according to one of the preceding claims, characterized in that the at least one compression space ( 60 ) at least one second connection ( 84 ) is assigned, can be discharged via the compressed medium. Free-piston device according to claim 13, characterized in that at the second connection a controllable valve device ( 86 ) is arranged. Free-piston device according to one of the preceding claims, characterized in that the medium is a gas. Free-piston device according to one of the preceding claims, characterized in that the medium is an oxidizer for the combustion of fuel in the at least one expansion space ( 26 ) and in particular is air. Free-piston device according to one of the preceding claims, characterized in that the at least one compression space ( 60 ) with respect to a change in volume inversely to the at least one resilience space ( 50 ), wherein a volume increase of the resilience space ( 50 ) a synchronous volume reduction of the at least one compression space ( 60 ) and a volume reduction of the at least one resilience space ( 50 ) a synchronous increase in volume of the at least one compression space ( 60 ) causes. Free-piston device according to claim 17, characterized in that the at least one compression space ( 60 ) and the at least one resilience space ( 50 ) in a common housing ( 66 ) or housing part are arranged, wherein one of the second piston side ( 52 ) opposite piston side ( 62 ), which in particular on the piston ( 20 ) with the second piston side ( 52 ) is formed, the at least one compression space ( 60 ) limited. Free-piston device according to claim 17, characterized in that the at least one compression space ( 132 ) and the at least one resilience space ( 128 ) in different housings ( 124 ; 130 ) or housing parts are arranged. Free-piston device according to one of the preceding claims, characterized in that the at least one expansion space ( 26 ) and the at least one compression space ( 112 ) are arranged inversely with respect to a volume change, wherein an increase in volume of the at least one expansion space ( 26 ) a synchronous volume reduction of the at least one compression space ( 112 ) and a volume reduction of the at least one expansion space ( 26 ) a synchronous increase in volume of the at least one compression space ( 112 ) causes. Free-piston device according to claim 20, characterized in that the at least one compression space ( 112 ) and the at least one expansion space ( 26 ) in a same housing ( 110 ) or housing part are arranged, wherein one of the first piston side ( 30 ) opposite piston side ( 114 ) the at least one compression space ( 112 ) and in particular the first piston side ( 30 ) and the at least one compression space ( 112 ) limiting piston side ( 114 ) on the same piston ( 20 ) are formed. Free-piston device according to one of the preceding claims, characterized in that the at least one expansion space ( 26 ) a first compression space ( 112 ) and the at least one resilience space ( 50 ) a second compression space ( 60 ), wherein the first compression space ( 112 ) and the second compression space ( 60 ) are separate rooms. Free-piston device according to one of the preceding claims, characterized by a linear drive ( 70 ) with one on the piston device ( 16 ) arranged magnetic device ( 72 ) and a coil device ( 76 ), relative to which the magnetic device ( 72 ) emotional. Method for operating a free-piston device according to one of the preceding claims, in which compressed medium is provided in the at least one compression space, which is provided to the at least one expansion space and / or the spring device arranged in the at least one compression space is used to drive the piston device. Method according to claim 24, characterized by a two-stroke operation. A method according to claim 25, characterized in that a valve device which is associated with the at least one compression space, is controlled so that the at least one compression space is either fluidly connected to a medium-containing environment or connected to a pressure storage device. A method according to claim 26, characterized in that when the piston device in a top dead center (OT _ex ) relative to the at least one expansion chamber, the valve device is controlled so that the at least one compression chamber is fluidly connected to the environment. A method according to claim 27, characterized in that when moving out of the piston device from the top dead center (OT _ex ) medium from the environment is sucked into the at least one compression chamber. A method according to claim 27 or 28, characterized in that the valve device in a top dead center (OT _r ) of the piston device based on the at least one resilience space is controlled so that the at least one compression space is fluidly connected to the pressure storage device. A method according to claim 29, characterized in that when moving out of the piston device from the top dead center (OT _r ) medium is compressed and the pressure storage device is supplied. Method according to one of claims 26 to 30, characterized in that compressed medium from the pressure storage device is provided to the at least one expansion space for a rinsing process at the end of an expansion phase of the piston device in the at least one expansion space. A method according to claim 24, characterized by a four-stroke operation. A method according to claim 32, characterized in that in a power stroke in which the piston device moved out of a top dead center (OT _ex ) with respect to the at least one expansion space, a valve device which is assigned to the at least one compression space is so controlled that Medium from the environment is sucked into the at least one compression chamber. A method according to claim 32 or 33, characterized in that in a Ausschiebetakt, which follows a power stroke and in which the piston means in the direction of top dead center (OT _ex ) moves, the valve means is driven so that medium in the at least one compression space is compressed and / or the spring device is compressed in the at least one compression space. A method according to claim 34, characterized in that in an intake stroke, which follows the Ausschiebetakt and the fresh gas flows into the at least one expansion space, the spring means the piston means from the top dead center (OT _ex ) based on the expansion space in the direction of bottom dead center (UT _ex ) moves and in particular medium in the at least one compression space forms a gas spring for the piston device. A method according to claim 35, characterized in that in a compression stroke, which follows the intake stroke and in which gas is compressed in the at least one expansion space, the valve device is driven so that medium flows out of the at least one compression space. A method according to claim 36, characterized in that outflowing compressed medium is provided to a pressure storage device.

Images