DE10120196A1 - Free piston engine has engine piston driven by staged hydraulic piston, section of which with lesser diameter is arranged in work cylinder and section with greater diameter in compression cylinder - Google Patents

Abstract

The free piston engine has an engine piston (6) driven by a staged hydraulic piston (8), the section of which with the lesser diameter is arranged in a work cylinder (14) and the section with the greater diameter in a compression cylinder (18). The compression stroke is activated with pressure medium from an accumulator (30) via a start valve (32). Pressure medium can be sucked into the work cylinder from a low pressure accumulator (24). During the expansion stroke, the pressure medium in one of the cylinders is used for charging a pressure medium accumulator. The pressure medium accumulator is of the high pressure type (30), connectable to both the work cylinder and the compression cylinder.

Description

The invention relates to a free piston engine according to the Preamble of claim 1.

A free piston engine is basically one after the 2-stroke internal combustion engine, which instead a crank mechanism a hydraulic circuit with piston pump as Drivetrain is connected downstream. This is the engine piston connected to a hydraulic cylinder, through which the during of an engine work cycle generated translatory energy without the classic detour via the rotational movement of a Crank drive directly to the hydraulic working medium leads. The downstream, storable hydraulics circuit is designed so that it the given Ar records, caches and depending on the performance may be a hydraulic output unit, for example feeds an axial piston machine.

In DE 40 24 591 A1 a free piston engine is the gat described appropriate type, also known as Brandl-Freikol benmotor is known. With this concept, the com compression movement of the engine piston by interacting with a hydraulic piston that has a 2/3-way switch valve with a high pressure accumulator or a low pressure accumulator is connectable. At the beginning of the compression stroke there is an egg ne acceleration of the engine piston by applying the Hydraulic cylinder with the pressure in the high pressure accumulator. At Reaching a predetermined engine piston speed the hydraulic cylinder is connected to the Low pressure accumulator connected so that the further compresses sionshub of the engine piston against the effective force from the Compression pressure of the working gas takes place. After the Errei Chen the outer dead center (AT), the working gas is ignited det and the engine piston towards the dead center (IT) accelerated. During this piston movement from AT to  IT becomes the connection to the high via the changeover valve pressure accumulator open, so that the engine piston abge brakes and its kinetic energy in potential hydrau electrical energy converted and the high-pressure accumulator released that will. Although the switching times of the changeover valve in Millisecond range, arise when opening and closing control the connection to the high pressure accumulator in the changeover valve throttling losses in the order of 10% the engine power may lie.

These disadvantages of the Brandl free-piston engine can be overcome with another free piston type, the so-called Clear out the INNAS motor, as described, for example, in WO 9603576 A1 is disclosed.

The hydraulic piston of this INNAS free piston engine is ben designed as a stepped piston and has two active surfaces, the first of which is larger in a compression cylinder is arranged, while the second smaller a pump ar limited space or cylinder. The larger area is pressurized in a compression cylinder beatable, while the working cylinder has non-return valves tile with a high pressure accumulator or a low pressure memory is connectable. This INNAS free piston engine has a much better compared to the Brandl free piston engine plexeren construction, so that the device engineering effort is relatively high.

In contrast, the invention is based on the object to further develop the generic free piston engine in such a way that the device engineering effort is minimized.

This task is accomplished with a free piston engine Features solved the claim 1.

The free-piston engine according to the invention has an abge graduated pistons, whose larger end face in compression  cylinder and its smaller end face in the working cylinder is led. Both the working cylinder and the comm compression cylinders are used to initiate the compression stroke or for charging during the expansion stroke with a ge common high-pressure accumulator connectable. Opposite the one INNAS free-piston engine described above has these variants te the advantage that only two pressure accumulators, d. H. on Low pressure accumulator and a high pressure accumulator for operation are sufficient, while the generic INNAS free piston motor three pressure accumulators with the assigned lines must be present. The system can therefore be essential more compact with less device complexity be built up so that the manufacturing costs of the free piston motors compared to the solutions described at the beginning are struggling.

Another advantage is that the hydraulic piston ben or the engine piston has an inner dead center position, the adjusts itself automatically due to the pressure conditions. If the pressure in the high-pressure accumulator is high, the engine piston must work against this high pressure during the expansion stroke ten, so that due to the balance of forces the expansion onshub earlier than at a lower pressure in high pressure accumulator is terminated. Because of this postponed Dead center position in the next cycle is that during com pressionshubes available acceleration stretch accordingly shorter. Because the pressure in high pressure on the larger forehead during the compression stroke this shorter acceleration distance compensated by the higher pressure, so that the motor col accelerated to about the same speed becomes, like at a lower pressure with longer loading acceleration distance. The energy supplied to the engine piston remains about the same as the energy that contributes to it a lower pressure of the high pressure accumulator and one longer acceleration distance is supplied.  

Another significant advantage of the invention The solution is that the suction of pressure medium after the return movement of the hydraulic piston from its dead point position practically over the entire path of the hydraulic piston bens takes place while described at the beginning Brandl free piston engine sucking the pressure medium out of the never the pressure accumulator only after reaching a predetermined acceleration of the hydraulic piston took place.

With this solution, then in the case in which the in nere dead center of the engine piston, for example due to egg ner misfire, the dead center is not reached by applying pressure to the working cylinder Low pressure storage can be achieved.

In a preferred solution, both the by larger end face limited compression space as well working space limited by the ring area during the Compression stroke connected to the hydraulic accumulator. While the compression stroke is from the high pressure accumulator Pressure medium supplied and at the same time the pressure medium the cylinder back to the high pressure accumulator leads - the effective piston area in the compression direction thus corresponds to the difference area between the larger End face and the ring surface of the preferably as Diffe rentialkolben executed piston. Through these variants can the pressure medium flows via a connection to High pressure accumulator on and off starting valve against significantly reduced over the conventional solutions become.

A version with a differential piston builds significantly the INNAS free-piston engine is shorter because the moderate solution of the compression cylinder for both the pressure loading during the compression stroke as well Charging the high pressure accumulator is used.  

Instead of a differential cylinder, a Kol ben can be used with a piston collar, the piston rod in the working cylinder and its piston section larger diameter is guided in the compression cylinder. To initiate the compression stroke, the ring face surface of the stepped piston connected to the high pressure accumulator, being on the smaller end face of the piston rod Pressure in the low-pressure accumulator acts, so that the compression onshub by sucking in the pressure medium from the low pressure memory is supported.

In the case of an advantageous further development, the stages piston with a control edge over which during the Compression stroke connects to the high pressure accumulator is controllable so that after a predetermined acceleration hydraulic piston under pressure Bypassing the start valve directly from the high pressure accumulator is fed into the compression cylinder. Since the Main pressure medium flow is not routed through the start valve throttle losses can be further reduced become.

In a particularly preferred variant, the free piston engine a directional control valve, via which the start valve surrounding start line can be opened so that a large area cross section is made available to accelerate the free piston when starting the engine. This directional valve remains during the operation of the Freikol benmotors open.

In this variant, it is preferred if the way valve as a logic valve with a graduated logic piston is executed. A smaller area of the logic piston is connected via an upstream release valve with the Pressure in the high-pressure accumulator can be applied during the larger cross-sectional area of the logic piston with the pressure is loaded in the compression cylinder.  

The release valve is preferably a 3/2-way valve executed, over which the smaller area cross section choice wise with the pressure in the high pressure accumulator or with the Tank pressure can be applied.

In the event that the engine piston due to a fault ignition or other interference not in its exterior The free piston can be moved back to the dead center position motor can be provided with a retraction device. there can the compression cylinder via a piston retraction arrangement to be connected to a tank so that the in Effective piston face in the direction of outer dead center is relieved of pressure.

In a particularly preferred embodiment the piston retraction assembly has a check valve in its Open position of the working cylinders with the compression cylinder is connected.

The piston retraction assembly also has a piston Retraction valve, via which the compression cylinder with the Tank is connectable.

According to the check valve in the hydraulics piston integrated. This solution has the advantage that due to the short connection paths between the compression cylinder and the working cylinder the throttling losses mini times are. Furthermore, this arrangement is very compact built up, because in the housing no own recordings for the Piston retraction arrangement must be provided. The Compactness can be further improved, even if that Check valve is integrated in the hydraulic piston.

One way of integrating the check valve and the check valve is that the hydraulic piston made in two parts with a collar and a piston rod  is, with the collar over a sliding sleeve on the Piston rod is slidable. The covenant closes in a shift position from a control cross section, so that the connection between the compression cylinder and the working cylinder is controlled. In his setback position, the control cross-section is opened accordingly ert.

This constructive solution is in one end piece the piston rod is axially displaceable by a closing body performed, the in a spring-loaded basic position low pressure in the compression cylinder a breakthrough in Cordoned off. When pressure builds up in the compression cylinder the closing body lifts off, so that the connection between the compression cylinder and the working cylinder first again by the axial displacement of the Federal is closed.

The stepped piston can be actively activated in the event of a fault Move towards the outer dead center if it is in In the direction of the outer dead center effective ring face with the Pressure can be applied in the high-pressure accumulator, at least least one of the surfaces of the Stu that are effective in the opposite direction the piston is relieved of pressure. The return is special it’s easy if the engine piston side ring face with a larger area than that towards inner dead effective ring face of the stepped piston is.

To influence the compression pressure to a certain extent can flow in the never leading to the low pressure accumulator derdruckkanal a bypass line can be provided via the the check valve there is bypassable. This bypass line device can be shut off via a metering valve.

Other advantageous developments of the invention are the subject of further subclaims.  

Preferred embodiments of the Invention explained with reference to schematic drawings. Show it:

Fig. 1 shows an embodiment of a free-piston engine having been executed as a differential piston hydraulic piston;

FIGS. 2 and 3 different operating positions of the free-piston engine from FIG. 1;

. Fig. 4 shows the free-piston engine of Figure 1 with a one direction for dispensing of the compression pressure;

Figure 5 retractor the free-piston engine of Figure 1 with a piston..;

Fig. 6 shows an embodiment of a free-piston engine having been executed as a stepped piston hydraulic piston;

FIG. 7 shows a variant of the exemplary embodiment shown in FIG. 6 with a piston retraction device;

Fig. 8 shows an embodiment of a free-piston engine with modified starting device and a piston retraction arrangement, which is partially integrated in the hydraulic piston and

Fig. 9 is a constructive solution of the hydraulic piston of Fig. 8.

Fig. 1 shows a schematic of a first embodiment of a free piston engine 1. This has an engine housing 2 , in the combustion cylinder 4 of which an engine piston 6 is guided. This is in operative connection with a coaxially arranged hydraulic piston 8 , which is guided in an axial bore 10 . An annular end face 12 of the hydraulic piston 8 delimits a working cylinder 14 , while the larger end face 16 of the hydraulic piston 8 delimits a compression cylinder 18 .

A pressure channel 20 and a low pressure channel 22 open into the working cylinder 14 . The latter is connected to a low pressure accumulator 24 , a pressure medium flow from the working cylinder 14 to the low pressure accumulator 24 being prevented by a check valve 26 .

The compression cylinder 18 is connected via a Hochdruckka nal 28 with a high-pressure accumulator 30, the high-pressure channel 28 established via a configured as a 2/2-way valve 32 and start valve is zusteuerbar. The pressure channel 20 opens into the high pressure channel 28 . A further check valve 34 prevents flow of pressure medium from the high-pressure accumulator 30 into the working cylinder 14 .

The combustion cylinder 4 is provided with an outlet channel 36 , through which exhaust gas from the combustion chamber 38 limited by the engine piston 6 can be removed.

The hydraulic piston 8 facing back of the motor piston 6 limits an inlet space 40 , which has its minimum volume in the inner dead center position of the engine piston 6 . The inlet space 40 is connected to the combustion space 38 by an overflow duct 42 .

The fresh air can be supplied during the compression stroke of the engine piston 6 via an inlet channel 44 with an inlet valve 46 . The free-piston engine is ignited by injecting fuel via an injection valve 48 opening into the combustion cylinder.

The function of the free piston engine shown in FIG. 1 is explained below. At the beginning of a cycle, the combustion chamber 38 is filled with fresh air, the start valve 32 is closed and the engine piston 6 and the hydraulic piston 8 are in their dead center position (IT) shown in FIG. 1.

To initiate the compression stroke, the Startven valve 32 is opened so that the high pressure accumulator 30 is connected to the compression cylinder 18 . Due to the pressure acting on the larger end face 16 , the hydraulic piston is accelerated out of its dead center position and this acceleration is transmitted to the engine piston 6 . The pressure medium in the working cylinder 14 is conveyed back into the pressure channel 28 via the check valve 34 and the pressure line 20 . That is, the end face 16 and the annular end face 12 of the hydraulic piston 8 are acted upon by the pressure in the high-pressure accumulator 30 , so that the end face corresponding to the surface of the piston rod is effective in the direction of the outer dead center (AT). The connec tion to the low pressure accumulator 24 is blocked by the check valve 26 .

Referring to FIG. 2 6 fresh air via the inlet channel 44 and the open inlet valve 46 is space in the expanding inlet 40 is sucked during the compression stroke of the engine piston. The acceleration of the engine piston 6 takes place against the compression pressure of the fresh air, which increases polytropically in the combustion cylinder 38 . As a result, the engine piston 6 is braked and comes to a standstill at the outer dead center (AT).

As soon as the engine piston 6 is braked in its AT, fuel is injected via the injection valve 48 and ignited by the high temperature of the fresh air, so that the engine piston 6 - as shown in FIG. 3 - by the build-up of combustion pressure in the combustion chamber 38 from the AT in Towards IT is accelerated. This acceleration is transmitted to the hydraulic piston 8 so that it is moved to the left according to FIG. 3 towards its IT. Due to the resulting enlargement of the annular space of the working cylinder 14 , pressure medium is sucked in via the low-pressure channel 22 and the check valve 26 from the low-pressure accumulator 24 . At the same time, the pressure medium in the compression cylinder 18 is displaced into the high pressure duct 28 - the hydraulic accumulator 30 is loaded. That is, in the embodiment shown in FIGS . 1 to 3, the loading of the hydraulic accumulator 30 takes place simultaneously with the after-leaching of the pressure medium from the low-pressure accumulator. Since this suction takes place along the entire return movement of the hydraulic piston 8 , no cavitation phenomena occur in the working space 14 .

During the return movement, the engine piston 6 and the hydraulic piston 8 reduce their kinetic energy against the accumulator pressure in the high-pressure accumulator 30 until they are braked in the IT. During this process, the combustion cylinder 38 is purged by the fresh gas flowing over the overflow channel 42 from the inlet space 40 . After the engine piston 6 and the hydraulic piston 8 have reached their IT, the start valve 32 is brought into its blocking position - the free-piston engine 1 is ready for the next cycle.

Fig. 4 shows a free piston engine during the compression stroke, the above-described exemplary embodiment being supplemented by a device for metering the compression energy. This device has a bypass line 50 through which the check valve 26 in the low pressure channel 22 is bypassable. In the bypass line 50 , a metering valve 52 designed as a 2/2-way valve is provided, which shuts off the bypass line 50 in its blocking position.

When the metering valve 52 is shut off, the exemplary embodiment shown in FIG. 4 corresponds to that from the previously described drawings. By opening the metering valve 52 connected to the motor control, the working space 14 can be connected directly to the low-pressure accumulator 24 , so that the annular end face 12 is acted upon by the pressure in the low-pressure accumulator 24 . As a result, the hydraulic piston 8 does not have to be accelerated against the pressure in the high-pressure accumulator 30 during the compression stroke, so that, for example, the compression energy to be supplied can be increased at the beginning of the compression stroke.

In the event of malfunctions in the control of the free-piston engine, for example in the event of a misfire, it can happen that the engine piston 6 and the hydraulic piston 8 could not be properly returned to the IT. In order to facilitate the return to IT, the free-piston engine 1 in the variant shown in FIG. 5 is designed with a piston retraction system. This can be formed, for example, by a piston retraction valve 54 that is connected to the pressure channel 20 . In a designated basic position of the piston retraction valve 54 , the Druckka channel 20 is connected in the manner described above with the high pressure channel 28 , so that the function corresponds to that of the above-described embodiments. If a malfunction occurs, the start valve 32 is closed and the piston return valve 54 is brought into the position shown with b, in which the high-pressure channel 28 is connected to a tank T. The pressure medium located in the compression cylinder 18 is then expanded towards the tank T, so that the hydraulic piston 8 and thus the engine piston 6 can be moved back into its inner dead center position by the pressure of the low-pressure accumulator 24 in the working space 14 .

Fig. 6 shows an embodiment of a free-piston engine 1 , in which the hydraulic piston 8 is a stepped piston with two piston rods 56 , 58 and a collar 60 leads out. In this embodiment, the working cylinder 14 is limited by the end face 62 of the piston rod 56 on the right in FIG. 6. The compression cylinder 18 is delimited by the ring end face 64 of the collar 60 facing the piston rod 56 . The piston rod 58 and the left annular surface 66 of the hydraulic piston 8 delimit an annular cylinder 68 of the axial bore 10 receiving the hydraulic piston 8 . The low-pressure accumulator 24 is connected to the working cylinder 14 adjoining the piston rod 56 , as in the exemplary embodiment described above, via a low-pressure channel 22 and a check valve 26 . In this cylinder 14 also opens the pressure channel 20 connected to the high pressure accumulator 30 with the check valve 30th

The high-pressure accumulator 30 is also connected via the high-pressure channel 28 to the compression cylinder 18 delimited by the right annular end face 64 . In the high pressure channel 28 , the start valve 32 is arranged. The start valve 32 can be bypassed via a bypass duct 72 , in which a check valve 70 is arranged, which allows a backflow of the pressure medium from the compression cylinder 18 to the high pressure accumulator 30 .

About the outer peripheral edge of the annular end face 64 of the collar 60 , a pressure line 74 can be turned on who who opens downstream of the check valve 70 in the high pressure channel 28 .

Otherwise, the free piston engine shown in FIG. 6 corresponds to that from the above-described exemplary embodiments, so that further explanations are unnecessary.

To initiate the compression stroke, the Startven valve 32 is brought from its blocking position into its through position, so that the high-pressure accumulator 30 is connected via the Druckka channel 28 to the compression cylinder 18 . Due to the pressure acting on the annular end face 64 , the hydraulic piston 8 is accelerated, the engine piston 6 is moved to its AT and the fresh air present in the combustion cylinder 38 is compressed. After a predetermined Axialver shift of the hydraulic piston 8 controls the peripheral edge of the annular end face 64 on the pressure line 74 , so that the pressure medium can enter the compression cylinder 18 directly bypassing the start valve 32 . The throttle loss through the start valve 32 can thereby be minimized since the pressure medium only flows through the start valve 32 at the beginning of the compression stroke. During the compression stroke, pressure medium is drawn into the working cylinder 14 from the low-pressure accumulator 24 via the low-pressure channel 22 and the opening check valve 26 . The engine piston 6 is braked by the increasing compression pressure in the combustion chamber 38 in AT. The start valve 32 is closed and 48 injected fuel via the injector, thereby igniting the resulting mixture. The engine piston 6 and the hydraulic piston 8 are accelerated from AT to IT, the pressure line 74 being controlled when the hydraulic piston 8 moves back. The expansion movement takes place against the pressure in the working cylinder 14 and in the compression cylinder 18 , so that when the check valve 34 is open, the high-pressure accumulator 30 is loaded via the pressure channel 20 or via the high-pressure channel 28 .

Fig. 7 shows a variant of the free piston engine shown in FIG. 6 with hydraulic piston 8 designed as a stepped piston, this being equipped with a piston retraction system via which the motor piston 6 and the hydraulic piston 8 can be returned to their IT position in the event of a fault are. In the embodiment shown in FIG. 7, the piston retraction system has a return channel 76 connected to the high-pressure accumulator 30 , which opens into the ring cylinder 68 . The connection between the ring cylinder 68 and the high pressure accumulator 30 can be shut off or opened via a switching valve 78 designed as a 2/2-way valve. In the event of a fault, for example a misfire, the ring cylinder 68 can be connected to the high-pressure accumulator 30 via the changeover valve 78 , so that the ring end face 66 is acted upon by a pressure acting in the IT direction. In the exemplary embodiment shown in FIG. 7, the area of the piston rod 58 is smaller than that of the piston rod 56 , so that the resultant force acting on the two end faces 66 , 64 of the collar 60 acts in the IT direction.

The pressure in the working cylinder 14 can be reduced via a working cylinder 14 connected to the downstream of the check valve 26 arranged part of the low-pressure channel 22 relief channel 80 . This can be opened or closed via a control valve 82 . In other words, when the piston retracts, the control valve 82 is brought into its open position so that the pressure medium is fed from the working cylinder 14 via the relief channel 80 into the low-pressure accumulator 24 when the hydraulic piston 8 moves back.

The annular end face 66 of the hydraulic piston 8 can also be connected via a channel 84 with a further changeover valve 86 to the relief channel 80 and thus directly to the low-pressure accumulator 24 , so that, for example, the back of the hydraulic piston 8 is subjected to a lower pressure during the compression stroke is cash. The control valve 82 is brought into its blocking position.

Fig. 8 shows a schematic representation of that area of a free-piston engine 1 , in which the hydraulic piston 8 is arranged to drive the engine piston, not shown. In the exemplary embodiment shown in FIG. 8, similar to the exemplary embodiment according to FIG. 4, the low-pressure accumulator 24 is connected to the annular working space of the working cylinder 14 via a check valve 26 . The check valve 26 can be bypassed via a bypass line 50 with a metering valve 52 , so that the compression energy supplied at the beginning of the compression stroke can be influenced by directly switching on the low-pressure accumulator 24 .

The high-pressure accumulator 30 is connected to the compression cylinder 18 via the high-pressure duct 28 and the start valve 32 and the pressure duct 20 . In the illustrated embodiment, the check valve 34 is integrated in the hydraulic piston 8 .

Similar to the embodiment shown in FIG. 5, the free-piston engine has a piston retraction arrangement 84 , which, however, is formed by a check valve 86 and a retraction valve 88 in the solution shown. The check valve 86 is also integrated in the hydraulic piston 8 . The pull-back valve 88 is designed as a 2/2-way valve which, in its spring-biased basic position, shuts off a channel 92 extending between a tank channel 90 and the pressure channel 20 and opens this connection in its switching position.

The high-pressure channel 28 is bypassing the Startven valve 32 via a directional valve 94 directly connected to the compression cylinder 18 , which is integrated in the motor housing 2 of the free-piston engine 1 . In the embodiment shown in Fig. 8, the directional valve 94 is designed as a logic valve ( 2 / 2- way cartridge valve) with graduated logic piston 96 . The end face of the logic piston 96 with a larger cross-sectional area 98 is biased against a valve seat 100 . In the area of this valve seat 100 , a radial connection 102 is formed, which is connected to the high-pressure duct 28 via a bypass line 104 . In other words, with the logic piston 96 resting on the valve seat 100 , the connection between the bypass line 104 and the compression space 18 is blocked off.

The other end portion of the logic piston 96 with small rem surface cross-section 106 is guided into a control chamber 108 which can be connected to the tank channel 90 or the high-pressure channel 28 via a control channel 110 and a release valve 112 . The release valve 112 is designed in the embodiment shown as a 3/2-way valve that connects the high pressure channel 28 with the control channel 110 in its spring-biased basic position. In the Schaltpo position, the connection to the high pressure duct 28 is blocked and the control duct 110 is connected to the tank duct 90 .

In addition, by the pressure in the control chamber 108 , the logic piston 96 is biased by the force of a spring 112 in the closing direction against the seat 104 .

To start the free-piston engine, the release valve 112 is brought into its switching position, so that the smaller cross-sectional area 106 is acted upon by the tank pressure. The spring 112 is designed so that the control piston is initially still biased against the valve seat 100 when the engine is started. The start valve 32 is opened so that the compression cylinder 18 is acted upon by the pressure in the high-pressure accumulator - the hydraulic piston 8 is accelerated by the increasing pressure. As a result, the pressure acting on the larger cross-sectional area 98 of the logic piston 96 rises, so that it opens, lifts off the valve seat 100 and the radial connection 102 and thus the connection to the high-pressure accumulator 30 is opened - the logic valve 94 opens completely.

An advantage of this variant is that the Logic piston ben 96 receives its energy for opening via its own control edge, so that no pilot valve is required. The opening movement takes place very quickly, so that the pressure in the compression cylinder 18 can be increased with high dynamics. During the operation of the free-piston engine 1 , the logic piston 96 remains in its open position.

To stop the free-piston engine the starting valve 32 is closed and the release valve 112 in its sition switched Grundpo, so that the smaller cross-section area 106 of the logic piston 96 acted upon by the pressure in the high pressure accumulator. The free piston engine 1 then comes to a standstill when the start valve 32 and the logic valve 94 are closed. In other words, in the solution described above, the logic valve 94 also acts as a check valve, via which the connection from the compression cylinder 18 to the high-pressure accumulator 30 can be controlled.

As can be seen from the schematic illustration in FIG. 8, the check valve 86 is struck in the closing direction by the force of a closing spring 114 and in the opening direction by the pressure in the compression cylinder 18 . When the shut-off valve 86 is open, the cylinder 14 is connected to the compression cylinder 18 via the check valve 34 . Accordingly, the Sperrven valve 86 is brought into its open position in the above-described pressure build-up in the compression cylinder 18 , so that during the compression stroke the pressure in the working cylinder 14 to build pressure via the check valve 34 and the high pressure channel 28 can be used to charge the high-pressure accumulator 30 .

Fig. 9 shows a possible constructive solution in tegration of the check valve 84 and the check valve 86 in the hydraulic piston 8. Accordingly, this is executed as a split piston having a collar 116 and a relation to the outer diameter of the collar 116 of reduced diameter piston rod 118th The collar 116 and the piston rod 118 are connected to each other via a sliding sleeve 120 . For connection in the axial direction, the piston rod 118 has an enlarged end piece 122 which is arranged within the sliding sleeve 120 . In the illustrated stop position, a rear stop surface 124 bears against a stop ring 126 of the sliding sleeve 120 . The end piece 122 is made with a guide bore 128 in which a closing body 130 is axially displaceable. This is biased by a compression spring 132 towards the collar 116 . This is cup-shaped and has an opening 137 in a bottom 134 . In the basic position shown, this opening 137 is closed by the closing body 130 which is biased against it, so that the connection between the compression cylinder 18 and the working cylinder 14 is blocked. The closing body 130 thus forms a seat 136 for the collar 116 .

According to FIG. 9, the closing body 130 has Ausgleichsboh stanchions 138, may occur via the pressure medium from the working cylinder 18 in a spring space 140. The closing body 130 has a guide pin 142 which plunges sealingly into an axial bore 144 of the piston rod 118 . The force of the compression spring 132 and the area difference between the left seat-side end face and the right spring chamber-side ring end face is selected so that the closing body 130 is still biased into its closed position at a pressure in the working cylinder 18 , which is below the pressure in the low-pressure accumulator 24 . When a higher pressure in the working cylinder 18 is reached, the closing body 130 is moved to the right against the force of the compression spring 132 until it runs onto a stop shoulder 146 . Due to the pressure in the working cylinder 18 , the collar 116 is displaced relative to the piston rod 118 in the axial direction to the right (view according to FIG. 9) until it runs onto the closing body 130 , so that the opening 137 is blocked off. If during the compression stroke the pressure in the working cylinder 14 increases to a pressure ≧ than the pressure in the compression cylinder 18 , the collar 116 is lifted by the pressure difference acting on its end face from the closing body 130 and the connection between the working cylinder 14 to the compression cylinder 18th turned on - the high pressure accumulator is loaded. In other words, in this exemplary embodiment, the collar 116 acts as a check valve for opening the connection between the working cylinder 14 and the compression cylinder 18 . The closing body 130 with the compression spring 132 acts practically as a check valve, which is brought into its open position when the pressure in the compression cylinder 18 rises. This check valve closes only when the pressure in the compression cylinder 18 is lower than the pressure in the low-pressure accumulator 24 . Such a low pressure is set when the free piston is to be specifically moved back to its starting position.

In particular, the above-described solution is characterized by an extremely compact structure, the throttle losses being minimal due to the direct connection between the working and compression cylinders of the 14 , 18 . The solutions shown in Figs. 8 and 9 also explained in the above embodiments can be reali principle Sieren.

Which represent in the above-described embodiments provided additional equipment can in principle both of the aforementioned variants with step or differenti Use the pistons individually or in combination.

Instead of the 3/2-way valve shown in FIG. 5, a 2/2-way valve can also be used as the piston return valve 54 , in which case the check valve 34 should be designed to be lockable.

A free piston engine with an engine piston is disclosed ben that can be driven by a graduated hydraulic piston is. The larger diameter of the hydraulic piston is in one compression cylinder, while the smaller one Diameter is arranged in a working cylinder. Wuh The compression cylinder is included with the compression stroke a high-pressure accumulator and the working cylinder with one Low pressure accumulator or a high pressure accumulator connected.  

The high pressure accumulator becomes during an expansion stroke by the pressure medium displaced from the cylinder rooms load.  

Reference list

1

Free piston engine

2nd

Motor housing

4

Combustion cylinder

6

Engine pistons

8th

Hydraulic pistons

10th

Axial bore

12th

Ring face

14

Working cylinder

16

Face

18th

Compression cylinder

20th

Pressure channel

22

ND channel

24th

LP storage

26

RV

28

HD channel

30th

HD storage

32

Start valve

34

RV

36

Exhaust duct

38

Combustion chamber

40

Inlet space

42

Overflow channel

44

Inlet duct

46

Inlet valve

48

Injector

50

Bypass line

52

Dosing valve

54

Piston directional valve

56

Piston rod

58

Piston rod

60

Ring collar

62

Small face

64

right ring face

66

Ring surface

68

Ring cylinder

70

check valve

72

Bypass channel

74

Pressure line

76

Return channel

78

Diverter valve

80

Relief channel

82

Control valve

84

Piston retraction arrangement

86

Check valve

88

Return valve

90

Tank channel

92

channel

94

Directional control valve

96

Logic pistons

98

larger cross-sectional area

100

Valve seat

102

Radial connection

104

Bypass line

106

small cross-sectional area

108

Control room

110

Control channel

112

feather

114

Closing spring

116

Federation

118

Piston rod

120

Sliding sleeve

122

Tail

124

Abutment surface

126

Stop ring

128

Pilot hole

130

Closing body

132

Compression spring

134

ground

136

Seat

137

breakthrough

138

Compensating hole

140

Spring chamber

142

Guide pin

144

Axial bore

146

Stop shoulder

Claims (15)

1. Free-piston engine with an engine piston ( 6 ) which can be driven via a graduated hydraulic piston ( 8 ), the section with a smaller diameter in a working cylinder ( 14 ) and the section with a larger diameter in a compression cylinder ( 18 ) is arranged during the compression stroke via a start valve ( 32 ) with pressure medium from a Druckmit telspeicher ( 30 ) can be acted upon, wherein in the Ar beits cylinder ( 14 ) pressure medium from a low pressure memory ( 24 ) can be sucked in, while during the expansion stroke the pressure medium in one of the cylinders ( 14 , 18 ) can be used to load a pressure medium accumulator, characterized in that the pressure medium accumulator is a high-pressure accumulator ( 30 ) which can be connected to both the working cylinder ( 14 ) and the compression cylinder ( 18 ). 2. Free-piston engine according to claim 1, wherein a larger end face ( 16 ) of the piston ( 8 ) with the high pressure accumulator ( 30 ) and a smaller ring end face ( 12 ) of the piston ( 8 ) via a check valve ( 34 ) with the high pressure accumulator ( 30 ) or via a second check valve ( 26 ) with the low-pressure accumulator ( 24 ) is bindable ver. 3. Free piston engine according to claim 1, wherein the hy draulic piston ( 8 ) is a stepped piston ( 8 ) with a cylinder in the Ar ( 14 ) guided piston rod ( 56 ), the piston section with a larger diameter ( 60 ) is guided in the compression cylinder ( 18 ). 4. Free-piston engine according to claim 2 or 3, with a pressure line ( 74 ) on the one hand in an area of the high-pressure channel ( 28 ) between the start valve ( 32 ) and high-pressure accumulator ( 30 ) and on the other hand in the compression cylinder ( 18 ), and which during Compression on stroke of the hydraulic piston ( 8 ) can be controlled, where in the section of the high pressure channel ( 28 ) arranged between the start valve ( 32 ) and the compression cylinder ( 18 ) via a line with a non-return valve ( 70 ) with the pressure line ( 74 ) is connectable. 5. Free piston engine according to claim 3 or 4, wherein from the high-pressure channel ( 28 ) a return channel ( 76 ) with a switching valve ( 78 ) branches off, and opens into a ring cylinder ( 68 ) penetrated by a white piston rod ( 58 ), so that at controlled switching valve ( 78 ) in the direction of the inner dead center of the engine piston ( 8 ) effective annular surface ( 66 ) can be pressurized with pressur. 6. Free piston engine according to claim 5, wherein the engine piston rod ( 58 ) has a smaller diameter than the other piston rod ( 56 ). 7. Free piston engine according to claim 2 with a directional valve ( 94 ), via the piston ( 96 ) of which the Startven valve ( 32 ) bypass line ( 104 ) can be opened. 8. Free piston engine according to claim 7, wherein the directional valve ( 94 ) is a logic valve, the logic piston ( 96 ) is graduated, with a smaller surface cross-section ( 106 ) via a release valve ( 112 ) with the pressure in the high-pressure accumulator ( 30 ) and whose larger cross-sectional area ( 98 ) is acted upon by the pressure in the compression cylinder ( 18 ). 9. Free-piston engine according to claim 8, wherein the free delivery valve ( 112 ) is a 3/2-way valve which, in its switching positions, acts on the smaller area cross-section ( 106 ) with the pressure in the high-pressure accumulator ( 30 ) or a pressure in a tank channel ( 90 ) . 10. Free-piston engine according to one of the preceding claims, with a piston return valve arrangement ( 54 ) via which the compression cylinder with the tank (T) or with the high-pressure accumulator ( 30 ) can be connected. 11. Free-piston engine according to claim 10, wherein the Kol benzugzuganordnung ( 54 ) a check valve ( 86 ) for connecting the working cylinder ( 14 ) to the compression cylinder ( 18 ) and a return valve ( 88 ) for connecting the compression cylinder ( 18 ) to the tank ( 90 ), the check valve ( 86 ) being integrated in the hydraulic piston ( 8 ). 12. Free-piston engine according to claim 11, wherein the high-pressure accumulator ( 30 ) associated check valve ( 34 ) is also integrated in the hydraulic piston ( 8 ). 13. Free piston engine according to claim 12, wherein a larger piston diameter forming collar ( 160 ) of the hydraulic piston ( 8 ) via a sliding sleeve ( 120 ) is connected to a piston rod ( 118 ) which is axially displaceable in the slide with an end piece ( 122 ) cuff ( 120 ) is guided, the collar ( 116 ) in a displacement position closes a control cross section ver, so that a connection between the compression cylinder ( 14 ) and the working cylinder ( 18 ) is interrupted. 14. Free-piston engine according to claim 13, wherein in the end piece ( 122 ) a closing body ( 130 ) is guided, which is biased by means of a compression spring ( 132 ) against an opening in the bottom ( 134 ) of the collar ( 116 ), the pressure in the compression cylinder ( 18 ) through compensating bores ( 138 ) of the closing body ( 130 ) in a spring space ( 140 ) for the compression spring ( 132 ) is reported and the effective area in the closing direction of the closing body ( 130 ) is less than the effective face area in the opening direction Closing body ( 130 ) is. 15. Free-piston engine according to one of the preceding patent claims, wherein in a low-pressure channel ( 22 ) between the working cylinder ( 14 ) and the low-pressure accumulator ( 24 ) a check valve ( 26 ) bypass bypass ( 50 ) is provided, which via a metering valve ( 52 ) can be locked.