EP3091230A1 - Hydrostatic piston machine - Google Patents

Abstract

Disclosed is a hydrostatic piston engine with a plurality of stepped piston, which are guided in a respective associated cylinder. Each stepped piston has a first partial piston and on the outer circumference at least one further partial piston which can be moved relative to the first partial piston. Each cylinder has a first working space and at least one of them separated by the stepped piston further working space. Each sub-piston limits a working area with an associated working space. The first working space can be switched on and off via one or two first switching valves, and each further working space can be switched on and off via one or two further switching valves. Thus, each sub-piston of the stepped piston can be activated and deactivated independently of the other sub-piston.

Description

The invention relates to a hydrostatic piston volume adjustable in its stroke volume according to the preamble of patent claim 1.

To adjust the stroke volume of hydrostatic axial piston machines at a constant speed, it is known to infinitely adjust a swivel angle of a swash plate or a cylinder drum and so to change the stroke of the coupled thereto or the piston guided therein during a revolution. Thus, the displacement is adjusted in relation to the speed.

Furthermore, from the prior art piston machines are known in which subsets of their cylinders can be completely deactivated. This happens, for example, via valves that are assigned to the cylinders. The cylinders to be deactivated are not connected alternately with the high-pressure side and the low-pressure side of the machine via the valves, but always with one of the two sides-usually with the low pressure side. This results in a stepped adjustment of the stroke volume of the piston engine wherein the number of gradation options depends on the number of cylinders. In the design of such piston engines aspects of the symmetry of the remaining active cylinder must be considered because of a uniform as possible torque introduction at the periphery and the pulsation of the pressure medium.

In the publication DE 10 2009 035 893 A1 a piston engine is disclosed in which each piston has an inner piston part and an outer piston part, which together define a working space of the associated cylinder. The outer piston part can be hydraulically blocked and thus deactivated. For this purpose, valves are provided for each piston, via which the pressure of a back space of the outer piston part can be changed. This results in a two-stage adjustment of the stroke volume of the piston engine.

A disadvantage of such reciprocating engines is that only one (outer) sub-piston can be activated and deactivated while the other (inner) sub-piston always remains active.

On the other hand, the object of the invention is to provide a piston engine in which all partial pistons can be activated and deactivated.

This object is achieved by a piston engine having the features of patent claim 1.

The claimed hydrostatic piston engine has at least one - preferably more - piston, which is guided in a respective associated cylinder. Each piston has a first partial piston and a second partial piston which is relatively movable relative to the first partial piston. According to the invention, each cylinder has a first working space and a second working space separated therefrom by the piston. Each sub-piston limits a working area with an associated working space. The first working space can be activated and deactivated via a first shut-off valve, and the second working space can be activated and deactivated via a second shut-off valve. Thus, each piston part of the piston can be activated and deactivated independently of the other sub-piston. The inventive Piston engine is particularly suitable for pre-stressed closed circuits as well as in systems with a charge pump. In conjunction with a continuously variable further machine (pump or motor) results in a transmission, wherein the piston engine according to the invention is always operated in the stage that gives maximum efficiency of the transmission. Preferred applications are a direct drive of the crank of a press with creep speed and rapid traverse, an extruder drive with variable speed, a wing-side engine of a wind turbine drive and a winch drive in marine technology.

Particularly preferred in the piston engine according to the invention is a rotationally symmetrical and concentric design of the cylinder and the piston, including its partial pistons. In this case, the second partial piston can engage around the first partial piston.

Further advantageous embodiments of the invention are described in the dependent claims.

The possibilities of variation of the stroke volume of the piston engine according to the invention are expanded if the piston has a third part piston which is relatively movable against the other part piston, and if the cylinder has a third working space which is separated from the other working spaces via the piston. The third limited part piston with a third working surface the working space. The third working space can be activated and deactivated via a third shut-off valve. Thus, each of the three pistons of the piston can be activated and deactivated independently of the other piston part. Further such sub-pistons and work spaces are possible and increase the possible variations of the stroke volume of the piston engine according to the invention.

In rotary piston machines, such as e.g. in axial piston machines or radial piston machines, several pistons and cylinders uniformly distributed over the circumference are preferred, each shut-off valve being arranged between a working port of the piston engine which can be used as a feed or a branch to the several comparable work spaces of all cylinders. Thus, with a shut-off valve, all allocated work spaces distributed around the circumference can be activated and deactivated, as a result of which a uniform torque introduction of the partial pistons on the circumference always takes place.

On the outlet side, in the case of a unidirectionally operated piston engine, only one branch is necessary, via which all working chambers of all cylinders are connected to the outlet-side working connection of the piston engine.

In order to be able to operate the piston machine according to the invention bidirectionally, it requires a further working connection which can be used as an inlet. Then also this work connection further branches are assigned, the number - as well as the number of the first-mentioned branches - that of the work spaces per cylinder corresponds. Each of these further branches - like the first-mentioned branches - connects the comparable working spaces of all cylinders. Respective further shut-off valves are arranged between the further working connection and each further branch, the number of which - like the number of the first-mentioned shut-off valves - corresponds to that of the partial pistons per cylinder. This results in a doubling of the branches and the shut-off valves with respect to the above-described embodiment.

According to the above-appreciated prior art, there is only a two-stage adjustment of the stroke volume of the reciprocating engine. In contrast, the adjustment of the piston engine according to the invention is refined when the first working space facing first working surface of the first part piston has a size that does not correspond to the size of the second working space facing second working surface of the second part piston. Since only the smaller work surface or only the larger work surface or both work surfaces can be activated, there are three levels of adjustment of the stroke volume.

With more than two (e.g., three) sub-pistons per piston, it is preferred that all (e.g., three) work surfaces be different in size. This further levels of adjustment of the stroke volume are given.

It is structurally particularly preferred if the piston has a piston base body which is movable in the cylinder and which is also movable relative to all partial pistons. The piston main body is arranged substantially on the side facing away from the working surfaces of the partial piston.

Preferably, the piston main body for guiding - similar to a conventional piston - fitting the inner circumference of the cylinder. Then, the piston main body has a total cross-sectional area corresponding to the sum of all work surfaces.

The piston main body can have a contact surface for each partial piston, via which the partial piston in the activated state transfers the force of the pressure medium in the working space from the working surface via the contact surface to the piston main body.

In the case of a radial piston machine, a rolling element or a roller may be mounted on the piston main body and roll over cams. Thus, the Kobengrundkörper has a mechanical coupling to the invention Kobenmaschine.

Preferably, in each contact surface opens a connected to a housing interior or a tank discharge channel. This allows a relative movement of the piston main body relative to the associated deactivated partial piston, since pressure medium or air can flow into an enlarging intermediate space between the piston main body and the partial piston.

The first sub-piston may be used in sections to his leadership in a recess of the piston body. The recess is preferably - like the entire piston with its sub-piston - rotationally symmetrical.

In the development with three partial pistons, it is particularly preferred if the second partial piston engages around the first partial piston, and if the third partial piston engages around the piston main body.

In this case, the first partial piston can be circular-cylindrical, while the second partial piston and the third partial piston are annular.

For the cyclic filling and emptying of the working spaces, the following three developments are preferred:

Upstream and downstream of each working space, a check valve can be arranged simply in terms of device technology. In the preferred embodiment with the plurality of cylinders and the plurality of pistons, these check valves are arranged between the branch and each working space.

Upstream of each working space may be provided a switching valve. When operating the piston engine always in one direction extends downstream of each cylinder another switching valve. With a bidirectionally operable Piston engine is depending on the operating direction serves one of two different channels as an inlet and is arranged upstream, so that per working space in each of the two channels, a switching valve is needed.

Control slots may also be provided upstream and downstream of the work spaces in a control plate or manifold plate.

Several embodiments of a piston engine according to the invention are shown in the drawings. With reference to the figures of these drawings, the invention will now be explained in more detail.

• Figur 1 in einem Längsschnitt einen Zylinder mit Kolben und einen Teil eines Schaltplans einer erfindungsgemäßen Radialkolbenmaschine gemäß einem ersten Ausführungsbeispiel mit maximalem Volumenstrom,
• Figur 2 den Längsschnitt und den Schaltplan aus Figur 1 mit reduziertem Volumenstrom,
• Figur 3 den Längsschnitt und den Schaltplan aus Figur 1 mit reduziertem Volumenstrom,
• Figur 4 in einem Längsschnitt einen Zylinder mit Kolben und einen Teil eines Schaltplans einer erfindungsgemäßen Radialkolbenmaschine gemäß einem zweiten und einem dritten Ausführungsbeispiel mit maximalem Volumenstrom,
• Figur 5 den Längsschnitt und den Schaltplan aus Figur 4 mit reduziertem Volumenstrom,
• Figur 6 den Längsschnitt und den Schaltplan aus Figur 4 mit reduziertem Volumenstrom,
• Figur 7 in einem Längsschnitt einen Zylinder mit Kolben und einen Teil eines Schaltplans einer erfindungsgemäßen Radialkolbenmaschine gemäß einem vierten und einem fünften Ausführungsbeispiel,
• Figuren 8 bis 13 jeweils in einem Längsschnitt einen Zylinder mit Kolben einer erfindungsgemäßen Radialkolbenmaschine gemäß einem sechsten Ausführungsbeispiel mit einem Volumenstrom, der auf verschiedene Weisen reduziert ist,
• Figur 14 in einem Längsschnitt den Zylinder mit Kolben aus Figur 8 mit maximalem Volumenstrom und mit einer ersten Variante eines Schaltplans und
• Figur 15 in einem Längsschnitt den Zylinder mit Kolben aus Figur 8 mit maximalem Volumenstrom und mit einer zweiten Variante eines Schaltplans.

Show it

• FIG. 1 3 a longitudinal section through a cylinder with a piston and a part of a circuit diagram of a radial piston machine according to the invention according to a first exemplary embodiment with a maximum volume flow,
• FIG. 2 the longitudinal section and the circuit diagram FIG. 1 with reduced volume flow,
• FIG. 3 the longitudinal section and the circuit diagram FIG. 1 with reduced volume flow,
• FIG. 4 3 shows a longitudinal section of a cylinder with a piston and a part of a circuit diagram of a radial piston machine according to the invention according to a second and a third embodiment with maximum volume flow,
• FIG. 5 the longitudinal section and the circuit diagram FIG. 4 with reduced volume flow,
• FIG. 6 the longitudinal section and the circuit diagram FIG. 4 with reduced volume flow,
• FIG. 7 3 shows a longitudinal section of a cylinder with a piston and a part of a circuit diagram of a radial piston machine according to the invention according to a fourth and a fifth exemplary embodiment,
• FIGS. 8 to 13 in each case in a longitudinal section a cylinder with pistons of a radial piston machine according to the invention according to a sixth embodiment with a volume flow which is reduced in various ways,
• FIG. 14 in a longitudinal section of the cylinder with piston FIG. 8 with maximum flow and with a first variant of a circuit diagram and
• FIG. 15 in a longitudinal section of the cylinder with piston FIG. 8 with maximum flow and with a second variant of a circuit diagram.

FIG. 1 shows a cylinder 1 with a guided therein piston 2, on which a rolling element 4 is mounted. This arrangement is provided several times and evenly distributed on the circumference of a (not shown) rotor of the first embodiment of the radial piston machine according to the invention. The pistons 2 are supported on the respective rolling elements 4 at a arranged on the outer circumference of the radial piston machine stroke curve 6, wherein at the lifting cam 6, a plurality of cams 8 are evenly distributed.

The first embodiment of the radial piston engine according to the invention is used as a pump. It has a low-pressure leading inlet-side working port 10 and a high-pressure leading downstream additional working port 12. The radial piston pump is connected in a closed circuit with a hydrostatic motor 14. Since the delivery volume of the first embodiment of the radial piston pump according to the invention can be adjusted in three stages, the motor 14 can be adjusted in three stages in the case of a constant motor at a constant input speed of the radial piston pump. If the motor 14 is an adjusting motor, can be achieved by the three stage, an optimization of the efficiency of the transmission.

The three-stage adjustment of the delivery volume of the radial piston pump according to the first embodiment is realized in that the piston 2 is designed as a stepped piston and the cylinder 1 as a stepped cylinder. More specifically, both have a central concentric tapered section. As a result, a middle first working space A1 and an annular second working space A2 are formed in the cylinder 1. The first working space A1 is delimited by a first working surface A1, which is formed on a first part piston K1. The second working space R2 is bounded by an annular second working surface A2, which is formed on a second part piston K2. The first part piston K1 is circular cylindrical and peg-like. The second part piston K2 is annular and surrounds the first part piston K1.

Furthermore, a piston base body 16 of the piston 2 is guided in the cylinder 1, at the outer (in FIG. 1 lower) end portion of the rolling elements 4 is mounted and at its inner (in FIG. 1 Upper) end portion on the one hand, the first part piston K1 is inserted into a concentric recess 18 and on the other hand, the second part piston K2 can be brought into contact with the front side. At the bottom of the recess 18 of the piston body 16 has a first contact surface 20 for the first part piston K1 and on its side facing away from the rolling element 4 end face a second contact surface 22 for the second part piston K2.

At the in FIG. 1 shown stage with maximum delivery volume are the two sub-piston K1, K2 always on the associated contact surface 20, 22 of the piston base 16, so that at each stroke of the piston 2 in the cylinder 1 always both working spaces R1, R2 are increased and decreased. For this purpose, two inlet-side channels 24, 26, each with associated branches 28, 30 are provided downstream of the working connection 10, wherein a shut-off valve 32, 34 is provided in each channel 24, 26 between the working connection 10 and the branch 28, 30. Each shut-off valve 32, 34 is formed as a 2/2-way valve, which is shut off in a by a spring-biased home position, and that in a by an electric Actuator open switching position the associated branch 28, 30 connects to the working port 10. The first branch 28 branches off to the first working spaces R1 of all the cylinders 1, while the second branch 28, 30 branches off to the second working spaces R2 of all the cylinders 1. For reasons of clarity, only three cylinders 1 were assumed.

On the outlet side, only one common further channel 36 is necessary, which connects a further branch 38 to the further working connection 12. About the further branch 38, the pressure medium under high pressure of the working spaces R1, R2 of all cylinders 1 is brought together. For the in FIG. 1 shown maximum delivery volume of the radial piston pump, the two shut-off valves 32, 34 energized and therefore open.

In order to enable the movement of the piston base body 16 toward and away from the deactivated partial piston K2 or K2, a branched relief channel 42 is provided, which extends in the interior of the piston main body 16, and which connects a housing interior of the radial piston pump with the two contact surfaces 20, 22.

FIG. 2 shows the arrangement FIG. 1 , wherein the radial piston pump is set to a reduced delivery volume. For this purpose, only the (in this embodiment three) first working spaces R1 of the radial piston pump are activated, while the (in this embodiment three) second working spaces R2 are deactivated. For this purpose, the second shut-off valve 34 was closed by its spring. This leaves the second sub-piston K2 always in the in FIG. 2 shown position, while the first sub-piston K1 perform together with the piston main bodies 16, the lifting movement.

For cyclic filling and emptying in the conveying direction of the radial piston pump R1 R2 is on the inlet side and drain side for each working space Check valve 40 is provided. More specifically, between each branch 28, 30, 38 and the respective working space R1, R2, a check valve 40 is provided, the (in this embodiment, three) check valves 40, between the drain side further channel 36 and the deactivated second working spaces R2 of all cylinders. 1 are arranged, are always closed in this operating condition, as in the other channel 36 always high pressure prevails, while in the second working spaces R2 always low pressure prevails. All check valves 40, which are assigned to the first work spaces R1, open and close cyclically in this operating state.

FIG. 3 shows the arrangement Figures 1 and 2 , wherein the radial piston pump is set to a reduced delivery volume. For this purpose, only the (in this embodiment three) second working spaces R2 of the radial piston pump are activated, while the (in this embodiment three) first working spaces R1 are deactivated. For this purpose, the first shut-off valve 32 was closed by its spring. Thus, the first part piston K1 always remain in the in FIG. 2 shown position, while the second sub-piston K2 perform together with the piston main bodies 16, the lifting movement.

The (three in this embodiment) check valves 40 which are arranged between the drain-side further channel 36 and the deactivated first working spaces R1 of all cylinders 1, are always closed in this operating condition, as in the other channel 36 always high pressure prevails, while in the first working spaces R1 always low pressure prevails. All check valves 40, which are assigned to the second work spaces R2, open and close cyclically in this operating state.

Since the first working surface A1 is smaller than the circumferential second working surface A2, the delivery volume is in operation according to FIG. 3 greater than the delivery volume during operation according to FIG. 2 , Overall, the show FIGS. 1 to 3 the three different stages of the delivery volume of the first embodiment of the radial piston pump according to the invention.

The FIGS. 4 to 6 show in a respective common representation a second and a third embodiment of the radial piston engine according to the invention, which is also operated as a radial piston pump. The illustrated operating states or stages, the cylinder 1, the piston 2, the rolling elements 4, the channels 24, 26, 36 with the branches 28, 30, 38 and the two shut-off valves 32, 34 correspond to those of the first embodiment according to the FIGS. 1 to 3 , Also supplied by the radial piston pump hydrostatic motor 14 corresponds to the previous embodiment.

Notwithstanding the first embodiment according to the FIGS. 1 to 3 is the cyclic or alternating connection of the working spaces R1, R2 in synchronism with the edges of the cam 8 of the lifting cam 6 according to the second embodiment via respective inlet-side switching valves 44 and a common downstream additional switching valve 46 or according to the third embodiment via a slot control with a control mirror A, B and a distributor plate 48 possible. In the FIGS. 4 to 6 these two embodiments are shown together.

Due to the pressure difference between the hydraulic bias in the channels 24, 26 and the housing pressure is a force that can extend the partial piston K1, K2 and presses the rolling elements 4 to the lifting cam 6. This ensures an uninterrupted run of the rolling elements 4 on the cam 8 of the lifting cam 6. Are all inlet-side channels 24, 26 open in pump mode, all work spaces R1, R2, R3 filled with pressure medium and promoted by the cam lift in the direction of drain channel 36 ,

If a group of identical partial pistons K1, K2 of all cylinders 1 is switched off via a shut-off valve 32, 34, these partial pistons K1, K2 are pressed against mechanical upper stops of the cylinders 1, but are not mechanically moved again in the direction of the lifting curve 6. When shutting off a group of work spaces R1, R2, the remaining pressure medium is conveyed from these working spaces R1, R2 into the drain-side channel 36 during the next stroke. After that, no return stroke of the disconnected partial pistons K1, K2 to the lifting cam 6 takes place. Through the relief channels 42, the internal pressure of the housing forces the deactivated partial pistons K1, K2 against the upper stops of the cylinders 1, there is no further delivery.

FIG. 7 shows a part of a fourth and a fifth embodiment of the radial piston machine according to the invention. It can be operated bidirectionally with maximum flexibility. The cylinder 1, the piston 2, the rolling element 4, the lift curve 6, and the connection of the working port 10 via the two channels 24, 26 with the cylinder 1 and the common representation of the switching valves 44 with the control mirror A, B and the distributor plate 48th correspond to the second and third embodiments according to FIG. 4

To enable a reversal of the operating direction and the other working port 12 via two separate further channels 36 with the first working spaces R1 of all cylinders 1 and the second working spaces R2 of all cylinders 1 is connected. For this purpose, a further shut-off valve 50 and a further branch 38 and a further switching valve 46 or a corresponding slot control is provided in each further channel 36. This results in a total symmetrical structure of the circuit diagram and a similar connection of both working ports 10, 12 with the cylinders 1. The shutdown of the desired group of similar work spaces R1 or R2 then takes place depending on the operating direction of the radial piston engine by the inlet-side shut-off valve 32, 34 or 50th

The FIGS. 8 to 13 each show in a longitudinal section a cylinder 101 with a piston 102 according to a sixth embodiment of the radial piston machine according to the invention, which offers further stages of its stroke volume. The piston main body 116 has an additional outermost circumferential third contact surface 122 for an annular third partial piston K3, which defines with its peripheral third working surface A3 a third working space R3 of the cylinder 101. While the second partial piston - as in the previous embodiments - abuts the outer periphery of the first partial piston K1, the third partial piston K3 engages around the piston main body 116th

In order to maximize the number of stages of the adjustable stroke volume, all three sub-pistons K1, K2, K3 have differently sized work surfaces A1, A2, A3. FIG. 8 shows an operating state in which the first and the second working space R1, R2 are activated, while the third working space R3 is deactivated. FIG. 9 shows an operating state in which the first and the third working space R1, R3 are activated, while the second working space R2 is deactivated. FIG. 10 shows an operating state in which the second and the third working space R2, R3 are activated, while the first working space R1 is deactivated. FIG. 11 shows an operating state in which only the first working space R1 is activated. FIG. 12 shows an operating state in which only the second working space R2 is activated. FIG. 13 shows an operating state in which only the third working space R3 is activated.

FIGS. 14 and 15 each show in a longitudinal section the cylinder 101 with the piston 102 according to the sixth embodiment of the FIGS. 8 to 13 , The discharge channel 142 of this embodiment has a branch to the three abutment surfaces 20, 22, 122, so that at each deactivated or deactivated partial piston K1, K2, K3 pressure medium from the housing interior can be sucked into the intermediate space formed between the affected piston part K1, K2, K3 and the piston body 116.

FIG. 14 additionally shows the circuit diagram of the cylinder 101 of a bidirectionally operable radial piston machine. Each working space R1, R2, R3 are assigned, on the one hand, a switching valve 44 and, on the other hand, a further switching valve 46, both of which are switched as a function of the momentarily traveled edge of the cams 8 of the lifting cam 6.

FIG. 15 additionally shows the circuit diagram of the cylinder 101 of a radial piston machine, which is to be operated only in one direction. In the process, a common further switching valve for the three working spaces R1, R2, R3 of the cylinder 101 is emitted from the outlet side.

As already described above, instead of the switching valves 44, 46, a slot control with a control mirror A, B and a distributor plate 148 may also be provided.

Disclosed is a hydrostatic piston engine with a plurality of stepped piston, which are guided in a respective associated cylinder. Each stepped piston has a first partial piston and on the outer circumference at least one further partial piston which can be moved relative to the first partial piston. Each cylinder has a first working space and at least one of them separated by the stepped piston further working space. Each sub-piston limits a working area with an associated working space. The first working space can be switched on and off via one or two first switching valves, and each further working space can be switched on and off via one or two further switching valves. Thus, each partial piston of the stepped piston be activated and deactivated independently of the other sub-piston.

LIST OF REFERENCE NUMBERS

1; 101

cylinder

2; 102

piston

4

rolling elements

6

stroke curve

8th

cam

10

working port

12

another work connection

14

engine

16; 116

Piston base body

18

recess

20

first contact surface

22

second contact surface

24

first channel

26

second channel

28

first branch

30

second branch

32

first shut-off valve

34

second shut-off valve

36

another channel

38

further branching

40

check valve

42; 142

relief channel

44

switching valve

46

another switching valve

48; 148

distribution plate

50

another shut-off valve

122

third contact surface

A, B

A control plate

A1

first work surface

A2

second work surface

A3

third workspace

K1

first part piston

K2

second partial piston

K3

third partial piston

R1

first working space

R2

second workspace

R3

third workspace

Claims (15)

A hydrostatic piston machine having at least one piston (2; 102) movable in an associated cylinder (1; 101), the piston (2; 102) having a first sub-piston (K1) and a relatively movable against the first sub-piston (K1) second partial piston (K2), characterized in that the cylinder (1; 101) has a first working chamber (R1) and a second working chamber (R2) separated therefrom by the piston (2; 102), each partial piston (K1, K2 ) a working space (R1, R2) limited, and wherein the first working space (R1) via a first shut-off valve (32) can be activated and deactivated, and wherein the second working space (R2) via a second shut-off valve (34) can be activated and deactivated. Piston engine according to claim 1, wherein the piston (102) has a third part piston (K3) which is relatively movable against the other part pistons (K1, K2), and wherein the cylinder (101) has a third working space (R3) passing through the piston (102) is separated from the other working spaces (R1, R2), and wherein the third part piston (K3) limits the third working space (R3), and wherein the third working space (A3) can be activated and deactivated via a third shut-off valve. A piston engine according to claim 1 or 2, comprising a plurality of pistons (2, 102) and cylinders (1, 101), each shut-off valve (32, 34) being connected between a working port (10) of the piston engine and a manifold (28, 30) among the several similar ones Work spaces (R1, R2, R3) of all cylinders (1, 101) is arranged. Piston engine according to claim 3 with further shut-off valves (50) whose number corresponds to those of the partial pistons (K1, K2, K3) per cylinder (1, 101), each further shut-off valve (50) between a further Working connection (12) of the piston engine and a further branch (38) to the plurality of similar work spaces (R1, R2, R3) of all cylinders (1, 101) is arranged. Piston engine according to one of the preceding claims, wherein a said first working space (R1) facing first working surface (A1) of the first part piston (K1) has a size which is not equal to a size of the second working space (R2) facing the second working surface (A2) of the second Partial piston (K2) is. Piston engine according to one of the preceding claims, wherein the piston (2; 102) has a piston main body (16; 116) which is movable in the cylinder (1; 101) and which is movable relative to the partial pistons (K1, K2, K3). Piston engine according to claim 5 and 6, wherein the piston base body (16; 116) has a cross-sectional area which corresponds to the sum of the working surfaces (A1, A2, A3). Piston engine according to claim 6 or claim 7, wherein the piston main body (16; 116) has a contact surface (20, 22, 122) for each partial piston (K1, K2, K3). Piston engine according to claim 8, wherein in each bearing surface (20, 22, 122) a connected to a pressure medium sink relief channel (42, 142) opens. Piston engine according to one of claims 6 to 9, wherein the first part piston (K1) in a recess (18) of the piston body (16; 116) is inserted. Piston engine according to claim 2 and according to one of claims 6 to 8, wherein the second part piston (K2) surrounds the first part piston (K1), and wherein the third part piston (K3) engages around the piston main body (116). Piston engine according to claim 11, wherein the first part piston (K1) is circular cylindrical, and wherein the second part piston (K2) and the third part piston (K3) are annular. Piston engine according to one of the preceding claims, wherein upstream of and downstream of each working space (R1, R2, R3), a check valve (40) is arranged. Piston engine according to one of claims 1 to 12, wherein upstream of each working space (R1, R2, R3), a switching valve (44) is provided, and downstream of each cylinder (1) or each working space (R1, R2, R3), a further switching valve ( 46) is arranged. Piston engine according to one of claims 1 to 12, wherein upstream and downstream of the working spaces (R1, R2, R3) is provided Schlitzteuerung.

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