EP2324245B1 - Hydrostatic piston engine having a pulsation reduction device - Google Patents

Abstract

The invention relates to a hydrostatic piston engine having at least one piston chamber. A piston is arranged in the piston chamber in a displaceable manner, wherein the piston chamber can be connected alternately to a first control opening (2) or to a second control opening (3) of a control part (1) through a piston chamber opening (4). A first and a second reversing region (5, 6) are formed between the first control opening (2) and the second control opening (3). The piston chamber opening (4) can be connected to an accumulator element (7), which opens into the first reversing region (5) through a connection (8). The connection of the reversing region (5) to the accumulator element (7) comprises a valve device (10). Through said valve device (10), the flow cross-section of the connection (8) can be varied relative to the control part (1) over time decoupled from a position angle (a) of the piston chamber opening (4).

Description

The invention relates to a hydrostatic piston engine.

Hydrostatic piston machines, such as axial piston pumps, generate a pulsating volume flow due to their mode of operation at the pump outlet. In addition, a pressure difference must be overcome in the transition from the suction side to the pressure side. For this purpose, it is known, in the Umsteuerbereich, in which a piston chamber is not connected to the suction side or the delivery pressure side, to use the occurring there piston stroke for compression of the pressure medium located in the piston chamber. However, such an increase in the pressure on the delivery-side pressure level is usually not fully adjusted. As a result, there are vibrations, noise and even Kravitationsschädigungen due to the flow rates that occur through the remaining pressure differences.

From the DE 197 06 116 A1 It is known for improving the Pulsationsminderung to use a storage element which is connected to a Umsteuerbereich between a Saugniere and a Förderdruckniere the piston machine. In this connection, a check valve is arranged, which opens in the direction of the outlet in Umsteuerbereich out. The connection of the piston chamber opening with the storage element is thus limited to the time in which an overlap between the mouth of the connection and the piston chamber opening due to the corresponding position angle of the piston chamber and thus the piston chamber opening is given to the control part and further as long as the pressure in the storage element higher than in the piston chamber. On the other hand, the pressure in the piston increases again due to a stroke movement of the piston Piston chamber, so closes the check valve. In order to refill the storage element, a non-return valve bypass line section or a separate line is provided, which is permanently connected to the storage element. Thus, the flow-through cross section in the connection between the Umsteuerbereich and the storage element is varied by the check valve.

However, the solution described has the disadvantage that a control takes place solely because of the existing pressure differences. An optimization with regard to different operating conditions of the piston engine by timed adjustment of the different flow cross sections for the charging and discharging of the memory element, however, can not be done.

The invention is therefore based on the object to provide a hydrostatic piston engine with improved pulsation reduction.

The object is achieved by the hydrostatic piston engine according to the invention with the features of claim 1.

A hydrostatic piston engine according to the present invention has at least one piston chamber in which a piston is slidably disposed. The piston chamber is alternately connected via a piston chamber opening with a first control opening and a second control opening, which are both arranged in a control part. Between the first control opening and the second control opening, a first Umsteuerbereich or at the other Totpunktsbereich a second Umsteuerbereich is formed. The hydrostatic piston engine also has a storage element which can be connected to the piston chamber opening via a connection which opens out into the first reversing region. Furthermore, the connection has a valve device. These Valve device is designed so that a flow cross-section of the connection decoupled from a position angle of the piston chamber opening relative to the control part is temporally variable by them. The position angle defines the relative position of a piston chamber opening to the control part.

The valve device comprises at least one electromagnetically or piezoelectrically actuated valve.

By such a temporal variation of the flow cross section, in which the time at which the flow cross section of the connection changes, is adjustable, it is possible to optimally adapt the pulsation reduction device to the respective operating state of the machine. The adjustment of the flow cross sections for the charging of the storage element and the discharge of the storage element and thus the precompression of the pressure medium in the piston chamber can thus be controlled in time.

In the dependent claims advantageous developments of the hydrostatic piston engine according to the invention are carried out.

An electromagnetically operable valve is able to realize the required short switching times. It is particularly advantageous if a simple switching valve is used as a valve. Such valves are inexpensive and small and therefore can be easily integrated into a machine according to the invention. The control via an electromagnet also has the advantage that the operating conditions are already known for example in a control unit and therefore from the other control specifications, a corresponding control signal for timing the actuation of the solenoid-operated valve can be derived. By means of the valve is particularly preferred the Interrupt connection temporarily completely. This improves the efficiency of the engine and allows further precompression by the piston stroke.

It is advantageous if the solenoid-operated valve is a switching valve with variable stroke limitation. In such a case, the connection can only fail as a simple line, since the change in cross section is easily accessible from a first flow-through cross-section to a second flow-through cross section for the charging or discharging by this stroke-limited switching valve. In addition, the connection can also be completely interrupted.

According to an alternative embodiment, the connection has a first connection line section and a second connection line section. In this case, a single electromagnetically actuated switching valve is preferably arranged in each connecting line section. With such an arrangement, it is possible to allocate one connecting line section to the charging process and the other connecting line section to the discharging process. Thus, the cross section can be determined via the line and it can be used in both lines identical valves. The limitation of the flow cross section takes place via the line cross section and not over the stroke limit of the switching valve as in the previous example. This requires the use of particularly simple constructed switching valves.

The embodiment with the two connecting line sections may be advantageously developed further in that each of the connecting line sections has a separate opening in the reversing area. The two discharge openings are arranged offset to one another in the direction of movement of the piston chamber opening relative to the control part. Since in a relative movement of the Piston chamber opening with respect to the control part due to the geometry of the piston chamber opening at some point the connection with the first orifice is completed, during a further relative movement of the piston chamber opening whose connection with the second orifice for a charging of the memory element can be used. The usable position angle range between the piston chamber opening and the control part is thus increased and the available time or, in the case of an axial piston machine, the rotational angle of the cylinder drum, which is available for the precompression and the subsequent charging of the storage element, is increased.

According to another preferred embodiment, in the case of a single orifice as the mouth of the connection in the first Umsteuerbereich this orifice is arranged relative to the first control port so that via the piston chamber opening, a connection between the first control port with the orifice can be generated. During a rotation, for example, of the cylinder drum of an axial piston machine, a connection between the first control opening and the outlet is thus produced after the pressure in the piston chamber has been increased by supplying pressure medium from the storage element through the piston chamber opening. Thus, when, for example, in the case of the axial piston pump, the first control port is the high pressure side, recharging of the memory element is enabled.

On the other hand, the orifice is preferably arranged so that a connection of the second control opening with the orifice via the piston chamber opening is impossible solely due to the geometric conditions. This ensures that it is not possible to reduce pressure from the storage element into the low-pressure area of the pump, regardless of a possible valve position.

Furthermore, it is advantageous if, in addition, the first reversing region can be connected to the first control opening by means of the valve device. Thus, the pressure equalization between the high pressure region of the pump and the piston chamber can be continued by removing pressure medium from the first control port after adjusting the pressure in the piston chamber and the storage element. The pressure can thus be further increased, so that by removing pressure medium from the high pressure side via the valve device, the pressure in the piston chamber can be adapted to the high pressure side. For this purpose, only the valve device is actuated, is then generated by the connection from the first control port to the orifice in the first Umsteuerbereich.

According to the above pressure equalization or pressure increase in the piston chamber during the transition from the suction side to the pressure side of a pump and a pressure reduction during the transition from the high pressure side to the low pressure side is required. For this purpose, it is advantageous according to a further development, if a second connection of the memory element is provided, which opens into the second Umsteuerbereich. This second connection has a second valve device. By virtue of this second valve device, in turn, the flow cross-section of the second connection can be decoupled in time from a positional angle of the piston chamber opening relative to the control part. This can also be done to adapt the relaxation of the piston chamber to the pressure level of the low pressure side. The temporal adaptation thus makes it possible to adapt the axial piston machine or, in general, a hydrostatic piston machine to different operating points. The filling of the storage element from the already degraded pressure at the transition from the high pressure to the suction side also leads to an improvement in efficiency, since the stored Liquid quantity is not removed from the delivery volume.

In accordance with the arrangement of the orifice in the first reversing region, the opening of the second connection in the second reversing region is also arranged so that it can be connected to the second control orifice by means of the piston chamber opening.

By means of the second valve device, the opening of the second connection in the second reversing region can also be connected to the second control opening. This has a similar effect as previously described for the high pressure side. After a partial approximation by connection of the orifice with the storage element is carried out and thus a partial pressure reduction was carried out in the piston chamber, a further pressure reduction, which is no longer possible in the already filled storage element, now on the low pressure side, so the second control port, respectively.

As already described above, it is preferable that the hydrostatic piston machine is a pump, in particular an axial piston pump, wherein the first control port is the high pressure control port and the second control port is the low pressure control port. That is, the first control port is connected to the delivery side of the pump and the second control port is connected to the suction side of the pump. The first Umsteuerbereich then characterized in a pump, which is driven only in one direction, the transition of a piston chamber opening from the suction side to the pressure side. This is also referred to as a pressure buildup page. Therefore, the second switching area corresponds to the pressure reduction side.

Fig. 1

ein Ausführungsbeispiel einer ventilgestützten Pulsationsminderungseinrichtung einer hydrostatischen Kolbenmaschine;

Fig. 2

ein zweites Ausführungsbeispiel mit einer ventilgesteuerten Pulsationsminderungsvorrichtung;

Fig. 3

ein drittes Ausführungsbeispiel, das ebenfalls ventilgesteuert arbeitet und ein hubbegrenztes Schaltventil verwendet;

Fig. 4

ein viertes Ausführungsbeispiel mit zwei Ausmündungsöffnungen im ersten Umsteuerbereich;

Fig. 5

einen beispielhaften Verlauf der Querschnittsflächen im Falle einer ventilgesteuerten Pulsationsminderungsvorrichtung nach Fig. 4;

Fig. 6

einen ersten Zeitpunkt eines fünften Ausführungsbeispiels einer ventilgestützten Pulsationsminderungsvorrichtung beim Betrieb der hydrostatischen Kolbenmaschine;

Fig. 7

einen zweiten Zeitpunkt der Anordnung der Fig. 6;

Fig. 8

einen dritten Zeitpunkt der Anordnung nach Fig. 6; und

Fig. 9

ein abgewandeltes Ausführungsbeispiel der Fig. 6 mit einem weiteren Speicherelement, das über die Hochdruckseite aufladbar ist.

Embodiments are shown in the schematic drawing and are explained in detail below. Show it:

Fig. 1

an embodiment of a valve-based Pulsationsmindernseinrichtung a hydrostatic piston engine;

Fig. 2

a second embodiment with a valve-controlled Pulsationsminderungsvorrichtung;

Fig. 3

a third embodiment, which also operates valve-controlled and uses a stroke-limited switching valve;

Fig. 4

a fourth embodiment with two Ausmündungsöffnungen in the first Umsteuerbereich;

Fig. 5

an exemplary profile of the cross-sectional areas in the case of a valve-controlled Pulsationsminderungsvorrichtung after Fig. 4 ;

Fig. 6

a first time of a fifth embodiment of a valve-supported Pulsationsminderungsvorrichtung in the operation of the hydrostatic piston engine;

Fig. 7

a second time of the arrangement of Fig. 6 ;

Fig. 8

a third time of the arrangement after Fig. 6 ; and

Fig. 9

a modified embodiment of Fig. 6 with another storage element that can be charged via the high-pressure side.

For the following statements it is assumed that the hydrostatic piston engine is an axial piston pump, which is intended for only one direction of rotation. However, it is also possible to provide, for example, a radial piston machine with a corresponding device. Also at Machines working in two directions can use the proposed solution. Because of the separate control via a valve or via the valve-supported control, it is in fact possible to provide a second, analogously constructed pulsation reduction device, which is used in the case of the reverse direction of rotation. The fact that a temporally variable adjustment of the flow cross section is possible by means of the solution according to the invention, can be shut down when reversing the direction of rotation Pulsationsminderungsvorrichtung and another put into operation.

In the Fig. 1 In order to explain the hydrostatic piston machine according to the invention with Pulsationsminderungsvorrichtung a plan view of a control part 1 is shown. This control part 1 has a first control opening, hereinafter referred to as high-pressure kidney 2, and a second control opening, hereinafter referred to as suction kidney 3, on. The high-pressure control kidney 2 and the suction kidney 3 are approximately kidney-shaped and extend along a common circle. The better clarity of Fig. 1 Because of only exemplarily a piston chamber opening 4 is shown, which connects a front side of a cylinder drum of the axial piston machine with a piston chamber arranged therein. In the piston chamber pistons are displaceably arranged for generating a delivery stroke. In a real cylinder drum, a plurality of such piston chambers are arranged distributed along a circumference circle.

The basic structure of an axial piston machine is known, which is why a complete explanation can be dispensed with. The cylinder drum rotates with the direction of rotation in the Fig. 1 indicated by the arrow d. During the rotation of the cylinder drum thus the individual piston chamber openings are successively alternately with the high-pressure kidney 2 or 3 Saugniere brought into connection. This is a pressure medium flow from the Piston space in the high-pressure kidney 2 at a corresponding pressure stroke of the piston allows. On the other hand, during the suction stroke of the arranged in the piston chamber piston, a suction of pressure medium in the piston chamber from the suction kidney 3 allows.

Between the high-pressure kidney 2 and the suction kidney 3, a first reversing area 5 at the so-called outer dead center AT and a second reversing area 6 at the inner dead center IT are arranged. The two Umsteuerbereiche are the dead zones of the piston movement. The first Umsteuerbereich 5 is that Umsteuerbereich in which in a promotion of pressure medium through the axial piston machine, a transition of the piston chamber opening 4 from the suction kidney 3 to the high-pressure kidney 2 takes place.

As long as the piston chamber opening 4 is in contact with the suction kidney 3, the piston chamber is filled with pressure medium during the suction stroke of the piston. The pressure level in the piston chamber is therefore approximately equal to the pressure level in the suction kidney 3. In order to reduce the pressure surge, which would take place in contact with the high-pressure kidney 2, a Pulsationsminderungsvorrichtung is provided. The pulsation reduction device comprises a storage element 7, in which pressure medium can be stored under high pressure. The memory element 7 is connected via a connection 8 with the first Umsteuerbereich 5. The connection 8 opens at an orifice 9 in the first Umsteuerbereich 5 so that in a relative movement of the piston chamber opening 4 to the control part of the suction kidney 3 to the high-pressure kidney 2 temporarily a contact with the orifice 9 and thus the connection 8 exists. In the illustrated embodiment, the connection 8 has a first connecting line section 8.1 and a second connecting line section 8.2. The first connecting line section 8.1 and the second connecting line section 8.2 are formed parallel to each other and open together via the Outlet 9 in the first Umsteuerbereich 5 off. In the second connecting line section 8.2, a throttle is formed, which may be given for example by the line cross section of the second connecting line section 8.2.

In the first connecting line section 8.2, a valve is provided which in this case alone forms a valve device 10. In the example shown, this valve device 10 is designed as a switching valve which can open or close the connecting line section 8.1. The valve device 10 forms a discharge valve, which is held by a spring in its rest position. In this position, the connection of the first connecting line section 8.1 is interrupted. From this rest position, an unthrottled connection of the first connecting line section 8.1 can be generated by means of an electromagnet, which acts on the valve against the force of the spring.

The function for pulsation reduction is explained below. In the Fig. 1 takes the piston chamber opening 4 a position angle relative to the outer dead center AT, in which there is already a contact with the orifice 9. Therefore, a connection between the piston chamber and the storage element 7 is made at least via the throttle in the second connecting line section 8.2. In order to allow a rapid filling of the piston chamber and thus an increase in pressure for precompression, in addition to the cross section, which is present through the throttle point in the second connecting line section 8.1, the valve device 10 is actuated for the unloading process. The solenoid-operated valve opens and releases the flow path of the first connecting line section 8.1 in addition. For a quick pressure equalization between the storage element 7 and the piston chamber is possible. After the Druckangleich is done, in a further rotation of the cylinder drum, so a further movement of the Piston chamber opening 4 in the direction of arrow d, the control signal for the electromagnet of the valve withdrawn. The valve is in its closed position and there is only the connection via the second connecting line section 8.2. In a further movement of the piston chamber opening 4 in the direction of the high-pressure kidney 2, at a certain position angle α, which characterizes a position of the cylinder drum with respect to the control part 1, a connection between the high-pressure kidney 2 and the outlet 9 is generated by the piston chamber opening 4 , This ensures that the storage element 7 can be filled again with the pressure of the high-pressure kidney 2. With this arrangement, it is possible to raise the pressure in the piston chamber to a pressure lying between the suction pressure and the high pressure. How far the pressure in the piston chamber can be raised depends on the volume of the storage element 7.

A second embodiment, which in contrast to the only valve-supported embodiment of Fig. 1 is valve controlled, is in the Fig. 2 shown. The same reference numerals mean the same elements. Their complete re-description is omitted to avoid unnecessary repetition.

The connection 8 consists, as in the first embodiment, of a first connecting line section 8.1 and a second connecting line section 8.2. However, the valve device is now realized by a first valve 10.1 and a second valve 10.2. The first valve 10.1 corresponds to the already from the Fig. 1 known switching valve. A corresponding second valve is now also arranged in the second connecting line section 8.2. The connection between the memory element 7 and the first Umsteuerbereich 5 can thus be completely separated. This can be achieved by the incipient piston stroke movement Exceeding the outer dead center AT in the first reversing region 5 by the piston stroke further compression of the pressure medium located in the piston chamber and thus an increase of the prevailing pressure to the pressure level of the high pressure kidney 2 takes place without pressure fluid already flows to load the storage element 7. In the embodiment of the Fig. 2 Therefore, after adjusting the pressure of the storage element 7 and the pressure in the piston chamber, the first valve 10.1 is closed. The second valve 10.2 is still in its closed position. Only when the pressure level of the high-pressure kidney 2 is reached, the second valve 10.2 is opened. This is advantageously done before the piston chamber opening 4 is open to the high pressure kidney 2, so that the storage element 7 can damp an overshoot of the pressure in the piston chamber. From the piston chamber and, when the piston chamber opening 4 is in communication with the high-pressure kidney 2, from the high-pressure side, charging of the storage element 7 to the pressure level of the high-pressure side is now possible. After refilling the storage element 7, the second valve 10.2 is closed again. After the next (in the Fig. 2 not shown) piston chamber opening is in contact with the orifice 9, then the first valve 10.1 is opened again.

In order to influence the charging process of the storage element 7 and the discharging process of the storage element 7, the flow cross sections via the first connecting line section 10.1 or the second connecting line section 10.2 are different. The loading and unloading processes can therefore be adapted specifically and in particular be controlled independently of time.

Such an adaptation of the flow cross sections for the loading and unloading process is also in the Fig. 3 shown. In contrast to the two preceding embodiments is in the Fig. 3 the connection 8 formed only by a conduit. In this line, the valve device 10 'is arranged, which is realized in this case by a stroke-limited switching valve. By means of the stroke limitation, a flow cross-section between the fully closed position of the valve device 10 'and the unthrottled position of the valve device 10' can be adjusted for the discharge. Thus, the formation of a second connecting line section can be omitted. Such a stroke-controlled switching valve can therefore effect both the function of adjusting the flow cross-section during the charging and discharging process as well as the complete separation of memory element 7 and reversing area 5.

In the Fig. 4 an embodiment is shown in which the usable angle of rotation of the cylinder barrel over the embodiment with only one orifice 9 is increased. The charging and discharging process is again effected via a first connecting line section 18.1 or a second connecting line section 18.2. While the first connecting line section 18.1 for discharging opens at a first opening 9.1 in the first reversing area 5, the second connecting line section 18.2 opens at a second opening in the first reversing area 5. The first and the second orifice 9.1 and 9.2 together form the orifice 9 of the connection 8. The arrangement of the first orifice 9.1 and the second orifice 9.2 can therefore be carried out in the Umsteuerbereich so that a larger angular position range can be used in a rotation of the cylinder drum. If the piston chamber opening 4 is located in the outer dead center labeled AT, then the first valve 10.1 is opened for the unloading process. As a result, the pressure in the piston chamber is increased from the storage element 7 until a pressure equilibrium between the piston chamber and the Memory element 7 is reached. Thereafter, the first valve 10.1 is closed. As has already been described above, starting from the outer dead center AT, the pressure in the piston chamber is increased by the piston stroke when the valves 10.1 and 10.2 are closed. The time of opening of the first valve 10.1 and the time of its closing is adjusted so that the entire Vorkompressionsvorgang, ie the discharge of pressure medium from the storage element 7 in the piston chamber and the subsequent precompression by the piston stroke generates a high pressure in the piston chamber, which Entry into the high-pressure kidney 2 corresponds to the pressure prevailing there. A second phase of precompression could also be done by an additional notch. In addition, it may alternatively also be provided that the second discharge opening 9.2 does not open out in the first reversing area 5, but directly in the high-pressure kidney 2. This is particularly advantageous in combination with the additional notch. If the piston chamber opening 4 comes into contact with the high-pressure kidney 2 by a further rotation of the cylinder drum, the second valve 10.2 is opened and the charging process of the storage element 7 can begin. The piston chamber opening 4 no longer has to be in connection with the first orifice 9.1 for this purpose. As a result, the total rotation angle available for a loading and unloading operation is increased. As a result, in particular the usable for the pre-compression piston stroke is increased. If, for example, a nine-piston pump is used, the maximum change in the position angle α of the cylinder drum relative to the control part 1 of 40 degrees is available before the precompression operation for the next piston chamber begins. The second valve 10.2 must therefore be closed before the first valve 10.1 is opened again. Such a nine-piston pump has an opening angle of the piston chamber opening 4 of z. B. about 30 degrees. When using only one orifice, as in the examples of Fig. 1 to 3 is therefore only a change in the position angle of the cylinder drum of 30 degrees available.

A schematic representation of the respective flow-through cross-sections A above the position angle α of a piston chamber opening 4 relative to the control part 2 is in the Fig. 5 shown. It can be seen how, in the portion indicated by Nd, the flow-through cross section with which the suction kidney 3 and the piston space opening 4 are connected to each other toward the outer dead center AT (α = 360 °) is reduced by the rotation of the cylinder barrel , Approximately in the outer dead center AT then opens the first valve 10.1 of the valve device 10 and connects the storage element 7 for loading the piston chamber via the first connecting line section 18.1 with the first orifice 9.1. After increasing the pressure in the piston chamber, the first valve 10.1 is closed again at a position angle of approximately 5 degrees n.AT.

After the first valve 10.1 is closed again, the charging of the storage element 7 can be started by bringing the second valve 10.2 into its open position, as shown by the curve portion with a positional angle of about 372 ° to about 396 °. Shortly after the opening of the second valve 10.2, an increasing connection between the piston chamber opening 4 and the high-pressure kidney 2 is produced, as shown by the curve section Hd. The timing of the first valve 10.1 and the second valve 10.2 is adapted to the respective operating state. In particular, the pressure increase can be taken into account by the piston stroke, so that between the closing of the first valve 10.1 and the opening of the second valve 10.2 and one of the in the Fig. 5 shown time sequence changed timing can occur.

The Fig. 6 to 8 show a further embodiment, at different times of loading and unloading. In addition to the already familiar elements, the are provided with matching reference numerals, the orifice 9 in the first Umsteuerbereich 5 via the valve device 10 with the high-pressure kidney 2 is connected. The valve device 10 is designed for this purpose as a 3/2-way valve. It can be set variably between its two end positions. In a first end position, which is predetermined as a rest position by means of a spring, the orifice 9 is connected via a line 11 to the high-pressure kidney 2. In contrast, in the second end position of the valve device 10, the connection 8 between the outlet 9 and the storage element 7 is made as already described.

Furthermore, the second reversing region 6 can be connected via a further line 12 as a second connection to the connection 8. The connection point between the connection 8 and the further line 12 lies between the valve device 10 and the memory element 7. A direct connection of the two Umsteuerbereiche 5 and 6 is thus avoided. In the further line 12, a further valve device 14 is arranged. The further valve device 14 allows an unthrottled flow through the further line 12 in its rest position, which is also predetermined by a spring. In the opposite direction, the valve device 14 can be adjusted by the force of an electromagnet in the direction of the second end position. In the second end position, a second orifice 13, with which the further line 12 terminates in the second reversing region 6, is connected to the suction kidney 3. For this purpose, a Saugnierenleitung 15 is provided, which connects the second valve device 14 with the suction kidney 3.

As already indicated above, a pressure equalization in the piston chamber is also required in the transition from the high pressure side to the low pressure side. A piston chamber opening 4.1, which just has no contact with the high-pressure kidney 2 due to the rotation of the cylinder drum, is replaced by the second Umsteuerbereich 6 closed. After exceeding the so-called inner dead center IT, a relaxation of the pressure medium in the piston chamber is made possible due to the lifting movement. The relaxation is carried out not only via the piston movement, but also via a connection of the second Umsteuerbereichs 6 with the storage element 7. After passing through the inner dead center IT, a connection between the piston chamber opening 4.1 and the other outlet 13 is made. The second valve device 14 is located in the in Fig. 6 shown first end position. Thus, a connection between the second Umsteuerbereich 6 and the memory element 7 is generated via the further line 12. There is a pressure equalization between the piston chamber of the first piston chamber opening 4.1 and the storage element 7 and pressure energy is recovered. If pressure equalization has taken place, further charging of the storage element 7 from the piston chamber of the piston chamber opening 4.1 is no longer possible. The second valve device 14 is actuated and the second outlet 13 is connected to the suction kidney 3. Thus, a further reduction of the pressure in the piston chamber of the piston chamber opening 4.1 can now take place by the escape of pressure medium from the piston chamber opening 4.1 in the suction kidney 3. Here, at this time, the connection is given only via the suction kidney 15, but the piston space opening 4.1 is not yet in contact with the suction kidney 3.

During the pressure reduction of the pressure in the piston chamber of the piston chamber opening 4.1 in the memory 7 and then in the suction kidney 3, the first valve device 10 is initially unchanged in its in the Fig. 6 shown rest position. After another piston chamber opening 4.3 has passed the outer dead center AT and comes into contact with the orifice 9 in the first Umsteuerbereich 5, the valve device 10 is actuated and made a connection between the storage element 7 and the orifice 9. As a result, the charged memory 7 in the piston chamber opening 4.3 and thus the associated piston chamber to the pressure equalization between the piston chamber and the storage element 7 relaxed. At this time, a connection of the storage element 7 with the second orifice 13 is not given, since the second valve device 14 in the in the Fig. 7 is shown switching position. This moment, in which the valve device 10 is brought into its switching position and the connection between the orifice 9 and the storage element 7 is made, is in the Fig. 7 shown.

In a further rotation, at a time when a pressure increase in the piston chamber of the piston chamber opening 4.3 by unloading the memory 7 is no longer possible, the first valve device 10 is returned to its rest position. This condition is in the Fig. 8 shown. Furthermore, the shows Fig. 8 on that the second valve device 14 is returned to its rest position. This is done after the connection between the piston chamber opening 4.1 and the second outlet 13 is interrupted.

For the pressure reduction of the piston chamber opening 4.1 subsequent piston chamber opening at the transition from the high pressure side to the low pressure side is thus the second valve device 14 ready again and creates the connection between the further orifice 13 and the memory element 7. Thus, the charging and discharging of the memory element described. 7 and associated therewith the equalization or adjustment of the pressure in the piston chambers at the transition from the high-pressure to the low-pressure side or the low-pressure side to the high-pressure side.

A modified version of the Pulsationsminderungsvorrichtung the Fig. 6 to 8 is in the Fig. 9 shown. Here is another memory element 17 is provided. In contrast to the embodiment of the Fig. 6 to 8 the valve device 10 now comprises switching valve 10.1 ', which corresponds to the first valve 10.1 provided for the unloading process Fig. 2 and 4 equivalent. In addition, an additional switching valve 10.3 is provided. About the switching valve 10.1 ', the storage element 7 is connected to the outlet 9. The third switching valve 10.3 is arranged in the line 11, so that regardless of the switching state of the switching valve 10.1 a connection of the orifice 9 can be made with the high-pressure kidney 2. In the conduit 11, a throttle 19 is further arranged. The second storage element 17 is connected via a storage line branch 16 to the line 11 between the throttle point 19 and the third switching valve 10.3. In this way, charging of the second storage element 17 via the throttle 19 from the high-pressure kidney 2 is possible.

In order to allow after adjusting the pressure between the storage element 7 and the piston chamber of the piston chamber opening 4.3 a further pressure increase in the direction of the prevailing in the high pressure kidney 2 high pressure, after the pressure equalization between the storage element 7 and the piston chamber of the piston chamber opening 4.3, the switching valve 10.1 'in brought his closed position. This condition is in the Fig. 9 shown. Thereafter, the third switching valve 10.3 is brought into its open position and thus the second storage element 17 unthrottled connected to the outlet 9. While an unthrottled removal of the pressure medium from the storage element 17 and thus a further pressure increase in the piston chamber of the piston chamber opening 4.3 is possible, after adjusting the pressure to the high pressure of the high-pressure kidney 2, the third switching valve 10.3 can be closed again. When the third switching valve 10.3 is closed again, there is a charging of the second memory 17 via the throttle point 19. Thus, the charging cycle of the second memory 17 is extended and equalization of the pressure in the high pressure region of the axial piston machine achieved.

Incidentally, the execution corresponds to the Fig. 9 already with reference to the Fig. 6 to 8 described. As there increases the removal of the pressure fluid from the piston chambers to their required pressure reduction, the efficiency of the piston engine. However, this does not charge the storage element 7 to the level of the high-pressure side. As a result, the pressure level attainable by the precompression discharge operation is lower than in the embodiments of FIGS Fig. 1-4 , In the example below Fig. 9 This is avoided by the use of the second memory 17.

The invention is not limited to the illustrated embodiments. In particular, it is possible to advantageously combine individual features of the various embodiments with each other.

Claims (11)

1. Hydrostatic piston engine with at least one piston space, in which a piston is arranged displaceably, the piston space being connectable via a piston-space port (4, 4.i) alternately to a first control port (2) or a second control port (3) of a control part (1), and a first and a second reversing region (5, 6) being formed between the first control port (2) and the second control port (3), and with an accumulator element (7) which is connectable to the piston-space port (4, 4.i) via a connection (8) which issues in the first reversing region (5), this connection (8) having a valve device (10), characterized in that, by means of this valve device, the flow cross section of the connection (8) can be varied in time in relation to the control part (1) in a manner decoupled from a position angle (α) of the piston-space port (4), and in that the valve device (10) comprises at least one electromagnetically or piezoelectrically actuated valve (10.1, 10.2, 10.3, 10', 10.1').
2. Hydrostatic piston engine according to Claim 1, characterized in that the electromagnetically actuated valve (10') is a switching valve with variable stroke limitation.
3. Piston engine according to Claim 1 or 2, characterized in that the connection (8) has a first and a second connecting-line portion (8.1, 8.2), and an electromagnetically or piezoelectrically actuated switching valve (10.1, 10.2) is arranged in each connecting-line portion (8.1, 8.2).
4. Piston engine according to Claim 3, characterized in that the first connecting-line portion (8.1) has a first issue (9.1) into the first reversing region (5), and the second connecting-line portion (8.2) has a second issue (9.2) into the first reversing region (5) or into the high-pressure kidney region (2), the first and the second issue (9.1, 9.2) being arranged so as to be offset with respect to one another in relation to the control part (1) in the direction of movement (d) of the piston-space port (4).
5. Piston engine according to one of Claims 1 to 3, characterized in that the issue (9) of the connection (8) in the first reversing region (5) is arranged such that the first control port (2) is connectable to the issue (9) by means of the piston-space port (4).
6. Piston engine according to one of Claims 1 to 5, characterized in that the issue (9) of the connection (8) in the first reversing region (5) is arranged such that a connection between the second control port (3) and the issue (9) via a piston-space port (4, 4.i) is geometrically not possible.
7. Piston engine according to one of Claims 1 to 5, characterized in that the first reversing region (5) is connectable to the first control port (2) by means of the valve device (10).
8. Piston engine according to one of Claims 1 to 6, characterized in that a second connection (12) of the accumulator element (7) is provided, which issues in the second reversing region (6), and in that the second connection (12) has a second valve device (14), by means of which the flow cross section of the second connection (12) can be varied in time in relation to the control part (1) in a manner decoupled from a position angle of the piston-space ports (4, 4.i).
9. Piston engine according to Claim 7, characterized in that a second issue (13) of the second connection (12) in the second reversing region (6) is arranged such that the said second issue is connectable to the second control port (3) by means of the piston-space port (4, 4.i).
10. Piston engine according to Claim 7 or 8, characterized in that the second issue (13) of the second connection (12) into the second reversing region (6) is connectable to the second control port (3) via the second valve device (14).
11. Piston engine according to one of Claims 1 to 9, characterized in that the hydrostatic piston engine is a pump and the first control port (2) is connected to the delivery side of the pump and the second control port (3) to the suction side of the pump, and the first reversing region (5) corresponds to the pressure buildup side defined by a direction of movement (d) of the piston-space port (4, 4.i) in relation to the control part (1).

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