DE102022213955A1 - Valve arrangement and hydraulic circuit - Google Patents

Abstract

A hydraulic valve arrangement is disclosed for supplying feed pressure medium and control pressure medium to a hydraulic circuit, with a pressure chamber for connection to a pressure medium source, a feed pressure chamber for connection to at least one working line of the circuit and a control pressure chamber for connection to a control line of the circuit, wherein the pressure chamber is fluidically connected to the feed pressure chamber via a first pressure medium flow path and is at least fluidically connectable to the control pressure chamber via a second pressure medium flow path that is fluidically parallel to the first or branched off from the first, wherein the pressure medium flow paths are fluidically connectable to a pressure medium sink via a pressure limiting valve of the valve arrangement, the valve body of which is prestressed in the closing direction and has control surfaces, a first of which is subjected to a feed pressure to be limited in the opening direction and a second to a pilot pressure. A hydraulic circuit with the valve arrangement is also disclosed.

Description

Technical area

The present disclosure relates to a valve arrangement according to the preamble of claim 1 for supplying feed pressure medium and control pressure medium to a hydraulic circuit, as well as to a hydraulic circuit with the valve arrangement according to claim 18.

The applicant's technical data sheet RD 92770 shows a hydraulic pump in a closed hydraulic circuit with feed pressure medium and control pressure medium supply by a feed pump coupled to the hydraulic pump. The feed is carried out via a respective check valve in the working line of the circuit that has the lower pressure. The feed pressure and the control pressure are set and limited by the same pressure relief valve. The hydraulic pump has a reversible displacement volume for reversing the delivery direction with a constant direction of rotation. The displacement volume is adjusted proportionally to an electromagnetic or hydraulic control signal. A zero position, i.e. a zero displacement volume, is achieved by spring centering of a pressure-balanced adjustment cylinder. The pressure compensation can be triggered by a separately actuated connection valve. However, the zero position created in this way is not guaranteed for all operating pressures and speeds.

The publication EN 10 2017 215 726 A1 The applicant's application shows a hydraulic pump in a closed circuit with make-up and flushing. The make-up and its pressure limitation are carried out in a similar way to the above solution according to RD 92770. Flushing is carried out via a further pressure relief valve, to which the lower pressure of the circuit is applied and which is effective in the opening direction. The opening pressure can be overridden, i.e. changed, depending on operating parameters (oil temperature, change in direction of travel), in particular to prevent unnecessary or operationally hazardous flushing, for example when the oil is still cold.

The applicant's data sheet RD 92035/2020-02-12 shows an adjustable hydraulic pump for the closed circuit. The feed pressure medium and control pressure medium supply, as well as their adjustment and limitation, are carried out analogously to the solution according to RD 92770. In contrast to this, electrically directly controlled pressure reducing valves are provided to pressurize the adjustment cylinder.

The publication EN 10 2011 121 052 A1 The applicant shows an adjustable hydraulic pump in a closed circuit with feed pressure medium and control pressure medium supply, analogous to the solution according to RD 92770. In addition, the response behavior of the pressure relief valve, which sets/limits the feed and supply pressure, can be varied in order to influence the level of the feed and supply pressure. The influence is implemented by an electromagnetically adjustable pressure reducing valve supplied from the feed pressure, the output pressure of which acts on a control surface of the said pressure relief valve.

The applicant's data sheet RD 58032/2022-02-02 shows a pressure reducing valve that can be used in the solutions in question.

In contrast, the invention is based on the object of providing a valve arrangement for supplying feed pressure medium and control pressure medium to a hydraulic circuit with an increased range of functions. A further object is to provide a hydraulic circuit with a feed pressure medium and control pressure medium supply with an increased range of functions.

The first object is achieved by a valve arrangement having the features of patent claim 1, the second by a hydraulic circuit having the features of patent claim 18. Preferred developments of the inventions are described in the respective dependent patent claims.

A hydraulic valve arrangement for supplying feed pressure medium and control pressure medium to a hydrostatic circuit has a pressure chamber for connection to a pressure medium source of the circuit, a feed pressure chamber for connection to at least one working line of the circuit and a control pressure chamber for connection to a control line of the circuit. The chamber can be a cavity, a channel, a line or a connection in the sense of the present disclosure. The pressure chamber can be or is connected to the feed pressure chamber via a first pressure medium flow path and to the control pressure chamber via a second pressure medium flow path that is fluidically parallel to the first or branched off from the first. Both pressure medium flow paths can be fluidically connected to a pressure medium sink via a pressure limiting valve of the valve arrangement. The valve body of the valve assembly is prestressed in the closing direction of this pressure medium connection, in particular via a spring or another pressure equivalent. In addition, it has control surfaces, a first of which is subjected to the feed pressure to be limited in the opening direction and a second to a pilot pressure that can be provided separately. According to the invention, the valve arrangement also has a valve device which is in hydraulic ically connected to the control pressure chamber or at least can be brought into such a way that the control pressure there can be changed via it.

In this way, a valve arrangement for a hydraulic circuit with an increased range of functions is provided, which includes the functions of feed pressure medium supply, control pressure medium supply, feed pressure change and control pressure change.

In a further development, the second control surface is effective in the opening direction, so that the pilot pressure is basically effective in the direction of a reduction in the feed pressure and thus the available control pressure. In this way, the feed pressure and the available control pressure can be adapted to the operating conditions of the circuit. Alternatively, the second control surface can be effective in the closing direction, so that it is effective in the direction of an increase in the feed pressure and the available control pressure.

In a particularly compact design, the pilot-controlled valve device has a valve body with a control surface that is subjected to the same pilot pressure as the second control surface. The same pilot pressure is thus used to influence both the feed pressure and the control pressure.

In order to enable the control pressure to be switched on or off without the feed pressure being influenced too much, the valve device and the pressure relief valve are coordinated in such a way that a threshold value of the pilot pressure at which the valve body of the valve device responds is lower, preferably about an order of magnitude lower, than a value set on the pressure relief valve at which the valve body of the pressure relief valve responds. The response can be an opening or closing control, depending on which development (explained below) is present. The coordination relates in particular to the design and/or setting, in particular with regard to a respective size of the control surface of the valve device and the second control surface of the DBV, as well as a pressure equivalent that is effective with or against the respective control surface. The threshold value is preferably between 1.5 and 5 bar, in particular between 2 and 3 bar. The value set on the DBV is preferably between 35 and 45 bar and is in particular 40 bar.

In a preferred development, a pressure control device is provided which can be controlled with a setpoint signal and at whose output the pilot pressure can be adjusted depending on the setpoint signal. The output is then preferably fluidically connected to the second control surface and to the control surface of the valve body of the valve device.

In a further development, the valve device is designed in such a way that in the event of a failure of the control of the pressure control device and/or a drop in the pilot pressure below a predetermined threshold value, which can be the case in the event of a power failure, for example, the second pressure medium flow path is blocked or at least throttled. In this way, the control pressure supply is interrupted or at least severely throttled, so that an adjustment device of the circuit that is dependent on the control pressure can automatically move into a neutral position or location, whereby a so-called "fail-safe" function can be fulfilled.

In terms of device technology, the "fail-safe" function is fulfilled in a simple way if, in the case mentioned, the control pressure chamber is connected to the pressure medium sink or at least can be connected. This can be done directly, for example via a direct line to the tank. Alternatively, it can be done indirectly, for example via the connection to the output of the pressure control device, if the connection of the output to the pressure medium sink is intended to be opened when there is no power.

In a preferred embodiment, the pressure control device is a pressure reducing valve (DRE). It is supplied with pressure medium in an efficient manner by being connected to the pressure medium source and sink of the circuit. For example, by connecting a pressure connection of the DRE to the first pressure medium flow path and a low-pressure connection of the DRE being connectable to the pressure medium sink. A valve body of the DRE is preferably pre-tensioned in the direction of the connection of the outlet to the tank and can be actuated in the direction of the connection of the outlet to the pressure connection, in particular electromagnetically.

According to one possible variant, the valve body of the valve device is arranged in the second pressure medium flow path. The valve body, which is pre-controlled with the pilot pressure, can thus act as a supply control.

For example, the control surface of the valve body of the valve device is effective in the direction of opening the second pressure medium flow path and a pressure in the first pressure medium flow path is effective on the valve body in the direction of closing the second pressure medium flow path.

According to a further development, such a variant is designed with a check valve that can be unlocked by the pilot pressure.

In an alternative development, the valve device is designed as a directional valve, in particular a 3/2-way valve, with a pressure connection, a control pressure connection and a low pressure connection and two end positions, which enables an actuating force that is independent of the pressure conditions at the feed pressure connection and control pressure connection. The pressure connection is fluidically connected to the pressure chamber, the control pressure connection is fluidically connected to the control pressure chamber and the low pressure connection is fluidically connected, directly or indirectly, to the pressure center sink. The valve body of the directional valve is preloaded into a blocking position in which the pressure connection is blocked and the control pressure connection is connected to the low pressure connection. The valve body can be actuated by the pilot pressure into an open position in which the control pressure connection is connected to the pressure connection and the low pressure connection is blocked. In an alternative development, the low pressure connection of the directional valve is fluidically connected to the output of the pressure control device so that it can be or is connected to the pressure center sink via the pressure control device.

According to another variant, the valve body of the valve device is arranged outside the second pressure medium flow path.

One possibility, for example, is that it is arranged in a third pressure medium flow path that extends from the control pressure chamber to the outlet. The valve body, which is pilot-controlled with the pilot pressure, can then act as a sequence control.

For this purpose, the control surface of the valve body of the valve device can be effective in the direction of closing the third pressure medium flow path, and/or the pilot pressure regulated at the output of the valve body of the valve device is effective in the direction of closing the third pressure medium flow path.

In this variant, the valve device can, for example, have a check valve that can be blocked by the pilot pressure.

In order to prevent a drop in the feed pressure in the first pressure medium flow path, according to a further development, a throttle device with a fixed or changeable throttle device is arranged in the second pressure medium flow path. In particular, in this case the third pressure medium flow path branches off from the second pressure medium flow path between the throttle device and the control pressure chamber.

A hydraulic circuit has a hydraulic valve arrangement according to the invention, which is designed according to at least one aspect of the previous description. The circuit has a pressure medium source, in particular a feed pump, which is connected to the pressure chamber of the valve arrangement, at least one working line that can be connected to the feed pressure chamber of the valve arrangement and a control line that is connected to the control pressure chamber of the valve arrangement. In addition, a hydraulic machine with an adjustable displacement volume and with a hydraulic adjustment cylinder with at least one cylinder chamber is provided, which can be fluidically connected to the control line and to a pressure medium sink via a respective control valve of the circuit assigned to it. The adjustment cylinder is preferably designed to be double-acting with a spring-centered neutral position. The control valve is, for example, electrically directly controlled ("ET") or electrically proportionally actuated ("EP") and is designed in particular as a pressure reducing valve. Preferably, it has a negative overlap so that in the event of a failure of its actuation, control and/or energization, the control line is fluidically connected to the pressure medium sink via the control valve and the adjusting cylinder automatically adjusts itself to its neutral position.

• 1 einen hydraulischen Schaltplan eines erfindungsgemäßen hydraulischen Kreises mit einem ersten Ausführungsbeispiel einer Ventilanordnung,
• 2 einen hydraulischen Schaltplan eines erfindungsgemäßen hydraulischen Kreises mit einem zweiten Ausführungsbeispiel einer Ventilanordnung,
• 3 einen hydraulischen Schaltplan eines erfindungsgemäßen hydraulischen Kreises mit einem dritten Ausführungsbeispiel einer Ventilanordnung,
• 4 einen hydraulischen Schaltplan eines erfindungsgemäßen hydraulischen Kreises mit einem vierten Ausführungsbeispiel einer Ventilanordnung,
• 5 einen hydraulischen Schaltplan eines hydraulischen Kreises mit einer ersten Variante einer Speisedruckmittel- und Steuerdruckmittelversorgung,
• 6 einen hydraulischen Schaltplan eines hydraulischen Kreises mit einer zweiten Variante einer Speisedruckmittel- und Steuerdruckmittelversorgung, und
• 7 einen hydraulischen Schaltplan eines hydraulischen Kreises mit einer dritten Variante einer Speisedruckmittel- und Steuerdruckmittelversorgung.

In the following, various embodiments of the invention are described in detail with reference to the figures. They show:

• 1 a hydraulic circuit diagram of a hydraulic circuit according to the invention with a first embodiment of a valve arrangement,
• 2 a hydraulic circuit diagram of a hydraulic circuit according to the invention with a second embodiment of a valve arrangement,
• 3 a hydraulic circuit diagram of a hydraulic circuit according to the invention with a third embodiment of a valve arrangement,
• 4 a hydraulic circuit diagram of a hydraulic circuit according to the invention with a fourth embodiment of a valve arrangement,
• 5 a hydraulic circuit diagram of a hydraulic circuit with a first variant of a feed pressure medium and control pressure medium supply,
• 6 a hydraulic circuit diagram of a hydraulic circuit with a second Variant of a feed pressure medium and control pressure medium supply, and
• 7 a hydraulic circuit diagram of a hydraulic circuit with a third variant of a feed pressure medium and control pressure medium supply.

1 shows an embodiment of a hydraulic circuit 1 according to the invention - in particular a closed one - which is provided, for example, on a mobile work machine and is part of a travel drive. A hydraulic machine 2 designed as a variable displacement pump is provided for supplying pressure medium, from which a hydrostatic variable displacement or constant displacement motor (not shown) can be driven by means of two working lines 4, 6 and associated working connections A, B, which is coupled, for example, to an axle or a wheel.

The variable displacement pump 2 is driven by a drive motor (not shown) via a drive shaft 8, which can be designed as an internal combustion engine or electric machine, for example. A pressure medium source or feed pump 10 designed as a constant pump is also coupled to the drive shaft 8 via a rigid mechanical coupling. This pumps feed or replacement pressure medium from a pressure medium sink T designed as a tank via a feed line 12 and via one of two check valves 14 into the low-pressure one of the two working lines 4, 6.

A control line 15 branches off from the feed line 12 and is connected to cylinder chambers 20, 22 of a double-acting adjusting cylinder 24 of the variable displacement pump 2 via two control valves 16, 18, each of which is designed as an electrically directly controlled pressure reducing valve.

A valve arrangement 26 according to the invention is provided for controlling the supply of feed pressure medium and control pressure medium via the respective feed line 12 and control line 15. This has a pressure connection 28 connected to the pressure side of the feed pump 10, a feed pressure connection 30 that can be connected to the respective working line 4, 6 via the check valves 14 and a control pressure connection 32 connected to the control line 15.

Alternatively - in particular in the case of a design of the valve arrangement 26 integrated into a control block - the connections 28, 30, 32 can each be designed as a cavity, channel or line.

Within the valve arrangement 26, a first pressure medium flow path 34 extends from the pressure connection 28 to the feed pressure connection 30, from which in turn a second pressure medium flow path 36 branches off to the control pressure chamber 32.

The above-mentioned branching point of the two pressure medium flow paths 34, 36 can alternatively be located differently. For example, in an alternative embodiment they can branch directly from the pressure connection 28.

According to the disclosure, the pressure medium flow paths 34, 36 can be fluidically connected together via just one pressure relief valve 38 (DBV) of the valve arrangement 26 to the pressure medium sink designed as a tank T, which keeps the device-related effort for controlling and limiting the pressure for both pressure medium flow paths 34, 36 to a minimum. A valve body of the pressure relief valve 38 is preloaded by a spring 40 in the closing direction of this pressure medium connection. Two control surfaces 42, 44 are provided on the valve body. The first control surface 42 is acted upon by the feed pressure to be limited at the feed pressure connection 30 in the opening direction of this pressure medium connection. In order to variably adjust the feed pressure and provide control pressure for changing operating states of the circuit 1, the second control surface 44 can be acted upon by a separately provided, changeable pilot pressure. In the embodiment shown, this second control surface 44 has the same effect as the first 42, i.e. it acts against the closing force of the spring 40. Its application of pilot pressure thus enables a targeted reduction in a response pressure of the pressure relief valve 38, and as a result a targeted reduction in both the feed pressure available at the feed pressure connection 30 and the control pressure that can be made available at the control pressure connection 32.

In an alternative embodiment, the second control surface 44 can counteract the first 42, i.e. act with the spring 40 in the closing direction. Applying pilot pressure to it then enables a targeted increase in the available feed pressure and the control pressure that can be provided

To provide the pilot pressure, the valve arrangement 26 has a pressure control device 46, which, according to the disclosure, is designed as a pressure reducing valve (DRE) in the form of a 3/2-way valve. In the embodiment shown, a supply connection of the pressure reducing valve 46 is fluidically connected to the first pressure medium flow path 34 (cf. 1 above the DBV 38). Alternatively, the pressure reducing valve 46 could of course be supplied from a separate pressure medium source. A low-pressure connection of the Pressure reducing valve 46 is connected to the tank T and an output 50, at which the pilot pressure is regulated, is connected to the second control surface 44. The valve body of the pressure reducing valve 46 is loaded by a spring 48 in the direction of a connection of the output 50 to the tank T, that is, in the direction of a minimum pilot pressure.

To influence the pilot pressure, an electromagnet coupled to the valve body of the pressure reducing valve 46 can be controlled via a signal line 52 with a setpoint signal that corresponds to the desired pilot pressure - and indirectly to the desired feed pressure and available control pressure. The pilot pressure acting on the second control surface 44 results in an additional force on the valve body of the pressure relief valve 38 that is effective in the opening direction. In this way, the response pressure or opening pressure of the pressure relief valve 38 can be continuously reduced depending on the setpoint signal, which, when controlled accordingly, results in the above-mentioned reduction in the feed pressure.

According to the disclosure, the valve arrangement 26 has a pilot-controlled valve device 54 which is in hydraulic operative connection with the control pressure chamber 32. This operative connection makes it possible to specifically change the control pressure actually provided at the control pressure connection 32. In this way, different levels of control pressure can be provided to the control valves 16, 18 for pressurizing the cylinder chambers 20, 22.

In the embodiment according to 1 the pilot-controlled valve device 54 is designed as a releasable check valve 56, which is arranged directly in the second pressure medium flow path 36. On the valve body of the check valve 56, the feed pressure at the feed pressure connection 30 is effective in the closing direction and the control pressure at the control pressure connection 32 is effective in the opening direction. In order to enable the supply of the control pressure connection 32, the check valve 56 can be controlled open in a targeted manner. For this purpose, a pilot line 58 is provided, via which the outlet 50 is connected to a control surface of the valve body of the check valve 56 that is effective in the opening direction.

• - In einem „fail-safe“ oder stromlosen Modus erfährt das Druckreduzierventil 46 keine Ansteuerung mit einem Sollwertsignal über die Signalleitung 52. Am Ventilkörper des Druckreduzierventils 46 wirken somit lediglich Schließkräfte, insbesondere die Kraft der Feder 48. Der Ventilkörper wird so in die Stellung geschoben, in der der Ausgangs 50 mit der Druckmittelsenke T verbunden ist. Der Vorsteuerdruck am Ausgang 50 ist dann null oder Tankdruck. Die zweite Steuerfläche 44 des Ventilkörpers des Druckbegrenzungsventils 38 und die Steuerfläche des Ventilkörpers des Rückschlagventils 56 sind somit druckentlastet. Gemäß den obigen Ausführungen führt das dazu, dass am Druckbegrenzungsventil 38 in Öffnungsrichtung lediglich der Speisedruck auf der ersten Steuerfläche 42 lastet. Im Resultat wird der Speisedruck nicht oder zumindest nicht nennenswert abgesenkt, sondern am Speisedruckanschluss 30 steht der über die Feder 40 voreingestellte, bestimmungsgemäße Speisedruck an. In Analogie dazu ist die in Öffnungsrichtung wirksame Steuerfläche des Ventilkörpers des Rückschlagventils 56 über die Vorsteuerleitung 58 druckentlastet. Das hat zur Folge, dass das Rückschlagventil 56 und der zweite Druckmittelströmungspfad 36 zugesteuert bleiben. Dadurch ist der Steuerdruckanschluss 32 von der Druckmittelquelle 10 (Speisepumpe) getrennt. Vorzugsweise weisen Ventilkörper der Druckreduzierventile 16, 18 jeweils eine negative Überdeckung mit Bezug zu Steuerkanten ihres Ventilgehäuses auf, sodass in diesem Modus in der Steuerleitung 15 stehendes Steuerdruckmittel über die Druckreduzierventile 16, 18 zum Tank T abströmt. In der Konsequenz sind die Zylinderräume 20, 22 mit Tankdruck druckausgeglichen und über die Federzentrierung des Verstellzylinders 24 wird die Verstellpumpe 2 gezielt in ihre „Nulllage“ mit null Verdrängungsvolumen zurückgestellt.
• - In einem „Normal“-Modus erfolgt die Ansteuerung des Druckreduzierventils 46 mit einem Sollwertsignal, aus dem am Ausgang 50 ein Schwellwert des Vorsteuerdrucks resultiert, der gerade ausreicht, das Rückschlagventil 56 und damit den zweiten Druckmittelströmungspfad 36 aufzusteuern. Sowohl am Speisedruckanschluss 30 als auch am Steuerdruckanschluss 32 steht dann im Wesentlichen der am Druckbegrenzungsventil 38 über die Feder 40 eingestellte, „normale“ Speisedruck/Steuerdruck zur Verfügung. Ein üblicher Wert hierfür ist beispielsweise etwa 40 bar. Zu beachten ist, dass (wie oben beschrieben) der Vorsteuerdruck nicht nur das Rückschlagventil 56 öffnet, sondern auch an der zweiten Steuerfläche 44 des Druckbegrenzungsventils 38, im Sinne einer Reduzierung des Speisedrucks, wirksam ist. Um die Aufsteuerung des Rückschlagventils 56 zu ermöglichen und gleichzeitig den an der Feder 40 eingestellten Speisedruck nicht zu stark abzusenken, ist daher erfindungsgemäß die Steuerfläche des Ventilkörpers des Rückschlagventils 56 derart auf die zweite Steuerfläche 44 abgestimmt, dass der Schwellwert des Vorsteuerdrucks, ab dem das Rückschlagventil 56 anspricht (öffnet), verglichen mit dem Speisedruck gering ist, beispielweise 2-3 bar. Der zum Aufsteuern des zweiten Druckmittelströmungspfades 36 notwendige Schwellwert resultiert dann in einer vernachlässigbaren Absenkung des Speisedrucks. Im „Normal“-Modus kann insbesondere der höchste verfügbare Steuerdruck bereitgestellt werden, was eine hohe Verstelldynamik ermöglicht, und eine Nachspeisung und Spülung bewegen sich in den Grenzen eines bestimmungsgemäßen Betriebes des Kreislaufs 1.
• - In einem dritten oder „Absenk“-Modus ist das Ziel, die Energieeffizienz des Kreislaufs zu erhöhen und einen geringeren Speisedruck bereitzustellen, was darin begründet ist, dass ein abgesenkter Speisedruck zu einer verringerten Nachspeisung und in Folge Spülung der Arbeitsleitungen 4, 6 führt. Die Spülung dient beispielsweise dem Ersatz von kontaminiertem Druckmittel und insbesondere der Rückkühlung des im Betrieb erhitzten Druckmittels. Ist das Druckmittel jedoch nicht kontaminiert oder (noch) kalt, insbesondere bei Inbetriebnahme- oder Anfahrvorgängen, ist die Spülung nicht notwendig, sondern stellt vielmehr einen überflüssigen Energieverlust dar. In diesen oder anderen Betriebssituationen wird daher der „Absenk“-Modus angewendet, um die Spülung und den Energieverlust so gering wie möglich zu halten. Hierfür wird das Druckreduzierventil 46 mit einem höheren Sollwertsignal angesteuert, das zu einem Vorsteuerdruck oberhalb des zuletzt genannten Schwellwertes führt. Je höher der Vorsteuerdruck ist, umso stärker ist die daraus resultierende Absenkung des Speisedrucks und natürlich auch des am Steuerdruckanschluss 32 bereitgestellten Steuerdrucks. Zu beachten ist die Randbedingung, dass der Speisedruck einen Mindestwert einhalten muss, üblicherweise etwa 10 bar, um eine ausreichende, niederdruckseitige interne Schmierung der Verstellpumpe 2 sicherzustellen. Da das Rückschlagventil 56 ober des Schwellwertes des Vorsteuerdrucks stets aufgesteuert ist, steht am Steuerdruckanschluss 32, wie bereits im „Normal-Modus“, ein Steuerdruck in der Höhe des Speisedrucks am Speisedruckanschluss 30 zur Verfügung.

The operation of the valve arrangement 56 according to the first embodiment has at least three modes:

• - In a "fail-safe" or powerless mode, the pressure reducing valve 46 is not controlled with a setpoint signal via the signal line 52. Only closing forces, in particular the force of the spring 48, act on the valve body of the pressure reducing valve 46. The valve body is thus pushed into the position in which the output 50 is connected to the pressure medium sink T. The pilot pressure at the output 50 is then zero or tank pressure. The second control surface 44 of the valve body of the pressure relief valve 38 and the control surface of the valve body of the check valve 56 are thus relieved of pressure. According to the above statements, this means that only the feed pressure on the first control surface 42 is applied to the pressure relief valve 38 in the opening direction. As a result, the feed pressure is not reduced, or at least not significantly, but the intended feed pressure preset via the spring 40 is present at the feed pressure connection 30. Analogously, the control surface of the valve body of the check valve 56, which is effective in the opening direction, is relieved of pressure via the pilot line 58. This means that the check valve 56 and the second pressure medium flow path 36 remain closed. This separates the control pressure connection 32 from the pressure medium source 10 (feed pump). Preferably, the valve bodies of the pressure reducing valves 16, 18 each have a negative overlap with respect to the control edges of their valve housing, so that in this mode, control pressure medium in the control line 15 flows out to the tank T via the pressure reducing valves 16, 18. As a result, the cylinder chambers 20, 22 are pressure-balanced with tank pressure and the spring centering of the adjustment cylinder 24 is used to specifically return the adjustment pump 2 to its “zero position” with zero displacement volume.
• - In a "normal" mode, the pressure reducing valve 46 is controlled with a setpoint signal, from which a threshold value of the pilot pressure results at the output 50, which is just sufficient to open the check valve 56 and thus the second pressure medium flow path 36. The "normal" feed pressure/control pressure set on the pressure relief valve 38 via the spring 40 is then essentially available both at the feed pressure connection 30 and at the control pressure connection 32. A common value for this is, for example, around 40 bar. It should be noted that (as described above) the pilot pressure not only opens the check valve 56, but is also effective on the second control surface 44 of the pressure relief valve 38, in the sense of reducing the feed pressure. In order to enable the check valve 56 to be controlled and at the same time not to reduce the feed pressure set on the spring 40 too much, according to the invention the control surface of the valve body of the return check valve 56 is matched to the second control surface 44 in such a way that the threshold value of the pilot pressure at which the check valve 56 responds (opens) is low compared to the feed pressure, for example 2-3 bar. The threshold value required to open the second pressure medium flow path 36 then results in a negligible reduction in the feed pressure. In "normal" mode, in particular, the highest available control pressure can be provided, which enables high adjustment dynamics, and refilling and flushing are within the limits of proper operation of circuit 1.
• - In a third or "reduction" mode, the aim is to increase the energy efficiency of the circuit and to provide a lower feed pressure, which is due to the fact that a reduced feed pressure leads to a reduced make-up and subsequent flushing of the working lines 4, 6. The flushing serves, for example, to replace contaminated pressure medium and in particular to recool the pressure medium heated during operation. However, if the pressure medium is not contaminated or (still) cold, in particular during commissioning or start-up processes, flushing is not necessary, but rather represents an unnecessary loss of energy. In these or other operating situations, the "reduction" mode is therefore used to keep the flushing and energy loss as low as possible. For this purpose, the pressure reducing valve 46 is controlled with a higher setpoint signal, which leads to a pilot pressure above the latter threshold value. The higher the pilot pressure, the greater the resulting reduction in the feed pressure and of course also in the control pressure provided at the control pressure connection 32. The boundary condition that must be observed is that the feed pressure must adhere to a minimum value, usually around 10 bar, in order to ensure sufficient internal lubrication of the variable displacement pump 2 on the low pressure side. Since the check valve 56 is always opened above the threshold value of the pilot pressure, a control pressure equal to the feed pressure at the feed pressure connection 30 is available at the control pressure connection 32, as in the "normal mode".

As explained, the feed pressure and the control pressure are firmly coupled for pilot pressure values above its threshold value, and in the limiting case they are equal. However, there is a conflict of objectives between the lowest possible feed pressure - to achieve a low flushing volume and pumping energy of the feed pump 10 (high energy efficiency) and the highest possible control pressure - to achieve high adjustment dynamics. For operating situations in which high adjustment dynamics and high energy efficiency are required at the same time - for example, with high acceleration requirements during commissioning (dynamic adjustment, cold pressure medium), the requirements for the feed pressure or control pressure are contradictory. In this case, the requirements are preferably prioritized manually or automatically, and the corresponding pilot pressure and the corresponding setpoint signal for the pressure reducing valve 46 are determined.

The examples of the following 2 to 4 are based on the one according to 1 and differ from this with regard to their respective valve arrangement 126; 226; 326 and valve device 154; 254; 354. Their illustration and description is limited to these differences. The differences compared to the embodiment according to 1 Unchanged components are provided with the same reference symbols. Their repeated description is omitted and reference is made to the disclosure of the 1 referred to.

Deviating from the embodiment according to 1 is in the embodiment according to 2 the pilot-controlled valve device 154 is designed as a directional valve with three connections and two end positions (3/2-way valve). Its valve body is loaded by a spring in the direction of a blocking position a, in which the control pressure connection 32 is separated from the second pressure medium flow path 36 and connected to the tank T. In the direction of an open position b, in which the control pressure connection 32 is connected to the second pressure medium flow path 36 and separated from the tank T, a control surface of this valve body is connected to the pilot line 58 and thus to the outlet 50. In contrast to the statements on the "fail-safe" or powerless mode of the aforementioned embodiment, the control line 15 to the tank is thus relieved via the blocking position a of the valve device 154. The pressure reducing valves 16, 18 can therefore be designed either with or without negative overlap.

Also in the embodiment according to 3 the blocking position a of the valve device 254 serves to connect the control pressure port 32 to the tank T in the “fail-safe” or powerless mode. Deviating from the embodiment according to 2 the low pressure connection of the pilot valve device 254 is connected, instead of directly to the tank T, via a tank line 60 to the pilot line 58, which is fluidically connected to the outlet 50 of the pressure reducing valve 46, which is connected to the tank T anyway in the “fail-safe” or powerless mode as described above. The pressure on the control line 15, which is necessary for pressure equalization on the adjusting cylinder 24, must be relieved via the pressure reducing valve 46.

The 3/2-way valve of the valve devices 154; 254 can be designed as a switching valve or as a continuously adjustable valve.

• - „Fail-safe“ oder stromloser Modus: Das Druckreduzierventil 46 wird nicht angesteuert. Der Vorsteuerdruck am Ausgang 50 ist null oder Tankdruck. Es erfolgt daher keine Absenkung des Speisedrucks und die Schließkraft des Rückschlagventils 356 ist relativ gering, da dessen Ventilkörper nur von der Feder in die Sperrstellung belastet wird (kein Vorsteuerdruck auf der Steuerfläche). Entsprechend kann der in der Steuerleitung 15 anstehende Steuerdruck das Rückschlagventil 356 öffnen, was zu einem Abfall des Steuerdrucks und zum vorgenannten Druckausgleich am Verstellzylinder 24 führt. Die Drosseleinrichtung 62 verhindert ein übermäßiges Abströmen von Druckmittel aus dem ersten Druckmittelströmungspfad 34 und damit den Einbruch des Speisedrucks, sodass die Schmierung aufrechterhalten wird.
• - „Normal“-Modus: Die Ansteuerung des Druckreduzierventils 46 erfolgt mit dem Sollwertsignal, aus dem am Ausgang 50 ein Schwellwert des Vorsteuerdrucks resultiert, zu dem die am Rückschlagventil 356 wirksamen Schließkräfte (Feder und Vorsteuerdruck) ausreichen, den dritte Druckmittelströmungspfad 64 zu sperren. Aus der Steuerleitung 15 kann Steuerdruckmittel nur noch über die Druckreduzierventile 16, 18 abströmen und am Speisedruckanschluss 30 und am Steuerdruckanschluss 32 steht im Wesentlichen der am Druckbegrenzungsventil 38 über die Feder 40 eingestellte, „normale“ Speisedruck/Steuerdruck an.
• - „Absenk“-Modus: wie zuvor beschrieben erfolgt mit zunehmendem Vorsteuerdruck die zunehmende Absenkung des Speisedrucks und des bereitgestellten Steuerdrucks.

The pilot-controlled valve device 354 according to 4 differs conceptually from the previous 54;154;254 in that its valve body, which can be acted upon by the pilot control pressure, is not arranged in the second pressure medium flow path 36. The valve device 354 has a fixed throttle device 62 in the second pressure medium flow path 36 instead. The throttle device 62 can alternatively be designed to be adjustable. A third pressure medium flow path 64 also branches off between the throttle device 62 and the control pressure connection 32, via which the control pressure connection 32 can be fluidically connected to the outlet 50. To control this pressure medium connection, a check valve 356 is provided which opens from the control pressure connection 32 to the outlet 50, the valve body of which is loaded into its blocking position by a spring and the pilot control pressure at the outlet 50. All three modes described above ("fail-safe", "normal", "lowering") can also be operated with the valve arrangement 354, but differ in the pressure medium flow paths that are formed:

• - "Fail-safe" or power-free mode: The pressure reducing valve 46 is not activated. The pilot pressure at the output 50 is zero or tank pressure. There is therefore no reduction in the feed pressure and the closing force of the check valve 356 is relatively low, since its valve body is only loaded into the blocking position by the spring (no pilot pressure on the control surface). Accordingly, the control pressure in the control line 15 can open the check valve 356, which leads to a drop in the control pressure and to the aforementioned pressure equalization at the adjustment cylinder 24. The throttle device 62 prevents excessive pressure medium from flowing out of the first pressure medium flow path 34 and thus a drop in the feed pressure, so that lubrication is maintained.
• - "Normal" mode: The pressure reducing valve 46 is controlled by the setpoint signal, which results in a threshold value of the pilot pressure at the output 50, at which the closing forces (spring and pilot pressure) acting on the check valve 356 are sufficient to block the third pressure medium flow path 64. Control pressure medium can only flow out of the control line 15 via the pressure reducing valves 16, 18, and the "normal" feed pressure/control pressure set on the pressure relief valve 38 via the spring 40 is essentially present at the feed pressure connection 30 and the control pressure connection 32.
• - “Reduction” mode: as previously described, the feed pressure and the control pressure provided are gradually reduced as the pilot pressure increases.

The 5 to 7 show three examples of a valve arrangement that can be configured to either influence the control pressure provided or to reduce the feed pressure. A basic circuit diagram of the associated circuit is based on 1 in combination with 4 . In contrast to these, however, no valve device is provided as described above. Neither in the second pressure medium flow path 36 nor in the flow path previously referred to as the "pilot line" is a valve body that can be subjected to pilot pressure provided. Instead, specifically placed closures are used for configuration to block hydraulic paths.

According to 5 closures 400 and 500 are set in the second pressure medium flow path 36 and in the path from the outlet 50 to the second control surface 44. In addition, the outlet 50 is connected to the control pressure connection 32 without further throttling. As a result, the feed pressure is fixed (cannot be reduced) at the pressure relief valve 38 and the pressure reducing valve 46 provides the control pressure at the outlet 50 depending on the control. In the de-energized state, the control pressure is zero or tank pressure.

Deviating from 5 is in accordance with 6 Instead of the closure 400 in the second pressure medium flow path 35, the throttle device 62 is set, which prevents a drop in the feed pressure in the de-energized state.

Deviating from 6 is in accordance with 7 the closure 500 is removed and a closure 600 is placed in the third pressure medium flow path 64. The feed pressure is reduced as described by applying the pilot pressure to the second control surface 44. The control pressure provided is not variable, however, but always maximum, even in "fail-safe" or powerless mode, since it is independent of the control of the pressure reducing valve 46.

Disclosed is a valve arrangement which functionally combines a feed pressure medium supply and a control pressure medium supply, as well as a change in the feed pressure and control pressure, for a hydraulic circuit.

Furthermore, a hydraulic circuit, in particular a closed hydraulic circuit, with such a valve arrangement is disclosed.

List of reference symbols

1

hydraulic circuit

2

Variable displacement pump

4, 6

Work management

8th

drive shaft

10

Feed pump

12

Feed line

14

check valve

16, 18

Control valve

20, 22

Cylinder chamber

24

Adjusting cylinder

26; 126; 226; 326

Valve arrangement

28

Pressure connection

30

Feed pressure connection

32

Control pressure connection

34

first pressure medium flow path

36

second pressure medium flow path

38

Pressure relief valve

40

Feather

42

first control surface

44

second control surface

46

Pressure control device

48

Feather

50

Exit

52

Signal line

54; 154; 254; 354

pilot-controlled valve device

56; 156; 256; 356

Valve of the pilot-controlled valve device

58

Pilot line

60

Tank line

62

Throttle device of the pilot-controlled valve device

64

third pressure medium flow path

400, 500, 600

Closure

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 102017215726 A1 [0003]
• DE 102011121052 A1 [0005]

Claims (20)

Hydraulic valve arrangement (26; 126; 226; 326) for supplying feed pressure medium and control pressure medium to a hydrostatic circuit (1), with a pressure chamber (28) for connection to a pressure medium source (10), a feed pressure chamber (30) for connection to at least one working line (4, 6) and a control pressure chamber (32) for connection to a control line (15) of the circuit (1), wherein the pressure chamber (28) is fluidically connected to the feed pressure chamber (30) via a first pressure medium flow path (34) and is at least fluidically connectable to the control pressure chamber (32) via a second pressure medium flow path (36) which is fluidically parallel to the first or branched off from the first, wherein the two pressure medium flow paths (34, 36) are fluidically connectable to a pressure medium sink (T) via a pressure relief valve (38) of the valve arrangement (26), the valve body of which is prestressed in the closing direction and Has control surfaces (42, 44), of which a first (42) is acted upon in the opening direction by a feed pressure to be limited and a second (44) by a pilot pressure, characterized by a pilot-controllable valve device (54; 154; 254; 354) which is in hydraulic operative connection with the control pressure chamber (32), so that a control pressure there can be changed via it. Valve arrangement according to 1, wherein the valve device (54; 154; 254; 354) has a valve body with a control surface which is acted upon by the pilot pressure. Valve arrangement according to Claim 1 or 2 , wherein the valve device (54; 154; 254; 354) and the pressure relief valve (38) are coordinated with one another in such a way that a threshold value of the pilot pressure, from which the valve body of the valve device (54; 154; 254; 354) responds, is lower, preferably approximately one order of magnitude lower, than a value set on the pressure relief valve (38) from which its valve body responds. Valve arrangement according to one of the Claims 1 until 3 with a pressure control device (46) which can be controlled with a setpoint signal and has an output (50) at which the pilot pressure can be adjusted depending on the setpoint signal. Valve arrangement according to Claim 4 , wherein the valve device (54; 154; 254; 354) is designed such that in the event of a failure of a control of the pressure control device (46) and/or a drop in the pilot pressure below a predetermined threshold value, the second pressure medium flow path (36) is blocked or at least throttled. Valve arrangement according to Claim 4 or 5 , wherein the valve device (154; 254) is designed such that in the event of a failure of a control of the pressure control device (46) and/or a drop in the pilot pressure below a predetermined threshold value, the control pressure chamber (32) is connected to the pressure medium sink (T). Valve arrangement according to one of the Claims 4 until 6 , wherein the valve device (254) is designed such that, in the event of a failure of a control of the pressure control device (46) and/or a drop in the pilot pressure below a predetermined threshold value, the control pressure chamber (32) is connected to the output (50). Valve arrangement according to one of the preceding claims, wherein the valve body of the valve device (54; 154; 254) is arranged in the second pressure medium flow path (36). Valve arrangement according to Claim 8 , wherein the control surface of the valve body of the valve device (54; 154; 254) is effective in the direction of opening the second pressure medium flow path (36). Valve arrangement according to Claim 8 or 9 , wherein a pressure in the first pressure medium flow path (34) is effective on the valve body of the valve device (54) in the direction of closing the second pressure medium flow path (36). Valve arrangement according to one of the preceding, wherein the valve device (54) is designed as a check valve that can be unlocked by the pilot pressure. Valve arrangement according to one of the preceding claims, wherein the valve device (154; 254) is designed as a 3/2-way valve with a pressure connection, a control pressure connection and a low pressure connection and two end positions (a, b), wherein the pressure connection is fluidically connected to the pressure chamber (28), the control pressure connection is fluidically connected to the control pressure chamber (32) and the low pressure connection is fluidically connected, indirectly or directly, to the pressure center sink (T), wherein the valve body of the 3/2-way valve is prestressed into a blocking position (a) in which the pressure connection is blocked and the control pressure connection is connected to the low pressure connection, and wherein the valve body of the 3/2-way valve can be actuated by the pilot pressure into an open position (b) in which the control pressure connection is connected to the pressure connection and the low pressure connection is blocked. Valve arrangement according to Claim 12 , wherein the low-pressure connection of the 3/2-way valve is fluidically connected to the outlet (50) of the pressure control device (46), so that it can be or is connected to the pressure center sink (t) via the pressure control device (46). Valve arrangement according to one of the Claims 1 until 7 , wherein the valve body of the valve device (354) is arranged outside the second pressure medium flow path (36). Valve arrangement at least according to Claim 4 , wherein the valve body of the valve device (354) is arranged in a third pressure medium flow path (64) which extends from the control pressure chamber (32) to the outlet (50). Valve arrangement according to Claim 15 , wherein the control surface of the valve body of the valve device (354) is effective in the direction of closing the third pressure medium flow path (64), and/or wherein the pilot pressure regulated at the output (50) on the valve body of the valve device (354) is effective in the direction of closing the third pressure medium flow path (64). Valve arrangement according to one of the Claims 14 until 16 , wherein the valve device (354) has a check valve that can be blocked by the pilot pressure. Hydraulic circuit with a hydraulic valve arrangement (26; 126; 226; 326) which is designed according to one of the preceding claims, with a feed pump (10) which is connected to the pressure chamber (28) of the valve arrangement (26; 126; 226; 326), at least one working line (4, 6) which can be connected to the feed pressure chamber (30) of the valve arrangement (26; 126; 226; 326) and a control line (15) which is connected to the control pressure chamber (32) of the valve arrangement (26; 126; 226; 326). Cycle after Claim 18 with a hydraulic machine (2) with adjustable displacement volume and with a hydraulic adjustment cylinder (24) with at least one cylinder chamber (20, 22) which can be fluidically connected to the control line (15) and to a pressure medium sink (T) via an associated control valve (16, 18) of the circuit (1). Cycle after Claim 19 , wherein the control valve (16, 18) is designed such that in the event of a failure of its actuation, its control, and/or its energization, the control line (15) is fluidically connected to the pressure medium sink (T).

Images