EP2600012A2 - Hydraulic system - Google Patents

Abstract

The system has a hydraulic pilot system for controlling main control valves (2, 3). The pilot system and/or the valves are designed such that the valves are successively opened. The valves comprise valve springs (6, 7) with different spring forces for opening the valves at different control pressures. The valves include different valve rods and/or valve housings for opening the valves at different strokes. The valves are subjected with counter pressure, which counteracts actuating pressure, where the counter pressure is constant.

Description

The present invention relates to a hydraulic system with at least two main control valves and with a hydraulic pilot control system for controlling the main control valves.

If multi-circuit hydraulic systems are supplied with high pressure from a common hydraulic supply or if several hydraulic supplies supply a common consumer, this requires a complex adjustment of the main control valves to the power control of the pressure supply. For this purpose, conventionally complicated electronic controllers are therefore usually used in the prior art.

The object of the present invention is to provide a simpler and more reliable system.

This object is achieved by a hydraulic system according to claim 1.

The hydraulic system according to the invention comprises at least two main control valves and a hydraulic pilot control system for controlling the main control systems. According to the invention, it is provided that the hydraulic pilot control system and / or the main control valves are constructed such that the at least two main control valves open in succession. According to the invention can be achieved via the hydraulic or mechanical design of the hydraulic system so that the main control valves are opened in a certain sequence and so a cascade circuit is realized. In particular, the system can be constructed such that the at least two main control valves open at different control pressures of a common control transmitter. This also makes it possible, in a hydraulically piloted multi-circuit system, to realize a cascade circuit in which the main control valves open in a certain sequence. The main control valves can be used to control one or more consumers.

In a first variant, the cascade connection can be realized via mechanically and / or hydraulically differently designed main control valves.

In particular, the at least two main control valves can be equipped with springs of different spring force, so that the main control valves open by the different spring force at different control pressures. For example, the spring of a first main control valve may open in a first control pressure range while the spring of a second main control valve opens in a second control pressure range. Otherwise, the main control valves can be constructed identically.

Alternatively or additionally, the at least two main control valves may have different valve rods and / or valve housings, which lead to an opening of the at least two main control valves at different strokes. In this variant, the opening starts of the main control valves are set mechanically differently on the valve rods or the valve housings. This can be done for example in the form of grooves or holes on the valve rods.

As a result, a cascade circuit can be created without corresponding circuit logic by valve hardware. The valves open so at different stroke and thus at different control pressure.

Furthermore, it can be provided according to the invention that at least one of the main control valves is acted upon by a back pressure, which counteracts the control pressure. In this way, the same effect can be achieved as by an increased spring strength, since the back pressure is added to the spring pressure and must be overcome only by the control pressure to lead to an opening of the main control valve. In particular, the back pressure can be constant. Advantageously, a corresponding pressure source is provided for this purpose.

Furthermore, the cascade circuit can also be implemented by a corresponding configuration of the pilot control unit. Thus, identical main control valves can be used.

In particular, it can be provided that at least one of the main control valves is controlled via a pressure reducing valve whose output pressure is controlled via the control pressure for another main control valve. As a result, another control pressure for the one main control valve can be generated via the pressure reducing valve. In particular, the pressure reducing valve can have a pressure ratio not equal to 1 between control pressure and output pressure, so that the output pressure for controlling the one main control valve is in a fixed ratio to the control pressure for the other main control valve.

Alternatively or additionally, it can be provided that at least one of the main control valves is acted upon via a pressure shut-off valve with a counter control pressure, which counteracts the control pressure. Advantageously, the pressure shut-off valve is acted upon by the control pressure, so that the counter-control pressure rises to a shut-off pressure with the control pressure. This also makes it possible to achieve a later start of opening in the case of the main control valve, which is acted upon by the counter-control pressure.

Of course, combinations of the possibilities described above are conceivable. In particular, a first main control valve can be actuated via a pressure-reducing valve, while a second main control valve is acted upon by a counter-pressure via a pressure shut-off valve.

Furthermore, the possibilities described above can of course also be used with more than two main control valves.

Thus, in the first-described variants, which operate with mechanically and / or hydraulically differently designed main control valves, correspondingly different spring strengths or respectively differently machined valve rods or valve housings can be used.

Furthermore, more than one pressure-reducing valve or more than one pressure shut-off valve can be used in a cascade connection via the pilot control unit, which then work correspondingly with different pressure ratios or with different shut-off pressures.

Advantageously, the hydraulic system according to the invention has a common control transmitter, via which the at least two main control valves can be actuated. In particular, this control transmitter can generate a control pressure for driving the at least two main control valves. The inventive design of the main control valves and the pilot unit then ensures despite the common control transmitter for different opening starts of the main control valves.

In a first embodiment, the hydraulic system according to the invention further comprises a common high-pressure supply for supplying the at least two main control valves with hydraulic pressure on. Advantageously, the high-pressure supply thereby comprises a variable-displacement pump, which is controlled as required by the connected consumer or consumers. The cascading of the opening starts according to the invention allows the use of such a pressure supply despite hydraulic pilot control.

Advantageously, according to the invention, the variable displacement pump is controlled via a load-sensing arrangement. In particular, the variable displacement pump is controlled so that a certain pressure drop is maintained over all main control valves, and at the same time a maximum pressure is not exceeded. Advantageously, a subsequent summation for controlling the load-sensing arrangement takes place.

In a second embodiment variant, the at least two main control valves can be supplied with hydraulic pressure via at least two separate high-pressure supplies, in particular via separate variable displacement pumps.

The cascade control according to the invention ensures that at low flow rates required only one of the two main control valves opens and thus only one of the two hydraulic pumps is used to supply the consumer or consumers. If more power is needed, opens the other main control valve, so that the second hydraulic pump is used for supply.

Again, it may be advantageously provided that the variable displacement pumps are each controlled via a load-sensing arrangement.

Of course, the system according to the invention can also be used with more than two main control valves and / or more than two separate high-pressure supplies.

In a first variant of the hydraulic system according to the invention, the at least two main control valves control separate consumers.

For example, two hydraulic cylinders can be controlled via the two control valves. For example. the two hydraulic cylinders can be used for successive extension or retraction of different elements, eg. for telescoping or telescoping telescopic slides.

As described above, one or more hydraulic pumps can be used for the pressure supply.

In a second embodiment, the at least two main control valves control the same consumer. This is particularly advantageous if the required maximum control quantity is not made available via a single main control valve.

As described above, the two main control valves are particularly advantageously supplied with hydraulic fluid via separate hydraulic pumps. Alternatively, however, the pressure supply can also take place via only one hydraulic pump.

The present invention further includes, besides the hydraulic system, a pilot control system as described above. In particular, this is a pilot control system which implements the cascade circuit according to the invention hydraulically. In particular, as described above, a pressure-reducing valve and / or a pressure shut-off valve can be used to control at least one of the main control valves.

Furthermore, the present invention comprises a set of at least two main control valves for a hydraulic system, as described above. In particular, the main control valves are designed mechanically and / or hydraulically different. In particular, the two main control valves in this case, springs with different spring force, and / or mechanically differently processed valve rods or valve housing, which lead to an opening start at different stroke.

Advantageously, the pilot control system or the set of at least two main control valves are designed as described in more detail above.

The present invention further comprises a hydraulically powered implement having a hydraulic system as described above. In particular, it is a mobile working device. Particularly preferably, the present invention is used in construction, earthmoving and / or handling equipment. In particular, the present invention comprises a hydraulic excavator with a hydraulic system according to the invention.

In particular, the implement may include at least two separate hydraulic pumps for supplying consumers of the implement with hydraulic fluid, wherein the at least two main control valves are supplied separately from the at least two separate hydraulic pumps with hydraulic pressure.

Advantageously, the two main control valves supply the same consumer with hydraulic fluid.

In this case, the consumer, which is acted upon by hydraulic pressure from both main control valves, can be a slewing gear, a chassis and / or a hydraulic cylinder, in particular for lifting and / or moving a jib or tool.

However, the two main control valves can also be used to supply two separate consumers with hydraulic fluid.

The at least two consumers may be, for example, a slewing gear, a running gear and / or hydraulic cylinders for lifting and / or moving a jib or a tool.

Figur 1:

ein erstes Ausführungsbeispiel eines erfindungsgemäßen Hydrauliksystems mit Hauptsteuerventilen mit unterschiedlichen Federstärken,

Figur 2:

ein zweites Ausführungsbeispiel eines erfindungsgemäßen Hydrauliksystems mit Hauptsteuerventilen mit unterschiedlich gearbeiteten Ventilstangen,

Figur 3:

ein drittes Ausführungsbeispiel eines erfindungsgemäßen Hydrauliksystems mit einer über die Vorsteuereinheit realisierten Kaskadierung,

Figuren 4a bis 4d:

vier Ausführungsbeispiele für den Einsatz der erfindungsgemäßen Kaskadenschaltung mit einer oder mehreren Hydraulikpumpen und/oder einem oder mehreren Verbrauchern,

Figur 5:

ein Ausführungsbeispiele für den Einsatz der erfindungsgemäßen Kaskadenschaltung mit mehr als zwei Hauptsteuerventilen und/oder Pumpen.

The present invention will now be described in more detail with reference to embodiments and drawings. Showing:

FIG. 1:

A first embodiment of a hydraulic system according to the invention with main control valves with different spring strengths,

FIG. 2:

A second embodiment of a hydraulic system according to the invention with main control valves with differently worked valve rods,

FIG. 3:

A third embodiment of a hydraulic system according to the invention with a realized via the pilot unit cascading,

FIGS. 4a to 4d:

four embodiments for the use of the cascade circuit according to the invention with one or more hydraulic pumps and / or one or more consumers,

FIG. 5:

An exemplary embodiments of the use of the cascade circuit according to the invention with more than two main control valves and / or pumps.

The embodiments of the present invention relate to a hydraulic system with two main control valves, in particular as part of an LS multi-circuit system with downstream summation, which are operated hydraulically piloted. In this case, a cascade circuit is provided according to the invention, through which the hydraulic control slide used as the main control valves are opened in a certain sequence.

The control of the system is carried out via a common pilot control 2, in particular a control handle, via which a desired control pressure for pilot control is generated. The pilot control device may be, for example, a joystick. The pilot controller 1 can via a pilot pressure source 15, as shown for example in FIG. 3 is shown, are acted upon by a constant pilot pressure and reduces this to the desired control pressure. The constant pilot pressure can be, for example, 35 bar.

The hydraulic system according to the invention now allows by its mechanical or hydraulic structure, despite this common control, a cascading of the opening times. On the one hand, the cascade connection can be realized via different valve springs of the main control valves, or via different slide opening starts of the main control valves. Likewise, a hydraulic cascade pilot control unit may be provided, so that the cascade connection takes place via the pilot control. These three alternatives are now once again based on the in the FIGS. 1 to 3 shown embodiments will be explained in more detail.

In FIG. 1 are two main control valves 2 and 3 are shown, which are respectively acted upon at their control pressure ports 4 and 5 with the same control pressure of the pilot control 1. According to the invention, the valve springs 6 and 7 of the two main spool 2 and 3 are chosen so that z. B. the spring of the slider 2 in a first pressure range and the spring of the slider 3 in a second pressure range responds. For example, the spring 6 of the slider 2 may be chosen so that it responds in a pressure range between 0 and 20 bar, while the spring 7 of the slider 3 of 20 to 35 bar responds. Due to the different valve springs so different opening starts are achieved.

Alternatively or additionally, one of the slides (in Fig. 1 the slide 3) a pressure source or corresponding circuit 9 may be provided, which this subjected to a back pressure. In this way, the same effect is achieved as by mechanically reinforcing the spring strength of the slider 3. In this case, the valve 3 is acted upon by the counter control pressure port 8 with a counter control pressure from the circuit 9, wherein the back pressure is advantageously constant.

In this way, the same spring strength as the slider 2 can be used, which is now reinforced via the pressure source 9, since the back pressure adds to the spring pressure. For example, the spring strength for the valve 3 may also be between 0 and 20 bar and be amplified by 10 bar from the pressure source 9.

At the in FIG. 2 shown variant, the opening starts of the main spool 2 'and 3', however, are set mechanically different on the valve rods 10 and 11. This can be done depending on the manufacturer of the primary slide in the form of grooves or holes. As a result, a cascade circuit can be created without appropriate circuit logic by slider hardware.

As in FIG. 2 Although both pistons 10 and 11 thus have the same stroke 12, the piston of the main control valve 2 'already opens after a short distance, while the piston of the main control valve 3' opens later only at the stroke 13. This is achieved in the embodiment in that the groove 14 on the valve rod 11 of the main control valve 3 'is shorter than the groove 14' on the valve rod 10 of the main control valve 2 ', and so only at a larger stroke the pressure supply P with leading to the consumer Opening A or A 'connects.

The valve springs 6 'and 7' can also be made identical in this embodiment, so that the different opening starts only by the mechanical configuration of the valve rods. Alternatively, this could also be done by another mechanical configuration of the valve housing. At the in FIG. 3 the variant shown, the cascade circuit, however, realized via a corresponding configuration of the pilot valve unit. In particular, the main spool 2 'and 3' can be used unchanged. Here are in FIG. 3 again combined two different variants, which, however, can also be used individually.

On the one hand, a pressure reducing valve 16 may be provided, which is acted upon by the constant pilot pressure from the pilot pressure source 15. The pressure reducing valve 16 is acted upon by the control pressure 17 of the pilot control 1 and has a certain pressure ratio x, so that at the pressure outlet 18 of the pressure reducing valve 16, the x-times the control pressure 17 is applied. The first main control valve 2 'is acted upon by the actual control pressure 17, the second main control valve 3' with the changed control pressure 18 of the pressure reducing valve. On the piston 5 of the main control valve 3 'thus acts x times the control transmitter predetermined control pressure, while acting on the piston 4 of the main control valve 2' the simple control transmitter 1 predetermined control pressure.

Alternatively or additionally, a pressure shut-off valve 19 may be provided, which is acted upon by the control pressure from the pilot pressure transducer 1 and has a defined cut-off pressure. By way of the pressure from the pressure shut-off valve 19, a back pressure is exerted on the piston 4 of the main control valve 2 '. Therefore, as long as the control pressure is below the shut-off pressure of the shut-off valve 19, acts on both sides a and b of the main control valve 2 ', the same pressure, so that it stops in the neutral position. If the control pressure preset at the control transmitter 1 now increases above the deactivation pressure set in the pressure shut-off valve 19, the pressure at the piston 4 only increases a-side, while the pressure set in the shut-off valve 19 stops on the b-side, so that the piston 4 now also deflects via the pressure difference between a and b. As in FIG. 3 shown both variants can also be combined, so that the one valve is acted upon by the pressure shut-off valve with back pressure, while the other valve is controlled via the pressure reducing valve.

It would also be conceivable to use several pressure reducing valves with different pressure intensification, and / or several pressure shut-off valves with different shut-off pressures in the case of several valves.

Furthermore, even with two main control valves, the pressure for both main control valves could in each case via pressure reducing valves with different pressure ratio, or via Druckabschaltventile with different cut-off pressure.

In FIGS. 4a to 4d four exemplary embodiments for the use of the cascade circuit according to the invention with one or more hydraulic pumps and / or one or more consumers are shown.

In Fig. 4a Both main control valves 2 and 3 are completely connected in parallel. They are supplied by a common hydraulic pump 30 and control the same load 40.

In Fig. 4b the two main control valves 2 and 3 are connected in parallel only with regard to the pump side. They are therefore powered by a common hydraulic pump 30, but control separate consumers 41 and 42 at.

In Fig. 4c the two main control valves 2 and 3 are connected in parallel only with regard to the consumer side. They are therefore supplied by two separate hydraulic pumps 31 and 32, but drive the same load 40 at.

In Fig. 4d the two main control valves 2 and 3 are connected in parallel neither in terms of the consumer side, nor in terms of the pump side. you will be therefore powered by two separate hydraulic pumps 31 and 32 and control separate consumers 41 and 42 at.

In Fig. 5 an embodiment is shown in which more than two main control valves 50 to 53 are each supplied separately from the hydraulic pumps 31 to 34 on the pump side, but drive the same load 40.

Advantageously, the hydraulic system is designed so that the more than two main control valves 50 to 53 open or close in a defined order.

The present invention makes it possible, in particular in the case of a high-pressure supply of a multicircuit system via a load-sensing control with a downstream summation, to operate the main control valves hydraulically piloted and still achieve a cascade connection.

Hydraulic systems according to the invention can be used in particular in mobile working machines, such as, for example, a hydraulic excavator.

Claims (15)

Hydraulic system with at least two main control valves and with a hydraulic pilot control system for controlling the main control valves,
characterized,
in that the hydraulic pilot control system and / or the main control valves are constructed in such a way that the at least two main control valves open in succession. Hydraulic system according to claim 1, wherein the at least two main control valves have springs with different spring force, which lead to an opening of the at least two main control valves at different control pressures. Hydraulic system according to claim 1 or 2, wherein the at least two main control valves different valve rods and / or valve housing which lead to an opening of the at least two main control valves at different strokes. Hydraulic system according to one of the preceding claims, wherein at least one of the main control valves is acted upon by a back pressure, which counteracts the control pressure, wherein the back pressure is advantageously constant. Hydraulic system according to one of the preceding claims, wherein at least one of the main control valves is controlled via a pressure reducing valve whose output pressure is controlled by the control pressure of another main control valve, wherein the pressure reducing valve advantageously has a pressure ratio not equal to 1 between control pressure and output pressure. Hydraulic system according to one of the preceding claims, wherein at least one of the main control valves is acted upon via a pressure shut-off valve with a counter control pressure, which counteracts the control pressure and increases up to a cut-off pressure with the control pressure. Hydraulic system according to one of the preceding claims, wherein the at least two main control valves are actuated via a common control transmitter, wherein the control transmitter advantageously generates a pilot pressure for driving the at least two main control valves. Hydraulic system according to one of the preceding claims, wherein the at least two main control valves are supplied via a common high-pressure supply with hydraulic pressure, in particular via a common variable, wherein the variable displacement is advantageously controlled by a load-sensing arrangement, further advantageously carried out a subsequent summation. Hydraulic system according to one of claims 1 to 7, wherein the at least two main control valves are supplied via at least two separate high-pressure supplies with hydraulic pressure, in particular via separate variable displacement pumps, wherein the variable displacement advantageously be controlled via a load-sensing arrangement. Hydraulic system according to one of the preceding claims, wherein the at least two main control valves control different consumers. Hydraulic system according to one of claims 1 to 9, wherein the at least two main control valves drive the same consumer. Pilot control system and / or set of at least two main control valves for a hydraulic system according to one of the preceding claims. Hydraulically driven implement with a hydraulic system according to one of the preceding claims, in particular mobile implement, in particular construction, earthmoving and / or handling equipment, in particular hydraulic excavator. Hydraulically driven implement according to claim 13, with at least two separate hydraulic pumps for supplying consumers of the implement with hydraulic fluid, wherein the at least two main control valves are supplied separately from the at least two separate hydraulic pumps with hydraulic pressure and advantageously provide the same consumer with hydraulic fluid. Hydraulically driven implement according to claim 14, wherein it is the consumer, which is acted upon by two main control valves with hydraulic pressure, a slewing gear, a chassis and / or a hydraulic cylinder, in particular for lifting and / or moving a boom or tool.

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