EP2927371A1 - Circuit - Google Patents

Abstract

A circuit arrangement for controlling hydraulic consumers (10, 12, 14) which are connected in series and which are supplied for their operation by at least one load-sensing control pump (17) via a pressure supply port (P), each by means of an assignable valve means between a Standby operation and a working operation and vice versa is operable, which is arranged between the pressure supply port (P) and a supply line (A1) at least one hydraulic consumer (10) and having an actuatable valve (40), characterized in that the valve ( 40) is exclusively hydraulically controllable, that at least one actuation signal for the pending actuation of a load tap (34) originates at least at one of the hydraulic consumers (10), and that a metering orifice (46) between the valve (40) and at least one hydraulic consumer (10) is connected in the assignable supply line (A1).

Description

The invention relates to a circuit arrangement for controlling hydraulic consumers, which are connected in series and which are supplied for their operation by at least one load-sensing control pump via a pressure supply port, each operable by means of an assignable valve means between a standby mode and a working mode and vice versa is, which is arranged between the pressure supply port and a supply line of at least one hydraulic consumer and having an actuatable valve.

Mobile working machines, such as so-called Winterdienststreuer be built with a variety of carrier vehicles as a means of transport. Such work machines regularly have different controllable and operable hydraulic consumers, for example in the form of hydraulically driven constant motors. Thus, in the case of the mentioned winter service spreaders, for example, a consumer with his hydraulic motor can serve to drive a transport screw, for the purpose of transporting road salt; another consumer with a corresponding engine can then include a spreading plate for distributing the road salt on the road and another consumer with controllable motor to drive a feed pump to bring, for example, a liquid road salt mixture of winter maintenance spreader on the road. The pertinent consumer enumeration is only an example and a Many other consumers, even for other applications, in other types of machinery or work equipment would be conceivable. In order to be able to supply with the already mentioned Winterdienststreufahrzeugen with the smallest possible pump volume, the normally 2 to 4 hydraulically powered consumers accordingly, they are regularly connected in series, ie each consumer is the complete pump flow available. As a pump while a constant pump is used. A hydraulic circuit diagram showing the known solution is the subject of Fig. 1 the present protective law.

Since the mentioned carrier vehicles are increasingly equipped with so-called load-sensing pumps (LS pumps), there is a fundamental desire to be able to operate the series connection with such pumps. Due to the principle, the respective LS pump must be operated as a fixed displacement pump, since in the series connection the excess volume flow must flow to the tank via individual pressure compensators, with the result that the LS pump would then swing out to a maximum delivery volume.

In order to prevent this behavior, the LS pump is regularly operated as a fixed displacement pump with an upstream throttle valve. By closing the throttle valve, the LS pump can be switched to standby mode, with the upcoming load sensing pressure in the fluid flow direction behind the throttle valve ultimately representing the control fluid flow for the actuatable LS pump. The pump flow itself, however, is determined by the free cross section of the throttle valve.

A well-known series circuit with so-called LS-Vorschaltventil is exemplary in the Fig. 2 in the following description text.

Although the latter genus-forming solution is very advantageous and in particular allows safe operation of the LS supply pump, it represents a certain effort both from the control side and from the cost side ago to electrically control the additional ball valve to control the LS pump.

Based on this prior art, the present invention seeks to ensure the known solutions, while maintaining their advantages, namely a meaningful, functionally reliable operation, to further improve that achieved by both the manufacturing effort and on the part of the control effort to be operated a reduction is.

This object is achieved by a circuit arrangement with the features of claim 1 in its entirety.

Characterized in that according to the characterizing part of patent claim 1, the valve is exclusively hydraulically controlled, that at least one actuation signal for the pending actuation of a load tap originates at least at one of the hydraulic consumers, and that a metering orifice between the valve and at least one hydraulic consumer in the can be assigned assignable supply line, the circuit arrangement can switch hydraulically between an active operation and a standby mode automatically back and forth without the use of electrical control. The hydraulic control is without electrical components and is therefore very reliable in use. Also can be dispensed with a complicated, costly electronic control structure.

In order to switch the LS pump back and forth between active operation and standby mode, it is necessary to change the volumetric flow demand. For this purpose, according to a preferred embodiment of the invention, a metering orifice is switched on and off by a hydraulically actuated directional control valve. The switching signal to this comes preferably from a Lastdruckabgriff to the individual, connected to the circuit hydraulic consumers.

In order to allow the pressure to build up on the consumer, it is preferably provided that a low standby volume flow continues to flow. This is controlled by a second aperture which always remains open within the circuitry.

If all connected loads are inactive, the load sensing control line is depressurized and the directional control valve is closed. Thus, the pump only promotes the volume flow through the small aperture is requested. The pressure is determined by the load-sensing pressure difference of the pump.

If a consumer is now switched on by the operator of the working machine, the pressure in the LS control line rises due to the fact that the standby volume flow flows to the consumer. As a result of this increase in pressure, the directional valve switches over and releases the "large aperture". Thus, according to the "large aperture", the volumetric flow demand to the pump increases and this swings out to provide the required operating volume flow for the series connection.

The functionality of the series connection remains completely unaffected. By replacing the directional control valve with a suitable plug, the system can also be operated on a fixed displacement pump.

Further advantageous embodiments of the solution according to the invention are the subject of the dependent claims.

In the following, the solution according to the invention is based on three hydraulic circuit diagrams according to the Fig. 1 to 3 explained in more detail, wherein the Fig. 1 and 2 Solutions in the prior art relate.

To the structure and operation of the solution according to the invention after the Fig. 3 First, the state of the art according to the content of the Fig. 1 and 2 explained in more detail.

The Fig. 1 shows a circuit arrangement for driving three hydraulic consumers 10, 12, 14 in the form of hydraulic constant - speed motors, which, as shown in the Fig. 1 are connected in series and which are supplied for their operation by means of a constant displacement pump 16 via a pressure supply port P from a storage reservoir, such as a hydraulic tank 15, with predetermined fluid pressure. In the Fig. 1 shown outer frame 18 relates to the actual area of the circuit arrangement, wherein the respective consumer 10, 12, 14 via supply lines A1, A2 and A3 and return lines B1, B2, B3 to the circuit arrangement to be described later fluid or media leading connected.

The respective circuit arrangements shown in the figures are intended to be used in particular for winter service gritting vehicles, wherein the first load 10 with its hydraulic motor can serve to drive a transport screw not shown for the purpose of transporting Road salt. The second consumer 12 may include with its engine a spreading plate for distributing a road salt on the road and the last consumer 14 with its controllable constant motor can drive a feed pump used to bring, for example, a liquid road salt mixture of winter maintenance spreader on the road. For the sake of simplicity, the graphic reproduction of transport screw, spreading plate and application pump was dispensed with. Furthermore, it goes without saying that the respective circuit arrangement according to Fig. 1 to 3 can also be used for other purposes as Winterdienststreuer use, but in which the hydraulic consumers 10, 12, 14 are always arranged in the series connection shown to each other.

Between the respective inlet and return lines A1, B1; A2, B2 and A3, B3 of each hydraulic consumer 10, 12, 14, a pressure compensator 20 is connected, wherein each pressure compensator 20 as shown in the Fig. 1 on the input and output side is connected to a common supply line 22. The input C1 of the common supply line 22 opens into the supply line A1 and the output C2 of the supply line 22 opens into the last return line B3 of the indicated series circuit. Furthermore, the return line B3 discharges from the last consumer 14 into the tank connection T. Between the pressure supply port P and the tank port T is an adjustable and electro-magnetically actuated pressure limiting valve 24 is connected, for example, set to a pressure of 200 bar to secure the respective hydraulic circuit in the case of over-supply, in particular in the form of an overpressure, from the pump side Fluid path via a connecting line 26 between the pressure supply port P and tank connection T produces.

About control lines 28, 30, which are arranged on opposite sides each acting on the control piston of each pressure compensator 20, is always the inlet-side pressure in the supply lines A1, A2, A3 of each hydraulic consumer 10, 12, 14 and by means of a throttle or Aperture 32 throttled pressure in the form of a Lastabgriffs 34, which is arranged in the respective supply line A1, A2 and A3 behind a 2/2-way proportional directional control valve 36. Furthermore, the pressure compensators 20 are constructed in the manner of a 2/2 proportional directional control valve concept.

To get along with the smallest possible pump flow rates, as in Fig. 1 shown, the individual hydraulic consumers 10, 12, 14 connected in series with each other, so that each consumer 10, 12 or 14, the complete pump flow is available. In order to produce a reliable supply of the individual consumers 10, 12, 14, which are otherwise switchable due to the directional control valves 36 within the circuit and thus go into active operation, the constant displacement pump 16 must hold in a correspondingly high fluid with a predetermined pressure and should If the total volume is not consumed by the hydraulic consumers, the excess portion is given to the tank connection side T via the respective pressure compensator 20 then addressed. A pertinent loss operation via the pressure compensators 20 is indeed reliable, but leads to energy losses, resulting in particular from the operation of the feed pump 16.

To counteract the pertinent disadvantages, is in a circuit arrangement according to the illustration of the Fig. 2 It has already been proposed to replace the otherwise otherwise disadvantageous constant pumps for the pressure supply of the circuit arrangement by load sensing pump concepts 17, wherein also known in such case circuit arrangements, for example according to the Fig. 2 , the fundamental problem is that when not removed hydraulic fluid through the connected in series consumers 10, 12, 14, the excess medium on the individual pressure compensators 20 must be placed depending on the application in an energy-neutralizing manner on the tank side T. So a solution in which the constant pump 16 after the Fig. 1 is replaced by a LS pump 17, which would then also be operated as a constant pump, then makes no sense in this respect.

To address the pertinent disadvantage is in the solution after the Fig. 2 proposed to provide an electrically controllable throttle valve 40, which is connected in the first supply line A1 between the pressure supply port P and the input C1 of the supply line 22 for the individual pressure compensators 20. In the direction of the Fig. 2 seen behind the throttle valve 40 in the manner of an electrically controllable 2/2-way proportional directional valve output side of the control pressure in the inlet line A1 tapped and via an LS control line 42 which is connected to a LS port of the valve assembly, for controlling the delivery volume forwarded to the corresponding control device of the LS pump 17. By selectively driving and closing the directional control valve 40, the connected on the pressure supply side P LS pump 17 can be switched to the so-called. Standby operation, which is addressed by the addressed LS tap on the LS control line 42, the pump flow through the shared cross-section of the throttle valve 40 is determined.

Since the proposed circuit arrangement is particularly preferred for winter maintenance equipment, especially in the form of gritting vehicles, application and is often required in this technical area, that the control is very inexpensive, not all devices and machines mentioned above have the possibility of said ballast in the form of the throttle valve 40 to control the LS pump 17 to use. In particular already delivered Winterdienstgeräte can be with the in Fig. 2 retrofit the solution presented very poorly, as is often the case not readily available the connections are available for the electrical control of the throttle valve 40th

The in the Fig. 2 shown circuit has been explained only insofar as they differ significantly from the solution to the Fig. 1 differs, the previously used reference numerals and components of Fig. 1 in the Fig. 2 are provided with the same reference numerals and the extent already taken so far apply to the components according to the Fig. 2 , Furthermore, in turn for the Fig. 3 the same reference numerals are used for the same components, so that in this respect also the statements made so far for the circuit diagram representation according to the Fig. 3 apply, which is explained, moreover, only in so far as they are authoritative, that is, inventive of the above-known solutions according to the Fig. 1 and 2 different.

In the solution after the Fig. 3 is the corresponding valve 40 to the valve solution after the Fig. 2 designed as only hydraulically operated directional control valve, which in his in the Fig. 3 shown blocking position under the action of an energy storage in the form of a compression spring 41 is provided that there is no hydraulic control on the opposite control side of the valve 40. For the pertinent hydraulic control, the directional control valve 40 on its side facing away from the compression spring 41, opposite control side on an input for the LS control line 42, which receives its input pressure via another LS control line 44, the load tap 34 of each hydraulic consumer 10, 12, 14 coming on the LS control line 42 is opened with open check valve 43. The directional control valve 40 is designed in the manner of a 2/2-way switching valve and, in the case of a corresponding hydraulic actuation via the LS control lines 42 and 44, the valve 40 is switched into its fluid-conducting passage position.

Furthermore, a metering orifice 46 is connected between the valve 40 and the entry point C1 of the supply line 22 in the first supply line A1, which preferably has a correspondingly large opening cross-section. Instead of the metering orifice 46, a correspondingly designed throttle can also occur. Furthermore, behind the metering orifice 46 and in front of the inlet of the valve 40 in the direction of the pressure supply port P, a parallel branch 48 is connected to a further second orifice 50, which allows the flow of a low standby volume flow, which will be explained in more detail below. Furthermore, like that Fig. 3 shows, the other LS control line 44 connected by means of a third orifice 52 or throttle in relieving manner to the tank side T of the circuit arrangement, for which the corresponding connection line of the third aperture 52 opens into the return line B3.

In order to be able to switch the LS pump 17 back and forth between operation and standby, the volumetric flow demand is changed. For this purpose, the metering orifice 46 is connected behind the directional control valve 40 and the flow of the orifice 46 can be controlled by the hydraulically actuated directional control valve 40, in particular switched on and off. The actual switching signal for the hydraulic control of the directional control valve 40 comes from the respective Lastdruckabgriff 34 in the supply lines A1, A2 and A3 to the individual hydraulic consumers 10, 12, 14. In order to allow the pressure build-up at each consumer 10, 12, 14 safely a low standby volume flow is permitted, which is controlled via the second orifice 50, which always remains open with a predeterminable cross section.

If all consumers 10, 12, 14 inactive, the LS line 42, 44 is depressurized and the hydraulically controllable directional control valve 40 is closed. Thus, the LS pump 17 promotes only the flow rate through the small aperture 50 is requested. The pressure is determined by the necessary load sensing differential pressure of the pump 17.

If at least one of the consumers 10, 12 or 14 is now switched on in this order, the pressure in the LS control line 42, 44 increases because the standby volume flow now flows to the respectively assigned consumer. As a result of this increase in pressure, the directional control valve 40 switches over and releases the large diaphragm 46. Thus, according to the large opening cross-section of the orifice 46, the volumetric flow requirement rises to the pump 17, which then pivots controlled by the pressure in the load-sensing connection LS in order to provide the required operating volume flow for the consumers 10, 12, 14. The functionality of the indicated series connection remains completely unaffected by the pertinent measure.

By replacing the directional valve 40 by a corresponding end plug (not shown) in the hydraulic circuit, the system can then in turn be operated on a fixed displacement pump 16, as already shown. While with the solutions after the Fig. 1 and 2 In the prior art, the pressure relief valve 24 is electrically actuated, was in the solution after the Fig. 3 in turn selected an exclusively hydraulic solution that gets along with the hydraulic control pulse in the connecting line between the pressure supply port P and tank port T.

Claims (10)

Circuit arrangement for controlling hydraulic consumers (10, 12, 14) which are connected in series one behind the other and which are supplied for their operation by at least one load-sensing control pump (17) via a pressure supply connection (P), each by means of an assignable valve device between a standby Operation and a working operation and vice versa is operable, which is arranged between the pressure supply connection (P) and a supply line (A1) at least one hydraulic consumer (10) and an actuatable valve (40), characterized in that the valve (40) can be controlled only hydraulically, that at least one actuation signal for the pending actuation comes from a load tap (34) at least at one of the hydraulic consumers (10), and that a metering orifice (46) between the valve (40) and at least one hydraulic consumer (10 ) is connected in the assignable supply line (A1). Circuit arrangement according to claim 1, characterized in that in parallel connection (48) to the valve (40) and the metering orifice (46), a further orifice (50) is connected, which remains permanently open fluid leading and bypassing the valve (40) and the Measuring orifice (46) allows a standby volume flow from the pressure supply port (P) to at least one of the hydraulic consumers (10). Circuit arrangement according to claim 1 or 2, characterized in that the free opening cross-section of the measuring diaphragm (46) is dimensioned significantly larger than the opening cross-section of the further diaphragm (50). Circuit arrangement according to one of the preceding claims, characterized in that in the case of inactive hydraulic consumers (10, 12, 14) of the pressure in the load sensing control line (42, 44) via a discharge orifice (52) is degraded, so that with the elimination of the actuation signal in the form of a hydraulic dynamic pressure, the valve (40) closes. Circuit arrangement according to one of the preceding claims, characterized in that the valve (40) of the valve device is a hydraulically actuated directional control valve, which is preferably designed as a 2/2-way valve via a compression spring (41) is held in the non-actuated state in its blocking neutral position. Circuit arrangement according to one of the preceding claims, characterized in that in the supply line (A1) for the first hydraulic consumer (10) within the series circuit, a proportional valve (36) is connected, that, starting from this hydraulic consumer (10) whose return line ( B1) into the feed line (A2) of the consumer downstream in the series (12), in turn a proportional valve (36) is connected, and that this sequence for any subsequent, further hydraulic consumers (14) is maintained. Circuit arrangement according to one of the preceding claims, characterized in that between the inlet (A1, A2, A3) - and return line (B1, B2, B3) of each hydraulic consumer (10, 12, 14) a pressure compensator (20) is connected and that Each pressure balance (20) on the input and output side is connected to a common supply line (22). Circuit arrangement according to one of the preceding claims, characterized in that the respective pressure compensator (20) on its opposite control sides once the supply pressure in the respective supply line (A1) of the hydraulic consumer (10) and once the load sensing pressure supplemented by the pressure of an energy storage, such as a compression spring, has pending. Circuit arrangement according to one of the preceding claims, characterized in that the load tap (34) for detecting the current load-sensing pressure in the load-sensing control line (42, 44) in the respective supply line (A1) between the proportional valve (36) and the hydraulic consumer (10) to which the load-sensing control line (42, 44) is connected. Circuit arrangement according to one of the preceding claims, characterized in that the actuating signal for the valve (40) of the valve device in the form of a control pressure from the load sensing control line (42, 44) comes against the action of a compression spring (41) on the opposite control side the valve piston of the valve (40) acts.

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