DE19707722A1 - Valve arrangement and method for controlling such a valve arrangement - Google Patents

Abstract

The present invention pertains to a valve system designed to drive a consuming element (116) as well as to the production process, characterized in that an oil inlet and a regulating nozzle (6, 8) can be actuated independantly of each other. When using simply operating consuming elements, the regulating nozzle (6) is actuated in such a way that, once the desired rate of hydraulic oil is reached, the opening section of the regulating nozzle (6) is at a maximum, resulting in a substantially reduced loss of energy (120).

Description

The invention relates to a valve arrangement for control of a consumer according to the preamble of Pa claim 1 and a method for controlling a such valve arrangement.

Such valve arrangements are used in the mobile hydraulic lik to control single and double acting Ver users, such as hydraulic motors or power jacks used. It is in the Ar leading to the consumer power lines, d. H. in the inlet pipe and in the Ab a throttle device is switched in each case, over which the incoming or outgoing hydraulic oil volume flow is throttled.

In Figs. 1 to 3, to which reference is here already ge taken, some examples are shown of such known throttle devices.

Fig. 1 shows a valve arrangement for controlling egg nes double-acting consumer, which can be, for example, a lifting cylinder 200 . A working line 206 and 208 are connected to the cylinder space and the ring space of the lifting cylinder 200 . To extend the lifting cylinder 200 , the hydraulic oil is supplied to the lifting cylinder 200 via the working line 206 , the hydraulic oil displaced from the annular space being returned to the tank through the working line 208 acting as a drain line.

For throttling the hydraulic oil inlet and outlet two Ven throttles 210 , 212 are arranged in the two working lines 206 and 208 , the valve members of which are mechanically coupled. The ratio of the inlet and outlet opening of the valve throttles is predetermined by the mechanical coupling of the opening edges of the common valve spool, so that a certain setting of the valve throttle 210 also results in a pressure loss Δp2 in the outlet line (working line 208 ). This pressure loss is particularly undesirable when connecting single-acting users, since it is not a useful function. The pressure loss leads to energy losses, heating of the hydraulic oil and possibly premature wear of the valve throttle.

In Fig. 2, a valve arrangement for controlling egg NES fan motor 214 is shown. In this variant, who uses the two independently meterable valve throttles 210 , 212 , which can be used in a motor with two directions of rotation for throttling the hydraulic oil volume flow in the supply line. When using a motor with one direction of rotation, the flow throttling - in this case the valve throttle 212 in the drain line 208 - generates unnecessary pressure losses, so that the above-mentioned disadvantages also exist in such a valve arrangement.

Fig. 3 shows an application in which a lifting cylinder 200 is used for lifting or lowering a boom 215 of a lifting tool 216 . To raise the load m, the cylinder space of the lifting cylinder 200 is provided with hydraulic oil ver, so that the cylinder extends and the boom 215 is moved upwards in the illustration according to FIG. 3. The hydraulic oil in the annulus is displaced by the extension movement and returned to the tank. By pulling on the arm 215 acts load m a result de force to the lift cylinder 200, which is maximum in horizontal ver running boom 215 and decreases with pivoting of the boom 215 of this horizontal position. The further the boom 215 drops to the horizontal position, the more the weight increases on the outlet side of the lifting cylinder 200 , so that it is pressed downward in the illustration according to FIG. 3. Due to the increasing discharge volume flow Q2, cavitation can occur in the supply line, which is further supplied with an inlet volume flow Q1, which stresses the components of the valve arrangement to the greatest extent and can also lead to instabilities in the control. For this purpose, it is also necessary to adapt the flow restriction to the lifting conditions of the lifting device. Such a flow restriction generates pressure losses under certain operating conditions, which are not acceptable for the reasons mentioned above.

To avoid such unnecessary pressure drops one, for example, in engine applications for agricultural tractors so-called "unpressurized tank returns" available provides that to the drain side of the engine by means of a Quick coupling can be connected and the Ab throttle can be bypassed. A disadvantage of one of the like auxiliary construction is that the vehicle with a own tank neck must be provided with quick coupling and that the operator ma unpressurized tank return must connect. Such an auxiliary construction is can only be used sensibly if the respective operating should be maintained for a long time. At a change in consumer control, for example a change in the direction of rotation of the motor etc., must be On conclusions are changed, so that the operating effort is significant.

In contrast, the invention is based on the object a valve arrangement and a method for controlling a Valve arrangement to create those with minimized before directional effort the energy losses in the process can be reduced to a minimum by a consumer.  

This task is accomplished with regard to the device the features of claim 1 and in terms of Method by the features of claim 7 ge solves.

By the measure, the valve arrangement with throttle Execute directions in the inlet and outlet line and to interpret them in such a way that they are independent of a To throttle can be controlled, each as a sequence throttle device when connecting a specialized consumers, etc. to a maximum Flow cross section can be set so that the Pressure losses in the drain are minimized. The hydraulic oilvo The lumen flow is controlled by an inlet throttle Directional control valve set.

It is preferred to use the throttle device with two Functions to provide, in one function as unlockable check valve acts and in the other Function by means of an additional dosing edge for the throttle Inlet or outlet volume flow can be used can.

A particularly simple control of the throttle device tion and the directional control valve acting as an inlet throttle one if one control side of the directional valve and one of the Throttle devices each with the same control signal be charged.

The throttle device can be used as a directional control valve Non-return switch position and several continuously adjustable Flow positions or as a throttle device with ge separated functional elements, such as with main cone and push piston are formed mechanically are coupled together.  

To control the valve arrangement according to the invention three variants have proven to be particularly advantageous posed.

In the first variant, only the tax is initially pressure for the outlet-side throttle device increased, weh rend the other control pressure for the inlet throttle device kept constant - preferably at zero becomes. The first control pressure is increased until sets a predetermined control pressure differential across which the directional valve acting as an inlet throttle in a vorbe certain position is movable to the hydraulic oil volume adjust current. Then both control pressures while maintaining the control pressure difference increased until the Control pressure for controlling the outlet throttle direction reaches a maximum value in which it is complete dig is turned on.

This procedure ensures that the throttle device on the running side is completely open and thus generates a minimal pressure loss, whereby any pressure difference at the inlet throttle (directional valve) can set reference.

In an alternative method, the tax press ke for the outlet-side throttle device and the inlet side throttle device increased at the same time, the the former control pressure faster than the latter Control pressure is increased. This increase in the two Control pressures continue until the predetermined Has set pressure difference and the control pressure for the discharge-side throttle device fully open is so that this in turn with minimal pressure loss is flowed through.

In another alternative procedure, first of all both control pressures brought to their maximum value and then  the control pressure for the throttle device on the inlet side lowered until the predetermined control pressure difference on the directional control valve. This variant is also ge ensures that the outlet-side throttle device at Setting the control pressure difference completely open is.

Other advantageous developments of the invention are the subject of further subclaims.

Preferred embodiments of the Invention explained with reference to schematic drawings. Show it:

Figure 1 shows a known valve arrangement for controlling a consumer with a supply and a drain throttling.

Figure 2 shows a known valve arrangement for controlling a fan drive having a direction of rotation.

Fig. 3 shows a known valve arrangement for controlling a lifting device;

Fig. 4 is a greatly simplified schematic diagram of the valve assembly according to the invention;

Fig. 5 is a sectional view of a valve assembly according to the invention;

FIG. 6 shows a partial illustration of the valve arrangement from FIG. 5; FIG.

FIG. 7 shows a simplified hydraulic circuit diagram of the valve arrangement from FIG. 5;

Fig. 8 is a hydraulic circuit diagram of a second exporting approximate shape of the valve assembly according to the invention;

9 is a diagram for explaining the control of the valve assemblies of the invention according to a first method.

Fig. 10 is a diagram for explaining the control of the valve assemblies of the invention by a second process, and

Fig. 11 is a diagram for explaining the control of the valve assemblies of the invention according to a third method.

In Fig. 4, the logic of a valve assembly according to the invention for controlling a consumer 116 is Darge. At these two working lines are connected as inlet and outlet lines, in each of which a throttle device 6 for controlling the volume flow is arranged so that the volume flow of the hydraulic oil to and / or from the consumer is adjustable. In the case of a double-acting consumer, the two throttle devices 6 are controlled in such a way that the volume flow of the inlet line Q1 is equal to the volume flow in the outlet line Q2. The control takes place via control signals 1 , 2 , which are emitted by a control device, not shown. The independent inlet and outlet control according to the invention makes it possible, when connecting single-acting consumers, to open the throttle device 6 in the outlet line completely, so that the pressure loss in the outlet line and thus also heating of the hydraulic oil and wear of the components to a minimum is reduced.

In FIGS. 5 and 6, a concrete execution example is shown of such a valve assembly for controlling single and double acting consumers. Such a valve arrangement is described in the applicant's prior application 196 46 443.9, the disclosure of which is to be included in the content of the present application.

Fig. 5 shows a sectional view through a valve arrangement, which is designed in disc construction. The valve disc or plate forms a valve housing 2 , in which receiving holes for a continuously adjustable Wegeven valve 4 and two throttle devices 6 , 8 are formed.

The two throttle devices 6 , 8 are arranged along a common axis which runs parallel to the axis of the directional control valve 4 .

In the valve housing 2 are further two pilot valves 10 , 12 screwed in cartridge design, via which the directional control valve 4 and the two throttle devices 6 , 8 can be controlled. These pilot valves 10 , 12 are, for example, electrically operable Druckmin derventile, via which the pressure at a pump connection P, which is guided via a pump channel 14 to radial connections 16 of the pilot valves 10 , 12 , to a system pressure at the axial outlet connection 18 of the respective Pilot valve 10 , 12 is reducible. Each pilot valve 10 , 12 still has a radial connection 19 , which opens into a tank channel 20 , via which excess hydraulic fluid can be returned to a tank connection T.

The output port 18 of each pilot valve 10 , 12 mün det in a control channel 22 and 24 , respectively, in a valve bore 26 , in which a valve spool 28 of the directional valve 4 is guided. The two control channels 22 , 24 mün on both sides of the valve spool end faces, so that these are acted upon with the pressure in the respective control channel 22 , 24 , ie with the output pressure of the pilot valve 10 or 12 .

The valve slide 28 is further biased by two acting on the end faces compression springs 30 , 32 in its Darge zero position. The valve springs are supported on the inner bore of caps 34, which are screwed into the valve housing 2, and thus the axial close the valve hole 26 form. The other end of the compression springs 32 , 34 is in each case on a spring plate 36 , which is supported in the illustrated zero position with a circumferential section on a housing shoulder.

The detailed structure of the directional control valve 4 and a throttle device 6 will be described below with reference to FIG. 6 illustrates that shows these components in an enlarged view.

In the left in Fig. 6 end portion of the valve slide 28 a blind hole-shaped inner bore 38 is introduced, in which a pressure compensator piston 40 is axially displaceably guided. . In the embodiment shown in Figure 6 is zero setting of the pressure compensator piston 40 is located - referred to below as piston 40 - with a radial collar 42 at a bearing shoulder 46 of the in nenbohrung 38 at. The piston 40 is biased in the direction of this contact position by a control spring 44 . The control erfeder 44 is in turn supported on an end screw 46 , which is screwed into the annular jacket of the valve slide 28 and which together with the annular jacket end face forms the contact surface for the spring plate 36 (left in Fig. 6). The piston 40 has a connecting bore with an axial blind bore and a Radialdrosselboh tion, which opens on the outer circumference of the piston 40 .

In the region of the radial collar 42 , a compensating bore 52 is formed in the annular casing of the valve slide 28 , which opens into a control annulus 54 , which is connected via a line indicated by dashed lines to a control connection LS, so that a control pressure corresponding to the load pressure can be applied in the spring chamber.

In the central region of the valve slide 28 , an output bore star 56 is formed, to which two annular spaces 58 and 60 are assigned, which are connected to connecting channels 62 and 64 , respectively. These connection channels 62 , 64 lead to input connections of the throttle devices 6 and 8 ge. The annular spaces 58 , 60 are hen with chamfering 66 verses, the fine control of the output bore star 56 made possible with an axial displacement of the valve spool 28 . The axial length of the piston 40 is selected so that in the zero position (Fig. 6) of the outlet bore star 56 is sen by the right end portion of the piston 40 verschlos. The radial throttle bore 50 is then closed by the inner circumferential wall of the inner bore 38 .

In the area of the inner end portion of the inner bore 38 opens an input bore star 68, which is closed in the neutral position by a web 70 formed between the pump channel 14 and a pump branch channel is a ausgebil det fourteenth The two pump channels 14 , 14 a extend approximately in the radial direction to the valve bore 26 . The inner bore 38 is in turn provided with chamfers 66 for fine control in the area of the web 70 .

Through the input bore star 68 and the pump channels 14 , 14 a with the corresponding annular spaces, a ver adjustable measuring orifice is formed, while a measuring throttle is formed through the piston 40 and the output bore star 56 , via which the system pressure downstream of the measuring orifice to the load pressure in the Connection channels 62 and 64 is throttled. By connecting the measuring orifice and the measuring throttle in series, it is ensured that the pressure drop across the measuring orifice (input bore star 68 ) remains constant regardless of the pressure in the connecting channels 62 , 64 .

As already mentioned at the beginning, the spring spaces of the compression springs 30 , 32 are connected to the control channels 22 and 24, respectively, so that the control pressure prevails at the end faces.

The two throttle devices 6 , 8 have an identical structure, so that, for the sake of simplicity, only the throttle device 6 shown in FIG. 6 is described. This has a main cone 72 , which is pressed via a return spring 74 with a conical section against egg nen valve seat 76 , so that in this closed position, the connection from the connecting channel 62 to a working channel 78 is interrupted.

In the exemplary embodiment shown, the main cone 72 is formed with a pre-opening 80 which is closed with a ball 82 which is pressed against a pre-opening seat by means of the return spring 74 and a spring plate. In the spring chamber of the check spring 74 opens a throttle bore 84 , which in turn mün det in the working channel 78 . A hub-shaped projection 86 is formed on the right-hand end section in FIG. 6, on the outer circumference of which an annular groove 88 is provided. The inner bore of the hub-shaped projection 86 tapers towards the pre-opening 80 .

The annular end face 90 of the projection 86 serves as a contact surface for an push piston 92 which is guided coaxially to the main cone 72 in a receiving bore 94 . At its end portion adjacent to the main cone 72 , the pushing piston 92 has a plunger 96 which plunges into the inner bore of the hub-shaped projection 86 and whose end section has a smaller diameter than the pre-opening 80 , so that the plunger 96 can also dip into this pre-opening 80 . The push piston 92 is biased by a spring 98 against the end face of an annular space 100 of the receiving bore 94 . In this stop position, there is a predetermined gap between the ring end face 90 and the adjacent end face of the pushing piston 92 , which gap is greater than the distance between the end section of the plunger 96 and the outer circumference of the ball 82 .

On the outer circumference of the push piston 92 are in the region of a opening in the receiving bore 94 tank channel 102 a plurality of recesses 104 distributed over the circumference from ge, via which the axial displacement of the push piston 92 of the tank channel 102 is ver with the working channel 62 , which is connected via a Annulus 109 in the receiving bore 94 opens.

In the plunger 92 , a relief bore is also formed, the axial section 108 opens into the - according to FIG. 6 - left end face and which opens via a radial section 110 between the annular space 106 of the tank channel 102 and the annular space 100 (basic position). The annular space 106 of the tank channel 102 is in turn provided with fine control phase 107 . The axial section 108 opens radially within the ring end face in the inner bore of the pre jump 86th

As can also be seen in FIG. 6, the left part of the main cone 72 is guided in the inner bore of a closure plug 112 which is screwed into the left end portion of the receiving bore for the check valve. The control channel 22 is from the left end of the Ven tilschiebers 28 to the area of the sealing plug 112 and from there - as indicated by dashed lines - extended to the annular space 100 , so that in this the valve pressure applied by the Pilotven 10 is adjustable, which the pushing piston 92 strikes against the force of the spring 98 .

As can be seen from Fig. 5, the tank channel 102 is guided to the annular space 106 of the (right) throttle device 8 and the annular space 100 is connected via the dashed Ka channel to the control channel 24 , so that the piston 92 of the throttle device 8 through the the pilot valve 12 is applied to the applied control pressure in the direction of the main cone 72 , while the pushing piston 92 of the throttle device 6 is controlled by the pilot valve 10 .

When the main cone 72 of the throttle device 8 is lifted off, a connection to a working channel 114 is opened which leads to a working connection B of the valve arrangement. The working channel 78 of the throttle device 6 is guided to a working connection A. The two connections A, B can be connected to a consumer, for example to the cylinder space or the annular space of a lifting cylinder 116 . The connection can be made, for example, via hose couplings.

Between the tank channel 102 and the working channel 114 , a connecting channel is provided, into which a conventional check valve 118 is connected, which allows a flow from the tank channel 102 to the working channel 114 in the event of excessive pressure build-up in the tank T, but prevents a reverse flow.

The function of the valve arrangement shown in FIGS . 5 to 6 will be briefly explained below.

To extend the lifting cylinder 116 , the cylinder chamber must be supplied with hydraulic fluid via the working port A. For this purpose the pilot valves 10 and 12 are energized, so that a control pressure difference is established whose Resul animal end to the valve spool works in Fig. 5 right-hand end face 28 so that the valve spool shifted 28 against the bias of the compression spring 30 to the left and the entrance bore star 68 opened and hydraulic fluid can enter the inner bore 38 from the pump channel 14 . The control pressure applied via the pilot valve 10 is so low, for example, that the throttle device 6 remains in its non-return position. The piston 40 is lifted from its stop position by the pump pressure, so that the output bore star 56 is opened against the force of the control spring 44 and the load pressure until an equilibrium is established between the piston spring side and the front side (on the right in FIG. 5). The hydraulic likfluid can now enter from the inner bore 38 through the controlled output bore star 56 into the connec tion channel 62 so that the main cone 72 in opening direction - ie against the force of the return spring 74 - be opened. With sufficient pump pressure - or more precisely, outlet pressure at the pressure compensator - the main cone 72 is lifted off its valve seat, so that the hydraulic fluid can flow through the working channel 78 to port A and from there into the cylinder space of the lifting cylinder 116 .

Due to the pressure build-up in the cylinder chamber, hydraulic fluid is displaced from the annular space of the lifting cylinder 116 , which is guided to the throttle device 8 via the connection B and the working channel 114 .

The control pressure which arises when the pilot valve 12 is energized also exists in the annular space 100 and thus on the rear side of the push-open piston 92 , so that it is moved to the right against the force of the spring 98 ( FIG. 6) in the illustration according to FIG. 5. After a predetermined stroke ge reaches the plunger 96 of the push piston 92 in contact with the ball 82 so that it is lifted against the bias of the return spring 74 from its seat. The main cone 72 is still in place. By the Axialbewe supply of the push piston 92 , the radial portion 110 of the compensating bore is opened by the control edge of the annular space 106 , so that the tank pressure prevails in the compensating bore and in the bore of the projection 86 .

Since the throttle bore 84 has a much smaller diameter than the pre-opening 80 , the pressure in the spring chamber of the non-return spring 74 decreases, since the small throttle bore 84 cannot allow hydraulic fluid to flow out of the working channel 114 quickly enough. This relieves the spring side of the main cone 72 . Due to the effect of the control pressure, the pushing piston 92 is moved with its ball 82 opened into its stop position against the jump of the main cone 72 , so that the latter is carried by the pushing piston 92 and is lifted off its valve seat. In this stop position, the end face of the push piston 92 and the annular end face 90 of the main cone 72 are sealingly against one another, so that the inner bore of the projection 86 is sealed off from the outer circumference. By axial displacement of the poppet piston 92 and the adjacent thereto main poppet 72 of the working channel 114 is connected via the annular groove 88 with the annular space 109, which is in turn connected via the recesses 104 with the tank passage 102, the latter compound by the Ausneh rules is turned on 104th The hydraulic fluid can now flow back from the working channel 114 into the tank channel 102 and thus back to the tank connection T.

The extension of the lifting cylinder 116 is ended by switching off the pilot valve 12 so that both main cones 72 of the throttle device 6 , 8 are moved back into their closed position and the hydraulic fluid is clamped between the throttle devices 6 , 8 and the lifting cylinder 116 without leakage oil.

FIG. 7 shows the basic diagram of the valve construction according to FIGS. 5 and 6, the individual valve elements (throttle devices 6 , directional valve 4 ) being shown as greatly simplified symbols which can be carried out in a much more varied manner.

The directional control valve 4 is designed with two output connections A, B and a pump connection P, to which a hydraulic pump 124 is connected. At the two working connections A, B leading to the consumer 116 lines 120 and 122 are connected, in each of which one of the identically constructed throttle devices 6 are arranged. As indicated in Fig. 7, a check valve is realized by each of the throttle devices 6 , which has an additional metering edge for adjusting the hydraulic oil volume flow. In the specific embodiment shown in FIGS . 5 and 6, the check valve is practically formed by the main cone 72 and the metering edge by cooperation of the push piston 92 with the main cone 72nd The mechanical coupling of the piston 92 on the main cone 72 is indicated schematically in Fig. 7.

A control signal can be applied to the left control side of the directional valve 4 designed as a proportional valve in FIG. 7, which can also be applied to the control side of the throttle device 6 biased by the return spring 74 in its return position. Accordingly, a second Steueri signal is applied to the other control side of the directional control valve 4 , which is also guided to the control side of the outlet-side throttle device 6 . The control signals can be pilot pressures p1, p2, for example. Of course, electrical signals can also be used instead of control pressures.

When a pressure difference p2-p1 is applied, the valve spool of the directional control valve 4 is brought from the (0) marked middle blocking position into one of the (b) flow positions in which the connections P and A are connected to one another. The control pressure p1 is selected so that the throttle device 6 remains in the check position shown in FIG. 7. Due to the higher signal pressure p2, the throttle device 6 is brought in the work line 122 (outlet side) from the check position into the throttle position, in which the volume flow can be throttled by the additional metering edge. In the case of single-acting consumers 116 , for example, control of the volume flow in the drain line working line 122 is not necessary, so that the control pressure p2 is selected such that the outlet-side throttle device 6 is brought into a flow position with a maximum opening cross section, and thus, according to the inventive method the pressure drops in the drain line 122 are reduced to a minimum.

The method for controlling the invention Valve arrangement is explained in more detail below.

In Fig. 8, the valve logic of a further exemplary embodiment of a valve arrangement according to the invention is shown. This valve arrangement differs from the valve arrangement shown in FIG. 7 only in the basic structure of the throttle devices 6 . In the embodiment shown in FIG. 7, each throttle device 6 was formed by a check valve arrangement and egg ne the additional metering edge realizing valve arrangement, which were mechanically coupled to one another. In the embodiment shown in Fig. 8, the throttle device 6 is realized by a continuously adjustable We geventil, which acts in a (f) marked end position as a check valve that prevents backflow from the consumer to the directional control valve 4 . In the flow position marked with (e), the hydraulic oil volume flow is throttled in the work lines 120 and 122 and in the end position labeled (d) the valve slide of the throttle device 6 is in a position in which the opening cross section assumes a maximum value, so that the hydraulic oil can flow back with minimal energy losses from the consumer 116 to the tank T. The other components of the valve arrangement shown in FIG. 8 correspond to the construction shown in FIG. 7, so that a description of the further components can be dispensed with. The two Drosselein devices 6 are biased by the return spring 74 in their return position. As soon as a force is applied by the control pressure p1, p2 to the control side of the throttle device 6 , which exceeds the return spring force, the valve spool of the throttle device 6 is brought into its flow positions marked with (d) and (e), which provide a backflow from the consumer Allow 116 to tank T.

Based on the following figures, several are now Method for controlling the valve arrangement described above explained.

Fig. 9 shows a diagram in which the inlet and outlet volume flows QA and QB as well as the control pressures p1, p2 applied to the control side of the directional valve 4 and to the throttle devices 6 are shown as a function of time t. Since the volume flows QA and QB are the same, they are summarized with Q in the diagram according to FIG. 9 for the sake of simplicity. According to the control method shown in FIG. 9, the control pressure p2 for the outlet-side throttle device 6 in the work line 122 is initially increased continuously within a time interval (t ₁ -t ₀ ). By the applied signal pressure p2, the valve spool of the directional control valve 4 is brought into one of the flow positions marked with (b), in which the pump connection P is connected to the working connection A, so that hydraulic oil is led through the working line 120 to the inlet-side throttle device 6 . Since the signal pressure p1 is still zero in this time interval, the throttle device 6 remains in its non-return position. Through the applied signal pressure p2, the bias voltage of the return spring 74 of the discharge line throttle device 6 arranged in the working line 122 is overcome so that it is brought into one of its flow positions, in which the flow volume flow is throttled.

Accordingly, the hydraulic oil volume flow Q and the pressure loss Δp _B at the outlet-side throttle device 6 increase, this increase taking place only after a time t * in which the control pressure p2 has reached a value at which the force of the biasing spring of the directional valve 4 can be wound to move the directional spool valve.

After the time t ₁ , the control pressure p2 is initially kept at a constant level, so that a desired volume flow Q is established. Correspondingly, there is no further increase in pressure loss Δp _B in the time interval t ₂ -t ₁ . After setting a constant volume flow Q, both control pressures p2 and p1 are then increased with an identical pressure gradient, so that the control pressure difference (p2-p1) remains unchanged. This increase in the control pressures takes place until the control pressure p2 for the throttle device 6 on the _{outlet side} has reached a maximum value (p _2max ). At this control pressure, the opening cross section of the throttle device 6 ( Figure 7 or Figure 8) is maximum, so that the pressure drop Apo drops to a minimum value accordingly. This minimum value of the pressure drop ApB is reached after a time t ₃ , from which the two control pressures p2 and p1 are kept at a constant level.

Ie, after the time t ₃ is applied by applying the pressure difference p2-p1, the volume flow Q via the Wegeven valve 4 to the desired value, the inlet side throttle device 6 is in the non-return position, which is a backflow of the hydraulic oil from the consumer 116 to the directional control valve 4 is prevented and the outlet-side throttle device 6 is fully opened, so that the pressure loss Δp _{B is} reduced to a minimum value. It should be ensured, however, that the signal pressure p1 for the inlet-side throttle device 6 is set to a value such that the force acting on the control side is smaller than that of the return spring 74 , so that the inlet-side throttle device 6 remains in its return position.

The control method shown in Fig. 9 is suitable for al le above-described design variants.

In the variants shown in FIGS. 5 to 7, in which the throttle devices have a check valve arrangement and an additional, structurally separate Do sierkante 92 , which are realized for example by the main cone 62 and the push piston 92 , it can happen that at Exceeding a signal pressure p1 the metering edge of the inlet-side throttle device 6 opens the connection to the tank T, so that a "short circuit" takes place in which both the working port A of the Wegeven valve and the consumer are connected to the tank T. Such a short circuit is excluded by the control method shown in Fig. 9, since there the signal pressure for the outlet-side throttle device is first increased to a high value before the control pressure p1 for the inlet-side throttle device increases.

In the following figures, control methods are Darge, in which such a short circuit can not be excluded, so that these control methods are particularly suitable for valve arrangements that show the structure shown in Fig. 8.

Referring to FIG. 10, both control pressures to be increased at the same time and with different pressure gradients p2 and p1, so that the control pressure p2 increases steeply for the drain-side throttle device 6 in the second alternate control method. When a control pressure difference is reached, the force of the compression spring 30 of the directional control valve 4 is overcome, so that it is brought into one of the flow positions b accordingly, so that the hydraulic oil volume flow then increases accordingly. The Steuerdruckgra served are chosen such that the control pressure p2 reaches a maximum value when the predetermined control pressure difference (p2-p1) is set, which is required to set the desired volume flow Q. That is, the pressure gradients in the method shown in FIG. 10 are preferably selected so that the control pressure for the inlet-side throttle device 6 and the control pressure p2 for the outlet-side throttle device 6 always reach a maximum value, so that the outlet throttle is set to a maximum flow cross section is. After setting the maximum control pressure p2 and the desired control pressure difference (p2-p1), both control pressures p1, p2 are kept at a constant level, so that the volume flow Q remains constant at the predetermined value.

In Fig. 11, a third alternative is shown to the invention of an OF INVENTION control method. Accordingly, both control pressures p1 and p2 are set to a maximum value at the start of the control, so that the same control pressures are applied to both control sides of the directional control valve 4 - accordingly, the control pressure difference at the start of the control is zero. By this measure, the directional valve 4 remains in its locked position (0) and both the inlet-side and the outlet-side throttle device 6 are brought into a position in which there is a maximum opening cross-section. After a time t ₀ , the control pressure p1 for the inlet-side throttle device 6 is lowered and the control pressure p2 set to the maximum value is maintained. The control pressure p1 is reduced until the desired control pressure difference p2-p1 is set. By lowering the control pressure p1, a control pressure difference is reached after a time t ₁ , which is sufficient to overcome the force of the compression spring 30 of the directional control valve 4 , so that the ses is brought into its flow positions marked with (b) and the volume flow Q increases to consumer 116 . Simultaneously, pressure through the descending control p1 of the opening cross section of the inlet-side throttle device controlled closed 6, so that, after reaching which can be brought against certain control pressure difference, the throttle device 6 by the force of the check spring 74 in its return position. After reaching the predetermined control pressure difference (p2-p1), both control pressures p1, p2 are kept constant, so that the hydraulic oil flow Q remains at a constant level.

All of the above-described methods have in common that the outlet-side throttle device is opened so far after setting the predetermined control pressure difference that the pressure losses in the backflow of the hydraulic oil from the consumer via the throttle device 6 to the tank T are reduced. By this measure, the use of additional devices, such as unpressurized tank returns, can be dispensed with, so that the structural design of the hydraulic system is minimal compared to conventional solutions.

Another advantage is that the invention according valve arrangement can be used very flexibly, because at minimal energy loss, for example, motors with a and two directions of rotation can be controlled.

The invention can be used particularly advantageously in commercial vehicles, such as agricultural tractors, the following applications being possible:

• - Sequence control for pulling loads;  
• - Stroke of a single-acting cylinder without sequence control tion of the unloaded cylinder side
• - Motor operation with clockwise rotation and
• - Motor operation with left direction of rotation,

the inlet volume flow and the opening of the Ab throttle by suitable control elements by the operator are adjustable.

For setting the direction of action and for predetermination of the volume flow (quantity) could, for example, be separate Control elements such as a switch and potentio meters, or both functions could also be selected in a single lever element, such as a joystick be summarized. The desired mode for the process control can be done, for example, using switches (single or Multi-position switch) or via a suitable menu Set control on a display so that the operator the desired inlet and outlet taxes in a simple manner can adjust.

A valve arrangement for controlling egg is disclosed consumer and a method for controlling the Ven valve arrangement in which an inlet throttle device and a drain throttle device independently are controllable. For single-acting consumers, the Drain throttle device controlled so that at Er range of the desired hydraulic oil volume flow of the opening voltage cross section of the flow restrictor is maximum, so that the Reduce energy losses in the drain line to a minimum are adorned.

Claims (11)

1. Valve arrangement for controlling a consumer, with a continuously adjustable directional control valve ( 4 ) acting as an inlet throttle, via which a pump connection with consumer connections (A, B) can be connected, the consumer ( 116 ) via working lines ( 120 , 122 ) the directional valve ( 8 ) is connected and a throttle device ( 6 ) is arranged in each working line ( 120 , 122 ), via which the discharge volume flow of the hydraulic oil from the consumer ( 116 ) can be adjusted, characterized in that each throttle device ( 6 ) is independent of a Ven tilschieberstellung the directional valve ( 4 ) is fully controllable. 2. Valve arrangement according to claim 1, characterized in that the throttle device ( 6 ) in a switching position in which it acts as a check valve and can be brought into further positions with variable flow. 3. Valve arrangement according to claim 2, characterized in that a control side of the throttle device ( 6 ) and a control side of the directional control valve ( 4 ) with the same chen control signal (p1, p2) can be acted upon. 4. Valve arrangement according to one of the preceding claims, characterized in that the Drosseleinrich device ( 6 ) a hydraulic oil flow towards the consumer ( 116 ) and against a valve seat biased main cone ( 72 ) and a push piston ( 92 ) which by means of Control pressure (p2) can be brought into a system position on the main plug ( 72 ) in order to effect the flow restriction. 5. Valve arrangement according to one of claims 1 to 3, characterized in that the throttle device ( 6 ) is designed as a throttle directional control valve with a check position (f) and a plurality of continuously adjustable flow positions (d, e). 6. Valve arrangement according to one of the preceding claims, characterized in that the directional valve ( 4 ) is a continuously adjustable 3-way valve, with a blocking position (0) and inlet positions (a, b), in which the pump connection (P) with a the two work lines ( 120 , 122 ) is connected. 7. Method for controlling a valve arrangement, in particular for controlling a valve arrangement according to one of the preceding claims, with a directional control valve ( 4 ) acting as an inlet throttle, via which a pump line is connected to a working line ( 120 ) of a consumer ( 116 ), and with throttling devices ( 6 ) with a check valve and a metering control edge in the working lines ( 120 , 122 ) for throttling the flow volume flow from the consumer, with the steps:

• a) Setting the inlet volume flow to the consumer ( 116 ) by controlling the directional valve ( 4 ) and
• b) complete control of the outlet-side throttle device ( 6 ), wherein
  Step a) can be carried out before or after step b).

8. The method according to claim 7 with the steps:

• - Applying a control pressure difference (p1-p2) to the tax sides of the directional control valve ( 4 ) and
• - Applying the control pressures (p1, p2) forming the control pressure difference (p1-p2) to the control side of the outflow or inflow-side throttle device ( 6 ),
  the control pressures (p1, p2) being selected such that the throttle device ( 6 ) arranged in the inlet-side working line ( 120 ) is brought into the non-return position and the outlet-side throttle device ( 6 ) is brought into the position with the maximum opening cross section.

9. The method according to claim 8 with the steps:

• - Increase the control pressure (p2) for the outlet-side throttle device ( 6 ) while the control pressure (p1) remains the same for the inlet-side throttle device ( 6 ) until the predetermined control pressure difference (p2-p1) is set on the directional control valve ( 4 ),
• - Increase both control pressures (p1, p2) while maintaining the control pressure difference (p2-p1) until the outlet-side throttle device ( 6 ) is completely open.

10. The method according to claim 8 with the steps:

• - Increase the control pressure (p2) for the outlet-side throttle device ( 6 ) with a greater pressure gradient than that for the inlet-side throttle device ( 6 ) until the control pressure difference (p2-p1) is established and the outlet-side throttle device ( 6 ) is fully controlled.

11. The method according to claim 8 with the steps:

• - Setting a maximum control pressure (p1, p2) so that both throttle devices ( 6 ) are fully opened,
• - Lowering the control pressure (p1) for the inlet-side throttle device ( 6 ) and maintaining the other control erdruck (p2) until the predetermined Steuerdruckdif reference (p2-p1) on the directional control valve ( 4 ).