EP1664551B1 - Control system and method for supplying pressure means to at least two hydraulic consumers - Google Patents

Abstract

Disclosed are a control arrangement and a method for the pressure medium supply of at least two hydraulic consumers that are supplied with pressure medium through the intermediary of a variable displacement pump. In the pressure medium flow path between the consumers and the variable displacement pump a respective meter-in orifice is provided. An adjustment of the variable displacement pump and of the meter-in orifices takes place electronically through the intermediary of a control means in dependence on the target values input by an operator. In accordance with the invention, the meter-in orifice associated with the consumer having the highest load pressure is controlled to open completely, so that the pressure loss across this meter-in orifice is minimum.

Description

The invention relates to a control arrangement for pressure medium supply of at least two hydraulic consumers according to the preamble of claim 1 and a method for controlling such consumer according to the preamble of claim. 6

To control several consumers hydraulic systems are used, in which the consumers are supplied via a pump with adjustable delivery volume (variable displacement) with pressure medium. Between the variable and each consumer often a metering orifice and a pressure compensator is provided, the latter may be upstream or downstream of the metering orifice. One distinguishes between LS systems operating according to the current controller principle and systems operating according to the current divider principle in which the pressure compensator of the metering orifice is always connected downstream. These current divider systems are also referred to as LUDV systems, which represent a subgroup of the LS systems. In LS systems, the variable displacement pump is adjusted depending on the highest load pressure of the actuated hydraulic consumers so that the inlet pressure is above the highest load pressure by a certain pressure difference.

In LUDV systems, the downstream pressure compensators in the opening direction of the pressure to the respective metering orifice and in the closing direction of a control pressure, which usually corresponds to the highest load pressure of all driven consumers acted upon. If the metering orifices are opened so far in a simultaneous actuation of several hydraulic consumers, that the pressure medium supplied by the hydraulic pump to the stop is smaller than the total required pressure medium, the pressure fluid quantities flowing to the individual hydraulic consumers will be independent of the respective load pressure of the hydraulic consumers reduced (load-independent flow distribution).

In systems operating according to the current regulator principle, the pressure compensator upstream or downstream of the metering orifice is acted upon in the closing direction by the pressure before the metering orifice and in the opening direction by the individual load pressure of the respective hydraulic consumer, so that no load-independent flow distribution is obtained. With simultaneous actuation of several hydraulic consumers and not enough of the variable displacement pressure fluid supplied only the pressure of the highest-pressure consumer flowing pressure medium quantity is reduced.

Such a control arrangement is for example in the EP 0 972 138 B1 disclosed, wherein the pressure compensators are connected upstream of the metering orifices. In the DE 100 27 382 A1 an LS control arrangement is shown, in which the pressure compensators are connected downstream of the metering orifices.

In all LS / LUDV systems described above, the variable displacement pump is actuated depending on the highest load pressure picked up via an LS line such that a pressure is established in the pump line which is equivalent to the force of a control spring of a pump control valve pressure difference above the highest load pressure lies. In the journal O + P "Oil hydraulics and pneumatics" 38 (1994), No. 8, pages 473ff is a so-called Electrohydraulic LS system described in which the control of the pump setting is carried out electronically. Among other things, the effective at the consumers pressures, the pump pressure, the drive speed and the drive torque of the variable is detected and issued depending on eg. Via a joystick predetermined setpoints control signals to the pump control valve and the consumers upstream proportional valves. In this known electrohydraulic system, the function of the individual pressure compensators assigned to the metering orifices is implemented electronically.

Also in this solution, the pump pressure is adjusted so that it is above the highest load pressure by a predetermined pressure difference, so that in this type of control corresponding system losses occur.

In the EP 0 275 969 B1 an electro-hydraulic LS control arrangement is shown, in which the individual pressure compensators are connected upstream of the metering orifices. In this known method, the set values for the metering orifices set via actuators, for example joysticks, are detected and from this a total volume flow is determined. The adjustment of the variable displacement pump then takes place in such a way that a slight undersupply occurs, so that the metering orifice of the load-pressure-highest consumer is opened and thus the abovementioned pressure difference between the pump pressure and the highest load pressure is reduced. However, this undersupply reduces the operating speed of the consumers.

From the DE 35 46 336 C2 and the DE 36 44 736 A1 Electro-hydraulic LS systems are known in which the Total volumetric flow either from the deflections of the directional control valves forming the metering or from the settings of the setpoint generator (joysticks) determined and this sum volume flow is compared with a maximum flow rate of the pump. In the case in which more flow is requested, the stroke of all controlled directional control valves is electrically reduced so far that the respective flow rates are proportionally reduced and thus the set trajectory of the driven consumers is maintained at a reduced adjustment speed.

Even with these solutions occurs at the metering orifice of the most heavily loaded consumer, a pressure drop, which corresponds to the difference between the pump pressure and the individual load pressure.

The document EP 0 587 902 A1 , which represents the closest prior art, relates to a control arrangement in which the maximum load pressure is used to drive the pump. The valve associated with the maximum load pressure hydraulic cylinder is maximally opened to minimize pressure loss across this valve.

In contrast, the invention has the object, a control arrangement and a method for pressure medium supply of at least two hydraulic consumers in such a way that a control of multiple consumers with a predetermined speed with reduced energy losses is possible.

This object is achieved with regard to the control arrangement by the features of claim 1 and in terms of the method by the features of claim 4.

According to the invention, the individual load pressures of the consumers are detected via suitable sensors and the load-pressure-highest consumers are determined from these signals. The metering orifice associated with the load-pressure-highest consumer is completely opened by the setting resulting from the predetermined setpoint, so that the pressure loss exceeds that which is the highest in the load associated metering orifice is minimal. With sufficiently accurate coordination between the pressure medium volume flows through the metering orifices and the delivery rate specified by the nominal values, only a minimal pressure difference is produced at the metering orifice of the highest-load consumer. In the case in which this metering orifice is associated with an individual pressure compensator, this is also completely controlled, as well as a small excess of the funded by the pump pressure medium flow at the fully open metering orifice can not produce a pressure drop, the pressure compensator against the force of one of these associated control spring could adjust in the closing direction.

The control arrangement according to the invention or the method according to the invention can be used in control arrangements in which the individual pressure compensators are arranged upstream or downstream of the metering orifices.

In the case in which the control arrangement is designed with a further sensor for detecting the system pressure, ie the pressure upstream of the metering orifices, the pressure difference across the respective metering orifices can be determined via the signals detected by the pressure sensors. About the electronics of the control arrangement, the metering orifices are then adjusted so that the desired pressure medium flow rate flows to the consumers. That is, in such a variant, the function of the individual pressure compensators is realized electronically, but in contrast to the aforementioned document (O + P), the metering orifice of the load pressure highest consumer is always completely turned on, so that the energy losses compared to the known solution are reduced.

As an alternative to the above-described solution, in which the function of the individual pressure compensators is met by software, the control arrangement according to the invention with the metering orifices upstream or downstream individual pressure compensators is executed, which are acted upon in the closing direction of the pressure upstream of the metering orifice and in the opening direction of the pressure downstream of the metering orifice.

In the variant in which the pressure compensators are arranged downstream of the metering orifices, there is a structure which is similar to that of LUDV directional control valves. This makes it possible to provide identical or at least similar housings as semi-finished products for the control arrangement according to the invention and LUDV control arrangements, so that the production costs can be reduced.

In the case of a pulling load, this can be detected by the sensors used according to the invention and the variable displacement pump can be reset and the pressure medium can be sucked into the low pressure side of the consumers via suction valves.

In the method according to the invention, in the case of an undersupply, the flow rates of the metering orifices associated with the lower-load consumers can be reduced proportionally. This reduction is preferably in the ratio of the maximum pump delivery to the desired target amount.

In one embodiment of the method according to the invention, the load pressures simultaneously actuated consumers are compared and in the case in which these load pressures differ by less than the rule Δp of the pressure compensator, the metering orifice of the load pressure lower consumer further opened than that of Setpoint is specified, so that this pressure difference is compensated.

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

• Figur 1 eine erfindungsgemäße Steueranordnung mit den Zumessblenden nachgeschalteten Individualdruckwaagen;
• Figur 2 eine Variante der Steueranordnung aus Figur 1 mit vorgeschalteter Individualdruckwaage;
• Figur 3 eine Steueranordnung, bei der die Funktion der Individualdruckwaagen elektronisch realisiert ist und
• Figur 4 eine Steueranordnung mit den Zumessblenden nachgeschalteten Individualdruckwaagen.

In the following preferred embodiments of the invention will be explained in more detail with reference to schematic drawings. Show it:

• FIG. 1 an inventive control arrangement with the Zumessblenden downstream individual pressure compensators;
• FIG. 2 a variant of the control arrangement FIG. 1 with upstream individual pressure scale;
• FIG. 3 a control arrangement in which the function of the individual pressure compensators is realized electronically and
• FIG. 4 a control arrangement with the Zumessblenden downstream individual pressure compensators.

In the FIG. 1 illustrated control arrangement 1 operates on the current regulator principle, in which a plurality of current regulator are connected in parallel. The illustrated control arrangement 1 has a variable displacement pump 2, via which two or more consumers 4, 6 can be supplied with pressure medium. Their control is carried out by means of a control device, such as a joystick 8, are discharged via the control signals to an electronic control device 10. These signals represent a command to move the loads at a certain speed and along a given trajectory.

The output of the variable displacement pump 2 is connected to a pump line 12, which in two supply lines 14, 16 branches. In each supply line 14, 16 an electronically proportionally adjustable metering orifice 18 and 20 is arranged, which are each adjustable via a proportional solenoid 22, which is controlled by the control device 10.

The metering orifices 18, 20 formed, for example, by a proportional valve are respectively followed by a pressure compensator 24 or 26, which is acted upon in the opening direction by the force of a control spring and by the pressure downstream of the metering orifices 18, 20 and in the closing direction by the pump or system pressure is tapped off from the pump line 12 via a branching control line 28.

The outputs of the pressure compensators 24, 26 are connected via flow lines 30 and 32 to the consumers 4, 6. In the present case, these consumers are 4, 6 hydraulic cylinders whose cylinder chambers are connected to the flow line 30 and 32, respectively. In the hydraulic diagram according to FIG. 1 For the sake of simplicity, the return and discharge lines connecting the cylinder chambers to the tank T are omitted, whose flow cross-sections are also opened or closed via the proportional valve forming the metering orifice 18, 20.

According to the invention, the load pressures of the consumers 4, 6 are detected and the setting of the metering orifices 18, 20 changed as a function of these load pressures. In the illustrated embodiment, these load pressures are detected by pressure sensors 34, 36, which are arranged in the flow lines 30, 32 and whose signals are processed by the control device 10. As shown in FIG. 1 are the pressure sensors 34, 36 and the joystick 8 via signal lines to the control device Control signals via signal lines to the electrically operated pump control valve as well as the two proportionally adjustable metering orifices 18, 20 are delivered via the then corresponding to the predetermined set values and the detected load pressures.

Instead of a variable displacement pump with variable tilt angle, for example, a constant displacement pump with variable speed drive can be used.

The variable displacement pump 2 is preferably designed with a pressure sensor for detecting the pump pressure, a speed sensor for detecting the pump speed and a swivel angle sensor for detecting the pump swivel angle. Furthermore, the characteristic curves of the variable displacement pump 2 and the two proportionally adjustable metering orifices 18, 20 are stored in the control device so that with the aid of all or some of the aforementioned sensors and characteristic curves an extremely exact volume flow control via the variable displacement pump 2 is possible. The function of the control arrangement according to the invention is as follows.

To actuate the two consumers 4, 6 8 control signals are generated by the operator via one or more joysticks, which are delivered to the control device 10. For the corresponding control of the consumers 4, 6, the variable displacement pump 2 must provide a certain pressure medium volume flow which corresponds to the sum of the setpoint volume flows set via the joystick 8. That is, the variable displacement pump 2 must be adjusted in dependence on the setting of the joystick 8 to a swivel angle at which this sum volume flow is delivered. The corresponding setting of the variable displacement pump 2 can be easily determined by detecting the current pump pressure as a function of the desired value. the current pump speed and the set swivel angle via the pump curve.

According to the pump controller thus receives no pressure signal, which usually corresponds to the highest load pressure, but the control of the variable displacement pump 2 takes place in dependence on the desired values. This eliminates the need to tap the load pressures over complex shuttle valve assemblies to the consumers and lead over comparatively long lines to the variable displacement pump 2.

Due to the setpoint adjustment via the joystick 8 volumetric flow errors due to volumetric losses of the variable displacement pump 2 can be compensated because the operator immediately readjusted via the joystick 8, if the consumers 4, 6 are not operated at the desired speed. The highest load pressure then adjusts accordingly to the most heavily loaded consumer and the pressure difference to the lower-load consumers is throttled away by current control of the individual pressure compensators 24, 26.

According to the invention, the consumer is determined via the pressure sensors 34, 36, to which the highest load pressure is applied. For this purpose, the signals detected by the pressure sensors 34, 36 are compared with each other in the control device 10 and delivered to the metering orifice 18, 20, which is assigned to the consumer 4, 6 with the highest load pressure, a control signal through which these metering orifice 18, 20 completely is opened. At this metering orifice 18, 20 then only a minimal pressure difference arises, so that the system losses are reduced compared to the regulations described above. The associated pressure compensator 24 and 26 of the load pressure highest consumer 4 and 6 is then also completely open, since the pressure difference across the associated metering orifice 18 and 22 is not sufficient to adjust the pressure compensator against the force of the control spring in the closing direction.

At the in FIG. 1 illustrated embodiment, the current regulator circuit with the metering orifices 18, 20 downstream pressure compensators 24, 26 executed. Since in the LUDV systems described above, the pressure compensators always have to be connected downstream of the metering orifices, for the in FIG. 1 shown system and used for LUDV systems identical or only slightly modified housing.

As in FIG. 2 indicated, the control arrangement according to the invention can also be realized in circuits in which the individual pressure compensators 24, 26 are connected upstream of the metering orifices 18 and 20 respectively. These pressure compensators are also acted upon in the opening direction by the pressure downstream of the metering orifices 18, 20 and in the closing direction by the pressure upstream of the metering orifices 18, 20, ie the pump pressure supplied by the variable displacement pump 2. The other structure and function of in FIG. 2 shown control arrangement correspond to the embodiment according to FIG. 1 , so that further explanations are dispensable.

In FIG. 3 a variant is shown in which the metering orifices 18, 20 are assigned no individual pressure compensators. In this embodiment, the function of the individual pressure compensators is practically taken over by the electronics. For this purpose, the pressure in the pump line 12, ie the pressure upstream of the metering orifices 18, 20 must be detected via a further pressure sensor 38. From this pressure and the pressure detected via the pressure sensors 34, 36, downstream of the metering orifices 18, 20 can then calculate the pressure drop across the metering orifices 18, 20. With knowledge of these pressure drops across the metering orifices 18, 20, the flow cross section of the respective metering orifices 18, 20 can then be adjusted via the control device 10 using the stored characteristic curves so that the desired volume flow flows to the consumers 4, 6. The setting of the variable displacement pump 2 takes place in the manner described above in dependence on the set values set via the joystick 8.

The above-described systems differ from the LS systems known hitherto in that the variable-displacement pump is set to the desired total flow and the individual pressure medium flows are distributed to the consumers by suitable control of the valve diaphragms, with the metering orifice associated with the load-pressure-highest consumer being completely opened.

Such a control makes it possible, for example in the case of an undersupply, ie in the case in which the desired amount is greater than the maximum pump quantity, to proportionally reduce the flow through the metering orifices of the load-pressure-reduced consumers. In other words, with the control arrangement according to the invention, a LUDV behavior can be generated practically by reducing the opening cross sections of the metering orifices 18, 20 having lower load pressure. This reduction can be done, for example, in the ratio of the maximum pump delivery rate to the target amount. This will be explained with reference to an example in which the control arrangement according to the invention is designed to control three consumers. It is further assumed that the set on joysticks 8 at the three consumers set currents 40, 60 and 20 liters / minute, ie, the target total volume flow is 120 liters / minute, the Lastdruckhöchste consumers should be supplied with 20 liters / minute. The maximum flow rate of the pump is for example 100 liters / minute - there is thus a shortage. This deficiency is compensated according to the invention in that the setpoint values for the two lower-load consumers (40, 60 liters / minute) are reduced via the control device 10 in the ratio of the maximum delivery rate of the pump to the total volume flow, ie in the ratio 100/120. That is, the first-mentioned consumer is supplied with 33.33 liters / minute, the second-named consumer with 50 liters / minute (per unit time). The metering orifice of the load pressure-highest consumer is fully controlled according to the invention - the adjusting volume flow over this metering orifice is 16.66 liters / minute, so that the maximum flow rate of the pump of 100 L / minute divided proportionally and thus practically a load-independent flow distribution (LUDV) is realized ,

In the case where a pulling load acts (for example downhill), this can be detected via the pressure sensors 34, 36 and the pump can be reset accordingly. The sucking in the low pressure side of the consumer 4, 6 then takes place via not shown Nachsaugventile from the high pressure side. That In comparison with conventional circuits today, the losses can be further reduced in the case of a pulling load.

In particular, the basis of the FIGS. 1 and 2 explained embodiments are characterized by a low susceptibility to vibration.

The setpoint values can be determined instead of via the electric joystick 8 also in the case of proportional valves with spool travel measurement from the spool travel actual value of the metering orifices 18, 20.

Of course, the system according to the invention is also effective when only a single consumer is driven - in this case, the metering orifice of this consumer is completely opened and controlled the pressure medium flow through the variable displacement pump 2.

FIG. 4 shows a control arrangement in which the individual load pressures of the consumers 4, 6 are not detected by pressure sensors or the like. It is again a flow control system, wherein the two individual pressure compensators 24, 26 are connected downstream of the two proportionally adjustable metering orifices 18, 20. That is, apart from the two non-existing sensors 34, 36 corresponds to in FIG. 4 shown control arrangement of those FIG. 1 , Also in the control arrangement according to FIG. 4 the variable displacement pump 2 is adjusted as a function of the set values set via the joystick 8 so that it delivers the desired total pressure medium flow. The division of this pressure medium total flow then takes place via the flow regulators (metering orifices 18, 20, pressure compensators 24, 26), the metering orifices 18, 20 in turn being adjusted as a function of the setpoint values set on the joystick 8. About the individual pressure compensators 24, 26 is then applied to the output of the metering orifices 18, 20 load pressure corresponding approximately to the highest effective load pressure of the consumer, throttled to the individual load pressures. In contrast to the above-described embodiment, however, the load pressure higher consumers associated metering orifice remains on depending on the given Setpoints set opening cross-section and is not fully open.

Disclosed are a control arrangement and a method for pressure medium supply of at least two hydraulic consumers, which are supplied via a variable displacement pump with pressure medium. In the pressure medium flow path between the consumers and the variable displacement each metering orifice is provided. The setting of the variable displacement pump and the metering orifices is carried out electronically via a control device as a function of the setpoint values entered by an operator. According to the invention, the metering orifice associated with the load-pressure-highest consumer is completely opened, so that the pressure loss across this metering orifice is minimal.

LIST OF REFERENCE NUMBERS

1

control arrangement

2

variable

4

consumer

6

consumer

8th

joystick

10

control device

12

pump line

14

supply line

16

supply line

18

metering orifice

20

metering orifice

22

proportional solenoid

24

pressure compensator

26

pressure compensator

28

control line

30

supply line

32

supply line

34

Pressure sensor (load pressure)

36

Pressure sensor (load pressure)

38

Pressure sensor (pump pressure)

Claims (7)

1. A control arrangement for the pressure medium supply of at least two hydraulic consumers (4, 6), comprising a variable displacement pump arrangement (2) which has a variable capacity, and comprising at least two adjustable meter-in orifices (18, 20) each associated with a respective one of the consumers (4, 6) and respectively adjustable in dependence on a target value set at a target value entry means (8) through the intermediary of a control means (10), and comprising a means (10) outputting a control signal to the variable displacement pump (2) in dependence on the set target values, comprising a sensor (34, 36) provided in the pressure medium flow path downstream from the meter-in orifice for detecting the individual load pressure, and comprising a means (10) for detecting the consumer (4, 6) having the highest load pressure based on the signals detected by the sensors (34, 36) and for controlling open the meter-in orifice (18, 20) associated with the consumer (4, 6) having the highest load pressure,
   characterized in that upstream or downstream from each meter-in orifice (18, 20) a pressure compensator (24, 26) is arranged which is subjected in the closing direction to the pressure upstream from the meter-in orifice (18, 20), and in the opening direction to the pressure downstream from the associated meter-in orifice (18, 20).
2. The control arrangement in accordance with claim 1, comprising an anti-cavitation valve for replenishing pressure medium on the low-pressure side of the consumers (4, 6).
3. The control arrangement in accordance with any one of claims 1 and 2, wherein the target value entry means is at least one joystick (8).
4. A method for actuating a control arrangement for the pressure medium supply of at least two hydraulic consumers, comprising a variable displacement pump (2) arrangement which has a variable capacity, and comprising at least two adjustable meter-in orifices (18, 20) each associated with a respective one of the consumers (4, 6) and respectively adjustable in dependence on a target value set at a target value entry means (8) through the intermediary of a control unit (10), and comprising a means (10) outputting a control signal to the variable displacement pump (2) in dependence on the set target values, wherein the individual load pressures of the consumers (4, 6) are detected, and the meter-in orifice (18, 20) associated with the consumer (4, 6) having the highest load pressure is controlled to open completely, characterized in that a pressure compensator (24, 26) arranged upstream or downstream from each meter-in orifice (18, 20) is subjected in the closing direction to the pressure upstream from the meter-in orifice (18, 20), and in the opening direction to the pressure downstream from the associated meter-in orifice (18, 20).
5. The method in accordance with claim 4, wherein in the case of an insufficient supply the cross-sections of flow of the meter-in orifices (18, 20) associated with the consumers (4, 6) having the lower load pressure are reduced, preferably at the ratio of the maximum pump capacity to the target cumulative flow rate.
6. The method in accordance with claim 4 or 5, wherein a pulling load is recognized by evaluating the signals detected by the sensors (34, 36), and the variable displacement pump (2) is regulated down accordingly.
7. The method in accordance with any one of claims 4 to 6, wherein in the case of a concurrent actuation of several consumers (4, 6), their load pressures are compared, and in the case of a differential load pressure being less than the control Δp of the pressure compensator, the meter-in orifice (18, 20) associated with the consumer (4, 6) having the lower load pressure is controlled to open to such a degree that this load pressure difference is compensated.

Images