DE102013206973A1 - control arrangement - Google Patents

Abstract

What is disclosed is a hydraulic control arrangement that is used to control and supply a hydraulic consumer - in particular a cylinder or motor. The control arrangement has an inlet line in which an inlet valve designed as a seat valve is arranged, and a return line in which a lowering brake valve is arranged. Its valve body is acted upon in the closing direction by a spring and in the opening direction by a control pressure tapped from the supply line. A speed that is higher than the speed specified by the inflow volume flow can thus be avoided in the case of loads pulling on the consumer. A main slide of the feed valve is set - at least in part - via an electrical output signal from a position controller. This is - preferably amplified via power electronics - transmitted to an electromagnetic actuator of the inlet valve. According to the invention, the output signal of the position controller can be changed via a damping controller or a control circuit with a damping controller in order to act actively on the inflow volume flow and thus dampen vibrations of the pressure in the inflow line or at the input of the consumer when pulling loads.

Description

The invention relates to a control arrangement according to the preamble of claim 1.

In the field of mobile working machines, such as hydraulic excavators, tractors, backhoe loaders or forklifts, three basic types of hydraulic control systems for the pressure medium supply of the working hydraulics have been established. These are so-called load-sensing systems with upstream individual pressure compensators (LS systems), load-sensing systems with downstream individual pressure compensators (LUDV systems (load pressure-independent flow distribution)) and throttle control in open-center circuits with constant or demand-adjusted volume flow supply through the Pump (OC systems). The individual control systems have a partly clearly different character in their control behavior and have also found their place in various mobile applications because of their different control behavior. LS systems are mainly offered in tractors, forklifts and combine harvesters, LUDV systems in hydraulic excavators in Europe and OC systems in hydraulic excavators in Asia. The control systems have the common feature that the opening and closing flow of a consumer defining opening cross-sections of volume flow measuring panels are changed together by a spool.

Frequently, the valves located in the inlet and in the return are designed as seat valves. The valve located in the inlet releases a proportional to an electrical control signal opening cross-section between a pump channel (in OC systems and LUDV systems) or an intermediate channel (LS systems) and the consumer channel (load channel) free, so that with appropriate training a Pressure difference over this opening cross section adjusts an inlet flow. In order to ensure the appropriate pressure difference across the opening cross section, the consumer pressure (load pressure) must be reported in a special load signaling channel (LS channel) - mainly for LS and LUDV valves. The reported load pressure is then forwarded, for example, to a flow regulator of the connected pump with adjustable delivery volume, which ensures the desired provision of the inflow volume flow.

In the EP 2 171 285 B1 a control assembly is shown in dissolved construction, in which both in the inlet and in the return a continuously adjustable orifice plate is arranged, each associated with a Senkbremsventil, which are thus effective depending on the direction of movement of the driven consumer. The lowering brake valves are designed with a non-return function, so that the supply of pressure medium to the consumer is possible. Each located in the return lowering brake valve is acted upon in the direction of a closed position by the force of a spring and in the opening direction of the pressure in the return. In addition, it is provided in this known solution to act on an effective in the opening direction control surface of the lowering brake valve with the pressure downstream of the then effective inlet orifice plate. With driven loads, the lowering brake valve opens completely and releases a large opening cross-section between the consumer and the return channel. When driving (pulling) loads, the lowering brake valve goes into a control position and sets a cross section so that the corresponding set return flow is limited in the form that the pressure on the inlet side not over a certain, given in the broadest sense of the spring biasing force of the lowering brake valve Pressure can drop. In this way cavitations can be reliably prevented when the load is pulled.

Such control arrangements with so-called lowering brake valves in the return thus have a feedback of the inlet pressure of the consumer (in many cases a hydraulic cylinder or a hydraulic motor) on the return flow and thus also on the pressure build-up in the return. With unfavorable tuning of the system parameters such control arrangements tend to an unstable operating behavior, which can lead to strong fluctuations in the load pressure curve.

In contrast, the invention is based on the object to provide a control arrangement with improved stability.

This object is achieved by a control arrangement having the features of patent claim 1.

Further advantageous embodiments of the invention are described in the dependent claims.

The hydraulic control arrangement according to the invention serves to control and supply a hydraulic consumer, in particular a cylinder or engine. The control arrangement has a supply line in which a valve designed as a seat valve inlet valve is arranged, the main slide is adjustable via an electrical output signal of a position controller and an electromagnetic actuator. Furthermore, the control arrangement has a return line, in which a lowering brake valve is arranged, whose valve body is acted upon in the closing direction by a spring. The lowering brake valve is connected via an inlet control line to the supply line whose control pressure acts in the opening direction on the valve body. This can be avoided at loads pulling on the consumer a speed that is higher than the predetermined by the inlet flow rate. According to the invention, the output signal of the position controller can be changed via a damping controller to actively intervene on the inlet volume flow and thus to dampen oscillations of the pressure in the supply line or at the input of the consumer at pulling loads. If the consumer is a differential cylinder, thus pressure oscillations in the supplied from the supply line annular chamber or piston head chamber of the differential cylinder are thus avoided. When pulling loads, the lowering brake valve is in normal operation and partially closed. In normal operation, the lowering brake valve (against the force of the spring) is fully open.

The control arrangement can also be doubled, so that the supply line can also serve as a return line and the return line as a supply line. Then the consumer can be operated bidirectionally.

The output signal of the position controller and an output signal of the damping controller are preferably summed at a summation point to an input signal of a drive.

An input signal of the damping controller preferably depends on the pressure and thus on pressure oscillations at an input of the consumer or in the supply line.

In a particularly preferred embodiment of the control arrangement according to the invention while the main spool of the inlet valve is not pressure balanced, and the input signal of the damping controller depends on a force and thus of power vibrations on the main spool. Thus, pressure or pressure oscillations are determined indirectly via force or force oscillations on the main spool. There is thus no additional sensor for a position control or for the active vibration damping required, whereby costs and space can be saved.

In this case, the force or force oscillation on the main slide can preferably be determined via an armature of the actuator fastened thereto. This is done by detecting the current of a coil of the actuator.

A particularly effective damping is achieved when the input signal of the damping controller is formed via a control loop with an attenuator.

The output signal of the damping controller can be limited or limited via a manipulated variable restriction. This can be avoided, especially during the start of movement of the consumer at very high pressure peaks in the supply line, a very high value for the withdrawal of the stroke of the main spool. Without command value limitation, the inflow volume flow could drop sharply and consequently increase only very slowly until it has reached its actual setpoint.

The damping controller can be arranged to save space in or on a housing of the consumer or better directly on the directional control valve or the valve block.

Preferably, two apertures are provided in the inlet control line, between which a tank control channel is connected and branches, in which a tank aperture is arranged. This provides passive damping even if the active damping fails.

Preferably, the lowering brake valve is acted upon in the closing direction via a flow control line connected to the return line with control pressure. In the flow control line two panels are provided, between which a tank control channel is connected and branches off, in which a tank panel is arranged. This provides passive damping even if the active damping fails.

A preferred development has a pilot channel, which connects the return line with a force acting in the opening direction of the Senkbremsventils Aufsteuerfläche the valve body of the Senkbremsventils. Since no shutter is provided in this control channel acts on pulling load on the consumer first, a delay-free force in the opening direction of the lowering brake valve, and then on the shutter assemblies delayed forces.

Preference is given to an inlet valve having a rear space which is delimited by an end face of the main slide acting in the closing direction. Furthermore, the inlet valve has an inlet space which can be connected to a pump, and which is delimited by an opening face acting in the end face of the main spool, which is smaller than the acting in the closing direction end face. The inlet valve has a drainage chamber, which can be connected to the consumer, and which is connected together with the inlet chamber via a shuttle valve to the back room. Thus, by the pressure in the back space in conjunction with the larger end face on the main slide always acts a total force in the closing direction and ensures tightness regardless of the magnitude and sign of the pressure difference between pump pressure in the inlet chamber and consumer pressure in the outlet chamber.

In the following, an embodiment of the invention will be described in detail with reference to FIGS. Show it

1 a circuit diagram of the embodiment of the control arrangement according to the invention,

2 a course of the pressure in the supply line of the control arrangement according to 1 without active stabilization,

3 a profile of the input signal of the control of the control arrangement according to 1 without active stabilization,

4 a course of the pressure in the supply line of the control arrangement according to 1 with active stabilization,

5 a profile of the input signal of the control of the control arrangement according to 1 with active stabilization, and

6 the inlet valve of the control arrangement according to 1 ,

In 1 shown is a circuit diagram of the embodiment of the hydraulic control arrangement for supplying a differential cylinder 2 trained hydraulic consumer. It has an electrically operated inlet valve 92 in a supply line 42 , and a lowering brake valve 72 in a return line 44 , After actuation of the inlet valve 92 by impressing an electrical current on an electromagnet of its electrical actuator 4 sets the inlet valve 92 a proportional to the electric current opening cross section between a pump channel and the supply line 42 one. It acts a spring 24 in the closing direction. With the formation of a corresponding pressure difference across the opening cross-section, an inlet volumetric flow which is dependent on the opening cross-section flows in the piston-bottom space serving as inlet space in this exemplary embodiment 1 of the differential cylinder 2 , In the case of load-sensing systems, a pump (not shown) is pivoted so far until a pump pressure sets in which is higher than the reported load pressure from the supply line by a defined pressure difference 42 is.

Because the lowering brake valve 72 is initially still in the closed position, no volume flow from the annulus 3 of the differential cylinder 2 via the return line 44 flow into the tank T. Thus, due to the builds in the supply line 42 flowing volume flow to an inlet pressure. This is via a shutter arrangement 50 . 52 . 56 filtered on an end face of a pounding piston 60 the lowering brake valve 72 transfer. At the same time acts through a diaphragm arrangement 64 . 66 . 70 a filtered of itself in the annulus 3 build-up back pressure dependent intermediate pressure on the face of a slider of the lowering brake valve 72 in closing direction. By a suitable adjustment of the individual diaphragm cross sections of the diaphragm arrangement 64 . 66 . 70 can thus the pressure force in the opening direction, which from the on an annular surface 138 acting return pressure, counteracted. The slider of the lowering brake valve 72 can thus be executed stationary pressure balanced or force balanced. Since the return pressure but unfiltered acts on the annular surface in the opening direction and initially filtered on the end face in the closing direction, high pressure fluctuations / pressure peaks in the return line 44 be reduced faster. The movement behavior thus has a DT behavior, which has a positive effect on the stability of the control arrangement.

Increases the filtered inlet pressure on the face of the pounding piston 60 far enough that the resulting compressive force on the topping piston 60 becomes larger than that at the Venitlkörper the lowering brake valve 72 adjacent forces, in the optimal case, this is stationary only the force of a spring 29 , the slide of the lowering brake valve moves 72 and gives an opening cross section between the return line 44 and the tank free. It can thus flow a return flow and the differential cylinder 2 can extend. The return flow is in this case by the pressure in the supply line 42 specified. If the pressure in the supply line drops 42 , the opening cross-section is reduced by the slide of the lowering brake valve 72 and a lower return flow rate can flow. The differential cylinder 2 is slowed down when pulling loads and thus fits its speed after the piston in the floor space 1 inflowing inlet flow. Without active stabilization via the inlet valve 92 The above-described only tends via aperture arrangements 48 . 50 . 52 respectively. 64 . 66 . 70 damped control arrangement in consumers with very high inertia and large hydraulic capacities in unfavorable tuning of the setting parameters to an unstable behavior.

1 further shows the electrically operated inlet valve 92 with a non-pressure compensated main spool 19 , There will be an additional active intervention on the system stability through the inlet valve 92 , realized by an appropriate control strategy and a suitable sensor concept to achieve improved system stability or to further attenuate a decaying vibration. If pressure oscillations or increases in pressure occur the supply line 42 , these can be sensed via a suitable arrangement. In the form of a modified input signal 8a a control 8th becomes active the position of the main slider 19 and thus the opening cross section of the inlet orifice of the inlet valve to be released 92 affected. Thus, the opening cross-section decreases with increasing pressure in the supply line 42 and as a result, a smaller inflow volume flow into the supply line 42 flow. The pressure build-up speed drops and the inlet pressure can not increase any further, the system behavior continues to stabilize.

To the pressure oscillations and the position of the main slide 19 Without being able to sense an additional sensor (displacement and / or pressure sensor), inherent measuring effects of the electromagnetic actuator become apparent 4 used. Knowing the interlinked flux of the magnetic circuit and changing it when the electric current changes and the position of an armature changes 23 (see. 6 ) can affect the actual position of the main slider 19 getting closed. The actual position of the main slider 19 is compared with its nominal position and as a control deviation to a position controller 6 to hand over. That from a control 8th received control signal or control signal 8b is about a power electronics 9 converted into a current value (eg via pulse width modulation of the input voltage of the actuator 4 ) and a coil 22 (see. 6 ) imprinted. It turns the desired position of the main slide 19 A, an opening cross-section is released and after the formation of a pressure difference across the inlet orifice of the inlet valve 92 an inflow volume flow flows into the piston bottom space 1 of the differential cylinder 2 ,

Should the system be differential cylinder 2 and lowering brake valve 72 have an unstable behavior, so arise aufklingende pressure oscillations in the supply line 42 , Because the main slider 19 of the inlet valve 92 is not pressure compensated, the propagated in the pump channel pressure oscillation can act as a resultant compressive force vibration in the closing direction. About measuring the current value with an ammeter 10 a signal equivalent to the pressure oscillation is available (low-frequency oscillations in the current must be detectable since a position controller 6 corrects the interference caused by oscillating pressure forces). This signal is through an attenuator 11 filtered and from this the unfiltered signal at a summation point 12 deducted. The resulting deviation is a damping controller 13 as input signal 13a fed, which as an output signal 13b generates an additional manipulated variable. At a summation point 7 is the additional manipulated variable from the damping controller 13 the manipulated variable from the position controller 6 added (added).

By a manipulated variable restriction 14 If necessary, the manipulated variable can be limited in value. Without the command value limitation 14 especially during the beginning of exercise at very high pressure peaks in the supply line 42 a very high value for the withdrawal of the stroke of the main spool 19 arise. As a result, the supply flow drops sharply and increases in consequence only very slowly until it has reached its actual setpoint.

2 to 5 show for the control arrangement with and without active stabilization, the time profiles of the inlet pressure and the drive signal 8b shortly before introduction into the power electronics 9 , It shows 3 the drive signal without active stabilization, but with passive stabilization by the aperture arrangements 48 . 50 . 52 respectively. 64 . 66 . 70 , 2 shows the resulting pressure in the supply line 42 , 5 shows the drive signal 8b with additional active stabilization. 4 shows the resulting pressure in the supply line 42 , In the control arrangement without active stabilization, a clearly unstable behavior can be detected, especially in the first few seconds after the movement has been initiated. Stabilizing behavior results from the condition that the differential cylinder 2 retracts and he thus anfährt a more stable position - natural frequencies increase. The drive signal remains constant. The system with active stabilization reaches its steady-state pressure value almost immediately after initiation of the movement after a short pressure increase. Clearly visible is the modified drive signal 8b ,

6 shows the solenoid-operated inlet valve 92 , It can assume two operating states. Either it is closed and thus disconnects its pump connection 27 from his consumer outlet 17 , or it is in a controlled opening position and releases a defined opening cross-section for a flow of oil.

In non-actuated operating conditions, the requirement for tightness must be met. There is a volume flow from the consumer connection 17 in the pump connection 27 or even via a tank connection 28 to stop in the tank. For this it is necessary that the main slider 19 in the non-actuated operating state in a sealing seat 25 is pressed. About a shuttle valve 18 is the pressure from the pump connection 27 with the pressure in the consumer connection 17 compared and always the higher pressure in a back room 15 of the main slider 19 directed. By suitable choice of the geometry of the main slide 19 , in particular the Diameter, that is achieved that the main slider 19 is not pressure balanced. Thus works by the pressure in the back space 15 in conjunction with the larger area on the main slide 19 always a total force in the closing direction and ensures tightness regardless of the magnitude and sign of the pressure difference between pump and consumer pressure. The also in the back room 15 arranged spring 24 provides additional functional reliability even in the case when the pump pressure with the consumer pressure is at the same level.

As soon as a volume flow is required, the coil must 22 of the actor 4 be energized. The anchor 23 then move a message slider 21 until he hits the main gate 19 is applied. A pressure message in an LS channel 20 can be done and the flow controller pivots the pump (both not shown) accordingly. An inlet valve 92 upstream (also not shown) pressure compensator provides over the opening cross-section of a fine control geometry 26 a defined pressure difference between the pump and the consumer pressure. Only then can the message slider 21 pushed on and thus the main slide 19 to be moved. In a first step then the sealing seat 25 opened and subsequently via the fine control geometry 26 of the main slider 19 a defined cross section for a volume flow from the pump connection 27 to the consumer connection 17 Approved. The released cross-section increases with the stroke of the main slider 19 , Thus, the inflow volume flow depending on the position of the main spool 19 be set exactly.

The force of the electromagnetic actuator 4 is limited and depends on the energization of the coil 22 , To a movement of the main slider 19 through the actor 4 To facilitate it is an additional attached bypass panel 16 intended. This is hubabhängig a cross-sectional opening between the rear space 15 and the consumer connection 17 free. It flows with a small volume flow from the pump connection 27 over the shuttle valve 18 in the back room 15 and then on to the consumer connection 17 , The pressure in the back room 15 , which initially sets at the level of pump pressure, thereby decreases depending on the shared cross-sectional area at this bypass panel 16 something off. This reduces the force on the main slide 19 works in the closing direction. Consequently, the required magnetic force is around the inlet valve 92 open, lowered. Thus, it is easier the inlet valve 92 to press. About the current dependence of the magnetic force, the recording of electrical power also has a positive effect on the operation of such an inlet valve 92 out. With a lowering of the current also decreases the power consumption. Furthermore, it is possible the resulting power reserve of the actuator 4 to increase the dynamics of the inlet valve 92 to use. With such a bypass panel 16 Not only can the required force level be lowered in general, but by adjusting the cross section to be released via the valve lift directly the load characteristic of the sum of all opposing forces on the armature 23 to be influenced. As a result, it is on the one hand possible the resolution of the actuator 4 in areas of operation that are relevant to operation, and to avoid unstable areas over the hub.

In order to realize an active stabilization according to the invention according to the above-described principle, according to this embodiment, a (possible) oscillation of the main spool 19 of the inlet valve 92 sensed. There are inherent measurement effects of the electromagnetic actuator 4 used for distance measurement. Depending on the position of the anchor 23 changes the magnetic resistance and thus the inductance of the coil 22 due to a changing air gap length. Over the course of current (alternatively the voltage course) of the electric magnet can on the position of the anchor 23 getting closed. The basic procedure of the position determination on the basis of a stored map, with which the position of inductance and electric current is determined, can be applied. Another possible method of determining the position uses the phase shift between the input voltage of the actuator 4 and the voltage across a downstream capacitor (not shown) in combination with a stored map to the current position of the armature 23 close.

Alternatively, a Senkbremsventil is possible, the rear space of the spring-loaded end face is connected only via an aperture arrangement with the tank channel and a formation of a load pressure dependent intermediate pressure in an intermediate channel which acts on the spring-loaded end face does not occur.

Disclosed is a hydraulic control arrangement, which serves to control and supply a hydraulic consumer - in particular a cylinder or engine. The control arrangement has a supply line in which a valve designed as a seat valve inlet valve is arranged, and a return line in which a lowering brake valve is arranged. Whose valve body is acted upon in the closing direction by a spring and in the opening direction of a tapped from the supply line control pressure. This can be avoided at loads pulling on the consumer a speed that is higher than the predetermined by the inlet flow rate.

A main spool of the inlet valve is - at least proportionally - set via an electrical output signal of a position controller. This is - preferably amplified by power electronics - transmitted to an electromagnetic actuator of the inlet valve. According to the invention, the output signal of the position controller can be changed via a damping controller or a control circuit with a damping controller to actively act on the inlet flow and so dampen vibrations of the pressure in the supply line or at the entrance of the consumer at pulling loads.

LIST OF REFERENCE NUMBERS

1

Piston head space

2

differential cylinders

3

annulus

4

actuator

6

position controller

6b

output

7

Summation point

8th

control

8a

input

8b

control signal

9

power electronics

10

ammeter

11

attenuator

12

Summation point

13

SAS

13a

input

13b

output

14

Deputy size limit

15

backcourt

16

bypass panel

17

consumer connection

18

shuttle valve

19

main slide

20

Load-sensing channel

21

reporting slide

22

Kitchen sink

23

anchor

24

Return spring

25

sealing seat

26

Fine control geometry

27

pump connection

28

tank connection

29

feather

42

supply line

44

Return line

48

Inflow control line

50

cover

52

cover

54

Tank control channel

55

Tank control channel

56

tank panel

60

topping

62

Flow control line

64

cover

66

tank panel

70

cover

72

lowering valve

92

inlet valve

138

ring surface

140

Gating channel

T

tank

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• EP 2171285 B1 [0004]

Claims (12)

Hydraulic control arrangement for controlling and supplying a consumer ( 2 ) with a supply line ( 42 ), in which a valve designed as a seat valve inlet valve ( 92 ), whose main slide ( 19 ) via an electrical output signal ( 6b ) of a position controller ( 6 ) and an electromagnetic actuator ( 4 ) is adjustable, and with a return line ( 44 ), in which a lowering brake valve ( 72 ) is arranged in the closing direction of a spring ( 29 ) is applied, and that via an inlet control line ( 48 ) to the supply line ( 42 ) is connected, whose control pressure in the opening direction of the lowering brake valve ( 72 ), characterized in that the output signal ( 6b ) of the position controller ( 6 ) via a damping controller ( 13 ) is changeable. Control arrangement according to claim 1, wherein the output signal ( 6b ) of the position controller ( 6 ) and an output signal ( 13b ) of the damping controller ( 13 ) to an input signal ( 8a ) an activation ( 8th ) for the inlet valve ( 92 ) are summed up. Control arrangement according to claim 1 or 2, wherein an input signal ( 13a ) of the damping controller ( 13 ) of a pressure at an input of the consumer ( 2 ) or from a pressure in the supply line ( 42 ) depends. Control arrangement according to claim 3, wherein the main slide ( 19 ) is not pressure compensated, and where the input signal ( 13a ) of a force on the main slide ( 19 ) depends. Control arrangement according to claim 4, wherein the force on the main slide ( 19 ) via one on the main slide ( 19 ) anchors ( 23 ) of the actuator ( 4 ) and thus over the current of a coil ( 22 ) of the actuator ( 4 ) is determined. Control arrangement according to one of claims 3 to 5, wherein the input signal ( 13a ) via a control circuit with an attenuator ( 11 ) is formed. Control arrangement according to one of claims 2 to 6, wherein the output signal ( 13b ) of the damping controller ( 13 ) via a manipulated variable restriction ( 14 ) is limited. Control arrangement according to one of the preceding claims, wherein the damping controller ( 13 ) at the consumer ( 2 ) or directly attached to a valve body or to a housing of a valve block. Control arrangement according to one of the preceding claims, wherein in the feed control line ( 48 ) two apertures ( 50 . 52 ) between which a tank control channel ( 54 ), in which a tank panel ( 56 ) is arranged. Control arrangement according to one of the preceding claims, wherein the lowering brake valve ( 72 ) in the closing direction via a with the return line ( 44 ) associated flow control line ( 62 ) is subjected to control pressure, wherein in the flow control line ( 62 ) two apertures ( 64 . 70 ) between which a tank control channel ( 55 ), in which a tank panel ( 66 ) is arranged. Control arrangement according to one of the preceding claims with a control channel ( 140 ), the return line ( 44 ) with an opening direction of the lowering brake valve ( 72 ) acting annular surface ( 138 ) of the lowering brake valve ( 72 ) connects. Control arrangement according to one of the preceding claims, wherein the inlet valve ( 92 ) a back room ( 15 ), of a acting in the closing direction end face of the main slide ( 19 ), and wherein the inlet valve ( 92 ) has a Zulaufraum of an acting in the opening direction end face of the main slide ( 19 ), which is smaller than the end face acting in the closing direction, and wherein the inlet valve ( 92 ) has a drainage space, which together with the Zulaufraum via a shuttle valve ( 18 ) to the back room ( 15 ) connected.

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