EP2636908A2 - Control assembly - Google Patents

Abstract

The control unit has inlet orifice plates (26,28), and lower brake valves (30,32) that are associated with each actuator. The opening of lower brake valve is opened based on the supply pressure, so that pressure medium flow in return pipe is throttled when pulling the load. An individual pressure compensator (34) is associated with inlet orifice plates so that bypass flow of pressure fluid from load to tank is allowed by the lower brake valve and inlet orifice plate.

Description

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

In mobile work machines, such as hydraulic excavators or tractors, the transfer of power converted by a primary energy converter, such as a diesel engine, to the individual hydraulic linear or rotary consumers of the work equipment is accomplished by hydraulic drive and control units. The pump driven by the diesel engine delivers a pressure fluid flow to a valve block that distributes the oil to the hydraulic consumers.

A control arrangement for supplying pressure medium to the consumer is known from EP 2 171 285 B1 known. In this control arrangement, several consumers are supplied via a control block with pressure medium, wherein in the inlet and in the flow of each consumer, a continuously adjustable orifice, referred to below metering orifice, is arranged. Between the metering orifice and the consumer port, a lowering brake valve is provided in each case, wherein the lowering brake valve located in the inlet releases the pressure medium connection to the consumer and the lowering brake valve located in the drain is acted upon by the pressure in the inlet in the direction of its open position, so that, for example, in pulling load of the pressure medium volume flow in the process can be throttled. Through this resolved design, the two metering orifices associated with the consumer can be controlled independently of one another, wherein a platform concept can be realized on account of the simple valve designs.

The problem with the known solution, however, is that no load pressure independent control of the consumer is possible.

In particular, in the pressure medium supply mobile work machines so-called load-sensing controls are used, in which the highest load pressure the consumer is reported to a variable displacement pump and this is controlled so that in a pump line is applied to a lying by a predetermined pressure difference across the load pressure pump pressure.

The metering orifices of a load-sensing control can be assigned individual pressure compensators, which also maintain a constant pressure difference across the metering orifices of the respective load-pressure-lower hydraulic consumers, so that a load-pressure-independent activation of the respective consumer is made possible.

In a control arrangement conventionally referred to as LS control, the individual pressure compensators are arranged upstream of the respective metering orifices and throttle the pressure medium volume flow between the pump line and the metering orifices such that the pressure before the metering orifices is independent of the pump pressure only by a specific pressure difference above the individual load pressure lies. Here, with a shortage of the load Jastdruckhöchste consumers slower, because the pending before its metering orifice pump pressure drops and thus the pressure difference across this metering orifice is smaller.

In a so-called LUDV control (gauge pressure-independent flow distribution), the individual pressure compensators are arranged downstream of the metering orifices and throttle between the metering and the consumer the fluid flow so strong that the pressure after all Zumessblenden same, preferably equal to the highest load pressure or slightly above this , Here, when there is insufficient supply to the pressure downstream of the metering orifice changes nothing. In front of all metering orifices, the pump pressure is applied in the same way, so that the pressure difference changes in the same way at all metering orifices, if the pump pressure decreases in the case of an undersupply and the current distribution between the metering orifices is maintained - accordingly, the speed of all consumers is reduced proportionally.

Such a circuit is for example in the US 5,878,647 disclosed. In this LUDV control arrangement, each direction of movement of the consumer are respectively assigned to two metering orifices with downstream individual pressure compensator, wherein a metering orifice with assigned individual pressure compensator at a pressure fluid flow to the respective consumer port and the other metering orifice with associated individual pressure compensator from the respective consumer connection flowing pressure medium flow is effective, so that both the inlet volume flow and the drainage volume flow can be adjusted load compensated. Disadvantage of this solution is a considerable device complexity, since each consumer four orifices and four individual pressure compensators are assigned.

The US Pat. No. 7,905,088 B2 discloses a control arrangement for use in mobile work machines, in particular hydraulic excavators in a disassembled design, which shows similar disadvantages as the above-described solution.

Compared to the above-described prior art, the present invention seeks to provide a control arrangement that allows the pressure medium supply of multiple consumers with low device complexity.

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

Advantageous developments of the invention are the subject of the dependent claims.

In the control arrangement according to the invention, each of a plurality of consumers on the inlet side and the outlet side each associated with a continuously adjustable inlet orifice and a lowering brake valve, the latter allows bypassing the inlet orifice an outflow of pressure fluid from the consumer to a tank. The opening cross section of the lowering brake valve is essentially dependent on the pressure in the inlet, so that when the load is pulled, the pressure medium volume flow in the respective outlet is throttled. According to the invention, at least one individual pressure compensator is assigned to the two metering orifices associated with a load for load-pressure-independent activation of the consumers. In the sense of a LS or LUDV control, the pressure drop across the inlet orifice in the inlet can be controlled via this be kept constant, so that a substantially load pressure independent pressure medium supply of the consumer is ensured.

In one variant, the control arrangement is designed as a LS system, wherein the individual pressure compensator is acted upon in the sense of reducing its opening cross-section of the pressure upstream of the associated inlet orifice plate and in the sense of increasing the opening cross section of the load pressure of the respective consumer.

Alternatively, the control arrangement can also be designed as LUDV system, wherein the individual pressure compensator is then arranged downstream of the associated inlet orifice plate and is acted upon in the opening direction by the pressure downstream of the inlet orifice and in the closing direction of the highest load pressure of the consumer.

In such a variant, it is preferred if between the consumer and the downstream of the associated inlet orifice arranged individual pressure compensator, a check valve is provided which blocks an outflow of the pressure medium from the consumer in the direction of the pressure compensator.

An exemplary embodiment of the control arrangement provides for associating an individual pressure compensator with each of two inlet metering orifices assigned to a consumer.

The device complexity in such a solution can be reduced if the functionality of these two pressure compensators is summarized in a pressure compensator unit.

According to the invention, it is preferred if the lowering brake valves and also the inlet metering orifice are designed in the manner of a seat valve, wherein both valve types have a blocking position, which lock leakage of pressure medium from the consumer without leaks.

In one embodiment of the invention, a float position valve is provided for setting a floating position, via which an effective in the opening direction control chamber of the respective lowering brake valve with a control pressure, preferably the pump pressure can be acted upon.

The lowering brake valves can each be designed with an additive offset so that it only opens when a pressure corresponding to the offset in the sequence is exceeded. In this way, a drain-side clamping of the consumer is guaranteed.

To avoid a malfunction of the intake brake valve located in the inlet, a shuttle valve may be provided, the inputs on the one hand in control oil connection with a line leading the inlet pressure and a control chamber of the downstream lowering brake valve and on the other hand in control oil connection with a drain pressure line and a control chamber of standing in the inlet lowering brake valve and whose output is connected to a line carrying the load pressure.

The control arrangement according to the invention is preferably designed as a load-sensing control, wherein a pump pressure of a pump is controlled so that it is above the highest load pressure of the consumer by a predetermined pressure difference.

This pump can be designed as a variable displacement pump or a constant displacement pump with a bypass valve.

In particular for applications in mobile technology, it is preferred if the control arrangement is designed as a valve block, wherein each consumer is associated with a valve disc with inlet orifices, lowering brake valves and individual pressure compensator.

• Figur 1 ein stark vereinfachtes Schaltschema einer erfindungsgemäßen Steueranordnung mit Ventilblock;
• Figur 2 eine Ventilscheibe eines derartigen Ventilblocks als LS-System;
• Figur 3 das LS-System aus Figur 2 mit einer Freigangschaltung;
• Figur 4 eine als LUDV-System ausgeführte Ventilscheibe eines Ventilblocks gemäß Figur 1;
• Figur 5 eine Variante des LUDV-Systems gemäß Figur 3 und
• Figur 6 eine konkrete Ausgestaltung eines Senkbremsventils für eine Steueranordnung gemäß den Figuren 1 bis 5.

A preferred embodiment of the invention will be explained in more detail below with reference to schematic drawings. Show it:

• FIG. 1 a highly simplified circuit diagram of a control arrangement according to the invention with valve block;
• FIG. 2 a valve disc of such a valve block as LS system;
• FIG. 3 the LS system off FIG. 2 with a release circuit;
• FIG. 4 a designed as LUDV system valve disc of a valve block according to FIG. 1 ;
• FIG. 5 a variant of the LUDV system according to FIG. 3 and
• FIG. 6 a concrete embodiment of a lowering brake valve for a control arrangement according to the FIGS. 1 to 5 ,

The control arrangements explained below are intended to supply hydraulic consumers with a pressure medium volumetric flow which can be switched over and controlled in both directions of consumption. The supply of pressure medium into the inlet of the consumer takes place load-compensated and is thus largely dependent only on the opening cross-section of an inlet orifice plate which will be explained in more detail below. In order to realize the dependence of the self-adjusting consumer speed only on the inlet flow, in the embodiments described below in the valve-side return channels of consumers from the inlet pressure unlockable and controllable check valves are provided. Both the inlet valves and the unlocked by the inlet pressure check valves in the return are preferably designed as pilot operated and pressure balanced poppet valves. The control of the inlet and return valves in engagement takes place independently of each other (resolved control edges). This resolved design makes it possible, without the use of additional pressure sensors required in the prior art, to make the return flow rate at pulling loads dependent on the build-up of pressure in the inlet channel. Thus, during operation, the sink rate can largely be predetermined by the inflow volume flow. The inventive Solution allows the realization of a platform concept in which the essential elements, such as the proportionally controllable inlet valve in seat valve design, the proportionally adjustable shut-off valve in the return channel in seat valve design, various shuttle valves can be used both in control arrangements in LS technology as well as control arrangements in LUDV technology. Such a platform concept is not to realize in valves in which a main spool valve maps all opening cross-sections. Reason is the sometimes very complex commissioning and adjustment of inlet and outlet orifice cross-sections, especially in LUDV valves with the main application in hydraulic excavators. The seat valves described below ensure freedom from leaks, so the LS version requires no additional measures, such as check valves.

FIG. 1 shows a highly simplified circuit diagram of a control arrangement according to the invention for supplying pressure to several consumers of a mobile implement, such as an excavator, a backhoe, a mini and compact excavator, a telehandler or the like. The pressure medium supply of the consumer 2, shown here by way of example a differential cylinder, via a control block 4, which has a plurality of valve disks (directional valve sections 4), each of which is associated with one of the consumer 2. Each of the directional control valve sections 4 has two working connections A, B, which can be connected via the valve arrangement described below to connections P, T, T 'and LS of the control block 4.

The control arrangement has a pump, in the present case a variable displacement pump 6 whose pressure connection is connected via a pump line 8 to the pressure port P of the control block 4. As mentioned above, instead of a variable displacement pump, a constant displacement pump with a bypass valve can also be used. In the illustrated embodiment, the variable displacement pump 6 is designed for example as an axial piston pump whose pivot angle is adjustable via a control cylinder 10. The actuation of the actuating cylinder 10 via a pump control valve 12. In the illustrated embodiment, the pivot angle is acted upon by a return device 14 in the direction of the maximum pivot angle, while the actuating cylinder 10 can be adjusted to reduce the pivot angle against the force of the return device 14. The pump control valve 12 is by the force of a control spring sixteenth and biased the control pressure in a LS line 18 in the direction of a relief of the actuating cylinder 10, wherein a control oil connection is opened up between an opening in the control room of the actuating cylinder 10 control line 20 to a tank T. In the LS line 18 is the highest load pressure of the driven consumers, which is tapped at the LS port of the valve block 4. The tank connection T of the valve block 4 is connected via a tank line 22 to the tank T.

Contrary to the force of the control spring 16 and the highest load pressure acts on the valve spool of the pump control valve 12, the pump pressure, which is tapped at the pump line 8. This pump pressure is also applied to a pressure port P of the pump control valve 12. When controlling the variable displacement pump 14, the pump volume flow and thus the pump pressure in the pump line 18 increases until at the end faces of the pump control valve 12, an equilibrium of forces from the pressure force of the pump pressure on the one hand and on the other hand from the load pressure of the load pressurehöchsten consumer and the force of the control spring 16 sets. The pump pressure is then higher by the given by the spring force pressure difference than the highest load pressure. The basic function of such a pump control is known from the prior art, for example from the aforementioned EP 2 171 285 B1 known, so that further explanations are unnecessary.

FIG. 2 shows a first embodiment of a directional control valve section 24 of a valve block 4 according to FIG. 1 , This directional valve section 24 is designed with consumer connections A, B, a pressure connection P, a tank connection T, an LS connection LS and a further tank connection T ', the latter connections P, T, LS, T' being in pressure medium connection with the adjacent directional control valve sections can.

In the directional control valve sections 24 described below, each consumer connection A, B is assigned a metering orifice 26, 28 as well as a respective lowering brake valve 30, 32. For load compensation at least one individual pressure compensator 34 is provided, via which the pressure drop across the respective inlet orifice 26, 28 can be kept constant. At the in FIG. 2 The solution shown is the Directional control valve section 24 designed as LS system, wherein a single individual pressure compensator 34 is associated with the two inlet orifices 26, 28.

An input terminal of the spring-biased individual pressure compensator 34 is connected via a pressure channel 36 to the pressure port P of the directional valve section 24. An output of the individual pressure compensator 34 is connected via a branching inlet channel 38 to a respective pressure port P of the two metering orifices 26, 28. The individual pressure compensator 34 is - as explained above - acted upon in the closing direction by the pressure upstream of the inlet orifices 26, 28 and in the opening direction of the individual load pressure of the connected load, which is tapped via an LS channel 40. This leads to an input of a shuttle valve 42, at the other input, the highest load pressure of the other consumer is applied, which is tapped via a shuttle valve cascade, not shown. The output of the shuttle valve 42 is connected to the LS port, so that the respective highest load pressure to the above-described pump control valve or to another connected directional valve section is reported.

The two identical feed orifices 26, 28 are each designed as electrically controllable, proportionally adjustable seat valves whose working ports A, B are connected via channels to the working ports A, B. In the following description, it is assumed that the consumer port A is in the inlet and the consumer port B is in progress. According to this assumption, the channel leading to the consumer port A is referred to as the flow channel 44 and the channel leading to the consumer port B is referred to as the return channel 46. The end faces of the two inlet orifices 26, 28 are pressure balanced.

By energizing a proportional magnet 48, 50, the metering orifices 26, 28 can be adjusted from the illustrated blocking position in which an outflow from the consumer in the direction of the pressure compensator 34 is leak-free shut in an opening direction, wherein the opening cross section of the energization of the proportional magnet 48, 50th depends. The pressure downstream of the respective inlet orifice 26, 28 is tapped off at an LS connection of the inlet orifices 26, 28. This pressure is applied to the inputs of another shuttle valve 52 whose output is connected to the aforementioned LS channel 40. The load pressure at the LS connection of the inlet metering orifice 26 is also signaled via a load tap channel 54 to the signal pressure chamber of the lowering brake valve 32 located in the outlet B and thus in the outlet. In a corresponding manner, the load pressure at the connection LS of the other metering orifice 28 is connected via a load tap channel 56 to the signal pressure chamber of the inlet-side lowering brake valve 30. Accordingly, the two signal pressure chambers of the lowering brake valves 30, 32 are separated from each other via the further shuttle valve 52. The two Lastabgriffskanäle 54, 56 are connected via a respective aperture 64, 66 in connection with the tank connection T '. These orifices 64, 66 thus serve to relieve pressure in order to avoid an uncontrolled pressure build-up due to leaks in the case of non-actuated valves and thus uncontrolled slide movements of the individual pressure compensator 34 or the lowering brake valves 30, 32 and a resulting uncontrolled operating behavior.

The two lowering brake valves 30, 32 are designed as hydraulically pilot-operated seat valves. An input port P of the two lowering brake valves is connected in each case via a channel 58 or 60 to the associated flow channel 44 or the return channel 46. An outlet connection T of the lowering brake valves is in each case via a tank channel 62, 64 in pressure medium connection with the tank connection T of the directional valve section 24.

In the illustrated embodiment, the pressure in the flow channel 44 and in the return channel 46 is limited by designed in the valve seat design pressure relief valves 68, 70. When exceeding a maximum pressure set to this open a pressure fluid connection to a connected to the tank port T relief channel 67th

When energizing the proportional solenoid 48, as stated above, opened an opening cross-section of the inlet orifice 26, wherein the load pressure tapped via the LS port of the inlet orifice 26 and reported via the shuttle valve 52 in the effective in the opening direction of the individual pressure compensator 34 control room. In the opposite direction of the pressure acts in the inlet channel 38. In a control position of the individual pressure compensator 34, the pressure in the inlet channel 38 to that of the spring force the individual pressure compensator 34 resulting pressure difference greater than the reported individual load pressure, so that the pressure drop across the inlet orifice 26 remains constant load pressure independent. The load pressure downstream of the inlet orifice 26 is tapped via the Lastabgriffskanal 54 and reported to the signal pressure chamber located in the drain lowering brake valve 32 so that it is controlled in proportion to the inlet pressure and releases a flow cross section. In this case, the check valve 32 opens completely under a pressing load. In a pulling load, the lowering brake valve 32 is moved to a control position, wherein the flow restricting the cross section established in such a way that the returning volume flow is only so large to adjust on the inlet side a pressure can be approximately the pressure equivalent of the spring force Return spring 74, 76 of the downstream lowering brake valve 32 corresponds. In this way cavitation can be reliably prevented.

LS systems are widely used for tractor applications. For some functions, there is a requirement for a floating position in which both sides of the consumer are connected to each other or to the return line. Such a floating position is required, for example, for attachments that are pulled behind the tractor or when leaving rotary consumers.

In FIG. 3 is a variant of the embodiment according to FIG. 2 represented, wherein a floating position is realized. For this purpose, an electrically switchable float valve 78 is provided, which is designed as a 3/2-way valve, wherein a terminal C is connected via a branching control line 80 to the inputs of two further shuttle valves 82, 84. The float position valve 78 is biased by a spring into a basic position in which the port C is connected to a tank port T, which opens into a tank control line 86. In this the above-described aperture 66 is arranged.

A pressure port P of the float valve 78 is connected via a connecting channel 88 to the pressure channel 36. The two other inputs of the shuttle valves 82, 84 are connected to the load tap channel 54 and 56, respectively. The output of the shuttle valves 82, 84 is then in fluid communication with the two Signal pressure chambers of the lowering brake valves 32 (shuttle valve 82) and 30 (shuttle valve 84).

In the illustrated spring biased home position of the float valve 78, the function of the circuit according to FIG FIG. 3 of those FIG. 2 , so that further explanations are dispensable.

By switching the float position valve 78 to its switching position (b), the pressure channel 86 is connected to the inputs of the two shuttle valves 82, 84, so that they are adjusted to a position in which this pump pressure is reported in the signal pressure chambers of the lowering brake valves 30, 32 so that they are completely opened and release an opening cross-section in the valve-internal discharge channel 67 for both consumer sides.

The pump pressure is sufficient even with non-actuation of the inlet orifices 26, 28 to open the lowering brake valves 30, 32, as a result of system even when not operating the inlet orifices 26, 28 at least the pressure from the spring preload of the control spring 16 of the pump control valve 12 resulting pressure difference.

FIG. 4 shows a directional valve section 24, which is designed as LUDV system. In the following description, for components corresponding to those of the circuit according to FIG FIG. 2 correspond, the same reference numerals used for simplicity. Accordingly, the directional valve section 24 has two inlet orifices 26, 28, which are also again designed as proportionally adjustable, pressure balanced poppet valves and from a spring-biased locking position shown by energization of proportional magnets 48, 50 are adjustable in the direction of an open position.

Each inlet orifice 26, 28 is associated with an individual pressure compensator 34 and 90, respectively. Furthermore, two lowering brake valves 30, 32 are provided which can be opened by the pressure in the respective inlet in order to connect the flow channel 44 and the return channel 46 to the tank T. In their basic position are the Lowering brake valves 30, 32 biased into a position in which an outflow from the consumer to the tank T is locked leak-free. The maximum pressure in the channels 44, 46 is again limited by pressure relief valves 68, 70. These are like the inlet orifices 26, 28 and the lowering brake valves 30, 32 formed as seat valves.

The inlet of the two pressure compensators 34, 90 is connected in each case via a connecting channel 92 or 94 to the outlet connection A of the inlet measuring orifice 26 or to the outlet connection B of the inlet measuring orifice 28. Their input ports P are connected via the pressure channel 36 to the pressure port P of the directional valve section 24 as in the embodiment described above.

Similar to the exemplary embodiments described above, the pressure downstream of the respective inlet orifice 26, 28 is applied to the LS connections of the feed orifices 26, 28. This load pressure is reported in an LS reporting line 96 in which a check valve 98 is provided. This opens when the load pressure is greater than the pressure which acts on the LS port of the directional valve section 24. D. h., The greater of these pressures is reported in a branching pressure compensator 100, via which the spring-loaded end faces of the two individual pressure compensators 34, 90 are acted upon by this load pressure. D. h., The individual pressure compensators 34, 90 are acted upon in the direction of its closed position by the force of the weak pressure balance spring and the highest load pressure of the consumer. In the opening direction, the pressure acts downstream of the respective inlet orifice 26, 28, which is tapped off at the connection channels 92, 94 via a control line 102, 103. The output of the two individual pressure compensators 34, 90 is connected to the flow channel 44 and the return channel 46. In these two channels 44, 46 a check valve 104, 106 is arranged in each case. These prevent the consumer loads acting directly on the end faces of the lowering brake valves 30, 32. In the area between these check valves 104, 106 and the respective pressure compensator 34, 90 branch from the channels 44, 46 tap channels 108, 110, via which the load pressure downstream of each individual pressure compensators 34, 90 reported in the signal pressure chambers of the associated lowering brake valve 32 and 30 respectively is, so that the lowering brake valve 32 through the pressure downstream of the pressure compensator 34 and the lowering brake valve 30 can be controlled by the pressure downstream of the pressure compensator 90.

In the FIG. 4 shown and unspecified diaphragms have the same function as in the embodiment described above - they are used to depressurize the signal lines to prevent uncontrolled pressure build-up due to leakage in non-actuated valves.

As explained at the outset, the pressure drop across the inlet-side inlet orifices 26, 28 is kept constant via the individual pressure compensators 34, 90 acted upon in the closing direction by the highest load pressure, the consumer rate of all consumers being proportionally reduced in the event of an undersupply of the consumer.

The other functionality corresponds to that of the above-described embodiments. As with the LS systems open the lowering brake valves 30, 32 at pushing loads completely. When pulling loads adjusts an opening cross-section at the drain-side lowering brake valve 30, 32, so that on the inlet side, a pressure is adjusted, the height of which essentially depends on the biasing force of the return springs 74, 76.

FIG. 5 shows a variant of the embodiment according to FIG. 4 , wherein the functionality of the two individual pressure compensators 34, 90 is combined in a pressure compensator unit 112. This practically forms a two-way adjustable individual pressure compensator, wherein it is biased by a pressure compensator spring assembly 114 into a blocking position in which the pressure medium connection between the connecting channels 92, 94 to the flow channel 44 and to the return channel 46 is shut off. The basis FIG. 4 explained pressure balance line 100 is connected in this embodiment to an input port LS of the pressure compensator unit 112. This connection is also blocked in the basic position shown. Of the two connection channels 92, 94 branch off the two control lines 102, 103, wherein the control line 102 to an effective in adjustment (a) end face and the control line 103 to an effective in the adjustment direction (b) face of the pressure compensator unit 114 leads. In the control line 102, 103, a check valve 116, 118 is arranged in each case.

The pressure compensator unit 112 further has two control terminals X, Y. The aforementioned end faces of the pressure compensator slide are acted upon by signal lines 120, 122 with the signal pressures at the terminals X, Y. In an adjustment of the pressure compensator slide in the direction (a) or (b) of the LS port of the pressure compensator unit 112 is connected in a corresponding manner with the control port Y or X, so that the respective end face of the pressure compensator slide by the higher of the pressures in the connecting channel 92, 94 or the LS port of the directional valve section 24 is acted upon. When current flows through the inlet orifice plate 26, it accordingly releases an opening cross section between the pressure channel 36 and the connection channel 92. The increasing pressure in the connection channel 92 is then applied to the in FIG. 5 reported left end face of the pressure compensator unit 112 and are, even before the actual pressure compensator shutter comes in control position, a cross section free. About this pre-opened cross section of the pressure from the pressure balance line 100 of the entire system to the opposite end face (right in FIG. 5 ), so that the pressure compensator unit 112 can go to its control position. The lowering brake valve 32 located in the outlet is then in turn completely opened when the load is pressed, so that the pressure medium can flow away from the consumer. The pulling load function corresponds to that of the above-described embodiment.

FIG. 6 shows a concrete embodiment of a lowering brake valve, as it is usable in the embodiments described above. It is assumed that it is the lowering brake valve 32 from the previously described embodiments. The other lowering brake valve 30 has a corresponding structure. The illustrated embodiment is designed in cartridge construction, wherein in a valve bore 124, the actual lowering brake valve 32 is inserted. This valve bore 124 is formed in the control block 4 and has two radial ports, into which the load pressure-carrying channel 60 and connected to the tank T relief channel 67 open. In the axial direction, a control port is formed, on which the respective inlet pressure acts, the example in the embodiment according to FIG. 2 tapped by the load pick-off channel 54. This pressure will be in the aforementioned Signal pressure chamber 126 reported, which is bounded by a control piston 128. The actual lowering brake valve has a main stage with a main piston 130 which is biased by the force of the return spring 76 against a valve seat 132, so that a pressure medium connection from the channel 60 to the discharge channel 67 is shut off. In the opposite direction, the main stage acts as a check valve. The lowering brake valve 32 further has a pilot stage with a pilot piston 134, which is also biased by the return spring 76 against a pilot valve seat 136. The return spring 76 acts on a spring plate 138 on an axial projection of the pilot piston 134 and thus biases both the main piston 130 and the pilot piston 134 in the direction of its closed position. An end face 114 of the axial projection of the pilot piston 134 bears against the control piston 128. The rear of the main piston 130 remote from the valve seat 132 defines a control chamber 142 which is connected via a connecting channel 144 to a space 146, which in turn forms via a shutter forming control notches 148, which in the FIG. 6 designated region are connected to a rear space 150 which is adjacent to the valve seat 136. The in FIG. 6 Located to the left of the pilot valve seat 136 area of a receiving bore for the pilot piston 134 is in fluid communication with the discharge channel 67. The in FIG. 6 right end face of the pilot piston 134 is relieved of pressure to the discharge channel 67. The connection channel 144 is connected to the channel 60 via a nozzle 152.

Since the basic structure of the lowering brake valve 32 is known in principle, for example, from the Applicant's EHR23 valve series, further explanation of the design features can be dispensed with. The only significant difference between the known lowering brake valves and the solution presented here is that in the known solutions, the pilot stage is adjusted by means of a proportional solenoid, while in the presented solution, a hydraulic adjustment by the inlet pressure.

The inlet pressure in the channel 60 acts via the nozzle 152 in the control chamber 142, so that the main piston is tensioned against the force of the return spring 76 against its valve seat 32. About the pressure in the inlet of the control piston 128 is moved to the right and takes the pilot piston 134 against the force of the return spring 76 so that the Pilot piston 134 lifts from the pilot valve seat 136. As a result of this opening movement, the diaphragm cross section formed by the fine control notches 148 is opened so that a connection between the connecting channel 144 and the relief channel 67 is established after a predetermined path (additive offset). As a result, the pressure in the control chamber 142 is lowered and the main piston 130 begins to open by the load effective in the opening direction and an effective opening direction in the opening direction, wherein the aperture formed by the fine control notches is reduced again, until in the control chamber 10 an equilibrium corresponding intermediate pressure - the main level thus follows the pilot level.

In the case of a towing load (load pressure in the channel 60 greater than the inlet pressure einzuregelnde in Lastabgriffskanal 54) adjusts an inlet pressure in the inlet, which corresponds approximately to the pressure equivalent of the force of the return spring 76, wherein flow forces are not taken into account. In this case, an opening cross-section of the main stage, which determines the return flow and thus a sink speed of the consumer, so that the formation of cavitations is prevented on the inlet side.

Disclosed is a control arrangement for a plurality of consumers, wherein each consumer port is associated with a metering orifice and a lowering brake valve. At least one inflow-side metering orifice is in operative connection with an individual pressure compensator. In the case in which each metering orifice is associated with an individual pressure compensator, these can be integrated into a single pressure compensator unit.

LIST OF REFERENCE NUMBERS

1

control arrangement

2

consumer

4

control block

6

variable

8th

pump line

10

actuating cylinder

12

Pump control valve

14

Reset device

16

control spring

18

LS line

20

parking management

22

tank line

24

Directional control valve section

26

metering orifice

28

metering orifice

30

lowering valve

32

lowering valve

34

Individual pressure compensator

36

pressure channel

38

inlet channel

40

LS-channel

42

shuttle valve

44

forward channel

46

Return channel

48

proportional solenoid

50

proportional solenoid

52

shuttle valve

54

Lastabgriffskanal

56

Lastabgriffskanal

58

channel

60

channel

62

tank channel

64

cover

66

cover

67

relief channel

68

Pressure relief valve

70

Pressure relief valve

72

relief channel

74

Return spring

76

Return spring

78

Float valve

80

control line

82

shuttle valve

84

shuttle valve

86

control line

88

connecting channel

90

Individual pressure compensator

92

connecting channel

94

connecting channel

96

LS-signaling line

98

check valve

100

Pressure balance line

102

control line

103

control line

104

check valve

106

check valve

108

Abgriffskanal

110

Abgriffskanal

112

Pressure compensator unit

114

Pressure balance spring assembly

116

check valve

118

check valve

120

signal line

122

signal line

124

valve bore

126

Signal pressure chamber

128

spool

130

main piston

132

valve seat

134

pilot piston

136

Pilot valve seat

138

spring plate

140

face

142

control room

144

connecting channel

146

room

148

Metering notches

150

backcourt

152

jet

Claims (13)

Control arrangement for controlling a plurality of hydraulic consumers, wherein each consumer on the inlet side and the outlet side an inlet orifice plate (26, 28) and a lowering brake valve (30, 32) is associated, the opening cross-section is substantially dependent on the inlet pressure, so that when pulling load of the pressure medium volume flow in the return can be throttled, characterized in that the inlet-side metering orifice (26, 28) is associated with an individual pressure compensator (34, 90) and that the lowering brake valve (30, 32) when bypassing the inlet orifice (26, 28) an outflow of pressure medium from the consumer to the tank (T) allows. Control arrangement according to claim 1, wherein the individual pressure compensator (34) is acted upon by the load pressure of the respective consumer in the sense of reducing its opening cross section from upstream pressure of the associated inlet orifice plate (26, 28) and in the sense of enlarging the opening cross section. Control arrangement according to claim 1, wherein the individual pressure compensator (34, 90) is acted upon in the opening direction by the pressure downstream of the associated inlet orifice plate (26, 28) and in the closing direction of the highest load pressure of the consumer. Control arrangement according to claim 3, wherein the individual pressure compensator (34, 90) seen in the inlet direction downstream of the metering orifice (26, 28) is arranged and between the consumer and the individual pressure compensator, a check valve (104, 106) is arranged. Control arrangement according to claim 3 or 4, wherein each metering orifice (26, 28) of a consumer an individual pressure compensator (34, 90) is connected downstream. Control arrangement according to claim 5, wherein the function of the inlet-side and the outlet-side individual pressure compensators (34, 90) in a pressure compensator unit (112) is integrated, which is designed starting from a basic position adjustable in two directions. Control arrangement according to one of the preceding claims, wherein the lowering brake valves (30, 32) and the inlet orifices (26, 28) are designed in a poppet valve construction with a blocking position. Control arrangement according to one of the preceding claims, with a float position valve (78) via which effective in the opening direction signal pressure chambers of the lowering brake valves (30, 32) for setting a floating position with a control pressure, preferably the pump pressure can be acted upon. Control arrangement according to one of the preceding claims, wherein the lowering brake valves (30, 32) are designed with an additive offset, so that they open only when a pressure corresponding to the offset is exceeded. Control arrangement according to one of the preceding claims, with a shuttle valve (52) whose inputs on the one hand in control oil connection with a line leading to the inlet pressure and a signal pressure chamber of the lowering brake valve (30, 32) and on the other hand with a line leading the discharge pressure and a signal pressure chamber in the inlet located lowering brake valve (32, 30) is and whose output is connected to a line carrying the individual load pressure. Control arrangement according to one of the preceding claims, comprising a pump (6) whose pump pressure is controlled so that it is above the highest load pressure of the consumer by a predetermined pressure difference. Control arrangement according to claim 11, wherein the pump (6) is a variable displacement pump or a fixed displacement pump with a bypass valve. Control arrangement according to one of the preceding claims, wherein this is designed as a control block (4) and each consumer a valve disc associated with inlet orifices (26, 28), lowering brake valves (30, 32) and at least one pressure compensator (34, 90).

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