EP1766146A1

EP1766146A1 - Lifting gear valve arrangement

Info

Publication number: EP1766146A1
Application number: EP05772453A
Authority: EP
Inventors: Sönke Jessen; Gerhard Keuper; Heinrich Lödige; Reiner Kunz
Original assignee: Bosch Rexroth AG
Current assignee: Bosch Rexroth AG
Priority date: 2004-07-09
Filing date: 2005-07-06
Publication date: 2007-03-28
Anticipated expiration: 2025-07-06
Also published as: EP1766146B2; DE102004033315A1; ATE524617T1; WO2006005496A1; US8020485B2; EP1766146B1; US20070277519A1

Abstract

Disclosed is a lifting gear valve arrangement for controlling a double-action lifting gear or an add-on unit with a continuously adjustable directional control valve and with an individual pressure compensator via which a pressure medium volume flow to and from a lifting cylinder of the lifting gear can be controlled. A proportionally adjustable pressure limiting valve is provided in the pressure medium flow path between an outlet connection of the directional control valve and a working connection of the lifting gear valve arrangement, via which the pressure inside this area can be limited to a maximum value. The adjustment of the pressure limiting valve is preferably performed as a function of the operating states of the lifting gear or of the type of add-on unit.

Description

description

lifting gear

The invention relates to a Hubwerksventilanordnung for controlling a double-acting hoist or an attachment of a mobile working device according to the preamble of claim 1.

In modern tractors of the medium and upper performance class, increasingly electrically controllable directional control valves for the control of work functions of coupled devices are used in the working hydraulics. These hydraulic functions are controlled by means of a very compact control block, in which the control system with all the essential directional and control valves is combined into one unit. Such a control block is described for example in the catalog 1 987 760 507 (electronic-hydraulic hitch control for Trakto¬ Ren) of the applicant.

Figure 1, to which reference is already made, shows the basic structure of the working hydraulics of a tractor 1 or other mobile implement. The Trak¬ gate 1 is designed according to Figure 1 with a Heckhubwerk 2 and a front lifting 4, the lifting cylinder 6, 8 via a control block 10 with pressure medium of a hydraulic pump 12 are supplied. In the illustrated prior art, the two hoists 2, 4 single-acting (ew) ausge¬ leads - but there are also known solutions in which both the front hoist 4 and the Heckhubwerk 2 double acting (dw) are performed. The control block 10 contains each of the consumers 6, 8, etc. associated electro-hydraulically actuated directional control valves 14, which are controlled by an electrical control unit 16. The setpoints are eg. Via a front panel 18 or a rear control unit 20, which are arranged in the interior of the tractor cabin 22 or via a rear side arranged on the tractor rear switch 22 or a front button (not shown) set.

For detecting the occurring forces, pressures, speeds and hoist positions, a multiplicity of sensors, for example pressure sensors 26, rotational speed sensors 28, position sensors 30, force sensors 32 or speed sensors 34 are provided on the tractor 1, their signals being transmitted via the control unit 16 are processable.

As already mentioned, the Heckhubwerk 2 is single-acting in most known solutions, wherein the lifting cylinder 6 is extended by supplying pressure medium via the pump 12 and the lowering by the weight of the Heckhubwerks 2 and possibly attached ange¬ device such as a plow 36 follows.

For example, for sowing with a seed drill, the Heckhubwerk 2 is brought into a floating position, so that the attachment rests on the ground due to its own weight and overflows any bumps.

However, with the conventional single-acting rear elevators, the contact pressure can not be actively changed, since these hoists can not be operated in the "pressure" work area. For this purpose, double-acting Heckhubwerke are required, the basic structure of which corresponds to that used in the usual way double-acting Fronthub¬ works. The double-acting Heckhubwerke 2 make it possible to control the lifting cylinder 6 in the direction of "pressing", so that, for example, an active Pflugein¬ pull is possible. This operating state can for Example can also be used to rear the tractor to Wech sel of the rear, large wheels so that it is on the pendulum front axle and on the operated by the Heckhubwerk attachment or directly on the lower links.

The previously used pressure sensor, for example, in the front lift is arranged on the wear side, there is a relief pressure control - the contact pressure remains unknown or is not used for control.

In contrast, the invention has the object zugrun¬ de to provide a Hubwerksventilanordnung, which makes it possible to set and limit a contact pressure with minimal effort.

This object is achieved by a Hubwerksventilanordnung with the features of claim 1.

According to the invention, the Hubwerksventilanordnung a steadily adjustable directional control valve, the one or more pressure compensators upstream or downstream. Two working ports of the lifting gear valve assembly are connected to the effective in lifting and lowering pressure chambers of the hoist - or more precisely, the lifting cylinder of the hoist. According to the invention, a pressure-limiting valve or the like, which can be displaced in an operating line, is provided by means of which the pressure in this working line can be limited to a variable maximum value. According to the invention, the pressure in this working line is limited via the pressure limiting valve as a function of certain operating states, so that the contact pressure can be variably adjusted. The term hoist is to be understood in general a device over which a mobile working device associated working tool, attachment or the like relative to a reference plane movable or can be pressed against them.

This very simply designed Hubwerksventilanordnung makes it possible to adapt the contact pressure by controlling the pressure relief valve in an extremely simple and kosten¬ favorable manner to different operating conditions.

In a preferred embodiment of the invention, the maximum pressure can be adjusted via the pressure limiting valve in a range between 0 and 250 bar. When setting a minimum Auflage¬ pressure (for example, 5 to 8 bar), the function of the running with the Hubwerksventilanordnung invention hoist is equal to that of a single-acting hoist. In normal operation, the driver adjusts the pressure relief valve to its maximum value, so that the contact pressure can reach a maximum value accordingly.

The setting of the maximum pressure takes place as a function of different operating conditions - for example when lifting the rear axle for Reifen¬ change, when pressing a quick-entry switch for a fastest lowering movement, when pressing the Heck¬ button, etc., each set appropriate maximum pressures become. In normal operation, the driver sets the maximum pressure.

In the hoist valve arrangement according to the invention, the activation preferably takes place via a control unit, via which the continuously adjustable directional control valve is activated as required. chen of the pressure relief valve in a neutral position (dw) or in a floating position (ew) is adjustable.

In a particularly preferred embodiment, to limit the pressure in the other working line, i. preferably provided in the working direction connected to the working in the direction of "lifting" pressure line a secondary pressure relief valve.

In the working lines downstream of the two output ports of the continuously variable directional control valve in each case a drain module is provided which acts in a Grundpo¬ position as a pilot-operated check valve and acts on admission with a control pressure as a discharge pressure balance.

The Hubwerksventilanordnung invention is vor¬ preferably designed as a LS system, the pressure compensator as an individual pressure compensator is preceded by a continuously variable directional control valve forming a variable metering orifice. The pressure compensator is acted upon in the opening direction by the highest load pressure of the driven consumers. This highest load pressure is also reported to a pump and this regulated so that in the Pumpen¬ line is a lying by a predetermined pressure difference above the load pressure pump pressure.

The Hubwerksventilanordnung can be performed with a manually operated emergency lowering, via which the higher pressure leading working line is connected to the tank.

The solution according to the invention is preferably used in a rear lifting gear of a tractor. However, it is also conceivable to use attachments, for example plows and outside of agricultural applications. For example, for operating shields, as they are spielsweise used in snow clearers.

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

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

Figure 1 is a basic diagram of the working hydraulics of a conventional tractor;

FIG. 2 shows a schematic representation of different operating states of a double-acting rear lift, which is designed with a lifting valve arrangement according to the invention;

Figure 3 is a hydraulic circuit diagram of the Heckhubwerks, with which the operating conditions are adjustable in accordance with Figure 2;

FIG. 4 shows a detailed representation of the lifting mechanism valve arrangement from FIG. 3;

5 is a sectional view of a Hubwerksventil- arrangement, which is used in the circuit according to Figure 3 and

FIG. 6 shows a diagram for clarifying the control structure for controlling the lifting gear valve arrangement from FIG. 3.

It is assumed that the tractor 1 shown in FIG. 1 has a double-acting rear lift 2 instead of a single-acting one, wherein the pressure medium supply supply of the two pressure chambers of the lifting cylinder 6 takes place via a Hubwerksventilanordnung invention, which is zusam¬ zusam¬ together with the directional control valves for controlling the other consumers of the tractor 1 to a control block 10.

A Heckhubwerk 2 according to Figure 1 can be - as shown in Figure 2 - use in different operating conditions. In the working area "carrying", the rear lifting mechanism and optionally attached attachments 36 are either lifted off the ground or are carried in contact with the ground with a predetermined supporting force. This work area occurs, for example, when plowing or when cultivating.

In Figure 2 left, the Hubkraftverlauf is shown on the lifting height - this lifting force must be applied by the lifting cylinder 6 of the Heckhubwerks 2. For example, for sowing with a seed drill, a load-free intermediate position is taken, in which the Heckhubwerk 2 is not acted upon with a force, so that the attachment rests on the ground due to its own weight. Such a load-free intermediate position is usually - as described below - adjusted by adjusting the directional control valve 14 in a floating position.

As mentioned above, to set the working range "pressing", the rear lift 2 can be controlled so that a pressure force acting in the direction of the ground is applied. Such an adjustment is required, for example, during active plowing or in a packer. In the working area "pressing", the rear axle of the tractor 1 can also be raised, so that a tire change is possible. By means of the hoist valve arrangement 14 described in more detail below, the pressure force acting in the working range "pressing" can be limited to different values, this limit value being varied as a function of operating states described in more detail below.

FIG. 3 shows a circuit diagram of a rear lifting mechanism 2, which is controlled via a hoisting gear arrangement 14 according to the invention. This is accommodated in a disk-type housing and has a pressure port P, a tank port T and two working ports A, B. The pressure port P is connected via a pump line with a variable displacement pump 38, the discharge pressure in response to the highest, the consumers of the Tractor 1 applied load pressure is set. This load pressure is tapped at an LS connection. However, such a LS control is not a prerequisite for the system according to the invention.

The pressure port P is connected via an inlet channel 40 to an input port P ^{1 of} an individual pressure compensator 42 whose output port A 'is connected to an input port P ¹ ' of a continuously adjustable directional control valve 44. Its return port R is connected via a return passage 46 to the tank port T of Hub¬ works valve assembly 14. The directional control valve 44 has two working ports A ¹ 'and B ", which are connected via working ports 48, 50 to the two working ports A, B of the lifting gear valve assembly 14.

In each working channel 48, 50 a sink module 52, 54 is provided which serves in a basic position as a pilot-operated check valve for leak-free clamping of the lifting cylinder 6 of the rear lifting mechanism 2 and in FIG a control position which flows back from the lifting cylinder 6 the pressure medium volume flow in the sense of a flow control.

The working channel 50 can be connected to the tank connection T downstream of the sink module 54 via a pilot-controlled, proportionally adjustable pressure-limiting valve 56. The pressure in the other working channel 48 is limited by a secondary pressure relief valve 58. The lifting cylinder 6 is - as mentioned - double-acting ausge¬ leads, with an effective in the direction of "lowering" annular space 60 with the working port B and in the direction "lifting" effective pressure chamber 62 is connected to the working port A of Hubwerksventilanordnung 14. On the. Hubzy¬ cylinder 6 are pivotally mounted on a lifting shaft 64 mounted arm 66 and other coupling elements operated on which, for example, an attachment, such as a Drillma¬ machine or a plow 68 is grown.

Details of the Hubwerksventilanordnung 14 will be explained with reference to the enlarged view in Figure 4.

A pressure compensator piston 69 of the pressure compensator 42 is acted upon by a pressure compensator spring 70 and by the pressure in the opening direction tapped via a channel 72 by a load-signaling channel 74 connected to the LS connection and by the pressure in a control channel 76 in the closing direction, which is between the pressure compensator 42 and the directional control valve 44 branches off from the inlet channel 40. The LS channel 74 leads to a control connection LS '' of the directional control valve 44. This has two more control terminals X, the output side control terminals XA and XB are zugeord¬ net.

The actuation of the directional control valve 44 takes place via a pilot valve 78 or a pilot valve shown in FIG. Valve arrangement, which is formed in the illustration of Figure 4 by two electro-hydraulic VorSteuerelemente 75, 77. The triangle 19 indicates the pressure supply of these pilot control elements 77, 75. Via the pilot valve 78 or the pilot control elements 77, 75, control oil can each be fed to a control chamber of the directional control valve 44 until a valve slide 80 assumes a working position. This is detected by a position transducer 128. Once the position transducer 128, the desired position is reported, the pilot element 77, 75 is brought back into its neutral position. The position of the valve slide 80 is maintained in a regulated manner by the pilot elements 77, 75 being controlled in accordance with the signal of the displacement transducer 128. The pilot control elements 77, 75 are connected via control lines 82 and 84 to the pressure supply 79. The valve spool 80 is biased via a centering spring assembly 86 in its illustrated basic position (0), in which the LS channel 74 is connected to the tank channel 46 and all other vor¬ called connections are shut off.

The valve bodies of the two sink modules 52, 54 are each acted upon by a spring 88 and by the individual load pressure tapped at the outlet A ¹ 'or B' ¹ via pressure compensator ducts 90, 92 downstream of the directional control valve 44 into its basic position (a) the sink modules 52, 54 act as check valves, which allow a pressure medium flow to the terminals A, B. In the opening direction, the valve bodies of the sink modules 52, 54 are each acted upon by the control pressure applied to the connection XA or XB, which is tapped off via an unlocking channel 94, 96. This control pressure may correspond, for example, to the inlet pressure of the pilot valve arrangement 78. The structure of the Hubwerksventilanordnung with the indi- vidualdruckwaage 42, the continuously adjustable directional control valve 44 and the two downstream sink modules 52, 54 substantially corresponds to the conventional solution of the valve SB23 LS, so that in the consequence only the understanding of the invention essential elements are described and otherwise referred to in this regard on the existing state of the art for directional control valve SB23 LS.

If, for example, the lifting cylinder 6 is to be moved to lift the plow 68, then the valve slide 80 of the directional control valve 44 is displaced into one of its control positions designated by (b) via the pilot valve arrangement 78. Depending on the position, a metering orifice is opened, which is connected downstream of the individual pressure compensator 42. Depending on the orifice size, the pressure compensator 42 adjusts to a control position in which the pressure drop across the orifice plate is kept constant and thus a pressure medium flow rate independent of the load pressure is set. This pressure medium volume flow is regulated in the positions indicated by (b) via the pressure compensator 42, the pressure port P ¹ 'and the outlet port A ^? 'of the directional control valve 44 to the input terminal PDW of the sink module 52 and via its output connection ADW to the working connection A of the lifting valve arrangement 14 and from there into the bottom-side pressure chamber 62 - the lifting cylinder 6 extends. The pressure medium displaced from the annular space 60 flows via the working connection B of the lifting valve arrangement 14, the working duct 50, the outlet connection BDW and the input connection PDW of the sink module 54 to the connection B "of the directional control valve 44 and from there via the return connection R, the tank duct 46 and the tank connection T back to the tank. This return flow is made possible by the fact that the input pressure applied to the pilot valve arrangement 78 is transmitted via the control connection X and tapped off the output terminal XB of the directional control valve 44 and acted on the Entsperrkanal 96 the valve body in the opening direction, so that the sink module 54 unlocked and allows the backflow of the pressure medium to the tank T out. In these positions (b) of the sink module 54, this acts as a discharge pressure balance, via which the outflowing pressure medium volume flow is regulated to a certain extent.

For pressing on an attachment mounted on the lifting mechanism, the directional control valve 44 is displaced into one of its control positions marked (b), so that the supply of pressure medium via the lowering module 54 in its return function to the annular space 60 takes place the pressurized fluid flowing out of the bottom-side pressure chamber 62 flows via the unlocked drain module 52 and the directional control valve 44 to the tank. Unlocking takes place via the control pressure, which is routed via the control connections X, XA of the directional control valve 44 and the release valve 94 to the control surface of the sink module 52 which is effective in opening direction.

For load-free application, the directional control valve 44 is moved into its floating position (end position c) in which both sink modules 52, 54 are unlocked and moved into their through position marked with (b) and the working connections A, B and the control connection LS are connected to the tank connection T. and the input terminal P "is shut off.

In the work area "pressing" - as will be explained in more detail below - the maximum pressure in the working channel 50 is limited to a value of, for example, between 0 and 250 bar by suitably setting the proportionally adjustable directional control valve 44. Figure 5 shows a section through a valve disc, through which the Hubwerksventilanordnung 14 is realized. The valve disc has a disc-shaped housing 98, in which the pressure compensator 42, the directional control valve 44, the two sink modules 52, 54, the pilot valve 78, the secondary pressure relief valve 58 and the proportionally adjustable pressure relief valve 56 are integrated.

The valve disk 98 shown in FIG. 5 furthermore contains an emergency discharge valve 100 which is shown only schematically and can be actuated manually, by way of which the working conduits 48 and 50 can be connected to the tank T.

In the solution shown in FIG. 5, the emergency drain valve 100 is arranged in a connecting channel 102 between the working channels 48, 50. It has a ball 104, which is biased via an externally accessible grub screw 106 into a closed position in which a connection to the tank channel 46 and thus to the return port R is shut off. By releasing the grub screw 106, the previously clamped ball 104 is released and can therefore be brought by the higher pressure in the working channel 48 or 50 in an open position in which the connection to the tank channel 46 is opened - the Druckmit¬ tel can from the pressurized working channel 48th or 50 are drained.

Via the secondary pressure limiting valve 58, the pressure in the working channel 48 (port A) is limited to a maximum pressure set below the pump pressure. The construction of such secondary pressure limiting valves is known, so that further explanations are required. The structure of the pilot-operated proportional adjustable pressure relief valve 56 is known per se - a piston 108 of the pressure relief valve 56 is connected via a weak compression spring 110 and through the Pressure in the spring chamber against a valve seat loaded in a closed position. The pressure in the spring chamber is limited by the force applied to a closing cone 114 by means of a proportional magnet 112.

The control of the proportional magnet 112 takes place in the manner described below via the control unit 16.

The lifting and lowering modules 52, 54 also have a conventional construction, wherein a modulatory piston 116 is prestressed via a closing spring 118 into a closed position. The spring chamber of the closing spring 118 is acted upon by the pressure in the working channel 48 or 50 in the closed position of the module piston 116. In the bottom of the Modul¬ piston 116, a pilot valve body 120 is arranged, which is also biased by the closing spring 118 in its Schließ¬ position and thereby closes a pilot port. The pilot valve body 120 has a projection which can be brought into abutment against a Aufstσßkolben 122. This topping piston can be acted upon at the rear by the pressure at the control connection XA (XB), which can be tapped off via the directional control valve 54 and its connection X. That When the poppet piston 122 of the lowering module 52 or 54 is acted upon, the pilot valve body 120 is raised from its pilot seat against the force of the closing spring 118 - the modulo piston 116 is then pressure compensated and can be counterbalanced by the poppet piston 122 against the force of the closing spring 118 be lifted off his seat, so that pressure fluid from the working port A or B to the tank T can flow out.

The reference numerals 124, 126, 130, 132, 134 pressure sensors are referred to, via which the pressures in the working channels 48, 50, the pressure at the pressure port P, the load pressure and other pressures can be detected. The pilot valve 78 according to FIG. 5 is designed as a 4/3-way valve, its output connections being connected to the control lines 82 and 84, which are routed to the frontal control chambers 136 and 138, respectively, of the directional control valve 44. On the left in Figure 5 end face of the valve spool 80 of the directional control valve 44, a Wegaufneh¬ mer 128 is arranged, via which the valve spool stroke can be detected.

Since - as I said - the basic structure of the Hubwerksventil- arrangement 14 according to Figure 5 - apart from Druckbegren¬ relief valve 56, the emergency exhaust 106 and the positioning of the secondary pressure relief valve 58 and the Druck¬ sensors 124, 126, 130, 132, 134 - already from Be¬ known valve SB23 LS are known, can be omitted on the Be¬ description of further constructive details of vorbe¬ prescribed valve components.

To set the operating range "pressing", the pilot valve 78 is actuated so that in the Steuerräu¬ men 136, 138 acts a control pressure difference through which the valve spool 80 is shifted from the spring-biased home position shown in Figure 5 to the left, so that pressure fluid from the pressure port P, via the pressure compensator 42, the branching input port P ¹ 'of the directional control valve 44, the outlet port B'', which is in its check valve opening Senken¬ module 54 and the working channel 50 to the working port B and from there to the annular space 60 is promoted. The pressure medium displaced from the bottom-side pressure chamber 62 is returned to the tank T via the working port A, the drain module 52 unlocked in the manner described above, the port A ¹ 'of the directional control valve 44, the tank passage 46 and the return port R. The maximum contact pressure can be set by suitably setting the pressure limit. 56 limited to a depending on the attached implement or depending on the task to the rear link 2 predetermined value.

According to FIG. 4, the pressure-limiting valve 56 can be preceded or followed by a switching valve 140 which can be moved into a throttle position via a magnet, so that the pressure medium can not flow out to the tank via the pressure-limiting valve 56. The switching valve 140 is actuated when the contact pressure is to be set to a value which is above the value which can be set on the pressure limiting valve 56 (for example when changing tires).

In the following, the control concept of Hubwerksan¬ control is explained based on different operating conditions.

As a rule, the rear linkage is operated double-acting. The pressure sensors 124, 126, 130, 132, 134 enable a position / tension control, but the function is also guaranteed without this pressure detection, since a protection in the working range "pressing" via the pressure limiting valve 56 is possible. When using the expansion stage shown in Figure 5 with pressure sensors 124, 126, 130, 132, 134 of Auflage¬ pressure / relief pressure can be controlled via the pressure sensors. The protection in the working area "pressing" then takes place again via the pressure limiting valve 56, this then being automatically adjustable as a function of the bearing / relief pressure. The basic concept of the control according to the invention will be explained with reference to the expansion stage without pressure sensors shown in FIG. 3 - this basic concept is also applicable to the expansion stage illustrated in FIG. 5, the essential difference to the solutions without pressure sensors therein is that the adjustment of the pressure relief valve 56 in response to the set contact pressure, which is to be controlled via the pressure control means of Drucksen¬ sensors. As will be explained below, both expansion stages make it possible to operate the rear lift both double-acting and single-acting.

1. Basic function

Let it be assumed that the rear lift 2 is to be operated in the working region "pressing" (see FIG. 2) in order, for example, to feed in a plow. By adjusting the rear operating device 20 or another operating element, the driver generates an actuating signal via which the directional control valve 44 is displaced to the left in one of its lowering positions (b) (FIG. 4). At the same time, the maximum contact pressure in the working channel 50 is limited by suitable adjustment of the pressure limiting valve 56. This maximum pad pressure may vary depending on the attached implement - or as described below - depending on certain operating conditions. It is assumed that the pressure relief valve 56 is set to a pressure of 50 bar. The pressure medium volume flow is conveyed via the working port B into the annular space 60 of the Hubzy¬ Linders 6 and returned from the bottom pressure chamber 62 via the controlled drain module 52 and the Wegeven¬ til 44 to the tank T - the Heckhubwerk 2 is lowered and retracted, for example, the plow. This lowering takes place according to the regulation which is input via the control unit 16, for example a position control. Upon reaching a predetermined maximum contact pressure - ie when exceeding the set maximum pressure of for example 50 bar in the working channel 50, opens the pressure relief valve 56 and the pressure medium flows no longer via the working port B to the lifting cylinder 6 but from the tank T down - the Heckhubwerk 2 stops, the control unit 20 is still set to "sinks". From the "stopping" of the Heckhubwerks 2, the driver detects the achievement of the desired, preset contact pressure (50 bar) - the directional control valve 44 can also be switched neutral, so that this set, non-regulated pressure is maintained. Since this pressure can vary due to unevenness in the ground, etc. or due to external forces, motion monitoring (motion control) is performed in the working range "pressing". This control concept will be explained with reference to FIG.

The system is initially in the idle state according to FIG. 6, ie the driver has not yet switched over to the "sinks" work area. After switching to lowering, the path and time intervals for motion monitoring are calculated first. For this purpose, there are a variety of possibilities, with only two methods were selected by way of example. In the solution shown in FIG. 6, the expected normal stroke speed v is first determined via a control map stored in the memory of the control unit 16 on the basis of the control signal output by the control unit 16 to the directional control valve 44 or the pilot valve 78. A further characteristic diagram is used to calculate a suitable path interval dw from this hoist speed v. From the quotient dw / v, a monitoring time interval dt is then determined. The aforementioned maps are tuned so that in the main work area "pressing" a possible constant path interval dw of about 1/30 of the total stroke results. As long as during the calculated time interval the ascertained path carries at least about 90% of the aforementioned travel interval (1/30 of the total travel), the control recognizes that the rear lift 2 is still lowered. If this moves during the time interval by less than 10% of the calculated path interval (1/30 of the total stroke), the controller recognizes that the rear lift 2 "stops" - the directional control valve 44 is moved to its neutral position (0). posed.

In the case in which, furthermore, a sink setpoint signal is applied by the electrohydraulic hoist control

(Desired position not yet reached) and - as described above - the lowering movement is switched off

(Directional control valve 44) in neutral position (O)) is switched to a motion monitoring mode. For this purpose, a "pressure measurement" is carried out during a predetermined time interval, which does not have to be identical to the time interval described above for detecting the "stop" state. For this purpose, the directional control valve 44 is again moved to one of its "sinks" position (b), i. , it is activated a lowering movement over a fixed ramp to make the "measure pressure". As a result, the rear lifting mechanism 2 is lowered and can adapt to the current floor situation. After this lowering movement, the directional control valve 44 is returned to the neutral position (0) - the monitoring is carried out until the lowering signal has been withdrawn via the operating device 20.

In the case where a hoist movement upwards due to external forces (for example Überfah ren ren a bump, the above-described renewed lowering movement is started immediately after the occurrence of this upward hoist movement, which are independent of the set time interval (for example, 5 seconds) After the sinking signal has been withdrawn, the system is again in its rest state shown on the left in FIG. In the above-described control concept, the time and distance intervals are determined from characteristic fields. In a simplified solution, instead of this relatively complicated method for determining the time / distance intervals from characteristic fields, the hoist speed can also be used, which is detected anyway in the context of the electrohydraulic control (for example via the sensor 30). A "stop" of the Heckhubwerks 2 is then detected when the lowering speed falls below a Mindestgeschwin¬ speed during a predetermined time interval. This means that instead of the travel interval, the hoist speed is evaluated directly.

2. Single-acting function of the rear lift

As mentioned, the Heckhubwerk can also be operated single acting. For this purpose, the pressure of the pressure limiting valve 56 is set to a minimum value, for example 5 to 8 bar, so that a minimum pressure is set at the working connection B and thus in the annular space 60 of the lifting cylinder 6. If a lowering signal is now output via the electrohydraulic hoist control (EHR) and the above-described motion monitoring is activated, since the actual travel change of the hoisting gear (lifting shaft angle) is less than 10% of the expected travel change per unit time (or the hoisting gear speed below) the limit value is), so the directional control valve 44 is not adjusted as in the double-acting function in the neutral position (0) but in the floating position (c) - the hoist can adapt to any unevenness of the soil. The set behavior corresponds to that of conventional single-acting lifting gear valves. 3. Fast entry

To actuate the fast retraction, a quick-entry switch is actuated, so that the rear lifting mechanism is lowered by double action at maximum speed until the support pressure set on the pressure limiting valve 56 has been reached. When this contact pressure is reached, in contrast to the basic function described above, the directional control valve 44 is not switched to its neutral position (0), but remains in its lowering position 8b), so that the rear lifting mechanism 2 can immediately follow a further lowering movement.

In the event that the driver operates the quick-entry switch for a longer period of time (longer than, for example, 10 seconds) and the rear lift 6 stops during this time, the directional control valve 44 is moved into its neutral position (0) in order to avoid unnecessary pressure medium heating to avoid.

During operation in the lowering direction, the pump of the working hydraulics may be in the saturation region, i. Under certain circumstances, no other consumer can be actuated.

4. Tailgate

When the return button 24 (FIG. 1) is actuated, the pressure-limiting valve is-preferably automatically-adjusted to a comparatively low pressure of, for example, 5 bar. In this case, the stroke of the stern lifting mechanism 2 takes place with a defined load-compensated speed, wherein the speed can be increased in accordance with a ramp, depending on the way. In this operating mode is a sensitive coupling / uncoupling attachments possible. The empty hoist can be lowered quickly.

5. Lift the tractor

As explained in the introduction, it is desirable, for example, to change the tire, lift the tractor rear axle on the Heckhubwerk 2, so that the tractor 1 is on the oscillating front axle and a possibly not stable attachment, so that there is a significant risk of tipping. In order to reduce this, the maximum inflation pressure is limited to a comparatively low pressure, for example 50 bar - a tire change is then not possible without further ado.

To change tires, the pressure of the pressure limiting valve 56 must be increased, whereby this mode can be set only after a few queries, so that there is a deliberate operator restriction. Based on these safety queries can be checked, for example, whether the handbrake is tightened, the required pressure on the pressure relief valve (250 bar) is set or the switching valve 140 is moved to its blocking position, if the maximum pressure of the pressure limiting valve 56 is not sufficient (50 bar).

By means of the above-described control concepts in cooperation with the hoist valve arrangement, the rear hoist 2 can be controlled with high precision and operational reliability in the "pressure" working area with very low control engineering and device technical expenditure.

Instead of the above-described adjustable Druckbe¬ delimitation valve 56 can also be a fixed Pressure limiting valve can be used, which, however, a loss of comfort is associated.

Disclosed is a Hubwerksventilanordnung for An¬ control of a double-acting hoist or an attachment with a continuously adjustable directional control valve and an individual pressure compensator, via which a pressure medium volume flow to and from a lifting cylinder of the hoist is controlled. In the pressure medium flow path between an output port of the directional control valve and a working port of the Hubwerksventilanordnung a proportionally adjustable pressure limiting valve is provided, via which the pressure in this area is be¬ limited to a maximum value. The adjustment of the pressure limiting valve preferably takes place as a function of the operating states of the lifting mechanism or the type of attachment.

LIST OF REFERENCE NUMBERS

1 tractor

2 rear lift

4 front lift

6 lifting cylinders

8 lifting cylinders

10 control block

12 pump

14 Hubwerksventilanordnung

16 control unit

18 HMI device

20 HMI device

22 cabin

24 rear push button

26 pressure sensor

28 speed sensor

30 position sensor

32 force sensor

34 speed sensor

36 attachment

38 variable displacement pump

40 inlet channel

42 pressure balance

44 way valve

46 tank channel

48 working channel

50 working channel

52 lowering module

54 lowering module

56 pressure relief valve

58 secondary pressure limiting valve1

60 annulus

62 pressure chamber 4 lifting shaft poor

attachment

Pressure regulator piston

Compensator spring

channel

LS-channel

pilot element

control channel

Vorsteuere1ement

Pilot valve assembly

Control oil supply

Venti1schieber

control line

Return spring arrangement

feather

Pressure balance channel

Entsperrkanal

valve disc

emergency discharge valve

connecting channel

Bullet

Madensehraube

piston

compression spring

proportional solenoid

closing cone

module piston

closing spring

Pilot valve body

topping

pressure sensor

transducer 130 pressure sensor

132 pressure sensor

134 pressure sensor

136 control room

138 control room

140 switching valve

Claims

claims

1. Hubwerksventilanordnung for controlling a dop¬ peltwirkenden hoist (2, 4) or an attachment of in particular an agricultural Nutzfahr¬ convincing, with a continuously adjustable, a Zumess¬ aperture forming directional control valve (44) associated with a individual dual pressure balance (42) via which a pressure medium volume flow to a working port (A, B), flows, via another working port

(A, B) flows back via the directional control valve (44) to a low-pressure or tank connection (T), and with a pressure relief valve, which in a working line (48, 50) between the directional control valve (44) and the working connection ( A, B) is arranged, characterized in that the Druckbegrenzungsven¬ til (56) - is preferably adjustable - adjustable, so that the pressure in the Arbeitslei¬ device (38, 50) depending on different operating conditions to different maximum values can be limited ,

2. Hubwerksventilanordnung according to claim 1, wherein the pressure limiting valve (56) in the working direction with a "depressions" effective pressure chamber (60) of Hub¬ plant (2, 4) or the attachment Ar¬ beitsleitung (50) is arranged.

3. Hubwerksventilanordnung according to claim 1 or 2, wherein the pressure limiting valve (56) is adjustable to values between 0 and 250 bar.

4. Hubwerksventilanordnung according to any one of the preceding claims, wherein the maximum pressure in dependency of different setpoint value bern / operating parts (18, 20, 24) can be adjusted ein¬ different.

5. Hubwerksventilanordnung according to claim 1 or 2, comprising a control device (16) via which the directional control valve (44) after response of the pressure relief valve (56) in a neutral position (0) or a floating position (c) is adjustable.

6. Hubwerksventilanordnung according to any one of the preceding claims, wherein in the other working line (48) a secondary pressure limiting valve (58) is angeord¬ net.

7. Hubwerksventilanordnung according to any one of the preceding claims, wherein in the working lines (48, 50) in each case a lowering module (52, 54) is arranged for leaking oil-free shut-off of the pressure medium.

8. Hubwerksventilanordnung according to claim 7, wherein the sink module (52, 54) aus¬ forms as a discharge pressure balance, which is adjustable by a control pressure in a Durch¬ flow position.

9. Hubwerksventilanordnung according to any one of the preceding claims, wherein the individual pressure compensator (42) upstream of the directional control valve (44) and in Öff¬ tion of the highest load pressure (LS) and the force of a pressure compensator spring (70) and in Schließrich¬ direction of the pressure upstream of Directional valve (44) be¬ aufschlagt.

10. Hubwerksventilanordnung according to any one of the preceding claims, with a manually operable emergency drain (100) via which a connection of the pressure working line (48, 50) with the tank T can be controlled.

11. Hubwerksventilanordnung according to any one of the preceding claims, wherein the hoist is a Heckhubwerk (2) or a front lift of a tractor (1).

12. Hubwerksventilanordnung according to any one of the preceding claims with a pressure limiting valve (56) upstream switching valve (140).