EP1496009A1 - Hydraulic suspension - Google Patents

Abstract

Hydraulic spring, especially for a cantilever arm, has at least a hydraulic cylinder (10) with chambers (14, 16), a control valve (22) that is connected to at least one of the chambers via a hydraulic line (18, 20) and provides a connection to a hydraulic oil pump (30) and tank (28). Linking the two chambers is a connection line (40). A control unit (54) monitors and regulates the position of the cylinder piston using a sensor (50) and a pressure limiting unit (44) connected to the connection line.

Description

Hydraulic suspension, especially for a boom of a Loader vehicle, with at least one hydraulic cylinder, which has at least one chamber, a control valve, which via at least one hydraulic line with the at least one Chamber is connected and which optionally a connection to a hydraulic oil pump and a hydraulic oil tank manufactures, and a connection line.

Tractors with front loaders, as well as wheel loaders, telescopic loaders, Crane vehicles and similar land vehicles are used after current state of the art with suspension / damping systems provided, consisting of one or more gas-filled Hydraulic accumulators are made, depending on your needs with a hydraulic lifting cylinder of a respective boom connected Be aware of the effects of vibrations from the boom to dampen a vehicle chassis and vice versa. One speaks in this connection of "passive" suspension systems. The disadvantage is that passive suspension systems in usually subject to a constant suspension characteristic and thus in their suspension characteristics not on one the lifting cylinder or boom load acting variable react. A load-dependent variably responsive suspension can usually only by means of hydraulic accumulators consuming nozzle and valve arrangements can be achieved.

An example of such a passive suspension system is disclosed in DE 42 21 943 C2. This is a hydraulic system for a mobile equipped with implements Work machine with one from at least one hydraulic accumulator existing load suspension system proposed. To the variable Alignment of the load pressure of the hydraulic accumulator to the respective load pressure of a lift cylinder is at least one Nozzle in conjunction with multiple directional valves between the Load suspension system and the lifting cylinder provided. This System is complex and space consuming.

"Active" vibration damping has been around for several years Heckkrafthebern known on agricultural tractors. These "active" damping systems measure the loads that to act on the vehicle due to vibrations and adjust the loads according to the lifting cylinder one Krafthebers such that the exciting vibrations what counteracts the stimulating vibrations weakens. Since the power lift from the hydraulic system depending on Load condition is actively raised and lowered, speaks one of an "active" vibration damping.

An "active" vibration damping system is described in DE 100 46 546 A1 discloses. This is a large manipulator with Vibration damper proposed, the means of damping mechanical vibrations in a articulated mast of a Concrete pump system has. The vibration damper changed the pressures in the individual hydraulic cylinders of the articulated mast of the concrete pump system such that the tail from the the liquid concrete flows relatively quietly in its position stands. The vibration damping system is very complex because every hydraulic cylinder with two pressure sensors as well as each Articulated joint must be equipped with a rotation angle sensor. Furthermore, a very complex control algorithm is used, that for the active suspension of a boom of a Charging vehicle is unsuitable.

DE 100 06 908 A1 discloses an agricultural Work machine, with the front a telescopic Boom is connected. This boom is from a hydraulic piston-cylinder unit raised or lowered. To realize a preselectable support force for a from Boom taken attachment is a Hydraulic circuit proposed, which is a releasable Seat valve and an adjustable pressure control valve has, so that in a piston bottom side cylinder space a constant pressure is maintained and that Attachment always with one and the same bearing force on the Floor rests, regardless of whether the floor is level or uneven. The disadvantage is that the proposed hydraulic circuit only to a predeterminable Pressure limiting designed and thus in the form not for one active suspension system is suitable.

The object underlying the invention is seen therein a hydraulic suspension of the type mentioned indicate that overcomes the aforementioned problems become. In particular, an active suspension is created which are based on the load conditions of a cantilever of a loader vehicle reacts variably.

The object is achieved by the teaching of Patent claim 1 solved. Further advantageous embodiments and further developments of the invention will become apparent from the dependent claims out.

According to the invention, a hydraulic suspension of the above mentioned type, in which a control unit and a contain the position of the hydraulic cylinder indicating sensor is and in which the connecting line is a function of Sensor signal has controllable pressure limiting unit. at The hydraulic cylinder can be a double-acting or act to a single-acting hydraulic cylinder. The suspension system according to the invention is therefore arbitrary Hydraulic cylinder can be used. The invention Suspension system is, for example, in a Telescopic cylinder used, whose individual telescope segments enclose a pressurizable chamber. By Pressurization of this chamber, the individual Telescopic segments of the hydraulic cylinder are extended. Based on the sensor signal-dependent control according to the invention the pressure limit is the pressure in the chamber or in the Chambers of the hydraulic cylinder regulated so that at a Deflection of the hydraulic piston from an original position the Deflection movement dampened by the regulated pressure limitation is and the hydraulic piston back to its original position is moved. This creates a suspension system which load-independent on the deflection of the hydraulic piston and can respond to the deflection of the boom. Regardless of the height of a load of the boom can use it active and optimized for the load condition Deflection movements of the boom, caused by dynamic Forces (e.g., shock or acceleration forces) become.

In a preferred embodiment of the invention connects the Connecting the at least one chamber with the Hydraulic oil tank. This is especially useful when it is is single-acting hydraulic cylinder. The least a hydraulic line, which the at least one chamber with connects to the control valve, provides for a single-acting Hydraulic cylinder is a stroke-side hydraulic line dar a pressure increase in the pressure chamber of the single-acting Hydraulic cylinder, for example, caused by a Impact or sudden movement of the hydraulic piston increases the hydraulic oil pressure in the connection line such that the controllable pressure relief unit opens and excess Hydraulic oil drain into the hydraulic oil tank and the Retracting or compressing hydraulic piston can. simultaneously a sensor signal is registered by the control unit, which leads to an altered pressure limitation in the controllable Pressure limiting unit performs, so that the pressure limiting unit closes again and from the hydraulic oil pump Subsequent hydraulic oil will increase the hydraulic piston again leaves.

In a further particularly preferred embodiment of the Invention, the hydraulic cylinder has a stroke side and a vertical chamber on. In such a double-acting Hydraulic cylinders are the two chambers over the Connecting line connected to each other. Furthermore, here is each chamber via a hydraulic line to the control valve connected. The control valve is designed such that one of the hydraulic lines connected to the hydraulic oil tank is when a hydraulic oil flow from the hydraulic oil pump in the other chamber takes place. At a pressure increase in one of the chambers of the double-acting hydraulic cylinder, for example, caused by a shock or sudden Movement of the hydraulic piston, the hydraulic oil pressure rises in the connection line such that the controllable Pressure limiting unit opens and excess hydraulic oil in the hydraulic oil tank or in the corresponding other chamber drain and the hydraulic piston on or extend or on or can rebound. At the same time, the control unit registered a sensor signal, which changed to a Pressure limitation in the controllable pressure limiting unit leads, so that the pressure limiting unit closes again and from the hydraulic oil pump nachfließendes hydraulic oil Hydraulic piston can rise or fall again.

In a particularly preferred embodiment of the invention the connecting line contains a first shut-off valve, with which by opening and closing the hydraulic suspension can be activated or deactivated. Will the first check valve opened and the control valve switched to a stroke position, then there is a constantly circulating volume flow, the starting from the hydraulic oil pump through the control valve via the lift-side line to the lift-side chamber, via the Connecting line through the pressure limiting unit and through the check valve, to the lower side chamber and over the vertical line through the control valve flows into the tank. Analogously, this turns out to be one-sided Hydraulic cylinder a constantly circulating flow, the starting from the hydraulic oil pump through the control valve via the hydraulic line into the chamber and over the Connecting line through the pressure limiting unit and through the check valve flows into the tank. The sensor supplies too Beginning a position signal for the hydraulic piston, which as to be observed reference value (setpoint) from the control unit is registered. Now changes the position of the Hydraulic piston due to a change in position of the boom (The boom is raised by an external force or lowered) is based on a by the Control unit generated control signal in response to the currently tapped sensor signal (actual value) the Pressure limiting unit controlled by the control unit or regulated. By increasing or decreasing the pressure through the Pressure limiting unit, the pressure in the chamber changes or in the chambers of the hydraulic cylinder such that the Position of the hydraulic piston is changed until the original position of the hydraulic piston sets again or the difference between sensor signal and reference variable equal to or below a predefinable threshold lies. The resulting dynamics in the control process leads to a damping of the movement of the hydraulic piston by a the movement counteracting the pressure build-up. Will be the first Lock valve closed, then no more hydraulic oil circulate, causing a pressure in the lifting chamber or in the chamber of the single-acting hydraulic cylinder builds up, which raises the hydraulic piston. Similarly builds with a double-acting hydraulic cylinder closed first check valve, a pressure in the lower side Chamber on when the control valve in a lowered position is switched.

In a further preferred embodiment of the invention contains the connecting line, preferably in double-acting hydraulic cylinders in the direction of the stroke-side chamber closing check valve. The check valve may be required if z. B. no check valve is contained in the connecting line. Since individual pressure limiting units, such as throttles or orifices, are permeable in both directions or seal leak-free other pressure limiting units in one direction, they can be secured by a check valve, so that no oil feed can take place in the connecting line from the lower-side chamber to the hubseitigen chamber.
In a further preferred embodiment of the invention, the pressure limiting unit is a controllable, preferably electrically adjustable pressure relief valve. Upon reaching a limit pressure on a stroke side of the hydraulic system, which is determined by the control position of the controllable pressure limiting valve, the pressure relief valve opens, so that the pressure on the lift side of the hydraulic system can drop. As soon as the limit pressure is undershot, the pressure relief valve closes again, so that the pressure on the lift side of the hydraulic system can rise again. By appropriate control positions of the pressure relief valve, the limit pressure can be varied or regulated by the control unit and thus the position of the hydraulic piston can be changed.

In a further preferred embodiment of the invention the pressure limiting unit an adjustable or controllable Throttle. Similar to opening and closing the Pressure relief valve is at the adjustable or controllable throttle the passage cross-section of the throttle the control unit increases or decreases. As a result This regulation drops the pressure on the lifting side of the Hydraulic arrangement from or increases the pressure, so that As a result, the position of the hydraulic piston is variable. When adjustable throttle is here, for example, a diaphragm, a adjustable flow control valve or another controllable or adjustable means for controlling the flow area considered.

In a further preferred embodiment of the invention the control valve has a closed position. In the Closed position is closed when the first check valve Hydraulic piston held in position. When open first check valve is for a double-acting Hydraulic cylinder realized a floating position in which the Hydraulic piston by external forces in its position changeable is or the boom by a on the hydraulic piston acting force can be lowered or raised.

In a further preferred embodiment of the invention arranged in the lift-side line a load-holding valve. The Load-holding valve provides a safety function and ensures a controlled lowering of the boom in one Accident, such as at a pipe break the lift side Management.

In a further particularly preferred embodiment of the Invention is between hydraulic pump and control valve one provided with a pressure relief valve and with the tank in Compound pressure limiting line arranged. at closed control valve is thereby ensured that at weiterfördernder hydraulic pump, the hydraulic oil in the Tank is routed and a circulation of hydraulic oil is maintained. The pressure oil supply can For example, done by a constant pump, with a Pressure limitation by the pressure limiting line and the Pressure relief valve is ensured. In place of one Pressure oil supply by a constant pump is also a Pressure oil supply by means of a variable conceivable, the Frame of a hydraulic load-sense system is controlled.

In a further preferred embodiment of the invention the control unit regulates the controllable pressure limiting unit depending on a change from the variable Sensor signal and a setpoint signal resulting Differential signal, wherein the setpoint signal to the sensor signal at Activation of the hydraulic suspension corresponds and the Difference signal reaches a predetermined threshold. By Opening the first shut-off valve is not closed Control valve, the suspension activated and the reference variable or the setpoint based on the signal supplied by the sensor certainly. When changing the position of the hydraulic piston is determined on the basis of the continuously tapped sensor signal (actual value) a difference value to the setpoint determined. In dependence of the control unit generates the difference value Control signal or a manipulated variable for the controllable Pressure control unit. A regulation is only here performed when the difference value is a preset Threshold reached. This threshold can also be zero amount, which would mean that the scheme already at lowest deviations between setpoint and actual value intervenes.

If the suspension is activated, an actuation of the Control valve by the operator and thereby becomes a Change the position of the hydraulic piston causes, is this additionally signals the control unit. The new Position of the hydraulic piston is then used as a measure of the new setpoint for generating the control signal used. This will ensure that too activated suspension, a retraction and retraction of the Hydraulic piston is possible or that when activated suspension and actuation of the control valve sends a signal to the Control unit goes out, by which an adjustment of the Cantilever can be taken into account so that a "newer" Setpoint is set when while suspension is activated a desired adjustment of the boom takes place.

In a further preferred embodiment of the invention, especially for double-acting hydraulic cylinders, is a second vertical line with a second check valve containing the vertical chamber with the tank combines. This embodiment of the invention provides a Demand-driven hydraulic suspension is because here the control valve is in a closed position and only opened when needed. The hydraulic suspension is active with the first and second shut-off valves open. Of Further is as a controllable pressure limiting unit the adjustable pressure relief valve used. Join one now Position change of the hydraulic piston such that the Hydraulic piston sinks, hydraulic oil can over the second Drain the vertical pipe to the tank. At the same time from the control unit generates a control signal, whereupon the control valve is opened and hydraulic oil for lifting the Hydraulic piston can flow. Once the original one Position is reached again, enters the control unit Signal to close the control valve off.

In a further preferred embodiment of the invention the hydraulic cylinder contains means for measuring load, in particular a pressure sensor. A load measurement, for example, arranged by a hydraulic piston Pressure sensor allows the use of a variable throttle Place the controllable pressure relief valve demand-controlled hydraulic suspension. The Stress measurement may be needed to help with this closed control valve no hydraulic oil on the first and second check valve can drain and only when it reaches a specifiable limit pressure in one of the two chambers the first and second check valve are opened. Such a Boundary pressure is reached when, for example, a shock on the Cantilever acts and spring the hydraulic piston or should rebound. The load measuring device signals the Control unit, a limit pressure signal, whereupon the check valves be opened. As a result, the hydraulic piston will ever lowered or raised in the direction of impact, whereupon the Control unit generates a control signal, the controllable Throttle controls and the control valve opens so that Hydraulic oil can flow and the hydraulic piston its original position resumes. Will the original Reached position, the check valves and the Control valve closed.

A hydraulic suspension according to the invention can be particularly advantageous on different types of boom vehicles, such as B. wheel loader, backhoe loader, telescopic loader, skid steer loader or on tractors with front loaders and the like be used. Other uses are z. B. at mowing tables of harvesters such as combine harvesters and Shredders.

Furthermore, it has an advantageous effect that such hydraulic suspension in conjunction with hydraulic Cylinders can be used with so-called Load holding valves are designed without the function of Override load holding valves. With that you can existing safety standards are preserved.

Furthermore, the volume flow supply normal, already on Vehicle existing control valves (lifting and lowering of the Cantilever) can be used. Own normal control valves a certain positive overlap to the valve spool to get a leak pouch. Such valves can in the Stationary hydraulics in the realization of control systems often not used, because the positive coverage during the changeover from work connection A to B due to construction Dead times leads to the construction of a control algorithm considerably more difficult or even preventable. For this Reason is usually set in the stationary hydraulics so-called servo valves, which have a low to no Have zero coverage and are very expensive and prone to failure.

As compared to passive suspension systems fewer parts or Components are required, an inventive hydraulic suspension can be designed more cost-effective, as well as on conventional components without special Valve development be resorted to.

The installation space for an active suspension system according to the invention is much smaller than passive suspension systems because For example, no voluminous hydraulic accumulator needed become.

Reference to the drawing, the several embodiments of the Invention shows, the invention and others Advantages and advantageous developments and refinements the invention described and explained.

Fig. 1

einen erfindungsgemäßen Hydraulik-Schaltplan mit ständig umfließendem Volumenstrom und regelbarem Druckbegrenzungsventil,

Fig. 2

einen erfindungsgemäßen Hydraulik-Schaltplan mit ständig umfließendem Volumenstrom und verstellbarer Drossel,

Fig. 3

einen erfindungsgemäßen Hydraulik-Schaltplan mit bei Bedarf fließendem Volumenstrom und regelbarem Druckbegrenzungsventil und

Fig. 4

einen erfindungsgemäßen Hydraulik-Schaltplan mit bei Bedarf fließendem Volumenstrom und verstellbarer Drossel,

Fig. 5

einen erfindungsgemäßen Hydraulik-Schaltplan gemäß Figur 1 ohne ein erstes Sperrventil,

Fig. 6

einen erfindungsgemäßen Hydraulik-Schaltplan gemäß Figur 1 mit einem Rückschlagventil anstelle des Sperrventils,

Fig. 7

einen erfindungsgemäßen Hydraulik-Schaltplan gemäß Figur 2 mit einem Rückschlagventil anstelle des Sperrventils,

Fig. 8

einen erfindungsgemäßen Hydraulik-Schaltplan mit ständig umfließendem Volumenstrom und regelbarem Druckbegrenzungsventil für einen einfach wirkenden Hydraulikzylinder und

Fig. 9

einen erfindungsgemäßen Hydraulik-Schaltplan gemäß Figur 8 für einen Teleskopzylinder.

It shows:

Fig. 1

a hydraulic circuit diagram according to the invention with continuously circulating flow and adjustable pressure relief valve,

Fig. 2

a hydraulic circuit diagram according to the invention with constantly flowing volume flow and adjustable throttle,

Fig. 3

a hydraulic circuit diagram according to the invention with if necessary flowing flow and adjustable pressure relief valve and

Fig. 4

a hydraulic circuit diagram according to the invention with, if necessary, flowing volume flow and adjustable throttle,

Fig. 5

1 a hydraulic circuit diagram according to the invention according to FIG. 1 without a first shut-off valve,

Fig. 6

1 shows a hydraulic circuit diagram according to the invention according to FIG. 1 with a check valve instead of the check valve,

Fig. 7

2 shows a hydraulic circuit diagram according to the invention according to FIG. 2 with a check valve instead of the check valve;

Fig. 8

a hydraulic circuit diagram according to the invention with constantly flowing volume flow and adjustable pressure relief valve for a single-acting hydraulic cylinder and

Fig. 9

a hydraulic circuit diagram according to the invention according to Figure 8 for a telescopic cylinder.

FIG. 1 shows a hydraulic cylinder 10 with a Hydraulic piston 12, which is used to raise and lower a boom a loader vehicle (both not shown) is used. Of the Hydraulic cylinder 10 has a stroke-side chamber 14 and a lowering chamber 16 on. The lift-side chamber 14 is over a lift-side hydraulic line 18 and the lower-side chamber 16 via a vertical hydraulic line 20 with a electrically switchable control valve 22 is connected.

The control valve 22 is via a drain line 24 and over a pressure limiting line 26 with a hydraulic oil tank 28th connected. A hydraulic oil pump 30 delivers hydraulic oil the control valve 22 in the respective hydraulic lines 18, 20th

The control valve 22 is switchable in three positions, in one Closed position, in which no flow for both Hydraulic lines 18, 20 takes place, a stroke position, in the lift-side hydraulic line 18 with hydraulic oil is supplied, wherein the vertical-side hydraulic line 20 Hydraulic oil to the hydraulic tank 28 delivers, and a Senkstellung in which the vertical hydraulic line 20 with Hydraulic oil is supplied, the hub side Hydraulic line 18 Hydraulic oil to the hydraulic tank 28th emits.

The pressure limiting line 26 includes a pressure relief valve 32, which opens upon reaching a limit pressure and a flow from the hydraulic oil pump 30 to Hydraulic oil tank 28 allows. The hydraulic oil pump 30 can in this way, even when the control valve 22 is closed Promote hydraulic oil.

The lift-side hydraulic line 18 includes a load-holding valve 34, which via a bypass line 36 a hydraulic oil flow in the direction of the hydraulic cylinder 10 permits. about Control lines 38, the load-holding valve in case of overload in Direction of the hydraulic oil tank 28 is opened, so that a Hydraulic oil flow to the hydraulic oil tank 28 may take place.

Between the lift side and the lower side hydraulic line 18, 20 is a connecting line 40 is arranged, which a electrically switchable first check valve 42 contains. The first check valve includes a blocking position in which in both Directions no flow takes place and one Open position, in which a flow in both directions is possible. Furthermore, the connection line contains 40 a controllable pressure relief valve 44, which via a Control line 46 in the direction of the vertical hydraulic line 20 opens. The control pressure to open the Pressure relief valve can be controlled by a regulator 48 become.

Furthermore, a position sensor 50 with a piston rod 52 connected to the hydraulic cylinder 10 and provides a the Position of the hydraulic piston 12 reproducing sensor signal to a control unit 54. The control unit 54 is provided with a Switching device 56 is connected, via which the control unit 54 and thus the hydraulic suspension can be activated.

According to Figure 1, the hydraulic active suspension with a constantly flowing volume flow realized. This is the Control unit 54 activated via the switching device 56, wherein the control unit 54, the first check valve 42 opens and the control valve 22 switches to the stroke position. The Hydraulic oil pump 30 delivers the hydraulic oil through the Control valve 22 and the load-holding valve 34 for Hydraulic cylinder 10 of the boom. There is a build up certain pressure, which by means of the controllable Pressure limiting valve 44 is set. As soon as a Adjusted pressure balance, takes the hydraulic piston 12 a certain position, with excess, from the Hydraulic oil pump delivered hydraulic oil over the Pressure limiting valve 44 and the first check valve 42nd flows to the hydraulic tank.

The basic operating principle is that the pressure on the stroke side of the hydraulic cylinder 10 thereby controlled is that a certain inflow of hydraulic oil to the lift side controlled to the hydraulic tank 28 can drain again. Of the Pressure is generated such that the hydraulic oil only against a certain resistance, which by the Pressure limiting valve 44 is specified to the hydraulic tank 28 can flow, this pressure is so high that he has a Load acting on the hydraulic cylinder 10, can counteract.

So that the volume flow can flow, the check valve 42 must be switched to its open position. If this is not the case, a pressure builds up on the lifting side of the hydraulic cylinder 10 and thus in the lifting-side chamber 14, which extends the piston and thus causes the boom to rise.
About the controllable pressure relief valve 44, the pressure which is to prevail on the stroke side of the hydraulic cylinder 10, adjusted as needed by the control unit 54.

The position of the boom or the position of the piston rod 52 and the hydraulic piston 12 is via the position sensor 50 constantly measured and serves as a controlled variable (actual value) for Adjusting the pressure on the lifting side of the hydraulic cylinder 10. This position can be measured in different ways Way. One possibility is shown in FIG. 1, in which the Position of the piston rod 52 is tapped. Also also suitable would be the lifting angle of the boom.

Upon activation of the control unit 54, the control activated and the original position of the boom as to be observed reference variable (setpoint) held. The Control unit 54 determined via an integrated processor (not shown) from the reference variable and the current, measured control variable (actual value) the deviation (Control difference) from each other to on this basis the Adjustment of the pressure relief valve 54 by means of a Make manipulated variable.

If the control unit detects that the boom is too low has dropped, the pressure relief valve 54 is a set higher value, so that the pressure on the Lifting side of the hydraulic cylinder 10 increases and the Hydraulic piston 12 is extended.

If the control unit 54 determines that the boom is too high has been raised, the pressure relief valve 54 is a Lowered value, so that the pressure on reduces the stroke side of the hydraulic cylinder and the Hydraulic cylinder is retracted.

Does it happen, for example, due to road bumps Accelerations (shocks and vibrations), which on the Suspension, these accelerations are due to the Mass inertia transferred to the boom. The acceleration generated by the mass of the boom, a force that turns out to be Disturbance on the hydraulic cylinder 10 transmits and thus the Hydraulic oil on the lifting side of the hydraulic cylinder 10th displaced or relieved.

In a shock, which can retract the hydraulic piston 12, the oil from the stroke side of the hydraulic cylinder 10 through displaces the hydraulic piston 12 and flows over the Pressure limiting valve 44 from. Because of the repressed Hydraulic oil volume decreases the boom, which in turn as Control difference is detected by the control unit 54, whereupon the control unit opens the opening pressure of the Pressure limiting valve 44 is increased by the control unit 54 the manipulated variable determined according to the control difference. Due to the Increasing the opening pressure and the constant of control valve 22 flowing volume flow is the boom again raised until the control difference returns to zero or up has reduced a presettable threshold.

In a shock, which can extend the hydraulic piston 12, The hydraulic oil is on the stroke side of the hydraulic cylinder 10 relieved by the movement of the hydraulic piston 12 and an increase in volume of the stroke-side chamber 14 occurs. The constantly flowing volume flow from the control valve 22 fills this volume increase, so that the hydraulic cylinder 10 can extend without the risk of generating a Vacuum occurs. At the same time a rule difference of the control unit 54 detected, whereupon the control unit 54 reduces the opening pressure of the pressure limiting valve 44, by the control unit 54 according to the corresponding manipulated variable the control difference determined. Due to the reduction of Hydraulic oil flows from the lift side of the opening pressure Hydraulic cylinder 10 via the pressure relief valve 44 from and the boom lowers until the control difference back to zero or to a presettable threshold has decreased.

It is possible that to speed up or slow down the Reduction of the control difference, the control valve 22 in his Opening cross section additionally depending on the current need is variably changed, so that more volume flow to Hydraulic cylinder 10 can flow. In the extreme case would be through a lowering also a reversal of the volume flow direction conceivable to the hydraulic piston 12 faster to enter.

The actuation of the control valve 22 may be electrical, pneumatically or otherwise. Also is conceivable that the controllable pressure relief valve 44th pneumatically or hydraulically and not as in FIG is shown electrically driven. This can be at high Press and / or high flow rates be advantageous since then very high forces are applied by the adjusting mechanism have to.

Instead of the electrically controllable pressure relief valve 44th can also, as shown in Figure 2, an electric adjustable throttle 58 are used. The basic However, the principle of action remains intact.

The hydraulic oil flowing through the lift-side pipe flows with open check valve 42 constantly on the throttle 58 for Hydraulic tank 28 down from. According to the throttle equation above the throttle 58 a certain pressure drop, the from the volume flow and the opening cross section of the throttle 58 depends, so that on the lifting side of the hydraulic cylinder 10th a certain dynamic pressure arises, which causes a sagging of the Cantilever prevented.

The height of the back pressure can be determined by the flow rate of the Control valve 22 or via the adjustable opening cross-section the throttle 58 are changed.

The position of the boom is also constantly measured and serves as a controlled variable (actual value) for setting the dynamic pressure to be measured on the lifting side of the hydraulic cylinder 10 can this position also in different ways and Wise. It would be conceivable, as shown in Figure 2, the position of Piston rod 52 or the lifting angle of the boom.

If the control is activated, the control unit 54 generates analogous to the example of Figure 1, a manipulated variable, with the the opening cross section of the throttle 58 via a Throttle controller 60 regulated and / or a change in the Volumetric flow is caused by the control valve 22.

If the control unit 54 detects that the boom is too deep has dropped, the opening cross section of the throttle is 58th set to a smaller value, so that the Dynamic pressure on the lifting side of the hydraulic cylinder 10 is increased and the hydraulic piston 12 is extended. Also can in this case either only or simultaneously the Volume flow can be increased by the control valve 22 to the Increase dynamic pressure.

If the control unit 54 determines that the boom is too high has been raised, the opening cross section of the throttle 58 set to a higher value, so that the back pressure reduced on the lifting side of the hydraulic cylinder 10 and the Hydraulic piston 12 is retracted. Also in this Case either only or simultaneously the volume flow from Control valve 22 can be reduced to the back pressure reduce.

In a shock, which can retract the hydraulic cylinder 10, The hydraulic oil is removed from the lift side of the hydraulic cylinder 10 compressed by the hydraulic piston 12 and the back pressure in front of the throttle 58 increases. By increasing the Back pressure also increases the pressure drop over the Throttle 58, allowing a higher volume flow through the throttle 58 drains off. At the same time the boom sinks, what as Control difference is detected by the control unit 54, whereupon the control unit 54 the opening cross-section of the Throttle 58 is reduced by the control unit 54 the corresponding manipulated variable determined according to the control difference. Due to this reduction of the opening cross section of Throttle 58, it comes to an increase in back pressure, which the boom is raised again until the Control difference back to zero or to a presettable Threshold has decreased.

In a shock, which can extend the hydraulic cylinder 10, The hydraulic oil is on the stroke side of the hydraulic cylinder 10 relieved by the movement of the hydraulic piston 12 and an increase in volume of the stroke-side chamber 14 occurs. The constantly flowing volume flow from the control valve 22 fills the increase in volume, so that the hydraulic piston 12th can extend without the risk of generating a Vacuum occurs. Due to the added Hydraulic oil volume raises the boom, which in turn is recognized as a control difference by the control unit 54, whereupon the control unit 54 the opening cross-section of the Throttle 58 increases by the control unit 54 the Manipulated variable determined according to the control difference. by virtue of this reduction in back pressure flows more hydraulic oil from the lifting side of the hydraulic cylinder 10 via the throttle 58th can flow as volume flow from the control valve 22. Of the Boom lowers until the control difference again Zero or reduced to a presettable threshold Has.

It is also conceivable that in extreme cases, a reversal the volume flow direction is adjusted to the Hydraulic piston 12 to retract faster.

Furthermore, the electrically controllable throttle 58, as well also the first check valve 42 or the control valve 22, be controlled pneumatically or hydraulically.

In further exemplary embodiments, as in FIGS. 3 and 4 is shown, is a second vertical-side line 62nd provided from the first vertical line 20 to Hydraulic tank 28 leads and with a second check valve 64th is provided, wherein the first and the second check valve 42, 64 may be identical.

In the illustrated in Figures 3 and 4 Embodiments are on-demand Suspension systems in which, unlike those in the Figures 1 and 2 illustrated embodiments, only at Requires a volume flow from the control valve 22 via a Load holding valve 34 to the hydraulic cylinder 10 of the boom flows. The control valve 22 is thus located in the closed position and will be provided by the Control unit 54 in the corresponding other positions connected.

FIG. 3 shows the demand-controlled hydraulic suspension the electrically controllable pressure relief valve 44, as it can also be seen in Figure 1.

If the control is activated by the switching unit 56 is the originating position of the boom as to be maintained Reference value (setpoint) and the control unit determined from this command and the current, measured position (controlled variable) the deviation (Control difference) from each other to on this basis the To perform regulation of the pressure relief valve 44 and the Height of the volume flow of control valve 22 by another Adjust manipulated variables.

So that the hydraulic piston 12 of the hydraulic cylinder 10th due to disturbances acting on it must the check valves 42, 64 switched to their open positions be.

About the electrically controllable pressure relief valve 44 is the pressure on the stroke side of the hydraulic cylinder 10th should act, as needed by the control unit 54th regulated.

If the control unit 54 detects that the boom is too deep has dropped, the pressure relief valve 44 to a set higher value and the control valve 22 is opened, so that due to the flowing volume flow, the pressure on the Lifting side of the hydraulic cylinder 10 increases and the Hydraulic cylinder 10 is extended.

If the control unit 54 determines that the boom is too high has been raised, the pressure relief valve 44 to a set lower value, so that the pressure on the Hubseite the hydraulic cylinder 10 is reduced and the Hydraulic piston 12 is retracted. The hydraulic oil used by the stroke side of the hydraulic cylinder 10 then over the Pressure limiting valve 44 and the first check valve 42 for Lower side of the hydraulic cylinder 10 flows, flows from there via the second check valve 64 to the hydraulic tank 28th

In a shock, which can retract the hydraulic piston 12, The hydraulic oil is removed from the lift side of the hydraulic cylinder 10 displaced by the hydraulic piston 12 and flows over the Pressure relief valve 44 and via the check valves 42, 64 from. Due to the displaced oil volume of the boom drops, which again detected as a control difference by the control unit 54 is whereupon the control unit 54 the opening pressure of the Pressure relief valve 44 increases and the control valve 22 in Lifting position brings, so that a flow to the lifting side of the Hydraulic cylinder 10 flows, the manipulated variables by the Control unit 54 are determined according to the control difference. Due to the increase of the opening pressure and of the Control valve 22 flowing volume flow is the boom raised again until the control difference returns to zero or reduced to a presettable threshold.

It is conceivable in this case that to speed up the Lifting the check valve 42 is closed so that no Hydraulic oil to the hydraulic tank 28 from the lift side of Hydraulic cylinder 10 can flow out her.

In a shock, which can extend the hydraulic cylinder 10, The hydraulic oil is on the stroke side of the hydraulic cylinder 10 relieved by the movement of the hydraulic piston 12 and an increase in volume of the lift-side chamber 14 occurs, as hydraulic oil from the lower-side chamber 16 to Hydraulic tank 28 is displaced towards. This lifting of the Jib is from the control unit 54 as a control difference detected and brought the control valve 22 in the stroke position to by means of a volume flow, the resulting volume on the Hub side of the hydraulic cylinder 10 to fill. Due to the added hydraulic oil volume remains the boom raised, which remains as a rule difference from the Control unit 54 is detected, whereupon the control unit 54 reduces the opening pressure of the pressure limiting valve 44, by the control unit 54, the manipulated variable in accordance with Control difference determined. In addition, the switches Control unit 54, the control valve 22 back in Closed position. Due to the reduction of the opening pressure Hydraulic oil flows from the lift side of the hydraulic cylinder 10 via the pressure relief valve 44 and the boom lowers itself off until the control difference returns to zero or up has reduced a presettable threshold.

It is also conceivable that after lifting the boom for Lower the boom to make the hydraulic cylinder faster to be able to retract, a reversal of the flow direction takes place by the control unit 54, the control valve 22 in a lowering position switches and the check valve 42, 64 closes.

The control valves 22 and shown in Figures 1 to 4 Check valves 42, 64 are shown electrically switchable, However, they can also be pneumatically, hydraulically or on a be driven in another way.

Another embodiment is shown in FIG. The difference from the previous, shown in Figure 3 Embodiment is that, as in Figure 2 shown, a variable throttle 58 in place of adjustable pressure relief valve 44 is used. The however, the basic principle remains the same. In addition, however, a pressure sensor 66 is on the lift side of Hydraulic cylinder 10 is arranged, which is required to a Opening signal for the check valves 42, 64 to the Dispense control unit 54. Alternatively, you can do it differently kind of accelerometers, with the help of the Loads on the hydraulic cylinder 10 are measured can be used.

The measurement of the load on the hydraulic cylinder 10 is required to determine when the check valves 42, 64 must be opened, otherwise on the variable throttle 58th the hydraulic oil from the stroke side of the hydraulic cylinder 10th can drain and the boom would sink.

Are the two check valves 42, 64 open, it turns according to the throttle equation over the throttle 58 a certain Volume flow, in front of and behind the pressure difference the throttle 58, the opening cross section of the throttle 58 and depends on the hydraulic oil viscosity.

The determination of a manipulated variable for setting the back pressure takes place analogously to the exemplary embodiment according to FIG. 2.

If the control is activated, the load of the Hydraulic cylinder 10 directly via the pressure sensor 66 or alternatively indirectly via an acceleration sensor measured. This burden is combined with the Origin of the boom as to be maintained Reference variable (setpoints) recorded.

Does the control unit 54 now a certain deviation of the Hydraulic cylinder load fixed, opens the control unit 54th the control valve 22 and the two check valves 42, 64, so that a volume flow can flow. This volume flow generated by the throttling on such a back pressure the stroke side of the hydraulic cylinder 10 that on the Hydraulic cylinder 10 acting load is worn.

After opening the valves, the control unit 54 determines one or more manipulated variables in the presence of control deviation in order to adjust the opening cross section of the throttle 58 and / or the change in the volume flow of the control valve 22.
If the control unit 54 determines that the boom has fallen too low after opening the control valve 22 and the check valves 42, 64, the opening area of the throttle 58 is set to a smaller value, so that the dynamic pressure on the lift side of the hydraulic cylinder 10 increases and the hydraulic piston 12 is extended.

If the control unit 54 determines that the boom after the Open the control valve 22 and the check valves 42, 64 to was raised high, the opening cross section of the throttle 58 set to a larger value, so that the Dynamic pressure on the lifting side of the hydraulic cylinder 10 decreases and the hydraulic piston 12 is retracted. The Hydraulic oil, from the lifting side of the hydraulic cylinder 10th then via the throttle 58 and the check valve 42 to the lowering side the hydraulic cylinder 10 flows, flows from there via the Shut-off valve 64 to the hydraulic tank 28.

In a shock, a force on the stroke-side chamber 14th exercises the control unit 54 generates due to the Opening signal by the pressure sensor 66 is a manipulated variable, the to open the control valve 22 and the check valves 42, 64th leads, so that the hydraulic piston 12 can retract. The Hydraulic oil from the lifting side of the hydraulic cylinder 10 is displaced by the hydraulic piston 12 and flows over the Throttle 58 and the check valves 42, 64 from. Due to the displaced hydraulic oil volume, the boom drops, what again as a control difference is detected by the controller, whereupon the control unit 54 the opening cross section of the throttle 58th reduced. Due to the resulting increase in Back pressure and of the control valve 22 flowing Volumetric flow, the boom is raised again until the Control difference back to zero or to a presettable Threshold has decreased.

It is conceivable in this case that to speed up the Lifting the check valve 42 is closed so that no Hydraulic oil to the tank from the lift side of the hydraulic cylinder 10 ago can flow out.

In a shock, which exerts a force on the lower-side chamber 16, the control unit 54 generates a manipulated variable due to the opening signal by the pressure sensor 66, which leads to the opening of the control valve 22 and the check valves 42, 64, so that the hydraulic piston 12 can extend , By the movement of the hydraulic piston 12, the hydraulic oil is relieved on the stroke side of the hydraulic cylinder 10 and an increase in volume of the stroke-side chamber 14 occurs because oil is displaced from the lower-side chamber 16 to the hydraulic tank 28 out. This raising of the boom is detected by the control unit 54 as a control difference and the control valve 22 is opened to fill by means of a volume flow, the resulting increase in volume on the stroke side of the hydraulic cylinder 10. Due to the added hydraulic oil volume of the boom remains raised, which is still recognized as a control difference from the control unit 54, whereupon the control unit increases the opening cross section of the throttle 58. In addition, the control unit 54 closes the control valve 22 again. Due to the increase in the opening cross-section of the throttle 58 hydraulic oil from the lift side of the hydraulic cylinder 10 via the throttle 58 and the boom lowers until the control difference has reduced back to zero or to a presettable threshold.
It is also conceivable that after lifting the boom for accelerated lowering of the boom, a reversal of the flow direction of flow from the control valve 22 takes place and the check valves 42, 64 are closed.

FIGS. 5 to 7 show simplified embodiments of the invention Invention, which is essentially the same in FIGS. 1 and 2 correspond to described embodiments, only that the first check valve is omitted.

Figure 5 shows the simplest of the illustrated Embodiments, in comparison to Figure 1, the first Lock valve 42 was saved. The illustrated in Figure 5 Pressure relief valve 44 is then not activated Suspension to a correspondingly high pressure limiting value regulated, so that the connecting line 40 substantially is closed, similar to how it cause a check valve 42 would. Only when activated suspension is the Pressure limiting valve 44 by the control unit 54 to a Control range, which is essentially one Control range according to the principle of operation Figure 1 corresponds. Incidentally, analogous to the already described operating principle for the embodiment in Figure 1 method.

To a leak-free sealing in the in FIG. 5 illustrated embodiment in the direction of the stroke side Chamber 14 to ensure, preferably a Check valve 68 are used, as in Figure 6 is shown.

A further embodiment is shown in FIG. 7, in the comparison to Figure 2, the first check valve 42 by a check valve 68 has been replaced. This Embodiment provides compared to Embodiment according to Figure 2 is a variant, with the Switching operations for the first check valve 42 can be saved can. The throttle 58 shown in Figure 7 is then at not activated suspension on a correspondingly small, a high back pressure generating, passage cross section regulated or closed accordingly, so that the Passage cross section of the throttle is substantially zero and the connection line 40 is substantially closed, similar to how it would cause a check valve 42. Only at; only when activated suspension, the throttle 58 through the Control unit 54 to a control area with a larger, one lower back pressure generating, passage cross-section regulated or opened accordingly, the control range in Essentially a control area according to the Operating principle with respect to Figure 2 corresponds. Incidentally, will analogous to the already described functional principle for the Embodiment proceed in Figure 2. The check valve 68 is necessary to provide an inflow in the direction of Hubseitigen chamber 14 through the connecting line 40 at activated suspension to avoid, as a throttle 58 or Aperture is permeable in both directions. Furthermore can also be on the throttle 58 with suspension disabled Leaks in the direction of the hubseitigen chamber 14 occur, the can be avoided by the check valve 68. The Check valve 68 thus contributes to a perfect Function of the load-holding valve 34 at. In a hydraulic Suspension without load-holding valve 34 could be on the Check valve 68 are omitted, because then always Hydraulic oil can flow from the hubseitigen chamber.

Figures 8 and 9 show embodiments for single-acting lifting cylinder 10. FIG. 8 shows that that is essentially about the hydraulic circuit Figure 1 is. Here is a single-acting hydraulic cylinder 10 is used, the hydraulic line 20 is omitted, so that the connecting line 40 now the lift-side chamber 14 of the Hydraulic cylinder 10 with a control valve 72 or over the Control valve 72 connects to the hydraulic oil tank 28. The Control valve 72 is designed such that it in the Lowering the connecting line 40 with the hydraulic oil pump 30 and the lift-side hydraulic line 18 with the Hydraulic oil tank 28 connects. To lower the Hydraulic cylinder 10 is behind the connection to Control line 38 in the connecting line 40 a Check valve 70 is provided. Only through the check valve 70, the hydraulic cylinder 10 can be lowered. The Control valve 72 is placed in lowered position, whereby the Hydraulic oil pump 30 due to the pump in the conveying direction closing check valve 70 has an opening pressure in the Control line 38 is generated, so that the load-holding valve 34th opened and the hydraulic oil from the chamber 14 through the Hubseitige hydraulic line 18 in the hydraulic oil tank 28th can drain away. Furthermore, the check valve 42 is connected to the Embodiment with a single-acting lifting cylinder 10th adjusted, since here only one hydraulic oil flow in one direction too is expected. Similarly, the changes can also be made in Compound with those shown in Figures 2 and 5 to 7 Hydraulic circuits are made, so the use a single-acting hydraulic cylinder 10 in the in the Figures 2 and 5 to 7 illustrated embodiments is also possible.

By way of example, the following will be described with reference to FIGS. 8 and 9 illustrated embodiments, the operation of a Suspension for a single-acting hydraulic cylinder 10 to be discribed. In contrast to FIG. 8, in FIG. 9 a telescopic cylinder arranged as a hydraulic cylinder 10. The How the suspension works but does not affected. With reference to FIG. 9, it is merely intended to show that also telescopically working hydraulic cylinder 10 can be used are.

According to the figures 8 and 9, the hydraulic active Suspension for a single-acting hydraulic cylinder 10 both with a constantly flowing volume flow and with a demand-controlled volume flow can be realized. at a constantly flowing volume flow is the control unit 54 activated via the switching device 56, wherein the Control unit 54, the check valve 42 opens and the Control valve 72 switches to the stroke position in which the Hydraulic oil pump 30 with the lift-side hydraulic line 18th is connected. The hydraulic oil pump 30 promotes that Hydraulic oil via the control valve 72 and over the Load holding valve 34 to the hydraulic cylinder 10 of the boom. There a certain pressure builds up, which by means of the adjustable pressure relief valve 44 is set. As soon as a pressure equilibrium has set, the takes Hydraulic piston 12 a certain position, wherein excess, promoted by the hydraulic oil pump 30 Hydraulic oil in the connecting line 40 via the Pressure limiting valve 44 and the first check valve 42nd and via the check valve 70 to the hydraulic tank 28th flows. Is it now with activated suspension (check valve 42 is open) for compression of the hydraulic piston 12, generated the control unit 54 due to the signal of the position sensor 50, a control signal for the pressure limiting valve 44, which then the pressure in the lift-side hydraulic line 18th rise until the hydraulic piston 12 his again Starting position has taken.

The basic mode of action therefore also corresponds to a single-acting hydraulic cylinder 10, whether conventional or formed as a telescopic cylinder, the in Figure 1 described principle, so that the pressure in the stroke side Chamber 14 of the single-acting hydraulic cylinder 10 thereby that controls a certain inflow of hydraulic oil to the lifting side (to the chamber 14) controlled to the hydraulic tank 28th can drain over the connecting line 40. For one Further description of the mode of action, in particular at Occurrence of shocks is hereby preceded Embodiments referenced in particular to Figure 1.

With an active suspension with demand-controlled volume flow is the control valve 72 after lifting or lowering the Hydraulic cylinder 10 (via the lifting or lowering position of Control valve 72) is switched to its middle position, in the both the hydraulic line 18 and the connecting line 40 are connected to the hydraulic oil tank 28. In this Position flows from the hydraulic oil pump 30 ago no Hydraulic oil through the lines 18 and 40. It comes now activated suspension (check valve 42 is open) for example, by shocks to a pressure increase in the Hubseitigen chamber 14, with a sinking or compression the hydraulic piston 12 is connected, this is by the Position sensor 50 detected. The control unit 54 registers the change and generates a control signal by which the Control valve 72 is switched to its stroke position. It follows the renewed lifting of the hydraulic piston 10 until the Starting position of the hydraulic piston 10 is reached again. As soon as the starting position is reached, the Control unit 54, the control valve 72 back into the Middle position.

Although the invention is based only on some Embodiments has been described open up for the expert in the light of the above description and the Drawing many different alternatives, modifications and variants which fall under the present invention.

Claims (13)

Hydraulic suspension, in particular for a jib of a loader vehicle, having at least one hydraulic cylinder (10) which has at least one chamber (14, 16), a control valve (22) which has at least one chamber via at least one hydraulic line (18, 20) (14, 16) and which optionally connects to a hydraulic oil pump (30) and a hydraulic oil tank (28), and a connecting line (40), characterized in that a control unit (54) and a position of the hydraulic cylinder (10 ) is contained sensor (50) and that the connecting line (40) has a controllable in dependence of the sensor signal pressure limiting unit (44, 58). Hydraulic suspension according to claim 1, characterized in that the connecting line (40) connects the at least one chamber (14, 16) with the hydraulic oil tank (28). Hydraulic suspension according to claim 1 and 2, characterized in that the hydraulic cylinder (10) has a stroke-side and a lower-side chamber (14, 16) which are connected to each other via the connecting line (40) and the control valve via a first senkseitige line (20 ) and via a lift-side line (18) with the chambers (14, 16) is connected. Hydraulic suspension according to one of the preceding claims, characterized in that the connecting line (40) includes a first check valve (42), with which by opening and closing the hydraulic suspension can be activated or deactivated. Hydraulic suspension according to claim 3 to 4, characterized in that the connecting line (40) in the direction of the stroke-side chamber (14) closing check valve (68). Hydraulic suspension according to one of the preceding claims, characterized in that the pressure limiting unit is a controllable pressure limiting valve (44). Hydraulic suspension according to one of claims 1 to 5, characterized in that the pressure limiting unit is an adjustable throttle (58). Hydraulic suspension according to one of the preceding claims, characterized in that the control valve (22) has a closed position. Hydraulic suspension according to one of the preceding claims, characterized in that in the at least one hydraulic line (18, 20) a load-holding valve (34) is arranged. Hydraulic suspension according to one of the preceding claims, characterized in that between the hydraulic pump (30) and control valve (22) is provided with a pressure relief valve (32) and with the hydraulic tank (28) in communication pressure limiting line (26). Hydraulic suspension according to one of the preceding claims, characterized in that the control unit (54) regulates the controllable pressure limiting unit (44, 58) as a function of a difference signal resulting from the variable sensor signal and a setpoint signal, the setpoint signal corresponding to the sensor signal upon activation of the hydraulic signal Suspension corresponds and the difference signal reaches a predetermined threshold. Hydraulic suspension according to one of claims 3 to 11, characterized in that a second vertical line (62) with a second check valve (64) is included, which connects the lower-side chamber (16) with the hydraulic tank (28). Hydraulic suspension according to one of the preceding claims, characterized in that the hydraulic cylinder (10) comprises means for measuring load, in particular a pressure sensor (66).

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