EP1574626A1 - Hydraulic system - Google Patents

Abstract

The hydraulic drive assembly (10), for agricultural machinery mounted on a tractor, is a passive spring system with a hydraulic cylinder (26) divided by a piston (29) into two chambers (28,30). The control (12) has an additional switch position, apart from the three workings to raise and lower the equipment and a neutral condition, to give a spring setting which links the supply line for the second cylinder chamber to the hydraulic tank (20) and, at the same time, breaks the connection between the first (22) and second cylinder supply lines and the pump (18).

Description

The invention relates to a hydraulic arrangement for a passive suspension system, with a first and a second Chambered hydraulic cylinder, a hydraulic tank, a hydraulic fluid conveying means, a Hydraulic accumulator, one between hydraulic accumulator and first Chamber arranged hydraulic line, one in the Hydraulic line arranged switching valve, a first Supply line for the first chamber, a second Supply line for the second chamber, one in the first Supply line arranged pipe rupture protection device and a control unit with at least three switch positions, which a lifting position, a lowered position and a Include neutral position for the hydraulic cylinder.

In agricultural machines, such as e.g. Telescopic handlers, Wheel loaders or front loaders on tractors, it is known, a hydraulic suspension system to use the boom or the rocker cushions to a total of the vehicle improved suspension comfort, especially while driving, to achieve. This is done by means of a suitable hydraulic arrangement of valves the lifting side of a Hydraulic cylinder connected to a hydraulic accumulator around one To effect suspension through the hydraulic accumulator. Furthermore, the Lower side of the hydraulic cylinder with a hydraulic tank connected, on the one hand to a cavitation on the lowering side avoid and on the other hand a free movement of the piston rod to allow during the suspension process. To increase the security against a sudden drop of the boom or the rocker, these suspension systems, for Securing the hydraulic cylinder against hose breaks, with Be provided load holding valves. To lower the Hydraulic cylinder, it is then required the Tank connection to the lower side of the hydraulic cylinder close, so that a required pressure can build up, to open the load-holding valve. Only when that Load holding valve is opened, can be oil from the lift side of the Drain hydraulic cylinder.

A hydraulic arrangement for such a suspension system is disclosed in EP 1 157 963 A2. It will be a Suspension system for the boom of a telehandler proposed, which for hedging the boom against Fall a load-holding valve or a Pipe rupture protection device provides. On the one hand the To be able to open load holding valve and on the other hand a Suspension function also in neutral position of the To provide hydraulic cylinder is a separate Switching valve arranged, which must be closed to a connection made to the tank for the suspension Close and necessary for opening the load-holding valve Be able to build pressure in the supply line. This Circumstance makes it necessary that the "lowering function" recorded for the hydraulic cylinder at a suitable location or monitored and in the switching logic of the suspension to the closure the switching valve must take into account what is especially with purely mechanically operated control units as elaborate and problematic. In this context EP 1 157 963 A2 relates to a monitoring device pointed in the form of a sensor on the control unit, with the is to be detected, whether the boom should lower or Not. Without or with defective monitoring device for the Control unit or for the "lowering function" it could Faulty circuits in the hydraulic arrangement come.

The object underlying the invention is seen therein a hydraulic arrangement of the type mentioned above create by which an effort to realize the "lowering function" is reduced. In particular, a malfunction should the hydraulic arrangement for the "lowering function" at nonexistent or defective monitoring device be excluded.

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 arrangement of the above mentioned type designed such that the control unit, a has further switching position, which is a suspension position represents, in which by the control unit at least the second supply line is connectable to the tank and at the same time connections of both supply lines to Subsidies are interrupted. By doing that, the controller has a fourth switching position, can on a second Switching valve for connecting the second chamber of Hydraulic cylinder with a tank, as with conventional Solutions provided is waived. With it reduced the technical effort is considerable, especially because of because monitoring the "lowering function" for the Hydraulic cylinder is eliminated. Thus, preferably only one Switching valve used with the only the stroke side of the Hydraulic cylinder is connected to the hydraulic accumulator.

A fourth shift position according to the invention provides the Advantage that in addition to a lifting position and a lowered position furthermore a neutral position for the hydraulic cylinder can be provided in both supply lines are closed. In the neutral position, the connection should between the lower side of the hydraulic cylinder and the tank preferably be closed, since there are applications with Wheel loaders, telehandlers and front loaders are, where a certain contact pressure under one on the boom attached tool is to be produced, resulting in a permanent connection to the tank would not be possible and so on would lead to a disadvantage compared to competing products. It is therefore an advantage of a fourth invention To add switching position and both the lifting and To provide lowering and neutral position.

The control unit may be configured such that fourth Switching a so-called floating position switched becomes. In the floating position is the first supply line interconnected with the second supply line and both supply lines connected to the tank, the second input to the control unit is closed, so no Supply on the part of the subsidy takes place. A Floating position as fourth switching position is not mandatory required, it is sufficient if the fourth Switch position only the second chamber of Hydraulic cylinder connects to the tank.

In the suspension position, the controller connects the second Supply line or the second and the first Supply line directly to tank, i. there will be no other valves or means needed (except one Connecting line from the control unit to the tank). The control unit can be designed manually or electrically operated, Of course, other methods are conceivable are, for example, pneumatic or hydraulic methods, which, however, should not be explained in detail.

The switching valve preferably has a closed position and an open position, wherein the switching valve in the Closed position in one or both flow directions closes, but in the open position in both Flow directions opens so that a suspension function in Connection with the hydraulic accumulator occurs. The Switching valve may be formed such that in the Closed position hydraulic fluid from the hydraulic cylinder to Hydrospeicher can flow through, so that the hydraulic accumulator is always preloaded with the highest load pressure during a work cycle occurs. Furthermore, the switching valve also be designed such that it in the closed position seals in the opposite direction or in both directions. Furthermore, there are also bypasses of Switching valve by means of check valves and diaphragms conceivable to charge the hydraulic accumulator. The switching valve is preferably electrically actuated. It goes without saying also conceivable that other types of actuation of the switching valve be used, for example, a manual, pneumatic or hydraulic actuation.

Now the suspension should be activated, which means a Switch can happen that the operator in the cabin of the Vehicle actuated, or for example by a Speed signal, so the switching valve is in his Open position and the controller in its fourth Switched position switched to the first chamber of the Hydraulic cylinder to connect to the tank. During one Excitation by the chassis of the working machine can impulsive accelerations by the free swinging of the Jib or the rocker be damped, so that a Increase of driving comfort is achievable.

If the boom or the rocker with activated suspension is lowered by adjusting the control unit in the Lowering automatically the connection of the second chamber of the Hydraulic cylinder with the tank closed and Hydraulic fluid flows into the second chamber of the Hydraulic cylinder, where now a sufficiently high pressure can be constructed to open the load-holding valve, what mandatory for lowering the boom or swingarm is required. With the market-standard suspension systems with Load-holding valve or with a pipe rupture protection device a second switching valve is required, which for a Suspension function produces required connection to the tank and which must be closed to the required To ensure pressure build-up.

If the boom or the rocker with activated suspension lifted with the lifting position of the control unit is automatically the second chamber of the hydraulic cylinder with the Tank connected so that the displaced by the lifting process Hydraulic fluid from the hydraulic cylinder to the tank can flow. Should be a shock on the Boom or transferred to the swingarm, this can or this without the risk of cavitation compress, as the second chamber is relieved to the tank.

Only in the neutral position of the control unit must Switching valve, which is the first chamber with the hydraulic accumulator connects, be closed, since here at the compression of the Jib or swingarm is the danger that in the second chamber of the hydraulic cylinder, a negative pressure (Cavitation) arises, which seals the seals Hydraulic cylinder can damage. To make it a easy operation of the boom or the swingarm come can, the switching valve is preferably always then automatically closed, d. H. brought into the closed position, when the controller is in its neutral position, while the suspension is active. Preferably, this means intended to determine whether the valve in its closed neutral position or not. This can be implemented, for example, in the form of a switch, in conjunction or depending on the Neutral position is switched on the control unit. at electrohydraulically controlled control units is a Such a switch usually not required because this task taken from the software of an electronic control unit can be. It is also irrelevant how and where the switching position of the control unit is detected because only the result as such is of interest. An above This switch can be connected to a joystick, to a Operating mechanism incl. Cable or directly on the Control unit are attached. It is also conceivable here Sensor that receives a proportional signal which is in a suitable evaluation in an electrical signal is converted, which the switching valve in the closed position on. Also, it would be possible to use a pressure switch or Pressure sensor to use, the pilot pressure, the pressure of a hydraulic joystick as a control signal to the Control unit is sent, determined. It thus results a variety of ways the switching position of the Control unit to determine.

To allow that with active suspension the Neutral position is passable, without that immediately in the Closed position of the switching valve is switched in a preferred embodiment of the invention Time delay element provided. A passing of the For example, neutral position may be required if the neutral position on the control unit directly between the lifting and Lowering position is arranged and from a lifting position to be switched directly into a lowered position. The Time delay element provides that when simple Passing the neutral position switching the switching valve is not made. Only when a presettable Retention time is reached in neutral position, the Switching valve brought into the closed position.

In an electronically or electrohydraulically controlled Control unit can, for example, in the control software also be taken into account that, for example, not operated joystick the control unit with activated suspension basically not in its neutral position but in the fourth switching position is moved. It would be too conceivable that, as usual with some wheel loaders, during the Lifting and lowering of the boom or the rocker the Suspension is always disabled. As a very simplified version of the system it would also be conceivable that the suspension is only active when the Control unit is located in its fourth switching position. On This type of electronic effort could be considerably reduce, since only one switch is needed, the Switching valve opens or closes.

The control device is preferably as a slide valve formed, which four switch positions, each with two Has inputs and outputs. In the individual positions are the supply lines in different ways according to the setting function (lifting, lowering, neutral position (Hold) and suspension) of the control unit with the funding or connected to the tank or closed.

The pipe rupture protection device preferably comprises a in Direction of the control unit closing check valve and a pressure relief valve, wherein the pressure relief valve through prevailing in the connecting lines pressures is controllable. The control is done by Pilot pressure lines, which of the pressure relief valve in lead the first and the second supply line. The Check valve is in a pressure relief valve arranged bypass bypass, wherein the Check valve opens towards the first chamber. Other Possibilities for pipe burst protection are also conceivable. For example, duck switches can also be used in case of pressure drop, actuate a switching valve.

Compared to conventional suspension systems results cheaper hydraulic arrangement, since the required second switching valve and its tubing on the side the second chamber of the hydraulic cylinder is eliminated and held whose a commercial slide valve with Floating position function can be used. By the Elimination of a second switching valve is also the number possible sources of error because one component less is used. Furthermore, there are cheaper creative possibilities, since less space is required becomes.

Especially with tractors with front loader, it is common that the hydraulic and electrical connection between front loader and tractor ensured by means of so-called multi-couplers that is a quick and easy connect and disconnect enable. By using an inventive hydraulic arrangement can maintain these multi-couplers be because no additional hose to connect the Lower side of the hydraulic cylinder with the tank required is. Due to the internal connection of the control unit in his fourth switching position with the tank, the second Chamber of the hydraulic cylinder by means of the already existing second supply hose to be supplied.

Reference to the drawing, which is an embodiment of the invention shows, the invention and other advantages and advantageous developments and refinements of Invention described in more detail and explained.

Fig. 1

eine hydraulische Anordnung für ein Federungssystem eines Hydraulikzylinders und

Fig. 2

eine schematische Darstellung eines Teleskopladers mit einer hydraulischen Anordnung aus Figur 1.

It shows:

Fig. 1

a hydraulic arrangement for a suspension system of a hydraulic cylinder and

Fig. 2

a schematic representation of a telescopic loader with a hydraulic arrangement of Figure 1.

A hydraulic arrangement 10 shown in FIG. 1 shows Inventive embodiment for realizing a Suspension. The hydraulic assembly 10 includes a switchable Control unit 12, for example, a slide valve, which via Hydraulic lines 14, 16 with a pump 18 and a Hydraulic tank 20 is connected, wherein the control unit 12 in four operating positions, lifting, neutral, lowering and Suspension position, is switchable. The switching of the control unit 12 is preferably done by hand, but can also electrically, hydraulically or pneumatically.

Via a first and second supply line 22, 24 is the Control unit 12 connected to a hydraulic cylinder 26, wherein the first supply line 22 into a first chamber 28 of the Hydraulic cylinder 26 and the second supply line 24 in a second chamber 30 of the hydraulic cylinder 26 leads. One Piston 29 separates the two chambers 26, 28 from each other. The first chamber 28 of the hydraulic cylinder 26 provides the piston-side or lift-side chamber, whereas the second chamber 30, the piston rod side and the lower side Represents chamber of the hydraulic cylinder.

In the first supply line 22 is a Load holding valve arrangement or pipe rupture protection device 32 intended. The pipe rupture protection device 32 includes a pressure and spring-controlled pressure relief valve 34, as well a hydraulic cylinder side opening check valve 36, which via a bypass line 38 parallel to Pressure relief valve 34 is arranged. About a first Pressure line 40 is a pressure connection from Pressure limiting valve 34 to the hydraulic cylinder side Section of the first supply line 22 made. about a second pressure line 42 is another pressure connection from the pressure relief valve 34 to the second supply line 24th produced. Furthermore, a spring 44 holds the Pressure limiting valve 34 in the closed position.

A hydraulic line 46 connects the first chamber 28 and the first supply line 22 with a hydraulic reservoir 48, wherein the end 50 not connected to the hydraulic accumulator 48 the hydraulic line 46 between the first chamber 28 and the Pipe rupture protection device 32 is arranged.

In the hydraulic line 46, a switching valve 52 is arranged. The switching valve 52 is an electrically switchable Seat valve is, which via a spring 54 in Closed position is held and a solenoid 56 in an open position can be brought. The switching valve 52 seals in the closed position in the direction of Hydraulic accumulator 48 from. Here, the switching valve can also be designed so that it is in both directions seals leak-free. In the open position is to Production of a suspension function between hydraulic cylinders 26 and hydraulic accumulator 48 a hydraulic flow in both Directions guaranteed.

The individual operating states can now via the Control unit 12 and controlled via the switching valve 52 become. As shown in Fig. 1, the control unit 12th held in neutral position by adjusting springs 60, 62. The Switching valve 52 is in a closed position. about a control signal or, as shown in Figure 1, by manual operation, the control unit 12 by means of a Actuator 58 from the neutral position in the Lifting, lowering or suspension position brought. It can to be a manual, electric, hydraulic or pneumatic actuator 58 act.

Based on a connected to the actuator 58 Switch or sensor 64 will be the neutral position of Controller 12 detects and a signal to a control unit 66 sent. The control unit 66 is connected to the switching valve 52 connected and holds or brings the switching valve 52 in Closed position when the control unit 12 in Neutral position is located. Preferably, the control unit 66 provided with a time delay element which causes only after a presettable dwell time of the controller 12 in the neutral position, the control unit 66, the switching valve 52 brings in the closed position. This will ensure that not every time the controller 12 switches, if only is switched over the neutral position, the Control unit 66, the switching valve 52 closes. The switching valve 52 is brought into the closed position only if the Control unit 12 actually switched to the neutral position becomes.

In the lifting position, the connection of the first Supply line 22 to the pump 18 and the connection of second supply line 24 with the hydraulic tank 20th produced. The pump 18 connected to the hydraulic tank 20 filled via the first supply line 22 and over the Check valve 36 of the pipe rupture device 32 (the Pressure relief valve 34 of the load-holding arrangement 32 is located in the closed position), the first chamber 28 of Hydraulic cylinder 26. As a result, the piston moves 29 in the direction of the second chamber 30 and pushes there existing oil through the second supply line 24 out in the hydraulic tank 20. Will now return to the neutral position switched, the controller 12 interrupts the connections to the pump 18 and the hydraulic tank 20, so that the pressure in the retained two chambers 28, 30 of the hydraulic cylinder 26 and the movement of the piston 29 is canceled. The piston 29 stands still.

In the lowering position, the connection of the first Supply line 22 to the hydraulic tank 20 and the Connection of the second supply line 24 with the pump 18th produced. The pump delivers oil into the second chamber 30 of the Hydraulic cylinder 26, wherein in the second Supply line 24 building up the pressure Pressure limiting valve 34 via the second pressure line 42 of the Pipe rupture device 32 opens. At the same time the Piston 29 moves in the direction of the first chamber 28, so that the from the first chamber 28 flowing oil over the first Supply line 22 and over the open Pressure limiting valve 34 enters the hydraulic tank 20.

The pipe rupture device 32 thus ensures that the hydraulic cylinder 26 in neutral position maintains or in lifting and neutral position no oil from the pressurized first chamber 28 escape and that in Lowering the oil from the first chamber 28 over the open Pressure relief valve 34 can drain. To this, too should or should ensure Pipe rupture device 32 useful way shown on the lifting side of the hydraulic cylinder 26th be arranged, the lifting side of the side of the Hydraulic cylinder 26 is in which a pressure for lifting a load is built. In the embodiments illustrated here the stroke side is the first chamber 28 of the hydraulic cylinder 26, by turning the hydraulic cylinder 26 and the second Chamber 30 could serve as a lifting side. The first pressure line 40 represents an overload protection, so that too high Operating pressures in the first chamber 28 of the hydraulic cylinder 26, for example, caused by excessive loads can, in the first pressure line 40 reaches a limit pressure is that opens the pressure relief valve 34 to reduce pressure.

In the suspension position shown in Figure 1 on the control unit 12 as lowest position is shown, the connection is the second supply line 24 with the hydraulic tank 20th produced. The connection of the first supply line 22 to the pump 18 or to the hydraulic tank 20 is closed or the connection remains closed when out of neutral is switched out into the suspension position. When alternative solution may also be in the suspension position Floating position to be switched. In such a Floating position is then the first supply line 22 through the control unit 12 with the second supply line 24th connected, wherein both supply lines 22, 24 with the Hydraulic tank 20 connected and the input to the control unit, on the pump 18 is connected to be closed. So long the switching valve 52 is in the closed position, i. as long as the Hydraulic accumulator 48 is separated from the hydraulic cylinder 26 and thereby the suspension is deactivated, the Piston 29 in the suspension position only in the direction of the second Move chamber 30. Only by activating the suspension, i. by adding the hydraulic accumulator 48, the Move plunger 29 resiliently, ie traversing in both directions. The suspension is activated via a Activation switch 68, which sends an activation signal to the Control unit 66 outputs, whereupon they the switching valve 52 in Opening position brings. Alternatively, the activation of the Suspension can also be done automatically by a Activation signal is generated as soon as the control unit 12 in the fourth switching position is switched.

In der Senkstellung (oberste Schaltstellung des Steuergeräts aus Figur 1) wird die erste Versorgungsleitung 22 mit dem Hydrauliktank 20 und die zweite Versorgungsleitung 24 mit der Pumpe verbunden. In der zweiten Versorgungsleitung 24 bzw. in der zweiten Kammer 30 baut sich ein entsprechender Druck auf, durch den das Druckbegrenzungsventil 34 über die Druckleitung 42 geöffnet wird, so dass Öl aus der ersten Kammer 28 über die erste Versorgungsleitung 22 in den Hydrauliktank 20 abfließen kann. Gleichzeitig kann der Kolben 29 federnde Bewegungen ausführen, da eine Verbindung zum Hydraulikspeicher 48 auf der Hubseite und eine Verbindung auf der Senkseite zum Hydrauliktank 20 hergestellt ist.

In der Neutralstellung (von oben zweite Schaltstellung des Steuergeräts 12 aus Figur 1) werden alle Ein- und Ausgänge am Steuergerät 12 geschlossen, d. h. es kann kein Öl durch die Versorgungsleitungen 22, 24 fließen. Falls es in dieser Stellung zu einem Einfedern des Kolbens 29 kommen würde, bestände die Gefahr einer Kavitationswirkung in der zweiten Kammer 30 des Hydraulikzylinders 26, wodurch Dichtungen im Hydraulikzylinder 26 beschädigt werden könnten. Um dieses zu verhindern signalisiert der Schalter bzw. Sensor 64 ein Signal, welches von der Steuereinheit 66 aufgenommen wird. Die Steuereinheit 66 erzeugt daraufhin unter Berücksichtigung einer Zeitverzögerung, zur Bestätigung einer Verweilzeit in der Neutralstellung, ein Schließsignal für das Schaltventil 52. Sobald das Schaltventil 52 geschlossen ist, kann der Kolben 29 keine Bewegungen mehr ausführen, da alle Leitungen 22, 24, 46 geschlossen sind. Sobald das Steuergerät 12 in eine andere Stellung geschaltet wird, gibt der Sensor 64 ein Signal zum Öffnen des Schaltventils 52 frei. Das Signal des Sensors 64 ist somit dem Aktivierungssignal des Aktivierungsschalters 68 in der Schaltlogik der Steuereinheit 66 übergeordnet, damit trotz eines Öffnungssignals vom Aktivierungsschalter 68 das Schaltventil 52 durch ein Schließsignal des Sensors 64 geschlossen werden kann.

In der Hebestellung (von oben dritte Schaltstellung des Steuergeräts 12 aus Figur 1) wird die erste Versorgungsleitung 22 mit der Pumpe 18 und die zweite Versorgungsleitung 24 mit dem Hydrauliktank 20 verbunden. In der ersten Versorgungsleitung 22 bzw. in der ersten Kammer 28 baut sich ein entsprechender Druck auf, durch den der Kolben 29 angehoben wird, so dass Öl aus der zweiten Kammer 30 über die zweite Versorgungsleitung 24 in den Hydrauliktank 20 abfließen kann. Gleichzeitig kann der Kolben 29 federnde Bewegungen ausführen, da eine Verbindung zum Hydraulikspeicher 48 auf der Hubseite und eine Verbindung auf der Senkseite zum Hydrauliktank 20 hergestellt ist.
Sollte während eines Senk- oder Hebevorgangs ein Stoß auf den Kolben 29 übertragen werden, kann dieser ohne Gefahr der Kavitation einfedern, da die Senkseite zum Hydrauliktank 20 hin entlastet ist.

In der Federungsstellung (unterste Schaltstellung des Steuergeräts 12 aus Figur 1) wird die erste Versorgungsleitung 22 geschlossen und die zweite Versorgungsleitung 24 mit dem Hydrauliktank 20 verbunden. Der Kolben 29 kann in dieser Stellung frei federn. Bewegt er sich durch einen auf ihn übertragenden Stoß abwärts, wird das Öl aus der ersten Kammer 28 in den Hydraulikspeicher 48 gedrängt. Der sich im Hydraulikspeicher 48 aufbauende Druck lässt das Öl wieder zurück in die erste Kammer 28 strömen, so dass der Kolben 29 sich wieder aufwärts bewegt. Diese federnde Bewegung wiederholt sich gegebenenfalls, bis der Stoß vollständig kompensiert wurde. Des Weiteren kann vorgesehen sein, dass sobald das Steuergerät 12 aus der Federungsstellung heraus in eine andere Stellung bewegt bzw. geschaltet wird, anhand des Sensors 64 in der Steuereinheit 66 ein Deaktivierungssignal für die Federung generiert und dadurch das Schaltventil 52 durch ein Schließsignal geschlossen wird.

For the open position of the switching valve 52, ie for the activated suspension resulting in accordance with the various switching positions of the control unit 12, the following states:

In the lowered position (top switching position of the control unit of Figure 1), the first supply line 22 to the hydraulic tank 20 and the second supply line 24 is connected to the pump. In the second supply line 24 and in the second chamber 30, a corresponding pressure builds up, through which the pressure limiting valve 34 is opened via the pressure line 42, so that oil from the first chamber 28 via the first supply line 22 can flow into the hydraulic tank 20 , At the same time, the piston 29 can perform resilient movements, since a connection to the hydraulic accumulator 48 on the lifting side and a connection on the lowering side to the hydraulic tank 20 is made.

In the neutral position (from the top second switching position of the controller 12 of Figure 1) all inputs and outputs are closed at the control unit 12, that is, no oil can flow through the supply lines 22, 24. If it would come in this position to a compression of the piston 29, there would be the risk of cavitation in the second chamber 30 of the hydraulic cylinder 26, whereby seals in the hydraulic cylinder 26 could be damaged. To prevent this, the switch or sensor 64 signals a signal which is received by the control unit 66. The control unit 66 then generates a closing signal for the switching valve 52, taking into account a time delay for confirming a residence time in the neutral position. Once the switching valve 52 is closed, the piston 29 can no longer perform any movements since all lines 22, 24, 46 are closed are. As soon as the control unit 12 is switched to another position, the sensor 64 releases a signal for opening the switching valve 52. The signal of the sensor 64 is thus superior to the activation signal of the activation switch 68 in the switching logic of the control unit 66, so that despite an opening signal from the activation switch 68, the switching valve 52 can be closed by a closing signal of the sensor 64.

In the lifting position (from the top third switching position of the controller 12 of Figure 1), the first supply line 22 to the pump 18 and the second supply line 24 is connected to the hydraulic tank 20. In the first supply line 22 and in the first chamber 28, a corresponding pressure builds up, through which the piston 29 is raised, so that oil from the second chamber 30 via the second supply line 24 can flow into the hydraulic tank 20. At the same time, the piston 29 can perform resilient movements, since a connection to the hydraulic accumulator 48 on the lifting side and a connection on the lowering side to the hydraulic tank 20 is made.
If a shock is transmitted to the piston 29 during a lowering or lifting operation, it can deflect without risk of cavitation, since the lowering side is relieved to the hydraulic tank 20.

In the suspension position (lowermost switching position of the control unit 12 of FIG. 1), the first supply line 22 is closed and the second supply line 24 is connected to the hydraulic tank 20. The piston 29 can spring freely in this position. If it moves downwards through a shock transmitted to it, the oil from the first chamber 28 is forced into the hydraulic accumulator 48. The pressure building up in the hydraulic accumulator 48 causes the oil to flow back into the first chamber 28, so that the piston 29 moves upward again. This resilient movement is repeated, if necessary, until the shock has been completely compensated. Furthermore, it can be provided that as soon as the control unit 12 is moved or switched from the suspension position to another position, based on the sensor 64 in the control unit 66 generates a deactivation signal for the suspension and thereby the switching valve 52 is closed by a closing signal.

A use for that shown in Fig. 1 Exemplary embodiments are illustrated in FIG. 2. Fig. 2 shows a mobile telescopic loader 82 with a on a housing 84th or frame of the telehandler 82 pivotally hinged, Telescopically extendable outrigger 86. Between outrigger 86 and housing 84 is a hydraulic cylinder 26 for lifting and Lowering of the boom 86 is arranged. The hydraulic cylinder 26 is at a first and a second bearing 88, 90th hinged pivotally, wherein the piston rod side 92 at the second bearing 90 on the boom 86 and the piston bottom side 94 is hinged to the first bearing 88 on the housing 84. Furthermore, the hydraulic tank 20, the pump 18 and the Control unit 12 is positioned on or in the housing 84 and over Hydraulic lines 14, 16, 96 connected to each other. Further are the supply lines 22, 24 between the control unit 12 and hydraulic cylinders 26 in FIG. 2. The Pipe burst protection device 32 and the switching valve 52nd are located in a common valve block directly on the Hydraulic cylinder 26. The hydraulic accumulator 48 is preferably also arranged directly on the hydraulic cylinder 26, so that between the common valve block and the Hydraulic accumulator 48, the hydraulic line 46 as a rigid Connection can be formed, no separate Raw rupture protection device required. About one not Control shown are generated control or switching signals, with which the control unit 12 and the switching valve 52 (see Fig. 1) are controlled or switched. According to the previously described switch positions can the Hydraulic cylinder 26 are operated such that the boom 86 raised, held, lowered or held resiliently can be. With activated suspension and in spring position is ensures that during a suggestion, for example by the landing gear of the telehandler 82, jerky Accelerations due to free swinging of the boom 86 will be dampened, leading to an increase in Fahrkomforts comes, especially if with a Work tool 98 loads are absorbed and moved.

Even if the invention only by way of two Embodiments has been described, opening 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. So For example, the hydraulic arrangement on other Vehicles are applied, for example, on wheel loaders or Front loaders or even on excavators or cranes, the hydraulic have actuatable components which are raised or can be lowered and where a suspension makes sense appears.

Claims (9)

Hydraulic arrangement for a passive suspension system, comprising a hydraulic cylinder (26) having a first and a second chamber (28, 30), a hydraulic tank (20), a hydraulic fluid conveying means (18), a hydraulic accumulator (48), one between hydraulic accumulators (48) and first chamber (28) arranged hydraulic line (46) arranged in the hydraulic line (46) switching valve (52), a first supply line (22) for the first chamber (28), a second supply line (24) for the second chamber (30), one in the first supply line (22) arranged pipe rupture protection device (32) and a control device (12) with at least three switching positions, which comprise a lifting position, a lowered position and a neutral position for the hydraulic cylinder (26), characterized that the control unit (12) has a further switching position, which represents a suspension position, in which by the control unit ( 12) at least the second supply line (24) with the hydraulic tank (20) is connectable and at the same time connections of both supply lines (22, 24) to the conveyor (18) are interrupted. Hydraulic arrangement according to claim 1, characterized in that in the suspension position, the first and the second connecting line (22, 24) by the control unit (12) with the hydraulic tank (20) are connectable. Hydraulic arrangement according to claim 1 or 2, characterized in that the switching valve (52) has a closed position and an open position. Hydraulic arrangement according to claim 3, characterized in that the switching valve (52) closes in the closed position in one or both flow directions. Hydraulic arrangement according to one of the preceding claims, characterized in that means (64, 66) are provided which bring the switching valve (52) in a closed position when the control unit (12) is in the neutral position. Hydraulic arrangement according to one of the preceding claims, characterized in that means (64, 66) are provided which bring the switching valve (52) in a closed position when the control unit (12) is not in the suspension position. Hydraulic arrangement according to one of claims 3 to 5, characterized in that a time delay element is provided, which causes a presettable time delay for the switching of the switching valve (52) in the closed position at neutral position of the control device (12). Hydraulic arrangement according to one of the preceding claims, characterized in that the control device (12) is a slide valve having at least two inputs and two outputs for each switching position. Hydraulic arrangement according to one of the preceding claims, characterized in that the pipe rupture protection device (32) in the direction of the control unit (12) closing check valve (36) and a pressure relief valve (34), wherein the pressure relief valve (34) by in the supply lines (22 , 24) prevailing pressures can be controlled.

Images