SE535692C2 - Apparatus and method for leveling a structural part of an off-road vehicle - Google Patents

Abstract

23 SUMMARY Features and method for leveling a structural component (3) of an off-road vehicle (1), which structural member is supported by at least one front hydraulic cylinder, which is arranged on a first side of a vertical plane of the vehicle, and at least one second hydraulic cylinder, which is arranged on a second side the perpendicular plane. According to the invention, the device has means (25) for allowing the flow of hydraulic fluid from at least one first accumulator tank (17, 18) to name at least one first hydraulic cylinder (5, 6) and from name at least one second hydraulic cylinder (7, 8) to at least one second accumulator tank ( 21, 22), partly to spar the river of hydraulic fluid in the opposite directions, when vehicle slopes to the first side, and to partly allow the river of hydraulic fluid from said at least one second accumulator tank to said at least one second hydraulic cylinder and from said at least one first hydraulic cylinder to said at least one front accumulator tank, secondly, sparring the river of hydraulic fluid in opposite directions, as the vehicle leans to the other side. Fig. 2 P2406SE T01 2010-12-07

Description

20 25 30 35 535 B92 This of course has a negative effect on the forwarder's stability and means that the swinging or tilting cargo space risks hitting and damaging uncultivated forest when the forwarder is driven in wooded terrain.

To solve this problem, it is possible to arrange wider base roads for exporting the timber, which the landowner usually opposes, or to limit the forwarder's load height, which means that the transport economy deteriorates, and that the forwarder is forced to drive several turns, which risks giving large ground damage.

A better alternative is to equip the forwarder with a hydraulic system, which levels the load carrier. A known way of achieving this is to provide the forwarder's hydraulic system with a control system comprising hydraulic pumps, which actively pump hydraulic oil into and out of the hydraulic cylinders to maintain the load space in the transverse direction of the forwarder in a flat position regardless of the terrain. However, in order to be able to handle fast and powerful processes, which can occur if one of the forwarder's wheels runs down from a high stump or into a deep hole, the hydraulic pumps and associated valves must be heavily dimensioned to be able to deliver the hydraulic oil flow required to lift the heights of the cargo space. In addition, the forwarder's motor must be able to deliver the power required to drive the hydraulic pumps in these situations. It is understood that the forwarder would be unreasonably expensive if the control system were dimensioned so that it could handle all extreme situations that may arise when driving the forwarder in the terrain.

An additional problem with active control systems, ie. system where hydraulic pumps actively pump hydraulic oil to and from the resilient hydraulic cylinders to level the cargo space, is that they are relatively slow.

In fast and strong processes, e.g. In the above-mentioned case, when one of the forwarder's wheels runs down from a high stump, valves and hydraulic pumps risk not having time to adjust and deliver the required amount of hydraulic oil to the relevant hydraulic cylinder or cylinders before the cargo space slope exceeds a critical limit. is difficult or even impossible to cancel.

Preventing swinging movements of a cargo space is thus a problem in off-road trucks in general and in the removal of timber in particular. The object of the present invention is to solve this problem and to provide a device and a method which allows simple and efficient leveling of a structural part, e.g. a cargo space or a driver's cab, in an off-road vehicle, e.g. a forwarder.

The device according to the invention is characterized in that it comprises means for: - partly allowing flows of hydraulic fluid from at least one first accumulator tank to said at least one first hydraulic cylinder and from said at least one second hydraulic cylinder to at least one second accumulator tank, partly blocking flows of hydraulic fluid in the opposite directions, when the vehicle is inclined to the first side, and - partly allow flows of hydraulic fluid from said at least one second accumulator tank to said at least one second hydraulic cylinder and from said at least one first hydraulic cylinder to said at least one first accumulator tank, partly block flows of hydraulic fluid in the opposite directions, when the vehicle is tilted to the other side. The method according to the invention is characterized by: - that flows of hydraulic fluid are allowed from at least one first accumulator tank to said at least one first hydraulic cylinder and from said at least one second hydraulic cylinder to at least one second accumulator tank, and that flows of hydraulic fluid in the opposite directions is blocked when the vehicle is inclined to the first side, and - flows of hydraulic fluid are allowed from said at least one second accumulator tank to said at least one second hydraulic cylinder and from said at least one first hydraulic cylinder to said at least one first accumulator tank, and that flows of hydraulic fluid in the opposite directions are blocked as the vehicle leans to the other side.

Preferably, said means comprises a tilt-controlled hydraulic valve, which is arranged to direct the flow of hydraulic oil between the hydraulic cylinders and the accumulator tanks on each side of the vertical plane as a function of the inclination of the vehicle. When the vehicle is on a slope, where one side of the vehicle is lower than the other side, control signals from a inclination sensor will cause the hydraulic valve to direct the hydraulic oil flow between said at least one hydraulic cylinder and said at least one accumulator tank on each side of the vehicle. On the valley side, ie. the side of the vehicle currently facing downhill, the hydraulic valve will allow a flow of hydraulic fluid from the accumulator tank to the hydraulic cylinder, but block the flow of hydraulic fluid in the opposite direction. On the mountain side, ie. the side of the vehicle currently facing up the slope, the hydraulic valve will allow a flow of hydraulic fluid from the hydraulic cylinder to the accumulator tank, but block the flow of hydraulic fluid in the opposite direction. This ensures that hydraulic fluid is only allowed to flow between the hydraulic cylinders and the accumulator tanks so that the structural part is leveled, ie. so that a slope of the structural part is counteracted.

Unlike known active leveling systems, where hydraulic fluid is pumped to and from the hydraulic cylinders to level the component, the device according to the invention is completely passive in that the inertia of the component relative to the chassis is used to cause hydraulic fluid to flow to and from the hydraulic cylinders at a desired way. If the chassis is suddenly tilted a predetermined number of degrees in either direction, the structural member tends to maintain its original orientation for a short time before following the movement of the chassis. In a system with damping but without leveling, the structural part will then swing forward and eat around an equilibrium position, which is defined by the inclination of the chassis, until the oscillation of the structural part is damped and the structural part assumes the same inclination as the chassis. In the device according to the invention, this inertia of the structural part relative to the chassis is used to drive hydraulic fluid to and from the hydraulic cylinders so that the structural part is leveled. This allows efficient level control to be obtained without the need to supply energy. The leveling according to the invention is thus passive in the sense that it does not require any external energy supply.

The device according to the invention is simple and comprises few moving parts. Thereby, the device allows a very fast and efficient leveling, which does not exhibit the inertia and delay associated with known, active leveling systems.

Since the device according to the invention uses the inertia of the structural part relative to the chassis to level the structural part, the device functions more efficiently the larger and faster the change in inclination of the chassis. This should be compared with known, active leveling systems, which work less well with large and rapid changes in slope.

The invention will be described in more detail below with reference to the accompanying drawings.

Figure 1 schematically shows a forwarder, which comprises a device according to the invention.

Figure 2 schematically shows a hydraulic diagram of the hydraulic system of the forwarder according to figure 1.

Figure 3 schematically shows a hydraulic valve of the hydraulic diagram, which hydraulic valve is in a first position.

Figure 4 shows the hydraulic valve in a second position.

Figure 5 shows the hydraulic valve in a third position.

Figure 6 shows the hydraulic valve in a fourth position.

The device according to the invention will in the following be described in more detail on the basis of an off-road vehicle in the form of a forwarder, where the device according to the invention is used to level a construction part in the transverse direction of the forwarder in the form of a cargo space. It will be appreciated, however, that the device according to the invention is applicable to other types of off-road vehicles, and that the device can be used to level other types of structural parts, e.g. a cab.

Figure 1 shows a forwarder 1 in a rear view. The forwarder 1 comprises a chassis 2 and a load carrier 3 in the form of a load bank, which defines an elongate cargo space 4, which extends in the longitudinal direction of the forwarder 1.

The load carrier 3 is supported in a known manner by four double-acting hydraulic cylinders 5, 6, 7, 8 (see figure 2), of which only two are visible in figure 1.

The hydraulic cylinders are arranged between the chassis 2 and the load carrier 3 to spring the load carrier 3 when the forwarder 1 is driven in uneven terrain. Each hydraulic cylinder 5, 6, 7, 8 is connected at its piston end 9 to the chassis 2 and at its rod end 10 to the load carrier 3. Each hydraulic cylinder S, 6, 7, 8 has at its piston end 9 a first, lower hydraulic chamber 11 and at its rod end 10 a second, upper hydraulic chamber 12. The hydraulic chambers 11, 12 are separated by a hydraulic piston 13. The hydraulic piston 13 is connected to a piston rod 14, which in turn is connected to the load carrier 3. Said suspension is obtained by causing hydraulic fluid to flow into and out of the hydraulic cylinders 11, 12 of the hydraulic cylinders 5, 6, 7, 8.

The hydraulic cylinders 5 and 6 are arranged on the left side of the longitudinal axis of the forwarder 1. In the longitudinal direction of the forwarder 1, the hydraulic cylinder S is arranged behind the hydraulic cylinder 6. In the following, therefore, the hydraulic cylinders 5 and 6 will be called the first or left, rear hydraulic cylinder 5 and the first or left, front hydraulic cylinder 6. The hydraulic cylinders 7 and 8 are correspondingly arranged on the right-hand side of the longitudinal axis of the forwarder 1. In the following, therefore, the hydraulic cylinders 7 and 8 will be referred to as the second or right, rear hydraulic cylinder 7 and the second or right, front hydraulic cylinder 8, respectively.

In the transverse direction of the forwarder, the rear hydraulic cylinders 5, 7 are preferably placed opposite each other and also the front hydraulic cylinders 6, 8. The left hydraulic cylinders 5 and 6 are connected to each other in series in a known manner by a hydraulic line 15, which connects the upper hydraulic chamber 12 of the rear left hydraulic cylinder 5 to the lower hydraulic chamber of the front left hydraulic cylinder 6. In the same way, the right hydraulic cylinders 7 and 8 are connected in series with each other through a hydraulic line 16, which connects the upper hydraulic chamber of the rear right hydraulic cylinder 7 to the lower hydraulic chamber of the front right hydraulic cylinder 8.

According to the invention, the hydraulic system of the forwarder 1 comprises a first group of accumulator tanks 47, which in the embodiment shown comprise two first accumulator tanks 17 and 18, which are connected in parallel via throttle valves 19 and 20, and two second accumulator tanks 21 and 22, which are connected in parallel with each other. via throttle valves 23 and 24.

According to a preferred embodiment of the invention, the hydraulic system of the forwarder 1 comprises a hydraulic valve 25, which has a first port g, which connects to the accumulator tanks 17 and 18 via a hydraulic line 26, a second port §, which connects to the lower hydraulic chamber 11 of the rear left hydraulic cylinder 5. via a hydraulic line 27, a third port Q, which connects to the accumulator tanks 21 and 22 via a hydraulic line 28 and a fourth port Q, which connects to the lower hydraulic chamber of the rear right hydraulic cylinder 7 via a hydraulic line 29.

The hydraulic valve 25 comprises two two-position slide valves 30, 31 (see Figure 3), each of which has ports 3, b, 3 and Q, the flow passages a ~ b and gQ being open in one valve position and closed in the other valve. the situation. The slide valves 30 and 31 are connected by a first hydraulic oil passage or hydraulic line 32 of the hydraulic valve 25, whereby the port Q of the first slide valve 30 is connected to the port 3 of the second slide valve 31. Likewise, the port Q of the the first slide valve 30 connected to the port 9 of the second slide valve 31 through a second hydraulic oil passage or hydraulic line 33 of the hydraulic valve 25.

The port 3 of the first slide valve 30 is connected to the port Q of the hydraulic valve 25, and the port g of the slide valve 30 is connected to the port Q of the hydraulic valve 25. Likewise, the port b of the second slide valve 31 is connected to the port g of the hydraulic valve 25, and the port Q of the slide valve 31 is connected to hydraulic valve 25 port Q.

The hydraulic valve 25 further comprises a third hydraulic line 34, which runs via a non-return valve 35 between the port Q of the hydraulic valve 25 and the hydraulic line 32, a fourth hydraulic line 36, which runs via a non-return valve 37 between the port Q of the hydraulic valve 25 and the hydraulic line 33, a fifth hydraulic line 38 , which runs via a non-return valve 39 between the port Q of the hydraulic valve 25 and the hydraulic line 32 and a sixth hydraulic line 40, which runs via a non-return valve 41 between the port Q of the hydraulic valve 25 and the hydraulic line 33.

The hydraulic valve 25 is thus adjustable in four positions: a first position where both the slide valves 30 and 31 are open, as shown in Figure 3, a second position where the slide valve 30 is open and the slide valve 31 is closed, as shown in Figure 4, a third position where the slide valve 30 is closed and the slide valve 31 is open, as shown in Figure 5, and a fourth position where both slide valves 30 and 31 are closed, as shown in Figure 6.

In the first position, when both slide valves 30 and 31 are open, hydraulic fluid in the form of hydraulic oil can flow freely in both directions between ports g and g and between ports Q and Q via the slide valves 30, 31, respectively. flow passages aQ and QQ, respectively.

In the second position, when the slide valve 30 is open and the slide valve 31 is closed, the non-return valve 39 allows a flow of hydraulic oil from the port Q to the port Q via the flow passage QQ of the first slide valve 30, and the non-return valve 41 allows a flow of hydraulic oil from the port Q to port Q via the flow passage QQ of the first slide valve 30. However, the non-return valve 39 prevents hydraulic oil from flowing from port Q to port Q, and the non-return valve 41 prevents hydraulic oil from flowing from port Q to port Q. Thus, hydraulic oil is allowed to flow from port Q to port Q respectively from the port Q to the port Q when the slide valve 30 is open and the slide valve 31 is closed, while the hydraulic oil flow in the opposite direction, i.e. from gate Q to gate Q and from gate Q to gate Q, respectively, is blocked.

In the third position, when the slide valve 30 is closed and the slide valve 31 is open, the non-return valve 35 allows a flow of hydraulic oil from the port Q to the port Q via the flow passage 5-Q of the second slide valve 31, and the non-return valve 37 allows a flow of hydraulic oil from the port Q to the port Q via the flow passage QQ of the second slide valve 31. However, the non-return valve 35 prevents hydraulic oil from flowing from the port Q to the port Q, and the non-return valve 37 prevents hydraulic oil from flowing from the port Q to the port Q. Thus, hydraulic oil is allowed to flow from the port Q to port Q and from port Q to port Q, respectively, when the slide valve 30 is closed and the slide valve 31 is open, while the hydraulic oil flow in the opposite direction, i.e. from gate Q to gate Q and from gate Q to gate Q, respectively, is blocked.

In the fourth position, when both slide valves 30 and 31 are closed, the non-return valve 39 prevents hydraulic oil from flowing from port Q to port Q, and the non-return valve 37 prevents hydraulic oil from flowing from port Q to port Q. Likewise, the non-return valve 35 prevents hydraulic oil from flowing from port § to port 5, and the non-return valve 41 prevents hydraulic oil from flowing from port Q to port Q. Thus, no hydraulic oil is allowed to flow between ports g and § and between Q and Q, respectively, as both the slide valves 30, 31 are closed.

In addition to said accumulator tanks 17, 18, 21, 22 in the first group of accumulator tanks 47, the hydraulic system comprises a second group of accumulator tanks 48 (see Figure 2), which comprises a first accumulator tank 42 and a second accumulator tank 43. The first accumulator tank 42 is connected to the the lower hydraulic chamber 11 of the rear left hydraulic cylinder S via a throttle valve 44. The second accumulator tank 43 is correspondingly connected to the lower hydraulic chamber of the rear right hydraulic cylinder 7 via a throttle valve 45. The accumulator tanks 42 and 43 are thus connected directly to the hydraulic cylinders S and 7, respectively.

According to a preferred embodiment of the invention, the forwarder 1 also comprises a inclination sensor 46 (see Figure 1), which in the embodiment shown is placed on the forwarder's chassis 2 and is arranged to sense the inclination of the forwarder 1 in its transverse direction. More specifically, the inclination sensor 46 is arranged to sense the deviation of the chassis 2 from the vertical plane extending in the longitudinal direction of the forwarder 1. The inclination sensor 46 is arranged to send control signals to the hydraulic valve 25, which control signals are a function of this deviation. More specifically, the inclination sensor 46 is arranged to send control signals to the hydraulic valve 25 to open and close the slide valves 30 and 31 as a function of the inclination of the forwarder 1. Preferably, these control signals are electrical, and the slide valves 30 and 31 are preferably electrically controlled to be able to receive these control signals.

When the forwarder 1 is driven on a flat surface, the chassis 2 does not deviate from its horizontal position. In other words, the chassis 2 does not tilt in any direction when the forwarder is driven in this way and the inclination sensor 46 detects no deviation from the vertical plane. In such operating situations, the inclination sensor 46 sends control signals to the hydraulic valve 25 which causes the hydraulic valve 25 to assume its first position, i.e. a position where both the slide valves 30 and 31 are open, as shown in Figure 3.

As described above, hydraulic oil is allowed to flow freely between the ports g and § and between the ports Q and Q, respectively, in this position, and consequently hydraulic oil can flow between the accumulator tanks 17 and 18 and the left hydraulic cylinders 5 and 6 and between the accumulator tanks 21 and 22 and the right hydraulic cylinders 7 and 8. Thus, in this position, the accumulator tanks 17, 18, 21 and 22 in the first accumulator tank group 47 contribute to the damping of the movements of the cargo space 4 together with the accumulator tanks 42 and 43 in the second accumulator tank group 48.

If the inclination sensor detects that the inclination of the chassis 2 to the left or right exceeds a predetermined limit value, which is preferably in the range 1-5 degrees and most preferably is about 2 degrees, the inclination sensor 46 sends a new control signal to the hydraulic valve 25.

For example, if the tilt sensor 46 detects that the chassis 2 is tilted to the right, the tilt sensor 46 sends a control signal to the hydraulic valve 25 which causes the hydraulic valve 25 to assume its second position, i.e. a position where the slide valve 30 is open and the slide valve 31 is closed, as shown in Figure 4. In this position, hydraulic oil is allowed to flow from the gate § to the gate Q and from the gate g to the gate Q, respectively, while the hydraulic oil flow in the opposite direction is blocked.

Consequently, in this position, hydraulic oil can flow from the accumulator tanks 21 and 22 to the right hydraulic cylinders 7 and 8 and from the left hydraulic cylinders 5 and 6 to the accumulator tanks 17 and 18, respectively, while hydraulic oil flows in the opposite directions are blocked. In other words, the hydraulic oil flow between the hydraulic cylinders and the accumulator tanks on the respective side of the forwarder is unidirectional. Due to the care of the accumulator tanks 42 and 43, which are connected directly to the hydraulic cylinders, the cargo space 4 will always to at least some extent pivot or tilt back and forth in the transverse direction of the forwarder 1, even when the forwarder 1 is inclined. As the cargo space 4 turns to the right, an overpressure arises in the lower hydraulic chambers of the right hydraulic cylinders 7 and 8 and a negative pressure arises in the lower hydraulic chambers of the left hydraulic cylinders 5 and 6. , hydraulic oil will only be able to flow to the accumulator tank 43 and from the accumulator tank 42, respectively, which provides a damping of the oscillation of the cargo space 4 to the right. Then the load compartment 4 then turns again to the left, ie. again towards the vertical plane, a negative pressure arises in the lower hydraulic chambers of the right hydraulic cylinders 7 and 8 and an overpressure in the lower hydraulic chambers of the left hydraulic cylinders 5 and 6 13. Since the hydraulic valve 25 allows hydraulic oil flows from the accumulator tanks 21 and 22 position hydraulic oil to flow from the right accumulator tanks 21 and 22 to the lower hydraulic chambers of the right hydraulic cylinders 7 and 8 and from the lower hydraulic chambers 13 and 6 of the left hydraulic cylinders 5 and 6 to the left accumulator tanks 17 and 18. With other In other words, hydraulic oil will flow from the right accumulator tanks 21 and 22 to the right hydraulic cylinders 7 and 8 and from the left hydraulic cylinders 5 and 6 to the left accumulator tanks 17 and 18 each time the cargo space 4 pivots back towards the vertical plane, while hydraulic oil flows in the opposite directions are then blocked the cargo space 4 turn ger ate right.

This unidirectional direction of the hydraulic oil flows will thus strive to return the cargo space 4 to and maintain the cargo space 4 in a flat position when the chassis 2 is inclined. In fact, this function of maintaining the cargo space 4 in its flat position works better the stronger and faster the chassis 2 tilts, as it increases the negative pressure and overpressure that drives hydraulic oil to the right hydraulic cylinders 7 and 8 and from the left hydraulic cylinders 5 and 6, respectively. each time the cargo space 4 swings back towards the vertical plane. Consequently, in this second position, the accumulator tanks 17, 18, 21 and 22 in the first accumulator tank group 47 will strive to maintain the cargo space 4 in its flat position, while the accumulator tanks 42 and 43 in the second accumulator tank group 48, which are connected directly to the hydraulic cylinders 5- 8, will provide the damping of the cargo space 4.

If the inclination sensor 46 detects that the cargo space 4 is inclined to the left, the inclination sensor 46 sends a control signal to the hydraulic valve 25, which causes the hydraulic valve 25 to assume its third position, i.e. a position where the slide valve 30 is closed and the slide valve 31 is open, as shown in Figure 5. In this position, hydraulic oil is allowed to flow from the gate g to the gate § and from the gate Q to the gate Q, respectively, while the hydraulic oil flow is blocked in the opposite direction.

Consequently, in this position, hydraulic oil can flow from the accumulator tanks 17 and 18 to the left hydraulic cylinders 5 and 6 and from the right hydraulic cylinders 7 and 8, respectively, to the accumulator tanks 21 and 22, while hydraulic oil flows in the opposite directions are blocked. In the same manner as described above, the unidirectional direction of the hydraulic oil flows will strive to maintain the cargo space 4 in a flat position when the chassis 2 is inclined, since hydraulic oil will flow to the left hydraulic cylinders 5 and 6 and from the right hydraulic cylinders 7 and 8 each time. the cargo space 4 turns again towards the vertical plane. Thus, even in this position, the accumulator tanks 17, 18, 21 and 22 in the first accumulator tank group 47 will ensure that the cargo space 4 is aligned with the horizontal position, while the accumulator tanks 42 and 43 in the second accumulator tank group 48 will provide the attenuation of the cargo space 4.

Finally, if the hydraulic valve 25 is caused to assume its fourth position, where both slide valves 30 and 31 are closed, as shown in Figure 6, the accumulator tanks 17, 18, 21 and 22 in the first accumulator tank group 47 are disconnected from the hydraulic cylinders 5-8. this position thus disables the function of straightening the cargo space 4 away and the pivoting movements of the cargo space 4 are damped in a conventional manner by means of the accumulator tanks 42 and 43 in the second accumulator tank group 48. It may be desirable to use this fourth position if the forwarder is to be driven on a surfaces that are expected to be flat, e.g. if the forwarder is to be driven on a paved country road.

It will be appreciated that the above-described function of straightening the cargo space is completely passive in that no hydraulic oil is pumped or actively forced into the hydraulic cylinders on the side to which the cargo space is inclined. It is understood, however, that the system according to the invention can be combined or supplemented with an active system, where the inclination sensor also sends control signals to pumps and valves to actively turn the cargo space to the horizontal position. Such a supplement can be advantageous in vehicles which are expected to be subjected to relatively slow heeling processes, since the device according to the invention is less efficient in such.

The invention has been described above on the basis of a specific embodiment. It will be appreciated, however, that other embodiments fall within the scope of the invention. For example, it will be appreciated that the above-mentioned one-way flow of hydraulic oil may be accomplished by valve configurations other than those described above.

It will also be appreciated that the number of hydraulic cylinders and accumulator tanks on either side of the vertical plane may differ from that described above. For example. the invention is equally applicable if only a hydraulic cylinder and an accumulator tank are located on each side of the vertical plane.

It will also be appreciated that the inclination sensor may be located in positions other than the chassis to sense the inclination of the forwarder. The inclination sensor can e.g. be placed on the structural part that the device is to level. However, this may be less preferred, since there is normally a delay between the position change of the chassis and the change of position of the structural part, which delay may involve a lag in the leveling. It is also possible to place a inclination sensor on the chassis and an inclination sensor on the structural part to be leveled and control the hydraulic valve as a function of the signals from both of these inclination sensors.

Claims (12)

10 15 20 25 30 35 535 B92 17 PATENT REQUIREMENTS Device for leveling a structural part (3) of an off-road vehicle (1), which structural part (3) is supported by at least one first hydraulic cylinder (5, 6), which is arranged on a first side of a vertical plane of the vehicle (1). 1), and at least one second hydraulic cylinder (7, 8), which is arranged on a second side of the vertical plane, characterized in that the device comprises: at least one first accumulator tank (17, at least one second accumulator tank (21, a hydraulic valve (25) and 18), 22), a inclination sensor (46), which is arranged to register the inclination of the vehicle (1) around the vertical plane and emit control signals to the hydraulic valve (25), the inclination sensor (46) being arranged to emit control signals to the hydraulic valve (25) to cause the hydraulic valve (25) to: on the one hand allow flows of hydraulic fluid from said at least one first accumulator tank (17, 18) to said at least one first hydraulic cylinder (5, 6) and from said at least one second hydraulic cylinder (7, accumulator tank (21, 8) to the said min a second 22), partly blocking flows of hydraulic fluid in the opposite directions, when the inclination sensor (46) detects that the inclination of the vehicle (1) on the first side exceeds a predetermined first limit value, and partly allowing flows of hydraulic fluid from said at least one second accumulator tank (21, 22) to said at least one second hydraulic cylinder (7, 8) and from said at least one first hydraulic cylinder (5, 6) to said at least one first accumulator tank (17, 18), partly blocking flows of hydraulic fluid in the opposite directions, when the inclination sensor (46) detects that the inclination of the vehicle (1) on the other side exceeds a predetermined second limit value. 10 15 20 25 30 35 535 B92 18 Device according to claim 1, characterized in that the hydraulic valve (25) has a first port (A), which is connected to said at least one first accumulator tank (17, 18), a second port (§), which is connected to said at least one first hydraulic cylinder (5, 6), a third port (Q), which is connected to said at least one second accumulator tank (21, 22), and a fourth port (Q), which is connected to said at least one second hydraulic cylinder (7, 8). Device according to claim 2, characterized in that said at least one first accumulator tank (17, 18) and said at least one second accumulator tank (21, 22) are included in a first group of accumulator tanks (47), and that the device comprises a second group of accumulator tanks ( 48), comprising at least one first accumulator tank (42) connected to said at least one first hydraulic cylinder (5, 6) via a first throttle valve (44), and at least one second accumulator tank (43) connected to said at least one second hydraulic cylinder (7, 8) via a second throttle valve (45). Device according to one of Claims 2 and 3, characterized in that the hydraulic valve (25) comprises: - a first slide valve (30) and a second slide valve (31), each of which has a first port (a), a second port (Q), a third port (g) and a fourth port (Q), each slide valve (30, 31) being adjustable partly in a first valve position, where a first flow passage (5-Q) between the first port (3) and the second port (Q) and a second flow passage (gQ) between the third port (g) and the fourth port (Q) are open, partly in a second valve position, where said flow passages (3-Q, 3-Q) are closed, and - a first hydraulic oil passage (32), which connects the second port (Q) of the first slide valve (30) to the first port (a) of the second slide valve (31), and a second hydraulic oil passage (33), which connects the fourth port (Q) of the first slide valve (30) to the third port (9) of the second slide valve (31), the first port (5) of the first slide valve (30) is connected to the first port (5) of the hydraulic valve (25), the second port (Q) of the second slide valve (31) is connected to the second port (§) of the hydraulic valve (25), the third port (E ) of the first slide valve (30) is connected to the third port (Q) of the hydraulic valve (25), and the fourth port (Q) of the second slide valve (31) is connected to the fourth port (Q) of the hydraulic valve (25). Device according to claim 4, characterized in that the hydraulic valve (25) comprises: - a third hydraulic oil passage (34), which runs via a first non-return valve (35) between the first port (Q) of the hydraulic valve (25) and the first hydraulic oil passage (32), - a fourth hydraulic oil passage (36), which via a second non-return valve (37) third port (§) and the second hydraulic oil passage (33), - a fifth hydraulic oil passage (38), which via a third non-return valve (39) runs between the second port (§) of the hydraulic valve (25) and the first hydraulic oil passage (32), and runs between the hydraulic valve (25) - a sixth hydraulic oil passage (40), which via a fourth non-return valve (41) fourth port (Q) and the second hydraulic oil passages (33). runs between the hydraulic valve (25) Device according to claim 5, characterized in that the hydraulic valve (25) is adjustable in: - a first position, where the first slide valve (30) and the second slide valve (31) are open, the hydraulic fluid being allowed to flow freely in both directions between the first port (è) of the hydraulic valve (25) and the second port (§) and between the third port Q and the fourth port (Q) of the hydraulic valve (25) via the first flow passage (5-Q) of the slide valves (30, 31) and second flow passage (EQ), a second position, where the first slide valve (30) is open and the second slide valve (31) is closed, the third non-return valve (39) partly allowing a flow of hyd raw fluid from the second port (Q) of the hydraulic valve (25) to its first port (Q) via the first flow passage (Qa) of the first slide valve (30), and prevents a flow of hydraulic fluid from the first port (g) of the hydraulic valve (25) to its second port (Q), and wherein the fourth non-return valve (41) allows a flow of hydrogen hydraulic fluid from the third port (Q) of the hydraulic valve (25) to its fourth port (Q) via the second flow passage (5-Q) of the first slide valve (30), and prevents a flow of hydraulic fluid from the fourth port (Q) of the hydraulic valve (25) to its third port (Q), and - a third position, where the first slide valve (30) is closed and the second slide valve (31) is open, the first non-return valve (35) allowing a flow of hydraulic fluid from the hydraulic valve ( 25) first port (Q) to its second port (§) via the second flow passage (§ ~ §) of the second slide valve (31), partly preventing a flow of hydraulic fluid from the second port (§) of the hydraulic valve (25) ) to its first port (A), and wherein the second non-return valve (37) allows a flow of hydraulic fluid from the fourth port (Q) of the hydraulic valve (25) to its third port (Q) via the second flow passage (QQ) of the second slide valve (31). ), and prevents a flow of hydraulic fluid from the third port (Q) of the hydraulic valve (25) to its fourth port (Q) Q). Device according to claim 6, characterized in that the hydraulic valve (25) is also adjustable in a fourth position, where both the first slide valve (30) and the second slide valve (31) are closed, the first non-return valve (35) ) and the second non-return valve (38) prevents a flow of hydraulic fluid between the first port (g) of the hydraulic valve (25) and the second port (Q) of the hydraulic valve (25), and wherein the third non-return valve (37) ) and the fourth non-return valve (41) prevents a flow of hydraulic fluid between the third port (Q) of the hydraulic valve (25) and the fourth port (Q) of the hydraulic valve (25). Device according to any one of claims 6 and 7, characterized in that the inclination sensor (46) is arranged to bring the hydraulic valve (25) to the third position if it detects that the inclination of the vehicle (1) on the first side exceeds said predetermined first limit value, and that the inclination sensor (46) is arranged to bring the hydraulic valve (25) to the second position if it detects that the inclination of the vehicle (1) on the other side exceeds said predetermined second limit value. Device according to any one of the preceding claims, characterized in that said first and second limit values are in the range 1-5 degrees and that said vertical plane extends in the longitudinal direction of the vehicle (1). Off-road vehicle (1), characterized in that it comprises a device according to any one of claims 1-9. Off-road vehicle according to claim 10, characterized in that the off-road vehicle is a forwarder (1) and that said structural part is a load carrier (3) of the forwarder (1). Method for leveling a structural part (3) of an off-road vehicle (1), which structural part (3) is supported by at least a first hydraulic cylinder (5, 6), which is arranged on a first side of a vertical plane of the vehicle ( 1), and at least one second hydraulic cylinder (7, 8), which is arranged on a second side of the vertical plane, characterized in: - that flows of hydraulic fluid are allowed from at least one first accumulator tank (17, 18) to said at least one first 535 G92 22 hydraulic cylinder (5, 6) and from said at least one second hydraulic cylinder (7, 8) to at least one second accumulator tank (21, 22), and that flows of hydraulic fluid in the opposite directions are blocked when the vehicle (1) inclined to the first side, and that flows of hydraulic fluid are allowed from said at least one second accumulator tank (21, 22) to said at least one second hydraulic cylinder (7, 8) and from said at least one first hydraulic cylinder (5, 6) to said at least one first accumulator tank (17, 18), and that flows of hydrate ul fluid in the opposite directions is blocked when the vehicle (1) is tilted to the other side.