Steering procedure for operating a forklift truck, forklift truck

Abstract

Steering method for operating a forklift truck (1), wherein the forklift truck (1) has at least two front wheels (2.1, 2.2) and at least one rear wheel (3.1, 3.2), wherein a steering angle sensor (5) is actuated to initiate a turn around a steering pole (P) and the at least two front wheels (2.1, 2.2) and / or the at least one rear wheel (3, 3.1, 3.2) are steered, wherein when steering the wheels (2.1, 2.2, 3, 3.1, 3.2) the steering pole (P) is moved on a steering line (S), characterized in that a distance (L, Q) of the steering line (S) to the vehicle center (M) of the forklift truck (1) is controlled semi- or fully automatically.

Description

[0001] The present invention relates to a steering method for operating a forklift truck and to a forklift truck for carrying out such a steering method.

[0002] Such steering methods are known from the prior art in a multitude of different configurations. In particular, single-axle steering methods, in which the wheels of only one axle are steered, multi-axle steering methods, in which the wheels of more than one axle are steered, and all-wheel steering methods, in which all wheels can be steered, especially each wheel individually, are known.

[0003] To initiate a turn with a forklift, a turning radius is typically set using a steering angle sensor, such as a steering wheel or joystick. Subsequently, one or more steerable wheels of the forklift rotate or steer around an axis parallel to the forklift's vertical axis, so that the steered wheels are no longer parallel to the forklift's longitudinal or transverse direction. A distinction can be made between actively steerable wheels, i.e., wheels that have a steering gear or drive for rotating or steering the respective wheel or wheel suspension, and passively steerable wheels, i.e., those that are not motor-driven for steering but are, for example, designed as trailing wheels. Due to the angled position of the steered wheels relative to the forklift's longitudinal or transverse direction, the forklift executes a turn around a steering axis.

[0004] The steering center is the point where straight lines perpendicular to the wheels of the industrial truck, each coinciding with its respective axis of rotation, can intersect. Advantageously, the lines of all steered wheels meet at a common steering center, thus essentially preventing slippage or rubbing.

[0005] Typically, the steering center is shifted along a steering line when a turn is initiated. For example, when traveling straight ahead, all wheels of the forklift are typically parallel to each other. In this case, the steering center is at infinity. When a turn is initiated by actuating a steering angle sensor, the steering center moves along the steering line from infinity towards the forklift. If one or more wheels of the forklift do not steer when the turn is initiated—that is, if one or more wheels of the forklift do not rotate around an axis parallel to the vertical axis—the steering line becomes a straight line that intersects the center point of the unsteered wheel.

[0006] It should be clear that the vertical axis (z-axis), longitudinal axis (x-axis), and transverse axis (y-axis) of the forklift truck are orthogonal to each other and typically intersect at the center of the vehicle. The longitudinal axis intersects the vehicle's center point and is typically aligned with the direction in which the truck is operated in its main direction of travel. A transverse axis intersects the longitudinal axis orthogonally at the vehicle's center point and typically lies in the plane along which the forklift truck can be moved perpendicular or laterally to its main direction of travel, for example, when shifting the truck laterally.

[0007] From publication EP 2 956 350 B1, a three-wheeled industrial truck and a steering method applicable to it are known, in which, during longitudinal driving operation, also called front-loading operation, two front wheels of the industrial truck are arranged non-steered or permanently parallel to the longitudinal axis to initiate a turn, and the vehicle is steered by rotating a rear wheel of the industrial truck. Here, the rear wheel can be aligned obliquely to the longitudinal axis, particularly proportionally to an angle of adjustment of the steering angle sensor, so that the industrial truck performs a rotation about a steering pole which is arranged on a steering line that extends as a straight line through the two front wheels.

[0008] Furthermore, for example, DE 10 2012 105 831 A1 and DE 10 2009 021 693 A1 each disclose a steering method in which the steering line, along which the steering pole moves during steering, is designed to be displaceable or shiftable. In particular, the steering line can be changed to a predefined position and / or into a predefined shape, such as a straight line or circular path, by manually selecting a steering program, so that various movement possibilities of the vehicle result, in particular rotation around a pivot point.

[0009] Furthermore, EP 2 947 044 B1 discloses a steering method in which the steering line is set depending on the operating mode of a control system. Here too, the operating mode is selected manually.

[0010] Furthermore, DE 199 60 946 A1 discloses a counterbalance forklift with two non-steerable front wheels and two steerable rear wheels, wherein the front wheels are parallel displaceable to change the axle spacing in the longitudinal direction of the vehicle. However, the steering axis always remains in the same position.

[0011] It has been shown that the steering methods known from the prior art have disadvantages. In particular, the inflexible steering line makes it difficult to maneuver the forklift truck, especially in narrow aisles. If the forklift truck is equipped with forks for picking up a load, such as pallets or the like, the operator must always take into account the possibility of unintended fork movement when steering and approaching the load.

[0012] It is therefore the object of the present invention to provide a steering method for operating a forklift truck and a forklift truck which do not have the disadvantages of the prior art and make it possible to always design the driving and steering behavior of the forklift truck optimally and comfortably.

[0013] This problem is solved by a steering method having the features of claim 1 and by a forklift truck having the features of claim 12.

[0014] According to the invention, the steering method is particularly suitable for industrial trucks which, viewed in the direction of longitudinal travel, have at least two front wheels and at least one rear wheel. It is also conceivable that the industrial truck has more than two front wheels and one rear wheel, for example, two front wheels and two rear wheels. Furthermore, it is conceivable that the industrial truck has three or more front and / or rear wheels and / or one, two, or more wheels on additional axles, which, with respect to the longitudinal axis of the industrial truck, are arranged in front of the front wheels, between the front and rear wheels, and / or behind the rear wheels. The industrial truck in question can, in particular, be designed as a forklift truck.

[0015] A front wheel, as defined in the present invention, can be arranged, in particular, on the side area, especially the front area, of the industrial truck that faces a load-handling device of the industrial truck. A rear wheel, as defined in the present invention, can be arranged on the area of ​​the industrial truck that faces away from a load-handling device. If the load-handling device is located approximately in the center of the industrial truck, a front wheel can be understood, in particular, as the wheel that leads or is located at the front in the main direction of travel of the industrial truck, and correspondingly, a rear wheel can be understood as the wheel that trails or is located at the rear in the main direction of travel of the industrial truck.

[0016] To propel the industrial truck, at least one of the front wheels and / or at least one rear wheel is driven, particularly in the circumferential direction. The drive systems for the wheels can be independent of each other; for example, each driven wheel can have its own drive motor, which can be controlled independently of the other drive systems. The drive system can be an electric motor. However, it is also conceivable that the drive system consists of an internal combustion engine, a pneumatic motor, or a hydraulic motor. Furthermore, each drive system can be individually controlled depending on the steering angle of the respective wheel and / or the industrial truck. It is particularly preferred that only the two front wheels are driven to propel the industrial truck.

[0017] Furthermore, it is stipulated that all wheels of the industrial truck are steerable. It is conceivable that the industrial truck has actively steerable wheels (i.e., steerable wheels driven for steering) and passively steerable wheels (i.e., wheels not driven for steering), such as a trailing roller. The steerable wheels driven for steering can have a steering gear or each have its own steering drive, such as a steering drive motor, to rotate the respective wheel around its vertical axis, which is parallel to the vertical axis of the industrial truck. The steering drives can, in particular, be controlled independently of one another, so that each steerable wheel equipped with a steering drive can be steered individually. For the sake of clarity, only the "wheel" is referred to here as the steerable component.Of course, it can also be provided that an entire wheel suspension with one or more individual wheels is rotated or steered around a vertical axis of the wheel suspension by means of a steering gear or steering drive.

[0018] To initiate a turn around the steering axis, the steering angle sensor is activated. The steering angle sensor can be, for example, a steering wheel, a joystick, a slider, a rotary control, or a pedal assembly. It is also conceivable that the steering angle sensor is a sensor for automatically initiating a turn, for example, along a predetermined path, or a computer configured to initiate a pre-programmed or situation-dependent turn. Upon activation of the steering angle sensor, the at least two front wheels and / or the at least one rear wheel are steered; that is, the at least two front wheels and / or the at least one rear wheel are each rotated about an axis parallel to the vertical axis of the industrial truck. It is particularly preferred that both the at least two front wheels and the at least one rear wheel are steered to initiate a turn.

[0019] According to the invention, the distance of the steering line to the center of the industrial truck is controlled semi- or fully automatically. This advantageously allows the position of the steering line to be adjusted depending on the situation. The behavior of the industrial truck during steering varies significantly depending on the position of the steering line. For example, if the steering line lies on a front axle, the industrial truck remains relatively stable when cornering, while a load, such as one mounted on the forks of the industrial truck, is pivoted over greater distances. However, if the steering line intersects the forks of the industrial truck, the load on the forks is pivoted less when cornering. It has therefore been found that the individual arrangement of the steering line can be particularly advantageous for certain situations. In particular, semi- or fully automatic control...Shifting the steering line based on predefined criteria, such as, very generally speaking, "external conditions or circumstances," can be particularly advantageous. For example, the position of the steering line and / or its shift can be determined based on external environmental conditions, such as the current driving speed, the road surface, the intensity, especially the speed, of the steering angle sensor's movement, and / or other circumstances influencing the steering and maneuverability of the industrial truck. For this purpose, the industrial truck can be equipped with sensors to detect the external environment and environmental conditions, such as a distance sensor and / or acceleration sensor, which can be monitored by a control unit and thus used to regulate the steering line.

[0020] Advantageous embodiments and further developments of the invention can be found in the dependent claims and in the description with reference to the drawings.

[0021] According to a preferred embodiment of the present invention, the industrial truck can be operated in longitudinal and / or transverse driving modes. In longitudinal driving mode, as defined by the present invention, the industrial truck travels straight ahead along its longitudinal axis, particularly in the main direction of travel. In transverse driving mode, as defined by the present invention, the industrial truck travels straight ahead along its transverse axis. According to this preferred embodiment, in longitudinal driving mode, the controlled distance is a longitudinal distance corresponding to the distance between the steering line and the transverse axis. Furthermore, in transverse driving mode, the controlled distance is a transverse distance corresponding to the distance between the steering line and the longitudinal axis.This makes it advantageously possible to control the steering line in the two important operating modes, longitudinal travel and lateral travel, parallel to the respective straight-ahead direction, and thus to implement situation-dependent changes in the position of the steering line adapted to the respective operating mode.

[0022] According to a further preferred embodiment of the present invention, the distance is regulated depending on an operating parameter of the industrial truck. This advantageously makes it possible to adjust the position of the steering line (semi-)automatically. An operator therefore does not need to worry about setting the steering line. This significantly simplifies the operation of the industrial truck.

[0023] Preferably, the operating parameter includes the geometry and / or center of gravity of a loaded load. In this context, the geometry of the load refers specifically to its area or volumetric extent, particularly its contour. For example, long loads such as profiles or beams regularly result in a driving behavior of the industrial truck that is entirely different from that of short, compact loads. Therefore, in this preferred embodiment, the geometry of the loaded load is detected automatically or manually, and the steering line can be shifted based on this parameter. For instance, with particularly long loads, the steering axis of the industrial truck can be positioned at the geometric center of the load, allowing the industrial truck and the long load to rotate and maneuver in the smallest possible circle.By taking the center of gravity of the loaded load into account, it is recognized that, especially with heavy loads, it is advisable to orient the steering line around the load's center of gravity. In this case, significantly fewer problems arise with the load's inertia when initiating and negotiating a turn. Of course, a combination of considering the geometry and the center of gravity of the loaded load is also possible. In this case, the steering axis does not necessarily have to be located at the geometric center or the center of gravity of the load or the entire vehicle including the load, but can also be positioned somewhere in between, particularly with asymmetrical loads.

[0024] Alternatively or additionally, it is preferably provided that the operating parameter includes the center of gravity of the industrial truck. This advantageously ensures that the inertia of the industrial truck is taken into account when initiating and negotiating a curve. In particular, it is provided that the operating parameter includes an overall center of gravity. The overall center of gravity takes into account the center of gravity of the industrial truck and the center of gravity of the load. The overall center of gravity is therefore the center of gravity of the loaded industrial truck.

[0025] According to a further preferred embodiment of the present invention, the operating parameter includes an inclination angle of the industrial truck. The inclination angle can, for example, be an inclination angle about a front axle of the industrial truck. A front axle, as defined in the present invention, intersects the at least two front wheels at their respective centers. This advantageously allows for the consideration of a particularly heavy load. It is also conceivable that the inclination angle is an inclination angle about the transverse axis of the industrial truck. This advantageously allows for the consideration of the shift in the steering line during upward or downward travel in longitudinal operation. Furthermore, it is conceivable that the inclination angle is an inclination angle about the longitudinal axis of the industrial truck. This advantageously allows for the consideration of the shift in the steering line during upward or downward travel in longitudinal operation.Downward travel in lateral operation must be taken into account. It is conceivable that the industrial truck has a position sensor to account for the angle of inclination.

[0026] According to a further preferred embodiment of the present invention, the operating parameter includes an expected or already occurring swaying or shaking of the industrial truck, particularly due to uneven road surfaces. "Expected" in this context means, in particular, that the industrial truck may include a detection device, especially optical sensors, which detects, in particular scans, the ground surface spatially in front of the industrial truck in the direction of travel, and based on the information obtained therefrom, operating parameters are determined for the swaying or shaking of the industrial truck expected when driving over the uneven ground.Based on this information, the steering line can be optimally controlled, particularly to prevent the forklift from slipping or rubbing against the ground and / or the load from shifting relative to the forklift when driving through curves. This enables anticipatory driving.

[0027] According to a further preferred embodiment of the present invention, the operating parameter comprises the intensity, in particular the speed, of the operation of the steering angle encoder of the industrial truck, wherein the operating parameter can be detected, in particular, by means of a magnetic sensing device, such as a Hall sensor. For example, it can be provided that when the steering wheel is turned relatively quickly, the steering line is shifted towards the center of the industrial truck, and when the steering wheel is turned relatively slowly, the steering line is shifted away from the center of the industrial truck. This can result in particularly advantageous driving dynamics characteristics.

[0028] According to a further preferred embodiment of the present invention, the operating parameter includes a maneuvering space available around the industrial truck. A maneuvering space within the meaning of the present invention is the space around the industrial truck that is available to the truck for maneuvering. Preferably, the available maneuvering space is detected by environmental sensors. These environmental sensors can be, for example, radar, lidar, ultrasonic, laser, or optical sensors. This advantageously allows the distance of the steering line to the vehicle's center of gravity to be adapted to the external conditions. This enables comfortable driving on wide paths as well as easy maneuvering, for example, in narrow aisles.

[0029] It is particularly preferred that the operating parameter includes a manual selection. The manual selection can be a choice between a reach truck mode and a forklift mode. In reach truck mode, the steering line is arranged during longitudinal travel such that it intersects the forks of the forklift. Particularly preferably, in reach truck mode, the steering line intersects the forks at their front end during longitudinal travel. In forklift mode, the steering line is arranged during longitudinal travel such that it is positioned between the forks and the at least one rear wheel.

[0030] According to a further preferred embodiment of the present invention, it is provided that, in longitudinal travel mode, the longitudinal distance of the steering line from the transverse axis is controlled depending on the distance of the steering pole to the longitudinal axis, and furthermore, in transverse travel mode, the transverse distance of the steering line from the longitudinal axis is controlled depending on the distance of the steering pole to the transverse axis. For example, it is conceivable that the longitudinal distance of the steering pole to the transverse axis is increased as the transverse distance of the steering pole to the longitudinal axis decreases. In other words, the steering pole can be moved forward, for example, when turning with small radii. It is also conceivable that, when turning with small radii, the steering pole is arranged on a fork tine or between the forks of the industrial truck, i.e., in the area of ​​the transported load. This has the advantage that, especially in confined spaces, rotation occurs around a point close to the load of the industrial truck.For example, the pivot point can be set at a corner of the load or at the load's center of gravity. This allows the forklift to rotate around the load or around a corner of the load. This is particularly advantageous when pivoting the forklift into a narrow aisle or load drop-off area to the side of the forklift.

[0031] Alternatively, the longitudinal distance of the steering pole to the transverse axis can be reduced as the lateral distance decreases. This pulls the steering pole towards the operator of the industrial truck when turning in tight curves. This allows the vehicle to rotate on its own axis, which is particularly advantageous when reversing.

[0032] Another object for solving the problem stated at the outset is a forklift truck which has a steering device configured by controlling the steering line to carry out the steering method according to the invention. The steering device of the forklift truck according to the invention controls the distance of the steering line from the center of the forklift truck. The steering device can include the steering angle sensor, electrical components, hydraulic components, and / or a microcomputer.

[0033] All advantages, features and details of the steering method according to the invention mentioned in the description text also refer to the industrial truck according to the invention.

[0034] Further details, features, and advantages of the invention will become apparent from the drawings and from the following description of preferred embodiments with reference to the drawings. The drawings merely illustrate exemplary embodiments of the invention, which do not limit the inventive concept.

[0035] They show: Fig. 1: A schematic view of a forklift truck according to an exemplary embodiment of the present invention in straight-ahead driving in longitudinal mode, Fig. 2: a schematic view of the in Fig. 1. Forklift truck shown in straight-ahead driving in lateral operation, Fig. 3: a schematic view of the in Fig. 1. Forklift truck shown in cornering mode, longitudinal driving operation, Fig. 4: A schematic view of a forklift truck according to a further exemplary embodiment of the present invention in cornering during longitudinal driving operation, Fig. 5: a schematic view of a forklift truck according to a further exemplary embodiment of the present invention in cornering during longitudinal driving operation, Fig. 6: a schematic view of a forklift truck according to a further exemplary embodiment of the present invention in cornering mode, Fig. 7: a schematic view of a forklift truck according to a further exemplary embodiment of the present invention in straight-ahead travel in longitudinal travel mode in push mast mode and Fig. 8: a schematic view of the in Fig. 6 shown industrial trucks driving straight ahead in longitudinal driving mode in front forklift mode.

[0036] The Fig. Figures 1 to 8 each show industrial trucks 1 according to an exemplary embodiment of the present invention. The industrial trucks 1 shown have a left front wheel 2.1 and a right front wheel 2.2 as well as a rear wheel 3 ( Fig. 1, Fig. 2, Fig. 6 and Fig. 7) or a left rear wheel 3.1 and a right rear wheel 3.2 ( Fig. 3, Fig. 4 and Fig. 5). The industrial trucks 1 each have a steering angle sensor 5, for example in the form of a steering wheel. For the sake of clarity, the steering angle sensor 5 is not shown in every one of the figures shown here. Furthermore, the industrial trucks 1 have steering devices (not shown) configured to carry out the steering method according to the invention.

[0037] Fig. Figure 1 shows the industrial truck 1 traveling straight ahead in longitudinal mode. The front wheels 2.1, 2.2 and the rear wheel 3 are aligned parallel to a longitudinal axis X of the industrial truck 1. The longitudinal axis X is orthogonal to a transverse axis Y of the industrial truck 1 and intersects it at the vehicle's center M.

[0038] The front axle V is arranged parallel to the transverse axis Y and centrally intersecting both front wheels 2.1 and 2.2, which are oriented for straight-ahead travel in longitudinal driving mode. In the context of the present invention, the front axle V is not a mechanical component, but a geometric position designation.

[0039] In longitudinal driving mode, the rear axle H is also arranged parallel to the transverse axis Y and intersects the rear wheel 3, which is aligned for straight-ahead driving in longitudinal driving mode, in the middle ( Fig. 1) Within the scope of the invention, the rear axle H, also called rear wheel axle, merely describes a geometric position designation and not a mechanical component.

[0040] Fig. 2 shows that in Fig. The forklift truck 1 shown is traveling straight ahead in lateral operation. The front wheels 2.1, 2.2 and the rear wheel 3 are aligned parallel to the transverse axis Y of the forklift truck 1.

[0041] In the Fig. For clarity, the rear axle H and the front axle V are not shown in figures 3 to 8. These figures depict industrial trucks 1 driving around curves. The curves are executed around a steering center point P. The steering center point P is the intersection of straight lines perpendicular to the centers of all wheels 2.1, 2.2, 3, 3.1, 3.2 of the respective industrial truck 1. The curve radius is the distance between the steering center point P and the vehicle center point M. When driving straight ahead, the steering center point P is at infinity. When the steering angle sensor 5 is activated, initiating a curve, the steering center point P moves from infinity along a steering line S in the direction of the industrial truck 1.

[0042] According to the invention, a distance L, Q of the steering line S to the vehicle center M of the industrial truck 1 is regulated. This is described in the Fig. 1, Fig. 2, Fig. 6 and Fig. 7 is indicated by a double arrow on the steering line S. Fig. Figures 1 to 4 and 6 to 7 show industrial trucks 1 in longitudinal driving mode. In longitudinal driving mode, travel along the longitudinal axis X of the industrial truck 1 is planned when driving straight ahead. Here, the controlled distance of the steering line S to the vehicle center M of the industrial truck 1 is a longitudinal distance L, which corresponds to the distance L of the steering line S to the transverse axis Y. Fig. Figure 5 shows a forklift truck 1 in a lateral driving mode while cornering. In lateral driving mode, the truck 1 travels along its lateral axis Y when traveling straight ahead. The controlled distance of the steering line S to the vehicle center M in lateral driving mode is a lateral distance Q, which corresponds to the distance Q of the steering line S to the longitudinal axis L.

[0043] In the figures shown, the distance L, Q is controlled depending on an operating parameter of the industrial truck 1. Fig. Figure 3 shows, for example, a forklift 1 with a load 4. The load 4 rests on a fork 6 of the forklift 1. In the embodiment shown here, the longitudinal distance L of the steering line S from the vehicle center M is controlled by an operating parameter that includes the center of gravity 4.1 of the load 4 and the center of gravity 1.1 of the forklift 1. A combined center of gravity 8 is calculated using the center of gravity 4.1 of the load 4 and the center of gravity 1.1 of the forklift 1. In the example shown, the longitudinal distance L is controlled such that the steering line S passes through the combined center of gravity 8.

[0044] The in Fig. The forklift truck 1 shown in Figure 4 has environmental sensors 7 which detect the available maneuvering space and incorporate this information into the operating parameters for controlling the position of the steering line S. In the illustration, the available maneuvering space is limited by rack walls 9. The forklift truck 1 controls the longitudinal distance L of the steering line S from the vehicle center M so that the forklift truck 1 exhibits optimal steering behavior for the available maneuvering space.

[0045] The in Fig. The forklift truck 1 shown in Figure 5 regulates the lateral distance Q of the steering line S to the longitudinal axis L in the lateral driving operation shown here such that the steering line S passes through the center of gravity 4.1 of the load 4 resting on the forks 6 of the forklift truck 1. The operating parameter for regulating the lateral distance Q is therefore the center of gravity 4.1 of the load 4. In the example shown, both the center of gravity 4.1 of the load 4 and the vehicle center M lie on the longitudinal axis L of the forklift truck 1. The lateral distance Q of the steering line S to the longitudinal axis L is therefore zero. For the sake of clarity, the lateral distance Q and the longitudinal axis L are not shown here.

[0046] In the Fig. 6 and Fig. Figure 7 shows a forklift truck 1 in which the distance of the steering line S to the vehicle center M is controlled such that the operating parameter includes a manual selection. The manual selection here is a selection between one in Fig. 6 shown pusher mast mode and one in Fig. Figure 7 shows the front forklift mode. In reach truck mode, the steering line S intersects the forks 6 of the forklift 1. If an operator of the forklift 1 selects the front forklift mode instead of the reach truck mode, the steering line S is positioned further back, namely between the forks 6 and the rear wheel 3, for example on the front axle V.

[0047] In the Fig. Figure 8 shows a forklift truck 1 in which the distance of the steering pole P to the transverse axis Y is controlled depending on the distance of the steering pole P to the longitudinal axis X. In the embodiment shown here, the steering line S shifts forward as the transverse distance Q decreases. This means that as the transverse distance Q decreases, the longitudinal distance L increases. This is particularly advantageous when maneuvering in very confined spaces.

[0048] It should be clear that the examples of steering line design and arrangement shown here are not exhaustive. For example, the following can also be used: Fig.Figure 8 shows an exemplary parabolic steering line with its straight section arranged at the height of the front wheel axle V. Advantageously, the steering line S never crosses the center of a front wheel 2.1, 2.2 or a rear wheel 3, 3.1, 3.2, but always runs laterally past them. This means that, for example, when turning from straight-ahead driving, the industrial truck 1 is initially steered exclusively via the rear wheel 3. The front wheels 2.1, 2.2 initially remain unsteered, in particular aligned parallel to the longitudinal axis X. From a predefined steering angle of the rear wheel 3 with respect to the longitudinal axis X, preferably 40°, the steering center P is deflected or displaced laterally next to the front wheel axle V by the curve of the steering line S, so that the steering center P does not pass through the center of either of the front wheels 2.1, 2.2 during further steering.This means that the front wheels 2.1, 2.2 will only be steered from a predefined steering angle, in particular of the rear wheel 3. The front wheels 2.1, 2.2 can always maintain the rotational movement controlled by drive motors (not shown) in the same direction.

[0049] All details and features shown above for longitudinal driving operation also apply mutatis mutandis to transverse driving operation and vice versa. Reference symbol list: 1 forklift truck 1.1 Center of gravity of the industrial truck 2.1 left front wheel 2.2 right front wheel 3 rear wheel 3.1 left rear wheel 3.2 right rear wheel 4 Last 4.1 Center of gravity of the load 5 Steering angle sensors 6 Forks 7 environmental sensors 8 Overall focus 9 shelving unit H Rear axle L Longitudinal distance M vehicle center P Steering pole Q Lateral spacing S steering line Vehicle length V front axle X Longitudinal axis Y transverse axis

Claims

[1] Steering method for operating a forklift truck (1), wherein the forklift truck (1) has at least two front wheels (2.1, 2.2) and at least one rear wheel (3.1, 3.2), wherein a steering angle sensor (5) is actuated to initiate a turn around a steering pole (P) and the at least two front wheels (2.1, 2.2) and / or the at least one rear wheel (3, 3.1, 3.2) are steered, wherein when steering the wheels (2.1, 2.2, 3, 3.1, 3.2) the steering pole (P) is moved on a steering line (S), characterized by , that a distance (L, Q) of the steering line (S) to the vehicle center (M) of the industrial truck (1) is controlled semi- or fully automatically. [2] Steering method according to claim 1, characterized by, that the industrial truck (1) can be operated in longitudinal driving mode and / or in transverse driving mode, wherein in longitudinal driving mode the industrial truck (1) travels straight ahead along a longitudinal axis (X) of the industrial truck, wherein in transverse driving mode the straight ahead of the industrial truck (1) is arranged along a transverse axis (Y) of the industrial truck (1), wherein the longitudinal axis (X) and the transverse axis (Y) are arranged orthogonally to each other and intersect at the vehicle center (M), wherein in longitudinal driving mode the controlled distance (L) is a longitudinal distance (L) which is the distance (L) of the steering line (S) to the transverse axis (Y) and wherein in transverse driving mode the controlled distance (Q) is a transverse distance (Q) which is the distance (Q) of the steering line (S) to the longitudinal axis (X). [3] Steering method according to one of claims 1 or 2, characterized by , that the distance (L, Q) is regulated depending on an operating parameter of the industrial truck (1). [4] Steering method according to claim 3, characterized by , that the operating parameter includes the geometry and / or the center of gravity (4.1) of a loaded load (4). [5] Steering method according to one of claims 3 to 4, characterized by , that the operating parameter includes the center of gravity (1.1) of the industrial truck (1), wherein the operating parameter preferably includes an overall center of gravity (S), wherein the overall center of gravity (8) is the center of gravity of the industrial truck (1) with the loaded load (4). [6] Steering method according to any one of claims 3 to 5, characterized by , that the operating parameter includes an inclination angle of the industrial truck (1). [7] Steering method according to any one of claims 3 to 6, characterized by, that the operating parameter includes an expected or occurring oscillation or shaking of the industrial truck (1), in particular on an uneven road surface, wherein the operating parameter can be detected in particular by means of an optical sensor. [8] Steering method according to any one of claims 3 to 7, characterized by , that the operating parameter includes an intensity, in particular speed, of the operation of the steering angle encoder (5) of the industrial truck (1), wherein the operating parameter can be detected in particular by means of a magnetic detection device, such as a Hall sensor. [9] Steering method according to any one of claims 3 to 8, characterized by , that the operating parameter includes the maneuvering space available around the industrial truck (1), wherein the available maneuvering space is preferably detected by environmental sensors (7). [10] Steering method according to any one of claims 3 to 9, characterized by, that the operating parameter includes a manual selection, wherein the manual selection preferably includes the selection between a reach truck mode in which the steering line (S) intersects a fork (6) of the industrial truck (1) and a front loader mode in which the steering line (S) is arranged between the fork (6) and the at least one rear wheel (3, 3.1, 3.2). [11] Steering method according to any one of claims 3 to 10, characterized by , that in longitudinal driving mode the longitudinal distance (L) of the steering line (S) from the transverse axis (Y) is controlled depending on the distance of the steering pole (P) to the longitudinal axis (X) and / or wherein in transverse driving mode the transverse distance (Q) of the steering line (S) from the longitudinal axis (X) is controlled depending on the distance of the steering pole (P) to the transverse axis (Y). [12] Industrial truck (1), characterized by, that the industrial truck (1) has a steering device which is configured by a control of the steering line (S) to carry out a steering procedure according to one of the preceding claims.

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