Steering method for operating an industrial truck, and industrial truck

Abstract

The invention relates to a steering method for operating an industrial truck (1), wherein the industrial 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 in order to initiate cornering around a steering pole (P), and both the at least two front wheels (2.1, 2.2) and the at least one rear wheel (3, 3.1, 3.2) can be steered, wherein the industrial truck (1) has a longitudinal axis (X) and a transverse axis (Y) which intersect in a vehicle centre (M), wherein, when the industrial truck (1) is steered, a longitudinal distance (L) of the steering pole (P) from the transverse axis (Y) is controlled depending on a transverse distance (Q) of the steering pole (P) from the longitudinal axis (X).

Description

[0001] HUBTEX Maschinenbau GmbH & Co. KG Werner-von-Siemens Str. 8 36041 Fulda

[0002] Steering procedure for operating an industrial truck, industrial truck

[0003] The present invention relates to a steering method for operating an industrial truck and to an industrial truck for carrying out such a steering method.

[0004] Such steering methods are known in the art in a variety 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, in particular each wheel individually.

[0005] To initiate a turn of an industrial truck, a turn radius is typically specified using a steering angle sensor, such as a steering wheel or joystick. One or more steerable wheels of the industrial truck then rotate or steer around an axis parallel to a vertical axis of the industrial truck, so that the steered wheels are no longer arranged parallel to a longitudinal or transverse direction of the industrial truck. A distinction can be made here between actively steerable wheels, namely wheels that have a steering gear or a steering drive for turning or steering the respective wheel or wheel suspension, and passively steerable wheels, namely those that are not motor-controlled for steering but are designed, for example, as trailing rollers. By positioning the steered wheels at an angle to the longitudinal or transverse direction of the industrial truck, the industrial truck executes a turn around a steering pole.

[0006] The steering center is the point at which orthogonal straight lines on the wheels of the industrial truck, which coincide with a respective rotational axis, can intersect. Advantageously, the straight lines of all steered wheels converge at a common steering center, thus essentially preventing slipping or friction.

[0007] Typically, the steering center of gravity is moved along a steering line when a turn is initiated. For example, when traveling straight ahead, all of the industrial truck's wheels are typically parallel to one another. The steering center of gravity is at infinity. If a turn is initiated by actuating a steering angle sensor, the steering center moves along the steering line from infinity towards the industrial truck. If one or more of the industrial truck's wheels do not steer when a turn is initiated, i.e. if one or more of the industrial truck's wheels do not rotate about an axis parallel to the vertical axis when a turn is initiated, the steering line becomes a straight line that intersects the center of the non-steered wheel.

[0008] It should be clear that the vertical axis, also called the z-axis, a longitudinal axis, also called the front-rear axis or x-axis, and a transverse axis of the industrial truck, also called the y-axis, are orthogonal to each other and typically intersect in the center of the vehicle.

[0009] From the publication EP 2 956 350 B1, a three-wheeled industrial truck and a steering method applicable thereto are known. In longitudinal travel mode, also known as front-loader operation, two front wheels of the industrial truck are non-steered or permanently arranged parallel to the longitudinal axis to initiate cornering, and the vehicle is steered exclusively by turning a rear wheel of the industrial truck. In particular, the rear wheel can be aligned diagonally to the longitudinal axis, so that the industrial truck rotates around a steering pole arranged on a steering line extending as a straight line through the two front wheels. The steering line therefore lies on a front axle, also known as the front wheel axle, of the industrial truck.In transverse driving mode, also known as sideloader mode, according to EP 2 956 350 B1, the rear wheel remains permanently aligned parallel to a transverse axis of the vehicle, while the vehicle is steered exclusively via the two steerable front wheels. The steering line runs, in particular, through a rotational axis of the rear wheel, which, if the rear wheel is centrally positioned, can correspond to the longitudinal axis of the vehicle.

[0010] It has been shown that the steering methods known from the prior art have disadvantages. For example, in narrow rack aisles in particular, it is difficult to maneuver the industrial truck due to the inflexible guidance of the steering line. If, for example, the industrial truck is equipped with a fork for picking up a load, such as pallets or the like, the operator of the industrial truck must always take into account the possibility of unintentional movement of the fork when steering and starting the load. Furthermore, as implemented in the example of EP 2 956 350 B1, it is sometimes necessary, particularly when the steering pole moving along the steering line runs through the vertical axis of a wheel and the direction of rotation of this wheel must be reversed due to physical limitations.

[0011] It is therefore the object of the present invention to provide a steering method for operating an industrial truck and an industrial truck which do not have the disadvantages of the prior art and in particular make it much easier to maneuver safely under difficult spatial conditions.

[0012] This object is achieved by a steering method having the features of claim 1 and by an industrial truck having the features of claim 15.

[0013] According to the invention, the steering method is particularly suitable for industrial trucks which - viewed in the longitudinal direction of travel - have at least two front wheels and at least one rear wheel. It is conceivable for the industrial truck to have more than two front wheels and one rear wheel, for example two front wheels and two rear wheels. It is also conceivable for the industrial truck to have three or more front and / or rear wheels and / or one, two or more wheels on further 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 present industrial truck can be designed, in particular, as a forklift truck.

[0014] At least one of these wheels can be driven to drive the industrial truck, particularly in the circumferential direction. Preferably, at least one front wheel and at least one rear wheel are motor-driven. The wheels can be driven independently of one another; 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 configured, for example, as an electric motor. Furthermore, each drive system can be controlled individually depending on the steering angle of the respective wheel and / or the industrial truck.

[0015] Furthermore, it is intended that all wheels of the industrial truck be steerable. It is conceivable that the industrial truck has actively steerable wheels, or steerable wheels driven for steering, and passively steerable wheels, or non-driven wheels, 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 for rotating the respective wheel about its vertical axis 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, reference is made here only to the "wheel" 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.

[0016] To initiate cornering around the steering pole, the steering angle sensor is actuated. The steering angle sensor can be, for example, a steering wheel, a joystick, a slide control, a rotary control or a pedal arrangement. However, it is also conceivable for the steering angle sensor to be a sensor for automatically initiating cornering, for example along a predetermined path, or a computer which is configured to initiate pre-programmed or situation-dependent cornering. Upon actuation of the steering angle sensor, both the at least two front wheels and the at least one rear wheel are steered, i.e. the at least two front wheels and the at least one rear wheel are each rotated about an axis parallel to the vertical axis of the industrial truck.

[0017] When initiating a curve - especially from straight-line travel - the steering pole is moved along a steering curve from infinity towards the industrial truck. According to the invention, a longitudinal distance of the steering pole to a transverse axis of the industrial truck is regulated as a function of a transverse distance of the steering pole to a longitudinal axis of the industrial truck. When considering the course of the steering pole as a whole, this results in a steering line which does not necessarily have to be a straight line. Rather, the steering line can have different gradients in sections with respect to the longitudinal and / or transverse axis of the industrial truck. In particular, the steering line is not necessarily a straight line parallel to the front axle or to a rear axle, also known as the rear wheel axle, of the industrial truck. This enables the industrial truck to be maneuvered particularly safely and easily in every respect.

[0018] Advantageous embodiments and further developments of the invention can be found in the dependent claims, the description and the drawings.

[0019] Preferably, when steering the industrial truck, the steering pole is guided along a steering line, the steering line being formed at least in sections at an angle to the transverse axis and / or at an angle to the longitudinal axis. In particular, it can be provided that at least one section of the steering line is not arranged parallel to the transverse axis of the industrial truck and / or not parallel to the longitudinal axis of the industrial truck. This can result, for example, in front-loader operation, in a steering line which, viewed over its entire length, in particular in sections, has different distances from the transverse axis of the industrial truck. Consequently, it is possible that - depending on the set steering angle - the point around which the industrial truck is steered, in particular the steering pole, can be arranged at different distances not only from the longitudinal axis, but also from the center of the vehicle.

[0020] According to a preferred embodiment, when steering the industrial truck, the steering pole is guided along a steering line, the steering line being designed as a straight line at least in sections and / or curved in sections. A curved line, as defined by the present invention, is a non-straight line, for example a parabola. The steering line can therefore be designed as a curved function - particularly in certain driving situations. Overall, the steering line can therefore have both a straight section and a curved section. This allows the industrial truck to be steered in such a way that - depending on the steering angle - it can negotiate particularly small curve radii and curved paths, making it particularly maneuverable overall.

[0021] According to a particularly preferred embodiment, when steering the industrial truck, the steering pole is guided along a steering line, wherein the steering line has an inclination angle with respect to the longitudinal axis and / or the transverse axis, which angle changes depending on the longitudinal distance and / or transverse distance of the steering pole. The steering line can, for example, have two straight sections which have different inclines with respect to the longitudinal or transverse axis. This consequently results in a steering line which has two straight sections and an inflection point connecting the two sections. The connection between the two straight sections is preferably curved, so that when the steering pole is turned and moved via the connection between the two straight sections, the wheel is not turned or steered too quickly.

[0022] Particularly preferably, it is provided that when steering the industrial truck, the steering pole is guided along a steering line, wherein the steering line always runs at a distance from a respective vertical axis of the front wheels as well as a distance from a vertical axis of the rear wheel. Or to put it another way: in this design, the steering pole is never in the center of a wheel or crosses it. This eliminates the need for a wheel, particularly one on the inside of a curve, to be stopped or even reversed in its rotational movement during sharp steering. Rather, it is provided that each wheel rotates exclusively in one direction, the direction of travel, when steering and - at least from a predefined steering angle - contributes to the steering.

[0023] It can be provided that the steering line is mirrored on the longitudinal axis of the industrial truck. The mirroring of the steering line on the longitudinal axis results in symmetrical steering when turning left and right. It is conceivable that the steering line has a discontinuity at the intersection with the longitudinal axis, in particular a liftable discontinuity. If the steering line is mirrored on the longitudinal axis of the industrial truck and is curved on both sides of the longitudinal axis, this leads to very intuitive behavior of the industrial truck when cornering. However, it is also conceivable that the steering line - as explained above - has straight sections on both sides of the longitudinal axis. These straight sections can, for example, be arranged non-parallel to the transverse axis. It is also conceivable that the steering line is mirrored on the transverse axis of the industrial truck.The mirroring of the steering line on the transverse axis can enable a symmetrical steering process, especially when driving transversely.

[0024] According to a further preferred embodiment of the present invention, a steering ratio is set as a function of a steering angle to initiate cornering. The steering angle within the meaning of the present invention can be inversely proportional to the transverse distance of the steering pole to the longitudinal axis of the industrial truck. At small steering angles, i.e. at large transverse distances, large curve radii are traveled. The industrial truck steers only slightly. At high steering angles, i.e. at small transverse distances, small curve radii are traveled. The industrial truck steers sharply. The steering ratio within the meaning of the present invention determines the proportionality of the extent to which the steering angle sensor is actuated and the resulting curve radius. In other words, at a low steering ratio, the industrial truck steers less sharply when the steering wheel is turned than at a high steering ratio.If, as in the case of this preferred embodiment, the steering ratio is dependent on the steering angle, then smaller movements at the steering angle sensor, for example when traveling straight ahead, have a smaller effect on the travel of the industrial truck than when traveling sharply, for example, when cornering sharply. This makes it easier for the operator to handle the industrial truck, particularly when maneuvering in confined spaces. It is conceivable that the dependence of the steering ratio on the steering angle is a linear relationship. However, it is also conceivable that the dependence of the steering ratio on the steering angle is a non-linear relationship. It is conceivable that the dependence of the steering ratio on the steering angle can be individually adjusted by the operator. This advantageously makes it possible to adapt the behavior of the industrial truck to the operator's personal preferences.

[0025] According to a further preferred embodiment of the present invention, the longitudinal distance of the steering pole from the transverse axis is increased as the transverse distance of the steering pole from the longitudinal axis decreases. In other words, the steering pole can be pushed forward, for example, with small curve radii. For example, it is conceivable that the steering pole is arranged on a fork or between the forks of the industrial truck, i.e. in the area of ​​the transported load, with small curve radii. This has the advantage that, especially in confined spaces, rotation takes place 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 a center of gravity of the load. This enables the vehicle to rotate around the load or around a corner point of the load. This is particularly advantageous when pivoting the vehicle into a narrow aisle or load storage area located to the side of the vehicle.

[0026] Furthermore, it can also be provided that the longitudinal distance of the steering pole to the transverse axis is reduced as the transverse distance of the steering pole to the longitudinal axis decreases. As a result, the steering pole is drawn towards the operator of the industrial truck on small curve radii. This enables the truck to rotate on its axis. This is particularly advantageous when reversing. It should be noted that the steering line can, in principle, also run in opposite directions in some sections, so that the two aforementioned features of increasing or decreasing the longitudinal distance of the steering pole to the transverse axis with decreasing transverse distance do not necessarily exclude each other.Rather, the steering line can be designed in a first section such 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, and can be designed in a second section such that the longitudinal distance of the steering pole to the transverse axis is reduced as the transverse distance of the steering pole to the longitudinal axis decreases.

[0027] According to a further preferred embodiment of the present invention, it is provided that the maximum longitudinal distance of the steering pole from the transverse axis corresponds to half the vehicle length. If the industrial truck is designed as a forklift truck with forks, it is particularly preferably provided that the maximum longitudinal distance of the steering pole from the transverse axis corresponds to the distance from the front end of the fork to the transverse axis. In particular, it can be provided that the steering pole is arranged at the level of the front end of the fork when the steering pole is arranged on the longitudinal axis of the industrial truck. In other words, it is particularly provided that the industrial truck can perform a carousel travel, with the center of the carousel travel lying between the ends of the forks. This advantageously makes it possible to approach a load easily and precisely even in very confined conditions.

[0028] It is particularly preferred that, when at least two front wheels are arranged parallel to the longitudinal axis of the industrial truck, a front axle is defined which intersects the at least two front wheels centrally and is arranged orthogonally to the longitudinal axis of the industrial truck, and at least in longitudinal travel mode, a steering line on which the steering pole is guided when steering the industrial truck, coincides at least partially with the front wheel axis and is designed such that the steering pole is initially moved in the direction of the inside front wheel when cornering in longitudinal travel mode, in particular lying on the front wheel axis, and the steering pole is deflected and spaced from the front wheel axis at a predefined distance from a vertical axis of the inside front wheel, in particular when the steering angle of the rear wheel in relation to the longitudinal axis of the industrial truck is equal to or more than 40°, preferably more than 45°.particularly preferably of more than 60°. In other words: If, in front-loader operation, the steering line coincides at least partially with the front wheel axle, the steering pole is deflected from a predefined steering angle of the rear wheel in relation to the longitudinal axis of the industrial truck, in particular equal to or more than 40° from the front wheel axle, and consequently, according to this embodiment, lies outside the front axle when cornering in longitudinal travel mode of the industrial truck. In particular, the steering pole does not cross the vertical axis of the inside wheel when turning. This means that when turning in front-loader operation, the industrial truck is initially steered only by the rear wheel until it reaches or exceeds the predefined steering angle. From this moment, at least two front wheels also steer. As a result,The fact that the steering center is no longer located on the front axle when cornering, starting at the predefined steering angle of at least one rear wheel, results in advantageous driving dynamics characteristics of the industrial truck. In particular, when cornering in longitudinal travel mode, the steering center does not run through the vertical axis of the inside wheel, but is always spaced from it.

[0029] A front axle within the meaning of the present invention is defined in that the front axle is a straight line that intersects the center of the at least two front wheels when these are arranged parallel to the longitudinal axis of the industrial truck and is arranged orthogonally to the longitudinal axis of the industrial truck. A rear axle within the meaning of the present invention is defined in that the rear axle is a straight line in longitudinal travel mode that intersects the center of the at least one rear wheel when this is arranged parallel to the longitudinal axis of the industrial truck and is arranged orthogonally to the longitudinal axis of the industrial truck, and in transverse travel mode it intersects the center of the at least one rear wheel when this is arranged parallel to the transverse axis of the industrial truck and is arranged orthogonally to the transverse axis of the industrial truck. Front and rear axles within the meaning of the present invention are therefore not mechanical components, but a geometric position designation.

[0030] Longitudinal travel mode within the meaning of the present invention, also referred to as front-loader operation, is a shuttle operation in which the industrial truck travels straight ahead along the truck's longitudinal axis. Transverse travel mode within the meaning of the present invention, also referred to as side-loader operation, is a shuttle operation in which the industrial truck travels straight ahead along the truck's transverse axis.

[0031] The previously described steering pattern can also be applied accordingly in transverse travel mode. In this case, it is preferably provided that, with at least one rear wheel arranged orthogonally to the longitudinal axis of the industrial truck, a rear axle is defined that intersects the rear wheel centrally and is arranged parallel to the longitudinal axis of the industrial truck. At least in transverse travel mode, a steering line along which the steering pole is guided when steering the industrial truck coincides at least partially with the rear wheel axis and is designed such that, when cornering in transverse travel mode, the steering pole is initially moved toward the inside rear wheel, in particular lying on the rear wheel axis, and the steering pole is deflected and spaced from the rear wheel axis at a predefined distance from a vertical axis of the inside rear wheel - if there are multiple rear wheels -in particular, when at least one front wheel has a steering angle of equal to or greater than 40°, preferably greater than 45°, particularly preferably greater than 60°, relative to the transverse axis of the industrial truck. Or, to put it another way: when, in sideloader operation, the steering line coincides at least partially with the rear wheel axle, the steering center is deflected from a predefined steering angle of at least one of the front wheels relative to the transverse axis of the industrial truck, for example, equal to or greater than 40°, from the rear wheel axle. Consequently, according to this embodiment, when cornering in transverse operation of the industrial truck, the steering center does not cross the vertical axis of the rear wheel when turning. This means that when turning in frontloader operation, the industrial truck is initially steered only by the front wheels.until one of these reaches or exceeds the predefined steering angle. From this moment, at least one rear wheel also steers. The fact that the steering center no longer falls on the rear axle when cornering from a predefined angle results in advantageous driving dynamics characteristics of the industrial truck. In particular, when cornering in transverse travel mode, the steering center does not run through the vertical axis of one of the at least one rear wheels, but is always spaced apart from it. Consequently, it can be provided that the steering center is not located on the front axle when cornering in longitudinal travel mode of the industrial truck from a predefined steering angle, and that the steering center is not located on the rear axle when cornering in transverse travel mode of the industrial truck from a predefined steering angle.

[0032] According to a particularly preferred embodiment of the present invention, both the longitudinal distance of the steering pole from the transverse axis and the transverse distance of the steering pole from the longitudinal axis are controlled by a single input on the steering angle sensor. In other words, for example, turning a steering wheel is sufficient to control both the transverse and longitudinal distance of the steering pole. "Just one input" in the context of the present invention means that only a single input is necessary. An input can, for example, be a movement of the steering angle sensor by the operator of the industrial truck.

[0033] According to a further preferred embodiment of the present invention, at least one predefined steering pole can be selected independently of the steering angle sensor. For example, such a steering pole can be selected directly by the operator using a button or touchpad. Such a predefined steering pole can, for example, be a steering pole at the free end of a fork. After selecting the steering pole, the vehicle rotates accordingly around this steering pole when the steering sensor is rotated.

[0034] A further object for solving the initially stated problem is an industrial truck having a steering device configured to implement the steering method according to the invention by regulating the position of the steering pole. The steering device of the industrial truck according to the invention regulates the longitudinal distance of the steering pole from the transverse axis depending on the transverse distance of the steering pole from the longitudinal axis. The steering device can comprise the steering angle sensor, electrical components, hydraulic components, and / or a microcomputer. All advantages, features, and details of the steering method according to the invention mentioned in the description also relate to the industrial truck according to the invention.

[0035] Further details, features, and advantages of the invention will become apparent from the drawings and 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 scope of the invention.

[0036] They show:

[0037] Fig. 1 : a schematic view of an industrial truck according to an exemplary embodiment of the present invention in straight-ahead travel in longitudinal travel mode,

[0038] Fig. 2: a schematic view of the industrial truck shown in Figure 1 in

[0039] cornering,

[0040] Fig. 3: another schematic view of the device shown in Figure 1

[0041] Industrial truck cornering,

[0042] Fig. 4: a schematic view of an industrial truck according to another exemplary embodiment of the present invention in curve travel,

[0043] Fig. 5: a schematic view of an industrial truck according to another exemplary embodiment of the present invention in curve travel,

[0044] Fig. 6: a schematic view of the industrial truck shown in Figure 1 in

[0045] Straight-ahead travel in transverse travel mode, and Fig. 7: a schematic view of an industrial truck according to a further exemplary embodiment of the present invention when cornering.

[0046] Figures 1 to 7 each show an industrial truck 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 (Figures 1 to 3 and 5 to 7) or a left rear wheel 3.1 and a right rear wheel 3.2 (Figure 4). Furthermore, a steering angle sensor 5, here in the form of a steering wheel, is shown. Furthermore, the industrial trucks 1 have steering and control devices (not shown) that are configured to implement the steering method according to the invention.

[0047] Figure 1 shows the industrial truck 1 in longitudinal travel mode, traveling straight ahead. Longitudinal travel mode, also known as front loader mode, means that the industrial truck 1 moves primarily towards or away from the loading forks 4 arranged on the industrial truck 1. During straight-ahead travel in longitudinal travel mode, as shown in Figure 1, 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. Figure 6 shows the industrial truck 1 in transverse travel mode, traveling straight ahead. Transverse travel mode, also known as side loader mode, means that the industrial truck 1 moves in a main direction of travel, which essentially corresponds to a direction perpendicular to the arrangement of the loading forks 4 on the industrial truck 1. During straight-ahead travel in transverse travel mode, as shown in Figure 6, the front wheels 2.1, 2.2 and the rear wheel 3 are aligned parallel to a transverse axis Y of the industrial truck 1.Figures 2 to 5 and 7 show the industrial truck 1, for example, with steered wheels 2.1, 2.2, 3, 3.1, 3.2 for performing a steering or turning movement of the industrial truck 1.

[0048] The longitudinal axis X is orthogonal to the transverse axis Y of the industrial truck 1. The longitudinal axis X intersects the transverse axis Y in the vehicle center M. A third axis can be formed by a vertical axis of the industrial truck 1 (not shown), which is orthogonal to the longitudinal axis X and orthogonal to the transverse axis Y. Also shown is a vehicle length T, which extends from the rear end of the industrial truck 1 to the front end of the fork 4 of the industrial truck 1.

[0049] A front axle V is arranged parallel to the transverse axis Y and intersects the two front wheels 2.1 and 2.2 in the middle. If the front wheels 2.1 and 2.2 of the industrial truck 1 - as shown in Figure 1, for example - are aligned for straight-ahead travel in longitudinal travel mode, then both wheel axles of the front wheels

[0050] 2.1 and 2.2 on the front axle V. The front axle V in the sense of the present invention is not a mechanical component, but a geometric position designation.

[0051] A rear axle H intersects the rear wheel 3 in the middle and forms its wheel axis. If the rear wheel 3 of the industrial truck 1 - as shown, for example, in Figure 1

[0052] - is aligned for straight-ahead travel in longitudinal operation, then the rear axle H is arranged parallel to the transverse axis Y. If the rear wheel 3 of the industrial truck 1

[0053] - as shown for example in Figure 6 - is aligned for straight-ahead travel in transverse driving mode, then the rear axle H lies on or parallel to the longitudinal axis X. In the context of the invention, the rear axle H also only describes a geometric position designation and not a mechanical component.

[0054] In Figures 2 to 5 and 7, the rear axle H, the front axle V and the vehicle length T are not shown for the sake of clarity. These figures show industrial trucks 1 cornering. The cornering is carried out around a steering center P. The steering center P is the intersection point of straight lines that are orthogonal to the centers of all wheels 2.1, 2.2, 3, 3.1,

[0055] 3.2 of the respective industrial truck 1. The curve radius is the distance between the steering center P and the vehicle center. When traveling straight ahead, the steering center P is at infinity. If the steering angle sensor 5 is actuated, thereby initiating a curve, the steering center P moves from infinity along a steering line S toward the industrial truck 1.

[0056] In the following, only longitudinal driving mode is considered. What is shown and the corresponding description can be applied mutatis mutandis to transverse driving mode. In particular, the same steering lines and the same driving behavior can result. The closer the steering pole P is moved on the steering line S in the direction of the longitudinal axis X, the tighter the curve to be negotiated and the smaller the curve radius. A transverse distance Q of the steering pole P to the longitudinal axis X is controlled by the steering angle sensor 5. Here, a steering angle is set on the steering angle sensor 5 and the position of the steering point P on the steering line S in relation to the longitudinal axis X is set using a steering ratio. The steering ratio is preferably dependent on the steering angle. The greater the steering angle selected on the steering angle sensor 5, the greater the steering ratio is set.This means that entering a steering angle, for example when driving straight ahead, results in a smaller change in the lateral distance Q of the steering pole P from the longitudinal axis X by using a lower steering ratio. However, if, for example, the steering wheel is already turned and the industrial truck 1 is cornering, entering a steering angle by using a higher steering ratio results in a greater change in the lateral distance Q of the steering pole P from the longitudinal axis X.

[0057] According to the invention, a longitudinal distance L of the steering pole P to the transverse axis Y is controlled depending on the transverse distance Q of the steering pole P to the longitudinal axis X. In other words, the steering pole P moves forwards or backwards during steering.

[0058] Figures 2 to 4 show industrial trucks 1 in which the longitudinal distance L of the steering pole P from the transverse axis Y decreases with decreasing transverse distances Q of the steering pole P from the longitudinal axis X. In the embodiments shown in these figures, the maximum longitudinal distance L of the steering pole P from the transverse axis Y corresponds to half the vehicle length T and is reached at a transverse distance Q of the steering pole P from the longitudinal axis X of 0. In other words, the steering line S is designed here such that the industrial truck 1 can perform a carousel travel around a point centrally between the ends of the forks 4 of the industrial truck 1. Of course, the steering line S shown in Figures 1 to 4 can also have any other technically possible curved shape.Figure 5 shows a preferred embodiment of the industrial truck 1 according to the present invention, in which the longitudinal distance L of the steering pole P is reduced as the transverse distance Q of the steering pole P from the longitudinal axis X decreases. Here, the steering pole P moves toward the vehicle center M as the steering angle increases.

[0059] For the sake of clarity, the steering lines S shown in Figures 1 to 5 are merely curved and at least partially not parallel to the front axle V or the rear axle H. The steering line S can, of course, have other shapes. Furthermore, the steering line S can also be shifted along the longitudinal axis X and / or the transverse axis Y or arranged at an angle—especially while maintaining the same design.

[0060] Figure 7 shows a particularly preferred embodiment of the industrial truck 1 according to the present invention. In longitudinal travel mode, the steering line S lies with a substantially straight section within the front wheel axle V. As a result, in longitudinal travel mode, the industrial truck 1 is initially steered exclusively via the rear wheel 3 when turning from straight-ahead travel. 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 of 40°, the steering pole P is deflected or offset laterally next to the front wheel axle V by the curved shape of the steering line S, so that the steering pole P does not run through the center of one of the front wheels 2.1, 2.2 during further steering. Accordingly, the invention provides that the front wheels 2.1, 2.2 can only be steered from a predefined steering angle, especially of the rear wheel 3. The front wheels 2.1, 2.2 maintain the rotational movement in the same direction, controlled by drive motors (not shown) for rotating the wheels.

[0061] In particular, it can be provided that 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 past them at a laterally spaced distance, so that the rotational direction of one of the front wheels 2.1, 2.2 or the rear wheel(s) 3, 3.1, 3.2 is never reversed. This enables, in particular, advantages in terms of driving dynamics.

[0062] Reference list:

[0063] 1 industrial truck

[0064] 2.1 left front wheel

[0065] 2.2 right front wheel

[0066] 3 rear wheel

[0067] 3.1 left rear wheel

[0068] 3.2 right rear wheel

[0069] 4 forks

[0070] 5 steering angle sensors

[0071] H rear axle

[0072] L Longitudinal distance

[0073] M Vehicle center

[0074] P Steering pole

[0075] Q Transverse distance

[0076] S steering line

[0077] T Vehicle length

[0078] V front axle

[0079] X Longitudinal axis

[0080] Y transverse axis

Claims

Patent claims:

1. Steering method for operating an industrial truck (1), wherein the industrial 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 cornering around a steering pole (P), and both the at least two front wheels (2.1, 2.2) and the at least one rear wheel (3, 3.1, 3.2) are steerable, wherein the industrial truck (1) has a longitudinal axis (X) and a transverse axis (Y) which intersect in a vehicle center (M), wherein, when the industrial truck (1) is steered, a longitudinal distance (L) of the steering pole (P) to the transverse axis (Y) is regulated as a function of a transverse distance (Q) of the steering pole (P) to the longitudinal axis (X).

2. Steering method according to claim 1, characterized in that when steering the industrial truck (1) the steering pole (P) is guided on a steering line (S), wherein the steering line (S) is formed at least in sections at an angle to the transverse axis (Y) and / or at an angle to the longitudinal axis (X).

3. Steering method according to one of claims 1 or 2, characterized in that when steering the industrial truck (1) the steering pole (P) is guided on a steering line (S), wherein the steering line (S) is formed at least in sections as a straight line and / or in sections curved.

4. Steering method according to one of the preceding claims, characterized in that when steering the industrial truck (1) the steering pole (P) is guided on a steering line (S), wherein the steering line (S) has a gradient angle with respect to the longitudinal axis (X) and / or the transverse axis (Y), which angle changes depending on the longitudinal distance (L) and / or transverse distance (Q) of the steering pole (P).

5. Steering method according to one of the preceding claims, characterized in that when steering the industrial truck (1) the steering pole (P) is guided on a steering line (S), wherein the steering line (S) always runs at a distance from a respective vertical axis of the front wheels (2.1, 2.2) and / or a vertical axis of the rear wheel (3, 3.1, 3.2).

6. Steering method according to one of claims 2 to 5, characterized in that the steering line (S) is mirrored on the longitudinal axis (X) of the industrial truck (1).

7. Steering method according to one of the preceding claims, characterized in that a steering ratio is set as a function of a steering angle to initiate cornering.

8. Steering method according to one of the preceding claims, characterized in that the longitudinal distance (L) of the steering pole (P) to the transverse axis (Y) is increased with decreasing transverse distance (Q) of the steering pole (P) to the longitudinal axis (X).

9. Steering method according to one of the preceding claims, characterized in that the longitudinal distance (L) of the steering pole (P) to the transverse axis (Y) is reduced with decreasing transverse distance (Q) of the steering pole (P) to the longitudinal axis (X).

10. Steering method according to one of the preceding claims, characterized in that the industrial truck (1) preferably has a fork (4) and the maximum longitudinal distance (L) of the steering pole (P) to the transverse axis (Y) corresponds to the distance of the front end of the fork (4) to the transverse axis (Q), wherein the steering pole (P) is arranged at the level of the front end of the fork (4) in particular when the steering pole (P) is arranged on the longitudinal axis (X) of the industrial truck (1).

11. Steering method according to one of the preceding claims, characterized in that parallel to the longitudinal axis (X) of the Industrial truck (1) arranged, at least two front wheels (2.1, 2.2) a front axle (V) is defined which intersects the at least two front wheels (2.1, 2.2) centrally and is arranged orthogonally to the longitudinal axis (X) of the industrial truck (1), and at least in a longitudinal travel mode of the industrial truck (1), a steering line (S), on which the steering pole (P) is guided when steering the industrial truck (1), coincides at least in sections with the front wheel axle (V) and is designed such that the steering pole (P) is initially moved in the direction of the inside front wheel (2.1, 2.2) when cornering in the longitudinal travel mode, in particular on the front axle (V), and is deflected and spaced from the front axle (V) at a predefined distance from a vertical axis of the inside front wheel (2.1, 2.2), in particular at a steering angle of the at least one Rear wheel (3, 3.1, 3.2) with respect to the longitudinal axis (X) of equal to or more than 40°.Steering method according to one of the preceding claims, characterized in that, with at least one rear wheel (3, 3.1, 3.2) arranged orthogonally to the longitudinal axis (X) of the industrial truck (1), a rear axle (H) is defined which intersects the rear wheel (3, 3.1, 3.2) centrally and is arranged parallel to the longitudinal axis (X) of the industrial truck (1), and at least in a transverse travel mode of the industrial truck (1), a steering line (S), on which the steering pole (P) is guided when steering the industrial truck (1), coincides at least in sections with the rear axle (H) and is designed such that the steering pole (P) is moved, when cornering in the transverse travel mode, initially in the direction of the inside rear wheel (3, 3.1, 3.2), in particular on the rear axle (H), and at a predefined distance from a vertical axis of the inside rear wheel (3, 3.1, 3.2) is deflected and spaced from the rear wheel axle (H), in particular at least at a steering angle of at least one of the front wheels (2.1, 2.2) with respect to the transverse axis (Y) of equal to or more than 40°. Steering method according to one of the preceding claims, characterized in that both the longitudinal distance (L) of the steering pole (P) to the transverse axis (Y) and the transverse distance (Q) of the steering pole (P) to the longitudinal axis (X) are controlled exclusively by an input at the steering angle sensor (5). Steering method according to one of claims 1 to 12, characterized in that at least one predefined steering pole (P) is selectable, in particular independently of the steering angle sensor (5). Industrial truck (1), characterized in that the industrial truck (1) has a steering device which is configured to carry out a steering method according to one of the preceding claims by regulating the position of the steering pole (P).

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