TRANSPORT VEHICLE

Description

[0001] The invention relates to a transport vehicle with at least four wheels, wherein a steering pole is displaced by actuating a steering setpoint transmitter along a steering pole axis, which in particular cannot be displaced relative to the vehicle.

[0002] In this document, the term "steering pole" refers to a point to which the axles of the wheels - at least in the embodiment with exactly one unarticulated axle - are aligned when cornering.

[0003] The vehicle has at least one unsteered axle, which can also be referred to as an unsteered vehicle wheel axle, with two drive wheels, each of which is unsteered and driven by its own electric drive motor. In this document, the term "unsteered vehicle wheel axle" refers in particular to a vehicle wheel axle on which unsteered wheels are arranged, preferably exclusively.

[0004] The vehicle has at least one steered axle, which can also be referred to as a steered vehicle wheel axle, with at least two non-driven, steerable load wheels. In the context of this document, the term "steered vehicle wheel axle" refers in particular to a vehicle wheel axle on which steered wheels are arranged, preferably exclusively. In one embodiment, exactly two steered wheels, in particular load wheels, are arranged on a steered vehicle wheel axle. In another embodiment, more than two, approximately four, steered wheels, in particular load wheels, are arranged on a steered wheel axle.

[0005] A two-axle transport vehicle with four wheels is known, for example, from WO 01 / 70556 A1. In this vehicle, one steering program, also called "all-wheel steering," can be switched while driving to a second steering program for the same-direction rotation of the steering pole axes of all wheels by actuating the steering setpoint transmitter, also called "diagonal steering." When the steering setpoint transmitter is actuated, the steered wheels in all-wheel steering are actuated such that their axes of rotation always intersect at the steering pole. In contrast, with diagonal steering, the wheels are steered depending on the actuation of the steering setpoint transmitter so that the axes of rotation of the wheels are parallel—in other words, so that the steering pole lies at infinity.When the steering setpoint sensor is actuated when diagonal steering is selected, the vehicle changes direction without changing its orientation, whereas when all-wheel steering is selected, the orientation of the vehicle follows the change in direction.

[0006] In order to be able to change the orientation of the vehicle relative to its direction of travel, if necessary, regardless of the currently selected steering program, this vehicle is equipped with an additional control element, which can be actuated simultaneously with the steering setpoint transmitter if necessary. Actuation of this second control element leads to the correction of the steering angles of the wheels of at least one axle in a manner that does not correspond to the selected steering program, and is approximately proportional to the deflection of this control element, which is designed as a joystick.

[0007] EP 3 015 415 A1 claims a steering method for an industrial truck with a drive axle and a steering axle, in which, in a special (second) cornering mode, a tighter turning radius is enabled by correspondingly different drive of the front drive wheels than would be expected from the position of the steerable rear wheels. In this way, even in vehicles with a steering angle limited, for example, by a tie rod, very tight cornering can be achieved at the cost of increased tire wear. Also disclosed is a vehicle in which the geometry of the steered wheels corresponds to a kingpin steering system, but the steering angle is not limited.

[0008] EP 2 145 812 A2 relates to a method for steering control of a wheel of a forklift truck.

[0009] EP 0 982 220 A2 shows an electrically powered three-wheeled vehicle in which the rotational speed of the drive wheels is calculated from the steering angle. This avoids, in particular, the problem of friction between the steered wheels of an axle. To achieve optimal rotational performance even at low driving speeds, the motor current is routed through a freewheeling diode of a chopper circuit. This also improves the rotational efficiency of an outer and an inner wheel. A change in the direction of rotation of the drive wheels, in particular a counter-rotating direction, is not provided for in this vehicle.

[0010] The disadvantage of the above-cited state of the art is that the vehicle is quite complex to manufacture and steering such a vehicle requires considerable practice and also considerable concentration in daily operation if undesirable, sometimes difficult to control, driving situations are to be avoided.

[0011] The invention is therefore based on the object of creating a vehicle which is improved with regard to at least one of the disadvantages mentioned.

[0012] This object is achieved by the vehicle recited in claim 1.

[0013] According to the invention, the electronic control device is configured to reverse the direction of rotation of a drive motor at a steering angle at which the axles of the load wheels point toward the drive wheel driven by this motor. In other words, the electronic control device is configured to reverse the direction of rotation of one of the drive motors when the center of rotation passes the drive wheel driven by this drive motor along the steering pole axis—at a specific steering angle.

[0014] In one embodiment, the transport vehicle is two-axle. In another embodiment, as is known from some trucks, it is three-axle or has more than three vehicle wheel axles.

[0015] In one embodiment, the vehicle has exactly one unsteered axle. In another embodiment, the vehicle has two or more unsteered axles.

[0016] In one embodiment, the vehicle has exactly one steered axle. In another embodiment, the vehicle has two or more steered axles.

[0017] Each wheel is preferably either steered or driven. And only non-driven wheels are preferably steered.

[0018] With the aid of the steering setpoint transmitter, each of these load wheels can be steered from a position in which the axis of this load wheel runs parallel to an axis of the drive wheels to a position in which the axis of this load wheel is aligned with a steering center located between the drive wheels. Such a large steering range enables the vehicle to be highly maneuverable.

[0019] Thus, preferably, all of the vehicle's load wheels are not driven, and more preferably, all of the vehicle's drive wheels are not steered. If the drive wheels are unsteered, the steering pole axis cannot be displaced relative to the vehicle, and the vehicle—at least in the embodiment with exactly one unsteered axle—has only exactly one steering pole axis. In the embodiment with exactly one unsteered axle, the steering pole axis coincides with the axis of the two drive wheels.

[0020] The vehicle has a device for detecting the steering angle of at least one load wheel. This device can also be referred to as a steering angle sensor.

[0021] The device for detecting the steering angle of at least one load wheel can comprise an angle sensor arranged on the load wheel, thus detecting the actual steering angle. Since the position of the steering pole can already be determined from the steering angle of exactly one load wheel, it is fundamentally conceivable to provide only one device for detecting the steering angle of exactly one of the load wheels.

[0022] It is also possible to provide precisely one device for detecting the steering angles of several, preferably all, load wheels, or to provide several devices for detecting the steering angles of several, preferably all, load wheels. Detecting the steering angles of all load wheels is particularly preferred when, as in one embodiment, a steering control device is provided.

[0023] The device for detecting the steering angle of at least one load wheel can be provided on the steering setpoint transmitter, so it can detect the target steering angle.

[0024] Both the target value of the steering angle and the actual value can be recorded and a steering control device can be provided, for example in the electronic control device, to approximate the actual value to the target value in the event of a deviation.

[0025] An electronic control device is provided which is designed to influence the speed of the drive motors depending on the steering angle.

[0026] The electronic control device is also designed to reverse the direction of rotation of at least one of the drive motors depending on the steering angle.

[0027] The electronic control device is preferably designed - at least in the embodiment with exactly one unsteered axle - such that at exactly a specific steering angle of at least one of the load wheels it reduces the speed of one of the drive motors to zero and reverses the direction of rotation of this drive motor when the steering angle is further increased.

[0028] The electronic control unit can also preferably be referred to as an electronic differential gear. The position of the load wheels thus preferably determines how fast and in which direction the drive motors drive the corresponding wheel via the electronic control unit, in order to at least largely prevent skidding on the ground.

[0029] The electronic control device preferably has an input that is operatively connected to the device for detecting the steering angle of at least one load wheel. The electronic control device preferably has a further input that is operatively connected to the speed setpoint transmitter.

[0030] The electronic control device preferably has an output that is operatively connected to one of the drive motors, and more preferably has another output that is preferably operatively connected to another drive motor. The electronic control device preferably has a separate output for each drive motor.

[0031] A vehicle with such a control device can, in principle, also allow a shift and / or rotation of the steering pole axis, for example if it is all-wheel steered - unlike the vehicle according to the invention - and can then be designed as an extremely maneuverable two- or multi-way vehicle. In contrast, a shift and / or rotation of the steering pole axis is excluded in the vehicle according to the invention due to the unsteered drive wheels. Surprisingly, it has been shown that the inventive combination of such an electronic control device with non-steerable drive wheels results in a vehicle that, on the one hand, can already be highly maneuverable - compared to a vehicle with tie rod steering, for example - and, on the other hand, can be designed to be inexpensive to manufacture and easy to steer due to the non-steerable drive wheels - compared to an all-wheel steered vehicle, for example.

[0032] Preferably, each load wheel can be steered from a position in which its axis runs parallel to the axis of the drive wheels to a position in which its axis is aligned with a steering center located exactly centrally between the drive wheels of an unsteered axle. In this way, maneuverability can be further increased.

[0033] The steering setpoint transmitter can be designed, for example, as a steering wheel or a joystick.

[0034] The load wheels of a steered axle are preferably spaced apart from each other; therefore, they are preferably not twin wheels. The same preferably applies to the drive wheels.

[0035] The electronic control system can influence the speed of the drive motors by means of open-loop or closed-loop control. If this is done by closed-loop control, speed sensors are preferably provided on the drive wheels. These sensors detect the actual speed of the drive wheels. This is compared with the value specified by the speed setpoint generator and, if there is a deviation, adjusted accordingly.

[0036] In this publication, the term "load wheel" refers in particular to any non-driven wheel.

[0037] Preferably, a separate drive motor is directly flanged to each drive wheel.

[0038] In one embodiment, the diameter of the load wheels is smaller than the diameter of the drive wheels. In another embodiment, the diameter of all wheels is the same.

[0039] If the electronic control device is set up in such a way that it automatically reverses the direction of rotation, the vehicle is particularly easy to control.

[0040] In one embodiment, the axles of at least two load wheels can be aligned perpendicular to each other. This allows the vehicle to be brought into a parking position.

[0041] In the preferred embodiment, the load wheels of a steered axle are not mechanically connected to each other—for example, by means of a tie rod. Therefore, each load wheel can preferably be steered independently of any other load wheel.

[0042] Preferably, at least one, preferably each load wheel can be steered by a steering angle of more than 90°.

[0043] In one embodiment, at least one, preferably each load wheel is steerable by a steering angle of less than 180°, more preferably less than 135°.

[0044] In another embodiment, at least one, preferably each load wheel, can be steered by 360° or endlessly.

[0045] The load wheels are electrically steered and each load wheel has its own electric steering motor.

[0046] The distance between the load wheels can be smaller than the distance between the drive wheels.

[0047] In one embodiment, the drive wheels are designed as front wheels and the load wheels as rear wheels of the vehicle.

[0048] In the preferred embodiment, the vehicle is designed as a forklift.

[0049] The vehicle preferably has an upright mast on which a fork assembly is arranged so that it can be raised and lowered. The drive wheels are preferably arranged on the side of the vehicle facing the fork assembly, and the load wheels are preferably arranged on the side of the vehicle facing away from the fork assembly.

[0050] Preferably, the electronic control device is configured to influence the speed of the drive motors depending on the distance of the respective drive wheel from the center of rotation, which results from the steering angle of a load wheel. This preferably occurs according to the mathematical relationship between the circumference of the circular path on which the respective drive wheel runs and its distance from the center of the circle defined by the steering pole, i.e., the radius of this circle.

[0051] The electronic control device preferably stores the unchanging position of at least one load wheel perpendicular to the axles of the drive wheels, and more preferably parallel thereto, as determined by the vehicle geometry. The electronic control device preferably determines the respective distance of a drive wheel from the steering center predetermined by the steering angle from this stored position and the steering angle with the aid of angular functions, such as the tangent.

[0052] A possible embodiment of the invention will be described below by way of example with reference to the accompanying drawings. They show: Fig. 1- schematically - a two-axle transport vehicle using the example of a forklift truck in a side view; Fig. 2 a schematic diagram of the Fig. 1 shown transport vehicle in a view from above when driving straight ahead; Fig. 3 in Fig. 2shown illustration when cornering; Fig. 4 in Fig. 2 shown illustration with a center of rotation located between the drive wheels.

[0053] The embodiment of the transport vehicle according to the invention, designated as a whole by 100, shown in the drawings is, as Fig. 1 shows, designed as a two-axle forklift truck, with a steering setpoint transmitter 2 designed as a steering wheel. The diameter of the load wheels 5, 5' is, as the Fig. 2 to 4 show, smaller than the diameter of the drive wheels 3, 3' (in Fig. 1 the load wheels and the drive wheels are shown as the same size for simplicity).

[0054] Fig. 1 shows that the vehicle has an upright mast 12 on which a fork arrangement 13 (in the Figures 2 to 4 not shown for the sake of simplicity).

[0055] The two load wheels 5, 5' are rotatable about wheel axles 6, 6' and each by one in the Figures 2 to 4 Steering axis X running perpendicular to the plane of the drawing is arranged so that it can be steered.

[0056] The Fig. 1 and 2 The speed setpoint generator 11 shown is designed as an "accelerator pedal" and specifies the setpoint for the drive power of the drive motors 4, 4'.

[0057] In the embodiment shown, the distance between the load wheels 5, 5' is smaller than the distance between the drive wheels 3, 3'.

[0058] For example, Fig. 2 It can be seen that the vehicle has four wheels 1. A steering pole O, to which the axes P of the wheels 1 are aligned when cornering, is determined, as can be seen from a comparison of the Figures 3 and 4 shows, is shifted along a steering pole axis A by actuating the steering setpoint transmitter 2. The arrow C shows the direction of travel of the vehicle in all figures.

[0059] Fig. 2 also shows that the vehicle has an unsteered vehicle wheel axle E with two drive wheels 3, 3'. Each of these drive wheels 3, 3' is unsteered and driven by its own electric drive motor 4, 4'.

[0060] The vehicle has a steered vehicle wheel axle F with two steerable load wheels 5, 5', each of which is not driven.

[0061] As a comparison of the Figures 2 , 3 and 4 shows, each of the load wheels 5, 5' is connected to the steering setpoint transmitter 2 from a position in which its axis 6, 6' is parallel to the axis 7 of the drive wheels 3, 3' (shown in Fig. 2 ) into a position in which its axle 6, 6' is aligned with a steering pole (O) located between the drive wheels 3, 3' (shown in Fig. 4 ).

[0062] In Fig. 2It can also be seen that a device 9 (symbolized as a triangle) is provided for detecting the steering angle α of a load wheel 5'. In the exemplary embodiment shown in the figures, a device 9 for detecting the steering angle α of this load wheel 5' is provided only on exactly one load wheel 5'. This device 9 detects the steering angle α starting from the zero position, which in Fig. 2 shown, in both possible steering directions. To determine the position of the center of rotation O, it is sufficient to detect exactly one steering angle α. However, a device for detecting the steering angle of this load wheel can also be provided on the other load wheel 5.

[0063] A separate drive motor 4, 4' is directly flanged to each drive wheel 3, 3'.

[0064] Fig. 2 shows a (for the Figures 3 and 4(not shown for the sake of simplicity) electronic control device 10. This electronic control device has inputs that are operatively connected to the steering angle detection device 9 and the speed setpoint generator 11 and outputs that are operatively connected to the two drive motors 4, 4'. It is designed to influence the speed of the drive motors 4, 4' depending on the steering angle α detected by the device 9 and to reverse the direction of rotation of one of the two drive motors 4, 4' depending on the steering angle α. This occurs in such a way that when cornering, such as in Fig. 3 shown, the inside drive wheel 3' is driven more slowly than the outside drive wheel 3, as shown by the two differently long arrows B in Fig. 3is shown. If the electronic control device 10 detects from the detected steering angle α that the center of rotation O has reached and exceeded the position of a drive wheel 3' (as is the case between the Figures 3 and 4 has happened), then it automatically reverses the direction of rotation of this wheel 3', as shown by the arrows B pointing in different directions in Fig. 4 is shown.

[0065] The electronic control device 10 is designed to influence the speed of the drive motors as a function of the distance r1, r2 of the respective drive wheel 3, 3' from the center of rotation O, determined by the steering angle α, in accordance with the mathematical relationship between the circumference of the circular path on which the respective drive wheel 3, 3' runs and its distance r1, r2 from the center of the circle defined by the steering pole O, i.e. the radius of this circle.

[0066] Fig. 4shows the situation in which the axles 6, 6' of the load wheels 5, 5' are aligned to a steering pole O located exactly centrally between the drive wheels 3, 3'.

[0067] Such as Fig. 4 As shown, each load wheel 5, 5' can be steered through a steering angle α of more than 90°. Each load wheel can be steered infinitely.

[0068] In the embodiment shown, the load wheels 5, 5' are steered electrically by means of an electric steering motor 8, 8'. List of reference symbols:

[0069] 100Transport vehicle 1Wheels 2Steering setpoint sensor 3, 3'Drive wheels 4, 4'Electric drive motor 5, 5'Load wheels 6, 6'Load wheel axles 7Drive wheel axle 8, 8'Steering motor 9Device for detecting the steering angle 10Electronic control device 11Speed setpoint sensor 12Mast 13Fork arrangement ALeercing pole axis BParrows CParrow Unsteered axle FSteered axle OLeering pole PReering axles XLeering axles αSteering angle

Claims

1. Transport vehicle (100) with at least four wheels (1) and a steering setpoint value transducer (2), wherein a steering pole (O) is displaced by actuation of the steering setpoint value transducer (2) along a steering pole axis (A), with at least one non-steered axle (E) having two drive wheels (3, 3'), each of which is non-steered and driven by its own electric drive motor (4, 4'), and with at least one steered axle (F) having at least two non-driven steerable load wheels (5, 5'), each of which can be steered with the aid of the steering setpoint value transducer (2) from a position, in which its axis (6, 6') is parallel to an axis (7) of the drive wheels (3, 3'), into a position, in which its axis (6, 6') is aligned with a steering pole (O) lying between the drive wheels (3, 3'), wherein each steerable load wheel (5, 5') has its own electric steering motor (8, 8'), and with an apparatus (9) for detecting the steering angle (α) of at least one load wheel (5, 5'), wherein an electronic control device (10) is provided which is designed such that it influences the speed of the drive motors (4, 4') as a function of the steering angle (α) and reverses the direction of rotation of at least one of the drive motors (4, 4') as a function of the steering angle (α), and the electronic control device (10) is designed so as to automatically reverse the direction of rotation and reverse the direction of rotation of one of the drive motors (4, 4') when the steering pole (O) passes the drive wheel (3, 3'), which this drive motor (4, 4') drives, along the steering pole axis (A).

2. Transport vehicle according to Claim 1, characterized in that the load wheels (5, 5') are not connected to each other by way of a track rod, and each load wheel (5, 5') is steerable independently of another load wheel (5, 5').

3. Transport vehicle according to Claim 1 or 2, characterized in that a dedicated drive motor (4, 4') is directly flange-connected to each drive wheel (3, 3').

4. Transport vehicle according to one of Claims 1 to 3, characterized in that the axes (6, 6') of at least two load wheels (5, 5') can be aligned perpendicularly with respect to each other.

5. Transport vehicle according to one of Claims 1 to 4, characterized in that each load wheel (5, 5') is steerable by more than 90°.

6. Transport vehicle according to Claim 5, characterized in that each load wheel (5, 5') is steerable by 360° or endlessly.