forklift

Abstract

A forklift truck (1) designed as a pallet truck, comprising a drive unit (2) and a load unit (3) that can be raised and lowered relative to the drive unit (2), wherein the forklift truck (1) has a four-wheel chassis, which has two load roller assemblies (5a, 5b) spaced apart in the transverse direction (Q) of the vehicle on the load unit (3), and a driven and steerable drive wheel (6) and a support roller (7) spaced laterally from the drive wheel (6) in the transverse direction (Q) of the vehicle on the drive unit (2), wherein the drive wheel (6) is arranged on a wheel carrier (10) which is height-adjustable on a vehicle frame (11) of the drive unit (2), characterized in that a sensor device (20) is provided which determines the position of the height-adjustable wheel carrier (10) on which the drive wheel (6) is arranged relative to a roadway (F) or the position of the height-adjustable wheel carrier (10) on which the drive wheel (6) is arranged,the position of the vehicle frame (11) is determined, wherein the sensor device (20) is in operative communication with an electronic control unit (21) which determines the tire wear of the drive wheel (6) arranged on the wheel carrier (10) from the position determined by means of the sensor device (20).

Description

[0001] The invention relates to an industrial truck which is designed as a lifting truck and has a drive part and a load part which can be raised and lowered relative to the drive part, wherein the industrial truck has a four-wheel chassis which has two load roller devices spaced apart in the transverse direction of the vehicle on the load part and has a driven and steerable drive wheel on the drive part and a support roller laterally spaced apart from the drive wheel in the transverse direction of the vehicle, wherein the drive wheel is arranged on a wheel carrier which is arranged in a height-adjustable manner on a vehicle frame of the drive part.

[0002] Industrial trucks of this type are usually designed as pallet trucks, such as low-lift or high-lift pallet trucks, as tractors, or as order pickers, such as low-level or high-level order pickers. Such industrial trucks can be operated in pedestrian or rider mode. For rider mode, a fixed or foldable operator platform can be provided. For rider mode, the truck can be designed as a stand-alone or ride-on unit.

[0003] The drive part of this type of industrial truck with a four-wheel chassis is supported on the roadway by a steerable and driven drive wheel and a support roller laterally spaced from the drive wheel. The drive wheel is actively steered and is connected to a steering drawbar operated by an operator or a steering drive, such as an electric steering motor. The drive wheel's travel drive also brakes the drive wheel, with the travel drive, such as an electric travel motor, acting as a service brake through regenerative operation. A parking brake also acts on the drive wheel. The support roller is not driven and is generally not braked. The support roller is generally not actively steered and is designed as a trailing roller.A load section of such an industrial truck, which is usually formed by two laterally spaced load arms or support arms, is supported on the roadway by two load roller devices, which are usually located at the tips of the load arms or support arms. To compensate for uneven road surfaces with such a four-wheel chassis, the drive wheel is mounted on a wheel carrier that is height-adjustable on a vehicle frame of the drive section.

[0004] Due to the drive and braking forces transmitted to the drive wheel, greater wear occurs on the outer running surface of the drive wheel during industrial truck operation than on the support roller, which is not driven and not actively steered. As the drive wheel wears, the transferable drive and braking forces can change and deteriorate the handling characteristics of the industrial truck. Furthermore, when the drive wheel reaches its wear limit, it must be replaced.

[0005] To determine the wear of an industrial truck wheel, it is already known from DE 10 2009 010 983 A1 to incorporate electrical and / or magnetic components into the outer wear layer of a wheel as wear markers, the presence or absence of which is detected using a component detector. However, to determine the wheel wear, special wheels equipped with wear markers are required.

[0006] DE 10 2011 053 961 A1 discloses a method for determining tire wear on an industrial truck. The method involves determining the speed and torque of the drive motor driving the drive wheel at specific operating points and comparing them with reference values. Since the wheel diameter changes with the wear of the drive wheel, tire wear can be determined from the change in speed or torque at a specific operating point. However, such a method is complex to implement.

[0007] EP 1 868 838 B1 discloses an industrial truck in which a sensor is provided to determine the tire wear of the drive wheel, which sensor measures the radial distance to the drive wheel.

[0008] DE 101 18 442 A1 discloses an industrial truck with a safety device to increase lateral tipping stability.

[0009] DE 44 08 757 A1 discloses an industrial truck designed as a lift truck, in which a drive wheel and a steered wheel are mounted on a swing arm. Associated with the swing arm is a stabilizing device that moves the swing arm to its center position and locks it in that position when a predetermined lifting height is exceeded.

[0010] The present invention is based on the object of providing an industrial truck of the type mentioned above which enables the tire wear of the drive wheel to be determined with a simple construction effort.

[0011] This object is achieved according to the invention in that a sensor device is provided which determines the position of the height-adjustable wheel carrier on which the drive wheel is arranged relative to a roadway or the position of the height-adjustable wheel carrier on which the drive wheel is arranged relative to the vehicle frame, wherein the sensor device is operatively connected to an electronic control device which determines the tire wear of the drive wheel arranged on the wheel carrier from the position determined by means of the sensor device. With increasing wear of the drive wheel, its outer diameter decreases, so that with a height-adjustable drive wheel, the position of the wheel carrier provided with the drive wheel relative to the vehicle frame or relative to the road surface changes permanently and long-term during operation of the industrial truck.With a sensor device that detects the position of the height-adjustable wheel carrier relative to the vehicle frame or the road surface, tire wear can be determined and inferred from the change in position during operation of the industrial truck with little construction effort.

[0012] The wheel carrier can be arranged on a guide on the vehicle frame of the industrial truck and can be adjusted in the vertical direction.

[0013] According to a preferred embodiment of the invention, the wheel carrier is designed as a swing arm that is pivotably mounted on the vehicle frame about a horizontal pivot axis running in the vehicle's longitudinal direction. With such a pivotable swing arm, the height of the drive wheel can be adjusted with minimal construction effort by pivoting the swing arm about the pivot axis.

[0014] According to a further development of the invention, the drive wheel and the laterally spaced support roller are arranged on the rocker arm. In an industrial truck with a four-wheel chassis, this makes it easy to ensure contact between the drive wheel, the support roller, and both load roller assemblies with the road surface even when the road surface is uneven.

[0015] The support roller is expediently arranged on the swing arm opposite the drive wheel with respect to the pivot axis.

[0016] According to an advantageous embodiment of the invention, the sensor device detects the distance of the swing arm relative to the vehicle frame or the tilt angle of the swing arm about the pivot axis. The sensor device thus uses the distance or tilt angle to detect the inclination and skew resulting from wear on the drive wheel, and thus the change in position of the swing arm relative to the vehicle frame.

[0017] For this purpose, the sensor device is preferably arranged on the vehicle frame at a distance from the pivot axis in the transverse direction of the vehicle. This allows the sensor device, which detects the distance between the swing arm and the vehicle frame, to be installed on the vehicle frame in a manner protected from damage and contamination.

[0018] According to an advantageous development of the invention, the distance signal provided by the sensor device can be utilized by the electronic control device generating a maintenance signal to replace the drive wheel when a wear limit is reached. This allows for a timely replacement of a worn drive wheel to be indicated with minimal construction effort.

[0019] If, according to a further development of the invention, the support roller is arranged on the drive part in a height-adjustable manner, the signal from the sensor device can be used to generate a maintenance signal for adjusting the height of the support roller via the electronic control device, depending on the tire wear. The stability and driving characteristics of the industrial truck change with the inclination and slant of the rocker arm. Thus, when a certain level of wear is reached on the drive wheel, a corresponding maintenance signal can be used to adjust the height of the support roller to realign the rocker arm to a horizontal position, thus achieving high stability and good performance of the industrial truck.

[0020] If the tilting movement of the swing arm about the pivot axis can be blocked, the signal from the sensor device can be used to generate an indication signal by means of the electronic control device depending on the tire wear, to block the swing arm against a pivoting movement, or to block the swing arm automatically by means of the electronic control device depending on the tire wear.

[0021] According to a preferred embodiment of the invention, the sensor device can be designed as a contactless sensor or according to an alternative embodiment of the invention as a contact sensor, in particular a contact switch.

[0022] The sensor device can be designed as an inductive sensor or as a capacitive sensor or as a magnetic sensor or as a photoelectric sensor or as a laser sensor or as a distance meter.

[0023] Further advantages and details of the invention are explained in more detail with reference to the embodiment shown in the schematic figures. Fig. 1 an industrial truck according to the invention in a side view, Fig. 2 a section along the line AA of the Fig. 1 and Fig. 3 another section along the line AA of the Fig. 1.

[0024] In Fig. 1 shows a side view of an industrial truck 1 according to the invention, designed as a lifting truck, for example a forklift truck. The industrial truck 1 has a drive part 2 and a load part 3 that can be raised and lowered relative to the drive part 2. The load part 3 has two laterally spaced load arms 4a, 4b, which are each supported on a track F by at least one load roller device 5a, 5b. In the side view of the Fig. 1, the two load arms 4a, 4b are arranged one behind the other.

[0025] In the area of ​​the drive part 2, the industrial truck 1 is located - as in connection with the Fig. 2 and Fig. 3, in which a section through the drive part 2 according to the line AA of the Fig. 1 - with a steerable and driven drive wheel 6 and with a support roller 7 laterally spaced from the drive wheel 6 in the transverse direction Q of the industrial truck 1 on the roadway F. The drive wheel 6 is steered about a vertical steering axis L. A steering drawbar (not shown in detail) or a steering motor, for example an electric steering motor, can be provided for steering the drive wheel 6.

[0026] The drive part 2 contains the units required to drive the industrial truck 1, for example an electric drive motor 9 for driving the drive wheel 6 and an electric pump motor which drives a hydraulic pump to supply a hydraulic lifting device for raising and lowering the load part 3.

[0027] The load part 3, which is arranged on the drive part 2 so as to be liftable and lowerable, can further comprise a battery compartment 8 for a traction battery which supplies the electric drive system of the industrial truck 1 with electrical energy.

[0028] In the industrial truck 1 according to the invention with a four-wheel chassis, the drive wheel 6 is located on one side of the vehicle and the support roller 7 is located on the opposite side of the vehicle in the drive part 2.

[0029] The drive wheel 6 is arranged on a wheel carrier 10 which is arranged on a vehicle frame 11 of the drive part 2 so as to be height adjustable in the vertical direction V.

[0030] In the illustrated embodiment, the wheel carrier 10 is designed as a rocker 12 on which the drive wheel 6 and the laterally spaced support roller 7 are arranged.

[0031] The rocker arm 12 is pivotally mounted on the vehicle frame 11 about a horizontal pivot axis 15, for example a pivot joint, running in the vehicle's longitudinal direction X. The inclination adjustment of the rocker arm 12 about the pivot axis 15 thus results in a height adjustment of the wheel carrier 10 in the region of the drive wheel 6 in the vertical direction V.

[0032] The support roller 7 is arranged on the swing arm 12 opposite the drive wheel 6 with respect to the pivot axis 15.

[0033] The drive motor 9 is also mounted on the rocker arm 12. The rocker arm 12, equipped with the drive motor 9 and the steerable drive wheel 6, thus forms a drive unit of the industrial truck 1.

[0034] The drive wheel 6 is mounted on a turntable 16 for rotation about a rotation axis D. The turntable 16 is mounted on the swing arm 12 for rotation about the steering axis L.

[0035] The support roller 7 is designed as a trailing roller which is mounted rotatably about a rotation axis D in a carrier 17 which is mounted rotatably about a vertical trailing axis NA on the rocker 12.

[0036] According to the invention, a sensor device 20 is provided that detects and determines the distance A between the height-adjustable wheel carrier 10 and the vehicle frame 11. The sensor device 20 is operatively connected to an electronic control device 21, which determines the tire wear of the drive wheel 6 from the distance determined by the sensor device 20.

[0037] In the illustrated embodiment, the sensor device 20 detects the vertical distance A of the swing arm 12 to the vehicle frame 11 and thus the inclination of the swing arm 12 about the pivot axis 15 relative to the vehicle frame 11.

[0038] For this purpose, the sensor device 20 is arranged on the vehicle frame 11 at a distance from the pivot axis 15 of the rocker arm 12 in the vehicle transverse direction Q and is aligned with the rocker arm 12, for example its upper side, in order to detect the vertical distance A.

[0039] In the Fig. 2 shows the condition of a new, unworn drive wheel 6. Fig. 3 shows the condition of worn drive wheel 6.

[0040] During operation of the industrial truck 1, greater wear occurs on the drive wheel 6 than on the support roller 7. This difference in the wear behavior of the drive wheel 6 and the support roller 7 leads, with increasing wear of the drive wheel 6 and thus increasing reduction of the outer diameter of the drive wheel 6, to a long-term permanent inclination α of the wheel carrier 10 formed by the rocker 12 around the pivot axis 15, as shown in the Fig. 3. This permanent inclination α of the wheel carrier 10 formed by the rocker arm 12 relative to the vehicle frame 11 is detected by the sensor device 20. The permanent inclination α of the wheel carrier 10 formed by the rocker arm 12 represents a measure of the wear of the drive wheel 6 during the operation of the industrial truck 1.

[0041] The signal of the sensor device 20 detecting the inclination of the rocker arm 12 is used in the control device 21 to determine the wear of the drive wheel 6 and, when a wear limit is reached, to generate a maintenance signal for replacing the drive wheel 6. Furthermore, the signal of the sensor device 20 can be used in the control device 21 to generate a maintenance signal for adjusting the height of the support roller 7 depending on the tire wear. By adjusting the height setting of the support roller 7, the wheel carrier 10 can be returned to the horizontal position of the Fig.2 and the negative influences on the driving behavior and stability of the industrial truck 1 caused by the lateral inclination of the wheel carrier 10 are eliminated. Furthermore, the signal from the sensor device 20 in the control device 21 can be used to block the inclination of the wheel carrier 10 about the pivot axis 15 depending on the tire wear.

[0042] The sensor device 20 according to the invention makes it possible to provide the operator with information about the wear and service life of the drive wheel 6 with minimal construction effort. Furthermore, timely replacement of the drive wheel 6 or a height adjustment of the support roller 7 makes it possible to ensure high stability of the industrial truck 1 and good driving characteristics of the industrial truck 1.

Claims

[1] Industrial truck (1) which is designed as a lifting truck and has a drive part (2) and a load part (3) which can be raised and lowered relative to the drive part (2), wherein the industrial truck (1) has a four-wheel chassis which has two load roller devices (5a, 5b) spaced apart in the vehicle transverse direction (Q) on the load part (3) and has a driven and steerable drive wheel (6) on the drive part (2) and a support roller (7) laterally spaced apart from the drive wheel (6) in the vehicle transverse direction (Q), wherein the drive wheel (6) is arranged on a wheel carrier (10) which is arranged in a height-adjustable manner on a vehicle frame (11) of the drive part (2), characterized bythat a sensor device (20) is provided which determines the position of the height-adjustable wheel carrier (10), on which the drive wheel (6) is arranged, in relation to a roadway (F) or determines the position of the height-adjustable wheel carrier (10), on which the drive wheel (6) is arranged, in relation to the vehicle frame (11), wherein the sensor device (20) is operatively connected to an electronic control device (21) which determines the tyre wear of the drive wheel (6) arranged on the wheel carrier (10) from the position determined by means of the sensor device (20). [2] Industrial truck according to claim 1, characterized by that the wheel carrier (10) is designed as a rocker (12) which is arranged on the vehicle frame (11) so as to be pivotable about a horizontal pivot axis (15) running in the vehicle longitudinal direction (X). [3] Industrial truck according to claim 2, characterized bythat the drive wheel (6) and the laterally spaced support roller (7) are arranged on the rocker (12). [4] Industrial truck according to claim 2 or 3, characterized by that the support roller (7) is arranged on the rocker (12) opposite the drive wheel (6) with respect to the pivot axis (15). [5] Industrial truck according to one of claims 2 to 4, characterized by that the sensor device (20) detects the distance (A) of the rocker arm (12) to the vehicle frame (11) or the inclination angle (α) of the rocker arm (12) about the pivot axis (15). [6] Industrial truck according to claim 5, characterized by that the sensor device (20) is arranged on the vehicle frame (11) in the vehicle transverse direction (Q) at a distance from the pivot axis (15). [7] Industrial truck according to one of claims 1 to 6, characterized by that the electronic control device (21) generates a maintenance signal for replacing the drive wheel (6) when a wear limit is reached. [8] Industrial truck according to one of claims 1 to 7, characterized by that the support roller (7) is arranged on the drive part (2) in a height-adjustable manner and the electronic control device (21) generates a maintenance signal for adjusting the height of the support roller (7) as a function of the tire wear. [9] Industrial truck according to one of claims 2 to 8, characterized by that the tilting movement of the rocker (12) about the pivot axis (15) can be blocked and the electronic control device (21) generates an indication signal depending on the tire wear to block the rocker (12) against a pivoting movement, or the electronic control device (21) automatically blocks the rocker (12) depending on the tire wear. [10] Industrial truck according to one of claims 1 to 9, characterized by that the sensor device (20) is designed as a contactless sensor or as a contact sensor, in particular a contact switch. [11] Industrial truck according to one of claims 1 to 10, characterized by that the sensor device (20) is designed as an inductive sensor or as a capacitive sensor or as a magnetic sensor or as a photoelectric sensor or as a laser sensor or as a distance meter.

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