WO2010097173A1

WO2010097173A1 - Drive system, in particular for driverless industrial trucks

Info

Publication number: WO2010097173A1
Application number: PCT/EP2010/000945
Authority: WO
Inventors: Matthias Könemann; Winfried Schroer
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2009-02-25
Filing date: 2010-02-16
Publication date: 2010-09-02
Also published as: DE102009010527A1

Abstract

In a drive system (1), in particular for driverless industrial trucks, the intent is to increase the efficiency, reduce the wear on the wheels (7) and ensure the highest possible protection against contamination, while ensuring low expenditure for maintenance. This is achieved by a plurality of wheels (7) positioned in wheel suspensions (6) on a wheel carrier (2) that is acted on by a rotary drive (4, 5), wherein the angles of the wheel axles (8) can be adjusted via the respective wheel suspension (6) by means of a control drive (13) during a revolution of the wheel carrier (2).

Description

"Travel drive, especially for driverless floor vehicles"

The invention is directed to a traction drive driverless transport vehicles.

A universal transportable heavy transport vehicle, as it may represent the starting point of the present invention is known for example from DE 38 41 971 A, where there the type of wheels characterizes the particular mobility of the vehicle.

The possible movement behavior of a driverless transport vehicle is determined by the number of degrees of freedom of the chassis. A distinction is made between movable and movable vehicles. Each vehicle basically has three degrees of freedom of movement in its driving plane:

> Movement in longitudinal and transverse direction (X- / Y-position)

> Rotation around the vertical axis (so-called yaw, yaw angle)

In a line movable vehicle, these are not independently adjustable, since the orientation of the vehicle frame is fixed relative to the trajectory by the chassis. This results in cornering to an increased space requirement. In contrast, in the case of a surface-mobile vehicle, the orientation of the vehicle frame can be set independently of the vehicle position. It is both during driving and from the stand out all movements (translational and rotational) of the vehicle frame possible.

Disadvantages of known suspension solutions include the following: Area movable chassis can be produced so far only by the combination of individually steered wheels, by rotating differential drives or by the so-called "Mecanum Drive". In a combination of several steered wheels is to ensure a proper kinematics of the chassis by a lever mechanism ("steering linkage") or a control-side coupling of the wheels.

Geometric prerequisite is e.g. compliance with the Ackermann condition, according to which the wheel axles of a steered vehicle must pass through a common point. If, for example, In order to carry higher loads or to reduce the surface load of the floor, steered wheels are provided in larger numbers, the constructive effort for realizing a perfect chassis cabinetry increases greatly. Due to this fact is often dispensed with a mobility in the area in favor of line kinematics for chassis with multiple steered and / or driven wheels.

In the field of industrial trucks (especially in driverless systems), the realization of surface movable chassis by means of two steering drives is common. In these suspensions, the steering drives are usually used in conjunction with several of the support serving passive castors. Alternatively, rotatable differential drives are used, which are also supplemented by a number of passive castors to a complete chassis. A common disadvantage of these principles is that the passive rollers can cause inaccuracies in the driving curve when changing direction. These are caused by the uncontrolled "turning over" of the support rollers rotatably mounted about the vertical axis.

A rapid change of the direction of travel is drove and the rotary differential drives subject to problems, since this either the standstill of the drive or a rotation of the drive unit (s) is required by 180 °. A steering movement of the wheels is due to the then acting static friction with an increased steering moraent or increased wear of the tires and the ground connected. As a result, direction changes are initiated in practice by a reversal or change in direction of rotation of the motors. The reversal of the direction of rotation is associated with further functional disadvantages. In the case of drives that can be reversed in principle, such as electric drives, the drive is decelerated to a standstill to reverse the direction of rotation.

The kinetic energy stored in the drive can thus not be used, or only to a small extent (for example, by energy recovery systems). The inertia of the rotating masses present in the drive system also leads to a reduction of the acceleration capacity for the entire vehicle. Drives, such as Internal combustion engines, which have a fixed direction of rotation, require additional technical effort in the form of a reversing gear for changing the direction of rotation or direction of travel.

The steering drives of industrial trucks are often designed as so-called steered wheel hub drives. These are characterized in that the drive with the wheel forms a pivotal unit. Thus, a flexible transfer of energy from the chassis to the drive motor is required, which is usually implemented in the conventional designs by means of cable chains or conductor lines.

Depending on the torque / speed characteristic of the drive motor used in conventional suspensions required for an acceleration of the vehicle Operating point to be produced by a reduction gear. Especially with flat running torque / speed characteristics that occur eg in internal combustion engines, only a good acceleration capacity or a good utilization of the possible final speed can be achieved by a fixed gear ratio.

In practice, in this case, manual transmissions, adjustable friction drives, hydrostatic adjusting gears or even hydrodynamic transducers are used, which mean a correspondingly high level of technical complexity. While the frictional and fluid-based converter systems adhere to power losses, the technical disadvantages of the manual transmissions are mainly the interruption of the power flow during the switching operations.

Drives that can develop no torque from a standstill, usually require switching or starting clutches that decouple the chassis with the vehicle stationary from the drive train or the engine.

The surface pressure of the wheels of conventional chassis of industrial trucks often causes damage to the floor and leads to the formation of lanes. These can in turn lead by dirt accumulation to reduce traction and to extend the braking distance. This negative effect is a known problem particularly in driverless transport vehicles with precisely defined driving courses.

In addition to avoiding the above disadvantages, the object of the invention is to increase the efficiency in the generic drive, to reduce the wear of the wheels to ensure the highest possible protection against contamination while maintaining low maintenance. With the drive according to the invention, this object is achieved according to the invention by a plurality of wheels positioned in wheel suspensions on a wheel carrier acted upon by a rotary drive, the wheel axles being adjustable via the respective wheel suspension by means of a control drive at an angle during one revolution of the wheel carrier.

Visible, the drive according to the invention also has a number of advantages. Thus, he avoids the above-mentioned additional effort in connection with the direction of travel change as well as an additional energy transfer to the wheels, since they do not have their own drive. Another advantage is u.a. also in that the drive according to the invention has the function of a continuously variable transmission and thus makes an additional speed and torque conversion superfluous. Since the drive according to the invention is also able to accelerate from standstill at full engine speed, eliminating the need for a starting clutch.

Normally, vehicles require mechanical holding brakes, which in themselves make it possible to hold onto inclines. Due to the self-suspension of the chassis according to the invention additional holding brakes are unnecessary.

From DE 91 05 811 Ul a universally horizontally movable platform is known.

In contrast to the present invention, the wheel carrier is not rotatably mounted or formed circumferentially. The wheels of the platform described therein are actively driven in contrast to the present invention. The wheel suspensions are not adjusted in such a way that the wheel axles run through a point, the adjustment is much more such that the wheel axles are parallel. Also, a stepless mechanical controllability is not possible.

The US 5,374,879 A also shows no rotating wheel carrier, whereby also there the wheels are not adjustable. Also, as in the above-mentioned utility model, there is no control drive. The wheel axles do not run through a common control point, so that even this reference gives no suggestion to the present invention.

Embodiments of the invention will become apparent from the dependent claims. It can be provided that each suspension is equipped perpendicular to its axis of rotation with a linear guide, the suspension of the opposite free end is hinged to a common adjusting pin for all suspensions, which can also be provided that the adjusting pin about two at right angles to each other Actuators in its relative position to the center of the rotational circle of the wheel carrier is adjustable.

At this point it should be noted that in addition to the linear guides according to the invention, other adjustment of the suspension are possible, for example by electronically controlled servomotors od. Like.

The invention also provides that the adjustment pin is positioned on a sliding sleeve, which in turn is guided on elements of the vehicle support frame.

The invention is not limited to single wheels per suspension. It also provides that, for example, multiple roller wheels are used or wheels that are designed as conical rollers. The invention relates not only to a traction drive as such, but also a suitably equipped vehicle that is equipped with at least one traction drive according to the invention, wherein also several traction drives can be provided.

Different suspension designs are also possible according to the invention.

The rotational movement of the suspension drive according to the invention causes a reaction torque, which must be compensated in a suitable manner. This results in possible suspension or arrangement variants.

The compensation of the reaction torque can be done for example by additional passive support or compensation roles. It arises regardless of the number of provided support rollers thus a line movable chassis with a so-called three-wheel kinematics. A kinematic condition for the construction of a functioning line kinematics is that the wheel axles of the compensation rollers do not face the center of rotation of the wheel circle. If the contact surface of the wheel circle can ensure a sufficient tilting stability of the vehicle, a chassis construction with only one compensating roller (inside or outside the wheel circle) is conceivable.

The support rollers thus have a dual function in the construction of the chassis. In addition to the compensation or support of the reaction torque, a wheel base or contact area is generated. Full surface mobility is achieved by combining two or more suspension drives. The reaction moments of both drives compensate each other in this chassis variant. There are both suspensions with small Radkreisdurchmessern as well as with large Radkreisdurchmessern conceivable. Small wheel circle diameters require additional support rollers, which ensure the required stability of the vehicle. In chassis drives with large wheel circle diameters, which can form a tilt-stable wheel base for a vehicle, only the support of the reaction torque (eg by rolling) is required.

In principle, the use in vehicles of all kinds is conceivable. A special suitability of the invention for vehicles for which an exact positioning accuracy and high mobility in the area is required. This is the case, for example, with automatic or manually operated industrial trucks. Due to the reduced surface load with a large number of wheels, there is a particular suitability for heavy-duty applications:

> Driverless transport vehicles (AGV)

> Manually operated industrial trucks (for example forklifts, towing vehicles etc.

> Heavy duty vehicles (eg container handling)

> Belt drive

> Conveyor element

> Stepless friction gear

Further areas of application result from a reversal of the principle, wherein the chassis is stationary and generates the relative movement of a surface. Such an application is, for example, the drive of a conveyor belt. By placing the drive at any point a continuously variable propulsion of the belt can be done. At a tap of the rotational movement of a roller creates a continuously variable friction gear. If the chassis drive is installed overhead (ie with rollers pointing upwards), a product with a flat base (containers, cartons, plate material etc.) can be conveyed or positioned in any direction and speed. There is thus the possibility in principle to realize conveyor lines, points and discharges for suitable piece goods.

Further details, features and advantages of the invention will become apparent from the following description and from the drawing. This shows in

1 is a simplified sectional view through a drive according to the invention,

Fig. 2 is a simplified plan view according to arrow II in Fig. 1 and in

3 is a bottom view approximately according to arrow III in Fig. 1st

The traction drive generally designated 1 in the figures comprises a wheel carrier 2 rotatably mounted on a chassis 3 only indicated by means of a drive motor 4, e.g. via a chain drive or similar, is set in rotation.

On the wheel carrier 2 three suspensions 6 are arranged in a circular shape in the illustrated example, the wheels 7 wear. To adjust the axles 8 of the wheels 7, the wheel 6 are each equipped with a pivot 9, the wheels 7 opposite end of a linear guide 10 is acted upon such that the wheel axle 8 is pivotable in the horizontal plane. For exerting an adjusting force on the wheel axles 8 via the linear guide 10 whose free ends are fastened to a common adjusting pin 11, which in turn passes through a sliding sleeve 12 which is movably guided on the chassis 3 and is movable in its horizontal position via two actuators 13, wherein the Movement eg via spindle drives 14 is triggered.

The controller is set up so that per revolution of the wheel carrier 12, driven by the drive motor 4, the axes 8 of the wheels 7 are adjusted so that, as desired, a certain direction of advance of the chassis 3 is generated.

Of course, the described embodiment of the invention is still to be modified in many ways, without departing from the spirit. Thus, a plurality of rotating wheel carriers can be positioned on the chassis 3 as well as additional support rollers, and the wheels can also rotate in a different curve than the circular shape. Of course, the invention is not limited to the illustrated type of adjustment of the wheel axles on the illustrated mechanism, here also other drives and adjustment can be provided.

Claims

Claims:

1. Drive, in particular for driverless floor vehicles, characterized by a plurality of wheel suspensions (6) positioned wheels (7) on one of a rotary drive (4,5) acted upon wheel carrier (2), wherein the wheel axles (8) via the respective suspension (6) by means of a control drive (13) in its angle during a revolution of the wheel carrier (2) are adjustable.

2. Drive according to claim 1, characterized in that each suspension (6) is equipped perpendicular to its axis of rotation with a linear guide (10), the suspension of the opposite free end to a common adjustment pin (11) for all suspension (6) is articulated ,

3. Drive according to claim 1 or 2, characterized in that the adjusting pin (11) via two mutually perpendicular to each other actuators (13,14) in its relative position to the center of the rotational circle of the wheel carrier (2) is adjustable.

4. Drive according to one of the preceding claims, characterized in that the adjusting pin (11) on a sliding sleeve (12) is positioned, which in turn is guided on elements of the vehicle supporting frame (3).

5. Drive according to one of the preceding claims, characterized in that each wheel (7) is formed as a Mehrfachrollenrad.

6. Drive according to one of the preceding claims, characterized in that each wheel (7) is designed as a conical roller.

7. land vehicle, characterized in that it is equipped with at least one traction drive (1) according to one of the preceding claims.

8. land vehicle according to claim 7, characterized in that it is equipped with support rollers in addition to the traction drives (1).

9. land vehicle according to claim 7 or 8, characterized in that it is provided with a square or rectangular arrangement of the wheels (7) which are provided with a common circumferential chain-like drive.