Patent Publication Number: US-2023159083-A1

Title: Steering axle for a steerable vehicle, and industrial truck

Description:
RELATED APPLICATIONS 
     This application claims the benefit of and right of priority under 35 U.S.C. § 119 to German Patent Application no. 10 2021 213 068.2, filed on 22 Nov. 2021, the contents of which are incorporated herein by reference in its entirety. 
     FIELD OF THE DISCLOSURE 
     The invention relates to a steering axle for a steerable vehicle and to a corresponding industrial truck. 
     BACKGROUND 
     Various embodiments of power-assisted steering units, which either support a manual steering command of a driver or, as a response to an electric signal, adjust in a self-acting manner a desired steering angle, are known in the prior art. A hydraulic cylinder or an electric motor typically serve as an actuator therein. These steering units, besides the actuator, typically comprise a steering gear in a concentric construction mode and have a shaft as the drive output. The steering units are constructed in the manner of columns, having a pedestal in the lower region, said pedestal serving for fastening to a chassis of the vehicle. The upper region of the steering unit is able to be rotated in relation to the lower region so as to adjust a steering angle at the steerable wheels. 
     In this context, a power-assisted steering unit for vehicles, which comprises a steering column having a pedestal as well as an electrically assisted steering apparatus having a housing and an electric motor, is known from DE 10 2019 116 644 A1, the housing in relation to the pedestal being movable in terms of one degree of freedom. The steering column in turn furthermore comprises a lower axle which is rotatably connected to the pedestal and in part is contained in the latter. The electric motor is configured such that said electric motor by way of an output shaft can set the lower axle in rotation. 
     SUMMARY 
     The known power-assisted steering units however are disadvantageous in that said power-assisted steering units, by virtue of the construction mode in the manner of a column, require a large amount of space and are subject to unfavorable mechanical loads, the latter in turn potentially leading to increased wear and a failure of the power-assisted steering units. 
     It is an object of the present invention to propose an improved drive for a steering axle of an industrial truck. 
     This object is achieved according to the invention by the steering axle for a steerable vehicle, as disclosed herein. Advantageous design embodiments and refinements of the invention are derived from the present disclosure. 
     The invention relates to a steering axle for a steerable vehicle, comprising an axle housing and a steering drive having an electric motor and a motor shaft, having a first planetary stage comprising a first sun gear, first planet gears and a first planet carrier, having a last planetary stage comprising a last sun gear, last planet gears and a last planet carrier, and having a ring gear, the steering drive being configured such that a force flux from the motor shaft runs by way of the first sun gear and the first planet gears to the first planet carrier, and that the force flux furthermore runs by way of the last sun gear to the last planet gears. The steering axle according to the invention is distinguished in that the force flux furthermore runs from the last planet gears to the ring gear, the ring gear in relation to the axle housing being mounted so as to be rotatable about a pivot axis, and the last planet carrier being connected in a rotationally fixed manner to the axle housing. 
     A steering axle, that is to say an axle having two steerable wheels, which is suitable for use in a vehicle is thus provided. The vehicle is preferably a commercial vehicle such as an agricultural machine, a work machine, or an industrial truck. 
     The steering axle comprises an axle housing on which all further components of the steering axle are disposed. The axle housing thus represents a kind of basic frame of the steering axle. 
     The steering axle furthermore comprises a steering drive, the steering drive in turn comprising an electric motor having a motor shaft. This is preferably a three-phase brushless electric motor. 
     The steering drive moreover comprises a first and a last planetary stage having a first or last sun gear, first or last planet gears, a first or last planet carrier, respectively, and a ring gear. 
     The electric motor and the planetary stages are disposed in such a manner that force flux from the electric motor runs by way of the motor shaft to the first sun gear. The motor shaft and the first sun gear here are preferably connected in a rotationally fixed manner to one another, for example by way of a spline connection or by way of a welded connection. The motor shaft and the first sun gear are particularly preferably integrally configured. 
     The force flux from the first sun gear runs further to the first planet gears, at least two first planet gears being provided. The first planet gears mesh with the first sun gear. The first planet gears are rotatably held by the first planet carrier such that the force flux runs further to the first planet carrier. 
     In turn, the first planet carrier is, at least indirectly, connected to the last sun gear, and the force flux accordingly runs from the first planet carrier to the last sun gear, optionally by way of a number of intermediate elements. 
     The first planet carrier and the last sun gear are preferably connected in a rotationally fixed manner to one another, in particular even integrally configured. 
     Alternatively, it is preferably provided that the steering drive furthermore comprises at least one intermediary planetary stage which in turn comprises an intermediary sun gear, intermediary planet gears, and an intermediary planet carrier, the force flux from the first planet carrier running by way of the intermediary sun gear and the intermediary planet gears to the intermediary planet carrier, the force flux furthermore running from the intermediary planet carrier to the last sun gear. The force flux in the at least one intermediary planetary stage thus runs in a manner analogous to that of the force flux in the first planetary stage. 
     The at least one intermediary planetary stage here is operatively disposed between the first planetary stage and the last planetary stage, meaning that the force flux from the first planet carrier is guided into a first intermediary planetary stage and optionally a second, third, etc., planetary stage. 
     To the extent that at least one intermediary planetary stage is provided, the first planet carrier is preferably connected in a rotationally fixed manner to the intermediary sun gear, and the force flux accordingly runs from the first planet carrier to the intermediary sun gear. 
     The first planet carrier and the intermediary sun gear are preferably also integrally configured. 
     In the case of a plurality of intermediary planetary stages being provided, it is advantageous for the planet carrier of the preceding intermediary planetary stage to be in each case connected in a rotationally fixed manner to the sun gear of the subsequent intermediary planetary stage, in particular to be integrally configured therewith. 
     The force flux from the last planet carrier of the single or last intermediary planetary stage, respectively, runs further into the last sun gear of the last planetary stage. In this case too, the connection between the intermediary planet carrier and the last sun gear is configured in a rotationally fixed manner and in particular so as to be integral. 
     According to the invention it is now provided that the force flux furthermore runs from the last planet gears to the ring gear. The ring gear in relation to the axle housing is mounted so as to be rotatable about a pivot axis, the pivot axis being coaxial with the first, with the last, and optionally with all, intermediary planetary stages. The last planet carrier is finally connected in a rotationally fixed manner to the axle housing. 
     A rotation of the motor shaft thus results in a rotating movement of the ring gear, whereas the last planet carrier is fixedly established on the axle housing. 
     This results in the advantage that the steering drive has a construction mode which is very short in comparison to that of the prior art, and the steering axle is accordingly configured in a comparatively space-saving manner. 
     The steering axle moreover preferably also comprises two steerable wheels. 
     According to one preferred embodiment of the invention it is provided that the ring gear is rotatably mounted on a housing of the steering drive. For example, the ring gear can radially encompass the housing and be rotatably mounted on the housing. Likewise, the ring gear per se can also be part of the housing of the steering drive and mounted so as to be rotatable in relation to the remaining part of the housing of the steering drive. 
     According to one further preferred embodiment of the invention it is provided that the ring gear is composed of a multiplicity of individual ring gears which are concentrically disposed. In particular, the ring gear is composed of two individual ring gears, of which a first individual ring gear meshes with the last planet gears. A second individual ring gear can mesh with the last planet gears, for example. This results in the advantage of the steering drive being easier to assemble on the steering housing. 
     According to one further preferred embodiment of the invention it is provided that the ring gear on an external side has at least one steering arm. In this way, a rotating movement of the ring gear can be readily converted into a steering movement of the steerable wheels of the steering axle. For example, the steering arm can activate a steering linkage of the steering axle. 
     According to one further preferred embodiment of the invention it is provided that the ring gear has a hub carrier for a steerable wheel of the steering axle. In this case, the axle of the ring gear is at the same time the steering axis of rotation of the axle-pivot steering system. One of the steerable wheels is thus disposed directly on the ring gear. Wheel forces are transmitted directly into the axle housing by way of the mountings of the ring gear. 
     According to one further preferred embodiment of the invention it is provided that the electric motor is disposed so as to be coaxial with the pivot axis. In this case, the motor shaft can advantageously be configured so as to be integral to the first sun gear. Moreover, this results in the steering drive being comparatively easy to assemble. 
     According to one alternatively preferred embodiment of the invention it is provided that the electric motor is disposed so as to be parallel to the pivot axis. As a result, the construction height of the steering drive is reduced, this offering advantages in terms of the usability and potential applications of the steering axle according to the invention. An advantage is derived here in particular in comparatively compact vehicles such as, for example, industrial trucks. 
     According to one particularly preferred embodiment of the invention it is provided that the motor shaft and the first sun gear are operatively connected by way of a belt drive, a chain drive or a spur wheel mechanism. Besides offering a reliable transmission of the force flux, this at the same time also enables the rotating speed to be reduced prior to the force flux reaching the first planetary stage. Apart from the shortened construction mode, in certain circumstances this results in the further advantage that an intermediary planetary stage can be dispensed with. 
     The invention furthermore relates to an industrial truck comprising a steering axle according to the invention. As a result, the advantages which have already been mentioned in the context of the steering axle according to the invention are also derived for the industrial truck according to the invention. 
     The invention will be explained in an exemplary manner hereunder by means of embodiments illustrated in the FIGURES. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       In the FIGURES: 
         FIG.  1    shows in an exemplary and schematic manner a potential embodiment of a steering axle according to the invention for a steerable vehicle. 
     
    
    
     Identical items, functional units and equivalent components are provided with the same reference signs in all the figures. These items, functional units and equivalent components in terms of the technical features are of identical embodiment, unless otherwise derived explicitly or implicitly from the description. 
     DETAILED DESCRIPTION 
       FIG.  1    shows in an exemplary and schematic manner a potential embodiment of a steering axle  1  according to the invention (illustrated only in fragments) for a steerable vehicle, for example for an industrial truck. The steering axle  1  comprises an axle housing  18  and a steering drive  24 . The steering drive  24  in turn comprises an electric motor  2  having a motor shaft  3 . According to the example, the steering drive  19  furthermore comprises a first planetary stage  20  having a first sun gear  4 , first planet gears  5  and a first planet carrier  6 . The first planet carrier  6  is connected in a rotationally fixed manner to the intermediary sun gear  7 , which meshes with the intermediary planet gears  8 , the latter in turn driving the intermediary planet carrier  17 . The intermediary planet carrier  17  is connected in a rotationally fixed manner to the last sun gear  9 , the latter in turn meshing with the last planet gears  10  and driving the latter. The last planet gears  10  are held by the last planet carrier  16 . However, the last planet carrier  16  is connected in a rotationally fixed manner to the axle housing  18  and is thus prevented from performing a rotating movement. However, the last planet gears  10  also mesh with the ring gear  11  which is composed of three concentrically disposed individual ring gears  11 ′,  11 ″,  11 ′″, for example. The ring gear  11  is mounted so as to be rotatable about an axis  19 . The steering drive  24  of  FIG.  1    is thus configured such that a force flux from the motor shaft  3  runs by way of the first sun gear  4  and the first planet gears  5  to the first planet carrier  6 , and that the force flux furthermore runs by way of the intermediary sun gear  7  to the intermediary planet gears  8  and from the latter to the intermediary planet carrier  17 . The force flux from the intermediary planet carrier  17  furthermore runs to the last sun gear  9 , onward to the last planet gears  10 , and finally to the ring gear  11 . As can be seen, the motor shaft  3  is mounted by way of the mounting  23 , and the ring gear is mounted by way of the mounting  13 , in an upper housing part  14  of the housing  25  of the steering drive  24 . Moreover, the ring gear  11  by way of the mounting  15  is mounted on the last planet carrier  16 . A steering arm  12  enables a steering link, not illustrated in  FIG.  1   , to be actuated by way of a rotating movement of the ring gear  11 . Likewise, the steering arm  12  can be configured as a hub carrier having at least one cylindrical region for receiving a hub mounting. In this way, a steerable wheel of the steering axle  1  can be articulated directly by way of the ring gear  11 . The pivot axis  19  of the ring gear  11  in this case is at the same time the steering axis of the axle-pivot steering system. In this instance, wheel forces can be transmitted to the axle housing  18  by way of the mountings  13  and  14 . 
     LIST OF REFERENCE SIGNS 
     
         
           1  Steering axle 
           2  Electric motor 
           3  Motor shaft 
           4  First sun gear 
           5  First planet gears 
           6  First planet carrier 
           7  Intermediary sun gear 
           8  Intermediary planet gears 
           9  Last sun gear 
           10  Last planet gears 
           11  Ring gear 
           11 ′,  11 ″,  11 ′″ Individual ring gear 
           12  Steering arm 
           13  Mounting 
           14  Upper housing part 
           15  Mounting 
           16  Last planet carrier 
           17  Intermediary planet carrier 
           18  Axle housing 
           19  Pivot axis of the ring gear 
           20  First planetary stage 
           21  Intermediary planetary stage 
           22  Last planetary stage 
           23  Mounting 
           24  Steering drive 
           25  Housing of the steering drive