DE102023202216B3 - Electric steering axle for a work machine and work machine - Google Patents

Abstract

The invention relates to an electric steering axle (1) for a work machine. The steering axle (3) according to the invention is characterized in that the steering axle (1) has a first (2) and a second joint housing (3), at least one electric motor (6, 7) with a motor shaft (8) designed as a worm shaft (8). , a first (9) and a second worm wheel (10) and a first (13, 19) and a second spur gear pair (14, 20), wherein a first drive connection for producing a first steering angle of at least one electric motor (6, 7) via the worm shaft (8), the first worm wheel (9) and the first pair of spur gears (13, 19) to the first joint housing (2), with a second drive connection for producing a second steering angle from at least one electric motor (6, 7) via the Worm shaft (8), the second worm wheel (10) and the second pair of spur gears (14, 20) to the second joint housing (3), the first pair of spur gears (13, 19) due to tooth surfaces (17, 18) deviating from a circular path has a variable first point of engagement and/or wherein the second pair of spur gears (14, 20) has a variable second point of engagement due to tooth surfaces (21, 22) deviating from a circular path, so that an intersection of a wheel axis of rotation (4) of a first wheel with a wheel axis of rotation ( 5) a second wheel for each steering angle lies on a straight line which runs parallel to the steering axis (1) at a predetermined distance.

Description

The invention relates to an electric steering axle for a work machine according to the preamble of claim 1 and a corresponding work machine.

Different forms of steering axles for work machines, such as construction machines or tractors, are known in the prior art. As a rule, these steering axles support a driver's manual or mechanical steering input using a hydraulic system, which includes a hydraulic cylinder in addition to a hydraulic pump. The hydraulic pump generates the required hydraulic pressure and the hydraulic cylinder acts as an actuator that sets the desired steering angle in accordance with the driver's steering input.

From the DE 102 16 961 A1 In this context, a steering axle with a steering cylinder to support the steering of a motor vehicle is known.

The DE 10 2017 222 887 A1 relates to a steering device for a vehicle, comprising an actuator which is intended to apply an axial force to a push rod, the push rod being articulated on both sides with a respective tie rod. The respective tie rod is in turn connected in an articulated manner to a respective tie lever, the respective tie rod being used to rotate a respective wheel of a vehicle axle about a
respective steering axle is operatively connected to a respective wheel carrier in accordance with an axial movement of the push rod. The track levers each have a first and a second lever section, the two lever sections of the respective track lever being axially displaceable relative to one another in order to change a gear ratio of the steering device while the wheels are turning and to reduce the axial force on the actuator.

The DE 10 2022 211 817 B3 discloses a steering axle for an industrial truck, comprising an axle housing, a first steering knuckle, a second steering knuckle, a steering gear and a steering motor. The steering gear has a gear input and a first gear output and a second gear output, wherein the first steering knuckle is drivingly coupled to the first gear output and wherein the second steering knuckle is drivingly coupled to the second gear output. In this case, a pair of spur gears between the transmission input and the second transmission output have a variable engagement point due to a tooth surface that deviates from a circular path, so that an intersection of a first wheel axis of rotation with a second wheel axis of rotation lies on a straight line for each steering angle, which is parallel to the steering axis at a predeterminable distance runs.

However, the known steering axles for work machines are disadvantageous in that they cannot be actuated electrically due to the high steering forces or steering torques required, since electric motors cannot easily generate the forces required for this. Another disadvantage is the previously low durability and reliability of such electric steering axles, which are, however, absolutely necessary for trouble-free and safe continuous operation.

Furthermore, there is no effective option to steer one or any number of steering axles in such a way that all wheel rotation axes intersect at a common point or to eliminate the steering angle error between the different steering axles of a vehicle.

It is an object of the present invention to propose an electric steering axle for a work machine.

This object is achieved according to the invention by the electric steering axle for a work machine according to claim 1. Advantageous refinements and further developments of the invention emerge from the dependent claims.

The invention relates to an electric steering axle for a work machine. The steering axle according to the invention is characterized in that the steering axle comprises a first and a second joint housing, at least one electric motor with a motor shaft designed as a worm shaft, a first and a second worm wheel and a first and a second pair of spur gears, with a first drive connection for producing a first steering angle from at least one electric motor via the worm shaft, the first worm wheel and the first spur gear pair to the first joint housing, wherein a second drive connection spur gear pair for producing a second steering angle from at least one electric motor via the worm shaft, the second worm wheel and the second to the second joint housing exists , wherein the first pair of spur gears has a variable first engagement point due to tooth surfaces deviating from a circular path and / or wherein the second pair of spur gears has a variable second engagement point due to tooth surfaces deviating from a circular path, so that an intersection of a first wheel axis of rotation with a second wheel axis of rotation for each Steering angle lies on a straight line which runs parallel to the steering axis at a predetermined distance.

A steering axle is therefore provided, i.e. an axle with two steerable steering knuckles or joint housings or wheels, which can be pivoted relative to an axle body of the steering axle to set a predeterminable steering angle. The steering axle is also suitable for use in a work machine such as a wheel loader or a tractor due to its load capacity, size and robustness.

In addition to the first and second steering housings, the steering axle also includes at least one electric motor, the motor shaft of which is designed as a worm shaft, and two worm wheels, each of which meshes with the motor shaft. A rotational movement of the at least one electric motor can thus be transmitted to the worm wheels via the worm shaft. Advantageously, the speed is reduced and the torque is increased accordingly, so that the steering movement - in contrast to the steering axles of work machines known in the prior art - can be provided via an electric motor with a comparatively low output torque, instead of requiring hydraulic actuation or a comparatively requiring expensive spur gears to reduce the electric motor. By using the worm drive, the at least one electric motor can be operated with comparatively low torques - and thus at comparatively low operating currents - so that the load on the at least one electric motor and thus its wear are reduced. This improves the durability and reliability of the steering axle.

The motor shaft preferably extends from both axial ends of the electric motor, so that the first worm wheel can be driven via a first side of the motor shaft and the second worm wheel can be driven via a second side of the motor shaft. The two worm wheels are therefore advantageously located on opposite sides of the electric motor.

The first worm gear now drives the first pair of spur gears directly or indirectly, and the second worm gear also drives the second pair of spur gears directly or indirectly. Accordingly, the first pair of spur gears is also arranged on a first side of the electric motor and the second pair of spur gears is arranged on a second side of the electric motor.

At least one of the two pairs of spur gears mentioned is designed according to the invention in such a way that it has toothing surfaces that deviate from a circular path, so that an engagement point of the wheels of the spur gear pair that changes depending on the angle of rotation results.

This means that the rotational movement of an output gear of the respective spur gear pair is not in a fixed relationship to the rotational movement of an input gear of the spur gear pair, but rather depends on a current point of contact and the radius of curvature of the output gear and the input gear at the point of contact, i.e. at the point of engagement. The larger the radius of curvature of the output gear at the engagement point compared to the radius of curvature of the input gear at the engagement point, the less or the slower the output gear rotates relative to the input gear and vice versa.

The toothing surfaces of the spur gear pair, which deviate from the circular shape, are designed according to the invention in such a way that the first wheel rotation axis and the second wheel rotation axis - and thus the first and second joint housings or the first and second vehicle wheels of the steering axle - are aligned with each other in the so-called Ackermann angle at each adjustable steering angle , i.e. that an intersection of the first wheel rotation axis with the second wheel rotation axis lies on a straight line for each steering angle, which runs parallel to the steering axis at a predetermined distance.

The first wheel axis of rotation runs through the first joint housing and the second wheel axis of rotation runs through the second joint housing.

It is preferably provided that the at least one electric motor, the worm shaft, the first and a second worm wheel and the first and second pair of spur gears are housed in a housing which is connected to the axle body. Particularly preferably, it can also be a first housing which houses the elements mentioned on a first axle bridge of the steering axle and is connected to the first axle bridge, as well as a second housing which houses the elements mentioned on a second axle bridge of the steering axle and with connected to the second axle bridge.

The housing or the first and second housings can each have at least one cylindrical region for receiving and guiding a contacting seal, which are in contact with a cylindrical region between the first and second pair of spur gears and the first and second joint housing.

Unless the steering axle only includes a first pair of spur gears that have a circular path has different toothing surfaces, but also the second pair of spur gears encompassed by the steering axis has toothing surfaces that deviate from a circular path, then at least the input wheels or the output wheels of the first and second pair of spur gears are advantageously designed identically.

In a particularly cost-effective embodiment of the invention, only a single wheel is equipped with tooth surfaces that deviate from a circular path, but this wheel is used for both pairs of spur gears both as an input wheel and as an output wheel, so that a total of four identical wheels are used.

The first and second input gears and the first and second output gears are preferably manufactured by sintering. This represents a cost-effective form of production.

According to a preferred embodiment of the invention, it is provided that the steering axle further has a first and a second spur gear or a first and a second bevel gear, the first worm gear being non-rotatably connected to the first spur gear or the first bevel gear, the second worm gear being non-rotatably connected is connected to the second spur gear or the second bevel gear, wherein the first spur gear or the first bevel gear is in drive connection with the first pair of spur gears and wherein the second spur gear or the second bevel gear is in drive connection with the second pair of spur gears.

The first and second spur gears are not part of the first and second pair of spur gears but are provided in addition to the first and second pair of spur gears.

As an alternative to the first and second spur gears, a first and a second bevel gear can also be provided.

Because the first worm wheel is connected in a rotationally fixed manner to the first bevel gear or the first spur gear, a rotational movement of the worm shaft can be transmitted from the first worm wheel to the first bevel gear or to the first spur gear. In an analogous manner, a rotational movement of the worm shaft can also be transmitted from the second worm gear to the second bevel gear or to the second spur gear.

The first spur gear or the first bevel gear and the first worm gear preferably have a common axis of rotation. Just as preferably, the second spur gear or the second bevel gear and the second worm gear also have a common axis of rotation.

According to a further preferred embodiment of the invention, it is provided that the steering axle has a first electric motor with a first motor shaft designed as a first worm shaft and a second electric motor with a second motor shaft designed as a second worm shaft, the first electric motor being in driving connection with the first worm wheel stands and the second electric motor is in driving connection with the second worm wheel. The use of two electric motors, namely the first electric motor and the second electric motor, leads to redundancy and thus increased reliability compared to the use of only one electric motor.

It is preferably provided that the first electric motor and the second electric motor have a common motor shaft, which is designed as a worm shaft. This means that the ability to adjust steering movements on both wheels is fully retained even if an electric motor is no longer functional.

According to a further preferred embodiment of the invention, it is provided that a first helix angle of the first bevel gear corresponds to a first camber of the first joint housing and that a second helix angle of the second bevel gear corresponds to a second camber of the second joint housing. By using a first and a second bevel gear, which mesh with the first and second pair of spur gears, an inclination of the first and second pair of spur gears can be achieved in a simple manner, with the inclination of the first and second pair of spur gears corresponding to the first and second Helix angle corresponds. This makes it possible for the first joint housing or the second joint housing to be driven directly by the output gear of the first pair of spur gears or the second pair of spur gears when the camber of the first joint housing or the second joint housing corresponds to the helix angle of the first bevel gear or the second bevel gear .

The first helix angle and the second helix angle are preferably identical.

According to a further preferred embodiment of the invention, it is provided that an output gear of the first pair of spur gears is connected in a rotationally fixed manner to the first joint housing and that an output gear of the second pair of spur gears is connected in a rotationally fixed manner with the second joint housing. This allows a rotary movement of the output gear of the first pair of spur gears or a rotary movement of the output gear of the second pair of spur gears can be converted directly into a steering movement of the first or second joint housing.

Advantageously, the output gear of the first spur gear pair and the first joint housing have a common axis of rotation and the output gear of the second spur gear pair and the second joint housing also have a common axis of rotation.

According to a further preferred embodiment of the invention, it is provided that the toothing surfaces of the first pair of spur gears that deviate from a circular path and/or the toothing surfaces of the second pair of spur gears that deviate from a circular path are conical. Thus, any backlash of the gears of the spur gear pairs can be advantageously adjusted by axial spacing if the gearing was manufactured with relatively low precision.

According to a further preferred embodiment of the invention, it is provided that the at least one electric motor is arranged in the region of an axial center of the steering axle. This results in the advantage that the worm shaft bridges an equal distance in both axial directions from the at least one electric motor to the first or second worm wheel. This results in an even load on the worm shaft and an even power transmission to both worm wheels.

The term “in the area of an axial center” is preferably understood to mean an axial length range in the axial center between the two axial ends of the steering axle, which makes up a maximum of 20% of the axial length of the steering axle.

According to a further preferred embodiment of the invention, it is provided that the steering axle is designed to be self-locking. A force acting on the steering axle via one of the wheels cannot therefore move the steering and in particular cannot adjust the steering angle.

The self-locking effect is preferably achieved by appropriately designing the first worm wheel and the first worm wheel shaft or the second worm wheel and the second worm wheel shaft.

According to a further preferred embodiment of the invention, it is provided that the steering axle is a drivable axle. The axle can therefore also be used to drive the work machine.

The steering axle is preferably electrically drivable, i.e. it has one or more electric motors which provide a driving force for driving the wheels of the steering axle.

Alternatively, the steering axle can also be driven via an electric motor arranged outside the steering axle in the work machine.

The invention further relates to a work machine comprising at least one steering axle according to the invention. This results in the advantages already described in connection with the steering axle according to the invention also for the work machine according to the invention.

According to a preferred embodiment of the invention, it is provided that the work machine has an electric drive train. This means that the machine is driven exclusively by electric motors and does not have an internal combustion engine. When using the steering axle according to the invention, there is a synergistic effect that the electrical infrastructure that is already present in the work machine due to the electric drive train can be used, for example an electrical energy storage and an electrical on-board network can be used directly to operate the steering axle. The electric steering axle, in turn, has a comparatively greater efficiency than a hydraulically actuated steering axle.

The invention is explained below by way of example using the embodiments shown in the figures.

• 1 beispielhaft und schematisch eine mögliche Ausbildungsform einer erfindungsgemäßen elektrische Lenkachse für eine Arbeitsmaschine.

It shows:

• 1 By way of example and schematically, a possible embodiment of an electric steering axle according to the invention for a work machine.

The same objects, functional units and comparable components are designated with the same reference numerals across the figures. These objects, functional units and comparable components are identical in terms of their technical features, unless the description explicitly or implicitly states otherwise.

1 shows by way of example and schematically a possible embodiment of an electric steering axle 1 according to the invention for a work machine (not shown in 1 ) in a side view ( 1a) and a top view ( 1b) .

According to the example, the work machine is a purely electrically driven work machine, namely an electrically driven wheel loader.

The steering axle 1 comprises a first joint housing 2 and a second joint housing 3, a first electric motor 6 and a second electric motor 7 with a common motor shaft 8 designed as a worm shaft 8, a first worm wheel 9 and a second worm wheel 10, a first bevel gear 11 and a second bevel gear 12 and a first pair of spur gears 13, 19 and a second pair of spur gears 14, 20.

As can be seen, the first electric motor 6 and the second electric motor 7 are arranged in the area of an axial center of the steering axle 1.

According to the example, the steering axle 1 also has a first bevel gear 11 and a second bevel gear 12. The first bevel gear 11 is connected in a rotationally fixed manner to the first worm gear 9, so that the first bevel gear 11 and the first worm gear 9 have a common axis of rotation 23. Likewise, the second bevel gear 11 is connected in a rotationally fixed manner to the second worm gear 10, so that the second bevel gear 11 and the second worm gear 10 also have a common axis of rotation 24. The first bevel gear 11 drives the first pair of spur gears 13, 19 and the second bevel gear 12 drives the second pair of spur gears 14, 20.

A first drive connection for setting a first steering angle exists from the first electric motor 6 via the worm shaft 8, the first worm wheel 9, the first bevel gear 11 and the first spur gear pair 13, 19 to the first joint housing 2.

In an analogous manner, there is a second drive connection for setting a second steering angle from the second electric motor 7 via the worm shaft 8, the second worm wheel 10, the second bevel gear 12 and the second spur gear pair 14, 20 to the second joint housing 3.

The first spur gear pair 13, 19 consists of a first input gear 13 and a first output gear 19, which have tooth surfaces 17, 18 that partially deviate from a circular path and therefore also have a variable first engagement point. In addition, the first input gear 13 and the first output gear 19 also have a circular toothing area 15, 25.

The second pair of spur gears 14, 20 consists of a second input gear 14 and a second output gear 20, which also have toothing surfaces 21, 22 that partially deviate from a circular path and therefore also have a variable first engagement point. In addition, the second input gear 14 and the second output gear 20 also have a circular toothing area 16, 26.

A first helix angle of the first bevel gear 11 leads to an inclination of the first pair of spur gears 13, 19 driven by the first bevel gear 11. The inclination of the first pair of spur gears 13, 19 is identical to the first helix angle. Since the first output wheel 19, for example, is connected in a rotationally fixed manner to the first joint housing 2 and both have a common axis of rotation 4, namely the first wheel axis of rotation 4, the inclination of the first pair of spur gears 13, 19 also corresponds to the camber of the first joint housing 2.

In an identical manner, a second helix angle of the second bevel gear 12 leads to an inclination of the second pair of spur gears 14, 20 driven by the second bevel gear 12. The inclination of the second pair of spur gears 14, 20 is identical to the second helix angle. Since the second output wheel 20, for example, is connected in a rotationally fixed manner to the second joint housing and both have a common axis of rotation 5, namely the second wheel axis of rotation 5, the inclination of the second pair of spur gears 14, 20 also corresponds to the camber of the second joint housing 3.

The design of the toothing surfaces 17, 18 of the first pair of spur gears 13, 19 that deviate from the circular path and the design of the toothing surfaces 21, 22 of the second pair of spur gears 14, 20 that deviate from the circular path are such that an intersection of a first wheel rotation axis with a second wheel rotation axis for Each steering angle lies on a straight line which runs parallel to the steering axis 1 at a predetermined distance. The so-called Ackermann angle can thus be set by the steering axle 1 at any time and for any steering angle.

Reference symbols

1

Steering axle

2

first joint housing

3

second joint housing

4

first wheel rotation axis, rotation axis

5

second wheel rotation axis, rotation axis

6

first electric motor

7

second electric motor

8th

Motor shaft, worm shaft

9

first worm wheel

10

second worm wheel

11

first bevel gear

12

second bevel gear

13

first input gear of the first pair of spur gears

14

first input gear of the second pair of spur gears

15

circular toothing area of the first input wheel

16

circular toothing area of the second input gear

17

Tooth surfaces of the first output gear deviating from a circular path

18

Gear surfaces of the first input wheel that deviate from a circular path

19

first output wheel

20

second output wheel

21

Gear surfaces of the second output gear that deviate from a circular path

22

Gear surfaces of the second input wheel that deviate from a circular path

23

common axis of rotation

24

common axis of rotation

25

circular toothing area of the first output gear

26

circular toothing area of the second output gear

Claims (11)

Electric steering axle (1) for a work machine, characterized in that the steering axle (1) has a first (2) and a second joint housing (3), at least one electric motor (6, 7) with a motor shaft (8) designed as a worm shaft (8). ), a first (9) and a second worm wheel (10) and a first (13, 19) and a second pair of spur gears (14, 20), wherein a first drive connection for producing a first steering angle from at least one electric motor (6, 7 ) via the worm shaft (8), the first worm wheel (9) and the first pair of spur gears (13, 19) to the first joint housing (2), with a second drive connection for producing a second steering angle from at least one electric motor (6, 7). the worm shaft (8), the second worm wheel (10) and the second pair of spur gears (14, 20) to the second joint housing (3), the first pair of spur gears (13, 19) due to tooth surfaces (17, 18) deviating from a circular path. has a variable first engagement point and/or wherein the second spur gear pair (14, 20) has a variable second engagement point due to tooth surfaces (21, 22) deviating from a circular path, so that an intersection of the wheel rotation axis (4) of a first wheel with a wheel rotation axis (5) of a second wheel for each steering angle lies on a straight line which runs parallel to the steering axis (1) at a predetermined distance. Steering axle (1). Claim 1 , characterized in that the steering axle (1) further has a first and a second spur gear or a first (11) and a second bevel gear (12), the first worm gear (9) being connected in a rotationally fixed manner to the first spur gear or the first bevel gear (11), wherein the second worm gear (10) is connected in a rotationally fixed manner to the second spur gear or the second bevel gear (12), wherein the first spur gear or the first bevel gear (11) is in driving connection with the first spur gear pair (13, 19) and wherein the second spur gear or the second bevel gear (12) is in driving connection with the second pair of spur gears (14, 20). Steering axle (1) according to at least one of the Claims 1 and 2 , characterized in that the steering axle (1) has a first electric motor (6) with a first motor shaft (8) designed as a first worm shaft (8) and a second electric motor (7) with a second motor shaft (8) designed as a second worm shaft (8). 8), wherein the first electric motor (6) is in drive connection with the first worm wheel (9) and wherein the second electric motor (7) is in drive connection with the second worm wheel (10). Steering axle (1) according to at least one of the Claims 1 until 3 , characterized in that a first helix angle of the first bevel gear (11) corresponds to a first camber of the first joint housing (2) and that a second helix angle of the second bevel gear (10) corresponds to a second camber of the second joint housing (3). Steering axle (1) according to at least one of the Claims 1 until 4 , characterized , that an output gear (19) of the first pair of spur gears (13, 19) is connected in a rotationally fixed manner to the first joint housing (2) and that an output gear (20) of the second pair of spur gears (14, 20) is connected in a rotationally fixed manner with the second joint housing (3). Steering axle (1) according to at least one of the Claims 1 until 5 , characterized in that the toothing surfaces (17, 18) of the first pair of spur gears (13, 19) that deviate from a circular path and/or the toothing surfaces (21, 22) of the second pair of spur gears (14, 20) that deviate from a circular path are conical. Steering axle (1) according to at least one of the Claims 1 until 6 , characterized in that the at least one electric motor (6, 7) is arranged in the area of an axial center of the steering axle (1). Steering axle (1) according to at least one of the Claims 1 until 7 , characterized in that the steering axle (1) is designed to be self-locking. Steering axle (1) according to at least one of the Claims 1 until 8th , characterized in that the steering axle (1) is a drivable axle. Work machine, comprising at least one steering axle (1) according to at least one of Claims 1 until 9 . working machine Claim 10 , characterized in that the work machine has an electric drive train.

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