CA2380247A1

CA2380247A1 - Improvement of steering capability

Info

Publication number: CA2380247A1
Application number: CA002380247A
Authority: CA
Inventors: Otto Becker
Original assignee: Individual
Current assignee: Grove US LLC
Priority date: 1999-07-27
Filing date: 2000-06-28
Publication date: 2001-02-01
Also published as: CN1373717A; DE19935160A1; JP2003505290A; EP1200282A1; WO2001007279A1; KR20020019585A

Abstract

The invention relates to a device for improving the steerability of driven axles. A central transmission transfers driving torque to steered wheels via drive shafts. The central transmission is mounted in such a way that it can rotate around a vertical axis.

Description

Improvement of Steering Capability BACKGROUND OF T'HE INVENTION
1. Field of the Invention The present invention relates to a device for enhancing the steerability of driven axles in which a central gear mechanism transmits the drive moment via driveshafts to steered wheels. More particularly, the present invention may be employed in multi-axle vehicles comprising independently suspended and drives wheels on steered axles, like for instance mobile cranes.

2. Description of Priox Art In the case of such mobile cranes, the maximum wheel deflection, as eonvcntionally achievable at present on the driven axles of two and three axle vehicles, is roughly 38.5°, i.e. the universal joint shafts connecting the central gear mechaaisrn to the wheel drives would actually permit a maximum deflection angle of 42°, however, with singlo-wheel suspensions, the steering movenoeats are superimposed with the spring excursion movements of the shock absoxbeas so that a steering angle of only roughly 3?.5°C is achievable for maximum spring excursion with an angle of diffraetio~a of 4z°. To enhance the maneuverabdiry of such vehicles, once should, however, strive to achieve the highest possible steering angle, Known from DE 36 02 400 A1, is an arrangement of an axle shaft in a wheel suspension system. It is here suggested to shift the central gear mechanism horizontally from the center point of the axle-line to optimize the resuking steering eagle. Aithou$h by these measures, the maximal steering eagle can be increasexi to approximately 39°, this value is still in need of improvement.
A composite steering mechanism is known from EP 0 785 124 A1 in accordance with the preamble of parent claim 1, wherein overlapped steering is provided is which in addition to the steeritt<; deflection of the wheels also the entire steering gear arraagemerit can be positioned obliquely by rotation about a vertical axis..The steering shown here, however, is involving resativcly high Gffort and it is delicate due to the swinging ann.
and cannot increasB the arrangement freedom op the drive propehor shafts themselves.
SUMhL4R~'' OF THE nYY.IaNTION
It is thus the object of ~e present invention to provide a device by means of which the maneuverability of vehicles having driven axles is substantially improved, in particular that tbs steerabiliry be fly enhanced by obtaining very large steering angles.
This object is achieved in accordance with the invention in that the central gear mechanism of the respective driven axle is mounted rotatably around a vertical axis, Advantageously, with large steering angles, a rotation of the central gear ~chanism around this axis can improve the positional relacionshigs of the drive elements to one another such that very large resulting steering angles are arhicvable to, thus, m~oa~e than compensate for tbc losses m ~e maximum sttezing angle which occur due to spring excursion of the shock absorbers.
In other words, the central gear mecbanGsxn is enabled to take up a turned position allowing dz'ive elements such as, e.g., the univorsal joint shafts (secured by universal joints w the central gear mechanism and the wheel drive) to assume positions permitting an optimally increased steering a~qgle, (~ceatiag this additional degree of freedom in the rotating movement of the central gear mechanism thus permits a further optimization of the steering angle, even when conventional drive eompoaenc~ are employed, which may, for instance, attain 43°. Thus, the maneuverability of correspondingly equipped vehicles is substantially increased.
In accordance with the invention, the central gear mechanism is so connected to the steering that a can rotate contrary to wheel deflection in proportion to the axlo eteeting action i.e. it being pivotally dailected is this way, >;JJue to this pivotal deflection contrary to wheel deflection, the necessary freedom of arrangement of the drive-universal joist shafts is created to achieve the resulting high steering angle. In this artaagement, ii is conceivable within the scope of the invention to coanea the ceanral gear mechanism, to the steering for couplingldecoupIing thereto to permit controlled application of the steering mechanism in accordance with the invention, i.e. for example, deactivating the central gear xnerbanism in fast straight-ahe"dd travel and activating it open country or in sharp cozner situations.
In one embodiment of the device in accordance with the invention, the central gear mechanism is mounted under the frame on a rotary bear3ag fitted to the frame.
xn this ~r~~~~ ~ oral gear mechanism may be mounteti so that it is at least able to rotate by an angle of approximately 10° in both directions around the vertical axis.
In another embodiment of the device in accordance with the invention, the central gear mechanism is pivotally deflectable via a coupling rod, pivotally mounted on th,e steering azui of a wheel, and, via a deflection arzn, pivotally motmsed on the coupling rod. In particular, the ateeri~g arm connected to the coupling rod may be the steering arm of an axle to which the steering movement is transmitted via a tie rod from the steering arm of the opposite wheel.
In order to furthrer incxease the resulting steering angle, in accordance with the invention the possibility exists to fixedly arrange the central goat mechanism horizomally displaced from the center point of as axle-line, more particularly, displaced forwards in the longitudinal direction of the vehicle, so as to optimize tile steering az~le. rt is also possible to aaange the oeatt'aI gear mechanism displaced upwards or downwards fn optimize the pivoting eagle on wheel spring excursion. Using this addftional feature, steering angles of approximately 48 ° are then achievable, which is impossible with conventional axle arrangements.
Brief Description of the nrawings The invention will now be detailed by way of example embodiments with reference too the attached drawings in which;
Fig. 1: Is a view of a driven a~tIe incorporating as arrangement of the central gear mechanism in accordance wig the invention;
~$~ 2: is a view of an axle, as seen from above, in its original condition;

Fig. 3: is a view, as shown in Fig. 2, illustrating cornering at a wheel deflection of 38° with the central gear mechanism fixed;
Fig. 4: is a view of an axle, configured in accordance with the invention, as shown in Fig. 3, illustrating cornering with the central gear mechanism pivotally deflectc;d and maximum wheel deflection;
Fig. 5: is an illustration of one embodiment of the invention in which the central gear mechanism is fixedly displaced forwards, however, rotatably arranged, with the central gear mechanism pivotally detlected and maximum wheel deflection (wheel deflection 48°), and Fig. 6: is a detailed positional illustraoion of the steering and drive parts in the straight-ahead position and at maximum deflection as a direct comparison.
Detailed Description Referring now to Fig. l, illustrated is a view of a steered driven axle between the two wheels 4 of a vehicle, in this case, of a mobile crane. Fitted to the frame 18, are the two shock absorbers 7 to which the wheels are secured which are, thus, independently suspended and comprise wheel drives 3 with planetary gears. The wheels are steered via the parts of the shock absorbers 7 protruding downwards, i.e. via a steering mechanism, of which a steering arm 10 and a tie rod 14 are evident in Fig. 1. The functioning of the steering will be described in detail later with reference to Fig. 6.
The drive of both wheels 4 occurs via the universal joint shafrs 2, provided at both sides with universal joints. The drive moment is supplied from the central gear mechanism 1 which receives engine torque by conventional ways and means.
The central gear mechanism 1 is fixed to the frame 18 via the fastener 5 which comprises at its lower end the rotary connection 6. This rotary connection 6 thus rotatably couples the cenaal gear mechanism to the fastener 5 such that it permits pivotal deflecting around the vertical axis 20 in both directions of rotation.
This arrangement occurs by steering via a coupling rod 8 which is connected to the steering arm of the right wheel 4, and is, likewise, pivotally mounted at the deflection arm 9 which, in turn, is tixedly seated at its other end on the central gear mechanism 1.
By means of this construction, the central gear mechanism 1 may, in accordance with the present invention, be rotated around the axle 20 in response to a steering deflection by the deflection arm 9 to achieve uhe intended high steering deflections. More detailed information as to the steering kinematics employed is given in the later description relative to Fig. 6.
With reference to Figs. 2 to 5, the principle functioning of the device in accordance with the invention will now be described. Each of these drawings are views as seen from above an axle having two driven wheels, individually suspended. As simply illustrated in accordance with Figs. Z to S, the steering movzment is transmitted via a steering rod 13 to an arm of the steering arm 10 of the lower wheel 4 is, this being best evident from Figs. 3 to 5. Engaging the other arm of the steering arm 10 is the tie rod 14, which transmits the steering force to the steering arm of the upper wheel and slaves it in the steering action. It is generally to be understood as regards the illustrations as shown in Figs. 4 and 5 chat the central gear mechanism 1 is coupled to the steering.
This coupling is shown in detail for one embodiment of the invention in Fig. 6 to be explained later. In connection with Figs. 2 to 5, the basic principle of the invention will be comprehensibly explained without going into too much detail.
Fig. 2 shows the axle in a state in which it is not being influenced by any particular driving state and which could be termed the "original" state. If one describes the line connecting the two projected wheel steering axles as an axle-line, then, in this "original"
state, the vertical axis 20 of the central gear mechanism 1, indicated by broken lines in this view, is located on the axle-line, and the steering rod 13, the steering arm 10, the tie rod 14 and the universal joint shafts 2 are arranged so that the wheels 4 are not pivotally deflected when the central gear mechanism 1 is not deflected. 'this is the state of this axle in straight-ahead travel.
Fig. 3 illustrates an axle with a wheel deflected for a turn to the right.
This turn to the right, coo, is still negotiated without the maximum possible steering angle supported by turning of the central gear mechanism 1, it thus being evident chat for such a conventional "full deflection" a steering angle of merely 38° is achievable. The steering angle, in this case, being measured as the angle between the rotational axis of the pivoted wheel and the Iine connecting the two points around which the wheel is steered pivotally deflected.
These are always located on the respective longitudinal axis of the shock absorbers.
Feferring now to Figs. 4 and 5, it now becomes clear how the resulting steering angle can be increased in accordance with the invention by a rotary-mounted central gear mechanism 1, whereby Fig. 4 shows a state in which the vertical axis 20 of the cenual gear mechanism 1 is located on the line which, in this representation, connects the longitudinal axes of the shock absorbers 7, i.e. the wheel steering axes. Here too, the state shown is that of a full deflection in a turn to the right, but now a resulting steering angle of 45° is achieved. The reason for this is chat the central gear mechanism I, in accordance with the invention, is deflected in its rotary-mount, i.e. in a rotational direction contrary to the wheel deflection. Thus, when the wheels as shown in Fig. 4 are turned anti-clockwise, the central gear mechanism is turned clockwise around the vertical axis 20, this being approximately 10° in the present embodiment. Here, those universal joints of the universal joint shafts 2, which are directly secured to the central gear mechanism 1, are shifted in their longitudinal direction; the upper connecting point between the central gear mechanism 1 and the universal joint shaft 2 shifts further to the right (rear) in Fig. 4, while the lower connecting point between the universal joint shaft 2 and the central gear mechanism 1 moves slightly to the Left (fore). This shift in position, and the rotation of the universal joint shafts involved, create at each connecting point of the universal joint shafts to the wheel drive a certain free angle which may be exploited for further wheel detlection. Due to the rotation of the central gear mechanism 1, the universal joints at the wheel drives thus receive an additional range of movement for larger deflection angles of the wheels 4.
This is why the resulting higher steering angle of 45° is achievable.
The steering deflection may be further optimized in a construction such as that represented in Figure 5. In this axie, the central gear mechanism is fixed so that the vertical axis 20 is located just before the line connecting the projecting wheel steering axles 7, thereby a further shift of the kinematics is achieved resulting in the lower wheel 4 being pivotally deflected to a resulting steering angle of 48°. This also occurs by a deflection of the central gear mechanism 1 of merely 10°.
Referring to Fig. 6, it will now be explained in detail how a steering in accordance with the invention is achieved. Fig. b illustrates two states, namely the pivotally deflected state, as indicated by the bold lines, and the state for straight-ahead travel, as indicated by the broken lines, to clearly show how the components change positions.
Starting at the hydraulic power steering source 17, the force generated therein is transmitted via the steering rod 13 to the lower steering arm 10, i.e. to the left arm thereof.
Likewise, pivotally mounted on this left arm of the steering arm 10 is the steering cylinder 11, which is secured pivotally mounted on its other end to a fixed point in the vehicle.
Via the right arm of the steering arm 10, the steering action is transmitted by means of the tie rod 14 to the steering arm 10' of the other wheel, shown at the top, thus resulting in both wheels 4 being steered uni-directionally.
The steering arm 10' further comprises a pivotally mounted fastener for the coupling rod 12 which is steered, in turn, at its other end connecting the deflection arm 16. This deflection arm 16 is then fixedly connected at its ocher end to the central gear mechanism 1 so that turning of the steering arm 10', coupling rod 12 and the deflection arrn 16 during a steering action results a rotation of the rotary-mounted central gear mechanism 1, i.e. always in the direction opposite to that of the wheel deflection. In accordance with the invention, it is this turninb of the central .gear mechanism that achieves the increased, and optimized, wheel deflection angle in the manner already described with reference to Fig. 5. This increased deflection angle of the wheel brings about a corresponding improvement in maneuverability of the vehicle.

Claims

What is claimed is:

1, A device for enhancing the steerability of driven axles in which a central gear mechanism (1) transmits the drive moment via driveshafts (2) to steered wheels, wherein said central gear mechanism (1) is mounted rotatably around a vertical axis (20), characterized in that said central gear mechanism (1) is connected to a steering, more particularly being connected coupled to/decoupled from a steering, so that it is pivotally deflected contrary to the wheel deflection in proportion to said axle steering action.

2. The device as set forth in claim 1, characterized in that said central gear mechanism (1) is mounted under the frame (18) in a rotary bearing (6) fixedly attached to said frame (18).

3. The device as set forth in claims 1 or 2, characterized in that said central gear mechanism (1) is so mounted that it is at least able to rotate by an angle of approximately 10° in both directions around said vertical axis (20).

4. The device as set forth in any one of the claims 1 to 3, characterized in that said central gear mechanism (1) is pivotally deflectable via a coupling rod (12) pivotally mounted to the steering arm (10, 10') of a wheel (4) and via a deflection arm (16) which is pivotally mounted on said coupling rod (12).

5. The device as set forth in claim 4, characterized in that said steering arm (10') connected to said coupling rod (12), is the steering arm of an axle to which the steering movement is transmitted via a tie rod (14) from the steering arm (10) of the opposite wheel.

6. The device as set forth in any one of the claims 1 to 5, characterised in that said central gear mechanism (1) is fixedly arranged on the frame, horizontally or vertically displaced from the center point of an axle-line, more particularly displaced forwards in the longitudinal direction of the vehicle, to further optimize said steering angle.

7. The device as set forth in any one of the claims 1 to 6, characterized in that said central gear mechanism (1) is pivotally deflectable such that a steering angle of 45° of said wheels (4) is attained relative to the axle-line.

8. The device as set forth in claim 6, characterized in that said control gear mechanism (1) is pivotally deflectable such that, in an optimized arrangement of said central gear mechanism (1) as set forth in claim 6, a steering angle of 48° is achieved relative to the axle-line.