DE3840783C1 - Parking and manoeuvring aid for motor vehicles - Google Patents

Abstract

The subject matter of the invention is a parking and manoeuvring aid for motor vehicles with at least two steerable drive wheels. When necessary, in particular when manoeuvring into or out of a parking space, it permits a special manoeuvring operation for particularly flexible and manoeuvrable movement of the vehicle in an extremely small space, and also lateral parallel displacement movements, rotational movements on the spot or at least swinging movements of the front of the vehicle. The invention achieves this object without special manoeuvring devices on the drive gear with wheels with normal tyres and in a normal arrangement, namely essentially by means of drive switch-over devices, for example in the central differential (in the case of all-wheel-driven four-wheel vehicles) or in the axle differentials, specifically front wheels and rear wheels or right-hand and left-hand wheels are driven with opposite directions of rotation for the special manoeuvring operations. As a result, preferably the traction force components in the direction of the longitudinal axis of the motor vehicle are cancelled out and the traction force components which act transversely thereto are added or form vertical axis torques and thus permit the abovementioned vehicle movements. For this purpose, for example, steering locks for right-hand and left-hand wheels in opposite directions are produced, preferably by means of servo-motor-powered tract rod longitudinal adjustment, so that the tyres roll tangentially on a turning circle without grinding.

Description

The present invention relates to a parking and maneuvering aid which is intended to enable a special maneuvering operation for motor vehicles for particularly flexible and agile maneuvering in a confined space, essentially by switching (s) in the mechanical engine (gearbox) system of the correspondingly equipped Motor vehicle This should include lateral parallel displacement movements of the motor vehicle (exemplary embodiments: FIGS. 1, 2, 7 and 8), rotational movements of the motor vehicle on the spot with the smallest possible turning circle diameter ( FIGS. 3, 5 and 6) or at least pivoting movements of the motor vehicle bow with strong reduced turning circle ( Fig. 4 and 9) are made possible.

Such skills of a motor vehicle are known not only for obstacles or off-road driving, but also in normal road traffic desirable, e.g. B. for the rapid use of scarce parking spaces. Car handlebars get into situations, especially when parking and exiting, which require difficult maneuvering in a confined space. As special serious examples are mentioned

lateral parking in a narrow niche that just corresponds to the length of the vehicle,
or parking out of an equally short parking space along the edge of the road if adjacent vehicles have been parked bumper to bumper while not complying with the required minimum clearances,
or parking out of a narrow parking space when parking perpendicular to the edge of the lane or in parking lots without parking area markings, if the space left behind by the rear of the vehicle hardly corresponds to the length of the vehicle.

Although parking spaces are so narrow due to the disabilities themselves are inadmissible, they are nevertheless part of everyday life in the big city and represent often significant demands on the routine of the vehicle driver or a nightmare for the less experienced driver. In such cases then namely according to the conventional method the car to be parked centimeters forward and back with changing steering locks not infrequently with an imperfect overview about the rear of the vehicle and often under time pressure if namely, the flow of traffic is hindered by the maneuvering process.  

There has been no lack of diverse efforts and attempts, this one To remedy evils and to provide motor vehicles with shunting devices that allow a reduction in the turning circle diameter, ideally even a turning of the vehicle on the spot or a sideways movement (parallel movement) transverse to the longitudinal axis of the motor vehicle. According to the state of the art require such maneuvering options either instead of the usual wheels Special wheels or other special ground contact elements (e.g. according to the Swiss Patent No. 5 40 811, see below on page 3, penultimate paragraph) or - with the road vehicles of sole interest here with normal frosted wheels - switchable additional wheels or lifting / turning devices. In the proposals of this type that have become known, the Realization, however, too much technical and cost expenditure, these auxiliary devices usually have to be hydraulically activated and will be provided with special drive mechanisms. Such before directions have so far not been able to establish themselves in practice.

In contrast, the present invention addresses this shunting problem operation in a confined space with simpler means without such special Shunting devices and if possible without any basic ones Solve changes to the chassis, namely with the four normal tires alone Wheels. Here, for. B. for cars if possible on another Increasing the maximum steering angle of the front wheels waived because such an increase in construction with disproportionate great effort and, for example, for cars with inevitable disadvantages would be connected to the space available in the passenger and engine compartments. Otherwise, the weight expenditure for the application of the Invention, if possible, at most only a few thousandths of the vehicle Empty weight.

The invention is based on the following basic idea, which however first questions the free rolling of the driven wheels and therefore seems to violate basic kinematic laws, and which at first glance seems to be absurd:

If you drive a four-wheel motor vehicle, which preferably has all-wheel drive and all-wheel steering, but at least two steerable drive wheels, by switching the transmission system, the front and rear wheels in different directions of rotation (!), I.e. with speed ratios of different signs the traction force components F _x (longitudinal forces) of the front wheels and the rear wheels, which are directed parallel to the longitudinal axis of the motor vehicle, are now counter to one another and even cancel each other out with a suitable torque distribution ( FIG. 1); As a result of the traction forces acting on the motor vehicle, essentially only the lateral components F _y (lateral forces) of the driven drive wheels acting transversely to the motor vehicle's longitudinal axis remain, and with the help of these the drive axles can then be traversed correspondingly transversely to the motor vehicle's longitudinal axis . In this way, it becomes possible, without any other special shunting devices, to move the vehicle with all-wheel drive, all-wheel steering and conventional chassis by generating certain steering locks either parallel to its longitudinal axis sideways ( Fig. 1 and 2) or on the spot to rotate a vertical axis ( Fig. 3). At least, however, the motor vehicle, if it only has front-wheel drive and / or front-wheel steering, can be pivoted with the bow around the rear axle as a fulcrum ( Fig. 4).
Analogous effects can also be achieved in that instead of the front and rear wheels, the right and left drive wheels are driven with different directions of rotation (!) ( Fig. 5-9), especially if at the same time there are also opposite steering locks for left and right wheels or drive wheels can be realized ( Fig. 6-9), for. B. adjustment by means of a servo-motor tie rod lengths, as explained in application example 4.

A similar drive system with analog maneuvering options is already available in Swiss Patent No. 5 40 811 (priority of 1970) but only for special vehicles with four specially designed for it Rollers with helical contact elements or with four Drive wheels, the small inclined rotatable along its circumference Wear discs or rollers, with all driving and turning maneuvers exclusively by varying the speed and the direction of rotation of the four drive elements be generated. In contrast, the present invention uses the normal rubber tires and above all steerable motor vehicle drive wheels and thus guarantees the following properties for ordinary road vehicles:

Through the above measures, the turning circle diameter can be Cars with four-wheel drive down to the absolute minimum, namely unattractive drive the vehicle length, be reduced, at least for vehicles with front-wheel drive so far that the turning circle diameter at most is only about the wheelbase longer than the vehicle length.  

For turning the motor vehicle on the spot, it is even possible, under certain conditions, to ensure that the wheels roll freely on the road surface without erasing, using suitable steering locks for right and left wheels ( Fig. 6). The maneuverability and maneuverability of the motor vehicle can be decisively improved or even optimized by the invention, not only by turning in a confined space, but in particular also by the possibility of moving the motor vehicle parallel to its longitudinal axis. This option not only serves the convenience of the drivers of the vehicles equipped in this way, but is also economically advantageous for the general public, because it enables faster and more effective use of limited parking spaces and also reduces the frequency of damage, among other things because the flowing area when parking and exiting Traffic may only be hindered for a short time and is no longer irritated by reverse parking.

The invention is preferably suitable for four-wheel vehicles with at least two steerable drive wheels, especially for cars, commercial vehicles, buses or all-wheel drive vehicles with all-wheel drive and all-wheel steering. Four wheel drive and All-wheel steering is by no means a prerequisite for the application of the Invention; however, this is the case for four-wheel vehicles, for their equipment four-wheel drive and possibly even four-wheel steering is already provided, u. U. a particularly little additional effort for the particularly advantageous application of Invention, e.g. B. with only one additional reversing gear and one servo-motor tie rod length adjustment. The invention can, however same little additional effort, but with less versatile maneuverability, also for vehicles with front-wheel drive and / or only with front wheel steering be applied. (In principle, it is also conceivable to apply the invention to use single-track vehicles. This would, for example, on a two-wheeled "motorcycle with two-wheel drive and one or two-wheel steering" run out without any practical meaning, but can with the theoretical Investigation of the basic traction problems that occur to reduce the necessary calculations to a minimum).

Since the example of a four-wheel vehicle with all-wheel drive and all-wheel steering is the easiest way to show and overlook all the possible components of the traction forces of a four-wheel vehicle, application example 1 should start with such a vehicle, initially with opposite steering of the front and rear wheels, so that lateral parallel displacement movements for the motor vehicle ( Fig. 1 and 2) are made possible.

Application example (Motor vehicle with four-wheel drive and four-wheel steering, rear wheels driven and steered in opposite directions to the front wheels, Fig. 1-2)

Fig. 1 shows the principle of the invention schematically first in the simplest form and illustrates the interaction of all traction forces (driving forces) on the chassis. F _a ₁, F _a ₂, F _a ₃ and F _a ₄ are then the static traction forces of the individual wheels in the shunting operation carried out according to the invention; they each act in the direction of the wheel planes, given by the respective steering angles, the front wheels are to be driven in the forward direction when the first gear of the manual transmission is engaged, the rear wheels according to the invention are to be driven in the reverse direction when the first gear is engaged. The front wheels are labeled 1 (right front wheel) and 2 (left front wheel), the rear wheels with 3 (left rear wheel) and 4 (right rear wheel). Only later in application example 4 (page 35) is it explained in more detail how the steering locks can also be effected for the rear wheels 3 and 4 for the maneuvering operation according to the invention, e.g. B. by means of servo-motor tie rod length adjustment, and possibly even larger steering angle than usual for normal four-wheel steering for the rear wheels (rear wheel additional steering).

Furthermore, the various parts of the transmission system are shown schematically in FIG. 1: The distribution gear (center differential) 5 distributes the drive torque M _A to the rear and front axles (M _Ah , M _Av ) in a specific ratio m _hv (= M _Ah / M _Av ); To produce a reversal of the direction of rotation for the rear wheels 3, 4 in the special shunting operation, this transfer case 5 is supplemented according to the invention by an additional reversing gear, which can also be completely integrated into the transfer case 5 from the outset. More details are given below on page 20 ff. Furthermore, Fig. 1 shows schematically the front axle differential 6 , with which the front axle drive torque M _{Av is divided} nominally into the right front wheel 1 and the left front wheel 2 in a ratio of 1: 1 (F _a ₁ = F _a ₂ = F _av ), and finally the rear axle differential 7 , with which the rear axle drive torque M _{Ah is divided} nominally into the left rear wheel 3 and the right rear wheel 4 in a ratio of 1: 1 (F _a ₃ = F _a ₄ = F _ah ). The differentials 5, 6 and 7 compensate for the different wheel speeds that result from steering locks, cornering, etc.

The above statements and the following formula relationships are based on the assumption that friction losses in the differentials 5, 6 and 7 can be neglected, and that none of the wheels begin to spin on the given road surface and the differential locks that may be present (e.g. in the rear wheel differential 7 ) are initially not activated.

For the illustration in Fig. 1 it was assumed that the front wheels 1 , 2 are turned to the left (in the mathematically positive sense of rotation); the associated steering angle δ ₁, δ ₂ (<0) for both front wheels differ only by the steering differential angle (track differential angle). The steering differential angle is neglected in the drawing and in part also in the following calculations by assuming δ ₁ = δ ₂ = δ _v , where δ _v is approximately the mean steering angle of the front wheels. Consideration of the steering differential angle can be dispensed with anyway, if steering deflections are artificially generated by servo-motor-driven tie rod length adjustment, as is fundamentally possible for all exemplary embodiments (see embodiment example 4). The sum of the two front wheel driving forces F _a ₁ and F _a ₂, ie the total front axle driving force F _Av , has the angle w _v - taking into account the steering differential angle, if necessary. The front wheels 1 , 2 are normally steered in opposite directions to the rear wheels 3, 4 in normal four-wheel steering at low driving speeds; also for the maneuvering operation according to the invention in a confined space, namely for the parallel displacement operation shown here in FIG. 1 in the y direction, that is to say transversely to the x direction (direction of the motor vehicle longitudinal axis, normal straight-ahead direction of travel), the rear wheels are opposite to the front wheels 1, 2 , ie here to the right (in the mathematically negative sense of rotation), struck. The associated steering angle δ ₃, δ ₄ (<0) for both rear wheels may also differ only by the associated steering differential angle, which is neglected in the following calculations for the reasons mentioned. The sum of the two rear wheel drive forces F _a ₃ and F _a ₄, ie the total rear axle drive force F _Ah , then has the angle δ _h ; this corresponds approximately to the mean steering angle of the rear wheels.

From Fig. 1 then there are essentially the following in the tire contact patches of the wheels 1, 2, 3, 4 acting on the motor vehicle wheel drive forces F _a ₁, F _a ₂, F _a ₃, F _a ₄ (with DIN according to designations:

F _a ₁ = F _a ₂ = F _av static traction forces of the front wheels 1, 2 (acting in the direction of the wheel planes ( δ ₁, δ ₂)),
F _Av resulting static front axle driving force (acting in the direction of the angle δ _v ), can be broken down into
F _xv = F _x ₁ + F _x ₂ longitudinal force (in x direction, vehicle longitudinal axis),
R _yv = F _y ₁ + F _y ₂ lateral force (in the y direction, transverse to the x axis),
F _a ₃ = F _a ₄ = F _ah static traction forces of the rear wheels 3, 4 (acting in the direction of the wheel planes ( δ ₃, δ ₄)),
F _Ah resulting static rear axle driving force (acting in the direction of the angle δ _h ), can be broken down into
F _xh = F _x ₃ + F _x ₄ longitudinal force (in the x direction, vehicle longitudinal axis),
F _yh = F _y ₃ + F _y ₄ lateral force (in the y direction, transverse to the x axis).

In addition, especially when sliding or erasing the wheels, frictional forces on the wheel contact patches, which are directed against the erasing movement; these frictional forces are not shown in the sketch in FIG. 1. You act z. B. in the parallel displacement operation taking place in the y direction, as will be considered here first, with its resultant counter to the y direction (to the right, based on the driver's seating position pointing in the x direction) and thereby act on a parallel displacement movement of the motor vehicle in the y direction; they are analyzed in more detail below (pages 13ff.). In the following, all traction force components F _x , F _y in the x direction (forward) and in the y direction (to the left) are counted as positive, opposite force components (backwards and to the right) as negative. The torque ratio required for maneuvering

m _hv = M _Ah / M _Av = F _ah / F _av

between the rear and front axles according to the invention should be negative for the execution examples 1-2 (m _hv <0), because in these the rear axle drive torque M _Ah and the front axle drive torque M _Av due to the different directions of rotation for the maneuvering operation according to the invention on the narrowest Room should have different signs.

The wheelbase I is the distance from the front axle center 6 to the rear axle center 7 , the track width b is DIN-according to the distance from the right wheel plane to the left wheel plane (when driving straight ahead), with no differences between the track width of the front and rear axles here should be taken into account, since they are usually only a few millimeters or centimeters, particularly in the case of cars. For the sake of simplicity, the influences of camber, spreading, caster, etc., are also neglected for the following idealized principle representations, and in some cases also the steering differential angle, if this serves the clarity of the formula relationships.

For the traction forces, a resulting longitudinal force component in the x direction results in the maneuvering operation according to the invention

Σ F _x = F _x ₁ + F _x ₂ + F _x ₃ + F _x ₄
= F _av ((cos δ ₁ + cos δ ₂) + m _hv (cos δ ₃ + cos δ ₄))

and a resulting lateral force component in the y direction

Σ F _y = F _y ₁ + F _y ₂ + F _y ₃ + F _y ₄
= F _av ((sin δ ₁ + sin w ₂) + m _hv (sin δ ₃ + sin δ ₄)),

where m _hv <0.

If you now add all the traction forces acting on the motor vehicle F _a ₁ + F _a ₂ = F _Av , F _a ₃ + F _a ₄ = F _Ah vectorially, this results in a resultant driving force, based initially on the wheelbase center 8 as a reference point in the case of symmetry F _Ages , which acts at an angle ε to the x axis or to the longitudinal axis of the vehicle:

tan ε = Σ F _y / Σ F _x
= (sin δ ₁ + sin δ ₂) + m _hv (sin δ ₃ + sin δ ₄) / (cos δ ₁ + cos δ ₂) + m _hv (cos δ ₃ + cos δ ₄)
= approx. (sin δ _v + m _hv sin w _h ) / (cos δ _v + m _hv cos δ _h ).

In addition, the traction forces result in a torque acting on the vehicle chassis about a vertical axis through the wheelbase center 8 , which is often also approximately in the area of the vehicle's center of gravity,

M ( 8 ) _tot = F _av ( b / 2 ((cos δ ₁ - cos δ ₂) - m _hv (cos δ ₃ - cos δ ₄))
+ I / 2 ((sin δ ₁ + sin δ ₂) - m _hv (sin δ ₃ + sin δ ₄))).

The forces (scalar values) F _a ₃, F _a ₄, F _ah and the associated F _xh component for the rear wheels have a negative sign in the present example ( FIG. 1) because of the opposite direction of rotation of the rear wheels; on the other hand, F _a ₁, F _a ₂, F _av , and the associated F _xv and F _yv components for the front wheels all have positive signs, as does the F _yh component for the rear wheels (with reversal of the direction of rotation and _{simultaneously} negative angles δ ₃, δ ₄, δ _h ). All lateral forces F _yv and F _yh are thus positive in the present case, that is to say they all act in the y direction, ie to the left (in relation to the driver's seating position pointing in the x direction).

In order to be able to transmit the greatest possible lateral forces F _y , the amounts of the steering angle / δ _v /, / w _h / should be chosen as large as possible. By optimizing the steering and torque distribution, ie by suitable selection of the steering angles to be selected for the maneuvering operation according to the invention and by adaptation to the torque _ratio m _hv given in this _{maneuvering operation} (or vice versa by adapting m _hv ), namely by fulfilling the condition

(cos δ ₁ + cos δ ₂) / (cos δ ₃ + cos δ ₄) = - m _hv (<0),

can be achieved that the longitudinal forces F _x exerted by the traction on the vehicle almost cancel each other:

Σ F _x = F _x ₁ + F _x ₂ + F _x ₃ + F _x ₄ = F _xv + F _xh = 0.

If this compensation condition is met and thus the longitudinal forces F _x approximately cancel each other out in the maneuvering operation carried out according to the invention, the angle of the resulting total traction force against the longitudinal axis of the vehicle is ε = approx. 90 °, ie essentially only the lateral forces F _y remain Remaining, the vehicle is then moved in the lateral direction (90 ° transversely to the longitudinal axis), provided that the drive torque of the engine at the given gear ratio is sufficient to cause the wheels to rotate slowly when engaged, despite their tension. Not only the frictional forces on the wheel contact patches of the wheels have to be overcome, but also the inertial forces caused by the vehicle mass. In addition, the traction forces (without considering the frictional forces) exert a torque on the chassis around the vertical axis in the wheelbase center 8 :

The torque component from the second line is assuming the same steering angles of the right and left wheels ( δ ₁ = δ ₂ = δ _v , δ ₃ = δ ₄ = δ _h ) zero or at least - taking into account the steering difference - as a rule negligible. If the steering deflections for the special maneuvering operation are generated by servo-steering tie rod length adjustment (see below, embodiment 4), the steering differential angles that occur during normal steering no longer play a role anyway, since the steering angles of the right and left wheels are then selected independently of one another can. The remaining torque is from the third line and thus the total vertical axis torque

M ( 8 ) _tot = F _av I (sin δ _v + (cos δ _v / cos δ _h ) sin δ _h )

disappears with four-wheel steering with equal amounts ("symmetrical"), but front and rear steering turns in opposite directions ( δ _h = - δ _v , ie δ ₁ = δ ₂ = - δ ₃ = - δ ₄ = δ ).

At other ratios of the steering angles / w _h / δ _v / than 1: 1 (/ δ _h / </ δ _v /), the high-axis torque M _tot becomes zero if it is referenced to another reference point 9 on the connecting line between 6 and 7 instead of point 8 . This reference point 9 has the distance from the wheelbase center 8

Δ x = I / 2 (tan / δ _v / -tan / δ _h / / tan / δ _v / + tan / δ _h /) (< I / 2)

and can then be understood as the point of attack for the remaining shear force Σ F _y :

Σ F _y (= F _Ages ) = F _av 2 sin δ _v (1 + tan / δ _h / / tan / w _v /).

However, this lateral force is only partially available as a driving force for the lateral parallel displacement of the motor vehicle (acceleration in the y direction); it is reduced by the frictional forces of the wheels, which depending on the steering angle act partly as circumferential forces, partly as transverse forces, but overall counteract the direction of parallel displacement (y direction), as will be explained in more detail below.

It is advantageous if the point of application 9 of the transverse force resultant is identical to the center of gravity of the vehicle or can be placed in its vicinity. This is possible if the center of gravity is between the front axle (point 6 ) and the wheelbase center 8 , as is the case for. B. in the case of cars with a front engine arrangement at least with only a small load, for example when driving in city traffic with little luggage in the rear trunk.

The vehicle can then by the lateral force Σ F _y (= F _Ages ) when starting z. B. from an extremely narrow parking space, which is only a few centimeters longer than the length of the vehicle, can be maneuvered out without moving forward or backward, namely by a mere displacement (parallel movement) to the left as if all four wheels were at a turning angle of brought about 90 °. With this variant of the shunting operation, a dream of many drivers is realized. In order to understand this process, which at first glance is astonishing, it can be imagined that the centimeter-by-inch forward and backward maneuvers that are otherwise required in such cases are eliminated to a certain extent by the fact that these two movements (back and forth with a lateral component) are carried out simultaneously, whereby the front axle takes over the drive for the advance movement and the rear axle takes over the drive for the superimposed reset movement (or vice versa, if, for example, the reverse gear is engaged instead of the first gear, see further below in the explanations for Fig. 2).

Particularly simple and clear conditions for lateral parallel displacement motion of Figure 1 is obtained by first -. Considered "balanced" four-wheel steering (ie, four-wheel steering with magnitude same steering angles for rear as for the front wheels), again it - only for the inventive shunting It is assumed that the steering locks for the front and rear wheels are in opposite directions for this maneuvering operation:

sin δ ₁ + sin δ ₂ = - (sin w ₃ + sin δ ₄) (<0)

respectively.

δ _v = - δ _h = δ (<0).

In this case, the torque ratio rear axle / front axle m _hv = -1, after the above compensation equation (Σ F _x = 0) can be made (M _Ah = -M _Av, with torque split 1: 1 between the front and rear axle), and it occurs with any - more or less - steering angle the desired compensation of the longitudinal force components F _x , because the compensation equation for each pair of angles / δ _h / = / δ _v / is fulfilled. In order to obtain the greatest possible lateral forces, the largest possible steering angles δ should of course be chosen.

The torque acting on the chassis about the vertical axis in the wheelbase center 8 in the maneuvering operation according to the invention completely disappears in this "symmetrical" four-wheel steering with opposing steering angles of the front and rear wheels in this case. All that remains is a shear force component in the y direction that acts at point 8

Σ F _y (= F _Ages ) = 4 F _av sin δ

left, reduced by the frictional forces that act on the wheel contact patches partly in the circumferential, partly in the transverse direction, but with their resultants act against the parallel displacement movement. The factor sin δ characterizes the reduction that the overall effective traction forces experience - even without taking into account the inhibiting frictional resistances of the erasing wheels - in the event of an insufficient steering angle δ .

If the wheelbase center 8 is not also the center of gravity of the vehicle, then an additional rotary movement overlaps the parallel displacement movement on the spot, the extent and direction of which depends on the position of the center of gravity. If emphasis is placed on avoiding this rotary movement, the ratio of the steering locks / δ _h / δ _v / and accordingly also the torque ratio / m _hv / for the maneuvering operation according to the invention must be chosen accordingly, so that the point of application of Σ F _{y is} moved to point 9 (at a distance Δ x from the wheelbase center 8 ), which corresponds approximately to the center of gravity of the vehicle:

tan / δ _h / / tan / δ _v / = (1- (2 Δ x / I ) / 1 + (2 Δ x / I ).

However, it must be pointed out that the more or less "symmetrical" four-wheel steering (/ δ _h = / δ _v /), if it is used at all, is only useful for the maneuvering operation carried out according to the invention. For normal driving and maneuvering, on the other hand, only a variable rear-wheel additional steering with relatively small steering angles of the rear wheels comes into question. An increase in the steering angle for the rear wheels would be problematic in normal driving for various reasons, even if the significantly increased space required for the wheel arches of the rear wheels could be met: For example in the case of δ _h = - δ _v (with the same amount, but opposite front and rear wheel steering locks), a car parked close to the curb or against a wall would drive to the left with the right rear wheel against the curb or with the tail swinging against the wall.

In order to understand the invention, it is helpful, because of the engine system modified in an unusual manner, to analyze this special shunting operation according to FIG. 1 with the conventional methods of motor vehicle technology and to compare it with the "normal" driving operating state. For the clear case of the assumed "symmetrical" four-wheel steering ( δ _h = - w _v ), an analysis of the parallel shift operation can be achieved in a very simple manner using an intellectual trick:

Namely, the lateral movement of the vehicle shown in Figure 1 as "forward" movement in the Y direction of a chassis to be construed, in which the wheels 2 and 3, the front wheels, the wheels 1 and 4, are the rear wheels. the gauges would then be approximately identical to the original wheelbase I from this point of view. For the four wheels of the chassis considered in this way, which then have a uniform direction of rotation towards the front (namely in the y direction), the result is an exceptionally large slip angle α in the form of positive toe angles a = 90 ° - δ (or associated negative toe-in angle - α = δ -90 ° with "minus" track). As is known, toe-in or toe-in angles result in track resistances F _v which are usually negligible at small slip angles, but can be considerable at large slip angles.
The toe-in angle (slip angle α ) amounts to more than 45 °, z. B. in a car with a maximum steering angle of δ = 37 ° is α = 53 °, in a bus with a maximum steering angle of w = 79 °, however, only α = 11 °. The wheels can not roll in the direction of the drive forces F _a , but are forced by the inward compensation forces F _x originating from the respective other axis to "roll" in the y direction, inevitably in the contact patches of the tires in the side Direction (perpendicular to the wheel rim plane) an additional etching must occur.

In the following, an attempt is made to estimate the forces that can be transmitted by acting on each tire in the footprint in a highly simplified manner; In terms of symmetry, these are each a circumferential force of the amount F _a (but opposite to the direction shown in FIG. 1) and an opposing compensation force (caused by the opposite wheel of the other axle) of the amount F _x (= F _av cos δ ). If one superimposes these forces vectorially and breaks them down into longitudinal components (in the circumferential direction, i.e. in the direction of the wheel rim plane) and in transverse components (transverse to the wheel rim plane), then the neglected tire deformations (see below) result in the desired one occurring on every tire

Circumferential force (tire longitudinal force) F _u = F _av - F _x cos δ = F _av sin² δ

and

Lateral force (tire lateral force) F _s = F _x sin δ = F _av cos δ sin δ .

The effective traction forces F _u per wheel in the circumferential direction and by static friction are compared to the "normal" driving state (slip angle α = 0 at steering angle δ = 90 °, F _u = F _av ) by the factor

sin² δ (e.g. in the case of cars to at least sin² δ = sin² 37 ° = 36%,
with omnibus only on sin² δ = sin² 79 ° = 96%)

reduced. The key to understanding the whole process lies in this regularity, albeit derived from the simplifications. By reducing the effective traction forces, the inhibiting influence of the otherwise normally negligible, at larger slip angles α due to increasing tire deformations increasing track resistance F _V (see below). If you could increase the steering angle to δ = approx. 90 ° ( a = approx. 0 °), the normal driving condition with normal static friction would be given again for movement in the y direction, whereas without any steering lock ( δ → 0 °) the special maneuvering method cannot be carried out at all due to the lack of lateral friction. For the proper functioning of the special maneuvering method in a car steering angle of z. B. δ = 37 ° a sufficient grip of the road surface is required so that the wheels do not spin even in the deteriorated traction conditions. The usual road surfaces usually also meet these requirements when it is wet and slippery, especially since the invention is preferably only used in the range of creep speeds.

Due to the deformation of the tire due to skewing (toe-in or Toe) is superimposed on the (tire) lateral force calculated aboveF _s   yet another, from the wheel driving forceF _a  independent lateral force F _sV . For measurements on individual tires, this is known to be from Slip angleα dependent: It first takes off at a small slip angleα proportional toα to, whereby the proportionality factor is the so-called. The tire is skewed. With larger slip angles α it then only increases degressively, d. H. the proportional range is left, and the (tire) lateral forceF _sV  reaches a maximum; this is due to the fact that the lateral force is no longer in the middle the tire contact patch, but in the circumferential direction postponed. This maximum lateral force is - depending on the normal force in the tire contact patch and depending on the tire and road grip - on average around slip anglesα between 10 ° (ice cover) and 20 ° (dry road surface). In the above - under disregard Allow tire deformation - calculated case of z. T. each other compensating traction forces of the wheels1, 2 and3, 4 would Maximum traction lateral forcesF _s  =F _av  cosδ sinδ = 0.5F _av  sin 2α  at a slip angle = 45 ° can be reached. One overlays plus the side forces caused by the tire deformationF _sV , so this results in a shiftΔα of the maximum lateral force. TheyComponent (cosδComponent) of the lateral force is then the associated track resistanceF _V , d. H. the contrary to theyDirection Inhibitory force (related to a wheel):

F _V = (F _av cos δ sin δ + F _sV ) cos δ = F _av sin² α cos α + F _sV sin a .

Up to larger slip angle α , this track resistance F _V increases continuously with increasing slip angle α ; therefore, the slip angle α must not be too large, so the steering angle δ (= 90 ° - α ) should not be chosen too small for parallel shift operation.

When leaving the proportional range of F _sV , a _{partial erasing} occurs in the rear area of the tire contact area, which spreads forward with increasing slip angle a (ie smaller steering angle δ) . At a slip angle α → 90 ° ( δ → 0 °) the entire contact area would eventually change to the sliding state, provided that the vehicle is moving in the y direction; the slip would then go against 100%.

In the "rolling" process taking place in the y direction, a lateral erasing speed inevitably occurs on the contact patches of the tires, which is associated with a lateral slip λ _y = sin α = cos δ ; For example, for a car with a maximum steering angle δ = 37 °, this slip would still be 80%, for smaller steering angles it would be even greater, for a bus with a maximum steering angle w = 79 °, the slip would be only 19%. The unusually large static lateral forces F _s acting transversely to the wheel rims and acting flat - partly as a result of the corresponding component of the compensating force F _x of the opposite wheel on the other axle - deform the tires elastically; of course, it is assumed that the tires are dimensioned and coordinated with the rims in such a way that they are able to withstand the lateral tire forces F _s , which are higher than in normal operation, and that the tires cannot jump off the rims, even with reduced tire pressure . If necessary, a drop resistance that is too low must be prevented by using suitable rims or a more suitable tire-wheel system.

With the unusually large slip angles of z. B. α = 53 ° (in a car with a maximum δ = 37 °) and the resulting erasing and flexing work of the tires is of course associated with greater wear compared to normal driving. The additional tire wear on a maneuvering distance of z. B. 2-3 meters is limited, since the maneuvering is carried out in the range of creep speeds. Comparatively, the wear is much less than that which, for. B. would normally be expected if the same vehicle is braked with the same length of braking distance of 2-3 meters on the same surface with blocked wheels (from low speed to standstill); in addition, wear is distributed more evenly across the entire circumference of the tire. After all, because of the higher tire wear and the increased fuel consumption, the type of maneuvering according to the invention should only be used when necessary and not unnecessarily often, especially not when there is enough time, space and routine for normal maneuvering. Otherwise, tires, rims and gears would have to be dimensioned to be more robust from the outset, especially when using this special shunting operation not only as a parking aid, but to increase the maneuverability of an off-road vehicle or the like.

In contrast to Fig. 1, in which the vehicle z. B. was moved parallel to the left during parking, Fig. 2 shows the analog process with parallel shift to the right, z. B. when parking. Here, the signs of the steering angle are swapped ( δ _v = - δ _h = δ <0), and accordingly all side forces F _y and, accordingly, the resultant Σ F _y = 4 F _av sin δ receive a negative instead of a positive sign. The vehicle is accordingly offset parallel to its longitudinal axis to the right, as z. B. would be required for parking in a parking niche that only just corresponds to the length of the vehicle.

A parallel displacement movement of the motor vehicle to the right could also be achieved with wheel positions according to FIG. 1, namely if for the maneuvering operation according to the invention the reverse gear is engaged instead of the first (forward) gear and thus the front axle is driven in the reverse direction and the rear axle in the forward direction . In principle, both methods are equivalent, unless the stronger translation of the reverse gear is considered even more advantageous. Compared to FIG. 1, the directions of all drive forces and their components and accordingly the direction of parallel displacement would then be reversed. However, the lateral forces F _{s of} the tires (transverse to the wheel rim planes) occurring during the sideways movement due to the large slip angle would no longer be directed outwards but inwards, instead of large toe-in angles (with "minus" track) would be large toe-in angles (with " Plus "lane), the tires would be deformed exactly in the opposite direction in contrast to FIG. 1, and the shift Δα of the maximum lateral force would also have the opposite sign. Conversely, a parallel displacement movement of the motor vehicle to the left can also be achieved with wheel positions according to FIG. 2 by engaging the reverse gear (with reversal of direction of all drive forces and their components and of course also the direction of movement in FIG. 2).

Continued Execution example 1 (Motor vehicle with four-wheel drive and steering, rear wheels driven in opposite directions, but steered in the same direction to the front wheels, Fig. 3)

A second possible variant of the process - initially still under the embodiment 1 for a motor vehicle with four-wheel drive and four-wheel steering -... Shows 3. In contrast to Figures 1 and 2 in this variant of the invention carried out shunting the rear wheels are in the same direction how the front wheels are steered, ie the steering angle δ _v , δ _h are given the same sign, ie in the case used again as an example the "symmetrical" four-wheel steering used for the special shunting mode applies:

δ _v = δ _h = δ (<0).

In this variant of the method, when the longitudinal forces F _x approximately cancel each other out, the lateral forces of the front wheels F _{yv are} positive, those of the rear wheels F _yh are negative, _i.e. oppositely directed, so that the motor vehicle does not have a parallel _{displacement movement} , but rather a rotation on the 3, in the example shown in FIG. 3 in the mathematically positive direction of rotation (counterclockwise) around a vertical axis around the center of the wheelbase 8 . The turning circle diameter, which is normally 10-12 m in a 4-5 m long motor vehicle, is reduced to the theoretically possible minimum, namely with bumpers rounded to the side almost to the vehicle length, at least to less than 50% of the normal turning circle diameter been. The resulting total traction force F _Ages is 0, but a correspondingly large torque arises around the vertical axis at the wheelbase center 8

M ( 8 ) _tot = 2 F _av I sin δ ,

that acts on the vehicle chassis and leads to the rotary movement. However, the wheels 2 , 4 erase much more than the wheels 1, 3 on the road surface, as can be seen in FIG. 3, because the slip angle α of the wheels relative to the respective tangent to the track circle 10

α ₂ = α ₄ = arctan (I / b) + δ

α ₁ = α ₃ = arctan (I / b) - δ

are different in amount: If the front wheels are turned to the left δ <0, if the track width b significantly exceeds the wheelbase (I <b) , the wheels 2, 4 are more or less perpendicular to the track circle tangent, so that these wheels practically do not contribute to the motor vehicle rotation. In the case / α ₂ /, / α ₄ / ≧ 90 °, the wheels 2, 4 would even erase against the motor vehicle rotation, unless this is compensated for by the front axle and rear axle differentials 6 and 7 . At slip angles of z. B. of the order of 90 °, the lateral friction force components of the erasing tires 2, 4 directed tangentially to the track circle 10 result in a considerable inhibition of the rotary movement. However, these inhibiting sliding friction forces are overcome by the traction forces of the driving wheels 1, 3 , which are applied mainly by static friction, so that rotation occurs on the spot, albeit with little efficiency. This may result in an uneven tire wear along the circumference for the wheels with the large slip angle, in particular with unlocked differentials 6 and 7 ; under certain circumstances it can be advantageous to lock the differentials. In order to avoid these differences in the slip angle and in particular the inhibitions of the rotary movement caused by the wheels 2, 4 and thus to optimize the turning operation, these wheels 2, 4 would have to be turned in the opposite direction and driven with the opposite direction of rotation (see below, embodiment 4, FIG . 6).

In the present case ( Fig. 3), if all wheels are turned in the opposite direction to Fig. 3 (change of sign for δ , δ <0), or if the reverse gear is engaged (change of sign for all drive forces and their components), the Vertical axis rotation in the opposite direction, ie now in a mathematically negative direction of rotation (clockwise). The reversal of this vertical axis direction of rotation by reversing the steering angles - but not by engaging the reverse gear - has the result that then no longer the wheels 2, 4, but the wheels 1, 3 are approximately transverse to the track tangent and erase accordingly.

As already explained, the invention is particularly well suited for use on four-wheel motor vehicles in which all-wheel drive and all-wheel steering are already provided, for. B. also for off-road vehicles. All-wheel drive and all-wheel steering are also desirable safety features for normal cars, they do not in themselves bring such blatant advantages in everyday operation that the large mass of car buyers would be willing to accept a significant increase in the price of vehicles for these advantages . The invention makes it possible to provide the striking solution to an everyday problem, namely maneuvering in a confined space, to the side-to-side parallel displacement movement and the rotational movement of the motor vehicle on the spot, for only a relatively small additional outlay for vehicles with four-wheel drive and four-wheel steering. Since practically a dream of many motorists is realized with such capabilities of a motor vehicle, the invention is also particularly suitable as a supplement and as an additional sales argument for the safety features of all-wheel drive and all-wheel steering. But it is also for cars. B. only with front wheel steering, possibly also only with front-wheel drive applicable (see below, execution examples 2 and 4, Fig. 4 and 9).

For the practical implementation of the invention, it is usually necessary or expedient to divide the drive torque between the front and rear axles in a defined manner for the intended maneuvering operation, if necessary in the case of four-wheel drive, and, if appropriate, for four-wheel steering, the ratio of the steering angles of the front and rear wheels accordingly adapt. The then required for "symmetrical" four-wheel steering (/ δ _h / = / δ _v /) steering turns for the rear wheels, which would be much larger for the special maneuvering operation than for normal four-wheel steering (so-called. Rear wheel additional steering), z. B. can be realized relatively easily by means of servo-motor tie rod length adjustment (see embodiment example 4), but usually require more space for wheel arches etc. at the rear. The otherwise necessary additional effort for the invention would then only exist in such an equipped motor vehicle that, in addition to the transfer case (intermediate or center differential 5 , or integrated in this transfer case), a reversing gear is provided, which is intended for the intended special shunting operation in a confined space reverses the direction of rotation for the rear axle.

This reversing gear (speed ratio usually i = n _h / h _v = -1) then together with the other transfer case gives the desired negative torque _ratio m _hv = M _Ah / M _Av in this case. This reversing gear consists, for. B. in the simplest case according to a well-known model essentially of two bevel gears sitting on the output axis, which are driven in opposite directions by a third bevel gear transverse to it, and from a shift-actuated turning sleeve, which optionally couples one of the two bevel gears to the output axis. There are additional elements if the coaxial instead of an angular arrangement of the input and output axes of the reversing gear is to be guaranteed. Should the changeover of the reversing gear be possible even while driving, e.g. B. for temporary improvement of maneuverability in off-road vehicles, a lock synchronization is useful. When using the invention as a pure parking aid, on the other hand, the actuation of the reversing gear can be restricted to standstill and the switching device can be carried out correspondingly simply; In this case, however, an additional precaution is advantageous, which enables the gearbox to be switched - and coupled with it the servo-motorized enlargement of the steering locks for the rear wheels - only when the vehicle is at a standstill and also only when the first (forward) gear or reverse gear is engaged.

The integration of the reversing gear into the associated transfer case (center differential) 5 is more elegant and space-saving. There are numerous possible solutions for such an optionally switchable reversal of the direction of rotation, e.g. B. according to a known model with intermediate wheels, so that the execution of further details is unnecessary. Is advantageous for the shunting operation according to the invention. U. an even stronger translation; For this purpose, an appropriately dimensioned additional forward and reverse gear (creep speed gear) may be provided for this maneuvering operation or a significantly more geared reverse gear in connection with a separately switchable reversing gear.

In the described variants of exemplary embodiment 1 ( FIGS. 1, 2 and 3), the four-wheel steering is not “symmetrical” (/ δ _h / = / δ _v /) with respect to the amounts of the steering locks in maneuvering operation according to the invention, but only as in normal operation as a rear axle -Extra steering performed (/ δ _h / </ δ _v /), and the steering angles of the rear wheels for this maneuvering operation should not be much larger than with four-wheel steering in normal driving or maneuvering operation, so that no particularly large wheel arches for the rear wheels 3, 4 are required, then the desired compensation of the longitudinal force components F _{x can} normally only occur at a very specific, defined steering wheel position with certain assigned steering angle δ _v , w _h , depending on how the constant torque _ratio m _{hv was selected} for the maneuvering operation according to the invention. Locking the steering in the relevant position is recommended for special shunting operations. Of course, the rear steering _{angle is also advisably} not chosen too small, because otherwise the lateral forces F _yv and F _{yh will be} too different in _{terms of} amount and then real lateral parallel displacement movements ( FIGS. 1 and 2) or real rotary movements on the spot ( FIG. 3 ) u. U. are no longer easily possible, but possibly only mixed forms, z. B. in the borderline case, when the rear axle is no longer steered at all, only swiveling movements of the motor vehicle bow (see below, embodiment 2, FIG. 4).

Basically, then according to the compensation equation ( Σ F _x = 0)

cos δ ₁ + cos δ ₂ / cos δ ₃ + cos δ ₄ = -m _hv

the torque _ratio m _hv for the _{maneuvering operation according} to the invention should be less than 1 because usually (cos δ ₁ + cos δ ₂) will always be less than (cos δ ₃ + cos δ ₄); this means that in this maneuvering operation the front axle - the amount - greater drive torque, the rear axle must receive the smaller, z. B. in the ratio

/ m _hv / = 0.80, 0.82, 0.87, 0.95 etc.

At the front middle steering angle for a car of z. B. / δ _v / = 37 ° this could be done with rear steering angles of

/ δ _h / = 3 °, 13 °, 23 °, 33 ° etc.

to reach. For this purpose, a center differential 5 is required with a special nominal torque ratio / m _hv / at / δ _h / </ δ _v / which generally differs in magnitude from 1: 1. For this purpose, a suitable planetary gear differential 5 is expediently used, possibly also with a selectively switchable torque _ratio m _hv , which is different for normal operation and for special shunting operation, possibly also for parallel shifting operation and for rotary operation. The device for reversing the direction of rotation for the rear axle (reversing gear) can then also be integrated in this center differential 5 .

If in the case of δ ₁ = δ ₂ = δ _v , δ ₃ = δ ₄ = δ _h the compensation condition Σ F _x = 0 is fulfilled by m _hv = - (cos δ _v / cos δ _h ), the result is asymmetrical four-wheel steering ( / δ _h / </ δ _v /) considerable differences in the lateral forces on the two axes:

F _yv = F _y ₁ + F _y ₂ = 2 F _av sin δ _v

F _yh = F _y ₃ + F _y ₄ = -2 F _av (cos δ _v / cos δ _h ) sin δ _h ;

they differ by the factor:

F _yh / F _yv = -tan δ _h / tan δ _v .

As a result, in parallel shift operation ( FIG. 1, δ _v <0, δ _h <0) the total traction force F _Ages acts instead of at the wheelbase center 8 in a reference point 9 shifted by the distance Δ x more from the front axle:

Δ x = I / 2 ((/ tan δ _v / - / tan δ _h /) / (tan δ _v / + / tan δ _h /)).

The closer this reference point 9 is to the vehicle's center of gravity, e.g. B. in vehicles with a front engine arrangement, the cheaper; otherwise, a noticeable additional rotary movement can overlap during parallel displacement operation.

Likewise, no pure turning operation on the spot ( FIG. 3, δ _v <0, δ _h <0) will be possible according to this method, because if the compensation condition Σ F _x = 0 is not fulfilled at the same time

Σ F _y = 2 F _av (sin δ _v - (cos δ _v / cos δ _h ) sin w _h )

Can be zero; this would namely require / δ _v / = / δ _h /, ie "symmetrical" four-wheel steering, if one starts from the same steering angle for right and left wheels. (With unequal steering locks for right and left wheels, Σ F _y = 0 can also be guaranteed at the same time. Corresponding exemplary embodiments are explained below).

Therefore, in this embodiment 1, the motor vehicle with asymmetrical four-wheel steering instead of a pure rotary movement will execute a rotary movement on the spot with a superimposed sideways movement (initially to the left in FIG. 3) if no further remedial measures are taken. This sideways movement is due to the fact that the rear axle, because of the lower traction _{force component} F _yh acting there, is not pulled to the right as much as the front axle is _pulled to the left by the traction _{force component} F _yv acting there. However, the direction of the "sideways" movement is continuously changed due to the continuously progressing rotation of the motor vehicle; it changes from the initial y direction after a quarter turn (90 °) into the minus x direction and after reaching a half turn (180 °) into the minus y direction. If one compares the start and end position of the motor vehicle after such a half turn, it has been shifted apart from the turn (U-turn) in the direction of the original minus x direction, ie in the direction of the original longitudinal axis. The motor vehicle has therefore performed a pivoting movement about a pivot point which lies between points 7 and 8 . (In the case of / δ _h / = / δ _v / this pivot point is identical to the center of the edge position 8 ( FIG. 3), in the case of / δ _h / = 0 with point 7 , as explained in the next embodiment example 2.)

The superimposed vehicle displacement in the direction of the original x-direction can thereby take into account that an opposite longitudinal movement in the x direction from the outset to allow for the rotation operation, that is Σ F _x does not become zero. However, because of the continuous rotation of the motor vehicle, this then results in an additional lateral displacement of the motor vehicle in the direction of the original y direction. Instead of compensating for the longitudinal forces, as is done by fulfilling the condition m _hv = - (cos w _v / cos δ _h ), it can be more favorable for the rotary movement, instead of reducing the overall transverse forces or compensating them entirely ( Σ F _y = 0). To ensure the latter, one would have to have equal amounts of lateral forces on the front and rear axles

F _yv = F _av 2 sin δ _v

F _yh = F _av 2 m _hv sin δ _h

bring about; this would be a torque ratio for rotary operation

m _hv = - (sin δ _v / sin δ _h ) <-1

required, and then there would be a non-zero longitudinal force resulting

Σ F _x = F _av 2 (cos δ _v - (sin δ _v / sin δ _h ) cos δ _h )
= F _av 2 cos w _v (1 + / tan δ _v / tan δ _h /)

surrender. However, this would have the consequence that an additional longitudinal movement, initially beginning in the original x- direction, overlaps the rotary movement and the vehicle therefore needs a little more space in front of the bow on the left side (at δ <0). After a half turn, the motor vehicle would then have been moved parallel to the U-turn in the direction of the original y- direction.

Between the two conditions Σ F _x = 0 and Σ F _y = 0, which can only be fulfilled together with the symmetrical four-wheel steering (/ δ _v / = / δ _h /) according to the above relationships - with the same steering deflections on the left and right with asymmetrical four-wheel steering (/ δ _v / </ δ _h /) a compromise corresponding to the desired requirements can be made. You get even more options if you create different and possibly even opposite steering locks for right and left wheels, for example by means of servo-motor tie rod length adjustment, as will be explained later in application example 4.

In maneuvering operation according to the invention, in particular in parallel displacement operation, if the longitudinal movements of the motor vehicle are to be suppressed, the compensation condition Σ F _x = 0 according to the equation given for this does not necessarily have to be met with a corresponding torque _ratio m _hv . The longitudinal movements can instead be automatically suppressed by a self-locking center differential 5 , z. B. a Torsen differential, or a differential with automatically controlled lock, z. B. with electronically-hydraulically controlled slat lock is used. With the slightest difference in speed between the front and rear wheels, regardless of their different direction of rotation according to the invention, for example, the Torsen differential automatically assigns the larger drive torque to the slower rotating drive shaft, so that the same average number of revolutions are guaranteed for front and rear wheels and on them Longitudinal movements can be suppressed by automatically adjusting the torque ratio m _hv . The suppression of the longitudinal movements is also possible in this way if the compensation condition Σ F _x = 0 otherwise (with a non-locking center differential 5 ) due to the torque _ratio m _hv and the steering lock ratio / w _h / δ _v / would not be met or only approximately.

Regardless of the center differential 5 , to avoid asymmetries, as already mentioned, it may be appropriate for various reasons to provide locks for the axle differentials 6 and 7 , for. B. so that the same wheel revolutions of the left and right wheels are forced for the special shunting operation.

Alternatively, a transfer case 5 with a continuously variable distribution of the drive torque can also be used, e.g. B. according to a known model with electronically and / or hydraulically controllable torque ratio m _hv . This serves z. B. a planetary center differential combined with a viscous lock and a parallel connected continuously variable transmission (V-belt, push link belt gear or the like); With the continuously variable transmission, speed differences between the axes can be simulated and the drive torques M _Ah , M _Av can be redistributed as required. If such an arrangement is present in a motor vehicle with all-wheel drive anyway and allows a continuous redistribution, it makes sense to control or regulate the device electronically in such a way that the longitudinal movements or the longitudinal forces F _x or the transverse forces in the special shunting mode F _{y are} automatically compensated, ie, for example, the motor vehicle does not make any movements in the x direction during parallel displacement operation or carries out certain other desired movements in the sense of the present invention.

Instead of locking the center differential 5 itself 50302 00070 552 001000280000000200012000285915019100040 0002003840783 00004 50183 or, as explained above, equip it with a variable torque ratio m _hv and then switch or regulate some applications accordingly during the transition from normal driving to special shunting mode The following much simpler alternative is possible: You can design the reversing gear as a countershaft and give it a specific speed ratio / i / , which also differs from 1: 1, for the special shunting operation and also possibly the center differential 5 or additionally the axle differentials 6 and 7 Block partially or completely. (With a 100% degree of locking for the center differential 5, for example, the average speeds of the front and rear wheels are then completely balanced and the driving forces are distributed to the front and rear wheels according to the static friction conditions). You can now tune the speed ratio between the rear and front axles i = n _h / n _v with the steering angles δ ₁, δ ₂, δ ₃, w ₄ for the parallel shift operation so that no motor vehicle movements in x Direction. The constants k ₁, k ₂, k ₃, k ₄ used for the four wheels (see below) can be determined by experiments; they depend on the locked state, the torque distribution and the friction conditions. One can assume that these constants are not the same, but that they change approximately by the same factor if the road surface or the wheel load changes - almost equally on all four wheels. This results in the following calculation for the required speed ratio i of the reversing gear:

The vehicle is in this maneuvering, z. B. with locked center differential 5 , the distance in a differential period Δ t in the x direction

Δ x = n _v Δ t (k ₁ cos δ ₁ + k ₂ cos δ ₂) + n _h Δ t (k ₃ cos δ ₃ + k ₄ cos δ ₄)

return. In order to keep the distance Δ x to zero and thus to compensate for the longitudinal forces F _x, the reversing transmission is a specific, possibly from i = i-1 to give deviating speed ratio, namely

i = n _h / n _v = - (k ₁ cos δ ₁ + k ₂ cos δ ₂) / (k ₃ cos δ ₃ + k ₄ cos δ ₄),

In the case of asymmetrical four-wheel steering, the rear axle speed must generally be reduced accordingly for the special shunting operation. Because of Δ x = 0, longitudinal movements of the motor vehicle are then omitted, i.e. the motor vehicle essentially carries out a lateral displacement of the front axle and the rear axle depending on the steering deflections selected for maneuvering and parking operation, possibly overlaid by a more or less pronounced rotation on the spot, caused by the high axis torque. With a suitably chosen speed ratio i there is always at least one steering lock combination δ ₁, δ ₂, δ ₃, δ ₄, in which only lateral components of the resulting traction force occur.

Already because of the neglections and simplifications made in the calculations, in principle, all dimensions for / m _hv /, / w _h /, / i / etc., which are to be carried out according to this description, are required anyway. B. for the design of the locking characteristic of the center differential 5 , corresponding attempts to take into account all influencing variables that go into the desired vehicle movements.

Another alternative way of redistributing the drive torques in special shunting mode is simply that either the rear wheels or the drive shaft to the rear wheels are braked directly at the center differential. In particular, if the effective torque ratio / m _hv / was designed for normal operation to be at least equal to or greater than 1, the desired optimization can in any case be brought about by braking to a suitable extent, possibly also using existing ABS components. This braking causes the center differential 5 to automatically assign a higher torque component to the front axle, ie / m _hv / is correspondingly reduced and, in the limit case, approaches zero when completely blocked (see exemplary embodiment 6). The various measures listed above can also be automatically controlled in such a way that the longitudinal forces F _x or the transverse forces F _{y are} compensated for or the motor vehicle only executes certain desired movements.

Embodiment 2 (Motor vehicle with four-wheel drive and front wheel steering, front and rear axles driven in opposite directions, Fig. 4)

If no rear wheel steering is provided for the vehicle at all, but only the usual front wheel steering, then w _h = 0 must be set in the above formula relationships. This eliminates the lateral force on the rear axle F _yh (= 0). With a suitable choice of the front axle steering lock

w _v = ± arccos (- m _hv ) = ± arccos (/ m _hv /),

or the torque ratio of the rear axle / front axle

m _hv = - cos δ _v ,

or if z. B. to be maneuvered with a completely locked center differential 5 , with a correspondingly selected speed ratio for the reversing gear

i = n _h / n _v = - (k ₁ + k ₂ / k ₃ + k ₄) cos δ _v

the longitudinal forces F _{x are} almost compensated again. In the case of equal constants for the front and rear wheels k _v = k _h , the compensation of the longitudinal forces occurs when steering angles of z. B.

/ δ _v / = 37 °, 32 °, 27 °, 22 ° etc.

the torque ratio rear axle / front axle / m _hv / (or alternatively the speed ratio for the reversing gear / i / =)

= 0.80, 0.85, 0.89, 0.93 etc.

is chosen. Deviations are possible again if a self-locking center differential 5 , z. B. a Torsen differential is used.

If the steering angle w _v is correctly coordinated with the torque or speed ratio, then in the first (forward) gear there is a space-saving swiveling out of the motor vehicle with the front axle, e.g. B. with a positive steering angle to the left, such as when only the side force F _{yv acts} on the front axle, in turn connected with a corresponding torque about the vertical axis in the rear axle center 7 ,

M ( 7 ) _tot = 2 F _av I sin δ _v ,

see Fig. 4. When reverse gear is engaged, the reverse process occurs in the opposite direction. In this process, practically only the steered front axle is pulled to the left or right on the motor vehicle, and the front wheels on the track circle 11 are pivoted approximately around the rear axle (point 7 ) as the fulcrum. The contact points of the front tires move approximately on the track circle 11 ; the slip angles (between the tangent to the track circle and the intersection of the wheel plane with the road surface) are for wheels 1 and 2

α ₁ = arctan (2 I / b ) - δ

α ₂ = arctan (2 I / b ) + δ ,

are very different and lead to different degrees of erasing of the front wheels on the road surface. When turning the front wheels to the left ( δ <0), the left wheel is again approximately transversely to the track tangent as in FIG. 3 and can thus contribute practically nothing to the rotary movement; it would even, if only with a very slight effect, erase against the movement on the track circle 11 , insofar as this is not compensated for by the transfer case, here the front axle differential 6 . (It may be advisable to lock the front axle differential 6 in order to allocate the same number of revolutions to both wheels and to ensure more even wear of the tires along the circumference.) If the steering angle is negative (to the right) or the reverse gear is selected so that all drive directions of rotation reverse, the processes are reversed in comparison to FIG. 4. In order to avoid the strong erasing of the front wheel 2 , which is approximately transverse to the track tangent, as well as the resulting inhibiting frictional forces, the increased and uneven tire wear and the poor efficiency of this pivoting operation, the left front wheel 2 would have to be turned and driven in the opposite direction to the right front wheel 1 ( see below, embodiment 5, FIG. 9); this even makes it possible to ensure that the front wheels 1, 2 roll on the track circle 11 (or 12 ) without erasing.

Space-saving maneuvering is also possible in this exemplary embodiment 2, in particular parking and parking in the tightest parking spaces or turning on a narrow lane. The track circle 11 has a radius r that is only slightly larger than the wheelbase I (more precisely r = I + b ² / (8 I) , the additional element usually only making up a few percent and can therefore be neglected). If one assumes that the front overhang in a motor vehicle is usually approximately equal to the rear overhang, the approximate law results for this pivoting movement

Turning circle diameter approx. = Vehicle length + wheelbase,

d. H. the turning circle diameter that is used for a 4-5 m long car  usual turns is 10-12 m, is at least 6.5-8 m, at least by a third.

For the transition from normal driving to special maneuvering operation (and / or from parallel shifting operation to turning operation), the nominal torque ratio of the rear axle / front axle / m _hv / in the transfer case can be switched over again, if necessary, as already explained in exemplary embodiment 1, by speed ratio i between The rear and front axles, locking or braking measures or the like are influenced and, if necessary, automatically controlled so that the longitudinal forces F _x or the transverse forces F _{y are} compensated or the motor vehicle only executes the desired parallel displacement, turning or pivoting movements. In the borderline case, it is even possible to cause a vehicle with normal four-wheel or front-wheel drive and normal front-wheel steering to swivel with the bow only by braking measures (see exemplary embodiment 6 at the end of the description).

Embodiment 3 (Motor vehicle with four-wheel drive, with front-wheel or four-wheel steering, right and left wheels driven in opposite directions, Fig. 5)

Another embodiment of the invention is that the longitudinal components F _{x of} the traction forces F _a for the shunting operation according to the invention are compensated by the fact that not the front and rear wheels, but the right and left wheels are driven with different directions of rotation . Fig. 5 shows the example of a motor vehicle with four-wheel drive, in which for this purpose the right wheels 1 and 4 are driven forward, the left wheels 2 and 3 are driven backwards; this is achieved, for example, by means of a reversing gear assigned to the respective differential gear 6 or 7 or integrated therein. If the vehicle has a so-called H-drive has, in which not front wheels 1, 2 and rear wheels 3, 4 are combined to drive units, but instead right wheels 1, 4 and left wheels 2, 3 , so even a single reversing gear for the differential, such. B. integrated into the downforce for the left wheels. The following resulting force and torque amounts result for the traction forces:

Σ F _x = F _a ₁ ((cos δ ₁ - cos δ ₂) - m _hv (cos δ ₃ - cos δ ₄))

Σ F _y = F _a ₁ ((sin δ ₁ - sin δ ₂) - m _hv (sin δ ₃ - sin δ ₄))

M ( 8 ) _tot = F _a ₁ ( b / 2 (cos δ ₁ + cos δ ₂ + m _hv (cos δ ₃ + cos δ ₄))
+ I / 2 (sin δ ₁ - sin δ ₂ + m _hv (sin δ ₃ - sin δ ₄))).

With the same steering angle of the front wheels δ ₁ = δ ₂ = w and the rear wheels ( δ ₃ = δ ₄, the latter remaining anyway with pure front wheel steering, δ ₃ = δ ₄ = 0), both the sum of the longitudinal forces and also for reasons of symmetry of the lateral forces is always zero ( Σ F _x = 0, Σ F _y = 0), and that without requiring a specific torque _ratio m _hv . This torque ratio

m _hv = F _a ₄ / F _a ₁ = F _a ₂ / F _a ₃

is by definition always positive in the present exemplary embodiment because the directions of rotation of the right wheels 1, 4 are both the same and also that of the left wheels 2, 3 are both the same. The torque ratio does not necessarily have to be 1: 1 (m _hv = 1), but it can possibly be a self-locking center differential 5 , e.g. B. a Torsen differential can be used. This would automatically supply more torque to the drive axle (or, in the case of H drives, the drive side) at the lower speed. Without taking this locking effect into account, there is a torque about the vertical axis in the wheelbase center 8 with pure front wheel steering

M ( 8 ) _tot = F _a ₁ b (cos δ + m _hv )

or with symmetrical four-wheel steering (with opposite or opposite steering angles of the front and rear wheels, δ ₁ = δ ₂ = - δ ₃ = - δ ₄ = δ or δ ₁ = δ ₂ = δ ₃ = δ ₄ = δ )

M ( 8 ) _tot = F _a ₁ b cos δ (1 + m _hv ).

This torque can be reduced by turning the front wheels to the left or right (or possibly also the rear wheels), at m _hv = 1 slightly by 10% or 20% in a car with a maximum steering angle of the front wheels δ = 37 °, in contrast, by around 40% or 80% for a bus with a maximum steering angle of the front wheels δ = 79 °. The vehicle then carries out, at least if the latter is about the vertical axis in the center wheel base 8 made in the region of the vehicle center of gravity as shown in Fig. 3, a rotary movement on the spot in a mathematically positive direction of rotation. The centers of the tire contact patches in the case of symmetry describe an approximately common track circle 10 with the track circle radius r . The rotational movement can be influenced by the steering or by braking, preferably only individual drive sides, axles or wheels, possibly using existing ABS components or the handbrake. The tires erase again on the road, the slip angles are calculated as in example 1 (page 18), in the case δ ₁ = δ ₂ = δ ₃ = δ ₄ = 0 they are all the same α = arctan (I / b) . In the limit, if one could implement steering locks up to / δ / → 90 ° with four-wheel steering, the wheels would even erase completely uselessly without the motor vehicle turning. When engaging the reverse gear (reversing all directions of rotation of the drive), there is a high-axis torque in the mathematically negative direction of rotation (clockwise).

In an analysis of the rotational movement, this rotation of the motor vehicle can be seen on the point according to FIG. 5, if the steering deflections δ ₁, δ ₂, δ ₃, δ ₄ ( δ _v = δ _h = 0) are created think as if it were a car with wheels 2 and 3 being the right and left "front" wheels, wheels 1 and 4 being the right and left "rear" wheels. In this fictitious motor vehicle created by cyclically swapping the wheels, the y- axis would in itself be the normal direction of travel, as was already the case in the analysis of the parallel shift operation in FIG. 1 on page 13ff. assumed, and all wheels would then normally be driven "forwards" (in the y direction); here, however, in Fig. 5 the motor vehicle turns on the spot because the "front" wheels 2 and 3 turn from the y direction by approximately 90 ° to the left, the "rear" wheels 1 and 4 from the y direction are turned approx. 90 ° to the right.

Incidentally, this rotary movement is based on a technical principle as described in similarly so far only for vehicles with special ground contact elements (see page 3, penultimate paragraph) or for tracked vehicles appeared practicable, namely if one z. B. the latter by running forward one and at the same time the other track runs backwards on the Would turn the spot. (In fact, with tracked vehicles, one such rotation is usually caused by braking a chain.) Compared to the present invention, however, the crucial ones are missing Features of the exclusive wheel drive (road contact only via rubber tires) and the possibility of influencing and supporting by steering turns of the drive wheels, such as. B. at the next execution example. Appropriate steering locks can be used like the next one Exemplary embodiment shows a multiplication of the high-axis torques and also, under certain conditions, an almost eraser-free one Roll off the tires.  

Embodiment 4 (Cars with four-wheel, front or rear drive, right and left drive wheels driven in opposite directions, right and left wheels as well as front and rear wheels steered in opposite directions, Fig. 6 and analogously to Fig. 9)

. The rotational movement according to Figure 5 can be particularly effective support and influenced when opposing steering angles of the left to the right wheels and simultaneously preferably symmetrical opposing steering of the front and rear wheels realized (δ ₁ = - δ ₂ = δ ₃ = - δ ₄ = δ , Fig. 6). How such steering locks in a relatively simple manner, for. B. can be realized by means of servo-motor tie rod length adjustment is explained below. You get four-wheel drive

Σ F _x = 0

Σ F _y = F _a ₁ (1 - m _hv ) 2 sin δ

M ( 8 ) _tot = F _a ₁ (1 + m _hv ) (b cos δ + I sin δ ).

The resulting lateral force Σ F _y can be made zero by m _hv = 1, it can be kept at least negligibly small, so that there is no significant superimposed parallel displacement movement in the y direction. In comparison to embodiment 3 ( FIG. 5), the high-axis torque M ( 8 ) _total to be achieved with the maximum steering lock w _{max is} by the factor

cos δ _max + (I / b) sin δ _max

larger, e.g. B. in normal cars usually about a factor of 2, in relatively long vehicles such as buses many times larger. In addition, M (8) _ges continuously reduced by opposite (negative) steering angles and steering angles δ = -arctan (I / b) are also made to be zero; M ( 8 ) _ges can also be made negative by means of opposite (negative) steering deflections, so that the direction of rotation of the high-axis rotary movement is reversed without the reverse gear having to be engaged and thus all drive directions of rotation are reversed.

In FIG. 6, the track circle 10 (with the track circle radius r) is entered for the motor vehicle turning on the spot. It can be seen that the slip angles of the tires 1, 2, 3 and 4 are all the same and relatively small in the symmetry case; they amount to

α = arctan (I / b) - / δ / = arccos (b / 2 r) - / δ /

and are therefore below 30 ° in normal cars (with maximum steering angle of e.g. 37 °). However, in vehicles with a relatively small wheelbase or with a very large maximum steering angle as in FIG. 6

/ δ / = arct (I / b) = arccos (b / 2 r) ,

e.g. B. in an omnibus with / δ / = 79 °, I = 5.14 b, even zero. In this case, the intersection lines of the wheel planes with the road surface are tangential to the track circle 10 shown , so that the wheels can really "roll" during the turning process without a large slip angle and the tires hardly rub against the road surface. In this way, e.g. B. the maneuverability of small two-seater city vehicles as well as that of tractor units or buses can be optimized.

The erase-free rolling can also with different amounts of steering steering angles for the front and rear wheels are guaranteed, namely with

/ δ _v / = arctan (I -2 Δ x / b) = arccos (b / 2 r _v )

/ δ _h / = arctan (I +2 Δ x / b) = arccos (b / 2 r _h );

the vehicle vertical axis pivot shifts by the distance Δ x (<0) from the wheelbase center 8 towards the rear axle (point 7 ), and the front wheels then roll on a slightly larger track circle 12 (radius r _v ), the rear wheels on one smaller circle (radius r _h ) around the same fulcrum (see track circle 12 , fulcrum 13 and smaller circle 14 as in Fig. 9, there, however, without steering angles δ _{h of} the rear wheels 3, 4 , which are then at a different point than the fulcrum 7 can also not roll without erasing). In this way, e.g. B. a tractor unit by arranging the pivot in the pivot point 13 so that it can turn on the spot around the pivot without the trailer being moved at the same time; Such an optimal maneuverability would otherwise (with right and left steering directions in the same direction) only feasible with steering angle δ _v of more than ± 90 °.

The turning operation with the front and possibly rear wheels rolling tangentially and without erasure on a circle can also be done in the same way in vehicles only with front-wheel drive (m _hv = 0) or only with rear-wheel drive (m _hv = ∞, F _a ₁ = 0 ) will be realized; in this case, even if F _yh = 0 or F _yv = 0, the wheels will not roll differently than specified by the steering, _i.e. as in Fig. 6 (/ δ _h / = / w _v /) or Fig. 9 ( 0 ≦ / δ _h / </ δ _v /).

The economic feasibility of this embodiment 4 ( Fig. 6-9) and the following embodiment 5 ( Fig. 9) and the possible variants depends on the fact that for the maneuvering operation according to the invention with little effort opposite steering locks of the right and left wheel each drive axis can be realized. The easiest way to do this is to use a servo-motor tie rod length adjustment. If it is, for example, a front wheel steering with split tie rods, two preferably coaxial rod-shaped parts which fit into one another for the purpose of positive guidance are integrated into these tie rods, namely, for. B.

• 1. a hollow rod and
• 2. a sliding rod or the like guided therein,

one part of which is a rack and the other is a rack an electric or hydraulic servomotor driven pinion contains. By driving the pinion, the effective length of the concerned can two-piece tie rod extended, later by driving the pinion with reverse direction of rotation can be shortened again. After switching to the shunting operation according to the invention runs - preferably regardless of the previous starting position of the steering - until an end contact z. B. on the steering knuckle reports that the wheel in question has reached predetermined steering angle; after switching off the In special shunting operations, the drive runs in the opposite direction long until a stop contact z. B. reports on the tie rod that this back to normal length and steering back to its previous starting point has reached position.

This servo-motor tie rod length adjustment only takes place when the vehicle is at a standstill or at most at creeping speeds or low maneuvering speeds; it therefore does not cause any noteworthy safety problems, provided effective measures have been taken to prevent unintentional operation during normal driving. It allows you to generate certain steering angles, if necessary. B. - regardless of the indispensable steering differential angles in normal driving - exactly the same or opposite steering angle for right and left wheels of a drive axle. It can also be used for the rear wheel steering ( Fig. 1-3, 6-9) as well as in all other embodiments of the invention as a steering aid for the front wheels as well, to relieve the driver of the need to operate even those required for maneuvering according to the invention To produce steering locks.

Continued Execution example 4th (Motor vehicle with four-wheel drive, right and left wheels driven in opposite directions and steered in opposite directions, front and rear wheels steered in the same direction, Fig. 7 and 8)

. The rotational movement according to Figure 6 may Example also suppressed in a variant of this execution, and instead be a parallel displacement generates motion when the steering deflections of the rear wheels are not selected in the opposite direction to the front wheels, but the same direction as these: δ ₁ = - δ ₂ = - w ₃ = δ ₄ = δ ( Fig. 7). In this case of symmetrical (front and rear same, right and left but opposite directions) steering turns

Σ F _x = 0

Σ F _y = F _a ₁ (1 + m _hv ) 2 sin δ

M ( 8 ) _tot = F _a ₁ (b (1 + m _hv ) cos δ + I (1 - m _hv ) sin δ ).

If one does not relate the high-axis torque M _tot to the wheelbase center 8 , but to the point of application 9 of the resultant transverse force Σ F _y , which lies from point 8 by the distance Δ x on the connecting line between points 6 and 7 , this changes Torque compared to M ( 8 ) _total by the value

Δ M _tot = - F _a ₁ Δ x 2 (1 + m _hv ) sin δ .

Since the vertical axis torque must be zero at the actual point of application of the transverse force Σ F _y = F _Ages , the position of this point of application can be calculated from this. If m _hv = 1, this point of attack is at Δ x = b / (2 tan δ ), that is, in the case of Δ x <0 (δ <0), this distance from the wheelbase center 8 is shifted towards the front axle point 6 , however, in the case of Δ x <0, δ <0) in the direction of the rear axle point 7 pushed ver. If m _hv deviates from 1, we get with

Δ x = b / (2 tan δ ) - ( m _hv - 1 / m _hv + 1) I / 2

an additional shift towards the rear axle. The torque ratio m _hv , which may be selected by switching for the rotary operation according to the invention, can be coordinated with the associated steering angle δ depending on its sign (and possibly depending on the engaged forward or reverse gear) so that the point of attack 9 alone remaining transverse force resultant Σ F _{y is} approximately shifted to the expected center of gravity of the vehicle and the vertical axis torque there becomes zero.

While δ <0 was assumed in Fig. 7 and a parallel displacement movement of the motor vehicle to the left was achieved, there is a parallel displacement movement to the right when reverse gear is engaged and all drive directions are reversed ( Fig. 8) or when all steering locks are reversed.

Because of the center of gravity, it may be useful, for. B. a motor vehicle equipped for the turning operation according to FIG. 5 or 6 does not have the parallel displacement operation according to FIG. 7 or 8 described above carried out, but instead the one according to FIGS. 1 and 2 (or vice versa one for the turning operation according to FIG. 3 equipped motor vehicle instead of the parallel shift operation according to FIGS. 1 and 2 the one according to FIGS. 7 and 8). In such cases it would be necessary to be able to reverse the direction of rotation of the rear wheels (or the front wheels) or the left wheels (or the right wheels). For this you could use 3 switchable reversing gears and these z. B. either assign the rear axle drive and the drive shafts of the two left wheels or z. B. the drive waves of the two rear wheels and the left front wheel, for vehicles with H-drive z. B. either the drive for the left wheels and the drive shaft of the rear wheels or z. B. the drive shafts of the two left wheels and the right rear wheel. Ideal for this purpose, but very expensive, would be a switchover from normal four-wheel drive to H-drive; in this case, 1 or at most 2 reversing gears would suffice for the application of the invention.

In the case of electric vehicles with wheel drive motors for the individual wheels, for example with 4 electric wheel hub inner pole motors, the effort for the reversing gear could be reduced. U. be reduced to simple polarity reversal switches. These separately switchable polarity reversal options would then in principle - but only with regard to engine switching - enable the special shunting operation according to the invention, e.g. B. to drive the left wheels in the opposite direction of rotation to the right wheels. With the mere possibility or with the actual implementation of a correspondingly suitable polarity reversal circuit, if such a thing should have existed at some point, the present invention with its special objectives for parking and maneuvering normal road vehicles would not yet be possible mechanical engine anticipated. The maneuvering operation carried out according to the invention includes other decisive features, including the generation of very specific, e.g. T. opposite steering deflections of all drive wheels if possible and their targeted coordination either with the torque ratio (e.g. targeted compensation of all longitudinal forces Σ F _x = 0) or with the wheelbase-track width ratio (ensuring tangential rolling of the wheels on the track circle when turning on the spot).

There are also other simplified variants of embodiment 4 possible. For example, the right and left drive wheels can be used driven in different directions, but only the front Wheels are steered. This simplified procedure is u. a. also for motor vehicles only applicable with front-wheel drive:

Embodiment 5 (Cars with four-wheel or front-wheel drive, right and left front wheels driven in opposite directions and steered in opposite directions, right and left rear wheels without steering, but possibly driven in opposite directions, Fig. 9)

If in a motor vehicle with four-wheel or front-wheel drive only the front wheels 1, 2 are steered in opposite directions and driven with different directions of rotation, then again there are pivoting movements of the motor vehicle with the front wheels on a track circle 12 (with the radius r _v ) around a pivot point 13 ( FIG . 9). If it is a motor vehicle with four-wheel drive and the rear axle is also driven in special maneuvering, an additional high-axis torque of the rear wheels occurs and changes the position of the pivot point 13 depending on the torque _ratio m _hv , i.e. this pivot point 13 becomes with an increasing torque ratio m _hv shifted from point 7 in the direction of point 8 , so that it lies a distance Δ x (<0) from the wheelbase center 8 . Characterized the radius is r _v of the tracking circuit 12 of the front wheels even smaller than, for example, the radius of the track circle 11 in Fig. 4. While lie in a motor vehicle with pure front wheel drive of the pivot point 13 in the Hinterachsmittelpunkt 7 (Fig. 4, Δ x = -I / 2), it will lie in the limit of a motor vehicle with four-wheel drive and symmetrical four-wheel steering (m _hv = 1) in the wheelbase center 8 ( Fig. 6, Δ x = 0). (The calculation corresponds to that of point 9 in exemplary embodiment 4, FIG. 7, except that here the steering angle of the rear wheels may have to be set at δ _h = 0.)

In vehicles with a relatively short wheelbase I or when using a relatively large maximum steering angle / δ _v / = arccos (b / 2 r _v ), it is possible, as in exemplary embodiment 4, for the tires of the front wheels 1, 2 to also have a slip angle α _v = 0 , i.e. without significant erasing on the road surface, rolling tangentially to the track circle 12 (radius r _v ). The rear wheels would move depending on the slip angle α _h = / α ₃ / = / α ₄ / = arccos (b / 2 r _h ) more or less erasing on a concentric smaller circle 14 (radius r _h ) around the same pivot point 13 . (In order to allow the rear wheels to roll off completely radially, in addition to the front wheels, one would have to provide at least one additional rear wheel steering with suitably selected smaller steering angle w _h , as described for example 4, see page 34 above.)

This embodiment of the invention can, for. B. with front-wheel drive by means of a servo-motor tie rod length adjustment (see above page 35) and by means of a reversing gear integrated in the differential 6 z. B. can be realized for the left front wheel 2 . If the rear wheels are also to be driven in a motor vehicle with four-wheel drive during rotary operation (with or without the mentioned rear wheel additional steering), then a further reversing gear can be integrated into the differential 7 for the left rear wheel 3 ; the center differential 5 then compensates for the different cycle paths of the rear and front wheels.

Numerous other embodiments are possible. For the application of the Invention is like the above embodiment 5 and also that The following embodiment 6 show, by no means all-wheel drive and also not all-wheel steering requirement. With front-wheel drive and front wheel steering alone limits the additional effort in terms of weight for the application of the invention to a few thousandths of the vehicle empty weighted and is compared to other maneuvering and parking aids that afford with additional wheels or the like, minimal.  

Embodiment 6 (Cars with four-wheel or front-wheel drive and front-wheel steering, blocking option for the drive shaft of the rear wheels or for rear wheels)

The following particularly greatly simplified variant, derived from exemplary embodiment 2, is - in the case of normal frictional relationships between tires and road surface - less effective in terms of reducing the turning circle diameter than all other exemplary embodiments, but does not require a specific and also negative torque _ratio m _hv , So there is no reversal of the direction of rotation of the rear axle for the special shunting operation, nor are there any measures for the steering system.

In an all-wheel drive motor vehicle, the opposite drive of the rear wheels 3, 4 for the special shunting operation can be replaced in that the entire rear axle is completely "braked" by z. B. blocked the drive shaft from the center differential 5 to the rear axle differential 7 . The prerequisite here is, of course, that the engine and transmission parts involved are able to withstand the stresses of such transmission braking. Due to this blocking of the rear axle drive, the drive torque is now allocated by the transfer case 5 to the front wheels 1, 2 , the longitudinal forces F _x are partially compensated for by the fact that the normal rear wheel drive (m _hv <0) is omitted and thus only propulsion-inhibiting static or sliding friction forces Rear wheels 3, 4 appear.

The balance between the two rear wheels 3, 4 remains ensured via the rear axle differential 7 ; the transition from static friction to sliding friction occurs only for one of the wheels. (By locking the rear axle differential 7 , the locking can be extended to both wheels at any time.) Because of the remaining side forces F _{yv of} the front drive, which is only effective, the motor vehicle _swivels with the bow to the left about the rear axle. Because of the incomplete compensation of the longitudinal forces F _x , with at least one of the rear wheels starting to slide to a significant extent, a slight longitudinal movement in the respective x direction remains superimposed on this pivoting movement. As a result, the radius of the track circle 11 is somewhat larger than the wheelbase, and is comparatively somewhat larger than in the method according to FIG. 4; at the same time, the turning circle diameter, especially in good static friction conditions between the rear tire and the road surface, remains significantly smaller than in normal driving and maneuvering.

In principle, roughly the same effect, but without the possibility of compensating between the two rear wheels 3, 4 , can be achieved with a front drive motor vehicle if one firmly applies a handbrake acting on the rear wheels and in this or other way - possibly also through the use of ABS components, if applicable - the rear wheels 3, 4 blocked: When turning the steering wheel z. B. strongly to the left, the vehicle with blocked rear wheels would then describe a slightly narrower curve to the left when starting slowly than it corresponds to the normal turning circle. This effect comes about because the longitudinal forces F _{xv of} the front wheels 1, 2 counteract the frictional forces of the blocking rear wheels 3, 4 , so that the side forces F _yv generated by the front wheels being _driven dominate. However, the F _x components are only compensated for to an even smaller extent, the static friction of the blocking rear wheels changes into sliding friction (unless, for example, a wheel chock is also used for at least one of the rear wheels, see below).

The method shown above of a "static" Incidentally, cornering with at least one blocked rear wheel is not anticipated by certain people known from rallying "Dynamic" method of hand brake application in the curve. Is known e.g. B. that rally drivers with all-wheel-drive vehicles in a spike Hairpin curve like to jerkily apply the handbrake to the vehicle force faster in the opposite direction. Or in security trainings will B. recommended for emergency braking, in certain critical Situations if necessary by actuating the handbrake and Tearing the steering an energy-consuming rotary motion of the Initiate vehicle. Such handbrake effects are based on the elimination the cornering forces with blocking rear wheels, but not on one Compensation of the longitudinal components of the driving forces and therefore have nothing to do with the general inventive idea here.  

In order to ensure the maximum possible coefficient of adhesion for braking or blocking a rear wheel and thus to reduce the turning circle diameter to a minimum, namely approx. Vehicle length + wheelbase, one can - preferably as a makeshift for vehicles that are not equipped for maneuvering according to the invention - also use the following procedure: For a swiveling movement of the vehicle bow to the left, the left rear wheel 3 is preferably locked approximately stationary by a wheel claw attached to this wheel, which surrounds the tire in a U-shape at one point, or by a wheel chock or the like 3 prevented from rolling forward and will continue to describe a small circle on the road around the obstacle (wheel claw, wheel chock or the like) with the tire contact area of the locked rear wheel during the further turning process. The wheel claw or wheel chock can consist, for example, of a lower part adhering to the road surface under load and an upper part rotatable thereon for receiving the tire; They are shaped for the purpose mentioned so that even when the vehicle bow is pivoted in the course of the turning process (up to at least 90 °, possibly up to 180 °), the rear tire always remains locked without being damaged until - after a slight reset of the vehicle - the Wheel claw or the wheel chock can be removed again.

Claims (23)

1. the parked and maneuvering aid for motor vehicles comprising at least two steerable driving wheels, and associated mechanical transmission-steering system as in the following:
While the chassis, wheels and tires of the vehicle are designed conventionally without a special parking or maneuvering aid, a special shunting mode for particularly flexible parking and maneuvering in a confined space is essentially achieved by switching (s) in the mechanical drive (transmission) system enabled by switching through these
either the drive axles, e.g. B. the front and rear axles,
or the drive wheels on the right and left
are driven according to the invention in different directions of rotation, namely the front axle and possibly the rear axle, preferably with the torque ratio selected in this way,
firstly, that all traction force components in the direction of the vehicle's longitudinal axis cancel each other out (sum of all longitudinal forces = 0) and longitudinal movements of the vehicle are suppressed,
and that, secondly, preferably if at the same time certain steering directions in the same direction or in opposite directions are generated, the traction forces which remain effective on the drive wheels and do not cancel out in the overall effect on the motor vehicle
either as transverse forces (transversely to the longitudinal axis of the vehicle) all point in one direction and thereby cause a lateral parallel displacement movement of the vehicle (exemplary embodiments: FIGS. 1, 2, 7 or 8),
or preferably point as transverse forces in opposite directions and thereby cause the motor vehicle to rotate on the spot about a vertical axis (exemplary embodiments: FIGS. 3, 6),
with different directions of rotation of the right and left wheels, even without steering locks, point as longitudinal forces in opposite directions and thereby also cause the motor vehicle to turn on the spot ( FIG. 5),
or as differently large forces on the front and rear axles simultaneously effect parallel displacement and rotation of the motor vehicle, so that a pivoting movement preferably takes place with the vehicle bow (exemplary embodiments: FIGS. 4 and 9). 2. Parking and maneuvering aid according to claim 1, preferably for motor vehicles with four-wheel drive and steering, and the associated transmission and steering system, characterized as follows:
If necessary - for the special shunting operation according to claim 1 - the front wheels ( 1 ), ( 2 ) with respect to the rear wheels ( 3 ), ( 4 ) are driven in opposite directions, ie with the opposite direction of rotation, and to generate the necessary lateral forces
either the rear wheels turned in opposite directions to the front wheels, so that the motor vehicle performs more or less only lateral parallel displacement movements transversely to its longitudinal axis, to the left ( FIG. 1) or to the right ( FIG. 2) depending on whether the front wheels ( 1 ) , ( 2 ) to the left or to the right and the rear wheels ( 3 ), ( 4 ) are turned in opposite directions and whether a forward gear ( FIGS. 1 and 2) or a reverse gear is engaged,
or the front and rear wheels are turned in the same direction, so that the motor vehicle performs approximately a rotational movement on the spot in a mathematically positive ( FIG. 3) or negative rotational direction about a vertical axis, but at least a pivoting movement preferably with the vehicle bow, depending on whether the wheels ( 1 ), ( 2 ), ( 3 ), ( 4 ) are all turned to the left ( Fig. 3) or to the right and whether a forward gear ( Fig. 3) or reverse gear is engaged. 3. Transmission system according to claim 2, preferably for four-wheel drive motor vehicles, characterized as follows:
For the intended reversal of the direction of rotation of an axis, a reversing gear is provided, either integrated in the transfer case or center differential ( 5 ) or in addition to this gear ( 5 ), while instead in vehicles with so-called. H-drive, in which the right and left wheels are combined to form drive units, separate reversing gears are provided for both rear wheels ( 3 ), ( 4 ). 4. Transmission and steering system according to claim 2, characterized as follows:
If necessary, four-wheel steering with a steering angle ratio of rear wheels / front wheels of 1: 1 and accordingly four-wheel drive with a torque distribution of rear axle / front axle of 1: 1 is used for the special maneuvering operation according to claim 1. 5. Transmission and steering system according to claim 2, characterized as follows:
If necessary - for the special shunting operation according to claim 1 - the torque ratio of the rear axle / front axle is made correspondingly smaller in the case of a stronger steering lock for the front wheels than for the rear wheels, so that the motor vehicle can carry out the movements provided for in claim 2. 6. Transmission and steering system according to claim 2, characterized as follows:
The torque ratio of the rear axle / front axle is made switchable, e.g. B. according to the known model by a correspondingly designed transfer case ( 5 ), preferably by a planetary gear, with switchable load distribution on the rear and front axles, whereby the motor vehicle if necessary - in the special shunting mode according to claim 1 - with certain steering locks provided according to claim 2 Can perform movements. 7. Transmission system according to claim 2, characterized as follows:
The torque ratio of the rear axle / front axle is kept continuously variable by a corresponding design of the transfer case ( 5 ) according to the known model and is controlled if necessary - for the special shunting operation according to claim 1 or certain variants thereof - so that the motor vehicle performs the movements provided for in claim 2 can perform. 8. Transmission system according to claim 1, 2, 3 or 7, characterized as follows:
If necessary - for the special shunting operation according to claim 1 - the center differential of the transfer case ( 5 ) is completely or partially locked and / or a speed ratio ratio deviating in magnitude from 1: 1 is set for the reversing gear so that the longitudinal forces essentially cancel each other out and thereby Suppression of vehicle movements in the longitudinal direction is guaranteed. 9. Transmission and steering system according to claim 2, preferably for motor vehicles with four-wheel drive and front wheel steering, characterized as follows:
If necessary, only the front wheels ( 1 ), ( 2 ) are turned in - for the special maneuvering operation according to claim 1 - and the torque ratio rear axle / front axle selected so that the longitudinal forces cancel each other out at the intended steering angle,
so that the front axle depending on whether the front wheels are turned to the left or right and depending on whether a forward or reverse gear is engaged, is pulled to the left ( Fig. 4) or right and the vehicle thereby a corresponding swiveling movement with the vehicle bow executes, in which the front wheels ( 1 ), ( 2 ) are moved on a track circle ( 11 ) around the rear axle center ( 7 ). 10. Parking and maneuvering aid according to claim 1, preferably for motor vehicles with four-wheel drive and the associated transmission and steering system, characterized as follows:
If necessary - for the special shunting operation according to claim 1 - the left and right drive wheels are driven with opposite directions of rotation, for. B. in four-wheel drive motor vehicles, the right drive wheels ( 1, 4 ) forward, the left drive wheels ( 2, 3 ) backwards ( Fig. 5), so that preferably the sum of all longitudinal components and the sum of all transverse components of the traction forces are compensated and the motor vehicle then, depending on the support, braking or any other influence by the front wheels ( 1, 2 ) and possibly the rear wheels ( 3, 4 ), it rotates or swivels in the mathematically positive direction of rotation (counterclockwise). 11. Parking and maneuvering aid according to claim 10 and associated steering system, characterized as follows:
The steered wheels are not turned in the same direction as in normal steering, but are provided with opposite steering angles to support and influence the rotary movement, e.g. B. the right front wheel ( 1 ) is turned to the left, the left front wheel ( 2 ) is turned to the right,
in addition, if necessary, the rear wheels, if they are also steered, are steered in opposite directions to the front wheels, e.g. B. the left rear wheel ( 3 ) is turned to the left, the right rear wheel ( 4 ) to the right, so that there is approximately a pure rotary movement on the spot ( Fig. 6),
or instead, the steered rear wheels are not steered in opposite directions, but in the same direction with the front wheels, namely z. B. the left rear wheel ( 3 ) like the left front wheel ( 2 ) is turned to the right, the right rear wheel ( 4 ) like the right front wheel ( 1 ) is turned to the left, so that the vehicle z. B. instead of a rotary movement in the mathematically positive sense of rotation approximately a parallel displacement movement to the left ( Fig. 7) (or to the right if all drive directions of rotation ( Fig. 8) or all steering angles are reversed). 12. Parking and maneuvering aid according to claim 11, preferably for motor vehicles with four-wheel steering with a relatively short wheelbase or large maximum front-wheel steering angle, and the associated steering system, characterized as follows:
For the special turning operation on the spot according to claim 1, 2 or 11 with opposite steering angles of the right and left front wheels and opposite steering angles of the front wheels and the rear wheels, the steering angle of the drive wheels are calculated according to the formula / δ / = arccos (track width / 2 × Track circle radius) selected so that all four drive wheels on the common track circle ( 10 ) ( Fig. 6) or the front and rear wheels on different track circles ( 12 ) and ( 14 ) ( Fig. 9) approximately tangential, ie without slip angle and can roll off without significant tire erasing. 13. Transmission system according to claim 10, 11 or 12, preferably for four-wheel drive motor vehicles, characterized as follows:
To generate the reversal of direction z. B. for the left drive wheels, a reversing gear is used, which is preferably integrated into the associated axle differential, while in vehicles with H drive, a reversing gear is used instead, which is integrated at the center differential in the output for the left wheels. 14. Parking and maneuvering aid according to claim 10-13, preferably for motor vehicles with front-wheel drive and front wheel steering, and associated transmission and steering system, characterized as follows:
By a reverse gear z. B. for the left front wheel ( 2 ) this - for the special swivel operation (rotating operation) according to claim 1, 10 or 11 - driven backwards, while the right front wheel ( 1 ) is driven forward, and an opposing steering angle is generated (right Front wheel ( 1 ) to the left, left front wheel ( 2 ) turned to the right), so that the vehicle swivels with the bow to the left around the pivot point ( 13 ) (between the rear axle center ( 7 ) and the wheelbase center ( 8 )) with the track circle ( 12 ) ( Fig. 9) executes (or to the right if the drive directions of rotation or the steering locks of the front wheels are reversed), wherein if the vehicle has four-wheel drive, z. B. the left rear wheel forward, the right rear wheel can be driven backwards, so that the radius r _{v of} the track circle ( 12 ) of the front wheels may be smaller than the wheelbase by the resulting additional high-axis torque. 15. Parking and maneuvering aid according to claim 14, preferably for motor vehicles with front-wheel drive and front-wheel steering with a relatively short wheelbase or large maximum steering angle, and the associated steering system, characterized as follows:
For the special swivel operation (turning operation) according to claim 1, 11 or 14 with opposing steering angles of the right and left front wheels ( 1 ), ( 2 ) ( Fig. 9), the steering angle according to the amount according to the formula / α / = arccos (track width / (2 × track circle radius)) selected so that the front wheels can roll approximately tangentially on a track circle ( 12 ) around the pivot point ( 13 ) without slip angle and without significant tire erasing. Any additional rear wheel steering system is preferably designed so that the rear wheels can also roll approximately tangentially on a correspondingly smaller circle around the same pivot point ( 13 ). 16. Parking and maneuvering aid according to claim 1, 2, 10-13 and associated transmission system, characterized as follows:
The transmission system is equipped with, for example, a total of up to 3 reversing gearboxes for reversing the direction of rotation, optionally of the rear wheels (or the front wheels) or the left wheels (or right wheels) so that, for. B. parallel displacement movements of the motor vehicle preferably according to claim 2 or z. B. rotations of the motor vehicle preferably according to claim 10-12 (or conversely rotations according to claim 2 and parallel displacement movements according to claim 11) can take place; the 3 selectable reversing gearboxes are z. B. either the rear axle drive and the drive shafts of the two left wheels or z. B. assigned to the drive shafts of the two rear wheels and the left front wheel, for vehicles with H-drive z. B. either the drive for the left wheels and the drive shafts of the rear wheels or z. B. the drive shafts of the two left wheels and the right rear wheel, while with the option of switching from normal four-wheel drive to H-drive 1 or 2 reversing gear are sufficient. 17. Transmission system according to claims 1-15, characterized as follows:
A self-locking transmission is used as the center differential ( 5 ), e.g. B. a Torsen differential, or a transmission with automatically preferably controlled by wheel sensors lock, z. B. with electronically-hydraulically controlled multi-plate lock to distribute the driving forces on the front and rear axles for the special shunting operation according to claim 1 so that longitudinal movements of the motor vehicle are avoided or - in motor vehicles with H-drive and self-locking center differential or the like - transverse movements of the vehicle. 18. Parking and maneuvering aid according to claims 1-17 and associated transmission system, characterized as follows:
The special maneuvering operation according to claim 1 is carried out in the more strongly geared reverse gear, or in an additional, particularly strongly geared forward and reverse gear. 19. Steering device according to claim 12-13 or steering system and steering aid according to claim 1-18, characterized as follows:
To achieve a certain, possibly also opposite steering angle of the wheels of an axle, the steering-geometrically effective length of the tie rods (or at least one tie rod) is lengthened and shortened again by electric or hydraulic servomotors, for which purpose in this tie rod (n each) z. B. two preferably coaxial, for the purpose of positive guidance fit into each other rod-shaped parts, namely a hollow rod and a guided therein, displaceable rod or the like. Each of which contains a rack and the other a pinion driven by an electric or hydraulic servo motor . 20. Steering device or steering aid with servo-motor tie rod length adjustment according to claim 19, characterized as follows:
The servomotor drive of the pinion runs - preferably regardless of the previous starting position of the steering - until an end contact z. B. on the steering knuckle reports that the wheel in question has reached the predetermined steering angle; later the drive runs in the opposite direction until a stop contact z. B. on the tie rod reports that it has returned to its normal length and the steering has returned to its previous starting position. 21. Parking and maneuvering method analogous to claim 1 or 2, preferably for motor vehicles with front wheel steering and with front or four-wheel drive, and associated transmission, steering and braking system, characterized as follows:
If necessary - for the special maneuvering operation analogous to claim 1 - at least one rear wheel or each of the rear wheels ( 3 ), ( 4 ) or, in the case of vehicles with four-wheel drive, the drive shaft for the rear wheels ( 3 ), ( 4 ) braked or blocked in order to at least partially compensate for the longitudinal forces, so that when starting with the maximum set front wheels, a swiveling movement of the vehicle with the vehicle bow around the braked or blocked rear axle is possible. 22. Parking and maneuvering method according to claim 21, and associated wheel claw or wheel chock for blocking a rear wheel, characterized as follows:
In order to reduce the turning circle diameter, one of the rear wheels is locked approximately stationary, ie prevented from rolling forward, preferably by means of a wheel attached to this wheel, preferably as a makeshift on vehicles which are not equipped for the maneuvering operation according to the invention, for the duration of the turning maneuver a location of a U-shaped wheel claw or by means of a wheel chock, so that the motor vehicle is pivoted in the course of the turning maneuver preferably around the lower part of the wheel claw or wheel chock adhering to the road surface as a fulcrum. 23. Parking and maneuvering aid analogous to claim 1 or 2 and associated mechanical transmission and steering system, characterized as follows:
Only a steerable drive wheel is used, e.g. B. in a 3-wheel vehicle only a steerable, arranged in the middle front drive wheel.