Abstract:
A method for turning at least one steerable wheel of a motor vehicle during parking on a longitudinal inclination of a roadway, having the following steps: activating a parking brake of the motor vehicle, ascertaining the inclination angle of the vehicle inclination that is effected by the longitudinal inclination of a roadway, turning the steerable wheel to achieve a wheel angle as a function of at least one specifiable and/or ascertained parameter. It is provided that the setting of the magnitude of the wheel angle take place as a function of at least one surroundings situation of the motor vehicle, ascertained using at least one sensor. Furthermore, a device for turning at least one steerable wheel of a motor vehicle during parking on a longitudinal roadway inclination, particularly for executing the method, which cooperates with a parking brake, an inclination angle sensor and a steering device of the motor vehicle, a surroundings recording device being provided having at least one sensor for recording the immediate surroundings of the motor vehicle.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method for turning at least one steerable wheel of a motor vehicle when parking on a longitudinal inclination of a roadway. The present invention also relates to a device directed towards this, especially for carrying out the method. 
       BACKGROUND INFORMATION 
       [0002]    The parking of motor vehicles on longitudinally inclined roadways requires particular circumspection on the part of the driver, in order to secure the motor vehicle against unintended rolling away in the direction of the longitudinal inclination of the roadway. 
         [0003]    A method for warning the driver, during the parking of the motor vehicle on a longitudinally inclined roadway, is described in German Patent No. DE 10 2004 050 052, which reminds the driver to secure his motor vehicle if he forgets, when parking the vehicle on a longitudinally inclined roadway, to set a wheel angle that will prevent the unintended rolling away of the motor vehicle. The method provided in that document steers the attention of the driver to the necessity of securing against rolling away, that is still to be undertaken. It is true that an active action of the driver is required for this, namely, indeed, undertaking the securing, particularly by setting the suitable wheel angle/steering angle. It is optionally provided to have the wheel angle corrected or set with the aid of the roadway inclination ascertained, for instance, by a parking assistant function, which acts upon the steering of the motor vehicle. In unfavorable cases, however, these measures are insufficient for effecting sufficient securing of the motor vehicle against unintended rolling away. 
       SUMMARY OF THE INVENTION 
       [0004]    The method according to the present invention makes possible, in a far more inclusive manner, the secure parking of motor vehicles on a longitudinally inclined roadway, and in doing so, takes into account the different circumstances of the most varied surroundings conditions, in the most inclusive manner. 
         [0005]    For this purpose, a method is provided for turning at least one steerable wheel of a motor vehicle during parking on a longitudinal inclination of a roadway, having the following steps:
       activating a parking brake of the motor vehicle,   ascertaining an angle of inclination of a vehicle inclination that is effected by the longitudinal inclination of the roadway,   turning the steerable wheel to achieve a wheel angle as a function of at least one specifiable and/or ascertained parameter.       
 
         [0009]    It is provided that the setting of the magnitude of the wheel angle take place as a function of at least one surroundings situation of the motor vehicle, ascertained using at least one sensor, in this context. Accordingly, the motor vehicle is parked and the parking brake of the motor vehicle is activated. By parking brake one should understand, in this case, any form of braking device that; in the parked state, is intended to prevent the vehicle from rolling away, by the action of braking devices of the motor vehicle, such as brake disks or brake drums, that is, parking brakes or hand brakes. The activation of the parking brake, in this instance, may be performed by the driver or by an independent system that is completely configured by the driver, for example, a Key-off Apply or a Hill Hold Control. Thereupon the angle of inclination is ascertained, which the vehicle assumes (vehicle inclination), and which is effected by parking along the longitudinally inclined roadway (in the driving direction or the opposite direction). The magnitude of the angle of inclination enables making predictions with respect to the force acting on the motor vehicle that would favor the rolling away of the motor vehicle. There then follows the turning of the steerable wheel (of course, a plurality of steerable wheels could also be steered), and this taking place as a function of at least one specifiable and/or ascertained parameter. The manner in which the at least one steerable wheel is steered thus depends on at least one parameter. The wheel angle is not always the same, but it is ascertained as a function of the at least one parameter. 
         [0010]    For this purpose, the surroundings situation of the motor vehicle is ascertained by at least one sensor. By surroundings situation one should understand, in this instance, the direct surroundings of the motor vehicle, in the widest meaning of the term. For example, one may ascertain whether there are obstacles, for instance, other motor vehicles, in front of, or behind the motor vehicle, particularly in the direction of the longitudinal inclination (downhill gradient). For, when the vehicle starts to roll, the avoidance of which is the purpose of the method, the turned steering angle is not only supposed to prevent the rolling away of the motor vehicle, but preferably also to prevent the motor vehicle from rolling into an obstacle, such as a motor vehicle parked ahead of it, and damaging it. The wheel angle is always selected, in this instance, in such a way that rolling away of the motor vehicle, especially onto the roadway, is avoided in the same way as an undesired rolling of the motor vehicle into obstacles which could lead to damage. 
         [0011]    In one preferred method development, during the ascertainment of the surroundings situation, it is detected whether a curb is present. Curbs are very suitable for avoiding the rolling away of the motor vehicle, by selecting the wheel angle so that at least one steerable wheel of the motor vehicle strikes against the curb already during the parking of the motor vehicle, or else in that a vehicle starting to roll, whose parking brake is not sufficiently effective, is braked by the curb that the turned, steerable wheel is running into. 
         [0012]    In one preferred method development, during the ascertainment of the surroundings situation, it is detected how high the curb is. The height of the curb above the roadway level permits a judgment of the question as to whether the curb, for instance, at a given wheel diameter of the motor vehicle, is able effectively to prevent its rolling away. In the case of very large wheel diameters, it is required that the curb have a certain minimum height, since the steerable wheel would otherwise roll beyond the curb, in response to sufficient energy of motion of the vehicle that is starting to roll, provided the curb is hit at a certain angle. The wheel angle that is necessary effectively to avoid the rolling away of the motor vehicle is accordingly set as a function also of the height of the curb and, for instance, the wheel diameter of the steerable wheel. The wheel diameter, in this instance, may be taken from a look-up table stored in a device of the motor vehicle. In order to take into account safety interests, it is preferred to assume the largest possible wheel diameter that is admissible for the vehicle, provided another wheel diameter, corresponding to the mounted wheel, is not specified in a dedicated manner. 
         [0013]    In one additional preferred specific embodiment, it is detected, during the ascertaining of the surroundings situation, how far the vehicle is laterally distant from the curb. In the regular case, one assumes that the vehicle is parked essentially parallel to the roadway edge of the longitudinally inclined roadway. As a function of the lateral distance from the curb, the motor vehicle is able to cover a differently long path if it starts to roll based on the failure or insufficient holding force of the parking brake. The longer this path is, that the vehicle is able to cover before reaching the curb, the larger is the energy of motion attained, which, in the case of a given wheel diameter, is able to lead to riding over the curb at a certain wheel angle. For this reason, in determining the wheel angle while ascertaining the surroundings situation, the lateral distance of the vehicle from the curb is taken into account, and the wheel angle that is to be selected for the situation that is found, is adjusted. 
         [0014]    In a further preferred specific embodiment, while ascertaining the surroundings situation, it is detected what the diameter is of the wheel of the vehicle facing the curb. As was described before, in that way one is able to ascertain in that manner the wheel angle at which most favorably the rolling over the curb can be avoided, which is used as the path limiter for the vehicle that may perhaps start to roll. The detection of the wheel diameter takes place, in this instance, with the aid of the actually mounted wheels, and not from values stored in a table, for example. This is made possible, for example, by clear communication means between the wheel and the motor vehicle, perhaps by contact-giving alignments, message transfer means, such as RFID chips mounted on the wheels and corresponding receivers on the motor vehicle, or other devices making possible unequivocal signaling. In this way it is ensured that the wheel angle, ascertained as being favorable, constantly takes into account the actually given, constructional specifications of the vehicle. In particular, when wheels are changed, for instance, from summer to winter wheels, which frequently have a lower diameter than summer wheels, the favorable wheel angle is thus ascertained newly and reliably, in an advantageous manner. 
         [0015]    In one additional advantageous specific embodiment, it is detected, during the ascertaining of the surroundings situation, on which side of the vehicle the curb is located. A safer functioning of the method is thereby even ensured if the vehicle parks counter to the travel direction, and the curb expected by the system is thus found to be on the other than the usual side of the vehicle, for example, on the left in countries having right-hand traffic or right in countries having left-hand traffic. In a very advantageous manner, one may take into account the actual surroundings of the vehicle, and safer parking may be ensured even in uncommon parking situations. 
         [0016]    In another particularly preferred method development, when no curb is detected during the ascertainment of the surroundings situation, the steerable wheel is turned into a wheel angle of specified magnitude and direction, which prevents the rolling of the vehicle onto the roadway. This angle is preferably an angle such that it effects a (possible) start of rolling of the vehicle to the roadway edge, that is, in such a way that the vehicle cannot roll into the roadway, or which prevents the starting to roll at the angle of inclination found, for example, by extreme transverse positioning. In this instance, the wheel angle preferably has such a magnitude that, for the starting to roll of the vehicle, considerable force would have to be afforded, that is, the longitudinal inclination of a roadway would have to be considerable. In the overwhelming majority of all parking and stopping situations of a motor vehicle, one is thus able to effect safe parking and sufficient assurance against rolling away. 
         [0017]    Furthermore, a device is provided for turning at least one steerable wheel of a motor vehicle while parking on a longitudinal inclination of a roadway, which cooperates with a parking brake, an inclination angle sensor and a steering device of the motor vehicle. It has a surroundings recording device having at least one sensor for recording the immediate surroundings of the motor vehicle. The surroundings recording device is used, in this case, to control and evaluate the at least one sensor for recording conditions of the immediate surroundings of the motor vehicle, which are drawn upon for judging the risk of rolling away and the possibilities of preventing such an undesired rolling away. In this instance, it is particularly possible to use the surroundings recording device using sensors of the motor vehicle, and use such sensors as are present in the motor vehicle in any case, for instance, such as the ones of a proximity warning system, of a parking assistant of a parking warning system or the like. The surroundings recording device is particularly used in this case for carrying out the abovementioned method for turning the at least one steerable wheel during parking on a longitudinal inclination of the roadway. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  shows a side view of a motor vehicle parked along a longitudinal inclination of a roadway. 
           [0019]      FIG. 2  shows the same motor vehicle in a schematic, sectional top view. 
           [0020]      FIG. 3  shows an exemplary method flow chart. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]      FIG. 1  shows a motor vehicle  1 , which is supported by wheels  2  on a roadway  3 , and is parked, the roadway  3  having a longitudinal roadway inclination  4  by an angle of inclination α in travel direction  5  of motor vehicle  1 . Accordingly, motor vehicle  1  is parking on a downhill gradient  6  in the situation shown. Of the wheels  2 , front wheels  7 , that is, wheels  2  mounted on a front axle of motor vehicle  1 , are steerable wheels  8 . It is assumed, in this instance, that motor vehicle  1  has at least essentially a vehicle inclination angle β, based on its chassis, that is not shown here in greater detail and the wheel suspensions not shown here in greater detail and the front and rear axles not shown here, and that this angle β is at least essentially identical to angle of inclination α of longitudinal roadway inclination  4  to the horizontal  9 , angle of inclination α and vehicle inclination angle β being angles of the same size. The inclination angle of the vehicle is recorded using an inclination sensor  39  situated in motor vehicle  1 . 
         [0022]      FIG. 2  shows the same motor vehicle  1  in an only schematic sectional representation, in a top view, motor vehicle  1  parking on roadway  3  shown in  FIG. 1 , and roadway  3  having a curb  10  on the right, and essentially parallel to motor vehicle  1 , which is elevated above the level of roadway  3 . To turn steerable wheels  8  (namely front wheels  7 ), motor vehicle  1  has a steering device  11 , which is able to be operated by a driver (not shown) via a steering wheel  12 , as well as by a steering assistance system  13 . Steering assistance system  13  supports a parking assistant not shown here, for instance, and/or a lane keeping assistant. It is important that steering assistance system  13  have a direct operation of steering device  11 , independent of the action of the unshown driver, and is thus able to effect the turning in of steerable wheels  8 , that is independent of a positive activity of the unshown driver. Motor vehicle  1  has at its disposal a body  14 , at whose outer corners  15  sensors  16  are situated, which record surroundings  17  of motor vehicle  1 , for example, via radar waves or ultrasonic waves, and transmit the data thus obtained via suitable data connections  18 , for instance, via electric lines or a data bus, to a surroundings evaluation device  19 . Together with the at least one sensor  16 , surroundings evaluation device  19  forms a surroundings recording device  20 . Surroundings recording device  20  acts together with steering assistance system  13  to set a steering angle γ, steering angle γ coming about between straight-line roll-away direction  21  of the at least one steerable wheel  8  and a parallel  22  to travel direction  5  (which corresponds to a vehicle longitudinal axis  23  when the motor vehicle is parked). 
         [0023]    In order to park motor vehicle  1  on longitudinally inclined roadway  3 , steering angle γ, of the at least one steerable wheel  8 , is set in such a way that rolling away of motor vehicle  1  onto roadway  3 , or onto detected obstacles, does not take place if a parking brake (not shown here) does not apply sufficient holding force against the gravity-conditioned rolling inclination of motor vehicle  1  along longitudinal roadway inclination  4 . In the example shown, steering angle γ is set in such a way that curb  10 , detected by surroundings recording device  20 , would be hit by (right) front wheel  7  if motor vehicle  1  started to roll, and motor vehicle  1 , when starting to roll, would be braked in this way in its slantwise forward motion directed towards curb  10 . The setting of steering angle γ takes place without the action of the unshown driver, just based on the data obtained by surroundings recording device  20  using sensors  16  and surroundings evaluation device  19 . In this connection, particularly the presence of curb  10 , or the lack of it, are taken into account, as well as the wheel diameter of the at least one steerable wheel  8 , which is used for running onto possibly present curb  10 . A respectively different steering angle γ may be required as a function of the wheel diameter and of the height of curb  10 , in order to prevent motor vehicle  1  as advantageously as possible from rolling away, or even from starting to roll. Furthermore, it is taken into account whether there is a distance  24  between motor vehicle  1  and curb  10  or, in the case where there is no curb  10 , a distance from a roadway edge or another suitable obstacle. This distance  24  is also relevant, with respect to the first-time hitting of the at least one steerable wheel  8 , that is used for preventing rolling away towards a suitable obstacle, that would stop the motion of rolling away. 
         [0024]    Moreover, it is provided that a measuring device (not shown) ascertain the increase in the force that is required for setting steering angle γ to the desired position. For, if steerable wheel  8  hits the curb, for instance, before steering angle γ is set, the force required for the further movement of steerable wheel  8  increases very greatly in a short period. This increase in force may be used as an indication that steerable wheel  8  is taking up such a position at curb  10 , in an impacting manner, that curb  10  acts as a wedge, and consequently, the rolling away of motor vehicle  1  is prevented. The (additional) adjustment of steering angle γ is then interrupted. Damage to steerable wheel  8  may also advantageously be avoided thereby. The determination of the force required for setting steering angle γ on steerable wheel  8  may take place indirectly, for example, by measuring a current, the current consumption required by steering assistance system  13  for moving steering device  11  being measured from the voltage supply system of motor vehicle  1 . A sudden increase in the required current strength leads to the conclusion that there is a blockage in the motion of steering device  11  by steering assistance system  13 , and, with that, that steerable wheel  8  is hitting curb  10 . 
         [0025]      FIG. 3  shows a method flow chart  25  for turning the at least one steerable wheel  8  of motor vehicle  1  described in  FIGS. 1 and 2 . To the extent that reference numerals are not given by  FIG. 3  itself, one should consult  FIGS. 1 and 2  in addition. The method begins at step  26 , namely, the activation of the parking brake of motor vehicle  1 . In following step  27 , longitudinal inclination  4  of the roadway is recorded via vehicle angle of inclination β and equated to angle of inclination α of roadway  3  (as described above, based on the constructional conditions of motor vehicle  1  it is assumed that, in the case of a vehicle angle of inclination β, recorded by an inclination angle sensor that is mounted in motor vehicle  1 , there exists at least essentially an equality to angle of inclination α of roadway  3 ). In next step  28  it is checked whether angle of inclination α exceeds a specified or a specifiable threshold value x, that is, whether there is a certain minimum slope of roadway  3 . Threshold value x, in this instance, takes into account particularly the weight of motor vehicle  1 , as well as constructively specified frictional resistances or mechanical losses, which counteract the motion of motor vehicle  1  in the mechanics of the vehicle. If this is not the case (in the present flow chart of  FIG. 3 , negated conditions are always characterized by n and affirmed conditions always by y), then in a step  29  the method is ended, since an especial securing of motor vehicle  1  from rolling away is not necessary. If the checking for the exceeding by angle of inclination α of a threshold value x is affirmed, then in a step  30 , following step  28 , surroundings  17  of motor vehicle  1  are recorded using surroundings recording device  20 , and particularly via sensors  16 , that are mounted on motor vehicle  1 . In subsequent checking step  31 , it is checked whether a curb  10  is present and, if necessary, its distance d from motor vehicle  1 . If no curb is detected, that is, the checking question in step  31  as to the presence of curb  10  is negated, in step  32  the turning of the at least one steerable wheel  8  slantwise to the roadway direction (essentially slantwise to vehicle longitudinal axis  23 ) is effected, that is, a steering angle γ is set at a sufficiently slanting direction to vehicle longitudinal axis  23 . If checking step  31  is affirmed, then in following step  33 ; the distance, is ascertained of the at least one steerable wheel  8 , which is closest to curb  10 , and from the wheel diameter of this wheel  8 , the height of curb  10  and distance d of curb  10  from steerable wheel  8 , optimal steering angle γ is ascertained. The wheel diameter is relevant for the determination of the question as to how easily a curb of a given height is able to be overcome by a vehicle starting to roll, and how steering angle γ is to be set to avoid the rolling over of that curb  10  that is actually found. Distance d of the at least one steerable wheel  8  from curb  10  is relevant for the determination of the question as to how much energy of motion motor vehicle  1  is able to assume when starting to roll at given angle of inclination α, until motor vehicle  1  is stopped by contact of the at least one steerable wheel  8  with curb  10 . If the kinetic energy of motor vehicle  1  is high, based on a large angle of inclination α and a relatively large distance d from curb  10 , it is possible, in response to an unfavorable steering angle γ, that curb  10  is overcome in an undesired manner, and is rolled over by steerable wheel  8 . Accordingly, steering angle γ should be set in such a way that only as short as possible a rolling path is possible, that is, highly slantwise to travel direction  5  or vehicle longitudinal axis  23 . Equally relevant is the determination of distance d between steerable wheel  8  and curb  10  for the ascertainment of steering angle γ that is possible at a given wheel diameter (for if motor vehicle  1  is standing very close to curb  10 , a large steering angle γ, that is, a highly slantwise setting of steerable wheel  8  with respect to vehicle longitudinal axis  23 , is not possible, because steerable wheel  8 , at its outer circumference, is already running up against or hitting an edge of curb  10 ). 
         [0026]    According to flow chart separating line  34 , shown here in dash-dotted fashion, which, after a step  33  making possible an end of method  33 , permits an optional continuation of the method, in a decision step  35  checking is provided by steering device  11 , especially steering assistance system  13 , for a force increase, that is, an increase of the force to be afforded so as to set steerable wheel  8  further in the direction of calculated steering angle γ. If such a force increase is detected, it is assumed that steerable wheel  8  has touched an edge of curb  10 , so that the starting to roll of motor vehicle  1  is no longer possible, because curb  10  acts, so to speak, as a wedge under steerable wheel  8 . If the calculated steering angle γ has not yet been reached at the time of the determination of the increase of the force P to be applied, the setting of steering angle γ is interrupted, and the value present at this time is maintained. The method is then ended in step  36 . If no increase is determined during the setting of steering angle γ in checking step  35 , in the following checking step  37  it is checked whether the calculated steering angle γ has been achieved. If calculated steering angle γ is not yet at hand, the setting of steerable wheel  8  is continued or repeated in a loop branching back after step  35 , checking for a force increase, until calculated steering angle γ has been achieved and steerable wheel  8  has the wheel angle that was calculated and is required. If the achieving of steering angle γ is recognized, the method is ended in a final step  38 .