The invention relates to a device for modifying the wheel camber of a wheel on a motor vehicle. Such active camber adjusters modify the wheel camber depending on the appropriate driving situation, for example, when driving around curves, when braking, or when accelerating.
For example, from DE 102 49 159 A1, a guide device for a wheel, especially on a motor vehicle, has become known, with a circular arc guide, whose axis lies in the region of the intersection line between the driving surface and the center plane of the wheel, wherein the circular arc guide runs in the region of the wheel bearing. This guide device can be used in numerous existing wheel suspensions. For a relative displacement of the wheel relative to the circular arc guide, the wheel camber is manipulated. Practical embodiments do not follow from DE 102 49 159 A1. Furthermore, according to this disclosure, the rotational point of the pivot bearing is located approximately underneath the wheel contact plane, thus approximately underneath the driving surface. Indeed, the effective lever arm is kept small, wherein the lever arm is formed by the distance between the force application point of the wheel forces and the rotational point of the pivot bearing. If the rotational point of the pivot bearing lies, as here, under the street, the vehicle body moves somewhat to the left relative to the wheels when driving along a curve to the right, if the outer wheel in the curve is adjusted to a negative camber and the inner wheel in the curve is adjusted to a positive camber. This can represent a car body reaction that is incomprehensible for the driver.
The objective of the present invention is to create a device according to the features of the preamble of claim 1, in which this disadvantage is eliminated.
According to the invention, this objective is met in that the position of a virtual rotational point of the pivot bearing is above the wheel contact plane and on the side of the center plane of the wheel facing the vehicle, thus axially inside of the center plane of the wheel. The smaller the distance above the street, the smaller the torque that is required to be introduced by the actuator. The undesired car body reaction described above fails to appear. A preferred field, which is to contain the rotational point of the pivot bearing, is found in order to enable optimal activation of the pivot bearing. First, as a zero point or reference point, an intersection point is formed by a Y-axis intersecting the rotational axis of the wheel and lying in the center plane of the wheel and an X-axis lying in the wheel contact plane, wherein the X-value should be smaller than 150 mm and the Y-value should be smaller than 150 mm.
Within this field, a radius vector can be given, on which the rotational point of the pivot bearing is to lie with reference to a properly proportioned loading of the actuator. This radius vector intersects the intersection point of the X-axis lying in the wheel contact plane with the already defined Y-axis, wherein the radius vector covers an angular region, whose lower value relative to the X-axis equals approximately 30° and whose upper value equals approximately 60°. Within this angular region, X-values and Y-values can also be set, which are greater than 150 mm, in order to achieve properly proportioned loading of the actuator.
For a 17″ wheel, for example, good positioning of the rotational point is given with the following values: starting with the intersection point named above as the zero point, suitable value pairs are X=35 mm and Y=30 mm, X=50 mm and Y=50 mm, and X=103 mm and Y=140 mm. With this positioning of the rotational point, the work to be performed by the actuator is properly proportioned for the various driving situations. In any case, the rotational point should lie on the inside of the wheel, thus facing towards the vehicle. Then the virtual lever is in the wheel contact plane and the rotational point of the pivot bearing has a properly proportioned ratio both for curves to the left and also to the right.
Preferably, the pivot bearing has a fixed pivot bearing part, which is fixed relative to the wheel carrier, and a pivoting pivot bearing part arranged so that it can pivot in the pivot plane relative to the fixed pivot bearing part. In this case, the wheel can be supported on the pivoting pivot bearing part so that it can rotate, for example, by means of a conventional wheel bearing.
In this arrangement, it is especially advantageous when an electromechanical actuator is used, which, on one side, is supported opposite the wheel carrier and, on the other side, engages the pivoting pivot bearing part. Such electromechanical actuators have an electric motor powered by the electric on-board power supply of the motor vehicle. Because the position of the virtual rotational point is properly proportioned according to the invention for all driving situations, conventional electric motors can be used, which can be operated without any trouble with the electric energy provided by the on-board power supply.
For the use of the electromechanical actuator in the previously described arrangement, positions of the virtual rotational point are also conceivable, which lie outside of the indicated defined region.
Preferably, the electromechanical actuator includes an electric motor and a roller body screw drive, whose spindle nut is supported on a threaded spindle so that it can rotate. Such known electromechanical actuators reliably convert a rotational motion into a translational motion. The translational motion is used as an adjustment motion for adjusting the pivoting pivot bearing part.
Preferably, the spindle nut is embodied as a rotor of the electric motor, wherein the threaded spindle is then locked in rotation. This has the advantage that the threaded spindle can be held, for example, directly on the pivoting pivot bearing part.
The electric motor heats up under loading. This heat must be dissipated, so that the engine does not overheat, especially at low driving speeds after prior extreme loading. Cooling by air alone is possibly inadequate. To further cool the electric motor, it is mounted directly on the wheel carrier according to an improvement of the invention. The connection is provided in that a contact with very good heat transfer from the electric motor to the wheel carrier usually formed from metal is guaranteed. Consequently, the heat is discharged into the wheel carrier. The point of introduction is preferably one that is cooler than the motor. A suitable position can be, for example on the wheel carrier above the transverse suspension arm. Due to the relatively large mass of the wheel carrier in comparison to the size of the electric motor, its heat storage capacity can be taken advantage of. This position is also protected from impacts from stones and undesired contact with the ground by the vehicle.
It was already mentioned that the threaded spindle can preferably be locked in rotation with the pivoting pivot bearing part. Furthermore, in an improvement according to the invention, the threaded spindle is held on this pivoting pivot bearing part so that it cannot move in the axial direction, wherein the pivoting part makes rocking movements relative to the threaded spindle about a rocking axis transverse to the threaded spindle. When the electric motor is activated, in this selected example arrangement, the threaded spindle is displaced along its axis. If the axis of the threaded spindle is designated as one leg and the connection line between the virtual rotational point and the connection point to the threaded spindle on the pivoting pivot bearing part is designated as a second leg, the connection point represents the intersection point of the two legs, for example, at a camber adjustment of 0°, an output angle between these two legs is set. By activating the actuator, this angle changes. The previously described rocking arrangement in the attachment point consequently prevents undesired transverse forces or bending torques from being introduced into the threaded spindle.
In order to enable, on one hand, a play-free attachment of the pivoting pivot bearing part and, on the other hand, problem-free rocking motion, it is proposed to support a peg, which is arranged transverse to the threaded spindle, in the radial direction on the threaded spindle by means of an especially biased roller bearing, especially a needle roller bearing, wherein the peg can be mounted on the pivoting pivot bearing part. This play-free connection between the pivoting pivot bearing part and the threaded spindle is used for trouble-free, precise attachment conditions. Alternatively, it is also possible to lock the peg in rotation on the threaded spindle and to support the peg in the radial direction by means of radial roller bearings on the pivoting pivot bearing part.
The present invention is also suitable for driven wheels. To guarantee the movement freedom of the wheels, optionally the wheel gauge can be increased somewhat in order not to impact the wheel housings and spring arms; then, optional changes to the wheel housings and spring arms do not have to be performed. Furthermore, the bending angle of the steering drive shaft is critical during spring deflection and rebound and during steering of the wheel. The main influencing parameter, in addition to the steering angle and spring paths, is primarily the length of the drive shaft between the joints. When the wheel is adjusted to a negative camber, the bending angle may not be increased too much. This results in the requirement that the axial installation length of the pivot bearing according to the invention may not become too large. However, in order to support the bending torques resulting from the lateral guide forces on the wheel on the pivot bearing, for strength reasons, a certain camber length is necessary, which defines the necessary installation space in the axial direction. All of these criteria are taken into account, such that an improvement according to the invention provides the lead through of the drive shaft through the wheel bearing. The drive shaft does not have to be unduly shortened and the bending angle does not have to be increased. Preferably the pivot bearing, the wheel bearing, and the drive shaft are arranged one inside the other. In comparison with known arrangements without the pivot bearing according to the invention, there results only an insignificant or even no shortening at all of the drive shaft in the extreme case of the greatest adjustable negative camber, because in this position, the necessary wheel gauge increase nearly balances out the theoretical shortening of the drive shaft when adjusted into this position.
The provision of the pivot bearing according to the invention possibly requires additional spatial requirements. In addition, trouble-free lubrication of the pivot bearing must be ensured. An improvement according to the invention provides that the pivot bearing, the wheel bearing, and the joint of the drive shaft are arranged in a common lubricating space provided with lubricant. Consequently, only one lubricating space is necessary, so that additional installation space is minimized. The pivot bearing, the wheel bearing, and the cardan shaft can be lubricated with a suitable heavy-duty grease. The lubricating space is preferably defined by a common seal, especially by a folding or rolling bellows, which contacts, on one side, the fixed pivot bearing part and, on the other side, the cardan shaft. While this seal can be arranged on the side of the fixed pivot bearing part in a fixed and sealed way, an improvement according to the invention provides that a seal packing supported on the cardan shaft so that it can rotate is arranged between the seal and the cardan shaft. This seal packing can be provided, for example, with seal lips.
On the outside of the wheel, a seal for the pivot bearing is similarly to be provided. The wheel bearing can be sealed itself by means of a sheet gasket. The pivot bearing can be sealed by means of a rolling bellows. In comparison with a folding bellows seal, this rolling bellows has the advantage that it can have a very small radial dimension due to the large bending radii of elastomer with small wall thickness and also can be very short in the axial direction. The bending bead moves only about half the amount for a certain stroke of the pivot bearing. This sealing system enables a solid seal, wherein a sliding sealing lip can be eliminated. With this seal, which is small in the axial and radial directions, the tight space within a brake disk can be used optimally. A collar, either as an additional part or also formed integrally on the pivoting pivot bearing part, can be attached to the pivoting pivot bearing part on the outer side of the wheel. With its closed surrounding surface, this collar simultaneously enables the holding of the rolling bellows seal and provides for a uniform introduction of the actuator forces and the braking torque into the pivoting pivot bearing part.
The threaded spindle of the actuator can be housed in a seal, which can also be embodied as a folding or rolling bellows. In this way, the threaded spindle is protected from undesired contamination in a trouble-free way.
So that a trouble-free pivoting motion between the fixed pivot bearing part and the pivoting pivot bearing part can be realized even under large loads, in an improvement according to the invention, a roller bearing is provided between the fixed pivot bearing part and the pivoting pivot bearing part, in which roller bodies roll on arc-shaped tracks. The diameter of the roller body is adapted to the pivot angle to be realized, wherein the goal can be, for example, for a camber adjustment by 3°, to turn the loaded roller body at least once over its complete roller extent. In this way, undesired plastic deformation and premature damage can be avoided and uniform loading of the tracks can be ensured.
Preferably, for such a roller bearing, at least one endless roller body channel is provided, in which the roller bodies can circulate endlessly, wherein the roller body channel has a load section with the arc-shaped tracks, a return section, and two deflection sections connecting the load section to the return section to form an endless path. In contrast to a finite roller body chain, which performs only a back and forth motion, here it can be ensured that each roller body of the roller body chain can pass each position of the tracks during operation, thus it can also perform, if necessary, a complete circulation in the roller body channel.
Preferably, the pivoting pivot bearing part and the fixed pivot bearing part are arranged one inside the other and provided with the arc-shaped tracks on facing outer surfaces. In addition, one of the two pivot bearing parts is provided with the return sections. These return channels can be embodied, for example, as straight bore holes. The deflection sections are preferably provided on head pieces, which can be flange mounted, for example, on ends of the pivot bearing facing away from each other.
The outer fixed or pivoting pivot bearing part can be provided as a hollow profile and can be assembled from two longitudinal parts, wherein the longitudinal axis of this pivot bearing part lies in the plane separating the two longitudinal parts.
Dividing this pivot bearing part into two longitudinal parts has the advantage that on the appropriate inner side of each longitudinal part, the tracks for the roller bearing can be produced without trouble, for example, in one grinding process. If these two parts are then joined together again, proper positioning is necessary. This can be simplified if this pivot bearing part embodied as a hollow profile is first embodied as a single component, wherein desired fracture points are provided along the separating plane. This component can now be broken apart along the desired fracture points, so that the two longitudinal parts are formed, wherein the two longitudinal parts are provided at their fracture points lying in the separating plane and facing each other with fracture surfaces, which enable a precisely fitting joining of the two longitudinal parts.
The pivoting or fixed pivot bearing part, in this case on the inside, can be provided with a tubular shape viewed in cross section and can be provided on its outer surface with several ridges distributed over the periphery and arranged concentric to the rotational point of the pivot bearing, wherein the ridges carry the tracks. Preferably, these ridges are provided with the tracks for the roller bodies on opposing peripheral sides.
In order to lock the set camber position of the wheel in the case of loss of power or when parked, an improvement according to the invention provides a fail-safe device, with which a camber position of the wheel can be detachably locked. If, for example, an electromechanical actuator is provided, in which a threaded spindle and the spindle nut arranged so that it can rotate on the threaded spindle are provided, the fail-safe device preferably has a positive-fit part for a positive-fit connection of the spindle nut with a part fixed to the frame.
For example, the nut of the spindle drive can be mechanically blocked reliably by means of a pin and a spring. If sufficient power-supply voltage is provided, the pin can be pulled, for example, magnetically, from its locked position, wherein then a rotational motion of the nut is enabled by the electric motor and thus active camber adjustment. This magnet can be mounted, for example, on the wheel carrier. Through end teeth provided with a defined angle, in which a pin engages with an angled tip, it is possible to use the electric motor actively for releasing the locked position. This is especially advantageous when the pin is to be tight due to contamination, and the magnetic force alone is not sufficient. In this case, the magnetic force can be dimensioned so that the pin is guaranteed to be held in the open position. Such a setup enables a space-saving configuration and a reduced electric power consumption, because during the entire control process for the camber, this pin is held in the opened position.
The invention is explained in more detail below with reference to two embodiments illustrated in a total of 13 figures. Shown are:
a a detail from
Pivoting movements of the pivot bearing 4 in the pivot plane have a rotational point D, which, in the present case, is selected to be on the inside of the wheel somewhat above the road surface. This rotational point D is virtual. This virtual rotational point D is due to the configuration of the pivot bearing 4, which is discussed in more detail farther below.
For determining an optimum position of the rotational point D, reference is made to
On its inner periphery, the outer pivot bearing part 7 has several longitudinal grooves 15 distributed over the periphery, wherein peripheral walls of the longitudinal groove 15 have tracks 16 for the roller bodies 14. The tracks 13 and 16 are arc-shaped, so that the tracks 13, 16 have the same rotational axis D of the pivot bearing 4.
It follows from
It follows from
It follows from
In a greatly enlarged view,
Furthermore, it follows from
The wheels shown in
Furthermore, it follows from
To protect the threaded spindle 27 of the electromechanical actuator 23 against contamination and damage, a seal cap 42, which is mounted on the electric motor 24, is provided on the end of the threaded spindle 27 facing away from the lever arm 28. Furthermore, another folding bellows 42, which surrounds the threaded spindle 27, is provided on the end of the threaded spindle 27 facing the lever arm 28.
While a neutral camber is shown for the driving situation shown in
The electromechanical actuator 23 is further provided with a fail-safe device 43 in order to block the rotor 25. This fail-safe device 43 is shown in FIGS. 8 to 11. The rotor 25 locked in rotation with the spindle nut 26 is provided on the end with a locking washer 44, which is provided on one of its ends with end teeth 45. The end teeth 45 can be seen clearly in
In
Here, an electromechanical actuator 54 is also used, which matches the previously described electromechanical actuator. However, the difference with the previously described embodiment is that the electric motor 55 is mounted in an articulated way on the pivoting pivot bearing part 53. The threaded spindle 56 is provided with a spindle nut not shown in more detail, wherein the spindle nut is held on the fixed pivot bearing part 52. When the not-shown rotor of the electric motor 55 rotates, the threaded spindle 56 turns, wherein the pivoting pivot bearing part 53 pivots. The position of the rotational point of the pivot bearing 50 is selected under the same considerations as in the previously described embodiment.
List of Reference Numbers
Number | Date | Country | Kind |
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10348682.8 | Oct 2003 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP04/09479 | 8/25/2004 | WO | 4/3/2006 |