Abstract:
The invention relates to a setting device for an adjustable gearing mechanism, in particular, for selecting a parking position in an automatic transmission. The inventive setting device comprises a mechanical setting element, an intermediate gearing mechanism for transferring the setting motion of the setting element to a control element of the adjustable gearing mechanism. A mechanical energy store, which can be replenished once again by the setting element, is provided for driving the intermediate mechanism when the setting element malfunctions.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a continuation of co-pending International Application No. PCT/DE01/04159 filed Oct. 30, 2001 which designates the United States, and claims priority to German application number DE10054977.2 filed Nov. 6, 2000. 
     
    
     
       TECHNICAL FIELD OF THE INVENTION  
         [0002]    The invention relates to a setting device for an adjustable gearing mechanism, in particular for selecting a parking position in an automatic transmission.  
         BACKGROUND OF THE INVENTION  
         [0003]    Conventional automatic transmissions for automobiles usually have four preselection ranges for the different operating states of the automobile, namely a park position, a reverse position, a neutral position, and a drive position. In the park position, a mechanical locking mechanism (park lock) prevents the output shaft of the automatic transmission, and therefore the wheels of the automobile, from turning, thus preventing the automobile from rolling away unintentionally.  
           [0004]    The desired preselection range is set by the driver by actuating a gearshift lever, while the link between the gearshift lever and the automatic transmission can be effected, for example, by means of electric cables, this shifting principle being known as “shift by wire”. At the same time it must, however, be ensured that the park lock can also be activated even in the event of a total failure of the vehicle electronics system.  
           [0005]    As a solution to this problem, a setting device for an automatic transmission is known from DE 44 22 257 C1, said device comprising, in addition to an electric motor for setting the desired preselection range in normal operation, also a spring which enables the park lock to be activated if the electric motor or the power supply fails. For this purpose, the driver simply has to release the spring, which is under tension during normal operation, by means of a Bowden cable, whereupon the spring activates the park lock.  
           [0006]    However, a disadvantage with this known setting device is the fact that in order to activate the park lock in the event of a failure of the power supply, a manual intervention is still required by the driver, in that the latter actuates the Bowden cable.  
           [0007]    Furthermore, EP 0 198 114 B1 discloses a setting device for a two-stage gearing mechanism, in which an electric motor axially displaces a rod in order to set the desired gearing mechanism stage, said rod being linked via a spring to a likewise axially movable carriage which carries the selection lever of the gearing mechanism. In this arrangement, the carriage can be locked in two positions by means of a stationary electromagnetically controllable locking element in the form of a solenoid, the two positions of the carriage each corresponding to a gearing mechanism stage. Thus, owing to the locking of the carriage by the locking element, the displacement of the rod by the electric motor does not lead to a change in the gearing mechanism stage, but simply leads to a tensioning of the spring. When the carriage is unlocked, the tensioned spring then drives the carriage into the respective other position, thus causing the other gearing mechanism stage to be set. However, the locking element fixes the carriage in the idle state to ensure that a failure of the power supply or a malfunction of the locking element does not lead to a change in the gearing mechanism stage. Rather, with the known setting device described in the foregoing, in the event of a failure of the power supply the gearing mechanism remains in the gearing mechanism stage just set.  
         SUMMARY OF THE INVENTION  
         [0008]    The object of the invention is therefore to create a setting device for an automatic transmission in which the automatic transmission is controlled via electric cables, the park lock being activated automatically even in the event of a total failure of the vehicle electronics system.  
           [0009]    The object is achieved, based on a known setting device for an adjustable gearing mechanism according to a setting element having a setting motion; an intermediate gearing mechanism for transferring the setting motion of the setting element to a control element of the adjustable gearing mechanism, the intermediate gearing mechanism comprising a movably mounted carrier linked to the setting element via a spindle, a carriage mounted in a linearly movable manner in parallel with the carrier and linked to the control element, and a controllable locking element to link the carriage to the carrier or separate it from the carrier; and a mechanical energy store for driving the carriage in the event of a failure of the setting element.  
           [0010]    The invention comprises the general technical principle of providing a mechanical energy store in addition to the normal mechanical setting element for selecting the preselection range of the automatic transmission, said mechanical energy store enabling the park lock to be activated in the event of a failure of the normal setting element. An energy store of this type preferably comprises a spring, for example in the form of a helical or flat spiral spring, although other types of energy store which permit the park lock to be activated are also possible.  
           [0011]    In a conventional automatic transmission, the preselection range of the automatic transmission is usually set via a control shaft, the angle position of which determines the preselection range. However, the rotation of the control shaft usually requires relatively large torques of up to 12 Nm, with the result that the energy needed for selecting the preselection range of the automatic transmission is transmitted by the mechanical setting element to the control shaft determining the preselection range via an intermediate gearing mechanism.  
           [0012]    According to the invention, energy is introduced into the intermediate gearing mechanism via a movably mounted carriage, the carriage being linked on one hand to the energy store and on the other hand, via a controllable locking element, to the setting element. In the locked state, the setting element therefore acts on the carriage and thus enables the desired preselection range to be set. If the setting element fails, on the other hand, the locking element is unlocked, with the result that the movably mounted carriage is now linked only to the energy store and is pushed by the latter into the desired position, causing the automatic transmission to assume the desired preselection range. The controllable locking element for linking the carriage to the setting element preferably comprises an electromagnet, such that the locking element is automatically unlocked in the event of a power failure and thus releases the movably mounted carriage.  
           [0013]    The carriage is preferably movable in a linear direction, but in principle it is also conceivable that the carriage is moved on a circular path or a path curved in some other way.  
           [0014]    In the preferred embodiment, the setting element is linked to a carrier which is movably mounted parallel to the carriage, the locking element either linking the carriage to the carrier or separating it from the carrier. In normal operation with a properly functioning power supply, the locking element therefore links the carriage to the carrier, which is driven by the setting element such that the setting element moves the carriage and thereby sets the desired preselection range of the automatic transmission. If the power supply fails, on the other hand, the locking element severs the link between the carrier and the carriage, with the result that the setting element no longer acts on the carriage, which is then moved into the desired position by the energy store.  
           [0015]    In an embodiment of the energy store as a spring, the spring can be disposed, for example, between the carrier and the carriage and can pretension the carrier with respect to the carriage. As an alternative to this, however, it is also possible that the spring is disposed between the carriage and a thrust bearing fixed in space and pretensions the carriage independently of the carrier with respect to the thrust bearing. In both cases, when carriage and carrier are unlocked, the energy of the tensioned spring leads to the carriage being moved by the spring, whereupon the automatic transmission assumes the desired preselection range.  
           [0016]    In a variant of the invention, the carrier has a guide for the movable mounting of the carriage, such that the carriage can be moved relative to the carrier. In another variant of the invention, in contrast, a separate guide is provided both for the carrier and for the carriage. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    The invention is explained in more detail below in connection with the description of the preferred exemplary embodiments with reference to the figures, which show:  
         [0018]    [0018]FIG. 1 shows a setting device according to the invention, wherein the carriage is guided by the carrier,  
         [0019]    [0019]FIG. 2 a  and  2   b  show a setting device according to the invention, wherein the carrier and the carriage each have a separate guide, the carriage being pretensioned by a spring having a thrust bearing fixed in space,  
         [0020]    [0020]FIG. 3 a  and  3   b  show a setting device according to the invention having a separate guide for the carriage and the carrier, the carriage being pretensioned by a spring disposed between the carriage and the carrier,  
         [0021]    [0021]FIG. 4 a - 4   d  show different forms of compensating elements for compensating for minor setting errors,  
         [0022]    [0022]FIG. 5 a  and  5   b  show an alternative exemplary embodiment of a setting device according to the invention having a stationary unlocking device, and  
         [0023]    [0023]FIG. 6 shows a further alternative exemplary embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    The setting device shown in FIG. 1 as a preferred exemplary embodiment of the invention enables the preselection range to be set for an automatic transmission for an automobile, the preselection range of the automatic transmission being specified by the angle position of a control shaft  1 .  
         [0025]    A lever  2  is fixed to the control shaft  1 , because torques of up to 12 Nm are required for a rotation of the control shaft  1 .  
         [0026]    These torques are generated by an electric motor  3  having a worm shaft  4 , the worm shaft  4  offering the advantage of being self-locking. As an alternative to the worm shaft  4 , a shaft without self-locking can also be used for driving the spindle housing  5 , however.  
         [0027]    The worm shaft  4  acts on a spindle nut, which is disposed in a movably mounted spindle housing  5 , such that the spindle housing  5  can be moved by the electric motor  3 .  
         [0028]    The spindle housing  5  further comprises a guide for a carriage  6 , such that the carriage  6  is movable relative to the spindle housing  5  and parallel to this spindle housing.  
         [0029]    The spindle housing  5  and the carriage  6  can, however, by locked together by means of an electromagnetic locking element  7 , thereby preventing the carriage  6  shifting relative to the spindle housing  5 .  
         [0030]    The carriage  6  comprises a pivot point, via which the carriage  6  is linked to the lever  2 , such that a displacement of the carriage  6  causes a rotation of the lever  2  and the control shaft  1 , as a result of which the desired preselection range of the automatic transmission can be set.  
         [0031]    Finally, also provided is an energy store in the form of a spring  8 , which is disposed between the spindle housing  5  and the carriage  6  and pretensions the carriage  6  with respect to the spindle housing  5 .  
         [0032]    In the following, the normal operation of the setting device shown in FIG. 1 will now be described first. In this state, the power supply of the automobile is operational, such that the locking element  7  locks together the spindle housing  5  with the carriage  6 . The electric motor  3  can therefore move both the spindle housing  5  and the carriage  6  via the worm shaft  4  and thereby rotate the lever  2  into the desired position.  
         [0033]    The following description now explains the mode of operation of the setting device shown in FIG. 1 in the event of a power supply failure. In this case, the locking element  7  releases the lock between the spindle housing  5  and the carriage  6 , with the result that the carriage  6  can move freely, independently of the position of the spindle housing  5 . The pretensioning of the spring  8  then leads to the lever  2  being rotated counterclockwise, with the result that the automatic transmission assumes the park position.  
         [0034]    The exemplary embodiment shown in FIGS. 2 a  and  2   b  largely corresponds to the exemplary embodiment shown in FIG. 1 and described above, so the same reference characters are used below for corresponding components and reference is made to the foregoing description in order to avoid repetition.  
         [0035]    Here, FIG. 2 a  shows the status of the setting device with a properly functioning power supply, whereas FIG. 2 b  depicts the status of the setting device in the case of a power supply failure.  
         [0036]    A special feature of the exemplary embodiment of a setting device according to the invention shown in FIG. 2 a  and  2   b  is that a separate guide  9 ,  4  is provided in each case for the spindle housing  5  and for the carriage  6 .  
         [0037]    A further special feature is that the spring  8  does not act on the spindle housing  5 , but on a separate thrust bearing  10  that is fixed in space. In this case, the spring  8  therefore pretensions the carriage  6  with respect to the thrust bearing  10 .  
         [0038]    The exemplary embodiment of a setting device according to the invention shown in FIGS. 3 a  and  3   b  largely corresponds to the exemplary embodiment described above and shown in FIGS. 2 a  and  2   b , so the same reference characters are used below and reference is made to the foregoing description in order to avoid repetition.  
         [0039]    The difference between the exemplary embodiment shown in FIGS. 3 a  and  3   b  and the exemplary embodiment shown in FIGS. 2 a  and  2   b  is essentially that the spring  8  is disposed between the spindle housing  5  and the carriage  6  and pretensions the carriage  6  with respect to the spindle housing  5 .  
         [0040]    Finally, FIGS. 4 a  to  4   d  shows different exemplary embodiments of compensating elements which can compensate for minor angle setting errors of the setting device according to the invention.  
         [0041]    Thus, in the case of the compensating elements according to FIG. 4 a , the control shaft  1  of the automatic transmission is linked via an elastic toothed belt  11  to an auxiliary shaft  12 , which is rotated by the lever  2 .  
         [0042]    In the case of the compensating element according to FIG. 4 b , in contrast, the lever  2  acts on an auxiliary shaft  13 , a segment-shaped lever  14  having likewise segment-shaped cutouts  15  being mounted on the control shaft of the automatic transmission, within which cutouts the lever  2  can be turned. Mounted between the lateral edges of the segment-shaped cutout  15  and the lever  2  in this case are springs  16 , which press the lever  2  into a center position within the segment-shaped cutout without external forces.  
         [0043]    In the exemplary embodiment according to FIG. 4 c , the control shaft  1  of the automatic transmission has segment-shaped cutouts  17 , in which the buffer elements of an elastic damping material engage, the buffer elements being appropriately adapted in shape and fixed on an auxiliary shaft  18 , which is turned by the lever  2 .  
         [0044]    Finally, the lever  2  in the compensating element according to the invention as shown in FIG. 4 d  is elastic and can, for example, assume the positions  2 ′ and  2 ″ in order to compensate for minor setting errors.  
         [0045]    The exemplary embodiment of a setting device according to the invention shown in FIGS. 5 a  and  5   b  largely corresponds to the exemplary embodiment described above and shown in FIGS. 3 a  and  3   b , so the same reference characters are used below and reference is made to the foregoing description in order to avoid repetition.  
         [0046]    The special feature of the exemplary embodiment shown in FIGS. 5 a  and  5   b  is that the unlocking element is stationary, as described in the following.  
         [0047]    In order to lock together the spindle housing  5  with the carriage  6 , there is provided a locking lever  19  which is pivotably mounted on the top of the spindle housing  5 , the locking lever  19  being able to swivel between a locking position and an unlocking position. In the locking position, a bolt mounted on the front side of the locking lever  19  engages in a corresponding cutout on the top of the carriage  6 , causing the carriage  6  to be locked together with the spindle housing  5 . The locking element further comprises a spring  20 , which pretensions the locking lever  19  in the direction of the locking position, such that the locking lever  19  locks together the carriage  6  with the spindle housing  5  when no external forces act upon the locking lever  19 . On the side opposite to the bolt, the locking lever  19  has an unlocking button  21 , which must be pressed down in order to unlock the locking element.  
         [0048]    In order to actuate the locking lever  19 , the locking element also has an unlocking lever  22 , also referred to as a cam sword, which is pivotably mounted in a housing  23 , the unlocking lever  22  being able to swivel about an axis  24  between an unlocking position and a locking position. The unlocking lever  22  is pretensioned here in the direction of the unlocking position by a spring  25 . Also provided is an electromagnet  26  in order to maintain the unlocking lever  22  in the locking position shown in FIG. 5 a  against the pretensioning force of the spring  25 . To this end, there is disposed at the top of the unlocking lever  22  a clamping plate  27 , which can be gripped by the electromagnet  26 . In this arrangement, the clamping plate  27  is pivotably mounted on the housing  23 .  
         [0049]    The status shown in FIG. 5 a  will now be described below, wherein the carriage  6  is locked together with the spindle housing  5 . In this state, the locking lever  19  engages in the latching projection at the top of the carriage, causing the carriage  6  to be locked together with the spindle housing  5 . The locking lever  19  is maintained in this position by the spring  20  until an external force acting on the unlocking button  21  causes the locking lever  19  to rotate in a clockwise direction.  
         [0050]    In the locking state shown in FIG. 5 a , the electromagnet  26  is energized and consequently attracts the clamping plate  27 , thus causing the unlocking lever  22  to be maintained in the locking position shown in FIG. 5 a  against the pretensioning force of the spring  25 .  
         [0051]    In the following, the transition from the locking state shown in FIG. 5 a  to the unlocking state shown in FIG. 5 b  will now be described. This transition takes place if, for example, the power supply fails. In this case, the electromagnet  26  is de-energized, causing the clamping plate  27  to be released, with the result that the spring  25  turns the unlocking lever  22  counterclockwise. The underside of the unlocking lever  22  then comes into contact with the unlocking button  21  of the locking lever  19  and turns the locking lever  19  in a clockwise direction until the bolt mounted on the front side of the locking lever  19  releases the latching projection on the top of the carriage, thus causing the carriage  6  to be disengaged from the link housing. A spring  28  mounted between the spindle housing  5  and the carriage  6  then causes the carriage  6  to be pushed to the left and finally assume the park position.  
         [0052]    The transition from the locking state shown in FIG. 5 a  to the unlocking state shown in FIG. 5 b  was described above for the situation in which the power supply fails. However, this transition can also take place if the electromagnet  26  is driven with opposite polarity, causing the electromagnet  26  to repel the clamping plate  27 .  
         [0053]    In the following, the transition from the unlocking or park position shown in FIG. 5 b  to the locking position shown in FIG. 5 a  will now be described. This transition takes place if the power supply of the electromagnet  26  is restored after a temporary failure. In this case, the electric motor  3  rotates the worm shaft  4 , causing the spindle housing  5  to be pushed to the left in the direction of the carriage  6 . In this process, the spring  28  is put under tension once more in order to be able to push the carriage  6  into the park position again in the event of a subsequent power failure. In addition, a load pin  29  flips out on the top of the spindle housing  5  when the locking lever  19  is unlocked; when the spindle housing  5  moves in the direction of the carriage  6 , this load pin causes the unlocking lever  22  to be raised to a point where the electromagnet  26  can grip and attract the clamping plate  27 . For this purpose, the unlocking lever  22  has a guide called a load curve, in which the load pin  29  travels along and at the same time raises the unlocking lever  22 .  
         [0054]    Upon reaching the carriage  6 , the locking lever  19  automatically engages in the latching projection on the top of the carriage  6 , causing the carriage  6  to lock together once again with the spindle housing  5 .  
         [0055]    It should further be mentioned that on the underside of the unlocking lever  22  there is mounted a projection  30  which, in the park position, prevents the carriage  6  from being unlocked from the spindle housing  5 . In the park position, namely, the spindle housing  5  is located beneath the projection  30 , with the result that the unlocking lever  22  cannot be pressed down so far that the locking lever  19  is turned accordingly.  
         [0056]    Instead of the projection  30 , however, a cutout can also be disposed on the front side of the unlocking lever  22 , said cutout being located above the unlocking button  21  and preventing the unlocking lever  22  from pressing down the unlocking button  21  as long as the spindle housing  5  is in the park position.  
         [0057]    As an alternative to the embodiment of the locking lever  19  shown in FIGS. 5 a  and  5   b , the locking lever  19  can also be implemented as an articulated lever, the lever arms on both sides of the swiveling axis being at an angle to each other. In this arrangement, a better transmission ratio can be achieved.  
         [0058]    The exemplary embodiment shown in FIG. 6 largely corresponds to the exemplary embodiment described above and shown in FIGS. 5 a  and  5   b , so in order to avoid repetition, reference is made to the foregoing description and the same reference characters are used below.  
         [0059]    The special feature of the exemplary embodiment shown in FIG. 6 is the manner in which the spindle housing  5  is unlocked from the carriage  6 . To this end, there is provided a rotatably mounted camshaft  31 , which is disposed above the locking lever  19  and is driven by an electric motor  32 . In the position shown in FIG. 6, the camshaft  31  is in the locking position, i.e. the camshaft  31  is not in contact with the unlocking button  21  of the locking lever  19 . Conversely, in order to unlock the spindle housing  5  from the carriage  6 , the camshaft  31  is rotated through 90°, causing the locking lever  19  to be pressed down.  
         [0060]    In one variant, the cross-section of the camshaft  31  deviates from the circular form only over a small angle range of, for example, 90°. As a result, the transmission of energy to achieve the necessary lift is worse than with a radius increasing over the entire circumference of the camshaft  31 . The advantage, however, lies in the possibility of the camshaft  31  being supported by the housing along the entire length of the carriage movement. Suitable stops are provided in the end positions. As a result, no motor position control is required. The electric motor  32  must be able to turn in both directions.  
         [0061]    In another variant, the electric motor  32  turns in one direction only. This simplifies the control of the electric motor  32 . Depending on the operating time, the electric motor  32  may operate the locking lever  19  a number of times, one actuation being sufficient for correct unlocking.  
         [0062]    In a further variant, the camshaft has a radius that increases over its entire circumference, which results in a better transmission of energy. Stops are provided at the end positions, with the result that no motor position control is required. In this case, the electric motor  32  must be able to turn in both directions.  
         [0063]    Finally, the camshaft  31  can also exhibit an increasing radius over its entire circumference, the transition being rounded. In this case the electric motor  32  turns in one direction only. This simplifies the control of the electric motor  32 . Depending on the operating time, the electric motor  32  may operate the locking lever  19  a number of times, one simple actuation being sufficient for correct unlocking.  
         [0064]    If no stops are provided at the end positions of the camshaft, it is necessary to provide either a sensor system for determining the angle position or a clutch between the electric motor  32  and the camshaft  31 .  
         [0065]    Behind the lever  2  in the pivoting plane of the lever  2  there is further disposed a sensor mat, which enables the setting angle of the lever  2  to be determined.  
         [0066]    The invention is not limited to the above-described exemplary embodiments according to the invention. Rather, a plurality of variants and adaptations that make use of the inventive idea are conceivable and therefore also fall within the scope of protection.