Abstract:
A rear view element folding device for a motor vehicle is disclosed for approaching at least one pivot position of an element housing relative to an element foot that can be mounted on the motor vehicle. The rear view element folding device locks or unlocks at least one resting position of the element housing relative to the element foot. A method for triggering such a rear view element folding device is also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from German Patent Application No. 20 2015 106 118.8 filed on Nov. 12, 2015. The disclosure of which is incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    This invention relates in general to rear view devices. In particular, the invention relates to a rear view element folding device for a motor vehicle for approaching at least one pivot position of an element housing relative to an element foot that can be mounted on the motor vehicle, and for locking or unlocking at least one resting position of the element housing relative to the element foot. The invention further relates to a method for triggering such a rear view element folding device. 
         [0003]    A drive folding mechanism for a rear view element is known from EP 2 439 106 B1, which is designed to be attached to a motor vehicle. This mechanism comprises a drive folding housing, which can be mounted between an element housing and an element foot that can be mounted on a motor vehicle. Further, a coupling member is provided which is brought into engagement with the element foot using a first spring means, wherein the coupling detent can be axially moved from a locking position and/or engagement position, in which coupling arresting elements hold back a relative rotation between the coupling member and the element foot in a form-fit manner, and an unlocking and/or non-engagement position, in which a friction engagement torque only somewhat holds back the relative rotation between the coupling member and the element foot around an element head axis, wherein the coupling member permits the element housing to be manually moved in relation to the element foot. Additionally, the mechanism comprises an electrical drive train for generating a relative rotation between the drive folding housing and the coupling member around the element head axis, wherein when the coupling member is in the non-engagement position and the electrical drive train generates a relative rotation between the drive folding housing and the coupling member, the drive folding housing rotations relative to the element foot until a drive stop surface of a drive stop means achieves a detent induces counter-torque, wherein the counter-torque is greater than the friction engagement torque, and thus stops the rotation of the drive folding housing in relation to the element foot, and instead causes the coupling member to rotation until the coupling member has reached an engaged position. The drive stop means is movably mounted on the drive folding housing, and the drive stop surface is engaged with the detent element mounted on the element foot, wherein the drive stop surface is biased axially towards the detent. The drive stop surface moves with the drive folding housing between:
       a forward position, in which the drive folding housing and the element head are in a forward folding position;   a rearward position, in which the drive folding housing and the element head are in a rearward folding position; and   a drive position in which the drive folding housing and the element head are in an extended position, the coupling member is in the engagement position and the drive stop surface lies between the detent and the drive folding housing in order to provide a form-fit and repeatable stop.       
 
         [0007]    The known rear view element folding device uses a single motor for changing between the engagement position and the non-engagement position, i.e. for locking and unlocking, as well as for approaching the forward position, rearward position and drive position, i.e. for twisting, which leads to a complex structure. 
         [0008]    The invention provides a rear view element folding device for a motor vehicle which has a simple structure, without reducing safety during locking. Large noise developments when approaching different positions of the rear view element should also be avoided. In addition, it should be possible to quickly approach any desired position. 
       SUMMARY OF THE INVENTION 
       [0009]    This invention relates to rear view element folding device for a motor vehicle for approaching at least one rotational position of an element housing relative to an element foot that can be mounted on the motor vehicle, and for locking or unlocking at least one resting position of the element housing relative to the element foot, which is characterized by
       a first actuator for a translation movement of a first engagement element that is firmly connected to the element housing relative to a second engagement element that is connected to the element foot along a rotation axis, wherein the first engagement element and the second engagement element in a locking position, such as a locked resting position of the element housing, stand in a fixed engagement with each other and in an unlocking position, such as an unlocked resting position of the element housing, the engagement is released by a certain translation movement, and   a second, separate actuator for a rotational movement for rotating the first engagement element relative to the second engagement element around the rotation axis, wherein through a first rotational movement, a first rotation position of the element housing can be approached from the unlocked resting position, and through a second rotational movement of the element housing, which is counter to the first rotational movement, the unlocked resting position can be approached from the first rotational position.       
 
         [0012]    Here it can be provided that at least one spring element in the locking position applies a force onto the first and/or second engagement element, and the first actuator moves the first or second engagement element against the force of the spring element during the change from the locking position into the unlocking position, in particular with a lifting movement, wherein preferably, the first actuator holds the unlocking position for a certain period of time. 
         [0013]    It is preferred according to the invention that the first actuator uses an active material, in particular as a shape memory alloy (SMA) drive, piezo drive or a drive designed with an electroactive polymer, wherein preferably, the SMA drive uses at least one SMA element, in particular in the form of an SMA wire or an SMA spring, on which a current can be applied for the change from the locking position into the unlocking position, in particular in form of at least one current surge and/or over a certain period of time, preferably pulsed. 
         [0014]    Here it can be provided that the spring element comprises a spiral spring, concentrically to which the SMA element(s) run, in particular in an evenly distributed manner, and/or each SMA element is shortened trough heating when the current is applied, so that the spring element is compressed from a locking state into an unlocking state, while during the cooling of the SMA element, the spring element returns from the unlocking state, in particular automatically, into the locking state, and/or the first actuator can be adjusted depending on a first travel sensor and/or by means of end switches, in particular mechanical end switches. 
         [0015]    With the invention, it is also suggested that the second actuator uses an active material, a magnetic angle adjuster or a motor, in particular an electric motor, which preferably engages via a gear stage onto the first engagement element, and/or the second actuator can be adjusted depending on a second travel sensor and/or by means of end switches, in particular mechanical end switches. 
         [0016]    Embodiments according to the invention can be characterized in that the first engagement element comprises at least one protrusion for engagement into a recess, which is preferably designed to be complementary to the protrusion, in the second engagement element and/or the second engagement element comprises at least one protrusion for engagement into a recess, preferably designed to be complementary to the protrusion in the first engagement element, wherein preferably, a plurality of protrusions is provided, and/or preferably, each protrusion comprises a trapezoid form in its profile, and/or preferably, the first engagement element comprises a first ring and the second engagement element comprises a second ring, wherein the rings are arranged concentrically to the rotation axis AΦ, and/or the first engagement element is formed as a first gear ring and/or a first clamping element, brake element and/or latching element, and the second engagement element is formed as a second gear ring and/or a second clamping element, brake element and/or latching element. 
         [0017]    Further, it is suggested according to the invention that the element foot comprises a basic body, in particular having a cylindrical form, or is firmly connected thereto, the spring element engages on the basic body and the second engagement element, and the first actuator engages on the basic body and the second engagement element, so that a locking device is provided in a cylindrical form, in particular a hollow cylindrical form. 
         [0018]    It can also be provided that a control or regulating device for the first and/or second actuator interacts with at least one sensor device, and/or the control or regulating device, the first actuator and/or the second actuator are arranged at least partially in the locking device, in particular in the hollow cylinder. 
         [0019]    Here, it is in turn suggested that the sensor device comprises a first sensor for sensing a travel path of the first actuator, such as in the form of a resistance sensor, Hall effect sensor, temperature sensor or current sensor in combination with at least one stop, a second sensor for sensing a travel path of the second actuator, such as in the form of a rotation angle sensor or current sensor in combination with at least one stop, a third sensor for detecting obstacles in the area of the rear view element, a fourth sensor for capturing vibrations, and/or a fifth sensor for capturing the road and/or driving motion. 
         [0020]    The rear view element can comprise at least one mirror element and/or a camera. 
         [0021]    Preferably, according to the invention, in the locking position, a form fit is provided between the first and second engagement element. 
         [0022]    The invention also provides a method for controlling the rear view element folding device according to the invention, characterized in that the travel path of the first actuator in the form of an SMA actuator is set using a temperature and/or resistance regulation and/or using the sensor device, and/or the travel path of the second actuator is set using a temperature and/or resistance regulation and/or using the sensor device, and/or the control and regulating device sets a current source for applying current impulses to the first and/or second actuator, preferably depending on stored and/or self-learned pulse sequences. 
         [0023]    The invention uses two actuators, namely one for a locking and/or unlocking, and another for a rotation of an element housing relative to an element foot in a rear view element of a motor vehicle. This hybrid form not only leads to a simple structure, but also to a reduction in noise and an increase in adjustment speed or folding up speed, simultaneously with an unreduced service life. 
         [0024]    Of particular advantage according to the invention is when at least the actuator, which carries out an unlocking, uses at least one shape memory element (SMA element) and thus is an SMA actuator. An SMA element such as an SMA wire or an SMA spring, actually can namely be heated via a brief current surge so that it contracts and can itself act against the force of a spring element while contracting in order to release a lock which is secured by the spring element, preferably in a form-fit manner. Then in a cooling down phase, in which the SMA element returns to its original length, the spring element can also return to its original position in which it secures a lock, which in the case of a form-fit connection can also withstand relatively large forces. Only in the unlocked state, in which the spring element does not enforce a lock, a rotation can be conducted via the second actuator. This rotation can be enabled by means of any drive, for example again via an SMA actuator or a standard electromotor. 
         [0025]    The controlling of both actuators can occur in dependence on output values of sensors, on the one hand for the precise setting of the respective movement, i.e. the translation movement of the first actuator and the rotational movement of the second actuator. On the other hand, the sensors also make it possible to react to external circumstances, such as for example an obstacle close to a rear view element. If for example an obstacle is captured on the passenger side, the rear view element on the passenger side can quickly be folded up to the motor vehicle via the rear view element folding device according to the invention, in order to avoid a damage occurring. Such a folding-up is also possible on the driver side, although coupled with a driving speed, for example up to a speed of  6 km per hour, which is generally associated with parking or reversing out of a parking space. However, folding up in reaction to captured vibrations, caused either by a driving motion per se or by the area surrounding the motor vehicle, for example in cases of bad weather is also possible with a rear view element folding device according to the invention. 
         [0026]    Various aspects of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  a is a profile view through a rear view element folding device according to the invention, in a locking position. 
           [0028]      FIG. 1 b    is a profile view through a rear view element folding device according to the invention, in an unlocking position. 
           [0029]      FIG. 1 c    is a profile view through a rear view element folding device according to the invention, when approaching a rotational position. 
           [0030]      FIG. 2  is a flow chart of an approach of a rotational position by means of the rear view element folding device as shown in  FIGS. 1 a   - 1   c.    
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0031]      FIGS. 1 a  to 1 c    show a rear view element folding device according to the invention for example in form of a rear view mirror folding device  1 , which uses a basic body  2  which is either provided by a mirror foot, not shown, or is firmly attached thereto, in order to support further elements. Thus, a drive motor  3  is arranged as part of an actuator for a rotational movement in the basic body  2 , which comprises a hollow cylinder form, and is also affixed there in order to engage a rotation element  4  via a gear stage, not shown, said rotation element for its part being attached to a mirror housing or mirror head, not shown, wherein a mirror element is provided in the mirror head. The rotation element  4  is firmly connected to an engagement element  5  or is formed with said element. According to  FIG. 1   a,  this engagement element  5  firmly engages with a further engagement element  6 , when a locking position is adopted. Between the engagement element  6  and the basic body  2 , a spring element  7  is arranged concentrically to the basic body  2 . 
         [0032]    Around the spring element  7  runs concentrically a plurality of SMA wires  8  or an SMA wire, having several coils as part of a further actuator. Each SMA wire  8  here engages on the engagement element  6  on the one hand, and on the other hand on the basic body  2 , as does the spring element  7 . 
         [0033]    In the locking position shown in  FIG. 1   a,  which represents a locked resting position, the spring element  7  presses the engagement element  6  onto the engagement element  5  for locking purposes. Here, trapezoid protrusions  10  on the engagement element  5  engage in complementary recesses  11  of the engagement element  6 . The engagement elements  5 ,  6  can be formed as gear rings. The engagement elements  5 ,  6  can however also be formed as clamping, braking or latching elements, i.e. also function as frictionally engaged brakes, for example. 
         [0034]    If a mechanical torque is applied to the rotation element  4 , due to the trapezoid form of the protrusions  10  and thus also of the recesses  11 , the engagement between the two engagement elements  5 ,  6  can be released, whereby the spring element  7  is compressed. This is used for the so-called child&#39;s head test, which tests whether the rear view mirror folds away when a rear view mirror collides with a child&#39;s head. 
         [0035]    If a current impulse is applied to the SMA wires  8 , these heat up and contract as a result, so that the spring element  7  is compressed, as can be seen in  FIG. 1   b.  Here, a gap ΔS is opened along the translation direction S between the two engagement elements  5  and  6 , and thus the engagement of the protrusions  10  on the recesses  11  is released, so that an unlocking occurs as is shown in  FIG. 1   b.  In other words, the contraction of the SMA wires  8  leads to an actuating power which is greater than the pressure force of the spring element  7 . This leads to a decoupling of the engagement elements  5  and  6 , so that the rotation element  4  together with the engagement element  5  is then only radially mounted around a guide contour of the basic body  2 , while a linear displacement, i.e. a translation, of the rotation element  4  together with the engagement element  5  is no longer possible. 
         [0036]    In the unlocked resting state shown in  FIG. 1   b,  it is possible to affect a rotation of the engagement element  5  relative to the engagement element  6  by switching on the drive motor  3 , namely around the rotation axis AΦ by a certain rotation angle ΔΦ, as indicated in Figure lc. The drive motor thus generates a low torque following activation, which is guided over the gear stage onto the engagement element  5  together with the rotation element  4 , so that a rotation of these two parts occurs. 
         [0037]    In order to monitor the travel path of the drive motor  3 , a rotation angle sensor, such as a potentiometer, a Hall effect sensor or also an induction sensor, can be used. Alternatively, it is also possible to query all positions by means of mechanical end switches. 
         [0038]    For unlocking purposes, it is advantageous when a current is applied to all SMA wires  8  at the same time, preferably in each case with a brief current surge, so that an even unlocking does in fact take place. As soon as no further current is applied to the SMA wires  8 , these wires cool down again, so that a renewed locking automatically occurs, since the SMA wires  8  expand respectively into their original length. In order to lengthen the time period of the unlocking procedure, several brief current surges can be applied to the SMA wires  8 . 
         [0039]    The travel path which acts to open the gap AS when the SMA wires  8  contract can occur in such a manner that it is controlled via a Hall effect sensor, a current control device, a resistance measurement or similar. 
         [0040]    Instead of SMA wires, SMA tension springs can also be used, for example evenly distributed around the circumference of the spring element  7 . The dimensioning of the force of the SMA actuator can be conducted over the number of SMA wires  8 . The higher the required actuating force is, the more SMA wires are needed. Monitoring of the travel path of the SMA wires can be conducted via resistance regulation. Here, the change in electric resistance can be monitored via a measurement amplifier. These changes are significant with increasing ΔS. In case of critical resistance values or an identification of a certain gradient of the resistance changes over the time, a set stop point can automatically be determined. The recording of a set stop point can alternatively be achieved via a mechanical end switch. A two-position controller can record the signal of a stop point and in the logical state of the current source for the SMA wires can switch between a “heating” and “cooling” parameter by switching the current supply on and off. 
         [0041]    In  FIG. 2 , the progress of a folding up procedure of a rear view element with a rear view element folding device  1  according to the invention is again shown. In a first step  100 , the device  1  is switched on and then in a second step  101  the rotation direction of the drive motor  3  required for folding down is determined. In a third step  102 , an unlocking is effected via the SMA actuator, namely by applying a current pulse to each of the SMA wires  8 , as shown in  FIG. 1   b.  Then, a rotation from the extended resting position into the folding down position is conducted via the drive motor  3 , preferably in a timed manner, during a plurality of cycles, each with a duration of  0 . 5  sec, as indicated by the step sequence  103 ,  104  and  105 . 
         [0042]    In the same timing, further current impulses are applied onto the SMA wires  8 , in order to keep them warm and thus shortened, so that an unlocking is guaranteed. If in a next step  106  a signal is issued from a sensor in the form of e.g. an end switch that the desired end position has been achieved, the rotation is ended, as indicated by steps  107  and  108 , so that finally, in step  109 , the device  1  can be switched off. 
         [0043]    If due to a termination of an application of current on the SMA wires  8  a cooling of said wires occurs, these SMA wires  8  contract, wherein they enforce a sliding in of the protrusions  10  into the recesses  11 , so that the unlocking position according to  FIG. 1 a    is again taken up. 
         [0044]    The SMA wires  8  can be kept “warm” at a first temperature by suitable application of current impulses, in order to be able to complete a certain rotation procedure. The SMA wires can be kept at a second temperature in order to still ensure a locking, but also to enable fast unlocking. In other words, via the setting of the temperature of the SMA wires  8  a control of the hybrid system of the rear view element folding device  1  according to the invention can be effected. 
         [0045]    The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.