Abstract:
An electromotive actuator for deflecting a motor vehicle part includes a rotatable component and a non-rotatable component. The rotatable component can be driven by an electric motor in such a way that it can be moved linearly relative to the non-rotatable component between a first position and a second position. In order to create a compact adjustment device, the two components of the actuator are configured respectively as a threaded spindle and a threaded nut, whereby the rotatable component (threaded spindle or threaded nut) is non-rotatably connected to the rotor of the electric motor and can act directly or indirectly on the vehicle part that is to be deflected.

Description:
Priority is claimed to German Patent Application No. DE 10 2006 042 477.8, filed on Sep. 9, 2006, the entire disclosure of which is incorporated by reference herein. 
     The present invention relates to an electromotive actuator for deflecting a motor vehicle part. 
     BACKGROUND 
     Modern vehicles contain a relatively large number of electric actuators with which the rotational movement generated by an electric motor that can be actuated by a control device is converted into a linear or rectilinear movement of the vehicle component that is to be moved. A special area of application of such actuators is in the automatic actuation of a starting and shifting clutch of a motor vehicle, whereby the component that is to be actuated can be, for example, a so-called central clutch release device of the friction clutch. During actuation, such a central clutch release device acts, for example, on the diaphragm spring of the clutch in such a way that it is released or brought into a slip position in which the clutch can transmit no torque at all or only a reduced torque from the drive engine of the vehicle to the gear. 
     Various deflection gears have become known for purposes of converting the rotational movement of the rotor of the electric motor into a rectilinear movement. Thus, for example, deflection gears are used in conjunction with actively controllable multi-disk clutches and these deflection gears are used on axle or middle differentials as differential locks and in a power train with selectable four-wheel drive as a selectable clutch of a drive axle that can be activated as needed. By means of the deflection gear, an externally generated controlling torque is continuously converted at a high transmission ratio into an axial contact force in order to actuate, that is to say, in order to at least partial close, an associated multi-disk clutch. 
     Two embodiments of a differential gear with a disk lock that can be actuated by means of an electric motor via such a deflection gear are described in EP 0 368 140 B1. According to a first embodiment, in FIG. 1, the differential gear is configured with a bevel wheel design. A support ring is drive-connected via a bevel wheel of a reduction gear to an electric motor that is affixed to the housing. An adjusting ring is mounted non-rotatably and axially movably on the housing side and is connected directly to the support ring via cam tracks. Hence, a rotation of the support ring is converted into an axial movement of the adjusting ring which is connected—via an axial thrust bearing, via an outer pressure plate that rotates together with the differential cage via several tappets that penetrate the differential cage and via an inner pressure plate—to the multi-disk clutch, whose disks are arranged operatively between the differential cage and one of the two output bevel wheels. 
     In a second variant according to FIG. 2 in the above-mentioned application, the differential gear is configured with a planetary design. The support ring here is mounted non-rotatably and axially immovably on the housing side. In contrast, the adjusting ring is mounted rotatably and axially movably and, on the one hand, it is drive-connected via the pinion of a reduction gear to an electric motor that is affixed to the housing, and on the other hand, it is connected to the support ring via several ball grooves that ascend on the circumference side and via rolling elements arranged therein. Therefore, a rotation of the adjusting ring is converted by a rolling movement of the rolling elements between the opposing axially ascending ball grooves into an axial movement of the adjusting ring which is connected—via an outer axial thrust bearing, via an outer pressure plate that rotates together with the differential cage, via several first tappets that penetrate the differential cage, via a first inner pressure plate, via an inner axial thrust bearing, via a thrust washer, via several second tappets that penetrate the center pin of the planetary carrier and via a second inner pressure plate—to the multi-disk clutch, whose disks are arranged operatively between the differential cage and the sun wheel of the differential gear. 
     Another differential gear with a disk lock that can be actuated by means of an electric motor via a similar deflection gear is known from U.S. Pat. No. 4,805,486 A. With this differential gear, a support ring is mounted non-rotatably and axially immovably on the housing side. An adjusting ring is supported rotatably as well as axially movably, and on the one hand, it is drive-connected via the pinion of a reduction gear to an electric motor that is affixed to the housing and, on the other hand, it is connected—either via cam surfaces that ascend on the circumference side (see FIG. 2 there) or via ramp surfaces that ascend on the circumference side and via rolling elements arranged therein (see FIG. 3 there)—to the support ring. A rotation of the adjusting ring is thus converted by a sliding movement of the opposing axially ascending cam surfaces or by a rolling movement of the rolling elements between the opposing axially ascending ramp surfaces into an axial movement of the adjusting ring which is connected—via an outer axial thrust bearing, via an outer pressure plate, via several pistons that penetrate the differential cage and via an inner pressure ring—to the multi-disk clutch, whose disks are arranged operatively between the differential cage and one of the two output bevel wheels of the differential gear. 
     Only for the sake of completing the known state of the art, reference is hereby made to German patent application DE 103 48 312 A1 that discloses an actuation device for a friction coupling device with which a clutch actuator equipped with the described ball ramps can be actuated by means of a bowden cable. 
     All of these known deflection gears have in common the fact that the axially ascending ramp and cam surfaces are oriented towards the circumference. As a consequence, the corresponding operative contours are each limited to a relatively small rotational angle sector of the input element, disadvantageously resulting in a relatively small transmission ratio between the rotational movement and the torque of the input element as well as the axial movement and the axial contact force of each associated output element. A precise setting of a desired locking power or closing power by means of the axial contact force acting on the appertaining multi-disk clutch is thus hardly possible and moreover, presupposes a considerable absence of play on the transmission path between the electric actuating drive and the input element. Moreover, there is a need for a very precise manufacture of the cam or ramp surfaces of the input element and output element, as a result of which the production of this component is complicated and hence expensive. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a deflection gear of the above-mentioned type that, with a structure that can be produced simply and inexpensively and that is also compact, has an even further increased transmission ratio. 
     A structural combination of an electric motor with a spindle thread-spindle nut drive unit can be very advantageously used to deflect parts in a motor vehicle. This relates primarily to parts in the power train of a motor vehicle, but such an actuator can also be used in other areas of the motor vehicle. 
     Accordingly, the invention provides an electromotive actuator for deflecting a vehicle part, comprising a rotatable component and a non-rotatable component, which are arranged coaxially inside each other, whereby the rotatable component can be driven by an electric motor in such a way that it can be moved linearly relative to the non-rotatable component between a first position and a second position. According to the invention, it is now provided that the two components of the actuator are configured as a threaded spindle and a threaded nut, whereby the rotatable component (threaded spindle or threaded nut) is non-rotatably connected to the rotor or to the armature of the electric motor and can act directly or indirectly on the vehicle part that is to be moved linearly. 
     The person skilled in the art is generally familiar with spindle thread-spindle nut drive units but their special use in a motor vehicle actuator is a part of the invention. In this context, as far as the technical success of the subject matter of the invention is concerned, it does not matter whether the threaded spindle or the threaded nut is arranged non-rotatably. Therefore, the description provided below of an electromotive actuator according to the invention also applies, of course, to its mechanically reversed construction, namely, if it is not the threaded spindle but rather the threaded nut that is arranged stationarily and non-rotatably. 
     Therefore, according to a first embodiment of this actuator, it is provided that the threaded spindle is arranged stationarily as well as non-rotatably and the threaded nut is arranged rotatably. 
     On its two axial ends, the threaded nut preferably has a ring flange facing radially towards the outside as well as a ring flange facing radially towards the inside, whereby the ring flange facing radially towards the outside is situated away from the vehicle part that is to be actuated while the ring flange facing radially towards the inside is situated on the threaded nut close to the vehicle part that is to be actuated. 
     According to another feature of the invention, it is provided that the radially inner circumferential surface of the threaded nut has a screw thread that engages with a correspondingly configured screw thread on the threaded spindle. As is known, through a concrete configuration of the screw thread, the actuator&#39;s conversion of the rotational movement of the electric motor into an axial movement can be set as needed. 
     The above-mentioned ring flange facing radially towards the inside—with its one axial surface—forms a stop for an axial movement of the threaded nut on the threaded spindle, so that the threaded nut is secured in a first actuation direction against unwinding from the threaded spindle. 
     Moreover, it is provided that, in the area of its ring flange facing radially towards the inside, the threaded nut has a thread—for example, a fine thread—on its radially outer circumferential surface, onto which an armature nut with a corresponding thread can be screwed. 
     In a refinement of this inventive detail, it is provided that the armature or rotor of the electric motor is arranged and clamped between the armature nut screwed onto the threaded nut and the ring flange facing radially towards the outside. As a result, a rotational movement generated by the electric motor can be transmitted directly to the threaded nut which then, as a function of the current rotational direction of the armature, moves in a screwing motion on the threaded spindle, thereby executing an axial movement. 
     As far as the threaded spindle is concerned, it can be provided that it is placed non-rotatably onto a preferably hollow-cylindrical guide tube or is formed in one piece with such a guide tube which itself is connected to a non-rotatable part of the motor vehicle. This non-rotatable part of the motor vehicle can be, for example, a clutch bell housing or a gear housing. 
     In another embodiment of the invention, the stator winding of the electric motor is attached to a stator yoke that, in turn, is firmly connected to a stator mounting plate, whereas the stator mounting plate is connected to the non-rotatable part of the motor vehicle. 
     Moreover, it can be provided that a sensor wheel having detectable profiling is clamped between the armature nut and the armature by means of a radial clamping section. This profiling can be configured in a generally known manner, that is to say, for example, in the form of external teeth on the sensor wheel or in the form of recesses on the outer circumference. 
     In another concrete embodiment of the sensor wheel, it is provided that, starting from the radial clamping section, the sensor wheel has a first axial section axially overlapping the armature nut, at least partially, that, starting from the first axial section, there is a radial section and subsequently, an axially receding second axial section having the detectable profiling is configured on the sensor wheel. 
     According to another aspect of the invention, it is provided that a ring-shaped stator carrier is arranged radially above the sensor wheel and the stator yoke is attached to said stator carrier, which is firmly connected via a spacer ring to the above-mentioned stator mounting plate. 
     A speed sensor and/or a torque angle sensor facing radially towards the inside is attached to the stator carrier and the profiling of the sensor wheel can be detected by said speed sensor and/or a torque angle sensor and transferred to a control unit associated with the electromotive actuator. 
     The stator carrier and the sensor wheel are arranged coaxially inside each other. Since the stator carrier is arranged non-rotatably and the sensor wheel is arranged rotatably, they do not touch each other. Nevertheless, they form the partially open housing of the electromotive actuator according to the invention. 
     Another feature of the invention is that the front surface of the armature nut facing the vehicle part that is to be actuated is directly or indirectly operatively connected to this vehicle part, and hence it can actively move it in at least one direction. 
     According to a concrete design, it is provided here that the front surface of the armature nut facing the vehicle part that is to be actuated is operatively connected to a clutch release bearing that, in turn, acts upon the vehicle part that is to be moved. Here, it can be provided that the front surface of the armature nut facing the vehicle part that is to be actuated can be laid axially against an outer ring of the clutch release bearing, while the front surface of the inner ring of the clutch release bearing facing away from the threaded nut lies against the vehicle part that is to be actuated. 
     In order to guide the outer ring of the clutch release bearing inside the electromotive actuator, it can be provided that the outer ring of the clutch release bearing has an axial section with which it lies on the radially outer circumferential surface of the armature nut so as to be axially movable. 
     In this context, it is considered to be advantageous if an uncoupling spring is arranged axially between the outer ring of the clutch release bearing and the sensor wheel or the armature so that, when the threaded nut executes an axial movement away from the vehicle part that is to be actuated and all the way to the stop, this uncoupling spring holds the outer ring in a desired position relative to the inner ring and also holds the inner ring in contact with this vehicle part, even when a force exerted by this vehicle part onto the inner ring of the clutch release bearing drops to the value of zero. Preferably, this uncoupling spring is configured as a helical compression spring. 
     In another embodiment, a sealing element is arranged between the threaded nut and the threaded spindle in the area of the ring flange of the threaded nut facing radially towards the outside. This advantageously prevents the penetration of dirt into the screw thread of the threaded nut and of the threaded spindle. 
     Moreover, it is felt to be advantageous for the thread of the threaded nut and of the threaded spindle as well as for the thread of the armature nut to be configured so as to be self-locking. This ensures that an adjustment position that has been assumed cannot be changed inadvertently due to the slight forces that are exerted during operation, but rather that the force of the electric motor is necessary for this purpose. Consequently, special components to ensure non-rotatability can be dispensed with in this design. 
     Finally, the described electromotive actuator is part of a motor vehicle actuating device, whereby the vehicle part that has been mentioned a number of times is a starting and shifting clutch or its diaphragm spring, a gear brake, a shift track actuator or a gear actuator or a slip coupling of a gear coupling device and/or a gear synchronization device of an automatic transmission or a shifting clutch on a differential gear. The actuator presented here can be constructed to be very small in terms of the actuation forces needed in a given application case, so that it can be used as a very precise adjustment device, also inside the housing of the above-mentioned aggregates or components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to elucidate the invention, the description is accompanied by a drawing in which an embodiment of an actuator structured according to the invention is depicted. 
     
    
    
     DETAILED DESCRIPTION 
     The single FIGURE shows an electromotive actuator  1  configured according to the invention, in a perspective and cutaway view. The part that is to be actuated in this embodiment is a vehicle component, especially a diaphragm spring  2  of a friction clutch, that is used as starting and shifting clutch in conjunction with an automatic transmission. Here, the actuator  1  is configured as a so-called central clutch release device that opens or closes the friction clutch as a function of control commands of a control device (not shown here) or else that brings it into certain slip operational positions. 
     For this purpose, the actuator  1  has an electric motor  3  that can be operated in two rotational directions, as a function of the particular actuation. This electric motor  3  is connected to a deflection gear in the form of a spindle thread-spindle nut arrangement that converts the rotational movement of the electric motor  3  into an axial, linear movement of the control unit of the actuator  1  so that ultimately, the diaphragm spring  2  can be axially deflected. 
     Below, the structural design of this actuator will be discussed in greater detail. The spindle thread-spindle nut arrangement consists of a threaded spindle  4  with a screw thread  11  onto which a threaded nut  5  with a corresponding screw thread  10  is screwed. In the embodiment shown here, the threaded spindle  4  is placed non-rotatably and axially immovably onto a hollow cylindrical guide tube  14  that is connected via a mounting plate  16  to a non-rotatable and stationary part  39  of the motor vehicle, for instance, to the gear housing. For this purpose, the mounting plate  16  has bores  38  through which fastening screws can be inserted. 
     The threaded nut  5  has a ring flange  7  facing radially towards the outside and a ring flange  8  extending radially towards the inside, whereby the latter has a stop surface  9  that, in order to limit the axial mobility of the threaded nut  5 , can come to rest against an associated stop surface on the threaded spindle  4 . 
     A sealing element  36  is clamped between the ring flange  7  of the threaded nut  5  facing radially towards the outside and the threaded spindle  4  and this sealing element  36  can reliably keep dirt out of the area of the screw threads  10 ,  11 . 
     The ring flange  7  facing radially towards the outside serves as a ring shoulder for the axial placement of the armature  6  of the electric motor  3  which is its rotatable component, that is to say, its rotor. This armature  6  is slipped onto the radially outer circumferential surface of the threaded nut  5 . An armature nut  13  screwed onto an outer thread  12  of the threaded nut  5  clamps the armature  6  between itself and the ring flange  7  facing radially towards the outside. This construction firmly connects the armature  6  to the threaded nut  5  so that said armature  6  can rotationally drive the threaded nut  5 . 
     The stator of the electric motor  3  is arranged at a radial distance from the armature  6  and the winding  37  of this stator is supported by a stator yoke  15 . The stator yoke  15 , in turn, is firmly connected to the stator mounting plate  16  via a stator carrier  23  made of sheet metal and via a spacer ring  24 , whereby as already mentioned, said stator mounting plate  16  is connected to a non-rotatable and stationary part of the motor vehicle. 
     As the single FIGURE shows, a sensor wheel  17  having detectable profiling  18  is secured between the armature nut  13  and the armature  6  by means of a radial clamping section  19  of the sensor wheel. Starting from the radial clamping section  19 , the sensor wheel  17  has a first axial section  20  that axially overlaps the armature nut  13 , at least partially, thus exerting a certain protective function for this area. This first axial section  20  is followed by a radial section  21 , which, in turn, is followed by a second axial section  22  of the sensor wheel  17  that overlaps the first axial section  20 , said sensor wheel  17  having the detectable profiling  18 . 
     The profiling  18  in this embodiment is formed by cutouts in the second axial section  22  of the sensor wheel  17  that are arranged one after the other relative to the circumference. 
     A ring-shaped sensor carrier plate portion of the stator carrier  23  projects radially over the sensor wheel  17  and partially overlaps it axially. In this axial overlapping area, a sensor carrier  26  is arranged on the ring-shaped sensor carrier portion of the stator carrier  23  onto which a speed sensor or torque angle sensor  25  is attached. The sensitive side of this sensor  25  faces the profiling  18  of the sensor wheel  17  so that, when this profiling  18  is moved past the sensor, sensor signals are triggered that are transmitted to the control unit (not shown here). Using these sensor signals, the control unit generates control commands pertaining to the rotational direction and to the activation or stoppage of the electric motor  3 , so that the axial travel of the actuator  1  can be set very precisely. 
     The structural design of the actuator  1  that has been described so far is actually sufficient for this actuator  1  to move vehicle parts  2  linearly. For this purpose, the front surface of the ring flange  8  extending radially towards the inside merely has to act upon such a vehicle part and/or has to be non-positively connected to this part. Such a utilization of the actuator  1  is practical, for example, if the vehicle part that is to be deflected does not execute a rotational movement. In contrast, in order to deflect rotating parts, a rotation uncoupling from the actuator  1  is necessary, which will be described below. 
     For purposes of the rotation uncoupling, between the diaphragm spring  2 —which is to be actuated and which is rotating at the speed of the drive engine—and the threaded nut  5 , a clutch release bearing  28  is arranged on the actuator  1  which, in this embodiment, is configured as a single-row angular ball bearing in which bearing balls  30  are arranged between an outer ring  29  and an inner ring  31 . Here, the front surface  27  of the armature nut  13  facing the diaphragm spring  2  lies axially against the outer ring  29  of the clutch release bearing  28 , while the inner ring  31  with its front surface  32  facing away from the threaded nut  5  lies against the diaphragm spring  2  that is to be actuated and it has no contact with the spindle nut  5 . 
     In order to radially and axially guide the clutch release bearing  28 , it is provided for the outer ring  29  to have an axial section  33  with which it lies on the radially outer circumferential surface  34  of the armature nut  5  so as to be axially movable. 
     Moreover, axially between the outer ring  29  of the clutch release bearing  28  and the sensor wheel  17  or the armature  6 , there is an uncoupling spring  35  that, when the threaded nut  5  executes an axial movement away from the diaphragm spring  2  and all the way to the stop (stop surface  9 ), holds the outer ring  29  in a desired position relative to the inner ring  31  and also holds the inner ring  31  in contact with the diaphragm spring  2 , even when a force F exerted by the diaphragm spring  2  onto the inner ring  31  of the clutch release bearing  28  drops to the value of zero. The uncoupling spring  35  is configured here as a helical compression spring. 
     As mentioned above, the screw threads  10 ,  11  and  12  of the threaded nut  5  and of the threaded spindle  4  as well as optionally also the thread of the armature nut  13  are configured so as to be self-locking and they are also capable of absorbing radial forces. The latter can also be achieved in that the above-mentioned threads have an additional, preferably radial contact surface in their core diameter or root diameter.