Patent Publication Number: US-2016223082-A1

Title: Parking Lock for Motor Vehicles

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of PCT International Application No. PCT/EP2014/069847, filed Sep. 18, 2014, which claims priority under 35 U.S.C. §119 from German Patent Application No. 10 2013 220 396.9, filed Oct. 10, 2013, the entire disclosures of which are herein expressly incorporated by reference. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The invention relates to a parking lock for motor vehicles, in particular for motor vehicles which have an automatic transmission, an automated transmission or an electric drive. In particular, the invention relates to a parking lock having an activation device with a shaft for coupling to an actuator, wherein the shaft can be pivoted about an activation axis between an activation position and a release position. A latching device is coupled to the activation device and has a latch which is pivotable about the activation axis between a latching position and an unlatching position. A pawl is pivotable about a pawl bearing axis between a locking position and a release position, and a parking lock gearwheel is rotatable about a parking lock axis and is coupled to a motor vehicle wheel. In its locking position, the pawl engages in the parking lock gearwheel in such a way that rotation of the parking lock gearwheel about the parking lock axis is blocked, and in its release position, the pawl is spaced apart from the parking lock gearwheel. The result is that rotation of the parking lock gearwheel about the parking lock axis is released. In its activation position, the shaft of the activation device pushes the latch into its latching position, and the latch pushes the pawl into its locking position. And, in the release position of the shaft, the latch assumes its unlatching position in which the pawl is released. 
     Such a parking lock for motor vehicles of the generic type is already known from DE 10 2010 027 826 A1, and provides the advantage, owing to the few individual parts and the small number of elements which can be moved relative to one another, in particular the latching device, that it has a comparatively low fabrication complexity and wear. This permits a long service life of the parking lock together with reliable functioning. In addition, the latch of the latching device requires only a small amount of space for itself and for its pivoting movement, resulting in a particularly compact design. 
     On the other hand, the mounting of the actuator on the activation device and the high level of loading of the actuator when the parking lock is activated prove problematic. Furthermore, in the case of misuse, that is to say when the parking lock is engaged when in travel, undesirably strong vibrations occur in the drive train, and the parking lock is damaged. In addition, it has become apparent that a vehicle on a slope is not reliably prevented from rolling away by the above-described parking lock. 
     Therefore, the object of the invention is to provide a parking lock in which one or more of the described disadvantages from the prior art are eliminated. 
     According to the invention, this and other objects are achieved by a parking lock of the type mentioned at the beginning, which additionally has at least one of the following features: 
     (i) an axial end of the shaft is designed to connect in a positively locking fashion to the actuator as a multi-toothed or polygonal element; 
     (ii) a leaf spring and a ratchet element which is connected to the shaft in a rotationally fixed fashion are provided, wherein the leaf spring and the ratchet element form a ratchet connection both in the activation position and in the release position of the shaft; 
     (iii) the parking lock gearwheel has teeth and tooth gaps which alternate in the circumferential direction, wherein the teeth have a saddle-roof-shaped head contour; 
     (iv) the latch and/or the pawl have at least one recess for reducing the moment of inertia; and/or 
     (v) the latch and the pawl interact in the latching position of the latch in such a way that self-locking occurs between the latch and the pawl. 
     These individual features contribute overall to a parking lock which is easy to mount and activate and which reliably makes available a large securing force in the locking position, and in the case of misuse prevents undesired vibrations in the drive train and relatively severe damage. 
     In order to reliably ensure a large securing force in the locking position of the parking lock, the pawl preferably has an undercut into which the latch engages in its latching position. This gives rise to what is referred to as self-locking between the latch and the pawl and means, in other words, that the parking lock, to be more precise the pawl of the parking lock, can be released from the latching position into the unlatching position only by active pivoting of the latch. On the other hand, the parking lock cannot be released by parking lock gearwheel torque acting on the pawl, since the pawl cannot be pivoted into its release position when such loading occurs, owing to the undercut and the resulting self-locking. 
     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The single Figure is a perspective view of a parking lock for motor vehicles, in particular for motor vehicles having an automatic transmission, an automated transmission or an electric drive, according to an exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWING 
     The single figure shows a parking lock  10  for motor vehicles, in particular for motor vehicles which have an automatic transmission, an automated transmission or an electric drive. The parking lock includes an activation device  12  with a shaft  14  for coupling to an actuator  16 . The shaft  14  can be pivoted about an activation axis A between an activation position and a release position illustrated in the figure. A latching device  18  is coupled to the activation device  12  and has a latch  20  which is pivotable about the activation axis A between a latching position and an unlatching position illustrated in the figure. A pawl  22  is pivotable about a pawl bearing axis B between a locking position illustrated in the figure and a release position. And, a parking lock gearwheel  24  is rotatable about a parking lock axis C and is coupled to a motor vehicle wheel in a rotationally fixed fashion. 
     In the locking position, a locking tooth  26  of the pawl  22  engages in the parking lock gearwheel  24  in such a way that rotation of the parking lock gearwheel  24  about the parking lock axis C is blocked. On the other hand, in the release position of the pawl  22  the locking tooth  26  is spaced apart from the parking lock gearwheel  24 , with the result that rotation of the parking lock gearwheel  24  about the parking lock axis C is released. In addition, a limb spring  28 , which pushes the pawl  22  into its release position, is provided in the region of the pawl bearing axis B. 
     As it pivots into its activation position, the shaft  14  of the activation device  12  pushes the latch  20  into its latching position, wherein as it pivots into its latching position the latch  20  in turn pushes the pawl  22  into its locking position counter to the spring force of the limb spring  28 . The latch  20  is mounted here on the shaft  14  so as to be pivotable to a limited degree, wherein a limb spring  30 , which pushes the latch  20  relative to the shaft  14  with a spring force acting in the direction of the latching position, is arranged between the shaft  14  and the latch  20 . 
     In contrast, in the release position of the shaft  14 , the latch  20  is held in its unlatching position, wherein the pawl  22  is released in this unlatching position and moves into its release position owing to the spring loading by the limb spring  28 . 
     Since the parking lock  10  which is illustrated in the figure corresponds largely in terms of its general design and its general functional principle to the parking lock according to DE 10 2010 027 826 A1, reference is made in this respect specifically to the description in DE 10 2010 0217 826 A1, whose contents are incorporated by reference herein. Only differences and advantages of the parking lock  10  are explored in more detail in the following text. 
     For example, in its latching position, the latch  20  interacts with the pawl  22  in such a way that self-locking occurs between the latch  20  and the pawl  22 . For this purpose, an undercut  32 , into which the latch  20  engages in its latching position, is formed in the pawl  22 . This means that during its movement from the latching position into the unlatching position, the latch  20  firstly pivots the pawl  22  counter to the spring force of the limb spring  28  toward the parking lock gearwheel  24  before it then releases the pawl  22 , with the result that the latter is moved in a spring-loaded fashion away from the parking lock gearwheel  24  and into its release position. Therefore, the undercut  32  of the pawl  22  easily ensures a particularly large securing force of the activated parking lock  10 . 
     The parking lock gearwheel  24  has teeth  34  and tooth gaps  36  which alternate in the circumferential direction, wherein in the locking position of the pawl  22  the locking tooth  26  engages in one of the tooth gaps  36  in order to block rotation of the parking lock gearwheel  24  about the parking lock axis C. In this case, the parking lock  10  is activated, wherein the rotationally fixed coupling between a vehicle wheel and the blocked parking lock gearwheel  24  reliably prevents the motor vehicle from rolling away. 
     According to the figure, the teeth  34  of the parking lock gearwheel  24  have a saddle-roof-shaped head contour  38  on their radial outer side. Therefore, the head contour  38  of each tooth  34  comprises two oblique faces  40  which adjoin one another and which enclose an angle α of 155°≦α≦175°, in particular α≈165°. 
     If the parking lock  10  is activated in what is referred to as a “case of misuse” at vehicle speeds above a crawling speed, the head contour  38  prevents relatively severe damage to the vehicle transmission and/or the parking lock  10 . Owing to the head contour  38 , the pawl  22  is in fact deflected in a particularly low-impact fashion by the quickly rotating parking lock gearwheel  24  which is coupled in a rotationally fixed fashion to the vehicle wheel, and reliably prevents the locking tooth  26  from engaging in the tooth gaps  36 . 
     In order to prevent undesirably strong vibrations in the drive train of the motor vehicle in the case of misuse, it has also proven advantageous to minimize the moments of inertia of the latch  20  and of the pawl  22  as a result of which, in the case of misuse, the energy which is introduced into the vehicle transmission via the parking lock gearwheel  24  is also drastically reduced. 
     In the present case, the latch  20  and the pawl  22  have recesses  42  in order to reduce the moment of inertia. These recesses  42  can be embodied, for example, as milled portions, as illustrated on the latch  20 , or as through-bores parallel to the pawl bearing axis B, as illustrated on the pawl  22 . 
     In order to mount the actuator  16  on the activation device  12  of the parking lock  10 , an axial end  44  of the shaft  14  is embodied as a multi-toothed or polygonal element. Such a positively locking and essentially rotationally fixed multi-tooth or polygonal connection permits advantageous, positionally defined mounting of the actuator  16  on the parking lock  10  at low cost. 
     According to the figure, a leaf spring  46  and a ratchet element  48  which is connected to the shaft  14  in a rotationally fixed fashion are also provided, wherein the leaf spring  46  and the ratchet element  48  form a ratchet connection both in the activation position and in the release position of the shaft  14 . In this context, the leaf spring  46  has an attachment end  50  for mounting the leaf spring  46  in such a way that it is fixed to the bodywork, and an opposite ratchet end  52  which is pushed against the ratchet element  48  by a spring section  54  of the leaf spring  46 . The ratchet element  48  has a recess  56  which is assigned to the activation position, and a recess  58  which is assigned to the release position, with the result that the ratchet end  52  of the leaf spring  46  engages in one of the recesses  56 ,  58  in both positions of the shaft  14 , and forms a ratchet connection. 
     Adjacent to the attachment end  50 , the leaf spring  46  has the essentially planar spring section  54  which, at the ratchet end  52  of the leaf spring  46 , is bent over toward the ratchet element  48 , in particular rolled up, and forms a ratchet projection  60 . 
     In the present case, the leaf spring  46  therefore acts as a ratchet spring whose ratchet projection  60  clips into one of the recesses  56 ,  58  both in the activation position and in the release position of the shaft  14 , in order to secure the shaft  14 . 
     According to the figure, the ratchet element  48  is a ratchet plate which extends perpendicularly with respect to the activation axis A and has, in each case, a notch as recesses  56 ,  58 , into which the ratchet projection  60  of the leaf spring  46  can engage. 
     In this way, the parking lock  10  can be activated with particularly low loading of the actuator  16 , which has a positive effect on the service life and energy consumption thereof. 
     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.