Parking Lock for Motor Vehicles

A parking lock for motor vehicles includes an activation device with a shaft for coupling to an actuator. The shaft is pivotable about an activation axis between an activation position and a release position. A latching system is coupled to the activation device and has a latch 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 coupled to a motor vehicle wheel. The parking lock additionally has at least one of the following features: an axial end of the shaft is designed as a multi-toothed or polygonal element for form-fittingly engaging the actuator; a leaf spring and a ratchet element secured to the shaft for conjoint rotation therewith are provided, the leaf spring and the ratchet element forming a ratchet connection both in the actuation position and in the release position of the shaft; the parking lock gearwheel has teeth and tooth spaces that alternate in the circumferential direction, the teeth having a saddleback-shaped head contour; the latch and/or the pawl have at least one recess, in order to reduce the moment of inertia; and the latch and the pawl co-operate in the latching position of the latch such that a self-locking effect is created between the latch and the pawl.

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.

DETAILED DESCRIPTION OF THE DRAWING

The single figure shows a parking lock10for 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 device12with a shaft14for coupling to an actuator16. The shaft14can be pivoted about an activation axis A between an activation position and a release position illustrated in the figure. A latching device18is coupled to the activation device12and has a latch20which is pivotable about the activation axis A between a latching position and an unlatching position illustrated in the figure. A pawl22is pivotable about a pawl bearing axis B between a locking position illustrated in the figure and a release position. And, a parking lock gearwheel24is 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 tooth26of the pawl22engages in the parking lock gearwheel24in such a way that rotation of the parking lock gearwheel24about the parking lock axis C is blocked. On the other hand, in the release position of the pawl22the locking tooth26is spaced apart from the parking lock gearwheel24, with the result that rotation of the parking lock gearwheel24about the parking lock axis C is released. In addition, a limb spring28, which pushes the pawl22into its release position, is provided in the region of the pawl bearing axis B.

As it pivots into its activation position, the shaft14of the activation device12pushes the latch20into its latching position, wherein as it pivots into its latching position the latch20in turn pushes the pawl22into its locking position counter to the spring force of the limb spring28. The latch20is mounted here on the shaft14so as to be pivotable to a limited degree, wherein a limb spring30, which pushes the latch20relative to the shaft14with a spring force acting in the direction of the latching position, is arranged between the shaft14and the latch20.

In contrast, in the release position of the shaft14, the latch20is held in its unlatching position, wherein the pawl22is released in this unlatching position and moves into its release position owing to the spring loading by the limb spring28.

Since the parking lock10which 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 lock10are explored in more detail in the following text.

For example, in its latching position, the latch20interacts with the pawl22in such a way that self-locking occurs between the latch20and the pawl22. For this purpose, an undercut32, into which the latch20engages in its latching position, is formed in the pawl22. This means that during its movement from the latching position into the unlatching position, the latch20firstly pivots the pawl22counter to the spring force of the limb spring28toward the parking lock gearwheel24before it then releases the pawl22, with the result that the latter is moved in a spring-loaded fashion away from the parking lock gearwheel24and into its release position. Therefore, the undercut32of the pawl22easily ensures a particularly large securing force of the activated parking lock10.

The parking lock gearwheel24has teeth34and tooth gaps36which alternate in the circumferential direction, wherein in the locking position of the pawl22the locking tooth26engages in one of the tooth gaps36in order to block rotation of the parking lock gearwheel24about the parking lock axis C. In this case, the parking lock10is activated, wherein the rotationally fixed coupling between a vehicle wheel and the blocked parking lock gearwheel24reliably prevents the motor vehicle from rolling away.

According to the figure, the teeth34of the parking lock gearwheel24have a saddle-roof-shaped head contour38on their radial outer side. Therefore, the head contour38of each tooth34comprises two oblique faces40which adjoin one another and which enclose an angle α of 155°≦α≦175°, in particular α≈165°.

If the parking lock10is activated in what is referred to as a “case of misuse” at vehicle speeds above a crawling speed, the head contour38prevents relatively severe damage to the vehicle transmission and/or the parking lock10. Owing to the head contour38, the pawl22is in fact deflected in a particularly low-impact fashion by the quickly rotating parking lock gearwheel24which is coupled in a rotationally fixed fashion to the vehicle wheel, and reliably prevents the locking tooth26from engaging in the tooth gaps36.

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 latch20and of the pawl22as a result of which, in the case of misuse, the energy which is introduced into the vehicle transmission via the parking lock gearwheel24is also drastically reduced.

In the present case, the latch20and the pawl22have recesses42in order to reduce the moment of inertia. These recesses42can be embodied, for example, as milled portions, as illustrated on the latch20, or as through-bores parallel to the pawl bearing axis B, as illustrated on the pawl22.

In order to mount the actuator16on the activation device12of the parking lock10, an axial end44of the shaft14is 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 actuator16on the parking lock10at low cost.

According to the figure, a leaf spring46and a ratchet element48which is connected to the shaft14in a rotationally fixed fashion are also provided, wherein the leaf spring46and the ratchet element48form a ratchet connection both in the activation position and in the release position of the shaft14. In this context, the leaf spring46has an attachment end50for mounting the leaf spring46in such a way that it is fixed to the bodywork, and an opposite ratchet end52which is pushed against the ratchet element48by a spring section54of the leaf spring46. The ratchet element48has a recess56which is assigned to the activation position, and a recess58which is assigned to the release position, with the result that the ratchet end52of the leaf spring46engages in one of the recesses56,58in both positions of the shaft14, and forms a ratchet connection.

Adjacent to the attachment end50, the leaf spring46has the essentially planar spring section54which, at the ratchet end52of the leaf spring46, is bent over toward the ratchet element48, in particular rolled up, and forms a ratchet projection60.

In the present case, the leaf spring46therefore acts as a ratchet spring whose ratchet projection60clips into one of the recesses56,58both in the activation position and in the release position of the shaft14, in order to secure the shaft14.

According to the figure, the ratchet element48is a ratchet plate which extends perpendicularly with respect to the activation axis A and has, in each case, a notch as recesses56,58, into which the ratchet projection60of the leaf spring46can engage.

In this way, the parking lock10can be activated with particularly low loading of the actuator16, which has a positive effect on the service life and energy consumption thereof.