Return stop and transfer case with such a return stop

The following documents are incorporated herein by reference as if fully set forth: German Patent Application No. DE 10 2015 201 403.7, filed Jan. 28, 2015.

The invention relates to a return stop, comprising a rotating inner ring and a stationary, fixed outer ring, as well as a cage arranged between the inner ring and the outer ring with several roller pairs each consisting of two rollers, wherein at least one spring element is arranged between the two rollers of each roller pair for spring-loading the rollers at least against the outer ring, wherein a clamping ramp is formed on an outer peripheral surface of the inner ring for each roller of the respective roller pair.

The invention further relates to a transfer case for a motor vehicle, wherein this transfer case comprises such a return stop.

From the generally known prior art, transfer cases have become known that are equipped with coupling gear for setting a variable torque. The magnitude of the torque to be transferred by the coupling gear is here dependent on a clamping force of an actuator acting on the coupling gear. Usually the actuator is driven by an electric motor via a worm gear, in order to set the position of the coupling gear and thus the magnitude of the torque. The set position is then held by maintaining the power to the electric motor. One disadvantage is the resulting power consumption. Switching off the electric motor would be accompanied by a loss of the previously set position.

From DE 195 81 436 C1, a clamp-like locking device formed of a housing with an inner cylindrical clamping surface with drive elements and driven elements that can rotate relative to the housing and are arranged coaxial to the cylindrical clamping surface. The driven element is provided with clamping ramps that face the clamping surface and on which there are clamping roller pairs—formed from two clamping rollers following each other in the circumferential direction—whose two clamping rollers are spring-loaded away from each other by means of a spring element arranged between them against the clamping surface and the clamping ramps. Furthermore, the driven element is provided with stops for claws of the drive element, wherein these claws engage between two clamping roller pairs that are adjacent to each other. Here, the claws have, on their sides facing the stops, stops for each clamping roller of a clamping roller pair, wherein a circumferential clearance is formed between the stops and the claws that is greater than a circumferential clearance between the contacts and the clamping rollers. In addition, the driven element has a thin-wall sheet metal part that is drawn radially inward at multiple positions distributed around the circumference through the formation of recesses, wherein walls of the recesses arranged on the circumferential side form the stops and border plateaus provided with the clamping ramps on the circumferential side.

The object of the present invention is to create an especially reliable, two-sided acting return stop that can be used, in particular, in a transfer case.

This objective is achieved according to the invention in that on the outer circumferential surface of the inner ring there is at least one cam that is formed radially on the outside and engages in a groove formed on the cage, wherein the at least one cam is formed smaller in the circumferential direction than the groove, wherein through a relative movement of the cage relative to the inner ring, the respective roller of each roller pair contacts both the respective clamping ramp and also the outer ring. In other words, an activation of the locking function of the return stop initially requires a positioning of the respective roller of each roller pair on the respective clamping ramp. By each roller coming into contact with the respective clamping ramp and outer ring, each roller is able to trigger a locking of the inner ring in the direction of rotation of the inner ring reverses itself. Due to a symmetric construction and the roller pair, this function applies to both directions of rotation of the return stop. Thus, the return stop features two-sided action.

Advantageously, directly adjacent to each clamping ramp, a radial recess is formed on the inner ring, so that only one roller of each roller pair contacts the inner ring and outer ring at the same time and the other roller of the respective roller pair does not come into contact at least with the inner ring due to the respective radial recess. In this way, simultaneous contact of both rollers of a respective roller pair on the respective clamping ramp and on the outer ring is prevented so that mutual clamping of the rollers can be prevented.

In an especially preferred way, the two clamping ramps of each roller pair are formed pointing away from each other in opposite directions in the circumferential direction. Consequently, only one roller of each roller pair is brought into rotation by rotating the cage on the respective clamping ramp. Advantageously, the two clamping ramps of each roller pair can be formed tapered in opposite directions relative to each other in the circumferential direction.

According to one preferred embodiment, two spring elements are arranged between the two rollers of the respective roller pair, wherein each of the two spring elements is supported on a respective connecting piece formed on the cage. In this way, the respective spring element contacts the respective roller and the respective connecting piece in the circumferential direction. The arrangement of a single spring element that is supported directly on the two rollers is also conceivable, however.

According to another preferred embodiment, three roller pairs are distributed uniformly across the circumference on the cage. Alternatively, however, two roller pairs could also be arranged opposite each other on the cage. For larger loads, the arrangement of more than three roller pairs uniformly across the circumference on the cage is also conceivable.

According to another preferred embodiment, three cams are distributed uniformly across the circumference on the inner ring. Consequently, the cage also has three grooves accordingly. Between every two grooves there is a roller pair. Stop surfaces on which contacting of the cage on the cams is realized when the cage rotates are formed on the circumferential side on the cams and also on the grooves. The formation of only one cam that interacts with a groove is also conceivable. Depending on the size of the torque to be transferred, the number of cams and thus also the number of grooves can vary.

The invention provides that the inner ring and the outer ring are produced at least by a deep-drawing method from a metallic sheet-metal material. Furthermore, other processing steps, such as bending or stamping, are also conceivable. In contrast, the cage is formed from a polymer or a sintered metal, whereby, in particular, a production close to the final shape is possible.

Features of the invention are explained in more detail below based on the drawings together with the description of preferred embodiments of the invention. In the drawings:

FIG. 1A is a schematic sectional view for illustrating the construction of a return stop according to the invention, comprising an inner ring, an outer ring, and a cage arranged radially in-between, wherein the cage is located in a first position,

FIG. 1B is a schematic sectional view for illustrating the construction of the return stop according to the invention from FIG. 1A , wherein the cage is located in a second position,

FIG. 1C is a schematic sectional view for illustrating the construction of the return stop according to the invention from FIGS. 1A and 1B , wherein the cage is located in a third position,

FIG. 2 is a perspective view for illustrating the cage from FIGS. 1A to 1C ,

FIG. 3 is a perspective view for illustrating the inner ring from FIGS. 1A to 1C , and

FIG. 4 is a schematic view of a section of a transfer case according to the invention with a return stop according to FIG. 1A .

According to FIGS. 1A, 1B, and 1C , a return stop 1 according to the invention has a rotating inner ring 2 and a stationary outer ring 3 that is fixed on a housing—not shown here—and also a cage 4 arranged radially between the inner ring 2 and the outer ring 3 . Here, the inner ring 2 and the outer ring 3 are produced in a deep-drawing process from a metallic sheet-metal material. In contrast, the cage 4 is made from a polymer in an injection-molding process. In the cage 4 there are three roller pairs 5 a , 5 b , 5 c distributed uniformly around the circumference of the cage 4 . Between the two rollers 6 a , 6 b of each roller pair 5 a , 5 b , 5 c there are two spring elements 7 a , 7 b for spring-loading the rollers 6 a , 6 b , wherein each of the two spring elements 7 a , 7 b is supported on a respective connecting piece 12 a , 12 b formed on the cage 4 . A clamping ring 8 a , 8 b is formed on an outer circumferential surface of the inner ring 2 for each roller 6 a , 6 b of each roller pair 5 a , 5 b , 5 c . The two respective clamping ramps 8 a , 8 b of each roller pair 5 a , 5 b are formed pointing away from each other in opposite direction in the circumferential direction.

Furthermore, on the outer circumferential surface of the inner ring 2 there are also three cams 9 a , 9 b , 9 c that are formed radially on the outside and engage in grooves 10 a , 10 b , 10 c formed on the cage 4 . The cams 9 a , 9 b , 9 c are formed smaller in the circumferential direction than the grooves 10 a , 10 b , 10 c , so that through a relative movement of the cage 4 relative to the inner ring 2 , each roller 6 a , 6 b of each roller pair 5 a , 5 b , 5 c contacts both the respective clamping ramp 8 a , 8 b and also an outer ring 3 . In addition, directly adjacent to each clamping ramp 8 a , 8 b there is a radial recess 11 a , 11 b on the inner ring 2 , so that only one roller 6 a , 6 b of each roller pair 5 a , 5 b , 5 c simultaneously contacts the inner ring 2 and the outer ring 3 and the other roller 6 b , 6 a of each roller pair 5 a , 5 b , 5 c comes into contact at least not with the inner ring 2 due to the respective radial recess 11 b , 11 a.

FIG. 1A shows a middle position of the return stop 1 . In this position, neither the roller pairs 5 a , 5 b , 5 c contact the inner ring 2 , nor the cams 9 a , 9 b , 9 c on the cage 4 .

In contrast, FIG. 1B shows a second position of the return stop 1 , wherein only the cage 4 was rotated in the counterclockwise direction. In this way, the respective rollers 6 a contact the respective clamping ramp 8 a and trigger a blocking function for an undesired reversal of the direction of rotation. The respective rollers 6 b are held on the cage 4 such that contact on the respective clamping ramp 8 b is reliably prevented. Furthermore, here the respective radial recess 11 b also makes a contribution.

According to FIG. 1C , the return stop is located in a third position. The cage 4 contacts the cams 9 a , 9 b , 9 c on the circumferential side and allows the inner ring 2 to be carried along. Through the respective rollers 6 a , the freewheeling operation is realized. An undesired reversal in the direction of rotation of the inner ring 2 would cause a blocking of the return stop by means of the respective rollers 6 a.

FIG. 2 shows a perspective view of the cage 4 . In this view, the grooves 10 a , 10 b , 10 c and the connecting pieces 12 a , 12 b formed on the cage 4 can be seen particularly well.

FIG. 3 shows a perspective view of the inner ring 2 . The inner ring 2 is formed according to this preferred embodiment with a cup-shaped design. In this view, the clamping ramps 8 a , 8 b with the associated radial recesses 11 a , 11 b and the cams 9 a , 9 b , 9 c can be seen particularly well.

According to FIG. 4 , a transfer case 13 according to the invention in a motor vehicle—not shown here—has a coupling unit 14 , an actuator 15 , an electric motor 16 , and also the return stop 1 described above. The electric motor 16 here drives the cage 4 of the return stop 1 via a drive shaft 17 . The cage 4 transfers the rotational movement as described above to the inner ring 2 , which is in turn connected to a driven shaft 18 . The actuator 15 controlling the coupling unit 14 is connected to the return stop 1 via the driven shaft 18 .

1 Return stop

2 Inner ring

3 Outer ring

4 Cage

5 a - 5 c Roller pair

6 a , 6 b Roller

7 a , 7 b Spring element

8 a , 8 b Clamping ramp

9 a - 9 c Cam

10 a - 10 c Groove

11 a , 11 b Radial recess

12 a , 12 b Connecting piece

13 Transfer case

14 Coupling unit

15 Actuator

16 Electric motor

17 Drive shaft

18 Driven shaft