Freewheel coupling

A form-fitting freewheel coupling, which has a first and second clamping track with latching structures, a gap space between the clamping tracks, and a clamping ring arranged in the gap space. The clamping ring has clamping tongues facing toward the first clamping track and clamping tongues facing toward the second clamping track. A drag ring is arranged in the gap space. The drag ring is pivotable to a limited extent, relative to the clamping ring and is spring-loaded against one of the clamping tracks and interacts with the clamping ring in such a way that, in the event of a rotation of the first clamping track relative to the second clamping track in the freewheel direction, the clamping ring is lifted fully from one of the clamping tracks, while the clamping tongues, which face away from the clamping track, protrude into the latching structures of the opposite clamping track.

This application is a 371 of PCT/EP2008/057665 filed Jun. 18, 2008, which in turn claims the priority of DE 10 2007 029 812.0 filed Jun. 27, 2007, the priority of both applications is hereby claimed and both applications are incorporated by reference herein.

FIELD OF INVENTION

The invention relates to a positive freewheel coupling also designated as a ratchet.

BACKGROUND OF THE INVENTION

A positively operating freewheel coupling mechanism is known, for example, from EP 0 811 788 B1. This freewheel mechanism is provided for torque converters and is to be distinguished in that impact noises are suppressed. EP 0 811 788 B1 discloses two different forms of construction, in the first form of construction of the freewheel a first running ring being displaceable axially in relation to a second running ring, while, in the second form of construction, the two running rings are spaced apart from one another in an axially invariable manner. In both forms of construction, an intermediate element is arranged between the running rings and cooperates with teeth on the running rings.

OBJECT OF THE INVENTION

The object on which the invention is based is to develop further a positive freewheel, with respect to the prior art, in such a way that, based on a single structural principle, an especially simple adaptation of the mechanical properties to the operating conditions is possible.

SUMMARY OF THE INVENTION

This object is achieved, according to the invention, by means of a positive freewheel coupling having the features of patent claim1. This freewheel coupling comprises two clamping tracks in each case having a number of latching structures, a clamping ring and a drag ring being arranged in the gap space formed between the clamping tracks. The latching structures comprise, for example, clamping ramps or clearances. The clamping ring is intended, in cooperation with the drag ring and with the latching structures, for preventing a rotation of the first clamping track in relation to the second clamping track in a first direction of rotation, whereas a rotation in the opposite direction is enabled. In the first instance, that is to say, with the freewheel blocked, a first group of clamping tongues connected to the clamping ring and formed, in particular, in one piece with the latter engages into latching structures on the first clamping track, while a second group of clamping tongues of the clamping ring engages into latching structures of the second clamping track. By the positive connection between the clamping tracks being made via the clamping tongues, on the one hand, a reliable blocking of the freewheel coupling in the locking direction is afforded and, on the other hand, the conduction of the force flux and torque flux through the clamping tongues offers the possibility of implementing further advantageous mechanical properties in addition to the straightforward blocking action. In particular, the clamping tongues can be configured elastically in such a way that force and torque peaks occurring at the moment of blocking are damped.

During the transition from the locked position of the freewheel into the operation of the freewheel, the drag ring, which is pivotable to a limited extent in relation to the clamping ring and is sprung toward one of the clamping tracks, ensures that the clamping ring is displaced in the gap space, at the same time lifting off completely from one of the clamping tracks, while the clamping tongues facing away from this clamping track penetrate into the latching structures of the opposite clamping track. Freewheel operation without rattling or clicking noises is consequently afforded. In contrast to the clamping ring, the drag ring does not exert a blocking action in any operating state. A moment of friction occurring between the drag ring and one of the clamping tracks during freewheel operation can be set, independently of the form of the clamping ring, by means of the configuration and/or springing of the drag ring. The drag ring may be configured in such a way that it serves at the same time as a plain bearing between the clamping tracks. In contrast to the clamping ring, during the transition from the freewheel operation into the blocked state of the freewheel coupling, the drag ring is not displaced orthogonally between the clamping tracks.

In a first form of construction, designated as an axial ratchet, the clamping ring and the drag ring are arranged axially between the clamping tracks. In a preferred refinement, in this case, a spring ring is arranged in the gap space in addition to the clamping ring and to the drag ring. This spring ring loads at least the drag ring with an axial force in the direction toward one of the clamping tracks. Preferably, by means of the spring ring, the clamping ring is also acted upon by a force in the same direction. In a form of construction which, overall, is narrow and can be produced efficiently, the spring ring has two annular marginal strips which are connected to one another by means of webs running in the radial direction, in each case a spring tongue projecting out of each web on both sides. In this case, one of the spring tongues is intended for springing the clamping ring, while the other spring tongue springs the drag ring. The spring action arises at least partially, preferably for the most part, as a result of the torsion of the web between the marginal strips. Consequently, in an advantageous way, the spring forces acting on the clamping ring and on the drag ring exert a mutual influence one upon the other. A springing of the drag ring onto one of the clamping tracks which is strong in comparison with the spring forces acting on the clamping ring can be implemented in a simple way in that the spring tongue contacting the drag ring is shorter than the spring tongue contacting the clamping ring. The three parts, namely the spring ring, clamping ring and drag ring, can be inserted into the gap space loosely, that is to say without any firm connection with one another or with one of the clamping tracks. To simplify assembly, it is also possible to fix the spring ring to the inner ring. In both instances, the axial distance between the clamping tracks is invariable during the operation of the freewheel coupling.

In a second form of construction of the freewheel coupling, designated as a radial ratchet, the clamping ring and the drag ring are arranged radially between the clamping tracks. In contrast to the first form of construction, preferably no separate spring is provided in this form of construction. Instead, the clamping ring may function as a spring element. The clamping ring is in this case designed essentially as a bent band, between the ends of which a slot remains free. The clamping ring, which is under mechanical tension, springs the drag ring onto one of the clamping tracks, preferably onto the inner ring. Additionally or alternatively, the drag ring may be designed in such a way that it acts as a spring element. The drag ring is also preferably slotted in a similar way to the clamping ring.

With regard to both the axial and the radial ratchet, the clamping ring is preferably shaped in such a way that each clamping tongue facing the first clamping track forms, together with a clamping tongue facing the second clamping track, a double clamping tongue which, for example, is held between two marginal strips of the clamping ring by means of a web, the double clamping tongues and the webs being formed in one piece with the marginal strips. The webs run in the radial direction of the freewheel coupling in the case of the axial ratchet, and in the axial direction thereof in the case of the radial ratchet. In both instances, especially with regard to the radial ratchet, a resilient torsion of the double clamping tongue about the web is possible at least to a slight extent.

According to an alternative form of construction suitable especially for the transmission of higher torques, a higher torsional rigidity of the clamping tongues can be achieved if the clamping tongues are designed as clamping pockets connected to the marginal strips. In this case, a clamping pocket is connected in one piece to the marginal strips along at least half of its length measured in the circumferential direction, preferably along its entire extent in this direction. Torsion within the clamping ring may in this case occur in circumferential portions outside the clamping pockets. The number of the clamping pockets facing the first clamping track is not necessarily identical to the number of the clamping pockets facing the second clamping track.

In a section drawn orthogonally to the clamping tracks, the clamping tongues preferably have in each case an inner portion and an outer portion, the outer portion being inclined to a lesser extent in relation to the marginal strip of a clamping ring than the inner portion. The end of the outer portion of the clamping tongue is in this case intended to bear against a stop face delimiting a clamping structure, for example a clamping ramp or a clearance designed as a through orifice. The surface normal of the stop face preferably encloses a right angle with the axis of rotation of the freewheel coupling.

The clamping ring and the drag ring can be produced especially efficiently as sheet metal parts formed in a non-cutting manner. While the clamping ring is preferably manufactured from steel, for example brass or bronze is also suitable, as well as steel, for producing the drag ring. In a preferred refinement, irrespective of the material, the drag ring has marginal strips and control faces which are inclined in relation to these and which are intended to cooperate with the clamping ring, that is to say to displace the clamping ring within the gap space. Plastics, especially fiber-reinforced plastics, are also suitable for manufacturing the drag ring. The clamping tracks are formed by parts which are produced, for example, by means of broaching, deep drawing or sintering or from sheet metal. These parts are designated as the inner ring and outer ring and the corresponding clamping tracks as the inner clamping track and outer clamping track without any restriction in generality.

Four exemplary embodiments of the invention are explained in more detail below with reference to a drawing in which:

DETAILED DESCRIPTION OF THE DRAWING

Mutually corresponding or identically acting parts are identified in all the figures by the same reference symbols. Each of the embodiments explained below is suitable especially for use in a torque converter.

A freewheel coupling1illustrated inFIGS. 1 to 8is designed as an axial ratchet and has an outer ring2and an inner ring3, the outer ring2being connected to a shaft and the inner ring3to a guide wheel in a way not illustrated. Between the outer ring2and the inner ring3is formed an annular gap space4in which a clamping ring5, a drag ring6and a spring ring7are arranged. The outer ring2and the inner ring3form clamping tracks8,9which in each case have latching structures10,11, in the present case in the form of clamping ramps. The number of clamping ramps10on the outer ring2is higher than the number of clamping ramps11on the inner ring3. The distance, designated by H, between the clamping tracks8,9is constant in any operating state of the freewheel coupling1. The position of the axis of rotation A of the freewheel coupling1is indicated by a dashed and dotted line.

The clamping ring5has two circumferential marginal strips12,13, the inner marginal strip12being connected to the outer marginal strip13by means of webs14running in the radial direction. Clamping tongues15,16are formed on each web14on both sides, this producing what are known as double clamping tongues17. Each clamping tongue15,16has an inner portion18adjoining the web14and an outer portion19bent in relation to the inner portion, the last-mentioned portion19lying essentially in a plane normal to the axis of rotation A, while the inner portion18is inclined to a greater extent with respect to the marginal strips12,13. If the freewheel coupling1is in the blocking position, as illustrated inFIG. 2, the ends of the outer portions19bear against stop faces20which delimit the clamping ramps10,11. By contrast, the inner portions18have no contact with the clamping ramps10,11and ensure, in cooperation with the webs14, an at least slight elastic flexibility of each double clamping tongue17.

The drag ring6, also designated as a drag cage, is arranged essentially axially between the clamping ring5and the outer ring2, individual control faces21of the drag ring6projecting beyond the marginal strips12,13of the clamping ring5in the axial direction. The control faces21in each case engage into an aperture22in the clamping ring5and are intended to cooperate with the double clamping tongues17.

The individual control faces21are arranged between marginal strips23of the drag ring6and are formed in a similar way to the clamping tongues15,16with the aid of stamping and bending processes.

The spring ring7is arranged on that side of the clamping ring5which faces the inner ring3and serves for springing both the drag ring6and the clamping ring5onto the outer ring2. In a basically comparable way to the clamping ring5and to the drag ring6, the spring ring7also has circumferential marginal strips24which are connected to one another by means of webs25running in the radial direction. Where the spring ring7is concerned, two spring tongues26,27are formed onto each web25, the shorter spring tongue26being intended for springing the drag ring6and the longer spring tongue27for springing the clamping ring5. The spring action of the two spring tongues26,27is mainly produced as a result of the torsion of the web25.

The transition between the blocked position of the freewheel1and freewheel operation is illustrated byFIGS. 6 to 8. As soon as the outer ring2commences to rotate in relation to the inner ring3(FIG. 6), as indicated by arrows, the drag ring6is shifted, after initially co-rotating, with the outer ring2under the clamping ring5in such a way that the control faces21displace the double clamping tongues17and consequently the entire clamping ring5in the direction of the inner ring3. The clamping tongues16facing the clamping track9on the inner ring3in this case penetrate into the corresponding clamping ramps11, until the clamping ring5is lifted off completely from the outer ring2(FIG. 8). In freewheel operation, while the clamping ring5, the drag ring6and the spring ring7are stationary with respect to the inner ring3, only a drag moment between the drag ring6and the outer ring2has to be overcome. This drag moment is sufficient to convert a pivoting movement of the drag ring6into an axial movement of the clamping ring5. This applies both during the transition into freewheel operation and during the reverse action, that is to say during the renewed blocking of the freewheel coupling1.

The embodiment according toFIGS. 9 to 14relates, in contrast to the embodiment according toFIGS. 1 to 8, to a radial ratchet. In this case, the gap space4is formed radially between the outer ring2and the inner ring3. The clamping ring5can be produced from a stamped sheet metal band, with material being utilized very efficiently, a slot28remaining between the ends of the band bent into a ring. The entire clamping ring5is designed as a spring element and is pressed against the inner ring3. There is therefore no need for a separate spring element. Located radially between the clamping ring5and the inner ring3is the drag ring6which in this case, too, has control faces21. The drag ring6may also be slotted in a way not illustrated. When the drag ring6is shifted under the clamping ring5(FIGS. 12-14) in the cancellation of the blocking of the freewheel coupling1, said clamping ring is expanded somewhat. At the same time, a slight torsion of each double clamping tongue17about the associated web14takes place. The basic functioning of the radial ratchet according toFIGS. 9 to 14otherwise corresponds to the functioning of the axial ratchet according toFIGS. 1 to 8.

The embodiment according toFIGS. 15 to 17relates to a radial ratchet which differs from the embodiment according toFIGS. 9 to 14in the configuration of the double clamping tongues17: the clamping tongues15,16are designed as deep-drawn clamping pockets, the double clamping tongue17being connected to the marginal strips12,13along its entire tangential extent. In comparison with the exemplary embodiment according toFIGS. 9 to 14, therefore, the double clamping tongues17in the exemplary embodiment according toFIGS. 15 to 17have a lower elastic flexibility, with the result that a higher torque can be transmitted.

The exemplary embodiment according toFIGS. 18 to 23shows a freewheel coupling1which is designed as an axial ratchet and the basic functioning of which is identical to that of the form of construction according toFIG. 1. In contrast to this form of construction, however, the clamping tongues15,16are designed as deep-drawn clamping pockets, in a similar way to the embodiment according toFIGS. 15 to 17.

As may be gathered from the various views inFIG. 21, the clamping ring5of the freewheel coupling1according toFIG. 18has only five apertures22between which in each case three clamping pockets15,16are located. Of these, a middle clamping pocket15faces the outer ring2, while two outer clamping pockets16adjacent to the inner clamping pocket15face the inner ring3. The control faces21of the drag ring6cooperating with the clamping ring5are designed as pocket-shaped depressions in a comparable way to the portions18,19of the clamping ring5which are formed by the clamping pockets15,16.

As in the other embodiments, the latching structures10on the outer ring2are formed by clamping ramps, whereas the latching structures11on the inner ring3are implemented in the form of clearances29. The number of clamping ramps10amounts to fifteen and therefore to 1.5 times the number of clearances29.

As may be gathered fromFIG. 18, the outer ring2has an outer wall30which is in the form of the surface area of a cylinder and surrounds the clamping ring5, the drag ring6and the spring ring7and this has adjoining it radially inward a rim31which surrounds the inner ring3in such a way that all the components2,3,5,6,7of the freewheel coupling1are captively connected to one another as a structural unit.