DE102021122104B3 - Bearing assembly with overrunning function, linear actuator and method of operating a linear actuator - Google Patents

Abstract

A bearing arrangement (1) with a freewheel function that can be used in particular in a linear actuator (27) comprises a roller bearing (3) having two bearing elements (4, 5) that can rotate in opposite directions and contact roller bodies (7). A cage (8) guiding the rolling bodies (7) of the rolling bearing (3) is designed as a component of an overrunning clutch (10) that is effective when the rolling bearing (3) is mechanically loaded, with at least the locking part of the cage (8) being rigid in itself .

Description

The invention relates to a bearing arrangement which has a freewheel function. Furthermore, the invention relates to a linear actuator and a method for operating a linear actuator.

From the DE 1 145 446 A is designed as a one-way clutch bearing, namely radial ball bearings known. The well-known bearing, which is also intended to provide a freewheel function, includes an inner and an outer race, as well as balls rolling between the races, which also interact with a locking ring with inclined surfaces. As a locking ring is in the case of DE 1 145 446 A a split cage having asymmetrically designed pockets is provided, both parts of which are axially spread apart by the rolling elements, ie balls, during relative rotation of the races in the blocking direction and pressed against conical surfaces of the bearing rings. In contrast, the locking ring is moved by the balls in the freewheeling direction. Overall, the arrangement is as follows DE 1 145 446 A for a frictional freewheel.

Another bearing-freewheel arrangement, in which one and the same races have both a function within a one-way clutch and represent roller bearing rings, is from DE 10 2007 040 029 A1 known. In this case, the entire bearing-freewheel arrangement is designed as a three-ring bearing.

Other bearing-freewheel combinations are in the documents DE 42 19 143 A1 , DE 10 2009 022 206 B3 and DE 44 42 404 C2 described. In all of these cases, rolling bodies on the one hand and clamping elements on the other hand contact different surface areas of the respective bearing/freewheel arrangement.

the EP 2 895 772 B1 discloses a combined vehicle brake which includes a hydraulically actuatable service brake and an electromechanically actuatable parking brake device. In order to convert a rotation into a linear movement, the electromechanically actuable parking brake device has a spindle drive in the form of a ball screw drive. A collar can be formed on a threaded spindle of the spindle drive, which collar is encompassed by a cup-shaped torque transmission element, with a freewheel mechanism acting between the torque transmission element and the collar, which can be designed as a ramp-roller element arrangement.

one in the DE 10 2014 202 189 A1 described braking device, which also includes a service brake and a parking brake, has a pawl which is effective between a spindle nut and a brake caliper housing. The pawl is intended to interact with a wall of the caliper housing such that movement of the spindle nut away from a brake disc of the parking brake is blocked. The pawl has a function within an automatic wear adjustment of the braking device after DE 10 2014 202 189 A1 .

Various braking devices comprising self-locking gears are in the documents DE 103 20 907 B4 and DE 10 2005 055 085 B4 described. Braking devices comprising worm gears are for example in the documents EP 2 207 982 B1 , EP 2 069 655 B1 and EP 1 945 966 B1 disclosed.

Out of DE 838 844 B a roller bearing with a freewheel locking mechanism has become known, in whose cage pockets of the bearing a device that brings about the blocking is housed. Each locking device consists of a locking roller, the brake shoe and a flexible support for the locking roller. The compliant support is provided by a synthetic rubber peg.

The invention is based on the object of specifying bearing-freewheel arrangements which are more advanced than the prior art and which are particularly suitable for use in linear actuators, for example in electromechanically actuated brakes, and which are characterized by a particularly favorable ratio between outlay in terms of equipment, space requirement and if a motor drive is provided, mark the energy consumption.

This object is achieved according to the invention by a bearing arrangement having the features of claim 1. The object is also achieved by a linear actuator comprising such a bearing arrangement according to claim 8. The object is also achieved by a method for operating a linear actuator according to claim 9 The configurations and advantages of the invention explained in connection with the operating method also apply analogously to the devices, ie the bearing arrangement and the linear actuator, and vice versa.

The bearing arrangement has a freewheel function and comprises a roller bearing which has two bearing elements which can rotate relative to one another and which contact the roller bodies of the bearing. Here, the bearing elements can be formed by rings or disks or directly by a housing or a shaft. In any case, the rolling elements of the bearing or a subset of the rolling elements are in out of a cage, which is also a component of an overrunning clutch. The bearing can be an axial bearing, a radial bearing or an angular roller bearing or angular ball bearing, ie a bearing provided both for the transmission of axial forces and for the transmission of radial forces. In all cases, the one-way clutch, which includes the cage, can be designed as either a positive clutch or a friction clutch. At least that part of the cage which locks as part of the one-way clutch is inherently rigid. This means that the cage is either designed in one piece or the cage parts forming the cage, which have a function within the overrunning clutch, are firmly connected to one another.

The rotating component of the roller bearing, i.e. typically the rotating bearing ring, the rotating bearing disk or a shaft coupled in a rotationally fixed manner to the relevant ring or said disk, is therefore not directly locked when the overrunning clutch is locked, but rather indirectly, namely via the cage of the roller bearing. This freewheel function comes into effect when the bearing is mechanically loaded. If, on the other hand, there is no power flow from the first bearing element via at least part of the rolling elements to the second bearing element, there is no freewheel function. This is particularly the case when all rolling bodies are arranged between the bearing elements with play.

If the roller bearing is an axial bearing, the rotating bearing disk, i.e. the shaft disk, which can be held in place by means of the overrunning clutch, is typically coupled to other rotatable components in such a way that a torque can be transmitted between the shaft disk and the other components, This means that the additional components mentioned can also be prevented from rotating in a specific direction by means of the overrunning clutch. Separate means for stopping the other components directly are not required for this. This also applies in an analogous manner to other designs of roller bearings with an integrated overrunning clutch partially formed by the cage.

In various embodiments, one of the two bearing elements of the bearing arrangement, which in all cases represents a combined bearing-freewheel arrangement, is rotatable, while the other bearing element is a component arranged in a rotationally fixed manner in a surrounding structure. Notwithstanding the above, embodiments are also possible in which both bearing elements are rotatable. Both in the case of an embodiment of the bearing arrangement as an axial bearing and in the case of an embodiment of the bearing arrangement as a radial bearing or as a combined axial-radial bearing, designs can also be implemented in which the housing represents a machine component that can be rotated as a whole.

A particular advantage of blocking not the shaft or shaft washer, but the cage of the rolling bearing, in particular axial rolling bearing, is that when the overrunning clutch is loaded in the blocking direction, it is possible to overcome the holding torque generated by the blocked cage, so that the overrunning clutch in a certain operating range, namely below the holding torque, fulfills a blocking function and acts as a brake at higher torques. In the latter state, the axial roller bearing has been converted into a plain bearing.

The holding torque, which in various possible configurations is in a range that can be overcome by a motor drive, thus defines a possible switching point between using the bearing-freewheel arrangement as a roller bearing with a freewheel function on the one hand and using the same arrangement as a plain bearing on the other hand, whereby the use in the latter case with the reverse direction of rotation compared to the first case. It is not necessary to have a separate slide bearing ready for one of two possible directions of rotation.

The axial bearing, radial bearing or other roller bearing, which also functions as a freewheel, can be constructed as a single-row or multi-row bearing. If there is a multi-row, in particular two-row, structure, the rolling bodies of the different rows of rolling bodies can be guided either through a common cage or through separate cages. In the latter case, for example, only the outermost cage or a cage adjacent to an end face of the bearing arrangement is designed as a freewheel component, while the at least one other cage exclusively has a function within the roller bearing. With this structure, a distribution of axial and/or radial loads as well as a reduction of the braking torque during operation in the blocking direction can be achieved.

There are various design options for engaging the overrunning clutch when it is integrated into an axial bearing: According to a first design principle, the overrunning clutch is effective between the housing disc and the cage. Here, the one-way clutch can be connected directly between the housing washer and the cage. Alternatively, while maintaining this design principle, the freewheel disk can be connected between the housing, on which the housing disk is held, and the cage of the axial roller bearing. Another design principle provides that the overrunning clutch is connected between the shaft washer and the cage.

Regardless of whether the rolling bearing is an axial bearing or a radial bearing, the overrunning clutch is between the cage on the one hand and a rotating or non-rotating machine element on the other side, i.e. typically a shaft or a housing in which the shaft is mounted, effective. In any case, when the roller bearing is in operation, relative torsion can occur between the cage and said machine element, which is either rotating or non-rotating. The rotational speed of this relative rotation, which means operation of the overrunning clutch in the freewheeling direction, corresponds to approximately half the rotational speed of the shaft in conventional bearing constructions, assuming a stationary housing. This applies both to variants in which the rolling elements roll on separate bearing rings or bearing discs and in cases in which the rolling elements roll directly on a shaft and/or on a surface of a more complex component, in particular the housing surface.

According to one possible development, the bearing arrangement that absorbs forces in the axial direction includes an additional axial bearing that does not have a freewheel function, it being possible for both axial bearings to have a common shaft washer. In this case, the bearing arrangement is suitable for the transmission of axial forces in both directions. Irrespective of whether the bearing arrangement comprises a single or two axial bearings, a spring element, in particular in the form of a plate spring, can be provided to generate a prestressing force acting in the axial direction. In principle the same way, a freewheel bearing arrangement that absorbs forces exclusively or predominantly in the radial direction can also be loaded by spring force, with the spring force only acting on part of the rolling elements in the case of a purely radial bearing.

Even in cases in which the overrunning clutch is integrated into a radial bearing, there are numerous design options as far as the arrangement of the overrunning clutch within the bearing-overrunning arrangement is concerned. For example, the overrunning clutch can be effective between the inner ring of the roller bearing and the cage. Alternatively, the bearing-freewheel arrangement can include a freewheel mechanism which acts either between the cage of the roller bearing and its outer ring or directly between the cage and a housing surrounding the outer ring.

The component of the overrunning clutch provided by the cage is also referred to, without loss of generality, as the inner freewheel component, and the second component of the overrunning clutch that interacts directly with the cage is also referred to as the outer freewheel component. In principle, the outer freewheel component can engage, for example, on the outer circumference and/or on an end face of the cage. In terms of the available, usable installation space, in the case of axial bearings with an integrated overrunning clutch, variants can be implemented in which the outer freewheel component contacts contours on the outer peripheral surface of the essentially annular disk-shaped cage. If a bearing is designed as a single-row or multi-row radial bearing, in particular one end face of the cage, which in this case can have a cylindrical basic shape, is available for the outer freewheel component to engage. Variants in which outer freewheel components interact with the cage on both end faces of the cage are also possible. Furthermore, variants are possible in which the cage of the radial bearing extends beyond the rolling elements in the axial direction of the bearing, with the freewheel mechanism being located in the section of the cage that protrudes beyond the rows of rolling elements. In this case, the second freewheel component can act on the inner and/or outer peripheral surface of the cage, wherein an attack on the inner peripheral surface can be constructed in a particularly space-saving manner, whereas an attack on the outer peripheral surface has the advantage of longer effective lever arms and thus higher torques that can be absorbed. All explanations given in this paragraph regarding the various freewheel components apply to both frictional and positive-locking freewheels.

The overrunning clutch of the bearing arrangement is designed, for example, as a ratchet lock. Here, the pawls of the overrunning clutch can interact directly with external teeth or with teeth on the face of the roller bearing cage. Alternatively, the pawls or other latching elements, for example displaceable, spring-loaded latching bolts, can engage, for example, in holes that are located in the cage. In general, the pawl has a detent geometry provided by the cage.

As far as the arrangement of the pawls on the circumference of the cage or on its front side is concerned, there are various design options with specific advantages and disadvantages: Firstly, there is the possibility of distributing the individual pawls on the circumference of the externally toothed or otherwise toothed cage, particularly in equal angular distances so that all pawls engage simultaneously in the toothing of the cage and can thus lock the freewheel. The forces to be absorbed with a locking freewheel who the case evenly distributed to all pawls, for example, three or five pawls. Alternatively, there is the possibility of selecting the angular distances between the pawls, based on the central axis of the cage, in such a way that only a subset of the pawls, in extreme cases only a single pawl, has a locking effect at the same time, i.e. engages in the toothing of the cage while the other handles remain without a blocking function at the same time. In this case, the forces and moments to be transmitted are concentrated on a smaller number of pawls, but there are a larger number of angular positions of the cage in which the freewheel locks.

The rolling elements, in particular balls, needles or rollers, of the axial roller bearing, radial roller bearing or other roller bearing are typically guided individually in pockets in the cage, which at the same time represents a component of the overrunning clutch. The retaining element, which can be accommodated by the overrunning clutch in the blocking direction, can be influenced with a specifically different pocket play in the circumferential direction of the cage.

Furthermore, the holding torque is largely dependent on the loads acting on the bearing arrangement, in the case of an axial bearing in particular on the axial force acting between the bearing disks. In the case of a radial bearing, there is a relationship between the radial force acting on the bearing and the locking effect that occurs when the bearing is under load. The axial force and/or radial force can inevitably result from the operation of a machine comprising the bearing arrangement and/or can be set in a controlled manner, in particular by applying hydraulic pressure. Configurations are also possible in which a mechanical load, which ensures that the one-way clutch is ready for operation, is at least partially predetermined by a passive element, in particular a spring element.

There is also the possibility of applying a prestressing force in the roller bearing, in which the overrunning clutch is integrated, by a rotating element of a spindle drive which is mounted with the aid of the roller bearing and is supported in the axial direction on a non-rotating element of the spindle drive. If the spindle drive is designed as a roller screw drive, in particular a ball screw drive, axial forces that preload the roller bearing are transmitted via the rolling elements of the spindle drive. In general, with both axial and radial bearings, there can be a variety of preloading means that can be used to generate a preloading force that loads the roller bearing and thus makes the overrunning clutch ready for operation or at least supports it.

The bearing arrangement is particularly suitable for use in a linear actuator, in which case it can be provided in particular for supporting a spindle of a screw drive. In such a screw drive, the spindle represents the rotating spindle drive component. Alternatively, the spindle nut can form the rotating spindle drive component, while the associated spindle can be displaced in a manner secured against rotation. In any case, the spindle drive can be designed, for example, as a simple movement thread, in particular in the form of a non-self-locking trapezoidal thread with a large pitch, as a ball screw drive or as a planetary roller screw drive, with the latter two screw drives having rolling elements being able to have a comparatively small pitch. With the help of a non-self-locking design of a ball screw drive or a planetary screw drive, the linear actuator can be operated with a particularly low drive power, which is to be applied in particular by an electric motor drive of the screw drive.

In order to prevent the screw drive from turning back automatically, which would by definition be secured in the case of a self-locking design, the locking effect of the freewheel of the bearing arrangement comes into operation automatically as soon as forces are exerted on the spindle, which act in the sense of turning back.

The transmission ratio of the spindle drive and the blocking effect of the freewheel are selected in an advantageous embodiment, taking into account given frictional forces, so that the screw drive cannot be reset by a purely axial load on the threaded spindle in the event of forces occurring during normal operation. This means that a reset of the screw drive, ie an adjustment against the freewheeling direction, is only possible with a rotary drive of the threaded spindle, through which the roller bearing locking effect of the overrunning clutch is overcome. Despite this restoring operating mode of the linear actuator, which overcomes a braking torque, together with the operating mode in the freewheeling direction, which is characterized by particularly smooth running, a high overall efficiency of the linear actuator can be achieved overall. This also applies to embodiments in which the screw drive, ie rotary-linear gear, is preceded by another gear, typically in the form of a rotary-rotary gear.

The linear actuator is suitable, for example, for use in an electromechanical parking brake, ie parking brake, of a vehicle. This can either be a purely electromechanical brake or a brake which, in a manner known per se, can also be actuated hydraulically as a service brake.

If the overrunning clutch is a friction-locking clutch, it can be designed, for example, as a wrap spring clutch, as a clamping roller freewheel or as a sprag freewheel. In this regard, reference is made to the documents by way of example WO 2020/164652 A1 , WO 2010/051785 A1 and DE 10 2006 004 491 A1 pointed out.

The rolling elements of the bearing arrangement, which also acts as a freewheel, are selected depending on the requirements given in the individual case and can have any known shape, in particular the shape of cylindrical rollers, tapered rollers, needles or balls. In typical configurations, the cage, which is both a component of the roller bearing and a component of the overrunning clutch, is a metal part. All metal parts of the bearing assembly can be heat treated as required.

The cage, which has a multiple function, namely a function as a component of a roller bearing and a function as a freewheel component, can be produced efficiently, in particular using metal forming processes, with machining processes and shaping by archetypes, for example casting, sintering or 3D, also being possible - Pressure, come into consideration. In all cases, the surface of the cage can be coated to reduce wear and/or friction and/or the surface layer can be hardened. The same applies to the rolling elements and the bearing washers or other bearing elements of the bearing arrangement.

• 1 ein erstes Ausführungsbeispiel einer Lageranordnung mit Freilauffunktion in schematisierter Schnittdarstellung,
• 2 und 3 weitere Lageranordnungen mit Freilauffunktion in Darstellungen analog 1,
• 4 eine in einem Untersetzungsgetriebe verwendbare, zwei Axialwälzlager umfassende Lageranordnung mit Freilauffunktion in vereinfachter geschnittener Darstellung,
• 5 eine stirnseitige, geschnittene Ansicht der Lageranordnung nach 4,
• 6 die Anordnung nach 4 in Explosionsdarstellung,
• 7 einen Bremsaktuator, welcher einen Spindeltrieb mit einer Lageranordnung mit Freilauffunktion umfasst,
• 8 den Bremsaktuator in stirnseitiger, geschnittener Ansicht,
• 9 ein Detail aus 8,
• 10 ein weiteres Ausführungsbeispiel einer Lageranordnung mit Freilauffunktion in einer Darstellung analog 1,
• 11 ausschnittsweise eine mit einem reibschlüssigen Freilauf arbeitende Lageranordnung mit Freilauffunktion,
• 12 - 14 in jeweils einem Diagramm die Verstellung des die Lageranordnung mit Freilauffunktion umfassenden Aktuators nach 7,
• 15 in einem weiteren Diagramm Variationsmöglichkeiten eines Haltemoments der Freilaufkupplung der in einem Aktuator verwendbaren Lageranordnung nach 1.

Several exemplary embodiments of the invention are explained in more detail below with reference to a drawing. Show in it:

• 1 a first embodiment of a bearing assembly with freewheel function in a schematic sectional view,
• 2 and 3 other bearing arrangements with freewheel function in representations analogous 1 ,
• 4 a bearing arrangement with a freewheel function, which can be used in a reduction gear and comprises two axial roller bearings, in a simplified sectional view,
• 5 an end-side, sectional view of the bearing assembly 4 ,
• 6 according to the arrangement 4 in exploded view,
• 7 a brake actuator, which includes a spindle drive with a bearing arrangement with a freewheel function,
• 8th the brake actuator in a front, sectional view,
• 9 a detail out 8th ,
• 10 another embodiment of a bearing arrangement with a freewheel function in an analog representation 1 ,
• 11 a detail of a bearing arrangement working with a frictionally engaged freewheel with a freewheel function,
• 12 - 14 in one diagram each, the adjustment of the actuator comprising the bearing arrangement with a freewheel function 7 ,
• 15 in a further diagram, possible variations of a holding torque of the overrunning clutch of the bearing arrangement that can be used in an actuator 1 .

Unless otherwise stated, the following explanations relate to all exemplary embodiments. Parts that correspond to one another or have the same effect in principle are identified by the same reference symbols in all figures.

A bearing arrangement 1 is installed in a housing 2 and comprises a thrust roller bearing 3, namely a thrust roller or needle bearing, with a freewheel function. In the exemplary embodiments, the housing 2 is a non-rotating machine element. Embodiments with a rotating housing 2 can also be implemented.

In the housing 2 a housing washer 4 is used, which is attributable to the axial roller bearing 3 . A shaft washer 5 , which is connected to a shaft 6 , is also to be attributed to the axial roller bearing 3 . The central axis of the shaft 6 and thus of the entire bearing assembly 1 is denoted by MA. During operation of the bearing arrangement 1, an axial force Fax can act on the shaft washer 5. The rolling bodies, ie needles or rollers, of the axial roller bearing 3 are denoted by 7 and are guided in pockets 9 of a cage 8 , which at the same time represents an inner coupling part of an overrunning clutch 10 . An associated outer clutch part of the overrunning clutch 10 is denoted by 11 .

In the embodiment after 1 the outer clutch part 11 is fastened in the housing 2. The functionally identical arrangement of the outer clutch part 11 is in the arrangement shown in FIG 2 given, in which case the outer clutch part 11 is fixed to the housing disc 4. In contrast to the embodiments according to the 1 and 2 is in the embodiment 3 the outer clutch part 11 is non-rotatably connected to the shaft washer 5 and thus represents a rotatable component of the bearing arrangement 1.

In the embodiments according to 1 until 10 the overrunning clutch 10 is designed as a positively acting clutch which interacts directly with the cage 8 as the inner clutch part. As in particular from the 5 and 9 shows, the outer clutch part 11 comprises a plurality of pawls 12 which are spring-loaded by means of coil springs 13, the coil springs 13 being supported on support blocks 14, i.e. spring support blocks, which are provided by the outer clutch part 11. The pawls 12 engage in an external toothing 26 of the cage 8, which is generally referred to as a locking geometry. The cage 8 can be produced using forming methods.

In the embodiment according to 4 until 6 Bearing arrangement 1 is installed in a rotary-rotary gear, which is designed as a reduction gear and represents the first gear stage of a two-stage gear arrangement of an electromechanical actuator. In this exemplary embodiment, there is a second axial bearing 18 in addition to the axial roller bearing 3 functioning as a freewheel, with both axial bearings 3 , 18 sharing a common shaft washer 5 . In the case of the second axial bearing 18 , a cage guiding a rolling body 20 is denoted by 19 and a housing washer by 22 . An axial force Fax is exerted on the housing disk 22 with the aid of a plate spring 23, which loads the bearing arrangement 1 as a whole and thus determines the maximum holding torque of the overrunning clutch 10.

The outer clutch part 11 includes in the in the 4 until 6 The example shown includes a sleeve component 15 which is fixed to the housing and is also referred to as a lock housing and in which there are recesses 16 which can be used for mounting the coil springs 13 . In addition to the housing-fixed sleeve component 15 is a spring support cover 21. The outer diameter of the externally toothed cage 8 is in the case of 4 larger than the outer diameter of the second axial bearing 18. The two axial roller bearings 3, 18 have a matching pitch circle diameter in the present case. The shaft 6 is provided with a connection contour 17 for the transmission of a torque. The bearing arrangement 1 according to 4 until 6 is suitable for integration into an actuator, not shown, in which case the axial force Fax does not already result from the operation of the actuator as a result of the design, but is generated in a targeted manner by means of the spring element 23 in order to make the overrunning clutch 10 usable. The housing 2 is composed of several housing parts 24, 25. The term cage lock is also used for the one-way clutch 10 .

In the embodiment according to 7 until 9 the bearing assembly 1 with a freewheel function is part of a linear actuator 27 for actuating the brakes in a motor vehicle. In this case, the shaft 6 is firmly connected to a threaded spindle 29 of a spindle drive 28 or formed directly by the threaded spindle 29 . An associated spindle nut 32 is arranged on a brake piston 30, which can also be actuated hydraulically in a manner known per se. A bellows 31 is provided to protect against contamination. The brake disc that can be fixed with the help of the linear actuator 27 is denoted by 35 .

In the present case, the spindle drive 28 is designed as a ball screw drive, with balls (not shown) rolling in a thread turn 34 of the threaded spindle 29 , which balls contact the spindle nut 32 at the same time. The spindle drive 28 is a non-self-locking gear for converting a rotation into a linear movement. A shaft-fixed element designated 33, that is to say an element rigidly connected to the shaft 6, exerts an axial force Fax on the bearing arrangement 1, which in this case is single-row. In this case, the function of a second row of bearings supporting in the opposite direction is taken over by the rolling bodies, ie balls, which roll between the threaded spindle 29 and the spindle nut 32 . When the brake disc 35 is fixed by means of the linear actuator 27, the axial force Fax increases continuously up to a maximum value. In this position, ie when the parking brake is applied, the axial roller bearing 3 is blocked by the overrunning clutch 10 .

The blockage of the linear actuator 27 is positive only insofar as there is a positive fit between the cage 8 as the inner coupling part and the pawls 12 . In contrast, there is no form fit between the bearing disks 4 , 5 of the axial roller bearing 3 . The consequence of this is that the lock effected by the one-way clutch 10 can be canceled by introducing a sufficiently large torque into the shaft 6 in the direction of reverse rotation. This is possible with the help of an electric motor, not shown, which is used to actuate the linear actuator 27 in both directions. Since the overrunning clutch 10 remains locked when the shaft 6 rotates in the release direction, the axial roller bearing 3 is used as a plain bearing in this operating phase.

If the linear actuator 27 is subsequently tightened again, i.e. the transition to a parking position as a position in which the brake disc 35 is blocked with the aid of brake pads (not shown), the overrunning clutch 10 is again operated in the overrunning direction, with the pawls 12 only applying a small braking torque is exerted on the cage 8. On average over all operating phases, the linear actuator 27 can be operated in an energy- and material-saving manner, in particular as far as the electric motor used to drive the shaft 6 is concerned.

In 10 the structure of a bearing assembly 1 is illustrated, which is a modification of the embodiment 1 represents. In the case of 10 the axial bearing 3 is constructed in two rows, with an inner row of rolling elements being denoted by 36 and an outer row of rolling elements by 37 . The designated 38 cage of the inner row of rolling elements 36 represents a pure roller bearing cage and has no freewheel function. The freewheeling function is only taken over by the cage 8, which surrounds the inner cage 38 in a ring and has the same function as in the exemplary embodiment according to FIG 1 Has. In contrast to the embodiment according to 1 retains in the embodiment 1 the inner row of rolling elements 36 has its rolling bearing function in every operating state. This is the locking effect and braking effect of the freewheel 10 in the case of 10 less pronounced than in the case of 1 .

In 11 the structure of a possible bearing assembly 1 is outlined, which is constructed as a combined radial bearing-freewheel assembly. In this case, the rolling bodies 7 of the radial bearing roll directly on an inner peripheral surface of the housing 2 . Likewise, a separate bearing ring 4, ie outer ring, could be present in a manner not shown, in which the rolling elements 7 roll. A rolling element clearance is in 11 exaggerated. The inner ring 5 is fixedly connected to an inner ring 42 of the overrunning clutch 10 via the shaft 6, not shown here, the rings 5, 42 being offset relative to one another in the axial direction in this case.

The one-way clutch 10 of the bearing assembly 1 after 11 is designed as a clamping roller freewheel and is effective between the inner ring 42 and the cage 8 . The cage 8 is firmly connected or made in one piece with cage elements 39, which individually cushion the rollers designated 40, ie pinch rollers. The inner ring 42 has a ramp contour 43, which ensures that a relative rotation between the cage 8 and the inner ring 42 is only possible in a defined direction and thus the desired freewheeling effect is given.

the 12 until 14 each relate to three operating phases Ph1, Ph2, Ph3 of the bearing arrangement 1, wherein in the first operating phase Ph1, referred to as the forward stroke, the linear actuator 27 is actuated in the freewheeling direction, i.e. the brake is applied, in the second operating phase Ph2, i.e. the holding phase, the Brake remains tight, and in the third operating phase Ph3, which is referred to as reverse stroke, the linear actuator 27 is actuated in the opposite direction to the original direction, that is, the brake is released again. In 12 is the travel SW, i.e. the stroke of the linear actuator 27, in the three operating phases Ph1, Ph2, Ph3, in 13 the axial force Fax acting in the bearing assembly 1 is shown.

the 14 shows three idealized characteristic curves K1, K2, K2, which stand for the driving torque when the brake is applied (K1), a holding torque (K2), and a reverse torque (K3). The reverse rotation of the linear actuator 27 can be interrupted at any point, with the linear actuator 27 always remaining in its current position, that is to say it is self-locking. The self-locking can only be overcome if an additional, in the present case to be generated by an electric motor, reverse rotating moment acts on the shaft 6 . The speed of the adjustment can be stably controlled in both adjustment directions. In particular, during the transition between the operating phases Ph2 and Ph3, since the overrunning clutch 10 remains locked, there is no sudden relaxation of a locking mechanism. This allows for a smooth return towards the parking brake open position at all times.

The diagram after 15 shows basic possibilities for varying a holding torque Mh, which can be absorbed by the overrunning clutch 10, and applies in principle to all exemplary embodiments. A mechanical load on the bearing arrangement 1 is generally denoted by FL. The holding torque Mh can be determined, among other things, by a constant load (F _const ), which is independent of the current operating state. In particular, the bearing arrangement 1 can be loaded with a spring element 23 for this purpose. In addition, variable loads (F _var ) occur on the overrunning clutch 10, which are linearly dependent on the bearing load FL. Overall, the summation of these two curves (Fconst+Fvar=Fres) results in the holding torque Mh, which must be overcome in order to rotate the bearing elements 4, 5 against one another in the blocking direction of the overrunning clutch 10, which then acts as a brake.

Reference List

1

bearing arrangement

2

Housing

3

Thrust roller bearing with freewheel function

4

Bearing element, housing washer, bearing ring, outer ring

5

Bearing element, shaft washer, bearing ring, inner ring

6

Wave

7

rolling elements

8th

Cage, inner clutch part

9

pocket

10

overrunning clutch

11

outer clutch part

12

pawl

13

coil spring

14

spring support block

15

housing-fixed sleeve component

16

recess

17

Connection contour of the shaft

18

second thrust bearing

19

Second thrust bearing cage

20

Rolling elements of the second thrust bearing

21

spring support cover

22

Housing washer of the second thrust bearing

23

Spring element, plate spring, pre-tensioning device

24

housing part

25

housing part

26

Cage toothing 8, detent geometry

27

linear actuator

28

spindle drive

29

lead screw

30

brake piston

31

bellows

32

spindle nut

33

waveproof element

34

thread

35

brake disc

36

inner row of rolling elements

37

outer row of rolling elements

38

Inner row cage

39

Cage element of the overrunning clutch

40

Role of the overrunning clutch

41

Overrunning clutch spring element

42

Overrunning clutch inner ring

43

Ramp contour of the inner ring 42

fax

axial force

Fconst

constant bearing load

FL

bearing load

fresh

resulting bearing load

fvar

variable bearing load

K1... K3

characteristics

M

moment

MA

central axis

Mh

holding torque

Ph1 ... Ph3

phases

SW

travel

Claims (10)

Bearing arrangement (1) with a freewheel function, comprising a roller bearing (3) having two bearing elements (4, 5) which can be rotated in opposite directions and contact roller bodies (7), characterized by a cage (8) guiding the roller bodies (7) of the roller bearing (3), which as a component of a one-way clutch (10) effective in the mechanically loaded state of the roller bearing (3), at least the locking part of the cage (8) being rigid in itself. Bearing arrangement (1) according to claim 1 , characterized in that the roller bearing (3) is designed as an axial bearing and the overrunning clutch (10) at least indirectly between the cage (8) on the one hand and a shaft (6) mounted by means of the axial bearing (3) or a housing (2) in which the shaft (6) is mounted, on the other hand is connected. Bearing arrangement (1) according to claim 1 , characterized in that the roller bearing (3) is designed as a radial bearing and the overrunning clutch (10) as a frictionally or positively effective clutch Bearing arrangement (1) according to one of Claims 1 until 3 , characterized in that the Overrunning clutch (10) is designed as a ratchet lock, the cage (8) having a locking geometry (26) which interacts directly with pawls (12) of the overrunning clutch (10). Bearing arrangement (1) according to one of Claims 1 until 4 , characterized in that the rolling bearing (3) is constructed in multiple rows, with only one cage (8) provided for guiding a single row of rolling bodies (37) being designed as a component of the overrunning clutch (10), whereas a cage (38) of at least one further row of rolling bodies (36) has no freewheel function. Bearing arrangement (1) according to one of Claims 1 until 5 characterized by a prestressing means (23) which is designed to generate a prestressing force which loads the roller bearing (3) and thus makes the overrunning clutch (10) ready for operation or at least supports it. Bearing arrangement (1) according to one of Claims 1 until 6 , characterized in that the cage (8) has the rolling elements (7) guiding pockets (9) with non-uniform play in the circumferential direction. Linear actuator (27), comprising a spindle drive (28) and for mounting a rotatable spindle drive component (29, 32) of the spindle drive (28) provided according to claim 1 trained bearing assembly (1) with freewheel function. Method for operating a linear actuator (27). claim 8 , wherein when the spindle drive (28) is adjusted in a first adjustment direction, the bearing arrangement (1) is operated in the freewheeling direction, i.e. in a first operating mode (Ph1), and then in a second operating mode (Ph2) the spindle drive (28) is self-retaining takes place by means of the overrunning clutch (10) integrated into the bearing arrangement (1), and when the spindle drive (28) is subsequently adjusted in the opposite direction, i.e. in a third operating mode (Ph3), the bearing arrangement (1) is operated in the blocking direction, and wherein in the latter operating mode (Ph3) the overrunning clutch (10) remains blocked and the bearing elements (4, 5) are twisted against one another while overcoming frictional forces. procedure after claim 9 , characterized in that a holding torque (Mh) of the overrunning clutch (10) by a bearing arrangement (1) acting load (FL) which includes at least one of the components constant load (Fconst) and variable load (Fvar) is adjusted.

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