Freewheeling element

Abstract

The invention relates to a freewheeling element (4) having a plurality of clamping bodies (10) and a cage (5), wherein the cage (5) has axially extending bars (8) distributed equidistantly along its circumference and pockets in which one of the clamping bodies (10) is received in each case; the bars (8) have a higher elasticity than the clamping bodies (10); and the bars (8) are formed with a U-shaped cross section as seen in the axial direction.

Description

[0001] Freewheel element

[0002] DESCRIPTION

[0003] The invention relates to a freewheel element.

[0004] Freewheel elements are used, for example, in directional clutches that transmit or support torque in one direction through frictional engagement and allow freewheeling in the opposite direction. In sprag clutches, sprags are located within a clamping gap in the so-called clamping position when they transmit torque forcefully, i.e., frictionally, and in the so-called freewheeling position when they allow freewheeling.

[0005] In addition to the sprags, conventional sprag freewheels have, among other things, a sprag cage (hereinafter also simply referred to as the cage) into which the sprags are accommodated, and metal springs that hold the sprags in position by means of spring force (so-called spring loading of the sprags). Such sprag freewheels of known designs therefore consist of at least three different components, which entails correspondingly high manufacturing costs. The sprag freewheel described in EP 2 660 488 A1, on the other hand, does not require metal springs. There, the spring loading is achieved by elastically designed webs of the cage. A disadvantage of EP 2 660 488 A1, however, is that the spring travel achievable through the elastic webs is relatively small. This means that the tolerance requirements for the elements of the sprag freewheel and the components connected by the sprag freewheel are high.In addition, eccentricities occurring during operation of the sprag freewheel, for example, lead to the clamping gap varying and individual sprags generating an increased drag torque, while other sprags are no longer sufficiently spring-loaded.

[0006] The object of the present invention is to provide a simply constructed freewheel element which remains functional over a relatively large tolerance range and even in the case of eccentricities occurring in the clamping gap.

[0007] This object is achieved by a freewheel element having the features of claim 1. Advantageous embodiments of the freewheel element are described in the subclaims.

[0008] The freewheel element according to the invention comprises a plurality of clamping bodies and a cage. The cage has axially extending webs distributed equidistantly along its circumference, as well as pockets in each of which one of the clamping bodies is accommodated. The webs have greater elasticity than the clamping bodies and are formed with a U-shaped cross-section when viewed in the axial direction.

[0009] Due to the greater elasticity of the webs of the sprag cage compared to the sprags, these act as spring elements. This type of design therefore eliminates the need for metallic springs, resulting in a sprag freewheel that is particularly simple in design and easy to manufacture. “Greater elasticity” here means that the webs are made from a material that has greater elastic behavior than the material from which the sprags are made. The sprags are preferably made from a metallic material, e.g. steel. Accordingly, the webs then have an elasticity that is greater than the elasticity of metallic materials. The U-shaped cross-section of the webs, viewed in the axial direction, increases the possible spring travel. In other words, the web acts similarly to a spiral spring.The positioning of the clamping bodies therefore requires less precision and is less susceptible to eccentricities in the clamping gap or dimensional inaccuracies in the connecting components. This makes the freewheel element particularly suitable for thin-walled connecting components.

[0010] Preferably, the opening of the U-shaped cross-section faces radially inward or outward. This orientation of the cross-section allows the lateral end regions of each web to be contacted by the adjacent clamping bodies, and the resilient effect of the cross-sectional shape can be maximized.

[0011] In an advantageous embodiment, the freewheel element further comprises at least one cage rim, and each web is connected to the cage rim by a torsion spring bar. In other words, a torsion spring bar is arranged between the cage rim and the web. This allows the web to rotate relative to the cage rim. The torsion spring bar thus acts like a torsion spring. This makes the freewheel element even less susceptible to eccentricities in the clamping gap or dimensional inaccuracies in the connecting components.

[0012] The connection point between the web and the torsion spring bar can be located at one end of the U-shaped cross-section. This effectively overlaps the bending spring effect of the web and the torsion spring effect of the torsion spring bar.

[0013] Advantageously, the clamping bodies are accommodated in the pockets in a form-fitting manner, particularly in the form of a locking or snap-in connection. This allows for easy assembly and disassembly of the freewheel element, while also ensuring secure storage of the clamping bodies during operation. Utilizing the elastic properties of the webs, the clamping body pocket can be elastically expanded to engage or snap the clamping body into the pocket.

[0014] In general, the clamping bodies have a first contact zone for contact with a first adjacent web and a second contact zone for contact with a second adjacent web. The first contact zone and the second contact zone preferably differ from one another in their position in the radial direction. In other words, one of the contact zones is located further inward (i.e., closer to the center axis of the freewheel element) than the other contact zone. This makes it possible to apply a torque to the clamping body and thus, for example, influence the spring action of the clamping body. The magnitude and direction of the torque, in turn, can be adjusted by the relative position of the contact zones to one another.

[0015] In a further advantageous embodiment, the first contact zone and / or the second contact zone are formed as a surface corresponding to the lateral end region of the U-shaped cross-section of the web. In other words, the contact zone of the clamping body has a curvature or shape that corresponds to a negative image of the curvature / shape of the web. This enables a particularly defined and reproducible contact between the web and the clamping body.

[0016] In an advantageous embodiment, at least the webs and the torsion spring bars are made of a polymer material, in particular a polyamide. The polymer material preferably contains fillers, in particular in the form of fibers and / or spheres. If reinforcing fibers are used, they are preferably oriented along the longitudinal direction of the U-shaped cross-section of the webs.

[0017] Glass fibre reinforced polyamide is particularly suitable as a material, particularly PA 46 GF 15 (polyamide 46 with 15% glass fibre content).

[0018] The webs and / or torsion spring bars, as well as the entire clamp body cage, can be made of the above-mentioned materials. By using the above-mentioned materials, a particularly advantageous spring behavior can be achieved.

[0019] The invention is further explained using an exemplary embodiment in the drawing figures. They show:

[0020] Fig. 1 is a sectional view of a sprag freewheel with inner ring, outer ring and freewheel element arranged between them;

[0021] Fig. 2 shows a section of a sectional view of the freewheel element from Fig. 1;

[0022] Fig. 3 is a side view of the freewheel element from Fig. 1;

[0023] Fig. 4 is a perspective view of the freewheel element from Fig. 1;

[0024] Fig. 5 shows a section of a perspective view of a cage of the freewheel element from Fig. 1; and

[0025] Fig. 6 shows a section of a sectional view of the freewheel element from Fig. 1.

[0026] Fig. 1 shows a sectional view of a sprag freewheel 1. The

[0027] Sprag freewheel 1 has an inner ring 2 and an outer ring 3. The outer ring 3 is arranged coaxially with the inner ring 2. A gap, the so-called sprag gap, forms between the inner ring 2 and the outer ring 3. The freewheel element 4 is arranged within this gap. This freewheel element 4 is described in more detail in Figures 2 to 6.

[0028] The freewheel element 4 is essentially annular and has a cage 5 made of a fiber-reinforced polymer material (polyamide 46 with 15% glass fiber content). The cage 5 has a first cage rim 6 and a second cage rim 7 offset in the axial direction. Equidistantly distributed, axially extending webs 8 are arranged between the first cage rim 6 and the second cage rim 7. For reasons of clarity, not all elements that are present multiple times are provided with a separate reference numeral in the figures. For example, in Fig. 1, only one web 8 is provided with a reference numeral. The webs 8 are each connected to one of the cage rims 6, 7 via a torsion spring bar 9. The elements of the first cage rim 6, the second cage rim 7, the webs 8, and the torsion spring bars 9 together form the cage 5.

[0029] The space between each two adjacent webs 8 and the cage edges 6, 7 forms a pocket for accommodating a clamping element 10. The connection between the clamping element 10 and the cage 5 is designed as a snap connection. The clamping elements 10 are made of a steel material. The cage 5 is thus made of a material with greater elasticity than the material from which the clamping elements 10 are made.

[0030] The webs 8 have a U-shaped cross-section when viewed in the axial direction. The opening of the U points radially inward, i.e., toward the center axis of the freewheel element. The curved section of the U points radially outward. The lateral elements (legs) of the U each contact one of the clamping bodies 10 adjacent to the respective web 8. In other words, a clamping body 10 contacts a first adjacent web 8 in a first contact zone 11 and a second adjacent web in a second contact zone 12. The first contact zone 11 and the second contact zone 12 differ from one another in their position in the radial direction. More precisely, the second contact zone 12 is located further inward than the first contact zone 11.

[0031] The webs 8 are connected in a lateral end region of the U-shaped cross-section via a torsion spring bar 9 to the first cage rim 6 and the second cage rim 7. Apart from this connection, the webs 8 are self-supporting, i.e., there is no further connection to the cage rims 6, 7. Thus, the webs 8 possess high flexibility and bending and torsional capacity.

[0032] With reference to Fig. 6, the functioning of the freewheel element 4 will be explained in more detail, whereby for a better understanding of the

[0033] Clamping body 10a is shown in the clamping position, clamping body 10b in a central position, and clamping body 10c in the free position. In reality, all clamping bodies 10a, 10b, 10c would be in the same position. In the clamping position, the clamping bodies 10a, 10b, 10c form a frictional connection with the inner ring 2 and the outer ring 3, allowing torque to be transmitted between the inner ring 2 and the outer ring 3. In a freewheeling position, however, the clamping bodies 10a, 10b, 10c allow a rotational movement of the inner ring 2 relative to the outer ring 3.

[0034] In every position in the area of ​​the first contact zone 11 and the second contact zone 12, the clamping bodies 10a, 10b, 10c contact the webs 8 located between them. Due to their elasticity and U-shaped cross-section, the webs act like a bending spring. The webs 8 resiliently support the clamping bodies 10a, 10b, 10c and in doing so change their shape, i.e. the II shape widens or becomes narrower. In addition, the torsion spring bars 9 can twist under torsional load. Overall, this allows the clamping bodies 10a, 10b, 10c to be reliably spring-loaded and also reduces the displacement resistance within the cage 5. This in turn means that the freewheel element 4 remains functional over a relatively large tolerance range and even with eccentricities occurring in the clamping gap, without having to resort to metallic springs for spring loading.

[0035] Areas of application for the freewheel element 4 are particularly suitable in installation situations where thin-walled connecting components are present, such as freewheels on two-wheeled vehicles (bicycles, e-bikes or similar).

[0036] Cage 5 is made of glass-fiber-reinforced polyamide, with suitable injection points during injection molding ensuring that the reinforcing fibers are oriented in the longitudinal direction of the U-shaped cross-section of the webs. To achieve the most homogeneous material distribution possible, as many or all of the webs as possible should be connected to the injection mold. Injection points in the center of the webs 8 have also proven advantageous in this context.

[0037] LIST OF REFERENCE SYMBOLS

[0038] 1 sprag freewheel

[0039] 2 inner ring

[0040] 3 Outer ring

[0041] 4 freewheel element

[0042] 5 cage

[0043] 6 First cage board

[0044] 7 Second cage board

[0045] 8 bridge

[0046] 9 torsion spring bar, 10a, 10b, 10c clamping body

[0047] 11 First investment zone

[0048] 12 Second investment zone

Claims

CLAIMS 1 . Freewheel element (4) with a plurality of clamping bodies (10) and a cage (5), wherein: the cage (5) has axially extending webs (8) distributed equidistantly along its circumference and pockets in which one of the clamping bodies (10) is received; the webs (8) have a higher elasticity than the clamping bodies (10); and the webs (8) are formed with a U-shaped cross-section as seen in the axial direction.

2. Freewheel element (4) according to claim 1, wherein the opening of the U-shaped cross section points inwards or outwards in the radial direction.

3. Freewheel element (4) according to one of the preceding claims, further comprising at least one cage rim (6, 7), each web (8) being connected to the cage rim (6, 7) by a torsion spring bar (9).

4. Freewheel element (4) according to claim 3, wherein the torsion spring bar (9) is connected to the web (8) in an end region of the U-shaped cross section.

5. Freewheel element (4) according to one of the preceding claims, wherein the clamping bodies (10) are received in the pockets in a form-fitting manner, in particular in the manner of a locking or snap connection.

6. Freewheel element (4) according to one of the preceding claims, wherein each clamping body (10) has a first contact zone (11) for contact with a first adjacent web (8) and a second contact zone (12) for contact with a second adjacent web (8).

7. Freewheel element (4) according to claim 6, wherein the first contact zone (11) and the second contact zone (12) differ from one another in their position in the radial direction.

8. Freewheel element (4) according to one of the preceding claims, wherein the cage (5) consists of a polymer material, in particular of a polyamide, and the clamping bodies (10) consist of a steel material.

9. Freewheel element (4) according to one of the preceding claims, wherein at least the webs (8) consist of a glass fiber reinforced polyamide, in particular PA 46 GF 15.

10. Freewheel element (4) according to claim 9, wherein the reinforcing fibers are oriented along the longitudinal direction of the U-shaped cross section of the webs (8).

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