TOOTH DISC

Description

[0001] The invention relates to a toothed disc according to the preamble of claim 1. The invention further relates to a toothed belt drive with such a toothed disc and to a two-wheeler with such a toothed belt drive.

[0002] Timing belts can transmit significantly higher torques than comparable flat or V-belts, but they are also susceptible to disruptions in tooth engagement caused by contamination. While a closed tooth profile allows the drive belt teeth to make optimal contact with the pulley, foreign particles can accumulate within the tooth profile. This can impair the contact between the belt or its teeth and the pulley, and in particular, reduce the depth of the pulley's profile to such an extent that the belt may slip off the pulley. Furthermore, this can subject the belt to increased bending stress, which can mechanically weaken the belt and increase the risk of failure, such as belt breakage.

[0003] Therefore, toothed belt drives with toothed pulleys that have openings at their tooth base pointing towards the interior of the toothed pulley for the removal of foreign bodies or contaminants, so-called open toothed pulleys, are known in the prior art, for example in toothed belt drives for two-wheelers or for other drive or conveying systems in rough, stony or dusty environments.

[0004] Generally speaking, the meshing action of the tooth pair between the pulley and the timing belt during rotation results in completely different engagement conditions – depending on the kinematics and the tooth profile design – than, for example, when rolling meshing gears with the involute teeth commonly used there. Thus, in a belt drive, the profile designs of the timing belt and the pulley can be configured either so that the belt webs, i.e., the areas between the belt teeth, are supported on the tooth tips of the pulley teeth, or so that the timing belt is supported with its tooth tip surface in the tooth gaps of the pulley teeth.

[0005] In some applications, and especially when the meshing conditions change due to deposits or contamination between the teeth, both bearing surfaces or supports interact in a more or less uncontrollable way. While this is less of an issue with open toothed pulleys, it still leads to increased wear of the belts and wheels. Generally speaking, a bearing surface of the timing belt webs on the tooth tips of the pulley teeth is considered less advantageous.

[0006] One of the disadvantages of open timing belt pulleys is that, due to the openings at the base of the pulley teeth, the belts tend to rest on the tooth tips of the pulley teeth. This can lead to stress on the belt body and especially on the tensile members embedded in the belt, which can shorten the belt's service life.

[0007] Another disadvantage is that the openings on open toothed pulleys can also cause problems. For example, if the openings are too large, meaning the tooth root is milled too wide, the belt teeth can be forced into the opening under high load, preventing clean disengagement from the teeth. Conversely, while a small opening allows the timing belt to properly seat against the teeth of the pulley, it can prevent dirt from being carried away between the teeth. Therefore, proper design and adjustment are extremely difficult.

[0008] DE 10 2019 213 096 A1 relates to a toothed pulley with openings at its tooth root extending across a portion of the tooth width towards the interior of the pulley for the removal of foreign bodies or contaminants between the teeth. One tooth flank of each tooth of the toothed pulley has a support profile for partially receiving a tooth head of the timing belt, and the other tooth flank has a guide profile for the removal of foreign bodies or contaminants.

[0009] Unfortunately, the timing belt only supports parts of its tooth head surface on the support profiles of the pulley teeth, which can further lead to an uneven distribution of mechanical stresses in the belt.

[0010] To prevent timing belts from slipping off the pulleys due to lateral forces, guide elements, often designed as ring-shaped flanges attached laterally to the pulley, are generally used. This is particularly important for helical gears, which, while quieter than spur gears, can be prone to pulley slippage due to their inherent axial force component. However, even with spur gear drives, safeguards against slippage caused by lateral forces are crucial, for example, in the timing belt drives of bicycles.

[0011] DE 10 2019 213 105 A1 relates to a toothed pulley with guide elements arranged on one or both sides for the timing belt, wherein the guide elements are designed as a plurality of guide flanges distributed over the circumference of the toothed pulley and each extending over a partial circumference of the toothed pulley, the guide flanges laterally delimiting at least one of the tooth gaps over at least a partial portion of the tooth height. The toothed pulley has openings at its tooth root, extending over a portion of the tooth width to the interior of the toothed pulley, for the removal of foreign bodies or contaminants between the teeth.

[0012] Another method for guiding timing belts is the so-called center guide. This involves guide profiles in the toothed area. EP 2 289 792 A1 discloses a self-centering system in which the belt has a recess or groove in the center of its teeth and the timing belt pulley has a projecting centering rib or flange running centrally between the tooth flanks, which engages in the groove of the timing belt as it rotates.

[0013] A similar system is disclosed in US 2018 003273 A1, in which a rising fin is also provided between the tooth flanks of the pulley to engage in a groove formed in the belt teeth.

[0014] TW I577903 B reveals another variant of a belt drive, in which the belt is guided by a guide groove of the pulley.

[0015] A disadvantage of known solutions is that the timing belt is only supported on the tooth heads of the pulley teeth by the webs of the timing belt, which can lead to high local loads in the timing belt and / or to an uneven distribution of mechanical stresses in the belt.

[0016] The object of the invention is to provide a toothed pulley for a toothed belt drive that can dissipate dirt accumulating between the teeth of the pulley and, at the same time, offers improved engagement with the teeth of a toothed belt compared to known solutions, thus ensuring a more uniform mechanical stress distribution within the toothed belt. Additionally or alternatively, the toothed pulley should be easy and / or cost-effective to manufacture and capable of transmitting high power in conjunction with a toothed belt. Additionally or alternatively, the toothed belt surrounding the toothed pulley should be able to be guided laterally through the pulley.

[0017] The solution to this problem is achieved by a toothed disc having the features of independent claim 1.

[0018] Further advantageous embodiments are disclosed in the dependent claims, as well as in the general description and the exemplary embodiments.

[0019] The present application relates to a toothed pulley for a toothed belt drive, in which a toothed belt wraps circumferentially around the toothed pulley with its toothed drive side, and the teeth of the toothed pulley and toothed belt mesh together. The toothed pulley has openings at each tooth gap between two teeth, extending over a portion of a tooth width towards the interior of the toothed pulley, for the removal of foreign bodies or contaminants, and a circumferentially circumferential guide rib for guiding the toothed belt axially. The toothed pulley has at least one rib arranged circumferentially between each pair of teeth, the rib being designed to at least partially receive a tooth head of the toothed belt. The guide rib has a radially extending lead-in chamfer.

[0020] In other words, the guide rib can be wedge-shaped in the radial direction, with its width increasing inwards in a wedge shape. This advantageously improves the engagement of the guide rib in a corresponding guide groove of a toothed belt, even when individual pulleys are misaligned or offset from one another.

[0021] The guide rib has a width extending in the axial direction. The width of the guide rib is smaller than the tooth width and smaller than the width of the rib.

[0022] The rib allows the tooth head of the timing belt to be at least partially supported across its width, thus preventing the belt ribs from bearing directly on the teeth of the pulley. In other words, the timing belt rests on the rib of the pulley teeth with a portion of its tooth head surface, resulting in a more even load distribution across the belt. This reduces wear on the timing belt and / or extends its service life. Additionally or alternatively, the timing belt can transmit higher power.

[0023] The toothed disc can be manufactured in one piece or in multiple parts. Manufacturing several individual parts that can subsequently be assembled or joined together to form a toothed disc can lead to simpler and more cost-effective production, especially in the case of particularly complex geometries or undercuts.

[0024] While toothed belts can transmit significantly higher torques than comparable flat or V-belts, they are also susceptible to disruptions in tooth engagement caused by contamination. With a closed tooth profile, the teeth of the drive belt can make optimal contact with the toothed pulley, but foreign matter can accumulate within the tooth profile. This can impair the contact between the belt or its teeth and the toothed pulley, and in particular, reduce the depth of the toothed pulley's profile to such an extent that the belt teeth can slip against the pulley, or the belt can break due to mechanical weakening caused by increasing buckling stress. This can be advantageously and reliably prevented by the openings in the toothed pulley according to the invention.

[0025] According to a further aspect of the present invention, the width of the bridge is smaller than the tooth width. This advantageously ensures a sufficiently large opening for dirt drainage. The maximum depth or width of the opening is obtained by subtracting the width of the bridge from the tooth width.

[0026] Preferably, the toothed disc is symmetrically designed, such that the ridge is centrally located and an opening extends axially from the ridge and / or the toothed disc body to the left, and another opening extends axially from the ridge and / or the toothed disc body to the right. In this embodiment, the maximum depth or width of the left or right opening is obtained by subtracting the width of the ridge from the tooth width and dividing by two. The depth or width of the openings can taper off via radii and terminate in a plane spanned by the tooth faces. In other words, the depth or width of the openings can approach or reach zero in the circumferential direction from a maximum value.

[0027] The toothed disc can be designed as a two-part structure with respect to its zenith plane. This simplifies the manufacturing process, as two similar or identical parts are produced that can then be joined together to form a single toothed disc.

[0028] According to a further aspect of the present invention, the web connects two teeth to each other. This advantageously ensures that the tooth head of the timing belt is fully supported or received by the web, at least over a portion of the timing belt width.

[0029] According to a further aspect of the present invention, the guide rib connects two teeth. This advantageously ensures that the toothed belt can be guided through the toothed pulley in the axial or transverse direction, at least over a portion of its length. The ability to absorb transverse forces over a large area advantageously enables a uniform force distribution into the toothed belt across the largest possible cross-section, thereby preventing the occurrence of stress peaks.

[0030] By designing the guide rib in this way, the use of flange discs for guiding the timing belt in the axial or transverse direction can be dispensed with, and yet a forced guidance of the timing belt can be achieved in a very effective manner.

[0031] According to a further aspect of the present invention, the radial height of the guide rib corresponds at most to the height of the teeth. In a particularly preferred embodiment, the radial height of the guide rib is less than the height of the teeth. The smaller the height of the guide rib, the shallower the depth of the groove arranged in the toothed belt and correspondingly engaged with the guide rib can be, thereby only slightly reducing the mechanical strength of the toothed belt.

[0032] According to a further aspect of the present invention, the guide rib has recesses for dirt removal. Preferably, a recess is arranged between each pair of teeth. In other words, the recesses can be designed as an axially extending bore that passes through the entire width of the guide rib. This advantageously improves the removal of dirt that accumulates in the spaces between the teeth. Furthermore, the recesses can reduce the weight of the pulley.

[0033] According to a further aspect of the present invention, the toothed pulley has a pulley body from which the teeth of the pulley cantilever out axially on one or both sides. The toothed pulley teeth are connected to the pulley body or the web at the tooth root only over a portion of the tooth width. In addition to the resulting weight savings, this allows for sufficient support and torque transmission by the toothed belt, adapted to the respective load situation and power transmission, and also ensures reliable and clean removal of contaminants, since the cantilever creates correspondingly large openings in the tooth root area.

[0034] The invention further relates to a toothed belt drive with a toothed pulley according to the invention and a toothed belt, wherein the toothed belt has a circumferentially extending groove, the guide rib of the toothed pulley being designed to engage in the groove of the toothed belt and to guide the toothed belt in the axial direction. The aforementioned properties and advantages can thus be transferred to any toothed belt drive, which can preferably be used in a contaminated environment.

[0035] The aforementioned properties and advantages can also be transferred to a two-wheeler, in particular a bicycle or a motorcycle and their derivatives, with a toothed belt drive according to the invention.

[0036] In the aforementioned applications, the toothed belt drive is often exposed to dusty or dirty environments without protection. The design according to the invention then provides reliable belt guidance and sufficient power transmission even in contaminated conditions.

[0037] It is expressly pointed out that the embodiments of the invention described above can each be combined with the subject matter of claim 1, either individually or in any technically meaningful combination with each other.

[0038] The following schematically illustrates and explains exemplary embodiments of the invention with reference to the drawings.

[0039] It shows: Fig. 1 shows a toothed disc according to the invention. Fig. 2 shows a partial view of the toothed disc according to the invention. Fig. 1 .

[0040] The above figures are described in cylindrical coordinates with a longitudinal axis X, a radial direction R perpendicular to the longitudinal axis X, and a circumferential direction U rotating around the longitudinal axis X. The longitudinal axis X, the radial direction R, and the circumferential direction U can also be collectively referred to as spatial directions X, R, U or as cylindrical spatial directions X, R, U.

[0041] Fig. 1 Figure 1 shows schematically and in a perspective view a toothed disc 1 of a toothed belt drive according to the invention.

[0042] The toothed disc 1 has a web 4 arranged in the circumferential direction U between each pair of teeth 3, the web 4 being designed to at least partially receive a tooth head of a toothed belt. The web 4 connects each pair of teeth 3 of the toothed disc 1 arranged next to each other in the circumferential direction U.

[0043] The web 4 has a width that is less than the width Bz of a tooth 3 of the toothed disc 1. The size of an opening 2 for dirt removal between two teeth 3 is obtained by subtracting the width of the web 4 from the tooth width Bz. Since the toothed disc 1 is symmetrical, the web 4 is centrally located, so that opening 2 extends from a toothed disc body 7 and / or web 4 in the axial direction X or along the longitudinal axis to the left, and opening 2 extends from the toothed disc body 7 and / or web 4 in the axial direction or along the longitudinal axis X to the right. Thus, the maximum depth of the left opening 2 and the right opening 2 is obtained by subtracting the width of the web 4 from the tooth width Bz and dividing by two. The depth of the openings 2 tapers off radii and terminates in a plane spanned by the tooth faces.

[0044] The toothed disc 1 has a guide rib 6, which is arranged between each pair of teeth 3 that connect two adjacent teeth 3 in the circumferential direction U. The height of the guide rib 6 corresponds to the height of the teeth 3 in the radial direction R. The guide rib 6 has a width BF extending in the axial direction X. The width BF of the guide rib is smaller than the tooth width Bz and smaller than the width of the rib 4. The guide rib 6 also has recesses 8 for dirt removal, with one recess 8 arranged between each pair of teeth 3. The recesses 8 are designed as bores extending in the axial direction X and passing through the entire width of the guide rib 6. This advantageously improves the removal of dirt that accumulates in the inter-tooth spaces 5.

[0045] The toothed disc 1 has openings 2 at its tooth base extending over a portion of the tooth width Bz towards the interior of the toothed disc 1, namely for the removal of foreign bodies or contaminants between the teeth 3. The teeth 3 of the toothed disc 1 are projecting from the toothed disc body 7 on both sides.

[0046] Fig. 2 shows a partial view of the toothed disc 1 according to the invention. Fig. 1 from the side. Clearly visible are the guide rib 6, the toothed disc body 7, and the ribs 4 extending radially R into the interdental spaces 5. Reference symbol list (part of the description)

[0047] 1 Toothed disc 2 Opening 3 Tooth 4 Bridge 5 Tooth gap 6 Guide bridge 7 Toothed disc body 8 Recess for dirt removal BF Guide width BzTooth width RRadial direction UCircular direction XLLongitudinal axis, axial direction

Claims

1. Toothed pulley (1) for a toothed belt drive, wherein a toothed belt wraps circumferentially around the toothed pulley (1) with its toothed driving side and the toothings of the toothed pulley (1) and the toothed belt mesh with one another, wherein the toothed pulley (1) has, in each tooth space (5) between two teeth (3), openings (2) extending over part of a tooth width (Bz) and pointing toward the interior of the toothed pulley (1) for discharging foreign bodies or contaminants, wherein the toothed pulley (1) has a circumferentially (U) extending guide rib (6) for guiding the toothed belt in an axial direction (X), wherein the toothed pulley (1) comprises at least one web (4) arranged in the circumferential direction (U) between two teeth (3), the web (4) being configured for at least partially receiving a tooth tip (10) of the toothed belt, characterized in that the guide rib (6) has a lead in chamfer extending in the radial direction (R).

2. Toothed pulley (1) according to claim 1, characterized in that a width of the web (4) is smaller than the tooth width (Bz).

3. Toothed pulley (1) according to any one of the preceding claims, characterized in that the web (4) connects two teeth (3).

4. Toothed pulley (1) according to any one of the preceding claims, characterized in that the guide rib (6) connects two teeth (3).

5. Toothed pulley (1) according to any one of the preceding claims, characterized in that the height of the guide rib (6) in the radial direction (R) is at most equal to the height of the teeth (3).

6. Toothed pulley (1) according to any one of the preceding claims, characterized in that the guide rib (6) comprises recesses (8) for dirt discharge.

7. Toothed pulley (1) according to any one of the preceding claims, characterized in that the toothed pulley (1) comprises a pulley body (7) from which the teeth (3) of the toothed pulley (1) are formed so as to project cantilevered in the axial direction (X) on one or both sides.

8. Toothed belt drive comprising a toothed pulley (1) according to any one of claims 1 to 7 and a toothed belt, wherein the toothed belt comprises a groove extending in the circumferential direction (U), wherein the guide rib (6) of the toothed pulley (1) is configured to engage in the groove of the toothed belt and to guide the toothed belt in the axial direction (X).

9. Two wheeled vehicle comprising a toothed belt drive according to claim 8.