DE102023204832A1 - Chain drive and sprocket with reversed teeth and a randomly or intentionally different circular tooth profile - Google Patents

Abstract

The chain drive (1) with an irregular sprocket (2) has teeth (4) that engage with a chain (3) to transmit a relative movement between them, the plurality of teeth (4) being distributed over the circumference of the sprocket and tooth gaps being present between them, at least one tooth (4) differing from the other teeth (4) in its outer contour and/or at least one tooth gap (5) being designed differently from the other tooth gaps (5). A surface (6) of a tooth (4) designed for chain contact runs between an inlet contact point (7) and an outlet contact point (8) along at least one circular arc.

Description

The invention relates to a chain drive with an irregular sprocket that has teeth that engage with a chain in order to transmit a relative movement between them. The gear thus drives the chain or the chain drives the gear. A large number of teeth are distributed over the circumference of the sprocket (e.g. unevenly across the circumference) (or have an uneven geometric design across the circumference). Between these teeth there are tooth gaps (e.g. unevenly distributed or unevenly geometrically designed across the circumference), with at least one tooth differing from the other teeth in its outer contour and/or at least one tooth gap being designed differently from the other tooth gaps. Of course, such irregularities can occur more frequently.

Chain drives and chain drives have been around for a long time. Unfortunately, it has also been known for at least as long that the unwanted noise emissions they produce are quite high. Due to the discrete nature of chains, chain drives often suffer from a high level of pure tone noise.

To solve this problem, irregular sprockets, also known as randomized sprockets, were invented.

“Randomized sprockets” are already known from the state of the art, i.e. sprockets with an irregular outer contour.

• eine Kette mit durch Verbindungsglieder miteinander verbundenen Stiften wobei jeder Stift eine mittlere Achse aufweist, und eine Kettenteilung besitzt, die als ein Abstand zwischen der mittleren Achse benachbarter Stifte definiert ist, wobei die Kettenteilung konstant ist; ferner umfassend ein Kettenrad mit mehreren Zähnen und Zahnlücken, die um den Umfang des Kettenrads beabstandet sind, wobei jede der Zahnlücken zwischen benachbarten Zähnen positioniert ist, wobei jede der Zahnlücken eine radiale Zahnlückenposition aufweist, die als ein Abstand zwischen der Mitte des Kettenrads und einem entlang den Zahnlücken am nächsten zur Mitte des Kettenrads in einer Radialrichtung befindlichen Punkt definiert ist; und umfassend mindestens einen Satz von vier aufeinander folgenden Zahnlücken, die als eine erste Zahnlücke, eine zweite Zahnlücke, eine dritte Zahnlücke und eine vierte Zahnlücke definiert sind, wobei die erste Zahnlücke und die vierte Zahnlücke eine gemeinsame radiale Position aufweisen und die zweite Zahnlücke und die dritte Zahnlücke eine voneinander und von der ersten und der vierten Zahnlücke verschiedene radiale Position aufweisen, und der Satz von vier aufeinander folgenden Zahnlücken zwei verschiedene Verbindungswinkel aufweist, mit einem ersten Verbindungswinkel, der zwischen einer Mittellinie eines ersten Verbindungsglieds und einer Mittellinie eines zweiten Verbindungsglieds definiert wird, und einem zweiten Verbindungswinkel, der zwischen der Mittellinie des zweiten Verbindungsglieds und der Mittellinie eines dritten Verbindungsglieds definiert wird, wobei die Mittellinie des ersten Verbindungsglieds durch die mittlere Achse eines Stifts in der ersten Zahnlücke und die mittlere Achse eines Stifts in der zweiten Zahnlücke definiert wird, wobei die Mittellinie des zweiten Verbindungsglieds durch die mittlere Achse eines Stifts in der zweiten Zahnlücke und die mittlere Achse eines Stifts in der dritten Zahnlücke definiert wird, wobei die Mittellinie des dritten Verbindungsglieds durch die mittlere Achse eines Stifts in der dritten Zahnlücke und die mittlere Achse eines Stifts in der vierten Zahnlücke definiert wird.

For example, the DE 11 2010 000 786 B4 a chain drive comprising:

• a chain having pins connected to one another by links, each pin having a central axis and a chain pitch defined as a distance between the central axis of adjacent pins, the chain pitch being constant; further comprising a sprocket having a plurality of teeth and tooth gaps spaced around the circumference of the sprocket, each of the tooth gaps positioned between adjacent teeth, each of the tooth gaps having a radial tooth gap position defined as a distance between the center of the sprocket and a point along the tooth gaps closest to the center of the sprocket in a radial direction; and comprising at least one set of four consecutive tooth gaps defined as a first tooth gap, a second tooth gap, a third tooth gap and a fourth tooth gap, wherein the first tooth gap and the fourth tooth gap have a common radial position and the second tooth gap and the third tooth gap have a radial position different from each other and from the first and fourth tooth gaps, and the set of four consecutive tooth gaps has two different connection angles, with a first connection angle defined between a center line of a first connecting member and a center line of a second connecting member, and a second connection angle defined between the center line of the second connecting member and the center line of a third connecting member, wherein the center line of the first connecting member is defined by the center axis of a pin in the first tooth gap and the center axis of a pin in the second tooth gap, wherein the center line of the second connecting member is defined by the center axis of a pin in the second tooth gap and the center axis of a pin in the third tooth gap, wherein the center line of the third connecting member is defined by the center axis of a pin in the third tooth gap and the middle axis of a pin is defined in the fourth tooth gap.

• eine Nabe sowie eine Vielzahl von Zähnen, die von der Nabe radial auswärts hervorstehen und mittels einer Vielzahl von Zahnlücken voneinander getrennt sind. umfassend einen ersten und zweiten elastomeren Dämpfungsring, die an einer gegenüberliegenden ersten und zweiten axialen Seite der Zähne mit der Nabe verbunden sind, wobei der erste und zweite Dämpfungsring jeweils eine Vielzahl von Druckpolstern abgrenzen, die durch sich axial erstreckende Rillen, die jeweils mit den Zahnlücken ausgerichtet sind und radial einwärts dazu angeordnet sind, umfänglich voneinander getrennt sind, wobei jedes der Druckpolster eine ebene äußere Fläche umfasst, die um einen umfänglichen Mittelpunkt symmetrisch abgegrenzt ist und sich zwischen einem vorderen Ende und einem hinteren Ende erstreckt und diese umfasst, wobei das vordere Ende und das hintere Ende jedes Druckpolsters in einem gemeinsamen radialen Abstand von einer Mitte der Nabe angeordnet sind, um die sich das Kettenrad dreht.

The DE 603 05 682 T2 a sprocket comprising:

• a hub and a plurality of teeth projecting radially outward from the hub and separated from one another by a plurality of tooth spaces, comprising first and second elastomeric damping rings connected to the hub on opposite first and second axial sides of the teeth, the first and second damping rings each defining a plurality of pressure pads circumferentially separated from one another by axially extending grooves each aligned with and disposed radially inwardly of the tooth spaces, each of the pressure pads including a planar outer surface symmetrically defined about a circumferential center and extending between and encompassing a front end and a rear end, the front end and rear end of each pressure pad being disposed at a common radial distance from a center of the hub about which the sprocket rotates.

Further and parallel state of the art is known from the US 8,323,671 B2 , the US 8,435,145 B2 , the US 2018/0363753 A1 and the US 6,325,734 B1 known.

It is the object of the present invention to eliminate or at least mitigate the problems known from the prior art. In particular, noise and vibrations are to be minimized.

This is achieved according to the invention in that, in a generic chain drive on a surface of a tooth designed for chain contact, this surface runs between an entry contact point and an exit contact point along at least one circular arc. The entry contact point is understood to be the first contact point of the chain with a specific tooth during operation, whereas the exit contact point is the last contact point of the chain with exactly this tooth when the relative movement is passed on between the two drive partners consisting of chain and gear. The entry contact point and the exit contact point therefore each lie on a circular arc that also forms the surface of the tooth between these two points. In particular, the entry contact point and the exit contact point form an end point of the respective circular arc.

The noise and vibrations caused by the periodic impact/intermeshing between the chain and the sprockets and by the periodic transverse movement of the chain relative to the axis of rotation of the sprockets, also known as the tendon effect or polygon effect, are now reduced. Due to the even distribution of the sprocket teeth along the sprocket circumference, vibration and noise otherwise occur at the basic meshing frequency and its positive integer multiples. This problem, which is particularly well solved in the US 8,323,671 B2 explained is now solved. The relevant description is considered to be integrated here.

In fact, to solve the problem described, the uniform tooth profile around the sprocket circumference is modified so that the time intervals between two successive impacts are unequal. This breaks the uniform pattern and "distributes" the noise and vibrations over a wider frequency spectrum, while the amplitudes of the engagement orders are reduced and ultimately masked. A reduction in the pure tones of the interaction between the chain and sprocket is expected, but not necessarily a reduction in the overall level of noise and vibration.

The sprockets / toothed sprockets with so-called inverted teeth can have different tooth profiles. Although the use of involutes has proven successful in the past, this is deliberately avoided. Now the focus is on a number of (circular) arcs, each with a constant radius. Straight lines or surfaces or a combination of these are avoided. The surface is therefore formed exclusively by one or more circular arcs (sections). If there are several circular arcs, these are directly adjacent to one another.

Preferably, the surface is formed by only a small number of circular arcs, the number being, for example, between 1 and 5.

The core of the invention is that the inlet contact point and the outlet contact point define one or more circular arcs for the area between them. Typically, the definition of the active tooth profile consists of one or a plurality of arcs with a constant radius. These are connected to the head and root diameters, which are located in front of the inlet contact point and behind the outlet contact point, by arc-shaped head and root sections. This means that the number (1 or more) of circular arcs that define the surface between the inlet contact point and the outlet contact point is followed by a (concavely curved) arc-shaped root section to the inlet contact point and a (convexly curved) arc-shaped head section starting from the outlet contact point.

Preferably, these arcuate sections have different radii. Outside of the at least one circular arc between the inlet contact point and the outlet contact point, different radii lead to the number of circular arcs towards or away from

According to a preferred embodiment, the active profile between the inlet contact point and the outlet contact point is formed by a common circular arc with a single radius.

According to a preferred alternative embodiment, several circular arcs, in particular a maximum of 2 to 5, form the surface between the inlet contact point and the outlet contact point. In a particularly preferred embodiment, the surface is formed by exactly two circular arcs or a maximum of 3 circular arcs.

The multiple, in particular two, circular arcs preferably have different radii. The radii preferably differ by at least 25% and more preferably by at least 50%. In some embodiments, the radii differ by at least a factor of 2 or even a factor of 3 and, for example, by a maximum factor of 3 or 5.

In a preferred embodiment, the radius in the area of the foot-side inlet contact point is larger than the radius in the area of the head-side outlet contact point. This embodiment has proven to be particularly advantageous.

Alternatively, a reverse design can be provided in which the foot-side radius is smaller than the head-side radius.

In a preferred embodiment, the multiple circular arcs have different circle centers. Overall, a desired contour of the active profile, i.e. the surface between the inlet contact point and the outlet contact point, can be formed by appropriately selecting the positioning of the circle centers and the length of the radii.

In a preferred embodiment, both the radii and the position of the circle centers differ.

The tooth shape is arranged around the rotation axis of the sprocket with a constant angular step. The uniform control increment for all teeth is therefore 360° divided by the number of teeth Z.

• - nur Außenflankeneingriff: nur die Außenflanken der Kettenglieder haben Kontakt mit den Zähnen des Kettenrades,
• - progressiver Flankenangriff: zuerst berühren die Innenflanken der Kettenglieder die Kettenradzähne, dann die Außenflanken der Kettenglieder,
• - nur Innenflankeneingriff: nur die Innenflanken der Kettenglieder haben Kontakt mit den Kettenradzähnen.

When the sprocket rotates at a constant angular velocity, the contact between a chain link and the sprocket occurs at equal time intervals as in an angle of rotation of the sprocket of 360°/Z, where "Z" is the number of teeth on the sprocket. A specialist familiar with the design of toothed chains knows that chains can be divided into three types based on the kinematics of the engagement between the chain and the sprocket:

• - only outer flank engagement: only the outer flanks of the chain links have contact with the teeth of the sprocket,
• - progressive flank attack: first the inner flanks of the chain links touch the sprocket teeth, then the outer flanks of the chain links,
• - inner flank engagement only: only the inner flanks of the chain links are in contact with the sprocket teeth.

It should be noted that a progressive mesh chain with a low tooth count sprocket can become an internal mesh type when paired with a high tooth count sprocket. To better illustrate the kinematics of chain mesh, reference is made to SAE papers from 2006. The most relevant document here is number 2006-01-0619 and entitled "Kinematic Analysis of Chordal Action and Transmission Errors of Silent Chains" by the authors Chintien Huang and Kuen-Chuan Lin and Leo Kosasih, which can be accessed from the SAE International database.

To disrupt the regular pattern of contact initiation, the proposed solution is a variable tooth profile on the circumference of the sprocket. Such a pattern can consist of a few selected sprocket tooth profiles which are then arranged in a pseudo-random pattern. Pseudo-random pattern means that for a mass-produced sprocket there is only one pattern for all parts produced and no random production. Such a pattern can be selected by dynamic simulation, NVH testing or a combination of both. The Cloyes patent, US 6,325,734 B1 , describes such a process for a roller chain. The relevant technical content is considered to be integrated here.

It is clear that tooth profile variation can be achieved by changing any parameter for an active single radius profile, but it has been found that the most effective and preferred method is to change the "offset" and "radius" parameters, which control a "tilt" of the tooth profile. "Offset" is understood as the choice of the center of a given circular arc.

In a profile with two radii, the "tilt" of the gear ring can also be controlled by the second radius. When multiple radii are used, changing all or any of these radii will contribute to changing the tooth profile.

For an involute profile, the key parameter defining the tooth profile is the pressure angle. Consequently, a randomly selected sprocket with an involute profile will have a variable pressure angle around the circumference of the sprocket.

It should be noted that the preferred design is a profile with a common circular arc with one radius or with two circular arcs with two radii, where the parameter "offset" in the circumference of the sprocket is chosen randomly. According to one embodiment, the radii of the individual teeth are identical for each tooth and only the offset, i.e. the choice of the position of the circle centers, differs for the different teeth distributed around the circumference of the sprocket. In this way, the "Herz" contact geometry of chain and sprocket is, in the worst case, identical to that of the standard uniform sprocket, which means that the maximum Contact pressures between chain and sprocket remain the same for the fully seated chain links.

It is also worth mentioning that according to a preferred embodiment, each tooth has a different profile. Such a pattern results from a random algorithm. However, the algorithm itself is not the subject of the present invention.

In addition, such an embodiment offers an advantage over the variable pitch polygon sprockets described in the prior art. The pitch polygon remains regular, which means that no significant changes in the chain load will occur due to the polygon “runout”. The “runout” of the polygon and its attenuation are in the US 2018/0363753 A1 well described. What is disclosed in this regard is to be considered integrated here.

Profile randomization can also be applied to sprockets that have non-round / distorted polygons. Such sprockets serve to reduce the chain load and are also called “oval sprockets”.

It is also advantageous if the radius defining the respective circular arc shape is larger than the tooth height, but preferably smaller than the gear circumference. However, it should be twice the width of the tooth gap in the narrowest area.

It has also proven to be useful if the tooth mirror is designed symmetrically to its central axis, i.e. the respective tooth is designed mirror-symmetrically to its central axis.

An advantageous embodiment is also characterized in that the circular arc has a different transition radius on the outside of the area between the inlet contact point and the outlet contact point, i.e. the active profile. This means that the previously mentioned arcuate foot section/head section have a different (transition) radius from the radius of the at least one circular arc in the area of the active profile.

Preferably, the transition radii present on both sides of the area differ from each other.

As already mentioned, the circular arc in one design variant is determined by a single common radius for the inlet contact point, the outlet contact point and the surface in between or vice versa.

If the chain is made up of several links that are connected to each other via pins, a chain drive with different lengths can be designed to suit requirements.

It is advantageous if the link is designed with a side surface to rest on the tooth surface which has a circular arc shape in cross-section (transverse to the axis of rotation).

The invention is explained in more detail below with the help of a drawing. For background information, reference is made to the cited prior art, the SAE paper and specialist books. Relevant figures are not included here, however, but are to be considered as included.

• 1 das Zusammenwirken einer Kette mit einem erfindungsgemäß gestalteten Kettenrad, um einen erfindungsgemäßen Kettentrieb zu erhalten,
• 2 eine Vergrößerung des Bereichs II aus 1,
• 3 ein erfindungsgemäßes Zahnrad / Kettenrad,
• 4 eine Vergrößerung des Bereichs IV aus 3,
• 5 eine Vergrößerung des Bereichs V aus 3.

They show:

• 1 the interaction of a chain with a sprocket designed according to the invention in order to obtain a chain drive according to the invention,
• 2 an enlargement of area II 1 ,
• 3 a gear / sprocket according to the invention,
• 4 an enlargement of area IV 3 ,
• 5 an enlargement of the area V 3 .

In 1 a chain drive 1 according to the invention is shown. It consists, among other things, of an irregular sprocket / gear 2 and a chain 3.

The sprocket 2 has a plurality of teeth 4, with gaps 5 between the teeth 4.

In the 2 On the surface 6 of the tooth 4, an inlet contact point is referenced with the reference number 7 and an outlet contact point is referenced with the reference number 8. In the exemplary embodiment, the inlet contact point 7 is also referred to as a foot-side inlet contact point, which is therefore oriented in the foot area of the tooth 4 and thus towards the center of the chain wheel 2. The outlet contact point 8 is also referred to as a head-side run-out contact point 8, since it is oriented towards the head area of the tooth 4. In the exemplary embodiment, the area in between is formed by several and in particular exactly two circular arcs. These preferably have different radii R1 and R2. In addition, their circle centers M1 and M2 are also different from one another and are therefore in different positions.

The two circular arcs begin and end respectively at the inlet contact point 7 and the outlet contact point 8. Preferably, the radius R1, which begins at the foot-side inlet contact point 7, is larger than the radius R2, which ends at the head-side outlet contact point 8.

The two circular arcs have a different offset O1, O2.

The offset O1, O2 is understood here as the distance between an auxiliary line h1, which runs through the center A of the pin opening 15 near the tooth of an imaginary chain link 9 and parallel to a second auxiliary line h2. The imaginary chain link 9 lies completely in two adjacent tooth gaps 5. The second auxiliary line h2 is defined by the flank 16 of the assumed chain link 9 facing the respective tooth 4, when this lies completely and thus symmetrically in the two adjacent tooth gaps 5 (see also 2 ).

They therefore also have a different offset with respect to a respective tooth center Z (whose contour is determined by the radii). The tooth center is defined, for example, by the intersection point Z between a (radial) center axis 11 and a (circumferential) center axis 12 of a respective tooth. The choice of the offset of the two circular arcs is preferably different for different teeth. In particular, all teeth have different offsets, which are chosen in particular according to the random principle.

As an alternative to the variant shown with two circular arcs and two different radii, the surface between the inlet contact point 7 and the outlet contact point 8 is defined by a common radius and a common circular arc. The radii R1 and R2 therefore have a common circle center (centre) and are both the same size.

A chain link 9 thus first contacts the inlet contact point 7 and ends the contact at the outlet contact point 8. Within the circular arc, a side surface 10 of the chain link 9 thus comes into contact with the surface 6 in the area of the circular arc between the inlet contact point 7 and the outlet contact point 8.

The 3 to 5 then illustrate the design of different teeth 4 on a sprocket / gear 2.

In the 4 and 5 the already mentioned central axis 11 of a respective tooth 4 is shown. This typically runs in a radial or at least approximately radial direction or an axis of rotation of the gear 2 and is therefore also referred to here as the radial central axis 11.

list of reference symbols

1

chain drive

2

sprocket / gear

3

Chain

4

Tooth

5

tooth gap

6

surface of the tooth

7

entry contact point

8

run-out contact point

9

chain link

10

side surface

11

central axis (radial)

12

central axis (circumferential)

15

bolt opening

16

flank

R1, R2

radius

M1, M2

circle centers

Z

dental center

A

center bolt opening

h1

first auxiliary line

h2

second auxiliary line

O1, O2

offset

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 11 2010 000 786 B4 [0005]
• DE 603 05 682 T2 [0006]
• US 8,323,671 B2 [0007, 0010]
• US 8,435,145 B2 [0007]
• US 2018/0363753 A1 [0007, 0032]
• US 6,325,734 B1 [0007, 0026]

Claims (14)

Chain drive (1) with an irregular sprocket (2) which has teeth (4) which engage with a chain (3) in order to transmit a relative movement between them, wherein the plurality of teeth (4) is distributed over the circumference of the sprocket and there are tooth gaps between them, wherein at least one tooth (4) differs from the other teeth (4) in its outer contour and/or at least one tooth gap (5) is designed differently from the other tooth gaps (5), characterized in that a surface (6) of a tooth (4) designed for chain contact runs between an inlet contact point (7) and an outlet contact point (8) along at least one circular arc. Chain drive (1) after claim 1 , characterized in that the surface (6) is formed exclusively by one or more circular arcs. Chain drive (1) after claim 1 or 2 , characterized in that the surface runs along a common circular arc, and the inlet contact point (7) and the outlet contact point (8) lie on this common circular arc. Chain drive (1) after claim 1 or 2 , characterized in that the surface extends along several circular arcs, the number of circular arcs preferably being between 2 and 5 and in particular being 2. Chain drive (1) according to the preceding claim, characterized in that the plurality of circular arcs have different radii. Chain drive (1) according to the preceding claim, in which the radii of the circular arcs differ by at least 25% and preferably by at least 50%. Chain drive (1) according to one of the Claims 4 until 6 , in which the radius in the area of the foot-side inlet contact point (7) is larger than the radius in the area of the head-side outlet contact point (8). Chain drive (1) according to the preceding claim, characterized in that the plurality of circular arcs have different circle centers. Chain drive (1) according to one of the preceding claims, characterized in that the radius defining the circular arc shape of the at least one circular arc is greater than the tooth height. Chain drive (1) according to one of the preceding claims, characterized in that the tooth (4) is mirror-symmetrical to its central axis (11). Chain drive (1) according to one of the preceding claims, characterized in that the circular arc has a different transition radius on the outside of the region between the inlet contact point (7) and the outlet contact point (8). Chain drive (1) according to the preceding claim, characterized in that the transition radii present on both sides of the region differ from one another. Chain drive (1) according to one of the preceding claims, characterized in that the chain (3) is constructed from several links (9) which are connected to one another via pins. Chain drive (1) according to one of the preceding claims, characterized in that the link / chain link (9) is designed with a side surface (10) for contact with the tooth surface which is circular in section.

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