DE102017118317A1 - Synchron belt drive and belt pulley for synchronous belt drive - Google Patents

Abstract

Proposed are a synchronous belt drive and a non-round pulley therefor, comprising a toothed belt (7) and two or more toothed belt wheels (1, 2, 3, 4), the teeth of which mesh with the teeth of the toothed belt, wherein the toothing of at least one of Pulley wheels (4) has n tooth spaces (8) and a line of action, which is formed as a polynomial with the following properties: - The polynomial is at n nodes PNTaus n polynomials P composed, deviates from the circular shape about the rotation axis M of this pulley (4) and At the node PNTdifferential- the length L of the polynomials Pist is equal, so that for the circumference U of the polynomial pull the equation holds: U = n • L- the polynomial pull is not concave at any point, so that at each point for its curvature the relation the tooth gaps extend circumferentially substantially symmetrically to an axis of symmetry passing through the respective node PNT and its center of curvature M - the Polyno mzug is unbalanced, with this pulley at the nodes PNTWirkradien R = [PNTM], of which for some or all Rdie inequality holds: R ≠ r = U / (2 • π).

Description

The invention relates to a synchronous belt drive and in particular a timing belt drive gear of an internal combustion engine. The synchronous belt drive comprises a toothed belt and two or more toothed pulleys whose teeth mesh with the teeth of the toothed belt, the toothing of at least one of the pulleys having n tooth spaces and a line of action as a polynomial train deviating from the circular about the axis of rotation of this pulley is trained.

The invention also relates to a pulley for synchronous belt drive.

Synchronous belt drives with non-round pulleys are known in the art from numerous publications. The runout counteracts the vibration excitation, which are introduced in the case of a timing belt drive gear through the camshaft alternating torques in the synchronous drive. Relevant prior art in this regard are the EP 1 448 916 B1 and the US 2008/0085799 A1 called.

Other sources of unwanted vibration may be the excitation due to the serration-related polygon effect on the belt or the friction generated excitation in the inlet and outlet of the intermeshing teeth. This excitation is at least acoustically particularly critical if it is in the range of the resonance frequency of the synchronous drive.

The present invention has for its object to provide a synchronous belt drive of the type mentioned with an acoustically and mechanically acceptable vibration behavior.

1. 1. Der von der Kreisform um die Drehachse M dieses Riemenrads abweichende Polynomzug ist an n Knoten PNT_i aus n Polynomen P_i zusammengesetzt und an den Knoten PNT_i differenzierbar. Aus der Differenzierbarkeit des Polynomzugs an den Knoten folgt, dass die Polynome mit jeweils derselben Steigung (1. Ableitung) knickfrei an den Knoten zusammengesetzt sind.
2. 2. Die (gestreckte) Länge L der Polynome P_i ist gleich, so dass für den Umfang U des Polynomzugs die Gleichung gilt: U = n • L.
3. 3. Der Polynomzug ist an keiner Stelle konkav, so dass an jeder Stelle für dessen Krümmung die Beziehung gilt: κ ≥ 0
4. 4. Die Zahnlücken erstrecken sich umfänglich im wesentlichen symmetrisch zu einer Symmetrieachse, die durch den jeweiligen Knoten PNT_i und dessen Krümmungsmittelpunkt M_i verläuft. Unter dem Begriff „im wesentlichen symmetrisch“ ist zu verstehen, dass die Zahnlücken lediglich im Übergang zum unrunden Kopfkreis der Verzahnung nicht notwendigerweise achsensymmetrisch sind. In Verbindung mit der konstanten Länge L der Polynome P_i ergibt sich, dass auch die Zahnteilung des unrunden Riemenrads umfänglich konstant ist.
5. 5. Der Polynomzug ist unsymmetrisch, wobei das unrunde Riemenrad an den Knoten PNT_i Wirkradien R_i = [PNT_i M] hat, von denen für einige oder alle R_i die Ungleichung gilt: R_i ≠ r = U / (2 • π). In Worten ausgedrückt: der die Wirklinie bildende Polynomzug ist weder dreh- noch achsensymmetrisch, wobei die Größe der Wirkradien R_i , d.h. der effektiven Hebelarme des Zahneingriffs zwischen dem Zahnriemen und dem unrunden Riemenrad durch die Verbindungsstrecke zwischen dem jeweiligen Knoten PNT_i und der Drehachse M des Riemenrads gegeben ist und wobei die Größe von zumindest einiger der Wirkradien R_i ungleich dem Wirkradius r einer kreisrunden Wirklinie ist, die denselben Umfang wie die Wirklinie des unrunden Riemenrads hat.

The solution to this problem arises from the features of claim 1. Accordingly, the polynomial of the at least one pulley should continue to have the following properties:

1. 1. The polynomial train deviating from the circular shape around the rotation axis M of this pulley is at n nodes PNT _i composed of n polynomials P _i and at the nodes PNT _i differentiable. From the differentiability of the polynomial train at the nodes, it follows that the polynomials each have the same slope ( 1 , Derivation) kink-free at the nodes are composed.
2. 2. The (extended) length L of the polynomials P _i is the same, so that for the circumference U of the polynomial train the equation holds: U = n • L.
3. 3. The polynomial pull is not concave at any point, so that at each point for its curvature the relation holds: κ ≥ 0
4. 4. The tooth spaces extend circumferentially substantially symmetrically to an axis of symmetry through the respective node PNT _i and whose center of curvature M _i extends. The term "substantially symmetrical" means that the tooth gaps are not necessarily axisymmetric only in the transition to the non-circular head circle of the toothing. In conjunction with the constant length L of the polynomials P _{i, it} follows that the pitch of the non-circular pulley is also circumferentially constant.
5. 5. The polynomial train is unbalanced, with the non-circular pulley at the node PNT _i Impact radii R _i = [PNT _i M] has, of which for some or all R _i the inequality holds: R _i ≠ r = U / (2 • π). Expressed in words, the polynomial tract forming the line of action is neither rotational nor axisymmetric, and the size of the effective radii R _i , ie the effective lever arms of the tooth engagement between the toothed belt and the non-circular pulley through the connecting path between the respective node PNT _i and the axis of rotation M of the pulley is given and wherein the size of at least some of the effective radii R _i is not equal to the effective radius r of a circular line of action which has the same circumference as the line of action of the non-circular pulley.

The radius difference ( R _i - r) the different radii of action of r R _i can follow one another within arbitrary signs and of any size within the conditions resulting from the other properties.

The problem is also solved by a pulley with n tooth spaces and such a line of action.

Advantageous embodiments of the invention are the subject of the dependent claims. For the effective radii R _i ≠ r the equation: | R _i - r | = constant. Expressed in words: the amounts of the radii differences (R _i -r) of those effective radii R _i , which are different from the effective radius r of the circumferential, circular pulley, are identical for all these differences in radius. In this case, the radius difference (R _i -r) can follow one another with any sign in the context of the conditions of the other properties.

In the event that the number of teeth n of the non-circular pulley is straight, all radii R _i be different from r and for the radii of action R _i and R _{i + 1 of} all immediately adjacent nodes PNT _i and PNT _{i + 1,} the relationship apply: (R _i - r) / (R _{i + 1} - r) <0. In words: the radius difference (R _i - r) alternates, so that they for one of the nodes PNT _i is positive or negative and for the immediately adjacent node PNT _{i + 1} inversely negative or is positive. In this case, the radius difference (R _i -r) can follow one another within the conditions of the other properties with any size including constant size.

• 1 den Synchronriementrieb, der als Zahnriemensteuertrieb eines Verbrennungsmotors ausgebildet ist,
• 2 eine Darstellung der Wirklinie des unrunden Riemenrads gemäß 1,
• 3 eine weitere Darstellung der Wirklinie gemäß 2,
• 4 die Geometrie einer Zahnlücke des unrunden Riemenrads gemäß den vorstehenden 1 bis 3,
• 5 die Radiendifferenzen des unrunden Riemenrads gemäß den vorstehenden Figuren als Balkendiagramm,
• 6 die Radiendifferenzen des zweiten Ausführungsbeispiels eines unrunden Riemenrads als Balkendiagramm.

Further features of the invention will become apparent from the following description and from the drawings, in which an inventive synchronous belt drive with two embodiments of non-circular pulleys is shown schematically. Show it:

• 1 the synchronous belt drive, which is designed as a toothed belt control drive of an internal combustion engine,
• 2 a representation of the line of action of the non-circular pulley according to 1 .
• 3 a further representation of the line of action according to 2 .
• 4 the geometry of a tooth gap of the non-circular pulley according to the above 1 to 3 .
• 5 the radii differences of the non-circular pulley according to the preceding figures as a bar chart,
• 6 the radii differences of the second embodiment of a non-circular pulley as a bar chart.

1 shows a known timing belt timing drive of an internal combustion engine with the pulleys 1 and 2 two camshafts, the pulley 3 the crankshaft, the pulley 4 a water pump, a tensioner 5 and a pulley 6 as well as the endless toothed belt 7 which rotates in the indicated arrow direction. The pulleys 1 to 4 are all about an external toothing with the teeth of the belt 7 in synchronous engagement. The outer circumferential surfaces of the tensioning roller are looped around by the untoothed belt back and are - as usual - without teeth.

Experiments by the applicant have shown that the belt rim between the pulley 4 the water pump and the tension pulley 5 is excited to vibrate to an undesirably high degree, if it is conventionally shaped with a circular action line. As follows from the 2 to 5 explained by way of example, this vibration excitation to a considerable extent by the inventive non-circular shape of the pulley 4 be improved.

The 2 and 3 show different representations of the action line of the pulley 4 , as a non-circular polynomial around the axis of rotation M of the pulley 4 is trained. The polynomial is composed of n = 21 polynomials P _i with i = 1 to 21 at correspondingly many nodes PNT _i assembled and at the nodes PNT _i differentiable by placing two each at the node PNT _i composite endpoints of the polynomials P _{i have} the same slope. The stretched length L of all polynomials P _i is the same, so that the circumference of the polynomial pull U = n • L = 21 • L and the pitch is circumferentially constant. This can be caused by Riementrumkräfte stretching the belt 7 by mutually different tooth pitches of the toothed belt 7 on the one hand and the pulley 4 on the other hand compensate.

The polynomial is neither axis nor rotationally symmetric. Consequently, there is neither an axis separating the polynomial train into two mirror-symmetric halves, nor can the polynomial train be imaged onto itself by rotation through certain angles.

The one at the node PNT _i effective lever arm of the line of action is the effective radius R _i passing through the link between each node PNT _i and the rotation axis M, ie [ PNT _i M] is given. In the figures, only the effective radius R ₁ for the node PNT _{1 is located} .

3 shows the line of action with the associated course of the curvature κ of the polynomial train. For the curvature the relation holds at every point of the polynomial train: κ ≥ 0, which consequently and obviously is not concave anywhere. The illustrated radius of curvature 1 / κ ₁ at the node PNT ₁ illustrates that the associated center of curvature M ₁ does not necessarily coincide with the axis of rotation M.

4 shows a greatly enlarged representation of one of the tooth gaps 8th the pulley 4 , Each of the n = 21 tooth gaps 8th is substantially axisymmetric to an axis of symmetry through the respective node PNT _i and whose center of curvature M _i extends. The tooth gaps 8th are not necessarily completely axisymmetric, as compared to the polynomial action line radially smaller contact circle of the teeth slight differences in height of the tooth flanks 9 in the transition to the head circle 10 which is equidistant to the line of action. The distance of the line of action to the top circle 10 follows the amount that the timing belt has between the root circle of its teeth and the neutral bending fiber within its belt back.

In the 4 continued drawn line 11 radially outward of the line of action of the non-circular pulley 4 runs, symbolizes the line of action of a conventional circular pulley with the same circumference U = n • L = r • 2π. It becomes clear that the through the rotation axis M and the node PNT _i formed effective radius R _i of the non-round Pulley (s. 2 ) and the radius r of circumferentially equal round pulley are different in size. For some or all nodes PNT _i the inequality holds: R _i ≠ r with r = U / (2 • π).

5 shows the radii deviating from r of the round pulley R _i of the non-round pulley 4 with 21 knots PNT _i according to the 2 and 3 as a bar chart in which the radius difference (R _i -r) for each node PNT _i is applied. The diagram illustrates the random character in the sequence of radii differences (R _i - r) whose values are both in the amount of | R _i - r | and in the sign of (R _i -r) fluctuate irregularly, with all the radii of action R _i are different from r.

In an alternative embodiment, not shown, the radii differences (R _i -r) can be constant amounts | R _i - r | and only fluctuate in the sign of (R _i -r).

In 6 are the radii differences (R _i - r) of the second embodiment of an even-numbered non-circular pulley n = 22 knots PNT _i applied. All radii differences (R _i -r) are different from 0 and alternate in sign. Consequently, for immediately adjacent nodes PNT _i and PNT _{i + 1} the relation: (R _i -r) / (R _{i + 1} -r) <0.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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 assumes no liability for any errors or omissions.

Cited patent literature

• EP 1448916 B1 [0003]
• US 2008/0085799 A1 [0003]

Claims (4)

Synchronous belt drive, comprising a toothed belt (7) and two or more toothed belt wheels (1, 2, 3, 4), the toothing with the teeth of the toothed belt (7) is engaged, wherein the toothing of at least one of the belt wheels (4) n Tooth gaps (8) and has a line of action, which is formed as a polynomial with the following properties: - The polynomial is at n nodes PNT _i composed of n polynomials P _i , deviates from the circular shape about the axis of rotation M of this pulley (4) and is at the node PNT _i differentiable - the length L of the polynomials P _i is equal, so that for the circumference U of the polynomial train the equation holds: U = n • L - the polynomial is not concave at any point, so that at each point for the Curvature the relation holds: κ ≥ 0 - the tooth gaps (8) extend circumferentially substantially symmetrically to an axis of symmetry passing through the respective node PNT _i and its center of curvature M _i - the polynomial is unbalanced, where in this pulley (8) at the nodes PNT _{i has} effective radii R _i = [PNT _i M], of which for some or all R _i the inequality holds: R _i ≠ r = U / (2 • π). Synchronous belt drive to Claim 1 , characterized in that the equation applies to the effective radii R _i ≠ r: | R _i - r | = constant. Synchronous belt drive to Claim 1 or 2 , characterized in that n is straight and the effective radii are different from r, so that for the radii of action R _i and R _{i + 1 of} all immediately adjacent nodes PNT _i and PNT _{i + 1} the relation holds: (R _i - r) / (R _{i + 1} - r) <0. Geared pulley (4) with n tooth spaces (8) and a line of action according to one of the preceding claims.

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