MXPA99005807A - Random engagement roller chain sprocket with staged meshing and flank relief to provide improved noise characteristics - Google Patents

Abstract

A random engagement roller chain sprocket for use primarily in automotive engine chain drive applications which incorporates different asymmetrical tooth profiles for improved noise reduction. In particular, the sprocket includes a first plurality of sprocket teeth each having a first tooth profile including a first engaging flank, a first engaging root, and a first flat positioned between the first engaging flank and first engaging root wherein a first roller initially contacts the first flat at the onset of the first roller meshing with the sprocket. The sprocket also includes a second plurality of sprocket teeth each having a second tooth profile different from the first tooth profile and including a second engaging flank, a second engaging root, and a second flat tangent to the second engaging root remote from the second engaging flank wherein a second roller initially contacts the second flat at the onset of meshing between the second roller and the sprocket.

Description

CORONA DENTATED CHAIN OF RANDOM COUPLING ROLLER WITH GEAR BY STAGES AND COLLECTION OF FLANK TO PROVIDE IMPROVED NOISE CHARACTERISTICS DESCRIPTION OF THE INVENTION This application claims the benefit of the U.S. Provisional Patent Application Serial No. 60 / 032,379 filed December 19, 1996. The present invention relates to the automotive timing chain technique. It finds particular application together with a unidirectional roller chain toothed crown for use in automotive camshaft drive applications and will be described with particular reference thereto. However, the present invention may also find application in conjunction with other types of chain drive systems and applications where reduction of the noise levels associated with the drive of the chains is desired. Roller chain toothed crowns for use in motor shaft cam drives are typically manufactured in accordance with the ISO standard (International Organization for Standardization) 606: 1994 (E).

ISO-606 specifies the requirements for short pitch precision roller chains and associated chain wheels or sprockets.

Figure 1 illustrates a symmetrical tooth shape for a crown gear that conforms to ISO-606. The tooth space has a radius Ri of root or continuous fillet from one flank of the tooth (ie, lateral) with respect to the flank of the adjacent tooth. A chain with a connecting pitch P has rollers of diameter Di in contact with the spaces of the tooth. The ISO toothed crown also has a tail section of a length P, a root diameter D2 and a number Z of teeth. The radius Rf of the flank of the tooth, the diameter PD of the circle of the pitch, the diameter of the tip OD, the angle A of the tooth (equal to 360 ° / Z), and the angle of settlement of the roller a further define the ring gear that complies with ISO-606. The maximum and minimum roll settlement angle a is defined as: max = (140 ° -90 °) / Z and arain = (120 ° -90 °) / Z With reference to Figure 2, a drive system 10 Roller chain that complies with ISO-606 by way of example rotates in an equal clockwise direction as shown by arrow 11. Chain drive system 10 includes drive gear 12, a drive gear ring 14 and a roller chain 16 having a number of rollers 18. The gear wheels 12, 14, and the chain 16 each generally comply with the ISO-606 standard.

The roller chain 16 engages and wraps around the ring gears 12 and 14 and has two intervals extending between the ring gears, the loose section 20 and the tensioned section 22. The roller chain 16 is under tension with the coil 16. or it is shown by arrows 24. The tensioned section 22 can be guided from the gear ring 14 driven to the drive gear 12 with a chain guide 26. A first roller 28 is shown at the start of the engagement in a position that marks the twelve clock hours in the drive gear 12. A second roller 30 is adjacent to the first roller 28 and is located near the roller to engage with the drive gear 12. Chain transmission systems have various components that produce undesirable noise. A major source of roller chain noise is the sound generated as the roller leaves the space and collides with the ring gear during gearing. The noise of the resulting impact is repeated with a frequency generally equal to that of the frequency of the gearing of the chain with the ring gear. The intensity of the impact noise is a function of the impact energy (EA) that must be absorbed during the gearing process. The energy of the absorbed impact is related to the speed of the motor, the mass of the chain, and the speed of impact between the chain and the ring gear at the start of the gearing. The impact speed is affected by the geometry of the chain-toothed crown coupling, of which a pressure angle Y of the flank engaged (Figure 3) is a factor, where: EA = -20 £ 00-. vA2 * • ? = - 180-A-c- and EA = Impact Energy [N.m] VA = Vel. impact of the roller Y = Coupling flank pressure angle n = Motor speed w = Chain mass [Kg / m] Z = Number of teeth of the ring gear A = Angle of the tooth a = Angle of settling roll P = chain spacing (chordal spacing) The impact energy equation (EA) assumes that the chain transmission kinematics will generally conform to an almost static analytical model and that it will occur by transmission contact of the chain. Toothed roller-crown at a tangent point TP (Figure 3) of the radii of the root and the flank as the ring gear picks up a roller from the interval. As shown in Figure 3, at an angle? pressure is defined as the angle between a line A extending from the center of the normal coupling roll 30 with respect to and through the tangent point TP of the radius Rf of the coupling flank to the radius Ri, of the root, and a line B which connects the centers of an imaginary roller completely seated on the diameter PD of theoretical spacing and the coupling roller 30 when it is fully seated on the diameter PD of theoretical spacing. The angles of settlement of the roller and the angles? of pressure listed in Figure 27 are calculated from the previously defined equations. It will be appreciated that? it is minimal when a is maximum. The gear ring of 12 of 18 teeth that complies with ISO-606 as an example of Figure 3, an angle? of pressure in the range of 12.5 ° to 22.5 ° as shown in Figure 27. Figure 3 also shows the coupling path (rollers in dotted lines) and the contact position of the gearing of the roller 30 (solid lines) to measure that the drive gearwheel 12 rotates in the direction of the arrow 11. Figure 3 illustrates the theoretical case with the chain roller 28 seated on the root diameter D2 of a crown gear of maximum material with both the spacing of the chain as the chordal spacing of the ring gear equal to the theoretical P spacing. For this theoretical case, the noise that occurs at the beginning of the roller coupling has a radial component FIr as a result of the roller 30 striking the root surface Ri and a tangential component FIt generated as the same roller 30 strikes the flank of the coupling tooth at the TP point as the roller moves towards the drive contact. It is believed that the radial impact occurs first, afterwards achieving the tangential impact almost simultaneously. The impact velocity of the roller VA is shown to act through, and is substantially normal with respect to, the tangent TP point of the coupling flank with the roller 30 in drive contact at the point TP. The impact energy equation (EA) counts only for one impact of the tangential roller during gearing. The coupling of the real roller, which is added has a tangential and radial impact (which occurs in any order), therefore it would seem to be variable with respect to the equation of the impact energy (EA). The application of this almost static model, which is used in a beneficial way as a directional tool, allows an analysis of those characteristics that can be modified to reduce the impact energy that must be absorbed during the tangential toothed roller-crown collision at the beginning of the geared. The radial impact during gearing, and its effect on fluid levels, can be evaluated separately from the impact energy (EA) equation. Under the actual conditions as a result of the characteristic dimensional tolerances, there will be a mismatch of spacing between the chain and the ring gear, with an increased mismatch as the components wear out with use. This mismatched coincidence of spacing serves to move the impact point of the geared, occurring even the radial shock on the root surface Rl f but not necessarily on D2. The tangential shock will usually be close to the TP point, but this contact can be made well above the coupling side of the radius of root R2 or even radially outward from the point TP on the radius of the coupling flank Rf as a function of the mismatch of the spacing of the actual serrated crown-chain. By reducing the angle? The pressure of the coupling flank reduces the meshing noise levels associated with roller chain drives, as predicted by the impact energy equation (EA) discussed above. Is it feasible, but not recommended, to reduce the angle? of pressure while maintaining a symmetrical profile of the tooth, which can be achieved by simply increasing the roll settling angle, effectively decreasing the pressure angle for both flanks. This profile as described requires that a worn chain, as the roller travels around a ring gear shell (discussed below), interferes with a steeper inclination and that the rollers necessarily ride well above the flank of the coast before leaving the turn. Another source of chain drive noise is the broadband mechanical noise generated in part by the torsional vibrations of the shaft and the slight dimensional inaccuracies between the chains and the ring gears. Also contributing to a greater degree of broadband mechanical noise level is the vibratory or intermittent contact that occurs between a worn roller chain and the ring gear as the rollers travel around the return of the ring gear. In particular, the normal wear of the chain drive system comprises wear of the tooth face of the ring gear and wear of the chain. Chain wear is caused by wear of the bearing at the chain joints and can be characterized as elongation of the spacing. It is believed that a worn chain that engages a toothed crown that conforms to the ISO standard will have only one roller in drive contact and will be loaded in a maximum load condition. Referring again to Figure 2, the actuation contact at the maximum load occurs as a roller enters a turn 32 of the drive gear in the coupling. - The coupling roller 28 is shown in contact by drive and charged to a maximum load condition. The load on the roller 28 is mainly the gearing impact load and the tension load of the chain. The following several rollers in turn 32 after roller 28 share the tension load of the chain, but at a progressively decreasing range. The loading of the roller 28 (and to a lesser degree for the various subsequent rollers in the turn) serves to keep the roller in solid or hard contact with the root surface 34 of the ring gear. A roller 36 is the last roller in the turn 32 of the drive gear before entering the loose section 20. The roller 36 is also in hard contact with the drive gear 12, but at some point above (for example radially outward) on the surface 34 of the root. With the exception of the rollers 28 and 36, and several rollers forward of the roller 28 that share the stress load of the chain, the rest of the rollers in the turn 32 of the drive gear ring are not in hard contact with the roller. the root surface 34 of the ring gear, and therefore are free to vibrate against the root surfaces of the ring gear as they travel around the loop, thereby contributing to the generation of unwanted broadband mechanical noise . A roller 38 is the last roller in a turn 40 of the drive gear 14 before entering the stretch 22 taut. The roller 38 is in drive contact with the ring gear 14. As with the roller 36 in the turn 32 of the drive gear, a roller 42 in the turn 40 of the ring gear is in hard contact with a radius of the root 44 of the drive gearwheel 14, generally not in the diameter of the root. It is known that providing a space in the spacing line (PLC) between the teeth of the ring gear promotes hard contact between the chain rollers and the ring gear in the turn of the ring gear as the chain wears . The amount of space in the spacing line added to the tooth space defines a length of a short arc that is centered in the tooth space and forms a segment of the root diameter D2. The radius Rx of the root fillet is tangent to the radius Rf of the skinny and the segment of the arc of the root diameter. The profile of the tooth is still symmetrical, however Rj. it is no longer a continuous fillet radius from a flank radius to the radius of the adjacent flank. This has the effect of reducing the broadband mechanical radio component of a chain transmission system. However, the addition of space in the line of spacing between the teeth of the ring gear does not reduce the noise of the drive of the chain caused by the impact of the toothed roller-crown on impact. The situation of the rope, or the rise and fall of the rope, is another important factor that affects the smoothness of the operation and the noise levels of a chain drive, particularly at high speeds. The action of the rope occurs as the chain enters the ring gear from the free interval during gearing and can cause a movement of the free chain in a direction perpendicular to the chain travel, but in the same plane as the chain. chain and toothed crowns. This movement of the chain resulting from the action of the rope will contribute a component of the objectionable noise level to the noise levels of the gearing, so it is beneficial to reduce the action of the rope inherent in a roller chain drive. Figures 4a and 4b illustrate the action of the rope for a 'crown gear that complies with the ISO-606 standard of 18 teeth, which has a rope spacing of 9,525 mm. The elevation of the rope 45 can be defined conventionally as the displacement of the center line of the chain as the ring gear rotates through an angle A / 2, where: Rope lift = rp-rc = rp [1-cos (180 ° / Z] where rc is the degree of the string, or the distance from the center of the ring gear to a spacing string of length P; rP is the theoretical theoretical spacing radius; and Z is the number of teeth of the ring gear. It is known that a short spacing crown provides reduced rope action as compared to a larger spacing chain having a similar spacing radius. Figures 4a and 4b show only the drive gear and assume a driven gear (not shown) that also has 18 teeth and is in phase with the drive gear shown. In other words, at T = 0 (Figure 4a), both toothed crowns will have a center of the tooth in the position marked twelve o'clock. Accordingly, this chain drive arrangement under quasi-static conditions will have an upper or taut section that will move up and down in a uniform manner at a distance equal to that of the rope lift. At T = 0, a roller 46 is at the start of the gearing, with a spacing of the rope P horizontal and in line with the stretched section. At T = 0 + (A / 2), (Figure 4b), the roller 46 has moved to the position that marks the 12 o'clock clock. For many chain drives, the driven gears and the drive will be different sizes and will not necessarily be in phase. The chain guide 26 (Figure 2) has the primary purpose of controlling the vibration of the chain section in the free interval. The geometry of the chain guide interface also defines the length of the free interval chain on which the fall and the elevation of the rope are allowed to articulate. Figure 5 is a large view of Figure 2 showing the first roller 28 at the start of the coupling and the second roller 30 as the next roller that is about to engage with the sprocket 12. In this example, the guide 26 The chain controls and guides the coupling position of the stretched section 22 except for 5 unsupported spacings or "free" joints extending between the chain guide 26 and the coupling roller 28. This length of unsupported joining spaces for the coupling position of the stretched section 22 in this example is horizontal when the roller 28 is in the position that marks the 12 o'clock clock. With references to Figures 6 and 7, the drive gear 12 is rotated clockwise to advance the roller 28 to a new angular position (A / 2) + ?, where? it is the angle of added rotation as determined by an almost static coupling geometry with the roller 28 which is fully seated and the roller 30 is at the moment of engagement of the gear. As shown in Figure 6, the roller 28 is considered to be seated and in hard contact with the root surface at D2 at the start of the engagement of the roller 30, and a straight line is assumed for the chain interval from the roller 28 to a chain pin center 48, around which the unsupported or "free" range is considered to rotate from the pin 48 to the coupling roller 30. As a result of the action of the rope, the free coupling interval is no longer horizontal to satisfy the coupling geometry of the roller. This is in contrast to the drive of the chain as described in Figure 4a in which the action of the rope causes the taut section to move uniformly, but in a horizontal path, due to the drive and the driven toothed rings. that have the same number of teeth and the teeth of the ring gear are in phase. It will be appreciated that assuming a straight line is only valid 'in an almost static model. The amount of movement or deviation from the straight line assumed will be a function of the dynamics of the drive, the devices and drive chain control and the geometry of the ring gear. The location and interface contour of the chain of the chain guide 26 will determine the number of free interval spaces around which the articulation will take place as a result of the raising and falling of the cord during the roller engaging process. As best seen in Figure 7, assuming that the rollers 28 and 30 are in hard contact with the root surfaces of the ring gear at D2, the rope lift is the perpendicular displacement of the roller center 30 (located on the space diameter PD) from the trajectory of the stretched section 22 as it moves from its initial engaged position shown to the position currently occupied by the roller 28. Consequently, it is desirable to develop a novel and improved roller chain transmission system that meets the needs before and overcome the above disadvantages as well as others while providing better and more advantageous results.

BRIEF DESCRIPTION OF THE INVENTION In accordance with one aspect of the present invention, a ring gear is described. The ring gear includes a first plurality of teeth of the ring gear each having a first tooth profile including a first coupling flank, a first coupling root and a first plane placed between the first coupling flank and the first root of coupling, a first roller that makes contact initially with the first plane at the start of the engagement of the first roller with the ring gear. The ring gear further includes a second plurality of teeth of the ring gear each having a second profile of the tooth different from the first profile of the tooth and including a second coupling flank, a second coupling root and a second tangent plane with respect to the second coupling root distant from the second coupling flank, a second roller that initially makes contact with the second plane at the start of the engagement between the second roller and the ring gear. In accordance with another aspect of the present invention, a ring gear is described. The ring gear includes a first plurality of toothed ring teeth each having a first asymmetric tooth profile which is constructed to provide a tangential contact with a first roller at the beginning of the engagement of the first roller with the ring gear, and a second plurality of teeth of the toothed crown each having a second asymmetric tooth profile which is constructed to provide radial contact with a second roller at the start of engagement of the second roller with the ring gear. According to a further aspect of the present invention, a unidirectional roller chain transmission system is disclosed. The unidirectional roller chain drive system includes a first ring gear, a second ring gear and a roller chain having rollers in mating engagement with the first and second ring gear. At least one of the first and second toothed ring includes a first plurality of toothed ring teeth each having a first tooth profile including a first coupling flank, a first coupling root and a first plane placed between the first coupling flank and first coupling root, wherein the first roller initially makes contact with the first plane at the start of engagement of the first roller with the ring gear. At least one of the first and second ring gear also includes a second plurality of teeth of the ring gear each having a second tooth profile different from the first tooth profile and including a second coupling flank, a second root of coupling and a second tangent plane with respect to the second coupling root far from the second coupling flank, a second roller that initially makes contact with the second plane at the start of the engagement between the second roller and the ring gear. According to yet another aspect of the present invention, a method for modifying a gearing impact frequency of the gearing of the roller chain with a ring gear is described. The method includes (a) rotating the ring gear to cause the first roll of the roller chain to make tangential contact with a coupling flank of a tooth of a first ring gear at the start of engagement of the first roller with the tooth of the ring gear. first toothed ring, and (b) rotating the ring gear to make a second roller of the roller chain make radial contact with a root surface of a tooth of a second ring gear at the start of engagement of the second roller with the tooth of the second gear ring. An advantage of the present invention is the provision of a roller chain toothed crown that incorporates a flank plane on a mating tooth surface that facilitates alternating the mating contact from a first tooth profile to a second tooth profile .

Another advantage of the present invention is the provision of a roller chain toothed crown that incorporates a flank plane on a coupling tooth surface that effects a delay between an initial contact of the roller with the tooth profile of the first ring gear and an initial contact of the roller to the tooth profile of the second ring gear. Another advantage of the present invention is the provision of a roller chain toothed crown incorporating a flank plane on a mating tooth surface of a first tooth profile which facilitates phasing a frequency of initial roll-to-flank contacts. coupling of the first tooth profile with respect to the initial roller contacts to coupling flanks of a second tooth profile to alter the rhythm of the initial roller contacts to the first coupling flank and of the roller to the second coupling flank. Another advantage of the present invention is the provision of a roller chain toothed crown incorporating a non-coincidence of added spacing between the ring gear and the roller chain to facilitate a roller-to-ring impact "stepwise". Still another advantage of the present invention is the provision of a roller chain toothed crown incorporating a root surface inclined on a coupling flank, a sidewall, or both a coupling flank and a sidewall to provide spacing of tooth space. Still another advantage of the present invention is the provision of a roller chain toothed crown that minimizes the impact noise generated by the impact of the toothed roller-wheel during engagement. A further advantage of the present invention is the provision of a roller chain toothed crown that minimizes the broadband mechanical noise generated by the discharged rollers in one turn of the ring gear. Still another advantage of the present invention is the provision of a roller chain toothed crown that provides a "stepwise" roller impact where a tangential impact occurs first by a radial impact to the complete gear. Another additional advantage of the present invention is the provision of a roller chain toothed crown that extends the roller coupling for a significant time interval to provide a more gradual load transfer, thereby reducing the impact of the toothed roller-ring and the inherent noise generated by it.

Yet another advantage of the present invention is the provision of a roller chain toothed crown having two sets of teeth of the ring gear that incorporate different tooth profiles that cooperate to reduce the noise levels of the chain drive system below. of a level of noise that any tooth profile used alone would produce. Other advantages of the present invention will be apparent to those skilled in the art upon reading and understanding the following detailed description of the preferred embodiments. BRIEF DESCRIPTION OF THE DRAWINGS The invention may take the form of various component and component arrangements, and be in various stages and stages arrangements. The drawings are for illustrative purposes only of a preferred embodiment and are not considered to be limiting of the invention. Figure 1 illustrates a symmetric tooth shape for a roller chain toothed crown that conforms to ISO-606; Figure 2 is an exemplary roller chain transmission system having a driving toothed crown that conforms to ISO-606, the driven gear and the roller chain; Figure 3 shows a coupling trajectory (with dotted lines) and a roller (with solid lines) in a drive position as an ISO-606 compliance with a drive toothing that rotates clockwise; Figure 4a shows a roller at the start of the engagement with a toothed crown of 18 teeth as an example; Figure 4b shows the driving toothed crown of Figure 4a rotated clockwise until the roller is in a position that marks the 12 o'clock clock; Figure 5 is an enlarged view of the drive gear of Figure 2 with a roller completely seated in a tooth space and a second roller about to engage with the drive gear. Figure 6 shows the driving gear of Figure 5 rotated in an equal clockwise direction until the second roller initially contacts the driving gear. Figure 7 is an enlarged view of Figure 6 showing that the second roller initially contacts a root surface (i.e. radial impact) of the driving gear, under theoretical conditions; Figure 8 illustrates a roller chain transmission system having a roller chain drive gear ring and a drive gear ring incorporating the aspects of the present invention therein; Figure 9 illustrates the roller chain drive gear of Figure 8 with an asymmetric tooth space shape according to one embodiment of the present invention; Figure 10 is an enlarged view of the shape of the asymmetric tooth space of Figure 9 showing a roller in two points contact with the ring gear; Figure 11 shows a coupling path (with dotted lines) at the time of complete meshing (solid lines) of a roller as the driving toothed crown of Figure 8 rotates in a clockwise direction; Figure 12 is an enlarged view of the driving gear of Figure 8 with a first roller fully seated in a tooth space and a second roller as the next roller to be picked up from a taut section of the roller chain; Figure 13 shows the drive gear of Figure 12 rotated in the clockwise direction until the second roller initially contacts the drive gear; Figure 14 is an enlarged view of Figure 13 showing the first roller in contact with two points and the second roller in initial tangential contact with the drive toothed crown; Figure 14a illustrates the progression of the first and second rollers as the driving toothed crown of Figure 14 rotates in the clockwise direction; Figure 14b is an enlarged view of the driving gear of Figure 14 rotated clockwise to advance the second roller at the time of full gearing in a position that marks 12 o'clock; Figure 15 illustrates a roller chain drive gear with an asymmetric tooth space shape according to another embodiment of the present invention; Figure 16 is an enlarged partial view of Figure 8 showing the progression of contact as the rollers travel around the turn of the drive gear; Figure 17 is an enlarged view of a roller exiting a turn of the ring gear of the ring gear of Figure 16; Figure 18 illustrates a roller chain toothed crown with an asymmetric tooth space shape according to another embodiment of the present invention; Figure 19 illustrates a roller chain toothed crown with an asymmetric tooth space shape according to a further embodiment of the present invention; Figure 20 is a side view of an exemplary random coupling roller chain toothed crown embodying aspects of the present invention; Figure 21 is an enlarged view of the ring gear of Figure 2 showing an asymmetric tooth space shape incorporating the coupling flank recess and space separation of the tooth according to the present invention; Figure 21a is an enlarged view of the ring gear of Figure 21 showing an inclined root surface thereof providing the recess of the flank and space separation of the tooth; Figure 22 is another embodiment of the inclined root surface of the Figure. 21a that only provides the recess of the flank; Figure 23 illustrates the asymmetric tooth space shape of Figure 9 overloaded with the shape of the asymmetric tooth space of Figure 21; Figure 24 illustrates the progression of engagement of a first roll and the engagement of a second adjacent roll with the ring gear of Figure 20 as it is rotated in a clockwise direction; Figure 25 illustrates the gear of the Figure with a first roller in contact with two points, a second roller in initial tangential contact and a third roller about to engage with the drive gear; Figure 26 illustrates the ring gear of Figure 25 rotated clockwise until the initial engagement of the third roller on a root surface of the ring gear; Figure 27 is a table that lists the angles of the roller set and the angles? pressure for a number of different ring gear sizes that comply with ISO-606; and Figure 28 is a table listing the maximum Beta (ß) angles and the corresponding pressure angles (?) for three different asymmetric tooth space profiles (1-3) of varying sizes of the ring gear. Referring now to Figure 8, a roller chain drive system 110 includes a drive gear 112 and a drive gear 114 that incorporate the features of the present invention. The roller chain drive system 110 further includes a roller chain 116 having a number of roller 118 that engage and turn around the ring gears 112 and 114. The roller chain rotates in a direction equal to clockwise as shown by arrow 11. Chain 116 of the roller has 2 separations that extend between the ring gears, section 120 loose and section 122 stretched. The chain 116 of the roller is under tension as shown by the arrows 124. A central portion of the tensioned section 122 can be guided from the driven ring gear 114 to the drive ring 112 with a chain guide 126. A first roller 128 is shown fully seated in a position indicating the 12 o'clock clock on the drive gear 112. A second roller 130 is adjacent to the first roller 128 and is about to engage with the drive gear 112.

To facilitate a description of the present invention with respect to the asymmetric tooth profiles, reference will be made only to the drive gear 112. However, with asymmetric tooth profiles of the present invention they can also be applied to the driven ring gear 114, as well as other types of gear wheels such as idler gearwheels and gearwheels associated with counter rotating balancing arrows. With reference to Figures 9 and 10 the ring gear 112 includes a first tooth 132 having a coupling flank 134 and a second tooth 136 having a coast flank 138 or decoupling. The coupling flank 134 and the coast flank 138 cooperate to define a tooth space 140 received by the coupling roller 128 (shown with dotted lines). The coupling roller 128 has a diameter Di of the roller and is shown fully seated in contact with two points within the tooth space 140 as described below. In a very particular way, the coupling roller 128, when it is completely seated in the tooth space, makes contact with two lines B and C extending axially to each surface or tooth face of the ring gear (i.e. orthogonal direction with respect to the plane of the drawings). However, to facilitate a description thereof, the lines A, B and C are subsequently shown and are referred to as contact points within the tooth space. The coupling flank 134 has a radius Rf that is tangent to a radially extreme end of the flank plane 144. The radius Rf of the symmetrical coupling skinny is smaller than the radius Rfiso specified by the ISO-606 standard. However, the magnitude of the radius Rf of the asymmetric coupling flank must be as large as possible as long as it satisfies the engagement of the roller (coupling) and the decoupling geometry. The location of plane 144 of the flank is defined by an angle β, the plane orientation being normal or perpendicular to a line passing through point B and the center of roll 128 when the roller makes contact with the ring gear at the points B and C. The length of the flank plane, which extends radially outwardly from point B, affects a delay between an initial tangential impact between the ring gear 112 and the roller 128 at a first contact point A along the plane 144 of the flank, and a subsequent radial impact at point C. It is believed that the roller remains in contact with the flank plane from its initial tangential contact at point A until the roller moves to full engagement to a position of contact in two points at points B and C. The angle? of pressure, the amount of mismatch of the spacing between the chain and the ring gear, and the length of the flank plane can be varied to achieve a desired initial roll contact point A at the start of meshing of the ring gear-roller. It will be appreciated that flank contact (tangential) always occurs first, with radial contact occurring afterwards always at point C despite the length of the spreading of the chain. In contrast, with known tooth shapes (for example), those asymmetrical and complying with the standard (ISO-606), which incorporate the contact at an individual point (for example individual line contact), a roller coupling must move to a driving position after making radial contact. The angles ? of pressure assume therefore that the coupling roller will make contact at the tangent point of the radius flank diagonal radius of root. Therefore, the engagement position of the gearing of the individual tooth / dot tooth shapes is "sensitive" to the spacing to determine when the radial impact as well as the tangential impact will occur. The angle ß of settlement of the roll of the flank of coupling (Figure 9) and the angle ß of settlement of the roll of the flank from that coupling replace the angle ß 'of settlement of the roller that complies with ISO-606 (the ISO profile shown with dotted lines). The pressure angle a is a function of the settlement angle Y of the coupling flank roller ß. That is to say, as ß increases, Y decreases. A minimum asymmetric pressure angle can be determined from the following equation where: I min = JJmax - .0-max 1 4 + l iso rain) Therefore, an asymmetric pressure angle Ymin = 0 when ßmax = (ama ? / 2 + Yiso ram) as illustrated in Figure 28. Figure 28 lists the maximum Beta (ß) angles and corresponding pressure angles Y for various ring sizes of three different asymmetric tooth tooth profiles (1-3). It will be appreciated that reducing the coupling flank pressure angle Y reduces the FIA component (Figure 14) of the tangential impact force and therefore the contribution of the tangential impact noise to the overall noise level at the start of the coupling. . That is, the impact force F? A is a function of the impact velocity which in turn is related to the pressure angle Y. As the pressure angle Y is reduced, it provides a corresponding reduction in the speed of impact between the chain and the ring gear at the start of the gearing. Likewise, a minimum pressure angle Y facilitates a greater separation or distance between the tangential contact points A and B to further increase or increase the "graduation" of the coupling. In the preferred embodiment, the pressure angle Y of the coupling flank is in the range of about -2.0 ° to about + 5 ° to optimize the stepwise impact between the roller and the ring gear. In the embodiment described, the roll settlement angle ß is greater than ISO amax / 2 in a maximum material condition and ß can be adjusted until a desired coupling flange pressure Y is achieved. For example, the settlement angle ß of the roller of Figure 9 provides a pressure angle Y that is less than zero, or a negative value. The negative pressure angle Y is best seen in Figure 11, in contrast, the profile of the tooth that complies with ISO-606 of Figure 3 with a positive pressure angle Y. It is believed that a small negative pressure angle for the theoretical chain / crown gear interface beneficially provides a pressure angle Y closer to zero (0) for a "nominal" system or for a system with wear. However, the settlement angle ß of the coupling flank roller can be set beneficially so as to provide any coupling flank pressure angle Y having a value less than the minimum pressure angle and ISO-606.

Referring again to Figures 9 and 10, a first radius Ri is tangent to a radially inner end of the plane 144 of the flank, and tangent to a radially outer end of an inclined root surface 146. As best seen in Figure 10, a radius Ri - of - root maximum must be equal to, or less than, a radius 0.5D? of the minimum roll to facilitate full coupling of the two-point / in-line contact at points B and C. Accordingly, this will define a small space between Ri and coupling flank 134 and roller 128 at the two-point coupling / line. The plane 144 of the flank and the inclined root surface 146 necessarily extend within the points B and C respectively to facilitate the contact of two points / line of the roller in the coupling as well as the space Ri required for the roller 128. One second radius Ri 'is tangent to a radially internal end of the inclined root surface 146 on line 150. The coast edge has a radius of Rf' with its arc center defined by the lateral roller settlement angle ß 'of decoupling. The radius Rf 'can have a value on the scale of ISO-606. The inclined root surface 146 is a flat surface having a finite length defining a tooth spacing (TSC). The spacing of the tooth space compensates for the lengthening of the chain spacing or chain wear by accommodating a specific degree of elongation? P of the chain spacing. In other words, the spacing of the tooth space TSC allows the rollers of a worn chain to keep in contact with the inclined root surface of the teeth of the ring gear. Likewise, the surface 146 of the inclined root facilitates the reduction of the radial reaction force thereby reducing the noise contribution of the radial impact of the roller to the overall noise level. The inclined root surface 146 can be inclined at any angle f necessary to satisfy a specific transmission geometry and the elongation of the chain spacing. As shown in Figure 9, the angle f of the inclined root surface is measured from a line 152 passing through the center of the roller 128 at the center of the ring gear to a second line 154 - which also passes through from the center of roll 128 and point C. Sloped root surface 146 is normal with respect to line 154, and the inclined root surface extends radially inwardly to line 150 where it is tangent to Ri '. In the embodiment described, the angle f of the inclined root surface is preferably in the range of about 20 ° to about 35 °. Figure 12 is an enlarged view of Figure 8 showing the first roll 128 in full engagement in contact with two points / line through the thickness or width of the tooth profile of the ring gear, and the second roll 130 as the following roller about to engage with the ring gear 112. As with the drive system 10 which complies with ISO-606, the chain guide 126 controls and guides a central portion of the tensioned section 122 except five joint spacings unsupported extending between the chain guide 126 and the coupling roller 128 (and except unsupported joint spacings extending between the driven gear and the chain guide). The stretched section 122 is horizontal when the roller 128 is in the position indicating 12 o'clock. Figure 13 shows the drive gear 112 rotated in a direction (A / 2) +,, clockwise, as determined by the moment of engagement of the ring gear by roller 130. The line Straight is assumed for the chain interval from the roller 128 to a chain pin center 156, around which the unsupported interval from the center 156 of the pin to the coupling roller 130 is considered to rotate. It will be appreciated that the assumption of the straight line is only valid in an almost static model. The amount of movement (or deviation from the assumed straight line) mentioned above will be a function of the dynamics of the drive as well as the geometry of the ring gear and drive. The contact of the ring gear at the beginning of the engagement for the roller 130, occurs earlier than for the ISO-606 counterpart, thereby reducing the amount of rope lift and, equally importantly, allowing beneficially to occur the initial contact at a desired pressure angle Y on the coupling flank at the point A. Likewise, the contact of the radial crown for the roller 130, with its contribution to the overall noise level, does not occur until the rotation of the ring gear places the roller 130 in "the position indicating the 12 hours This is referred to as a stepped coupling, Figure 14, which is an enlarged view of the Figure 130, shows more clearly the beginning of the gearing for the roller 130 just before the start of the gearing, it is assumed that the roller 128 carries all the load Fr¿ + F0, of the stretched section, whose load is shown as arrows of vector of force. Actually, the arrows represent reaction forces with respect to the strength of the chain of the stretched section. At the time of engagement for the roller 130, a tangential impact occurs as shown by the vector F:? impact force. The tangential impact is not equal to the load of the chain of the stretch tense; in particular, the impact load or the impact force is related to the VA impact velocity. It is known that impact occurs during a collision within two bodies, which results in relatively large forces over a comparatively short time interval. A radial impact force vector Fi is shown only as an outline in which the radial impact does not occur until the ring gear has rotated sufficiently to place the roller 130 in a position indicating 12 o'clock. Figure 14a shows the same positions (with solid lines) for rollers 128 and 130 as shown in Figure 14, but also shows the positions of the roller (with dotted lines) with respect to the profile of the ring gear once the roll 130 reaches its gearing in two points / line in the position that indicates 12 o'clock. As a result of the mismatch of the spacing between the chain and the ring gear, the roller 128 must move to a new position. In particular, as the roller 130 moves from the initial contact to full engagement, the roller 128 advances forward in its tooth space. The small separations in the links of the chain, however, reduce the amount of forward progression required for the roller 128. Also occurs at the start of the gearing, the start of load transfer of the tensioned section from the roller 128 to the roller 130. The asymmetric profile comes the "stepwise" gearing described above. In particular, with reference again to Figure 14, tangential contact occurs at point A at the start of the gearing, with its force FJA. of related impact. It is believed that the roller 130 is kept in contact with the coupling flank 134, as the rotation of the toothed chain moves the roller, it has fully engaged with its resultant radial contact at point C. The radial impact force FIC (vector strength shown as a sketch) does not occur until the ring gear has rotated sufficiently to place the roller 130 in radial contact at point C. FIG. 14b is an enlarged view of FIG. 14, except that the ring gear 112 has rotated to advance the roller 130 at the moment of complete engagement in the position indicating the 12 o'clock clock. At this moment of complete gearing, the radial impact force Fc occurs and the load transfer of the stretch is considered complete. At the moment of radial collision of roll 130 at point C, with its resultant radial impact force FLC, the tangential impact force of FIA has already occurred and is no longer a factor. The delay (coupling "quotation marks per stage") between tangential and radial toothed roller-crown collisions effectively diffuses the impact energy that must be absorbed during the gearing process over a longer time interval, thereby reducing its contribution at the level of the noise generated at the frequency of the gearing. In addition, it is believed that the profile of the tooth of the asymmetric toothed crown of the present, beneficially allows load transfer of the more gradual stretch from a roller 128 fully engaged to a gearing roller 130 as the gearing roller 130 it moves from its initial gearing at Point A to its full gearing position at two points. With reference again to Figure 14, the rise (and fall) of the rope with the asymmetric profile of the present is the perpendicular displacement of the center of the roll 130 from the path of the tensioned section 122 that moves from its initial engagement contact point A to the engagement position which currently occupies the roller 128. It is believed that the roller 130 will remain in contact with the coupling flank 134 as the roller moves from the initial tangential contact to the complete engagement, and consequently, the rope lift is reduced to as the distance between points A and B increases. As shown in Figure 14, the spacing Pc is beneficially greater than the spacing Ps of the ring gear 112.

Referring now to Figure 15, the length of the inclined root surface 146 (Figure 10) can be reduced to (0), thereby eliminating the inclined root surface 146 and allowing the root radius R_- to be tangent to the root surface and roller 128 at point C. That is, R-. 'is tangent to a short plane at point C, and the plane is tangent to RL. If the inclined root surface 146 is removed, the pressure angle Y of the coupling flank will generally be on the scale from some positive value to zero, however, usually not less than zero. The reason is that a negative angle Y requires a reduction in the spacing of the rope so that the roller can exit the return 60 of the ring gear (Figure 16) without interfering with Rr. Figure 16 shows the contact of the roller to the profile of the ring gear 112 for all the rollers on the turn 60. The roller 128 is in full gearing at two points, as shown on line 160 it shows the contact point for each of the roller, as well as the contact progression as the rollers travel around the turn. The mismatch of the inherent spacing between the ring gear and the roller chain causes the rollers to climb the sidewall of the coast as they move around the ring gear. With the sum of the reduction of the appreciable rope spacing, the degree to which the rollers rise along the lateral sidewall of the coast increases. It is important to note that reducing the spacing of the rope is required when the pressure angle Y has a negative value. Otherwise, as shown in Figures 16 and 17, the rollers 136 would interfere with the coupling flank (with a toothed crown of maximum material and a theoretical (smallest) spacing chain) as it leaves the turn. 60 back to the interval. That is, the reduction of the spacing of the rope allows the roll 136 to come out of the turn 60 with a spacing 163 for the coupling flank. Likewise, the spacing of the reduced rope helps the gearing of stages as mentioned previously. Figure 17, which shows the progression of the roller contact on turn 60, also serves to show why the shallow angle ß and the space separation of the tooth TSC helps to maintain the contact of the "hard" toothed roller-crown for the teeth. rollers in the turn. In addition, the roller seating angle ß 'of the coupling flank (Figure 9) can be adjusted to have a maximum value equal to a min / 2 or even less. This angle ß 'of settling of the reduced roller promotes a faster separation when the roller leaves the ring gear and enters the interval. This reduced angle ß 'also allows the roller in a worn chain to ride on the surface of the sidewall at a less severe angle as the roller moves around the ring gear in the turn. Consequently, the reduction of rope spacing, if used in this mode, should make a small value. It is contemplated that the characteristics of the symmetric tooth profile described above may be altered without substantially deviating from the kinematics of the chain gearing and the ring gear that produces the noise reduction advantages of the present invention. For example, the profile of the asymmetric coupling flank could be approximately in a wraparound shape, and the uncoupled asymmetric flank profile could be of a different unwinding shape. Slight changes can be made to the asymmetric profiles of the tooth for reasons of manufacturing and / or quality control, or simply to improve the sizing of the part. These changes are within the scope of the invention as described herein. In a further embodiment, the inclined root surface 126 of the coupling flank (Fig. 9) can be replaced with an inclined root surface 164 of the coast flank as shown in Figure 18. The inclined root surface 164 of the flank of Costa provides tooth space spacing (TSC) in the same manner as described in the previous one with respect to the inclined root surface 146. further, the inclined root surface 164 of the coupling plant, beneficially moves the roller to a preferred radially outward position as the chain wears. Alternatively, the flank inclined root surface 164 may be included with the coupling flank surface 146 as shown in Figure 19. The flank flank coupling and inclined flank surfaces 146, 164 cooperate to provide separation. of the tooth space (TSC) in the same way as described in the previous one. Referring now to Figure 20, any of the above-described asymmetric tooth profile embodiments of Figures 9, 15, 18 and 19 may be incorporated into the ring gear 300 of the random coupling roller chain. Toothed crown 300 is shown as an 18-tooth toothed crown. However, the ring gear 300 can have more or fewer teeth, as desired. Toothed crown 300 includes a first group of arbitrarily placed toothed teeth 302 each having a profile incorporating the flank plane 144 shown in Figures 9, 15, 18 and 19. Likewise, the teeth 302 of the crown notched may incorporate any, one or both surfaces 146, 164 of inclined root as shown in Figures 9, 15, 18 and 19. The rest of the teeth 304 of the ring gear (teeth 1, 3, 4, 9, 13, 14 and 16 of the ring gear) are arranged randomly around the ring gear and incorporate a tooth profile different from that profile of the first group of teeth 302 of the ring gear. As described below, the first and second group of teeth 302, 304 of the ring gear cooperate to reduce the noise levels of the chain transmission system below a noise level than any tooth profile used alone. it would produce. Figure 21 illustrates an exemplary tooth profile for one of the teeth 304 of the ring gear. A coupling flank 306 and a coast flank 308 or decoupling from an adjacent tooth cooperate to define a tooth space 310 receiving a coupling roller 314 (shown in dotted lines). The coupling roller 314 has a roller diameter D-. and is shown fully seated with an individual tip contact (line) within the tooth space 310. As best seen in Figure 21a, the coupling roller 314 does not contact the coupling flank 306 at the beginning of the engagement, moving in place from the range to the full engagement root contact on a root surface 316. inclined at a contact point C located radially outward from the contact point C in a direction towards the coupling flank 306. The contact point C is a roller / tooth contact line extending axially along each tooth surface of the ring gear (ie, in a direction orthogonal to the plane of the drawings). As shown in Figures 21 and 21a, the first radius or spokes RS of coupling root is tangent to the inclined root surface 316 on line 319, and is also tangent to Rr as defined by the angle β. The angle ß has no specific functional requirements at the beginning of the roller engagement since the contact of the roller / flank will not be made with the profile 304 of the tooth. It should be noted that R, can be equal to root radius ISO-606 for profile 304 of the tooth. The length of the root surface inclined from the point C to its radially outer end on the line 319 is determined by the amount of flank deflection required to ensure that the roller does not contact the coupling flank for any elongation of the spacing. the expected chain (wear) throughout the life of the design. In the preferred embodiment, the side deviation 323 is in the range of about 0.025 to about 0.13 mm. The deviation 323 of the flank is an extension of the inclined root surface 316 that provides tooth space spacing (TSC) in the same manner as described above with respect to the surface 146. As mentioned in the above, the separation of the tooth space compensates for the lengthening of the chain spacing or chain wear by accommodating a specific degree of elongation of the chain spacing. In other words, the spacing of the tooth space TSC allows the rollers of a worn chain to keep in contact with the inclined root surface of the teeth of the ring gear. In addition, the inclined root surface 316 facilitates the reduction of the radial reaction force thereby reducing the contribution of the roller radial impact roll to the overall noise level. The inclined root surface 316 can be tilted to any angle f necessary to satisfy a specific chain drive geometry and elongation of chain spacing. The inclined root surface angle f is measured from a line 320 passing through the center of the roller 314 and the center of the ring gear to a second line 322 that also passes through the center of the roller 314 and through the point of contact C. The inclined root surface 316 is normal with respect to line 322, and the inclined root surface extends radially inward to line 318 where it is tangent to RA. In the embodiment described, the angle f of the inclined root surface is preferably in the range of about 201 to about 35 °. Figure 22 shows another embodiment of the tooth profile 304 where no separation of the tooth space TSC is provided. That is, the portion of the flat surface of the root surface inclined from line 318 to line 322 is not present. Therefore, the profile of the tooth 304 from the point C to the tip or outer diameter on the decoupling side of the tooth space is substantially identical to the profile of the tooth shown in Figure 15. The portion 323 of the remaining flat surface of the root surface 316 inclined from the line 322 to the line 329 operates solely to provide the deflection of the coupling flank as described above. It will be appreciated that the portion of the inclined root surface of the coupling flank from line 318 to line 322 can be replaced with a root surface 164 inclined to the cost flank as in Figure 18. That is, profile 304 of the tooth it may be substantially identical to the ring gear 112 shown in Figure 18 from the contact point C to the outer diameter of the coast flank 138. The inclined root surface 164 of the coast flank provides tooth space spacing (TSC) in the same manner as on the inclined root surface 316. Likewise, the inclined root surface of the coast flank beneficially moves the roller to a preferred radially outward position as the chain wears. Alternatively, the inclined root surface 164 of the coast flank may be included with the inclined root surface 316 of the coupling flank as in Figure 19. Therefore, the profile 304 of the tooth may also be substantially identical to the ring gear 112. shown in Figure 19 from the contact point C to the external diameter of the coast flank 138. The mismatch of the spacing is inherent in a chain / ring gear interface except for one condition, -the theoretical condition that is defined as a chain at its shortest spacing (the shortest being the theoretical spacing) and a toothed gear more short. This theoretical condition therefore defines a limit (zero, or non-coincidence of spacing) of the tolerance range of the mismatch relationship of spacing of the chain and the ring gear. The other limit is defined when using a chain (built in its place) longer with a crown gear in minimal material conditions, or in other words, a gear with a minimum profile. This limit produces the greatest amount of mismatch of spacing. The range of non-coincidence of spacing is therefore determined by the characteristic tolerances of the part. The mismatch of additional spacing can be introduced to facilitate a delay, or geared "in stages", between the initial tangential contact at point A and the contact completely seated at points B and C for profile 302 of the tooth. It will be appreciated that the step contact for the profile 302 improves due to the plane 144 of the flank which causes the initial contact to occur higher on the coupling flank. This results in reduced gearing frequency noise levels because the point and the rhythm of the initial contact of the roller to the ring gear is altered for each tooth profile 302, 304 since the profile 304 does not have a tangential contact . The spacing of the crown rope is necessarily shorter than the spacing of the chain to facilitate the "stepwise" contact of the tooth-roller. Furthermore, the reduction of the spacing of the rope also provides a separation of the roller to the flank as the roller leaves the return of the ring gear back to the section. The reduction in rope spacing, when used, is preferably in the range of about 0.005 to about 0.030 mm. The step roller contact for the profile 302 of the tooth can further be assisted by providing a pressure angle Y of the tooth of the ring gear that is substantially less than ISO-606. Pressure angles Y equal to or very close to zero (0), or even negative pressure angles, are considered. Figure 23 illustrates the profile 304 of the overlapped tooth for the profile 302 of the tooth. A coupling roller is shown at the beginning of the initial tangential contact at point A along the coupling flank of profile 302 of the tooth. The coupling roller will remain in contact with the coupling flank until it is fully engaged and seated at points B and C as described above with reference to Figure 9. Profile 304 of the tooth is superimposed on the profile 302 of the tooth to show that a coupling roller only has radial contact on the inclined root surface of the tooth profile 304 (see Figures 21a and 22) and has no tangential contact with the tooth profile 304. The pressure angle Y for the tooth profile 304 has no functional purpose during the start of the roller engagement since the roller does not contact the coupling flank. The pressure angle Y302 for the tooth profile 302 is shown as a negative value. Therefore, Y ", in can be a negative value, and Yma? it can be a positive value equal to some value less than the minimum pressure angle Y ISO-606. As a result, the initial contact of the roller to the ring gear for the tooth profile 302 of the gear 300 (FIG. 20) occurs at point A followed by the complete coupling contact at points B and C. The ring gear 300 it may or may not incorporate the reduction of the spacing of the additional string, and may or may not incorporate tooth space spacing (TSC), as described above. Figure 24 shows the coupling path of an additional roller 342 from the initial contact at point A (dotted lines) to contact (solid lines) at two points completely seated on a tooth 302 of the ring gear, and a coupling path of the roller 314 is coupled to a tooth 304 of the adjacent ring gear of the random coupling ring gear 300. At the start of the gearing for the roller 314, a small portion of the chain load transfer is effected with the tooth 304 which collects a part of the load. However, the tooth 302 continues to carry a larger portion of the chain load until a coupling roller meshes with another tooth 304 with its flank contact attached. Reference 1 in Figure 24 indicates the amount of "graduation" for tooth 302 from the initial contact at point A to the full engagement contact at points B and C.

Figures 25 and 26 illustrate the gearing delay between the tooth profiles 302, 304. In particular, as shown in Figure 25, the ring gear 300 has an additional roller 344 completely seated in contact at two points with a toothed crown tooth incorporating the profile 302 of the tooth. The roller 342 is shown at the moment of the initial tangential contact at the point A of a second tooth of the ring gear that incorporates the tooth profile 302 for itself. The roller 314 is the next roller in the range and will mesh with a tooth of the ring gear that incorporates the profile 304 of the tooth. The crown gear 300 must rotate through an angle t for the roller 342 to move from its initial contact position at point A for full engagement, seated at the two point contact, with the profile 302 of the tooth in position which indicates the 12 o'clock clock. With reference to Figure 26, the ring gear 300 of Figure 25 is shown rotated clockwise until the roller 314 is at the beginning of the engagement with the profile 304 of the tooth. The ring gear 300 must now rotate through a smaller angle K so that the roller 314 is seated in the position indicating the 12 o'clock clock. Therefore, the ring gear 300 must rotate through an angle T-K so that a coupling roller is fully seated in the profile 302 of the tooth. Referring again to Figure 20, the two sets of tooth profiles 302, 304 are arranged in a random pattern in order to modify the frequency of the engagement impact by altering the point and rhythm of the initial roller contact to the crown. toothed However, the two sets of tooth profiles 302, 304 may be arranged in many different random patterns. Likewise, it is also considered that the sets of profiles 302, 304 of the tooth can be arranged in many regular patterns that will work equally well. In all cases, the arrangement of the two sets of different tooth profiles on a ring gear provides a means for breaking the noise of the frequency impact of the gear normally associated with and induced by a total complement of the teeth of the ring gear configured substantially in identical form. The reduction of the frequency of the gearing is achieved by altering the point and the rhythm of the initial contact of the roller to the ring gear. The toothed crown of the camshaft, usually the smallest toothed crown of the chain drive, is usually the one that contributes the most to noise. The toothed ring gear of the typically larger driven camshaft, however, will also contribute to the noise levels generated, but generally to a lesser degree than the camshaft sprocket. However, the driven gear, in particular if it is almost the same size - or smaller than the drive gear, can be the primary noise generator, as in the case of gearwheels of balance arrows and pump toothed crowns. Therefore, the features of the present invention can also be advantageously used with driven or camshaft gears as well. It will be appreciated that the profile characteristics of the tooth of Figures 20-26 can be altered slightly without substantially deviating from the kinematics of the chain gearing and the ring gear that produces the noise reduction-benefits of the present invention. For example, the profile of the asymmetrical coupling flank may be approximately spirally shaped, and the profile of the uncoupled asymmetric flank may be of a different roughly non-enveloping shape. You can make slight changes to the profile for reasons of manufacturing and / or quality control, or simply to improve the dimensions of the part. The invention has been described with reference to preferred embodiments. Obviously, others may devise modifications after reading and understanding this specification and this invention which is intended to include same as long as they fall within the scope of the appended claims or the equivalents thereof.

Claims (26)

1. CLAIMS 1. A gear wheel characterized in that it comprises: a first plurality of teeth of the gear wheel each having a profile of the tooth including a first coupling flank, a first coupling root and a first plane placed between the first plane of coupling and the first coupling root, a first roller making contact initially with the first plane at the beginning of the engagement of the first roller with the ring gear; and a second plurality of gearwheel teeth each having a different profile from the first profile of the tooth and including a second coupling flank, a second coupling root and a second tangent plane with respect to the second far coupling root from- - the second coupling flank, initially contacting a second roller with the second plane at the start of the engagement between the second roller and the ring gear. The crown gear according to claim 1, characterized in that the first and second tooth profiles are symmetrical tooth profiles. The ring gear according to claim 1, characterized in that the first plurality of the teeth of the ring gear are arbitrarily positioned relative to the second plurality of the teeth of the ring gear. The crown gear according to claim 1, characterized in that the second plane includes a first portion and a second portion, the first portion provides a deviation of the flank and the second portion provides a space separation of the tooth. The ring gear according to claim 1, characterized in that the second plurality of the teeth of the ring gear include a decoupling flank and a third plane positioned along the decoupling flank to provide a clearance of the tooth space. The ring gear according to claim 1, characterized in that the first plurality of the teeth of the ring gear each include a third tangent plane with respect to the first remote coupling root from the first coupling flank to provide a separation of the first ring. tooth space. The ring gear according to claim 1, characterized in that the first plurality of teeth of the ring gear includes a decoupling flank and a third plane positioned along the decoupling flank to provide a space separation of the tooth. The ring gear according to claim 1, characterized in that the first roller makes contact with the ring gear at two points along the first profile of the symmetrical tooth in a fully engaged position. The ring gear according to claim 1, characterized in that a beam of the first coupling root is smaller than a beam of the first roller. A ring gear characterized in that it comprises: a first plurality of teeth of the gear wheel each having a profile of the symmetrical tooth including means for providing a tangential contact with a first roller at the start of the engagement of the first roller with the ring gear; and a second plurality of teeth of the ring gear each having a second profile of the asymmetric tooth including means for providing radial contact with the second roller at the start of engagement of the second roller with the ring gear. The ring gear according to claim 10, characterized in that: the first means include a first coupling flank, a first coupling root and a first plane placed between the first coupling flank and the first coupling root, the first The roller initially makes contact with the first plane at the beginning of the engagement of the first roller with the ring gear; and the second means include a second coupling flanka second coupling root and a tangent second plane with respect to the second toothed coupling root from the second coupling flank, the second roller initially contacting the second plane at the start of the engagement between the second roller and the ring gear. The crown gear according to claim 11, characterized in that the first and second tooth profiles are symmetrical tooth profiles. The ring gear according to claim 11, characterized in that the first plurality of the teeth of the ring gear are arbitrarily positioned relative to the second plurality of the teeth of the ring gear. The crown gear according to claim 11, characterized in that the second plane includes a first portion and a second portion, the first portion provides a deviation of the flank and the second portion provides a space separation of the tooth. The ring gear according to claim 11, characterized in that the first roller makes contact with the ring gear at two points along the first profile of the symmetrical tooth in a fully engaged position. The ring gear according to claim 11, characterized in that a beam of the first coupling root is smaller than a beam of the first roller. 17. A unidirectional roller chain drive transmission including a first ring gear, a second ring gear and a roller chain having rollers in mating engagement with the first and second ring gear, wherein at least one First and second crowns comprise: a first plurality of teeth of the gear wheel each having a profile of the tooth including a first coupling flank, a first coupling root and a first plane placed between the first coupling plane and the first coupling root, a first roller making contact initially with the first plane at the beginning of the engagement of the first roller with the ring gear; and a second plurality of gearwheel teeth each having a different profile from the first profile of the tooth and including a second coupling flank, a second coupling root and a second tangent plane with respect to the second coupling root remote from the second coupling flank, initially contacting a second roller with the second plane at the start of the engagement between the second roller and the ring gear. 18. The roller chain drive system according to claim 17, characterized in that the first and second tooth profiles are symmetrical tooth profiles. 19. The roller chain drive system according to claim 17, characterized in that the first plurality of the teeth of the ring gear are arbitrarily positioned relative to the second plurality of the teeth of the ring gear. 20. The roller chain drive system according to claim 17, characterized in that the second plane includes a first portion and a second portion, the first portion provides a deviation of the flank and the second portion provides a space separation of the tooth . 21. The roller chain drive system according to claim 17, characterized in that the first roller makes contact with the ring gear at two points along the first profile of the symmetrical tooth in a fully engaged position. 22. The roller chain drive system according to claim 17, characterized in that a beam of the first coupling root is smaller than a beam of the first roller. 23. A method for modifying the engagement frequency of a roller chain meshing with a ring gear, characterized in that it comprises: (a) rotating the ring gear to make a first roll of the roller chain contact tangentially with a coupling flank of a tooth of the first ring gear at the start of engagement of the tooth of the first ring gear; and (b) rotating the ring gear to make the second roller of the roller chain make radial contact with the tooth root surface of the second ring gear at the start of the engagement of the second roller with the tooth of the second ring gear. . 24. The method according to claim 23, characterized in that step (a) includes the step of: rotating the ring gear to make the first roller of the roller chain make contact with a plane of the flank at the start of the engagement of the first roller with the tooth of the first gear. 25. The method of compliance with the claim 23, characterized in that step (b) includes the step of: rotating the ring gear to make the second roller of the roller chain contact an inclined plane at the start of engagement of the second roller with the tooth of the second ring toothed 26. The method according to claim 23, characterized in that it further includes the step of: (c) after step (a), further rotating the ring gear to make the first roller of the roller ring make contact with the tooth of the first ring gear at two other points along the first profile of the symmetrical tooth in a fully engaged position of the first roller.