JP2012220009A - Silent chain transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a chain transmission device while suppressing noise.SOLUTION: By using a hob cutter having an inside flank, a pitch and a pressure angle common to a silent chain 1, a sprocket 2 is cut by such gear cutting addendum modification as it is determined by the following formula: (D/2) cos(π/2z)≤H≤(D/2) cos(π/4z), where H is a distance between the advancing direction pitch line PLc of the silent chain 1 and the center of a sprocket 2, z is the number of teeth of the sprocket 2, and D is the diameter of a pitch circle in such a state that the silent chain 1 is wound around the sprocket 2.

Description

  The present invention relates to a silent chain transmission device using a silent chain.

  A silent chain transmission configured by winding an endless silent chain that flexibly connects a large number of link plates having a pair of V-shaped link teeth around a sprocket is, for example, a drive for a camshaft or a balancer shaft of a four-cycle engine Widely used for applications.

  The silent chain transmission device bulges the center part of the inner flank of each link plate to suppress noise caused by the cordal action of the silent chain, and temporarily moves the link plate when the silent chain enters the sprocket. Lifting. However, in this case, since the lifting amount of the link plate does not change even if the number of teeth of the sprocket changes, the effect of suppressing noise is insufficient when combining sprockets having different numbers of teeth.

  Therefore, by using a rack-shaped hob cutter with a common inner flank, pitch, and pressure angle of the silent chain, the sprocket is chopped and the gear shifting amount is set appropriately to minimize noise caused by cordal action. Has been proposed (Patent Document 1). In other words, if the amount of gear shifting is set according to the number of sprocket teeth so that the silent chain approaching direction pitch line is in contact with the pitch circle when the silent chain is wound and seated, regardless of the number of sprocket teeth, the silent chain The chordal action can be substantially eliminated. Note that the outer flank of the silent chain is contoured by envelopes that are in contact with all the sprocket tooth forms having different numbers of teeth, and is smoothly seated on all the sprocket tooth forms.

JP 2002-106652 A

  According to such conventional technology, there is no margin between the inner chain flank and the tip of the sprocket teeth, and the contact area between the outer flank and the sprocket teeth is small, resulting in excessive wear on the inner flank of the silent chain. There is a problem that the durability may be lowered due to the occurrence or the unstable seating of the silent chain on the sprocket.

  Therefore, in view of the problems of the prior art, the object of the present invention is to improve the durability while suppressing the noise caused by the cordal action by improving the tooth shape of the link plate of the silent chain and the sprocket tooth shape of the sprocket. It is to provide a silent chain transmission.

  In order to achieve the above object, the structure of the present invention includes an endless silent chain that connects a plurality of link plates having a pair of V-shaped link teeth with a connecting pin, and a plurality of sprockets having sprocket teeth that mesh with the silent chain. Each sprocket has a rack-shaped hob cutter with the same inner flank, pitch and pressure angle of the silent chain, and the distance H between the silent chain approaching direction pitch line and the sprocket center is (D / 2) · cos (π / 2z) ≤ H ≤ (D / 2) · cos (π / 4z) has a sprocket tooth profile that is chopped with a gear shift amount, and the outer chain flank of the silent chain is In contact with all sprocket teeth of sprockets with different number of teeth when the silent chain is wound and seated As its gist in that it comprises a curved portion. Here, z is the number of teeth of the sprocket, and D is the diameter of the pitch circle when the silent chain is wound around the sprocket and seated.

  According to the configuration of the present invention, the pitch line of the silent chain in the approach direction is 1/8 to 1 of the sprocket from the radius of the pitch circle perpendicular to the approach direction pitch line with respect to the pitch circle when the silent chain is wound around the sprocket. / 4 pitch angle will be reached in front, and as a result, the silent chain will produce a small chordal action equivalent to 1/8 to 1/4 pitch angle of the sprocket. On the other hand, between the inner flank of the silent chain and the sprocket teeth, based on this cordal action, for example, a minimum clearance of at least about 15 μm can be secured for a sprocket with a range of 16 to 100 teeth. There is no excessive wear on the plate or sprocket. Furthermore, since the contact area between the outer flank and the sprocket teeth can be made sufficiently large, there is no excessive wear on the outer flank or sprocket teeth, and the silent chain seating on the sprocket does not become unstable. The required durability can be easily achieved while keeping the noise caused by the cordal action small.

  The reason why the silent chain approaching direction pitch line reaches the pitch circle at a distance corresponding to 1/8 to 1/4 pitch angle from the radius of the pitch circle perpendicular to the silent chain is as follows. In other words, if the pitch angle is less than 1/8, the required minimum clearance cannot be secured between the inner flank and the sprocket teeth, and there is a risk that the processing accuracy of the link plate and the sprocket and the wear during use may not be dealt with. Yes, if the pitch angle exceeds 1/4, the chord action of the silent chain becomes large, and noise may be excessive. However, the silent chain starts meshing with the sprocket teeth first by the inner flank, and then meshes with the outer flank to transmit power while being wound around and seated on the sprocket.

Main part configuration schematic explanatory diagram Link plate configuration illustration Main part configuration explanatory diagram of hob cutter Main part enlarged schematic explanatory diagram Operation explanatory diagram (1) Operation explanatory diagram (2) Main part enlarged operation diagram

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The silent chain transmission device includes an endless silent chain 1 and a sprocket 2 (FIG. 1). However, in FIG. 1, the silent chain 1 is wound around two or more sprockets 2 having the same or different number of teeth z, and enters the direction of arrow K1 as the sprocket 2 rotates in the direction of arrow K2, 2 can be rotated while meshing.

  The silent chain 1 is configured by knitting a large number of link plates 10, 10... In a finger-like manner via connecting pins 1 a, 1 a. Each link plate 10 has a pair of V-shaped link teeth 11 and 11 and pin holes 12 and 12 for a pair of connecting pins 1a (FIG. 2). The inner side of each link tooth 11 is a linear inner flank 13 having a pressure angle α, and the outer side is a curved outer flank 14. When the silent chain 1 is stretched linearly on the pitch line PLc, the outer flank 14 of each link plate 10 is hidden by the inner flank 13 of another adjacent link plate 10 (solid line, dotted line in FIG. 2). . However, in FIG. 2, the pitch P of the silent chain 1 and the pitch line PLf of the inner flank 13 and 13 are shown together, the interval P / 2 of the inner flank 13 and 13 on the pitch line PLf, the pitch line PLc, The interval Hc is PLf.

  On the outer periphery of the sprocket 2, sprocket teeth 2 a, 2 a... With the number of teeth z engaging with the silent chain 1 are formed at an equal pitch (FIG. 1). The sprocket teeth 2a, 2a... Of the sprocket 2 can be cut using a rack-shaped hob cutter 30 having the same pitch P and pressure angle α as the inner flank 13, 13,.

  The hob cutter 30 forms tooth forms 31, 31... With a pressure angle α on the tooth form pitch line PL3a for each pitch P, and appropriate addendum a and dedendam b are set above and below the pitch line PL3a. ing. Such a hob cutter 30 can be used in common for all the sprockets 2 having different number of teeth z, and for hobbing away from the pitch line PL3a of the tooth profile by an appropriate gear shifting amount X according to the number of teeth z. The sprocket 2 is geared based on the pitch line PL3b. Note that the sprocket 2 to be cut in this way has the gear cutting pitch circle diameter Dp = P · z / π determined by the number of teeth z, and the tooth shape of each sprocket tooth 2a, that is, the sprocket tooth shape, has the number of teeth z, It is formed from an involute curve determined by the gear dislocation amount X.

  Each outer flank 14 of each link plate 10 is formed to include upper and lower curved portions 14a and 14b that are convex outward, and an intermediate concave curved portion 14c that smoothly connects the curved portions 14a and 14b. (FIGS. 2 and 4). The upper and lower curved portions 14a and 14b are in contact with the tip and root portions of the sprocket teeth of all the sprockets 2 having different numbers of teeth z, and the curved portions 14a and 14b are all sprocket teeth. It can be formed as an arcuate curve approximate to the envelope line in contact with the tooth tip portion and the tooth root portion. The intermediate curved portion 14c is determined so as to avoid an involute curve of the sprocket tooth profile of the sprocket 2 having the smallest number of teeth z (FIG. 4A). However, FIGS. 4 (A) to 4 (D) are schematic views of the main part showing the contact state of the outer flank 14 of the link plate 10 with the sprocket teeth 2a of the sprocket 2 having the number of teeth z = 16, 32, 50, 100, respectively. is there.

  As shown in FIG. 1, when the silent chain 1 meshes with the sprocket 2 and sits wound around in a polygonal shape, assuming that the diameter D of the pitch circle through which the connecting pins 1a, 1a,... Passes, the radius D / 2 = (P / 2). / Sin (θp / 2) = (P / 2) / sin (π / z). However, θp = 2π / z is the pitch angle of the sprocket 2 having the number of teeth z.

On the other hand, the position of the pitch line PLc of the silent chain 1 when entering the sprocket 2, that is, the distance H between the incoming direction pitch line PLc of the silent chain 1 and the center of the sprocket 2 is the pitch line PLc, PLf of the silent chain 1. , And a relative relationship between the gear dislocation amount X of the hob cutter 30 when the sprocket 2 is geared. Therefore, the gear dislocation amount X of the sprocket 2 can be set so that H1 ≦ H ≦ H2. However,
H1 = (D / 2) .cos (.pi. / 2z) = (D / 2) .cos (.theta.p / 4)
H2 = (D / 2) .cos (.pi. / 4z) = (D / 2) .cos (.theta.p / 8)
It is.

  Now, when the gear shifting amount X is set so that the distance H is equal to H1, a series of movements from the entry of the silent chain 1 to the seating with respect to the sprocket 2 focusing on a specific link plate 10 of the silent chain 1 Is shown in FIGS. 5 and 6.

  When the link plate 10 advances on the approach direction pitch line PLc of the silent chain 1 (in the direction of arrow K1 in FIG. 5A), the specific sprocket teeth 2a come into contact with the inner flank 13 on the front side in the moving direction. The meshing with the sprocket 2 is started. In FIG. 5A, the symbol Cp indicates a pitch circle through which the connecting pins 1a, 1a... Of the silent chain 1 wound around the sprocket 2 are seated. The symbol Rp is the radius of the pitch circle Cp perpendicular to the approach direction pitch line PLc of the silent chain 1, and the symbol Lp is the tangent of the pitch circle Cp parallel to the approach direction pitch line PLc.

  The pitch line PLc in the approach direction of the silent chain 1 reaches the pitch circle Cp in front of the angle θ1 = θp / 4 = π / 2z from the radius Rp of the pitch circle Cp perpendicular to the silent chain 1 (FIG. 5B). . Therefore, when the connecting pin 1a on the front side of the link plate 10 advances from the radius Rp to the front by an angle θ1 = θp / 4 (FIG. 5B), the connecting pin 1a on the front side thereafter becomes a pitch circle Cp. The link plate 10, the silent chain 1 thus produces the final chordal action δ1 = D / 2−H1 when entering the sprocket 2. Therefore, when the connecting pin 1a on the front side advances to the radius Rp of the pitch circle Cp and the approach direction pitch line PLc coincides with the tangent line Lp of the pitch circle Cp (FIG. 6A), the link plate 10 is The position rises from the position of 5 (B) by an amount corresponding to the angle θ1 = θp / 4 and is positioned highest.

  Subsequently, the connecting pin 1a on the rear side of the link plate 10 extends from the radius Rp of the pitch circle Cp to a position just before the angle θ1 = θp / 4 (the position of the connecting pin 1a on the front side in FIG. 5B). As it advances (FIG. 6 (B)), the link plate 10 is seated on the sprocket teeth 2a, 2a of the sprocket 2 through the outer flank 14, 14, and together with the sprocket 2 along the pitch circle Cp. Rotate. Note that the distance Hp = (P / 2) / tan (π / z) between the pitch line PLc of the link plate 10 and the center of the sprocket 2 at this time. Further, the other link plate following the link plate 10 is at the position shown in FIG. 5B, and can be operated similarly thereafter.

  Next, when the gear shift amount X of the sprocket 2 is set so that the distance H = H2 between the pitch line PLc in the approach direction of the silent chain 1 and the center of the sprocket 2, the behavior of the link plate 10 at that time is shown in FIG. 5. In FIG. 6, the distance H1 is changed to the distance H2, the angle .theta.1 = .theta.p / 4 = .pi. / 2z is changed to the angle .theta.2 = .theta.p / 8 = .pi. / 4z, and the chordal action .delta.1 = D / 2-H1 is set. There is no particular change except that the chordal action δ2 = D / 2−H2.

  That is, the link plate 10 sets the gear dislocation shift amount X of the sprocket 2 by the hob cutter 30 so as to satisfy H1 ≦ H ≦ H2, so that FIG. Since a small chordal action δ1 to δ2 corresponding to the angle θ1 to θ2 is passed through until the seat is wound around, the tip of the sprocket tooth 2a and the tip of the sprocket tooth 2a are independent of the number of teeth of the sprocket 2 and the size of the dedendam b of the hob cutter 30. A necessary minimum gap is ensured between the inner flank 13 and 13, and there is no possibility of excessive wear on the inner flank 13 and 13. In addition, the link plate 10 seated on the sprocket 2 comes into contact with the sprocket teeth 2a and 2a via the upper and lower curved portions 14a and 14b of the outer flank 14 regardless of the number z of teeth of the sprocket 2 (see FIG. 4, FIG. 7), a sufficiently large contact area can be realized, and the seating does not become unstable. In the seated link plate 10, the inner flank 13, 13 does not contact the tip of the sprocket tooth 2 a (FIG. 7), and only the outer flank 14, 14 contacts the corresponding sprocket tooth 2 a, 2 a. .

  The present invention can be widely and suitably applied not only for driving the camshaft and balancer shaft of an engine but also for any other application.

P ... Pitch α ... Pressure angle X ... Decision shift amount Cp ... Pitch circle PLc ... Pitch line 1 ... Silent chain 1a ... Connecting pin 2 ... Sprocket 2a ... Sprocket tooth 10 ... Link plate 11 ... Link tooth 13 ... Inner flank 14 ... Outer flank 14a, 14b ... Curve part 30 ... Hob cutter

Patent Applicant Enuma Chain Manufacturing Co., Ltd.

Claims (1)

  An endless silent chain for connecting a large number of link plates having a pair of V-shaped link teeth with a connecting pin, and a plurality of sprockets having sprocket teeth meshing with the silent chain, each of the sprockets, Using a rack-shaped hob cutter with the same inner flank and pitch and pressure angle of the silent chain, the distance H between the pitch line of the silent chain and the sprocket center is (D / 2) · cos (π / 2z ) ≦ H ≦ (D / 2) · cos (π / 4z), and the sprocket tooth shape is chopped with a gear dislocation amount so that the outer flank of the silent chain is wound around the silent chain. The upper and lower curved parts that touch all the sprocket teeth of the sprocket with different number of teeth are included. Silent chain transmission device, characterized in that. Here, z is the number of teeth of the sprocket, and D is the diameter of the pitch circle when the silent chain is wound around the sprocket and seated.

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