This application claims priority on the basis of Japanese patent application 2008-012590, filed Jan. 23, 2008. The disclosure of Japanese application 2008-012590 is hereby incorporated by reference.
This invention relates to a silent chain having improvements by which the forces that act on the link plates as a result of tension applied to the chain are more uniformly distributed.
A typical silent chain comprising rows of plates, defined as guide rows and non-guide rows respectively. Each guide row is composed of a pair of opposed guide plates and a plurality of inner guide row plates disposed between the guide plates. Each of the inner guide row plates has a pair of pin holes. Each non-guide row is composed of a plurality of non-guide row plates, and each of the non-guide row plates also has a pair of pin holes. The number of non-guide row plates in each non-guide row exceeds, by one, the number of inner guide row plates in each guide row. The guide rows and non-guide rows are arranged alternately along the length of the chain, and the plates of the each non-guide row are interleaved with the plates of two adjacent guide rows and extend between the guide plates of the adjacent guide rows. Connecting pins, which are fixed to the guide plates, extend through pin holes in the interleaved inner guide row plates and non-guide row plates in order to connect the guide rows and the non-guide rows in articulating relationship.
As shown in
The pitch P of the connecting pins 511 and 512 is the same as that of the pin holes of the inner guide row plates 526, 527, 528 and 529. Equal annular clearances C exist between outer circumferential surfaces of the pins 511 and 512 and the inner circumferential surfaces of pin holes 551, etc., of the respective inner link plates 526, 527, 528 and 529.
When a tensile force acts on the silent chain 500, deflection occurs in the pins 511 and 512. As the deflections of the pins 511 and 512 increase, the pins come into abutting contact with the inner circumferential surfaces of the pin holes of the inner link plates 527 and 528, which are farthest from the outer link plates.
The tensile load becomes concentrated in the guide plates 521 and 522 and in the inner guide row plates 527 and 528. On the other hand, in the non-guide link row 530, tensile forces are concentrated in the outermost link plates 531 and 535 as a result of deflections of the pins 511 and 512, as explained in U.S. Pat. No. 5,989,141.
However, the conventional silent chain, wear, elongation and rupture are liable to occur in the link plates in which the load is concentrated. To increase the plate strength, countermeasures such as increasing the plate thickness can be adopted. However, in the case of a chain used in the valve timing system of an engine, for example, where compactness and lightness in weight are important, increasing plate thickness has not been a satisfactory solution.
Another problem was flexion of the connecting pins as a result of tensile loads applied to the chain caused a concentration of load on the edges of the pin holes of the plates, causing wear, chain elongation, and rupture of the plates.
Accordingly, an object of the invention is to solve the above-described problems and to provide a silent chain, which is light in weight, compact, and torque resistant, and in which tensile force is more uniformly distributed despite deflection of the connecting pins, so that wear, elongation and the likelihood of rupture, are reduced.
The silent chain according to the invention comprising rows of plates, defined as guide rows and non-guide rows respectively. Each guide row is composed of a pair of opposed guide plates and a plurality of inner guide row plates disposed between the guide plates. Each of the inner guide row plates has a pair of pin holes. Each non-guide row is composed of a plurality of non-guide row plates, and each of the non-guide row plates also has a pair of pin holes. The number of non-guide row plates in each non-guide row exceeds, by one, the number of inner guide row plates in each guide row. The guide rows and non-guide rows are arranged alternately along the length of the chain, and the plates of the each non-guide row are interleaved with the plates of two adjacent guide rows and extend between the guide plates of the adjacent guide rows. Connecting pins extend through pin holes in the interleaved inner guide row plates and non-guide row plates in order to connect the guide rows and the non-guide rows in articulating relationship. The chain is characterized by the fact that the pitches of the pin holes in the plates of each non-guide row vary with increasing distance from the guide plates.
When a tensile force is exerted on the silent chain, causing its pins to be flexed, the tensile force is substantially uniformly transmitted to the link plates of the non-guide link row. Therefore, concentration of load on specific link plates is avoided. Wear, chain elongation, and likelihood of rupture are reduced. Moreover, these effects can be achieve in a chain that is both light in weight and compact, and that exhibits high torque resistance.
The pin holes of the link plates of the non-centrally located non-guide link rows are preferably slanted whereby, when the connecting pins are flexed by tension applied to the chain, in each pin hole of the link plates of the non-guide link rows, the inner peripheral surface thereof more closely conforms to the surface of the connecting pin extending therethrough. In other words, the inclination of the inner circumferential surfaces of the pin holes follows the deflection of the pin so that contact pressure is not concentrated on sharp edges of the pin holes, and wear, chain elongation, and the likelihood of rupture are further reduced.
In an alternative embodiment, the pitches of the pin holes in the plates of each guide row can also vary with increasing distance from the guide plates. Therefore concentration of load on specific inner link plates of the guide rows is avoided, and wear, chain elongation, and likelihood of rupture are still further reduced.
As in the case of the non-guide row plates, the pin holes of the non-centrally located inner link plates of the guide rows can also be slanted whereby, when the connecting pin is flexed by tension applied to the chain, in each pin hole of the link plates of the guide rows, the inner peripheral surface thereof more closely conforms to the surface of the connecting pin extending therethrough, so that contact pressure is not concentrated on sharp edges of the pin holes, and wear, chain elongation, and the likelihood of rupture are still further reduced.
In the chain according to the invention, the pitches of the pin holes of the non-guide row plates, and, optionally, the pitches of the pin holes of the inner guide row plates, vary according to the distance from the guide plates of the chain. Varying the pitches of the pin holes tends to equalize the forces applied to the link plates when the connecting pins are deflected as a result of tension applied to the chain.
As shown in
Connecting pins 111 and 112 are respectively inserted into and fixed to, front and rear pin holes of the guide plates 121 and 122. Each pin extends through pin holes of the link plates 126, 127, 128, 129, 131, 132, 133, 134 and 135, connecting the interleaved rows of plates together while allowing articulation of the chain.
The inner diameters of pin holes 123 and 124 in the respective guide plate 121 and 122 are smaller than the outer diameters of pins 111 and 112. And the pins 111 and 112 are press-fit into the guide plates 121 and 122. Further, the inner diameters of the pin holes of the inner link plates of the guide rows 120 and the inner diameters of the pin holes of the link plates of the non-guide link rows 130 are larger than the outer diameters of pins 111 and 112 so that toothed link plates can rotate relative to the connecting pins.
As shown in
The inner link plates 126, 127, 128 and 129 of the guide link row 120 are all the same size, and, as shown in
As shown in
As shown in
When tensile force is exerted on the silent chain 100, as shown in
As seen in
In a second embodiment, shown in
In the inner link plates 226, 227, 228 and 229 of the guide link row 220, as shown in
The holes of the non-guide row link plates 231, 232, 233, 234 and 235 have the same pitch relationship as that of the guide plates in the first embodiment, as shown in
The chain can, of course, have an odd number of inner guide row plates, in which case, the centrally located guide row plate preferably has holes that are perpendicular to the faces of the plates. Moreover, in such a case, the number of non-guide row plates will ordinarily be even, and all of the non-guide row plates will have slanted pin holes.
When tensile force is exerted on the silent chain 200, as shown in
Furthermore, as a result of the inclination of the pin holes both in the non-guide rows and in the guide rows, the pin holes in both the guide rows and in the non-guide rows conform more closely to the surfaces of the pins when the pins are flexed. Load concentrations are reduced, and the load on each pin hole is more uniformly distributed, thus reducing the likelihood of rupture.
In the embodiments described, the pitches of the front and rear pin holes of particular link plates are equal to the pitches of the front and rear holes of the connecting pins. It should be understood, however, that the pitches of the holes in the link plates can be selected depending on materials, pin size, flexion characteristics of the connecting pins, conditions of use, etc., and that chains according to the invention can be made without any of the non-guide row plates and inner guide row plates having a pin-hole pitch equal to the pitch of the pin holes in the guide plates.
Number | Date | Country | Kind |
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2008-012590 | Jan 2008 | JP | national |