CHAIN FOR V-PULLEY

Abstract: A chain for a V-pulley which is used by being endlessly trained between a pair of V-pulleys (1) and in which blocks (30) each having an end surface (31) for coming into contact with the V-pulley (1) are respectively disposed on the outer sides of outer link plates. The end surface of the block (31) is formed into a convex surface constituted by the whole or part of a conical surface which has substantially the same apex angle as that of the inner wall (3) of the V-pulley (1) and has an axis parallel to the axis of a connecting pin (20). The block (30) may be fixed with respect to the outer link plate or may be made rotatable about the axis of the cone.

Description: The present invention relates to a chain, as defined by the features set out in the preamble of claim 1, which is wound around a V-pulley and is suitably used for a continuously variable transmission of an automobile or other transmissions in general. Such a chain is known from US-A 2550 431, in which the block is part of the connecting pin. In recent years, a continuously variable transmission system comprising a pair of V-pulleys and an endless belt or chain has come to be used for a continuously variable transmission which is coupled with an engine of such as an automobile having a relatively large torque. Specifically, this continuously variable transmission system is arranged as follows. A pair of V-pulleys in which an interval between their inner walls can be varied are mounted on a drive shaft and a driven shaft, respectively, an endless belt or chain is trained between the two V-pulleys, and the interval between the inner walls of each V-pulley is varied by, for instance, hydraulic means in response to speed change commands. This causes the winding radius of the endless belt or chain trained between the V-pulleys to be varied relatively and continuously, thereby effecting a continuously variable transmission between the drive shaft and the driven shaft. An endless belt described above is disclosed in Japanese Patent Publication No. 6783/1980. This is a metal V-belt which is arranged such that metal blocks with a thickness of about 2 mm each having a surface of contact with an inner wall of a V-pulley are fitted with practically no gap with a hoop formed by superposing a plurality of thin metal sheets with no gap therebetween. The transmission of a driving force in this V-belt is effected as follows: The torque of the drive shaft-side V-pulley is transmitted to the blocks via a frictional force, and the driving force between the blocks is transmitted to the preceding blocks through a pushing force. Meanwhile, the driving force at the driven shaft-side V-pulley is converted again to torque through a frictional force. That is, the driving force does not substantially act on the hoop, and the hoop serves as a binding member for preventing the blocks from becoming separated. Accordingly, with this V-belt, no fracture of the hoop takes place, and it has been considered that it excels in terms of durability and noise. However, since the driving force is transmitted by the pushing force exerted among the blocks, the V-belt on the driven shaft-side V-pulley acts to escape in the direction of the outer periphery of the V-pulley. Consequently, there has been a drawback in that the friction between the V-belt and the V-pulley is made disadvantageously small, thereby causing a decline in the driving force-transmitting capabilities. In addition, it has been very difficult to fabricate a hoop formed by superposing a plurality of thin metal sheets without leaving any gap therebetween, and much manpower and time have been required in the fabrication thereof. Accordingly, a chain for a V-pulley has been proposed in which blocks coming into contact with the V-pulley are fixedly secured to an ordinary chain. According to this chain for a V-pulley, since the driving force is transmitted through a pulling force of the chain, it is possible to overcome the problem of a decline in the driving force-transmitting capabilities, which is the drawback of the above-described V-belt. Such chains for V-pulleys are disclosed in, for instance, Japanese Patent Laid-Open Nos. 226729/1984, 226730/1984, 26831/1985, and 143243/1985. However, these prior arts are generally concerned with techniques for attaching blocks to the chain, or forming the blocks on the link plates or on the opposite ends of the connecting pins. Thus, the end faces of the blocks which are brought into contact with the inner wall of V-pulley have generally been formed into flat surfaces with no particular concern being paid to the configuration of the end faces of the blocks. As an example in which the configuration of the end face of the block is made not flat, it is possible to cite a technique disclosed in, for instance, Japanese Utility Model Laid-Open No. 196850/1988 published on 19/12/88. In this technique, a cylindrical body having an axis in the longitudinal direction of a chain abuts at a peripheral surface thereof against an inner wall of a V-pulley. However, the inner wall of the V-pulley is conically shaped, and, with this technique, the blocks and the V-pulley can theoretically be only brought into point contact with each other, so that it is considered that it is disadvantageous in terms of the driving force-transmitting capabilities. In this respect, if the end face of the block is formed with a flat surface having the same inclination as that of the inner wall of the V-pulley (i.e., half the apex angle), it is possible for the end face of the block and the inner wall of the V-pulley to be theoretically brought into contact with each other at a linear line of contact, and this arrangement is advantageous in the transmission of the driving force. However, when the block starts to be engaged with the V-pulley, the block is brought into contact with the V-pulley at a front edge thereof, and when it begins to be disengaged with the V-pulley, the block is brought into contact with the V-pulley at a rear edge thereof. In other words, at the beginning of engagement and disengagement, the block and the V-pulley are not brought into smooth linear contact with each other and the block comes into contact with the V-pulley at its edge, thereby causing a decline in the driving force-transmitting capabilities. In addition, during a period from the time when the block enters the V-pulley and is engaged therewith and until the block is disengaged therefrom, the block rotates back and forth about an axis parallel to the axis of the connecting pin. Since this rotation of the block is effected under high pressure, rotational friction occurs between the block and the V-pulley, causing abrasion of both the block and the V-pulley and a loss in the driving force. In addition, since the portion of the end face of the block which becomes worn is fixed, it is impossible to obtain a chain for a V-pulley having an extended life. Furthermore, since the chain disposed between the two V-pulleys vibrates in the axial direction of the connecting pin, the block collides against the inner wall of the V-pulley at the time of entering the V-pulley, thereby generating noises due to this collision. To solve these problems, the present inventors proposed a technique (Japanese Patent Laid-Open No. 219937/1988 published on 13/09/88) in which the block is connected to the tip of the connecting pin in the form of a universal joint without the block being fixed to the link plate, and the end face of the block is made rotatable and swingable to a certain degree about the axis of the connecting pin while maintaining the same inclination as that of the inner wall of the V-pulley. According to this technique, the block is rotatable, the rotational friction caused by the rotation of the block occurring at the time of entrance into the V-pulley does not occur, and the block is swingable. Therefore, it had been expected that the colliding sound occurring when the block collides against the inner wall of the V-pulley during entrance into the V-pulley would be reduced. However, it was not possible to attain a reduction of the noises to the extent that had been expected. As the reason for this problem, it can be conjectured that since the end face of the block was formed into a flat surface, the block and the V-pulley could not maintain smooth linear contact. Accordingly, a primary object of the present invention is to further develop the generic chain and to provide a chain for a V-pulley in which an end face of a block can constantly maintain smooth linear contact with an inner wall of the V-pulley thereby avoiding the drawbacks associated with the abrasion of the block and the V-pulley and preventing a decline in the driving force-transmitting capabilities. A second object of the present invention is to provide a chain for a V-pulley which is capable of reducing the noises caused by the collision between the block and the V-pulley as the block enters the V-pulley. These objects are met by the features of the characterizing portion of claim 1. Further advantageous details are outlined in the dependent claims. Fig. 1 is a perspective view of an embodiment not in accordance with of the present invention; Fig. 2 is a cross-sectional view taken along the line A-A of Fig. 1; Figs. 3A to 3D are diagrams illustrating different postures of a block with respect to a V-pulley when the end face of the block is formed into a flat surface; Fig. 4 is a diagram illustrating lines of contact between the end face of the block and the inner wall of the V-pulley when the end face of the block is formed into a flat surface; Figs. 5A and 5B are diagrams illustrating different postures of the block with respect to the V-pulley when the end face of the block is formed into a convex surface in accordance with the present invention; Fig. 6 is a diagram illustrating lines of contact between the end face of the block and the inner wall of the V-pulley when the end face of the block is formed into a convex surface in accordance with the present invention; Fig. 7 is a partial side elevational view of a embodiment of the present invention; Fig. 8 is a cross-sectional view taken along the line A-A of Fig. 7; and Fig. 9 is a graph in which a comparison is made in the noise level between the chain in accordance with the present invention and a conventional chain. A chain for a V-pulley is shown in Figs. 1 and 2 comprises a plurality of link plates 10, a plurality of connecting pins 20, and a plurality of blocks 30. The link plates 10 are arranged such that transverse rows each having four link plates and transverse rows each having three link plates are disposed in such a manner as to be alternately offset from each other, the former being hereinafter referred to as main link plates 11 and the latter as subsidiary link plates 13 for the sake of explanation. The connecting pin 20 penetrates a hole 15 formed in each of the main link plates 11 and subsidiary link plates 13, and the connecting pin 20 is fixedly secured only to an outermost link plate 12 among the main link plates 11 and is rotatable with respect to the other link plates. The main link plates 11 and the subsidiary link plates 13 are thus connected to each other in such a manner as to be bendable, thereby forming a chain. A block 30 is provided on the outside of an outer link plate opposed to an inner wall 3 of the V-pulley 1 in such a manner as to be fixed with respect to the outer link plate. In this embodiment, the outer link plate opposed to the inner wall of the V-pulley refers to the outermost link plate 12 among the main link plates 11, and an outermost link plate 14 among the subsidiary link plates 13 is not opposed to the inner wall of the V-pulley. However, if the link pitch is formed longer, the outermost link plate 14 among the subsidiary link plates 13 can also be used as the outer link plate opposed to the inner wall of the V-pulley. In that case, a block may be provided on the outside of the outermost link plate 14 among the subsidiary link plates 13 in such a manner as to be fixed with respect to the outermost link plate 14. In this embodiment, the block 30 is fixed with respect to the outermost link plate 12 among the main link plates 11, and, as for the fixing means, the block 30 may be fixedly secured to or formed integrally with the outermost link plate 12. In addition, although, in this embodiment, one block 30 is provided substantially in the center of the outermost link plate 12 among the main link plates 11, the block 30 may be provided in such a manner as to be offset from the center. Alternatively, a plurality of blocks 30 may be provided on the outermost link plate 12 as a row arranged in the longitudinal direction thereof. In that case, block 30 may be secured to the connecting pin 20 by being force fit therewith. The block 30 has a convex surface 31 which abuts against the inner wall 3 of the V-pulley 1. The convex surface 31 is formed into a configuration obtained by cutting a conical surface. This cone has an apex angle β which is substantially identical with an apex angle α of the inner wall 3 of the V-pulley, and is provided with an axis 32 which is parallel with an axis 21 of the connecting pin 20 and is hence parallel with an axis 2 of the V-pulley 1. Although, in Figs. 1 and 2, a case is shown in which the axis 32 of the cone is disposed at the upper surface of the link plate to facilitate an understanding of the fact that the convex surface 31 is a curved surface obtained by cutting a cone, the position of the axis 32 is not particularly restricted to this arrangement. A description will now be given of the operation of the chain for a V-pulley thus constructed. Figs. 3A to 3D are diagrams schematically illustrating different postures of the block in a case where an end face 35 of the block is formed with a flat surface having an inclination identical with that (half the apex angle α) of the inner wall 3 of the V-pulley 1. Specifically, Fig. 3A illustrates the posture of the block at the time when the block begins to be engaged with the V-pulley; Fig. 3B, the posture immediately after engagement; Fig. 3C, the posture immediately before disengagement; Fig. 3D, the posture immediately after disengagement. In the drawings, the configuration of the end face 35 is formed to be rectangular so as to facilitate an understanding. If the end face 35 is formed into a flat surface, the block and the V-pulley are brought into contact with each other at a straight line A located within a plane P which passes through the axis 2 of the V-pulley 1 and is perpendicular to the end face 35. Accordingly, when the block starts to be engaged with the V-pulley, the block abuts against the V-pulley at a front edge thereof, as shown in Fig. 3A. When the block is about to be disengaged therefrom, the block is in contact with the V-pulley at a rear edge thereof, as shown in Fig. 3D. The line of contact A thus moves. The contact between the end face 35 of the block and the inner wall 3 of the V-pulley in the meantime is schematically shown in Fig. 4. In the drawing, the end face 35 and the inner wall 3 are brought into contact with each other at the line of contact A, i.e., an extension of a straight line which passes through the axis 2 of the V-pulley 1 and is perpendicular to the end face 35. Subsequently, when the end face 35 rotates back and forth by ϑ° about an axis parallel to the axis of the connecting pin, the line of contact A then moves to a line A′ and, at the same time, the line of contact newly moves to a line B. The rotation of the end face invariably occurs when the block begins to be engaged with or disengaged from the V-pulley and also occurs at the time of speed change. When seen with respect to the end face 35 side, the above-described movement of the line of contact is movement from the line A′ to the line B, a distance therebewteen being equal between the upper side and the lower side of the end face 35. On the other hand, when seen with respect to the inner wall 3 side of the V-pulley, the movement of the line of contact is movement from the line A to the line B. In other words, the line of contact moves by ϑ° in terms of the angle seen from the axis 2 of the V-pulley, and that distance is longer for the upper side of the end face 35 than the lower side thereof. Accordingly, the movement of the line of contact cannot be effected smoothly, the rotation of the end face 35 by ϑ° occurs in a frictional manner. Thus, the movement of the line of contact involving frictional movement takes place, resulting in abrasion, creaks, etc. The posture of the block at the time of engagement shown in Fig. 3A and the posture at the time of disengagement shown in Fig. 3D illustrate an ideal case. Actually, however, it is estimated that the block rotates more irregularly, in which case it becomes difficult for the end face 35 to be easily located within the the above-described plane P. Consequently, it becomes impossible for the block to abut against the inner wall 3 of the V-pulley in the internal area of the end face 35, so that the edge of the end face 35 is brought into contact with the inner wall 3 of the V-pulley at an acute angle. This results in a decline in the driving capabilities, noises, partial abrasion, and the like. On the other hand, however, in the present invention, the end face is not formed into a flat surface but a conically convex surface 31 which has an axis 32 parallel to the axis 21 of the connecting pin 20 and hence parallel to the axis 2 of the V-pulley and has an apex angle substantially identical with that of the inner wall 3 of the V-pulley. If this arrangement is adopted, the inner wall 3 of the V-pulley and the convex surface 31 are brought into contact with each other at the straight line of contact A located within the plane P including the axis 2 of the V-pulley 1 and the axis 32 of the convex surface. Accordingly, the posture of the block at the time of engagement becomes like the one shown in Fig. 5A, while its posture at the time of disengagement becomes like the one shown in Fig. 5B. Hence, the rotation of the block from engagement until disengagement does not occur, with the result that the amount of abrasion can be reduced. Nevertheless, this is an ideal case of engagement and disengagement, and in actual cases it is estimated that the block is engaged and disengaged with postures that are different from those shown in Figs. 5A and 5B and that the block consequently rotates. In that case, the convex surface 31 and the inner wall 3 of the V-pulley are brought into contact with each other at the straight line of contact A located within the plane P including the axis 2 of the V-pulley and the axis 32 of the convex surface, as schematically shown in Fig. 6. Subsequently, when the convex surface 31 is rotated back and forth by ϑ°, the line A moves to the line A′, but, at the same time, the line of contact also moves to the line B. That is, the movement of the line of contact, when seen with respect to the the convex surface 31 side, is movement from the line A′ to the line B, while, when seen with respect to the inner wall 3 side of the V-pulley, it is movement from the line A to the line B. Accordingly, the rotation of the convex surface 31 takes place in a frictional manner. However, the amount of movement of the line of contact in conjunction with the rotation is appreciably small, so that the convex surface 31 and the inner wall 3 of the V-pulley can be brought into contact with each other in the form of smooth contact, not in the form of contact at the edge. Hence, this arrangement makes it possible to overcome the problems of the decline in driving capabilities, noises, partial abrasion, etc. In Fig. 6, a case where the convex surface 31 is formed into a semiconical shape is illustrated to facilitate an understanding of the fact that the convex surface 31 is a curved surface cut from a cone. In this case, the block has a smooth linear contact within a range in which the block rotates back and forth 180°. If the block is formed as a cone or a truncated cone, a smooth linear contact is maintained within the range of 360° rotation, i.e., in any manner. However, if the estimated rotation is between the line A′ and the line B shown in Fig. 6, it suffices if that portion is formed into a convex surface cut from the cone described above, and the other portions are formed in such a manner as not to abut the inner wall 3. Each of the link plates 10 is subjected to a force applied by the V-pulley 1 through the convex surface 31 of the block 30 and a force applied by the preceding and following link plates via the connecting pins 5. These forces constitute couple to cause the rotation of the block 30. Accordingly, in order to reduce couple itself which causes the rotation, as for the position of the axis 32 of the cone forming the convex surface 31 regarding the longitudinal direction of the link plate 10, it is preferred that the axis 32 is located in any position within a plane which includes the axis 21 of the connecting pin and is perpendicular to the longitudinal direction of the link plate 10. In this case, two blocks 30 are provided in a juxtaposed manner on the outermost link plate 12 among the main link plates 11. In addition, in this case, as a means of fixing the block 30 with respect to the outermost link plate 12 among the main link plates 11, the block 30 may be fixedly secured to the outermost link plate 12, or may be integrally formed therewith. As an alternative means, the block 30 may be fixedly secured to the connecting pin 20, or formed at the end face of the connecting pin 20, and subsequently the connecting pin 20 may be fixedly secured to the outermost link plate 12. Although in the above-described third and fourth embodiments the block is fixed with respect to the connecting pin. As shown in Figs. 7 and 8, the block is made rotatable with respect to the connecting pin and each end of the connecting pin 20 has a convex spherical surface 28, while a receiving portion of the block 30 for fitting therewith has a bottom surface 37 composed of a concave spherical surface having a radius of curvature which is greater than that of the convex spherical surface 28. Thus, the arrangement is such that when the block 30 is fitted with the connecting pin 20, the two members are brought into contact with each other at an area including the axis 32 of the connecting pin, thereby facilitating the rotation of the block 30. In addition, on the side surface of the block 30, a stepped portion 38 projecting from its body is formed, while, on the outside of the stepped portion 38, an annular leg 41 having a cut portion 43 in circumferential direction is fitted with the side surface of the block with a small gap therebetween. The legs 41, 41 respectively fitted on the outer sides of the opposing stepped portions 38, 38 of the block are coupled with each other by means of a tabular coupling member 42. Thus, the legs 41, 41 and the coupling member 42 constitute a stopper member 40 for retaining the block. This embodiment is constructed as described above, and since it is unnecessary to forcedly force fit the block with respect to each opposite end of the connecting pin and can be fitted loosely therewith, the block is not subjected to a large compressive stress. Hence, the block is less susceptible to damage and can rotate easily. It is preferred in terms of the suppression of noises that the chain pitch, i.e., the interval between the adjacent connecting pins, is not formed uniformly regardless of whether the blocks are fixed with respect to the link plate or made rotatable. This is because the resonance of the chain can be reduced. In addition, even if the chain pitch is uniform, if the interval between the adjacent blocks is formed non-uniformly, the frequency of the sound caused by the collision between the blocks and the V-pulley during constant-velocity running does not become uniform, thereby making it possible to reduce the noises. If the outer width dimension between the two blocks provided on the respective sides of the chain, i.e., the distance between the end face of the block on one side and the end face of the block on the other, is formed to be non-uniform, the radial position of the V-pulley brought into contact with the block varies. Hence, since the frequency of the sound does not become uniform as in the above-described case, it is possible to reduce noises. Finally, a description will be given of an actual measurement of noises occurring when the blocks where fixedly secured to the opposite ends of the connecting pins, and the connecting pins were made rotatable with respect to the link plates. Various dimensions of the chain will be described. The chain pitch, i.e., the interval between the adjacent connected pins, were set to three kinds of 10.1, 8.6, and 7.7 mm. Generally, the smaller the chain pitch, the more the noises generated by the chain are reduced, but the strength declines, and difficulties in fabrication increase. In the light of strength, the chain pitch of 7.7 mm is considered to be a lower limit as a chain for a continuously variable transmission. The height of the link plates, i.e., the height of the chain was set to 10.4 mm in all cases. Four link plates were used for the main link plates, and their thickness was set to 2.0 mm for the outermost link plate, and 1.8 mm for the others. In addition, three link plates were used for the subsidiary link plates, and their thickness was set to 2.6 mm. Thus, the overall thickness of the main link plates and that of the subsidiary link plates were made as uniform as possible. As for the connecting pins, their diameter was set to 3.8 mm for the chain having a chain pitch of 7.7 mm, and to 4.5 mm for the chain having chain pitches of 8.6 mm and 10.1 mm. The block was formed into a configuration in which a cylinder having a diameter of 7.5 mm and a height of 4.9 mm is combined with a cone. Since the apex angle α of the inner wall of the V-pulley was formed at 158°, the apex angle β of the cone of the block was similarly set at 158°. Actually, however, variations on the order of ±2° occurred with respect to β, and these blocks were used as they were. Next, a description will be given of the materials of the respective parts of the chain. The link plates were formed of a Cr-Mo steel, the connecting pins were formed of a Ni-Cr-Mo steel or die steel provided with austemper treatment, the blocks were formed of a Cr-Mo steel, and conical portions serving as contact surfaces were provided with surface hardening processing through nitriding. In addition, the V-pulley was formed of a Cr steel whose surface was hardened. The above-described chain was mounted on the V-pulley, and the noise level was measured. The measured results are shown in Fig. 9. In the drawing, character A denotes the noise level of the chain having the chain pitch of 7.7 mm in accordance with the present invention, while character B denotes the noise level of the chain disclosed in aforementioned Japanese Patent Laid-Open No. 219937/1988 by the present inventors, and its chain pitch was also 7.7 mm. This drawing shows that, in the case of the chain in accordance with the present invention, the noise level can be relatively reduced by 10 dB. In addition, a measurement was also made of a chain having an irregular chain pitch, i.e., in which portions having a chain pitch of 7.7 mm and those having a chain pitch of 8.6 mm were arranged at random, and a comparison of the noise level was made between this chain and the chain having a fixed chain pitch of 7.7 mm. As a result, it was found that the noise level was lower by several dB in the case of the chain having different chain pitches arranged at random. In addition, the sound which was heard by the human ears was softer than the chain having a fixed chain pitch, and was less irritating to the ears. This phenomenon is conceivably attributable to a decline in the resonance. Furthermore, after a rotation test corresponding to 10,000 km running was conducted, the chain was removed from the V-pulley, and the blocks were visually inspected. As a result, the entire conical surface of each block, i.e., the surface of contact with the V-pulley, displayed gloss. This shows that the entire conical surface of the block was in contact with the V-pulley at random since the block rotates appropriately, and this fact is very advantageous in suppressing abrasion.

Claims: A chain for a V-pulley having a plurality of link plates (10) and a plurality of connecting pins (20) connecting adjacent ones of said link plates (10) in such a manner as to be bendable and used by being endlessly trained between a pair of V-pulleys (1), said chain comprising: a plurality of blocks (30) each provided on the outside of each of a plurality of outer link plates (11, 12) opposed to an inner wall (3) of said V-pulley (1), each of said blocks (30) having a convex surface which is brought into contact with said inner wall (3) of said V-pulley (1), said convex surface being formed into the configuration of a cone or a truncated cone which has an apex angle substantially identical to that of said inner wall (3) of said V-pulley (1), each of said blocks (30) being rotatable about the axis of said cone or said truncated cone, wherein the axis of said cone or said truncated cone is in alignment with the axis of said connecting pin (20), characterized in that said block (30) is rotatable with respect to said connecting pin (20), and opposing ones of said blocks (30) are retained by a stopper member (40) comprising a pair of legs (41) and a coupling member (42) coupling the same. The chain of claim 1, wherein the interval between adjacent connecting pins (20) is substantially non-uniform. The chain of claim 1 or 2, wherein a radius on said V-pulley where said block (30) is brought into contact therewith during constant-velocity running of said chain is substantially non-uniform. The chain of any of claims 1 to 3, wherein each end of said connecting pin (20) has a convex spherical surface (28) while a receiving portion of said block (30) for fitting therewith has a bottom surface (37) composed of a concave spherical surface having a radius of curvature which is greater than that of the convex spherical surface (28). The chain of any of claims 1 to 4, wherein a stepped portion (38) is provided on the side surface of said block (30), and an annular leg (41) of said stopper member (40) is fitted on the outside of the stepped portion (38) whereby said annular leg has a cut portion (43) in circumferential direction.

Inventors: HOSHIRO, TAKESHI, IZUMI, SHINICHIRO, OKUBO, YUKIO, UEDA, SEITARO
Applicants: HITACHI METALS, LTD., MITSUBOSHI BELTING LTD.
Application year: 1989
Main classification: F16G5
IPC codes: F16G5