WO1997039256A1

WO1997039256A1 - Power transmission chain

Info

Publication number: WO1997039256A1
Application number: PCT/NL1996/000165
Authority: WO
Inventors: Lambertus Vervelde
Original assignee: Lambertus Vervelde
Priority date: 1996-04-17
Filing date: 1996-04-17
Publication date: 1997-10-23
Also published as: AU5408596A

Abstract

In operative condition, the disclosed power transmission chain has at least one chain section curved in a plane of curvature and at least one most rectilinear chain section. The chain is composed of a plurality of links (1) overlapping in longitudinal direction of the chain, each of the links (1) being provided with at least one opening (3) and a plurality of pins (2). Each of the pins (2) extends transversely to the longitudinal direction through the openings (3) of at least two successive, overlapping links (1). By providing the chain with stops (4, 5) for precluding successive overlapping links (1) from pivoting beyond the most rectilinear condition when pivoting relative to each other from the curved condition towards the most rectilinear condition, a chain is obtained of which the most rectilinear ends oscillate substantially less when in operation, so noise emissions and wear of the chain are substantially reduced.

Description

TITLE; Power transmission chain

TECHNICAL FIELD

The invention relates to a power transmission chain or chain-belt for transferring a torque from an input drive shaft to an output drive shaft of a transmission.

BACKGROUND ART

In operative condition, conventional power transmission chains include at least one chain section curved in a plane of curvature about pulleys or sprocket wheels, at least one most rectilinear chain section, a plurality of links overlapping in longitudinal direction of the chain, each of these links being provided with at least one opening; and a plurality of pins, each of these pins extending transversely to the longitudinal direction through the openings of at least two successive, overlapping links. An example of such a power transmission chain is disclosed in U.S. patent 1 564 798. Generally, such chains are provided in an endless form and extend about two pulleys or sprocket wheels.

Further developments of similar chains are disclosed in (in chronological order): German "Auslegeschrift" 1 145 871, French patent 1 283 629, Dutch patent application 79 06 681, Dutch patent application 81 02 868, German patent application 31 29 631, European patent application 0 102 673 and U.S. patent 4 708 701.

Compared with push belts including endless metal bands and an array of load blocks or plates movable along the bands, manufacturing costs of such pull belt chains are substantially lower. Push belts are used in practice in continuously variable transmissions. Dutch patent application 75 11 879 discloses an example of such a push belt.

A disadvantage of pull belts including overlapping, mutually hinged links is that the noise level emitted by transmissions including such belts during operation is relatively high. To alleviate this problem, many suggestions have been made such as damping the noise (e.g. U.S. patent 4 464 152) and modifying the noise pattern (e.g. U.S. patents 4 516 964 and 4 516 965). However, these suggestions do not have an effect on the cause of the generated noise level, but only dampen or change the noise.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a drive belt which combines low manufacturing costs similar to those of pull belts with overlapping, mutually hinged links with reduced noise emissions when in operation in a transmission. According to the invention, this object is achieved by providing a drive chain of the initially-identified type with stops for precluding successive overlapping links from pivoting beyond the most rectilinear condition when pivoting relative to each other from the curved condition towards the most rectilinear condition.

Since the chain is precluded from flexing from its curved condition beyond the most rectilinear condition, in operation a substantially stiffer most rectilinear chain section is obtained which is substantially less susceptible to oscillating. In particular, oscillations in the form of essentially standing waves in the most rectilinear chain section are substantially decreased. This in turn results in substantially reduced noise emissions and substantially reduced wear. Another advantage of the chain according to the invention is that it requires relatively little pre-tension to refrain the returning end of the chain from swinging too much.

Particular embodiments and advantages of the present invention are described in more detail in the description with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is an enlarged side view of a curved section of a chain-belt according to the present invention; Fig. 2 is an enlarged side view of a most rectilinear section of the chain-belt shown in Fig. 1;

Fig. 3 is an enlarged top plan view of a chain section as shown in Fig. 2;

Fig. 4 is an enlarged view in cross-section along the line IV-IV in Fig. 3 in combination with wall sections of a dual-cone-shaped pulley;

Fig. 5 is a further enlarged side view of a portion V of a chain as shown in Fig. 2;

Fig. 6 is a side view according to Fig. 5 of the same chain portion in a curved condition;

Fig. 7 is a side view according to Fig. 5 of a portion VII of a chain as shown in Fig. 1 (the same chain portion as shown in Figs. 5 and 6 in a maximally curved condition);

Fig. 8 is top plan view of a pin of a chain according to a second embodiment of the present invention;

Fig. 9 is a side view of a pin as shown in Fig. 8, and

Fig. 10 is a view in cross-section along the line X-X in Fig. 3 in combination with a further pin and some links interconnected by these pins.

MODES FOR CARRYING OUT THE INVENTION

The invention is first described with reference to the presently most preferred embodiment shown in the Figs. 1-7. Subsequently, the alternative embodiment shown in Figs. 8-10 is described. Corresponding parts of the shown embodiments are designated by mutually identical reference numerals.

In operative condition, the power transmission chain according to Figs. 1-7 includes a chain section which is curved in a plane of curvature 7 (Fig. 4) as shown in Figs. 1, 6 and 7, which curved section extends around a pulley and a most rectilinear chain section as shown in Figs. 2, 3 and 5, which most rectilinear chain section extends between two pulleys.

The chain is formed by a plurality of links 1 overlapping in longitudinal direction of the chain and a plurality of pins 2 (not all the links, pins and openings in the Figs. 1-4 are designated by reference numerals). Each of the links 1 is provided with two openings 3 and each of the pins 2 extends transversely to the longitudinal direction through the openings 2 of successive, overlapping links 1. The chain is provided with stops 4, 5 for precluding successive overlapping links 1 from pivoting beyond the most rectilinear condition when pivoting relative to each other from the curved condition (Fig. 1) towards the most rectilinear condition (Fig. 2). It is noted that in Figs. 1 and 2 not all stops are designated by reference numerals. As appears from Figs. 1, 6 en 7, the stops 4, 5 are spaced apart when the chain is in curved condition. The pins 2 and the openings 3 are shaped such that the pins 2 are each tiltable in the respective one of the openings 3. When the chain is in its most rectilinear condition, as shown in Figs. 2 and 5, the stops 4 and 5 abut and preclude the chain from bending beyond its most rectilinear condition. This results in a chain of which, in operation, the rectilinear sections are substantially stiffer and less susceptible to oscillating than the rectilinear sections of conventional chains which are held in essentially rectilinear condition by the tension exerted by the pulleys. Such rectilinear sections of conventional chains have oscillating properties similar to those of strings of a musical instrument. Since the chain is precluded from bending beyond its most rectilinear condition, relatively little pre-tension in the chain is sufficient for keeping the returning end of the chain from oscillating too much.

The most rectilinear condition of the chain according to the invention can be rectilinear within a tolerance range. Alternatively, the most rectilinear chain sections of the chain according to the invention can be curved in the same sense as the more curved parts of the same chain, but with a very large radius of curvature. Thus, somewhat wider manufacturing tolerances and more flexibility of the components of the chain can be accepted without obtaining a situation in which the chain can bend beyond its most rectilinear condition. Moreover, if the most rectilinear sections of the chain are slightly curved, some elasticity of the rectilinear sections in longitudinal direction thereof is obtained which contributes to absorbing irregularities in the chain drive. Such irregularities may be caused by "chordal action" of links of a chain on a driving pulley or sprocket forming a polygonal trajectory and/or by other causes, for instance, oscillations of a drive motor and/or of other transmission parts. Furthermore, if the most rectilinear condition of the chain is slightly curved, longitudinal tension in the chain urges the chain into its most rectilinear condition which helps to refrain the chain from oscillating into and out of its most rectilinear condition. Each pin 2 of the chain according to Figs. 1-7 is in contact with a leading and a trailing load transfer surface 6, 8. As appears most clearly from Figs. 6 and 7, the contact between each of the pins 2 in the curved chain section and the respective leading and trailing load transfer surfaces 6, 8 is a rolling contact between the pin and a curved section of the respective load transfer surface. The contact between each of the pins 2 in the most rectilinear chain section and the respective leading and trailing load transfer surfaces 6, 8 includes a plurality of contact positions spaced apart in a direction parallel to the plane of curvature 7. Due to these features, a simple construction is obtained in which, on the one hand, energy losses and wear due to friction between the pins 2 and the openings 3 are very low, and, on the other hand, successive links 1 are precluded from pivoting relative to each other beyond a configuration forming the most rectilinear configuration. As appears most clearly from Figs. 3 and 4, the chains includes twelve arrays of links 1 so that a belt-like, generally flat configuration of the chain is obtained.

The contact between the pins 2 and the opposite load transfer surfaces 6, 8 in the most rectilinear configuration of each chain section can in principle be a contact in two or more points or lines. In the chain according to Figs. 1-7, each of the leading and trailing load transfer surfaces 6, 8 and surfaces 4 of respective pins 2 include matching surface portions (also forming the stops) 4, 5 which are in surface contact in the most rectilinear chain section or sections (see Figs. 2 and 5) . In the curved section or sections of the chain, these corresponding matching surface portions 4, 5 are spaced apart (see Figs. 1, 6 and 7) . Due to the surface contact between the matching surface portions 4, 5 when the respective section of the chain is in its most rectilinear condition, an even distribution of loads over the stops 4, 5 is obtained, wear and deformation of the stops are reduced and the stiffness of the rectilinear chain sections is further increased, which further contributes to reducing noise emissions and wear due to oscillations of the chain.

In the chain as shown in the Figs. 1-7, the load transfer surfaces 6, 8 are formed by wall portions of the openings 3. Thus, a simple, light construction with direct load transfer from a single pin extending through each transversal array of openings to the respective links is obtained.

The load transfer surfaces 6, 8 include tensile load transfer surfaces 8 facing away from the nearest end 13 in longitudinal direction of the respective link 1 for transferring tensile loads in the chain. Wall portions of the openings 3 further include guide surfaces 9 (Figs. 5-7) facing towards corresponding tensile load transfer surfaces 8. The guide surfaces 9 restrict movement of the pin 2 in the opening 3 to movement in rolling contact with the tensile load transfer surface 8 of the respective opening 3, so that even under influence of substantial centrif gal forces, the respective chain section changes from a curved configuration into its most rectilinear configuration when leaving a pulley and vice versa without any substantial sliding movement of the pins 2 over the tensile load transfer surfaces 8 of the respective openings 3. Thus, wear between the pins 2 and the tensile load transfer surface 8 of the respective openings 2 is substantially reduced. Moreover, energy losses due to friction are also substantially reduced. Friction between the pins 2 and the guide surfaces 9 is substantially lower than friction between the pins 2 over the tensile load transfer surfaces 8, because the guide surfaces extend mainly in longitudinal direction of the chain and are therefore not substantially loaded by pre-tension and driving forces in longitudinal direction of the chain. Via the matching surface portions 5 of each opening 3 facing away from the nearest end 13 in longitudinal direction of the respective link 1, tensile loads in the chain are evenly distributed over these portions 5 of the walls 6 of the openings and the portions 4 of the pins in contact therewith.

Compressive loads in the rectilinear chain portions are evenly distributed over matching surface portions of each opening 3 facing towards the nearest end 13 in longitudinal direction of the respective link 1. These matching surface portions facing towards the nearest end 13 in longitudinal direction of the respective link 1 are located at the side of the neutral line of the chain which forms the outside when the respective portion of the chain is in curved condition. In contrast, the matching surface portions facing away from the nearest end 13 in longitudinal direction of the respective link 1 are located at the side of the neutral line of the chain which forms the inside when the respective portion of the chain is in curved condition. These surfaces are simultaneously loaded with compressive forces by the respective pins when the respective section of the chain is urged to its most rectilinear condition. Since in the rectilinear sections of the chain, both tensile and compressive loads are transmitted via matching surfaces in surface contact with each other, a particularly stiff and stable rectilinear chain section is obtained, which further reduces noise emissions and increases the durability of the chain.

In the chain according to Figs. 1-7, each pin 2 has a continuous, constant profile extending through the openings 3 of overlapping links 1. Thus, the surfaces of the pin co¬ operating with successive links can be manufactured in a single operation, which provides a reduction of manufacturing costs. The manufacturing costs of the pins 2 of the chain according to Figs. 1-7 are particularly low, because the whole pin has a continuous, constant cross-section so that the pins can be manufactured by cutting a continuous profile to length and assembly of the chain is particularly facilitated.

End surfaces 10 of each of the pins 2 (see Figs. 3 and 4) converge in a direction transverse to the longitudinal direction of the chain as appears from Fig. 4. Thus, the end surfaces 10 of the pins 2 of a section of a chain passing over a pulley of a continuously variable transmission fit to the conical surfaces 11 of the pulleys of such a transmission, which conical surfaces converge at an angle corresponding to the angle at which the end surfaces 10 of the pins 2 converge. Since the size of the end surfaces 10 of the pins 2 transverse to the longitudinal direction of the chain is substantially larger than the size of these end surfaces 10 in longitudinal direction of the chain, the end surfaces 10 of the pins 2 have a good fit to the conical surfaces 11 of the pulleys over a wide range in radial direction of these conical surfaces.

Since the pins are to some extent freely tiltable in the respective openings when the chain is in a condition between its most rectilinear condition and its most curved condition, the positioning of the pins 2 on the conical surfaces is self-adjusting which substantially reduces "chordal action" . The rolling contact with the walls of the openings 3 and a suitable profile of the surface portions in rolling contact, further contribute to a smooth operation with little or no "chordal action". For obtaining a particularly smooth transmission of driving power it is further advantageoaus if the surfaces 4 of the pins 2 and the surfaces 6, 8 of the links 1 are shaped such that the pitch of the pins 2 at the neutral line in the curved sections of the chain measured along the curved neutral line along the pulleys is the same as the pitch between the pins 2 in the rectilinear chain sections.

The chain according to the alternative embodiment of which a section is shown in Figs. 8-10 also includes arrays of links 1 interconnected by pins 2. The pins 2 are provided with recesses 12 forming the matching surface portions 4 of the pins 2 which are in surface contact with opposite matching surface portions 5 of the openings 3 when the respective section of the chain is in its most rectilinear condition. An advantage of the chain according to this embodiment is that the wall portions of the openings 3 forming the load transfer surfaces 6, 8 have a rectilinear shape, which facilitates manufacturing of the openings to narrow manufacturing tolerances.

It is noted that the opposite load transfer surfaces in rolling contact with the pins in curved sections of the chain and in contact with the pin in at least two positions in the most rectilinear sections of the chain can also be formed by, for example, a surface of a second pin extending through each transversal array of openings or by any other intermediate element arranged in the same openings as the respective pin.

Claims

1. A power transmission chain comprising: at least one chain section curved in a plane of curvature; at least one most rectilinear chain section; a plurality of links (1) overlapping in longitudinal direction of the chain, each of said links (1) being provided with at least one opening (3); and a plurality of pins (2), each of said pins (2) extending transversely to said longitudinal direction through the openings (3) of at least two successive, overlapping links (1) , characterized by stops (4, 5) for precluding successive overlapping links (1) from pivoting beyond said most rectilinear condition when pivoting relative to each other from said curved condition towards said most rectilinear condition.

2. A chain according to claim 1, wherein each pin (2) is in contact with at least a leading and a trailing load transfer surface (6, 8) and the contact between each of the pins (2) in said curved chain section and at least one of the respective leading and trailing load transfer surfaces (6, 8) is a rolling contact; and wherein the contact between each of the pins (2) in said most rectilinear chain section and each of the respective leading and trailing load transfer surfaces (6, 8) includes at least two contact positions spaced apart in a direction parallel to said plane of curvature.

3. A chain according to claim 2, wherein each of said leading and trailing load transfer surfaces (6, 8) and surfaces of respective pins (2) include matching surface portions (4, 5) , the corresponding matching surface portions (4, 5) in said most rectilinear chain section being in surface contact and the corresponding matching surface portions (4, 5) in said curved section of said chain being spaced apart.

4. A chain according to claim 2 or 3, wherein wall portions of said openings (3) form said load transfer surfaces (6, 8) .

5. A chain according to claim 4, wherein said load transfer surfaces include tensile load transfer surfaces (8) facing away from the nearest end (13) in longitudinal direction of the respective link (1) for transferring tensile loads in said chain and wherein wall portions of said openings (3) further include guide surfaces (9) facing towards corresponding tensile load transfer surfaces (8), the guide surfaces (9) of each opening (3) restricting movement of the pin (2) in that opening (3) to movement in rolling contact with the tensile load transfer surfaces (8) of the respective opening (3) .

6. A chain according to any one of the claims 2-5, wherein at least one matching surface portion (5) faces away from the nearest end (13) in longitudinal direction of the respective link (1) for transferring tensile loads in said chain.

7. A chain according to any one of the claims 2-6, wherein at least one matching surf ce portion (5) faces towards the nearest end (13) in longitudinal direction of the respective link (1) for transferring compressive loads in said chain.

8. A chain according to any one of the preceding claims, wherein each pin (2) has a section with a continuous constant profile extending through at least two openings (3) of overlapping links (1) .

9. A chain according to any one of the preceding claims, wherein end surfaces (10) of each of said pins (2) converge in a direction transverse to the longitudinal direction of said chain.

10. A chain according to any one of the preceding claims, wherein the pins (2) are to some extent freely tiltable in the respective openings (3) if the respective section of the chain is in a condition between its most rectilinear condition and its most curved condition.

11. A chain according to claims 2 and 10, wherein the surfaces (4) of the pins (2) and the opposite tensile load transfer surfaces (8) in rolling contact with the pins (2) are shaped such that the pitch between successive pins (2) at the neutral line in the curved condition of the respective chain section measured along the curved neutral line is the same as the pitch between the same pins (2) if that chain section is in its most rectilinear condition.