WO2014023336A1

WO2014023336A1 - Transmission chain with rollers or bushings with inner link with convex back and with smaller outer link with a peanut shape

Info

Publication number: WO2014023336A1
Application number: PCT/EP2012/065425
Authority: WO
Inventors: Giuseppe Baddaria
Original assignee: Borgwarner Inc.
Priority date: 2012-08-07
Filing date: 2012-08-07
Publication date: 2014-02-13

Abstract

A description is given of a chain (100) with rollers or bushings built to bear against a chain tensioner for distribution chains for the automotive sector, with at least one row constituted by a succession of outer links (1) connected to a succession of inner links (2), and which is provided along the direction of its thickness with at least one inner link and one outer link, wherein the inner links (2) have a "convex" back, while the outer links (1) are in the shape of a peanut or "figure of eight" and have a smaller height compared to that of the inner links (2).

Description

TRANSMISSION CHAIN WITH ROLLERS OR BUSHINGS WITH INNER LINK WITH CONVEX BACK AND WITH SMALLER OUTER LINK WITH A PEANUT SHAPE DESCRIPTION

The present invention relates to a transmission chain with rollers or bushings with inner link with convex back and smaller outer link with a "figure of eight" or peanut shape, particularly suitable for the transmission of motion between rotating shafts in the automotive field.

Chain transmissions are among the means most used for transmitting power between two or more parallel rotating shafts: the chains used for the commanding of distribution in internal combustion engines are generally constituted by metal chains of the type with rollers or with bushings and provide for the use of chain tensioner and of chain guides for maintaining the proper tension of the chain itself should these chains be used in the automotive field.

Roller and bushing chains formed by links with "figure of eight" shape are normally used in transmissions in the motorcycle and industrial chains world: these chains are not used in the automotive sector in that the lack of contact surface provided by the "figure of eight" profile for the guide and chain tensioner slides would entail an excessive contact pressure and consequently excessive wear of the plastic surface of the slides. It is in order to limit this wear that many chains for applications in the automotive field provide inner and outer links with straight back (flat) so as to provide the chain tensioner with a large contact surface, reducing the pressure on this area.

A further improvement of these chains for automotive use is represented by chains composed of "curved" (convex) inner and outer links and no longer straight with an appropriate radius on the back.

This configuration in fact, although it entails an increase in the pressure on the surface due to the decrease in the contact surface between the slide of the chain tensioner and the back of the links, allows a reduction in losses due to friction to be achieved since the coefficient of friction of the plastics with which the chain tensioner slides are made decreases as the contact pressure increases. This leads to improved engine efficiency and fuel economy compared to the chains with straight back.

There is still however in the automotive industry the need to further improve the performances of the distribution chains, in particular as regards the reduction in the coefficient of plastic-chain friction, at the same time reducing also its overall weight without however worsening the fatigue limit (tensile strength) of the chain and the efficiency of distribution. The object of the present invention is that of overcoming, at least in part, the disadvantages of the prior art by providing an improved distribution chain for automotive use, in particular as regards the reduction in the coefficient of friction between the plastic of the chain tensioner and chain guides and the chain itself, and the reduction in its overall weight without worsening the fatigue limit (tensile strength).

A further objective is that of providing such a chain that is also easy to make, economical and which can be obtained with the least possible amount of scrap.

These objects are achieved by the chain in accordance with the invention having the features listed in the appended independent claim 1.

Advantageous embodiments of the invention are disclosed by the dependent claims.

An objective of the present invention relates to a chain with rollers or bushings built to bear against chain tensioner and chain guides for distribution chains for automotive use, with at least one row, constituted by a succession of outer links connected to a succession of inner links so as to be provided, along the direction of its thickness, with at least one inner link and one outer link, wherein the inner links are with "convex" back, while the outer links are in the shape of a peanut or "figure of eight".

Moreover said outer links have a lower height compared to that of the inner links so that the profile of each inner link projects, both above and below, in relation to that of each outer link. In this way the slides (or sliding elements) of the chain tensioner or guide will only come into contact with the convex back of the inner links, obtaining a considerable reduction in the friction with respect to the chain with all the links with curved back (convex) thanks to the smaller contact surface offered by the present chain.

Moreover also the overall weight of the chain will be lower than that of the chains with all the links with curved back in light of the smaller size of the outer links, that is to say of the smaller height and of their "figure of eight" shape.

Additionally, since the outer links do not come into contact with the slides (or sliding elements) it is possible to avoid their surface finish normally performed for smoothing the surface of contact with the slides: this allows costs to be reduced and a less expensive chain to be obtained compared to those known.

"Outer link" here is intended to identify that which in the art is also referred to as link with pins, i.e. a pair of pins with parallel axes restrained one to the other by two outer connection plates rigidly connected one to the other.

"Inner link" here is intended to identify that which in the art is also referred to as a link- block, i.e. a rigid block formed by two bushings with parallel axes, optionally carrying two respective rollers, restrained one to the other rigidly by two plates (bushing link) generally with the same pitch of the pins of the outer link, said bushings being rotatably mounted on the pins of adjacent outer links.

Chains with single row (or at least one row) are intended here to identify chains where each inner link (link-block) is connected to two adjacent outer links (links with pins) connecting them one to the other, and where an outer link (link with pins) is connected to two adjacent inner links (links-block), connecting them one to the other, said connection being formed by means of the insertion of the aforesaid pins in the aforesaid rollers or bushings. Further features of the invention will be made clearer by the following detailed description, referred to one of its embodiments purely by way of a non-limiting example illustrated in the accompanying drawings, wherein:

Figs, la and lb are respectively a front view and a plan view of a portion of chain according to the present invention;

Fig. lc is an enlarged front view of some links forming the portion of chain of Fig. la; Fig. 2 is a perspective view of some links forming the portion of chain of Fig. la; Fig. 3 is a perspective view illustrating the layout of the chain of the invention on a car engine in combination with a chain tensioner and a chain guide;

Fig. 4 is a plan view showing schematically the process of blanking of plates of the outer links;

Fig. 5 is a perspective view of some links, partially sectioned, forming the portion of chain of Fig. la.

Referring to the drawings a description will now be given of an embodiment of a chain according to the invention, denoted by reference numeral 100, formed by a single row (or tier) of inner and outer links.

This chain 100 is formed by a succession of inner links 2 whose plates are provided with a convex back 3, which are arranged adjacent one to the other and in succession so as to form at least one row of inner links 2 (Fig. 2).

Each plate of each inner link 2 has a pair of holes for receiving respective rollers or bushings which allow the connection one to the other of the two plates forming the inner link 2, keeping them distanced at the same time. The distance, D, between the two plates of an inner link 2 (Fig. lb) is not binding for the purpose of the present invention and depends on the conditions wherein this chain will have to operate and on the dimensions, Φ, of the rollers or bushings: generally this distance D is comprised between 3.50 mm and 5.72 mm. In an exemplary embodiment this distance D is approximately 5.50 mm.

The distance between the two holes (or rather between their central axes) of a same inner link plate 2 is not binding for the purpose of the present invention and depends on the conditions wherein this chain will have to operate: generally this distance P is comprised between 7 mm and 9.525 mm. In an exemplary embodiment this distance, or pitch P (Fig. la), between said holes of each inner link 2, is approximately 9.525 mm.

Also the diameter Φ of the two openings of a same inner link plate 2 is not binding for the purpose of the present invention and depends on the conditions wherein this chain will have to operate and on the dimensions of the rollers or bushings to be inserted in said openings: generally this diameter Φ is comprised between 4 mm and 6.35 mm. In an exemplary embodiment the diameter of each bushing or roller of the inner links 2 is approximately 6.35 mm.

The inner links 2 placed in succession are moreover connected one to the other also by means of respective outer links 1, placed also in succession and adjacent one to the other: each outer link 1 is formed by two plates positioned externally with respect to the plates of the inner links 2 and staggered with respect to said plates of inner links 2.

Each plate of each outer link 1 has also a pair of holes for receiving respective pins 4 which allow the connection one to the other of the outer links 1 to the inner links 2 when said pins 4 are inserted simultaneously in the holes of the outer links 1 and inside the bushings or rollers of the inner links 2, after having aligned coaxially with said bushings or rollers with said holes of said outer links 1. The distance between the two central axes of two adjacent holes belonging to two outer links 1 is not binding for the purpose of the present invention but is substantially equal to the distance between the two central axes of the two holes of a same inner link 2, i.e. to the pitch P: generally this pitch P is comprised between 7 mm and 9.525 mm. In an exemplary embodiment said pitch p between said outer links 1 is approximately 9.525 mm.

These outer links 1 of the present chain 100 are characterised in that formed by plates having a "figure of eight" or peanut shape. Moreover, as apparent from Figures la and lc, each inner link 2 projects, both above and below, with respect to each outer link 1 since the maximum height of each outer link 1 taken on the vertical at the axis of a pin 4, here also denoted by H_e, is smaller in relation to the height of each inner link 2 taken on the same vertical, also denoted here by Hi. In this way the contact of the slide (sliding element) with said outer links 1 is prevented. "Chain tensioner" here is intended to identify any known tensioning device, generally with slide, used to keep the chain taut and attached to the engine block, provided with a slide or sliding element which is pushed by hydraulic or elastic means against a strand of the chain in order to compensate for a certain slack of the chain. An example of such a chain tensioner is illustrated in Figure 3 with reference numeral 7. "Chain guide" here is intended to identify any element suitable for guiding the movement of the chain without exerting any thrust, generally positioned on the opposite side to the slide (or sliding element) of the chain tensioner. An example of this chain guide is illustrated in Figure 3 with reference numeral 5.

The heights ¾ and H_e of the links, respectively, inner 2 and outer 1 of the present chain 100 are not binding for the purpose of the present invention: generally the overall height H_e of the outer link 1 is comprised between 6.10 mm and 9.20 mm. In a preferred embodiment the overall height H_e of the outer link 1 is approximately 9.18 mm while that of the inner link 2 is approximately 9.78 mm.

Preferably the overall difference between the two heights, ¾-¾ is generally comprised between 0.2 mm and 1 mm at most: in a preferred embodiment this difference of heights Hj-He is approximately 0.6 mm, i.e. the profile of the inner link 2 projects, both above and below, in relation to that of the outer link 1 by approximately 0.3 mm.

Moreover the plates of the outer links 1 have a thickness SI calculated so as to generate a section A_e resistant to traction which is equivalent to the section A; of the inner links 2 of thickness S2, as illustrated in Fig. 5.

The areas A_e and Aj considered above are those resulting from the vertical section made at the axis of a pin 4.

Generally the thickness SI of the plates of the outer link 1 is comprised between 1.0 mm and 1.4 mm, preferably it is approximately 1.27 mm; the thickness S2 of the plates of the inner link 2 is generally comprised between approximately 1.20 mm and 1.8 mm, preferably it is 1.53 mm.

The radius of curvature R of the back 3 of the plates of the inner link 2 is comprised between 50-200 mm, preferably 150 mm.

The plates of the inner links 2 and the outer links 1 are formed by means of a process of blanking: in particular the plates of the outer links 1 with a "figure of eight" shape are obtained from a sheet 6 whereon the holes are first formed for the passage of pins 4 and subsequently the plates with a "figure of eight" or peanut shape are blanked in positions staggered one in relation to the other, as shown in Fig. 4. The advantages of the present chain 100 are not only technical in nature but also economic since the "figure of eight" profile makes it possible to obtain, for the same sheet, a greater number of figure of eight links compared to that of other shapes of links, thanks to the complementarity of shape between the curves of the "figure of eight" and the notch between said two curves which allows the figures of the blanking mould to be brought closer together: in fact the area left free by the notch between the two curves of the figure of eight of a first link is occupied by one of the two curves of the figure of eight of a second adjacent link thus reducing the scrap after blanking. Moreover the cost of the present chain is smaller not only because for every outer link a smaller amount of material is used (thanks to the smaller height and thickness of the plates), but also because the back 8 of the outer links (Figure 5), which does not come into contact with the chain guide 5 or with the chain tensioner slide 7, does not have to be surface finished, contraiy to what occurs in chains with links with curved or flat back where all the links come into contact with the chain tensioner and chain guides.

From the technical point of view the present chain 100 has the advantage of having both a reduced coefficient of plastic-chain friction but also a reduced overall weight without however reducing the fatigue limit (tensile strength) of the chain, which is comparable to that of other chains which can be adopted for the same use, and the efficiency of distribution.

The present invention is not limited to the particular embodiments described previously and illustrated in the accompanying drawings, but instead numerous detail changes can be made thereto within the reach of the person skilled in the art, without departing from the scope of the same invention, as defined in the appended claims.

Claims

1. Chain (100) with rollers or bushings built to bear against chain tensioners (7) and chain guides (5) for transmissions of motion between rotating shafts in the automotive field, comprising

a first succession of inner links (2) with convex back (3) arranged adjacent one to the other, each inner link (2) being formed by a pair of plates connected rigidly one to the other and provided, each, with a pair of holes for receiving respective rollers or bushings, a second succession of outer links (1) adjacent one to the other, each outer link (1) being formed by a pair of plates rigidly connected one to the other and provided with a pair of holes for receiving respective pins (4), said plates being positioned externally and in a staggered manner with respect to said plates of said inner links (2),

each inner link (2) of said first succession being connected to two adjacent outer links (1) of said second succession, by means of said pins (4) inserted in said rollers or bushings, characterised in that the outer links (1) are in the shape of a peanut or "figure of eight" with a maximum height (H_e), taken on the vertical at the axis of one of said pins (4), less than the height (¾) of said inner links (2), taken on the same vertical, so as to prevent the contact of said slides with said outer links (1).

2. Chain (100) according to claim 1 wherein the distance (D) between the two plates of each inner link (2) is comprised between 3.50 mm and 5.72 mm.

3. Chain (100) according to claim 1 or 2 wherein the pitch (P) of the outer links (1), i.e. the distance between the two central axes of the two holes of each plate of each outer link (1), is comprised between 7 mm and 9.525 mm.

4. Chain (100) according to any one of the preceding claims wherein the height (Hi) of each inner link (2) is greater than the height (H_e) of each outer link (1) by a total value comprised between 0.2 mm and 1 mm.

5. Chain (100) according to any one of the preceding claims wherein the overall height (H_e) of the outer link (1) is comprised between 6.10 mm and 9.20 mm.

6. Chain (100) according to any one of the preceding claims wherein the thickness (SI) of each plate of each outer link (1) is calculated so as to generate, in a vertical section taken on the axis of a pin (4), an area Ae resistant to traction which is equivalent to the area Ai of a vertical section taken on the same axis of each plate of each inner link (2) of thickness (S2).

7. Chain (100) according to claim 6 wherein the thickness (SI) of the plates of the outer link (1) is comprised between 1.0 mm and 1.4 mm while the thickness (S2) of the plates of the inner link (2) is comprised between approximately 1.20 mm and 1.8 mm.

8. Chain (100) according to any one of the preceding claims wherein the convex back (3) of each plate of each inner link (2) has a radius of curvature (R) comprised between 50-200 mm, preferably 150 mm.

9. Chain (100) according to any one of the preceding claims wherein the diameter Φ of each bushing or roller of each inner link (2) is comprised between 4 mm and 6.35 mm.