TRANSMISSION CHAIN WITH PIVOT PINS AND INTERMEDIATE PIECES WITH ROLLING CONTACT ACTION

Abstract: Transmission chain for a cone pulley drive with intercoupled links (2a...2c) and pivot pins (4a, 4b) inserted through link openings, the end surfaces of which cooperate with the cone surfaces, and where between each pivot pin (4a, 4b), on the one hand, and the opposite-lying upright opening sides of a number of adjacent links, on the other, an intermediate piece (6a...6d) with rolling contact action is inserted whose first longitudinal side (12) is coupled to the link opening side and of which the oppposite-lying second longi­ tudinal surface (10) forms the rolling contact surface cooperates with the longitudinal side of the pin, a number of grooves (24) running between the first and the second longitudinal side being formed in each intermediate piece (10) in at least the narrow longitudinal side facing the inside of the chain.

Description: The invention relates to a transmission chain according to the preamble of Claim 1, and as known from EP-A-0 060 008 or EP-A-0 102 673. In such a transmission chain (which is in particular intended for use in a continuously variable transmission) premature wear of the cooperating longitudinal sides of intermediate piece and pivot pin respectively sometimes occurs, the cause of which must be attributed to inadequate local lubrication. The result of such wear is premature extension of the chain, which means that the transmission can no longer function properly. An obvious solution to this problem would be to run the chain through an oil bath. However, in view of the high running speeds (up to 50 m/s) which are used, this produces considerable energylosses. Another solution is achieved by providing the lubrication by spraying pressurized oil from inside of the transmission chain against the passing chain parts; in the curved chain track parts oil carried along is worked to the outside by the centrifugal force, and the oil must find its way between the pivot pins and the intermediate pieces. However, in practice, this lubricating action is not always found to be adequate in particular at high speeds. The object of the invention is to produce a solution to this problem. This object is achieved according to the invention by the measures described in the characterizing part of Claim 1. Advantageous embodiments are described in the Sub-claims, and as regards the measure described in Claim 8 it is pointed out that these transitions make the assembly of the transmission chain considerably easier. During assembly, after the fitting of the links round the pivot pins, the intermediate pieces are inserted between pivot pins and links and the rounded parts present in the preferred embodiment thereby serve as a "locating edge" by means of which the assembly is speeded up considerably. In particular, when the grooves are formed by cold deformation it is possible through trimming always through the center of an oil groove of a length of suitably shaped material provided with a series of grooves to obtain in a simple manner intermediate pieces with this configuration. It has been found in practice that with the measures according to the invention excellent lubrication of the cooperating surfaces of pivot pins, on the one hand, and intermediate pieces, on the other, is achieved, so that with a measure which hardly increases the manufacturing costs of the chain (the grooves can be formed in the pins in a simple manner by cold deformation) the service life of the transmission chain is considerably extended. The invention is explained with reference to the drawing, in which: Figure 1 is an end view of three transmission chain links with their pivot pins and intermediate pieces shown in the position which these parts take up in the right-hand part of the transmission chain; Figure 2 is a corresponding side view of the parts in a curved part of the chain, at a part curved to a certain radius of curvature; Figure 3 is a part of Figure 1 on a considerably larger scale; Figure 4 is a part of Figure 2 on a considerably larger scale; Figure 5 is a side view of an intermediate piece according to the invention; Figure 6 is a perspective view of a link used in a transmission chain according to the invention; Figure 7 is a perspective view of a pivot pin used in such a transmission chain; Figure 8 is a perspective view of an intermediate piece used in such a transmission chain. In a transmission chain of the type to which the invention relates one link always cooperate with two pins, and each side face of each pin always cooperates with a rolling face of an intermediate piece which is disposed between the pin in question and a supporting surface situated in the link opening; when they run between the cone pulleys the pins are clamped between them and carried along. In such a transmission chain the torque is transmitted by the difference between the tensile forces in the two stretched chain parts. Figure 1 shows in end view a part of three links 2a-2c, and the pivot pins 4a-4b. The pin 4a cooperates with the links 2a, 2b, and the pin 4b with the links 2b, 2c. Each pin 4a, 4b cooperates with the appropriate links by means of two intermediate piece with rolling contact action, for the pin 4a the pieces 6a, 6b, and for the pin 4b the pieces 6c, 6d. A number of links lying in the transverse direction of the chain rest on each intermediate piece, as known per se. The intermediate piece has a flat longitudinal side 10 which forms the rolling surface with the pivot pin (see Figure 3); the other longitudinal side 12 bears along part of its length a projecting rib 14 which fits into a groove in the link. The intermediate piece is fixed by this rib relative to the link. There are also two narrow longitudinal sides 16a, 16b. Each pivot pin has two end faces 18a, 18b (figure 7). These end faces cooperate with the cone pulleys, as known per se. The transverse section of the pins is also characterized by the central body 15, the widened top part 17, and the widened bottom part 19 (Figures 3 and 4). The intermediate pieces are disposed between these widened parts of the pin section (as known per se). This configuration is also known per se. It is, of course, of crucial importance for a long service life of such a transmission chain that there should be excellent lubrication between the longitudinal faces 20a, 20b of the pivot pins and the longitudinal faces of the intermediate pieces, thus the faces 10, cooperating there with. For this, oil is sprayed under pressure through a suitable nozzle against the inside of the chain, e.g. in the direction of the arrow 22 in Figure 1; the oil carried along is flung out by the centrifugal force in the curved track part of the chain, and during operation sufficient oil must penetrate between the intermediate pieces and the pivot pins to ensure a good lubrication. The object of the invention is to ensure this. According to the invention, to this end a series of grooves is disposed in at least the inward-facing narrow longitudinal side 16a of each intermediate piece, lying at right angles to the longitudinal axis thereof, indicated by reference numbers 24 in Figure 5. In order to prevent special attention having to be paid to the orientation of the intermediate pieces during the assembly of the transmission chain, both the narrow longitudinal sides 16a and 16b will preferably be provided with such grooves, as Figure 5 shows. These grooves are designed in such a way that, as shown in particular by the detail cross-sections in Figures 3 and 4, they widen out from the longitudinal side 12 to the longitudinal side 10, while the groove bottom in the preferred embodiment shown has a circular limitation without sharp transitions. The way in which these grooves work follows from a comparison of Figures 3 and 4. Figure 3 shows the position of the intermediate pieces relative to the pins in the right-hand part of the transmission chain, which is assumed to move in the direction of the arrow 28. Oil which is sprayed, for example, in the direction of the arrow 22 against the chain penetrates into the space between the groove bottom 26 of the groove 24 and the face 35 of the widened part 19 of the pin and fills the groove 24. On running into the curved part, i.e. on reaching the position shown in Figure 4, the position of the intermediate pieces relative to the pivot pins changes in such a way that the situation shown in Figure 2 is reached, shown on an enlarged scale in Figure 4: it can be seen that the oil caught in the groove 24 can move into the free space between intermediate pieces and pin longitudinal side under the influence of the centrifugal force. A good lubrication is thus ensured. Good functioning is ensured if in the right-hand part of the chain the narrow ends of the grooves are open - see Figure 3 - and in the curved state (in which the chain links assume a radius of curvature R) - see Figure 4 - the angle α formed between a line R′, running from the center of curvature M to the outermost point 26′ of the lubrication groove bottom and a plane indicated by m touching the groove bottom 26 is at least 90°. This also means that in a curved part of the chain the angle γ included between the rolling face of the intermediate piece and a plane touching the groove bottom is less than 90°. In the usual chain construction this means, assuming the largest radius of curvature which the chain can take up on the pulley, that the angle of flare of the groove 24 is greater than 2°. The figures show an embodiment in which nine grooves of the above-mentioned type are disposed along the narrow longitudinal sides, the groove bottom of each of which has a circular cross-section, as indicated by the circle 25 shown by the dashed and dotted line. Of course, this number is not restrictive: the number of grooves can be determined for each transmission chain and each transmission chain situated on the basis of experience already gained with such transmissions. In the case of a heavily loaded transmission chain operating at high running speeds more grooves will, of course, be used than in the case of a chain with only a low load and running slowly. If the grooves are provided (e.g. by cold deformation) with such spacing between them that each end face of an intermediate piece divides an oil groove through the middle and the intermediate pieces are formed by trimming a suitable shaped preformed piece of material, two "locating edges" 27 are obtained without additional working on each of the ends, and these facilitate the insertion of the intermediate pieces during assembly of the chain.

Claims: 1. Transmission chain for a cone pulley drive, comprising a number of intercoupled links (2a...2c) each accommodating two pivot pins (4a, 4b) which lie at right angles to the link plane and are inserted through link openings, and the end surfaces (18a, 18b) of which cooperate as friction faces with the cone surfaces of a pulley, and whose longitudinal sides (20) constitute rolling surfaces with a radius of curvature different from that of the rolling surface cooperating therewith, and where between each pivot pin (4a, 4b), on the one hand, and the opposite-lying upright sides of the link openings of a number of adjacent links, on the other, an intermediate piece (6a...6d) with rolling contact action is inserted whose first longitudinal side (12) is coupled to said upright sides, and whose opposite-lying second longitudinal side (10) forms the rolling contact surface cooperating with the longitudinal side of the pin, characterized in that a number of grooves (24) running between the first (12) and the second (10) longitudinal side are formed in each intermediate piece (6a...6d) in at least the narrow longitudinal side (16a) which is facing the inside of the chain. 2. Transmission chain according to Claim 1, characterized in that the grooves (24) widen in the direction of said second longitudinal side (10). 3. Transmission chain according to Claims 1-2, characterized in that the grooves (24) are at right angles to said two longitudinal sides (10, 12) of said intermediate piece. 4. Transmission chain according to Claims 1-3, characterized in that in the position in which the chain assumes a radius of curvature (R) the angle γ included between said second longitudinal side (10) of the intermediate piece and a plane touching the groove bottom (26) is less than 90°. 5. Transmission chain according to Claims 2-3, characterized in that the angle of flare of the grooves (24) is greater than 2°. 6. Transmission chain according to Claims 1-4, characterized in that the groove bottom (26) has a circular cross-section. 7. Transmission chain according to Claims 1-5, characterized in that the number of grooves (24) is equal to the number of links cooperating with the particular intermediate piece. 8. Transmission chain according to Claims 1-6, characterized in that the grooves (24) are disposed in both narrow longitudinal sides (16a, 16b). 9. Transmission chain according to Claim 8, characterized in that each intermediate piece has on its end faces two diverging transitions (27) to the respective narrow longitudinal sides (16a, 16b), each formed by a part of a groove. 10. Process for the production of a transmission chain according to one or more of the preceding Claims, characterized in that the grooves (24) of said intermediate pieces are formed by cold deformation. 11. Process according to Claim 10, characterized in that said intermediate pieces are formed by trimming through the center of a groove a length of material of suitable cross-sectional configuration, after the grooves have been formed.

Inventors: CADEE, THEODORUS PETRUS MARIA, VAN ROOIJ, JACOBUS HUBERTUS MARIA
Applicants: VOLVO CAR ST.TRUIDEN N.V.
Application year: 1989
Main classification: F16H9
IPC codes: F16H9, F16G5