Segmented friction member

Abstract: A segmented friction member (10) for use in a clutch assembly. The friction member is circular and constructed from a paper-like friction layer. An oil groove (20) extends completely through each friction member segment defining inner and outer segments joined by first (22) and second (23) bridges positioned adjacent the fluid inlet and fluid outlet, respectively.

Description: Background of the Invention Circular friction members are well known in the art and are often used in clutch assemblies. The term clutch assembly as used in the present specification and claims is used as a generic term and includes apparatus such as torque converters in addition to many other "clutches". United States Patent No. 5,669,474 discloses the use of a circular friction lining used in a torque converter assembly. This patent also discloses oil grooves defined in the friction lining. The friction members are often constructed from a paper based friction material having a frictional outer surface. The generally circular friction member is positioned on one or both sides of a circular support disc, which is normally a metal disc. This overall disk assembly is then positioned within a clutch assembly. Segmented friction members are also known in the art. A segmented friction member is, for example, shown in United States Patent No. 5,332,075. It is also known in the prior art to provide grooves in the friction lining to serve as paths for a cooling fluid, such as oil. The oil is used to cool the disc assembly. For efficient cooling, the volume of oil must be substantial. At one time in the prior art, the groove depth in the prior art friction members was approximately 25% to 50% of the thickness of the friction member. However, to increase the cooling capacity, it is not unusual to extend the oil groove completely through the friction member. This maximizes the heat transfer from the oil coming in direct contact with the support plate. It has been found that these through grooves in the prior art render the prior art friction member weak and difficult to handle before bonding to a support plate. With the oil groove extending completely through the prior art friction member, it was often necessary to cut the oil grooves after bonding the prior art friction member to the support plate or in the alternative, to use a separate support member, such as a support ring to hold the pieces of the prior art friction member segments in a proper position before bonding to the support disc or plate. The support rings were removed after bonding. EP 0838611 discloses a hydrokinetic device having a clutch assembly which utilises paper-based friction rings. The friction rings have circumferentially overlapping portions which define oil grooves therebetween the portions defining each oil groove, being connected together by a bridge portion which restricts the flow area of the groove. Summary of the Invention The present invention provides a segmented friction member for use in a clutch assembly, the friction member being generally circular with circular inner and outer peripheries and having a top surface and a bottom surface, said friction member including a plurality of arcuate segments having opposed ends engaged with mating ends of adjoining arcuate segments, an elongated oil groove defined in each arcuate segment and extending in a generally arcuate path, said oil groove separating the arcuate segment into inner and outer elongated sections the oil groove having a first end in communication with an oil groove inlet adjacent the outer periphery of the friction member and a second end in communication with an oil outlet adjacent the inner periphery of the friction member, and first and second bridges extending across each oil groove between the inner and outer sections of the arcuate segment and connecting said inner and outer sections, the oil groove extending completely through the arcuate segment except at the location of the bridges, the first bridge being positioned adjacent the oil inlet the oil groove at the first bridge having a smaller flow channel area than the oil groove adjacent the first bridge, the second bridge being positioned adjacent the oil outlet, and the oil groove at the second bridge being wider than and having the same flow channel area as the oil groove adjacent the second bridge. One preferred use of the friction member is in a torque converter. With the present invention, a desired pressure increase occurs at the inlet, due to the reduced flow channel area there, whereas there is no pressure build-up at the second bridge, adjacent the outlet, thus allowing an unrestricted flow of oil at the outlet and hence, an improved cooling of the clutch assembly. Advantageously, the friction member can comprise a paper based friction layer and each of the bridges can be formed by compressing a portion of the friction layer. A bridge thickness of between 50% and 75% of the thickness of the friction member has been found to be advantageous. Further advantageously, the oil groove can define a serpentine path, longer than the arc between the oil inlet and the oil outlet. Brief Description of the Drawings Fig. 1 is a plan view of a segmented friction member, according to the present invention; Fig. 2 is a cross-sectional view, on an enlarged scale, taken along the line that 2-2 of Fig. 1; Fig. 3 is a cross-sectional view, on an enlarged scale, taken along the line 3-3 of Fig. 1; Fig. 4 is a cross-sectional view, on an enlarged scale, taken along the line 4-4 of Fig. 1; Fig. 5 is a cross-sectional view, on an enlarged scale, taken along the line 5-5 of Fig. 1; Fig. 6 is a plan view of a segment of another embodiment of a friction member, according to the present invention; and Fig. 7 is a perspective view of a disc assembly including the Fig. 6 embodiment of a segmented friction member, according to the present invention. Detailed Description of the Preferred Embodiments Referring to Fig. 1 a segmented friction member, according to the present invention, is indicated in Fig. 1 by the reference number 10. The friction member is circular and is normally constructed of a paper-like material. However, the friction member 10 may be constructed from other materials such as plastics, metals, nylon and carbon, including non-woven carbon materials. The segmented friction member 10 has a top surface 11 and a bottom surface 12. The segmented friction member 10 includes a plurality of arcuate segments 14a, 14b, 14c, 14d, and 14e. Each of the segments 14a-14e has opposed ends 15 and 16. In the present embodiment, the opposed end 15 defines a tab 17 while the opposed end 16 defines a mating recess 18. The opposed ends 15 and 16 of the segments 14a-14e mate with one another as shown in Fig. 1 to form the overall circular segmented friction member 10. Each of the segments 14a-14e defines an elongated oil groove 20. In the present embodiment, illustrated in Fig. 1, the oil groove 20 has a serpentine path extending along the arcuate length of the segment 14 and extends completely through the segments 14 with the exception of a pair of bridges 22 and 23. Normally, two bridges are utilized. However, more bridges can be used and fall within the scope of the present invention. Each of the segments 14a-14e defines an oil inlet 25 adjacent the outer periphery 26 of the friction member 10 and an oil outlet 27 adjacent the inner periphery 28 of the friction member 10. Preferably the bridge 22 is positioned adjacent the oil inlet 25 and the bridge 23 is positioned adjacent the oil outlet 27. Additional oil inlets and outlets may be provided, which communication with the groove 20. The remainder of the oil groove 20 extends completely through the segmented friction member 10 from the top surface 11 to the bottom surface 12. The ;present construction allows the segmented friction member 10 to be die cut during manufacture as opposed to, for example, having the oil groove milled after the friction member 10 is adhered or positioned on the support plate of the overall disc assembly. By having the oil groove 20 extended completely through the segmented friction member 10, maximum desired fluid cooling is achieved. The bridges 22 and 23 are normally formed with a forming die which compresses the bridges 22 and 23 to their desired thickness. In a preferred embodiment, the bridges 22 and 23 are integral with inner section 24 and outer section 29. The bridges 22 and 23 hold the inner section 24 and outer section 29 together as a unit even though the remaining portion of the oil groove 20 extends from the top surface 11 to the bottom surface 12. In the embodiment shown in Fig. 1, the inlet bridge 22 is compressed less than 50% of the depth defined by the top surface 11 and bottom surface 12 of the friction member 10. The height or thickness of the bridges 22 and 23 is between 50% and 75% of the thickness of the lining or friction member 10. Preferably, the inlet 22 has a thickness of 70% of the thickness of the friction member 10. The outlet bridge 23 has a preferable thickness of approximately 50% of the thickness of the friction member 10. This restricts oil flow across the bridge 22, thereby adjusting the pressure of the oil within the groove 20. Fig. 2 illustrates a cross-section of the oil groove 20 at the location of the bridge 22. A reduced area flow channel 30 is illustrated while Fig. 3 shows a cross-section of the oil groove 20 immediately on the downstream side of the bridge 22. A completely open flow channel section 31 is shown. At the other end of the segments 14, the outlet bridge 23 (see Fig. 5) has a reduced thickness and defines a more open flow channel 33. The oil groove 20 has a narrower width flow channel 34 than the flow channel 33 at the bridge location in Fig. 5. The flow channel 33 has been widened to provide the same flow area as in found in the flow channel 34, illustrated in Fig. 4. Therefore, because the areas of the flow channels 33 and 34 are the same, there is no flow restriction or change of pressure at the location of the bridge 23. Normally, the thickness of the bridges 22 and 23 are 75% to 50% of the overall thickness of the segments 14a-14e, as defined by the top surface 11 and bottom surface 12. As indicated above, the first bridge 22 is compressed during bonding to restrict or control the flow rate while the second bridge 23 is compressed forming a wider channel 33 to maintain the oil groove cross-sectional area so as not to restrict oil flow. The bridges may be designed to control the restriction of the inlet or outlet or to render the bridges non-restrictive. The segmented friction member 10, according to the present invention, utilizes significantly less friction material than that of a full friction material ring and is more economical as compared to cutting the oil grooves after bonding or using a support ring to hold the separated segments together during bonding and then removing the supporting ring. Another embodiment of a segmented frictional member, according to the present invention is shown in Figs. 6 and 7 and is generally indicated by the reference number 40. The segmented friction member 40 is again constructed preferably of a friction paper layer and is mounted on a cover, piston or plate 41. When used in a torque converter, the plate 41 would normally include drive teeth (not shown) on the outer circumference or on the inner periphery. In the present embodiment, referring to Fig. 7, a second segmented friction member 40 is mounted on the opposite side of the plate or disc 41 to form an overall disc assembly 42. The segmented friction member 40 includes a plurality of interlocked segments 44a-44e. As best shown in Fig. 6, each of the segments 44a-44e includes a first end 46 which defines a recess 47 and a second end 48 which defines a tab 49. The tabs and recesses 47 and 49 of the segments 44a-44e, are interlocked with the adjacent segments to form the complete circular segmented friction member 40, as shown in Fig. 7. A groove 51 extends completely through the individual segments 44a-44e and follows a path which is generally concentric with the outer periphery 52 of the friction member 40. An inlet 54 extends from the outer periphery. 52 and an outlet 56 extends from the opposite end of the groove 51 to an inner circumference 57 of the segmented friction member 40. A first bridge 59 is provided at the fluid inlet 54 adjacent the groove 51 and a second bridge 60 is provided in the fluid outlet 56 adjacent the groove 60. In the present embodiment, the thickness of the bridge 59 is more than 50% of the thickness of the segmented friction member 40 while the second bridge 60 is approximately 50% of the thickness of the segmented friction member 40. Normally, the bridges are compressed to a thickness of between 50% and 75% of the thickness of the friction member. Therefore, as fluid, such as oil enters the inlet 54, the area of the inlet is reduced at the first bridge 59 thereby increasing the pressure a desired amount while the cross-sectional area of the second bridge 60 closely approximates the adjacent area of the oil groove 60. This allows a flow of cooling fluid, such as oil across the second bridge 60 without a pressure build up.

Claims: A segmented friction member (10; 40) for use in a clutch assembly, the friction member being generally circular with circular inner and outer peripheries (28; 57 and 26; 52) and having a top surface (11) and a bottom surface (12), said friction member including a plurality pf arcuate segments (14a to 14e; 44a to 44e) having opposed ends (15; 16) engaged with mating ends (17; 18) of adjoining arcuate segments, an elongated oil groove (20; 51) defined in each arcuate segment (14a to 14e; 44a to 44e) and extending in a generally arcuate path, said oil groove separating the arcuate segment into inner and outer elongated sections (24, 29) the oil groove (20; 51) having a first end in communication with an oil groove inlet (25; 54) adjacent the outer periphery (26; 52) of the friction member (10; 40) and a second end in communication with an oil outlet (27; 56) adjacent the inner periphery (28; 57) of the friction member (10; 40), and first and second bridges (22, 23; 59, 60) extending across each oil groove (20; 51) between the inner and outer sections (24, 29) of the arcuate segment and connecting said inner and outer sections, the oil groove (20; 51) extending completely through the arcuate segment except at the location of the bridges, the first bridge (22; 59) being positioned adjacent the oil inlet (25; 54) the oil groove (20; 51) at the first bridge (22; 59) having a smaller flow channel area than the oil groove (20; 51) adjacent the first bridge (22; 59), the second bridge (23; 60) being positioned adjacent the oil outlet (27, 56)and the oil groove (20; 51) at the second bridge (23; 60) being wider than and having the same flow channel area as the oil groove (20; 51) adjacent the second bridge (23; 60). A segmented friction member in accordance with claim 1, characterised in that the segmented friction member (10; 40) comprises a paper based friction layer (10; 40) and each of the bridges (22, 23; 59, 60) comprises a compressed portion of the paper based friction layer. A segmented friction member in accordance with claim 1 or 2, characterised in that the first and second bridges (22, 23; 59, 60) have a thickness of between 50% and 75% of the thickness of the friction member (10; 40). A segmented friction member according to any one of claims 1 to 3, characterised in that the oil groove (20; 51) defines a serpentine path, longer than the arc between the oil inlet (25; 54) and the oil outlet (27; 56). A segmented friction member according to any one of claims 1 to 4, characterised in that five arcuate segments (14a to 14e; 44a to 44e) are required to form a complete circular friction member (10; 40). An arcuate segment (14a to 14e; 44a to 44e) for use in the segmented friction member (10; 40) according to any of the preceding claims, the arcuate segment (14a to 14e; 44a to 44e) having opposed ends (15; 16) for engaging with mating ends (17; 18) of adjoining arcuate segments, an elongated oil groove (20; 51) extending in a generally arcuate path, said oil groove separating the arcuate segment into inner and outer elongated sections (24, 29) the oil groove (20; 51) having a first end in communication with an oil groove inlet (25; 54) adjacent the outer periphery (26; 52) of the arcuate segment and a second end in communication with an oil outlet (27; 56) adjacent the inner periphery (28; 57) of the arcuate segment, and first and second bridges (22, 23; 59, 60) extending across each oil groove (20; 51) between the inner and outer sections (24, 29) of the arcuate segment and connecting said inner and outer sections, the oil groove (20; 51) extending completely through the arcuate segment except at the location of the bridges, the first bridge (22; 59) being positioned adjacent the oil inlet (25; 54) the oil groove (20; 51) at the first bridge (22; 59) having a smaller flow channel area than the oil groove (20; 51) adjacent the first bridge (22; 59), the second bridge (23; 60) being positioned adjacent the oil outlet (27, 56)and the oil groove (20; 51) at the second bridge (23; 60) being wider than and having the same flow channel area as the oil groove (20; 51) adjacent the second bridge (23; 60).

Inventors: SULLIVAN CHRISTOPHER, SULLIVAN, CHRISTOPHER
Applicants: BORG WARNER INC, BORGWARNER INC.
Application year: 2001
Main classification: F16D13
IPC codes: F16D69, F16D13