Friction disc with segmented friction facing

Abstract: A friction disc (110) includes a pair of segmented friction facings (112) adhered to the opposing sides of annular core (114). The friction facings (112) are composed of three arcuate segments (116) of sintered material or paper impregnated with a resin interjoined together at match lines (118) located generally 120° apart. Each arcuate segment (116) includes opposed ends having tab and slot configurations which are designed to have a pair of arcuate edge lines (124, 126), (124', 126') located in an opposed relationship proximate the annular centerline of the width of the segment (116). An interconnector edge line (128), (128') is located angularly across the annular centerline of the segment (116) and joined tangentially to the arcuate match lines (124, 126), (124', 126'). The remaining end of each arcuate match line (124, 126), (124', 126') is then joined to the respective inside annular edge (134) and outside annular edge (136) of each arcuate segment (116).

Description: This invention relates to friction discs for use in clutch or brake assemblies. Friction plate facings are conventionally bonded to metal plates or cores to form friction discs which are then incorporated into interleaved clutch packs. The clutch packs, generally, are interconnected with inner hubs and outer drums of a clutch assembly and are commonly engaged and disengaged through the use of a hydraulically or spring actuated piston. The typical friction disc used in such clutch packs commonly incorporates an annular steel ring or core and a pair of friction facings which are bonded to the opposed sides of the core. The friction facings are commonly blanked out as one piece rings from continuous rolls of friction material such as a sintered metal or paper impregnated with a resin which is fed through a blanking press. As the costs of such friction paper raw material increase and as industry becomes more accountable for its scrap and the need to properly dispose of the scrap, it has become a major objective to economize the amounts of friction paper utilized in manufacturing friction facings and, concomitantly, reduce the amount of scrap or offal remaining without compromising the strength or integrity of the end product friction ring. One of the first proposed solutions for achieving greater economy in the manufacture of friction facings is featured in US-A-4 260 047 (Nels) which generally discloses a friction disc for use in a clutch or brake assembly, comprising an annular core plate and at least one substantially annular friction facing adhered thereto, the friction facing being composed of a plurality of arcuate segments with means for securing the segments together to form the friction facing. More particularly, Nels provides four ninety degree arcuate segments stamped from a rectangular sheet of pregrooved friction material. The segments are interconnected by opposed tab and slot structures to form a complete annular friction facing which is then bonded on to an annular metal core. It has been discovered, however, that the match lines or junctions formed between the facing segments when the arcuate segmented facings are interjoined to create the annular ring create areas of structural weakness in the overall integrity of the friction facing. It has been particularly noticed that match lines or junctions which are disposed ninety degrees apart suffer from the greatest potential for premature failure. Further, the opposed tab/slot configurations utilized by the facings of the type shown in Nels have shown a tendency to isolate the forces applied to the match lines on the facings to specific fragile areas of interconnection. This tendency may then also increase the potential for premature failure. Thus, it is an object of the present invention to reduce significantly the amounts of material utilized in the manufacture of friction facings without compromising the structural integrity of the final friction disc product. In accordance with the present invention as claimed, this object is achieved by the aforementioned generally disclosed friction disc wherein three such arcuate segments form the friction facing, and wherein the securing means include an interlocking tab and slot edge on one end of each of the arcuate segments and a mirror image tab and slot edge on the opposed end of each of the arcuate segments whereby the confrontinq tab and slot edges of the adjacent arcuate segments interconnect to create a match line angularly situated across the arc formed by the joinder of the two adjacent arcuate segments. The angular match line produced by the interconnecting tab and slot edges in the friction disc of the invention provides opposing forces on the match between the adjacent segments which emanate from the centre of the match line to provide resistance to forces applied in multiple directions, thereby equalizing the forces across the match line, by which to reinforce the match line area to prevent potential damage to the material of the friction facing prior to the final bonding thereof to the annular core plate. Preferably the segments from which the annular friction facing is formed each generally comprise a 120° arc. Thus, each annular facing includes three segments whose match lines are not separated by 90° intervals. Thus, the opposing forces encountered at the match lines or joints of the interjoined facings are easily absorbed without overstressing areas of structural weakness. It is envisaged that the facings may be assembled in such a manner as to permit the use of alignment pins for handling, orientation and alignment of the segments for assembly and bonding as well as oil circulation throughout the friction disc for cooling. Porous tape may be used to reinforce the match line between the segments. Attention is also drawn to US-A-4 674 616, issued to Mannino, which provides another solution to achieving a reduction in the waste amounts of friction material and the waste amounts of steel in the production of friction discs, wherein the annular core plate is also segmented with interlocking end portions to form the annular ring to which the segmented friction facings are bonded. Such a construction is, like the Nels proposal, prone to potential failure. In order that the present invention may be well understood there will now be described two embodiments thereof, given by way of example, reference being made to the accompanying drawings, in which: Fig. 1 is an elevational view of a prior art friction disc having four segmented friction facings with tab and slot configured match lines located on 90° orientations; Fig. 2 is an elevational view of a prior art friction disc having flat match lines located on a 90° orientation; Fig. 3 is a perspective view of a friction disc embodying the present invention having friction facings composed of three segments having match lines oriented 120° apart; Fig. 4 is an elevational view of the friction disc of Fig. 3; Fig. 5 is a sectional view of the match line taken along line 5-5 of Fig. 3; Fig. 6 is the sectional view of Fig. 5 showing the interlocked segments of Fig. 5 in a separated position; and Fig. 7 is a diagrammatic view of an alternative embodiment of friction disc with a more complex match line. Referring first particularity to Fig. 1, a common prior art embodiment of a friction disc 10 is shown wherein the friction facing 12 is adhered to an annular core 14. The facing 12 is composed of four individual arcuate segments 16 joined at match lines 18 to create the annular facing 12. Fig. 1 discloses a match line 18 similar to that disclosed by the aforementioned US-A-4 260 047 to Nels. These match lines 18 are formed from a tab 20 located at one end of the segment 16 engaging with a slot 22 located at the opposed end of an adjacent segment 16. Referring now to Fig. 2, another embodiment of a prior art friction disc 10' is shown having an annular friction facing 12' adhered to an annular core 14'. The facing 12' is composed of four individual arcuate segments 16' joined at match lines 18'. The match lines 18' are created from the ends of adjacent the segments 16' abutting one another to form the annular facing 12'. The embodiments shown in Figs. 1 and 2 represent common prior art facing segments that the present invention intends to improve upon. Referring now to Figs. 3 and 4, the preferred embodiment of the friction disc 110 of the present invention is shown. The friction disc 110 includes a pair of annular segmented friction facings 112 which are adhered to the opposed sides of an annular core 114. The friction facings 112 are composed of three arcuate segments 116 of sintered material or paper impregnated with a resin. The arcuate segments 116 are interjoined together at match lines 118 located generally 120° apart. In the preferred embodiment, each end of each arcuate segment 116 includes a tab and slot configuration, detailed in Figs. 5 and 6. The tab and slot configured edge 120 formed on one end of any given arcuate segment 116 is, preferably, the mirror image of the tab and slot configured edge 122 located on the opposed end of the given arcuate segment 116. Thus, when a series of three 120° segments 116 are laid end to end to form an annular friction ring 112, the edges 120, 122 of the juxtaposed segments 116 interjoin together to form the match line 118. Each tab and slot configured edge 120, 122 include a pair of arcuate edge lines 124, 126 and 124', 126' respectively, which are located in opposed relationship proximate the annular centreline of the width of the segment 116. The preferred diameter (D) of each arcuate edge line 124, 126 and 124', 126' is equal to 3/7 of the segment 116 width (W): D = 3/7W After the diameters of the arcuate edge lines 124, 126 and 124', 126' are calculated, the edge lines 124, 126 and 124', 126' are located along the centreline of the width of the segment 116 at each segment end. An interconnector edge line 128, 128' located angularly across the annular centreline of the segment 116, is tangentially engaged between the respective arcuate edge lines 124, 126 and 124', 126'. The remaining free end of each arcuate edge line 124, 126 and 124', 126' is tangentially engaged with a second arcuate edge line 130, 132 and 130', 132' respectively, which second arcuate edge line 130, 132 and 130', 132' is extended radially to the respective inside 134 and outside 136 annular edges of the arcuate segment 116. The preferred radius (R) for each of the second arcuate edge lines is equal to .08 of the segment 116 width (W): R = .08W The location of the centre of the radius R is, preferably, positioned perpendicularly to the interconnector edge line 128, 128' from the annular centreline of the segment 116 at a distance (d) equal to .3 of the segment width (W): d = .3W Thus, the second arcuate edge lines 130, 132 and 130', 132' are tangentially engaged with their respective arcuate edge lines 124, 126 and 124', 126' and then extended radially to their respective inside and outside annular edges 134, 136. The preferred angle between the radial extensions of the second arcuate edge lines is 3.4°. As seen in Figs. 3-6, the mirror image tab and slot edges 120, 122 located on each end of the segments 116 are joined to create a strong annular match line 118 across the centreline of the engaged arcuate segments 116. This shape of the match line 118 produced by the engaged tab and slot edges 120, 122 will provide for the distribution of opposing forces from the centre of each match line, allowing the opposing edges 120, 122 to provide resistance to forces in multiple directions. One tab and slot edge 120 will not receive stronger or greater forces than its mating tab and slot edge 122. Forces are equalized across the match line 118 with equivalent distributions. Referring now to Fig. 7, an alternative embodiment of the present invention is shown in which the mirror image tab and slot edge lines 220, 222 are generally formed at the one-third and two-third position of the width of the arcuate segment 216. The tab and slot edge lines 220, 222 are formed using the same principles that guided the design of the preferred embodiment, however, each edge line 220, 222 of each end of each arcuate segment 216 includes two pairs of arcuate edge lines 224A, 2248 and 224A', 224B' respectively, in opposition relationship with arcuate edge lines 226A, 226B and 226A', 226B' respectively. Each set of opposed arcuate edge lines 224A, 226A and 224A', 226A' are interjoined by an interconnector edge line 228A, and arcuate edge line 2248, 226B and 2248', 226B' are interjoined by an interconnector edge line 228B, 228B'. Lines 228A, 228A' and 2288, 2288' are extended tangentially between their respective opposed arcuate edge lines so as to angularly cross the one-third and two-third positions of the width of the segment 216. Each of the arcuate edge lines 224A, 2268 and 224A', 226B' positioned proximate the inside annular edge 234 and outside annular edge 236 of the arcuate segment 216 are tangentially engaged with respective second arcuate edge lines 230, 232 and 230', 232' respectively, which second arcuate edge lines 230, 232 and 230' and 232' are extended radially to the inside 234 and outside 236 annular edges, respectively. Thus, as with the preferred embodiment, the mirror image tab and slot edges 220, 222 of the embodiment shown in Fig. 7 are joined to create a strong angular match line 218 positioned across the width of the interjoined segments 216. The match line 218 produced by the engaged tab and slot edges 220, 222 will provide for opposing forces distributed in multiple directions, thereby equalizing the forces across the full match line. Finally, it is envisaged that these segmented facings which are typically assembled into full rings and then moved to a bonding machine for final bonding to a friction plate can be structurally fragile and can easily be damaged in the material handling process. To produce greater strength at the match lines of the annular friction facings, tape (not shown), preferably porous tape, is adhered to the segments over the match lines. The segments may then be locked together by the porous tape and this taped intersection may be used with match lines that vary from simple straight cuts to the complex interlocking tabs as shown in Figs. 3-6. The tape is placed on the segmented facings so that the end assembly of the friction disc has the porous tape sandwiched between the facing and the annular core plate during the bonding process. By using the sandwiched construction, the tape is permanently bonded into the assembly with no visible or functional evidence of the tape being present. Preferably the tape being used is of a porous paper or fibrous cloth material that has adhesive on one side. During the final bonding process, the porous tape will allow the bonding adhesive to saturate through the tape and bond the metal plate to the entirety of the friction material, through the porous tape.

Claims: A friction disc for use in a clutch or brake assembly, comprising an annular core plate (114) and at least one substantially annular friction facing (112) adhered thereto, the friction facing (112) being composed of a plurality of arcuate segments (116; 216) with means (120, 122; 220; 222) for securing the segments (116; 216) together to form the friction facing (112), wherein three such arcuate segments (116; 216) form the friction facing (112), and wherein the securing means (120, 122; 220; 222) include an interlocking tab and slot edge (120; 220) on one end of each of the arcuate segments (116; 216) and a mirror image tab and slot edge (122; 222) on the opposed end of each of the arcuate segments (116; 216), whereby the confronting tab and slot edges (120, 122; 220, 222) of adjacent arcuate segments (116; 216) interconnect to create a match line (118; 218) angularly situated across the arc formed by the joinder of the two adjacent arcuate segments (116; 216). A friction disc as claimed in claim 1, wherein each of the arcuate segments (116; 216) is formed as a 120° arc having a given radius. A friction disc as claimed in claim 1 or claim 2, wherein the tab and slot edges (120, 122; 220, 222) interconnect to create at least one other match line positioned to intersect the first-mentioned match line (118; 218) thereby creating at least one angle of intersection between the first match line (118; 218) and the other match line or lines. A friction disc as claimed in claim 3, wherein the angle of intersection is defined by the mating of a first arcuate edge line (124; 224A; 224B) on one of the adjacent arcuate segments (116; 216) with a second arcuate edge line (126'; 226A'; 226B') on the other of the adjacent arcuate segments (116; 216) as the arcuate segments (116; 216) are joined at the tab and slot edges (120, 122; 220, 222). A friction disc as claimed in claim 4, wherein the engagement of the tab and slot edges (120, 122; 220, 222) of the interjoined arcuate segments (116; 216) further creates a third match line positioned to intersect the first match line (118; 218) at an end opposed to the intersection by the second match line, thereby creating a second angle of intersection between the first match line (118; 218) and the second match line. A friction disc as claimed in claim 5, wherein the second angle of intersection is defined by the mating of a first arcuate edge line (124'; 224A'; 224B') on said other of the adjacent arcuate segments (116; 216) with a second arcuate edge line (126; 226A; 226B) on said one of the adjacent arcuate segments (116; 216) as the adjacent arcuate segments (116; 216) are joined at the tab and slot edges (120, 122; 220, 222). A friction disc as claimed in claim 6, wherein the first (124, 224A, 224B, 124', 224A', 224B') and second (126, 226A, 226B, 126', 226A', 226B') arcuate edge lines are positioned in opposition to each other. A friction disc as claimed in any of claims 4 to 7, wherein the first (124, 224A, 224B, 124', 224A, 224B') and second (126, 226A, 226B, 126', 226A', 226B') arcuate edge lines each have a diameter substantially equivalent to 3/7 of the width of the respective segment (116). A friction disc as claimed in claim 7 or claim 8, wherein the opposed arcuate edge lines (124, 126; 224A, 226A; 224B, 226B; 124', 126'; 224A', 226A'; 224B', 226B') are tangentially interjoined by an interconnector edge line (128; 228A; 228B; 128'; 228A'; 228B') angularly situated across the arc formed by the joinder of the adjacent, arcuate segments (116; 216), the interconnector edge lines (128, 128'; 228A, 228A'; 228B, 228B') of the respective interjoined segments (116; 216) matching to create the first match line (118; 218). A friction disc as claimed in any of claims 7 to 9, wherein the first (124, 124') and second (126, 126') arcuate edge lines are substantially centred between the inside arcuate edge (134) and the outside arcuate edge (136) of the respective arcuate segment (116). A friction disc as claimed in claim 9, wherein the tab and slot edge (220) on said one end of each of the arcuate segments (216) includes a pair of said first arcuate edge lines (224A, 224B) and a pair of said second arcuate edge lines (226A, 226B) which are respectively positioned in opposition to the pair of first arcuate edge lines (224A, 224B), one (224A) of the pair of first arcuate edge lines (224A, 224B) and the one (226A) of the pair of second arcuate edge lines (226A, 226b) which is positioned in opposition thereto being oriented generally one-third of the radial distance from the outside arcuate edge (236) of the segment (216) to the inside arcuate edge (234) thereof, and the other (224B) of the pair of first arcuate edge lines (224A, 224B) and the other (226B) of the pair of second arcuate edge lines (226A, 226B) positioned in opposition thereto being oriented generally two-thirds of the radial distance from the outside arcuate edge (236) to the inside arcuate edge (234); and the tab and slot edge (222) on said opposed end of each of the arcuate segments (216) includes a pair of said first arcuate edge lines (224A', 224B') and a pair of said second arcuate edge lines (226A', 226B') which are respectively positioned in opposition to the pair of first arcuate edge lines (224A', 224B'), one (224A') of the pair of first arcuate edge lines (224A', 224B') and the one (226A') of the pair of second arcuate edge lines (226A', 226B') which is positioned in opposition thereto being oriented generally one-third of the radial distance from the outside arcuate edge (236) to the inside arcuate edge (234), and the other (224B') of the pair of first arcuate edge lines (224A', 224B') and the other (226B') of the pair of second arcuate edge lines (226A', 226B') positioned in opposition thereto being oriented generally two-thirds of the radial distance from the outside arcuate edge (236) to the inside arcuate edge (234). A friction disc as claimed in claim 11, wherein the tab and slot edge (220) on said one end of each of the arcuate segments (216) further includes a pair of said interconnector edge lines (228A, 228B) a first said interconnector edge line (228A) being angularly positioned to engage tangentially the first arcuate edge lines (224A) with the second arcuate edge line (226A), and a second said interconnector edge line (228B) being angularly positioned to engage the first arcuate edge line (224B) with the second arcuate edge line (226B), the first arcuate edge line (224A) and the second arcuate edge line (226B) being connected together at a position substantially radially centred between the inside arcuate edge (234) and the outside arcuate edge (236); and the tab and slot edge (222) on said opposed end of each of the arcuate segments (216) further includes a pair of said interconnector edge lines (228A', 228B'), a first said interconnector edge line (228A') being angularly positioned to engage tangentially the first arcuate edge line (224A') with the second arcuate edge line (226A'), and a second said interconnector edge line (228B') being angularly positioned to engage tangentially the first arcuate edge line (224B') with the second arcuate edge line (226B'), the first arcuate edge line (224B') and the second arcuate edge line (226A') being further connected together at a position substantially centred between the inside arcuate edge (234) and the outside arcuate edge (236). A friction disc as claimed in any of the preceding claims, wherein the securing means further includes porous tape applied across the match line created by the joinder of the two arcuate segments (116; 216) at the confronting tab and slot edges (120, 122; 220, 222). A friction disc as claimed in claim 13, wherein the friction facing (112) is oriented with respect to the core plate (114) such that said tape is interposed between the friction facing (112) and the core plate (114).

Inventors: GRONOWSKI GERALD, HYKEN SHAWN, QUIGLEY JAMES, VEIT RICHARD, GRONOWSKI, GERALD, HYKEN, SHAWN, QUIGLEY, JAMES, VEIT, RICHARD
Applicants: BORG WARNER AUTOMOTIVE, BORG-WARNER AUTOMOTIVE, INC.
Application year: 1993
Main classification: F16D13
IPC codes: F16D65, F16D13