[0001] The present invention relates to friction clutches and plates, and more particularly to a wet-type friction clutch with a plurality of friction plates, each plate having a segmented friction material. Such friction clutches may be uses for example in motor vehicle transmissions.

BACKGROUND

[0002] The friction material in wet-type friction clutches generally operates in an oil submerged environment and is often paper-based material used to form friction material rings. To reduce waste during manufacture, the wet friction material ring may be stamped out in segments and then bonded to the plate to form the friction material rings. However, the edges between the segments can cause premature material failure and reduce the life of the wet friction material. One reason for premature material failure is due in part to the ability of fluid to enter the uncompressed edge of the cut joint.

[0003] U.S. Patent No. 6,585,096 describes a joint with reduced thickness and U.S.

Patent No. 7,165,664 has a depressed fiat area at the joint.

SUMMARY OF THE INVENTION

[0004] Highly compressing the entire segment at the joint can improve durability, but the reduced thickness caused by compressing at the joint also can lead to fluid flow between the inner diameter and the outer diameter of the friction material ring and cause some oil leakage during engagements.

[0005] The present invention provides a friction material part comprising a first segment and a second segment, an end of the first segment overlapping an end of the second segment to form a joint that is compressed more than intermediate portions of the first and second segments.

[0006] The present invention also provides a method for manufacturing a friction material part comprising overlapping an end of a first friction material segment and an end of a second friction material segment; and compressing the overlapped ends to form a compressed joint.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present invention will be further described in a non-limiting manner on the basis of the drawing of preferred embodiments in which:

[0008] Figs, la, lb and l c show schematically a process of forming a friction material part according to one embodiment of the present invention;

[0009] Fig. 2 shows a friction plate comprising four of the segments shown in the embodiment of Figs, la, lb and l c; and

[00010] Fig. 3 shows schematically a friction clutch with a plurality of the friction plates shown in Fig. 2.

DETAILED DESCRIPTION

[00011] Figs, la, lb and l c show schematically a process of forming a friction material part 10 according to one embodiment of the present invention. In one preferred embodiment, friction material part 10 is made of a fibered textile composite friction lining. As shown in a schematic side view in Fig. la, two separate friction material segments 12, 14 each included respective first ends 12a, 14a and second ends 12b, 14b. Friction material segments 12, 14 are aligned such that second end 12b and first end 14a overlap each other, with second end 12b being on top of first end 14a. In this preferred embodiment, friction material segments 12, 14 are of the same thickness T and both friction material segments 12, 14 are of a uniform thickness throughout their length. Friction material segments 12, 14 may include glue or another adhesive on their entire lower surfaces. For example, friction material segments 12, 14 may be cut from a roll of friction material and the adhesive may applied to the back of the entire material strip, usually before the entire material strip is cut into segments 12, 14 from the roll of friction material (i.e., the roll of friction material is unwrapped, adhesive is applied to the back side, then each segment is cut out and applied to the plate, on for example base 120 shown in Fig. 2). In one alternative embodiment, the adhesive may be applied to the plate itself. Overlapping ends 12b, 14a may then be bonded together at a bonding area 16 by highly compressing the overlapping ends 12b, 14a as they are joined by the adhesive to form friction material part 10 shown in a schematic side view in Fig. lb and in a schematic perspective view in Fig. l c. In alternative embodiments, overlapping ends 12a, 14b may highly compressed before or after they are bonded by the adhesive. Overlapping ends 12a, 14b may be highly compressed, for example by stamping using a die, so that joint 18 is made of highly compressed friction material by flattening overlapping ends 12a, 14b. The separate friction material segments 12, 14 may be compressed to a degree before they are brought together, bonded and highly compressed.

Accordingly, as used herein, highly compressed describes a degree of compression that is greater than the degree of compression, if any, of the separate friction material segments 12, 14 before they are brought together.

[00012] Friction material segment 10 has two ends 12a, 14b, with ends 12b, 14a of friction material segments 12, 14 being bonded to form joint 18. In this embodiment, friction material part 10 has a uniform thickness, with ends 12a, 14b having the same thickness as joint 18. The compressing of ends 12b, 14a during the bonding of friction material segments 12, 14 provides a durable joint 18, while the uniform thickness of friction material part 10 may prevent fluid from flowing across friction material segment at joint 18.

[00013] The thick compressed joint 18 in this embodiment thus can provide friction area to reduce unit pressure for a friction plate, while also aiding in preventing oil seepage between an inner diameter ID and an outer diameter OD.

[00014] As shown for example in Fig. 2, friction plate 100 comprises a base 120, for example a plate made of metal, and a friction surface formed of four segments, including segments 12, 14 shown in the embodiment of Figs, la, lb, lc and two other segments 112, 114 similar to segments 12, 14. Segments 12, 14, 112, 114 are bonded to adjacent segments to form friction ring 150 having four joints 18, 118, 218, 318. Both ends of each segment 12, 14, 112, 114 are highly compressed at the corresponding joints 18, 118, 218, 318 and bonded together with adhesive. These segments 12, 14, 112, 114 can for example be glued or otherwise adhered to base 120 to form friction ring 150 of friction plate 100. The ends of segments 12, 14, 112, 114 can be curved to fit together as shown, although other edge shapes are possible such as interlocking edges. [00015] In a preferred embodiment, segments 12, 14, 112, 114 may be aligned in a ring shape with ends of segments 12, 14, 112, 114 overlapping with ends of adjacent segments. For example, ends 14a, 12b overlap each other as shown in Fig. l a, and in a similar manner, ends 114a, 14b overlap each other, ends 112a, 114b overlap each other and ends 12a, 112b overlap each other. Adhesive may be placed 12, 14, 112, 114 on segments as described above with respect to segments 12, 14. The overlapping ends may then all be compressed, for example by stamping using a die, at the same time so that ends 14a, 12b form joint 18, ends 114a, 14b form joint 118, ends 112a, 114b form joint 218 and ends 12a, 112b form joint 318 simultaneously and the overlapping ends are flattened. In alternative embodiments, joints 18, 118, 218, 318 may be formed sequentially or joints 18, 118, 218, 318 may be formed in pairs. Also, in further embodiments, the ends may be overlapped and brought together by adhesive sequentially, then compressed together at the same time.

[00016] In a preferred embodiment, after highly compressed joints 18, 118, 218, 318 are formed and segments 12, 14, 112, 114 are bonded together to form friction ring 150, friction ring 150 has a uniform thickness. Flow between outer diameter OD and inner diameter ID is thus blocked by or reduced by joints 18, 118, 218, 318, which may provide improved durability. As noted above, in this preferred embodiment, segments 12, 14, 112, 114 are of the same uniform thickness before being joined and compressed. Accordingly, ends of segments 12, 14, 112, 114 are compressed by approximately fifty percent on average to form joints 18, 118, 218, 318, making the ends of segments 12, 14, 112, 114 approximately twice as dense as intermediate portions 12c, 14c, 112c, 114c extending between joints 18, 118, 218, 318. In alternative embodiments, segments 12, 14, 112, 114 may not be of uniform thickness. For example, depending on the desired compression and density of ends 12a, 12b after bonding to form joints 18, 318, segment 12 may be formed such that ends 12a, 12b are thicker or thinner than intermediate portion 12c before ends 12a, 12b are highly compressed. If joints 18, 318 and correspondingly ends 12a, 12b are desired to be less than twice as dense as intermediate portion 12c, ends 12a, 12b may be thinner than intermediate portion 12c before ends 12a, 12b are overlapped with ends 112b, 14a, respectively, and flattened. If joints 18, 318 and

correspondingly ends 12a, 12b are desired to be more than twice as dense as intermediate portion 12c, ends 12a, 12b may be thicker than intermediate portion 12c before ends 12a, 12b are overlapped with ends 112b, 14a, respectively, and flattened. [00017] Fig. 3 shows schematically a wet-type friction clutch 50 of a motor vehicle transmission having a plurality of friction plates 100, 200, 300, with friction plates 200, 300 being similar to friction plate 100 as described in Fig. 2 for example. The axially-movable plates 100, 200, 300 can be pressed against axially-movable separator plates by a piston 52, for example a hydraulically-actuated piston, to provide frictional engagement.

[00018] The highly compressed ends can be manufactured by compressing the ends of a friction material segment while leaving a further part of the friction material segment uncompressed. While two or more segments may be used to form a ring, preferably at least four are used to form a ring. Other embodiments are within the scope of the claims.