Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Nonwoven fabric – Including particulate material other than strand or fiber...
Reexamination Certificate
2000-11-06
2003-10-07
Dixon, Merrick (Department: 1774)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Nonwoven fabric
Including particulate material other than strand or fiber...
C442S073000, C442S101000, C442S148000, C442S074000, C428S304400, C428S332000, C428S364000, C428S367000, C428S292100, C427S203000, C427S386000, C427S201000
Reexamination Certificate
active
06630416
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a non-asbestos, non-metallic fibrous base material comprising a first layer of fibrillated aramid fibers, (and optionally cotton fibers, carbon fibers, carbon particles and a filler material, such as diatomaceous earth) and a second layer of friction modifying particles. The invention further relates to a composite friction material comprising the above described fibrous base material impregnated with a phenolic resin or a phenolic based resin blend.
The friction material of the present invention has improved anti-shudder characteristics and improved strength, porosity, wear resistance and noise resistance.
BACKGROUND ART
New and advanced transmission systems and braking systems are being developed by the automotive industry. These new systems often involve high energy requirements. Therefore, the friction materials technology must be also developed to meet the increasing energy requirements of these advanced systems.
In particular, a new high energy type friction material is needed. The new high energy friction material must be able to withstand high speeds wherein surface speeds are up to about 65 m/seconds. Also, the friction material must be able to withstand high facing lining pressures up to about 1500 psi. It is also important that the friction material be useful under limited lubrication conditions.
The friction material must be durable and have high heat resistance in order to be useful in the advanced transmission and braking systems. Not only must the friction material remain stable at high temperatures, it must also be able to rapidly dissipate the high heat that is being generated during operating conditions.
The high speeds generated during engagement and disengagement of the new transmission and braking systems mean that a friction material must be able to maintain a relatively constant friction throughout the engagement. It is important that the frictional engagement be relatively constant over a wide range of speeds and temperatures in order to minimize “shuddering” of materials during braking or the transmission system during power shift from one gear to another. It is also important that the friction material have a desired torque curve shape so that during frictional engagement the friction material is noise or “squawk” free.
In particular, transmission and torque-on-demand systems incorporate slipping clutches mainly for the fuel efficiency and driving comfort. The role of the slip clutch within these systems varies from vehicle launching devices, such as wet start clutches, to that of a torque converter clutches. According to the operating conditions, the slip clutch can be differentiated into three principle classes: (1) Low Pressure and High Slip Speed Clutch, such as wet start clutch; (2) High Pressure and Low Slip Speed Clutch, such as Converter Clutch; and (3) Extreme Low Pressure and Low Slip Sped Clutch, such as neutral to idle clutch.
The principal performance concerns for all applications of the slip clutch are the prevention of shudder and the energy management of the friction interface. The occurrence of shudder can be attributed to many factors including the friction characteristics of the friction material, the mating surface's hardness and roughness, oil film retention, lubricant chemistry and interactions, clutch operating conditions, driveline assembly and hardware alignment, and driveline contamination. The friction interface energy management is primarily concerned with controlling interface temperature and is affected by the pump capacity, oil flow path and control strategy. The friction material surface design also contributes to the efficiency of interface energy management.
Previously, asbestos fibers were included in the friction material for temperature stability. Due to health and environmental problems, asbestos is no longer being used. More recent friction materials have attempted to overcome the absence of the asbestos in the friction material by modifying impregnating paper or fiber materials with phenolic or phenolic-modified resins. These friction materials, however, do not rapidly dissipate the high heat generated, and do not have the necessary heat resistance and satisfactory high coefficient of friction performance now needed for use in the high speed systems currently being developed.
The present invention is an improvement over the Seitz U.S. Pat. No. 5,083,650 reference which involves a multi-step impregnating and curing process; i.e., a paper impregnated with a coating composition, carbon particles are placed on the paper, the coating composition in the paper is partially cured, a second coating composition is applied to the partially cured paper, and finally, both coating compositions are cured.
In other friction materials, metallic fibers combined with carbon materials were included in the friction material for wear resistance. For example, Fujimaki et al. U.S. Pat. No. 4,451,590 describes a friction material having metallic fibers, filler, carbon particles, carbon fibers and phenolic resin. However, the metallic based friction materials do not have sufficient porosity and compressibility to be capable of high fluid permeation capacity during use. Also, the metallic based friction materials are not sufficiently resilient or elastic, yet resistant to compression set to be capable of withstanding high facing lining pressures of up to about 1500 psi (approximately 105 kg/cm
2
). The metallic based friction material also is not capable of withstanding high surface speeds of up to about 65 m/second which are generated during engagement and disengagement of the new transmission and braking systems.
The present invention is also an improvement over earlier co-owned patents by the assignee herein, BorgWarner Inc., for friction materials. In particular, U.S. Pat. No. 5,998,307 relates to a friction material having a base impregnated with a curable resin where a porous primarily layer comprises at least one fibrous material and a secondary layer comprises carbon particles covering at least about 3 to about 90% of the surface of the primary layer. The U.S. Pat. No. 5,858,883 relates to a base material having a primary layer of less fibrillated aramid fibers, synthetic graphite, and a filler, and a secondary layer comprising carbon particles on the surface of the primary layer. U.S. Pat. No. 5,856,224 relates to a friction material comprising a base impregnated with a curable resin. The primary layer comprises less fibrillated aramid fibers, synthetic graphite and filler; the secondary layer comprises carbon particles and a retention aid. The U.S. Pat. No. 5,958,507 relates to a process for producing the friction material where at least one surface of the fibrous material which comprises less fibrillated aramid fibers is coated with carbon particles and a retention aid when at least 3 to 90% of the surface, impregnating with a phenolic or modified phenolic resin and curing. The U.S. Pat. No. 6,001,750 relates to a friction material comprising a fibrous base material impregnated with a curable resin. The porous primarily layer comprises less fibrillated aramid fibers, carbon particles, carbon fibers, filler material, phenolic novoloid fibers, and optionally, cotton fibers. The secondary layer comprises carbon particles which cover the surface at about 3 to about 90% of the surface.
It is to be understood that the various primary layers described in the above-referenced BorgWarner patents are useful with the present invention and are fully incorporated herein by reference.
In addition, various base materials, as described in commonly owned BorgWarner Inc. U.S. Pat. Nos. 5,753,356 and 5,707,905 (which describe base materials comprising less fibrillated aramid fibers, synthetic graphite and filler) are also contemplated as being useful with the present invention and as such are fully incorporated herein by reference. Yet another commonly owned patent, U.S. Pat. No. 6,130,176, relates to non-metallic fibrous base materials comprising less fibrillated aramid fibers, carbon fibers
Chen Yih Fang
Lam Robert C.
Borg-Warner Inc.
Dixon Merrick
Emch, Schaffer, Schaub & Porcello & Co., L.P.A.
LandOfFree
Friction material formed by deposition of friction modifiers... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Friction material formed by deposition of friction modifiers..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Friction material formed by deposition of friction modifiers... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3135766