Coupling assembly including wet friction material with colloidal silica coating

Abstract

A coupling assembly for a motor vehicle powertrain includes a rigid carrier and a wet friction material attached to a surface of the rigid carrier. The wet friction material includes a base material enclosing a fiber matrix and filler particles embedded in the fiber matrix; a binder embedded in the base material; and a colloidal silica coating applied to an outer surface of the base material.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Non-Provisional Application No. 17 / 681,307, filed February 25, 2022, the entire disclosure of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates generally to friction clutches and disks used in torque converters and other automotive powertrain components, and more particularly to a clutch assembly incorporating a wet friction material. BACKGROUND

[0003] The friction material in wet friction clutches is generally used in an oil-immersed environment and is typically a paper-based material used to form friction material rings. It is known to form the friction material through a papermaking process using a Fourdrinier machine. SUMMARY

[0004] A clutch assembly for an automotive drivetrain includes a rigid carrier and a wet friction material secured to a surface of the rigid carrier. The wet friction material includes a base material including a fiber matrix and filler particles embedded in the fiber matrix; a binder embedded in the base material; and a colloidal silica coating applied to an outer surface of the base material.

[0005] In some embodiments of the coupling assembly, the base material in which the binder is embedded may include 25 to 45 wt.% fibers, 25 to 40 wt.% filler material, and 25 to 40 wt.% binder. The filler material may include calcined kaolin clay. The base material in which the binder is embedded may include 25 to 45 wt.% fibers, 10 to 20 wt.% diatomaceous earth, 15 to 30 wt.% calcined kaolin clay, and 30 to 40 wt.% tung oil-modified phenolic resin. The base material in which the binder is embedded may include 28 to 38 wt.% fibers, 28 to 38 wt.% filler material, and 30 to 35 wt.% binder. The base material in which the binder is embedded may include 28 to 38 wt% fibers, 10 to 20 wt% diatomaceous earth, 18 to 28 wt% calcined kaolin clay, and 30 to 40 wt% tung oil modified phenolic resin.The base material in which the binder is embedded may include 28 to 38 wt% fibers, 8 to 18 wt% diatomaceous earth, 15 to 25 wt% calcined kaolin clay, and 30 to 35 wt% tung oil-modified phenolic resin. The base material in which the binder is embedded may include 20 to 35 wt% cellulose fibers, 5 to 15 wt% aramid fibers, 20 to 35 wt% diatomaceous earth and / or calcined kaolin clay, 1 to 5 wt% carbon fibers, 1 to 15 wt% graphite, and 30 to 35 wt% phenolic resin. The base material in which the binder is embedded may include 25 to 30 wt% cellulose fibers, 5 to 10 wt% aramid fibers, 25 to 35 wt% diatomaceous earth and / or calcined kaolin clay, 2 to 4 wt% carbon fibers, 1 to 5 wt% graphite, and 30 to 35 wt% phenolic resin. The colloidal silica coating may be formed from colloidal silica particles with an average diameter of 20 to 25 nm.

[0006] Also provided is a method for manufacturing a clutch assembly for a motor vehicle. The method includes attaching a wet friction material to a surface of a rigid substrate, providing a base material comprising a fiber matrix and filler particles and a binder embedded in the fiber matrix; and applying a solution containing colloidal silica to an outer surface of the base material to form a colloidal silica coating on the base material.

[0007] In some embodiments of the method, attaching the wet-running friction material to the surface of the rigid support may include attaching the base material to the rigid member to provide a cured base material on the rigid member, and applying the colloidal silica-containing solution to the outer surface of the base material to form the colloidal silica coating on the cured base material after attaching the base material to the rigid member. The method may further include curing the binder prior to applying the colloidal silica-containing solution to the outer surface of the base material to form the colloidal silica coating on the base material. The colloidal silica-containing solution may include 30 to 50 wt.% colloidal silica and 50 to 60 wt.% water.Particles of colloidal silica may be spherical and non-porous. Particles of colloidal silica may have an average diameter of 20 to 25 nm. Applying the colloidal silica-containing solution to the outer surface of the base material to form the colloidal silica coating on the base material may involve applying a concentration of 1 to 10 mg / cm. 2 of the suspension onto the base material. The base material may include 30 to 45 wt.% fibers, 25 to 35 wt.% filler material, 1 to 15 wt.% friction modifiers, and 25 to 40 wt.% binder.

[0008] A method of manufacturing a wet friction material includes providing a base material including a fiber matrix and filler particles and a binder embedded in the fiber matrix; and applying a solution containing colloidal silica to an outer surface of the base material to form a colloidal silica coating on the base material. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present disclosure will be described below with reference to the following drawings in which: Fig. 1a schematically shows a wet friction material in which a binder is added to the base material; Fig. Figure 1b schematically shows the binder-impregnated base material and a rigid part joined together to form a friction assembly; Fig.Figure 1c schematically shows a colloidal silica-containing solution applied to the base material to form a colloidal silica coating on the base material. Fig. Figure 2 shows a graph illustrating the benefits of coating the wet friction base material with a colloidal silica coating; Fig. 3 shows a wet friction material layer connected to clutch discs in a clutch pack; and Fig. 4 shows a wet friction material layer connected to a clutch disc in a torque converter. DETAILED DESCRIPTION

[0010] Next-generation wet friction materials for electric and hybrid applications must deliver higher torque, which requires a higher coefficient of friction. To achieve this, the friction material must achieve and maintain the desired coefficient of friction.

[0011] The present disclosure provides a friction material comprising a base material formed from fibers, fillers, a binder, and optionally one or more friction modifiers. The base material is coated with a colloidal silica coating to achieve higher coefficients of friction and stabilize the coefficient of friction at different pressures and temperatures.

[0012] The Fig. 1a to 1c schematically illustrate a method of forming a wet friction material according to an embodiment of the present disclosure.

[0013] A wet-running friction material 12 includes a base material 13 formed from fibers, filler material, and a binder. The fibers may be aramid fibers, cellulose fibers, and / or carbon fibers. The cellulose fibers may be in the form of cotton linter or wood pulp. The filler material may be particles of diatomaceous earth and calcined kaolin clay. The binder may be a phenolic resin. Optionally, a friction modifier such as graphite may also be included in the base 12.

[0014] Fig.Figure 1a schematically shows a wet-running friction material 12 with a binder added to a base material 13. The base material 13 is formed by a plurality of diatomaceous earth particles 14 embedded in a matrix of fibers 16 between a first outer surface—i.e., an upper outer surface 13a in the view of the figures—and a second outer surface 13b—i.e., a lower outer surface 13a in the view of the figures—of the base material 13. The base material 13 may also include one or more friction modifiers.

[0015] Fibers 16, particles 14, and any friction modifiers are combined in a pulping process, which involves forming a mixture of the fibers 16, particles 14, and any friction modifiers together, immersing them in a liquid solution, and then drying the mixture to remove the liquid. After the fibers 16 and particles 14 are combined by the liquid solution, the wet-running friction material 12 includes a matrix formed by fibers 16 and diatomaceous earth particles 14, defining a network of voids.

[0016] After fibers 16, particles 14, and any friction modifiers have been bonded together, the base material 13 is impregnated with a binder 18, for example, in the form of phenolic resin. The binder 18 penetrates through the outer surface 13a into the interior of the wet-running friction material 12, so that the cavities within the wet-running friction material 12 are impregnated with the binder 18, but the outer surface 13a remains exposed.

[0017] As in Fig.1b, the base material 13, including the binder contained therein, is then placed on top of a rigid part 30, which may be formed of metal, and the binder-impregnated base material 13 and the part 30 are bonded together to form a friction assembly. Before joining the layer and the part 30, the binder is first cured to a degree, referred to as the B-stage, at which the base material 13 is reasonably flexible. Joining the base material 13 and part 30 includes pressing the base material 13 against the metal part 30 with a hot plate to complete the curing of the binder 24 by forming a cured base material 13, thereby securing the base material 13 and the metal part 30 together.The force with which the heater plate is pressed against the outer surface 13a of the base material 13 while the inner surface 13b of the base material 13 rests on an outer layer 30a of the metal part 30 causes the binder to accumulate at an interface between the inner surface 13b of the base material 13 and the outer surface 30a of the metal part 30, while the curing of the binder by the heat of the heater plate creates a permanent bond between the metal part 30 and the base material 13. The binder solidifies and cures within the base material 13 in contact with the filler material 14 and the fibers 16. In a preferred embodiment, the heat at a surface of the heater plate contacting the outer surface 13a of the base material 13 is 375 to 425 degrees F.

[0018] As in Fig.1c, a colloidal silica-containing solution is then applied to the base material 13 to form a colloidal silica coating 20 on the particles 14 and fibers 16 on the outer surface 13a of the base material 13. The colloidal silica coating 20 can be applied to the outer surface 13a by spraying, rolling, or brushing after the base material 13 has been cured and attached to the metal part 30. During the application of the colloidal silica coating 20, the colloidal silica-containing solution can also drip into the base material 13 and cover at least some of the particles 14 and fibers 16 inside the base material 13 formed between the outer surfaces 13a, 13b. The colloidal silica coating 20 thus covers at least the outer surface 13a, which is defined as a surface in the plane of the base material 13 that contacts a planar surface pressed onto the base material 13.For example, the planar surface may be considered as a part against which the friction material 12 is pressed for frictional engagement or that is pressed against the friction material 12 for frictional engagement.

[0019] The colloidal silica-containing solution may include colloidal silica suspended in an aqueous solution. The colloidal silica-containing solution may include 30 to 50 wt.% colloidal silica and 50 to 60 wt.% water. The silica particles are spherical in shape and non-porous. The colloidal silica-containing solution may also contain other compounds, including an ionic charge modifier. The colloidal silica-containing solution may include 2 to 10 wt.% of the ionic charge modifier. The ionic charge modifiers may be ethylene glycol or aluminum hydroxide. The colloidal silica-containing solution may include 2 to 5 wt.% aluminum hydroxide or 5 to 10 wt.% ethylene glycol.

[0020] In an advantageous embodiment, the silica particles have an average size of 20 to 25 nm. The silica particles can have a surface area of ​​130 to 150 m 2 / g. The silica particles can have a specific gravity of 1.2 to 1.5.

[0021] In an advantageous embodiment, the step of applying the colloidal silica-containing solution includes applying 1 to 10 mg / cm 2 the suspension onto the base material 13 after the binder has cured and the base material 13 is attached to the metal part 30.

[0022] After applying the colloidal silica-containing solution to the base material 13, the water is removed by drying the colloidal silica-containing solution to complete the formation of the colloidal silica coating 20, which defines an upper outer surface 13a of the wet-running friction material 12.

[0023] In some advantageous embodiments, the colloidal silica layer 20 includes, after drying, 60 to 100 wt.% colloidal silica and has an average thickness of 50 to 125 micrometers.

[0024] In some advantageous embodiments, the base material 13, in which the binder is embedded, of the wet friction material 12 may include 25 to 45 wt.% fibers, 25 to 40 wt.% filler material, and 25 to 40 wt.% binder. More specifically, the base material 13, in which the binder is embedded, of the wet friction material 12 may advantageously include 25 to 45 wt.% fibers, 10 to 20 wt.% diatomaceous earth, 15 to 30 wt.% calcined kaolin clay, and 30 to 40 wt.% tung oil-modified phenolic resin.

[0025] The base material 13, in which the binder is embedded, of the wet-running friction material 12 may advantageously include 28 to 38 wt% fibers, 28 to 38 wt% filler material and 30 to 35 wt% binder.

[0026] The base material 13, in which the binder is embedded, of the wet friction material 12 may advantageously include 28 to 38 wt% fibers, 10 to 20 wt% diatomaceous earth, 18 to 28 wt% calcined kaolin clay, and 30 to 40 wt% tung oil modified phenolic resin.

[0027] In a particularly advantageous embodiment, the base material 13, in which the binder is embedded, of the wet friction material 12 may advantageously include 28 to 38 wt% fibers, 8 to 18 wt% diatomaceous earth, 15 to 25 wt% calcined kaolin clay and 30 to 35 wt% tung oil modified phenolic resin.

[0028] In another preferred embodiment, the base material 13 of the wet-running friction material 12, after curing, attachment to part 30, and coating with the colloidal silica layer 20, may include 30 to 45 wt.% fibers, 25 to 35 wt.% filler material, 1 to 15 wt.% friction modifiers, and 25 to 40 wt.% binder. More specifically, the wet-running friction material 12 may include 27 to 42 wt.% fibers, 25 to 30 wt.% filler material, 1 to 15 wt.% friction modifiers, and 30 to 35 wt.% binder.

[0029] In a particularly advantageous embodiment, the resin-saturated base material 13 may include 20 to 35 wt% cellulose fibers, 5 to 15 wt% aramid fibers, 20 to 35 wt% diatomaceous earth, 1 to 5 wt% carbon fibers, 1 to 15 wt% graphite and 30 to 35 wt% phenolic resin.

[0030] In a more specific advantageous embodiment, the resin-saturated base material 13 may include 25 to 30 wt% cellulose fibers, 5 to 10 wt% aramid fibers, 25 to 35 wt% diatomaceous earth, 2 to 4 wt% carbon fibers, 1 to 5 wt% graphite, and 30 to 35 wt% phenolic resin.

[0031] Fig. Figure 2 shows a graph illustrating the advantages of coating the base material 13 with a colloidal silica coating 20. The results from Fig. 2 were obtained by testing a colloidal silica coated friction material with a base friction material constructed in essentially the same manner as the colloidal silica coated friction material, but without the colloidal silica coating. Fig.Figure 2 shows a friction versus speed graph illustrating an uncoated friction material 50 and a friction material 52 coated with colloidal silica particles. Uncoated friction material 50 includes 34 wt% cellulose fibers, 20 wt% calcined kaolin clay, 13 wt% diatomaceous earth, and 33 wt% tung oil-modified phenolic resin. The colloidal silica-coated material, coated friction material 52, includes 33 wt% cellulose fibers, 20 wt% calcined kaolin clay, 13 wt% diatomaceous earth, and 33 wt% tung oil-modified phenolic resin. For the colloidal silica-coated friction material, the colloidal silica suspension was applied to the finished part and allowed to dry completely prior to testing. All tests were conducted using FORD ultra-low viscosity (ULV) automatic transmission fluid, which has a viscosity of 19.2 cSt at 40°C and 4.5 cSt at 100°C.

[0032] As in Fig. 2, the friction material 52 exhibits a surprisingly higher dynamic coefficient of friction than the friction material 50 over a range of application pressures at a fluid temperature of 40°C and at various speed ranges, solely due to the fact that the friction material 52 is colloidal silica. Table 1 Coated with colloidal silica Uncoated Applied pressure (MPa) Temperature (C) Speed ​​(rpm) Friction coefficient efficient Applied pressure (MPa) Temperature (C) Speed ​​(rpm) Friction coefficient efficient 1,0 40 5 0,182 1,0 40 5 0,174 10 0,183 10 0,178 30 0,180 30 0,174 40 0,176 40 0,171 50 0,173 50 0,170 1,5 40 5 0,179 1,5 40 5 0,172 10 0,180 10 0,172 30 0,174 30 0,167 40 0,172 40 0,166 50 0,170 50 0,166 2,0 40 5 0,180 2,0 40 5 0,170 10 0,179 10 0,170 30 0,173 30 0,164 40 0,171 40 0,163 50 0,170 50 0,163 2,5 40 5 0,178 2,5 40 5 0,169 10 0,179 10 0,168 30 0,172 30 0,163 40 0,171 40 0,162 50 0,169 50 0,162

[0033] Accordingly, Fig.2, that in a range of 5 rpm to 50 rpm, a range of 1.0 MPa to 2.5 MPa, and a fluid temperature range of 40°, the colloidal silica coated friction material 52 surprisingly consistently performs better than the uncoated friction material 50. In particular, the friction material 52 has a friction coefficient range of 0.169 to 0.183 for a range of 5 rpm to 50 rpm and a range of 1.0 MPa to 2.5 MPa, and in a fluid temperature of 40°. In contrast, friction material 50 has a friction coefficient range that drops to 0.162.

[0034] Table 1 lists some advantageous slip speed and pressure ranges, which are not limited to the specific subsets listed below.

[0035] At a speed of 5 rpm, the friction material 52 has a coefficient of friction of at least 0.178 and in particular 0.178 to 0.182 at an applied pressure range of 1.0 to 2.5 MPa.

[0036] At a speed of 10 rpm, the friction material 52 has a coefficient of friction of at least 0.179 and in particular 0.179 to 0.183 at an applied pressure range of 1.0 to 2.5 MPa.

[0037] At a speed range of 5 to 10 rpm, the friction material 52 has a coefficient of friction of at least 0.178 and in particular 0.178 to 0.183 at an applied pressure range of 1.0 to 2.5 MPa

[0038] At a speed of 30 rpm, the friction material 52 has a coefficient of friction of at least 0.172 and in particular 0.172 to 0.180 at an applied pressure range of 1.0 to 2.5 MPa.

[0039] At a speed of 40 rpm, the friction material 52 has a coefficient of friction of at least 0.171 and in particular 0.171 to 0.176 at an applied pressure range of 1.0 to 2.5 MPa.

[0040] At a speed of 50 rpm, the friction material 52 has a coefficient of friction of at least 0.169 and in particular 0.169 to 0.173 at an applied pressure range of 1.0 to 2.5 MPa.

[0041] At a speed range of 30 to 50 rpm, the friction material 52 has a coefficient of friction of 0.169 and in particular 0.169 to 0.176 at an applied pressure range of 1.5 to 2.5 MPa.

[0042] Fig.Figure 3 shows the wet friction material layer 12 connected to a plurality of clutch plates 60 in a clutch pack 62. A piston 64 compresses the clutch plates 60 to couple the members 66, 68 together such that the members 66, 68 rotate together when the clutch pack 62 is engaged.

[0043] Fig. 4 shows a wet friction material layer 12 connected to a clutch disc 70 in a torque converter 72. The fluid presses the clutch disc 70 against the cover 74, so that the friction material layer 12 bonds the clutch disc 70 and the cover 74 together such that the clutch disc 70 and the cover 74 rotate together when the clutch disc 70 is engaged.

[0044] In the foregoing description, the disclosure has been described with reference to specific exemplary embodiments and examples thereof. However, it will be apparent that various modifications and changes may be made therein without departing broadly from the spirit and scope of the disclosure as set forth in the following claims. The description and drawings are accordingly to be considered as illustrative and not restrictive. List of reference symbols 12 wet-running friction material layer 13 Base material 13a Outer surface 13b inner surface 14 filler particles 16 fibers 18 Binders 20 colloidal silica coating 30 metal part 30a Outer surface 50 uncoated friction material 52 friction material coated with colloidal silica 60 clutch discs 62 clutch pack 64 pistons 66, 68 rotating parts 70 clutch disc 72 torque converter 74 Cover QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 17 / 681,307

[0001]

Claims

[1] Clutch arrangement for a motor vehicle drive train, comprising: a rigid support; and a wet friction material comprising: a base material including a fiber matrix and filler particles embedded in the fiber matrix; a binder embedded in the base material; and a colloidal silica coating applied to an external surface of the base material. [2] A coupling assembly according to claim 1, wherein the base material in which the binder is embedded includes 25 to 45 wt% fibers, 25 to 40 wt% filler material and 25 to 40 wt% binder. [3] The coupling assembly of claim 2, wherein the filler material includes calcined kaolin clay. [4] A coupling assembly according to claim 3, wherein the base material in which the binder is embedded includes 25 to 45 wt% fibers, 10 to 20 wt% diatomaceous earth, 15 to 30 wt% calcined kaolin clay and 30 to 40 wt% tung oil modified phenolic resin. [5] A coupling assembly according to claim 2, wherein the base material in which the binder is embedded includes 28 to 38 wt% fibers, 28 to 38 wt% filler material and 30 to 35 wt% binder. [6] A coupling assembly according to claim 5, wherein the base material in which the binder is embedded includes 28 to 38 wt% fibers, 10 to 20 wt% diatomaceous earth, 18 to 28 wt% calcined kaolin clay and 30 to 40 wt% tung oil modified phenolic resin. [7] A coupling assembly according to claim 5, wherein the base material in which the binder is embedded includes 28 to 38 wt% fibers, 8 to 18 wt% diatomaceous earth, 15 to 25 wt% calcined kaolin clay and 30 to 35 wt% tung oil modified phenolic resin. [8] A coupling assembly according to claim 1, wherein the base material in which the binder is embedded includes 20 to 35 wt% cellulose fibers, 5 to 15 wt% aramid fibers, 20 to 35 wt% diatomaceous earth and / or calcined kaolin clay, 1 to 5 wt% carbon fibers, 1 to 15 wt% graphite and 30 to 35 wt% phenolic resin. [9] A coupling assembly according to claim 1, wherein the base material in which the binder is embedded includes 25 to 30 wt% cellulose fibers, 5 to 10 wt% aramid fibers, 25 to 35 wt% diatomaceous earth and / or calcined kaolin clay, 2 to 4 wt% carbon fibers, 1 to 5 wt% graphite and 30 to 35 wt% phenolic resin. [10] Coupling assembly according to claim 1, wherein the colloidal silica coating is formed from colloidal silica particles having an average diameter of 20 to 25 nm. [11] A clutch assembly according to claim 1, wherein the wet friction material has a dynamic friction coefficient in the range of 0.17 to 0.18 in automatic transmission fluid having a temperature of 40°C in a speed range of 5 rpm to 50 rpm and at an applied pressure range of 1.0 to 2.5 MPa. [12] A method for producing a clutch assembly for a motor vehicle, comprising: Attaching a wet-running friction material to a surface of a rigid support, wherein the wet-running friction material is produced by: Providing a base material including a fiber matrix and filler particles and a binder embedded in the fiber matrix; and Applying a solution containing colloidal silica to an outer surface of the base material to form a colloidal silica coating on the base material. [13] The method of claim 12, wherein attaching the wet friction material to the surface of the rigid support includes attaching the base material to the rigid member to provide a cured base material on the rigid member, wherein the colloidal silica-containing solution is applied to the outer surface of the base material to form the colloidal silica coating on the cured base material after attaching the base material to the rigid member. [14] The method of claim 13, further comprising curing the binder prior to applying the colloidal silica-containing solution to the outer surface of the base material to form the colloidal silica coating on the base material. [15] The method of claim 12, wherein the colloidal silica-containing solution includes 30 to 50 wt% colloidal silica and 50 to 60 wt% water. [16] The method of claim 12, wherein the particles of colloidal silica have a spherical shape and are non-porous. [17] The method of claim 12, wherein the particles of colloidal silica have an average diameter of 20 to 25 nm. [18] The method according to claim 12, wherein applying the colloidal silica-containing solution to the outer surface of the base material to form the colloidal silica coating on the base material comprises applying 1 to 10 mg / cm 2 the suspension on the base material. [19] The method of claim 12, wherein the base material in which the binder is embedded includes 25 to 45 wt% fibers, 10 to 20 wt% diatomaceous earth, 15 to 30 wt% calcined kaolin clay, and 30 to 40 wt% tung oil modified phenolic resin.

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