The present disclosure relates generally to friction clutches and plates used in torque converters and other motor vehicle drivetrain components and more specifically to a clutch assembly including a wet friction material.
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. It is known to form the friction material by a paper making process using a Fourdrinier machine.
A clutch assembly for a motor vehicle drivetrain includes a rigid support and a wet friction material fixed to a surface of the rigid support. The wet friction material includes a base material including a matrix of fibers and filler particles embedded in the matrix of fibers; a binder embedded in the base material; and a colloidal silica coating applied onto an outer surface of the base material.
In some embodiments of the clutch assembly, the binder embedded base material may include, by percent weight, 25 to 45% fibers, 25 to 40% filler material and 25 to 40% binder. The filler material may include calcined kaolin clay. The binder embedded base material may include, by percent weight, 25 to 45% fibers, 10 to 20% diatomaceous earth, 15 to 30% calcined kaolin clay and 30 to 40% tung oil modified phenolic resin. The binder embedded base material may include, by percentage weight, 28 to 38% fibers, 28 to 38% filler material and 30 to 35% binder. The binder embedded base material may include, by percent weight, 28 to 38% fibers, 10 to 20% diatomaceous earth, 18 to 28% calcined kaolin clay and 30 to 40% tung oil modified phenolic resin. The binder embedded base material may include, by percent weight, 28 to 38% fibers, 8 to 18% diatomaceous earth, 15 to 25% calcined kaolin clay and 30 to 35% tung oil modified phenolic resin. The binder embedded base material may include, by percentage weight, 20 to 35% cellulose fibers, 5 to 15% aramid fibers, 20 to 35% diatomaceous earth and/or calcined kaolin clay, 1 to 5% carbon fibers, 1 to 15% graphite, and 30 to 35% phenolic resin. The binder embedded base material may include, by percentage weight, 25 to 30% cellulose fibers, 5 to 10% aramid fibers, 25 to 35% diatomaceous earth and/or calcined kaolin clay, 2 to 4% carbon fibers, 1 to 5% graphite, and 30 to 35% phenolic resin. The colloidal silica coating may be formed of colloidal silica particles having a mean diameter of 20 to 25 nm.
A method of making a clutch assembly for a motor vehicle is also provided. The method includes fixing a wet friction material to a surface of a rigid support; providing a base material including a matrix of fibers and filler particles and a binder embedded in the matrix of fibers; and applying a colloidal silica containing solution on an outer surface of the base material to form a colloidal silica coating on the base material.
In some embodiments of the method, the fixing of the wet friction material to the surface of the rigid support may include attaching the base material to the rigid part to provide a cured base material on the rigid part, and the colloidal silica containing solution is applied on the outer surface of the base material to form the colloidal silica coating on the cured base material after the attaching of the base material to the rigid part. The method may further include curing the binder prior to the applying of the colloidal silica containing solution on the outer surface of the base material to form the colloidal silica coating on the base material. The colloidal silica containing solution may include, by percent weight, 30 to 50% by weight of colloidal silica and 50 to 60% by weight of water. Particles of the colloidal silica may have a spherical shape and may be non-porous. Particles of the colloidal silica may have a mean diameter of 20 to 25 nm. The applying of the colloidal silica containing solution on the outer surface of the base material to form the colloidal silica coating on the base material may include applying 1 to 10 mg/cm2 of the suspension the base material. The base material may include, by percent weight, 30 to 45% fibers, 25 to 35% filler material, 1 to 15% friction modifiers and 25 to 40% binder.
A method of making a wet friction material layer includes providing a base material including a matrix of fibers and filler particles and a binder embedded in the matrix of fibers; and applying a colloidal silica containing solution on an outer surface of the base material to form a colloidal silica coating on the base material.
The present disclosure is described below by reference to the following drawings, in which:
Next generation wet friction materials for electric and hybrid applications need to provide higher torque which requires a higher friction coefficient. To achieve this the friction material will need to reach and maintain the desired friction coefficient.
The present disclosure provides a friction material with a base material formed fibers, fillers, a binder and optionally one or more friction modifiers. The base material is coated with a colloidal silica coating to achieve higher friction coefficients, and to stabilize the friction coefficient over various pressures and temperatures.
A wet friction material 12 includes a base material 13 formed of fibers, filler material and a binder. The fibers can be aramid fibers, cellulose fibers and/or carbon fibers. The cellulose fibers can be in cotton linter or wood pulp form. 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 base 12.
Fibers 16, particles 14 and any friction modifiers are joined together in a pulping process, which involves forming a mixture of the fibers 16, particles 14 and any friction modifiers submerged together in a liquid solution, then drying the mixture to remove the liquid. After fibers 16 and particles 14 are joined together by the liquid solution, wet friction material 12 includes a matrix formed by fibers 16 and diatomaceous earth particles 14 that define a network of voids.
After fibers 16, particles 14 and any friction modifiers are joined together, base material 13 is saturated with a binder 18, for example in the form of phenolic resin. The binder 18 penetrates past outer surface 13a into the interior of the wet friction material 12 such that voids in the interior of wet friction material 12 are saturated with the binder 18, but the outer surface 13a is exposed.
As schematically shown in
As schematically shown in
The colloidal silica containing solution may include colloidal silica suspended in an aqueous solution. The colloidal silica containing solution may include 30 to 50% by weight of colloidal silica and 50 to 60% by weight of water. The silica particles have a spherical shape that is non-porous. The colloidal silica containing solution may also include other compounds, including an ionic charge modifier. The colloidal silica containing solution may include 2 to 10% by weight 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% by weight of aluminum hydroxide or 5 to 10% by weight of ethylene glycol.
In one advantageous embodiment, the silica particles have a mean size of 20 to 25 nm. The silica particles may have a specific surface area of 130 to 150 m2/g. The silica particles may have a specific gravity of 1.2 to 1.5.
In one advantageous embodiment, the step of applying the colloidal silica containing solution includes applying 1 to 10 mg/cm2 of the suspension is applied to base material 13 after the binder is cured and the base material 13 is attached to metal part 30.
After the colloidal silica containing solution is applied to the base material 13, the water is removed by drying the colloidal silica containing solution to finalize the formation of colloidal silica coating 20, which defines an upper outer surface 13a of wet friction material 12.
In some advantageous embodiments, colloidal silica layer 20, after drying, includes 60 to 100% by weight of colloidal silica and has a mean thickness of 50 to 125 microns.
In some advantageous embodiments, the binder embedded base material 13 of wet friction material 12 may include, by percent weight, 25 to 45% fibers, 25 to 40% filler material and 25 to 40% binder. More specifically, binder embedded base material 13 of wet friction material 12 may advantageously include, by percent weight, 25 to 45% fibers, 10 to 20% diatomaceous earth, 15 to 30% calcined kaolin clay and 30 to 40% tung oil modified phenolic resin.
The binder embedded base material 13 of wet friction material 12 may advantageously include, by percentage weight, 28 to 38% fibers, 28 to 38% filler material and 30 to 35% binder.
The binder embedded base material 13 of wet friction material 12 may advantageously include, by percent weight, 28 to 38% fibers, 10 to 20% diatomaceous earth, 18 to 28% calcined kaolin clay and 30 to 40% tung oil modified phenolic resin.
In a specific advantageous embodiment, the binder embedded base material 13 of wet friction material 12 may advantageously include, by percent weight, 28 to 38% fibers, 8 to 18% diatomaceous earth, 15 to 25% calcined kaolin clay and 30 to 35% tung oil modified phenolic resin.
In another preferred embodiment, base material 13 of wet friction material 12, after curing, attachment to part 30 and coating with colloidal silica layer 20, may include, by percentage weight, 30 to 45% fibers, 25 to 35% filler material, 1 to 15% friction modifiers and 25 to 40% binder. More specifically, wet friction material 12 may include, by percentage weight, 27 to 42% fibers, 25 to 30% filler material, 1 to 15% friction modifiers and 30 to 35% binder.
In a specific advantageous embodiment, the resin saturated base material 13 may include, by percentage weight, 20 to 35% cellulose fibers, 5 to 15% aramid fibers, 20 to 35% diatomaceous earth, 1 to 5% carbon fibers, 1 to 15% graphite, and 30 to 35% phenolic resin.
In a more specific advantageous embodiment, the resin saturated base material 13 may include, by percentage weight, 25 to 30% cellulose fibers, 5 to 10% aramid fibers, 25 to 35% diatomaceous earth, 2 to 4% carbon fibers, 1 to 5% graphite, and 30 to 35% phenolic resin.
As shown in
Accordingly,
Table 1 provides a number of beneficial slip speed and applied pressure ranges, not limited to the specific subsets set forth hereafter.
For a speed of 5 RPM, friction material 52 has a friction coefficient of at least 0.178, and more specifically 0.178 to 0.182 for an applied pressure range of 1.0 to 2.5 MPa.
For a speed of 10 RPM, friction material 52 has a friction coefficient of at least 0.179, and more specifically 0.179 to 0.183 for an applied pressure range of 1.0 to 2.5 MPa.
For a speed range of 5 to 10 RPM, friction material 52 has a friction coefficient at least 0.178, and more specifically 0.178 to 0.183 for an applied pressure range of 1.0 to 2.5 MPa
For a speed of 30 RPM, friction material 52 has a friction coefficient of at least 0.172, and more specifically 0.172 to 0.180 for an applied pressure range of 1.0 to 2.5 MPa.
For a speed of 40 RPM, friction material 52 has a friction coefficient of at least 0.171, and more specifically 0.171 to 0.176 for an applied pressure range of 1.0 to 2.5 MPa.
For a speed of 50 RPM, friction material 52 has a friction coefficient of at least 0.169, and more specifically 0.169 to 0.173 for an applied pressure range of 1.0 to 2.5 MPa.
For a speed range of 30 to 50 RPM, friction material 52 has a friction coefficient of 0.169, and more specifically 0.169 to 0.176 for an applied pressure range of 1.5 to 2.5 MPa.
In the preceding specification, the disclosure has been described with reference to specific exemplary embodiments and examples thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of disclosure as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative manner rather than a restrictive sense.