Title of Invention	AN ENGAGEABLE CLUTCH ASSEMBLY AND A METHOD OF CONTROLLING FLUID FLOW AT A FRICTION INTERFACE OF ENGAGEABLE CLUTCH ASSEMBLY
Abstract	A clutch plate assembly is provided having a friction interface and internal fluid passages for delivering pressurized fluid to the friction interface to cool the interface, and to reduce spin losses through the clutch assembly. The fluid passages comprise a plurality of primary passages extending inward from a clutch plate inner or outer diameter, and a plurality of secondary fluid passages intersecting the primary fluid passages for conducting fluid to the friction interface. Fluid is directed to the friction interface during clutch engagement for cooling thereof when the clutch assembly is engaging, and separates the clutch plates to reduce spin losses when the clutch assembly is disengaged. A method is also provided for controlling fluid flow at the friction interface, including providing fluid directly to the interface for cooling when the clutch plate assembly is engaging, and for reducing spin losses when the clutch plate assembly is substantially disengaged.

Title of Invention

AN ENGAGEABLE CLUTCH ASSEMBLY AND A METHOD OF CONTROLLING FLUID FLOW AT A FRICTION INTERFACE OF ENGAGEABLE CLUTCH ASSEMBLY

Abstract

A clutch plate assembly is provided having a friction interface and internal fluid passages for delivering pressurized fluid to the friction interface to cool the interface, and to reduce spin losses through the clutch assembly. The fluid passages comprise a plurality of primary passages extending inward from a clutch plate inner or outer diameter, and a plurality of secondary fluid passages intersecting the primary fluid passages for conducting fluid to the friction interface. Fluid is directed to the friction interface during clutch engagement for cooling thereof when the clutch assembly is engaging, and separates the clutch plates to reduce spin losses when the clutch assembly is disengaged. A method is also provided for controlling fluid flow at the friction interface, including providing fluid directly to the interface for cooling when the clutch plate assembly is engaging, and for reducing spin losses when the clutch plate assembly is substantially disengaged.

Full Text	GP-308124-PTT-DLT 1 CLUTCH PLATE WITH INTERNAL FLUID CHANNELS TECHNICAL FIELD [0001] The present invention relates to a clutch assembly having a clutch plate with a plurality of internal fluid passages configured for conducting pressurized fluid directly to the friction interface for cooling of the interface and for reducing spin losses. BACKGROUND OF THE INVENTION [0002] In an automotive transmission, clutch assemblies are commonly used to transmit rotational motion or torque between two rotating members, such as an engine crankshaft and a transmission driveshaft. Standard friction-type clutch assemblies, or friction clutches, include a series of alternating friction and reaction plates that together make up a clutch pack, with the clutch pack being disposed within an outer clutch drum. The friction plate typically has a layer of rough friction material which is bonded or otherwise attached to the primary contact surfaces of a metal core plate, while the reaction plate typically has a relatively smooth contact surface configured to oppose the friction plate when the friction clutch is engaged. The friction clutch is engaged or applied using a controllable hydraulic force supplied by a transmission pump. The force actuates an apply mechanism, such as a clutch-apply piston, to selectively compress the friction and reaction plates of the clutch pack. Once compressed, the alternating plates become interlocked due to the friction forces imparted by the apply force and the friction material, thereby allowing the rotating members to rotate in unison. [0003] Friction clutches may be of the dry-plate or wet-plate variety, with wet- plate friction clutches providing enhanced thermal performance due to the cooling qualities of the pressurized lubricating fluid. In particular, the enhanced thermal performance is accomplished by passing or directing the pressurized fluid, such as transmission fluid or oil, through and around the mating clutch surfaces to dissipate heat generated by the friction forces in proximity to the friction interface between the surfaces. Lubricated surface cooling of friction clutch plates is often provided via a series of shallow radial channels or grooves along the contact surfaces of the friction plates, with GP-308124-PTT-DLT 2 the grooves being pressed into or formed on a separate bonded friction material layer, or defined by the gaps between discrete patches of friction material. However, as such patches and/or surface grooves reduce the total contact area between the mating clutch surfaces, surface temperature may increase along the remaining contact surfaces, resulting in less than optimum overall plate cooling. Also, spin losses may occur while the clutch assembly is disengaged as friction forces create drag between the plates. SUMMARY OF THE INVENTION [0004] Accordingly, an engageable clutch assembly is provided having a friction interface adapted for use with a pressurized fluid, the assembly comprising at least one clutch plate having at least one internal fluid passage and at least one reaction surface at least partially defining the friction interface, wherein the at least one fluid passages is configured to conduct the pressurized fluid directly to the friction interface for cooling of the friction interface when the clutch assembly is engaging, and for reducing spin losses through the clutch assembly when the clutch assembly is disengaged. [0005] In one aspect of the invention, there are a plurality of internal fluid passages, with at least one of the fluid passages being plugged at one end to prevent flow of fluid in one direction as needed. [0006] In another aspect of the invention, the fluid passages include at least one main or primary fluid passage and at least one secondary fluid passage intersecting at least one of the main or primary fluid passages in a perpendicular direction. [0007] In another aspect of the invention, the thickness of the clutch plate and the diameter of at least one of the primary and secondary fluid passages are proportionately related by a ratio of approximately 2:1. [0008] In another aspect of the invention, the clutch plate is a unitary friction/reaction plate with friction material on one side. [0009] In another aspect of the invention, a method is provided for controlling fluid flow at the friction interface of a clutch plate assembly. The method includes providing fluid directly to the friction interface to cool the interface when the clutch plate GP-308124-PTT-DLT 3 assembly is engaging, and providing fluid to the friction interface when the clutch plate assembly is disengaged to thereby reduce spin losses through the clutch plate assembly. [0010] The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0011] FIGURE 1 is an exploded view of a friction clutch assembly having a dual reaction plate and friction plate with a friction interface according to the invention; [0012] FIGURE 2A is a fragmentary side view of a portion of a reaction plate between adjacent friction plates, each forming a friction interface with the reaction plate according to one embodiment of the invention; [0013] FIGURE 2B is a fragmentary top view of a portion of the reaction plate according to the invention; [0014] FIGURE 3A is a fragmentary perspective view of a reaction plate having a blind hole according to a second embodiment of the invention; [0015] FIGURE 3B is a fragmentary perspective view of a portion of a reaction plate having an alternately oriented blind hole according to the second embodiment of the invention; [0016] FIGURE 3C is a fragmentary perspective view of a portion of a reaction plate having a selectively pluggable inner orifice according to a third embodiment of the invention; [0017] FIGURE 4A is an exploded view of a friction clutch assembly having unitary friction/reaction plates according to a fourth embodiment of the invention; and [0018] FIGURE 4B is a fragmentary side view of a portion of pair of unitary friction/plates forming a friction interface therebetween according to the fourth embodiment of the invention. GP-308124-PTT-DLT 4 DESCRIPTION OF THE PREFERRED EMBODIMENTS [0019] Referring to the drawings wherein like reference numbers correspond to like or similar components throughout the several figures, there is shown in Figure 1 an exploded view of a clutch plate assembly 10 having a friction plate 14 and a reaction plate 18, and a friction interface 65 therebetween. For simplicity, only one friction plate 14 is shown, however those skilled in the art will recognize that clutch plate assembly 10 may consist of any number of alternately arranged friction plates 14 and reaction plates 18, depending on the specific clutch application. Friction plate 14 has a core plate 36 having a first and second main surface 28, 29, respectively, the core plate 36 preferably constructed of a suitable grade of stainless steel and having a plurality of inwardly- extending splines 24 configured to mate or interlock with alternating grooves of an adjoining clutch hub (not shown). [0020] Preferably, first and second main surfaces 28, 29 each have a layer of friction material 20A, 20B, respectively, which is bonded or otherwise attached to surfaces 28, 29 of the core plate 36, although friction material such as 20A, 20B may also be bonded directly to a unitary friction/reaction plate (not shown). The friction material 20A, 20B is preferably ring-shaped and sized to cover the primary surface 28, 29 of the core plate 36 to which the friction material is bonded, and further includes a plurality of surface fluid channels 16 that separate the friction material layer 20A, 20B into substantially equal patches or segments for directing pressurized fluid 15 between the outer diameter 38 and the inner diameter 13 of the core plate 36, or between the inner diameter 13 and the outer diameter 38, depending on the design of the clutch assembly 10. While the friction material 20A, 20B as shown in Figure 1 have fluid channels 16 as shown, other styles or designs of friction material may also be used within the scope of the invention, including, for example, smooth or grooveless material, or a series of surface channels or grooves that are pressed partially through the thickness of the friction material 20A, 20B. [0021] Friction plate 14 is configured to press against and synchronize with the speed of the mating reaction plate 18 when a controllable source of hydraulic pressure, preferably a positive displacement transmission pump 11, actuates or engages an apply GP-308124-PTT-DLT 5 mechanism such as clutch-apply piston (not shown) to selectively compress the alternating friction plates 14 and reaction plates 18 that make up the clutch assembly 10. As plates 14, 18 become interlocked due to the friction forces imparted by the layer of friction material 20B, the clutch plate assembly is thereby engaged, and the mating plates 14, 18 are permitted to rotate in unison. [0022] Reaction plate 18 is a preferably circular metallic ring of a suitable grade of stainless steel having an outer and inner diameter 22, 12, respectively, and includes a plurality of outwardly extending splines 32 configured to mate or interlock with a plurality of grooves positioned on the inside surface of a mating clutch drum (not shown). The reaction plate 18 has a first main surface 37 and a reverse or second main surface 39 (see Figure 2A), with main surfaces 37, 39 being at least as wide as the width of friction material 20A, 20B to allow for maximum frictional contact area between mating plates such as plates 14 and 18. The reaction plate 18 also has outer and inner lateral or side surfaces 48, 58, respectively, each having a width/height sufficient to provide the reaction plate 18 with adequate bending and surface strength without adding excessive weight for a given clutch application, and with sufficient thickness to accommodate the drilling of fluid passages therein as described hereinbelow. [0023] Reaction plate 18 is further provided with a plurality of primary fluid passages 42 extending radially inward through the reaction plate 18 from outer lateral surface 48 to inner lateral surface 58, preferably perpendicularly with respect to the lateral surfaces 48, 58 as shown in Figure 1 and substantially parallel to the main surfaces 37, 39. Each of primary fluid passages 42 are in fluid communication with a source 11 of pressurized fluid 15 which is configured to deliver the fluid 15 through one of the outer or inner orifices 34, 50 of primary fluid passage 42, depending on the application. Orifices 34, 50, along with primary fluid channels 42, are preferably circular or cylindrical in shape so as to minimize the effects of fluid friction and are preferably positioned approximately midway up lateral surfaces 48, 58 and approximately halfway between main surfaces 37, 39 of reaction plate 18, and approximately midway between each of the outer splines 32, so as to minimize the amount of material that must be removed from the reaction plate 18 during forming or drilling of the primary fluid GP-308124-PTT-DLT 6 passages 42. However, those skilled in the art will recognize that the location of the outer orifices 34 may be positioned in alternate locations along or around the outer lateral surface 48. For example, each of outer orifices 34 may be positioned on a respective spline face 33 of an outer spline 32 to thereby increase the area of potential fluid/metal contact for an enhanced fluid cooling effect. [0024] Turning to Figure 2A, which is a side view of a portion of the clutch plate assembly 10, a reaction plate 18 is disposed between a pair of friction plates 14A, 14B, forming or defining a pair of boundary or friction interfaces 65 A, 65B between the friction plates 14A, 14B and the reaction plate 18, respectively. Outer orifice 34 admits a flow of pressurized fluid 15 from outer lateral surface 48 into the reaction plate 18, as previously explained herewithin. For delivery of fluid 15 directly to the friction interfaces 65 A, 65B for the cooling of main surfaces 37, 39, the reaction plate 18 is further provided with a preferably circular or cylindrical secondary fluid passage 62 having a pair of circular or cylindrical first and second orifices 40 and 70, respectively, each in fluid communication with primary fluid passage 42 through the secondary fluid passage 62. [0025] In the preferred embodiment, first and second orifices 40, 70 are each positioned on main surfaces 37, 39, respectively, at opposite ends of secondary fluid passage 62 and open to the friction interfaces 65A, 65B between reaction plate 18 and friction plates 14A, 14B, respectively. First orifice 40 is positioned on the main surface 37 of reaction plate 18 directly above primary fluid passage 42 and approximately midway between the respective outer and inner diameters 22, 12 of the reaction plate 18, and second orifice 70 is positioned on the second primary surface 39 directly below primary fluid passage 42. While Figure 1 shows just one first and second orifice 40, 70, those skilled in the art will recognize that additional orifices substantially identical to first and second orificies 40, 70 may be added as needed depending on the size/width of the reaction plate and/or desired cooling/lubricating requirements of a given clutch plate assembly design. [0026] During a transient high temperature, low relative velocity condition, i.e. the low speed conditions most likely to cause shudder or vibration due to slippage, the secondary fluid passage 62 takes advantage of the relatively low viscosity of the fluid 15 GP-308124-PTT-DLT 7 under high temperature conditions to draw the fluid from primary fluid passage 42 directly to the low local pressure region created in proximity to the first and second orifices 34, 70. Without requiring a reduction in contact surface area of the friction material 20A, 20B, shudder or vibration at low relative rotational speed is thereby reduced in part by delivering the fluid 15 directly to the friction interfaces 65A, 65B as needed. When the clutch assembly 10 is rotating in unison at relatively high rates of speed, the low pressure region formed in proximity to first and second orifices 40, 70, respectively, between the disparately rotating plates 14, 18 disappears, and the various plates of the clutch assembly 10 are pressed together, thereby substantially blocking the flow of fluid 15 through the orifices 40, 70. In this manner, loss of excess fluid 15 into the friction interfaces 65A, 65B helps to preserve fluid and prevent flooding of the friction interfaces 65A, 65B, thus minimi/ing the hydroplaning effect between friction plates 14A, 14B and reaction plate 18. Those skilled in the art will recognize that when clutch assembly 10 is disengaged, fluid 15 will continue to be fed at line pressure through the orifices 40, 70, which will provide a hydraulic force at the friction interfaces 65 A, 65B sufficient to separate the various adjacent plates, such as friction plates 14 and reaction plate 18 and reducing or minimizing the spin losses or drag therebetween. [0027] In a second embodiment shown in Figure 3A, a blind primary fluid passage 142 is shown extending or penetrating from the outer lateral surface 48 to a closed or blind end 72 of primary fluid passage 142 which is short of the inner diameter 12 of reaction plate 18. As configured, fluid 15 may enter the outer orifice 34, pass through primary fluid passage 142, and exit first and second orifices 40, 70 as previously explained herewithin. However, due to the blind end 72 of primary fluid passage 142, the fluid 15 is blocked or prevented from passing all the way through to the inner diameter 12. Fluid 15 is conserved in this manner while still being drawn by the local low pressure zone between plates 14A, 14B and 18 through secondary fluid passages 62 to reach the friction interface 65A, 65B (see Figure 2A). Alternately, as shown in Figure 3B, in situations or configurations in which flow of the fluid 15 initiates from the inner lateral surface 58 of internal diameter 12, an alternate primary fluid passage 242 may extend or penetrate from the inner diameter 12 to a closed or blind end 74 of primary fluid passage GP-308124-P'IT-DLT 8 242. The blind end 74 is short of the outer diameter 22 of reaction plate 18. Both blind ends 72 and 74 are preferably positioned approximately % of the distance between the inner diameter 12 and outer diameter 22 of reaction plate 18 to allow for some additional core cooling of reaction plate 18, although other distances are also within the scope of the invention. [0028] In a third embodiment as shown in Figure 3C, primary fluid passage 42 extends all the way through reaction plate 18 from inner diameter 12 to outer diameter 22, and is capped or otherwise blocked, preferably by a plug 67 that is inserted into the inner orifice 50, thus blocking fluid 15 from flowing all the way through reaction plate 18. This embodiment facilitates a drilling or boring process initiating from within the inner diameter 12 of the reaction plate 18, as may be required to produce the embodiment of Figure 3B, particularly in situations in which the reaction plate 18 is relatively small in diameter. Preferably, the plug 67 is constructed of suitable material such as stainless steel when the plus is to be inserted into inner orifice 50 and secured with epoxy or other adhesive material (not shown) with sufficient strength and materials properties to retain the plug 67 within the inner orifice 50 in the presence of fluid 15 for the operational lifetime of the reaction plate 18. [0029] While a multi-plate design is preferred, a fourth embodiment includes unitary friction/reaction plates 110A, 110B as shown in Figure 4, which are stacked without a separate core plate 36 (see Figure 1). Friction material 26 is bonded or attached directly to one surface 137A, 137B of each unitary plate 110A, 110B, respectively, with each unitary plate 110A, 110B having respective alternating internally and externally projecting splines 124, 132. Unitary plate 110A has an internal orifice 150A and an external orifice 134A disposed at either end of at least one primary fluid passage 342, each of which is intersected by a secondary fluid passage 162 having a single orifice 170. Likewise, unitary plate 110B has an internal orifice 150B and an external orifice 134B disposed at either end of at least one primary fluid passage 342, with primary fluid passages 342 being substantially identical to passage 42 as previously described hereinabove (see Figure 1). In this fourth embodiment, as* shown in partial side view in Figure 4B, only one friction interface 65C will be formed relative to each pair of unitary GP-308124-PTT-DLT 9 plates 110A, 110B, and accordingly, only a single orifice 170 would be required opening thereto from each of primary fluid passages 342, although multiple secondary passages 162 and orifices 170 may be added as needed to deliver more fluid 15 to the friction interface 65C as required. Orifices 134A and 150A, and primary fluid passage 342 may also be configured using blind or plugged holes as previously described herewithin as the application or clutch design requires. [0030] While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims. GP-308124-PTT-DLT 10 CLAIMS 1. An engageable clutch assembly having a friction interface adapted for use with a pressurized fluid, said clutch assembly comprising a clutch plate with at least one internal fluid passage and at least one reaction surface on a side thereof at least partially defining one friction interface; wherein said internal fluid passage is configured to conduct said pressurized fluid directly to said one friction interface for cooling thereof when said clutch assembly is engaging, and for reducing spin losses through said clutch assembly when said clutch assembly is disengaged. 2. The clutch assembly of claim 1, wherein said at least one fluid passage is plugged at one end to prevent flow of said fluid in one direction. 3. The clutch assembly of claim 1, wherein said at least one fluid passage includes at least one primary fluid passage and at least one secondary fluid passage intersecting said at least one primary fluid passage in a substantially perpendicular direction. 4. The clutch assembly of claim 3, wherein the thickness of said clutch plate and the diameter of at least one of said primary and said secondary fluid passages are proportionately related by the ratio of approximately 2:1. 5. The clutch assembly of claim 1, including a friction plate at least partially defining said friction interface, wherein said clutch plate is a reaction plate. 6. The clutch assembly of claim 1, wherein said clutch plate is a unitary friction/reaction plate having friction material thereon at least partially defining another friction interface. GP-308124-PTT-DLT 11 7. An engageable reaction plate for use in combination with a friction interface within a friction clutch assembly, the plate comprising at least one reaction surface, an outer diameter, an inner diameter, a plurality of primary fluid passages communicable with a source of pressurized fluid, and a plurality of secondary fluid passages each in fluid communication with said at least one reaction surface and one of said primary fluid passages; wherein said primary fluid passages are in fluid communication with at least one of said inner and outer diameters and are configured to deliver pressurized fluid from one of said diameters to said at least one reaction surface for cooling said friction interface when said assembly is engaging, and for reducing spin losses in said assembly when said assembly is disengaged. 8. The reaction plate of claim 7, wherein each of said secondary fluid passages intersects at least one of said primary fluid passages in a substantially perpendicular direction. 9. The reaction plate of claim 7, wherein the thickness of said reaction plate and the diameter of at least one of said primary and secondary fluid passages are proportionately related by a ratio of approximately 2:1. 10. The reaction plate of claim 6, wherein at least one of said plurality of primary fluid passages is a blind passage leading from one of said outer and inner diameters and extending approximately % of the distance to the other of said diameters. 11. A method of controlling fluid flow at the friction interface of a clutch plate assembly, the method including providing fluid directly to said friction interface to cool said friction interface when said clutch plate assembly is engaging; and GP-308124-PTT-DLT 12 providing said fluid directly to said friction interface at line pressure when said clutch plate assembly is disengaged to thereby reduce spin loss. 12. The method of claim 11 including a reaction plate at said friction interface, wherein said fluid is provided to said friction interface via a plurality of fluid passages within said reaction plate. 13. The method of claim 11, wherein each of said plurality of fluid passages includes at least one primary fluid passage and at least one secondary passage intersecting said at least one primary fluid passage, wherein said at least one primary fluid passage is configured to conduct said fluid through said reaction plate and into said secondary fluid passage, and wherein said secondary fluid passage is configured to conduct said fluid directly to said friction interface as needed. 14. The method of claim 13, wherein said at least one main fluid passage is configured to prevent flow in one direction. 15. The method of claim 13, wherein said at least one secondary fluid passage is substantially perpendicular to the at least one primary fluid passage it intersects. 16. The method of claim 13, wherein the thickness of said reaction plate and the diameter of at least one of the said at least one primary fluid passage and said at least one secondary fluid passage are proportionately related by a ratio of approximately 2:1. A clutch plate assembly is provided having a friction interface and internal fluid passages for delivering pressurized fluid to the friction interface to cool the interface, and to reduce spin losses through the clutch assembly. The fluid passages comprise a plurality of primary passages extending inward from a clutch plate inner or outer diameter, and a plurality of secondary fluid passages intersecting the primary fluid passages for conducting fluid to the friction interface. Fluid is directed to the friction interface during clutch engagement for cooling thereof when the clutch assembly is engaging, and separates the clutch plates to reduce spin losses when the clutch assembly is disengaged. A method is also provided for controlling fluid flow at the friction interface, including providing fluid directly to the interface for cooling when the clutch plate assembly is engaging, and for reducing spin losses when the clutch plate assembly is substantially disengaged.

Full Text

GP-308124-PTT-DLT
1
CLUTCH PLATE WITH INTERNAL FLUID CHANNELS
TECHNICAL FIELD
[0001] The present invention relates to a clutch assembly having a clutch plate
with a plurality of internal fluid passages configured for conducting pressurized fluid
directly to the friction interface for cooling of the interface and for reducing spin losses.
BACKGROUND OF THE INVENTION
[0002] In an automotive transmission, clutch assemblies are commonly used to
transmit rotational motion or torque between two rotating members, such as an engine
crankshaft and a transmission driveshaft. Standard friction-type clutch assemblies, or
friction clutches, include a series of alternating friction and reaction plates that together
make up a clutch pack, with the clutch pack being disposed within an outer clutch drum.
The friction plate typically has a layer of rough friction material which is bonded or
otherwise attached to the primary contact surfaces of a metal core plate, while the
reaction plate typically has a relatively smooth contact surface configured to oppose the
friction plate when the friction clutch is engaged. The friction clutch is engaged or
applied using a controllable hydraulic force supplied by a transmission pump. The force
actuates an apply mechanism, such as a clutch-apply piston, to selectively compress the
friction and reaction plates of the clutch pack. Once compressed, the alternating plates
become interlocked due to the friction forces imparted by the apply force and the friction
material, thereby allowing the rotating members to rotate in unison.
[0003] Friction clutches may be of the dry-plate or wet-plate variety, with wet-
plate friction clutches providing enhanced thermal performance due to the cooling
qualities of the pressurized lubricating fluid. In particular, the enhanced thermal
performance is accomplished by passing or directing the pressurized fluid, such as
transmission fluid or oil, through and around the mating clutch surfaces to dissipate heat
generated by the friction forces in proximity to the friction interface between the surfaces.
Lubricated surface cooling of friction clutch plates is often provided via a series of
shallow radial channels or grooves along the contact surfaces of the friction plates, with

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the grooves being pressed into or formed on a separate bonded friction material layer, or
defined by the gaps between discrete patches of friction material. However, as such
patches and/or surface grooves reduce the total contact area between the mating clutch
surfaces, surface temperature may increase along the remaining contact surfaces,
resulting in less than optimum overall plate cooling. Also, spin losses may occur while
the clutch assembly is disengaged as friction forces create drag between the plates.
SUMMARY OF THE INVENTION
[0004] Accordingly, an engageable clutch assembly is provided having a friction
interface adapted for use with a pressurized fluid, the assembly comprising at least one
clutch plate having at least one internal fluid passage and at least one reaction surface at
least partially defining the friction interface, wherein the at least one fluid passages is
configured to conduct the pressurized fluid directly to the friction interface for cooling of
the friction interface when the clutch assembly is engaging, and for reducing spin losses
through the clutch assembly when the clutch assembly is disengaged.
[0005] In one aspect of the invention, there are a plurality of internal fluid
passages, with at least one of the fluid passages being plugged at one end to prevent flow
of fluid in one direction as needed.
[0006] In another aspect of the invention, the fluid passages include at least one
main or primary fluid passage and at least one secondary fluid passage intersecting at
least one of the main or primary fluid passages in a perpendicular direction.
[0007] In another aspect of the invention, the thickness of the clutch plate and the
diameter of at least one of the primary and secondary fluid passages are proportionately
related by a ratio of approximately 2:1.
[0008] In another aspect of the invention, the clutch plate is a unitary
friction/reaction plate with friction material on one side.
[0009] In another aspect of the invention, a method is provided for controlling
fluid flow at the friction interface of a clutch plate assembly. The method includes
providing fluid directly to the friction interface to cool the interface when the clutch plate

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assembly is engaging, and providing fluid to the friction interface when the clutch plate
assembly is disengaged to thereby reduce spin losses through the clutch plate assembly.
[0010] The above features and advantages and other features and advantages of
the present invention are readily apparent from the following detailed description of the
best modes for carrying out the invention when taken in connection with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIGURE 1 is an exploded view of a friction clutch assembly having a dual
reaction plate and friction plate with a friction interface according to the invention;
[0012] FIGURE 2A is a fragmentary side view of a portion of a reaction plate
between adjacent friction plates, each forming a friction interface with the reaction plate
according to one embodiment of the invention;
[0013] FIGURE 2B is a fragmentary top view of a portion of the reaction plate
according to the invention;
[0014] FIGURE 3A is a fragmentary perspective view of a reaction plate having a
blind hole according to a second embodiment of the invention;
[0015] FIGURE 3B is a fragmentary perspective view of a portion of a reaction
plate having an alternately oriented blind hole according to the second embodiment of the
invention;
[0016] FIGURE 3C is a fragmentary perspective view of a portion of a reaction
plate having a selectively pluggable inner orifice according to a third embodiment of the
invention;
[0017] FIGURE 4A is an exploded view of a friction clutch assembly having
unitary friction/reaction plates according to a fourth embodiment of the invention; and
[0018] FIGURE 4B is a fragmentary side view of a portion of pair of unitary
friction/plates forming a friction interface therebetween according to the fourth
embodiment of the invention.

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DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] Referring to the drawings wherein like reference numbers correspond to
like or similar components throughout the several figures, there is shown in Figure 1 an
exploded view of a clutch plate assembly 10 having a friction plate 14 and a reaction
plate 18, and a friction interface 65 therebetween. For simplicity, only one friction plate
14 is shown, however those skilled in the art will recognize that clutch plate assembly 10
may consist of any number of alternately arranged friction plates 14 and reaction plates
18, depending on the specific clutch application. Friction plate 14 has a core plate 36
having a first and second main surface 28, 29, respectively, the core plate 36 preferably
constructed of a suitable grade of stainless steel and having a plurality of inwardly-
extending splines 24 configured to mate or interlock with alternating grooves of an
adjoining clutch hub (not shown).
[0020] Preferably, first and second main surfaces 28, 29 each have a layer of
friction material 20A, 20B, respectively, which is bonded or otherwise attached to
surfaces 28, 29 of the core plate 36, although friction material such as 20A, 20B may also
be bonded directly to a unitary friction/reaction plate (not shown). The friction material
20A, 20B is preferably ring-shaped and sized to cover the primary surface 28, 29 of the
core plate 36 to which the friction material is bonded, and further includes a plurality of
surface fluid channels 16 that separate the friction material layer 20A, 20B into
substantially equal patches or segments for directing pressurized fluid 15 between the
outer diameter 38 and the inner diameter 13 of the core plate 36, or between the inner
diameter 13 and the outer diameter 38, depending on the design of the clutch assembly
10. While the friction material 20A, 20B as shown in Figure 1 have fluid channels 16 as
shown, other styles or designs of friction material may also be used within the scope of
the invention, including, for example, smooth or grooveless material, or a series of
surface channels or grooves that are pressed partially through the thickness of the friction
material 20A, 20B.
[0021] Friction plate 14 is configured to press against and synchronize with the
speed of the mating reaction plate 18 when a controllable source of hydraulic pressure,
preferably a positive displacement transmission pump 11, actuates or engages an apply

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mechanism such as clutch-apply piston (not shown) to selectively compress the
alternating friction plates 14 and reaction plates 18 that make up the clutch assembly 10.
As plates 14, 18 become interlocked due to the friction forces imparted by the layer of
friction material 20B, the clutch plate assembly is thereby engaged, and the mating plates
14, 18 are permitted to rotate in unison.
[0022] Reaction plate 18 is a preferably circular metallic ring of a suitable grade
of stainless steel having an outer and inner diameter 22, 12, respectively, and includes a
plurality of outwardly extending splines 32 configured to mate or interlock with a
plurality of grooves positioned on the inside surface of a mating clutch drum (not shown).
The reaction plate 18 has a first main surface 37 and a reverse or second main surface 39
(see Figure 2A), with main surfaces 37, 39 being at least as wide as the width of friction
material 20A, 20B to allow for maximum frictional contact area between mating plates
such as plates 14 and 18. The reaction plate 18 also has outer and inner lateral or side
surfaces 48, 58, respectively, each having a width/height sufficient to provide the reaction
plate 18 with adequate bending and surface strength without adding excessive weight for
a given clutch application, and with sufficient thickness to accommodate the drilling of
fluid passages therein as described hereinbelow.
[0023] Reaction plate 18 is further provided with a plurality of primary fluid
passages 42 extending radially inward through the reaction plate 18 from outer lateral
surface 48 to inner lateral surface 58, preferably perpendicularly with respect to the
lateral surfaces 48, 58 as shown in Figure 1 and substantially parallel to the main surfaces
37, 39. Each of primary fluid passages 42 are in fluid communication with a source 11 of
pressurized fluid 15 which is configured to deliver the fluid 15 through one of the outer
or inner orifices 34, 50 of primary fluid passage 42, depending on the application.
Orifices 34, 50, along with primary fluid channels 42, are preferably circular or
cylindrical in shape so as to minimize the effects of fluid friction and are preferably
positioned approximately midway up lateral surfaces 48, 58 and approximately halfway
between main surfaces 37, 39 of reaction plate 18, and approximately midway between
each of the outer splines 32, so as to minimize the amount of material that must be
removed from the reaction plate 18 during forming or drilling of the primary fluid

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passages 42. However, those skilled in the art will recognize that the location of the outer
orifices 34 may be positioned in alternate locations along or around the outer lateral
surface 48. For example, each of outer orifices 34 may be positioned on a respective
spline face 33 of an outer spline 32 to thereby increase the area of potential fluid/metal
contact for an enhanced fluid cooling effect.
[0024] Turning to Figure 2A, which is a side view of a portion of the clutch plate
assembly 10, a reaction plate 18 is disposed between a pair of friction plates 14A, 14B,
forming or defining a pair of boundary or friction interfaces 65 A, 65B between the
friction plates 14A, 14B and the reaction plate 18, respectively. Outer orifice 34 admits a
flow of pressurized fluid 15 from outer lateral surface 48 into the reaction plate 18, as
previously explained herewithin. For delivery of fluid 15 directly to the friction interfaces
65 A, 65B for the cooling of main surfaces 37, 39, the reaction plate 18 is further provided
with a preferably circular or cylindrical secondary fluid passage 62 having a pair of
circular or cylindrical first and second orifices 40 and 70, respectively, each in fluid
communication with primary fluid passage 42 through the secondary fluid passage 62.
[0025] In the preferred embodiment, first and second orifices 40, 70 are each
positioned on main surfaces 37, 39, respectively, at opposite ends of secondary fluid
passage 62 and open to the friction interfaces 65A, 65B between reaction plate 18 and
friction plates 14A, 14B, respectively. First orifice 40 is positioned on the main surface
37 of reaction plate 18 directly above primary fluid passage 42 and approximately
midway between the respective outer and inner diameters 22, 12 of the reaction plate 18,
and second orifice 70 is positioned on the second primary surface 39 directly below
primary fluid passage 42. While Figure 1 shows just one first and second orifice 40, 70,
those skilled in the art will recognize that additional orifices substantially identical to first
and second orificies 40, 70 may be added as needed depending on the size/width of the
reaction plate and/or desired cooling/lubricating requirements of a given clutch plate
assembly design.
[0026] During a transient high temperature, low relative velocity condition, i.e.
the low speed conditions most likely to cause shudder or vibration due to slippage, the
secondary fluid passage 62 takes advantage of the relatively low viscosity of the fluid 15

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under high temperature conditions to draw the fluid from primary fluid passage 42
directly to the low local pressure region created in proximity to the first and second
orifices 34, 70. Without requiring a reduction in contact surface area of the friction
material 20A, 20B, shudder or vibration at low relative rotational speed is thereby
reduced in part by delivering the fluid 15 directly to the friction interfaces 65A, 65B as
needed. When the clutch assembly 10 is rotating in unison at relatively high rates of
speed, the low pressure region formed in proximity to first and second orifices 40, 70,
respectively, between the disparately rotating plates 14, 18 disappears, and the various
plates of the clutch assembly 10 are pressed together, thereby substantially blocking the
flow of fluid 15 through the orifices 40, 70. In this manner, loss of excess fluid 15 into
the friction interfaces 65A, 65B helps to preserve fluid and prevent flooding of the
friction interfaces 65A, 65B, thus minimi/ing the hydroplaning effect between friction
plates 14A, 14B and reaction plate 18. Those skilled in the art will recognize that when
clutch assembly 10 is disengaged, fluid 15 will continue to be fed at line pressure through
the orifices 40, 70, which will provide a hydraulic force at the friction interfaces 65 A,
65B sufficient to separate the various adjacent plates, such as friction plates 14 and
reaction plate 18 and reducing or minimizing the spin losses or drag therebetween.
[0027] In a second embodiment shown in Figure 3A, a blind primary fluid
passage 142 is shown extending or penetrating from the outer lateral surface 48 to a
closed or blind end 72 of primary fluid passage 142 which is short of the inner diameter
12 of reaction plate 18. As configured, fluid 15 may enter the outer orifice 34, pass
through primary fluid passage 142, and exit first and second orifices 40, 70 as previously
explained herewithin. However, due to the blind end 72 of primary fluid passage 142, the
fluid 15 is blocked or prevented from passing all the way through to the inner diameter
12. Fluid 15 is conserved in this manner while still being drawn by the local low pressure
zone between plates 14A, 14B and 18 through secondary fluid passages 62 to reach the
friction interface 65A, 65B (see Figure 2A). Alternately, as shown in Figure 3B, in
situations or configurations in which flow of the fluid 15 initiates from the inner lateral
surface 58 of internal diameter 12, an alternate primary fluid passage 242 may extend or
penetrate from the inner diameter 12 to a closed or blind end 74 of primary fluid passage

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242. The blind end 74 is short of the outer diameter 22 of reaction plate 18. Both blind
ends 72 and 74 are preferably positioned approximately % of the distance between the
inner diameter 12 and outer diameter 22 of reaction plate 18 to allow for some additional
core cooling of reaction plate 18, although other distances are also within the scope of the
invention.
[0028] In a third embodiment as shown in Figure 3C, primary fluid passage 42
extends all the way through reaction plate 18 from inner diameter 12 to outer diameter
22, and is capped or otherwise blocked, preferably by a plug 67 that is inserted into the
inner orifice 50, thus blocking fluid 15 from flowing all the way through reaction plate
18. This embodiment facilitates a drilling or boring process initiating from within the
inner diameter 12 of the reaction plate 18, as may be required to produce the embodiment
of Figure 3B, particularly in situations in which the reaction plate 18 is relatively small in
diameter. Preferably, the plug 67 is constructed of suitable material such as stainless steel
when the plus is to be inserted into inner orifice 50 and secured with epoxy or other
adhesive material (not shown) with sufficient strength and materials properties to retain
the plug 67 within the inner orifice 50 in the presence of fluid 15 for the operational
lifetime of the reaction plate 18.
[0029] While a multi-plate design is preferred, a fourth embodiment includes
unitary friction/reaction plates 110A, 110B as shown in Figure 4, which are stacked
without a separate core plate 36 (see Figure 1). Friction material 26 is bonded or attached
directly to one surface 137A, 137B of each unitary plate 110A, 110B, respectively, with
each unitary plate 110A, 110B having respective alternating internally and externally
projecting splines 124, 132. Unitary plate 110A has an internal orifice 150A and an
external orifice 134A disposed at either end of at least one primary fluid passage 342,
each of which is intersected by a secondary fluid passage 162 having a single orifice 170.
Likewise, unitary plate 110B has an internal orifice 150B and an external orifice 134B
disposed at either end of at least one primary fluid passage 342, with primary fluid
passages 342 being substantially identical to passage 42 as previously described
hereinabove (see Figure 1). In this fourth embodiment, as* shown in partial side view in
Figure 4B, only one friction interface 65C will be formed relative to each pair of unitary

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plates 110A, 110B, and accordingly, only a single orifice 170 would be required opening
thereto from each of primary fluid passages 342, although multiple secondary passages
162 and orifices 170 may be added as needed to deliver more fluid 15 to the friction
interface 65C as required. Orifices 134A and 150A, and primary fluid passage 342 may
also be configured using blind or plugged holes as previously described herewithin as the
application or clutch design requires.
[0030] While the best modes for carrying out the invention have been described
in detail, those familiar with the art to which this invention relates will recognize various
alternative designs and embodiments for practicing the invention within the scope of the
appended claims.

GP-308124-PTT-DLT
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CLAIMS
1. An engageable clutch assembly having a friction interface
adapted for use with a pressurized fluid, said clutch assembly comprising a clutch
plate with at least one internal fluid passage and at least one reaction surface on a
side thereof at least partially defining one friction interface; wherein said internal
fluid passage is configured to conduct said pressurized fluid directly to said one
friction interface for cooling thereof when said clutch assembly is engaging, and
for reducing spin losses through said clutch assembly when said clutch assembly
is disengaged.
2. The clutch assembly of claim 1, wherein said at least one fluid
passage is plugged at one end to prevent flow of said fluid in one direction.
3. The clutch assembly of claim 1, wherein said at least one fluid
passage includes at least one primary fluid passage and at least one secondary
fluid passage intersecting said at least one primary fluid passage in a substantially
perpendicular direction.
4. The clutch assembly of claim 3, wherein the thickness of said
clutch plate and the diameter of at least one of said primary and said secondary
fluid passages are proportionately related by the ratio of approximately 2:1.
5. The clutch assembly of claim 1, including a friction plate at least
partially defining said friction interface, wherein said clutch plate is a reaction
plate.
6. The clutch assembly of claim 1, wherein said clutch plate is a
unitary friction/reaction plate having friction material thereon at least partially
defining another friction interface.

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7. An engageable reaction plate for use in combination with a friction
interface within a friction clutch assembly, the plate comprising at least one
reaction surface, an outer diameter, an inner diameter, a plurality of primary fluid
passages communicable with a source of pressurized fluid, and a plurality of
secondary fluid passages each in fluid communication with said at least one
reaction surface and one of said primary fluid passages; wherein said primary
fluid passages are in fluid communication with at least one of said inner and outer
diameters and are configured to deliver pressurized fluid from one of said
diameters to said at least one reaction surface for cooling said friction interface
when said assembly is engaging, and for reducing spin losses in said assembly
when said assembly is disengaged.
8. The reaction plate of claim 7, wherein each of said secondary fluid
passages intersects at least one of said primary fluid passages in a substantially
perpendicular direction.
9. The reaction plate of claim 7, wherein the thickness of said
reaction plate and the diameter of at least one of said primary and secondary fluid
passages are proportionately related by a ratio of approximately 2:1.
10. The reaction plate of claim 6, wherein at least one of said plurality
of primary fluid passages is a blind passage leading from one of said outer and
inner diameters and extending approximately % of the distance to the other of said
diameters.
11. A method of controlling fluid flow at the friction interface of a
clutch plate assembly, the method including providing fluid directly to said
friction interface to cool said friction interface when said clutch plate assembly is
engaging; and

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providing said fluid directly to said friction interface at line pressure when
said clutch plate assembly is disengaged to thereby reduce spin loss.
12. The method of claim 11 including a reaction plate at said friction
interface, wherein said fluid is provided to said friction interface via a plurality of
fluid passages within said reaction plate.
13. The method of claim 11, wherein each of said plurality of fluid
passages includes at least one primary fluid passage and at least one secondary
passage intersecting said at least one primary fluid passage, wherein said at least
one primary fluid passage is configured to conduct said fluid through said reaction
plate and into said secondary fluid passage, and wherein said secondary fluid
passage is configured to conduct said fluid directly to said friction interface as
needed.
14. The method of claim 13, wherein said at least one main fluid
passage is configured to prevent flow in one direction.
15. The method of claim 13, wherein said at least one secondary fluid
passage is substantially perpendicular to the at least one primary fluid passage it
intersects.
16. The method of claim 13, wherein the thickness of said reaction
plate and the diameter of at least one of the said at least one primary fluid passage
and said at least one secondary fluid passage are proportionately related by a ratio
of approximately 2:1.

A clutch plate assembly is provided having a friction interface and internal
fluid passages for delivering pressurized fluid to the friction interface to cool the
interface, and to reduce spin losses through the clutch assembly. The fluid passages
comprise a plurality of primary passages extending inward from a clutch plate inner or
outer diameter, and a plurality of secondary fluid passages intersecting the primary fluid
passages for conducting fluid to the friction interface. Fluid is directed to the friction
interface during clutch engagement for cooling thereof when the clutch assembly is
engaging, and separates the clutch plates to reduce spin losses when the clutch assembly
is disengaged. A method is also provided for controlling fluid flow at the friction
interface, including providing fluid directly to the interface for cooling when the clutch
plate assembly is engaging, and for reducing spin losses when the clutch plate assembly
is substantially disengaged.

AN ENGAGEABLE CLUTCH ASSEMBLY AND A METHOD OF CONTROLLING FLUID FLOW AT A FRICTION INTERFACE OF ENGAGEABLE CLUTCH ASSEMBLY

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