Abstract:
A torque converter clutch for a constant slip application including a cover, a friction plate secured to the cover, and at least one channel between the cover and the friction plate. In another embodiment, the torque converter clutch may further include a one-way valve operatively arranged to permit a fluid to flow out of a channel, while preventing the fluid from flowing in through the channel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This patent application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 60/708,407, filed Aug. 15, 2005, which application is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to torque converter clutches, more particularly, to a torque converter clutch for a constant slip application, and, more specifically, to a durable, high cooling efficiency torque converter clutch for a constant slip application.  
       BACKGROUND  
       [0003]     Hydraulic torque converters, devices used to change the ratio of torque to speed between the input and output shafts of the converter, revolutionized the automotive and marine propulsion industries by providing hydraulic means to transfer energy from an engine to a drive mechanism, e.g., drive shaft or automatic transmission, while smoothing out engine power pulses. A torque converter includes three primary components, an impeller, sometimes referred to as a pump, directly connected to the engine&#39;s crankshaft, a turbine, similar in structure to the impeller, however the turbine is connected to the input shaft of the transmission, and a stator, located between the impeller and turbine, which redirects the flow of hydraulic fluid exiting from the turbine thereby providing additional rotational force to the pump. This additional rotational force results in torque multiplication. Thus, for example, when the impeller speed is high and the turbine speed is low, torque may be multiplied by a 2:1 or higher ratio, whereas when the impeller and turbine speeds are approximately the same, torque can be transferred at about a 1:1 ratio.  
         [0004]     Although torque can be transferred at approximately a 1:1 ratio, there remains an amount of slippage between the impeller and turbine. Slippage results in lower fuel efficiency and therefore is less desirable. The push for increased fuel economy and gas mileage encouraged the development of torque converters having a clutch, i.e., a lock-up mechanism. When the speed of a vehicle having a torque converter clutch reaches a predetermined level, e.g., 40 miles per hour, hydraulic fluid in the stator shaft is pressurized, activating the clutch piston, which locks the torque converter output shaft to the converter housing, and thus connecting the engine output shaft to the transmission input shaft. The activated clutch piston, i.e., an engaged clutch, eliminates slippage, and thus improves fuel economy and gas mileage.  
         [0005]     More recently, slipping clutches have been included in torque converter designs, as similar benefits to a locking system may be realized. Slipping clutches may be engaged sooner, i.e., at a lower engine speed or rotations per minute (RPM), as a result of the superior drivetrain isolation achieved with a slipping system. A result of the aforementioned non-locking system is that the clutch piston is constantly slipping along the housing cover. As is well-known, when two surfaces slip with respect to each other, frictional forces promote the generation of heat energy. An increase in temperature of the torque converter, and thus the hydraulic fluid within the converter, accelerates the degradation of both the fluid and the friction material used between the piston and the converter housing. Hence, since the introduction of torque converters having a slipping mechanism, the need to dissipate heat energy from the torque converter clutch has also existed.  
         [0006]     Various methods and apparatus have been employed to minimize the increase in torque converter clutch temperature. For example, U.S. Pat. No. 4,423,803 (Malloy) teaches a torque converter clutch having a temperature regulator valve. Once hydraulic fluid in the apply chamber reaches a predetermined temperature, a bi-metallic valve opens, thereby permitting hydraulic fluid to flow between the apply chamber and the release chamber. Thus, the increased flow of fluid between the two chambers provides cooling for the clutch mechanism.  
         [0007]     Additionally, grooves within the friction material or converter housing have been included to permit fluid flow from the apply chamber to the release chamber. Similar to the aforementioned bimetallic valve arrangement, heat is transferred away from the clutch region. However, both groove configurations have drawbacks. When grooves are formed within the friction material, they must be sufficiently deep to permit flow over an extended period of time, as the material wears away with use. Additionally, friction materials are typically poor conductors of heat energy and therefore can not be used to effectively remove heat from the torque converter clutch. Lastly, grooves in the cover have the tendency to prematurely wear the friction material, i.e., a cheese grater effect.  
         [0008]     As can be derived from the variety of devices and methods directed at removing heat from the torque converter clutch, many means have been contemplated to accomplish the desired end, i.e., lengthy fluid and part life, without sacrificing the higher fuel efficiency and gas mileage afforded by a lock-up mechanism. Heretofore, tradeoffs between fluid and/or part life and fuel efficiency were required. Thus, there has been a longfelt need for a torque converter clutch having high cooling efficiency and durability.  
       BRIEF SUMMARY OF THE INVENTION  
       [0009]     The present invention broadly includes a torque converter clutch having a cover and a friction plate, wherein the friction plate is secured to the cover, and at least one channel, having a channel input and a channel output, located between the friction plate and the cover. In one embodiment the friction plate is welded to the cover, while in another embodiment the friction plate and cover are secured by brazing, and in yet another embodiment the friction plate and cover are secured by an adhesive material. The at least one channel is operatively arranged to allow hydraulic fluid to flow between the cover and friction plate, thereby drawing heat away from the torque converter clutch. In yet another embodiment, the at least one channel includes a one-way valve operatively arranged to permit hydraulic fluid to flow out of the channel through the channel output, while preventing fluid from flowing into the channel output.  
         [0010]     A general object of the invention is to enable efficient transfer of heat away from a torque converter clutch.  
         [0011]     Another object of the invention is to extend the useful life of a torque converter clutch by preventing the deterioration of friction material and/or hydraulic fluid.  
         [0012]     These and other objects, features, and advantages of the present invention will become readily apparent to one having ordinary skill in the art upon reading the detailed description of the invention in view of the drawings and appended claims.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which:  
         [0014]      FIG. 1  is a perspective view of a torque converter;  
         [0015]      FIG. 2  is a cross-sectional view of the torque converter shown in  FIG. 1 , taken generally along line  2 - 2  of  FIG. 1 ;  
         [0016]      FIG. 3A  is a front elevational view of a cover and friction plate of the present invention having internally located channels with channel inputs proximate other channel inputs;  
         [0017]      FIG. 3B  is a front elevational view of a cover and friction plate of the present invention having internally located channels with channel inputs proximate channel outputs;  
         [0018]      FIG. 4  is a perspective view of the friction plate of the present invention showing a plurality of channels;  
         [0019]      FIG. 5  is a cross-sectional view of the friction plate shown in  FIG. 4 , taken generally along line  5 - 5  of  FIG. 4 ; and,  
         [0020]      FIG. 6  is an enlarged cross-sectional view of an embodiment of the cover and friction plate of the present invention shown in the encircled region  6  of  FIG. 2  having a one-way valve operatively arranged at a channel output. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements of the invention. While the present invention is described with respect to what is presently considered to be the preferred embodiment, it is to be understood that the invention as claimed is not limited to the preferred embodiment.  
         [0022]     Furthermore, it is understood that this invention is not limited to the particular methodology, materials and modifications described and as such may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention.  
         [0023]     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. Although any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the preferred methods, devices, and materials are now described.  
         [0024]     Adverting now to the figures,  FIG. 1  shows a perspective view of torque converter  10 . Torque converter  10  includes first housing cover  12 , second housing cover  14 , and housing hub  16 . In a preferred embodiment, torque converter  10  is operatively arranged to transfer torque between an engine and a transmission, as described supra. Thus, converter  10  is positioned so that first housing cover  12  may be coupled to a flywheel of the engine (not shown), stator shaft  32  (see  FIG. 2 ) may be coupled to a fixed transmission mount (not shown), and transmission input shaft  34  (see  FIG. 2 ) may be engaged with turbine hub  35  (see  FIG. 2 ). Because converter  10  is fixedly secured to the engine flywheel, converter  10  rotates as the flywheel rotates. The result of such rotation is described above, and further described infra. As the engine and transmission are not particularly germane to this invention, they are not discussed in detail.  
         [0025]      FIG. 2  shows a cross-sectional view of torque converter  10 , taken generally along line  2 - 2  of  FIG. 1 . Converter  10  generally includes first and second housing covers  12  and  14 , respectively, wherein pump  18 , stator  20 , turbine  22 , piston  24  which includes friction material  26 , friction plate  28 , damper  30 , stator shaft  32 , transmission input shaft  34 , and turbine hub  35  are located. Hydraulic fluid (shown as arrows) enters converter  10  through first cavity  36 , the volume created between the inner wall of stator shaft  32  and the outer wall of transmission input shaft  34 , and subsequently pressurizes the fluid volume contained within piston  24  and first and second housing covers  12  and  14 , respectively, i.e., apply cavity  40 . Although fluid entry and pressurization, in this embodiment, is described as occurring through first cavity  36 , one of ordinary skill in the art recognizes that such entry and pressurization may also occur in the volume between housing hub  16  and stator shaft  32 . Due to the rotation of converter  10 , the hydraulic fluid is transferred via centrifugal force from pump  18  to turbine  22 , whereby engine torque is also transmitted to turbine  22 . As a result of the shape of turbine  22 , the hydraulic fluid is then returned to pump  18 , through stator  20 . Stator  20  alters the flow direction of the hydraulic fluid thereby improving the torque multiplication of converter  10 .  
         [0026]     As described supra, torque converters may include lock-up mechanisms to provide improved efficiency and gas mileage. In the embodiment shown in  FIG. 2 , converter  10  includes friction plate  28  fixedly secured to inner surface  38  of first housing cover  12 . In a preferred embodiment friction plate  28  is welded to inner surface  38 , however as one of ordinary skill in the art appreciates, other means of securing are possible, e.g., brazing and adhesives, and such other means are within the metes and bounds of the invention as claimed. Piston  24  including friction material  26  comprise the lock-up mechanism of converter  10  and are fixedly secured to damper  30 . Damper  30  is operatively arranged to reduce vibration conducted from the engine to the transmission (not shown).  
         [0027]     Throughout operation, pressurized hydraulic fluid fills apply and release cavities  40  and  42 , respectively. At initial startup or under conditions when it is inappropriate to lock turbine shaft  34  to first housing cover  12 , the lock-up mechanism is not engaged. Therefore, hydraulic fluid pressure in apply and release cavities  40  and  42 , respectively, is typically low, e.g., 30 pounds per square inch, and approximately equal. As torque converter  10  and turbine shaft  34  approach a predetermined rotational rate with respect to each other, and the vehicle having such torque converter approaches a predetermined velocity, the hydraulic fluid pressure in apply cavity  40  is increased, e.g., 150 pounds per square inch, whereby piston  24  and friction material  26  are releasably engaged with friction plate  28 . Under the aforementioned lock-up condition, and more specifically due to frictional forces between friction plate  28  and friction material  26 , the vehicle engine is directly connected to the transmission and thus the vehicle&#39;s efficiency and gas mileage are improved. As converter  10  is brought under conditions that are not conducive for lock-up, e.g., the vehicle begins to slow in velocity, hydraulic fluid pressure in apply cavity  40  is reduced, and subsequently the constant pressure contained within release cavity  42 , being sufficient to overcome the reduced pressure in apply cavity  40 , causes friction material  26  to release from friction plate  28 .  
         [0028]     Typically, while the lock-up mechanism is engaged, no hydraulic fluid is permitted to flow from apply cavity  40  to release cavity  42 . Hence, when converter  10  is under slipping conditions, heat energy may build up within the hydraulic fluid in apply cavity  40 , thereby promoting the aforementioned fluid degradation. Thus, in this embodiment, friction plate  28  having channel input  44 , channel  46  and channel output  48  (see  FIG. 6 ), permits the flow of hydraulic fluid from apply cavity  40  to release cavity  42 , thereby removing heat energy from friction plate  28  via the hydraulic fluid. As friction plate  28 , in a preferred embodiment, is constructed from metal material, and metal being an efficient conductor of heat, the heat energy generated between friction plate  28  and friction material  26  may be substantially removed from this area by flowing hydraulic fluid through channel  46 . Upon exiting channel  46  through channel output  48 , the fluid enters release cavity  42 , and subsequently exits converter  10  through second cavity  50 , a bore located along the central axis of turbine shaft  34 . After the hydraulic fluid exits converter  10 , it may be cooled and then reintroduced through first cavity  36  as described supra.  
         [0029]      FIG. 3A  shows a front elevational view of cover  12  and friction plate  28  having channels  46  with channel inputs  44  and channel outputs  48 . In this embodiment, friction plate  28  is fixedly secured to cover  12  by continuous weld  57 . As continuous weld  57  seals the circumference of friction plate  28 , entrance of hydraulic fluid into channel  46  is limited by channel input  44 . Furthermore, in this embodiment, channel inputs  44  are operatively arranged so that each input  44  is proximate another input  44 , and all inputs  44  are located adjacent the outer radius of friction plate  28 , i.e., proximate continuous weld  57 . Additionally, as maintaining the tolerances of depth and width of channels  46  may be difficult during manufacture, in this embodiment the rate of hydraulic fluid flow within channel  46  is controlled by the diameter of channel input  44 . Although the manufacturing reproducibility of the diameter of channel input  44  is more easily maintained, and thus is typically the means of controlling rate of fluid flow, it is within the scope of this invention to control the size and shape of channel  46  or the diameter of channel output  48 , and thereby fix the rate of fluid flow through channel  46 . It will also be appreciated by one of ordinary skill in the art that although channels  46  are depicted as zig-zag patterns, any pattern connecting channel input  44  with channel output  48  is possible, e.g., straight line or complex lattice, and such variations are within the scope of the invention.  
         [0030]      FIG. 3B  shows a front elevational view of another embodiment of cover  12  and friction plate  28  having channels  47  with channel inputs  45  and channel outputs  49 . In this embodiment, channels  47  comprise a honeycomb pattern, wherein hydraulic fluid is transferred from inputs  45  to outputs  49 . Thus, the rate of hydraulic fluid flow through channel  47  is controlled by the diameter of outputs  49 . Contrary to the embodiment shown in  FIG. 3A , in this embodiment friction plate  28  is fixedly secured to cover  12  by spot-welds  56  and continuous weld  57  about the outer and inner circumferences of plate  28 , respectively. As described supra, other configurations of channel construction, e.g., straight lines or zig-zag patterns, as well as controlling the rate of fluid flow by maintaining the tolerances of channel  47  or the size of inputs  45 , are within the scope of the invention as claimed.  
         [0031]      FIG. 4  is a perspective view of friction plate  28  showing a plurality of channels  46  according to  FIG. 3A . In this embodiment, channels  46  are formed within surface  52  of friction plate  28 . Subsequently, plate  28  is fixedly secured to first housing cover  12 , as described above, having surface  52  of friction plate  28  in contact with surface  38  of first housing cover  12 . Although in this embodiment channels  46  are formed in surface  52 , one of ordinary skill in the art will appreciate that channels  46  may also be formed within first housing cover  12 . Thus, channel inputs  44  must merely be aligned to the channels formed in first housing cover  12 , prior to fixedly securing friction plate  28  to cover  12  with continuous weld  57  (see  FIG. 3A ).  
         [0032]      FIG. 5  is a cross-sectional view of friction plate  28 , taken generally along line  5 - 5  of  FIG. 4 . Although in the embodiments disclosed, the rate of fluid flow within channel  46  is primarily controlled by the diameter of channel input  44 , in part the rate of flow may be controlled by the width and depth of channel  46 . Thus, by forming a wider and/or deeper channel  46 , the resistance to fluid flow within channel  46  may be decreased and therefore less pressure within apply cavity  40  (see  FIG. 2 ) is required to drive the fluid through channel  46  to release cavity  42 .  
         [0033]      FIG. 6  is an enlarged cross-sectional view of an embodiment of cover  12  and friction plate  28  of the present invention shown in the encircled region  6  of  FIG. 2 , and also shown in the front elevational view of  FIG. 3B . This embodiment further includes one-way valve  54  operatively arranged at channel output  49 . As described supra, friction plate  28  may be fixed secured to first housing cover  12  by spot-welds  56  and continuous weld  57 , whereby channels  47  are sealed, thus limiting fluid entrance and exit to channel inputs  45  and channel outputs  49 , respectively. In this embodiment, one-way valve  54  precludes fluid flowing from release cavity  42  to apply cavity  40 . Hence, when one-way valve  54  is incorporated in the instant invention, and the lock-up mechanism is engaged, hydraulic fluid may only flow from apply cavity  40  to release cavity  42 , and flow is prevented in the opposite direction. Although not depicted, the instant invention may also be used without one-way valve  54 , and as such, the pressure differential between apply and release chambers  40  and  42 , respectively, controls the direction of flow within channels  47 .  
         [0034]     Thus, it is seen that the objects of the present invention are efficiently obtained, although modifications and changes to the invention should be readily apparent to those having ordinary skill in the art, which modifications are intended to be within the spirit and scope of the invention as claimed. It also is understood that the foregoing description is illustrative of the present invention and should not be considered as limiting. Therefore, other embodiments of the present invention are possible without departing from the spirit and scope of the present invention.