Abstract:
A blade for a stator in a torque converter including a first face, which includes a first step, and a second face located substantially circumferentially opposite the first face. In one embodiment, the first face includes first and second disjointed or misaligned segments, and the first step connects the first and second segments. In another embodiment, the second face includes a second step. In yet another embodiment, the second face includes third and fourth disjointed or misaligned segments, and the second step connects the first and second segments.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 60/966,323 filed Aug. 27, 2007 and U.S. Provisional Application No. 60/928,437 filed May 9, 2007. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to improvements in apparatus for transmitting force between a rotary driving unit (such as the engine of a motor vehicle) and a rotary driven unit (such as the variable-speed transmission in the motor vehicle). In particular, the invention relates to new stator blade cross-sectional profiles. 
     BACKGROUND OF THE INVENTION 
     Torque converters including stators with blades are known in the art. Conventional stator blades typically have profiles substantially similar to an airfoil. It would be desirable to create a stator blade which increases the mass flow rate through the stator at both high and low speed ratios. An improved mass flow is known to lower the k-factor, and therefore increase the torque capacity of the torque converter. 
     It should be appreciated that one could increase the mass flow rate by spacing adjacent stator blades farther apart. However, spacing the blades farther apart would also have the undesirable consequence of reducing channeling. Reduced channeling is known in the art to reduce efficiency of a torque converter. Thus, unfortunately, modifying a stator or stator blades to improve one torque converter parameter, such as torque capacity, typically results in an undesirable reduction in other parameters, such as torque ratio or efficiency. 
     Thus, there is a long-felt need for a stator blade that enables an increase in torque capacity while maintaining previous values for other parameters such as torque ratio and efficiency. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention broadly comprises a blade for a stator in a torque converter including a first face, which includes a first step, and a second face located substantially circumferentially opposite the first face. In one embodiment, the first face includes first and second disjointed or misaligned segments and the first step connects the first and second segments. In another embodiment, the second face includes a second step. In another embodiment, the second face includes third and fourth disjointed or misaligned segments, and the second step connects the first and second segments. In yet another embodiment, the blade includes a first body portion and a second body portion offset with respect to the first body portion, and a step body portion connects the first second body portions. 
     The present invention also broadly comprises a blade assembly for a stator in a torque converter including a first blade with a first face including first and second disjointed segments connected by a first step and a second blade with a second face including third and fourth disjointed segments connected by a second step. During operation of the stator, respective fluid pressures on the first and second step surfaces are less than fluid pressures on the first or second and third or fourth disjointed segments, respectively. During operation of the stator, the first step surface enables an increase in fluid flow between the first and second blades. The increase in fluid flow decreases a k-factor for the torque converter. 
     The present invention further broadly comprises a blade for a stator in a torque converter including a first face including first and second disjointed segments connected by a step and a second face located substantially circumferentially opposite the first face. 
     These and other objects and advantages of the present invention will be readily appreciable from the following description of preferred embodiments of the invention and from the accompanying drawings and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1A  is a perspective view of a cylindrical coordinate system demonstrating spatial terminology used in the present application; 
         FIG. 1B  is a perspective view of an object in the cylindrical coordinate system of  FIG. 1A  demonstrating spatial terminology used in the present application; 
         FIG. 2  is a profile of present invention stepped stator blades demonstrating fluid flow through a stator of a torque converter at a low speed ratio; 
         FIG. 3  is a profile of the stepped stator blades shown in  FIG. 2  demonstrating fluid flow through the stator at a high speed ratio; 
         FIG. 4  is a profile of present invention stator blades having one stepped surface and one constant surface demonstrating fluid flow through the stator at a low speed ratio; and, 
         FIG. 5  is a diagram comparing the performances of a present invention stepped stator blade and a constant surface blade. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     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 embodiments, it is to be understood that the invention as claimed is not limited to the disclosed embodiments. 
     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, which is limited only by the appended claims. 
     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. 
       FIG. 1A  is a perspective view of cylindrical coordinate system  80  demonstrating spatial terminology used in the present application. The present invention is at least partially described within the context of a cylindrical coordinate system. System  80  has a longitudinal axis  81 , used as the reference for the directional and spatial terms that follow. The adjectives “axial,” “radial,” and “circumferential” are with respect to an orientation parallel to axis  81 , radius  82  (which is orthogonal to axis  81 ), and circumference  83 , respectively. The adjectives “axial,” “radial” and “circumferential” also are regarding orientation parallel to respective planes. To clarify the disposition of the various planes, objects  84 ,  85 , and  86  are used. Surface  87  of object  84  forms an axial plane. That is, axis  81  forms a line along the surface. Surface  88  of object  85  forms a radial plane. That is, radius  82  forms a line along the surface. Surface  89  of object  86  forms a circumferential plane. That is, circumference  83  forms a line along the surface. As a further example, axial movement or disposition is parallel to axis  81 , radial movement or disposition is parallel to radius  82 , and circumferential movement or disposition is parallel to circumference  83 . Rotation is with respect to axis  81 . 
     The adverbs “axially,” “radially,” and “circumferentially” are with respect to an orientation parallel to axis  81 , radius  82 , or circumference  83 , respectively. The adverbs “axially,” “radially,” and “circumferentially” also are regarding orientation parallel to respective planes. 
       FIG. 1B  is a perspective view of object  90  in cylindrical coordinate system  80  of  FIG. 1A  demonstrating spatial terminology used in the present application. Cylindrical object  90  is representative of a cylindrical object in a cylindrical coordinate system and is not intended to limit the present invention in any manner. Object  90  includes axial surface  91 , radial surface  92 , and circumferential surface  93 . Surface  91  is part of an axial plane, surface  92  is part of a radial plane, and surface  93  is part of a circumferential plane. 
       FIG. 2  is a profile of present invention stepped stator blades  100  demonstrating fluid flow through a stator (not shown) of a torque converter (not shown) at a low speed ratio. Stator blade  100  has face, or surface,  102  and face, or surface,  112 , with the faces located substantially circumferentially opposite each other. Face  102  includes surface segments  106  and  108 , and step, or step surface,  104 . In a preferred embodiment, step  104  is located on face  102 , as shown. Surface segments  106  and  108  are disjointed and are connected by step  104 . By disjointed we mean that segments  106  and  108  do not form a surface with a smooth curvature, because of the presence of step  104 . That is, face  102  does not have a smooth curvature, particularly at step  104 . Alternately stated, segments  106  and  108  are misaligned. 
     Blade  100  includes body portion  122  and body portion  124  connected by step body portion  120 . Portions  122  and  124  are misaligned, or disjoint, with respect to each other. 
     Arrow  110  represents the direction of the flow of fluid through the stator at low speed ratios of the torque converter, when blades  100  are installed in the stator. Two blades are shown in  FIG. 2 ; however, it should be understood that a stator using blades  100  is not limited to a particular number of blades  100 . The direction of the fluid changes as the fluid passes through the stator, specifically, between blades  100 . The turning of the fluid occurs because the fluid contacts segment  106 , the blade reacts to the force from the fluid, and the blade redirects the fluid down the stator blade towards segment  108 . The fluid pressure at step  104  is substantially lower than fluid pressure at least one of segments  106  and  108 . The step provides redirection for the fluid as the fluid travels to segment  108 . The curvature of segment  108  continues directing the flow of fluid until the fluid exits out of the stator. The redirection of the fluid by step  104  enables the fluid to smoothly transition from segment  106  to segment  108 , and therefore provide better turning of the fluid. For example, the angle at which the fluid turns in response to contacting segment  106  is advantageously reduced. As a result, the fluid slows down less as the fluid transitions from segment  106  to segment  108 . The maintained speed of the fluid and the reduced turning angle of the fluid noted supra increase fluid flow rate past blades  100 , increase the mass flow rate past blades  100 , and increase the capacity of the torque converter. 
       FIG. 3  is a profile of stepped stator blades  100  shown in  FIG. 2  demonstrating fluid flow through the stator at a high speed ratio. The following should be viewed in light of  FIGS. 2 and 3 . Face  112  includes surface segments  116  and  118 , and step  114 . The discussion of  FIG. 2  regarding face  102 , segments  106  and  108  and step  104  is applicable to face  112 , segments  116  and  118 , and step  114 . 
     Arrow  111  represents the general direction of the flow of fluid through the stator at high speed ratios of the torque converter, when blades  100  are installed in the stator. At high speed ratios the capacity of the torque converter is proportional to the mass flow of fluid through the stator. The mass flow is limited by a minimum flow area. The minimum flow area is represented in one dimension by distance  126  which is shown perpendicularly between the end of segment  108  on blade  100 A and step  114  on blade  100 B. Blades  100 A and  100 B are the same as blades  100 , but are given identifying letters to differentiate them from each other in this particular figure. The second dimension which defines the minimum flow area is the width of the stator blade (not shown). The width of the stator blades is not germane to the invention, and any width known in the art for stator blades may work. However, the width is assumed to be consistent from blade to blade for comparison of the performances of differently profiled blades. Thus, due to the stepped configuration of blades  100 , distance  126  and the minimum flow area, and consequently, the mass flow between blades  100 A and  100 B is increased. For example, the stepped configuration results in surface  108  of blade  100 A being axially and circumferentially further from blade  100 B and also results in step  114  of blade  100 B being axially and circumferentially further from blade  100 A. 
       FIG. 4  is a profile of present invention stator blades  150  having face, or surface,  152  and face, or surface,  162  demonstrating fluid flow through the stator at a low speed ratio. In this embodiment, face  152  is substantially similar to face  102  on stator blade  100 . Face  152  includes segment  156  and segment  158  connected by step  154 . Face  162  does not contain a step and is an example of a constant surface, airfoil shape, typical for conventional stator blades. 
     Arrow  160  represents the direction of fluid through the stator at low speed ratios of the torque converter, when blades  150  are installed in the stator. The discussion in the description of  FIG. 2  regarding flow  110  is applicable to flow  160  in  FIG. 4 . That is, flows  110  and  160  behave in substantially the same way. Fluid contacts segment  156 , the blade reacts to the force from the fluid, and the blade redirects the fluid down the blade towards segment  158 . The fluid pressure at step  154  is substantially lower than the fluid pressure at least one of segments  156  and  158 . The step provides redirection for the fluid as the fluid travels to segment  158 . The redirection of the fluid by step  154  enables the fluid to smoothly transition from segment  156  to segment  158 , and therefore provide better turning of the fluid. Despite the constant surface of second face  162 , the flow of fluid remains substantially similar to the flow of fluid in the first embodiment, as illustrated in  FIG. 2 . Therefore, the absence of a second step on blade  150  does not significantly affect the turning properties of the fluid at high speed ratios. 
       FIG. 5  is a diagram comparing the performances of present invention stepped stator blades and prior art constant surface blades in a stator (not shown) in a torque converter (not shown). It should be understood that the torque converter referenced in  FIG. 5  can be any applicable torque converter known in the art. The following should be viewed in light of  FIGS. 2-5 . In  FIG. 5 , the present invention blades are blades  100 , although it should be understood that in general, a present invention blade provides the benefits, with respect to a prior art blade, shown in  FIG. 5  and described infra. Conventional, constant surface blades do not contain steps, for example, step  104  in  FIG. 2 . That is, a conventional blade has a profile that closely resembles the shape of an airfoil. As discussed supra, present invention stepped blades, for example, blade  100  in  FIGS. 2 and 3 , provide improved fluid turning for low speed ratios and increased minimum fluid flow area for high speed ratios. Some beneficial results of the fluid turning and increased mass flow are shown in  FIG. 5 . 
     Curves  208  and  210  illustrate the relationship between the speed ratio and the k-factor, or torque capacity, for a torque converter using the stepped stator blade and the torque  10  converter using a prior art constant surface stator blade, respectively. As is known in the art, lowering the k-factor results in an increase in torque capacity. At a zero speed ratio, curve  210  is lower than curve  208 . As the speed ratio increases to 0.8, the difference between the respective curves (k-factors) increases. The lower k-factor for curve  208  indicates a substantial improvement in torque capacity for a torque converter using a present invention blade. 
     Curve  200  represents the relationship between the speed ratio and mass flow for the torque converter using the present invention stepped blade noted supra. Curve  202  represents the speed ratio and mass flow for the torque converter using the constant surface blade noted supra. The mass flow is advantageously higher for the stepped blade. As previously described, the stepped blade results in the increased mass flow by providing improved fluid turning at low speed ratios and a larger minimum flow area at higher speed ratios. Increasing the mass flow results in an improvement in k-factor and therefore torque capacity, as shown in curves  208  and  210 . 
     The relationship between the speed ratio and torque ratio for the torque converter using the stepped blades and the constant surface blades are illustrated as curves  204  and  206 , respectively. Curves  212  and  214  represent the relationship between the speed ratio and efficiency for the torque converter using the stepped stator blades and constant stator blades, respectively. As noted supra, using prior art blades, an increase in one of the k-factor, torque ratio, or efficiency, is only possible by decreasing one or both of the remaining parameters. However, the torque ratio and the efficiency associated with blades  100  and the prior art blades are nearly identical. Therefore, the stepped stator blade advantageously enables a significant improvement in k-factor, which represents a significant and desirable gain in torque capacity, while maintaining virtually the same efficiency and torque ratio. 
     It should be appreciated that the present invention stepped stator blade can be manufactured by casting, stamping, or any other blade manufacturing process known in the art. 
     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.