Title of Invention

" A STATOR FOR A TORQUE CONVERTER OF A VEHICLE."

Abstract

A stator (6) disposed between an impeller (4) and a turbine (5) of a torque converter is provided that comprises: an annular shell (111); an annular core (112) disposed radially outside the shell (111); and a plurality of stator blades (113) connecting the shell (111) and the core (112), each blade (113) comprising a leading edge (114) neighboring the turbine (5), a trailing edge (115) neighboring the impeller (4), a streamlined concave surface (116) extending from the leading edge (114) to the trailing edge (115) and substantially facing the turbine (5), and a streamlined convex surface (117) extending from the leading edge (114) to the trailing edge (115) and substantially facing the impeller (4), wherein a cross-sectional area of the stator blade (113) increases as it approaches the shell (111), and a predetermined gap is formed between the neighboring stator blades (113) such that the neighboring stator blades (113) do not overlap each other.

Full Text

connecting the annular shell and the annular core. The stator blades are located circumferentially and equidistant from each other, and each stator couples the outer peripheral surface of the shell to the inner peripheral surface of the core. Fuel economy of a vehicle provided with such a torque converter deteriorates because the impeller rotates even during engine idling, and this increases engine load. Therefore, it is an important factor to decrease the load caused by the stator while the engine idles, and it is also important to increase the torque-transferring efficiency of the torque converter. When the engine rotates, the working fluid is forced to a radial outer portion of the torque converter by the impeller, and it is directed toward the turbine. However, the working fluid flows from a radial inner portion of the turbine and heads back toward a radial inner portion of the impeller. As shown in FIG. 1, a general torque converter 1 comprises an impeller 4, a turbine 5, and a stator 6 that are rotatable along an axis O-O. An engine (not shown) and a transmission (not shown) are respectively disposed at left and right sides of the torque converter 1. The torque converter is a hydraulic unit for transferring torque from the engine to the transmission. A front cover 3 is provided in a front side toward where the engine is connected. The front cover 3 is welded to the impeller 4 such that a chamber is formed therebetween, and the chamber is full of working fluid. The impeller is connected to a crankshaft of the engine, and engine torque is transmitted from the impeller to the turbine through an operation of the working fluid. The turbine is connected to an input shaft of the transmission so the engine torque is transmitted to the transmission, and torque is also transmitted from the transmission to the engine. When an engine is running, the rotating impeller causes fluid to be thrown toward turbine vanes. When this occurs with sufficient force to overcome the resistance to rotation, the turbine begins to turn, turning the transmission input shaft. When the turbine rotates, the fluid flow leaving the turbine 5 arrives at the impeller 4 by way of the stator 6. The stator 6 redirects the fluid flow from the turbine 5 to the impeller 4 in the same direction as impeller rotation, thereby assisting impeller rotation. As shown in FIG. 2, in the torque converter utilized in an automatic transmission, the stator 6 consists of an annular shell 11, an annular core 12, and a series of stator blades 13 connecting the annular shell 11 and the annular core 12. The shell 11 is generally coupled to a stator shaft (not shown) fixed to a transmission housing through a support, and the core 12 is disposed outside the shell 11. The stator blades 13 connect the shell 11 and the core 12, and they are circumferentially disposed at constant intervals. As shown in FIGs. 3 and 4, the stator blade 13 comprises a leading edge 14, a trailing edge 15, a concave surface 16, and a convex surface 17. When the working fluid flows around the stator blade, pressure acting on the concave portion 16 is greater than that on the convex portion 17. For this A STATOR FOR A TORQUE CONVERTER OF A VEHICLE FIELD OF THE INVENTION The present invention relates to a stator of a torque converter of an automotive automatic transmission. BACKGROUND OF THE INVENTION A torque converter is a hydraulic unit that transfers torque between an engine and an automatic transmission. The torque converter comprises an impeller, a turbine, and a stator that are disposed in a steel shell that is full of working fluid at all times. The impeller is disposed at a rear portion of the steel shell, and it turns with a crankshaft of an engine. The turbine is disposed at a front portion of the steel shell and is generally splined to a transmission input shaft. The turbine is free to rotate independently from the impeller. The working fluid flows from the impeller toward the turbine in a radial outer portion of the torque converter, and it flows from the turbine toward the impeller by way of the stator in a radial inner portion of the torque converter. The stator is disposed between the impeller and the turbine, and it is fixedly coupled to a stator shaft through a one-way clutch. The stator shaft is generally connected to a non-rotating member fixedly coupled to a transmission housing. The stator is generally made of synthetic resins or an aluminum alloy, and consists of an annular shell, an annular core, and a series of stator blades reason, the concave surface 16 may be referred as a high-pressure surface, and the convex surface 17 may be referred as a low-pressure surface. Both the concave and convex surface are streamlined. Because of a pressure difference between each side of the stator blade, 5 the stator 6 can rotate. The stator 6 is disposed between the impeller 4 and the turbine 5 such that the leading edge 14 is located toward the turbine 5, and the trailing edge 15 is located toward the impeller 4. The streamlined concave surface 16 faces the impeller 4, and the 10 streamlined convex surface 17 faces the turbine 5. As shown in FIG. 3, in the prior art, the leading edge and the trailing edge of the stator blade are substantially parallel and cross-sectional areas of the stator blade gradually decrease approaching the shell 11. That is, the cross-sectional area near the core 12 is greater than the sectional area near the mid 15 span, and the sectional area of near the mid span is greater than the sectional area near the shell 11. The efficiency of the torque converter using the stator blade as described in the above may be supposed from a diagram of a static pressure coefficient Cp. The static pressure coefficient is a non-dimensional value. 20 A pressure distribution around the stator blade can be supposed from the static pressure coefficient, and the efficiency of the transfer of the torque can also be supposed from the pressure distribution. The static pressure coefficient Cp can be obtained from the following equation 1. Therefore, a new shape of the stator blade that is capable of reducing the axial size and maintaining the overall hydraulic performance is demanded. SUMMARY OF THE INVENTION In a preferred embodiment of the present invention, the stator comprises an annular shell; an annular core disposed radially outside the shell; and a plurality of stator blades connecting the shell and the core, each blade comprising a leading edge neighboring the turbine, a trailing edge neighboring the impeller, a streamlined concave surface extending from the leading edge to the trailing edge and substantially facing the turbine, and a streamlined convex surface extending from the leading edge to the trailing edge and substantially facing the impeller. A cross-sectional area of the stator blade increases as it approaches the shell, and a predetermined gap is formed between the neighboring stator blades such that the neighboring stator blades do not overlap each other. Preferably, the trailing edge of each stator blade is declined such that a gap between the trailing edge and the impeller is maintained to be constant. It is also preferable that the predetermined gap is in a range of from 1.5D to2.5D. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, serve to explain the principles of the invention, where: FIG. 1 is a schematic sectional view of the torque converter according [Equation 1 ](Equation Removed) where P is the static pressure, PREF is the reference static pressure at inlet, Dis a density of the working fluid (about 813kg/D), Y is a radius of the stator, and Dis a rotation speed of the impeller (about 2500rpm). FIG. 5 shows graphs illustrating the variations of the static pressure coefficient Cp on both sides of the stator blade when the speed ratio (e) at a rotational speed (D) of the impeller to a rotation speed (No) of the turbine is 0. In the core section, a maximum difference between the high-pressure side of the stator blade and the low-pressure side of the stator blade is approximately between 2 and 2.5. Similarly, in the shell section, a maximum difference between the high-pressure side of the stator blade and the low-pressure side of the stator blade is approximately between 2 and 2.5. The difference of the static. pressure coefficient is proportional to the difference of the pressure. Therefore, as the difference of the static pressure coefficient increases, the generated torque becomes greater so that the torque transferring efficiency is improved. To reduce the axial size and weight of the automatic transmission, flattening of the torque converter is needed. A dominant factor in flattening of the torque converter is a reduction in an axial size of the stator. However, if the axial size of the stator is reduced, the overall hydraulic performance of the torque converter may deteriorate. to the prior art; FIG. 2 is a front view of the stator of the torque converter according to the prior art; FIG. 3 is a side sectional view of the torque converter of the prior art; FIG. 4 is a sectional view of the stator of the torque converter according to the prior art; FIG. 5 is graph illustrating a static pressure coefficient of the stator blade of the torque converter according to the prior art; FIG. 6 is a front view of the stator of the torque converter according to the present invention; FIG. 7 is a side sectional view of the torque converter of the prior art; FIG. 8 shows a sectional view of the stator blade of the torque converter and a pattern of working fluid flow; and FIG. 9 shows a static pressure coefficient diagram of the stator blade of the torque converter according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. As shown in FIG. 6, the stator 6 of the torque converter comprises an annular shell 111, an annular core 112, and a plurality of stator blades 113. These are preferably made of synthetic resins or an aluminum alloy as one element. The shell 111 is connected to a stator shaft (not shown) that is fixed to a transmission housing, and the core 112 is disposed radially outside the shell The stator blades 113 are connected to both the shell 111 and the core 112, and they are circumferentially disposed at constant intervals. Each of them is connected to an inner surface of the core 112 and an outer surface of the shell 111. As shown in FIGs. 7 and 8, the stator blade 113 comprises a leading edge 114, a trailing edge 115, a concave surface 116, and a convex surface 117. When the working fluid flows around the stator blade 113, pressure force acting on the concave surface 116 is greater than that acting on the convex surface 117. Both the concave and convex surfaces 116 and 117 are streamlined surfaces. For this reason, the concave surface 116 is generally referred as a high-pressure surface or a positive pressure side, and the convex surface 117 is generally referred as a low-pressure surface or a negative pressure side. Because of a pressure difference between both sides of the stator blade, the stator 6 can rotate. The stator 6 is disposed between the impeller 4 and the turbine 5 such that the convex surface 117 substantially faces the turbine 5, and the concave surface 116 substantially faces the impeller 4. When the torque converter rotates in the forward direction, a high pressure is produced in the concave surface 116, and a low pressure is produced in the convex surface 117. As shown in FIG. 8, cross-sectional areas of the stator blade 113 gradually increase as it approaches the shell 111. That is, the cross-sectional area near the core 112 is less than the cross-sectional area near the mid span, and the cross-sectional area of near the mid span is less than the cross-sectional area near the shell 111. As shown in FIG. 7, a gap between the trailing edge 115 and the impeller 4 is maintained to be substantially constant from the shell 111 to the core 112. That is, the leading edge 114 is formed in a direction parallel to a radial direction, and a length from the leading edge 114 to the trailing edge 115 increases as it approaches the shell 111. The trailing edge 115 is declined toward the shell 111 and extended toward the impeller 4 so that the concave surface 116 and the convex surface 117 respectively have substantially trapezoidal shapes. A predetermined gap between the neighboring stator blades is maintained, and it is preferable that the gap is in a range of 1.5n to 2.5D. Consequently, a window portion where the stator blades overlap each other is eliminated, and the axial size of the stator significantly decreases, so it is possible to manufacture the stator through a casting method. As shown in FIG. 8, when the torque converter 1 rotates, a high pressure region is formed near the leading edge 114, and the high pressure acts on the stator blade 113 in a rotation direction of the stator blade 113. Also, a low pressure region is formed near the trailing edge 115, and the high pressure acts on the stator blade 113 in a rotation direction of the stator blade 113. Flow characteristics in the torque converter with the stator according to the present invention will be explained by a computational flow analysis using STAR-CD® and the experiment results. Inlet and outlet angles of the impeller, the turbine, and the stator of the torque converter are set as follows. (Table Removed) The surface area of the stator is 1425D, and the solidity D is 0.7. The solidity is defined as l/s, where I is the length of the chord and s is the distance between the trailing edge and the core. Through the 3-dimensional flow analysis, the torques on each of the three components of the torque converter can be calculated by summing the partial torques, which are products of the pressure forces on each sector of the blades and the radius from the central axis. Consequently, the torque of each blade can be calculated. Using the equation 1, the static pressure coefficient Cp can be obtained, and FIG. 9 shows the result. Here, the density of the working fluid D is 843kg/D, and the rotational speed of the impeller D is 2500rpm. As shown in FIG. 9, when the speed ratio e is 0, a difference of the static pressure coefficient Cp between the high-pressure surface 116 and the low-pressure surface 117 is 3 to 4 near the core 112, and near the shell 111, a difference of the static pressure coefficients between the high-pressure surface 116 and the low-pressure surface 117 is 3 to 3.5. That is, in the stator according to the present invention, there is a difference of the static pressure coefficients between the high-pressure region and the low-pressure region. Consequently, this indicates that the torque transferring efficiency is good in comparison with the prior art stator. If the difference of the static pressure coefficient becomes larger, the torque difference becomes larger. The speed ratio e of the torque converter is defined as No/Nj, where N0 is a turbine rpm and Nj is an impeller rpm. While idling, the speed ratio is 0 because the turbine does not rotate. Further, if the torque difference becomes greater, a torque ratio also increases. The torque ratio is defined as turbine torque/impeller torque, and a torque efficiency is defined as (the torque ratio/the speed ratio)*100. Therefore, output efficiency of the torque converter according to the present invention is improved relative to the prior art torque converter. The number of blades of the stator according to the present invention has been decreased, and the thickness of the stator has also been decreased so the window has been eliminated. Consequently, the thickness of the stator has been decreased and it has become possible to manufacture the stator through a casting method. By extending the trailing edge toward the impeller, the gap between the leading edge and the impeller is maintained to be constant so that the surface of the flow is increased and the torque loss by the collision of the working to the impeller is decreased. Therefore, it is possible to reduce the thickness of the stator and increase the efficiency of the torque converter. Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concepts herein taught which may appear to those skilled in the present art will still fall within the sprit and scope of the present invention, as defined in the appended claims. We claim: 1. A stator (6) disposed between an impeller (4) and a turbine (5) of a torque converter, the stator (6) comprising: an annular shell (111); an annular core (112) disposed radially outside the shell (111); and a plurality of stator blades (113) connecting the shell (111) and the core (112), each blade (113) comprising a leading edge (114) neighboring the turbine (5), a trailing edge (115) neighboring the impeller (4), a streamlined concave surface (116) extending from the leading edge (114) to the trailing edge (115) and facing the turbine (5), and a streamlined convex surface (117) extending from the leading edge (114) to the trailing edge (115) and facing the impeller (4), wherein a cross-sectional area of the stator blade (113) increases as it approaches the shell (111), and a predetermined gap is formed between the neighboring stator blades (113) such that the neighboring stator blades (113) do not overlap each other. 2. The stator (6) of claim 1, wherein the trailing edge (115) of each stator blade (113) is declined such that a gap between the trailing edge (115) and the impeller (4) is maintained constant. 3. The stator (6) of claim 1, wherein the predetermined gap is in a range of from 1.5 mm to 2.5 mm.

Documents:

716-del-2002-Abstract-(06-05-2011).pdf

716-del-2002-abstract.pdf

716-del-2002-Claims-(06-05-2011).pdf

716-del-2002-claims.pdf

716-del-2002-Correspondence-Others-(06-05-2011).pdf

716-del-2002-correspondence-others.pdf

716-del-2002-correspondence-po.pdf

716-del-2002-description (complete).pdf

716-del-2002-Drawings-(06-05-2011).pdf

716-del-2002-drawings.pdf

716-del-2002-form-1.pdf

716-del-2002-form-18.pdf

716-del-2002-form-2.pdf

716-del-2002-form-26.pdf

716-del-2002-Form-3-(06-05-2011).pdf

716-del-2002-form-3.pdf

716-del-2002-form-5.pdf

716-del-2002-Petition 137-(06-05-2011).pdf