# SAE J641V002

SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.TO PLACE A DOCUMENT ORDER: (724) 776-4970 FAX: (724) 776-0790SAE WEB ADDRESS http://www.sae.orgCopyright 2000 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001RECOMMENDEDPRACTICESubmitted for recognition as an American National StandardJ641REAF.MAR2000Issued 1951-01Reaffirmed 2000-03Superseding J641 AUG1993Hydrodynamic Drives Terminology1. Scope—Since the torque converter and fluid coupling have become commonly used components ofautomatic transmissions in industry, the SAE appointed a committee to standardize terminology, testprocedure, data recording, design symbols, and so forth, in this field. The following committeerecommendations will facilitate a clear understanding for engineering discussions, comparisons, and thepreparation of technical papers.The recommended usages represent the predominant practice or the acceptable practice. Where agreementis not complete, alternates have been included for clarification.EXAMPLE—Two systems of blade angle designations are described. Consequently when a blade angle isspecified, the system should be designated.This SAE Recommended Practice deals only with the physical parts and dimensions and does not attempt tostandardize the design considerations, such as the actual fluid flow angle resulting from the physical bladeshape.2. References2.1 Applicable Publication—The following publication forms a part of this specification to the extent specifiedherein. Unless otherwise indicated, the latest version of SAE publications shall apply.2.1.1 SAE PUBLICATION—Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001.SAE J1087—One-Way Clutches—Nomenclature and Terminology3. Definitions3.1 Hydrodynamic Drive—In contrast with electrical or mechanical drives, a hydrodynamic drive transmits powersolely by dynamic fluid action in a closed recirculating path.3.2 Fluid Coupling—A hydrodynamic drive which transmits power without ability to change torque. (Torque ratiois unity at all speed ratios.) See Figure 1.SAE J641 Reaffirmed MAR2000-2-FIGURE 1—FLUID COUPLING3.3 Torque Converter—A hydrodynamic drive which transmits power with ability to change torque. (Torque ratiochanges as speed ratio changes.) See Figure 2.FIGURE 2—TWO-PHASE, SINGLE-STAGE TORQUE CONVERTER(SINGLE-PHASE, SINGLE-STAGE IF ONE-WAY CLUTCH IS DELETED)SAE J641 Reaffirmed MAR2000-3-3.4 Element—An element consists of a single row of flow directing blades. See Figure 3.FIGURE 3—THREE-MEMBER, SIX-ELEMENT, SINGLE-PHASE,THREE-STAGE TORQUE CONVERTER3.5 Member—A member is an independent component of a hydrodynamic unit such as an impeller, reactor, orturbine. It may comprise one or more elements. See Figure 3.3.6 Stage (Single-, Two-, Three-, etc.)—A stage is a turbine element interposed between elements of othermembers. The number of stages is the number of such elements of the turbine member. See Figures 2 and 3.3.7 Phase (Single-, Two-, Three-, etc.)—Applied to a torque converter, refers to the number of functionalarrangements of the working elements when the functional change is produced by a one-way clutch or othermechanical means such as a clutch or brake. See Figures 2 and 3.3.8 Impeller—Designates the power input member.3.9 Turbine—Designates the output member.3.10 Reactor (or Stator)—Designates the reaction member.3.11 One-Way Clutch—See SAE J1087.SAE J641 Reaffirmed MAR2000-4-3.12 Clutch-Type Torque Converter—A hydrodynamic torque converter using a clutch to provide a directmechanical drive. See Figure 4.FIGURE 4—CLUTCH-TYPE TORQUE CONVERTER3.13 Clutch Piston—A friction element device which can mechanically couple the impeller to the output. SeeFigure 4.3.14 Spring Damper (or Flexible Coupling)—A device that reduces the amplitude of torsional vibration to theoutput. See Figure 4.3.15 Naming of Multiple Members—Multiple members that perform basically the same function in both polyphaseand multistage torque converters are named in the order of fluid circulation in normal operation:a. First impeller, second impeller, etc.b. First turbine, second turbine, etc.c. First reactor, second reactor, etc.3.16 Blade—Within an element, designates the means of directing fluid flow.3.17 Variable Blade—Designates a blade provided with control means to vary the angular position and thus varythe direction of fluid flow.SAE J641 Reaffirmed MAR2000-5-3.18 Torus Section—Designates the confines of a flow circuit in a radial plane of a torque converter or fluidcoupling.3.19 Shell—Designates the outside wall of the torus section in any member. See Figures 1 and 2.3.20 Core—Designates the inside wall of the torus section in any member. See Figures 1 and 2.3.21 Design Path—The path of the assumed mean effective flow, used for definition of blade angles, entrance andexit radii, etc. See Figures 1 and 2.3.22 Bias (Entrance and Exit)—At the entering and exit blade edges, designates the angular variance with respectto an axial plane at the design path. The angle is measured as viewed in an axial direction. See Figure 5.FIGURE 5—BLADE TERMINOLOGY (TURBINE)3.23 Scroll—The angle between the two planes containing the intersection of the design path and the entering andleaving edges of the blade when the blade does not lie in one axial plane. See Figure 5.3.24 Torque Converter Size—In general terms, is designated by the maximum diameter of the flow path. SeeFigure 1.SAE J641 Reaffirmed MAR2000-6-3.25 Design Radii (Entrance or Exit)—Design radii of any member are taken at the point of intersection of thedesign path with the theoretical blade edges. See Figure 5.3.26 Slip—Designates the difference between input speed (Ni) and output speed (No). It may also be expressed asa percent of input speed.3.27 Speed Ratio—Designates the output speed divided by the input speed (No/Ni).3.28 Torque Ratio—Designates the output torque divided by the input torque (To/T i).3.29 Capacity Factor for a Hydrodynamic Drive—The input speed in rpm (Ni) divided by the square root of theinput torque (Ti) (see Equation 1).(Eq. 1)3.30 Stall Torque Ratio—Designates the torque ratio when the turbine is restrained from rotating.3.31 Stall Start—Accomplished by restraining the vehicle with the brakes, opening the throttle fully, andsubsequently releasing the brakes after the engine has attained maximum stall speed.3.32 Stall Speed—Designates the input speed in rpm at a specified input torque when the turbine is restrained fromrotating.3.33 Racing Speed—Designates the input speed in rpm at a specified input torque when the turbine is notrestrained from rotating.3.34 Torque Conversion Range—Designates the range of operation where torque multiplication exists.3.35 Coupling Range—Designates the range of operation at which torque ratio is unity.3.36 Coupling Point—Designates the point where the torque conversion range ends and the coupling rangebegins.3.37 Hydrodynamic Unit Charge Pressure—Designates the externally applied hydraulic fluid pressure underwhich the hydrodynamic unit operates.3.38 Mean Camberline—Mean camberline is the locus of the centers of the series of circles which are tangent toboth surfaces of the blade profile. See Figure 6.This method of mean camberline determination is shown for a continuously varying double surface type ofhydrofoil. The same system applies to all other types of blade profiles, including cases where discontinuitiesarise, because of edge modifications, as with sheet metal blades.3.39 Blade Angles—Unless otherwise specified, a blade angle is measured from a zero reference to the linetangent to the mean camberline extended in the direction of flow from the point of interest on the design path.The variation of angle at points other than on the design path must be specified. A blade is generally identifiedby the angles at its entrance and exit edges.3.40 Blade Angle Systems—See Figure 7.KNiTi---------=SAE J641 Reaffirmed MAR2000-7-FIGURE 6—DEVELOPED SECTION OF BLADE AT INTERSECTION WITH DESIGN PATH SURFACEFIGURE 7—BLADE ANGLE SYSTEMSSAE J641 Reaffirmed MAR2000-8-3.40.1 SYSTEM A—In this system, the zero reference is the plane containing the axis of rotation and the point oftangency on the blade mean camberline.Angle limits are −90 and +90 degrees. A positive angle is one whose side tangent to the mean camberlineextends in the direction of impeller rotation. A negative angle is one whose tangent side extends opposite tothe direction of impeller rotation. In this system, the sine and tangent functions of the blade angle, as used intorque converter design, have the same sign as the angle, and the cosine function is always positive.3.40.2 SYSTEM B—In this system, the zero reference is the line extended from the point of tangency in the directionof impeller rotation and normal to the plane containing the axis of rotation and the point of tangency.Angle limits are 0 and 180 degrees. The angle is less than 90 degrees when the side tangent to the meancamberline extends in the direction of impeller rotation. It is more than 90 degrees when the tangent sideextends opposite to the direction of impeller rotation. In this system, a trigonometric function of a bladeangle, as used in torque converter design, derives its plus or minus sign from the appropriate table for thecorresponding quadrant.PREPARED BY THE SAE TERMINOLOGY STANDARDS COMMITTEESAE J641 Reaffirmed MAR2000Rationale—Not applicable.Relationship of SAE Standard to ISO Standard—Not applicable.Application—Since the torque converter and fluid coupling have become commonly used components ofautomatic transmissions in industry, the SAE appointed a committee to standardize terminology, testprocedure, data recording, design symbols, and so forth, in this field. The following committeerecommendations will facilitate a clear understanding for engineering discussions, comparisons, and thepreparation of technical papers.The recommended usages represent the predominant practice or the acceptable practice. Whereagreement is not complete, alternates have been included for clarification.EXAMPLE—Two systems of blade angle designations are described. Consequently when a blade angleis specified, the system should be designated.This SAE Recommended Practice deals only with the physical parts and dimensions and does notattempt to standardize the design considerations, such as the actual fluid flow angle resulting from thephysical blade shape.Reference SectionSAE J1087—One-Way Clutches—Nomenclature and TerminologyDeveloped by the SAE Terminology Standards Committee