Torque Converter as a Vibration Damper and Its Transient Characteristics T. Ishihara Institute of Industrial Science, University of Tokyo R. I. Emori* Defense Research Laboratories, General Motors Corp. MANY VEHICLES on the road today use automatic transmis­ sions with a hydrodynamic drive, namely, a fluid coupling or a hydrodynamic torque converter. Although much work (1-3)** has been done to improve steady-state characteristics of such drives and some standard design practices (7) have been introduced recently, studies on its nonsteady-state char­ acteristics have not been very popular (4-6). Time incre­ ments of steady-state characteristics have been used to com­ pute the speed change of an accelerating vehicle. Is this method valid? The analysis of torsional vibrations of a ve­ hicle with a hydrodynamic drive in its transmission line has not been conclusive because of unknown damping character­ istics for torsional vibrations. If equations of nonsteady-state characteristics of torque converters were obtained, the varying speed of a vehicle in the course of acceleration could be computed. And if the equations were linearized for perturbations around a steady- state operating point, then the damping characteristics of torque converters for torsional vibrations could be clarified. It is the purpose of this paper to establish these criteria. THEORETICAL ANALYSIS EQUATION OF MOTION OF WORKING FLUID - The anal­ ysis will be done on three member, two phase torque con­ verter, since it is popular in automotive applications and fundamental in principle. The steady-state characteristics of torque converters are obtained by equating the net input energy to the total flow loss in the torque converter (1-3). But for a nonsteady-state motion, the net input energy is used not only to compensate the flow loss, but also to accelerate the fluid in the torque converter. By this basic principle, the equation of motion for nonsteady-state flow is obtained. Let us assume that the working fluid is concentrated on the mean flow path and that the space between members is negligibly small, as shown in Fig. 1. Using the recom­ mended practice of SAE for torque converter terminology, let wi = Angular velocity of impeller wT = Angular velocity of turbine Ri, RT, RR = Exit radii of impeller, turbine, and reactor *Now with the University of California, Los Angeles. ** Numbers in parentheses indicate References at the end of this paper. ABSTRACT — Equations of nonsteady-state motion of a torque converter were established and its speed changing performance was obtained. Damping effects of a torque converter on torsional vibrations were clarified by linearizing the equations around a steady-state operating point. Theoretical results showed good agreements with experiments. It was found that steady- state characteristics may be used in the analysis of a non­ steady-state phenomenon. Torque converters were successfully simulated by a vibra­ tion model, which simplified the vibration analysis of a sys­ tem. Downloaded from SAE International by University Of Newcastle, Thursday, August 09, 2018Ri' ,RT', RR' = Entrance radii of impeller, turbine, and reactor F = Fluid velocity of torus flow 1 = Length along the torus flow Ai, AT, AR = Net flow area normal to axial plane at impeller, turbine and reactor exits Ai', AT', AR' = Net flow area normal to axial plane at impeller, turbine and reactor entrance ai, aT, aR = Blade exit angles of impeller, turbine, and reactor (system "A" of SAE rec­ommended practice) ai', aT' ,aR' = Blade entrance angles of impeller, tur­bine, and reactor (system "A" of SAE recommended practice) and let subscript 0 represent a reference section (generally impeller exit), then where L = Total frictional loss coefficient of flow, is an integral around the torus, and Ф, Si, and ST are de- termined by torus and blade geometry. EQUATION OF MOTION OF INPUT AND OUTPUT MEM­ BERS - Applying Newto