Patent GB-1499114-A (GB)
Title: Torque converter
IPC: F16H33/08
Filed: 1974-12-23
Abstract: 1499114 Variable-speed gear NATIONAL RESEARCH DEVELOPMENT CORP 9 Feb 1976 [23 Dec 1974] 55452/74 Heading F2D In a torque converter of the kind in which a pulsator 12, Fig. 2, driven by a rotary input member 10 is coupled to an output member 16 through an intermediate member 13 which drives the output member through coupling means 15 when the pulsator delivers torque in one sense but is held against rotation by means 14 when the pulsator delivers torque in the opposite sense the inertia of the intermediate member is determined such that the torque characteristics of the converter are suited to automative application, although the invention is not confined to that application. In an arrangement in which the ratio of peak torque delivered by the pulsator, expressed in Nm., to the square of the angular velocity of the input member, in radians/sec., is a constant, the inertia of the intermediate member, in kg. m.<SP>2</SP> is made equal to a predetermined multiple, in the range 3À6 N to 4À4 N, of that constant, where N is the number of revolutions of the input member required to produce one complete cycle of alternating torque applied to the intermediate member when the latter is held stationary. Alternatively, the inertia of the intermediate member may be defined in terms of a critical value of the inertia, lying within the range 1À1 to 0À9 times that critical value which is defined as the value at which torque from the pulsator is just not sufficient to accelerate the intermediate member from zero to the speed of the input member during one cycle of alternating torque from the pulsator with the output member unloaded and in the absence of internal friction in the pulsator. A suitable kind of pulsator consists of a disc 17, Fig. 3, driven by the input member, a toothed sun wheel 22 secured to the intermediate member, and planetary pinions 20, 21 rotatably mounted on the disc to mesh with the sun and carrying out-of-balance weights 26, 27. The pinions may have the same number of teeth as the sun, as shown, in which case one revolution of the disc causes the application of one cycle of alternating torque to be applied to the sun when the latter is stationary, or the number of teeth on the planets may be in the ratio of, e.g. 5 : 3 to the number on the sun. Direct drive is obtained when, in operation, the sun has accelerated to the same speed as the disc and the pinions remain stationary on their spindles 18, 19. With a constant input speed the arrangement exhibits a rising torque characteristic as output speed increases and two expedients are adopted to modify this characteristic to suit automative application. One consists in boosting the low-speed torque available by the use of friction-damped springs between the reaction member of the one-way device 14 and its fixed anchorage, and/or at a point between the intermediate member 13 and the output shaft 16. The other consists in limiting the torque at high speeds by determining the inertia of the intermediate member as described above. In the diagrammatic arrangement in Fig. 14, the intermediate member, whose inertia is represented by the disc 45, consists of a shaft 49 fixed to a member 48 constituting the outer part of the two one-way devices 14, 15, the device 15 driving the output shaft through a quill shaft 37 constituting a spring damped by means 47, and the device 14 reacting against a fixture through a torsion spring tube 41 damped by a device 46. Preferably the quillshaft is damped by a floating mass type of torsional damper at its left-hand end. Torque fluctuations in the final output are damped by a flywheel 50 and resilient coupling 51 which may be constituted by the vehicle propeller shaft &c. In a compact arrangement according to Fig. 16 the torsion spring 41 is folded back on itself and anchored at 54, and a tube 56 splined at 55 to the quill shaft 40 carries a flywheel 50. The various bearings 62, 63, 64, 65 may provide sufficient friction for spring damping. Performance may be adjusted by provision of means for clutching in or out additional masses, or means for pumping fluid into or out of a flywheel to vary its inertia.