A HYDRAULIC TRANSMISSION

A hydraulic transmission (1) connected to a prime mover (2), and comprising an input shaft (A), a first hydraulic machine (4), a second hydraulic machine (6), each of the hydraulic machines comprising a plurality of working chambers having a volume which varies cyclically with rotation of a respective rotatable shaft, a hydraulic circuit (14, 34, 47, 48) extending between a group of one or more working chambers of the first hydraulic machine and the second hydraulic machine, each working chamber of each hydraulic machine comprising a low-pressure valve which regulates the flow of hydraulic fluid between the working chamber and a low-pressure manifold and a high-pressure valve which regulates the flow of hydraulic fluid between the working chamber and a high-pressure manifold, each hydraulic machine being configured to actively control at least the low-pressure valves of the group of one or more working chambers to select the net displacement of hydraulic fluid by each working chamber on each cycle of working chamber volume, and thereby the net displacement of hydraulic fluid by the group of one or more working chambers, responsive to a demand signal. In such a hydraulic transmission it should be possible to recover energy. To this end a rotatable shaft of the first hydraulic machine (4) or the input shaft (A) is in driven engagement with a first input/output shaft of a speed/torque summing assembly (5), a rotatable shaft of the second hydraulic machine (6) is in driven engagement with a second input/output shaft of the speed/torque summing assembly (5), and the output shaft (7) is in driven engagement with a third input/output shaft of the speed/torque summing assembly (5). L'invention concerne une transmission hydraulique (1) reliée à un moteur primaire (2), et comprenant un arbre d'entrée (A), une première machine hydraulique (4), une seconde machine hydraulique (6), chacune des machines hydrauliques comprenant une pluralité de chambres de travail ayant un volume qui varie cycliquement avec la rotation d'un arbre rotatif respectif, un circuit hydraulique (14, 34, 47, 48) s'étendant entre un groupe d'une ou plusieurs chambres de travail de la première machine hydraulique et de la seconde machine hydraulique, chaque chambre de travail de chaque machine hydraulique comprenant une soupape basse pression qui régule le flux d'un fluide hydraulique entre la chambre de travail et un collecteur basse pression et une soupape haute pression qui régule le flux d'un