A drug injection device (1) comprising a dose expelling mechanism for expelling drug from a reservoir through a reservoir outlet, the dose expelling mechanism comprising: a first component (40), a second component (10, 10, 15, 10", 15"), and a torsion spring element (20) for inducing relative rotation between the first component (40) and the second component (10, 10, 15, 10", 15") to execute a dose expelling operation, the torsion spring element (20) extending along a longitudinal axis and comprising: a first spring end portion (22) being rotationally restrained with respect to the first component (40), and a second spring end portion (23) exhibiting an end portion inner diameter in a relaxed state of the torsion spring element (20), wherein the second spring end portion (23) is fitted over a spring receiving portion (11) of the second component (10, 10, 15, 10", 15"), the spring receiving portion (11) having a transversal dimension which is larger than the end portion inner diameter, and the fitting of the second spring end portion (23) over the spring receiving portion (11) being configured to provide a sticking friction engagement between the two when the torsion spring element (20) is strained to exert a maximum in-use torque.La présente invention concerne un dispositif dinjection de médicament (1) comprenant un mécanisme déjection de dose pour éjecter un médicament à partir dun réservoir à travers une sortie de réservoir, le mécanisme déjection de dose comprenant : un premier composant (40), un second composant (10, 10 , 15 , 10 ", 15 "), et un élément de ressort de torsion (20) afin dinduire une rotation relative entre le premier composant (40) et le second composant (10, 10 , 15 , 10 ", 15 ") pour exécuter une opération déjection de dose, lélément de ressort de torsion (20) sétendant le long dun axe longitudinal et comprenant : une première partie dextrémité du ressort (22) étant retenue de manière rotative par rapport au premier composant (40), et une second
