PROBLEM TO BE SOLVED: To attain a preferable realization of at least one of a piezoelectric element and a movable plate and adhering of the piezoelectric element and a supporting member.SOLUTION: An actuator unit for a liquid injection device is installed at a nozzle unit comprising a liquid chamber of which inner volume can be made variable under deformation of a diaphragm at the liquid chamber side and an injection pipe for injecting liquid from the liquid chamber. The actuator unit for the liquid injection device comprises a movable plate contacted with the diaphragm at the liquid chamber side, a piezoelectric element adhered at one end in an extending or retracting direction to the movable plate to cause the movable plate to be deformed and a supporting member adhered at the other end in an extending or retracting direction of the piezoelectric element to the piezoelectric element. At least one of adhesion between the movable plate and the piezoelectric element and adhesion between the piezoelectric element and the supporting member is realized by adhesive agent containing hard material having hard material with a larger elastic modulus than that of the hardened adhesive agent.SELECTED DRAWING: Figure 11【課題】圧電素子および可動板、並びに圧電素子および支持部材の接着の少なくとも一方を好適に実現すること。【解決手段】液体噴射装置用アクチュエーターユニットは、液体室側ダイヤフラムの変形によって、室内容積が変動可能な液体室と、液体室から液体を噴射するための噴射管とを備えたノズルユニットに装着される。液体噴射装置用アクチュエーターユニットは、液体室側ダイヤフラムと接触する可動板と、伸縮方向の一端において可動板に接着され、可動板を変形させる圧電素子と、圧電素子の伸縮方向の他端において、圧電素子に接着された支持部材とを備える。可動板および圧電素子の接着、並びに圧電素子および支持部材の接着の少なくとも一方は、硬化した状態の接着剤よりも弾性率が大きい硬質材が混合されている硬質材入り接着剤によって実現されている。【選択図】図１１
