7 is opened the spring neutral point of the plate spring is returned to the position s 0 and the spring constant returns to the original one or h as shown in fig9 a and this time the hammer 1 is attracted toward the core by the attraction energy represented b returning to the standby position according to the present invention the printing energy represented by a in fig9 b can be increased and therefore a higher speed operation can be achieved and in addition since the current flowing through the electromagnetic coil can be decreased while increasing the printing energy as compared with the conventional method it is possible to realize as compared to the conventional device a low cost printing head capable of performing continuous printing with less heat generation moreover when applying voltage to the piezoelectric element 7 if a high voltage controlled and determined experimentally for suppressing the rebound phenomenon normally occuring when the hammer is returned is applied it is possible to suppress the rebound phenomenon minimize noise generation and remarkably reduce the wear of the hammer and core fig1 shows the dynamic characteristic of the tips of hammer pins in the prior art the attenuation time t s of the hammer attributed to the rebound phenomenon is relatively long and the printing period t rep is considerably longer than the flying time t f on the other hand in the present invention t 39 s is relatively small and the printing period t 39 rep is relatively short and thus high speed operation is effected furthermore the rebound phenomenon is not present the wear of the plate spring and the magnetic pole which has been considered as one of the.