Kallionrikkomislaitteen iskulaite, menetelmä iskulaitteen ohjaamiseksi

The invention relates to a percussion device of a rock breaking device, a method for controlling the percussion device and a rock drilling unit. The percussion device (11) comprises a percussion piston (33), the work cycle of which is controlled by means of a control valve (40, 77). During the movement of the percussion piston, a pressure pulse is generated by closing a pressure connection (Y1, Y2) from at least one impulse space (44, 45) surrounding the percussion piston. The pressure pulse is used to change the position of the valve from one extreme position to an other. The impulse space is an annular space defined in a radial direction by the percussion piston and the frame (25).The frame is further provided with at least one impulse channel (58, 59) for transmitting a pressure pulse to the pressure surface of the control valve.