the user know ink amount information in the ink cartridge timely the ink cartridge 1 is further provided with a detecting mechanism for detecting the residual amount of ink after the above mounting and detecting of the ink cartridge are completed the ink cartridge needs to be continuously mounted by a certain distance and then the inclined plane 313 a crosses the inclined plane 411 a and thereby the inclined plane 313 b abuts against the inclined plane 411 b as the push rod moves towards a direction opposite to the inserting direction of the ink cartridge the pushing force of the inclined plane 313 b on the inclined plane 411 b is gradually reduced and therefore the movable body 41 gradually moves up in height direction under an elastic restoring force of the elastic member 42 and restores to the initial position as shown in fig8 the second detecting mechanism 40 enters the signal path of the second sensor 102 again and shields or changes path of the light signal emitted by the light transmitting part of the second sensor 102 again this principle has been described above and is not repeated here after the ink cartridge in a mounted state has performed a certain amount of printing operations ink in the ink storage chamber is gradually consumed and the ink in the ink cup 50 is gradually reduced until fully consumed as shown in fig9 light emitted by the light transmitting part of the second sensor 102 is irradiated to the reflective plane 51 a or 51 b of the prism 51 after being reflected by the inclined plane 412 a and at this time there is no ink in the ink cup 50 light.