31 directly into the substrate 37 the clean air 31 that has cooled the head driving substrate 37 flows toward a conveyor belt 4 the substrate 37 can thus be cooled without using any dedicated cooling fan a slight amount of air that flows toward the conveyor belt 4 from a gap between the ink jet head 1 and a head supporting member not shown is part of clean air 31 including no dust thus there is no danger that dust will be attached to the ink jet head 1 an image recording apparatus according to a third embodiment of the present invention will be described with reference to fig1 the same constituting elements as those of the first embodiment are indicated by the same reference numerals and their detailed descriptions are omitted fig1 shows an enlarged view of a discharge outlet 23 and its periphery an ink jet head 1 a conveyor belt 4 a conveyor belt driving roller 5 a recording medium 7 a discharge roller 38 and a partition plate 39 with a slit are arranged close to the discharge outlet 23 they are included in the image recording apparatus as shown in fig1 in the first embodiment the clean air 31 flows toward the discharge outlet 23 through the space 33 between.