Patent ID: 7156509

Claim:
An image forming apparatus, comprising: an ink containing section for retaining ink; and an ink supplying path for supplying the ink from the ink containing section to a print head, wherein: the ink supplying path therein includes a filter, which generates negative pressure when the ink is supplied, the negative pressure being smaller than ink absorbing pressure of a nozzle of the print head, wherein: the ink containing section therein includes a porous ink absorbing body for retaining ink, the image forming apparatus satisfies: 4 ·η/D N −|Ph |>4 ·η/F′>|Pμ|+|Pi| P μ=( k/A )□{μ· L ·( N·R ) 2 /S}·Q (where the coefficient (k/A)=485, F′=F when an opening of the filter is circle; F′=√2·F in other cases), where Ph (Pa) expresses a head pressure between an ink discharging throat of the nozzle of the print head and an ink supplying throat of the ink containing section; Pi (Pa) expresses a head pressure of the ink containing section which occurs when the ink is going to be supplied to the print head via the ink supplying throat when the ink containing section is filled with the ink; Pμ (Pa) expresses a pressure loss due to a viscosity resistance of the ink containing section; F(m) expresses a filtration accuracy of the filter; D N (m) expresses a diameter of the nozzle of the print head; η (N/m) expresses a surface tension of the ink; N (cells/m) expresses a cell density of the ink absorbing body before the ink absorbing body is contained in the ink containing section; R expresses a compressibility which is a volume ratio of the ink absorbing body when the ink absorbing body is contained in the ink containing section in a compressed state to the ink absorbing body before the ink absorbing body is contained in the ink containing section; S (m 2 ) expresses a cross-sectional area of the ink absorbing body when the ink absorbing body is contained in the ink containing section in a compressed state; and L expresses a length (m) of the ink absorbing body when the ink absorbing body is contained in the ink containing section in a compressed state.