Patent ID: 8213836

Claim:
A developing device having stirring members for stirring a developer-tank-contained developer containing toner and carrier inside a developer tank while conveying the developer along conveying passages and a developer holder disposed adjacent to said stirring members to supply the stirred developer-tank-contained developer to an electrostatic latent image holder, comprising: a developer replenishing tank for replenishing the toner and the carrier to said developer tank, and a discharging mechanism for discharging an excessive amount of the developer-tank-contained developer outside said developer tank from a discharge opening section when the amount of the developer-tank-contained developer to be conveyed using said stirring members inside said developer tank exceeds a predetermined amount, wherein said stirring members comprises an upper stirring member and a lower stirring member disposed so as to be opposed to said upper stirring member, said conveying passages include an upper conveying passage in which said upper stirring member is disposed, a lower conveying passage in which said lower stirring member is disposed, a circulating flow outlet provided in a side wall on the downstream side of said upper conveying passage and on the side opposed to said lower conveying passage and a communicating passage for connecting the downstream side of said lower conveying passage to the upstream side of said upper conveying passage, and also include a circulation passage through which the developer-tank-contained developer circulates using said upper conveying passage, said circulating flow outlet, said lower conveying passage and said communicating passage, said discharging mechanism is disposed in the downstream end section of said upper conveying passage, said circulating flow outlet is positioned above the level of the developer-tank-contained developer conveyed on the upstream side of said lower conveying passage, and the circulating flow outlet is formed by cutting out an upper portion of a partition wall for partitioning the space between the lower conveying passage and the upper conveying passage, so that the developer-tank-contained developer is configured so as to climb over an upper end section of the cut out partition wall and to flow down toward the lower conveying passage like a waterfall.