A developing cartridge that generally contains toner is removably installed in a main body of an image forming apparatus, such as a laser printer. The developing cartridge is provided in its case with a toner chamber configured to contain toner, an agitator rotatably disposed in the toner chamber, a supply roller configured to supply the toner, a developing roller configured to carry the toner thereon, a layer-thickness regulating blade configured to form a thin layer of toner on the developing roller.
As the developing cartridge is driven after being installed in the main body, the toner in the toner chamber is supplied to the supply roller according to the rotation of the agitator. Thereafter, the toner is supplied to the developing roller in accordance with the rotation of the supply roller. Then, the toner passes between the layer-thickness regulating blade and the developing roller in accordance with the rotation of the developing roller, and is carried on the developing roller as a think layer. A developing bias is applied to the developing roller. An electrostatic latent image formed on a photoconductive drum is developed by the toner carried on the developing roller.
The developing cartridge includes a gear mechanism configured to drive the developing roller, the supply roller, and the agitator. For example, Japanese Laid-Open Patent Publication No. 2003-295614 discloses the gear mechanism provided in one sidewall of the case of the developing cartridge. The gear mechanism in the developing cartridge includes an input gear to which the drive force is input from the main body of the image forming apparatus.
A bearing member configured to support an end of the developing roller is provided on the other sidewall of the case of the developing cartridge. The bearing member is integrally formed with a feeding member configured to apply developing bias to the developing roller.
In the developing cartridge disclosed in Japanese Laid-Open Patent Publication No. 2003-295614, a line, parallel to the developing roller shaft, passing through the input gear provided on one sidewall and another line, parallel to the developing roller shaft, passing through the feeding member provided on the other sidewall, are disposed parallel to each other with some distance therebetween. If such rotation or torsion power is exerted on the developing cartridge that produces rotation or torsion of the developing cartridge about the input gear when drive force is input to the input gear from the main body of the image forming apparatus, the feeding member provided on the other sidewall is placed out of position, resulting in poor power supply or power feeding from the main body of the image forming apparatus.