In a typical electrophotographic printing process, a photoconductive member is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member selectively dissipates the charge thereon in the irradiated areas. This records an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material including toner into contact therewith. Generally, the developer material is made from toner particles adhering triboelectrically to carrier granules. The toner particles are attracted from the carrier granules to the latent image forming a toner powder image on the photoconductive member. The toner powder image is then transferred from the photoconductive member to a copy sheet. Heat via the fuser roller(s) is applied to the toner particles to permanently affix the powder image to the copy sheet.
Some problems may occur when the recording sheet with toner passes through the fuser rollers. One such problem occurs when the toner on the recording sheet adheres to one of the fuser rollers resulting in image contamination as the toner does not adhere to the correct location on the recording sheet or remains on the roller and is not transferred to the recording sheet. An additional problem occurs when the recording sheet is inadvertently wound around one of the fuser rollers causing a paper jam.
Oil is applied to one or both of the fuser rollers to overcome these problems. The oil reduces the amount of toner that adheres to the rollers and also lessens the likelihood of the recording sheet becoming entangled. An oil applicator is positioned adjacent to the rollers for distributing the oil. The application of oil to the fuser rollers may result in additional problems if the correct amount is not applied. Any suitable oil can be used in the present invention such as the oils disclosed in U.S. Pat. No. 7,214,462; the disclosure of U.S. Pat. No. 7,214,462 is incorporated by reference into the present disclosure.
Inconsistent oil transfer to the rollers during the life of the oil applicator could cause other problems. Many designs result in an over-abundance of oil being transferred to the fuser roller early in the life of the applicator. Too much oil distributed onto the rollers may be transferred to the recording sheet resulting in oil spots that are visible to the user thereby ruining the sheet. The same applicators often do not apply an adequate amount of oil during the end of their life. When applying inadequate oil, results in toner adhering to the fuser rollers and/or the recording sheet sticking to the fuser rollers, both of which are unacceptable results. Inconsistent oil application also makes it difficult to predict the expected life of the oil applicator.
In prior art systems, variations in the oil surface thickness, oil temperature or oil viscosity generally requires a total redesign of the oil application structure. Each system has a fixed oil application operating temperature, oil viscosity, and an applied film thickness. This is a serious disadvantage that is overcome by the present invention. There was little, if any, variation control of variable oil rate application.