The present invention relates to a method of adjusting a doctor gap and an adjustment structure thereof by which the position of a doctor blade is adjusted with respect to a development roller in a development device of an image formation apparatus employing a so-called electrophotographic system, such as an electrophotographic printer.
An image formation apparatus such as an electronic copy machine, a laser printer and the like which uses so-called electrophotographic system is known in which, the image formation apparatus forming an electrostatic latent image by exposing a surface composed of a photoconductive material of a photoconductive drum which has been charged in advance with a predetermined polarity, developing the latent image by adhering toner particles on the photoconductive drum in accordance with the latent image, and transferring the toner image onto a recording medium and fixing the same at a fixing unit paper and fixing the same.
There are various methods of development in the electrophotographic system, but in many cases, a so-called magnetic brush development method is employed, wherein charged toner is adhereed to a multiplicity of magnetic particles and further adhered to an electrostatic latent image when the magnetic particles are contacted with the surface on which the latent image is formed.
The magnetic brush development method employs a so-called two-component developer composed of non-magnetic toner particles and magnetic carrier particles mixed in a predetermined ratio, but recently employed is a so-called 1.5 component development method, wherein a multiplicity of single component charging type magnetic toner particles is used and a magnetic carrier has been adhered in advance to a development roller.
A development device to which the magnetic brush method or the 1.5 component development method is applied in such a manner that a magnetic sleeve is rotatably inserted around the outer circumference of a magnetic roller to form a development roller and the sleeve of the development roller is rotated to sequentially supply toner to a development area, i.e., a contact area of the development roller and the photoconductive drum.
To develop a fine toner image, the height of the magnetic brush, i.e., the thickness of the carrier and toner on the development roller, must be regulated with pinpoint accuracy, and thus a doctor blade is provided in confrontation with the outer circumference of the development roller spaced apart from the outer circumference of the development roller by a predetermined gap, i.e., a doctor gap, thereby regulating the height of the magnetic brush.
The doctor gap is adjusted in such a manner that a flat plate-shaped gauge having the same thickness as that of the doctor gap is held between an outer circumference of the development roller and an extreme end of the doctor blade, and the doctor blade is uniformly pressed and fixed.
However, with the above conventional method of adjusting a doctor gap, the gauge must be horizontally abutted against, or fixed, to the outer circumference of the development roller and the doctor blade must be evenly pressed against the gauge along a longitudinal direction thereof by a uniform force and fixed not to be moved. Thus, a problem arises in that the adjustment operation of the doctor gap is very time consuming and an adjustment with pinpoint accuracy is very difficult.
Further, since the gauge is held between the outer circumference of the development roller and the doctor blade, there is a possibility that the outer circumference of the development roller and the extreme end of the doctor blade will be scratched.