Image forming apparatus

Abstract

An image forming apparatus includes an image forming section for forming a plurality of toner images on a plurality of image bearing members respectively by an electrographic system; an endless belt to which the plurality of toner images are to be superimposedly transferred from the plurality of image bearing members, the endless belt being arranged close to the image forming section; a driving roller which the endless belt is placed on and is adapted to drive the endless belt; a driven roller which the endless belt is placed on; a detector for detecting a surface condition of the endless belt; and a controller for controlling at least one of the surface speed of the image bearing member and the moving speed of the endless belt in accordance with an output from the detector.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view showing a schematic structure of a tandem type color printer according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical structure of a main part of the printer.

FIG. 3 is a schematic diagram showing a construction of an optical detector, and a detection under the condition where an appropriate amount of toner particles adhere to an intermediate transfer belt.

FIG. 4 is a schematic diagram showing a detection by an optical detector under the condition where no toner particles adhere to the intermediate transfer belt.

FIG. 5 is a schematic diagram showing a detection by the optical detector under the condition where toner particles unproperly adhere to the intermediate transfer belt.

FIG. 6 is a graph showing a relation between a coverage factor calculated by the optical detector and an actual toner concentration.

FIG. 7 is a graph showing a relation between a corrected coverage factor calculated based on a durability and an actual toner concentration.

Claims

1. An image forming apparatus comprising: an image forming section for forming a plurality of toner images on a plurality of image bearing members respectively by an electrographic system;an endless belt to which the plurality of toner images are to be superimposedly transferred from the plurality of image bearing members, the endless belt being arranged close to the image forming section;a driving roller which the endless belt is placed on and is adapted to drive the endless belt;a driven roller which the endless belt is placed on;a detector for detecting a surface condition of the endless belt; and,a controller for controlling at least one of the surface speed of the image bearing member and the moving speed of the endless belt in accordance with an output from the detector.

2. An image forming apparatus according to claim 1, wherein the controller controls the surface speed of the image bearing member while keeping the moving speed of the endless belt constant.

3. An image forming apparatus according to claim 1, wherein the output of the detector is associated with a friction coefficient of the surface of the endless belt; and, the controller increases a difference between the surface speed of the image bearing member and the moving speed of the endless belt when the friction coefficient decreases.

4. An image forming apparatus according to claim 1, wherein the detector includes an optical detecting unit.

5. An image forming apparatus according to claim 4, wherein the controller carries out the speed control in accordance with a durability of the endless belt that is calculated from an output from the optical detecting unit.

6. An image forming apparatus according to claim 4, wherein the optical detecting unit takes up a predetermined pattern image formed on the endless belt by the image bearing member for calculation of a concentration of toner adhered on the endless belt based on a measurement of the predetermined pattern image.

7. An image forming apparatus according to claim 1, wherein the moving speed of the endless belt driven by the driving roller is higher than the surface speed of the image bearing member.

8. An image forming apparatus according to claim 1, wherein the controller includes: a first calculating section for calculating a parameter value correlated with a surface condition of the endless belt based on an output from the detector; and,a second calculating section for carrying out a calculation to control at least one of the surface speed of the image bearing member and the moving speed of the endless belt based on the parameter value.

9. An image forming apparatus according to claim 8, wherein the controller further includes a third calculating section for calculating a concentration of toner on the endless belt based on an output from the detector, and calculating a correction amount for a predetermined image forming condition based on the obtained toner concentration.