1. Field of the Invention
The present invention relates to an image forming apparatus, more specifically relates to an improvement in an image forming apparatus including detect means for detecting a toner image formed on an image carrier (photosensitive member, intermediate transcribing member or the like).
2. Description of the Related Art
There is an image forming apparatus which is known as a printer, a copier or the like for detecting a toner image formed on an image carrier by detect means and making an image forming condition adjustable based on an output of the detect means. For example, JP-A-7-219302 describes a constitution in which a test pattern image is formed on an intermediate transcribing drum, a toner adhering amount is measured from the test pattern image by adhering amount measuring means, and various recoding processes are controlled based on a value of the measurement.
The image carrier is brought into contact with sheet when the toner image is transcribed onto sheet. There is a case in which a foreign substance of paper powder, dust and dirt or the like on sheet adheres to the image carrier by the contact. Almost all of the foreign substance adhered to the image carrier is removed by a cleaner for cleaning the image carrier, there is also a foreign substance adhered to a detecting face of detect means by passing through the cleaner, and when the foreign substance is adhered to the detecting face, the adherence causes to make the output of the detect means unstabilized or bring about erroneous detection.