Field of the Invention
One disclosed aspect of the embodiments relates to an image forming apparatus, such as a printer, a copying machine, or a multifunction peripheral, that forms an image on a sheet.
Description of the Related Art
An image forming apparatus forms an electrostatic latent image by irradiating a photosensitive member with a laser beam, and forms a toner image by developing this electrostatic latent image with toner. The image forming apparatus then transfers the formed toner image onto a sheet, and fixes the toner image with heat. The image forming apparatus thus forms an image on a sheet. The image forming apparatus sets an image forming condition, e.g., an optimum fixing temperature and a sheet conveyance speed, according to sheet characteristics. Examples of the sheet characteristics include a sheet thickness, a sheet surface condition, and a sheet type. The sheet characteristics are set by a user operation via an operation unit provided on the image forming apparatus and/or a print setting screen of a printer driver. Some commercialized image forming apparatuses detect sheet characteristics with a built-in sensor (hereinafter referred to as “medium sensor”), and automatically set an image forming condition according to the detection result. Using the medium sensor eliminates need for setting the sheet characteristics by the user, thereby enhancing usability.
In such an image forming apparatus, either “automatic detection mode” or “user specification mode” is selectable as an operation mode. The automatic detection mode is provided to detect the sheet characteristics by using the medium sensor. The user specification mode is provided to set the sheet characteristics through the user operation. Detection of sheet characteristics by using the medium sensor is difficult depending on types of sheet characteristics. To that end, the image forming apparatus has the user specification mode for manually setting the sheet characteristics without using the medium sensor. The user designates the operation mode.
The medium sensor is generally provided on a sheet conveyance path between a sheet feed cassette and a transfer position. The medium sensor detects the sheet characteristics when the conveyed sheet arrives at a position where the medium sensor is provided. The image forming apparatus adjusts each part in the image forming apparatus, in order to form an image under an image forming condition according to the sheet characteristics detected by the medium sensor. Meanwhile, the conveyance of the sheet is in a waiting state. To suppress the occurrence of such a waiting state, United States Patent Publication Application No. 2011/0001996 discusses an image forming apparatus that forms an image by using sheet characteristics detected from a first sheet, without detecting sheet characteristics of second and subsequent sheets, among sheets fed from the same sheet feed cassette. This image forming apparatus needs not to detect the sheet characteristics of the second and subsequent sheets, and thus can suppress the occurrence of the waiting state, which reduces image forming time period.
Setting of the user specification mode causes the image forming apparatus not to detect the sheet characteristics with the medium sensor, even in a case where the sheets are fed from the same sheet feed cassette. As a result, in a case where the operation mode is changed from the user specification mode to the automatic detection mode, the sheet characteristic detection is performed, and conveyance of sheets becomes in a waiting state, causing the occurrence of waiting time. This increases the time necessary for an image forming process.
One disclosed embodiment is directed to an image forming apparatus that suppresses additional image forming time due to detection of sheet characteristics, even in a case where an operation mode is switched.