1. Field of the Invention
The present invention relates to a feeding device that extracts a recording sheet from a plurality of stacked recording sheets and conveys the extracted sheet, and a recording apparatus including the feeding device.
2. Description of the Related Art
A feeding device is provided in a recording apparatus such as a copier, a printer, or a facsimile, to feed a recording sheet or the like. The feeding device separates a plurality of stacked recording sheets one by one with a feeding roller and a separating mechanism, and conveys the recording sheet to a downstream side. In many cases, a stacking portion in which the recording sheets are stacked is provided with a pressure plate that presses the stacked recording sheets to the feeding roller.
A sheet detecting portion that detects presence of a recording sheet is provided downstream of the feeding roller. After a feeding operation is started, the presence of the recording sheet is checked, so as to check whether a recording sheet is stacked on the feeding device or not, and whether the feeding operation is successfully performed or not. If the sheet detecting portion does not detect a recording sheet within a predetermined time from the start of the feeding operation, the feeding operation is performed again at a speed, which is equivalent to or slower than a feeding speed of the first feeding operation. Such an operation is generally called retry feeding.
If, for example, paper dust adheres on the feeding roller and a friction coefficient is reduced, a slip may occur between the feeding roller and a recording sheet during feeding. The recording sheet may not be extracted from the stacking portion by the first feeding operation. Even when the recording sheet could be extracted from the stacking portion, the recording sheet may not be conveyed to the sheet detecting portion. Also, when the number of recording sheets stacked in the stacking portion is small, the pressure plate may be bounded during pressing, and hence, the conveying force of the feeding roller is not sufficiently provided. In this case, similarly to the situation with a slip, the recording sheet may not be extracted from the stacking portion by the first feeding operation, or the recording sheet may not be conveyed to the sheet detecting portion. Then, the retry feeding is performed, so that the recording sheet is conveyed to a recording portion.
Even when the recording sheet is conveyed to the sheet detecting portion, if sheet detection is delayed, normal feeding of the recording sheet to the recording portion may not performed. Therefore, a relief operation is performed for complementing the feeding, so as to convey the recording sheet to the recording portion.
With the feeding device of the related art, damage, such as a scratch or a wrinkle, may be applied to the recording sheet as a result of a slip between the feeding roller and the recording sheet when the retry feeding or the relief operation is performed. In addition, a time necessary for the retry feeding or the relief operation is seriously longer than a time necessary for the normal feeding operation. Hence, a recording time containing the feeding time may be markedly increased.
Also, a feeding device is provided, in which a feeding roller is coupled with a cam mechanism, and a drive rotation amount of the feeding roller for a single feeding operation is constant. In such a device, a feed and the numbers of normal rotations and reverse rotations may be increased when normal rotation feeding and reverse rotation feeding of a recording sheet are performed to align the recording sheet with a recording-start position. Hence, damage, such as a scratch or a wrinkle, may be applied to the recording sheet, or a recording time containing a feeding time may be markedly increased as a result of the retry feeding or the relief operation. In particular, when a recording sheet with a glossy surface for an enhancement of color developability is used, for example, a slip mark likely remains on the surface and the slip mark may affect image formation.