CROSS-REFERENCE TO RELATED APPLICATION

The present application is based on and claims priority of Japanese Patent Applications No. 2018-229531 filed on Dec. 7, 2018; and No. 2019-220716 filed on Dec. 5, 2019, the disclosure of which is incorporated herein.

TECHNICAL FIELD

The present invention relates to a sheet stacking apparatus for stacking sheets, and an image forming system for forming images on sheets.

BACKGROUND ART

Conventionally, image forming systems have been known where an image forming apparatus performs printing processing on sheets, printed sheets are once stacked on a processing tray (first stacking section) to perform post-processing such as binding processing and shift sheet discharge processing, and the sheets are discharged to a stack tray (second stacking section) (for example, Patent Document 1). In such an image forming system, in recent years, there has been a growth of the inkjet type of image forming section, and a system is also known where post-processing is performed on sheets printed by the inkjet type (for example, Patent Document 2).

PRIOR ART DOCUMENT

Patent Document

[Patent Document 1] Japanese Patent Application Publication No. 2015-16970[Patent Document 2] Japanese Patent Application Publication No. 2017-132636

DISCLOSURE OF INVENTION

Problems to be Solved by the Invention

However, when image formation is performed by the inkjet type as in Patent Document 2, in the case where an image ratio is high (e.g., printing of an entire surface solid image), stiffness of the sheet decreases, while weight is increased, and there is a possibility that a coefficient of friction increases with respect to other member, sheet and the like. In this case, in processing a sheet in a post-processing apparatus and discharging the sheet from a processing tray to a stack tray, slidability is poor between the sheet (in forming a bunch of sheets, the sheet discharged to the processing tray first in a job) and the processing tray, stack tray, or sheet already placed on the stack tray, and there is the risk that the sheet is normally not discharged and that a discharge defect occurs. Therefore, conventionally, it has been desired to suppress the discharge defect based on an image ratio of the sheet.

Therefore, it is an object of the present invention to provide a sheet stacking apparatus and image forming system capable of properly suppressing a discharge defect corresponding to an image ratio of a sheet, also in the case where a coefficient of friction is different according to the image ratio of an image formed on the sheet, in discharging the sheet from the processing tray to the stack tray.

Means for Solving the Problem

A sheet stacking apparatus of the present invention is a sheet stacking apparatus for stacking sheets with images formed in an image forming apparatus, and is provided with a first stacking section that enables a sheet to be stacked, a discharge section that discharges the sheet with an image formed in the image forming apparatus to the first stacking section, a transport section that transports the sheet stacked on the first stacking section, a second stacking section that enables the sheet transported from the first stacking section by the transport section to be stacked where an upstream end of the sheet in a transport direction by the transport section is disposed lower in a vertical direction than a downstream-side end portion of the first stacking section in the transport direction, and an air blowing section that enables air to be blown toward a downstream side in the transport direction from between the downstream-side end portion of the first stacking section and an upstream-side end portion of the second stacking section, where when an image ratio of the image formed on the sheet by the image forming apparatus is a first value, the air blowing section sets an air quantity blown to the sheet at a first air quantity, while when the image ratio is a second value higher than the first value, setting the air quantity blown to the sheet at a second air quantity larger than the first air quantity.

Further, a sheet stacking apparatus of the present invention is a sheet stacking apparatus for stacking sheets with images formed in an image forming apparatus, and is provided with a first stacking section that enables a sheet to be stacked, a discharge section that discharges the sheet with an image formed in the image forming apparatus to the first stacking section, a transport section that transports the sheet stacked on the first stacking section, a second stacking section that enables the sheet transported from the first stacking section by the transport section to be stacked where an upstream end of the sheet in a transport direction by the transport section is disposed lower in a vertical direction than a downstream-side end portion of the first stacking section in the transport direction, an air blowing section that enables air to be blown toward a downstream side in the transport direction from between the downstream-side end portion of the first stacking section and an upstream-side end portion of the second stacking section, and a wind direction changing section that enables an air blow direction from the air blowing section to be changed, where when an image ratio of the image formed on the sheet by the image forming apparatus is a first value, the wind direction changing section sets the air blow direction to the sheet by the air blowing apparatus at a direction inclined a first angle with respect to a horizontal direction, while when the image ratio is a second value higher than the first value, setting the air blow direction to the sheet by the air blowing apparatus at a direction inclined a second angle larger than the first angle with respect to the horizontal direction.

An image forming system of the present invention is provided with an image forming apparatus provided with an image forming section for forming an image on a sheet, and the above-mentioned sheet stacking apparatus for stacking sheets with images formed in the image forming apparatus.

Advantageous Effect of the Invention

According to the sheet stacking apparatus and image forming system of the present invention, it is possible to properly suppress a discharge defect corresponding to an image ratio of a sheet, also in the case where a coefficient of friction is different according to the image ratio of an image formed on the sheet, in discharging the sheet from the processing tray to the stack tray.

