A sheet processing apparatus for processing sheets includes: a stack tray on which a sheet is stacked; a discharge roller pair composed of first and second rollers and configured to discharge a sheet onto the stack tray, the second roller being configured to be movable between a pressure contact position to contact with the first roller and a retracting position to separate from the first roller; and a pressure contact/separation mechanism for moving the second roller from the retracting position to the pressure contact position. The pressure contact/separation mechanism changes the timing at which the second roller reaches the pressure contact position according to the type of a sheet to be discharged.

A recording medium conveyance device includes a storage, a conveyer that conveys a conveyed object, an ultrasonic sensor that outputs a value indicating an attenuation amount of an ultrasonic wave caused by the conveyed object, and a hardware processor. The hardware processor executes a type detection process of detecting a type of the conveyed object based on output of the ultrasonic sensor and storing the type in the storage and an overlay detection process of detecting whether the conveyed object is in an overlay state in which a gap is present based on output of the ultrasonic sensor, and switches to either one of the type detection process and the overlay detection process. The hardware processor executes the type detection process when the type is not stored in the storage and executes the overlay detection process when the type is stored in the storage.

A sheet processing apparatus for processing sheets includes: a stack tray on which a sheet is stacked; a discharge roller pair composed of first and second rollers and configured to discharge a sheet onto the stack tray, the second roller being configured to be movable between a pressure contact position to contact with the first roller and a retracting position to separate from the first roller; and a pressure contact/separation mechanism for moving the second roller from the retracting position to the pressure contact position. The pressure contact/separation mechanism changes the timing at which the second roller reaches the pressure contact position according to the type of a sheet to be discharged.

An image forming apparatus including an image forming portion, a fixing device, a pressure switching mechanism, and a controller. The fixing device includes a fixing member, a heating portion, and a pressing member. The pressure switching mechanism is configured to switch pressure between the fixing member and the pressing member. The controller is configured to execute an operation in an image forming mode in which the image is capable of being formed on an envelope. The controller is configured to cause the pressure switching mechanism to switch the pressure to a first pressure when an instruction to form the image on an address side of the envelope is inputted and to cause the pressure switching mechanism to switch the pressure to a second pressure when an instruction to form the image on a non-address side of the envelope is inputted. The second pressure is higher than the first pressure.

An image forming apparatus includes an image forming portion; a fixing device including a fixing member, a heating portion and a pressing member; a pressure switching mechanism configured to switch pressure between the fixing member and the pressing member; and a controller capable of executing an operation in an image forming mode in which the image is capable of being formed on the envelope by causing the pressure switching mechanism to switch the pressure to first pressure when an instruction to form the image on an address side of the envelope is inputted and by causing the pressure switching mechanism to switch the pressure to second pressure higher than the first pressure when an instruction to form the image on a non-address side of the envelope is inputted.

A recording medium conveyance device includes a storage, a conveyer that conveys a conveyed object, an ultrasonic sensor that outputs a value indicating an attenuation amount of an ultrasonic wave caused by the conveyed object, and a hardware processor. The hardware processor executes a type detection process of detecting a type of the conveyed object based on output of the ultrasonic sensor and storing the type in the storage and an overlay detection process of detecting whether the conveyed object is in an overlay state in which a gap is present based on output of the ultrasonic sensor, and switches to either one of the type detection process and the overlay detection process. The hardware processor executes the type detection process when the type is not stored in the storage and executes the overlay detection process when the type is stored in the storage.