Image forming apparatus with fixing via rotary heater and bonding via heater configured to move in thickness direction

1 . An image forming apparatus comprising:

an electrophotographic image forming portion including (1) a scanner configured to emit light, (2) a plurality of process cartridges including a first process cartridge containing powder adhesive and one or more second process cartridges containing printing toner, and (3) a transfer unit including a transfer belt and a transfer roller, the electrophotographic image forming portion being configured to form an image on a sheet by using the printing toner and apply the powder adhesive onto the sheet;

a fixing device including (1) a tubular fixing film configured to rotate, (2) a fixing heater disposed in an internal space of the tubular fixing film and configured to be in contact with an inner surface of the tubular fixing film and to heat the tubular fixing film, and (3) a pressing roller that is configured to form a nip portion between the tubular fixing film and the pressing roller, the fixing device being configured to perform a fixing process in which the fixing device fixes the image and the powder adhesive to the sheet by heating and pressing the sheet while nipping and conveying the sheet in the nip portion;

a stacker on which a plurality of sheets that have passed through the fixing device are stacked;

a longitudinal-alignment reference plate;

a semicircular roller configured to move each of the plurality of sheets toward the longitudinal-alignment reference plate, to align the plurality of sheets stacked on the stacker in a longitudinal direction;

a lateral-alignment jogger configured to move in a lateral direction to align the plurality of sheets stacked on the stacker in the lateral direction, the lateral direction being orthogonal to the longitudinal direction; and

a bonding device configured to perform a bonding process in which the bonding device bonds the plurality of sheets to each other with the powder adhesive, the bonding device including (1) a heating plate configured to move in a thickness direction of the plurality of sheets stacked on the stacker, (2) a pressing plate configured to face the heating plate in the thickness direction and support end portions of the plurality of sheets stacked on the stacker, (3) a bonding heater disposed on an opposite side from the pressing plate with respect to the heating plate in the thickness direction and arranged in contact with the heating plate, and (4) a pressing lever configured to move the bonding heater and the heating plate toward the pressing plate in the thickness direction,

wherein the heating plate is configured to be brought into contact with one of the plurality of sheets in the bonding process,

wherein the heating plate has a plate shape elongated in the longitudinal direction and includes a single protruding portion protruding in the thickness direction and elongated in the longitudinal direction,

wherein, when viewed in the longitudinal direction, the protruding portion includes a flat portion and curved portions formed on both sides of the flat portion,

wherein a pressed region, in which the sheet is pressed by the heating plate in the bonding process, is elongated in the longitudinal direction and has a width in the lateral direction that is greater than a width of the flat portion and that is less than a width of the nip portion of the fixing device in a sheet conveyance direction at the nip portion,

wherein a width of an application region onto which the powder adhesive is applied is greater than the width of the pressed region when viewed in the longitudinal direction,

wherein the powder adhesive is applied in an amount of 0.55 mg/cm 2 ,

wherein P1 is equal to or higher than 0.1 MPa and equal to or lower than 0.2 MPa, P2 is equal to or higher than 0.3 MPa and equal to or lower than 0.4 MPa, and P1<P2 is satisfied, where P1 (MPa) is a peak value of pressure received by the sheet in the fixing process, and P2 (MPa) is a peak value of pressure received by the sheet in the bonding process,

wherein a total pressure applied to the sheet from the heating plate in the bonding process is larger than a total pressure applied to the sheet in the nip portion between the tubular fixing film and the pressing roller in the fixing process, and

wherein a surface temperature of the tubular fixing film in the fixing process is lower than a surface temperature of the heating plate in the bonding process, and the surface temperature of the heating plate in the bonding process is equal to or lower than 200° C.

2 . The image forming apparatus according to claim 1 , wherein the image forming apparatus is configured such that G1<G2 is satisfied, where G1 (Pa) is a storage modulus of the powder adhesive in the fixing process, and G2 (Pa) is a storage modulus of the powder adhesive in the bonding process.

3 . The image forming apparatus according to claim 1 , wherein the bonding device is configured to bond three or more sheets together by performing one round of the bonding process.

4 . The image forming apparatus according to claim 3 , wherein if a first sheet is the most separated sheet from the heating plate in the three or more sheets that are bonded together in the one round of the bonding process, and a second sheet is a sheet in the three or more sheets that is bonded to the first sheet with a layer of the powder adhesive, a peak temperature of the layer of the powder adhesive in the bonding process is lower than a peak temperature of the layer of the powder adhesive in the fixing process.

5 . The image forming apparatus according to claim 1 , wherein the pressed region has a shape in which a length of the pressed region in the longitudinal direction is larger than the width of the pressed region in the lateral direction, and

wherein the longitudinal direction is a direction along a first edge of the sheet, and the lateral direction is a direction along a second edge of the sheet that intersects with the first edge.

6 . The image forming apparatus according to claim 1 , wherein an area of the pressed region is smaller than an area of a region in which the sheet is pressed in the nip portion.

7 . The image forming apparatus according to claim 1 , wherein the longitudinal direction of the heating plate is parallel to one side of a sheet.

8 . The image forming apparatus according to claim 1 , wherein the heating plate is formed of aluminum,

wherein the pressing plate is made of silicone rubber and has a thickness of 2.0 mm,

wherein a total pressure applied in the fixing process is 25 kgf,

wherein a total pressure applied in the bonding process is 30 kgf,

wherein P1 is 0.2 MPa,

wherein P2 is 0.3 MPa,

wherein a surface temperature of the tubular fixing film in the fixing process is 175° C., and

wherein a surface temperature of the heating plate in the bonding process is 200° C.

9 . The image forming apparatus according to claim 8 , wherein when five sheets are bonded together in the one round of the bonding process, a temperature of the powder adhesive between a lowermost one of the five sheets and a sheet stacked directly thereon is equal to or higher than 80° C.

10 . The image forming apparatus according to claim 9 , wherein the powder adhesive has a storage modulus of 2.2×104 Pa at 100° C. and 3.2×105 Pa at 80° C.

11 . The image forming apparatus according to claim 10 , wherein the flat portion has a width of 1.0 mm, and wherein each of the curved portions has a radius of curvature of 1.5 mm.

12 . The image forming apparatus according to claim 11 , wherein the width of the pressed region in the lateral direction is 2.0 mm,

wherein the width of the nip portion in the sheet conveyance direction is 9.0 mm,

wherein the width of the application region in the lateral direction is 4.0 mm, and

wherein the heating plate has a length of 300 mm in the longitudinal direction.