JP7558705B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming device that forms an image on a sheet.

Conventionally, when creating documents such as pay slips that require confidentiality and therefore need to be sealed, preprinted paper with adhesive applied to it was prepared in advance, variable data was printed on the preprinted paper, and then the paper was sealed as a post-processing step. This method took time to create the preprinted paper, which required the application of adhesive, and was inefficient when only a small number of documents were required.

Patent Document 1 proposes an image forming device that uses an adhesive toner (powder adhesive) in addition to an image forming toner using an electrophotographic process to output a sealed document using a single device while using plain paper. The adhesive toner is designed to melt at a lower temperature than the image forming toner, and is applied to a sheet, which is a recording medium, by being transferred in the same electrophotographic process as the image forming toner. The sheet is then folded so that the surfaces on which the adhesive toner image is formed face each other. Finally, the sheet is nipped in a nip between a pressure roller made of an elastic material such as silicone rubber and a roller facing the pressure roller, and the sheets are bonded by heating the sheets while the adhesive surfaces of the sheets are in close contact with each other via the adhesive toner. This method is efficient even for applications requiring a small amount of paper, since the printing process and the adhesive process are completed in a single image forming device. In addition, the method of bonding by heating and melting the adhesive does not require strong pressure, which is advantageous for making the device smaller and quieter.

JP 2006-171607 A

However, pressure rollers made of an elastic material such as silicone rubber can cause the sheet conveying speed to fluctuate due to thermal expansion of the rubber. This can cause the sheet conveying speed at the nip formed by the pressure roller to be slower than the conveying speed of the conveying roller that conveys the folded sheet toward the nip. In that case, the sheet can sag (loop) between the conveying roller and the pressure roller, which can cause the sheet to wrinkle or shift in the folding position of the sheet.

Therefore, the present invention aims to prevent slack from occurring in the sheet before it is bonded.

One aspect of the present invention is an image forming means for forming a toner image on a sheet using a printing toner and applying a powder adhesive to the sheet, a fixing means for heating the toner image formed on the sheet by the image forming means and the powder adhesive applied to the sheet to fix the toner image to the sheet, and a folding means for folding the sheet that has passed through the fixing means with the surface on which the powder adhesive has been applied being inward, the folding means comprising a pair of guide rollers for transporting the sheet, a pull-in section for pulling in the sheet that has passed between the pair of guide rollers from its leading edge, and a pair of folding rollers for folding the sheet from the middle of the sheet pulled in to the pull-in section and discharging the sheet with the folded part at the front, the folding means being arranged in a roller axial direction perpendicular to the sheet transport direction. an image forming apparatus equipped with a folding means having a length of a portion where the folding roller pair clamps a sheet that is longer than the sheet width in the sheet conveying direction , and an adhesive means having a pair of rotating bodies and heating the sheet folded by the folding means while transporting it with the pair of rotating bodies , thereby adhering the sheet with the powder adhesive, wherein the length of the portion where the rotating body pair clamps the sheet is longer in the roller axial direction than the sheet width , wherein the distance from the folding roller pair to the rotating body pair is shorter than the length of the folded sheet in the sheet conveying direction, and the sheet conveying speed by the rotating body pair is faster than the conveying speed at which the folding roller pair sends the sheet toward the adhesive means.

The present invention makes it possible to prevent sagging of the sheet before it is bonded.

1 is a schematic diagram of an image forming apparatus according to a first embodiment. 3A and 3B are diagrams for explaining attachment of a post-processing unit to an apparatus body of the image forming apparatus according to the first embodiment. 3 is a schematic diagram showing a layer of toner and powder adhesive transferred to a sheet in Example 1. FIG. 3A and 3B are diagrams illustrating a sheet transport path in the image forming apparatus according to the first embodiment. 4A to 4F are diagrams for explaining the contents of a folding process according to the first embodiment. FIG. 1 is a perspective view showing an external appearance of an image forming apparatus according to a first embodiment. 3A to 3C are diagrams illustrating examples of products output by the image forming apparatus according to the first embodiment. FIG. 2 is a schematic diagram of a process cartridge according to the first embodiment. FIG. 4 is a schematic diagram of a first fixing unit according to the first embodiment. FIG. 2 is a schematic diagram of the inside of a post-processing unit according to the first embodiment. FIG. 13 is a diagram for explaining a case where a loop is formed in a sheet before bonding. 1A and 1B are diagrams for explaining the effect of loops generated in a sheet before bonding. 3A and 3B are diagrams for explaining a one-way clutch according to the first embodiment; FIG. 11 is a diagram for explaining a distance sensor according to a second embodiment.

An exemplary embodiment of the present invention will now be described with reference to the drawings.

(Overall device configuration)
First, the overall configuration of the image forming apparatus will be described with reference to Figures 1, 2, and 6. Figure 1 is a schematic diagram showing a cross-sectional configuration of an image forming apparatus 1 including an image forming apparatus main body (hereinafter referred to as an apparatus main body 10) according to a first embodiment and a post-processing unit 30 connected to the apparatus main body 10. The image forming apparatus 1 is an electrophotographic image forming apparatus (electrophotographic system) including the apparatus main body 10 equipped with an electrophotographic printing mechanism and the post-processing unit 30 as a sheet processing device.

Figure 6 is a perspective view showing the exterior of the image forming device 1. The post-processing unit 30 is attached to the top of the device body 10. The image forming device 1 has a sheet cassette 8 at the bottom, an openable tray 20 on the right side, and a first discharge tray 13 on the top.

First, the internal structure of the device main body 10 will be described. As shown in FIG. 1, the device main body 10 includes a sheet cassette 8 as a sheet storage section that stores sheets P as a recording medium, an image forming unit 1e as an image forming means, a first fixing device 6 as a fixing means, and a housing 19 that houses these. The device main body 10 has a printing function that forms a toner image on a sheet P fed from the sheet cassette 8 by the image forming unit 1e, and creates a printed matter that has been subjected to a fixing process by the first fixing device 6. It should be noted that, for example, paper is used as the sheet P as a recording medium.

The sheet cassette 8 is inserted into the housing 19 at the bottom of the device main body 10 so that it can be pulled out, and stores a large number of sheets P. The sheets P stored in the sheet cassette 8 are fed from the sheet cassette 8 by a feeding member such as a feeding roller, and are transported by the transport roller 8a in a state where they are separated one by one by a separation roller pair. It is also possible to feed sheets set in the open tray 20 (Figure 6) one by one.

The image forming unit 1e is a tandem-type electrophotographic unit equipped with four process cartridges 7n, 7y, 7m, and 7c, a scanner unit 2, and a transfer unit 3. A process cartridge is a unit in which multiple parts that are responsible for the image forming process are integrated and replaceable. The device main body 10 is provided with a cartridge support section 9 supported by a housing 19, and each of the process cartridges 7n, 7y, 7m, and 7c is removably mounted in the mounting sections 9n, 9y, 9m, and 9c provided on the cartridge support section 9. The cartridge support section 9 may be a tray member that can be pulled out from the housing 19.

Each process cartridge 7n, 7y, 7m, 7c has a substantially common configuration, except for the type of powder contained in the four powder containers 104n, 104y, 104m, 104c. That is, each process cartridge 7n, 7y, 7m, 7c includes a photosensitive drum 101 which is an image carrier, a charging roller 102 which is a charger, a powder container 104n, 104y, 104m, 104c which contains the powder, and a developing roller 105 which performs development using the powder.

Of the four powder containers, the three powder containers 104y, 104m, and 104c on the right side of the figure contain yellow, magenta, and cyan printing toners Ty, Tm, and Tc, respectively, as toners (first powder, powder developer) for forming a visible image on the sheet P. In contrast, the powder container 104n on the leftmost side of the figure contains powder adhesive Tn, which is a toner (second powder) for performing an adhesive process after printing. The powder containers 104y, 104m, and 104c are all examples of first containers that contain printing toner, and the powder container 104n is an example of a second container that contains powder adhesive. In addition, the process cartridges 7y, 7m, and 7c are all examples of first process units that form a toner image using printing toner, and the process cartridge 7n is an example of a second process unit that forms an image of powder adhesive in a predetermined application pattern.

In this embodiment, when printing black images such as text, they are expressed using process black, which is a combination of yellow (Ty), magenta (Tm), and cyan (Tc) toners. However, for example, a fifth process cartridge using black printing toner may be added to image forming unit 1e, so that black images can be expressed using black printing toner. This is not a limitation, and the type and number of printing toners can be changed depending on the application of image forming device 1.

The scanner unit 2 is disposed below the process cartridges 7n, 7y, 7m, and 7c and above the sheet cassette 8. The scanner unit 2 is an exposure means in this embodiment that irradiates the photosensitive drum 101 of each process cartridge 7n, 7y, 7m, and 7c with laser light G to write an electrostatic latent image.

The transfer unit 3 is equipped with a transfer belt 3a as an intermediate transfer body (secondary image carrier). The transfer belt 3a is a belt member wound around a secondary transfer inner roller 3b and a tension roller 3c, and its outer circumferential surface faces the photosensitive drums 101 of each process cartridge 7n, 7y, 7m, and 7c. On the inner circumferential side of the transfer belt 3a, a primary transfer roller 4 is disposed at a position corresponding to each photosensitive drum 101. In addition, a secondary transfer roller 5 as a transfer means is disposed at a position facing the secondary transfer inner roller 3b. The transfer nip 5N between the secondary transfer roller 5 and the transfer belt 3a is a transfer section (secondary transfer section) where a toner image is transferred from the transfer belt 3a to the sheet P.

The first fixing device 6 is disposed above the secondary transfer roller 5. FIG. 9 is a detailed view of the first fixing device 6. The first fixing device 6 has a cylindrical fixing film (endless belt) 6a, a heater 6a1 that contacts the inner surface of the fixing film 6a, and a pressure roller 6b that forms a fixing nip 6N with the heater 6a1 via the fixing film 6a. The fixing film 6a and the pressure roller 6b function as a pair of rotating bodies (first rotating body pair) that rotate while sandwiching the sheet P. The fixing film 6a has a base layer with a thickness of 30 to 70 μm made of a heat-resistant resin such as polyimide, polyamide, or PEEK, or a metal such as stainless steel. The fixing film 6a is a cylindrical rotating body with an outer diameter of 24 mm, which is provided on the base layer with an elastic layer with a thickness of 0.1 to 1 mm made of silicone rubber or the like, and a release layer with a thickness of 5 to 30 μm made of a fluororesin such as PFA or PTFE.

The pressure roller 6b is a rotating body with an outer diameter of 24 mm, which has a core 6b1 made of iron or aluminum, an elastic layer 6b2 made of silicone rubber or the like and having a thickness of 2 to 4 mm, and a release layer made of a fluororesin such as PFA or PTFE provided on the outermost surface.

The heater 6a1 as the heating means (first heating means) has a heating resistor 6a12 such as Ag/Pd (silver palladium) that generates heat when electricity is applied, and an insulating protective layer (glass layer in this embodiment) 6a13 on a thin plate-shaped substrate 6a11 mainly composed of ceramics such as alumina. A temperature detection element 6a2 such as a thermistor is in contact with the substrate 6a11 and is connected to a CPU 6a3 as a control unit mounted on the image forming apparatus 1. The heater 6a1 heats up by supplying electricity to the heating resistor 6a12. The temperature rise is detected by the temperature detection element 6a2, and the CPU 6a3 controls the current to the heating resistor 6a12 via the triac 6a4. For example, if the temperature detected by the temperature detection element 6a2 is lower than a predetermined set temperature, the amount of power supplied to the heating resistor 6a12 is increased so that the heater 6a1 heats up, and if the temperature detected by the temperature detection element 6a2 is higher than the set temperature, the amount of power is decreased so that the heater 6a1 cools down, thereby keeping the heater 6a1 at a constant temperature.

The heater 6a1 is held by a holding member 6a5 made of a heat-resistant resin such as LCP (liquid crystal polymer). The holding member 6a5 also has a guide function for guiding the rotation of the fixing film 6a. A force is applied to the holding member 6a5 in a direction approaching the pressure roller 6b from a spring (not shown) attached to a metal stay 6a6. The pressure roller 6b is pressed toward the heater 6a1 via the fixing film 6a with a total pressure of 10 to 30 kgf by a pressure means such as a spring member (not shown). As a result, a fixing nip 6N with a width of 7 to 9 mm in the sheet conveying direction is formed between the pressure roller 6b and the heater 6a1 and holding member 6a5 that constitute the nip portion forming unit.

The pressure roller 6b receives power from a motor (not shown) and rotates in the direction of the arrow r1 in FIG. 9. The rotation of the pressure roller 6b causes the fixing film 6a to rotate accordingly. The sheet P carrying an unfixed toner image is transported in the sheet transport direction through the fixing nip 6N together with the fixing film 6a while the surface (image surface) of the sheet P carrying the toner image and powder adhesive Tn is in close contact with the outer surface of the fixing film 6a. This configuration is characterized by the fact that the thermal capacity of the fixing film and heater is particularly small, and the holding member 6a5 is also made of a material with high thermal insulation properties, so that it is possible to heat the surface of the fixing film 6a to a high temperature more quickly with a small amount of heat supply.

The housing 19 is provided with a discharge port 12 (first discharge port) which is an opening for discharging the sheet P from the device body 10, and a discharge unit 34 is disposed in the discharge port 12. The discharge unit 34, which is the discharge means in this embodiment, uses a so-called triple roller system having a first discharge roller 34a, an intermediate roller 34b, and a second discharge roller 34c. In addition, a switching guide 33, which is a flap-shaped guide that switches the transport path of the sheet P, is provided between the first fixing device 6 and the discharge unit 34. The switching guide 33 can rotate around the shaft portion 33a so that the tip 33b reciprocates in the direction of the arrow c in the figure.

The device main body 10 is equipped with a mechanism for double-sided printing. A motor (not shown) is connected to the discharge unit 34, and the direction of rotation of the intermediate roller 34b can be rotated forward and backward. In addition, a double-sided conveying path 1r is provided as a conveying path connected in a loop to the main conveying path 1m. The sheet P, on which an image is formed on the first side while passing through the main conveying path 1m, is sandwiched and conveyed by the first discharge roller 34a and the intermediate roller 34b by the switching guide 33 rotated clockwise (broken line position). After the trailing end of the sheet P in the traveling direction passes through the switching guide 33, the switching guide 33 rotates counterclockwise (solid line position) and the intermediate roller 34b rotates in reverse, and the sheet P is reversed and conveyed to the double-sided conveying path 1r. Then, while the sheet P passes through the main conveying path 1m again in an inverted state, an image is formed on the second side of the sheet P. After double-sided printing, the sheet P is guided to the switching guide 33 (solid line position) rotated counterclockwise, is sandwiched and transported between the intermediate roller 34b and the second discharge roller 34c, and is discharged from the device body 10.

In addition, the conveying path passing through the conveying roller 8a, the transfer nip 5N, and the fixing nip 6N in the device main body 10 constitutes the main conveying path 1m where image formation is performed on the sheet P. When viewed from the main scanning direction during image formation (the width direction of the sheet perpendicular to the conveying direction of the sheet conveyed through the main conveying path 1m), the main conveying path 1m extends from below to above passing one side of the horizontal direction relative to the image forming unit 1e. In other words, the device main body 10 of this embodiment is a so-called vertical conveying type (vertical path type) printer in which the main conveying path 1m extends in a substantially vertical direction. Note that when viewed vertically, the first discharge tray 13, the intermediate path 15, and the sheet cassette 8 overlap each other. Therefore, the movement direction of the sheet when the discharge unit 34 discharges the sheet P in the horizontal direction is opposite to the movement direction of the sheet when the sheet P is fed from the sheet cassette 8 in the horizontal direction.

1 (when viewed in the main scanning direction during image formation), it is preferable that the horizontal occupancy of the main body portion of the post-processing unit 30, excluding the second discharge tray 35, is within the occupancy of the device main body 10. By storing the post-processing unit 30 in the space above the device main body 10 in this way, it is possible to install the image forming device 1 with adhesive printing function in an installation space approximately the same as that of a normal vertical pass printer.

(Post-processing unit)
2, the post-processing unit 30 is attached to the upper part of the apparatus main body 10. The post-processing unit 30 is a post-processing unit in which a folder 31 as a folding means and a second fixing device 32 as an adhesive means (second fixing means) are housed in a housing (second housing) 39 and integrated with each other.

The second fixing device 32 in this embodiment has the same configuration as the first fixing device 6 as shown in FIG. 10. It has a cylindrical heating film (endless belt) 32b and a pressure roller 32a, and the sheet P folded by the folder 31 is sandwiched and conveyed by the adhesive nip 32N (second fixing nip) which is the nip between the heating film 32b and the pressure roller 32a. The pressure roller 6b is a rotating body with an outer diameter of 24 mm having a core metal 32a1 made of iron or aluminum, an elastic layer 32a2 made of silicone rubber or the like and having a thickness of 2 to 4 mm, and a release layer made of fluororesin such as PFA or PTFE provided on the outermost surface. The heating film 32b and the pressure roller 32a function as a rotating body pair (second rotating body pair) that rotates while sandwiching the sheet P. The inner side of the heating film 32b is provided with a heater 32b1 and a temperature detection element 32b2 as heating means, as in the first fixing device 6. The heating film 32b rotates in response to the pressure roller 32a rotating in the direction of the arrow r2, so that the sheet P is sandwiched and transported in the adhesive nip 32N. During this process, the sheet P is heated and pressurized, so that the powder adhesive Tn applied to the sheet P softens again, and the sheet P is adhered in a folded state.

The post-processing unit 30 is provided with a first discharge tray 13 that rotatably holds the tray switching guide 13a, an intermediate path 15, and a second discharge tray 35. The first discharge tray 13 is provided on the upper surface of the post-processing unit 30 and is located on the upper surface of the entire image forming apparatus 1 (FIG. 1). The functions of each part of the post-processing unit 30 will be described later.

The post-processing unit 30 is provided with a positioning portion (e.g., a convex shape that engages with a concave portion of the housing 19) for positioning the housing 39 relative to the housing 19 (first housing) of the device body 10. The post-processing unit 30 is also provided with a drive source and control unit separate from the device body 10, and is electrically connected to the device body 10 by connecting the connector 36 of the post-processing unit 30 with the connector 37 of the device body 10. This allows the post-processing unit 30 to operate based on commands from the control unit provided in the device body 10 using power supplied via the device body 10.

(Process cartridge)
As described above, each of the process cartridges 7n, 7y, 7m, and 7c has a substantially common configuration, except for the type of powder contained in the four powder containers 104n, 104y, 104m, and 104c. Here, the process cartridge 7n will be described as a representative. FIG. 8 is a cross-sectional view showing a schematic configuration of the process cartridge 7n. The process cartridge 7n is composed of a photoconductor unit CC including a photoconductor drum 101 and the like, and a development unit DT including a development roller 105 and the like.

The photosensitive drum 101, which is a drum-shaped electrophotographic photosensitive member (image carrier), is rotatably attached to the photosensitive unit CC via a bearing (not shown). The photosensitive drum 101 receives a driving force from a motor serving as a driving means (driving source) (not shown) and is driven to rotate in a clockwise direction (arrow w) in the figure during image formation operation. In addition, the photosensitive unit CC has a charging roller 102 for charging the photosensitive drum 101 and a cleaning member 103 arranged around the photosensitive drum 101.

The developing unit DT is provided with a developing roller 105 as a developer carrier that contacts the photosensitive drum 101 and rotates in a counterclockwise direction (arrow d) in the figure. The developing roller 105 and the photosensitive drum 101 each rotate so that their surfaces move in the same direction at the opposing portion (contact portion).

The developing unit DT is also provided with a developer supply roller (hereinafter simply referred to as "supply roller 106") as a developer supply member that rotates in a clockwise direction (arrow e) in the figure. The supply roller 106 and the developing roller 105 rotate so that their surfaces move in the same direction at the opposing portion (contact portion). The supply roller 106 supplies powder adhesive (printing toner in the case of process cartridges 7y, 7m, and 7c) onto the developing roller 105. At the same time, the supply roller 106 acts to strip off the powder adhesive (printing toner in the case of process cartridges 7y, 7m, and 7c) remaining on the developing roller 105 from the developing roller 105. The developing unit DT is also provided with a developing blade 107 as a developer regulating member that regulates the layer thickness of the powder adhesive (printing toner in the case of process cartridges 7y, 7m, and 7c) supplied onto the developing roller 105 by the supply roller 106.

The powder storage section 104n stores a powder adhesive (printing toner in the case of the process cartridges 7y, 7m, and 7c). A rotatably supported transport member 108 is provided within the powder storage section 104n. The transport member 108 rotates in a clockwise direction (arrow f) in the figure to agitate the powder stored in the powder storage section 104n and transport the powder to the development chamber 109 in which the development roller 105 and supply roller 106 are provided.

Here, the photoconductor unit CC and the development unit DT can be separately configured as a photoconductor unit cartridge and a development unit cartridge, respectively, and can be configured to be detachable from the main body of the image forming apparatus. Also, it is possible to configure a powder cartridge that has only the powder storage section 104 and the transport member 108, separate from the process cartridge having the photoconductor and developer carrier, and is detachable from the main body of the apparatus.

(Printing toner)
As the printing toners Tm, Tc, and Ty of this embodiment, conventionally known printing toners can be used. Among them, printing toners using a thermoplastic resin as a binder resin are preferred. The thermoplastic resin is not particularly limited, and those used in conventional printing toners such as polyester resin, vinyl resin, acrylic resin, and styrene-acrylic resin can be used. A plurality of these resins may be contained. Among them, printing toners using styrene-acrylic resin are more preferred. In addition, the printing toner (printing developer) may contain a colorant, a magnetic material, a charge control agent, a wax, and an external additive.

(powder adhesive)
In addition, as the powder adhesive Tn of this embodiment, a powder adhesive containing a thermoplastic resin can be used. The thermoplastic resin is not particularly limited, and examples thereof include known thermoplastic resins such as polyester resin, vinyl resin, acrylic resin, styrene-acrylic resin, polyethylene, polypropylene, polyolefin, ethylene-vinyl acetate copolymer resin, and ethylene-acrylic acid copolymer resin. A plurality of these resins may be contained.

The powder adhesive Tn preferably further contains a wax. The wax may be any known wax, such as an ester wax, which is an ester of an alcohol and an acid, or a hydrocarbon wax, such as paraffin wax.

The powder adhesive Tn may also contain a colorant. Known colorants such as black colorants, yellow colorants, magenta colorants, and cyan colorants can be used as the colorant. The content of the colorant in the powder adhesive is preferably 1.0% by mass or less, and more preferably 0.1% by mass or less. Furthermore, the powder adhesive Tn may contain a magnetic material, a charge control agent, a wax, and an external additive.

In order to form an adhesive portion on a sheet P using a powder adhesive by electrophotography, the weight average particle diameter of the powder adhesive Tn is preferably 5.0 μm or more and 30 μm or less, and more preferably 6.0 μm or more and 20 μm or less. Note that printing toner may be used as the powder adhesive Tn as long as it satisfies the adhesive properties.

(Example of powder adhesive manufacturing)
A method for producing the powder adhesive Tn will be exemplified below. First, the following materials were prepared.
Styrene 75.0 parts n-Butyl acrylate 25.0 parts Polyester resin 4.0 parts (Polyester resin having a weight average molecular weight (Mw) of 20,000, a glass transition temperature (Tg) of 75° C., and an acid value of 8.2 mgKOH/g)
Ethylene glycol distearate 14.0 parts (ester wax obtained by esterifying ethylene glycol and stearic acid)
Hydrocarbon wax (HNP-9, manufactured by Nippon Seiro) 2.0 parts Divinylbenzene 0.5 parts

The mixture of the above materials was kept at 60°C and stirred at 500 rpm using a T.K. Homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to dissolve uniformly, preparing a polymerizable monomer composition.

Meanwhile, 850.0 parts of 0.10 mol/L-Na ₃ PO ₄ aqueous solution and 8.0 parts of 10% hydrochloric acid were added to a vessel equipped with a high-speed stirring device Clearmix (manufactured by M Technique Co., Ltd.), the rotation speed was adjusted to 15,000 rpm, and the mixture was heated to 70° C. 127.5 parts of 1.0 mol/L-CaCl ₂ aqueous solution was added thereto to prepare an aqueous medium containing a calcium phosphate compound.

After adding the above polymerizable monomer composition to the aqueous medium, 7.0 parts of the polymerization initiator t-butyl peroxypivalate was added, and the mixture was granulated for 10 minutes while maintaining a rotation speed of 15,000 rpm. The high-speed agitator was then replaced with a propeller agitator, and the mixture was reacted at 70°C for 5 hours while refluxing, after which the liquid temperature was increased to 85°C and the mixture was reacted for an additional 2 hours.

After the polymerization reaction was completed, the resulting slurry was cooled, and hydrochloric acid was added to the slurry to adjust the pH to 1.4 and the slurry was stirred for 1 hour to dissolve the calcium phosphate salt. The slurry was then washed with three times the amount of water, filtered, dried, and classified to obtain powder adhesive particles.

Then, 2.0 parts of silica fine particles (number average particle size of primary particles: 10 nm, BET specific surface area: 170 ^m2 /g) that had been hydrophobized using dimethyl silicone oil (20% by mass) were added as an external additive to 100.0 parts of the powder adhesive particles. The powder adhesive particles to which the silica fine particles had been added were mixed at 3000 rpm for 15 minutes using a Mitsui Henschel mixer (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) to obtain a powder adhesive. The weight average particle size of the obtained powder adhesive was 6.8 μm.

(Example of the production of printing toner)
Next, a method for producing the printing toners Ty, Tm, and Tc will be exemplified. First, the following materials were prepared.
Styrene 60.0 parts Colorant 6.5 parts (C.I. Pigment T Blue 15:3, Dainichi Seika Chemicals Co., Ltd.)

The above materials were placed in an attritor (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) and further dispersed using zirconia particles with a diameter of 1.7 mm at 220 rpm for 5 hours to obtain a pigment dispersion.

In addition, the following materials were prepared:
Styrene 15.0 parts n-Butyl acrylate 25.0 parts Polyester resin 4.0 parts (Polyester resin having a weight average molecular weight (Mw) of 20,000, a glass transition temperature (Tg) of 75° C., and an acid value of 8.2 mgKOH/g)
Behenyl behenate 12.0 parts (ester wax obtained by esterifying behenic acid and behenyl alcohol)
Divinylbenzene 0.5 parts

The above materials were mixed and added to the pigment dispersion. The resulting mixture was kept at 60°C and stirred at 500 rpm using a T.K. Homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to dissolve and disperse uniformly, preparing a polymerizable monomer composition.

Meanwhile, 850.0 parts of 0.10 mol/L-Na ₃ PO ₄ aqueous solution and 8.0 parts of 10% hydrochloric acid were added to a vessel equipped with a high-speed stirring device Clearmix (manufactured by M Technique Co., Ltd.), the rotation speed was adjusted to 15,000 rpm, and the mixture was heated to 70° C. 127.5 parts of 1.0 mol/L-CaCl ₂ aqueous solution was added thereto to prepare an aqueous medium containing a calcium phosphate compound.

After adding the above polymerizable monomer composition to the aqueous medium, 7.0 parts of the polymerization initiator t-butyl peroxypivalate was added, and the mixture was granulated for 10 minutes while maintaining a rotation speed of 15,000 rpm. The high-speed agitator was then replaced with a propeller agitator, and the mixture was reacted at 70°C for 5 hours while refluxing, after which the liquid temperature was increased to 85°C and the mixture was reacted for an additional 2 hours.

After the polymerization reaction was completed, the resulting slurry was cooled, and hydrochloric acid was added to the slurry to adjust the pH to 1.4. The slurry was then stirred for one hour to dissolve the calcium phosphate salt. The slurry was then washed with three times the amount of water, filtered, dried, and classified to obtain toner particles.

Then, 2.0 parts of silica fine particles (number average particle diameter of primary particles: 10 nm, BET specific surface area: 170 ^m2 /g) that had been hydrophobized using dimethyl silicone oil (20% by mass) were added as an external additive to 100.0 parts of the toner particles. The toner particles to which the silica fine particles had been added were mixed at 3000 rpm for 15 minutes using a Mitsui Henschel mixer (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) to obtain a toner. The weight average particle diameter of the obtained printing toner was 6.5 μm.

(Method of measuring weight average particle size)
The weight average particle diameter of the printing toners Ty, Tm, Tc and the powder adhesive Tn is calculated as follows. The measurement device is a precision particle size distribution measurement device using the pore electrical resistance method, "Coulter Counter MulTisizer 3" (registered trademark, manufactured by Beckman Coulter, Inc.), equipped with a 100 μm aperture tube. The measurement conditions are set and the measurement data is analyzed using the accompanying dedicated software "Beckman Coulter MulTisizer 3 Version 3.51" (manufactured by Beckman Coulter, Inc.). The measurement is performed with an effective measurement channel count of 25,000 channels.

The electrolyte solution used for the measurements is one in which special grade sodium chloride is dissolved in ion-exchanged water to give a concentration of 1% by mass, for example "ISOTON II" (manufactured by Beckman Coulter).

Before performing measurements and analysis, the dedicated software is set as follows. On the "Change Standard Measurement Method (SOM)" screen of the dedicated software, the total count number in the control mode is set to 50,000 particles, the number of measurements is set to 1, and the Kd value is set to the value obtained using "Standard particle 10.0 μm" (manufactured by Beckman Coulter). The threshold and noise level are automatically set by pressing the "Threshold/Noise Level Measurement Button." In addition, the current is set to 1600 μA, the gain to 2, the electrolyte to ISOTON II, and "Flush aperture tube after measurement" is checked. On the "Pulse to particle size conversion setting" screen of the dedicated software, the bin interval is set to logarithmic particle size, the particle size bin to 256 particle size bin, and the particle size range to 2 μm to 60 μm.

The specific measurement method is as follows.
(1) Pour 200 mL of the electrolyte solution into a 250 mL round-bottom glass beaker made exclusively for the MulTisizer 3, set it on the sample stand, and stir the stirrer rod counterclockwise at 24 revolutions per second. Then, remove dirt and air bubbles from inside the aperture tube using the "Aperture Tube Flush" function of the dedicated software.
(2) 30 mL of the aqueous electrolyte solution is placed in a 100 mL flat-bottom glass beaker, and 0.3 mL of a dilution of "Contaminon N" (a 10% aqueous solution of a neutral detergent for cleaning precision measuring instruments with a pH of 7, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) diluted 3 times by mass with ion-exchanged water is added thereto as a dispersant.
(3) Prepare an ultrasonic disperser "UlTransonic Dispersion SysTem TeTora150" (manufactured by Nikkaki Bios Co., Ltd.) that has two built-in oscillators with an oscillation frequency of 50 kHz and a phase shift of 180 degrees and an electrical output of 120 W. Place 3.3 L of ion-exchanged water in the water tank of the ultrasonic disperser, and add 2 mL of Contaminon N to this water tank.
(4) The beaker (2) is set in the beaker fixing hole of the ultrasonic disperser described above, and the ultrasonic disperser is operated. Then, the height position of the beaker is adjusted so that the resonance state of the liquid surface of the electrolyte solution in the beaker is maximized.
(5) While the electrolyte solution in the beaker in (4) is being irradiated with ultrasonic waves, the toner or powder adhesive is added to the electrolyte solution in small amounts of 10 mg at a time and dispersed. The ultrasonic dispersion process is then continued for another 60 seconds. During the ultrasonic dispersion process, the water temperature in the water tank is appropriately adjusted to be 10°C or higher and 40°C or lower.
(6) Using a pipette, the electrolyte solution (5) in which the toner or powder adhesive is dispersed is dropped into the round-bottom beaker (1) placed in the sample stand to adjust the measurement concentration to 5%. Measurements are then continued until the number of particles measured reaches 50,000.
(7) The measurement data is analyzed using dedicated software provided with the device to calculate the weight average particle diameter.

(Image Formation Operation)
Next, the image forming operation performed by the image forming apparatus 1 of this embodiment will be described with reference to Figures 1 to 8. Figure 3 is a schematic diagram showing a layer of toner and powder adhesive transferred to a sheet. Figures 4 (a, b) are diagrams showing the sheet transport path in the image forming apparatus 1. Figures 5 (a to f) are diagrams for explaining the contents of the folding process. Figures 7 (a to c) are diagrams showing examples of products output by the image forming apparatus 1.

When data of an image to be printed and a command to execute printing are input to the image forming device 1, the control unit of the image forming device 1 starts a series of operations (image forming operation) in which the sheet P is transported to form an image and, if necessary, post-processing is performed by the post-processing unit 30. In the image forming operation, first, as shown in FIG. 1, the sheets P are fed one by one from the sheet cassette 8 and transported toward the transfer nip 5N via the transport roller 8a.

In parallel with the feeding of the sheet P, the process cartridges 7n, 7y, 7m, and 7c are driven in sequence, and the photosensitive drum 101 is rotated in the clockwise direction (arrow w) in the figure. At this time, the photosensitive drum 101 is uniformly charged on its surface by the charging roller 102. The scanner unit 2 also irradiates the photosensitive drum 101 of each process cartridge 7n, 7y, 7m, and 7c with laser light G modulated based on image data, forming an electrostatic latent image on the surface of the photosensitive drum 101. Next, the electrostatic latent image on the photosensitive drum 101 is developed into a powder image by the powder carried by the developing roller 105 of each process cartridge 7n, 7y, 7m, and 7c.

The powder adhesive layer formed on the photosensitive drum 101 by development with the powder adhesive Tn differs from a toner image (normal toner image) of printing toner for recording images such as figures and text on a recording medium in that it is not intended to transmit visual information. However, in order to apply the powder adhesive Tn to the sheet P in a predetermined application pattern, the layer of powder adhesive Tn developed in a shape corresponding to the application pattern by the electrophotographic process may also be considered as one of the "toner images."

The transfer belt 3a rotates in the counterclockwise direction (arrow v) in the figure. The toner images formed in each process cartridge 7n, 7y, 7m, and 7c are primarily transferred from the photosensitive drum 101 to the transfer belt 3a by the electric field formed between the photosensitive drum 101 and the primary transfer roller 4.

As shown in FIG. 1, process cartridge 7n, which uses powder adhesive Tn, is located most upstream of the four process cartridges in the rotation direction of transfer belt 3a. Yellow, magenta, and cyan process cartridges 7y, 7m, and 7c are lined up in this order from process cartridge 7n toward the downstream side in the rotation direction of transfer belt 3a. Therefore, as shown in FIG. 3, when the four types of toner images are superimposed on transfer belt 3a, powder adhesive Tn becomes the bottom layer (the layer that contacts transfer belt 3a), and yellow (Ty), magenta (Tm), and cyan (Tc) printing toners are superimposed on top of it in this order.

The toner image carried by the transfer belt 3a and reaching the transfer nip 5N is secondarily transferred to the sheet P transported along the main transport path 1m by the electric field formed between the secondary transfer roller 5 and the secondary transfer inner roller 3b. At that time, the toner layer is turned upside down. That is, on the sheet P that has passed through the transfer nip 5n, the printing toners of cyan (Tc), magenta (Tm), and yellow (Ty) are layered from the bottom layer (the layer that contacts the sheet P), and a layer of powder adhesive Tn is formed on top of that. Therefore, in the toner image transferred to the sheet P, the layer of powder adhesive Tn becomes the outermost surface.

Then, the sheet P carrying the unfixed toner image is sandwiched and transported through the fixing nip 6N together with the fixing film 6a while the image side of the sheet P is in close contact with the outer surface of the fixing film 6a. During this sandwiching and transporting process, heat from the heater 6a1 is applied to the image side of the sheet P through the fixing film 6a, and the printing toners Ty, Tm, Tc and the powder adhesive Tn melt and are fixed onto the sheet P. Having passed through the fixing nip 6N, the sheet P is curvature-separated from the fixing film 6a while still retaining the fixed toner image, and the image fixed to the sheet P is obtained.

Regardless of whether single-sided or double-sided printing is being performed, the sheet P discharged from the device body 10 is sandwiched between the intermediate roller 34b and the second discharge roller 34c as shown in Figures 3 and 4, and is transported to the first path R1 or the second path R2 by the tray switching guide 13a.

The first path R1 shown in FIG. 3 is a path along which the sheet P that has passed through the first fixing device 6 is discharged to the first discharge tray 13 by the discharge unit 34 in a normal printing mode that does not use the post-processing unit 30. The second path R2 shown in FIG. 4 is a path along which the sheet P that has passed through the first fixing device 6 is discharged to the second discharge tray 35 via the discharge unit 34, the folder 31, and the second fixing device 32 in an adhesive printing mode.

An intermediate path 15 is provided between the first fixing device 6 and the folder 31 in the second route R2. The intermediate path 15 is a sheet transport path that passes through the upper surface (top surface) of the image forming device 1, and extends below the first discharge tray 13 and approximately parallel to the first discharge tray 13. The intermediate path 15 and the first discharge tray 13 are inclined vertically upward toward the folder 31 with respect to the horizontal direction. Therefore, the entrance of the folder 31 (the guide roller pair 312 described below) is located vertically above the exit of the device main body 10 (the nip between the intermediate roller 34b and the second discharge roller 34c).

The folder 31 has four rollers, a first guide roller 31c, a second guide roller 31d, a first folding roller 31a, and a second folding roller 31b, and a retraction section 31e. The first guide roller 31c and the second guide roller 31d form a pair of guide rollers 312 that sandwich and transport the sheet P received from the transport path (intermediate path 15 in this embodiment) upstream of the folder 31. The first folding roller 31a and the second folding roller 31b form a pair of folding rollers 311 that feeds the sheet P while folding it.

The distance M (FIG. 1) from the second discharge roller 34c to the first guide roller 31c in the sheet transport direction along the second path R2 is configured to be shorter than the overall length L (FIG. 5(a)) in the transport direction of the sheet P before folding. In other words, the distance M from the second discharge roller 34c to the first guide roller 31c determines the lower limit of the length in the transport direction of the sheet that can be processed by the post-processing unit 30. This configuration allows the sheet P to be smoothly delivered from the discharge unit 34 to the pair of guide rollers 312.

The folding process by the folder 31 will be described with reference to Figures 5(a-f). When performing the folding process, the first guide roller 31c and the first folding roller 31a rotate in a clockwise direction in the figure, and the second guide roller 31d and the second folding roller 31b rotate in a counterclockwise direction in the figure. First, the leading edge q of the sheet P sent out from the discharge unit 34 is pulled into the pair of guide rollers 312 as shown in Figure 5(a). As shown in Figure 5(b), the leading edge q of the sheet P is guided downward by the guide wall 31f and contacts the first folding roller 31a, and is then pulled into the opposing first folding roller 31a and second guide roller 31d and abuts against the wall 31g of the pull-in section 31e.

As the guide roller pair 312 pulls in the sheet P, the leading edge q slides against the wall 31g and advances deeper into the pull-in section 31e. Eventually, the leading edge q hits the end 31h of the pull-in section 31e as shown in FIG. 5(c). The pull-in section 31e forms a space below the intermediate path 15 that extends approximately parallel to the intermediate path 15, and at the stage shown in FIG. 5(c), the sheet P is wrapped around the second guide roller 31d and bent into a U-shape.

When the sheet P is further pulled in by the guide roller pair 312 from the state shown in FIG. 5(c), it starts to bend at the middle part r as shown in FIG. 5(d). Eventually, as shown in FIG. 5(e), the middle part r comes into contact with the second folding roller 31b, and is pulled into the nip of the folding roller pair 311 by the frictional force received from the second folding roller 31b. Then, as shown in FIG. 5(f), the sheet P is folded with the middle part r as the crease, and is discharged by the folding roller pair 311 with the middle part r at the front.

Here, the depth N of the retraction section 31e (FIG. 5(e)), i.e., the distance from the nip of the pair of folding rollers 311 to the end 31h of the retraction section 31e, is set to half the overall length L of the sheet P. This allows the folder 31 to fold the sheet P in half (center folding). Note that by changing the depth N of the retraction section 31e, the position of the fold can be changed as desired.

The folder 31 described above is an example of a folding means, and a folding mechanism may be used that, for example, presses a blade against the sheet P and pushes it into the nip between a pair of rollers to form a crease. The folding process is not limited to folding in half, and a folding mechanism that performs, for example, a Z-fold or a triple fold may be used. Since the folder 31 of this embodiment is composed of rotating rollers and a fixed retraction section 31e, the drive mechanism can be simplified compared to a folding mechanism that uses a reciprocating blade. Furthermore, since the folder 31 of this embodiment only requires the retraction section 31e with a depth N of half the sheet length in addition to the four rollers, the post-processing unit 30 can be made smaller.

The sheet P folded by the folder 31 is transported to the second fixing device 32, where it is subjected to a bonding process in which it is heated and pressurized while being sandwiched and transported through the bonding nip 32N. The sheet P is subjected to a bonding process (a second thermal fixation of the image surface to which the powder adhesive has been applied) so that it is bonded in the folded state as shown in FIG. 10. That is, when the sheet P passes through the bonding nip 32N, the powder adhesive Tn on the sheet P is heated and pressurized again in a softened state, so that the inner surfaces of the sheets P are bonded (bonded) together via the powder adhesive Tn.

As shown in FIG. 4, the sheet P that has been subjected to the adhesive process by the second fixing device 32 is discharged to the left side in the figure from the discharge outlet 32c (second discharge outlet) provided in the housing 39 of the post-processing unit 30. It is then stored in the second discharge tray 35 (see FIG. 1) provided on the left side surface of the device main body 10. This completes the image formation operation when the sheet P is transported along the second path R2.

In addition, the bonding location of the folded sheet P can be changed by the application pattern of the toner Tn for pressure application on the sheet P. Figures 7(a) to 7(c) show examples of deliverables (outputs of an image forming device) with different application patterns of the toner Tn for pressure application. Figures 7(a) and 7(b) are examples of deliverables (semi-adhesive deliverables) intended for use by the recipient to open. In the case of a pressure-adhesive postcard 51 in Figure 7(a), the toner Tn for pressure application is applied to the entire surface 51a of one side of the base paper, and the paper is folded and pressure-adhesive at the central crease 51b. In the case of a pay slip 52 in Figure 7(b), the toner Tn for pressure application is applied to the entire circumference 52a of the outer periphery of one side of the base paper, and the paper is folded and pressure-adhesive at the central crease 52b. Figure 7(c) shows a paper bag (medicine bag) 53 as an example of a deliverable (fully-adhesive deliverable) intended for use that is not intended to be opened. In this case, the pressure-bonding toner Tn is applied to the U-shaped area 53a so that the three sides of the folded sheet, including the crease 53b, are joined.

As described above, the image forming apparatus 1 of this embodiment can output a product that is bonded by an adhesive process from a base paper such as blank paper that is not preprinted paper. The bonding points of the folded sheet P can be changed by applying the powder adhesive Tn to the sheet P in a different pattern. For example, it is possible to create semi-adhesive products that are intended to be peeled off later, such as envelopes for enclosing documents or pay slips. Furthermore, the image recorded by the image forming apparatus 1 using printing toner can include a format (unchanging part) when preprinted paper is used, and a variable part such as personal information. Furthermore, the image forming apparatus 1 of this embodiment can be used for applications in which preprinted paper is used as a recording medium and printing and adhesive processes are performed on the variable parts.

(Configuration of the folder and the second fixing device)
11 is a perspective view showing a part of the folder 31 and the second fixing device 32. Here, a relationship between the sheet conveying speed of the pair of folding rollers 311 that sends the sheet P toward the second fixing device 32 while folding it, and the sheet conveying speed of the second fixing device 32 will be described. In this embodiment, the sheet conveying speed of the pair of folding rollers 311 is set to be slightly faster than the sheet conveying speed of the second fixing device 32.

The first folding roller 31a and the second folding roller 31b rotate in the direction of the arrow in the figure by receiving a driving force transmitted from a motor, which is a driving source, via a drive transmission unit (31a1, 31b1, 31b2) such as a gear train. As a result, the sheet P is transported in the sheet transport direction indicated by the arrow H from the nip portion 31N of the first folding roller 31a and the second folding roller 31b toward the adhesive nip 32N of the second fixing device 32.

As shown in FIG. 11, a slackness (hereinafter, a loop) of the sheet may occur between the nip portion 31N of the folding roller pair 311 and the adhesive nip 32N of the second fixing device 32. For example, the sheet P may not be able to smoothly enter the adhesive nip 32N due to a slight bend in the leading edge (the downstream end in the sheet conveying direction represented by the arrow H) of the sheet P. In such a case, a loop L1 of the sheet P may be formed between the nip portion 31N of the folding roller pair 311 and the adhesive nip 32N of the second fixing device 32.

Here, if the sheet conveying speed of the second fixing device 32 is always designed to be relatively faster than the sheet conveying speed of the folding roller pair, even if loop L1 occurs temporarily, loop L1 will not grow and will be eliminated while sheet P is being conveyed. Conversely, if the sheet conveying speed of the second fixing device 32 is always designed to be relatively slower than the sheet conveying speed of the folding roller pair, loop L1 will occur while sheet P is being conveyed, and loop L1 will gradually become larger (the degree of slackness will increase). When loop L1 occurs, wrinkles L2 may occur in sheet P, or a misalignment L3 of the folding position of sheet P (misalignment between the opposing surfaces when folded) may occur.

Using Figures 12(a) and 12(b), the disadvantages of misalignment of the folded sheet will be explained. In a normal paper bag 53, as shown in Figure 12(a), corners c1 and c2, and corners c3 and c4 of the sheet are stuck together in an overlapping state to form a bag shape. In contrast, when the folded sheet is misaligned, corners c1 and c2 do not overlap, and corners c3 and c4 do not overlap, as shown in Figure 12(b). This not only distorts the shape of the paper bag 53, but also prevents sufficient adhesive strength from being obtained because the areas 53a where the powder adhesive is applied do not overlap, which may result in peeling of the adhesive surface.

One of the causes of the loop L1 between the folding roller pair 311 and the second fixing device 32 is that the outer diameter of the pressure roller 32a, which is the roller member of this embodiment, varies with temperature changes. The pressure roller 32a has an elastic layer 32a2 (FIG. 10) made of silicone rubber or the like, so as the pressure roller 32a is heated by continuously performing the adhesive printing operation, the elastic layer 32a2 thermally expands and the outer diameter of the pressure roller 32a gradually increases. Therefore, the sheet conveying speed of the second fixing device 32 depends on the temperature of the pressure roller 32a. When the temperature of the pressure roller 32a is high, such as during continuous use of the image forming device 1, the sheet conveying speed increases, and when the temperature of the pressure roller 32a is low, such as immediately after power-on, the sheet conveying speed decreases. Even if the pressure roller 32a is made of a material other than silicone rubber, the sheet conveying speed may vary with temperature changes depending on the thermal expansion coefficient of the material.

In this embodiment, the sheet conveying speed of the second fixing device 32 is set to 101 mm/sec at room temperature (e.g., 20°C), and the sheet conveying speed of the folding roller pair 311 is set to 100 mm/sec. It is desirable to set the sheet conveying speed of the second fixing device 32 to a value that is 0.1% to 10% higher than the sheet conveying speed of the folding roller pair 311. In other words, if the sheet conveying speed of the folding roller pair 311 is V1 and the sheet conveying speed of the second fixing device 32 is V2, it is preferable that 1.001≦V2/V1≦1.1. This establishes a relationship in which the sheet conveying speed of the second fixing device 32 is faster than the folding roller pair 311 both immediately after power-on and during continuous use.

The sheet conveying speed of the second fixing device 32 refers to the peripheral speed of the pressure roller 32a and the heating film 32b, which are a pair of rotating bodies that sandwich and convey the sheet. The sheet conveying speed of the folding roller pair 311 refers to the peripheral speed of the first folding roller 31a and the second folding roller 31b before the leading edge of the sheet P reaches the adhesive nip 32N of the second fixing device 32.

13(a, b) are schematic diagrams showing the drive transmission configuration of the folding roller pair 311. FIG. 13(a) shows a cross-sectional configuration along the rotation axis direction of the folding roller pair 311 (longitudinal direction of the nip portion 31N), and FIG. 13(b) shows a cross-sectional configuration in a cross section perpendicular to the rotation axis of the folding roller pair 311. A first gear 31a1 is attached to the rotation shaft of the first folding roller 31a, and a second gear 31b1 meshing with the first gear 31a1 is attached to the rotation shaft of the second folding roller 31b. A driving force is transmitted from a motor, which is a driving source, to a transmission gear 31b2 meshing with the second gear 31b1, so that the first folding roller 31a and the second folding roller 31b rotate in predetermined rotation directions r3 and r4, as shown in FIG. 13(b). As a result, the pair of folding rollers 311 transports the sheet P held in the nip portion 31N in the sheet transport direction indicated by the arrow H toward the adhesive nip 32N of the second fixing device 32.

Here, it is preferable to provide a one-way clutch 31b3 between the second gear 31b1 that receives the driving force from the driving source and the rotation shaft of the second folding roller 31b. The one-way clutch 31b3 allows the second folding roller 31b to rotate faster than the second gear 31b1 in the rotation direction r4 for conveying the sheet P, and restricts the second folding roller 31b from rotating slower than the second gear 31b1 in the rotation direction r4. In other words, the one-way clutch 31b3 is in a locked state when a torque load acts from the second folding roller 31b on the second gear 31b1 in the direction opposite to the rotation direction r4, and is in a free state when a torque load acts in the rotation direction r4.

Until the leading edge of the sheet P (the downstream end in the sheet conveying direction indicated by the arrow H) reaches the adhesive nip 32N, the sheet P is conveyed by the folding roller pair 311 by the drive transmission via the one-way clutch 31b3 in the locked state. When the leading edge of the sheet P reaches the adhesive nip 32N and comes into contact with both the folding roller pair 311 and the pressure roller 32a, the sheet P starts to accelerate to the sheet conveying speed of the second fixing device 32. At this time, the one-way clutch 31b3 is in a free state, and the roller pair 311 rotates idly while following the sheet P being pulled toward the adhesive nip 32N. In addition, in order to ensure the conveying force of the second fixing device 32, it is preferable that the contact pressure and nip width of the adhesive nip 32N are larger than the contact pressure and nip width of the nip portion 31N of the folding roller pair 311. By providing the one-way clutch 31b3 in this manner, the pulling of the sheet P caused by the speed difference between the second fixing device 32 and the pair of folding rollers 311 is prevented.

As described above, in this embodiment, the sheet transport speed of the second fixing device 32 is configured to be faster than the sheet transport speed of the folding roller pair 311 that transports the sheet P toward the adhesion nip 32N of the second fixing device 32. This makes it difficult for loops to occur in the sheet P before adhesion between the folding roller pair 311 and the second fixing device 32, reducing the possibility of wrinkles in the sheet or misalignment of the folding position due to loops, and making it possible to obtain an adhesive printout without wrinkles or misalignment.

In the second embodiment, a configuration example using a detection means for detecting slack in the sheet between the pair of folding rollers 311 and the second fixing device 32 will be described. In the following, elements with the same reference numerals as in the first embodiment have substantially the same configuration and function as in the first embodiment, and differences from the first embodiment will be mainly described.

As shown in FIG. 14, this embodiment includes a distance sensor 40 as a detection means. The distance sensor 40 is an optical sensor arranged between the nip portion 31N of the folding roller pair 311 and the adhesive nip 32N of the second fixing device 32 in the sheet conveying direction. The distance sensor 40 can detect whether the position in the thickness direction (normal direction of the surface) of the sheet P conveyed from the folding roller pair 311 toward the second fixing device 32 has shifted from a reference position in which the sheet P is taut without slack between the nip portion 31N and the adhesive nip 32N.

The control unit of the image forming device adjusts the sheet conveying speed of the second fixing unit 32 based on the detection signal of the distance sensor 40. For example, if the detection signal of the distance sensor 40 indicates that a loop has occurred in the sheet P, a control signal is sent to the motor that drives the pressure roller 32a to accelerate the rotation speed of the pressure roller 32a and eliminate the loop.

In addition, various detection methods are known for optical sensors that can measure the distance to an object, such as those based on triangulation or those based on the time difference between when light emitted by a light-emitting unit is reflected by an object and when it reaches a light-receiving unit; however, the detection method is not limited as long as it has an appropriate level of accuracy.

A sensor that combines a flag that swings when it comes into contact with the sheet P and a photointerrupter that is blocked by the flag can also be used as the detection means. In this case, for example, if the loop amount of the sheet P is smaller than a predetermined value, the flag moves out of the photointerrupter detection position and the output becomes 0 (Low). If the loop amount of the sheet P is larger than the predetermined value, the flag moves to the photointerrupter detection position and the output of the loop sensor becomes 1 (Hi).

In this embodiment, the detection means is used to detect sheet slack and feeds it back into the control of the sheet conveying speed, so the sheet slack can be controlled with higher accuracy. The configuration of this embodiment is advantageous, for example, when dealing with long sheets in a large image forming device.

In addition, this embodiment does not necessarily have to be configured as in the first embodiment in which the sheet conveying speed of the second fixing device 32 is always faster than the sheet conveying speed of the pair of folding rollers 311. In other words, the sheet conveying speed of the second fixing device 32 is usually set equal to the sheet conveying speed of the pair of folding rollers 311, and the second fixing device 32 may be accelerated only when the distance sensor 40 detects a sheet loop.

Other Embodiments
In the first and second embodiments, a film-type image heating device having excellent quick start properties is used as the first and second fixing devices 6 and 32, but the configuration of the image heating device is not limited to this. For example, a method of heating the toner and powder adhesive on the sheet P via a heating roller pressed against the pressure roller 6b may be used. The heating roller is, for example, a metal cylinder having an elastic layer such as silicone rubber and a release layer such as fluororesin formed on its outer periphery. In addition, the nip forming unit in the film type is not limited to one in which the heater directly contacts the inner surface of the film, but may be configured such that the heater contacts the film via a sheet material having high thermal conductivity such as iron alloy or aluminum. In addition, the heating means is not limited to one using a heating resistor, but may be, for example, a halogen lamp or an induction heating mechanism.

1...Image forming device / 1e...Image forming means (image forming unit) / 6...Fixing means (first fixing device) / 31...Folding means (folding device) / 32...Adhesive means (second fixing device) / 32a...Roller member (pressure roller) / 40...Detection means (distance sensor) / Tn...Powder adhesive / Ty, Tm, Tc...Printing toner

Claims (5)

an image forming means for forming a toner image on a sheet using a printing toner and applying a powder adhesive to the sheet;
a fixing means for heating the toner image formed on the sheet by the image forming means and the powder adhesive applied to the sheet, thereby fixing the toner image to the sheet;
a folding means for folding the sheet that has passed through the fixing means with the surface on which the powder adhesive has been applied being inward, the folding means comprising a pair of guide rollers for conveying the sheet, a pull-in section for pulling in the leading edge of the sheet that has passed between the pair of guide rollers, and a pair of folding rollers for folding the sheet from the middle of the sheet pulled into the pull-in section and discharging the folded part at the leading edge, the length of the portion of the folding rollers that pinches the sheet in a roller axial direction perpendicular to the sheet conveying direction being longer than the sheet width ;
an adhesive means having a pair of rotating bodies , and heating the sheet folded by the folding means while conveying the sheet by the pair of rotating bodies , thereby adhesively bonding the sheet with the powder adhesive , wherein a length of a portion of the pair of rotating bodies that sandwiches the sheet in the roller axial direction is longer than a width of the sheet ;
An image forming apparatus comprising:
a distance from the pair of folding rollers to the pair of rotating bodies is shorter than a length of the folded sheet in the sheet conveying direction;
a conveying speed of the sheet by the pair of rotating bodies is faster than a conveying speed of the pair of folding rollers sending out the sheet toward the bonding means;
1. An image forming apparatus comprising: the folding means includes a drive transmission unit that transmits a drive force of a drive source to the pair of folding rollers,
the drive transmission unit has a one-way clutch that allows the pair of folding rollers to rotate by being pulled by the sheet when the sheet is in contact with both the pair of folding rollers and the pair of rotating bodies .
2. The image forming apparatus according to claim 1, a conveying speed of the sheet by the pair of rotating bodies is greater than a conveying speed by the pair of folding rollers at a rate of 0.1% to 10%.
3. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction. The bonding means includes a cylindrical film which is one of the pair of rotating bodies , a heater disposed on the inner surface side of the film , and a roller member which is the other of the pair of rotating bodies and is in contact with the outer surface of the film to form a nip portion between the roller member and the heater, and heats the sheet with heat from the heater while conveying the sheet while sandwiching it between the roller member and the film in the nip portion.
4. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction. a detection unit for detecting a slack in the sheet between the folding unit and the bonding unit in the sheet conveying direction,
a conveying speed of the sheet by the pair of rotating bodies is controlled based on a detection signal from the detection means so that slack in the sheet between the folding means and the bonding means is reduced;
5. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi- color image forming apparatus.

Images