JP7463094B2 - Image forming apparatus and sheet processing apparatus - Google Patents

Description

The present invention relates to an image forming apparatus that forms an image on a sheet and a sheet processing apparatus that processes the sheet.

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

Patent documents 1 and 2 propose an image forming device that performs an electrophotographic process using a toner for pressure application (powder adhesive) in addition to a toner for printing, thereby outputting a sealed product while omitting the step of preparing preprinted paper. In these devices, the toner for printing and the toner for pressure application are transferred to a sheet, the transferred toner is thermally fixed to the sheet, the sheet is folded, and pressure is applied while the sheet is heated to perform the pressure application process.

JP 2006-171607 A JP 2007-193004 A

However, in the methods described in the above documents, image transfer could occur when the sheet was folded before the printing toner heated in the first heating step (thermal fixing) had cooled sufficiently. In other words, before the heated printing toner had cooled and firmly fixed to the image side of the sheet, it came into contact with the opposing side of the sheet facing the image side in the folded state and adhered to the opposing side, and when the printed matter was opened, there was a possibility that part of the image would transfer to the opposing side.

The present invention aims to provide an image forming apparatus and a sheet processing apparatus that can reduce the possibility of toner images adhering when a sheet is folded.

One aspect of the present invention is an image forming apparatus comprising: an image forming means for forming a toner image on a sheet; a fixing means for heating the toner image formed by the image forming means and fixing it to the sheet; a folding means for folding the sheet which has been subjected to the fixing process of the toner image by the fixing means; and a pressing means for heating and pressing the sheet folded by the folding means, wherein the image forming apparatus further comprises: a pair of conveying rollers for conveying the sheet which has passed through the fixing means toward the folding means ; and a guide member which forms a conveying path for the sheet from the pair of conveying rollers toward the folding means, wherein at least a portion of the guide member is exposed when the image forming apparatus is viewed from above, and which is configured to release at least a portion of the heat of the sheet heated by the fixing means into a space above the image forming apparatus, wherein the position of an entrance portion where the sheet conveyed from the pair of conveying rollers enters the folding means is above the nip portion of the pair of conveying rollers, and the conveying path is inclined upward in the horizontal direction from the pair of conveying rollers toward the folding means.

Another aspect of the present invention is a sheet processing apparatus connected to an image forming apparatus including an image forming means for forming a toner image on a sheet, a fixing means for heating the toner image formed by the image forming means to fix the toner image onto the sheet, and a discharge roller for discharging the sheet that has passed through the fixing means, the sheet processing apparatus comprising: a folding means for folding the sheet that has been subjected to the toner image fixing process by the fixing means; a pressing means for heating and pressing the sheet folded by the folding means; and a guide member that forms a conveying path for the sheet from the discharge roller to the folding means , wherein at least a portion of the guide member is exposed when the sheet processing apparatus is viewed from above, and the guide member is configured to release at least a portion of the heat of the sheet heated by the fixing means into a space above the sheet processing apparatus, the position of an entrance portion where the sheet conveyed from the discharge roller pair enters the folding means is above the nip portion of the discharge roller pair, and the conveying path is inclined upward in the horizontal direction from the discharge roller pair toward the folding means.

The present invention can reduce the possibility of toner images adhering when the sheet is folded.

1 is a schematic diagram of an image forming apparatus according to a first embodiment. 5A and 5B are diagrams for explaining how a pressure bonding unit is attached to the main body of the image forming apparatus according to the first embodiment. 5A to 5C are schematic diagrams for explaining the state of a toner image transferred onto a sheet in the first embodiment. 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. 1 is a schematic diagram of an image forming apparatus according to a comparative example. 4A and 4B are cross-sectional views showing a first discharge tray according to the first embodiment. FIG. 13 is a cross-sectional view showing a first discharge tray according to a first modified example of the first embodiment. FIG. 11 is a schematic diagram of an image forming apparatus according to a second modified example of the first embodiment. FIG. 11 is a schematic diagram of an image forming apparatus according to a second embodiment.

Below, an exemplary embodiment of the present invention will 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 for storing sheets P as recording media, 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 for forming a toner image on the sheets P fed from the sheet cassette 8 by the image forming unit 1e, and creating a printed matter that has been subjected to a fixing process by the first fixing device 6. Note that as the sheets P as recording media, various sheet materials of different sizes and materials can be used, such as paper such as plain paper and cardboard, paper with a surface treatment such as plastic film, cloth, and coated paper, and sheet materials of special shapes such as index paper.

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 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, and 7c has a substantially common configuration, except for the type of toner. That is, each process cartridge 7n, 7y, 7m, and 7c includes a photosensitive drum 101, which is an image carrier, a charging roller 102, which is a charger, a toner storage section 104n, 104y, 104m, and 104c, which stores toner, and a developing roller 105, which performs development using the toner.

Of the four toner storage sections, the three toner storage sections 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 toners) for forming an image on a recording medium. In contrast, the toner storage section 104n on the leftmost side of the figure contains pressure-bonding toner Tn, which is a toner (second toner) for performing a pressure-bonding process after printing. The toner storage sections 104y, 104m, and 104c are all examples of first storage sections that contain printing toner, and the toner storage section 104n is an example of a second storage section that contains pressure-bonding toner. 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 pressure-bonding toner in a predetermined application pattern.

The main component of the toner for pressure application Tn can be the same material (e.g., styrene acrylic resin) as the toners for printing Ty, Tm, and Tc. In addition, PE (polyethylene) resin may be added to increase the adhesive strength. The toner for pressure application Tn is designed to have a lower melting point than the toners for printing Ty, Tm, and Tc, for example, by increasing the amount of wax component added to the main component. Therefore, the lower limit of the optimum fixing temperature of the toner for pressure application Tn is lower than that of the toners for printing Ty, Tm, and Tc. In this embodiment, the toner for pressure application Tn is colorless and transparent, and when printing a black image such as text, it is expressed by process black in which yellow (Ty), magenta (Tm), and cyan (Tc) toners are superimposed. However, for example, a fifth process cartridge using black printing toner may be added to the image forming unit 1e so that the black image can be expressed by black printing toner. Not limited to this, the type and number of printing toners can be changed depending on the application of the 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 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. The first fixing device 6 is a thermal fixing type fixing device having a heating roller 6a as a fixing member and a pressure roller 6b as a pressure member. The heating roller 6a is heated by a heating element such as a halogen lamp or ceramic heater or a heating mechanism of an induction heating type. The pressure roller 6b is pressed against the heating roller 6a by a biasing member such as a spring, and generates a pressure force to pressurize the sheet P passing through the nip portion (fixing nip 6n) between the heating roller 6a and the pressure roller 6b.

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 body 10 is equipped with a mechanism for performing double-sided printing. Specifically, the discharge unit 34 is connected to a motor capable of forward and reverse rotation, for example, so that the first discharge roller 34a and the intermediate roller 34b can reverse the conveying direction of the sheet P and perform switchback conveyance. Furthermore, a double-sided conveyance path 1r is provided as a conveyance path connected in a loop to the main conveyance path 1m, for conveying the sheet P switched back by the discharge unit 34 to the main conveyance path 1m again. In the case of double-sided printing, the sheet P with an image formed on its first side while passing through the main conveyance path 1m is switched back by the discharge unit 34 and conveyed to the double-sided conveyance path 1r. Then, while the sheet P passes through the main conveyance path 1m again in an inverted state, an image is formed on the second side of the sheet P. The conveyance path of the sheet P after double-sided printing is switched by the switching guide 33, as in the case of single-sided printing.

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 a pressure-bonding printing function in an installation space approximately the same as that of a normal vertical pass printer.

(Crimping unit)
As shown in Fig. 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 a pressing means (second fixing means) are housed and integrated in a housing (second housing) 39. The post-processing unit 30 is also provided with a first discharge tray 13, an intermediate path 15 having a function as a sheet cooling section, 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 section 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.

When the post-processing unit 30 is not attached, the printed sheet P is discharged to the main body discharge tray 19a provided on the top surface of the device main body 10. In that case, if a process cartridge using black printing toner is attached to the cartridge support portion 9 instead of the process cartridge 7n (Figure 1) using pressure-bonding toner Tn, the device main body 10 will operate as a general full-color printer. In other words, the image forming device 1 can be used in either a form that does not include the post-processing unit 30 or the form shown in Figure 1 in which the optional post-processing unit 30 is attached, without changing the basic configuration of the device main body 10.

(Image Forming 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 for explaining the state of a toner image transferred to a sheet P. Figures 4(a, b) are diagrams showing the sheet transport path in the image forming apparatus 1. Figures 5(a-f) are diagrams for explaining the contents of the folding process. Figures 7(a-c) are diagrams showing examples of products output by the image forming apparatus 1. Figure 8 is a schematic diagram of an image forming apparatus 401 according to a comparative example. Figures 9(a, b) are cross-sectional views showing the first discharge tray of this embodiment.

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 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 toner image by the toner carried by the developing roller 105 of each process cartridge 7n, 7y, 7m, and 7c.

The toner layer formed on the photosensitive drum 101 by development with the colorless and transparent pressure-bonding toner 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 the following explanation, the layer of pressure-bonding toner developed in a shape corresponding to the application pattern by the electrophotographic process in order to apply pressure-bonding toner to the sheet P in a predetermined application pattern is also treated 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 pressure-bonding toner 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 of 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, pressure-bonding toner 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 pressure-bonded toner Tn is formed on top of that. Therefore, in the toner image transferred to the sheet P, the layer of pressure-bonded toner Tn becomes the outermost surface.

Then, the sheet P is transported to the first fixing device 6 and undergoes a thermal fixing process. That is, when the sheet P passes through the fixing nip 6n, the toner image on the sheet P is heated and pressurized, causing the printing toners Ty, Tm, and Tc and the pressure-bonding toner Tn to melt and then solidify, resulting in an image fixed on the sheet P.

The conveying path of the sheet P conveyed through the main conveying path 1m in the device main body 10 and passing through the first fixing device 6 branches into two paths, the first path R1 and the second path R2, as shown in Fig. 4(a,b). The first path R1 shown in Fig. 4(a) is a path in which the sheet P passing through the first fixing device 6 is discharged to the first discharge tray 13 by the discharge unit 34 in the normal printing mode. The second path R2 shown in Fig. 4(b) is a path in which the sheet P passing 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 the pressure printing mode. When the sheet P is conveyed through the first path R1, the switching guide 33 guides the leading edge of the sheet P (the downstream end in the sheet conveying direction) to the nip portion between the first discharge roller 34a and the intermediate roller 34b of the discharge unit 34. Furthermore, when the sheet P is transported along the second path R2, the switching guide 33 guides the leading edge of the sheet P to the nip between the intermediate roller 34b and the second discharge roller 34c of the discharge unit 34.

The first path R1 is used during normal image forming operations (hereinafter referred to as normal printing) that do not use pressure-bonding toner Tn. In normal printing, the development process of the process cartridge 7n that uses pressure-bonding toner Tn is not performed. Therefore, a toner image composed only of yellow (Ty), magenta (Tm), and/or cyan (Tc) printing toner is transferred to the sheet P at the transfer nip 5n. Then, as shown in FIG. 4(a), the sheet P is subjected to a thermal fixing process in the first fixing device 6, and then discharged by the discharge unit 34 and loaded onto the loading surface 130, which is the upper surface of the first discharge tray 13.

The second path R2 is used during image formation using pressure-bonded toner Tn (hereinafter referred to as pressure-bonded printing). In the case of pressure-bonded printing, as described with reference to FIG. 3, a toner image having a layer of pressure-bonded toner Tn on the top surface is transferred onto the sheet P that has passed through the transfer nip 5n. Then, the sheet P that has passed through the first fixing device 6 and undergone a thermal fixing process (first thermal fixing) is transported to the folder 31 by the discharge unit 34 as shown in FIG. 4(b).

Between the first fixing device 6 and the folder 31 in the second route R2, an intermediate path 15 is provided. 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 (31c, 31d) 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 are a pair of guide rollers 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 are a pair of folding rollers that send out 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)) of the sheet P in the transport direction 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 of the sheet in the transport direction that can be processed by the post-processing unit 30. This configuration allows the sheet P to be transferred smoothly from the discharge unit 34 to the pair of guide rollers.

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 (31c, 31d) 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 sheet P is pulled in by the pair of guide rollers (31c, 31d), the leading edge q slides against the wall 31g and advances further 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 (31c, 31d) 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 (31a, 31b) by the frictional force it receives 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 (31a, 31b) 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 (31a, 31b) to the end 31h of the retraction section 31e, is set to half the total 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 that has passed through the folder 31 is conveyed to the second fixing device 32 as shown in FIG. 4(b). The second fixing device 32 has a thermal fixing configuration similar to the first fixing device 6. That is, the second fixing device 32 has a heating roller 32a as a heating member and a pressure roller 32b as a pressure member. The heating roller 32a is heated by a heating element such as a halogen lamp or a ceramic heater or a heating mechanism of an induction heating type. The pressure roller 32b is pressed against the heating roller 32a by a biasing member such as a spring, and generates a pressure force to pressurize the sheet P that passes through the nip portion (pressure nip) between the heating roller 32a and the pressure roller 32b.

The sheet P folded by the folder 31 is subjected to a bonding process (a second heat fixing to the image surface to which the bonding toner is applied) by the second fixing device 32, so that the sheet P is bonded while still folded. That is, when the sheet P passes through the bonding nip, the bonding toner Tn on the sheet P is heated and remelted and pressurized, so that it adheres to the opposing surface (the surface facing the image surface of the sheet to which the toner image of the bonding toner Tn is transferred in the folded state). Then, the bonding toner Tn cools and hardens, so that the image surface and the opposing surface of the sheet P are bonded (adhered) together using the bonding toner Tn as an adhesive.

Here, the heating roller 6a of the first fixing device 6 directly contacts the toner image, whereas the heating roller 32a of the second fixing device 32 indirectly heats the toner Tn for pressure application through the folded sheet P. At this time, as described above, by setting the melting point of the toner Tn for pressure application lower than the melting points of the toners Ty, Tm, and Tc for printing, the fixing temperature of the second fixing device 32 can be suppressed to a level at which image transfer does not occur. That is, it is possible to avoid the possibility of remelting the toners Ty, Tm, and Tc for printing, which is a concern when the fixing temperature of the second fixing device 32 is increased, and a part of the image being transferred from the image surface to the opposing surface (hot offset). The fixing temperature of the second fixing device 32 (the set temperature of the heating roller 32a) may be set lower than the fixing temperature of the first fixing device 6 (the set temperature of the heating roller 6a), or may be set higher than the fixing temperature of the first fixing device 6 in consideration of the indirect heating.

As shown in FIG. 4(b), the sheet P that has been subjected to the pressing 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 bonding on the sheet P. Figures 7(a) to 7(c) show examples of deliverables (outputs of an image forming apparatus) with different application patterns of the toner Tn for pressure bonding. 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 the pressure-bonded postcard 51 in Figure 7(a), the toner Tn for pressure bonding is applied to the entire surface 51a of one side of the base paper, and the paper is folded and pressure-bonded at the central crease 51b. In the case of the pay slip 52 in Figure 7(b), the toner Tn for pressure bonding 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-bonded at the central crease 52b. Figure 7(c) shows a bag (medicine bag) 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 L-shaped area 53a so that the three sides of the folded sheet, including the crease 53b, are joined.

The image forming apparatus 1 of this embodiment can output any of the products shown in Figs. 7(a-c) in one stop without preparing preprinted paper. That is, in parallel with the operation of recording an image on one or both sides of a base paper using printing toner, it is possible to apply pressure toner in a predetermined application pattern and output a product in a state where folding and pressure bonding have been performed. For example, when outputting the product of Figs. 7(a-c), one side of the sheet used as the base paper becomes the outside of the product, and the other side becomes the inside of the product. Therefore, as the image forming operation for the first side in double-sided printing, an image for the outer side is formed with printing toner, and as the image forming operation for the second side, an image for the inner side is formed with printing toner and pressure toner is applied in a predetermined application pattern.

The image recorded by the image forming device 1 using printing toner can include the format (unchanging parts) when preprinted paper is used, and variable parts such as personal information. Therefore, as described above, in this embodiment, a product can be output that is pressed by a pressing process from a base paper such as blank paper that is not preprinted paper. However, the image forming device 1 of this embodiment can also be used for applications in which preprinted paper is used as a recording medium and printing and pressing processes of variable parts are performed.

(Cooling of the sheet before folding)
Here, the cooling of the sheet P transported from the first fixing device 6 to the folding device 31 will be described. In the case of the image forming operation in which the folding process and the pressing process are performed in the post-processing unit 30, as described above, the sheet P subjected to the thermal fixing process in the first fixing device 6 is transported to the folding device 31 via the second route R2 and folded (FIG. 4B). At this time, if the sheet P is folded before the toner image melted by the thermal fixing process is sufficiently cooled and solidified, the toner image of the printing toner may be transferred from the image surface of the sheet P to the opposing surface. That is, a part of the printing toner that should be fixed only to the image surface comes into contact with the opposing surface in a state where it is not sufficiently cooled, and an adhesive force is generated between the opposing surface. Then, when the printed matter discharged from the image forming apparatus 1 after the pressing process in the second fixing device 32 is opened, there is a possibility that a part of the image composed of the printing toner may be transferred from the image surface to the opposing surface.

Therefore, in this embodiment, as shown in FIG. 1, an intermediate path 15 is provided as a cooling section between the first fixing device 6 and the folder 31 in the second route R2. By dissipating heat from the sheet P while passing through the intermediate path 15, the possibility of image transfer as described above occurring can be reduced.

The fixing temperature of the first fixing device 6 is set within a range that satisfies the optimum fixing temperature for both the printing toner and the pressure-bonding toner, for example, 160°C, which is higher than the melting point of the printing toner. In contrast, the temperature of the sheet P when it is folded in the folder 31 is preferably equal to or lower than the glass transition temperature of the pressure-bonding toner (50°C), for example, in order to effectively reduce image transfer. In other words, when pressure-bonding printing is performed continuously on multiple sheets P, it is preferable that the cooling section has a cooling performance that can cool the sheet P that has been thermally fixed at the above fixing temperature to approximately the glass transition temperature of the pressure-bonding toner before it enters the folder 31.

1, the intermediate path 15 in this embodiment is provided with a length F that is slightly smaller than the distance M between the second discharge roller 34c and the first guide roller 31c. In order to increase the amount of heat dissipated from the sheet P until it reaches the folder 31, it is advantageous to have a longer intermediate path 15. However, if the intermediate path 15 is too long, the device will become larger, so it is desirable to keep it to a minimum. Therefore, the intermediate path 15 is provided in a range that overlaps with the first discharge tray 13 in the conveying direction of the sheet P. In other words, the cooling section in this embodiment is a sheet conveying path that constitutes the second path R2, and is a sheet conveying path in a range that overlaps with the position of the first discharge tray 13 in the sheet conveying direction in the second path R2. In this way, by arranging the cooling section and the first discharge tray 13 so as to overlap in the conveying direction of the sheet, it is possible to achieve both cooling of the toner image on the sheet and miniaturization of the device. In this embodiment, as described above, the entrance of the folder 31 is located vertically above the exit of the device main body 10, and the intermediate path 15 is inclined. This makes it possible to keep the horizontal width of the intermediate path 15 small while still ensuring the length F required for cooling.

In addition, in this embodiment, the second path R2 including the intermediate path 15 is provided on the upper surface of the image forming apparatus 1, that is, so as to constitute a part of the upper surface of the image forming apparatus 1. The reason for this will be explained with reference to FIG. 8. FIG. 8 shows the layout of the image forming apparatus 401 in the reference example, in which a toner image is formed on a sheet by a process cartridge 407p using a printing toner and a process cartridge 407n using a pressure-bonding toner, and a thermal fixing process is performed by the first fixing device 406. The sheet that has been subjected to the thermal fixing process is folded in the folding device 431, and then subjected to a pressure bonding process by the second fixing device (not shown). However, in this configuration, the path from the first fixing device 406 to the folding device 431 is located deep inside the image forming apparatus 401, and the heat of the first fixing device 406, which is a heat source, is likely to be trapped. Therefore, as described above, when the sheet is folded by the folding device 431, the toner image adheres to the opposing surface, and there is a concern that the image may be transferred.

In contrast, the intermediate path 15, which is the cooling section in this embodiment, is provided on the upper surface of the image forming device 1, and the heat of the sheet P heated by the first fixing device 6 is released into the external space above the image forming device 1, thereby effectively cooling the sheet P.

9A, the intermediate path 15 is a sheet transport path formed by an upper guide surface 15a, which is the lower surface of the first discharge tray 13, and a lower guide surface 15b provided on the housing 39 of the post-processing unit 30. In other words, the first discharge tray 13 is a discharge tray that supports the sheets discharged on the first path R1 with the stacking surface 130, which is its upper surface, and is a guide member that guides the upper surface of the sheet passing through the second path R2 with the upper guide surface 15a, which is its lower surface. This first discharge tray 13 is arranged so that at least a part of it is exposed when viewed from above in the vertical direction, and is a member that is exposed to the outside air on the upper surface side. This makes it possible to efficiently cool the sheet P passing through the intermediate path 15.

The first discharge tray 13, which is a guide member in this embodiment, is a member that can be opened and closed between an open state in which the intermediate path 15 is opened as shown in FIG. 9(b) and a closed state as shown in FIG. 9(a). By opening the intermediate path 15, for example, when a jam of a sheet P occurs in the folder 31, the user can remove the sheet P by himself and handle the jam. In the illustrated configuration example, the first discharge tray 13 is provided with a finger hole 13b, which is a hole shape that penetrates from the upper surface to the lower surface, and the user can lift the first discharge tray 13 upward by putting a finger in the finger hole 13b. Note that the downstream end 132 of the first discharge tray 13 in the conveying direction of the sheet P is releasably engaged with the housing 39 of the post-processing unit 30, and is detached from the housing 39 when the first discharge tray 13 is lifted. In addition, the finger hole 13b is provided in the center of the loading surface 130 of the first discharge tray 13 in the sheet width direction perpendicular to the conveying direction of the sheet P.

When the first discharge tray 13 is closed, the inside of the intermediate path 15 is connected to the space above the image forming device 1 via the finger hole 13b. Therefore, when the internal temperature of the intermediate path 15 rises due to the passage of the sheet P, the rise in the internal temperature of the intermediate path 15 is suppressed by air convection through the finger hole 13b. Therefore, the finger hole 13b contributes to the cooling efficiency of the intermediate path 15 (cooling section).

(Modification)
Note that instead of configuring the first discharge tray 13 as a guide member to be removable from the housing 39 of the post-processing unit 30, a guide member that is rotatable with respect to the housing 39 around the upstream end 131 or the downstream end 132 in the sheet conveying direction may be used. The direction in which the guide member is openable and closable can be changed depending on, for example, which of the folder 31 and the discharge unit 34 has priority in jamming processability.

Finger hole 13b of first discharge tray 13 is an example of an opening of a guide member. Multiple holes 13a may be provided as shown in FIG. 10 as variant 1. These holes 13a function as ventilation holes, for example, by arranging them in a lattice at regular intervals, and the rise in the internal temperature of intermediate path 15 is suppressed by air convection through holes 13a. Note that holes 13a as ventilation holes may also be used as finger holes 13b, or only holes 13a may be provided in first discharge tray 13 without finger holes 13b. For example, a cover portion (finger guard) may be provided to cover holes 13a, or holes 13a may be formed in a lattice shape finer than the thickness of a typical finger when viewed from above, or in a slit shape extending in the conveying direction with a width narrower than the thickness of a finger.

Also, a blower fan may be arranged in the image forming device 1 to allow airflow to flow through the intermediate path 15. For example, a configuration may be made in which a portion of the airflow generated by a blower fan provided in the device body 10 passes through the intermediate path 15 and escapes to the outside of the image forming device 1. This configuration allows air to be blown onto the sheet P, which also contributes to the cooling efficiency of the intermediate path 15 (cooling section).

Also, if the guide member constituting the guide surface of the sheet transport path as the cooling section is arranged in contact with the outside air, the same cooling efficiency as the intermediate path 15 of this embodiment can be expected, so the upper surface of the guide member may not be used as a discharge tray. For example, as shown in FIG. 11 as modified example 2, a configuration in which the first path R1 is arranged below the second path R2 is also possible. In this configuration, the upper guide 13A of the intermediate path 15 is not covered by the sheet P discharged on the first path R1, so the cooling efficiency of the intermediate path 15 can be further improved. Note that elements in FIG. 11 that are given the same reference numerals as those in Example 1 have the same functions as those described above in Example 1, so their explanations are omitted.

In addition, instead of a configuration in which the post-processing unit 30 is attached as an option to the device body 10 of the image forming device, the functions of each part of the post-processing unit 30 may be integrated into the device body.

As described above, in this embodiment, a cooling section for cooling the toner image on the sheet is provided between the first fixing device 6 and the folder 31, and the cooling section is disposed on the upper surface of the image forming device 1. As a result, the sheet P that has been thermally fixed by the first fixing device 6 is cooled before it reaches the folder 31, making it possible to reduce adhesion of the toner image when the sheet is folded by the folder 31, which contributes to improving the quality of the final product.

Next, the configuration of Example 2 will be described with reference to FIG. 12. In this example, a cooling section is disposed on the upper surface of the post-processing unit 301 in an image forming system 100 configured such that the post-processing unit 301 is connected laterally to the image forming apparatus main body (hereinafter referred to as the apparatus main body) 201. Note that elements with the same reference numerals as those in Example 1 have the same functions as those described above in Example 1, and description thereof will be omitted.

The configuration of the device body 201 is the same as that of the first embodiment, except that the discharge unit 34 discharges the sheet P to the side of the device body 201 (to the right in the figure). That is, in the device body 201, a toner image of the printing toner and the pressure-bonding toner is transferred to the sheet P fed from the sheet cassette 8, and the first fixing device 6 performs a thermal fixing process. The conveying path of the sheet P that has passed through the first fixing device 6 is switched between the first path R1 and the second path R2 by the switching guide 33. The first path R1 is a path for discharging the sheet P without folding and pressing the sheet P, and the second path R2 is a path for discharging the product obtained by folding and pressing the sheet P. The post-processing unit 301 is equipped with the same folder 31 and second fixing device 32 as in the first embodiment, and performs folding and pressing processes on the sheet P sent to the second path R2 and discharges it to the second discharge tray 35.

Here, an intermediate path 215 serving as a cooling section in this embodiment is provided between the first fixing device 6 and the folder 31 on the second path R2. The intermediate path 215 is a sheet transport path in a range that overlaps with the position of the first discharge tray 213 in the sheet transport direction on the second path R2. The intermediate path 215 is also a sheet transport path that passes through the upper surface of the post-processing unit 301. It is preferable to provide an opening, as exemplified in Figures 9(a) and 9(b) and 10, in the first discharge tray 213 that constitutes the upper guide surface of the intermediate path 215.

When the sheet P is transported through the second path R2, the toner image on the sheet P is cooled while the sheet P, which has been thermally fixed by the first fixing device 6, is transported through the intermediate path 215 toward the folder 31. Therefore, even in a configuration in which the post-processing unit 30 serving as a sheet processing device is disposed to the side of the device main body 201 as in this embodiment, it is possible to reduce the adhesion of the toner image to the opposing surface when the sheet is folded by the folder 31.

1e...image forming means (image forming unit)/6...fixing means (first fixing device)/7n...second process unit (process cartridge)/7y, 7m, 7c...first process unit (process cartridge)/8...sheet storage section (sheet cassette)/1,201...image forming device/13...guide member (first discharge tray)/130...upper surface of guide member, loading surface/13a...opening (hole)/13b...opening (finger hole)/15,215...cooling section (intermediate path)/19...first housing/30,301...sheet processing device (post-processing unit)/31...folding means (folder)/32...pressing means (second fixing device)/39...second housing/R1...first path/R2...second path/Tn...toner for pressing/Ty,Tm,Tc...printing toner

Claims (12)

an image forming means for forming a toner image on a sheet;
a fixing unit for heating the toner image formed by the image forming unit to fix the toner image on a sheet;
a folding means for folding the sheet on which the toner image has been fixed by the fixing means;
a pressing means for heating and pressing the sheet folded by the folding means;
An image forming apparatus comprising:
a pair of conveying rollers for conveying the sheet that has passed through the fixing means toward the folding means;
a guide member that forms a conveying path of the sheet from the conveying roller pair toward the folding means, at least a part of the guide member being exposed when the image forming apparatus is viewed from above, and that is configured to release at least a part of the heat of the sheet heated by the fixing means into a space above the image forming apparatus;
Equipped with
an entrance portion where the sheet conveyed from the conveying roller pair enters the folding means is located above a nip portion of the conveying roller pair;
the conveying path is inclined upward in a horizontal direction from the pair of conveying rollers toward the folding means;
1. An image forming apparatus comprising: a conveying path of the sheet that has passed through the fixing means is branched into a first path for discharging the sheet without passing through the folding means and the pressing means, and a second path including the conveying path for conveying the sheet via the folding means and the pressing means ;
2. The image forming apparatus according to claim 1 , an upper surface of the guide member is a stacking surface on which the sheets discharged through the first path are stacked;
3. The image forming apparatus according to claim 2 , The guide member is provided with an opening extending from an upper surface of the guide member to a lower surface of the guide member.
4. The image forming apparatus according to claim 1 , wherein the first and second electrodes are arranged in a first direction. the guide member is configured to be openable and closable between a closed state in which the transport path is formed and an open state in which the transport path is opened,
The opening includes a hole shape that allows a user to open and close the guide member.
5. The image forming apparatus according to claim 4 . The opening includes a plurality of holes provided in the guide member.
6. The image forming apparatus according to claim 4 , wherein the image forming apparatus is a multi-color image forming apparatus. a sheet storage section for storing sheets to be fed to the image forming means,
the image forming means is disposed above the sheet storage section, and the guide member is disposed above the image forming means,
The guide member , the image forming means, and the sheet storage unit are overlapped when viewed in the vertical direction.
7. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-color image forming apparatus. the image forming unit and the fixing unit are disposed in a first housing,
the guide member , the folding means and the crimping means are provided in a second housing attached to an upper portion of the first housing;
8. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction. When viewed in a sheet width direction perpendicular to a sheet conveying direction, the ranges occupied by the guide member, the folding means and the crimping means in the horizontal direction are within the range occupied by the first housing in the horizontal direction.
9. The image forming apparatus according to claim 8, A blowing means for generating an air flow is provided,
At least a part of the airflow generated by the blowing means passes through the transport path .
10. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction. The image forming means includes a first process unit for forming the toner image using a printing toner by an electrophotographic process, and a second process unit for applying a pressure-bonding toner to a sheet for bonding the sheet by the bonding means by an electrophotographic process.
11. The image forming apparatus according to claim 1, A sheet processing apparatus connected to an image forming apparatus including: an image forming unit that forms a toner image on a sheet; a fixing unit that heats the toner image formed by the image forming unit to fix the toner image on the sheet ; and a pair of discharge rollers that discharge the sheet that has passed through the fixing unit ,
a folding means for folding the sheet on which the toner image has been fixed by the fixing means;
a pressing means for heating and pressing the sheet folded by the folding means;
a guide member that forms a conveying path of the sheet from the pair of discharge rollers toward the folding means, at least a part of the guide member being exposed when the sheet processing device is viewed from above, and that is configured to release at least a part of the heat of the sheet heated by the fixing means into a space above the sheet processing device;
Equipped with
an inlet portion where the sheet conveyed from the pair of discharge rollers enters the folding means is located above a nip portion of the pair of discharge rollers;
the conveying path is inclined upward in a horizontal direction from the pair of discharge rollers toward the folding means;
A sheet processing apparatus comprising:

Images