JP2005274764A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which the removal of abnormal conveyance of paper is facilitated and the possibility of image quality deterioration caused by blister or offset is made little even in the event of abnormal conveyance. <P>SOLUTION: When determined that paper is in contact with the nip area of a first fixing section 3 at a point in time that a jam sensor Sj detects the occurrence of a jam in a cutting section 6, the image forming apparatus 100 stops the paper after conveying the paper to a position between the first fixing part 3 and a second fixing part 5 so as not to bring the paper into contact with the nip areas of the first fixing part 3 and the second fixing part 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for controlling the conveyance of a sheet when a sheet conveyance abnormality occurs in an image forming apparatus.

2. Description of the Related Art There is known an electrophotographic image forming apparatus that increases or decreases the glossiness of an image surface by properly using two fixing devices as necessary. Such an image forming apparatus is generally provided with a low-gloss roller-type fixing device and a high-gloss belt-type fixing device as disclosed in Patent Document 1, for example. .
Here, the operation of the image forming apparatus including the roller-type fixing device and the belt-type fixing device will be described with reference to FIG. As shown in the figure, the roller-type fixing device 3 includes a fixing roll 30 and a pressure belt 31 provided at positions facing each other across the sheet conveyance path, and a pair of these members. The paper is heated and pressurized in the nip region formed by the contact between 30, 31 and the toner is melted and fixed on the paper. On the other hand, the belt-type fixing device 5 includes a fixing roll 50, a pressure roll 51, a smooth fixing belt 52 stretched around the fixing roll 50 and the like, and a cooling device disposed along the fixing belt 52. 53. The fixing roll 50 and the pressure roll 51 are provided at positions facing each other across the sheet conveyance path, and the sheet is heated and heated in the nip region formed by the contact between the pair of rolls 50 and 51. The toner is melted by applying pressure. Further, when the sheet is cooled by the cooling device 53 while the sheet is conveyed by the fixing belt 50 while the toner on the sheet is in a molten state, the surface of the toner image is solidified while being smooth, and a high gloss image can be formed.
When such an image forming apparatus is used, a thermoplastic resin layer is provided on the surface in order to increase the smoothness of the surface of the toner image and to finish the portion where the toner image is not formed to be highly glossy. The provided paper is often used.

However, when such an image forming apparatus is used, there are concerns about the following problems.
In the image forming apparatus, a paper conveyance abnormality called a jam may occur. In the event of a jam, in order to prevent further jamming of the jammed portion, the conveyance of the paper is immediately stopped, the user etc. takes out the paper causing the jam, and the jam is resolved. In general, the sheet conveyance is resumed. However, at this time, if the paper stops in the nip region N ₁ of the roller type fixing device 3 or the nip region N ₂ of the belt type fixing device 5 as shown in FIG. When heated excessively, bubbles called blisters are generated on the recording surface of the paper due to moisture and air bubbles inside the paper, thereby degrading the image quality. In addition, a phenomenon called “offset” occurs in which the toner on the paper melts and adheres to the fixing belt in the nip areas N ₁ and N ₂ , and this offset causes stains on an image formed thereafter. It will cause adverse effects such as letting you. In particular, when a sheet having a thermoplastic resin layer on the surface is used, not only the toner but also the resin layer melts and adheres to the fixing belt, and the effect of offset becomes more prominent.

  In order to eliminate this offset, for example, a method is generally used in which several sheets of white paper are passed through a belt-type fixing device for cleaning, and the toner or resin layer adhering to the fixing belt is copied onto the white paper. However, such a method not only consumes paper more than necessary, but also wastes time for cleaning, which reduces the paper cost and operating efficiency of the image forming apparatus. There is a problem of end.

  In addition, instead of stopping the conveyance of the paper, a method of discharging all the paper in the middle of image formation when a jam occurs can be considered. However, when such a method is selected, when the jam occurrence location is, for example, a post-processing device such as the cutting unit 6 of FIG. 1, a large amount of paper is carried into the jam occurrence location and becomes jammed. This will make it more difficult to resolve jams.

JP-A-5-158364

  The present invention has been made in view of the above-described problems, and the object thereof is to facilitate the elimination of a conveyance abnormality and to cause a deterioration in image quality due to a blister or an offset even when a conveyance abnormality occurs. An object of the present invention is to provide an image forming apparatus with a small amount of image data.

In order to solve the above-described problem, an image forming apparatus according to the present invention includes a first member in which an image forming unit that forms a toner image on a recording material and a pair of members facing each other across the conveyance path of the recording material contact each other. In the nip region, a first fixing unit that fixes the toner image to the recording material by heating and pressurizing the recording material, and a pair of members facing each other across the conveyance path of the recording material are in contact with each other. In the nip region, the second fixing means for fixing the toner image on the recording material again by heating and pressurizing the recording material on which the image has been fixed by the first fixing means, and the first nip. A recording material detecting means for determining whether or not the recording material is in contact with the area or the second nip area; and a position in the conveying direction of the recording material as viewed from a position where the second fixing means is provided. The record on the downstream side A conveyance abnormality detecting means for detecting whether or not a conveyance abnormality occurs, and the conveyance abnormality detecting means detects the occurrence of a conveyance abnormality, and the recording material detection means is configured to detect the first nip region or the second nip region. If the recording material is determined to be in contact with the nip region, a conveyance control unit is provided that conveys and stops the recording material to a position where the recording material does not contact the first nip region and the second nip region.
According to such an image forming apparatus, by stopping the recording material, it is possible to prevent the recording material from being carried into the location where the conveyance abnormality has occurred, and the recording material does not stop in the nip region. Occurrence can be prevented.

In a more preferred aspect of the image forming apparatus of the present invention, an interval between the first nip region and the second nip region is longer than a length of a side along the recording material conveyance direction. ing.
In this way, the recording material can be stopped between the first nip region and the second nip region.

In a more preferred aspect of the image forming apparatus of the present invention, the recording material detection unit is provided at a predetermined position upstream in the transport direction as viewed from the position of the first nip region. A first sensor that detects the presence or absence of the recording material at a first position, and a first sensor that is provided at a predetermined position between the first nip region and the second nip region and detects the presence or absence of the recording material at the position. 2, and when the occurrence of a conveyance abnormality is detected by the conveyance abnormality detection unit, the recording material detection unit detects the recording material based on the detection result of the first sensor. The conveyance control means causes the recording material to pass through the first nip region based on the detection result of the first sensor or the second sensor. To the nip area Position and transports the recording material is stopped until not.
In this way, even when the recording material is in contact with the first nip region when the conveyance abnormality occurs, the recording material is conveyed based on the detection results of the first sensor and the second sensor. By controlling, it becomes possible to stop the recording material without contacting the first nip region and the second nip region.

In a more preferred aspect of the image forming apparatus of the present invention, the recording material detection unit is provided at a predetermined position upstream in the transport direction as viewed from the position of the first nip region. A first sensor that detects the presence or absence of the recording material at a first position, and a first sensor that is provided at a predetermined position between the first nip region and the second nip region and detects the presence or absence of the recording material at the position. 2, and when the occurrence of conveyance abnormality is detected by the conveyance abnormality detection means, the recording material detection means is based on the detection result of the first sensor or the second sensor, and the recording material Is present between the first nip region and the second nip region, and the conveyance control means determines that it is not in contact with either the first nip region or the second nip. Carrying the recording material As it is to stop without.
According to this configuration, even when the recording material exists between the first nip region and the first nip region when the conveyance abnormality occurs, the detection result of the first sensor and the second sensor is used. By stopping the conveyance of the recording material immediately, it is possible to stop the recording material without contacting the first nip region and the second nip region.

In a more preferred aspect of the image forming apparatus of the present invention, the recording material detection unit is provided at a predetermined position upstream in the transport direction as viewed from the position of the first nip region. A first sensor that detects the presence or absence of the recording material at a first position, and a first sensor that is provided at a predetermined position between the first nip region and the second nip region and detects the presence or absence of the recording material at the position. 2 and a third sensor that is provided at a predetermined position downstream of the transport direction as viewed from the position of the second nip region and detects the presence or absence of the recording material at the position, When the occurrence of conveyance abnormality is detected by the conveyance abnormality detection unit, the recording material detection unit is in contact with the first nip region based on the detection result of the first sensor. And said If it is determined that the second recording material is in contact with the second nip region based on the detection result of the sensor No. 3, the conveyance control unit is configured to transfer the first sensor, the second sensor, or the second sensor. 3, based on the detection result of the sensor 3, the first recording material is passed through the first nip region, and the first recording material is conveyed to a position where the first recording material does not contact the second nip region, and The second recording material is passed through the second nip region and conveyed to a position where it does not contact the second nip region and stopped.
In this case, a plurality of images are formed continuously and at high speed, and the recording material is placed between the first nip region and the first nip region when a conveyance abnormality occurs. Even in such a case, the conveyance of the recording material is controlled based on the detection results of the first sensor, the second sensor, and the third sensor, so that the first nip region and the second nip region can be controlled. It is possible to stop the recording material without contact.

According to another aspect of the present invention, the image forming unit that forms a toner image on a recording material and a pair of members that face each other across the conveyance path of the recording material are in contact with each other. In one nip region, a first fixing unit that fixes the toner image on the recording material by heating and pressurizing the recording material and a pair of members facing each other across the conveyance path of the recording material are in contact with each other. A second fixing unit that fixes the toner image on the recording material again by heating and pressurizing the recording material on which the image has been fixed by the first fixing unit in a second nip region; A second fixing unit provided at a position such that an interval between the first nip region and the second nip region is shorter than a length of a side along the conveyance direction of the recording material; 1 nip area and the second A first conveyance roll provided between the nip areas; a second conveyance roll provided between the first conveyance roll and the second nip area; and the recording in the first nip area. A first sensor for determining whether or not the material is in contact; and determining whether or not a leading end in the transport direction of the recording material exists between the second transport roll and the second nip region. Whether a recording material conveyance abnormality has occurred on the downstream side in the recording material conveyance direction when viewed from the position where the second fixing unit is provided and the recording material detection unit having the second sensor A conveyance abnormality detection means for detecting the above, a conveyance control means for controlling conveyance of the recording material by rotating the first conveyance roll and the second conveyance roll, and the conveyance control means, The conveyance abnormality is detected by the conveyance abnormality detection means. When the recording material detecting means determines that the recording material is in contact with the first nip area, the rotation of the second transport roll is stopped and the first transport roll is stopped. , And when it is determined that the end of the recording material in the conveyance direction is no longer in contact with the first nip region, the first conveyance roll is stopped.
According to such an image forming apparatus, even when the distance between the first nip area and the second nip area is shorter than the length of the side along the conveyance direction of the recording material, the first conveyance roll And the second transport roll are used to deflect the recording material between the first nip region and the second nip region, so that the recording material is not in contact with the first nip region and the second nip region. It can be stopped.

In a more preferred aspect of the image forming apparatus according to the present invention, the conveyance control unit includes a storage unit that stores a conveyance speed of the recording material, and when the conveyance abnormality is detected by the conveyance abnormality detection unit. The recording material is in contact with the first nip region by the recording material detection means, and the leading end in the conveyance direction of the recording material is between the second conveyance roll and the second nip region. If it is determined that the second recording medium is present, the second sensor immediately before the leading end of the recording material in the transport direction contacts the second nip region based on the determination result of the second sensor and the transport speed. Immediately after stopping the rotation of the transport roll, the end of the recording material in the transport direction is no longer in contact with the first nip region based on the determination result of the first sensor and the transport speed. Stopping the first conveyor rolls.
In this way, the recording material can be bent between the first nip region and the second nip region with a smaller amount of bending.

Further, in the image forming apparatus of the present invention, as a more preferable aspect, the conveyance abnormality of the recording material has occurred on the upstream side in the conveyance direction of the recording material when viewed from the position where the second fixing unit is provided. A second conveyance abnormality detecting means for detecting whether or not the second conveyance abnormality detection means detects the conveyance abnormality, and enters the first fixing means or the second fixing means. The recording material being discharged is discharged from the fixing means regardless of its position.
In this case, when a recording material conveyance abnormality occurs on the upstream side in the recording material conveyance direction as viewed from the position where the second fixing unit is provided, the recording material stops in the nip region. Can be prevented without complicated operations.

(1) First Embodiment FIG. 1 is a diagram showing a configuration of an image forming apparatus 100 according to a first embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 100 includes an image forming unit 1, a paper feeding unit 2, a first fixing unit 3, a conveyance switching unit 4, a second fixing unit 5, and a cutting unit. 6 and a control unit 7.
The image forming apparatus 100 according to the present embodiment includes a low-gloss image by a general electrophotographic method using normal paper (hereinafter referred to as “plain paper”), and a thermoplastic resin layer on the paper surface. This is an image forming apparatus capable of forming two types of high-gloss high-quality images using a provided sheet. In the following, a specific configuration for realizing such image formation will be described in detail.

The image forming unit 1 rotates in the direction of the arrow a in the figure, and the photoreceptors 10Y, 10M, and 10D on which toner images of yellow (Y), magenta (M), cyan (C), and black (K) are formed. 10C, 10K, chargers 11Y, 11M, 11C, 11K for uniformly charging the photoconductors 10Y, 10M, 10C, 10K, and photoconductors charged with exposure light modulated based on image data of each color of YMCK. Exposure units 12Y, 12M, 12C, and 12K that form electrostatic latent images of each color YMCK by irradiating 10Y, 10M, 10C, and 10K, and electrostatic latent images formed on the photoreceptors 10Y, 10M, 10C, and 10K And developing units 13Y, 13M, 13C, and 13K that form toner images on the photoconductors 10Y, 10M, 10C, and 10K, and developing units 13Y, 13M, and 1 C, and includes toner box 14Y supplies toner of each color to 13K, 14M, 14C, and 14K.
Further, the image forming unit 1 is stretched around a backup roll 18 and a drive roll 19 and circulates and moves in the direction of arrow b in the figure while contacting the photoreceptors 10Y, 10M, 10C, and 10K, and an intermediate transfer belt 15 A nip region is formed with the photoreceptors 10Y, 10M, 10C, and 10K with the transfer belt 15 interposed therebetween, and a primary transfer is performed in which the toner images on the peripheral surfaces of the photoreceptors 10Y, 10M, 10C, and 10K are transferred to the intermediate transfer belt 15 in the nip region. Rolls 16Y, 16M, 16C, and 16K, and a secondary transfer roll 17 that forms a nip region with the backup roll 18 with the intermediate transfer belt 15 interposed therebetween, and that secondarily transfers the toner image on the intermediate transfer belt 15 to a sheet. ing.

  The sheet feeding unit 2 stores various sheets in a plurality of sheet trays 20 and supplies sheets according to the image to be formed. The paper is transported by a plurality of transport rolls 21, and a toner image is transferred in a nip region formed by the secondary transfer roll 17 and the backup roll 18. In the present embodiment, the paper feed unit 2 includes a paper tray 20N that stores plain paper and a paper tray 20C that stores coated paper.

FIG. 2 is a cross-sectional view showing the configuration of the coated paper. As shown in the figure, a water absorption preventing resin layer L ₂ for preventing moisture permeation into the base material layer L ₁ is formed on both surfaces of the base material layer L ₁ of the coated paper, Further, an image receiving resin layer L ₃ for embedding toner is formed on the print surface. As the base material layer L ₁ , a material such as cellulose usually used for paper may be arbitrarily selected. However, in order to form an image such as a photograph with high gloss, the whiteness is high and the thickness is 150 to 250 μm. A thing of a grade is suitable. Water preventing resin layer L ₂ is a thermoplastic resin such as polyethylene for example, a thickness of about 5~30μm is desirable. As the image receiving resin layer L ₃ , a styrene- (meth) acrylic copolymer, a styrene-butadiene copolymer, a polyester resin, an epoxy resin, a polyurethane resin, or the like can be used alone or in combination. Considering the properties and mechanical strength, it is desirable to use a polyester resin. Further, in order to improve the releasability on the fixing belt 52 of the second fixing unit 5 described later, paraffin wax or the like may be included in the image receiving resin layer L ₃ as a release agent. When the image receiving resin layer L ₃ is 2 μm or less, unevenness occurs when the toner image is embedded and sufficient smoothness cannot be obtained. When the image receiving resin layer L ₃ is 20 μm or more, cracks occur when the paper is bent. Since (cracking) is likely to occur, the thickness of the image receiving resin layer L ₃ is preferably about 10 μm.
In the following, the dimension of the side along the sheet conveyance direction is referred to as “length” of the sheet, and the dimension of the side adjacent to this side is referred to as “width” of the sheet.

Here, returning to FIG. 1, the description of each part of the image forming apparatus 100 will be continued.
The first fixing unit 3 includes a fixing roll 30, a pressure belt 31, and a pressure pad 32, and the fixing roll 30 and the pressure belt 31 form a sheet on which a toner image is formed by the image forming unit 1. The toner image is fixed on the surface of the sheet by heating and pressurizing in the nip region N ₁ to be performed.
FIG. 3 is a diagram showing the configuration of the first fixing unit 3 in more detail. For example, the fixing roll 30 has an elastic layer 302 made of silicone rubber having a rubber hardness (JIS-A) of about 33 ° on the surface of a core 301 made of aluminum having a thickness of 1.5 mm, an outer diameter of 25 mm, and a length of 380 mm. The release layer 303 made of a 30 μm thick PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) tube is further coated on the surface of the elastic layer 302. Is formed. Inside the fixing roll 30, a heat source 304 such as a halogen lamp is provided as a heat source. The surface temperature of the fixing roll 30 depends on a predetermined temperature (depending on the melting temperature of the toner, and in the present embodiment, 140 to 190. Heat from the inside so that The pressure belt 31 has a release layer 311 made of a PFA tube having a thickness of 30 μm on the surface of a polyimide belt having a thickness of 75 μm, an outer diameter of 30 mm, and a length of 330 mm. A pressure pad 32 that presses the pressure belt 310 against the fixing roll 30 to form a nip is disposed inside the pressure belt 31. The pressing load of the pressure pad 32 is 336 N, for example, and the nip width is 6.5 mm.

The conveyance switching unit 4 includes a switching member 40, a conveyance roll 41, and a conveyance roll 42. The switching member 40 is rotatably provided on the upper part of the first fixing unit 3 and switches the conveyance direction of the sheet discharged from the first fixing unit 3 to either the path A or B in the drawing. The paper transported to the path A is discharged to the paper discharge tray T ₁ by the transport roll 41, and the paper transported to the path B is transported to the second fixing unit 5 by the transport roll 42.

The second fixing unit 5 is provided in order to make the paper surface highly glossy. That is, the coated paper on which a toner image of an image such as a photograph is formed is conveyed to the second fixing unit 5. Hereinafter, a specific configuration for the second fixing unit 5 to make the paper surface highly glossy will be described.
FIG. 4 is a diagram showing the configuration of the second fixing unit 5 in detail. As shown in the figure, the second fixing unit 5 includes a fixing roll 50, a pressure roll 51, a fixing belt 52, a cooler 53, a peeling roll 54, a steering roll 55, and a guide member. 56 and a transport roll 57.

The fixing roll 50 is a member having a release layer 502 in which a fluororesin such as PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) is coated around a metal core 501 having high thermal conductivity. . The core 501 includes a heat source 500 such as a halogen lamp. The surface of the fixing roll 50 is heated so as to reach a predetermined temperature, whereby the conveyed paper surface (print surface) is niped. heating in the region N _2. Further, the fixing roll 50 is rotated in the direction of the arrow r ₁ in the drawing by using a driving device (not shown) around the center.

The pressure roll 51 is covered with an elastic body layer 512 made of silicone rubber or the like having a rubber hardness (JIS-A) of about 40 ° around a metal core 511 having high thermal conductivity, and the surface thereof is fixed. A release layer 513 similar to the roll 50 is tubed. Inside the core 511 is equipped with a heat source 510 such as a halogen lamp, by the surface of the pressure roll 51 is heated to a predetermined temperature, in the nip area N ₂ of the sheet conveyed While heating from the back side, it is pressed toward the fixing roll 50 with a predetermined pressure.

The fixing belt 52 is a member in which a coating layer made of fluorine rubber, silicone rubber, or the like is formed on the surface (surface in contact with paper) of an endless film made of, for example, thermosetting polyimide, and includes a fixing roll 50, a peeling roll 54, and a steering wheel. It is stretched by the roll 55 and moved in the direction of the arrow r ₂ in the figure following the rotating fixing roll 50. On the sheet heated in the nip region N ₂ , the toner and the image receiving resin layer L ₃ are in a molten state, and in this state, the sheet surface is finished smoothly by being in close contact with the fixing belt 52.

The cooler 53 is in contact with the inner peripheral surface of the fixing belt 52 between the fixing roll 50 and the peeling roll 54 and absorbs heat of the fixing belt 52, thereby cooling the sheet heated in the nip region N ₂ . Although the cooling temperature of the cooler 53 varies depending on the type of toner and paper used, it is desirable to cool the paper surface to about 60 to 80 ° C. By cooling the sheet in this way, the toner and the image receiving resin layer L ₃ on the sheet surface are solidified while maintaining smoothness, and the sheet can be easily peeled from the fixing belt 52.

  The steering roll 55 is provided to correct a deviation (a phenomenon in which the fixing belt 52 moves toward one end of the steering roll 55) that occurs when the fixing belt 52 is continuously rotated. . One end of the central axis of the steering roll 55 is fixed (hereinafter referred to as “fixed end”), and the other end is movable in the directions of arrows S1 and S2 in the drawing with respect to the fixing roll ( Hereinafter, this is referred to as a “moving end”). For example, when the fixing belt 52 gradually deviates toward the fixed end, the deviation is corrected by moving the moving end in the direction of the arrow S1, and conversely. When the fixing belt 52 is gradually biased toward the moving end, the moving end moves in the arrow S2 direction to correct this bias.

The peeling roll 54 rotates following the movement of the fixing belt 52. When the peeling roll 54 is stretched while winding the fixing belt 52, the moving direction of the fixing belt 52 is changed, so that the paper is naturally peeled at the peeling position E by the rigidity of the paper itself. The outer diameter of the peeling roll 54 and the winding angle θ with the fixing belt 52 are determined according to the rigidity of the paper and the adhesive force between the paper and the fixing belt 52.
The guide member 56 guides the sheet peeled at the peeling position E to the transport roll 57. The transport roll 57 transports the transported paper to the cutting unit 6.

Here, the positional relationship between the first fixing unit 3 and the second fixing unit 5 and the sensor group provided in the vicinity will be described with reference to the drawings.
FIG. 5 is a diagram for explaining the positional relationship between the first fixing unit 3 and the second fixing unit 5. In the image forming apparatus 100 of the present embodiment, the first fixing unit 3 and the second fixing unit 5 are not arranged on a straight line as shown in FIG. For the sake of convenience, the positional relationship between the first fixing unit 5 and the second fixing unit 5 is illustrated.
As shown in the figure, the second fixing unit 5 is disposed with a distance D from the first fixing unit 3. Here, when the length of the paper used in the present embodiment is L, the interval D satisfies the relationship of D> L with respect to the length L. In other words, in the present embodiment, when the sheet stops between the first fixing unit 3 and the second fixing unit 5, it is possible to enter a state in which neither the nip region N ₁ nor the nip region N ₂ comes into contact. It is.

FIG. 6 is a diagram for explaining a sensor group as recording material detection means provided around the first fixing unit 3 and the second fixing unit 5. As shown in the figure, three sensors S ₁ , S ₂ , and S ₃ are provided around the first fixing unit 3 and the second fixing unit 5. These sensors are, for example, optical sensors provided with a light emitting element and a light receiving element (not shown). The sensor measures the intensity of reflected light from the irradiated surface, that is, the reflectance, and sends data corresponding to the measurement result to the control unit. 7 is supplied. The control unit 7 stores the reflectance of the sheet, and determines the presence or absence of the sheet at the position of each sensor based on the data supplied from these sensors. Sensor S ₁ measures the reflectivity of the portion spaced in the opposite direction by a distance l ₁ from the conveying direction of the sheet from the nip area N ₁ of the first fixing portion 3. The sensor S ₂ measures the reflectivity of the portion spaced in the opposite direction by a distance l ₂ from the conveying direction of the sheet from the nip area N ₂ of the second fixing portion 5. Further, the sensor S ₃ measures the reflectance of a portion separated from the nip region N ₂ of the second fixing unit 5 by a distance l _{3 in the} sheet conveyance direction. Note that the values of the distances l ₁ , l ₂ , and l ₃ are preferably as small as possible. In particular, for the distance l ₂ , the relationship of l ₂ <D−L must be satisfied.
For convenience of explanation, in the following, when the sensors S ₁ , S ₂ , and S ₃ do not detect the paper, the sensor response is “OFF”, and the case where the paper is detected is the sensor. Is “ON”.

Here, returning to FIG. 1 again, the description of each part of the image forming apparatus 100 will be continued.
The cutting unit 6 is provided to cut four sides of the paper and obtain an image without a border. In general, in an electrophotographic image forming apparatus, it is difficult to form an image on the entire surface of a sheet, and some margins are generated on the four sides. For example, there is no border in a general L size photograph or the like. Images are preferred. For this reason, the image forming apparatus 100 according to the present embodiment can obtain a borderless image by cutting the blank portion with the cutting unit 6. Hereinafter, a specific configuration in which the cutting unit 6 cuts four sides of the paper will be described.

The cutting unit 6 includes a rolling cutter 60, a guillotine cutter 61, a plurality of transport rolls 62, and a chip space 63. The rolling cutter 60 is a rotating disk-shaped cutter, and cuts the paper conveyed by the conveyance roll 62 in parallel with the conveyance direction. FIG. 7 is a view of the cutting section 6 as viewed from above. As shown in FIG. 7, the rolling cutters 60 are provided at two locations separated by a predetermined distance. Cut both ends at the same time. The guillotine cutter 61 is two plate-like cutters extending perpendicularly to the paper transport direction, and these cutters cut the paper transported by the transport roll 62 so as to sandwich it. The paper cut in this way is discharged to the paper discharge tray T ₂ by the transport roll 62, while chips generated by cutting the paper are stored in the chip space 63.
In the image forming apparatus 100, the size of the paper used and the size of the paper after the cutting are not particularly limited. However, in the present embodiment, when obtaining a high-gloss borderless image, a postcard is used. Assume that four sides of a sheet of size (width 100 mm × length 148 mm) are cut and output in L size (width 89 × length 127 mm).

Further, the image forming apparatus 100 according to the present exemplary embodiment includes a jam sensor S _j as a conveyance abnormality detection unit inside the cutting unit 6. The jam sensor S _j includes, for example, a light emitting element, a light receiving element, and a timer. The light receiving element receives reflected light of light emitted from the light emitting element, and optically detects the passage of the paper. As a jam determination method, for example, when the jam sensor S _j continues to detect the paper even after a predetermined time corresponding to the paper size and the conveyance speed has passed, or after the predetermined time has passed. In this case, the jam sensor S _j determines that a jam has occurred and notifies the control unit 7 of the determination result. The control unit 7 determines that a jam has occurred.
As can be seen from the above description, the timing at which the control unit 7 determines that a jam has occurred based on the notification from the jam sensor S _j and the timing at which a jam actually occurs in the cutting unit 6 are not necessarily the same. It doesn't match. However, in the following, in order to avoid complicated explanation, “when a jam occurs” and “when a jam occurs” are referred to as “the control unit 7 detects a jam based on a notification from the jam sensor S _j. It is assumed that it means “the timing at which it is determined that occurrence has occurred”.
Although not particularly illustrated, the image forming apparatus 100 includes a jam sensor similar to the jam sensor S _j , that is, a conveyance abnormality detection unit in each unit other than the cutting unit 6, and these jam sensors correspond to each other. If it is determined that a jam has occurred in each unit, the determination result is notified to the control unit 7.

The control unit 7 includes a CPU (Central Processing Unit), a timer, and the like (not shown), and controls the operation of each unit of the image forming apparatus 100. Specifically, control of toner image formation of each color in the image forming unit 1, control of paper selection and conveyance timing in the paper feeding unit 2, or fixing temperature control in the first fixing unit 3 and the second fixing unit 5 Etc. The control unit 7 includes a memory 70. The memory 70 includes values such as l ₁ , l ₂ , and l ₃ described above, the length L of the sheet, the first fixing unit 3 and the second fixing unit 5. A value such as the interval D or the sheet conveyance speed v is stored.

With the configuration described above, the image forming apparatus 100 forms a toner image on the paper supplied from the paper supply unit 2. When forming a general low-gloss image, the image forming apparatus 100 supplies paper (plain paper) from a paper tray 20N that stores plain paper in the paper supply unit 2, and forms a toner image on the paper. after formation, the first fixing portion 3 is fixing the toner image, the conveying direction of the sheet switched to path a in the conveyance switching unit 4 to discharge the sheet on which an image has been formed into a sheet discharge tray T _1. On the other hand, when the image forming apparatus 100 forms a high-gloss image, paper (coated paper) is supplied from the paper tray 20C that stores coated paper in the paper supply unit 2, and a toner image is formed on the paper. After the first fixing unit 3 fixes the toner image, the conveyance switching unit 4 switches the conveyance direction of the sheet to the path B, and the second fixing unit 5 performs processing to make the printing surface of the sheet highly glossy. , cutting the margin in the cutting unit 6, to discharge the sheets of L size which high gloss image is formed frameless to the discharge tray T _2.
When the image forming apparatus 100 detects that a jam has occurred in the cutting unit 6 while forming a high gloss image, the nip region N ₁ of the first fixing unit 3 and the nip of the second fixing unit 5 are detected. paper in the region N ₂ controls the conveyance of the sheet so as not to stop. The specific control method will be described in detail in the following operation example.

(2) Example of Operation FIG. 8 is a flowchart showing an operation when a jam occurs during image formation in the image forming apparatus 100 of the present embodiment. As shown in the drawing, there are various methods for conveying a sheet when a jam occurs, depending on the position of the sheet in the first fixing unit 3 and the second fixing unit 5 when the jam occurs. Therefore, in the following, each method will be described as an individual operation example while explaining along the flowchart of FIG.

(2-1) Operation example 1
In this operation example, for example, as shown in FIG. 9, the sheet P ₁ is in contact with the nip region N ₁ of the first fixing unit 3 when a jam occurs in the cutting unit 6. Will be described. At this time, the sheets are continuously conveyed with sufficient intervals.
First, while the image forming apparatus 100 is performing image formation (step S01), a jam sensor provided in each part of the image forming apparatus 100 always determines the presence or absence of a jam (step S02). If no jam has occurred (step S02; NO), image formation is repeated until all image forming jobs are completed (step S10; NO → step S01), and when all image forming jobs are completed. (Step S10; YES), this process is terminated.

On the other hand, the jam sensor determines the occurrence of a jam (step S02; YES), and particularly when the jam occurrence location is the cutting unit 6 (that is, the jam sensor S _j has determined the occurrence of the jam). (Step S03; YES) Subsequently, the control unit 7 determines whether or not the sheet is in contact with the nip region N ₁ inside the first fixing unit 3 based on the detection result of the sensor S ₁ (Step S04). Specifically, when the response of the sensor S ₁ is “ON”, the control unit 7 determines that the sheet is in contact with the nip region N ₁ of the first fixing unit 3.
At this time, if it is determined by the sensor S ₁ that a sheet (hereinafter referred to as sheet P ₁ ) is in contact with the nip area N ₁ , the control unit 7 subsequently moves another sheet to the nip area N _2. whether or not the contact to determine the result of the detection sensor S ₂ (step S05). Specifically, when the response of the sensor S ₂ is “ON”, the control unit 7 determines that another sheet is in contact with the nip region N ₂ of the second fixing unit 5. If this determination is negative, that is, only the nip region N ₁ is in contact with the sheet in the two nip regions (step S05; NO), the control unit 7 immediately stops the conveyance of the sheet. _First , the sheet P ₁ is moved by a certain distance, and the sheet P ₁ is stopped at a position where it does not contact the nip regions N ₁ and N ₂ (step S06). Specifically, the control unit 7 conveys the paper P ₁ until the response of the sensor S ₁ is “OFF” and then the response of the sensor S ₂ is “ON”, thereby removing the paper P ₁ from the nip region. It can be moved to a position where it does not contact N ₁ and N ₂ .

When the conveyance of the paper P ₁ is stopped in this way, the control unit 7 then repeats the determination whether the paper causing the jam has been removed by the user (step S07), and when the paper is removed ( In step S07; YES), a return cycle is executed to prepare for subsequent image formation (step S08), and the paper conveyance is restarted and all the papers that have been stopped are discharged (step S09), and the image continues. Formation is executed (step S01).

(2-2) Operation example 2
In this operation example, for example, as shown in FIG. 10, when a jam occurs in the cutting unit 6, the sheet P ₂ is placed between the first fixing unit 3 and the second fixing unit 5 in the nip region N ₁ and A method for conveying a sheet when it is not in contact with any of N ₂ will be described. At this time, it is considered that the sheets are continuously conveyed with sufficient intervals. Since the operation up to step S04 is the same as that of the operation example 1 described above, the description thereof is omitted here.

In the determination in step S04, since the sheet P ₂ is not in contact with the nip region N ₁ in this operation example, this determination is negative. Specifically, when the response of the sensor S ₁ is “OFF”, the control unit 7 determines that the sheet is not in contact with the nip region N ₁ of the first fixing unit 3.
Subsequently, the control unit 7 determines whether or not the sheet is in contact with the nip region N ₂ of the second fixing unit 5 based on the detection results of the sensors S ₂ and S ₃ (step S11). Specifically, when the response of the sensor S ₂ is “ON” and the response of the sensor S ₃ is “OFF”, the control unit 7 detects that the sheet is in the nip region N ₂ of the second fixing unit 5. Judged to be in a non-contact state.
When the paper P ₂ is in such a state at the time of jam occurrence (step S11; NO), the control unit 7 stops the paper P ₂ immediately without conveying the paper any more, so that the paper P ₂ is in the nip region. A state in which neither N ₁ nor N ₂ is in contact is maintained (step S12). Incidentally, the affirmative determination at step S11 described above, that is, if a state where the paper is in contact with the nip area N ₂ of the second fixing unit 5, the control unit 7 second fixing portion by discharging the sheet 5 can be prevented.

Do to stop the conveyance of the sheet P ₂ as in step S12, or When to discharge the sheet as in step S13, followed by the control unit 7 determines whether the paper causing the jam has been removed by the user Is repeated (step S07), and if it is determined that the sheet has been removed (step S07; YES), a return cycle is executed to prepare for the subsequent image formation (step S08), and the sheet conveyance is resumed and stopped until then. All the sheets that have been discharged are discharged (step S09), and image formation is subsequently executed (step S01).

(2-3) Operation example 3
In the above-described operation examples 1 and 2, the paper transport method focusing on only one paper has been described. This means that there is a sufficient gap between the paper of interest and the paper that caused the jam, and there is no paper before or after the paper of interest, or there is enough space to be negligible. It is assumed that the sheet is provided and the sheet is conveyed. However, in actual image formation, a plurality of images may be formed continuously and at high speed. When a jam occurs in such a case, it is necessary to consider the position of the sheet being conveyed before and after the focused sheet. Therefore, in this operation example, as shown in FIG. 11, the sheets P ₃ and P ₄ are in contact with the nip region N ₁ of the first fixing unit and the nip region N ₂ of the second fixing unit, respectively. A method of conveying the paper when there is will be described. Since the operation up to step S05 is the same as that in the above-described operation example 1, the description thereof is omitted here.

In the determination in step S05, in the present operation example, the sheet P ₄ is in contact with the nip region N ₂ , so this determination is affirmative. Specifically, when the response of the sensor S ₃ is “ON”, the control unit 7 determines that the sheet is in contact with the nip region N ₂ of the second fixing unit 5.
In such a state, the control unit 7 first discharges the paper P ₄ that is in contact with the second fixing unit 5, and simultaneously removes the paper P ₃ that is in contact with the first fixing unit ₃ at the nip region N _1. And N ₂ are stopped at positions where they do not contact any of these nip regions N ₁ and N ₂ (step S014). Although not shown, the control unit 7 stops the sheet on the upstream side of the sheet P _{3 with} respect to the sheet conveyance direction at a position where it does not contact the nip region N ₁ . Since these specific operations conform to the above-described operation examples 1 and 2, they are omitted.
In this way, it is possible to minimize the influence of jamming or the like due to jam, and to prevent the second fixing unit 5 from being damaged by dirt or the like.

  Subsequently, the control unit 7 repeatedly determines whether or not the sheet causing the jam has been removed by the user (step S07). If it is determined that the sheet has been removed (step S07; YES), a return cycle is performed. In preparation for subsequent image formation after execution (step S08), paper conveyance is resumed and all the sheets that have been stopped are discharged (step S09), and image formation is subsequently executed (step S01).

(2-4) Operation example 4
In the above-described operation examples 1 to 3, the paper transport method when a jam occurs downstream from the cutting unit 6, that is, the second fixing unit 5, in the paper transport direction has been described. In this operation example, the sheet conveyance control when a jam occurs in the upstream side of the second fixing unit 5, for example, in the image forming unit 1, the first fixing unit 3, or the conveyance switching unit 4, is shown in the flowchart of FIG. It explains along.

While the image forming apparatus 100 is performing image formation (step S01), the jam sensor provided in each part of the image forming apparatus 100 always determines whether or not a jam has occurred (step S02). Then, the jam sensor determines the occurrence of a jam (step S02; YES), and when the jam occurrence location is a place other than the cutting section 6 (step S03; NO), the cutting section 6 has no conveyance abnormality. Therefore, since it is not necessary to stop the sheet between the first fixing unit 3 and the second fixing unit 5, the control unit 7 immediately stops the conveyance of the sheet upstream from the jam occurrence point, and at the same time, the jam With respect to the sheet downstream from the occurrence location, the normal image forming process is executed to discharge all of them to the discharge tray T ₁ or T ₂ (step S15). Thereafter, the control unit 7 repeatedly determines whether or not the sheet causing the jam has been removed by the user (step S07). When the sheet is removed (step S07; YES), a return cycle is executed and the subsequent steps are performed. In preparation for image formation (step S08), the paper conveyance is resumed and all the paper that has been stopped is discharged (step S09), and image formation is subsequently executed (step S01).

As explained above, according to the image forming apparatus 100 of the present embodiment, it is possible to prevent the sheet is stopped in the nip region N ₂ in the nip area N ₁ and the second fixing portion 5 of the first fixing portion 3 Therefore, even when a jam occurs, damage to the apparatus main body is eliminated, and as a result, it is possible to prevent waste of paper and time by cleaning.

Note that, in the above-described operation example, a jam occurs on the downstream side of the cutting unit 6, that is, the second fixing unit 5, and only the sheet conveyance control when the sheet is in contact with the nip region N ₁ at this time. As described above, of course, there is a case where a jam occurs upstream of the second fixing unit 5. However, in such a case, it is not necessary to stop the sheet between the nip region N ₁ and the nip region N ₂ as described above. When a jam occurs, the sheet on the downstream side of the jam occurrence point is not All of them may be discharged to the discharge trays T ₁ and T ₂ . This is because the sheet conveyance control described in the above-described operation example is performed in order to prevent the sheet from being carried in even after the occurrence of the jam. That is, when a jam is detected by a jam sensor other than the cutting unit 6, in other words, by a jam sensor other than the jam sensor S _j , the control unit 7 it is sufficient to discharge the discharge tray T ₁ or T ₂ regardless of its position.

(3) Second Embodiment In the above-described embodiment, the image forming apparatus 100 is configured such that the interval between the first fixing unit 3 and the second fixing unit 5 is longer than the length of the sheet. However, there is a demand for further downsizing of the image forming apparatus. Thus, there may be a case where a sufficient interval between the first fixing unit and the second fixing unit cannot be secured. In the above-described embodiment, a postcard-size paper is assumed. However, when a paper having a larger size is used, as described above, any one of the first fixing unit and the second fixing unit is used. It may be impossible to stop the sheet without contacting the nip region.
Therefore, in the present embodiment, even when the interval between the first fixing unit and the second fixing unit cannot be sufficiently ensured as described above, any nip region between the first fixing unit and the second fixing unit. An image forming apparatus capable of stopping the sheet without contacting the sheet will be described. Note that the image forming apparatus of the present embodiment is different from the image forming apparatus 100 of the first embodiment described above only in the configuration around the first fixing unit 3 and the second fixing unit 5, and other parts will be described. Is omitted. The same parts as those of the image forming apparatus 100 will be described with the same reference numerals.

FIG. 12 is a diagram showing the configuration of the first fixing unit 3 and the second fixing unit 5 and their surroundings. In the image forming apparatus according to the present embodiment, the first fixing unit 3 and the second fixing unit 5 are not arranged on a straight line as shown in FIG. The positional relationship of the second fixing unit 5 will be described and illustrated in this manner for convenience of comparison with the first embodiment described above.
In the figure, the only difference from the first embodiment (FIG. 5) is the distance between the first fixing unit 3 and the second fixing unit 5 and the presence of the transport rolls R ₁ and R ₂ . In this embodiment, the distance D ′ between the first fixing unit 3 and the second fixing unit 5 is shorter than the length L of the paper. The transport rolls R ₁ and R ₂ are provided so as to be able to rotate and stop at different speeds by driving means (not shown), and the transport roll R ₁ is fed from the nip region N ₁ of the first fixing unit 3 to the sheet. The conveyance roll R ₂ is provided at a position separated by a distance d _{1 with} respect to the conveyance direction, and the conveyance roll R ₂ is separated from the nip region N ₂ of the second fixing unit 5 by a distance d _{2 in} a direction opposite to the sheet conveyance direction. It is provided at the position. Further, the transport roll R ₂ is provided upstream of the sensor S _{2 in the} paper transport direction.

Under such a configuration, for example, as shown in FIG. 13, a sheet when a jam occurs in the cutting unit 6 with the sheet P ₅ in contact with the nip region N ₁ of the first fixing unit 3. described method of transporting P _5.
Control unit 7, when the jam is determined that the paper P ₅ to the nip area N ₁ of the first fixing portion 3 at the time of the occurrence are in contact at the cutting portion 6, first, the paper P ₅ tip of the transfer roll R ₂ The sheet is conveyed to the position, and the conveyance of only the leading end portion of the sheet P ₅ is stopped before contacting the nip region N ₂ of the second fixing unit 5. Specifically, when the sensor S ₁ detects the sheet P ₅ , the control unit 7 conveys the sheet P ₅ using the conveyance rolls R ₁ and R ₂ and stops only the conveyance roll R ₂ immediately after the sensor S ₂ detects the sheet. . Since longer than the length L the distance D between the first fixing portion 3 second fixing portion 5 of the sheet P _5, the as the sheet P ₅ in contact with the nip area N ₁ of the first fixing portion 3 at this point state It is.
Thereafter, by rotating the transport roll R ₂ transport roll R ₁ while it is stopped, since the transport roll R ₂ is transported roll R ₁ while the tip were fixed paper P ₅ is to try to convey the sheet P ₅ Then, the sheet P ₅ is bent into a state as shown in FIG. Thus, the control unit 7 rotates the transport roll R ₁ while stopping the transport roll R _2, the sensor S ₁ is also transporting rolls R ₁ after that no longer detects the paper P ₅ is stopped, the sheet P ₅ becomes the state shown in FIG. 15, it is possible to be stopped in a state that does not contact the one of the nip area N ₁ and N ₂ between the first fixing portion 3 of the second fixing portion 5.

(4) Modifications The application of the present invention is not limited to the above-described embodiment, and various modifications as shown below are possible.
First, in the above-described embodiment, whether or not the sheet is in contact with the nip area is determined only by ON / OFF of the response of the sensor. However, the position of the nip area and the sensor is actually separated from each other. Therefore, strictly speaking, at the moment when the sheet passes through the position of the sensor, the sheet is still in contact with the nip region, or conversely, the sheet is not yet in contact with the nip region. Therefore, if the sensor response speed is high or the paper transport speed is low, it may not be possible to determine whether the paper is in contact with the nip region by simply turning the sensor response ON / OFF. . In such a case, a predetermined time difference may be provided after the response of the sensor is switched, and it may be determined whether or not the sheet is in contact with the nip region when this time has elapsed. The above-described time difference can be easily obtained from the distance between the sensor and the nip region and the sheet conveyance speed.

Here, a specific example will be described. For example, let us consider a case where the sheet conveyance speed is v in the configuration shown in FIG. In the figure, it is assumed that l ₁ and l ₂ are both smaller than L. At this time, if the response of the sensor S ₁ is the time elapsed since switching from "OFF" to "ON" and T _1, the time from the switching response of the sensor S ₁ "l ₁ / v" has elapsed sheet Is in contact with the nip region N ₁ , the paper is not in the nip region even if the sensor response is “ON” while the elapsed time T ₁ satisfies the relationship of “T ₁ <l ₁ / v”. It is in a position not in contact with N ₁ . Therefore, even if the jam sensor S _j detects a jam, and the sensor S ₁ is “ON” at this time, it may be less than the time “l ₁ / v” after the response of the sensor S ₁ is switched to “ON”. For example, the control unit 7 may stop the conveyance of the paper immediately.
When the time “l ₁ / v” elapses after the response of the sensor S ₁ is switched to “ON”, the sheet comes into contact with the nip region N ₁ , but when the sheet further advances by the distance L, the sheet again comes into the nip region N _1. The position is not touching. That is, while the elapsed time T ₁ satisfies the relationship “l ₁ / v ≦ T ₁ ≦ l ₁ + L / v”, the sheet is in contact with the nip region N ₁ . If the sheet is in such a position when the jam sensor S _j detects the jam, the control unit 7 does not immediately stop the conveyance of the sheet as described in the above-described embodiment. The sheet is transported and stopped until the sheet reaches a position where it does not come into contact with any of the nip areas N ₁ and N ₂ .
If the elapsed time T ₁ satisfies the relationship of “l ₁ + L / v <T ₁ ”, the paper will not contact the nip region N ₁ , but if the paper is conveyed as it is, the paper will now be It will contact the nip area N _2. Specifically, if the elapsed time after the response of the sensor S ₁ is switched from “OFF” to “ON” is T ₂ , the elapsed time T ₂ is “T” in the same manner as the elapsed time T _{1. While} the relationship ₂ <l ₂ / v ”is satisfied, the sheet is not in contact with the nip region N ₂ even if the response of the sensor S ₂ is“ ON ”. Therefore, the elapsed time T ₁ satisfies the relationship of “l ₁ + L / v <T ₁ ”, and at the same time, the response of the sensor S ₂ is “OFF” or the elapsed time T ₂ is “T ₂ <l ₂ / When the relationship “v” is satisfied, the control unit 7 may immediately stop the conveyance of the sheet.
Further, as in the case of the above-described elapsed time T ₁ , while the elapsed time T ₂ satisfies the relationship “l ₂ / v ≦ T ₂ ≦ l ₂ + L / v”, the sheet enters the nip region N ₂ . In contact. That is, when the elapsed time T ₁ satisfies the relationship “l ₁ + L / v <T ₁ ” and the elapsed time T ₂ satisfies the relationship “l ₂ / v ≦ T ₂ ≦ l ₂ + L / v”. In this case, the controller 7 does not stop the conveyance of the sheet immediately, but conveys the sheet until the elapsed time T ₂ is equal to or longer than “l ₂ + L / v”, that is, the position where the sheet does not contact the nip region N _2. Then stop.

Incidentally, by performing the determination in consideration of the conveying speed of the distance and the sheet between the sensor and the nip region as described above, the determination of the presence or absence of paper sensors S ₃ In the embodiment described above has been performed, the sensor S ₂ Can be substituted. Therefore, in this case, the sensors are not necessarily provided at three places.
In the above-described embodiment, the sensor for detecting the paper is an optical sensor. However, the present invention is not limited to such a sensor, and for example, the paper is physically detected. A contact-type sensor may be used.

Further, in the second embodiment described above, when it is determined that the paper P ₅ is in contact with the nip region N ₁ of the first fixing unit 3 at the time when the jam occurs in the cutting unit 6, the control unit 7 detects the sensor S _It has been described that only the transport roll R ₂ is stopped immediately after ₂ detects the sheet. However, since there is a distance l ₂ between the sensor S ₂ and the nip region N ₂ , the conveyance roll R ₂ must actually be stopped immediately after the sensor S ₂ detects the sheet. There is no. Specifically, the control unit 7 calculates the time to move the sheet based on the value of the conveying speed v of the distance l ₂ and the paper stored in the memory 70, sensor S ₂ is the time from detection of the paper " By stopping the conveyance of the sheet after elapse of “l ₂ / v”, the sheet can be brought into a state where it does not come into contact with the nip region N ₂ while approaching. Similarly, when the transport roll R ₁ is stopped, considering the movement of the paper, the transport of the paper is stopped after the time “l ₁ / v” has elapsed since the sensor S ₁ no longer detects the paper. Then, the sheet can be brought into a state where it does not come into contact with the nip area N ₁ . In this way, by adjusting the timing for stopping the paper based on the moving speed of the paper, the amount of flexure of the paper can be reduced. FIG. 16 is a diagram illustrating this, but comparing this figure with FIG. 15, it can be seen that the amount of flexure of the paper P ₆ is small even if it is the same length as the paper P ₅ . If the amount of bending is reduced in this way, the space to be secured for bending the paper can be reduced, so that the apparatus can be further downsized.

  In the above-described embodiment, the cutting unit 6 is shown as an example of the post-processing device. However, the present invention is not limited to such a mode. For example, in the image forming apparatus including a sorter, the sorter The operation described above may be performed when a jam occurs in a portion.

1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. It is sectional drawing which showed the structure of the coated paper used based on the embodiment. FIG. 2 is a diagram illustrating in detail a configuration of a first fixing unit according to the embodiment. FIG. 3 is a diagram illustrating in detail a configuration of a second fixing unit according to the embodiment. FIG. 4 is a diagram for explaining a positional relationship between a first fixing unit and a second fixing unit in the embodiment. It is a figure for demonstrating the sensor group as a recording material detection means concerning the embodiment. It is a figure at the time of seeing the cutting part concerning the embodiment from the upper part. 6 is a flowchart illustrating an operation when a jam occurs during image formation in the embodiment. It is a figure for demonstrating the operation | movement in the operation example 1 of the embodiment. It is a figure for demonstrating the operation | movement in the operation example 2 of the embodiment. It is a figure for demonstrating the operation | movement in the operation example 3 of the embodiment. FIG. 4 is a diagram illustrating a configuration of a first fixing unit and a second fixing unit and a periphery thereof in an image forming apparatus according to another embodiment of the present invention. FIG. 10 is a diagram for describing a sheet conveyance method according to the embodiment. It is a figure showing signs that a sheet is conveyed in the embodiment. It is a figure showing signs that a sheet is conveyed in the embodiment. It is a figure showing signs that a sheet is conveyed in the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus, 1 ... Image forming part, 10Y, 10M, 10C, 10K ... Photoconductor, 11Y, 11M, 11C, 11K ... Charger, 12Y, 12M, 12C, 12K ... Exposure device, 13Y, 13M, 13C , 13K ... developer, 14Y, 14M, 14C, 14K ... toner box, 15 ... intermediate transfer belt, 16Y, 16M, 16C, 16K ... primary transfer roll, 17 ... secondary transfer roll, 18 ... backup roll, 19 ... drive Roll, 2 ... Paper feed unit, 20, 20N, 20C ... Paper tray, 21 ... Paper transport roll, 3 ... First fixing unit, 30 ... Fixing roll, 31 ... Pressure belt, 32 ... Pressure pad, 4 ... Transport Switching unit, 40 ... switching member, 41 ... transport roll, 42 ... transport roll, 5 ... second fixing unit, 50 ... fixing roll, 51 ... pressure roll, 52 ... fixing belt, 53 ... cold Vessel, 54 ... peeling roll, 55 ... steering roller, 56 ... guide member, 57 ... transport _{rolls, S 1, S 2, S} 3 ... sensor (recording material detecting means), 6 ... cutting portion, 60 ... rolling cutter, 61 ... Guillotine cutter, 62 ... Conveying roll, 63 ... Chip space, S _j ... Jam sensor (conveyance abnormality detecting means), 7 ... Control unit (conveying control means).

Claims (8)

Image forming means for forming a toner image on a recording material;
A first fixing unit that fixes the toner image on the recording material by heating and pressurizing the recording material in a first nip region where a pair of members facing each other across the conveying path of the recording material contact; ,
In the second nip region where a pair of members facing each other across the recording material conveyance path are in contact with each other, the recording material on which the image has been fixed by the first fixing unit is heated and pressed to form the toner image. A second fixing means for fixing the recording material again;
Recording material detecting means for determining whether or not the recording material is in contact with the first nip region or the second nip region;
A conveyance abnormality detection unit that detects whether or not a conveyance abnormality of the recording material has occurred on the downstream side in the conveyance direction of the recording material when viewed from the position where the second fixing unit is provided;
When the conveyance abnormality detection unit detects the occurrence of conveyance abnormality and the recording material detection unit determines that the recording material is in contact with the first nip region or the second nip region, An image forming apparatus comprising: a conveyance control unit configured to convey and stop the recording material to a position where it does not contact the first nip region and the second nip region. The image forming apparatus according to claim 1, wherein an interval between the first nip region and the second nip region is longer than a length of a side along a conveyance direction of the recording material. The recording material detection means includes
A first sensor provided at a predetermined position on the upstream side in the transport direction when viewed from the position of the first nip region, and detecting the presence or absence of the recording material at the position;
A second sensor provided at a predetermined position between the first nip region and the second nip region and detecting the presence or absence of the recording material at the position;
When the occurrence of conveyance abnormality is detected by the conveyance abnormality detection means, the recording material detection means determines that the recording material is in contact with the first nip region based on the detection result of the first sensor. Then, based on the detection result of the first sensor or the second sensor, the conveyance control unit passes the recording material through the first nip region to a position where it does not reach the second nip region. The image forming apparatus according to claim 2, wherein the recording material is conveyed and stopped. The recording material detection means includes
A first sensor provided at a predetermined position on the upstream side in the transport direction when viewed from the position of the first nip region, and detecting the presence or absence of the recording material at the position;
A second sensor provided at a predetermined position between the first nip region and the second nip region and detecting the presence or absence of the recording material at the position;
When the occurrence of conveyance abnormality is detected by the conveyance abnormality detection unit, the recording material detection unit detects the recording material from the first nip region based on the detection result of the first sensor or the second sensor. And the second nip area, and the conveyance control means does not convey the recording material when it is determined that it is not in contact with either the first nip area or the second nip area. The image forming apparatus according to claim 2, wherein the image forming apparatus is stopped as it is. The recording material detection means includes
A first sensor provided at a predetermined position on the upstream side in the transport direction when viewed from the position of the first nip region, and detecting the presence or absence of the recording material at the position;
A second sensor that is provided at a predetermined position between the first nip region and the second nip region and detects the presence or absence of the recording material at the position;
A third sensor provided at a predetermined position on the downstream side in the transport direction when viewed from the position of the second nip region, and detecting the presence or absence of the recording material at the position;
When the occurrence of conveyance abnormality is detected by the conveyance abnormality detection unit, the recording material detection unit detects that the first recording material contacts the first nip region based on the detection result of the first sensor. And determining that the second recording material is in contact with the second nip region based on the detection result of the third sensor,
The transport control means allows the first recording material to pass through the first nip region based on a detection result of the first sensor, the second sensor, or the third sensor, and The first recording material is transported to a position where the second recording material does not contact the nip region, and the second recording material is passed through the second nip region to a position where the second recording material does not contact the second nip region. The image forming apparatus according to claim 2, wherein the second recording material is conveyed and stopped. Image forming means for forming a toner image on a recording material;
A first fixing unit that fixes the toner image on the recording material by heating and pressurizing the recording material in a first nip region where a pair of members facing each other across the conveying path of the recording material contact; ,
In the second nip region where a pair of members facing each other across the recording material conveyance path are in contact with each other, the recording material on which the image has been fixed by the first fixing unit is heated and pressed to form the toner image. A second fixing unit for fixing the recording material again, wherein an interval between the first nip region and the second nip region is shorter than a length of a side along the conveyance direction of the recording material; A second fixing means provided at such a position;
A first transport roll provided between the first nip region and the second nip region;
A second transport roll provided between the first transport roll and the second nip region;
A first sensor for determining whether or not the recording material is in contact with the first nip region; and a leading end in the conveyance direction of the recording material between the second conveyance roll and the second nip region. A recording material detecting means having a second sensor for judging whether or not
A conveyance abnormality detection unit that detects whether or not a conveyance abnormality of the recording material has occurred on the downstream side in the conveyance direction of the recording material when viewed from the position where the second fixing unit is provided;
A conveyance control means for controlling conveyance of the recording material by rotating the first conveyance roll and the second conveyance roll;
When the conveyance abnormality is detected by the conveyance abnormality detection unit, the conveyance control unit determines that the recording material is in contact with the first nip region by the recording material detection unit. When the rotation of the second transport roll is stopped and the first transport roll is rotated, and it is determined that the end of the recording material in the transport direction is no longer in contact with the first nip region, the first transport roll Image forming apparatus for stopping the operation. The transport control means includes storage means for storing a transport speed of the recording material,
When the conveyance abnormality is detected by the conveyance abnormality detection means, the recording material is in contact with the first nip area by the recording material detection means, and the second conveyance roll and the second If it is determined that a leading edge in the conveyance direction of the recording material exists between the nip regions of the recording material, the leading edge in the conveyance direction of the recording material is determined based on the determination result of the second sensor and the conveyance speed. The rotation of the second transport roll is stopped immediately before contacting the second nip region, and the end of the recording material in the transport direction is determined based on the determination result of the first sensor and the transport speed. The image forming apparatus according to claim 6, wherein the first transport roll is stopped immediately after the first nip region is not contacted. A second conveyance abnormality detection unit configured to detect whether or not a conveyance abnormality of the recording material has occurred on the upstream side in the conveyance direction of the recording material when viewed from a position where the second fixing unit is provided;
When the second conveyance abnormality detecting unit detects the conveyance abnormality, the recording material entering the first fixing unit or the second fixing unit is removed from the fixing unit regardless of the position. The image forming apparatus according to claim 1, wherein the image forming apparatus is discharged.

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