JP6601247B2 - Image forming apparatus, image forming system, and air blowing control method - Google Patents

Description

  The present invention relates to an image forming apparatus, an image forming system, and an air blowing control method.

  In general, an image forming apparatus (printer, copier, facsimile, etc.) using an electrophotographic process technology generates an electrostatic latent image by irradiating (exposing) a charged photoconductor with a laser beam based on image data. Form. Then, by supplying toner from the developing device to the photosensitive member (image carrier) on which the electrostatic latent image is formed, the electrostatic latent image is visualized to form a toner image. Further, after the toner image is directly or indirectly transferred to the paper, the toner image is formed on the paper by fixing it by heating and pressing with a fixing device. The paper that has passed through the fixing device passes through a pair of paper discharge rollers for discharge and is discharged onto a paper discharge tray.

  The fixing device for fixing the toner image as described above is formed by a fixing surface side member such as a fixing roller or a fixing belt and a back surface side supporting member such as a pressure roller or a pressure belt that is pressed against the fixing surface side member. There is a heat-fixing type fixing device that heats and pressurizes a sheet on which a toner image has been transferred through the fixing nip.

  By the way, the toner of the toner image on the paper is heated when passing through the fixing nip, and therefore has adhesive force. As a result, the sheet that has passed through the fixing nip is wound around the surface of the fixing surface side member and is not separated, and there is a risk of causing a winding jam. In addition, even if no wrapping jam occurs, the paper transport posture becomes unstable and the paper may come into contact with the separation claw or the conveyance guide plate, which may cause image defects or wear of the separation claw or the conveyance guide plate. is there. In view of this, air separation means of a system (air separation system) that blows air toward the paper discharge side of the fixing nip and separates the paper from the fixing surface side member has been used.

  The problem that the paper wraps around the surface of the fixing surface side member is that the fixing surface has increased due to the increase in the size of the fixing device due to the recent increase in the speed of the image forming apparatus and the handling of thinner paper due to the demand for paper type expansion. It has become more difficult to peel off the paper from the side member.

  Therefore, from the viewpoint of reliably separating the paper from the fixing surface side member and stabilizing the paper transport posture, the state of the paper is directly detected, and the amount of air blown toward the paper discharge side of the fixing nip is determined according to the detection result. A control technique has been proposed (see, for example, Patent Document 1). In the technique described in Japanese Patent Application Laid-Open No. 2004-133620, the discharged sheet and the heating rotator are discharged during the discharge operation of one sheet from the start of discharge of the front end of the sheet from the fixing nip portion to the end of discharge of the rear end of the sheet. The amount of air blown toward the paper is changed as needed according to the close contact state (wrapping state) with the (fixing surface side member).

JP 2011-186189 A

  In the technique disclosed in Patent Document 1, a detection unit for directly detecting the contact state between the discharged paper and the fixing surface side member is additionally provided in the fixing device. However, there is a problem that the inside of the fixing device is in a high heat environment, and in order to arrange the detecting means in the fixing device, it is necessary to provide a heat-resistant means in the detecting means. In addition, there is a problem that a space for disposing the detection means in the fixing device is required, or that a new detection means is provided, resulting in an increase in cost.

  An object of the present invention is to provide an image forming apparatus, an image forming system, and an air blowing control method capable of stabilizing a paper transport posture without newly providing a detection unit.

An image forming apparatus according to the present invention includes:
An image forming unit that forms a toner image on paper;
A registration roller unit that sends out the paper at a predetermined conveyance timing to the image forming unit;
A fixing unit that heats and pressurizes a sheet on which a toner image is formed by the image forming unit in a fixing nip to fix the toner image on the sheet;
A blowing unit that separates the sheet from a fixing member of the fixing unit by blowing toward the sheet from the downstream side of the fixing nip in the sheet conveyance direction;
A rotating member disposed on the downstream side of the fixing nip in the paper transport direction and rotating by contacting the paper that has passed through the fixing nip;
A paper passage detection unit that detects passage of the paper by detecting rotation of the rotating member;
The first passage time from when the nth (n: integer greater than or equal to 1) sheets are sent out by the registration roller section until the passage of the nth sheet is detected by the sheet passage detection section When the conveyance posture of the sheet that has passed through the fixing nip is longer than the maximum allowable passing time within a proper range, the blowing amount of the blowing unit is increased, and the n + 1th sheet is increased by the registration roller unit. When the second passage time from when the paper is sent to when the passage of the (n + 1) th sheet is detected by the paper passage detection unit is longer than the maximum passage time, the first passage time and the second passage time According to the magnitude relationship with the passage time of the control unit for controlling the blowing amount of the blowing unit,
Is provided.

An image forming system according to the present invention includes:
An image forming system including a plurality of units including an image forming apparatus,
An image forming unit that forms a toner image on paper;
A registration roller unit that sends out the paper at a predetermined conveyance timing to the image forming unit;
A fixing unit that heats and pressurizes a sheet on which a toner image is formed by the image forming unit in a fixing nip to fix the toner image on the sheet;
A blower unit that separates the sheet from a fixing member of the fixing unit by blowing air toward the sheet from the downstream side of the fixing nip in the sheet conveyance direction;
A rotating member disposed on the downstream side of the fixing nip in the paper transport direction and rotating by contacting the paper that has passed through the fixing nip;
A paper passage detection unit that detects passage of the paper by detecting rotation of the rotating member;
A first passing time from when the n (n: integer greater than or equal to 1) sheets are sent out by the registration roller section until the passage of the nth sheet is detected by the sheet passage detecting section When the conveyance posture of the sheet that has passed through the fixing nip is longer than the maximum allowable passing time within a proper range, the blowing amount of the blowing unit is increased, and the n + 1th sheet is increased by the registration roller unit. When the second passage time from when the paper is sent to when the passage of the (n + 1) th sheet is detected by the paper passage detection unit is longer than the maximum passage time, the first passage time and the second passage time According to the magnitude relationship with the passage time of the control unit for controlling the blowing amount of the blowing unit,
Is provided.

The air flow control method according to the present invention includes:
An image forming unit that forms a toner image on paper;
A registration roller unit that sends out the paper at a predetermined conveyance timing to the image forming unit;
A fixing unit that heats and pressurizes a sheet on which a toner image is formed by the image forming unit in a fixing nip to fix the toner image on the sheet;
A blowing unit that separates the sheet from a fixing member of the fixing unit by blowing toward the sheet from the downstream side of the fixing nip in the sheet conveyance direction;
A rotating member disposed on the downstream side of the fixing nip in the paper transport direction and rotating by contacting the paper that has passed through the fixing nip;
A paper passage detection unit that detects passage of the paper by detecting rotation of the rotating member;
A blowing control method in an image forming apparatus comprising:
The first passage time from when the nth (n: integer greater than or equal to 1) sheets are sent out by the registration roller section until the passage of the nth sheet is detected by the sheet passage detection section When the conveyance posture of the sheet that has passed through the fixing nip is longer than the maximum allowable passing time within a proper range, the blowing amount of the blowing unit is increased, and the n + 1th sheet is increased by the registration roller unit. When the second passage time from when the paper is sent to when the passage of the (n + 1) th sheet is detected by the paper passage detection unit is longer than the maximum passage time, the first passage time and the second passage time The amount of air blown from the blower is controlled according to the magnitude relationship with the passage time of the air.

  According to the present invention, using the existing detection means (rotating member, paper passage detection unit), the time from when the paper is sent out by the registration roller unit until the passage of the paper is detected by the paper passage detection unit, in other words, It is possible to indirectly detect the conveyance posture of the sheet that has passed through the fixing nip, and to control the blowing amount of the blowing unit so as not to cause a winding jam or the like. Therefore, it is possible to stabilize the paper transport posture without newly providing a detection unit.

1 is a diagram schematically showing an overall configuration of an image forming apparatus in the present embodiment. FIG. 2 is a diagram illustrating a main part of a control system of the image forming apparatus according to the present embodiment. FIG. 2 is a diagram schematically illustrating a configuration of a fixing unit of the image forming apparatus according to the present embodiment. It is a figure which shows the arrangement configuration of the conveyance roller pair and rotation member in this Embodiment. 6 is a flowchart illustrating a blowing control operation of the image forming apparatus according to the present embodiment.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings. FIG. 1 is a diagram schematically showing an overall configuration of an image forming apparatus 1 according to an embodiment of the present invention. FIG. 2 shows the main part of the control system of the image forming apparatus 1 in the present embodiment. An image forming apparatus 1 shown in FIGS. 1 and 2 is an intermediate transfer type color image forming apparatus using electrophotographic process technology. That is, the image forming apparatus 1 primarily transfers the Y (yellow), M (magenta), C (cyan), and K (black) toner images formed on the photosensitive drum 413 to the intermediate transfer belt 421. After the four color toner images are superimposed on the intermediate transfer belt 421, the toner images are formed by performing secondary transfer onto the paper S.

  Further, in the image forming apparatus 1, the photosensitive drums 413 corresponding to the four colors of YMCK are arranged in series in the running direction of the intermediate transfer belt 421, and the respective color toner images are sequentially transferred to the intermediate transfer belt 421 in one step. Tandem system is adopted.

  As shown in FIG. 2, the image forming apparatus 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a paper transport unit 50, a fixing unit 60, a paper passage detection unit 80, and a control unit. 100.

  The control unit 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, and the like. The CPU 101 reads a program corresponding to the processing content from the ROM 102 and develops it in the RAM 103, and centrally controls the operation of each block of the image forming apparatus 1 in cooperation with the developed program. At this time, various data stored in the storage unit 72 is referred to. The storage unit 72 includes, for example, a nonvolatile semiconductor memory (so-called flash memory) or a hard disk drive.

  The control unit 100 transmits and receives various data to and from an external device (for example, a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 71. Do. For example, the control unit 100 receives image data transmitted from an external device, and forms a toner image on the paper S based on the image data (input image data). The communication unit 71 is composed of a communication control card such as a LAN card, for example.

  The image reading unit 10 includes an automatic document feeder 11 called an ADF (Auto Document Feeder), a document image scanning device 12 (scanner), and the like.

  The automatic document feeder 11 transports the document D placed on the document tray by a transport mechanism and sends it out to the document image scanning device 12. The automatic document feeder 11 can continuously read images (including both sides) of a large number of documents D placed on a document tray all at once.

  The document image scanning device 12 optically scans a document conveyed on the contact glass from the automatic document feeder 11 or a document placed on the contact glass, and reflects light from the document to a CCD (Charge Coupled Device). ) An image is formed on the light receiving surface of the sensor 12a, and an original image is read. The image reading unit 10 generates input image data based on the reading result by the document image scanning device 12. The input image data is subjected to predetermined image processing in the image processing unit 30.

  The operation display unit 20 is configured by, for example, a liquid crystal display (LCD) with a touch panel, and functions as the display unit 21 and the operation unit 22. The display unit 21 displays various operation screens, an image status display, an operation status of each function, and the like in accordance with a display control signal input from the control unit 100. The operation unit 22 includes various operation keys such as a numeric keypad and a start key, receives various input operations by the user, and outputs an operation signal to the control unit 100.

  The image processing unit 30 includes a circuit that performs digital image processing on input image data according to initial settings or user settings. For example, the image processing unit 30 performs gradation correction based on the gradation correction data (gradation correction table) under the control of the control unit 100. Further, the image processing unit 30 performs various correction processes such as color correction and shading correction, a compression process, and the like on the input image data in addition to the gradation correction. The image forming unit 40 is controlled based on the image data subjected to these processes.

  The image forming unit 40 is based on the input image data, and image forming units 41Y, 41M, 41C, 41K, and an intermediate transfer unit 42 for forming an image using colored toners of Y component, M component, C component, and K component. Etc.

  The Y component, M component, C component, and K component image forming units 41Y, 41M, 41C, and 41K have the same configuration. For convenience of illustration and description, common components are denoted by the same reference numerals, and in order to distinguish each, Y, M, C, or K is added to the reference numerals. In FIG. 1, only the components of the Y-component image forming unit 41Y are denoted by reference numerals, and the constituent elements of the other image forming units 41M, 41C, and 41K are omitted.

  The image forming unit 41 includes an exposure device 411, a developing device 412, a photosensitive drum 413, a charging device 414, a drum cleaning device 415, and the like.

  The photosensitive drum 413 has, for example, an undercoat layer (UCL), a charge generation layer (CGL), a charge transport layer (CGL) on the peripheral surface of an aluminum conductive cylinder (aluminum tube). It is a negatively charged organic photoreceptor (OPC: Organic Photo-conductor) in which CTL (Charge Transport Layer) is sequentially laminated. The charge generation layer is made of an organic semiconductor in which a charge generation material (for example, phthalocyanine pigment) is dispersed in a resin binder (for example, polycarbonate), and generates a pair of positive charges and negative charges by exposure by the exposure device 411. The charge transport layer consists of a material in which a hole transport material (electron donating nitrogen-containing compound) is dispersed in a resin binder (for example, polycarbonate resin), and transports positive charges generated in the charge generation layer to the surface of the charge transport layer. To do.

  The control unit 100 controls the drive current supplied to a drive motor (not shown) that rotates the photosensitive drum 413 to rotate the photosensitive drum 413 at a constant peripheral speed.

  The charging device 414 uniformly charges the surface of the photoconductive drum 413 to a negative polarity. The exposure device 411 is composed of, for example, a semiconductor laser, and irradiates the photosensitive drum 413 with laser light corresponding to the image of each color component. A positive charge is generated in the charge generation layer of the photosensitive drum 413 and is transported to the surface of the charge transport layer, whereby the surface charge (negative charge) of the photosensitive drum 413 is neutralized. An electrostatic latent image of each color component is formed on the surface of the photosensitive drum 413 due to a potential difference from the surroundings.

  The developing device 412 is, for example, a two-component developing type developing device, and forms a toner image by visualizing the electrostatic latent image by attaching toner of each color component to the surface of the photosensitive drum 413.

  The drum cleaning device 415 includes a drum cleaning blade that is slidably contacted with the surface of the photosensitive drum 413, and removes transfer residual toner remaining on the surface of the photosensitive drum 413 after primary transfer.

  The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422, a plurality of support rollers 423, a secondary transfer roller 424, a belt cleaning device 426, and the like.

  The intermediate transfer belt 421 is an endless belt, and is stretched around a plurality of support rollers 423 in a loop shape. At least one of the plurality of support rollers 423 is configured by a driving roller, and the other is configured by a driven roller. For example, it is preferable that the roller 423A disposed downstream of the K component primary transfer roller 422 in the belt traveling direction is a drive roller. This makes it easy to keep the belt running speed constant in the primary transfer portion. As the driving roller 423A rotates, the intermediate transfer belt 421 travels in the direction of arrow A at a constant speed.

  The primary transfer roller 422 is disposed on the inner peripheral surface side of the intermediate transfer belt 421 so as to face the photosensitive drum 413 of each color component. The primary transfer roller 422 is pressed against the photosensitive drum 413 with the intermediate transfer belt 421 interposed therebetween, thereby forming a primary transfer nip for transferring a toner image from the photosensitive drum 413 to the intermediate transfer belt 421.

  The secondary transfer roller 424 is disposed on the outer peripheral surface side of the intermediate transfer belt 421 so as to face the backup roller 423B disposed on the downstream side in the belt traveling direction of the drive roller 423A. The secondary transfer roller 424 is pressed against the backup roller 423B with the intermediate transfer belt 421 interposed therebetween, thereby forming a secondary transfer nip for transferring the toner image from the intermediate transfer belt 421 to the paper S.

  When the intermediate transfer belt 421 passes through the primary transfer nip, the toner images on the photoconductive drum 413 are primarily transferred onto the intermediate transfer belt 421 in sequence. Specifically, a primary transfer bias is applied to the primary transfer roller 422, and an electric charge having a polarity opposite to that of the toner is applied to the back side of the intermediate transfer belt 421 (the side in contact with the primary transfer roller 422). It is electrostatically transferred to the intermediate transfer belt 421.

  Thereafter, when the sheet S passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred to the sheet S. Specifically, a toner image is applied by applying a secondary transfer bias to the secondary transfer roller 424 and applying a charge having a polarity opposite to that of the toner to the back side of the paper S (the side in contact with the secondary transfer roller 424). Is electrostatically transferred to the paper S. The sheet S to which the toner image is transferred is conveyed toward the fixing unit 60.

  The belt cleaning unit 426 includes a belt cleaning blade that is in sliding contact with the surface of the intermediate transfer belt 421 and removes transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer. Instead of the secondary transfer roller 424, a configuration (so-called belt-type secondary transfer unit) in which a secondary transfer belt is looped around a plurality of support rollers including the secondary transfer roller is adopted. Also good.

  The fixing unit 60 includes an upper fixing unit 60A having a fixing surface side member disposed on the fixing surface (surface on which the toner image is formed) of the paper S, and the back surface (surface opposite to the fixing surface) of the paper S. A lower fixing unit 60B having a rear side support member to be disposed, a heating source 60C, and the like are provided. When the back surface side support member is pressed against the fixing surface side member, a fixing nip for nipping and transporting the paper S is formed.

  The fixing unit 60 fixes the toner image on the paper S by heating and pressurizing the paper S on which the toner image is secondarily transferred and conveyed at the fixing nip. The fixing unit 60 is disposed in the fixing device F as a unit. The fixing device F is provided with an air separation unit 60D that separates the sheet S from the fixing surface side member by blowing air. Details of the fixing unit 60 will be described later.

  The paper transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, a transport path unit 53, and the like. In the three paper feed tray units 51a to 51c constituting the paper feed unit 51, paper S (standard paper, special paper) identified based on basis weight, size, or the like is stored for each preset type. . The conveyance path unit 53 includes a plurality of conveyance roller pairs such as registration roller pairs 53a.

  The sheets S stored in the sheet feed tray units 51 a to 51 c are sent one by one from the top and are conveyed to the image forming unit 40 by the conveyance path unit 53. At this time, the registration roller portion provided with the registration roller pair 53a corrects the inclination of the fed paper S and adjusts the conveyance timing. In the image forming unit 40, the toner image on the intermediate transfer belt 421 is secondarily transferred onto one side of the sheet S at a time, and a fixing process is performed in the fixing unit 60. The sheet S on which the image has been formed is discharged out of the apparatus by a discharge unit 52 having a discharge roller 52a.

  Next, the configuration of the fixing unit 60 will be described with reference to FIG. FIG. 3 is a diagram schematically illustrating the configuration of the fixing unit 60.

  The upper fixing unit 60A includes an endless fixing belt 61 (functioning as a “fixing member” of the present invention) that is a fixing surface side member, a heating roller 62, an upper pressure roller 63, and a stretching member 64 (belt heating method). ). The fixing belt 61 is stretched between a heating roller 62, an upper pressure roller 63, and a stretching member 64 with a predetermined belt tension (for example, 400 N).

  The fixing belt 61 is formed by, for example, coating the outer peripheral surface of a base made of PI (polyimide) with a heat-resistant silicone rubber as an elastic layer, and further covering or coating a PFA (perfluoroalkoxy) tube, which is a heat-resistant resin, on the surface layer. Do it.

  The fixing belt 61 comes into contact with the paper S on which the toner image is formed, and heat-fixes the toner image on the paper S in a fixing allowable temperature range. Here, the fixing allowable temperature range is a temperature at which a heat amount necessary for melting the toner on the paper S can be supplied, and varies depending on the paper type of the paper S on which an image is formed.

  The heating roller 62 heats the fixing belt 61. The heating roller 62 includes a heating source 60 </ b> C (halogen heater) that heats the fixing belt 61. The heating roller 62 is covered with a resin layer obtained by coating the outer peripheral surface of a cylindrical metal core made of aluminum or the like with PTFE, for example.

  The temperature of the heating source 60C is controlled by the control unit 100. The heating roller 62 is heated by the heating source 60C, and as a result, the fixing belt 61 is heated.

  The upper pressure roller 63 is a resin in which a solid metal core made of a metal such as iron is coated with heat-resistant silicon rubber as an elastic layer, and further coated with PTFE which is a heat-resistant resin with low friction It is coated with a layer. The upper pressure roller 63 is brought into pressure contact with the lower pressure roller 65 driven and rotated by a main drive source (not shown) in the fixing unit 60 via the fixing belt 61.

  The lower fixing unit 60B includes, for example, a lower pressure roller 65 that is a back surface side support member (roller pressure method). The lower pressure roller 65 covers the outer peripheral surface of a base material layer made of PI (polyimide) with a heat-resistant silicone rubber as an elastic layer, and further uses the outer peripheral surface of the elastic layer as a surface release layer to form a resin layer of a PFA tube. It is coated with.

  The control unit 100 controls the main drive source (drive motor) to rotate the lower pressure roller 65 in the counterclockwise direction in the drawing. Drive control of the drive motor (for example, rotation on / off, peripheral speed, etc.) is performed by the control unit 100.

  The lower pressure roller 65 incorporates a heating source 65A such as a halogen heater. When the heating source 65A generates heat, the lower pressure roller 65 is heated. The control unit 100 controls the power supplied to the heating source 65A and controls the lower pressure roller 65 to a predetermined temperature.

  The lower pressure roller 65 is pressed against the upper pressure roller 63 with a predetermined fixing load via the fixing belt 61. In this manner, a fixing nip NP that nipping and transporting the paper S is formed between the fixing belt 61 and the lower pressure roller 65.

  When the lower pressure roller 65 is driven and rotated in the counterclockwise direction in the figure, the fixing belt 61 is driven to rotate in the clockwise direction in the figure. Accordingly, the upper pressure roller 63 is driven to rotate clockwise in the drawing. Further, the tension member 64 is rotated in the clockwise direction in the drawing. When the sheet S is fixed, the peripheral speed of the fixing belt 61 is equal to the peripheral speed of the lower pressure roller 65.

  The air separation unit 60 </ b> D includes a fan blower 66 (functioning as a “blower” of the present invention) and a blower duct 67. The air separation unit 60D blows air toward the fixing belt 61 from the paper discharge side of the fixing nip NP.

  The fan blower 66 is a cylindrical multi-blade fan (so-called sirocco fan) in which a large number of forward blades 66a are erected on the circumference. The proximal end side of the air duct 67 is connected to the air blowing port 66 b formed on the side surface of the fan air blowing unit 66. Further, the air discharge port 67a on the front end side of the air duct 67 is arranged so that air is blown to the vicinity of the fixing nip NP, for example, at a position 15 mm from the nip end. The outlet (air discharge port 67a) of the air duct 67 is smaller than the inlet (connecting part with the fan air blowing part 66) so that air can be blown at a high speed to ensure the separation performance of the paper S (for example, area) The ratio is set to about 1/20.

  In the fan blower 66, air is sucked from the center of the fan and sent out in the centrifugal direction. The sent air passes through the blower duct 67 and is blown uniformly in the axial direction from the air discharge port 67 a toward the fixing belt 61. The air blow timing (fan rotation on / off) by the fan air blower 66, the air flow (%) (the air flow ratio with respect to the maximum air flow), and the like are controlled by the controller 100. The amount of air blown by the fan blower 66 is the amount of air necessary to separate the paper S from the fixing belt 61, and varies depending on the type (paper type, basis weight) of the paper S on which an image is formed.

  Note that a plurality of (for example, five) air separation units 60D may be arranged in parallel in the axial direction of the upper pressure roller 63 (corresponding to the paper width direction of the paper S). In this case, from the viewpoint of stabilizing the transport posture in the paper width direction of the paper S that has passed through the fixing nip NP, the control unit 100 seems to have a different airflow rate between the central portion and the end portion of the paper S in the paper width direction. In addition, a plurality of fan blowers 66 may be controlled.

  In the fixing unit 60, the upper fixing unit 60 </ b> A, the lower fixing unit 60 </ b> B, and the heating source 60 </ b> C fix the unfixed toner image on the sheet S by conveying the sheet S while heating and pressing at the fixing nip NP. . The air separation unit 60D separates the paper S from the fixing belt 61 by blowing air to the leading edge of the paper S that has passed through the fixing nip NP. Accordingly, it is possible to prevent the sheet S that has passed through the fixing nip NP from being wound around the surface of the fixing belt 61 and being separated and causing a winding jam or the like.

  On the downstream side of the fixing nip NP in the sheet conveyance direction, a rotating member 82 (actuator in the present embodiment) that rotates around the rotation fulcrum 82a by contacting the sheet S that has passed through the fixing nip NP is disposed. Yes. The rotating member 82 is provided so as to protrude upward from the vicinity of the rotation fulcrum 82a, and the upper part is pushed by the sheet S guided to the fixing nip NP and rotates counterclockwise in FIG.

  On the downstream side of the rotation member 82 in the sheet conveyance direction, a conveyance roller pair 84 that conveys the sheet S that has passed through the fixing nip NP is disposed. In the present embodiment, the conveyance roller pair 84 is divided into a plurality of conveyance roller pairs 84a, 84b, 84c, and 84d in the direction of the rotation axis, as shown in FIG. The rotation member 82 is arranged between the conveyance roller pair 84b and the conveyance roller pair 84c in the rotation axis direction of the conveyance roller pair 84 and overlaps the conveyance roller pair 84 in a side sectional view. The upper part of the rotating member 82 is pushed by the sheet S guided to the fixing nip NP, and rotates in the upward direction (arrow direction) in FIG. The length d1 of the rotation member 82 in the rotation axis direction of the conveyance roller pair 84 is shorter than the length d2 of the rotation member 82 in the sheet conveyance direction.

  The paper passage detection unit 80 is provided below the transport roller pair 84, and detects the passage of the paper S at a predetermined position of the transport roller pair 84 in the paper transport direction by detecting the rotation of the rotating member. In the present embodiment, the paper passage detection unit 80 emits light from a predetermined light emitting element toward the rotating member 82, and the reflected light from the rotating member 82 is detected by the light receiving element, thereby allowing the paper S to pass. It is a non-contact type reflection type photo sensor for detecting the light. For example, when the rotating member 82 rotates by contacting the sheet S that has passed through the fixing nip NP, the sheet passage detecting unit 80 detects the reflected light from the rotating member 82 by the light receiving element, thereby detecting the passage of the sheet S. To detect. On the other hand, when the rotating member 82 does not rotate without coming into contact with the paper S that has passed through the fixing nip NP, the paper passage detecting unit 80 detects the passage of the paper S because the light reflected from the rotating member 82 is not detected by the light receiving element. do not do.

  The paper passage detection unit 80 and the rotation member 82 are also provided in the conventional image forming apparatus 1. The detection result of the paper passage detection unit 80 is used for transport speed control of the paper S and detection of paper jam.

  By the way, the problem that the paper S does not wrap around the surface of the fixing belt 61 and does not separate and causes a winding jam or the like is caused by the increase in the size of the fixing device (fixing unit 60) due to the recent increase in the speed of the image forming apparatus 1, or the paper. The separation of the paper S from the fixing belt 61 has become more difficult with the handling of thinner paper S due to the request for seed expansion.

  Therefore, in the present embodiment, from the viewpoint of reliably separating the paper S from the fixing belt 61 and stabilizing the transport posture of the paper S, the control unit 100 uses the detection result of the paper passage detection unit 80 to transport the paper S. The posture is indirectly detected, and the amount of air blown toward the paper discharge side of the fixing nip NP is controlled according to the detection result.

  In FIG. 3, Sa indicates the paper S in which the amount of air blown by the fan blower 66 is less than an appropriate amount and the transport posture is in an upwardly convex state (that is, a bent state). In this case, the sheet S that has passed through the fixing nip NP is wound around the surface of the fixing belt 61 and is not separated, which may cause a winding jam. Further, even if no wrapping jam occurs, the conveyance posture of the paper S becomes unstable and the paper S comes into contact with the separation claw and the conveyance guide plate, thereby causing image defects and wear of the separation claw and the conveyance guide plate. There is a fear.

  Further, Sb indicates the paper S in which the amount of air blown by the fan blower 66 is an appropriate amount and the transport posture is in a stable state (that is, an unbent state). The control unit 100 controls the amount of air blown by the fan blower 66 so that the transport posture of the paper S becomes Sb.

  In addition, Sc indicates the paper S in which the amount of air blown by the fan blower 66 is larger than the appropriate amount and the transport posture is in the downward convex state (that is, the bent state). In this case, the conveyance posture of the paper S that has passed through the fixing nip NP becomes unstable and the paper S comes into contact with the conveyance guide plate, which may cause image defects and wear of the conveyance guide plate.

  Whether the transport posture of the paper S is Sa, Sc, or Sb varies depending on the time from when the paper S is sent out by the registration roller unit until the passage of the paper S is detected by the paper passage detection unit 80. To do. Specifically, when the time until the passage of the paper S is detected by the paper passage detection unit 80 is long, it can be estimated that the transport posture of the paper S is Sa and Sc, and when the time is short, It can be estimated that the transport posture of S is Sb. Therefore, the control unit 100 controls the amount of air blown by the fan blower 66 so that the time from when the paper S is sent out by the registration roller unit to when the passage of the paper S is detected by the paper passage detection unit 80 is shortened. To do.

  FIG. 5 is a flowchart illustrating an example of the air blowing control operation of the image forming apparatus 1 in the present embodiment. The process of step S100 in FIG. 5 is executed when the image forming apparatus 1 is turned on and the execution of the image forming process corresponding to the print job is started.

  First, the control unit 100 substitutes 1 for a control variable n indicating the number of sheets S of the current image formation target (step S100). Next, the control unit 100 sets the air flow rate Q by the fan air blowing unit 66 according to the type (paper type, basis weight) of the paper S on which an image is formed (step S120). Note that the amount of air blown by the fan blower 66 can be set in multiple stages.

  Next, the control unit 100 has a maximum passage time T (n) from when the sheet S (n) is sent out by the registration roller unit to when the passage of the sheet S (n) is detected by the sheet passage detection unit 80. It is determined whether it is longer than time Tmax (step S140). Here, the maximum passage time Tmax is a passage time allowed to the maximum within a range in which the transport posture of the paper S that has passed through the fixing nip NP is appropriate.

  As a result of the determination, when the passage time T (n) is not longer than the maximum passage time Tmax (step S140, NO), the control unit 100 substitutes n + 1 for the control variable n (step S180). Thereafter, the process returns to before step S140. On the other hand, when the passage time (n) is longer than the maximum passage time Tmax (step S140, YES), it is estimated that the transport posture of the paper S is in an unstable state (Sa in FIG. 3). Increases the air flow rate Q (n + 1) by the fan air blowing unit 66 by one step (step S160).

  Next, the control unit 100 determines that the passage time (n + 1) from when the paper S (n + 1) is sent out by the registration roller unit to when the passage of the paper S (n + 1) is detected by the paper passage detection unit 80 is the maximum passage time. It is determined whether or not it is longer than Tmax (step S200). As a result of the determination, when the passage time (n + 1) is not longer than the maximum passage time Tmax (step S200, NO), the control unit 100 substitutes n + 2 for the control variable n (step S220). Thereafter, the process returns to before step S140.

  On the other hand, when the passage time T (n + 1) is longer than the maximum passage time Tmax (step S200, YES), the control unit 100 determines whether or not the passage time (n + 1) is longer than the passage time (n) (step S240). ). As a result of the determination, if the passage time (n + 1) is not longer than the passage time (n) (step S240, NO), the passage time is shortened due to the increase in the amount of blown air in step S160, and the transport posture of the paper S is in an appropriate state (FIG. Therefore, the control unit 100 increases the air flow rate Q (n + 2) by the fan air blowing unit 66 by one step (step S280). Thereafter, the process proceeds to step S300.

  On the other hand, when the passage time T (n + 1) is longer than the passage time T (n) (step S240, YES), the passage time is increased due to the increase in the air flow amount in step S160, and the transport posture of the sheet S is in an appropriate state (FIG. 3 (see Sb of FIG. 3), it is estimated that the controller 100 is approaching a more unstable state (Sc in FIG. 3), and therefore the control unit 100 sets the air flow rate Q (n + 2) by the fan air blowing unit 66 in two stages. Decrease (step S260). Thereafter, the process proceeds to step S300.

  In step S300, the control unit 100 substitutes n + 2 for the control variable n.

  As described above in detail, in the present embodiment, the image forming apparatus 1 sends the paper S to the image forming unit 40 at a predetermined conveyance timing, and the image forming unit 40 that forms a toner image on the paper S. A registration roller unit, a fixing unit 60 that heats and pressurizes the paper S on which the toner image is formed by the image forming unit 40 in the fixing nip NP to fix the toner image on the paper S, and the fixing nip NP in the paper conveyance direction. An air blowing unit (air separation unit 60D) that separates the paper S from a fixing member (fixing belt 61) of the fixing unit 60 by blowing air toward the paper S from the downstream side, and a downstream side of the fixing nip NP in the paper transport direction. And a rotation member 82 that rotates by contacting the sheet S that has passed through the fixing nip NP, and the rotation of the rotation member 82 is detected. The paper passage detection unit 80 that detects the passage of the paper S, and the sending of the blower unit according to the time from when the paper S is sent by the registration roller unit until the passage of the paper S is detected by the paper passage detection unit 80. And a control unit 100 for controlling the air volume.

  According to the present embodiment configured as described above, the sheet detection unit 80 uses the existing detection means (the rotating member 82 and the sheet passage detection unit 80) and the sheet passage detection unit 80 transmits the sheet S after the sheet S is sent out. The time until the passage of S is detected, in other words, the conveying posture of the paper S that has passed through the fixing nip NP is indirectly detected, and the air blowing amount of the air blowing unit can be controlled so that no wrap jam or the like occurs. . Therefore, the conveyance posture of the paper S can be stabilized without newly providing a detection unit.

  In the present embodiment, the conveyance roller pair 84 is divided into a plurality of conveyance roller pairs 84a, 84b, 84c, and 84d in the direction of the rotation axis, as shown in FIG. Further, the rotating member 82 is disposed so as to overlap the conveyance roller pair 84 in a side sectional view. With such a configuration, it is possible to detect the passage of the sheet S while the conveyance roller pair 84 holds the sheet S therebetween. As a result, when the transport roller pair 84 is not holding the paper S, even if the transport posture of the paper S is different as in Sa, Sb, and Sc shown in FIG. This is to prevent problems such as the sheet S not coming into contact with the rotating member 82 when the sheet S is transported in the Sa posture, for example, Sa.

  In the present embodiment, the length d1 of the rotation member 82 in the rotation axis direction of the conveyance roller pair 84 is shorter than the length d2 of the rotation member 82 in the sheet conveyance direction. With such a configuration, the rotation of the rotating member 82 due to the influence of the air blow by the fan blower 66 is suppressed. As a result, the paper S is passed by the paper passage detector 80 after the paper S is sent out by the registration roller part. Can be detected with high accuracy.

  The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. That is, the present invention can be implemented in various forms without departing from the gist or main features thereof.

  The present invention can be applied to an image forming system including a plurality of units including an image forming apparatus. The plurality of units include external devices such as post-processing devices and network-connected control devices, for example.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Image reading part 20 Operation display part 21 Display part 22 Operation part 30 Image processing part 40 Image forming part 50 Paper conveyance part 60 Fixing part 60A Upper fixing part 60B Lower fixing part 60C, 65A Heating source 60D Air separation Unit 61 Fixing belt 62 Heating roller 63 Upper pressure roller 64 Stretching member 65 Lower pressure roller 66 Fan blower unit 67 Blower duct 71 Communication unit 72 Storage unit 80 Paper passage detection unit 82 Rotating members 84, 84a, 84b, 84c, 84d conveying roller pair 100 control unit 101 CPU
102 ROM
103 RAM
NP fixing nip

Claims (6)

An image forming unit that forms a toner image on paper;
A registration roller unit that sends out the paper at a predetermined conveyance timing to the image forming unit;
A fixing unit that heats and pressurizes a sheet on which a toner image is formed by the image forming unit in a fixing nip to fix the toner image on the sheet;
A blowing unit that separates the sheet from a fixing member of the fixing unit by blowing toward the sheet from the downstream side of the fixing nip in the sheet conveyance direction;
A rotating member disposed on the downstream side of the fixing nip in the paper transport direction and rotating by contacting the paper that has passed through the fixing nip;
A paper passage detection unit that detects passage of the paper by detecting rotation of the rotating member;
The first passage time from when the nth (n: integer greater than or equal to 1) sheets are sent out by the registration roller section until the passage of the nth sheet is detected by the sheet passage detection section When the conveyance posture of the sheet that has passed through the fixing nip is longer than the maximum allowable passing time within a proper range, the blowing amount of the blowing unit is increased, and the n + 1th sheet is increased by the registration roller unit. When the second passage time from when the paper is sent to when the passage of the (n + 1) th sheet is detected by the paper passage detection unit is longer than the maximum passage time, the first passage time and the second passage time According to the magnitude relationship with the passage time of the control unit for controlling the blowing amount of the blowing unit,
An image forming apparatus comprising: Wherein, when the pre-Symbol second passage time is longer than the previous SL first passage time, the one for reducing the air blowing amount of the blower unit, before Symbol second transit time before Symbol first passage time When it is below, increase the air volume of the air blowing part,
The image forming apparatus according to claim 1. An image forming system including a plurality of units including an image forming apparatus,
An image forming unit that forms a toner image on paper;
A registration roller unit that sends out the paper at a predetermined conveyance timing to the image forming unit;
A fixing unit that heats and pressurizes a sheet on which a toner image is formed by the image forming unit in a fixing nip to fix the toner image on the sheet;
A blowing unit that separates the sheet from a fixing member of the fixing unit by blowing toward the sheet from the downstream side of the fixing nip in the sheet conveyance direction;
A rotating member disposed on the downstream side of the fixing nip in the paper transport direction and rotating by contacting the paper that has passed through the fixing nip;
A paper passage detection unit that detects passage of the paper by detecting rotation of the rotating member;
The first passage time from when the nth (n: integer greater than or equal to 1) sheets are sent out by the registration roller section until the passage of the nth sheet is detected by the sheet passage detection section When the conveyance posture of the sheet that has passed through the fixing nip is longer than the maximum allowable passing time within a proper range, the blowing amount of the blowing unit is increased, and the n + 1th sheet is increased by the registration roller unit. When the second passage time from when the paper is sent to when the passage of the (n + 1) th sheet is detected by the paper passage detection unit is longer than the maximum passage time, the first passage time and the second passage time According to the magnitude relationship with the passage time of the control unit for controlling the blowing amount of the blowing unit,
An image forming system comprising: Wherein, when the pre-Symbol second passage time is longer than the previous SL first passage time, the one for reducing the air blowing amount of the blower unit, before Symbol second transit time before Symbol first passage time When it is below, increase the air volume of the air blowing part,
The image forming system according to claim 3. An image forming unit that forms a toner image on paper;
A registration roller unit that sends out the paper at a predetermined conveyance timing to the image forming unit;
A fixing unit that heats and pressurizes a sheet on which a toner image is formed by the image forming unit in a fixing nip to fix the toner image on the sheet;
A blowing unit that separates the sheet from a fixing member of the fixing unit by blowing toward the sheet from the downstream side of the fixing nip in the sheet conveyance direction;
A rotating member disposed on the downstream side of the fixing nip in the paper transport direction and rotating by contacting the paper that has passed through the fixing nip;
A paper passage detection unit that detects passage of the paper by detecting rotation of the rotating member;
A blowing control method in an image forming apparatus comprising:
A first passing time from when the n (n: integer greater than or equal to 1) sheets are sent out by the registration roller section until the passage of the nth sheet is detected by the sheet passage detecting section When the conveyance posture of the sheet that has passed through the fixing nip is longer than the maximum allowable passing time within a proper range, the blowing amount of the blowing unit is increased, and the n + 1th sheet is increased by the registration roller unit. When the second passage time from when the paper is sent to when the passage of the (n + 1) th sheet is detected by the paper passage detection unit is longer than the maximum passage time, the first passage time and the second passage time The ventilation control method which controls the ventilation volume of the said ventilation part according to the magnitude relationship with passage time of . When pre-Symbol second passage time is longer than the previous SL first passage time, while reducing the air blowing amount of the blower, when pre-Symbol second passage time is equal to or less than before Symbol first passage time, Increasing the amount of air blown from the air blowing unit,
The ventilation control method according to claim 5.

Images