JP2015156005A - image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can prevent the occurrence of image defects, such as fixing failure or unevenness in glossiness of images.

SOLUTION: An image forming apparatus 1 includes: a fixing member (fixing belt 61) that is used for heating a toner image at a fixing nip NP to fix the toner image on a sheet S; an air blowing part (air separation unit 60E) that blows the air from a sheet ejection side of the fixing nip NP toward the fixing member; a heating part (heat sources 60C and 60D, and heating roller 62) that heats the fixing member; a first power supply part (main power source 80) that supplies power to the heating part; a second power supply part (sub power source 90) that is different from the first power supply part and supplies power to the heating part; and a control unit 100 that controls the first power supply part and second power supply part so that the temperature of the fixing member is maintained within a fixing allowable temperature range. The control unit 100 starts power supply by the second power supply part in response to a decrease in temperature of the fixing member due to an air blowing operation of the air blowing part.

COPYRIGHT: (C)2015,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus.

  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, it is fixed by heating and pressurizing to form an image on the paper.

  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 paper that has passed through the fixing nip is wound around the surface of the fixing surface side member and is not separated, which may cause a jam. 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.

  However, when the air separation unit blows air toward the paper discharge side of the fixing nip, the fixing surface side member causes an unintended temperature decrease, and insufficient supply of heat to the paper occurs during the subsequent fixing process. . As a result, there is a problem that fixing failure and uneven gloss of the image, that is, image failure occurs.

  In relation to the above problem, Patent Document 1 discloses that a heating roller and a sheet of paper that advances from a nip portion of a fixing unit that includes a pressure roller (or pressure belt) that is pressed against the heating roller and the heating roller, A technique is disclosed that includes hot air blowing means for blowing hot air to separate the heating roller and the paper. According to the technique described in Patent Document 1, it is possible to prevent the paper that advances from the nip portion from being wrapped around the heating roller without affecting the fixing operation.

  Patent Document 2 discloses a technique for preventing a temperature drop of a fixing member (fixing roller) when paper is passed. The technique described in Patent Document 2 heats the fixing member by causing the heating element and the auxiliary heating element to generate heat by supplying power from the auxiliary power supply in addition to the main power supply.

JP 2007-94327 A JP 2005-17564 A

  However, in the technique described in Patent Document 1, a hot air blowing unit is newly required and the configuration of the fixing device is complicated, and members other than the heating roller are heated by the hot air blown from the hot air blowing unit. There was a problem. Further, the technique described in Patent Document 2 has a problem that it cannot cope with a temperature decrease of the fixing member except when paper is passed.

  An object of the present invention is to provide an image forming apparatus capable of preventing the occurrence of image defects such as fixing defects and uneven glossiness of images.

An image forming apparatus according to the present invention includes:
A fixing member used to heat and fix the toner image on the paper in the fixing nip;
A blower that blows air from the paper discharge side of the fixing nip toward the fixing member;
A heating section for heating the fixing member;
A first power supply unit for supplying power to the heating unit;
A second power supply unit for supplying power to the heating unit, different from the first power supply unit;
A control unit that controls the first power supply unit and the second power supply unit so that the temperature of the fixing member is maintained within a fixing allowable temperature range;
With
The control unit starts power supply by the second power supply unit in response to a temperature drop of the fixing member due to a blowing operation of the blowing unit.

  According to the present invention, since the power supply by the second power supply unit is started in response to the temperature decrease of the fixing member due to the air blowing operation of the air blowing unit, until the fixing member returns to a fixable temperature before the air blowing. The time can be shortened. As a result, it is possible to prevent insufficient supply of heat to the paper during the subsequent fixing process, and to prevent image defects such as fixing defects and uneven glossiness of images.

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 temperature change of the fixing belt according to the electric power supply operation | movement and ventilation operation | movement in this Embodiment. It is a figure which shows the example of the electric power supply operation | movement in this Embodiment, and a ventilation operation | movement. It is a table | surface which shows the relationship of the electric power supply amount by the basic weight of paper, ventilation volume, a main power supply, and a subpower supply. 6 is a table showing the relationship between the amount of power supplied by a sub power source and the separation and fixing properties of paper.

  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 a main part of the control system of the image forming apparatus 1 according to 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 transfers the toner images of Y (yellow), M (magenta), C (cyan), and K (black) formed on the photosensitive drum 413 to the intermediate transfer belt 421 (primary transfer). Then, after superposing four color toner images on the intermediate transfer belt 421, the toner images are transferred to the paper S (secondary transfer) to form an image.

  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 main power supply 80, a sub power supply 90, and A control unit 100 is provided.

  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 an 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 a display unit 21 and an 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 explanation, common constituent elements are denoted by the same reference numerals, and Y, M, C, or K are added to the reference numerals when distinguished from each other. 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 an undercoat layer (UCL) and a charge generation layer (CGL) on the peripheral surface of an aluminum conductive cylinder (aluminum tube) having a drum diameter of 80 mm, for example. It is a negatively charged organic photoconductor (OPC) in which a generation layer (CTL) and a charge transport layer (CTL) are sequentially stacked. 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 a drive current supplied to a drive motor (not shown) that rotates the photosensitive drum 413, so that the photosensitive drum 413 rotates 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 a roller 423B (hereinafter referred to as “backup roller 423B”) disposed on the downstream side of the driving roller 423A in the belt traveling direction. 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 arranged, and heating sources 60C and 60D 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 60E that separates the sheet S from the fixing surface side member or the back surface side support 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 fixing unit 60 and the control unit 100 function as a fixing device. The fixing unit 60 and the control unit 100 may be configured as a unit and attached to the image forming apparatus 1, or may be separately incorporated in the image forming apparatus 1 and function as a fixing device. .

  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 the heating roller 62, the upper pressure roller 63, and the stretching member 64 with a predetermined belt tension (for example, 400 [N]).

  The fixing belt 61 has, for example, an outer diameter of 120 [mm], a heat-resistant silicone rubber having a thickness of 200 [μm] using an outer peripheral surface of a base made of PI (polyimide) having a thickness of 70 [μm] as an elastic layer. The surface layer is coated or coated with a tube of PFA (perfluoroalkoxy), which is a heat-resistant resin having a thickness of 30 [μm], on the surface layer.

  The fixing belt 61 contacts 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 (for example, 165 to 200 [° C.]). 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 heating sources 60 </ b> C and 60 </ b> D (halogen heaters) that heat the fixing belt 61. The outer diameter of the heating roller 62 is 58 [mm], and for example, the outer peripheral surface of a cylindrical metal core made of aluminum or the like is covered with a resin layer coated with PTFE.

  The temperatures of the heating sources 60C and 60D are controlled by the control unit 100. The heating roller 62 is heated by the heating sources 60C and 60D, and as a result, the fixing belt 61 is heated. The heating sources 60C and 60D and the heating roller 62 function as the “heating unit” of the present invention.

  The main power supply 80 (functioning as the “first power supply unit” of the present invention) supplies power for heating the heating roller 62 to the heating source 60 </ b> C under the control of the control unit 100.

  The sub power supply 90 (functioning as the “second power supply unit” of the present invention) supplies the power for heating the heating roller 62 to the heating source 60D under the control of the control unit 100. The sub power supply 90 has a power storage unit 92 that stores power received from the main power supply 80 or a self-generating power source (not shown), and supplies the power stored in the power storage unit 92 to the heating source 60D. In addition, the electrical storage part 92 is comprised by electrical storage cells, such as a lead storage battery, a nickel hydride battery, a lithium ion battery, a lithium ion capacitor, an electric double layer capacitor, as an example. As an example, the self-power generation type power source includes a power generation cell such as a solar cell, a thermoelectric conversion element, a vibration power generation element, or a wireless power generation element.

  The control unit 100 controls the main power supply 80 and the sub power supply 90 so that the temperature of the fixing belt 61 is maintained within the fixing allowable temperature range.

  The upper pressure roller 63 has, for example, an outer diameter of 70 [mm], and a solid metal core made of metal such as iron is used as an elastic layer with a heat-resistant silicon rubber (hardness of 20 [mm]). : JIS-A10 [°]), and further coated with a resin layer coated with PTFE, which is a low-friction, heat-resistant resin having a thickness of 5 to 30 [μm]. 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 has an outer diameter of 70 [mm], and heat resistant silicon rubber (hardness JIS- with the outer peripheral surface of a base layer made of PI (polyimide) having a thickness of 70 [μm] as an elastic layer. A30 [°]), and the outer peripheral surface of the elastic layer is covered with a resin layer of a PFA tube having a thickness of 30 to 100 [μm] as a surface release layer.

  The control unit 100 controls the main drive source (drive motor) to rotate the lower pressure roller 65 in the arrow B direction (counterclockwise direction). Drive control of the drive motor (for example, rotation on / off, peripheral speed, etc.) is performed by the control unit 100. The peripheral speed of the lower pressure roller 65 is, for example, 460 [mm / s].

  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 (for example, 80 to 120 [° C.]).

  The lower pressure roller 65 is pressed against the upper pressure roller 63 via the fixing belt 61 with a predetermined fixing load (for example, 2650 [N]). 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. The contact pressure (surface pressure) between the fixing belt 61 and the lower pressure roller 65 in the fixing nip NP is, for example, 30.67 [N / cm 2].

  When the lower pressure roller 65 is driven and rotated in the direction of arrow B, the fixing belt 61 is driven to rotate in the direction of arrow C (clockwise direction). Along with this, the upper pressure roller 63 is driven to rotate in the direction of arrow D (clockwise direction). Further, the tension member 64 is driven to rotate in the direction of arrow E (clockwise direction). 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 (for example, 460 [mm / s]).

  The air separation unit 60 </ b> E (functioning as the “air blowing unit” of the present invention) includes a fan air blowing unit 66 (functioning as the “air blowing fan” of the present invention) and an air duct 67. The air separation unit 60E blows air toward the fixing belt 61 from the paper discharge side of the fixing nip NP. The air separation unit 60E may have a configuration in which a plurality of (for example, five) air separation units 60E are arranged in the axial direction of the upper pressure roller 63.

  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 base end side of the air duct 67 is connected to the air blowing port 66 c 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 of 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 and the air flow [%] (the air flow ratio with respect to the maximum air flow) are controlled by the control unit 100.

  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 60E separates the paper S from the fixing belt 61 by blowing air onto the leading edge of the paper S that has passed through the fixing nip NP.

  Next, the control operation before and after the first sheet S of the print job reaches the fixing nip NP when the print job is executed will be described. FIG. 4 is a diagram illustrating changes in the surface temperature of the fixing belt 61 according to the power supply operation and the air blowing operation in the present embodiment. The control unit 100 supplies power by the main power supply 80 while the print job is being executed. As shown in FIG. 4, the control unit 100 controls the fan blower 66 to fix the first sheet S of the print job from the sheet discharge side of the fixing nip NP before reaching the fixing nip NP. A blowing operation for blowing air toward the belt 61 is started (blowing operation ON). In the present embodiment, it takes 1.0 [seconds] from the start of the air blowing operation until the air blowing amount set in advance according to the basis weight of the paper S is reached. Here, as shown by a curve L2 in FIG. 4, during the period from the start of air blowing toward the fixing belt 61 from the paper discharge side of the fixing nip NP until the leading edge of the paper S reaches the fixing nip NP. 61 causes an unintended temperature drop and deviates from the fixing allowable temperature range (in the example of FIG. 4, the range from the fixing possible temperature of 165 [° C.] to the set temperature of 180 [° C.]). As a result, during the subsequent fixing process, heat supply to the paper S is insufficient, and defective fixing or uneven gloss of the image, that is, defective image occurs.

  Therefore, in the present embodiment, the control unit 100 starts the power supply by the sub power source 90 in accordance with the temperature drop of the fixing belt 61 due to the air blowing operation of the air separation unit 60E. More specifically, the control unit 100 uses the sub-power supply 90 after the time when the air blowing operation of the air separation unit 60E is started until the amount of air blown by the fan air blower 66 reaches a preset air volume. Power supply is started (power supply operation ON). Thereafter, the control unit 100 stops the power supply by the sub power source 90 when the leading edge of the sheet S reaches the fixing nip NP (power supply operation OFF). As a result, as shown by a curve L1 in FIG. 4, the temperature of the fixing belt 61 is prevented from decreasing after the air blowing operation of the air separation unit 60E is started until the leading edge of the sheet S reaches the fixing nip NP. Can do.

  In a short time until the leading edge of the sheet S reaches the fixing nip NP, a power supply operation is performed from the sub power source 90 having the power storage unit 92 that can store a large amount of power in a short time and can be used at once. Is desirable. When the power supply operation from the main power supply 80 to the heating source 60C is performed, the power supply amount of the main power supply 80 (for example, 1000 [W]) is large, and it is difficult to control the temperature of the fixing belt 61 in a short time. This is because it exceeds the temperature (180 [° C.] in the example of FIG. 4). The power storage unit 92 accumulates the electric power received from the main power supply 80 or the self-power generation type power supply at a timing other than the time from when the air blowing operation of the air separation unit 60E is started until the leading edge of the sheet S reaches the fixing nip NP. .

  After the power supply by the sub power supply 90 is stopped, the control unit 100 keeps the temperature of the fixing belt 61 within the allowable fixing temperature range by supplying power only from the main power supply 80 while the air separation unit 60E continues the air blowing operation. With the power supply control described above, the power supply by the auxiliary power supply 90 is started in response to the temperature drop of the fixing belt 61 due to the air blowing operation of the air separation unit 60E, so that the temperature of the fixing belt 61 deviates from the fixing allowable temperature range. Can be prevented. As a result, it is possible to prevent insufficient supply of heat to the paper S during the subsequent fixing process, and to prevent image defects such as fixing defects and uneven glossiness of images.

  It should be noted that the control unit 100 can perform any timing as long as it is between the time when the air separation operation of the air separation unit 60E is started and before the leading edge of the first sheet S of the print job reaches the fixing nip NP. Then, the power supply by the sub power supply 90 may be started. Further, the control unit 100 may start the power supply by the sub power supply 90 at an arbitrary timing before the air blowing operation of the air separation unit 60E is started. Further, the control unit 100 may stop the power supply from the sub power source 90 when the fixing belt 61 is in a fixable state where the temperature of the fixing belt 61 can be maintained within the allowable fixing temperature range by supplying power only from the main power source 80. From the viewpoint of preventing the occurrence of image defects on all the sheets of the print job, the control unit 100 makes the fixing possible state before the leading edge of the first sheet S of the print job reaches the fixing nip NP. It is desirable to control the sub power supply 90.

  Moreover, as shown in FIG. 5, the control part 100 starts the electric power supply by the sub power supply 90 at the time of the ventilation operation | movement of the air separation unit 60E being started, and after that, the ventilation volume by the air separation unit 60E increases. Accordingly, the sub power supply 90 may be controlled so as to increase the amount of power to be supplied stepwise. As a result, the temperature of the fixing belt 61 can be maintained within the allowable fixing temperature range until the leading edge of the sheet S reaches the fixing nip NP while minimizing the power consumption of the sub power supply 90. The controller 100 may increase the amount of power supplied from the sub power supply 90 linearly or non-linearly, not stepwise, as the amount of air blown by the air blowing operation of the air separation unit 60E increases. Further, the control unit 100 starts power supply by the sub power source 90 after the air blowing operation of the air separation unit 60E is started, and the power amount supplied from the sub power source 90 is increased as the air flow amount by the air separation unit 60E increases. You may increase in steps.

  FIG. 6 is a table showing the relationship between the basis weight of the paper S, the amount of air blown by the air separation unit 60E, and the amount of power supplied by the main power supply 80 and the sub power supply 90. Here, the amount of power supplied from the main power supply 80 to the heating source 60C is set to 1000 [W]. As shown in FIG. 6, when the basis weight of the paper S is 129 or more, the separation performance of the paper S with respect to the fixing belt 61 is good, and the preset air flow rate for separating the paper S from the fixing belt 61 is 30. The temperature drop of the fixing belt 61 due to the air blowing operation of the air separation unit 60E is small. Therefore, the control unit 100 sets the power supply amount by the sub power supply 90 to be small (200 [W]). On the other hand, when the basis weight of the sheet S is 128 or less, the separation performance of the sheet S with respect to the fixing belt 61 is poor, and the preset air flow rate for separating the sheet S from the fixing belt 61 is as large as 80 [%]. The temperature drop of the fixing belt 61 due to the air blowing operation of the air separation unit 60E is large. Therefore, the control unit 100 sets the power supply amount by the sub power supply 90 to be large (600 [W]).

  FIG. 7 is a table showing the relationship between the amount of power supplied by the sub power supply 90 and the separation and fixing properties of the paper S. Here, the basis weight of the sheet S is 128, and the air blowing amount for separating the sheet S from the fixing belt 61 is set to 80 [%]. As shown in FIG. 7, when the power supply amount by the sub power supply 90 is 0 [W] or 300 [W], the separation property of the paper S with respect to the fixing belt 61 is good, but the fixing property of the paper S is bad. (Fixing failure). That is, the power supply amount of the sub power supply 90, and hence the heating amount of the heating source 60D with respect to the fixing belt 61, is small, and the temperature decrease of the fixing belt 61 due to the air blowing operation of the air separation unit 60E cannot be sufficiently prevented. On the other hand, when the power supply amount by the sub power supply 90 is 600 [W], the separation property of the paper S with respect to the fixing belt 61 and the fixing property of the paper S are good. That is, the power supply amount of the sub power supply 90, and hence the heating amount of the heating source 60D with respect to the fixing belt 61 is large, and the temperature drop of the fixing belt 61 due to the air blowing operation of the air separation unit 60E can be sufficiently prevented.

  As described above in detail, in the present embodiment, the image forming apparatus 1 includes the fixing member (fixing belt 61) used for heating and fixing the toner image on the sheet S in the fixing nip NP, the fixing nip, and the fixing nip. An air blowing unit (air separation unit 60E) for blowing air from the paper discharge side of the NP toward the fixing member, a heating unit (heating sources 60C and 60D and the heating roller 62) for heating the fixing member, and supplying power to the heating unit The first power supply unit (main power supply 80), the second power supply unit (sub power supply 90) that supplies power to the heating unit, which is different from the first power supply unit, and the fixing member temperature is allowed to be fixed. And a control unit 100 that controls the first power supply unit and the second power supply unit so as to be held in the temperature range. The control unit 100 starts power supply by the second power supply unit in response to a temperature decrease of the fixing member due to the air blowing operation of the air blowing unit.

  According to the present embodiment configured as described above, since the power supply by the second power supply unit is started in response to the temperature decrease of the fixing member due to the air blowing operation of the air blowing unit, the fixing member is It is possible to shorten the time required to return to the fixing temperature. As a result, it is possible to prevent insufficient supply of heat to the paper S during the subsequent fixing process, and to prevent image defects such as fixing defects and uneven glossiness of images.

  In the above embodiment, the case where the sheet S is separated from the fixing belt 61 (fixing member) by blowing air from the sheet discharge side of the fixing nip NP toward the fixing belt 61 has been described. It is not limited. For example, when the lower pressure roller 65 is cooled by blowing air from the paper discharge side of the fixing nip NP toward the lower pressure roller 65 to prevent the surface temperature of the lower pressure roller 65 from becoming too high. The present invention can be applied. In this case, if the surface temperature of the lower pressure roller 65 decreases, the fixing belt 61 that contacts the lower pressure roller 65 causes an unintended temperature decrease, and heat is supplied to the paper S during the subsequent fixing process. A shortage occurs. As a result, defective fixing or uneven gloss of the image, that is, defective image occurs. Therefore, the control unit 100 supplies power from the sub power supply 90 after the start of the air blowing operation to the lower pressure roller 65 and before the leading edge of the first sheet S of the print job reaches the fixing nip NP. Let it begin. Thereby, the temperature drop of the fixing belt 61 due to the blowing operation with respect to the lower pressure roller 65 can be prevented. Therefore, it is possible to prevent the occurrence of image defects such as fixing defects and uneven gloss of images.

  In the above-described embodiment, the fixing nip NP has been described as an example in which the upper fixing unit 60A is configured by a belt fixing method including the heating roller 62 and the fixing belt 61 in addition to the upper pressure roller 63. Is not limited to this. For example, the fixing nip NP may be configured by a roller fixing method in which the upper fixing unit 60A includes only the heating roller 62 that functions as a fixing member.

  In the above embodiment, the example in which the lower fixing unit 60B includes the lower pressure roller 65 has been described, but the present invention is not limited to this. For example, the lower fixing unit 60 </ b> B may be configured by a belt pressing method having a heating roller and a pressure belt in addition to the lower pressure roller 65.

  In the above-described embodiment, an example in which the heating roller 62 includes two heating sources 60C and 60D has been described, but the present invention is not limited to this. For example, the heating roller 62 may incorporate one or three or more heating sources. When the heating roller 62 includes only one heating source, the heating source is supplied with power from both the main power source 80 and the sub power source 90.

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, 60D Heating source 60E Air separation Unit 61 Fixing belt 62 Heating roller 63 Upper pressure roller 64 Stretch member 65 Lower pressure roller 66 Fan air blower 67 Air blow duct 71 Communication unit 72 Storage unit 80 Main power supply 90 Sub power supply 92 Power storage unit 100 Control unit 101 CPU
102 ROM
103 RAM
NP fixing nip

Claims (8)

A fixing member used to heat and fix the toner image on the paper in the fixing nip;
A blower that blows air from the paper discharge side of the fixing nip toward the fixing member;
A heating section for heating the fixing member;
A first power supply unit for supplying power to the heating unit;
A second power supply unit for supplying power to the heating unit, different from the first power supply unit;
A control unit that controls the first power supply unit and the second power supply unit so that the temperature of the fixing member is maintained within a fixing allowable temperature range;
With
The image forming apparatus according to claim 1, wherein the control unit starts power supply by the second power supply unit in response to a temperature decrease of the fixing member due to a blowing operation of the blower unit.   The control unit starts power supply by the second power supply unit after the time when the air blowing operation of the air blowing unit is started and before the leading edge of the first sheet of the print job reaches the fixing nip. The image forming apparatus according to claim 1, wherein:   The control unit stops the power supply by the second power supply unit when the fixing unit is in a fixable state in which the temperature of the fixing member can be maintained within the allowable fixing temperature range by supplying power only from the first power supply unit. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises:   The control unit controls the second power supply unit so that the fixing is possible before a leading edge of a first sheet of a print job reaches the fixing nip. The image forming apparatus according to any one of 1 to 3.   The image according to any one of claims 1 to 4, wherein the power supply unit includes a power storage unit that stores power, and supplies the power stored in the power storage unit to the heating unit. Forming equipment.   The said control part controls the said 2nd electric power supply part so that the electric power supplied may be increased as the ventilation volume by the said ventilation part increases, The any one of Claims 1-5 characterized by the above-mentioned. The image forming apparatus described in 1.   The image according to any one of claims 1 to 6, wherein the air blowing unit separates the paper from the fixing member by blowing air from the paper discharge side of the fixing nip toward the fixing member. Forming equipment.   The image forming apparatus according to claim 1, wherein the blower unit includes a blower fan.

Images