JP2011253113A - Fixing device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce degradation of sheet-cooling performance and suppress a fall of a fixing temperature while securing a sheet separating function by use of separation air.SOLUTION: A heat sink 46 is disposed at a downstream from a fixing section 31 in a conveyance passage of sheet P so as to cool the sheet P. A blower fan 36 sucks air heated by heat radiation of the heat sink 46, and blows the sucked air as separation air. A blower duct 37 is disposed between the fixing section 31 and the heat sink 46, and leads the separation air from the blower fan 36 toward a sheet ejection side of the sheet P in a fixing nip section NP.

Description

  The present invention relates to a fixing device and an image forming apparatus.

  2. Description of the Related Art Conventionally, electrophotographic image forming apparatuses are known as printers, copiers, and the like. In this image forming apparatus, when a toner image is formed on a sheet, the toner image is transferred to the sheet, and then the sheet passes through a pair of fixing members in the fixing device to fix the toner image on the sheet.

  For example, Patent Document 1 discloses an image forming apparatus including a cooling device that cools a sheet after fixing. This cooling device is disposed downstream of the fixing device in the sheet conveyance direction, and specifically includes a heat radiating member such as a heat sink disposed on an inner peripheral surface portion of an endless belt that conveys the sheet. The sheet after fixing is conveyed by the endless belt and passes through the heat radiating member, whereby the sheet is cooled. The heat dissipating member is provided with an exhaust duct connected to an intake fan, and discharges hot air to the outside of the apparatus.

  In addition, in this type of image forming apparatus, there is a problem that the sheet that has passed through the fixing nip portion is wound around the fixing member and is not separated from the fixing member because fixing is performed by heating and pressing. In view of this, an image forming apparatus that separates a sheet from a fixing member by blowing air onto the sheet from the sheet discharge side of the fixing nip portion is disclosed (for example, see Patent Document 2).

JP 2010-14805 A Japanese Patent Laying-Open No. 2005-258035

  However, according to the technique disclosed in Patent Document 1, heat from the fixing device is transferred to the heat radiating member, which may reduce the cooling performance of the paper. Further, according to the technique disclosed in Patent Document 2, since the separation air is blown onto the fixing member, the surface temperature of the fixing member is lowered, and the fixing temperature may be lowered.

  The present invention has been made in view of such circumstances, and an object thereof is to suppress a decrease in fixing temperature while suppressing a decrease in sheet cooling performance and obtaining a sheet separating function by a separation wind.

  In order to solve this problem, according to a first aspect of the present invention, a sheet is passed through a fixing nip formed by press-contacting a pair of fixing members, and the toner image transferred to the sheet is heated by a heating unit. A fixing unit for fixing the toner image on the sheet, a blowing unit for separating the sheet from the fixing member by blowing gas to the sheet from the sheet discharge side in the fixing nip, and a sheet conveyance path And a heat dissipating member disposed downstream of the fixing unit to cool the paper. Here, the air blowing unit is disposed between the fixing unit and the heat radiating member, and is arranged between the fixing unit and the heat radiating member for sucking the gas heated by the heat radiation from the heat radiating member and blowing the sucked gas as a separation wind. And an air duct that guides the separation air from the sheet to the paper discharge side in the fixing nip portion.

  Here, the first invention further includes a duct internal temperature detection unit that detects the temperature of the gas flowing through the air duct as the duct internal temperature, and a control unit that controls the amount of gas blown by the air blowing unit. Is preferred. In this case, it is preferable that the control unit determines the air volume necessary for the heat radiating member to maintain the cooling performance of the paper as the gas air volume by the air blowing unit, based on the duct internal temperature detected by the duct internal temperature detection unit. .

  In the first aspect of the invention, it is desirable that the control unit determines the power to be supplied to the heating unit based on the determined gas flow rate and the duct internal temperature.

  According to a second aspect of the present invention, an image forming unit that transfers a toner image onto a sheet, a fixing unit that performs a fixing process on the sheet onto which the toner image has been transferred, and a downstream of the fixing unit in the sheet conveyance path. And a heat radiating member that cools the paper, and the fixing unit heats the toner image transferred onto the paper by passing the paper through a fixing nip formed by pressing the pair of fixing members. A fixing unit that fixes the toner image on the sheet by applying heat from the unit; and a blowing unit that separates the sheet from the fixing member by blowing gas to the sheet from the sheet discharge side in the fixing nip unit. An image forming apparatus having Here, the air blowing unit is disposed between the fixing unit and the heat radiating member, and is arranged between the fixing unit and the heat radiating member for sucking the gas heated by the heat radiation from the heat radiating member and blowing the sucked gas as a separation wind. And an air duct that guides the separation air from the sheet to the paper discharge side in the fixing nip portion.

  Here, according to the second aspect of the present invention, the air blowing unit is configured to detect the temperature of the gas flowing in the air duct as the air temperature in the duct, and the air blowing means performs air blowing based on the air temperature in the duct detected by the air temperature detector. It is preferable to further include a control unit that controls the air volume of the gas to be performed.

  Moreover, it is preferable that a control part determines the electric power supplied to a heating means based on the air volume of the gas which a ventilation means blows, and the temperature in a duct.

  In the second invention, it is preferable that the control unit determines the air volume of the gas by the blowing unit based on the type of the paper passing through the fixing unit in the image forming mode in which the toner image is formed on the paper in accordance with the print command. .

  In this case, the control unit estimates the heat loss of the fixing unit due to the gas blown from the blowing unit based on the duct internal temperature detected by the duct internal temperature detection unit and the determined gas flow rate. It is desirable to determine the power supplied to the heating means based on the above.

  In the second aspect of the invention, in the standby mode in which the control unit waits for a print command in a state where image formation is possible, the heat radiating member has a sheet cooling performance based on the duct internal temperature detected by the duct internal temperature detection unit. It is preferable to determine the air volume necessary for maintaining the air volume as the gas air volume by the blowing means.

  In this case, the second invention may further include a wind direction plate for switching the direction of the gas flowing in the air duct. The control unit controls the wind direction plate to suppress the amount of gas blown out to the fixing nip, and reduces the power supplied to the heating unit as compared with the reference power corresponding to the predetermined fixing temperature. It is preferable to make it.

  In the second invention, in the sleep mode for suppressing power consumption, the control unit stops the blowing from the blowing unit and compares the power supplied to the heating unit with a reference power corresponding to a predetermined fixing temperature. Therefore, it is preferable to lower the thickness.

  Furthermore, in the second invention, the control unit controls the wind direction plate by increasing the power supplied to the heating means to the reference power corresponding to the predetermined fixing temperature in the return mode in which the sleep mode is switched to the standby mode. It is preferable to determine the amount of air necessary for the heat radiating member to maintain the cooling performance of the sheet as the amount of gas blown by the blowing unit while suppressing the amount of gas blown to the fixing nip portion.

  According to the present invention, since the duct functions as a buffer layer because the duct exists between the fixing unit and the heat dissipation member, heat transfer from the fixing unit to the heat dissipation member can be suppressed. Thereby, the fall of the cooling performance of the paper by a heat radiating member can be suppressed. Moreover, the temperature of a separation wind can be raised by utilizing the gas heated by the thermal radiation from a heat radiating member as a separation wind. Accordingly, it is possible to suppress a decrease in the fixing temperature while obtaining the air separation function of the paper by the separation wind.

Configuration diagram schematically showing image forming apparatus 1 Sectional drawing which shows typically the principal part of the image forming apparatus 1 centering on the fixing device 30 Sectional drawing which shows typically the principal part of the image forming apparatus 1 centering on the fixing device 30 Block diagram schematically showing a control system of the image forming apparatus 1 A flowchart showing a control procedure by the fixing controller 70 in the standby mode. A flowchart showing a control procedure by the fixing control unit 70 in the image forming mode. A flowchart showing a control procedure by the fixing control unit 70 in the sleep mode. A flowchart showing a control procedure by the fixing control unit 70 in the transition mode.

  FIG. 1 is a configuration diagram schematically showing an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 is an electrophotographic image forming apparatus such as a copying machine, for example, and forms a full-color image by arranging a plurality of photoconductors facing a single intermediate transfer belt in a vertical direction. A tandem type color image forming apparatus.

  The image forming apparatus 1 mainly includes a document reading device (not shown), exposure units 15Y, 15M, 15C, and 15K, charging / developing units 20Y, 20M, 20C, and 20K, an intermediate transfer belt 23, and a fixing device (fixing unit) 30. These are housed in a single housing.

  The document reading apparatus has an automatic document feeder (not shown) provided at the upper part of the apparatus housing, reads an image of a document being conveyed, and performs image processing on the obtained image signal. Specifically, the document reading device irradiates an image of the document with a lamp and forms an image of the reflected light on the light receiving surface of the image sensor. The image sensor photoelectrically converts incident light and outputs a predetermined image signal. The document reading apparatus performs processing such as A / D conversion, shading correction, and compression on the image signal, and outputs the image signal to the image formation control unit 60 (see FIG. 4) described later. Note that the image data input to the image forming control unit 60 is not limited to the data read by the document reading device, and is, for example, data received from a personal computer connected to the image forming device 1 or another image forming device. There may be.

  Each of the exposure units 15Y to 15K includes a laser light source, a polygon mirror, a plurality of lenses, and the like. Each of the exposure units 15Y to 15K scans and exposes the surfaces of photosensitive drums 21Y, 21M, 21C, and 21K, which will be described later, with a laser beam corresponding to output information output from the image formation control unit 60 based on the image data. To do.

  The charging / developing unit 20Y is mainly composed of a photosensitive drum 21Y and a charging / developing unit 22Y disposed around the photosensitive drum 21Y, and forms a toner image corresponding to yellow on the photosensitive drum 21Y. The remaining charging / developing units 20M, 20C, and 20K have the same configuration as that of the charging / developing unit 20Y, and charging / developing units 22M, 22C, and 22K are provided around the photosensitive drums 21M, 21C, and 21K, respectively. The toner images corresponding to magenta, cyan, and black are formed on the photosensitive drums 21M, 21C, and 21K, respectively.

  The surface of each of the photoconductive drums 21Y to 21K is uniformly charged by the charging / developing units 22Y to 22K, and each of the photoconductive drums 21Y to 21K is scanned and exposed by the above-described exposure units 15Y to 15K. A latent image is formed. Further, the charging / developing units 22Y to 22K develop latent images on the photosensitive drums 21Y to 21K by developing with toner. As a result, toner images are formed on the photosensitive drums 21Y to 21K. The toner images formed on the individual photosensitive drums 21 </ b> Y to 21 </ b> K are sequentially transferred to predetermined positions on the intermediate transfer belt 23.

  On the other hand, as indicated by an arrow A, the paper P is fed from a paper storage tray (not shown), and is transported to the transfer roller 24 via a paper feed roller 50 and a registration roller 51 provided in the transport path. The transfer roller 24 transfers the toner image transferred onto the intermediate transfer belt 23 onto the paper P sent out by the registration roller 51 at the timing.

  Each of these elements, that is, the exposure units 15Y to 15K, the charging / developing units 20Y to 20K, the intermediate transfer belt 23, and the transfer roller 24 constitute an image forming unit. That is, the image forming unit (1) charges the photosensitive drums 21Y to 21K. (2) The exposure units 15Y to 15K form electrostatic latent images on the photosensitive drums 21Y to 21K. (4) The toner images on the photosensitive drums 21Y to 21K are primarily transferred to the intermediate transfer belt 23. (5) The toner images on the intermediate transfer belt 23 are transferred onto the paper P. The toner image is transferred to the paper P through a series of processes of next transfer.

  The sheet P having the transferred toner image, that is, the unfixed toner image on the fixing target surface, is sent to the fixing device 30 via the conveyance belt 52. The fixing device 30 fixes the toner image on the paper P by pressurizing and heating the paper P as will be described later.

  The paper discharge unit 40 includes a paper discharge roller, a guide member (not shown), and the like. The paper discharge unit 40 conveys the paper P that has undergone the fixing process by the fixing unit 25 and is attached to the external side surface of the apparatus housing (paper tray ( The paper P is discharged to a not shown.

  Further, when image formation is performed also on the back surface of the paper P, the paper discharge unit 40 conveys the paper P after the fixing processing of the toner image on the front surface to the reversing roller 41 below by the guide member. The reverse roller 41 sandwiches the rear end of the paper P, reverses the paper P by reverse feeding, and sends the paper P to the refeed conveyance path 42.

  Further, in the present embodiment, the paper discharge unit 40 includes a paper cooling unit 45 that cools the paper P after passing through the fixing device 30, and the paper cooling unit 45 is in the conveyance path of the paper P. It is arranged downstream. The paper cooling unit 45 has a heat sink (heat radiating member) 46 having a plurality of heat radiating fins on the surface of a plate-like member made of metal such as aluminum or copper, which easily conducts heat, and the conveyance path of the paper P It arrange | positions in the state which surface-contacted with the member which comprises. The heat sink 46 absorbs heat of the transport path and the paper P transported through the transport path and dissipates the heat, thereby cooling the paper P heated in the fixing device 30.

  In addition, the sheet cooling unit 45 includes a cooling fan 47 and an outside air introduction duct 48. By operating the cooling fan 47, air outside the apparatus housing is supplied to the heat sink 46 via the outside air introduction duct 48. can do. By supplying outside air to the heat sink 46 by the cooling fan 47, the heat exchange (heat radiation) efficiency in the heat sink 46 can be improved.

  Here, on the side facing the sheet cooling unit 45 through the sheet P conveyance path, a sheet conveyance unit 49 that conveys the sheet P along the lower surface of the sheet cooling unit 45 is provided. The sheet conveying unit 49 is, for example, a belt conveying mechanism mainly composed of an endless belt 49a, and the endless belt 49a is held by a plurality of rollers (not shown). The endless belt 49a rotates at a predetermined speed in the direction of the arrow in the drawing when each of the rollers that hold the belt is driven to rotate.

  The paper transport unit 49 further includes a suction duct 49b and a suction fan 49c. The suction fan 49 is provided in an adsorption duct 49 provided below the endless belt 49a. When the suction fan 49 sucks air, the conveyed paper P is adsorbed toward the endless belt 49a. Thereby, the conveyance performance of the paper P is improved. For example, the suction duct 49 is connected to an exhaust duct 37e described later.

  FIG. 2 is a cross-sectional view schematically showing a main part of the image forming apparatus 1 with the fixing device 30 as the center. The fixing device 30 includes a fixing unit 31 and a blower unit 35.

  The fixing unit 31 is mainly composed of an upper fixing roller 32 and a lower fixing roller 33. The upper fixing roller 32 and the lower fixing roller 33 are arranged in pressure contact with each other, and a fixing nip portion NP is formed at the press contact portion between the upper fixing roller 32 and the lower fixing roller 33. Here, when the sheet P passes through the fixing nip NP, the upper fixing roller 32 is disposed above the sheet surface, and the lower fixing roller 33 is disposed below the sheet surface.

  The fixing upper roller 32 is configured by laminating an elastic layer such as silicone rubber and a release layer made of fluorine resin on the surface of a cylindrical steel or aluminum pipe. Inside the upper fixing roller 32, a heater 34 is incorporated as a heating means for heating the upper fixing roller 32, that is, for thermally fixing the toner image on the paper P. The fixing upper roller 32 is heated by the radiant heat from the heater 34. The fixing upper roller 32 is rotationally driven in accordance with the passing speed of the paper P by receiving power from a driving means (for example, a motor) (not shown).

  The lower fixing roller 33 is configured by laminating an elastic layer such as silicone rubber and a release layer made of fluorine resin on the surface of a cylindrical steel or aluminum pipe. Note that the lower fixing roller 33 can include a heater (not shown) in the same manner as the upper fixing roller 32, and is configured to be able to apply heat supplementarily for thermal fixing.

  The sheet P is conveyed in such a manner that the surface to be fixed faces the upper fixing roller 32 and passes through the fixing nip NP in the process of conveying the sheet P. As a result, the toner image is fixed on the fixing target surface of the paper P through the pressure applied by the upper fixing roller 32 and the lower fixing roller 33 and the heat action of the upper fixing roller 32.

  The blower unit 35 is configured by a blower fan 36 and a blower duct 37, and is disposed downstream of the fixing unit 31 in the conveyance path of the paper P. A plurality of blower fans 36 are arranged around a heat sink 46 that is a sheet cooling unit 45, and a blower duct 37 is disposed between the heat sink 46 and the fixing upper roller 32, specifically, from the heat radiation of the heater 34 to the heat sink 46. It is arranged in such a way as to block out. The air blown from the blower fan 36 flows through the blower duct 37 and is then discharged from the end of the blower duct (blower port 37a). The paper P is fixed by the wind pressure of the air (separate wind) blown from the blower port 37a. Separated from the upper roller 32 (air separation).

  The blower fan 36 is a blower unit that blows air (separated air) with a rotating fan, and is a multi-blade fan that includes a large number of forward blades that can rotate. The blower fan 36 of the present embodiment can blow the separated wind, stop the blow of the separated wind, and adjust the volume of the separated wind by controlling the rotation speed. The blower fan 36 is arranged so that the air intake port faces the heat sink 46, and air from the cooling fan 47 via the heat sink 46 or air from the periphery of the heat sink 46 via the heat sink 46 to the inside. The air is sucked and blown as separated air. That is, the blower fan 57 sucks in the gas heated by the heat radiation of the heat sink 46 and blows it as separated air.

  The air duct 37 is a duct made of a metal such as aluminum and having substantially the same width as the fixing upper roller 32 in the paper surface direction of FIG. The air duct 37 is configured by an air outlet 37a that blows air toward the fixing nip portion NP and an air guide portion 37b that guides air toward the air outlet 37a. The air blown from the blower fan 36 is guided by the blower guide portion 37b and discharged from the blowout port 37a.

  The blower outlet 37a of the blower duct 37 is located at a position shifted from the front side of the discharge side of the fixing nip NP (on the conveyance path of the paper P) toward the fixing upper roller 32, and from the tangential direction of the roller to the upper fixing roller. It is arranged at a position where the separation wind flows to 32. Such an arrangement of the air outlet 37a is such that the fixing upper roller 32 that contacts the fixing target surface of the paper P among the upper fixing roller 32 and the lower fixing roller 33 that are in contact with the paper P in the fixing nip NP is more paper. This is based on the knowledge that the winding tendency of P is strong.

  On the other hand, the air blowing guide portion 37b of the air blowing duct 37 includes a duct wall surface so as to face the fixing upper roller 32 (heater 34), and receives heat radiated from the fixing upper roller 32 (radiant heat caused by the heater 34). It becomes a reception area. For this reason, the air duct 37 receives heat radiated from the heat receiving surface to exchange heat with the air (separated air) flowing through the air blowing guide portion 37b, thereby heating the separated air. it can. Further, the heat from the heater 34 is absorbed by the separated wind by such heat exchange, and the air flowing in the air duct 37 functions as a buffer layer. Heat transfer to the heat sink 46 can be suppressed.

  The air duct 37 includes an exhaust duct 37e for exhausting the separated air flowing through the air blowing guide portion 37b, and a wind direction plate for suppressing the amount of the separated air blown from the outlet 37a by changing the flow of the separated air. 37c and 37d are provided. One wind direction plate (first wind direction plate) 37c has a function of regulating the flow of the separated wind reaching the outlet 37a, and the other wind direction plate (second wind direction plate) 37d is an exhaust gas. It plays a function of regulating the flow of the separation wind to the duct 37e. Each of the wind direction plates 37c and 37d is configured to be rotatable by a drive mechanism (not shown), and the flow of the separated wind can be changed by changing the rotation position.

  As shown in FIG. 2, when the wind direction plates 37c and 37d are set to the normal position, the first wind direction plate 37c opens the flow path leading to the outlet 37a, and the second wind direction plate 37d. Closes the opening connected to the exhaust duct 37e. In this case, the separated air from the blower fan 36 is discharged from the blower outlet 37a and blown to the fixing nip portion NP.

  On the other hand, as shown in FIG. 3, when the wind direction plates 37c and 37d are set to the blowout stop position, the first wind direction plate 37c closes the flow path to the blowout port 37a, and the second The wind direction plate 37d opens an opening connected to the exhaust duct 37e. In this case, the separated air from the blower fan 36 is not discharged from the blower outlet 37a but flows to the exhaust duct 37e, whereby the blowout to the fixing nip portion NP is stopped.

  Further, the rotational position of the wind direction plates 37c and 37d can be set to an arbitrary position between the normal position and the blowing stop position (hereinafter referred to as “intermediate position”), and according to the intermediate position, It is also possible to adjust the air volume of the separated air discharged from the air outlet 37a.

  FIG. 4 is a block diagram schematically showing a control system of the image forming apparatus 1 according to the present embodiment. The control system of the image forming apparatus 1 mainly includes an image formation control unit 60 and a fixing control unit 70. The image formation control unit 60 and the fixing control unit 70 are configured to be able to communicate with each other.

  As the image formation control unit 60, for example, a microcomputer mainly composed of a CPU, a ROM, a RAM, and an I / O interface can be used. The image formation control unit 60 performs various calculations according to the control program stored in the ROM, and controls the operation state of the image forming apparatus 1 based on the calculation results.

  The image forming control unit 60 is configured based on information set through an operation unit (not shown) provided in the upper part of the main body of the image forming apparatus 1 or information received together with input image data from a personal computer or other image forming apparatus. The printing conditions, for example, single-sided / double-sided printing type, paper type (for example, paper type such as size, plain paper / thick paper, amount of paper, etc.), image density, magnification, etc. can be acquired. As the operation unit, for example, a touch panel capable of performing an input operation according to information displayed on the display can be used.

The image forming control unit 60 controls each unit of the image forming apparatus 1 to execute a series of processes shown below, thereby transferring the toner image onto the conveyed paper P.
(1) Charge the photosensitive members 21Y to 21K. (2) Form electrostatic latent images on the photosensitive members 21Y to 21K by the exposure units 15Y to 15K. (3) Adhere toner to the formed electrostatic latent images ( 4) Primary transfer of toner images on photoreceptors 21Y to 21K to intermediate transfer belt 23 (5) Transport of paper P (6) Secondary transfer of toner image on intermediate transfer belt 23 to paper P

  Further, the image formation control unit 60 controls the cooling fan 47 so that the heat sink 46 can obtain an air volume necessary for maintaining the cooling performance of the paper P. The control of the cooling fan 47 may be controlled by the fixing control unit 70 described later in correspondence with the control of the blower fan 36 for the separated wind.

  As the fixing control unit 70, for example, a microcomputer mainly composed of a CPU, a ROM, a RAM, and an I / O interface can be used. The fixing control unit 3 performs various calculations according to a control program stored in the ROM, and controls the operation state of the fixing device 30 based on the calculation results.

  Detection signals from various sensors including the duct internal temperature sensor 75 and the fixing temperature sensor 76 are input to the fixing control unit 70. The duct internal temperature sensor 75 is provided inside the air duct 37 and detects the temperature of the separated air in the air duct 37 (hereinafter referred to as “duct temperature”). The fixing temperature sensor 76 is a sensor that detects the surface temperature of the fixing upper roller 32, and detects the temperature (fixing temperature) of heat fixing by the fixing unit 31 through this surface temperature.

  The fixing control unit 70 includes a main control unit 71, a heater control unit 72, and a fan control unit 73 when this is functionally grasped.

  The main control unit 71 controls fixing of the toner image onto the paper P by controlling each unit of the fixing device 30 with reference to signals from the image formation control unit 60 and various sensor signals. For example, the main control unit 71 controls the rotation timing and rotation speed of the upper fixing roller 32 and the lower fixing roller 33 based on a signal from the image formation control unit 60.

  In relation to the present embodiment, the main control unit 71 calculates an air flow command value that is a command value of the air flow of the separated air by the blower fan 36 based on various sensor signals, or an electric power command for the heater 34. Calculate the value. Normally, the main control unit 71 sets the reference air volume (reference air volume) as the air volume command value, but calculates a value changed from the reference air volume according to the operation scene of the image forming apparatus 1 as the air volume command value. Note that the air volume as a control parameter indicates the output of the separated wind blown from the blower fan 36, and is used to include not only the air volume but also state quantities such as wind speed and wind pressure. The main control unit 71 sets the heater power (reference power) corresponding to the fixing temperature necessary for fixing the toner image on the paper P as a power command value, but according to the operation scene of the image forming apparatus 1. A value changed from the reference power is calculated as a power command value. Then, the main control unit 71 outputs an air volume command value, a power command value, and the like to the heater control unit 72 and the fan control unit 73.

  The heater control unit 72 refers to the power command value acquired from the main control unit 71 and is the power (heater power) supplied to the heater 34 built in the upper fixing roller 32, that is, the output of the heater 34. Control the fixing temperature.

  The fan control unit 73 refers to the air volume command value acquired from the main control unit 71, and controls the state of the blower fan 36, specifically, the air volume of the separated wind from the blower fan 36.

  Hereinafter, a control procedure by the fixing control unit 70 will be described with reference to FIGS. The fixing control unit 70 has four control modes including “standby mode”, “image forming mode”, “sleep mode”, and “transition mode” corresponding to the operation scene of the image forming apparatus 1.

(1) Standby Mode “Standby mode” is control executed in a state where a print command is awaited (standby state) in a state where image formation is possible, and the fixing control unit 70 follows the flowchart shown in FIG. The fixing device 30 is controlled. Note that the “standby mode” is executed at a predetermined cycle until the mode shifts to the “image forming mode” or the “sleep mode”.

  First, in step 10 (S10), the main control unit 71 reads the duct internal temperature detected by the duct internal temperature sensor 75.

  In step 11 (S11), the main control unit 71 determines a heat sink cooling air volume. This air volume for cooling the heat sink is an air volume of the blower fan 36 necessary for the heat sink 46 to maintain the cooling performance of the paper P. The air separation fan 36 takes in air from the heat sink 46 side and blows the separated air, so that the heat sink 46 is cooled by the air passing through the heat sink 46 when the blower fan 36 operates. Further, since the separated air supplied to the fixing nip NP through the air duct 37 is air that has passed through the heat sink 46, the temperature inside the duct, which is the temperature of the separated air, is the temperature state of the heat sink 46. It is reflected. Therefore, the cooling capacity of the heat sink 46 can be estimated through this duct internal temperature. For example, it is estimated that the higher the temperature in the duct, the lower the cooling capacity by the heat sink 46.

  Therefore, the main control unit 71 takes into consideration the cooling ability of the heat sink 46 to the paper P, so that the temperature in the duct becomes a certain value or less, that is, the predetermined heat cooling capacity is secured by the heat sink 46. Determine the airflow for cooling the heat sink. For example, the main control unit 71 has a reference temperature for determining the cooling capability of the heat sink 46, and the higher the duct internal temperature is, the higher the air volume that is higher than the reference air volume is. And so on.

  Then, the main controller 71 outputs the determined heat sink cooling air volume to the fan controller 73 as an air volume command value. Accordingly, the fan control unit 73 controls the blower fan 36 based on the heat sink cooling air volume that is the air volume command value.

  In step 12 (S12), the main control unit 71 controls the wind direction plates 37c and 37d to control the wind direction plates 37c and 37d from the normal position to the blowing stop position. By setting the wind direction plates 37c and 37d to the blowing stop position, the blowing of the separation wind to the fixing unit 31 is stopped, so that it is possible to suppress a decrease in fixing temperature due to heat sink cooling. The main control unit 71 may continue the wind direction plates 37c and 37d at the normal position or control them to the intermediate position when it is determined that the temperature in the duct is high enough not to cause a decrease in the fixing temperature. .

  In step 13 (S 13), the main control unit 71 outputs a predetermined power command value to the heater control unit 72 in order to suppress the power consumption of the heater 34. With the control of the wind direction plates 37c and 37d in step 12, the blowing of the separation wind to the fixing unit 31 is suppressed. Therefore, the temperature drop of the fixing unit 31 is suppressed as compared with a scene in which the blowing of the separation wind is continued to the fixing unit 31. Therefore, the power of the heater 34 for maintaining the fixing temperature can be set low as the blowing of the separation air stops. In step 13, from such a viewpoint, the main control unit 71 determines power lower than the reference power as a power command value, and instructs the heater control unit 72. The heater control unit 72 that has acquired the power command value controls the power of the heater 34 based on the power command value.

(2) Image Forming Mode Mode The “image forming mode mode” is control executed when a toner image is formed on the paper P in accordance with a print command, and the fixing control unit 70 performs fixing according to the flowchart shown in FIG. 30 is controlled. When the main control unit 71 obtains a print command from the image formation control unit 60 in response to the input of the image data, the main control unit 71 shifts from the “standby mode” to the “image formation mode mode”.

  First, in step 20 (S20), the main control unit 71 determines the air volume necessary for air separation (hereinafter referred to as “separation”) based on the printing conditions (specifically, the type of paper) acquired from the image formation control unit 60. The air volume ”). In the air separation, there is an appropriate air volume for separating the paper P from the fixing upper roller 32 in accordance with the type (size, type of paper P, haze, etc.) of the paper P to be fixed. For example, for plain paper, it is sufficient if the reference air volume is the separation air volume. However, since thin paper requires a larger air volume when it is wound around the fixing upper roller 32 than the normal paper, the air volume larger than the reference air volume is separated. It seems that it is necessary to use the air volume. Therefore, by acquiring the correspondence between the type of paper P and the separation air volume through experiments and simulations, the main control unit 71 is provided with a map that defines the relationship. The main control unit 71 sets a separation air volume according to the type of the paper P after referring to the map.

  Then, the main control unit 71 outputs the determined separation air volume to the fan control unit 73 as an air volume command value. Accordingly, the fan control unit 73 controls the blower fan 36 based on the separation air volume that is the air volume command value. Moreover, the main control part 71 is controlled to a normal position, when the wind direction plates 37c and 37d are set to other than a normal position.

  In step 21 (S21), the main control unit 71 reads the duct internal temperature detected by the duct internal temperature sensor 75.

  In step 22 (S22), the main control unit 71 controls the heater power based on the separation air volume and the duct internal temperature. Since the separation wind is variable according to the type of the paper P, the temperature of the fixing unit 31 may be lowered from a predetermined fixing temperature depending on the volume of the separation wind and the temperature of the separation wind. Therefore, in step 22, first, the main control unit 71 calculates the temperature decrease amount of the fixing unit 31 with respect to the fixing temperature, that is, the temperature loss, from the separation air volume and the duct internal temperature. The calculation of the temperature loss may be performed by obtaining a necessary data through experiments or simulations, and may be calculated from a map for inputting the separation air volume and the duct internal temperature, or may be calculated from an arithmetic expression. . Then, the main control unit 71 determines the heater power that can maintain the fixing temperature in the fixing unit 31 in consideration of the temperature loss. For example, the main controller 71 determines a value larger than the reference power as the heater power as the temperature loss increases.

  Then, the main control unit 71 outputs the determined heater power to the heater control unit 72 as a power command value. Accordingly, the heater control unit 72 controls the heater 34 based on the power command value.

  In step 23 (S23), the main control unit 71 determines whether or not the final sheet has passed through the fixing unit 31, that is, among the one or more sheets P to be fixed included in one job. It is determined whether or not the sheet P to be subjected to the fixing process has passed through the fixing nip NP. If an affirmative determination is made in step 23, that is, if the final sheet has passed through the fixing unit 31, the present process is terminated. On the other hand, if a negative determination is made in step 23, that is, if the paper P that has passed through the fixing unit 31 is not the final paper, the process proceeds to step 24 (S24).

  In step 24, the main control unit 71 reads the surface temperature of the upper fixing roller 32 from the fixing temperature sensor 76. Then, returning to step 22, the main control unit 71 performs feedback control of the heater power with reference to the surface temperature of the upper fixing roller 32.

(3) Sleep Mode “Sleep mode” is control executed in a sleep state in which the image forming apparatus 1 is operated in a state where power consumption is suppressed, and the fixing control unit 70 follows the flowchart shown in FIG. To control. The main control unit 71 performs the above-described “standby” when the print command is not continuously input for a predetermined time after the image forming operation corresponding to the most recent print command is turned on after the power is turned on or when the user instructs the print command. “Mode” to “Sleep Mode”.

  First, in step 30 (S30), the main controller 71 controls the wind direction plates 37c and 37d to control the wind direction plates 37c and 37d from the normal position to the blowing stop position.

  In step 31 (S31), the main control unit 71 outputs an air volume command value to the fan control unit 73 such that the air volume from the blower fan 53 becomes zero. Accordingly, the fan control unit 73 controls the blower fan 36 based on the air volume command value, and thereby the operation of the blower fan 36 is stopped.

  In step 32 (S32), the main controller 71 outputs a predetermined low power consumption to be set in the sleep state to the heater controller 72 as a power command value in order to suppress the power consumption of the heater 34. And the heater control part 72 which acquired the electric power command value controls the electric power of the heater 34 based on the said electric power command value.

(4) Transition Mode The “transition mode” is a control executed when shifting from the “sleep mode” to the “standby mode”, and the fixing control unit 70 follows the flowchart shown in FIG. To control. When the main control unit 71 obtains a return command to the standby state from the image forming control unit 60, the main control unit 71 shifts from the “sleep mode” to the “transition mode” and executes the “transition mode” and then enters the “standby mode”. And migrate.

  First, in step 40 (S40), the main control unit 71 determines the reference power as a power command value to increase the heater power from the low power consumption state in the sleep state to the state in which heat fixing is possible. A power command value is instructed to the heater control unit 72.

  In step 41 (S40), the main control unit 71 controls the wind direction plates 37c and 37d to control the wind direction plates 37c and 37d from the normal position to the blowing stop position or the intermediate position. By setting the wind direction plates 37c and 37d to the blowing stop position, the blowing of the separation wind to the fixing unit 31 is stopped, so that it is possible to suppress a decrease in fixing temperature due to heat sink cooling.

  In step 42 (S42), the main controller 71 reads the duct internal temperature from the duct internal temperature sensor 75.

  In step 43 (S43), the main control unit 71 considers the cooling ability of the heat sink 46 to the paper P in the same manner as in step 11 described above, so that the temperature in the duct becomes a certain value or less, that is, the heat sink. The air volume for cooling the heat sink is determined so that a predetermined sheet cooling capacity is secured by 46. For example, the main control unit 71 has a reference temperature for determining the cooling capability of the heat sink 46, and the higher the duct internal temperature is, the higher the air volume that is higher than the reference air volume is. And so on.

  In the process of step 41, the main control unit 71 sets the airflow direction plates 37c and 37d to the blowing stop position from the viewpoint of suppressing the fixing temperature from being lowered due to the setting of the airflow for cooling the heat sink. However, since the fixing temperature in the fixing unit 31 is set to a temperature that takes into account the separation air (reference air volume) from the blower fan 36, the fixing temperature is set by setting the air direction plates 37c and 37d to the blowing stop position. It can be considered that it increases transiently.

  Therefore, the main control unit 71 may delay the timing of controlling the wind direction plates 37c and 37d from the normal position to the blowing stop position in the process of step 41. The timing for delaying is such that the delay is made until the temperature in the duct becomes below a certain level.

  As described above, in the present embodiment, the image forming apparatus 1 includes the heat sink 46 that is disposed downstream of the fixing unit 31 in the conveyance path of the paper P and cools the paper P. Further, in the fixing device 30, the blower unit 35 sucks air heated by heat radiation from the heat sink 46 and blows the sucked air as separated air, and between the fixing unit 31 and the heat sink 46. And a blower duct 37 that guides the separated air from the blower fan 36 to the paper discharge side of the paper P in the fixing nip NP.

  According to such a configuration, the air duct 37 exists between the fixing unit 31 and the heat sink 46, and the separated air that passes through the air duct 37 passes through the air duct 37. Acts as a layer. Thereby, heat transfer from the fixing unit 31 to the heat sink 46 can be suppressed. Therefore, it is possible to suppress a decrease in the cooling performance of the paper P by the heat sink 46. Further, by using the air heated by heat radiation from the heat sink 46 as the separation wind, the temperature of the separation wind can be increased. Thereby, it is possible to suppress a decrease in the fixing temperature while obtaining an air separation function of the paper P by the separation wind.

  In addition, since the separated air also serves as exhaust heat of the heat sink 46, the exhaust heat can be effectively used and the heat circulation efficiency can be improved. As a result, the energy efficiency of the apparatus can be increased, and consequently the heater power can be suppressed.

  Furthermore, it is not necessary to separately prepare a heat insulating member by using the air duct 37 for air separation as a buffer layer. Therefore, it is possible to suppress an increase in the size of the apparatus and an increase in the number of parts without causing a complicated structure.

  Further, in the present embodiment, the fixing control unit 70 determines the air volume necessary for the heat sink 46 to maintain the cooling performance of the paper P as the air volume of the separated air by the blower fan 36 based on the duct internal temperature. In addition, the fixing control unit 70 determines the power to be supplied to the heater 34 based on the determined separation air volume and the duct internal temperature.

  The temperature in the duct serves as a guideline for knowing the cooling capability of the heat sink 46, and thus, the air flow necessary for the heat sink 46 to maintain the cooling performance of the paper P can be obtained by the blower fan 36. Further, the temperature in the duct and the air volume of the separation air serve as a guideline for knowing the temperature loss of the fixing temperature of the fixing unit 31, whereby the heater power can be controlled so as to keep the fixing temperature constant. . Therefore, it is possible to suppress a decrease in the cooling performance of the paper P by the heat sink 46 and to suppress a decrease in the fixing temperature. As a result, the heater power can be appropriately controlled, so that unnecessary power consumption can be suppressed.

  Further, in the present embodiment, the fixing control unit 70 determines the amount of separation air by the blower fan 36 based on the type of the paper P that passes through the fixing unit 31 in the image forming mode. According to such a configuration, the air volume of the separation air can be appropriately determined according to the paper P, so that the paper P can be effectively separated by the separation air. Further, since the separation wind is heated by the heat radiation of the heat sink 46, heat loss of the fixing unit 31 can be reduced as compared with a case where the separated wind is not heated.

  Here, the fixing control unit 70 estimates the heat loss of the fixing unit 31 due to the separation air blown from the blower fan 36 based on the temperature in the duct and the air volume of the separation air determined according to the type of the paper P. The electric power supplied to the heater 34 is determined based on the estimation result. According to such a configuration, since the separated wind is heated by the heat radiation of the heat sink 46, heat loss of the fixing unit 31 can be reduced compared to a case where the separated wind is not heated. Further, although separation air is blown to the fixing unit 31 in order to realize air separation, since the heater power is controlled in consideration of this heat loss, it is possible to effectively suppress a decrease in fixing temperature.

  Further, in the present embodiment, the fixing control unit 70 uses the air volume necessary for the heat sink 46 to maintain the cooling performance of the paper P as the air volume of the separated air by the blower fan 36 based on the temperature in the duct in the standby mode. Has been decided. According to such a configuration, it is possible to suppress a decrease in the cooling performance of the paper P by the heat sink 46.

  Here, the fixing control unit 70 controls the air direction plates 37c and 37d to suppress the amount of separated air blown to the fixing nip portion NP, and the electric power supplied to the heater 34 corresponds to a predetermined fixing temperature. Compared to the standard power. According to such a configuration, since the air volume of the separated wind can be suppressed by the wind direction plates 37c and 37d, a decrease in the fixing temperature can be suppressed. As a result, the heat loss of the fixing unit 31 due to the separation wind can be suppressed, so that the heater power can be suppressed. Thereby, suppression of electric power consumption can be aimed at.

  In the present embodiment, in the sleep mode, the fixing control unit 70 stops the air blowing from the blower fan 36 and reduces the power supplied to the heater 34 compared to the reference power corresponding to a predetermined fixing temperature. I am letting. According to such a configuration, the power consumption of the apparatus can be reduced by reducing the heater power. Moreover, the power consumption of the apparatus can be further contributed by stopping the blower fan 36. Here, there is a concern that the heat dissipating capability of the heat sink 46 is reduced by stopping the blower fan 36, but there is no particular problem because the paper P is not passed in the sleep mode.

  In the present embodiment, in the return mode, the fixing controller 70 increases the power supplied to the heater 34 to the reference power corresponding to a predetermined fixing temperature, and controls the wind direction plates 37c and 37d to fix the fixing nip portion NP. Suppresses the volume of the separated air blown out. Further, the fixing control unit 70 determines the air volume necessary for the heat sink 46 to maintain the cooling performance of the paper P as the air volume of the separated air by the blower fan 36. According to such a configuration, the heat dissipation capability of the heat sink 46 can be recovered. In addition, since the air volume of the separated wind is suppressed by the wind direction plates 37c and 37d, heat loss of the fixing unit 31 can be suppressed.

  The image forming apparatus according to the embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the invention. . For example, although a control unit for controlling the fixing device is provided individually, such a function may be realized by a control unit of the image forming apparatus.

  Further, the fixing device itself constituting the image forming apparatus also functions as part of the present invention. Here, in the above-described embodiment, the image forming apparatus includes the sheet cooling unit as a part of the paper discharge unit, that is, includes the fixing device and the sheet cooling unit as separate elements. However, the sheet cooling unit can be configured as a part of the fixing device, and the mode can be freely changed.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 15Y-15K Exposure part 20Y-20K Charging / development unit 23 Intermediate transfer belt 24 Transfer roller 30 Fixing device 31 Fixing part 32 Fixing upper roller 33 Fixing lower roller 34 Heater 35 Blower part 36 Blower fan 37 Blower duct 37a Blow Exit 37b Air guide 37c Air direction plate 37d Air direction plate 37e Exhaust duct 40 Paper discharge unit 41 Reversing roller 42 Refeed conveyance path 45 Paper cooling unit 46 Heat sink 47 Cooling fan 48 Outside air introduction duct 50 Paper supply roller 51 Registration roller 52 Conveyance belt 60 Image formation control unit 70 Fixing control unit 71 Main control unit 72 Heater control unit 73 Fan control unit 75 Duct temperature sensor 76 Fixing temperature sensor

Claims (12)

A fixing unit that fixes a toner image on a sheet by passing the sheet through a fixing nip formed by pressing a pair of fixing members and applying heat from a heating unit to the toner image transferred to the sheet. When,
A blower unit that separates the sheet from the fixing member by blowing gas to the sheet from the sheet discharge side in the fixing nip;
A heat dissipating member that is disposed downstream of the fixing unit in the paper transport path and cools the paper,
The blowing section is
A blowing means for sucking in a gas heated by heat radiation from the heat radiating member and blowing the sucked gas as a separation wind;
An air duct disposed between the fixing unit and the heat radiating member to guide the separation air from the air blowing unit to the paper discharge side of the fixing nip portion;
A fixing device. A duct temperature detector that detects the temperature of the gas flowing in the air duct as the temperature in the duct;
A controller that controls the volume of gas blown by the blowing means, and
The control unit determines, based on the duct internal temperature detected by the duct internal temperature detection unit, an air volume necessary for the heat radiating member to maintain the cooling performance of the paper as a gas air volume by the blowing unit. The fixing device according to claim 1, wherein the fixing device is characterized.   The fixing device according to claim 2, wherein the control unit determines electric power to be supplied to the heating unit based on the determined air volume of the gas and the temperature in the duct. An image forming unit for transferring a toner image onto paper;
A fixing unit for performing a fixing process on the paper on which the toner image is transferred;
A heat dissipating member that is disposed downstream of the fixing unit in the paper transport path and cools the paper,
The fixing unit includes:
Fixing for fixing a toner image on a sheet by passing the sheet through a fixing nip formed by pressing a pair of fixing members and applying heat from a heating unit to the toner image transferred onto the sheet. And
A blowing unit that separates the sheet from the fixing member by blowing gas to the sheet from the sheet discharge side in the fixing nip unit;
The blowing section is
A blowing means for sucking in a gas heated by heat radiation from the heat radiating member and blowing the sucked gas as a separation wind;
An air duct that is disposed between the fixing unit and the heat radiating member and guides the separation air from the air blowing unit to the paper discharge side of the fixing nip portion;
An image forming apparatus comprising: A duct temperature detector that detects the temperature of the gas flowing in the air duct as the temperature in the duct;
Based on the duct internal temperature detected by the duct internal temperature detection unit, a control unit for controlling the amount of gas blown by the air blowing means,
The image forming apparatus according to claim 4, further comprising:   The image forming apparatus according to claim 5, wherein the control unit determines electric power to be supplied to the heating unit based on an amount of gas blown by the blowing unit and a temperature in the duct.   The control unit, in an image forming mode in which a toner image is formed on a sheet in response to a print command, determines an air volume of the gas by the blowing unit based on a type of the sheet passing through the fixing unit. 6. The image forming apparatus described in 6.   The control unit estimates the heat loss of the fixing unit due to the gas blown from the blowing unit based on the duct internal temperature detected by the duct internal temperature detection unit and the determined gas flow rate, 8. The image forming apparatus according to claim 7, wherein electric power supplied to the heating unit is determined based on an estimation result.   In order to maintain the cooling performance of the sheet by the heat radiating member based on the duct internal temperature detected by the duct internal temperature detection unit in a standby mode in which a print command is waited in a state where image formation is possible. The image forming apparatus according to claim 5, wherein a necessary air volume is determined as a gas air volume by the blowing unit. A wind direction plate for switching the direction of the gas flowing in the air duct;
The control unit controls the wind direction plate to suppress the amount of gas blown out to the fixing nip, and compares the power supplied to the heating unit with a reference power corresponding to a predetermined fixing temperature. The image forming apparatus according to claim 9, wherein the image forming apparatus is lowered.   In the sleep mode that suppresses power consumption, the control unit stops blowing air from the blowing unit and lowers the power supplied to the heating unit as compared with a reference power corresponding to a predetermined fixing temperature. The image forming apparatus according to claim 5, wherein the image forming apparatus is an image forming apparatus.   The control unit increases power supplied to the heating unit to a reference power corresponding to a predetermined fixing temperature in a return mode in which the sleep mode shifts to the standby mode, and controls the wind direction plate to control the fixing nip. The air volume required for the said heat radiating member to maintain the cooling performance of a sheet | seat while determining the air volume of the gas blown to a part is determined as a gas air volume by the said ventilation means. The described image forming apparatus.

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