JP2019219477A - Image formation device - Google Patents

Abstract

To achieve further improvement in a configuration provided with cooling means.SOLUTION: An image formation device has: an image formation unit that forms a toner image on a recording material; a fixation unit that fixes the toner image on the recording material while conveying the recording material having the toner image formed by the image formation unit in the nip part; a discharge loading part that piles up a plurality of recording materials discharged from the nip part, and loads the piled-up recording materials; cooling means that is capable of cooling the recording material discharged from the nip part until the recording material is loaded by the discharge loading part; and a control unit that controls an action of the cooling means. When executing a first job in which the number of pieces of the recording material to be loaded in the discharge loading part is the first number of pieces, the control unit is configured to act the cooling means during the execution of the first job, and when executing a second job in which the number pieces of the recording material to be loaded in the discharge loading part is the second number of pieces smaller than the first number of pieces, the control unit is configured not to act the cooling means during the execution of the second job.SELECTED DRAWING: Figure 11

Description

  The present invention relates to an image forming apparatus capable of forming an image on a recording material, such as a copying machine, a printer, a facsimile, or a multifunction machine having these functions, which employs an electrophotographic method.

  Conventionally, an image forming apparatus employing an electrophotographic method or the like forms an unfixed toner image on a recording material, and heats and presses it with a fixing device to melt and fix the unfixed toner image on the recording material. ing.

  In recent years, in order to increase the image forming speed, a material having a low melting point is selected as the toner, and the control unit of the fixing device shortens the conveyance interval of the recording material, and the toner is instantaneously fixed to the recording material. Thus, measures such as raising the fixing temperature are taken.

  However, when the toner is fixed on the recording material under the above conditions, and the toner is stacked on the discharge unit, a large amount of the high-temperature recording material is sequentially stacked in the same place. The loading section is kept at a high temperature. When the toner after fixing is kept at a high temperature and the toner temperature reaches the toner softening point or higher, the toner on the recording material once fixed is re-softened, and other recording materials stacked on the upper surface thereof or a two-sided image is formed. In this case, the toner adheres to the toner on the recording material on the upper surface. As a result, there arise problems such as the stacked recording materials not being peeled off from each other, the toner on the fixed recording material being peeled off, thereby contaminating other recording materials, and causing a defect in the fixed image.

  Therefore, as means for preventing the stacked recording materials from adhering to each other, Patent Document 1 discloses, for example, using a temperature detection unit that detects the temperature of the recording materials to be discharged and stacked, so that the temperature of the recording materials is reduced to a predetermined value or less. Until the next image forming operation is prohibited / fixing speed is reduced / fixing temperature is reduced. Alternatively, in order to increase the cooling time of the recording material stacked on the paper discharge unit, the transport interval is increased / the transport distance is increased.

  There is also a method of providing a cooling mechanism for cooling a recording material stacked on a paper discharge unit (Patent Document 2). As a result, the temperature of the stacked recording materials is kept below the softening point of the toner, and as a result, the stacked recording materials do not peel off from each other, or the toner on the fixed recording material peels off, thereby contaminating other recording materials. In addition, it is possible to prevent problems such as the occurrence of defects in fixed images and the like.

JP 2009-31651 A JP-A-10-90965

  However, in Patent Literature 1, the throughput may be reduced, and in Patent Literature 2, unnecessary increase in power consumption may occur due to the constant operation of the cooling unit.

  In view of this point, an object of the present invention is to aim at further improvement in a configuration in which a cooling unit is provided.

  In order to achieve the above object, an image forming apparatus according to the present invention includes an image forming unit that forms a toner image on a recording material, and a nip portion that conveys the recording material on which the toner image is formed by the image forming unit. A fixing unit for fixing the toner image on the recording material; a discharge stacking unit for stacking a plurality of recording materials discharged from the nip; and a recording material discharging the recording material discharged from the nip. A cooling unit capable of cooling before being stacked on the stacking unit, and a control unit for controlling the operation of the cooling unit, wherein the number of recording materials to be stacked on the discharge stacking unit is a first number. When executing the first job that is the number of sheets, the control unit operates the cooling unit during execution of the first job, and the number of recording materials to be stacked on the discharge stacking unit is equal to the first number. The second number that is a second number less than the number When performing a job, the control unit is characterized in that it does not operate the cooling means during the execution of the second job.

  Further, another image forming apparatus according to the present invention includes an image forming unit that forms a toner image on a recording material, and a toner image formed by conveying the recording material on which the toner image has been formed by the image forming unit in a nip portion. A fixing unit for fixing the recording material on the recording material, a discharge stacking unit for stacking a plurality of recording materials discharged from the nip, and a recording material discharged from the nip to the discharge stacking unit. A cooling unit capable of cooling before loading, and a control unit for controlling the operation of the cooling unit, wherein M and N are loaded on the discharge loading unit when M and N are natural numbers satisfying M <N. When a first job is executed in which the number of recording materials to be formed is N and the maximum amount of applied toner per unit area is the first amount, and a toner image is formed on each of the N recording materials. The control unit is executing the first job The cooling unit is operated to record M toner images in which the number of recording materials to be stacked on the discharge stacking unit is M and the maximum amount of applied toner per unit area is the first amount. When executing the second job formed on each of the materials, the control unit does not operate the cooling unit during the execution of the second job.

  Further, another image forming apparatus according to the present invention includes an image forming unit that forms a toner image on a recording material, and a toner image formed by conveying the recording material on which the toner image has been formed by the image forming unit in a nip portion. A fixing unit that fixes the recording material on the recording material, a discharge stacking unit that stacks a plurality of recording materials discharged from the nip, and a second unit that conveys the recording material fixed by the fixing unit to the discharge stacking unit. A first conveyance path, a second conveyance path that branches from the first conveyance path, and a second conveyance path that conveys the recording material fixed in the fixing unit to the image forming unit; A cooling unit that can cool the recording material located on the path after the second conveyance path is branched out of the conveyance path, and an acquisition unit that acquires information on the number of recording materials to be stacked on the discharge stacking unit Based on the information obtained by the obtaining unit, And having a control unit for controlling the operation of the.

  According to the present invention, it is possible to provide an image forming apparatus that can suppress a decrease in throughput and a reduction in power consumption due to the operation of a cooling unit while suppressing sticking of recording materials in a discharge stacking unit.

Sectional schematic diagram of the image forming apparatus in the present embodiment Schematic cross section of fixing device and block diagram of control system Longitudinal front schematic view of the fixing device Block diagram of the controller unit 100 and the control circuit unit 90 Configuration diagram of paper bundle loading amount detection sensor S Diagram showing the relationship between the number of stacked paper bundles (position) from below and the paper bundle temperature when the final number of stacked papers is loaded The figure which shows the calculation result of the permissible maximum loading amount F (x) in each loading number when the total output number N = 300. The figure which shows the calculation result of the permissible maximum loading amount F (x) in each loading number when the total output number N = 800. Comparison diagram between the second embodiment and the conventional example (relationship between the number of passed sheets and the maximum allowable load F (x)) Comparison diagram between the second embodiment and the conventional example (relationship between the number of sheets passed and productivity) Flowchart of operation control of a discharge fan in the second embodiment

  Hereinafter, a specific configuration of a preferred embodiment of the present invention will be described in detail with reference to the drawings.

(Image forming device)
FIG. 1 is a schematic cross-sectional view of a printer 1 according to the present embodiment. The printer 1 is a tandem-intermediate transfer type full-color printer, and is an image of each color toner of yellow (Y), magenta (M), cyan (C), and black (Bk) (hereinafter referred to as toner image). ) Are formed in four image forming units UY, UM, UC, and UBk.

  Each image forming unit includes a photosensitive drum 2, a charger 3, a laser scanner 4, a developing unit 5, a primary transfer charger 6, and a drum cleaner 7, respectively. In order to avoid complication of the drawing, reference numerals for these devices in the image forming units UM, UC, and UBk other than the image forming unit UY are omitted. Further, since the electrophotographic process and the image forming operation of these image forming units are known, the description thereof is omitted.

  The toner images of the respective colors are primary-transferred onto the intermediate transfer belt 8 rotating from the drum 2 of each image forming unit in a predetermined superimposed manner. As a result, a toner image of four colors is formed on the belt 8. On the other hand, a recording material (sheet, paper) P is fed one by one from the cassette 9 or 10 or the manual feed tray 11, passes through the conveyance path 12 and presses the belt 8 and the secondary transfer roller 13 at a predetermined control timing. Into the secondary transfer nip. As a result, the toner images of four colors superimposed on the belt 8 are collectively and secondarily transferred onto the sheet P. The paper P is introduced into the fixing device 40 and undergoes a fixing process of the toner image.

  The sheet P exiting from the fixing device 40 is guided toward the transport path 15 under the control of the flapper 14 in the case of the single-sided image forming mode, and is placed on the sheet discharge tray 16 as a stacking discharge section for stacking a plurality of sheets. It is discharged face down. Alternatively, the paper is guided toward the transport path 17 and discharged face-up onto the paper discharge tray 18.

  In the case of the double-sided image forming mode, the sheet P exiting from the fixing device 40 is once guided by the control of the flapper 14 to the side of the transport path 15 as the first transport path, and is then transported in a switchback manner. It is introduced on the side of a two-sided conveyance path 19 as a second conveyance path branched from the path. Then, the toner image is again introduced into the secondary transfer nip through the transport path 12 in a state where the toner image is reversed, and a toner image is formed on the other surface. Thereafter, as in the case of single-sided image formation, the sheet is introduced into the fixing device 40 and discharged to the discharge tray 16 or 18 as a double-sided image formed product.

  In the drawing, reference numeral 20 denotes a cooling fan serving as a sheet discharging cooling unit that blows air across the path of the first transport path after the second transport path is branched, which will be described in detail later.

(Fixing device)
Next, the fixing device 40 according to the present embodiment will be described. FIG. 2 is a schematic cross-sectional view of a main part of the fixing device 40 and a block diagram of a control system. FIG. 3 is a schematic vertical sectional front view of the fixing device 40, in which a part of the main part is omitted. The front of the fixing device 40 is a surface viewed from the paper introduction side.

  The fixing device 40 is an image heating device of a heating belt type, and is roughly divided into a belt unit (film unit) 60, an elastic pressure roller 70, and an apparatus housing 41 in which these are arranged and accommodated almost in parallel. And

  The belt unit 60 includes a heater (heating body) 600 that functions as a nip portion forming member, a heater holder 601 that fixedly supports the heater 600, and a support stay 602 that supports the heater holder 601. Further, a thin fixing member (first rotating body) having an endless belt-like (cylindrical) flexibility as a heat transfer member loosely fitted to an assembly of these members. (Film-like) fixing belt (hereinafter, belt) 603. The belt 603 is rotatable while the inner surface of the belt 603 is in sliding contact with the heater 600 as a sliding member.

  A pressure roller 70 as a second fixing member (second rotating body) nips (fixing nip) a sheet P carrying an unfixed toner image T between the belt and the belt 603 to heat the sheet P. Form N. The pressure roller 70 has a function of contacting the heater 600 of the belt unit 60 via the belt 603.

  In the fixing device 40 according to the present embodiment, the heater 600 presses the belt 603 in the direction of the pressure roller 70 so that the nip portion N has a predetermined width in the paper transport direction (recording material transport direction) a. . In the process of nipping and conveying the sheet P at the nip N, heat generated by the heater 600 is applied to the sheet P via the belt 603, and the unfixed toner image T on the sheet P is fixed to the sheet P by heat and pressure. It is fixed as an image.

  In the present embodiment, the heater 600 is a so-called ceramic heater. The heater 600 includes a substrate 610 and a resistance heating element (hereinafter referred to as a heating element) 620 as a resistance heating layer that generates heat by energization on the substrate 610. Further, a thermistor (TH) 630 as temperature detecting means (temperature sensor) for detecting the temperature of the heater 600 is provided. The heater 600 is fixedly supported by being fitted into a concave portion 601a provided along the length on the lower surface of the heater holder 601.

  In the present embodiment, a heating element 620 is provided on the back side of the substrate 610 (the side that does not contact the belt 603). The thermistor 630 is provided on the back side of the heater 600. However, the present invention is not limited to this, and the heating element 620 may be provided on the surface side of the substrate 610 (the side that contacts the belt 603).

  The heater holder 601 (hereinafter, holder 601) is a member that holds the heater 600 in a state of being pressed toward the belt 603. The holder 601 has a substantially semi-circular cross-sectional shape, and has a function of regulating the rotation trajectory of the belt 603. The holder 601 is made of a resin having high heat resistance.

  A support stay (hereinafter, stay) 602 is a member that supports the heater 600 via the holder 601. It is desirable that the stay 602 be made of a material that does not easily bend even when a large load is applied. In the present embodiment, SUS304 (stainless steel) is used.

  As shown in FIG. 2, the stay 602 is supported by flanges 411a and 411b at both ends in the longitudinal direction. The flanges 411a and 411b are collectively called a flange 411. The flange 411 regulates the movement of the belt 603 in the longitudinal direction and the shape in the circumferential direction. For the flange 411, a heat-resistant resin or the like is used.

  The flanges 411 (a, b) are engaged with guide slits 43 (a, b) provided on one side plate 41 (a, b) on one end side and the other end side of the device housing 41, respectively. It has a degree of freedom to slide in a direction approaching the roller 70 and in a direction away from the roller 70. The pressure spring 415 (a, b) is provided between the flange 411 (a, b) and the pressure arm 414 (a, b) in a contracted state.

  With the above configuration, the elastic force of the pressure spring 415 is transmitted to the heater 600 via the flange 411, the stay 602, and the holder 601. Then, the belt 603 is pressed with a predetermined pressing force against the pressing roller 70 by the heater 600 or the heater 600 and the holder 601. As a result, a nip portion N having a predetermined width is formed between the belt 603 and the pressure roller 70 in the sheet conveyance direction a. The applied pressure in this embodiment is about 156.8 N on one end side and the other end side, respectively, and the total applied pressure is about 313.6 N (32 kgf).

  The connector 500 is a power supply member electrically connected to the heater 600 to apply a voltage to the heater 600, and is detachably attached to one longitudinal end of the heater 600.

  In the present embodiment, the pressure roller 70 is a driving rotator that forms a nip N for heating the toner image T on the sheet in cooperation with the belt 603 and rotates the belt 603.

  Both ends of the pressure roller 70 are rotatably held between side plates 41a and 41b at one end and the other end of the apparatus housing 41 via bearings 42 (a and b), respectively. A gear G is provided at one end of the pressure roller 70 to transmit the rotational driving force of a motor (drive unit: drive means) M to the pressure roller 70.

  The motor M is driven by a motor drive circuit 93 controlled by a control circuit section (control means) 90. Then, the pressure roller 70 driven by the motor M rotates in the direction of arrow R70 in FIG. 1 and transmits the driving force to the belt 603 at the nip N to rotate the belt 603 in the direction of arrow R603. . In this embodiment, the motor drive circuit 93 is controlled by the control circuit 90 so that the surface speed of the pressure roller 70 becomes 200 mm / sec.

(Control unit of fixing unit)
The control circuit unit 90 illustrated in FIG. 2 is a circuit including a CPU that performs operations associated with various controls and a storage unit that includes a nonvolatile medium such as a ROM or a RAM and a volatile medium. The ROM stores various programs and various tables for reference, and the CPU reads them out and executes various controls.

  The heater 600 is energized through a connector 500 from a heater drive circuit (power supply) 92 controlled by the control circuit unit 90. By this energization, the heating element 620 of the heater 600 generates heat, and the effective heating width region of the heater 600 rises sharply. Then, the temperature of the heater 600 is detected by the thermistor 630, and an output corresponding to the detected temperature information is transmitted to the control circuit unit 90 via the A / D converter 80.

  The control circuit unit 90 controls the power supplied to the heater 600 by reflecting the temperature information acquired from the thermistor 630 in the energization control of the heater drive circuit 92. In the present embodiment, a method of adjusting the amount of heat generated by the heater 600 by performing wave number control or phase control on the output of the heater drive circuit 92 is used. Is raised to a predetermined temperature and maintained (temperature controlled).

  As described above, the pressure roller 70 is rotationally driven by the driving of the motor M. Along with this, the belt 603 is driven to rotate while its inner surface slides in close contact with the surface of the heater 600 or the surface of the heater 600 and a part of the outer surface of the holder 601. In addition, energization control for the heater 600 is performed, and the heat generation area of the heater 600 is raised to a predetermined temperature to control the temperature.

  In this apparatus state, the sheet P carrying the unfixed toner image T is introduced into the fixing device 40 from the image forming unit side, enters the nip N, and is nipped and conveyed. Thus, the toner image is heated and pressed on the paper at the nip N. The sheet P having passed through the nip N is separated from the surface of the belt 603 by a curvature and is discharged and conveyed.

(Detection of maximum amount of applied toner on recording material)
FIG. 4 is a block diagram of the controller unit 100 and the control circuit unit 90. The controller unit 100 functions as a video controller unit, and the control circuit unit 90 functions as an engine controller unit.

  In the controller section 100, a CPU 1001 is a CPU (Central Processing Unit) for giving instructions to each section constituting the controller section 100, and a ROM 1002 is a boot ROM (read-only memory) for storing a startup program. The nonvolatile storage unit 1006 is a hard disk drive that stores a control program of the video controller unit 100, input image data, and the like. The RAM 1003 is a random access memory that stores work data of a control program of the video controller unit 100.

  The image processing unit 1004 performs image processing on the input image data according to the characteristics of the image forming apparatus.

  The pixel counting unit 1011 integrates the input image data with the density value of each pixel constituting the image data of each color for each of the Y, M, C, and K color components (hereinafter, this value is referred to as the pixel value ). In the present embodiment, the density value of each pixel has a gradation of 8 bits (0 to 255). As an example, if the density value of the first pixel of the Y image data is 100 and the density value of the second pixel is 50, the sum of the pixel values of the first pixel and the second pixel is 150. Such integration of pixel values is performed for all color components for all pixels in a predetermined area.

  The pixel value calculated by the pixel counting unit 1011 is stored in a register (not shown) inside the pixel counting unit 1011. When the pixel counting unit 1011 finishes counting pixels in a specified area, an interrupt signal is sent to the CPU 1001. Send out. In the controller unit 100, the CPU 1001 reads this register based on the control program with the interrupt signal as a trigger, so that the pixel value at that time can be obtained. Also, the highest pixel value in the plane is calculated by the calculation unit 1012 based on the pixel value obtained by the pixel count unit 1011.

  The controller unit 100 performs image processing by the image processing unit 1004 and pixel counting by the pixel counting unit 1011 in synchronization with the operation of the image forming apparatus main body in accordance with an instruction from the CPU 1001 based on the control program. In this manner, the maximum amount of applied toner per unit area on the recording material (hereinafter, the maximum amount of applied toner) can be obtained by the controller unit 100 (second obtaining unit as an obtaining unit) during the printing operation.

  The maximum amount of toner that can be applied to the recording material is obtained by obtaining an allowable amount of toner that can be formed for each of the stacked recording materials, based on the estimation of the internal temperature information of the bundle of recording materials stacked on the discharge tray described later. This is compared with the acquisition result of the first acquisition unit (function of the control circuit unit 90). Then, based on the magnitude relationship, the operation of the discharge fan 20 that can be cooled by air blowing is controlled.

  Then, for image formation, an image signal is sent to the PWM output unit 904 of the control circuit unit 90. The PWM output unit 904 is connected to the image processing unit 1004 of the controller unit 100, and generates a PWM (Pulse Width Modulation) signal based on the image signal transmitted from the image processing unit 1004.

  The I / O unit 906 is connected to various actuators and sensors (not shown) provided in the image forming apparatus 100, and the control circuit unit 90 drives each unit of the image forming apparatus 1 according to an instruction of the CPU 901 based on a control program. Printing is performed by an electrophotographic process method.

  The controller unit 100 and the control circuit unit 90 include three-wire serial communication IFs 1005 and 905, respectively, and the CPU 1001 and the CPU 901 transmit and receive data via these.

  From the controller unit 100 to the control circuit unit 90, information about the print job, such as the size and resolution of the input image data, detailed information (to be described later) of the recording material to be used, and pixel values, and the arithmetic unit 1012 The highest pixel value in the calculated plane is notified. The control circuit unit 90 controls the discharge fan 20 of the image forming apparatus 1 based on the notified information.

(Discharge cooling control)
Next, using an electrophotographic image forming apparatus (manufactured by Canon Inc., trade name: imageRUNNER-ADVANCE C5051) modified so that sticking prevention control of the recording materials discharged onto the paper discharge tray can be performed. 4 shows sheet discharge cooling control in the embodiment.

  FIG. 1 is a schematic cross-sectional view of the image forming apparatus according to the present embodiment, and includes a discharge tray temperature detection sensor A on a discharge tray as a stacking discharge unit. The discharge tray temperature detection sensor A is a contact-type temperature sensor that acquires the sheet bundle bottom temperature T of the recording material stacked on the discharge tray. Further, a paper bundle loading amount detection sensor S for acquiring the paper bundle loading amount on the paper discharge tray is provided near the paper discharge port.

  As shown in FIG. 5, the stacking amount detection sensor S includes a contact type lever 306 for detecting the stacking amount H of the recording material P on the sheet discharge tray, a sensor flag 305, and photo interrupters 302 and 303. . The recording material P is discharged by the discharge roller rows 307 and 308, and the contact type lever 306 rotates according to the stacking amount on the discharge tray, and rotates the sensor flag 305. By reading the rotation amount of the sensor flag 305 by the photo interrupters 302 and 303, the paper bundle stacking amount H is detected.

FIG. 2 is a block diagram illustrating the configuration of the present embodiment. The control circuit section 90 controls the sheet discharge cooling operation. The sheet discharge cooling control controls the OFF / ON of the cooling fan 20 (FIG. 1) for the recording material on which an image has been formed and has passed through the fixing device 40, so that the recording material is being discharged to the discharge tray. The cooling control is performed for. The controller unit 100 receives image data from the network unit 101 and develops a print image while checking a request from the operation unit 102.
The control circuit unit 90 controls the recording unit 91, the heater drive circuit 92, the motor drive circuit 93, and the sensors 94, and performs a fixing process of the unfixed toner image T.

(Cooling fan operation control)
In the present embodiment, the internal temperature (highest temperature) of the bundle of paper stacked on the discharge tray after printing is estimated based on the total number of prints N of the print reservation information as the job reservation information before the start of image formation. Then, it is determined whether or not the cooling fan 20 needs to be operated. Specifically, the control circuit unit 90 (FIG. 2) functions as estimating means for estimating the internal temperature (highest temperature) of the sheet bundle stacked on the sheet discharge tray. The cooling fan drive circuit 95 (FIG. 2) functions as a control unit that controls the operation of the cooling fan 20 based on the temperature estimated by the estimating means.

  The control unit that controls the operation of the cooling fan does not operate the cooling fan (remains off) when the estimated internal temperature does not exceed the predetermined value. On the other hand, when the estimated internal temperature exceeds the predetermined value, the cooling fan is operated (turned on) for at least one recording material discharged to the discharge tray.

  More specifically, the maximum allowable loading amount F (x) (unit is%) with respect to the number of stacked sheets (integrated number) x is calculated as follows, and the maximum amount of toner (unit: %) Exceeds the allowable maximum applied amount F (x). If the allowable maximum load amount F (x) is not exceeded, the sheet passing operation is performed with the cooling fan N turned off. This is because paper discharge adhesion does not occur even when the maximum amount of applied toner on the recording material is 100%. On the other hand, if the allowable load amount F (x) is exceeded, the cooling fan N is turned on and the sheet passing operation is performed.

  Hereinafter, a method of calculating the allowable maximum load amount F (x) with respect to the number of stacked paper bundles (hereinafter, the number of stacked sheets) x will be described with reference to FIGS. As shown in FIG. 6, the adhesion occurrence temperature at which the adhesion between the recording materials occurs can be roughly estimated from the maximum applied amount of the toner on the recording material. In FIG. 6, the temperature at which the adhesion occurs at the maximum loading amount of 30% is shown to be substantially equal to the stacked sheet width temperature near the 400th sheet position, which is an intermediate value when the total output number N of the print reservation information is N = 800. ing.

  Further, the temperature at which the bond occurs at the maximum applied amount of 100% is shown as a temperature lower than the temperature at which the bond occurs at the maximum applied amount of 30%. Specifically, it is shown that the total sheet number N of the print reservation information is approximately equal to the stacked sheet width temperature at the 300th sheet position or the 600th sheet position when N = 800.

  Here, as shown in FIG. 7, the allowable maximum load F (x) for the number of sheets N is calculated from the relationship between the adhesion occurrence temperature at the maximum load 100% shown in FIG. Is done. FIG. 7 shows a calculation result of the allowable maximum loading amount F (x) at each loading number when the total output number N = 300. When the stacking paper bundle temperature is lower than the adhesion occurrence temperature at the maximum loading amount of the recording material of 100%, the allowable maximum loading amount is calculated as 100% as shown in FIG.

  Here, FIG. 6 shows the stacked paper width temperature at each total output number N in a state where the stacking of the recording materials discharged from the nip portion on the discharge tray is completed. The horizontal axis indicates the number of stacked paper bundles (hereinafter referred to as stacked number) from below the paper stack (the bottom surface of the paper discharge tray), and the vertical axis indicates the internal temperature at each stacked number.

  For example, in a case where the total output number N of the print reservation information is N = 200, when a series of printing operations is completed, a bundle of 200 sheets is stacked on the discharge tray. At this time, if the printing operation is performed at a fixed throughput, the position near the 100th sheet from the bottom of the sheet bundle on which the 200th sheet as the final sheet is stacked (near the middle in the thickness direction of the stacked sheet bundle). The temperature inside the paper bundle is the highest.

  This is due to the fact that heat is stored inside the paper bundle because the next recording material is sequentially discharged and stacked on it before the recording material discharged onto the discharge tray cools down. is there. Similarly, when N = 200, 600, 800, and 1000, the temperatures near the 100th, 300th, 400th, and 500th sheet positions, which are intermediate values, respectively, become the highest.

  Here, when the internal temperature of the bundle of paper stacked on the paper discharge tray is high (when the temperature exceeds the adhesion occurrence temperature as a predetermined value), the adhesion between the recording materials occurs. That is, when the maximum load amount of the recording material is larger than the maximum allowable load amount F (x) corresponding to the maximum allowable load amount F (x) corresponding to the internal temperature of the bundle of sheets stacked on the sheet discharge tray, Adhesion between recording materials occurs. The adhesion between the recording materials is more likely to occur as the amount of applied toner loaded on the recording materials increases.

  Although the details are omitted here, the temperature at which adhesion occurs depends on the smoothness of the recording material surface and the like. This is because the surface property of the toner on the recording material after fixing changes due to the smoothness of the surface of the recording material itself, so that the contact state between the adjacent recording material and toner changes, and the toner on the recording material changes. This is because the fixing strength varies depending on the smoothness of the surface of the recording material itself.

  In this manner, in the present embodiment, by obtaining the total output number N of the print reservation information, it is possible to estimate the ultimate temperature at each position inside the bundle of paper stacked on the paper discharge tray, and The allowable maximum load amount F (x) is determined based on the estimated information. When the maximum amount of applied toner on the recording material does not exceed the allowable maximum applied amount F (x), the sheet passing operation is performed with the cooling fan N turned off.

<< 2nd Embodiment >>
Also in the present embodiment, it is determined that the cooling unit needs to be activated based on the fact that the first number of sheets is stacked as a recording material on the discharge tray as the discharge stacking unit and the temperature information by the estimation unit exceeds a predetermined value. During execution of the determined first job, the cooling unit is operated. Then, based on the fact that the second number smaller than the first number is loaded on the discharge loading section and the temperature information by the estimation means does not exceed the predetermined value, it is determined that the operation of the cooling means is unnecessary. Do not activate the cooling means during the execution of the job.

  Here, when the recording material of the first job and the recording material of the second job are the same type of recording material, the basis weight, paper type (such as coated paper and plain paper), and size are all the same paper. .

  Also in the present embodiment, the first obtaining unit that obtains an allowable mounting amount that can be formed for each stacked recording material based on the temperature information estimated by the estimating unit, and the maximum mounting amount on the recording material during a printing operation. And second acquisition means for acquiring information, and compares the magnitudes of the acquisition results.

  It is determined that the cooling unit needs to be activated based on the fact that the first number of sheets is loaded as a recording material on the discharge loading unit and the acquisition result of the second acquisition unit exceeds the acquisition result of the first acquisition unit. In a first job, the cooling means is activated.

  Then, based on the fact that the second number smaller than the first number is loaded on the discharge loading unit and the acquisition result of the second acquisition unit does not exceed the acquisition result of the first acquisition unit, the operation of the cooling unit is performed. In the second job determined to be unnecessary, the cooling means is not operated.

  Then, in the present embodiment, in the first job, the cooling unit is operated from the third number of recording materials on the way to the first number. Then, in the first job, the cooling unit is not operated (turned off) from the recording material which is in the middle of the first number and is the fourth number larger than the third number. More specifically, the third number is smaller than the intermediate value of the first number, and the fourth number is larger than the intermediate value of the first number.

  As shown in FIG. 8, when the total number of output sheets N = 800, the maximum allowable load F (x) for each number of stacked sheets is 100% with respect to the 300th sheet. Do not operate the cooling fan at times. However, since the 300th to 599th sheets are 30% of the 400th sheet which is an intermediate value of 800 sheets, the cooling fan is operated at the time of discharging the 300th to 599th sheets. .

  That is, when the first number is N and L and N are natural numbers satisfying 1 <L <N, the control unit operates the cooling fan in the first job from the L-th sheet of the first job. Let it.

  In addition, since it is 100% for the 600th sheet to the 800th sheet (the 400th sheet having an intermediate value is considered to be substantially symmetrical to the 299th sheet), the 600th sheet to the 800th sheet Do not operate the cooling fan during the discharge.

  That is, when M is a natural number satisfying 1 <L <M <N, in the first job, the control unit stops the cooling fan at the Mth sheet of the first job.

  Here, a comparison between the conventional control (control for reducing the throughput) and the present embodiment will be described with reference to FIGS. Referring to FIG. 9, in the conventional control, at the 300th to 599th sheets where the discharge adhesion occurs, the discharge adhesion occurs unless the loaded amount is reduced to 30%. Therefore, as shown in FIG. 10, the productivity was reduced to 80% after the 300th sheet.

  In contrast, in the present embodiment, by blowing the cooling fan at a full speed of 24 V, the maximum allowable load F (x) is 100%, so that the sheet can be discharged with the productivity being 100%. Therefore, it is possible to greatly reduce the trouble of the user's time required to discharge the paper.

  Next, the sheet discharge cooling FAN control using the maximum allowable load F (x) will be described with reference to the sheet discharge cooling FAN control flowchart of FIG. When printing is started, the allowable maximum load F (x) is calculated from the total output number N of the print reservation information input from the network unit 102 and the operation unit 103 to the controller unit 100, and the process proceeds to S2. Then, in S2, the number X of image formation is set to X = 1, and the process proceeds to S3.

  In S3, it is determined whether or not the discharge cooling fan is on. If it is not on, the process proceeds to S4, and if it is on, the process proceeds to S5. In S4, the X-th image formation is started, and the process proceeds to S6. In S5, the X-th image formation is started, and the process proceeds to S10.

  In S6, the maximum load amount M of the X-th sheet is acquired, and in S7, the magnitude relationship between the maximum load amount M on the recording material and the allowable maximum load amount F (x) is compared. In S7, if M <F (x), the process proceeds to S9, and if M ≧ F (x), the process proceeds to S8. In S8, control is performed to activate (turn on) the discharge cooling fan, and the cooling fan continues to be blown up to the x-th sheet where M <F (x).

  On the other hand, if M <F (x), the process proceeds to S9, and in S9, the discharge fan is not operated (turned off), and the process proceeds to S10. If the printing is completed in S10, the operation is completed. If the printing is not completed, the image forming sheet number X is set to X + 1 in S11, and the recording is updated in the recording unit 91, and the process proceeds to S3. Such control is performed by the control circuit unit 90 shown in FIG.

  As described above, in the present embodiment, the internal temperature of the sheet bundle stacked on the sheet discharge tray is estimated from the total number of output sheets N of the print reservation information, and the maximum allowable load F (x) is calculated only at the start of printing. For this reason, the calculation amount is smaller than the calculation of the allowable maximum load amount of each print job, and there is no concern about a decrease in FCOT and a delay in starting printing due to a prolonged processing time.

  Also, if a 300-sheet job arrives immediately even if the job is initially 200 sheets, the current controller is apparently indistinguishable, resulting in a total of 500 jobs. For this reason, unless the cooling fan is blown in the middle, the temperature reaches the temperature at which the sheet is discharged and adhered. Therefore, a cooling fan for discharging the paper must be blown. In that case, the cooling fan is operated (turned on) for 300 sheets and up to the 500th sheet to perform the cooling operation, so that the discharge adhesion can be prevented.

  As described above, in each of the above-described embodiments, it is possible to provide an image forming apparatus capable of suppressing a decrease in throughput and a reduction in power consumption due to the operation of the cooling unit while suppressing sticking of recording materials in the discharge stacking unit. .

(Modification)
In the above-described embodiment, a preferred embodiment of the present invention has been described, but the present invention is not limited to this, and various modifications can be made within the scope of the present invention.

(Modification 1)
In the above-described embodiment, the first and second acquisition units relating to the applied amount are used. However, the cooling fan may be turned on / off according to the number of jobs regardless of the applied amount. That is, when executing the first job in which the number of recording materials to be stacked on the discharge stacking unit is the first number, the control unit operates the cooling fan during execution of the first job. On the other hand, when executing the second job in which the number of recording materials to be stacked on the discharge stacking unit is the second number smaller than the first number, the control unit activates the cooling fan during execution of the second job. Do not operate.

  More specifically, when the first number is N, and L and N are natural numbers satisfying 1 <L <N, the control unit determines, in the first job, the L number of the first job. Operate the cooling fan from the eyes. Then, when M is a natural number satisfying 1 <L <M <N, in the first job, the control unit stops the cooling unit at the Mth sheet of the first job.

(Modification 2)
In the above-described embodiment, the first and second acquisition units relating to the applied amount are used, but the cooling fan is turned on / off according to the number of jobs for the recording materials having the same applied amount as follows. You may do it.

  That is, when M and N are natural numbers satisfying M <N, a toner image in which the number of recording materials to be stacked on the discharge stacking unit is N and the maximum amount of applied toner per unit area is the first amount. The cooling fan is operated during the execution of the first job formed on each of the N recording materials. On the other hand, the number of recording materials to be stacked on the discharge stacking unit is M, and a toner image in which the maximum amount of applied toner per unit area is the same first amount is formed on each of the M recording materials. The cooling fan is not operated during the execution of the second job.

  More specifically, when K is a natural number satisfying 1 <K <N, in the first job, the control unit operates the cooling fan from the Kth sheet of the first job. When L is a natural number satisfying 1 <K <L <N, in the first job, the control unit stops the cooling fan at the L-th sheet of the first job.

(Modification 3)
In the above-described embodiment, in the first job, from the third number, which is on the way to the first number and is smaller than the intermediate value of the first number, to the fourth number, which is larger than the intermediate value of the first number Although the cooling means was operated only during the period up to, the present invention is not limited to this. In the first job, the cooling unit may be operated for at least one recording material discharged to the discharge stacking unit.

13. Secondary transfer roller, 16 discharge tray, 20 cooling fan for discharge, 70 pressure roller, 90 control circuit section, 95 discharge cooling fan drive circuit, 100 ..Controller section, 603..Fixing belt

Claims (18)

An image forming unit that forms a toner image on a recording material;
A fixing unit that fixes the toner image on the recording material while conveying the recording material on which the toner image has been formed by the image forming unit at the nip portion;
A discharge stacking unit that stacks and stacks a plurality of recording materials discharged from the nip unit,
Cooling means capable of cooling the recording material discharged from the nip portion until the recording material is stacked on the discharge stacking portion;
A control unit for controlling the operation of the cooling unit,
Has,
When executing the first job in which the number of recording materials to be stacked on the discharge stacking unit is the first number, the control unit operates the cooling unit during execution of the first job, and When executing the second job in which the number of recording materials to be stacked on the discharge stacking unit is the second number smaller than the first number, the control unit performs the cooling while the second job is being executed. An image forming apparatus wherein the means is not operated. When the first number is N and L and N are natural numbers satisfying 1 <L <N,
2. The image forming apparatus according to claim 1, wherein in the first job, the control unit operates the cooling unit from the L-th sheet of the first job. 3. M is a natural number satisfying 1 <L <M <N,
The image forming apparatus according to claim 2, wherein in the first job, the control unit stops the cooling unit at the M-th sheet of the first job. A conveyance path for conveying the recording material fixed in the fixing unit to the discharge stacking unit,
The image forming apparatus according to claim 1, wherein the cooling unit cools a recording material located on the conveyance path. A first conveyance path for conveying the recording material fixed by the fixing unit to the discharge stacking unit;
A second conveying path for conveying the recording material fixed by the fixing unit to the image forming unit, the conveying path branching from the first conveying path;
Has,
4. The apparatus according to claim 1, wherein the cooling unit cools a recording material located on a path of the first transport path after the second transport path is branched. 5. The image forming apparatus as described in the above.   The image forming apparatus according to claim 5, wherein the cooling unit is a fan that blows air across a path of the first transport path after the second transport path is branched.   The image forming apparatus according to claim 1, wherein the recording material of the first job and the recording material of the second job are the same type of recording material. An image forming unit that forms a toner image on a recording material;
A fixing unit that fixes the toner image on the recording material while conveying the recording material on which the toner image has been formed by the image forming unit at the nip portion;
A discharge stacking unit that stacks and stacks a plurality of recording materials discharged from the nip unit,
Cooling means capable of cooling the recording material discharged from the nip portion until the recording material is stacked on the discharge stacking portion;
A control unit for controlling the operation of the cooling unit,
Has,
When M and N are natural numbers satisfying M <N,
A first method for forming a toner image in which the number of recording materials to be stacked on the discharge stacking unit is N and the maximum amount of applied toner per unit area is the first amount is formed on each of the N recording materials. When executing the first job, the control unit operates the cooling unit during the execution of the first job, and the number of recording materials to be stacked on the discharge stacking unit is M, and When executing a second job for forming a toner image whose maximum applied toner amount is the first amount on each of the M recording materials, the control unit may perform the cooling during the execution of the second job. An image forming apparatus wherein the means is not operated. K is a natural number satisfying 1 <K <N,
9. The image forming apparatus according to claim 8, wherein in the first job, the control unit operates the cooling unit from the Kth sheet of the first job. 10. L is a natural number satisfying 1 <K <L <N,
The image forming apparatus according to claim 9, wherein in the first job, the control unit stops the cooling unit at the L-th sheet of the first job.   The number of recording materials to be stacked on the discharge stacking unit is the N number of sheets, and the maximum amount of applied toner per unit area is a second amount smaller than the first amount. 11. The apparatus according to claim 8, wherein when executing the third job to be formed on each of the materials, the control unit does not operate the cooling unit during execution of the third job. 12. The image forming apparatus as described in the above.   12. The image forming apparatus according to claim 8, further comprising: an acquisition unit configured to acquire a maximum amount of applied toner per unit area of a toner image formed on a recording material to be stacked on the discharge stacking unit. The image forming apparatus as described in the above. A conveyance path for conveying the recording material fixed in the fixing unit to the discharge stacking unit,
The image forming apparatus according to claim 8, wherein the cooling unit cools a recording material located on the conveyance path. A first conveyance path for conveying the recording material fixed by the fixing unit to the discharge stacking unit;
A second conveying path for conveying the recording material fixed by the fixing unit to the image forming unit, the conveying path branching from the first conveying path;
Has,
13. The apparatus according to claim 8, wherein the cooling unit cools a recording material located on a path of the first transport path after the second transport path is branched. The image forming apparatus as described in the above.   15. The image forming apparatus according to claim 14, wherein the cooling unit is a fan that blows air across a path of the first transport path after the second transport path is branched.   16. The image forming apparatus according to claim 8, wherein the recording material of the first job and the recording material of the second job are the same type of recording material. An image forming unit that forms a toner image on a recording material;
A fixing unit that fixes the toner image on the recording material while conveying the recording material on which the toner image has been formed by the image forming unit at the nip portion;
A discharge stacking unit that stacks and stacks a plurality of recording materials discharged from the nip unit,
A first conveyance path for conveying the recording material fixed by the fixing unit to the discharge stacking unit;
A second conveying path for conveying the recording material fixed by the fixing unit to the image forming unit, the conveying path branching from the first conveying path;
Cooling means capable of cooling a recording material located on a path of the first conveyance path after the second conveyance path is branched;
An acquisition unit configured to acquire information on the number of recording materials to be stacked on the discharge stacking unit;
A control unit that controls the operation of the cooling unit based on the information acquired by the acquisition unit;
An image forming apparatus comprising: When the acquisition unit is a first acquisition unit,
A second acquisition unit that acquires a maximum amount of applied toner of a toner image formed on a recording material to be stacked on the discharge stacking unit,
18. The method according to claim 17, wherein the control unit controls the operation of the cooling unit based on information acquired by the first acquisition unit and information acquired by the second acquisition unit. The image forming apparatus as described in the above.