JP2019152692A - Image forming apparatus and control method - Google Patents

Abstract

To quickly perform printing even when heat is not sufficiently stored in a heating unit without waiting for heat storage of the heating unit.SOLUTION: A control unit executes acquisition processing (S12) of acquiring, in print data, the area of images present in predetermined areas including a rear end part in a conveyance direction and on the rear side of a center part in the conveyance direction on a head page on which a developer image is initially formed, heating processing of heating a heating unit so that the temperature of a heating unit becomes a fixing temperature, and supply processing (S17, S18) of starting supply of a sheet with a sheet supply unit after the lapse of a predetermined time from a predetermined timing. When the area of the images present in the predetermined areas on the head page in the print data is equal to or less than a predetermined area (S14: Yes), the control unit sets the predetermined time Zth in the supply processing to a time (first time Z1) shorter than a time when the area of the images is larger than the predetermined area.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an image forming apparatus including a fixing device that heats a sheet, and a sheet supply unit that supplies the sheet, and a control method.

  Conventionally, in order to increase the printing speed, the sheet supply timing is advanced so that the timing at which the temperature of the heating unit reaches the fixing temperature is the same as the timing at which an area on the sheet reaches the heating unit. The thing is known (refer patent document 1).

JP 2010-271410 A

  By the way, in the fixing device, when the first sheet reaches the heating unit after printing is started, the heating unit may not store heat sufficiently. In this case, the heat of the heating unit is deprived at the leading portion in the sheet conveyance direction, the temperature of the heating unit is lowered, and there is a possibility that fixing failure occurs at the rear side portion in the sheet conveyance direction. Therefore, when the heating unit is not sufficiently stored, the sheet must be supplied after waiting for the heating unit to store enough heat, and there is a problem that quick printing cannot be performed. Arise.

  Therefore, an object of the present invention is to perform printing promptly without waiting for heat storage of the heating unit even when the heating unit is not sufficiently stored.

In order to solve the above problems, an image forming apparatus according to the present invention includes a sheet supply unit that can switch between a stopped state and a conveyance state of a sheet, a developer image forming unit that forms a developer image on the sheet, and a heating sheet. A fixing unit having a heating unit and a control unit.
The control unit acquires an area of an image existing in a predetermined region at least behind the central part in the transport direction including the rear end part in the transport direction on the first page on which the developer image is first formed in the print data. An acquisition process, a heating process for heating the heating unit such that the temperature of the heating unit becomes a fixing temperature, and a supply process for starting sheet supply by the sheet supply unit after a predetermined time from a predetermined timing are executed. When the area of the image existing in the predetermined area on the first page of the print data is equal to or smaller than the predetermined area, the predetermined time in the supply process is set to be shorter than that when the area of the image is larger than the predetermined area. Set.

The control method according to the present invention includes a sheet supply unit that can switch between a stopped state and a conveyance state of a sheet, a developer image forming unit that forms a developer image on the sheet, and a heating unit that heats the sheet. And a control method for the image forming apparatus.
When printing processing is started, the area of an image existing in a predetermined area at least behind the center in the transport direction, including the rear end in the transport direction, on the first page of the first developer image in the print data. Acquisition processing for acquiring the heating portion, heating processing for heating the heating portion so that the temperature of the heating portion becomes the fixing temperature, and supply of the sheet by the sheet supply portion after a predetermined time from a predetermined timing after the start of the printing processing. The supply process to be started is executed.
When the area of the image existing in the predetermined area on the first page of the print data is equal to or smaller than the predetermined area, the predetermined time in the supply process is set to a shorter time than when the area of the image is larger than the predetermined area. To do.

  When the area of the image existing in the predetermined area at the rear end portion in the transport direction of the first page is equal to or smaller than the predetermined area, fixing failure hardly occurs even if the amount of heat applied to the rear portion in the transport direction of the sheet is small. Therefore, when the area of the image existing in the predetermined area at the rear end portion in the transport direction of the first page is equal to or smaller than the predetermined area, the predetermined time is set to a short time to advance the timing of starting the supply of the first sheet. Thus, even when the heating unit is not sufficiently stored, printing can be performed quickly without waiting for the storage unit to store heat.

  The predetermined timing may be a timing at which the heat treatment is started.

  In addition, in the heating process, the control unit heats the heating unit so that the temperature of the heating unit becomes a first temperature lower than the fixing temperature in parallel with the acquisition process. Then, after the first heat treatment is finished, a second heat treatment for heating the heating portion so that the temperature of the heating portion becomes a fixing temperature may be executed.

  According to this, since the acquisition process is performed during the first heat treatment, printing can be started more quickly.

  The predetermined timing may be a timing at which the second heat treatment is started.

  The predetermined timing may be a timing at which the temperature of the heating unit reaches a second temperature lower than the fixing temperature after the heat treatment is started.

  The predetermined area may be a rectangular area having a predetermined length from the rear end in the transport direction to the front in the transport direction on the first page of the print data.

  The predetermined area is a rectangular area having a predetermined length from the rear end in the transport direction to the front in the transport direction on the first page of the print data and having a predetermined width from both ends in the width direction toward the center. It may be.

  The predetermined area may be an area whose width decreases from the rear end in the transport direction to the head in the transport direction on the first page of the print data.

  In addition, when receiving the print data in the acquisition process, the control unit executes a development process for developing the print data into object data composed of vector data or bitmap data, and the object data existing in the predetermined area The area of the circumscribed rectangle may be acquired as the area of the image.

  According to this, since the area of the image can be defined at the time when the print data is developed into the object data, the processing speed of the acquisition process can be increased.

  Further, the control unit expands the object data for each color in the expansion process, and acquires a value obtained by adding the area of the circumscribed rectangle of the object data of each color existing in the predetermined area as the area of the image Good.

  Further, the predetermined area may be zero.

  The control unit may acquire the number of dots of the image as the area of the image in the acquisition process.

  In addition, when printing a plurality of sheets in the supply process, the control unit supplies the sheets so that each of the plurality of sheets has a predetermined interval, and the predetermined time corresponds to the area of the image. When the time is set to be shorter than the case where it is larger than the predetermined area, the second sheet is supplied so that the interval between the first sheet and the second sheet is larger than the predetermined interval. Also good.

  According to this, by increasing the interval between the first sheet and the second sheet, the time from when the first sheet is fixed until the second sheet reaches the heating unit is increased. As a result, the heating unit can sufficiently store heat in that time, and it is possible to suppress the occurrence of fixing failure on the second sheet.

  In addition, the image forming apparatus further includes a pressure roller that sandwiches the sheet with the heating unit, and the predetermined area is transported from a position separated from the head of the page in the transport direction by a distance n times the circumferential length of the pressure roller. It may be a region on the rear side in the direction.

  Further, the control unit may set the predetermined area as a larger area as the humidity or the sheet thickness is larger.

  The greater the humidity or the thickness of the sheet, the more easily the heat of the heating part is taken away by the sheet. Therefore, the larger the humidity or the thickness of the sheet, the larger the predetermined area, so that the first sheet has poor fixing. Occurrence can be suppressed.

  According to the present invention, even if the heating unit is not sufficiently stored, printing can be performed quickly without waiting for the storage unit to store heat.

1 is a cross-sectional view illustrating a color printer according to an embodiment of the present invention. It is a block diagram which shows the structure of a control part. It is figure (a)-(c) which shows the example of a predetermined field. It is a figure which shows the expansion | deployment process which expand | deploys print data to a raster image. It is a flowchart which shows control of a heater and a motor. It is a flowchart which shows drive / stop control of a pickup roller. It is a time chart which shows an example of operation | movement of a control part. It is a time chart which shows operation | movement of the control part in the condition where the temperature of a heating part is below predetermined temperature. It is a flowchart which shows operation | movement of the control part which concerns on a modification. It is a figure which shows a predetermined area setting map.

Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 1, the color printer 1 is an example of an image forming apparatus that forms an image on a sheet S, and a process as an example of a sheet conveying unit 20 and a developer image forming unit in a main body housing 2. A unit 30, a fixing device 80, and a control unit 100 are provided.

  The sheet conveying unit 20 includes a supply tray 21, a pickup roller 23 as an example of a sheet supply unit, a separation roller 24, a separation pad 25, and a registration roller 29. The sheet conveying unit 20 supplies the sheet S in the supply tray 21 toward the separation roller 24 by the pickup roller 23 and separates the sheet S into one sheet between the separation roller 24 and the separation pad 25. Specifically, the pickup roller 23 is a roller that can switch between a stopped state and a conveying state of the sheet S, and starts rotating from a state in which the pickup roller 23 comes into contact with the sheet S in the supply tray 21 and stops. Sheet S is sent out. The registration roller 29 aligns the position of the leading edge of the sheet S, and then conveys the sheet S toward the process unit 30. Specifically, the registration roller 29 comes into contact with the conveyed sheet S in a stopped state, aligns the position of the leading edge of the sheet S, and starts to rotate to send out the sheet S. The sheet S sent out by the sheet conveying unit 20 passes through the process unit 30 and the fixing device 80 and is conveyed to the outside of the color printer 1.

  The process unit 30 is a part that forms a developer image on the sheet S, and includes four LED units 40, four process cartridges 50, and a transfer unit 70.

  The LED unit 40 is an exposure apparatus having a plurality of light emitting units arranged in the left-right direction.

  The process cartridge 50 includes a drum cartridge 510 and a developing device 530. The drum cartridge 510 includes a photosensitive drum 51, a charger 52, and a cleaning roller 55. The developing device 530 includes a developing roller 53 and a developer storage chamber 54 that stores the developer.

  In the process cartridge 50, those indicated by reference numerals 50K, 50Y, 50M, and 50C containing toners for black, yellow, magenta, and cyan are arranged in this order from the upstream side in the sheet S conveyance direction. ing.

  The transfer unit 70 includes a drive roller 71, a driven roller 72, a conveyance belt 73, and a transfer roller 74.

  The driving roller 71 and the driven roller 72 are arranged in parallel with a space in the front-rear direction, and a conveyance belt 73 formed of an endless belt is stretched between them. Inside the conveyance belt 73, four transfer rollers 74 that sandwich the conveyance belt 73 with the respective photosensitive drums 51 are arranged to face the respective photosensitive drums 51.

  In the process unit 30 configured as described above, first, the surface of each photosensitive drum 51 is charged by the charger 52 and then exposed by each LED unit 40. Thereby, an electrostatic latent image based on the image data is formed on each photosensitive drum 51. Thereafter, toner is supplied from the developing roller 53 to the electrostatic latent image, whereby a developer image is formed on the photosensitive drum 51. As the sheet S supplied on the conveyance belt 73 passes between the photosensitive drums 51 and the transfer rollers 74, the developer images formed on the photosensitive drums 51 are transferred onto the sheets S. The

  The fixing device 80 is disposed on the downstream side in the conveyance direction of the sheet S with respect to the process unit 30. The fixing device 80 includes a heating unit 81 that heats the sheet S to fix the developer image on the sheet S, and a pressure unit 82 that is pressed against the heating unit 81. The heating unit 81 is a cylindrical heating roller and is made of metal or the like. A heater 83 for heating the heating unit 81 is provided inside the heating unit 81. As the heater 83, a halogen lamp that has a filament as a resistor and heats a range through which the sheet S of the heating unit 81 passes by radiant heat can be employed. The pressure unit 82 is a pressure roller having an elastic layer on the surface.

  The heating unit 81 and the pressurizing unit 82 are configured to rotate by receiving a driving force from the motor M controlled by the control unit 100. The fixing device 80 heats the sheet S with the heater 83 and fixes the developer image on the sheet S while the sheet S is conveyed while being sandwiched between the rotating heating unit 81 and the pressing unit 82.

  The fixing device 80 includes a temperature detection unit 84 that detects the temperature of the heating unit 81. The temperature detection unit 84 faces the surface of the heating unit 81 in a non-contact manner. The temperature detected by the temperature detector 84 is output to the controller 100. The control unit 100 acquires the temperature of the heating unit 81 based on the detection result of the temperature detection unit 84.

  As shown in FIG. 2, the control unit 100 includes a CPU, a RAM, a ROM, and an input / output circuit, and print data output from the external computer 200 and information output from the temperature detection unit 84. Control is executed by performing various arithmetic processes based on programs and data stored in a ROM or the like. Specifically, the control unit 100 includes a calculation unit 110 such as a CPU, a control circuit 120 that controls the heater 83, the motor M, and the like, and a memory 130 such as a RAM and a ROM.

  The control unit 100 can execute an acquisition process, a heating process, and a supply process.

  The heating process is a process of heating the heating unit 81 so that the temperature of the heating unit 81 becomes the fixing temperature. The fixing temperature is a temperature that is set according to the thickness of the sheet S, the conveyance speed, and the like in order to fix the developer image formed on the sheet S to the sheet S. In the present embodiment, the fixing temperature is a predetermined fixing temperature TH. And In the heat treatment, the control unit 100 heats the heating unit 81 so that the temperature of the heating unit 81 becomes the first temperature T1 lower than the fixing temperature TH, and after the first heat treatment, The second heat treatment is performed to heat the heating unit 81 so that the temperature of the unit 81 becomes the fixing temperature TH.

  Specifically, when receiving the print data, the control unit 100 performs the first heating process in parallel with the acquisition process described later. In addition, in the first heat treatment, the control unit 100 sets the target value of the temperature of the heating unit 81 to the first temperature T1, and the temperature of the heating unit 81 detected by the temperature detection unit 84 (hereinafter also referred to as a detected temperature Ts). .) Is controlled so that the heater 83 is energized to the first temperature T1. And the control part 100 is 1st heat processing, when two conditions of predetermined time ZA having passed since the start of 1st heat processing, and the completion | finish of the expansion | deployment process mentioned later being satisfied are satisfy | filled. And the second heat treatment is started. In the second heat treatment, the control unit 100 sets the target value of the temperature of the heating unit 81 to the fixing temperature TH, and controls energization to the heater 83 so that the detected temperature Ts becomes the fixing temperature TH.

  The supply process is a process of starting the supply of the sheet S by the pickup roller 23 after a predetermined time Zth from a predetermined timing. In the present embodiment, the predetermined timing is the timing at which the second heat treatment is started. In addition, when printing a plurality of sheets S in the supply process, the control unit 100 is configured to supply the sheets S such that the intervals between the plurality of sheets S are a predetermined interval. Further, the control unit 100 is configured to rotate the motor M at a predetermined timing to start driving the fixing device 80, specifically, rotation of the heating unit 81 and the pressure unit 82.

  In the acquisition process, the area of an image existing in a predetermined area at least behind the center in the transport direction, including the rear end in the transport direction, in the data of the first page on which the developer image is first formed in the print data is acquired. It is processing to do. Hereinafter, data corresponding to one page of print data is referred to as page data. The predetermined area can be set to an area as shown in FIGS. 3A to 3C, for example.

  A predetermined area A1 shown in FIG. 3A is a rectangular area having a predetermined length L1 from the rear end E3 in the transport direction to the front end E2 in the transport direction in the first page data PD of the print data. The length L1 is smaller than the length L3 from the transport direction center portion CP of the page data PD to the transport direction rear end E3. The predetermined area A1 is set from one end E1 to the other end E4 in the width direction of the page data PD.

  Here, the width direction is a direction along the width of the page data PD, that is, the width of the sheet S, and is a direction orthogonal to the conveyance direction of the sheet S. Further, both ends E1 and E4 in the width direction of the page data PD refer to both ends E1 and E4 with respect to the center line CL located at the center in the width direction of the page data PD. Here, the sheet S is conveyed so that the center in the width direction of the sheet S and the center line CL coincide with each other regardless of the dimension in the width direction.

  Further, the distance L2 from the leading E2 in the conveyance direction of the page data PD to the predetermined area A1 is longer than the length of n times the circumferential length of the pressure unit 82 that is a pressure roller. That is, the predetermined area A1 is an area on the rear side in the transport direction from a position separated from the head E2 in the transport direction of the page data PD by a distance n times the circumferential length of the pressure unit 82.

  Here, n is a natural number, and can be appropriately set by experiments or the like according to the heat storage amount of the pressurizing unit 82. Here, the amount of heat stored in the pressure unit 82 gradually decreases because the sheet S is deprived of heat in the process of fixing the sheet S from the leading side in the conveyance direction. Then, the natural number n can be set from the number of rotations of the pressurizing unit 82 when the heat storage amount of the pressurizing unit 82 decreases to the vicinity of the limit suitable for fixing the sheet S.

  A predetermined area A2 shown in FIG. 3B has a predetermined length L4 from the rear end E3 in the transport direction to the front end E2 in the transport direction in the first page data PD of the print data, and both ends E1, E4 in the width direction. Is a rectangular area having a predetermined width B2 from the center to the center line CL. For example, when the maximum width of the sheet S that can be printed by the color printer 1 is A4 or letter / legal width, the predetermined area A2 can be an area that is 90 mm or more away from the center line CL.

  A predetermined area A3 shown in FIG. 3C is an area in which the width decreases from the rear end E3 in the transport direction to the top E2 in the transport direction in the first page data PD of the print data. One predetermined area A3 is provided on each of the one end E1 side and the other end E4 side in the width direction of the first page data PD of the print data, and has a predetermined length L5 from the rear end E3 in the transport direction toward the head E2 in the transport direction. have.

  The control unit 100 is configured to execute a deployment process in the acquisition process. The expansion process is a process of expanding the received print data into a raster image. As shown in FIG. 4, in the expansion process, the control unit 100 performs a first process of expanding the received print data into object data D1 to D4 including vector data or bitmap data when print data is received. The second process of arranging the object data D1 to D4 in the virtual sheet SV and developing the raster data RI including a plurality of band data BD1 to BD15 can be executed.

  Here, the print data is data created by an external device such as a computer and configured in a page description language or the like, and cannot be handled as exposure data for the color printer 1. Therefore, the control unit 100 performs an expansion process for expanding print data composed of a page description language or the like into a raster image RI that is exposure data.

  The object data D1 to D4 are vector data or bitmap data. In the vector data, vector information as a contour and a fill are defined. Each object data D1 to D4 is associated with position information on the virtual sheet SV, size, and the like. In the first process, the received print data is expanded and the coordinate P located at one vertex of a rectangular frame circumscribing each object data D1 to D4, the width direction (X direction), and the transport direction (Y direction). Get the size. In FIG. 4, the origin coordinates of the virtual sheet SV are represented as P0, the object data D1 to D4, and the origin coordinates of the object data D1 to D4 on the virtual sheet SV are represented as P1 to P4, respectively.

  Each of the band data BD1 to BD15 includes a predetermined number, for example, 10 line data. That is, the raster image RI is composed of a plurality of line data. The line data is binary data corresponding to ON / OFF of the plurality of light emitting units of each LED unit 40, and corresponds to the plurality of dots of the electrostatic latent image formed in the rotation axis direction of the photosensitive drum 51. . In the second process, the control unit 100 arranges the object data D1 to D4 on the virtual sheet SV based on the position information, and sets the band data BD1 to BD15, specifically the line data, in the transport direction of the virtual sheet SV. It generates in order from one end. When generating line data, the control unit 100 refers to all object data included in the line. The control unit 100 executes the expansion process for each page of the sheet S.

  After the expansion process, the control unit 100 acquires the area of the circumscribed rectangle of the object data existing in the predetermined area as the area of the image existing in the predetermined area. Specifically, when a part of the circumscribed rectangle of the object data enters the predetermined area and the other part is located outside the predetermined area, the control unit 100 determines the area of the circumscribed rectangle as an image in the predetermined area. Get as an area.

  Further, the control unit 100 expands the object data for each color in the expansion process, and acquires a value obtained by adding the circumscribed rectangle areas of the object data of each color existing in the predetermined area as the area of the image in the predetermined area. Here, even when the circumscribed rectangles of the object data of each color are arranged in a predetermined region, the control unit 100 obtains the area of the circumscribed rectangle of the object data for each color and adds these areas. To do.

  Then, the control unit 100 determines whether or not the area of the image acquired in the acquisition process is equal to or less than a predetermined area. When the area is equal to or less than the predetermined area, the control unit 100 sets the predetermined time Zth in the supply process to be less than the predetermined area. It has a function to set a shorter time than when it is large. Specifically, the control unit 100 sets the predetermined time Zth to the first time Z1 when the area of the image acquired by the acquisition process is equal to or smaller than the predetermined area, and sets the predetermined time Zth when the area is larger than the predetermined area. Is set to a second time Z2 longer than the first time Z1. The predetermined area may be set in any way, and can be set to 0, for example.

  Next, the operation of the control unit 100 will be described in detail. The control unit 100 executes the control of the heater 83 and the motor M according to the flowchart shown in FIG. 5, and the driving / stopping control of the pickup roller 23 according to the flowchart shown in FIG.

  As shown in FIG. 5, the control unit 100 determines whether print data has been received (S1). If it is determined in step S1 that print data has not been received (No), the control unit 100 ends this control.

  If it is determined in step S1 that print data has been received (Yes), the control unit 100 starts the first heating process (S2). In step S2, the control unit 100 determines a first condition whether or not the specified time ZA has elapsed from the start of the first heating process and a second condition that determines whether or not the unfolding process is completed. If it is determined that both the second condition and the second condition are satisfied, the first heat treatment is terminated.

  After step S2, the control unit 100 rotates the motor M to start the rotation of the heating unit 81 and the pressure unit 82 (S3).

  After step S3, the control unit 100 starts the second heating process (S4). After step S4, the control unit 100 determines whether printing has ended (S5). If it is determined in step S5 that printing has not ended (No), the control unit 100 returns to the process of step S4. If it is determined in step S5 that printing has ended (Yes), the control unit 100 ends this control.

  In the control shown in FIG. 6, the control unit 100 first determines whether print data has been received (S11). In the present embodiment, the printing process is started based on the reception of the print data. If it is determined in step S11 that print data has not been received (No), the control unit 100 ends this control.

  If it is determined in step S11 that the print data has been received (Yes), the control unit 100 executes the expansion process for the first page of the print data (S12). After step S12, the control unit 100 acquires the area of the image existing in the predetermined region at the rear end portion in the transport direction of the first page (S13).

  After step S13, the control unit 100 determines whether the area of the image acquired in step S13 is equal to or smaller than a predetermined area (S14). If it is determined in step S14 that the area of the image is equal to or smaller than the predetermined area (Yes), the control unit 100 sets the predetermined time Zth to the first time Z1 (S15). If it is determined in step S14 that the area of the image is not less than or equal to the predetermined area (No), the control unit 100 sets the predetermined time Zth to a second time Z2 that is longer than the first time Z1 (S16).

  After step S15 or step S16, the control unit 100 determines whether or not the elapsed time Z from the start of the second heat treatment is equal to or longer than the predetermined time Zth (S17). In step S17, the control unit 100 repeats the process of step S17 until Z ≧ Zth (No), and if it is determined that Z ≧ Zth (Yes), the pickup roller 23 is driven to supply one sheet S. (S18).

  After step S18, the control unit 100 determines whether printing has ended (S19). If it is determined in step S19 that printing has not ended (No), the control unit 100 returns to step S18 and supplies the second and subsequent sheets S at a predetermined timing. Specifically, for the second and subsequent sheets S, the current sheet S is supplied after a predetermined time has elapsed since the sheet S was supplied last time so that the interval between the sheets S becomes a predetermined interval. It is supplied at a preset timing.

  If it is determined in step S19 that printing has ended (Yes), the control unit 100 ends this control.

Next, an example of the operation of the control unit 100 in the ready mode will be described with reference to FIG. The ready mode is a state in which the heating unit 81 is held at a ready temperature TR lower than the fixing temperature TH in order to perform printing in a relatively short time when print data is received.
As shown in FIG. 7, in the ready mode (time t0 to t1), the control unit 100 controls energization to the heater 83 so that the detected temperature Ts becomes a predetermined ready temperature TR.

  When receiving the print data in the ready mode (time t1), the control unit 100 starts the first heating process and the acquisition process. When the area of the image existing in the predetermined area acquired in the acquisition process is equal to or less than the predetermined area, the control unit 100 sets the predetermined time Zth in the supply process to the first time Z1 and is larger than the predetermined area. Sets the predetermined time Zth to the second time Z2 longer than the first time Z1.

  When the specified time ZA has elapsed from the start of the first heat treatment and the development processing is completed, the control unit 100 shifts from the first heat treatment to the second heat treatment, and rotates the motor M to rotate the heating unit 81 and The pressure unit 82 is rotated (time t2). Then, when a predetermined time Zth (Z1 or Z2) elapses from the start of the second heat treatment (time t2), the control unit 100 starts supplying the sheet S (time t3 or time t4). Thereby, the heat from the heater 83 can be stored in the pressurizing unit 82 for the predetermined time Zth.

  Here, when the area of the image existing in the predetermined area at the rear end portion in the conveyance direction of the first page is equal to or less than the predetermined area, fixing failure hardly occurs even if the amount of heat applied to the rear portion in the sheet conveyance direction is small. Therefore, when the area of the image existing in the predetermined area at the rear end of the leading page in the transport direction is equal to or smaller than the predetermined area, the predetermined time Zth is set to the short first time Z1 and the supply of the first sheet S is started. By advancing the timing, the printing can be quickly performed without waiting for the heat storage of the heating unit 81 or the pressurizing unit 82 even when the heating unit 81 or the pressurizing unit 82 is not sufficiently stored. it can.

  As described above, according to the present embodiment, the following effects can be obtained in addition to the effects described above.

  Since the acquisition process is performed in parallel with the first heating process, printing can be started more quickly.

  By acquiring the area of the circumscribed rectangle of the object data existing in the predetermined area as the area of the image, the area of the image can be defined at the time when the print data is expanded into the object data, so the processing speed of the acquisition process can be increased. .

  Since the target temperature in the first heating process performed in parallel with the acquisition process is set to the first temperature T1 lower than the fixing temperature TH, the heating unit 81 is heated unnecessarily when the acquisition process takes time. Can be suppressed.

  In addition, this invention is not limited to the said embodiment, It can utilize with various forms so that it may illustrate below. In the following description, the same reference numerals are given to substantially the same components as those in the above embodiment, and the description thereof is omitted.

  In the above embodiment, the operation of the control unit 100 when print data is received in the ready mode is illustrated, but the present invention is not limited to this, and as shown in FIG. 8, the temperature of the heating unit 81 in the sleep mode or the like. May be applied to a situation where the temperature is below a predetermined temperature. The sleep mode is a state in which energization to the heater 83 is stopped in order to reduce power consumption after a predetermined time has elapsed since the end of the previous printing. At this time, the heating unit 81 is at a temperature lower than the ready temperature TR. Even when the print data is received in the sleep mode, the control unit 100 performs the same operation as in the above-described embodiment, and thus can achieve the same effect. In this case, it is preferable to set the specified time ZA, the first time Z1, or the second time Z2 to a value different from the ready mode.

  In the above embodiment, the predetermined area at the rear end of the page conveyance direction and the interval between the sheets S for determining the supply timing of the second and subsequent sheets S are fixed values, but the present invention is not limited to this. Depending on the conditions, the predetermined area and the interval between the sheets S may be changed. Specifically, the control unit 100 may perform control according to the flowchart shown in FIG. The flowchart shown in FIG. 9 includes the steps S11 to S19 in the flowchart shown in FIG. 6 and also includes new steps S31 to S37.

  If the control unit 100 determines that the print data has been received in step S11 (Yes), the control unit 100 executes the process of step S31. In step S31, the control unit 100 acquires the thickness of the sheet S based on the print data, and acquires the humidity from a humidity detection unit (not shown).

  After step S31, the control unit 100 sets a predetermined area based on the acquired thickness and humidity (S32). Specifically, in step S32, the control unit 100 sets a predetermined area based on, for example, a predetermined area setting map shown in FIG. The predetermined area setting map is a map showing the relationship among the area, thickness, and humidity of the predetermined area, and is appropriately created by experiments or the like.

  The predetermined area setting map is configured such that the predetermined area is set to a larger area (area) as the humidity or the thickness of the sheet S is larger. Here, the area of the predetermined region is changed by changing the length of the predetermined region in the transport direction.

  Returning to FIG. 9, the control part 100 performs the process of step S12-S14 sequentially after step S32. When it is determined in step S14 that the area of the image in the predetermined area is equal to or smaller than the predetermined area (Yes), the control unit 100 sets a flag F indicating that the predetermined time Zth is set to the short first time Z1 to 1. (S33), the process of step S15 is executed. If it is determined in step S14 that the area of the image in the predetermined area is not equal to or smaller than the predetermined area (No), the flag F is set to 0 (S34), and then the process of step S16 is executed.

  After steps S15 and S16, the control unit 100 sequentially executes the processes of steps S17 and S18. After step S18, the control unit 100 determines whether or not the flag F is 1 (S35).

  When it is determined in step S35 that F = 1 (Yes), the control unit 100 sets the interval between the first sheet S and the second sheet S to a larger interval than the predetermined interval. (S36), the flag F is returned to 0 (S37). After step S37, the control unit 100 executes the process of step S19, and when it is necessary to print the second and subsequent sheets S (No), the control unit 100 returns to step S18.

  In step S18, if the sheet interval has been changed to a large interval in step S36, the supply timing of the second sheet S is set to a timing that is later than the normal timing corresponding to the predetermined interval. The sheet S of eyes is supplied. That is, when the predetermined time Zth is set to the short first time Z1, the control unit 100 sets the second sheet so that the interval between the first sheet S and the second sheet S is larger than the predetermined interval. Sheet S is supplied. In step S18, the control unit 100 supplies the third and subsequent sheets S at a supply timing corresponding to a predetermined interval.

  When it is determined in step S35 that F = 1 is not satisfied (No), the control unit 100 skips steps S36 and 37 and executes the process of step S19. Thus, when the predetermined time Zth is not set to the short first time Z1, the control unit 100 sets the supply timing of the second sheet S as a timing corresponding to the predetermined interval.

According to this embodiment, the following effects can be obtained.
By increasing the interval between the first sheet S and the second sheet S, the time from when the first sheet S is fixed until the second sheet S reaches the heating unit 81 is increased. Therefore, the heating unit 81 can be sufficiently stored in that time, and the occurrence of poor fixing in the second sheet S can be suppressed.

  The greater the humidity or the thickness of the sheet S, the more easily the heat of the heating unit 81 and the pressure unit 82 is taken away by the sheet S. By setting the predetermined region to a larger region as the humidity or the thickness of the sheet S increases, It is possible to suppress the occurrence of fixing failure in the first sheet S.

  In the above-described embodiment, the region on the rear side in the transport direction from the position separated by a distance n times the circumferential length of the pressure unit 82 that is a pressure roller is set as the predetermined region, but the present invention is not limited to this. A region on the rear side in the transport direction from a position separated by a distance n times the circumferential length of the heating unit 81 that is a heating roller may be set as the predetermined region. However, since the pressure roller has a larger heat capacity than the heating roller and greatly contributes to the fixability, it is preferable to set the predetermined region based on the circumference of the pressure roller.

  In the embodiment, the predetermined timing is the timing at which the second heating process is started. However, the present invention is not limited to this, and the predetermined timing may be a timing based on a predetermined state after the start of the printing process. Good. For example, it may be the timing when the heat treatment is started, or may be the timing when the temperature of the heating portion reaches the second temperature T2 (see FIG. 8) lower than the fixing temperature after the heat treatment is started. .

  In the embodiment, in the acquisition process, the area of the circumscribed rectangle of the object data is acquired as the area of the image, but the present invention is not limited to this. For example, in the acquisition process, the number of dots of the image in the predetermined area may be acquired as the area of the image.

  In the above-described embodiment, the pickup roller 23 is exemplified as the sheet supply unit. However, the present invention is not limited to this, and the sheet supply unit can switch the stop and conveyance of the sheet S by the control unit 100. Good. For example, the sheet supply unit may be the registration roller 29 or a supply roller for supplying a sheet on the manual feed tray.

  The sheet S may be paper such as thick paper, postcard, and thin paper, or may be an OHP sheet.

  The developer image forming unit is arbitrarily configured. For example, a developer image forming unit that exposes the photosensitive drum by a scanner that emits laser light may be used as the exposure device.

  In the above embodiment, a cylindrical heating roller is exemplified as the heating unit 81, but the present invention is not limited to this, and the heating unit is, for example, a nip plate that sandwiches an endless belt with a pressurizing unit. Also good.

  In the embodiment, the rotation of the heating unit 81 and the pressing unit 82 is started by rotating the motor M, that is, the driving of the fixing device 80 is started. However, the present invention is not limited to this. For example, when the fixing device is connected to the motor via a clutch, the control unit may start driving the fixing device by turning on the clutch.

  In the above-described embodiment, the heater 83 has a filament that is a resistor, and the halogen lamp that heats the heating unit 81 by radiant heat is exemplified. However, the present invention is not limited to this, and the heater 83 has a resistance heating element. It may be a ceramic heater or the like, and may be configured to heat the heating unit 81 by heat conduction.

  In the said embodiment, although the temperature detection part 84 which does not contact the surface of the heating part 81 was illustrated, this invention is not limited to this, The temperature detection part may be contacting the surface of the heating part.

  In the above embodiment, the present invention is applied to the color printer 1, but the present invention is not limited to this, and the present invention may be applied to other image forming apparatuses such as monochrome printers, copiers, and multifunction machines. .

  In the above-described embodiment, the control unit 100 of the color printer 1 executes the expansion process for expanding the print data and the acquisition process for acquiring the area of the image existing in the predetermined area at the rear end in the transport direction on the first page of the print data. However, the present invention is not limited to this, and one or both of the expansion process and the acquisition process may be executed by a computer that transmits print data or an external device that performs communication. .

  Moreover, you may implement combining each element demonstrated by above-described embodiment and modification arbitrarily.

DESCRIPTION OF SYMBOLS 1 Color printer 23 Pickup roller 30 Process part 80 Fixing device 81 Heating part 100 Control part A1 Predetermined area S Sheet TH Fixing temperature Z1 1st time Zth Predetermined time

Claims (16)

A sheet supply unit capable of switching between a stopped state and a conveying state of the sheet;
A developer image forming unit for forming a developer image on the sheet;
A fixing device having a heating section for heating the sheet;
A control unit,
The controller is
When starting the printing process,
An acquisition process for acquiring an area of an image existing in a predetermined area at least on the rear side of the central part in the transport direction, including the rear end part in the transport direction in the first page where the developer image is first formed in the print data;
A heat treatment for heating the heating unit such that the temperature of the heating unit becomes a fixing temperature;
A supply process of starting the sheet supply by the sheet supply unit after a predetermined time from a predetermined timing after the start of the printing process,
When the area of the image existing in the predetermined area on the first page of the print data is equal to or smaller than the predetermined area, the predetermined time in the supply process is set to a shorter time than when the area of the image is larger than the predetermined area. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the predetermined timing is a timing at which the heat treatment is started. The controller is
In the heating process, in parallel with the acquisition process, a first heating process for heating the heating unit so that the temperature of the heating unit becomes a first temperature lower than the fixing temperature;
2. The image forming apparatus according to claim 1, wherein after the first heat treatment is finished, a second heat treatment is performed to heat the heating portion so that a temperature of the heating portion becomes a fixing temperature.   The image forming apparatus according to claim 3, wherein the predetermined timing is a timing at which the second heat treatment is started.   The image forming apparatus according to claim 1, wherein the predetermined timing is a timing at which the temperature of the heating unit reaches a second temperature lower than the fixing temperature after the heat treatment is started.   The said predetermined area | region is a rectangular area | region which has predetermined length from the conveyance direction rear end in the said 1st page toward the conveyance direction head, The one of Claims 1-5 characterized by the above-mentioned. Image forming apparatus.   The predetermined region is a rectangular region having a predetermined length from the rear end in the transport direction to the front in the transport direction and having a predetermined width from both ends in the width direction toward the center. The image forming apparatus according to any one of claims 1 to 5.   6. The image forming apparatus according to claim 1, wherein the predetermined area is an area whose width decreases from the rear end in the transport direction to the head in the transport direction on the first page. . The controller is
In the acquisition process,
When the print data is received, an expansion process for expanding the print data into object data composed of vector data or bitmap data is executed.
9. The image forming apparatus according to claim 1, wherein an area of a circumscribed rectangle of the object data existing in the predetermined region is acquired as an area of the image. The controller is
Expand the object data for each color in the expansion process,
The image forming apparatus according to claim 9, wherein a value obtained by adding an area of a circumscribed rectangle of the object data of each color existing in the predetermined region is acquired as the area of the image.   The image forming apparatus according to claim 1, wherein the predetermined area is zero.   The image forming apparatus according to claim 1, wherein the control unit acquires the number of dots of the image as an area of the image in the acquisition process. The controller is
In the supply process, when printing a plurality of sheets, the sheets are supplied so that each of the plurality of sheets has a predetermined interval.
When the predetermined time is set to be shorter than the case where the area of the image is larger than the predetermined area, the interval between the first sheet and the second sheet is made larger than the predetermined interval. The image forming apparatus according to claim 1, wherein a second sheet is supplied. A pressure roller that sandwiches the sheet with the heating unit;
14. The predetermined region is a region on the rear side in the transport direction from a position separated from the head of the page in the transport direction by a distance n times the circumferential length of the pressure roller. The image forming apparatus according to any one of the above.   The image forming apparatus according to claim 1, wherein the control unit sets the predetermined region to a larger region as the humidity or the thickness of the sheet increases. Control of an image forming apparatus having a sheet supply unit capable of switching between a stopped state and a conveying state of a sheet, a developer image forming unit that forms a developer image on the sheet, and a fixing unit that includes a heating unit that heats the sheet A method,
When starting the printing process,
An acquisition process for acquiring an area of an image existing in a predetermined region at least on the rear side of the central portion in the transport direction including the rear end portion in the transport direction in the first page in which the developer image is first formed in the print data;
A heat treatment for heating the heating unit such that the temperature of the heating unit becomes a fixing temperature;
A supply process of starting the sheet supply by the sheet supply unit after a predetermined time from a predetermined timing after the start of the printing process,
When the area of the image existing in the predetermined area on the first page of the print data is equal to or smaller than the predetermined area, the predetermined time in the supply process is set to a shorter time than when the area of the image is larger than the predetermined area. A control method characterized by:

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