Image forming apparatus

Abstract

The invention relates to an image forming apparatus. An image forming apparatus includes: an execution section for operating in a borderless image forming mode in which a toner image is formed in an edge portion of a recording material and for operating in a normal image forming mode in which no toner image is formed in the edge portion; an image forming section; a fixing device; a heating unit; a nip forming portion; and a temperature detection unit. And a controller. In the case of the borderless image forming mode, the controller controls the heating portion such that the temperature thereof becomes a first control temperature in a first period in which the recording material passes through the fixing nip. In a normal image forming mode, the controller controls the heating portion such that a temperature thereof becomes a second control temperature higher than the first control temperature in the first period.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine having a plurality of functions of these machines. Background Art

[0002] As an image forming apparatus, in addition to an image forming apparatus that can operate in an image forming mode in which a margin is provided in an edge portion of a recording material and image formation is performed, an image forming apparatus that can operate in a borderless image forming mode in which image formation is performed on an edge portion of a recording material is also known.

[0003] In the operation in the borderless image forming mode, an image is formed in a size larger than the size of the recording material and then transferred onto the recording material. Therefore, toner is likely to be deposited on the edge of the recording material. The toner deposited on the edge of the recording material is not easily fixed on the recording material and is easily peeled off when the user touches the toner, so that the toner is deposited on a portion other than the recording material, thereby causing contamination inside the image forming apparatus. For this reason, in Japanese Patent Laid-Open Application No. 2019-53198, a technique is proposed in which cleaning means for cleaning the toner deposited on the edge of the recording material is provided, and then the side surface of the recording material is cleaned after the fixing step. Summary of the Invention

[0004] According to one aspect of the present invention, there is provided an image forming apparatus that can perform operations in a borderless image forming mode in which a toner image is formed in an edge portion of a recording material of a predetermined size and in an image forming mode in which a toner image is not formed in the edge portion of the recording material of the predetermined size. The image forming apparatus includes: an image forming unit configured to form a toner image on a recording material; a fixing device including a fixing member, a heating unit for heating the fixing member, a nip forming unit for forming a fixing nip that clamps and conveys the recording material between itself and the fixing member and for fixing the toner image on the recording material when the recording material carrying the toner image passes through the fixing nip, and a temperature detection unit for detecting the temperature of the fixing member or the heating unit; and a controller configured to control the heating unit based on the detection result of the temperature detection unit. In a case where an operation in the image forming mode is performed for a recording material of a predetermined size, the controller controls the heating unit so that the temperature becomes a first control temperature during a first period that is a period in which the recording material passes through the fixing nip. And in a case where an operation in the borderless image forming mode is performed for a recording material of a predetermined size, the controller controls the heating unit so that the temperature becomes a second control temperature higher than the first control temperature during the first period.

[0005] According to another aspect of the present invention, there is provided an image forming apparatus that can perform operations in a borderless image forming mode in which a toner image is formed in an edge portion of a recording material of a predetermined size and an image forming mode in which a toner image is not formed in an edge portion of a recording material of a predetermined size. The image forming apparatus includes: an image forming unit configured to form a toner image on a recording material; a fixing device including a fixing member, a heating unit for heating the fixing member, a nip forming unit for forming a fixing nip that holds and conveys the recording material between itself and the fixing member and for fixing the toner image on the recording material when the recording material carrying the toner image passes through the fixing nip, and a temperature detection unit for detecting the temperature of the fixing member or the heating unit; and a controller configured to control the heating unit based on the detection result of the temperature detection unit. In a case where an operation in the image forming mode is performed for a predetermined recording material, the controller controls the heating unit such that the temperature becomes a first control temperature in a second period from the upstream end of the first recording material with respect to the conveyance direction passing through the fixing nip until the downstream end of the second recording material after the first recording material with respect to the conveyance direction reaches the fixing nip. In a case where an operation in the borderless image forming mode in which an image is formed in an edge portion of the predetermined recording material with respect to the conveyance direction is performed, the controller controls the heating unit such that the temperature becomes a second control temperature higher than the first control temperature in the second period.

[0006] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a schematic cross-sectional view of an image forming apparatus according to a first embodiment.

[0008] Figure 2 is a control block diagram of the image forming apparatus according to the first embodiment.

[0009] Figure 3 Part (a) of... is a schematic cross-sectional view of a fixing device in the first embodiment, and Figure 3 Part (b) of... is a schematic view showing the arrangement of a thermistor in the longitudinal direction and the heat generation amount of a fixing heater in the longitudinal direction in the fixing device in the first embodiment.

[0010] Figure 4 Parts (a) and (b) of... are schematic views showing a first example and a second example of the fixing heater in the first embodiment, respectively.

[0011] Figure 5Parts (a) and (b) are graphs showing the control temperature and temperature progress in the operations in the image formation mode and the borderless image formation mode in the first embodiment.

[0012] Figure 6 is a flowchart of the image forming operation in the first embodiment.

[0013] Figure 7 is a schematic diagram showing the temperature distribution in the longitudinal direction in the image formation mode and the borderless image formation mode in the second embodiment.

[0014] Figure 8 is a flowchart of the image forming operation in the second embodiment.

[0015] Figure 9 is a graph showing the control temperature and temperature progress of the fixing belt in the borderless image formation mode in the third embodiment.

[0016] Figure 10 is a flowchart of the image forming operation in the third embodiment.

[0017] Figure 11 is a schematic diagram showing the images in the image formation mode and the borderless image formation mode. Detailed Description of the Invention

[0018] <First Embodiment>

[0019] The first embodiment will be described using Figures 1 to 6 and Figure 11 First, the overall structure of the image forming apparatus according to this embodiment will be described using Figure 1 .

[0020] [Image Forming Apparatus]

[0021] The image forming apparatus 1 is an electrophotographic full-color printer, which includes four image forming units Py, Pm, Pc, and Pk provided corresponding to four colors of yellow, magenta, cyan, and black, respectively. In this embodiment, a tandem type is adopted, in which the image forming units Py, Pm, Pc, and Pk are arranged along the rotation direction of an intermediate transfer belt 105 described later. The image forming apparatus 1 forms a toner image (image) on a recording material according to an image signal from an image reading unit (original image reading device) not shown or a host device such as a personal computer communicably connected to the image forming apparatus 1. Examples of the recording material include a sheet, a plastic film, a cloth, and the like.

[0022] Each of the image forming units Py, Pm, Pc, and Pk includes a photosensitive drum 101 of an image bearing member, a charging roller 102 as a charging device, a developing device 104, a primary transfer roller 111 as a primary transfer device, a drum cleaner 107 as a cleaning device, etc. The photosensitive drum 101 is rotationally driven in the counterclockwise direction indicated by the arrow in Figure 1 during its rotation at a predetermined processing speed (circumferential speed). The photosensitive drum 101 is charged to a predetermined polarity by the charging roller 102 during its rotation.

[0023] Based on the input image information, the charged surface of the photosensitive drum 101 is exposed to the laser light 103 output from the exposure device 110. By outputting the laser light 103 modulated (on / off) corresponding to the time series electro-digital pixel signals of the image information from an image signal generating device such as an image reading unit (not shown), the exposure device 110 scans and exposes the surface of the photosensitive drum 101. Through this scanning exposure, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 101. Incidentally, the laser light 103 output from the exposure device 110 is deflected to the exposure position of the photosensitive drum 101 by the mirror 109.

[0024] The developing device 104 develops the electrostatic latent image formed on the photosensitive drum 101 with a developer. In each of the developing devices 104 of the image forming units Py, Pm, Pc, and Pk, toner of a color corresponding to the associated image forming unit is accommodated, and a toner image of that color is formed on the photosensitive drum 101 of the associated image forming unit. The toner image on the photosensitive drum 101 is primarily transferred onto the surface of the intermediate transfer belt 105 in the primary transfer section T1, which is the contact portion between the photosensitive drum 101 and the intermediate transfer belt 105 as an intermediate transfer member. Specifically, the primary transfer roller 111 arranged opposite the photosensitive drum 101 with the intermediate transfer belt 105 therebetween discharges from the back side of the intermediate transfer belt 105 to the photosensitive drum 101, and a primary transfer bias of a polarity opposite to that of the toner is applied to the photosensitive drum 101. Thereby, the toner image on the photosensitive drum 101 is transferred onto the surface of the intermediate transfer belt 105. Incidentally, the toner remaining on the surface of the photosensitive drum 101 after primary transfer is removed by the drum cleaner 107.

[0025] The above cycle of charging, exposure, development, primary transfer, and drum cleaning is repeated in the respective image forming units, thereby forming a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image on the photosensitive drums 101 of the image forming units. Then, in the respective primary transfer sections T1, the toner images of each color are successively superimposed and transferred onto the intermediate transfer belt 105, thereby forming a full-color image on the intermediate transfer belt 105.

[0026] The toner image on the intermediate transfer belt 105 is secondarily transferred onto the recording material in a concentrated manner in the secondary transfer section T2. The secondary transfer section T2 is the contact portion between the outer peripheral surface of the intermediate transfer belt 105 tensioned by the inner secondary transfer roller 106a and the outer secondary transfer roller 106b, and a secondary transfer bias is applied to the secondary transfer section T2 such that the toner image is secondarily transferred from the intermediate transfer belt 105 onto the recording material passing through the secondary transfer section T2. The recording material is accommodated in a cassette 113, and the recording material fed from the cassette 113 is conveyed to the registration roller pair 114 and waits at the registration roller pair 114. Thereafter, the timing is controlled such that the registration roller pair 114 aligns the recording material with the toner image on the intermediate transfer belt 105, and the registration roller pair 114 conveys the recording material to the secondary transfer section T2. Incidentally, the toner remaining on the intermediate transfer belt 105 after the secondary transfer is removed by the belt cleaner 108.

[0027] The recording material onto which the toner image has been transferred in the secondary transfer section is conveyed to the fixing device 100 and is heated and pressed in the fixing device 100 such that the toner image carried on the recording material is fixed onto the recording material. The recording material passing through the fixing device 100 is discharged to the outside of the image forming apparatus 1, thereby ending a series of image forming operations. Incidentally, in the case where images are formed on both sides (surfaces) of the recording material (double-sided printing), when the transfer and fixing of the toner image onto the first side (front side) of the recording material are completed, the recording material is turned upside down by the reverse conveyance section 115, and then the transfer and fixing of the toner image onto the second side (back side) of the recording material are performed, and the recording material is discharged to the outside of the image forming apparatus 1.

[0028] The image forming apparatus 1 of the present embodiment can perform Figure 11 the (normal) printing and borderless printing as shown in Figure 11 That is, the image forming apparatus 1 can perform operations in a borderless image forming mode (borderless printing) in which a toner image is formed in the edge portion of the recording material and operations in a (normal) image forming mode ((normal) printing) in which a toner image is not formed in the edge portion of the recording material. During printing, an electrostatic latent image is formed on the surface of the photosensitive drum 101 within a range narrower than the recording material, as shown in the schematic image view of

[0029] "printing", and a margin of approximately 2 to 5 mm is provided in the edge portion (all edges) of the recording material in the final product. Figure 11As shown in the schematic image view of "borderless printing", no margin is provided in the edge portion of the recording material in the final product. Figure 11 The schematic image view of "borderless printing" shows an example of borderless printing, and image formation is performed such that no margin is provided in at least one of the edge portions of the four edges on both sides with respect to the conveyance direction of the recording material and on both sides with respect to the width direction intersecting the conveyance direction. For example, in Figure 11 the schematic image view of "borderless printing", in the first image view (1) starting from the left (hand) side, image formation is performed on the entire surface of the recording material in the final product, that is, in the edge portions of all four edges. Further, in the second image view (2) starting from the left side, margins are provided in the edge portions on both sides with respect to the conveyance direction of the recording material in the final product, while no margin is provided in the edge portions on both sides with respect to the width direction. In the third image view (3) starting from the left side, margins are provided in the edge portions on both sides with respect to the width direction in the final product, while no margin is provided in the edge portions on both sides with respect to the conveyance direction of the recording material. In the fourth image view (4) starting from the left side, margins are provided in the edge portions on both sides with respect to the conveyance direction of the recording material in the final product, while no margin is provided in the edge portion on one side with respect to the width direction. The type of "borderless printing" is not limited to Figure 11 the image view, but it may only be required to form a toner image in the (one or more) edge portions of the recording material.

[0030] [Controller]

[0031] The image forming apparatus 1 is provided with a control circuit unit 21 represented by a CPU (Central Processing Unit) or the like, and an operation panel 112 that serves as an interface for communicating with a user or an external device and for accessing the image forming apparatus 1. The operation panel 112 as an operation unit is composed of a liquid crystal touch panel, buttons, etc., and by operating these, various settings of the image forming apparatus 1 can be made.

[0032] Figure 2 is a control block diagram of the image forming apparatus 1. The control circuit unit 21 as a controller is connected to the operation panel 112, the image forming units Py, Pm, Pc, and Pk, the recording material conveyance unit 116, and the fixing device 100, and controls the overall operation of the image forming apparatus 1 by integrating the command chains between the respective devices. The recording material conveyance unit 116 includes a motor for driving a roller for conveying the recording material inside the image forming apparatus 1 and a sensor for detecting the recording material.

[0033] The control circuit unit 21 includes a CPU, a ROM (Read Only Memory), and a RAM (Random Access Memory). The CPU reads the program stored in the ROM corresponding to the control process and simultaneously executes the control of the corresponding units. Additionally, working data and input data are stored in the RAM, and the CPU executes control by referring to the data stored in the RAM based on the above program and the like.

[0034] Furthermore, the control circuit unit 21 includes a fixing drive controller 14, a heater drive controller 28, and a cooling controller 31. The fixing drive controller 14 controls the fixing drive unit 15. The heater drive controller 28 controls the fixing heater 16 based on the detection results of the thermistors 18 and 19. The cooling controller 31 controls the cooling fan 29 and the shutter 30. The configurations of these components will be described later.

[0035] In this embodiment, the user can select the borderless image formation mode and the (normal) image formation mode from the operation panel 112 or the host device. Additionally, in the case of the borderless image formation mode, as described above with reference to Figure 11 it also becomes possible to select whether to form an image in which edge portion of the recording material. Further, when the image read by the image reading unit connected to the image forming apparatus 1 or the image data transmitted from the host device is an image to be formed in the edge portion, the control circuit unit 21 performs operations in the borderless image formation mode according to the image data.

[0036] [Fixing Device]

[0037] Next, the fixing device 100 will be described using Figure 3 part (a) to Figure 4 part (b) thereof. Figure 3 Part (a) thereof is a cross-sectional structural view of the fixing device 100 along a direction perpendicular to the longitudinal direction of the fixing device 100, and Figure 3 part (b) thereof is a schematic diagram showing the arrangement of the thermistors 18 and 19 and the cooling fan 29 with respect to the longitudinal direction of the fixing device 100 and the calorific value of the fixing heater 16 with respect to the longitudinal direction of the fixing heater 16. Figure 4 Parts (a) and (b) thereof are schematic diagrams respectively showing two examples of the structures of the heating elements 16a and 16b and the heating elements 16c and 16d of the fixing heater 16.

[0038] The fixing device 100 includes a fixing belt 20, a fixing heater 16 as a heating unit, a pressure roller 22 as a nip forming member, thermistors 18 and 19 as a temperature detection unit, etc. The fixing belt 20 is a cylindrical endless belt including an elastic layer. The fixing heater 16 is supported by a heater holder 17 having a substantially trough-shaped cross section and having heat resistance properties, and heats the fixing belt 20. The pressure roller 22 forms a fixing nip 27 between itself and the fixing belt 20, holds and conveys a recording material in the fixing nip 27, and fixes the toner image on the recording material when the recording material carrying the toner image passes through the fixing nip 27.

[0039] In the present embodiment, the fixing heater 16 is joined and fixed to the lower surface of the heater holder 17 along the longitudinal direction, and is configured to be slidable with respect to the fixing belt 20. In addition, the fixing belt 20 is externally joined to the outside of the heater holder 17 around the heater holder 17. The longitudinal direction is the longitudinal direction of the fixing belt 20, and is also a direction (width direction) intersecting the recording material conveyance direction.

[0040] With respect to the longitudinal direction, the fixing heater 16 can change the temperature in the end portion and the central portion of the area where the recording material passes through the fixing nip 27. Specifically, as shown in parts (a) and (b) of Figure 4 , with respect to the longitudinal direction, the fixing heater 16 includes heating elements 16a or 16c as first heating elements having a larger calorific value in the central portion than in the end portion of the area where the recording material passes through the fixing nip 27, and includes heating elements 16b or 16d as second heating elements having a larger calorific value in the end portion than in the central portion of the area where the recording material passes through the fixing nip 27. Hereinafter, the heating of the heating element by energization is referred to as lighting (energization), and the ratio of the energization time between the heating elements is referred to as the lighting ratio (energization ratio).

[0041] Figure 4 The heating elements 16a and 16b shown in part (a) of

[0042] Figure 4The heating elements 16c and 16d shown in part (b) have different lengths in the longitudinal direction. The heating element 16c is disposed in the central portion with respect to the longitudinal direction, while the heating element 16d is disposed at the end with respect to the longitudinal direction. That is, the heating elements 16c and 16d are different from each other in the heating region with respect to the longitudinal direction. For this reason, when the lighting ratio of the heating element 16c and the heating element 16d is large, the calorific value of the entire fixing heater 16 becomes larger in the central portion than at the end with respect to the longitudinal direction. On the other hand, when the lighting ratio of the heating element 16c and the heating element 16d is small, the calorific value of the entire fixing heater 16 becomes larger at the end than in the central portion with respect to the longitudinal direction. The length and position of each of the heating elements 16c and 16d with respect to the longitudinal direction correspond to the length of the recording material passing through the fixing nip 27 in the width direction, and as will be described later, the lighting ratio is controlled according to the size of the recording material. Incidentally, in the fixing heater 16, as described above, three or more heating elements having different calorific values with respect to the longitudinal direction are provided, and the lighting ratio of each heating element can be finely controlled according to the size, basis weight, and type (e.g., coated paper, plain paper, etc.) of the recording material.

[0043] A specific example of controlling the lighting ratio of the heating element according to the size of the recording material will be described. The lighting ratio between the heating element 16a or 16c and the heating element 16b or 16d is controlled by the control circuit unit 21 via the heater drive controller 28. Further, for example, in the case of the recording material of the maximum size, lighting is performed at a lighting ratio of 50 (heating element 16a or 16c):50 (heating element 16b or 16d). Further, in the case of the recording material of a small size, control is performed at a lighting ratio of 70 (heating element 16a or 16c):30 (heating element 16b or 16d) so that the temperature of the end with respect to the longitudinal direction where the recording material does not pass can be reduced.

[0044] The fixing belt 20 is an endless belt and has a structure in which a silicone rubber layer (elastic layer) having a thickness of about 300 μm is formed on a base material formed of cylindrical stainless steel having a thickness of about 30 μm, and the elastic layer is coated with a PFA (perfluoroalkoxy alkane) resin tube (outermost layer) having a thickness of about 30 μm as a surface layer. The pressure roller 22 has a structure in which a silicone rubber layer having a thickness of about 2.5 mm and a PFA resin tube having a thickness of about 50 μm are laminated on the surface of a core metal of Fe. The opposite (two) ends of the core metal of this pressure roller 22 are rotatably held between the opposite side plates of the fixing device 100.

[0045] Above the pressure roller 22, a fixing unit 200 including a fixing heater 16, a heater holder 17, and a fixing film belt is provided. This fixing unit 200 is arranged in parallel with the pressure roller 22 to contact the pressure roller 22 on the side of its fixing heater 16. The heater holder 17 is formed of a liquid crystal polymer having high heat resistance properties and has the functions of holding the fixing heater 16 and guiding the circulation track of the fixing belt 20. Opposite ends of the heater holder 17 are urged along the axial direction of the pressure roller 22 by a pressing mechanism (not shown). For example, the force on one side is 157 N, that is, a total of 314 N. As a result, the surface of the fixing heater 16 is pressed against the elastic layer of the pressure roller 22 by the fixing belt 20 with a predetermined pressing force, so that a fixing nip 27 having a predetermined width necessary for fixing is formed.

[0046] The fixing heater 16 is a ceramic heater. That is, the fixing heater 16 includes heating resistors (heating elements 16a or 16c, heating elements 16b or 16d), which are prepared by applying a conductive paste containing a silver / palladium alloy in a uniform film thickness of about 10 μm to a ceramic substrate of alumina or aluminum nitride according to the screen printing method. In addition, a glass coating is formed on the heating element to ensure voltage resistance.

[0047] Thermistors 18 and 19 detect the temperatures of the fixing belt 20 and the fixing heater 16. Specifically, as shown in part (a) of Figure 3 , the thermistor (also referred to as the heater back thermistor) 19 is provided on the surface (also referred to as the back surface) on the side opposite to the sliding surface of the fixing heater 16 and has the function of detecting the back temperature of the fixing heater 16. The thermistor (also referred to as the belt back thermistor) 18 is provided at a plurality of positions above the heater holder 17 so as to elastically contact the inner peripheral surface of the fixing belt 20 and has the function of detecting the inner surface temperature of the fixing belt and the function of discriminating the temperature in the edge portion of the recording material.

[0048] The belt back thermistor 18 is mounted at the free end of an arm 25 formed of stainless steel fixedly supported by the heater holder 17. In addition, the arm 25 swings elastically, so that even in a state where the movement of the inner surface of the fixing belt 20 becomes unstable, a state is formed in which the belt back thermistor 18 stably contacts the inner surface of the fixing belt 20. The belt back thermistor 18 includes a plurality of thermistors 18a to 18f, as shown in part (b) of Figure 3 . That is, the belt back thermistor is arranged at a plurality of positions, and the temperature of the fixing belt 20 detected at positions corresponding to the ends of recording materials having different sizes with respect to the longitudinal direction of the fixing belt 20. In addition, in part (a) of this article Figure 3 , any one of these thermistors 18a to 18f is also simply referred to as the thermistor 18 in some cases.

[0049] The thermistors 18a and 18b are arranged at opposite ends in the width direction of the area where the recording material of the maximum size passes through the fixing roller nip 27 (this area is also referred to as the maximum sheet passing area). The thermistors 18c and 18d are arranged at opposite ends in the width direction of the area where the recording material of a size smaller than the maximum size in the width direction passes through the fixing roller nip 27 (this size is A4R in this embodiment). The thermistors 18e and 18f are arranged at opposite ends in the width direction of the area where the recording material of an even smaller size in the width direction (for example, the recording material of the minimum size) passes through the fixing roller nip 27. Incidentally, the recording material of A4 size passing through the fixing roller nip 27 means that the recording material of A4 size passes through the fixing roller nip 27 in a direction perpendicular to the short side direction of the recording material of A4 size, and the recording material of A4R size passing through the fixing roller nip 27 means that the recording material of A4R size passes through the fixing roller nip 27 in a direction perpendicular to the longitudinal direction of the recording material of A4R size.

[0050] The heater-back thermistor 19 and the belt-back thermistor 18 are connected to the control circuit unit 21 via the A / D converters 64 and 65, respectively. This control circuit unit 21 samples the outputs from each thermistor at a predetermined cycle period and has a configuration that reflects the temperature information thus obtained in the temperature control.

[0051] That is, the control circuit unit 21 determines the content of the temperature adjustment control of the fixing heater 16 based on the outputs of the belt-back thermistor 18 and the heater-back thermistor 19, and controls the energization of the fixing heater 16 through the heater drive controller 28 which is a power supply unit. In the fixing device 100 of the temperature control type, the supply power value to the heater is mainly determined so that the detected temperature value of the belt-back thermistor 18 can be stably maintained at the desired temperature. As a specific method thereof, the power is changed so that the temperature reaches the target temperature (hereinafter also referred to as the control temperature) earlier, and it is stably maintained by calculating from the target temperature, the detected temperature, the temperature change amount per unit time, the heater input power value, and the PI control parameters of the belt-back thermistor 18. At this time, the direct heat source is the fixing heater 16, so in order not to cause excessive sharp fluctuations in the temperature of the fixing belt 20, the PI control is also assisted for the detected temperature and the temperature change amount of the heater-back thermistor 19 to stabilize the inner surface temperature of the fixing belt 20 earlier.

[0052] When the image forming operation starts, the control circuit unit 21 drives the fixing driving unit 15 through the fixing driving controller 14 so that the pressure roller 22 is rotationally driven in the arrow direction at a predetermined rotational speed. The fixing driving unit 15 is, for example, a motor for rotationally driving the pressure roller 22. The fixing belt 20 in a pressure contact relationship with the pressure roller 22 is rotationally driven at a predetermined speed by following the pressure roller 22. At this time, the inner peripheral surface of the fixing belt 20 is in a state of following rotation along the outer periphery of the heater holder 17 in the arrow direction and is in close contact with the sliding surface of the fixing heater 16. On the inner peripheral surface of the fixing belt 20, heat-resistant grease is applied to ensure the sliding property with the heater holder 17 and the fixing belt 20.

[0053] When the pressure roller 22 is rotationally driven and the cylindrical fixing belt 20 is also in a following rotation state, power is supplied to the fixing heater 16. Then, when the temperature of the fixing belt 20 becomes the desired temperature, the recording material P carrying the unfixed toner image t is guided along the inlet guide 23 and introduced into the fixing nip 27.

[0054] In the fixing nip 27, the recording material P is in close contact with the outer peripheral surface of the fixing belt 20 on the toner image bearing surface side so that the recording material P moves together with the fixing belt 20. During the nip feeding of the recording material P in the fixing nip 27, the heat of the fixing belt 20 is transferred to the recording material P, thereby melting and fixing the unfixed toner image t on the recording material P. The recording material P passing through the fixing nip 27 is separated by curvature and discharged by the fixing discharge roller pair 26.

[0055] The fixing device 100 is formed in a long shape with respect to the width direction (axial direction) which is the longitudinal direction of the fixing belt 20. As Figure 3 shown in part (b) of Figure 3 the region Q of the recording material passing through the fixing nip 27 (hereinafter, this region is referred to as the fixing sheet passing region Q) changes according to the width of the recording material with respect to the longitudinal direction of the fixing belt 20 (the left-right direction of part (b) of

[0056] On the other hand, when a sheet of recording material of a small size (e.g., A4R) passes through, this area is divided into a fixing film sheet passing area Q2 through which the recording material P always passes and small-size non-sheet passing areas R on both sides where the small-size recording material P does not pass. Above the fixing belt 20, a pair of cooling fans 29 and baffles 30 are provided at positions corresponding to the respective small-size non-sheet passing areas R. That is, the cooling fan 29 blows air toward the fixing belt 20 at the end in the longitudinal direction associated therewith. In addition, the baffle 30 is arranged between the cooling fan 29 and the fixing belt 20 and can change the opening width of the opening through which the air blown from the cooling fan 29 to the fixing belt 20 can pass.

[0057] These cooling fans 29 and baffles 30 constitute a fixing cooling unit for cooling the non-sheet passing area in order to suppress the temperature rise in the associated non-sheet passing area R of the fixing belt 20 for small sizes. The cooling fans 29 and baffles 30 provided for the non-baffle area R for small sizes perform the following cooling control operations based on the operation instructions of the cooling controller 31 by the control circuit unit 21.

[0058] First, when a small-size recording material narrower than the maximum-size recording material is used as the recording material P for image formation and the image fixing of the small-size recording material is continuously performed, the recording material P does not pass through the non-sheet passing area R as described above. Therefore, the heat absorption in the small-size non-sheet passing area R of the fixing belt 20 is eliminated, causing the temperature to rise. The temperature in the small-size non-sheet passing area R of the fixing belt 20 is detected by the associated belt-back thermistor 18a or 18b for the maximum size. In addition, when the detected temperature of the belt-back thermistor 18a or 18b reaches a predetermined temperature, the opening width of the baffle 30 is changed to a width depending on the small-size sheet passing width (e.g., the width of A4R, the width of the small-size recording material), and then the cooling operation of the cooling fan 29 is started. Thereby, the temperature rise in the small-size non-sheet passing area R of the fixing belt 20 is suppressed.

[0059] When the recording material passing through the fixing roller nip 27 is an A4R recording material, the backside thermistors 18c and 18d of the belt are arranged within the width (since the width of A4R is 210 mm, it is at a position 104 mm from the center of the fixing belt 20 in the longitudinal direction). When the recording material passing through the fixing roller nip 27 is the smallest-size recording material, the backside thermistors 18e and 18f of the belt are arranged within the width (the minimum width through which the sheet can pass) (in the case where the minimum width is, for example, 100 mm, it is at a position 48 mm from the center of the fixing belt 20 in the longitudinal direction). Therefore, the backside thermistors 18c, 18d, 18e, and 18f for detecting the temperature within the sheet passing area of the recording material having a size smaller than the maximum size detect or estimate the edge portion temperature of the small-size recording materials (in this embodiment, A4R and the smallest-size recording material).

[0060] Figure 3 The lower side curve diagram of part (b) shows the heat generation characteristics of the heating elements 16a (or 16c) and the heating elements 16b (or 16d) with respect to the longitudinal direction. In this embodiment, the heat generation amount of the heating element 16a (or 16c) in the fixing sheet passing area Q2 is greater than the heat generation amount in the non-sheet passing area R, and the heat generation amount of the heating element 16b (or 16d) in the non-surface area R is greater than the heat generation amount in the fixing sheet passing area Q2. Additionally, as Figure 3 shown in the upper side view of part (b), each of a pair of cooling fans 29 and baffles 30 located on each of the opposite sides is arranged outside the position corresponding to the width of the smallest-size recording material with respect to the longitudinal direction. Additionally, when a recording material with a size smaller than the maximum size passes through, by appropriately changing the opening width of the baffle 30, the cooling fan 29 can blow air toward the area of the fixing belt 20 where the recording material does not pass through.

[0061] [Control in the Operation in the Borderless Image Forming Mode]

[0062] Next, the control in the operation in the borderless image forming mode will be described. As described above, in the case of performing borderless printing, the toner image is formed to be larger than the size of the recording material and then transferred to the recording material. However, when the toner image larger than the recording material size is transferred to the recording material, the toner is deposited on the edge (portion) of the recording material. The toner deposited on the edge portion is not easily fixed on the recording material and is easily peeled off when the user touches the toner, causing the toner to be deposited on parts other than the recording material, resulting in contamination.

[0063] However, through the verification by the inventor, as shown in Table 1 below, it was found that by increasing the temperature of the fixing belt 20 near the edge portion of the recording material, the toner in the edge portion can be fixed on the recording material. According to this verification, it was found that when the temperature of the fixing belt 20 near the edge portion of the recording material is 200 °C, the peeling of the toner from the edge portion can be suppressed.

[0064] Table 1

[0065]

[0066] *1: "Temperature" is the belt temperature near the edge portion.

[0067] *2: "Toner peeling" is the peeling of the toner in the edge portion.

[0068] Therefore, in the present embodiment, when performing an operation in the (normal) image forming mode for a predetermined recording material, the control circuit unit 21 controls the fixing heater 16 so that the temperature detected by the backside belt thermistor 18 becomes a first control temperature (temperature control temperature) during the first period (sheet passing period) when the recording material passes through the fixing nip 27. On the other hand, when performing an operation in the borderless image forming mode for a predetermined recording material, the control circuit unit 21 controls the fixing heater 16 so that the temperature detected by the backside belt thermistor 18 becomes a second control temperature (temperature control temperature) higher than the first control temperature during at least any one of the first period (sheet passing period) when the recording material passes through the fixing nip 27 and the second period (sheet interval) from when the upstream end of the first recording material in its conveyance direction passes through the fixing nip 27 until the downstream end of the second recording material after the first recording material in the conveyance direction reaches the fixing nip 27. The backside belt thermistor 18 at this time is the sensor among the above-mentioned thermistors 18a to 18f that is used to detect the belt temperature near the end of the passing area Q of the fixing sheet according to the size of the recording material passing through the fixing nip 27.

[0069] Incidentally, the backside heater thermistor 19 can be used instead of the backside belt thermistor 18.

[0070] For example, the backside belt thermistor 18 is omitted, and as the backside heater thermistor 19, in addition to the thermistor in the central portion with respect to the longitudinal direction, thermistors are also provided at positions corresponding to the above-mentioned thermistors 18a to 18f with respect to the longitudinal direction. Thus, control similar to the control using the above-mentioned thermistors 18a to 18f can be performed.

[0071] Figure 5Part (a) shows the control temperature and temperature progression of the fixing belt 20 during (normal) printing, i.e., during operation in the (normal) image forming mode. At the control temperature during operation in the image forming mode, it can be understood that the temperature of the fixing belt 20 near the edge portion of the recording material (edge (portion) belt temperature) is lower than the edge (portion) fixable temperature during passage of the recording material through the fixing nip 27 (during sheet passage). For this reason, in the present embodiment, as shown in Figure 5 part (b), the control temperature of the fixing heater 16 is controlled. Figure 5 Part (b) shows the control temperature and temperature progression of the fixing belt 20 during borderless printing, i.e., during operation in the borderless image forming mode.

[0072] As is apparent from Figure 5 parts (a) and (b), during printing, the surface temperature of the fixing belt 20 is controlled to be not lower than the temperature at which the toner image is fixed on the printing surface (toner image carrying surface) side, but during borderless printing, the surface temperature of the fixing belt 20 is controlled to be not lower than the edge fixable temperature that is higher than the temperature at which the toner image is fixed on the printing surface, in order to fix the toner on the recording material in the edge portion. Here, in Figure 5 parts (a) and (b), the abscissa represents time and the ordinate represents the temperature of the fixing belt 20. Additionally, the "edge portion fixable temperature" is, for example, 200 °C as described in Reference Table 1 and varies depending on the size, basis weight, and type of the recording material. The "printing surface fixable temperature" is, for example, the temperature at which the toner image can be fixed on the surface of the recording material during (normal) printing and varies depending on the size, basis weight, and type. The "center belt temperature (belt center)" is the temperature in the center portion of the fixing belt 20, and the "edge (end) belt temperature (belt edge)" is the temperature of the fixing belt 20 near the end (edge portion) of the fixing sheet passage area Q depending on the size of the recording material.

[0073] In addition, the "rising control temperature (rise)" is the control temperature during the rising period from when the fixing heater 16 starts heating (i.e., starts being energized) until the downstream end of the first recording material with respect to the conveyance direction reaches the fixing nip 27. The "control temperature during sheet passage (during S.P.)" is the control temperature during the period (the first period, during sheet passage) when the recording material passes through the fixing nip 27. The "sheet interval control temperature (S.I.)" is the control temperature during the period (the second period, sheet interval) from when the upstream end of the first recording material with respect to the conveyance direction passes through until the downstream end of the second recording material after the first recording material with respect to the center portion reaches the fixing nip 27. In the present embodiment, in the case of an operation in either the (normal) image forming mode or the borderless image forming mode, the rising control temperature and the sheet interval control temperature are made lower than the control temperature during sheet passage.

[0074] In the present embodiment, in the case of performing an operation in the borderless image forming mode, the control circuit unit 21 controls the fixing heater 16 at the second control temperature during the first period (during sheet passage). That is, regarding the rising temperature control and the sheet interval temperature control, the control temperature is the same between the operation in the image forming mode and the operation in the borderless image forming mode, and regarding the temperature control during sheet passage, the control temperature in the operation in the borderless image forming mode is made higher than the control temperature in the operation in the image forming mode. Incidentally, also regarding the rising temperature control and the sheet interval temperature control, the control temperature in the operation in the borderless image forming mode can be made higher than the control temperature in the operation in the image forming mode.

[0075] In addition, the relationship between the control temperature (the first control temperature) in the operation in the above-described image forming mode and the control temperature (the second control temperature) in the operation in the above-described borderless image forming mode is the relationship in the case of using the same recording material (the same basis weight, the same sheet (paper) type) between the operation in the image forming mode and the operation in the borderless image forming mode. Thus, in the case of performing an operation in the image forming mode for a predetermined recording material, the fixing heater 16 is controlled at the first control temperature, and in the case of performing an operation in the borderless image forming mode for the same recording material as the predetermined recording material, the fixing heater 16 is controlled at the second control temperature higher than the first control temperature.

[0076] Next, the image forming process in the present embodiment will be described along the Figure 6 flowchart.

[0077] When the control circuit unit 21 receives an image formation signal for an image formation job (S1), the control circuit unit 21 sets operations in the image formation mode (print mode) based on the received information (S2). In the present embodiment, the control circuit unit 21 determines a target basic temperature Tb and a print speed S for temperature control of the fixing belt 20 by the backside thermistor 18 of the belt from an internal table using the recording material information (type, basis weight, size), image information (monochrome mode / color mode, with margin / without margin), and ambient (external air) temperature information used in image formation.

[0078] For example, in the case of plain paper (basis weight: 64 g / m 2 ), color mode, and an environment of 25°C, Tb = 190°C and S = 100% are determined.

[0079] Next, the control circuit unit 21 determines whether the mode of the image formation process to be executed is borderless printing (borderless image formation mode) or (normal) printing ((normal) image formation mode) based on the received information (S3).

[0080] First, the process for the case of (normal) printing will be described. When the control circuit unit 21 determines in S3 that the image formation process is (normal) printing (the "No" in S3), the control circuit unit 21 determines the target basic temperature Tb set in S2 above as the fixing target temperature (S4). Then, the control circuit unit 21 executes image formation while controlling the fixing heater 16 at this fixing target temperature (first control temperature) (S5). In addition, the control circuit unit 21 determines whether the recording material for image formation is the final recording material in the image formation job (S6). When the recording material is not the final recording material (the "No" in S6), the image formation operation in S5 is repeated until the recording material becomes the final recording material, and when the recording material becomes the final recording material (the "Yes" in S6), the final recording material is discharged to the outside of the image forming apparatus 1, and thus, the image formation job ends.

[0081] Next, the process of the borderless printing case will be described. When the control circuit unit 21 determines in S3 that the image forming process is borderless printing (Yes in S3), the control circuit unit 21 calculates a correction amount (e.g., 15°C) for the target basic temperature Tb set in S2 above (S7). Then, the control circuit unit 21 determines the temperature obtained by adding the calculated correction amount to the target basic temperature Tb as the fixing target temperature (e.g., 205°C) (S8). Then, the control circuit unit 21 performs image formation while controlling the fixing heater 16 at this fixing target temperature (second control temperature) (S5). In addition, the control circuit unit 21 determines whether the recording material on which image formation is performed is the final recording material in the image formation job (S6). When the recording material is not the final recording material (No in S6), the image formation operation in S5 is repeated until the recording material becomes the final recording material, and when the recording material becomes the final recording material (Yes in S6), the final recording material is discharged to the outside of the image forming apparatus 1, and thus, the image formation job ends.

[0082] As described above, in the present embodiment, during borderless printing, the toner image is fixed on the recording material by the fixing device 100 while controlling the fixing heater 16 at a fixing target temperature higher than the fixing target temperature during (normal) printing. Thus, by increasing the fixing temperature in the edge portion of the recording material, the toner can be reliably fixed on the edge portion of the recording material. For this reason, the toner deposited on the edge portion of the recording material is not easily peeled off, and thus, deposition of the toner on a portion other than the recording material can be suppressed. In addition, in the present embodiment, only the control temperature of the fixing heater 16 is controlled, and thus, for example, a configuration for cleaning the edge portion of the recording material does not need to be added. As a result, while suppressing complication and enlargement of the device, deposition of the toner on a portion other than the recording material after fixing in the operation in the borderless image formation mode can be suppressed.

[0083] <Second Embodiment>

[0084] will be used Figure 7 and Figure 8 to describe the second embodiment. In the first embodiment described above, the fixing target temperature is controlled such that when image formation is performed, the temperature of the entire recording material becomes higher during borderless printing than during (normal) printing. On the other hand, in the present embodiment, during borderless printing in the edge portion of the recording material parallel to the recording material conveyance direction (e.g., Figure 11For the image views (2) and (4)), control is executed so that the temperature near the edge portion of the recording material parallel to the recording material conveyance direction is not lower than the edge (portion) fixable temperature. Other configurations and operations are the same as those in the first embodiment above. For this reason, the components similar to those in the first embodiment are omitted from the description and illustration, or briefly described by adding the same reference numerals or symbols thereto. Hereinafter, the differences from the first embodiment will be mainly described.

[0085] In Figure 7 it shows the temperature distribution during borderless printing and (normal) printing. Generally, when the fixing belt 20 is heated by the fixing heater 16, since the fixing belt 20 dissipates heat at the opposite ends in the longitudinal direction, there is a tendency that the surface temperature of the fixing belt 20 becomes lower in the central portion in the longitudinal direction than at the ends. In the operation in the borderless image forming mode, an image can be formed in the edge portion of the fixing belt 20 in the longitudinal direction of the recording material that intersects the recording material conveyance direction. In addition, during borderless printing in which an image is formed on the recording material in the edge portion (in the edge portion of the recording material parallel to the conveyance direction) in the longitudinal direction of the recording material, it is required to fix the toner in the edge portion on the recording material by increasing the temperature of the fixing belt 20 near the edge portions on both sides in the width direction of the recording material.

[0086] As a method of increasing the temperature of the fixing belt 20 near the edge portions on both sides in the width direction of the recording material, as shown in Figure 4 part (a) of, there is such a method: by using the fixing heater 16 to increase the lighting ratio of the heating element 16b to the heating element 16a, the fixing heater 16 is provided with a heating element 16a having a calorific value greater than that of each end in the central portion in the longitudinal direction and a heating element 16b having a calorific value greater than that of the central portion at each end in the longitudinal direction. In addition, as shown in Figure 4 part (b) of, even in the method of using the fixing heater 16 provided with a plurality of heating elements 16c and 16d having different heating regions in the longitudinal direction, by increasing the lighting ratio of the heating element 16c corresponding to the edge portions on both sides of the recording material, a similar effect can be obtained.

[0087] In addition, as described above, by using the cooling fan 29 for cooling the non-sheet passing area and the baffle 30 capable of changing its opening width, for example, when the size of the recording material is small, control is performed by combining the calorific value of the fixing heater 16, the airflow rate of the cooling fan 29, and the opening width of the baffle 30, so that it becomes possible to increase the temperature of the fixing belt 20 near the edge portions on both sides of the recording material.

[0088] In the present embodiment, as described above, any one of the thermistors 18a to 18f of the belt-back thermistor 18 detects the temperature near each end of the non-sheet passing area Q according to the size of the recording material passing through the fixing nip 27. That is, any one of the thermistors 18a to 18f as the temperature detection unit detects the temperature of the fixing nip 27 at a position corresponding to the associated end of the recording material passing through the fixing nip 27 with respect to the longitudinal direction. In the present embodiment, when performing an operation (borderless printing) in a borderless image forming apparatus that forms an image on an edge portion with respect to the longitudinal direction, the control circuit unit 21 changes the calorific value of the fixing heater 16 with respect to the longitudinal direction so that the temperature (at the end of the fixing heater 16) detected by the thermistor (belt-back thermistor 18) at the position corresponding to the end of the recording material with respect to the longitudinal direction becomes the second control temperature during the first period (during sheet passing). Specifically, the control circuit unit 21 makes the lighting ratio of the heating element 16b (or 16d: second heating element) to the heating element 16a (or 16c: first heating element) higher during the operation in the borderless image forming mode than during the operation in the (normal) image forming mode for a predetermined recording material.

[0089] In addition, in the present embodiment, as described above, the cooling fan 29 blows air toward the end of the fixing belt 20 with respect to the longitudinal direction, and the baffle 30 is disposed between the cooling fan 29 and the fixing belt 20 and can change the opening width of the opening 30a through which the air blown from the cooling fan 29 to the fixing belt 20 can pass. When performing an operation in the borderless image forming mode, the control circuit unit 21 not only controls the airflow rate of the cooling fan 29 but also changes the opening width of the baffle 30 so that the temperature detected by the belt-back thermistor 18 becomes the second control temperature during the first period.

[0090] For example, when performing "(normal) printing" and forming an image on a large-size (A4) recording material, as Figure 7As shown in the upper left column of , the control circuit unit 21 stops the cooling fan 29 and closes the opening 30a of the shutter 30. In addition, the control circuit unit 21 controls the fixing heater 16 so that the temperature detected by each belt-back thermistor 18 (thermistors 18a and 18b) becomes the first control temperature for A4-size recording material during the first period. Incidentally, the energization control of the fixing heater 16 including control using the detected temperature of the heater-back thermistor 19 is as described in the first embodiment above, and is substantially the same as the energization control in the first embodiment except that the fixing target temperatures (the first control temperature and the second control temperature) are different only based on the detection results of the belt-back thermistors 18 between (normal) printing and borderless printing.

[0091] Next, in the case of performing "borderless printing" and forming an image on a large-size (A4) recording material, as Figure 7 shown in the lower left column of , the control circuit unit 21 stops the cooling fan 29 and closes the opening 30a of the shutter 30. In addition, the control circuit unit 21 changes the heat generation amount of the fixing heater 16 in the longitudinal direction so that the temperature detected by each belt-back thermistor 18 (thermistors 18a and 18b) becomes a second control temperature higher than the first control temperature for A4-size recording material ( Figure 7 the case of the upper left column of ). Specifically, the lighting ratio of the heating element 16b (or 16d) to the heating element 16a (or 16c) during the first period is made higher in the case of performing an operation in the borderless image formation mode than in the case of performing an operation in the (normal) image formation mode.

[0092] Next, in the case of performing (normal) printing and forming an image on a small-size (A4R) recording material, as Figure 7 shown in the upper right column of , the control circuit unit 21 drives the cooling fan 29 and changes the opening width of the opening 30a of the shutter 30 to an opening width corresponding to the small-size recording material. In addition, the control circuit unit 21 changes the heat generation amount of the fixing heater 16 in the longitudinal direction so that the temperature detected by each belt-back thermistor 18 (thermistors 18c and 18d) becomes the first control temperature for A4R-size recording material.

[0093] In addition, in the case of performing borderless printing and forming an image on a small-size (A4R) recording material, as Figure 7 shown in the lower right column of , the control circuit unit 21 drives the cooling fan 29 and changes the opening width of the opening 30a of the shutter 30 as described below. That is, the opening width of the opening 30a of the shutter 30 is made smaller than in the case of performing "(normal) printing" and forming an image on a small-size (A4R) recording material ( Figure 7The opening width of the opening in the upper right column). Specifically, the position and the opening width of the opening 30a of the baffle 30 are changed so that the air from the cooling fan 29 does not blow toward the end portion of the small-size recording material in the width direction, and so that the air from the cooling fan 29 blows toward the end portion of the fixing belt 20, in order to suppress the temperature rise at the end portion of the fixing belt 20 in the width direction. At this time, the air volume of the cooling fan 29 is made smaller than the air volume of the cooling fan 29 during (normal) printing. Further, the control circuit unit 21 changes the heat generation amount of the fixing heater 16 in the longitudinal direction so that the temperature detected by each of the belt back thermistors 18 (thermistors 18c and 18d) in the first period becomes higher than the first control temperature for the A4R-size recording material ( Figure 7 in the case of the upper right column).

[0094] Incidentally, in the case of performing "borderless printing" and forming an image on a small-size (A4R) recording material and in the case of performing "(normal) printing" and forming an image on a small-size (A4R) recording material, any one of the heat generation amount of the fixing heater 16 in the longitudinal direction, the air volume of the cooling fan 29, and the opening width of the baffle 30 can be changed, or two of these can be changed. For example, in the case of performing "(normal) printing" and forming an image on a small-size (A4R) recording material, only the heat generation amount of the fixing heater 16 in the longitudinal direction can be changed, or in addition to changing the heat generation amount of the fixing heater 16 in the longitudinal direction, any one of the air volume of the cooling fan 29 and the opening width of the baffle 30 can be changed. Further, without changing the heat generation amount of the fixing heater 16 in the longitudinal direction, in the case of performing "(normal) printing" and forming an image on a small-size (A4R) recording material, any one of the air volume of the cooling fan 29 and the opening width of the baffle 30 can be changed.

[0095] Here, without changing the heat generation amount of the fixing heater 16, in the case of performing "(normal) printing" and forming an image on a small-size (A4R) recording material, it is preferable to change both the air volume of the cooling fan 29 and the opening width of the baffle 30. That is, without changing the heat generation amount of the fixing heater 16, the temperature rise at the end portion of the fixing belt 20 becomes larger, and correspondingly, the air volume of the cooling fan 29 is made larger. However, when the air volume of the cooling fan 29 is made larger, the end portion of the recording material is excessively cooled, and therefore, by narrowing the opening width of the baffle 30, the air from the cooling fan 29 is prevented from blowing toward the edge portion of the recording material.

[0096] Next, along Figure 8The flowchart describes the image forming process in this embodiment. When the control circuit unit 21 receives an image forming signal of an image forming job (S101), the control circuit unit 21 sets the operations in the image forming mode (printing mode) based on the received information (S102). In this embodiment, the control circuit unit 21 determines the target basic temperature Tb and the printing speed S for temperature control of the fixing belt 20 by the backside thermistor 18 of the belt from an internal table using the recording material information (type, basis weight, size), image information (monochrome mode / color mode, with margin / without margin), and environmental (external air) temperature information used in image formation. For example, in the case of plain paper (basis weight: 64 g / m 2 ), color mode, and an environment of 25°C, Tb = 190°C and S = 100% are determined. Next, the control circuit unit 21 discriminates whether the mode of the image forming process to be executed is borderless printing (borderless image forming mode) or (normal) printing ((normal) image forming mode) based on the received information (S103).

[0097] First, the flow of the case of (normal) printing will be described. When the control circuit unit 21 discriminates in S103 that the image forming process is (normal) printing (the "No" of S103), the control circuit unit 21 determines the target basic temperature Tb set in S102 above as the fixing target temperature (S104). Then, the control circuit unit 21 executes image formation while controlling the fixing heater 16 at this fixing target temperature (first control temperature) (S105). In addition, the control circuit unit 21 discriminates whether the recording material for image formation is the final recording material in the image forming job (S106). In the case where the recording material is not the final recording material (the "No" of S106), the image forming operation of S105 is repeated until the recording material becomes the final recording material, and in the case where the recording material becomes the final recording material (the "Yes" of S106), the final recording material is discharged to the outside of the image forming apparatus 1, and thus, the image forming job ends.

[0098] Next, the flow of the case of borderless printing will be described. When the control circuit unit 21 discriminates in S103 that the image forming process is borderless printing (the "Yes" of S103), the control circuit unit 21 confirms the size of the recording material set in S102 above (S107). For example, in the case of forming an image on a recording material of A4 with a maximum size of A4 (the "Yes" of S107), the temperature in the edge portion of the A4-sized recording material is increased by changing the calorific value (heater load) so that the lighting ratio of the heating element 16b (or 16d) with a greater calorific value at each end than in the center is increased compared to the heating element 16a (16c) with a greater calorific value in the center than at each end.

[0099] Then, the control circuit unit 21 causes the backside belt thermistor 18 (thermistors 18a and 18b in the case of A4 size) to detect the temperature of the end of the A4-size recording material, and discriminates whether the detected temperature is not less than the edge (portion) fixable temperature (S109). In S109, when the detected temperature of the backside belt thermistor 18 does not reach the edge fixable temperature ("No" in S109), the sequence returns to S108, and the calorific value of the fixing heater 16 is changed so that the temperature in the edge portion of the recording material increases. For example, a correction amount for the target basic temperature Tb set in S102 described above is calculated, and the temperature obtained by adding the calculated correction amount to the target basic temperature Tb is determined as the fixing target temperature. Then, the control circuit unit 21 changes the calorific value of the fixing heater 16 in the longitudinal direction so that the temperature detected by the backside belt thermistor 18 becomes the fixing target temperature (second control temperature, edge fixable temperature).

[0100] In S109, when the detected temperature of the backside belt thermistor 18 reaches the edge fixable temperature ("Yes" in S109), an image forming operation is performed (S105). In addition, the control circuit unit 21 discriminates whether the recording material on which the image has been formed is the final recording material in the image forming job (S106). When the recording material is not the final recording material ("No" in S106), the operation is repeated from S103 until the recording material becomes the final recording material, and when the recording material is the final recording material ("Yes" in S106), the final recording material is discharged to the outside of the image forming apparatus 1, and then the image forming job is ended.

[0101] On the other hand, in S107, when the size of the recording material is a small size (e.g., A4) that is not the maximum size ("No" in S107), depending on the size, the calorific value of the fixing heater 16, the air volume of the cooling fan 29, and the opening width of the baffle 30 are changed (S110). For example, by reducing the lighting ratio of the heating element 16b (or 16d) whose calorific value in the end portion in the longitudinal direction is greater than that in the central portion compared with the heating element 16a (or 16c) whose calorific value in the central portion in the longitudinal direction is greater than that in the end portion, by reducing the air volume of the cooling fan 29, and by closing the opening width of the baffle 30 by a predetermined amount, the calorific value (heater load) of the fixing heater 16, the air volume of the cooling fan 29, and the opening width of the baffle 30 are changed. Thereby, the temperature in the end portion of the small-size recording material increases.

[0102] Then, the control circuit unit 21 causes the backside belt thermistors 18 (thermistors 18c and 18d in the case of A4R size) to detect the temperature of the end portion of the small-size recording material, and discriminates whether the detected temperature is not less than the edge (portion) fixable temperature (S111). In S111, when the detected temperature of the backside belt thermistor 18 does not reach the edge fixable temperature ("No" in S111), the sequence returns to S110, and the heat generation amount of the fixing heater 16, the air volume of the cooling fan 29, and the opening width of the shutter 30 are changed so that the temperature in the edge portion of the small-size recording material increases.

[0103] In S111, when the detected temperature of the backside belt thermistor 18 reaches the edge fixable temperature ("Yes" in S111), the image forming operation is executed (S105). In addition, the control circuit unit 21 discriminates whether the recording material on which the image has been formed is the final recording material in the image forming job (S106). When the recording material is not the final recording material ("No" in S106), the operations are repeated from S103 until the recording material becomes the final recording material, and when the recording material is the final recording material ("Yes" in S106), the final recording material is discharged to the outside of the image forming apparatus 1, and then the image forming job is ended.

[0104] In Figure 8 the flowchart, as a method for controlling the temperature in the edge portion of the recording material, a method of changing all of the heat generation amount of the fixing heater 16, the air volume of the cooling fan 29, and the opening width of the shutter 30 is described. However, as described above, the method for controlling the temperature in the edge portion of the recording material can be executed by using any one or more of these parameters. In addition, in the above example, borderless printing is performed on the edge portions on both sides of the recording material parallel to the recording material conveyance direction (that is, the edge portions on both sides with respect to the width direction), but during borderless printing on the edge portion on one side of the recording material parallel to the recording material conveyance direction, temperature control can also be executed so that the heat generation amount of the fixing heater 16, the air volume of the cooling fan 29, and the opening width of the shutter 30 on the side corresponding to the edge portion where borderless printing is performed are changed.

[0105] As described above, in the present embodiment, during borderless printing in the (one or more) edge portions of the recording material parallel to the recording material conveyance direction, the temperature near the (one or more) edge portions of the recording material parallel to the recording material conveyance direction is controlled to be equal to or higher than the edge fixable temperature. Thus, the fixing temperature of the (one or more) edge portions of the recording material increases, so that the toner can be reliably fixed to the (one or more) edge portions of the recording material. For this reason, the toner deposited on the (one or more) edge portions of the recording material is not easily peeled off, thereby suppressing the deposition of the toner in portions other than the recording material. Further, in the present embodiment, only the components (parameters) already provided in the image forming apparatus 1, such as the calorific value of the fixing heater 16, the air volume of the cooling fan 29, and the opening width of the shutter 30, are controlled. Therefore, there is no need to add, for example, a configuration for cleaning the (one or more) edge portions of the recording material. As a result, it is possible to suppress the deposition of the toner on portions other than the recording material after fixing during the operation in the borderless image forming mode, while suppressing the complication and enlargement of the image forming apparatus.

[0106] <Third Embodiment>

[0107] The third embodiment will be described using Figure 9 and Figure 10 In the above-described first embodiment, the fixing target temperature is controlled such that the temperature of the entire recording material becomes higher during borderless printing than during (normal) printing when performing image formation. On the other hand, in the present embodiment, during borderless printing in the edge portion that is either the leading end or the trailing end of the recording material (e.g., Figure 11 image view (3)), control is performed such that the temperature near the edge portion that is either the leading end or the trailing end of the recording material is not less than the edge (portion) fixable temperature. Other configurations and operations are the same as those in the first embodiment described above. For this reason, components similar to those in the first embodiment are omitted from the description and illustration, or are briefly described by adding the same reference numerals or symbols thereto. Hereinafter, the differences from the first embodiment will be mainly described.

[0108] In Figure 9 shows the temperature progress of the fixing belt 20 during the passage of the continuous sheet, where a plurality of recording materials pass through the fixing nip 27. In Figure 9In the figure, the solid line indicates the temperature in the central portion of the fixing belt 20 with respect to the longitudinal direction under the condition of performing the control in this embodiment ("controlled: belt center"), while the dashed line indicates the temperature in the central portion of the fixing belt 20 with respect to the longitudinal direction under the condition of not performing the control in this embodiment (during the rising period, the control of not increasing the control temperature in the sheet interval) ("uncontrolled: belt center"). Generally, when continuous sheets are passed, there is a tendency as indicated by the dashed line that the surface temperature of the fixing belt 20 gradually decreases at the trailing end (the upstream end with respect to the conveying direction) of the first recording material compared to the leading end (the downstream end with respect to the conveying direction) of the first recording material. During borderless printing, it is required to fix the toner in the edge portion on the recording material by increasing the temperature of the fixing belt 20 near the edge portions at the leading and trailing ends of the recording material.

[0109] As a method of increasing the temperature of the fixing belt 20 near the edge portions at the leading and trailing ends of the recording material, for example, the control temperature during the sheet interval (the second period) is set to be higher than the control temperature during the sheet passing period (the first period) of the recording material.

[0110] In addition, regarding the leading end portion of the recording material, when the recording material passes through the fixing nip 27, the control temperature is switched to the control temperature during the sheet passing period so that the temperature in the edge portion as the leading end portion of the recording material ensures the edge fixable temperature or higher. On the other hand, regarding the trailing end portion of the recording material, there is such a method: when the recording material comes off the fixing nip 27, the control temperature is switched to the control temperature during the sheet passing period so that the temperature in the edge portion as the trailing end portion of the recording material ensures the edge fixable temperature or higher.

[0111] This will be specifically described. First, in this embodiment, when operating in the borderless image forming mode, the control circuit unit 21 controls the fixing heater 16 at the second control temperature during the second period (sheet interval). The second control temperature at this time is higher than the first control temperature during the period (the first period) when the recording material passes through the fixing nip 27 during the operation in the (normal) image forming mode for the same recording material. In particular, in this embodiment, the second control temperature is higher than the third control temperature during the period (the first period) when the recording material passes through the fixing nip 27 during the operation in the borderless image forming mode. That is, as Figure 9As shown, in the case of performing an operation in the borderless image forming mode on a predetermined recording material, the control circuit unit 21 not only controls the fixing heater 16 so that the temperature detected by the backside of the belt thermistor 18 becomes the third control temperature (control temperature during sheet passing, printing control temperature) in the first period, but also controls the fixing heater 16 so that the temperature detected by the backside of the belt thermistor 18 becomes a second control temperature (sheet interval control temperature) higher than the temperature in the first period in the second period.

[0112] In addition, in the present embodiment, in the case of performing an operation in the borderless image forming mode, the control circuit unit 21 controls the fixing heater 16 so that the temperature detected by the backside of the belt thermistor 18 becomes the second control temperature (rise control temperature) in the rising period from the start of heating of the fixing heater 16 until the downstream end (front end) of the first recording material reaches the fixing nip 27. This control temperature is also higher than the first control temperature and the third control temperature. Thus, regarding the edge portion of the front end portion of the first recording material in the image forming operation, the control temperature can also be made equal to or higher than the edge fixable temperature.

[0113] Incidentally, in the present embodiment, in the case of (normal) printing, the control temperature during the rising period is controlled to be slightly lower than the control temperature during sheet passing (printing control temperature). In addition, when the sheet interval is shorter than a predetermined time, the sheet interval control temperature is made the same as the printing control temperature, and when the sheet interval is longer than a predetermined time, the sheet interval control temperature is made lower than the printing control temperature.

[0114] In addition, in borderless printing, the switching timing from the rising control temperature to the control temperature during sheet passage and the switching timing from the sheet interval control temperature to the control temperature during sheet passage are changed according to the temperature difference between the rising control temperature and the control temperature during sheet passage and the temperature difference between the sheet interval control temperature and the control temperature during sheet passage, respectively. When the temperature difference between the rising temperature (or the sheet interval control temperature) and the control temperature during sheet passage is large, the switching can be performed before the leading end of the recording material enters the fixing nip 27. This is because the temperature near the edge portion, which is the leading end portion, can be made equal to or higher than the edge fixable temperature while the recording material passes through the fixing nip 27. On the other hand, when the temperature difference between the rising control temperature (or the sheet interval control temperature) and the control temperature during sheet passage is small, the control temperature immediately drops to the control temperature during sheet passage after the control temperature is switched, so there is a possibility that the temperature near the edge portion, which is the leading end portion of the recording material, cannot be made equal to or higher than the edge fixable temperature. For this reason, when the temperature difference is small, it is preferably possible to perform the switching after the leading end of the recording material enters the fixing nip 27. In short, it is only required to switch from the rising control temperature (or the sheet interval control temperature) to the control temperature during sheet passage at the timing when the temperature near the edge portion, which is the leading end portion of the recording material, becomes equal to or higher than the edge fixable temperature while the leading end of the recording material passes through the fixing nip 27.

[0115] In addition, in borderless printing, the switching timing from the control temperature during sheet passage to the sheet interval control temperature is before the trailing end of the recording material disengages from the fixing nip 27. This timing also changes according to the temperature difference between the control temperature during sheet passage and the sheet interval control temperature. That is, it is only required to switch from the control temperature during sheet passage to the sheet interval control temperature at the timing when the temperature near the edge portion, which is the trailing end portion of the recording material, becomes equal to or higher than the edge fixable temperature while the trailing end of the recording material passes through the fixing nip 27. When the temperature difference is large, the power supply to the fixing heater 16 becomes large during the switching of the control temperature, and thus the temperature rise becomes sharp. On the other hand, when the temperature difference is small, the change in the power supply to the fixing heater 16 during the switching of the control temperature is small, so that the temperature rise becomes gentle. For this reason, at the timing depending on the rising temperature speed, the control temperature is switched from the control temperature during sheet passage to the sheet interval control temperature.

[0116] In Figure 9In this case, the switching timing from the rising control temperature to the control temperature during the passage of the sheet is the timing when the leading end of the first recording material enters the fixing nip 27. Further, the switching timing from the control temperature during the passage of the sheet to the sheet interval control temperature is before the trailing end of the recording material disengages from the fixing nip 27. Further, the switching timing from the sheet interval control temperature to the control temperature during the passage of the sheet is after the leading end of the recording material enters the fixing nip 27. These timings are determined by the temperature difference between the associated control temperatures as described above, and thus are not limited to Figure 9 the example shown

[0117] Next, the image forming process in this embodiment will be described along the Figure 10 flowchart. When the control circuit unit 21 receives an image forming signal for an image forming job (S201), the control circuit unit 21 sets the operation in the image forming mode (printing mode) based on the received information (S202). In this embodiment, the control circuit unit 21 determines a target basic temperature Tb and a printing speed S for temperature control of the fixing belt 20 by the backside thermistor 18 of the belt from an internal table using the recording material information (type, basis weight, size), image information (monochrome mode / color mode, with margin / without margin), and ambient (outside air) temperature information used in image formation. For example, in the case of plain paper (basis weight: 64 g / m 2 ), color mode, and an ambient temperature of 25°C, Tb = 190°C and S = 100% are determined. Next, the control circuit unit 21 discriminates whether the mode of the image forming process to be executed is borderless printing (borderless image forming mode) or (normal) printing ((normal) image forming mode) based on the received information (S203).

[0118] First, the flow of the case of (normal) printing will be described. When the control circuit unit 21 discriminates in S203 that the image forming process is (normal) printing (No in S203), the control circuit unit 21 determines the target basic temperature Tb set in S202 above as the fixing target temperature (S204). Then, the control circuit unit 21 executes image formation while controlling the fixing heater 16 at this fixing target temperature (first control temperature) (S205). Further, the control circuit unit 21 discriminates whether the recording material for which image formation is performed is the final recording material in the image forming job (S206). When the recording material is not the final recording material (No in S206), the image forming operation in S205 is repeated until the recording material becomes the final recording material, and when the recording material becomes the final recording material (Yes in S206), the final recording material is discharged to the outside of the image forming apparatus 1, and thus the image forming job ends.

[0119] Next, the process in the case of borderless printing will be described. When the control circuit unit 21 determines in S203 that the image forming process is borderless printing (Yes in S203), the control circuit unit 21 sets each of the rising control temperature and the sheet interval control temperature to be 15°C higher than the control temperature (printing control temperature) during the sheet passing period (S207). In addition, the control circuit unit 21 starts the image forming operation (S208) and increases the temperature of the fixing belt 20 by controlling the fixing heater 16 at the corrected rising control temperature (S209). Then, during the period when the leading edge of the recording material passes through the fixing nip 27, at the timing when the temperature near the edge portion, which is the leading edge portion of the recording material, can ensure the necessary temperature, that is, at the timing when the temperature near the edge portion becomes equal to or higher than the edge fixable temperature, the control circuit unit 21 switches the control temperature from the rising control temperature to the printing control temperature (S210). Then, the control circuit unit 21 controls the fixing heater 16 at the printing control temperature so that the recording material passes through the fixing nip 27 (S211).

[0120] Then, before the trailing edge of the recording material disengages from the fixing nip 27, the control temperature is switched from the printing control temperature to the corrected sheet interval control temperature (S212). Then, the control circuit unit 21 controls the fixing heater 16 at the corrected sheet interval control temperature (S213).

[0121] In addition, the control circuit unit 21 determines whether the recording material on which the image has been formed is the final recording material in the image forming job (S214). When the recording material is not the final recording material (No in S214), the operations are repeated from S208 until the recording material becomes the final recording material, and when the recording material is the final recording material (Yes in S214), the final recording material is discharged to the outside of the image forming apparatus 1, and then the image forming job is ended.

[0122] Incidentally, in the above embodiment, borderless printing for the edge portions at the leading and trailing edges of the recording material has been described.

[0123] However, during borderless printing for any one of the edge portions of the front end portion and the rear end portion of the recording material, temperature adjustment (temperature control) can be performed only on the edge portion where borderless printing is performed. For example, in the case of performing borderless printing on the front end portion of the recording material and (normal) printing on the rear end portion of the recording material, each of the rising control temperature and the sheet interval control temperature is made higher than the control temperature during sheet passage, and the switching timing from the rising control temperature to the control temperature during sheet passage and the switching timing from the sheet interval control temperature to the control temperature during sheet passage are the above-mentioned timings. On the other hand, the switching timing from the control temperature during sheet passage to the sheet interval control temperature is made similar to the switching timing during (normal) printing. Additionally, in the case of performing borderless printing on the rear end of the recording material and (normal) printing on the front end of the recording material, the sheet interval control temperature is made higher than the control temperature during sheet passage, and the switching timing from the control temperature during sheet passage to the sheet interval control temperature is the above-mentioned timing. On the other hand, the switching timing from each of the rising control temperature and the sheet interval control temperature to the control temperature during sheet passage is made similar to the switching timing during (normal) printing.

[0124] As described above, in the present embodiment, during borderless printing for any one of the (one or more) recording material edge portions of the front end portion and the rear end portion of the recording material, the temperature near any one of the (one or more) recording material edge portions of the front end portion and the rear end portion of the recording material is controlled to be equal to or higher than the edge fixable temperature. Consequently, the fixing temperature in the (one or more) edge portions of the recording material increases, so that the toner can be reliably fixed to the (one or more) edge portions of the recording material. For this reason, the toner deposited on the (one or more) edge portions of the recording material is not easily peeled off, thereby suppressing the deposition of toner in portions other than the recording material. Additionally, similar to the first and second embodiments, it is possible to suppress the deposition of toner on portions other than the recording material after fixing during the operation in the borderless image forming mode, while suppressing the complication and enlargement of the image forming apparatus.

[0125] The second and third embodiments described above can be combined with each other. That is, in the case of performing borderless printing on any one of the edge portions of the front end portion and the tail end portion of the recording material and any one of the edge portions on both sides of the recording material parallel to the recording material conveyance direction, or in the case of performing borderless printing on the entire surface of the recording material, the first embodiment described above can be executed, but the second and third embodiments can be executed in combination with each other. In this case, when operating in the borderless image forming mode, the control circuit unit 21 changes the calorific value of the fixing heater 16 with respect to the longitudinal direction so that the temperature detected by the backside of the belt thermistor 18 becomes the second control temperature during the rising period in the first period (sheet passing period) and the second period (sheet interval), and not only controls the air volume of the cooling fan 29 but also changes the opening width of the baffle 30 so that the temperature detected by the backside of the belt thermistor 18 becomes the second control temperature.

[0126] For example, while changing the belt temperature in any one of the edge portions of the front end portion and the tail end portion of the recording material so that the control temperature is higher than the printing control temperature during the rising period and during the sheet interval period, in any one of the edge portions of the front end portion and the tail end portion of the recording material, by increasing the lighting ratio of the heating element 16b (or 16d) that generates more heat in the end portion with respect to the longitudinal direction than in the central portion compared to the heating element 16a (or 16c) that generates more heat in the central portion than in the end portion with respect to the longitudinal direction, the temperature of the fixing belt 20 near the associated edge portion of the recording material is increased. At this time, the belt temperature in the edge portion of the recording material cannot be completely controlled only by the ratio of the calorific value of the fixing heater 16, so while driving the cooling fan 29, the opening width of the baffle 30 is controlled according to the width of the passing recording material. Incidentally, regarding the control of the fixing heater 16 for any one of the edge portions that are the relative end portions of the recording material with respect to the width direction, a certain control is performed until the end of the image forming operation regardless of whether there is a recording material in the fixing nip 27. That is, during any one of the sheet passing period and the sheet interval period, a control is performed to increase the lighting ratio of the heating element 16b (or 16d) compared to the lighting ratio of the heating element 16a (or 16c).

[0127] According to the present invention, while suppressing the complication and enlargement of the image forming apparatus, it is possible to suppress toner from being deposited on parts other than the recording material after fixing during the operation in the borderless image forming mode.

[0128] Although the present invention has been described with reference to exemplary embodiments, it should be understood that the present invention is not limited to the disclosed exemplary embodiments. The scope of the following claims should be given the broadest interpretation to cover all such modifications as well as equivalent structures and functions.

Claims

1. An image forming apparatus, comprising: An execution unit configured to operate in a borderless image forming mode in which a toner image is formed in an edge portion of a recording material of a predetermined size and in an image forming mode in which a toner image is not formed in the edge portion of the recording material of the predetermined size; An image forming unit configured to form a toner image on the recording material; A fixing device including a fixing member, a heating unit for heating the fixing member, a nip forming unit for forming a fixing nip for holding and conveying the recording material between itself and the fixing member and for fixing the toner image on the recording material when the recording material carrying the toner image passes through the fixing nip, and a temperature detection unit for detecting the temperature of the fixing member or the heating unit; And A controller configured to control the heating unit based on a detection result of the temperature detection unit, wherein, when an operation in the image forming mode is performed on a recording material of a predetermined size, the controller controls the heating unit such that the temperature becomes a first control temperature in a first period, which is a period during which the recording material passes through the fixing nip, and wherein, when an operation in the borderless image forming mode is performed on the recording material of the predetermined size, the controller controls the heating unit such that the temperature becomes a second control temperature higher than the first control temperature in the first period.

2. The image forming apparatus according to claim 1, wherein, in an operation in the borderless image forming mode, the image forming apparatus is capable of forming an image in an edge portion of the recording material in a longitudinal direction of the fixing member that intersects a conveying direction of the recording material.

3. The image forming apparatus according to claim 2, wherein, Relative to the longitudinal direction, the heating unit is capable of changing temperature control in an end portion and a central portion of a region where the recording material passes through the fixing nip, wherein the temperature detection unit detects the temperature of the fixing member or the heating unit at a position corresponding to an end portion of the recording material passing through the fixing nip relative to the longitudinal direction, and the controller controls an end portion of the heating unit in the first period such that the temperature becomes the first control temperature when an operation in the image forming mode is performed on a predetermined recording material, and such that the temperature becomes the second control temperature when an operation in the borderless image forming mode of forming an image in an edge portion of the predetermined recording material relative to the longitudinal direction is performed on the predetermined recording material.

4. The image forming apparatus according to claim 3, wherein the heating unit includes a first heating element having a calorific value greater in a central portion of the region relative to the longitudinal direction than in an end portion of the region relative to the longitudinal direction, and the heating unit includes a second heating element having a calorific value greater in the end portion of the region relative to the longitudinal direction than in the central portion of the region relative to the longitudinal direction, and The controller causes the lighting ratio of the second heating element to the first heating element in the first period when operating in the borderless image forming mode to be higher than that when operating in the image forming mode.

5. The image forming apparatus according to claim 3 or 4, further comprising a fan configured to blow air toward an end portion of the fixing member with respect to the longitudinal direction, wherein when operating in the borderless image forming mode, the controller controls the air volume of the fan so that the temperature detected by the temperature detection unit becomes a second control temperature in the first period.

6. The image forming apparatus according to claim 5, further comprising a baffle provided between the fan and the fixing member and capable of changing an opening width of an opening through which the air blown from the fan to the fixing member can pass, wherein when operating in the borderless image forming mode, the controller controls the air volume of the fan and changes the opening width of the baffle so that the temperature detected by the temperature detection unit becomes a second control temperature in the first period.

7. The image forming apparatus according to claim 3, further comprising: a fan configured to blow air toward an end portion of the fixing member with respect to the longitudinal direction, and a baffle provided between the fan and the fixing member and capable of changing an opening width of an opening through which the air blown from the fan to the fixing member can pass, wherein the temperature detection unit detects the temperature of the fixing member or the heating unit at a position corresponding to an end portion of the recording material passing through the fixing nip with respect to the longitudinal direction, and wherein when operating in the borderless image forming mode, the controller controls the air volume of the fan and changes the opening width of the baffle so that the temperature detected by the temperature detection unit becomes a second control temperature in the first period.

8. The image forming apparatus according to claim 1, wherein a period from when an upstream end of a first recording material with respect to the conveyance direction passes through the fixing nip until a downstream end of a second recording material after the first recording material with respect to the conveyance direction reaches the fixing nip is a second period, and wherein the controller controls the temperature of the heating unit so that the temperature of the heating unit in the second period when operating in the image forming mode for a predetermined recording material is the same as the temperature of the heating unit in the second period when operating in the borderless image forming mode for the predetermined recording material.

9. An image forming apparatus, comprising: an execution unit configured to operate in a borderless image forming mode in which a toner image is formed in an edge portion of a recording material of a predetermined size and in an image forming mode in which a toner image is not formed in an edge portion of a recording material of a predetermined size; an image forming unit configured to form a toner image on a recording material; A fixing device, the fixing device including a fixing member, a heating unit for heating the fixing member, a nip forming unit for forming a fixing nip for nipping and conveying a recording material between itself and the fixing member and for fixing a toner image on the recording material when the recording material carrying the toner image passes through the fixing nip, and a temperature detection unit for detecting the temperature of the fixing member or the heating unit; and a controller configured to control the heating unit based on the detection result of the temperature detection unit, wherein in the case of performing an operation in an image forming mode for a predetermined recording material, the controller controls the heating unit such that the temperature becomes a first control temperature in a second period from the upstream end of the first recording material in the conveyance direction passing through the fixing nip until the downstream end of the second recording material after the first recording material in the conveyance direction reaches the fixing nip, and wherein in the case of performing an operation in a borderless image forming mode for forming an image in an edge portion of the predetermined recording material in the conveyance direction, the controller controls the heating unit such that the temperature becomes a second control temperature higher than the first control temperature in the second period.

10. The image forming apparatus according to claim 9, wherein in the case of performing an operation in the borderless image forming mode, the controller controls the heating unit such that the temperature detected by the temperature detection unit becomes the second control temperature in a rising period from when the heating unit starts heating until the downstream end of the initial recording material in the conveyance direction reaches the fixing nip.

11. The image forming apparatus according to claim 9, wherein the period during which the recording material passes through the fixing nip is a first period, and wherein in the case of performing an operation in an image forming mode for forming an image in an edge portion of the predetermined recording material in the conveyance direction, the controller controls the heating unit such that the temperature of the heating unit in the second period is higher than the temperature of the heating unit in the first period.

12. The image forming apparatus according to claim 1 or 9, further comprising: a fan configured to blow air toward an end portion of the fixing member in the longitudinal direction, and a baffle provided between the fan and the fixing member and capable of changing the opening width of an opening through which the air blown from the fan to the fixing member can pass, wherein, with respect to the longitudinal direction of the fixing member intersecting the conveyance direction of the recording material, the heating unit can change the temperature control in the end portion and the central portion of the area where the recording material passes through the fixing nip, wherein the temperature detection unit detects the temperature of the fixing member or the heating unit at a position corresponding to the end portion of the recording material passing through the fixing nip in the longitudinal direction, wherein the period from the upstream end of the first recording material in the conveyance direction passing through the fixing nip until the downstream end of the second recording material after the first recording material in the conveyance direction reaches the fixing nip is the second period, and wherein in the case of performing an operation in the borderless image forming mode The controller changes the temperature control of the heating unit relative to the longitudinal direction so that the temperature detected by the temperature detection unit becomes the second control temperature in the first period and the second period, and the controller controls the air volume of the fan and changes the opening width of the baffle so that the temperature detected by the temperature detection unit becomes the second control temperature in the first period.

13. The image forming apparatus according to claim 1, wherein the fixing member is an endless fixing belt.

14. The image forming apparatus according to claim 1, wherein the heating unit is a ceramic heater.

15. The image forming apparatus according to claim 13, wherein the heating unit heats the fixing belt in contact with the inner peripheral surface of the fixing belt.

16. The image forming apparatus according to claim 13, wherein the heating unit forms a fixing nip in cooperation with the nip forming unit through the fixing belt.

17. The image forming apparatus according to claim 1, wherein the temperature detection unit is provided at a plurality of positions corresponding to the ends of the fixing member in the longitudinal direction that intersect the conveyance direction of the recording material passing through the fixing nip with respect to recording materials of different sizes, and the temperature of the fixing member is detected at each of the positions.

18. The image forming apparatus according to claim 1, wherein the borderless image forming mode is a mode of forming a toner image larger than a predetermined recording material and then transferring the toner image onto the predetermined recording material.

Images