Fixation device and image formation apparatus

Abstract

To provide a fixation device in which cooling units for cooling each of a heating member and a pressure member can be arranged and controlled in a scalable manner, from a low-speed machine to a high-speed machine, in accordance with their respective characteristics.SOLUTION: A cooling unit 40 of a fixation device 30 comprises a first cooling unit 40A having a first cooling fan 41A and a first air duct 42A for blowing air over at least a region wider than a first size in a width direction of a pressure roller 32, and at least one of a second cooling unit 40B having a second cooling fan 41B and a second air duct 42B for blowing air over a region equal to or less than the first size in the width direction of a fixing belt 31 and a third cooling unit 40C having a third cooling fan 41C and a third air duct 42C for blowing air over a region exceeding a second size being greater than the first size in the width direction of the fixing belt 31. A control unit is configured to independently control the first cooling fan 41A, the second cooling fan 41B, and the third cooling fan 41C.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a fixing device and an image forming apparatus.

Background Art

[0002] In electrophotographic image forming apparatuses such as copiers and printers, a heat fixing method is widely known as a method for fixing an unfixed toner image transferred onto a recording medium such as paper onto the paper. The paper is heated and pressed as it passes through a fixing nip portion where a heating member and a pressing member are in contact, and the unfixed toner image is fixed. In such a heat fixing method, overheating that occurs in the non-paper-passing regions at both axial ends of each of the heating member and the pressing member has been a problem, and countermeasures have been taken conventionally.

[0003] For example, a conventional fixing device disclosed in Patent Document 1 heats a recording material carrying a toner image while transporting it through a nip portion between a first fixing member and a second fixing member, and fixes the toner image onto the recording material. The fixing device includes a first fan that blows air into the non-paper-passing region of the first fixing member and a second fan that blows air into the non-paper-passing region of the second fixing member. Thereby, the non-paper-passing regions of both the first fixing member and the second fixing member can be efficiently cooled.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the configuration of the conventional technology, a problem has been that the cooling units for cooling each of the heating member heated by a heat source and the pressing member pressed against the heating member to form a fixing nip portion are not optimally shared according to their respective characteristics.

[0006] The present invention has been made in view of the above points, and an object thereof is to provide a fixing device and an image forming apparatus capable of arranging and controlling a cooling unit for cooling each of a heating member and a pressing member in a scalable manner from a low-speed machine to a high-speed machine according to respective characteristics.

Means for Solving the Problems

[0007] To solve the above problems, the present invention provides a fixing device for fixing a toner image formed on a recording medium to the recording medium by inserting the recording medium into a fixing nip portion between a heating member and a pressing member and heating and pressing the recording medium. The fixing device includes a cooling unit having a cooling fan and a blowing duct, and a control unit. The blowing duct blows the air flow generated by the cooling fan to a predetermined region in the width direction orthogonal to the conveyance direction of the recording medium for cooling. The control unit controls the cooling unit. The cooling unit includes a first cooling unit and at least one of a second cooling unit and a third cooling unit. The first cooling unit has a first blowing duct and a first cooling fan that blow air to a region exceeding at least a first size in the width direction of the pressing member. The second cooling unit has a second blowing duct and a second cooling fan that blow air to a region equal to or smaller than the first size in the width direction of the heating member. The third cooling unit has a third blowing duct and a third cooling fan that blow air to a region exceeding a second size larger than the first size in the width direction of the heating member. The control unit can independently control each of the first cooling fan, the second cooling fan, and the third cooling fan.

Effects of the Invention

[0008] According to the configuration of the present invention, by adopting a configuration that combines a plurality of cooling units, it becomes possible to scale the necessary cooling units from low speed to medium speed and high speed. As a result, with the configuration of a common fixing device, a highly flexible design can be achieved that can handle overheating in the non-printing area from low speed to high speed. Further, by appropriately fixing and arranging the cooling paths in advance according to the respective characteristics of the cooling of the pressure member and the heating member, it is possible to handle various paper sizes with the fixed cooling path configuration without changing the cooling path for each model.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following content.

[0011] FIG. 1 is a schematic cross-sectional front view of the image forming apparatus 1 according to the embodiment. As an example of the image forming apparatus 1 of the present embodiment, it is a so-called multifunction machine corresponding to monochrome that has functions such as printing, scanning (image reading), and facsimile transmission. Note that the image forming apparatus 1 may be, for example, a device such as a copier or a printer, and may also be a color-compatible machine.

[0012] As shown in FIG. 1, in the image forming apparatus 1, a document conveyance unit 3 is placed on the upper surface of its main body 2, and an image reading unit 4 is arranged inside the main body 2 below it. The image of the document stacked on the document conveyance unit 3 or the image of the document placed on the contact glass (not shown) on the upper surface of the image reading unit 4 is read by the image reading unit 4.

[0013] The image forming apparatus 1 further includes a paper supply unit 5, a paper conveyance unit 6, an exposure unit 7, an image forming unit 8, a transfer unit 9, a fixing device 30, a paper discharge unit 11, and a control unit 12.

[0014] The paper supply unit 5 stores a plurality of sheets of paper (recording media) S before printing, and separates and feeds out the sheets of paper S one by one during printing. The paper conveyance unit 6 conveys the sheet of paper S sent out from the paper supply unit 5 to the transfer unit 9 and the fixing device 30, and further conveys the sheet of paper S after fixing to the paper discharge unit 11. The exposure unit 7 irradiates the image forming unit 8 with laser light controlled based on image data.

[0015] The image forming unit 8 includes a photosensitive drum 81 which is an image carrier, and a developing unit 82. In the image forming unit 8, an electrostatic latent image of the original image is formed on the surface of the photosensitive drum 81 by the laser light irradiated from the exposure unit 7. The developing unit 82 supplies toner to the electrostatic latent image on the surface of the photosensitive drum 81 for development to form a toner image. The transfer unit 9 transfers the toner image on the surface of the photosensitive drum 81 to the paper S. The fixing device 30 heats and presses the paper S onto which the toner image has been transferred to fix the toner image on the paper S.

[0016] The paper S on which the toner image has been fixed and the printing is completed is conveyed to the paper discharge unit 11. The paper discharge unit 11 is disposed below the image reading unit 4. The paper discharge unit 11 has an opening on the front side, and the printed paper (printed matter) is taken out from the front side.

[0017] The control unit 12 includes a CPU, an image processing unit, a storage unit, and other electronic circuits and electronic components (all not shown). The CPU controls the operations of the respective components provided in the image forming apparatus 1 based on the control programs and data stored in the storage unit, and performs processes related to the functions of the image forming apparatus 1. Each of the paper supply unit 5, the paper conveyance unit 6, the exposure unit 7, the image forming unit 8, the transfer unit 9, and the fixing device 30 receives individual commands from the control unit 12 and cooperates to perform printing on the paper S. The storage unit is composed of a combination of a non-volatile storage device such as a program ROM (Read Only Memory) and a data ROM (both not shown) and a volatile storage device such as a RAM (Random Access Memory).

[0018] Regarding the control of the operation of the fixing device 30, the function of the control unit 12 may be provided in the fixing device 30.

[0019] Subsequently, the configuration around the fixing device 30 will be described with reference to FIG. 2. FIG. 2 is a cross-sectional front view of the periphery of the fixing device 30 of the image forming apparatus 1 in FIG. 1.

[0020] In FIG. 2, for the sake of convenience of explanation, a configuration is depicted in which the fixing belt (heating member) 31 is disposed above the fixing nip portion N and the pressure roller (pressing member) 32 is disposed below. On the left side of FIG. 2 is the upstream side (transfer unit 9 side) in the paper conveyance direction with respect to the fixing device 30, and on the right side is the downstream side (paper discharge unit 11 side) in the paper conveyance direction with respect to the fixing device 30.

[0021] As shown in FIG. 2, the fixing device 30 includes a fixing belt 31, a pressure roller 32, a heating source 33, a heating source holding member 34, a support member 35, a temperature detection unit 36, and a cooling unit 40.

[0022] The fixing belt 31 is rotatably supported by the housing portion of the fixing device 30 around a horizontal axis. The fixing belt 31 is endless and is configured, for example, in a cylindrical shape with an outer diameter of 30 mm, and is longer than the pressure roller 32 in the rotational axis direction (the width direction orthogonal to the conveyance direction of the paper S, the depth direction of the paper surface in FIG. 2). The fixing belt 31 is rotatable along the conveyance direction of the paper S which is the recording medium.

[0023] The fixing belt 31 has a laminated structure in which an elastic layer and a release layer are provided on the outer peripheral side of the base layer. The base layer is composed of, for example, a metal film such as nickel with a thickness of 30 μm to 50 μm, or a polyimide film with a thickness of 70 μm to 90 μm. The elastic layer is composed of, for example, silicon rubber or the like with a thickness of 200 μm to 500 μm. The release layer is composed of, for example, a fluororesin such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) with a thickness of 30 μm to 50 μm.

[0024] The pressure roller 32 is rotatably supported by the housing portion of the fixing device 30 around a horizontal axis. The pressure roller 32 is configured in a cylindrical shape and is shorter than the fixing belt 31 in the rotational axis direction (the paper width direction, the depth direction of the paper surface in FIG. 2). A predetermined pressure is applied to the pressure roller 32 toward the fixing belt 31 side by a pressing mechanism (not shown). Thereby, the pressure roller 32 contacts the outer peripheral surface of the fixing belt 31. A fixing nip portion N is formed between the pressure roller 32 and the fixing belt 31.

[0025] The pressure roller 32 is connected to a drive source (not shown) including a motor, for example, obtains power from the motor, and rotates clockwise in FIG. 2. The pressure roller 32 contacts the outer peripheral surface of the fixing belt 31 and applies a rotational driving force to the fixing belt 31. The operation of the fixing belt 31 is controlled by the control unit 12.

[0026] The pressure roller 32 has a laminated structure in which an elastic layer and a release layer are provided on the outer peripheral side of the core metal. The core metal is made of a metal such as iron or aluminum with a diameter of, for example, 20 mm to 25 mm. The elastic layer is made of, for example, silicon rubber with a thickness of about 5 mm and has an outer diameter of 30 mm to 35 mm. The release layer is made of a fluororesin such as PFA with a thickness of about 10 μm to 50 μm.

[0027] The heating source 33 is disposed inside the fixing belt 31, facing the pressure roller 32 with the fixing belt 31 in between. The heating source 33 contacts the inner peripheral surface of the fixing belt 31 and forms a fixing nip portion N with the pressure roller 32 via the fixing belt 31.

[0028] The heating source 33 extends along the rotational axis direction of the fixing belt 31 (the paper width direction, the depth direction of the paper surface in FIG. 2). With respect to the axial direction of the fixing belt 31, the length of the heat generating portion of the heating source 33 is shorter than that of the fixing belt 31. The heating source 33 is composed of, for example, a resistance heating element, and directly heats the fixing belt 31 at the fixing nip portion N by contacting the fixing belt 31. The operation of the heating source 33 is controlled by the control unit 12.

[0029] The heating source holding member 34 is disposed inside the fixing belt 31, facing the pressure roller 32 with the fixing belt 31 in between. The heating source holding member 34 is shorter than the fixing belt 31 along the rotational axis direction of the fixing belt 31 (the paper width direction, the depth direction of the paper surface in FIG. 2). The heating source holding member 34 is curved along the inner surface of the fixing belt 31 on the upstream side and the downstream side of the fixing nip portion N with respect to the conveyance direction of the paper S. The heating source holding member 34 holds the heating source 33 and maintains the contact state between the heating source 33 and the fixing belt 31.

[0030] The support member 35 is located inside the fixing belt 31, near the radial center of the fixing belt 31, and is arranged adjacent to the heat source holding member 34. The support member 35 extends longer than the fixing belt 31 along the rotation axis direction of the fixing belt 31 (the paper width direction, the depth direction of the paper surface in FIG. 2). The support member 35 is held by a side plate (not shown) provided on the outer side in the axial direction of the fixing belt 31, and ensures a pressure-applyable strength between the support member 35 and the pressure roller 32. The support member 35 is composed of, for example, a prismatic member, and supports the heat source holding member 34 between the inner surface of the fixing belt 31.

[0031] The temperature detection unit 36 includes a heat source temperature sensor 36h and a plurality of belt temperature sensors (heating member temperature sensors) 36c, 361, 362, 363 (see FIGS. 4 to 8).

[0032] The heat source temperature sensor 36h is arranged, for example, to face the fixing nip portion N across the heat source 33. The heat source temperature sensor 36h is composed of, for example, a thermistor or the like and contacts the heat source 33. The heat source temperature sensor 36h detects the temperature of the heat source 33.

[0033] The plurality of belt temperature sensors 36c, 361, 362, 363 (see FIGS. 4 to 8) are composed of, for example, a thermistor or a thermopile, and are arranged in contact with or non-contact with the outer peripheral surface of the fixing belt 31 to detect the temperature of the fixing belt 31.

[0034] With the above configuration, the fixing device 30 inserts the paper S into the fixing nip portion N between the fixing belt 31 and the pressure roller 32, and fixes the toner image formed on the paper S to the paper S by heating and pressurizing.

[0035] The cooling unit 40 has a cooling fan 41 and a blower duct 42.

[0036] The cooling fan 41 is composed of, for example, an axial flow fan, a centrifugal fan, etc. The exhaust part of the cooling fan 41 is connected to the air duct 42. The cooling fan 41 generates an air flow in the air duct 42.

[0037] The air duct 42 is arranged adjacent to each of the fixing belt 31 and the pressure roller 32. An air flow generated by the cooling fan 41 circulates in the air duct 42. The upstream end of the air duct 42 in the air flow direction is connected to the exhaust part of the cooling fan 41. An opening 43 is formed at the downstream end of the air duct 42 in the air flow direction. The air outlet 43 of the air duct 42 faces each of the fixing belt 31 and the pressure roller 32 and extends long in the paper width direction. Thereby, the air duct 42 blows and cools the air flow generated by the cooling fan 41 to a predetermined area in the paper width direction.

[0038]

Table 1

[0039] Table 1 shows the main paper types that can be inserted into the fixing nip portion N of the fixing device 30 and their paper widths [mm]. Among the symbols representing the main paper types in the upper row, "A6T", "A5T", "B5T", "A4T", "B5Y", and "A4Y" indicate the papers in Series A and Series B according to the JIS (Japanese Industrial Standards) standard. The trailing "T" means the way of placing the longitudinal direction of the rectangular paper in accordance with the paper conveyance direction of the image forming apparatus 1. The trailing "Y" means the way of placing the longitudinal direction of the rectangular paper in accordance with the paper width direction of the image forming apparatus 1. "STT" (Statement) and "LTT" (Letter) are papers mainly used in Europe and America. "SRA3" indicates the paper in Series SRA according to the ISO (International Organization for Standardization) standard. "13in" indicates a paper with a width of 13 inches. "Width / 2" is the length of half of the paper width.

[0040] FIG. 3 is an explanatory diagram showing an example of a configuration pattern of the cooling unit 40 of the fixing device 30 in FIG. 2. On the left side of FIG. 3, an example of a configuration pattern is shown in which two cooling configurations are provided on the pressure side (pressure roller 32 side) and one cooling configuration is provided on the heating side (fixing belt 31 side). On the right side of FIG. 3, an example of a configuration pattern is shown in which one cooling configuration is provided on the pressure side and two cooling configurations are provided on the heating side.

[0041] Regarding these two cooling configurations, in the present embodiment, as shown in FIG. 3, a configuration pattern is exemplified in which the printing speed of the image forming apparatus 1 is divided into three categories: a low-speed machine, a medium-speed machine, and a high-speed machine, and the configuration of the cooling unit 40 is scaled and developed. Note that the "main paper" in FIG. 3 is the same as that in Table 1, and some descriptions are omitted (for details, refer to Table 1). The "distance" in FIG. 3 indicates the distance from the center in the paper width direction corresponding to each main paper. The hatched portion in FIG. 3 indicates that the cooling configuration is arranged.

[0042] In the low-speed machine (for example, 40 sheets or less per minute), only the cooling configuration in the region exceeding the sizes near the paper types "B5T", "A4T", and "LTT" in the paper width direction of the pressure roller 32 (cooling side) can ensure the printing productivity of papers S of various sizes. Since the printing speed of the low-speed machine is low and the temperature rise in the non-paper-passing area is not large, the necessary cooling performance can be obtained by the cooling configuration only in the region exceeding the sizes near "B5T", "A4T", and "LTT".

[0043] In the medium-speed machine (for example, 40 to 65 sheets per minute), the necessity of cooling performance for small-sized papers S with sizes equal to or smaller than those near "B5T", "A4T", and "LTT" increases. Accordingly, in the medium-speed machine, in addition to the cooling configuration in the region exceeding the sizes near "B5T", "A4T", and "LTT" in the paper width direction of the pressure roller 32, the cooling configuration in the region equal to or smaller than the sizes near "B5T", "A4T", and "LTT" in the paper width direction of the fixing belt 31 (heating side) or the pressure roller 32 is combined.

[0044] In a high-speed machine (for example, 65 sheets or more per minute), in addition to cooling the pressure roller 32, a cooling configuration for regions exceeding the sizes near the paper types "LTY" and "A4Y" in the paper width direction of the fixing belt 31 is also combined. The cooling region for the fixing belt 31 overlaps with the cooling region for the pressure roller 32. Thereby, it becomes possible to improve the cooling performance and ensure the printing productivity of the paper S of sizes such as "A4Y" and "LTY" with high usage frequency. By combining the cooling configuration for the pressure roller 32 and the cooling configuration for the fixing belt 31, it is effective when expanding the image forming apparatus 1 to a high-speed machine capable of printing on paper S of "A4Y" size or larger.

[0045] As described above, the cooling unit 40 of the fixing device 30 can increase the cooling configuration as the printing speed increases, based on the configuration of the low-speed machine. Thereby, in each of the low-speed machine, the medium-speed machine, and the high-speed machine, the basic frame structure of the fixing device 30 can be made the same, and the design concept of the cooling unit 40 can be made common. That is, the cooling configuration can be expanded in a scalable manner.

[0046] FIG. 4 is a schematic diagram showing the positional relationship between the components of the fixing device 30 of Example 1 (high-speed machine) and the paper S. In FIG. 4, in the paper width direction (the horizontal direction on the left and right in FIG. 4), the positional relationship of each region of the fixing belt 31, the pressure roller 32, the heat source 33, the cooling unit 40, and the papers S1, S2, S3, S4, S5 is illustrated. Note that the vertical positional relationship in FIG. 4 does not illustrate the vertical positional relationship of the configuration in the actual fixing device 30, but is schematically illustrated for convenience of explanation. The same applies to FIGS. 5 to 8 and FIG. 12 described later.

[0047] In FIG. 4, sheet S1 corresponds to the area through which the "A6T" sheet in Table 1 passes. Sheet S2 corresponds to the area through which sheets including "STT", "A5T", and "B5T" in Table 1 pass. Sheet S3 corresponds to the area through which sheets including "A4T" and "LTT" in Table 1 pass. Sheet S4 corresponds to the area through which sheets including "B5Y", "LTY", and "A4Y" in Table 1 pass. Sheet S5 corresponds to the area through which sheets including "SRA3" and "13in" in Table 1 pass.

[0048] The cooling unit 40 includes a first cooling unit 40A, a second cooling unit 40B, and a third cooling unit 40C. The first cooling unit 40A has a first cooling fan 41A and a first air duct 42A. The second cooling unit 40B has a second cooling fan 41B and a second air duct 42B. The third cooling unit 40C has a third cooling fan 41C and a third air duct 42C.

[0049] Note that the control unit 12 can independently control each of the first cooling fan 41A, the second cooling fan 41B, and the third cooling fan 41C.

[0050] The cooling configuration of the fixing device 30 in Embodiment 1 shown in FIG. 4 is, for example, a cooling configuration for a high-speed machine capable of printing 65 sheets or more per minute. The cooling unit 40 includes a first cooling unit 40A and a second cooling unit 40B, which are cooling units on the pressurizing side, and a third cooling unit 40C, which is a cooling unit on the heating side.

[0051] The first cooling unit 40A blows air against the pressure roller 32 to cool the pressure roller 32. The outlet 43A of the first air duct 42A faces an area exceeding the first size in the paper width direction of the pressure roller 32. Note that the first size corresponds to the paper width of paper types "B5T", "A4T", and "LTT". That is, the outlet 43A of the first air duct 42A faces an area exceeding the size near the paper types "B5T", "A4T", and "LTT" in the paper width direction of the pressure roller 32.

[0052] As a result, the first air duct 42A blows air into an area exceeding the size near the paper types "B5T", "A4T", and "LTT" in the paper width direction of the pressure roller 32.

[0053] The second cooling unit 40B blows air against the pressure roller 32 to cool the pressure roller 32. The air outlet 43B of the second air duct 42B faces an area within the first size or less in the paper width direction of the pressure roller 32. That is, the air outlet 43B of the second air duct 42B faces an area within the size or less near the paper types "B5T", "A4T", and "LTT" in the paper width direction of the pressure roller 32.

[0054] As a result, the second air duct 42B blows air into an area within the size or less near the paper types "B5T", "A4T", and "LTT" in the paper width direction of the pressure roller 32. In the present embodiment, as shown in FIG. 4, the second air duct 42B is configured to blow air into an area exceeding the size near "A6T", but it may be configured to blow air into an area within the "A6T" size or less.

[0055] The third cooling unit 40C blows air against the fixing belt 31 to cool the fixing belt 31. The air outlet 43C of the third air duct 42C faces an area exceeding the second size in the paper width direction of the fixing belt 31. The second size is larger than the above-described first size and corresponds to the paper widths of the paper types "LTY" and "A4Y". That is, the air outlet 43C of the third air duct 42C faces an area exceeding the size near the paper types "LTY" and "A4Y" in the paper width direction of the fixing belt 31.

[0056] As a result, the third air duct 42C blows air into an area exceeding the size near the paper types "LTY" and "A4Y" in the paper width direction of the fixing belt 31.

[0057] Note that in Fig. 4, a single cooling fan 41 is provided for each of the first air duct 42A, the second air duct 42B, and the third air duct 42C. However, a configuration in which the cooling fans 41 are provided individually for both ends in the paper width direction may also be adopted. Regarding the number of cooling fans and the air passage configuration of the air duct 42, etc., it can be adjusted arbitrarily as appropriate based on various conditions such as the performance of the cooling fan 41, the air blowing loss caused by the shape and length of the air duct 42, the required cooling performance, the layout constraints, and the cost.

[0058] Fig. 5 is a schematic diagram showing the positional relationship between the components of the fixing device 30 of the modification of Example 1 and the paper S. The cooling unit 40 includes a first cooling unit 40A which is a cooling unit on the pressurizing side, and a second cooling unit 40B and a third cooling unit 40C which are cooling units on the heating side. That is, as shown in Fig. 5, the second air duct 42B may blow air to a region below the size near the paper types "B5T", "A4T", and "LTT" in the paper width direction of the fixing belt 31.

[0059] Fig. 6 is a schematic diagram showing the positional relationship between the components of the fixing device 30 of Example 2 (medium-speed machine) and the paper S. The cooling configuration of the fixing device 30 of Example 2 shown in Fig. 6 is a cooling configuration of a medium-speed machine capable of printing about 45 to 60 sheets per minute, for example. The cooling unit 40 includes a first cooling unit 40A and a second cooling unit 40B which are cooling units on the pressurizing side.

[0060] The first air duct 42A blows air to a region exceeding the size near the paper types "B5T", "A4T", and "LTT" in the paper width direction of the pressurizing roller 32. The second air duct 42B blows air to a region below the size near the paper types "B5T", "A4T", and "LTT" in the paper width direction of the pressurizing roller 32. The fixing device 30 of the medium-speed machine which is Example 2 is not provided with the third cooling unit 40C provided in the high-speed machine.

[0061] FIG. 7 is a schematic diagram showing the positional relationship between the components of the fixing device 30 of the modified example of Example 2 and the sheet S. The cooling unit 40 includes a first cooling unit 40A which is a cooling unit on the pressurizing side and a second cooling unit 40B which is a cooling unit on the heating side. That is, as shown in FIG. 7, the second air duct 42B may blow air to an area within the size near the paper types "B5T", "A4T", and "LTT" in the paper width direction of the fixing belt 31.

[0062] FIG. 8 is a schematic diagram showing the positional relationship between the components of the fixing device 30 of Example 3 (low-speed machine) and the sheet S. The cooling configuration of the fixing device 30 of Example 3 shown in FIG. 8 is a cooling configuration for a low-speed machine capable of printing about 40 sheets or less per minute. The cooling unit 40 includes a first cooling unit 40A which is a cooling unit on the pressurizing side.

[0063] The first air duct 42A blows air to an area exceeding the size near the paper types "B5T", "A4T", and "LTT" in the paper width direction of the pressurizing roller 32. In the fixing device 30 of the low-speed machine which is Example 3, the second cooling unit 40B and the third cooling unit 40C provided in medium-speed machines and high-speed machines are not provided.

[0064] Regarding the present invention, the cooling unit 40 includes a first cooling unit 40A that blows air to an area exceeding the size (first size) near "B5T", "A4T", and "LTT" in the paper width direction of at least the pressurizing roller 32. Further, the cooling unit 40 includes at least one of a second cooling unit 40B that blows air to an area within the size (first size) near "B5T", "A4T", and "LTT" in the paper width direction of the fixing belt 31 and a third cooling unit 40C that blows air to an area exceeding the size (second size) near "LTY" and "A4Y" which is larger than the size (first size) near "B5T", "A4T", and "LTT" in the paper width direction of the fixing belt 31. And the control unit 12 can independently control each of the first cooling fan 41A, the second cooling fan 41B, and the third cooling fan 41C.

[0065] According to the above configuration, by adopting a configuration that combines a plurality of cooling units, it becomes possible to scale the necessary cooling units from low speed to medium speed and high speed. As a result, with the configuration of the common fixing device 30, a highly flexible design can be achieved that can respond to overheating in the non-printing area from low speed to high speed. In addition, by appropriately fixing and arranging the cooling paths in advance according to the respective characteristics of the cooling of the pressure roller 32 and the cooling of the fixing belt 31, it is possible to correspond to various paper sizes with the fixed cooling path configuration without changing the cooling path for each model.

[0066] Also, as shown in FIGS. 4 to 8, the temperature detection unit 36 includes a plurality of belt temperature sensors (heating member temperature sensors) 36c, 361, 362, and 363. The plurality of belt temperature sensors 36c, 361, 362, and 363 are arranged for each of a plurality of regions along the paper width direction including the central portion in the paper width direction. In other words, the plurality of belt temperature sensors 361, 362, and 363 are arranged so as to be able to detect the temperature of the outer side (non-printing area) of the paper width such as a size with high usage frequency or a size that requires high printing productivity corresponding to the configurations of the first cooling unit 40A, the second cooling unit 40B, and the third cooling unit 40C.

[0067] The central belt temperature sensor 36c is arranged at the central portion in the paper width direction. The central belt temperature sensor 36c is arranged opposite to the fixing belt 31 in the region within the area of the smallest paper width size where the paper S of the paper type "A6T" passes, and detects the temperature of the fixing belt 31 in that region.

[0068] The first belt temperature sensor 361 is disposed opposite to the fixing belt 31 in a region exceeding the size of the paper type "A4Y", and detects the temperature of the fixing belt 31 in this region. For example, when a paper S such as "A4Y", "LTY", "B5Y", etc. (paper width from "B5Y" or more to near "A4Y") passes through the fixing nip portion N, the first belt temperature sensor 361 detects the temperature of the fixing belt 31 in the region exceeding the size of "A4Y". That is, the first belt temperature sensor 361 is disposed at a position where the peak temperature of the non-paper passing region for "A4Y" and "LTY", which is most important for maintaining printing productivity, can be detected.

[0069] The second belt temperature sensor 362 is disposed opposite to the fixing belt 31 in a region exceeding the sizes of the paper types "A4T" and "LTT" and less than the size of "SRA3", and detects the temperature of the fixing belt 31 in this region. For example, when a paper S such as "A4T", "LTT", etc. (paper width less than "B5Y" and more than "A4T") passes through the fixing nip portion N, the second belt temperature sensor 362 detects the temperature of the fixing belt 31 in the region exceeding the sizes of "A4T" and "LTT" and less than the size of "SRA3". That is, the second belt temperature sensor 362 is disposed at a position where the peak temperature of the non-paper passing region for "A4T" and "LTT" can be detected.

[0070] The third belt temperature sensor 363 is disposed opposite to the fixing belt 31 in a region exceeding the sizes of the paper types "A5T" and "STT" and less than the size of "B5Y", and detects the temperature of the fixing belt 31 in this region. For example, when a paper S such as "A6T", "STT", "A5T", "B5T", etc. (paper width less than "A4T") passes through the fixing nip portion N, the third belt temperature sensor 363 detects the temperature of the fixing belt 31 in the region exceeding the sizes of "A5T" and "STT" and less than the size of "B5Y". That is, the third belt temperature sensor 363 is disposed at a position where the peak temperature of the non-paper passing region for "A5T" and "STT" can be detected.

[0071] According to the above configuration, when the image forming apparatus 1 is expanded from a low-speed machine to a medium-speed machine and then to a high-speed machine, the temperature of the non-paper-passing area of the fixing belt 31 with respect to sheets S of various sizes can be detected with high precision. Further, in each of the low-speed machine, the medium-speed machine, and the high-speed machine, the basic arrangement configuration of the temperature detection unit 36 can be made the same, and the design concept of the cooling unit 40 can be shared. That is, the cooling configuration can be expanded in a scalable manner.

[0072] Subsequently, a control method of the cooling unit 40 by the control unit 12 will be described.

[0073] For example, in the case where the cooling unit 40 includes only the first cooling unit 40A as in the low-speed machine, it will be described along the flow shown in FIG. 9 with reference to Table 1 and FIG. 8. FIG. 9 is a flowchart showing the flow of cooling control in the fixing device 30 of the low-speed machine. Note that the cooling control is performed by the control unit 12, but it may also be performed by separately providing a control unit in the fixing device 30. Further, in the following description, the magnitude relationship of the predetermined temperatures is "Ta < Tb < Tc".

[0074] At the start of printing, the operation of the cooling unit 40 is stopped, and the air blowing and cooling by the cooling unit 40 for the fixing device 30 are OFF.

[0075] Then, along with the start of printing, the control unit 12 starts the cooling control shown in FIG. 9 ("Start" in FIG. 9).

[0076] First, the control unit 12 determines the size of the sheet S inserted into the fixing device 30 (step S11).

[0077] In step S11, when the sheet S is of a size equal to or larger than "B5Y" (S ≧ B5Y), the control unit 12 refers to the detected temperature T of the first belt temperature sensor 361 (step S12).

[0078] In step S12, when the detected temperature T of the first belt temperature sensor 361 becomes equal to or higher than a predetermined temperature Ta (T ≥ Ta), the control unit 12 turns on the air blowing and cooling by the first cooling unit 40A (step S15). Also, in step S12, when the detected temperature T of the first belt temperature sensor 361 becomes equal to or higher than a predetermined temperature Tb (T ≥ Tb), the control unit 12 does nothing (when there is a third cooling unit 40C as in the high-speed machines shown in FIGS. 4 and 5, the control unit 12 turns on the air blowing and cooling by the third cooling unit 40C). Further, in step S12, when the detected temperature T of the first belt temperature sensor 361 becomes equal to or higher than a predetermined temperature Tc (T ≥ Tc), the control unit 12 reduces the number of printed sheets per minute (step S16).

[0079] Note that in step S12, when the detected temperature T of the first belt temperature sensor 361 is lower than the predetermined temperature Ta (T < Ta), the control unit 12 ends the cooling control process according to FIG. 9 ("End" in FIG. 9).

[0080] Also, in step S11, when the paper S is of a size equal to or larger than "A4T" and smaller than "B5Y" (B5Y > S ≥ A4T), the control unit 12 refers to the detected temperature T of the first belt temperature sensor 361 or the second belt temperature sensor 362 (step S13).

[0081] In step S13, when the detected temperature T of either the first belt temperature sensor 361 or the second belt temperature sensor 362 becomes equal to or higher than a predetermined temperature Ta (T ≥ Ta), the control unit 12 turns on the air blowing and cooling by the first cooling unit 40A (step S15). Also, in step S13, when the detected temperature T of either the first belt temperature sensor 361 or the second belt temperature sensor 362 becomes equal to or higher than a predetermined temperature Tb (T ≥ Tb), the control unit 12 does nothing (when there is a third cooling unit 40C as in the high-speed machines shown in FIGS. 4 and 5, the control unit 12 turns on the air blowing and cooling by the third cooling unit 40C). Further, in step S13, when the detected temperature T of either the first belt temperature sensor 361 or the second belt temperature sensor 362 becomes equal to or higher than a predetermined temperature Tc (T ≥ Tc), the control unit 12 reduces the number of printed sheets per minute (step S16).

[0082] In step S13, when the detected temperature T of each of the first belt temperature sensor 361 and the second belt temperature sensor 362 is lower than a predetermined temperature Ta (T < Ta), the control unit 12 ends the cooling control process according to FIG. 9 ("End" in FIG. 9).

[0083] Also, in step S11, when the sheet S is less than "A4T" (A4T > S), the control unit 12 refers to the detected temperature T of the first belt temperature sensor 361, the second belt temperature sensor 362, or the third belt temperature sensor 363 (step S14).

[0084] In step S14, when the detected temperature T of any one of the first belt temperature sensor 361, the second belt temperature sensor 362, and the third belt temperature sensor 363 becomes equal to or higher than the predetermined temperature Ta (T ≥ Ta), the control unit 12 turns on the air blowing and cooling by the first cooling unit 40A (step S15). Also, in step S14, when the detected temperature T of any one of the first belt temperature sensor 361, the second belt temperature sensor 362, and the third belt temperature sensor 363 becomes equal to or higher than the predetermined temperature Tb (T ≥ Tb), the control unit 12 does nothing (when there is a third cooling unit 40C as in the high-speed machine shown in FIGS. 4 and 5, the control unit 12 turns on the air blowing and cooling by the third cooling unit 40C). Also, in step S14, when the detected temperature T of any one of the first belt temperature sensor 361, the second belt temperature sensor 362, and the third belt temperature sensor 363 becomes equal to or higher than the predetermined temperature Tc (T ≥ Tc), the control unit 12 reduces the number of printed sheets per minute (step S16).

[0085] In step S14, when the detected temperatures T of all of the first belt temperature sensor 361, the second belt temperature sensor 362, and the third belt temperature sensor 363 are lower than the predetermined temperature Ta (T < Ta), the control unit 12 ends the cooling control process according to FIG. 9 ("End" in FIG. 9).

[0086] Also, when the ON condition of the first cooling unit 40A is no longer satisfied, the control unit 12 turns off the air blowing and cooling by the first cooling unit 40A.

[0087] Also, the above cooling control is basically performed based on the temperature of each region of the fixing belt 31 and the size in the width direction of the paper S. However, it may be additionally assisted to control the air blowing by the cooling unit 40 based on the number of consecutive recording sheets or the consecutive recording time for the paper S. According to this configuration, it becomes possible to suitably control the timing of cooling by the cooling unit 40. Thereby, an excessive temperature rise in the non-paper-passing regions of both the fixing belt 31 and the pressure roller 32 can be suppressed.

[0088] For example, in the case where the cooling unit 40 includes a first cooling unit 40A and a second cooling unit 40B that cools the fixing belt 31, such as in a medium-speed machine, it will be described along the flow shown in FIG. 10 while referring to Table 1 and FIG. 7. FIG. 10 is a flowchart showing the flow of cooling control in the fixing device 30 of the medium-speed machine. Note that the cooling control is implemented by the control unit 12, but it may also be implemented by separately providing a control unit in the fixing device 30. Also, in the following description, the magnitude relationship of the predetermined temperatures is "Ta < Tb < Tc".

[0089] At the start of printing, the operation of the cooling unit 40 is stopped, and the air blowing and cooling by the cooling unit 40 for the fixing device 30 are OFF.

[0090] Then, at the start of printing, the control unit 12 starts the cooling control shown in FIG. 9 ("Start" in FIG. 9).

[0091] First, the control unit 12 determines what size the paper S inserted into the fixing device 30 is (step S21).

[0092] In step S21, when the paper S is of a size equal to or larger than "B5Y" (S ≥ B5Y), the control unit 12 refers to the detected temperature T of the first belt temperature sensor 361 (step S22).

[0093] In step S22, when the detected temperature T of the first belt temperature sensor 361 becomes equal to or higher than a predetermined temperature Ta (T ≥ Ta), the control unit 12 turns on the air blowing and cooling by the first cooling unit 40A (step S25). Also, in step S22, when the detected temperature T of the first belt temperature sensor 361 becomes equal to or higher than a predetermined temperature Tb (T ≥ Tb), the control unit 12 does nothing (when there is a third cooling unit 40C as in the high-speed machines shown in FIGS. 4 and 5, the control unit 12 turns on the air blowing and cooling by the third cooling unit 40C). Further, in step S22, when the detected temperature T of the first belt temperature sensor 361 becomes equal to or higher than a predetermined temperature Tc (T ≥ Tc), the control unit 12 decreases the number of printed sheets per minute (step S26).

[0094] Note that in step S22, when the detected temperature T of the first belt temperature sensor 361 is lower than the predetermined temperature Ta (T < Ta), the control unit 12 ends the cooling control process according to FIG. 10 ("End" in FIG. 10).

[0095] Also, in step S21, when the paper S is of a size equal to or larger than "A4T" and smaller than "B5Y" (B5Y > S ≥ A4T), the control unit 12 refers to the detected temperature T of the first belt temperature sensor 361 or the second belt temperature sensor 362 (step S23).

[0096] In step S23, when the detected temperature T of either the first belt temperature sensor 361 or the second belt temperature sensor 362 becomes equal to or higher than a predetermined temperature Ta (T ≥ Ta), the control unit 12 turns on the air blowing and cooling by the first cooling unit 40A (step S25). Also, in step S23, when the detected temperature T of either the first belt temperature sensor 361 or the second belt temperature sensor 362 becomes equal to or higher than a predetermined temperature Tb (T ≥ Tb), the control unit 12 does nothing (when there is a third cooling unit 40C as in the high-speed machines shown in FIGS. 4 and 5, the control unit 12 turns on the air blowing and cooling by the third cooling unit 40C). Further, in step S23, when the detected temperature T of either the first belt temperature sensor 361 or the second belt temperature sensor 362 becomes equal to or higher than a predetermined temperature Tc (T ≥ Tc), the control unit 12 decreases the number of printed sheets per minute (step S26).

[0097] In step S23, when the detected temperature T of each of the first belt temperature sensor 361 and the second belt temperature sensor 362 is lower than a predetermined temperature Ta (T < Ta), the control unit 12 ends the cooling control process according to FIG. 10 ("End" in FIG. 10).

[0098] Also, in step S21, when the sheet S is less than "A4T" (A4T > S), the control unit 12 refers to the detected temperature T of the first belt temperature sensor 361, the second belt temperature sensor 362, or the third belt temperature sensor 363 (step S24).

[0099] In step S24, when the detected temperature T of any one of the first belt temperature sensor 361, the second belt temperature sensor 362, and the third belt temperature sensor 363 becomes equal to or higher than the predetermined temperature Ta (T ≥ Ta), the control unit 12 turns on the air blowing and cooling by the first cooling unit 40A and the second cooling unit 40B (step S27). Also, in step S24, when the detected temperature T of any one of the first belt temperature sensor 361, the second belt temperature sensor 362, and the third belt temperature sensor 363 becomes equal to or higher than the predetermined temperature Tb (T ≥ Tb), the control unit 12 does nothing (when there is a third cooling unit 40C as in the high-speed machine shown in FIGS. 4 and 5, turns on the air blowing and cooling by the third cooling unit 40C). Also, in step S24, when the detected temperature T of any one of the first belt temperature sensor 361, the second belt temperature sensor 362, and the third belt temperature sensor 363 becomes equal to or higher than the predetermined temperature Tc (T ≥ Tc), the control unit 12 reduces the number of printed sheets per minute (step S26).

[0100] In step S24, when the detected temperatures T of all of the first belt temperature sensor 361, the second belt temperature sensor 362, and the third belt temperature sensor 363 are lower than the predetermined temperature Ta (T < Ta), the control unit 12 ends the cooling control process according to FIG. 10 ("End" in FIG. 10).

[0101] Also, when the ON condition of the first cooling unit 40A is no longer satisfied, the control unit 12 turns off the air blowing and cooling by the first cooling unit 40A. Also, when the ON condition of the second cooling unit 40B is no longer satisfied, the control unit 12 turns off the air blowing and cooling by the second cooling unit 40B.

[0102] Also, the above cooling control is basically performed based on the temperature of each area of the fixing belt 31 and the size in the width direction of the paper S. However, it is also possible to additionally assist in controlling the air blowing by the cooling unit 40 based on the number of consecutive recording sheets or the consecutive recording time with respect to the paper S. According to this configuration, it becomes possible to suitably control the timing of cooling by the cooling unit 40. Thereby, it is possible to suppress an excessive temperature rise in the non-paper passing areas of both the fixing belt 31 and the pressure roller 32.

[0103] For example, in the case where the cooling unit 40 includes a first cooling unit 40A, a second cooling unit 40B that cools the fixing belt 31, and a third cooling unit 40C, as in a high-speed machine, it will be described along the flow shown in FIG. 11 while referring to Table 1 and FIG. 5. FIG. 11 is a flowchart showing the flow of cooling control in the fixing device 30 of the high-speed machine. Note that the cooling control is performed by the control unit 12, but it may also be performed by separately providing a control unit in the fixing device 30. Also, in the following description, the magnitude relationship of the predetermined temperatures is "Ta < Tb < Tc".

[0104] At the start of printing, the operation of the cooling unit 40 is stopped, and the air blowing and cooling by the cooling unit 40 for the fixing device 30 are OFF.

[0105] Then, along with the start of printing, the control unit 12 starts the cooling control shown in FIG. 9 ("Start" in FIG. 9).

[0106] First, the control unit 12 determines the size of the paper S inserted into the fixing device 30 (step S31).

[0107] In step S31, when the sheet S is of a size equal to or larger than "B5Y" (S ≧ B5Y), the control unit 12 refers to the detected temperature T of the first belt temperature sensor 361 (step S32).

[0108] In step S32, when the detected temperature T of the first belt temperature sensor 361 becomes equal to or higher than a predetermined temperature Ta (T ≧ Ta), the control unit 12 turns on the air blowing and cooling by the first cooling unit 40A (step S35). Also, in step S32, when the detected temperature T of the first belt temperature sensor 361 becomes equal to or higher than a predetermined temperature Tb (T ≧ Tb), the control unit 12 turns on the air blowing and cooling by the third cooling unit 40C (step S36). Further, in step S32, when the detected temperature T of the first belt temperature sensor 361 becomes equal to or higher than a predetermined temperature Tc (T ≧ Tc), the control unit 12 reduces the number of printed sheets per minute (step S37).

[0109] Note that in step S32, when the detected temperature T of the first belt temperature sensor 361 is lower than the predetermined temperature Ta (T < Ta), the control unit 12 ends the cooling control process according to FIG. 11 ("End" in FIG. 11).

[0110] Also, in step S31, when the sheet S is of a size equal to or larger than "A4T" and smaller than "B5Y" (B5Y > S ≧ A4T), the control unit 12 refers to the detected temperature T of the first belt temperature sensor 361 or the second belt temperature sensor 362 (step S33).

[0111] In step S33, when the detected temperature T of either the first belt temperature sensor 361 or the second belt temperature sensor 362 becomes equal to or higher than a predetermined temperature Ta (T ≧ Ta), the control unit 12 turns on the air blowing and cooling by the first cooling unit 40A (step S35). Also, in step S33, when the detected temperature T of either the first belt temperature sensor 361 or the second belt temperature sensor 362 becomes equal to or higher than a predetermined temperature Tc (T ≧ Tc), the control unit 12 reduces the number of printed sheets per minute (step S37).

[0112] Also, in step S33, when the detected temperature T of either the first belt temperature sensor 361 or the second belt temperature sensor 362 becomes equal to or higher than a predetermined temperature Tb (T≧Tb), the control unit 12 determines whether the detected temperature of the first belt temperature sensor 361 is higher than the detected temperature of the second belt temperature sensor 362 (step S38). When the detected temperature of the first belt temperature sensor 361 is higher than the detected temperature of the second belt temperature sensor 362 (Yes in step S38), the control unit 12 turns on the air blowing and cooling by the third cooling unit 40C (step S36).

[0113] In addition, in step S33, when the detected temperature T of each of the first belt temperature sensor 361 and the second belt temperature sensor 362 is lower than a predetermined temperature Ta (T<Ta), the control unit 12 ends the cooling control process according to FIG. 11 ("End" in FIG. 11).

[0114] Also, in step S31, when the paper S is less than "A4T" (A4T>S), the control unit 12 refers to the detected temperature T of the first belt temperature sensor 361, the second belt temperature sensor 362, or the third belt temperature sensor 363 (step S34).

[0115] In step S34, when the detected temperature T of any one of the first belt temperature sensor 361, the second belt temperature sensor 362, and the third belt temperature sensor 363 becomes equal to or higher than a predetermined temperature Ta (T≧Ta), the control unit 12 turns on the air blowing and cooling by the first cooling unit 40A and the second cooling unit 40B (step S39). Also, in step S34, when the detected temperature T of any one of the first belt temperature sensor 361, the second belt temperature sensor 362, and the third belt temperature sensor 363 becomes equal to or higher than a predetermined temperature Tc (T≧Tc), the control unit 12 reduces the number of printed sheets per minute (step S37).

[0116] Also, in step S34, when the detected temperature T of any one of the first belt temperature sensor 361, the second belt temperature sensor 362, and the third belt temperature sensor 363 becomes equal to or higher than a predetermined temperature Tb (T ≧ Tb), the control unit 12 determines whether the detected temperature of the first belt temperature sensor 361 is higher than the detected temperatures of both the second belt temperature sensor 362 and the third belt temperature sensor 363 (step S40). When the detected temperature of the first belt temperature sensor 361 is higher than the detected temperatures of both the second belt temperature sensor 362 and the third belt temperature sensor 363 (Yes in step S40), the control unit 12 turns on the air blowing and cooling by the third cooling unit 40C (step S36).

[0117] In addition, in step S34, when the detected temperatures T of all of the first belt temperature sensor 361, the second belt temperature sensor 362, and the third belt temperature sensor 363 are lower than a predetermined temperature Ta (T < Ta), the control unit 12 ends the cooling control process according to FIG. 11 ("End" in FIG. 11).

[0118] Also, when the ON condition of the first cooling unit 40A is no longer satisfied, the control unit 12 turns off the air blowing and cooling by the first cooling unit 40A. Also, when the ON condition of the second cooling unit 40B is no longer satisfied, the control unit 12 turns off the air blowing and cooling by the second cooling unit 40B. Also, when the ON condition of the third cooling unit 40C is no longer satisfied, the control unit 12 turns off the air blowing and cooling by the third cooling unit 40C.

[0119] Also, the above cooling control is basically performed based on the temperature of each region of the fixing belt 31 and the size in the width direction of the paper S, but it is also possible to additionally assist in controlling the air blowing by the cooling unit 40 based on the number of consecutive recording sheets or the consecutive recording time for the paper S. According to this configuration, it becomes possible to suitably control the timing of cooling by the cooling unit 40. As a result, excessive temperature rise in the non-paper passing regions of both the fixing belt 31 and the pressure roller 32 can be suppressed.

[0120] As described above, after the start of insertion of the sheet S into the fixing nip portion N, the control unit 12 controls the air blowing by the cooling unit 40 based on the temperature of each region of the fixing belt 31 detected by each belt temperature sensor and the size of the sheet S in the width direction. By scalably expanding the cooling configuration, it becomes possible to unify the design concept for the control of the cooling unit 40 in each of the low-speed machine, medium-speed machine, and high-speed machine. And for each of the low-speed machine, medium-speed machine, and high-speed machine, the cost-performance balance can be optimized.

[0121] FIG. 12 is a schematic diagram showing the positional relationship between the components of the fixing device 30 of Example 4 (medium-speed machine) and the sheet S.

[0122] The heating source 33 includes a first heating source 331 and a second heating source 332 that are divided in the sheet width direction (the left-right horizontal direction in FIG. 12). The first heating source 331 is disposed at the central portion in the sheet width direction of the fixing device 30 and has a length corresponding to the region through which the sheet S3 (sheets including "A4T" and "LTT" in Table 1) passes in the sheet width direction. The second heating source 332 is disposed outside in the sheet width direction following both end portions of the first heating source 331 in the sheet width direction.

[0123] The operations of the first heating source 331 and the second heating source 332 are individually controlled by the control unit 12. For example, when a sheet having a size equal to or smaller than the sheet S3 (sheets including "A4T" and "LTT" in Table 1) passes through the fixing nip portion N, the control unit 12 turns on the first heating source 331 and turns off the second heating source 332. Also, when a sheet having a size larger than the sheet S3 passes through the fixing nip portion N, the control unit 12 turns on both the first heating source 331 and the second heating source 332.

[0124] The temperature detection unit 36 includes a central heat source temperature sensor 36hc, a first heat source temperature sensor 36h1, and a third heat source temperature sensor 36h3 as a plurality of heat source temperature sensors.

[0125] The central heat source temperature sensor 36hc is disposed at the center in the paper width direction. The heat source temperature sensor 36hc is disposed opposite to the first heating source 331 in the region within the area of the minimum paper width where the paper S of the paper type "A6T" size passes, and detects the temperature of the first heating source 331 in the region. The first heat source temperature sensor 36h1 is disposed opposite to the second heating source 332 in the region exceeding the size of the paper type "A4Y", and detects the temperature of the second heating source 332 in the region. The third heat source temperature sensor 36h3 is disposed opposite to the first heating source 331 in the region exceeding the sizes of the paper types "A5T" and "STT" and less than the size of "A4T", and detects the temperature of the first heating source 331 in the region.

[0126] Then, after the start of insertion of the paper S into the fixing nip portion N, the control unit 12 controls the air blowing by the cooling unit 40 based on the temperature of each of the first heating source 331 and the second heating source 332 detected by the first heat source temperature sensor 36h1 and the third heat source temperature sensor 36h3, and the size in the width direction of the paper S. The control unit 12 executes the cooling control in the same manner as the control using the belt temperature sensor described above. The control unit 12 uses the temperature information of the heating source 33 detected by the heat source temperature sensor instead of the temperature information of the fixing belt 31 detected by the belt temperature sensor as the temperature information used for the cooling control.

[0127] FIG. 13 is a flowchart showing the flow of the cooling control in the fixing device 30 of the medium-speed machine in FIG. 12. The cooling control is performed by the control unit 12, but it may be performed by separately providing a control unit in the fixing device 30. In the following description, the magnitude relationship of the predetermined temperatures is "Ta < Tb < Tc".

[0128] At the start of printing, the operation of the cooling unit 40 is stopped, and the air blowing and cooling by the cooling unit 40 for the fixing device 30 are OFF.

[0129] Then, upon the start of printing, the control unit 12 starts the cooling control shown in FIG. 13 (the "start" in FIG. 13). First, the control unit 12 determines the size of the paper S inserted into the fixing device 30 (step S41).

[0130] In step S41, when the paper S is of a size equal to or larger than "B5Y" (S ≧ B5Y), the control unit 12 refers to the detected temperature T of the first heat source temperature sensor 36h1 (step S42).

[0131] In step S42, when the detected temperature T of the first heat source temperature sensor 36h1 becomes equal to or higher than the predetermined temperature Ta (T ≧ Ta), the control unit 12 turns on the air supply and cooling by the first cooling unit 40A (step S45). Also, in step S42, when the detected temperature T of the first heat source temperature sensor 36h1 becomes equal to or higher than the predetermined temperature Tb (T ≧ Tb), the control unit 12 does nothing (when there is a third cooling unit 40C as in the high-speed machine shown in FIGS. 4 and 5, the air supply and cooling by the third cooling unit 40C are turned on). Further, in step S42, when the detected temperature T of the first heat source temperature sensor 36h1 becomes equal to or higher than the predetermined temperature Tc (T ≧ Tc), the control unit 12 reduces the number of printed sheets per minute (step S46).

[0132] Note that in step S42, when the detected temperature T of the first heat source temperature sensor 36h1 is lower than the predetermined temperature Ta (T < Ta), the control unit 12 ends the cooling control process according to FIG. 13 (the "end" in FIG. 13).

[0133] Also, in step S41, when the paper S is of a size equal to or larger than "A4T" and smaller than "B5Y" (B5Y > S ≧ A4T), the control unit 12 refers to the detected temperature T of the first heat source temperature sensor 36h1 (step S43).

[0134] In step S43, when the detected temperature T of the first heat source temperature sensor 36h1 becomes equal to or higher than a predetermined temperature Ta (T ≥ Ta), the control unit 12 turns on the air blowing and cooling by the first cooling unit 40A (step S45). Also, in step S43, when the detected temperature T of the first heat source temperature sensor 36h1 becomes equal to or higher than a predetermined temperature Tb (T ≥ Tb), the control unit 12 does nothing (when there is a third cooling unit 40C as in the high-speed machine shown in FIGS. 4 and 5, the control unit 12 turns on the air blowing and cooling by the third cooling unit 40C). Further, in step S43, when the detected temperature T of the first heat source temperature sensor 36h1 becomes equal to or higher than a predetermined temperature Tc (T ≥ Tc), the control unit 12 decreases the number of printed sheets per minute (step S46).

[0135] Note that in step S43, when the detected temperature T of the first heat source temperature sensor 36h1 is lower than the predetermined temperature Ta (T < Ta), the control unit 12 ends the cooling control process according to FIG. 13 ("End" in FIG. 13).

[0136] Also, in step S41, when the sheet S is less than "A4T" (A4T > S), the control unit 12 refers to the detected temperature T of the first heat source temperature sensor 36h1 or the third heat source temperature sensor 36h3 (step S44).

[0137] In step S44, when the detected temperature T of either the first heat source temperature sensor 36h1 or the third heat source temperature sensor 36h3 becomes equal to or higher than a predetermined temperature Ta (T ≥ Ta), the control unit 12 turns on the air blowing and cooling by the first cooling unit 40A and the second cooling unit 40B (step S47). Also, in step S44, when the detected temperature T of either the first heat source temperature sensor 36h1 or the third heat source temperature sensor 36h3 becomes equal to or higher than a predetermined temperature Tb (T ≥ Tb), the control unit 12 does nothing (when there is a third cooling unit 40C as in the high-speed machine shown in FIGS. 4 and 5, the control unit 12 turns on the air blowing and cooling by the third cooling unit 40C). Further, in step S44, when the detected temperature T of either the first heat source temperature sensor 36h1 or the third heat source temperature sensor 36h3 becomes equal to or higher than a predetermined temperature Tc (T ≥ Tc), the control unit 12 decreases the number of printed sheets per minute (step S46).

[0138] In step S44, when all the detected temperatures T of the first heat source temperature sensor 36h1 and the third heat source temperature sensor 36h3 are lower than the predetermined temperature Ta (T < Ta), the control unit 12 ends the cooling control process according to FIG. 13 ("End" in FIG. 13).

[0139] When the ON condition of the first cooling unit 40A is no longer satisfied, the control unit 12 turns off the air blowing and cooling by the first cooling unit 40A. When the ON condition of the second cooling unit 40B is no longer satisfied, the control unit 12 turns off the air blowing and cooling by the second cooling unit 40B.

[0140] The above cooling control is basically performed based on the temperature of each region of the heat source 33 and the size in the width direction of the sheet S. However, it is also possible to additionally assist in controlling the air blowing by the cooling unit 40 based on the number of consecutive recording sheets or the consecutive recording time for the sheet S. According to this configuration, when dealing with the situation where it is difficult to accurately detect the belt temperature by only using the heat source temperature sensor without the belt temperature sensor, it becomes possible to cope with such a situation. That is, when there is no belt temperature sensor, it becomes possible to suitably control the timing of cooling by the cooling unit 40. Thereby, excessive temperature rise in the non-sheet passing regions of both the fixing belt 31 and the pressure roller 32 can be suppressed.

[0141] Note that in the above, for the sake of easy understanding of the control intention, the temperature sensors referred to as judgment conditions are described separately according to the sheet width. However, if all the temperature sensors referred to are defined by OR conditions, the reference conditions for the temperature sensors can be made common.

[0142] Also, the above cooling control is just an example and can be adjusted arbitrarily as appropriate based on various conditions such as the fixing system configuration, cooling performance, heating source configuration, temperature sensor arrangement, etc. For example, in the above cooling control, the paper size was classified into three paper width categories to control the blowing and cooling ON / OFF by the cooling unit 40. However, it is also possible to further subdivide the paper size classification and the determination conditions of the temperature sensor for more refined cooling control.

[0143] In addition, the control unit 12 implements more appropriate cooling control according to the paper size by controlling the air volume of the cooling fan 41. According to this configuration, it becomes possible to more finely adjust the cooling control for various paper sizes by the cooling unit 40.

[0144] Although the embodiments of the present invention have been described above, the scope of the present invention is not limited thereto, and various modifications can be made and implemented without departing from the gist of the invention.

[0145] For example, in the above embodiment, the image forming apparatus 1 was assumed to be an image forming apparatus for monochrome printing. However, it is not necessarily limited to such a model. The image forming apparatus 1 may be, for example, an image forming apparatus for color printing.

Industrial Applicability

[0146] The present invention can be used in a fixing device and an image forming apparatus.

Explanation of Reference Numerals

[0147] 1 Image forming apparatus 8 Image forming section 12 Control unit 30 Fixing device 31 Fixing belt (heating member) 32 Pressing roller (pressing member) 33 Heating source 36 Temperature detection section 36c Central belt temperature sensor 36h Heat source temperature sensor 36hc Central heat source temperature sensor 36h1 First heat source temperature sensor 36h3 Third heat source temperature sensor 40 Cooling unit 40A First cooling unit 40B Second cooling unit 40C Third cooling unit 41 Cooling fan 41A First cooling fan 41B Second cooling fan 41C Third cooling fan 42 Air duct 42A First air duct 42B Second air duct 42C Third air duct 331 First heating source 332 Second heating source 361 First belt temperature sensor (heating member temperature sensor) 362 Second belt temperature sensor (heating member temperature sensor) 363 Third belt temperature sensor (heating member temperature sensor) N Fixing nip section S, S1, S2, S3, S4, S5 Paper (recording medium)

Claims

1. A fixing device that fixes a toner image formed on a recording medium to the recording medium by inserting the recording medium into a fixing nip portion between a heating member and a pressure member and applying heat and pressure to the recording medium, a cooling unit having a cooling fan and an air blowing duct that blows an air flow generated by the cooling fan to a predetermined region in a width direction perpendicular to a conveying direction of the recording medium to cool the recording medium; A control unit that controls the cooling unit; Equipped with The cooling unit includes: a first cooling unit having a first air blowing duct and a first cooling fan that blow air to at least an area of ​​the pressing member that exceeds a first size in the width direction; at least one of a second cooling section having a second air blowing duct and a second cooling fan that blow air to an area of ​​the heating member that is equal to or smaller than the first size in the width direction, and a third cooling section having a third air blowing duct and a third cooling fan that blow air to an area of ​​the heating member that exceeds a second size that is larger than the first size in the width direction, The fixing device, wherein the control unit is capable of independently controlling each of the first cooling fan, the second cooling fan, and the third cooling fan.

2. a plurality of heating member temperature sensors arranged in each of the plurality of regions along the width direction including a central portion in the width direction, the plurality of heating member temperature sensors detecting temperatures in each of the plurality of regions of the heating member; The fixing device according to claim 1, characterized in that the control unit controls the air blowing by the cooling unit based on the temperature of each of the areas of the heating member detected by the heating member temperature sensor after insertion of the recording medium into the fixing nip portion is started and the size of the recording medium in the width direction.

3. A plurality of heating sources for heating a plurality of locations along the width direction of the heating member; A plurality of heat source temperature sensors for detecting the temperatures of the plurality of heat sources; Equipped with The fixing device according to claim 1, characterized in that the control unit controls the air blowing by the cooling unit based on the temperature of each heating source detected by the heat source temperature sensor and the width direction size of the recording medium after insertion of the recording medium into the fixing nip portion begins.

4. 4. The fixing device according to claim 2, wherein the control section controls the air blown by the cooling section based on the number of continuous recordings or the continuous recording time for the recording medium.

5. 4. The fixing device according to claim 2, wherein the control unit controls an air volume of the cooling fan.

6. The fixing device according to claim 1 ; an image forming section that forms the toner image on the recording medium, the toner image being fixed by the fixing device; An image forming apparatus comprising:

Images