Patent Publication Number: US-2021181658-A1

Title: Image forming apparatus with individually controllable heating members

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-227231, filed on Dec. 17, 2019, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to an image forming apparatus. 
     BACKGROUND 
     A fixing device of an on-demand type is known as a fixing system for an image forming apparatus. The fixing device comprises a plurality of heating elements arranged in a main scanning direction. The fixing device generates heat by the heating elements in accordance with an image area within a sheet on which an image is to be formed and fixed. In such fixing device, the greater the number of the heating elements or number of divisions in a heating element group, the more efficiently heating of sheets having different sizes can be performed. 
     However, the amount of toner transferred onto a sheet of any size varies depending on the particular image being formed on the sheet. Therefore, in some instance, increasing the number of the heating elements (or finely dividing the heating element group) may achieve efficient heating only to some limited extent, rather than what might be considered maximum possible efficiency in view a consideration of the image size being printed on the sheet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts an external view of an image forming apparatus according to an embodiment. 
         FIG. 2  depicts a block diagram of an image forming apparatus according to an embodiment. 
         FIG. 3  depicts a fixing device in a front cross-sectional view according to an embodiment. 
         FIG. 4  depicts a heater unit in a schematic view according to an embodiment. 
         FIG. 5  depicts a heating element group in a case of a heat generation mode of a control A type according to an embodiment. 
         FIG. 6  depicts a heating element group in a case of a heat generation mode of a control B 1  type according to an embodiment. 
         FIG. 7  depicts a heating element group in a case of a heat generation mode of a control B 2  type according to an embodiment. 
         FIG. 8  depicts a heating element group in a case of a heat generation mode of a control B 3  type according to an embodiment. 
         FIG. 9  is a diagram of a correspondence between an image type, an operation mode, and a control mode according to an embodiment. 
         FIG. 10  is a flowchart of control by a controller of an image forming apparatus according to an embodiment. 
         FIG. 11  is a diagram of a correspondence between an operation mode and a control mode according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     According to one or more embodiments, an image forming apparatus includes a transfer unit (e.g., a transfer belt), a heating unit, and a controller. The transfer unit transfers a toner image corresponding to a document image to a sheet. The heating unit comprises a plurality of heating members in a direction orthogonal to a sheet conveyance direction and is configured to heat the sheet to which the toner image has been transferred. The controller is configured to control heat generation of the plurality of heating members in accordance with an operation mode set according to a type of the document image or the like. 
     Hereinafter, an image forming apparatus according to example embodiments will be described. 
       FIG. 1  is an external view illustrating an overall configuration example of an image forming apparatus  100  according to the embodiment.  FIG. 2  is a hardware block diagram of the image forming apparatus  100  according to the embodiment. The image forming apparatus  100  is, for example, a multifunction peripheral (MFP) device. As shown in  FIG. 1 , the image forming apparatus  100  includes a display  110 , a control panel  120 , an image forming unit  130 , and a sheet storage unit  140 . As shown in  FIG. 2 , the image forming apparatus  100  includes a storage unit  150 , a controller  160 , and an image reading unit  200 . 
     The image forming apparatus  100  forms an image on a sheet by using a developer. The developer is fixed to the sheet by being heated. The sheet is, for example, a paper or a label sheet. In general, sheet may be any material as long as the image forming apparatus  100  can form and fix an image on a surface thereof. 
     The display  110  is an image display device such as a liquid crystal display, an organic EL (Electro Luminescence) display, or the like. The display  110  displays various kinds of information related to the image forming apparatus  100 . 
     The control panel  120  includes a plurality of buttons. The control panel  120  receives an operation performed by a user. The control panel  120  outputs a signal corresponding to the operation performed by the user to the controller  160  of the image forming apparatus  100 . The display  110  and the control panel  120  may be configured as an integrated touch panel. 
     The image forming unit  130  forms an image on the sheet based on image information generated by the image reading unit  200  and/or image information received from, for example, an external device through a communication path. The image forming unit  130  includes, for example, a developing device  10 , a transfer device  20 , and a fixing device  30 . The image forming unit  130  forms an image by, for example, the following processes. The developing device  10  of the image forming unit  130  forms an electrostatic latent image on a photosensitive drum based on the generated or received image information. The developing device  10  of the image forming unit  130  forms a visible image by attaching a developer to a electrostatic latent image. One example of the developer is a toner. Examples of the toner include a decolorable toner, a non-decolorable toner (or a normal toner), and a decorative toner (e.g., a specialized toner). Decolorable toner is a toner that loses color due to heating process. In the following description, the developer will be described as comprising a normal toner. 
     The transfer device  20  of the image forming unit  130  transfers a toner image corresponding an image to be printed on to a sheet. The fixing device  30  of the image forming unit  130  heats and presses the toner image onto the sheet. The sheet on which the image is to be formed may be a sheet accommodated in the sheet storage unit  140  or may be a sheet fed by a manual feed. 
     The sheet storage unit  140  accommodates a sheet or a plurality of sheets used for image formation in the image forming unit  130 . The storage unit  150  may be a storage device such as a magnetic hard disk device or a semiconductor storage device. The storage unit  150  stores data and/or programs to be used when the image forming apparatus  100  operates. The storage unit  150  may temporarily store the image information of the image formed in the image forming apparatus  100 . 
     The controller  160  may comprise a processor such as a central processing unit (CPU) and a memory. The controller  160  reads out a program stored in the storage unit  150  in advance and executes the program. The controller  160  controls the operation of each device and unit included in the image forming apparatus  100 . 
     The controller  160  controls an amount of heat generated by each heating element by controlling electric power supplied to a heating element group  45  shown in  FIG. 3 . For example, the control of the electric power may be performed by controlling an energization amount. The control of the energization amount may be, for example, a phase control, or a wave number control. 
     The image reading unit  200  reads image information to be read as brightness and darkness of reflected light from a document or the like. The image reading unit  200  records the read image information. The recorded image information may be transmitted to another information processing apparatus via a network. The recorded image information may then be formed as a visible image on a sheet by the image forming unit  130 . The image reading unit  200  may include an auto document feeder (ADF). 
       FIG. 3  is a front cross-sectional view of the fixing device  30  according to the embodiment. The fixing device  30  of the embodiment includes a pressure roller  30   p  and a film unit  30   h.    
     The pressure roller  30   p  is configured to press a surface thereof against the film unit  30   h  and to be rotatably driven. The pressure roller  30   p  forms a nip N with the film unit  30   h  when the roller surface is pressed against the film unit  30   h . The pressure roller  30   p  applies pressure to the visible toner image on the sheet that has entered the nip N. When the pressure roller  30   p  is driven to rotate, the pressure roller  30   p  conveys the sheet according to the rotation. The pressure roller  30   p  includes, for example, a core metal  32 , an elastic layer  33 , and a release layer (not separately depicted). 
     The core metal  32  is formed of a metal material such as stainless steel in a columnar shape. Both ends of the core metal  32  in the axial direction are rotatably supported. The core metal  32  is driven to rotate by a motor or the like. The core metal  32  contacts a cam member or the like. 
     The elastic layer  33  is formed of an elastic material such as silicone rubber. The elastic layer  33  is formed to have a constant thickness on an outer peripheral surface of the core metal  32 . A release layer (not separately depicted) is formed on the outer peripheral surface of the elastic layer  33 . The release layer is formed of a resin material such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer). 
     The pressure roller  30   p  rotates by being driven to rotate by a motor. When the pressure roller  30   p  rotates in a state where the nip N is formed, a cylindrical film  35  of the film unit  30   h  rotates in a driven manner. The cylindrical film may be a thin film. The pressure roller  30   p  rotates in a state where the sheet is disposed in the nip N, and thereby conveys the sheet in the conveyance direction W. 
     The film unit  30   h  heats the image on the sheet that has entered the nip N. The film unit  30   h  includes a cylindrical film  35  (e.g., a belt, drum, or the like), a heater unit  40 , a heat transfer member  49 , a support member  36 , a stay  38 , a heater temperature sensor  62 , a thermostat  68 , and a film temperature sensor  64 . 
     The cylindrical film  35  is in a tubular shape. The cylindrical film  35  includes, in order from the inner peripheral side, a base layer, an elastic layer, and a release layer. The base layer is formed of a material such as nickel (Ni) in a cylindrical shape. The elastic layer is laminated on the outer peripheral surface of the base layer. The elastic layer is formed of an elastic material such as silicone rubber. The release layer is laminated on the outer peripheral surface of the elastic layer. The release layer is formed of a material such as a PFA resin. 
       FIG. 4  is a schematic view of the heater unit  40 . The heater unit  40  is provided downstream of the transfer device  20  in the sheet conveyance direction. 
     The heater unit  40  includes a substrate (may also be referred to as a heating element substrate herein)  41  and a heating element group  45 . The substrate  41  is formed of a metal material such as stainless steel or nickel, a ceramic material such as aluminum nitride, or the like. The substrate  41  is formed in a plate shape having a thin rectangular shape. The substrate  41  is disposed on the inner side in the radial direction of the cylindrical film  35 . In the substrate  41 , the axial direction of the cylindrical film  35  is a longitudinal direction. 
     The heating element group  45  is formed on the surface of the substrate  41 . The heating element group  45  includes a plurality of heating elements. Each heating element is an example of a heating member that heats the sheet. Each heating element is formed using a heating resistor such as a silver-palladium alloy. In the example of  FIG. 4 , the heating element group  45  includes 15 heating elements S 1  to S 15 . When the heating elements S 1  to S 15  are not distinguished from each other herein, they will be referred to as heating elements S or, collectively, a heating element S. An energization amount (e.g., supplied current) for each of the heating elements S is independently controlled by the controller  160 . As shown in  FIG. 4 , the plurality of heating elements S are orthogonal to the conveyance direction W of the sheet. 
     Referring back to  FIG. 3 , the heater unit  40  is disposed inside the cylindrical film  35 . A lubricant is applied to the inner peripheral surface of the cylindrical film  35 . The heater unit  40  contacts the inner peripheral surface of the cylindrical film  35  via the lubricant. When the heater unit  40  generates heat, viscosity of the lubricant decreases. This reduces friction between the heater unit  40  and the cylindrical film  35 . In the present embodiment, the cylindrical film  35  is a belt-shaped thin film that slides on the surface of the heater unit  40  while being in contact with the heater unit  40  on one surface. 
     The support member  36  is formed of a resin material such as a liquid crystal polymer. The support member  36  supports the heater unit  40 . The support member  36  supports the inner peripheral surface of the cylindrical film  35  at both ends of the heater unit  40 . 
     The stay  38  is formed of a steel plate material or the like. The cross section of the stay  38  may be formed in a U-shape, for example. The stay  38  is mounted so as to close the opening portion of the U shape by the support member  36 . Both end portions of the stay  38  are fixed to a housing of the image forming apparatus  100 . As a result, the film unit  30   h  is supported by the image forming apparatus  100 . 
     The heater temperature sensor  62  is disposed near the heater unit  40 . The heater temperature sensor  62  measures a temperature of each heating element S. 
     The thermostat  68  is disposed in the substantially same manner as the heater temperature sensor  62 . When the measured temperature of the heater unit  40  exceeds a predetermined temperature, the thermostat  68  cuts off an energization of the heating element group  45 . 
     Next, control of a heat generation amount of the heating element S will be described. The control of the heat generation amount includes 2 control patterns of a control A and a control B in a roughly divided manner. The control A is an example of a first control. The control B is an example of a second control. A control pattern common to both the control A and the control B is that the heating element(s) S corresponding to a region through which the sheet does not pass through does not generate heat. Control patterns of the heating elements S in the following description are for those corresponding to the region through which the sheet passes, unless otherwise specified. 
     The control A causes all the heating elements S to generate heat at predetermined power (hereinafter, also referred to as “power X”). In the present embodiment, the power X is a maximum power that can be supplied to the heating element S. Therefore, the heat generation at the power X maximizes the heat generation from the heating element S. The control A is a control in which the printing quality can be maintained even when the toner is transferred to an entire surface of a sheet (so-called solid coating or complete coverage). Therefore, the control A is suitable for image formation of a document image (for example, a photograph or the like) in which a relatively large amount of toner is transferred. 
     On the other hand, the control B causes at least some of the heating elements S to generate heat less than the power X. In the control B, the power of at least one of the heating elements S is less than the power X. Therefore, the control B is a control for reducing the amount of heat generation as compared to the control A. The control B is a control suitable for a case where a document image is formed of a character, a letter, a symbol, a text or the like (may be collectively referred to as a text image herein). The control B enables the sheet to be efficiently heated without causing the heating element S to generate heat more than necessary for a producing a text image. Therefore, in the control B, it is possible to limit the power consumption. 
     The control A and the control B will be described in further detail with reference to  FIGS. 5 to 8 . In  FIGS. 5 to 8 , the heating elements S 1 , S 2 , S 14 , and S 15  are heating elements corresponding to a region through which the sheet does not pass. Therefore, the controller  160  does not generate heat with these heating elements S 1 , S 2 , S 14 , and S 15 . In  FIGS. 5 to 8 , the heating elements S indicated by white indicates that no heat is generated, and the heating elements S indicated by a color other than white (e.g., black fill, diagonal line, hatching, or shading) indicates that heat is generated. 
       FIG. 5  is a diagram illustrating a heat generation mode in the control A. The control A is a control for causing the heating elements S 3  to S 13  to generate heat with the power X. Therefore, in  FIG. 5 , all of the heating elements S 3  to S 13  are shown in black. 
       FIGS. 6, 7 and 8  are diagrams illustrating heat generation modes in the control B. The control B includes three types of controls: a control B 1 , a control B 2 , and a control B 3 .  FIG. 6  is a diagram illustrating a heat generation mode of the control B 1 . The control B 1  is a control for causing a part of the plurality of heating elements S to generate heat. In the example of  FIG. 6 , the controller  160  causes the heating elements S 3 , S 5 , S 7 , S 9 , S 11 , and S 13  to generate heat with the power X. On the other hand, the controller  160  does not generate heat of the heating elements S 4 , S 6 , S 8 , S 10 , and S 12 . The controller  160  generates heat only for some of the heating element S, thereby suppressing the amount of heat generation compared to the control A. 
     Each of the controls B 2  and B 3  is a control in a case where the heating element S can be variably controlled (e.g., with varying power levels). In the variable control, the heating element S can be controlled by a power between the power X and the power 0, not only just by ON (power X) and off (power 0).  FIG. 7  is a diagram illustrating a heat generation mode of the control B 2 . The control B 2  is a control for causing the heating element S to generate heat at a different power. In the example of  FIG. 7 , the controller  160  causes the heating elements S 3 , S 5 , S 7 , S 9 , S 11 , and S 13  to generate heat with the power X. The controller  160  causes the heating elements S 4 , S 6 , S 8 , S 10 , and S 12  to generate heat with a power Y (0&lt;power Y&lt;power X). When the heat generation amount of the heating element S can be variably controlled as in this example, the heat generation amount of the heating element S can be controlled more accurately than the control B 1 , so that it is possible not only to efficiently heat the sheet, but also to improve the printing quality. 
       FIG. 8  is a diagram illustrating a heat generation mode of the control B 3 . The control B 3  is a control for causing the heating element S to generate heat with a power Z (0&lt;power Z&lt;power X). In the example of  FIG. 8 , the controller  160  causes the heating elements S 3  to S 13  to generate heat with the power Z. When the heat generation amount of the heating element S can be variably controlled as in this example, the heat generation amount of the heating element S can be controlled more accurately than the control B 1 , so that it is possible not only to more efficiently heat the sheet, but also to further improve the printing quality. In addition, since a temperature of the heating element S is uniform as compared to the control B 2 , unevenness is less likely to occur. 
     The controls B 1 , B 2 , and B 3  described above are examples of the control B, but the control B may be any control as long as the control is capable of suppressing the amount of heat generation. 
     The controller  160  controls any one of the control A and the control B in accordance with an operation mode. The operation mode is determined based on a type of the document image. As a type of the document image, there are a character image type in which a document image is formed of characters and a photograph image type in which a document image represents a photograph. The character image type and the photo image type are set by a user via, for example, the control panel  120  ( FIG. 2 ). The type set by the user is stored in the storage unit  150  by the controller  160 . The character image type may also be referred to as a text image type. 
       FIG. 9  is a diagram illustrating a correspondence between a type, an operation mode, and a control. When the type is a photo image, the controller  160  operates in a photograph mode and controls the heating element S in the control A. When the type is a character image (or a text image), the controller  160  operates in a character mode and controls the heating element S in the control B. 
       FIG. 10  is a flowchart illustrating a flow of control performed by the controller  160  according to one embodiment. The processing illustrated in the flowchart is executed when an image formation is started. The controller  160  acquires the type stored in the storage unit  150  (ACT  101 ). The controller  160  determines whether the acquired type is a photograph image (ACT  102 ). If the acquired type is a photo image (ACT  102 : YES), the controller  160  controls the heating element S in the control A (ACT  103 ) and ends the processing. If the acquired type is not a photograph image (ACT  102 : NO), the controller  160  controls the heating element S in the control B (ACT  104 ) and ends the processing. The control by the controller  160  is executed until the image formation is completed. 
     In this way, when the type is a photograph image, the controller  160  can maintain the print quality by controlling the heating element S in the control A. When the type is a character image, the controller  160  can heat the sheet without causing the heating element S to generate heat more than necessary. Thus, overall power consumption can be reduced. 
     Modifications 
     While the photograph mode and the character mode have been described as examples of the operation mode, another example mode of operation will be described herein.  FIG. 11  is a diagram illustrating a correspondence between another operation mode and a control mode. 
     In the example of  FIG. 11 , there are two types of operation modes: an operation mode of a setting system according to a setting made by a user; and an operation mode of a non-setting system which does not depend on a setting made by a user. Examples of the operation mode of the setting system include a color printing mode and a monochrome printing mode. In a case of the color printing mode, since toner of the colors CMYK is transferred to a sheet, more heating is required as compared with a case of the monochromatic printing mode. Therefore, in a case of the color printing mode, the controller  160  controls the heating element S in the control A, and in a case of the monochrome printing mode, the controller  101  controls the heating element S in the control B. Accordingly, while the printing quality in the color printing mode is maintained, the sheet can be efficiently heated without causing the heating element S to generate heat more than necessary in the monochrome printing mode. Thus, the overall power consumption can be reduced. 
     Examples of the operation mode of the non-setting system include a facsimile mode and an ambient temperature mode. The facsimile mode is an operation mode in which a toner image indicating an image received by a facsimile is transferred to a sheet. An image received by a normal facsimile is a binary image and is monochrome printing. Therefore, in the facsimile mode, the controller  160  controls the heating element S in the control B. This makes it possible to efficiently heat the sheet without causing the heating element S to generate heat more than necessary. Thus, the overall power consumption can be reduced. 
     The ambient temperature mode is an operation mode in which the image forming apparatus  100  operates in accordance with an ambient temperature of the image forming apparatus  100 . For example, comparing a case where the ambient temperature is lower than 10° C. and a case where the ambient temperature is 30° C. or higher, a temperature of the sheet, a temperature of the conveyance path, and the like are significantly different from each other. In one embodiment, a device capable of measuring the ambient temperature is provided in the image forming apparatus  100 , and the ambient temperature is acquired from the device. Alternatively, the image forming apparatus  100  acquires the ambient temperature measured by another apparatus via a network or communication between these apparatuses. The image forming apparatus  100  controls the heating element S in the variably controllable control B 2  and control B 3  in accordance with the acquired ambient temperature. Accordingly, it is possible to efficiently heat the sheet without causing the heating element S to generate heat more than necessary. Thus, the overall power consumption can be reduced. 
     In other embodiments, the image forming apparatus  100  may operate with a combination of some or all of the above-described operation modes (the photograph mode, the character mode, the color printing mode, the monochrome printing mode, the facsimile mode, and the ambient temperature mode) with each other. For example, in a case of printing a color photographic image, an operation mode in which the photograph mode and the color printing mode are combined may be utilized. 
     In such combination of the operation modes, when there is an operation mode in the control A among the combined operation modes, the operation of the image forming apparatus  100  may be performed in the control A, and when there is no operation mode in the control A among the combined operation modes, the operation may be performed in the control B. That is, when there is at least one operation mode in the control A, the image forming apparatus  100  may control the heating element S by the control A. In the control A, the printing quality can be maintained in any of the operation modes, but in the control B, for example, the toner cannot be sufficiently heated fora color photograph image, and the printing quality may not be properly maintained. 
     Another control example may be a combination of the ambient temperature mode controlled by the controls B 2  and B 3  and the other operation modes. For example, the operation mode in which the character mode and the ambient temperature mode are combined is controlled by the same control B. In this combination, for example, the image forming apparatus  100  may perform: control in the control B 3  when the ambient temperature is less than 10° C.; control in the control B 2  when the ambient temperature is in a range of 10° C. or more and less than 30° C.; and control in the control B 1  when the ambient temperature is 30° C. or more. Such operation with the combined operation modes makes it possible to heat the sheet without causing the heating element S to generate heat more than necessary. Thus, the overall power consumption can be reduced. 
     According to the image forming apparatus  100  of the embodiments described above, it is possible to provide an image forming apparatus capable of efficiently heating a sheet. 
     In other embodiments, it is possible to obtain not only an effect of efficiently heating a sheet but also other effects. 
     In the embodiments where the criterion for determining which control to perform is based on one or more of a setting by a user, whether a facsimile is received, an ambient temperature, and the like, the control criterion does not require an analysis of an image information of a document image. 
     On the other hand, in a case where an image information is analyzed and only a heating element corresponding to a position where the toner is transferred is caused to generate heat, such analysis of an image information requires hardware and the like, and a cost of the image forming apparatus increases. 
     Since the operation control according to the determination criterion that does not require the image information analysis can be realized by software, it is possible to significantly reduce a cost or prevent a cost increase. For example, since the determination based on the above setting can be realized by a simple “if sentence” as illustrated in  FIG. 10 , the cost can be reduced as compared with a case where additional hardware is added. Further, since many document images are images in which toner is transferred other than margins provided on upper, lower, left, and right sides of a sheet, it is possible to maintain the print quality for practical use without analyzing an image information. 
     Accordingly, the image forming apparatus  100  according to one or more of the present embodiments can maintain the print quality, can efficiently heat a sheet without causing heat generation of the heating element S more than necessary, and can further reduce manufacturing cost. Additionally, power consumption can be reduced. 
     The functions of the image forming apparatus according to the above-described embodiments may be realized by a computer executing program instructions. In this case, a program for realizing a function or functions may be recorded in a computer-readable recording medium, and the program may be read into a computer system and executed by the computer system. Note that the “computer system” as used in this context may include hardware, peripheral devices, and an operating system (OS), and the like. A “computer-readable recording medium” refers to a portable medium, such as a flexible disk, a magneto-optical disk, a ROM, or a CD-ROM, or a built-in storage device such as a hard disk of a computer system. Furthermore, a “computer-readable recording medium” may be a cloud-based storage system or a file server connected by a communication line in a case where a program is transmitted via a network such as the Internet or a communication line such as a telephone line. The program may be for realizing a part of the above-described functions or may be for realizing the above-described functions in combination with a program already recorded in the computer system. 
     While certain embodiments have been described, these embodiments have been presented by way of example only and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The embodiments and modifications thereof are included in the scope and spirit of the invention, and are included in the invention described in the claims and the equivalent scope thereof.