Patent Publication Number: US-11029629-B2

Title: Image forming apparatus and image forming method with temperature control

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of co-pending U.S. application Ser. No. 16/255,310 filed Jan. 23, 2019, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to an image forming apparatus and an image forming method. 
     BACKGROUND 
     An MFP (Multifunction Peripheral) forms an image by transferring a visible image onto a sheet. The visible image is formed by using a recording material such as a toner. 
     The recording material includes a decolorizing recording material (hereinafter referred to as a decolorizing toner), the color of which disappears by heating. A sheet on which an image is formed by the decolorizing toner is heated to a predetermined temperature (hereinafter referred to as a decolorizing temperature), whereby the toner is decolorized and the sheet can be reused. 
     An image forming apparatus has a function of decolorizing a decolorizing toner. In printing using a normal toner (hereinafter referred to as normal printing), a temperature of a fixing part is set to be higher than that of printing using the decolorizing toner (hereinafter referred to as decolorizing printing). In order to decolorize the decolorizing toner, it is required to set the temperature of the fixing part higher than the temperature of the printing using the normal toner. 
     Therefore, when the decolorizing printing is performed after the normal printing and decolorizing processing, the decolorizing printing cannot be executed until a temperature drops to a predetermined fixing temperature (e.g., the temperature needed for fixing the toner onto the print medium) so as to prevent an image to be printed from being decolorized. Accordingly, a long period of waiting time is needed until the temperature drops to the predetermined fixing temperature. 
     Further, each of the operations of normal printing, decolorizing processing, and decolorizing printing cannot be executed until the temperature rises to a predetermined fixing temperature. Therefore, the waiting time until the temperature rises to the predetermined fixing temperature can be long. The above-mentioned problems are not limited to the decolorizing printing. The problems are common to various processes when the fixing temperature is different and requires change. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an external diagram illustrating an overall configuration example of an image forming apparatus; 
         FIG. 2  is a block diagram illustrating a function of the image forming apparatus; 
         FIG. 3  is a schematic diagram illustrating a configuration example of a fixing part provided in a printer; 
         FIG. 4  is a graph illustrating a relationship between printing density of a decolorizing toner and a fixing temperature; 
         FIG. 5  is a specific example illustrating a temperature threshold value of each operation mode; 
         FIG. 6  is a graph illustrating a relationship between a rotation time of a fixing part and a temperature of the fixing part; and 
         FIG. 7  is a flow chart illustrating a flow of printing of the image forming apparatus. 
     
    
    
     DETAILED DESCRIPTION 
     An exemplary embodiment provides an image forming apparatus capable of reducing a waiting time until a fixing part reaches a predetermined temperature. 
     In general, according to one embodiment, an image forming apparatus includes a fixing roller, a heater, a heater controller, and a roller controller. The fixing roller conveys a sheet by rotation and fixes a recording material formed on the sheet to the sheet. The heater heats the fixing roller. The heater controller controls a temperature of the heater. The roller controller controls a rotation speed of the fixing roller. When a fixing part temperature indicating a temperature of the fixing roller satisfies a predetermined condition indicating not to be suitable for operation, the roller controller increases a rotation speed to be higher than a rotation speed in a case in which the fixing part temperature does not satisfy the predetermined condition. 
     Hereinafter, an image forming apparatus and an image forming method according to an exemplary embodiment will now be described with reference to the drawings. 
       FIG. 1  is an external diagram illustrating an overall configuration example of an image forming apparatus  100  according to an exemplary embodiment. The image forming apparatus  100  is, for example, a multifunction machine. The image forming apparatus  100  includes a display  110 , a control panel  120 , a printer  130 , a sheet storage part  140 , and an image reading part  200 . The printer  130  of the image forming apparatus  100  may be an apparatus for fixing a toner image or an ink jet type apparatus. 
     The image forming apparatus  100  forms an image on a sheet by using a developer such as a toner, and the like. The sheet is, for example, paper or label paper. The sheet may be any object on the surface of which the image forming apparatus  100  can form an image. 
     The display  110  is an image display apparatus such as a liquid crystal display, an organic EL (Electro Luminescence) display, and the like. The display  110  displays various types of information in connection with the image forming apparatus  100 . 
     The control panel  120  has a plurality of buttons. The control panel  120  receives operation of a user. The control panel  120  outputs a signal corresponding to the operation performed by the user to a controller of the image forming apparatus  100 . Further, the display  110  and the control panel  120  may be configured as an integrated touch panel. 
     The printer  130  forms an image on a sheet based upon image information generated by the image reading part  200  or image information received through a communication path. The printer  130  forms an image by, for example, processes as described hereinafter. An image forming part of the printer  130  forms an electrostatic latent image on a photoconductive drum based upon the image information. The image forming part of the printer  130  forms a visible image by attaching a developer to the electrostatic latent image. A toner is a specific example of the developer. A transfer part of the printer  130  transfers the visible image onto the sheet. A fixing part of the printer  130  fixes the visible image on the sheet by heating and pressurizing the sheet. Further, the sheet on which the image is formed may be a sheet stored in the sheet storage part  140  or a sheet handled by a hand. 
     As examples of the toner, there exist a decolorizing toner, a non-decolorizing toner (normal toner), a decorative toner, and the like. The decolorizing toner has a characteristic of performing decolorization by external stimuli. The decolorization means that an image formed in a color different from a background color of paper (including not only a chromatic color but also an achromatic color such as white and black) becomes invisible to the eyes. For example, the external stimuli can be a temperature, light of a specific wavelength, and pressure. In the exemplary embodiment, the decolorizing toner performs the decolorization when its temperature becomes higher than a specific decolorizing temperature. Further, the decolorizing toner develops a color when its temperature becomes equal to or lower than a specific restoration temperature after decolorization. 
     Any toner may be used as the decolorizing toner as long as the toner has the characteristics described above. For example, a leuco dye may be used as a colorant of the decolorizing toner. The decolorizing toner may be appropriately combined with a developer, a decolorizing agent, a discoloring temperature adjusting agent, and the like. 
     The sheet storage part  140  stores a sheet used for image formation in the printer  130 . 
     The image reading part  200  reads image information which is an object to be read as light and darkness of light. The image reading part  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 be formed as an image on the sheet by the printer  130 . 
       FIG. 2  is a block diagram illustrating a function of the image forming apparatus  100  according to an exemplary embodiment. The image forming apparatus  100  includes the control panel  120 , the printer  130 , a storage part  300 , and a controller  400 . Further, the description of the control panel  120 , which is already described in  FIG. 1 , is omitted. 
     The printer  130  includes a fixing part  50 . The fixing part  50  fixes a toner on the sheet by heating the sheet at a fixing temperature, and decolorizes the toner fixed on the sheet by heating the sheet at a decolorizing temperature. The fixing part  50  will be described with reference to  FIG. 3 . 
       FIG. 3  is a schematic diagram illustrating a configuration example of the fixing part  50  provided in the printer  130  according to an exemplary embodiment. The fixing part  50  is provided with a heat roller  501 , an HR lamp  502 , an HR thermistor  503 , a pressurizing belt  510 , a pressurizing pad  511 , a pad holder  512 , a pressurizing roller  513 , a tension roller  514 , a belt heat roller  515 , a pressurizing belt lamp  516 , a pressurizing thermistor  517 , and a cooling part (not shown). 
     The heat roller  501  is a fixing member formed in a cylindrical shape. The heat roller  501  heats the sheet to fix or decolorize the image transferred onto the sheet. For example, the heat roller  501  is formed in a cylindrical shape. For example, the heat roller  501  is provided with the HR lamp  502  inside. The HR lamp  502  is provided inside the heat roller  501 . The HR lamp  502  heats the heat roller  501  by generating the heat. 
     The HR thermistor  503  measures a surface temperature of the heat roller  501 . The surface temperature of the heat roller  501  measured by the HR thermistor  503  is approximately the same as a temperature of a fixing nip part which will be described later. Therefore, in the exemplary embodiment, the temperature of the fixing part  50  is set as the temperature measured by the HR thermistor  503 . However, if the temperature of the fixing part  50  is a temperature reflecting the temperature of the nip part, the temperature of the fixing part  50  may be a temperature acquired by any measurement method. 
     The pressurizing belt  510  is held by the pressurizing roller  513 , the tension roller  514 , and the belt heat roller  515 . The pressurizing belt  510  is pressurized to the heat roller  501  and then comes into contact therewith by the pressurizing pad  511 , the pressurizing roller  513 , and the belt heat roller  515 . The fixing nip part is formed between the pressurizing belt  510  and the heat roller  501  by the pressurizing contact. 
     The pressurizing pad  511  is held in a state of being pressurized to the heat roller  501  and then coming into contact therewith through the pressurizing belt  510 . The pressurizing pad  511  clamps the pressurizing belt  510  and pressurizes the pressurizing belt  510  to the heat roller  501  and then the pressurizing belt  510  contacts the heat roller  501 . The pad holder  512  pressurizes the pressurizing pad  511  to the heat roller  501  and then the pressurizing pad  511  contacts the heat roller  501 . 
     The pressurizing roller  513  is disposed downstream in a conveyance direction of the sheet. The pressure roller  513  pressurizes the pressurizing belt  510  to the heat roller  501  and then the pressurizing belt  510  contacts the heat roller  501 . An outlet of the fixing nip part is formed by the pressurizing roller  513 . 
     The tension roller  514  is disposed at a position apart from the pressurizing roller  513  and the belt heat roller  515 , thereby applying tension to the pressurizing belt  510 . The belt heat roller  515  is disposed upstream in the conveyance direction of the sheet. The belt heat roller  515  is formed in a hollow cylindrical shape. 
     The pressurizing belt lamp  516  is provided inside the belt heat roller  515 . The pressurizing belt lamp  516  heats the belt heat roller  515  by generating heat. The pressurizing belt lamp  516  is configured, for example, by using a halogen lamp. The pressurizing thermistor  517  measures a surface temperature of the pressurizing belt  510  in a vicinity of the belt heat roller  515 . Further, the fixing part  50  described above is one example, and in the exemplary embodiment, the fixing part  50  may be configured to be provided with at least the heat roller  501  and the pressurizing roller  513 . 
     Referring back to  FIG. 2 , the storage part  300  is configured by using a storage apparatus such as a magnetic hard disk apparatus, a semiconductor storage apparatus, and the like. The storage part  300  stores a program for operating the image forming apparatus  100  representing mode setting of operation (hereinafter referred to as an operation mode) in advance. For example, in the exemplary embodiment, three processes of decolorization, decolorizing printing, and normal printing are set as the operation mode performed by the image forming apparatus  100 . For example, the storage part  300  stores the program for operating the decolorization, the decolorizing printing, and the normal printing. 
     Further, the storage part  300  stores a threshold value of a predetermined temperature (hereinafter referred to as a temperature threshold value) with respect to the fixing part  50 . The temperature threshold value is a predetermined threshold value set for each operation mode. The temperature threshold value will be described later in  FIG. 5 . 
     The controller  400  is configured by using a processor such as a CPU (Central Processing Unit), and the like. The processor executes a program, such that the controller  400  functions as a mode controller  410 , a temperature determination part  420 , a heater controller  430 , and a roller controller  440 . 
     The mode controller  410  controls the operation mode such as the decolorizing printing, the normal printing, decolorization, and the like. The mode controller  410  operates the image forming apparatus  100  in an operation mode received from a user. For example, the mode controller  410  reads a program of the operation mode from the storage part  300 , thereby causing the image forming apparatus  100  to execute the program. Further, selection of the operation mode may be received by the control panel  120  or may be received from an external apparatus via a network, and the like. 
     The temperature determination part  420  determines whether or not a selected operation mode is executable temperature based upon the temperature of the fixing part  50  acquired from the HR thermistor  503 . First, the temperature determination part  420  acquires a predetermined temperature threshold value in each operation mode. Next, the temperature determination part  420  acquires a temperature of the heat roller  501  (hereinafter referred to as a fixing part temperature) from the HR thermistor  503 . The temperature determination part  420  determines whether or not the selected operation mode is executable temperature based upon the temperature threshold value and the fixing part temperature. The determination processing of the temperature determination part  420  is described with reference to  FIG. 5  which will be described later. 
     The heater controller  430  controls a heater based upon a determination result of the temperature determination part  420 . When it is determined that the fixing part temperature is lower than or equal to the predetermined temperature threshold value, the heater controller  430  causes the HR lamp  502  to generate heat. When it is determined that the fixing part temperature is higher than the predetermined temperature threshold value, the heater controller  430  stops the heat generation of the HR lamp  502 . 
     The roller controller  440  controls a roller based upon an operation mode selected by the mode controller  410 . When it is determined that the selected operation mode is not executable, the heater controller  430  rotates the fixing part  50  at a speed higher than a normal rotation speed. When warming the fixing part  50  by rotating the fixing part  50  at a high speed, the temperature of the fixing part  50  can be quickly uniformized. Further, when the fixing part  50  is cooled by rotating the fixing part  50  at a high speed, the temperature of the fixing part  50  can be quickly lowered by heat radiation during the rotation. 
       FIG. 4  is a graph illustrating a relationship between printing density of the decolorizing toner and the fixing temperature according to an exemplary embodiment. The printing density of the decolorizing toner varies from printing density, in which visualization can be performed, to printing density, in which visualization cannot be performed, by the fixing temperature of the fixing part  50  during the printing. In  FIG. 4 , a temperature threshold value at which printing density of the non-decolorizing toner starts to decrease is described as 99° C. 
     The decolorizing toner has a characteristic of performing heat decolorization when exceeding a predetermined temperature threshold value after the decolorizing toner is heated and fixed to the sheet. Therefore, when the fixing temperature exceeds 99° C. and the decolorizing printing is performed, the printing is performed at the printing density in which visualization cannot be performed. In  FIG. 4 , when the fixing part temperature exceeds the temperature threshold value of 99° C. and approaches 105° C., the printing density starts to deteriorate due to the image decolorization. Thereafter, when the fixing part temperature exceeds 120° C., an image printed by the decolorizing toner is completely decolorized. In the exemplary embodiment, a standard fixing temperature when performing the decolorizing printing is 99° C. 
       FIG. 5  is a specific example illustrating a temperature threshold value of each operation mode according to an exemplary embodiment.  FIG. 5  illustrates temperature threshold values of the decolorizing printing, the normal printing, and the decolorization as an example of the operation mode of the exemplary embodiment. Hereinafter, the processing of the temperature determination part  420  and the temperature threshold value in each operation mode will be described. 
     Decolorization 
     When the selected operation mode is the decolorization, the temperature determination part  420  acquires a predetermined temperature threshold value Th 1  in the decolorization. The temperature threshold value Th 1  is a lower limit temperature for performing the decolorization. For example, the temperature threshold value Th 1  of the decolorization indicates a case in which the fixing part temperature becomes 120° C. 
     When the fixing part temperature is higher than the predetermined temperature threshold value Th 1 , the temperature determination part  420  determines that the fixing part temperature is a temperature at which the decolorization is executable. When the fixing part temperature is equal to or lower than the predetermined temperature threshold value Th 1 , the temperature determination part  420  determines that the fixing part temperature is a temperature at which the decolorization is not executable and sends a determination result to the heater controller  430  and the roller controller  440 . 
     Normal Printing 
     When the selected operation mode is the normal printing, the temperature determination part  420  acquires a predetermined temperature threshold value Th 2  in the normal printing. The temperature threshold value Th 2  is a lower limit temperature for the normal printing. For example, the temperature threshold value Th 2  in the normal printing indicates a case in which the fixing part temperature becomes 115° C. 
     When the fixing part temperature is higher than the predetermined temperature threshold value Th 2 , the temperature determination part  420  determines that the fixing part temperature is a temperature at which the normal printing is executable. When the fixing part temperature is equal to or lower than the predetermined temperature threshold value Th 2 , the temperature determination part  420  determines that the fixing part temperature is a temperature at which the normal printing is not executable and sends a determination result to the heater controller  430  and the roller controller  440 . 
     Decolorizing Printing 
     A temperature threshold value in the decolorizing printing is lower than the temperature threshold value in the normal printing. Further, the decolorizing toner is decolorized when the fixing part temperature is high. Therefore, inconsideration of the fixing temperature in the decolorizing printing, two values of an upper limit and a lower limit are required as the temperature threshold value. 
     When the selected operation mode is the decolorizing printing, the temperature determination part  420  acquires a predetermined temperature threshold value Th 3  and a predetermined temperature threshold value Th 4  in the decolorizing printing. The temperature threshold value Th 3  is an upper limit for performing the decolorizing printing. The temperature threshold value Th 4  is a lower limit for performing the decolorizing printing. For example, the temperature threshold value Th 3  in the decolorizing printing indicates a case in which the fixing part temperature becomes 105° C. For example, the temperature threshold value Th 4  in the decolorizing printing indicates a case that the fixing part temperature becomes 99° C. 
     When the fixing part temperature is within a range from the lower limit Th 4  to the upper limit Th 3  of the temperature threshold value, the temperature determination part  420  determines that the fixing part temperature is a temperature at which the decolorizing printing is executable. When the fixing part temperature is equal to or lower than the temperature threshold value Th 4 , the temperature determination part  420  determines that the fixing part temperature is a temperature at which the decolorizing printing is not executable and sends a determination result to the heater controller  430  and the roller controller  440 . When the fixing part temperature is higher than the temperature threshold value Th 3 , the temperature determination part  420  determines that the fixing part temperature is a temperature at which the decolorizing printing is not executable and sends a determination result to the heater controller  430  and the roller controller  440 . 
       FIG. 6  is a graph illustrating a relationship between a rotation time of the fixing part and the temperature of the fixing part according to an exemplary embodiment. As an example,  FIG. 6  represents a time descending from a fixing temperature (115° C.) at which the decolorizing printing cannot be executed by the fixing part temperature to a fixing temperature (99° C.) at which the decolorizing printing can be executed by the fixing part temperature. 
     In  FIG. 6 , for example, when the fixing part  50  is rotated at an equal speed, a waiting time from 115° C. to 99° C. is about 80 seconds. For example, when the fixing part  50  is rotated at 1.2 times speed, the waiting time from 115° C. to 99° C. is about 45 seconds. Further, for example, when the fixing part  50  is rotated at 1.4 times speed, the waiting time from 115° C. to 99° C. is about 30 seconds. As described above, it is possible not only to increase the heat radiation effect, but also to efficiently lower the fixing part temperature by rotating the fixing part  50  at a high speed. 
       FIG. 7  is a flow chart illustrating a flow of printing of the image forming apparatus  100  according to an exemplary embodiment. 
     The image forming apparatus  100  receives selection of an operation mode from a user through the control panel  120  and the network (ACT 101 ). The mode controller  410  determines whether or not the operation mode received from the user is the decolorizing printing (ACT 102 ). 
     When the operation mode is the decolorizing printing (ACT 102 -YES), the temperature determination part  420  determines whether or not the temperature of the fixing part  50  is higher than Th 3  (ACT 103 ). When the operation mode is not the decolorizing printing (ACT 102 -NO), it is determined whether or not the operation mode is the normal printing (ACT 110 ). When the temperature of the fixing part  50  is higher than Th 3  (ACT 103 -YES), the heater controller  430  stops the heat generation of the fixing part  50  (ACT 104 ). Further, when the heat generation of the fixing part  50  is already stopped, the heater controller  430  transfers the process to ACT 105  as it is without performing any process. The roller controller  440  rotates the fixing part  50  at a speed higher than the normal rotation speed (ACT 105 ). 
     When the temperature of the fixing part  50  is lower than Th 3  (ACT 103 -NO), the temperature determination part  420  determines whether or not the temperature of the fixing part  50  is lower than Th 4  (ACT 106 ). When the temperature of the fixing part  50  is lower than Th 4  (ACT 106 -YES), the heater controller  430  causes the fixing part  50  to generate heat (ACT 107 ). Further, when the fixing part  50  already generated heat, the heater controller  430  transfers the process to ACT 108  as it is without performing any process. The roller controller  440  rotates the fixing part  50  at a speed higher than the normal rotation speed (ACT 108 ). When the temperature of the fixing part  50  is higher than Th 4  (ACT 106 -NO), the decolorizing printing is executed (ACT 109 ). 
     Next, when the operation mode is the normal printing (ACT 110 -YES), the temperature determination part  420  determines whether or not the temperature of the fixing part  50  is lower than Th 2  (ACT 111 ). When the temperature of the fixing part  50  is lower than Th 2  (ACT 111 -YES), the heater controller  430  causes the fixing part  50  to generate the heat (ACT 112 ). When the fixing part  50  already generated the heat, the heater controller  430  transfers the process to ACT 113  as it is without performing any process. The roller controller  440  rotates the fixing part  50  at a speed higher than the normal rotation speed (ACT 113 ). When the temperature of the fixing part  50  is higher than Th 2  (ACT 111 -NO), the normal printing is executed (ACT 114 ). 
     Next, when the operation mode is not the normal printing (ACT 110 -NO), the temperature determination part  420  determines whether or not the temperature of the fixing part  50  is lower than Th 1  in order to perform the decolorization (ACT 115 ). When the temperature of the fixing part  50  is lower than Th 1  (ACT 115 -YES), the heater controller  430  causes the fixing part  50  to generate the heat (ACT 116 ). When the fixing part  50  already generated the heat, the heater controller  430  transfers the process to ACT 117  as it is without performing any process. The roller controller  440  rotates the fixing part  50  at a speed higher than the normal rotation speed (ACT 117 ). When the temperature of the fixing part  50  is higher than Th 1  (ACT 115 -NO), the decolorization is executed (ACT 118 ). 
     According to the image forming apparatus  100  of the exemplary embodiments configured as described above, the waiting time until the fixing part  50  reaches the predetermined temperature can be reduced by rotating the fixing part  50  at a high speed. When the temperature of the fixing part  50  is lowered, heat can be efficiently radiated by rotating the fixing part  50  at the high speed, thereby reducing the waiting time. When the temperature of the fixing part  50  is raised, the temperature thereof can be efficiently uniformized by rotating the fixing part  50  at the high speed, thereby reducing the waiting time. 
     Modifications 
     In the operation modes of the decolorization and the normal printing, high-speed rotation may not be performed, and the high-speed rotation may be performed only in the operation mode of the decolorizing printing. The high-speed rotation may be performed in the operation mode of the decolorizing printing, and in the operation mode of at least one of the decolorization and the normal printing. 
     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 accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.