Image forming apparatus

Abstract

An image forming apparatus includes a main container (241) that stores ink, a first storage container (243) that stores ink supplied from the main container (241), an inkjet head (245) that ejects ink, a first supply flow path (R1) that supplies ink from the main container (241) to the first storage container (243), a second supply flow path (R2) that supplies ink from the first storage container (243) to the inkjet head (245), a heating portion (242) that is provided in the first supply flow path (R1) and heats ink, and a circulation flow path (R4) that returns ink in the second supply flow path (R2) to between the main container (241) and the heating portion (242) in the first supply flow path (R1).

Description

Technical Field

[0001] This disclosure relates to an image forming apparatus. Background Technology

[0002] Japanese Patent Application Publication Nos. 2021-70279, 2007-229997, 2006-103016, 2014-188926, and 2011-126219 all disclose an image forming apparatus that forms an image on a recording medium by ejecting ink from an inkjet head onto the recording medium. Typically, in such image forming apparatuses, inkjet head ejection defects occur. This is primarily because ink components (e.g., pigments) adhere to or remain on the walls of the ink flow path between the inkjet head and the main ink container (tank), resulting in uneven ink concentration and ink clogging of the inkjet head.

[0003] Japanese Patent Application Publication No. 2021-70279 discloses a technology for eliminating ink clogging in the nozzle of an inkjet head by repeatedly performing a detection process that accompanies the ink ejection action.

[0004] Japanese Patent Application Publication No. 2007-229997 discloses a technique for eliminating pigment adhesion or retention in ink flow paths by applying voltage to the ink flow path to cause the pigment in the ink that is attached or retained in the ink flow path to vibrate.

[0005] Japanese Patent Application Publication No. 2006-103016 discloses a technology for eliminating blockages in ink flow paths by using an ink stirring device to stir pigment inks.

[0006] Japanese Patent Application Publication No. 2014-188926 discloses a technique for eliminating ink concentration deviations by circulating ink in a circulating flow path.

[0007] Japanese Patent Application Publication No. 2011-126219 discloses a technology that eliminates inkjet head clogging by returning ink flowing out of the ink cartridge to the ink cartridge.

[0008] In image forming apparatuses that form images on recording media by ejecting ink, a heating section located midway through the ink flow path is sometimes used to heat the ink in order to increase its viscosity. In such cases, the inventors have addressed the problem that when the ink remains in the flow path connecting the main container and the heating section for an extended period, uneven ink composition occurs due to heat conduction from the heating section.

[0009] In contrast, none of the aforementioned patent documents 1 to 5 are based on an image forming apparatus having a heating section in the middle of the ink flow path. Therefore, none of the patent documents 1 to 5 consider eliminating the unevenness of ink composition caused by the heating section. Summary of the Invention

[0010] One object of this disclosure is to suppress the unevenness of ink composition caused by the heating element in an image forming apparatus having a heating element in the middle of the ink flow path.

[0011] An image forming apparatus according to a certain aspect of the present disclosure includes: a main container for storing ink; a first storage container for storing ink supplied from the main container; an inkjet head for ejecting ink; a first supply flow path for supplying ink from the main container to the first storage container; a second supply flow path for supplying ink from the first storage container to the inkjet head; a heating unit disposed in the first supply flow path for heating the ink; and a circulation flow path for returning ink in the second supply flow path to the space between the main container and the heating unit in the first supply flow path.

[0012] Preferably, a circulation valve is provided in the circulation path. The image forming apparatus also includes a circulation valve control unit that controls the opening and closing of the circulation valve.

[0013] Preferably, the circulation valve control unit opens the circulation valve when at least one of the following conditions is met: the power to the image forming apparatus is turned on, or the circulation operation between the main container and the heating unit, in which the ink in the second supply flow path is returned to the first supply flow path, has not been performed for more than a first predetermined time.

[0014] The preferred image forming apparatus further includes: a supply pump for supplying ink from a main container to a heating unit; a first sensor for detecting the amount of ink in a first storage container; and a determination unit for determining that an abnormality has occurred if the amount of ink in the first storage container has not reached a first threshold within a second predetermined time after the supply pump is started. If the determination unit determines that an abnormality has occurred, a circulation valve control unit opens a circulation valve.

[0015] The preferred image forming apparatus further includes: a supply pump for supplying ink from a main container to a heating unit; a first sensor for detecting the amount of ink in a first storage container; and a determination unit that determines an abnormality has occurred if the amount of ink in the first storage container does not reach a first threshold within a second predetermined time after the supply pump is started, and a circulation valve control unit opens a circulation valve when the determination unit determines an abnormality has occurred. The image forming apparatus further includes: a circulation pump for supplying ink from a second supply path to the main container and the heating unit in the first supply path; and a circulation pump control unit for controlling the operation of the circulation pump. The circulation pump control unit operates the circulation pump when the circulation valve is open, and the operation time of the circulation pump when the determination unit determines an abnormality has occurred is longer than the operation time of the circulation pump when the image forming apparatus is powered on or when the circulation operation has not been performed for more than a first predetermined time.

[0016] The preferred image forming apparatus further includes a second storage container disposed in a second supply flow path, which stores ink supplied from the first storage container.

[0017] Preferably, a circulating pump is positioned between the first and second storage containers in the second supply flow path to supply ink from the first storage container to the second storage container.

[0018] Preferably, a supply valve is provided in the second supply flow path. The image forming apparatus further includes: a supply valve control unit for controlling the opening and closing of the supply valve; and a second sensor for detecting the ink volume in the second storage container. When the ink volume in the second storage container is less than a second threshold, the supply valve control unit opens the supply valve. The circulation pump control unit drives the circulation pump when the supply valve is open.

[0019] The preferred ink contains multiple wax components with different melting points. The temperature of at least a portion of the first supply flow path is greater than or equal to the melting point of the first wax component with the lowest melting point among the multiple wax components, i.e., a first temperature, and less than the melting point of the second wax component with the highest melting point among the multiple wax components, i.e., a second temperature.

[0020] The preferred heating element melts the ink to a sol state.

[0021] The above and other objects, features, aspects and advantages of the invention will become clear from the following detailed description relating to the invention, which will be understood in conjunction with the accompanying drawings. Attached Figure Description

[0022] Figure 1 This is a diagram showing the image forming apparatus in Embodiment 1.

[0023] Figure 2 This is a diagram illustrating an example of the hardware structure of the image forming apparatus in Embodiment 1.

[0024] Figure 3 This is a diagram showing the structure of the inkjet head unit in Embodiment 1.

[0025] Figure 4 It is a graph representing the temperature of the separated temperature regions.

[0026] Figure 5 This is a diagram showing an outline of the process for controlling the flow direction of ink in the image forming apparatus of Embodiment 1.

[0027] Figure 6 This is a flowchart illustrating the sequence of cyclic processing of the image forming apparatus in Embodiment 1.

[0028] Figure 7 This is a diagram showing an outline of the process for controlling the flow direction of ink in the image forming apparatus of Embodiment 2.

[0029] Figure 8 This is a flowchart illustrating the sequence of cyclic processing when an abnormality occurs in the image forming apparatus of Embodiment 2. Detailed Implementation

[0030] Hereinafter, embodiments and variations of the present disclosure will be described with reference to the accompanying drawings. In the following description, the same reference numerals will be used to denote the same parts and components. Their names and functions are also the same. Therefore, detailed descriptions will not be repeated. Furthermore, the embodiments and variations described below can be appropriately and selectively combined.

[0031] [Implementation Method 1]

[0032] <A. Overview of the Image Forming Apparatus>

[0033] Reference Figure 1 The outline of the image forming apparatus in Embodiment 1 will be described.

[0034] Figure 1 This is a diagram illustrating the image forming apparatus in Embodiment 1. (Refer to...) Figure 1 In Embodiment 1, the image forming apparatus 1 is an inkjet printer that ejects ink to form an image on a recording medium P. The image forming apparatus 1 can be either a monochrome inkjet printer or a color inkjet printer. As an example, the image forming apparatus 1 in this embodiment is a color inkjet printer that ejects four colors of ink: yellow, magenta, cyan, and black.

[0035] Liquid inks are used. For example, in the image forming apparatus 1 of this embodiment, gel ink is used for image forming. Gel ink contains a gelling agent, which has the property of changing into a gel or sol state with temperature and solidifying upon irradiation with energy rays such as ultraviolet light. The ink contains multiple wax components with different melting points.

[0036] The image forming apparatus 1 includes a supply unit 10, an image forming unit 20, an ejection unit 30, and a control unit 60. In the image forming apparatus 1, a recording medium P housed in the supply unit 10 is conveyed to the image forming unit 20, where an image is formed on the recording medium P. The recording medium P with the formed image is then conveyed to the ejection unit 30. The recording medium P can be various media capable of curing ink sprayed onto a surface, such as paper or sheet resin.

[0037] The supply unit 10 conveys the recording medium P to the image forming unit 20. The supply unit 10 includes a supply tray 11 on which the recording medium P is placed and a supply section 12 that supplies the recording medium P from the supply tray 11 to the image forming unit 20. The supply section 12 has an annular belt 13 supported by two rollers. With the recording medium P placed on the belt 13, the rollers rotate, thereby conveying the recording medium P from the supply tray 11 to the image forming unit 20.

[0038] The image forming unit 20 forms an image on the recording medium P. The image forming unit 20 includes a transport roller 21, a first transfer unit 22, a recording medium heating unit 23, an inkjet head unit 24, a fixing unit 25, and a second transfer unit 26.

[0039] The transport roller 21 is a component for transporting the recording medium P. The transport roller 21 is cylindrical. The transport roller 21, while holding the recording medium P on the transport surface 21a, which is its outer circumference, winds around... Figure 1 A rotating shaft extending in a direction perpendicular to the paper surface rotates, thereby conveying the recording medium P in the conveying direction along the conveying surface 21a. The conveying roller 21 is connected to a motor for rotating the conveying roller 21 and rotates at an angle proportional to the amount of rotation of the motor.

[0040] The first transfer unit 22 is a unit that receives the recording medium P from the supply unit 10 and conveys it to the conveyor roller 21. The first transfer unit 22 is provided between the supply unit 12 and the conveyor roller 21.

[0041] The recording medium heating unit 23 is a mechanism for heating the recording medium P. The recording medium heating unit 23 is disposed between the first transfer unit 22 and the inkjet head unit 24. The recording medium heating unit 23 heats the recording medium P in a manner that keeps the temperature of the recording medium P within a specified range.

[0042] The inkjet head unit 24 is a unit that ejects ink onto the recording medium P to form an image. The inkjet head unit 24 has an inkjet head that ejects ink. The inkjet head unit 24 is configured such that the surface from which the ink is ejected from the inkjet head faces the transport surface 21a. The inkjet head unit 24 ejects ink onto the recording medium P at appropriate timing corresponding to the rotation of the transport roller 21 that holds the recording medium P, thereby forming an image on the recording medium P.

[0043] The inkjet head unit 24 is configured according to each color of ink. In this embodiment, inkjet head unit 24Y that ejects yellow ink, inkjet head unit 24M that ejects magenta ink, inkjet head unit 24C that ejects cyan ink, and inkjet head unit 24K that ejects black ink are sequentially arranged from the upstream side of the transport path of the recording medium P.

[0044] In the following description, without distinguishing between inkjet head unit 24Y, inkjet head unit 24M, inkjet head unit 24C, and inkjet head unit 24K, it will be referred to as "inkjet head unit 24".

[0045] The fixing unit 25 fixes the ink on the recording medium P by irradiating it with energy rays such as ultraviolet light onto the recording medium P placed on the transport roller 21.

[0046] The second handover unit 26 is a unit that receives the recording medium P conveyed by the conveyor roller 21 and conveys it to the discharge unit 30.

[0047] The discharge section 30 includes a plate-shaped discharge tray 31 that holds the image-formed recording medium P that has been transported from the image forming section 20.

[0048] <B. Example of the hardware structure of image forming apparatus 1>

[0049] Reference Figure 2 The hardware structure of the image forming apparatus 1 in Embodiment 1 will be described.

[0050] Figure 2 This diagram illustrates an example of the hardware structure of the image forming apparatus in Embodiment 1. The image forming apparatus 1, besides... Figure 1 In addition to the supply unit 10, image forming unit 20, discharge unit 30, and control unit 60 shown, the system also includes a communication interface 40 and a memory card interface 50. The supply unit 10, image forming unit 20, discharge unit 30, communication interface 40, memory card interface 50, and control unit 60 are electrically connected via bus 99.

[0051] The communication interface 40 is responsible for receiving and transmitting data between the image forming apparatus 1 and the external device 500. The external device 500 is, for example, a terminal device used by a user. As an example, the communication interface 40 receives image data of the printing object from the external device 500.

[0052] The control unit 60 includes a processor 61, a memory 62, and a storage unit 63. The processor 61 is configured, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit). The memory 62 is configured, for example, a volatile storage device such as DRAM (Dynamic Random Access Memory) or SRAM (Static Random Access Memory). The storage unit 63 is configured, for example, a non-volatile storage device such as an SSD (Solid State Drive) or flash memory. The storage unit 63 stores a program 631. The program 631 contains computer-readable commands for controlling the image forming apparatus 1. The processor 61 performs various processes of this embodiment by expanding and executing the program 631 stored in the storage unit 63 in the memory 62.

[0053] The program 631 is provided by storing it in a storage medium such as a memory card 50A. The program 631 is read from the memory card 50A via the memory card interface 50 and installed in the image forming apparatus 1.

[0054] Program 631 may also be provided as part of any program, rather than as a standalone program. In this case, it cooperates with any program to implement the processing of this embodiment. Even a program that does not include such a module does not depart from the spirit of the image forming apparatus 1 of this embodiment. In addition, some or all of the functions provided by program 631 may also be implemented by dedicated hardware.

[0055] Alternatively, instead of installing the program 631 stored in the memory card 50A into the image forming apparatus 1, a program downloaded from a distribution server or the like can be installed into the image forming apparatus 1.

[0056] <C. Structure of the inkjet head unit 24 of the image forming apparatus 1>

[0057] Reference Figure 3 and Figure 4 The inkjet head unit 24 in Embodiment 1 will be described. Figure 3 This is a diagram showing the structure of the inkjet head unit in Embodiment 1. Figure 4It is a graph representing the temperature of the separated temperature regions.

[0058] Reference Figure 3 The inkjet head unit 24 includes a main container 241, a heating element 242, a first storage container 243, a second storage container 244, an inkjet head 245, a supply pump P1, a circulation pump P2, a supply valve V1, a circulation valve V2, a discharge valve V3, a first sensor M1, a second sensor M2, and an ink flow path. The ink flow path is the path for supplying ink. The ink flow path includes a first supply flow path R1, a second supply flow path R2, a maintenance flow path R3, and a circulation flow path R4.

[0059] The first supply flow path R1 is a flow path that supplies ink from the main container 241 to the first storage container 243. The main container 241 stores ink. The first storage container 243 stores the ink supplied from the main container 241. A heating unit 242 is provided in the first supply flow path R1. The first supply flow path R1 includes a flow path R11 connecting the main container 241 and the heating unit 242, and a flow path R12 connecting the heating unit 242 and the first storage container 243.

[0060] A supply pump P1 is installed in flow path R11 of the first supply flow path R1. The supply pump P1 is controlled by the control unit 60 described above. With this drive, the supply pump P1 supplies ink from the main container 241 to the heating unit 242.

[0061] The heating unit 242 heats the ink supplied from the main container 241. Specifically, the heating unit 242 heats the ink supplied from the main container 241 until it melts to a sol state. As a result, the viscosity of the ink is increased. The ink heated by the heating unit 242 is supplied to the first storage container 243 via the flow path R12 by the supply pump P1, and is stored in the first storage container 243.

[0062] The first sensor M1 detects the amount of ink in the first storage container 243. The first sensor M1 can be a liquid level sensor that measures the height of the ink level in the first storage container 243, or a weight sensor that measures the weight of the ink in the first storage container 243.

[0063] The first sensor M1 outputs the detection result to the control unit 60. If the control unit 60 determines, based on the detection result received from the first sensor M1, that the ink level in the first storage container 243 is insufficient to a reference value, it instructs the supply pump P1 to be driven. The reference value is a value that is less than a first threshold by a predetermined amount.

[0064] The second supply flow path R2 is a flow path for supplying ink from the first accumulation container 243 to the inkjet head 245. A second accumulation container 244 is provided in the second supply flow path R2 to accumulate the ink supplied from the first accumulation container 243. The second supply flow path R2 includes a flow path R21 connecting the first accumulation container 243 and the second accumulation container 244, and a flow path R22 connecting the second accumulation container 244 and the inkjet head 245.

[0065] A supply valve V1 is installed in flow path R21 of the second supply flow path R2. The supply valve V1 is a control valve that controls the flow direction of ink from the first storage container 243 to the second storage container 244. The opening and closing of the supply valve V1 is controlled by the control unit 60. The supply valve V1 is controlled to be in the open (ON) state only when ink is supplied from the first storage container 243 to the second storage container 244, and in the other cases, it is controlled to be in the closed (OFF) state.

[0066] A circulation pump P2 is also provided in flow path R21 of the second supply flow path R2. The circulation pump P2 is controlled by the control unit 60. When the supply valve V1 is open, the circulation pump P2 supplies ink from the first storage container 243 to the second storage container 244. In addition, when the circulation valve V2 (described later) is open, the circulation pump P2 supplies ink from the second supply flow path R2 to the space between the main container 241 and the heating unit 242 in the first supply flow path R1.

[0067] The second sensor M2 detects the amount of ink in the second storage container 244. The second sensor M2 can be a liquid level sensor that measures the height of the ink level in the second storage container 244, or a weight sensor that measures the weight of the ink in the second storage container 244.

[0068] The second sensor M2 outputs the detection result to the control unit 60. If the control unit 60 determines, based on the detection result received from the second sensor M2, that the ink volume in the second storage container 244 is less than a second threshold, it opens the supply valve V1 and instructs the circulation pump P2 to drive. Thus, ink is supplied from the first storage container 243 to the second storage container 244.

[0069] By providing the inkjet head unit 24 with a second storage container 244, insufficient ink ejected from the printhead 245 can be suppressed.

[0070] The inkjet head 245 ejects ink based on the instructions of the control unit 60, thereby forming an image on the recording medium P.

[0071] A maintenance flow path R3 connects the inkjet head 245 to the first accumulation container 243. A discharge valve V3 is provided in the maintenance flow path R3. The discharge valve V3 is a control valve that controls the flow direction of ink from the second accumulation container 244 via the inkjet head 245 to the first accumulation container 243. The opening and closing of the discharge valve V3 is controlled by the control unit 60. The discharge valve V3 is only controlled to be open during maintenance of the inkjet head 245, and is controlled to be closed in other situations. Maintenance refers to removing air bubbles that have entered the inkjet head 245. During maintenance, the control unit 60 opens the discharge valve V3. As a result, ink flows from the second accumulation container 244 through the inkjet head 245 to the first accumulation container 243, thus removing air bubbles that have entered the inkjet head 245.

[0072] The circulation path R4 is a path used to return ink in the second supply path R2 to the main container 241 and the heating unit 242 in the first supply path R1. The circulation path R4 is a path that does not pass through the inkjet head 245. In this embodiment, the circulation path R4 returns ink in the flow path R21 of the second supply path R2 to the flow path R11.

[0073] A circulation valve V2 is provided in the circulation path R4. The circulation valve V2 is a control valve that controls the flow direction of ink from the second supply path R2 to the main container 241 and heating unit 242 in the first supply path R1. The opening and closing of the circulation valve V2 is controlled by the control unit 60. The circulation valve V2 is only opened when the ink in the second supply path R2 is returned to the main container 241 and heating unit 242 in the first supply path R1; otherwise, it is closed. Hereinafter, the process of returning the ink in the second supply path R2 to the main container 241 and heating unit 242 in the first supply path R1 will be referred to as the "circulation operation".

[0074] In at least one of the following situations—the image forming apparatus 1 being powered on (ON) and the cyclic operation not being performed for a first predetermined time or more—the control unit 60 opens the circulation valve V2 and instructs the circulation pump P2 to drive. That is, in either the case of the image forming apparatus 1 being powered on or the cyclic operation not being performed for a first predetermined time or more, the control unit 60 may open the circulation valve V2 and instruct the circulation pump P2 to drive; or it may only open the circulation valve V2 and instruct the circulation pump P2 to drive when the image forming apparatus 1 is powered on; or it may only only open the circulation valve V2 and instruct the circulation pump P2 to drive when the cyclic operation has not been performed for a first predetermined time or more.

[0075] The first specified time is determined based on the time within the separation temperature zone AR described later until the high-melting-point wax component in the ink begins to separate. By opening the circulation valve V2, the circulation pump P2 is driven, and the ink in the second supply flow path R2 flows into the space between the main container 241 and the heating unit 242 in the first supply flow path R1.

[0076] The separation temperature region AR shown in the figure is an area in the first supply flow path R1 where the ink composition is highly likely to become uneven due to heat transfer from the heating unit 242. The separation temperature region AR is an example of a region representing "at least a portion" of the first supply flow path R1 in this disclosure. Figure 4 As shown, the temperature of the separation temperature region AR is greater than or equal to the melting point of the first wax component with the lowest melting point among the multiple wax components in the ink, i.e., the first temperature T1, and less than the melting point of the second wax component with the highest melting point among the multiple wax components, i.e., the second temperature T2.

[0077] Generally, if the ink remains in the separation temperature zone AR for an extended period, the low-melting-point wax components within the ink begin to melt and flow easily, while the higher-melting-point wax components separate and accumulate in the flow channel R11, resulting in uneven ink composition. When the ink composition becomes uneven, the ink flow path or the inkjet head 245 may become clogged, potentially causing malfunction of the image forming apparatus 1. Furthermore, uneven ink composition may lead to a decrease in the image quality of the printed material.

[0078] In contrast, in the image forming apparatus 1 of Embodiment 1, the cyclic operation is performed when at least one of the following conditions occurs: the power to the image forming apparatus 1 is turned on, or the cyclic operation has not been performed for a first predetermined time or more. Through the cyclic operation, the ink in the second supply flow path R2, i.e., the melted, high-temperature ink, flows into the space between the main container 241 and the heating unit 242 in the first supply flow path R1. Therefore, the wax component with a higher melting point that remains in the separation temperature region AR easily melts and flows, thus making the ink composition more uniform. Therefore, the image forming apparatus 1 according to this embodiment can suppress the non-uniformity of ink composition caused by the heating unit 242.

[0079] Furthermore, the circulation path R4 is a path that does not pass through the inkjet head 245, thus enabling both the circulation operation and the ejection of ink from the inkjet head 245 to be performed simultaneously. Therefore, there is no need to stop the ejection of ink from the inkjet head 245 to perform the circulation operation, thereby preventing a decrease in the productivity of printed materials.

[0080] Furthermore, a second storage container 244 is provided in the second supply flow path R2 to store the ink supplied from the first storage container 243 and supplied to the inkjet head 245. Therefore, even during printing, the supply valve V1 can be kept closed, thus enabling a cyclic operation even during printing. Therefore, there is no need to stop ink ejection from the inkjet head 245 to perform the cyclic operation, thereby preventing a decrease in printing productivity.

[0081] Furthermore, the inkjet head unit 24 may include at least a main container 241, a heating element 242, a first storage container 243, an inkjet head 245, a first supply flow path R1, a second supply flow path R2, and a circulation flow path R4. In a structure where the inkjet head unit 24 does not include the second storage container 244, the flow path connecting the first storage container 243 and the inkjet head 245 becomes the second supply flow path R2.

[0082] <D. Processing for controlling the flow direction of ink in image forming apparatus 1>

[0083] Reference Figure 5 and Figure 6 The process for controlling the flow direction of ink in the image forming apparatus 1 of Embodiment 1 will be described.

[0084] (D1: Summary of the Process)

[0085] Figure 5 This diagram illustrates an outline of the process for controlling the flow direction of ink in the image forming apparatus of Embodiment 1. The image forming apparatus 1 includes a power button 111, a cycle operation management unit 112, a cycle valve control unit 113, a cycle pump control unit 114, a second container management unit 115, a supply valve control unit 116, a first container management unit 117, a supply pump control unit 118, an operation button 119, a maintenance management unit 120, a discharge valve control unit 121, an ejection control unit 122, a cycle valve V2, a cycle pump P2, a supply valve V1, a supply pump P1, a discharge valve V3, an inkjet head 245, a first sensor M1, and a second sensor M2.

[0086] The circulation operation management unit 112, circulation valve control unit 113, circulation pump control unit 114, second container management unit 115, supply valve control unit 116, first container management unit 117, supply pump control unit 118, maintenance management unit 120, discharge valve control unit 121, and discharge control unit 122 are implemented by the processor 61 executing program 631.

[0087] First, the loop processing used to control the above-mentioned loop operation will be explained. The power button 111 is a button used to turn on the power to the image forming apparatus 1. When the power button 111 is pressed, the loop operation management unit 112 determines that the image forming apparatus 1 is powered on (ON). The loop operation management unit 112 manages the loop operation. The loop valve control unit 113 controls the opening and closing of the loop valve V2. The loop pump control unit 114 controls the driving of the loop pump P2.

[0088] When the start condition for the cycle operation is met, the cycle operation management unit 112 outputs an instruction to the cycle valve control unit 113 to open the cycle valve V2. The start condition for the cycle operation can be that the image forming apparatus 1 is powered on (ON), or that the cycle operation has not been performed for a first predetermined time or more. That is, the cycle operation management unit 112 outputs an instruction to the cycle valve control unit 113 to open the cycle valve V2 when at least one of the following conditions is met: the image forming apparatus 1 is powered on (ON) or the cycle operation has not been performed for a first predetermined time or more.

[0089] The circulation valve control unit 113 opens the circulation valve V2 according to the instruction from the circulation operation management unit 112, and outputs a signal indicating that the circulation valve V2 is open to the circulation operation management unit 112. When the circulation operation management unit 112 receives the signal indicating that the circulation valve V2 is open, it outputs an instruction to the circulation pump control unit 114 to start driving the circulation pump P2. The circulation pump control unit 114 drives the circulation pump P2 according to the instruction from the circulation operation management unit 112, and continues to output a signal indicating that the circulation pump P2 is being driven to the circulation operation management unit 112 while the circulation pump P2 is being driven. With the circulation valve V2 open and the circulation pump P2 driven, the ink in the second supply flow path R2, i.e., the melted high-temperature ink, flows into the first supply flow path R1 between the main container 241 and the heating unit 242.

[0090] The cycle operation management unit 112 counts the driving time of the cycle pump P2 based on the signal received from the cycle pump control unit 114 indicating that the cycle pump P2 is in operation. When the driving time of the cycle pump P2 reaches 60 seconds, the cycle operation management unit 112 outputs an instruction to the cycle pump control unit 114 to stop the driving of the cycle pump P2. The cycle pump control unit 114 stops the driving of the cycle pump P2 according to the instruction from the cycle operation management unit 112 and outputs a signal indicating that the driving of the cycle pump P2 has stopped to the cycle operation management unit 112.

[0091] When the circulation operation management unit 112 receives a signal indicating that the circulation pump P2 has stopped, it outputs an instruction to the circulation valve control unit 113 to close the circulation valve V2. The circulation valve control unit 113 closes the circulation valve V2 according to the instruction from the circulation operation management unit 112 and outputs a signal indicating that the circulation valve V2 is closed to the circulation operation management unit 112.

[0092] Therefore, in at least one of the following situations—when the image forming apparatus 1 is powered on (ON) or when the cyclic operation has not been performed for more than a first predetermined time—the cyclic operation is performed for 60 seconds, thus suppressing the ink composition from becoming uneven. Furthermore, the driving time of the circulation pump P2 is only required to suppress the unevenness of the ink composition, and is not limited to 60 seconds. The driving time of the circulation pump P2 can be shorter or longer than 60 seconds.

[0093] Next, the process for controlling the supply of ink to the second storage container 244 will be described. The second container management unit 115 manages the amount of ink in the second storage container 244. The supply valve control unit 116 controls the opening and closing of the supply valve V1.

[0094] When the conditions for starting the operation of supplying ink to the second storage container 244 are met, the second container management unit 115 outputs an instruction to the supply valve control unit 116 to open the supply valve V1. The starting condition for supplying ink to the second storage container 244 is that the amount of ink in the second storage container 244 is less than a second threshold. Based on the detection result received from the second sensor M2, the second container management unit 115 determines whether the amount of ink in the second storage container 244 is less than the second threshold.

[0095] The supply valve control unit 116 opens the supply valve V1 according to the instruction from the second container management unit 115, and outputs a signal indicating that the supply valve V1 is open to the second container management unit 115. Upon receiving the signal indicating that the supply valve V1 is open, the second container management unit 115 outputs an instruction to the circulation pump control unit 114 to start driving the circulation pump P2. The circulation pump control unit 114 drives the circulation pump P2 according to the instruction from the second container management unit 115, and continues to output a signal indicating that the circulation pump P2 is driven to the second container management unit 115 while the circulation pump P2 is driven. By opening the supply valve V1 and driving the circulation pump P2, ink is supplied from the first storage container 243 to the second storage container 244.

[0096] When the ink level in the second storage container 244 exceeds a second threshold, the second container management unit 115 outputs an instruction to the circulation pump control unit 114 to stop the operation of the circulation pump P2. The circulation pump control unit 114 stops the operation of the circulation pump P2 according to the instruction from the second container management unit 115 and outputs a signal indicating that the operation of the circulation pump P2 has stopped to the second container management unit 115.

[0097] When the second container management unit 115 receives a signal indicating that the circulation pump P2 has stopped, it outputs an instruction to the supply valve control unit 116 to close the supply valve V1. The supply valve control unit 116 closes the supply valve V1 according to the instruction from the second container management unit 115 and outputs a signal to the second container management unit 115 indicating that the supply valve V1 is closed.

[0098] Therefore, when the amount of ink in the second storage container 244 is less than the second threshold, ink is supplied from the first storage container 243 to the second storage container 244. Thus, insufficient ink ejected from the inkjet head 245 can be suppressed.

[0099] Next, the process for controlling the supply of ink to the first storage container 243 will be described. The first container management unit 117 manages the amount of ink in the first container 243. The supply pump control unit 118 controls the drive of the supply pump P1.

[0100] When the conditions for starting the ink supply operation to the first storage container 243 are met, the first container management unit 117 outputs an instruction to the supply pump control unit 118 to start driving the supply pump P1. The starting condition for starting the ink supply operation to the first storage container 243 is that the ink volume in the first storage container 243 is less than a reference value. Based on the detection result received from the first sensor M1, the first container management unit 117 determines whether the ink volume in the first storage container 243 is less than the reference value.

[0101] The supply pump control unit 118 drives the supply pump P1 according to the instruction from the first container management unit 117, and continues to output a signal indicating that the supply pump P1 is driven to the first container management unit 117 while the supply pump P1 is driven. By driving the supply pump P1, ink is supplied from the main container 241 to the first storage container 243 via the heating unit 242.

[0102] Based on the detection result received from the first sensor M1, the first container management unit 117 determines whether the ink volume in the first storage container 243 has reached a first threshold. If the ink volume in the first storage container 243 reaches the first threshold, the first container management unit 117 outputs an instruction to the supply pump control unit 118 to stop driving the supply pump P1. The supply pump control unit 118 stops driving the supply pump P1 according to the instruction from the first container management unit 117 and outputs a signal indicating that the driving of the supply pump P1 has stopped to the first container management unit 117.

[0103] Therefore, when the ink level in the first storage container 243 is less than a reference value, ink is supplied from the main container 241 to the first storage container 243 via the heating unit 242. Thus, since the ink in the first storage container 243 will not run out, when the ink level in the second storage container 244 is less than a second threshold value, ink can be immediately supplied from the first storage container 243 to the second storage container 244.

[0104] Next, the processing for controlling the maintenance operation of the inkjet head 245 will be explained. The maintenance operation refers to the flow of ink from the second storage container 244 to the first storage container 243 via the inkjet head 245. The maintenance management unit 120 manages the maintenance operation of the inkjet head 245. The discharge valve control unit 121 controls the opening and closing of the discharge valve V3.

[0105] When the conditions for initiating the maintenance operation of the ink head 245 are met, the maintenance management unit 120 outputs an instruction to the discharge valve control unit 121 to open the discharge valve V3. The conditions for initiating the maintenance operation of the ink head 245 are, for example, the condition that the operation button 119 is pressed.

[0106] The discharge valve control unit 121 opens the discharge valve V3 according to the instruction from the maintenance management unit 120, and outputs a signal to the maintenance management unit 120 indicating that the discharge valve V3 is open. By opening the discharge valve V3, ink flows from the second storage container 244 to the first storage container 243 via the inkjet head 245.

[0107] When the maintenance management unit 120 receives a signal indicating that the release valve V3 is open and a preset time, which is the maintenance time, has elapsed, it outputs an instruction to the release valve control unit 121 to close the release valve V3. The release valve control unit 121 closes the release valve V3 according to the instruction from the maintenance management unit 120 and outputs a signal indicating that the release valve V3 is closed to the maintenance management unit 120.

[0108] Therefore, when the conditions for starting the maintenance operation of the inkjet head 245 are met, ink flows from the second storage container 244 through the inkjet head 245 to the first storage container 243. Thus, air bubbles entering the inkjet head 245 can be removed.

[0109] Next, the process for controlling the ink ejection operation will be described. The ejection control unit 122 controls the ejection of the inkjet head 245. When a printing instruction is received, the ejection control unit 122 controls the ejection of the inkjet head 245 based on the image data contained in the printing instruction. As a result, ink is ejected from the inkjet head 245, thereby forming an image on the recording medium P.

[0110] (D2: Processing order)

[0111] Figure 6 This is a flowchart illustrating the sequence of cyclic processing of the image forming apparatus in Embodiment 1. Figure 6 The loop processing shown is executed by the processor 61 described above.

[0112] In step S11, the processor 61 determines whether the power supply to the image forming apparatus 1 has just been turned on. If the power supply to the image forming apparatus 1 has just been turned on (yes in step S11), the processor 61 causes the process to proceed to step S12.

[0113] In step S12, processor 61 opens circulation valve V2.

[0114] In step S13, processor 61 drives circulation pump P2.

[0115] In step S14, the processor 61 determines whether the driving time of the circulating pump P2 has reached 60 seconds. If the driving time of the circulating pump P2 has reached 60 seconds (yes in step S14), the processor 61 causes the process to proceed to step S15.

[0116] In step S15, processor 61 stops driving the circulating pump P2.

[0117] In step S16, processor 61 closes circulation valve V2.

[0118] In step S17, the processor 61 determines whether the power supply to the image forming apparatus 1 is off. If the power supply to the image forming apparatus 1 is off (yes in step S17), the processor 61 ends the loop processing. On the other hand, if the power supply to the image forming apparatus 1 is not off (no in step S17), the processor 61 returns the processing to step S11.

[0119] If the power to the image forming apparatus 1 has just been turned on (in step S11, "No"), the processor 61 causes the processing to proceed to step S18.

[0120] In step S18, the processor 61 determines whether 3 hours have elapsed since the last loop operation. 3 hours is an example of the "first predetermined time" mentioned above. If 3 hours have elapsed since the last loop operation (yes in step S18), the processor 61 causes the process to proceed to step S12.

[0121] pass Figure 6 The illustrated cyclic process is performed in either the case where the image forming apparatus 1 is powered on or when 3 hours have elapsed since the last cyclic operation. Alternatively, the cyclic operation may be performed only when the image forming apparatus 1 is powered on, or only when 3 hours have elapsed since the last cyclic operation. Furthermore, the first predetermined time is not limited to 3 hours; it can be determined based on the time until the wax component with a higher melting point in the ink within the separation temperature zone AR begins to separate.

[0122] Thus, the image forming apparatus 1 in Embodiment 1 includes a main container 241, a heating unit 242, a first storage container 243, an inkjet head 245, a first supply flow path R1, a second supply flow path R2, and a circulation flow path R4. This allows the ink in the second supply flow path R2, i.e., the melted, high-temperature ink, to return to the space between the main container 241 and the heating unit 242 in the first supply flow path R1. Therefore, the higher-melting-point wax component in the ink remaining in the separation temperature region AR between the main container 241 and the heating unit 242 easily melts and flows, resulting in a more uniform ink composition. Therefore, the image forming apparatus 1 according to this embodiment can suppress the non-uniformity of ink composition caused by the heating unit 242.

[0123] Furthermore, in the above example, assuming the ink contains multiple wax components with different melting points, but the melting points of the wax components range from X degrees to Y degrees (X < Y), the ink may contain only one type of wax component. Typically, the wax components in ink are of natural origin, thus the melting points of the wax components vary. Therefore, even with only one type of wax component, a portion melts at a relatively low temperature (e.g., X degrees), but the remainder melts only at a relatively high temperature (e.g., Y degrees). In the case where the ink contains wax components with such a wide melting point range, even if the ink contains only one type of wax component, a portion of that wax component easily melts and flows, but the remaining portion may separate and accumulate in the flow path R11. That is, uneven ink composition caused by the heating section 242 may occur. However, according to the image forming apparatus 1 of this embodiment, since the ink in the second supply flow path R2 can be returned between the main container 241 in the first supply flow path R1 and the heating section 242, uneven ink composition caused by such a heating section 242 can be suppressed.

[0124] [Implementation Method 2]

[0125] The image forming apparatus 1 in Embodiment 1 is configured to perform a cyclic operation when at least one of the following conditions is met: the image forming apparatus 1 is powered on (ON) or the cyclic operation has not been performed for a first predetermined time or more. In the following description, the condition of the image forming apparatus being powered on (ON) or the cyclic operation not being performed for a first predetermined time or more will also be referred to as the "normal condition". Furthermore, in the following description, the cyclic operation performed under the normal condition will also be referred to as the "normal cyclic operation". The image forming apparatus in Embodiment 2 is configured to perform a cyclic operation not only under the normal condition but also under abnormal conditions. In the following description, the cyclic operation performed under abnormal conditions will also be referred to as the "abnormal cyclic operation".

[0126] Figure 7 This is a diagram illustrating a general outline of the process for controlling the flow direction of ink in the image forming apparatus of Embodiment 2. The image forming apparatus 1A in Embodiment 2 includes the same components as referenced... Figures 1 to 4 The image forming apparatus 1 in Embodiment 1 described herein has the same structure, therefore the same reference numerals are used to label the same structures, and their description will not be repeated. Furthermore, in Figure 7 The image forming apparatus 1A and reference in Embodiment 2 shown Figure 5 In the image forming apparatus 1 of the described embodiment 1, the same reference numerals are used to label the same structures, and their descriptions are not repeated.

[0127] Figure 7 The image forming apparatus 1A and reference in Embodiment 2 shown Figure 5 The difference in the image forming apparatus 1 of the described embodiment 1 is that the image forming apparatus 1A also includes a cycle operation management unit 112A and a first container management unit 117A instead of the cycle operation management unit 112 and the first container management unit 117A, and also includes a determination unit 123A.

[0128] The loop action management unit 112A, the first container management unit 117A, and the determination unit 123A are implemented by the processor 61 executing the program 631.

[0129] In addition to the processing performed by the first container management unit 117A as described above, the first container management unit 117A also outputs a signal indicating that the supply pump P1 is in operation to the determination unit 123A during the period when the supply pump P1 is in operation.

[0130] The determination unit 123A determines whether an abnormality has occurred. Specifically, the determination unit 123A determines that an abnormality has occurred if the amount of ink in the first storage container 243 does not reach the first threshold within a second predetermined time after the supply pump P1 is started.

[0131] As an example, the determination unit 123A counts the driving time of the supply pump P1 based on the signal received from the first container management unit 117A indicating that the supply pump P1 is being driven. When the driving time of the supply pump P1 reaches a second predetermined time, the determination unit 123A determines that an abnormality has occurred.

[0132] The second predetermined time is determined based on the time from the start of driving the supply pump P1 until the ink volume in the first storage container 243 reaches the first threshold, assuming the ink in the first supply flow path R1 is not clogged. That is, the second predetermined time is set to be a longer time than the time required for the ink volume in the first storage container 243 to reach the first threshold from a reference value, assuming the supply pump P1 is driven when the ink in the first supply flow path R1 is not clogged. Therefore, even if the driving time of the supply pump P1 reaches the second predetermined time, if the determination unit 123A receives a signal from the first container management unit 117A indicating that the supply pump P1 is driven, it anticipates that the ink in the first supply flow path R1 will become clogged, i.e., the ink composition in the ink flow path will become uneven. Therefore, when the driving time of the supply pump P1 reaches the second predetermined time, the determination unit 123A determines that an abnormality has occurred. In the case of determining an abnormality, the determination unit 123A outputs an error signal to the cycle operation management unit 112A.

[0133] Similar to the aforementioned cycle operation management unit 112, the cycle operation management unit 112A outputs instructions to the cycle valve control unit 113 and the cycle pump control unit 114 to perform cycle operation when at least one of the following conditions is met: the image forming apparatus 1A is powered on (ON) or the cycle operation has not been performed for a first predetermined time or more. That is, under normal circumstances, the cycle operation management unit 112A outputs instructions to the cycle valve control unit 113 and the cycle pump control unit 114 to perform cycle operation.

[0134] Furthermore, the cycle operation management unit 112A outputs instructions to the cycle valve control unit 113 and the cycle pump control unit 114 to ensure that the cycle operation continues even in the event of an abnormality.

[0135] In detail, when the cycle operation management unit 112A receives an error signal from the judgment unit 123A, it outputs an instruction to the cycle valve control unit 113 to open the cycle valve V2.

[0136] The circulation valve control unit 113 opens the circulation valve V2 according to the instruction from the circulation operation management unit 112A, and outputs a signal indicating that the circulation valve V2 is open to the circulation operation management unit 112A. When the circulation operation management unit 112A receives the signal indicating that the circulation valve V2 is open, it outputs an instruction to the circulation pump control unit 114 to start driving the circulation pump P2. The circulation pump control unit 114 drives the circulation pump P2 according to the instruction from the circulation operation management unit 112A, and continues to output a signal indicating that the circulation pump P2 is driven to the circulation operation management unit 112A during the driving of the circulation pump P2. With the circulation valve V2 open and the circulation pump P2 driven, the ink in the second supply flow path R2, that is, the melted high-temperature ink, flows into the first supply flow path R1 between the main container 241 and the heating unit 242.

[0137] The cycle operation management unit 112A counts the driving time of the cycle pump P2 based on the signal received from the cycle pump control unit 114 indicating that the cycle pump P2 is in operation. When the driving time of the cycle pump P2 reaches 120 seconds, the cycle operation management unit 112A outputs an instruction to the cycle pump control unit 114 to stop the driving of the cycle pump P2. The cycle pump control unit 114 stops the driving of the cycle pump P2 according to the instruction from the cycle operation management unit 112A and outputs a signal indicating that the driving of the cycle pump P2 has stopped to the cycle operation management unit 112A.

[0138] When the circulation operation management unit 112A receives a signal indicating that the circulation pump P2 has stopped, it outputs an instruction to the circulation valve control unit 113 to close the circulation valve V2. The circulation valve control unit 113 closes the circulation valve V2 according to the instruction from the circulation operation management unit 112A and outputs a signal indicating that the circulation valve V2 is closed to the circulation operation management unit 112A.

[0139] Thus, the normal operating time of the circulation pump P2 is 60 seconds, while the operating time of the circulation pump P2 is 120 seconds when the determination unit 123A determines that an abnormality has occurred. When the determination unit 123A determines that an abnormality has occurred, there is a high probability that ink will become clogged in the first supply flow path R1, and the ink composition within the ink flow path will become uneven. However, since the circulation pump P2 operates for a longer time than usual, the circulation operation during the abnormal situation is longer than the normal circulation operation. Therefore, the unevenness of the ink composition is eliminated.

[0140] Furthermore, the driving time of the circulation pump P2 in the event that the determination unit 123A determines an abnormality has occurred is only required to eliminate the unevenness of the ink composition, and is not limited to 120 seconds. The driving time of the circulation pump P2 in the event that the determination unit 123A determines an abnormality has occurred can be shorter or longer than 120 seconds.

[0141] Furthermore, when the determination unit 123A determines that an abnormality has occurred, the driving time of the circulation pump P2 can be the same as the driving time of the circulation pump P2 under normal circumstances, or it can be shorter than the driving time of the circulation pump P2 under normal circumstances.

[0142] Figure 8 This is a flowchart illustrating the sequence of cyclic processing performed by the image forming apparatus in Embodiment 2 when an anomaly occurs. Cyclic processing when an anomaly occurs refers to processing used to control cyclic actions when an anomaly occurs. Figure 8 The loop processing shown is executed by the processor 61 described above.

[0143] In step S21, the processor 61 determines whether the supply pump P1 is activated. If the supply pump P1 is activated (yes in step S21), the processor 61 proceeds to step S22.

[0144] In step S22, the processor 61 determines whether a second predetermined time has elapsed. If the second predetermined time has elapsed (yes in step S22), the processor 61 proceeds to step S23. On the other hand, if the second predetermined time has not elapsed (no in step S22), the processor 61 proceeds to step S28.

[0145] In step S23, processor 61 opens circulation valve V2.

[0146] In step S24, processor 61 drives circulation pump P2.

[0147] In step S25, the processor 61 determines whether the driving time of the circulation pump P2 has reached 120 seconds. If the driving time of the circulation pump P2 has reached 120 seconds (yes in step S25), the processor 61 causes the process to proceed to step S26.

[0148] In step S26, processor 61 stops driving the circulating pump P2.

[0149] In step S27, processor 61 closes circulation valve V2.

[0150] In step S28, the processor 61 determines whether the power supply to the image forming apparatus 1A is off. If the power supply to the image forming apparatus 1A is off (yes in step S28), the processor 61 terminates the process. Figure 8 The loop process is shown. On the other hand, if the power supply to the image forming apparatus 1A is not turned off (not in step S28), the processor 61 returns the process to step S21.

[0151] Furthermore, in Embodiment 2, the processing sequence of the image forming apparatus 1A for controlling the cyclic operation during normal operation is compared with the reference... Figure 6 The processing steps described are the same, so they will not be repeated.

[0152] Thus, the image forming apparatus 1A according to Embodiment 2 performs a cyclic operation not only under normal conditions but also in the event of an abnormality. In the event of an abnormality, ink blockage may occur in the first supply channel R1, and the ink composition within the ink channel may become uneven. However, in the image forming apparatus 1A according to Embodiment 2, since the cyclic operation is performed in the event of an abnormality, this unevenness in ink composition is eliminated.

[0153] [Implementation Method 3]

[0154] The image forming apparatus 1A in Embodiment 2 is configured to perform a cyclic operation not only under normal circumstances but also under abnormal circumstances. In contrast, the image forming apparatus in Embodiment 3 is configured to not perform a cyclic operation under normal circumstances, but only under abnormal circumstances.

[0155] According to the image forming apparatus of Embodiment 3, a cyclic operation is performed in case of an abnormality, thereby eliminating the unevenness of ink composition.

[0156] [Note]

[0157] The above-described embodiments and variations include the following technical ideas.

[0158] [Structure 1]

[0159] An image forming apparatus comprising:

[0160] Main container, storing ink;

[0161] A first storage container stores the ink supplied from the main container;

[0162] The inkjet head ejects the ink;

[0163] A first supply flow path is used to supply the ink from the main container to the first storage container;

[0164] A second supply path is used to supply ink from the first storage container to the inkjet head;

[0165] A heating element, disposed in the first supply path, heats the ink; and

[0166] The circulation path allows the ink in the second supply path to return to the space between the main container and the heating element in the first supply path.

[0167] [Structure 2]

[0168] According to the image forming apparatus of structure 1, wherein...

[0169] A circulation valve is installed in the circulation path.

[0170] The image forming apparatus also includes a circulation valve control unit that controls the opening and closing of the circulation valve.

[0171] [Structure 3]

[0172] According to the image forming apparatus of structure 2, wherein,

[0173] The circulation valve control unit opens the circulation valve if at least one of the following conditions is met: the power to the image forming apparatus is turned on, or the circulation operation between the main container and the heating unit, in which the ink in the second supply path is returned to the first supply path, has not been performed for more than a first predetermined time.

[0174] [Structure 4]

[0175] According to the image forming apparatus of structure 2 or 3, wherein...

[0176] The image forming apparatus further comprises:

[0177] A supply pump supplies the ink from the main container to the heating section;

[0178] A first sensor detects the volume of ink in the first storage container; and

[0179] If the determination unit determines that an abnormality has occurred if the liquid volume in the first storage container does not reach a first threshold within a second predetermined time after the supply pump is activated,

[0180] If the determination unit determines that an abnormality has occurred, the circulation valve control unit opens the circulation valve.

[0181] [Structure 5]

[0182] According to the image forming apparatus described in structure 3, wherein...

[0183] The image forming apparatus further comprises:

[0184] A supply pump supplies the ink from the main container to the heating section;

[0185] A first sensor detects the volume of ink in the first storage container; and

[0186] If the determination unit determines that an abnormality has occurred if the liquid volume in the first storage container does not reach a first threshold within a second predetermined time after the supply pump is activated,

[0187] If the determination unit determines that an abnormality has occurred, the circulation valve control unit opens the circulation valve.

[0188] The image forming apparatus further comprises:

[0189] A circulating pump supplies the ink from the second supply path to the space between the main container and the heating element in the first supply path; and

[0190] The circulating pump control unit controls the drive of the circulating pump.

[0191] The circulation pump control unit drives the circulation pump when the circulation valve is open.

[0192] The driving time of the circulation pump when the determination unit determines that an abnormality has occurred is longer than the driving time of the circulation pump in at least one of the cases where the power to the image forming apparatus is turned on and the circulation operation has not been performed for more than the first predetermined time.

[0193] [Structure 6]

[0194] According to the image forming apparatus described in structure 5, wherein...

[0195] The image forming apparatus further includes a second storage container disposed in the second supply path, which stores the ink supplied from the first storage container.

[0196] [Structure 7]

[0197] According to the image forming apparatus described in structure 6, wherein...

[0198] The circulating pump is positioned between the first and second storage containers in the second supply path to supply the ink from the first storage container to the second storage container.

[0199] [Structure 8]

[0200] According to the image forming apparatus described in structure 7, wherein...

[0201] A supply valve is installed in the second supply flow path.

[0202] The image forming apparatus further comprises:

[0203] A supply valve control unit controls the opening and closing of the supply valve; and

[0204] The second sensor detects the amount of ink in the second storage container.

[0205] If the liquid volume in the second storage container is less than the second threshold, the supply valve control unit opens the supply valve.

[0206] The circulation pump control unit drives the circulation pump when the supply valve is open.

[0207] [Structure 9]

[0208] The image forming apparatus according to any one of structures 1 to 8, wherein,

[0209] The ink contains multiple wax components with different melting points.

[0210] The temperature of at least a portion of the first supply flow path is greater than or equal to the melting point of the first wax component with the lowest melting point among the plurality of wax components, i.e., the first temperature, and less than the melting point of the second wax component with the highest melting point among the plurality of wax components, i.e., the second temperature.

[0211] [Structure 10]

[0212] According to the image forming apparatus comprising any one of 1 to 9, wherein...

[0213] The heating element melts the ink to a sol state.

[0214] Embodiments of the present invention have been described, but should be considered as illustrative rather than limiting in all respects. The scope of the invention is indicated by the scope of protection of the invention and is intended to include all modifications within the same meaning and scope as the scope of protection of the invention.

Claims

1. An image forming apparatus comprising: Main container, storing ink; A first storage container stores the ink supplied from the main container; The inkjet head ejects the ink; A first supply flow path is used to supply the ink from the main container to the first storage container; A second supply path is used to supply ink from the first storage container to the inkjet head; A heating element is disposed in the first supply flow path to heat the ink; as well as The circulation path allows the ink in the second supply path to return to the space between the main container and the heating unit in the first supply path. A circulation valve is installed in the circulation path. The image forming apparatus further includes a circulation valve control unit that controls the opening and closing of the circulation valve. The circulation valve control unit opens the circulation valve if at least one of the following conditions is met: the power to the image forming apparatus is turned on; or the circulation operation between the main container and the heating unit, in which the ink in the second supply path returns to the first supply path, has not been performed for more than a first predetermined time. The image forming apparatus further comprises: A supply pump supplies the ink from the main container to the heating section; A first sensor detects the volume of ink in the first storage container; and If the determination unit determines that an abnormality has occurred if the liquid volume in the first storage container does not reach a first threshold within a second predetermined time after the supply pump is started, If the determination unit determines that an abnormality has occurred, the circulation valve control unit opens the circulation valve. The image forming apparatus further comprises: A circulating pump supplies the ink from the second supply path to the space between the main container and the heating element in the first supply path; and The circulating pump control unit controls the drive of the circulating pump. The circulation pump control unit drives the circulation pump when the circulation valve is open. The driving time of the circulation pump when the determination unit determines that an abnormality has occurred is longer than the driving time of the circulation pump in at least one of the cases where the power to the image forming apparatus is turned on and the circulation operation has not been performed for more than the first predetermined time.

2. The image forming apparatus according to claim 1, wherein, The image forming apparatus further includes a second storage container disposed in the second supply path, which stores the ink supplied from the first storage container.

3. The image forming apparatus according to claim 2, wherein, The circulating pump is positioned between the first and second storage containers in the second supply path to supply the ink from the first storage container to the second storage container.

4. The image forming apparatus according to claim 3, wherein, A supply valve is installed in the second supply flow path. The image forming apparatus further comprises: A supply valve control unit controls the opening and closing of the supply valve; and The second sensor detects the amount of ink in the second storage container. If the liquid volume in the second storage container is less than a second threshold, the supply valve control unit opens the supply valve. The circulation pump control unit drives the circulation pump when the supply valve is open.

5. The image forming apparatus according to claim 1, wherein, The ink contains multiple wax components with different melting points. The temperature of at least a portion of the first supply flow path is greater than or equal to the melting point of the first wax component with the lowest melting point among the plurality of wax components, i.e., the first temperature, and less than the melting point of the second wax component with the highest melting point among the plurality of wax components, i.e., the second temperature.

6. The image forming apparatus according to claim 1, wherein, The heating element melts the ink to a sol state.

Images