Image forming apparatus, its control method and program

Abstract

This invention provides an image forming apparatus, a control method, and a program for the same, which change the conditions for stirring and liquid delivery according to the state of the ink in the ink tank to stabilize the stirring and liquid delivery of the ink. [Solution] The image forming apparatus includes an ink tank 51 for storing ink to be supplied to the inkjet head 23, a stirring unit 52 for stirring the ink in the ink tank 51, and a stirring control unit that controls the stirring unit 52 to stir the ink according to stirring conditions corresponding to the state of the ink in the ink tank 51.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus, a control method thereof, and a program.

Background Art

[0002] In an inkjet type image forming apparatus, in addition to an ink tank having a large capacity, there is a type that includes a small capacity sub-tank near the inkjet head. The ink in the ink tank is fed to the sub-tank by a liquid feeding pump or the like. Then, the ink in the sub-tank is adjusted to a predetermined viscosity or the like by heating or the like and ejected from the inkjet head. In such an image forming apparatus, when the ink in the ink tank is gelled, there is a risk of image formation defects due to thickening of the ink and reduction of the liquid feeding amount. To address this, for example, Patent Document 1 describes an image forming apparatus that stirs the ink in the ink tank as needed and feeds it to the sub-tank. Patent Document 2 describes an image recording apparatus that vibrates a piezoelectric member to stir the ink in the ink chamber near the nozzle in order not to thicken the ink.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] As with the image forming apparatus described in Patent Document 1, stirring conditions such as the rotation speed, stirring time, and stirring frequency of the ink in the ink tank can be predetermined. Similarly, liquid delivery conditions such as the capacity and delivery time of the liquid delivery pump can also be predetermined. However, the load on the motor that stirs the ink in the ink tank and the amount of liquid delivered per unit time by the liquid delivery pump vary depending on the viscosity of the ink in the ink tank. Furthermore, while Patent Document 2 determines the strength of stirring based on the time the ink is left standing without stirring, the stirring is performed near the nozzle and is not intended for large-capacity ink tanks.

[0005] The viscosity of ink in an ink tank varies not only depending on the time the ink has been left standing, but also on the ink's temperature, formulation, and type. High viscosity ink can lead to problems such as poor ink delivery, motor failure due to increased load during agitation, and poor print quality due to uneven mixing of the ink itself. The present invention was made to solve the aforementioned problems, and aims to provide an image forming apparatus, a control method therefor, and a program that stabilizes the stirring and liquid delivery of ink by changing the stirring and liquid delivery conditions according to the state of the ink in the ink tank. [Means for solving the problem]

[0006] To solve these problems, the imaging apparatus, control method and program according to the present invention have the following configurations (1) to (32). (1) An ink tank for storing ink to be supplied to an inkjet head; an agitator for agitating the ink in the ink tank; and an agitator control unit that controls the agitator to agitate the ink according to the agitator conditions corresponding to the state of the ink in the ink tank. An image forming apparatus equipped with the following features.

[0007] (2) The image forming apparatus according to (1), further comprising means for detecting temperature, wherein the stirring control unit changes the stirring conditions when the detected temperature is below a predetermined threshold. (3) The image forming apparatus according to (2), wherein the stirring control unit changes the stirring conditions when the temperature to be detected is below the threshold for a predetermined period of time. (4) The image forming apparatus according to (2), further comprising a main thermometer for detecting the temperature of the ink in the ink tank, wherein the stirring control unit changes the stirring conditions according to the temperature of the ink in the ink tank.

[0008] (5) The image forming apparatus according to (4), wherein the main thermometer detects the temperature of the ink by contacting the ink. (6) The image forming apparatus according to (4), wherein the main thermometer detects the temperature of the ink without contacting the ink. (7) The image forming apparatus according to (6), wherein the main thermometer is installed at a height where it is not exposed to ink splashes.

[0009] (8) The image forming apparatus according to (2), wherein a sub-tank having a secondary thermometer for detecting the temperature of the ink is further provided downstream of the ink tank, and the stirring control unit changes the stirring conditions according to the temperature of the ink in the sub-tank. (9) The image forming apparatus according to (2), comprising an ambient temperature sensor for detecting ambient temperature, wherein the stirring control unit changes the stirring conditions according to the ambient temperature. (10) The image forming apparatus according to (1), further comprising a remaining amount detection unit for detecting the remaining amount of ink in the ink tank, wherein the stirring control unit changes the stirring conditions according to the remaining amount of ink in the ink tank detected by the remaining amount detection unit.

[0010] (11) The image forming apparatus according to (1), comprising a torque meter for detecting the torque used by the stirring unit to stir the ink, and the stirring conditions being changed according to the torque. (12) The image forming apparatus according to (1), wherein the stirring control unit calculates the time elapsed when the ink is not stirred, and changes the stirring conditions when the time elapsed exceeds a predetermined length. (13) The image forming apparatus according to (1), wherein the stirring control unit changes the stirring conditions according to the ink color of the ink tank.

[0011] (14) The image forming apparatus according to (13), wherein the stirring control unit sets the stirring conditions when the ink color of the ink tank is white to be different from the stirring conditions when the ink color of the ink tank is other than white. (15) The image forming apparatus according to any one of (1) to (14), wherein the stirring conditions are the rotational speed of the stirring section or the stirring time. (16) The image forming apparatus according to any one of (1) to (12), wherein the stirring control unit changes the stirring conditions for stirring immediately after startup.

[0012] (17) The image forming apparatus according to (1), further comprising: a liquid supply unit that supplies ink from the ink tank to the inkjet head; and a liquid supply control unit that controls the supply of ink to the liquid supply unit according to the liquid supply conditions corresponding to the state of the ink in the ink tank. (18) The image forming apparatus according to (17), comprising means for detecting temperature, wherein the liquid delivery control unit changes the liquid delivery conditions when the detected temperature is below a predetermined threshold. (19) The image forming apparatus according to (18), wherein the liquid delivery control unit changes the liquid delivery conditions when the temperature to be detected is below the threshold for a predetermined period of time.

[0013] (20) The image forming apparatus according to (18), further comprising a main thermometer for detecting the temperature of the ink in the ink tank, wherein the liquid supply control unit changes the liquid supply conditions according to the temperature of the ink in the ink tank. (21) The image forming apparatus according to (18), wherein a sub-tank having a secondary thermometer for detecting the temperature of the ink is further provided downstream of the ink tank, and the liquid supply control unit changes the liquid supply conditions according to the temperature of the ink in the sub-tank. (22) The image forming apparatus according to (18), further comprising an ambient temperature sensor for detecting ambient temperature, wherein the liquid supply control unit changes the liquid supply conditions according to the ambient temperature.

[0014] (23) The liquid supply control unit changes the liquid supply conditions according to the ink color of the ink tank in the image forming apparatus according to (17). (24) The liquid supply conditions are the air pressure or the liquid supply time of the liquid supply unit in the image forming apparatus according to any one of (17) to (23).

[0015] (25) A control method for an image forming apparatus including an ink tank for storing ink to be supplied to an inkjet head and a stirring unit for stirring the ink in the ink tank, the method including a step of a stirring control unit controlling the stirring unit under stirring conditions according to the temperature of the ink in the ink tank. (26) A control method for an image forming apparatus including an ink tank for storing ink to be supplied to an inkjet head and a stirring unit for stirring the ink in the ink tank, the method including a step of a stirring control unit controlling the stirring unit under stirring conditions according to the color of the ink in the ink tank.

[0016] (27) A control program for causing an image forming apparatus including an ink tank for storing ink to be supplied to an inkjet head and a stirring unit for stirring the ink in the ink tank to execute a procedure for obtaining the temperature of the ink in the ink tank and a procedure for causing the stirring unit to stir the ink under stirring conditions according to the temperature of the ink. (28) A control program for causing an image forming apparatus including an ink tank for storing ink to be supplied to an inkjet head and a stirring unit for stirring the ink in the ink tank to execute a procedure for obtaining the color of the ink in the ink tank and a procedure for causing the stirring unit to stir the ink under stirring conditions according to the color of the ink.

[0017] (29) A control method for an image forming apparatus including an ink tank for storing ink to be supplied to an inkjet head and a liquid supply unit for supplying ink from the ink tank to the inkjet head, the method including a step of a liquid supply control unit controlling the liquid supply unit to supply ink under liquid supply conditions according to the temperature of the ink in the ink tank. A control method for an image forming apparatus including an ink tank that stores ink to be supplied to an inkjet head and a liquid supply unit that supplies the ink from the ink tank to the inkjet head, the control method including a step of controlling the liquid supply unit to supply the ink under a liquid supply condition corresponding to the color of the ink in the ink tank.

[0018] A control program for causing an image forming apparatus including an ink tank that stores ink to be supplied to an inkjet head and a liquid supply unit that supplies the ink from the ink tank to the inkjet head to execute a procedure for acquiring the temperature of the ink in the ink tank and a procedure for causing the liquid supply unit to supply the ink under a liquid supply condition corresponding to the temperature of the ink. A control program for causing an image forming apparatus including an ink tank that stores ink to be supplied to an inkjet head and a liquid supply unit that supplies the ink from the ink tank to the inkjet head to execute a procedure for acquiring the color of the ink in the ink tank and a procedure for causing the liquid supply unit to supply the ink under a liquid supply condition corresponding to the color of the ink. [Advantages of the Invention]

[0019] According to the present invention, it is possible to provide an image forming apparatus, a control method thereof, and a program that change the conditions of stirring and liquid supply according to the state of the ink in the ink tank and achieve stabilization of ink stirring and liquid supply. [Brief Description of the Drawings]

[0020] [Figure 1] It is a schematic diagram illustrating the arrangement of each device of the image forming apparatus according to the embodiment. [Figure 2] It is a block diagram illustrating the hardware configuration of the image forming apparatus according to the embodiment. [Figure 3] It is a schematic diagram illustrating a device and a path responsible for ink supply. [Figure 4] It is a block diagram illustrating the functional configuration of the ink supply control unit according to the embodiment. [Figure 5A]This graph illustrates how the load on the stirring motor changes with ink temperature. [Figure 5B] This graph illustrates how the load on the stirring motor changes depending on the ink volume. [Figure 5C] This graph illustrates how the load changes depending on the rotation speed setting of the stirring motor. [Figure 5D] This is an example of the relationship between ink color and the load on the stirring motor. [Figure 6] This flowchart illustrates the process for changing stirring conditions when detecting ink temperature. [Figure 7] This flowchart illustrates the process for initializing the stirring conditions. [Figure 8] This flowchart illustrates a process that detects the ink temperature and changes the stirring conditions only for the initial stirring immediately after startup. [Figure 9] This flowchart illustrates a process that calculates the standing time and modifies the stirring conditions only for the initial stirring immediately after startup. [Figure 10] This flowchart illustrates the process of changing the stirring conditions when detecting the remaining ink level in an ink tank. [Figure 11] This flowchart illustrates the process for changing stirring conditions when detecting stirring torque. [Figure 12] This flowchart illustrates the process for changing the ink supply conditions when detecting the ink temperature with a main thermometer. [Figure 13] This flowchart illustrates the process for initializing the fluid delivery conditions. [Modes for carrying out the invention]

[0021] Embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments or modifications, and various design changes are possible. Furthermore, each embodiment and each modification can be combined as appropriate. The use of directional terms, including up, down, left, and right, in the description is merely an example of a relative positional relationship and does not limit the direction of use. Furthermore, in drawings where some components are omitted, the size, shape, and positional relationships of each component may be exaggerated.

[0022] [First Embodiment] The image forming apparatus 1 according to the first embodiment will be described with reference to Figures 1 to 5D. The image forming apparatus 1 is an inkjet type image forming apparatus that ejects ink from the nozzles of an inkjet head to form an image on a recording medium. As illustrated in Figure 1, the image forming apparatus 1 comprises a paper feeding unit 10, an output unit 40, an operation unit 80, an image forming unit 20, a storage unit 50, a liquid supply unit 60, and a control unit 30. The following describes each component of the image forming apparatus 1.

[0023] (Paper feeding section and output section) The paper feeding unit 10 is a device that stores the recording medium for image formation and feeds it towards the image forming unit 20. The paper feeding unit 10 has multiple paper trays 12, which can classify and store the recording medium. The material of the recording medium can be paper, cloth, resin, etc. The output unit 40 is a device that outputs and stores image-formed recording media. The output unit 40 can sort and output recording media into multiple output trays 42. Although Figure 1 illustrates the case of sheet paper cut to a predetermined size, the paper feeding unit 10 and the output unit 40 can also be devices that can handle roll-shaped recording media.

[0024] (Operation unit) The operation unit 80 is a device for inputting operations and settings related to the image forming apparatus 1. The operation unit 80 can also display information such as the operating status of the image forming apparatus 1. The operation unit 80 can be, for example, a touch panel. There are no particular restrictions on the location of the operation unit 80; it may be located away from the image forming unit 20, etc. Furthermore, the operation unit 80 may be an external terminal such as a personal computer.

[0025] (Image forming unit) The image forming unit 20 is a device that forms an image on a conveyed recording medium. The image forming unit 20 may have multiple ejection units 21. In this case, the image forming unit 20 has four ejection units 21, corresponding to, for example, cyan (C), magenta (M), yellow (Y), and black (K). There are no particular restrictions on the number of ejection units 21, nor on the ink colors. The image formation method may be either a scanning method in which the inkjet head moves back and forth, or a single-pass method in which the head is fixed.

[0026] (Discharge part) The ejection unit 21 is a device that temporarily stores ink before ejection and ejects it toward the recording medium. As illustrated in Figure 2, the ejection unit 21 includes an inkjet head 23, a sub-tank 22, a heating unit 24, and a secondary thermometer 25. The inkjet head 23 is a device that ejects ink droplets from nozzles. The inkjet head 23 can eject ink supplied from the sub-tank 22, for example, by utilizing the deformation of a piezoelectric element.

[0027] The sub-tank 22 is located downstream of the ink tank 51 and is a container that holds the ink supplied from the ink tank 51. The ink in the sub-tank 22 is heated by the heating unit 24 and maintained at a predetermined temperature suitable for dispensing. The heating unit 24 is a heating device and is controlled by the control unit 30. The auxiliary thermometer 25 is a device that detects the temperature of the ink in the sub-tank 22. Here, the auxiliary thermometer 25 is located inside the sub-tank 22, but it may also be located near the outside of the sub-tank 22. As illustrated in Figure 3, the supply of ink to the sub-tank 22 is carried out by the storage unit 50 and the liquid supply unit 60.

[0028] (Storage section) The storage unit 50 is a device for storing and managing ink. The storage unit 50 includes an ink tank 51, a stirring unit 52, and a main thermometer 53. The ink tank 51 is a container for storing ink and can hold, for example, 30 liters of ink. The ink tank 51 stores the ink that is supplied to the inkjet head 23. In this case, the storage unit 50 has four ink tanks 51, but there is no particular limit to the number of ink tanks 51.

[0029] The stirring unit 52 is a device that stirs the ink in the ink tank 51. The stirring unit 52 stirs the ink 59 by rotating the stirring screw 521 inside the ink tank 51 with the stirring motor 522. Here, the stirring screw 521 is connected to the stirring motor 522 by a rotating shaft 523. The stirring motor 522 is an electric motor and is controlled by the control unit 30. The control unit 30 can acquire information such as the rotation speed of the stirring motor 522. Ink 59 can be a phase-transition ink. A phase-transition ink is an ink that undergoes a phase transition between a fluid sol state and a non-fluid gel state. The phase transition temperature is, for example, 80°C, and as the temperature decreases, the viscosity of the ink increases and it becomes a gel state. When the sol state of the phase-transition ink is ejected from the inkjet head 23, it becomes a gel state on the recording medium it reaches, enabling the formation of high-quality images. Even in the gel state, the phase-transition ink can be pumped using a general-purpose pump by applying mechanical shear through stirring.

[0030] The main thermometer 53 is a device that detects the temperature of the ink in the ink tank 51. The main thermometer 53 is located inside the ink tank 51. Here, the main thermometer 53 is a contact thermometer 531 that measures the temperature of the ink 59 by contacting it.

[0031] (Liquid delivery section) The liquid supply unit 60 is a device that supplies ink from the ink tank 51 to the inkjet head 23. Here, the liquid supply unit 60 is provided for each of the four ink tanks 51 and supplies ink from the ink tank 51 to the sub-tank 22. From the sub-tank 22, ink is supplied sequentially to the inkjet head 23 via the supply path 26 according to the amount of ink ejected. As illustrated in Figure 3, the liquid supply unit 60 includes a supply pump 61, a valve 62, manifold valves 63 and 64, and regulators 65 and 66. The supply pump 61 and valve 62 are located on the ink supply path. In the ink supply path, the ink tank 51, supply pump 61, valve 62, and sub-tank 22 are arranged in this order and connected to each other by a liquid supply pipe 67. Note that Figure 3 illustrates the ink supply path to one discharge unit 21. If there are multiple discharge units 21, an ink tank 51 corresponding to each discharge unit 21 can be provided, and multiple ink supply paths can also be provided.

[0032] The supply pump 61 is a pump that transports ink. The valve 62 is a check valve. The supply pump 61 and valve 62 are air-driven here, but they may also be electrically driven. Regulators 65 and 66 are devices that take in outside air, compress it, and generate compressed air at a predetermined air pressure. Regulators 65 and 66 are controlled by the control unit 30, which sets the air pressure. Manifold valves 63 and 64 are devices that branch the compressed air and send it to the supply pump 61 and valve 62. The opening and closing of manifold valves 63 and 64 are controlled by the control unit 30. Regulators 65 and 66 and manifold valves 63 and 64 can be shared by multiple ink supply paths.

[0033] (Control Unit) The control unit 30 is a device that controls each component of the image forming apparatus 1. The control unit 30 controls the entire image forming apparatus 1, including paper feeding, image forming, output, ink supply, etc. As illustrated in Figure 2, the control unit 30 includes a CPU 31 which is a central processing unit, a main memory 32, an auxiliary memory 33, and a communication unit 34. These are connected to each other via a bus and are further connected to each device of the image forming apparatus 1.

[0034] The CPU 31 is a processing unit that executes various programs. The main memory 32 is, for example, RAM (Random Access Memory) and temporarily stores various data during the execution process of the CPU 31. The main memory 32 also temporarily stores programs that start each device. The auxiliary storage device 33 is a hard disk or SSD (Solid State Drive) and stores programs for the CPU 31 to control each device, information about the processing functions of each device, and print data received from the communication unit 34. The communication unit 34 is a network interface card that handles communication with the outside world. The communication unit 34 is connected to a network via a local area network (LAN), etc., and can send and receive data with external client computers, etc.

[0035] The control unit 30 uses a transport unit (not shown) to transport the recording medium from a specific paper tray 12 of the paper feeding unit 10 to the image forming unit 20, and performs image formation. In image formation, the control unit 30 generates bitmap data for cyan, magenta, yellow, and black (CMYK) for printing from the print data and sends it to the image forming unit 20. The control unit 30 then controls the inkjet head of the image forming unit 20 to form an image on the recording medium, transports the recording medium, and outputs it to the output tray 42. Furthermore, the control unit 30 controls the supply of ink from the storage unit 50 to the discharge unit 21. The ink supply is controlled by the ink supply control unit 35, which is a means for controlling the ink supply. As illustrated in Figure 4, the ink supply control unit 35 includes a stirring control unit 36, a liquid delivery control unit 37, and a heating control unit 38.

[0036] The liquid delivery control unit 37 is a means for controlling the delivery of liquid from the ink tank 51 to the discharge unit 21. The liquid delivery control unit 37 controls each device of the liquid delivery unit 60. The heating control unit 38 is a means for controlling the heating of the ink. The heating control unit 38 controls the heating unit 24 of the ejection unit 21 and can maintain the temperature of the ink in the sub-tank 22 within a predetermined range.

[0037] The stirring control unit 36 ​​is a means for controlling the stirring unit 52. The stirring control unit 36 ​​controls the stirring unit 52 to stir the ink according to the stirring conditions corresponding to the state of the ink in the ink tank 51. The state of the ink refers to the amount, properties, and conditions that affect the stirring and delivery of the ink, and in this case, it refers particularly to the viscosity of the ink. Viscosity changes depending on the temperature of the ink in the ink tank 51, the amount of ink remaining, the time that has passed without the ink being stirred (hereinafter sometimes referred to as "standing time"). Viscosity, which is a state of the ink, also changes depending on the ink formulation and color. Here, the ink temperature is detected as an indicator of the state of the ink in the ink tank 51. The stirring control unit 36 ​​changes the stirring conditions when the ink temperature in the ink tank 51 is below a predetermined threshold.

[0038] For temperature determination, it is preferable to determine that the temperature is below a predetermined threshold if the detected temperature remains below a predetermined threshold for a predetermined period of time. Furthermore, it is preferable to change the stirring conditions only when the detected temperature remains below a predetermined threshold for a predetermined period of time. This allows the stirring control unit 36 ​​to suppress the effects of accidental detection errors and the like. The same applies to other embodiments and modifications. The predetermined time for temperature detection corresponds to the number of consecutive detections when temperature detection is performed at regular time intervals. For example, if temperature detection is repeated at a frequency of once every 10 seconds and the predetermined time is set to 1 minute, the stirring control unit 36 ​​determines that the temperature is below the predetermined threshold for the predetermined time of 1 minute if the detected value is below the predetermined threshold for 7 consecutive times, and changes the stirring conditions.

[0039] The stirring conditions refer to the settings for the rotational speed and stirring time of the stirring unit 52. The rotational speed of the stirring refers to the rotational speed of the stirring screw 521, that is, the number of rotations of the stirring screw 521 per unit time. The stirring time refers to the time for which the stirring motor 522 is driven continuously. In addition, the time interval at which stirring is repeated based on the rotational speed and stirring time can also be set as part of the stirring conditions. Changing the stirring conditions refers to making a temporary change to the stirring conditions that are set as the normal stirring conditions in the initial settings. The normal stirring conditions are those that are carried over from the previous operation or that are set as the initial settings when the image forming apparatus 1 is started up. In other words, the stirring control unit 36 ​​changes from the normal stirring conditions to stirring conditions suitable for ink that has become highly viscous due to a decrease in temperature when the temperature of the ink in the ink tank 51 is below a predetermined threshold for a predetermined period of time. When changing the stirring conditions, if continuous stirring is counted as one stirring cycle based on the length of the stirring time, the system can be set to return to the normal stirring conditions after one stirring cycle with the changed stirring conditions. Alternatively, the system can be set to return to the normal stirring conditions after multiple stirring cycles with the changed stirring conditions.

[0040] As illustrated in Figure 5A, as the temperature decreases, the viscosity of the ink increases, and the load on the stirring motor 522 of the stirring unit 52 increases. An increased load on the stirring motor 522 may cause the image forming apparatus 1 to stop due to abnormality detection or cause the stirring motor 522 to fail. By changing the stirring conditions to reduce the rotation speed of the stirring motor 522, it is possible to avoid the image forming apparatus 1 stopping due to abnormality detection and to avoid the failure of the stirring motor 522. A predetermined threshold for ink temperature can be set, for example, using 80% of the rated load torque of the stirring motor 522 as a guideline. The guideline line 5201 in Figure 5A illustrates the load torque at which 80% of the rated torque is reached. Based on Figure 5A, since 80% of the rated torque is reached at 15°C, the ink temperature threshold can be set to 15°C.

[0041] As illustrated in Figure 5C, increasing the rotational speed of the stirring motor 522 increases the load torque of the stirring motor 522. Therefore, when the ink temperature falls below a threshold, the load torque of the stirring motor 522 can be reduced by lowering the rotational speed of the stirring motor 522 when changing the stirring conditions. According to Figure 5C, the load torque at a rotational speed of 240 rpm is 83% at 210 rpm and 75% at 200 rpm. Based on this data, the rotational speed of the stirring motor 522 can be changed. On the other hand, if the rotation speed of the stirring motor 522 is reduced, the ink in the ink tank 51 may not be sufficiently stirred. In particular, at the first startup in the morning, the ink in the ink tank 51 has wax separation and is at a low temperature, so simply reducing the rotation speed of the stirring motor 522 is likely to result in insufficient ink stirring. Therefore, extending the stirring time allows the ink in the ink tank 51 to be sufficiently stirred. In other words, when reducing the rotation speed of the stirring motor 522, it is preferable to also extend the stirring time. It is preferable that the extension of the stirring time be set considering the decrease in productivity due to the inability to start the next process.

[0042] Furthermore, excessive stirring, such as stirring at too high a rotation speed of the stirring motor 522 or stirring for too long, can cause the ink to foam and generate bubbles, which is problematic. In the image forming apparatus 1, degassing is performed at the discharge unit 21 after the ink is delivered from the ink tank 51. Bubbles in the ink can affect this degassing process and may cause a decrease in the quality of image formation. For this reason, it is preferable to set the stirring conditions to appropriate conditions that suppress the generation of bubbles, that is, conditions that take into account the balance between the rotation speed of the stirring motor 522 and the stirring time. For example, if the ink is highly viscous, the rotational speed of the stirring motor 522 can be reduced to lessen the load on the stirring motor 522, and the stirring conditions can be set to increase the stirring time to a degree that does not cause problems in generating bubbles, in order to homogenize the ink.

[0043] The image forming apparatus 1, having the configuration described above, focuses on the ink temperature as an indicator of the state of the ink in the ink tank and, by changing the conditions for stirring the ink, can stably stir and deliver the ink regardless of its state. This suppresses failure of the stirring motor due to increased load and allows for uniform stirring of the ink. As a result, errors in image formation caused by insufficient stirring or delivery of the ink can be suppressed, and the quality of image formation can be improved. The image forming apparatus 1 can perform stable ink stirring and liquid delivery by reducing the stirring rotation speed and increasing the stirring time in response to the increased stirring load due to the decrease in the temperature of the ink in the ink tank.

[0044] The main thermometer 53 may be a non-contact thermometer 532 that measures the temperature of the ink without contacting the ink 59. If a non-contact thermometer 532 is used, it is preferable to install it at a height where it will not be splashed with ink. Ink splashes may occur when replenishing ink to the ink tank 51 or when stirring by the stirring unit 52.

[0045] [Differentiation] Next, a modified example of the image forming apparatus 1 will be described. The first modification is one in which the ambient temperature is detected as an indicator of the state of the ink. The first modification has an ambient temperature meter 55 for detecting the ambient temperature, and the stirring control unit 36 ​​changes the stirring conditions according to the ambient temperature. The stirring control unit 36 ​​can determine that the temperature of the ink in the ink tank 51 is decreasing if the ambient temperature is below a predetermined temperature. The stirring control unit 36 ​​may change the stirring conditions when the ambient temperature is below a predetermined threshold, or it may change the stirring conditions when the ambient temperature remains below a predetermined threshold for a predetermined period of time.

[0046] The ambient temperature sensor 55 is a device for detecting the ambient temperature and can be placed on the outer surface of the image forming apparatus 1, for example, the paper feeding section 10. The ambient temperature sensor 55 may also be installed at a distance from the image forming apparatus 1. In the first modified example, the main thermometer 53 does not need to be provided. By not providing the main thermometer 53, damage to the sensor inside the ink tank 51 and false detections can be avoided.

[0047] The second modification involves detecting the temperature of the ink in the sub-tank 22 as an indicator of the ink's state. In the second modification, the stirring control unit 36 ​​changes the stirring conditions based on the temperature of the ink in the sub-tank 22. The sub-tank 22 is located downstream of the ink tank 51 and has a secondary thermometer 25 for detecting the ink temperature. In the second modification, the stirring conditions are changed when the temperature of the ink in the sub-tank 22 is below a predetermined threshold, or when it remains below a predetermined threshold for a predetermined period of time. The dispensing unit 21 is equipped with a secondary thermometer 25 for detecting the temperature of the ink in the sub-tank 22. The sub-tank 22 is also equipped with a heating unit 24 for heating the ink in the sub-tank 22. However, after the image forming apparatus 1 stops operating, the sub-tank 22 is not heated by the heating unit 24. Therefore, the temperature of the ink in the sub-tank 22 decreases with the ambient temperature, similar to the temperature of the ink in the ink tank 51. Accordingly, the stirring control unit 36 ​​can determine that if the ink temperature of the sub-tank 22 at startup is below a predetermined temperature, the temperature of the ink in the ink tank 51 has decreased, and stirring to handle high viscosity is necessary.

[0048] The third modification involves detecting the remaining ink level in the ink tank 51 as an indicator of the ink's condition. The third modification includes an ink level detection unit 56 that detects the remaining ink level in the ink tank 51. The stirring control unit 36 ​​then changes the stirring conditions based on the remaining ink level in the ink tank 51. The ink level detection unit 56 is a device that detects the remaining ink level in the ink tank 51. The remaining ink level may be detected, for example, by the weight including the ink tank 51, or by the height of the ink level 59 inside the ink tank 51. When detecting by the liquid level, the ink level detection unit 56 is located inside the ink tank 51.

[0049] As illustrated in Figure 5B, a larger ink volume increases ink viscosity, which increases the load on the stirring unit 52. Therefore, in the third modified example, the stirring conditions are changed when the remaining ink amount exceeds a predetermined threshold. The predetermined threshold can be set using 80% of the rated load torque of the stirring motor 522 as a guideline, similar to the case of ink temperature. The guideline line 5202 in Figure 5B illustrates the load torque that corresponds to 80% of the rated torque. Based on Figure 5B, since 80% of the rated torque is reached when the ink capacity is 20 liters (L), the stirring conditions can be changed when the remaining ink exceeds 20 liters. It is preferable to change the stirring conditions by lowering the rotation speed to suppress malfunctions of the stirring unit 52 and extending the stirring time to ensure uniform stirring.

[0050] The fourth modification is one in which the ink color of the ink tank 51 is obtained as an indicator of the ink state. In the fourth modification, the stirring control unit 36 ​​changes the stirring conditions according to the ink color of the ink tank 51. In the fourth modification, stirring conditions can be set separately for each of the ink tanks 51. In the image forming apparatus 1, normal stirring conditions common to all ink tanks 51 are set. However, the specific gravity and viscosity of the inks differ depending on the color. In the fourth modification, it is possible to set separately for each ink tank 51 whether or not to change the stirring conditions from the normal conditions, depending on the ink color. However, in the fourth modification, the change in stirring conditions is not limited to one or more changes, but rather the stirring is performed repeatedly with the changed stirring conditions without an upper limit on the number of times.

[0051] The stirring conditions can be changed, for example, at startup, by acquiring the ink color information for each ink tank 51 as the initial stirring condition. The initially set stirring conditions are maintained until different initial settings are made. The ink color information is entered by the user when the ink tanks 51 are installed and updated by the user when the ink tanks 51 are replaced, etc. The ink color information can be stored in the control unit 30. The stirring control unit 36 ​​changes the stirring conditions of the ink tank 51 based on the acquired ink color information if the ink color requires a change in stirring conditions. If the stirring conditions are not changed, the normal stirring conditions are maintained.

[0052] As illustrated in Figure 5D, the load torque for white ink is 17% greater than that for yellow ink. On the other hand, the difference in load torque is small for inks other than white. For this reason, it is preferable that the stirring control unit 36 ​​sets the stirring conditions when the ink color in the ink tank 51 is white to be different from the stirring conditions when the ink color in the ink tank is other than white. In the fourth modification, appropriate stirring conditions can be set for the ink tank 51, particularly for white ink, depending on the ink color.

[0053] The fifth modification is a modification that detects the stirring torque as an indicator of the state of the ink. In the fifth modification, the stirring control unit 36 ​​changes the stirring conditions based on the torque at which the stirring unit 52 stirs the ink, and controls the stirring unit 52 to stir the ink under stirring conditions corresponding to the torque. As the viscosity of the ink in the ink tank 51 increases, the torque required to agitate the ink increases. In the fifth modification, the torque of the agitation motor 522 is detected, and the agitation conditions are changed when the torque exceeds a predetermined threshold.

[0054] As illustrated in Figure 3, torque can be detected by placing a torque meter 524 on the rotating shaft 523 of the stirring motor 522. Alternatively, torque can be estimated by acquiring the current value and rotational speed of the stirring motor 522. Torque can be a relative value and may be substituted with the current value or rotational speed value. A predetermined threshold can be, for example, 80% of the rated torque of the stirring motor 522, and the stirring conditions are changed when the torque exceeds 80% of the rated torque. The stirring conditions can be changed, for example, by reducing the rotational speed by lowering the current supplied to the stirring motor 522. The stirring time can then be extended to ensure uniform stirring.

[0055] The sixth modification is a modification that calculates the time elapsed when the ink is left undisturbed as an indicator of the state of the ink. The stirring control unit 36 ​​in the sixth modification changes the stirring conditions according to the standing time. In the sixth modification, the stirring conditions are changed when the standing time exceeds a predetermined length. If the ink in the ink tank 51 is left undisturbed, the temperature will drop, causing the phase-transition ink to gel, which may prevent proper liquid delivery. Therefore, the stirring unit 52 shears the ink through stirring, reducing its viscosity. In this case as well, it is preferable to change the stirring conditions by reducing the rotation speed to prevent malfunction of the stirring unit 52 and extending the stirring time to uniformly stir the ink.

[0056] Furthermore, the ink used in the image forming apparatus 1 may contain wax as an additive. Wax is added for purposes such as improving the scratch resistance of the ink adhering to the recording medium. If the ink is left undisturbed, the wax and ink components may separate due to differences in specific gravity, which may degrade the quality of image formation. The separated wax layer has a higher viscosity than the ink layer, especially at low temperatures, which can lead to high viscosity problems. To uniformly agitate the ink from which the wax has separated, it is preferable to reduce the rotation speed and extend the agitation time. In particular, stirring is not performed for a long period of time from the shutdown of the image forming apparatus 1 at night until the first startup in the morning. The stirring control unit 36 ​​can calculate the time from shutdown to startup as the standing time. In the sixth modification, even in the case of ink with added wax, stirring can be performed by changing the stirring conditions to suit the state of the ink at the first startup in the morning. The state of the ink is that the wax separates due to standing, and furthermore, the viscosity becomes high due to the low temperature. In response to this, the stirring control unit 36 ​​can reduce the load on the stirring motor 522 by changing the stirring conditions to reduce the rotation speed and extend the stirring time, thereby uniformly stirring the ink and stabilizing the liquid delivery while suppressing the occurrence of problems such as malfunctions. It is preferable to set the extended stirring time to a length that does not cause problems such as the generation of air bubbles in the ink.

[0057] In the first embodiment and its modified form, the stirring control unit 36 ​​can change the stirring conditions for the stirring immediately after startup. The stirring immediately after startup refers to the first stirring after the image forming apparatus 1 has been started up. The stirring control unit 36 ​​can change the stirring conditions only for the first stirring after power-on, for example. Immediately after startup, the ink has high viscosity and separates after being left for a certain period of time due to its thixotropic properties. Therefore, it is preferable to thoroughly stir the ink under appropriate stirring conditions. The stirring control unit 36 ​​then continues stirring under normal stirring conditions or the initially set stirring conditions in order to maintain low viscosity and uniformity.

[0058] Furthermore, two or more of the first embodiment and its modifications can be combined. The stirring control unit 36 ​​can, for example, detect the ink temperature using both the main thermometer 53 and the sub-thermometer 25, and change the stirring conditions if either temperature is below a threshold. The threshold values ​​for the main thermometer 53 and the sub-thermometer 25 can be different from each other. In addition, detection of ambient temperature may be combined.

[0059] Next, the process flow S1A for stirring the ink in the ink tank 51 in the image forming apparatus 1 according to the first embodiment will be explained with reference to Figure 6. First, when the image forming apparatus 1 is started (step S10), the stirring control unit 36 ​​performs initial settings for the stirring conditions (step S20). Step S20 will be described later. Note that step S20 can be skipped, in which case the initial settings from the previous operation will be carried over. The same applies to the processing flow from Figure 8 onwards.

[0060] Next, the stirring control unit 36 ​​detects the ink temperature of the ink tank 51 using the main thermometer 53 (step S40). If the ink temperature is below a threshold (step S41: Yes), the stirring control unit 36 ​​changes the stirring conditions (step S42) and starts stirring (step S45). The stirring conditions refer to the stirring rotation speed and stirring time. If the ink temperature exceeds the threshold (step S41: No), the stirring control unit 36 ​​starts stirring with the initial stirring conditions without changing the stirring conditions (step S45). When determining whether the ink temperature is below the threshold (step S41), it is preferable to determine this by checking whether the ink temperature remains below the threshold for a predetermined period of time.

[0061] The stirring control unit 36 ​​performs stirring under the changed stirring conditions or the initial stirring conditions, and when a predetermined stirring time has elapsed (step S46), it returns the stirring conditions to the initial settings (step S62). If stirring control is to be continued (step S64: No), the process returns to the ink temperature detection process in step S40 and is repeated. If stirring control is to be terminated (step S64: Yes), the process in Figure 6 is terminated. Note that the processing flow S1A in Figure 6 is common to both the first modified example, in which the ambient temperature is detected by the ambient temperature gauge 55, and the second modified example, in which the ink temperature of the sub-tank 22 is detected by the auxiliary thermometer 25.

[0062] Next, the process flow for initial setting of the stirring conditions (step S20) will be explained with reference to Figure 7. Figure 7 corresponds to the fourth modified example and is an example of a process in which the stirring conditions are changed when the ink color is white, and the normal stirring conditions are used for other colors. First, the stirring control unit 36 ​​checks whether to set stirring conditions for each ink tank. If it does not set conditions (step S21: No), it sets the normal stirring conditions for all ink tanks (step S22), and the process shown in Figure 7 is completed.

[0063] When setting stirring conditions for each ink tank (Step S21: Yes), the stirring control unit 36 ​​selects one ink tank 51 (Step S23) and obtains the ink color information for that ink tank 51 (Step S24). If the ink color is white (Step S25: Yes), it sets the stirring conditions to white (Step S27); otherwise, it sets the stirring conditions to normal (Step S26). This is repeated until there are no unset ink tanks 51 (Step S28), and the process in Figure 7 is completed.

[0064] Next, in the first embodiment, the process flow S1B for changing the stirring conditions immediately after startup will be explained with reference to Figure 8. In process flow S1B, the stirring control unit 36 ​​changes the stirring conditions for the first stirring after startup based on the detected temperature, and thereafter stirs with the initial stirring conditions. Similar to the processing flow S1A in Figure 6, when the image forming apparatus 1 is started (step S10), the stirring control unit 36 ​​performs initial settings for the stirring conditions (step S20).

[0065] Next, the stirring control unit 36 ​​detects the ink temperature of the ink tank 51 using the main thermometer 53 (step S40). If the ink temperature is below a threshold (step S41: Yes), the stirring control unit 36 ​​changes the stirring conditions (step S42A) and starts the first stirring (step S45A). After a predetermined stirring time has elapsed (step S46A), the stirring control unit 36 ​​finishes the first stirring (step S47A), and after a predetermined time interval set as the time interval until the second stirring has elapsed (step S60A), it starts stirring with the initial stirring conditions (step S62A) (step S45). Then, when a predetermined time corresponding to the stirring time has elapsed (step S46), stirring is terminated (step S47). After a predetermined time set as the time interval until the next stirring has elapsed (step S60), the stirring control unit 36 ​​returns to starting stirring under the initial stirring conditions (step S45) and repeats if it wants to continue stirring control (step S64: No). If it wants to terminate stirring control (step S64: Yes), the process in Figure 8 is terminated.

[0066] If the ink temperature exceeds the threshold (Step S41: No), the stirring control unit 36 ​​starts stirring under the initial stirring conditions without changing the stirring conditions (Step S45). Thereafter, until stirring control is terminated (Step S64: Yes), the process returns to starting stirring (Step S45) and repeats stirring under the initial stirring conditions. In the process flow S1B shown in Figure 8, if the ink temperature immediately after startup is below the threshold, the stirring conditions are changed only for the first stirring, and the initial stirring conditions are used for subsequent stirrings. If the ink temperature immediately after startup exceeds the threshold, the stirring conditions are not changed, and stirring is performed using the initial stirring conditions from the first stirring onwards.

[0067] Next, the processing flow S1C for detecting the standing time will be explained with reference to Figure 9. In processing flow S1C, the stirring control unit 36 ​​changes the stirring conditions for the first stirring after startup based on the standing time, and thereafter stirs with the initial stirring conditions. Similar to the processing flow S1A in Figure 6, when the image forming apparatus 1 is started (step S10), the stirring control unit 36 ​​performs initial settings for the stirring conditions (step S20).

[0068] Next, the stirring control unit 36 ​​calculates the time from the shutdown to the startup of the image forming apparatus 1 as the time during which stirring was not performed, i.e., the standing time. If the standing time exceeds a threshold (step S30: Yes), the stirring control unit 36 ​​changes the stirring conditions (step S42A) and starts the first stirring (step S45A). The subsequent processing is the same as the processing flow S1B in Figure 8. Furthermore, if the standing time is below the threshold (step S30: No), the stirring control unit 36 ​​starts stirring with the initial stirring conditions without changing the stirring conditions (step S45). Thereafter, until stirring control is terminated (step S64: Yes), it returns to starting stirring (step S45) and repeats stirring with the initial stirring conditions. If stirring control is terminated (step S64: Yes), the process shown in Figure 9 ends.

[0069] Next, the process flow S1D for detecting the remaining ink level during agitation will be explained with reference to Figure 10. The process flow S1D in Figure 10 corresponds to the third modified example. First, when the image forming apparatus 1 is started up (step S10), the stirring control unit 36 ​​performs initial settings for the stirring conditions (step S20).

[0070] Next, the stirring control unit 36 ​​detects the remaining ink level in the ink tank 51 (step S50). If the remaining ink level exceeds a threshold (step S51: Yes), the stirring control unit 36 ​​changes the stirring conditions (step S52) and starts stirring (step S45). The stirring conditions, such as the stirring rotation speed and stirring time, can be set to different values ​​than those used to detect the ink temperature. If the ink temperature exceeds the threshold (step S51: No), the stirring control unit 36 ​​starts stirring with the initial stirring conditions without changing the stirring conditions (step S45). When determining whether the remaining ink level is below the threshold (step S41), it is preferable to make the determination by repeatedly checking that it is below the threshold over multiple measurements.

[0071] The stirring control unit 36 ​​performs stirring under the changed stirring conditions or the initial stirring conditions, and when a predetermined stirring time has elapsed (step S46), it returns the stirring conditions to the initial settings (step S62). If stirring control is to be continued (step S64: No), the process returns to the ink remaining amount detection process in step S50 and is repeated. If stirring control is to be terminated (step S64: Yes), the process in Figure 10 is terminated.

[0072] Next, the stirring process flow S1E when detecting the stirring torque will be explained with reference to Figure 11. The process flow S1E in Figure 11 corresponds to the fifth modified example. First, when the image forming apparatus 1 is started (step S10), the stirring control unit 36 ​​performs initial settings for stirring conditions (step S20), starts stirring (step S45), and starts measuring the torque of the stirring motor 522 (step S55). If the torque is below a predetermined threshold (step S56: No), stirring continues until the stirring time under the initial stirring conditions has elapsed. If the torque exceeds a predetermined threshold (step S56: Yes), the stirring conditions are changed (step S57), and stirring is performed until the stirring time under the changed stirring conditions has elapsed.

[0073] When stirring is completed under the initial stirring conditions or the modified stirring conditions (step S58), the stirring control unit 36 ​​returns the stirring conditions to the initial settings (step S62) after a predetermined time interval set as the time interval until the next stirring has elapsed (step S60). If the stirring control unit 36 ​​decides to continue stirring control (step S64: No), it returns to the start of stirring (step S45) and repeats. If it decides to terminate stirring control (step S64: Yes), the process shown in Figure 11 ends.

[0074] [Second Embodiment] Next, an image forming apparatus 2 according to the second embodiment will be described. The second embodiment differs from the first embodiment in that the liquid is delivered under liquid delivery conditions corresponding to the state of the ink in the ink tank 51, and stirring is performed under normal stirring conditions; otherwise, it is the same. Note that the state of the ink is, for example, viscosity, which changes depending on the ink temperature, standing time, ink color, etc. The image forming apparatus 2 controls the ink supply control unit 37 to supply ink to the ink supply unit 60 according to the ink supply conditions corresponding to the state of the ink in the ink tank 51.

[0075] For example, the ink supply control unit 37 changes the ink supply conditions to conditions suitable for ink that has become highly viscous due to the temperature drop when the temperature of the ink in the ink tank 51 remains below a predetermined threshold for a predetermined period of time. Changing the ink delivery conditions refers to making a temporary change to the ink delivery conditions that are already set as the normal delivery conditions. The normal delivery conditions are those that are carried over from the last operation or that are initially set when the image forming apparatus 2 is started up.

[0076] Here, the supply pump 61 is air-driven, and the amount of ink delivered per unit time can be increased by increasing the air pressure. The liquid delivery conditions refer to the settings for the air pressure or liquid delivery time of the supply pump 61 in the liquid delivery unit 60. The liquid delivery time is the time during which the supply pump 61 is driven, the valve 62 is opened, and liquid delivery continues. The image forming apparatus 2 can compensate for the decrease in the amount of ink dispensed due to high viscosity, for example, when the ink in the ink tank 51 is high viscosity, by increasing the air pressure or extending the liquid dispense time. However, increasing both the air pressure and the liquid dispense time may result in an excessive amount of liquid dispensed, so it is sufficient to increase only one of them. When increasing the air pressure and extending the liquid dispense time, care should be taken to set the liquid dispense conditions so that overflow does not occur in the sub-tank 22.

[0077] The liquid supply control unit 37 can change the liquid supply conditions if the ink temperature in the ink tank 51 is below a predetermined threshold for a predetermined period of time. The liquid supply control unit 37 can also change the liquid supply conditions if the ink temperature in the ink tank 51 at startup is below a predetermined threshold. The liquid supply control unit 37 may also change the liquid supply conditions if the ambient temperature is below a predetermined threshold. Furthermore, the liquid supply control unit 37 can change the liquid supply conditions according to the ink color of the ink tank 51. In addition, the liquid supply control unit 37 can set the liquid supply conditions when the ink color of the ink tank 51 is white to be different from the liquid supply conditions when the ink color of the ink tank 51 is anything other than white.

[0078] The image forming apparatus 2 according to the second embodiment can suppress the occurrence of ink supply failures due to high viscosity, thereby improving profitability and image forming quality. In inkjet-type image forming apparatuses, UV inks that cure with ultraviolet (UV) light are sometimes used. UV inks exhibit significant viscosity changes with temperature. The viscosity tends to be low at high temperatures and high at low temperatures, and at low temperatures in particular, the increased viscosity can reduce the amount of ink delivered by the ink delivery pump, which is a problem. The image forming apparatus 2 can compensate for the decrease in the amount of ink delivered to the discharge unit 21 by increasing the air pressure of the supply pump 61 or extending the delivery time. Furthermore, the liquid delivery conditions can be set separately for each ink tank 51.

[0079] Next, the process flow S2 for supplying ink to the ink tank in the image forming apparatus 2 will be explained with reference to Figure 12. Figure 12 shows the process flow when the ink temperature is detected by the main thermometer 53 as an indicator of the state of the ink in the ink tank 51. First, when the image forming apparatus 2 is started (step S10), the liquid delivery control unit 37 performs initial settings for the liquid delivery conditions (step S70). Step S70 will be described later. Step S70 can be skipped, in which case the initial settings from the previous operation will be carried over. Although not shown in Figure 12, after startup, stirring is performed by the stirring control unit 36.

[0080] The liquid delivery control unit 37 detects the ink temperature with the main thermometer 53 (step S81). If the ink temperature is not below a threshold (step S82: No), it repeats detecting the ink temperature with the main thermometer 53 (step S81). Preferably, the temperature is determined to be above a predetermined threshold if the detected temperature exceeds a predetermined threshold for a predetermined period of time. If it is detected that the ink temperature is below a threshold (Step S82: Yes), the liquid delivery control unit 37 changes the liquid delivery conditions (Step S83). Here, the liquid delivery conditions are either the liquid delivery time or the air pressure of the supply pump 61, which are determined in the subsequent process. If the air pressure of the supply pump 61 is increased (Step S84: Yes), the liquid delivery control unit 37 does not change the liquid delivery time and sets it to the initial setting (Step S86). If the air pressure is not increased (Step S84: No), the liquid delivery control unit 37 sets it to an extended liquid delivery time (Step S85).

[0081] The liquid delivery control unit 37 detects the ink temperature with the main thermometer 53 (step S87). If the ink temperature exceeds the threshold (step S88: Yes), it returns the liquid delivery conditions to the initially set conditions (step S89) and returns to step S81 to detect the ink temperature with the main thermometer. If the ink temperature does not exceed the threshold (step S88: No), it continues the changed liquid delivery conditions and returns to step S87 to repeat the detection of the ink temperature with the main thermometer. The liquid delivery control unit 37 delivers liquid to the sub-tank 22 according to the liquid delivery conditions at that time, in response to a liquid delivery request.

[0082] Next, the process flow for initializing the liquid delivery conditions (step S70) will be explained with reference to Figure 13. Figure 13 shows an example of a process in which the liquid delivery conditions are changed when the ink color is white, and the normal liquid delivery conditions are used for other colors. First, the liquid supply control unit 37 checks whether to set liquid supply conditions for each ink tank. If it does not set conditions (step S71: No), it sets the normal liquid supply conditions for all ink tanks (step S72), and the process shown in Figure 13 is completed.

[0083] When setting ink supply conditions for each ink tank (Step S71: Yes), the ink supply control unit 37 selects one ink tank 51 (Step S73) and obtains the ink color information of that ink tank 51 (Step S74). If the ink color is white (Step S75: Yes), it sets the ink supply conditions to white (Step S77); otherwise, it sets the conditions to normal (Step S76). This is repeated until there are no more unset ink tanks 51 (Step S78), and the process in Figure 13 is completed.

[0084] Furthermore, the second embodiment can be combined with one or more of the first embodiment and its modifications. If the stirring and liquid delivery conditions are fixed to account for the high viscosity state at low temperatures, as in conventional image forming apparatuses, it can lead to problems such as decreased productivity due to extended stirring and liquid delivery times, negative impacts on degassing due to excessive foaming, and ink overflow due to excessive liquid delivery. The second embodiment, when combined with the first embodiment and its modifications, that is, by controlling the stirring conditions and liquid delivery conditions according to the state of the ink, allows for more appropriate setting of the stirring motor's rotation speed, stirring time, liquid delivery volume, etc., according to the ink color, temperature, remaining ink amount, standing time, etc., in the ink tank. This makes it possible to further stabilize ink stirring and liquid delivery, and improve the quality of image formation.

[0085] [Control Method] The control method according to this embodiment is a method for operating an image forming apparatus as an image forming apparatus according to this embodiment. The control method is a control method for an image forming apparatus comprising an ink tank for storing ink to be supplied to an inkjet head, and a stirring unit for stirring the ink in the ink tank, the method comprising the step of a stirring control unit controlling the stirring unit with stirring conditions corresponding to the temperature and color of the ink in the ink tank.

[0086] The control method is a control method for an image forming apparatus comprising an ink tank for storing ink to be supplied to an inkjet head, and a liquid supply unit for supplying ink from the ink tank to the inkjet head, and includes the step of controlling the liquid supply control unit to supply ink to the liquid supply unit under liquid supply conditions corresponding to the temperature and color of the ink in the ink tank.

[0087] [Control Program] The control program according to this embodiment is a program that is loaded into the control unit of the image forming apparatus to cause the image forming apparatus to function as the image forming apparatus according to this embodiment. The control program causes an image forming apparatus, which includes an ink tank for storing ink to be delivered to an inkjet head and an agitator for agitating the ink in the ink tank, to execute a procedure for acquiring the temperature and color of the ink in the ink tank, and a procedure for agitating the ink in the agitator under agitation conditions corresponding to the temperature and color of the ink.

[0088] Furthermore, the control program causes an image forming apparatus, which includes an ink tank for storing ink to be delivered to an inkjet head and a liquid delivery unit for delivering ink from the ink tank to the inkjet head, to execute a procedure for acquiring the temperature and color of the ink in the ink tank, and a procedure for delivering ink to the liquid delivery unit according to the liquid delivery conditions corresponding to the temperature and color of the ink.

[0089] The image forming apparatus may be controlled by a computer loaded with a control program. The control program can be obtained via telecommunications lines and recorded on a computer-readable recording medium. [Explanation of Symbols]

[0090] 1. Image forming apparatus 10 Paper feed section 20 Image forming unit 21 Discharge part 22 Sub-tanks 23 Inkjet heads 24 Heating section 25 Sub-thermometer 30 Control Unit 35 Ink supply control unit 36 Stirring control unit 37. Fluid delivery control unit 38 Heating control unit 40 Output section 50 Storage section 51 Ink Tanks 52 Stirring section 521 Agitation screw 522 Stirring motor 53 Main thermometer 60 Liquid delivery section 80 Control section

Claims

1. An ink tank that stores the ink that is supplied to the inkjet head, A stirring unit for stirring the ink in the aforementioned ink tank, A stirring control unit controls the stirring of the ink in the stirring section according to stirring conditions corresponding to the state of the ink in the ink tank, An image forming apparatus equipped with the following features.

2. Equipped with means for detecting temperature, The stirring control unit changes the stirring conditions when the detected temperature is below a predetermined threshold. The image forming apparatus according to claim 1.

3. The stirring control unit changes the stirring conditions when the detected temperature is below the threshold for a predetermined period of time. The image forming apparatus according to claim 2.

4. The system includes a main thermometer for detecting the temperature of the ink in the aforementioned ink tank, The stirring control unit changes the stirring conditions according to the temperature of the ink in the ink tank. The image forming apparatus according to claim 2.

5. The main thermometer detects the temperature of the ink by contacting it. The image forming apparatus according to claim 4.

6. The main thermometer detects the temperature of the ink without contacting it. The image forming apparatus according to claim 4.

7. The main thermometer is installed at a height where it will not be exposed to ink splashes. The image forming apparatus according to claim 6.

8. A sub-tank is further provided downstream of the aforementioned ink tank, which has a secondary thermometer for detecting the temperature of the ink. The stirring control unit changes the stirring conditions according to the temperature of the ink in the sub-tank. The image forming apparatus according to claim 2.

9. Equipped with an outside temperature sensor to detect the outside temperature, The stirring control unit changes the stirring conditions according to the ambient temperature. The image forming apparatus according to claim 2.

10. The system includes a remaining ink level detection unit that detects the remaining amount of ink in the ink tank, The stirring control unit changes the stirring conditions based on the amount of ink remaining in the ink tank detected by the remaining amount detection unit. The image forming apparatus according to claim 1.

11. The stirring unit is equipped with a torque meter that detects the torque used to stir the ink, The stirring conditions are changed by the torque. The image forming apparatus according to claim 1.

12. The stirring control unit calculates the time elapsed during which the ink has not been stirred, If the aforementioned standing time exceeds a predetermined length, the stirring conditions are changed. The image forming apparatus according to claim 1.

13. The stirring control unit changes the stirring conditions according to the ink color of the ink tank. The image forming apparatus according to claim 1.

14. The stirring control unit sets the stirring conditions when the ink color of the ink tank is white to be different from the stirring conditions when the ink color of the ink tank is anything other than white. The image forming apparatus according to claim 13.

15. The stirring conditions are the rotational speed or stirring time of the stirring unit. An image forming apparatus according to any one of claims 1 to 14.

16. The stirring control unit modifies the stirring conditions for stirring immediately after startup. An image forming apparatus according to any one of claims 1 to 12.

17. A liquid supply unit that supplies ink from the ink tank to the inkjet head, A liquid delivery control unit controls the delivery of ink to the liquid delivery unit under liquid delivery conditions corresponding to the state of the ink in the ink tank, The image forming apparatus according to claim 1, comprising:

18. Equipped with means for detecting temperature, The liquid delivery control unit changes the liquid delivery conditions when the detected temperature is below a predetermined threshold. The image forming apparatus according to claim 17.

19. The liquid delivery control unit changes the liquid delivery conditions when the detected temperature is below the threshold for a predetermined period of time. The image forming apparatus according to claim 18.

20. The system includes a main thermometer for detecting the temperature of the ink in the aforementioned ink tank, The liquid delivery control unit changes the liquid delivery conditions according to the temperature of the ink in the ink tank. The image forming apparatus according to claim 18.

21. A sub-tank is further provided downstream of the aforementioned ink tank, which has a secondary thermometer for detecting the temperature of the ink. The liquid delivery control unit changes the liquid delivery conditions according to the temperature of the ink in the sub-tank. The image forming apparatus according to claim 18.

22. Equipped with an outside temperature sensor to detect the outside temperature, The liquid delivery control unit changes the liquid delivery conditions according to the ambient temperature. The image forming apparatus according to claim 18.

23. The liquid supply control unit changes the liquid supply conditions according to the ink color of the ink tank. The image forming apparatus according to claim 17.

24. The aforementioned liquid delivery conditions are the air pressure or delivery time of the liquid delivery unit. An image forming apparatus according to any one of claims 17 to 23.

25. A control method for an image forming apparatus comprising an ink tank for storing ink to be supplied to an inkjet head, and a stirring unit for stirring the ink in the ink tank, The stirring control unit controls the stirring unit under stirring conditions corresponding to the temperature of the ink in the ink tank. A control method including

26. A control method for an image forming apparatus comprising an ink tank for storing ink to be supplied to an inkjet head, and a stirring unit for stirring the ink in the ink tank, The stirring control unit controls the stirring section according to stirring conditions corresponding to the color of the ink in the ink tank. A control method including

27. An image forming apparatus comprising an ink tank for storing ink to be supplied to an inkjet head, and a stirring unit for stirring the ink in the ink tank, A procedure for obtaining the temperature of the ink in the aforementioned ink tank, A procedure for stirring the ink in the stirring section under stirring conditions corresponding to the temperature of the ink, A control program to execute the program.

28. An image forming apparatus comprising an ink tank for storing ink to be supplied to an inkjet head, and a stirring unit for stirring the ink in the ink tank, A procedure for obtaining the color of the ink in the aforementioned ink tank, A procedure for stirring the ink in the stirring section under stirring conditions corresponding to the color of the ink, A control program to execute the program.

29. A control method for an image forming apparatus comprising an ink tank for storing ink to be supplied to an inkjet head, and a liquid supply unit for supplying ink from the ink tank to the inkjet head, The step of controlling the liquid supply control unit to supply ink to the liquid supply unit under liquid supply conditions corresponding to the temperature of the ink in the ink tank. A control method including

30. A control method for an image forming apparatus comprising an ink tank for storing ink to be supplied to an inkjet head, and a liquid supply unit for supplying ink from the ink tank to the inkjet head, The liquid supply control unit controls the liquid supply unit to supply ink according to the liquid supply conditions corresponding to the color of the ink in the ink tank. A control method including

31. An image forming apparatus comprising an ink tank for storing ink to be supplied to an inkjet head, and a liquid supply unit for supplying ink from the ink tank to the inkjet head, A procedure for obtaining the temperature of the ink in the aforementioned ink tank, A procedure for supplying ink to the liquid supply unit under liquid supply conditions corresponding to the temperature of the ink, A control program to execute the program.

32. An image forming apparatus comprising an ink tank for storing ink to be supplied to an inkjet head, and a liquid supply unit for supplying ink from the ink tank to the inkjet head, A procedure for obtaining the color of the ink in the aforementioned ink tank, A procedure for supplying ink to the liquid supply unit under liquid supply conditions corresponding to the color of the ink, A control program to execute the program.

Images