JP2007268891A - Ink-jet image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink-jet image forming device which is so good in operability that troubles including a failure of a recording head do not occur when operated by anyone. <P>SOLUTION: When a printer or the ink-jet image forming device is turned on, an ink level sensor 51 detects an ink level, and if the ink level detected by the ink level sensor 51 falls in a predetermined range, it is determined that the printer is in an ordinary activation state, i.e. the printer in a used state is turned on again. On the other hand, if the ink level detected by the ink level sensor 51 is below the predetermined range, it is determined that the printer is in an initial activation state, i.e. a sub-tank 52a of the printer is not filled with ink. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inkjet image forming apparatus that forms an image by ejecting ink from a recording head onto a recording medium.

  2. Description of the Related Art An inkjet recording type image forming apparatus (inkjet type image forming apparatus) that forms an image by discharging ink from a recording head (printing head) onto a recording medium such as paper is widely known. This inkjet image forming apparatus includes a type that forms an image while moving the recording head and the recording medium in directions orthogonal to each other, and a type that forms an image while moving only the recording medium with the recording head fixed (fixed type). ) In recent years, along with the widening of the recording head, there is an increasing tendency for fixed types that are advantageous for high-speed printing and downsizing of the apparatus.

  The above-described ink jet type image forming apparatus is also used in high-speed and large-scale printing as the ink jet recording system technology advances. When high-speed and large-scale printing is executed using an inkjet image forming apparatus, the amount of ink ejected from the recording head increases, so that the consumed ink also has a large capacity. For this reason, an ink tank that can accommodate a large volume of ink is required. Since it is difficult to design a large-capacity ink tank in the vicinity of the recording head, the large-capacity ink tank is often installed at an appropriate position away from the recording head. In such a case, ink is supplied from the ink tank to the recording head by a separately provided ink supply mechanism.

  As a mechanism for supplying ink from an ink tank to a recording head, a mechanism is known in which a sub tank for temporarily storing ink is disposed in the middle of an ink supply path. In this mechanism, ink is supplied to the recording head while adjusting an ink supply amount for supplying ink from the sub tank to the recording head, a negative pressure that acts on (applies to) an ink discharge port of the recording head, and the like.

  In the ink jet recording method described above, when gas (bubbles) is mixed in the ink in the recording head, the ink may not be normally discharged from the ink discharge port of the recording head. When a large amount of air bubbles is mixed in the ink in the recording head, there is a possibility that ink is not ejected from the ink ejection port (ink ejection is impossible). In order not to cause such a problem of ink ejection, it is desirable not to mix bubbles in the ink in the recording head.

As a technique for preventing air bubbles from being mixed into the ink in the recording head, a technique for removing bubbles from the ink in the recording head by continuously supplying ink to the recording head and circulating the ink between the recording head and the sub tank is known. It has been. In this technique, the ink is circulated by applying a pressure (ink supply pressure) to the ink by a known ink supply mechanism, and the ink is also supplied to the ink discharge port of the recording head by the ink supply pressure, together with the ink from the ink discharge port. The ink discharge ports are filled with ink by extruding bubbles. The operation of pushing out ink and bubbles from the ink discharge port and filling the ink discharge port with ink is called a recovery operation for performing stable ink discharge. The ink pushed out from the ink discharge port is stored in a cap arranged so as to cover the face surface on which the ink discharge port is formed, and returned to the sub tank or the like by a known suction and recovery mechanism. The ink returned in this way is reused as recycled ink (see, for example, Patent Document 1).
JP 2001-328283 A

  By the way, when the power of the ink jet type image forming apparatus is turned on (the main switch is turned on), the above recovery operation and the like are usually automatically executed in order to prepare for image formation (printing). ing. However, for example, in an unused inkjet image forming apparatus that is installed for the first time after shipment from a factory (initial installation), the supply tube of the ink supply mechanism and the recording head are not filled with ink. For this reason, if a recovery operation or the like is executed when the power is turned on, the print head is caused to perform an ink discharge operation without ink, which may cause trouble such as a failure of the print head. . In particular, if the image forming apparatus is a large industrial type and the position of the ink tank and the sub-tank, the position of the sub-tank and the recording head are separated, and the flow path is long, the flow path is not filled with ink. When ink is poured, bubbles are generated in the ink. When the bubbles reach the recording head, the bubble-like ink is pushed out from the nozzles of the recording head and bubbles further, and the ink does not fit in the cap disposed under the recording head and overflows. For this reason, the inside of the machine may be contaminated with ink or leak out of the machine.

  Such troubles can be avoided by determining whether or not the operator is in the initial installation and taking appropriate measures such as gradually filling the ink with time over the initial installation. However, in an industrial image forming apparatus, the recording head may be frequently changed, and a different operator may operate the inkjet image forming apparatus during shift work. It is inconvenient to determine whether the operator himself or herself is initially installed each time.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an easy-to-use inkjet image forming apparatus that does not cause troubles such as a recording head failure regardless of who is operated.

In order to achieve the above object, an inkjet image forming apparatus according to the present invention includes a subtank that stores ink supplied to a recording head that discharges ink, and forms an image by discharging ink from the recording head onto a recording medium. In the inkjet image forming apparatus,
(1) Based on the ink water level in the sub tank,
(1-1) The inkjet image forming apparatus has a normal startup state in which the ink water level is within a predetermined range, or
(1-2) It is characterized in that it is determined that the ink water level is any of an initial rising state that is different from the normal rising state and is less than the predetermined range.

here,
(2) The determination may be made when power is supplied to the inkjet image forming apparatus.

further,
(3) When the normal rising state is determined, a recovery operation for discharging the ink from the recording head and recovering the recording head may be executed.

Furthermore,
(4) When the initial rising state is determined, ink may be filled in the sub tank and an ink supply path from the sub tank to the recording head.

Furthermore,
(5) When it is determined that the initial start-up state is satisfied, only the sub tank may be filled with ink.

  The “normal start-up state” here means a state in which the power of an already-used (in use) inkjet image forming apparatus is turned off (main switch is turned off) and turned on again. Say. The “initial startup state” means, for example, a state of an unused inkjet image forming apparatus that has been installed (initial installation) for the first time after shipment from the factory, or a new supply tube or sub tank of the ink supply mechanism. This is the state when the ink is replaced, and is the state where the ink is not filled in the supply tube or sub tank of the ink supply mechanism.

  According to the present invention, it is determined whether the inkjet image forming apparatus itself is in a normal startup state or an initial startup state based on the ink water level in the sub tank. A user-friendly device can be obtained.

  The present invention has been realized in an ink jet printer that forms an image by ejecting ink from a recording head onto a recording medium.

  A printer to which the present invention is applied will be described with reference to FIGS. 1 and 2.

  FIG. 1 is a front view showing a schematic configuration of a printer as an example of an ink jet image forming apparatus to which the present invention is applied. FIG. 2 is a perspective view showing a schematic configuration of the printer of FIG.

  The printer 10 includes an image forming unit (recording head unit) 20 on which recording heads 12a, 12b, 12c, 12d, 12e, and 12f for forming an image by ejecting ink onto a recording medium such as recording paper, and a recording. And a transport unit 40 that transports the medium in the direction of arrow A (recording medium transport direction). Black, cyan, light cyan, magenta, light magenta, and yellow ink are ejected from the recording heads 12a, 12b, 12c, 12d, 12e, and 12f, respectively. The image forming unit 20 includes a head up / down motor 118 (see FIG. 5) that moves the recording heads 12a to 12f to a cap position, a printing position, and a wipe position. The image forming unit 20 is fixed to a plate-like engine base 30 and moves up and down (up and down) together with the engine base 30 as will be described later.

  The engine base 30 to which the image forming unit 20 is fixed has a rectangular shape, and its four corners are fixed to nuts 32. These nuts 32 are fitted into a screw shaft 34, and the nut 32 moves up and down as the screw shaft 34 rotates. Sprockets 36 are fixed to the lower portions of the four screw shafts 34, and a chain 38 is stretched around these four sprockets 36. By rotating the chain 38 with a drive motor (not shown), the screw shaft 34 rotates in synchronism, and the image forming unit 20 moves up and down together with the engine base 30.

  The transport unit 40 includes four transport belts 42 that allow the recording medium to pass under the image forming unit 20. The conveyor belt 42 is stretched around driven rollers 44, 45, 46, an encoder roller 47, and a driving roller 48, and tension is applied by a tensioner 49. The conveying belt 42 is configured to rotate in the recording medium conveying direction (arrow A direction) by rotating the driving roller 48 by a timing belt 43 that rotates around the driving motor 41.

  In addition, the printer 10 includes an ink supply unit 50 that supplies ink to the image forming unit 20. Inside the ink supply unit 50, sub tanks 52a to 52f storing ink supplied to the recording heads 12a to 12f, an ink tank 53a storing ink supplied to the sub tanks 52a to 52f, and the like (FIG. 4). Reference) is arranged. Each ink tank and each sub tank 52a to 52f are connected by a tube 56 (see FIG. 4), and ink is supplied from each ink tank 53a to each sub tank 52a. The ink supply unit 50 to the image forming unit 20 are detachably connected (connected) by an ink flow path formed by bundling the ink supply tubes 60a to 60f and the ink regression tubes 62a to 62f. Ink supplied from the sub tanks 52a to 52f to the recording heads 12a to 12f passes through the ink supply tubes 60a to 60f. Ink that returns (returns) from the recording heads 12a to 12f to the sub tanks 52a to 52f passes through the ink return tubes 62a to 62f. The image forming unit 20 incorporates a recovery unit 22 (see FIG. 4) that recovers the ink ejection state from the recording heads 12a to 12f to the initial state.

  The connection between the image forming unit 20 and the ink supply unit 50 will be described with reference to FIG.

  FIG. 3 is a perspective view showing an ink supply tube and an ink return tube in which the image forming unit and the ink supply unit are connected.

  The image forming unit 20 includes recording heads 12a to 12f (see FIG. 1) in which ink discharge ports corresponding to the width of the recording image are formed side by side. Each of the recording heads 12a to 12f is mounted so that each row of ink discharge ports is sequentially arranged in a direction orthogonal to the recording medium conveyance direction (the direction of arrow A in FIG. 1). When forming a full-color image, each of the recording heads 12a to 12f ejects black, cyan, light cyan, magenta, light magenta, and yellow ink from the upstream side in the recording medium conveyance direction (upstream side in the arrow A direction), respectively. The ink supply unit 50 is arranged away from the image forming unit 20, and the sub tanks 52a to 52f of the ink supply unit 50 and the recording heads 12a to 12f of the image forming unit 20 are connected to the ink supply tubes 60a to 60f and the ink regression. They are connected by tubes 62a to 62f.

  The ink flow paths of the image forming unit 20 and the ink supply unit 50 will be described with reference to FIG.

  FIG. 4 is a schematic diagram showing the ink flow paths of the image forming unit and the ink supply unit. Here, the recording head 12a and the sub tank 52a are taken as an example, but the same applies to the other recording heads 12b to 12f.

  The ink tank 53a in which black ink is stored is connected to the sub tank 52a by an ink suction tube 56, and a suction pump 58 that sucks ink from the ink tank 53a and sends it to the sub tank 52a in the middle of the ink suction tube 56. Is arranged. In the state shown in FIG. 4, the valves 81, 85 are closed, the valves 82, 83, 84 are opened and the suction pump 58 is driven, whereby the ink in the ink tank 53a is sucked and sent to the sub tank 52a. Two sets of ink tanks 53a are mounted so as not to run out of ink during printing. When ink in one of the ink tanks 53a runs out, the valves 83, 84, 85, and 86 are switched appropriately. The suction tube 56 is connected to the other ink tank 53a.

  The inside of the sub tank 52a is connected to the atmosphere communication hole 88a. By opening the valve 88, the inside of the sub tank 52a is connected to the outside air and becomes atmospheric pressure. In addition, an ink water level sensor (liquid level detection sensor) 51 including electrodes 51a, 51b, 51c for detecting the presence or absence of ink and the ink water level is attached to the sub tank 52a. The presence or absence of ink is detected based on the change in resistance between these electrodes 51a, 51b and 51c, and the ink water level is controlled to be always constant. The sub-tank 52a and the recording head 12a are arranged at a position where an optimum negative pressure is applied to the ink discharge port of the recording head 12a due to a water head difference.

  The sub tank 52a and the recording head 12a are connected by an ink supply tube 60a and an ink return tube 62a so that ink can be circulated between them. The sub tank 52a and the ink supply tube 60a are connected via an ink supply pump 59. By driving the ink supply pump 59, the ink in the sub tank 52a is supplied to the recording head 12a. A recovery unit 22 is located below the recording head 12a, and the ink pushed out of the recording head 12a is received by the recovery unit 22. The recovery unit 22 and the sub tank 52a are connected by a part of the ink recovery tube 57 and the ink suction tube 56, and the ink received by the recovery unit 22 by driving the suction pump 58 by closing the valve 82 and opening the valve 81. Is collected in the sub tank 52a.

  An ink initial filling operation for filling the recording heads 12a to 12f from the ink tanks 53a and the like when the printer 10 is newly installed will be described.

  The initial ink filling operation is executed when the printer 10 is determined to be in the initial startup state. This determination will be described later. When the printer 10 is in the initial startup state, the sub tank 52a, the ink suction tube 56, the ink supply tube 60a, the ink return tube 62a, and the recording head 12a have no ink. In the initial ink filling operation, either the sub tank 52a, the ink supply tube 60a, and the ink return tube 62a are filled with ink, or only the sub tank 52a is filled with ink.

  In the ink filling operation of filling the sub tank 52a, the ink supply tube 60a, and the ink return tube 62a with ink, the ink supply tube 60a and the recording head 12a are disconnected before supplying ink from the sub tank 52a to the recording head 12a. The sub tank 52a and the ink supply tube 60a are filled with ink from the main tank 53a. Thereafter, the ink supply tube 60a is connected to the recording head 12a, and the ink in the ink supply tube 60a is supplied to the recording head 12a. The face surface 12as to which the ink is attached is wiped off by the cleaning blade 22b as will be described later after the completion of the initial ink filling operation.

  In order to leave the ink supply tube 60a and the recording head 12a unconnected and fill the ink supply tube 60a with ink, one end portion 60at of the ink supply tube 60a and one end portion 62at of the ink return tube 62a are directly or indirectly connected. And the ink supply pumps 58 and 59 are driven, and the ink is circulated between the main tank 53a through the sub tank 52a, the ink supply tube 60a, and the ink return tube 62a. As a result, the air present in the ink supply tube 60a is replaced with ink, and the ink supply tube 60a is almost filled with ink. Subsequently, the connection between the ink supply tube 60a and the ink return tube 62a is released, the ink supply tube 60a is connected to the recording head 12a, and the ink in the ink supply tube 60a is supplied to the recording head 12a. Thereby, air does not enter the recording head 12a from the ink supply tube 60a. As a result, the generation of bubbles in the recording head 12a is suppressed, so that when ink is pushed out from the recording head 12a to the cap 22a, the ink is not pushed out together with a large amount of bubbles, and ink leakage from the cap 22a is prevented. it can. As described above, in the initial ink filling operation, only the sub tank 52a may be filled with ink from the ink tank 53a. In this case, the valves 81 and 87 are closed and the valve 82 is opened, and the suction pump 58 is driven.

  The electrical system of the printer 10 will be described with reference to FIG.

  FIG. 5 is a block diagram showing an electrical system of the printer of FIG.

  Recording data and commands transmitted from the host PC 11 are received by the CPU 100 via the interface controller 102. The CPU 100 is an arithmetic processing unit that performs overall control such as reception of recording data and recording operation in the printer 10. After analyzing the received command, the CPU 100 renders the image data of each color component of the recording data by developing a bitmap on the image memory 106. As an operation process before recording, the capping motor 122 and the head up / down motor 118 are driven via the input / output port 114 and the motor driving unit 116, and the recording heads 12a to 12f are separated from the cap 22a (see FIG. 6). Move to the recording position (image forming position).

  Subsequently, the front end position of the recording medium is detected by a front end detection sensor (not shown) for determining the timing (recording timing) at which ink starts to be ejected onto the conveyed recording medium. Thereafter, in synchronization with the conveyance of the recording medium by the output signal from the encoder roller 47 (see FIG. 1), the CPU 100 sequentially reads the recording data of the corresponding color from the image memory 106, and the read data is read from each recording head 12a. To 12 f via the recording head control circuit 112.

  The operation of the CPU 100 is executed based on a processing program stored in the program ROM 104. The program ROM 104 stores processing programs and tables corresponding to the control flow. A work RAM 108 is used as a working memory. During the cleaning and recovery operations of the recording heads 12a to 12f, the CPU 100 controls the pressurization and suction of ink by driving the pump motor 124 via the input / output port 114 and the motor drive unit 116.

  The print preparation work of the printer 10 will be described with reference to FIGS.

  FIG. 6 is a schematic diagram showing the state of the recording head during print preparation. FIG. 7 is a schematic diagram showing a procedure for wiping ink from the ink ejection surface, (a) showing before the start of wiping, (b) showing immediately after wiping is finished, and (c) showing standby after wiping is finished. Indicates the state.

  The print preparation work of the printer 10 is executed when the printer 10 is determined to be in a normal startup state. This determination will be described later. When the printer 10 is turned on (the main switch is turned on) and the printer 10 is determined to be in a normal startup state by a method described later, the ink water level in the sub tank 52a is set to a predetermined value described later. It is within the range (the sub tank 52a is filled with ink within a certain range). In the normal start-up state, as shown in FIG. 6, the print preparation work is performed with the ink guide 22c arranged in the cap 22a of the recovery unit 22 being brought close to the face surface 12as.

  When this print preparation work is performed, the valves 81, 87, 88 (see FIG. 4) are opened, the valve 82 is closed, and the ink supply pump 59 (see FIG. 4) is driven. Thus, the ink in the sub tank 52a is supplied to the recording head 12a through the ink supply tube 60a (see FIG. 4). The ink supplied to the recording head 12a returns (returns) to the sub tank 52a through the ink return tube 62a (see FIG. 4). For this reason, the ink circulates between the sub tank 52a and the recording head 12a, and the nozzles of the recording head 12a are filled with the ink. For this reason, even if thickened ink or bubbles are present in the nozzles of the recording head 12a, these are pushed out together with the ink from the nozzles. In the state where these are pushed out, the ink adheres to the face surface 12as and becomes dirty. In order to remove the dirt, the face surface 12as of the recording head 12a is cleaned as shown in FIG.

  In cleaning the face surface 12as, the face surface 12as is wiped with a wiper 22b fixed to the capping mechanism 22, as shown in FIG. In this operation, first, as shown in FIG. 7A, the recording head 12a moves above the recovery cap 22a. Subsequently, as the recovery cap 22a moves in the direction of arrow B, as shown in FIG. 7B, dirt such as ink adhering to the face surface 12as is wiped off by the wiper 22b. This operation is called a wiping operation. After the wiping operation is completed, as shown in FIG. 7C, the capping mechanism 22 moves to the side of the recording head 12a and is ready to print on the recording medium.

  An ink water level sensor that detects the ink water level in the sub tank will be described with reference to FIGS. FIG. 8 is a side view schematically showing the inside of the sub tank without ink. FIG. 9 is a side view schematically showing the inside of the sub tank in which a small amount of ink is stored. FIG. 10 is a side view schematically showing the inside of the sub tank in which the upper limit amount of ink within the predetermined range according to the present invention is stored. FIG. 11 is a side view schematically showing the inside of the sub tank in which the lower limit amount of ink within the predetermined range according to the present invention is stored. In these drawings, the same components as those shown in FIG. 4 are denoted by the same reference numerals.

  An ink water level sensor (liquid level detection sensor) 51 including electrodes 51a, 51b, and 51c for detecting the presence / absence of ink and the ink water level is attached to the sub tank 52a. The presence or absence of ink is detected based on the change in resistance between these electrodes 51a, 51b and 51c, and the ink water level is controlled to be always constant. When there is no ink in the sub tank 52a, the resistance between the three electrodes 51a, 51b, 51c is infinite as shown in FIG.

  In order to supply ink from the ink tank 53a to the sub tank 52a, the valve 81 (see FIG. 4) is closed, the valve 82 is opened, and the suction pump 58 is driven. When a small amount of ink is stored in the sub tank 52a, the ink contacts the electrode 51a and the electrode 51b as shown in FIG. 9, but the ink does not contact the electrode 51c. In this case, the resistance between the electrode 51a and the electrode 51b becomes a predetermined value corresponding to the type of ink from infinity (the resistance value is smaller than that in the case of FIG. 8), so this resistance value is detected. Thus, it is detected that a small amount of ink has accumulated in the sub tank 52a. That is, the ink water level of a small amount of ink is detected. When the ink amount increases from the state shown in FIG. 9 and reaches the ink amount shown in FIG. 10, the resistance between the electrodes 51a and 51b and the electrode 51c changes from infinity to a predetermined value corresponding to the type of ink. (The resistance value is smaller than in the case of FIG. 9). From this change in resistance value, it is detected that the upper limit amount of ink within the predetermined range according to the present invention is stored in the sub tank 52a. The detection signal is transmitted to the motor driving unit 116 via the input / output port 114 as shown in FIG. 5, and the suction pump 58 (see FIG. 4) is stopped (or driven) by the control of the motor driving unit 116. ).

  Even during printing, the ink water level sensor 51 continues to detect the ink water level in the sub tank 52a. The ink in the sub tank 52a is consumed by the ink ejection from the recording head 12a (see FIG. 4 etc.), the contact between the ink and the electrode 51c is lost as shown in FIG. 11, and the resistance between the electrodes 51a, 51b and the electrode 51c is reduced. Change (from the predetermined value to infinity). Accordingly, the ink water level sensor 51 detects that the ink water level in the sub tank 52a has dropped below the upper limit amount within a predetermined range. In this state, when a predetermined number of inks (equivalent to 10 g) are ejected from the recording head 12a and the ink level drops to L shown in FIG. 9, the suction pump 58 (see FIG. 4) is driven to set the ink tank. Ink is supplied (supplemented) from 53a to the sub tank 52a. At the end of printing, the ink is replenished to the maximum shown in FIG. 10. Therefore, when the printer 10 is turned on, the water level in the sub tank 6 is the maximum (upper limit) shown in FIG. The range L shown in FIG. 9 is a value determined in advance according to the capacity of the sub tank 52a and the like, and is stored in the CPU 100 (see FIG. 5). A signal carrying the ink level detected by the ink level sensor 51 is sent to the CPU 100 (see FIG. 5) via the input / output port 114 and compared with the above range L.

  In the printer 10 that has already been used, at the end of printing, the sub tank 52a is replenished with ink up to the maximum shown in FIG. Accordingly, when the main switch is turned off after the printer 10 has finished printing and then the main switch is turned on (this is an example of a normal start-up state according to the present invention), ink is stored in the sub tank 52a to the maximum extent. ing. On the other hand, for example, an unused printer 10 that has been installed (initially installed) for the first time after shipment from the factory, or a printer when the ink supply tube 60a (see FIG. 4 etc.), the ink return tube 62a, and the sub tank 52a are replaced with new ones. In FIG. 10, the ink supply tube 60a, the ink return tube 62a, and the sub tank 52a are not filled with ink (this is an example of the initial rising state according to the present invention, for example, the state shown in FIG. 8).

  10 is stored in the program ROM 104 (see FIG. 5) so that the ink water level sensor 51 detects the ink water level when the printer 10 is turned on, and the ink water level detected by the ink water level sensor 51 is the maximum shown in FIG. The CPU 100 (see FIG. 5) determines whether there is no limit or no water level shown in FIG. 8 (or the ink water level shown in FIG. 9). When the ink water level detected by the ink water level sensor 51 is determined to be the maximum as shown in FIG. 10, it can be determined as a normal rising state. On the other hand, when the ink water level sensor 51 cannot detect the ink water level (as shown in FIG. 8) or when it is determined that the ink water level is as shown in FIG.

  When the CPU 100 (see FIG. 5) determines the normal startup state as described above, the printer 10 performs the print preparation work as described with reference to FIGS. On the other hand, when the CPU 100 determines that it is in the initial start-up state, the ink initial filling operation is executed as described with reference to FIG.

  As described above, the printer 10 itself determines whether the normal startup state is the initial startup state based on the ink water level in the sub tank 52a. The printer 10 is easy to use.

1 is a front view illustrating a schematic configuration of a printer that is an example of an inkjet image forming apparatus to which the present invention is applied. FIG. 2 is a perspective view illustrating a schematic configuration of the printer of FIG. 1. FIG. 5 is a perspective view showing an ink supply tube and an ink return tube in which an image forming unit and an ink supply unit are connected. FIG. 4 is a schematic diagram illustrating ink flow paths of an image forming unit and an ink supply unit. FIG. 2 is a block diagram illustrating an electrical system of the printer of FIG. 1. It is a schematic diagram which shows the state of the recording head in preparation for printing. It is a schematic diagram which shows the procedure of wiping off an ink from an ink discharge surface, (a) shows before wiping start, (b) shows immediately after completion | finish of wiping, (c) shows the standby state after completion | finish of wiping. It is a side view which shows typically the inside of a sub tank without ink. FIG. 6 is a side view schematically showing the inside of a sub tank in which a slight amount of ink is stored. FIG. 3 is a side view schematically showing the inside of a sub tank in which an upper limit amount of ink within a predetermined range according to the present invention is stored. FIG. 3 is a side view schematically showing the inside of a sub tank in which a lower limit amount of ink within a predetermined range according to the present invention is stored.

Explanation of symbols

10 Printer 12a, 12b, 12c, 12d, 12e, 12f Recording head 51 Ink water level sensors 51a, 51b, 51c Electrode 52a Sub tank 53a Main tank

Claims (5)

In an inkjet image forming apparatus that includes a sub tank that stores ink to be supplied to a recording head that discharges ink, and forms an image by discharging ink from the recording head to a recording medium.
Based on the ink water level in the sub tank,
The inkjet image forming apparatus has a normal rising state in which the ink water level is within a predetermined range, or an initial rising in which the ink water level is less than the predetermined range, which is different from the normal rising state. An ink jet type image forming apparatus, characterized in that it is determined to be in any state. The inkjet image forming apparatus according to claim 1, wherein the determination is performed when power is supplied to the inkjet image forming apparatus. 3. The inkjet image formation according to claim 1, wherein when the normal rising state is determined, a recovery operation for discharging ink from the recording head and recovering the recording head is executed. apparatus. The ink is filled in the sub tank and an ink supply path from the sub tank to the recording head when it is determined that the initial rising state is set. The inkjet image forming apparatus according to Item. 5. The inkjet image forming apparatus according to claim 1, wherein when the initial rising state is determined, only the sub-tank is filled with ink. 6.

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