Inkjet recording device and control method for inkjet recording device

Abstract

To provide an ink jet recording device and a control method of the ink jet recording device which can suppress the discharge failure of ink while preventing increase in the size and cost of the device and reducing the number of recording media used in preliminary discharge.SOLUTION: An ink jet recording device comprises a conveyance device including: a conveyance path part which conveys a recording medium so as to pass through an ink discharge section in which ink is discharged to the recording medium in an image formation part and a fixation section in which fixation of an image is performed in a fixation part; a return path part which returns the recording medium to the upstream side of the image formation part from the downstream of the fixation part in the conveyance direction of the conveyance path part; and an inversion path part which inverts the recording medium returned to the upstream of the image formation part in the conveyance direction. The conveyance device includes a conveyance control part which controls a conveyance path of the conveyed recording medium. The conveyance control part circulates a recording medium for preliminary discharge multiple times in the conveyance device via the return path part and the inversion path part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an inkjet recording apparatus and a method for controlling the inkjet recording apparatus.

Background Art

[0002] Conventionally, an inkjet recording apparatus that forms (records) an image on a recording medium such as paper by ejecting ink from a plurality of nozzles provided in an inkjet head has been used. Further, as an inkjet recording apparatus, a single-pass type inkjet recording apparatus using an inkjet head configured to have a length covering the recording medium in the width direction orthogonal to the conveyance direction of the recording medium has been used.

[0003] Ink used in an inkjet recording apparatus increases in viscosity when left for a long time, which causes image defects. Therefore, conventionally, in an inkjet recording apparatus that forms an image on a recording medium, an absorption sheet that absorbs ink is conveyed between the conveyed recording media, and pre-ejection for ejecting ink irrelevant to image recording from the nozzles is performed on the absorption sheet (Patent Document 1). In Patent Document 1, ejection failure is suppressed by periodically performing pre-ejection of ink on the absorption sheet.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in a configuration where ink is pre-ejected onto the absorbent sheet periodically, the pre-ejection occurs only on one side of the absorbent sheet, increasing the number of absorbent sheets that require pre-ejection. Furthermore, because a separate transport system is needed for feeding, transporting, and collecting the absorbent sheets, in addition to the storage medium transport system, the equipment becomes larger and more expensive.

[0006] Therefore, the present invention aims to provide an inkjet recording apparatus and a control method for an inkjet recording apparatus that can prevent the apparatus from becoming larger and more expensive, and can reduce the number of recording media used for pre-ejection, thereby suppressing ink ejection defects. [Means for solving the problem]

[0007] To solve the above problems and achieve the objectives of the present invention, the inkjet recording apparatus of the present invention includes an image forming unit having a plurality of nozzles, which eject ink from the plurality of nozzles onto a transported recording medium to form an image. It also includes a fixing unit that fixes the image formed in the image forming unit onto the recording medium, and an ejection control unit that controls the image forming unit to pre-eject ink from the nozzles to a predetermined position on the transported pre-ejection recording medium. Furthermore, it includes a transport path unit that transports the recording medium through an ink ejection section where ink is ejected onto the recording medium in the image forming unit and a fixing section where the image is fixed in the fixing unit, a return path unit that returns the recording medium from downstream of the fixing unit to upstream of the image forming unit in the transport direction of the transport path unit, and a reversal path unit that reverses the recording medium that is returned to the upstream side of the image forming unit in the transport direction. Furthermore, it includes a transport control unit that controls the transport device to circulate the pre-ejection recording medium multiple times through the return path unit and the reversal path unit. The ejection control unit controls the image forming unit to perform multiple preliminary ejections on the front and back surfaces of each preliminary ejection recording medium that has been returned to the upstream side of the image forming unit in the transport direction via the return path unit, or the return path unit and the inversion path unit, and to perform preliminary ejections on the front and back surfaces of each preliminary ejection recording medium at a position different from the position where a preliminary ejection image has already been formed by preliminary ejection.

[0008] The control method for the inkjet recording apparatus of the present invention pre-discharges ink from multiple nozzles provided in the image forming unit onto a predetermined position on a pre-discharge recording medium that has been transported. Next, the pre-discharged ink is fixed onto the pre-discharge recording medium. Then, if there is a margin on the pre-discharge recording medium on which the pre-discharged ink has been fixed, the pre-discharge recording medium is returned to the upstream side of the image forming unit in the transport direction via a return path that returns it to the upstream side of the image forming unit in the transport direction and a reversal path that inverts the front and back sides of the recording medium. Furthermore, ink is pre-discharged again from multiple nozzles provided in the image forming unit onto the returned pre-discharge recording medium. The system performs multiple pre-ejection operations on both the front and back surfaces of the pre-ejection recording medium, and performs pre-ejection operations on both the front and back surfaces of the pre-ejection recording medium at positions different from those where pre-ejection images have already been formed. [Effects of the Invention]

[0009] According to the present invention, it is possible to prevent the device from becoming larger and more expensive, and to reduce the number of recording media used for preliminary ejection, thereby suppressing ink ejection failures. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of an inkjet recording apparatus according to the first embodiment of the present invention. [Figure 2] This table shows the pre-dispensing frequency when using water-based ink A. [Figure 3] This table shows the pre-dispensing frequency when using water-based ink B. [Figure 4] This is a flowchart illustrating the control method during pre-ejection in the inkjet recording device 1. [Figure 5] Figure 5A shows an example of the first surface Pb-1 of a pre-discarding recording medium Pb that has been pre-discarded according to the flow in Figure 4. Figure 5B shows an example of the second surface Pb-2 of a pre-discarding recording medium Pb that has been pre-discarded according to the flow in Figure 4. [Figure 6] This is a schematic diagram of an inkjet recording apparatus 50 according to a second embodiment of the present invention. [Figure 7]Figure 7A shows an example of the first surface Pb-1 of a pre-dispensing recording medium Pb in which multiple check chart images 29 have been formed at multiple locations by multiple pre-dispensing cycles during pre-dispensing. Figure 7B shows an example of the second surface Pb-2 of a pre-dispensing recording medium Pb in which multiple check chart images 29 have been formed at multiple locations by multiple pre-dispensing cycles. [Modes for carrying out the invention]

[0011] Hereinafter, an example of an inkjet recording apparatus and a control method for an inkjet recording apparatus according to an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following example. In the figures described below, common components are denoted by the same reference numerals.

[0012] <1. First Embodiment> 1-1. Inkjet recording device Figure 1 is a schematic diagram of an inkjet recording apparatus 1 according to the first embodiment of the present invention. As shown in Figure 1, the inkjet recording apparatus 1 of this embodiment comprises a main body 100 having a paper feeder 2, an image forming unit 3, a transporter 5, a fixing unit 4, and a paper discharger 11, and a control device 200. The inkjet recording apparatus 1 of this embodiment can be used with various print media that can fix ink deposited on a sheet-like main surface, such as paper, fabric, or resin film, as the recording medium. Furthermore, the inkjet recording apparatus 1 of this embodiment is configured to use a sheet-fed recording medium.

[0013] [Paper feeder] The paper feeder 2 comprises a first recording medium storage section 10 and a second recording medium storage section 9. The first recording medium storage section 10 houses a desired recording medium Pa used during normal image formation, stacked on a planar plate (not shown) that moves vertically. The recording medium Pa housed in the first recording medium storage section 10 is not particularly limited, but sheet-fed recording media such as paper, cloth, or resin film are applicable.

[0014] In the second recording medium storage unit 9, a recording medium Pb for preliminary ejection, which is used for preliminary ejection, is loaded and stored on a flat plate (not shown) that moves vertically. As the recording medium Pb for preliminary ejection, a recording medium similar to the recording medium Pa stored in the first recording medium storage unit 10 may be applied, but it is preferable to use a recording medium composed of a material that can absorb the ejected ink more. Therefore, as the recording medium Pb for preliminary ejection, for example, a non-coated recording medium without a surface treatment such as a lamination treatment on the surface is preferably used.

[0015] Also, in this embodiment, as will be described later, the preliminary ejection and fixing are repeatedly performed multiple times on one recording medium Pb for preliminary ejection. Therefore, as the recording medium Pb for preliminary ejection, in order to prevent curling, cockling, etc., for example, a recording medium with a thicker paper thickness than the normal recording medium Pa for image formation is preferably used. Further, the width in the width direction orthogonal to the conveyance direction in the conveyance plane of the recording medium Pb for preliminary ejection stored in the second recording medium storage unit 9 is larger than the length in the width direction of the image forming unit 3 described later.

[0016] In the first recording medium storage unit 10 and the second recording medium storage unit 9, the plate moves vertically according to the loading amounts of the loaded recording media Pa and Pb, so that the uppermost recording medium is sequentially sent out to the conveyance device side at a predetermined timing. In the following description, when the recording medium Pa for image formation and the recording medium Pb for preliminary ejection are not particularly distinguished, they are simply referred to as the recording medium P.

[0017] [Conveyance Device] The conveyance device 5 includes a conveyance path unit 6, a return path unit 7, and a reverse path unit 8. In the following description, the direction orthogonal to the conveyance direction of the recording medium P in the conveyance device 5 and within the conveyance plane of the recording medium P is defined as the width direction.

[0018] The conveyance path section 6 is composed of a plurality of conveyance rollers 30, a first conveyance section 20, and a second conveyance section 23, and has a conveyance path for conveying the recording medium P fed from the paper feeding device 2 to the paper discharging device 11. Each conveyance roller 30 is composed of a pair of rollers arranged vertically across the conveyance path. Each conveyance roller 30 rotates so as to convey the recording medium P conveyed from the upstream side in the conveyance direction to the downstream side.

[0019] The first conveyance section 20 includes a drive roller 21, a driven roller 22, and an endless conveyance belt 31. The drive roller 21 and the driven roller 22 are cylindrical members whose length in the width direction is longer than the length in the width direction of the recording medium P to be conveyed. Also, the drive roller 21 is rotationally controlled by a control drive section (not shown). The driven roller 22 is driven in response to the rotational operation of the drive roller 21 by the endless conveyance belt 31 being stretched between the drive roller 21 and the driven roller 22.

[0020] Here, for example, a steel belt is used as the endless conveyance belt 31. The conveyance belt 31 is stretched between the drive roller 21 and the driven roller 22 and moves in a circular motion (moving operation). The recording medium P is placed on the placement surface on the outer peripheral surface of the conveyance belt 31 (the placement surface of the recording medium P) facing upward and horizontally, and is conveyed along with the circular motion of the conveyance belt 31. In this section, the recording medium P and the conveyance belt 31 face the surface (ink ejection surface) from which ink is ejected from the nozzles of the respective cartridges 3C, 3M, 3Y, 3K of the image forming section 3 described later.

[0021] The second conveyance section 23 receives the recording medium P conveyed by the first conveyance section 20 and conveys the recording medium P while passing through the ink fixing section by the fixing section 4 described later. The second conveyance section 23 has a drive roller 24, a driven roller 25, and an endless conveyance belt 32. Since the configuration of each part of the second conveyance section 23 is the same as the configuration of the first conveyance section 20, a detailed description of the second conveyance section 23 is omitted.

[0022] The ink ejected by the image forming unit 3 on the first transport unit 20 and deposited onto the recording medium P is not fixed to the recording medium P when it is transferred to the second transport unit 23. In the second transport unit 23, the recording medium P transferred from the first transport unit 20 is fixed to the recording medium P by a fixing unit 4 located opposite the section on the outer surface (mounting surface) of the transport belt 32 where the recording medium P is placed and moved parallel to.

[0023] The height of the section of the outer surface (mounting surface) of the conveyor belt 32 of the second conveying unit 23 on which the recording medium P is placed and moved parallel to is set to be equal to the height of the section of the outer surface (mounting surface) of the conveyor belt 31 of the first conveying unit 20 on which the recording medium P is placed and moved parallel to. In this way, the recording medium P is directly transferred from the conveyor belt 31 of the first conveying unit 20 to the conveyor belt 32 of the second conveying unit 23, so that the height of the recording medium P does not change and it is moved and transported within a single plane.

[0024] In this context, "equal" does not mean strictly equal, but rather that an accuracy of approximately equality, as visually apparent in the assembly and setup of a typical machine, is sufficient. For example, it means being equal within a range of approximately 1 cm or less, more preferably 1 mm or less.

[0025] In the transport device 5, the recording medium P transported via the first transport section 20 and the second transport section 23 is either discharged to the paper discharge device 11 side by the transport roller 30 or transported to the return path section 7 side.

[0026] The return path section 7 is composed of multiple transport rollers 30 and branches off from the transport path between the second transport section 23 and the paper discharge device 11. It has a transport path that transports the recording medium P that has been transported in the transport path section 6 back to the transport path section 6 while returning it to the upstream side in the transport direction of the first transport section 20. In the return path section 7, multiple pairs of transport rollers 30 are provided so as to sandwich the transport path, and the recording medium P is transported by the rotation of the transport rollers 30.

[0027] The inversion path section 8 is composed of multiple transport rollers 30 and has a transport path that inverts the front and back sides of the recording medium P that has been transported in the return path section 7 and merges with the transport path section 6 on the upstream side in the transport direction of the first transport section 20. That is, the recording medium P that is transported again from the return path section 7 to the transport path section 6 via the inversion path section 8 is transported again to the first transport section 20 with its front and back sides inverted in the inversion path section 8. In the inversion path section 8, there are also multiple pairs of transport rollers 30 provided so as to sandwich the transport path, and the recording medium P is transported by the rotation of the transport rollers 30.

[0028] [Image Forming Unit] The image forming unit 3 is positioned at a predetermined interval between the conveyor belt 31 of the first conveyor unit 20 and the surface on which the recording medium P is placed, in the conveying direction of the recording medium P. The image forming unit 3 has carriages 3C, 3M, 3Y, and 3K, each individually provided for cyan (C), magenta (M), yellow (Y), and black (K). The carriages 3C, 3M, 3Y, and 3K are arranged, for example, in the order of carriage 3C, 3M, 3Y, and 3K from the upstream side in the conveying direction of the recording medium P.

[0029] Each carriage 3C, 3M, 3Y, and 3K is configured to extend in a direction perpendicular to the transport direction of the recording medium P (the width direction of the recording medium P), and is set to a width that allows ink to be ejected at a predetermined position on the transported recording medium P. In other words, the inkjet recording device 1 is a one-pass line-head type inkjet recording device. The four carriages 3C, 3M, 3Y, and 3K have the same configuration as each other, except that they eject different colored inks.

[0030] Each carriage 3C, 3M, 3Y, and 3K has an inkjet head (not shown) equipped with nozzles for ejecting ink. Multiple nozzles on the inkjet heads of each carriage 3C, 3M, 3Y, and 3K eject ink of the corresponding color. The ink ejected from the nozzles lands on the transported recording medium P.

[0031] In this embodiment, based on the control of the ejection control unit 203 in the control device 200, inks of each color, C, M, Y, and K, are ejected sequentially from each carriage 3C, 3M, 3Y, and 3K onto the recording medium P, thereby forming a desired image on the recording medium P. Furthermore, in this embodiment, based on the control of the ejection control unit 203, pre-ejection is performed at predetermined timings from the inkjet heads of each carriage 3C, 3M, 3Y, and 3K. The timing of pre-ejection will be described in detail later.

[0032] The ink used in the inkjet recording device 1 of this embodiment is, for example, a water-based ink, which is fixed to the recording medium P by drying with air or heat. In this embodiment, a water-based ink that is dried by applying heat in the fixing unit 4 is used as an example, but the inkjet recording device 1 can also use ultraviolet (UV) curing ink. UV curing ink undergoes a phase change between a gel state and a liquid (sol) state when not irradiated with UV light. Over time, the materials constituting the ink separate and change to a gel state, and by stirring, the materials constituting the ink mix together and change to a liquid state.

[0033] [Fixing section] The fixing unit 4 fixes the ink that has landed on the recording medium P on the mounting surface of the conveyor belt 32 to the recording medium P. The fixing unit 4 is equipped with a heating unit for drying the water-based ink that has landed on the recording medium P. In addition, when an ultraviolet-curable ink is used as the ink, the fixing unit 4 is equipped with an ultraviolet irradiation unit and uses the irradiation unit to irradiate the ultraviolet-curable ink on the recording medium P with ultraviolet light. In this case, the irradiation unit provided in the fixing unit 4 can be a low-pressure mercury lamp, a mercury lamp with an operating pressure of several hundred Pa to 1 MPa, a light source that can be used as a germicidal lamp, a cold cathode tube, an ultraviolet laser light source, a metal halide lamp, or an LED. Among these, a light source that can irradiate ultraviolet light at a higher intensity and consumes less power (e.g., an LED) is more desirable.

[0034] Furthermore, the fixing unit 4 can be configured in various ways depending on the type of ink, such as drying the ink by applying heat to the recording medium P, curing the ink by irradiating it with ultraviolet light, or applying a liquid that causes a chemical change to the ink.

[0035] [Paper output device] The paper discharge device 11 is located downstream of the fixing unit 4 in the transport direction of the recording medium P. The paper discharge device 11 has a first recording medium paper discharge unit 13 and a second recording medium paper discharge unit 12, which respectively place and hold recording mediums Pa and Pb that are transported by the second transport unit 23 and not transported to the return path unit 7. The first recording medium paper discharge unit 13 contains recording medium Pa on which the desired image has been formed by the image forming unit 3. On the other hand, the second recording medium paper discharge unit 12 contains recording medium Pb that was used for preliminary discharge. The first recording medium paper discharge unit 13 and the second recording medium paper discharge unit 12 are each equipped with a flat discharge tray (not shown). Recording medium P on which image recording has been completed is stacked sequentially on the discharge tray. The discharge tray may be adjustable up and down depending on the amount of recording medium P discharged.

[0036] [Control device] The control device 200 controls the operation of each part of the main unit 100, which consists of a paper feeder 2, a transporter 5, an image forming unit 3, a fixing unit 4, and a paper discharger 11, and is composed of a computer such as a microcomputer. The computer includes a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). Furthermore, the computer may also include non-volatile storage and a network interface.

[0037] One of the controls performed by such a control device 200 is a characteristic control that will be described in detail in the control method of the inkjet recording device 1 described later. The procedure for this characteristic control is a control program for controlling the operation of each part of the inkjet recording device 1, which is either a program stored in ROM or a program loaded from an external device into RAM or non-volatile storage. This control program causes the computer to execute the steps described later in the control method of the inkjet recording device 1.

[0038] The inkjet recording apparatus 1 of this embodiment is characterized by a control method during pre-ejection, which is performed at a predetermined timing. Therefore, the configuration of each part related to the control method during pre-ejection, among the components of the control device 200, will be described in particular.

[0039] The control device 200 in this embodiment includes a discharge frequency setting unit 201, a transport control unit 202, and a discharge control unit 203.

[0040] The ejection frequency setting unit 201 sets the pre-ejection frequency (per second) based on environmental conditions determined by the ambient temperature and humidity during image formation, and the type of ink being used. Figure 2 is a table showing the pre-ejection frequency when using water-based ink A. Figure 3 is a table showing the pre-ejection frequency when using water-based ink B.

[0041] As shown in Figures 2 and 3, the pre-ejection frequency (per second) is predetermined for each type of ink, depending on the ambient temperature and humidity. The ejection frequency setting unit 201 refers to a table, such as the one shown in Figure 2 or 3, according to the type of ink and environmental conditions, and sets the frequency of pre-ejection, determining how often pre-ejection should be performed. For example, when using ink A, if the ambient temperature is 23°C and the ambient humidity is 55%RH, the ejection frequency setting unit 201 sets the pre-ejection frequency to perform one pre-ejection every 45 seconds.

[0042] The transport control unit 202 controls the timing of feeding the recording medium Pb for pre-discharge based on the pre-discharge frequency set in the discharge frequency setting unit 201, and also controls the transport path of the transported pre-discharge recording medium Pb. In this embodiment, pre-discharge is performed in between normal image formation. That is, the pre-discharge recording medium Pb is fed between the image formation recording medium Pa and the image formation recording medium Pa. Therefore, the transport control unit 202 controls the timing of feeding the image formation recording medium Pa and the timing of feeding the pre-discharge recording medium Pb based on the pre-discharge frequency set in the discharge frequency setting unit 201. As a result, the transport device 5 transports the image formation recording medium Pa and the pre-discharge recording medium Pb at predetermined timings.

[0043] Furthermore, in this embodiment, multiple pre-discharge operations are performed on the entire surface of a single pre-discharge recording medium Pb, including the front surface (hereinafter referred to as the first surface) and the back surface (hereinafter referred to as the second surface) of the recording medium Pb. Therefore, the transport control unit 202 determines whether or not there is remaining space on the first or second surface of the pre-discharge recording medium Pb that can be pre-discharged. If it determines that there is space, the transport control unit 202 controls the transport device 5 to bring the pre-discharge recording medium Pb back to the upstream side of the first transport unit 20 in the transport direction via the return path unit 7 and the reversal path unit 8.

[0044] On the other hand, if the transport control unit 202 determines that there is no margin in the pre-discharge recording medium Pb, and if the transported recording medium P is a normal image forming recording medium Pa, it controls the transport device 5 so that the recording medium P passes through the image forming unit 3 and the fixing unit 4 and is then discharged to the paper discharge device 11.

[0045] Incidentally, the space on the recording medium Pb required for one pre-discharge and the size of the pre-discharge recording medium Pb to be used are known in advance. Therefore, the number of possible pre-discharges for one pre-discharge recording medium Pb can be calculated in advance. Accordingly, the transport control unit 202 controls the transport device 5 to circulate the pre-discharge recording medium Pb within the transport device 5 for the number of possible pre-discharges per recording medium Pb.

[0046] The ejection control unit 203 controls the timing of ejection to the image-forming recording medium Pa and the pre-ejection recording medium Pb that are being transported, under the control of the transport control unit 202. When the image-forming recording medium Pa is being transported, the ejection control unit 203 performs ejection control related to normal image formation. On the other hand, when the pre-ejection recording medium Pb is being transported, it performs ejection control related to pre-ejection. If pre-ejection has already been performed on the transported pre-ejection recording medium Pb, in order to prevent overlap of pre-ejection positions, the ejection control unit 203 determines the pre-ejection position according to the number of cycles of the pre-ejection recording medium Pb and controls the timing of pre-ejection. That is, for recording medium Pb that has already undergone pre-ejection, the ejection control unit 203 controls the ejection timing so that pre-ejection is performed with a phase shift from the already formed pre-ejection position.

[0047] With the above configuration, in this embodiment, the recording medium Pb for pre-discharge is circulated within the transport device 5, and the pre-discharge position is controlled, thereby enabling multiple pre-discharges to be performed on the first and second surfaces of the recording medium Pb for pre-discharge.

[0048] 1-2. Control method for inkjet recording device Next, the control method for the inkjet recording device 1 of this embodiment will be described. This embodiment is characterized by the control method during pre-ejection. Therefore, the control method related to the pre-ejection of the inkjet recording device 1 will be described here.

[0049] Figure 4 is a flowchart showing the control method during pre-ejection in the inkjet recording device 1. Figure 5A shows an example of the first surface Pb-1 of the pre-ejection recording medium Pb after pre-ejection performed according to the flowchart in Figure 4. Figure 5B shows an example of the second surface Pb-2 of the pre-ejection recording medium Pb after pre-ejection performed according to the flowchart in Figure 4. In this embodiment, the case in which ink is ejected simultaneously from all nozzles of each carriage 3C, 3M, 3Y, and 3K during pre-ejection will be explained as an example.

[0050] First, printing is started in response to an input instruction from an input unit (not shown) provided in the inkjet recording device 1 or from an external terminal (not shown) connected via a network or the like (step S1). In step S1, under the control of the transport control unit 202, the transport device 5 starts transporting the image-forming recording medium Pa fed from the paper feed device 2. Then, in the image forming unit 3, under the control of the ejection control unit 203, ink is ejected from the nozzles of each carriage 3C, 3M, 3Y, and 3K at predetermined timings, thereby forming the desired image on the transported image-forming recording medium Pa.

[0051] As printing begins, the transport device 5, under the control of the transport control unit 202, starts feeding the recording medium Pb for preliminary ejection from the paper feed device 2 based on the preliminary ejection frequency set in the ejection frequency setting unit 201 (step S2). For example, if the preliminary ejection frequency set in the ejection frequency setting unit 201 is 45 seconds, the transport control unit 202 controls the transport device 5 so that the recording medium Pb for preliminary ejection is transported on the first transport unit 20 every 45 seconds. The paper feeding frequency in step S2 is adjusted in step S5, described later, taking into account the timing when the recording medium Pb for preliminary ejection circulates within the transport device 5 and is transported again to the upstream side of the first transport unit 20 in the transport direction.

[0052] Once the transport of the pre-ejection recording medium Pb begins, the image forming unit 3, under the control of the ejection control unit 203, performs pre-ejection from the nozzles of the inkjet heads of each carriage 3C, 3M, 3Y, and 3K at the timing when the pre-ejection recording medium Pb is transported by the first transport unit 20 (step S3). As a result, a pre-ejection image 28 (see Figures 5A and 5B) is formed on the pre-ejection recording medium Pb. In this embodiment, during pre-ejection, ink is ejected simultaneously from all nozzles of each carriage 3C, 3M, 3Y, and 3K.

[0053] After the preliminary ejection image 28 is formed, the preliminary ejection recording medium Pb is heated by the fixing unit 4 when it is being transported by the second transport unit 23, thereby fixing the preliminary ejection image 28 to the preliminary ejection recording medium Pb (step S4).

[0054] Next, under the control of the transport control unit 202, the transport device 5 transports the pre-discharge recording medium Pb, on which the pre-discharge image 28 has been fixed by the fixing unit 4, to the return path unit 7, and also to the upstream side of the first transport unit 20 in the transport direction via the inversion path unit 8 (step S5). In step S5, the pre-discharge recording medium Pb is returned to the transport path unit 6 via the inversion path unit 8. For this reason, the pre-discharge recording medium Pb is inverted and transported so that the side opposite to the side on which the pre-discharge image 28 was formed in the previous step (for example, the first surface Pb-1) (for example, the second surface Pb-2) faces the image forming unit 3.

[0055] Next, under the control of the ejection control unit 203, the image forming unit 3 performs preliminary ejection from the nozzles of the inkjet heads of each carriage 3C, 3M, 3Y, and 3K at the timing when the recording medium Pb for preliminary ejection is transported by the first transport unit 20 (step S6). In this embodiment, the recording medium for preliminary ejection is inverted in step S5. Therefore, if a preliminary ejection image 28 is formed on the first surface Pb-1 of the recording medium Pb for preliminary ejection in step S3, then in step S6, the preliminary ejection image 28 is formed on the second surface Pb-2 of the recording medium Pb for preliminary ejection.

[0056] Subsequently, in the same manner as in step S4, the recording medium Pb for pre-discharge is heated by the fixing unit 4 when it is being transported by the second transport unit 23, and the pre-discharge image 28 is fixed to the recording medium Pb for pre-discharge (step S7).

[0057] Next, the transport control unit 202 determines whether or not there is any margin on the pre-dispensing recording medium Pb (step S8). The determination in step S8 can be made by comparing the number of pre-dispensing operations possible for one pre-dispensing recording medium Pb with the number of pre-dispensing operations that have already been performed. Alternatively, the determination in step S8 may be made by detecting the margin portion of the pre-dispensing recording medium Pb being transported based on the reading results of the image reading unit (not shown).

[0058] If the transport control unit 202 determines that there is no margin, that is, if "NO" is determined in step S8, the transport device 5, under the control of the transport control unit 202, discharges its reserve discharge recording medium Pb to the paper discharge device 11.

[0059] On the other hand, if the transport control unit 202 determines that there is a blank space, that is, if it determines "YES" in step S8, it returns to step S5. In other words, as long as it is determined in step S8 that there is a blank space in the pre-discharge recording medium Pb that is the subject of the determination, steps S5 to S8 are repeated multiple times to perform pre-discharge in the blank space.

[0060] As shown in Figures 5A and 5B, if the first pre-extrusion is performed on the first surface Pb-1, the second pre-extrusion is performed on the second surface Pb-2. Subsequently, the third pre-extrusion is formed on the first surface at a position that does not overlap with the pre-extrusion image 28 from the first pre-extrusion.

[0061] Thus, in this embodiment, the recording medium for preliminary ejection is inverted and pre-ejected in steps S5 to S8. Then, in step S6, under the control of the ejection control unit 203, the preliminary ejection image 28 is formed so as not to overlap with the portion in which the preliminary ejection image 28 has already been formed.

[0062] As described above, in this embodiment, by repeatedly fixing the preliminary ejection image 28 and inverting the recording medium Pb for preliminary ejection, preliminary ejection can be performed multiple times on the first surface Pb-1 and the second surface Pb-2 of the recording medium Pb for preliminary ejection, while shifting the ejection position. This increases the number of times that preliminary ejection is permissible for a single recording medium Pb. As a result, the consumption of the recording medium Pb for preliminary ejection can be reduced, and costs can be lowered.

[0063] Furthermore, in this embodiment, the pre-ejection recording medium Pb is fed in between the transport of the normal image-forming recording medium Pa, allowing pre-ejection to be performed while normal image formation is taking place. This makes it possible to perform pre-ejection without stopping the normal printing operation in the inkjet recording device 1, thus preventing a significant decrease in printing efficiency.

[0064] Furthermore, as a recording medium for preliminary ejection, a recording medium Pb may be used whose length in the transport direction is shorter than the distance between the two image-forming recording media Pa that are sequentially transported along the transport path 6. In this case, by feeding the preliminary ejection recording medium Pb between the image-forming recording media Pa, it is not necessary to shift the timing of normal image formation. This makes it possible to maintain printing efficiency while suppressing ejection defects.

[0065] In this embodiment, when circulating the recording medium Pb for pre-discharge within the transport device 5, the recording medium Pb is constantly inverted via the inversion path section 8, so that it is transported in such a way that it is alternately pre-discharged onto the first side Pb-1 and the second side Pb-2. However, the transport method for the recording medium Pb for pre-discharge is not limited to this. For example, after multiple pre-discharges onto the first side Pb-1 of the recording medium Pb are completed, the recording medium Pb may be inverted via the inversion path section 8 to perform multiple pre-discharges onto the second side Pb-2 of the recording medium Pb.

[0066] Furthermore, in this embodiment, the recording medium Pb for pre-discharge may be the same type of paper as the recording medium Pa used for image formation, or a recording medium with better absorbency than the recording medium Pa used for image formation may be used. In this embodiment, the number of allowable pre-discharges per pre-discharge recording medium Pb increases, thus reducing the consumption of the recording medium.

[0067] In this embodiment, the configuration is such that ink is ejected simultaneously from the nozzles of the inkjet heads of each carriage 3C, 3M, 3Y, and 3K. However, the present invention may also be configured to eject ink from each nozzle individually. The configuration in which ink is ejected from each nozzle in the inkjet heads of each carriage 3C, 3M, 3Y, and 3K will be described below.

[0068] <2. Second Embodiment> Figure 6 is a schematic diagram of an inkjet recording apparatus 50 according to a second embodiment of the present invention. The inkjet recording apparatus 50 according to the second embodiment differs from the first embodiment in that it has an image reading unit 40 and an image analysis unit 204. Therefore, in Figure 6, the same reference numerals are used for parts corresponding to those in Figure 1, and redundant explanations are omitted.

[0069] In the second embodiment, the image reading unit 40 is positioned between the image forming unit 3 and the fixing unit 4 and reads the image of the recording medium P being transported along the transport path unit 6. The image read by the image reading unit 40 is transmitted to the image analysis unit 204. The image analysis unit 204 detects nozzles with ejection defects based on the image read by the image reading unit 40 (check chart image 29 (see Figure 7)).

[0070] In this embodiment, when pre-discharging onto the pre-discharging recording medium Pb, the ejection timing is made different for each nozzle in the inkjet head of each carriage 3C, 3M, 3Y, and 3K. That is, in the second embodiment, in steps S3 and S6 of Figure 4, pre-discharging is performed by making the ejection timing different for each nozzle in the inkjet head of each carriage 3C, 3M, 3Y, and 3K. This makes it possible to form a check chart image 29 on the pre-discharging recording medium Pb for determining the ejection status of each nozzle.

[0071] Figure 7A shows an example of the first surface Pb-1 of a pre-dispensing recording medium Pb in which multiple check chart images 29 have been formed at multiple locations by multiple pre-dispensing cycles during pre-dispensing. Figure 7B shows an example of the second surface Pb-2 of a pre-dispensing recording medium Pb in which multiple check chart images 29 have been formed at multiple locations by multiple pre-dispensing cycles.

[0072] In the second embodiment, as in the flow shown in Figure 4, the pre-discharge recording medium Pb is repeatedly transported while being inverted, and check chart images 29 can be formed multiple times on the first surface Pb-1 and the second surface Pb-2. The check chart images 29 formed on the pre-discharge recording medium Pb in the image forming unit 3 are read by the image reading unit 40 and then analyzed by the image analysis unit 204. This makes it possible to detect nozzles with discharge defects at any time. In addition, the same effects as in the first embodiment can be obtained in the second embodiment as well.

[0073] The embodiments described above are explained in detail for the purpose of clearly illustrating the present invention and are not necessarily limited to those comprising all the configurations described. For example, it is possible to replace some of the configurations of the embodiments with other configurations, and it is also possible to add other configurations to the configurations of the embodiments. Furthermore, it is possible to add, delete, or replace some of the configurations of the embodiments with other configurations. [Explanation of Symbols]

[0074] 1…Inkjet recording device, 2…Paper feed device, 3…Image forming unit, 3C, 3M, 3Y, 3K…Carriage, 4…Fusing unit, 5…Conveyor device, 6…Conveyor path unit, 7…Return path unit, 8…Inversion path unit, 9…Second recording medium storage unit, 10…First recording medium storage unit, 11…Paper discharge device, 12…Second recording medium paper discharge unit, 13…First recording medium paper discharge unit, 20…First transport unit, 21…Drive roller, 22…Driven roller, 23…Second transport unit, 24…Drive roller, 25…Driven roller, 28…Preliminary ejected image, 29…Check chart image, 30…Conveyor roller, 31…Conveyor belt, 32…Conveyor belt, 40…Image reading unit, 50…Inkjet recording device, 100…Device body, 200…Control device, 201…Ejection frequency setting unit, 202…Conveyor control unit, 203…Ejection control unit, 204…Image analysis unit

Claims

1. An image forming unit having multiple nozzles, which ejects ink from the multiple nozzles onto a conveyed recording medium to form an image, A fixing unit for fixing the image formed by the image forming unit onto the recording medium, A discharge control unit controls the image forming unit to pre-discharge ink from the nozzle at a predetermined position on the pre-discharge recording medium being transported, A transport device having a transport path section that transports the recording medium so that it passes through an ink ejection section in the image forming section where ink is ejected onto the recording medium and a fixing section in the fixing section where the image is fixed; a return path section in the transport direction of the transport path section that returns the recording medium from downstream of the fixing section to upstream of the image forming section; and a reversal path section that reverses the recording medium that is returned to the upstream side of the image forming section in the transport direction. The transport control unit controls the transport device so that the pre-discharge recording medium is circulated multiple times within the transport device via the return path and the reversal path, The ejection control unit controls the image forming unit to perform multiple pre-dispense operations on the front and back surfaces of each pre-dispense recording medium that has been returned to the upstream side of the image forming unit in the transport direction via the return path, or via the return path and the inversion path, and to perform pre-dispense operations on the front and back surfaces of each pre-dispense recording medium at a position different from the position where a pre-dispense image has already been formed by pre-dispense. Inkjet recording device.

2. If the transport control unit determines that there is space on the pre-discharge recording medium on which the pre-discharge image has been fixed by the fixing unit, it transports the pre-discharge recording medium to the return path unit. The inkjet recording apparatus according to claim 1.

3. The system includes a paper feeder for feeding the aforementioned pre-discharge recording medium, The width of the pre-discharge recording medium housed in the paper feed device in the width direction perpendicular to the transport direction within the transport surface is greater than the length of the image forming unit in the width direction. The inkjet recording apparatus according to claim 1.

4. The paper feeding device comprises a first recording medium storage section for storing a recording medium for preliminary ejection, and a second recording medium storage section for storing a recording medium for image formation used in normal image formation. The transport control unit controls the transport device to transport the pre-dispensing recording medium between the image-forming recording mediums that are sequentially transported along the transport path. The inkjet recording apparatus according to claim 3.

5. The system includes a paper output device for receiving the recording medium on which the image has been fixed by the fixing unit, The paper discharge device comprises a first recording medium discharge section for storing a recording medium for preliminary discharge, and a second recording medium discharge section for storing a recording medium used for image forming in normal image forming. The inkjet recording apparatus according to claim 1.

6. The ejection control unit controls the timing of pre-ejection according to the type of ink used in the image forming unit, the ambient temperature, and the ambient humidity. The inkjet recording apparatus according to claim 1.

7. The length of the pre-discharge recording medium in the transport direction is smaller than the width between the image-forming recording media sequentially transported in the transport path. The inkjet recording apparatus according to claim 3.

8. The ejection control unit pre-dispenses ink from each nozzle provided in the image forming unit to a predetermined position on the pre-dispense recording medium transported by the transport device, and controls the image forming unit to form a check chart image capable of determining the ejection state of each nozzle. The inkjet recording apparatus according to claim 1.

9. The image forming unit includes an image reading unit that reads the image formed on the recording medium, The system includes an image analysis unit that analyzes the image read by the image reading unit, The image reading unit reads the check chart image, and the image analysis unit determines the discharge state of each nozzle from the check chart image read by the image reading unit. The inkjet recording apparatus according to claim 8.

10. Pre-discharge ink from multiple nozzles provided in the image forming unit onto a predetermined position on the pre-discharge recording medium that has been transported. The pre-discharged ink is fixed onto the pre-discharge recording medium. If there is a margin on the pre-dispensing recording medium on which the pre-dispensed ink has been fixed, the pre-dispensing recording medium is returned to the upstream side of the image forming unit in the transport direction via a return path and an inversion path that reverses the front and back sides of the recording medium, The ink is again pre-discharged from the multiple nozzles provided in the image forming unit onto the pre-discharge recording medium that has been returned. Multiple pre-ejection operations are performed on both the front and back surfaces of the pre-ejection recording medium, and the pre-ejection is performed on each of the front and back surfaces of the pre-ejection recording medium at a location different from the location where a pre-ejection image has already been formed. A method for controlling an inkjet recording device.

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