JP7669709B2 - CLEANING DEVICE, IMAGE FORMING APPARATUS AND WINDING CONTROL METHOD - Google Patents

Description

The present invention relates to a cleaning device, an image forming device, and a winding control method.

Conventionally, there is known an inkjet image forming device that forms (records) an image on a recording medium by ejecting ink from multiple nozzles provided in an inkjet head of a head unit onto the recording medium transported by a transport device.

The inkjet head of an inkjet image forming device ejects ink from multiple nozzles. Pressure is applied to each nozzle individually, and ink ejection is controlled according to the image to be recorded. The ink ejection openings of the nozzles are aligned and open on one surface (nozzle surface) of the head unit (inkjet head) that faces the recording medium when forming an image.

In an inkjet image forming device with such a configuration, if there is foreign matter adhering to the nozzle surface, residual ink that has dried and thickened, or air bubbles mixed in, the ink cannot be ejected properly to form an image. Therefore, head cleaning is performed to maintain good ink ejection conditions.

Head cleaning involves discharging the ink from inside the nozzles by applying pressure from the upstream side of the nozzle or by suction from the nozzle face side, thereby eliminating (purifying) foreign matter, dried and viscous ink, and trapped air bubbles along with the ink that is discharged.

Furthermore, after ink is discharged as part of such a cleaning operation, a wiping operation is performed in which a wiping member (cleaning member) is brought into contact with and moved against the nozzle face to clean (remove) any ink remaining on the nozzle face (see, for example, Patent Document 1). In the wiping operation, a wiping member such as a wiper blade that scrapes off the ink or an absorbent sheet member is used.

The above-mentioned Patent Document 1 describes a technique in which the face of the recording head is cleaned with a portion of a sheet-like member as a cleaning member, and then the sheet-like member is wound up so that an unused portion of the sheet-like member comes into contact with the face of the recording head in the next cleaning. The technique described in the above-mentioned Patent Document 1 takes into consideration the fact that the longer the time that has elapsed since the operation of wiping off the ink adhering to the face of the recording head (wiping operation), the more the ink adhering to the sheet-like member spreads and bleeds (specifically, the width of the wiping mark gradually increases), and controls the amount of the sheet-like member wound up after wiping to increase.

JP 2013-226804 A

However, in the technology described in the above Patent Document 1, when the time elapsed since cleaning (wiping operation) is short, the amount of winding of the cleaning member (sheet-like member) after cleaning is always small. Therefore, when cleaning the nozzle surfaces of multiple head units continuously, specifically, when cleaning the first nozzle surface on which the ink ejection ports of the nozzles ejecting the first ink are open, and then winding up the cleaning member, and cleaning the second nozzle surface on which the ink ejection ports of the nozzles ejecting the second ink, which is different in color from the first ink, the amount of winding of the cleaning member is small, so that the part of the cleaning member on which the first ink is attached may come into contact with the second nozzle surface. In this case, the first ink is transferred (adheres) from the cleaning member to the second nozzle surface, and the first ink enters the ink ejection ports opening on the second nozzle surface. As a result, there was a problem that the first ink and the second ink are mixed, and the mixed ink is ejected from the ink ejection ports opening on the second nozzle surface, causing a deterioration in the quality of the image formed on the recording medium.

The object of the present invention is to provide a cleaning device, an image forming apparatus, and a winding control method that can prevent ink mixing when cleaning ink remaining on the nozzle surface of a head unit.

The cleaning device according to the present invention comprises:
a cleaning member that comes into contact with a nozzle surface of a head unit that forms an image on a recording medium by an inkjet head and cleans ink remaining on the nozzle surface;
a winding section that winds up the cleaning member such that an unused portion of the cleaning member contacts the second nozzle surface when cleaning the second ink remaining on the second nozzle surface after cleaning the first ink remaining on the first nozzle surface;
a control unit that controls the winding unit to reduce a winding amount of the cleaning member when the first ink and the second ink have the same color, compared to when the first ink and the second ink have different colors;
Equipped with
In the winding direction of the cleaning member, when the length of the first ink adhered to the cleaning member by cleaning with the first ink is α and the winding amount of the cleaning member is β, if the color of the first ink and the color of the second ink are the same, the following formula (1) is satisfied, and if the color of the first ink and the color of the second ink are different, the following formula (2) is satisfied .
0.5×α≦β<α...(1)
1.2×α≦β...(2)

The image forming apparatus according to the present invention comprises:
The cleaning device;
The head unit;
Equipped with.

The winding control method according to the present invention comprises the steps of:
a cleaning member that comes into contact with a nozzle surface of a head unit that forms an image on a recording medium by an inkjet head and cleans ink remaining on the nozzle surface;
a winding unit that winds up the cleaning member such that an unused portion of the cleaning member contacts the second nozzle face when cleaning a second ink remaining on a second nozzle face after cleaning a first ink remaining on the first nozzle face, the winding unit comprising:
When the color of the first ink and the color of the second ink are the same, a control is performed to reduce a take-up amount of the cleaning member compared to when the color of the first ink and the color of the second ink are different;
In the above control, when the length of the first ink adhered to the cleaning member by cleaning with the first ink in the winding direction of the cleaning member is α and the winding amount is β, β satisfies the following formula (1) when the color of the first ink and the color of the second ink are the same, and satisfies the following formula (2) when the color of the first ink and the color of the second ink are different .
0.5×α≦β<α...(1)
1.2×α≦β...(2)

According to the present invention, it is possible to prevent ink mixing when cleaning ink remaining on the nozzle surface of the head unit.

FIG. 1 is a diagram illustrating a schematic configuration of an inkjet image forming apparatus. FIG. 2 is a schematic diagram illustrating a configuration of a head unit. 1 is a block diagram showing a main functional configuration of an inkjet image forming apparatus; 2A and 2B are diagrams illustrating the configuration and operation of a cleaning device. FIG. 1 is a diagram illustrating a problem with the conventional technology. 11 is a table showing the relationship between the take-up amount of the cleaning member and color mixing and liquid absorbency. 6A and 6B are diagrams illustrating the length of ink adhering to the cleaning member. 6 is a flowchart showing an example of a take-up control operation of the inkjet image forming apparatus. 13A and 13B are diagrams illustrating a modified example of a configuration for detecting the take-up amount of the cleaning member.

Figure 1 is a diagram showing the schematic configuration of an inkjet image forming device 1 (functioning as the "image forming device" of the present invention). The inkjet image forming device 1 includes a paper feed section 10, an image forming section 20, a paper discharge section 30, and a control section 40 (see Figure 3).

Under the control of the control unit 40, the inkjet image forming device 1 transports the recording medium P stored in the paper feed unit 10 to the image forming unit 20, forms an image on the recording medium P in the image forming unit 20, and transports the recording medium P with the image formed thereon to the paper discharge unit 30. As the recording medium P, various media capable of fixing the ink that has landed on the surface, such as paper such as plain paper or coated paper, fabric or sheet-like resin, can be used.

The paper feed unit 10 has a paper feed tray 11 that stores the recording medium P, and a media supply unit 12 that transports and supplies the recording medium P from the paper feed tray 11 to the image forming unit 20. The media supply unit 12 has a ring-shaped belt supported by two rollers on the inside, and transports the recording medium P from the paper feed tray 11 to the image forming unit 20 by rotating the rollers with the recording medium P placed on this belt.

The image forming unit 20 includes a conveying unit 21, a transfer unit 22, a heating unit 23, a head unit 24, a fixing unit 25, and a delivery unit 28.

The transport unit 21 holds the recording medium P placed on the transport surface 211a (mounting surface) of the cylindrical transport drum 211, and performs a transport operation to transport the recording medium P on the transport drum 211 in the transport direction (Y direction) by rotating and moving the transport drum 211 around a rotation axis (cylindrical axis) that extends in the X direction (perpendicular to the paper surface of Figure 1).

The transport drum 211 has a claw portion and an air intake portion (not shown) for holding the recording medium P on its transport surface 211a. The recording medium P is held on the transport surface 211a by having its ends pressed down by the claw portion and being drawn to the transport surface 211a by the air intake portion. The transport portion 21 is connected to a transport drum motor (not shown) for rotating the transport drum 211. The transport drum 211 rotates by an angle proportional to the amount of rotation of the transport drum motor.

The transfer unit 22 transfers the recording medium P transported by the medium supply unit 12 of the paper feed unit 10 to the transport unit 21. The transfer unit 22 is provided at a position between the medium supply unit 12 of the paper feed unit 10 and the transport unit 21, and holds and picks up one end of the recording medium P transported from the medium supply unit 12 with the swing arm unit 221, and transfers it to the transport unit 21 via the transfer drum 222.

The heating unit 23 is provided between the position of the transfer drum 222 and the position of the head unit 24, and heats the recording medium P transported by the transport unit 21 so that the temperature of the recording medium P falls within a predetermined temperature range. The heating unit 23 has, for example, an infrared heater, and energizes the infrared heater based on a control signal supplied from the control unit 40 to cause the infrared heater to generate heat.

The head unit 24 ejects ink from ink ejection ports (nozzle openings) provided on a nozzle surface (ink ejection surface) facing the transport surface 211a of the transport drum 211, at appropriate timing according to the rotation of the transport drum 211 holding the recording medium P, to form an image on the recording medium P. The head unit 24 is positioned so that the nozzle surface and the transport surface 211a are separated by a predetermined distance.

In the inkjet image forming device 1 of this embodiment, four head units 24 corresponding to the four colors of ink, yellow (Y), magenta (M), cyan (C), and black (K), are arranged at predetermined intervals from the upstream side in the transport direction of the recording medium P in the order of Y, M, C, and K.

Figure 2 is a schematic diagram showing the configuration of the head unit 24. Here, the nozzle surface 245 (see Figure 4) of the head unit 24 that faces the transport surface 211a of the transport drum 211 is shown.

The head unit 24 includes four inkjet heads 242 attached to a mounting member 244. Each inkjet head 242 is provided with a plurality of image forming elements (recording elements), each of which has a pressure chamber for storing ink, a piezoelectric element provided on the wall of the pressure chamber, and a nozzle 243. When a drive signal is input to deform the piezoelectric element, the image forming element deforms the pressure chamber due to the deformation of the piezoelectric element, changing the pressure within the pressure chamber, and ejects ink from the nozzle 243 that communicates with the pressure chamber.

In the inkjet head 242, two nozzle rows are formed, each consisting of nozzles 243 arranged at equal intervals in a direction intersecting the transport direction of the recording medium P (in this embodiment, a direction perpendicular to the transport direction, i.e., the X direction). These two nozzle rows are arranged such that the arrangement positions of the nozzles 243 are shifted from each other in the X direction by half the arrangement interval of the nozzles 243 in each nozzle row.

The four inkjet heads 242 are arranged in a staggered pattern so that the nozzle row's X-direction range is continuous without breaks. The X-direction range of the nozzles 243 included in the head unit 24 covers the X-direction width of the area on the recording medium P transported by the transport unit 21 where an image is formed, and the position of the head unit 24 is fixed relative to the rotation axis of the transport drum 211 during image formation. In other words, the head unit 24 has a line head capable of ejecting ink across the image-formable width in the X-direction on the recording medium P, and the inkjet image forming device 1 is a single-pass type inkjet image forming device.

The number of nozzle rows in the inkjet head 242 may be one or three or more, instead of two. The number of inkjet heads 242 in the head unit 24 may be three or less, or five or more, instead of four.

The ink ejected from the nozzle 243 of the image forming element is a pigment-containing ink, for example, a white ink containing titanium dioxide or the like as a pigment. The ink ejected from the nozzle 243 of the image forming element is a gel ink that contains a gelling agent, changes phase to a gel or sol state depending on the temperature, and hardens when exposed to energy rays such as ultraviolet light. In this embodiment, a pigment-containing gel ink is used as the ink ejected from the nozzle 243 of the image forming element.

The head unit 24 includes an ink heating section (not shown) that heats the ink stored in the head unit 24. The ink heating section operates under the control of the control section 40, and heats the ink to a temperature at which it becomes a sol.

The inkjet head 242 ejects ink that has been heated and turned into a sol. When this sol ink is ejected onto the recording medium P, the ink droplets land on the recording medium P, and then the ink quickly turns into a gel and solidifies on the recording medium P due to natural cooling.

The fixing unit 25 has a light-emitting unit arranged across the width of the transport unit 21 in the X direction, and irradiates the recording medium P placed on the transport unit 21 with energy rays such as ultraviolet rays from the light-emitting unit to harden and fix the ink (gel ink) ejected onto the recording medium P. The light-emitting unit of the fixing unit 25 is arranged opposite the transport surface 211a in the transport direction between the position of the head unit 24 and the position of the transfer drum 281 of the delivery unit 28.

The delivery unit 28 has a cylindrical transfer drum 281 that transfers the recording medium P from the transport unit 21 to the belt loop 282, and a belt loop 282 with a circular belt supported on the inside by two rollers. The recording medium P transferred from the transport unit 21 onto the belt loop 282 by the transfer drum 281 is transported by the belt loop 282 and sent to the paper discharge unit 30.

The paper discharge section 30 has a plate-shaped paper discharge tray 31 on which the recording medium P sent from the image forming section 20 by the delivery section 28 is placed.

In the inkjet image forming device 1, if there is any foreign matter adhering to the nozzle surface 245 on which the nozzles 243 that eject ink are formed, if there is any residual ink that has dried and thickened, or if there are any air bubbles mixed in, the ink cannot be ejected properly to form an image. Therefore, head cleaning is performed to maintain a good ink ejection state.

For head cleaning, a purging operation is performed in which the ink inside the nozzle is forcibly expelled by applying pressure from the upstream side of the nozzle or by suction from the nozzle face 245 side, thereby eliminating (purifying) foreign matter, dried and viscous ink, and trapped air bubbles along with the expelled ink.

Furthermore, after ink is discharged as part of such a cleaning operation, a wiping operation is performed in which a cleaning member is brought into contact with and moved against the nozzle surface 245 to clean off any ink remaining on the nozzle surface 245. In the wiping operation, a cleaning member such as an absorbent sponge member or cloth member (e.g., cloth or nonwoven fabric), or a rubber blade (blade member) that scrapes off the ink is used.

Figure 3 is a block diagram showing the main functional configuration of the inkjet image forming device 1. The inkjet image forming device 1 includes a heating unit 23, a head driving unit 241 and an inkjet head 242, a fixing unit 25, a control unit 40, a transport driving unit 51, an operation display unit 52, an input/output interface 53, and a cleaning device 55.

The head driver 241 supplies a drive signal to the image forming element of the inkjet head 242 at an appropriate timing to deform the piezoelectric element in accordance with the image data, thereby causing the nozzle 243 of the inkjet head 242 to eject an amount of ink in accordance with the pixel value of the image data.

The control unit 40 has a CPU 41 (Central Processing Unit), a RAM 42 (Random Access Memory), a ROM 43 (Read Only Memory), and a memory unit 44.

The CPU 41 reads out various control programs and setting data stored in the ROM 43, stores them in the RAM 42, and executes the programs to perform various calculation processes. The CPU 41 also controls the overall operation of the inkjet image forming device 1.

RAM 42 provides working memory space for CPU 41 and stores temporary data. RAM 42 may include non-volatile memory.

The ROM 43 stores various control programs and setting data executed by the CPU 41. Note that a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used instead of the ROM 43.

The storage unit 44 stores print jobs (image formation commands) input from the external device 2 via the input/output interface 53, image data related to the print jobs, and the like. The print job includes information specifying the image data related to the image to be formed, as well as information related to the type of recording medium P on which the image is to be formed (e.g., the size and thickness of the recording medium P). For example, a hard disk drive (HDD) is used as the storage unit 44, and a dynamic random access memory (DRAM) or the like may also be used in combination.

The transport drive unit 51 supplies a drive signal to the transport drum motor of the transport drum 211 based on a control signal supplied from the control unit 40 to rotate the transport drum 211 at a predetermined speed and timing.

The transport drive unit 51 also supplies drive signals to motors for operating the medium supply unit 12, the transfer unit 22, and the delivery unit 28 based on control signals supplied from the control unit 40, thereby supplying the recording medium P to the transport unit 21 and discharging it from the transport unit 21.

The operation display unit 52 includes a display device such as a liquid crystal display or an organic EL display, and an input device such as operation keys and a touch panel arranged over the screen of the display device. The operation display unit 52 displays various information on the display device, and converts user input operations on the input device into operation signals and outputs them to the control unit 40.

The input/output interface 53 mediates the transmission and reception of data between the external device 2 and the control unit 40. The input/output interface 53 is, for example, composed of any one of various serial interfaces, various parallel interfaces, or a combination of these.

The external device 2 is, for example, a personal computer, and supplies print jobs, image data, etc. to the control unit 40 via the input/output interface 53.

The cleaning device 55 cleans ink remaining on the nozzle surface 245 by a wiping operation in which the head unit 24 is moved while a cleaning member 70 (see FIG. 4) is in contact with the nozzle surface 245 of the head unit 24. In this embodiment, an absorbent fabric member (e.g., cloth, nonwoven fabric) is used as the cleaning member 70.

Figure 4 is a diagram illustrating the configuration and operation of the cleaning device 55. As shown in Figure 4, the cleaning device 55 includes a pressure contact/separation unit 60, a pay-out roller 62, a wind-up roller 64 (functioning as the "wind-up unit" of the present invention), and a cleaning member 70 stretched between the pay-out roller 62 and the wind-up roller 64. The control unit 40 and the cleaning device 55 function as the "cleaning device" of the present invention.

The unwinding roller 62 unwinds the wound cleaning member 70 while rotating under the control of the control unit 40. The winding roller 64 winds up the cleaning member 70 unwound by the unwinding roller 62 while rotating under the control of the control unit 40.

Between the payout roller 62 and the take-up roller 64, a backup member 61 is provided to support the cleaning member 70 from below. The backup member 61 is a flat plate-like member made of, for example, a porous body that allows air to pass through (for example, porous ceramics, liquid-permeable resin). The backup member 61 is parallel to the nozzle surface 245 of the head unit 24, and supports the cleaning member 70 so that it is parallel to the nozzle surface 245 by abutting against the inside of the cleaning member 70. The pressure contact separation unit 60 has a known configuration, and under the control of the control unit 40, the backup member 61 is moved upward to press the cleaning member 70 against the nozzle surface 245 of the head unit 24, or the backup member 61 is moved downward to separate the cleaning member 70 from the nozzle surface 245 of the head unit 24.

Figure 4A shows the state before cleaning by the cleaning device 55. In this state, the control unit 40 controls the pressure contact/separation unit 60 to move the backup member 61 downward, thereby separating the cleaning member 70 from the nozzle surface 245 of the head unit 24. Ink 80 remains on the nozzle surface 245 of the head unit 24.

Figure 4B shows the state in which cleaning is being performed by the cleaning device 55. In this state, the control unit 40 controls the pressure contact/separation unit 60 to move the backup member 61 upward, thereby pressing the cleaning member 70 against the nozzle surface 245 of the head unit 24. As a result, the ink 80 remaining on the nozzle surface 245 of the head unit 24 is absorbed (adsorbed) by the cleaning member 70 and cleaned.

In this embodiment, the ink 80 remaining on the nozzle surface 245 is cleaned by a wiping operation (rubbing operation) in which a cleaning member 70 is brought into contact with the nozzle surface 245 and the head unit 24 is moved. Note that this wiping operation is not necessarily a required operation.

Figure 4C shows the state after cleaning by the cleaning device 55. In this state, the control unit 40 controls the pressure contact/separation unit 60 to move the backup member 61 downward, thereby separating the cleaning member 70 from the nozzle surface 245 of the head unit 24.

Figure 4D shows the state in which the cleaning member 70 is wound up so that an unused portion of the cleaning member 70 contacts the nozzle surface 245 of the head unit 24 during the next cleaning by the cleaning device 55. The control unit 40 controls the pay-out roller 62 and the take-up roller 64 to pay out and take up the wound cleaning member 70.

In this embodiment, a stepping motor is used as a drive motor that rotates and drives the unwinding roller 62 and the winding roller 64. The control unit 40 detects the winding amount of the cleaning member 70 based on the number of drive pulses output to the stepping motor. The control unit 40 then controls the unwinding roller 62 and the winding roller 64 so that the detected winding amount becomes the desired winding amount.

However, in the conventional technology (technology described in Patent Document 1), if the time elapsed since cleaning (wiping operation) is short, the amount of winding of the cleaning member (sheet-like member) after cleaning is always small. Therefore, when continuously cleaning the nozzle surfaces 245 of multiple head units 24, specifically when cleaning the first nozzle surface 245 in which the ink ejection ports of the nozzles 243 that eject the first ink are open, and then winding up the cleaning member 70, and cleaning the second nozzle surface 245 in which the ink ejection ports of the nozzles 243 that eject the second ink that is different in color from the first ink are open, the portion of the cleaning member 70 to which the first ink is attached may come into contact with the second nozzle surface 245 due to the small amount of winding up of the cleaning member 70.

In this case, the first ink 80 is transferred (adhered) from the cleaning member 70 to the second nozzle surface 245, and the first ink 80 enters the ink ejection port opening in the second nozzle surface 245. FIG. 5A is a diagram showing the state before the portion of the cleaning member 70 to which the first ink 80 is attached comes into contact with the second nozzle surface 245. FIG. 5B is a diagram showing the state after the portion of the cleaning member 70 to which the first ink 80 is attached comes into contact with the second nozzle surface 245. When the portion to which the first ink 80 is attached comes into contact with the second nozzle surface 245, the first ink 80 enters the ink ejection port opening in the second nozzle surface 245, causing the first ink 80 and the second ink to mix, and the mixed ink is ejected from the ink ejection port opening in the second nozzle surface 245, causing a problem of a deterioration in the quality of the image formed on the recording medium P.

In this embodiment, the purpose is to prevent ink mixing when cleaning ink remaining on the nozzle surface 245 of the head unit 24, and when cleaning the second ink remaining on the second nozzle surface 245 after cleaning the first ink remaining on the first nozzle surface 245, the control unit 40 controls the take-up roller 64 to reduce the amount of ink taken up by the cleaning member 70 when the first ink color and the second ink color are the same, compared to when the first ink color and the second ink color are different. In other words, when the first ink color and the second ink color are different, the control unit 40 controls the take-up roller 64 to increase the amount of ink taken up by the cleaning member 70, compared to when the first ink color and the second ink color are the same.

As a result, when the colors of the first ink and the second ink are different, the amount of winding of the cleaning member 70 is greater (i.e., insufficient winding is prevented) than when the colors of the first ink and the second ink are the same, and the portion of the cleaning member 70 to which the first ink 80 is attached is prevented from contacting the second nozzle surface 245. As a result, the first ink 80 is transferred (adhered) from the cleaning member 70 to the second nozzle surface 245, and the first ink 80 is prevented from entering the ink ejection port opening in the second nozzle surface 245. In addition, it is possible to prevent the first ink 80 and the second ink from mixing, and to prevent a deterioration in the quality of the image formed on the recording medium P by ink ejection from the ink ejection port opening in the second nozzle surface 245.

In this embodiment, when the color of the first ink and the color of the second ink are the same, the control unit 40 controls the winding roller 64 to satisfy the following formula (1) in the winding direction of the cleaning member 70, where α is the length of the first ink adhered to the cleaning member 70 by cleaning with the first ink, and β is the winding amount of the cleaning member 70.
0.5×α≦β<α...(1)

On the other hand, when the colors of the first ink and the second ink are different, the control unit 40 controls the winding roller 64 to satisfy the following formula (2) in the winding direction of the cleaning member 70, where α is the length of the first ink adhering to the cleaning member 70 due to cleaning of the first ink and β is the winding amount of the cleaning member 70.
1.2×α≦β...(2)

Here, the results of an experiment conducted by the inventor to confirm the effectiveness of this embodiment will be described. In the experiment, the length α of the first ink attached to the cleaning member 70 was set to 40 mm, and the take-up amount β of the cleaning member 70 was changed in increments of 10 mm in the range from 10 mm to 60 mm, while the "occurrence of color mixing between the first ink 80 and the second ink" and the "liquid absorption of the second ink" were evaluated based on the following evaluation criteria. Regarding the occurrence of color mixing, an image was formed on the recording medium P after cleaning the second ink remaining on the second nozzle surface 245, and the image was observed. Regarding the liquid absorption of the second ink, the remaining state of the second ink on the second nozzle surface 245 was visually observed after cleaning the second ink remaining on the second nozzle surface 245.

(Occurrence of color mixing)
○: No color mixing occurred.
Δ: A slight amount of color mixing occurred, but there was no problem with the quality of the image formed on the recording medium P.
×: Color mixing occurred, and there was a problem with the quality of the image formed on the recording medium P.

(Absorbency of the second ink)
◯: No second ink remained on the second nozzle surface 245.
Δ: A small amount of the second ink remained on the second nozzle surface 245 .
×: The second ink clearly remained on the second nozzle surface 245 .

Figure 6A shows the occurrence of color mixing between the first ink 80 and the second ink and the liquid absorbency of the second ink when the first ink and the second ink are the same color.

As shown in FIG. 6A, when the color of the first ink and the color of the second ink are the same and the take-up amount β of the cleaning member 70 is 10 mm, the second ink clearly remained on the second nozzle surface 245. Also, when the take-up amount β of the cleaning member 70 is 20 mm, a small amount of the second ink remained on the second nozzle surface 245. Also, when the take-up amount β of the cleaning member 70 is 30 mm or more (30 mm, 40 mm, 50 mm, 60 mm), no second ink remained on the second nozzle surface 245.

From the above, when the color of the first ink and the color of the second ink are the same, the adhesion length α of the first ink attached to the cleaning member 70 and the winding amount β of the cleaning member 70 satisfy the above formula (1), particularly 0.5 × α ≦ β, by controlling the winding roller 64, it is possible to prevent a decrease in the liquid absorption of the second ink. Also, when the color of the first ink and the color of the second ink are the same, even if the first ink is transferred (adhered) from the cleaning member 70 to the second nozzle surface 245 and the first ink 80 enters the ink ejection port opened in the second nozzle surface 245, color mixing does not occur in the first place. Therefore, by controlling the winding roller 64 so that the adhesion length α of the first ink attached to the cleaning member 70 and the winding amount β of the cleaning member 70 satisfy the above formula (1), particularly β < α, it is possible to minimize the winding amount of the cleaning member 70 and reduce the consumption of the cleaning member 70.

Figure 6B shows the occurrence of color mixing between the first ink 80 and the second ink and the liquid absorbency of the second ink when the colors of the first ink and the second ink are different.

As shown in FIG. 6B, when the colors of the first ink and the second ink were different and the take-up length β of the cleaning member 70 was 10 mm, color mixing occurred, causing problems with the quality of the image formed on the recording medium P. In addition, the second ink was clearly remaining on the second nozzle surface 245.

When the take-up length β of the cleaning member 70 was 20 mm, some color mixing occurred, but there was no problem with the quality of the image formed on the recording medium P. Also, a small amount of the second ink remained on the second nozzle surface 245.

When the take-up length β of the cleaning member 70 was 30 mm, some color mixing occurred, but there was no problem with the quality of the image formed on the recording medium P. Also, no second ink remained on the second nozzle surface 245.

When the take-up length β of the cleaning member 70 was 40 mm, some color mixing occurred, but there was no problem with the quality of the image formed on the recording medium P. Also, no second ink remained on the second nozzle surface 245.

Furthermore, when the take-up length β of the cleaning member 70 was 50 mm or more (50 mm, 60 mm), no color mixing occurred. Furthermore, no second ink remained on the second nozzle surface 245.

In view of the above, when the colors of the first ink and the second ink are different, by controlling the winding roller 64 so that the adhesion length α of the first ink adhered to the cleaning member 70 and the winding amount β of the cleaning member 70 satisfy the above formula (2), i.e., 1.2 × α≦β, it is possible to prevent the first ink and the second ink from mixing and to prevent a decrease in the absorbency of the second ink.

Figure 7 is a diagram explaining the adhesion length α of ink adhered to the cleaning member 70. As shown in Figure 7A, the adhesion length α is defined as the length (also called the "bleed length") of the first ink 80 remaining on the nozzle surface 245 of the head unit 24 that is absorbed (adsorbed) by the cleaning member 70 in the winding direction of the cleaning member 70. In particular, the adhesion length α is defined as being equal to or greater than the length between the most distant nozzles on the nozzle surface 245 of the head unit 24 in the winding direction of the cleaning member 70 (see symbol d in Figure 2).

As shown in FIG. 7B, when ink 80 remaining on the nozzle surfaces 245A, 245B of multiple head units 24A, 24B is cleaned simultaneously, the adhesion length α is defined as the length in the winding direction of the cleaning member 70 between the most upstream position where the first ink 80 remaining on the nozzle surface 245A of head unit 24A is absorbed (adsorbed) by the cleaning member 70, and the most downstream position where the first ink 80 remaining on the nozzle surface 245B of head unit 24B is absorbed (adsorbed) by the cleaning member 70.

In this embodiment, the control unit 40 obtains the measurement results of a known measurement unit 110 (e.g., a CCD camera) that measures the adhesion length α, and controls the take-up roller 64 to change the take-up amount β of the cleaning member 70 according to the actual adhesion length α while satisfying the above formulas (1) and (2). This makes it possible to reliably prevent the first ink and the second ink from mixing, and to prevent a decrease in the absorbency of the second ink, regardless of whether the first ink and the second ink are the same or different colors.

The control unit 40 may control the take-up roller 64 so that the take-up amount β increases as the inclination angle of the nozzle surface 245 relative to the horizontal direction of the head unit 24 increases. This is because, as the inclination angle of the nozzle surface 245 relative to the horizontal direction of the head unit 24 increases, the ink tends to spread due to gravity in the take-up direction of the cleaning member 70 (specifically, the downward direction of the nozzle surface 245), and the adhesion length α of the first ink adhered to the cleaning member 70 increases.

The control unit 40 may also control the take-up roller 64 so that the take-up amount β increases as the water repellency of the nozzle surface 245 of the head unit 24 decreases. This is because as the water repellency of the nozzle surface 245 of the head unit 24 decreases, the ink tends to spread in the take-up direction (upstream direction and downstream direction) of the cleaning member 70, and the adhesion length α of the first ink adhered to the cleaning member 70 increases.

Next, the winding control operation of the inkjet image forming apparatus 1 will be described. FIG. 8 is a flow chart showing an example of the winding control operation of the inkjet image forming apparatus 1 (corresponding to the "winding control method" of the present invention) when the nozzle surfaces 245 of the multiple head units 24 are continuously cleaned, specifically, when the first nozzle surface 245 on which the ink ejection ports of the nozzles 243 ejecting the first ink are open is cleaned, and then the cleaning member 70 is wound up, and the second nozzle surface 245 on which the ink ejection ports of the nozzles 243 ejecting the second ink, which is different in color from the first ink, are cleaned. Step S100 in FIG. 8 is started when an instruction to perform head cleaning is issued in the inkjet image forming apparatus 1.

First, the control unit 40 controls the pressure contact/separation unit 60 to move the backup member 61 upward to bring the cleaning member 70 into pressure contact with the first nozzle surface 245 of the head unit 24 (step S100). As a result, the ink 80 remaining on the first nozzle surface 245 of the head unit 24 is absorbed (adsorbed) by the cleaning member 70 and cleaned.

Next, the control unit 40 controls the pressure contact/separation unit 60 to move the backup member 61 downward to separate the cleaning member 70 from the first nozzle surface 245 of the head unit 24 (step S120).

Next, the control unit 40 determines whether the color of the first ink is different from the color of the second ink (step S140). If the result of the determination is that the color of the first ink is different from the color of the second ink (step S140, YES), the control unit 40 sets the length of the first ink adhered to the cleaning member 70 by cleaning the first ink in the winding direction of the cleaning member 70 as α, and sets the winding amount β of the cleaning member 70 so as to satisfy the above formula (2) (step S160). After that, the process proceeds to step S200.

On the other hand, if the color of the first ink and the color of the second ink are the same (step S140, NO), the control unit 40 sets the length of the first ink adhered to the cleaning member 70 by cleaning the first ink in the winding direction of the cleaning member 70 as α, and sets the winding amount β of the cleaning member 70 so as to satisfy the above formula (1) (step S180). After that, the process proceeds to step S200.

In step S200, the control unit 40 controls the unwinding roller 62 and the winding roller 64 to unwind and wind the cleaning member 70 by the winding amount β set in step S160 or S180 (step S200). Upon completion of the process of step S200, the inkjet image forming apparatus 1 ends the winding control operation.

As described above in detail, the inkjet image forming apparatus 1 (image forming apparatus) in this embodiment includes a cleaning member 70 that contacts the nozzle surface 245 of the head unit 24 that forms an image on the recording medium P by the inkjet head 242 and cleans the ink 80 remaining on the nozzle surface 245, a winding section (winding roller 64) that winds up the cleaning member 70 so that an unused portion of the cleaning member 70 contacts the second nozzle surface 245 when cleaning the second ink remaining on the second nozzle surface 245 after cleaning the first ink remaining on the first nozzle surface 245, and a control section 40 that controls the winding section to reduce the amount of winding of the cleaning member 70 when the first ink and the second ink are the same color, compared to when the first ink and the second ink are different colors.

According to the present embodiment configured as described above, when the color of the first ink and the color of the second ink are the same, the amount of winding of the cleaning member 70 is controlled to be smaller than when the color of the first ink and the color of the second ink are different. In other words, when the color of the first ink and the color of the second ink are different, the amount of winding of the cleaning member 70 is larger than when the color of the first ink and the color of the second ink are the same (i.e., insufficient winding is prevented), and the part of the cleaning member 70 to which the first ink is attached is prevented from contacting the second nozzle surface 245. As a result, the first ink is transferred (adheres) from the cleaning member 70 to the second nozzle surface 245, and the first ink is prevented from entering the ink ejection port opening in the second nozzle surface 245. In addition, it is possible to prevent the first ink and the second ink from mixing, and to prevent a deterioration in the quality of the image formed on the recording medium P by ink ejection from the ink ejection port opening in the second nozzle surface 245.

In the above embodiment, an example is described in which the amount of the cleaning member 70 taken up is detected based on the number of drive pulses output to the stepping motor that rotates the payout roller 62 and the winding roller 64, but the present invention is not limited to this. For example, as shown in FIG. 9, a rotating body 92 (disk) having a cutout portion 92A (slit) formed therein may be provided on the rotating shaft 64A of the winding roller 64. The rotating body 92 rotates in conjunction with the rotation of the winding roller 64. Then, the non-contact reflective photosensor 94 detects the number of times the notch portion 92A formed in the rotating body 92 passes (i.e., the amount of rotation) in response to the rotation of the rotating body 92, and outputs the detection result to the control unit 40. The control unit 40 detects the amount of the cleaning member 70 taken up based on the detection result output from the reflective photosensor 94.

In addition, in the above embodiment, a single-pass type inkjet image forming device 1 has been described as an example, but the present invention may be applied to an inkjet image forming device that records an image while scanning a head unit. Also, the present invention may be applied to an inkjet image forming device in which a single nozzle is provided in the head unit.

Furthermore, the above-mentioned embodiments are merely examples of the implementation of the present invention, and the technical scope of the present invention should not be interpreted in a limiting manner based on these. In other words, the present invention can be implemented in various forms without departing from its gist or main features.

REFERENCE SIGNS LIST 1 Inkjet image forming apparatus 2 External device 10 Paper feed section 11 Paper feed tray 12 Medium supply section 20 Image forming section 21 Transport section 211 Transport drum 211a Transport surface 22 Delivery unit 23 Heating section 24, 24A, 24B Head unit 241 Head driving section 242 Inkjet head 243 Nozzle 244 Mounting member 245, 245A, 245B Nozzle surface 25 Fixing section 28 Delivery section 30 Paper discharge section 31 Paper discharge tray 40 Control section 41 CPU
42 RAM
43 ROM
44 Memory section 51 Transport drive section 52 Operation display section 53 Input/output interface 55 Cleaning device 60 Pressing/separating section 61 Backup member 62 Feed-out roller 64 Winding roller 64A Rotating shaft 70 Cleaning member 80 Ink 92 Rotating body 92A Notch section 94 Reflective photosensor 110 Measurement section P Recording medium

Claims (10)

a cleaning member that comes into contact with a nozzle surface of a head unit that forms an image on a recording medium by an inkjet head and cleans ink remaining on the nozzle surface;
a winding section that winds up the cleaning member such that an unused portion of the cleaning member contacts the second nozzle surface when cleaning the second ink remaining on the second nozzle surface after cleaning the first ink remaining on the first nozzle surface;
a control unit that controls the winding unit to reduce a winding amount of the cleaning member when the first ink and the second ink have the same color, compared to when the first ink and the second ink have different colors;
Equipped with
In the take-up direction of the cleaning member, when an adhesion length of the first ink adhered to the cleaning member by cleaning with the first ink is denoted as α and a take-up amount of the cleaning member is denoted as β, if the color of the first ink and the color of the second ink are the same, the following formula (1) is satisfied, and if the color of the first ink and the color of the second ink are different, the following formula (2) is satisfied:
Cleaning equipment.
0.5×α≦β<α...(1)
1.2×α≦β...(2) the adhesion length is equal to or greater than the length between the nozzles on the first nozzle surface in the take-up direction of the cleaning member;
The cleaning device according to claim 1 . The control unit controls the winding unit to change the winding amount of the cleaning member in response to a measurement result of the measurement unit that measures the adhesion length.
3. The cleaning device according to claim 1 or 2 . the control unit controls the winding unit so as to increase the amount of winding of the cleaning member as the inclination angle of the first nozzle surface with respect to the horizontal direction of the head unit increases.
The cleaning device according to any one of claims 1 to 3 . the control unit controls the winding unit to increase a winding amount of the cleaning member as the water repellency of the first nozzle surface decreases.
The cleaning device according to any one of claims 1 to 4 . The winding section winds up the cleaning member while rotating,
the control unit detects the amount of the cleaning member taken up based on the number of drive pulses output to a stepping motor that rotates and drives the take-up unit.
The cleaning device according to any one of claims 1 to 5 . The winding section winds up the cleaning member while rotating,
a rotor having a notch formed therein is provided on a rotation shaft of the winding unit,
the control unit detects a take-up amount of the cleaning member based on a rotation amount of the notch portion detected in response to rotation of the rotating body.
The cleaning device according to any one of claims 1 to 6 . The cleaning member is a cloth member.
The cleaning device according to any one of claims 1 to 7 . A cleaning device according to any one of claims 1 to 8 ;
The head unit;
An image forming apparatus comprising: a cleaning member that comes into contact with a nozzle surface of a head unit that forms an image on a recording medium by an inkjet head and cleans ink remaining on the nozzle surface;
a winding unit that winds up the cleaning member such that an unused portion of the cleaning member contacts the second nozzle face when cleaning a second ink remaining on a second nozzle face after cleaning a first ink remaining on the first nozzle face, the winding unit comprising:
When the color of the first ink and the color of the second ink are the same, a control is performed to reduce a take-up amount of the cleaning member compared to when the color of the first ink and the color of the second ink are different;
In the control, when an adhesion length of the first ink adhered to the cleaning member by the cleaning with the first ink in a take-up direction of the cleaning member is defined as α, and the take-up amount is defined as β, β satisfies the following formula (1) when the color of the first ink and the color of the second ink are the same, and satisfies the following formula (2) when the color of the first ink and the color of the second ink are different from each other:
Winding control method.
0.5×α≦β<α...(1)
1.2×α≦β...(2)