JP7476486B2 - Inkjet image forming device - Google Patents

Description

The present invention relates to an inkjet image forming device.

Conventionally, there are inkjet image forming devices that transport a recording medium such as paper using a transport member such as a transport drum, and eject ink from nozzles of an ink ejection unit onto the recording medium on the transport member to form an image on the recording medium.

In addition, there is known an inkjet image forming device that uses ink that has the property of being cured by ultraviolet (UV) light (hereinafter referred to as "UV curable ink") and irradiates ink droplets (ink image) of the UV curable ink ejected onto a recording medium with ultraviolet light to cure the ink image. In such an inkjet image forming device, an ultraviolet irradiating unit for irradiating the ink image with ultraviolet light is positioned in a direction facing the ink image on the recording medium being transported (see, for example, Patent Document 1).

In addition, in such inkjet image forming devices, a plate-shaped partition member is placed between the ultraviolet ray irradiation unit and the opposing conveying member (or recording medium) to prevent deterioration of the performance of the ultraviolet ray irradiation unit due to the adhesion of dust, ink mist, etc. Such a partition member is made of a transparent material such as a glass plate that transmits ultraviolet rays.

In such inkjet image forming devices, if oxygen is present between the partition member and the recording medium, the curing of the UV-curable ink when irradiated with ultraviolet light may be inhibited, and image quality may deteriorate. This is caused by radicals generated in the early stages of the polymerization reaction combining with oxygen in the surrounding atmosphere.

In order to prevent the curing of such UV-curable ink from being inhibited by oxygen in the surrounding atmosphere, the technology of Patent Document 1 provides a gas supply unit that supplies an inert gas such as nitrogen, and the inert gas supplied from the gas supply unit is guided to the passage of the recording medium through the openings in the housing and the partition member.

JP 2017-132040 A

In the conventional inkjet image forming apparatus described above, the transport path of the recording medium in the area passing through the ultraviolet ray irradiation section is generally linear from the viewpoint of preventing leakage of the inert gas. Specifically, as described in Patent Document 1, it is common to have a configuration in which the recording medium is transported approximately parallel to the partition member described above.

In response to this, in recent years, there has been a demand to add the above-mentioned gas supply unit to inkjet image forming devices that convey a recording medium in a curved manner using a conveying member whose side shape has a curvature (is not straight), such as a conveying drum, and irradiate the ink on the recording medium with ultraviolet light.

However, when a gas supply unit is added to an inkjet image forming device having such a configuration, gas tends to leak from gaps near the ends of the partition member on the upstream and downstream sides in the transport direction of the recording medium, making it difficult to fully fill the ultraviolet ray irradiation area with the supplied inert gas.

The object of the present invention is to provide an inkjet image forming device that can suppress gas leakage in the transport path of the recording medium.

The inkjet image forming apparatus according to the present invention comprises:
a conveying member that conveys the recording medium onto which the ink has been ejected, using a conveying surface having a curvature;
an energy ray irradiation unit that irradiates the ink on the recording medium with an active energy ray;
a partition member that is disposed opposite the transport surface so as to separate a space between the transport member and the energy ray irradiation unit, that forms a gap between the transport surface and the partition member to serve as a transport space for the recording medium, and that transmits the active energy rays emitted from the energy ray irradiation unit;
a gas supply unit that supplies a gas to the transfer space;
a gap suppressing portion that is disposed between the transport surface of the transport member and at least one end side of the partition member along a transport direction of the recording medium so as to reduce a gap that forms the transport space between the transport surface of the transport member and at least one end side of the partition member along the transport direction of the recording medium;
a holding portion that holds the partition member on the upstream side and the downstream side in the conveying direction;
A frame that fixes the holding portion;
having
the gas supply unit is disposed on the upstream side of the partition member in the transport direction,
The gap suppression portion is provided in the vicinity of the holding portion,
The holding portion includes an upper member fixed to the frame, and a lower member that sandwiches and holds the partition member together with the upper member.
has.

The present invention makes it possible to suppress gas leakage in the transport path of the recording medium.

1 is a diagram showing a schematic configuration of an inkjet image forming apparatus according to an embodiment of the present invention; 1 is a block diagram showing a main functional configuration of an inkjet image forming apparatus according to an embodiment of the present invention; 11 is a side cross-sectional view for explaining problems etc. that arise when a gas supply unit is added to an inkjet image forming apparatus having a conventional configuration. 2 is a side cross-sectional view illustrating a configuration of a fixing unit and the like of the inkjet image forming apparatus according to the present embodiment. FIG. 11 is a perspective view illustrating an operation of inserting and removing the partition member into and from the fixing unit. FIG. FIG. 4 is an exploded view illustrating an example of the configuration of a holding portion. 4 is an enlarged cross-sectional side view showing a boundary region between the gas supply portion and the gap suppression portion. FIG. FIG. 8 is an enlarged side cross-sectional view of a portion of FIG. 7 .

Figure 1 is a diagram showing a schematic configuration of an inkjet image forming apparatus 1 in this embodiment. The inkjet image forming apparatus 1 includes a paper feed section 10, an image forming section 20, a paper discharge section 30, and a control section 40 (see Figure 2). Under the control of the control section 40, the inkjet image forming apparatus 1 transports a recording medium P stored in the paper feed section 10 to the image forming section 20, forms an image on the recording medium P in the image forming section 20, and transports the recording medium P on which the image has been formed to the paper discharge section 30. As the recording medium P, various media that can fix 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 has a transport drum 21, a delivery unit 22, a heating unit 23, a head unit 24, a gas supply unit 25 (see also FIG. 2), a fixing unit 26, and a delivery unit 27.

The transport drum 21 holds the recording medium P on its cylindrical outer curved surface (a transport surface having a curvature) and rotates about a rotation axis extending in a direction perpendicular to the plane of the drawing in FIG. 1 (hereinafter referred to as the "orthogonal direction") to transport the recording medium P in a transport direction along the transport surface. The transport drum 21 corresponds to the "transport member" of the present invention.

The transport drum 21 has a claw portion and an air intake portion (not shown) for holding the recording medium P on its transport surface. The recording medium P is held on the transport surface by having its edges pressed down by the claw portion and being drawn to the transport surface by the air intake portion. The transport drum 21 has a transport drum motor (not shown) for rotating the transport drum 21, and 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 drum 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 drum 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 drum 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 conveying surface of the conveying drum 21 and the recording medium P so that the recording medium P conveyed by the conveying drum 21 has a temperature 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 (see FIG. 2) to cause the infrared heater to generate heat.

The head unit 24 ejects ink from nozzle openings provided on an ink ejection surface facing the transport surface of the transport drum 21 onto the recording medium P at an appropriate timing according to the rotation of the transport drum 21 on which the recording medium P is held, to record (form) an image. The head unit 24 is positioned so that the ink ejection surface and the transport surface 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.

Each head unit 24 is equipped with an inkjet head 242 (see FIG. 2). The inkjet head 242 is provided with a number of image-forming 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. When a drive signal is input to deform the piezoelectric element, the image-forming element deforms the pressure chamber, changing the pressure in the pressure chamber, and ejects ink from a nozzle connected to the pressure chamber.

The nozzle arrangement range in the orthogonal direction of the inkjet head 242 covers the orthogonal width of the area on the recording medium P transported by the transport drum 21 where an image is to be recorded. The head unit 24 is used with its position fixed relative to the rotation axis of the transport drum 21 when recording an image. In other words, the inkjet image forming device 1 is a single-pass type inkjet image forming device.

The ink ejected from the inkjet head 242 has the property of changing into a gel or sol state depending on the temperature and curing when exposed to energy rays such as ultraviolet rays. In the present embodiment, ink is used that is in a gel state at room temperature and becomes a sol state when heated. 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 the ink becomes a sol. The head unit 24 ejects the ink that has been heated and turned into a sol state. When this sol-state ink is ejected onto the recording medium P, the ink droplets land on the recording medium P, and then the ink quickly becomes a gel state and solidifies on the recording medium P due to natural cooling.

The fixing unit 26 has a light-emitting unit arranged across the width of the transport drum 21 in the perpendicular direction. The fixing unit 26 imparts a predetermined energy to the ink ejected onto the recording medium P by irradiating the recording medium P placed on the transport drum 21 with energy rays of a predetermined wavelength (ultraviolet (UV) light in this example) from the light-emitting unit, thereby hardening and fixing the ink. The light-emitting unit of the fixing unit 26 is arranged opposite the transport surface of the transport drum 21, between the position of the most downstream head unit 24 in the transport direction and the position of the transfer drum 271 (delivery unit 27).

The gas supply unit 25 serves to purge oxygen from the space by supplying an inert gas (e.g., nitrogen gas) into the transport path (transport space S in FIG. 3) for the recording medium P formed between the fixing unit 26 and the transport surface of the transport drum 21, thereby maintaining the fixing performance of the fixing unit 26. The detailed configuration of the gas supply unit 25 will be described later.

The delivery section 27 has a belt loop 272 with a circular belt supported on the inside by two rollers, and a cylindrical transfer drum 271 that transfers the recording medium P from the transport drum 21 to the belt loop 272. The recording medium P transferred from the transport drum 21 to the belt loop 272 by the transfer drum 271 is transported by the belt loop 272 and sent to the paper discharge section 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 27 is placed.

Figure 2 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 section 23, an inkjet head driving section 241 and an inkjet head 242 in a head unit 24, a gas supply section 25, a fixing section 26, a control section 40, a transport driving section 51, and an input/output interface 52.

Based on the control of the control unit 40, the inkjet head driving unit 241 supplies a driving signal to the image forming element of the inkjet head 242 at an appropriate timing to deform the piezoelectric element according to the image data, thereby ejecting an amount of ink according to the pixel value of the image data from the nozzle of the inkjet head 242.

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 arithmetic processing. 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. Note that RAM 42 may include non-volatile memory.

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

The storage unit 44 stores print jobs (image recording commands) input from the external device 2 via the input/output interface 52 and image data related to the print jobs. For example, a hard disk drive (HDD) is used as the storage unit 44, and a dynamic random access memory (DRAM) may also be used in combination.

The transport drive unit 51 supplies a drive signal to the transport drum motor of the transport drum 21 based on a control signal supplied from the control unit 40, causing the transport drum 21 to rotate at a predetermined speed and timing. The transport drive unit 51 also supplies a drive signal to a motor for operating the medium supply unit 12, the delivery unit 22, and the delivery unit 27 based on a control signal supplied from the control unit 40, causing the recording medium P to be supplied to the transport drum 21 and discharged from the transport drum 21.

The input/output interface 52 mediates the transmission and reception of data between the external device 2 and the control unit 40. The input/output interface 52 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 image recording commands (print jobs) and image data, etc. to the control unit 40 via the input/output interface 52.

Figure 3 is a side cross-sectional view for explaining the configuration of the fixing unit 26 and other components of the inkjet image forming apparatus 1. For ease of explanation, the side cross-section shown in Figure 3 is shown from an angle different from the angle shown in Figure 1 (i.e., tilted clockwise), and this also applies to Figures 4, 7, and 8 described below.

As shown in FIG. 3, the fixing unit 26 has a frame 261 that is approximately trapezoidal in appearance when viewed from the side, and a UV irradiator 262 is fixed to the upper side of the frame 261, a transparent partition member 263 such as a glass plate is fixed to the lower side of the frame 261, and a reflector 265 is fixed to each side of the frame 261.

For ease of explanation, in FIG. 3, the reflector 265 on the near side of the page is omitted and part of the UV irradiator 262 is cut away, and this is also the case with FIG. 4 described later.

As shown in FIG. 3, the partition member 263 is disposed opposite the transport surface of the transport drum 21 so as to separate the space between the transport drum 21 and the UV irradiator 262, and has the function of transmitting ultraviolet light (UV light) emitted from the UV irradiator 262 and supplying it to the ink on the recording medium P.

The partition member 263, together with the lower part of the frame 261, forms a transport space S between the transport surface of the transport drum 21 and the partition member 263, which serves as a gap or passage for transporting the recording medium P.

The reflector 265 has the function of reflecting the UV light emitted from the UV irradiator 262 that is reflected by the inner surface of the frame 261 or the partition member 263, etc., and directing it to the transport surface of the transport drum 21 (the recording medium P onto which the ink is ejected).

In recent years, however, there has been a demand to add the above-mentioned gas supply unit 25 to models in which the recording medium P is conveyed in a curved manner by a conveying drum 21 whose side shape has a curvature (is not straight), as shown in FIG. 3, and the ink on the recording medium P is irradiated with ultraviolet light from a UV irradiator 262.

However, when adding a gas supply unit 25 to an inkjet image forming device 1 having such a configuration, gas tends to leak from gaps near the ends of the partition member 263 on the upstream and downstream sides in the transport direction, making it difficult to fully fill the ultraviolet ray irradiation area with the supplied inert gas.

Specifically, when using a conveying drum 21 whose side shape is not straight but has a curve, and when the partition member 263 is a plate-shaped member as described above that is arranged facing each other, there is a drawback in that gaps are likely to occur between the lower part of the frame 261 and the partition member 263, or between these members and the gas supply unit 25.

The above gap can cause gas in the transport space S, which serves as the passage for the recording medium, to leak to the outside, making it difficult to fully fill the transport space S with the inert gas supplied from the gas supply unit 25, and ultimately causing the oxygen remaining in the transport space S to inhibit the curing of the UV-curable ink.

To address this issue, it is possible to make the side shape of the partition member 263 have the same curvature as the transport surface of the transport drum 21, thereby making the distance (distance or gap) between the bottom surface of the partition member 263 and the transport surface of the transport drum 21 uniform. However, this type of configuration requires a lot of work to adjust the distance between the partition member 263 and the transport drum 21, and giving the side shape of the partition member 263 a curvature is also disadvantageous in terms of costs, etc.

In view of the above-mentioned circumstances, in this embodiment, the gas supply unit 25 is provided next to the fixing unit 26 (partition member 263), and various configurations (gap suppression units) are provided in the fixing unit 26 to sufficiently fill the transfer space S with the inert gas supplied from the gas supply unit 25. The configurations of the gas supply unit 25 and the fixing unit 26 in this embodiment will be described in detail below with reference to FIG. 4 and subsequent figures.

As shown in FIG. 4, in the inkjet image forming apparatus 1 of this embodiment, the gas supply unit 25 is disposed upstream of the fixing unit 26 in the transport direction of the recording medium P (see the arrow in the figure). Here, the side of the gas supply unit 25 is disposed so as to be in close contact with the side of the frame 261 in the fixing unit 26, and the bottom surface of the gas supply unit 25 is disposed opposite the transport surface of the transport drum 21. An opening nozzle 253 that supplies an inert gas is formed on the bottom side of the gas supply unit 25 so as to be inclined toward the side of the frame 261 in the fixing unit 26.

The gas supply unit 25 includes a hollow nozzle body 252, a supply pipe 250 connected to a tank that contains an inert gas (not shown in the figure, nitrogen gas in this example), and a connecting fitting 251 connected to the supply pipe 250 and the nozzle body 252.

The nozzle body 252 is a hollow structure in which the half sections 252-1 and 252-2 are combined with each other and fixed with a screw 254, forming an opening nozzle 253 at the tip end. Here, the nozzle body 252 and the opening nozzle 253 have a length that is approximately the same as the size of the opposing conveying drum 21 in the perpendicular direction.

The gas supply unit 25 fills the inside of the nozzle body 252 with nitrogen gas stored in a tank through the supply pipe 250, etc., and discharges the filled nitrogen gas to the outside from the opening nozzle 253. Here, the discharged nitrogen gas pushes out the atmosphere in the transport space S formed between the partition member 263, etc., and the transport surface of the transport drum 21, and is supplied into the transport space S.

In the present embodiment shown in FIG. 4, a gap suppression section is provided to reduce the gap between the transport drum 21 and the end side of the partition member 263 along the transport direction. This gap suppression section is primarily responsible for reducing or blocking the space on the end side of the partition member 263 in the transport space S described above. By providing such a gap suppression section, it is possible to effectively prevent or suppress leakage of the nitrogen gas supplied from the gas supply section 25 from within the transport space S.

In this embodiment, the gap suppression portion is provided mainly near the holding portion 264 that holds the end side of the partition member 263 along the conveying direction, and specifically, the extension portion 266 (266-1, 266-2), the eaves 268, and the filling member 269 function as the gap suppression portion. Also, in this embodiment, the side end portion 261-1 (see Figures 4 and 7) of the frame 261 provided on both ends in the width direction perpendicular to the conveying direction also functions as the gap suppression portion.

In other words, as can be seen by comparing Figures 3 and 4, in this embodiment, the lower portion of the frame 261 is extended, and the extended portion of the frame 261 functions as a gap suppression portion.

Of the above, the extension portion 266 is broadly divided into a first extension portion 266-1 provided on the upstream side in the transport direction of the recording medium P, and a second extension portion 266-2 provided on the downstream side of the same. For ease of explanation, they will be simply referred to as the "upstream side" and the "downstream side" below.

As can be seen by comparing with Figure 3, the first extension portion 266-1 is part of the frame 261 in the fixing section 26, and is formed so that the lower end on the upstream side of the frame 261 extends (prolongs) to a predetermined position, at which it bends in a direction parallel to the conveying surface of the conveying drum 21 to form a eaves-like portion.

In this embodiment, the first extension 266-1 is formed to extend to a predetermined position (in this example, a position below the bottom surface of the partition member 263), thereby reducing the gap (space) between the transport drum 21 and the partition member 263 and closing off the gap. In addition, the first extension 266-1 is bent from the above-mentioned predetermined position in a direction parallel to the transport surface of the transport drum 21 to form an eave-shaped portion, thereby reducing the gap between the gas supply unit 25 and the partition member 263.

The second extension 266-2 is also part of the frame 261 in the fixing section 26, and is formed so that the downstream lower end of the frame 261 extends (prolongs) to a predetermined position (similarly, a position below the bottom surface of the partition member 263), at which it bends in a direction parallel to the conveying surface of the conveying drum 21 to form a eaves-like portion.

According to this embodiment having such a configuration, the gap (space) in the transport space S between the partition member 263 and the transport surface of the transport drum 21 is reduced to become a closed space, and gas in the transport space S is prevented from leaking from the upstream and downstream sides of the frame 261. In addition, in this embodiment, the volume of the transport space S is significantly smaller than the space portion of Patent Document 1, so that the nitrogen gas supplied from the gas supply unit 25 tends to fill the space quickly, and the cost of consuming nitrogen gas can also be saved.

In addition, in this embodiment, as shown in FIG. 4, a canopy 268 is disposed under each surface of the extension portion 266 (266-1, 266-2) that is bent in a direction parallel to the conveying surface of the conveying drum 21.

In this embodiment, the first extension 266-1 and the upstream eaves 268 are disposed between the gas supply unit 25 and the partition member 263, and serve as a gap suppression unit that suppresses the gap between the conveying surface of the conveying drum 21 (in other words, the increase in the conveying space S). The provision of such a gap suppression unit helps to fill the conveying space S with nitrogen gas supplied from the gas supply unit 25.

The upstream eaves 268 may be omitted in some cases. However, since the upstream eaves 268 has various functions as described below, it is desirable to arrange it so that it overlaps the first extension 266-1 (the bent portion of the first extension 266-1 in this example) as shown in the figure.

In this embodiment, the upstream eaves 268 serve to make it easier to align the gas supply section 25 with the first extension section 266-1 by adding thickness to the end face of the frame 261 that is joined to the nozzle body 252.

In addition, the upstream eaves 268 also have the function of improving the flow of gas (nitrogen gas) supplied from the gas supply unit 25 (see the arrow in Figure 8).

Furthermore, the upstream eaves 268 also has the function of preventing leakage of UV light emitted from the UV irradiator 262 (i.e., directing the leaked UV light to the transport surface of the transport drum 21). In addition, in this embodiment, the bottom surface 252b (see FIG. 7) of the nozzle body 252 adjacent to the upstream eaves 268 also has the function of preventing leakage of UV light.

In this way, by giving the nozzle body 252 the function of preventing leakage of UV light, the distance between the opening nozzle 253 and the transfer space S can be shortened, and as a result, the nitrogen gas ejected from the opening nozzle 253 can be quickly supplied to the transfer space S.

On the other hand, as shown in FIG. 4, the downstream eaves 268 are longer in the conveying direction (dimension) than the upstream eaves 268. This is because there is no member on the downstream side that corresponds to the bottom surface 252b of the nozzle body 252 described above, and so in order to set the function of preventing UV light leakage to the same extent as on the upstream side, the length of the downstream eaves 268 is made longer than that of the upstream eaves 268.

From the viewpoint of supplying the nitrogen gas from the gas supply unit 25 to the transport space S without leakage, the first extension 266-1 and the eaves 268 on the upstream side in the transport direction are important elements, and the second extension 266-2 and the eaves 268 on the downstream side may be omitted. However, as described above, the second extension 266-2 and the eaves 268 below it are important elements in increasing the volume of the transport space S on the downstream side in the transport direction and strengthening the nitrogen gas retention performance.

Next, a more detailed configuration of the fixing unit 26 in the inkjet image forming apparatus 1 of this embodiment will be described with reference to FIG. 5 and subsequent figures as appropriate. Here, FIG. 5 is a perspective view showing the operation of moving (inserting and removing) the partition member 263 relative to the fixing unit 26. Also, FIG. 6 is an exploded view explaining an example of the configuration of the holding unit 264.

As shown in FIG. 5, in this embodiment, the partition member 263 can be moved relative to the frame 261 in the length direction (see the double-headed arrow in FIG. 5) to move the partition member 263 in and out of the fixing section 26.

Referring to Figures 4, 6 and 7, the partition member 263 is sandwiched between the holding parts 264 (264-1, 264-2) from above and below, and the holding parts 264 are fixed to the frame 261, so that the partition member 263 can move relative to a groove (see groove R in Figure 7) formed in the holding parts 264. In other words, the holding parts 264 hold the partition member 263 movably in a direction intersecting the transport direction of the recording medium P by a slide rail structure based on the groove R.

More specifically, the holding portion 264 has an upper member 264-1 that abuts against the upper surface side of the partition member 263 and a lower member 264-2 that holds the lower surface side of the partition member 263.

The upper member 264-1 of the holding part 264 is a pair of elongated members, each of which is provided with a number of (three in this example) screw holes 264-1h into which the screws 267 shown in FIG. 7 are screwed. In addition, the upper portion of the upper member 264-1 rises at an angle corresponding to the inclination angle of the corresponding frame 261, as shown in FIG. 4, and is fixed to the inner surface of the frame 261 by screws or the like (not shown).

The lower member 264-2 is provided with a number (six in this example) corresponding to the number of screw holes 264-1h of the upper member 264-1, and each is disposed at the position of the corresponding screw hole 264-1h. The lower member 264-2 has elongated holes 264-2h into which the screws 267 (see FIG. 7) are inserted.

In this embodiment, as shown in FIG. 6, multiple (three in this example) lower members 264-2 are arranged discretely (in other words, divided) with respect to one upper member 264-1, and each lower member 264-2 is provided with a long hole 264-2h into which a screw 267 is inserted, thereby absorbing errors that occur during thermal expansion.

Specifically, in the inkjet image forming apparatus 1, UV light is irradiated from the UV irradiator 262 onto the recording medium P during the image forming process, and the thermal energy of the UV light causes thermal expansion in the partition member 263, the holding portion 264, etc. At this time, differences in the materials of these parts (for example, when the partition member 263 is made of glass and the holding portion 264 is made of metal) result in different thermal expansion coefficients, and there is a risk of stress and even gaps occurring between the members due to thermal deformation.

To address this issue, the lower member 264-2 is arranged discretely (divided) and long holes 264-2h that extend along the length of the corresponding upper member 264-1 are provided in the lower member 264-2, thereby absorbing errors that occur during thermal expansion.

Thus, the holding parts 264 (264-1, 264-2) are incorporated inside the frame 261 and hold the partition member 263 in a sandwiched manner, thereby holding the position of the partition member 263 in an adjustable manner.

At this time, the holding parts 264 (264-1, 264-2) are positioned outside the multiple (four in this example) reflectors 265 arranged inside the frame 261. In other words, the holding parts 264 (264-1, 264-2) are positioned outside the irradiation range of the UV light emitted from the UV irradiator 262.

In this way, by arranging the holding parts 264 (264-1, 264-2) outside the UV irradiation area, it is possible to avoid a reduction in the irradiation range of the UV light, and also to reduce an increase in the temperature of the holding parts 264 caused by irradiation of the holding parts 264 with UV light.

As described above, the holding part 264 has a configuration in which multiple lower members 264-2 are discretely arranged with respect to one upper member 264-1, and each lower member 264-2 is provided with a long hole 264-2h for inserting a screw 267, so that the distortion caused by thermal deformation resulting from the difference in the thermal expansion coefficient between the holding part 264 and the partition member 263 can be released. Therefore, even after the partition member 263 is fixed inside the frame 261, the expansion error due to the difference in the thermal expansion coefficient between the partition member 263 (a glass plate in this example) and the holding part 264 (metal, etc. in this example) can be absorbed.

In this embodiment, it is desirable that the underside of the eaves 268 (first extension 266-1 if eaves 268 is not provided) on the upstream side in the transport direction be provided at the same height as the underside of the partition member 263, or be provided at a position closer to the transport surface of the transport drum 21 than the underside of the partition member 263 (see FIG. 7, etc.). In other words, it is desirable that the distance between the gap suppression part and the transport drum 21 be equal to or less than the minimum distance between the partition member 263 and the transport drum 21 (transport member).

Here, "minimum distance" refers to the distance between the partition member 263 and the transport drum 21 at the closest point, and in the illustrated example, it means the distance between the partition member 263 and the top of the transport drum 21 (the center in the transport direction).

That is, by configuring the height of the gas flow path from the opening nozzle 253 of the gas supply unit 25 toward the transport space S to be as low as possible under conditions that do not interfere with the recording medium P transported by the transport drum 21, the gas discharged from the opening nozzle 253 is more likely to fill the transport space S (see the arrow in FIG. 8). Also, by configuring in this way, contact between the recording medium P carrying ink and transported by the transport drum 21 and the partition member 263 is avoided or suppressed.

Also, as shown in Figures 4 and 7, the areas near the holding portion 264 on both ends of the frame 261 in the width direction are made into side end portions 261-1 that extend below the bottom surface of the partition member 263, so that they function as gap suppression portions that strengthen the closure of the transport space S.

Furthermore, it is desirable that the shape of the retaining portion 264 be such that it fills in any steps or gaps in the surrounding structures. For example, in the example shown in Figures 7 and 8, the lower portion of the lower member 264-2 is configured as a gap filler 264-2a (see Figure 8) that fills in the gap with the eaves 268.

In the example described in FIG. 6, multiple lower members 264-2 are arranged along the width direction, and gaps are formed between adjacent lower members 264-2. For this reason, it is advisable to fill such gaps with a filler member (not shown) as a gap suppression section to eliminate the step on the lower side of the frame 261 and the gap between the frame 261 and the holding section 264. Here, for example, a foam material can be used as the filler member.

By providing various gap suppression parts in this way, the airtightness of the transport space S between the partition member 263 and the transport member 21 is improved, and gas flows more easily within the transport space S (turbulent air flows are less likely to occur). This makes it easier for the nitrogen gas supplied from the opening nozzle 253 of the gas supply unit 25 to be introduced (see the arrow in Figure 8), and the introduced nitrogen gas fills the transport space S.

Thus, according to this embodiment, the gas supply unit 25 fills the inside of the nozzle body 252 with nitrogen gas stored in a tank through the multiple supply pipes 250, and discharges the filled nitrogen gas from the opening nozzle 253 to the outside. At this time, the nitrogen gas discharged from the opening nozzle 253 pushes out the atmosphere in the closed transport space S between the partition member 263 etc. and the transport surface of the transport drum 21, and is quickly filled into the transport space S. Then, leakage of the nitrogen gas filled in the closed transport space S from the transport space S to the outside is minimized.

In this way, according to this embodiment equipped with the various gap suppression units described above, the nitrogen gas supplied from the gas supply unit 25 can be sufficiently filled in the UV light irradiation area to promote the curing of the UV curable ink when irradiated with ultraviolet light, and the amount of additional nitrogen gas supplied from the gas supply unit 25 can be reduced.

Therefore, according to the inkjet image forming device 1 of this embodiment, a structure is adopted in which the recording medium P is transported by a transport member (transport drum 21) having a curvature, while suppressing gas leakage in the transport space S, i.e., the transport path of the recording medium P, and ensuring image quality.

In the above embodiment, an example has been described in which the extensions 266 (266-1, 266-2) are configured as part of the frame 261 in the fixing section 26. However, the configuration of the extensions 266 (266-1, 266-2) is not limited to this, and they may be configured as part of the above-mentioned holding sections 264 (264-1, 264-2), for example. In this case, referring to FIG. 3, each end of the upstream and downstream holding sections 264 may be configured to protrude from the frame 261.

In the above embodiment, a case has been described in which a UV-curable ink that is cured by irradiation with ultraviolet light is used, and the fixing unit 26 is provided with a UV irradiator 262. However, the ink used is not limited to this, and ink that is cured by other active energy rays such as electron beams may also be used. In this case, the fixing unit 26 may be configured to irradiate the active energy rays instead of the UV irradiator 262.

In the above-described embodiment, the case where the side shape of the partition member 263 is linear has been described. However, the side shape of the partition member 263 is not limited to this, and for example, even if the curvature of the side shape of the partition member 263 differs from the curvature of the side shape (conveyance surface) of the conveying drum 21, the same problem will arise, and the configuration of the above-described embodiment can be effectively applied.

The above embodiments are merely examples of the implementation of the 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 drum (transport member)
22 Delivery unit 23 Heating section 24 Head unit 25 Gas supply section 26 Fixing section 27 Delivery section 30 Paper discharge section 31 Paper discharge tray 40 Control section 41 CPU
42 RAM
43 ROM
44 Memory unit 51 Conveyor drive unit 52 Input/output interface 221 Swing arm unit 222 Delivery drum 241 Inkjet head drive unit 242 Inkjet head 250 Supply pipe 251 Connection fitting 252 Nozzle body 252-1, 252-2 Half unit 252b Bottom surface 253 Open nozzle 254 Screw 261 Frame 261-1 Side end (gap suppression unit)
262 UV irradiator (energy ray irradiation unit)
263 Partition member 264 (264-1, 264-2) Holding portion 264-1 Upper member 264-1h Screw hole 264-2 Lower member (gap suppression portion)
264-2a Gap filling section 264-2h Long hole 265 Reflector 266 (266-1, 266-2) Extension section (gap suppression section)
266-1 First extension part (gap suppression part)
266-2 Second extension part (gap suppression part)
267 Screw 268 Eaves (gap suppression part)
271 Delivery drum 272 Belt loop P Recording medium S Transport space R Groove of holding portion

Claims (14)

a conveying member that conveys the recording medium onto which the ink has been ejected, using a conveying surface having a curvature;
an energy ray irradiation unit that irradiates the ink on the recording medium with an active energy ray;
a partition member that is disposed opposite the transport surface so as to separate a space between the transport member and the energy ray irradiation unit, that forms a gap between the transport surface and the partition member to serve as a transport space for the recording medium, and that transmits the active energy rays emitted from the energy ray irradiation unit;
a gas supply unit that supplies a gas to the transfer space;
a gap suppressing portion that is disposed between the transport surface of the transport member and at least one end side of the partition member along a transport direction of the recording medium so as to reduce a gap that forms the transport space between the transport surface of the transport member and at least one end side of the partition member along the transport direction of the recording medium;
a holding portion that holds the partition member on the upstream side and the downstream side in the conveying direction;
A frame that fixes the holding portion;
having
the gas supply unit is disposed on the upstream side of the partition member in the transport direction,
The gap suppression portion is provided in the vicinity of the holding portion,
The holding portion includes an upper member fixed to the frame, and a lower member that sandwiches and holds the partition member together with the upper member.
having
Inkjet image forming device. The gap suppression portion includes a eaves-shaped portion that guides the gas supplied from the gas supply portion to the transfer space.
The inkjet image forming apparatus according to claim 1 . The distance between the gap suppression unit and the conveying member is equal to or less than the minimum distance between the partition member and the conveying member.
3. The inkjet image forming apparatus according to claim 1 or 2 . A frame for fixing the holding portion is provided,
The holding portion has an upper member fixed to the frame and a lower member that sandwiches and holds the partition member together with the upper member.
The inkjet image forming apparatus according to claim 1 . The gap suppression portion is configured by extending the lower side of the frame.
5. The inkjet image forming apparatus according to claim 1 or 4 . The gap suppression portion includes the lower member.
5. The inkjet image forming apparatus according to claim 1 or 4 . The lower member is provided with a gap filling portion that fills a gap in the transfer space.
7. The inkjet image forming apparatus according to claim 1 , 4, 5 or 6 . the holding unit is disposed outside an irradiation range of the active energy ray in a transport direction of the recording medium,
7. The inkjet image forming apparatus according to claim 1 , 4, 5 or 6 . The holding portion is configured to release a difference in thermal expansion coefficient between the holding portion and the partition member.
5. The inkjet image forming apparatus according to claim 1 or 4 . In the holding portion, a plurality of the lower members are arranged with respect to one of the upper members.
The inkjet image forming apparatus according to claim 9 . The holding portion has a structure in which the upper member and the lower member are connected with a screw, the upper member has a screw hole into which the screw is screwed, and the lower member has a long hole through which the screw is inserted that extends along the length direction of the upper member.
The inkjet image forming apparatus according to claim 9 or 10 . the holding portion includes a groove that holds the partition member movably in a direction intersecting the conveying direction,
12. The inkjet image forming apparatus according to claim 1 , 4, 5, 6, 7, 8 , 9, 10, or 11. The gap suppression portion is disposed on each of the upstream side and the downstream side of the partition member in the conveying direction.
The inkjet image forming apparatus according to claim 1 . the gap suppression portion disposed on the downstream side includes a canopy that suppresses the outflow of the gas introduced into the transfer space,
The inkjet image forming apparatus according to claim 13 .

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