JP2004175494A - Image recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that the flatness is impaired because of the generation of wrinkling and dancing on a string part of a conveying belt corresponding to a printing area by a recording head. <P>SOLUTION: The conveying belt 21 for conveying the paper 12 is hung between a conveying roller 27 and a tension roller 28, a guide member 31 for guiding the conveying belt 21, is mounted on a rear face side of the part corresponding to the printing area by the recording head 4, and the guide member 31 is mounted in a state of being projected to a recording head 4 side with respect to a tangent line 32 between the rollers 27, 28. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to an image recording apparatus, and more particularly to an image recording apparatus that conveys a sheet using a conveyance belt.
[0002]
[Patent Document 1] Japanese Patent No. 2897960 [Patent Document 2] Japanese Patent Application Laid-Open No. 7-53081
[Prior art]
2. Description of the Related Art As an image recording apparatus (or also referred to as an image forming apparatus) such as a printer, a facsimile, and a copying apparatus, for example, an ink jet recording apparatus is known. The ink jet recording apparatus is a sheet to which ink droplets including OHP and the like can be attached from an ink recording head to a sheet (also referred to as a recording medium, a recording medium, a recording sheet, or the like). It prints high-definition images at high speed with low running cost, low noise, and prints color images using multi-color inks. It has advantages such as easy operation.
[0004]
As the ink jet head, a piezoelectric actuator such as a piezoelectric element, a thermal actuator utilizing a phase change due to film boiling of a liquid using an electrothermal transducer such as a heating resistor, a shape memory alloy actuator using a metal phase change due to a temperature change, 2. Description of the Related Art There is known an electrostatic actuator using an electrostatic force or the like as an energy generating unit for discharging ink.
[0005]
By the way, in the ink jet recording method, since an ink is attached to paper, when an image is formed, there is a phenomenon that the paper is stretched by moisture contained in the ink. This phenomenon is called cockling. This cockling causes the paper to undulate, and the positions of the nozzles of the head and the surface of the paper change from place to place. If the degree of cockling becomes worse, in the worst case, the paper may come into contact with the nozzle surface of the head and stain the nozzle surface of the head, or the paper itself may become dirty, deteriorating the image quality. The impact position of the ink droplet may be shifted due to the influence.
[0006]
Further, in the conventional ink jet recording apparatus, paper is fed by rollers, and two sets of rollers (one is a combination of a spur and a roller as described above) are arranged with a printing area interposed therebetween. However, in this configuration, the paper feeding accuracy can be guaranteed only when the paper is engaged with the two sets of rollers.
[0007]
However, in recent years, since an increase in the image printing area is desired, a state in which the paper feeding accuracy cannot be assured in order to secure the printing area, that is, one of the two roller pairs is used. There is also an ink jet recording apparatus in which printing is performed in a state where only the sheet is bitten. However, in the state where the sheet is bitten by only one roller pair, if the sheet floats, it cannot be dealt with, or the feeding accuracy cannot be guaranteed because the sheet conveyance force cannot be secured, so the image quality also deteriorates. Problem arises.
[0008]
Therefore,
As described in Patent Literature 1 and Patent Literature 2, in order to maintain the flatness of the paper, an endless charging belt is provided, and the surface of the charging belt is charged to electrostatically attract the paper. An ink jet recording apparatus has been proposed in which a sheet is conveyed by rotating the charging belt in this state, thereby preventing the sheet from rising from the charging belt and maintaining high flatness.
[0009]
[Problems to be solved by the invention]
However, when the paper is transported in a state where the paper is electrostatically attracted using the transport belt as in the above-described conventional ink jet recording apparatus, the flatness of the transport belt is directly connected to the flatness of the paper.
[0010]
In this case, the conveyor belt is stretched between at least two rollers so that the chord portion corresponds to the printing area by the recording head. When the belt is rotated, a phenomenon in which the belt dances (fluctuates) at the chord portion may occur, and the flatness of the transport belt may decrease.
[0011]
As described above, even when the transport belt is used, if the flatness of the transport belt itself is reduced, the distance between the recording head and the paper fluctuates, and there is a problem that the image quality is reduced.
[0012]
The present invention has been made in view of the above problems, and has as its object to provide an image recording apparatus capable of recording with high image quality while maintaining the flatness of a conveyor belt.
[0013]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, an image recording apparatus according to the present invention is configured such that a transport belt that transports a sheet is supported by being stretched between at least two rollers, and a back surface of the transport belt corresponding to a printing area by a recording head. A guide member is provided on the side, and the upper surface of the guide member is configured to protrude more toward the recording head than the tangent of the two rollers supporting the transport belt.
[0014]
Here, it is preferable that at least one of the upstream side and the downstream side of the guide member is provided with a guide roller that can rotate in contact with the transport belt. Preferably, a plurality of grooves are formed on a contact surface of the guide member with the transport belt in a direction perpendicular to the transport direction.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a configuration diagram illustrating an overall configuration of an ink jet recording apparatus as an image recording apparatus according to the present invention, FIG. 2 is a plan view illustrating a main part of the recording apparatus, and FIG. 3 is an explanatory view illustrating a transport unit of the recording apparatus. is there.
[0016]
In the ink jet recording apparatus, a carriage 3 is slidably held in a main scanning direction by a guide rod 1 and a stay 2 which are guide members which are laterally mounted on left and right side plates (not shown). The moving scan is performed in the direction indicated by the arrow.
[0017]
The carriage 3 is provided with a plurality of ink ejection orifices through a recording head 4 composed of four inkjet heads for ejecting ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk). They are arranged in a direction crossing the main scanning direction, and are mounted with the ink droplet ejection direction facing downward.
[0018]
The ink jet head constituting the recording head 4 includes a piezoelectric actuator such as a piezoelectric element, a thermal actuator using an electrothermal conversion element such as a heating resistor to utilize a phase change due to film boiling of a liquid, and a metal phase change due to a temperature change. An actuator having a shape memory alloy actuator to be used, an electrostatic actuator using electrostatic force, or the like as an energy generating means for discharging ink can be used.
[0019]
Further, the carriage 3 is mounted with sub-tanks 5 of each color for supplying inks of each color to the recording head 4. The sub-tank 5 is supplied with ink from a main tank (ink cartridge) via an ink supply tube (not shown).
[0020]
On the other hand, as a paper feed unit for feeding paper 12 loaded on a paper loading unit (pressure plate) 11 such as a paper feed cassette 10, a half-moon roller that separates and feeds the papers 12 one by one from the paper loading unit 11 ( A sheet feed roller 13 and a separation pad 14 made of a material having a large friction coefficient are provided facing the sheet feed roller 13. The separation pad 14 is urged toward the sheet feed roller 13.
[0021]
As a transport unit for transporting the paper 12 fed from the paper feed unit below the recording head 4, a transport belt 21 for electrostatically attracting and transporting the paper 12 and a feed belt 21 A counter roller 22 for transporting the paper 12 sent through the guide 15 between the transport belt 21 and the paper 12 transported substantially vertically upward is turned by approximately 90 ° to copy the paper 12 onto the transport belt 21. A transport guide 23 for adjusting the pressure and a pressing roller 25 urged toward the transport belt 21 by a pressing member 24 are provided. Further, a charging roller 26 serving as a charging unit for charging the surface of the transport belt 21 is provided. Note that a holding roller 30 is provided at the tip of the holding member 24.
[0022]
Here, the transport belt 21 is an endless belt, is stretched between the transport roller 27 and the tension roller 28, and is configured to orbit in the arrow A direction (belt transport direction). As shown in FIG. 6, the transport belt 21 has a surface layer 21a serving as a sheet adsorption surface formed of a pure resin material having a thickness of about 40 μm and not having resistance control, for example, an ETFE pure material, and the same as the surface layer 21a. And a back layer (medium resistance layer, earth layer) 21b whose resistance is controlled by carbon.
[0023]
The thickness of the insulating layer (surface layer) 21a of the conveyor belt 21 affects the dielectric constant. As the thickness increases, the dielectric constant decreases, and the amount of electric charge placed on the belt when charged becomes smaller. Therefore, the electrostatic attraction force can be improved by taking into account the range of the film thickness that varies in manufacturing, and by making the layer thickness as thin as possible within the range where the layer thickness does not become 0 even when the belt is scratched in an actual machine. .
[0024]
The thickness of the back layer (medium resistance layer, earth layer) 21b of the conveyor belt 21 does not directly affect the electrostatic action, but as the total thickness of the belt increases, the rigidity increases and the belt is stretched on the actual machine. Sometimes it is difficult to ensure the flatness of the belt, while it cannot be made too thin to ensure the required strength. According to experiments, the thickness of the back layer 21b is preferably about 50 to 200 μm.
[0025]
By providing the resistance-controlled layer 21b on the entire back side of the conveyor belt 21 as a two-layer configuration in this way, after the electric charge is formed on the surface layer 21a which is an insulating layer in advance, the electric charge is further increased when the paper adsorbed on the belt comes into contact. It is possible to increase the electrostatic attraction force between the sheet and the conveyance belt 21 when the sheet is supplied. In the case of a single insulating layer, the suction force is reduced by half compared to the case of two layers, and in the case of a single layer, the position at which the paper starts to contact the belt faces the ground roller located inside the belt. However, such a restriction is eliminated by providing two layers.
[0026]
The charging roller 26 is arranged so as to be in contact with the surface layer of the transport belt 21 and rotate following the rotation of the transport belt 21, and apply 2.5 N to both ends of the shaft as a pressing force. The transport roller 27 also serves as the above-described ground roller, and is arranged in contact with the medium resistance layer (back layer) 21b of the transport belt 21 and is grounded.
[0027]
Further, as shown in FIGS. 3 and 4, a guide member 31 is arranged on the back side of the transport belt 21 so as to correspond to the printing area of the recording head 4. As shown in FIG. 5, the guide member 31 is held between frame members 35 holding the transport roller 22 and the tension roller 28 and the like.
[0028]
As shown in FIG. 4, the guide member 31 has an upper surface 31a projecting toward the recording head 4 beyond a tangent line 32 of two rollers (the transport roller 27 and the tension roller 28) supporting the transport belt 21. As a result, the transport belt 21 is pushed up and guided by the upper surface 31a of the guide member 31 in the printing area.
[0029]
Further, as shown in FIG. 5, a plurality of grooves 31b are formed in the main scanning direction, that is, in the direction orthogonal to the transport direction, on the side of the guide member 31 that contacts the rear surface of the transport belt 21. The contact area with the guide member 21 is reduced so that the transport belt 21 can move smoothly along the surface of the guide member 31.
[0030]
Furthermore, guide rollers 33 and 34 that abut on the back surface side of the transport belt 21 are rotatably disposed on the upstream side and the downstream side in the transport direction of the guide member 31, respectively. It is preferable that the guide rollers 33 and 34 are arranged near both ends of the guide member 31 in the transport direction.
[0031]
Further, as a paper discharge unit for discharging the paper 12 recorded by the recording head 4, a separation unit 41 for separating the paper 12 from the transport belt 21, a paper discharge roller 42 and a paper discharge roller 43, A paper output tray 44 for storing the paper 12 to be printed is provided. A double-sided paper supply unit 51 is detachably mounted on the back. The double-sided paper feeding unit 51 takes in the paper 12 returned by the rotation of the transport belt 21 in the reverse direction, reverses the paper 12, and feeds the paper 12 again between the counter roller 22 and the transport belt 21.
[0032]
In the ink jet recording apparatus configured as described above, the paper 12 is separated and fed one by one from the paper feeding unit, and the paper 12 fed substantially vertically upward is guided by the guide 15, and the transport belt 21 and the counter roller 22 And the leading end thereof is guided by a carrying guide 23 and pressed against the carrying belt 21 by a leading end pressing roller 25 to change the carrying direction by approximately 90 °.
[0033]
At this time, a positive output and a negative output are alternately repeated from the high voltage power supply to the charging roller 26 by a control circuit (not shown), that is, an alternating voltage is applied, and a charging voltage pattern in which the transport belt 21 alternates, that is, In the sub-scanning direction, which is the circling direction, plus and minus are alternately charged in a belt shape with a predetermined width. When the paper 12 is fed onto the positively and negatively charged conveyor belt 21, the paper 12 is polarized in the paper 12 to a charge opposite to the charged pattern, so that a capacitor connected in parallel is formed. The paper 12 is attracted to the transport belt 21, and the paper 12 is transported in the sub-scanning direction by the orbital movement of the transport belt 21.
[0034]
Therefore, by driving the recording head 4 in accordance with the image signal while moving the carriage 3, ink droplets are ejected onto the stopped paper 12 to record one line, and after the paper 12 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal indicating that the rear end of the sheet 12 has reached the recording area, the recording operation is terminated, and the sheet 12 is discharged to the discharge tray 44.
[0035]
Here, in this ink jet recording apparatus, the belt chord corresponding to the printing area is pushed up to the recording head 4 side by the guide member 31 arranged on the back side of the conveyor belt 21, and the guide member 31 Since the belt moves along the belt, no wrinkles or dances occur at the chord portion of the belt, high flatness can be maintained, and recording can be performed with high image quality.
[0036]
In addition, since the guide rollers 33 and 34 that are in contact with the back surface side of the transport belt 21 are rotatably disposed on the upstream side and the downstream side in the transport direction of the guide member 31, respectively, the transport belt 21 and the ends of the guide member 31 Can be reduced, the driving load of the conveyor belt 21 can be reduced, and the belt can be prevented from being fluctuated by rubbing against the end of the guide member 31. Thus, the chordal portion of the belt can be more reliably achieved. In this way, it is possible to prevent the occurrence of wrinkles, dances, and the like, and to maintain high flatness and record with high image quality.
[0037]
In the above embodiment, the present invention has been described as an example in which the present invention is applied to a serial type (shuttle type) ink jet recording apparatus in which a carriage scans. However, the present invention is similarly applied to a line type ink jet recording apparatus having a line type head. be able to.
[0038]
Further, the image recording apparatus according to the present invention can be applied to a facsimile apparatus, a copying apparatus, a printer / fax / copier multifunction peripheral, etc. in addition to the ink jet printer. Furthermore, the present invention can be applied to an image recording apparatus that ejects a liquid other than ink, for example, a resist or a DNA sample in the medical field.
[0039]
【The invention's effect】
As described above, according to the image recording apparatus of the present invention, the transport belt that transports the paper is supported between at least two rollers, and the back surface of the transport belt corresponds to the printing area of the recording head. The guide member is provided on the side, and the upper surface of the guide member is configured to protrude toward the recording head side from the tangent line of the two rollers supporting the transport belt. Variations can be prevented and images can be recorded with high image quality.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image recording apparatus according to a first embodiment of the present invention. FIG. 2 is an explanatory plan view of main parts of the recording apparatus. FIG. 3 is an explanatory view of main parts of the recording apparatus. FIG. 5 is an explanatory view for explaining an arrangement of a guide member of the recording apparatus. FIG. 5 is a perspective explanatory view of the guide member. FIG. 6 is an explanatory view for explaining a configuration of a transport belt of the recording apparatus.
DESCRIPTION OF SYMBOLS 3 ... Carriage, 4 ... Recording head, 12 ... Paper, 21 ... Conveying belt, 26 ... Charging roller, 27 ... Conveying roller, 28 ... Tension roller, 31 ... Guide member, 33, 34 ... Guide roller, 44 ... Discharge tray .

Claims (3)

In an image recording apparatus that charges a surface of an endless conveyance belt to convey a sheet and discharges droplets from a recording head to record an image on the sheet, the conveyance belt is supported by being stretched between at least two rollers. A guide member is provided on the back side of the transport belt corresponding to the printing area, and the upper surface of the guide member protrudes toward the recording head beyond a tangent of two rollers supporting the transport belt. An image recording apparatus characterized by the above-mentioned. The image recording apparatus according to claim 1, wherein a guide roller rotatable by contacting the transport belt is provided on at least one of an upstream side and a downstream side of the guide member. 3. The image forming apparatus according to claim 1, wherein a plurality of grooves are formed on a surface of the guide member that contacts the transport belt in a direction perpendicular to a transport direction. 4. .

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