JP2004244198A - Paper transport device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper transport device and an image forming apparatus capable of solving the problem in any conventional arrangement of such a structure that sheets of paper are transported by a transport belt set over between at least two rollers in which the belt is likely deviated owing to the degree of parallelism of the rollers or the load to result in a drop in picture quality. <P>SOLUTION: The paper transport device and the image forming apparatus are arranged so that the endless transport belt 21 set over between the transport roller 27 and the tension roller 28 is electrostatically charged by a charging roller 26 and each sheet of paper 12 is attracted electrostatically by the belt 21 and transported. The transport roller 27 and the tension roller 28 are furnished at the ends with flanges 27a and 28a whereto the end faces of the belt 21 can abut so as to prevent the belt 21 from running in deviation. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
[Industrial applications]
The present invention relates to a sheet transport device and an image forming device.
[0002]
[Prior art]
[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]
For this reason, in the ink jet recording apparatus, printing is performed on a platen provided with a dent that absorbs cockling of paper, and a spur having a protrusion on the periphery is provided as a presser for the paper, but scratches on the image due to this spur are generated. Is also a problem.
[0007]
Further, in a 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 print 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.
[0008]
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.
[0009]
In pursuit of higher image quality in the ink jet recording apparatus, the accuracy of the landing position of the ink droplet on the paper is required, and it is necessary to improve the flatness of the paper. In the case, paper fibers swell due to the moisture contained in the ink and deform in a wave-like manner, resulting in a shift in the dot landing position. So far, it has been found that it takes about 3 seconds or more after the ink adheres to the paper, and the paper is greatly deformed.
[0010]
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.
[0011]
[Problems to be solved by the invention]
However, when a sheet is transported by the transport belt and an image is recorded, the transport belt shifts due to the parallelism between the driving roller and the driven roller that bridge the transport belt and the load applied to the transport belt. There is a problem that. If the conveyance belt shifts during image formation, there is a problem in that the image formation position and the landing position of the ink droplet in ink jet recording are shifted, and the image quality is degraded.
[0012]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a sheet conveying device that eliminates a shift of a conveying belt and an image forming apparatus that is provided with the sheet conveying device and that prevents deterioration in image quality. And
[0013]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the paper transporting device according to the present invention has a configuration in which a flange portion is provided on both sides or one end of at least one of at least two rollers over which a transport belt is stretched.
[0014]
The paper transport device according to the present invention has a configuration in which at least two rollers around which a transport belt is stretched and at least one roller of a charging roller for charging the transport belt are provided with flange portions on both sides or one side end of at least one roller. did.
[0015]
The paper transport device according to the present invention has a configuration in which a flange portion is provided on both sides or one side end of at least two rollers of a charging roller for charging the transport belt and at least two rollers over the transport belt. did.
[0016]
The paper transport device according to the present invention includes a charging roller for charging the transport belt, and flange portions are provided at both end portions of the charging roller, and the charging roller is disposed near a driving roller that drives the transport belt. Configuration.
[0017]
An image forming apparatus according to the present invention has a configuration including any one of the sheet conveying apparatuses according to the present invention.
[0018]
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 an explanatory side view illustrating an overall configuration of an ink jet recording apparatus showing an example of an image forming apparatus according to the present invention including a sheet conveying apparatus according to the present invention, and FIG. 3 is an explanatory perspective view of a main part of the recording apparatus.
[0019]
In this ink jet recording apparatus, a carriage 3 is slidably held in a main scanning direction by a guide rod 1 and a guide rail 2 which are guide members which are laterally mounted on left and right side plates (not shown). 2 is moved and scanned in the direction indicated by the arrow in FIG. 2 (main scanning direction).
[0020]
The carriage 3 is provided with a plurality of ink ejection orifices through a recording head 7 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.
[0021]
As the ink-jet head constituting the recording head 7, a piezoelectric actuator such as a piezoelectric element, a thermal actuator utilizing an electrothermal conversion element such as a heating resistor and utilizing a phase change due to a film boiling of a liquid, and a metal phase change due to a temperature change are used. 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.
[0022]
Further, the carriage 3 is mounted with sub-tanks 8 of each color for supplying each color ink to the recording head 7. The sub tank 8 is supplied with ink from a main tank (ink cartridge) via an ink supply tube (not shown).
[0023]
On the other hand, as a paper feeding unit for feeding the paper 12 loaded on the paper loading unit (pressure plate) 11 such as the paper feed cassette 10, a half-moon roller that separates and feeds the papers 12 one by one from the paper loading unit 11 ( The paper feed roller 13 and the paper feed roller 13 are provided with a separation pad 14 made of a material having a large coefficient of friction. The separation pad 14 is urged toward the paper feed roller 13.
[0024]
As a transport unit for transporting the paper 12 fed from the paper feed unit below the recording head 7, 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.
[0025]
Here, the transport belt 21 is an endless belt, is stretched between a transport roller 27 and a tension roller 28, and rotates the transport roller 27 from a sub-scanning motor 31 via a timing belt 32 and a timing roller 33. By doing so, it is configured to go around in the direction indicated by the arrow in FIG. 2 (belt conveyance direction).
[0026]
The transport belt 21 has a surface layer serving as a paper adsorption surface formed of a pure resin material having a thickness of about 40 μm, for example, of which resistance is not controlled, for example, an ETFE pure material, and resistance control is performed with carbon using the same material as the surface layer. And a back layer (medium resistance layer, earth layer).
[0027]
A transport roller nip 18 is formed by the transport roller 27 and the counter roller 22, and a paper detection sensor 16 that detects the paper 12 is disposed at a predetermined position upstream of the transport roller nip 18 in the paper transport direction. . The paper detection sensor 16 detects the paper 12 by displacing the detection lever 17 of the paper 12 (the position indicated by the broken line in FIG. 1 is the ON position). The paper detection sensor 16 is for detecting paper feeding.
[0028]
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 functions as an earth roller, and is arranged in contact with the middle resistance layer (back layer) of the transport belt 21 and is grounded.
[0029]
As shown in FIGS. 2 and 3, flange portions 27a and 28a are formed on both ends of the transport roller 27 as a driving roller and the tension roller 28 as a driven roller, respectively.
[0030]
A guide member 36 is arranged on the back side of the transport belt 21 so as to correspond to the printing area of the recording head 4. The guide member 36 has an upper surface protruding toward the recording head 7 from a tangent line 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 of the guide member 36 in the printing area.
[0031]
In order to detect the leading end of the sheet 12 conveyed by the conveying belt 21, the carriage 3 is provided with a sheet sensor 41 composed of a reflection type photosensor as shown in FIG. The paper sensor 41 is provided at a position where the paper 12 can be detected on the upstream side of the recording position (printing area) of the recording head 7 in the paper transport direction. Further, the paper sensor 41 is provided on the side located on the recording area side (conveying belt 21 side) when the carriage 3 is at the home position.
[0032]
As shown in FIGS. 1 and 3, an encoder scale 42 having a slit is provided on the front side of the carriage 3, and a transmission type photosensor for detecting the slit of the encoder scale 42 is provided on the front side of the carriage 3. And an encoder sensor 43 for detecting the position of the carriage 3 in the main scanning direction (the position with respect to the home position).
[0033]
Further, as a paper discharge unit for discharging the paper 12 recorded by the recording head 7, a separation unit for separating the paper 12 from the transport belt 21, a paper discharge roller 52 and a paper discharge roller 53, and a paper discharge And a discharge tray 54 for storing the sheets 12 to be printed.
[0034]
A double-sided paper feeding unit 61 is detachably mounted on the back. The double-sided paper feeding unit 61 takes in the paper 12 returned by the rotation of the transport belt 21 in the reverse direction, reverses the paper, and feeds the paper 12 again between the counter roller 22 and the transport belt 21.
[0035]
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 °.
[0036]
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.
[0037]
Then, by driving the recording head 7 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.
[0038]
In the case of double-sided printing, when the recording of the front side (the side to be printed first) is completed, the transported belt 21 is rotated in the reverse direction, so that the recorded paper 12 is fed into the double-sided paper feeding unit 61, The sheet 12 is turned over (with the back side being the printing surface) and fed again between the counter roller 22 and the conveyor belt 21, and the timing is controlled, and the sheet is conveyed onto the conveyor bell 21 in the same manner as described above. After recording on the back surface, the paper is discharged to the paper discharge tray 44.
[0039]
Here, when the paper 12 is electrostatically attracted to the transport belt 21 and is transported in the printing area by the recording head 7, the ends of the transport belt 21 in the direction orthogonal to the transport direction are the transport rollers 27 and the tension rollers 28. Since the conveyor belt 21 is guided by the flange portions 27a and 28a provided at both ends, when the transport belt 21 starts to lean toward a side substantially orthogonal to the transport direction, the transport belt 21 abuts on the flange portion 27a or the flange portion 28a. Be suppressed.
[0040]
As a result, it is possible to prevent the position of the paper 12 in the main scanning direction and the like from fluctuating due to the shift of the transport belt 21 during recording, thereby preventing the ink droplet landing position from fluctuating, thereby suppressing a decrease in image quality.
[0041]
In addition, by providing the flange portions on both the transport roller 27 and the tension roller 28, that is, two or more rollers that bridge the transport belt, the transport belt 21 can be more reliably prevented from being twisted. However, the present invention is not limited to this, and deviation is suppressed by providing a flange portion to which the end portion of the conveyor belt can abut on both ends or one end of at least two rollers of the at least two rollers for bridging the conveyor belt. be able to.
[0042]
Next, another embodiment of the present invention will be described with reference to FIG. FIG. 3 is a schematic perspective explanatory view similar to FIG. 3 for explaining the embodiment.
In this embodiment, a flange 26a is provided at both ends or one end of the charging roller 26 so that the end of the conveyor belt 21 can abut. When the charging roller 26 is provided with the flange portion 26 a as described above, it is preferable that the charging roller 26 a be disposed near the transport roller 27. Thus, the position of the transport belt 21 can be corrected immediately before the transport belt 21 comes into contact with the transport roller 27 serving as a driving roller.
[0043]
In this case, either or both of the transport roller 27 and the tension roller 28 may be provided with a flange portion in the same manner as in the above-described embodiment, but preferably, the charging roller 26 and the tension roller 28 are provided with a flange portion. That is, when all the flanges of the rollers that bridge or contact the conveyor belt 27 are provided, the positional accuracy in the axial direction between the rollers is required.
[0044]
In the above embodiment, the image forming apparatus according to the present invention has been described as an example of a shuttle type ink jet recording apparatus using a carriage, but the present invention can also be applied to a line type ink jet recording apparatus using a line type head, The present invention can be applied not only to an ink jet recording apparatus but also to an image forming apparatus such as a copying machine, a facsimile machine, and a multifunction machine of a copying machine / printer / facsimile machine. Further, the paper transporting device according to the present invention can be applied to a device for transporting a paper as a document of an image reading device.
[0045]
【The invention's effect】
As described above, according to the paper transport apparatus of the present invention, at least one of the at least two rollers over which the transport belt is bridged is provided with a flange portion on both sides or one end thereof, or the transport belt is stretched. Since the flange portion is provided at both ends or at one end of at least one of the transferred at least two rollers and at least one of the charging rollers, it is possible to suppress the shift of the transport belt.
[0046]
The paper transporting device according to the present invention has a configuration in which flange portions are provided on both sides or one end of a charging roller for charging the transporting belt, and the charging roller is disposed near a driving roller that drives the transporting belt. Deviation can be suppressed.
[0047]
Since the image forming apparatus according to the present invention includes any one of the sheet conveying apparatuses according to the present invention, it is possible to prevent a decrease in image quality.
[Brief description of the drawings]
FIG. 1 is a side view showing an example of an image forming apparatus provided with a sheet conveying device according to the present invention; FIG. 2 is a plan view showing a main part of the apparatus; FIG. 3 is a perspective view showing a main part of the apparatus; 4 is an explanatory perspective view of a main part for explaining another embodiment of the present invention.
DESCRIPTION OF SYMBOLS 3 ... Carriage, 7 ... Recording head, 10 ... Feeding tray, 12 ... Paper, 13 ... Feeding roller, 15 ... Guide, 21 ... Conveying belt, 22 ... Counter roller, 26 ... Charging roller, 27 ... Conveying roller, 28 ... tension rollers, 26a, 27a, 28a ... flange portions.

Claims (5)

In a paper transport apparatus in which a transport belt that adsorbs and transports a paper is stretched between at least two rollers, a flange portion is provided on both sides or one end of at least one of the rollers that stretches the transport belt. A sheet transport device. In a paper transport device having a charging belt for charging the transport belt, a transport belt for adsorbing and transporting the paper is bridged between at least two rollers. A sheet conveying device, wherein flanges are provided on both sides or one end of one roller. In a paper transport device having a charging belt for charging the transport belt, a transport belt for adsorbing and transporting the paper is bridged between at least two rollers. A sheet conveying device, wherein a flange portion is provided at both ends or one end of two rollers. In a paper transport apparatus having a charging roller for charging the transport belt by bridging a transport belt for adsorbing and transporting the paper between at least two rollers, flange portions are provided at both end portions of the charging roller. And a charging roller disposed near a driving roller for driving the conveying belt. An image forming apparatus for forming an image on a sheet by an image forming unit while conveying a sheet by a sheet conveying apparatus provided with a conveying belt, wherein the sheet conveying apparatus according to any one of claims 1 to 4. An image forming apparatus, comprising:

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