JP4111497B2 - Image forming apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an image forming apparatus.
[0002]
[Patent Document 1]
JP-A-7-53082 [Patent Document 2]
Japanese Patent Laid-Open No. 8-295438
[Prior art]
As an image forming apparatus (or image recording apparatus) such as a printer, a facsimile machine, and a copying apparatus, for example, an ink jet recording apparatus is known. The ink jet recording apparatus is a recording head to a sheet of paper (not limited to paper but includes OHP or the like, which means that an image is formed and is also referred to as a recording medium, a recording medium, or recording paper). It is a recording method that ejects ink, can record high-definition images at high speed, has low running costs, has low noise, and uses multi-color inks to record color images. Has advantages such as being easy.
[0004]
As an inkjet head, a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change due to liquid film boiling using an electrothermal transducer such as a heating resistor, a shape memory alloy actuator that uses a metal phase change due to a temperature change, 2. Description of the Related Art An electrostatic actuator using an electrostatic force or the like is known as an energy generating unit for ejecting ink.
[0005]
There is also an electrophotographic system as an image forming apparatus, which forms a toner image on a photosensitive member by a charging unit, an exposing unit, and a developing unit disposed around the photosensitive drum, and transfers the toner image onto the photosensitive unit. Then, the image is transferred to a sheet and fixed by fixing means.
[0006]
As a sheet conveying device in such an image forming apparatus, a sheet conveying apparatus that conveys a sheet fed downward from oblique information as it is in a substantially horizontal direction and ejects it after recording (Patent Document 1), There is a type (Patent Document 2) in which a sheet fed in a substantially vertical direction from below is temporarily converted into a horizontal direction of approximately 90 ° using a member having an R-shaped cross section and discharged after recording.
[0007]
Further, as conveying means for conveying the sheet, a sheet conveying sheet using a conveying roller, and an endless charging belt as described in [Patent Document 1] and [Patent Document 2] are provided, By charging the surface of the charging belt and electrostatically adsorbing the paper, and rotating the charging belt in this state to transport the paper, it is possible to prevent the paper from lifting from the charging belt and maintain high flatness. There is something that was made.
[0008]
In the image forming apparatus described in [Patent Document 2], a sheet fed in a substantially vertical direction from below is brought into contact with a conveyance guide that follows the peripheral surface (R-shaped conveyance path) of the conveyance belt. The paper is transported in the horizontal direction by changing the paper transport direction by approximately 90 °.
[0009]
[Problems to be solved by the invention]
As in the image forming apparatus described in [Patent Document 2] described above, the sheet fed in a substantially vertical upward direction is changed by 90 ° while being guided by a conveyance guide on a conveyance path having an R-shaped cross section, and conveyed in the horizontal direction. In this case, if the sheet is a sheet such as plain paper, the resistance at the position of the conveyance guide is small, and even with a conveyance belt having a small friction coefficient μ, the sheet can be conveyed with high accuracy without any problem.
[0010]
However, in particular, in an inkjet recording apparatus, glossy paper or cardboard such as a postcard is used to improve image quality. However, such thick paper has a large resistance when changing the direction of the paper. When a conveying belt having a small friction coefficient μ is used, the resistance when changing the direction exceeds the conveying force, and a phenomenon occurs in which the paper slides on the conveying belt.
[0011]
When transporting paper that requires a large transport force in this way, a transport belt with a small friction coefficient μ cannot generate a large transport force, leading to unstable paper transport and paper jams. There is a problem that it becomes easy.
[0012]
SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can stably convey a sheet that requires a large conveyance force by changing the conveyance direction.
[0013]
[Means for Solving the Problems]
In order to solve the above-described problems, an image recording apparatus according to the present invention includes a counter roller for transporting a fed sheet between a transport belt or a transport roller, and the linear speed of the counter roller is transported. is set slower the belt or the linear speed of the conveying roller, counter-roller has a configuration which is dynamic drive via a clutch means for idling the speed difference between the conveyor belt or conveyor rollers.
[0014]
Here, the sheet can be transported after passing through the transport belt or between the transport roller and the counter roller with the transport direction changed by approximately 90 °.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a configuration diagram for explaining the overall configuration of an ink jet recording apparatus as an image forming apparatus according to the present invention, FIG. 2 is a plan view of an essential part of the recording apparatus, and FIG. FIG.
[0016]
In this 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 horizontally mounted on left and right side plates (not shown), and a main scanning motor (not shown) is used in FIG. Move and scan in the direction of the arrow.
[0017]
The carriage 3 is provided with a recording head 4 composed of four ink jet heads that eject ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk), and a plurality of ink ejection openings. They are arranged in a direction crossing the main scanning direction, and are mounted with the ink droplet ejection direction facing downward.
[0018]
As the ink jet head constituting the recording head 4, a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change caused by film boiling of a liquid using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change. A shape memory alloy actuator to be used, an electrostatic actuator using an electrostatic force, or the like as an energy generating means for discharging ink can be used.
[0019]
The carriage 3 is also equipped with sub-tanks 5 for each color for supplying ink of each color to the recording head 4. Ink is supplied to the sub tank 5 from a main tank (ink cartridge) through an ink supply tube (not shown).
[0020]
On the other hand, as a paper feeding unit for feeding the paper 12 stacked on the paper stacking unit (pressure plate) 11 such as the paper feeding cassette 10, a half-moon roller (separately feeding the paper 12 one by one from the paper stacking unit 11) The sheet feeding roller 13 and the sheet feeding roller 13 are opposed to each other, and a separation pad 14 made of a material having a large friction coefficient is provided. The separation pad 14 is urged toward the sheet feeding roller 13 side.
[0021]
As a transport unit for transporting the paper 12 fed from the paper feed unit on the lower side of the recording head 4, a transport belt 21 for electrostatically attracting and transporting the paper 12 and a paper feed unit A counter roller (first pressure roller) 22 for transporting the paper 12 fed through the guide 15 while being sandwiched between the transport belt 21 and the paper 12 fed substantially vertically upward is changed by approximately 90 °. A conveying guide 23 for following the conveying belt 21, and a tip pressure roller 25 urged toward the conveying belt 21 by a pressing member 24. In addition, a charging roller 26 as a charging unit for charging the surface of the transport belt 21 is provided.
[0022]
Here, the conveyance belt 21 is an endless belt, and is configured to be wound around the conveyance roller 27 and the tension roller 28 and to circulate in the direction indicated by the arrow A (belt conveyance direction). This transport belt 21 is a surface layer that is a sheet adsorbing surface formed of a resin material having a pure thickness of about 40 μm that is not subjected to resistance control, for example, ETFE pure material, and resistance control by carbon is performed using the same material as the surface layer. It has a back layer (medium resistance layer, ground layer).
[0023]
The thickness of the insulating layer (surface layer) of the conveyor belt 21 affects the dielectric constant, and as the thickness increases, the dielectric constant decreases and the amount of charge placed on the belt decreases when charged. Therefore, in consideration of the range of film thickness that varies in manufacturing, and the thickness of this layer does not become zero even if scratches occur on the belt in the actual machine, the electrostatic adsorption force can be improved by making it as thin as possible. .
[0024]
Further, the thickness of the back layer (medium resistance layer, ground layer) of the conveyor belt 21 does not directly affect the electrostatic action, but when the total thickness of the belt increases, the rigidity increases and the belt is stretched on the actual machine. In addition, it is difficult to ensure the flatness of the belt, while it cannot be so thin to ensure the required strength.
[0025]
In this way, by providing a resistance-controlled layer on the entire back side of the conveyor belt 21 as a two-layer structure, charges are further supplied when the sheet adsorbed on the belt comes into contact after the charges are formed on the surface layer that is an insulating layer in advance. The electrostatic attractive force between the paper and the belt 21 can be increased. For example, in the case of a single insulating layer, the adsorption force is halved compared to the case of two layers, and in the case of a single layer, the position where the paper starts to contact the belt faces the ground roller located inside the belt. However, by using two layers, such a restriction is eliminated.
[0026]
The charging roller 26 is disposed so as to contact the surface layer of the conveyor belt 21 and rotate following the rotation of the conveyor belt 21, and applies 2.5N to both ends of the shaft as a pressing force. The conveyance roller 27 also serves as the above-described earth roller, and is in contact with the middle resistance layer (back layer) of the conveyance belt 21 and is grounded.
[0027]
In addition, a guide member 31 is disposed on the back side of the conveyance belt 21 so as to correspond to a printing area by the recording head 4. The upper surface of the guide member 31 protrudes closer to the recording head 4 than the tangent line of the two rollers (the conveyance roller 27 and the tension roller 28) that support the conveyance belt 21. As a result, the conveyor belt 21 is pushed up and guided by the upper surface of the guide member 31 in the printing region, and high flatness can be maintained.
[0028]
Furthermore, a plurality of grooves are formed in the main scanning direction, that is, a direction orthogonal to the transport direction, on the surface side of the guide member 31 that contacts the back surface of the transport belt 21 to reduce the contact area with the transport belt 21. The conveying belt 21 can be moved along the surface of the guide member 31 smoothly.
[0029]
Further, guide rollers 33 and 34 that are in contact with the back side of the conveyor belt 21 are rotatably arranged on the upstream side and the downstream side in the conveyance direction of the guide member 31. The guide rollers 33 and 34 are preferably arranged close to both ends of the guide member 31 in the conveying direction.
[0030]
Further, as a paper discharge unit for discharging the paper 12 recorded by the recording head 4, a separation claw 41 for separating the paper 12 from the transport belt 21, a paper discharge roller 42 and a paper discharge roller 43, and a discharge A paper discharge tray 44 for stocking paper 12 to be printed is provided.
[0031]
A double-sided paper feeding unit 51 is detachably attached to the apparatus main body. The double-sided paper feeding unit 51 takes in the paper 12 returned by the reverse rotation of the transport belt 21, reverses it, and feeds it again between the counter roller 22 and the transport belt 21.
[0032]
Here, the drive system of the counter roller 22 will be described with reference to FIGS.
This drive system rotates the transport belt 22 by rotating the transport roller 27 via the timing belt 63 and the timing gear 63 attached to the shaft 27 a of the transport roller 27 by the sub-scanning motor 61.
[0033]
As shown in FIG. 4, an intermediate gear 66 including a one-way clutch 65 that is a clutch means that idles due to a speed difference between the conveyance roller 27 and the counter roller 22 is attached to the shaft 27 a of the conveyance roller 27. 66 and the drive gear 67 provided on the shaft 22 a of the counter roller 22, the counter roller 22 is connected from the sub-scanning motor 61 through the shaft 27 a of the transport roller 27, the one-way clutch 65, the intermediate gear 66, and the drive gear 67. Rotational driving force is transmitted to
[0034]
In this case, the one-way clutch 65 transmits the rotation of the shaft 27a to the intermediate gear 66 when the transport roller 27 rotates in the direction indicated by the arrow in FIG. 4 (the forward transport direction of the paper 12), and the direction opposite to the direction indicated by the arrow in FIG. It is set so that the rotation of the shaft 27a is not transmitted to the intermediate gear 66 when rotating in the direction in which the paper 12 is fed into the duplex printing mechanism 51 for duplex printing.
[0035]
Further, in this drive system, the linear speed of the counter roller 22 is slower than the linear speed of the conveyor belt 21, and the ratio is set so that the linear speed of the counter roller 22 is about 2% slower than the linear speed of the conveyor belt 21. It is set. In this recording apparatus, setting about 2% later was the most effective from the experimental results.
[0036]
In the ink jet recording apparatus configured as described above, the sheets 12 are separated and fed one by one from the sheet feeding unit, and the sheet 12 fed substantially vertically upward is guided by the guide 15 as shown in FIG. , Both of which are sandwiched between the conveyor belt 21 and the counter roller 22 that are rotationally driven, conveyed and sent, and further guided by the conveyance guide 23 and pressed against the conveyance belt 21 by the tip pressure roller 25. The conveyance direction is changed by about 90 °.
[0037]
At this time, since both the transport belt 21 and the counter roller 22 are driven to rotate by receiving a rotational driving force, the paper 12 is a stiff paper such as glossy paper or thick paper, and the friction coefficient with the transport guide 23 is large. Even if the friction coefficient μ of the conveyor belt 21 is small, the conveyor belt 21 can be fed and changed in direction on the conveyor belt 21 without causing slippage.
[0038]
In this case, if only the counter roller 22 is driven, the counter roller 22 and the conveyor belt 21 may be moved between the counter roller 22 and the conveyor belt 21 due to variations in the diameter of the counter roller 22 with respect to the linear velocity of the conveyor belt 21, expansion due to temperature, and wear. There is a possibility that a speed difference may occur. When such a speed difference occurs, the paper 12 is frictionally charged, a load due to friction increases, and a load torque varies from device to device.
[0039]
Therefore, in this recording apparatus, the counter roller 22 is driven via the one-way clutch 65. Therefore, when the linear velocity of the conveyor belt 21 is higher than the linear velocity of the counter roller 22, the counter roller 22 is idling. It is possible to rotate (follow the conveyor belt 21).
[0040]
Furthermore, since the linear speed of the counter roller 22 is set slower than the linear speed of the conveyor belt 21 (as described above, it is about 2% slower here), the one-way clutch 65 of the drive system of the counter roller 22 has a speed difference. As a result, the conveyor belt 21 and the counter roller 22 are almost at the same speed, and the sheet 12 is frictionally charged, the load is increased by friction, and the load torque is increased. It is possible to reduce the occurrence of variations among devices.
[0041]
On the other hand, when the linear velocity of the conveyor belt 21 is set to be slower than the linear velocity of the counter roller 22, the load on the drive system of the conveyor belt 21 increases and the load torque varies between the devices.
[0042]
Note that during double-sided printing, the conveyor belt 21 rotates in the direction opposite to the direction indicated by the arrow A in FIG. 4, but at this time, the driving force is not transmitted to the counter roller 22 by the one-way clutch 65, and the counter roller 22 is applied to the conveyor belt. After the paper is rotated and the feeding of the paper 12 to the double-sided paper feeding unit 51 is completed, the transport belt 21 rotates again in the direction of arrow A to feed the paper 12 from the double-sided paper feeding unit 51. This also works in the same manner as described above.
[0043]
As described above, the paper 12 is fed onto the conveyor belt 21. Here, since a positive output and a negative output are alternately repeated from the high voltage power source to the charging roller 26 by a control circuit (not shown), that is, an alternating voltage is applied, the conveying belt 21 has an alternating charging voltage pattern, In other words, plus and minus are alternately charged in a band shape with a predetermined width in the sub-scanning direction that is the circumferential direction. When the paper 12 is fed onto the conveyance belt 21 charged alternately with plus and minus, the charge is polarized in the opposite direction to the charge pattern in the paper 12, so that a capacitor connected in parallel is formed. 12 is adsorbed by the conveyance belt 21, and the paper 12 is conveyed in the sub-scanning direction by the circular movement of the conveyance belt 21.
[0044]
Therefore, by driving the recording head 4 according to the image signal while moving the carriage 3, the 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 that the trailing edge of the paper 12 has reached the recording area, the recording operation is finished and the paper 12 is discharged onto the paper discharge tray 44.
[0045]
In the above embodiment, the present invention has been described with reference to an example in which the present invention is applied to a serial (shuttle type) ink jet recording apparatus that is scanned by a carriage. However, the present invention is similarly applied to a line type ink jet recording apparatus having a line type head. be able to. Further, although the recording apparatus using a conveyance belt has been described, the present invention can be similarly applied to a recording apparatus that conveys a sheet using only conveyance rollers.
[0046]
The image forming apparatus according to the present invention can be applied to a facsimile machine, a copying machine, a printer / fax / copier multifunction machine, etc. in addition to an ink jet printer, and the recording method is not limited to the ink jet recording method. The present invention can be similarly applied to an image forming apparatus using an electrophotographic system. Furthermore, the present invention can also be applied to an image forming apparatus that discharges a liquid other than ink, such as a resist or a DNA sample in the medical field.
[0047]
【The invention's effect】
As described above, according to the image recording apparatus of the present invention, the counter roller for transporting the fed paper between the transport belt and the transport roller is provided, and the linear velocity of the counter roller is transported. is set slower the belt or the linear speed of the conveying roller, counter roller, since the configuration is dynamic drive via a clutch means for idling the speed difference between the conveyor belt or conveyor rollers, affecting the transportability and image Therefore, even a paper requiring a large transport force can be stably transported by changing the transport direction without causing an increase in load due to frictional charging and friction.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a plan view of an essential part of the recording apparatus. FIG. 3 is an explanatory view of an essential part of the recording apparatus. Explanatory drawing for explaining the drive system of the counter roller of the recording apparatus
DESCRIPTION OF SYMBOLS 3 ... Carriage, 4 ... Recording head, 12 ... Paper, 21 ... Conveyor belt, 22 ... Counter roller, 26 ... Charging roller, 27 ... Conveyance roller, 28 ... Tension roller, 31 ... Guide member, 44 ... Discharge tray, 61 ... sub-scanning motor, 65 ... one-way clutch, 66 ... intermediate gear, 67 ... drive gear.

Claims (4)

In an image forming apparatus that conveys a sheet by charging and rotating the endless conveyance belt surface,
A counter roller for transporting the fed paper sandwiched between the transport belt,
The linear speed of the counter roller is set slower than the linear speed of the conveyor belt,
It said counter roller, an image forming apparatus according to claim <br/> be dynamic drive via a clutch means for idling the speed difference between the conveyor belt. The image forming apparatus according to claim 1, wherein the sheet is conveyed with a conveyance direction changed by approximately 90 ° after passing between the conveyance belt and the counter roller. In an image forming apparatus that transports paper with a transport roller,
A counter roller for transporting the fed paper sandwiched between the transport rollers;
The linear speed of the counter roller is set slower than the linear speed of the transport roller ,
It said counter roller, an image forming apparatus according to claim <br/> be dynamic drive via a clutch means for idling the speed difference between the transport rollers. 4. The image forming apparatus according to claim 3, wherein the sheet is conveyed with a conveyance direction changed by approximately 90 [deg.] After passing between the conveyance roller and the counter roller.

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