JP2010030742A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus that suppresses errors such as mounting accuracy of a rotary encoder to a conveyance roller, parts accuracy such as eccentricity of the conveyance roller, slippage during conveyance of a sheet, and kicking out when a sheet passes through a nip portion of the conveyance roller. It is to provide.
SOLUTION: Transport mechanisms 121 and 127 for transporting a recording medium 112, image forming units 103 and 107 for forming an image, transport drive means 104 and 131 for driving the transport mechanisms 121 and 127, and a transport amount are detected. Carrying amount detecting means 136, mark forming means 50 for marking the recording medium 112, mark reading means 51 for reading a mark, control means 200 for controlling an input value input to the carrying driving means, And an image forming apparatus having a moving means 53 for moving the mark reading means 51 in the transport direction.
[Selection] Figure 12

Description

  The present invention relates to an image forming apparatus such as a printer, a facsimile machine, a copying machine, and a multi-function machine that conveys paper using a conveyance mechanism.

2. Description of the Related Art Conventionally, in an image forming apparatus used for electrophotography, a printer, and the like, a conveyance amount or a conveyance speed when conveying a recording medium (hereinafter also referred to as a sheet) on which an image is formed is determined by a rotary encoder. It is known that the amount of rotation (movement amount) of the conveyance roller is used as a substitute and controlled as the conveyance amount or conveyance speed of the paper.
With the above configuration, since the conveyance amount of the sheet itself is not directly measured, the accuracy of mounting the rotary encoder to the conveyance roller, the accuracy of the parts such as the eccentricity of the conveyance roller, the slip and the sheet during conveyance of the conveyance roller There is a problem that an error occurs between the detected amount of the actual paper conveyance amount due to kicking out when the nip portion passes, and this causes image disturbance.
In addition, when conveying a sheet using a conveyance belt, a method is known in which marking is performed on the conveyance belt to correct a conveyance amount and a conveyance speed (for example, see Patent Documents 1 and 2).
Japanese Patent Laid-Open No. 10-1000048 Japanese Patent No. 3703471

However, according to the techniques disclosed in the conventional documents, errors in component accuracy such as the accuracy of attaching the rotary encoder to the conveying roller and the eccentricity of the conveying roller can be ignored. Errors such as kicking out when exiting the nip part remain in the past, causing a problem of image distortion.
Accordingly, an object of the present invention is to perform marking directly on a sheet in consideration of the above-described situation, detect the position of the marking, and correct the conveyance amount, so that the accuracy of attaching the rotary encoder to the conveyance roller, the conveyance roller It is an object of the present invention to provide an image forming apparatus that suppresses errors such as part accuracy such as eccentricity of the sheet, slip during conveyance of the sheet, and kicking out when the sheet passes through the nip portion of the conveyance roller.

In order to solve the above-described problems, the invention described in claim 1 includes a transport mechanism that transports a recording medium, an image forming unit that forms an image on the recording medium, and a transport drive that drives the transport mechanism. Means, a carry amount detecting means for detecting the carry amount of the carry mechanism, a mark forming means for marking the recording medium, a mark reading means for reading a mark described in the mark forming means, and the carry drive In the image forming apparatus having a control unit that controls an input value input to the unit and a moving unit that moves the mark reading unit by a predetermined amount in the transport direction, the control unit reads the mark by the mark reading unit. The transport amount of the transport mechanism is corrected based on the content.
According to a second aspect of the present invention, the image forming unit is configured by a carriage that mounts a recording head and reciprocates on the recording medium to form an image.
The invention according to claim 3 is characterized in that the mark reading means is a CCD sensor.
According to a fourth aspect of the invention, there is provided the image forming apparatus according to the first or second aspect, wherein the mark reading means is a CMOS sensor.
The invention according to claim 5 further comprises mark deletion means for deleting the mark in order to erase the mark on the recording medium formed by the mark formation means. The image forming apparatus is characterized.
According to a sixth aspect of the present invention, the image forming apparatus according to any one of the first to fifth aspects is characterized in that the mark formed on the recording medium by the mark forming means is transparent.
According to a seventh aspect of the present invention, in the method according to any one of the first to sixth aspects, the mark formed by the mark forming unit is formed on a side opposite to a surface on which the image of the recording medium is formed. An image forming apparatus is characterized.
Further, in the invention described in claim 8, the mark reading unit continuously detects the mark during conveyance of the recording medium, and controls the conveyance driving unit of the recording medium based on the detection result. Item 8. The image forming apparatus according to any one of Items 1 to 7.

  According to the present invention, by marking directly on the paper, detecting the position of the marking, and correcting the transport amount of the paper, the accuracy of mounting the rotary encoder to the transport roller, the accuracy of the parts such as the eccentricity of the transport roller, It is possible to suppress errors such as slipping during paper conveyance and kicking out when the paper passes through the nip portion of the conveyance roller.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic side view showing the overall configuration of an image forming apparatus according to the present invention. FIG. 2 is a plan view showing a main part of the image forming apparatus of FIG. An example of an image forming apparatus according to the present invention provided with a droplet discharge head or a droplet discharge apparatus according to the present invention will be described with reference to FIGS.
In the image forming apparatus A, a carriage 103 is slidably held in a main scanning direction by a guide rod 101 and a guide rail 102 which are horizontally arranged on left and right side plates (not shown), and the carriage 103 is held in a main scanning motor. 104 moves and scans in the direction indicated by the arrow in FIG. 2 (main scanning direction) via the timing belt 105.
For example, the carriage 103 includes a plurality of recording heads 107 including four droplet ejection heads that eject ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). The ink discharge ports are arranged in a direction crossing the main scanning direction, and are mounted with the ink droplet discharge direction facing downward. In addition, as a droplet discharge head constituting the recording head 107, a droplet discharge head using a piezoelectric actuator such as a piezoelectric element is used.
The carriage 103 is also equipped with a sub-tank 108 for each color for supplying each color ink to the recording head 107. Ink is supplied to the sub tank 108 from a main tank (ink cartridge) through an ink supply tube (not shown).
In this embodiment, the sub-tank 108 and the recording head 107 constitute the liquid droplet ejection apparatus according to the present invention. However, the recording head 107 is composed of the liquid droplet ejection head according to the present invention, and a sub-tank 108 is provided separately. Alternatively, the ink cartridge can be mounted without using a sub tank.

On the other hand, as a paper feeding unit for feeding paper 112 stacked on a paper stacking unit (pressure plate) 111 such as a paper feeding cassette 110, a paper feeding roller for separating and feeding the paper 112 one by one from the paper stacking unit 111 (Half-moon roller) 113 and a separation pad 114 made of a material having a large friction coefficient are provided facing the sheet feeding roller 113, and the separation pad 114 is urged toward the sheet feeding roller 113 side.
As a transport unit for transporting the paper 112 fed from the paper feed unit below the recording head 107, a transport belt 121 for transporting the paper 112 by electrostatic adsorption and a guide 115 from the paper feed unit. And a counter roller 122 for sandwiching and transporting the paper 112 fed through the transport belt 121 with the transport belt 121.
In addition, the conveying unit is urged toward the conveying belt 121 by a conveying guide 123 for changing the direction of the sheet 112 sent substantially vertically upward by approximately 90 ° and following the conveying belt 121 and a pressing member 124. And a charging roller 126 which is a charging means for charging the surface of the conveyor belt 121.
Here, the conveyance belt 121 is an endless belt, is stretched between the conveyance roller 127 and the tension roller 128, and the conveyance roller 127 is rotated from the sub-scanning motor 131 via the timing belt 132 and the timing roller 133. By doing so, it is configured to circulate in the belt conveyance direction (sub-scanning direction) of FIG. A guide member 129 is disposed on the back side of the conveyance belt 121 in correspondence with the image forming area formed by the recording head 107.

In addition, a slit disk 134 is attached to the shaft of the transport roller 127, and a sensor 135 for detecting the slit of the slit disk 134 is provided as shown in FIG. An encoder 136 is configured.
The charging roller 126 is arranged so as to contact the surface layer of the conveyor belt 121 and rotate following the rotation of the conveyor belt 121, and applies 2.5N to both ends of the shaft as a pressing force.
Further, as shown in FIG. 1, an encoder scale 142 having slits is provided on the front side of the carriage 103, and an encoder sensor comprising a transmissive photosensor for detecting the slits of the encoder scale 142 on the front side of the carriage 103. The encoder 144 for detecting the position of the carriage 103 in the main scanning direction (position with respect to the home position) is configured.
Further, as a paper discharge unit for discharging the paper 112 recorded by the recording head 107, a separation unit for separating the paper 112 from the conveying belt 121, a paper discharge roller 152 and a paper discharge roller 153, and paper discharge A paper discharge tray 154 for stocking the paper 112 to be printed.
A double-sided paper feeding unit 161 is detachably attached to the back. The double-sided paper feeding unit 161 takes in the paper 112 returned by the reverse rotation of the transport belt 121 and reverses it, and feeds it again between the counter roller 22 and the transport belt 121.

In the image forming apparatus A configured as described above, the sheets 112 are separated and fed one by one from the sheet feeding unit, and the sheet 112 fed substantially vertically upward is guided by the guide 115, and includes the conveyance belt 121 and the counter roller. The front end is guided by a transport guide 123 and pressed against the transport belt 121 by a front end pressure roller 125, and the transport direction is changed by approximately 90 °.
At this time, a positive voltage output and a negative output are alternately repeated from the high voltage power source to the charging roller 126 by a control circuit (not shown), that is, an alternating voltage is applied, and a charging voltage pattern in which the conveying belt 121 alternates. That is, plus and minus are alternately charged in a band shape with a predetermined width in the sub-scanning direction, which is the circumferential direction.
When the paper 112 is fed onto the conveyance belt 121 charged alternately with plus and minus, the paper 112 is attracted to the conveyance belt 121 by electrostatic force, and the paper 112 is conveyed in the sub-scanning direction by the circular movement of the conveyance belt 121. Is done.
Therefore, by driving the recording head 107 according to the image signal while moving the carriage 103, ink droplets are ejected onto the stopped paper 112 to record one line, and after the paper 112 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 112 has reached the recording area, the recording operation is finished, and the paper 112 is discharged onto the paper discharge tray 154.

In the case of double-sided printing, when recording on the front surface (surface to be printed first) is completed, the recording belt 112 is fed into the double-sided paper feeding unit 161 by rotating the conveyor belt 121 in reverse. 112 is reversed (with the back side being the printing surface), and again fed between the counter roller 122 and the conveyor belt 121, the timing is controlled, and on the conveyor bell 121 as described above. After transporting and recording on the back surface, the paper is discharged onto a paper discharge tray 54.
Note that the image forming apparatus A according to the present invention can also be applied to a printer, a facsimile machine, a copying machine, a multi-function machine thereof, and the like. Further, the present invention can also be applied to a droplet discharge head or a droplet discharge device that discharges a liquid other than ink, such as a DNA sample, a resist, or a pattern material, or an image forming apparatus that includes these.

FIG. 3 is a schematic side view for explaining the first mark forming method of the image forming apparatus according to the present invention. 4 is a schematic plan view of the image forming apparatus of FIG. 3 as viewed from above. The configuration and operation of the main part of the present invention will be described with reference to FIGS.
As shown in FIGS. 1, 3, and 4, after the paper 112 is conveyed to a position where the leading edge of the paper is detected by a registration sensor (not shown) by a paper feed roller 113, the paper 112 that is sent substantially vertically upward is substantially omitted. The sheet is conveyed to the printing start position by the conveyance belt 121 through the conveyance guide 123 for changing the direction by 90 °.
The marking mechanism 50 discharges marking ink onto the paper 112 conveyed to the printing start position, thereby marking the paper 112. 3 and 4, reference numeral 114 denotes a separation pad, 125 denotes a tip pressure roller, 127 denotes a transport roller, 129 denotes a guide member, 152 denotes a paper discharge roller, and 153 denotes a paper discharge roller.
Thereafter, after the carriage 103 is moved and printing is performed, the paper 112 is also transported by a predetermined transport amount by the transport belt 121. However, the sheet 112 is stopped after the stop error is detected by the CCD sensor 51 serving as a mark reading unit or a marking detection unit when the stop position is aligned.
After the conveyance is completed, an image is formed on the paper 112 by the carriage 103. The transport error is corrected by repeating the above operation. Further, the ink marked by the marking mechanism 50 is removed by discharging a removing solution by the marking removing mechanism 52.

The above correction suppresses errors such as the accuracy of mounting the rotary encoder on the conveyance roller, the accuracy of parts such as the eccentricity of the conveyance roller, slippage during paper conveyance, and kicking out when the paper leaves the nip of the conveyance roller. it can.
In the configuration described above, marking is performed directly on the paper 112 from the marking mechanism 50, the marking position is detected by the CCD sensor 51 serving as a mark reading means, and the conveyance amount is corrected, whereby the rotary encoder 136 is fed to the conveyance roller. It is possible to suppress errors such as mounting accuracy, component accuracy such as eccentricity of the conveyance roller, slip during conveyance of the paper, and kicking out when the paper passes through the nip portion of the conveyance roller.
In the above configuration, the ink marked by the marking mechanism 50 can be removed by the marking removing mechanism 52. In addition, since marking is performed directly on the paper 112 in order to correct the conveyance amount, a means for removing the marking trace may be provided for the problem that the marking trace remains. Alternatively, the problem of marking marks is solved by making the marking itself invisible by visible light.

FIG. 5 is a schematic side view for explaining a second mark forming method of the image forming apparatus according to the present invention. 6 is a schematic plan view of the image forming apparatus of FIG. 5 as viewed from above. The configuration and operation of the main part of the present invention will be described with reference to FIGS.
In the configuration of the first mark forming method described above, when a liquid such as ink is used for marking or marking mark erasing means, if the image forming portion and the marking portion coincide with each other, the image is formed before the liquid is dried. There was a possibility of causing deterioration, and it was necessary to provide a drying time.
5 and 6, this problem is solved by setting the marking surface on the side opposite to the image forming surface, that is, the inner peripheral side of the conveying belt 121 in the drawing. As a configuration, a gap is formed in the central portion of the conveyance belt 121, and a marking mechanism 50, a marking detection unit 51, and a marking removal mechanism 52 are arranged in the gap.
A space necessary for disposing the marking mechanism 50 by configuring the marking mechanism 50, the marking detecting means 51, and the marking removing mechanism 52 inside the conveying belt 121 spanned between the conveying roller 127 and the tension roller 128. There is also an advantage that can be reduced. 5 and 6, reference numeral 114 denotes a separation pad, 123 denotes a conveyance guide, 125 denotes a tip pressure roller, 127 denotes a conveyance roller, 152 denotes a paper discharge roller, and 153 denotes a paper discharge roller.

FIG. 7 is a schematic side view for explaining a third mark forming method of the image forming apparatus according to the present invention. FIG. 8 is a plan view showing the main part of the third mark forming method of FIG. FIG. 9 is a schematic diagram for explaining a read image of the CCD sensor. The configuration and operation of the main part of the present invention will be described with reference to FIG. 1, FIG. 7, FIG. 8, and FIG.
In FIG. 7, for convenience, marking patterns 60 and 61 are formed above the conveying rollers 63 and 64. As shown in the explanatory diagram of reading by the CCD sensor 51 of FIG. It is conveyed to.
Marking ink is ejected to the paper 112 conveyed to the printing start position by the marking mechanism 50 (FIG. 8), and the paper 112 is marked. The mark formed by the mark forming means 50 may be transparent.
At that time, as shown in FIG. 9A, the marking pattern 60 of the marked paper 112 is read by the CCD sensor 51 which is a mark reading means. The read marking pattern 60 is arithmetically processed by a control unit shown in FIG. 12 described later, and the center position of the marking pattern 60 is obtained.

Thereafter, after the carriage 103 is moved and printing is performed, the CCD sensor 51 as the mark reading means moves along the sensor guide 53 as the movement guide member by the conveyance amount. Further, FIG. 8 shows a tip pressure roller 125 and a transport roller 127.
At the same time, the paper 112 is also transported by a predetermined transport amount by the transport belt 121. At the time of stop position alignment, the paper 112 reads the marking pattern 60 by the CCD sensor 51, which is a mark reading means, and obtains the center value by calculation. As shown in FIG. 9B, a position error is detected based on a deviation amount of the center value of the marking pattern 60 at the time of marking formation and alignment, and the stop error is corrected.
After the conveyance is finished, an image is formed on the paper 112 by the carriage 103. When the image is formed, the CCD sensor 51 serving as a mark reading unit performs an operation of returning to the marking position.
The transport error is corrected by repeating the above operation. Further, the ink marked by the marking mechanism (mark forming means) 50 is removed by discharging a removing solution by the marking removing mechanism 52.

FIG. 10 is a schematic diagram for explaining the movement of the CCD sensor. FIG. 11 is a schematic diagram for explaining a sensor detection image in relation to FIG. Marking is performed on the paper 112, which is a recording medium, at regular intervals, and the CCD sensor 51 moves on the sensor guide 53, which is a moving guide member, while sensing the marking.
When a deviation 60 ′ occurs in the marking pattern 60 as shown in FIG. 11B, the sheet is conveyed so that the marking pattern 60 detected by the controlled CCD sensor 51 is always at a fixed position (FIG. 11A). Feedback control. As a result, the sheet moves in the same manner as the CCD sensor 51. (If the speed of the CCD sensor 51 is increased, the paper is also increased).
The above correction suppresses errors such as the accuracy of mounting the rotary encoder on the conveyance roller, the accuracy of parts such as the eccentricity of the conveyance roller, slippage during paper conveyance, and kicking out when the paper leaves the nip of the conveyance roller. it can.
As described above, since the marking on the paper 112 that may occur in the configuration of the first embodiment is not uniform and has an error, the error in reading the marking by the sensor is described above. In the configuration, after marking is read at the time of marking and the CCD sensor 51 is moved with high accuracy, the marking before moving and the marking after moving can be compared to solve the marking error problem on the paper 112. .

According to the present invention, the cost can be reduced because only one sensor is required. A drive source and a drive mechanism are required instead of one sensor, but in order to cope with the recent high accuracy, the resolution of the sensor needs to be several μm, and such an image sensor is very expensive. As a result, the cost of the drive mechanism can be measured. Further, the drive source can be shared with the paper transport mechanism to reduce the cost.
There is no measurement error because measurement is performed with the same sensor. According to the method of having a plurality of sensors and comparing the images read by the respective sensors, an error also occurs in the paper position due to a reading error between the sensors. As described above, even if the same target is detected, if the sensors are different, deviation occurs in units of microns.
On the other hand, when the detection is performed by the same sensor, the target is always detected even when the target is moving, and the target is not lost. Therefore, both the deviation of the target and the detection error can be reduced. Further, since the movement of the sensor, which is a rigid body, can convey the paper with higher accuracy than the movement of the paper, the movement error of each conveyance of the sensor is not a problem.

FIG. 12 is a block diagram showing the overall configuration including the control unit of the image forming apparatus of the present invention. Finally, the overall configuration of the image forming apparatus of the present invention will be described as a block diagram. In FIG. 12, the conveyance mechanism, the conveyance drive unit, the conveyance amount detection unit, the image forming unit, and the like are described as a composite of individual members, and there is a risk of confusion, so no reference numerals are given.
1 and 12, the image forming apparatus A includes a transport mechanism that transports a paper 112 that is a recording medium, including a transport belt 121, a transport roller 127, and the like.
The conveyance drive means includes a main scanning motor 104, a sub-scanning motor 131, and the like, and the conveyance amount detection means for detecting the conveyance amount of the paper 112 is an encoder 136 composed of a slit disk 134 and a sensor 135. The image forming unit includes a carriage 103 and a recording head 107.
The control unit 200 includes a central processing unit (CPU), and performs feedback control of the paper 112 for correcting the deviation of the marking on the paper 112 by the CCD sensor 51 as mark reading means, control of the moving means 53 of the CCD sensor 51, and the like. Do.
The mark reading means may be not only the CCD sensor described above but also a CMOS sensor. The mark forming unit 50 and the mark removing unit 52 are also controlled by the control unit 200 to move the paper 112.

1 is a schematic side view showing an overall configuration of an image forming apparatus according to the present invention. FIG. 2 is a plan view showing a main part of the image forming apparatus in FIG. 1. It is a schematic side view for explaining a first mark forming method of the image forming apparatus according to the present invention. FIG. 4 is a schematic plan view of the image forming apparatus of FIG. 3 as viewed from above. It is a schematic side view explaining the 2nd mark formation method of the image forming apparatus concerning the present invention. FIG. 6 is a schematic plan view of the image forming apparatus of FIG. 5 viewed from above. It is a schematic side view explaining the 3rd mark formation method of the image forming apparatus concerning the present invention. FIG. 8 is a plan view showing the main part of the third mark forming method of FIG. 7. It is the schematic explaining the reading image of a CCD sensor. It is the schematic explaining the movement of a CCD sensor. It is the schematic explaining a sensor detection image in relation to FIG. 1 is a block diagram illustrating an overall configuration including a control unit of an image forming apparatus of the present invention.

Explanation of symbols

  A image forming apparatus, 50 mark forming means (marking mechanism), 51 mark reading means (marking detecting means, CCD sensor), 52 mark removing means, 53 moving means (moving guide member, sensor guide), 60 marking pattern, 103 image Forming part (carriage), 104 Conveying drive means (main scanning motor), 107 Image forming part (recording head), 112 Recording medium (paper), 121 Conveying mechanism (conveying belt), 127 Conveying mechanism (conveying roller), 134 Conveying Amount detecting means (slit disk), 135 Conveying amount detecting means (sensor), 136 Conveying amount detecting means (encoder), 200 Control means (control unit)

Claims (8)

A transport mechanism that transports the recording medium, an image forming unit that forms an image on the recording medium, a transport drive unit that drives the transport mechanism, a transport amount detection unit that detects the transport amount of the transport mechanism, Mark forming means for marking the recording medium, mark reading means for reading a mark described in the mark forming means, control means for controlling an input value input to the transport driving means, and the mark reading means An image forming apparatus having a moving unit that moves by a predetermined amount in the transport direction;
The image forming apparatus, wherein the control unit corrects the transport amount of the transport mechanism based on content read by the mark reading unit.   The image forming apparatus according to claim 1, wherein the image forming unit includes a carriage that mounts a recording head and performs image formation by reciprocating on the recording medium.   The image forming apparatus according to claim 1, wherein the mark reading unit is a CCD sensor.   The image forming apparatus according to claim 1, wherein the mark reading unit is a CMOS sensor.   5. The image forming apparatus according to claim 1, further comprising: a mark deleting unit that deletes the mark in order to erase the mark formed on the recording medium formed by the mark forming unit.   The image forming apparatus according to claim 1, wherein the mark formed on the recording medium by the mark forming unit is transparent.   7. The image forming apparatus according to claim 1, wherein the mark formed by the mark forming unit is formed on a side opposite to an image forming surface of the recording medium.   8. The mark reading unit continuously detects a mark during conveyance of the recording medium, and controls the conveyance driving unit of the recording medium based on the detection result. The image forming apparatus according to claim 1.

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