JP2001354337A - Sheet carrying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of a jam or inferior transfer and to stably carry sheets of many types. SOLUTION: The sheet carrying device comprises a sheet stacking means 1 for stacking sheets S, a sheet feeding means 2 for feeding the sheets S one by one from the sheet stacking means 1, a resisting means 3 for temporarily resisting feeding of the sheets S by the sheet feeding means 2 and restarting feeding of the sheets S at a prescribed timing after that, and an image processing means 3 for processing images of the sheets S fed again by the resisting means 3. The sheet carrying device also has a control means 5 for variably controlling the timing of feeding sheets by the sheet feeding means 2, the timing of restarting feeding of sheets by the resisting means 3, and the timing of image processing by the image processing means 4 according to the type of the sheet S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying device used in an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly, to a sheet conveying device capable of stably conveying many types of sheets. Related to the device.

[0002]

2. Description of the Related Art Conventionally, as a sheet feeding device used in an image forming apparatus such as an electrophotographic copying machine, a sheet loaded on a sheet tray is taken out by a nudger roll, and the taken out sheet is taken, for example, into a feed roll. The sheet is sent one by one by a separating mechanism consisting of a retard roll and a retard roll, and the sent paper is temporarily stopped by a pair of registration rolls to correct skew (skew), and thereafter, an image forming unit (transfer unit) By rotating the pair of registration rolls at the timing when the leading edge of the image formed in step 2 and the leading edge of the sheet match, the sheet is re-fed to the transfer unit while correcting the variation in the sheet feeding timing. Things are known.

In this type of sheet feeding apparatus, there is disclosed a technique for setting the sheet sending timing at a constant interval from the viewpoint of reliably maintaining the productivity (Japanese Patent Application Laid-Open No. 9-1997). No. 76587).

[0004]

However, in such a technique, when the feeding of the sheet is abnormally delayed, the leading edge of the sheet is delayed with respect to the leading edge of an image to be formed, and transfer failure occurs. There has been a technical problem that paper jams may occur due to the occurrence of paper jam or the leading edge of the next sheet hitting the trailing edge of the preceding sheet. In particular, for a sheet (sheet) that is difficult to take out or send out, such as a thick paper or an OHP sheet, such a technical problem is likely to occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above technical problems, and is intended to prevent the occurrence of jams and transfer defects and to stably convey many types of sheets. A transport device is provided.

[0006]

That is, according to the present invention, as shown in FIG. 1, a sheet stacking means 1 for stacking sheets S is provided.
Sheet feeding means 2 for separating and feeding sheets S one by one from the sheet stacking means 1; and sheet feeding means 2
Means 3 for temporarily damaging the sheet S fed by the register means and then re-feeding the sheet S at a predetermined timing; and image processing means 4 for image-processing the sheet S re-fed by the resist means 3. In the sheet conveying apparatus provided with, the sheet feeding timing by the sheet feeding unit 2, the sheet re-feeding timing by the registration unit 3, and the image processing timing by the image processing unit 4 are variable according to the type of the sheet S. It is characterized by comprising control means 5 for controlling.

In such technical means, the sheet stacking means 1 may be appropriately selected as long as the sheet S can be stacked, and the sheet feeding means 2 may be stacked on the sheet stacking means 1. As long as the sheets S can be separated and supplied one by one, a method of separating the sheets S may be appropriately adopted.

Further, the registration means 3 uses a roll pair, for example, as long as it temporarily dams the sheet S fed by the sheet feeding means 2 and then re-feeds the sheet S at a predetermined timing. A method such as a method using a nail pad may be appropriately selected.

The image processing means 4 has a function of performing image processing on the sheet S re-fed by the registration means 3, and includes, for example, an image reading means for reading an image recorded on the surface of the sheet S, And an image recording unit for recording an image on the surface of the sheet S, and a transfer unit for transferring the image formed on the image carrier to the sheet S.

Further, the control means 5 controls the sheet feeding timing by the sheet feeding means 2, the sheet re-feeding timing by the registration means 3, and the image processing timing by the image processing means 4 according to the type of the sheet S. Such a method of detecting the type of the sheet S includes, for example, a mode in which control is performed based on sheet type information from the sheet type detection unit 6 that detects the type of the sheet S. The control may be appropriately selected from various methods, such as a mode in which control is performed based on sheet type information from the sheet type input unit 7 for inputting the type of the sheet S. Then, it is preferable that the control unit 5 changes not only the respective timings described above but also a jam timer value for detecting a sheet jam according to the type of the sheet S.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. FIG. 2 shows an embodiment of a tandem image forming apparatus (color laser printer) to which the present invention is applied. In the figure, a tandem image forming apparatus according to the present embodiment has an image forming unit 22 (specifically, 22Y) of four colors (yellow, magenta, cyan, and black in the present embodiment) in a main body housing 21. , 22M, 22C, and 22K) are arranged in the horizontal direction, and above the transfer unit 23 including the intermediate transfer belt 230 that is circulated and conveyed along the arrangement direction of the image forming units 22, is disposed. A supply cassette 24 for accommodating the paper P is provided below the housing 21, and a paper transport path 25 serving as a transport path for the paper P from the supply cassette 24 is vertically arranged.

In this embodiment, each image forming unit 22 (specifically, 22Y, 22M, 22C, 22K)
Are, in order from the upstream in the circulation direction of the intermediate transfer belt 230,
These form toner images for yellow, magenta, cyan, and black, respectively.
, Each developing unit 33 and one common exposure unit 40. Here, the photoconductor unit 30
Is, for example, a photosensitive drum 31 and this photosensitive drum 31
(A charging roll in the present example) 32 for charging in advance
Cleaner 3 for removing residual toner on photoconductor drum 31
4 is integrated into a cartridge. Of these, the photosensitive drum 31 has a negatively charged photosensitive layer, and its diameter is φ30. The developing unit 33 develops the electrostatic latent image formed by exposure on the charged photosensitive drum 31 by the exposure unit 40 with a corresponding color toner (for example, negative polarity in the present embodiment). is there. Reference numeral 35 (specifically, 35Y, 35M, 35
C, 35K) are toner cartridges for replenishing the respective developing units 33 with the respective color component toners.

On the other hand, the exposure unit 40 includes, for example, four semiconductor lasers (not shown), one polygon mirror 42, an imaging lens (not shown), and each photoconductor unit 30 in a unit case 41. A mirror (not shown) is stored, the light from the semiconductor laser for each color component is deflected and scanned by the polygon mirror 42, and an optical image is formed on the corresponding exposure point on the photosensitive drum 31 via the imaging lens and the mirror. It is intended to lead.

In the present embodiment, the transfer unit 23 is, for example, one in which an intermediate transfer belt 230 is stretched between a pair of tension rolls (one of which is a drive roll) 231 and 232. A primary transfer device (primary transfer roll in this example) 51 is disposed on the back surface of the intermediate transfer belt 230 corresponding to the photosensitive drum 31. The primary transfer rolls 51 are each charged with a toner by a power source (not shown). By applying a voltage having a polarity opposite to the polarity, the toner image on the photosensitive drum 31 is electrostatically transferred to the intermediate transfer belt 230 side.

Further, a secondary transfer device 52 is disposed at a portion of the intermediate transfer belt 230 corresponding to the tension roll 232 on the downstream side of the most downstream image forming unit 22K, and the primary transfer on the intermediate transfer belt 230 is performed. The image is secondarily transferred (collectively transferred) to the recording paper P. Here, the secondary transfer device 52 includes a secondary transfer roller 521 that is disposed in pressure contact with the toner image bearing surface of the intermediate transfer belt 230, and a secondary transfer roller 52 that is disposed on the back surface side of the intermediate transfer belt 230.
And a backup roll (also used as a stretching roll 232 in this example) that forms one counter electrode.

In this embodiment, the intermediate transfer belt 2
Reference numeral 30 denotes a material in which a material for imparting conductivity such as carbon or an ionic conductive material is dispersed in a resin material such as polyimide, polycarbonate, or a fluorine-based resin, and has a resistance value of 10 ¹⁰ to
It is formed so as to be adjusted to about 10 ¹⁴ Ω · cm.

The primary transfer roll 51 is made by dispersing carbon in an elastic roll made of urethane foam or the like and has a resistance value of 10%.
^It is adjusted to about ⁶ to 10 ⁸ Ω · cm and formed into a size of φ18.

Further, a secondary transfer roll 521 is formed by injection molding a surface layer made of urethane resin on which carbon is also dispersed on the outer periphery of an elastic roll made of urethane foam in which carbon is dispersed, and then a fluorine-based material. It has a three-layer structure of φ28 coated with a resin surface layer of 20 μm, and its resistance is adjusted to about 10 ⁷ to 10 ⁸ Ω · cm.

In the present embodiment, the secondary transfer roll 521 is grounded, and a bias having the same polarity as the charged polarity of the toner is applied to the backup roll (stretch roll 232). Furthermore, the intermediate transfer belt 23
A belt cleaner 53 is disposed on the upstream side of the most upstream image forming unit 22Y of the intermediate transfer belt 230.
The upper residual toner is removed.

A nudger roll 61 for picking up the paper P is provided above the supply cassette 24. Immediately after the nudger roll 61, a separating mechanism 6 composed of a feed roll and a retard roll for separating and sending out the paper P is provided.
2 are provided. Further, on the downstream side of the separating mechanism 62, a takeaway roll 63 along the paper transport path 25, a registration roll (registration roll) for temporarily stopping the paper P while nipping the paper P and then supplying the paper P to the secondary transfer portion at a predetermined timing ) 64 are provided. On the other hand, a fixing device 65 is provided in the sheet transport path 25 located on the downstream side of the secondary transfer portion, and a first discharge roll 66 and a second discharge roll 6 for discharging recording paper are provided downstream of the fixing device 65.
7 is provided, and the discharged paper P is stored in a storage tray 68 formed on an upper portion of the main body housing 21.

Reference numeral 71 denotes a takeaway sensor provided between the separating mechanism 62 and the takeaway roll 63, reference numeral 72 denotes a registration sensor provided immediately before the registration roll 64, and reference numeral 73 denotes a first discharge roll 66 and a second discharge roller. Discharge roll 6
Reference numeral 81 denotes a paper thickness sensor for detecting the thickness of the conveyed paper P, and reference numeral 82 denotes an OHP for detecting whether or not the conveyed paper P is an OHP sheet. It is a sensor. Reference numeral 90 denotes a control device of the color laser printer, which controls the conveyance of the paper P in addition to the image forming control.

Next, an image forming process of the tandem type image forming apparatus according to the present embodiment will be described. In the tandem image forming apparatus shown in FIG. 2, when a print start switch (not shown) or an image input device such as a personal computer is turned on, an image forming process is executed. For example, when forming a full-color image, each image forming unit 22 (22
Y, 22M, 22C, 22K), the respective color component toner images are formed, and the respective color component toner images are sequentially multiplex-transferred onto the intermediate transfer belt 230. It is transferred all at once.

Here, in this embodiment, as shown in FIG. 3, after the paper supply is started, the paper P is detected based on the detection results of the paper thickness sensor 81 and the OHP sensor 82 provided in the paper transport path 25. Is a thick paper or an OHP sheet, the special mode is executed. Otherwise, the normal mode is executed.

FIG. 4 is a timing diagram in the normal mode, and FIG. 5 is a timing diagram in the special mode. 4 and 5, the symbol S
Is the circumference of the photosensitive drum 31, Ps is the leading end position of the paper P,
Pe indicates the rear end position of the sheet P, and the symbol G indicates the front end position of the image. Also, the symbol PA is a sheet supply pitch in the normal mode, and PB is a sheet supply pitch in the special mode. The size of the paper P used in each process is LETTER size (279.4 ×
215.9 mm).

According to the above, in the present embodiment, the paper supply pitch PA (see FIG. 4) in the normal mode is set to a length corresponding to the time required for the photosensitive drum 31 to make approximately three rotations. It can be understood that the paper supply pitch PB (see FIG. 5) in the special mode is set to a length corresponding to the time required for the photosensitive drum 31 to make approximately three and a half rotations.

The reason is as follows. FIG. 6 shows FIG.
FIG. 4 is an enlarged view of a portion from the supply cassette 24 to the secondary transfer device 52 in the timing diagram of the normal mode. In the figure, reference numeral Ps1 indicates the trajectory of the leading end Ps when the sheets P stacked in the supply cassette 24 are immediately taken out by the nager roll 61. Reference symbol Ps2 denotes a trajectory of the leading end Ps when the paper P stacked on the supply cassette 24 slides and is subsequently taken out by the nudger roll 61. 5 shows the trajectory of the tip Ps when the tip Ps is taken out after the end.
Reference numeral Ps2a indicates the case of Ps2 and no paper slip, and Ps2b indicates the case where the paper slightly slips. Further, reference symbol Ps3 indicates the trajectory of the leading end Ps when the paper P has already reached the separation mechanism at the start of paper feeding (when the next paper P is about to be fed at the time of feeding the previous paper P). Is shown. The symbols Pe1, Pe2, Pe2a, Pe2b, P
e3 is the trajectory Ps1, Ps2, Ps2a, Ps2b, P
This is the trail of the trailing edge of the sheet P corresponding to s3.

On the other hand, FIG. 7 is an enlarged view of a portion from the supply cassette 24 to the secondary transfer device 52 in FIG. 5 (timing diagram of the special mode). In the special mode, the sheet P to be conveyed is slippery (hard to take out) like an OHP sheet or a thick sheet. Therefore, the maximum allowable slip time LB allowed from the start of sheet feeding is the maximum allowable slip time LB in the normal mode described above. It is set longer than the slip time LA.

The paper supply pitch PB in the special mode is set to be longer than the paper supply pitch PA in the normal mode by the difference between the maximum allowable slip times LA and LB. Further, the re-supply pitch and the image forming pitch for re-supplying the sheet P from the registration roll 64 are also set to PA in the normal mode and to PB in the special mode.

By setting as described above, productivity can be improved when plain paper is used as the paper P, and when special paper such as an OHP sheet or thick paper is used as the paper P, It is possible to prevent the occurrence of a transfer failure such as a jam or a transfer position shift.

For example, when an OHP sheet or cardboard is used in the normal mode, as shown by a broken line in FIG. 4 (in this case, the slip time is the maximum allowable slip time L in the special mode).
B), the arrival timing of the sheet P (the leading end is indicated by a symbol Ps ′) is delayed with respect to the arrival timing of the image G at the secondary transfer position. It is understood that

In the present embodiment, the paper thickness sensor 81
Although the type of the sheet P is determined by the OHP sensor 82 or the OHP sensor 82, the present invention is not limited to this, and the setting may be performed from an image input device such as an operation panel of a printer or a personal computer (not shown).

In the color laser printer according to the present embodiment, the take away sensor 71 and the registration sensor 7
2. The jam sensor in the paper transport path 25 is detected by the discharge sensor 73, but it is preferable to change the jam timer value according to the normal mode and the special mode.

[0033]

As described above, according to the present invention,
The sheet feeding timing by the sheet feeding unit, the sheet re-feeding timing by the registration unit, and the image processing timing by the image processing unit are variably controlled according to the type of the sheet. This prevents many types of sheets from being stably conveyed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a sheet conveying device according to the present invention.

FIG. 2 is an explanatory diagram illustrating an outline of an embodiment of a color laser printer to which the sheet conveying device according to the present invention is applied.

FIG. 3 is a flowchart illustrating a process of selecting a sheet feeding process of the color laser printer according to the embodiment;

FIG. 4 is a timing diagram illustrating a relationship between sheet supply timing and image forming timing when a normal sheet supply process is selected.

FIG. 5 is a timing diagram illustrating a relationship between a sheet supply timing and an image forming timing when a special sheet supply process is selected.

FIG. 6 is a partially enlarged view of FIG. 4;

FIG. 7 is a partially enlarged view of FIG. 5;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sheet loading means, 2 ... Sheet feeding means, 3 ... Registration means, 4 ... Image processing means, 5 ... Control means, 6 ... Sheet type detection means, 7 ... Sheet type input means

Continued on the front page F term (reference) 2H027 DC02 DC14 ED17 ED24 EE02 2H072 AA09 AA12 AA13 AA17 AA22 AA29 AA36 AB07 AB15 BA03 BA12 BB07 BB08 CA01 3F048 AA02 AA04 AA05 AB01 AB04 AB06 BA07 DB04 CC03 DC12 EB22 EB24 EB30 3F102 AA02 AA10 AA11 AB01 AB02 AB05 BA02 BA07 BA09 CA03 CB01 CB02 CB07 DA08 EA03 EC07 3F343 FA02 FA06 FA09 FB02 FB03 FB04 FC03 GA01 GB01 GC01 GD01 JA01 MA03 MA09 MA27 MB04 MB13 MC08

Claims (5)

[Claims] 1. A sheet stacking means for stacking sheets, a sheet feeding means for separating and feeding sheets one by one from the sheet stacking means, and a sheet temporarily fed by the sheet feeding means. In a sheet conveying apparatus including a damming means and a resist means for re-feeding at a predetermined timing thereafter, and an image processing means for image-processing the sheet re-fed by the resist means, according to the type of sheet, A sheet conveying device comprising a control unit for variably controlling a sheet feeding timing by the sheet feeding unit, a sheet re-feeding timing by the registration unit, and an image processing timing by the image processing unit. 2. The sheet conveying apparatus according to claim 1, wherein the control unit changes a jam timer value for detecting a sheet jam according to a type of the sheet. 3. The sheet conveying apparatus according to claim 1, wherein the control unit performs control based on sheet type information from a sheet type detecting unit. 4. The sheet conveying apparatus according to claim 1, wherein the control unit performs control based on sheet type information from a sheet type input unit. 5. The sheet conveying apparatus according to claim 1, wherein the image processing unit is a transfer unit that transfers an image formed on the image carrier to a sheet.