JPH07172639A - Sheet material carrying device and image recorder - Google Patents

Abstract

PURPOSE:To attain carrying stability with small type constitution by selectively changing a loop quantity according to information on paper feed in a device having a regist part to correct a skew of a sheet material by forming a loop in the sheet material after the sheet material to be carried is once stopped. CONSTITUTION:A sheet material, for example, a recording paper P is first carried to a carrying part 50A through a carrying roller 45C from a paper feeding part 40. Next, when passing through plural curl applying rollers 46A to 46C, a prescribed quantity of curls is applied in the direction for being wound round a transfer drum 5. In succession, it is carried to a pair of regist rollers 44 through carrying rollers 47A and 47B, and is supplied to the transfer drum 5 through guides 48F and 48G after a paper loop R is formed by swinging of a guide 48D. In this case, a loop quantity in the loop R of the recording paper P is selectively changed according to information of paper feed. For example, the tip of the recording paper P is detected by a pre-regist sensor 49, and after prescribed time, the carrying rollers 47A and 47B are stopped, and are again driven according to image time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image recording apparatus such as a printer, a facsimile or a copying machine, an office equipment, etc. which employs an appropriate transfer type or direct type image forming process such as an electrophotographic method or an ink jet method. In various types of equipment that uses sheet materials, sheet materials (transfer paper, photosensitive paper, thermal paper, electrostatic recording paper, etc. Sheets such as printing paper, manuscripts, cards, envelopes, postcards, etc., the material of which is not limited to paper) are temporarily stopped to form a loop in the sheet material to correct skew of the sheet material, The present invention relates to a sheet material conveying device having a resist section that sends the sheet material to a next process section such as an image forming section, an information reading section, and a processing section at a predetermined timing.

Further, the sheet feeding section and the leading edge of the recording sheet fed from the sheet feeding section are temporarily stopped to form a loop in the recording sheet, thereby correcting skew of the recording sheet and recording the recording sheet. The present invention relates to an image recording apparatus having a registration unit that sends paper to an image forming unit at a predetermined timing.

[0003]

2. Description of the Related Art In FIG. 8, a paper feed unit and a leading edge of a recording paper as a sheet material fed from the paper feed unit are temporarily stopped to form a loop on the recording paper. The schematic configuration of an example of an image recording apparatus having a registration unit that corrects the skew feeding and sends the recording paper to the image forming unit at a predetermined timing is shown.

The image recording apparatus of this example is roughly divided into an image input section 90R and an image output section 90P.

The image input section 90R is, for example, an image information photoelectric reading mechanism, and inputs image information for recording,
After performing various processes, the image signal is sent to the image output unit 90R. The image forming unit 91 of the image output unit 90R converts the original image.
It is also possible to use an optical device for projecting, imaging and exposing the image carrier.

The image output section 90P is the transfer drum 9 in this example.
3 is a transfer type image recording mechanism using a photoconductor, a dielectric body by an appropriate image forming process such as an electrophotographic process, an electrostatic recording process, and a magnetic recording process according to the input image information to the image output unit 9R. Image forming unit 9 that forms a transferable recorded image such as a toner image on an image bearing member such as a magnetic body
1 and first to third paper feeding units 92A as paper feeding units
92B and 92C and the pre-registration transport unit 97 that transports the recording paper P as a sheet material fed from any one of the paper feeding units to the registration roller pair 96 as a registration unit.
The transfer drum 93 that holds the recording paper sent from the registration roller pair 96 and conveys it to the transfer portion T of the image forming portion 91, and the recording paper that has undergone the image transfer at the transfer portion T of the image forming portion 91. It is composed of a fixing unit 94 for fixing processing, a control unit 95 for controlling all operations of the apparatus, and the like.

First and second paper feed unit 92A.9
2B is an automatic single-sheet separating / feeding mechanism which is built in the image output unit 90P in two stages, upper and lower, and the recording sheets P stacked and stored in the sheet feeding cassette are connected to the sheet feeding rollers based on a sheet feeding start signal. By cooperation with the separating member, one sheet is separated and fed in order from the highest one. The third sheet feeding unit 92C is a manual sheet feeding device, and when the recording sheet P is inserted into the apparatus from the manual sheet feeding table, the recording sheet is drawn into the apparatus by the sheet feeding roller and is fed.

When the operation of the apparatus is started,
The recording paper P is fed from any one of the third paper feed units 92A, 92B, and 93C, and is conveyed to the registration roller pair 96 by the pre-registration conveyance section 97.

At the time when the leading edge of the conveyed recording paper P reaches the nip portion of the registration roller pair 96, the registration roller pair 96 is held in the rotation stopped state, and the leading edge of the conveyed recording paper P is in the rotation stopped state. The registration roller pair 96 abuts against the nip portion of the pair of registration rollers 96 and is received. After that, the pre-registration transport unit 97 continues transporting the recording paper for a predetermined time and then stops.

As a result, a predetermined bending loop (pre-registration loop) is formed on the leading end side of the recording paper, and the bending reaction force causes the leading end side of the recording paper to be parallel to the nip line of the registration roller pair 96. Skew correction is performed.

On the other hand, in the image forming section 91, image formation corresponding to the desired image information on the image carrier is executed,
The rotation of the registration roller pair 96 is started in synchronization with the image recording start signal, the pre-registration conveyance unit 97 is again in the recording paper conveyance state, and the recording paper is sent from the registration roller pair 96 to the rotary transfer drum 93 to perform recording. The paper is held on the outer surface of the rotary transfer drum 93 and conveyed to the transfer unit T, so that the images formed and carried by the image carrier of the image forming unit 91 are sequentially transferred.

As a method for holding the recording paper on the outer surface of the transfer drum 93, several methods such as electrostatic adsorption on a conveying medium made of a thin dielectric film or air suction can be considered.

The recording paper is fed out by the pair of registration rollers 96 when the leading edge of the image formed and carried on the image carrier of the image forming section 91 reaches the transfer section T, and the leading edge of the recording paper just reaches the transfer section T. Then, the sending-out timing is controlled so that they coincide with each other (registration).

The recording paper having undergone the image transfer at the transfer portion T is separated from the outer surface of the rotary transfer drum 93 and is fixed in the fixing unit 95.
Then, the transferred image is fixed by heat and / or pressure, and is discharged to a discharge tray outside the machine through a discharge unit.

By the way, the transfer drum 9 as in the above example.
In the case of an apparatus of a type in which the recording paper P is wound around the recording paper 3 and the image is transferred onto the surface of the recording paper P3, if the recording paper held on the transfer drum 93 has a slight floating or the like, the transferred image such as a change in image density or a transfer omission occurs May have an adverse effect. Therefore, in order to avoid this problem, for example, a curling mechanism for curling the recording paper is provided in the pre-registration transport unit 97, and the recording paper is arranged so as to easily follow the transfer drum 93. There is.

[0016]

However, the transfer drum 9
Even when the curl attachment mechanism is provided in the pre-registration transport section 97 in order to align and hold the recording paper P on the outer surface of the sheet 3, there are the following problems.

That is, the amount of curl attached to the recording paper by the pre-registration transport unit 97 is easy to follow the outer surface of the transfer drum 93.
It changes due to the cash register loop. For example, in the apparatus of this example, the pre-registration loop is formed in the direction opposite to the direction of the curvature of the transfer drum 93. The edges tend to float from the drum, which may cause image dropouts. Alternatively, in some cases, a phenomenon in which the recording paper peels off from the transfer drum 93 may be considered.

On the other hand, in the case of an apparatus for forming a pre-registration loop in the same direction as the curvature of the transfer drum 93, which is the opposite of the apparatus of this embodiment, the curl amount is increased more than necessary, so the transfer drum 93
There is a possibility that the middle part of the recording paper held in the above position will float, and at this time, transfer defects at that location and transfer image shift due to movement of the floating part are considered.

In order to prevent this, a method may be considered in which the curling amount on the recording paper is increased or decreased more than necessary in anticipation of a change due to the pre-registration loop, but this is uniformly determined for all recording papers having different thicknesses or rigidity. It's almost impossible. For example, the more rigid the paper, the greater the amount of change in curl due to the pre-registration loop, and conversely, the thinner the paper, the less the amount of change. In addition, curling more than necessary requires a great amount of performance in the curling mechanism, which is not efficient.

More strictly speaking, since the pre-registration loop is usually formed after the center of the recording paper, it does not affect the entire surface of the paper uniformly, and the leading end is hardly affected. .

From the above, it is desirable to prevent the pre-registration loop from affecting the curl as much as possible.

In consideration of this point, one method is to widen the pre-registration loop space as much as possible to reduce the curvature even with the same pre-registration loop amount, but it is difficult to secure the space, and the size of the apparatus is increased. Leads to. Further, there is a limit to simply reducing the pre-registration loop amount for the original purpose of removing resist from the recording paper. In particular, the increase in the number of paper feed units, which has become common in recent years, causes the paper path up to the registration roller pair 96 to become longer and more complicated. It is necessary to form a certain amount of pre-registration loop to absorb it.

Therefore, according to the present invention, the skew of the sheet material is corrected by temporarily stopping the leading end of the sheet material fed from the paper feeding section as described above to form a loop in the sheet material, For a sheet material conveying device having a resist portion for feeding a material to a next process portion at a predetermined timing, or an image recording device using the sheet material conveying device, avoiding an increase in size of the device and affecting a curl by a loop before registration. In order to prevent the stability of the feeding of the sheet material from being deteriorated, in the image recording apparatus, any paper type (sheet material) is located on the downstream side in the recording paper conveyance direction from the resist portion and its surface. It is an object of the present invention to maintain the recording paper holding performance of the transfer / conveyance unit for holding the recording paper and conveying it to the image transfer unit, and consequently to maintain good image quality.

[0024]

The present invention is a sheet material conveying apparatus and an image recording apparatus characterized by the following configurations.

(1) The skew of the sheet material is corrected by temporarily stopping the leading end of the sheet material fed from the paper feeding section to form a loop in the sheet material, and the sheet material is corrected at a predetermined timing. In a sheet material conveying apparatus having a registration section for sending to the next process section, the sheet material conveyance is controlled so that the amount of sheet material loops formed in the registration section is selectively changed according to the information of sheet feeding. apparatus.

(2) The sheet material conveying apparatus according to (1), wherein the information on the sheet feeding is the thickness or the rigidity of the sheet material to be fed.

(3) The above-mentioned paper feed information is paper feed unit selection information in a device having a plurality of paper feed units and feeding and conveying a sheet material from the selected paper feed unit (1) )
The sheet material conveying device described in.

(4) The sheet feeding section and the leading edge of the recording sheet fed from the sheet feeding section are temporarily stopped to form a loop on the recording sheet, thereby correcting skew of the recording sheet, In an image recording apparatus having a registration unit that sends recording paper to an image forming unit at a predetermined timing, the amount of recording paper loop formed by the registration unit is selectively changed and controlled to be selectively changed. Image recording device.

(5) The image recording apparatus according to (4), wherein the information on the paper feed is the thickness or rigidity of the recording paper to be fed.

(6) The paper feed information is paper feed unit selection information in an apparatus having a plurality of paper feed units and feeding and conveying recording paper from the selected paper feed unit (4) ) The image recording apparatus described in.

[0031]

In other words, by controlling so that the amount of sheet material loops formed in the resist portion is selectively changed according to the information of the paper feed, it is possible to prevent the apparatus from becoming large and to curl the pre-registration loop. It is possible to prevent the stability of feeding of the sheet material from being deteriorated without affecting, and in the image recording apparatus, regardless of the type of recording paper, a good image without image misalignment or image loss is always provided. can get.

[0032]

【Example】

<Embodiment 1> (FIGS. 1 to 6) FIG. 1 is a block diagram of an image recording apparatus as an embodiment of the present invention. The image recording apparatus of this example is a color image recording apparatus using a transfer type electrophotographic process, and has a digital color image reader unit 100 at the top and the printer unit 20 at the bottom.
Has 0.

(1) Reader unit 100 In the reader unit 100, the original 30 is placed on the original table glass 3
1 and the exposure lamp 32 performs exposure scanning. Then, the reflected light image from the original 30 is condensed by the lens 33 on the full-color sensor 34 to obtain a color-separated image signal. This signal is sent to the printer section 200 after undergoing various processing in a video processing unit (not shown) through an amplifier circuit (not shown).

(2) The image forming mechanism 1 of the printer unit 200 is a photosensitive drum as an image bearing member, and has a predetermined peripheral speed (process speed) in the clockwise direction indicated by the arrow around the central axis.
Is driven to rotate.

A pre-exposure lamp 11, a primary charger 2, an exposure optical system 3 such as a laser, a potential sensor 12, a developing device 4, a light quantity detection on the drum, facing the outer peripheral surface of the photosensitive drum 1 in the direction of its rotation. The means 13, the transfer drum 5, and the cleaning device 6 are arranged in this order.

The pre-exposure lamp 11 and the primary charger 2 apply a uniform amount of charge to the surface of the rotary photosensitive drum 1. Next, the optical system 3 exposes the light beam E, such as a laser beam, which is modulated according to the recorded image signal, onto the photosensitive drum 1 through the polygon mirror 3A, the lens 3B, the mirror 3C, etc. Form a latent image.

The electrostatic latent image is developed by the developing device 4. The developing device 4 includes four devices, that is, a yellow developing device 4Y, a cyan developing device 4C, a magenta developing device 4M, and a black developing device 4BK, which contain yellow, cyan, magenta, and black developers (toners), respectively.
By the operation of the eccentric cams 24Y, 24C, 24M, and 24BK, the eccentric cams are selectively moved closer to the photosensitive drum 1 to perform a developing action.

Then, the toner images formed and carried on the photosensitive drum 1 are sequentially transferred to the surface of the recording paper supplied and held on the transfer drum 5 at the transfer portion T, as will be described later.

The recording paper on which the toner image has been transferred is separated from the transfer drum 5 and introduced into the fixing unit 9 to undergo an image fixing process, and is discharged to a paper discharge tray 10 outside the apparatus or the transfer path is switched. It is introduced by a guide 19 into a conveyance vertical path 20 of a double-sided recording paper path described later.

The fixing unit 9 includes a fixing roller 9A having a heat source such as a halogen heater therein and the roller 9A.
Pressure roller 9B (which may also be provided with a heat source), and the above roller pair 9A and 9B
It comprises a conveying belt 9C for guiding the recording paper to the nip portion, an entrance guide 9D, and a discharge roller 9E for further guiding the recording paper discharged from the pair of rollers 9A and 9B to the outside of the apparatus.

The surface of the photosensitive drum 1 after the transfer of the toner image to the recording paper is cleaned by a cleaning device 6 to remove residual adhered substances such as transfer residual toner, and is repeatedly used for image formation.

(3) Paper Feeding Unit 40 The apparatus of this embodiment has a paper feeding unit below the image forming mechanism, and has four paper feeding units 41A.
It is equipped with 41B, 41C and 41D. First to third
The paper feeding units 41A, 41B, and 41C are automatic one-sheet separating / feeding mechanisms arranged in the upper, middle, and lower stages, respectively. Fourth
The paper feed unit 41D is a manual paper feed mechanism. An intermediate tray 22, a guide portion 23, and a double-sided recording paper path, which will be described later, are provided between the first and second paper feeding portions 41A and 41B in the upper and middle tiers.
An inversion path 21 is provided.

First to third paper feeding units 41A, 41B, 41
In each case C, the stacked recording paper sheets P in the paper feed cassette are separated one by one in order from the highest one by the cooperation of the pickup roller 42 and the separating member such as the separating claw.
The sheet is fed by the 3A / 43B, and the pickup roller 42 of the designated sheet feeding unit is driven to selectively perform the sheet feeding from the designated sheet feeding unit.

The manual paper feeding mechanism, which is the fourth paper feeding section 41D, puts the recording paper on the manual paper feeding base and inserts it into the apparatus to separate the recording paper from the paper feeding roller 42M (not shown). The pad is drawn into the apparatus and fed.

(4) Transfer / Conveyance Unit 50 (FIG. 2) The recording paper P fed from any one of the first to fourth paper feeding units 41A to 41D or the intermediate tray 22 is introduced into the transfer / conveyance unit 50. To be done.

The transfer / transport unit 50 is roughly divided into a transport unit 50A and the transfer drum 5. The transport unit 50A is shown in FIG.
It will be described based on a partially enlarged view of FIG. Guides 48A ・ 4 for guiding the recording paper by inheriting it from the paper feeding unit 40
8B, 48C, 48D, 48E, and transport roller 4
6A, 46B, 46C, 47A, 47B, and a pair of registration rollers 44 for sending the recording paper to the transfer drum 5 described later in accordance with the image forming timing of the image forming unit,
And suction guides 48F and 48G that guide the paper at that time.

Here, the transport rollers 46A, 46B, 4
6C has a curling function for recording paper.

The guide 48D is swingably supported in the direction of the arrow as shown by the solid line and the broken line in the figure. This is to secure a loop space before registration of the recording paper P that occurs when the leading end of the recording paper is temporarily stopped by the registration roller pair 44.

(5) Transfer Drum 5 (FIG. 3) As shown in FIG. 3, the transfer drum 5 has a recording paper holding sheet film 55S cylindrically wound around a frame 55F in which annular members 55A at both ends are connected by a connecting member 55B. The transfer drum 5 is formed. As the material of the film 55S,
For example PET (polyethylene terephthalate) or PVd
F (polyvinylidene fluoride) or the like is used.

At the position where the recording paper sent from the registration roller pair 44 enters the transfer drum 5, the suction roller 5G is supported so as to be separable from and in contact with the transfer drum 5, and the opposite side of the suction roller 59 with the film 55S interposed therebetween. On roller 5
A backup member and an electrostatic charger 5C for adsorption are arranged to counteract the pressing force of 9.

In the image transfer area (transfer section) T where the photosensitive drum 1 and the transfer drum 5 are opposed to each other, the film 55S is also provided.
A transfer charger 5B (FIG. 1) is disposed on the back side of the.
Further, a separating member for separating the recording paper, specifically, a discharging charger 5H, a separating claw 8A, a film pushing roller 8B, and the like are provided downstream thereof, and subsequently, a film discharging charger 5D, 5E is provided. The films 55S are arranged so as to sandwich them.

Further on the downstream side, the brush roller 14 for cleaning the toner, paper dust and the like adhering to the recording paper holding surface of the film 55S, the corona discharger or the brush type static eliminator 15, and the fixing unit 9 are used. The so-called oil may adhere to the film surface through the recording paper during double-sided recording (described later), and an oil removing roller 16 and a backup brush 17 for cleaning the oil are provided.

Here, the transfer drum portion 5 is constructed so as to be separable from and in contact with the photosensitive drum 1, and is separated from each other except during the normal operation. This is to prevent the transfer drum 5 and the photosensitive drum 1 from coming into contact with each other for a long time, and to prevent the recording paper or the like from coming into contact with the photosensitive drum 1 and damaging the surface during jam processing.

Further, in this apparatus, the transfer / conveyance unit 5
0 is configured to be pulled out from the main body to the front side by sliders 62A and 62B. This is to make jam processing or maintenance more reliable and easy.

(6) Double-sided recording paper path This apparatus has a mechanism for automatically recording images on both sides of the recording paper. That is, there is a transport path switching guide 19 immediately downstream of the fixing unit 9, whereby either one of a paper path for ejecting the recording paper on which one side recording has been completed from the fixing unit 9 to the outside of the machine and a double sided recording paper path. It will automatically select and guide you.

The double-sided recording paper path comprises a conveying vertical path 20, a reversing path 21A, a reversing roller 21B, an intermediate tray 22, and the like, and the recording paper on which one-side recording has been once guided to the reversing path 21A is reversed by the reversing roller 21B. When the paper is sent in, the rear end of the paper is taken as the leading end and the paper is withdrawn in the direction opposite to the direction in which the paper was sent in and is stored in the intermediate tray 22. Then, the paper is fed from the intermediate tray 22 again, and an image is formed on the other surface of the recording paper by the image forming process described above. The upper guide portion 23 of the intermediate tray 22 is configured to selectively move a plurality of guides up and down according to the size of the recording paper to be stored. As a result, sheets of any size can be stored and stacked at the top of the intermediate tray.

(7) Control Unit Although not shown in the drawing, the control unit is composed of a control board, a motor drive board, and the like for relatedly controlling the operation of the mechanism in each unit.

(8) Color (multi-color) image recording When an image forming operation start signal is issued, the cam 71 first makes a half rotation, and the transfer drum 5 swings close to the photosensitive drum 1 and moves to the operating position accordingly. Then, it rotates in synchronization with the photosensitive drum 1.

At the same time, the recording paper is fed from the paper feeding unit 40. Here, for the sake of convenience, the second paper feed unit in the middle stage is
It is assumed that the sheet feeding from the sheet feeding unit 41B is designated. That is, the pickup roller 42 of the second paper feed section 41B feeds the recording papers P one by one from the paper feed cassette. Then, the paper is guided between the paper feed guides by the paper feed rollers 43A and 43B and the transport rollers 45B and 45C and is transported to the transport unit 50A.

In the carrying section 50A, the paper is first curled by a predetermined amount in the direction in which it is wound around the transfer drum 5 when passing through the curling rollers 46A, 46B and 46C (FIG. 2).

After that, it is conveyed to the registration roller pair 44 by the action of the conveying rollers 47A and B and the paper guide. At that time, the registration roller pair 44 has stopped rotating, and the leading edge of the paper abuts against the nip portion of the registration roller pair 44. Then, after a certain period of time, the driving of the transport rollers 47A and 47B is stopped.

Then, while a loop R (FIG. 2) is generated in the paper during that time, the space required for it is formed by the swing of the guide 48D (it is automatically spread by the waist of the paper). The skew R of the recording sheet is corrected by the pre-registration loop R.

After that, the registration roller pair 44 and the transport rollers 47A and 47B start to rotate after a predetermined time with reference to the timing when the image forming unit starts forming an image. The timing of this rotation is set so that the paper P and the toner image on the photosensitive drum 1 exactly match in the image transfer area T.

When the recording paper rushes into and contacts the transfer drum 5, the recording paper is held by the holding sheet film 55S by the action of the corona discharge from the suction charging device 5C and the suction roller 5G.
It is electrostatically adsorbed on top. The suction roller 5G is normally separated from the transfer drum 5 to reduce the load, and is brought into pressure contact with the transfer drum 5 only when the paper enters.

The transfer drum 5 rotates in synchronism with the photosensitive drum 1, and the recording paper is conveyed to the image transfer area T while being held thereon. Therefore, after the toner image formed on the photosensitive drum 1 by the above-described process is transferred onto the surface thereof by the transfer charger 5B, the recording paper is conveyed to the separation section.

Since one color image is transferred at one time here, in the case of a single color image, the recording paper is separated from the transfer drum 5 by the operation described later, but a color (multicolor) image is formed. In this case, the recording paper is conveyed to the transfer area T again after being rotated once while being held on the transfer drum 5 without performing the separating operation. Then, the next toner image is further transferred onto the previous image, and this process is repeated a necessary number of times. By this multi-transfer process, a desired color (multicolor) image is compositely formed on the recording paper. The brush roller 14 and the like are supported so as to be separable from and in contact with the surface of the transfer drum, and are separated at least in the multiple transfer process.

When this is finished, the attraction force between the recording paper and the holding sheet film 55S of the transfer drum 5 is reduced by the action of the discharging charger 5H in the separating portion, and the recording paper is removed by the subsequent operation of the separating claw or the like. Separated from the transfer drum 5.

The recording paper separated from the transfer drum 5 is conveyed to the fixing unit 9 by the conveying belt 9C and accurately guided on the entrance guide 9D to the fixing roller nip portion. Then, the heat of the fixing roller 9A fixes the toner image on the surface of the paper. After that, the recording paper is conveyed by the paper ejection roller 9E and is ejected to the outside of the machine. Finally, the transfer drum 5 separates from the photosensitive drum 1 (withdrawal position), and the apparatus stops.

(9) Double-sided image recording Single-sided recorded recording paper exiting the fixing unit 9 is guided to the conveyance vertical path 20 by switching the switching guide 19, and thereafter, the recording paper is transferred by the reversing roller 21B via the reversing path 21A. It is inverted and stored in the intermediate tray 22. Then, after the required number of sheets are stacked, the recording papers P'having one side recorded are picked up one by one from the intermediate tray 22 by the pickup roller 25 and conveyed to the conveyance section 50A by the paper feed rollers 26A and 26B.

An image is recorded on the other side of the recording paper by going through the same process as described above. Finally, the switching guide 19 is not operated, and the double-sided recording paper is ejected out of the machine.

(10) Change of pre-registration loop amount In the present apparatus, the loop amount of the normal pre-registration loop R is set to 8 mm. This value represents the amount by which the paper is further fed after the tip of the paper hits the nip portion of the registration roller pair 44. This is because the timing at which the paper arrives at the registration unit 44 is most likely to vary.
Required to ensure stability of paper feed from 1C.

However, with this value kept, thick paper (for example, 16
When the paper is passed through (about 0 g paper), the curled recording paper loses most of the curl especially from the center to the rear end, and as a result, the rear end of the paper floats on the transfer drum 5 and the transfer occurs. Image dropouts are likely to occur.

In this apparatus, due to the limitation of the apparatus, the above-mentioned thick paper is limited to the manual feeding. Since the paper path for manual paper feeding is relatively short, there is little variation in paper feeding timing, and it is possible to set the pre-registration loop amount to 3 mm or less. Further, when using thick paper, the operation sequence needs to be changed to normal due to the fixing performance. Therefore, the user sets thick paper using an operation panel (not shown). Therefore, in this apparatus, the paper feeding sequence is changed so that the pre-registration loop amount becomes 3 mm when thick paper is set.

A specific description will be given with reference to FIG. In the figure, A is the time immediately before the leading edge of the paper reaches the transport rollers 47A and 47B, and the rollers 47A and 47B start rotating (ON). B is the point in time when the recording paper P sent out by the transport rollers 47A and 47B reaches the registration roller pair 44, from which it continues to rotate for time t ₁ (paper is 8 m
After being conveyed by m), the conveyance rollers 47A and 47B stop rotating in the state as shown in FIG. 5 (time C, OFF). Then, from the image transfer start timing E, the registration roller pair 44 and the transport rollers 47A and 47B start to rotate earlier by t ₂ (at the time D), and the leading edge of the recording paper in the transfer area T exactly matches the leading edge of the image on the photosensitive drum 1 side. The recording paper is conveyed and reaches as described above.

The above is the case of the normal paper, but when the thick paper mode is set, the stop time C of the transport rollers 47A and 47B is changed to C '(t ₁ is t ₁ ′, which corresponds to a loop of 3 mm). ) As a result, the state shown in FIG. 6 is obtained.
There is no change in other timing.

By the method described above, curl is hardly lost due to the pre-registration loop even on thick paper, and as a result, it is possible to maintain good image quality without image loss. It was also confirmed that the skew feeding correction capability of 3 mm is sufficient. Since thick paper is strong, even a small amount of loop can be corrected.

Here, in addition to changing the pre-registration loop according to the information on the thick paper, a method of switching according to the information on the manual paper feeding can be considered. That is, in the case of manual feeding, the uniform loop amount is set to, for example, 3 mm regardless of the paper type, and not limited to manual feeding, for example, 3 mm for paper feeding from the upper paper feeding unit 41A and manual feeding, and middle paper feeding. 6 mm from the paper feed section 41B, and 8 from the lower paper feed section 41C.
It is also possible to change the loop amount at each stage such as mm.

<Embodiment 2> (FIG. 7) In Embodiment 1, the feeding of thick paper is limited to manual feeding (the variation in timing is small). However, even thick paper has a long paper path (large variation in timing). Assuming that it is possible to feed paper from, the following configuration was implemented.

In the first embodiment, the variation in the paper arrival timing at the registration portion 44 is absorbed by the pre-registration loop amount, but in the present embodiment, the loop amount is kept constant and the paper stop time thereafter is changed. It is something that we try to deal with.

More specifically, in the first embodiment, the stop timing of the transport rollers 47A and 47B (time point C and C ').
Is calculated, that is, the recording paper is ideally sent. That is, the loop amount varies depending on the actual paper feeding. On the other hand, in this device, the pre-checkout sensor 49
C (FIG. 2) detects the leading edge of the conveyed sheet of paper and stops the conveying rollers 47A and 47B a predetermined time after that. Then, after that, it is re-driven in accordance with the image timing. As a result, the front end of the paper that actually passes through the sensor 49C can be used as a reference, and the loop amount hardly varies.

A detailed description will be added with reference to FIG. In the figure, the difference from the first embodiment is that the front edge of the paper is actually the pre-registration sensor 49C.
Is represented by F, and the transport rollers 47A and 47B are stopped after a certain time t ₃ + t ₁ ″ from that point (time C ″).

Here, at t _3, the paper is the pre-registration sensor 49C.
It is the time from when to reach the registration roller pair 44. Since the distance is short and the like, variations in time during this time can be ignored. Then, the time during which the loop is actually formed matches t ₁ ″, and the loop does not vary. Instead, the paper stop time t ₄ varies, so this time has a margin more than the variation. It is necessary.

At this time, the following points should be noted in the continuous paper feeding. In the first embodiment, when a certain recording paper is stopped by forming a loop in the registration section 44, the succeeding recording paper can be stopped at the same time (each roller is always driven and stopped at an ideal timing). Because). On the other hand, in the present embodiment as well, if the recording sheets that form a loop are stopped at the same time as the recording sheets that form a loop, the timing deviation of the recording sheets that form a loop will directly affect the conveyance timing of the succeeding recording sheets. Will give. To prevent this, stop the recording paper that created the loop.
It is necessary to control the transport timing and the stop / transport of the subsequent recording paper independently.

For example, when continuously feeding A4 size paper, after a certain recording paper forms a predetermined pre-registration loop, the transport rollers 47A and 47B and the curling roller 4 are used.
Stop 6A, 46B and 46C. On the other hand, the roller upstream from that conveys the succeeding recording paper regardless of that, and in the case of A3 size paper, the roller up to 45C is stopped, and the upstream roller is independently driven.

In this way, the roller is turned ON for each size.
By changing the OFF timing, the paper feeding unit 41A to 41A
It is possible to make the pre-registration loop amount constant regardless of the rank of 41C. Then, for example, even when the sheet is fed from the lower sheet feeding section 41C, the loop amount can be set to 3 mm. Therefore, even if it becomes possible to feed thick paper from the cassette in the future, it is possible to cope with it.

Up to this point, it has been described that the user determines whether or not thick paper is used, but in that case, it is not possible to cope with erroneous setting or forgetting the setting. Therefore, the device may have a built-in detection device for automatically detecting the paper type.
For example, a sensor that optically detects the thickness of the recording paper may be provided immediately after the paper feeding unit, and the loop amount may be changed according to the signal.

Although the thick paper mode has been described so far, the thin paper mode can also be set. In the case of thin paper, since the stiffness is weak, even a slightly large loop has almost no effect on the recording paper. Therefore, conversely, it is possible to set a large loop to improve the skew feeding correction capability. However, it is better to use less than regular paper. This is because if it is too large, the force will be directed in the direction of forming the loop, and the force of pushing the leading edge of the paper into the registration roller will be reduced. At this time, the mode may be set by the user or may be automatically detected.

As described above, in the present embodiment, an optimum loop amount can be set for each paper type from any paper feed stage, so that the device is highly versatile. In the present embodiment, the loop amount of thick paper [around 160 g / m ² ] is 3 mm, the loop amount of normal paper [around 100 g / m ² ] is 7 mm, and the loop amount of thin paper [around 64 g / m ² ] is 5 mm. Is set to.

Further, although the transfer means to the image forming portion has been described as the transfer drum, the present invention is not limited to this, and may be, for example, an endless belt wound between a plurality of rollers.

In addition, the image forming means is not limited to the electrophotography, but may be any device such as an ink jet system or a thermal transfer system as long as it requires a recording paper transport mechanism.

The skew feed correction / registration means 44, for example, as in the skew prevention method of Japanese Patent Laid-Open No. 57-189951, bites the leading end of the recording paper between the drive rollers and reverses the drive rollers. The skewed sheet may be corrected by pushing back the leading end of the recording sheet that has been taken in to form a pre-registration loop, and then the drive roller may be normally rotated at a predetermined timing to be conveyed to the next step. Alternatively, the opening / closing shutter member may receive the leading edge of the recording paper to form a pre-registration loop to perform skew correction, and then open the shutter member at a predetermined timing to convey the recording paper to the next step.

[0092]

As described above, according to the present invention, the skew of the sheet material is corrected by temporarily stopping the leading end of the sheet material fed from the sheet feeding section and forming a loop in the sheet material. , A sheet material conveying device having a resist portion for feeding the sheet material to a next stroke portion at a predetermined timing, or an image recording apparatus using the sheet material conveying device, avoiding an increase in the size of the device and providing a pre-registration loop. It is possible to prevent the stability of sheet material feeding from deteriorating without affecting the curl, and in the image recording device, regardless of the type of recording paper, a good image with no image misalignment or missing Can be stably obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an image recording apparatus according to a first embodiment.

FIG. 2 is a partially enlarged view of a transfer / conveyance unit.

FIG. 3 is a perspective view of a transfer drum

FIG. 4 is a timing chart of recording paper conveyance.

FIG. 5 is a diagram (part 1) showing a state in which a pre-registration loop of recording paper is formed.

FIG. 6 is a diagram showing how a pre-registration loop of recording paper is formed (Part 2)

FIG. 7 is a timing chart of recording paper conveyance of the apparatus according to the second embodiment.

FIG. 8 is a schematic diagram of the configuration of a conventional device.

[Explanation of symbols]

 1 Photosensitive Drum 5 Transfer Drum 6 Cleaning Device 9 Fixing Unit 40 Feeding Unit Section 44 Registration Roller Pair 45C / 47A / 47B Conveying Roller 46A / 46B / 46C Curling Roller 48A-48G Guide 49C Paper Detection Sensor 50 Transfer Conveying Unit 50A Registration Front transport section P / P 'Recording paper (sheet material)

Claims (6)

[Claims] 1. A skew of the sheet material is corrected by temporarily stopping the front end of the sheet material fed from the sheet feeding section to form a loop in the sheet material, and the sheet material is next conveyed at a predetermined timing. In a sheet material conveying apparatus having a resist section for sending to a stroke section, the sheet material conveying apparatus is characterized in that the sheet material loop amount formed by the resist section is controlled so as to be selectively changed according to information of sheet feeding. . 2. The sheet material conveying apparatus according to claim 1, wherein the information on the sheet feeding is the thickness or the rigidity of the sheet material to be fed. 3. The paper feed information is paper feed unit selection information in an apparatus having a plurality of paper feed units and feeding and transporting a sheet material from a selected paper feed unit. The sheet material conveying device described in. 4. The sheet feeding unit and the leading end of the recording sheet fed from the sheet feeding unit are temporarily stopped to form a loop on the recording sheet, thereby correcting skew of the recording sheet and recording the recording sheet. In an image recording apparatus having a registration unit that feeds paper to an image forming unit at a predetermined timing, the amount of recording paper loops formed by the registration unit is controlled so as to be selectively changed in accordance with information on paper feeding. Image recording device. 5. The image recording apparatus according to claim 4, wherein the information on the paper feed is the thickness or rigidity of the recording paper to be fed. 6. The sheet feeding information is sheet feeding unit selection information in an apparatus having a plurality of sheet feeding units and feeding and conveying a recording sheet from the selected sheet feeding unit. The image recording device described in 1.