JPH04235848A - Paper coneying device - Google Patents

Abstract

PURPOSE:To make distance between a preceding paper sheet and a following paper sheet constant on a paper conveying path before a register roller by compensating unevenness without reducing paper transfer capability even when unevenness occurs at the paper feed position of the preceding paper sheet and the following paper sheet and the position of the paper sheet cannot be detected in a continuous paper supply mode. CONSTITUTION:Distance between a preceding paper sheet and a following paper sheet is made constant by providing a paper supply sensor S3 on the paper outlet side of a retard roller 4 and a separation roller 5 as a paper supply port on a paper conveying path, detecting passage of the preceding paper sheet by the paper supply sensor S3 by a timing control means owing to a software when paper is supplied continuously, and compensating unevenness in the distance between the paper sheets on the paper outlet side of the rollers 4, 5 for paper which is supplied continuously on the paper transfer path before a register roller 9.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to, for example, an image reading device (
Paper fed from the paper feeding unit in recording devices (printers) as information output devices in scanners, personal computers, word processors, image forming devices such as copying machines and facsimiles, and various other paper-using devices. The present invention relates to a paper transport device that transports paper through a paper transport path including registration rollers to paper processing means that performs processing such as image formation on the paper.

[0002] In the above, paper or paper is, for example, recording paper, printing paper, photosensitive paper, electrostatic recording paper, printing paper, etc.
In addition to sheet materials (sheets of paper) such as OHP sheets, envelopes, and sheet manuscripts, the material is not limited to so-called paper, and includes those that unwind, cut, and feed a roll of long paper. The paper feeding unit includes a paper loading table, a tray, a deck, a removable paper feeding cassette, and a manual paper feeding unit that automatically separates and feeds sheets stacked and housed in a removable paper cassette.

0003

2. Description of the Related Art FIG. 14 is a schematic diagram of a laser beam printer or copying machine using a transfer type photographic process as an example of an image forming apparatus.

Reference numeral 50 denotes an electrophotographic photosensitive drum as an image carrier, which is rotated clockwise as indicated by an arrow at a predetermined circumferential speed (process speed).
During the rotation process, the peripheral surface is uniformly charged with a predetermined polarity and potential (primary charging) by the charging means 51 → image information scanning exposure L by the exposing means 52 → developed by the developing means 53, thereby forming the desired image. A toner image corresponding to the information is formed. The exposure means 52 is a laser scanner, which emits a laser beam modulated in accordance with time-series electrical digital pixel signals as image data transferred from an image reading unit (not shown) or a host device such as the same, a computer, or a word processor. The photosensitive drum 50 is output and the surface of the rotating photosensitive drum 50 is subjected to main scanning exposure. The exposure means may be an image-forming exposure means such as a moving optical system-fixed document table type or a fixed optical system-moving document table type.

The toner image formed on the surface of the rotating photosensitive drum 50 is sequentially transferred onto the surface of a copy sheet fed to a transfer section between the photosensitive drum 50 and the transfer means 54 at a predetermined timing. The paper that has received the toner image transfer in the transfer section is separated from the surface of the photosensitive drum 50 by a separating means 55, is transported to an image fixing means 57 by a conveyor belt 56, undergoes image fixing processing, and is transferred to a paper ejection tray by a paper ejection roller 58. It is discharged at 59. On the other hand, after the toner image has been transferred, the surface of the rotary photosensitive drum 50 is cleaned by cleaning means 60 to remove adhered contaminants such as residual toner, and is used repeatedly for image formation.

[0006] Reference numerals 61 and 62 are upper and lower two-stage paper feed cassettes that respectively store and accommodate copy paper (hereinafter referred to as paper), and upper and lower two-stage cassette mounting ports 63 and 64 are respectively disposed on the side of the printer. It is set in such a way that it can be attached and detached by inserting the tip end into the holder. Then, the upper or lower paper feed rollers 65, 66 are selectively driven by the paper feed signal, and the paper is separated from the upper or lower paper feed cassettes 61, 62 by a claw (not shown).
The sheets are separated and fed one by one by the cooperation of the printer and are conveyed to the transfer section 54 via the registration rollers 67.

The registration roller 67 is operated in synchronization with the operation of the exposure means 52 (transfer of image data of the document reading section, movement of the optical system or document table, etc.), that is, the rotation drum 50.
The paper is controlled to be conveyed to the transfer section 54 at the timing when the leading edge of the image portion formed on the surface reaches the transfer section 54 and the leading edge of the paper also reaches the transfer section 54. The one-dot chain line indicates a paper transport path (sheet path) from the upper or lower paper feed cassettes 61 and 62 to the paper discharge tray 59.

[0008] With this device configuration, multiple sheets of paper are continuously fed and conveyed to form an image and then are discharged. By keeping the inter-paper distance constant to the minimum value that allows image formation, the number of sheets conveyed per hour increases.

Generally, if the interval at which the paper is conveyed by the registration roller 67 is constant, the distance between the sheets after the registration roller 67 is kept constant and a plurality of sheets of paper are conveyed.
Before the registration rollers 67 are driven to rotate to convey the paper, it is sufficient that the leading end of the paper is received at the nip portion of the registration rollers 67 in a state where the rotational drive is stopped and a loop is formed to prevent skewing.

Further, in this configuration, the paper transport path from the leading edge of the paper in the paper feed cassette 61 or 62 to the registration roller 67 is short, and the leading edge of the paper reaches the registration roller 67 whose rotational drive is stopped and is connected to the registration roller 67. paper roller 65
or 66, the trailing edge of the paper remains in the cassette with a loop of paper formed between the two.

By the way, when a plurality of sheets are continuously fed, there may be variations in the sheet feeding position (the position of the leading edge of the paper in the cassette) each time the sheets are fed. In this case, since it is known that the preceding paper is at the registration roller 67 before feeding the next line of paper, taking this variation into account, the Feed the next paper after the time has elapsed.

In other words, the leading paper is the registration roller 67.
The rear end of the paper passes through the registration rollers 67, the rotational drive of the registration rollers 67 stops, and the leading edge of the paper in the next row is moved before the next row of paper is transported by the registration rollers 67. By causing the paper to hit the nip portion where the rotational drive is stopped, creating a predetermined paper loop, and waiting until the timing for conveying the next line of paper, the paper is continuously conveyed at a constant interval from the registration roller 67 onwards. I can do it. The paper distance after the registration roller 67 is set as Xa,
If the paper distance to the registration roller 67 is Xb, and the conveyance speed before and after the registration roller 67 is the same, then Xa≧X
Control is performed to achieve b.

FIG. 12 shows an example of the configuration of another printer. The printer shown in FIG. 14 is set by inserting the leading ends of the paper feed cassettes 61 and 62 into the cassette device openings 63 and 64 provided on the sides of the printer, so the rear ends of the cassettes 61 and 62 protrude outward. In contrast, in the printer shown in Fig. 12, the entire device becomes large, and additional space is required to install the device in order to insert and remove the cassette. The entire cassette 2 is housed in the main body of the apparatus and is configured to be taken in and out in a so-called front loading manner.This has the advantage that the entire apparatus can be made compact and the cassettes 1 and 2 can be taken in and out easily. In FIG. 12,
3 and 3 are pickup rollers (A rollers) that selectively feed copy paper from the upper and lower paper feed cassettes 1 and 2, respectively, and 4 and 4 are retards that transport the paper fed by the A roller 3. The rollers (B rollers) 5 and 5 rotate in the opposite direction to the rotation direction of the B roller 4 so as not to convey the paper below the paper fed by the A roller 3 together (double feeding). This is a separation roller (C roller) that frictionally separates the fed paper.

Paper is fed from the upper paper feed cassette 1 by the A roller 3, frictionally separated one by one by the B rollers 4 and C rollers 5, and then transported to the second transport roller 7 and the third transport roller 8. The paper then makes a U-turn above the paper feed cassette 1 and is transported in the opposite direction to the paper feed direction from the cassette 1 to reach the registration rollers 9 . Paper is fed from the lower paper feed cassette 2 by the A roller 3, frictionally separated one by one by the B rollers 4 and C rollers 5, and then transported via the first transport roller 6 to the second transport roller 7. Thereafter, the paper reaches the registration roller 9 along the same route as the paper is fed from the upper paper feed cassette 1.

When the leading edge of the paper reaches the nip portion of the registration roller 9, the rotational drive of the registration roller 9 is maintained in a stopped state, and the leading edge of the paper is received by the nip portion of the registration roller, thereby connecting the registration roller 9 and the third conveyor. A paper loop is formed between the rollers 8 and the paper is skewed. S1 is a pre-registration sensor that detects the position of the paper to create a loop that takes care of the oblique feeding of the paper. The registration rollers 9 start rotating in synchronization with the operation of a host device such as an image reading device (scanner), a computer, or a word processor (not shown), and convey the paper to the position of the recording head 10 at a predetermined timing. .

In this example, the recording head 10 is a head that discharges ink using a bubble jet method, which is a type of ink jet method, and is controlled in accordance with image data from the host device to print a target image onto the conveyed paper. Form an image for information. The image-formed paper that has passed the position of the recording head 10 is ejected from the apparatus by an ejection roller 11.

Reference numeral 12 denotes a manual paper feed roller, and when paper is manually fed from this opening, the manual paper sensor S2 detects that the paper is manually fed, and the manual paper is drawn into the apparatus by a pull-in roller 13 to be transferred to the third conveyor. The recording head 10 is timing-fed via the roller 8 and registration roller 9, and undergoes image formation. .

The one-dot chain line indicates a paper transport path from the upper or lower paper feed cassettes 1 and 2 or the manual paper feed port 12 to the ejection roller 11. Compared to the device shown in FIG.
The paper transport path from the leading edge of the paper to the registration rollers 9 is long.

When a plurality of sheets of paper are continuously fed and conveyed with this device configuration, depending on the paper size, the preceding (first sheet) may reach the registration rollers 9 as in the control of the configuration shown in FIG. If you feed the next (second) sheet from then on, the gap between the preceding sheet and the next sheet of paper will be too wide, so feed the preceding sheet and feed it at a certain position before it reaches the registration roller 9. When the next paper is reached, feed the next paper. When continuously feeding multiple sheets of paper, if there are variations in the paper feeding position (position of the leading edge of the paper in the cassette) each time the paper is fed, the preceding paper may be placed at a certain position before it reaches the registration roller 9. It also causes variations in
Even when feeding the next paper, the dispersion of this paper within the cassette is taken into account. That is, with the same paper distance control concept as in the configuration shown in FIG. 14, assuming that the distance between the sheets after the registration roller 9 is Xa, the distance between the sheets up to the registration roller 9 is Xb, and the conveyance speed before and after the registration roller 9 is the same. , Xa≧Xb
The following control is being carried out.

In comparing the device configuration of FIG. 12 with the device configuration of FIG. 14, FIG. 12 also has the following advantages. That is, Figure 1
In the case of No. 4, the paper is stored in the paper feed cassettes 61 and 62 with the front side (image forming surface) facing upward, and the paper feed rollers 65 and 66 are in contact with the front surface, so that the paper feed rollers 65 and 66 are in contact with the front surface of the paper.
・The roller pressure of 66 may stain the surface of the paper, or the paper may curl due to moisture, etc., which tends to be unfavorable for paper conveyance.
・The paper is stored in 2 with the back side facing upward, and the A roller (pickup roller) 3 is in contact with the back side of the paper and fed, and the fed paper is conveyed in a U-turn to the front side (image forming side). Since the image is formed by being conveyed facing upward facing the recording head 10, the above-mentioned problem does not occur.

[0021]

[Problems to be Solved by the Invention] In the device configuration shown in FIG. 14, when a plurality of sheets are continuously fed, if the variation in the sheet feeding position for each sheet feeding is Xc, the difference between the preceding sheet and the next sheet is The distance Xb cannot be smaller than Xc. In other words, the number of sheets of paper conveyed per hour is restricted by this.

In the device configuration shown in FIG. 12, when a plurality of sheets are continuously fed, if the dispersion in the sheet feeding position for each sheet feeding is Xc, then at a certain position before the preceding sheet reaches the registration roller 9, the next sheet is Due to variations in this position for feeding paper and variations in the next paper in the cassette, the inter-paper distance Xb between the preceding paper and the next paper cannot be made smaller than 2Xc. In other words, the number of sheets of paper conveyed per hour is limited by this.

Specifically, the B roller (retard roller)
4 and C roller (separation roller) 5, when the paper 2 in the paper feed cassette is
The paper feeding position (paper leading edge position) for 0 is either at the back of the cassette as shown in (A) in Figure 13, or when it is at the back of the cassette as shown in (B) due to friction between paper and paper or between paper and rollers. There are cases where it is on the tip side (at the B roller 4), and this variation is Xc. In this case, when trying to perform continuous paper feeding, the position of the first sheet of paper 20 in the cassette is uncertain within the range of Xc, and from which position within the range of Xc the first sheet of paper 20 is fed Even if the B roller 4 is moved to this first sheet of paper 2
If the rear end of 0 is not removed, the second sheet of paper 21 may also be in the position shown in (B), so the second sheet of paper 2
1 cannot be fed.

Therefore, when the first sheet of paper 20 is at the position (A), if the rear end of the first sheet of paper 20 passes through the B roller 4, the one sheet of paper 20 falls within the range of Xc. It will pass through the B roller 4 no matter where it is located.

FIG. 13(C) shows that the first sheet of paper 20 is (A)
The paper is fed from the position , and the trailing edge passes through the B roller 4. If the time it takes for the first sheet of paper 20 to be fed from position (A) to position (C) is t, then the first sheet of paper 20 is fed, and after t time, the second sheet of paper is fed. If it is paper, the paper feeding position of the first paper 20 and the second paper 21 is Xc.
Stable continuous paper feeding is possible anywhere in the range.

If the paper feeding position of the first sheet 20 varies within the range of Sheet paper 20
is at a position Xc away from the roller 4, as shown in FIG. 13(D). At this time, since the paper feeding position of the second sheet 21 also varies within the range of The distance between the paper 20 and the second paper 21 is 2X
It becomes c.

In other words, when the variation in the paper feeding position in the paper feeding cassette is Xc, if continuous paper feeding is attempted, the distance between the sheets at the paper feeding port (downstream of the conveyance, on the paper exit side of roller pair 4 and 5) is Xb. The maximum is 2Xc, and the registration roller 9
There was a drawback that the subsequent paper distance Xa could not be made less than 2Xc in some cases.

As a means to solve this problem, as shown in FIG. 12, a paper feed sensor S3 is disposed near the paper feed port to control the minimum inter-paper distance Xa as a variation Xc. However, with this control, variations in the paper feeding position are kept to a minimum, the paper distance after the registration rollers 9 is kept constant, and the paper is conveyed without reducing the copy speed.

That is, on the paper conveyance path before the registration roller 9, the paper is conveyed without the preceding paper and the next line colliding with each other due to variations in paper feeding, and without the paper distance exceeding Xa. . Therefore, problems such as jams are likely to occur due to slight fluctuations in paper transport such as deformation and slippage due to wear of the transport rollers and curling of the paper.

In the continuous paper feeding mode, even if the paper feeding position varies and the paper position cannot be detected, the present invention corrects the variation without reducing the paper conveyance ability and moves the paper before the registration roller. The purpose is to keep it constant on the conveyance path.

[0031]

[Means for Solving the Problems] The present invention transports paper fed from a paper feeding unit through a paper transport path including registration rollers to a paper processing unit that performs processing such as image formation on the paper. In the paper conveyance device, a paper detection means is provided near the paper feed port on the paper conveyance path, and in continuous paper feed mode, the paper detection means detects the passage of the preceding fed conveyed paper, and the passage of the preceding paper is detected. is detected, and in response to the detection of the passing of the preceding paper, the dispersion between the sheets of continuously fed paper at the above-mentioned paper feed port is corrected on the paper conveyance path before the registration roller, and the preceding paper and the next paper are This paper conveying device is characterized by having a control means for keeping the paper distance constant.

[0032] Furthermore, in the above, the paper conveyance device is characterized in that the paper processing means is an image forming means including an inkjet type recording head.

[0033]

[Function] That is, the present invention provides a simple and inexpensive paper detecting means such as a sensor as close as possible to the paper feed port downstream of the paper feed port on the paper transport path, and a timing adjustment using software. This system uses control to correct variations in the paper feeding position each time paper is fed during continuous paper feeding without reducing the paper conveyance capacity (copy speed, etc.) and maintains it constant on the conveyance path before the registration rollers. be. This paper detection means is used in cases where there are variations in the paper feeding position and the paper position cannot be detected, such as in a paper feed cassette with a paper friction separation paper feeding system. This is to correct as far downstream as possible.

[0034]

Embodiment Embodiment 1 (FIGS. 1 to 7, FIG. 12) In this embodiment, the present invention is applied to a printer having the mechanical configuration shown in FIG. 12 described above.

FIG. 1 is a block diagram of the control system of the printer of this embodiment. 30 is a D controller, CPU31, RAM32
, ROM 33, serial communication, GPIB, etc. control controller 3 for connecting with devices such as scanners and personal computers.
4. It is composed of an input/output section I/O 35. I/O3
5 is a main motor 36 (motor driver not shown)
, a release solenoid 37 for the A roller (pickup roller) 3, a paper feed clutch 38, a clutch 42 for the first conveyance roller 6, a clutch 39 for the second conveyance roller 7, a clutch 40 for the third conveyance roller 8, a clutch for the registration roller 9. (Registration clutch) 41, paper feed sensor S3, and pre-registration sensor S1 are connected. 49 is an external device such as a scanner or a personal computer.

Each of the rollers 3 to 9, 11, and 13 is rotated by the drive of a main motor 36. Upper and lower A rollers (
The pick-up rollers 3 and 3 are normally held at retracted positions where they are lifted up from the upper surface of the storage section in the paper feed cassettes 1 and 2 without contact by turning off the release solenoid 37, respectively.

When paper feeding from the upper paper feed cassette 1 is specified, the release solenoid 37 of the upper A roller 3 is turned ON, and the A roller 3 is lowered to feed the paper from the upper paper feed cassette 1. It comes into contact with the top surface of the stored paper and becomes ready for paper feeding. When feeding paper from the lower paper feed cassette 2 is specified, the release solenoid 37 of the lower A roller 3 is turned on, and the A roller descends to the upper surface of the paper stored in the lower paper feed cassette 2. When it makes contact, it becomes ready to feed paper.

[0038] A roller 3/B roller (retard roller)
4.C roller (separation roller) 5 has paper feed crack 38
By setting it to N, the driving force of the main motor 36 is transmitted and rotationally driven.

When the roller release solenoid 37 is turned on, the A roller 3 comes into contact with the surface of the uppermost paper in the upper or lower paper feed cassette 1 or 2, and when the paper feed clutch 38 is turned on, the A roller 3 is driven to rotate. Lower paper cassette 1
Or paper feeding starts from 2, and B roller 4 and C roller 5
As a result, one sheet separation feeding is executed.

Furthermore, in the case of feeding paper from the upper paper feeding cassette 1, the clutches 39 and 39 of the second and third conveyance rollers 7 and 8
40 is the clutch 4 of the first, second, and third transport rollers 6, 7, and 8 in the case of paper feeding from the lower paper feeding cassette 2.
2, 39, and 40 are turned on, and their conveyance rollers 7 and 8
Or, the drive of the main motor 36 is transmitted to the rollers 6, 7, and 8 to rotate those rollers, and the paper fed from the upper or lower paper feed cassette 1 or 2 is conveyed to the registration rollers 9. go.

The registration roller 9 is in a state where the registration clutch 41 is OFF and rotation is stopped until the leading edge of the conveyed paper reaches the nip portion of the roller, and receives the leading edge of the conveyed paper. Then, as the paper continues to be conveyed, a paper loop is formed between the registration roller 9 and the third conveyance roller 8, so that the paper is skewed. Thereafter, by turning on the registration clutch 41 at a predetermined timing, the drive of the main motor 36 is transmitted to the registration roller 9, and the registration roller 9 is also rotationally driven to feed the paper to the recording head 10 at a timing. be done. When the trailing edge of the paper passes the registration rollers 9, the clutch 41 of the roller is turned off, and the registration rollers 9 stop rotating and become ready to receive the leading edge of the next conveyed paper.

When paper is continuously fed and conveyed, for example, when the trailing edge of the preceding paper passes the paper feed sensor S3, the next paper is fed (release solenoid 37-ON, paper feed clutch 38-ON). As a result, the distance between the preceding paper and the next paper on the paper transport path up to the registration rollers 9 can be kept within a certain range, and the distance between the preceding paper and the next paper can be kept constant at the registration rollers 9. do it like this.

For the sake of convenience, paper feeding and conveyance from the upper paper feeding cassette 1 will be described below as an example. Figure 2 shows an ideal system when continuously feeding two sheets of A4 size paper, that is, the paper feeding position is at the paper feed port (
Paper feeding in the state (on the paper exit side of the B roller 4 and C roller 5) and in a state where the paper is set at the farthest side in the cassette 1 without scattering within the cassette ((A) in FIG. 13) It is a conveyance timing chart. (A), (B), (C) in Figure 3
is a diagram of the paper feeding and conveyance process.

When a device start key (not shown) is pressed, the main motor 36 is driven. When the paper feed clutch 38 is engaged, drive is transmitted to the A roller 3, B roller 4, and C roller 5, and these rollers become in a rotating state. When the release solenoid 37 of the A roller 3 is turned ON and the A roller comes into contact with the upper surface of the stacking storage section in the paper feed cassette 1, the uppermost paper (first sheet) 20 is fed, and the B roller 4 One sheet is separated and conveyed by the C roller 5.

[0045] It takes t1 time from the start of feeding of the first sheet of paper 20 until the leading edge of the paper 20 reaches (detects) the sheet feeding sensor S3. Next, before the leading edge of the paper 20 reaches the second conveyance roller 7, the conveyance clutches 39 and 40 are turned on.
Then, the second and third conveyance rollers 7 and 8 enter a rotating state, and the paper 20 is conveyed sequentially by these rollers 7 and 8.

If the second sheet 21 is not fed before the leading edge of the first conveyed sheet 20 reaches the registration roller 9, the paper distance Xl (=Xa) cannot be achieved.
Figure 3 where the trailing edge of the second sheet of paper 20 passes through the paper feed sensor S3 position
At point (A), the paper feed clutch 38 is turned on again and the paper feed clutch 38 is turned on again.
Feeding of the th sheet of paper 21 is started.

[0047] The timing of continuous paper feeding is as follows:
The second sheet of paper 21 may be fed after a certain time (count) after the paper feed sensor S3 detects the leading edge of the sheet.

When the second sheet 21 is also fed from the innermost part of the paper cassette 1 ((E) in FIG. 13), it reaches the paper feed sensor S3 after t1 time ((B) in FIG. 3). ). The distance between the first sheet of paper 20 and the second sheet of paper 21 is Xl.

When the leading edge of the first sheet of paper 20 reaches the pre-registration sensor S1, the leading edge of the first sheet of paper hits and is received by the nip of the registration roller 9, which is in a stopped rotation state, so that the leading edge of the first sheet of paper 20 is connected to the third registration roller 9. By forming an appropriate amount of loop 20a ((C) in FIG. 3) between the paper and the conveyance roller 8, the paper is skewed. Turn off the clutches 39 and 40 of the conveying rollers that convey this first sheet of paper 20,
At the same time, by turning off the paper feed clutches 38 of the A, B, and C rollers 3, 4, and 5 that feed and transport the second sheet of paper 21, the feeding and transport of the second sheet of paper is temporarily stopped. (Figure 3 (
C)). This state is at time A in FIG.

That is, the first sheet of paper 20 forms a loop 20a and is on standby for synchronization with an external device 49 (FIG. 1), such as a scanner, which is connected to the printer of this embodiment. It is during the state. second paper 21
The time from when is detected by the paper feed sensor S3 until it is stopped (time A) is t2.

For example, the standby of the printer of this example is good, but since the external device 49 completes standby after the time ts, the registration clutch 41 is turned on after the time ts, and the registration roller 9 is rotated, and the first sheet is not printed. paper 2
Timing conveyance of No. 0 to the recording head section 10 is started. At the same time, the paper feed clutch 38, the transport clutch 39,
40 is also turned ON, the A, B, and C rollers 3, 4, and 5 are also rotationally driven, and feeding and conveyance of the second sheet 21 is restarted. The registration clutch 41 is turned OFF when the rear end of the first sheet 20 passes through the registration roller 9, and the rotation of the roller 9 is stopped.

The tip of the second sheet of paper 21 hits the nip portion of the registration roller 9 in the stopped state and is received, forming a loop, and synchronizing with the external device 49, and the registration clutch 41 is activated. When turned ON, timing is fed to the recording head unit 10. Time B in FIG. 2 is the time when the clutch 41 is turned on.

The above is the timing and process of paper feeding and conveyance in an ideal system, but considering the variation in paper feeding position,
Timing chart in Figure 4, (A), (B), (
As shown in C), the first sheet of paper 20 is fed from the back of the cassette ((A) in FIG. 13), and the second sheet of paper 21 is fed from the front of the cassette ((B) in FIG. 13). , at B roller 4)
When the paper is fed from the beginning, the paper distance becomes Xm ((A) in FIG. 5). This paper distance Xm is constant up to the registration roller 9 as shown in FIGS. 5(B) and 5(C). That is, the paper distance on the conveyance path before the registration roller 9 is Xm to Xl (Xm<X
The paper distance is controlled by the registration roller 9 so that the paper distance becomes Xl.

FIG. 6 is a paper feeding and conveying timing chart on the conveying path before the registration roller 9, and FIG.
B), (C), and (D) are two A4 sheets of paper 20 as an example.
- It is a feeding and conveyance process diagram of No. 21. The first sheet of paper 20 is fed from the farthest side of the cassette ((A) in FIG. 13), and the second sheet of paper 21 is fed from the farthest side of the cassette ((A) of FIG. 7, (B)) The timing and operation of feeding the first sheet 20 are the same as in Figures 2 and 4. paper clutch 3
8 is turned on, the second sheet of paper 21 is fed from the front of the cassette as shown in FIG. ) time later, it reaches the paper feed sensor S3 ((B) in FIG. 7). The distance between the first sheet 20 and the second sheet 21 is Xm (<Xl).

When the leading edge of the first sheet of paper 20 reaches the pre-registration sensor S1 and is received by the nip of the registration roller 9, which is in a stopped state, and forms an appropriate amount of loop, this loop occurs at time A in FIG. The clutches 39 and 40 of the conveyance rollers 7 and 8 that convey the first sheet of paper 20 are turned off. At the same time, the paper feed clutch 38 is also turned off and the second paper 21
The feeding and conveyance of is temporarily stopped ((C) in FIG. 7). The time from when the leading edge of the second sheet of paper 21 is detected by the paper feed sensor S3 until the time A when the paper feed clutch 38 is turned off is t2.
'(>t2).

Thereafter, at a required timing, the registration clutch 41 is turned on, and the timing conveyance of the first sheet of paper 20 is started by the rotationally driven registration rollers 9. ((D) in Figure 7). Since the second sheet 21 is fed from the front of the cassette, the distance between it and the first sheet 20 is as small as Xm (<Xl). In order to correct this, the second sheet 21 is transferred to the paper feed clutch after (t1-t1') or (t2'-t2) time after the first sheet 20 is conveyed by the registration rollers 9. 38, feeding and conveyance is restarted by turning on the conveyance clutches 39 and 40.

t1 and t2 are values of the ideal system shown in FIGS. 2 and 3 described above. t1 is the time when the leading edge of the paper is detected by the paper feed sensor S3 when the paper is fed from the back of the cassette, and t2 is the time when the second sheet of paper is fed from the back of the cassette. This is the time it takes to stop at point A. Therefore, in Figure 7 (
After the state shown in D), the first sheet of paper 20 and the second sheet of paper 2
The paper spacing of 1 is Xl, and as shown in the timing chart of FIG. 6, the paper spacing at the pre-registration sensor S1 is also Xl. In other words, even if there are variations in the paper feeding position, the paper distance is
It can be controlled by keeping it constant at l.

The above-mentioned control is similar for continuous feeding of a plurality of sheets, such as the third sheet, fourth sheet, and so on. The timing chart also shows the paper size, the length of the transport path, the position of each transport roller, the transport speed, the position of the paper detection means (sensor),
Needless to say, it differs depending on the paper spacing, etc. Furthermore, although an example of feeding and transporting paper from the upper paper feed cassette 1 has been shown, the same control can be applied to paper feed cassettes with two, three, four stages, etc., decks, manual feed, etc. Further, the times t1' and t2' change each time the paper is fed due to variations in the paper feeding position. Therefore, t1' is a value that counts the time from when the paper feed clutch 38 is turned on until the paper feed sensor S3 detects the second sheet of paper, and is a time count.
have the means. Alternatively, from (t1-t1') = (t2'-t2), t2' (Fig. 6
It is sufficient to have either one of the means for counting the time (time up to point A in the timing chart).

<Embodiment 2> (FIGS. 8 and 9) In this embodiment, the paper spacing is controlled to be constant using a control mode different from that in Embodiment 1. Figure 8 shows the first and second sheets on the conveyance path before registration roller 9 when continuously feeding two sheets of A4 size paper.
It is a feeding conveyance timing chart of the 1st sheet of paper. In Figure 9 (
A), (B), (C), and (D) are feed and conveyance process diagrams of two sheets of paper 20 and 21 as an example. In this example, as in the first embodiment, it is assumed that the first sheet of paper 20 is fed from the back of the cassette, and the second sheet of paper 21 is fed from the front of the cassette.

The timing and operation of feeding the first sheet 20 are the same as in FIGS. 2 and 4. The second sheet of paper 21 is fed from the front of the cassette ((A) in FIG. 9), so t
After 1'(<t1) time, the leading edge reaches the paper feed sensor S3 ((B) in FIG. 9). The distance between the first sheet 20 and the second sheet 21 is Xm (<Xl).

Here, as shown in the timing chart of FIG. 2, if paper is fed from the back of the cassette,
At time t2 from when the paper feed sensor S3 detects the paper to when the paper stops at time A, the second sheet of paper 21 has stopped at the position shown in FIG. 3(C). In other words, no matter from which position the second sheet 21 is fed within the range of paper feeding position variations, it is t2 after the paper is detected by the paper feeding sensor S3.
By stopping this paper after a certain period of time, the first sheet of paper 20 hits the registration roller 9, and when it stops after making an appropriate amount of loop, the first sheet of paper 20 and the second sheet of paper 21
The paper spacing can be set to XL. That is, from the timing chart of FIG. 8, the second sheet of paper 21 is detected by the sheet feed sensor S3, the sheet feed clutch 38 is turned off after time t2, and the second sheet of paper 21 is stopped before the first sheet of paper 20 is stopped ( Figure 9
(C)). When the first sheet of paper 20 stops at time A, the distance between the first sheet of paper 20 and the second sheet of paper 21 is corrected to Xl ((D) in FIG. 9).

Next, the resist clutch 41 is turned on and 1
Timing conveyance of the sheet of paper 20 by the registration rollers 9 is started. At the same time, the paper feed clutch 38 and the transport clutches 39 and 40 are turned on, and the feeding and transport of the second sheet 21 is restarted. With this, the paper distance Xl is kept constant even at the pre-registration sensor S1. Therefore, even if there are variations in the paper feeding position, the position on the conveyance path before the registration roller 9 is fixed (
Although it varies depending on the paper size, in this example, the paper distance can be controlled to be kept constant at Xl from the position (D) in FIG. 9. In addition, in this embodiment, the value of t2 can be found by calculation and measurement in the ideal system shown in FIG. You don't necessarily need the means.

<Embodiment 3> (FIGS. 10 and 11) In this embodiment, the paper spacing is controlled to be constant using another control mode. FIG. 10 is a timing chart for feeding and conveying the first and second sheets of paper on the conveyance path before the registration roller 9 when continuously feeding two sheets of A4 size paper. In Figure 10 (
A), (B), (C), and (D) are feed and conveyance process diagrams of two sheets of paper 20 and 21 as an example. In this example, as in the first embodiment, it is assumed that the first sheet of paper 20 is fed from the back of the cassette, and the second sheet of paper 21 is fed from the front of the cassette.

The timing and operation of feeding the first sheet 20 are the same as in FIGS. 2 and 4, and the second sheet 21 is fed from the front of the cassette ((A in FIG. 10). )), t1
'(<t1) time later, the leading edge reaches the paper feed sensor S3 ((B) in FIG. 10). The distance between the first sheet 20 and the second sheet 21 is Xm (<Xl). (t1'<t1)
At this time, the paper feed clutch 38 is turned OFF, and this second sheet of paper 2 is
The feeding and conveyance of No. 1 is temporarily stopped ((B) in FIG. 11).

Then, after a time (t1-t1'), the paper feed clutch 38 is turned on again, and this second sheet of paper 21 is fed and conveyed. That is, the leading edge of the second sheet of paper 21 is located at the paper feed sensor S3.
When the second sheet of paper 21 is detected, the feeding and conveyance of the second sheet of paper 21 (
t1-t1') By stopping the time, the first sheet of paper 20
The distance between the sheets becomes Xl, and this sheet distance Xl is maintained when feeding and conveying is carried out again ((C) in FIG. 11).

The first sheet of paper 20 reaches the pre-registration sensor S1, hits the registration rollers 9, creates an appropriate amount of loop, and at time A, the conveying clutch 39 is conveying the first sheet of paper 20. Turn off 40. At the same time, turn off the paper feed clutch 38 that feeds and conveys the second sheet of paper 21.
Then, the conveyance is stopped ((D) in FIG. 11). Next, a registration clutch 41 is used to convey the first sheet of paper 20 at a timing.
is turned on and the registration rollers 9 are driven to rotate. At the same time, in order to feed and transport the second sheet of paper 21, the paper feed clutch 38 and transport clutch 39 (and 40) are turned on. With this, the paper distance Xl is kept constant even at the pre-registration sensor S1. Therefore, even if there are variations in the paper feeding position, the paper distance is
It can be controlled by keeping it constant at l.

Furthermore, the position where the second sheet 21 is stopped for a time (t1-t1') after being detected by the sheet feeding sensor S1 may not be immediately after being detected by the sheet feeding sensor S1, if possible.

[0068] t1' changes every time paper is fed due to variations in the paper feeding position. For this purpose, t1' is a value that counts the time from when the paper feed clutch 38 is turned on until the paper feed sensor S3 detects the second sheet of paper, and is a time count. have the means. In this example, the position of the paper feed sensor S3 or the paper feed port (B roller 4 and C roller
The closer the roller 5 is to the paper exit side of the roller 5, the more control can be made to suppress variations in the paper feeding position at the initial stage of feeding and conveyance (downstream of the conveyance path) and keep the paper distance constant. Further, control that combines the first embodiment, the second embodiment, and the third embodiment is also conceivable.

<Embodiment 4> In the above-mentioned Examples 1 to 3, the speed of the registration roller 9 is such that the transport rollers before the registration roller 9 (third transport roller 8, second transport roller 7, retard roller 4, pickup roller 3) ) increase the speed. By doing so,
Since it is sufficient that the paper spacing is Xl at the registration roller 9, it is possible to convey the paper with a paper spacing larger than Xl downstream (near the paper feed port) (ideal system).

[0070] If this happens, there will be variations in the paper feeding position,
When the second sheet of paper is at the forefront of the cassette during continuous sheet feeding, the distance between the first and second sheets of paper at around the sheet feed sensor S3 becomes larger than Xm.

[0071] Therefore, because the paper spacing is narrow, this is likely to occur.
To reduce the frequency of jams caused by slippage due to roller wear, paper curl, etc. Further, the paper feed sensor S3 can also be an actuator type sensor that is low in cost.

[0072]

Effects of the Invention As explained above, according to the present invention, the paper conveyance path from the paper feeding section to the registration rollers is long.
When performing continuous paper feeding with narrow paper gaps and uneven paper feeding positions, such as in friction separation type cassettes, a paper detection means is installed near the paper feed slot, and this paper detection means detects variations in the paper feeding position. By reducing the paper conveyance capacity (copy speed, etc.), jams are more likely to occur due to small fluctuations in paper conveyance such as deformation and slippage due to wear of the conveyance means, curling of paper, etc. due to narrow paper spacing. This has the effect of preventing this by widening the paper spacing to a certain extent.

[0073] Furthermore, by widening the paper spacing at a constant value without reducing the paper conveyance capacity, an inexpensive actuator type sensor can be used as the pre-registration sensor instead of an expensive transmission type sensor. .

[Brief explanation of the drawing]

[Fig. 1] Block diagram of the control system of the paper feed conveyance mechanism of the printer of Embodiment 1

[Figure 2] Operation timing chart of the paper feed conveyance mechanism

[Figure 3
] (A), (B), and (C) are diagrams of the continuous conveyance process of two sheets of paper according to this operation timing.

[Figure 4] Other operation timing charts

[Figure 5] (A), (B), and (C) are diagrams of the continuous conveyance process of two sheets of paper based on this operation timing.

[Figure 6] Still other operation timing chart

[Figure 7] (A
), (B), (C), and (D) are diagrams of the continuous conveyance process of two sheets of paper according to this operation timing.

[Fig. 8] Operation timing chart of the paper feed conveyance mechanism in Embodiment 2

[Figure 9] (A), (B), (C), and (D) are diagrams of the continuous conveyance process of two sheets of paper at this operation timing.

FIG. 10: Operation timing chart of the paper feed conveyance mechanism in Example 3

[Figure 11] (A), (B), (C), and (D) are diagrams of the continuous conveyance process of two sheets of paper at this operation timing.

[Figure 12]
Schematic diagram of an example printer

[Fig. 13] (A), (B), (C), (D), and (E) are explanatory diagrams of variations in paper feeding position and the relationship between sheets when paper is continuously fed and conveyed.

FIG. 14 Schematic diagram of another example of a printer

[Explanation of symbols]

Claims (2)

[Claims] Claim 1: A paper transport device that transports paper fed from a paper feed unit through a paper transport path including registration rollers to a paper processing unit that performs processing such as image formation on the paper, the paper transport path A paper detection means is provided near the upper paper feed port, and in the continuous paper feed mode, the paper detection means detects the passing of the preceding fed paper, and in response to the passing detection of the passing of the preceding paper, The present invention is characterized by having a control means that corrects variations in the distance between continuously fed sheets at the paper feed port on the paper conveyance path before the registration roller to keep the distance between the preceding sheet and the next sheet constant. paper conveyance device. 2. The paper conveyance device according to claim 1, wherein the paper processing means is an image forming means including an inkjet type recording head.