JP2002234629A - Paper carrying method, and imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent concentration of a load on a specific carrying roller, and reduce a load applied on a registration roller even when the stage number of paper feeding cassette parts is increased. SOLUTION: This imaging device is provided with a plurality of stages of paper feeding cassette parts 2, 3, and 4. In feeding a paper sheet from the paper feeding cassette part (4, for example) at the lowest stage, the paper sheet is carried by a plurality of carrying rollers 10, 11, and 12 to the registration roller 9, where driving to a part of the carrying rollers (11 or 12, for example) other than the carrying roller 10 at the uppermost stage is stopped in the middle of carrying. In feeding the paper sheet to the imaging part 13 by the registration roller 9 after that, the registration roller 9 is driven, and the driving-stopped carrying roller (11 or 12, for example) among the plurality of carrying rollers is re-driven.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus having a plurality of paper feed cassettes and a method of transporting the paper.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a laser printer, a copying machine, a facsimile machine, etc., a paper feed cassette unit accommodating a bundle of recording sheets is normally provided in the main body of the image forming apparatus. On the other hand, paper bundles of different sizes and colors are set in separate paper feed cassettes so that paper can be selectively fed from a desired paper feed cassette.
In some cases, an optional paper cassette unit can be stacked and installed below the image forming apparatus main body.

In any of the paper cassette units, the fed paper is temporarily conveyed to the position of a registration roller and stopped, and then the paper is formed in accordance with the image forming timing of the image forming unit. Department. At this time, the paper is transported by the transport roller on the paper cassette unit until the paper reaches the registration roller, and the transport roller on the paper cassette unit is driven when the paper is fed from the registration roller to the image forming unit. Instead, only the registration roller is driven, and the sheet is pulled up only by the force of the registration roller.

[0004]

In such an image forming apparatus, when the number of paper feed cassettes is increased and paper is fed from a relatively lower paper feed cassette, the leading edge of the paper is After reaching the registration roller, the plurality of transport rollers may be in a state of nipping the sheet at a predetermined pressure. In such a case, the load applied to the registration roller increases, and in the worst case, a conveyance failure may occur. If the power of the drive motor of the registration roller is increased to solve this problem, the cost of the drive motor and the power consumption of the apparatus are increased.

[0005] On the other hand, a method of re-driving the uppermost transport roller when driving the registration roller is also conceivable. In this method, the uppermost transport roller is moved both during the sheet feeding operation and during image formation. Since the driving is performed, the load may be concentrated on the uppermost conveying roller. As a result, the wear of the plurality of transport rollers may be uneven, and the durability of the uppermost transport roller may be reduced. Further, in this method, the uppermost transport roller has to temporarily stop after transporting the sheet to the registration roller, and then drive again in synchronization with the drive of the registration roller. For this reason, if it takes time from the stop of the conveyance roller to the start of driving and re-starting, the driving of the conveyance roller of the sheet cassette unit cannot start in time for the start of driving of the registration roller, and the registration roller can be accurately synchronized. There is also a possibility that problems such as not occurring may occur.

The present invention has been made in view of such a background, and an object of the present invention is to apply a load to a registration roller without concentrating a load on a specific conveyance roller even when the number of stages of a sheet feeding cassette unit increases. An object of the present invention is to provide a sheet conveying method and an image forming apparatus capable of reducing a load.

[0007]

In order to achieve the above object, a paper transport method according to the present invention provides a paper transport method in which a predetermined time has passed after the leading edge of a paper transported by a plurality of transport rollers has contacted a registration roller. A sheet conveyance method in an image forming apparatus that restarts sheet conveyance and feeds a sheet to an image forming unit, wherein when the plurality of conveyance rollers convey the sheet to the registration roller, the plurality of conveyance rollers include: The drive of some of the transport rollers other than the transport roller located immediately before the registration roller is stopped during the transport, and then, when the registration roller feeds the paper to the image forming unit, the plurality of It is characterized in that the transport roller, of which the drive has been stopped, is re-driven among the transport rollers. Here, the "predetermined time" is not necessarily a fixed time,
“After a predetermined time has elapsed” means that the image forming unit is ready to start the image forming process.

As described above, when the sheet is fed to the image forming section by the registration roller, one of the plurality of conveyance rollers is driven together with the registration roller, so that the plurality of conveyance rollers sandwich the registration roller. Even in the state, the load on the registration roller that pulls the sheet can be reduced. On the other hand, when a plurality of conveyance rollers convey a sheet to the registration roller, by temporarily stopping the driving of the conveyance roller that is driven together with the registration roller later, the load is concentrated on the conveyance roller. In addition to this, the control of stopping and re-driving the transport roller can be facilitated.

The period during which the driving of the transport roller is stopped is as follows:
For example, from the start of driving of the conveying roller located immediately before the registration roller to the start of driving of the registration roller.

In the case where at least three of the plurality of transport rollers are present, the stop and re-drive of the drive are performed in advance of at least two transport rollers other than the transport roller located immediately before the registration roller. It may be a specified specific conveying roller. Or,
When at least three of the plurality of transport rollers are present,
It is also possible to sequentially select at least two transport rollers other than the transport roller located immediately before the registration roller as a target to stop and restart the drive based on a predetermined selection criterion.

An image forming apparatus according to the present invention has an image forming section for forming an image on a sheet, a plurality of conveying rollers for conveying the sheet toward the image forming section, and a plurality of conveying rollers for conveying the sheet. A registration roller for feeding a sheet to the image forming unit in a timely manner,
Prior to image formation, when paper is fed toward the registration roller by the plurality of conveyance rollers, driving of some conveyance rollers other than the conveyance roller located immediately before the registration roller among the plurality of conveyance rollers is performed. The conveyance is stopped in the middle of the conveyance, and after the leading end of the paper comes into contact with the registration roller, the conveyance of the paper toward the image forming unit is restarted by the registration roller after a predetermined time has elapsed. Control means for controlling the plurality of transport rollers and the registration rollers so as to re-drive the transport rollers whose driving has been stopped.

The image forming apparatus includes, for example, a main body of the image forming apparatus, and a plurality of paper feed cassettes which can be mounted on a lower portion of the main body in a plurality of stages. A sheet transport path is formed from the superposed plurality of paper cassette units to the image forming apparatus main body.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of a laser printer as an example of an image forming apparatus to which the present invention is applied.

The image forming apparatus shown in FIG. 1 includes a main body 1 and a plurality of optional paper feed cassettes 2, 3, and 4 stacked below the main body. Although the number of stages of the sheet cassette is three here, the present invention can be applied to two or four or more stages.

The main body 1 picks up paper from a standard paper cassette by a paper feed roller 5 and feeds the paper to a transport path 25. The sheet reaches the registration roller 9 via the registration sensor 21, and is sent to the image forming unit 13 by the registration roller 9. The image forming unit 13 in this example includes:
A laser beam is modulated and scanned on a photosensitive drum according to an image signal given from an external host computer (not shown), and a latent image formed on the photosensitive drum is developed with toner and then transferred to paper. Thereafter, fixing is performed in the fixing device 14, and the sheet is discharged out of the device.

The paper feed cassettes 2, 3, and 4 respectively include paper feed rollers 6, 7, and 8 for picking up paper from its own paper cassette and feeding the paper to a transport path 25;
And transport rollers 10, 11, and 12 disposed on the transfer roller 5. Each transport roller has a function of transporting not only a sheet fed from its own sheet cassette unit but also a sheet fed from a sheet cassette unit below it to the registration roller 9. Each transport roller 10, 11, 12
Can be detected by the conveyance sensors 22, 23, and 24 respectively.

FIG. 2 is a block diagram showing main functions of the image forming apparatus shown in FIG. The main body 1 includes a central processing unit (CPU) 100 as control means for controlling the entire image forming apparatus, a paper conveyance control unit 103 for controlling operations of the paper feed roller 5 and the registration roller 9 in the main body 1, An image forming control unit 104 that controls the operation of the forming unit 13 and a sensor control unit 1 that monitors and controls sensors such as the registration sensor 21.
And a communication control unit 101 for controlling communication with the paper cassette units 2, 3, and 4. On the other hand, the sheet cassette units 2, 3, and 4 respectively include a CPU 200 that controls the entire sheet cassette unit and a communication control unit 1 of the main body 1.
01, communication control unit 201 for communicating with paper feed rollers 6, 7, 8 and transport rollers 10,
A sheet conveyance control unit 203 that controls 11 and 12 and a sensor control unit 205 that monitors and controls the conveyance sensors 22, 23 and 24.
It has. The main body 1 and the sheet cassette units 2, 3, and 4 are mutually connected by a communication line 300. It is also possible to additionally install another sheet feeding cassette section below the sheet feeding cassette section 4.

In the configuration of such an image forming apparatus,
For a better understanding of the present invention, the conventional operation will be described with reference to FIG. For example, the lowermost paper cassette unit 4
Consider the case where paper is fed from the printer. In this case, first, the paper feed roller 8 is driven by turning on a paper feed clutch (not shown) of the paper feed cassette unit 4 (t0), and further the driving of the transport roller 12 is started (t1), and the paper is transported. The sheet is conveyed toward the registration roller 9 by the roller 12. Paper feed roller 8
Is stopped when the sheet feeding is completed (t2). Next, the driving of the transport roller 11 of the middle paper cassette unit 3 is started (t3), and the driving of the transport roller 10 of the upper paper cassette unit 3 is started (t4). As an opportunity to start driving the transport rollers of the next paper cassette unit, a time when the leading edge of the sheet is detected by the transport sensors provided at the positions of the transport rollers can be used. In this way, when the leading edge of the sheet reaches the registration roller 9, all the registration rollers 10, 11, and 12 are once stopped (t5). At this time, in order to correct the skew of the paper,
Even after the leading edge of the sheet reaches the registration roller 9, the driving of the transport roller may be continued for a predetermined time to form a loop on the sheet. Thereafter, when it is time to start the image forming process of the main body, all the transport rollers 10, 1
While the rollers 1 and 12 are stopped, only the registration roller 9 starts to be driven (t6), and the sheet is conveyed to the image forming unit 13.
Time T from time t5 to time t6 is not always constant. As described above, depending on the paper size, at this time, when the paper is held between all the paper feed rollers 10, 11, and 12 (the length of the paper is longer than the distance from the registration roller 9 to the transport roller 12). When the registration roller 9 is driven, an excessive load is applied to the registration roller 9 (and, consequently, its drive motor).

On the other hand, in the present invention, when the sheet is conveyed to the registration roller 9, the driving force of any of the conveying rollers other than the uppermost conveying roller holding the sheet is cut off during the conveyance. Thereafter, the transport roller is driven to rotate, and then the transport roller whose driving force has been cut off is driven again when the registration roller 9 is driven. At this time, the transport roller that has been re-driven does not load the registration roller 9, so that the load on the registration roller 9 can be reduced.

FIG. 4 shows a first embodiment of the present invention.
Is shown. In this example, the conveyance roller to be stopped during driving of the sheet and to be re-driven together with the start of driving of the registration roller 9 is a lower conveyance roller 12 (first of a plurality of conveyance rollers involved in the sheet conveyance). Driven transport roller). That is, the time t
From 10 to t14 is the same as in FIG. 3, but
Immediately after that, at time t15, the driving of the lower conveying roller 12 is stopped. Thereafter, the drive of the transport rollers 11 and 10 is stopped at time t16, the drive of the registration roller 9 is started at time t17, and the drive roller 12 that has been temporarily stopped is driven again. In this case, as can be understood by comparing the timing charts of FIGS.
Is driven again, the same transport roller 12 is temporarily stopped during the period from the time point t4 to the time point t6, so that the drive time of the transport roller 12 does not substantially increase, but rather can be reduced. it can. In addition, even when the paper is being conveyed, by stopping the conveyance roller 12 at the time point t15, a relatively long pause period is obtained before re-driving, so that there is sufficient margin for stopping and re-driving the conveyance motor. Given. Other operations are the same as in the conventional case shown in FIG. In general, the transport speed of each transport roller until time t16 is set to be higher than the transport speed of the registration roller 9 and the transport roller 12 after time t17.

FIG. 5 shows a case where the paper is fed from the lower paper cassette unit 4 when the transport roller 1 of the middle paper cassette unit 3 is fed.
1 is temporarily stopped during conveyance (t25), and re-driven together with the driving of the registration roller 9 at time t27.
Another control mode is shown. From time t20 to time t24
The operation up to is the same as in the case of FIG. Specifically, at time t20, paper is fed from the paper feed roller 8 of the lower paper feed cassette unit 4, and at the subsequent time t21, driving of the transport roller 12 of the paper feed cassette unit 4 is started. Then, at time t23
Then, the driving of the transport roller 11 of the middle sheet cassette unit 3 is started, and at the subsequent time t24, the driving of the transport roller 10 of the upper sheet cassette unit 2 is started. Immediately at time t25, the driving of the transport roller 11 of the middle sheet cassette unit 3 is temporarily stopped. Thereafter, at time t26, the driving of the transport rollers 12, 10 is stopped, and at time t27, the driving of the registration rollers 9 and the driving of the transport rollers 11 are restarted. As in the case of FIG. 4, also in this control mode, the load on the registration roller 9 can be reduced. Further, even if the transport roller 11 is driven together with the driving of the registration roller 9, there is no adverse effect of increasing the drive time of the transport roller 11.

When the sheet is fed from the lower sheet feeding cassette section 4, which of the control modes shown in FIGS. 4 and 5 is used may be fixed in advance. Specifically, the transport roller of the paper cassette unit that has fed paper is normally driven the longest,
The driving of the transport roller is stopped. Alternatively, the driving time and the number of times of driving of each transport roller are stored, and the transport rollers to be driven are alternately (or sequentially) stopped so that the driving time and the number of times of each transport roller are averaged.
You may make it select. Thereby, the concentration of the load applied to the transport roller can be dispersed.

FIG. 6 shows a control mode when paper is fed from the middle paper cassette unit 3, that is, when the lower paper cassette unit 4 is not operated (or when there is no paper cassette unit 4). Is shown. As described above, the present invention can be applied to a case where at least two transport rollers exist upstream of the paper transport path to the registration roller 9. As shown in FIG. 6, in this case, the conveyance roller to be temporarily stopped / re-driven during the conveyance of the sheet is the conveyance roller 11 of the sheet cassette unit 3 in the middle stage. 4 is similar to that of FIG. 4 except that paper is fed from the paper feed roller 7 of the middle paper feed cassette unit 3 without operating the lower paper feed cassette unit 4. Different from the case. Specifically, at time t30, paper is fed from the paper feed roller 7 of the middle paper feed cassette unit 3, and at the subsequent time t31, driving of the transport rollers 11 of the paper feed cassette unit 3 is started. Then, at time t33
Then, the driving of the transport roller 10 of the upper paper feed cassette unit 2 is started, and the drive of the transport roller 11 is temporarily stopped at a time point t34 immediately after. After the drive of the transport roller 10 is stopped at time t35, the drive of the transport roller 11 is restarted at the time t36 along with the start of driving of the registration roller 9. The effect of this control mode is the same as in the case of FIG.

FIG. 7 is a flowchart showing an operation example of each section of the image forming apparatus according to the present embodiment. Here, as a substitute operation example, a description will be given of a process in a case where a sheet is supplied from the lowermost sheet cassette unit 4 in an apparatus having a three-stage sheet cassette unit as shown in FIG. .

In the main body 1, a lower paper feed cassette unit 4
When it is necessary to perform image formation by feeding paper from the printer, first, the CPU 100 of the main body 1 sends a paper feed instruction to the paper feed cassette unit 4 via the communication line 300 (S
10). The CPU 200 of the sheet cassette unit 4 receiving this
By driving a paper feed clutch (not shown) by the paper transport control unit 203, the paper feed roller 8 is driven to pick up one sheet from the paper cassette and starts driving the transport roller 12. Then, the conveyance of the sheet is started toward the downstream of the conveyance path (S41). When this sheet reaches the transport sensor 24 of the sheet cassette unit 4 (S4
2, Yes), this sensor ON information is notified to the main body 1 via the communication line 300 (S43).

The main body 1 receiving this notification instructs the middle sheet cassette unit 3 to start driving the transport roller 11 (S11). In response to this, the paper feed cassette unit 3 starts driving its own transport roller 11 (S
31). Thereafter, when the paper reaches the conveyance sensor 23 of the paper feed cassette unit 3 and this sensor is turned on (S32,
Yes), the main body 1 is notified to that effect (S33).

The main body 1 having received the notification instructs the upper sheet cassette unit 2 to start driving the transport roller 10 (S12). In response,
The paper feed cassette unit 2 starts driving its own transport roller 10 (S21). Thereafter, when the sheet reaches the conveyance sensor 22 of the paper feed cassette unit 2 and this sensor is turned ON (S22, Yes), the fact is notified to the main body 1 (S22).
23).

The main body 1 having received the notification instructs the lower sheet cassette unit 4 to stop the transport roller 12 (S13). In response to this, the paper feed cassette unit 4 stops driving the transport roller 12 (S44).

On the other hand, the upper paper feed cassette section 2 monitors the output of the registration sensor 21, and when this is turned ON (S24, Yes), this is notified to the main body 1 (S24).
25). Turning on the registration sensor 21 means that the leading edge of the conveyed sheet has reached the position of the registration roller 9.

After receiving the notification, the main body 1 waits for a predetermined amount of loop to be formed on the sheet, and then feeds the rollers 10 and 1.
An instruction is issued to the sheet cassette units 2 and 3 to stop the driving of No. 1 (S14). Accordingly, the transport roller 1
0 and 11 are stopped (S26, S34).

Thereafter, when the main body 1 is ready to start image formation (S15, Yes), the paper transport control section 103
To start the driving of the registration rollers 9 therein, and instruct the sheet feeding cassette unit 4 to start driving the transport rollers 12 (S16). In response to this instruction, the lower sheet feeding cassette unit 4 moves its own transport roller 12.
Is restarted (S45). Then the paper cassette unit 4
Monitors its own transport sensor 24, and when it is turned off (S46, Yes), sends a sensor OFF notification to the main body 1.
(S47).

The main body 1 having received the sensor OFF notification from the paper feed cassette unit 4 instructs the conveyance roller 12 to stop (S1).
7) In response to this, the paper feed cassette unit 4
Is stopped (S48). Further, after that, the main body 1 monitors the output of the registration sensor 21, and when it detects that this sensor has been turned off (Yes in S 18), the registration roller 9
Is stopped (S19). In this way, the conveyance of the sheet in the conveyance path is completed. Thereafter, the main body 1 continues the subsequent image forming process by the image forming control unit 104 (S
20).

While the preferred embodiment of the present invention has been described above, various modifications and changes other than those described above can be made without departing from the scope of the claims. For example, in the above embodiment, a laser printer has been described as an example, but the recording method of the image forming apparatus of the present invention is not limited to laser recording, nor is it limited to a printer. The present invention can be applied to any image forming apparatus as long as the apparatus includes a sheet conveying device capable of selectively feeding sheets (recording material) from a plurality of stacked sheet cassettes.

[0035]

According to the sheet conveying method and the image forming apparatus of the present invention, even if the number of stages of the sheet cassette is increased, the load applied to the registration roller is reduced without concentrating the load on a specific conveying roller. can do. Therefore, it eliminates the need for expensive drive motors, and
The life of the transport roller can be extended.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a laser printer as an example of an image forming apparatus to which the present invention is applied.

FIG. 2 is a block diagram illustrating main functions of the image forming apparatus illustrated in FIG.

FIG. 3 is a timing chart for explaining a conventional operation.

FIG. 4 is a timing chart showing a first control mode according to the embodiment of the present invention.

FIG. 5 is a timing chart showing a second control mode according to the embodiment of the present invention.

FIG. 6 is a timing chart showing a third control mode according to the embodiment of the present invention.

FIG. 7 is a flowchart illustrating an operation example of each unit of the image forming apparatus according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus main body 2,3,4 Paper cassette unit 5,6,7,8 Paper feed roller 9 Registration roller 10,11,12 Transport roller 13 Image forming unit 21 Registration sensor 22,23,24 Transport sensor 25 Transport path

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 ED17 EE02 EE05 EF09 3F049 DA12 DB02 LA02 LA05 LA07 LB03 3F343 FA02 FB02 FB03 FC22 GA01 GB01 GC01 GD01 HA16 KB06 LA03 LA14 LC17 LD10 MA03 MA15 MA23 MB04 MB15 MC08 MC21

Claims (9)

[Claims] An image forming apparatus for feeding a sheet to an image forming section by restarting the sheet conveyance after a predetermined time has elapsed after the leading end of the sheet conveyed by a plurality of conveying rollers abuts on a registration roller. A paper transport method, wherein when the plurality of transport rollers transport a sheet to the registration roller, driving of some transport rollers other than the transport roller located immediately before the registration roller among the plurality of transport rollers. Stopping in the middle of the conveyance, and thereafter, when feeding the sheet to the image forming unit by the registration roller, re-driving the conveyance roller of which the driving is stopped among the plurality of conveyance rollers. Paper transport method. 2. A period in which the driving of the transport roller is stopped,
2. The sheet conveying method according to claim 1, wherein the process is performed after the driving of the conveying roller positioned immediately before the registration roller is started until the driving of the registration roller is started. 3. When at least three of the plurality of transport rollers are present, the stop and re-drive of the at least two transport rollers other than the transport rollers located immediately before the registration rollers are performed as targets to be stopped. 3. The sheet conveying method according to claim 1, wherein the predetermined conveying roller is a predetermined conveying roller. 4. When at least three of the plurality of transport rollers are present, at least two transport rollers other than the transport roller located immediately before the registration roller are set as targets for stopping and re-driving the drive. 3. The paper transport method according to claim 1, wherein the paper is sequentially selected based on the selection criteria. 5. An image forming section for forming an image on a sheet, a plurality of conveying rollers for conveying the sheet toward the image forming section, and a sheet conveyed by the plurality of conveying rollers are timed. A registration roller for feeding the image to the image forming unit; and, prior to image formation, when feeding paper toward the registration roller by the plurality of conveyance rollers, immediately before the registration roller of the plurality of conveyance rollers. The driving of some of the transport rollers other than the transport roller positioned in the middle is stopped in the middle of the transport, and after the leading edge of the sheet abuts on the registration roller, the registration roller is directed toward the image forming section after a predetermined time has elapsed. The conveyance of the sheet is restarted, and at this time, the plurality of conveyance rollers and the plurality of conveyance rollers are re-driven so that the conveyance roller whose driving is stopped among the plurality of conveyance rollers is re-driven. An image forming apparatus characterized by comprising a control means for controlling the registration roller. 6. The image forming apparatus comprises: a main body of the image forming apparatus; and a plurality of paper feed cassettes which can be mounted on a lower portion of the main body in a plurality of stages. 6. The image forming apparatus according to claim 5, wherein a paper conveyance path is formed from the plurality of superposed paper feed cassette units to the image forming apparatus main body. 7. A period in which the driving of the transport roller is stopped,
7. The image forming apparatus according to claim 5, wherein a period from when driving of a conveyance roller located immediately before the registration roller is started to when driving of the registration roller is started. 8. When at least three of the plurality of transport rollers are present, the stop and re-drive of the at least two transport rollers of at least two transport rollers other than the transport roller located immediately before the registration roller are performed. 7. A predetermined specific conveying roller according to claim 5.
Or the image forming apparatus according to 7. 9. When at least three of the plurality of transport rollers are present, at least two transport rollers other than the transport roller located immediately before the registration roller are set as targets for stopping and re-driving the drive. The image forming apparatus according to any one of claims 5 to 8, wherein the selection is sequentially performed based on the selection criterion.