JPH0439236A - Sheet feeding device - Google Patents

Abstract

PURPOSE:To reliably correct the oblique feed of a sheet during waiting and to bite the tip of the sheet in an excellent state between resist rollers by conveying a sheet in a cured state, the height of which is lower than that of the curved state of a sheet during waiting at the resist rollers, when the sheet is fed from the resist rollers to a picture forming part. CONSTITUTION:A sheet fed from a sheet feed cassette is conveyed by conveyance rollers 22 and stopped by means of resist rollers 21 once. Even after the tip of the sheet is brought into contact with the resist rollers 21, the sheet is conveyed by the conveyance roller 22 for a specified time, and as a result the sheet is bent between the resist rollers 21 and the conveyance roller 22 to produce a first curved state. In the first curved state, a loop amount of the sheet is increased to a value enough for prevention of sheet breakage. By bringing a sheet loop part into strong contact with guide plates 23 and 24, the tip of the sheet can be sufficiently bitten between the resist rollers 21, and an oblique sheet feed is reliably corrected.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a paper feeding device for conveying paper.

[Conventional technology]

2. Description of the Related Art An image forming apparatus, such as a copying machine, is provided with a paper feeding device for conveying paper stored in a paper feeding cassette or the like to an image forming section that includes a photosensitive drum, a developing device, and the like. This paper feeding device includes a transport roller that transports the paper, and a registration roller that sends the paper to an image forming section in synchronization with an image forming operation.

When paper is transported by the paper feeding device as described above, so-called diagonal paper feeding may occur, in which the paper is fed while being tilted with respect to the transport direction. In order to correct this slanted paper feeding, by driving the transport roller for a predetermined period even after the leading edge of the paper reaches the registration roller, the paper is bent between the registration roller and the transport roller, and the leading edge of the paper is aligned with the registration roller. An operation is performed to uniformly contact the roller.

On the other hand, when conveying paper from the registration rollers to the image forming section, in order to reduce the load torque related to the registration rollers, both the registration rollers and the conveyance rollers are I try to drive them at the same time.

[Problem to be solved by the invention]

When correcting slanted paper feeding as described above, ensure that the paper has enough deflection (hereinafter referred to as the loop amount), make sure that the leading edge of the paper loop part strongly contacts the guide plate, and then press the leading edge of the paper against the registration roller. You need to press it firmly.

In such a state, if the registration roller and the conveyance roller are simultaneously driven to convey the paper as shown in the above publication, the loop portion of the paper may be conveyed with it being strongly pressed against the guide plate. As a result, frictional noise may occur between the guide plate and the paper.

SUMMARY OF THE INVENTION An object of the present invention is to provide a paper feeding device that can prevent friction noise and reliably correct slanted paper feeding.

[Means to solve the problem]

The paper feeding device according to the present invention includes: a registration roller that adjusts the transport timing and diagonal feeding to send the paper downstream in the transport direction; and a transport roller that is disposed upstream of the registration roller in the paper transport direction and transports the paper. The apparatus includes a registration roller drive means for driving the registration rollers, a conveyance roller drive means for driving the conveyance rollers, a first control means, and a second control means.

The first control means controls driving means for each roller so that the paper is in a first curved state between the registration roller and the conveyance roller when the paper is conveyed to the registration roller. . The second control means also controls each roller to maintain the paper in a second curved state with a lower curved height than the first curved state when the paper is transported from the registration rollers to the downstream side in the transport direction. This is for controlling the driving means of the.

[Effect]

In the present invention, paper fed from a paper feed cassette or the like is transported by a transport row and temporarily stopped by registration rollers. Even after the leading edge of the paper comes into contact with the registration rollers, the transport rollers transport the paper for a certain period of time, and as a result, the paper bends between the registration rollers and the transport rollers and enters the first curved state.

This first curved state is achieved by making the loop amount of the paper large enough to prevent the paper from folding, and by strongly hitting the paper loop portion against the guide plate, the leading edge of the paper is sufficiently bitten by the registration rollers. This allows you to reliably correct skewed paper feeding.

On the other hand, when conveying the paper from the registration rollers to the downstream side in the conveyance direction, the sheet is brought into a second curved state in which the amount of loops is smaller than the first curved state, and the paper is transported while maintaining this second curved state.

As a result, when the paper is transported from the registration rollers to the downstream side in the transport direction, the contact of the paper loop portion against the guide plate is reduced compared to the first curved state, and the contact between the guide plate and the paper is reduced. Fricative noise is suppressed.

〔Example〕

FIG. 1 is an overall configuration diagram of a copying machine employing an embodiment of the present invention.

The copying machine main body 1 is placed on a mounting table 2.

A document table 3 is fixed to the upper surface of the main body of the copying machine, and a document presser 4 is attached to the upper part of the document table 3 so as to be openable and closable. A paper discharge tray 5 is installed on the left side of the copying machine main body 1, from which copied sheets are discharged.

Inside the copying machine main body 1, an optical system 6 for reading image information of a document is provided at the top thereof. The optical system 6 is composed of a light source, a mirror, a lens, etc.

A photosensitive drum 7 on which a static 1tWl image is formed is disposed approximately at the center of the copying machine body 1. Around the photoreceptor drum 7, there is a charging device 8 for charging the photoreceptor drum 7 to a predetermined charge. a developing device 9 that develops one image; a transfer device IO1 that transfers the toner image onto paper;
A paper separating device 11 for separating paper from the photosensitive drum 7 and a cleaning device 12 for removing toner on the photosensitive drum 7 are arranged in this order.

A paper discharge transport path 13 is provided on the downstream side in the paper transport direction of the image forming section, which includes the photoreceptor drum 7, the developing device 9, and the like. Between the paper discharge conveyance path 13 and the paper discharge tray 5,
Fixing device 1 that fixes the toner image on the ejected paper
4 and a paper discharge roller 15 are provided.

A plurality of paper feed cassettes 16 are removably mounted inside the mounting table 2 on which the copying machine main body 1 is mounted. Each of these paper feed cassettes 16 can accommodate paper of different sizes. A paper feed roller 17 for feeding paper from the paper feed cassette 16 is provided above the tip of the paper feed cassette 16 (on the right side in FIG. 1). Further, on the right side of each paper feed cassette 16 in the figure, a conveyance path 1B is provided for conveying the paper from the paper feed cassette 16 to the copying machine main body 1 side. The transport path 18 is located at the front end of each paper feed cassette 16.
Each section is provided with a feed roller 19 for feeding the paper sent out by the paper feed roller 17 to the upper part of the conveyance path 18.

On the other hand, a paper feeding device 20 is provided at the bottom of the copying machine main body 1 for feeding the paper sent from the conveyance path 18 on the side of the placement table 2 to the image forming section.

An enlarged cross-sectional configuration diagram of this paper feeding device 20 is shown in FIG. 2, and a perspective view is shown in FIG. 3.

In FIGS. 2 and 3, a registration roller 21 is provided adjacent to an image forming section composed of a photosensitive drum 7 and the like. This registration roller 21 is for supplying paper to the image forming section at a predetermined timing. A conveyance roller 22 is arranged upstream of the registration roller 2 in the paper conveyance direction. In addition, the registration roller 21
An upper guide plate 23 and a lower guide plate 24 are arranged between the transport roller 22 and the transport roller 22 . Below the lower guide plate 24 and just before the registration rollers 21, the paper is placed under the registration rollers 21.
A resist switch 25 is provided for detecting that the number 1 has been reached. Further, a feed switch 26 is provided immediately before the conveyance roller 22 to detect when the paper has been conveyed to the conveyance roller 22 portion.

Note that, as shown in FIG. 3, the upper guide plate 23 has a trapezoidal notch at the center on the upstream side in the paper conveyance direction. An elastic member 43 is provided so as to close the notch 23a.The elastic member 43 is designed to prevent the paper from being transported when the paper is small in width direction and thick, such as a postcard. This is to absorb the amount of loops and prevent the registration rollers 21 and conveyance rollers 22 from being rotated due to the stiffness of the paper.

FIG. 4 shows an exploded perspective view of the registration clutch 30 for driving and controlling the registration rollers 21.

As shown in this figure, the registration clutch 3o includes a boss 31 to which the tip of the shaft 21a of the registration roller 21 is connected, a collar 32 whose rotation is prohibited or permitted by a solenoid (not shown), and a collar 32 which is rotated by a drive motor (not shown). The spring 34 has one end fixed to the boss 31 and the other end fixed to the collar 32.

In this resist clutch, rotation of the collar 32 is prohibited when the solenoid is off, so that the driving force from the gear 33 is not transmitted to the shaft 21a. When the solenoid is turned on, rotation of the collar 32 is allowed, and the diameter of the spring 34 is reduced.
4. Connect the boss portion of the gear 33 inserted inside the boss 31 to the boss 31. Thereby, the rotation of the gear 33 is transmitted to the boss 31 to rotate the shaft 21a.

Further, FIG. 5 shows an exploded perspective view of a feed franc 420 for driving and controlling the conveyance roller 22.

This feed clutch 42 has the functions of both an electromagnetic clutch and a spring clutch. Nm
The first disk 35 constituting the clutch is fixed to the roller shaft 22a of the conveyance roller 22 by a spring pin 36. One end of a spring 38 is locked to the second disk 37, and a gear 39 connected to a drive motor
When the second disk 37 rotates, the second disk 37 also rotates. The first disk 35 and the second disk 37 can freely rotate relative to each other when no driving force is supplied. Then, when the electromagnet 40 is excited,
The electromagnetic force connects the first disk 35 and the second disk 37 and locks the second disk 37. The first disk 35 is held by the spring 38, and the driving force is applied from the gear 39 and the boss 41 fixed thereto to the roller shaft 22a via the spring 38 and the first disk 35.
It is intended to be transmitted to

The copying machine includes a control section 50 as shown in FIG. The control unit 50 includes a microcomputer including a CPU RAM, a ROM, and the like. The control unit 50 includes a print key 51 on a key panel (not shown) arranged on the top surface of the copying machine main body 1, and a feed switch 26 and a registration switch 2 shown in FIGS.
5, and a timing switch 5 that detects the drive of the optical system 6.
2 and other input sections are connected. In addition, the control unit 50
The resist clutch 30 shown in FIGS. 4 and 5 is shown in FIG.
The feed clutch 42, an optical system drive section 53 for driving the optical system 6, and other output sections are connected.

Next, the operation of the embodiment will be described according to the control flowcharts shown in FIGS. 7A and 7B and the timing chart shown in FIG. 8.

When a main switch (not shown) is turned on, the program is started, and initial settings such as setting the number of copies to "1" and setting the fixing device 14 to a predetermined temperature are performed in step S1.

Next, in step S2, it is determined whether the print key 51 has been pressed. If the print key 51 is not pressed, the process moves to step S3.

In step S3, it is determined whether a key other than the print key 51 has been pressed. If those keys are not pressed either, the process returns to step S2. That is, in step S2 and step S3, a manual command from the key is awaited.

If a key other than the print key 51 is pressed, the process moves from step S3 to step S4.

In step S4, various processes are executed depending on the input key, and when the process is completed, the process returns to step S2.

When the print key 51 is pressed, the program moves from step S2 to step S5, and this step S
In step 5, a copy subroutine is executed. In the copying subroutine, the paper is conveyed from the selected paper feed cassette 16 to the paper feed device 20 via the feed roller 19 and the conveyance path 18,
The paper is temporarily stopped by the registration rollers 21. Then, the optical system 6 scans the original on the original platen 3. Based on the image information obtained from this document, the photosensitive drum 7
An electrostatic latent image is formed thereon, and this electrostatic latent image is developed by a developing device 9. The developed image is transferred onto the supplied paper by the transfer device 10. The paper onto which one image has been transferred is subjected to a fixing process by the fixing device 14, and then is discharged onto the paper discharge tray 5.

After performing such a copying operation a number of times corresponding to the specified number of copies and executing all of the copying subroutines, the program returns to the main routine.

Next, the control performed in the paper feeding device 20 in the copying subroutine will be explained with reference to the flowchart of FIG. 7B and the time chart of FIG. 8. In addition,
In FIG. 8, PK is a print key signal, R is a signal for controlling the resist clutch 3o, F is a signal for controlling the feed clutch 42, F and S/W are signals from the feed switch 26, R, S /W indicates a signal from the registration switch 25, and T and S/W indicate signals from the timing switch 52 generated when the optical system 6 is driven.

First, in step S6, it is determined whether a certain period of time has elapsed from the time LO when the print key 51 was pressed and the time L1 has arrived. When time t1 comes, the process moves from step S6 to step S7.

In step S7, the registration clutch 30 is turned on and the registration roller 21 is rotated for the TI period. Next, the process moves to step S8, and the feed clutch 42 is turned on to rotate the conveyance roller 21.

Thereby, the paper conveyed from the paper feed cassette 16 side is sent to the registration roller 21 side by the conveyance roller 22.

Next, in step S9, it is determined whether the registration switch 25 is turned on by the paper. By turning on the registration switch 25, it is determined that the paper has reached the registration rollers 21. If YES is determined in step S9, the process moves to step SIO. Step S
In IO, after a period of T2 has elapsed from time t3 when the registration switch 25 was turned on, the feed clutch 42 is turned off and the rotation of the conveyance roller 22 is stopped. In this way, after the registration switch 25 is turned on, the conveyance roller 22 is further driven for the period T2, so the paper is bent between the registration roller 21 and the conveyance roller 22, and each part of the paper is A loop portion as shown by the dashed dot line in FIG. 2 is formed.

By setting this T2 period sufficiently long so that paper folding does not occur, the paper is sufficiently pressed against the registration rollers 21, and the inclination of the paper can be reliably corrected even when crimp feeding occurs. .

Next, in step 311, it is determined whether the timing switch 52 is turned on. When the optical system 6 is driven and the timing switch 52 is turned on, the process moves from step Sll to step 312. In step S12, after a period of T3 has elapsed from time t4 when the timing switch 52 is turned on, the registration clutch 30 is turned on and the registration rollers 21 are rotated.Next, the process moves to step S13, and after the registration rollers 21 are turned on, T4 When the period has passed, the feed clutch 42 is turned on and the conveyance roller 2 is turned on.
Rotate 1. The T4 period is approximately 1/3 of the T2 period for forming a paper loop.

In this way, by first driving the registration rollers 21 for the period T4, the amount of paper loops that have been formed up to that point is reduced, and therefore the pressing force between the paper loop portion and the guide plates 23 and 24 is weakened. . Then, when the loop amount decreases, the conveyance roller 22 is also driven, so
The paper is conveyed to the image forming section while this loop amount is maintained.

Next, in step 514, it is determined whether the registration switch 25 is turned off. When the trailing edge of the paper passes and the registration switch 25 is turned off, the process moves to step S15. In step S15, the resist switch 25
After the resist clutch 3 is turned off, the resist clutch 3 is turned off after a predetermined period has passed.
0 to turn off and stop the rotation of the registration roller 21
Next, in step S16, it is determined whether or not the feed switch 26 is turned off. If the 0th order paper is conveyed and the feed switch 26 is turned on, the process returns to step S9, and from step S9 to step S16 Repeat the action. Further, if it is determined in step S16 that the feed switch 26 is off,
Proceeding to step S17, the feed clutch 42 is turned off to stop the rotation of the conveyance roller 22.

With this paper feed control operation, when the paper is in contact with the registration rollers 21 and waiting, it is possible to secure a sufficiently large loop amount of the paper to reliably correct the slanted paper feed, and also to It is possible to sufficiently engage the roller 21.

On the other hand, when conveying the paper from the registration rollers 21 to the image forming section, the registration rollers 21 are driven before the conveyance rollers 22 to reduce the amount of paper loops, so that loops may occur between the paper and the guide plate. This suppresses the fricative noise that occurs.

Furthermore, it is possible to prevent the conveyance roller 22 from rotating earlier than the registration roller 21 due to variations in the drive system such as the clutches 30, 42, etc., and it is possible to prevent the paper from folding or wrinkling.

That is, generally a solenoid type clutch is provided in the drive section of the registration roller, and an electromagnetic clutch is provided in the drive means of the conveyance roller. As a characteristic of these clutches, when they are used for a long time and the temperature rises, there is a delay in the suction force, especially in the solenoid type clutches that drive the registration rollers, and the conveyance rollers may be driven before the registration rollers. be. In such a case, the amount of paper loops increases further, and especially when the paper is thick, Z folds may occur or wrinkles may occur in the paper.

In this embodiment, since the registration rollers 21 are driven before the conveyance rollers 22, it is possible to absorb the above-mentioned timing deviation and prevent the paper from folding or wrinkling.

Here, the relationship between the loop amount (72 periods) and the advance amount (CT4 interval) is shown in the table below. The amount should be about 1/2 to 1/4 of the loop amount,
Furthermore, if the distortion of the rear end image is taken into account, it is desirable to set it to about 1/4. However, as is clear from the data for the loop amount of 17.3, if the loop amount is too large, Z-folding will occur.

[Other Examples]

(a) In the above embodiment, the present invention was applied to a front loading type copying machine in which the paper feed cassette was housed inside the mounting table 2 below the copying machine main body 1. The same applies to the types provided.

(b) In the embodiment described above, the paper feeding device of the present invention was provided immediately before the image forming section, but it may be provided on another conveyance path.

For example, in the device shown in FIG. 1, a plurality of paper feed cassettes 1-16 are arranged vertically inside the mounting table 2, but when paper is fed from the lower paper feed cassette, the transport Diagonal paper feeding is likely to occur in the middle of the path 18. Therefore, for example, the second feed roller 19 from the top may be used as a registration roller, and the paper may be made to wait between it and the feed roller 19 one position below it to form a loop.

Even in such a case, if the drive start timings of these two rollers 19 are made the same as in the embodiment described above, friction noise can be prevented.

〔Effect of the invention〕

As described above, in the present invention, when paper is fed from the registration rollers to the image forming section, it is conveyed in a curved state with a lower curved height than the curved state in which the paper is waiting with the registration rollers. Therefore, when the paper is on standby, it is possible to reliably correct the slanted paper feed and to improve the state of the paper being caught in the registration rollers, and furthermore, when the paper is conveyed from the registration rollers to the image forming section, it is possible to suppress the friction noise of the paper.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a copying machine employing a paper feeding device according to an embodiment of the present invention, FIG. 2 is an enlarged sectional configuration diagram of the paper feeding device, FIG. 3 is a perspective view thereof, and FIG. Figure 5 is an exploded perspective view of the resist clutch, Figure 5 is an exploded perspective view of the feed clutch, Figure 6 is a control block diagram of the copying machine, Figures 7A and 7B are its control flowchart, and Figure 8 is paper feed. 5 is a timing chart of control. 20... Paper feeding device, 21... Registration roller, 22
... Conveyance roller, 25 ... Registration switch, 26
... Feet switch, 30... Resist clutch, 42... Feed clutch, 50... Control section. Patent applicant Yukio Ono, agent of Mita Kogyo Co., Ltd., patent attorney

Claims (1)

[Claims] (1) Registration rollers that adjust transport timing and diagonal paper feeding to feed the paper downstream in the transport direction; transport rollers that are disposed upstream of the registration rollers in the paper transport direction to transport the paper; and the registration rollers. a registration roller drive unit for driving; a transport roller drive unit for driving the transport roller; and a transport roller drive unit for driving the transport roller so that the paper is in a first curved state between the registration roller and the transport roller when transporting the paper to the registration roller. a first control means for controlling a driving means for each of the rollers; and a second control means for controlling a driving means for each of the rollers; and a second control means for controlling a drive means for each roller; A paper feeding device comprising: second control means for controlling driving means for each of the rollers so that the rollers are maintained in a curved state.