JPH04283763A - Form conveyance device - Google Patents

Abstract

PURPOSE:To offer the form conveyance device which is smoothly reducible in form conveying force. CONSTITUTION:The form conveyance device 26 is equipped with an image formation part 7 which forms an image on a form and an image fixation device 27 which fixes the form where the image is formed. Further, the device 26 is equipped with a conveyance belt 42 arranged between the image formation part 7 and image fixation device 27, a conveyance fan 43 which gives a form suction force to the conveyance belt 42, a 1st control means which drives both the conveyance belt 42 and conveyance fan 43, and a 2nd control means which drives the conveyance belt 42 and does not drive the conveyance fan 43.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a paper conveying device, in particular,
The present invention relates to a paper conveyance device of an image forming apparatus that includes an image forming section that forms an image on a sheet of paper and an image fixing section that performs fixing on the sheet.

0002

[Prior Art] Generally, a copying machine (an example of an image forming device)
The image forming apparatus includes an image forming section including a photoreceptor drum or the like that forms an image on paper, and an image fixing section that fixes the image on the paper. A paper transport device is provided between the image forming section and the image fixing section to transport the paper from the image forming section to the image fixing section. The paper transport device includes a transport belt that carries and circulates the paper, and a transport fan that applies a paper suction force to the transport belt. This paper transport device transports the paper on which an image has been formed in the image forming unit from the image forming unit to the image fixing unit.

In a so-called full-color copying machine, it is necessary to lower the image fixing speed in the image fixing section in the full-color mode than in the monochrome mode. Therefore, for example, in the full-color copying machine disclosed in JP-A-61-1746, it has become possible to use two types of fixing speeds: a low fixing speed in full-color mode and a high fixing speed in single-color mode. ing. In addition, in order to prevent the conveyance speed from the image forming section to the image fixing section from decreasing even in full color mode, the conveyance speed of the paper conveyance device is adjusted immediately before the paper is supplied to the image fixing section by the paper conveyance device. A configuration is adopted in which both the fixing speed of the image fixing section is reduced. Here, the reason why only the fixing speed is not reduced is to prevent the conveying speed of the paper conveying device from becoming relatively high, which may cause a jam or the like in the fixing device.

0004

[Problems to be Solved by the Invention] In the conventional image forming apparatus, in order to reduce the fixing speed while maintaining the transport speed of the paper transport device in the full color mode, it is necessary to , a configuration is adopted in which the conveying speed and fixing speed are switched to the lower speed side. For this reason, the speed of the paper conveyance device changes rapidly and a strong impact is applied to the paper before fixing, resulting in an increase in toner scattering.

[0005] An object of the present invention is to provide a paper conveyance device that can smoothly reduce paper conveyance force.

[0006]

[Means for Solving the Problems] A paper conveyance device according to the present invention is an image forming apparatus that includes an image forming section that forms an image on paper, and an image fixing section that fixes the image on the paper. This is a paper conveyance device.

[0007] This device includes a conveyor belt disposed between the image forming section and the image fixing section, a suction force applying means for applying a paper suction force to the conveyor belt, and a suction force applying means for applying a paper suction force to the conveyor belt. The apparatus includes a first control means that drives both the force applying means, and a second control means that drives the conveyor belt but does not drive the suction force applying means.

[0008]

[Operation] In the paper conveyance device according to the present invention, when a strong paper conveyance force is to be obtained, both the conveyance belt and the suction force applying means are driven by the first control means. As a result, the suction force applying means applies a paper suction force to the conveyor belt, so that the paper conveyance force by the conveyor belt becomes stronger.

On the other hand, when the conveying force is to be weakened, the second control means drives the conveying belt and does not drive the suction force applying means. As a result, the application of the paper suction force by the suction force applying means is stopped, so that the paper conveyance force by the conveyance belt is reduced. Here, the paper conveyance force is changed by driving/stopping the suction force applying means rather than by changing the rotational speed of the conveyance belt, so that the paper conveyance force can be smoothly reduced.

0010

[Embodiment] Fig. 1 shows a full-color copying machine in which an embodiment of the present invention is adopted.A document table 2 on which a document is placed is arranged at the top of a copying machine body 1. ,
A document presser 3 is provided on the upper surface of the document presser 3 so as to be openable and closable. Further, a paper discharge tray 4 is arranged on the left side of the copying machine main body 1 in the figure, a plurality of paper feed cassettes 5 are arranged on the lower part of the figure, and a tray 6 for bypass paper feeding is arranged on the right side of the figure.

Inside the copying machine body 1, there is a photosensitive drum 7.
is located. Around the photosensitive drum 7, in addition to a charging device, a transfer device, a paper separation device, and a cleaning device, developing devices 10, 11, and 1 are arranged vertically side by side.
A developing device 8 having 2 and 13 is provided. Here, the developing devices are, from above, a magenta developing device 10, a cyan developing device 11, a yellow developing device 12, and a black developing device 1.
It is 3. These developing devices 10 to 13 are fixed within a movable frame 9, and the movable frame 9 is connected to a moving mechanism (not shown).
It can be moved up and down.

A transfer drum 1 is provided below the photosensitive drum 7.
5 are arranged close to each other. The transfer drum 15 has a number of slits (not shown) in the circumferential direction at one end thereof.
is formed, and a photointerrupter 16 is arranged in the slit portion. This photo interrupter 1
6, the rotation status of the transfer drum 15 can be detected.

A laser unit 22 is arranged above the photosensitive drum 7. A laser beam from the laser unit 22 can be irradiated onto the upper end surface of the photoreceptor drum 7. On the other hand, below the document table 2, a reader 23 including a CCD element is arranged. The reader 23 is driven in the left-right direction in the figure and can scan a document placed on the document table 2. Image information obtained by the reader 23 is output to the laser unit 22 as an electrical signal.

The lower part of the transfer drum 15 and the paper feed cassette 5
Paper feed conveyance devices 24 and 25 are arranged between the bypass paper feed tray 6 and the bypass paper feed tray 6, respectively. Between the transfer drum 15 and the paper ejection tray 4, in order from the transfer drum 15 side,
A paper discharge conveyance device 26 and an image fixing device 27 are arranged. A separation claw 28 for separating the paper on the transfer drum 15 from the transfer drum 15 is provided between the transfer drum 15 and the paper discharge conveyance device 26 . Further, an ejection switch 17 is arranged between the image fixing device 27 and the paper ejection tray 4 to detect that the paper from the image fixing device 27 is ejected to the paper ejection tray 4. Note that the fixing device 27 includes a pair of rollers 31 and 32 inside a case 30. Both rollers 31 and 32 are generally placed above and below each other in pressure contact with each other, and have a heater inside. As a result, the paper supplied to the image fixing device 27 can be subjected to fixing processing.

The paper conveying device 26 has a pair of rollers 40 and 41 spaced apart from each other. roller 40
, 41, a conveyor belt 42 is stretched across them. A conveyance fan 43 is provided in a space surrounded by a conveyance belt 42 between both rollers 40 and 41. A large number of ventilation holes are formed in the conveyor belt 42, and when the conveyor fan 43 is driven, an air flow can be generated from above to below the conveyor belt 42. As a result, the paper placed on the conveyor belt 42 is suctioned and adhered to the conveyor belt 42 .

Furthermore, a conveyance switch 44 that projects upward from the conveyance belt 42 is arranged near the roller 41. The conveyance switch 44 is for detecting the front end and the rear end of the sheet conveyed by the conveyance belt 42.

This copying machine has a control section 5 as shown in FIG.
It has 0. The control unit 50 includes a CPU, ROM, and R.A.
It includes a microcomputer consisting of M, etc. The I/O port 51 of the control unit 50 is connected to the copying machine main body 1 (FIG. 1).
A keyboard 52 arranged on the top surface, a photointerrupter 16, a conveyance switch 44, an ejection switch 17, a drive section for the conveyance belt 42, a drive motor for the conveyance fan 43, and other input/output sections are connected. ing.

Next, the operation of the above embodiment will be explained. When the print key on the keyboard 52 is pressed, paper is supplied from the paper feed cassette 5 or the tray 6 to the transfer drum 15. Meanwhile, the image of the document placed on the document table 2 is read and a latent image is formed on the photoreceptor drum 7, and the latent image on the photoreceptor drum 7 is developed by one of the developing devices 10 to 13. be done. This developed image is transferred to a sheet of paper wrapped around the transfer drum 15. The paper on which the image has been completely transferred is transferred from the transfer drum 15 to the paper transport device 2.
6 to the fixing device 27. Note that when the full color mode is selected, all the developing devices 10 to 13
Magenta, cyan, yellow, and black are developed using . On the other hand, when the monochrome mode is selected, black development is performed using only the black developer 13.

In the fixing device 27, both rollers 31 and 32 are heated to a predetermined temperature, and as the paper passes between the rollers 31 and 32, a fixing process is performed. The paper that has been subjected to the fixing process is discharged onto the paper discharge tray 4. This completes the image forming operation.

During the above operation, the paper transport device 26
The control flow executed for this is shown in FIG. Here, among various controls by the control unit 50, the paper conveying device 2
Only those related to 6 are extracted and shown. When the print key on the keyboard 52 is pressed, step S1 in FIG.
At this point, the conveyor belt 42 and the conveyor fan 43 are driven. In step S2, the controller waits until the transport switch 44 is turned on. When the paper is supplied to the paper transport device 26 from the transfer drum 15 side and the paper is moved to the image fixing device 27 side by the transport belt 42, the front end of the paper eventually turns the transport switch 44 on. As a result, the determination in step S2 becomes Yes.

In step S3, it is determined whether the mode specified in advance via the keyboard 52 is the full color mode. If full color mode is not specified (single color mode), the determination is No and the process moves to step S4. On the other hand, if it is determined in step S3 that full color mode is designated, the process moves to step S5.

In step S5, the transfer switch 44 waits for a predetermined time to elapse. Here, a predetermined time (for example, 163 msec) is measured based on the measurement of the amount of rotation of the transfer drum 15 by the photointerrupter 16. Note that during this predetermined period of time, after the leading edge of the paper turns on the conveyance switch 44, the leading edge of the paper reaches the image fixing device 2.
This corresponds to the time just before the rollers 7 are caught between the rollers 31 and 32 of No. 7.

[0023] When the predetermined time has elapsed, the process moves to step S6, and the transport fan 43 is stopped. As a result, the suction force by the conveyor fan 43 is stopped, so the conveyor belt 42
conveying force decreases. Therefore, in the full color mode, the fixing speed of the image fixing device 27 (rollers 31, 32
Even if the rotational speed of the image fixing device 27 is set low, the sheet may slip on the conveyor belt 42, resulting in a paper jam or the like caused by the difference between the fixing speed of the image fixing device 27 and the conveying speed of the paper conveying device 26. Prevented.

In step S7, the transport switch 44 is turned to O.
Wait until it becomes FF state. That is, it waits until the trailing edge of the paper leaves the paper transport device 26. When the conveyance switch 44 is turned off, the process moves to step S8 and a predetermined time is counted. The processing here is similar to the processing in step S5, and the predetermined time is, for example, 163 msec. Once the predetermined time has elapsed, the process moves to step S9. In step S9, the transport fan 43 is turned on again. When the process in step S9 is completed, the process moves to step S4.

In step S4, the discharge switch 17 is turned to O.
Wait until it becomes FF state. If the discharge switch 17 is turned OFF, this means that all image forming operations such as fixing processing on the paper have been completed, so the process moves to step S10 and both the conveyance belt 42 and the conveyance fan 43 are stopped.

Here, when a strong conveyance force is required, the paper is conveyed without stopping the conveyance fan 43,
If a reduction in the conveying force is required, the conveying fan 43 is temporarily stopped based on the processing in steps S5 to S9. Therefore, in this embodiment, the paper conveyance force can be smoothly reduced without reducing the circulation speed of the conveyance belt 42. Therefore, even in the full color mode, the paper conveyance force is smoothly reduced, so that problems such as an increase in toner scattering do not occur.

[0027]

Effects of the Invention The paper conveyance device according to the present invention has a first control means that drives both the conveyance belt and the suction force applying means, and a second control means that drives the conveyance belt but does not drive the suction force applying means.
and control means. Therefore, according to the present invention, it is possible to realize a paper transport device that can smoothly reduce paper transport force.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view of a copying machine employing an embodiment of the present invention.

FIG. 2 is a schematic block diagram of the control unit.

FIG. 3 is a control flowchart showing a part of the control flow.

[Explanation of symbols]

1 Image forming device main body 7 Photoreceptor drum 8 Developing device 26 Paper conveyance device 27 Image fixing device 42 Conveyor belt 43 Conveyance fan

Claims (1)

[Claims] Claim 1: An image forming unit that forms an image on paper;
A paper conveying device for an image forming apparatus, comprising: an image fixing unit that performs fixing on a sheet of paper on which an image has been formed; A suction force applying means for applying paper suction force to the belt, a first control means for driving both the conveyance belt and the suction force applying means, and a first control means for driving the conveyance belt and the suction force applying means. A paper conveyance device comprising: a second control means that does not drive.