JPH0251183B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printing apparatus that applies the principle of electrophotographic copying.

It has been known for a long time that printing can be performed using an electrophotographic method. For example, there is a zero printing system as disclosed in US Pat. Further, as an improvement on these, there is Japanese Patent Application No. 116766/1983. special request
No. 55-116766 discloses an electrophotographic copying mode in which an electrostatic latent image is formed by imagewise exposure on a photosensitive sheet each time according to a preset number of copies to be obtained from the same original, and a first imagewise exposure. It is disclosed that a printing mode is selected and operated using a printing master that forms a fixed toner image on a photosensitive sheet.

This method will be explained in further detail with reference to FIG. The printing mode consists of a plate-making process in which a toner image is fixed on a photosensitive sheet to create a printing master, and a printing process in which a large number of sheets are electrostatically printed at high speed using the printing master.

The print master is created as follows. After the photosensitive sheet 10 is wound around the drum 1 and supported, it is charged by a charging corotron 4. Next, the original on the original platen 3 illuminated by the original illumination lamp 14 is passed through the projection lens 2 onto the photosensitive sheet 1.
0 to form an electrostatic latent image. Next, the latent image is visualized by a developing device 5, and the toner image is fused and fixed onto photosensitive paper 10 by an infrared fixing device 7, thereby forming a printing master.

Electrostatic printing of a large number of sheets using this printing master is performed in the following manner. A printing master having a fixed toner image on a photosensitive sheet is charged with a charging corotron 4 and exposed uniformly over the entire surface with a uniform exposure lamp 13.

The charge on the uniformly charged photosensitive sheet 10 is
The toner image is washed away by uniform exposure leaving only the insensitive and non-photoconductive toner image areas. Therefore, a printing master is formed in which only the toner image portion has an electric charge, and this is visualized by the developing device 5. Next, transfer paper 1
1 is sent to the transfer unit in synchronization with the rotation of the rotary drum 1, and the toner image on the print master is transferred to the transfer paper by the transfer corotron 6, and then converted into a fixed image by the fixing device 9 and transferred to the paper output tray. A copy can be obtained by On the other hand, the residual toner on the print master after transfer is cleaned by the cleaning device 8, and one printing cycle is completed.

The printing cycle is then repeated for the number of copies required.

On the other hand, the copy mode is used when the number of copies required from the same document is relatively small. In other words, if print mode is used in such a case, the time required to form a print master will increase the time required to obtain one copy, and therefore the time required for each copy will be long. Since it is faster to take copies using an electrophotographic copying machine, the following copying mode is used.

In the copying mode, as shown in FIG. 1, after the photosensitive sheet 10 is wrapped around a drum and supported, it is charged by the charging corotron 4, and then the original on the original platen 3, which is illuminated by the original illumination lamp 14, is projected through the projection lens 2. An electrostatic latent image is formed by projecting it onto the photosensitive sheet 10.
Next, the latent image is visualized by a developing device 5, transferred to a transfer paper 11 sent out in synchronization with the rotation of the drum 1 by a transfer corotron 6, and fixed by a fixing device 9 to obtain a copy.

On the other hand, the residual toner on the photosensitive sheet after the transfer is cleaned and removed by the cleaning device 8, and one copying cycle is completed. The copying cycle is then repeated for the required number of copies. still,
This cleaning may be carried out by the cleaning device 8, but it may also be carried out by a cleaning and developing machine as disclosed in Japanese Patent Application No. 144785/1985.

Incidentally, it is desirable that the scanning speed in the above-mentioned print mode and copy mode be as fast as possible, since this will shorten the time required to obtain a copy. The scanning speed in print mode is mainly determined by the ability of the fixing device 9, and is approximately 300 mm/sec to 500 mm/sec.
(This is called the first scanning speed.). The scanning speed in copy mode is mainly determined by the sensitivity of the photosensitive sheet, and is approximately 100
The scanning speed is about mm/sec to 200 mm/sec (this is called the second scanning speed).

However, the following problems arise when using the copy mode and the print mode differently in this way. This is because there is a large difference in heating conditions (difference in scanning speed) between the copy mode and the print mode when fixing the toner image on the transfer paper with the fixing device 9. Therefore, in the print mode, the toner image on the transfer paper This tends to cause fusing failures in which the toner is not sufficiently melted, and in the copy mode, the toner on the transfer paper is excessively melted, which causes the toner to adhere to the heating roll of the fixing device 9, causing problems in the next copy print image. It was easy to cause contamination.

The present invention provides an electrostatic printing device that does not have the above drawbacks. That is, the present invention provides a heat roll fixing device that rotates at a first scanning speed that matches the printing mode in an electrostatic copying printing device that selectively operates both an electrophotographic copying mode and an electrostatic printing mode as described above. The transfer paper transport path between the transfer section that transfers the toner image on the photosensitive sheet to the transfer paper and the fixing section of the heat roll fixing device is set to be larger than the maximum length of the transfer paper used, and when in copy mode, The present invention is characterized by comprising a transfer paper conveying device that rotates at a second scanning speed in accordance with the copy mode until the trailing edge of the transfer paper leaves the transfer section, and then rotates at the first scanning speed. .

The present invention will be explained in detail based on the attached FIGS. 2 and 3.

In FIG. 2, reference numeral 21 denotes a rotating drum, and the photosensitive sheet 30 is wound and supported around the circumferential surface of the drum, and is housed inside the drum in a rolled form at both ends. Around the drum 21 are a removal corotron 28, a charging corotron 24, a uniform exposure lamp 33, a developing device 25, a transfer corotron 26, and a plate-making fixing device 2 for fixing the toner image on the photosensitive sheet 30.
7 grade equipment is installed.

First, I will explain the copy mode. The photosensitive sheet 30 supported on the circumferential surface of the rotating drum 21 is fully charged by the charging corotron 24 and placed on the document table 2.
3 is projected onto the photosensitive sheet 30 via the projection lens 22 in synchronization with the rotation of the drum 21, forming an electrostatic latent image. Next, the latent image is processed by developing machine 2.
5, and the toner image on the photosensitive sheet 30 is transferred to the transfer paper 31 by the transfer corotron 26.
transcribed into. Next, the transfer paper 31 is fed into the heat roll fixing device 29.

In the present invention, the transfer paper conveying device 34 that conveys the transfer paper 31 from the transfer section to the heat roll fixing device 29 is enlarged, and the length of the transfer paper conveyance path from the transfer section to the heat roll fixing device 29 is adjusted to match the transfer paper used. For example, the transfer paper 30 is longer than the maximum size of 420 mm for an A3 plate, and therefore the transfer paper 30 is simultaneously transferred to the rotating drum 2 in both the transfer section of the photosensitive sheet conveyance path and the heat roll fixing device 29.
1 will not be supported. The transfer paper 31 transferred in the transfer section is transferred by a transfer paper conveying device 34 that rotates at approximately the same speed as the circumferential speed of the drum 21 in the copy mode.
The transfer paper is transported at the second scanning speed until the trailing edge of the paper leaves the transfer section, and after the trailing edge of the paper leaves the transfer section, the speed is increased to the first scanning speed that matches the scanning speed of the print mode. transported.

The heat roll fixing device 29 rotates at the first scanning speed, and therefore, the conveying speed is adjusted on the transfer paper conveying device 34, so that the unfixed toner image on the transfer paper can be fixed without being disturbed. box office.

Adjustment of the scanning speed of the conveying device 34 is carried out as shown in FIG. Transfer paper conveyance device 34
A sprocket 37 receives the transmission drive from the rotation system of the drum 21, a one-way clutch 38 that transmits rotation in only one direction, a first rotation shaft 35 that drives the conveyor belt 41, and a rotation system of the heat roll fixing device 29. A sprocket 39 that receives the transmission drive, an electromagnetic clutch 40 that switches its rotation, and a second rotating shaft 36 that drives the conveyor belt 41 at increased speed.
The above-mentioned adjustment of the scanning speed is controlled by turning the electromagnetic clutch 40 ON and OFF. Further, the residual toner image on the photosensitive sheet 30 that has not been transferred is re-charged by the static eliminating corotron 28, neutralized by the uniform exposure lamp 33, and then cleaned and removed by the cleaning/developing device 25. , and one copying cycle is completed.

Next, the plate-making process and printing mode will be explained.
First, a toner image is formed on the photosensitive sheet.
The steps up to that point are almost the same as those in the copy mode described above. Photosensitive sheet 30 with charged corotron 24
The entire surface of the document is charged, and the document image on the document table 23 is projected onto the photosensitive sheet 30 to form an electrostatic latent image, which is then visualized by a developing machine. Transfer corotron 26
The toner image on the photosensitive sheet 30 is heated and melted by a plate-making fixing device (in particular, the flash fixing device 27 here), and the toner image on the photosensitive sheet 30 is omitted.
Fixed on the 0 side. In the above manner, the original platen 23
A print master corresponding to the above original is created.

Next, in the printing cycle, the aforementioned printing master is charged by the charging corotron 24 and the entire surface is exposed to light by the uniform exposure lamp 33, so that the charge on the photosensitive sheet is discharged leaving only the portion where the toner image is present. Next, the electrostatic latent image is visualized by the developing device 25 and transferred to the transfer paper 3.
1 to the transfer section in synchronization with the rotation of the rotary drum 21, and the transfer corotron 26 transfers the toner image on the printing master onto the transfer paper, and further, the toner image is transferred to the transfer paper at a first scanning speed that is approximately equal to the circumferential speed of the drum 21. The sheet is fixed by a heated roll fixing device 29 which rotates at 300 degrees, and then sent to a paper discharge tray 32.

In addition, residual toner images remaining on the print master without being transferred can be removed inside the developing machine 25 by performing development while cleaning with the developing machine cleaning device 25, as disclosed in Japanese Patent Application No. 144785/1985. will be collected.

As described above, the electrostatic copy printing apparatus of the present invention is configured to drive from both the drum 21 side and the fixing device 29 side, and a one-way clutch is provided for the rotation shaft on the drum side, and the fixing device side is rotated. An electromagnetic clutch is installed on the shaft, and the conveyance speed can be controlled by turning the electromagnetic clutch ON and OFF, and the length of the conveyance path of the transfer paper between the transfer section and the heat roll fixing section can be adjusted depending on the length of the transfer paper being used. By making the length larger than the length of the paper, it is possible to absorb and adjust the difference in scanning speed, and it is equipped with a heat roll fixing device that always rotates under a constant condition, that is, only at the first scanning speed. , which makes it possible to use both of the above-mentioned modes.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional electrostatic printing device, FIG. 2 is a sectional view of an example of an electrostatic copying printing device of the present invention, and FIG. 3 is a partially exploded perspective view of a conveying device used in the device shown in FIG. It is. Code in the figure: 1, 21...Rotating drum; 2, 22
...Projection lens; 3, 23 ... Document table; 4, 24
...Charging corotron; 5, 25...Developing machine; 6,
26...Transfer corotron; 7...Infrared fixing device;
8... Cleaning device; 9... Fixing device; 1
0,30...Photosensitive sheet;11,31...Transfer paper;12,32...Exit tray;13,33...
Uniform exposure lamp; 14...Original illumination lamp; 27
. . . Flash fixing device; 28 . Side sprocket; 38...
...One-way clutch; 39...Fuser side sprocket; 40...Electromagnetic clutch; 41...Transport belt.

Claims (1)

[Claims] 1 Electrophotographic copying mode in which a photosensitive sheet is charged and exposed each time to form an electrostatic latent image, and development, transfer, and fixation are repeated, and a printing master formed by fixing a toner image on a photosensitive sheet is charged and In an electrostatic copying printing device that selectively operates between an electrostatic printing mode in which an electrostatic latent image is formed by uniform exposure, and development, transfer, and fixing are repeated, a thermal roll fixing device rotates at a scanning speed that matches the printing mode. The transfer paper transport path between the transfer section and the fixing section is set to be larger than the maximum length of the transfer paper used, and in copy mode, the transfer paper is not copied until the rear edge of the transfer paper leaves the rear edge of the transfer section. An electrostatic copying printing apparatus comprising a transfer paper conveying device that rotates at a scanning speed that matches the print mode and thereafter rotates at a scanning speed that matches the printing mode.