JPH03248170A - Double-sided printing mechanism - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Prior art (Figure 3) Means for solving the problem to be solved by the invention (1st working example (a) One example (Fig. 2) (b) Description of other embodiments Effect diagram of the invention) [Summary] Regarding a double-sided printing mechanism that transfers and prints an image on an image carrier to both sides of a recording medium, transfer of the surface of the medium The purpose is to shorten the conveyance path from the transfer position to the transfer position on the back side and enable double-sided printing by sequential printing. In a double-sided printing mechanism that includes a transfer section that transfers an image on the image carrier to a recording medium being conveyed, and that transfers and prints the image on both sides of the recording medium, the image carrier is used as the transfer section. It has first and second transfer sections that transfer data at different positions to the recording medium, and the recording medium transferred by the first transfer section is guided, and the recording medium is reversely directed toward the second transfer section. A reversing section is provided for conveying the image in the direction, and the first transfer section transfers the image onto the front surface of the recording medium, and the second transfer section transfers the image onto the back surface of the recording medium.

(Industrial Application Field) The present invention relates to a double-sided printing mechanism that transfers and prints an image on an image carrier onto both sides of a recording medium.

Copying machines, printers, facsimile machines, etc. using electrophotographic devices have conventionally printed only on one side of paper.

With the recent demand for resource saving, there is a desire for something that can print on both the front and back sides of paper, and a double-sided printing mechanism has been developed.

It is desired that such a double-sided printing mechanism has a simple configuration and easy control.

[Conventional technology]

FIG. 3 is an explanatory diagram of the prior art, showing an electrophotographic printer.

Paper cassettes 10, 11, and 12 each have different sizes (
B4 size, A4 size, 83 size) paper is stored.

The paper in the paper cassette 10.11.12 is taken out by the pickup roller 13.14.15 and transferred to the paper feed path P.
The alignment and image synchronization are performed by passing through I and hitting the standby roller 30.

On the other hand, the photosensitive drum 20 is rotating in the direction of the arrow, and after being uniformly charged by the corona discharge of the charger 21, a recorded image is irradiated with light by the laser optical system 22, and a potential image (latent image) is formed on the photosensitive drum 20. is formed.

The developing device 23 supplies a developer made of toner and carrier to the photosensitive drum 20 to turn the latent image into a toner image.

The paper is fed out from the standby roller 30 and brought into contact with the photosensitive drum 20, and the transfer unit 2
4 transfer corona discharge is applied to transfer the toner on the photosensitive drum 20 to the paper.

Furthermore, due to the separating corona discharge of the transfer section 24, the drum 20
Neutralize and separate the paper that is electrically attracted to the paper.

As a result, the paper is separated from the drum 20 by gravity, and the toner is fixed onto the paper by the thermal fixing device 26.

On the other hand, the remaining toner is removed from the photosensitive drum 20 by a cleaner, and the photosensitive drum 20 returns to the charging process.

In the case of single-sided printing, the sheet printed on one side (front side) in this manner is guided to the discharge path P4 by the switching valve 31 and discharged onto the stacker 40.

On the other hand, in order to perform double-sided printing, the switching valve 31 guides the sheet to the reversing path P2, and the sheet is introduced into the reversing section 33.

In the reversing section 33, the paper is reversely fed, sent to the return path P3 from the switching valve 32, and then sent from the return bus P3 to the paper feed path P1.
and abut against the standby roller 30.

Then, as described above, the image is transferred to the back side of the paper, and is ejected onto the stacker 40 from the post-fixing ejection path P4.

In the case of double-sided printing as described above, conventionally, after transfer printing is performed on one side of the paper, the paper is reversely fed, guided to the paper feed side, and printed on the back side.

Also, after transfer printing on the surface of the paper, a reversal pass P2, a reversal section 3
3. If the next printing is performed after waiting until the paper is reversed through the return bus P3, the overall printing speed will be slow.

If you want to increase the print processing speed, after printing the first line on the front side of the first sheet of paper, while the first sheet of paper is being reversed, take out the second sheet of paper and print the second sheet. Print the third page on the front side of the first sheet of paper, then print the second page on the back side of the first sheet of paper that is flipped, eject it, and then print the fourth page on the back side of the second sheet of paper that is flipped. A method was adopted to do so.

[Problem to be solved by the invention]

However, the conventional technology has the following problems.

(2) Since the transport path required from the front side transfer to the back side transfer is long, the amount of skew associated with paper feeding is large, making it difficult to accurately align the printing positions on the front and back sides.

■ Similarly, due to the long conveyance path, there are many inspection points when paper jams occur, and recovery takes time.

■ To increase the print processing speed, to print one page in the order of 3 pages, 2 pages, and 4 pages as described above, either transfer the print data to the printer in that order, or transfer the 4 pages to the printer. It is necessary to either provide memory to store the data, and in the former case, the control becomes complicated due to changing the order of data transfer, which substantially slows down the processing speed, and in the latter case, a considerable amount of storage memory is required. , leading to higher prices.

Therefore, an object of the present invention is to shorten the conveyance path from the transfer position on the front side of the medium to the transfer position on the back side, and to provide a double-sided printing mechanism that enables double-sided printing by sequential printing.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle of the present invention.

As shown in FIG. 1, the present invention includes an endless image carrier 20, an image forming section 2 that forms an image on the image carrier 20, and a recording medium on which the image on the image carrier 20 is conveyed. In a double-sided printing mechanism that transfers and prints the image on both sides of the recording medium, the transfer unit 24 includes a first transfer unit 24 that transfers the image to the image carrier 20 at different positions. , has second transfer sections 24a and 24b, and guides the recording medium transferred by the first transfer section 24a, and conveys the recording medium in the opposite direction toward the second transfer section 24b. A reversing section 34 is provided, and the first transfer section 2
4a, the image is transferred onto the front surface of the recording medium, and the second transfer section 24b transfers the image onto the back surface of the recording medium.

[Effect]

In the present invention, two transfer positions are provided on the image carrier 20, and the recording medium transferred at the first transfer section 24a is reversed at the reversing section 34 and sent to the second transfer section 24b.
The front and back sides can be printed consecutively.

Therefore, since the conveyance path is shortened, the amount of skew caused by feeding is small, and printing positions on the front and back sides can be accurately aligned.Also, in the event of a jam, it is easy to identify the paper position, reducing recovery time. I can do it.

Furthermore, double-sided printing can be achieved using the same sequence as normal single-sided printing, and complicated control for double-sided printing is freed.

〔Example〕 (a) Description of one embodiment FIG. 2 is a configuration diagram of an embodiment of the present invention.

In the figure, the same parts as those shown in FIGS. 1 and 3 are indicated by the same symbols, and 26a is a first heat fixing section, which is provided after the first transfer section 24a, The first transfer section 24a thermally fixes the toner image formed on the surface of the paper, and 26b is a second heat fixing section;
4b, and heat-fixes the toner image formed on the back surface of the paper by the second transfer section 24b.

30a is a first standby roller, and the first transfer section 24a
A second standby roller 30b is provided in front of the second transfer section 24b and waits the paper.

35 is a feed direction switching valve, which switches the paper from the first heat fixing device 26a to the single-sided discharge bus P7 or the reversing bus P5; 36 is a feed roller, which is provided at the entrance of the reversing section 340 and rotates in forward and reverse directions; 37 is a feed roller, which is installed on the single-sided discharge bus P7 and feeds the single-sided printed paper along the single-sided discharge bus P7; 38 is a discharge roller that discharges the printed paper to the stacker 40. It is something to do.

Note that the image forming section 2 includes a charger 21, a laser optical system 22,
It corresponds to the developing device 23 and the cleaner 25.

In this embodiment, the buses for double-sided printing are paper feed bus PI,
The reversing bus P5 and the ejecting bus P6 form approximately a figure 7 shape, with the reversing part 34 in the valley of the figure 7 and the transfer parts 24a and 24 on both sides.
b is provided.

Next, the operation of the configuration shown in FIG. 2 will be explained.

A sheet is fed out by one of the pick rollers 13, 14, 15 from any one of the desired cassettes 10, 11, 12, passes through the paper feed bus P1, and is abutted against the standby roller 30-a.

A laser optical system 2 is mounted on the photosensitive drum 20 according to image information.
Laser light is irradiated from 2, and a toner image is obtained in the developing section 23.

The standby roller 30a starts rotating in synchronization with the position of the toner image on the photosensitive drum 20, and feeds the paper.

A high voltage having a polarity opposite to the charged polarity of the toner is applied to the first transfer portion 24a, and acts to transfer the toner image on the photosensitive drum 20 onto the paper.

After passing through the first transfer section 24a, the paper is transferred to the first fixing device 2.
6a, the toner image is fixed.

If it is one-sided printing, the switching valve 35 is set to the one-sided discharge path P.
Since the sheet is fed in seven directions, the sheet after fixing is introduced into the single-sided discharge bus P7 by the switching valve 35, sent by the feed roller 37, and discharged to the stacker 40 by the discharge roller 38.

On the other hand, in the case of double-sided printing, the switching valve operates to send the paper in the direction of the reversing bus P5.

Therefore, the paper after fixing is introduced into the reversing bus P5 by the feed roller 36.

When the trailing edge of the paper reaches the feed roller 36, the feed roller 36 rotates in the opposite direction.

The paper thus introduced into the reversing section 34 is sent toward the second standby roller 30b by the feed roller 36,
It abuts against the second standby roller 30b.

At this time, the back side of the paper on which the toner image is not printed becomes the photosensitive drum side.

At this point, the image information of the front page is displayed on the photosensitive drum 2.
The writing of 0 has been completed, and writing of image information for the back page for double-sided printing has started.

The second standby roller 30b rotates in synchronization with the toner image on the photosensitive drum 20, and the second transfer section 24b transfers the toner image on the photosensitive drum 2o onto the back surface of the paper.

Then, the paper is fixed by the second thermal fixing device 26b, and is discharged from the discharge roller 38 to the stacker 4o.

At the point when this paper passes through the second fixing device 26b,
The next sheet is fed out of the cassette 10.11.12.

In this way, after transfer printing is performed on the front side of the sheet in the first transfer section 24a, the paper is reversed at the reversing section 34, and sent to the second transfer section 24b, where transfer printing is performed on the back side, thereby realizing double-sided printing.

When the paper is reversed by the reversing unit 34, the trailing edge of the paper becomes the leading edge and moves toward the second transfer position. Therefore, for example, if writing on the front side is done from the beginning of the page, writing on the back side will be the same as that of the page. You need to do it in reverse starting from the end.

That is, the bitmap memory of image data is read out from the top of the first page on the front side and from the end of the second page on the back side, so that the vertical relationship on the front and back sides is the same.

As described above, since the bus (transport path) for double-sided printing is shortened, the amount of skew associated with paper feeding is reduced, and the printing positions on the front and back sides can be aligned.

In addition, since the conveyance path is short, there are fewer inspection points when a jam occurs, and recovery can be done in a short time.

Furthermore, since the conveyance path is short and there are two transfer positions, it is possible to print sequentially on the front and back sides, so high-speed printing can be performed without changing the order of printed pages as in the past.

In this embodiment, the reversing path P5 of the reversing section 34 is formed into an S-shape because a straight line would increase the size of the device. It makes it possible to

(2) Description of other embodiments In the embodiments described above, the transfer unit is a corona discharger, but it may also be a transfer roller. Fuser 26
a and 26b are unnecessary.

Also, although the optical system has been explained using a laser optical system, it may also be an LED array, etc., and it has been explained using an electrophotographic system.
Other transfer printing methods such as a transfer electrostatic recording method can be used.

Although the present invention has been described above using examples, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, the following effects are achieved.

■ Since the conveyance path from the front side transfer position to the back side transfer position is short, the amount of skew caused by feeding can be reduced and the printing positions on the front and back sides can be aligned.

■ Because the conveyance path is short, there are fewer inspection points in the event of a jam, making recovery easier.

(2) Since two transfer positions are provided and the conveyance path is short, sequential printing can be performed in the same way as single-sided printing, so double-sided printing can be performed without requiring complicated control such as changing the order of printed pages.

[Brief explanation of drawings]

Figure 1 is a diagram of the principle of the present invention. FIG. 2 is a configuration diagram of an embodiment of the present invention. FIG. 3 is an explanatory diagram of the prior art. In the figure, 2-image forming section; 20-image carrier, 24.24a, 24b 34- Inversion section. transcription department, Figure 1 Conventional charcoal, explanatory diagram Figure 3

Claims (1)

[Claims] An endless image carrier (20), and an image forming section (2) that forms an image on the image carrier (20).
), and a transfer section (24) that transfers the image on the image carrier (20) to a recording medium being conveyed, and a double-sided printing mechanism that transfers and prints the image on both sides of the recording medium, The transfer unit (24) includes first and second transfer units (24a, 2) that transfer images to the image carrier (20) at different positions.
4b), and a reversing section (24b) for guiding the recording medium transferred by the first transfer section (24a) and transporting the recording medium in the opposite direction toward the second transfer section (24b). 3
4), wherein the first transfer section (24a) transfers an image onto the front surface of the recording medium, and the second transfer section (24b) transfers an image onto the back surface of the recording medium.