JP2778456B2 - Electrophotographic printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic printing method and apparatus, and more particularly, to an electrophotographic printing method and apparatus capable of printing and outputting a predetermined image pattern on both sides.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic printing apparatus which prints predetermined information on both sides is disclosed, for example, in Japanese Utility Model Laid-Open No. 193243/1987 and Japanese Patent Laid-Open No. 4-130387.
No. pp. 147-64.

[0003] Among these, the one disclosed in Japanese Utility Model Laid-Open No. Sho 62-193243 uses a pair of photosensitive drums and transfer relay rollers that rotate while contacting each other. That is, in the conventional example described in Japanese Utility Model Laid-Open Publication No. 62-193243, information to be transferred onto one side of the sheet is first transferred from the photosensitive drum to the transfer relay roller, and then the other side of the sheet is Then, information to be transferred is formed on the photosensitive drum, and thereafter, a sheet for printing is externally fed between the photosensitive drum and the transfer relay roller. As a result, information added to each outer surface of the photosensitive drum and the transfer relay roller is simultaneously transferred to the paper.

Japanese Patent Application Laid-Open No. 4-130387 discloses a method in which information to be transferred to one side of a sheet is first transferred from a photosensitive drum to a transfer relay belt, and then to the other side of the sheet. Information to be formed on the photosensitive drum,
A sheet for printing is sent from the outside between the photosensitive drum and the transfer endless belt. As a result, information added to the outer surfaces of the photosensitive drum and the transfer relay belt is simultaneously transferred to the paper.

[0005]

However, of the above-mentioned prior arts, for example, the one disclosed in Japanese Utility Model Laid-Open Publication No. Sho 62-193243 has a relatively large photosensitive drum and a relatively large transfer drum. In addition to this, it is necessary to provide other components such as fixing means around it, which not only increases the size of the entire equipment, but also takes into account the time for transfer to paper and fixing, etc. There is a disadvantage that the printing time is twice as long as in the case.

In the device disclosed in Japanese Patent Application Laid-Open No. 4-130387, since the transfer endless belt is used instead of the transfer relay roller, the size of the entire equipment can be reduced. In this case, there is a disadvantage that the fixing means must be provided at a place far away from the fixing area due to the influence of the transfer relay belt.
When the time for fixing and the like is taken into account, there is an inconvenience that the printing time, which is much more than twice as long as the case of single-sided printing, is required.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to improve the disadvantages of the prior art, in particular, to reduce the size of the entire apparatus and reduce the time required for transferring and fixing information, thereby shortening the time required for duplex printing. It is an object of the present invention to provide an electrophotographic printing method and an apparatus therefor.

[0008]

According to the present invention, one side has
With a photosensitive drum and a corresponding transfer roller,
In addition, a pair of fixing heating rollers are provided on the other side.
One of the fixing heat rollers and the transfer roller
And a transfer relay endless belt
The image pattern is transferred to one side by the photosensitive drum
Guides the fed sheet to a pair of fixing heat rollers.
With the endless belt for transfer relay described above.
Established. Then, the back pattern retransfer fixing step and the front pattern fixing step are executed at substantially the same timing. This aims to achieve the above-mentioned object.

[0009]

First, when the entire apparatus is operated, first, an image pattern on the photosensitive drum 2 to which the toner 2a has been applied and developed is transferred to the photosensitive drum 2 and an endless belt 4 for transfer relay.
Is transferred onto one surface of the sheet P fed during the first transfer (first transfer step). The sheet P on which a predetermined image pattern has been added in the first transfer step is guided by a guide mechanism 14 and sent to a fixing unit including the heat rollers 8 and 10 .

The toner on the photosensitive drum 2 is sequentially transferred by the transfer of the image pattern in the first transfer step, and when the toner on the photosensitive drum 2 is exhausted, the printing on the other surface of the sheet P is immediately performed. The operation of forming the back side image pattern is started.

The image pattern for the back surface formed on the photosensitive drum 2 is obtained after the above-described first transfer step is completed and the sheet P is separated from the photosensitive drum 2 or
Is separated from the photosensitive drum 2 and at the same time
Is transferred to the endless belt 4 described above (second transfer step).

Therefore, an image pattern to be printed on one side of the sheet P is fixed together with the transferred sheet P.
It is sent to the means part . The back side image pattern to be printed on the other side of the paper P is sent to the above-described fixing unit together with the transferred endless belt 4.

When the paper P passes between the heat roller 10 and the endless belt 4, the heat roller 8
By the heat and pressure of the heat roller 10, the fixing of the toner 2b on the sheet P and the transfer and fixing of the toner 2c on the endless belt 4 to the sheet P are performed simultaneously. That is, in the fixing unit , the image pattern applied to one surface of the paper P is fixed (front pattern fixing step), and at the same time, the image pattern for the back surface applied to the endless belt 4 at the same timing is applied to the paper P. Is re-transferred to the other surface and fixed together (reverse pattern re-transfer fixing step).

[0014]

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, reference numeral 2 denotes a photosensitive drum, and reference numeral 4 denotes an endless belt for transfer relay.
The endless belt 4 is bridged between a transfer roller 6 provided facing the photosensitive drum 2 and one heat roller 8 arranged on the opposite side. The transfer endless belt 4 is formed of a heat-resistant member and is relatively thin.

One heat roller 8 is always in contact with the other heat roller 10 via the endless belt 4. The one and the other heat rollers 8 and 10 constitute a fixing unit . Also, the transfer roller 6
In this embodiment, is mounted so as to be constantly in contact with the photosensitive drum 2 via the endless belt 4. Then, the photosensitive drum 2 and an endless belt 4 which comes into contact with the photosensitive drum 2
, The printing paper P is fed.

The paper P sent to the contact portion between the photosensitive drum 2 and the endless belt 4 is transferred via the guide mechanism 14 after the image pattern on the photosensitive drum 2 is transferred to one surface thereof. The sheet is sent to the above-mentioned fixing means .

The guide mechanism 14 is disposed in a semicircular arc from the contact portion between the photosensitive drum 2 and the endless belt 4 to the above-mentioned fixing means portion . Reference numeral 14A is a part of the guide mechanism 14 arranged on a semicircular arc, and indicates a guide plate arranged outside.

In the guide plate 14A, for example, the upper end portion and the lower end portion of the sheet P (the portion to which no toner is applied) are brought into contact with the guide plate 14A and guided by the guide plate 14A to form the fixing means . It is to be sent.

Reference numeral 14B denotes a part of the guide mechanism 14 arranged on a semicircular arc, and a guide plate arranged inside. In this embodiment, the inner guide plate 14B is provided with a normal guide plate. For example, the inner guide plate 14B is formed of a porous transfer endless belt, and the transfer endless belt side is weakly negatively pressured. Set the state and fix the paper while fixing the paper.
A sheet separating mechanism for separating the sheet P from the conveying endless belt may be provided upstream of the fixing unit 12 while feeding the sheet P into the step portion .

Here, in addition to the above-described components, toner supply means, an optical system for forming an electrostatic latent image on a photosensitive drum, and other components required particularly for an electrophotographic printing apparatus. Is provided as it is in this embodiment.

Next, the operation of the above embodiment will be described.

First, when the entire apparatus is operated, first, an image pattern on the photosensitive drum 2 to which the toner 2a has been applied and developed is transferred to a paper sheet fed between the photosensitive drum 2 and an endless belt 4 for transfer relay. It is transferred to one surface of P (first transfer step). Reference numeral 2b indicates the toner transferred to one surface of the sheet P.

The sheet P on which a predetermined image pattern is provided in the first transfer step is guided by the guide mechanism 14 and is fixed.
It is sent to the means part .

The toner on the photosensitive drum 2 is sequentially transferred by the transfer of the image pattern in the first transfer step, and as soon as the toner on the photosensitive drum 2 runs out, the above-described printing on the other surface of the sheet P is immediately performed. The operation of forming the back side image pattern is started.

The image pattern for the back surface formed on the photosensitive drum 2 is obtained after the above-described first transfer step is completed and the sheet P is separated from the photosensitive drum 2, or
Is separated from the photosensitive drum 2 and at the same time
Is transferred to the endless belt 4 described above (second transfer step). Reference numeral 2c indicates the toner transferred to the endless belt 4.

Therefore, the image pattern to be printed on one side of the sheet P is fixed together with the transferred sheet P.
It is sent to the means part . The back side image pattern to be printed on the other side of the paper P is sent to the above-described fixing unit together with the transferred endless belt 4.

When the paper P passes between the heat roller 10 and the endless belt 4, the heat and pressure of one heat roller 8 and the other heat roller 10 cause the toner 2b on the paper P to be fixed. The transfer and fixing of the toner 2c on the endless belt 4 to the paper P are performed simultaneously.

That is, in the fixing unit , the image pattern applied to one surface of the paper P is fixed (front pattern fixing step), and at the same time, the image pattern for the back surface applied to the endless belt 4 at the same timing. The image is retransferred and fixed together on the other surface of the paper P (back pattern retransfer fixing step). Here, reference numeral 2f indicates toner forming a part of an image pattern as a front pattern fixed on the paper P, and reference numeral 2e indicates a part of a back image pattern as a back pattern fixed on the paper P. This shows the toner to be formed.

As described above, in this embodiment, since the paper P is separated from the photosensitive drum 2 and, at the same time, is transferred from the photosensitive drum 2 to the endless belt 4 for transfer relay, the second transfer step is performed. On the photosensitive drum 2 side, a transfer pattern can be continuously formed and transferred on the outer surface of the photosensitive drum 2 without interruption, and in the fixing unit , the front pattern fixing step and the back pattern retransfer fixing step are simultaneously performed. Therefore, the transfer and fixing steps for the paper P can be continuously performed, and therefore, the time required for the transfer and fixing can be significantly reduced.

[0031]

As described above, according to the present invention,
On one side, a photosensitive drum and a corresponding transfer roller
And a pair of fixing heat rollers on the other side.
First, one of the fixing heating rollers of the fixing heating roller is used.
Transfer endless belt installed between the roller and the transfer roller.
And the secondary transfer and fixing of the back surface of the paper and the fixing of the front surface of the paper are performed simultaneously , so that the configuration of the entire apparatus is simplified, and therefore, the size of the apparatus can be reduced, and the transfer and fixing can be performed. It is possible to provide an unprecedented excellent electrophotographic printing method and apparatus capable of shortening the entire time required for double-sided printing by shortening the time.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of an embodiment of the present invention.

[Explanation of symbols]

 2 photosensitive drum 4 endless belt as belt-type relay transfer body 6 transfer roller 8, 10 heat roller 14 guide mechanism P paper

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 15/00 G03G 15/16

Claims (2)

(57) [Claims] An image forming apparatus comprising: a photosensitive drum on one side and a transfer roller corresponding to the photosensitive drum; and a pair of fixing heating rollers on the other side. a said transfer roller and the erection transcription relay endless belt, a guide mechanism for guiding the image pattern on one side by the photosensitive drum is transferred sheet to the pair of fixing the heating roller portion, the transfer Along with the endless belt for relay
The transfer endless belt is provided with an image pattern on one surface.
The pattern for the back image is applied to the back side of the paper
An electrophotographic printing apparatus that relays the image from the photosensitive drum . 2. The transfer relay endless belt according to claim 1, wherein
Characterized by being formed of a heat resistant member
Item 1. An electrophotographic printing apparatus according to Item 1.