JP2748888B2 - Electrophotographic recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus, and more particularly to an electrophotographic recording apparatus such as a copying machine or a printer.

[0002]

2. Description of the Related Art For example, FIG.
2. Related Art An electrophotographic printer as shown in FIG. In the conventional example shown in FIG. 4, after the surface of the photosensitive drum 102 is uniformly charged by the charging unit 4, a laser beam 66 output from an optical system unit (not shown) is used.
, Part of the charge is eliminated to form an electrostatic latent image, and a developer (toner) is applied to the electrostatic latent image by a developing unit 68 to form a visible image (toner image) 18. ing.
After the development, the visible image 18 is transferred onto the recording medium 15 by the transfer roller 50, and the recording medium 15 is fixed to the fixing unit 5.
2 to fix the toner.

On the other hand, the toner remaining on the photosensitive drum 102 moves to the cleaning section 72 and is scraped off by the cleaning blade 38. Thereby, the photosensitive drum 1
02 is cleaned and charged again.

In the developing process, the toner 40 in the developing unit 68 is supplied by a supply roller 44 onto a developing roller 42 as a toner carrier. The excess toner is scraped off by the toner blade 46 to form a uniform thin toner layer 48. This toner layer 4
8 selectively adheres according to the magnitude of the charge on the surface of the photosensitive drum 102 to form a toner image 18.

The toner image 18 is transferred to the recording medium 1 by a transfer roller 50 to which a transfer bias (not shown) is applied.
5 at the same time as the toner image 1 by the transfer bias.
8 is electrostatically attracted to the recording medium 15.

The adsorbed toner image 18 is recorded on the recording medium 15.
And reaches the fixing unit 52 and passes between the heat roller 54 and the backup roller 56. At this time, the heat roller 54 is controlled by a heater 58 so as to have an appropriate constant temperature, and the toner image 18 is heated and melted when the recording medium 15 passes,
Fix to recording medium. The temperature of the heat roller 54,
The minimum necessary temperature at which the toner is fixed to the recording medium 15 is selected, and is usually selected within the range of 150 to 200 ° C. FIG.
Reference numerals 60 and 62 denote conveying rollers of the recording medium 15, and reference numeral 64 denotes a mixer.

[0007]

[SUMMARY OF THE INVENTION However, in the above prior art, in order to transfer the fixing are separated, there is a problem that causes the deterioration of printing quality is disturbed the toner image is slightly
Was .

In addition, since a separate fixing unit must be provided at a position distant from the transfer site, the configuration from development to fixing is complicated, and it is necessary to increase the conveyance accuracy of the recording medium.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrophotographic recording apparatus which can solve the disadvantages of the prior art, improve the printing quality, and reduce the size of the apparatus.
With that purpose.

[0010]

According to the first aspect of the present invention, a cylindrical photosensitive drum, a charging unit for uniformly applying a charge to the surface of the photosensitive drum, and a laser beam or the like are applied to the charged photosensitive drum. An optical system unit that forms an electrostatic latent image by irradiating a spot with part of an electric charge to form an electrostatic latent image, a developing unit that applies a developer to the electrostatic latent image on the photosensitive drum to form a visible image, and a photosensitive drum Development along the direction of rotation
The unit is located downstream of the unit,
Developing toner on the photosensitive drum on the recording medium
And a transfer / fixing unit for transferring and fixing the image.

A transfer / fixing unit is provided for the photosensitive drum.
Disposed downstream of the developing unit along the rotational direction.
A preheating applying means for the recording medium;
Heating means for fixing the developing toner on the recording medium
It is composed of Also, is the preheating application means external?
Equipped along the transport path of the recording medium inserted from
Dress belt-shaped heat transfer sheet and circulation of this heat transfer sheet
One and the other two guide rollers movably supported
Between the one and the other two guide rollers.
The specific range of the heat transfer sheet and recording medium
With the other guide roller pressed against the surface of the photosensitive drum.
And a pressure guide roller having a function of
You. Further, the above-mentioned heating means may be provided in the form of an endless belt.
With the other guide roller described above inside the heat transfer sheet
The configuration is such that it is disposed between the pressing guide roller .

According to a second aspect of the present invention, in the electrophotographic recording apparatus of the first aspect, the recording medium is provided.
Of the other guide roller located downstream of the
A cooling roller for cooling the recording medium . Also mentioned earlier
The heating means has a heating surface on the surface facing the photosensitive drum.
The heat transfer sheet has a structure in which the opposite side contacts the heat transfer sheet.
And a heater provided in the heat sink.
A configuration with a, has adopted a technique called.

According to the third aspect of the present invention, the above-mentioned claim is provided.
3. An electrophotographic recording apparatus according to claim 1, wherein
Indicates that the end surface on the photosensitive drum side described above is
The configuration is such that it is formed in a concave shape along the surface .

[0014]

The electrostatic latent image on the surface of the photosensitive drum is developed by the developing unit, and the recording medium preheated by the preheating applying means of the transfer / fixing unit is pressed against the surface of the photosensitive drum. Simultaneously with the pressing, the visible image is melted by the heat of the heating means, transferred onto the recording medium, and fixed by the pressing force.

[0015] Since the transfer and fixing unit has a cooling roller, visible image fixed by melting the recording medium is deprived of rapid heat cooling rollers, fixed to the early to the recording medium.

Further, since the heat transfer sheet of the preheating applying means is located before the portion where the recording medium is pressed and comes into contact with the heating means, the heat of the heating means is transferred to the heat transfer sheet by the contact, and the preheating is performed. Is stored.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention (an example of application to an electrophotographic printer) is shown in FIG. 1 (a cross-sectional view of a main part), FIG. 2 (an enlarged view of a main part), and FIG. It will be described based on the following. Here, the same portions as those of the above-described conventional example are denoted by the same reference numerals, and a duplicate description will be partially omitted.

As shown in FIG. 1, around a photosensitive drum 2 of an electrophotographic recording apparatus 1, a charging unit 4 for uniformly applying a charge to the surface of the photosensitive drum 2, and a laser beam An optical unit for forming a latent image by sequentially irradiating spots 6 to form part of the charge to form an electrostatic latent image; a developing unit 8 for applying a developer to the electrostatic latent image to form a visible image; A transfer / fixing unit 10 for performing transfer and fixing almost simultaneously and a cleaning unit 12 are sequentially arranged. In FIG. 1, reference numerals 14 and 16 indicate paper discharge rollers,
Reference numeral 15 denotes a sheet as a recording medium.

The charging unit 4 has a charging voltage VC.
(Not shown) is applied. After the photosensitive drum 2 is charged, a laser beam 6 is selectively irradiated from an optical system unit (not shown) to lose surface charges, thereby forming an electrostatic latent image. This electrostatic latent image is developed by the developing unit 8 as a toner image 18 (visible image).

The transfer / fixing unit 10 includes a preheating means 20 for preheating the paper 15,
Heating means 22 disposed opposite to the surface of the photosensitive drum 2
It is schematically composed of

The preheat applying means 20 is provided with an endless belt-shaped heat transfer sheet 24 which is in close contact with the sheet 15 on the upstream side of the photosensitive drum 2 in the conveying path of the sheet 15 and presses the sheet 15 against the surface of the photosensitive drum 2. And a guide roller group 26 for supporting the heat transfer sheet 24 in a circulating manner. The guide roller group 26 includes a large-diameter guide roller 26a.
And a cooling roller 26b having a large diameter and a hollow shape.
And the heat transfer sheet 24 together with the cooling roller 26b.
And a small-diameter guide roller 26c that presses the fixed range to the surface of the photosensitive drum 2. The cooling roller 26b is provided downstream of the heating unit 22 in the transport path of the sheet 15.

The heating means 22 has a hollow square heat sink 2 having a concave heating surface along the surface of the photosensitive drum 2 and having a contact surface with a heat transfer sheet 24 on the opposite side.
8 and a heater 30 provided in the heat sink 28.
It is composed of Since the heating surface of the heat sink 28 has a heating surface along the surface of the photosensitive drum 2 as described above, the pressing of the sheet 15 is not limited to the positive pressing by the heat transfer sheet 24, and This occurs when the paper 15 and the heat transfer sheet 24 pass through the gap between the sheets 15 in an overlapping state.

In FIG. 1, reference numerals 32a and 32b denote transport rollers for feeding the sheet 15, and reference numeral 34 denotes a transport plate. Then, the heat transfer sheet 24 and the sheet 1 are transported by the transport rollers 32a and 32b and the guide rollers 26a and 26c.
5 closely adheres before the press-contact portion.

Next, the transfer and fixing operations by the electrophotographic recording apparatus 1 will be described.

The toner image 18 formed by the developing unit 8 moves to the press-contact portion of the transfer / fixing unit 10 with the rotation of the photosensitive drum 2, and the transported paper 15
It is made to adhere to. Prior to this, when the paper 15 is conveyed in close contact with the heat transfer sheet 24,
And enters the press-contact portion in a preheated state. The paper 15 is further heated by the heating means 22 at the press contact portion. The heat of the heater 30 is transmitted to the sheet 15 through the heat sink 28 and the heat transfer sheet 24, so that the toner image 18 is heated and melted.

The heated and melted toner image 18 is transferred onto the sheet 15 by pressing and fixing, and then fixed on the sheet 15 by a cooling action in the conveying process. In this example, since the cooling roller 26b is provided downstream of the heating unit 22 in the transport direction of the sheet 15, the toner image 18 is rapidly cooled by the cooling roller 26b and fixed on the sheet 15. Then, together with the paper 15, the paper ejection rollers 14,
The paper is ejected through 16. The cooling roller 26
Although b may be solid, the cooling efficiency can be increased by making it hollow so that outside air can pass through.

Since the heat transfer sheet 24 comes into contact with the heating means 22 on the side opposite to the pressure contact portion, this contact makes the heating means 2
The heat of No. 2 is transmitted to the heat transfer sheet 24 and serves as a heat source for preheating. Since the heat transfer sheet 24 is in contact with the heating means 22 even at the press-contact portion, the heat transfer sheet 24 can also retain the amount of heat for preheating, but the heat transfer sheet 24 contacts the heating means 22 at a position different from the press-contact portion to obtain heat. Thus, the amount of heat for preheating can be reliably obtained. Further, if the heat transfer sheet 24 is brought into contact with the heating means 22 just before the portion where the sheet 15 is pressed and before the sheet 15 is in close contact with the sheet 15, a heat source for preliminary heating is separately provided. There is no need, and there is an advantage that the configuration can be simplified.

The residual toner remaining on the photosensitive drum 2 is transferred to the cleaning unit 12 as the photosensitive drum 2 rotates.
, Where it is scraped off by the cleaning blade 38. Then, the process moves to the charging step again.

Next, the temperature change on the surface of the sheet 15 will be described with reference to FIGS.

The horizontal axis of FIG. 3 represents the sections B to E shown in FIG. The heat transfer sheet 24 is heated in the section A,
This heat preheats the sheet 15 in the section B. Next, when the section 15 reaches the section C, the sheet 15 is rapidly heated by the heat of the heating unit 22, and the surface temperature of the sheet 15 rises above the fixing temperature. At this time, the toner on the photosensitive drum 2 is melted by heat and permeates the paper 15. After this, after being naturally cooled in the section D, it is further cooled in the section E by the cooling roller 26b,
It is separated after it is lowered to a temperature at which no offset occurs.

Note that the cooling roller 26b is not always necessary, and an air cooling effect during the conveyance process to the paper discharge rollers 14 and 16 can be used. Further, in this case, even if the heat transfer sheet 24 is not brought into contact with the opposite side of the heating means 22, the heat transfer sheet 24 can retain the heat amount for the preliminary heating by the heat transfer at the press-contact portion.

Further, in the above-described example, each component is shown in a specific shape and a specific arrangement form. However, the present invention is not limited to this, and can be appropriately set within a range where transfer and fixing can be performed almost simultaneously.

[0033]

As described above, according to the present invention, since the transfer and the fixing are performed almost simultaneously, the disturbance of the visible image due to the separation of the steps can be suppressed, and the print quality can be improved. be able to.

Further, according to the present invention, since there is no need to separately provide a fixing unit, it is possible to provide an unprecedented excellent electrophotographic recording apparatus capable of simplifying the configuration and reducing the size of the entire apparatus.

[Brief description of the drawings]

FIG. 1 is a partially omitted cross-sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a transfer / fixing unit disclosed in FIG. 1;

FIG. 3 is a graph showing a temperature transition of the recording medium disclosed in FIG.

FIG. 4 is a sectional view of a main part showing a conventional example.

[Explanation of symbols]

 Reference Signs List 2 photosensitive drum 4 charging unit 6 laser beam 8 developing unit 10 transfer / fixing unit 15 paper (recording medium) 18 visible image 20 preheating applying means 22 heating means 24 heat transfer sheet 26 guide roller group 26b cooling roller 40 toner (developer )

Claims (3)

(57) [Claims] 1. A cylindrical photosensitive drum, a charging unit for uniformly applying a charge to the surface of the photosensitive drum, and a laser beam or the like irradiating a spot on the charged photosensitive drum with a laser beam or the like to eliminate a part of the charge, thereby reducing static electricity. an optical system unit for forming a latent image, a developing unit that forms a visible image by applying a developer to the electrostatic latent image on the photosensitive drum, the rotational direction of the photosensitive drum
Along the downstream side of the developing unit and
Photosensitive drum on a recording medium fed along a
An electrophotographic recording apparatus comprising: a transfer / fixing unit for transferring and fixing a developing toner on a photosensitive drum;
The recording unit is disposed downstream of the developing unit along
A preheating applying means for the medium, and
Heating means for fixing the developing toner on the recording medium
The preheating means is configured to carry a recording medium inserted from outside.
Endless belt-like heat transfer sheet installed along the route
And one supporting the heat transfer sheet so that it can be circulated and moved.
The other two guide rollers and the one and the other two
The heat transfer sheet and recording device installed between the guide rollers
A certain area of the medium is sensed together with the other guide roller.
A pressure guide row with the function of pressing against the surface of the optical drum
And the heating means, the endless belt-shaped heat transfer sheet
And the other guide roller and the pressure contact guide row
Electrophotographic recording apparatus according to feature that is disposed between the La. 2. The method according to claim 1, wherein the recording medium is located downstream of a conveying path of the recording medium.
The other guide roller for cooling the recording medium.
A cooling roller, and the heating means is provided with a heating surface on a surface facing the photosensitive drum.
Yes and and structure the opposite side contacts the said heat transfer sheet
Heat sink and heat sink provided in this heat sink.
2. An electrophotographic recording apparatus according to claim 1 , wherein said apparatus is provided with a data processor. 3. The photosensitive drum side of the heating means.
The end surface of an electrophotographic recording apparatus according to claim 1 or 2, wherein it was characterized by being formed of <br/> is concavely along the surface of this photosensitive drum.