JPH11125940A - Electrophotographic printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of wrinkles of a printing medium and further, the occurrence of a jam, and to enhance the quality of an image. SOLUTION: This electrophotographic printer is provided with first and second rollers for carrying the printing medium, a photoreceptor drum 13 disposed on the downstream side from the first/second rollers, a transfer roller 14 and third and fourth rollers which are arranged on the downstream side from the drum 13 and the transfer roller 14 and rotated to carry the printing medium. The tangent of the first and second rollers is inclined toward a reference line M that connects the first contact part between the first and second rollers with a transferring part K2. The sagging of the printing medium occurs between the first contact part and the transferring part K2 and when the feed rate of the printing medium at the transferring part K2 is larger than that at the first contact part, the sagging of the printing medium is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic printer.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic printer, an electrostatic latent image is formed by exposing the surface of a photosensitive drum uniformly and uniformly charged, and the electrostatic latent image is developed to form a toner. An image is formed, the toner image is transferred to a recording medium, and fixed. FIG. 2 is a schematic diagram of a medium transport route of a conventional electrophotographic printer.

In the figure, reference numeral 11 denotes a pressure roller, 1
Reference numeral 2 denotes a registration roller, 13 denotes a photosensitive drum, 14 denotes a transfer roller, 15 denotes a heat roller, 16 denotes a backup roller, and 17 denotes a sheet as a print medium. The paper 17 fed by a hopping roller from a paper cassette or a front feeder unit (not shown) is sent to a registration unit K1 between a pressure roller 11 and a registration roller 12, which are disposed in pressure contact with each other and opposed to each other. Transfer section K between photosensitive drum 13 and transfer roller 14
2 and then to a fixing section K3 between the heat roller 15 and the backup roller 16.

A pressure roller 11 and a registration roller 12, and a photosensitive drum 13 and a transfer roller 1
4 is rotated by gear driving, and the heat roller 15 and the backup roller 16 are rotated by co-rotation. By the way, in the transfer section K2, when the transfer is performed by the ozone-less contact transfer method using the transfer roller 14, a transfer roller is added compared to the case where the transfer is performed by the corotron method, Paper 17 in transport of paper 17
Is reduced by that amount.

Accordingly, the peripheral speed of the registration rollers 12 and V _R, the peripheral speed of the transfer roller 14 and V _T, the peripheral speed of the heat roller 15 is taken as V _H, the peripheral speed balance of the rollers unit It is desirable that V _R ≧ V _T > V _H.

The peripheral speed V of the heat roller 15
If _H is equal to or higher than the peripheral velocity V _T of the transfer roller 14, the paper 1
7 is stretched in the direction of arrow B, and wrinkles are likely to occur. Further, since the transfer roller 14 is formed by a rubber roller having a low hardness such as a sponge, it is difficult to increase the accuracy of the outer dimensions in manufacturing. Therefore, even if a difference in speed between the left and right in the width direction of the transfer roller 14 (a decrease in running balance) occurs due to a variation in external dimensions, wrinkles are likely to occur on the sheet 17.

On the other hand, if the peripheral velocity V _T of the transfer roller 14 is higher than the peripheral velocity V _H of the heat roller 15, but the wrinkles hardly occur, the paper between the fixing portion K3 and the transfer unit K2 1
7, a slack in the direction of arrow A is formed. In particular, the slack accumulates on the long sheet 17 and a developing unit (not shown)
Unfixed toner touches the heat roller 15 and the like, so that contamination is likely to occur. Therefore, as sagging is not cumulative, the peripheral velocity V _T of the transfer roller 14 the heat roller 1
From 5 peripheral velocity V _H is slightly higher.

FIG. 3 is a diagram showing a medium transport route between a registration section and a transfer section in a conventional electrophotographic printer, and FIG. 4 is an enlarged view of the registration section in a conventional electrophotographic printer. In the figure, 11 is a pressure roller, 12
Is a registration roller, 13 is a photosensitive drum, 14 is a transfer roller, 17 is paper, 25 is an upper guide, and 26 is a lower guide.

[0009] Sheets 17 fed by a hopping roller from a sheet cassette or a front feeder section (not shown) are sent to a registration section K1 between a pressure roller 11 and a registration roller 12 which are disposed in pressure contact with each other and opposed to each other. In the resist portion K1,
After the skew of the sheet 17 is corrected, the sheet 17 is conveyed in the direction of arrow C toward the transfer portion K2 between the photosensitive drum 13 and the transfer roller 14. The feed amount of the sheet 17 in the registration section K1 and the sheet 1 in the transfer section K2
The ratio with the feed amount of 7 is set to 1: 1.

Then, the tangent line between the pressure roller 11 and the registration roller 12 coincides with the tangent line between the photosensitive drum 13 and the transfer roller 14. FIG. 5 is a diagram showing a medium transport route between a transfer section and a fixing section of a conventional electrophotographic printer, and FIG. 6 is an enlarged view of a fixing section in a conventional electrophotographic printer. In the figure, 13 is a developing unit 20
, A transfer roller, 15 is a heat roller, 16 is a backup roller, 21 is a heat-resistant resin-made fixing guide provided near the heat roller 15, and 22 is a chassis. is there.

The leading end 21 of the fixing guide 21
a, as the paper 17 passes through, and when the paper 17 reaches the fixing unit K3, the paper 1
7 at a predetermined angle and the shortest route between the photosensitive drum 13 and the heat roller 15, that is, the point a and the point b so that the front end of the heat roller 7 can be reliably engaged with the heat roller 15 and then bitten. And is formed in a region below the dashed line connecting.

[0012]

However, in the conventional electrophotographic printer, the transfer roller 14
Since it is difficult to increase the accuracy of manufacturing external dimensions of it can not be slightly higher than the peripheral velocity V _H of the heat roller 15 peripheral speed V _T of the transfer roller 14. Therefore, when the running load of the sheet 17 such as the peripheral speed difference in the width direction of the sheet 17 and the friction feed changes, the sheet 17
May fluctuate, the paper 17 may be stretched, and wrinkles may occur.

Particularly, a thin sheet (B4 size, A3 size) having a long width (55 kg, 70 kg) in the width direction and the conveyance direction.
In the case of using an A3 size, A3-size (328 × 453 [mm]) 17 or the like, the transport speed of the paper 17 tends to fluctuate. When the sheet 17 is sent to the fixing unit K3, the sheet 1
The toner adhering to the back side of the fixing guide 21
1a and adheres to the tip 21a. Then, the toner is piled up and solidified at the leading end portion 21a, and the solidified toner 23 is formed.
Jams the solidified toner 23 when its front end is caught.

Before the heat roller 15 and the backup roller 16 are engaged, the heat roller 1
5 is not uniform in the width direction of the sheet 17, causing wrinkles. further,
When the solidified toner 23 is formed, the sheet 17 cannot be sufficiently hardened at the front end portion 21a. Therefore,
It is not possible to prevent the paper 17 from being wrinkled due to a change in the transport speed of the paper 17.

A resist section K1 (FIG. 4) and a transfer section K
2, the paper 17 is sent in a tangential direction from the registration unit K1, but the difference between the diameter of the registration roller 12 and the diameter of the transfer roller 14 is caused by the partial If the feed amount of the paper 17 in the transfer unit K2 changes due to a poor feed failure or the like, the print pitch may be partially reduced in the print result. As a result, the image quality deteriorates.

When the paper 17 is thick, as shown in FIG. 4, a force is applied in the direction of arrow C by the pressure roller 11 and the registration roller 12 at the moment when the paper 17 separates from the registration portion K1, and the conveyance speed of the paper 17 is increased. Fluctuates instantaneously, causing horizontal streaks in the image. As a result, the image quality deteriorates. The present invention solves the problems of the conventional electrophotographic printer, prevents wrinkles from occurring on the print medium, and does not cause jams.
An object of the present invention is to provide an electrophotographic printer capable of improving image quality.

[0017]

For this purpose, in an electrophotographic printer according to the present invention, first and second rollers which are disposed in pressure contact with each other, rotate and convey a print medium, and the print medium are provided. A photoconductor drum disposed downstream of the first and second rollers in the conveyance direction of the photoconductor drum, a transfer roller disposed in pressure contact with the photoconductor drum, and forming a transfer unit together with the photoconductor drum; Downstream of the photoconductor drum and the transfer roller in the direction of transport of the print medium, there are third and fourth rollers which are disposed in pressure contact with each other and are rotated to transport the print medium.

The tangents of the first and second rollers are inclined with respect to a reference line connecting the first contact portion between the first and second rollers and the transfer portion. In another electrophotographic printer of the present invention, the first and second electrophotographic printers are arranged so as to be pressed against each other, and are rotated to convey a print medium.
A second roller, a photosensitive drum disposed downstream of the first and second rollers in the transport direction of the print medium, and a photosensitive drum disposed in pressure contact with the photosensitive drum; A transfer roller that forms a transfer portion and a third and a fourth roller that are disposed downstream of the photoconductor drum and the transfer roller in the transport direction of the print medium in pressure contact with each other, and are rotated to transport the print medium. And a roller.

A tangent line between the photosensitive drum and the transfer roller is inclined with respect to a reference line connecting the transfer portion and a second contact portion between the third and fourth rollers. In still another electrophotographic printer according to the present invention, first and second rollers which are disposed in pressure contact with each other and are rotated to convey a print medium, and the first and second rollers in the conveyance direction of the print medium are provided. A photoconductor drum disposed downstream of the second roller, a transfer roller disposed in pressure contact with the photoconductor drum to form a transfer section together with the photoconductor drum, and a photoconductor in a conveyance direction of the print medium. Disposed downstream of the drum and the transfer roller in pressure contact with each other;
And third and fourth rollers that rotate and convey the print medium.

The tangent line of the first and second rollers is inclined with respect to a reference line connecting the first contact portion between the first and second rollers and the transfer portion, A tangent line between the photosensitive drum and the transfer roller is inclined with respect to a reference line connecting the transfer portion and a second contact portion between the third and fourth rollers. In still another electrophotographic printer according to the present invention, first and second rollers which are disposed in pressure contact with each other and are rotated to convey a print medium are provided;
A photoreceptor drum disposed downstream of the first and second rollers in the transport direction of the print medium, and a transfer disposed in pressure contact with the photoreceptor drum to form a transfer unit together with the photoreceptor drum And a third roller and a fourth roller which are disposed downstream of the photoconductor drum and the transfer roller in the transport direction of the print medium and are pressed against each other, and are rotated to transport the print medium.

The first roller between the first and second rollers
Between the contact portion and the transfer portion, a slack forming means for forming a slack in the sent print medium is provided. In still another electrophotographic printer according to the present invention, first and second rollers which are disposed in pressure contact with each other and are rotated to convey a print medium, and the first and second rollers in the conveyance direction of the print medium are provided. A photoconductor drum disposed downstream of the second roller, a transfer roller disposed in pressure contact with the photoconductor drum to form a transfer section together with the photoconductor drum, and a photoconductor in a conveyance direction of the print medium. Disposed downstream of the drum and the transfer roller in pressure contact with each other;
And third and fourth rollers that rotate and convey the print medium.

A slack forming means for forming a slack in the fed print medium is provided between the transfer portion and the second contact portion between the third and fourth rollers. . In still another electrophotographic printer according to the present invention, first and second rollers which are disposed in pressure contact with each other and are rotated to convey a print medium, and the first and second rollers in the conveyance direction of the print medium are provided. A photoconductor drum disposed downstream of the second roller, a transfer roller disposed in pressure contact with the photoconductor drum to form a transfer section together with the photoconductor drum, and a photoconductor in a conveyance direction of the print medium. Disposed downstream of the drum and the transfer roller in pressure contact with each other;
And third and fourth rollers that rotate and convey the print medium.

The first roller between the first and second rollers
Between the transfer portion and the transfer portion, and between the transfer portion and the second contact portion between the third and fourth rollers, for forming a slack in the fed print medium. Forming means is provided. In still another electrophotographic printer according to the present invention, first and second rollers which are disposed in pressure contact with each other and are rotated to convey a print medium, and the first and second rollers in the conveyance direction of the print medium are provided. A photoconductor drum disposed downstream of the second roller, a transfer roller disposed in pressure contact with the photoconductor drum to form a transfer section together with the photoconductor drum, and a photoconductor in a conveyance direction of the print medium. A third and a fourth, which are disposed downstream of the drum and the transfer roller in pressure contact with each other and are rotated to convey the print medium.
And rollers.

Then, a print medium formed of a non-adhesive heat-resistant resin and sent is provided on a medium transport route between the transfer section and the second contact section between the third and fourth rollers. A guide roller that guides while rotating is rotatably supported.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing a medium transport route between a resist unit and a transfer unit according to the first embodiment of the present invention, and FIG. 7 is an enlarged view of the resist unit according to the first embodiment of the present invention.

In the figure, reference numeral 11 denotes a pressure roller as a first roller, 12 denotes a registration roller as a second roller pressed against the pressure roller 11, 1
Reference numeral 3 denotes a photosensitive drum, 14 denotes a transfer roller, and 17 denotes a sheet as a print medium. The pressure roller 11, the registration roller 12, the photosensitive drum 13, and the transfer roller 14
Is rotatably supported, is rotated by receiving rotation from a drive system (not shown), and conveys the paper 17.

Then, a resist portion K1 as a first contact portion is formed between the pressure roller 11 and the resist roller 12. The tangent N between the pressure roller 11 and the registration roller 12 is changed to the registration portion K1.
The transfer portion K2 is inclined at a predetermined angle α (several degrees) below a reference line M connecting the transfer portion K2 and the transfer portion K2. Therefore,
The angle between the line connecting the centers of the pressure roller 11 and the registration roller 12 and the vertical line is also set to α.

In this embodiment, the tangent N
Is set downward from the reference line M,
It can also be set upward. Further, the feed amount of the sheet 17 in the registration section K1 and the transfer section K2
Of the paper 17 is set to 1: 1. Note that the feed amount of the paper 17 in the registration unit K1 can be increased by several [%].

Then, the upper guide 41 and the lower guide 42 are arranged in such a shape that the paper 17 discharged from the resist section K1 can easily enter the transfer section K2. Next, the operation of the resist unit K1 having the above configuration will be described. First, the paper 17 fed by a hopping roller from a paper cassette or a front feeder unit (not shown)
It is hit against the resist unit K1 to correct the skew. Then, when the sheet 17 is abutted against the registration unit K1, the registration roller 12 is rotated in the direction of arrow D by the drive system, and the rotation force causes the sheet 17 to be sent out from the registration unit K1 in the direction of the tangent line N. .

Next, the fed sheet 17 reaches the photosensitive drum 13 along the lower guide 42. in this case,
The ratio of the feed amount of the paper 17 in the registration unit K1 to the feed amount of the paper 17 in the transfer unit K2 is set to 1: 1. However, slack of the paper 17 is formed between the registration unit K1 and the transfer unit K2. Is done. When the feed amount of the paper 17 in the transfer unit K2 is larger than the feed amount of the paper 17 in the registration unit K1, the slack of the paper 17 decreases in the direction of arrow G. Therefore, the peripheral speed difference in the width direction of the paper 17,
Even if the traveling load of the paper 17 such as a friction feed changes and the transport speed of the paper 17 fluctuates, the slack absorbs the fluctuation of the transport speed. As a result, the paper 17 is not stretched and wrinkles can be prevented from occurring.

As shown in FIG. 7, when the paper 17 is thick, even if a force is applied in the direction of arrow H by the pressure roller 11 and the registration roller 12 at the moment when the paper 17 separates from the registration portion K1, the reference line M A component force will act in the direction of. Therefore, the paper 17 is not directly pushed into the transfer section K2, and the transport speed of the paper 17 does not fluctuate, thereby preventing horizontal streaks from occurring in the image. As a result, it is possible to prevent the image quality from deteriorating.

Next, a second embodiment of the present invention will be described. FIG. 8 is a diagram showing a medium transport route between a resist unit and a transfer unit according to the second embodiment of the present invention, and FIG. 9 is an enlarged view of the resist unit according to the second embodiment of the present invention. In the figure, 11 is a pressure roller, 1
2 is a registration roller pressed against the pressure roller 11, 13 is a photosensitive drum as a third roller, 1
Reference numeral 4 denotes a transfer roller as a fourth roller, and reference numeral 17 denotes a sheet as a print medium.

The pressure roller 11, the registration roller 12, the photosensitive drum 13 and the transfer roller 14 are rotatably supported, are rotated by a rotation from a drive system (not shown), and convey the paper 17. Further, a resist portion K1 as a first contact portion is formed between the pressure roller 11 and the resist roller 12.

Then, adjacent to the resist portion K1,
A guide film 47 as a slack forming means such that a tangent line P between the registration roller 12 and the sheet 17 is inclined at a predetermined angle β (several degrees) upward from a reference line M connecting the registration unit K1 and the transfer unit K2. Are provided on the lower guide 46. The guide film 47 is made of an elastic member, and is bent (deflected) in the direction of arrow I when the slack of the paper 17 is reduced. Accordingly, the angle between the line extending perpendicular to the tangent line P and the vertical line is also set to β.

The ratio of the feed amount of the sheet 17 in the registration unit K1 to the feed amount of the sheet 17 in the transfer unit K2 is set to 1: 1. Note that the feed amount of the paper 17 in the registration unit K1 can be increased by several [%]. Then, the upper guide 45 and the lower guide 46 are arranged in such a shape that the paper 17 discharged from the registration unit K1 can easily enter the transfer unit K2.

In the present embodiment, the guide film 47 is disposed so as to be inclined above the lower guide 46, but may be disposed below the upper guide 45. Next, the operation of the resist unit K1 having the above configuration will be described. First, the sheet 17 fed by a hopping roller from a sheet cassette (not shown) or a front feeder unit is abutted against a registration unit K1 to correct a skew. And paper 1
When the registration roller 7 is abutted against the registration portion K1, the registration roller 12 is rotated in the direction of arrow D by the drive system, and the paper 17 is sent out from the registration portion K1 in the direction of the reference line M by this rotational force.

Next, when the fed sheet 17 advances in the direction of the reference line M and hits the guide film 47, the guide film 47 regulates the running direction of the sheet 17 so as to be away from the direction of the reference line M. Thereafter, the sheet 17 is transported along the upper guide 45 and reaches the transfer section K2. In this case, the ratio of the feed amount of the paper 17 in the registration unit K1 to the feed amount of the paper 17 in the transfer unit K2 is set to 1: 1 (the feed amount of the paper 17 in the registration unit K1 is increased by several [%]). However, a slack of the sheet 17 is formed between the registration unit K1 and the transfer unit K2. When the feed amount of the sheet 17 in the transfer unit K2 is larger than the feed amount of the sheet 17 in the registration unit K1, the slack of the sheet 17 decreases in the arrow J direction. Therefore, the running load of the paper 17 such as the peripheral speed difference in the width direction of the paper 17 and the friction feed changes, and the
Even if the transport speed fluctuates, the change in the transport speed is absorbed by the slack. As a result, the paper 17 is not stretched and wrinkles can be prevented from occurring.

When the paper 17 is thick, as shown in FIG. 9, even when a force is applied in the direction of arrow K by the pressure roller 11 and the registration roller 12 at the moment when the paper 17 separates from the registration portion K1, the reference line M A component force will act in the direction of. Therefore, the paper 17 is not directly pushed into the transfer section K2, and the transport speed of the paper 17 does not fluctuate, thereby preventing horizontal streaks from occurring in the image. As a result, it is possible to prevent the image quality from deteriorating.

Next, a third embodiment of the present invention will be described. FIG. 10 is a diagram showing a medium transport route between a transfer unit and a fixing unit according to a third embodiment of the present invention.
FIG. 1 is an enlarged view of a fixing unit according to a third embodiment of the present invention. In the drawing, reference numeral 13 denotes a photosensitive drum disposed in the developing unit 20, reference numeral 14 denotes a transfer roller, reference numeral 15 denotes a heat roller as a third roller, reference numeral 16 denotes a backup roller as a fourth roller, and reference numeral 32 denotes a medium transport route. And a medium guide section as a slack forming means for forming a slack on the paper 17 as a print medium. The photosensitive drum 13, the transfer roller 14, the heat roller 1
The backup roller 5 and the backup roller 16 are rotatably disposed, rotated by receiving rotation from a drive system (not shown), and transport the paper 17.

When the toner image on the photosensitive drum 13 is transferred to the sheet 17 at the transfer section K2 between the photosensitive drum 13 and the transfer roller 14, the sheet 17 is transferred from the transfer section K2 in the horizontal direction. The sheet is fed out at an angle inclined downward, and is transported along the medium guide section 32 to a fixing section K3 as a second contact section. The medium guide portion 32 is formed substantially horizontally in the vicinity of the transfer roller 14, but is curved before the fixing portion K 3, and its tip is directed to the heat roller 15. Therefore, paper 17
Is conveyed while curving along the medium guide portion 32, and is bitten by the fixing portion K3 after the front end reliably hits the point c on the heat roller 15.

That is, in the shortest route between the photosensitive drum 13 and the heat roller 15, that is, in a region below a dashed line connecting the points a and b, a considerable slack is formed on the sheet 17. In the present embodiment, the medium guide portion 32 is curved with a radius of curvature of R45 just before the fixing portion K3, and the rush angle θ with respect to the tangent line L1 at the point c is 35 °. In this case, the points a, b
The distance between them is about 93 [mm], while the medium transport route is about 5 [%] longer.

As described above, since the medium guide portion 32 in front of the fixing portion K3 is curved and a slack is formed in the sheet 17, the peripheral speed difference in the width direction of the sheet 17, the running of the sheet 17 such as friction feed, etc. Even if the load changes and the transport speed of the paper 17 changes, the slack absorbs the change in the transport speed. Therefore, the paper 17 is not stretched and wrinkles can be prevented.

Further, since the slack is formed in a region below the one-dot chain line connecting the points a and b, the developing unit 20
It is possible to prevent the unfixed toner from touching the heat roller 15 and the like, thereby preventing the occurrence of contamination. Therefore, image quality can be improved. In the present embodiment, the medium guide 32 is formed integrally. However, a separate fixing guide may be provided near the fixing section K3 in the medium guide 32.

FIG. 12 is a diagram showing the relationship between the surface temperature of the heat roller and the generation level of wrinkles, and FIG. 13 is a diagram showing the generation status of wrinkles in the medium transport route. In FIG. 12, the abscissa indicates the surface temperature of the heat roller 15 and the ordinate indicates the wrinkle generation level. In FIG. 13,
(A) shows the state of the sheet 17 at the wrinkle occurrence level 5 (no wrinkle), (b) shows the state of the sheet 17 at the wrinkle occurrence level 4, and (c) shows the state of the wrinkle occurrence level 3. (D) shows the state of the sheet 17 at the wrinkle occurrence level 2, and (e) shows the state of the sheet 17 at the wrinkle occurrence level 1.

In this case, when a solid black print pattern is printed, A3 size (ream 55 kg) paper 17 (FIG. 1)
The level of wrinkles occurring in 1) is
The comparison was made while changing the intrusion angle θ. Rush angle θ is about 20
The generation level of wrinkles in the case of [°] is indicated by line L2.
The line L3 indicates the wrinkle occurrence level when the rush angle θ is 35 °. The printing speed is 10 [PP
M] (A4 vertical feed), the outer diameter of the heat roller 15 is 28 [mm], the outer diameter of the backup roller 16 is 28.5 [mm], and the pressing force of the backup roller 16 is 4. 5 kg (one side), and the rubber hardness of the backup roller 16 is 20 °.

As shown in the drawing, the rush angle θ is set to 35 [°].
Then, the surface temperature of the heat roller 15 becomes 195 [°].
It can be seen that wrinkles do not occur until. Note that good results can be obtained when the radius of curvature of the curve formed in the medium guide section 32 before the fixing section K3 is R30 to R50. Next, a fourth embodiment of the present invention will be described.

FIG. 14 is a view showing a medium transport route between a transfer section and a fixing section according to a fourth embodiment of the present invention, and FIG. 15 is a plan view of a fixing guide according to the fourth embodiment of the present invention. FIG. 16 is a side view of a fixing guide according to a fourth embodiment of the present invention, and FIG. 17 is an enlarged view of a fixing unit according to the fourth embodiment of the present invention. In addition, about what has the same structure as 3rd Embodiment, the description is abbreviate | omitted by attaching the same code | symbol.

In the drawing, reference numeral 33 denotes a chassis portion, and reference numeral 35 denotes a fixing guide disposed in front of a fixing portion K3 as a second contact portion. A guide roller 36 is disposed at the tip of the fixing guide 35. Is established. The guide rollers 36 are formed of a non-adhesive heat-resistant resin, for example, PFA, and are arranged in a plurality in the width direction of the paper 17 (about 3 to 5 in accordance with the allowable paper width). While being freely supported, the E-shaped retaining ring 38 prevents the shaft 37 from slipping off.

The guide roller 36 is slightly protruded above a dashed line connecting the points a and b. Accordingly, when the paper 17 is stretched between the transfer unit K2 and the fixing unit K3 and wrinkles are likely to occur, the guide roller 36 guides the paper 17 while rotating, and gives an ironing. Becomes stable. As a result, it is possible not only to prevent wrinkles from occurring on the sheet 17, but also to correct even if wrinkles occur.

Further, since the guide roller 36 is formed of a non-adhesive heat-resistant resin, it is possible to prevent the toner adhering to the back side of the sheet 17 from adhering to the guide roller 36 when the sheet 17 is ironed. Can be prevented. Therefore, not only can the occurrence of jam be prevented, but also, before the paper 17 is bitten by the heat roller 15 and the backup roller 16, how the front end of the paper 17 hits the heat roller 15 depends on the width of the paper 17. Since the direction becomes uniform, it is possible to prevent wrinkles from occurring.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0052]

As described above in detail, according to the present invention, in the electrophotographic printer, the first and second rollers which are disposed in pressure contact with each other and are rotated to convey the print medium are provided. A photosensitive drum disposed downstream of the first and second rollers in the transport direction of the print medium; and a photosensitive drum disposed in pressure contact with the photosensitive drum to form a transfer portion together with the photosensitive drum. A transfer roller; and third and fourth rollers disposed downstream of the photosensitive drum and the transfer roller in the direction of transport of the print medium in pressure contact with each other and rotated to transport the print medium.

The tangents of the first and second rollers are inclined with respect to a reference line connecting the first contact portion between the first and second rollers and the transfer portion. In this case, a slack of the print medium is formed between the first contact portion and the transfer portion. Then, when the feed amount of the transfer medium is larger than the feed amount of the print medium in the first contact portion, the slack of the print medium is reduced. Therefore, even if the running speed of the print medium such as the peripheral speed difference in the width direction of the print medium and the friction feed changes, and the transport speed of the print medium changes, the slack absorbs the change in the transport speed. As a result, it is possible to prevent the print medium from being stretched and to prevent wrinkles from occurring.

When the print medium is thick, the print medium is not directly pushed into the transfer section even if a force is applied by the first and second rollers at the moment when the print medium is separated from the first contact section. Since the conveyance speed of the print medium does not fluctuate, horizontal streaks are prevented from occurring in the image.
As a result, it is possible to prevent the image quality from deteriorating.

In another electrophotographic printer according to the present invention, first and second rollers which are disposed in pressure contact with each other and which are rotated to transport a print medium, and the first and second rollers in the transport direction of the print medium are provided. A photoconductor drum disposed downstream of the second roller, a transfer roller disposed in pressure contact with the photoconductor drum to form a transfer section together with the photoconductor drum, Downstream from the photoconductor drum and the transfer roller, there are third and fourth rollers that are disposed in pressure contact with each other and that are rotated to convey the print medium.

The tangent line between the photosensitive drum and the transfer roller is inclined with respect to a reference line connecting the transfer portion and the second contact portion between the third and fourth rollers. In this case, a slack of the print medium is formed between the transfer portion and the second contact portion. When the feed amount of the print medium in the second contact portion is larger than the feed amount in the transfer portion, the slack of the print medium is reduced. Therefore, even if the running speed of the print medium such as the peripheral speed difference in the width direction of the print medium and the friction feed changes, and the transport speed of the print medium changes, the slack absorbs the change in the transport speed. As a result, it is possible to prevent the print medium from being stretched and to prevent wrinkles from occurring.

In still another electrophotographic printer according to the present invention, first and second rollers which are disposed in pressure contact with each other and are rotated to transport a print medium, and the first and second rollers in the transport direction of the print medium are provided. 1. a photosensitive drum disposed downstream of the second roller; a transfer roller disposed in pressure contact with the photosensitive drum to form a transfer section together with the photosensitive drum; and a conveying direction of the print medium. And a third roller and a fourth roller which are disposed in pressure contact with each other on the downstream side of the photosensitive drum and the transfer roller, and which are rotated to convey the print medium.

The tangent line of the first and second rollers is inclined with respect to a reference line connecting the first contact portion between the first and second rollers and the transfer portion, A tangent line between the photosensitive drum and the transfer roller is inclined with respect to a reference line connecting the transfer portion and a second contact portion between the third and fourth rollers. In this case, a slack of the print medium is formed between the first contact portion and the transfer portion. Then, when the feed amount of the transfer medium is larger than the feed amount of the print medium in the first contact portion, the slack of the print medium is reduced.

Further, a slack of the print medium is formed between the transfer portion and the second contact portion. When the feed amount of the print medium in the second contact portion is larger than the feed amount in the transfer portion, the slack of the print medium is reduced. Therefore,
Even if the transport speed of the print medium fluctuates due to a change in the peripheral speed difference in the width direction of the print medium, the friction load, or the like, the change in the transport speed is absorbed by the slack. As a result, it is possible to prevent the print medium from being stretched and to prevent wrinkles from occurring.

When the print medium is thick, the print medium is not directly pushed into the transfer section even when a force is applied by the first and second rollers at the moment when the print medium is separated from the first contact section. Since the conveyance speed of the print medium does not fluctuate, horizontal streaks are prevented from occurring in the image.
As a result, it is possible to prevent the image quality from deteriorating.

In still another electrophotographic printer according to the present invention, first and second rollers which are disposed in pressure contact with each other and are rotated to convey a print medium, and the first and second rollers in the conveyance direction of the print medium are provided. 1. a photosensitive drum disposed downstream of the second roller; a transfer roller disposed in pressure contact with the photosensitive drum to form a transfer section together with the photosensitive drum; and a conveying direction of the print medium. And a third roller and a fourth roller which are disposed in pressure contact with each other on the downstream side of the photosensitive drum and the transfer roller, and which are rotated to convey the print medium.

Then, the first roller between the first and second rollers
Between the contact portion and the transfer portion, a slack forming means for forming a slack in the sent print medium is provided. In this case, since the slack forming means is formed between the first contact portion and the transfer portion, the peripheral speed difference in the width direction of the print medium, the running load of the print medium such as the friction feed changes, and the print medium changes. Even if the transport speed fluctuates, the change in the transport speed is absorbed by the slack. Therefore, the print medium is not stretched, and the generation of wrinkles can be prevented.

In still another electrophotographic printer according to the present invention, first and second rollers which are disposed in pressure contact with each other and are rotated to convey a print medium, and the first and second rollers in the conveyance direction of the print medium are provided. 1. a photosensitive drum disposed downstream of the second roller; a transfer roller disposed in pressure contact with the photosensitive drum to form a transfer section together with the photosensitive drum; and a conveying direction of the print medium. And a third roller and a fourth roller which are disposed in pressure contact with each other on the downstream side of the photosensitive drum and the transfer roller, and which are rotated to convey the print medium.

Then, a slack forming means for forming a slack on the fed print medium is provided between the transfer portion and the second contact portion between the third and fourth rollers. . In this case, since the slack forming means is formed between the transfer portion and the second contact portion, the peripheral speed difference in the width direction of the printing medium, the running load of the printing medium such as the friction feed changes, and the printing medium changes. Even if the transport speed fluctuates, the change in the transport speed is absorbed by the slack. Therefore, the print medium is not stretched, and the generation of wrinkles can be prevented.

In still another electrophotographic printer according to the present invention, first and second rollers which are disposed in pressure contact with each other and are rotated to transport a print medium, and the second roller in the transport direction of the print medium are provided. 1. a photosensitive drum disposed downstream of the second roller; a transfer roller disposed in pressure contact with the photosensitive drum to form a transfer section together with the photosensitive drum; and a conveying direction of the print medium. And a third roller and a fourth roller which are disposed in pressure contact with each other on the downstream side of the photosensitive drum and the transfer roller, and which are rotated to convey the print medium.

Then, the first roller between the first and second rollers
Between the transfer portion and the transfer portion, and between the transfer portion and the second contact portion between the third and fourth rollers, for forming a slack in the fed print medium. Forming means is provided. In this case, since slack forming means is formed between the first contact portion and the transfer portion and between the transfer portion and the second contact portion, the circumferential speed difference in the width direction of the print medium, friction feed, etc. The running load of the print medium changes,
Even if the transport speed of the print medium changes, the slack absorbs the change in the transport speed. Therefore, the print medium is not stretched, and the generation of wrinkles can be prevented.

In still another electrophotographic printer according to the present invention, first and second rollers which are disposed in pressure contact with each other and which are rotated to convey a print medium, and the first and second rollers in the conveyance direction of the print medium are provided. 1. a photosensitive drum disposed downstream of the second roller; a transfer roller disposed in pressure contact with the photosensitive drum to form a transfer section together with the photosensitive drum; and a conveying direction of the print medium. And a third roller and a fourth roller which are disposed in pressure contact with each other on the downstream side of the photosensitive drum and the transfer roller, and which are rotated to convey the print medium.

Then, a print medium formed of a non-adhesive heat-resistant resin and sent is placed on a medium transport route between the transfer section and the second contact section between the third and fourth rollers. A guide roller that guides while rotating is rotatably supported. In this case, if the print medium is stretched between the transfer portion and the second contact portion and wrinkles are likely to occur,
Since the guide roller guides the print medium while rotating, and gives the ironing, the conveyance speed of the print medium is stabilized. As a result, it is possible not only to prevent wrinkles from occurring on the print medium, but also to correct even if wrinkles occur.

Further, since the guide roller is formed of a non-adhesive heat-resistant resin, when the printing medium is ironed, it is possible to prevent the toner adhering to the back side of the printing medium from adhering to the guide roller. can do. Therefore, occurrence of a jam can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a medium transport route between a registration unit and a transfer unit according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a medium transport route of a conventional electrophotographic printer.

FIG. 3 is a diagram showing a medium transport route between a registration unit and a transfer unit in a conventional electrophotographic printer.

FIG. 4 is an enlarged view of a registration unit in a conventional electrophotographic printer.

FIG. 5 is a diagram showing a medium transport route between a transfer unit and a fixing unit of a conventional electrophotographic printer.

FIG. 6 is an enlarged view of a fixing unit in a conventional electrophotographic printer.

FIG. 7 is an enlarged view of a resist unit according to the first embodiment of the present invention.

FIG. 8 is a diagram illustrating a medium transport route between a registration unit and a transfer unit according to a second embodiment of the present invention.

FIG. 9 is an enlarged view of a resist unit according to a second embodiment of the present invention.

FIG. 10 is a diagram illustrating a medium transport route between a transfer unit and a fixing unit according to a third embodiment of the present invention.

FIG. 11 is an enlarged view of a fixing unit according to a third embodiment of the present invention.

FIG. 12 is a diagram illustrating a relationship between a surface temperature of a heat roller and a wrinkle generation level.

FIG. 13 is a diagram illustrating the occurrence of wrinkles in a medium transport route.

FIG. 14 is a diagram illustrating a medium transport route between a transfer unit and a fixing unit according to a fourth embodiment of the present invention.

FIG. 15 is a plan view of a fixing guide according to a fourth embodiment of the present invention.

FIG. 16 is a side view of a fixing guide according to a fourth embodiment of the present invention.

FIG. 17 is an enlarged view of a fixing unit according to a fourth embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 11 pressure roller 12 registration roller 13 photoreceptor drum 14 transfer roller 15 heat roller 16 backup roller 17 paper 32 medium guide section 36 guide roller 46 lower guide 47 guide film K1 resist section K2 transfer section K3 fixing section M reference line

Claims (11)

[Claims] (A) first and second rollers which are disposed in pressure contact with each other and are rotated to convey a print medium;
(B) the first and second print media in the transport direction;
A photosensitive drum arranged downstream of the rollers of
(C) a transfer roller disposed in pressure contact with the photosensitive drum and forming a transfer portion together with the photosensitive drum; and (d) a transfer roller downstream of the photosensitive drum and the transfer roller in the transport direction of the print medium. And a third roller and a fourth roller which are disposed in pressure contact with each other, rotate and convey the print medium, and (e) a tangent line between the first and second rollers is:
An electrophotographic printer, wherein the printer is inclined with respect to a reference line connecting a first contact portion between the first and second rollers and the transfer portion. 2. (a) first and second rollers which are disposed in pressure contact with each other and are rotated to convey a print medium;
(B) the first and second print media in the transport direction;
A photosensitive drum arranged downstream of the rollers of
(C) a transfer roller disposed in pressure contact with the photosensitive drum and forming a transfer portion together with the photosensitive drum; and (d) a transfer roller downstream of the photosensitive drum and the transfer roller in the transport direction of the print medium. (E) a tangent line between the photoconductor drum and the transfer roller is provided between the transfer unit and the third and fourth rollers. The second between the fourth rollers
An electrophotographic printer which is inclined with respect to a reference line connecting between the contact portion and the contact portion. 3. (a) first and second rollers which are arranged in pressure contact with each other and are rotated to convey a print medium;
(B) the first and second print media in the transport direction;
A photosensitive drum arranged downstream of the rollers of
(C) a transfer roller disposed in pressure contact with the photosensitive drum and forming a transfer portion together with the photosensitive drum; and (d) a transfer roller downstream of the photosensitive drum and the transfer roller in the transport direction of the print medium. And a third roller and a fourth roller which are disposed in pressure contact with each other, rotate and convey the print medium, and (e) a tangent line between the first and second rollers is:
(F) a tangent line between the photosensitive drum and the transfer roller is inclined with respect to a reference line connecting the first contact portion between the first and second rollers and the transfer portion; An electrophotographic printer which is inclined with respect to a reference line connecting between the first roller and a second contact portion between the third and fourth rollers. And (a) first and second rollers which are arranged in pressure contact with each other and are rotated to convey a print medium;
(B) the first and second print media in the transport direction;
A photosensitive drum arranged downstream of the rollers of
(C) a transfer roller disposed in pressure contact with the photosensitive drum and forming a transfer portion together with the photosensitive drum; and (d) a transfer roller downstream of the photosensitive drum and the transfer roller in the transport direction of the print medium. (E) a first contact portion between the first and second rollers and the transfer portion, the third and fourth rollers being arranged to be in pressure contact with each other and rotating and conveying the print medium. Wherein a slack forming means for forming a slack on the sent print medium is provided. 5. (a) first and second rollers which are arranged in pressure contact with each other, rotate and convey a print medium;
(B) the first and second print media in the transport direction;
A photosensitive drum arranged downstream of the rollers of
(C) a transfer roller disposed in pressure contact with the photosensitive drum and forming a transfer portion together with the photosensitive drum; and (d) a transfer roller downstream of the photosensitive drum and the transfer roller in the transport direction of the print medium. (E) a second contact section between the transfer section and the third and fourth rollers, the third and fourth rollers being arranged to be in pressure contact with each other and rotating and conveying the print medium. Wherein a slack forming means for forming a slack on the sent print medium is provided. 6. (a) first and second rollers which are disposed in pressure contact with each other and are rotated to convey a print medium;
(B) the first and second print media in the transport direction;
A photosensitive drum arranged downstream of the rollers of
(C) a transfer roller disposed in pressure contact with the photosensitive drum and forming a transfer portion together with the photosensitive drum; and (d) a transfer roller downstream of the photosensitive drum and the transfer roller in the transport direction of the print medium. (E) a first contact portion between the first and second rollers and the transfer portion, the third and fourth rollers being arranged to be in pressure contact with each other and rotating and conveying the print medium. And the transfer portion and the third,
An electrophotographic printer, wherein a slack forming means for forming a slack in a fed print medium is provided between the fourth roller and a second contact portion between the fourth rollers. 7. The electrophotographic printer according to claim 4, wherein said slack forming means is an elastic member that regulates a print medium in a direction away from a reference line connecting the first contact portion and the transfer portion. . 8. The electrophotographic printer according to claim 5, wherein said slack forming means is an elastic member that regulates a print medium in a direction away from a reference line connecting the transfer section and the second contact section. . 9. The slack forming means restricts a print medium in a direction away from a reference line connecting the first contact portion and the transfer portion, and controls the transfer medium and the second contact portion. The electrophotographic printer according to claim 6, wherein the electrophotographic printer is an elastic member that regulates the print medium in a direction away from a reference line connecting the two. 10. The slack forming means curves a print medium before a second contact portion, and applies a front end of the print medium to one of the third and fourth rollers, and then performs the second The electrophotographic printer according to claim 8, wherein the electrophotographic printer has a shape to be engaged with the contact portion. 11. A first roller and a second roller which are arranged in pressure contact with each other and are rotated to convey a print medium, and (b) said first and second rollers in a direction in which said print medium is conveyed.
A photoconductor drum disposed downstream of the second roller;
(C) a transfer roller disposed in pressure contact with the photosensitive drum and forming a transfer section together with the photosensitive drum; and (d) a downstream side of the photosensitive drum and the transfer roller in the conveyance direction of the print medium. (E) a second contact portion between the transfer unit and the third and fourth rollers, the third and fourth rollers being arranged to be in pressure contact with each other and rotating and conveying the print medium. An electrophotographic printer characterized in that a guide roller formed of a non-adhesive heat-resistant resin and guiding the printed print medium while rotating is rotatably supported in a medium transport route between the print medium and the print medium.