JPH04267267A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image former that is capable of preventing any printing slip in a recording medium, and secure the extent of high printing quality in regard of this image former, installing a braking member in a medium guide, giving the specified braking force to the recording medium and making it a proceed into a surface of an image forming body. CONSTITUTION:In an image former which has a recording medium 2 conveyed by a conveyer means 4 a so as to make it adhere to an image forming body 51 from a tip of a medium guide 7 set up with the tip at the specified gap and angle with the image forming body 51, and transfers a toner image formed on the image forming body 51, it is so constituted that the medium guide 7 is provided with a braking member 8 giving the specified braking force to the recording medium 2 which passes through against the braking force of the braking member 8.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD The present invention relates to an image forming apparatus such as an electrophotographic printing apparatus, and more particularly, the present invention relates to an image forming apparatus such as an electrophotographic printing apparatus, and more particularly, the present invention relates to an image forming apparatus such as an electrophotographic printing apparatus.
The present invention relates to an image forming apparatus that can apply a predetermined braking force to a recording medium and cause the recording medium to enter the surface of an image forming body.

[0002] In recent years, with the development of office automation, there has been an increasing demand for character image information output devices that can use plain paper, have low noise, and produce beautiful prints. For this reason, copiers, facsimile machines, printers, etc. that utilize electrophotographic technology are provided.

In these devices, the printing paper enters the photosensitive drum so that it is in contact with the surface of the photosensitive drum, and the toner image on the photosensitive drum is transferred, but the adhesion between the photosensitive drum surface and the printing paper is poor, and printing omissions occur. Since printing quality easily deteriorates, a mechanism to improve this problem is desired.

0004

2. Description of the Related Art FIG. 3 shows an internal side view of an electrophotographic printing apparatus. In the figure, numeral 1 indicates a paper feed section that accommodates printing paper (hereinafter referred to as paper) 2a and is equipped with a feeding roller 3, 4a is a conveyance path, 5 is a printer section, and 6 is a stacker.

The printer section 5 includes an optical unit 50, a photosensitive drum 51a, a cleaner 52, a charging section 53, a developing section 54, a transfer section 55, a static eliminator 56, and a fixing section 57. With this configuration, when the power of the apparatus is turned on, the fixing section 57 is heated to a predetermined temperature and becomes ready for printing, and based on the print instruction signal, the paper 2a is fed out from the paper feed section 1 in the direction of arrow A, and the paper 2a is fed into the transport path. 4a is conveyed and sent above the photosensitive drum 51a. By this time, the photosensitive drum 51a
The charge is removed by the charge removal unit 56, residual toner is cleaned by the cleaner 52, and the charge is charged again by the charge unit 53.

Therefore, optical data irradiated from an optical unit 50 composed of a laser light source or the like is transmitted to a photosensitive drum 51.
a, and the electrostatic image formed on the photosensitive drum 51a is developed into a toner image at the developing section 54, transferred to the paper 2a at the transfer section 55, and then transferred to the heat roller 58 at the fixing section 57.
The paper 2a is sandwiched between the paper 2a and the pressure roller 59, heated and pressurized, and fixed, and then sent to the stacker 6.

Further, as shown in FIG. 4, a photosensitive drum 51a
A paper guide 7a formed of a substantially parallel upper plate 70 and a lower plate 71, a feed roller R1, and a press roller R2 are provided on the conveyance path 4a through which the paper 2a enters so as to be in contact with the upper surface. The tip of 7a is the photosensitive drum 5
It is located at a predetermined angle and gap with respect to the plane 1a.

A conveyance belt 40 for conveying the transferred paper 2a to the fixing section 57 is provided downstream of the transfer section 55, on the left side in the drawing, and is designed to attract the paper 2a to the conveyance belt 40. Further, the feed roller R1 and the conveyor belt 40 are connected to a motor (not shown) and are driven at the same feed speed.

[0009] Therefore, the feed roller R1 and the presser roller R
The paper 2a that has been conveyed while being sandwiched between the paper guides 7a enters from the tip of the paper guide 7a so as to be in contact with the surface of the photosensitive drum 51a, and the transfer section 55 starts transferring the toner image on the photosensitive drum 51a as described above. .

[0010] Thus, the photosensitive drum 51a has a predetermined winding angle θ1.
When the leading edge of the paper 2a reaches the conveyor belt 40, the paper 2a is moved between the conveyor belt 40 and the feed roller R1.
The paper 2a is conveyed by the holding roller R1 and the holding roller R2, and the transfer progresses, and eventually the rear end of the sheet 2a passes the feeding roller R1 and the holding roller R2, and the sheet 2a is conveyed by the conveying belt 40.

[0011]

[Problems to be Solved by the Invention] According to the above-mentioned conventional method, the leading edge of the paper has weak adhesion to the surface of the photosensitive drum until it reaches the conveyor belt, and the trailing edge of the paper and the feed roller and presser roller are in poor contact with each other. If it is removed from the nip, the adhesion to the surface of the photosensitive drum similarly weakens, and toner transfer is not performed sufficiently, which tends to cause missing prints, leading to a decline in print quality. Missing prints at the leading and trailing edges are largely influenced by the approach angle of the paper to the surface of the photosensitive drum, that is, the angle of the leading end of the paper guide to the surface of the photosensitive drum.If the approach angle is small, contact between the paper and the photosensitive drum may occur. The situation becomes smooth, so
Although printing omissions at the leading edge are improved, since the paper's stiffness weakens its adhesion to the photosensitive drum, printing omissions at the center and rear edges of the paper are more likely to occur. On the other hand, if the approach angle is large, the paper will bend significantly, which will strengthen the adhesion to the photosensitive drum and improve printing omissions at the center and rear edges.
Since there is a large amount of warpage at the tip, printing omissions are likely to occur.

[0012] Therefore, although paper guides are arranged so as to appropriately set the approach angle and prevent excessive print omissions from occurring at both the leading and trailing edges, it is not possible to completely prevent printing omissions, and the paper guides are placed at high There is a problem in that it cannot meet demands for printing quality.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that can prevent missing prints on a recording medium and provide high print quality.

[0014]

[Means for Solving the Problems] FIG. 1 is a diagram showing the basic configuration of the present invention. In the figure, 4 is a conveying means, 2 is a recording medium,
51 is an image forming body; 7 is a medium guide whose tip is arranged with a predetermined gap and angle with respect to the image forming body 51; 8 is a recording medium 2 provided on the medium guide 7 and conveyed by the conveying means 4; This is a braking member that applies a predetermined braking force to the brake.

Therefore, the recording medium 2 is configured to pass against the braking force of the braking member 8.

[0016]

[Operation] When the recording medium 2 conveyed by the conveying means 4 enters the image forming body 51 from the tip of the medium guide 7, the braking member 8 provided on the medium guide 7 causes the recording medium 2 to reach a predetermined level. A braking force is applied, and the recording medium 2 is conveyed against the braking force, so tension is generated in the recording medium 2, and the adhesion force with the surface of the image forming body 51 is increased, so that transfer is performed well. Print omissions can be prevented. In particular, even if the rear end of the recording medium 2 comes off the conveyance means 4, the recording medium 2 receives the braking force from the braking member 8 in the medium guide 7, so the tension is maintained until just before the surface of the image forming body 51. As a result,
Print omissions at the rear edge can be prevented.

[0017] In this way, printing omissions can be prevented and high printing quality can be obtained.

[0018]

Embodiment An embodiment of the present invention will be described below with reference to FIG. FIG. 2 shows a side view of essential parts of an embodiment in which the present invention is applied to the electrophotographic printing apparatus described in the conventional example.

[0019] Paper guide 7b, leaf spring 8a,
The paper 2a and the photosensitive drum 51a are attached to the medium guide 7 in FIG.
, the braking member 8, the recording medium 2, and the image forming body 51, respectively, and the conveyance path 4a, the feed roller R1, the press roller R2, and the conveyance belt 40 in FIG. 2 correspond to the conveyance means 4 in FIG.

As shown in FIG. 2, the lower plate 71a at the tip of the paper guide 7b is formed shorter than the upper plate 70a.
A leaf spring 8a is provided at the tip of a, and the tip of the leaf spring 8a is in contact with the vicinity of the tip of the upper plate 70a with a predetermined pressure. Here, the predetermined pressure is the feed roller R1, the press roller R2,
Alternatively, the pressure is such that the paper 2a conveyed by the conveyor belt 40 can pass through even though it is subjected to braking force.

Therefore, the paper guide 7b has an upwardly tapered shape, and the gap and angle of the paper guide 7b with respect to the surface of the photosensitive drum 51a are both set small. Further, when the diameter of the photosensitive drum 51a is D, and the gap between the photosensitive drum 51a and the tip of the paper guide 7b is g, d2 =
d expressed as (D/2+g)2 - (D/2)2
Since the length corresponds to an area where the rear end of the paper 2a does not have adhesive force, that is, an area where no printing is performed, D and g are set so that the length d is equal to or less than a desired value.

With this configuration, when the paper 2a is conveyed by the feed roller R1 and the press roller R2 and the leading edge enters the surface of the photosensitive drum 51a from the paper guide 7b, the braking force due to the friction of the leaf spring 8a is applied. Since the approach angle from the paper guide 7b is set to be sufficiently small, the paper can be brought into close contact with the photosensitive drum 51a at a winding angle θ2, and the leading edge can be transferred well.

After the leading edge of the paper 2a reaches the conveyor belt 40, it is conveyed by the conveyor belt 40, the feed roller R1, and the press roller R2, but is braked by the frictional force of the plate spring 8a and tension is applied to the paper 2a. occurs, the photosensitive drum 51a is brought into close contact with the photosensitive drum 51a at a winding angle θ2, the tension is converted into adhesion force, and the central portion of the paper 2a is transferred satisfactorily.

Further, even after the trailing edge of the paper 2a comes off the feed roller R1 and the press roller R2, tension is applied to the paper 2a by the plate spring 8a, and the paper 2a conveyed by the conveyor belt 40 is placed on the photosensitive drum 51a. They come into close contact at the winding angle θ2, and the tension is converted into adhesion force, so that the rear end of the paper 2a can be transferred satisfactorily.

In this way, the photosensitive drum 5 of the paper 2a
Rather than relying on the stiffness of the paper 2a, the adhesion to the surface of the paper 2a can be ensured by converting the tension applied to the paper 2a into adhesion. It is possible to prevent printing omissions and obtain high print quality.

In the above example, the case where the leaf spring 8a was used as the braking member was explained, but the tip of the leaf spring 8a is pressed against the upper plate 70 with a predetermined pressure.
Brake plate pressed near the tip of a or upper plate 70a
A similar effect can be obtained by using friction plates in which at least the tips of the friction plates, which are opposed to each other with a predetermined gap in the vicinity of the tips of the friction plates, are formed of a material having a high coefficient of friction.

[0027]

[Effects of the Invention] As explained above, according to the present invention, 1
) In claim 1, a braking member is provided on the medium guide to apply a braking force to the recording paper entering the surface of the image forming body from the medium guide, thereby applying tension to the recording medium and causing the surface of the image forming body to be applied to the recording medium. By improving adhesion, transfer is performed reliably and printing omissions at the center and rear edges of the recording medium can be prevented. 2) In claim 2, the braking member is formed of a sheet-like elastic material, and the distal end is arranged so as to be in contact with the upper guide surface of the medium guide, so that the braking member can be brought close to the surface of the image forming body. In addition, it is possible to set the angle of approach of the recording medium to the surface of the image forming body to be small, and it is possible to increase the adhesion force of the leading edge of the recording medium to the surface of the image forming body, so that transfer is performed reliably. Print omissions at the leading edge of the recording medium can be prevented.

[0028] Therefore, there is an effect that high print quality without printing omissions can be obtained.

[Brief explanation of the drawing]

[Figure 1] Principle diagram of the present invention

[Figure 2] Side view of main parts showing an embodiment of the present invention

[Figure 3]
Internal side view of an electrophotographic printing device to which the present invention is applied

[Figure 4] Side view showing conventional example

[Explanation of symbols]

2 is a recording medium, 2a is paper,
4 is a conveyance means, 4a is a conveyance path,
7 is the media guide;
7a, 7b are paper guides, 8 is a braking member,
8a is a leaf spring,
40 is a conveyor belt, 51 is an image forming body,
51a is a photosensitive drum;
R1 is a feed roller, R2 is a press roller,

Claims (2)

[Claims] 1. A recording medium (2) conveyed by a conveyance means (4) is conveyed by a medium guide (7) whose leading end is arranged with a predetermined gap and angle with respect to the image forming body (51).
An image forming apparatus that transfers a toner image formed on the image forming body (51) onto a recording medium (2) by entering the toner image forming body (51) from the leading end of the image forming body (51) in close contact with the toner image forming body (51). The medium guide (7) includes a braking member (8) that applies a predetermined braking force to the recording medium (2).
) passes through against the braking force of the braking member (8). 2. The image forming apparatus according to claim 1, wherein the braking member (8) is formed of a sheet-like elastic material, and is disposed such that its tip is in contact with the upper guide surface of the medium guide (7). Device.