JPH01210981A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent transfer defect by forming an guide means tip part near a passing part where a transfer material edge in parallel with the advancing direction of the transfer material at the position retreated from the surface of an image carrier. CONSTITUTION:The title device is provided with the rotary, cylindrical image carrier 1 and a pair of guide plates 2. The transfer material is fed in a direction shown by an arrow B. A recessed part S (reference position) and other recessed parts in response to the feeding width of the transfer material are placed on the leading edge of the guide plate 2 corresponding to both edges of the transfer material. A distance d1 from the leading edge of the guide plate 2 to the surface of the image carrier 1 is about 1.5mm, and a distance d2 from the bottom of the recessed part to the surface of the image carrier is about 5mm. The recessed part S and the other recessed parts are provided in corresponding positions of the other guide plate not shown here. When the transfer material is inserted, its both edges pass by the recessed parts, where the guide plate 2 is away from the image carrier 1 and a transfer electrifier 3. Therefore, even if toner near the edges jets outside the transfer material owning to the impact arising when the leading edge of the transfer material abuts on the image carrier, toner adhesion to the leading edge of the guide plate can be prevented, and transfer defect and the back taint of the transfer material can hence be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus that uses an electrostatic transfer process, such as an electrostatic copying machine and a printer thereof.

(Prior art and problem to be solved B) A sheet-like transfer material such as a piece of paper is brought into contact with a transferable toner image electrostatically formed on the surface of a moving image carrier, and while running in synchronization with this, Image forming apparatuses that are configured to transfer a toner image on the surface of an image carrier onto a transfer material by means of a transfer means such as a transfer charger disposed at a contact portion between the two have been widely used in the past.

5 and 6 are schematic side views of the main parts of such a well-known image forming apparatus, schematically showing transfer material conveyance and transfer parts, and the illustrated apparatuses are both rotated in the direction indicated by the arrow. A transfer charger 3 is disposed adjacent to the cylindrical image carrier l, and a guide member 2 is provided in the gap between the two.

It is assumed that transfer is performed by passing a transfer material (not shown) guided and fed in the direction of arrow B.

In the structure shown in FIG. 5, the tip of the guide member 2 is directly close to the image carrier, thereby bringing the transfer material into close contact with the surface of the image carrier, and as shown in FIG. In this case, the transfer material is brought into close contact with the surface of the image carrier via a pair of guide rollers 5 arranged close to the image carrier.

Although not shown in the drawings as they are not directly related to the present invention, it is noted that a charger, a developing device, a cleaning device, and other members necessary for image formation are disposed around the image carrier. Needless to say.

In the above-mentioned device, the tip of the guide member 2 or the guide roller pair 5 is usually It is located very close to the surface of the image carrier at 1 to 2 m+s.

By the way, this type of image forming apparatus is usually configured so that transfer materials of various sizes can be used. When positioned as a reference, naturally one or several other edges of transfer materials of other sizes will be located between the reference edge and the other edge of the heaviest transfer material.

As mentioned above, the guide members, guide rollers, etc. are very close to the surface of the image carrier, so when the toner image is present over the entire width of the transfer material.

When this transfer material comes into contact with the image carrier, the toner spills out from the edge of the transfer material due to the impact, and this toner
Due to the influence of the transfer corona of the transfer charger, toner tends to adhere to guide members, etc., which tend to be charged to a polarity opposite to that of the toner, and to contaminate the guide members.

For this reason, if a larger size transfer material is used after passing a large number of small size transfer materials, there is an inconvenience that the back side of the transfer material may be smeared with toner.

In order to avoid such drawbacks, measures are taken such as arranging the guide member etc. at a distance from the surface of the image carrier, or maintaining the guide member etc. at the same polarity potential as the toner to prevent spilled toner from adhering. Although the former method can prevent toner contamination, it deteriorates the original function of the guide member, which is to ensure that the transfer material comes into close contact with the image carrier at a predetermined position. The image quality is inevitably degraded due to

Further, the latter method is not preferable because it tends to encourage leakage of the transfer corona to the guide member and the like, causing transfer omission.

The present invention was made to deal with the above-mentioned situation, and does not require any special incidental mechanism! ! It is an object of the present invention to provide a transfer material conveying means for a single image forming apparatus that can obtain high quality images without the above-mentioned drawbacks with an extremely simple configuration.

(2) Structure of the invention (technical means for solving the problem and its operation) In order to achieve the above object, the present invention provides a method for bringing a transfer material into close contact with a transferable toner image formed on the surface of an image carrier. In an image forming apparatus in which a transfer material is fed through a guide means whose leading end is disposed close to an image carrier, in the vicinity of a portion through which an edge of the transfer material parallel to the traveling direction of the transfer material passes, This is characterized in that the leading end of the guide means is formed at a position recessed from the surface of the image carrier.

With this configuration, it is possible to prevent contamination of the guide member due to toner blowing out from the edge of the advancing transfer material, as well as transfer defects such as dirt on the back of the transfer material and transfer omissions caused by this. .

(Explanation of Examples) Figures 1 and 2 show the present invention as shown in Figure 5 above.
Main parts of the image bearing member and only one of the guide plates shown, especially when applied to an image forming apparatus equipped with a rotating cylindrical image carrier l and a guide member 2 consisting of a pair of guide plates. They are a slope view and a plan view.

In each figure, it is assumed that the transfer material is fed from the direction of the illustrated white arrow B, and in this case, the transfer material is advanced so that the line shown as the illustrated reference position is aligned with the right edge in the direction of movement. .

The maximum transfer material that can be processed with the illustrated device is A3
Size is vertically fed, and in that case, a recess is formed at the tip of the guide plate corresponding to both edges of the transfer material, as shown by symbols S and A3, and within the range, when using the reference line as a reference, Corresponding to each left edge in the case of vertical feeding of B4 size transfer material and vertical feeding of A4 size transfer material,
A similar recess B4 at the tip of the guide plate. It forms A4.

The distance di between the tip of the guide plate 2 and the surface of the image carrier is set to 1.5 mm, and the distance @d2 between the bottom of each recess and the surface of the image carrier is set to 5 mm.

Note that a guide member is formed. Similar recesses are formed in the other guide plate (not shown) at positions corresponding to the respective recesses described above.

With this structure, when the transfer material is inserted,
Since both edges of the transfer material are located at the recesses as they move forward, the guide member is located at a distance from the image carrier and the transfer charger near these edges, and the leading edge of the transfer material To prevent toner from adhering to the tip of a guide member even if toner near the edge of the transfer material is blown out of the area of the transfer material due to an impact when the toner contacts an image carrier. Can be done. Further, even when the guide member is maintained at the same polarity potential as the transfer corona in order to prevent transfer removal, the guide member is not contaminated with blown toner.

Furthermore, most of the transfer material is reliably guided to the vicinity of the image carrier by the guide member, so that it can be brought into close contact with the image carrier without any loss of image quality.

Note that when the guide member consists of a pair of guide plates as in the above case, one guide plate has a higher image bearing capacity than the other due to the shape and relative arrangement of other members such as the image carrier. In some cases, the tip of the guide plate is located at a distance of 3 m from the surface of the image carrier.
If the guide plate is further away than this, the same effect can be obtained without forming the above-mentioned recess in the guide plate.

FIG. 3 is a perspective view of a part of the device using a pair of guide rollers as shown in FIG. In addition, a plurality of pairs of guide rollers 5 are arranged close to the image carrier l so that there is an appropriate distance between the edges of each size of transfer material that is passed through one sheet. Just do it.

With this configuration, the same effects as those of the previous embodiment can be obtained.

As mentioned above, when positioning the transfer material using one edge of the transfer material as a reference, the shape of the tip of the transfer material guide member differs greatly between the reference position side and the opposite side. The influence of frictional force generated between the transfer materials may become uneven in the width direction of the transfer material, causing problems such as the traveling direction of the transfer material being bent.Figure 4 is designed to deal with such situations. This shows an example in which a guide member consisting of a guide plate is provided in the same manner as shown in FIGS. 1 and 2, and the tip portion of the guide plate is A roller 6 rotates as a result of the advancing transfer material.
6 is arranged.

With this configuration, it is possible to reduce the friction on the reference edge side of the transfer material and equalize its influence in the width direction of the transfer material.

In the above embodiment, the transfer material size is A3. A4.
Although we have described the case of B4, the same can be done for other sizes, and furthermore, in the above-mentioned apparatus, we have explained the case where the edge of the transfer material is used as the reference.
It will be easily understood that the present invention can be applied to the case of positioning based on the center of the transfer material or elsewhere.

(3) Effects of the Invention As is clear from the above description, according to the present invention, the transfer material, which is guided by the guide means and advances, is moved parallel to the traveling direction in order to come into close contact with the image carrier. Since the guide means is retracted from the image carrier only in the portion corresponding to the edge, there is no need for any special additional mechanism, and with an extremely simple structure, the guide means is moved by the toner blown out from the edge. It effectively prevents contamination and the staining of the transfer material caused by this, and also prevents toner scattering and transfer omissions during the transfer process, which greatly contributes to obtaining high-quality images.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of essential parts showing an embodiment of the present invention, FIG. 2 is a plan view of the same as above, FIGS. FIG. 6 is a schematic side view showing the main parts of a known image forming apparatus. i--Image carrier, 2.. Φ guide member, 3. .phi. transfer charger, 5. .phi. guide roller. Akane 1 [! I. Figure 2 Figure 3 Figure 4 - Akira

Claims (1)

[Scope of Claims] In order to bring the transfer material into close contact with the transferable toner image formed on the surface of the image carrier, the transfer material is fed through a guide means whose tip is disposed close to the image carrier. An image forming apparatus, wherein the leading end of the guide means is formed at a position recessed from the surface of the image carrier in the vicinity of a portion through which an edge of the transfer material parallel to the traveling direction of the transfer material passes.