JP2009133995A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent both of toner scattering and transfer void at a tip end in an image forming apparatus of noncontact transfer device using a corona discharging mechanism. <P>SOLUTION: An image forming apparatus includes: a noncontact transfer device 5 which transfers a toner image on an image carrier to a recording material P using a discharge mechanism, wherein a transfer charged area is modified or moved during transferring. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus (copier, facsimile, printer, etc.), and particularly as a transfer device for transferring a toner image on an image carrier, a transfer electric field is applied to a recording material by a discharge mechanism. The present invention relates to an image forming apparatus including a non-contact type transfer device.

  Conventionally, electrophotographic copying machines and laser beam printers are known as high-speed and high-quality image forming apparatuses. In this type of electrophotographic image forming apparatus, an image is formed on a recording material through steps of charging, exposure, development, transfer, and fixing.

  For example, a photosensitive drum as an image carrier is uniformly and uniformly charged by a charging device, and then exposed by an exposure device according to image information to be formed, thereby forming an electrostatic latent image. The electrostatic latent image on the photosensitive drum is developed by a developing device to form a toner image, and the toner image on the photosensitive drum is transferred onto a recording material by a transfer device. The toner image on the recording material is fixed on the recording material by a fixing device to form an image.

  The transfer device is disposed opposite to the photosensitive drum carrying the toner image, and corona discharge having a polarity opposite to that of the toner from the back surface of the recording material conveyed while being guided by the guide member to the transfer portion between the photosensitive drum and the transfer device. Is generated. The corona discharge generated from the transfer wire as the transfer electrode of the transfer device forms a transfer charging area at the transfer portion including the transfer point at the shortest distance of the corona discharge on the peripheral surface of the photosensitive drum, and transfers the toner image on the recording material. Transcript to.

  Here, in the transfer portion, the recording material needs to be in close contact with the photosensitive drum carrying the toner, and the recording material floats with respect to the photosensitive drum, that is, the recording material and the photosensitive drum are not in contact with each other. In the contact state, problems such as “transfer omission” in which the toner does not transfer onto the recording material and “transfer scattering” in which the toner on the recording material scatters occur.

  Various countermeasures have been proposed for such a problem in the transfer portion.

  In order to ensure the adhesion of the recording material to the photosensitive drum, a configuration has been proposed in which transfer assisting means for pressing the recording material toward the photosensitive drum during the transfer process is provided (see Patent Document 1). However, there is a concern that the transfer assisting unit may damage the photosensitive drum between the recording materials or in a small size recording material, or may contaminate the recording material due to toner adhesion. In order to solve these problems, there is a problem that requires a more complicated configuration.

  In addition, a configuration has been proposed in which the shield case of the transfer unit is moved to the downstream side of the recording material conveyance in accordance with the rigidity detecting means for detecting the rigidity of the recording material (see Patent Document 2). This is because the point of contact with the photosensitive drum changes depending on the rigidity of the recording material, and the shield case of the transfer portion is moved. Specifically, when the recording material has high rigidity, the transfer charging area is made equal between thick paper and thin paper by moving the shield case of the transfer device to the downstream side of the recording material conveyance or changing the direction. It is. However, this prevents a reduction in the transfer width, and does not mention the separate problems at the leading end and the leading end of one recording material.

  Regarding the shield case opening width of the transfer device, a configuration has been proposed in which the size of the transfer charger opening is varied in accordance with the moisture content of the recording material (see Patent Document 3). Specifically, when the moisture content of the recording material is large≈the resistance value of the recording material is small, the opening width of the transfer portion is reduced. This is intended to prevent the recording material that has absorbed moisture in a high humidity environment from becoming weak and reducing the separation from the photosensitive drum, and does not mention image defects during the transfer process.

  Also, a configuration has been proposed in which the line width of an image is changed by changing the shield case opening width of the transfer device (see Patent Document 4). This is an image line width adjusting means, and does not mention image defects during the transfer process.

Also, a configuration has been proposed in which the shield case opening width of the transfer device is switched between a single color image mode and a multicolor image mode (see Patent Document 5). This eliminates the density difference between the multi-color image mode in which the reverse transfer phenomenon occurs and the single-color image mode in which the reverse transfer phenomenon does not occur. Reference is made to image defects during the transfer process. Absent.
JP-A-60-169870 Japanese Patent Laid-Open No. 3-138678 JP 2005-249889 A JP-A-3-138679 JP 2003-255665 A

  In order to obtain a high-quality transfer image in a transfer portion of an image forming apparatus using a transfer device of a conventional corona discharge mechanism, the recording material needs to be in close contact with a photosensitive drum carrying toner. If the recording material is floating with respect to the photosensitive drum on the upstream side of the recording material conveyance, a transfer electric field acts before the recording material and the photosensitive drum come into close contact with each other, and the toner image on the photosensitive drum flies over the recording material. As a result, “transfer splattering” in which the toner on the recording material scatters occurs.

  In order to avoid this transfer scattering problem, the height of the guide member (transfer entrance guide) that guides the recording material between the photosensitive drum and the transfer device is increased, and recording is performed on the photosensitive drum at a position before the transfer portion. Adhere the material. When the recording material is wound around the photosensitive drum and the recording material is conveyed to the transfer charging region where the transfer electric field acts in a state where the photosensitive drum and the recording material are in close contact with each other, the scattering of the transfer can be reduced.

  However, when the height of the transfer entrance guide is increased, the leading edge of the recording material floats off the photosensitive drum due to the rigidity of the recording material in the transfer portion, and “tip transfer omission” (tip transfer failure) occurs. This is particularly likely to occur with a recording material having a large rigidity (or a large weight or a large thickness).

  Therefore, in the conventional image forming apparatus, there is a trade-off relationship between transfer splattering and leading edge transfer omission, and both the problems of transfer splattering and leading edge transfer omission occur moderately. Guide height, transfer charging area).

  SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an image forming apparatus capable of improving both transfer scattering and tip transfer omission in an image forming apparatus of a non-contact transfer apparatus having a corona discharge mechanism. is there.

  The above object is achieved by the following image forming apparatus according to the present invention.

  (1) In an image forming apparatus equipped with a non-contact type transfer device having a discharge mechanism for transferring a toner image on an image carrier to a recording material, the transfer charging area width is changed during the toner image transfer process to the recording material. The image forming apparatus.

  (2) In an image forming apparatus equipped with a non-contact transfer device having a discharge mechanism for transferring a toner image on an image carrier onto a recording material, the transfer charging area is moved during the toner image transfer process to the recording material. An image forming apparatus.

  (3) In the transfer unit that transfers the toner image on the image carrier to the recording material, the recording material front end portion is a transfer charging area including the recording material conveyance upstream side, and after the recording material front end portion, the recording material conveyance downstream side is transferred. The image forming apparatus according to (1) or (2), wherein the image forming apparatus is a charged region.

  (4) In the transfer unit that transfers the toner image on the image carrier to the recording material, the leading end of the recording material that is guided by the guide member and conveyed between the image carrier and the transfer device is downstream of the transfer unit. The transfer charging area including the upstream side of the recording material is supported until it is supported by the conveyance guide member disposed on the recording material. After the leading end of the recording material is supported by the conveyance guide member disposed on the downstream side of the transfer unit, the recording material is The image forming apparatus according to (3), wherein the downstream side of conveyance is a transfer charging region.

  (5) In an image forming apparatus having a double-sided printing function, the amount of change in the transfer charging area width during the transfer process of the recording material or the amount of movement of the transfer charging area is determined according to the first and second sides of the recording material. The image forming apparatus according to any one of (1) to (4), wherein the image forming apparatus is variable.

  (6) In any one of the above (1) to (4), the change amount of the transfer charging area width or the movement amount of the transfer charging area during the transfer process of the recording material is variable according to the characteristics of the recording material. This is an image forming apparatus.

  (7) The image formation according to any one of (1) to (4), wherein the change amount of the transfer charging area width or the movement amount of the transfer charging area during the transfer process of the recording material is variable depending on the environment. Device.

  (8) The image forming apparatus according to any one of (1) to (4), wherein a current value flowing through the transfer wire of the transfer device or a voltage value applied to the transfer wire is changed according to the width of the transfer charging area. is there.

  (1) According to the first aspect of the present invention, by changing the transfer charging area width during the transfer process, more specifically, by changing the opening width of the corona charging transfer device, Both problems of transfer omission can be improved.

  (2) According to the second aspect of the present invention, by moving the transfer charging area, more specifically, by moving the corona charging transfer device in the middle of the transfer process, The problem can be improved.

  (3) According to the invention described in claim 3, by performing transfer charging area width change or transfer charging area movement between the recording material leading edge and the recording material leading edge, transfer scattering and leading edge transfer omission are caused. Both problems can be improved.

  (4) According to the fourth aspect of the present invention, transfer splattering and tip transfer can be performed by executing transfer charge area width change or transfer charge area movement before and after the leading end of the recording material is supported by the conveyance guide member. Both problems of omission can be improved.

  (5) According to the fifth aspect of the present invention, the level of transfer splattering and tip transfer omission differs depending on the first side and the second side during double-sided printing. By setting the transfer charge area width change amount or the transfer charge area movement amount, it is possible to more effectively improve both the problems of transfer scattering and leading edge transfer omission.

  (6) According to the invention described in claim 6, the level of transfer scattering and tip transfer omission varies depending on the characteristics (rigidity / weight / thickness / resistance value, etc.) of the recording material. By setting the transfer charge area width change amount or the transfer charge area movement amount accordingly, both problems of transfer scattering and leading edge transfer omission can be improved more effectively.

  (7) According to the seventh aspect of the invention, the level of transfer scattering and tip transfer omission varies depending on the environment (temperature / humidity). By setting the area movement amount, it is possible to more effectively improve both the problems of transfer scattering and leading edge transfer omission.

  (8) According to the invention described in claim 8, even if the transfer charging area width is changed, the transfer current value flowing in the direction of the photosensitive drum can be maintained at a predetermined value, that is, good transfer performance can be obtained. Since it can be maintained, both the problems of transfer scattering and leading edge transfer loss can be improved more effectively.

  As described above, according to the present invention, it is possible to provide an image forming apparatus capable of improving both transfer scattering and leading edge transfer omission in an image forming apparatus of a non-contact transfer apparatus having a corona discharge mechanism.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  Embodiments of the present invention will be described with reference to the accompanying drawings. In addition, in these drawings, the same member is attached | subjected the same code | symbol and the overlapping description is abbreviate | omitted.

  A first embodiment according to the present invention will be described with reference to FIGS.

  In this embodiment, by changing the transfer charging area width during the transfer process, both the problems of transfer scattering and tip transfer omission, which are conventional problems, are improved.

  First, the image forming apparatus will be described.

  FIG. 1 is an example of a conventional image forming apparatus.

  In the image forming apparatus of FIG. 1, the photosensitive drum 1 as an image carrier rotates in the direction of the arrow, and the charging device 2 charges the surface of the photosensitive drum 1 uniformly, for example, negatively (for example, charging potential: −400 V). ). Next, the exposure device 3 irradiates the surface of the photosensitive drum 1 with laser light 3a corresponding to the image information, whereby an electrostatic latent image is formed on the photosensitive drum 1 (for example, exposure portion potential: −50 V). Next, the electrostatic latent image on the photosensitive drum 1 is negative by a developing sleeve 4a (for example, DC: -250 V, AC: 1 KVpp / 2.5 KHz) that is rotated in the direction of the arrow by applying a negative bias of the developing device 4. By developing the toner R charged on the photosensitive drum 1, a toner R image is formed on the photosensitive drum 1 irradiated with the laser beam. The toner R image on the photosensitive drum 1 is transferred to the transfer portion by a guide member (transfer inlet guide) 9 by a plus voltage (for example, DC: +8 KV) applied to the transfer wire 5a of the transfer device 5. Electrostatically transferred onto the top. Thereafter, the recording material P carrying the toner R image removes the positive charge of the recording material P by the negative voltage (for example, DC: −500 V, AC: 10 KVpp / 2 KHz) applied to the separation wire 6 a of the separation device 6. As a result, the recording material P is separated from the photosensitive drum 1. Then, the recording material P carrying the toner R image is conveyed to a fixing device 8 by a conveyance guide member (conveyance belt) 10, receives heat and pressure, and the toner R image is fixed on the recording material P, thereby recording material. An image is formed on P.

  On the other hand, the photosensitive drum 1 that has completed the transfer process, after the transfer residual toner on the photosensitive drum 1 is removed by the cleaning device 7, is uniformly charged again by the charging device 2 to prepare for the next image formation.

  Next, problems with the conventional image forming apparatus will be described.

  FIG. 2 is an enlarged view of a transfer portion of the conventional image forming apparatus described in FIG.

  As described above, in order to obtain a high-quality transfer image, it is necessary that the recording material P and the photosensitive drum 1 be conveyed in close contact with the transfer unit. As shown in FIG. 2, this is a transfer charging region T in which a transfer electric field acts when the recording material P is floating from the photosensitive drum 1 in the portion A on the upstream side of the recording material conveyance. A transfer electric field acts on the A portion before P and the photosensitive drum 1 are in close contact, and the toner on the photosensitive drum 1 flies over the recording material P, and the toner image on the recording material P scatters. appear. In particular, in characters and line drawings, the outline is blurred and a sharp image cannot be obtained.

Further, in the image forming apparatus equipped with the double-sided printing function, particularly the recording material P of thin paper (less than 150 g / m ² ) receives heat and pressure once through the fixing device 8 at the time of image formation on the first side. The recording material P is deformed into irregularities. Then, when the image on the second surface is formed, the transfer electric field acts on the portion A before the recording material P on the upstream side of the recording material conveyance and the photosensitive drum 1 come into close contact, and the toner on the photosensitive drum 1 flies over the recording material P. However, there is a problem that the same transfer splattering occurs. However, in this case, since the distance between the photosensitive drum 1 and the recording material P is different between the concave portion and the convex portion of the recording material P in the A portion, the transfer electric field strength is different and the toner scattering state is different. Accordingly, the transfer splatter on the second surface has different toner image scattering states depending on the unevenness of the recording material P, and therefore, the density unevenness particularly occurs in the halftone image, and a uniform halftone image cannot be obtained. Will occur. In particular, density unevenness occurs remarkably in a photographic image with many halftones, and a clear image cannot be obtained.

On the other hand, in an image forming apparatus equipped with a double-sided printing function, the recording material P of thick paper (150 g / m ² or more) may pass through the fixing device 8 and receive heat and pressure once during the image formation on the first side. Since the recording material P is thick and has high rigidity, the recording material P does not deform into irregularities, or the irregularities are very small. In this case, the scattering state of the toner image is uniform, density unevenness does not occur in the halftone image, and a uniform halftone image can be obtained. Therefore, in a photographic image having many halftones, density unevenness does not occur and a clear image can be obtained.

  Therefore, on the first side and the second side of the thick paper, the entire surface is uniformly scattered and a sharp image cannot be obtained. In particular, on the second side of the thin paper, the recording material P is unevenly transferred. Scattering occurs and a uniform halftone image cannot be obtained. Since the first surface and the second surface of the cardboard are uniformly transferred and scattered, the influence on the image is relatively small. However, since the second surface is non-uniformly scattered and scattered, the influence on the image is relatively large.

  FIG. 3 shows an example of a conventional image forming apparatus when the height of the transfer entrance guide 9 is increased.

  FIG. 4 is an example of a conventional image forming apparatus showing the behavior of the leading end of the recording material P when the height of the transfer entrance guide 9 is increased.

  In order to avoid the transfer scattering described with reference to FIG. 2, it is preferable to increase the height of the transfer inlet guide 9 as shown in FIG. This is a configuration in which the recording material P is brought into contact with the photosensitive drum 1 at a position before the transfer portion, and the recording material P is wound around the photosensitive drum 1. In this way, when the recording material P is transported to the transfer charging region T where the transfer electric field acts in a state where the photosensitive drum 1 and the recording material P are in close contact with each other, toner flying occurs in the portion A on the upstream side of the recording material transport. Therefore, it is possible to prevent the scattering of the transfer.

  However, when the height of the transfer entrance guide 9 is increased as shown in FIG. 3, the scattering of the transfer is improved, but the problem of transfer omission (transfer failure) occurs at the leading end of the recording material P.

  As shown in FIG. 4, when the height of the transfer entrance guide 9 is increased, the leading end of the recording material P floats away from the photosensitive drum 1 due to the rigidity of the recording material P in the transfer charging region T. As a result, the toner image on the photosensitive drum 1 cannot be transferred, and leading edge transfer omission where the image is missing occurs. When the leading edge of the recording material P passes through the transfer charging region T and reaches the conveying belt 10 and is supported, the recording material P is lifted in the direction of the photosensitive drum 1, so that the state shown in FIG. Therefore, this transfer omission does not occur when the leading edge of the recording material P is supported by the conveying belt 10, and thus is a transfer omission that occurs only at the leading edge of the recording material P. Further, the leading edge transfer omission is caused by the rigidity of the recording material P, and the leading end portion of the recording material P is lifted from the photosensitive drum 1, so that it is difficult to occur with thin paper and easily with thick paper.

  Therefore, in the conventional image forming apparatus, it is impossible to achieve both transfer scattering and leading edge transfer omission.

  Next, Example 1 of the present invention will be described.

  6 and 8 are examples of the image forming apparatus according to the first exemplary embodiment of the present invention.

  5 and 7 show an example of an image forming apparatus of an application example in which a problem occurs in the first embodiment of the present invention.

  The shield member 20 in FIGS. 5 to 8 is a shield member that shields the transfer electric field in the transfer charging region T on the upstream side of the recording material conveyance. The position is moved by a driving unit (not shown) to change the shield region. The transfer charging area width is changed.

  As shown in FIGS. 5 to 8, the height of the transfer entrance guide 9 is arranged between FIG. 2 (transfer entrance guide is low) and FIG. 3 (transfer entrance guide is high). Both are intermediate arrangements that occur moderately.

  As shown in FIG. 5, in a state where the front end of the recording material P is supported by the conveyance belt 10 and the transfer charging region T is a position where the shielding member 20 does not shield the transfer electric field, the B portion on the upstream side of the recording material conveyance The transfer electric field acts on the floating part of the photosensitive drum 1 and the recording material P, and transfer scattering occurs.

  Here, as shown in FIG. 6 which is the present embodiment, in a state where the leading end of the recording material P is supported by the conveying belt 10, the shielding member 20 that shields the transfer electric field moves and the recording material in the transfer charging region T is moved. A transfer charging area T1 in which the transfer electric field acts only on the recording material conveyance downstream side is narrowed on the conveyance upstream side. In this case, since the recording material P is conveyed to the transfer charging region T1 in close contact with the photosensitive drum 1, the transfer electric field does not act on the B portion, and transfer scattering does not occur.

  However, as shown in FIG. 7, the position where the shielding member 20 shields the transfer electric field upstream of the recording material conveyance in a state where the leading edge of the recording material P passes through the transfer charging region (transfer process of the leading edge of the recording material P). That is, in the case of the transfer charging region T1 where the transfer electric field acts only on the downstream side of the recording material conveyance, the tip of the recording material P floats from the photosensitive drum 1 in the transfer charging region T1 due to the rigidity of the recording material P (part c). Since the toner cannot be transferred onto the recording material P until the leading end of the recording material P is supported by the conveying belt 10, the leading end transfer is lost.

  Therefore, as shown in FIG. 8, which is the present embodiment, in a state where the leading edge of the recording material P passes through the transfer charging area (transfer process of the leading edge of the recording material P), the shielding member 20 is moved to transfer the charging area T1. The transfer charging region T in which the transfer electric field also acts on the upstream side of the recording material conveyance is widened. In this case, since the toner can be transferred by the transfer charging region T at the portion D where the leading end of the recording material P is in close contact with the photosensitive drum 1, no leading end transfer defect occurs.

  Therefore, in this embodiment, during the transfer process of the leading edge of the recording material P, as shown in FIG. 8, the shielding member 20 is moved to the position where the transfer electric field acts to the upstream side of the recording material conveyance, By doing so, it is possible to prevent the tip transfer from being lost.

  On the other hand, during the transfer process after the leading edge of the recording material P is supported by the conveying belt 10, as shown in FIG. 6, the transfer electric field does not act up to the recording material conveyance upstream side, that is, only on the recording material conveyance downstream side. By moving the shielding member 20 so that the transfer electric field acts to make the transfer charging region T1, transfer scattering can be prevented. Accordingly, since the transfer electric field acts only on the downstream side of the recording material conveyance, the transfer electric field does not act in the state where the recording material P on the upstream side of the recording material conveyance and the photosensitive drum 1 are floated, and thus toner flying occurs. It is possible to prevent both the above-described uniform transfer scattering on the first surface and the uneven transfer scattering due to the unevenness of the recording material P on the second surface.

  However, in this embodiment, since priority is given to preventing the transfer of the leading edge of the recording material, a slight amount of transfer scattering occurs at the leading edge of the recording material.

  Actually, in the image forming apparatus of this embodiment that operates the movable shielding member 20 shown in FIG. 6 and FIG. 8, as the recording material P, from the thin paper to the thick paper, and on both the first and second surfaces, the transfer scattering and the leading edge A sharp and clear transfer image without transfer omission was obtained.

9 and 10 show another example of the transfer device of the image image forming apparatus according to the first embodiment.
6 and 8, the configuration in which the transfer charging area width is changed by the movable shielding member 20 has been described. 9 and 10 show a configuration in which the transfer charging area width is changed by moving the transfer device shield plate on the upstream side.

  The transfer device 5 shown in FIG. 9 is divided into a downstream transfer shield 5b and an upstream transfer shield 5c. Although the downstream transfer shield 5b is fixedly arranged, the position of the upstream transfer shield 5c is movable by a driving means (not shown). The upstream transfer shield 5c is configured to move so as to be as shown in FIG. 9A when the transfer charging region T1 and FIG. 9B when the transfer charging region T, thereby changing the transfer charging region width.

  10 is divided into a downstream transfer shield 5b and an upstream transfer shield 5e. Although the downstream transfer shield 5b is fixedly arranged, the position of the upstream transfer shield 5e is movable by driving means (not shown) with the shield rotation support member 5d as a fulcrum. The upstream transfer shield 5e is configured to move so as to be as shown in FIG. 10A at the transfer charging region T1 and as shown in FIG. 10B at the transfer charging region T to change the transfer charging region width.

  Even if the transfer device 5 shown in FIGS. 9 and 10 is applied to the present embodiment, the effect is the same.

  Further, as a method of changing the transfer charging area width, other configurations than the configurations shown in FIGS. 6, 8, 9, and 10 may be adopted as long as the operation is the same.

  The change of the transfer charging area width during the transfer process in the present embodiment is preferably performed on both the first and second surfaces, but the first surface is less noticeable because the entire surface is uniformly transferred and scattered. Since the halftone density unevenness due to the unevenness of the recording material on the second surface is very conspicuous, a configuration in which the present embodiment is applied only to the second surface may be used depending on the image forming apparatus.

  Further, in order to improve the transfer scattering due to the unevenness of the recording material on the second surface, it is necessary to make the transfer charging area more downstream on the recording material conveyance side than to improve the transfer scattering on the first surface. It is necessary to increase the shielding amount for shielding the transfer charging area on the upstream side of the recording material conveyance by the member 20. Accordingly, the amount of change in the transfer charging area width after the leading edge of the recording material is set differently on the first side and the second side. Specifically, the shielding amount of the transfer charging area by the shielding member 20 is compared with that on the first side. It is better to set the second side to be larger.

  Accordingly, since the amount of change in the transfer charging area width during the recording material transfer process can be varied according to the first and second surfaces of the recording material, more detailed settings can be made. In contrast, a greater improvement effect can be obtained.

The transfer charging area width change in the middle of the transfer process of this embodiment is preferably performed for all recording materials, but the halftone density unevenness due to the unevenness of the recording material on the second side is thin paper (150 g / m ^2). only occurs in less than), since it does not occur in thick paper (150 g / m ² or more), may be only the configuration of the present embodiment is applied in thin (less than 150 g / m ^2).

  In addition, with regard to transfer scattering due to the unevenness on the second surface, unevenness due to the fixing device tends to be formed on the thin paper, and therefore, the halftone density unevenness is large. Accordingly, the second surface of the thin paper needs to have a relatively large transfer charging area after the leading end of the recording material on the downstream side of the recording material conveyance, that is, the shielding charging member 20 shields the transfer charging area on the upstream side of the recording material conveyance. The amount of shielding needs to be relatively large.

  On the other hand, since unevenness due to the fixing device is difficult to be formed on the thick paper, the halftone density unevenness is small. Accordingly, the second surface of the cardboard needs to have a relatively small transfer charging area after the leading end of the recording material on the downstream side of the recording material conveyance, ie, the shielding charging member 20 shields the transfer charging area on the upstream side of the recording material conveyance. A configuration in which the shielding amount is relatively small may be used.

  In addition, regarding the transfer of the leading edge, if the recording material has a large rigidity (if it is stiff), the leading edge of the recording material P and the photosensitive drum 1 have a large float, and the level of the leading edge transfer is not good. Therefore, for thick paper with high rigidity, it is necessary to expand the transfer charging area at the leading end of the recording material to the upstream side of the recording material conveyance, that is, the shielding member 20 shields the transfer charging area on the upstream side of the recording material conveyance. The amount should be relatively small.

  On the other hand, when the rigidity of the recording material is small (when the waist is weak), the floating between the leading end of the recording material P and the photosensitive drum 1 is small. Accordingly, it is relatively small for thin paper with low rigidity to expand the transfer charging area at the leading end of the recording material to the upstream side of the recording material conveyance, that is, the shielding member 20 shields the transfer charging area upstream of the recording material conveyance. The amount may be relatively large.

  Further, regarding the transfer scattering, the recording material having a low resistance value has a strong transfer electric field acting on the gap in the floating portion between the recording material P and the photosensitive drum 1 on the upstream side of the recording material conveyance, and the toner easily flies. Spattering is likely to occur. Therefore, in the low resistance recording material, the transfer charging area after the leading end of the recording material needs to be relatively downstream of the recording material conveyance, that is, the shielding member 20 shields the transfer charging area upstream of the recording material conveyance. The amount of shielding needs to be relatively large.

  On the other hand, a recording material having a high resistance value has a weak transfer electric field acting on the gap between the recording material P on the upstream side of the recording material conveyance and the photosensitive drum 1, and the toner is difficult to fly. Hateful. Accordingly, the high resistance recording material needs to have a relatively small transfer charging area after the leading end of the recording material on the recording material conveyance downstream side, that is, the shielding member 20 shields the transfer charging area on the recording material conveyance upstream side. The shielding amount may be relatively small.

  Accordingly, since the change amount of the transfer charging area width during the transfer process of the recording material can be made variable according to the characteristics (rigidity / weight / thickness / resistance value) of the recording material, more detailed settings can be made. It is possible to obtain a greater improvement effect against the scattering and the tip transfer omission.

  The recording material characteristics may be configured such that the image forming apparatus automatically detects the recording material characteristics by each detection unit (not shown) and reflects the change in the transfer charging area width. Alternatively, the recording material characteristics may be manually input to the image forming apparatus and reflected in the change amount of the transfer charging area width.

  The change of the transfer charging area width during the transfer process in the present embodiment is preferably performed in all environments. However, in the normal environment and the high humidity environment, the unevenness of the recording material occurs in the fixing device 1. However, in the low humidity environment, the recording material is dehumidified and the recording material is uneven even in the first surface. Therefore, the normal environment and the high humidity environment are only in the second embodiment. The low-humidity environment may be configured to apply this embodiment on both the first and second surfaces.

  Further, it has been described above that the level of transfer scattering varies depending on the resistance value of the recording material. The resistance value of the recording material varies depending on the characteristics unique to the recording material, but also varies depending on the environment, that is, the moisture content of the recording material. Accordingly, the level of transfer scattering varies depending on the environment.

  In a high humidity environment, the resistance value of the recording material decreases due to moisture absorption, the transfer electric field acting on the gap in the floating portion between the recording material P and the photosensitive drum 1 on the upstream side of the recording material conveyance is strong, and the toner is likely to fly. , Transfer scattering is likely to occur. Therefore, in a high humidity environment, the transfer charging area after the leading edge of the recording material needs to be relatively downstream of the recording material conveyance, that is, the shielding member 20 shields the transfer charging area upstream of the recording material conveyance. The amount needs to be relatively large.

  On the other hand, in the low humidity environment, the resistance value of the recording material increases due to dehumidification, the transfer electric field acting on the gap in the floating portion between the recording material P and the photosensitive drum 1 on the upstream side of the recording material conveyance is weak, and the toner flies. Because it is difficult, transfer scattering hardly occurs. Therefore, in a low humidity environment, the transfer charging area after the leading edge of the recording material needs to be relatively downstream of the recording material conveyance, that is, the shielding amount that shields the transfer charging area upstream of the recording material conveyance by the shielding member 20. May be relatively small.

  Here, as the moisture content of the environment, the moisture content of the recording material may be substituted by the absolute moisture content calculated from the temperature and humidity detected by a detection unit (not shown) provided in the image forming apparatus.

  Therefore, by making the change amount of the transfer charging area width during the transfer process of the recording material variable according to the environment, more detailed settings can be made. Can be obtained.

  Further, the leading edge shape on the second surface varies depending on conditions such as the image forming apparatus, the double-sided printing function, the characteristics (rigidity / weight / thickness) of the recording material, and the moisture content of the recording material determined by the environment. For example, the curl amount is large in the portion where the curvature of the recording material conveyance path of the double-sided printing function is small, the curl amount is large because the recording material is thin, and the curl amount is large. The amount of curl is large. That is, the leading edge of the second surface varies depending on conditions such as an upper curl shape, a straight shape, a lower curl shape, and a curl amount when it is conveyed to the transfer unit.

  When the leading end of the recording material has an upper curl shape, the leading end of the recording material P easily adheres along the photosensitive drum 1 and the amount of floating between the recording material P and the photosensitive drum 1 is small. Therefore, when the recording material front end portion has an upper curl shape, it is relatively small that the transfer charging region at the recording material front end portion needs to be widened to the upstream side of the recording material conveyance. The amount of shielding for shielding may be made relatively large.

  On the other hand, when the leading end of the recording material has a lower curl shape, the leading end of the recording material P is difficult to adhere away from the photosensitive drum 1 and the amount of floating between the recording material P and the photosensitive drum 1 is large, and leading end transfer omission occurs. Cheap. Therefore, when the recording material front end portion has a lower curl shape, it is relatively large that the transfer charging area at the recording material front end portion needs to be widened to the upstream side of the recording material conveyance. It is necessary to make the amount of shielding for shielding relatively small.

  Therefore, since the amount of change in the transfer charging area width during the transfer process of the recording material can be varied according to various conditions, more detailed settings can be made. An improvement effect can be obtained.

  By changing the transfer charging area width in this embodiment, that is, by changing the transfer device opening width, the transfer current flowing from the transfer device in the direction of the photosensitive drum is changed although there is a magnitude depending on the amount of displacement of the width change. When the transfer current in the photosensitive drum direction is small, the transfer electric field for transferring the toner is small, so that a transfer failure in which the toner cannot be transferred occurs. On the other hand, when the transfer current in the photosensitive drum direction is large, the transfer charge of the recording material increases, and the charge of the recording material is not sufficiently eliminated by the separating device, so that the recording material is difficult to separate from the photosensitive drum, resulting in a separation failure.

  Therefore, in order to make the transfer current in the photosensitive drum direction constant and the transfer performance and separation performance constant, the value of the current flowing through the transfer wire of the transfer device or the transfer wire is applied according to the change in the transfer charging area width. It is preferable that the voltage value be changed. The current value flowing through the transfer wire is the sum of the transfer current flowing toward the photosensitive drum and the current value flowing toward the shield member of the transfer device. By changing the current value flowing through the transfer wire, the voltage value applied to the transfer wire is inevitably changed.

  Specifically, when the transfer charging area width is increased, the transfer current in the photosensitive drum direction increases, so the value of the current flowing through the transfer wire is decreased (the voltage value applied to the transfer wire is decreased).

  On the other hand, when the width of the transfer charging area is reduced, the transfer current in the photosensitive drum direction is reduced. Therefore, it is preferable to increase the current value flowing through the transfer wire (increase the voltage value applied to the transfer wire).

  Therefore, by making the transfer wire current value variable according to the transfer charge area width, it is possible to obtain an improvement effect on transfer splatter and leading edge transfer omission while maintaining the transfer performance and separation performance constant. Can do.

  As described above, in this embodiment, in the image forming apparatus using the non-contact transfer method of the discharge mechanism, by changing the transfer charging area width during the transfer process, both the problems of transfer scattering and leading edge transfer omission are caused. An image forming apparatus that can be effectively prevented can be provided.

  More specifically, in the transfer portion, the recording material front end portion widens the transfer charging area so that the transfer electric field acts to the upstream side of the recording material conveyance to prevent the tip transfer omission. An image forming apparatus capable of effectively preventing both the problems of transfer splattering and tip transfer omission by narrowing the transfer charging area so that the transfer electric field acts only on the downstream side of the recording material conveyance and preventing transfer splattering. Can be provided.

  A second embodiment according to the present invention will be described with reference to FIGS.

  In this embodiment, by moving the transfer charging area in the middle of the transfer process, both the problems of transfer scattering and tip transfer omission, which are conventional problems, are improved.

  A second embodiment of the present invention will be described.

  12 and 14 show an example of an image forming apparatus according to the second embodiment of the present invention.

  11 and 13 show an example of an image forming apparatus of an application example in which a problem occurs in the second embodiment of the present invention.

  The transfer device 5 in FIGS. 11 to 14 has a configuration in which the position of the transfer device 5 is moved by a driving unit (not shown) to move the transfer charging region.

  As shown in FIGS. 11 to 14, the height of the transfer inlet guide 9 is arranged between FIG. 2 (lower transfer inlet guide) and FIG. 3 (higher transfer inlet guide). Both are intermediate arrangements that occur moderately.

  As shown in FIG. 11, in a state where the transfer device 5 is the transfer charging region T arranged as shown in FIG. 11 with the leading end of the recording material P supported by the conveyance belt 10, the B section on the upstream side of the recording material conveyance. The transfer electric field acts on the floating part of the photosensitive drum 1 and the recording material P, and transfer scattering occurs.

  Here, as shown in FIG. 12, which is the present embodiment, the transfer device 5 is moved and arranged as shown in FIG. 12 with the leading end of the recording material P supported by the conveying belt 10, and the recording material is conveyed downstream. A transfer charging region T2 in which a transfer electric field acts only on the side is assumed. In this case, since the recording material P is conveyed to the transfer charging region T2 in close contact with the photosensitive drum 1, the transfer electric field does not act on the B portion, and transfer scattering does not occur.

  However, as shown in FIG. 13, in a state where the leading end of the recording material P passes through the transfer charging region (transfer step of the leading end of the recording material P), the transfer charging region T2 where the transfer electric field acts only on the recording material conveyance downstream side. In this case, due to the rigidity of the recording material P, the leading end of the recording material P floats from the photosensitive drum 1 in the transfer charging region T2 (part c), and toner is recorded until the leading end of the recording material P is supported by the conveyance belt 10. Since the transfer is not performed on the material P, the transfer of the leading edge is lost.

  Therefore, as shown in FIG. 14 of the present embodiment, the transfer device 5 moves as shown in FIG. 14 in a state where the leading end of the recording material P passes through the transfer charging region (transfer step of the leading end of the recording material P). The transfer charging region T in which the transfer electric field acts also on the upstream side of the recording material conveyance is defined. In this case, since the toner can be transferred by the transfer charging region T at the portion D where the leading end of the recording material P is in close contact with the photosensitive drum 1, no leading end transfer defect occurs.

  Therefore, in this embodiment, during the transfer process of the leading edge of the recording material P, as shown in FIG. 14, the transfer device 5 is moved to a position where the transfer electric field acts to the upstream side of the recording material conveyance, By doing so, it is possible to prevent the tip transfer from being lost.

  On the other hand, during the transfer process after the leading edge of the recording material P is supported by the conveyance belt 10, as shown in FIG. 12, the transfer electric field does not act up to the recording material conveyance upstream side, that is, only on the recording material conveyance downstream side. By moving the transfer device 5 so that the transfer electric field acts to set the transfer charging region T2, it is possible to prevent the transfer scattering. Therefore, since the transfer electric field acts only on the downstream side of the recording material conveyance, the transfer electric field does not act in the state where the recording material P on the upstream side of the recording material conveyance and the photosensitive drum 1 are floated. It is possible to prevent both the above-described uniform transfer scattering on the first surface and the uneven transfer scattering due to the unevenness of the recording material P on the second surface.

  However, in this embodiment, since priority is given to preventing the transfer of the leading edge of the recording material, a slight amount of transfer scattering occurs at the leading edge of the recording material.

  Actually, in the image forming apparatus of the present embodiment in which the movable transfer device 5 shown in FIGS. 12 and 14 is operated, as the recording material P, from the thin paper to the thick paper, and on both the first and second surfaces, the transfer scattering and the leading edge A sharp and clear transfer image without transfer omission was obtained.

  Further, as a method of moving the transfer charging region, other than the configuration of moving the transfer device 5 as shown in FIGS. 12 and 14, other configurations may be adopted as long as the operation is the same, such as tilting the transfer device 5. May be.

  The transfer charging area movement during the transfer process in the present embodiment is preferably performed on both the first and second surfaces, but the first surface is not so noticeable because the entire surface is uniformly transferred and scattered. Since the halftone density unevenness due to the unevenness of the recording material on the second side is very conspicuous, a configuration in which the present embodiment is applied only to the second side may be used depending on the image forming apparatus.

  Further, in order to improve the transfer scattering due to the unevenness of the recording material on the second surface, it is necessary to make the transfer charging area more downstream on the recording material conveyance side than to improve the transfer scattering on the first surface. It is necessary to increase the amount of movement for moving the apparatus 5 to the recording material conveyance downstream side. Accordingly, the movement amount of the transfer charging area after the leading end of the recording material is set to be different between the first surface and the second surface. Specifically, the movement amount of the transfer device 5 to the recording material conveyance downstream side is different from that of the first surface. In comparison, the second surface may be set to be larger.

  Therefore, by making the amount of movement of the transfer charging area during the transfer process of the recording material variable according to the first side and the second side of the recording material, more detailed settings can be made. On the other hand, a greater improvement effect can be obtained.

The transfer charging area movement during the transfer process in this embodiment is preferably performed on all the recording materials, but the halftone density unevenness due to the unevenness of the recording material on the second side is thin paper (less than 150 g / m ^2). ), And not with thick paper (150 g / m ² or more), the present embodiment may be applied only to thin paper (less than 150 g / m ² ).

  In addition, with regard to transfer scattering due to the unevenness on the second surface, unevenness due to the fixing device tends to be formed on the thin paper, and therefore, the halftone density unevenness is large. Therefore, the second surface of the thin paper needs to have a relatively large transfer charging area after the leading end of the recording material on the downstream side of the recording material conveyance, that is, a relatively small amount of movement of the transfer device 5 to the downstream side of the recording material conveyance. It needs to be bigger.

  On the other hand, since unevenness due to the fixing device is difficult to be formed on the thick paper, the halftone density unevenness is small. Therefore, the second surface of the cardboard needs to have a relatively small transfer charging area after the leading end of the recording material on the downstream side of the recording material conveyance, that is, the transfer amount of the transfer device 5 to the downstream side of the recording material conveyance is relatively small. It may be configured to be small.

  In addition, regarding the transfer of the leading edge, if the recording material has a large rigidity (if it is stiff), the leading edge of the recording material P and the photosensitive drum 1 have a large float, and the level of the leading edge transfer is not good. Therefore, for thick paper with high rigidity, the transfer charging area at the leading end of the recording material needs to be expanded to the upstream side of the recording material conveyance, that is, the amount of movement of the transfer device 5 to the upstream side of the recording material conveyance is relatively large. Good.

  On the other hand, when the rigidity of the recording material is small (when the waist is weak), the floating between the leading end of the recording material P and the photosensitive drum 1 is small. Therefore, for thin paper with low rigidity, it is relatively small that the transfer charging area at the leading end of the recording material needs to be expanded upstream of the recording material conveyance, that is, the amount of movement of the transfer device 5 upstream of the recording material conveyance is relatively small. You may do it.

  Further, regarding the transfer scattering, the recording material having a low resistance value has a strong transfer electric field acting on the gap in the floating portion between the recording material P on the upstream side of the recording material conveyance and the photosensitive drum 1, and the toner easily flies. Spattering is likely to occur. Therefore, it is necessary for the low resistance recording material to have a relatively large transfer charging area after the recording material leading end portion on the downstream side of the recording material conveyance, that is, a relatively small amount of movement of the transfer device 5 to the downstream side of the recording material conveyance. It needs to be bigger.

  On the other hand, a recording material having a high resistance value has a weak transfer electric field acting on the gap between the recording material P on the upstream side of the recording material conveyance and the photosensitive drum 1, and the toner is difficult to fly. Hateful. Therefore, the high resistance recording material needs to have a relatively small transfer charging area after the leading end of the recording material on the downstream side of the recording material conveyance, that is, the movement amount of the transfer device 5 to the downstream side of the recording material conveyance is relatively small. It may be small.

  Accordingly, since the amount of movement of the transfer charging area during the transfer process of the recording material can be made variable according to the characteristics of the recording material (rigidity / weight / thickness / resistance value), more detailed settings can be made. As a result, a greater improvement effect can be obtained with respect to missing transfer of the tip.

  The recording material characteristics may be configured such that the image forming apparatus automatically detects the recording material characteristics by each detection unit (not shown) and reflects the movement amount of the transfer charging area. Alternatively, each recording material characteristic may be manually input to the image forming apparatus and reflected in the movement amount of the transfer charging area.

  The transfer charging area movement during the transfer process in the present embodiment is preferably performed in all environments. However, in a normal environment and a high humidity environment, unevenness of the recording material occurs once in the fixing device. In the low humidity environment, the recording material is dehumidified and the recording material is uneven even in the first surface. Therefore, the normal environment and the high humidity environment are only in the second embodiment. The low humidity environment may be applied so that both the first and second surfaces apply this embodiment.

  Further, it has been described above that the level of transfer scattering varies depending on the resistance value of the recording material. The resistance value of the recording material varies depending on the characteristics unique to the recording material, but also varies depending on the environment, that is, the moisture content of the recording material. Accordingly, the level of transfer scattering varies depending on the environment.

  In a high humidity environment, the resistance value of the recording material decreases due to moisture absorption, the transfer electric field acting on the gap in the floating portion between the recording material P and the photosensitive drum 1 on the upstream side of the recording material conveyance is strong, and the toner is likely to fly. , Transfer scattering is likely to occur. Therefore, in a high humidity environment, it is necessary to make the transfer charging area after the leading end of the recording material downstream of the recording material conveyance, that is, the amount of movement of the transfer device 5 downstream of the recording material conveyance relatively large. There is a need to.

  On the other hand, in the low humidity environment, the resistance value of the recording material increases due to dehumidification, the transfer electric field acting on the gap in the floating portion between the recording material P and the photosensitive drum 1 on the upstream side of the recording material conveyance is weak, and the toner flies. Because it is difficult, transfer scattering hardly occurs. Therefore, in a low humidity environment, it is necessary to make the transfer charging area after the leading edge of the recording material relatively downstream of the recording material conveyance, that is, the amount of movement of the transfer device 5 to the recording material conveyance downstream side is relatively small. May be.

  Here, as the moisture content of the environment, the moisture content of the recording material may be substituted by the absolute moisture content calculated from the temperature and humidity detected by a detection unit (not shown) provided in the image forming apparatus.

  Therefore, by changing the amount of movement of the transfer charging area during the transfer process of the recording material according to the environment, more detailed settings can be made. Obtainable.

  Further, the leading edge shape on the second surface varies depending on conditions such as the image forming apparatus, the double-sided printing function, the characteristics (rigidity / weight / thickness) of the recording material, and the moisture content of the recording material determined by the environment. For example, the curl amount is large in the portion where the curvature of the recording material conveyance path of the double-sided printing function is small, the curl amount is large because the recording material is thin, and the curl amount is large. The amount of curl is large. That is, the leading edge of the second surface varies depending on conditions such as an upper curl shape, a straight shape, a lower curl shape, and a curl amount when it is conveyed to the transfer unit.

  When the leading end of the recording material has an upper curl shape, the leading end of the recording material P easily adheres along the photosensitive drum 1 and the amount of floating between the recording material P and the photosensitive drum 1 is small. Therefore, when the recording material front end portion has an upper curl shape, it is relatively small that the transfer charging area at the recording material front end portion needs to be widened to the upstream side of the recording material conveyance, and the movement amount of the transfer device 5 to the upstream side of the recording material conveyance May be relatively small.

  On the other hand, when the leading end of the recording material has a lower curl shape, the leading end of the recording material P is difficult to adhere away from the photosensitive drum 1 and the amount of floating between the recording material P and the photosensitive drum 1 is large, and leading end transfer omission occurs. Cheap. Therefore, when the recording material front end portion has a lower curl shape, it is relatively large that the transfer charging area at the recording material front end portion needs to be widened to the upstream side of the recording material conveyance. Needs to be relatively large.

  Therefore, by making the amount of movement of the transfer charging area variable during the recording material transfer process according to various conditions, more detailed settings can be made. An effect can be obtained.

  In the transfer charging area movement of this embodiment, that is, the transfer device movement, since the transfer charging area width is the same and the position is only moved, the change in the transfer current flowing in the direction of the photosensitive drum is very small. Accordingly, since the transfer performance does not change, there is an advantage that it is not necessary to change the current value flowing through the transfer wire of the transfer device or the voltage value applied to the transfer wire in accordance with the change in the transfer charging area width of the first embodiment.

  As described above, in this embodiment, in the image forming apparatus using the non-contact transfer method of the discharge mechanism, the transfer charging area is moved in the middle of the transfer process, so that both the problems of transfer scattering and leading edge transfer omission are effective. Therefore, it is possible to provide an image forming apparatus that can prevent the problem.

  More specifically, in the transfer portion, the recording material front end moves the transfer charging area so that a transfer electric field acts to the upstream side of the recording material conveyance, and prevents the transfer of the front end. An image forming apparatus that can effectively prevent both transfer splattering and leading edge transfer omission by moving the transfer charging area so that the transfer electric field acts only on the recording material conveyance downstream side to prevent transfer splattering. Can be provided.

FIG. 10 is a schematic cross-sectional view illustrating an example of a conventional image forming apparatus. FIG. 10 is a schematic cross-sectional view illustrating a “transfer scattering” problem of a conventional image forming apparatus. FIG. 10 is a schematic cross-sectional view for explaining a countermeasure against “transfer scattering” of a conventional image forming apparatus. FIG. 6 is a schematic cross-sectional view for explaining a “tip transfer omission” problem of a conventional image forming apparatus. FIG. 3 is a schematic cross-sectional view illustrating a “transfer scattering” problem of the image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 3 is a schematic cross-sectional view illustrating “transfer scattering” countermeasures of the image forming apparatus according to the first embodiment of the present invention. FIG. 3 is a schematic cross-sectional view illustrating a “tip transfer omission” problem in the image forming apparatus according to the first exemplary embodiment of the present invention. FIG. 3 is a schematic cross-sectional view illustrating a countermeasure for “distal transfer at the tip” of the image forming apparatus according to the first embodiment of the present invention. It is a typical sectional view of an important section showing other examples of an image forming device concerning Example 1 of the present invention. It is a typical sectional view of an important section showing other examples of an image forming device concerning Example 1 of the present invention. FIG. 9 is a schematic cross-sectional view for explaining a “transfer scattering” problem in an image forming apparatus according to Embodiment 2 of the present invention. FIG. 10 is a schematic cross-sectional view for explaining a countermeasure against “transfer scattering” of an image forming apparatus according to Embodiment 2 of the present invention. FIG. 9 is a schematic cross-sectional view for explaining a “tip transfer omission” problem in an image forming apparatus according to Embodiment 2 of the present invention. FIG. 10 is a schematic cross-sectional view illustrating a countermeasure for “distal transfer at the tip” of the image forming apparatus according to the second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging apparatus 3 Exposure apparatus 4 Developing apparatus 5 Transfer apparatus 5a Transfer wire 6 Separating apparatus 7 Cleaning apparatus 8 Fixing apparatus 9 Guide member (transfer entrance guide)
10 Conveying guide member (conveying belt)
20 Shielding member T, T1, T2 Transfer charging area R Toner P Recording material

Claims (8)

In an image forming apparatus provided with a non-contact transfer device of a discharge mechanism for transferring a toner image on an image carrier to a recording material,
An image forming apparatus, wherein a transfer charging area width is changed during a toner image transfer process to a recording material. In an image forming apparatus provided with a non-contact transfer device of a discharge mechanism for transferring a toner image on an image carrier to a recording material,
An image forming apparatus, wherein a transfer charging area is moved during a toner image transfer process to a recording material.   In the transfer unit that transfers the toner image on the image carrier to the recording material, the recording material front end is a transfer charging area including the upstream side of the recording material conveyance, and the recording material conveyance downstream side is the transfer charging area after the recording material front end. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   In the transfer unit that transfers the toner image on the image carrier to the recording material, the leading end of the recording material that is guided by the guide member and conveyed between the image carrier and the transfer device is disposed downstream of the transfer unit. The transfer charging area including the recording material conveyance upstream side is supported until supported by the conveyance guide member, and the recording material conveyance downstream side after the leading end of the recording material is supported by the conveyance guide member arranged on the downstream side of the transfer unit The image forming apparatus according to claim 3, wherein a transfer charging region is used.   A double-sided printing function is provided, and the amount of change in the transfer charging area width or the amount of movement of the transfer charging area during the recording material transfer process can be varied according to the first and second sides of the recording material. The image forming apparatus according to claim 1.   5. The change amount of the transfer charging area width or the movement amount of the transfer charging area during the transfer process of the recording material is made variable according to the characteristics of the recording material. Image forming apparatus.   5. The image according to claim 1, wherein a change amount of the transfer charging area width or a movement amount of the transfer charging area during the transfer process of the recording material is made variable according to the environment. Forming equipment.   5. The image forming apparatus according to claim 1, wherein a value of a current flowing through the transfer wire of the transfer device or a voltage value applied to the transfer wire is changed in accordance with the width of the transfer charging region. .

Images