JP2007033540A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a cost by preventing transfer failure regardless of constant current control even when a narrow-width transfer material passes when using an elastic transfer blade. <P>SOLUTION: The elastic transfer blade has a high-rigidity part in a lengthwise direction in the vicinity of a transfer part, so that a photoreceptor drum and the transfer blade are separated in a paper non-passage part by thickness of the transfer paper when the narrow-width transfer paper passes. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having an elastic transfer blade.

  An image carrier and a transfer member that is pressed against the image carrier are provided, and a transfer material is passed between them. At this time, a bias voltage is applied to the transfer member to transfer the toner image on the image carrier to the transfer material. An image forming apparatus configured to do so has already been proposed.

  FIG. 8 is a schematic side view showing a typical example of such an image forming apparatus M.

  In the example shown in FIG. 8, the surface of the photosensitive drum 1 as a cylindrical image carrier having a diameter of 24 mm and having an axis line perpendicular to the paper surface and rotating in the direction indicated by the arrow X at a process speed of 115 mm / s is not shown. The image information is applied to the charged surface of the photosensitive drum 1 by a laser beam slit exposure or the like that is image-modulated by the image information writing means 3 after being uniformly charged to VD = −600 V through the charging roller 2 having a diameter of 12 mm by a power source of. And the exposed portion of the photosensitive drum 1 is attenuated to VL = -100 V, and an electrostatic latent image is formed. Next, toner is supplied to the latent image by the developing device 4 to form a toner image. When the photosensitive drum 1 as the image carrier rotates, the toner image reaches the transfer portion, which is a nip portion where the transfer roller 5 having a diameter of 18.0 mm, which is a transfer member, contacts the photosensitive drum 1, and the timing of the toner image. The transfer material P also reaches this transfer portion. At this time, a transfer bias is applied to the transfer roller 5 to apply a charge having the opposite polarity to the toner to the back surface of the transfer material, and the toner image on the photosensitive drum 1 is transferred. It shall be transferred to the material.

  In the illustrated apparatus, an OPC photosensitive drum is used as a photosensitive drum, and a charging roller 2 is negatively charged by being driven by pressure contact with the photosensitive drum 1 as charging means, and is also pressed against the photosensitive drum 1 as transfer means. Then, a semiconductive transfer roller 5 that gives a positive charge to the back surface of the transfer material was used.

  Image exposure is image exposure. When VDIV = -370 V is applied to the developing device 4, reversal development is performed with a negative toner.

  In such an image forming apparatus, constant current control and constant voltage control are performed for transfer bias control, and constant current control is performed when no transfer material is present at the transfer site, and the voltage at that time is stored, and the above-described voltage is stored. A voltage or an ATVC control for performing a constant voltage control at the time of feeding a voltage calculated based on this voltage is used.

As a conventional example, for example, Patent Document 1 can be cited.
Japanese Unexamined Patent Publication No. 2000-321890

  However, in the case of the transfer roller system using the elastic body as described above, since the transfer roller can be one factor that determines the transfer speed of the transfer material, it is necessary to tighten the outer diameter accuracy. In addition, since the resistance of the transfer roller, which is a transfer member, varies depending on manufacturing variations, environment, and usage conditions, the bias applied to the transfer member is usually preferably controlled by constant current. However, in the constant current control, when a transfer material having a narrow width is processed, the transfer member directly contacts the photosensitive drum at a portion where the transfer material is not present, so that most of the current flows at that portion and a transfer failure occurs.

  In addition, in the case of a transfer blade having elasticity in order to obtain good contact with the transfer material or to simplify parts such as a pressure spring and a holder, the transfer member is transferred similarly to the transfer roller. Since the portion where there is no material is in direct contact with the photosensitive drum, most of the current flows in that portion, resulting in transfer failure.

  Since the above problems occur, the control like the ATVC described above requires complicated control.

  In order to solve the above problems, the present invention provides an image forming means for forming a latent image on an image carrier, a developing means for developing a latent image formed by the image forming means to form a developer image, It has a blade-like conductive elastic transfer member in contact with the image carrier, and contacts the image carrier to form a transfer portion. In such an image forming apparatus, the rigidity of the blade-like conductive elastic transfer member in the longitudinal direction is higher than that in the transfer material conveyance direction (perpendicular to the longitudinal direction), particularly in the vicinity of the transfer portion.

  In the image forming apparatus of the present invention, since the transfer member is a blade-like conductive elastic transfer member, the transfer member does not greatly affect the conveyance speed, so that it is not necessary to obtain high accuracy. Further, the blade-like conductive elastic transfer member can obtain good transfer performance by pressing the transfer material to the image carrier well due to its elasticity, while it has rigidity in the vicinity of the transfer portion formed with the image carrier. In the case where a narrow transfer material is processed, the image carrier and the conductive elastic transfer member are formed in a portion where there is no transfer material due to the rigidity of the conductive elastic transfer member and the thickness of the transfer material. Even when the bias applied to the conductive elastic transfer member is a simple constant current control, current flows from the conductive elastic transfer member to the image carrier in a portion where there is no transfer material. The problem that the voltage drops, a sufficient current does not flow through the transfer material, and a transfer failure occurs is eliminated.

Example 1
FIG. 1 shows an image forming apparatus according to the present invention, that is, an image forming apparatus provided with a fixing device according to the present invention. 1 is a longitudinal sectional view showing a schematic configuration of a laser beam printer as an example of an image forming apparatus according to the present invention.

  First, the configuration of a laser beam printer (hereinafter referred to as “image forming apparatus”) will be described with reference to FIG.

  The laser beam printer shown in FIG. 1 includes a drum-type electrophotographic photosensitive drum (hereinafter referred to as “photosensitive drum”) 1 as an image carrier. The photosensitive drum 1 is rotatably supported by the apparatus main body M, and is driven to rotate at a predetermined process speed in the arrow X direction by a driving unit (not shown).

  The process cartridge C includes the photosensitive drum 1 and at least one process means. Here, as the process means, for example, a charging roller 2 (charging means) for charging the surface of the photosensitive drum, a developing means 4 for forming a toner image on the electrophotographic photosensitive drum, and a toner remaining on the surface of the electrophotographic photosensitive drum are cleaned. Cleaning means 6 and the like. The process cartridge C of the present embodiment is a process cartridge C in which a charging unit 2, a developing unit 4 and a cleaning unit 6 are arranged around a photosensitive drum 1, and these are covered with a frame and integrated. Is configured to be detachable from the apparatus main body M.

  In addition, a paper feed tray 7 that stores a sheet-like recording material P such as paper is disposed in the front portion of the apparatus main body M, and a paper feed roller is sequentially arranged from the upstream side along the conveyance path of the recording material P. 8, a transport roller 9, a transport guide 10, a fixing device 11, a paper discharge roller 12, and a paper discharge tray 13 are arranged.

  Next, the operation of the image forming apparatus having the above configuration will be described.

  The photosensitive drum 1 that is rotationally driven in the direction of arrow X by a driving means (not shown) is uniformly charged to a predetermined polarity and a predetermined potential by a charging roller 2.

  The photosensitive drum 1 after charging is subjected to image exposure L based on the image information by the exposure means 3 such as a laser optical system on the surface, and the charge of the exposed portion is removed to form an electrostatic latent image.

  The electrostatic latent image is developed by the developing device 4. The developing device 4 has a developing roller. A developing bias is applied to the developing roller, and the toner is attached to the electrostatic latent image on the photosensitive drum 1, thereby developing the toner image (visualization). I do.

  The toner image is transferred to the recording material P such as paper by the elastic transfer blade 15. The recording material P is stored in a paper feed tray 7, fed and transported by a paper feed roller 8 and a transport roller 9, and a transfer nip between the photosensitive drum 1 and the transfer roller 5 via a top sensor 9. It is conveyed to the part. At this time, the leading edge of the recording material P is detected by a top sensor (not shown) and synchronized with the toner image on the photosensitive drum 1. The elastic transfer blade 15 is fixed to the frame at a fixed angle so as to come into pressure contact with the photosensitive drum 1, and a transfer bias is applied, whereby the toner image on the photosensitive drum 1 is moved to a predetermined position on the recording material P. Is transcribed.

  The recording material P carrying the unfixed toner image on the surface by transfer is transported to the fixing device 11 along the transport guide 10, where the unfixed toner image is heated and pressurized and fixed on the surface of the recording material P. .

  The recording material P after the toner image is fixed is conveyed and discharged by a discharge roller 12 onto a discharge tray 13 on the upper surface of the apparatus main body M.

  On the other hand, after the toner image is transferred, the toner remaining on the surface without being transferred to the recording material P is removed by the cleaning blade of the cleaning device 6 to prepare for the next image formation.

  By repeating the above operation, image formation can be performed one after another.

  FIG. 2 is an enlarged cross-sectional view of the photosensitive drum 1 and the elastic transfer blade 15 which are features of the present embodiment.

  In FIG. 2, the elastic transfer blade 15 is brought into contact with the rotational direction X of the photosensitive drum 1 in the forward direction and is pressed by the elasticity of the elastic transfer blade 15 to form a transfer nip portion. A rigid member 15 a is fixed in the vicinity of the transfer nip of the elastic transfer blade 15. In this embodiment, the rigid member 15a is a PC having a thickness of 1.2 mm, a width of 3 mm, and the length in the longitudinal direction is the same as that of the elastic transfer blade 15. Reference numeral 16 denotes a metal electrode for applying a transfer bias to the elastic transfer blade 15 and is in contact with the elastic transfer blade 2 on the entire surface in the longitudinal direction.

The elastic transfer blade 15 is made conductive by adding an additive such as conductive carbon to a resin such as PET, and the one used in this example has a length in the longitudinal direction of 220 mm, a thickness of 200 μm, and a width. The resistance value was 30 mm, and the resistance value was about 10 ⁶ Ω when a voltage of 1 KV was applied by replacing the photosensitive drum 1 with an aluminum drum from the electrode.

  FIG. 3 is a perspective view of the transfer portion when the present embodiment is used and when the narrow recording material P of the conventional example is passed, and the downstream side in the conveyance direction of the recording material P at this time (arrow in FIG. 3) FIG. 4 shows a schematic diagram viewed from the (S direction). 3 and 4, (a) shows a case where the conventional elastic transfer blade 15 is used, and (b) shows a case where this embodiment is also used.

  4A, in the portion A where the recording material P is not present, the elastic transfer blade 15 contacts the photosensitive drum 1 due to its elasticity. In this case, when the bias applied to the elastic transfer blade 15 is controlled at a constant current, the current Ita flowing in the area A in direct contact with the photosensitive drum 1 becomes large, and the current Itp flowing through the recording material P is almost eliminated. As a result, transfer failure occurs.

  On the other hand, in FIG. 4B, which is the present embodiment, the rigidity of the elastic transfer blade 15 in the transfer nip portion is maintained by the rigid member 15a. Therefore, the portion without the recording material P depends on the thickness of the recording material P. The elastic transfer blade 15 is separated from the photosensitive drum 1. As a result, the current Ita flowing in the portion without the recording material P is almost eliminated, and a sufficient current Itp flowing through the recording material P can be secured even if constant current control is performed.

  As described above, by using this embodiment, the transfer bias can be easily controlled by adding one simple member, and the blade transfer method has low costs, ozoneless, downsizing, and the like. There is no loss of the benefits.

(Example 2)
FIG. 5 shows an enlarged cross-sectional view of the photosensitive drum 1 and the elastic transfer blade 25, which is a feature of this embodiment.

In this embodiment, unlike the above embodiment, the elastic transfer blade 25 itself is bent at its tip as shown in FIG. 3 to increase the rigidity in the longitudinal direction of the tip of the elastic transfer blade 25 near the transfer nip. Yes. The elastic transfer blade 25 used in this example was made substantially the same as the above example by adding an additive such as conductive carbon to a resin such as PET, and the one used in this example was The length in the longitudinal direction is 220 mm, the thickness is 200 μm, and the width is 33 mm. The resistance value is about 10 ⁶ Ω when the electrode is replaced with an aluminum drum from the electrode and a voltage of 1 KV is applied. I used one.

  The feature of this embodiment is that the tip of the elastic transfer blade 25 is folded 3 mm and fixed with double-sided tape.

  By using this embodiment, it is possible to obtain the same effect as that of the above embodiment at a low cost by a very simple method.

  In this embodiment, the elastic transfer blade 25 is completely bent so as to overlap at the tip, but the same effect can be obtained if the cross section is bent so as to be L-shaped or bent in the middle as shown in FIG. Can be obtained.

(Example 3)
FIG. 7 shows an enlarged cross-sectional view of the photosensitive drum 1 and the elastic transfer blade 35, which is a feature of this embodiment.

  In this embodiment, the elastic transfer blade 35 has substantially the same shape as that of the above embodiment and has a longitudinal length of 220 mm, a thickness of 200 μm, and a width of 30 mm. However, what is used in this embodiment is insulative unlike the above embodiment.

  In this embodiment, a conductive rigid electrode 35a is provided on a portion of the insulating elastic transfer blade 35 that contacts the photosensitive drum 1. The conductive rigid electrode 35a is made conductive by adding carbon to a resin having good slidability such as POM. Transfer is performed by applying a transfer bias to the electrode 35a from a power source (not shown).

  By using this embodiment, the same effects as in the above embodiment can be obtained, and the range in which the transfer bias affects the recording material P is limited to the vicinity of the transfer nip, so that the toner image on the photosensitive drum 1 is exposed to light. The problem of so-called image scattering, in which the drum 1 and the recording material P fly over the recording material before coming into close contact with each other and scatter around the original image, can be solved. Further, since the elastic transfer blade 35 does not require adjustment of the electric resistance value, it is relatively easy to manufacture and has an advantage that the contact pressure to the photosensitive drum 1 and the like are easily stabilized.

  Further, the use of a resin having good slidability for the portion that slides with the recording material P has an advantage that the rubbing noise between the recording material P and the elastic transfer blade 35 can be reduced.

  In this embodiment, the electrode is made of resin, but it may be made of metal or other material.

1 is a schematic cross-sectional view showing an example of an image forming apparatus of the present invention. FIG. 3 is a schematic cross-sectional view showing a transfer part of Example 1 of the present invention. FIG. 2 is a schematic perspective view showing a transfer part of Example 1 of the present invention. FIG. 2 is a schematic view showing a transfer part of Example 1 of the present invention. FIG. 5 is a schematic cross-sectional view showing a transfer part of Example 2 of the present invention. FIG. 5 is a schematic cross-sectional view showing a transfer part of Example 2 of the present invention. FIG. 5 is a schematic cross-sectional view showing a transfer part of Example 3 of the present invention. FIG. 10 is a schematic cross-sectional view illustrating an example of a conventional image forming apparatus.

Explanation of symbols

1 Photosensitive drum
2 Charging roller
3 Laser scanner
4 Developer
5 Transfer roller
6 Cleaning device
7 Paper tray
8 Feed roller
9 Transport roller
10 Transport guide
11 Fusing device
12 Paper discharge roller
13 Output tray
15,25,35 Transfer blade

Claims (5)

An image carrier, an image forming unit that forms an image on the image carrier, and an image carrier that is opposite to the image carrier and transferring a transfer material to a transfer portion between the image carrier and the image carrier. In an image forming apparatus having an elastic transfer means having a blade shape that passes through and is transferred to a transfer material,
An image forming apparatus, wherein the transfer means has a rigidity in a direction perpendicular to a transfer material traveling direction higher than a rigidity in the transfer material travel direction. The image forming apparatus according to claim 1.
An image forming apparatus comprising: a member for increasing rigidity of the transfer unit in a direction perpendicular to a transfer material traveling direction. The image forming apparatus according to claim 1, wherein
An image forming apparatus characterized in that the transfer means is bent in a direction perpendicular to a transfer material traveling direction in the vicinity of the transfer portion to increase rigidity. The image forming apparatus according to claim 1, wherein
An image forming apparatus, wherein a conductive member is provided at a transfer portion of the transfer unit in a direction perpendicular to the transfer material traveling direction, and the conductive member has higher rigidity than other insulating portions of the transfer unit. The image forming apparatus according to claim 1.
An image forming apparatus, wherein a bias applied to a transfer member is constant current control.

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