JP4049599B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus that includes an image carrier and a charger that charges the image carrier, and the charger is disposed to face the image carrier.
[0002]
[Prior art]
An image forming apparatus of the above-described type that forms a visible image on an image carrier is conventionally known and is configured as a copier, a facsimile, a printer, or a multifunction machine having at least two of these functions. In this type of image forming apparatus, a charger for charging the image carrier is provided, and a discharge product is generated by a discharge phenomenon when the charger is operated. When such a discharge product adheres to the image carrier, the discharge product absorbs moisture in the air to reduce the resistance when the humidity is high, so that the amount of discharge product attached to the image carrier increases. The resistance of the surface of the carrier is lowered, thereby causing an abnormality in the image formed on the image carrier. Such an abnormal image is referred to as image flow or image blur.
[0003]
Conventionally, various configurations have been proposed in order to eliminate or suppress the above-described drawbacks. For example, an image forming apparatus that detects the temperature and humidity around the image carrier and heats the image carrier based on the detection result to control the surface temperature of the image carrier and prevent the occurrence of abnormal images. Proposed. However, according to this configuration, the image carrier is heated, so that toner blocking is easily generated.
[0004]
Further, there has been proposed an image forming apparatus having a water applying member for applying water to the surface of the image carrier and a water removing member for removing water from the surface of the image carrier, and this configuration adheres to the surface of the image carrier. This utilizes the property that the discharge product is soluble in water. However, since the surface of the image carrier generally has hydrophobicity, when water is applied to the surface of the image carrier, the water becomes sparse water droplets due to the hydrophobicity of the surface of the image carrier. Adhere to the surface. Accordingly, when water is applied to the surface of the image carrier, even if the discharge product dissolves in the water, the aqueous solution containing the discharge product adheres to the surface of the image carrier in a sparse state as water droplets. Although such water droplets are wiped off, since the water droplets on the surface of the image carrier exist in a sparse state at the time of wiping, the image carrier surface portion where the water droplets are attached and the image carrier where no water droplets are present There is a difference in the effect of removing the discharge product between the body surface portion and the characteristics of the surface of the image carrier after wiping may be uneven.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide an image forming apparatus capable of preventing the occurrence of an abnormal image or effectively suppressing the occurrence thereof while avoiding the drawbacks of the configuration according to the conventional proposal.
[0006]
[Means for Solving the Problems]
  In order to achieve the above object, according to the present invention, in the image forming apparatus of the type described at the beginning, at least a portion of the charger that performs the charging operation is disposed in a drying chamber partitioned by a casing, A seal is provided to cover at least a gap on the upstream side in the moving direction of the image carrier surface with respect to the charged region where the image carrier is charged, among the gaps between the image carrier surface and the seal. An image forming apparatus is also proposed, which also serves as a charge removal member for removing charge.
[0007]
At this time, it is advantageous that the seal is in contact with the image carrier.
[0008]
In the image forming apparatus according to claim 1 or 2, it is advantageous that at least a portion of the seal contacting the image carrier is made of an elastic body (claim 3).
[0009]
Further, in the image forming apparatus according to any one of claims 1 to 3, it is advantageous to provide seals respectively covering gaps on the upstream side and the downstream side in the movement direction of the image carrier surface with respect to the charging area. 4).
[0010]
5. The image forming apparatus according to claim 4, wherein at least a portion of the seal that covers the gap on the downstream side in the moving direction of the image carrier surface with respect to the charging region has a volume resistivity of 10 in contact with the image carrier.⁵It is advantageous if it is set to Ω · cm or more.
[0011]
Furthermore, in the image forming apparatus according to any one of claims 1 to 5, a seal that covers a gap on the upstream side in the moving direction of the image carrier surface with respect to the charging area also serves as a cleaning member that cleans the surface of the image carrier. (Claim 6).
[0013]
  Furthermore, in the image forming apparatus according to any one of the first to sixth aspects, it is advantageous that the seal that covers the gap on the upstream side in the moving direction of the image carrier surface with respect to the charging area is formed of a blade. .
[0014]
  7. The image forming apparatus according to claim 1, wherein a seal that covers a gap on the upstream side in the moving direction of the image carrier surface with respect to the charging area rotates while contacting the surface of the image carrier. It is advantageous if it consists of (claim 8).
[0015]
  Furthermore, in the image forming apparatus according to any one of claims 1 to 8, it is advantageous to provide an air blowing means for blowing air to an image carrier surface portion upstream of the housing in the moving direction of the image carrier surface. (Claim 9).
[0016]
  In the image forming apparatus according to claim 9, the absolute humidity of the air blown to the surface of the image carrier by the air blowing unit is the same as or lower than the absolute humidity of the air in the housing. (Claim 10).
[0017]
  The image forming apparatus according to claim 9 or 10, wherein the image bearing member is in contact with the surface portion of the image bearing member upstream in the moving direction of the image bearing member relative to the air blowing position on the surface of the image bearing member. It is advantageous to provide an air flow separating member for separating the air flow flowing in the vicinity of the surface.
[0018]
  Furthermore, in the image forming apparatus according to any one of claims 1 to 11, the image carrier, the casing, the charger, and a static image formed on the image carrier charged by the charger. A developing device that visualizes the electrostatic latent image and a cleaning device that cleans the surface of the image carrier after the visible image is transferred to a transfer material are integrally formed as a process cartridge. It is advantageous that the container and the housing are detachably attached to the cartridge case of the process cartridge.
[0019]
  Further, in the image forming apparatus according to any one of claims 1 to 12, it is advantageous that the image carrier is made of an amorphous silicon photoconductor or a photoconductor having a surface layer in which a filler is dispersed (claim 13). .
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings.
[0021]
FIG. 1 is a schematic cross-sectional view showing an example of an image forming apparatus, and an image carrier 2 configured as a drum-shaped photoconductor is disposed in a main body 1 thereof. The image carrier 2 shown here is composed of a cylindrical conductive substrate having a photoconductive layer formed on the outer peripheral surface thereof. However, the image carrier 2 is an endless belt that is wound around a plurality of rollers and rotated. An image carrier made of a photoreceptor can also be used. FIG. 3 is a partially enlarged view of FIG.
[0022]
When the image carrier 2 is rotationally driven in the direction of arrow A, the image carrier 2 is uniformly charged to a predetermined polarity, for example, −600 V, by a charger 3 disposed opposite to the image carrier 2. The On the other hand, a laser writing unit 4 that is an example of an exposure apparatus emits laser light L that is on / off controlled according to image information, and the laser light L is irradiated on the charged surface of the image carrier 2. As a result, an electrostatic latent image is formed on the image carrier 2. The potential of the image carrier surface irradiated with the laser beam L is, for example, −200 V, and this is an electrostatic latent image, that is, an image portion, and the potential of the image carrier surface not irradiated with the laser beam is maintained at approximately −600 V. This is the background part. Such an electrostatic latent image is visualized as a toner image when it passes through the developing device 5. The toner charged to a predetermined polarity is electrostatically attached to the electrostatic latent image, and the electrostatic latent image is visualized.
[0023]
A sheet feeding device 6 is disposed below the image forming apparatus main body 1, and the transfer material P made of, for example, transfer paper accommodated in a cassette 7 of the sheet feeding device 6 is moved in the direction of arrow B by the rotation of the sheet feeding roller 8. Sent out. The transferred transfer material P is sent between the image carrier 2 and the transfer device 10 by the registration roller pair 9 at a predetermined timing. The transfer device 10 illustrated here has a bias roller 11 disposed opposite to the image carrier 2, a tension roller 12, and a transfer belt 13 wound around these rollers and driven to rotate in the direction of the arrow. A voltage having a polarity opposite to the charging polarity of the toner is applied to the bias roller 11, whereby the toner image on the image carrier is transferred onto the transfer material P.
[0024]
The transfer material onto which the toner image has been transferred is subsequently carried on the transfer belt 13 and conveyed, and then passes through the fixing device 14. At this time, the toner image is fixed on the transfer material by the action of heat and pressure. The transfer material that has passed through the fixing device 14 is discharged out of the apparatus by a pair of discharge rollers 15.
[0025]
The transfer residual toner adhering to the surface of the image carrier after the toner image transfer is removed by the cleaning device 16. The cleaning device 16 illustrated here includes a cleaning brush 17 that abuts on the surface of the image carrier, a cleaning blade 18, and a cleaning case 50 that accommodates them. The surface of the image carrier after the cleaning is irradiated with light from a static eliminator 19 composed of a static elimination lamp, and the surface potential thereof is initialized.
[0026]
In the above-described example, the toner image formed on the image carrier is directly transferred to the transfer material P made of transfer paper or the like, but the transfer material is a drum-like or endless belt-like intermediate transfer. The toner image on the image carrier can be transferred onto a transfer material made of this intermediate transfer member, and then the toner image can be transferred to a final transfer material such as transfer paper.
[0027]
As the charger, for example, a corona discharger, a charging blade, or a charging brush can be used, but in the illustrated example, a charging roller is used. As shown in FIG. 2, the charger 3 comprising such a charging roller has a conductive core shaft 20 made of, for example, metal and a resistance layer 21 concentrically fixed around the shaft 20, and the whole is cylindrical. Is formed. The resistance layer 21 is made of, for example, rubber or resin, and its volume resistivity is 10⁵-10¹²It is preferably set to Ω · cm. The charger 3 is disposed opposite to the image carrier 2.
[0028]
Spacer portions 22 are provided in each end region in the longitudinal direction of the resistance layer 21, and these spacer portions 22 are pressed against the surface of the image carrier, and the resistance layer portion between both spacer portions 22 is the image carrier 2. It is located with a small gap from the surface. When both spacer portions 22 come into contact with the image carrier 2, the charger 3 follows the rotation of the image carrier 2 in the direction indicated by the arrow C in FIG. Alternatively, the charger 3 can be driven to rotate in synchronization with the rotation of the image carrier 2 by a driving device (not shown).
[0029]
As described above, when the image carrier 2 and the charger 3 rotate, a charging voltage having a predetermined polarity, that is, a negative polarity in the illustrated example, is applied to the core shaft 20, thereby the charger 3 and the image carrier 2. A discharge is generated between the image carrier 2 and the image carrier 2 is uniformly charged to a predetermined polarity, in this example, minus. Without providing the spacer portion 22, the resistance layer may be configured to contact the surface of the image carrier over its entire length.
[0030]
As described above, the image forming apparatus of the present example includes the image carrier 2 and the charger 3 that charges the image carrier 2, and a charging voltage is applied to the charger 3 and is generated at this time. The image carrier 2 is configured to be charged by discharge. At this time, in this type of conventional image forming apparatus, a large amount of discharge products are generated by the above-described discharge, which may adhere to the surface of the image carrier and generate an abnormal image. The same applies to the case where a charger other than the charging roller is used.
[0031]
Although various substances are considered to exist as discharge products that generate abnormal images, the present inventor has devised to identify the discharge products, and as a result, has found ammonium nitrate as its main component. . This ammonium nitrate is considered to be produced as follows.
[0032]
First, NO generated by discharge₂And water (H₂O) and oxygen (O₂) Reacts with nitric acid (HNO)₃) And ammonia gas in the air (NH₃) And nitric acid (HNO)₃) Reacts with ammonium nitrate (NH₄NO₃) Is generated and is in an equilibrium state (see the following equation).
Water and NO₂Reaction with
4NO₂+ O₂+ 2H₂O → 4HNO₃
Ammonium nitrate formation reaction
NH₃+ HNO₃⇔NH₄NO₃
[0033]
It is considered that most of ammonium nitrate is generated as fine particles in the air and then adheres to the image carrier. In this way, since the discharge product adhering to the surface of the image carrier is water-soluble, it absorbs moisture in the air at high humidity and lowers the resistance value of the image carrier surface. As a result, the electrostatic latent image is blurred. When such an electrostatic latent image is converted into a toner image, this becomes an abnormal image in an image flow state, and the image quality is lowered. The occurrence of such a phenomenon depends on the humidity of the environmental conditions, and the occurrence becomes significant as the humidity increases.
[0034]
FIG. 5 shows an example of the relationship between the amount of discharge product ions adhering to the surface of the image carrier and absolute humidity. As can be seen from this figure, the amount of discharge product ions increases as the absolute humidity increases. In the example shown in FIG. 5, the ion generation amount is not linearly proportional to the absolute humidity, and the absolute humidity is 20 g / m.³If it becomes above, the amount of production will increase rapidly. The amount of ions adhering to the surface of the image carrier is 2.0 × 10^-10mol / cm²It has been confirmed by experiments that the image quality is extremely deteriorated when the above is reached.
[0035]
As can be seen from the above description, if the absolute humidity in the discharge generation region can be kept low, the amount of discharge products generated can be reduced and the occurrence of abnormal images can be prevented.
[0036]
Therefore, in the image forming apparatus of this example, as shown in FIG. 2 and FIG. 3, at least a portion that performs the charging operation of the charger 3 is disposed in the drying chamber R partitioned by the housing 23. Although the entire charger 3 may be disposed in the drying chamber, the discharge is generated between the portion that performs the charging operation of the charger 3 and the image carrier 2, so that at least the charger portion that performs the charging operation. It is sufficient to place it in the drying chamber. In the illustrated example, the entire resistance layer 21 that performs the charging operation is disposed in the drying chamber, and each end in the longitudinal direction of the core shaft 20 protrudes outside the housing 23.
[0037]
The housing 23 is made of, for example, a highly rigid material such as resin or metal, and includes a top wall 24, side walls 25 and 26 facing each other, and end walls 27 and 28 at respective longitudinal ends. The side facing the image carrier 2 is open. As shown in FIG. 2, each end region of the core shaft 20 of the charger 3 is rotatably supported by the end walls 27 and 28 of the case 23 via bearings. Are integrally assembled, and the charging device 60 is constituted by these. The top wall 24 of the housing 23 is provided with an inflow pipe 41 through which air flows in and an outflow pipe 42 through which air flows out. As shown in FIGS. 1 and 3, the inflow pipe 41 has a duct 29. The one end side is connected detachably. The other end side of the duct 29 is connected to a case 31 in which a desiccant 30 is accommodated, and a blower 32 is disposed in the duct. In the illustrated example, only the charging member 3 is disposed in the housing 23. The outflow pipe can also be abolished.
[0038]
When the blower 32 shown in FIG. 1 is activated, air outside the case 31 flows into the case 31 through the inlet 31A and passes through the desiccant 30. At this time, moisture in the air is absorbed by the desiccant 30, and the dried air is sent from the inflow pipe 41 to the drying chamber R in the housing 23 through the duct 29. Thereby, the absolute humidity in the drying chamber R is lowered, and the drying chamber R is kept in a dry state. The air that has passed through the drying chamber R is discharged from the outflow pipe 42 to the outside. In this way, the humidity in the discharge region between the charger 3 and the image carrier 2 is kept low, the generation of discharge products is greatly reduced, and the discharge products adhere to the surface of the image carrier 2. It is possible to prevent the occurrence of abnormal images due to this.
[0039]
A humidity detection sensor (not shown) is provided in the housing 23, and the blower 32 is operated only when the sensor detects that the absolute humidity in the housing has exceeded a predetermined value. It can also comprise so that dry air may be sent into the drying chamber R in the body 23. FIG.
[0040]
The case 31, the desiccant 30 and the duct 29 constitute an example of a dehumidifying means for keeping the drying chamber R in the housing 23 in a dry state, but a dehumidifying means other than this configuration can also be adopted. . For example, you may arrange | position a desiccant in the housing | casing 23 directly. In this case, the desiccant constitutes the dehumidifying means. As described above, the image forming apparatus of this example is provided with the dehumidifying means for keeping the air in the drying chamber in a dry state.
[0041]
The configuration of the image forming apparatus described above is common to specific examples of each image forming apparatus described below.
[0042]
Incidentally, since the housing 23 is formed in a box shape having an opening on the side facing the image carrier 2, a gap G <b> 1 is formed between the housing 23 and the surface of the image carrier as shown in FIG. 3. G2 is formed. If such a gap is left as it is, the sealing property of the housing 23 is lowered, and it becomes difficult to keep the absolute humidity in the drying chamber R therein low. A detailed examination of this point revealed the following facts.
[0043]
FIG. 14 shows the housing 23 in which the gaps G1 and G2 remain. When the image carrier 2 rotates in the direction of arrow A, a humid air layer AL exists in the vicinity of the image carrier surface upstream of the housing 23 in the direction of movement of the image carrier surface, which is the image carrier. With the rotation of 2, the image carrier surface moves in the moving direction, that is, in the direction of arrow F. In FIG. 14, the air layer AL is indicated by hatching (the same applies to FIG. 8). Such high-humidity air flows into the drying chamber R in the housing 23 through the gap G1. For this reason, even if the dried air is sent to the drying chamber R through the duct, the absolute humidity in the drying chamber R cannot be sufficiently lowered, and an abnormal image may be generated on the image carrier.
[0044]
Therefore, in the illustrated image forming apparatus, in order to improve the sealing property of the drying chamber R, the gaps G1, G1 between the side walls 25, 26 of the housing 23 and the surface of the image carrier 2 are shown in FIG. G2 is blocked by seals S1 and S2. When the area where the image carrier 2 is charged is referred to as a charging area, seals S1 and S2 are provided to cover the gaps G1 and G2 on the upstream side and the downstream side, respectively, in the image carrier surface movement direction from the charged area. It is. As will be described later, a roller or the like can be used as the seal, but in the example shown in FIG. 3, the seals S1 and S2 are constituted by blades. The base ends of the seals S1 and S2 are fixed to the side walls 25 and 26 of the housing 23, respectively, and the tips of the seals S1 and S2 are in contact with the surface of the image carrier 2.
[0045]
As described above, in the illustrated example, both the seal S1 on the upstream side and the seal S2 on the downstream side with respect to the charging region are provided, but the absolute humidity in the drying chamber R is lowered without providing the seal S2 on the downstream side. An effect is obtained. In order to clarify this point, the case where the above-described seals S1, S2 are not provided at all, the case where only the seal S2 on the upstream side of the charging region is provided, and further, the seals S1, S2 on the upstream side and the downstream side are provided. An experiment was conducted to confirm how the absolute humidity in the housing 23 changes when both are provided. FIG. 4 shows the result. FIG. 4 shows the absolute humidity in the drying chamber when the temperature and humidity of the drying chamber R in the housing 23 are measured and converted into absolute humidity, and the seals S1 and S2 are not provided.
[0046]
As can be seen from FIG. 4, the absolute humidity in the drying chamber R was hardly changed when only the downstream seal S2 was provided, compared to when no seals S1 and S2 were provided. When only the upstream seal S1 was provided, the absolute humidity in the drying chamber could be lowered, and the effect was recognized. On the other hand, if both the upstream side seal S1 and the downstream side seal S2 are provided, the absolute humidity in the drying chamber can be greatly reduced.
[0047]
Although the details of the reason why there is a difference in the effect of maintaining the low humidity state in the drying chamber between the case where only the upstream seal S1 is provided and the case where only the downstream seal S2 is provided are unknown, the upstream seal S1 is not known. Is provided, the wet air layer flowing in the vicinity of the surface of the image carrier can be peeled off by the seal S1, and the air can be prevented from flowing into the drying chamber R, whereas the seal S2 is provided only on the downstream side. It is considered that this effect cannot be obtained only by providing the air, and that moist air flows into the drying chamber.
[0048]
As can be understood from the above, in the gap between the housing and the surface of the image carrier, at least on the upstream side in the moving direction of the image carrier surface with respect to the charging area where the image carrier is charged. By providing a seal that covers the gap, the absolute humidity in the drying chamber can be kept low. Furthermore, by providing seals that cover the gaps on the upstream and downstream sides of the image carrier surface movement direction relative to the charging area, the effect of keeping the absolute humidity in the drying chamber can be further enhanced, and abnormal images can be generated. It can prevent more reliably.
[0049]
In the image forming apparatus of this example, as shown in FIG. 2, a seal S3 covering the gap G3 between the end walls 27 and 28 of the housing 23 and the surface of the image carrier is also provided. However, these seals S3 can be omitted. Each of the seals S3 shown here is also composed of a blade, the base end portion of which is fixed to the housing 23, and the front end portion thereof is in contact with the surface of the image carrier.
[0050]
The seals S1, S2, and S3 described above exhibit the effect of maintaining the low humidity in the drying chamber even if the tip and the surface of the image carrier are not in contact with each other, as long as the tips are in close proximity to the surface of the image carrier. However, if the seals S1, S2, and S3 are in contact with the surface of the image carrier 2 as in the illustrated example, the sealing inside the housing 23 is improved and the effect of maintaining low humidity is further improved. You can be sure.
[0051]
In particular, when a configuration in which the seals S1, S2, and S3 are brought into contact with the surface of the image carrier is adopted, at least a portion of the seal that is in contact with the surface of the image carrier is made of an elastic body such as rubber or a soft resin. If this is the case, the seal is in close contact with the surface of the image carrier, so that the effect of maintaining the low humidity in the drying chamber can be enhanced, and the problem of scratching the surface of the image carrier can be avoided. This configuration can also be adopted when the seal is configured in a form other than the blade.
[0052]
By the way, the downstream seal S2 is in contact with the surface of the image carrier 2 charged by the charger 3. If the charged potential on the surface of the image carrier greatly changes due to this contact, a desired image is obtained. May not be obtained, and an abnormal image may occur. FIG. 6 shows how the potential of the surface of the image carrier charged by the charger 3 changes after passing through the seal S2 when a rubber blade having different volume resistivity is used as the downstream seal S2. The experimental result which confirmed was shown. The horizontal axis of this graph represents the volume resistivity of the seal S2, and the vertical axis represents the absolute value of the value obtained by subtracting the surface potential when the seal S2 is provided from the surface potential of the image carrier when the seal S2 is not provided. That is, the amount of potential attenuation on the surface of the image carrier by the seal S2 is shown. Here, when there is a potential attenuation of about 50 V or more, which is confirmed as a change in image density, the abnormal image range is indicated, and this range is hatched.
[0053]
From FIG. 6, the volume resistivity of the seal S2 in contact with the image carrier is 10⁵If Ω · cm or more, it can be understood that no abnormal image occurs. For example, by using the seal S2 made of an insulating rubber blade or PET film, it is possible to suppress the potential attenuation on the surface of the image carrier after charging and to prevent the occurrence of abnormal images. In this way, the volume resistivity of the seal that covers the gap on the downstream side in the moving direction of the image carrier surface with respect to the charged region is at least the portion that contacts the image carrier.⁵By setting the resistance to Ω · cm or more, it is possible to prevent a decrease in image quality.
[0054]
By the way, in the image forming apparatus shown in FIG. 1, the surface of the image carrier after the toner image transfer is cleaned by the cleaning device 16, and then the surface potential is initialized by the charge eliminating device 19. The neutralization can be performed by the upstream seal S1.
[0055]
For example, as this seal S1, a urethane rubber blade (volume resistivity 10) that has been conventionally used in a cleaning blade of a cleaning device.¹⁰The transfer residual toner on the image carrier can be efficiently removed by pressing the tip of the Ω · cm) to the surface of the image carrier. At the same time, by using the seal S1 made of such a rubber blade and the downstream seal S2, the absolute humidity in the drying chamber R can be reduced by, for example, 30% compared to the case where the seals S1 and S2 are not provided.
[0056]
In this way, the cleaning device 16 can be eliminated by configuring the seal that covers the gap on the upstream side in the moving direction of the image carrier surface relative to the charging region to also serve as a cleaning member that cleans the surface of the image carrier. Thus, the configuration of the image forming apparatus can be simplified and downsized.
[0057]
Further, the upstream side seal S1 is constituted by, for example, a conductive blade, which is brought into contact with the surface of the image carrier, and connected to an electrical ground line of the image forming apparatus, and is a static eliminator comprising a static eliminator lamp. By disposing it adjacent to 19, the seal S <b> 1 can supplement the charge removal function of the charge removal device 19 and fulfill the charge removal function of the image carrier. As described above, the seal covering the gap on the upstream side in the moving direction of the image carrier surface with respect to the charging area also serves as a charge removal member for removing the surface of the image carrier, thereby enhancing the charge removal function of the image carrier. be able to.
[0058]
As described above, even if the upstream seal S1 is made of a conductive material, the seal S1 is positioned upstream of the charging region by the charger 3, and therefore the charged potential on the surface of the image carrier after charging. Will not be adversely affected.
[0059]
In the example shown in FIG. 3, the seal S1 that covers the gap on the upstream side in the moving direction of the image carrier surface with respect to the charging area is formed of a blade, so that the structure can be simplified and the manufacturing cost can be kept low. The seal S1 can be configured to perform the above-described cleaning function and removal function.
[0060]
On the other hand, as shown in FIG. 7, a seal covering the gap on the upstream side in the image carrier surface movement direction with respect to the charging region can be constituted by a roller SR that rotates while contacting the surface of the image carrier. The roller SR shown here is rotatably supported by the housing 32, for example, and is rotated in the arrow direction following the movement of the surface of the image carrier, or rotated in the arrow direction by a driving device (not shown). Driven. Thus, the seal formed by the roller SR rotates while abutting on the surface of the image carrier, whereby the moist air layer flowing in the vicinity of the surface of the image carrier is peeled off from the vicinity of the surface of the image carrier, and the moist air is It can prevent flowing into the drying chamber R without the body 23.
[0061]
When the seal S1 formed of the blade shown in FIG. 3 is used, when the moving speed of the surface of the image carrier increases, the minute movement of the blade cannot follow the movement of the image carrier, Although the entrainment phenomenon may occur, the use of the seal made of the roller SR can prevent such a problem from occurring. For the same reason, a roller that rotates while contacting the surface of the image carrier can also be used as the downstream seal S2 shown in FIG.
[0062]
Even when the upstream seal is composed of the roller SR, it is preferable that at least a portion in contact with the surface of the image carrier 2 is composed of an elastic body. For example, a roller SR whose peripheral surface is composed of hydrin rubber can be used.
[0063]
Further, in this example, as shown in FIG. 7, since the peripheral surface of the roller SR is in contact with the lower end edge of the side wall 25 in the housing 23, the sealing performance in the housing 23 can be particularly improved. On the other hand, as shown in FIG. 8, these can be separated so that a slight gap g is formed between the lower end edge of the side wall 25 and the peripheral surface of the roller SR. Even when separated from each other in this manner, the moist air layer AL does not flow into the housing 23, and low-humidity air is introduced into the drying chamber R in the housing 23 from the duct 29 (FIG. 1). Since the low-humidity air in the housing 23 flows out through the gap g due to the rotation of the roller SR, a large amount of moist air does not enter the drying chamber R in the housing 23.
[0064]
Even when the upstream seal is composed of the roller SR, for example, the roller SR can be configured to perform a charge removing function by being composed of a conductive material, and the roller SR cleans the surface of the image carrier. It can also be configured to double as a cleaning member. When the roller SR has a cleaning function, the roller SR rotates in the counter direction with respect to the direction shown in FIGS. 7 and 8, that is, the surface movement direction of the image carrier 2. It is preferable to rotationally drive the roller SR.
[0065]
Next, the basic configuration of the image forming apparatus shown in FIG. 9 is the same as that of the image forming apparatus shown in FIG. 1, and has an image carrier 2 and a charger 3 for charging the image carrier 2. The charger 3 is disposed opposite to the image carrier, and at least a portion for performing the charging operation of the charger 3 is disposed in the drying chamber R partitioned by the casing 23. The difference from the previous example is that air blowing means 33 for blowing air to the image carrier surface portion upstream of the housing 23 in the image carrier surface movement direction is provided. The air blowing means 33 shown in FIG. 9 has a duct 34 whose one end is open toward the surface of the image carrier, and a blower 36 disposed in the duct 34. Air is introduced from the opening on the other end side, and this air is blown to the image carrier surface portion upstream of the housing 23 in the image carrier surface movement direction. Thereby, the layer of moist air flowing near the surface of the image carrier can be blown off, and the air can be prevented from flowing into the housing 23.
[0066]
In the example shown in FIG. 10, the air blowing means 33 has a desiccant 35 disposed in the duct 34 shown in FIG. 9, and the other configuration is the same as that of the image forming apparatus shown in FIG. Absent. In the image forming apparatus shown in FIG. 10, the moisture in the air introduced into the duct 34 is removed by the desiccant 35, and the dried air can be sprayed onto the surface of the image carrier.
[0067]
11, the branch duct 29A is connected to the duct 29 shown in FIG. 1, the branch duct 29A is detachably connected to the duct 34, and the blower 36 is disposed in the duct 34 to constitute the air blowing means 33. An example is shown. In this example, part of the dried air that has flowed into the duct 29 flows into the branch duct 29A and the duct 34, and the air is further urged by the blower 36 and blown onto the surface of the image carrier. It is also possible to omit the blower 36 and to blow the air dried only by the blower 32 (FIG. 1) onto the surface of the image carrier.
[0068]
10 and 11, the absolute humidity of the air blown to the surface of the image carrier by the air blowing means 33 is the same as or lower than the absolute humidity of the air in the housing 23. Can do. As a result, even if the air blown onto the surface of the image carrier flows into the housing 23 through the gap G1, the air is dry, so that the humidity in the drying chamber in the housing 23 can be prevented from increasing. Thus, the occurrence of abnormal images can be more reliably prevented.
[0069]
According to the image forming apparatus shown in FIGS. 9 to 11, the number of parts increases, the cost increases, and the arrangement of the duct 34 may increase the size of the image forming apparatus as compared with the case where the seal S <b> 1 is used. However, the influence on the surface of the image carrier can be less than that of the seal S1 that contacts the surface of the image carrier. For example, there is a possibility that the surface of the image carrier may be damaged by the contact of the seal S1 made of a blade with the surface of the image carrier, but the configuration shown in FIGS. 9 to 11 prevents such a problem from occurring. The durability of the image carrier can be improved.
[0070]
In the example shown in FIG. 11, a part 34 </ b> A of the duct 34 forms the side wall of the housing 23, thereby simplifying the configuration of the image forming apparatus. Such a configuration can also be applied to the image forming apparatus shown in FIGS.
[0071]
Further, when the air blowing means 33 is provided as shown in FIGS. 9 to 11, the air bearing means 33 abuts on the surface of the image carrier upstream of the image carrier surface moving direction with respect to the air blowing position on the image carrier surface. In addition, an air flow separating member for separating the air flow flowing in the vicinity of the surface of the image carrier can be provided. For example, as shown in FIGS. 9 and 10, the image carrier on the surface of the image carrier in the moving direction is upstream of the air blowing position on the surface of the image carrier and downstream of the static eliminator 19. As shown in FIG. 11, an air flow separating member 37A composed of a roller that contacts and rotates on the surface of the image carrier is provided at the same position as the blade. Provide. The air flow peeling members 37 and 37A can peel a high-humidity air layer flowing in the vicinity of the surface of the image carrier, and can blow air flowing out of the duct 34 onto the surface of the image carrier after the peeling. Thereby, it is possible to more reliably prevent high-humidity air from flowing into the drying chamber R in the housing 23.
[0072]
Further, when the air flow separation members 37 and 37A are provided, an effect of preventing a foreign matter from entering the housing 23 and preventing the foreign matter from adhering to the charger 3 can be obtained. For example, the cleaning brush 17 of the cleaning device 16 is in contact with the surface of the image carrier while rotating. As a result, the toner is scattered in the vicinity of the surface of the image carrier, and the scattered toner is reattached to the surface of the image carrier. When this enters the casing 23 and the toner adheres to the peripheral surface of the charger 3, the charging function is lowered. On the other hand, when the air flow separation members 37 and 37A are provided, even if the scattered toner is reattached to the surface of the image carrier, the reattachment toner can be removed by the air flow separation members 37 and 37A. Can be prevented from entering the housing 23 and adhering to the charger 3.
[0073]
Also, the cleaning device 16 can be eliminated by using the air flow separating members 37 and 37A as a cleaning member for cleaning the surface of the image carrier. At that time, the air flow separation member can be made conductive, and a voltage can be applied thereto to capture the transfer residual toner on the surface of the image carrier. Further, by providing the air flow separation members 37 and 37A with conductivity, the image carrier can be neutralized by the members.
[0074]
By configuring the image forming apparatus by appropriately combining the configurations shown in FIGS. 9 to 11 and the configurations shown in FIGS. 1 to 8, the effect of maintaining the low humidity in the housing 23 can be further enhanced. it can.
[0075]
In the image forming apparatus having each configuration described above, the image carrier 2, the charger 3, the casing 23, the seals S1, S2, and S3, the developing device 5, the cleaning device 16, the static eliminating device 19, the duct 34, and the blower 36, the desiccant 35, the air flow separating members 37, 37A, and the like are integrally assembled in the cartridge case 38 to form a process cartridge 39, and the process cartridge 39 can be detachably attached to the image forming apparatus main body 1. It is configured. An example of the appearance of the process cartridge 39 is shown in FIG. Here, the cartridge case 38 is represented by a chain line.
[0076]
The components of the process cartridge 39 are not limited to those described above, and the process cartridge 39 may be configured by deleting some of the components described above or adding other components. At that time, at least the image carrier 2, the casing 23, the charger 3, and the developing device 5 that visualizes the electrostatic latent image formed on the image carrier 2 charged by the charger 3. And a cleaning device 16 that cleans the surface of the image carrier after the visible image is transferred to the transfer material, and is configured as a process cartridge 39, and the charger 3 and the housing 23 are connected to the process. When the charging device 60 including the charger 3 and the casing 23 is detachably mounted on the cartridge case 38 of the cartridge 39 and is configured as an element independent of other elements, the casing 23 is fluidized from the other elements. Since it can isolate, the sealing property in the housing | casing 23 can be improved. In addition, the charger 3 and the housing 23 can be easily replaced, and the maintainability can be improved.
[0077]
In the process cartridge 39 shown in FIG. 12, by opening the opening / closing cover 38A provided on the upper wall of the cartridge case 38 and pulling out the charger 3 and the housing 23 upward, these are removed from the cartridge case 38. It is configured to be separable. When the charging device 60 including the charger 3 and the housing 23 is attached to and detached from the cartridge case 38, the duct 29 and the branch duct 29 </ b> A are removed from the inflow pipe 41 and the duct 34.
[0078]
The housing 23 shown in FIG. 2 also serves as a holding member that holds the charger 3, and the housing 23 is configured by a member different from the cartridge case 38. The housing 23 can also be configured by parts. Further, the above-described seals S1, S2, S3 and the roller SR can be supported by the cartridge case 38 instead of being supported by the housing 23.
[0079]
In FIG. 13, a plurality of process cartridges 39Y, 39M, 39C, and 39BK are arranged to face the transfer belt 13, and the transfer material fed from the paper feeding device 6 is carried on the transfer belt 13 and conveyed. In addition, a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image formed on the image carrier of each process cartridge are superimposed and transferred, and the transferred toner image is fixed by the fixing device 14. . Each of the above-described configurations can also be employed in such an image forming apparatus. At that time, the air introduced into the duct 29 by the blower 32 and passed through the desiccant 30 is sent to the housing of each process cartridge by the branch pipes 29Y, 29M, 29C, 29BK of the duct 29. ing.
[0080]
By the way, as the image carrier 2 of the image forming apparatus described above, various types can be used. Especially, when an amorphous silicon photoconductor is used, since the surface has high hardness, the wear of the surface is suppressed, The life of the image carrier can be greatly extended. The same applies to a case where a photoconductor having a surface layer in which a filler made of alumina powder of 0.3 μm or less is dispersed is used as an image carrier. Conventionally, when an image carrier having such a high surface hardness and a small amount of wear is used, the discharge product adhering to the surface cannot be efficiently removed by a cleaning blade or the like, and an abnormal image is likely to occur. However, by adopting the above-described configurations, it is possible to prevent the occurrence of an abnormal image even if an image carrier having a high surface hardness is used. It is possible to achieve both a long life of the image carrier and an improvement in image quality.
[0081]
【The invention's effect】
According to the present invention, the generation of discharge products can be suppressed, the generation of abnormal images due to the discharge products adhering to the image carrier can be prevented, or the generation thereof can be effectively suppressed. it can.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus.
FIG. 2 is a partial cross-sectional view showing a relationship among a charger, a housing, and an image carrier.
FIG. 3 is a partially enlarged view of FIG. 1;
FIG. 4 is a diagram for explaining the relationship between absolute humidity in the housing and the location of the seal.
FIG. 5 is a diagram showing an example of the relationship between absolute humidity and the amount of generated discharge product ions.
FIG. 6 is a diagram showing the relationship between the volume resistivity of the downstream seal and the potential attenuation on the surface of the image carrier.
FIG. 7 is a schematic cross-sectional view showing an image forming apparatus in which a seal is a roller.
FIG. 8 is a diagram illustrating an example in which a side wall of a housing and a roller are separated from each other.
FIG. 9 is a cross-sectional view showing an image forming apparatus having air blowing means.
FIG. 10 is a cross-sectional view showing another example of an image forming apparatus having air blowing means.
FIG. 11 is a cross-sectional view showing still another example of an image forming apparatus having air blowing means.
FIG. 12 is an external perspective view of a process cartridge.
FIG. 13 is a schematic view of an image forming apparatus having a plurality of process cartridges.
FIG. 14 is a diagram illustrating a problem that occurs due to a gap between the housing and the surface of the image carrier.
[Explanation of symbols]
2 Image carrier
3 Charger
5 Development device
16 Cleaning device
23 Case
33 Air spraying means
37 Airflow separation member
37A Airflow separation member
38 Cartridge case
39 Process cartridge
G1 gap
G2 gap
G3 gap
P transfer material
R Drying room
S1 seal
S2 seal
S3 seal
SR Roller

Claims (13)

  In an image forming apparatus having an image carrier and a charger for charging the image carrier, the charger being disposed opposite to the image carrier, at least a portion of the charger performing a charging operation is a housing. In the gap between the housing and the surface of the image carrier, at least upstream of the charging region where the image carrier is charged in the gap between the housing and the surface of the image carrier. An image forming apparatus comprising a seal that covers a gap between the image bearing member and the seal that also serves as a charge eliminating member that removes the surface of the image carrier.   The image forming apparatus according to claim 1, wherein the seal is in contact with an image carrier.   The image forming apparatus according to claim 1, wherein at least a portion of the seal that contacts the image carrier is made of an elastic body.   4. The image forming apparatus according to claim 1, wherein seals are provided to cover gaps on the upstream side and the downstream side in the movement direction of the image carrier surface with respect to the charging area. The image according to claim 4, wherein the volume resistivity of at least a portion of the seal that covers the gap on the downstream side in the moving direction of the image carrier surface with respect to the charging region is set to 10 ⁵ Ω · cm or more. Forming equipment.   The image forming apparatus according to claim 1, wherein a seal that covers a gap on the upstream side in the movement direction of the image carrier from the charging area also serves as a cleaning member that cleans the surface of the image carrier.   The image forming apparatus according to claim 1, wherein a seal that covers a gap on the upstream side in the moving direction of the image carrier surface with respect to the charging area is formed of a blade.   7. The image forming apparatus according to claim 1, wherein a seal that covers a gap on the upstream side in the moving direction of the image carrier surface with respect to the charging area comprises a roller that rotates while contacting the surface of the image carrier.   The image forming apparatus according to claim 1, further comprising an air blowing unit that blows air to an image carrier surface portion upstream of the housing in the moving direction of the image carrier surface.   The image forming apparatus according to claim 9, wherein the absolute humidity of air blown onto the surface of the image carrier by the air blowing unit is the same as or lower than the absolute humidity of air in the housing.   An air flow separating member for contacting the image carrier surface portion upstream of the image carrier surface movement direction from the air blowing position on the image carrier surface and separating the air flow flowing in the vicinity of the image carrier surface. The image forming apparatus according to claim 9 or 10 provided.   The image carrier, the housing, the charger, a developing device for visualizing an electrostatic latent image formed on the image carrier charged by the charger, and transferring the visible image A process cartridge is integrally formed with a cleaning device for cleaning the surface of the image carrier after being transferred to the material, and the charger and the housing are detachably attached to a cartridge case of the process cartridge. Item 12. The image forming apparatus according to any one of Items 1 to 11.   The image forming apparatus according to claim 1, wherein the image carrier is made of an amorphous silicon photosensitive member or a photosensitive member having a surface layer in which a filler is dispersed.

Images