JP3742292B2 - Gap management method in non-contact charging device, image carrier unit and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
According to the present invention, the gap management members attached to both ends of the elastic roller portion are brought into contact with the image carrier, whereby the inner portion of the elastic roller portion to which the gap management member is attached and the surface of the image carrier. The present invention relates to a gap management method in a non-contact charging device in which a gap is formed between the two, and a non-contact charging device, and an image carrier unit and an image forming apparatus.
[0002]
[Prior art]
In an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile, etc., before forming an electrostatic latent image on the surface of a photoconductor as an image carrier, the photoconductor is uniformly formed by various methods. It is charged.
As one of the charging methods, in recent years, a charging roller formed in a roller shape with a conductive member is brought into contact with the surface of the photosensitive member, and in that state, a voltage is applied between the charging roller and the photosensitive member, Contact charging devices that charge the surface of a photoconductor have been put to practical use because they have the advantage of lowering ozone and lowering power.
[0003]
However, since the charging roller used in such a contact charging device has an elastic roller portion formed of conductive rubber on the outside of a metal core, for example, the elastic roller portion is photosensitive. If it is left for a long time in a state of being pressed against the surface of the body, a substance (for example, a plasticizer) contained in the elastic roller portion oozes out on the surface, which stains the surface of the photoreceptor. That happened.
[0004]
In the case of contact charging, charging is performed in a state where a charging member such as a charging roller is in contact with the surface of an image carrier such as a photosensitive member. In some cases, the toner or the like is transferred to the surface of the charging member and becomes dirty, which may cause the charging performance to deteriorate.
[0005]
Therefore, in order to solve such problems, gap management members made of spacers, tapes, etc. having a predetermined thickness are respectively attached to both ends of the elastic roller portion of the charging roller. There has been proposed a non-contact charging device in which the other portions except for the surface are in non-contact with the surface of the photoconductor and the photoconductor is charged in that state (for example, Japanese Patent Laid-Open No. 3-240076, JP-A-4-360167, JP-A-5-107871, etc.).
[0006]
According to this non-contact charging device, since the image forming effective area which is the inner area of the gap management member on both sides of the charging roller does not contact the photoconductor, the elastic roller portion of the charging roller which is a drawback of the above-described contact charging apparatus It is possible to solve the problem that the substance contained in the toner adheres to the photoconductor and the adhering material such as toner adhering to the surface of the photoconductor easily transfers to the surface of the charging roller.
[0007]
[Problems to be solved by the invention]
However, non-contact charging in which the portion of the image forming effective area is not in contact with the surface of the photosensitive member by fixing the gap management member having a predetermined thickness to both ends of the elastic roller portion of the charging roller. Even in the device, since the elastic roller part of the charging roller is usually made of rubber, the hardness of the part becomes low and swells in an environment of high temperature and high humidity. In some cases, the outer diameter of the elastic roller portion in the region increases, so that the portion easily comes into contact with the surface of the photoreceptor.
[0008]
As a result, when the swollen elastic roller portion comes into contact with the surface of the photoconductor, the substance contained in the elastic roller portion described above adheres to the photoconductor, or conversely on the surface of the photoconductor. The adhered matter such as the adhered toner is transferred to the surface of the charging roller.
Further, since the elastic roller portion comes into contact with the surface of the photosensitive member, the deterioration thereof is accelerated, so that the life of the charging roller is shortened.
[0009]
On the other hand, when the low temperature and low humidity environment is reached, the elastic roller portion of the charging roller becomes hard and the outer diameter of the roller becomes smaller. Therefore, since the gap becomes larger as it approaches the thickness of the gap management member, abnormal discharge traces are likely to occur.
In particular, the thickness of the gap management member is assumed in advance so that the elastic roller portion of the charging roller does not come into contact with the surface of the photoreceptor even under high-temperature and high-humidity environmental conditions. When the thickness is set to be thick, the gap becomes too large in a low-temperature and low-humidity environment, and abnormal discharge traces are likely to occur.
[0010]
The present invention has been made in view of the above problems, and even when used under both low temperature and low humidity environmental conditions and high temperature and high humidity environmental conditions, the elastic roller portion of the charging roller and an image carrier such as a photoreceptor. It is an object of the present invention to provide a stable charging performance by always maintaining a gap between the surface and the surface of the substrate substantially constant.
[0011]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention achieves the above by applying a charging roller having a gap management member attached to the outer periphery of both ends of the elastic roller portion, and pressing both ends of the charging roller toward the image carrier side by the urging force of the urging member. The gap management members on both sides are in contact with the image carrier, and a gap is formed between the inner portion of the elastic roller portion where the gap management member is provided and the surface of the image carrier, so that no contact is made. A gap management method in a non-contact charging device,
The gap is maintained at room temperature by increasing the urging force of each urging member for urging both ends of the charging roller in a low temperature and low humidity environment, and weakening in a high temperature and high humidity environment. Provided is a gap management method in a non-contact charging device that is substantially the same as a gap when wet.
[0012]
  The adjustment for increasing or weakening the urging force of each urging member may be performed by changing the compression amount of each urging member.
  In addition, the image bearing member includes a charging roller having gap management members attached to the outer periphery of both ends of the elastic roller portion, and a biasing member for biasing the both end portions of the charging roller toward the image bearing member side. The gap management members on both sides of the charging roller come into contact with the surface of the image carrier by the biasing force of the biasing member, and the inner portion of the elastic roller portion where the gap management member is provided and the surface of the image carrier In an image carrier unit in which a gap is formed between and
  Each urging memberIs formed of a resin that has a property of becoming hard in a low temperature and low humidity environment and softening in a high temperature and high humidity environment.
[0013]
  OrEach of the urging members may be formed of a foamed elastic body having a property of becoming hard in a low-temperature and low-humidity environment and softening in a high-temperature and high-humidity environment.
  Furthermore, an image forming apparatus provided with the image carrier unit is also provided.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing a non-contact charging device for carrying out a gap management method according to the present invention together with a photosensitive drum, and FIG. 2 is a joint portion of a tape material which is a gap management member wound around both ends of the charging roller. 1 is a front view showing only one end side, and FIG. 3 is an overall configuration diagram showing a small color printer which is an image forming apparatus provided with a plurality of non-contact charging devices and photosensitive drums in FIG. .
[0015]
A small color printer as an image forming apparatus shown in FIG. 3 is a four-drum full-color electrophotographic image forming apparatus. Within the apparatus main body 1, there are four image bearing unit units, ie, photosensitive unit 2A, 2B, 2C, and 2D are detachably attached to the apparatus main body 1, respectively.
In this small printer, a transfer belt 3 is stretched between a plurality of rollers so as to be rotatable in a direction indicated by an arrow A at a substantially central position in the apparatus main body 1.
[0016]
Then, the photosensitive unit 2A to the photosensitive drum 5 provided on each of the four photosensitive units 2A, 2B, 2C, and 2D are in contact with the upper surface of the transfer belt 3 in FIG. Each 2D is arranged.
In correspondence with the photoreceptor units 2A to 2D, developing devices 10A to 10D having different toner colors are disposed.
[0017]
A writing unit 6 is disposed above the photoreceptor units 2A to 2D, and a duplex unit 7 is disposed below.
Further, this small printer is equipped with a reversing unit 8 that inverts and discharges the transfer paper P after image formation or conveys it to the duplex unit 7 on the left side of the apparatus main body 1 in FIG.
[0018]
Between the transfer belt 3 and the reversing unit 8, there is provided a fixing device 9 for fixing the image of the transfer paper onto which the image has been transferred.
A reversal conveyance path 20 is formed on the downstream side of the fixing device 9 in the conveyance direction of the transfer sheet, and the transfer sheet P conveyed there can be discharged onto a discharge tray 26 by a discharge roller pair 25. .
[0019]
Further, in the lower part of the apparatus main body 1, paper feed cassettes 11 and 12 that can store transfer papers P of different sizes are arranged in two upper and lower stages.
Further, a manual feed tray 13 is provided on the right side surface of the apparatus main body 1 so as to be openable and closable in the direction indicated by the arrow B, and the manual feed tray 13 is opened so that manual feeding can be performed therefrom.
[0020]
The photoconductor units 2A to 2D are units having the same configuration, the photoconductor unit 2A forms an image corresponding to yellow, and the photoconductor unit 2B forms an image corresponding to magenta. 2C forms an image corresponding to the cyan color, and the photoreceptor unit 2D forms an image corresponding to the black color. They are arranged at intervals in the transfer paper conveyance direction.
[0021]
As shown in FIG. 1, the photoreceptor units 2 </ b> A to 2 </ b> D have a gap between the photoreceptor drum 5 that is an OPC drum type image carrier on which an electrostatic latent image is formed by exposure and the outer periphery of both ends of the elastic roller unit 17. A charging device 4 having a charging roller 14 to which tape members 18 and 18 as management members are respectively attached, and a pressure spring 19 as an urging member for urging both ends of the charging roller toward the photosensitive drum 5 side, respectively. 19.
[0022]
The photoconductor units 2A to 2D are formed in a unit shape as shown in FIG. 4 and are detachable from the apparatus main body 1 (FIG. 3). The surface of the photoconductor drum 5 is cleaned there. A cleaning roller 47 that constitutes a cleaning device, a cleaning blade 47 that slides the tip of the photosensitive drum 5 on the surface of the photosensitive drum 5 and scrapes off any residual transfer toner adhering to the surface, and a toner conveying auger. 48 and the charging roller cleaner 49 are also provided integrally.
[0023]
Then, the toner scraped off from the surface of the photosensitive drum 5 by the cleaning blade 47 is moved to the toner transport auger 48 side by the brush roller 15, and the waste toner recovered by rotating the toner transport auger 48 is changed to a predetermined amount. To the waste toner storage section.
[0024]
The charging roller cleaner 49 in contact with the surface of the elastic roller portion 17 of the charging roller 14 is made of, for example, a sponge, so that the toner or dust floating in the machine adheres to the surface of the elastic roller portion 17 even when the toner or dust floats on the surface. By rotating, the toner and dust can be cleaned.
[0025]
The photoconductor units 2A to 2D are provided with a positioning main reference portion 51 as a reference for attaching and detaching the photoconductor units 2A to 2D with respect to the apparatus main body 1 (see FIG. 3). The sub-reference portion 53 is integrally provided on the bracket 50, and when the photoconductor units 2A to 2D are mounted on the apparatus main body 1, the photoconductor units 2A to 2D are surely placed at predetermined mounting positions by the reference portions. Can be positioned.
[0026]
Each of the photosensitive drums 5 of the photosensitive units 2A to 2D rotates in the direction indicated by an arrow C in FIG. 4, and the linear speeds thereof are monochrome speed priority mode, monochrome image quality priority mode, color speed priority mode, color image quality. It can be adjusted in three stages of 185 mm / sec, 125 mm / sec, and 62.5 mm / sec according to several modes such as a priority mode and a cardboard / OHP paper feeding mode.
The photoconductor unit may be configured by removing the brush roller 15 from the configuration.
[0027]
As shown in FIG. 1, the charging device 4 has the charging roller 14 disposed so that a gap G is formed between the image forming effective area Ac and the photosensitive drum 5 by a configuration described later. A voltage is applied between the roller 14 and the photosensitive drum 5 to charge the surface to be charged of the photosensitive drum 5.
[0028]
The charging roller 14 of the charging device 4 is made of, for example, epichlorohydrin rubber at a portion excluding both ends of the outer peripheral surface of the cored bar 16 which is a metal shaft formed by, for example, SUM-Ni plating (steel surface is nickel-plated). The volume resistivity value is 1 × 10³~ 1x10⁸An elastic roller portion 17 having Ω · cm is formed.
[0029]
At both ends of the elastic roller portion 17, there is an adhesive sheet in which one side made of, for example, polyester or polyethylene terephthalate is formed on the adhesive surface, and the tape members 18, 18 as gap management members are placed with the adhesive surface side down. Wound in the circumferential direction.
[0030]
Then, as shown in FIG. 2 for the tape material 18 on one side, the edges 18a and 18b on both sides which are both ends in the circumferential direction do not overlap each other as shown in FIG. The adhesive surface side is fixed by sticking so that there is no portion where the tape material 18 does not exist in the axial direction of the roller indicated by the arrow J.
Therefore, as shown in the drawing, both end portions of each tape material 18 are cut obliquely so that the edges 18a and 18b of the respective cut ends face each other.
[0031]
As shown in FIG. 1, the charging device 4 is configured such that the charging roller 14 is brought into contact with the portions of the tape materials 18 and 18 at both ends of the photosensitive drum 5 outside the image forming effective area Ac, and the charging roller 14 is in contact with the charging roller 14. A surface of the photosensitive drum 5 is charged by applying a voltage from a power source (not shown) between the photosensitive drum 14 and the photosensitive drum 5.
[0032]
The charging roller 14 is pressed with a predetermined pressure on the photosensitive drum 5 side through sliding bearings 30 and 30 by pressure springs 19 and 19 which are biasing members at both ends of the cored bar 16. .
Therefore, due to the urging force of the pressure springs 19 and 19, the tape materials 18 and 18 on both sides of the charging roller 14 come into contact with the surface of the photosensitive drum 5, respectively, and the tape materials 18 and 18 of the elastic roller portion 17 are provided respectively. A gap G is formed between the inner portion of the formed portion and the surface of the photosensitive drum 5 so that the portion becomes non-contact.
[0033]
A driving gear 40 is fixed to one end on the right side of the cored bar 16 of the charging roller 14 in FIG. 1, and a driving force from a motor (not shown) is transmitted to the charging roller 14. I try to rotate at high speed.
As for the application of the voltage to the charging roller 14, for example, DC-700V is applied to the portion of the core metal 16 by constant voltage control, and an AC voltage is applied by constant current control.
[0034]
In the charging roller 14, for example, the outer diameter of the cored bar 16 is formed to φ8 mm, and the elastic roller portion 17 is formed in a rubber layer having an outer diameter of φ11 mm made of the above-described epichlorohydrin rubber having a wall pressure of 1.5 mm.
Furthermore, the elastic roller part 17 uses that whose test piece hardness of rubber itself is 60 degree | times, for example.
[0035]
Further, the photosensitive drum 5 is rotationally driven in a direction indicated by an arrow C in FIG. 4 by a motor that is rotationally driven via a drum driving timing belt and a drum driving pulley (both not shown).
[0036]
The developing devices 10A to 10D shown in FIG. 3 have the same configuration, and they differ only in the color of the toner used. The developing device 10A uses yellow toner, the developing device 10B uses magenta toner, the developing device 10C uses cyan toner, and the developing device 10D uses black toner. .
[0037]
The writing unit 6 shown in FIG. 5 is a writing unit of a 1 polygon motor having two 6-sided rotary polygon mirrors 22a and 22b, which is a laser diode (LD) type color 1 beam and monochrome 2 beam.
The writing unit 6 emits yellow scanning light, magenta scanning light, and cyan scanning light by rotating polygon mirrors 22a and 22b emitted from a laser diode (not shown) serving as a light source and rotated by a polygon motor 21. And the black scanning light is reflected separately on the right and left.
[0038]
The scanning light for yellow and the scanning light for magenta pass through the two-layer fθ lens 23, respectively, and the scanning light for yellow is reflected by the mirror 27, passes through the long WTL 24, and is exposed through the mirrors 28 and 29. Irradiated onto the photosensitive drum 5 of the body unit 2A.
The magenta scanning light is reflected by the mirror 31, passes through the long WTL 32, and is irradiated onto the photosensitive drum 5 of the photosensitive unit 2B via the mirrors 33 and 34.
[0039]
Further, the cyan scanning light and the black scanning light pass through the two-layer fθ lens 35, respectively, and the cyan scanning light is reflected by the mirror 36, passes through the long WTL 37, and passes through the mirrors 38 and 39. Irradiated onto the photosensitive drum 5 of the photosensitive unit 2C.
Further, the scanning light for black is reflected by the mirror 41, passes through the long WTL 42, and is irradiated onto the photosensitive drum 5 of the photosensitive unit 2D via the mirrors 43 and 44.
[0040]
A duplex unit 7 shown in FIG. 3 includes a pair of conveyance guide plates 45a and 45b and a pair of (four sets in this example) conveyance rollers 46, and forms a duplex image on both sides of a transfer sheet. In the formation mode, an image is formed on one side, conveyed to the reversing conveyance path 54 of the reversing unit 8, and transferred back-switched. The transfer paper P is received, and the image forming unit on which the photosensitive units 2A to 2D are provided. Re-carry toward the part.
[0041]
The reversing unit 8 includes a plurality of paired transport rollers and a plurality of paired transport guide plates. As described above, the reversing unit 8 reverses the transfer paper P when double-sided image formation is carried out to the double-sided unit 7. The transfer paper P after image formation is discharged out of the machine in the same orientation, or the paper is reversed outside and turned out of the machine.
Separating sheet feeding units 55 and 56 for separating and feeding the transfer sheets P one by one are provided in the sheet feeding unit in which the sheet feeding cassettes 11 and 12 are provided.
[0042]
This small printer employs a roller curvature separation method using the transfer belt 3, and four transfer brushes 57 are provided inside the transfer belt 3 in correspondence with the four photosensitive drums 5, respectively. .
[0043]
In this small printer, when the image forming operation is started, each photosensitive drum 5 rotates in the clockwise direction in FIG. The surface of each photosensitive drum 5 is uniformly charged by applying a voltage between the photosensitive drum 5 and the charging roller 14 of each charging device.
The charging unit 6 irradiates the charged surface of the photosensitive drum 5 of the photosensitive unit 2A with laser light corresponding to the yellow image.
[0044]
Further, a laser beam corresponding to a cyan image is written on the charging surface of the photosensitive drum 5 of the photosensitive unit 2B by the writing unit 6, and a magenta image is applied to the charging surface of the photosensitive drum 5 of the photosensitive unit 2C. Further, a laser beam corresponding to a black image is irradiated on the charging surface of the photosensitive drum 5 of the photosensitive unit 2D, and a latent image corresponding to each color is formed thereon.
Each latent image reaches the position of the developing devices 10A, 10B, 10C, and 10D by the rotation of the photosensitive drum 5, and is developed there by toners of yellow, magenta, cyan, and black, and then is divided into four colors. Toner image.
[0045]
On the other hand, the transfer paper P is fed from the selected paper feed stage of the paper feed cassette 11 or 12 by the separation paper feed unit 55 or 56, and the pair of registration rollers provided immediately before the photosensitive unit 2A. 59, the toner image is conveyed between the photosensitive drum 5 of the photosensitive unit 2A and the transfer belt 3 at an accurate timing coincident with the toner image formed on each photosensitive drum 5.
[0046]
At that time, the transfer paper P is charged to a positive polarity by a paper suction roller 58 disposed in the vicinity of the entrance of the transfer belt 3, and thereby electrostatically attracted to the surface of the transfer belt 3.
Then, while the transfer paper P is attracted to the transfer belt 3 and is conveyed in the same direction by the rotation of the transfer belt 3 in the direction of arrow A, yellow, magenta, cyan, and cyan are transferred to the upper surface in FIG. Each black toner image is sequentially transferred, and when passing through the photoreceptor unit 2D, a full-color toner image of four colors superimposed is formed.
[0047]
The transfer paper P is heated and pressed by the fixing device 9 to melt and fix the toner image, and then passes through the paper discharge system corresponding to the designated mode, and then the paper discharge tray 26 at the upper part of the apparatus main body. Or the paper is fed straight from the fixing device 9 and passes through the reversing unit 8 and is ejected straight.
[0048]
Alternatively, when the double-sided image forming mode is selected, the sheet is sent to the reversing conveyance path 54 in the reversing unit 8 described above, then switched back and conveyed to the double-sided unit 7, and is fed again from there to the photosensitive unit. The image forming unit provided with 2A to 2D is discharged after an image is formed on the back surface.
Thereafter, when two or more image formations are instructed, the above-described image forming process is repeated.
[0049]
By the way, in the photoconductor units 2A to 2D according to this embodiment, the thickness of each tape material 18 shown in FIG. 1 is 60 μm, the own weight of the charging roller 14 is 200 g, and the epichlorohydrin rubber forming the elastic roller portion 17 is formed. The right and left pressure springs 19, 19 press the charging roller 14 toward the pressure side via the sliding bearings 30, 30.₁, F₂Is 4N (Newton) respectively, the biasing force F of the pressure springs 19 and 19 in an environment of normal temperature and humidity with an ambient temperature of 23 ° C. and a humidity of 50%₁, F₂As a result of the compression of the portions on both sides of the elastic roller portion 17 where the tape members 18 are provided, the portion is crushed by about 40 μm and the gap G near the center in the longitudinal direction of the elastic roller portion 17 is about 20 μm. Become.
[0050]
However, the elastic roller portion 17 formed of rubber of the charging roller 14 is generally soft in a high temperature and high humidity environment and hard in a low temperature and low humidity environment.
Therefore, for example, when the environmental temperature becomes 32 ° C. and the humidity becomes 80% with the above-described configuration conditions, the elastic roller portion 17 becomes soft and is restrained by the tape materials 18 and 18 on both sides as shown in FIG. It expands by about 20 μm in diameter excluding the part where it is. Further, the softening makes it easy for the portions on both sides of the elastic roller portion 17 where the tape material 18 is provided to collapse, so the gap G near the center of the elastic roller portion 17 in the longitudinal direction.₁Becomes about 5 μm.
[0051]
Therefore, the frequency of the swollen elastic roller portion 17 coming into contact with the surface of the photosensitive drum 5 due to touch during rotation increases. Therefore, when there is transfer residual toner on the surface of the photosensitive drum 5, It becomes easy to transfer to the surface of the elastic roller portion 17.
Further, since the frequency with which the elastic roller portion 17 contacts the surface of the photosensitive drum 5 is increased, the deterioration of the charging roller 14 is also accelerated, so that the life of the charging roller 14 is shortened.
[0052]
On the contrary, if the environmental temperature is set to 10 ° C. and the humidity is set to 15% with the above-described configuration, the elastic roller portion 17 becomes hard, and this time, the diameter is reduced by about 20 μm. Further, since the hardened portion makes it difficult for the portions where the tape material 18 on both sides of the elastic roller portion 17 is provided to be crushed, the gap G near the center in the longitudinal direction of the elastic roller portion 17 is reduced.₁Becomes about 40 μm.
Accordingly, in this case, there is no possibility that the elastic roller portion 17 contacts the surface of the photosensitive drum 5, but the gap G₁Is 40 μm, which is twice as large as 20 μm at normal temperature and humidity, and abnormal discharge traces are likely to occur.
[0053]
Therefore, in the small printer having the photoconductor unit according to this embodiment, when the printer is used, the urging force F of the pressure springs 19 and 19 for urging both ends of the charging roller 14 shown in FIG.₁, F₂Are used at room temperature and normal humidity (temperature 23 ° C., humidity 50%), respectively, 4N (Newton).₁, F₂Each is increased to 6N (Newton).
Further, for example, when used in a high-temperature and high-humidity environment where the ambient temperature is 32 ° C. and the humidity is 80%, the biasing force F₁, F₂Are reduced to 2N (Newton).
[0054]
Thus, the urging force F of the pressure springs 19 and 19 is as follows.₁, F₂To increase or weaken the force F₁, F₂Can be performed by preparing in advance different ones of 6N, 4N and 2N and exchanging them.
The number of the plurality of pressure springs 19 having different urging forces prepared in advance is not limited to three, and can be adjusted more finely by increasing the number.
[0055]
Further, the urging force F of each pressure spring 19₁, F₂As shown in FIG. 7, for example, a spring abutment plate 61 that regulates the position of one end 19a of each pressure spring 19 is provided, and the position is adjusted in each expansion / contraction direction of the pressure spring 19 as shown in FIG. A plurality of grooves 63 that can be changed to positions may be provided, and the position of the spring contact plate 61 inserted into the grooves 63 may be changed to change the compression amount of each pressure spring 19. .
[0056]
As described above, the charging roller 14 having the tape members 18 and 18 attached to the outer circumferences of both ends of the elastic roller portion 17 shown in FIG. 1 and the both ends of the charging roller 14 by the urging force of the pressure springs 19 and 19, respectively. By applying pressure to the side 5, the tape materials 18, 18 on both sides come into contact with the photosensitive drum 5, respectively, and the inner portion of the elastic roller portion 17 where the tape materials 18, 18 are respectively provided and the photosensitive drum 5. As the gap management method for managing the gap G in the non-contact charging device in which the gap G is formed between the surface and the non-contact charging device, the method described above may be used.
[0057]
That is, by increasing the biasing force of the pressure springs 19 and 19 biasing both ends of the charging roller 14 in a low temperature and low humidity environment state, and weakening in a high temperature and high humidity environment state, the gap G If the gap management method is performed so that the gap G becomes substantially the same as the gap G when the temperature is normal temperature and humidity, it is suitable for the environmental conditions of low temperature and low humidity or high temperature and high humidity Since the charging roller 14 can be pressurized by the pressure spring 19 having a biasing force, the gap G can be set to substantially the same gap amount as 20 μm at normal temperature and humidity.
[0058]
FIG. 8 is a schematic view similar to FIG. 1 showing the vicinity of the charging roller of the embodiment of the photosensitive member unit in which the urging members for urging both ends of the charging roller to the image carrier side are formed of resin. .
In this embodiment, pressure springs 69 and 69 which are urging members for urging both ends of the charging roller 14 toward the photosensitive drum 5 with respect to the photosensitive units 2A to 2D described in FIG. Is different only in that it is made of a resin that is a hardness varying member having a property of becoming hard in a low temperature and low humidity environment and softening in a high temperature and high humidity environment.
[0059]
The resin used for the pressure springs 69, 69 is a thermoplastic resin that has the property of repeatedly softening and curing each time it is repeatedly exposed to high and low temperature environments, and is suitable for use as a spring. Any one can be used. And the urging force F of the pressure springs 69, 69₁, F₂However, when the temperature is 23 ° C. and the humidity is 50%, which is an environment of normal temperature and normal humidity, both are set to 4 N (Newton).
[0060]
Thereby, in the environment of normal temperature and humidity, the urging force F of the pressure springs 69 and 69₁, F₂By compressing the portion where the tape members 18, 18 on both sides of the elastic roller portion 17 are compressed, the portion is crushed by about 40 μm, so that the gap G near the center in the longitudinal direction of the elastic roller portion 17 is 20 μm. It will be about.
[0061]
Further, the pressure springs 69 and 69 are made of a thermoplastic resin as described above, and are hardened in a low temperature and low humidity environment state like the rubber material constituting the elastic roller portion 17 of the charging roller 14. Since it has a property of softening in an environment state of high temperature and high humidity, the environment in which the apparatus is placed is an environmental condition of high temperature and high humidity (for example, temperature 32 ° C., humidity 80%), or low temperature and low humidity (for example, temperature 10 ° C.). The pressure springs 69 and the elastic roller portions 17 are both softened or hardened when the humidity is changed to any of 15%).
[0062]
Accordingly, in an environment of high temperature and high humidity, the elastic roller portion 17 expands, so that the gap G near the center in the longitudinal direction of the elastic roller portion 17 becomes a condition. , 69 are softened, and the biasing force F₁, F₂Is weakened (F₁, F₂= 2N), since the pressure applied to the photosensitive drum 5 by the charging roller 14 is weakened, the gap G is maintained at approximately the same gap as 20 μm at normal temperature and humidity. Be drunk.
[0063]
On the other hand, in the environment of low temperature and low humidity, the elastic roller portion 17 is cured, so that the gap G near the center in the longitudinal direction of the elastic roller portion 17 is widened. , 69 harden, respectively,₁, F₂Will increase (F₁, F₂= 6N), and the pressure applied to the photosensitive drum 5 side of the charging roller 14 is strengthened, so that the gap G is kept substantially the same as 20 μm at normal temperature and humidity. Be drunk.
[0064]
As described above, according to the photoreceptor unit and the image forming apparatus using the same according to this embodiment, it is necessary to replace the pressure springs 69 and 69 with different urging forces each time the environment of temperature and humidity changes. There is no need to replace it.
[0065]
FIG. 9 is a schematic view similar to FIG. 8 showing the vicinity of the charging roller of the embodiment of the photoreceptor unit in which the urging members for urging both ends of the charging roller to the image carrier side are formed of a foamed elastic body. It is.
In the image carrier unit according to this embodiment, urging members 79 and 79 for urging both ends of the charging roller 14 toward the photosensitive drum 5 with respect to the photosensitive units 2A to 2D described in FIG. Is different only in that it is made of a foamed elastic body that is a hardness varying member having a property of becoming hard in a low-temperature and low-humidity environment and softening in a high-temperature and high-humidity environment.
[0066]
Even in this case, as in the embodiment of FIG. 8, the biasing force F is generated by softening the biasing members 79 on both sides in a high temperature and high humidity environment.₁, F₂Is smaller (F₁, F₂= 2N), and the pressure on the photosensitive drum 5 side of the charging roller 14 is weakened, so that the gap G is kept substantially the same as 20 μm at normal temperature and humidity. Be drunk.
[0067]
On the contrary, in the low temperature and low humidity environment, the biasing force F is obtained by curing the biasing members 79 on both sides.₁, F₂Will increase (F₁, F₂= 6N), and the pressure applied to the photosensitive drum 5 side of the charging roller 14 is strengthened, so that the gap G is kept substantially the same as 20 μm at normal temperature and humidity. Be drunk.
Therefore, the photoreceptor unit according to this embodiment and the image forming apparatus using the photoreceptor unit do not need to replace the urging members 79 and 79 with different urging forces each time the temperature and humidity environment changes. Save time and effort for replacement.
[0068]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained.
If the gap management method in the non-contact charging device according to claim 1 is carried out, the urging force of each urging member for urging both ends of the charging roller is increased in a low temperature and low humidity environment, By weakening in the environmental state, the gap between the charging roller and the image carrier can be made substantially the same as the gap at normal temperature and humidity.
[0069]
Accordingly, stable charging performance is always obtained, and the elastic roller portion of the charging roller does not come into contact with the surface of the image carrier even in an environment of high temperature and high humidity. It is possible to prevent the substances that are present from adhering to the surface of the image bearing member and the transfer of toner or the like from the image bearing member side to the surface of the charging roller.
In addition, the gap between the charging roller and the image carrier does not become too large even in a low-temperature and low-humidity environment, so that abnormal discharge traces can be prevented.
[0070]
If the gap management method in the non-contact charging device according to claim 2 is implemented, the adjustment to increase or decrease the urging force of each urging member is performed by changing the compression amount of each urging member. Since it is not necessary to prepare several different types of urging members, it is possible to save the trouble of parts management and to easily change the urging force.
[0071]
  Claim 3Or 4Image carrier unit and claim5According to the image forming apparatus, each urging member has a low temperature and low humidity.Hardens in environmental conditionsNaturally increase the energizing force, high temperature and high humiditySoftens in environmental conditionsAs a result, the biasing force naturally weakens, so that the gap can be made constant regardless of environmental conditions.
  In this way, the urging force of the urging member formed of resin or foamed elastic body depends on the environmental conditions.Since it changes naturally, it is not necessary to change the urging force consciously, so that it is possible to save time and to prevent erroneous assembly that replaces the urging force with a non-optimal one.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a non-contact charging apparatus for carrying out a gap management method according to the present invention together with a photosensitive drum.
FIG. 2 is a front view showing only one end side in order to explain a joint portion of a tape material which is a gap management member wound around both ends of the charging roller.
3 is an overall configuration diagram illustrating a small color printer that is an image forming apparatus including a plurality of non-contact charging devices and photosensitive drums in FIG. 1;
FIG. 4 is a configuration diagram showing a photosensitive unit provided in the small printer.
FIG. 5 is a configuration diagram showing a writing unit provided in the small printer of FIG. 3;
6 is a schematic view showing a state where an elastic roller portion is expanded in an environment where the charging roller provided in the non-contact charging device of FIG. 1 is in a high temperature and high humidity environment.
FIG. 7 is a schematic diagram showing an example in which adjustment of the urging force of a pressure spring that presses both ends of the charging roller is performed by changing the amount of compression of the spring.
FIG. 8 is a schematic view similar to FIG. 1 showing the vicinity of the charging roller of the embodiment of the photoreceptor unit in which the urging members for urging both ends of the charging roller toward the image carrier are made of resin. is there.
FIG. 9 is a schematic view similar to FIG. 8 showing the vicinity of the charging roller of the embodiment of the photoreceptor unit in which the urging members for urging both ends of the charging roller to the image carrier side are formed of a foamed elastic body. FIG.
[Explanation of symbols]
2A, 2B, 2C, 2D: Photosensitive unit (image carrier unit)
4: Charging device 5: Photosensitive drum (image carrier)
14: Charging roller 17: Elastic roller
18: Tape material (gap management member)
19, 69: Pressurizing spring (biasing member)
61: Spring contact plate 63: Groove
79: Energizing member (foamed elastic body)

Claims (5)

The charging rollers having gap management members attached to the outer circumferences of both ends of the elastic roller portion are pressed against the image carrier side by the urging force of the urging members, so that the gap management members on both sides are moved to the image carrier. And a gap in a non-contact charging device in which a gap is formed between an inner portion of the elastic roller portion where the gap management member is provided and a surface of the image carrier. A management method,
The biasing force of each biasing member that biases both ends of the charging roller is increased in a low temperature and low humidity environment state, and is decreased in a high temperature and high humidity environment state, so that the gap is kept at normal temperature. A gap management method in a non-contact charging device, characterized in that the gap is substantially the same as that in a wet state.   2. The gap management method for a non-contact charging device according to claim 1, wherein the adjustment for increasing or decreasing the urging force of each urging member is performed by changing the compression amount of each urging member. An image carrier, a charging roller having a gap management member attached to each outer periphery of both ends of the elastic roller portion, and a biasing member that biases both ends of the charging roller toward the image carrier. The gap management members on both sides of the charging roller are brought into contact with the surface of the image carrier by the urging force of the member, and the inner portion of the portion of the elastic roller portion where the gap management member is provided and the image carrier In an image carrier unit in which a gap is formed between the surface and the surface of
Each of the urging members is formed of a resin having a property of becoming hard in a low temperature and low humidity environment and softening in a high temperature and high humidity environment. An image carrier, a charging roller having a gap management member attached to each outer periphery of both ends of the elastic roller portion, and a biasing member that biases both ends of the charging roller toward the image carrier. The gap management members on both sides of the charging roller are brought into contact with the surface of the image carrier by the urging force of the member, and the inner portion of the portion of the elastic roller portion where the gap management member is provided and the image carrier In an image carrier unit in which a gap is formed between the surface and the surface of
Each of the urging members is formed of a foamed elastic body having a property of becoming hard in a low temperature and low humidity environment and softening in a high temperature and high humidity environment. An image forming apparatus including an image carrier unit according to claim 3 or 4, wherein.

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