JP4706830B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as an electrophotographic apparatus, an electrostatic copying machine, a printer, or a facsimile, and a ring-shaped gap member fixed to both ends of a charging roller provides a predetermined charging gap to an image carrier. The present invention relates to the technical field of an image forming apparatus which is set and non-contact charging the image carrier with this charging roller.

  2. Description of the Related Art Conventionally, as an image forming apparatus, there is known an image forming apparatus including a charging roller that places a predetermined charging gap with respect to an image carrier and charges the image carrier in a non-contact manner (see, for example, Patent Document 1). ). As shown in FIG. 6, a charging roller a used in the image forming apparatus disclosed in Patent Document 1 is provided with a resistance layer c made of an elastic member having conductivity on the outer peripheral surface of a cored bar b, and this resistance layer. The gap members d and e made of an insulating tape-like film member are respectively wound around and fixed to the outer peripheral surfaces of both ends of c in a ring shape, and the pair of gap members d and e is a photosensitive member as an image carrier. A predetermined charging gap G is set by contacting the outer peripheral surface of the body drum f. In this case, both the gap members are formed by pressing the rotating shafts g and h that are coaxially provided in the axial direction from both end faces of the cored bar b toward the photosensitive drum f by the urging force of a spring (not shown). d and e are brought into pressure contact with the outer peripheral surface of the photosensitive drum f.

The charging roller a charges the photosensitive drum f in a non-contact manner by the charging gap, so that generation of ozone can be suppressed and foreign matters such as toner adhering to the photosensitive drum f are applied to the charging roller a. Since it is possible to prevent adhesion or substances contained in the resistance layer c of the charging roller a from adhering to the photosensitive drum f, the charging performance of the photosensitive drum f by the charging roller a can be improved.
Although not shown, in general, the charging roller a has a driving gear fixed to the rotating shaft of the core metal b connected to a driving gear fixed to the rotating shaft of the photosensitive drum f via a power transmission gear train. The motor is rotated by transmitting the driving force from the motor to the driving gear of the charging roller a through the driving gear of the photosensitive drum f and the power transmission gear train.
JP 2001-296723 A.

  However, as described above, when the charging roller a is directly rotated by the driving force of the motor through the driving gear and the power transmission gear train of the photosensitive drum f, the charging roller a is pressed by the image carrier f. Since it is received in a direction away from the image carrier f, the charging gap G between the charging roller a and the photosensitive drum f changes and becomes unstable. For this reason, charging of the photosensitive drum f by the charging roller a does not become uniform in the axial direction, and there is a problem that it is difficult to obtain stable and favorable charging. In particular, when the charging roller a is formed of an inelastic material, this problem becomes a very big problem.

  Therefore, if the charging roller a is not directly driven via the gear train, the rotational driving force of the photosensitive drum f is applied to the charging roller a by utilizing friction between the gap members d and e and the photosensitive drum f. By transmitting, the charging roller a is rotationally driven. However, if the surrounding environment changes or the friction coefficient between the gap members d and e and the photosensitive drum f changes due to adhesion of foreign matters such as toner to the gap members d and e, the photosensitive member The rotational driving force of the drum f is not effectively transmitted to the charging roller a, and the rotation of the charging roller a becomes unstable. When the rotation of the charging roller a becomes unstable in this way, vibration due to contact between the charging roller a and the photosensitive drum f occurs, and the charging gap G slightly fluctuates. In particular, when the charging roller a is formed of an inelastic material, this vibration may appear remarkably. The reason is that the inelastic charging roller differs from the elastic charging roller made of rubber or the like in that the contact between the charging roller a and the photosensitive drum f is close to a line contact, so the charging roller a and the photosensitive drum f This is because it is difficult to secure a sufficient nip pressure for contact with the charging roller a, and it is difficult to stably rotate the charging roller a for a long period of time.

  The present invention has been made in view of such circumstances, and an object of the present invention is to perform stable and favorable charging by suppressing fluctuations in the charging gap caused by direct rotation driving of the charging roller, and to charge the charging roller. Is to stably rotate the image forming apparatus.

In order to solve the above-described problem, an image forming apparatus according to the first aspect of the present invention includes an image carrier in which rotation shafts provided at both ends are rotatably supported by a device main body via bearings, and both ends. At least a charging roller to which a gap member is fixed, and the gap member is pressed against the outer peripheral surface of the image carrier to set a charging gap between the image carrier and the charging roller. the in the charging roller in the image forming apparatus in a non-contact charging said image bearing member by said charging gap, Bei give a pressing member pressing towards each said gap member with provided rotatably said image bearing member, wherein at least one and said image bearing member of the pressing member is rotated together with the driving force of the same driving source, the charging roller, the frictional force between the gap member and said image bearing member In the friction force between the gap member and the pressing member, it is characterized by being rotated.

According to a second aspect of the present invention, a cleaning member is provided between the pressing members, and the pressing member and the cleaning member are provided on a rotating shaft that is driven to rotate by a driving force of a driving source. It is characterized by being.
Furthermore, the image forming apparatus of the invention of claim 3 is characterized in that the pressing member and the cleaning member are provided integrally.
Furthermore, the image forming apparatus of the invention of claim 4 is characterized in that the cleaning member presses the gap member toward the image carrier to bend the charging roller toward the image carrier .

  Furthermore, the image forming apparatus of the invention of claim 5 is characterized in that the pressing member is formed of an elastic member.

According to the image forming apparatus of the present invention configured as described above, both the pressing member and the image carrier are rotationally driven by the driving force of the same driving source. Further, the charging roller is pressed by the pressing member toward the image carrier through the gap member . The rotational driving force of the image carrier and the rotational driving force of the pressing member that are rotationally driven by the driving force of the same driving source are the frictional force between the image carrier and the gap member, and the frictional force between the pressing member and the gap member. Then, the charging roller is rotationally driven via the gap member . Accordingly , since the charging roller is not directly driven to rotate through the gear train, vibration due to gear driving can be suppressed and the influence of the pressing force from the gear provided on one side of the charging roller can be suppressed. As a result, long-term stable charging can be performed.

  In particular, even if the charging roller is not directly driven to rotate, it can be driven stably and reliably, so that vibration due to contact between the charging roller and the image carrier can be suppressed, and fluctuations in the charging gap are effective. Can be prevented. In this case, by forming the charging roller with an inelastic material, a sufficient nip pressure for contact between the charging roller and the image carrier can be secured, and this vibration can be effectively suppressed.

  Further, the charging roller and the image carrier can be forcibly bent in the same direction by pressing the portion of the charging roller between the pair of gap members toward the image carrier by the cleaning member. As a result, the charging gap between the charging roller and the image carrier can be set to a constant value (50 μm) or less and substantially constant in the axial direction. Therefore, the charging of the image carrier by the charging roller can be made uniform in the axial direction, and a stable and stable long-term charging can be obtained. In particular, since each deflection of the charging roller and the image carrier can be maximized at the same position of the center point between the pair of gap members, the charging gap can be made constant with higher accuracy in the axial direction. It is possible to perform more stable and favorable charging.

  Further, since the gap member is pressed toward the image carrier by the pressing member, the pressure contact of the gap member to the image carrier can be performed more reliably. Thereby, the charging gap can be formed more stably. Further, the pressing of the gap member by the pressing member makes it difficult for the charging roller to bend away from the image carrier as compared with the conventional case where the rotating shaft of the charging roller outside the gap member is pressed. Can do. Therefore, the charging gap can be set even more uniformly in the axial direction.

  Further, since the charging gap can be made constant in the axial direction even if the charging roller and the image carrier are bent, the outer diameter of the charging roller can be reduced, and the outer diameter and thickness of the image carrier can be reduced. . Therefore, it is possible to more effectively cope with the demands for downsizing and space saving which are increasingly demanded in recent years for image forming apparatuses.

  Further, since the pressing member and the cleaning member are integrated, the whole can be made compact, and space can be saved more effectively, and the cleaning roller can be used to connect the charging roller to the image carrier. The charging gap is adjusted by pressing and the charging roller is cleaned, so that stable charging can be performed for a longer period of time.

  Furthermore, by forming the pressing member with an elastic member such as rubber, vibration generated in the charging roller can be effectively suppressed, and the rotational driving force of the pressing member can be reliably transmitted to the charging roller via the gap member. The charging roller can be driven to rotate more stably.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram schematically and partially showing an example of an embodiment of an image forming apparatus according to the present invention.

  As shown in FIG. 1, the image forming apparatus 1 of this example includes a photoconductor 2 that is an image carrier on which an electrostatic latent image and a toner image are formed, and the photoconductor 2 is provided around the photoconductor 2. Are sequentially provided with a charging device 3, an optical writing device 4, a developing device 5, a transfer device 6, and a cleaning device 7 from the upstream side in the rotation direction (clockwise in FIG. 1).

  In this example, the photosensitive member 2 is composed of a photosensitive drum, and a photosensitive layer having a predetermined thickness is formed on the outer peripheral surface of a cylindrical metal base tube in the same manner as a conventionally known photosensitive drum. A conductive tube such as aluminum is used for the metal base tube in the photoreceptor 2 and a conventionally known organic photoreceptor is used for the photosensitive layer. The photosensitive member 2 is provided such that rotary shafts 2a and 2b (shown in FIG. 2) that are coaxially provided in the axial direction from both end surfaces thereof are rotatably supported by a device body (not shown) via a bearing. ing.

  The charging device 3 has a non-contact charging roller 3a of this example and a cleaning member 3h made of, for example, a roller. The charging roller 3a uniformly charges the photoreceptor 2 in a non-contact manner, and the cleaning member 3h cleans the charging roller 3a to remove foreign matters such as toner and dust attached to the charging roller 3a.

  As shown in FIG. 2, the non-contact charging roller 3a includes a cored bar 3b. The cored bar 3b is configured as a conductive shaft having conductivity, such as a metal shaft. As this conductive shaft, for example, a SUM 22 surface with Ni plating can be used.

  The resistance layer 3c is formed on the outer peripheral surface of the cored bar 3b by applying a conductive coating material by, for example, spray coating. The charging roller 3a is configured as an inelastic body. Gap members 3d and 3e made of a film member having a tape-like film thickness are fixed in a ring shape on the outer peripheral surfaces of both ends of the resistance layer 3c. The charging roller 3a includes rotating shafts 3f and 3g that are coaxially projected from both end surfaces of the cored bar 3b in the axial direction, and these rotating shafts 3f and 3g are rotatably supported by the apparatus body via bearings. Has been.

The pair of gap members 3d and 3e are pressed against the outer peripheral surface of the photosensitive member 2 to set a predetermined charging gap G between the resistance layer 3c and the photosensitive member 2 based on a predetermined film thickness of the film member. In that case, a pair of pressing members 8 and 9 for pressing the gap members 3d and 3e of the charging roller 3a are provided coaxially and integrally with the cleaning member 3h at both ends of the cleaning member 3h, respectively. Each of the pair of pressing members 8 and 9 is formed of an elastic member such as rubber, for example, in a cylindrical shape whose outer diameter is constant in the axial direction, and is fixed to the rotation shafts 3i and 3j of the cleaning member 3h. Yes.

The cleaning member 3h for cleaning the charging roller 3a is formed of a cylindrical sponge whose diameter is constant (straight) in the axial direction, and a portion 3a ₁ of the charging roller 3a inside the pair of gap members 3d and 3e. With a predetermined pressing force.
Then, the pressing members 8 and 9 respectively press the gap members 3d and 3e toward the photosensitive member 2, whereby the gap members 3d and 3e are pressed against the outer peripheral surface of the photosensitive member 2, and the cleaning member 3h is charged with the charging roller. The portion 3a ₁ of 3a is pressed toward the photoreceptor 2.

  A drive gear 10 for rotating the cleaning member 3h and the pressing members 8 and 9 is fixed to the rotation shafts 3i and 3j of the cleaning member 3h. A driving gear 11 for rotating the photosensitive member 2 is fixed to one end side (right end side in the illustrated example) of the photosensitive member 2. Both drive gears 10 and 11 are connected via an intermediate gear 12. Then, the driving force of a motor (not shown) (corresponding to the driving source of the present invention) is transmitted to the driving gear 11 of the photosensitive member 2 so that the photosensitive member 2 is rotationally driven. Then, the cleaning member 3h and the pressing members 8 and 9 are rotationally driven by being transmitted to the drive gear 10 of the cleaning member 3h.

  The optical writing device 4 writes an electrostatic latent image on the photosensitive member 2 with, for example, a laser beam. The developing device 5 includes a developing roller 5a, a toner supply roller 5b, and a toner layer thickness regulating member 5c. The toner T, which is a developer, is supplied onto the developing roller 5a by the toner supply roller 5b, and the toner T on the developing roller 5a is regulated in thickness by the toner layer thickness regulating member 5c. The electrostatic latent image on the photoconductor 2 is developed with the conveyed toner T, and a toner image is formed on the photoconductor 2.

  The transfer device 6 has a transfer roller 6a, and the transfer roller 6a transfers the toner image onto the photosensitive member 2 onto a transfer medium 13 such as transfer paper or an intermediate transfer medium. When the toner image is transferred to the transfer paper as the transfer medium 13, the toner image on the transfer paper is fixed by a fixing device (not shown) to form an image on the transfer paper, and the toner image is transferred to the transfer medium 13. When the toner image is transferred to the intermediate transfer medium, the toner image on the intermediate transfer medium is further transferred to the transfer paper, and then the toner image on the transfer paper is fixed by a fixing device (not shown) to form an image on the transfer paper. Is done.

  The cleaning device 7 includes a cleaning member 7a such as a cleaning blade. The photosensitive member 2 is cleaned by the cleaning member 7a, and the transfer residual toner on the photosensitive member 2 is removed and collected.

In the image forming apparatus 1 of this example configured as described above, the gap members 3d and 3e are pressed against the photosensitive member 2 by the pressing members 8 and 9, respectively. together is pressed against the outer peripheral surface, since the pressing portions 3a ₁ of the charging roller 3a by the cleaning member 3h toward the photosensitive member 2, charging the inside of the pair of gap members 3d, 3e as shown in FIG. 2 roller a The portion a ₁ is bent (bending deformation) Dr in a direction approaching the photosensitive member 2. Usually, the deflection Dr of the charging roller 3a is maximized at the axial center point between the pair of gap members 3d and 3e (center point between the pair of gap members 3d and 3e).

  Further, the photosensitive member 2 is bent in the same direction as the bending Dr of the charging roller 3a because the photosensitive member 2 is pressed by the pair of gap members 3d and 3e in the same manner as the above-described conventional image forming apparatus. Bending deformation) Do occurs. Usually, the deflection Do of the photosensitive member 2 becomes maximum at the axial center point (the center point between the pair of gap members 3d and 3e).

  As described above, when the charging roller 3a and the photosensitive member 2 are bent in the same direction, the charging gap G between the charging roller 3a and the photosensitive member 2 is not affected even if the charging roller 3a and the photosensitive member 2 are bent. It does not change greatly in the direction, and is set to 50 μm or less, being substantially constant in the axial direction. For this reason, the charging of the photosensitive member 2 by the charging roller 3a becomes uniform in the axial direction, and stable and good charging is performed over a long period of time. In particular, since the deflections of the charging roller 3a and the photosensitive member 2 are maximum and almost parallel at the same position at the center point between the pair of gap members 3d and 3e, the charging gap G is more accurately in the axial direction. It becomes constant and further stable and good charging is performed.

  Further, the photosensitive member 2 is rotationally driven by the driving force of the motor, and the cleaning member 3h and the pressing members 8 and 9 are rotationally driven via the intermediate gear 12, but the photosensitive member 2 and the pressing members 8 and 9 are rotated. When driven, the charging roller 3 a rotates due to friction between the gap members d and 3 e and the photosensitive member 2 and friction between the gap members d and 3 e and the pressing members 8 and 9. In that case, the friction between the gap members d and 3e and the photosensitive member 2 and the friction between the gap members d and 3e and the pressing members 8 and 9 are caused by the pressing force of the gap members d and 3e by the pressing members 8 and 9. Therefore, the rotational driving force of the photosensitive member 2 and the pressing members 8 and 9 is reliably transmitted to the charging roller 3a, and the charging roller 3a is stably and reliably rotated.

According to the image forming apparatus 1 of this example, the portion 3a ₁ of the charging roller 3a between the pair of gap members 3d and 3e is pressed toward the photosensitive member 2 by the cleaning member 3h. The bodies 2 can be forcibly bent in the same direction. As a result, the charging gap G between the charging roller 3a and the photosensitive member 2 can be kept constant in the axial direction below a certain value (50 μm). Therefore, the charging of the photosensitive member 2 by the charging roller 3a can be made uniform in the axial direction, and good charging stable for a long time can be obtained. In particular, since each deflection of the charging roller 3a and the photosensitive member 2 can be maximized at the same central point between the pair of gap members 3d and 3e, the charging gap G can be made constant with higher accuracy in the axial direction. The body 2 can be more stably and satisfactorily charged.

  Further, since the gap members 3d and 3e are pressed toward the photosensitive member 2 by the pressing members 8 and 9, respectively, the press contact of the gap members 3d and 3e to the photosensitive member 2 can be performed more reliably. Thereby, the charging gap G can be formed more stably. Further, when the gap members 3d and 3e are pressed by the pressing members 8 and 9, the charging roller 3a is made to be smaller than when the rotating shaft of the charging roller 3a outside the gap members 3d and 3e is pressed. It is possible to make it difficult to bend away from the photoreceptor 2. Therefore, the charging gap G can be set even more uniformly in the axial direction.

  Further, since the charging gap G can be made constant in the axial direction even when the charging roller 3a and the photosensitive member 2 are bent, the outer diameter of the charging roller 3a can be reduced, and the outer diameter and thickness of the photosensitive member 2 can be reduced. Can be reduced. Therefore, as described above, it is possible to more effectively cope with the demands for downsizing and space saving which are increasingly demanded in recent years for image forming apparatuses.

  Further, since the charging roller 3a is rotationally driven by the rotational driving force of the photosensitive member 2 and the pressing members 8 and 9 through the gap members 3d and 3e and is not directly driven through the gear train, the vibration due to the gear drive is not generated. It is possible to suppress the influence of the pressing force from the gear provided on one side of the charging roller 3a. As a result, long-term stable charging can be performed.

  In particular, even if the charging roller 3a is not directly driven to rotate, the charging roller 3a can be stably and reliably rotated, so that vibration due to contact between the charging roller 3a and the photoreceptor 2 can be suppressed, and the charging gap G Variations can be effectively prevented. In this case, since the charging roller 3a is formed of an inelastic material, a sufficient nip pressure for contact between the charging roller 3a and the photosensitive member 2 can be secured, and this vibration can be effectively suppressed.

  Further, since the pressing members 8 and 9 and the cleaning member 3h are integrated, the whole can be made compact, space saving can be achieved more effectively, and the charging roller 3a can be achieved with the cleaning member 3h. Is pressed toward the photosensitive member 2 to adjust the charging gap G and clean the charging roller 3a, whereby stable charging can be performed for a longer period of time.

  Further, since the pressing members 8 and 9 are formed of an elastic member such as rubber, vibration generated in the charging roller 3a can be effectively suppressed, and the rotational driving force of the pressing members 8 and 9 can be reduced by the gap members 3d and 3e. Thus, the charging roller 3a can be reliably transmitted to the charging roller 3a, and the charging roller 3a can be driven to rotate more stably.

  FIG. 3 is a diagram schematically showing a photoreceptor and a charging roller in another example of the embodiment of the image forming apparatus of the present invention. In the following description of each example, the same components as those in the previous example are denoted by the same reference numerals, and detailed description thereof is omitted.

In the image forming apparatus 1 of the embodiment shown in FIG. 2 described above, the charging roller 3a provided Kuringu member 3h of the pair of gap 3d in this Kuringu member 3h, charging between 3e rollers 3a portions 3a ₁ of the photosensitive member 2 However, as shown in FIG. 3, in the image forming apparatus 1 of this example, the cleaning member 3h is not provided, and the charging roller 3a is not pressed by the cleaning member 3h. Therefore, in the image forming apparatus 1 of this example, the pressing members 8 and 9 are fixed to the rotating shaft 3k where the cleaning member 3h is not provided, and the photosensitive member 2 of the gap members 3d and 3e by these pressing members 8 and 9 is used. Only pressing is performed. The drive gear 10 is fixed to one end side of the rotating shaft 3k.

According to the image forming apparatus 1 of this example, the above-described effects based on the pressing of the charging roller 3a by the cleaning member 3h cannot be obtained.
Other configurations and other functions and effects of the image forming apparatus 1 of this example are the same as those of FIGS. 1 and 2 described above.

FIG. 4 is a diagram schematically showing a photoconductor and a charging roller in still another example of the embodiment of the image forming apparatus of the present invention.
In the image forming apparatus 1 in the example shown in FIG. 3, the pressing members 8 and 9 are both fixed to the rotating shaft 3k. However, in the image forming apparatus 1 in this example as shown in FIG. Only one pressing member 9 is fixed. In this case, the other pressing member 8 rotates idler, but presses the gap member 3d toward the photosensitive member 2 in the same manner as in the above examples.
Other configurations and operational effects of the image forming apparatus 1 of this example are the same as those of FIGS. 1 and 3 described above.

FIG. 5 is a diagram schematically showing a photoreceptor and a charging roller in still another example of the embodiment of the image forming apparatus of the present invention.
In the image forming apparatus 1 of the example shown in FIG. 2 described above, the cleaning member 3h and the pressing members 8 and 9 are set separately from different materials, and the cleaning member 3h is formed in a straight shape with a constant diameter. However, as shown in FIG. 5, in the image forming apparatus 1 of this example, the pressing member is also formed from the cleaning member 3h, and is formed into a crown shape having a large central diameter as a whole. In that case, the cleaning member 3h is formed of sponge in the same manner as the cleaning member 3h in the example shown in FIG.
Other configurations and operational effects of the image forming apparatus of this example are substantially the same as those of the example shown in FIGS. 1 and 2 described above.

  By the way, when non-contact charging is performed with the charging gap G set by the gap members 3d and 3e, the charging roller 3a may be in contact with the photosensitive member 2 partially or entirely due to bending of the gap members 3d and 3e. Even in such a case, the maximum value of the charging gap G in the axial direction is equal to or less than the film thickness of the gap members 3d and 3e (that is, 0 ≦ maximum value of the gap G ≦ film thickness of the gap members 3d and 3e). ), There is no particular problem, and the desired effects of the present invention are achieved. Therefore, in the present invention, the non-contact charging performed in the charging gap G set by the gap members 3d and 3e includes such a case.

Next, an experiment conducted for demonstrating that the image forming apparatus of the present invention can obtain the above-described effects can be described with respect to an example belonging to the present invention and a comparative example not belonging to the present invention.
Table 1 shows the conditions of the photosensitive member 2, the conditions of the charging roller 3a, and the experimental results in the image forming apparatuses of Examples and Comparative Examples used in the experiment.

  In Table 1, each of the photoreceptors 2 used in Experiment Nos. 1 to 14 is used for the photoreceptor layer of the photoreceptor LP-9000C manufactured by Seiko Epson Corporation on the outer peripheral surface of an aluminum tube. This is a photoreceptor in which the same organic photoreceptor as that described above is applied to a film thickness of 25 μm to form a photosensitive layer. In that case, the outer diameter of the photoreceptor 2 in Experiment Nos. 1 to 5 is 40 mm, and the thickness of the aluminum base tube of the photoreceptors 2 and 2 is 1.5 mm. The thickness of the aluminum base tube of the photoreceptor 2 is 1.0 mm. The outer diameter of the photoreceptor 2 in No. 6 to 10 is 30 mm, and the thickness of the aluminum tube of the photoreceptor 2 in No. 6 and 7 is 1.5 mm, and the photoreceptor 2 in No. 8 The thickness of the aluminum base tube is 1.0 mm, and the thickness of the aluminum base tube of the photoconductors 2 of No. 9 and 10 is 0.75 mm. Further, the outer diameter of the photoreceptor 2 in Nos. 11 to 14 is 24 mm, and the thickness of the aluminum tube of the photoreceptor 2 in Nos. 11 and 12 is 1.0 mm. The thickness of the aluminum base tube of the body 2 is 0.75 mm. Each photoconductor 2 was selected and used with a shake accuracy of 0.01 or less.

  The charging roller 3a used in each of Experiment Nos. 1 to 14 was processed into a shape that can be mounted on the above-described printer LP-9000C using a metal shaft having a SUM 22 plated with Ni as a core metal. These metal shafts are subjected to centerless polishing, and the runout accuracy is processed to 0.01 or less. As shown in Table 1, the metal shafts of Experiment Nos. 1, 4, 6, 10, and 12 have an outer diameter of 12 mm, and the metal shaft of No. 3 has an outer diameter of 10 mm, , 7, 9, 11, 13, and 14 have an outer diameter of 8 mm.

Then, conductive tin oxide (SnO ₂ ) and polyurethane (PU) resin are mixed at a weight ratio (wt ratio) of 1: 9 on the outer peripheral surfaces of these metal shafts, and dispersed in the ionic conductive material and water. The coating liquid obtained by spraying was spray-coated to form a resistance layer having a thickness of 20 μm. Conductive SnO ₂ is available from Gemco Co., Ltd. shown in Table 2. Details of those are available on Gemco's website (http://www.jemco-mmc.co.jp/corporate/index.html). It is posted.

The conductive SnO ₂ used in this example and this comparative example is trade name “T-1” of Gemco Co., Ltd., and “T-1” is a tin-antimony oxide. Of course, other conductive SnO ₂ can be used in the present invention. In addition, the ion conductive material is for imparting conductivity to the conductive coating material, and the ion conductive material used in this example and this comparative example is “YP-12” (manufactured by Maruhishi Oil Chemical Co., Ltd.). ). Incidentally, the above coating solution used in the experiment was coated in a thickness of 20μm aluminum plate, was measured for volume resistivity was (1.0~5.0) × ¹⁰ 10 Ωcm.

The gap members 3d and 3e were formed by affixing a polyimide (PI) resin tape having a film thickness of 20 μm and a width of 5 mm to the outer peripheral surfaces of both ends of the charging roller 3a.
The pressing members 8 and 9 are made of hardness Asker C65 °, and a cylindrical urethane rubber having an outer diameter of 10 mm and an inner diameter of 5 mm is produced, and a SUS shaft having an outer diameter of 6 mm is passed through the hole of the cylindrical urethane rubber. Formed by.
Further, a cylindrical urethane sponge (trade name EPT-51, manufactured by Bridgestone Chemicals Tokyo) was used as the cleaning member 3h. In this case, the urethane sponge had an outer diameter of φ10 mm and an inner diameter of φ5 mm, the contact depth with respect to the charging roller 3a was set to 0.3 mm, and the runout tolerance was set to ± 0.1.

  As shown in Table 1, in the experiment Nos. 1, 5, 11, 12, and 14, as shown in Table 1, the load by the spring is applied to the bearing portions of the rotating shafts 3i, 3j of the charging roller (gap members 3d, 3e to 10 mm), the charging roller 3a was pressed. In this case, the bearing spring load is 500 gf for all of Nos. 1, 5, 12, and 14 and 200 gf for No. 11.

In No. 2, the gap members 3d and 3e were pressed by the pressing members 8 and 9 fixed to the rotating shaft 3k as shown in FIG. In that case, the pressing load of the gap member is 500 gf. Further, in Nos. 3 and 13, as shown in FIG. 2, the gap members 3d and 3e were pressed by the pressing members 8 and 9, and the portion 3a ₁ of the charging roller 3a was pressed by the sponge of the cleaning member 3h. In that case, the pressing load of the gap member is 800 gf in No. 3 and 200 gf in No. 13. Further, in Nos. 4, 7, 8, and 10, the gap members 3d and 3e and the charging roller 3a are formed by the cleaning member 3h formed of the same sponge and the crown shape as shown in FIG. 3a ₁ was pressed. In that case, the pressing load of the gap member is 400 gf for No. 4, 200 gf for No. 7, and 800 gf for No. 8 and 10. Further, in Nos. 6 and 9, as shown in FIG. 4, the gap members 3d and 3e were pressed by the pressing members 8 and 9 respectively fixed to the different rotating shafts 3i and 3j. In that case, the pressing load of the gap member is 500 gf for both No. 6 and No. 9. Each pressing force of the charging roller 3a was adjusted by calculating the load each time.

Further, in Nos. 1, 5, 11, 12 and 14, the photosensitive member 2 and the charging roller 3a are directly driven by rotation through a gear train, and in Nos. 2 to 4, 6, 7 to 10, and 13, As shown in FIGS. 2 to 5, the charging roller 3a is not directly driven by the photosensitive member 2 via the gear train, and the gap members 3d, 3e and the charging member are at least one of the pressing members 8, 9 and the cleaning member 3h. By pressing at least one of the portions 3a ₁ of the roller 3a, the charging roller 3a is driven by the rotational driving force of the photoreceptor 2 and the gap members 3d, 3e by at least one rotational driving force of the pressing members 8, 9 and the cleaning member 3h. And at least one of the portions 3a ₁ of the charging roller 3a.
As is clear from the above, Experiments Nos. 2 to 4, 6 to 10, and 13 are examples of the present invention, and Nos. 1, 5, 11, 12, and 14 are comparative examples.

  As the experimental apparatus for the image forming apparatus, a printer in which the above-described printer LP-9000C was partially modified so that this experiment can be performed was used. In this case, since the printer LP-9000C uses a photoconductor with an outer diameter of 40 mm, when performing an experiment using a photoconductor with an outer diameter other than 40 mm, the scale is the same as that of the printer LP-9000C. The image forming apparatuses with different image quality were prepared, and an image forming experiment was performed using the same engine as the printer LP-9000C.

In performing the image formation experiment, the peripheral speed of the photosensitive member 2 was set to about 210 mm / sec in all the experiments. The applied voltage V _C (V) of the charging roller 3a is obtained by superimposing the _AC voltage AC component V _AC (V) on the DC voltage DC component V _DC (V) in any experiment,
V _C = V _DC + V _AC = −650 + (1/2) V _PP · sin2πft
(Here, V _PP = 1750 V, f = 1.3 kHz, and V _AC is a sin wave.)
Set to. In the experiment, 500 sheets of 5% halftone monochrome printing were continuously performed on A3 plain paper in an indoor environment at a temperature of 23 ° C. and a humidity of 50%.

  Then, the 100th, 200th, 300th, 400th, and 500th printed matters are picked up and judged by visual observation. Only when there is no image unevenness on all of these printed matters, the charged matter is judged to be good. In Table 1, it is indicated by ◯, and when any one of these printed matter has image spots, it is determined that the charging is defective and is indicated by X in Table 1.

In each of the image forming apparatuses of Examples Nos. 2 to 4, 6 to 10, and 13, No., good charging was obtained. Further, in each of the comparative examples of Experiment Nos. 1, 5, 11, 12, and 14, image spots were generated and the result of poor charging was obtained.
According to this experiment, in the non-contact charging of the photosensitive member 2 by the charging roller 3, the charging roller 3a is pressed toward the photosensitive member 2 by the pressing members 8 and 9 that are directly driven to rotate through the gear train by the driving force of the motor. At the same time, the charging roller 3a is rotationally driven through the gap members 3d and 3e by the rotational driving force of the photosensitive member 2 and the rotational driving force of the pressing members 8 and 9, so that the operational effects of the present invention described above can be obtained. Has been demonstrated.

  The image forming apparatus of the present invention is an image forming apparatus such as an electrophotography, an electrostatic copying machine, a printer, a facsimile, or the like. By setting a predetermined charging gap with respect to the body, it can be suitably used in an image forming apparatus in which the photoreceptor is non-contact charged by a charging roller.

1 is a diagram schematically and partially showing an example of an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a diagram schematically illustrating a photoreceptor and a charging roller used in the image forming apparatus illustrated in FIG. 1. It is a figure which shows typically the photoreceptor and the charging roller in the other example of embodiment of the image forming apparatus of this invention. FIG. 10 is a diagram schematically showing a photoreceptor and a charging roller in still another example of the embodiment of the image forming apparatus of the present invention. FIG. 10 is a diagram schematically showing a photoreceptor and a charging roller in still another example of the embodiment of the image forming apparatus of the present invention. It is a figure which shows typically the behavior of the photoconductor and the charging roller in the conventional image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Photoconductor, 3 ... Charging device, 3a ... Charging roller, 3c ... Resistance layer, 3d, 3e ... Gap member, 8, 9 ... Pressing member, 3h ... Cleaning member, 3k ... Rotating shaft, DESCRIPTION OF SYMBOLS 10 ... Drive gear of pressing member, 11 ... Drive gear of photoconductor, 12 ... Intermediate gear

Claims (5)

The image forming apparatus includes at least an image carrier in which rotation shafts provided at both ends are rotatably supported by a main body of the apparatus via bearings, and a charging roller having a gap member fixed to each of both ends. Image formation in which a charging gap is set between the image carrier and the charging roller by being pressed against the outer peripheral surface of the carrier, and the charging roller non-contact charges the image carrier by the charging gap. In the device
E Bei pressing member pressing towards each said gap member with provided rotatably said image bearing member,
Both at least one of the pressing members and the image carrier are rotationally driven by the driving force of the same driving source ,
The image forming apparatus , wherein the charging roller is rotationally driven by a frictional force between the image carrier and the gap member and a frictional force between the pressing member and the gap member . A cleaning member for cleaning the charging roller by contacting the charging roller is provided between the pressing members, and the pressing member and the cleaning member are provided on a rotating shaft that is driven to rotate by a driving force of a driving source. The image forming apparatus according to claim 1, wherein the image forming apparatus is provided.   The image forming apparatus according to claim 2, wherein the pressing member and the cleaning member are provided integrally. 4. The image forming apparatus according to claim 2, wherein the gap member is pressed toward the image carrier by the cleaning member to bend the charging roller toward the image carrier .   The image forming apparatus according to claim 1, wherein the pressing member is formed of an elastic member.

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