JP2929916B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a printer, a copying machine,
The present invention relates to an image forming apparatus such as a facsimile, and more particularly, to a support structure for a rotating member that contacts a member to be charged.

[0002]

2. Description of the Related Art In a conventional image forming apparatus, a corona charger is often used as a means for charging or discharging a surface of an image carrier as a member to be charged such as a photoreceptor or a dielectric. This corona charger is effective as a means for uniformly charging or removing the charged surface of the image carrier to a predetermined polarity and potential, but requires an expensive high-voltage transformer to obtain a predetermined charging potential. However, ozone is generated by corona discharge, and it is necessary to provide an ozone filter as a countermeasure.

[0003] In order to solve such a problem,
For example, US Pat.
No. 32356, a contact charging device for contacting a charging member with a member to be charged to charge the member to be charged;
A contact transfer device and the like disclosed in U.S. Pat. No. 4,998,143 for charging a transfer member by bringing the transfer member into contact with the transfer member have been proposed.

[0004]

However, in the conventional image forming apparatus, a contact charging device using a charging roller will be particularly described as an example. Bearings for positioning the charging roller, springs for preloading the charging roller, etc. A pressurizing member and a conducting member for supplying a bias voltage to the charging roller are required, and there is a problem that the mechanism configuration of the contact charging device is complicated and large.

Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to apply a stable pressing force to a rotating member to maintain a stable contact state with a member to be charged.
An object of the present invention is to provide an image forming apparatus capable of stably charging or discharging an object to be charged. It is still another object of the present invention to provide an inexpensive and small-sized image forming apparatus which supports the rotating member, minimizes the number of peripheral members to which a voltage is applied by preloading the member, and has a high assembling efficiency.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an image forming apparatus in which a rotating member is arranged in contact with a member to be charged to form an electrostatic latent image on the member to be charged and visualize the same. The rotating member is directly supported by the shafts at both ends by the elastic member and pressed against the charged member, and a bias voltage is applied to the rotating member through the shaft from the elastic member.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments and drawings.

FIG. 1 is a sectional view of a main part of an image forming apparatus according to an embodiment of the present invention.

In FIG. 1, an image bearing member 3 which is a member to be charged is
, A charging roller 1, a developing device 4, a transfer roller 5, and a cleaning device 6 are arranged in this order. The image carrier 3 is a drum-shaped photoconductor. The image carrier 3 is an organic photoconductor in which a charge generation layer and a charge transport layer are formed in this order on an alumite-treated aluminum drum. After the image carrier 3 is charged to a predetermined potential by a charging unit, an electrostatic latent image is formed by an exposing unit, and toner is adhered to the electrostatic latent image by a developing unit to visualize the image. Is transferred to the sheet material conveyed from the paper supply means by the transfer means, and then the toner image is fixed to the sheet material by the fixing means, and the sheet material on which the desired image is formed is discharged by the paper discharge means. After the transfer, the residual toner on the surface of the image carrier 3 is removed by the cleaning unit, and then the process after charging is repeated again. This process is described in detail below.

In FIG. 1, reference numeral 1 denotes a charging roller serving as a charging means. The charging roller 1 is formed of a semiconductive elastic material such as rubber, for example, and rotates in an arrow A direction in the figure. DC by charging power supply 8 while following
When a bias of (−) 1.2 kV is applied, the image carrier 3 is charged to a charging potential of (−) 600 V to (−) 700 V.

As shown in FIG. 2, the charging roller 1 supports and positions the shaft portions 1-a at both ends with concave portions of the conductive elastic member 2, and slides and rotates with the sliding portions 1-b. At the same time, the elastic member 2 is pressed against the image carrier 3 with a total pressure of, for example, approximately 1 kg due to the deformation force. When the image carrier 3 rotates in the direction of the arrow A, the charging roller 1 rotates in the direction of the arrow B following the rotation, and the shaft portions 1 at both ends of the charging roller 1 are rotated.
-A and the conductive elastic member 2 are brought into conduction while sliding and rotating at the sliding portion 1-b. As described above, the charging roller 1 is supported and positioned only by the conductive elastic member 2, pressed against the image carrier 3, and a bias is applied to the charging roller 1. Thus, a stable pressure can be obtained on the image carrier 3. As a result, assembly can be performed in a short time, and a small and inexpensive image forming apparatus can be provided.

Next, the image carrier 3 is exposed by an exposure means such as a laser scanning means so that the potential of the image exposure portion of the image carrier 3 becomes (-).
It becomes 50V-(-) 150V. The electrostatic latent image on the image carrier 3 formed by the charging unit and the exposure unit is visualized by a developing device 4 including a developing unit that applies toner to the electrostatic latent image. (-) 200V ~
(−) A developing bias voltage of about 300 V is applied, and the toner charged to (−) is reversely developed on the image exposure portion of the image carrier 3.

Next, the toner image reversely developed on the image exposure portion of the image carrier 3 is transferred onto the sheet material by applying a bias of about (+) 1 kV DC to the transfer roller 5 from the transfer power supply 9. You. On the other hand, when the sheet material does not exist in the transfer portion, a bias of (−) DC of about 0.5 to 1 kV is applied to the transfer roller 5 from the second transfer power supply 10 to transfer the toner adhered to the transfer roller 5 to the image. It is returned to the carrier 3 to prevent toner contamination of the transfer roller 5 and back contamination of the sheet material. Thus, the transfer roller 5
Is to perform charging or static elimination processing using the sheet material or the image carrier 3 as a member to be charged. The transfer roller 5 is formed of, for example, a conductive foam, and the transfer roller 5 is directed to the image carrier 3 by using the conductive second elastic member 7 in the same manner as in FIG. By pressing with the total pressure, a transfer nip is formed, and the sheet N is rotated in the direction of arrow C with respect to the image carrier 3 with the sheet material P interposed therebetween.
Further, the sheet material P is transported toward the fixing unit.

After the transfer, the toner remaining on the image carrier 3 is scraped off by a cleaning device 6 including a cleaning blade pressing its ridge line against the image carrier 3 with a total pressure of several hundred g. The cleaned image carrier 3 can be shifted to the next image forming process again.
After the cleaning, in order to eliminate the electric potential remaining on the image carrier 3, a conductive elastic member supporting the same is connected to a ground or an AC power source by using a charge eliminating roller configured as in FIG. The surface potential of the image carrier 3 can be brought closer to the initial state. When the cleaning device 6 is omitted, the toner remaining on the image carrier 3 can be leveled by the same configuration. When the leveling roller is used, the image carrier 3 is charged or discharged. The applied bias voltage is applied to the conductive elastic member supporting the roller, so that the image carrier 3 can be simultaneously subjected to a charging process or a static elimination process.

FIG. 2 is a view showing this supporting structure, particularly taking a charging roller as an example. In the charging roller 1, the shaft portions 1-a at both ends are formed in a concave portion 2-a of a conductive elastic member 2.
And is pressed against the image carrier by the deformation force of the elastic member 2. The conductive elastic member 2
A plate spring member such as a stainless steel plate or a phosphor bronze plate having a thickness of 0.1 to 0.5 mm or a linear spring member pressed is used. Further, the mechanical holding of the charging roller 1 is performed on the peripheral surface of the shaft portion 1-a of the charging member 1, and the sliding conductivity can be configured from either the peripheral surface or the end surface of the shaft portion of the charging member 1. At this time, the spring bends, twists,
It goes without saying that any type of compression welding by compression can be freely selected.

As shown in FIG. 2, the structure in which the rotating member is brought into contact with the member to be charged to charge or charge the member to be charged is not limited to the charging roller, but also to the charge removing roller, the leveling roller, the transfer roller, and the like. It can also be applied to a cleaning roller, and the description is omitted because it has the same configuration.However, when each roller that is a rotating member is driven to rotate with respect to the member to be charged, it is stable without being affected by the driving force. Contact and stable bias application can be maintained.

(Embodiment 2) In this embodiment, an image forming apparatus is constructed similarly to FIG. 1, and a sliding portion 1-b between a shaft portion 1-a of a charging roller 1 and a conductive elastic member 2 is formed. In addition, by applying conductive grease to reduce the mechanical sliding resistance,
The sliding wear is suppressed, and the electrical conduction is stably performed. Similarly, the shaft 5-a of the transfer roller 5 and the second
The conductive grease is also applied to the sliding portion 5-b between the elastic member 7 and the sliding member 5-b.

When a durability printing test was performed on 10,000 sheets with the above configuration, a belt-shaped image without density unevenness could be formed as in the initial stage after the test. This indicates that the charging roller 1 stably came into contact with the image carrier 3 and the bias voltage was stably supplied.
Similarly, for the transfer roller 5, the stable contact state and the stable supply of the bias voltage are maintained. As described above, by applying the conductive grease to the sliding portion of the conductive elastic member, the electric sliding resistance can be stabilized, and even if a little abrasion (approximately in the endurance printing test of 10,000 sheets) is performed. Even if (abrasion of about 20 μm) occurs, the abrasion powder is taken into the grease to prevent damage to the rollers and the like and no electrical leakage. This is a more preferred embodiment of the present invention.

The conductive elastic member 2 is attached to a housing or an upper cover, and often has a cantilever structure. This housing or upper cover is generally made of plastic such as polystyrene in consideration of cost and weight, etc., and is particularly compatible with its compatibility so as not to generate distortion due to oils such as conductive grease. You have to be careful. For example, in polystyrene,
There are ABS type and HIPS type. HIPS type polystyrene is generally incompatible with most fats and oils.
Polystyrene is preferable because it generally has good compatibility with fats and oils. Experiments have confirmed that silicon-based conductive grease is the most suitable for conductive grease with little chemical change or deterioration even in long-term durability. Here, the silicon-based conductive grease is, for example,
Shin-Etsu Chemical's KS-660 and Nippon Mineral Oil's NPC grease were used. As described above, in consideration of compatibility with the resin and long-term durability, it is a more preferable embodiment of the present invention to apply the silicon-based conductive grease to the elastic member.

(Embodiment 3) FIG. 3 is a view showing a supporting structure of a charging roller in another embodiment of the present invention. In FIG. 3, the charging roller 11 has a shaft portion 11-a held in a concave portion 12-a of the conductive elastic member 12, and the image carrier 13 is deformed by the conductive elastic member 12.
Is pressed against. The conductive elastic member 12 is manufactured by pressing a plate material into a three-dimensionally bent shape, and the concave portion 12-a of the conductive elastic member 12 has a substantially U-shape, and only the ends are charged. The diameter is smaller than the diameter of the shaft 11-a of the roller 11. With such a shape, the charging roller 11 is formed into a U-shaped concave portion 12 of the conductive elastic member 12.
When assembling to -a, first, the conductive elastic member 12 is first attached to the housing or the upper cover, and then the charging roller 1 is pushed in so as to overcome the elastic resistance of the conductive elastic member 2 so that a simple operation can be performed. Can be easily installed. Further, the recess 1 of the conductive elastic member 12 is used.
The shape of 2-a is such that the charging roller 11
Is determined so that it does not fall under its own weight, and assembly and handling as a unit become very easy. Further, when conductive grease is applied to the space between the U-shaped concave portion 12-a of the conductive elastic member 12 and the shaft portion 11-a of the charging roller 11, the gap becomes an oil reservoir and the conductive grease is formed. The grease can be prevented from falling, the sliding resistance can be stabilized for a long time, the sliding durability can be improved, and the life can be extended.

In this embodiment, the charging roller has been described as an example of a rotating member. A bias voltage can be stably applied to the roller with a simple preload structure.

[0022]

As described above, according to the present invention, by using a conductive elastic member for the support member of the rotating member,
A member that applies a stable pressing force to the rotating member to maintain a stable contact state with the member to be charged, stably charges or removes the member to be charged, supports the rotating member, preloads and applies a voltage. The number of parts can be minimized (one part), and an inexpensive and compact image forming apparatus with high assembling efficiency can be provided.

Further, the sliding portion between the rotating member and the elastic member includes
By providing the conductive grease, the electric sliding resistance can be stabilized and the long-term durability can be improved.

Further, by rotating the rotating member with respect to the member to be charged, a stable contact state of the rotating member with the member to be charged can be maintained.

Further, the rotating member is a charging roller,
If at least one of the charge removing roller, the transfer roller, and the cleaning roller is used, stable charging or charge removal of the member to be charged can be performed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a support structure of a charging roller according to an embodiment of the present invention.

FIG. 3 is a diagram showing a support structure of a charging roller according to another embodiment of the present invention.

[Explanation of symbols]

 1, 11 Charging roller 1-a, 11-a Shaft portion of charging roller 1-b Sliding portion 2, 12 Conductive elastic member 2-a, 12-a Concave portion of conductive elastic member 3, 13 Image carrier 4 Developing device 5 Transfer roller 6 Cleaning device 7 Second elastic member A Rotation direction of image carrier B Rotation direction of charging roller C Rotation direction of transfer roller

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-303263 (JP, A) JP-A-2-29677 (JP, A) JP-A-5-119646 (JP, A) 64272 (JP, A) JP-A-5-351110 (JP, A) JP-A-5-323694 (JP, A) JP-A-3-2364 (JP, U) JP-A-60-159534 (JP, U) (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 15 / 02,15 / 16 G03G 21/06-21/10

Claims (8)

(57) [Claims] 1. An image forming apparatus in which a rotating member is arranged in contact with a member to be charged to form an electrostatic latent image on the member to be charged and visualized, wherein both ends of the rotating member are electrically conductive elastic members. An image forming apparatus, wherein a bias voltage is applied to the rotating member through the shaft portion from the elastic member by directly supporting the member to be charged by the shaft member. 2. The image forming apparatus according to claim 1, wherein a conductive grease is used for a sliding portion between a rotating shaft of the rotating member and the elastic member. 3. The image forming apparatus according to claim 1, wherein the rotating member is driven to rotate with respect to the member to be charged. 4. The image forming apparatus according to claim 1, wherein the rotating member is a charging roller that charges the member to be charged. 5. The image forming apparatus according to claim 1, wherein the rotating member is a charge removing roller that removes electricity from the charged member. 6. The image forming apparatus according to claim 4, wherein the rotating member is a leveling roller for leveling the toner remaining on the member to be charged. 7. The image forming apparatus according to claim 1, wherein the rotating member is a transfer roller that transfers toner on the member to be charged. 8. The image forming apparatus according to claim 1, wherein the rotating member is a cleaning roller that removes toner remaining on the member to be charged.