JP5232102B2 - Developing device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a developing device that visualizes a latent image as a developer image by applying a developer to a latent image carrier that carries the latent image, and an image forming apparatus including the developing device.

  A developing device of an image forming apparatus that employs electrophotography such as a copying machine or a laser printer transports a developer to a developing area facing the photoreceptor, and the electrostatic latent image formed on the photoreceptor is developed by the developer. A magnet roller for developing and visualizing is provided.

  As shown in FIG. 7, the magnet roller 300 includes a cylindrical sleeve 310 that rotates in a certain direction, a magnet 311, and flanges 312 fixed to both ends thereof. A fixed shaft 302 and a rotary shaft 308 are provided on the flange 312. The fixed shaft 302 side is supported by a fixed shaft bearing 303, and the rotary shaft 308 side is supported by a rotary shaft bearing 309.

  For example, in Japanese Patent Laid-Open No. 8-137369 (Patent Document 1) shown in FIG. 8, the magnet roller 101 is supported and supported by holders 111a and 111b that fix the cored bar portion 101a to the developing device main body 110. It is described that the shaft portion 111 c of the holder engages with the inner peripheral surface side of the flange 104 a constituting the developing sleeve 100.

JP-A-8-137369

  However, according to the configuration of Patent Document 1, the cored bar 101a of the magnet roller 101 is only supported by the holders 111a and 111b fixed to the developing device main body 110. When vibration occurs, the vibration is transmitted to the entire developing device, and the vibration is propagated as vibration to the entire process cartridge. As a result, the gap between the photoconductor and the magnet roller 101 becomes unstable, and the amount of toner developed on the photoconductor varies, causing problems such as image density unevenness.

  In particular, when an image having a large image area ratio such as a photograph is printed out compared to an image having a relatively small image area ratio such as a text sentence, the image density unevenness becomes conspicuous. In a single-color image with a large image area ratio, certain image density unevenness occurs in a striped shape in the sheet passing direction, and the aesthetic appearance of the image is impaired. Further, in a full-color image having a large image area ratio, image density unevenness of each color appears as a hue shift.

  In recent years, as the image quality is improved, the gap between the photoconductor and the magnet roller tends to be narrowed. Therefore, when the gap fluctuates, the fluctuation rate with respect to the gap increases as a result. Similarly, the amount of toner developed on the photoconductor also fluctuates greatly, so that unevenness in image density appears remarkably.

The present invention is a developing device provided with a bearing that supports a shaft of a magnet roller, the bearing can be fitted to a chuck supported by a main body frame, and the bearing is attached to a chuck supported by the main body frame. The bearing is pivotally supported by fitting.
The present invention is characterized in that the bearing of the developing device is on the fixed shaft side.

  The present invention further includes a magnet roller holding member, wherein the magnet roller holding member is positioned between the chuck and the magnet roller, and is in contact with the bearing, the chuck, and the magnet roller. It is a feature.

  The present invention also provides an image forming apparatus provided with the above-described developing device.

  According to the present invention, the fixed shaft bearing of the developing device is fitted into the chuck supported by the main body frame, and the bearing is pivotally supported, thereby suppressing the shake of the fixed shaft of the magnet roller, and eventually the magnet roller. Since fluctuations in the gap between the photoconductor and the magnet roller are reduced by suppressing circumferential shake, image density unevenness can be prevented.

  Further, since the bearing of the developing device is on the fixed shaft side of the magnet roller, it suppresses the shake of the fixed shaft of the magnet roller, and consequently suppresses the shake in the circumferential direction of the magnet roller, thereby preventing uneven image density. can do.

  Further, since the bearing of the developing device is in contact with the magnet roller holding member, the magnet roller does not move in the axial direction, and the shaft of the magnet roller can be stably supported.

  Further, according to the present invention, since the image forming apparatus including the developing device described above reduces the shake of the magnet roller, it is possible to improve the quality of an image output after development.

1 is a longitudinal sectional view schematically showing an outline of the entire configuration of a first embodiment of an image forming apparatus in which a developing device according to the present invention is mounted. It is a schematic sectional drawing of the image development apparatus of a present Example. It is a schematic sectional drawing of the magnet roller and bearing of a present Example. It is a fitting figure with the chuck | zipper supported by the main body frame of the magnet roller fixed axis | shaft of a present Example. (A) It is a figure which shows the state before fitting with the developing device and the chuck | zipper supported by the main body frame. (B) It is a figure which shows the state after a fitting with the chuck | zipper supported by the main body frame. It is a comparison figure of the prior art example of a magnet roller fixed shaft fixing method, and this invention. (A) It is a figure which shows the case where a magnet roller bearing and a magnet roller fixed shaft are supported by a main body frame (conventional example). (B) It is a figure which shows the case (this invention) when a magnet roller bearing is directly fitted and supported by the chuck | zipper supported by the main body frame. It is a graph which shows the displacement amount in a magnet roller rotation period with the prior art example of a magnet roller fixed shaft fixing method, and this invention. (A) It is a graph which shows the displacement amount when a magnet roller bearing and a magnet roller fixed shaft are supported by a main body frame (conventional example). (B) It is a graph which shows the displacement amount when a magnet roller bearing is directly fitted and supported by the chuck supported by the main body frame (invention). It is a schematic sectional drawing of the conventional magnet roller and a bearing. It is a schematic sectional drawing which shows the positional relationship with the holder which fixes the conventional magnet roller and a bearing to a developing device main body.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a longitudinal sectional view schematically showing an outline of the entire configuration of a first embodiment of an image forming apparatus on which a developing device 1 is mounted. FIG. 1 is an example that is simplified and described mainly with respect to main components of the image forming apparatus of the present embodiment.

  The image forming apparatus forms a color image including a plurality of photosensitive members 2 (four in this embodiment, for yellow images, for magenta images, for cyan images, and for black images) as electrostatic latent image carriers. The entire tandem color image forming apparatus is made possible. The image forming apparatus includes image data transmitted from various terminal devices (not shown) such as a PC (Personal Computer) connected via a network (not shown), and a document reading device (not shown) such as a scanner. And a printer function for forming a color image or a monochrome image on a sheet P to be a transfer material (recording medium).

  As shown in FIG. 1, the image forming apparatus has an image forming station 4 (4Y, 4M, 4C, 4Bk) having a function of forming an image on the intermediate transfer belt 3, and the image forming station 4 forms the image on the intermediate transfer belt 3. A secondary transfer station 5 having a function of transferring the toner image to the recording medium P, a fixing device 6 having a function of fixing the recording image transferred to the recording medium P, and a supply tray 7 on which the recording medium P is placed. A paper transport unit 8 having a function of transporting the recording medium P to the secondary transfer station 5 and the fixing device 6 is provided, and a belt cleaner 9 that removes transfer residual toner from the intermediate transfer belt 3 after the secondary transfer.

  The toner is supplied from the toner bottle 10 (10Y, 10M, 10C, 10Bk) containing the toner of each color to the developing device 1 of each color by a supply unit and a control unit (not shown).

  The image forming station 4 includes four image forming stations 4Y, 4M, 4C, and 4Bk for yellow image, magenta image, cyan image, and black image, respectively. In the rotation direction of the intermediate transfer belt 3, a yellow image forming station 4Y, a magenta image forming station 4M, a cyan image forming station 4C, and a black image forming station 4Bk are arranged in this order.

  The image forming stations 4Y, 4M, 4C, and 4Bk for each color have substantially the same configuration, and yellow, magenta, cyan, and black images are generated based on image data corresponding to each color. The images are formed on the intermediate transfer belt 3 so as to overlap with each other to form an image composed of toners of four colors, and transferred onto a sheet P serving as a transfer material (recording medium) at the secondary transfer station 5. Then, the toner image on the paper P is heated and pressed by the fixing device 6 to form a full-color image on the paper P.

  Note that the reference numerals of the component parts of the image forming stations 4 in FIG. 1 are representatively shown for the image forming station 4Y for yellow image, and the reference numerals of the constituent parts of the other image forming stations 4M, 4C, and 4Bk are omitted. It is.

  Each of the image forming stations 4Y, 4M, 4C, and 4Bk includes a photoreceptor 2 serving as a latent image carrier on which an electrostatic latent image is formed, and a charger 11 is disposed around the photoreceptor 2 in a circumferential direction. , A signal light 12, a developing device 1, a primary transfer device 13, and a photoreceptor cleaner 14 are disposed.

  The photosensitive member 2 has a substantially cylindrical drum shape having a photosensitive material such as OPC (Organic Photoconductor) on its surface, is disposed above the exposure unit 15, and is predetermined by a driving unit and a control unit. It is controlled to rotate in the direction (arrow direction in the figure).

  The charger 11 is a scorotron charging means for uniformly charging the surface of the photoconductor 2 to a predetermined potential, and is disposed close to the outer peripheral surface of the photoconductor 2.

  The exposure device 15 irradiates the surface of the photoreceptor 2 charged by the charger 11 with laser light based on the image data output from the image processing unit (not shown), thereby exposing the exposure position. It has a function of lowering the potential and writing and forming an electrostatic latent image corresponding to the image data on the surface. The exposure unit 15 receives the image data corresponding to yellow, magenta, cyan, or black according to each of the image forming stations 4Y, 4M, 4C, and 4Bk, and thereby the electrostatic latent image corresponding to the corresponding color. Is supposed to form. As the exposure device 15, in addition to a laser scanning unit (LSU) including a laser irradiation unit and a reflection mirror, a writing device (for example, a writing head) in which light emitting elements such as EL and LEDs are arranged in an array is used. it can.

  The developing device 1 includes a magnet roller 200 that serves as a developer carrier as shown in FIG. The magnet roller 200 is configured to convey the developer to a development area where the toner can move to the photoreceptor 2. In this embodiment, the developing device 1 uses a two-component developer containing toner and a carrier to invert the electrostatic latent image formed on the surface of the photosensitive member by the exposure device 15 with the toner. Development is performed to form a toner image (visible image).

  A yellow, magenta, cyan, or black developer is accommodated in accordance with image formation at each of the image forming stations 4Y, 4M, 4C, and 4Bk. This developer contains toner charged to the same polarity as the surface potential charged to the photoreceptor 2. Here, the polarity of the surface potential charged on the photosensitive member 2 and the charging polarity of the toner to be used are both negative here.

  The primary transfer unit 13 transfers the toner image on the photoreceptor 2 onto the intermediate transfer belt 3, and a primary voltage to which a bias voltage having a polarity opposite to the charging polarity of the toner (here, positive polarity) is applied. It has a transfer roller.

  The photoconductor cleaner 14 removes and collects toner remaining on the outer peripheral surface of the photoconductor 2 after image transfer onto the intermediate transfer belt 3, and applies a cleaning blade made of urethane rubber to the photoconductor surface. It touches.

  The intermediate transfer belt 3 is made of semiconductive polyimide, and a toner image made of four color toners is formed on the surface by superimposing the toner images formed on the photoconductors 2 of the image forming stations 4 of the respective colors. Is carried. As the intermediate transfer belt 3 rotates, the four color toner images are conveyed to the secondary transfer station 5. At the secondary transfer station 5, the secondary transfer roller 50 is brought into pressure contact with the intermediate transfer belt 3 through the recording paper P that is conveyed in synchronization with the conveyance of the toner image. At this time, a positive potential for attracting toner is applied to the secondary transfer roller 50, and the toner image on the intermediate transfer belt 3 is transferred to the recording paper P.

  The belt cleaner 9 removes and collects the toner remaining on the outer peripheral surface of the intermediate transfer belt 3 after image transfer onto the paper P as a transfer material. The cleaning blade is in contact with the intermediate transfer belt 3.

  The paper transport unit 8 includes a registration roller 80 that controls the transport timing of the recording paper P, and a paper guide 81 that defines the transport path of the paper P. A four-color toner image on the intermediate transfer belt 3 is transferred at the secondary transfer station 5. The transfer material P to be transferred is conveyed.

  The fixing device 6 includes a heating roller 60 and a pressure roller 61, and conveys the transfer material P to these nip portions so that the toner image transferred onto the paper P is thermocompression bonded onto the paper P. It is to fix.

  In the image forming apparatus configured as described above, the sheet P conveyed by the sheet conveying unit 8 is moved by the secondary transfer roller 50 when passing the position where the intermediate transfer belt 3 and the secondary transfer roller 50 are opposed to each other. The four color toner images on the intermediate transfer belt 3 are collectively transferred onto the paper P by the action of the transfer electric field. As a result, four color toner images are formed on the paper P. The sheet P as a transfer material onto which the toner image has been transferred in this manner is subjected to toner image fixing processing by the fixing device 6 and then sent to a paper discharge tray (not shown).

  FIG. 2 is a schematic cross-sectional view of the developing device 1 of the present embodiment, but redundant description of components having substantially the same functional configuration as the conventional example is omitted.

  The magnet roller 200 is supported by a bearing (not shown) with a predetermined gap from the photoreceptor 2. 2, a two-component developer is accommodated in the developing device 1, and is supplied from the toner bottle 10 (10 </ b> Y, 10 </ b> M, 10 </ b> C, 10 </ b> Bk) shown in FIG. The toner is replenished, and after being stirred and mixed with the two-component developer by the developing device stirring unit 201, the toner is sucked and conveyed onto the magnet roller 200 by a magnetic force. Thereafter, a desired developer layer thickness is set by a developer layer thickness regulating plate (doctor blade) (not shown), and the electrostatic latent image on the photoreceptor 2 is rubbed and visualized with toner.

FIG. 3 is a schematic cross-sectional view of the magnet roller and the bearing of the present embodiment.
The magnet roller 200 includes a cylindrical sleeve 210 that rotates in a certain direction, a magnet 211, and flanges 212 that are fixed to both ends thereof. The flange 212 is provided with a fixed shaft 202 and a rotary shaft 208. The fixed shaft 202 is supported by a fixed shaft bearing 203, and the rotary shaft 208 is supported by a rotary shaft bearing 209. The magnet roller fixed shaft 202 is supported by a fixed shaft bearing 203 that can be fitted to a chuck supported by the main body frame, and the fixed shaft bearing 203 is brought into contact with the magnet roller holding member 204.

  FIG. 4 is a fitting diagram of the magnet roller fixed shaft 202 of this embodiment and the chuck 206 supported by the main body frame 205.

  FIG. 4A shows a state before the developing device 1 and the chuck 206 supported by the main body frame 205 are fitted together.

  As shown in FIG. 4B, after the developing device 1 is inserted in the direction of arrow A and fitted with the chuck 206 supported by the main body frame 205, the developing device 1 is further pushed in the direction of arrow A to thereby chuck the chuck. 206 wraps around the fixed bearing 203 and is housed and supported by the main body frame 205.

  The magnet roller holding member 204 serves as a spacer between the fixed shaft bearing 203 and the chuck 206 supported by the main body frame 205, and is in contact with the bearing 203, the chuck 206 and the magnet roller fixed shaft 202.

  The chuck 206 may be anything as long as it can securely clamp the magnet roller fixed shaft 202. Specifically, any of a scroll chuck, a four-jaw chuck, and a collet chuck can be used. However, if the collet chuck is used, the magnet roller fixed shaft 202 is gripped by the entire inner surface of the chuck, so that the vibration can be suppressed because it can be more securely held. At the same time, the magnet roller fixing shaft 202 is not damaged, which is more desirable. For example, a pulling type (PULL type) collet chuck manufactured by Riken Seiki Co., Ltd. can be used.

  FIG. 5 shows a conventional example of a magnet roller fixing shaft fixing method and the present invention. (A) is a conventional example and (b) is the present application.

  When the magnet roller bearing 303 and the magnet roller fixing shaft 302 are supported by the main body frame 305 as shown in FIG. 5A, the circumferential deflection of the magnet roller 300 is 0 as shown in FIG. .05 (mm). Reference numeral 305a denotes a main body frame fitting portion.

  However, when the magnet roller bearing 203 is directly fitted and supported by the chuck 206 supported by the main body frame 205 as shown in FIG. 5B, the circumferential deflection of the magnet roller 200 is as shown in FIG. ), It was 0.02 (mm). Reference numeral 205b denotes a fitting portion with the chuck supported by the main body frame, and reference numeral 207 denotes a chuck support member.

  A developing device was assembled with the configuration shown in FIGS. 5 (a) and 5 (b), and a live-action test of 100,000 sheets was performed using A4 size paper by using a Sharp color MFP MX-7001N. . The paper passing speed is 360 (mm / sec).

  As a result, in the configuration of FIG. 5A, horizontal white stripes having a width of 5 (mm) were generated at a pitch of 29.7 (mm).

  However, with the configuration shown in FIG. 5B, there was no occurrence of horizontal white stripes, and a high-quality image without image density unevenness was obtained.

  In general, when the circumferential deflection of the magnet roller 200 increases, the gap between the photoconductor 2 and the magnet roller 200 becomes unstable and the amount of toner developed on the photoconductor 2 fluctuates, causing problems such as image density unevenness. In addition, when the gap between the photosensitive member 2 and the magnet roller 200 is narrow, as a result, the rate of shake with respect to the gap increases, and a monochrome image with a large image area ratio has a constant pitch in the sheet passing direction. Image density unevenness tends to occur.

  In the case of the Sharp color complex machine MX-7001N, the gap is as narrow as 0.40 (mm). Therefore, if the circumferential deflection of the magnet roller 200 is not less than 0.05 (mm), the image area is reduced. Since it is not possible to eliminate image density unevenness in a monochromatic image having a large rate, horizontal white streaks are generated in the configuration of FIG. 5A in which the circumferential deflection of the magnet roller 200 is 0.05 (mm). However, in the configuration of FIG. 5B in which the circumferential deflection of the magnet roller 200 is 0.02 (mm), there is no occurrence of horizontal white stripes and a high-quality image without image density unevenness can be obtained. It became.

  The outer diameter of the magnet roller 200 of the Sharp color MFP MX-7001N is Φ18 (mm), and the circumferential speed ratio of the magnet roller 200 to the photoreceptor 2 is 1.9. Due to the influence of the direction shake, the pitch when the horizontal white stripe is generated is 18 × π / 1.9 = 29.7 (mm).

  In the above-described embodiment, the tandem color image forming apparatus is illustrated, but other color image forming apparatuses and monochrome image forming apparatuses may be used. Further, although a developing device using a two-component developer is exemplified as the developing device, a developing type developing device using a non-magnetic one component may be used. Further, an example in which the developing device can be detachably installed as a developing unit on the main body of the image forming apparatus has been described. However, a process cartridge (process unit) in which a photosensitive drum, a charger, and a photosensitive member cleaning unit are also incorporated. ).

DESCRIPTION OF SYMBOLS 1 Developing apparatus 2 Photoconductor P Transfer material (recording medium)
3 Intermediate transfer belt 4 Image forming station (4Y, 4M, 4C, 4Bk)
5 Secondary transfer station 50 Secondary transfer roller 6 Fixing device 60 Heating roller 61 Pressure roller 7 Supply tray 8 Paper transport unit 80 Registration roller 81 Paper guide 9 Belt cleaner 10 Toner bottle (10Y, 10M, 10C, 10Bk)
DESCRIPTION OF SYMBOLS 11 Charger 12 Signal light 13 Primary transfer device 14 Photoconductor cleaner 15 Exposure device 200 Magnet roller 201 Developing device stirring unit 202 Magnet roller fixed shaft 203 Fixed shaft bearing (substantially integrated with roller)
204 Magnet roller holding member 205 Main body frame 205b Fitting portion 206 with chuck supported by the main body frame 206 Chuck 207 Chuck support member 208 Magnet roller rotating shaft (shaft)
209 Rotating shaft bearing 210 Sleeve 211 Magnet 212 Flange 300 Magnet roller 302 Magnet roller fixed shaft 303 Fixed shaft bearing (substantially integrated with the roller)
305 Main body frame 305a Main body frame fitting portion 308 Magnet roller rotating shaft (shaft)
309 Rotating shaft bearing 310 Sleeve 311 Magnet 312 Flange

Claims (4)

  A developing device provided with a bearing that supports a shaft of a magnet roller, the bearing being engageable with a chuck supported by a main body frame of the image forming apparatus, and fitting the bearing with the chuck. A developing device characterized in that the bearing is pivotally supported.   The developing device according to claim 1, wherein the bearing of the developing device is a bearing on a side to which the magnet roller is fixed.   The developing device includes a magnet roller holding member, and the magnet roller holding member is located between the chuck and the magnet roller, and is in contact with the bearing, the chuck, and the magnet roller. The developing device according to claim 2. An image forming apparatus comprising the developing device according to claim 1.