JP3643338B2 - Developing device and image forming apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic one-component developing device used for a copying machine, a printer, a facsimile machine and the like.
[0002]
[Prior art]
Conventionally, in a one-component development method using magnetic toner, a toner layer thickness regulating plate composed of a blade is provided with a clearance of 0.2 to 0.3 mm with respect to the outer peripheral surface of the development sleeve, A system in which the fixed magnetic pole is disposed opposite to the fixed magnetic pole is used. In this method, the thickness of the toner layer on the sleeve surface is regulated by a blade to a thin layer having a thickness of about 0.1 mm and conveyed to the development area, and the photoreceptor is subjected to flight development. The toner particles conveyed on the surface of the developing sleeve obtain a frictional charge necessary for development by rubbing against the blade and the sleeve surface when passing through the gap between the blade and the developing sleeve. In order to give a constant frictional charge to the toner on the surface of the developing sleeve without variation, it is necessary to eliminate variations in the amount of toner transported to the blade and the conveyance pressure in the longitudinal direction of the sleeve and keep them constant. Therefore, in the design of the developing device and the toner, the surface of the developing sleeve is roughened to adjust the toner transport effect and the triboelectric charging effect to a desired range.
[0003]
This surface roughness almost determines the chargeability and uniform thin layer property of the toner sandwiched between the blade and sleeve as the toner layer regulating member, and the surface roughness can be adjusted by, for example, blasting. is there. As a method for measuring the surface roughness, for example, ten-point average roughness Rz (μm) defined in JIS (Japanese Industrial Standards) B0601 Table 6 is used. The sleeve material is roughly divided into aluminum and stainless steel. Aluminum can be machined with a surface roughness Rz of less than 10 μm, while stainless steel can be machined with less than 7 μm. is there. Aluminum has a relatively large variation in surface roughness due to repeated development, and the triboelectric charge of the toner is not stable for a long period of time, so when the toner is used up, the low-speed machine, at least the photoconductor, and the development device are integrated. Suitable for replacing each unit. On the other hand, since the surface roughness of the product made of stainless steel is small, it is suitable for a system in which the developing device itself is extended to the same level as a photocopier or a long-life photoconductor, or toner is additionally supplied as needed.
[0004]
However, when a new unused developing device is replenished with toner from the toner container, both ends of the image area with respect to the longitudinal direction of the developing sleeve may cause background fogging. In particular, the occurrence frequency is high in a low humidity environment, and an early solution is desired. In order to investigate the cause, we observed the conveyance and retention state of the toner that was transported through the sleeve surface and slipped from the back side of the blade to the front side, and as a result, the retention of toner on the back side of both ends of the blade corresponding to the background fogging part was large. It was found to be prone to aggregation. Further, the thickness of the thin layer on the sleeve surface at this location was as thick as 0.2 to 0.3 mm with respect to about 0.1 mm of the normal portion, and in some cases, it was confirmed that the sleeve was in contact with the photoreceptor. Further, when the toner charge amount on the surface of the sleeve was examined by a suction method, it was confirmed that the toner in the normal part was increased to 15 to 20 μc / g while being about 7 to 8 μc / g. From these things, it is judged that the problem occurs in the following flow.
[0005]
First, a new developing sleeve has minute irregularities that cannot be measured with normal surface roughness, and the frictional charge with the toner seems to be particularly high in the initial stage.
Under such circumstances, the surface toner on both ends of the sleeve corresponding to the image defective portion has a large amount of toner remaining on the back side of the blade because the toner development amount in the image area is small, and the blade tip and the sleeve surface The conveying pressure when exiting through increases.
When the toner conveying pressure increases, the toner at both ends of the sleeve increases the triboelectric charge amount and the electrostatic attraction with the sleeve is high. Increases in thickness.
As a result, the toner at both ends of the sleeve has a narrower gap with the photoconductor than the normal portion, so that the toner can easily fly to the non-image portion (unexposed portion), leading to background fogging. Particularly in a low-humidity environment, triboelectric charges are likely to accumulate in the toner particles, so that the background fog density at both ends of the image is likely to be further increased.
Once the initial fog is generated, the fog is not eliminated unless the sleeve surface is specifically cleaned. Therefore, it is presumed that the highly charged aggregated toner on the surfaces of both ends of the developing sleeve is continuously adhered.
[0006]
In view of the situation described above, it is relatively effective to perform blasting with a high surface roughness Rz in order to increase the toner conveying effect on the sleeve surface. In particular, when Rz is 8 μm or more, fogging occurs. It has been confirmed that it is suppressed. However, the aluminum sleeve is difficult to use because the surface roughness greatly changes during repeated development as described above. In addition, since it is difficult to uniformly perform a surface-roughening treatment of 8 μm or more on a stainless steel sleeve, it is difficult to use because the toner on the sleeve surface is unevenly charged.
[0007]
On the other hand, a measure is taken to average the toner retention on the back side of the blade in the axial direction by extending a conveying means such as a spiral in the developing housing in parallel with the developing sleeve. However, although such countermeasures have some effects, the fundamental countermeasure effects have not been obtained. This is because, since a plurality of toner conveying units having different conveying directions are provided, the toner conveying effect in the axial direction is relatively weak at the communicating portions at both ends of the toner conveying unit in which the toner conveying direction is U-turned. As a result of observing the state of toner conveyance, there was a considerable amount of toner remaining between the communicating portions at both ends and the blade. Furthermore, since the toner directly behind the blade is held by the developing sleeve by magnetic force and electrostatic attraction, even if the toner conveying means is provided, the toner is not completely replaced.
[0008]
[Problems to be solved by the invention]
.
Accordingly, a first object of the present invention is to provide a developing device and an image forming apparatus that do not cause background fogging at both ends of an image area in a magnetic one-component developing system.
A second object of the present invention is to provide a developing device and an image forming apparatus that do not cause background fogging at both ends of an image area even in a low humidity environment.
A third object of the present invention is to provide a developing device and an image forming apparatus in which the maintenance cycle is extended in the magnetic one-component developing system.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a first aspect of the present invention is directed to a housing that contains magnetic toner, a developing sleeve that is rotatably held, a developing roller that includes a plurality of magnetic poles fixedly disposed therein, and a developing roller. A developing device having a toner layer thickness regulating plate that is provided in a sleeve axial direction and has a proximity end to the developing sleeve facing a magnetic pole at a predetermined position inside the developing sleeve and attached to the surface of the developing sleeve with a predetermined gap. , Inside the developing housing, a plurality of toner conveying means whose toner conveying directions are opposite to each other extend in parallel with the developing sleeve, and a partition wall is formed between the plurality of toner conveying means except for communicating portions at both ends. The sleeve surface opposite to the communicating portion is provided to suppress excessive frictional charging between the magnetic toner and the developing sleeve. It is characterized by applying metal soap. According to the invention of claim 1, the toner consumption amount is Corresponding to the communication section with less toner conveyance By applying metal soap to the surface of the developing sleeve, excessive frictional charging between the toner and the sleeve is suppressed. As a result, since the toner thin layer portion is not thickened due to the high suction force between the sleeve and the toner even at both ends of the development region, background fogging can be prevented. In particular, initial fogging is prevented when a new developing device is filled with toner for the first time.
[0010]
Further claims 2 The developing apparatus according to claim 1 is characterized in that the metal soap is zinc stearate. Claim 2 By using zinc stearate that can be easily formed into a stick shape, a uniform coating layer can be obtained simply by pressing the stick against the developing sleeve and turning the sleeve.
[0011]
Further, the invention of claim 3 is the developing device according to claim 1, wherein a seal member for preventing toner scattering is provided on the surface of the developing sleeve outside the metal soap application area of the developing sleeve in the axial direction. It is characterized by being coated.
[0012]
Further, the invention of claim 4 is the invention of claims 1 to 3. Any of An image forming apparatus using a developing device is provided. Claim 3 According to the present invention, an image forming apparatus capable of preventing the background fogging at both ends of the image region and extending the maintenance cycle can be obtained.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the apparatus main body constructed according to the present invention will be further described below with reference to the accompanying drawings. FIG. 1 is a perspective view showing an external configuration of a copying machine 100 according to the first embodiment of the present invention. FIG. 2 is a front view showing the internal configuration of the copying machine 100. FIG. 3 is a schematic diagram showing an open / close state of the document cover as viewed from the right side of the copying machine 100, with the document transport unit not shown.
4 is a cross-sectional view showing the internal configuration of the developing device 200 used in the copying machine 100, and FIG. 5 is a plan view of the developing device 200.
FIG. 6 schematically shows the positional relationship between the developing sleeve and the sheet passing area according to the present invention.
FIG. 7 schematically illustrates the manner in which zinc stearate is applied to the sleeve surface.
[0014]
As shown in FIGS. 1 and 2, the copying machine 100 is divided by a main body housing 11, an upper housing 11 </ b> U above the main body housing 11, and a document conveying section 14 that is placed openably on the upper portion of the upper housing. A sheet material stack space portion 12 is formed in an intermediate portion between the main housing 11 and the upper housing 11U from the right side surface inward in a substantially horizontal direction. The sheet material stack space 12 is provided with an upper sheet tray 1 and a lower sheet tray 2 for receiving and stacking sheet materials discharged laterally from the main body housing. As described above, in a so-called in-body discharge type image forming apparatus in which a sheet discharge unit is provided inside the machine body, it is necessary to provide an occupied space for the sheet stack space. However, a compact and low-cost one-component development method is advantageous.
[0015]
The upper housing 11U incorporates an exposure unit 15 for exposing a document at an image reading position and reading the image, and an operation panel 13 and a document placing plate 21 made of a transparent glass plate are disposed on the upper surface. Yes. Above the upper housing 11U, a document conveying section 14 for conveying the document to the image reading position R for reading the document image is placed. As shown in FIG. 3, the document cover 14d is supported on the upper housing by a hinge 9 on the back side of the machine so as to be openable. The document cover 14d is normally placed at a closed position indicated by a solid line, and can be opened to an open position indicated by a broken line. The copying machine 100 can perform two types of document image reading of a sheet through method and a document fixing method. First, the sheet-through method is a method in which an image of a document passing through the image reading position R is read by the exposure unit 15 which is fixedly disposed facing the image reading position by the closed document conveying unit 14. Further, the original fixing type is a method in which the original conveying unit 14 is opened, an original is placed on the upper surface of the original placing plate 21, and an image is read while moving the exposure unit 15. This embodiment will be described as an example based on the sheet-through method.
[0016]
The main body housing 11 can be partitioned into a lower housing 11D and a connecting housing 11C above the lower housing 11D. The lower housing 11D includes a paper feeding unit, an image forming unit for forming a toner image on the paper, and a fixing unit for fixing the toner image on the paper. The connecting housing 11C has a built-in sheet conveyance path for conveying the fixed sheet and discharging it toward the sheet tray in the sheet material stack space.
[0017]
The configuration of the upper housing 11U will be described with reference to FIGS.
An operation panel 13 is provided on the front side of the upper housing 11U. The document transport section 14 includes a document feed tray 14a, a document transport section main body 14b, a document discharge tray 14c, and a document cover 14d. The document discharge tray 14c is formed directly on a part of the upper surface of the document cover 14d. A document feed tray 14a is disposed at the upstream end on the extension of the document transport path d, and a document discharge tray 14c is disposed at the downstream end on the extension of the document transport path d. The document reading section main body 14b is provided with a pickup roller 22, a conveyance roller pair 23, a registration roller pair 24, and a discharge roller pair 25 from the upstream side to the downstream side in the document conveyance direction along the document conveyance path d. The conveyance roller pair 23 includes a driving roller 23a and a separation roller 23b. The separation roller 23b rotates in the opposite direction to the driving roller 23a only when the rotational load is lower than the predetermined torque, and is driven to rotate with the driving roller 23a when the rotational load exceeds the predetermined torque.
[0018]
An image reading unit R is provided between the registration roller pair 24 and the discharge roller pair 25. At the image reading position R, a white reference plate 26 for shading correction in a direction facing the document placement plate 21 and a white reference plate 26 that is above the white reference plate 26 and presses the white reference plate 26 against the document placement plate 21. The document pressing portion 26a is provided. The document conveyance path d is curved so as to be reversed between the conveyance roller pair 23 and the image reading position R. Each sensor is provided from the upstream side to the downstream side of the document conveyance path d. That is, the document detection sensor S1 is provided at the center of the document feed tray 14a, the feed sensor S2 is provided downstream of the transport roller pair 23, and the discharge sensor S3 is provided downstream of the discharge roller pair 25. .
[0019]
The following description proceeds based on a so-called sheet-through document reading method in which a document is exposed by a fixed exposure lamp while the document is transported and moved by a document transport unit. The M originals set on the original feeding tray 14a with the image surface facing upward are pressed against the pickup roller 22 with a predetermined pressure by the set original pressing member 6b biased upward by the spring member 6a. When the copy start button on the operation panel 13 is turned on, the pickup roller 22 and the transport roller 23 are rotationally driven by a primary paper feed driving means (not shown). A plurality of documents set on the document feed tray 14 a are usually fed from the upper surface side to the transport roller pair 23 by the pickup roller 22. The plurality of originals sent to the conveyance roller pair 23 are separated by the separation roller 23 b and only the uppermost one is separated and conveyed toward the registration roller pair 24. After the leading edge of the original is detected by the paper feed sensor S2, it is transported by a predetermined distance, and then the drive roller 23a of the transport roller pair 23 and the pick-up roller 22 are stopped from rotating due to the operation of the paper feed driving means being stopped. Ends. The document is stopped with its leading end pressed against the nip portion of the registration roller pair 24 and with its deflection formed.
[0020]
Secondary feeding is started after a lapse of a predetermined time from the end of primary feeding. That is, the registration roller pair 24 is rotationally driven by the operation of the secondary paper feed driving means (not shown). The original is conveyed toward the image reading position R and the discharge roller pair 25 by the registration roller pair 24, and is finally discharged onto the original discharge tray 14 c by the discharge roller pair 25. Completion of image reading of one original is detected by detecting the passage of the rear end of the original by a paper discharge sensor S3 provided on the downstream side of the discharge roller pair. The paper discharge sensor S3 has a counting function that counts the number of documents every time the document feed and conveyance is completed. If the document set detection sensor S1 detects a subsequent document, the second and subsequent documents are conveyed. Continued. When the document passes through the image reading position R, the white reference plate 26 and the document pressing portion 26a are transported while being lightly pressed on the surface of the document placing plate 21, and the document image surface is opposed to the document placing plate. Optical scanning is performed by the lamp 27.
[0021]
Next, the exposure unit 15 will be described. In FIG. 2, an exposure lamp 27, a reflection plate 28, a first mirror 29, a second mirror 30, a third mirror 31, a condenser lens 32, and an image sensor such as a line CCD 33 are provided. The exposure lamp 27 and the first mirror 29 are mounted on a first carriage (not shown), and the second mirror 30 and the third mirror 31 are mounted on a second carriage (not shown). In the setting for reading a document image by the sheet-through method, the first carriage moves immediately below the image reading position R, and the light irradiation light from the exposure lamp 27 exposes the moving document. Irradiation light reaches the CCD 33 through the first mirror 29, the second mirror 30, the third mirror 31, and the condenser lens 32, and is read out as an electric signal through a photoelectric conversion process. When the original image is read by the original fixing method, the original image placed on the original placement plate 21 is read and scanned by the exposure unit 15 to be reduced and imaged on the CCD 33 and subjected to photoelectric conversion processing. After that, it is read to become an electric signal.
[0022]
With reference to FIG. 2, the structure of the lower housing among the lower housing 11D and the connecting housing 11C forming the main body housing 11 will be described. A sheet cassette 34, an image forming unit 36, and a fixing device 37 are incorporated in the paper feeding unit below the lower housing 11D. The sheet material P accommodated in the sheet cassette 34 is fed out one by one by the feeding roller 34a. An openable and closable manual paper feed tray 35 is provided at the lower left portion of the lower housing 11D, and the sheet material P set in the manual paper feed tray 35 is also fed out one by one by the feeding roller 35a.
[0023]
Next, the image forming unit will be described. In the image forming unit 36, the photosensitive drum 38 is a positively chargeable amorphous silicon photosensitive drum, and rotates at a speed of 200 mm / second in the direction shown in the figure when driven. The surface of the photoconductive drum 38 is uniformly charged to +250 V by corona discharge generated from the main charger 39 to which a high voltage of 5 KV is applied, and then the light potential +10 V and the dark potential +250 V by irradiation of the beam light from the laser scanning unit 40. An electrostatic latent image consisting of these parts is formed. Further, the electrostatic latent image is rotated to the developing position by the rotation of the photosensitive member. The developing sleeve 214 inside the developing device 200 is made of non-magnetic stainless steel SUS304 having a surface roughness Rz of about 3 μm, and has a fixed magnet inside. The developing sleeve 214 is rotatably supported with a gap of 300 μm from the photosensitive drum, and rotates at the speed of 360 mm / second in the same direction as the photosensitive drum when driven. The developing unit 200 is filled with a positively charged magnetic toner having a volume average particle size of 9 μm (median diameter by Coulter counter), and a thin toner layer is formed on the surface of the developing sleeve by a magnetic blade (not shown). A developing bias voltage in which a DC voltage of +100 V and an AC electric field having a frequency of 2 KHZ and a peak-to-peak voltage of 2 KV are superimposed is applied to the developing sleeve 214. The toner transported to the development area flies from the sleeve surface by this development bias and develops the exposed portion of the photoreceptor surface.
[0024]
The sheet fed one by one from the sheet cassette 34 or the manual feed tray 35 and conveyed upward through the conveyance path 3 is registered with the registration roller in synchronization with the toner image on the photosensitive member approaching the roller transfer unit 42. 4, the conveyance timing is adjusted, and the sheet is conveyed between the photosensitive drum 38 and the transfer roller 42. As a result, most of the toner in the toner image is transferred onto the sheet when the leading end of the sheet coincides with the leading end of the toner image section and passes through the roller transfer section. Part of the toner that has not transferred onto the sheet and remains on the surface of the photosensitive drum is removed by a cleaning device 50 provided on the most downstream side. The sheet on which the toner image is transferred is sent to the fixing device 37. The fixing device 37 has a heat roller 38a and a pressure roller 38b, and a toner image is fixed on the paper by these roller pairs to obtain a copy.
[0025]
The sheet that has passed through the fixing nip is conveyed as it is along the vertical conveying path 42 in the vertical direction. When the vertical conveyance path 42 enters the connecting housing 11C and passes through the conveyance roller pair 43, it branches into a horizontal conveyance path 44 in the right direction and a conveyance path 45 obliquely above, and a branch claw that distributes the conveyance direction of the paper at that branch point. 46 is provided. In FIG. 2, the paper is distributed in the traveling direction to the horizontal conveyance path 44 and discharged onto the lower sheet tray 2.
[0026]
Next, the internal structure of the developing device will be described in detail with reference to FIGS. First, in FIG. 5, a two-dot chain line indicates an upper surface of the toner accommodated in the housing 2 including the first conveyance path 20 and the second conveyance path 22. The developing device 200 includes a developing housing 202 that stores a developer. For example, the housing 202 which can be integrally formed from an appropriate synthetic resin such as ABS resin has a bottom wall 204, a front side wall 206 extending upward from a front side edge in the longitudinal direction (left-right direction in FIG. 4) of the bottom wall 204, and a bottom A rear side wall 208 extending upward from the longitudinal rear side edge of the wall 204, and extending upward from a front end in the width direction (vertical direction in FIG. 4) of the bottom wall 204 and connected to the front side wall 206 and the front end of the rear wall 208. A front side wall 210 and a rear side wall 212 extending upward from the rear end in the width direction of the bottom wall 204 and connected to the rear end of the front side wall 206 and the rear wall 208 are included. The front side wall 206 includes a front side wall front portion 206a formed on the front side in the width direction of the housing 202, and a front side wall rear portion 206b formed on the rear side in the width direction of the housing 202, and the front side wall front portion 206a and the front side wall rear portion 206b. Are connected by a connecting wall 206c extending in the longitudinal direction. The front side wall rear portion 206b is formed to be present at a position protruding forward in the longitudinal direction of the housing 202 from the front side wall front portion 206a. Therefore, the longitudinal interval between the rear side wall 206b and the rear side wall 208 is set to be longer than the longitudinal interval between the rear side wall 206a and 206a. In the housing 202, the front in the longitudinal direction is the left in FIG. 4, the rear in the longitudinal direction is the right in FIG. 4, the forward in the width direction is the upper in FIG. 4, and the rear in the width is the lower in FIG. , Each meaning.
[0027]
The opening on the photosensitive drum side of the housing 202 includes a cylindrical sleeve member 214 that extends substantially horizontally in the longitudinal direction, and a magnet member 216 that is fixedly provided in the sleeve member 214. The sleeve member 214 is fixed to a rotating shaft and is driven to rotate counterclockwise in FIG. 5 by a driving means (not shown). The outer peripheral surface of the sleeve member 214 is disposed to face the outer peripheral surface of the photosensitive drum 38 with a gap of 0.3 mm, and the outer peripheral surface of the sleeve member 214 and the photosensitive member that are opposed to each other with the gap therebetween. The development surface is defined in cooperation with the outer peripheral surface of the drum 38. A regulating blade 218 for regulating the toner layer thickness extends in parallel with the outer peripheral surface of the sleeve member 214 with a gap of 0.3 mm between the front side wall front portion 206a and the rear side wall 208 of the housing 202. It is arranged to exist. This regulating blade 218 is a weakly magnetic SUS430 plate having a thickness of 2 mm. The amount of toner held on the outer peripheral surface of the sleeve member 214 and conveyed to the developing region is regulated to a predetermined layer thickness, and the sleeve member 214 is rotated. To charge to a predetermined charge.
[0028]
The magnet member 216 includes a main pole N1 disposed in a developing region closest to the outer peripheral surface of the photosensitive drum 201, a transport pole S1 on the downstream side in the rotation direction of the sleeve member 214 with respect to the main pole N1, and a transport pole S1. A transport pole S2 is provided on the downstream side and in the vicinity of the upstream side of the blade 218 with a gap therebetween. The main pole N1 is a magnetic pole for holding the toner on the outer peripheral surface of the sleeve member 214 and stably performing the jumping development with the toner. The transport pole S1 is a magnetic pole for drawing the developed toner into the developing housing 210 as required. The upstream conveying pole S2 of the blade 218 is a magnetic pole for holding an appropriate amount of toner in the developing housing 210 on the outer peripheral surface of the sleeve member 214.
[0029]
A first conveyance path 220 and a second conveyance path 222 are disposed in the housing 202 in parallel with the developing sleeve 214. In FIG. 4, the toner conveyance direction is defined such that the right side in the first conveyance path 220 is upstream and the left side is downstream, the left side in the second conveyance path 222 is upstream, and the right side is downstream. The first conveyance path 220 extends in parallel and horizontally along the sleeve member 214 between the front side wall front portion 206a and the rear side wall 208 at a substantially lower position of the sleeve member 214 at the rear position in the width direction. It is arranged to exist. The second transport path 222 is disposed so that the rear position in the width direction of the first transport path 220 extends parallel to the first transport path 220 and horizontally. The first conveyance path 220 and the second conveyance path 222 are formed by being partitioned by a partition wall 223. The partition wall 223 is formed integrally with the bottom wall 204 so as to extend upward from the bottom wall 204 and extend in the longitudinal direction at a predetermined height. Communication paths 224 and 225 that connect the first transport path 220 and the second transport path 222 to each other are disposed outside both ends of the partition wall 223 in the longitudinal direction. One communication path 224 is formed between the front end in the longitudinal direction of the partition wall 223 and the front side wall front portion 206a. The other communication path 225 is formed between the rear end in the longitudinal direction of the partition wall 223 and the rear side wall 208. Therefore, the one communication path 224 is arranged to communicate between the downstream end of the first transport path 220 and the upstream end of the second transport path 222, and the other communication path 225 is connected to the second transport path 222. The downstream end and the upstream end of the first conveyance path 220 are arranged to communicate with each other. In the housing 202, a piezoelectric toner sensor S is disposed in a position near the downstream side of the upstream end region of the second conveyance path 222 that faces the one communication path 224.
[0030]
The second transport path 222 is provided with second transport means 240 formed from a rotary shaft 242 and rotary blades 244 provided around the rotary shaft 242. The second conveying means 240 is controlled to rotate clockwise by a driving means (not shown in FIG. 5), and conveys toner from the left upstream side to the right downstream side. A paddle 246 for picking up the toner being conveyed is provided on the rotary blade 244 from the position facing the toner sensor S to the downstream side, and the stirring efficiency of the toner is maintained. A sheet member C for cleaning the surface of the toner sensor S is disposed at the upstream end of the paddle main body 246 of the second agitating and conveying member 240, and the surface of the toner sensor S is constantly cleaned.
[0031]
The first transport path 220 is provided with first transport means 230 formed from a rotary shaft 232 and rotary blades 234 provided around the rotary shaft 232. A paddle 236 for pumping toner is provided on the outer peripheral portion of the rotary blade 234 in parallel with the rotary shaft 232. The first conveying unit 230 is controlled to rotate clockwise by a driving unit (not shown in FIG. 5), and conveys toner from the upstream side on the right side to the downstream side on the left side. It also supplies. The upstream end (left side) of the second transport unit 240 and the downstream end (left side) of the first transport unit 230 correspond to the communication unit 224, and the downstream end (right side) of the second transport unit 240. And the upstream end (right side) of the first conveying means 230 correspond to the communicating portion 224.
[0032]
Further, the housing 202 is provided with a toner replenishing port 226 and a toner supply / conveying path 227 for receiving toner from a toner container (not shown). In the toner replenishing port 226, there is provided an impeller 228 that is rotatably disposed to feed the toner received from the toner container to the upstream end portion of the supply conveyance path 227. The supply conveyance path 227 is located on the upstream side of the second conveyance path 222, and the toner supply conveyance means 250 provided on the inner side of the supply conveyance path 227 shares the rotating shaft 242 with the second conveyance means 240 on the downstream side and around it. Is provided with a rotating blade 249. The toner supply / conveying means 250 is rotated simultaneously with the second conveying means 222 by a driving means (not shown) to convey the replenishment toner scraped from the impeller 228 from the upstream side (left side) to the downstream side (right side). Thus, the toner is conveyed to the second conveying means 240 side.
[0033]
Next, toner supply and conveyance when image formation is repeated will be described. When the toner sensor S detects toner empty in the second toner conveyance path, toner is supplied from a toner container (not shown) to the toner supply port 226. The replenished toner is scraped into the supply conveyance path 227 by the impeller 228 and is fed out to the second conveyance path 222 by the supply conveyance means 250. Then, it is transported from the left to the right by the second transport means, is fed out to the first transport path 222 through the communication portion 225, and is transported from the left to the right by the first transport means 230, while being padded by the paddle 236. Pumped up to the developing sleeve and used for development. The remaining toner is transported to the left end of the first transport unit 230 and returns to the second transport path through the communication unit 224. As described above, the toner circulates clockwise between the first conveyance path 222 and the second conveyance path through the communication portion, and newly supplies a toner reduction amount detected by the toner sensor from a toner container (not shown).
[0034]
The toner that has passed through the development area is held on the outer peripheral surface of the sleeve member 214 by the S1 pole of the magnet member 216 and drawn into the housing 2, and a part of the toner does not reach the magnetic force between the S1 pole and the S2 pole. In the process of passing through the region, it is peeled off from the outer peripheral surface of the sleeve member 214 by natural fall, and is prepared for replenishment of new toner. As a result, a phenomenon in which old toner is always adhered to the outer peripheral surface of the sleeve member 14 is avoided, and toner deterioration is reliably prevented.
[0035]
Next, the surface roughness of the developing sleeve 214 will be described. This surface roughness almost determines the charging property and uniform thin layer property of the toner sandwiched between the blade and the sleeve as the toner layer regulating member, and the surface roughness can be adjusted by, for example, blasting. . The surface roughness is measured by the ten-point average roughness Rz defined in JIS (Japanese Industrial Standards) B0601 Table 6. The toner charge amount is reduced by suctioning the toner adhering to the surface of the developing sleeve and collected by a filter. The charge amount of the toner is measured by a Q meter, and the ratio to the weight of the sucked toner is measured. Asked.
The effects of applying the metal soap to the specific position of the developing sleeve, which is a feature of the present invention, using the developing device described above will be described using the following examples and comparative examples. Here, in the examples and comparative examples, zinc stearate is used as the metal soap applied to the developing sleeve.
[0036]
Example
With reference to FIG. 6, the positional relationship between the image areas of the developing sleeve and the cutting plate will be schematically described. The developing sleeve 214 has an axial length of 327 mm, and an area having an axial length of 306 mm closer to the center is blasted to Rz = 3 μm. Of these blasting regions, the regions 10 mm inward from both ends are zinc stearate application regions. A seal member 260 having a width of 4 mm for preventing scattering of toner covers the sleeve surface further outside the zinc stearate application region on both ends, so that a thin toner layer is not formed on the sleeve surface. A region having an axial length of 306 mm excluding this portion is a blasting region and a spike formation region where a toner thin layer is formed on the surface of the developing sleeve 214. Then, the paper feeding area of the zinc stearate non-application area B having an axial length of 286 mm and the zinc stearate application area A area of 6 mm on both outer sides thereof are combined to form a maximum paper feeding area of 298 mm width.
Next, a method of applying zinc stearate to the sleeve surface will be described with reference to FIG. A rod-shaped stick 230 having a square shape of 10 mm × 10 mm and a length of 400 mm is held by a vertically movable aluminum holder 231 and perpendicular to a predetermined position on the sleeve surface. In a state where the sleeve 214 stands upright, zinc stearate is uniformly applied to the surface of the sleeve 214 by manually rotating the sleeve 214 once.
[0037]
Further, in the developing housing 202, two toner conveying means 234 and 244 having a spiral structure are provided in parallel with the developing sleeve 214, and two toner conveying units 234 and 244 that are separated from each other are provided outside the two ends. Communication portions 224 and 225 are provided so that the toner can communicate with the sleeve 214 in the vertical direction through the toner conveying means 234 and 244. The left and right communication portions 224 and 225 are formed so as to face the A region on the facing sleeve surface, and the partition wall 223 is formed so as to face the B region on the facing sleeve surface.
[0038]
Comparative example
A developing device 200 was prepared in the same manner as in the example except that zinc stearate was not applied to the surface of the sleeve 214.
[0039]
Using the image forming apparatus of the present embodiment described above, the test environment was set to 20 ° C. and 60%, and 1000 A4 size images were output continuously. The test environment was changed to 10 ° C. and 20%, and after leaving for 8 hours, 100 more images were output. The developing device mounts a newly assembled unused developing device 200 on the copying machine, starts a copy test from the toner container (not shown) through the toner supply port 226, and distributes the toner into the developing device 200. .
The image evaluation is performed on the output image of the 1000th sheet at 60 ° C. at 20 ° C. and the output image of the 100th image after switching to 20% at 10 ° C. The image was a blank sheet with no image in the range of 10 mm on each end. The toner charge amount on the surface of the developing sleeve at a position corresponding to the background fogging of 6 mm inward from both ends of the A4 size width as both ends of the image area was measured. Further, the toner charge amount on the surface of the developing sleeve at the position corresponding to the background fogging at the central portion of the A4 size width as the central portion of the image area was measured. As the evaluation criteria, when the fog density is less than 0.010, ○ and 0.010 or more are indicated as x, and ○ is determined to be acceptable with respect to the use criteria.
[0040]
In Example 1, the fog density at both ends of the image area at the end of the test was 0.003 at 20 ° C. and 60%, and the charge amount of the toner on the sleeve surface at the corresponding location was +9.5 μc / g. Although the fog density after the change to 10 ° C. and 20% rose to 0.005, it remained below 0.010. Further, toner aggregation on the back side of the blade was not observed.
Next, the fog density at the center of the image area was 0.002 at 60 ° C. at 20 ° C., and the charge amount of the toner on the sleeve surface at the corresponding position was +9.1 μc / g. The fog density after the change to 10 ° C. and 20% rose to 0.003, but was kept below 0.010. Further, toner aggregation on the back side of the blade was not observed. Further, the temperature was returned again to 20 ° C. and 60%, and 500,000 sheets of images were continuously output without newly applying zinc stearate. However, the background fogging was 0 in both the image area both ends and the image area center. It did not exceed 0.008 and passed the usage standards.
[0041]
Next, in the comparative example, the fog density at both ends of the image area at the end of the test is 0.011 at 60 ° C., and the charge amount of the sleeve surface toner at the corresponding location is +14.6 μc / g. The usage standard of less than 0.010 could not be satisfied. The fog density after the change to 10 ° C. and 20% further increased to 0.016. Further, toner aggregation on the back side of the blade was considerably observed.
Next, the fog density at the center of the image area was 0.006 at 60 ° C. at 20 ° C., and the charge amount of the sleeve surface toner at the corresponding position was +10.5 μc / g. Although the fog density after the change to 10 ° C. and 20% rose to 0.008, the usage standard of less than 0.010 was maintained. Further, toner aggregation on the back side of the blade was slightly observed.
As described above, it has been found that in the comparative example, the use standard is not satisfied because of fogging at both ends of the image area.
[0042]
In the present embodiment, the gap between the photosensitive drum 38 and the developing sleeve 214 is defined to be 0.3 mm, but is not limited thereto, and a range of 0.15 to 1.0 mm mm is preferably used. In addition, the clearance dimension between the magnetic blade 218 and the developing sleeve 214 is regulated to 0.3 mm, but not limited thereto, the range of 0.1 to 0.9 mm is preferably used.
[0043]
In the present embodiment, the stainless steel SUS430 plate is used as the layer thickness regulating plate, but the present invention is not limited to this, and various magnetic metal plates can be used.
[0044]
In this embodiment, the zinc stearate application area on both ends of the developing sleeve surface corresponding to the maximum sheet passing width is 6 mm, but the present invention is not limited to this, and can be set as appropriate. In addition, although zinc stearate was used as the metal soap to be applied, the present invention is not limited to this. is there. The shape used is a stick-like shape in this embodiment, but the shape is not limited to this, and a powder-like shape can also be used.
[0045]
【The invention's effect】
In an unused developing device that performs image output for the first time, toner that passes through the gap between the blade and the sleeve surface by applying metal soap such as zinc stearate to the developing sleeve surface corresponding to both ends of the image area where the toner consumption is low Therefore, the toner charge amount is prevented from aggregating and the toner charge amount is prevented from excessively rising. As a result, even at both end portions of the development region, the toner thin layer portion is prevented from being thickened due to the high suction force between the sleeve and the toner, so that the initial fog immediately after the start of use can be prevented. In the present invention, by applying metal soap to both ends of a new developing sleeve that is not used, the initial fog is prevented and the fog prevention effect is exhibited over a long period of time.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an external configuration of a copying machine 100 according to an embodiment of the present invention.
FIG. 2 is a front view showing the internal configuration of the copying machine 100 according to the embodiment of the present invention.
FIG. 3 is a schematic diagram showing an open / close state of a document conveying section as viewed from the right side surface of the copier 100 according to the embodiment of the present invention.
FIG. 4 is a plan view showing an internal configuration of a developing device 200 according to the present invention.
FIG. 5 is a cross-sectional view showing an internal configuration of the developing device 200 according to the present invention. 2 is a plan view of the developing device 200 in the same manner. FIG.
FIG. 6 schematically shows the positional relationship between a developing sleeve and a sheet passing area according to the present invention.
FIG. 7 is a schematic drawing of the application of zinc stearate to the sleeve surface.
[Explanation of symbols]
1 Upper sheet tray
2 Lower sheet tray
6a Spring member
6b Document holding member
9 Hinge part
11 Body housing
11U upper housing
11C Connecting housing
11D Lower housing
12 Sheet material stack space
13 Scanning panel
14 Document transport section
14a Document feed tray
14b Document transport unit body
14c Document output tray
14d Document cover
21 Document platen
22 Pickup roller
23 Conveying roller pair
23a Driving roller
23b Separation roller
24 Registration roller pair
25 discharge roller pair
26 White reference plate
26a Document pressing part
R Document reading position
S1 Document detection sensor
S2 Paper feed sensor
S3 Discharge sensor
27 Exposure lamp
28 Reflector
29 First mirror
30 Second mirror
31 Third mirror
32 condenser lens
33 CCD
34 Sheet cassette
34a Feeding roller
36 Image forming unit
37 Fixing device
37a Heat roller
38b Pressure roller
38 Photosensitive drum
39 Main charger
40 Laser scanning unit
42 Vertical transport path
43 Conveying roller pair
44 Horizontal transport path
45 Transport path
46 branch nails
50 Cleaning device
51 housing
51a Side plate
51b Upper plate
51c side plate
52 Cleaning roller
53 Spiral
53a Rotation area outer periphery
54 Cleaning blade
55 Toner moving space
56 Bulkhead
57 Scraper
58 Seal blade
60 Mounting stay
200 Developer
202 Development housing
204 Bottom wall
206 Front side wall
206a Front side wall front
206b front side wall rear
206c connecting wall
208 Rear side wall
210 Front side wall
212 Rear side wall
214 Sleeve member
216 Magnet member
218 Regulating blade
220 First transport path
222 Second transport path
223 Bulkhead
224 communication path
225 communication path

Claims (4)

A developing roller comprising a housing for storing magnetic toner, a developing sleeve that is rotatably held, and a plurality of magnetic poles fixedly disposed therein, and an end portion close to the developing sleeve that is provided in the axial direction of the developing sleeve is developed. A developing device having a toner layer thickness regulating plate attached to a surface of the developing sleeve with a predetermined gap while facing a magnetic pole at a predetermined position inside the sleeve;
Inside the developing housing, a plurality of toner conveying means whose toner conveying directions are opposite to each other extend in parallel with the developing sleeve, and a partition wall is formed between the plurality of toner conveying means except for communicating portions at both ends. Provided,
A developing device characterized in that a metallic soap for suppressing excessive frictional charging of the magnetic toner and the developing sleeve is applied to the sleeve surface facing the communicating portion . The developing device according to claim 1 , wherein the metal soap is zinc stearate.   The developing device according to claim 1, wherein a surface of the developing sleeve is covered with a seal member for preventing toner scattering on the outer side in the axial direction from the metal soap application area of the developing sleeve. An image forming apparatus using the developing device according to claim 1.

Images