JP4816168B2 - Development device - Google Patents

Description

  The present invention relates to a developing device used in an electrophotographic image forming apparatus. More specifically, the present invention relates to a developing device that suppresses toner leakage from the end of the developing roller by a seal member and maintains the quality of the seal member for a long period of time.

  2. Description of the Related Art Conventionally, as a developing device used in an electrophotographic image forming apparatus, a developing method for supplying non-magnetic one-component toner has been adopted. In general, a developing device of this type is opposed to an image carrier (for example, a photoconductive drum), a developing roller to which a predetermined developing bias is applied, a pressure contact with the developing roller, and a developing container toward the developing roller. A toner supply roller that supplies the toner inside, and a regulating roller that contacts the surface of the developing roller and regulates the amount of toner adhering to the developing roller.

Further, in order to prevent toner leakage from the end portion of the developing roller, a seal member is disposed in sliding contact with the end portion of the developing roller. As a material of the seal member, a resin material such as PTFE (polytetrafluoroethylene) is generally used. As this type of developing device, for example, there are developing devices disclosed in Patent Literature 1 and Patent Literature 2.
JP 2003-280372 A JP 2004-38076 A

  However, the conventional developing device described above has the following problems. That is, a part of the toner on the developing roller is blocked by the regulating roller and spreads toward the end portion in the axial direction. Further, a part of the toner moved to the end portion enters between the developing roller and the seal member. Then, the seal member is worn by the toner that has entered between the developing roller and the seal member. Therefore, the quality of the seal member cannot be maintained for a long time.

  The present invention has been made to solve the problems of the conventional developing device described above. That is, an object of the present invention is to provide a developing device that suppresses toner leakage from the end portion of the developing roller by the seal member and maintains the quality of the seal member over a long period of time.

A developing device for solving this problem has a developing roller that carries toner and conveys the toner toward an image carrier, and contacts the developing roller, and rotates in a counter direction with respect to the developing roller. and, a developing device having a regulating roller for regulating the thickness of the toner layer on the developing roller, and a sealing member in sliding contact with the end regions of the developing roller, the longitudinal direction of the region of the regulating roller, the developing roller A first region in contact with the image region, and a second region located at an end in the longitudinal direction and adjacent to the first region and including a portion facing the sliding contact region with the seal member of the developing roller. The surface roughness Ra of the two regions is larger than the surface roughness Ra of the first region.

  The developing device of the present invention is characterized by a regulating roller that is in pressure contact with the developing roller. In other words, the regulating roller of the developing device of the present invention has a surface roughness Ra of the first area where the surface roughness Ra of the second area facing the developing roller and the seal member is in contact with the image area of the developing roller in the longitudinal area. Greater than Ra. Since the surface roughness Ra of the second region is large, the toner is scraped off by the regulating roller when moving from the central portion to the end portion in the longitudinal direction. For this reason, toner that moves from the central portion to the end in the longitudinal direction, that is, toner that moves from the image region to the non-image region is reduced. Therefore, the toner that enters between the developing roller and the seal member is reduced, and the wear of the seal member is suppressed.

  Further, the regulating roller of the developing device of the present invention has a cored bar part and an elastic part that covers the cored bar part and contacts the developing roller, and the electric roller between the surface of the cored bar and the surface of the elastic part. The resistance is better if the second region is larger than the first region. Usually, a bias that presses the toner toward the developing roller is applied to the regulating roller. Therefore, the greater the electrical resistance, the weaker the pressing force against the developing roller. Therefore, the toner that enters between the developing roller and the seal member is reduced, and the wear of the seal member is suppressed.

Further, the regulating roller of the developing device of the present invention rotates in the counter direction with respect to the developing roller . The toner releasability is improved by rotating the regulating roller counter. Therefore, the infiltration of toner between the developing roller and the seal member is avoided, and wear of the seal member is suppressed.

  The longitudinal position of the boundary between the first area and the second area is preferably between the image area of the developing roller and the sliding contact area of the developing roller with the seal member. In other words, if there is a region where the toner transport amount is different within the image region of the developing roller, image unevenness due to the difference in the transport amount occurs. Further, if there is an area having the same conveyance amount as the image area in the sliding contact area with the seal member, toner conveyance to the seal member is not suppressed. Therefore, the boundary between the first area and the second area is preferably within the above range.

  According to the present invention, the movement of the toner toward the seal member is suppressed by defining the characteristics of the regulating roller. Therefore, a developing device that suppresses toner leakage from the end portion of the developing roller by the seal member and maintains the quality of the seal member over a long period of time has been realized.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings. In the present embodiment, the present invention is applied to an electrophotographic color printer having a developing device for storing and supplying non-magnetic one-component toner.

  As shown in FIG. 1, the image forming apparatus 100 according to this embodiment includes a photosensitive drum 11 that is an image carrier, and uniformly charges the surface of the photosensitive drum 11 around the photosensitive drum 11. A charging device 12, an exposure device 13 for forming an electrostatic latent image on the surface of the photosensitive drum 11, and an electrostatic latent image on the photosensitive drum 11 for making a visible image (toner image). The developing device 14, a transfer device 15 for transferring the toner image on the photosensitive drum 11 to a sheet, and a cleaning blade 16 for removing residual toner on the photosensitive drum 11 are rotated in the rotational direction of the photosensitive drum 11. In line with. Further, a timing roller 17 for adjusting the timing of conveying the sheet to the transfer position and a fixing device 18 for fixing the transferred toner image on the sheet are provided in the sheet conveying path. In this embodiment, the charging device 12, the transfer device 15, and the fixing device 18 are all roller-shaped.

  Next, an image forming operation by the image forming apparatus 100 will be briefly described. The image forming apparatus 100 starts operation by receiving a start signal, image data, and the like. The photosensitive drum 11 is rotationally driven in the direction of the arrow in FIG. Then, it is uniformly charged by the charging roller at a position facing the charging device 12. Next, exposure is performed by the exposure device 13, and an electrostatic latent image based on the image data is formed on the surface.

  Next, when the electrostatic latent image reaches the position of the developing device 14, the toner charged by the electric field formed between the developing bias voltage applied to the developing roller and the electrostatic latent image on the photosensitive drum 11 moves. Then, the electrostatic latent image is developed with toner.

  On the other hand, the paper transported through the paper transport path is timed by the timing roller 17 to the front end position of the image and transported between the photosensitive drum 11 and the transfer device 15. Then, the toner image on the photosensitive drum 11 is transferred to a sheet by the transfer device 15. Further, the sheet holding the transferred toner image is further conveyed, and heat and pressure are applied by the fixing device 18 to fix the toner image on the sheet. Further, the transfer residual toner which is not transferred onto the sheet by the transfer device 15 and remains on the photosensitive drum 11 is scraped off by the cleaning blade 16. Thereby, the image formation for one sheet is completed.

  Next, the developing device 14 will be described in detail. As shown in FIG. 2, the developing device 14 includes a developing container 1 that contains non-magnetic toner that is a one-component developer, and a developing roller 2 that carries the toner and conveys the toner toward the photosensitive drum 11. A toner supply roller 3 for supplying toner to the developing roller 2 and scraping off the toner on the developing roller 2; a regulating roller 4 for regulating the thickness of the toner on the developing roller 2 and charging the toner; And a toner neutralizing member 5 that neutralizes the remaining residual toner.

  Each member is connected to a power source. For example, a bias for moving the toner from the toner supply roller 3 toward the development roller 2 is applied between the developing roller 2 and the toner supply roller 3. Further, a bias that charges the toner on the developing roller 2 (presses the toner against the developing roller 2 side) is applied between the developing roller 2 and the regulating roller 4.

  The developing roller 2 is accommodated in the developing container 1, and a part of the developing roller 2 is exposed from the developing container 1 through the opening of the developing container 1. Further, the developing roller 2 is disposed to face the photosensitive drum 11 by rollers provided at both ends. The developing roller 2 is urged toward the photosensitive drum 11 because the toner supply roller 3 is in strong contact. For this reason, the developing roller 2 is disposed along the longitudinal direction of the photosensitive drum 11 so as to face each other with a slight gap.

  The toner supply roller 3 is accommodated in the developing container 1 and is in strong contact with the developing roller 2. The toner supply roller 3 is rotationally driven in the counter direction with respect to the developing roller 2.

  The regulating roller 4 is accommodated in the developing container 1 and is in contact with the developing roller 2 with a predetermined linear pressure. The regulation roller 4 is provided so as to be rotatable in the counter direction with respect to the developing roller 2. Further, as shown in FIG. 3, the regulating roller 4 includes a cored bar 41, a foamed elastic layer 42 made of a foamed member, which is positioned around the cored bar 41, and a non-foamed elastic layer covering the foamed elastic layer 42. Layer 43. Detailed contents of the regulating roller 4 will be described later.

  Further, as shown in FIG. 4, seal members 21 for closing gaps generated at the ends of the developing roller 2 are wound around both ends in the longitudinal direction of the developing roller 2 so as to be in sliding contact with the surface of the developing roller 2. It is disguised. The seal member 21 prevents the toner in the developing container 1 from leaking outside. As a material of the seal member 21, for example, PTFE is applicable. The developing roller 2 is divided into an image forming area 2A and a non-image area 2B in the longitudinal direction. Further, the seal member 21 is in sliding contact with the non-image area 2B. Hereinafter, the area in sliding contact with the seal member 21 in the non-image area 2B is referred to as “sliding area 2C”.

  In the developing device 14, the toner in the developing container 1 is transferred from the toner supply roller 3 to the development roller 2 by the potential difference between the toner supply roller 3 and the development roller 2 and the mechanical conveyance force of the toner supply roller 3 whose surface is foam. Transport. The toner supplied to the developing roller 2 is thinned while being frictionally charged by the regulating roller 4 as the developing roller 2 rotates, and the electrostatic latent image is visualized at a portion facing the photosensitive drum 11. Further, the toner remaining on the developing roller 2 after development is neutralized by the toner neutralizing member 5 and separated from the developing roller 2 by the toner supply roller 3.

[Evaluation of Embodiment]
Then, the evaluation result of the regulation roller concerning embodiment is demonstrated. In this evaluation, the same conditions as the “magicolor 2300DL” manufactured by Konica Minolta Co., Ltd. were reproduced with an external drive, and the evaluation was performed by changing the characteristics of the regulating roller. The main configuration of the developing device used in the evaluation machine is the same as that of the developing device 14 described above. The toner used was "magicolor 2300DL" toner.

  Specifically, in this evaluation machine, SUS having a diameter of 5 mm is used for the cored bar 41 of the regulating roller 4. In addition, as the metal core 41, any metal that has been subjected to rust prevention treatment is applicable. Further, the foamed elastic layer 42 of the regulating roller 4 is made of conductive foamed urethane having a diameter of 12 mm. The foamed elastic layer 42 may be an elastic member, and for example, foamed silicon is applicable. The regulation bias for the developing roller 2 was AC-100V (duty 35%).

  Further, in this evaluation, the longitudinal region of the regulating roller 4 is divided into a main region 4A located at the center in the longitudinal direction and end regions 4B located at both ends in the longitudinal direction as shown in FIG. The endurance of the seal member when using each regulating roller was evaluated by changing the characteristics (resistance, surface roughness) of the end region 4B. In addition, in this evaluation, durability of the seal member when the linear pressure between the developing roller 2 and the regulating roller 4 and the rotation direction of the regulating roller 4 were changed was evaluated.

The main area 4A is an area in contact with the image area 2A of the developing roller 2, and is wider than the image area 2A of the developing roller 2. The non-foamed elastic layer 43 on the surface of the main region 4A is a non-foamed polyamide having a thickness of 100 μm. The resistance of the main region 4A is 10 ⁶ [Ω]. Further, the surface roughness Ra of the main region 4A is 0.1 μm.

  The “resistance” in this evaluation is the electrical resistance (Ω) between the surface of the cored bar 41 of the regulating roller 4 and the surface of the non-foamed elastic layer 43 of the regulating roller 4. In other words, the electrical resistance of the elastic layer is a combination of the non-foamed elastic layer 43 and the foamed elastic layer 42. Specifically, the resistance of the roller is that the roller is placed on a copper plate that also serves as an electrode, a load of 500 g is applied to both ends of the core metal, and a direct current of 100 V is applied between the core metal and the copper plate. Is a value obtained based on the measured current value. Further, in this evaluation, the contact portion with the copper plate was rotated about 90 degrees four times, the resistance was obtained each time, and the average value thereof was defined as the resistance. The primer that connects the non-foamed elastic layer 43 and the foamed elastic layer 42 uses “hot melt” manufactured by Cemedine. Further, the “surface roughness” is the roughness Ra (μm) of the surface of the non-foamed elastic portion 43.

  The end region 4B is a region facing the sliding contact region 2C of the developing roller 2 with the seal member 21 interposed therebetween, and is wider than the sliding contact region 2C of the developing roller 2. Specifically, in this evaluation machine, the total length in the longitudinal direction of the regulating roller is 239 mm, and the width of each end region 4B is 10 mm. Further, the width of each non-image area 2B is 18.5 mm, and the width of the sliding contact area 2C (that is, the width of the seal member 21) is 7.0 mm.

In this evaluation, the amount of wear of the seal member after driving equivalent to 10K, 30K, and 60K sheets of A4 continuous white paper was measured. The “wear amount” in this evaluation is a value obtained by measuring the thickness of the seal member 44 after durability with a micrometer and subtracting the measured value from the initial value (130 μm). If the wear amount is 30 μm or less, (◯), if it is in the range of 30 μm to 50 μm, (□), if it is in the range of 50 μm to 70 μm, (Δ), if it is 70 μm or more, (×). did. The measurement results are shown in Table 1.

  As a result of this evaluation, when a blade was used as a restricting member (Example 1), the amount of wear was large, and it was difficult to maintain quality in printing on 60K sheets or more. In addition, when the resistance and surface roughness of the end region 4B are the same as those of the main region 4A (Example 2 and Example 3), the wear amount is large and it is difficult to maintain the quality in printing of 60K sheets or more. there were. This is the same result (Example 2 and Example 3) even when the linear pressure between the regulating roller 4 and the developing roller 2 is changed.

  On the other hand, when the surface roughness Ra of the end region 4B was increased (Example 4), wear was slightly suppressed. That is, the toner is scraped off by the end region 4B of the regulating roller 4 by roughening the surface of the end region 4B. For this reason, it is difficult for the toner to move in a portion in contact with the end region 4B. Therefore, the amount of toner transported to the sliding contact area 2C is reduced. As a result, the amount of toner reaching the seal member 21 is reduced and wear is suppressed.

  In addition, when the resistance of the end region 4B was increased (Example 5), the wear was slightly suppressed. That is, by making it difficult for the current to flow in the end region 4B, the force for pressing the toner toward the developing roller 2 is weakened. As a result, the amount of toner that enters between the developing roller 2 and the seal member 21 is reduced, and wear is suppressed. As a method for increasing the resistance, a resin was applied to the non-foamed elastic layer 43 in this evaluation.

  Further, when the resistance of the end region 4B was increased and the regulating roller 4 was further counter-rotated (Example 6), almost no wear occurred. That is, toner releasability is improved by rotating the regulating roller 4 counter. Thereby, the infiltration of toner between the developing roller 2 and the seal member 21 is avoided, and wear is further suppressed. The peripheral speed ratio with respect to the developing roller 2 during counter rotation was set to 1.

  In addition, when the improvement conditions so far were combined (Example 7), almost no wear occurred. That is, the surface roughness Ra of the end region 4B is increased, the resistance of the end region 4B is increased, and the regulating roller 4 is rotated counter-rotatingly with respect to the developing roller 2. Thereby, abrasion of the seal member 21 can be suppressed more reliably. This was the same result (Example 8) even when the linear pressure between the regulating roller 4 and the developing roller 2 was changed.

  The boundary between the main region 4A and the end region 4B of the regulating roller 4 is located between the end of the image region 2A of the developing roller 2 and the end of the sliding contact region 2C as shown in FIG. To do. That is, when the end region 4B having a different toner conveyance amount is in contact with the image region 2A, image unevenness due to the difference in the conveyance amount occurs. Further, when the sliding contact area 2C faces the main area 4A, the conveyance of the toner to the seal member 21 is not suppressed. Further, the seal member 21 is not evenly worn. Accordingly, the seal member 21 is distorted and refracted, and the quality cannot be maintained.

  As described above in detail, from the evaluation result of the developing device according to the present embodiment, when the regulating roller 4 satisfies at least one of the following three conditions, wear of the seal member 21 wound around the developing roller 2 is suppressed. I found out that

  The first condition is related to the surface roughness Ra of the end region 4B of the regulating roller 4. That is, the regulation roller 4 has a surface roughness Ra of the end region 4B larger than a surface roughness Ra of the main region 4A in the longitudinal direction region. In the end region 4B, since the surface roughness Ra is large, the toner on the developing roller 2 can be scraped off, and the toner moving from the center in the longitudinal direction to the end, that is, from the image region 2A of the developing roller 2 The toner traveling toward the sliding contact area 2C is reduced. Therefore, toner that enters between the developing roller 2 and the seal member 21 is reduced, and wear of the seal member 21 is suppressed.

  The second condition is related to the resistance of the end region 4B of the regulating roller 4. That is, the restriction roller 4 has a resistance in the end region 4B larger than a resistance in the main region 4A in the longitudinal direction region. For this reason, in the end region 4B, the force for pressing the toner toward the developing roller 2 is weak. Therefore, toner that enters between the developing roller 2 and the seal member 21 is reduced, and wear of the seal member 21 is suppressed.

  The third condition is related to the rotation direction of the regulating roller 4. That is, the regulating roller 4 is rotated in the counter direction with respect to the developing roller 2. The toner releasability is improved by rotating the regulating roller 4 counter. Therefore, the intrusion of toner between the developing roller 2 and the seal member 21 is avoided, and wear of the seal member 21 is further suppressed.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the present invention can be applied to various image forming apparatuses such as a color printer, a monochrome printer, a copier, and a facsimile.

  Further, although a roller-shaped photosensitive drum is used as the image carrier, a belt-shaped photosensitive belt may be used. In addition to the roller charging method, the charging device may use a corona discharge charging charger, blade, brush, or the like. The exposure apparatus may be a laser or LED. The transfer device may use a transfer charger in addition to the transfer roller. Alternatively, in addition to a method of directly transferring a toner image from a photosensitive member to a sheet, a method of providing an intermediate transfer member and performing transfer in two or more stages may be used. In addition to the fixing roller, the fixing device may use a fixing belt or a non-contact type.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment. 1 is a diagram illustrating a schematic configuration of a developing device according to an embodiment. It is sectional drawing which shows schematic structure of the control roller concerning embodiment. It is a figure which shows arrangement | positioning of a control roller and a developing roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing container 2 Developing roller 2A Image area 2B Non-image area 2C Sliding contact area 21 Seal member 3 Toner supply roller 4 Regulating roller 4A Main area (first area)
4B end region (second region)
41 Core metal (core metal part)
42 Foam elastic layer (elastic part)
43 Non-foamed elastic layer (elastic part)
11 Photosensitive drum 14 Developing device 100 Image forming apparatus

Claims (4)

A developing roller that carries toner and conveys the toner toward the image carrier, and abuts against the developing roller, rotates in a counter direction with respect to the developing roller, and reduces the thickness of the toner layer on the developing roller. In a developing device having a regulating roller for regulating and a seal member that is in sliding contact with an end region of the developing roller,
The longitudinal region of the regulating roller is:
A first area in contact with the image area of the developing roller;
A second region including a portion located at an end portion in the longitudinal direction and adjacent to the first region and facing a sliding contact region of the developing roller with the seal member;
The developing device according to claim 1, wherein the surface roughness Ra of the second region is larger than the surface roughness Ra of the first region. The developing device according to claim 1,
The regulation roller is
A metal core part, and an elastic part that covers the metal core part and contacts the developing roller;
The developing device according to claim 1, wherein an electric resistance between the surface of the core metal and the surface of the elastic portion is larger in the second region than in the first region. A developing roller that carries toner and conveys the toner toward the image carrier, and abuts against the developing roller, rotates in a counter direction with respect to the developing roller, and reduces the thickness of the toner layer on the developing roller. In a developing device having a regulating roller for regulating and a seal member that is in sliding contact with an end region of the developing roller,
The regulation roller is
A metal core part, and an elastic part that covers the metal core part and contacts the developing roller;
The longitudinal region of the regulating roller is:
A first area in contact with the image area of the developing roller;
A second region including a portion located at an end portion in the longitudinal direction and adjacent to the first region and facing a sliding contact region of the developing roller with the seal member;
The developing device according to claim 1, wherein an electric resistance between the surface of the core metal and the surface of the elastic portion is larger in the second region than in the first region. In the developing device according to any one of claims 1 to 3 ,
The longitudinal position of the boundary between the first area and the second area is between the image area of the developing roller and the sliding contact area of the developing roller with the seal member. apparatus.

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