JP2006084649A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of holding lubricant for a long period of time without excessively feeding the lubricant and without uselessly consuming the application quantity of the lubricant and capable of preventing the occurrence of image troubles such as defective cleaning and the occurrence of voids in transfer. <P>SOLUTION: The image forming apparatus comprises a photoreceptor, a developing device for supplying a developer to the photoreceptor, lubricant, and a brush roller for applying the lubricant to the photoreceptor. When a range obtained by expanding a theoretical image forming range to the vicinities of the front end and rear end of the theoretical image forming range in the sub-scanning direction of the photoreceptor is defined as an image range and an area between the image range and a succeeding image range is defined as a non-image range, an application condition for applying the lubricant to the photoreceptor in the non-image range is changed from an application condition for applying the lubricant to the photoreceptor in the image range. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus in which a lubricant is efficiently applied to a photoreceptor so as to eliminate poor cleaning and transfer loss.

  As a means for supplying the lubricant to the photoconductor, a system is generally used in which the lubricant is pressed against the brush roller, and the lubricant component is scraped off with brush fibers and applied to the photoconductor. In this method, the lubricant applying means is used. As a condition of the above, a condition in which an image defect does not occur is always set. That is, the condition is a condition that does not cause a cleaning failure or a transfer omission.

In an image forming apparatus having a contact type one-component developer as shown in Patent Document 1, at least a lubricant is used to prevent the occurrence of vertical streaks due to a large amount of lubricant applied after the process unit is replaced. When the supply means is newly replaced, control is performed to regulate the amount of lubricant supplied to the photosensitive member during preliminary rotation operation at the start of each image formation for a fixed number of outputs. The regulation of the lubricant supply amount is performed, for example, with the number of rotations of the brush roller being smaller than the normal value.However, especially when the process unit is new, the amount of lubricant supply becomes excessive, causing problems. In order to generate | occur | produce, supply of an initial stage lubricant is suppressed.
JP 2001-331063 A

  As described above, conventionally, when the process unit is new, the supply amount of the lubricant becomes excessive and a problem occurs. Therefore, as a means for suppressing the supply of the initial lubricant, the wasted time and waste of the preliminary rotation of the photosensitive member are avoided. However, in the present invention, the supply amount of the lubricant is not excessive, and the lubricant application amount is not wasted and the lubricant is long. It is an object of the present invention to provide an image forming apparatus that can maintain the life and does not cause image defects such as poor cleaning and occurrence of transfer omission.

  This object is achieved by any one of the following technical means (1) to (4).

  (1) In an image forming apparatus having a photoconductor, a developing device for supplying a developer to the photoconductor, a lubricant, and a brush roller for applying the lubricant to the photoconductor, sub-scanning of the photoconductor The lubricant in the non-image range when a range in which the theoretical image formation range in the direction is expanded to the vicinity of the front end and the rear end is defined as an image range, and a region between the image range and the next image range is defined as a non-image range. The image forming apparatus is characterized in that a coating condition for coating the photosensitive member is changed with respect to a coating condition for coating the lubricant in the image range on the photosensitive member.

  (2) The image forming apparatus according to (1), wherein the application condition for applying the lubricant to the photoconductor is the number of rotations of the brush roller.

  (3) Item (1) or (2), wherein the number of rotations of the developing sleeve of the developing device in the non-image range is also changed with respect to the number of rotations of the developing sleeve of the developing device in the image range. The image forming apparatus described in the item.

  (4) The image forming apparatus according to (3), wherein the change in the rotation speed of the phenomenon sleeve of the developing device in the non-image range is set to zero.

  According to the first aspect of the present invention, the life of the used lubricant (solid lubricant) is confirmed to last 30% or more, and image formation that does not cause image defects such as defective cleaning and occurrence of transfer loss A device is obtained. According to the second aspect of the present invention, the surface energy of the photosensitive member is lowered, the releasability is improved, and good transfer can be maintained. According to the third or fourth aspect of the present invention, the low surface energy of the photoreceptor surface can be maintained constantly, and the consumption of the lubricant can be suppressed to a particularly low level.

  Embodiments of the present invention will be described below. The description in this column does not limit the technical scope of the claims or the meaning of terms. In addition, the following assertive description in the embodiment of the present invention shows the best mode, and does not limit the meaning or technical scope of the terms of the present invention.

  FIG. 1 is a schematic configuration diagram showing a color image forming apparatus as an embodiment of the image forming apparatus of the present invention.

  The image forming apparatus 100 is called a tandem full-color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K and an endless belt-shaped intermediate transfer body unit 7 as an intermediate transfer body unit. And a sheet feeding / conveying means 21 and a fixing device 24. A document image reading device SC is disposed on the upper part of the main body A of the image forming apparatus.

  The image forming unit 10Y that forms a yellow image includes a drum-shaped photoconductor 1Y, a charging device 2Y disposed around the photoconductor 1Y, an image exposure unit 3Y, a developing unit 4Y, and a primary transfer unit as a primary transfer unit. It has a roller 5Y and a cleaning means 6Y. The image forming unit 10M that forms a magenta image includes a drum-shaped photoconductor 1M, a charging device 2M disposed around the photoconductor 1M, an image exposure unit 3M, a developing unit 4M, and a primary transfer as a primary transfer unit. It has a roller 5M and a cleaning means 6M. The image forming unit 10C for forming a cyan image includes a drum-shaped photoreceptor 1C, a charging device 2C disposed around the photoreceptor 1C, an image exposure unit 3C, a developing unit 4C, and a primary transfer unit as a primary transfer unit. It has a roller 5C and a cleaning means 6C. The image forming unit 10K that forms a black image includes a drum-shaped photoconductor 1K, a charging device 2K disposed around the photoconductor 1K, an image exposure unit 3K, a developing device 4K, and a primary transfer roller 5K as a primary transfer unit. And a cleaning means 6K.

  An endless belt-like intermediate transfer body unit 7 as an intermediate transfer body unit is wound around a plurality of rollers and is rotatably supported, and is an endless belt-like intermediate transfer body 70 as a semiconductive endless belt-like intermediate transfer body. Have

  The images of the respective colors formed by the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred and synthesized on the rotating endless belt-shaped intermediate transfer body 70 by the primary transfer rollers 5Y, 5M, 5C, and 5K. A color image is formed. A transfer material P such as a sheet as a recording medium accommodated in the sheet feeding cassette 20 is fed by a sheet feeding means 21, passes through a plurality of intermediate rollers 22 A, 22 B, 22 C, 22 D, and a registration roller 23, and is subjected to secondary transfer. The image is conveyed to a secondary transfer roller 5A as a means, and the color image is collectively transferred onto the transfer material P. The transfer material P onto which the color image has been transferred is fixed by the fixing device 24, is sandwiched between the paper discharge rollers 25, and is placed on a paper discharge tray 26 outside the apparatus.

  On the other hand, after the color image is transferred to the transfer material P by the secondary transfer roller 5A as the secondary transfer means, the residual toner is removed by the cleaning means 6A from the endless belt-shaped intermediate transfer body 70 from which the transfer material P is separated by curvature. The

  During the image forming process, the primary transfer roller 5K is always in pressure contact with the photoreceptor 1K. The other primary transfer rollers 5Y, 5M, and 5C are pressed against the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer roller 5A comes into pressure contact with the endless belt-shaped intermediate transfer body 70 only when the transfer material P passes through the secondary transfer roller 5A.

  Further, the housing 8 can be pulled out from the apparatus main body A through the support rails 82L and 82R.

  The housing 8 includes image forming units 10Y, 10M, 10C, and 10K and an endless belt-shaped intermediate transfer body unit 7.

  The image forming units 10Y, 10M, 10C, and 10K are arranged in tandem in the vertical direction. An endless belt-shaped intermediate transfer body unit 7 is disposed on the left side of the photoreceptors 1Y, 1M, 1C, and 1K in the figure. The endless belt-shaped intermediate transfer body unit 7 includes an endless belt-shaped intermediate transfer body 70 that can be rotated by winding rollers 71, 72, 73, 74, 76, and 77, primary transfer rollers 5Y, 5M, 5C, and 5K, and cleaning. Means 6A.

  The image forming units 10Y, 10M, 10C, and 10K and the endless belt-shaped intermediate transfer body unit 7 are integrally pulled out from the main body A by the drawer operation of the housing 8.

  In this way, a toner image is formed on the photoreceptors 1Y, 1M, 1C, and 1K by charging, exposure, and development, and the toner images of the respective colors are primarily transferred and superimposed on the endless belt-shaped intermediate transfer body 70, which are collectively collected. Then, the toner image is secondarily transferred to the transfer material P, and fixed and fixed by the fixing device 24 by pressure and heating. The photoreceptors 1Y, 1M, 1C, and 1K after the toner image is transferred to the endless belt-shaped intermediate transfer body 70 are the residual toners remaining on the photoreceptors at the time of transfer by the cleaning units 6Y, 6M, 6C, and 6K. After cleaning, the charging, exposure and development cycle described above is entered, and the next image formation is performed.

The embodiment of the present invention is an OPC having a diameter of 60 mm for each of the photoreceptors 1Y, 1M, 1C, and 1K, a developer is a two-component developer, a process speed is 220 mm / s, and an endless belt shape as an intermediate transfer member. An image forming apparatus employing an intermediate transfer body 70, which is a tandem full-color image forming apparatus 100, whose primary transfer roller is a sponge (registered trademark) roller having a diameter of 20 mm, and its resistance The value is 1 × 10 ⁷ Ω, and constant current control is used for transfer control of primary transfer.

  In the present invention, 5 mm is set as the length that extends in the vicinity of the front end and the rear end in the sub-scanning direction of the theoretical image forming range, and the range including this is set as the image range, and the range is sized with sufficient margin. is there. FIG. 6 is a timing chart showing 5 mm converted into a time expansion range.

  The present invention is an invention characterized in that the lubricant is applied to the photosensitive member so that the lubricant is effectively and efficiently used without causing a void or streak failure. To do.

  The surface energy of the photoreceptor varies depending on the amount of lubricant applied. The surface energy can be easily displayed by the surface tension. As shown in FIG. 8 (a), the surface tension is the magnitude of the contact angle Θ of a water droplet that hangs down on the surface of the photoreceptor on which the lubricant is applied. When the contact angle Θ is large, the surface energy is small and the releasability is improved. Conversely, when the contact angle Θ is small, the surface energy is large and the releasability is high. Deteriorate.

  Further, when transferring between the photosensitive member and the endless belt-shaped intermediate transfer member, the toner image as shown in FIG. 8B is transferred to the photosensitive member and the endless belt-like intermediate transfer member as shown in FIG. 8C. Since the toner tends to increase in the portion where the line intersects in the character image because it is sandwiched between the body and compressed, the toner may be hardened and solidified. It becomes difficult to release, and the whole lump remains on the photoconductor, so that a hollowing out phenomenon is likely to occur due to poor transfer as shown in FIG.

  As shown in the front sectional view of FIG. 2, brush rollers 1YP, 1MP, 1CP, 1KP are provided as application means for applying a lubricant to the photoreceptors 1Y, 1M, 1C, 1K. 1YP, 1MP, 1CP, and 1KP have a thickness of 6.25 denier, with 100,000 conductive acrylic fibers per square inch uniformly planted on the circumference of the roller, and the diameter of the hair tip is 12 mm. The line speeds of the brush rollers 1YP, 1MP, 1CP, and 1KP are set to 132 mm / s in the reverse rotation direction with respect to the photosensitive member, for example. The lubricant is solid lubricant 1YS, 1MS, 1CS, 1KS of 8 (width) × 5 (height) × 332 (length) mm, and has a hardness equivalent to pencil hardness HB. The brush roller is brought into contact with the brush roller with a substantially constant pressure such as a spring pressure.

  The lubricant is a lubricant of a fatty acid metal salt of zinc stearate containing at least Zn, and the toner used for the developer is a polymerized toner having a particle size of 6.5 μm, and the total amount of the lubricant is the same. The amount is 0.03% by mass or more (here 0.2% by mass common to all colors) based on the toner amount.

  Now, when the lubricant is applied to the photosensitive member by the rotation of the brush roller, the surface energy changes depending on the amount of application per unit time, that is, the rotation speed of the brush roller. The graph of FIG. 5 shows the speed as a parameter.

  When the rotational speed is increased from the stopped state to 210 rpm, as shown in the diagram (1), the surface energy is low, that is, the contact angle Θ is large (110 °) in a short time, and the rotational speed is increased to 105 rpm. When the speed is increased, as shown in the diagram of (2), the surface energy is low, that is, the contact angle Θ is large (110 °) in a relatively long time. As can be seen from the diagram, it takes a long time to reach a state where the surface energy is low, that is, a state where the contact angle Θ is large (110 °).

  On the other hand, when the rotation of the brush roller is stopped from the state where the surface energy is low, that is, the state where the contact angle Θ is large (110 °), the time for changing the state where the surface energy is high, ie, the state where the contact angle Θ is small (80 °). Is plotted in the graph of FIG.

  Thus, the increase in the contact angle in the state where the coating speed is fast shown in the diagram (1) of FIG. 5 is connected to the state of change in the contact angle after the coating stop shown in the diagram of FIG. As shown in FIG. 6, an operation diagram representing a state in which the contact angle is changed by applying a lubricant to the photoreceptor can be created.

  Then, the rotation speed of the brush roller, its rotation start timing, and its rotation stop timing are determined so that a sufficient contact angle Θ is obtained in the image range having a sufficient margin, and the rotation of the brush roller in the non-image range period is determined. Is stopped, for example, the contact angle in the image range is decreased from about 110 ° to about 80 °, and one cycle is started until the rotation speed is increased to 210 rpm again toward the image range, and the above cycle is repeated. In order to go, an operation diagram for changing the contact angle by the rotation of the brush roller is set. Here, the contact angle dropped within the period of repeating the cycle may be 80 ° or 70 °. Of course, when the cycle is repeated, the rotation speed of the brush roller at the beginning of the cycle for changing the contact angle is 0 rpm, and the rotation speed at the end of the cycle is also 0 rpm. In FIG. 6, such an operation diagram is drawn with phases shifted for Y, M, C, and K.

  The above is a case where the developing sleeve continues to rotate even in the non-image range as shown in FIG. 3, and in this case, the rotational speed of the lubricating brush roller with respect to the image range is preferably 105 rpm or more.

  However, it is most preferable that the rotation of the developing sleeve is stopped in the non-image range. In this case, as shown in the diagram of FIG. The size (110 °) does not change, and no lubricant is consumed. Nevertheless, good transfer conditions are maintained, which is very useful for extending the life of the lubricant. The entire operation diagram when this method is adopted is as shown in FIG. The timing of the rotational drive of each brush roller is the same as the diagram of FIG. 6, but since the cycle for stopping the rotational drive of the developing sleeve of each developing device in the non-image range is incorporated, the operation of each photoconductor The medium contact angle value of 110 ° is reliably maintained throughout the operation, and the occurrence of voids and poor cleaning is greatly reduced.

  The following confirmation test was conducted.

  Using the above-mentioned image forming apparatus, in the non-image area, the rotation of the brush roller was stopped, and the driving of the developing sleeve was stopped at the same timing as shown in FIG. did.

  The remaining amount of the solid lubricant is obtained by measuring the height at which the solid lubricant is reduced.

  The level of the void was determined from a 6-point dot image, and the evaluation was performed using the following five evaluation criteria.

5: Good with no voids, 5 and 4 are acceptable levels
4: No problem in practical use
3: Unstable in practical use 3, 2, 1 are unusable levels
2: Unstable in practical use
1: No practical use at all. Evaluation of poor cleaning was evaluated by evaluating the image silently, ○ was good, and vertical stripes could be confirmed.

  In the comparative example, the rotation speed of the brush roller to which the lubricant was applied was always 210 rpm (both the image range and the non-image range), and the others were the same as those of the present invention.

  The test results are shown in Table 1.

  It can be seen that the present invention shows a very stable and good result even with respect to the hollowing out phenomenon and poor cleaning, and is extremely useful in terms of lubricant consumption.

1 is a schematic configuration diagram illustrating a color image forming apparatus as an embodiment of an image forming apparatus of the present invention. 1 is a front sectional view showing a solid lubricant, a brush roller, and a photoreceptor to which the solid lubricant is used in an embodiment of an image forming apparatus of the present invention. Even if the rotation of the brush roller is stopped when the contact angle obtained by the rotation speed of each brush roller of 50/105/210 rpm becomes 110 °, the contact angle is increased with time when the phenomenon sleeve is rotating. It is a diagram which shows the state which falls. When the contact angle obtained by the rotation speed of each brush roller of 50/105/210 rpm reaches 110 °, the rotation of the brush roller is stopped and the phenomenon sleeve is also stopped. It is a diagram which shows the state which does not change with time. It is a diagram showing a state until the contact angle increases from 75 ° to 110 ° with time and stabilizes with the rotational speed of each brush roller of 50/105/210 rpm as a parameter. FIG. 6 is an operation diagram illustrating an example of timing of rotational driving of each brush roller and developing sleeve to each photoconductor. FIG. 10 is an operation diagram showing another example of timings of rotational driving of each brush roller and developing sleeve to each photoconductor. (A) is a schematic diagram showing the definition of the contact angle, (b) is a schematic diagram showing a state immediately before the toner image on the photosensitive member advances to the transfer position on the endless belt-like intermediate transfer member, (c) ) Is a schematic view showing a state where the toner image on the photosensitive member is at the transfer position on the endless belt-shaped intermediate transfer member, and the toner in the dense portion is compressed and solidified, and (d) is a diagram showing how the toner in the dense portion is solidified. FIG. 6 is a schematic diagram showing a state in which a blank portion called a hollow is generated at the center of a cross portion of an image, for example, left on a photosensitive member without being transferred.

Explanation of symbols

1Y, 1M, 1C, 1K Photoconductor 1YP, 1MP, 1CP, 1KP Brush roller 1YS, 1MS, 1CS, 1KS Solid lubricant 4Y, 4M, 4C, 4K Developer (Developer development sleeve)
6Y, 6M, 6C, 6K Cleaning means

Claims (4)

In an image forming apparatus having a photoconductor, a developing device for supplying a developer to the photoconductor, a lubricant, and a brush roller for applying the lubricant to the photoconductor, theoretically in the sub-scanning direction of the photoconductor When an image range is an image range that is a widening of the target image formation range in the vicinity of the front end and the rear end, and a region between the image range and the next image range is a non-image range, the lubricant in the non-image range is An image forming apparatus, wherein an application condition for applying to the body is changed with respect to an application condition for applying the lubricant in the image range to the photoconductor. The image forming apparatus according to claim 1, wherein the application condition for applying the lubricant to the photoconductor is the number of rotations of the brush roller. 3. The image forming apparatus according to claim 1, wherein the rotational speed of the developing sleeve of the developing device in the non-image range is also changed with respect to the rotational speed of the developing sleeve of the developing device in the image range. . 4. The image forming apparatus according to claim 3, wherein the rotation speed of the phenomenon sleeve of the developing device in the non-image range is changed to zero rotation speed.

Images