JP2006189512A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely remove discharge product formed on the peripheral surface of a photoreceptor drum. <P>SOLUTION: The image forming apparatus is constituted so that residual toner remaining on the peripheral surface of the photoreceptor drum 10 after transferring a toner image formed by supplying toner to an electrostatic latent image formed on the peripheral surface of the photoreceptor drum 10 to which charge is imparted and the discharge product produced when imparting the charge to paper P may be removed by the rotation of a cleaning roller 62 whose peripheral surface abuts on the peripheral surface of the photoreceptor drum 10 in an opposite direction to the photoreceptor drum 10. The apparatus is equipped with a temperature and humidity sensor 94 for detecting the temperature and the humidity of environment in which the cleaning roller 62 is put, and a control part for performing control to switch the rotational speed of the cleaning roller 62 at two stages in accordance with the result of detection by the temperature and humidity sensor 94. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer as output means connected to a computer. In particular, the present invention relates to a cleaning means for removing discharge products generated on the peripheral surface of a photosensitive drum. It is about improvement.

  In general, an electrophotographic image forming apparatus such as a copying machine irradiates a peripheral surface of a photosensitive drum as a charged body rotating around an axis with an optical signal based on image information read or transmitted. A toner image is formed on the electrostatic latent image formed by supplying toner from the developing device, and the toner image is transferred to a sheet to perform image forming processing. Residual toner remaining on the peripheral surface of the photosensitive drum after the transfer process to the paper is removed by a cleaning roller that rotates about its axis while the peripheral surface is in contact with the peripheral surface of the photosensitive drum.

  In such an image forming apparatus, a corona charger has been conventionally used as a means for charging a peripheral surface of a photosensitive drum with a charge having a predetermined polarity. The corona charger is disposed so as to face the peripheral surface of the photosensitive drum in a non-contact manner, and the peripheral surface of the photosensitive drum is exposed to a corona discharge emitted from the corona charger, thereby being predetermined. It is designed to be charged to a polar potential.

  In recent years, a contact-type charging device that generates less ozone has been proposed and put into practical use for such a non-contact type corona charger. In this contact type charging device, a charging member to which a charging bias is applied is brought into contact with the peripheral surface of the photosensitive drum, thereby charging the peripheral surface of the photosensitive drum. Examples of the charging member include a charging roller, a fur brush, a magnetic brush, and a charging blade. However, the charging roller is preferable in terms of uniformity and stability of charge application to the photosensitive drum, and is widely used. .

  Such a charging roller is formed of a conductive rubber material or foaming synthetic resin with a predetermined elasticity, and a predetermined voltage is applied while the peripheral surface is in contact with the peripheral surface of the rotating photosensitive drum. By being applied, the surface potential of the photosensitive drum starts to rise, and after reaching a predetermined potential, the charging potential increases or decreases in proportion to the value of the applied voltage. The threshold voltage in this case (the voltage that has reached the predetermined voltage) is set as the charging start voltage Vth. In order to obtain the surface potential Vo necessary for the photosensitive drum, it is necessary to apply a DC voltage of Vo + Vth to the charging roller. Such a charging method is called a DC charging method.

On the other hand, there is a case where a so-called AC charging method in which an AC voltage having a peak-to-peak voltage of 2 × Vth or more is superimposed on the DC voltage of Vo + Vth and applied to the charging roller may be employed. In such an AC charging method, it is possible to suppress fluctuations in the resistance value of the charging roller due to the operating environment (especially temperature and humidity) by the leveling action due to AC, and as a result, the surface potential of the photosensitive drum reaches its peak. Therefore, for example, it is possible to suppress the influence of the fluctuation of the resistance value of the charging roller made of a rubber material or the like due to temperature and humidity, thereby ensuring the uniformity of charging of the photosensitive drum. Can do.
JP 2003-345208 A

  However, when such an AC charging method is adopted, the amount of discharge in the vicinity of the photosensitive drum is larger than that in the case of the DC charging method, and in particular, the amount of discharge when a peak-to-peak voltage of 2 × Vth or more is applied is very large. Therefore, the amount of discharge products generated increases, and the discharge products generated in large quantities adhere to the peripheral surface of the photosensitive drum. Such a discharge product is removed by the cleaning roller, but the removal efficiency varies depending on the environment (particularly temperature and humidity) where the cleaning roller is placed, and thus it is difficult to always remove it reliably. There has been a problem that a so-called image flow phenomenon occurs in which a transfer image flows in the sheet conveyance direction due to the remaining discharge product.

  By the way, Japanese Patent Application Laid-Open No. H10-228688 describes a technique in which the amount of toner remaining on the peripheral surface of the photosensitive drum is detected and the number of rotations of the cleaning roller is increased in accordance with the detected amount of residual toner. However, simply increasing the number of rotations of the cleaning roller in accordance with the amount of residual toner remains a problem that it is not possible to cope with the number of discharge products generated depending on the environment in which the cleaning roller is placed.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can more reliably remove discharge products formed on a peripheral surface of a photosensitive drum.

  According to the first aspect of the present invention, after the toner image formed by supplying toner to the electrostatic latent image formed on the peripheral surface of the charged photosensitive drum is transferred onto a recording medium, the photosensitive image is transferred. Residual toner remaining on the peripheral surface of the photosensitive drum and discharge products generated during the charge application are removed by rotating the cleaning roller whose peripheral surface is in contact with the peripheral surface of the photosensitive drum in the direction opposite to the photosensitive drum. In the image forming apparatus configured as described above, a temperature / humidity sensor that detects a temperature / humidity of an environment in which the photosensitive drum is placed, and a rotation speed of the cleaning roller according to a detection result of the temperature / humidity sensor, A control unit that performs control to switch between a speed and a second speed higher than the second speed is provided.

  According to such a configuration, the control unit performs control to switch the rotation speed of the cleaning roller based on the detection result of the temperature / humidity sensor. Compared with the case of detecting the temperature, the temperature and humidity can be detected easily and accurately, so that highly accurate control is realized.

  According to a second aspect of the present invention, in the first aspect of the invention, the two-stage rotational speed of the cleaning roller is a predetermined low-speed rotation peripheral speed and a high-speed rotation peripheral speed that is a predetermined speed higher than the low-speed rotation. It is characterized by.

  According to such a configuration, the cleaning roller rotates in the opposite direction with its rotational speed set to be higher than the peripheral speed of the photosensitive drum at both the low speed and the high speed peripheral speed. The peripheral surface of the photosensitive drum is rubbed by the peripheral surface of the cleaning roller, whereby the adhering matter on the peripheral surface of the photosensitive drum is scraped by the peripheral surface of the cleaning roller and cleaned.

  Then, regarding the rotational speed of the cleaning roller, which rotational peripheral speed is employed in relation to the temperature and humidity is found by actually performing an effect confirmation test.

  The invention according to claim 3 is the invention according to claim 2, wherein the control unit determines whether or not the detection result of the temperature and humidity sensor is equal to or higher than a preset reference value; Based on the detection result of the temperature / humidity determination unit, a control signal for rotating the cleaning roller at a high speed peripheral speed is output when the detection result is a high temperature and high humidity environment equal to or higher than a reference value. And a control signal output unit that outputs a control signal for rotating the cleaning roller at a low rotational peripheral speed.

  According to such a configuration, the temperature / humidity determination unit determines whether the detection result is equal to or higher than a preset reference value based on the detection result from the temperature / humidity sensor, and the control signal output unit When the detection result is less than the reference value based on the determination result of the humidity determination unit, a control signal for rotating the cleaning roller at a low rotational peripheral speed is output, while when the detection result is less than the reference value, the cleaning roller is rotated at a low speed. To output a control signal that rotates at a rotational peripheral speed, the cleaning roller rotates at a high rotational speed when the temperature and humidity are above the reference value (that is, when the temperature and humidity are high), while the temperature and humidity are below the reference value. When (i.e., when the temperature and humidity is low), the motor rotates at a low rotational speed.

  When the temperature and humidity are high, the cleaning roller is rotated at a high rotational speed, while when the temperature and humidity is low, the cleaning roller is rotated at a low speed and the peripheral speed is low. This is because the amount of discharge product adhering to the photosensitive drum is more than usual, and in order to effectively remove this large amount of adhering material, the cleaning roller is rotated at a high rotational speed when the temperature and humidity are high. I am doing so.

  Note that when the temperature and humidity are low, even if a discharge product is generated, the discharge product does not absorb much moisture, so that the image flow phenomenon is unlikely to occur, so the rotation speed of the cleaning roller is excessively increased. There is no need to do this, and a low speed peripheral speed is set.

  In this way, wasteful energy consumption is achieved by rotating the cleaning roller at a high rotational speed when the temperature and humidity are above the reference value and rotating at a low speed when the temperature and humidity are below the reference value. In this way, deposits on the peripheral surface of the photosensitive drum are appropriately removed according to the temperature and humidity.

  According to a fourth aspect of the present invention, in the second or third aspect of the invention, the low-speed rotation peripheral speed is approximately 1.3 times the rotation peripheral speed of the photosensitive drum, and the high-speed rotation peripheral speed is It is characterized by being approximately 1.5 times the rotational peripheral speed of the photosensitive drum.

  According to this configuration, the low-speed rotational peripheral speed of the cleaning roller is set to approximately 1.3 times the rotational peripheral speed of the photosensitive drum, while the high-speed rotational peripheral speed of the cleaning roller is set to approximately 1 of the rotational peripheral speed of the photosensitive drum. By setting the ratio to 5 times, necessary and sufficient removal of discharge products adhering to the photosensitive drum is realized.

  Incidentally, the numerical values of approximately 1.3 times and 1.5 times are values derived as a result of performing many tests.

  According to the first aspect of the present invention, since the control unit performs control to switch the rotation speed of the cleaning roller in two stages, a reliable removal effect of the deposits from the circumferential surface of the photosensitive drum can be obtained. be able to.

  According to the second aspect of the present invention, by adopting a predetermined low-speed rotation peripheral speed and a high-speed rotation peripheral speed faster than the low-speed rotation as the two-stage rotation speed of the cleaning roller, In both cases, the peripheral surface of the photosensitive drum is the peripheral surface of the cleaning roller because the rotational speed is set to be higher than the peripheral speed of the photosensitive drum at both low speed and high rotational peripheral speed. By this, the deposit on the peripheral surface of the photosensitive drum can be scraped off by the peripheral surface of the cleaning roller.

  According to the third aspect of the present invention, the cleaning roller is rotated at the high speed rotation peripheral speed when the temperature and humidity are equal to or higher than the reference value, and is rotated at the low speed rotation peripheral speed when the temperature and humidity is less than the reference value. Further, it is possible to appropriately remove the deposits on the circumferential surface of the photosensitive drum according to the temperature and humidity while suppressing wasteful energy consumption.

  According to the fourth aspect of the present invention, the low-speed rotational peripheral speed of the cleaning roller is set to approximately 1.3 times the rotational peripheral speed of the photosensitive drum, while the high-speed rotational peripheral speed of the cleaning roller is set to the rotational peripheral speed of the photosensitive drum. By setting the speed to about 1.5 times the speed, the discharge products adhering to the photosensitive drum can be removed as necessary and sufficiently.

  FIG. 1 is an explanatory diagram showing an embodiment of a schematic configuration around a photosensitive drum in an image forming apparatus according to the present invention. As shown in FIG. 1, a photosensitive drum 10 configured to be integrally rotatable around a drum shaft 13 extending in a longitudinal direction (a direction orthogonal to the paper surface in FIG. 1) is positioned immediately above the circumferential surface. Toward the clockwise direction from the charging roller 20, a charging roller 20 for applying a charge to the photosensitive drum 10, an exposure device 30 provided slightly to the right of the charging roller 20, and a photosensitive member at a position directly below the exposure device 30. A developing device 40 provided on the right side of the drum 10, a transfer roller 50 provided via a conveyance belt 80 at a position directly below the photosensitive drum 10, and a cleaning device 60 provided on the left side of the photosensitive drum 10. And a static eliminating device 70 provided between the cleaning device 60 and the charging roller 20.

  The photosensitive drum 10 is for forming an electrostatic latent image on the peripheral surface thereof. The drum body 11 having a cylindrical shape made of a predetermined metal material and, for example, a vapor deposition process on the peripheral surface of the drum body 11. And the amorphous silicon layer 12 formed by laminating the amorphous silicon formed in (1).

  The amorphous silicon layer 12 is a solid solution of silica (Si) or a compound of silica (SiC, SiO, SiON, etc.), and is usually formed by physical vapor deposition such as sputtering. . Such an amorphous silicon layer 12 (particularly made of SiC) has excellent charging ability due to high resistance, and also has excellent wear resistance and environmental resistance, and is a material for forming an electrostatic latent image. Is preferred.

Further, when the amorphous silicon layer 12 is made of silica carbide (SiC), it is preferable that the ratio of silica (Si) and carbon (C) is specific. As such a carbonized silica, those having an X value of 0.3 to less than ₁ in “Si _1-X C _X ” are preferable, and those having an X value of 0.5 to 0.95 are more preferable.

The reason is that “Si _1-X C _X ” having such a value of _X has an extremely high resistance value of 10 ¹² to 10 ¹³ Ω. This is because there is little image flow of the electrostatic latent image in the rotation direction on the surface, and the electrostatic latent image maintaining ability is excellent, and the moisture resistance is also excellent.

  The charging roller 20 applies a voltage from a power supply (not shown) to the amorphous silicon layer 12 in a state where the peripheral surface is in contact with the peripheral surface of the photosensitive drum 10 (that is, the amorphous silicon layer 12). The photosensitive drum 10 rotates counterclockwise around the axis while following the clockwise rotation around the drum shaft 13, thereby forming a uniform charge on the amorphous silicon layer 12.

  The exposure device 30 irradiates a uniform charge surface formed on the amorphous silicon layer 12 by the charging roller 20 with a laser beam having strength and weakness based on image information that has been read or transmitted. An electrostatic latent image is formed on the peripheral surface (amorphous silicon layer 12) of the photosensitive drum 10 rotating around 13.

  The developing device 40 supplies toner to the amorphous silicon layer 12 of the photosensitive drum 10 formed by the exposure device 30 to form a toner image, and has a peripheral surface within a box-shaped developing device main body 41. The developing roller 42 is mounted with a part of the developing roller 42 exposed, and the developing roller rotating the toner loaded in the developing device main body 41 around an axis parallel to the drum shaft 13 of the photosensitive drum 10. A toner image is formed on the surface of the amorphous silicon layer 12 by supplying it to the amorphous silicon layer 12 of the image forming apparatus 10 rotating around the drum shaft 13 from the peripheral surface of 42.

  The transfer roller 50 peels off the toner image from the amorphous silicon layer 12 by applying a polarity opposite to the polarity of the charge of the toner image formed on the peripheral surface of the photosensitive drum 10, and the peeled toner image. Is transferred onto the sheet (recording medium) P being conveyed between the peripheral surface of the transfer roller 50 and the amorphous silicon layer 12 by the conveying belt 80.

  The transfer roller 50 is supported so as to be rotatable around an axis parallel to the drum shaft 13 of the photosensitive drum 10, and a voltage from a power supply (not shown) is applied to the transfer roller 50. By pressing the conveyor belt 80 upward, the sheet P being conveyed by the conveyor belt 80 comes into close contact with the peripheral surface of the photosensitive drum 10.

  The cleaning device 60 includes a discharge product formed by a chemical reaction with moisture in the atmosphere due to a discharge phenomenon generated when the charge is applied to the amorphous silicon layer 12 by the charging roller 20, and attached to the amorphous silicon layer 12. This is for removing residual toner remaining on the amorphous silicon layer 12 after the toner image on the surface of the amorphous silicon layer 12 of the photosensitive drum 10 is transferred to the paper P.

  The cleaning device 60 includes a cleaning roller 62 whose peripheral surface attached to the lower part of a box-shaped cleaning device main body 61 abuts on the peripheral surface (amorphous silicon layer 12) of the photosensitive drum 10, and a leading end which is the photosensitive drum 10. The cleaning blade 63 is mounted on the upper portion of the cleaning device main body 61 so as to abut on the peripheral surface of the cleaning device main body 61.

  The cleaning roller 62 is concentrically and integrally formed around a roller shaft 621 parallel to the drum shaft 13. The cleaning roller 62 is made of a synthetic resin material that can be elastically deformed and has excellent toughness. Incidentally, in the present embodiment, EPDM (ethylene / propylene / diene copolymer) having a hardness of 30 to 40 ° and a cell diameter of about 100 μm is used.

  Such a cleaning roller 62 is driven in the direction opposite to the photosensitive drum 10 (counterclockwise in the example shown in FIG. 1) at a peripheral speed faster than the peripheral speed of the photosensitive drum 10 around the roller shaft 621 by the driving motor 622. As a result, the discharge product adhering to the amorphous silicon layer 12 and the residual toner remaining on the amorphous silicon layer 12 are scraped off, whereby the amorphous silicon layer 12 is cleaned.

  The cleaning blade 63 is a finishing cleaning member for the peripheral surface of the photosensitive drum 10, and is formed in a plate shape by an elastic material such as rubber. The cleaning blade 63 is tilted forward toward the amorphous silicon layer 12 on the peripheral surface of the photosensitive drum 10 and is mounted at an upper position in the cleaning device main body 61. The blade blade 631 at the tip is slightly elastically deformed. Is in contact with the amorphous silicon layer 12. Accordingly, the amorphous silicon layer 12 that has reached the blade blade 631 via the cleaning roller 62 is scraped off the deposits that could not be removed by the cleaning roller 62 in accordance with the clockwise rotation of the photosensitive drum 10. Become.

  Then, the deposits (discharge products and residual toner) of the amorphous silicon layer 12 removed by the cleaning roller 62 and the cleaning blade 63 are introduced into the cleaning device main body 61 and temporarily stored, and then a predetermined conveying means is driven. As a result, the image is collected in an unillustrated collection bottle provided in the image forming apparatus.

  The static eliminator 70 is for removing charges remaining on the amorphous silicon layer 12 on the peripheral surface of the photosensitive drum 10 cleaned by the cleaning device 60 and returning it to the non-charged state, and irradiates the static elimination light. It is supposed to be. The peripheral surface of the photosensitive drum 10 from which the electric charge has been removed by the static eliminator 70 is returned to the charging roller 20 by the rotation of the photosensitive drum 10, and a new charging process is performed for the next transfer process.

  In the present invention, a temperature / humidity sensor 94 for detecting the temperature of the environment where the photosensitive drum 10 is placed is provided in the vicinity of the charging roller 20, and the control unit 90 is based on the detection result of the temperature / humidity sensor 94. Thus, the rotational speed of the cleaning roller 62 is controlled. Hereinafter, this control will be described with reference to FIG.

  FIG. 2 is a block diagram for explaining the rotation control of the cleaning roller 62 by the controller 90. As shown in FIG. 2, the control unit 90 includes a central processing unit (CPU) 91 that is a central processing unit, a read only memory (ROM) 92 attached to the CPU 91, and a random access memory (RAM) 93. And.

  The ROM 92 is a read-only storage device, and stores data that is rarely changed, such as a program used for the control and a setting value serving as a determination reference, whereas the RAM 93 is This is a readable / writable storage device for temporarily storing data obtained during the control. In the present embodiment, the temperature and humidity values (reference values (temperature 30 ° C., humidity 60% in the present embodiment)) serving as a determination criterion are stored in the ROM 92.

  The CPU 91 includes a temperature / humidity determination unit 911 for determining whether the detection result of the temperature / humidity sensor 94 is equal to or higher than a preset reference value, and a temperature / humidity sensor based on the detection result of the temperature / humidity determination unit 911. In the case of a high-temperature and high-humidity environment in which the detection result of 94 is equal to or higher than a reference value, a control signal for rotating the cleaning roller 62 at a high-speed rotation peripheral speed (second speed) is output toward the drive motor 622. A control signal output unit 912 that outputs a control signal for rotating the cleaning roller 62 at a low-speed rotation peripheral speed (first speed) toward the drive motor 622 when it is less than the reference value is provided.

  The high-speed rotation peripheral speed is set to “1.5” (that is, the speed ratio is 1.5) when the peripheral speed of the photosensitive drum 10 is “1”, whereas the low-speed rotation peripheral speed is the same. “1.3” (speed ratio 1.3) is set.

  When the detection result of the temperature / humidity sensor 94 with respect to the cleaning roller 62 is equal to or greater than the reference value, the speed ratio of the cleaning roller 62 to the photosensitive drum 10 is set to 1.5, whereas when the temperature / humidity is less than the reference value, the cleaning is performed. The so-called two-stage control in which the speed ratio of the roller 62 to the photosensitive drum 10 is set to 1.3 is performed for the following reason.

  That is, first, in Japan's climate, the temperature and humidity exceed the reference value when it is hot and humid in summer, and in such a case, a very large amount of moisture is present in the air around the photosensitive drum 10. In this state, the discharge product adhering to the amorphous silicon layer 12 forming the peripheral surface of the photosensitive drum 10 adsorbs moisture in the air. Image flow phenomenon is likely to occur.

  Therefore, in such a case, the speed ratio of the cleaning roller 62 to the photosensitive drum 10 is set to 1.5 to increase the rotational speed of the cleaning roller 62, so that the circumferential surface of the cleaning roller 62 with respect to the photosensitive drum 10 is increased. The rubbing is surely performed, and thereby, the deposits adhering to the amorphous silicon layer 12 are surely removed.

  On the other hand, when the temperature and humidity are less than the reference value (that is, when the temperature and humidity are not in a high-temperature and high-humidity environment of a predetermined level), the amount of moisture in the air around the photosensitive drum 10 is small, so the amorphous silicon layer The amount of moisture adsorbed by the discharge product adhering to the sheet 12 is reduced, thereby making it difficult for the image flow phenomenon to occur. Therefore, there is no problem even if the speed ratio of the cleaning roller 62 is lowered to 1.3.

  The two-stage control is performed because of the speed ratio of the cleaning roller 62 to the photosensitive drum 10 and so-called polishing in which the cleaning roller 62 polishes the peripheral surface of the photosensitive drum 10 to remove deposits. The relationship with the amount is not necessarily linear. Therefore, for example, it is meaningless to perform control such that the speed ratio of the cleaning roller 62 is proportional to the temperature / humidity value detected by the temperature / humidity sensor 94. Two-step control with a predetermined temperature and humidity value serving as a reference within a region where the peripheral surface of 10 can be polished is more practical and simple and practical. This is because control is realized.

  Then, each time the detection signal from the temperature / humidity sensor 94 is input, the temperature / humidity determination unit 911 determines whether the value of the detection signal (detected temperature / humidity value) exceeds a reference value. The determination result is output to the control signal output unit 912 as a command signal.

  The control signal output unit 912 outputs a control signal for setting the drive motor 622 to one of two stages toward the drive motor 622 based on the command signal from the temperature / humidity determination unit 911. When the detection result of the temperature / humidity sensor 94 is equal to or higher than the reference value, a control signal is output to the drive motor 622 so that the speed ratio of the cleaning roller 62 to the photosensitive drum 10 becomes 1.5, while the temperature / humidity sensor When the detection result of 94 is less than the reference value, a control signal is output to the drive motor 622 so that the speed ratio of the cleaning roller 62 to the photosensitive drum 10 is 1.3.

  Accordingly, the drive motor 622 to which such a control signal is input drives the cleaning roller 62 so as to have a speed ratio of 1.5 with respect to the photosensitive drum 10 when the temperature and humidity are equal to or higher than the reference value. Is less than the reference value, the cleaning roller 62 is driven at a speed ratio of 1.3 with respect to the photosensitive drum 10.

  As described above in detail, the image forming apparatus according to the present invention supplies a toner image formed by supplying toner to the electrostatic latent image formed on the peripheral surface of the photosensitive drum 10 to which a charge is applied. After the transfer onto P, the residual toner remaining on the peripheral surface of the photoconductive drum 10 and the discharge product generated at the time of applying the charge are the photoconductive drum of the cleaning roller 62 whose peripheral surface is in contact with the peripheral surface of the photoconductive drum 10. The temperature / humidity sensor 94 detects the temperature / humidity of the environment where the cleaning roller 62 is placed, and the detection result of the temperature / humidity sensor 94 corresponds to the detection result. And a control unit 90 that performs control to switch the rotational speed of the cleaning roller 62 in two stages.

  According to such a configuration, the control unit 90 performs control to switch the rotation speed of the cleaning roller 62 based on the detection result of the temperature / humidity sensor 94, so that the residual toner remaining on the photosensitive drum 10 and the like as in the related art. Compared with the case where the amount of adhering matter is detected, the temperature and humidity can be detected easily and accurately, so that highly accurate control can be realized.

  In addition, since the control unit 90 performs control to switch the rotation speed of the cleaning roller 62 in two stages, it is possible to reliably remove deposits (discharge products and residual toner) from the peripheral surface of the photosensitive drum 10 in accordance with the actual situation. An effect is obtained.

  Further, the two-stage rotation speed of the cleaning roller 62 is a low-speed rotation peripheral speed whose peripheral speed is slightly higher than the peripheral speed of the photosensitive drum 10, and a high-speed rotation peripheral speed that is a predetermined speed higher than this low-speed rotation. The cleaning roller 62 rotates in the opposite direction with its rotational speed set to be higher than the peripheral speed of the photosensitive drum 10 at both the low speed and the high rotational peripheral speed. The peripheral surface is rubbed and cleaned by the peripheral surface of the cleaning roller 62.

  Then, the control unit 90 detects based on the temperature / humidity determination unit 911 that determines whether the detection result of the temperature / humidity sensor 94 is equal to or higher than a preset reference value, and the detection result of the temperature / humidity determination unit 911. When the result is equal to or higher than the reference value, a control signal for rotating the cleaning roller 62 at a high speed peripheral speed is output. On the other hand, when the detection result is less than the reference value, a control signal for rotating the cleaning roller 62 at a low speed peripheral speed is output. The temperature / humidity determination unit 911 determines whether the detection result is equal to or higher than a preset reference value based on the detection result from the temperature / humidity sensor 94. At the same time, the control signal output unit 912 rotates to the cleaning roller 62 at a low rotational speed when the detection result is less than the reference value based on the determination result of the temperature / humidity determination unit 911. On the other hand, when the detection result is less than the reference value, a control signal for rotating the cleaning roller 62 at a low rotational peripheral speed is output. That is, it rotates at a high speed rotation peripheral speed (when it is in a high temperature and high humidity environment above a predetermined value), while it rotates at a low speed rotation peripheral speed when the temperature and humidity are below the reference value (that is, when it is not in the high temperature and high humidity environment). Will do.

  As described above, the cleaning roller 62 is rotated at a high rotational speed when the temperature and humidity are equal to or higher than the reference value, and is rotated at a low rotational speed when the temperature and humidity is less than the reference value. It is possible to appropriately remove deposits on the circumferential surface of the photosensitive drum 10 according to the temperature and humidity while suppressing consumption.

  In this embodiment, the low-speed rotation peripheral speed is set to 1.3 times the rotation peripheral speed of the photoconductor drum 10 (speed ratio 1.3), and the high-speed rotation peripheral speed is set to be equal to that of the photoconductor drum 10. Although it is set to 1.5 times the rotational peripheral speed (speed ratio 1.5), these values are derived as a result of carrying out many implementation tests.

  The present invention is not limited to the above embodiment, and includes the following contents.

  (1) In the above-described embodiment, the temperature 30 ° C. and the humidity 60% are adopted as the reference values of the temperature and humidity, which is a branching point of whether the speed ratio of the cleaning roller 62 is 1.5 or 1.3. However, the present invention is not limited to the temperature and humidity reference values being 30 ° C. and 60% humidity, and is optimal according to the type and installation status of the image forming apparatus, and the usage status, etc. It is preferable to find the value of.

  (2) In the above embodiment, as the temperature / humidity sensor 94, the product number “103AT-2-3P” which is a temperature sensor manufactured by Ishizuka Electronics Co., Ltd. and the product number “C10-M52R” which is a humidity sensor manufactured by Shineisha Although employed in combination, the present invention is not limited to the use of the temperature / humidity sensor 94 in combination with a temperature sensor manufactured by Ishizuka and a humidity sensor manufactured by Shineisha. Any manufacturer's temperature sensor and humidity sensor may be adopted as long as both can be detected appropriately. Further, if the temperature / humidity sensor is a combination of a temperature sensor and a humidity sensor from the beginning, it is not necessary to combine the temperature sensor and the humidity sensor one by one on the user side, which is convenient.

  (3) In the above embodiment, the paper P is used as the recording medium. However, the present invention is not limited to the recording medium being the paper P, and is stretched between a pair of rollers. A so-called transfer belt may also be used. When the transfer belt is employed, the toner image is once transferred from the photosensitive drum 10 to the transfer belt, and the toner image on the transfer belt is transferred to the paper.

  (4) In the above embodiment, when the temperature / humidity is equal to or higher than the reference value, the speed ratio of the cleaning roller 62 to the photosensitive drum 10 is set to 1.5, whereas when the temperature / humidity is lower than the reference value, the cleaning is performed. Although the speed ratio of the roller 62 to the photosensitive drum 10 is controlled in two stages so as to be set to 1.3, the present invention is limited to these speed ratios being 1.5 and 1.3. However, it is preferable to set an optimum value according to the model and installation status of the image forming apparatus, the usage status, the usage environment, and the like.

  In order to investigate the relationship between the AC voltage applied to the charging roller 20 and the discharge product adhering to the peripheral surface (amorphous silicon layer 12) of the photosensitive drum 10, image formation is performed after setting the AC voltage to various values. The apparatus was actually operated, and as a result, the weight of the discharge product generated in the amorphous silicon layer 12 was measured. A graph of the measurement results is shown in FIG.

  As shown in the graph of FIG. 3, when the AC voltage is in the range of 0 to 0.9 kV, the amount of discharge product generated (the amount of discharge product generated is extremely small, so it is difficult to actually measure as a weight. Therefore, normally, since the amount of generated discharge product is considered to be proportional to the value of the dynamic friction coefficient of the peripheral surface of the photosensitive drum 10, the value of the dynamic friction coefficient (μ) is displayed. In addition, it can be seen that the amount of discharge products suddenly increases when the voltage exceeds 0.9 kV, while the state is not changed.

  In the image forming apparatus, the AC voltage applied to the charging roller 20 is normally set to a very high voltage of about 1.0 kV at low temperature and low humidity, so that the amount of discharge products generated is very large. The importance of the present invention that effectively eliminates is recognized.

  The ratio (speed ratio) of the rotational peripheral speed of the cleaning roller 62 to the photosensitive drum 10 and the deposits (discharge product and residual toner) removed from the amorphous silicon layer 12 on the peripheral surface of the photosensitive drum 10 by the cleaning roller 62. In order to investigate the relationship with the amount (polishing amount) of the photosensitive drum 10, mg of deposits are previously applied to the amorphous silicon layer 12 of the photosensitive drum 10 and various speed ratios are set, and then the photosensitive drum 10 and the cleaning roller 62 are moved. I actually drove. The speed ratio in this operation and the amount (polishing amount) of the deposit removed by the cleaning roller 62 from the amorphous silicon layer 12 by this operation (displayed by the value of the dynamic friction coefficient as in the case of the discharge product). A graph of the relationship is shown in FIG.

  As shown in the graph of FIG. 4, the polishing amount is substantially constant when the speed ratio is 0.5 to 0.7, but starts to decrease when the speed ratio exceeds 0.7, and the speed ratio is approximately 1. 2 shows that the polishing amount reaches an extreme value, and after that, the polishing amount (that is, the amount of reduction in the dynamic friction coefficient) increases rapidly as the speed ratio increases.

  Thus, since the relationship between the speed ratio and the polishing amount is not linear, in the present invention, the cleaning roller 62 does not simply make the speed ratio of the cleaning roller 62 proportional to the temperature and humidity value. When the temperature / humidity is equal to or higher than the reference value, the speed ratio is set to 1.5 when the temperature / humidity is lower than the reference value in the range of the speed ratio where the deposits on the peripheral surface of the photosensitive drum 10 can be surely removed. The two-stage control for setting the speed ratio to 1.3 is performed.

  In order to confirm the relationship between the speed ratio of the cleaning roller 62 to the photosensitive drum 10 and the toner drop, the image forming apparatus is actually operated with the speed ratio set to various values, and the toner drop state is visually checked. Observed. Incidentally, “toner dropping” means that the adhered matter removed by the cleaning roller 62 from the peripheral surface of the photosensitive drum 10 falls to the lower part without being accommodated in the cleaning device main body 61. The observation results are shown in the table of FIG. In FIG. 5, “◯” indicates that no toner is dropped, and “X” indicates that toner is dropped.

  As can be seen from the table of FIG. 5, toner drop occurred when the speed ratio was less than 1.0, 0.5 and 0.8, but when the speed ratio was 1.0 or more (1.0, 1.2 and In 1.3), no toner drop occurred.

  This is the same as the cleaning roller 62 rotating in the opposite direction relative to the photosensitive drum 10 when the speed ratio is less than 1.0, and is therefore removed from the peripheral surface of the photosensitive drum 10. This is considered to be because the adhered matter is scraped downward and causes toner drop.

  In the present invention, since the speed ratios 1.3 and 1.5 at which toner does not fall are employed, there is no inconvenience that the paper P is contaminated by toner dropping.

When the speed ratio of the cleaning roller 62 to the photosensitive drum 10 is set to 1.5, there is a concern that the jitter level (slight shift of the transfer phase) is deteriorated. Therefore, the relationship between the temperature (air temperature) and the dark potential (potential of the portion not irradiated with the light beam) V ₀ formed on the amorphous silicon layer 12 of the photosensitive drum 10, and the temperature (air temperature) and the photosensitive drum 10. The relationship with the bright potential (potential of the portion irradiated with light) VL formed on the amorphous silicon layer 12 was examined by actual measurement.

  The measurement results are shown in the graph of FIG. 6 (temperature characteristics of a-Si (amorphous silica) drum). As shown in the graph of FIG. 6, the light potential VL gradually decreases as the temperature increases. This decrease in the light potential VL leads to a decrease in contrast (darkness difference) in the transferred image onto the paper P. This indicates that the difference in density of the transferred image is reduced in a high temperature and high humidity environment where the temperature exceeds 30 ° C.

  Therefore, even if the jitter level is deteriorated by setting the speed ratio to 1.5 in a high temperature and high humidity environment where the air temperature exceeds 30 ° C., the difference in density of the transferred image is reduced. Since the deterioration of the level became inconspicuous, it was confirmed that there was no problem in practical use.

FIG. 2 is an explanatory diagram showing an embodiment of a schematic configuration around a photosensitive drum in an image forming apparatus according to the present invention. It is a block diagram for demonstrating rotation control of the cleaning roller by a control part. It is a graph which shows the relationship between an alternating voltage and a discharge product. It is a graph which shows the relationship between a speed ratio and polishing amount. 6 is a table showing a relationship between a speed ratio and toner dropping. The relationship between the temperature and the dark potential V ₀ formed on the amorphous silicon layer of the photosensitive drum, and the bright potential (potential of the portion irradiated with light) VL formed on the amorphous silicon layer of the photosensitive drum It is a graph which shows the relationship.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Photosensitive drum 11 Drum main body 12 Amorphous silicon layer 13 Drum shaft 20 Charging roller 30 Exposure device 40 Developing device 41 Developing device main body 42 Developing roller 50 Transfer roller 60 Cleaning device 61 Cleaning device main body 62 Cleaning roller 621 Roller shaft 622 Drive motor 63 Cleaning blade 631 Blade blade 70 Static elimination device 80 Conveying belt 90 Control unit 91 CPU 911 Temperature / humidity determination unit 912 Control signal output unit 92 ROM
93 RAM 94 Temperature / humidity sensor P Paper

Claims (4)

The toner image formed by supplying toner to the electrostatic latent image formed on the peripheral surface of the photosensitive drum to which the electric charge was applied was transferred onto the recording medium, and then remained on the peripheral surface of the photosensitive drum. In an image forming apparatus configured to remove residual toner and a discharge product generated when the electric charge is applied by rotating a cleaning roller whose circumferential surface is in contact with the circumferential surface of the photosensitive drum in a direction opposite to the photosensitive drum. ,
A temperature and humidity sensor for detecting the temperature and humidity of the environment in which the photosensitive drum is placed;
And a control unit that performs control to switch the rotation speed of the cleaning roller between a first speed and a second speed higher than the first speed according to the detection result of the temperature and humidity sensor. An image forming apparatus.   2. The image forming apparatus according to claim 1, wherein the two-stage rotation speeds of the cleaning roller are a predetermined low-speed rotation peripheral speed and a high-speed rotation peripheral speed that is higher than the low-speed rotation by a predetermined speed.   The control unit determines whether the detection result of the temperature / humidity sensor is equal to or higher than a preset reference value, and the detection result is based on the detection result of the temperature / humidity determination unit. A control signal for rotating the cleaning roller at a high rotational speed in a high-temperature and high-humidity environment that exceeds the value, and a control for rotating the cleaning roller at a low rotational speed when the detection result is less than a reference value. The image forming apparatus according to claim 2, further comprising a control signal output unit that outputs a signal.   The low-speed rotation peripheral speed is approximately 1.3 times the rotation peripheral speed of the photosensitive drum, and the high-speed rotation peripheral speed is approximately 1.5 times the rotation peripheral speed of the photosensitive drum. The image forming apparatus according to claim 2 or 3.

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