JP2008164994A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that can suppress increase in the frictional coefficient on the surface of a photoreceptor upon aging, while applying a bias to a charging roller. <P>SOLUTION: A control unit sets a charging bias to a predetermined voltage (#7), when the temperature outside the machine is equal to or lower than T1 and the fixing temperature is equal to or lower than T2 (YES in #4), turns on the operation of a drum motor and a destaticizing unit (#8), applies the charging bias (#9) to the charging roller and detects a charging current (#10). The control unit turns on a developing motor, to apply a developing bias on the toner (#12), when the change in the charging current is large (NO in #11) and supplies the toner to the photoreceptor drum, to deposit the toner as a lubricant on the surface of the drum (#13). Then the control unit turns off the developing motor and stops the application of the developing bias (#14), and performing an aging operation on the charging roller for a predetermined time (#15). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention belongs to the technical field of image forming apparatuses such as printers, copiers, facsimile machines, and multifunction machines having these functions, and particularly relates to a structure for charging a photoreceptor surface using a charging roller.

Conventionally, a photosensitive drum, a charging mechanism that charges the surface of the photosensitive drum, a developing unit that supplies toner to the surface of the photosensitive drum, and a cleaning unit that removes toner adhering to the surface of the photosensitive drum There is known an image forming apparatus using an electrophotographic method. In recent years, as a charging mechanism in this type of image forming apparatus, there is a charging roller type charging mechanism having an elastic layer made of an ionic conductive material (a material having semiconductive characteristics) such as epichlorohydrin rubber. The charging mechanism is widely adopted because it can suppress generation of ozone.
JP-A-7-92752

  An image forming apparatus using this type of charging mechanism has the following problems. In other words, a charging roller having an elastic layer made of an ionic conductive material changes its resistance value when left in a low temperature environment for a long time (if it is not used for a long time), and even if a high charging bias is applied, a small charge is applied. Defects occur, and spotted fog occurs in the image. Therefore, when the charging roller is left for a long time in a low-temperature environment, a bias is applied to the charging roller and an aging operation is performed to reduce the resistance value of the charging roller. It can be avoided.

  However, this aging operation takes a relatively long time in the low temperature environment, and particularly when the photosensitive drum is made of amorphous silicon, the aging operation is performed over a relatively long time. The accumulation of discharge products on the surface of the photosensitive drum increases the friction coefficient of the surface of the photosensitive drum. As a result, when a blade made of urethane rubber is used as a cleaning device for the photosensitive member, there is a problem that a large load is applied to the cleaning blade and the edge of the blade is damaged.

  In Patent Document 1, for the purpose of stabilizing the charging potential on the surface of the image carrier, the surface of the image carrier is charged by a charging unit without performing a transfer operation for a predetermined time during non-image formation. Although the technology is disclosed, there is no description about this problem.

  The present invention has been made to solve the above-described problems, and can form an image that can suppress an increase in the coefficient of friction on the surface of the photosensitive member when aging is performed with a charging bias applied to a charging roller. An object is to provide an apparatus.

  According to a first aspect of the present invention, there is provided a charging roller for charging the surface of the photosensitive member, a bias applying unit for applying a charging bias to the charging roller, and an environmental temperature detecting unit for detecting an environmental temperature of the charging roller. A developing unit for making toner appear on the electrostatic latent image formed on the surface of the photoconductor, and an environmental temperature detected by the environmental temperature detecting unit from a predetermined temperature. A low image development unit that supplies toner to the developing unit at a predetermined time interval when an aging operation is performed in a state where a charging bias is applied to the charging roller by the bias applying unit. Device.

  According to the present invention, when the ambient temperature detected by the ambient temperature detection unit is lower than a predetermined temperature and the aging operation is performed in a state where a charging bias is applied to the charging roller by the bias application unit, Since the toner is supplied to the developing unit at a predetermined time interval, the toner is supplied to the cleaning unit, thereby increasing the polishing effect by the toner and attaching the discharge product to the surface of the photoreceptor. In addition, the toner external additive functions as a lubricant between the photosensitive member and the cleaning blade, and the frictional resistance of the surface of the photosensitive member can be reduced.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the image forming apparatus further includes a charging current detection unit that detects a charging current of the charging roller, and the development control unit is detected by the environmental temperature detection unit. When the ambient temperature is lower than a predetermined temperature and the change in the charging current detected by the charging current detection unit is greater than a predetermined value, the developing unit is supplied with toner. is there.

  According to the present invention, when the environmental temperature detected by the environmental temperature detection unit is lower than a predetermined temperature, in particular, the change in the charging current detected by the charging current detection unit is based on a predetermined value. Only when it is large, that is, when it is considered that it takes a long time to perform the aging operation unless the toner is supplied to the photosensitive member, the developing unit supplies the toner with a predetermined time interval. Therefore, the regular toner supply operation by the developing unit can be suppressed to a necessary minimum, and the change in the charging current detected by the charging current detection unit is larger than a predetermined value. By performing a regular toner supply operation by the developing unit, the accumulated amount of discharge products accumulated on the surface of the photosensitive drum is reduced as much as possible. It is possible to suppress an increase in the friction coefficient of the surface.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the photoconductor is a photoconductor made of amorphous silicon. According to this, when the photoconductor is made of amorphous silicon, the low temperature which is likely to occur in the photoconductor made of amorphous silicon by adopting the invention according to claim 1 or 2 is adopted. It is possible to prevent or suppress an increase in the coefficient of friction on the surface of the photoreceptor due to an aging operation for a long time in the environment.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the development control unit supplies magnetic single-component toner containing a magnetic substance as a component to the development unit. is there. According to this invention, by supplying a magnetic one-component toner containing a magnetic material as a component to the cleaning portion of the photoconductor, the magnetic powder contained in the toner acts as an abrasive and the discharge product adheres to the surface of the photoconductor. Can be efficiently prevented (discharge products adhering to the surface of the photoreceptor are efficiently removed).

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the development control unit supplies toner generated by a pulverization method to the development unit. According to the present invention, the toner generated by the pulverization method is a deformed toner having irregularities on the surface, and by supplying this toner to the developing unit, it is possible to ensure high polishing properties for the photoreceptor.

  According to the present invention, since the frictional resistance of the surface of the photoconductor can be reduced, the frictional force between the two acting when the cleaning blade is in sliding contact with the photoconductor can be reduced, and the edge of the cleaning blade can be reduced. Damage can be prevented.

  FIG. 1 is a cross-sectional view schematically showing an internal configuration of an image forming apparatus according to the present invention. The image forming apparatus according to the present invention is a multifunction machine, a printer, a facsimile machine, or the like that develops an electrostatic latent image using toner by an electrophotographic method. In the present embodiment, the printer 1 will be described as an example of the image forming apparatus.

  In the printer 1, an image forming unit 2 is provided in the printer main body 10. As shown in the figure, the image forming unit 2 forms an image on a sheet, and includes a photosensitive drum 3, a charging unit 4, an exposure unit 5, and a developing unit disposed around the photosensitive drum 3. 6, a transfer unit 7 and a cleaning unit 8 are provided.

  FIG. 2 is a partially enlarged view schematically showing the image forming unit 2. The photoconductor drum 3 is an image carrier that is rotatably supported in the direction of the arrow shown in the drawing. Here, as an example of the image carrier, a photoconductor drum (a-Si) made of amorphous silicon (a-Si) ( a-Si drum) is employed. This a-Si drum is formed by depositing an amorphous silicon film on the surface of a predetermined drum-like body (cylindrical body) by vapor deposition or the like. This amorphous silicon film has a characteristic that the film surface hardness is extremely high, and as a result, the photoconductor has high durability (environment resistance).

  The charging unit 4 uniformly charges the surface (drum surface) of the photosensitive drum 3 to a predetermined potential, for example, about + 250V. The charging unit 4 includes a charging roller 41 disposed opposite to the photosensitive drum 3, and performs charging while pressing the charging roller 41 against the photosensitive drum 3. The charging roller 41 is formed, for example, by forming an elastic layer made of an ion conductive material (a material having a semiconductive property) such as epichlorhydrin rubber on a predetermined core metal so that the roller diameter becomes, for example, about 12 mm. It is.

  The exposure unit 5 is a so-called laser scanner unit that exposes the photosensitive drum 3 with a laser beam. The exposure unit 5 irradiates the drum surface with a laser beam L output from a laser diode based on image data transmitted from an image data storage unit 40 and the like described later, thereby forming an electrostatic latent image on the drum surface. Form. The exposure unit 5 shown in FIG. 2 simply shows the exposure unit 5 in FIG.

  The developing unit 6 makes toner appear on the electrostatic latent image formed on the drum surface to make the image appear. The developing unit 6 includes a developing roller 61 that is disposed so as to face the photosensitive drum 3 in a non-contact manner, a toner storage unit 62 that stores toner, a regulation blade 63 (bread cutting plate), and the like. The regulation blade 63 regulates the amount of toner supplied from the toner storage unit 62 to the developing roller 61 to an appropriate amount. More specifically, the toner adhering to the surface of the sleeve (not shown) of the developing roller 61 in a so-called earing state (magnetic brush state) is cut off from the toner, that is, the layer thickness is regulated. The amount of adhesion is adjusted to be constant. By adjusting the amount of adhesion, a toner thin layer having substantially the same layer thickness is formed on the sleeve.

  The transfer unit 7 is for transferring the toner image onto the paper. Specifically, the transfer unit 7 includes a transfer roller 71 disposed opposite to the photosensitive drum 3, and the sheet P (transfer material) conveyed in the direction indicated by the arrow A is transferred to the photosensitive drum by the transfer roller 71. 3, the toner image that is made visible on the surface of the photosensitive drum 3 is transferred onto the paper P.

  The cleaning unit 8 includes a cleaning blade 81 and the like, and cleans toner remaining on the drum surface after transfer by the transfer unit 7. The cleaning blade 81 has, for example, an end portion that is in pressure contact with the drum surface, whereby residual toner on the drum surface is mechanically removed. Further, the cleaning unit 8 is provided with an unillustrated neutralizing unit (erase light source) (not shown) that neutralizes the surface of the photosensitive member with a neutralizing light beam such as LED light, that is, erases the residual potential (charge). .

  Returning to FIG. 1, the printer 1 includes a paper feeding unit 9 that feeds paper toward the image forming unit 2 (photosensitive drum 3), and a fixing unit 11 that fixes the toner image transferred to the paper. . The paper feed unit 9 includes a paper feed cassette 91 that stores sheets of various sizes, a pickup roller 92 for taking out the stored sheets, a transport path 93 that is a path for transporting the sheets, and a sheet in the transport path 93. A conveyance roller 94 for conveying the sheet is provided, and the sheets fed one by one from the sheet feeding cassette 91 are conveyed toward the nip portion between the transfer roller 71 and the photosensitive drum 3. The paper feeding unit 9 conveys the paper (the paper P) onto which the toner image has been transferred to the fixing unit 11 through the conveyance path 95, and further, the paper fixed by the fixing unit 11 is conveyed to the conveyance roller 96 and the discharge roller. The sheet is conveyed to a sheet discharge tray 12 provided at the upper part of the printer main body 10 by 97.

  The fixing unit 11 includes a heat roller 11a and a pressure roller 11b, and melts toner on the paper by the heat of the heat roller 11a, and applies pressure by the pressure roller 11b to fix the toner image on the paper. .

  FIG. 3 is a block diagram illustrating an example of an electrical configuration of the printer 1. As shown in FIG. 1, the printer 1 includes a network I / F (interface) unit 30, an image data storage unit 40, an operation panel unit 50, a recording unit 60, a sensor unit 70, and a control unit 100.

  The network I / F unit 30 controls transmission / reception of various data to / from an information processing apparatus (external device) such as a PC connected via a network such as a LAN. The image data storage unit 40 temporarily stores image data transmitted from a PC or the like via the network I / F unit 30. The operation panel unit 50 is provided on the front unit of the printer 1 and functions as an input key for inputting various instruction information (commands) from the user or displays predetermined information. The recording unit 60 includes the image forming unit 2, the paper feeding unit 9, and the fixing unit 11, and records (prints) image information on a sheet based on image data stored in the image data storage unit 40. Is to do. The sensor unit 70 includes various sensors provided at various locations of the printer 1. For example, a fixing temperature detection unit 701 that detects the temperature (fixing temperature) of the heat roller 11 a and an in-machine temperature detection unit that detects the in-machine temperature of the printer 1. 702, an in-machine humidity detection unit 703 for detecting the in-machine humidity of the printer 1 and an out-of-machine temperature detection unit 704 for detecting the outside temperature of the printer 1, and various operations and states of the printer 1 are detected. The temperature detected by the outside temperature detection unit 704 and the fixing temperature detection unit 701 is an example of the environmental temperature.

  The control unit 100 includes a ROM (Read Only Memory) that stores a control program of the printer 1, a RAM (Random Access Memory) that temporarily stores data, a microcomputer that reads and executes the control program from the ROM, and the like. The entire apparatus is controlled in accordance with predetermined instruction information input from the operation panel unit 50 and the like, and detection signals from various sensors (the sensor unit 70) provided in various parts of the printer 1. .

  In addition, the control unit 100 functionally includes a charging bias application unit 101, a charging current detection unit 102, and a development control unit 103.

  The charging bias application unit 101 applies a charging bias Vdc to the charging roller 41 (performs charging bias application control). A symbol Vdc indicates a direct current (DC) component of the charging voltage. The charging bias Vdc may be only a DC component, or may be an alternating current (AC) component superimposed thereon. However, the charging potential of the drum surface itself is determined by a DC component bias (DC bias) Vdc.

  The charging current detection unit 102 detects a charging current (DC current) Idc when the charging bias application unit 101 applies the charging bias Vdc to the charging roller 41. This charging current Idc may be detected on the charging roller 41 side, that is, for example, a charging current flowing through the charging roller 41 may be detected, or detected on the photosensitive drum 3 side, that is, for example, flow from the charging roller 41 to the drum surface. The charged current may be detected.

  The development control unit 103 controls the development operation performed by the development unit 6. In particular, in the present embodiment, when the printer 1 is turned on or returns from the sleep state, an aging operation (image formation) is performed. In the case where the preparatory operation is performed, when the internal temperature detected by the internal temperature detection unit 702 is low, an operation of supplying toner regularly (an example of a mode in which a predetermined time interval is left) is performed. 6 to do.

  FIG. 4 is a flowchart showing a series of charging processes by the control unit 100.

  As shown in FIG. 4, when the printer 1 is turned on (YES in step # 1), the control unit 100 detects the fixing temperature (step # 2), and detects the outside temperature and humidity and the inside temperature. In step # 3, it is determined whether or not the condition that the outside temperature is equal to or lower than the temperature T1 and the fixing temperature is equal to or lower than T2 is satisfied (step # 4).

  As a result, the control unit 100 does not complete the aging operation of the charging roller 41 when the condition that the outside temperature is equal to or lower than the temperature T1 and the fixing temperature is equal to or lower than T2 (NO in Step # 4). It is determined whether the condition that the flag indicating ON is ON and the outside temperature is equal to or lower than T1 is satisfied (step # 5). When the condition that the flag is on and the outside temperature is equal to or lower than T1 is satisfied (YES in step # 5), control unit 100 proceeds to the process of step # 7, but does not satisfy the condition. In this case (NO in step # 5), the process proceeds to step # 16.

  When the condition that the outside temperature is equal to or lower than temperature T1 and the fixing temperature is equal to or lower than T2 is satisfied in step # 4 (YES in step # 4), control unit 100 turns on the flag (step # 6). ), The charging bias is set to a predetermined voltage (step # 7). Further, the control unit 100 turns on a drum motor (not shown) that rotationally drives the photosensitive drum 3 and turns on the operation of the static elimination unit (step # 8), and the charging bias set to a predetermined voltage in step # 7. Is applied to the charging roller 41 (step # 9), and the charging current Idc is detected (step # 10).

  Next, the control unit 100 determines whether or not the change in the detected current value of the charging current Idc is in a predetermined state, for example, whether the difference from the current value detected three minutes ago is 1.5 μA or less (Step S100). # 11). This is a situation where the resistance of the charging roller 41 changes greatly when the detected current value changes greatly, and the charging aging must be continued for, for example, the above three minutes. In order to prevent an increase in the frictional resistance between the photosensitive drum 3 and the cleaning blade 81, it is necessary to supply toner to the cleaning unit 8. Therefore, it is detected whether this is the case. .

  When the detected change in the current value is not in a predetermined state (NO in step # 11), the control unit 100 turns on a developing motor (not shown) that drives the developing roller 61 and applies a developing bias to the toner. (Step # 12), toner is supplied to the photosensitive drum 3, and the toner is adhered to the surface of the photosensitive drum 3 as a lubricant (step # 13). As the toner used at this time, a well-known magnetic one-component toner containing a magnetic substance as a component or a toner generated by a well-known pulverization method can be employed. When a magnetic one-component toner is used as the toner, the magnetic powder contained in the toner acts as an abrasive to efficiently prevent discharge products from adhering to the surface of the photoconductor (the discharge adhering to the surface of the photoconductor). The product can be efficiently removed), and when the toner produced by the pulverization method is employed, there is an effect that high polishing properties for the photosensitive drum 3 can be secured.

  Thereafter, the control unit 100 turns off the developing motor and stops the application of the developing bias (step # 14), and executes the aging operation of the charging roller 41 for a predetermined time (step # 15). Control unit 100 repeatedly executes the processes of steps # 10 to # 15 until the detected current value change reaches a predetermined state, and when the detected current value change reaches the predetermined state (YES in step # 11). ), The flag is turned off (step # 16), the application of the charging bias to the charging roller 41 is stopped (step # 17), the drum motor is turned off, and the operation of the charge eliminating unit is turned off (step #). 18) A series of charging processes is terminated.

  As described above, when the charging roller 41 is in a low temperature environment, when the aging operation of the charging roller 41 is performed, toner is periodically supplied from the developing unit 6 to the photosensitive drum 3 to thereby clean the cleaning unit 8. When the toner is supplied to the surface of the photosensitive drum 3, the polishing effect by the toner is enhanced, and the discharge product can be prevented from adhering to the surface of the photosensitive drum 3. By functioning as a lubricant with the cleaning blade 81, the frictional resistance of the surface of the photosensitive drum 3 can be lowered. As a result, it is possible to prevent the edge of the cleaning blade 81 from being damaged during cleaning.

  In addition, since the toner is periodically supplied by the developing unit 6 only when the charging roller 41 is in a low temperature environment and the charging current of the charging roller 41 changes greatly, the developing unit 6 The regular toner supply operation by the developing unit 6 can be performed when the change in the charging current is larger than a predetermined value. Thus, the accumulation amount of the discharge product accumulated on the surface of the photosensitive drum 3 can be reduced as much as possible, and an increase in the friction coefficient on the surface of the photosensitive drum 3 can be suppressed.

  In addition, this case includes the following forms instead of or in addition to the above embodiments.

  (1) When a polishing roller for polishing the surface of the photosensitive drum 3 is provided in the cleaning unit 8, the discharge adhered to the surface of the photosensitive drum 3 by supplying toner to the polishing roller. The product can be removed, and the frictional resistance of the surface of the photosensitive drum 3 can be further reduced. Thereby, it is possible to further prevent the edge of the cleaning blade 81 from being damaged.

  (2) In the processing of the flowchart shown in FIG. 4, when the printer 1 is powered on, the processing of steps # 1 to # 18 is executed. As another example of the case of being left unattended, there is a sleep state (energy saving mode), for example, and it is preferable to execute the processes of steps # 1 to # 18 even when returning from the sleep state.

1 is a cross-sectional view schematically showing an internal configuration of an image forming apparatus according to the present invention. 2 is a partially enlarged view schematically showing an image forming unit. FIG. 2 is a block diagram illustrating an example of an electrical configuration of a printer. FIG. It is a flowchart which shows a series of charging processes by a control part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 2 Image formation part 3 Photosensitive drum 4 Charging part 6 Developing part 8 Cleaning part 41 Charging roller 61 Developing roller 62 Toner storage part 70 Sensor part 81 Cleaning blade 100 Control part 101 Charging bias application part 102 Charging current detection part 103 Development Control unit 701 Fixing temperature detection unit 702 In-machine temperature detection unit 703 In-machine humidity detection unit 704 Outside temperature detection unit

Claims (5)

A charging roller for charging the surface of the photoreceptor;
A bias applying unit for applying a charging bias to the charging roller;
An environmental temperature detector for detecting an environmental temperature of the charging roller;
A developing section for making toner appear on the electrostatic latent image formed on the surface of the photoconductor to reveal the image;
When the aging operation is performed in a state where the environmental temperature detected by the environmental temperature detection unit is lower than a predetermined temperature and a charging bias is applied to the charging roller by the bias applying unit, the developing unit is predetermined. An image forming apparatus comprising: a development control unit that supplies toner at a predetermined time interval. A charging current detector for detecting a charging current of the charging roller;
The development control unit is a case where the environmental temperature detected by the environmental temperature detection unit is lower than a predetermined temperature, and the change in the charging current detected by the charging current detection unit is based on a predetermined value. The image forming apparatus according to claim 1, wherein when the size is large, toner is supplied to the developing unit.   The image forming apparatus according to claim 1, wherein the photoconductor is a photoconductor made of amorphous silicon.   The image forming apparatus according to claim 1, wherein the development control unit supplies magnetic single component toner containing a magnetic material as a component to the development unit.   The image forming apparatus according to claim 1, wherein the development control unit supplies toner generated by a pulverization method to the development unit.

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