JP2009288416A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of maintaining image quality high by making internal environment environment suitable for image forming processing, when the internal environment is the environment affecting the image forming processing. <P>SOLUTION: The image forming apparatus includes: an intermediate transfer belt 24 which carries a toner image transferred to a transfer material; a heater 35 which is arranged in the vicinity of the intermediate transfer belt 24; a calculation section 37 which calculates the resistance value of the intermediate transfer belt 24 from the current value of the intermediate transfer belt 24 detected before an image forming operation; and a control circuit section 36 which heats the intermediate transfer belt 24 by the heater 35 until the resistance value calculated by the calculation section 37 becomes a threshold or less, when the resistance value exceeds the threshold. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image forming method, such as a copying machine, a printer, or a facsimile machine, or a multifunction machine having these functionally.

  Conventionally, for example, an intermediate transfer belt (intermediate transfer belt) that uses toner as a developer and forms a toner image to be transferred onto a transfer material by a plurality of developing devices arranged in parallel, such as a color printer employing a tandem method. And a plurality of transfer rollers that transfer a toner image formed on the surface of the intermediate transfer belt in a nip manner in cooperation with the intermediate transfer belt.

  In this case, when the transfer image is transferred to the transfer material (primary transfer) while the transfer material is nipped and conveyed by the cooperation of the intermediate transfer belt and the transfer roller, a transfer bias is applied to each transfer roller.

  The toner image primarily transferred to the intermediate transfer belt is superimposed on the intermediate transfer belt in accordance with the image data, and is subjected to secondary transfer collectively by a secondary transfer bias applied to the secondary transfer portion. .

  At this time, if the primary transfer current is increased, the primary transfer efficiency is increased, but the charge amount of the toner image transferred onto the intermediate transfer belt is also increased, and the adsorbing power of the toner image on the intermediate transfer belt is increased. The amount of current required during transfer increases.

  However, when an excessive voltage is applied at the time of secondary transfer, there is a problem that a white spot image is detected due to discharge between the transfer material and the intermediate transfer belt.

  Therefore, the bias settings at the time of primary transfer and secondary transfer are set in consideration of the primary transfer property and the secondary transfer property, respectively.

  However, it is known that the charge amount of the toner image transferred onto the intermediate transfer belt increases as the resistance value of the intermediate transfer belt increases.

  In addition, since the voltage applied during the secondary transfer also depends on the resistance value of the intermediate transfer belt, the optimum bias setting value varies depending on the resistance value of the intermediate transfer belt.

  In general, the intermediate transfer belt uses EPDM, hydrin, or the like as a conductive material. However, since these have environmental dependence, the resistance value becomes high in a low temperature and low humidity environment, and in a high temperature and high humidity environment. There is a tendency that the resistance value decreases.

  For this reason, when determining the current value applied at the time of transfer in order to stabilize the image quality against such variation in resistance value, the resistance value of the intermediate transfer belt is taken into consideration when the resistance value of the intermediate transfer belt is taken into consideration. Based on the detection value from the temperature / humidity detection sensor or the like, the image is formed after correcting to a primary transfer bias or a secondary transfer bias suitable for the environment.

In order to improve such correction accuracy, there is a technique for detecting the current value flowing through the intermediate transfer belt, calculating the resistance value of the intermediate transfer belt using the current value, and applying the optimum transfer current. It is known (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2000-147961

  However, if the resistance value of the intermediate transfer belt becomes too high in a low-temperature and low-humidity environment, a high voltage is applied with a small amount of applied current, so even if the minimum current required for primary transfer is applied, There is a problem that the charge amount of the toner image increases and a white spot image appears due to a discharge phenomenon between the transfer material and the intermediate transfer belt in the secondary transfer portion before reaching a current value that can satisfy the secondary transfer property. It was happening.

  For this reason, the secondary transferability becomes unsatisfactory, and the optimum transfer current setting range does not exist, and it is difficult to maintain the image quality even if the resistance value of the intermediate transfer belt is detected. There was a problem.

  Therefore, in consideration of the above circumstances, the present invention improves the image quality by making the internal environment suitable for the image forming process when the internal environment has an adverse effect on the image forming process. An object of the present invention is to provide an image forming apparatus capable of maintaining high quality.

  The image forming apparatus according to the present invention includes an intermediate transfer member that carries a toner image to be transferred to a transfer material, a heater that is disposed near the intermediate transfer member, and a current value of the intermediate transfer member that is detected before the image forming operation. A calculation unit for calculating the resistance value of the intermediate transfer body from the above, and when the resistance value calculated by the calculation unit exceeds a threshold value, the intermediate transfer body is heated by the heater until the resistance value becomes equal to or less than the threshold value. And a control circuit unit.

  At this time, the control circuit unit preferably drives the intermediate transfer member when the intermediate transfer member is heated by the heater.

  Furthermore, the image forming method of the present invention calculates a resistance value of the intermediate transfer body based on the current value detection step of detecting the current value of the intermediate transfer body before the image forming process and the detected current value of the intermediate transfer body. The resistance value calculating step is compared with the calculated resistance value and a threshold value, and when the resistance value is not greater than the threshold value, a heating step for heating the intermediate transfer member until resistance value ≦ threshold value is executed. And

  The image forming apparatus of the present invention maintains high image quality by making the internal environment suitable for image forming processing when the internal environment is adversely affecting the image forming processing. can do.

  Next, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram of a tandem color printer as an image forming apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of a main part of the image forming apparatus according to an embodiment of the present invention, and FIG. FIG. 4 is a flowchart showing an example of the relationship between the belt resistance value and the heating time in the image forming apparatus according to an embodiment of the present invention. It is explanatory drawing.

(overall structure)
As shown in FIG. 1, a tandem color printer 11 as an image forming apparatus according to an embodiment of the present invention stores a transfer paper (not shown) as a transfer material inside a printer main body 12. A paper cassette 13, a paper supply unit 14 that takes out transfer paper from the paper supply cassette 13, and an image formation processing unit 15 that performs image formation processing on transfer paper supplied from the paper supply cassette 13 or a manual feed tray (not shown). The transfer paper transport path 16 transports the transfer paper supplied from the paper feed cassette 13 or the manual feed tray, the registration sensor 17 detects the transfer paper transported by the transfer paper transport path 16, and the transfer paper transport path 16. Image forming processing (primary transfer) is performed on the registration roller pair 18 that controls the alignment and conveyance timing of the transferred transfer paper and the transfer paper transported on the transfer paper transport path 16 by the image forming processing unit 15. A secondary transfer unit 19 for transferring the toner image, and a fixing unit 20 for fixing the toner image transferred by the secondary transfer unit 19 to the transfer paper, the.

(Image formation processing unit 15)
For example, the image forming processing unit 15 employs a tandem system that performs image forming processing using toner (developer) of four colors of yellow (Y), magenta (M), cyan (C), and black (K). ing. In the following description, only in the case of color designation, the symbol of each arithmetic numeral is attached with a color (Y, M, C, K) in parentheses, and in the common case, only the arithmetic numeral is included. A description will be given with reference numerals.

  The image forming processing unit 15 includes a plurality of toner containers 21 storing replenishment toner corresponding to each color (Y, M, C, K), and each color toner included in print data transmitted from a personal computer or the like. A plurality of amorphous silicon photosensitive drums 22 that form toner images (transfer images) based on image data to be transferred, a plurality of developing units 23 that supply toner to the respective photosensitive drums 22, and a photosensitive drum 22 An endless intermediate transfer belt 24 to which the formed toner image is primarily transferred, a photosensitive drum 22 (K) disposed on the most downstream side in the rotational movement direction of the intermediate transfer belt 24, and the secondary transfer unit 19. A toner density sensor 25 for measuring the reflection density of the toner image on the intermediate transfer belt 24 and a toner density sensor 25 disposed on the opposite side of the toner density sensor 25 on the surface of the intermediate transfer belt 24. A cleaning device 26 for removing deposited the residual toner or the like, and includes an exposure device 27 for emitting a light beam flux on each photosensitive drum 22, a.

(Photosensitive drum 22)
Each of the photosensitive drums 22 is for carrying a toner image of each color on the surface thereof based on the beam flux emitted from the exposure device 27 and transferring the toner image to the intermediate transfer belt 24. In addition, it is disposed below the intermediate transfer belt 24. Further, around each photosensitive drum 22, a charging device 28, an exposure device 27, a developing device 23, a primary transfer roller 29, a cleaning device 30, and a charge eliminating device 31 are arranged in the order of the transfer process.

  The toner image transferred onto the intermediate transfer belt 24 at each primary transfer portion constituted by the cooperation of the photosensitive drum 22 and the primary transfer roller 29 passes through the transfer paper transport path 16 from the paper feed cassette 13 or the manual feed tray. The image is transferred by the secondary transfer unit 19 to the transfer paper conveyed through.

(Developer 23)
Each developing device 23 basically has the same configuration and is arranged adjacent to the lower side of the intermediate transfer belt 24 along the rotational movement direction. The specific configuration of the developing device 23 is not limited to the illustrated example as long as it is a known configuration, and is omitted here.

(Intermediate transfer belt 24)
The intermediate transfer belt 24 is an endless belt disposed in the printer body 12 so as to extend in the horizontal direction. The intermediate transfer belt 24 may maintain a tension state with the driven roller (backup roller) 33 as a tension roller, or a tension roller may be provided separately from the driving roller 32 and the driven roller 33. The state may be maintained.

  The secondary transfer roller 34 of the secondary transfer unit 19 is opposed to the surface of the intermediate transfer belt 24 that is folded back by the driven roller 33 so that the secondary transfer roller 34 and the intermediate transfer belt 24 are in contact with each other. The toner image formed on the intermediate transfer belt 24 is transferred to the transfer paper at the same time as the transfer paper is nipped and conveyed in cooperation with

  Further, the transfer paper on which the toner image is transferred by the secondary transfer unit 19 is fixed by the fixing unit 20 through the transfer paper transport path 16 and then guided to the end of the transfer paper transport path 16 to be sent to the printer main body 12. The sheet is discharged toward a sheet discharge tray 12a that is also used as the upper surface of the sheet.

  Further, a heater 35 is disposed inside the intermediate transfer belt 24 as shown in FIG.

  The heater 35 may be a known heating means such as a heating wire, a sheet type, or a halogen lamp. Further, the heaters 35 can be disposed at appropriate positions on the intermediate transfer belt 24 or on substantially the entire surface on one side in the rotational movement direction according to the type thereof. Further, the driving of the heater 35 is controlled by the control circuit unit 36. The intermediate transfer belt 24 detects a current value of the intermediate transfer belt 24 using a detection sensor (not shown) or the like, and the current value is supplied to a calculation unit 37 for calculating a resistance value of the intermediate transfer belt 24. Is output.

(Control circuit part 36)
The control circuit unit 36 controls heating (lighting) of the heater 35 based on the resistance value of the intermediate transfer belt 24 calculated by the calculation unit 37.

  The control circuit unit 36 receives print data output from a personal computer or the like, and based on the print data and the image data included in the print data, the paper feeding unit 14, the image formation processing unit 15, the secondary transfer unit The driving of the unit 19, the fixing unit 20, the driving roller 32, and the like is controlled. The control circuit unit 36 controls the various drive systems described above based on various control programs related to the overall image forming processing stored in the ROM 38, and supplies toner to each developer 23 and applies it to the developer 23. Calibration such as development conditions such as bias voltage, charging bias applied to the charging device 28, exposure conditions such as laser power of the exposure device 27, erase light quantity of the static elimination device 31, etc. is executed. At this time, the received image data and the like are stored in the hard disk drive 39, and various settings (for example, the number of copies to be printed and the enlargement / reduction ratio) of the received print data are stored in the RAM 40.

  The ROM 38 also stores a control program for driving the heater according to the present invention, and the control circuit unit 36 for executing the heater drive control program constitutes a microcomputer. Further, the ROM 38 stores a threshold value for heater heating control according to the present invention. The control circuit unit 36 determines the resistance value of the intermediate transfer belt 24 calculated by the calculation unit 37 and the threshold value stored in the ROM 38. In addition to the comparison, the control circuit unit 36 controls the driving of the heater 35, the driving roller 32, and the like according to the comparison result.

  Next, a control example of heater heating control by the control circuit unit 36 in the image forming apparatus of the present invention will be described with reference to FIG.

(Step S1)
In step S1, the control circuit unit 36 detects the current value of the intermediate transfer belt 24 using a resistance value detection sensor (not shown) before the image forming process, and stores the detected value in the RAM 40 or the like. The process proceeds to S2.

(Step S2)
In step S2, the control circuit section 36 causes the calculation section 37 to calculate the resistance value of the intermediate transfer belt 24 based on the current value of the intermediate transfer belt 24 detected in step S1, and the resistance value as the calculation result is stored in the RAM 40. And the process proceeds to step S3.

(Step S3)
In step S3, the control circuit unit 36 compares the resistance value calculated in step S2 with a threshold value stored in advance in the ROM 38 or the like. If resistance value> threshold value, the internal environment of the printer body 12 is low. It is determined that the humidity is low, and the process proceeds to step S4. If the resistance value is not greater than the threshold value, it is determined that the in-machine environment of the printer main body 12 is appropriate, and the process proceeds to step S9.

  The threshold value in this step S3 varies depending on, for example, the size of the internal space and the overall length, full width, material, thickness, etc. of the intermediate transfer belt 24, but in the range of 9.1 to 10.5 (log Ω · cm). This is preferably set, and in this embodiment, it is 10.1 (log Ω · cm).

(Step S4)
In step S4, the control circuit unit 36 drives (lights) the heater 35 and proceeds to step S5.

(Step S5)
In step S5, the control circuit unit 36 drives the drive roller 32 to rotate the intermediate transfer belt 24 in order to uniformly heat the intermediate transfer belt 24, and proceeds to step S6.

  As described above, step S5 may be omitted depending on the type of heater 35, the arrangement conditions, and the like. Further, when the heater 35 is disposed near the outside of the intermediate transfer belt 24, it is difficult to uniformly heat the intermediate transfer belt 24 without driving the intermediate transfer belt 24. Is driven (the intermediate transfer belt 24 is rotated). Further, FIG. 4 shows an example of a change in resistance value of the intermediate transfer belt 24 accompanying the driving (lighting) of the heater 35.

(Step S6)
In step S6, the control circuit unit 36 calculates and monitors the resistance value of the intermediate transfer belt 24 after driving the heater 35, and monitors whether or not the current resistance value ≦ threshold, and the resistance value ≦ threshold. If YES in step S7, the process proceeds to step S7. If resistance value> threshold is still satisfied, the process loops to step S4 to repeat steps S4 to S6.

(Step S7)
In step S7, the control circuit unit 36 stops driving (lighting) the heater 35 and proceeds to step S8.

(Step S8)
In step S8, the control circuit unit 36 stops driving the drive roller 32 and proceeds to step S9.

(Step S9)
In step S9, the control circuit 36 starts the actual image forming process and ends this routine because the in-machine environment is appropriate.

  The control circuit 36 starts step S1 at the time when the image forming process is completed.

  In the above configuration, the experiment was performed at the actual machine level. In addition, as the determination of the image quality, as the evaluation pattern, 100% printing was performed on the entire surface with two colors superimposed, and the determination of the density and the occurrence of white spots was performed.

  At this time, a solid image having a toner density of 1.2 or less after the secondary transfer was defined as NG (x), and a white dot confirmed visually was defined as NG (x).

  Further, in the experiment, the resistance value of the intermediate transfer belt 24 in the normal temperature environment (23.5 ° C. 50%) was 10.0 LogΩ, but the resistance value of the intermediate transfer belt 24 in the low temperature and low humidity environment (10 ° C. 15%). Is changed to 10.6 LogΩ, and the environmental temperature control (heater heating control) of the present invention is used (FIG. 5A), and the environmental temperature control (heater heating control) of the present invention is not used. In this case (Fig. 5B), the superiority of the image quality was confirmed.

  As a result of the experiment, when the environmental temperature control according to the present invention is used, the low temperature and low humidity environment changes so as to approach the normal temperature environment by turning on the heater 35, and accordingly, the resistance value of the intermediate transfer belt 24 becomes 10.6 LogΩ · It has been found that there is a set area in which a white spot image does not appear while the toner density of the solid image after the secondary transfer is 1.2 or more while decreasing from cm to 10.1 LogΩ · cm.

  Therefore, the image quality can be maintained at a high quality by setting the transfer current under such a setting area.

  When the environmental temperature control of the present invention is not used, the resistance value of the intermediate transfer belt 24 remains high, and it is difficult to ensure the toner density of the solid image after the secondary transfer is 1.2. In addition, the image quality cannot be maintained because there is no region where no white spot image appears.

  Moreover, the conditions of the peripheral members at the time of each experiment are as follows.

Intermediate transfer belt 24
Material PVDF + Elastic rubber (CR + ECO + EPDM) + PTFE urethane coat Inner diameter φ242.0 (mm)
Thickness 450 ± 50 (μm) [base material 100, elastic rubber 450, coat 1.5]
Resistivity Front surface: 9.7 [log (Ω / □)] Back surface: 9.7 [log (Ω / □)]
<1000V 10sec at 22 ° C 50% Rh>
Line speed 173.22 mm / sec
Heater 35
Output 4.5W × 2
Primary transfer roller 29
Material Foam EPDM
Outer diameter φ16.0 (mm) (Core metal diameter φ6 (mm))
Width 217 (mm)
Resistance value 6.0 [log (Ω)]
<-500V 10sec at 22 ° C 50% Rh>
Hardness 35 ± 5 (°) (Asker C)
Secondary transfer roller 34
Material Foam EPDM
Outer diameter φ18.80 (mm)
Core diameter φ6.0 (mm)
Width 216.5 (mm)
Resistance value 7.3 [log (Ω)]
<-1 kV 10 sec at 22 ° C. 50% Rh>
Hardness 32 (°) (Asker C)
In the above embodiment, the image forming apparatus according to the present invention is applied to the tandem color printer 11. However, the image forming apparatus can be applied to all image forming apparatuses such as a copying machine and a multifunction machine. is there.

1 is an explanatory diagram of a tandem color printer as an image forming apparatus according to an embodiment of the present disclosure. 1 is an explanatory diagram of a main part of an image forming apparatus according to an embodiment of the present invention. FIG. 5 is a flowchart of a control routine of a control circuit unit in the image forming apparatus according to an embodiment of the present invention. FIG. 6 is a graph explanatory diagram illustrating an example of a relationship between a belt resistance value and a heating time in the image forming apparatus according to an embodiment of the present invention. (A) is a chart of experimental results for confirming superiority in image quality when the environmental temperature control (heater heating control) of the present invention is used, and (B) does not use the environmental temperature control (heater heating control) of the present invention. 6 is a chart of experimental results for confirming the superior difference in image quality in the case of image quality.

Explanation of symbols

11. Color printer (image forming apparatus)
19 ... secondary transfer unit 24 ... intermediate transfer belt (intermediate transfer member)
29 ... Primary transfer roller 34 ... Secondary transfer roller 35 ... Heater 36 ... Control circuit unit 37 ... Calculation unit

Claims (3)

  An intermediate transfer member carrying a toner image to be transferred to a transfer material, a heater disposed in the vicinity of the intermediate transfer member, and a resistance value of the intermediate transfer member from a current value of the intermediate transfer member detected before an image forming operation And a control circuit unit that heats the intermediate transfer member by the heater until the resistance value is equal to or lower than the threshold value when the resistance value calculated by the calculation unit exceeds the threshold value. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the intermediate transfer member is driven when the intermediate transfer member is heated by the heater.   A current value detecting step for detecting the current value of the intermediate transfer member before the image forming process; a resistance value calculating step for calculating a resistance value of the intermediate transfer member based on the detected current value of the intermediate transfer member; and the calculated resistance And a heating step of heating the intermediate transfer member until the resistance value ≦ the threshold value is satisfied if the resistance value> the threshold value is not compared.

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