JP2006163266A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED To extend the life of a transfer roller.
The transfer roller life is determined by determining the degree of roller deterioration from the impedance of the transfer roller obtained from the results of ATVC, PTVC, etc., and changing the reverse bias sequence when the degree of deterioration has been set in advance. To prolong life.
[Selection] Figure 1

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile.

  Conventionally, in an electrophotographic image forming apparatus and an electrostatic recording image forming apparatus, a corona charger, a roller charger, and the like are provided as means for uniformly applying a charge to the back surface of a transfer material in order to transfer toner onto a transfer material such as paper. Brush chargers, blade chargers and the like have been used.

  However, the corona charger has a problem that ozone is generated at the time of charging or discharging and power consumption is large.

  Therefore, recently, contact chargers that generate less ozone and consume less power are often used. The contact charger uses a contact charging member having conductivity.

  As described above, the contact charging member has various shapes such as a roller shape, a brush shape, and a blade shape. From the viewpoint of durability, a roller-shaped transfer member (hereinafter referred to as “transfer roller”) is selected. Often done.

  In order to perform the transfer uniformly, the transfer roller is generally adjusted in resistance to the middle resistance region by dispersing a conductive filler imparting conductivity such as carbon black or metal oxide in the polymer elastomer material. However, the dispersion uniformity is not sufficient in manufacturing, and there is a problem that uneven resistance in the circumferential direction (circumferential unevenness) occurs, and as a result, uniform transfer cannot be performed.

  As a countermeasure against this circumferential unevenness, for example, a transfer formed by dispersing an ion conductive polymer represented by a polymer that binds a quaternary ammonium base or a block type polymer having a segment of polyethylene-epichlorohydrin copolymer or the like. The number of cases where members are used is increasing.

  Such a transfer member having ionic conductivity also has a problem that resistance variation due to the environment (absolute water content: weight of water contained in 1 kg of air) is large.

  However, this problem can be countered by adding so-called environmental control in which set values are provided for each environment (for example, temperature, humidity, and absolute water content). For example, it can be coped with by ATVC control (Active Transfer Voltage Control) (for example, refer to Patent Document 1). This is to detect the resistance of the transfer roller by applying a desired constant current from the transfer roller to the photosensitive drum during the non-printing process (non-image forming process) of the image forming apparatus and holding the voltage value at that time. In addition, a constant voltage corresponding to the resistance value is applied to the transfer roller as a transfer voltage during transfer in the printing process.

  As another applied transfer voltage control, there is a PTVC control (Programmable Transfer Voltage Control) (for example, see Patent Document 2). The ATVC control described above performs resistance detection of the transfer roller by constant current control, whereas PTVC control is performed only by constant voltage control, so that the circuit is simplified and the detection accuracy is improved. More specifically, a constant voltage is applied when the resistance of the transfer roller is detected, the output current value flowing through the photosensitive drum at this time is detected, and the voltage value is changed from the difference between the current value and the set current value to obtain a desired setting. The voltage that satisfies the flow of the current value is determined.

  Further, the transfer member having the ionic conductivity described above has a problem that when a current having the same polarity is applied continuously, the resistance value is increased.

This resistance increase of the ion conductive roller can be countered by applying a bias of both poles at a predetermined interval, and the transfer applied to the transfer member when the toner image is transferred onto a transfer material such as paper. A bias having a polarity opposite to that of the bias is applied at a predetermined timing. (For example, refer to Patent Document 2).
JP-A-2-123385 JP-A-5-181373

  However, conventionally, the ratio (time and number of times) at which a reverse polarity transfer bias is applied is applied to a transfer member when transferring a toner image onto a transfer material such as paper due to the productivity of the apparatus. Since it is sufficiently smaller than the transfer bias, the life of the transfer roller could not be extended beyond a certain level.

  Depending on the purpose of use of the user, it is possible to reduce the productivity of the apparatus to some extent and increase the ratio of applying a reverse bias to the transfer member.

  The present invention has been proposed in view of the above problems, and the invention according to claim 1 of the image forming apparatus according to the present invention includes an image carrier on which a toner image is formed, and the image carrier. A transfer member disposed in contact with the body, and the transfer member is inserted into a transfer portion between the image carrier and the transfer member, and a transfer bias is applied to the transfer member, whereby a transfer bias is applied to the transfer member. In the image forming apparatus for transferring the toner image to the transfer body, a sequence for outputting a transfer bias having a polarity opposite to that of the transfer bias and a means for detecting a degree of deterioration of the transfer member are provided, and the transfer portion includes the transfer body. When a transfer bias is applied to the transfer member in a state in which no transfer is present, the degree of deterioration of the transfer member is detected by means for detecting the degree of deterioration of the transfer member. polarity Characterized by comprising a mode of changing the sequence of the transfer bias.

  The invention according to claim 2 is based on a detected current value or a calculated current value that flows through the transfer member when a transfer bias is applied to the transfer member without the transfer target being interposed in the transfer portion. It is characterized by detecting the degree of deterioration.

  The invention according to claim 3 is based on a detection voltage value or a calculated voltage value applied to the transfer member when a transfer bias is applied to the transfer member in a state where the transfer target is not interposed in the transfer portion. It is characterized in that the degree of deterioration of the transfer member is detected.

  The invention according to claim 4 includes an environmental sensor that detects temperature and humidity around the transfer portion, and is detected when a transfer bias is applied to the transfer member in a state where the transfer target is not interposed in the transfer portion. The deterioration degree of the transfer member is detected based on the temperature / humidity information.

  According to a fifth aspect of the present invention, there is provided display means for prompting a user to select whether or not to change the reverse bias transfer bias sequence when the detected degree of deterioration reaches a certain value. It is characterized by having.

  The invention according to claim 6 is characterized in that the image carrier is a photosensitive member.

  The invention according to claim 7 is characterized in that the image carrier is an intermediate transfer member.

  The invention according to claim 8 is characterized in that the transfer member is a conductive member having ion conductivity.

  In the present invention, the degree of deterioration of the transfer roller is obtained from the resistance value of the transfer roller obtained from the result of ATVC or PTVC, and when the degree of deterioration of the transfer roller reaches a preset value, the reverse bias sequence is changed. As a result, the life of the transfer roller can be extended.

Example 1
FIG. 1 shows an image forming apparatus according to Embodiment 1 as an example of an image forming apparatus according to the present invention. The image forming apparatus shown in the figure is an electrophotographic printer, and the figure is a longitudinal sectional view showing a schematic configuration thereof.

  The image forming apparatus shown in FIG. 1 includes a drum-type electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 1 as an image carrier inside an image forming apparatus main body M. The photosensitive drum is rotationally driven at a predetermined process speed (circumferential speed) in the direction of arrow R1 by a driving means (not shown).

  A contact charging member 2 as contact charging means is in contact with the surface of the photosensitive drum 1. The surface of the photosensitive drum 1 is uniformly charged (primarily charged) to a predetermined polarity and potential by a charging bias applied to the contact charging member 2 by a charging bias application power source (not shown). In the present embodiment, the contact charging member 2 is a roller-shaped charging roller. The contact charging member 2 is driven to rotate in the direction of arrow R2 by the rotation of the photosensitive drum 1 in the direction of arrow R1.

  A laser beam scanner 3 as an image exposure unit outputs a laser beam L that is on / off modulated corresponding to image information input from an external device such as an image scanner (not shown) or a computer (not shown). Then, the charged surface of the photosensitive drum 1 is scanned and exposed. By this scanning exposure, an electrostatic latent image corresponding to target image information is formed on the surface of the photosensitive drum 1.

  In the developing device (developing device) 4, the developer (toner) is carried on the surface of the developing sleeve 4 a and is conveyed to a developing position facing the surface of the photosensitive drum 1 by the rotation of the developing sleeve 4 a. A developing bias is applied to the developing sleeve 4a by a developing bias applying power source (not shown), whereby the toner on the developing sleeve 4a is attached to the electrostatic latent image on the surface of the photosensitive drum 1 and the electrostatic latent image is converted into toner. Develop as an image.

  The paper feed cassette 5 stores a transfer material P such as paper or transparent film (hereinafter referred to as “paper” instead of “transfer material” as appropriate). The paper feed roller 6 is driven based on the paper feed start signal, the transfer material P in the paper feed cassette 5 is fed one by one, passes through the registration roller 7 and the paper path 8a, and the photosensitive drum 1 and the transfer roller ( It is introduced at a predetermined timing into a transfer nip portion (transfer portion) T which is a contact nip portion with the transfer member 9. That is, the transfer of the transfer material P is controlled by the registration roller 7 so as to synchronize with the timing at which the leading end of the toner image on the photosensitive drum 1 reaches the transfer nip T.

  The transfer material P supplied to the transfer nip T is sandwiched and conveyed by the transfer nip T, and at this time, a transfer bias controlled to a predetermined level is applied to the transfer roller 9 from a transfer bias application power source (not shown). . The control of the transfer roller 9 and the transfer bias will be described in detail later. By applying a transfer bias having a polarity opposite to that of the toner to the transfer roller 9, the toner image on the photosensitive drum 1 is electrostatically transferred onto the surface of the transfer material P at the transfer nip T.

  The transfer material P that has received the transfer of the toner image at the transfer nip T is separated from the photosensitive drum 1 and conveyed to the fixing device (fixing means) 11 through the paper path 8b. The transfer material P is nipped and conveyed by a fixing nip portion formed between the fixing roller 11a and the pressure roller 11b of the fixing device 11. At this time, the toner image is fixed on the surface by being heated and pressurized.

  On the other hand, after the toner image has been transferred, the toner (residual toner), paper dust, and the like remaining on the surface of the photosensitive drum 1 that has not been transferred to the transfer material P at the time of transfer are removed by the cleaning device 10 and then used for image formation. The

  When image formation is performed only on the surface (first surface) of the transfer material P after the toner image is transferred, the transfer material P is guided to the switching member 12 and passes through the paper path 8c. 14 is discharged. Thereby, the image formation on one side with respect to one transfer material P is completed.

  On the other hand, when image formation is performed on both surfaces (first surface and second surface) of the transfer material P, the transfer material P with the toner image fixed on the first surface (front surface) is the switching member 12. Is switched to the transport path 8d. The transfer material P guided to the transport path 8 d is once introduced into the reversing path 8 e by the switching member 15, then the transport direction is reversed, and is further transported to the intermediate path 8 f by switching the switching member 15. Thereafter, the transfer material P is again supplied to the transfer nip portion T by the registration roller 7 or the like, the toner image is transferred to the second surface (back surface), and further fixed by the fixing device 11, and then the paper path 8c is passed. Then, the paper is discharged onto the paper discharge tray 14 by the paper discharge roller 13. As a result, image formation on both sides of one transfer material P is completed.

  In the above-described image forming apparatus, the transfer roller 9 which is a contact rotation type transfer member is formed by a sponge roller having ionic conductivity. The transfer roller 9 is configured by providing a sponge rubber layer 9a in a cylindrical shape on the outer peripheral surface of the cored bar 9b.

  Next, control for determining a transfer bias for transferring the toner image on the photosensitive drum 1 to the transfer material P will be described.

  The idle rotation of the image forming apparatus from when the user presses the copy button or starts the printer operation until the actual image forming operation is performed is referred to as pre-rotation. Therefore, for the transfer roller 9 as a transfer member, the transfer material P and the toner image formed on the photosensitive drum 1 are transferred to the transfer nip portion after the user presses the copy button or starts the printer operation. The idle rotation until T is reached is the pre-rotation.

  During this pre-rotation, a predetermined voltage is applied to the transfer roller, and a current corresponding to the voltage is detected by a detecting means (not shown). The resistance value of the transfer roller can be obtained based on the detection result. The transfer bias is determined by the resistance value of the transfer roller, the type of transfer material, and the temperature and humidity environment conditions.

  Next, a case where the image forming apparatus shifts to the transfer roller life extension mode will be described with reference to FIGS. FIG. 2 is a flowchart relating to a transfer reverse bias sequence change, and FIG. 3 is a diagram showing an outline of a bias sequence applied to the transfer member.

  In FIG. 2, a bias voltage to be applied to the transfer roller during the image forming operation is determined by applying a predetermined voltage to the transfer roller during the aforementioned pre-rotation to obtain a resistance value of the transfer roller (201).

  Since the progress of the increase in the resistance value of the transfer roller becomes an index indicating the deterioration of the transfer roller, it is possible to determine the degree of deterioration of the transfer roller from the resistance value of the transfer roller.

  When the resistance value of the transfer roller indicating the predetermined degree of deterioration of the transfer roller is R1, if the resistance value of the transfer roller obtained in (201) of FIG. 2 is larger than R1, the process proceeds to (203) of FIG. When the resistance value of the transfer roller is equal to or less than R1, the image forming operation is performed in the normal mode (205). In (203), it is determined whether or not the transfer roller life extension mode is set. If the transfer roller life extension mode is set, the image forming operation is performed in the transfer roller life extension mode (204). If the transfer roller life extension mode is not set, the image forming operation is performed in the normal mode (205).

  It is also possible to prepare a plurality of setting values for the degree of deterioration of the transfer roller so that they can be selected according to the user's purpose of use.

  3A is a transfer bias application sequence in the normal mode, and FIG. 3B is a transfer bias application sequence in the transfer roller life extension mode.

  During the image forming operation, a transfer bias value determined by applying a predetermined voltage to the transfer roller during the pre-rotation is applied, and after the image forming operation is completed, a transfer reverse bias is applied as a cleaning bias for the transfer roller.

  In the transfer roller life extension mode, the application time of the transfer reverse bias applied in the transfer roller cleaning process is set longer than in the normal mode, thereby extending the time until the resistance value of the transfer roller rises and extending the life of the transfer roller. ing.

  In this embodiment, the resistance value of the transfer roller is obtained from the current value detected by applying a predetermined voltage to the transfer roller in the previous rotation, and the deterioration degree of the transfer roller is calculated therefrom. Needless to say, the resistance value of the transfer roller can be obtained from the voltage applied to the transfer roller 9 at that time, and the degree of deterioration of the transfer roller 9 can be calculated therefrom.

  In addition, the resistance value of the transfer roller of the ion conductive transfer roller may change greatly due to environmental changes. In that case, it is possible to obtain the degree of deterioration by providing an environmental sensor in the image forming apparatus and taking the detection result of the environmental sensor into consideration.

(Example 2)
The feature of the second embodiment is that, in addition to the first embodiment, when the resistance value of the transfer roller reaches a predetermined value, the user can select either “normal mode” or “transfer roller life extension mode”. It is provided on the operation panel (display means) 20 to be selected. For example, when the resistance value of the transfer roller reaches a certain degree of deterioration by the method of the first embodiment, a selective display as shown in FIG. 4 is performed on the operation panel 20. When the user presses the transfer roller life extension mode selection unit 21 in preference to the life extension of the transfer roller over the productivity of the image forming apparatus, the transfer is made to the transfer roller life extension mode similar to that in the first embodiment. Respond by changing the reverse bias sequence. Further, this information is more effective when combined with a means for notifying a service person or the like as maintenance information. Since the service person can grasp the replacement time of the transfer member based on this information, the service person can quickly respond when the replacement time comes.

(Example 3)
The third embodiment will be described with reference to FIG. The image forming apparatus shown in the figure includes four image forming units (image forming stations) in the image forming apparatus main body M, that is, a first image forming unit PA, a second image forming unit PB, and a third image forming unit. The part PC and the fourth image forming part PD are juxtaposed, and in each of the image forming parts PA to PD, for example, yellow, magenta, cyan, and black toner images are charged, exposed, developed, and transferred, respectively. It is formed through.

  Each of the image forming sections PA to PD has a dedicated photosensitive drum 1A, 1B, 1C, 1D, and these photosensitive drums 1A, 1B, 1C, 1D are charged by contact charging members 2A, 2B, 2C, 2D. After the electrostatic latent images are formed by the exposure laser beam scanners 3A, 3B, 3C, and 3D, toner is attached by the developing devices 4A, 4B, 4C, and 4D, and toner images of the respective colors are formed.

  In addition, an intermediate transfer belt (intermediate transfer member) 30 as a second image carrier is disposed adjacent to the photosensitive drums 1A to 1D. The intermediate transfer belt 30 is stretched around a driving roller 31, a driven roller 32, and a secondary transfer counter roller 33. Inside the transfer belt 30, primary transfer rollers (transfer members) 9A, 9B, 9C, and 9D are disposed. The intermediate transfer belt 30 is pressed against the photosensitive drums 1A to 1D by these primary transfer rollers 9A to 9D, whereby a primary transfer nip portion (transfer portion) is provided between the intermediate transfer belt 30 and the photosensitive drums 1A to 1D. T1 is formed. The yellow (first color) toner image formed on the photosensitive drum 1A is primary-transferred onto the intermediate transfer belt 30 by applying a primary transfer bias to the primary transfer roller 9A by a transfer bias application power source (not shown). Is done. Thereafter, in the same manner, magenta (second color), cyan (third color), and black (fourth color) toner images are sequentially primary-transferred and superimposed on the intermediate transfer belt 30.

  Note that the primary transfer bias applied to the primary transfer rollers 9A to 9D in the present embodiment is a desired primary transfer voltage based on the VI characteristics, as in the transfer bias control method of the first and second embodiments. The required control is performed.

  The four color toner images formed on the intermediate transfer belt 30 are transferred to the transfer material P supplied from the paper feed cassette 5. The transfer material P stored in the paper feed cassette 5 is fed by the feed roller 6 and is timed by the registration roller 7 between the intermediate transfer belt 30 and the secondary transfer roller (transfer member) 34. The toner is supplied to a secondary transfer nip portion (transfer portion) T2 as a transfer portion. At this time, a secondary transfer bias is applied to the secondary transfer roller 34 by a transfer bias application power source (not shown). As a result, the four color toner images on the intermediate transfer belt 30 are secondarily transferred onto the transfer material P all at once. At this time, the transfer voltage applied to the secondary transfer roller 34 is also determined in the same manner as the primary transfer bias described above.

  During the secondary transfer, the toner (transfer residual toner) that is not transferred to the transfer material P and remains on the intermediate transfer belt 30 is removed by a cleaner 35 that is an intermediate transfer member cleaning unit.

  The above-described intermediate transfer belt 30 is formed of a dielectric resin sheet such as a polyethylene terephthalate (PET) resin sheet, a polyvinylidene fluoride resin sheet, a polyurethane resin sheet, or a polyimide resin sheet. Joined, endless, or seamless (seamless) belts are used.

  In the above-described image forming apparatus, the transfer rollers include the primary transfer rollers 9A to 9D and the secondary transfer roller 34.

  A feature of the present embodiment is that an image forming apparatus using an intermediate transfer belt (intermediate transfer member) 30 is applied to the primary transfer rollers 9A to 9D and the secondary transfer roller 34 as in the first and second embodiments. The present invention is also applied to the secondary transfer bias.

  As described above, according to the present invention, in an image forming apparatus having an intermediate transfer body that can be used for various transfer materials, which is employed in recent full-color image forming apparatuses, a conductive roller having ionic conductivity is used as a transfer roller. The life of the transfer roller of the image forming apparatus in use can be extended.

1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to Embodiment 1. FIG. It is a flowchart regarding a transfer reverse bias sequence change. It is a figure which shows the outline of the sequence of the bias applied to a transfer member. FIG. 10 is a diagram illustrating an operation panel in which a user selects either “normal mode” or “transfer roller life extension mode” when the resistance value of the transfer roller reaches or is likely to reach a predetermined value in the second embodiment. FIG. 6 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus in Embodiment 3.

Explanation of symbols

1,1A, 1B, 1C, 1D Image carrier (photosensitive member, photosensitive drum)
9 Transfer member (transfer roller)
9A, 9B, 9C, 9D Transfer member (primary transfer roller)
20 Display means (operation panel)
30 Image carrier (intermediate transfer member, intermediate transfer belt)
34 Transfer member (secondary transfer roller)
50 Control means P Transfer object (transfer material)
T Transfer area (transfer nip area)
T1 transfer part (primary transfer nip part)
T2 transfer part (secondary transfer nip part)

Claims (8)

An image carrier having a toner image formed on a surface thereof, and a transfer member disposed in contact with the image carrier, and a transfer medium is inserted into a transfer portion between the image carrier and the transfer member. In the image forming apparatus for transferring the toner image on the image carrier to the transfer member by applying a transfer bias to the transfer member,
A sequence for outputting a transfer bias having a polarity opposite to that of the transfer bias;
A means for detecting the degree of deterioration of the transfer member;
A transfer bias is applied to the transfer member in a state where the transfer target is not present in the transfer portion, and the degree of deterioration of the transfer member is detected by means for detecting the degree of deterioration of the transfer member, and the detected degree of deterioration is constant. An image forming apparatus comprising a mode for changing a transfer bias sequence of the reverse polarity when the value is reached.   Detecting a degree of deterioration of the transfer member based on a detection current value or a calculated current value flowing through the transfer member when a transfer bias is applied to the transfer member in a state where the transfer target is not interposed in the transfer portion. The image forming apparatus according to claim 1, wherein:   When a transfer bias is applied to the transfer member without the transfer target being present in the transfer portion, the degree of deterioration of the transfer member is detected based on a detection voltage value or a calculated voltage value applied to the transfer member. The image forming apparatus according to claim 1.   An environmental sensor for detecting the temperature and humidity around the transfer unit is provided, and transfer is performed based on the detected temperature and humidity information when a transfer bias is applied to the transfer member without the transfer target being interposed in the transfer unit. The image forming apparatus according to claim 1, wherein a degree of deterioration of the member is detected.   The display device may further include a display unit that prompts a user to select whether or not to change the sequence of the reverse-polarity transfer bias when the detected degree of deterioration reaches a certain value. Item 5. The image forming apparatus according to Items 1 to 4.   6. The image forming apparatus according to claim 1, wherein the image carrier is a photoconductor.   7. The image forming apparatus according to claim 1, wherein the image carrier is an intermediate transfer member.   The image forming apparatus according to claim 1, wherein the transfer member is a conductive member having ion conductivity.

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