JPH11338328A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a high quality image by securely removing residual toner, thereby preventing the occurrence of image fogging or image memory. SOLUTION: After the removal of a jam, bias voltages Ve and Vf having polarities opposite to those used at the development time (during printing) are outputted to a developing roller 18a and a transfer roller 24, respectively. At the time, a bias of -400 V and a bias of 500 V are applied to the developing roller 18a and the transfer roller 24, respectively. Accordingly, residual toner 20 on the surface of a photoreceptive drum 12 is not transferred to the transfer roller 24, the photoreceptive drum 12 is electrified by an electrifier 14 from above the sticking toner 20 and exposed by an exposure unit 16, and the surface potential of the photoreceptive drum 12 is made to have about voltage V1 (voltage value: 100 V). Then the residual toner 20 on the developing roller 18a to which a negative bias has been applied is attracted. That is, the residual toner 20 is removed and recovered into a housing 18b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus,
In particular, the present invention relates to an image forming apparatus applied to, for example, a cleaning-less type electrophotographic copying machine, printer, and the like.
Here, the cleaning-less type image forming apparatus refers to another apparatus (for example, a developing apparatus) without using a cleaning apparatus.
And an image forming apparatus for cleaning the developer remaining on the photoconductor.

[0002]

2. Description of the Related Art One example of this type of conventional image forming apparatus is as follows.
Japanese Patent Publication No. 8-27 filed on March 21, 1996
No. 587 [G03G 21/14, G03G 15/0
6, G03G 15/08]. In this image forming apparatus, after the jam is cleared, the power supply of the motor, the charging and the discharging lamp is turned on, and the developing bias is turned on after the time required from the start of charging to the start of development. At this time, the same developing bias as during printing is applied, and the developer remaining on the surface of the photoconductor without being transferred is attracted to the developing roller and removed.

[0003]

In this prior art image forming apparatus, the same developing bias as during printing is applied, and the remaining developer is removed. Removal was insufficient. For this reason,
There is still a problem that image fogging and image memory still occur.

SUMMARY OF THE INVENTION Accordingly, a main object of the present invention is to provide an image forming apparatus which can reliably remove a large amount of developer due to the occurrence of a jam and has high print quality.

[0005]

According to the present invention, a developing means to which a developing bias voltage having a predetermined polarity is applied forms a visible image on the surface of a photoreceptor, and a transfer bias voltage having a predetermined polarity is applied. In an image forming apparatus for transferring a visible image by a transfer unit and removing a developer remaining on the surface of the photoreceptor after transfer by a developing unit, a first method for returning the developer on the photoreceptor to the developing unit after the jam has been eliminated. A first power supply means for applying a bias voltage to the developing means; and a second power supply means for applying a second bias voltage to the transfer means for preventing the developer on the photosensitive member from being transferred by the transfer means after the jam has been eliminated. An image forming apparatus characterized in that:

[0006]

After the jam has been eliminated, the removal of the developer remaining on the surface of the photoreceptor is started. The first power supply unit has a voltage having a polarity opposite to that of the developing bias, and applies a first bias voltage for returning the developer on the photoconductor to the developing unit. The second power supply unit applies a second bias voltage to the transfer unit, which is a voltage having a polarity opposite to that of the transfer bias and for preventing the developer on the photoconductor from being transferred by the transfer unit. The first bias voltage and the second bias voltage have opposite polarities. Further, the third power supply means includes:
A disturbance bias voltage having the same polarity as the second bias voltage is applied to the disturbance means. When the developer is removed after the jam has been eliminated, the charging unit is operated, and the photoconductor is uniformly charged.
The exposure means is operated, and the entire surface of the photoconductor is exposed.
At this time, a second bias voltage having a smaller absolute value is applied to the transfer unit. That is, it is only necessary that the second bias voltage is higher than the surface potential of the photosensitive member that has been entirely exposed.
Therefore, the developer remaining on the surface of the photoreceptor is not transferred to the transfer unit, but is disturbed by the disturbance unit, and is attracted to the development unit. That is, the residual toner is removed. If the exposure unit is not operated after the jam is cleared,
A second bias voltage having a larger absolute value is applied to the transfer unit. That is, the second bias voltage may be higher than the surface potential of the charged photoconductor.

[0007]

According to the present invention, the developer remaining on the photoreceptor after the elimination of the jam is not transferred to the transfer means but is surely removed by the developing means. Does not occur, and the printing quality can be improved. The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0008]

Referring to FIG. 1, an image forming apparatus 10 of this embodiment is of a cleaningless type, and
2 inclusive. The photosensitive drum 12 is provided substantially at the center of the main body of the image forming apparatus 10. A charging device 14 is provided above the photosensitive drum 12, and the surface of the photosensitive drum 12 is uniformly charged by operating the charging device 14. In this embodiment, as shown in FIG.
Is charged (charge bias voltage) V _d (voltage value; 80)
0V). In this embodiment, the photosensitive member is in the form of a drum, but may be in the form of a belt.

An exposing device 16 is provided diagonally above and right of the charging device 14. When the exposing device 16 is operated, the exposing device 1
An electrostatic latent image is formed on the surface of the photosensitive drum 12 by the laser beam from 6. This electrostatic latent image, as shown in FIG. 2 (B), lower than the voltage V _d V1 (voltage value: 100
V). A developing device 18 is provided on the right side of the photosensitive drum 12, and a developing roller 18 a provided in the developing device 18 is arranged to be in contact with the photosensitive drum 12. A developer (hereinafter, simply referred to as “toner”) 20 is stored in a housing 18 b of the developing device 18, and the developing roller 18 is
The toner 20 is applied to the electrostatic latent image formed on the surface of the photosensitive drum 12 by a. That is, the developing roller 18a
Is connected to a power supply device 22, and the developing roller 18a is biased by a bias (developing bias) voltage V _e (voltage value: 400 V) applied from the power supply device 22, and FIG.
As shown in (C), the toner 20 stored in the housing 18b is biased to 400 V by the developing roller 18a and is applied to the photosensitive drum 12. Therefore, the voltage V
The toner 20 is attracted to the electrostatic latent image formed in Step 1, and
A toner image is formed on the surface of the photosensitive drum 12.

A transfer roller 24 is provided below the photosensitive drum 12.
Is provided, and the transfer roller 24 is disposed so as to be in contact with the photosensitive drum 12. A power supply 26 is connected to the transfer roller 24, and when transferring the toner image onto a sheet (not shown), the power supply 26 supplies a bias (transfer bias) voltage V.
_f (voltage value: -1 kV) is applied, and as shown in FIG. 2D, the toner 20 is attracted to the paper (transfer roller 24). A fixing device 28 is provided on the left side of the transfer roller 24. In the fixing device 28, the toner image is fused and fixed on a sheet, and is discharged from the image forming apparatus 10. Power supply 22 and 26 are controlled by the microcomputer 30, the voltage value of the bias voltage V _e and V _f, polarity and applied Taimin'ngu are controlled.

The image forming apparatus 10 further includes a jam sensor 3
2a and 32b, and jam sensors 32a and 32b.
The microcomputer 30 determines whether a paper jam (jam) has occurred based on the output of 2b. Jam sensor 32
a and 32b are, for example, reflection type photo sensors,
If a sheet is detected, a high-level signal is output to the microcomputer 30. If a high-level signal is output for more than a predetermined time, the microcomputer 30 determines that a jam has occurred. If no paper is detected,
The jam sensors 32a and 32b output a low-level signal to the microcomputer 30.

Next, when printing (developing), the photosensitive drum 12 is rotated with the toner 20 not transferred in the previous development adhered thereto, and as shown in FIG. It is charged by the bias voltage V _d. Subsequently, as shown in FIG. 3B, an image to be developed next is exposed by the exposure device 16. Photosensitive drum 12 is further rotated, it is rotated to the developing roller 18a which is biased by the developing bias voltage V _e. In the developing roller 18a, FIG.
As shown in (C), the toner 20 remaining on the portion not exposed by the exposure device 16 is drawn to the developing roller 18a. In other words, the residual toner 20 is biased by the charging bias voltage V _d in the charging device 14, is attracted to the developing roller 18a of the voltage value from the charging bias voltage V _d is smaller developing bias voltage V _e. Further, the toner 20 adhering to the portion exposed by the exposure device 16 is not attracted to the developing roller 18a and is used for development as it is. The toner 20 attracted to the developing roller 18a is collected in the housing 18b. That is, the surface of the photosensitive drum 12 is cleaned. By repeating such operations, development and cleaning are performed.

On the other hand, if there is no next development, cleaning of the photosensitive drum 12 (printing end process) is executed,
The development is completed. The cleaning of the photosensitive drum 12 is performed in the same manner as the removal process described later. If a jam occurs during the development of the toner image, the operation of the image forming apparatus 10 is stopped in accordance with an instruction from the microcomputer 30. That is, the bias voltage to the charging device 14, the exposure device 16, the developing roller 18a, and the transfer roller 24 is turned off. At this time, a warning of the occurrence of a jam is notified from a display device (not shown) in accordance with an instruction from the microcomputer 30. Following the jam warning, the user removes the jammed paper.

When the jam is eliminated, the microcomputer 30 starts to remove a large amount of the toner 20 remaining on the surface of the photosensitive drum 12. That is, in accordance with an instruction from the microcomputer 30, the power supply devices 22 and 26 apply a bias (first bias) voltage V _e (voltage value; −) having a polarity opposite to the polarity during development (during printing).
300 V) and the second bias voltage V _f (voltage value; 50
0V) is applied to the developing roller 18a and the transfer roller 24, respectively. That is, from the power supply devices 22 and 26,
According to the instruction of the microcomputer 30, during the printing, the developing bias voltage _Ve and the transfer bias voltage _Vf are output.
In a process (removal process) for removing the toner 20 remaining on the surface of the photosensitive drum 12 after the jam is cleared, the first process is performed.
The bias voltage _Ve and the second bias voltage _Vf are output. Further, a drive motor (not shown) for rotating the photosensitive drum 12, a charging device 14 and an exposure device 16 are operated, the photosensitive drum 12 is rotated, is uniformly charged by the charging device 14, and is fully exposed by the exposure device 16. Is done.

More specifically, as shown in FIG. 4A, the transfer roller 24 is biased at a voltage value higher than the surface potential of the photosensitive drum 12, and the toner 20 remaining on the surface of the photosensitive drum 12 is transferred to the transfer roller 24. Is not transcribed.
The photosensitive drum 12 rotates, and charging is performed with the toner 20 adhered as shown in FIG. 4B. When the amount of the toner 20 is small, the surface of the photosensitive drum 12 is charged with almost no influence. However, when the amount of the toner 20 is large, the surface potential of the photosensitive drum 12 is lower than a predetermined potential. (In this embodiment, 500 V to 600 V
V). When the charging is completed, exposure is performed by the exposure device 16, and as shown in FIG. 4C, the surface potential of the photosensitive drum 12 differs depending on the portion where the toner 20 is attached and the portion where it is not attached. When the exposure is completed, FIG.
As shown in (D), the remaining toner 20 is attracted to the negatively biased developing roller 18a and collected by the housing 18b. When the photosensitive drum 12 makes a predetermined rotation (two rotations in this embodiment), the removal process is terminated. Subsequently, development of an image at the time of occurrence of a jam is performed by a normal operation (developing process). In this embodiment, the removal process is terminated when the photosensitive drum 12 makes two rotations. However, the number of rotations of the photosensitive drum 12 may be two or more. 12 is cleaned, but there is a problem that the time until the start of the next printing becomes long.

As shown in FIG. 5, the polarity and timing of the bias during development (during printing), when a jam occurs, and during the removal process are controlled by the microcomputer 30. In the timing chart of FIG. 5, the horizontal axis is 0 (off).
And the upper side is a positive bias with respect to the horizontal axis,
The lower side is a negative bias. As shown in FIG. 5A, the drive motor that rotates the photosensitive drum 12 is turned on at the time of development and at the time of the removal process. Charging device 1
The bias of No. 4 is positively biased at the time of development and at the time of the removal process, as shown in FIG. In the removal process, the charging bias is turned off as early as the time from the charging to the exposure, so that the charge due to charging remains on the photosensitive drum 12 is suppressed. As shown in FIG. 5C, the developing roller 18a is positively biased during development during the development process, but is negatively biased during the time from the start of charging to the start of development and during the removal process. As shown in FIG. 5D, the exposure device 16 is turned on / off in accordance with an image signal at the time of development, and is exposed in an on state during the removal process. As shown in FIG.
As shown in (E), the bias is negative during the transfer, but is positive during the time from the start of charging to the start of the transfer and during the removal process. As can be seen, no bias voltage is applied to all devices when a jam occurs.

The operation described above is performed by the microcomputer 30 shown in FIG.
The processing is performed according to the flowchart shown in FIG. Of the image forming apparatus 10
When the main power is turned on, the process starts, and in step S1, the process starts.
Determine if a jam has occurred. Here, "NO"
If so, proceed to step S5, but if "YES",
In step S3, it is determined whether the jam has been resolved.
If "NO" here, the process returns to the step S3.
If “YES”, it remains after the jam is cleared in step S5.
A process (removal process) for removing the retained toner 20 is performed.
Run. That is, the driving motor, the charging device 14 and the exposure
A bias voltage is applied to the heater 16 and the power supplies 22 and 2
From 4 the bias voltage V of the opposite polarity to that during printing _eAnd V_f
Is applied. Subsequently, in step S7, the photosensitive drum 1
It is determined whether or not 2 has rotated twice. Here, "NO"
If so, return to step S7, but if "YES"
If so, the process proceeds to step S9. In step S9, printing starts
Determine if it is possible. In other words, when the paper is set
Judge whether or not. Here, "NO"
Return to step S9, but if "YES",
Exposure is started in step S11. In the following step S13
Indicates that the formation portion (image area) of the electrostatic latent image reaches the development position
It is determined whether or not the processing has been performed.
13, but if “YES”, the flow proceeds to step S15.
Development bias voltage V _eOutput. Next steps
In S17, it is determined whether or not the image area has reached the transfer position.
to decide. If "NO" here, a step S17 is performed.
, But if “YES”, the transfer bias voltage V_f
Output. In the following step S21, the next printing
Judge whether there is any, and if "YES",
Returning to step S9, if "NO", the process proceeds to step S23.
Handles the print end process. In other words, the removal process
Executes the same cleaning of the photosensitive drum 12 as the processing
I do. In a succeeding step S25, the photosensitive drum 12 is
It is determined whether it has been turned over, and if "NO", the step
Returning to S23, if "YES", the process ends.
You.

According to this embodiment, after the jam is cleared,
Since bias voltages _Ve and _Vf having polarities opposite to those during printing are output to the developing roller 18a and the transfer roller 24, and the toner 20 remaining on the surface of the photosensitive drum 12 is removed.
A large amount of residual toner 20 can be reliably removed. Therefore, it is possible to improve the print quality after clearing the jam.

An image forming apparatus 1 according to another embodiment shown in FIG.
0 is the same as that of the embodiment of FIG. 1 except that the disturbance roller 34 and the power supply device 36 are provided. In the other embodiments, the disturbance means uses a roller-like material, but a brush-like material may be used. In the image forming apparatus 10, the disturbance roller 34 rotates together with the photosensitive drum 12 to disturb and remove the toner 20 remaining on the photosensitive drum 12. That is, the power supply device 36 is connected to the disturbance roller 34, and the power supply device 36 is connected to the microcomputer 3
Connected to 0. The power supply device 36 is controlled by the microcomputer 30 in the voltage value, the polarity, and the application timing similarly to the power supply devices 22 and 26. At the time of development, a bias (disturbance bias) voltage V _g (voltage value;
-400 V) is applied. Therefore, as shown in FIG. 8A, the positively charged toner 20 in the remaining toner 20 is attracted to the disturbance roller 34, and the negatively charged toner 20 is disturbed on the surface of the photosensitive drum 12. You. For this reason, it is possible to suppress light blocking during charging and light blocking during exposure. The toner 20 attached to the disturbance roller 34 is periodically cleaned (for example, every 100 sheets). The cleaning of the disturbance roller 34 is performed before printing is started or after printing is completed. When cleaning the disturbance roller 34, the developing roller 18a,
The transfer roller 24 and the disturbing roller 34 are biased to have polarities opposite to those during development. That is, as shown in FIG. 8B, the disturbance roller 34 applies the bias voltage V _g (voltage value: 40
0V), and the developing roller 18a and the transfer roller 24 are biased as in the above-described removal process. Therefore, the toner 20 attached to the disturbance roller 34 is attracted to the surface of the photosensitive drum 12, and the surface of the disturbance roller 34 is cleaned. Photosensitive drum 12
Is further rotated and charged by the charging device 14 from above the toner 20. When the charging is completed, the entire exposure is performed by the exposure device 16, that is, the surface potential of the photosensitive drum 12 is set to the voltage V1, and the remaining toner 20 is drawn to the developing roller 18a.

In the case where a jam occurs during development, FIG.
As in the embodiment, each bias voltage is turned off, and a warning of the occurrence of a jam is notified. When the user removes the jammed paper, the jam is eliminated. Once the jam is cleared, the removal process is processed. That is, the developing roller 18a, the transfer roller 24, and the disturbance roller 34 are supplied with the first bias voltage _Ve , the second bias voltage _Vf, and the third bias voltage _Vg having polarities opposite to those during printing. The third bias voltage V _g is the same as the bias voltage V _g at the time of cleaning.
It is the same voltage value as. In other words, as shown in FIG. 8B, the third bias voltage _Vg is applied to the disturbance roller 34, and the toner 20 remaining on the surface of the photosensitive drum 12 is not attracted to the disturbance roller 34, and the disturbance roller 34 Disturbed by Further, similarly to the cleaning, the toner 20 attached to the disturbance roller 34 is attracted to the photosensitive drum 12 and is attracted from the photosensitive drum 12 to the developing roller 18a. The removal process is terminated when the photosensitive drum 12 has been rotated a predetermined number of times (in this embodiment, two rotations), and then the image is developed when a jam occurs.

In the image forming apparatus 10, since the entire exposure is performed by the exposure unit 16 during the removal process as in the embodiment of FIG. 1, the voltage value of the bias voltage _Vf applied from the power supply unit 26 may be 500V. However, when no exposure is performed during the removal process, it is necessary to increase the bias voltage _{Vf in} order to prevent the toner 20 remaining on the surface of the photosensitive drum 12 from being transferred to the transfer roller 24.
At this time, the voltage value of the second bias voltage _Vf is set to, for example, 1 kV. Therefore, the third bias voltage V _g applied to disrupting roller 34, for example, 1.2kV
Is set to The bias voltage V _e and the charging bias voltage V _d applied from the power supply device 22 are the same as those in the embodiment of FIG.

As described above, in the power supply device 36, the disturbance bias voltage _Vg is output during development, but the third bias voltage _Vg is output during the removal process. In other words, at the time of the removal process, reverse polarity of the bias voltage V _g is applied at timing at which the song shown in FIG. 9 (F) and the cleaning time as well as during development (during printing). The microcomputer 30 processes the above operation according to the flowchart shown in FIG.
Note that the processing in FIG. 10 is almost the same as that in the flowchart in FIG. 6, and a duplicate description will be omitted.

In the process of the removal process in step S3,
Further instructs the opposite polarity during the printing bias voltage V _g which is output from the power supply 36. When printing is started after the removal process has been performed, the power supply 3
It gives an instruction to output disturbance bias voltage V _g to 6. According to another embodiment, since the disturbance roller 34 is further provided in the image forming apparatus 10 of the embodiment in FIG. 1, the removal (cleaning) of the remaining toner 20 can be efficiently performed. Therefore, a high-quality image can be formed.

In the removal process, the disturbance rollers 34
Since the toner 20 adhered to the photosensitive drum 12 is attracted to the photosensitive drum 12, cleaning of the disturbance roller 34 can be executed. Therefore, the disturbance does not adversely affect the development. In these embodiments, in the removal process, a negative bias (first
Bias) but so as to apply a voltage V _e, it is possible to remove the toner 20 remaining even by applying a bias voltage V _e of 0V.

[Brief description of the drawings]

FIG. 1 is an illustrative view showing one embodiment of the present invention;

FIG. 2 is an illustrative view showing movement of the toner shown in FIG. 1 during development;

FIG. 3 is an illustrative view showing movement of the toner shown in FIG. 1 during development;

FIG. 4 is an illustrative view showing movement during a toner removing process shown in FIG. 1 embodiment;

FIG. 5 is a timing chart showing the polarity of each bias voltage during the development and the removal process of the image forming apparatus shown in FIG. 1 embodiment.

FIG. 6 is a flowchart showing a part of the processing of the microcomputer shown in FIG. 1 embodiment;

FIG. 7 is an illustrative view showing another embodiment of the present invention;

8 is an illustrative view showing movement of the toner during the development and the removal process shown in the embodiment in FIG. 7;

FIG. 9 is a timing chart showing the polarity of each bias voltage during the development and the removal process of the image forming apparatus shown in FIG. 7 embodiment.

FIG. 10 is a flowchart showing a part of the processing of the microcomputer shown in the embodiment in FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus 12 ... Photosensitive drum 14 ... Charging device 16 ... Exposure device 18 ... Developing device 22, 26, 36 ... Power supply device 24 ... Transfer roller 30 ... Microcomputer 32a, 32b ... Jam sensor 34 ... Disturbing roller

Claims (11)

[Claims] 1. A visible image is formed on the surface of a photoreceptor by a developing means to which a developing bias voltage having a predetermined polarity is applied, and the visible image is formed by a transferring means to which a transfer bias voltage having a predetermined polarity is applied. An image forming apparatus for transferring and removing a developer remaining on the surface of the photoreceptor after transfer by the developing unit, wherein a first bias voltage for returning the developer on the photoreceptor to the developing unit after the jam has been resolved is provided. A first power supply unit for applying the developing unit; and a second power supply unit for applying a second bias voltage to the transfer unit so that the developer on the photoconductor is not transferred by the transfer unit after the jam is cleared. An image forming apparatus, comprising: 2. The image forming apparatus according to claim 1, wherein said first bias voltage has a polarity opposite to that of said developing bias. 3. The image forming apparatus according to claim 1, wherein the second bias voltage has a polarity opposite to that of the transfer bias. 4. The image forming apparatus according to claim 3, wherein the first bias voltage has a polarity opposite to that of the second bias voltage. 5. The image forming apparatus according to claim 1, wherein said first bias voltage is a voltage of 0V. 6. The image forming apparatus according to claim 1, further comprising a disturbance unit to which a disturbance bias voltage having a predetermined polarity is applied to disturb developer remaining on the photoconductor after transfer by the transfer unit. Image forming device. 7. A third bias applying a third bias voltage having a polarity opposite to that of the disturbance bias voltage to the disturbance means after the jam is eliminated.
The image forming apparatus according to claim 6, further comprising a power supply. 8. The image forming apparatus according to claim 7, wherein said third bias voltage has the same polarity as said developing bias. 9. The image forming apparatus according to claim 7, further comprising an exposure unit for exposing the entire surface of the photoconductor, operating the exposure unit after the jam is eliminated, and applying the second bias voltage having a smaller absolute value to the transfer unit. 9. The image forming apparatus according to 8. 10. The apparatus according to claim 7, further comprising an exposure unit for exposing the entire surface of the photoconductor, wherein the second bias voltage having a larger absolute value is applied to the transfer unit without operating the exposure unit after the jam is resolved. Or the image forming apparatus according to 8. 11. The image forming apparatus according to claim 1, further comprising a charging unit for uniformly charging the photosensitive member, wherein the charging unit is operated at least before image formation, after image formation, or after clearing a jam. Image forming device.