JP2002357931A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which can prevent 'fogging' and halftone stain irrespective of an environmental condition. SOLUTION: A temperature (humidity) sensor 37 is connected to a printer controller 12, and the printer controller 12 is provided with an electrification bias determination table 12b having temperatures as an environmental condition and the potentials by electrification of a photoreceptor drum 13 as a table. The sensor 37 detects a temperature in printing, and the temperature data are fetched in the printer controller 12. The printer controller 12 determines an electrification bias corresponding to the temperature with reference to the electrification bias determination table 12b with respect to the temperature data, and a determined potential by electrification is applied to the photoreceptor drum 13 with an electrification brush 14 through an electrification bias application circuit 15. Specifically, the potential by electrification is increased in a low temperature and a low humidity environment, and is decreased in a high temperature and a high humidity environment.

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 which problem images such as "fog" and "halftone" are hardly generated regardless of temperature and humidity environment.

[0002]

2. Description of the Related Art A cleanerless image forming apparatus generally includes a photosensitive drum, a charging member for charging the photosensitive drum to a predetermined charging potential, and an exposure for exposing an electrostatic latent image on the surface of the charged photosensitive drum. A developing unit that collects toner remaining on the photosensitive drum and develops an electrostatic latent image on the photosensitive drum, and a transfer unit that transfers the developed visual image on the photosensitive drum to recording paper.

[0003]

In the above-described image forming apparatus, the difference (absolute value) | Vc−Vb | between the charged potential (Vc) of the photosensitive drum surface and the developing potential (Vb) of the developing unit is a cleanerless value. This is a potential difference required for collecting toner adhered to the photosensitive drum in the apparatus of the formula.

[0004] However, as shown in FIG.
As −Vb | is larger, the ability to collect the normally charged toner (lower negative toner) adhering on the photosensitive drum in the developing unit is improved, but the reverse charge toner (upper plus toner) is transferred from the developing unit to the photosensitive drum. Adhesion tends to occur, and so-called “fogging” of printing tends to occur.

On the other hand, when | Vc−Vb | is small in FIG. 10, the reverse charge toner (upper plus toner)
Is less attached to the photosensitive drum, but the ability to collect the normally charged toner (the lower minus toner) is reduced.
The stain on the halftone image occurs.

[0006] Regarding environmental conditions, "fogging" is likely to occur in a high-temperature and high-humidity environment, and dirt in a halftone image is likely to occur in a low-temperature and low-humidity environment.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and has as its object to provide an image forming apparatus capable of preventing "fogging" and halftone contamination regardless of environmental conditions.

[0008]

According to a first aspect of the present invention, there is provided an image forming apparatus comprising: a photosensitive member; a charging member for charging the photosensitive member to a predetermined charging potential; An exposure section for exposing the electrostatic latent image on the surface of the photoconductor, a developing section for collecting toner remaining on the photoconductor and developing the electrostatic latent image on the photoconductor, and a developed section on the photoconductor. A sensor for detecting environmental conditions, and a controller for adjusting a difference between a charging potential of a photoconductor and a developing potential of a developing unit based on an output of the sensor. And characterized in that:

In this apparatus, the difference (potential difference) between the charging potential of the photosensitive member and the developing potential of the developing unit is adjusted according to the environmental conditions (temperature and humidity) detected by the sensor. High image quality can always be maintained. That is, "fogging" in a high-temperature and high-humidity environment and halftone stain in a low-temperature and low-humidity environment can be prevented.

The specific adjustment method is as described above.
Considering that the larger the potential difference is, the easier it is to generate fog, and the smaller the potential difference is, the easier it is to generate halftone stains. In addition, it is possible to make it difficult to generate a problem image under each environment.

In this device, the environmental condition detected by the sensor is at least one of temperature and humidity, but it is needless to say that both may be used. Further, the control unit adjusts the difference between the charging potential and the developing potential, for example, by changing the charging potential.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to embodiments.

FIGS. 1 (partial), FIGS. 2 and 3 show a schematic block diagram of the entire image forming apparatus according to the embodiment.
(Remaining part). This image forming apparatus is configured as a so-called multifunction device having a facsimile function and a copy function, and includes an MPU 1 and an NCU (network control circuit: Network control circuit).
Control Unit) 2, MODEM 3, ROM 4, RAM
5, image memory (DRAM) 6, CODEC (encoding /
Decoder: Coder and Decoder) 7, operation unit 8, scanner 9, and printer I / F (interface) 10 to which personal computer 11 is connected.

The MPU 1 controls each unit constituting the apparatus. The NCU 2 has a function of controlling connection with a telephone network (PSTN), a function of transmitting a dial signal corresponding to a telephone number (including a FAX number) of the other party, and a function of detecting an incoming call. MODEM3 is I
TU (International Telecommunication Union)-T Recommendation T. 30 based on a facsimile transmission control procedure according to V.30. 17, V.I. 2
7ter, V.I. Modulation of the transmission data and demodulation of the reception data according to 29 or the like. Alternatively, in addition to these, 3
4 and demodulates received data.

The ROM 4 stores a program for controlling this device. The RAM 5 temporarily stores data and the like. The image memory 6 temporarily stores received image data and image data read by the scanner 9. COD
EC7 transmits M to read the read image data.
Encoding by H, MR, MMR method, etc.
Then, the received image data is decoded. Operation unit 8
Is for the user to instruct facsimile transmission / reception, printing, and the like. The scanner 9 reads image data of a document when performing fax transmission.

The printer in this apparatus is provided with a printer controller (control unit) 12 for controlling various parts of the printer.
A temperature (humidity) sensor 37 for detecting humidity is connected. The printer controller 12 includes a transfer bias determination table 12 a having a current value and a transfer voltage when a test voltage is applied to the transfer roller (transfer section) 21 as a table, a temperature (humidity) detected by the sensor 37, and a photosensitive drum. (Photosensitive member) 13 and a charging bias determination table 12b that holds the charging potential of the photosensitive drum 13 as a table.

The printer controller 12 refers to the transfer bias determination table 12a and
And a function of adjusting the difference between the charging potential of the photosensitive drum 13 and the developing potential of the developing roller (developing unit) 18 based on the output of the sensor 37.

A photosensitive drum 13 having a photoconductive film on the outer peripheral surface as a photosensitive member is arranged inside the printer, and the photosensitive drum 13 is rotated by a driving source (main motor 41). A charging brush 14 is arranged around the photosensitive drum 13 as a brush roller type charging member, and a predetermined bias voltage is applied to the charging brush 14 by a charging bias application circuit 15. The charging brush 14 to which the bias voltage is applied uniformly charges the outer peripheral surface of the photosensitive drum 13 while rotating.

The LED print head 16 as an exposure unit disposed around the photosensitive drum 13 has a number of LEDs arranged in parallel, and irradiates the outer peripheral surface of the photosensitive drum 13 with light based on input image information. Then, an electrostatic latent image corresponding to the image information is formed on the outer peripheral surface.

Further, the developing section disposed around the photosensitive drum 13 is constituted by a supply roller 17, a developing roller 18, a blade 19, a developing device bias applying circuit 20, and the like. The supply roller 17 charges the toner from a toner case (not shown) containing the toner while the developing roller 18 is charged.
The developing roller bias application circuit 20 applies a predetermined bias voltage to the supply roller 17. A predetermined bias voltage is applied to a developing roller 18 arranged in contact with the supply roller 17 and the photosensitive drum 13 by a developing device bias applying circuit 20.

The blade 19 elastically contacts the outer peripheral surface of the developing roller 18 to make the layer thickness of the toner adhered to the outer peripheral surface of the developing roller 18 uniform. 20 applies a predetermined bias voltage.

Further, a transfer roller 21 as a transfer unit disposed around the photosensitive drum 13 is disposed so as to be in contact with the outer peripheral surface of the photosensitive drum 13 across the sheet transport path P, and a drive source (main motor 41) Is rotated by A predetermined bias voltage is applied to the transfer roller 21 by a transfer bias application circuit 22. The current of the transfer roller 21 is
The current value detected by the current detection unit 35 is stored in the printer controller 12. The printer controller 12 obtains a transfer voltage corresponding to the current value from the transfer bias determination table 12a during printing, and the transfer bias application circuit 22 applies the bias voltage to the transfer roller 21.

The fixing device disposed on the sheet feeding side of the sheet transport path P includes a heating roller 23 having a heater such as a halogen lamp, a heater driving circuit 24, a press roller 25, and the like. The heater of the heating roller 23 is heated by the heater driving circuit 2 so that the outer peripheral surface of the heating roller 23 has a predetermined temperature.
4 heated. Heating roller 23 and press roller 2
Reference numeral 5 fixes the toner image on the sheet by heating and pressing the sheet after the transfer by the transfer roller 21.

In this apparatus, a memory removing brush 26 is arranged around the photosensitive drum 13. The memory removing brush 26 is for removing a toner image (memory image) remaining along the outline of the image on the outer peripheral surface of the photosensitive drum 13 even after transfer, and the memory removing brush 26 has a memory removing brush voltage applying circuit. 27 applies a predetermined bias voltage.

Further, this apparatus has a PSS (PSS) as a sensor for detecting whether or not a sheet has been fed from a sheet feeding cassette (not shown) on the sheet conveying path P on the upstream side of the photosensitive drum 13 and the transfer roller 21. Paper Supply Senso
r) 30 is arranged. As will be described later, the PSS 30 is turned on when a sheet is fed from the sheet cassette.

On the paper supply side, the paper supply roller 40 and the main motor 41 are connected via a clutch 42, and when taking out paper from the paper supply cassette, the paper supply roller 40 is connected to the main motor 41 by the clutch 42. By rotating the paper feed roller 40, the paper in the paper feed cassette is taken out one by one.

In the image forming apparatus configured as described above, the printing operation is well known, but in brief, the photosensitive drum 13 is uniformly charged by the charging brush 14 and the photosensitive drum 13 is charged by the LED print head 16. An electrostatic latent image corresponding to the image information is formed, and the developing roller 18
As a result, the toner is attracted to the electrostatic latent image on the photosensitive drum 13 and a toner image is formed on the photosensitive drum 13. Then, the toner image on the photosensitive drum 13 is transferred to the sheet by the transfer roller 21. After the transfer, the sheet is heated and pressed by the heating roller 23 and the press roller 25, and the toner image is fixed on the sheet as a permanent image.

In this apparatus, the printer controller 12
However, it is characterized in that the difference between the charging potential of the photosensitive drum 13 and the developing potential of the developing roller 18 is adjusted based on the temperature (or humidity, or both, hereinafter omitted) detected by the sensor 37. That is, the printer controller 12 refers to the charging bias determination table 12b for the temperature detected by the sensor 37, determines the charging bias corresponding to the detected temperature, and charges the determined charging bias through the charging bias applying circuit 15. Photosensitive drum 1 by brush 14
3

More specifically, as described above, a halftone image is easily stained in a low-temperature and low-humidity environment, and "fogging" of printing is likely to occur in a high-temperature and high-humidity environment. The controller 12 controls the charging potential (absolute value) to be large in a low-temperature and low-humidity environment and to be small in a high-temperature and high-humidity environment.

Next, an outline of the printing operation of this apparatus will be described with reference to flowcharts of FIGS. 5 to 7 and an operation sequence diagram of FIG.

In FIG. 5, when the printing operation starts, first, in step ST1, the temperature (or humidity, or both, hereinafter omitted) is detected as an environmental condition by the sensor 37, and the detected temperature data is taken into the printer controller 12. Next, in step ST2, the charging temperature determination table 12b is added to the acquired temperature data.
, A charging potential corresponding to the temperature data is determined.

Thereafter, in step ST3, the main motor 41 is turned on, the charging bias is turned on, the developing bias (+) is turned on, the transfer bias (-) is turned on, and the memory removing brush 26 is turned on.

In the next step ST4, the timer T
1, T6 starts, and in step ST5, it is determined whether or not the timer T1 has expired. Here, the reason why the developing bias is turned ON at (+) is that the toner remaining on the uncharged portion (portion having a potential of approximately 0 V) on the outer peripheral surface of the photosensitive drum 13 is efficiently developed by the developing unit. It is to collect at. The reason why the transfer bias is turned on at (−) is to collect the toner adhered to the outer peripheral surface of the transfer roller 21 to the outer peripheral surface of the photosensitive drum 13.

When the timer T1 times out, in step ST6, the developing bias (-) is switched and the transfer bias is turned off. Then, in step ST7, the timer T2 is started, and in step ST8, it is determined whether or not the time of the timer T2 is up. When the timer T2 times out, in step ST9, a test voltage is applied to the transfer roller 21, and the FB sequence is started.

In the next step ST10, the timer T3 is started. In step ST11, the current value of the transfer roller 21 is detected by the current detecting unit 35, and the current value is sampled. In step ST12, it is determined whether or not the timer T3 has timed out. If not, the process returns to step ST11 to sample the current value, that is,
Continue the B sequence.

When the timer T3 times out, in step ST13, the sampled current value is held in the printer controller 12. Then, step ST
At 14, the transfer bias is turned off. And
In step ST15, the timer T4 starts,
In step ST16, it is determined whether or not the time of the timer T4 has expired.
Then, the transfer bias (-) is turned ON, and the transfer roller 21 is cleaned again.

Subsequently, in step ST18, the timer T5 is started. In step ST19, it is determined whether or not the timer T5 has timed out. When the time is up, the transfer bias is turned off in step ST20.
To Further, in step ST21, the timer T6
Is determined to have elapsed, and when the time has elapsed, in step ST22, it is determined whether the temperature increase of the fixing device (the heating roller 23 and the press roller 25) has been completed.

When the temperature rise of the fixing unit is completed, step ST
At 23, the paper feed clutch 42 is turned on, and at step ST24, the timer T7 starts. In step ST25, it is determined whether or not the PSS 30 has been turned on. If the PSS 30 has been turned off, it is determined in step ST26 whether the timer T7 has expired. PSS3 before timer T7 expires
If 0 remains OFF, it means that the paper has not been sent from the paper feed cassette to the PSS 30 due to a paper jam or the like, and the process proceeds to step ST27. In step ST27, the main motor 41, the charging bias, the developing bias, the transfer bias, the memory removing brush 26, and the fixing device are all turned off. In step ST28, a jam is displayed, and the printing process ends.

On the other hand, in step ST25, the PSS
When 30 is turned on, it means that the sheet has been sent, and the process proceeds to step ST29. Step ST
At 29, timers T8, T9, T10 start. In step ST30, it is determined whether or not the time of the timer T8 has expired. When the time has expired, in step ST31, exposure of the electrostatic latent image to the photosensitive drum 13 is started based on the charging potential determined in step ST2. In the next step ST32, the timer T
It is determined whether 9 has timed out and when the time is up,
In step ST33, a pre-transfer bias is applied to the transfer roller 21.

Next, in step ST34, it is determined whether or not the timer T10 has timed out. When the time has expired, in step ST35, the transfer bias determined by the FB sequence, that is, the current value obtained by the sampling, The transfer bias is determined by applying the transfer bias determination table 12a. Then, in step ST36, the determined transfer bias (+) is transferred to the transfer roller 21. Thereafter, the printing process is continued.

As described above, in this image forming apparatus, the temperature is detected by the sensor 37 at the time of printing, and the detected temperature is referred to the charging bias determination table 12b of the printer controller 12, and the temperature value (that is, the printing time) is obtained. Temperature / humidity environmental conditions), so the charging potential is determined regardless of the high temperature / high humidity environment or low temperature / low humidity environment.
"Fogging" and halftone contamination can be prevented, and not only can the image quality be improved, but also a high-quality image can be stably maintained.

In the above embodiment, the charging potential is determined by using the charging bias determination table 12b of the printer controller 12, but the charging potential may be determined by using a function.

In the above embodiment, the difference between the charging potential of the photosensitive drum 13 and the developing potential of the developing roller 18 is adjusted by changing the charging potential according to the environmental conditions. It is also possible to change, or to change both the charging potential and the developing potential.
However, it is important to keep the difference between the exposure potential and the development potential as constant as possible.

[0044]

As described above, according to the image forming apparatus of the present invention, the difference (potential difference) between the charging potential of the photoconductor and the developing potential of the developing unit is determined according to the environmental conditions (temperature and humidity). Since the adjustment is performed, high image quality can always be maintained regardless of environmental conditions. In other words, "fogging" in a high temperature and high humidity environment, and
Halftone dirt in a low humidity environment can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram (a part) of an entire image forming apparatus according to an embodiment.

FIG. 2 is a schematic block diagram (remaining portion) of the entire image forming apparatus according to the embodiment;

FIG. 3 is a schematic configuration block diagram (remaining portion) of the entire image forming apparatus according to the embodiment;

FIG. 4 is a graph showing the relationship between the low-temperature / low-humidity environment and the high-temperature / high-humidity environment and the charging potential of the photosensitive drum in the operation of the image forming apparatus.

FIG. 5 is a flowchart showing a printing operation of the image forming apparatus.

FIG. 6 is a flowchart that follows the flowchart of FIG. 5;

FIG. 7 is a flowchart following the flowchart of FIG. 6;

FIG. 8 is an operation sequence diagram of the image forming apparatus.

FIG. 9 shows the difference (absolute value) | Vc−Vb between the charging potential (Vc) of the photosensitive drum surface and the developing potential (Vb) of the developing roller.
It is a figure explaining the phenomenon when | is large.

FIG. 10 shows the difference (absolute value) | Vc−V between the charged potential (Vc) of the photosensitive drum surface and the developing potential (Vb) of the developing roller.
It is a figure explaining the phenomenon when b | is small.

[Explanation of symbols]

 Reference Signs List 12 Printer controller (control unit) 12a Transfer bias determination table 12b Charging bias determination table 13 Photosensitive drum (photoconductor) 14 Charging brush (charging member) 16 LED print head (exposure unit) 18 Developing roller (developing unit) 21 Transfer roller ( Transfer unit) 23 heating roller (fixing unit) 25 press roller (fixing unit) 37 temperature (humidity) sensor

Continued on front page F-term (reference) 2H027 DA11 DA14 DE07 DE09 EA01 EA05 EB01 EC06 EC20 EF06 2H073 AA03 BA02 BA12 BA13 BA33 2H077 AA37 AC04 AC16 AD06 AD13 AD31 2H134 GA01 GB02 HF13 JA11 KG03 MA02 MA11 2H200 GA01 GA23 GB HA02 HA29 HB07 HB12 HB22 JA02 JA29 JA30 PA03 PB05 PB27 PB28

Claims (3)

[Claims] A photoconductor, a charging member for charging the photoconductor to a predetermined charging potential, an exposure unit for exposing an electrostatic latent image on the surface of the charged photoconductor, and a toner remaining on the photoconductor. A developing unit that collects and develops the electrostatic latent image on the photoconductor,
In an image forming apparatus provided with a transfer unit for transferring a developed visual image on a photoconductor to a recording medium, a sensor for detecting environmental conditions, and a charging potential of the photoconductor based on an output of the sensor and development of the developing unit An image forming apparatus comprising: a control unit that adjusts a difference from a potential. 2. The image forming apparatus according to claim 1, wherein said sensor detects at least one of temperature and humidity. 3. The image forming apparatus according to claim 1, wherein the control section adjusts a difference between the charging potential and the developing potential by changing a charging potential.