JP2002328547A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which solves the problem of image minification caused by contraction of paper due to environment of temperature and humidity. SOLUTION: The image forming device is provided with a photoreceptor drum 13 on which an electrostatic latent image is formed based on a horizontal synchronizing signal, a developing roller 18 which develops the electrostatic latent image on the photoreceptor drum 13 by toner to obtain a toner image, a transfer roller 21 which transfers the toner image on the photoreceptor drum 13 onto paper and a heating roller 23 and a pressure roller 25 for fixing the transferred toner image on the paper. ROM4 has a HSYNC table 4a which possesses current value at the time of applying test voltage to the transfer roller 21 and a period of the horizontal synchronizing signal as a table. MPU1 decides the period of the horizontal synchronizing signal corresponding to the current value obtained at the time of applying test voltage to the transfer roller 21 by referring to the table 4a.

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 for preventing image shrinkage caused by shrinkage of a sheet due to temperature and humidity.

[0002]

2. Description of the Related Art A contact transfer type image forming apparatus is generally
A photosensitive drum on which an electrostatic latent image is formed based on a horizontal synchronization signal; a developing roller for developing the electrostatic latent image on the photosensitive drum with toner to form a toner image; and transferring the toner image on the photosensitive drum to paper And a fixing device for fixing the transferred toner image to paper.

[0003]

By the way, the size of the paper changes depending on the temperature and humidity. In a high-temperature, high-humidity environment, the paper is larger than in a low-temperature, low-humidity environment.
In a high-temperature, high-humidity environment, a toner image is transferred from a photosensitive drum to a sheet by a transfer roller, and after the transfer, the sheet is passed through a fixing device to fix the toner image on the sheet. There is a problem that an image on a sheet, particularly an image in the sub-scanning direction, is reduced due to evaporation and contraction of the sheet.

For example, as shown in FIG. 8A, in a high-temperature and high-humidity environment, when the sheet after the transfer of the toner image is passed through a fixing device, the sheet after passing is shown in FIG. It shrinks more greatly in the sub-scanning direction than in a low-temperature and low-humidity environment.

The present invention has been made in view of such a problem, and provides an image forming apparatus which solves the problem of image reduction caused by contraction of a sheet due to temperature and humidity environment. It is intended to be.

[0006]

According to another aspect of the present invention, there is provided an image forming apparatus, comprising: an image carrier on which an electrostatic latent image is formed based on a horizontal synchronizing signal; A developing member for developing the electrostatic latent image on the carrier with toner to form a toner image; a transfer member for transferring the toner image on the image carrier to paper; and fixing the transferred toner image to paper at least by heating And a control unit for determining a voltage to be applied to the transfer member, wherein the control unit includes:
The voltage applied to the transfer member is determined based on the current when the test voltage is applied to the transfer member, and the cycle of the horizontal synchronization signal is determined based on the current value at that time.

In this apparatus, based on a current value when a test voltage for determining a transfer voltage is applied to a transfer member,
That is, by estimating the environmental conditions of temperature and humidity from the current value and determining the period of the horizontal synchronization signal suitable for the environmental conditions at that time, the toner image on the paper after passing through the fixing device is reduced particularly in the sub-scanning direction. Thus, it is possible to prevent the toner from being fixed on the paper.

In this device, a storage unit is provided which holds the current value and the period of the horizontal synchronization signal as a table, and the control unit determines the period of the horizontal synchronization signal based on the table of the storage unit. The determination of the signal period can be easily performed by using a table.

If the test voltage applied to the transfer member is applied in a state where there is no paper between the image carrier and the transfer member, it is necessary to insert a sequence for directly measuring the moisture absorption of the paper. And it is easy to realize.

[0010]

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

FIG. 1 (partially) and FIG. 2 (remaining part) show schematic block diagrams of the entire image forming apparatus according to the embodiment. This image forming apparatus is configured as a so-called multifunction machine having a facsimile function and a copy function, and includes an MPU (control unit) 1 and an NCU (network control circuit: Netw
ork Control Unit) 2, MODEM 3, ROM 4, RA
M5, image memory (DRAM) 6, CODEC (Coder and Decoder) 7, operation unit 8, scanner 9, printer I / F (interface) 10 to which personal computer 11 is connected.

[0012] The MPU 1 controls each unit constituting the apparatus. Also, the MPU 1 stores H in the ROM 4 as described below.
With reference to the SYNC table (storage unit) 4a, a function of determining a cycle of a horizontal synchronization signal corresponding to a current value obtained when a test voltage is applied to the transfer roller (transfer member) 21 is provided. The NCU 2 controls connection with a telephone line network (PSTN), and also has a telephone number (including a FAX number) of a destination.
And a function for detecting an incoming call. MODEM3 is ITU
(International Telecommunication Union)-Recommendation T. 30 based on a facsimile transmission control procedure according to V.30. 17, V.I. 27t
er, V.E. Modulation of the transmission data and demodulation of the reception data according to 29 or the like. Alternatively, in addition to these, The modulation of the transmission data and the demodulation of the reception data according to S.34 are performed.

The ROM 4 stores a program for controlling this device. The ROM 4 stores the transfer roller 2
The table stores a current value flowing into the transfer roller 21 when the test voltage is applied to the transfer roller 1 and a cycle of a horizontal synchronization signal for forming an electrostatic latent image on the photosensitive drum 13 in accordance with the current value. It has an HSYNC table 4a as a unit. Specifically, as shown in FIG. 7, as described above, the shrinkage rate of the sheet after passing through the fixing device is higher in a high-temperature and high-humidity environment than in a low-temperature and low-humidity environment. The larger the value, the longer the cycle of the horizontal synchronization signal (HSYNC). Therefore, the HSYNC table 4a stores a table of the current value having such a relationship and the cycle of the horizontal synchronization signal.

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. CODEC7
Are MH, M for transmitting the read image data.
Encoding is performed by the R, MMR method or the like, and the received image data is decoded (decoded). The 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 includes a printer controller (control section) 12 for controlling each section of the printer. The printer controller 12 has a function of determining a voltage to be applied to the transfer roller (transfer member) 21, and 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 21 as a table. Having.

A photosensitive drum 13 having a photoconductive film on the outer peripheral surface as an image carrier 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 charger, and a predetermined bias voltage is applied to the charging brush 14 by a charging bias applying 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, a developing device disposed around the photosensitive drum 13 includes a supply roller 17, a developing roller 18 as a developing member, a blade 19, and a developing device bias application circuit 20.
And so on. The supply roller 17 supplies the toner to the developing roller 18 while charging the toner from a toner case (not shown) containing the toner.
, A predetermined bias voltage is applied by the developing device bias application circuit 20. The supply roller 17 and the photosensitive drum 1
A predetermined bias voltage is applied to a developing roller 18 arranged in contact with the developing roller 3 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 member disposed around the photosensitive drum 13 is disposed so as to come into contact with the outer peripheral surface of the photosensitive drum 13 with the sheet conveying path P interposed therebetween.
It is rotated by a drive source (main motor 41). 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 detected by the current detection unit 35, and the detected current value is held 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 outputs the bias voltage to the transfer roller 2.
Apply to 1.

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 sent from a sheet feeding cassette (not shown) in the sheet conveying path P, upstream 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 general, 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 MPU 1 controls the transfer roller 2
It is characterized in that the cycle of the horizontal synchronizing signal is determined according to the current value obtained when the test voltage is applied to [1] (when the FB sequence (feedback sequence)).

Next, an outline of a printing operation including determination of a cycle of a horizontal synchronizing signal of the apparatus will be described with reference to flowcharts of FIGS. 3 to 5 and an operation sequence diagram of FIG.

In FIG. 3, when the printing operation starts, first, in step ST1, 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 removal brush 26 is turned on.

In the next step ST2, the timer T
1, T6 starts, and in step ST3, it is determined whether or not the timer T1 has timed out, and if not, the process waits. Here, the reason why the developing bias is turned ON at (+) is that the toner remaining on the uncharged portion (the portion where the potential is substantially 0 V) on the outer peripheral surface of the photosensitive drum 13 is efficiently used as a developing device. 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 ST4, the developing bias (-) is switched and the transfer bias is turned off. Then, in step ST5, the timer T2 is started, and in step ST6, it is determined whether or not the time of the timer T2 is up. When the timer T2 times out, in step ST7, a test voltage is applied to the transfer roller 21, and the FB sequence is started. The application of the test voltage to the transfer roller 21 is performed in a state where there is no sheet between the photosensitive drum 13 and the transfer roller 21.

In the next step ST8, the timer T
3 starts, and in step ST9, the current value of the transfer roller 21 is detected by the current detection unit 35, and the current value is sampled. In step ST10, it is determined whether or not the time of the timer T3 has expired. If not, the process returns to step ST9, and the current value sampling, that is, the FB sequence is continued.

When the timer T3 expires, the printer controller 12 holds the sampled current value in step ST11. In addition, HS of ROM4
The period of the horizontal synchronization signal corresponding to the obtained current value is determined with reference to the YNC table 4a. Then, step S
At T12, the transfer bias is turned off. Then, in step ST13, the timer T4 is started. In step ST14, it is determined whether or not the timer T4 has timed out.
At 15, the transfer bias (-) is turned ON, and the transfer roller 21 is cleaned again.

Subsequently, in step ST16, the timer T5 is started. In step ST17, 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 ST18.
To Further, in step ST19, the timer T6
It is determined whether or not the time has elapsed, and when the time has elapsed, it is determined in step ST20 whether or not the temperature rise 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 21, the paper feed clutch 42 is turned on, and at step ST22, the timer T7 starts. In step ST23, 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 ST24 whether or not 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 ST25. In step ST25, 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 ST26, a jam is displayed, and the printing process ends.

On the other hand, in step ST23, the PSS
When 30 is turned on, it means that the paper has been sent, and the process proceeds to step ST27. Step ST
At 27, timers T8, T9, T10 start. In step ST28, it is determined whether or not the timer T8 has timed out. When the time has expired, in step ST29, exposure of the electrostatic latent image to the photosensitive drum 13 is started based on the cycle of the horizontal synchronization signal determined in step ST11. . In the next step ST30, it is determined whether or not the time of the timer T9 has expired.
1, a pre-transfer bias is applied.

Next, in step ST32, it is determined whether or not the timer T10 has timed out. When the time has expired, in step ST33, 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 ST34, 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 current value obtained when the test voltage is applied to the transfer roller 21 is referred to the HSYNC table 4a of the ROM 4, and the current value (that is, the temperature and humidity at the time of printing) is obtained. Since the cycle of the horizontal synchronizing signal suitable for (environmental conditions) is determined, an optimal electrostatic latent image can be formed on the photosensitive drum 13 irrespective of a high temperature / high humidity environment or a low temperature / low humidity environment. The problem that the image on the paper, particularly the image in the sub-scanning direction is reduced can be solved.

In the above embodiment, the HSYNC table 4 in the ROM 4 is used to determine the cycle of the horizontal synchronizing signal.
Although a is used, the cycle of the horizontal synchronization signal may be determined using a function. Further, an HSYNC table or function can be provided in the printer controller 12.

[0039]

As described above, according to the image forming apparatus of the first aspect of the present invention, based on the current value when the test voltage for determining the transfer voltage is applied to the transfer member, Estimate temperature and humidity environmental conditions from the values,
By determining the period of the horizontal synchronizing signal suitable for the environmental conditions at that time, it is possible to prevent the toner image on the paper after passing through the fixing device from being reduced in the sub-scanning direction and fixed on the paper. Become.

Further, according to the configuration of the second aspect, the cycle of the horizontal synchronizing signal can be easily determined by a table.

Further, according to the third aspect of the present invention, since a test voltage is applied to the transfer member in a state where there is no sheet between the image carrier and the transfer member, a sequence for directly measuring the moisture absorption of the sheet is inserted. There is no need to perform this, making it easy to realize.

[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 flowchart showing a printing operation of the image forming apparatus.

FIG. 4 is a flowchart following the flowchart of FIG. 3;

FIG. 5 is a flowchart that follows the flowchart of FIG. 4;

FIG. 6 is an operation sequence diagram of the image forming apparatus.

FIG. 7 is a graph showing a relationship between a current flowing into a transfer roller and a cycle of a horizontal synchronization signal for a photosensitive drum in a low-temperature / low-humidity environment and a high-temperature / high-humidity environment in the image forming apparatus.

FIG. 8A is a diagram showing the degree of contraction of a sheet after transfer in a high-temperature and high-humidity environment and after passing through a fixing device in a conventional image forming apparatus, and FIG. FIG. 9B is a diagram illustrating a degree of contraction of a sheet afterward.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 MPU (control part) 4 ROM 4a HSYNC table (storage part) 12 Printer controller (control part) 12a Transfer bias determination table 13 Photosensitive drum (image carrier) 14 Charging brush 16 LED print head 18 Developing roller (developing member) 21 Transfer roller (transfer member) 23 Heating roller (fixing device) 25 Press roller (fixing device)

Continued on front page F-term (reference) 2H027 DA01 DA38 DE07 DE09 EA03 ED04 EE02 EE08 EF06 ZA07 2H076 AB42 AB67 2H200 GA33 GA49 GA56 GB01 GB22 GB25 HA02 HA28 HB07 HB12 JA02 JA29 PA05 PA19

Claims (3)

[Claims] An image carrier on which an electrostatic latent image is formed based on a horizontal synchronization signal; a developing member for developing the electrostatic latent image on the image carrier with toner to form a toner image; A transfer member that transfers the upper toner image to the paper, a fixing device that fixes the transferred toner image to the paper by at least heating, and a control unit that determines a voltage to be applied to the transfer member, the control unit includes: An image forming apparatus, wherein an applied voltage to a transfer member is determined based on a current when a test voltage is applied to the transfer member, and a cycle of a horizontal synchronization signal is determined based on a current value at that time. 2. The apparatus according to claim 1, further comprising a storage unit that stores the current value and the cycle of the horizontal synchronization signal as a table, wherein the control unit determines the cycle of the horizontal synchronization signal based on the table of the storage unit. 2. The image forming apparatus according to 1. 3. The image forming apparatus according to claim 1, wherein the test voltage is applied in a state where there is no sheet between the image carrier and the transfer member.