JP2003156916A - Image forming apparatus, control method and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus and a control method for stably obtaining a high-quality full color image and preventing the trouble of the apparatus from being caused even when the transfer voltage selection value of ATVC (Automatic Transfer Voltage Control) is not appropriate due to an unexpected factor. SOLUTION: This image forming apparatus is provided with a plurality of image carriers, an intermediate transfer body, a plurality of transfer members opposed to the image carriers with the intermediate transfer body interposed therebetween, a plurality of voltage applying means for transferring a plurality of color toner images on the image carriers to transfer material by applying a plurality of levels of transfer voltages to the transfer members, a control means for selecting the transfer voltages by detecting voltage and current characteristics the voltage applying means exhibit, and a storage device in which information on the transfer voltages is stored. Further, it has the control means for correcting an abnormal value in conformity with a correction method by discriminating the abnormal value included in the selected transfer voltages and judging the correction method in the case of correcting the abnormal value on the basis of information on other selected transfer voltages and information on the transfer voltages stored in the storage device.

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 such as a copying machine, a printer, and a facsimile which uses an electrophotographic method, and more particularly, it conveys a toner image of a plurality of colors formed on a plurality of image carriers to a transfer material. A so-called in-line that forms a color image on the transfer material by sequentially superimposing and transferring on the transfer material on the belt, or by sequentially superimposing on the intermediate transfer belt and performing primary transfer, and then secondarily transferring on the transfer material collectively. Type image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, there is known an electrophotographic image forming apparatus which transfers a toner image formed on an image carrier using electrophotography to a transfer material to form an image on the transfer material. Among these, the need for a color image forming apparatus is increasing with the progress of the information society in recent years. Furthermore, in order to increase the speed of color image output, a plurality of image carriers are arranged in a line, and toner images are sequentially formed on each image carrier, and the toner images are directly or intermediately transferred to a transfer material. An in-line type image forming apparatus that transfers by transfer is drawing attention.

In order to reduce the size and cost of the apparatus, the direct transfer type having few system components is advantageous. On the other hand, the method using the intermediate transfer member is not easily affected by the basis weight and the moisture absorption state of the medium such as a recording medium, and thus has an advantage that excellent media compatibility can be obtained without being largely affected by environmental changes.

An example of an inline type full-color image forming apparatus of the intermediate transfer body type will be briefly described with reference to FIG.
The image forming apparatus includes four color image forming units (image forming stations) 10Y, 10M, 10C, and 10K of yellow (Y), magenta (M), cyan (C), and black (K). Photosensitive drum 7 as an image carrier
0 (70Y to 70K).

To form an image, first, the surface of the photosensitive drum 70 (70Y to 70K) at each station is uniformly charged by the charging roller 12 (12Y to 12K), and then the laser exposure device 13 (13Y to 13K) is used. The original is subjected to color separation image exposure to form an electrostatic latent image on the surface of the photosensitive drum 70 corresponding to the separated color of the original, and the latent image is developed by the developing device 1.
4 (14Y to 14K) to develop with a minus toner to form a toner image of each color on the surface of the photosensitive drum 70. The toner image of each color on the photosensitive drum 70 is transferred onto the intermediate transfer belt 80 as a primary transfer power source. Constant voltage power supply 48 (48Y ~
Primary transfer roller 5 to which a primary transfer voltage is applied from 48 K)
4 (54Y to 54K) to sequentially superimpose and perform primary transfer.

After that, the four color toner images on the intermediate transfer belt 80 are secondarily applied to the transfer material P conveyed to the intermediate transfer belt 80 by the secondary transfer voltage from the constant voltage power source 49 of the secondary transfer power source. Secondary transfer is collectively performed by the transfer roller 55, and the transfer material P after the secondary transfer is conveyed to the fixing device 40, and is pressed and heated to melt and mix the toners of four colors to be fixed on the transfer material P. Thus, a full-color image is formed on the transfer material P.

Here, the constant voltage power source 48 (48Y to 48Y)
Each primary transfer voltage applied to the primary transfer roller 54 (54Y~54K) by K), for each station, ATVC disclosed in JP-A-5-6112 Patent Publication (A uto
matic T ransfer V oltage C on
control). Specifically, it is the control that detects the voltage / current characteristics at each station's transfer section and selects and determines the optimum transfer voltage, which allows the surface layer of the photosensitive drum to be scraped, the resistance of the intermediate transfer belt and transfer roller to fluctuate. It is possible to obtain an image forming apparatus that forms a high-quality full-color image by preventing image defects due to transfer voltage mismatch caused by the above.

The purpose of this control is usually to clean the surface of the photosensitive drum during warm-up immediately after the power is turned on before starting the image forming operation, to make the surface potential uniform, to fix the fixing device, and to heat the pressure roller. Within the time called pre-multi-rotation, within the time called pre-rotation for the purpose of adjusting the surface potential of the photosensitive drum immediately before the image forming operation, and for cleaning, within the rotation time between images during continuous printing, etc. To be done.

[0009]

However, the transfer voltage of each station selected by the above-mentioned ATVC in the conventional example sometimes becomes an unsuitable value due to a sudden and unexpected factor. ATV accidentally happens when a temporary electrical contact failure occurs in the transfer system circuit.
When C is performed, or when a malfunction occurs in the electric circuit during ATVC execution due to the input of strong electric noise from the outside of the device, the transfer voltage determined by ATVC is one or several. Inappropriate at that station. In printing under this transfer voltage, good transferability of each color in a full-color image is impaired. Therefore, it is possible to re-execute the ATVC, but this is not preferable for improving the first print time and throughput.

Furthermore, when the ATVC execution frequency is reduced in order to improve the first print time and throughput, printing is continued under an inappropriate transfer voltage for a long time, which may lead to device failure. There is also. For example, under an excessively small voltage, a steady transfer failure in the transfer section continues to supply a large amount of transfer residual toner to the drum cleaner section, so toner scattering inside and outside the apparatus, cleaning failure, and the resulting photosensitive drum and There is concern that the toner may be fused to the charging roller. Further, under an excessive voltage, each transfer system constituent member may be damaged by repeated abnormal discharge or leakage. As described above, the malfunction of the ATVC causes a device failure, which may cause a continuous image defect.

The present invention has been made in view of the above situation, and even if the transfer voltage selection value by the ATVC is not appropriate due to an unforeseen factor, the transfer voltage at each station is always kept good and the image quality is high. It is an object of the present invention to provide an image forming apparatus and a control method capable of stably acquiring a full-color image and preventing a device failure in advance.

[0012]

The present invention can solve the above-mentioned problems by providing the following constitutions.

(1) A plurality of image bearing members, an intermediate transfer member rotating along the plurality of image bearing members, and a plurality of transfer members opposed to each other with the plurality of image bearing members sandwiching the intermediate transfer member. A plurality of voltage applying means for applying a plurality of constant-voltage-controlled transfer voltages to the plurality of transfer members to transfer toner images of a plurality of colors on the plurality of image carriers to a transfer material on the intermediate transfer body. An image forming apparatus comprising: a control unit that detects the voltage / current characteristics indicated by the plurality of voltage applying units and selects the plurality of transfer voltages; and a storage device that stores information regarding the transfer voltages, An abnormal value included in the selected plurality of transfer voltages is identified, and a correction method for making a correction is determined based on the information of other selected transfer voltages and the transfer voltage information stored in the storage device. Then, the abnormal value is corrected according to the correction method. Image forming apparatus characterized by comprising a control means for.

(2) A plurality of image carriers, a transfer material carrier that rotates along the plurality of image carriers, and a plurality of transfers that face each other across the plurality of image carriers and the transfer material carrier. A plurality of members, and a plurality of transfer voltages whose constant voltage is controlled are applied to the plurality of transfer members to transfer the toner images of the plurality of colors on the plurality of image carriers to the transfer material on the transfer material conveying body. Voltage applying means and a voltage indicated by the plurality of voltage applying means
Control means for detecting a current characteristic and selecting the plurality of transfer voltages; a storage device storing information on the transfer voltage;
An image forming apparatus having a plurality of transfer voltages selected, identifying abnormal values included in the plurality of selected transfer voltages, and based on information of other selected transfer voltages and information of the transfer voltage stored in the storage device. An image forming apparatus, comprising: a control unit for determining a correction method for correction and correcting the abnormal value according to the correction method.

(3) The transfer voltage information stored in the storage device is either or both of default transfer voltage information and past transfer voltage information. The image forming apparatus according to 1) or 2).

(4) A plurality of image bearing members, an intermediate transfer member or a transfer material transporting member that rotates along the plurality of image bearing members, a plurality of the image bearing members and the intermediate transfer member or a transfer material transporting member. A plurality of transfer members facing each other with a constant voltage controlled transfer voltage applied to the plurality of transfer members to form toner images of a plurality of colors on the plurality of image carriers on the intermediate transfer body or A plurality of voltage applying means for transferring to the transfer material on the transfer material conveying body, a control means for detecting the voltage / current characteristics indicated by the plurality of voltage applying means and selecting the plurality of transfer voltages, and information about the transfer voltage. And a storage device storing the storage device, and a step of identifying an abnormal value included in the plurality of selected transfer voltages, the information of the other selected transfer voltage, and Stored in storage device Method of controlling an image forming apparatus comprising: the step of determining a correction method in correcting on the basis of the information of the voltage, characterized in that it comprises a control step for correcting the abnormal value in accordance to the modification technique.

(5) A storage medium on which a program for realizing the control method of the image forming apparatus described in (4) above is stored.

That is, in the in-line type image forming apparatus, even if the transfer voltage selection value by ATVC is not appropriate in some stations, they are identified as abnormal values, and the voltage selection values in other stations and the internal storage device are stored. A high-quality full-color image is stable because it has a control mechanism that performs correction after determining the correction method when correcting it based on the transfer voltage information of the default setting stored in Then, it becomes possible to prevent device failures.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an image forming apparatus according to the present invention will be described below.

FIG. 1 is a flow chart showing the procedure of a method of controlling an image forming apparatus according to the first embodiment of the present invention, and FIG. 2 is a schematic sectional view showing a schematic configuration of the image forming apparatus according to the conventional example and the first embodiment. FIG. 3 is a block diagram showing a configuration example of an ATVC control system, FIG. 4 is a diagram showing current / voltage characteristics of the transfer roller in the first embodiment, and FIG. 5 is a schematic configuration of the image forming apparatus in the second embodiment. It is a cross-sectional schematic diagram.

(Embodiment 1) FIG. 2 is a schematic sectional view showing a schematic structure of an image forming apparatus according to Embodiment 1 of the present invention.

In FIG. 2, the image forming apparatus is configured as a "4-drum intermediate transfer system" full-color printer.

<Regarding Image Forming Apparatus and Operation> As shown in FIG. 2, the image forming apparatus of the present invention has four color image forming sections of yellow (Y), magenta (M), cyan (C), and black (K). (Image forming station) 10Y, 10M, 1
0C and 10K, and further includes a transfer device including the intermediate transfer belt 80 and the fixing device 40.

The image forming stations 10Y, 10M,
Image forming units 10C and 10K are provided, and photosensitive drums (drum-shaped electrophotographic photosensitive members) 70Y, 70M, 70C, and 70K, which are image bearing members, are rotatably installed in the direction of arrow a. The photosensitive drums 70Y and 70
Primary charging rollers 12Y, 12 for uniformly charging the surface of the photosensitive drum on the outer peripheral surfaces of M, 70C, 70K, respectively.
M, 12C, and 12K are disposed, and laser exposure devices 13Y and 1Y that expose the surface of the photosensitive drum with laser light modulated in accordance with an image signal are provided on the downstream side of the rotation direction of the photosensitive drum.
3M, 13c, 13K further develop the electrostatic latent image of each color formed on the surface of the photosensitive drum by laser exposure on the downstream side thereof using the corresponding yellow, magenta, cyan, and black toners. Developing devices 14Y, 14M,
14C and 14K are arranged.

Photosensitive drums 70Y, 70M, 70C, 70
At positions on the opposite side of the intermediate transfer belt 80 for K, primary transfer rollers 54Y, 54M, 54 that form a primary transfer portion together with the photosensitive drums 70Y, 70M, 70C, 70K.
C and 54K are installed opposite to each other. The primary transfer rollers 54Y, 54M, 54C and 54K have constant voltage power sources 48Y, 48M, 48C and 48 as primary transfer power sources, respectively.
K is connected and the primary transfer voltage V that can be changed and adjusted respectively
y, Vm, Vc and Vk are applied.

The intermediate transfer belt 80 includes a driving roller 51,
The photosensitive drums 70Y to 70K are installed by being stretched over three rollers, which are a tension roller 52 and a secondary transfer counter roller 53, and extend vertically through the image forming stations 10Y to 10K.
Is placed in contact with. The intermediate transfer belt 80 is rotationally driven by the drive roller 51 in the direction of arrow b in the figure.

A secondary transfer roller 55 is disposed opposite to the secondary transfer counter roller 53 at a position sandwiching the intermediate transfer belt 80, and a constant voltage power source 49 is connected as a secondary transfer power source.
A changeable and adjustable secondary transfer voltage W is applied.

Photosensitive drums 70, 70M, 70C, 70K
The drum cleaners 16Y, 16M, 16C, 1C, 1C are provided on the downstream side of the primary transfer rollers 54Y, 54M, 54C, 54K.
6K is installed. A belt cleaner 33 is arranged at the drive roller 51 of the intermediate transfer belt 80.

The image forming operation of the image forming apparatus configured as described above will be described by taking the yellow image forming station 10Y as an example.

In FIG. 2, the yellow station 10
The Y photosensitive drum 70Y has a photoconductive layer formed on the surface of a cylindrical body made of aluminum, and the surface is uniformly negatively charged (charging potential = − by the primary transfer roller 12Y in the process of rotating in the direction of arrow a). 550 V), and then image exposure is performed by the laser exposure device 13Y (surface potential after exposure = −150 V), and an electrostatic latent image corresponding to the yellow image component of the original is formed on the surface of the photosensitive drum 70Y. The latent image is developed by the developing device 14Y using the negatively charged yellow toner, and the latent image is visualized as a yellow toner image. The obtained yellow toner image is primarily transferred onto the intermediate transfer belt 80 by applying a primary transfer voltage Vy from the primary transfer power supply 48Y to the primary transfer roller 54Y. After the transfer, the transfer residual toner adhering to the surface of the photosensitive drum 70Y is removed by the cleaner 16Y and is used for the next image formation.

The above-mentioned image forming operation is performed at a predetermined timing in each of the image forming stations 10Y to 10K, and the toner images on the photosensitive drums 70Y to 70K are sequentially transferred onto the intermediate transfer belt 80 at their respective primary transfer portions. The primary transfer is performed by overlapping.

In the full-color mode, the toner images are sequentially transferred to the intermediate transfer belt 80 in the order of yellow, magenta, cyan, and black. In the single-color or 2-3-color mode, the toner images of the required colors are transferred. Are transcribed in the same order as above.

After that, the four color toner images on the intermediate transfer belt 80 are grounded by the secondary transfer roller 55 with the intermediate transfer belt 80 sandwiched therebetween as the intermediate transfer belt 80 rotates in the direction of arrow b. It is moved to the secondary transfer portion that is in contact with the next transfer opposing roller 53, and is collectively transferred onto the transfer material P that is supplied thereto by the paper feed roller 20 at a predetermined timing.
Next is transcribed. The secondary transfer is performed by applying a secondary transfer voltage W to the secondary transfer roller 55 from the constant voltage power source 49 of the secondary transfer power source.
Is applied.

Transfer material P to which the four color toner images are secondarily transferred
Is conveyed to a fixing device 40, where it is pressurized and heated to melt and mix the toners of four colors, and the toner is fixed on the transfer material P, thus forming a full-color image on the transfer material P. On the other hand, 2
The intermediate transfer belt 80, which has completed the next transfer, has residual toner remaining on the surface thereof removed by the belt cleaner 33.

In this embodiment, the photosensitive drums 70Y to 70K are used.
A negatively chargeable OPC drum having a diameter of 30.6 mm (photosensitive layer film thickness is 20 μm) is applied to the charging rollers 12Y to 12K, and a charging voltage in which an AC component is superimposed on a DC component is applied to the charging rollers 12Y to 12K. The surface was uniformly charged to about -550V. The laser exposure devices 13Y to 13K have a wavelength of 760.
nm near infrared laser diode and photosensitive drum 70Y
To 70K and a polygon mirror for scanning the laser beam, and the surface potential of the photosensitive drums 70Y to 70K at the exposure unit-
The voltage is lowered to 150 V to form an electrostatic latent image using this as an image portion.

The developing device is a contact developing type developing device using a non-magnetic two-component developer for all colors, and AC for the DC component.
By the developing voltage in which the components are superimposed, the photosensitive drum 70Y,
Inverse development is performed on the electrostatic latent images on 70M and 70C.

The primary transfer rollers 54Y to 54K have a diameter of 8
mm core metal is covered with an NBR / hydrin-based conductive rubber layer over a length of 310 mm to have a diameter of 16 mm, and each core metal has a high-voltage power source 48Y through a power supply spring (not shown). It is connected to 48K. The roller hardness is 35 ° in Asker C, and the resistance value is 24 m.
An aluminum cylinder with a diameter of 30 mm, which is driven to rotate at a peripheral speed of m / sec, has a primary transfer roller with a load of 500 g on both ends.
And a voltage of 50 V is applied between the cylinder and the primary transfer roller, and the measured value is about 1 × 10 ⁷ Ω.

The secondary transfer roller 55 is formed by covering a core metal having a diameter of 8 mm with a urethane-based conductive rubber layer over a length of 310 mm to form a diameter of 17 mm. The resistance value measured by the same method as that of the primary transfer roller is about 1 × 10 ⁷ Ω. The core metal of the secondary transfer roller 55 is also connected to the high-voltage power supply 49 via a power supply spring.

Drive roller 51, tension roller 52,
Each of the secondary transfer facing rollers 53 is made of an aluminum conductive roller having a diameter of 32 mm, and the cored bar portion is grounded via a power supply spring.

The intermediate transfer belt 80 is a single-layer seamless endless belt made of polyimide resin whose resistance is adjusted by carbon dispersion, and has dimensions of 75 μm in thickness, 1115 mm in circumferential length, and 310 mm in width direction perpendicular to the circumferential direction. is doing. In accordance with JIS-K6911, in order to obtain good contact between the electrode and the belt surface, a conductive rubber is used as the electrode, and the product is Advantest (trademark) R834.
0 Using an ultra-high resistance meter, the volume resistivity ρ of the intermediate transfer belt
When v and the surface resistivity ρs are measured, ρv = 5 × 10 ⁸ Ωcm and ρs = 1 × 10 ¹³ Ω when 100 V is applied for 10 seconds. Note that ρs has the same value on both the front and back surfaces of the belt.

The tension of the intermediate transfer belt 80 stretched around the three rollers 51, 52 and 53 is 6 kgf.
The distance between the drive roller 51 and the tension roller 52 is 50
0 mm, each image forming station 10Y to 10K
Photosensitive drums 70Y-70K and primary transfer roller 54Y-
The primary transfer portion composed of 54K and rollers 51, 52
They are arranged at equal intervals on the intermediate transfer belt 80 between them. Each primary transfer roller 54 is lifted by springs having a load of 500 gf provided at both ends.
The secondary transfer roller itself is in contact with the back surface of the intermediate transfer belt 80 by a force less the own weight of 150 g.

In this image forming apparatus, the maximum size of transfer material that can be used is A3. The process speed is 117
mm / sec. The primary transfer voltage Vy to Vk is approximately +4.
By setting the secondary transfer voltage W at 50 V to about +2.3 kV, good transferability on plain paper can be obtained for all colors.

<Regarding ATVC Control> Next, the ATVC control in this image forming apparatus will be described. Since this control is performed in all stations in the same way,
Take one station as an example.

In this ATVC, a means for digitally increasing or decreasing the voltage applied to the primary transfer roller 54 and the photosensitive drum 7 via the intermediate transfer belt 80 from the primary transfer roller 54.
The current flowing from the primary transfer roller to the photosensitive drum 70 is set to a constant value by using the means for detecting the current flowing into 0 and the means for determining whether or not the flowing current reaches a desired target current. The transfer constant voltage at that time is stored for each station and used as the primary transfer voltage during actual transfer.

Specific control is shown below.

Each station has an ATVC control system circuit shown in the block diagram of FIG. Photosensitive drum 7
The transfer roller 54 is in contact with 0 through the intermediate transfer belt 80, and a transfer voltage is applied to the core of the transfer roller 54 from the transfer high-voltage power supply 48. The transfer high-voltage power supply 48 is controlled by the signal HVTIN from the DC controller 483 during non-transfer. That is, when a digital signal is input from the DC controller 483 to the D / A converter 480, it is converted into an analog voltage of 0 to 5 V by the D / A converter 480, and the output voltage of the transfer high-voltage power supply 48 is 0 by this analog voltage. Linearly controlled to ~ 2KV.

A CPU (not shown) in the DC controller 483 performs the following control sequence.

The photosensitive drum 70 is driven by a driving device (not shown).
In the state where is driven to rotate, uniform charging to the VD potential on the surface of the photosensitive drum 70 is started. When the charging portion on the surface of the photosensitive drum 70 reaches the transfer nip portion formed by the photosensitive drum 70 and the intermediate transfer belt 80, the DC controller 4
83 to D / A converter 480 signal (HVTIN)
Is input and the operation of digitally changing the voltage starts.

When the D / A converter 480 outputs a constant voltage stepwise increased from 0 V, the transfer high-voltage power supply 48 also outputs a constant voltage sequentially increased from 0 V (40 V every 10 ms). Increase in increments),
The current flowing from the transfer roller 54 to the photosensitive drum 70 via the intermediate transfer belt 80 is input to the A / D converter 481 via the current detection circuit 482. This is 0-5V
Is converted into a voltage of HVTOUT and sent to the CPU in the DC controller 483 to be compared with the target value. As this target value, a preset target current (14 μA, which will be described later) is set to the A / D converter 481.
It is a value obtained by converting the current and voltage by.

Then, the value obtained by converting the detection current output from the current detection circuit 482 by the A / D converter 481 gradually increases, and after reaching the vicinity of the target value, the HV
The TIN value is increased / decreased at any time to perform fine adjustment, and the transfer high-voltage power supply 48 outputs a voltage that increases / decreases in 5 V intervals every 10 ms, and the target value and the value obtained by converting the detected current by the A / D converter 481 match. Sometimes it ends the control. At the same time, C in the DC controller 483
The value of the digital signal HVTIN that outputs a constant transfer voltage that allows the target current to flow is stored in PU. This transfer voltage is a voltage selection value by ATVC (Vytemp, Vmtemp, Vctem for each station).
p, Vktemp).

At the time of transfer, the DC controller 4
The transfer HVTIN value stored in the CPU in 83 is input to the D / A converter 480, and this voltage is applied to the transfer roller 54.

Here, the superiority of the ATVC will be described.

FIG. 4 shows the voltage applied to the transfer roller and the darkness on the photosensitive drum 70 due to manufacturing variations in the resistance value of the primary transfer roller 54 in the image forming apparatus of this embodiment in the initial stage of use in terms of durability under normal environment. Potential VD part (photoreceptor VD
3 is a graph showing the relationship between the amount of current flowing into the (part) (current flowing into the photoconductor). That is, FIG. 4 shows the transfer to the dark potential (−550 V) on the photosensitive drum 70 in each primary transfer roller 54 having the resistance measurement value of 5 × 10 ⁶ to 2 × 10 ⁷ Ω by the above-described measurement method. It shows the voltage and current characteristics.

As shown in the figure, when the current is larger than the boundary current a, density unevenness (nonuniformity of transfer efficiency) due to strong transfer defects occurs in the halftone image area, and the current is smaller than the boundary current b. Then, a density decrease occurs due to a transfer failure in a solid image portion or the like. Therefore, in the image forming apparatus 1
In the next transfer system, ATV with a target current of 14 μA
By performing C control independently at each station, good transferability of each color is maintained.

The voltage / current characteristic curve shown in FIG.
Not only the resistance of the primary transfer roller, but also the film thickness of the photosensitive drum and the resistance of the intermediate transfer belt. It is possible to always find the optimum transfer voltage by absorbing the influence of fluctuations of all these factors and following the environment and durability of the device.
Is the advantage of.

Next, the required time and execution timing of the ATVC control of this embodiment will be described. The time required for the ATVC control is about 2.5 seconds, including the actual voltage application time and the time for uniformly charging the surface of the photosensitive drum 70 before and after that. In addition, the control execution timing is 100 before conversion in multiple rotations immediately after the power is turned on and when converted to A3 size paper.
It is suppressed during pre-rotation for each page interval or between images during continuous printing. The timing of this implementation is to maintain the good transferability by following the changes in the voltage-current characteristics of the transfer system due to environmental changes and durability changes during use of the device, while securing the first print time and throughput of the image forming device. It is necessary and sufficient.

<Regarding Correction Control of ATVC Implementation Result>
Here, what is characteristic of the image forming apparatus of this embodiment is that one of the stations selected by the ATVC is used.
The abnormal value is identified from the next transfer voltage, and it is corrected based on the transfer voltage information of other stations, the past transfer voltage information stored in the main body storage device, and the default transfer voltage information. That is, the control means for performing the correction after determining the correction method for performing the correction is provided.

Details of this control will be described with reference to the flowchart shown in FIG.

As a result of performing ATVC at each station, the selected primary transfer voltage is set to Vytemp, Vmte.
mp, Vctemp, and Vktemp (step S
1). Next, according to the following identification standard A, if there is an abnormal value among these, it is identified (step S2).

<Identification Criteria A> Vytemp <300
[V], or Vy if Vytemp> 600 [V]
temp is an abnormal value.

Vmtemp <300 [V] or Vm
If temp> 600 [V], Vmtemp is an abnormal value.

Vctemp <300 [V] or Vc
If temp> 600 [V], Vctemp is an abnormal value.

Vktemp <300 [V] or Vk
If temp> 600 [V], Vktemp is an abnormal value.

The optimum primary transfer voltage of each station in the image forming apparatus at the initial stage of use concerning normal environment and durability is
Normally, depending on the resistance value variation of the primary transfer roller, about 3
It takes a value within the range of 00V to 600V (see FIG. 4). The above-mentioned standard is an abnormal value when the selected value by ATVC deviates from this voltage range. The primary transfer roller resistance, intermediate transfer belt resistance, photosensitive drum film thickness, etc. vary depending on the environment and the durability of the device, and the voltage / current characteristics of the transfer system also change. To be done.

Here, Vytemp, Vmtemp, V
If an abnormal value is present in ctemp or Vktemp, the process proceeds to step S3, and it is determined which correction method is used for correction according to the following criterion A.

<Judgment Criteria A> If the environmental zone has not changed since the previous execution of ATVC, the process proceeds to step S4,
The correction is performed according to the correction method A.

When the environmental zone is changing, Vytem
If an abnormal value and a non-abnormal value among p, Vmtemp, Vctemp, and Vktemp are mixed, the process proceeds to step S5, and correction is performed according to the correction method B.

If the environmental zones have changed and all four have abnormal values, the process proceeds to step S6, and correction is performed according to the correction method C.

The environment zone is preset based on environment (temperature and humidity) information acquired from an environment sensor provided in the main body. In the image forming apparatus, the absolute water content Wabs calculated from the temperature and humidity is used as an index to perform zone division at intervals of ΔWabs = 2 [g / m ³ ].

Next, the abnormal value is corrected by the following correction methods A, B,
Or, modify according to C.

<Correction Method A> The abnormal value is corrected to the voltage value of the station stored in the main body storage device and determined at the previous execution of ATVC.

<Correction Method B> The abnormal value is corrected by the arithmetic mean value of the stations which are not abnormal values.

That is, when the abnormal value is one, the other three normal voltage values are two, and when it is two, the other two normal voltage values are three,
In the case of one, it is corrected by the arithmetic mean value of the other one normal voltage value.

<Correction Method C> An abnormal value is set as a default setting value 450V stored in the main body storage device (a central value within the primary transfer voltage fluctuation range 300V to 600V due to variations in the resistance of the primary transfer roller during manufacturing). ) To fix.

The default setting value stored in the main body storage device is appropriately changed according to the environment and the durability state of the device, like the identification standard A.

After the above control, the primary transfer voltages Vy, Vm, Vc and Vk of each station are finally determined by the following formula (step S7).

Vy≡Vytemp Vm≡Vmtemp Vc≡Vctemp Vk≡Vktemp ...
Primary transfer voltage Vy, Vm, Vc, Vk of each station
Is determined by the above equation (1).

Next, a specific example of this correction control will be shown.

It is assumed that the primary transfer voltage shown in Table 1 below is selected by ATVC.

[0080]

[Table 1]

In this case, 1 at the cyan station
Since the next transfer voltage selection value Vctemp satisfies the identification criterion A, it is identified as an abnormal value.

If the environmental zone has not changed since the previous execution of ATVC, the cyan station voltage value (380 [V]) determined by the ATVC in the same environmental zone last time is used in accordance with the correction method A. To correct it (Table 2 below).

[0083]

[Table 2]

On the other hand, if the environmental zone is changing,
According to the correction method B, Vctemp≡ (Vytemp + Vmtemp + Vkt
emp) / 3 = (350V + 430V + 450V) / 3
= 410V is corrected (Table 3 below).

[0085]

[Table 3]

As another specific example, assume that the primary transfer voltage shown in Table 4 below is selected by ATVC.

[0087]

[Table 4]

In this case, the primary transfer voltage selection values at all stations satisfy the discrimination standard A and are discriminated as abnormal values.

Therefore, according to the correction method C, all the voltage values are corrected by the default setting value (450V) stored in the main body storage device (Table 5 below).

[0090]

[Table 5]

In Table 1 above, Vctemp is an abnormal value deviating from the normal primary transfer voltage fluctuation range of 300V to 600V. This is due to some unexpected factors.
This is a result of an improper voltage selection value by the TVC.

Therefore, in the control of this embodiment, if the environmental zone has not changed since the previous ATVC was carried out,
In accordance with the correction method A, the abnormal value is replaced with the voltage value determined at the previous ATVC execution. The reason why this is useful is as follows. Of the factors that change the voltage / current characteristics of the transfer system, the one having the highest environmental dependence is the transfer roller resistance. However, this change in resistance is also minute within the range of the single zone of the environmental zone division described above. Therefore, it is considered that the normal transfer voltage to be selected by the ATVC at the present time is almost the same as that when the ATVC was previously performed on the same roller.

On the other hand, when the environmental zone is changing, according to the correction method B, Vytemp, Vmtemp, and Vktem, which are normal values for abnormal values, are selected by ATVC.
We are working to replace with the arithmetic mean value of p. The reason why this is useful is as follows. Originally, the primary transfer rollers mounted in a single device belong to the same manufacturing lot, and there is little variation in resistance between them. Further, since the photosensitive drums and the primary transfer rollers of each station in the single device have the same durability history, the durability fluctuations of the drum film thickness and the roller resistance are about the same. Therefore, the voltage / current characteristics of each station are similar, and the voltage selection value of each station by ATVC is usually ± 5% from each other.
It is kept within a difference range of about 0V. Therefore, it can be said that the Vctemp modified as described above does not differ from the normal transfer voltage to be selected by ATVC by ± 50V or more.

Further, in Table 3 above, all voltages are abnormal values. In this case, in accordance with the correction method C, all are replaced by the central value representing the primary transfer voltage fluctuation range 300V to 600V due to the variation in the resistance value of the primary transfer roller during manufacturing.

As described above, the transfer voltage corrected according to the optimum correction method according to each situation is strictly A
Although it is different from the optimum voltage of each station selected by the TVC, it can be used as a substitute, and it is possible to suppress defective transfer and strong transfer of defects to a slight level. Thereby, good transferability of each color can be maintained.

Further, in the present image forming apparatus, an AT is used for the purpose of shortening the first print time and improving the throughput.
Since the execution frequency of VC is suppressed, continuous printing under an improper transfer voltage may cause a device failure. However, due to the transfer voltage modified as above,
This is also prevented beforehand.

As described above, according to this embodiment,
Even if the transfer voltage selection value by ATVC is not appropriate in some stations, it is identified as an abnormal value, and the voltage selection values of other stations and the transfer voltage information of the default setting stored in the main body storage device are stored. Since it has a control method that performs correction after determining the correction method when correcting it based on the information of the past transfer voltage, a high-quality full-color image can be stably obtained and device failure can be prevented. become able to.

(Embodiment 2) FIG. 5 is a schematic sectional view showing the schematic construction of Embodiment 2 of the image forming apparatus according to the present invention.

The image forming apparatus of this embodiment is obtained by modifying the intermediate transfer type image forming apparatus of the first embodiment shown in FIG. 2 into a multiple transfer type image forming apparatus.

<Regarding Image Forming Apparatus and Operation> In this embodiment, the intermediate transfer belt 80 of the image forming apparatus of Embodiment 1 is used.
Instead of the transfer belt 90, which is a belt-shaped transfer material transporter.
The transfer material P supplied from the paper feed roller 20 is carried on the transfer belt 90 and conveyed, and the photosensitive drums 70Y to 70K of the image forming stations 10Y to 10K are used.
The toner images of the respective colors on the photosensitive drums 70Y to 70K are transferred onto the transfer material P at a transfer portion facing the constant voltage power sources 48Y to 48K.
Transfer rollers 54Y to 54K to which a transfer voltage is applied from K
Multiple transfer by. After that, the transfer material P is separated from the transfer belt 90 and conveyed to the fixing device 40, and the four-color toner images are pressed and heated to form a full-color fixed image.

As the transfer belt 90 of this embodiment,
The same one as the intermediate transfer belt 80 is used. Further, the transfer rollers 54Y to 54K and the constant voltage power source 48Y to
For 48K, the one for primary transfer in the image forming apparatus of the first embodiment is used as it is. In addition, those not particularly described are the same as those of the image forming apparatus.

In this image forming apparatus, by setting the transfer voltage at each station to Vy to Vk at about 1200 V, good transferability on plain paper can be obtained for all colors.

<Regarding ATVC Control> The ATVC control in this embodiment is similar to that in the first embodiment. A means for digitally increasing / decreasing the voltage applied to the transfer roller 54 when the paper is not passed, a means for detecting a current flowing from the transfer roller 54 to the photosensitive drum 70 via the transfer belt 90, and a desired inflow current. And a means for determining whether or not the target current has been reached, the current flowing from the transfer roller 54 to the photosensitive drum 70 is converged to a constant value, and the transfer constant voltage at that time is stored and used for each station. To do.

In the image forming apparatus of this embodiment,
Transfer voltage selection values Vytemp, Vmtem of each station by ATVC with a target current of 14 μA
Transfer voltages Vy, Vm, Vc, and Vk obtained by adding the following corrections to p, Vctemp, and Vktemp are used during actual transfer.

Vy≡Vytemp × 2 Vm≡Vmtemp × 2 + 200 [V] Vc≡Vctemp × 2 + 300 [V] Vk≡Vktemp × 2 + 300 [V] (2) The validity of the correction formula (2) is as follows. Proved by

Under normal environment, two sets of transfer rollers (4 rollers each) having different manufacturing lots (that is, resistance levels) are attached to the image forming apparatus of this embodiment at the beginning of use regarding durability, and a target current of 14 μA is set. The voltage selection values Vytemp, Vmtemp, Vctemp by ATVC,
Tables 6 and 7 below show the relationship between Vktemp and the optimum transfer voltages Vy, Vm, Vc, and Vk at which good transferability for each color is obtained. Optimal transfer voltage Vy, Vm, Vc, V
Similarly to the first embodiment, k is a voltage at which good transferability of each color without transfer defects or transfer defects is obtained on A3 size plain paper.

[0107]

[Table 6]

[0108]

[Table 7]

From Tables 6 and 7 above, the voltage selection values Vytemp, Vm by ATVC using 14 μA as the target current
Double that for temp, Vctemp, and Vktemp, and 2 for each of M, C, and K stations.
It can be seen that the optimum transfer can be performed by the transfer voltage that has been corrected (contents of the correction formula (2)) by applying 00V, 300V, and 300V. Qualitatively, this correction qualitatively doubles to convert the transfer voltage selection value of the ATVC in the transfer portion when the paper is not passed to the voltage value when the paper is passed, and further, 200 to 300 V is added to it at the downstream station Therefore, it can be explained that the increase in the required transfer voltage corresponding to the charge up of the transfer material is compensated. The correction formula (2) is changed at any time depending on the environment, the durability of the apparatus, the type and size of the transfer material.

<Regarding Correction Control of ATVC Implementation Result>
Here, also in the image forming apparatus of this embodiment, the first embodiment
Similarly, the transfer voltage Vytemp, Vmtemp, Vctemp, V of each station selected by ATVC
The abnormal value is identified from the ktemp, and it is corrected by using the transfer voltage information of another station, the past transfer voltage information stored in the main body storage device, and the default setting transfer voltage information. A control method is provided.
The control flow at this time is the same as that in the first embodiment.

This will be described below.

The transfer voltages selected as a result of performing ATVC at each station are Vytemp, Vmtemp, and V.
Let ctemp and Vktemp. Next, according to the following identification standard A, if there is an abnormal value among these, it is identified.

<Identification Criteria A> Vytemp <300
[V], or Vy if Vytemp> 600 [V]
temp is an abnormal value.

Vmtemp <300 [V] or Vm
If temp> 600 [V], Vmtemp is an abnormal value.

Vctemp <300 [V] or Vc
If temp> 600 [V], Vctemp is an abnormal value.

Vktemp <300 [V] or Vk
If temp> 600 [V], Vktemp is an abnormal value.

The numerical values within the above criteria may be appropriately changed depending on the environment and the durability of the device.

Here, Vytemp, Vmtemp, V
If an abnormal value exists in ctemp or Vktemp, it is determined which correction method is used for correction according to the following criterion A.

<Judgment Criteria A> If the environmental zone has not changed since the previous ATVC was carried out, the correction is carried out according to the correction method A.

When the environmental zone is changing, Vytem
When an abnormal value and a non-abnormal value among p, Vmtemp, Vctemp, and Vktemp are mixed, correction is performed according to the correction method B.

When the environmental zone has changed and all four have abnormal values, the correction is performed according to the correction method C.

The environment zone is preset based on environment (temperature and humidity) information acquired from an environment sensor provided in the main body. In the image forming apparatus, the absolute water content Wabs calculated from the temperature and humidity is used as an index to perform zone division at intervals of ΔWabs = 2 [g / m ³ ].

Next, the abnormal value is corrected by the following correction methods A, B,
Or, modify according to C.

<Correction Method A> The abnormal value is corrected to the voltage value of the station stored in the main body storage device and determined at the previous execution of ATVC.

<Correction Method B> The abnormal value is corrected by the arithmetic mean value of the stations which are not abnormal values.

That is, when the abnormal value is one, the other three normal voltage values are two, and when it is two, the other two normal voltage values are three.
In the case of one, it is corrected by the arithmetic mean value of the other one normal voltage value.

<Correction Method C> An abnormal value is set to a default setting value 450V stored in the main body storage device (a transfer voltage fluctuation range 300V due to a variation in the resistance value of the transfer roller during manufacturing).
Correct to a center value within 600V).

The default setting value stored in the main body storage device is appropriately changed according to the environment and the endurance state of the device, like the identification standard A.

After the above control, the transfer voltages Vy, Vm, Vc and Vk of each station are finally determined by the above-mentioned correction formula (2).

Therefore, the transfer voltages Vytemp, Vmtemp, Vctemp and V selected by the ATVC are set.
Even if an abnormal value exists in ktemp, it is corrected and then substituted into the correction formula (2) to determine the transfer voltages Vy, Vm, Vc, and Vk during actual printing, thereby obtaining a high-quality full-color image. It is possible to obtain a stable value and prevent a device failure.

Since the present image forming apparatus is of a type in which toner images are directly transferred onto a transfer material in a multiple manner, the transfer voltage setting margin for obtaining good transferability of each color has an intermediate transfer type image formation. It is smaller than the device (primary transfer system).
This is particularly noticeable in high resistance paper and transfer materials having poor surface properties. In this case, needless to say, the correction control further increases its importance.

As described above, even in the image forming apparatus of the multi-transfer system, when the transfer voltage selection values by ATVC are not appropriate in some stations, they are identified as abnormal values and the voltage selection values of other stations are identified. ,
In addition, since it has a control method for performing correction after determining a correction method for correcting the transfer voltage based on the default transfer voltage information stored in the main body storage device and the past transfer voltage information, It is possible to stably obtain a high-quality full-color image and prevent device failure.

The control method according to the present invention is not limited to that in the image forming apparatus according to the above-described first and second embodiments, and the abnormal value of the ATVC result is identified, and the transfer voltage of another station and the , An in-line type of any form in which the correction is made after determining the correction method based on either the default transfer voltage stored in the main body storage device, the past transfer voltage, or both of them. It also includes all types of control methods in the image forming apparatus.

[0134]

As described above, according to the present invention,
In the in-line type image forming apparatus, even if the transfer voltage selection value by ATVC is not appropriate in some stations, they are identified as abnormal values and stored in the voltage selection values of other stations and in the main body storage device. The transfer voltage information of the default setting, the control method to determine the correction method when correcting it based on the information of the past transfer voltage, and has a control method to perform correction, stable high-quality full-color image can be obtained, This has the effect of preventing device failures.

[Brief description of drawings]

FIG. 1 is a flowchart showing a procedure of a control method of an image forming apparatus according to a first embodiment of the invention.

FIG. 2 is a schematic sectional view showing a schematic configuration of an image forming apparatus according to a conventional example and a first example.

FIG. 3 is a block diagram showing a configuration example of an ATVC control system.

FIG. 4 is a chart showing current-voltage characteristics of the transfer roller in the first embodiment.

FIG. 5 is a schematic sectional view showing a schematic configuration of an image forming apparatus according to a second embodiment.

[Explanation of symbols]

10Y-10K Image forming station 12Y-12K charging roller 48Y to 48K constant voltage power supply 50Y-50K constant current power supply 54Y-54K Transfer roller 70Y-70K Photosensitive drum 20 paper feed rollers 33 Belt cleaner 40 fixing device 49 constant voltage power supply 51 drive roller 52 Tension roller 53 Secondary transfer counter roller 55 Secondary transfer roller 80 Intermediate transfer belt 90 Transfer belt P transfer material

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koichi Hiroshima             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation F term (reference) 2H030 AA03 BB02 BB23 BB42 BB46                       BB54                 2H200 FA01 FA02 GA12 GA14 GA16                       GA23 GA34 GA44 GA45 GA47                       GA52 GA57 GA59 GB12 GB25                       HA02 HB12 HB22 JA02 JA25                       JA26 JA27 JA28 JA29 JA30                       JB07 JB10 JB25 JB32 JC04                       JC07 JC09 JC12 JC15 JC16                       JC17 JC18 JC19 JC20 MA03                       MA04 MA14 MA20 MB01 MB02                       MB04 MB05 MC01 MC02 NA02                       NA09 NA15 PA03 PA29 PB05                       PB26 PB27 PB28

Claims (5)

[Claims] 1. A plurality of image bearing members, an intermediate transfer member rotating along the plurality of image bearing members, and a plurality of transfer members facing each other with the plurality of image bearing members sandwiching the intermediate transfer member. A plurality of voltage application means for applying a plurality of constant-voltage-controlled transfer voltages to the plurality of transfer members to transfer toner images of a plurality of colors on the plurality of image carriers to a transfer material on the intermediate transfer body; An image forming apparatus comprising: a control unit that detects the voltage / current characteristics indicated by the plurality of voltage applying units and selects the plurality of transfer voltages; and a storage device that stores information regarding the transfer voltages. The abnormal values included in the plurality of transfer voltages that have been selected are identified, and a correction method for making a correction is determined based on the information of other selected transfer voltages and the information of the transfer voltage stored in the storage device. , The abnormal value is corrected according to the correction method. Image forming apparatus characterized by comprising a control means for. 2. A plurality of image bearing members, a transfer material transport member rotating along the plurality of image bearing members, and a plurality of transfer members facing each other with the plurality of image bearing members sandwiching the transfer material transport member. And a plurality of voltages for applying a plurality of constant-voltage-controlled transfer voltages to the plurality of transfer members to transfer toner images of a plurality of colors on the plurality of image carriers to the transfer material on the transfer material transport body. An image forming apparatus including: an application unit; a control unit that detects the voltage-current characteristics indicated by the plurality of voltage application units to select the plurality of transfer voltages; and a storage device that stores information about the transfer voltages. And a method of correcting when an abnormal value included in the selected plurality of transfer voltages is identified and corrected based on information of another selected transfer voltage and information of the transfer voltage stored in the storage device. And the abnormal value according to the correction method. Image forming apparatus characterized by comprising a control means for modifying. 3. The transfer voltage information stored in the storage device is either or both of default transfer voltage information and past transfer voltage information. Alternatively, the image forming apparatus described in 2. 4. An image carrier, a plurality of image carriers, an intermediate transfer member or a transfer material conveying member rotating along the plurality of image carriers, and a plurality of the image carriers and the intermediate transfer member or the transfer material conveying member. By applying a plurality of constant-voltage-controlled transfer voltages to the plurality of transfer members that face each other with the plurality of transfer members interposed therebetween, the toner images of the plurality of colors on the plurality of image carriers are transferred onto the intermediate transfer body or transferred. A plurality of voltage applying means for transferring to the transfer material on the material conveying body, a control means for detecting the voltage / current characteristics indicated by the plurality of voltage applying means and selecting the plurality of transfer voltages, and information about the transfer voltage. A method of controlling an image forming apparatus having a stored storage device, the method including the step of identifying an abnormal value included in the selected plurality of transfer voltages, the information of the other selected transfer voltage, and the storage. Transfer voltage stored in the device A step of determining a correction method when modifying the information based on the control method for an image forming apparatus characterized by comprising a control step for correcting the abnormal value in accordance to the modification technique. 5. A storage medium on which a program for realizing the control method of the image forming apparatus according to claim 4 is stored.