JPH05346724A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an image forming device by which a high-quality image is obtained by easily selecting optimum developing bias voltage even when the characteristic of the electric resistance of developer is changed. CONSTITUTION:The latent image of a reference pattern 700 is repetitively formed five times in a rotating direction at positions having different axial direction on the respective photosensitive drum surfaces of four colors. The five latent images in the rotating direction are developed by making the magnitude of the AC component (Vp-p) of the developing bias voltage different, and the toner images of respective colors are transferred on one recording paper 800. An operator compares and evaluates the plural images of the reference pattern, selects the optimum value of Vp-p (the peak of the AC component), and sets it as the standard condition of Vp-p in the case of forming the image next time. The reference pattern 700 is constituted of the solid image having three kinds of density. Present Vp-p is included in Vp-p at the time of forming the toner image. Upper and lower limit values are set to Vp-p, and an image producing process condition may be changed for the color where Vp-p is changed.

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 facsimile or a printer, and more specifically, it develops with a two-component developer under a developing bias voltage in which an AC voltage is superimposed on a DC voltage. The present invention relates to an image forming apparatus including a developing device.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus equipped with a developing device for developing with a two-component developer containing toner and carrier (hereinafter referred to as "developer"), a developing sleeve of the developing device receives a DC voltage and an AC voltage. A method of applying a developing bias voltage in which voltages are superimposed is known. A developing bias voltage (hereinafter referred to as AC
When a bias voltage) is applied to the developing sleeve to perform development, the developing ability is enhanced and the sleeve linear velocity ratio (linear velocity on the sleeve surface / linear velocity on the photosensitive drum surface) can be lowered. As a result, the occurrence of edge phenomenon is reduced, scratches due to the developer (brush marks) and the phenomenon that the toner is accumulated at the trailing edge of the solid image portion and the density is increased (sweep) are prevented. It is intended to improve uniform reproducibility, particularly reproducibility of a halftone solid image portion. For color copiers and color printers having many halftone solid image portions, uniform reproducibility of halftone solid image portions is particularly required.

By the way, in order to apply the AC developing bias voltage to the developing sleeve to obtain the above effect, it is necessary to consider the electric resistance of the developer. For example, when an AC developing bias voltage is applied when a low resistance developer is used, leakage occurs through the AC developing bias voltage developer, and conversely, when an AC developing bias voltage is used when a high resistance developer is used. When a voltage is applied, it is difficult to prevent the edge phenomenon from occurring. A suitable electrical resistivity value for the developer is a medium resistance of 10 ⁹ to 10 ¹² Ωcm at a measurement voltage of 500V. However, even when this medium resistance developer is used, the optimum value of the AC developing bias voltage differs depending on the difference in the electric resistivity. For example, when the electric resistivity of the developer is high, the optimum value of the peak-to-peak voltage (hereinafter referred to as Vp-p) of the AC component of the AC developing bias voltage is high, and when the electric resistivity is low, the AC developing bias voltage Vp- The optimum value of p is low.

[0004]

Conventionally, as a carrier of a developer, a spherical ferrite coated with a resin is used in order to obtain a desired electric resistivity and a desired life. The electric resistivity of the carrier coated with this resin is usually controlled by the thickness of the coating layer. The thickness of the coating layer is inevitably thin in order to obtain a medium resistance carrier. When a carrier having this thin coating layer is used, film abrasion occurs during development and the electric resistance of the carrier (≈
Since the electric resistance of the developer is likely to decrease greatly, the charge amount of the developer changes accordingly and the life of the developer is shortened.

As described above, when the electric resistance of the developer changes and the charge amount changes, V of the optimum AC developing bias voltage is obtained.
The pp application conditions change. Therefore, in order to extend the life of the developer, it is necessary to change the application condition of the AC developing bias voltage. Further, when the electric resistance of the developer changes and the charge amount changes, optimization of the direct current component (hereinafter, referred to as Vdc) of the development bias voltage is performed as in the conventional case.
It will also be impossible to make a judgment based on background stains and pencil character reproduction.

As a technique for preventing a change in image density due to a change in developer characteristics, a latent image of a reference pattern formed on an image carrier is not so greatly changed in developer characteristics due to a change in developer. A method is known in which development is performed under a specific AC developing bias voltage, the toner adhesion amount in the toner image of the reference pattern is measured, and the toner replenishment control is performed based on the measured value to appropriately control the toner density (special feature). (See Japanese Unexamined Patent Publication No. 60-131575). However, A
It is not a method of changing the C developing bias voltage to form images of a plurality of reference patterns and changing the setting to the optimum AC bias voltage based on the images.

The present invention has been made in view of the above problems, and an object thereof is to easily select an optimum developing bias voltage even when characteristics such as electric resistance of a developer are changed. An object of the present invention is to provide an image forming apparatus capable of obtaining a high quality image.

[0008]

To achieve the above object, the invention of claim 1 provides a developing means for developing with a two-component developer under a developing bias voltage in which an alternating voltage is superimposed on a direct voltage. In an image forming apparatus provided with the image forming apparatus, a reference latent image forming unit that repeatedly forms a latent image of a reference pattern on the surface of the image bearing body at least twice or more, and the developing process for the latent image of the reference pattern Development control means for controlling the developing bias power source so as to form a toner image of the reference pattern by changing at least the magnitude of the AC voltage of the bias voltage, and means for transferring the toner image of the reference pattern onto the transfer material. And is provided.

According to a second aspect of the invention, there is provided an image forming apparatus for forming a multicolor image, comprising a plurality of developing means for developing with a two-component developer under a developing bias voltage in which an alternating voltage is superimposed on a direct voltage. A reference latent image forming means for repeatedly forming a latent image of a reference pattern on the surface of the image carrier along its rotation direction at least twice, and at least an AC of the developing bias voltage for the latent image of the reference pattern. The developing control means for controlling the developing bias power source so as to form the toner image of the reference pattern by changing the magnitude of the voltage, and the means for transferring the toner image of the reference pattern onto the transfer material are provided. The latent image forming means is configured to form a latent image of the reference pattern so that images of the reference pattern of different colors do not overlap on the transfer material.

The invention of claim 3 is the same as claim 1 or 2.
In the above image forming apparatus, a reference pattern obtained by combining solid images having a density difference is used as the reference pattern.

The invention of claim 4 is the same as claim 1 or 2.
In the image forming apparatus, the upper limit value and the lower limit value are provided to the developing bias voltage used when forming the toner image of the reference pattern.

Further, the invention of claim 5 is the invention of claim 1 or 2.
In the image forming apparatus, the developing bias voltage used at the time of forming the toner image of the reference pattern includes the developing bias voltage used in the image forming process before the formation of the latent image of the reference pattern. To do.

According to a sixth aspect of the invention, in the image forming apparatus according to the second aspect, the developing means for changing the developing bias voltage based on the image on the transfer material on which the toner image of the reference pattern is transferred. The present invention is characterized in that a means for differentiating an image forming process condition is provided between a corresponding image forming process and an image forming process corresponding to the developing means which does not change the developing bias voltage.

[0014]

In the image forming apparatus of the first aspect, the reference latent image forming means forms the latent image of the reference pattern on the surface of the image carrier by repeating it twice or more along the rotation direction thereof. The case where the latent image of the reference pattern is formed by repeating five times will be described below. The five latent images of the reference pattern formed on the surface of the image bearing member are developed by the developing control means. The toner is developed by changing at least the magnitude of the AC voltage among the voltages, and the toner images of five reference patterns are formed. For example, the direct current component (Vdc) of the developing bias voltage is set to a constant voltage, and only the peak-to-peak voltage (Vp-p) of the alternating current component is changed in 200V steps to form five reference pattern toner images. It The toner image of this reference pattern is transferred onto the transfer material. The operator compares and evaluates the images of the plurality of reference patterns transferred on the transfer material, and determines and selects the optimum value of the developing bias voltage. Then, the optimum value of the selected developing bias voltage is set as the developing bias voltage in the next image forming process.

Further, in the image forming apparatus according to the present invention, the latent image of the reference pattern is formed on the surface of the image carrier with respect to the color for which the reference latent image forming means controls the optimization of the developing bias voltage. It is formed by repeating at least twice or more along the rotation direction of. For example, the latent image is formed 5 times or more. Next, the development control unit develops the plurality of latent images by varying at least the AC voltage of the developing bias voltage for the five latent images in the above example. By doing so, a toner image of the reference pattern is formed. For example, the direct current component (Vdc) of the developing bias voltage is set to a constant voltage,
Only the peak-to-peak voltage (Vp-p) of the AC component is 200V
The toner image of the reference pattern is formed by changing in steps. The toner image of this reference pattern is transferred onto the transfer material. For example, when the repetition is repeated 5 times and latent images of reference patterns for four colors are formed, a total of 20 reference pattern images are formed on the transfer paper. Here, the latent image of the reference pattern is formed so that the images of the reference pattern of different colors do not overlap on the transfer material. For example, the latent image of the reference pattern is formed so as not to overlap in the rotation axis direction of the image carrier.
The operator compares and evaluates the images of the plurality of reference patterns transferred on the transfer material to determine and select the optimum value of the developing bias voltage. Then, the optimum value of the selected developing bias voltage is set as the developing bias voltage in the next image forming process.

Further, in the image forming apparatus of the third aspect, as the reference pattern, a reference pattern obtained by combining solid images having a density difference is used. For example, a reference pattern in which halftone solid images having different densities are in contact with and combined with both sides of a black solid image is used. This allows
At the boundary between the two solid images, an edge phenomenon corresponding to the developing condition occurs, and the degree of occurrence of the edge phenomenon can be determined. Further, in the halftone solid image portion, the uniform reproducibility of the halftone portion can be judged.

In the image forming apparatus according to the fourth aspect, the developing bias voltage used when forming the toner image of the reference pattern has an upper limit value and a lower limit value.
This prevents the developing bias voltage from being set excessively or excessively low. By the way, the life of the developer is shortened due to the adhesion of the toner to the surface of the carrier or the abrasion of the coating film on the surface of the carrier. Here, as the toner adheres to the carrier surface, the toner charge amount decreases and the optimum Vp-p decreases, or the electric resistance of the carrier increases and the optimum Vp-p increases. Go
On the other hand, when the coating film on the carrier surface is worn away,
The electric resistance of the carrier becomes smaller and the optimum Vp-p
Is getting smaller. Therefore, the upper limit value and the lower limit value of the developing bias voltage, for example, Vp-p can be set as the time when the developer used at that time reaches the end of its life.

In the image forming apparatus according to the present invention, the developing bias voltage used in forming the toner image of the reference pattern is used in the image forming process before the latent image of the reference pattern is formed. Since the development bias voltage is included, it is possible to compare the image quality formed under the current development bias voltage before the development bias voltage is changed with the image quality after the development bias voltage is changed.

Further, in the image forming apparatus according to the sixth aspect, when the developing bias voltage, for example, Vp-p is changed, the developing γ characteristic (relationship between developing potential and developing toner adhesion amount) is also changed, which is high. Considering that the image may not be in gray balance in the light portion or the shadow portion, the image on the transfer material on which the toner image of the reference pattern is transferred is compared and evaluated to determine the optimum developing bias voltage. By doing so, the charging potential between the image forming process corresponding to the developing unit that changes the developing bias voltage from the current value and the image forming process corresponding to the developing unit that does not change the developing bias voltage,
The image forming process conditions such as the exposure amount are different. As a result, when the development γ characteristic is changed by changing the development bias voltage, for example, Vp-p, the image forming process condition for each color is set so that the development γ characteristic is matched between the respective colors.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter referred to as a copying machine) which is an image forming apparatus will be described below. FIG. 2 is an overall configuration diagram of a digital full-color copying machine according to an embodiment of the present invention. Referring to FIG.
The mechanical section of this copying machine is composed of an image scanner and a printer device. First, the image scanner will be described. A document 1 is placed on a platen (contact glass) 2, illuminated by fluorescent lamps 3a and 3b for illuminating the document, and a reflected light of the first mirror 4a and the second mirror 4a are movable. It is reflected by the mirror-4b and the third mirror 4c, and the imaging lens 5
Then, the light enters the dichroic prism 6 and is split into light of three wavelengths, red (R), green (G) and blue (B). The separated light enters CCDs 7r, 7g, and 7b, which are solid-state image pickup devices, respectively. That is, the red light is to the CCD 7r and the green light is to the CC
The blue light enters the D7g and the blue light enters the CCD 7b.

The fluorescent lamps 3a, 3b and the first mirror 4a are the first
The second carriage 9 is mounted on the carriage 8, and the second mirror 4b and the third mirror 4c are mounted on the second carriage 9.
By moving at a speed half that of the first carriage 8, the optical path length from the document 1 to the CCD is kept constant,
When reading the original image, the first and second carriages are scanned from right to left. The first carriage 8 is coupled to the carriage drive wire 12 wound around the carriage drive pulley 11 fixed to the shaft of the carriage drive motor 10, and the carriage drive wire 12 is wound around the moving pulley (not shown) on the second carriage 9. There is. This allows
By the forward and reverse rotations of the carriage drive motor 10, the first carriage 8 and the second carriage 9 move forward (original image reading scan) and return (return), and the second carriage 9 is half of the first carriage 8. Move at speed.

When the first carriage 8 is at the home position shown in FIG. 2, the first carriage 8 is detected by the home position sensor 39 which is a reflection type photo sensor. When the first carriage 8 is driven to the right by the exposure scanning and deviates from the home position, the home position sensor 39 does not receive light (carriage non-detection), and when the first carriage 8 returns to the home position, the home position sensor Reference numeral 39 indicates light reception (carriage detection), and when the non-light reception changes to light reception, the first carriage 8
Is stopped.

CCD 7r, 7 of the image scanner 200
The R, G, and B color image signals output by g and 7b are applied to the image processing unit 100 to be subjected to various processes, as shown in the block diagram of FIG. 3, and C (cyan), M (magenta) ), Y (yellow), and BK (black) image signals for recording, and the mode switching circuit 41
Applied to the laser writing unit 420 via 0.

The laser writing unit 420 includes a laser driver and semiconductor lasers 43bk, 43y, 43m and 43 provided in the respective color recording systems of BK, Y, M and C.
c is equipped. The laser light emitted from each laser is reflected by the rotating polygon mirrors 13bk, 13y, 13m and 13c, respectively, and the f-8 lenses 14bk, 14y,
After passing through 14m and 14c, the fourth mirror 15bk, 15
y, 15m and 15c and the fifth mirror 16bk, 16
The light is reflected by y, 16m and 16c, and passes through the polygonal mirror tilt correction cylindrical lenses 17bk, 17y, 17m and 17c, and the photoconductor drums 18bk, 18y and 18m.
And 18c are image-irradiated.

The rotary polygon mirrors 13bk, 13y, 13m and 13c are polygon mirror driving motors 41bk, 41y and 41, respectively.
The motors are fixed to the rotating shafts of m and 41c, and each motor rotates at a constant speed to drive the polygon mirror at a constant speed. By the rotation of the polygon mirror, the above-mentioned laser light is scanned in a direction perpendicular to the rotation direction (clockwise direction) of the photosensitive drum, that is, a direction along the drum axis.

The laser scanning system of the cyan color recording apparatus is shown in detail in FIG. 43c is a semiconductor laser. A sensor 44c, which is a photoelectric conversion element that receives laser light, is disposed at one end of laser scanning (two-dot chain line) in the direction along the axis of the photoconductor drum 18c. The sensor 44c detects laser light. , The start point of one-line scanning is detected at the time when the detection changes to non-detection. That is, the sensor 44c
Laser light detection signal (pulse) is processed as a line synchronization pulse for laser scanning. The configuration of the laser scanning system of the magenta recording device, the yellow recording device, and the black recording device is exactly the same as the configuration of the laser scanning system of the cyan recording device shown in FIG.

Further, referring to FIG. 2, the photosensitive drum 1
The surfaces of 8bk, 18y, 18m and 18c are uniformly charged by charge scorotrons 19bk, 19y, 19m and 19c connected to a negative voltage high voltage generator (not shown). When the laser light modulated by the recording signal is applied to the uniformly charged surface of the photoconductor, the photoconductive phenomenon causes the charge on the surface of the photoconductor to flow to the equipment ground of the drum body and disappear. Here, the laser is not turned on for the portion having a high original density, and the laser is turned on for the portion having a low original density. As a result, the photosensitive drums 18bk, 1
On the surface of 8y, 18m, and 18c, the portion corresponding to the dark portion of the original has a potential of −800V, and the portion corresponding to the portion having a light original has a potential of about −100V. A latent image is formed. This electrostatic latent image is developed by a black developing unit 20bk, a yellow developing unit 20y, a magenta developing unit 20m and a cyan developing unit 20c, respectively, and black, yellow and magenta are respectively formed on the surfaces of the photoconductor drums 18bk, 18y, 18m and 18c. And forming a cyan toner image. The toner in each developing unit is positively charged by stirring. The developing sleeves 61bk, 61y, 61m, and 61c of each developing unit have the structure shown in FIG.
The developing bias power source 470 applies a developing bias voltage in which an AC voltage (peak-to-peak voltage Vp-p = 1.2 kV, frequency 2 kHz) is superimposed on a DC bias voltage (Vdc = -600 V), and corresponds to the original. A toner image is formed. In addition, the photosensitive drums 18bk, 18y,
A surface electrometer 51, 5 is provided between the charge scorotron and the developing unit around 18 m and 18 c, respectively.
2, 53 and 54 are photosensitive drums 18bk, 18y,
It is provided so as to face the surfaces of 18m and 18c.
These surface electrometers measure the charging potential of each photoconductor drum. In this embodiment, in order to keep the charged potential of the photosensitive drum constant, the voltage applied to each charge scorotron is adjusted until the detected potential of each surface electrometer falls within a predetermined range, and then the image is adjusted. Are being formed.

On the other hand, the recording paper 800, which is the transfer material stored in the recording paper cassette 22, is sent out by the paper feeding operation of the sending roller 23, and is sent to the transfer belt 25 by the registration roller 24 at a predetermined timing. Transfer belt 2
The recording paper 800 placed on the sheet 5 sequentially passes under the photoconductor drums 18bk, 18y, 18m, and 18c by the movement of the transfer belt 25, and each photoconductor drum 18b.
While passing k, 18y, 18m, and 18c, transfer corotrons 29bk, 29y, and
Due to the action of 29 m and 29 c, the toner images of black, yellow, magenta and cyan are recorded on the recording paper 800.
Transferred on top. The transferred recording paper 800 is then sent to the thermal fixing unit 36, where toner is applied to the recording paper 800.
Then, the recording paper 800 is ejected onto the tray 37.
The residual toner on the surface of the photoconductor after the transfer is removed by the cleaner units 21bk, 21y, 21m and 21c. The transfer belt 25 is destaticized by the belt destaticizing charger 435.

The cleaner unit 21bk for collecting the black toner is connected to the black developing unit 20bk by a toner recovery pipe 42 so that the black toner collected by the cleaner unit 21bk is recovered by the developing unit 20bk. The black toner is reversely transferred from the recording paper 800 to the photoconductor drum 18y at the time of transfer, so that the cleaner units 21y, 21m, and 21c are transferred.
The yellow, magenta, and cyan toners collected in step 1 are mixed with the toner of the different color developing device in the preceding stage of those units, and are not collected for reuse.

Each developing unit is equipped with a toner concentration sensor (not shown), and a signal corresponding to the toner concentration of each developing unit is output to a toner concentration control unit (not shown). The toner concentration control unit is provided in each developing unit according to the output of each toner concentration sensor in order to replenish the toner consumed for forming the toner image and keep the toner concentration of each developing unit constant. The toner supply roller 46bk, 4 is provided on the rotation shaft of the toner supply motor for driving the toner supply motor.
6y, 46m and 46c are fixed respectively,
In response to the toner replenishment signal, each toner replenishment roller is driven to replenish toner to each developing unit.

The transfer belt 25 for feeding the recording paper 800 from the photoconductor drums 18bk to 18c is stretched around the idle roller 26, the drive roller 27, the idle roller 28 and the idle roller 30, and the drive roller 27 counterclockwise. Driven to rotate. The drive roller 27 has a shaft 32.
The lever 31 is pivotally attached to the left end of the lever 31. At the right end of the lever 31, a black mode setting solenoid plunger 35 (not shown) is pivotally mounted. A compression coil spring 34 is disposed between the plunger 35 and the shaft 32, and the compression coil spring 34 applies a rotational force in the clockwise direction to the lever 31. The transfer belt 25 on which the recording paper 800 is placed is in contact with the photoconductor drums 18bk, 18y, 18m and 18c. Therefore, when the recording paper 800 is placed on the transfer belt 25 and toner images are formed on all the drums, the toner images of the respective colors are sequentially transferred and overlapped on the recording paper 800 as the recording paper 800 moves to reproduce a color image.

FIG. 3 is a schematic diagram of an electric component section of the printer device of the copying machine of FIG. Referring to FIG. 3, the printer device includes a CPU, a ROM, a RAM, an I / O, and an A / D.
A control device 400 mainly including a microcomputer including converters and the like is provided. The control device 400 includes an operation board 300, a belt removing high voltage power source 430,
Various sensors 440, surface electrometers 51, 52, 53, 5
4, charging high voltage power source 450, transfer high voltage power source 460, developing bias high voltage power source 470, replenishment bias high voltage power source 481
0, drivers 490, 510, lamp control unit 52
0, heater control unit 530 and mode switching circuit 4
00 is connected. The charging high-voltage power supply 450 has four independent output terminals, each of which has a charge scorotron 19bk, 19y, 19m,
It is connected to 19c. The voltage of each output terminal is independently adjustable by an instruction from the control device 400.

The operation board 300 is provided with a large number of keys 301, 302, etc., similar to a general copying machine, among which a developing bias voltage check mode, a developing bias voltage standard setting mode, etc. are selected. Contains keys and keys to specify the color mode. As described later, the optimum value of the selected developing bias voltage is set by replacing the current standard value by inputting setting data in the developing bias voltage standard setting mode. Eight color modes, full color mode, black mode, cyan mode, magenta mode, yellow mode, red mode, green mode, and blue mode are provided, and can be arbitrarily selected by an instruction from the operator's operation board 300. It has become.

A 4-bit control signal is applied to the mode switching circuit 410 according to the selected color mode. The mode switching circuit 410 is composed of a gate circuit,
The permission / prohibition of passage of the recording image signals of each color of C, M, Y and BK is configured to be switched by a signal from the control device 400. That is, the combinations of passage / prohibition of C, M, Y, and BK color image signals in each color mode are as shown in Table 1 below.

[Table 1]

In the color recording system in which the passage of the image signal is permitted, the energizing signal corresponding to the original image is supplied to the laser writing unit 4.
20 is applied to the semiconductor laser to write a laser beam on the photosensitive drum, that is, an electrostatic latent image is formed.
A toner image is formed on each photosensitive drum. And
In the recording system of the color in which the passage of the image signal is prohibited, the level of the signal applied to the laser writing unit 420 is fixed to the non-recording level, so that the electrostatic latent image is not formed on the photosensitive drum, Therefore, no toner image is formed.

Further, in this example, the control of the normal recording process is executed also for the recording system not forming the toner image, and the photosensitive drums 18bk, 18y, 18m and 18 are formed.
By charging c to a constant potential and applying a bias voltage to the developing unit, the relationship between the potential of the surface of the photoconductor and the potential of the developing unit is constantly set to the condition that toner does not adhere to the surface of the photoconductor. The control is performed so that the toner does not adhere to the photosensitive drum of the recording system that does not perform image formation in modes other than the mode.

Next, the optimization control of the developing bias voltage in this embodiment will be described. Operation board 30 of FIG.
By a predetermined input operation from 0, the developing bias check mode is entered, and the data for the developing unit to be checked (hereinafter referred to as developing unit data) is set. The developing units 20bk, 20y, 20m, and 20c of the colors BK, Y, M, and C are set to correspond to 1, 2, 4, and 8, respectively,
The total value of the above values corresponding to the developing unit to be checked is input as the developing unit data. For example, B
"15" is input as the developing unit data in the case of all colors of K, Y, M, C, and "12" in the case of two colors of M, C. When the developing unit data is input, the image signals shown in Table 1 are determined.

Next, the latent image of the reference pattern stored in the RAM of the control device 400 is formed at a predetermined position on each photosensitive drum surface. FIG. 1A shows a reference pattern 700 in this embodiment. Three solid portions 710, 720, 730 of 15 mm square are arranged in the rotation direction of the photoconductor drum to form one reference pattern. These three solid parts have different densities, and
The development potential is 100 V, 500 from above (a).
V, 250 V (hereinafter, referred to as the first, second, and third solid portions from the top). The edge phenomenon of the image is determined at the boundary between the second solid portion 720, which is a high-density black solid portion, and the first or third solid portion 710, 730, which is a halftone solid portion. For example, the first solid portion 710 or the third solid portion which is a halftone solid portion indicated by an arrow in FIG.
The edge phenomenon is evaluated based on the density difference between the density of the boundary portion (Z portion) of the solid portion 730 and the second solid portion 720 and the halftone density other than the boundary portion. Also, the second solid black part
The first solid portion 710 or the third solid portion 730 of the solid portion 720.
And the second solid portion 72 other than the boundary density
The edge phenomenon may be evaluated from the density difference with the black solid density of 0. Further, the density of the boundary portion of the second solid portion 720 which is a black solid portion and the first solid portion 710 which is a halftone solid portion.
Alternatively, the edge phenomenon may be evaluated from the density difference between the third solid portion 730 and the density of the boundary portion (Z portion) with the second solid portion 720.

The latent image of the reference pattern 700 is formed in an area of A3 size on the surface of the photosensitive drum, and the latent image is 30 in the rotation direction.
It is formed by repeating 5 times at intervals of mm. Further, the position of the latent image of the reference pattern corresponding to each developing unit in the direction of the rotation axis of the photosensitive drum is determined in advance and corresponds to BK, Y, M, and C from the front side. The latent image of the reference pattern corresponding to the developing unit for which the developing bias is not checked is not formed.

In FIG. 1B, the latent images of a plurality of reference patterns formed corresponding to all colors are developed, and the toner images of the obtained reference patterns are transferred onto A3 size recording paper 800. 3 shows the positional relationship of typical images. The vertical direction of FIG. 1B corresponds to the rotation direction of the photosensitive drum, and the horizontal direction corresponds to the rotation axis direction of the photosensitive drum. In FIG. 1B, the columns of the latent image of the reference pattern are BK, Y, and
M and C, and the lines correspond to different developing bias voltages.

In this embodiment, the DC component Vdc of the developing bias voltage is set to a constant value, and only the peak-to-peak voltage Vp-p of the AC component is changed. At the left end of each reference pattern repeatedly formed at different positions in the rotation direction of the photoconductor drum, from the top, in correspondence with Vp-p used when developing the latent image of the reference pattern,
2, 1, 0, -1, -2 "is written (hereinafter, this number is referred to as Vp-p number). The Vp-p number corresponding to the current set value of Vp-p is" 0. Vp-p number "2,1" corresponds to Vp-p increased by two steps and one step from the current Vp-p, respectively.
The numbers "-1, -2" correspond to Vp-p reduced by one step or two steps from the current Vp-p, respectively. For example, if the magnitude of change in one step of Vp-p is set to 200V and the current value of Vp-p is 1200V, the Vp-p number "2, 1, 0, -1, -2" is set. The latent images of the corresponding reference patterns are 1600 and 140, respectively.
It will be developed at 0,1200,1000,800V. The current Vp-p in the developing unit for each color
Since the value of is not always the same, in developing the latent image of the reference pattern by the developing unit of each color,
Vp-p corresponding to Vp-p number "2, 1, 0, -1, -2"
The value of will be different.

When fine adjustment of Vp-p is performed,
The development bias fine adjustment mode can be selected. In that case, the latent image of the reference pattern is formed more than five times in the rotation direction of the photosensitive drum, and the magnitude of change in Vp-p for one step is set to a smaller value, for example, 50V. Is developed. In this case, the copy is performed on a plurality of A3 size recording sheets 800.

An upper limit value and a lower limit value are set for the developing bias voltage used when forming the toner image of the reference pattern in the above-described developing bias voltage optimization control. For example, the variable range of Vp-p is set to 200 to 2400V, and the variable range of Vdc is set to -200 to -800V.

The image corresponding to the reference pattern transferred onto the recording paper 800 is compared and evaluated by the operator, and the optimum value of Vp-p is selected for each color based on the comparison and evaluation.
The selected Vp-p is the operation board 3 shown in the electrical component section of FIG.
00 in standard setting mode. For example, the developing bias voltage (Vp-p) standard setting mode is selected on the operation board 300, setting data corresponding to Vp-p selected based on the image of the toner image of the reference pattern is input, and Vp- The standard setting of p is changed. Specifically, the variable range of the setting data that can be input from the operation board 300 is "1 to 12", and the standard value "6" is Vp-p.
Vp-p (= 16) corresponding to the Vp-p number “2” in the image on the recording paper 800.
00V) is selected, the above setting data is "
8 "is input and Vp-p corresponding to Vp-p number" -1 "
When (= 1000V) is selected, "5" is input as the above setting data, and the developing bias voltage (Vp-p)
The standard settings are changed.

By the way, if Vp-p is changed as described above, image characteristics such as development gamma may change. Therefore, in the present embodiment, in the plurality of developing units, the image forming process conditions such as the laser exposure amount corresponding to the developing unit whose Vp-p is changed, or the image forming process corresponding to the developing unit whose Vp-p is not changed. Change process conditions.

As described above, according to the present embodiment, the images corresponding to the latent images of the plurality of reference patterns having different Vp-p conditions for all colors are copied onto the recording paper 800. Based on the image of the reference pattern on 800, the optimum value of Vp-p in the developing unit of each color can be easily and definitely determined. Further, since the image of the reference pattern is copied onto one sheet or a minimum required number of sheets of recording paper 800, the optimum value of Vp-p in the developing unit for each color can be obtained in a short time and with a small number of copies. Can judge. Since the optimum value is set as Vp-p in the next image forming process, a desired image quality can always be obtained.

Further, as the reference pattern, a reference pattern in which a plurality of solid images having different densities are combined so as to be in contact with each other is used. Therefore, in the Vp-p optimization control,
The degree of occurrence of an edge phenomenon at the boundary of each solid image and the uniform reproducibility in a halftone solid image can be easily determined.

Further, since the upper limit value is set for Vp-p when the toner image of the above-mentioned reference pattern is formed, there is no possibility that a leak image is generated by the application of excessive Vp-p, and Vp-p Since the lower limit value corresponding to the life of the developer is provided in, the time when the developer reaches the life can be determined.

Further, since the Vp-p used in the current image forming process is included in the plurality of Vp-p used in forming the toner image of the reference pattern, Vp-p is the current value. Since it is possible to compare and evaluate how the image changes when the value is changed, it is possible to more reliably select and change the optimum value of Vp-p.

Further, since the Vp-p number corresponding to the Vp-p is written at the left end of the pattern group of each Vp-p reference pattern, the optimum value of the Vp-p without error is further selected. And the setting can be changed.

Further, the optimum value of the selected Vp-p is set by the developing bias voltage (Vp-p from the operation board 300).
p) Since this can be done as a change of standard setting conditions, the target Vp-
You can set p.

Also, if the image forming process conditions such as the laser exposure amount are different between the image forming process using the developing unit for changing the setting of Vp-p and the image forming process using the developing unit for not changing the setting of Vp-p. Means are provided. As a result, even if the development γ characteristic is changed by changing the setting of Vp-p, the image forming process condition can be set so as to match the development γ characteristic between the respective colors, and a color copy having a good color balance can be obtained. can get.

In this embodiment, only the AC developing bias voltage (Vp-p) of the developing bias voltage is optimized, but the developing bias voltage including the DC developing bias voltage (Vdc) is optimized. You may make it control-enable. According to this, the charge amount changes according to the characteristics of the developer, and V is determined by the background stain and pencil character reproducibility.
Even when the dc optimization control cannot be performed, the development bias voltage optimization control can be performed.

In this embodiment, 100V, 500V and 250V are used as the developing potentials of the three solid portions of the latent image of the reference pattern of FIG. 1 (a).
Since the value of the developing potential varies depending on the system, it may be freely set to suit the system. Further, the reference pattern is not limited to the above example, and for example, a pattern in which a black circle is written in the halftone solid part as shown in FIG. 1C may be used as the reference pattern.

Further, in this embodiment, the latent image of the reference pattern is formed by using the built-in pattern stored in the RAM in the digital system, but it may be formed by using an equivalent document in the analog system. ..

In this embodiment, the photosensitive drums 18bk, 18y, 18m and 18c corresponding to the respective colors are arranged in parallel along the transfer belt 25, and the latent image of the reference pattern of the corresponding color is formed on the surface of each photosensitive drum. This is an example of a 4-drum type color copying machine for forming an image, but the present invention is not limited to this, and can be applied to a 1-drum type color copying machine.
For example, using one photoconductor drum, formation, development, and development of a latent image of a reference pattern that is repeated in the rotation direction of the photoconductor drum.
And transfer to the same recording paper for each color sequentially,
An image of the same reference pattern as in this embodiment may be formed on the recording paper. Also in this case, the latent image of the reference pattern is formed on the surface of the photoconductor drum so that the image of the reference pattern corresponding to each color is formed on the recording paper at different positions in the rotation axis direction of the photoconductor drum. .. Also, a certain Vp-p
First, latent images of the reference patterns of the respective colors are formed on the surface of the photosensitive drum at different positions in the direction of the rotation axis, developed, and transferred to the same recording paper.
The image of the final reference pattern may be formed on the recording paper by repeating p times. In this case, the above process is controlled so that the image of the reference pattern corresponding to each Vp-p is formed on the recording paper at a position different in the rotation direction of the photosensitive drum.

[0057]

According to the image forming apparatus of the first aspect, since the images corresponding to the latent images of the plurality of reference patterns having different developing bias voltage conditions are formed on the transfer material, the transfer material is formed. The optimum value of the developing bias voltage in the developing means can be easily and definitely determined based on the image of the reference pattern. Further, since the image of the reference pattern is copied onto one transfer sheet or a minimum number of transfer materials, the optimum value of the developing bias voltage can be determined in a short time and with a small number of copies. Since the optimum value is set as the developing bias voltage in the next image forming process, a high quality image can be obtained.

According to the image forming apparatus of claim 2,
Images of a plurality of reference patterns with different development bias voltage conditions corresponding to a plurality of colors are copied onto a transfer material, so based on the image of the reference pattern on the transfer material,
The optimum value of the developing bias voltage in the developing unit for each color can be easily and definitely determined. Further, since the images of the plurality of reference patterns are copied onto one sheet or a minimum number of sheets of the transfer material, the developing bias voltage of the developing unit of the developing unit of each color can be obtained in a short time and with a small number of copies. Can determine the optimum value. Then, the optimum value is set as the developing bias voltage in the next image forming process, and a high quality multicolor image is obtained.

According to the image forming apparatus of claim 3,
As the reference pattern, a latent image pattern formed by combining solid images having a density difference is used, and in the optimization control of the developing bias voltage, the degree of occurrence of an edge phenomenon at the boundary of each solid image and the halftone solid pattern. Since the uniform reproducibility in the image can also be easily determined, a higher quality image can be obtained in the next image forming process.

According to the image forming apparatus of claim 4,
Since the upper limit value is set for the developing bias voltage when the toner image of the reference pattern is formed, a leak image is not generated by the application of an excessive developing bias voltage.
Further, since the upper limit value and the lower limit value of the developing bias voltage corresponding to the life of the developer are provided, it becomes possible to determine the time when the developer reaches the life, that is, the replacement time of the developer.

According to the image forming apparatus of claim 5,
Since the developing bias voltage used in the current image forming process is included in the plurality of developing bias voltages used when forming the toner image of the reference pattern, it is possible to change the developing bias voltage from the current value. Since it is possible to compare and evaluate how the image changes, it is possible to more reliably select the optimum value of the developing bias voltage and change the setting.

According to the image forming apparatus of claim 6,
The image forming process conditions are made different between the image forming process using the developing unit that changes the setting of the developing bias voltage and the image forming process using the developing unit that does not change the setting of the developing bias voltage. As a result, even if the development γ characteristic is changed by changing the setting of the developing bias voltage,
It is possible to match the development γ characteristics among the respective colors, and it is possible to obtain a high-quality multicolor image having a good color balance.

[Brief description of drawings]

1A is an explanatory diagram of a reference pattern in the present embodiment, FIG. 1B is an explanatory diagram of an image on a recording paper corresponding to a reference pattern of all colors (BK, Y, M, C), and (c). FIG. 8 is an explanatory diagram of another embodiment of the reference pattern.

FIG. 2 is a front view showing a schematic configuration of a copying machine according to an embodiment.

FIG. 3 is a block diagram showing a schematic configuration of an electric component section of the copying machine.

FIG. 4 is a perspective view of a laser scanning system of a cyan recording device of the copying machine.

[Explanation of symbols]

 300 Operation Board 400 Control Device 470 Development Bias Power Supply 700 Reference Pattern 800 Recording Paper

Claims (6)

[Claims] 1. An image forming apparatus comprising a developing means for developing with a two-component developer under a developing bias voltage in which an AC voltage is superimposed on a DC voltage, wherein a reference pattern is formed on the surface of an image carrier along its rotation direction. Of the latent image of the reference pattern and a toner image of the reference pattern by varying at least the magnitude of the AC voltage of the developing bias voltage with respect to the latent image of the reference pattern. An image forming apparatus comprising: a developing control unit that controls a developing bias power source to form a toner image; and a unit that transfers a toner image of the reference pattern onto a transfer material. 2. An image forming apparatus for forming a multicolor image, comprising a plurality of developing means for developing with a two-component developer under a developing bias voltage in which an AC voltage is superimposed on a DC voltage, the image forming apparatus comprising: Reference latent image forming means for repeatedly forming a latent image of a reference pattern along the rotation direction at least twice, and at least the magnitude of an AC voltage of the developing bias voltage with respect to the latent image of the reference pattern. And a developing control means for controlling a developing bias power source so as to form a toner image of the reference pattern, and a means for transferring the toner image of the reference pattern onto a transfer material. The image forming apparatus is configured to form a latent image of the reference pattern so that the images of the reference pattern do not overlap each other on the transfer material. 3. The image forming apparatus according to claim 1, wherein a reference pattern obtained by combining solid images having a density difference is used as the reference pattern. 4. The image forming apparatus according to claim 1, wherein the developing bias voltage used when forming the toner image of the reference pattern has an upper limit value and a lower limit value. 5. The developing bias voltage used when forming the toner image of the reference pattern includes the developing bias voltage used in the image forming process before the formation of the latent image of the reference pattern. The image forming apparatus according to claim 1. 6. An image forming process corresponding to the developing means for changing the developing bias voltage based on the image on the transfer material on which the toner image of the reference pattern is transferred, and the developing without changing the developing bias voltage. 3. The image forming apparatus according to claim 2, further comprising: a unit that makes an image forming process condition different from that of the image forming process corresponding to the unit.