JP5540747B2 - Image forming apparatus, image forming condition adjusting method, program, and recording medium - Google Patents

Description

  The present invention relates to an image forming apparatus such as an electrophotographic digital copying machine, a facsimile machine, a digital multifunction peripheral (multifunction printer: MFP), a laser printer, an image forming condition adjusting method in the image forming apparatus, and the above image forming apparatus. The present invention relates to a program for realizing a function necessary for a computer to be controlled (function related to the present invention) and a computer-readable recording medium on which the program is recorded. The present invention relates to a technique for suppressing variations in image density by performing image formation under image formation conditions that are predicted and determined according to the result.

  In the image forming apparatus as described above, an image bearing member that is rotated in the sub-scanning direction (previously charged uniformly) is exposed to form an electrostatic latent image on the image bearing member. The electrostatic latent image is developed with toner to form a toner image, the toner image is transferred onto a medium such as paper, and then a series of image forming processes for fixing the toner image on the medium is performed. Yes.

By the way, in the development process, the development history of the previous development sleeve (developer carrier) remains on the development sleeve, and the development history of the first round is generated as an afterimage during the development of the second round, resulting in density deviation. The technique shown to the following (1)-(4) is disclosed with respect to the subject made to make it.
In these methods, only the toner is transferred from the two-component developer carrying member to the developing sleeve, or a toner layer is formed on the developing sleeve using a layer thickness regulating member such as a regulating blade, and then a photosensitive member (image carrier). This is a technique related to a one-component development system that develops a toner.

  In the one-component development method, the toner layer or charge amount deviation occurs in the toner layer on the developing sleeve due to different development histories, and this appears in the image as an afterimage. Means for removing the toner and controlling the rotation operation time of the developing sleeve before image formation to eliminate the toner layer charge amount deviation have been proposed. In addition, in the two-component developer sleeve, which is a means for transferring only the toner to the developing sleeve, a means for suppressing the density deviation by defining the carrier particle size distribution and the circularity has been proposed.

(1) Patent Document 1
By forming an oscillating electric field between the developing sleeve and the electrode plate facing the developing sleeve, the oscillating electric field acts on the toner layer on the developing sleeve to relocate the toner, thereby suppressing afterimages and density deviation. Reduce.
(2) Patent Document 2
Only the toner from the two-component developer on the two-component developer carrier is transferred to the surface of the toner carrier to form a toner layer, and the toner is transferred from the toner layer to the surface of the photoreceptor on which the electrostatic latent image is formed. In a hybrid development method in which an electrostatic latent image is developed as a toner image by flying, the particle size distribution and circularity of the carrier are defined to reduce density unevenness.

(3) Patent Document 3
In the hybrid developing method, the toner remaining on the developing sleeve is peeled off to suppress the occurrence of an afterimage and reduce the density deviation.
(4) Patent Document 4
The idle stirring time of the developing device before development is adjusted according to the cumulative number of image formations, and the toner charge amount difference on the developing sleeve between the non-image area and the image area is eliminated to reduce the density deviation.

  The conventional examples shown in the above (1) to (4) are technologies related to the one-component development method. In the one-component development method, the development history remaining on the development sleeve is erased and the density deviation is suppressed by performing processing such as rearrangement, separation, and charging on the toner layer on the development sleeve after development. However, in the two-component development system, it has been confirmed that a density deviation occurs even if the developer on the developing sleeve is peeled off magnetically after development, and means for erasing the development history remaining on the developing sleeve is It is not an effective solution.

  The present invention has been made in view of the above points, and an object of the present invention is to suppress density deviation and obtain a good image in an image forming apparatus using a two-component development system.

  To achieve the above object, the present invention provides an image forming apparatus, an image forming condition adjusting method thereof, a program executed by a computer that controls the image forming apparatus, and a computer-readable recording that records the program. Provide media.

An image forming apparatus according to the present invention includes a charging unit that charges a latent image carrier, an exposure unit that exposes the latent image carrier charged thereby according to image information to form a latent image, and a toner and a carrier. And a latent image formed on the latent image carrier by the exposure means by the two-component developer toner from the developer carrier. An image forming apparatus of an electrophotographic system that includes a developing means for visualizing and forming an image by controlling those means, a temperature detecting means for detecting the temperature in the image forming apparatus, and the detection results and based on the difference in image density before and after switching of the image pattern in the image information, the density deviation occurring at a concentration deviation generated portion corresponding to the peripheral length pitch of the developer carrying member, the temperature sensing As the temperature sensed by the step is high, also those provided with estimation means for estimating the increases as the difference between the image density is large, and adjustment means for adjusting the image forming conditions in accordance with the prediction result.

The image forming condition is the development potential, and the adjustment unit increases the adjustment amount of the development potential as the density deviation predicted by the prediction unit increases, and the development potential decreases as the density deviation decreases. The adjustment amount should be reduced .
Moreover, you may make it the said adjustment means show in either of the following (1)-(5).

(1) The image forming conditions are adjusted by controlling the exposure power applied to the latent image carrier by the exposure unit according to the prediction result.
(2) The image forming conditions are adjusted by controlling the exposure time of the latent image carrier by the exposure means according to the prediction result.
(3) The image forming conditions are adjusted by controlling the voltage applied to the developer carrying member according to the prediction result.
(4) According to the prediction result, an exposure power for the latent image carrier by the exposure unit, an exposure time for the latent image carrier by the exposure unit, and a voltage applied to the developer carrier are selectively selected. The image forming conditions are adjusted by controlling.
(5) In accordance with the prediction result, the exposure power applied to the latent image carrier by the exposure unit, the exposure time applied to the latent image carrier by the exposure unit, and the voltage applied to the developer carrier are combined and controlled. As a result, the image forming conditions are adjusted.

The image forming condition adjusting method according to the present invention comprises a charging means for charging a latent image carrier, an exposure means for forming a latent image by exposing the latent image carrier charged thereby according to image information, and a toner. A developer carrying member for carrying and transporting a two-component developer comprising a carrier and a carrier, and the latent image formed on the latent image carrying member by the exposure means is converted into a two-component developer toner from the developer carrying member. Image forming conditions in an electrophotographic image forming apparatus that includes a developing means that makes a visible image by means of temperature and a temperature detecting means that detects the temperature in the image forming apparatus and that controls the means to form an image. a method for adjusting, based on the difference in image density before and after switching of the image pattern in the detection result and the image information by the temperature sensing means, corresponding to the circumferential length pitch of the developer carrying member That the concentration deviation generated in the density deviation occurrence point, as the temperature detected by said temperature detecting means is high, also predicted that the larger the difference between the image density is high, adjusting the image forming conditions in accordance with the prediction result To do.

The program according to the present invention comprises a charging unit for charging a latent image carrier, an exposure unit for exposing the latent image carrier charged thereby to form a latent image according to image information, a toner and a carrier. A developer carrying member for carrying and transporting the two-component developer, and the latent image formed on the latent image carrier by the exposure unit is visualized by the toner of the two-component developer from the developer carrying member; A developing unit that converts the temperature of the image forming apparatus to a computer that controls an electrophotographic image forming apparatus that performs image formation by controlling these units. based on the difference in image density before and after switching of the image pattern in the detection result and the image information by the detection means, at a density deviation occurs a portion corresponding to the peripheral length pitch of the developer carrying member Raw concentrations deviation, the higher the temperature detected by said temperature detecting means is high, also a prediction function of expected to be larger as the difference between the image density is high, adjustment function of adjusting an image forming condition in accordance with the prediction result It is a program for realizing.

A recording medium according to the present invention is a computer-readable recording medium on which the above program is recorded.
According to the present invention, the image forming apparatus (or the computer that controls the image forming apparatus) is generated at the density deviation occurrence location corresponding to the circumferential length pitch of the developer carrier based on the detection result by the temperature detection means and the image information. The density deviation is predicted, and the image forming conditions are adjusted according to the prediction result.

  According to the present invention, the image forming apparatus using the two-component development method can suppress the density deviation and obtain a good image.

1 is a diagram illustrating a schematic configuration example of a mechanism unit of a color printer using an electrophotographic system which is an embodiment of an image forming apparatus according to the present invention. It is a figure which shows the schematic structural example of the process unit which is an image formation means of FIG. FIG. 2 is a block diagram illustrating a hardware configuration example of a control system of the color printer illustrated in FIG. 1. It is a conceptual diagram for demonstrating the density | concentration deviation generation | occurrence | production area | region. It is a diagram which shows an example of the relationship between the difference of the image density before and behind image pattern switching, and a density deviation.

It is a diagram which shows an example of the relationship between machine temperature and a density | concentration deviation. It is a diagram showing an example of the relationship between the image density before and after the switching of the image pattern and the development potential corresponding to the image density (including the development potential for the density deviation predicted from the in-machine temperature immediately after the switching of the image pattern). 4 is a flowchart illustrating an example of a Y-color development potential adjustment process executed by a control unit of the color printer illustrated in FIG. 3. It is a diagram which shows an example of the relationship between the exposure power of LD light source in the exposure unit 11 of FIG. 1, and development potential. It is a diagram which shows an example of the relationship between the exposure time of LD light source in the exposure unit 11 of FIG. 1, and development potential.

FIG. 6 is a diagram showing an example of a relationship between a developing bias applied to the developing sleeve 126Y of FIG. 2 and a developing potential. It is a diagram which shows an example of the relationship between the product of the exposure power of LD light source in the exposure unit 11 of FIG. 1, exposure time, and development potential. It is a figure which shows an example of the quantitative evaluation in case the color printer shown in FIG. 1 implements the control regarding this invention on different conditions, respectively.

Hereinafter, embodiments for carrying out the present invention will be specifically described with reference to the drawings.
In the following embodiments, in an image forming apparatus using the two-component development method, the development history of the previous development sleeve remains on the development sleeve in the development process, and the development history of the first round remains after the development of the second round. As a result, the extent (value) of the density deviation that occurs at the density deviation occurrence location corresponding to the circumferential pitch of the developing sleeve is predicted from the output image information (image data). A feature is that the image forming conditions are determined in accordance with the prediction result.

First, a basic configuration of a color printer using an electrophotographic system as an embodiment of an image forming apparatus according to the present invention will be described with reference to FIGS.
FIG. 1 is a diagram illustrating a schematic configuration example of a mechanism unit of the color printer. FIG. 2 is a diagram illustrating a schematic configuration example of a process unit which is the image forming unit of FIG.

As shown in FIG. 1, the color printer of this embodiment is for Y (yellow), C (cyan), M (magenta), and K (black) as process units (image forming units) that are toner image forming means. 4 color process units 10Y, 10C, 10M, and 10K. In these, Y, C, M, and K toners of different colors are used as an image forming material for forming an image, but the other configurations are the same.
Taking a process unit 10Y for generating a Y toner image as an example, this includes a photoconductor unit 110Y and a developing unit 120Y as shown in FIG. The photosensitive unit 110Y and the developing unit 120Y are configured to be detachable from the printer main body.

  The photoreceptor unit 110Y removes and collects a drum-shaped photoreceptor (hereinafter referred to as “photoreceptor drum”) 111Y that is a latent image carrier and transfer residual toner attached to the photoreceptor drum 111Y. A drum cleaning device 112Y as a carrier cleaning means, a lubricant application brush 113Y and a lubricant (zinc stearate) 114Y for setting the surface friction coefficient of the photosensitive drum 111Y to predetermined values, and a lubricant 114Y are placed on the photosensitive drum 111Y. A lubricant application blade 115Y for uniformly applying toner, a charging roller 116Y for uniformly charging the photosensitive drum 111Y, and a charging roller cleaner 117Y for removing transfer residual toner and the like attached to the charging roller 116Y. I have.

  The charging roller 116Y uniformly charges the surface of the photosensitive drum 111Y that is rotationally driven in the direction of the arrow by a driving unit (not shown) by applying a charging bias obtained by superimposing a DC voltage on the AC voltage from a charging bias applying unit (not shown). . Subsequently, an electrostatic latent image is formed by exposure scanning with a laser beam emitted from an exposure unit 11 which is an exposure unit (not shown) corresponding to the image signal. An in-machine temperature sensor 118Y is disposed at a location in the vicinity of the photosensitive drum 111Y and the developing unit 120Y of the photosensitive unit 110Y. This in-machine temperature sensor 118Y (temperature detecting means) detects the in-machine temperature at the time of image formation.

The developing unit 120Y includes a first developer accommodating portion 122Y in which the first conveying screw 121Y is disposed, and a second developer accommodating portion 124Y in which the second conveying screw 123Y is disposed.
A toner concentration sensor 125Y (toner concentration detecting means) including a magnetic permeability sensor for detecting the magnetic permeability of a two-component developer (hereinafter also simply referred to as “developer”) is installed on the lower surface of the first developer accommodating portion 122Y. The toner mixture (not shown) is calculated so that the mixing ratio between the carrier particles and the toner, which is a magnetic substance constituting the developer, is calculated from the magnetic permeability (toner concentration) detected by the toner concentration sensor 125Y and becomes a predetermined toner concentration. The toner is replenished as needed by the apparatus.

The first conveying screw 121Y is rotationally driven by a driving means (not shown) to convey the developer in the first developer accommodating portion 122Y from the back side to the near side in the direction orthogonal to FIG. It enters the second developer accommodating portion 124Y through a communication port (not shown) provided in the partition wall between 122Y and the second developer accommodating portion 124Y.
The second conveying screw 123Y in the second developer accommodating portion 124Y is rotationally driven by a driving means (not shown) to convey the developer from the front side to the back side in the drawing.

Above the second conveying screw 123Y, a developing sleeve 126Y is disposed in a posture parallel to the second conveying screw 123Y, and the developing sleeve 126Y, which is a developer carrier, is rotationally driven in the direction of the arrow.
The developing sleeve 126Y is made of a non-magnetic material (aluminum) pipe, and the surface is roughened by sandblasting.

  A magnet (not shown) is disposed inside the developing sleeve 126Y, and a part of the developer conveyed by the second conveying screw 123Y is pumped up to the surface of the developing sleeve 126Y by the magnetic force generated by the magnet. Then, after the layer thickness is regulated by the doctor blade 127Y disposed so as to maintain a predetermined gap with the developing sleeve 126Y, the layer thickness is conveyed to a developing area facing the photosensitive drum 111Y, and a developing bias applying means (not shown) The developing bias applied to the developing sleeve 126Y causes toner to adhere to the electrostatic latent image formed on the photosensitive drum 111Y, thereby forming a toner image. The developer whose toner has been consumed by the development is returned to the second conveying screw 123Y as the developing sleeve 126Y rotates. And if it conveys to the innermost end in the figure, it will return in the 1st developer accommodating part 122Y via the communication port which is not shown in figure.

  The detection result of the magnetic permeability of the developer by the toner concentration sensor 125Y is sent as a voltage signal to a control unit described later. Since the magnetic permeability of the developer has a correlation with the actual toner concentration of the developer, the toner concentration sensor 125Y outputs a voltage having a value corresponding to the toner concentration. The control unit includes a non-volatile storage unit to be described later, in which the target value Vref of the output voltage from the toner density sensor 125Y is stored, and the output voltage value and the target value Vref from the toner density sensor 125Y. And a toner supply device (not shown) supplies toner in an amount corresponding to the comparison result from the rear side of the first developer accommodating portion 122Y of the developing unit 120Y, thereby adjusting the toner concentration in the developer. Maintain the desired value. The control by the toner density sensor and the toner supply device is performed for each color individually.

  Returning to FIG. 1, an exposure unit 11 is disposed below the process units 10Y, 10C, 10M, and 10K. An exposure unit 11 serving as an exposure unit (latent image writing unit) irradiates the surface of each process unit 10Y, 10C, 10M, and 10K with a laser beam modulated according to image information to be output. As a result, electrostatic latent images are formed on the photosensitive drums 111Y, 111C, 111M, and 111K. The exposure unit 11 scans laser light emitted from a laser diode (hereinafter also referred to as “LD” or “LD light source”) as a light source by a polygon mirror that is rotationally driven by a motor (not shown), and a plurality of optical lenses. And irradiating the photosensitive drums 111Y, 111C, 111M, and 111K via a mirror and a mirror. Instead of such a configuration, an exposure unit (exposure means) using another light source such as an LED array may be employed.

  Below the exposure unit 11, a first paper feed cassette 12 and a second paper feed cassette 13 are disposed so as to overlap in the vertical direction. Each of these paper feed cassettes 12 and 13 contains a bundle of recording papers as recording media, and the uppermost recording paper has a first paper feed roller and a second paper feed roller (not shown), respectively. It is in contact. When the first paper feeding roller or the second paper feeding roller is rotated counterclockwise at a predetermined timing by a driving means (not shown), the recording paper is fed from the first paper feeding cassette 12 or the second paper feeding cassette 13. Is discharged toward the paper feed path 14 arranged so as to extend in the vertical direction on the right side in the drawing. A plurality of conveying roller pairs 15 to 18 are disposed in the sheet feeding path 14, and the recording paper sent to the sheet feeding path 14 is conveyed upward by these conveying roller pairs 15 to 18.

A registration roller pair 19 is disposed in the paper feed path 14.
When the leading edge of the recording paper conveyed by the conveying roller pair 17 or the like reaches immediately before the registration roller pair 19, the leading edge is detected by a sensor (not shown) and is temporarily stopped in a state where the leading edge is nipped by the registration roller pair 19. The The registration roller pair 19 is driven at a predetermined timing in accordance with the timing at which the toner image formed on the intermediate transfer belt 20 reaches the secondary transfer nip, and the recording paper is sent out toward the secondary transfer nip. .

  Above each of the process units 10Y, 10C, 10M, and 10K in the figure, a transfer unit that moves the intermediate transfer belt 20 that is a surface endless moving body endlessly in the direction of the arrow while being stretched is disposed. In addition to the intermediate transfer belt 20, the transfer unit as a transfer unit includes a belt cleaning unit 21 as a cleaning unit, and primary transfer units (intermediate) disposed at positions facing the photosensitive drums 111Y, 111C, 111M, and 111K of the respective colors. Primary transfer rollers 22Y, 22C, 22M, and 22K, which are transfer means), a belt driving roller 23 that receives external driving and drives the intermediate transfer belt 20, a belt tension roller 24, and the like. The belt drive roller 23 also functions as a counter roller of the secondary transfer roller 25 that is a secondary transfer unit. The intermediate transfer belt 20 is endlessly moved in the direction of the arrow by the rotational drive of the belt driving roller 23 while being stretched around these rollers.

  The primary transfer rollers 22Y, 22C, 22M, and 22K are in contact with the photosensitive drums 111Y, 111C, 111M, and 111K with the intermediate transfer belt 20 interposed therebetween to form primary transfer nips. By applying a transfer bias having a polarity opposite to that of the toner image formed on each of the photosensitive drums 111Y, 111C, 111M, and 111K to the primary transfer rollers 22Y, 22C, 22M, and 22K, each of the toners. The image is transferred onto the intermediate transfer belt 20. The toner images of the respective colors formed by the process units 10Y, 10C, 10M, and 10K of the respective colors are sequentially primary transferred onto the intermediate transfer belt 20, and a color image is formed on the intermediate transfer belt 20.

A secondary transfer roller 25 is disposed outside the intermediate transfer belt 20 at a position facing the belt driving roller (secondary transfer counter roller) 23 with the intermediate transfer belt 20 in between. The secondary transfer roller 25 abuts on the belt driving roller 23 with a predetermined load by a spring load, and a secondary transfer nip is formed.
The color image formed on the intermediate transfer belt 20 is moved to the secondary transfer nip by the rotational drive of the intermediate transfer belt 20, and at the same time, is synchronized with the entry of the color image (toner image) from the registration roller pair 19 into the secondary transfer nip. The recording paper enters the secondary transfer nip.

The color image is secondarily transferred onto the recording paper by a secondary transfer electric field and a nip pressure formed between the secondary transfer roller 25 and a belt driving roller (secondary transfer counter roller) 23. The secondary transfer electric field is formed, for example, by applying a transfer bias having the same polarity as the toner to the belt driving roller 23 and grounding the secondary transfer roller 25.
On the intermediate transfer belt 20 after passing through the secondary transfer nip, a small amount of toner that has not been transferred to the recording paper remains and adheres. This is cleaned by the belt cleaning unit 21. In the belt cleaning unit 21, the cleaning blade 21 a is in contact with the surface of the intermediate transfer belt 20, whereby the transfer residual toner on the intermediate transfer belt 20 is scraped and removed.

The transfer residual toner removed from the intermediate transfer belt 20 is accommodated in the waste toner bottle 26 and discarded.
A fixing unit 27 is disposed above the secondary transfer nip. The fixing unit 27 includes a fixing roller 28 that includes an electromagnetic induction heat generating layer, a pressure roller 29 that is in contact with the fixing roller 28 with a predetermined pressure to form a predetermined nip width, a thermistor described later, and the like. On the left side of the fixing roller 28 in the figure, there is provided an IH coil unit 30 which is an electromagnetic induction means for generating heat in the electromagnetic induction heat generating layer in the fixing roller 28. The fixing roller 28 is heated by electromagnetic induction by the IH coil unit 30. Among the rollers, the pressure roller 29 is rotated in the clockwise direction (arrow direction) and the fixing roller 28 is rotated in the counterclockwise direction (arrow direction) by a driving unit (not shown). The fixing roller 28 may include a heater as a heating unit, and the fixing roller 28 may be heated by energizing the heater.

The recording paper that has passed through the secondary transfer nip is separated from the intermediate transfer belt 20 and then fed into the fixing unit 27. Then, in the process of being transported from the lower side to the upper side in the figure while being sandwiched between the fixing nips of the fixing unit 27, it is heated by the fixing roller 28 and simultaneously pressed by the fixing nip to record a color image (toner image). Fixed on paper.
The recording paper subjected to the fixing process in this manner is discharged out of the apparatus via a pair of discharge rollers (not shown) and stacked on the upper surface of the printer main body.

  Above the transfer unit, toner bottles 31Y, 31C, 31M, and 31K for respective colors that respectively store Y, C, M, and K toners are disposed. The toner of each color stored in each toner bottle 31Y, 31C, 31M, 31K is appropriately supplied to the developing unit of each color process unit 10Y, 10C, 10M, 10K. These toner bottles 31Y, 31C, 31M, and 31K are detachable from the printer main body, and can be replaced when the remaining amount of toner in the bottles is exhausted.

Next, a hardware configuration example of the control system of the color printer shown in FIG. 1 will be described with reference to FIG.
FIG. 3 is a block diagram showing a hardware configuration example of the control system of this color printer.
The control unit of the color printer includes a controller board 51, an engine main board 52, an engine sub board 53, a power supply unit (hereinafter referred to as “PSU”) 54, and the like.

  The controller board 51 uses a microcomputer including a CPU, a ROM, a RAM, and an ASIC (Application Specific Integrated Circuit), an external device (not shown) such as a personal computer, and a network interface such as a LAN (Local Area Network) (hereinafter “a local area network”). The interface is abbreviated as “I / F”) 71, IEEE1284 · I / F72, IEEE1394 · I / F73, IEEE802.11b · I / F74 Data such as a character code received from an external device by communication control is expanded on a memory (RAM) 75 and converted into image information (bitmap data) in a format printable by the engine unit, and then sent to the engine main board 52. Output.

  The controller board 51 sets information used for later-described control input from the operation unit 208 or the like, and stores and saves it in the NVRAM 76, HDD (hard disk device) 77, SD card 78, etc., which are nonvolatile storage means. I can leave. The controller board 51, together with an engine main board 52 and an engine sub board 53, which will be described later, functions as a prediction unit and an adjustment unit according to the present invention.

  The engine main board 52 uses the same microcomputer as that of the controller board 51, exchanges various signals with the engine sub board 53, and sets each of the components in the exposure unit 11 based on image information from the controller board 51. An LD (laser diode) light source 101 is modulated and driven, and the high-voltage power source 102 is controlled to drive the photosensitive units and developing units of the process units 10Y, 10C, 10M, and 10K shown in FIG.

  The engine sub board 53 also uses the same microcomputer as the controller board 51, and exchanges various signals with the engine main board 52 based on signals from the synchronization detection unit 201 in the exposure unit 11. Based on signals from various sensors 202 including a toner density sensor (including the toner density sensor 125Y of FIG. 2) and an in-machine temperature sensor (including the in-machine temperature sensor 118Y) provided in each of the process units 10Y, 10C, 10M, and 10K. Various motors 204 including a polygon motor 203 and a conveyance motor, and various clutches 205 are controlled, and a PSU (power supply unit) 54 is controlled based on a thermistor (temperature sensor) 206 in the fixing unit 27. The PSU 54 controls on / off of energization to the IH coil unit 30 in the fixing unit 27.

  Note that when the fixing roller 28 having a built-in heater is used, it is preferable to control on / off of the power supply to the heater. The operation unit 208 includes an input unit for performing various settings and a display unit for displaying various information.

  In the following, the parts related to the present invention in the color printer described with reference to FIGS. 1 to 3 will be described with reference to FIGS. Here, for convenience of explanation, only the part related to the process unit 10Y will be described, but the same applies to the other process units 10C, 10M, and 10K.

Here, fixed conditions at the time of image formation in the color printer of this embodiment are shown below.
(A) Charge potential of the photosensitive drum 111Y Vd: -700 [V]
(B) Rotational peripheral speed of the photosensitive drum 111Y Vp: 205 [mm / s]
(C) Rotational peripheral speed of developing sleeve 126Y Vs: 369 [mm / s]
(D) Diameter of developing sleeve 126Y Ds: 18 [mm]

First, the phenomenon in which the density deviation occurs, the location and the degree of the density deviation will be described with reference to FIG.
FIG. 4 is a conceptual diagram for explaining the density deviation occurrence region. The input image pattern in FIG. 4A shows an example of an image pattern that is formed by image forming processing based on image information and is not affected by the previous pattern. In addition, the output image pattern in FIG. 5B shows an example of an image pattern that is formed by image forming processing based on image information and is affected by the previous pattern.

  For example, as shown in FIG. 4B, an image immediately after the pattern is switched at a position where an image pattern (hereinafter also simply referred to as “image pattern”) formed by the image forming process on the photosensitive drum 111Y is switched. A density deviation generation region L, which is a density deviation band corresponding to the length of one round of the developing sleeve 126Y, is generated at the tip of the developing sleeve 126Y. This is a phenomenon in which the development history of the previous pattern remains on the developing sleeve 126Y and appears in the next pattern as an afterimage, and the amount of toner adhering to the developing sleeve 126Y changes before and after the pattern switching. Therefore, it is considered that the main cause is that the effective development potential fluctuates due to the action of the charge held by the toner.

The density deviation occurrence region L [mm] generated at the leading edge of the image immediately after the pattern is switched at the place where the image pattern is switched is the rotational peripheral speed Vp [mm / s] of the photosensitive drum 111Y and the rotational periphery of the developing sleeve 126Y. The speed Vs [mm / s] and the diameter Ds [mm] of the developing sleeve 126Y are obtained by L = πDs / (Vs / Vp). At the location where the image pattern is switched, the density deviation occurrence region L, which is a region where the density deviation can occur, is determined by the above formula, regardless of the image pattern before and after the switching. As an example, the density deviation occurrence region L under the above-described fixed conditions can be calculated as follows.
Density deviation generation region L = 3.14 × 18 / (369/205) ≈31 [mm]

  When the image pattern is switched, a density deviation occurs in the density deviation generation region L. The degree (value) of the density deviation differs depending on the combination of the image patterns before and after the switching point. FIG. 5 shows an example of the relationship between the difference in image density (image pattern ID difference) before and after image pattern switching and the density deviation (ΔID) generated there. Data indicating the relationship and data indicating other relationships described later are assumed to be stored in advance in the NVRAM 76 in FIG. 3, but other nonvolatile storage means such as an HDD (hard disk device) 77 and an SD card 78. Alternatively, it may be stored in advance in a ROM in the controller board 51 or the engine main board 52.

  As can be seen from FIG. 5, the density deviation is relatively large when the difference in image density before and after the switching of the image pattern is large, and the density difference is small when the difference in image density before and after the switching of the image pattern is small. Deviation is relatively small. The density deviation can be suppressed by determining an appropriate development potential (image forming condition) and performing image forming (image forming) processing on the density deviation predicted based on this relationship.

Therefore, each embodiment of control (control for the process unit 10Y) related to the present invention in this color printer will be described. Here, for convenience of explanation, only the process unit 10Y will be described, but the same applies to the other process units 10C, 10M, and 10K.
[First embodiment]
First, the first embodiment will be described.
First, an example of the relationship between the in-machine temperature and the concentration deviation is shown in FIG.

  As shown in FIG. 6, it has been confirmed that the concentration deviation increases when the in-machine temperature is high. Therefore, if the control unit (see FIG. 3) of this color printer is in a direction in which the density deviation increases due to fluctuations in the internal temperature, the adjustment amount of the development potential is increased, and conversely, in the direction in which the density deviation decreases. The density deviation is suppressed by reducing the adjustment amount of the development potential. An example of the relationship between the image density before and after the switching of the image pattern and the development potential corresponding to the image density (including the development potential for the density deviation predicted from the in-machine temperature immediately after the switching of the image pattern) is shown in FIG. The in-machine temperature can be detected (detected) by an in-machine temperature sensor 118Y (in-machine temperature detection means) in the various sensors 202 of FIG.

ID ₁ and ID ₂ shown in FIG. 7 are image densities before and after switching of the image pattern, V _P1 and V _P2 are development potentials for the respective image densities (image area ratio), and Ta and Tb are ( In-machine temperature IDa and IDb at the time of image formation (in the density deviation occurrence region L shown in FIG. 3B) indicate density deviations that occur after image pattern switching. Each image density before and after the switching of the image pattern (actually the image density of each input image pattern) ID ₁ and ID ₂ is predicted (calculated) by analyzing each corresponding image information before and after the image pattern switching. )it can.

Here, when the relationship between the in-machine temperatures Ta and Tb is Ta <Tb, the relationship between the density deviations IDa and IDb is IDa <IDb from the relationship shown in FIG.
These density deviations IDa (or IDb) are predicted based on the detected in-machine temperature Ta (or Tb), the predicted image density ID ₁ , ID ₂ and the relationship shown in FIG. 5 and FIG. By adjusting the development potential V _P to V _Pa (or V _Pb ), it can be suppressed as shown by the solid line in FIG.

FIG. 8 is a flowchart illustrating an example of Y-color development potential adjustment processing executed by the control unit of the color printer shown in FIG.
The control unit of this color printer starts the processing routine shown in FIG. 8 when starting image forming processing (image forming processing) having a different pattern according to image information (each image information) of a plurality of pages, and first proceeds to step S1. By analyzing the image information for the first two pages, the density of each image formed by each image information (each image density before and after the pattern change of each image) is predicted. The prediction result and other prediction results described later are stored in a storage unit such as NVRAM 76.

  Next, in step S2, the process waits for arrival immediately after the switching of the image pattern, and then proceeds to step S3, where the in-machine temperature sensor 118Y detects the in-machine temperature (actually the temperature in the vicinity of the photosensitive drum 111Y), and then in step S4. , And based on the difference between the image densities (ID difference) before and after the switching of the image pattern formed by the predicted image information for the first two pages, and the relationship shown in FIG. A density deviation (actually the degree) occurring in the density deviation occurrence area after switching is predicted. Further, based on the in-machine temperature detected this time and the relationship shown in FIG. 6, the concentration deviation (actually, the degree) that varies depending on the in-machine temperature is predicted.

Thereafter, the process proceeds to step S5, and the development potential is adjusted for the image forming process after the pattern change according to the prediction result in step S4. With this adjustment, the development potential for the image forming process after the pattern switching can be determined in another processing routine, and the image forming process after the pattern switching can be performed with the developing potential.
After adjusting the development potential in step S5, the process proceeds to step S6, where the presence or absence of image information on the next page (here, the third page) is checked. If there is no image information, the processing in FIG. 8 ends. .

  If there is image information of the next page, the process proceeds to step S7, and the image information is analyzed to predict the density of the image formed by the image information. Then, the process returns to step S2, and the next image The process proceeds to step S3 after waiting for arrival immediately after the switching of the pattern, and after the in-machine temperature sensor 118Y detects the in-machine temperature, the process proceeds to step S4 and the following processing is performed.

That is, the change in image pattern formed by the image information of the next two pages (here, the second page and the third page) predicted for the density deviation occurring in the density deviation generation area after the image pattern switching. Based on the difference between the respective image densities before and after (ID difference) and the relationship shown in FIG. 5, the density deviation (actually the degree) generated in the density deviation generation region after the switching of the image pattern is predicted. Further, based on the in-machine temperature detected this time and the relationship shown in FIG. 6, the concentration deviation (actually the degree) that varies depending on the in-machine temperature is predicted.
Thereafter, the process proceeds to step S5, and thereafter the same processing as described above is performed.

  Here, as described above, there is a problem that a density deviation band corresponding to the length of one round of the developing sleeve is generated at the leading edge of the image immediately after the pattern is switched at the position where the image pattern is switched. This is considered to be because the development history of the previous pattern remains on the developing sleeve and appears in the next pattern as an afterimage. This phenomenon fluctuates depending on the temperature in the machine, and when the temperature is different, the degree of density deviation is correspondingly different.

  On the other hand, in the first embodiment, the degree of density deviation occurring at the density deviation occurrence location is predicted in advance from the output image information, and the degree of density deviation fluctuated thereby is predicted from the in-machine temperature at the time of image formation. Then, by adjusting the image forming conditions in accordance with these prediction results and performing image formation under the adjusted image forming conditions, it is possible to suppress density deviation and obtain a uniform image.

[Second Embodiment]
Next, a second embodiment will be described.
In the second embodiment, among the same controls as in the first embodiment, the development potential is adjusted by controlling the exposure power for the photosensitive drum 111Y of the process unit 10Y by the exposure unit 11 (exposure means) in FIG. Is going.

An example of the relationship between the exposure power of the LD light source 101 (FIG. 3) in the exposure unit 11 of FIG. 1 and the development potential is shown in FIG. From this relationship, the density deviation is suppressed in FIG. 7 by controlling the exposure power in the density deviation generation region L (immediately after switching of the image pattern) shown in FIG. 4B to L _Pa (or L _Pb ). A possible development potential V _Pa (or V _Pb ) can be obtained. When another light source such as an LED array is used instead of an LD (laser diode), the exposure power can be controlled.

  In the second embodiment, the degree of density deviation occurring at the density deviation occurrence location is predicted in advance from the image information to be output, and the degree of density deviation fluctuating thereby is predicted from the in-machine temperature at the time of image formation. Since the image forming conditions are adjusted by controlling the exposure power to the photosensitive drum according to the result, and the image is formed under the adjusted image forming conditions, the toner adhesion amount on the photosensitive drum is adjusted. , Density deviation can be suppressed and a uniform image can be obtained.

[Third embodiment]
Next, a third embodiment will be described.
In the third embodiment, among the same controls as in the first embodiment, the development potential is adjusted by controlling the exposure time for the photosensitive drum 111Y of the process unit 10Y by the exposure unit 11 of FIG.
FIG. 10 shows the relationship between the exposure time of the LD light source 101 in the exposure unit 11 and the development potential. From this relationship, by controlling the exposure time in the density deviation generation region L shown in FIG. 4B to L _Ta (or L _Tb ), the development potential V _Pa (or the density deviation can be suppressed in FIG. 7) (or V _Pb ) can be obtained.

  In the third embodiment, the degree of density deviation occurring at the density deviation occurrence location is predicted in advance from the image information to be output, and the degree of density deviation that fluctuates accordingly is predicted from the in-machine temperature at the time of image formation. According to the result, the exposure time for the photosensitive drum is controlled to adjust the image forming conditions, and the image formation is performed under the adjusted image forming conditions, so that the toner adhesion amount on the photosensitive drum is adjusted. , Density deviation can be suppressed and a uniform image can be obtained.

[Fourth embodiment]
Next, a fourth embodiment will be described.
In the fourth embodiment, the voltage applied to the developing sleeve 126Y (developer carrier) of the process unit 10Y in FIG. 1 from the high-voltage power source 102 in FIG. This is done by controlling (development bias).
FIG. 11 shows the relationship between the developing bias applied to the developing sleeve 126Y of FIG. 2 and the developing potential. From this relationship, the development potential V _Pa (or V _Pb ) capable of suppressing the density deviation in FIG. 7 can be obtained by controlling the development bias in the density deviation occurrence region L to V _Ba (or V _Bb ).

  In the fourth embodiment, the degree of density deviation occurring at the density deviation occurrence location is predicted in advance from the image information to be output, and the degree of density deviation that fluctuates accordingly is predicted from the in-machine temperature at the time of image formation. According to the result, the applied voltage (development bias) to the developing sleeve is controlled to adjust the image forming conditions, and image formation is performed under the adjusted image forming conditions, thereby adjusting the toner adhesion amount on the photosensitive drum. Therefore, the density deviation can be suppressed and a uniform image can be obtained.

[Fifth embodiment]
Next, a fifth embodiment will be described.
In the fifth embodiment, among the same controls as in the first embodiment, the development potential is adjusted by controlling the exposure power and exposure time for the photosensitive drum 111Y of the process unit 10Y by the exposure unit 11 of FIG. ing.
FIG. 12 shows the relationship between the product (exposure energy) of the exposure power and the exposure time of the LD light source 101 (FIG. 3) in the exposure unit 11 and the development potential. From this relationship, by controlling the exposure energy in the density deviation occurrence region L shown in FIG. 4B to L _PTa (or L _PTb ), the development potential V _Pa (or that can suppress the density deviation in FIG. 7) (or V _Pb ) can be obtained.

  In the fifth embodiment, the degree of density deviation occurring at the density deviation occurrence location is predicted in advance from the image information to be output, and the degree of density deviation that fluctuates accordingly is predicted from the in-machine temperature at the time of image formation. The amount of toner adhering to the photosensitive drum is adjusted by adjusting the image forming conditions by controlling the exposure power and the exposure time for the photosensitive drum according to the result, and adjusting the image forming conditions after the adjustment. Therefore, the density deviation can be further suppressed and a uniform image can be obtained.

In addition to controlling the exposure power and the exposure time for the photosensitive drum according to the prediction result, each control of the second to fourth embodiments, that is, the exposure power, the exposure time, and the developing sleeve for the photosensitive drum. It is also possible to control the applied voltage with respect to any combination.
Further, it is possible to selectively control the exposure power for the photosensitive drum, the exposure time, and the voltage applied to the developing sleeve by an instruction from the outside (operation unit or the like).
Alternatively, the exposure power for the photosensitive drum, the exposure time, and the applied voltage to the developing sleeve can be selectively controlled according to the result of predicting the degree of density deviation occurring at the density deviation occurrence location.

  For example, in the place where the image pattern is switched, when the places where the density deviation actually occurs are aligned in the main scanning direction that is the axial direction of the photosensitive drum (for example, the entire non-image portion is switched to the full solid image, the density When the deviation band can be made uniform in the main scanning direction), the density deviation is suppressed by adjusting the image forming condition by controlling the developing bias (voltage applied to the developing sleeve). On the other hand, when density deviation occurrence points are irregularly arranged in the main scanning direction, it is desired to limit only those points. Therefore, the exposure amount (exposure power and exposure time) to the photosensitive drum is controlled to form image forming conditions. The density deviation is suppressed by adjusting. If the density deviation is inconspicuous enough to be handled by the developing bias, the developing bias is controlled to adjust the image forming conditions, and the exposure amount of the photosensitive drum 111Y is not adjusted more than necessary. It is possible to obtain a uniform image with suppressed density deviation while suppressing fatigue.

As a specific example, the control of the fourth and fifth embodiments is combined to prepare a plurality of input image patterns (actually corresponding image information), and density deviation occurs from the input image pattern under different in-machine temperature conditions. The density deviation in the area L is predicted, and the development potential is adjusted by controlling the three items of the exposure power to the photosensitive drum, the exposure time to the photosensitive drum, and the applied potential (developing bias) to the developing sleeve, and image formation is performed. You can also.
Actually, when the toner density of the developer is adjusted to 7 wt%, and the density deviation generated in the output image pattern is quantitatively evaluated as the density deviation ΔID between the density deviation generation region L and its surroundings, (a ) (B) Quantitative evaluation as shown in (c) was obtained. In those quantitative evaluations, the image patterns before and after the change are different, and differ depending on the reference condition and the adjustment condition. And all the above three items show that the density deviation ΔID is reduced by changing to the adjustment condition with respect to the reference condition, and the density deviation can be suppressed.

Note that the degree of density deviation that occurs at the location where density deviation occurs corresponding to the circumferential pitch of the developing sleeve is predicted from the output image information, and the degree of density deviation that fluctuates accordingly is predicted from the in-machine temperature during image formation. Furthermore, the toner density at the time of image formation is detected by the toner density sensor, the degree of density deviation that varies depending on the toner density is predicted from the detection result, and the image forming condition (development potential) is adjusted according to these prediction results. It is also possible.
The embodiment in which the present invention is applied to a color printer has been described above. However, the present invention is not limited to this, and other color image forming apparatuses such as a digital color copying machine, a color facsimile apparatus, and a digital color multifunction machine are of course used. The present invention can also be applied to various image forming apparatuses such as monochrome digital copying machines, facsimile machines, and digital multifunction machines.

[Program related to this invention]
This program is a program for causing a CPU, which is a computer that controls the image forming apparatus, to realize functions as a prediction unit and an adjustment unit according to the present invention. By causing the CPU to execute such a program, the above-described program is executed. It is possible to obtain the effect as described above.

Such a program may be stored in a ROM provided in the image forming apparatus from the beginning, a non-volatile memory (flash ROM, EEPROM, etc.), or a storage means such as an HDD, or a CD-ROM which is a recording medium Or a non-volatile recording medium (memory) such as a memory card, flexible disk, MO, CD-R, CD-RW, DVD + R, DVD + RW, DVD-R, DVD-RW, or DVD-RAM. You can also. The programs recorded on those recording media can be installed in the image forming apparatus and executed by the CPU, or each program described above can be executed by causing the CPU to read out and execute this program from those recording media. .
Furthermore, it is also possible to download and execute an external device that is connected to a network and includes a recording medium that records the program, or an external device that stores the program in the storage unit.

  As is apparent from the above description, according to the present invention, even when the two-component development method is used, a density deviation can be suppressed and a good image can be obtained. Therefore, it is possible to provide an image forming apparatus that can always acquire a high-quality image.

10Y, 10C, 10M, 10K: Process unit 11: Exposure unit 51: Controller board 52: Engine main board 53: Engine sub board 54: PSU 75: Memory 76: NVRAM
77: HDD 78: SD card 101: LD light source 102: High-voltage power supply 110Y: Photoconductor unit 111Y, 111C, 111M, 111K: Photoconductor drum 116Y: Charge roller 120Y: Development unit 121Y: First transport screw 122Y: First development Agent storage unit 123Y: Second conveying screw 124Y: Second developer storage unit 125Y: Toner density sensor 126Y: Development sleeve 201: Synchronization detection unit 202: Various sensors

JP-A-9-106175 JP 2007-264336 A JP 2007-86448 A JP 2006-220749 A

Claims (10)

A charging unit for charging the latent image carrier, an exposure unit for exposing the latent image carrier charged by the charging unit according to image information to form a latent image, and a two-component developer comprising a toner and a carrier A developer carrying member that carries and conveys the latent image formed on the latent image carrier by the exposure unit and visualized by the toner of the two-component developer from the developer carrier. An electrophotographic image forming apparatus that forms an image by controlling those means,
Temperature detecting means for detecting the temperature in the image forming apparatus;
Based on the difference in image density before and after switching of the image pattern in the detection result and the image information by the temperature sensing means, the density deviation said generated in density deviation occurs a portion corresponding to the circumferential length pitch of the developer carrying member, wherein Predicting means for predicting that the higher the temperature detected by the temperature detecting means and the greater the difference in image density ,
An image forming apparatus comprising: an adjusting unit that adjusts an image forming condition in accordance with a prediction result by the predicting unit. The image forming apparatus according to claim 1.
The image forming condition is a development potential, and the adjustment unit increases the adjustment amount of the development potential as the density deviation predicted by the prediction unit increases, and the adjustment amount of the development potential as the density deviation decreases. An image forming apparatus characterized by reducing the size of the image forming apparatus.   3. The image according to claim 1, wherein the adjustment unit adjusts the image forming condition by controlling an exposure power applied to the latent image carrier by the exposure unit according to the prediction result. Forming equipment.   3. The image according to claim 1, wherein the adjustment unit adjusts the image forming condition by controlling an exposure time for the latent image carrier by the exposure unit according to the prediction result. Forming equipment.   The image forming apparatus according to claim 1, wherein the adjusting unit adjusts the image forming condition by controlling a voltage applied to the developer carrying member according to the prediction result.   The adjusting unit selects an exposure power for the latent image carrier by the exposure unit, an exposure time for the latent image carrier by the exposure unit, and a voltage to be applied to the developer carrier according to the prediction result. The image forming apparatus according to claim 1, wherein the image forming condition is adjusted by controlling the operation of the image forming apparatus.   The adjusting unit combines an exposure power of the exposure unit with respect to the latent image carrier, an exposure time with respect to the latent image carrier of the exposure unit, and a voltage applied to the developer carrier according to the prediction result. The image forming apparatus according to claim 1, wherein the image forming conditions are adjusted by controlling the image forming conditions. A charging unit for charging the latent image carrier, an exposure unit for exposing the latent image carrier charged by the charging unit according to image information to form a latent image, and a two-component developer comprising a toner and a carrier A developer carrying member that carries and conveys the latent image formed on the latent image carrier by the exposure unit and visualized by the toner of the two-component developer from the developer carrier. And an image forming condition adjusting method in an electrophotographic image forming apparatus that forms an image by controlling those means, and temperature detecting means for detecting the temperature in the image forming apparatus,
On the basis of the difference in image density before and after switching of the image pattern in the detection result and the image information by the temperature sensing means, the density deviation said generated in density deviation occurs a portion corresponding to the circumferential length pitch of the developer carrying member, wherein Predicting that the higher the temperature detected by the temperature detecting means and the larger the difference in the image density, the larger the temperature ,
An image forming condition adjusting method, wherein the image forming condition is adjusted according to the prediction result. A charging unit for charging the latent image carrier, an exposure unit for exposing the latent image carrier charged by the charging unit according to image information to form a latent image, and a two-component developer comprising a toner and a carrier A developer carrying member that carries and conveys the latent image formed on the latent image carrier by the exposure unit and visualized by the toner of the two-component developer from the developer carrier. And a computer that controls an electrophotographic image forming apparatus that forms an image by controlling those means, and a temperature detecting unit that detects the temperature in the image forming apparatus.
On the basis of the difference in image density before and after switching of the image pattern in the detection result and the image information by the temperature sensing means, the density deviation said generated in density deviation occurs a portion corresponding to the circumferential length pitch of the developer carrying member, wherein A prediction function that predicts that the higher the temperature detected by the temperature detection means and the greater the difference in image density ,
A program for realizing an adjustment function for adjusting an image forming condition in accordance with a prediction result by the prediction function.   A computer-readable recording medium on which the program according to claim 9 is recorded.