CN100510996C - Image forming apparatus and output image density correction method - Google Patents

Abstract

An image forming apparatus comprising: an output image density control section that forms a patch image and determines an output image density control condition based on a comparison result of the density of the patch image with a preset target value; a pixel counting section that capable of counting the amount of image pixels at the time of image formation; a pixel count value accumulation memory section which accumulates and stores pixel count values; a toner supply section; a toner supply amount measuring section capable of measuring supply to a developing device the amount of toner; the toner supply amount accumulation memory section which accumulates and stores the toner supply amount; and the target value correction section which is based on the relationship between the pixel count accumulation value and the toner supply amount accumulation value The target value of the density of the patch image is corrected.

Description

Image forming apparatus and output image density correction method

technical field

The present invention relates to an image forming apparatus having an image forming engine that irradiates a light beam corresponding to image data to a uniformly charged image bearing body and an output image density correction method thereof. forming an electrostatic latent image on the surface of the surface, developing the image with a toner, transferring the toner image directly or through an intermediate transfer body, and fixing the transferred toner image to form image.

Background technique

Conventionally, an image forming apparatus (for example, a copying machine, a printer, a facsimile machine, or a multifunctional machine thereof) employing this type of electrophotographic method includes a charging section, a beam scanning section, a developing section, a transferring section, etc., which are provided in The periphery of the photoconductor drum as an image carrier is opposed to the peripheral surface of the photoconductor drum.

That is, the surface of the photoconductor drum is uniformly charged by applying a predetermined voltage to the charging portion, an electrostatic latent image is formed by the light beam from the beam scanning portion, the image is developed by supplying toner in the developing portion, and by the transfer portion The toner image is transferred onto an intermediate transfer body or the like, and then the image is finally transferred onto paper.

The image-transferred paper is fixed by the fixing section during conveyance up to the paper exit.

In such a conventional image forming apparatus, in order to reduce manufacturing cost and downsize the apparatus, a method of adjusting toner density in a developing portion and output image density by a single beam sensor (density sensor) has been invented. Specific examples include: forming toner density adjustment patches and image density adjustment patches at predetermined intervals; determining the toner density and image density by measuring the density of these patches using a beam sensor; Adjust the toner density and image density.

In order to stabilize image quality, the technique has been proposed.

The first prior art aims at obtaining uniform image density and fixing characteristics with a simple structure to maintain image quality at a high image ratio at the time of printing to stabilize image quality.

That is, the structure of this prior art includes a portion that counts the amount of dots, a memory that stores the dot count value, and a control portion that controls the toner developing bias, and raises the bias when the dot count value exceeds a predetermined value. pressure.

As a result, this prior art device counts the amount of dots of the image output each time, and increments the count value at the memory portion, and when the value exceeds the value at which the image quality begins to decline, the device raises its Developing bias to suppress quality degradation in density.

The second prior art proposes a reduction in solid density or a deterioration in character image quality caused by charging the developer due to an insufficient amount of toner discharged (developed) when outputting a plurality of low-density images that are almost blank paper ), and an improvement in running costs due to an acceleration of the toner consumption rate in the developing machine at high image densities (due to a reduction in toner charge).

That is, when the discharge amount is insufficient, the toner amount calculated in the discharge mode (by adjustment control of the developing machine) is discharged to consume more toner than a predetermined amount for a specific number of sheets. If the discharge amount is large, the toner is charged by operating the developing machine for a predetermined time.

The third prior art proposes to maintain a specific printing performance by correcting the developing bias to secure density, which is used in the field of electrophotographic high-speed printers because low concentration.

That is, the correction is performed step by step corresponding to the detection result of the developer consumption rate in order to prevent hue jumps due to the correction.

However, in the above-described image forming apparatus, even if the value measured by the above-described light beam sensor approaches the target toner density or image density, the actual toner density or image density often deviates greatly from the target. The reason for this is the dispersion of the developer amount (MOS) on the developing roller, the degree of dispersion of the patch image, or the dispersion of the developer, photoconductor, intermediate transfer member, etc., and in either case, if these values deviate greatly from their targets value, various problems may arise in terms of image quality.

Specifically, if the image density is higher than the target value, there is not only a problem with image quality such as ghosting or transfer failure, but also a problem that the life of the toner cartridge cannot be met due to a large amount of toner consumption. .

The correction disclosed in the first prior art is insufficient because it is not performed when the number of dots is smaller than the number at which the quality starts to drop. In addition, this prior art does not propose means for correction when the image density is high.

In addition, the second prior art is not effective for maintaining a constant image density during normal operation because it aims at suppressing the influence of toner charging or low charge.

Furthermore, the third prior art is not effective for maintaining a constant image density during normal operation because it aims at suppressing the influence of toner charging or low charge.

Contents of the invention

In view of the above-mentioned problems, an object of the present invention is to provide an image forming apparatus that, when correction is performed based on a comparison result of the density of a patch image used for output image density adjustment and a target value, even if there is dispersion or developer scattered by the patch image, , photoconductor, intermediate transfer member, etc., the image forming apparatus can accurately stabilize the density of an output image over a long period of time.

In addition to the above objects, another object of the present invention is to provide an image forming apparatus and a method of correcting the density of an output image, which can be used during the entire operation of the apparatus, that is, whether it is a transient period or a regular period. During operation, the density of the output image is stabilized.

[First aspect of the present invention]

A first aspect of the present invention provides an image forming apparatus having an image forming engine that uniformly charges the surface of the image carrier by irradiating the uniformly charged image carrier corresponding to image data. Light beams are used to form an electrostatic latent image, the image is developed using a toner by a developing device, the toner image is transferred directly or via an intermediate transfer body to a recording medium, and the transferred toner image is performing fixing to form an image, the image forming apparatus including: an output image density control section that forms a patch image for output image density correction, and determines an output based on a comparison result of the density of the patch image with a preset target value an image density control condition; a pixel counting section capable of counting an image pixel amount at the time of image formation; a pixel count value accumulation memory section which accumulates and stores pixel count values obtained by counting by the pixel counting section; a toner supply portion capable of quantitatively supplying toner to a developing device; a toner supply amount measuring portion capable of measuring the amount of toner supplied to the developing device by the toner supply portion; the toner supply an amount accumulation memory section which accumulates and stores the toner supply amount measured by the toner supply amount measurement section; and a target value correction section which accumulates pixels in the memory section based on the pixel count value stored in the The target value of the density of the patch image is corrected by the relationship between the counted cumulative value and the toner supply cumulative value stored in the toner supply cumulative memory portion.

According to the first aspect of the present invention, even when the change calculated from the integrated value of the pixel count and the integrated value of the toner supply amount (this change is hereinafter referred to as "slope" because it can be expressed as the accumulated value of the toner supply amount value relative to the pixel count cumulative value) to change the target value of the output image density, resulting in a change in the characteristics of the toner (including the carrier) or a difference in the physical characteristics of the photoconductor, thereby affecting the development characteristics, it is also possible to set Image density is controlled to a specific density. In addition, since the image density, that is, the toner consumption, is improved by making the change (slope) within a certain range, it is possible to suppress the occurrence of the problem that the toner cartridge is damaged due to the output image density being too high. service life cannot reach the target service life.

(principle of the first aspect of the present invention)

The principle of the first aspect of the invention will be described below.

FIG. 7 shows the relationship between the pixel count integrated value and the toner supply amount integrated value when the pixel count integrated value is set on the axis of abscissa and the toner supply amount integrated value is placed on the axis of ordinate. The dotted line indicates the upper limit value of the accumulated toner supply amount, that is, if the actual accumulated toner supply amount exceeds this line, it indicates that the toner supply amount is excessive, the amount of development is large, and the output image density is high.

FIG. 7 shows a case where the actual toner supply amount indicated by the solid line is slightly lower than the dotted line, showing that almost the desired toner consumption, ie, the desired output image density, is ensured.

FIG. 8 shows that the actual toner supply amount exceeds the dotted line, which means that the toner consumption is large, that is, the output image density is too high. If the density of the patch image used for the output image density control is higher than the target value, the device controls to reduce the output image density, as a result of suppressing the toner consumption, and also corrects the toner in the direction toward this dotted line Supply.

However, if the development characteristics change due to the characteristics of toner (including carrier) developer, or the physical characteristics of the photoconductor and intermediate transfer body, even if the actual output image density is high, for the output image The block image density of the density control is also sometimes determined to coincide with the target value. Since the output image density cannot be corrected in this case, the image continues to shift to high density, causing image quality problems such as transfer ghosts, transfer failure, or failure to meet the life of the toner cartridge.

Fig. 9 shows the operation of the apparatus of the first aspect, in which although the actual toner supply amount is higher than the dotted line in the initial period, the output image density is corrected to change the toner consumption, so that the toner consumption can be changed without exceeding the upper limit. The change (slope) of the toner supply cumulative value with respect to the actual pixel count cumulative value is changed in the case of the slope of the value.

FIG. 10 shows an enlarged view of FIG. 9, which shows the relationship between the change (slope) of the toner supply cumulative value relative to the actual pixel count cumulative value and the toner supply amount when the pre-specified pixel count cumulative value is reached. The slope of the limit value is compared, and by changing the target value of the output image density according to this condition, the change (slope) of the toner supply amount integrated value relative to the pixel count integrated value is changed.

[Second aspect of the present invention]

A second aspect of the present invention provides an image forming apparatus having an image forming engine that uniformly charges the surface of the image carrier by irradiating the uniformly charged image carrier corresponding to image data. Light beams are used to form an electrostatic latent image, the image is developed using a toner by a developing device, the toner image is transferred directly or via an intermediate transfer body to a recording medium, and the transferred toner image is Fixing is performed to form an image, the image forming apparatus includes: a standard output image density control condition data memory section that stores a relationship between an environmental condition in the case where the toner density is known and an output image density control condition; the output image a density control section that forms a block image for output image density correction, and determines an output image density control condition based on a comparison result of the density of the block image with a target value set in advance; an environmental sensor that detects at least the humidity of the environment constituting the image forming engine; a standard output image density condition reading section which reads out the humidity in the environment including the humidity detected by the environment sensor based on the standard output image density control condition data memory section a standard output image density control condition under a condition in which at least a toner density is known and in which the readout is performed in a predetermined device operation transition period; and a target value correction section based on the output image by the standard A difference between the standard output image density control condition read by the density condition reading section and the output image density control condition determined by the output image density control section corrects the target value of the density of the patch image.

(Summary of the second aspect of the present invention)

The second aspect of the invention is particularly performed during transitional periods of plant operation, whereas the first aspect of the invention is performed continuously and periodically during plant operation. As a result, the target value correction by the first aspect of the present invention can be rapidly stabilized.

That is, in the transient period of device operation, for example, when the image forming device is controlled by the user immediately after it is shipped from the factory, the toner consumption is very small (including no use) and the amount of processing is very small (including no processing), so The relationship between image and toner consumption has not been obtained. In other words, in terms of throughput, image forming operations of several hundreds of pages are required to obtain this relationship.

If the first aspect of the invention is carried out, it takes a very large amount of time for the target value to converge to a stable value from the transition of the device operation. This is not to negate the first aspect, but to clarify that the efficiency of the transitional period of plant operation is lower than that of the regular period.

(operation of the second aspect of the present invention)

According to the second aspect of the present invention, the relationship between the environmental conditions in the case where the toner density is known and the output image density control conditions is stored in the standard output image density control condition data storage section.

Here, in a preset device operation transition period in which at least the toner density is known, after the output image density control condition is determined by the output image density control section, the standard output image density condition reading section reads from the standard output The image density control condition data storage section reads out standard output image density control conditions of environmental conditions including humidity detected by the environmental sensor.

The target value correcting section corrects the target of the density of the patch image based on the difference between the standard output image density control condition read by the standard output image density condition reading section and the output image density control condition determined by the output image density control section. value.

During the transition period of device operation, since a difference from the standard output image density condition occurs according to environmental conditions due to the known toner density (due to the toner cartridge being new), the target value can be made by a specific estimate close to the optimum value.

[The third aspect of the present invention]

A third aspect of the present invention provides an output image density correction method, which is executed at a predetermined timing during the entire operation of the apparatus in an image forming apparatus to form a patch image for output image density correction, and based on the The output image density control condition is determined by comparing the density of the block image with a preset target value. The image forming apparatus has an image forming engine that uniformly charges the surface of the image carrier, and passes the image data together. Correspondingly, a uniformly charged image carrier is irradiated with a light beam to form an electrostatic latent image, the image is developed with a toner by a developing device, and the toner image is transferred to a recording medium directly or through an intermediate transfer body and fixing the transferred toner image to form an image, the method includes: obtaining an environmental condition at the time of determining the output image density control condition and wherein known in a preset device operation transition period outputting a difference between the standard output image density control conditions of toner density, and correcting the target value based on the difference; and accumulating image pixel amounts at the time of image formation in periods other than the device operation transition period, The toner supply amount supplied to the developing device is integrated, and the target value of the density of the patch image is corrected based on the relationship between the integrated value of the pixel amount and the integrated value of the toner supply amount.

The third aspect of the present invention enables maintaining a stable target value throughout the operation of the device by combining the first and second aspects of the present invention.

More specifically, since the device operation transition period occurs first, the second aspect of the present invention is performed during the device operation transition period, and then the first aspect is performed.

Description of drawings

Preferred embodiments of the present invention will be described in detail below based on the accompanying drawings, wherein:

FIG. 1 is a side view showing an image forming apparatus according to a first embodiment of the present invention;

Fig. 2 is a control block diagram of the engine part according to the first embodiment of the present invention;

3 is a block diagram showing output image density correction control and actual target value correction control according to the first embodiment of the present invention implemented in the main controller;

4 is a flow chart showing the flow of correction control of the actual target value according to the first embodiment of the present invention;

Fig. 5 is a characteristic diagram of the integrated value of the pixel count with respect to the integrated value of the toner supply amount according to the first embodiment of the present invention;

Fig. 6 is a characteristic diagram of the integrated value of the pixel count with respect to the integrated value of the toner supply amount according to the modified example of the first embodiment of the present invention;

Fig. 7 is a characteristic diagram of the integrated value of the pixel count with respect to the integrated value of the toner supply amount for explaining the principle of the first aspect of the present invention;

Fig. 8 is a characteristic diagram of the integrated value of the pixel count with respect to the integrated value of the toner supply amount for explaining the principle of the first aspect of the present invention;

Fig. 9 is a characteristic diagram of the integrated value of the pixel count with respect to the integrated value of the toner supply amount for explaining the principle of target value correction in the first aspect of the present invention;

Figure 10 is an enlarged view of Figure 9;

11 is a block diagram (transition period) showing output image density correction control and actual target value correction control according to the second embodiment of the present invention implemented in the main controller;

12 is a characteristic diagram of humidity with respect to standard output image density control conditions (developing bias voltage) according to the second embodiment of the present invention;

13 is a flowchart showing the flow of correction control of the actual target value according to the second embodiment of the present invention; and

FIG. 14 is a flowchart showing the flow of actual target value correction control for the device operation transition period and regular period according to the third embodiment of the present invention.

Detailed ways

[first embodiment]

(Schematic structure of image forming apparatus)

FIG. 1 shows the outline of an image forming apparatus 10 according to a first embodiment of the first aspect of the present invention. The image forming apparatus 10 includes an engine portion 12 , and a paper feeding unit 14 is provided at the bottom of the engine portion 12 .

The paper feed unit 14 includes a paper tray 22 in which paper is stacked, and a paper feed roller 24 for feeding paper from the paper tray 22 . The paper fed from the feed roller 24 passes through the paper feed path 30 by the paper conveying rollers 26 , 28 , and is conveyed to the transfer roller 74 .

The toner image is transferred onto paper by this transfer roller 74 and fixed by the fixing roller 32A of the fixing section 32 . Thereafter, the paper is output to the first paper output tray 16 or the second paper output tray 18 provided on top of the engine part 12 by the paper output roller 36 or the paper output roller 38 based on the position selection of the switching claw 34 .

In the case of double-sided printing, after the printing of the front side is completed in the above steps, the paper discharge roller 36 is reversed and the paper is supplied to the reverse path 40 before the paper is completely discharged to the first paper discharge tray 16 . The paper is then returned to the paper feed path 30 by transport rollers 42, 44, 46, 48 and the reverse side of the paper is printed. In the case of manual feed printing, when paper is placed on the manual feed tray 20, the paper is conveyed from the manual feed roller 49 to the paper feed path 30 by the conveyance roller 48 and printed.

In the fixing portion 32, the fixing roller 32A is heated to a predetermined temperature by illumination of a lamp (for example, a halogen lamp, etc.) to fix the toner image on paper by the heated fixing roller 32A by heating and pressing.

Four toner cartridges 64 filled with developers of various colors (including toner and magnetic carriers) are provided on the right side of the image forming apparatus 10 in FIG. 1 . These toner cartridges 64 are connected to developing devices 60Y, 60M, 60K, 60C (which will be described later) arranged in order from the top in FIG. The developing devices 60Y, 60M, 60K, 60C.

An exposure unit 62 is provided on the left side of the toner cartridge 64 in FIG. 1, and from the exposure unit 62 to the photoconductor drums 52Y, 52M, 52K, 52C (hereinafter simply referred to as 52 ) emits four laser beams L(Y), L(M), L(K), L(C) corresponding to image signals, thereby forming a latent image on the photoconductor drum 52 .

The photoconductor drums 52 are yellow ( 52Y ), magenta ( 52M ), black ( 52K ) and cyan ( 52C ) photoconductor drums in order from the top in FIG. 1 .

The exposure unit 62 includes: a light source section that outputs laser beams L(Y), L(M), L(K), and L(C) of various colors Y, M, K, and C (hereinafter collectively referred to as laser beams L) a modulation processing section that modulates and emits the laser beam L to perform scanning; and an optical system that includes an fθ lens for correcting a scanning speed on an exposure surface and a lens having lens optical power along a scanning direction Cylindrical lenses for surface tangle error correction, etc.

In the exposure unit 62, the laser beams L of various colors emitted from the light source section are incident on the modulation processing section, and are modulated based on the image information of the various colors, and then passed through the polyhedron rotated by the polyhedron motor 63 The mirror 67 is used for scanning (main scanning). The laser beams L of the respective colors scanned by the polygon mirror 67 are reflected by the mirror group 69 toward the photoconductor drums 52 corresponding to the respective colors and focused on the respective photoconductor drums 52 .

The photoconductor unit 50 has charging rollers 56 and recovery rollers 54 corresponding to the respective photoconductor drums 52 (in FIG. Each is in rotational contact with the photoconductor drum 52 . The charging roller 56 uniformly charges the photoconductor drum 52 so that the toner scattered from the magnetic roller 80 provided in the developing device 58 adheres to the surface of the photoconductor drum 52 . On the other hand, the recovery roller 54 discharges the photoconductor drum 52 to remove residual toner adhering to the surface of the photoconductor drum 52 , thereby preventing generation of ghost images and the like due to the residual toner on the surface of the photoconductor drum 52 .

A developing device 58 is provided at the bottom right of each photoconductor unit 50 in FIG. 1, and four developing devices 60Y, 60M, 60K, 60C are vertically arranged to correspond to each photoconductor drum 52 (52Y, 52M, 52K, 52C).

On the other hand, an intermediate transfer unit 66 including three drum-shaped intermediate transfer bodies 68 , 70 , 72 is provided on the left side of the light guide unit 50 in FIG. 1 . The two first intermediate transfer bodies 68, 70 are vertically arranged in a straight line, and the upper first intermediate transfer body 68 is kept in rotational contact with the two photoconductor drums 52Y, 52M disposed at the upper position among the photoconductor drums 52, while the lower one The first intermediate transfer body 70 is held in rotational contact with the two photoconductor drums 52K, 52C disposed at the lower position. The second intermediate transfer drum 72 is held in rotational contact with both the first intermediate transfer bodies 68 , 70 , while the aforementioned transfer roller 74 is held in rotational contact with this second intermediate transfer drum 72 .

In this way, the corresponding toner images are transferred from the photoconductor drums 52Y, 52M to the first intermediate transfer body 68 , and from the photoconductor drums 52K, 52C to the first intermediate transfer body 70 . The respective toner images having two colors respectively transferred to the first intermediate transfer body 68, 70 are transferred onto the second intermediate transfer drum 72 to collect four colors, and the four colors are transferred by the transfer roller 74 A toner image of one color is transferred to the paper.

In the vicinity of each of these intermediate transfer bodies 68 , 70 , 72 are provided a cleaning roller 76 and a cleaning brush 78 to scrape off residual toner on the surface of the intermediate transfer bodies 68 , 70 , 72 .

(Schematic configuration of the control system of the entire image forming apparatus)

FIG. 2 is a block diagram of a control system for image formation in the engine section 12. As shown in FIG.

A commercialized power supply (not shown) is connected to the main power control section 200 to generate a low voltage power supply (LVPS) and a high voltage power supply (HVPS), and these supplies power to the respective sections through power lines.

The user interface 204 is connected to the main controller 202 so that the user executes instructions for image formation and the like by operating the interface, and notifies the user of information when the image is formed and the like.

A network cable to an external host (not shown) is connected to the main controller 202 to input image data.

For example, when image data is input, the main controller 202 analyzes the print instruction information contained in the image data and the image data, converts them into a format suitable for the engine 12 (for example, bitmap data), and This image data is sent to the image forming process control section 206 constituting a part of the MCU.

The image forming process control section 206 synchronously controls the optical scanning system control section 208, drive system control section 210, charging device control section 212, developing device control section 214, and fixing control section 216 constituting the MCU based on input image data to perform image formation.

The state control section 218 is connected to the image forming process control section 206 to judge the operating state of the engine section 12 (for example, processing mode ON, sleep mode ON, activation from sleep mode, processing ON, etc.). The operating state determined by the state control section 218 is sent to the main controller 202 .

In order to detect the environment, a temperature sensor 221 and a humidity sensor 222 are connected to the main controller 202 . The temperature sensor 221 and the humidity sensor 222 detect the ambient temperature and humidity within the engine section 12 .

In addition, a density sensor 224 necessary to output image density correction and toner density correction is connected to the main controller 202 . This density sensor 224 is provided such that its detection surface faces the outer peripheral surface of the second intermediate transfer drum 72 . That is, the density sensor 224 is a reflective type that emits a light beam to the transfer roller 74 and detects its reflected light to output an electrical signal corresponding to its density value.

The output image density correction described here is used to determine whether the density of an image printed on paper is finally recorded with the same density as image data. In this process, first, a patch image (intermediate toner image) for output image density detection is formed in a state where paper is not conveyed, and is transferred onto the transfer roller 74 . Next, the density of the patch image on the transfer roller 74 is detected by the density sensor 224 . The detected density data is compared with an output image density target value to correct the amount of light, developing bias, and the like.

On the other hand, the toner density correction described here is used to determine whether the unit supply amount of toner in the developing device 58 is appropriate. In this process, first, a patch image (solid image) for toner density detection is formed in a state where paper is not conveyed, and is transferred to the transfer roller 74 . Next, the density of the patch image on the transfer roller 74 is detected by the density sensor 224 . The detected density data is compared with the toner density target value to correct the toner supply amount per pixel.

This first embodiment focuses on the output image density correction of the above two correction forms in an attempt to optimize the output image density correction.

That is, conventionally, the density data detected by the density sensor 224 is corrected according to the difference between this density of the output image and a fixed target value. However, if the difference is accumulated, comparison with a fixed output image density target value seriously affects image quality.

Then, the fixed output image density target value is corrected based on the accumulated value of the toner supply amount with respect to the accumulated pixel count corresponding to the image data to eliminate the accumulated error.

(Output image density target value correction control system)

FIG. 3 is a block diagram showing an output image density target value correction control system implemented in the main controller 202 . This block diagram divides the processing required for the output image density target value correction control from a functional point of view, but does not limit the hardware structure.

Image data is input to the printing control section 100 of the main controller 202 . The print control section 100 is connected to a user interface 204 . If a print instruction is supplied from the user interface 204, the print control section 100 instructs the image forming process control section 206 to execute printing.

The image forming process control section 206 controls the fixing control section 216, the charging device control section 212, the drive system control section 210, the developing device control section 214, and the optical scanning system control section 208 to execute the printing process as described above (see FIG. 2 ). The toner supply device 102 is connected to the developing device control section 214 to control the amount of toner supplied from the toner cartridge 64 to the developing devices 58 (developing devices 60Y, 60M, 60K, 60C).

The output image density correction execution control section 104 is connected to the image forming process control section 206 . Density data detected by the density sensor 224 is input to the output image density correction execution control section 104 . If an output image density correction patch image is formed at a predetermined timing, the density of the output image density correction patch image (hereinafter referred to as patch density) will be detected by the density sensor 224 .

The execution output image density target value memory 106 is connected to the output image density correction execution control section 104 . In the initial state (for example, when the toner cartridge 64 is replaced), the reference output image density target value is stored from the reference output image density target value memory 110 to This execution is output in the image density target value memory 106 .

The output image density correction execution control section 104 compares the block density detected by the above-mentioned density sensor 224 with an execution output image density target value (hereinafter referred to as an actual target value) read out from the execution output image density target value memory 106 , and A correction instruction signal is fed back to the image forming process control section 206 based on the comparison result thereof to correct the light amount, the developing bias voltage, and the like based on the comparison result thereof. As a result, output image density can be stabilized.

Incidentally, if output image density correction is repeatedly performed over a long period of time, cumulative errors will occur. This accumulated error gradually deviates the image density from an appropriate value, thereby making the density of the output image unstable.

This first embodiment does not necessarily make the actual target value a fixed value to eliminate the accumulated error, but can variably correct the accumulated error.

In this way, the toner supply amount (toner supply amount data) to be supplied to the developing device by the toner supply unit 102 is counted by the toner supply amount counting portion 112, and is counted by the toner supply amount accumulation portion 114 to accumulate the count value. At the same time, image data (pixel data) at the time of image formation by the image formation process control section 206 is counted by the pixel count section 116 , and the count value is accumulated by the pixel count accumulation section 118 . Meanwhile, pixel data is regarded as minimum unit data for determining the amount of toner.

The toner supply amount accumulation data accumulated by the toner supply amount accumulation section 114 and the pixel accumulation data accumulated by the pixel count value accumulation section 118 are input to the variation calculation section 120 .

A measured value temporary memory 122 is connected to the change calculation section 120 . This measured value temporary memory 122 stores the toner supply amount data and pixel accumulation data for the previous three times in addition to the transition period.

The change calculation section 120 calculates a change based on the currently obtained updated toner supply amount accumulation data and pixel accumulation data and the toner supply amount data and pixel accumulation data of the previous three times, and sends the change to the comparison section 124 . The reason for using the toner supply amount cumulative data and the pixel cumulative data for the previous three times is to improve the accuracy of the change to be calculated (to improve the accuracy of the inclined approximate curve), and in the transition period, based on the data before the previous two to calculate the change.

The specified value memory 126 is connected to the comparing section 124 . The specified value memory 126 stores specified values (upper limit value, lower limit value) for comparing the calculated changes. The specified value memory 126 sends the upper limit value and the lower limit value of the specified value corresponding to the current pixel count accumulation data to the comparison section 124 based on the information from the pixel count value accumulation section 118, and compares the calculated change with the upper limit value of the specified value. Each of the limit and lower limit values are compared. As a result, three kinds of comparison results of whether the change exceeds the upper limit value, whether the change is lower than the lower limit value, and whether the change is between the upper limit value and the lower limit value are sent to the output image density target value calculation section 128. value (see Figure 5).

If the result of the comparison is that the change exceeds the upper limit value, the output image density target value calculation section 128 generates actual target value correction data for reducing the image density, while on the other hand, if the change is below the lower limit value, outputs The image density target value calculation section 128 generates actual target value correction data for emphasizing image density, and sends them to the output image density target value correction section 108 .

The output image density target value correction section 108 is connected to the execution output image density target value memory 106 . When the actual target correction data is input, the output image density target value correction section 108 corrects the actual output image density target value stored in the execution output image density target value memory 106 .

The reset section 130 is connected to the image forming process control section 206 . If the image forming process control section 206 recognizes that the toner cartridge 64 has been replaced, it sends a toner cartridge replacement signal to the reset section 130 .

If a toner cartridge replacement signal is input, the reset section 130 sends a reset signal to the pixel count value accumulation section 118, the toner supply amount accumulation section 114, and the measured value temporary memory 122, and stores the reset signal in each of these sections. The data in is reset. In addition, the reset section 130 sends a reset signal to the output image density target value correction section 108 . When receiving this reset signal, the output image density target value correction section 108 reads out the reference output image density target value stored in the reference output image density target value memory 110 and stores it in the execution output image density target value memory 106 middle.

That is, when the toner cartridge 64 is replaced, all data related to the correction of the actual target value is cleared (reset) to return the state to the initial state.

The operation of the first embodiment will be described below.

(Flow of image forming process)

Image forming (printing) processing for each color by a known electrophotography method is performed around each photoconductor drum 52 as follows.

First, each photoconductor drum 52 is driven at a predetermined rotational speed.

Then, the surface of the photoconductor drum 52 is uniformly charged to a predetermined level by applying a direct current having a predetermined charging level (for example, about −800 V) to the charging roller 56 . Although according to the first embodiment, only a direct current is applied to the charging roller 56, this embodiment may also be configured so that an alternating current component is superimposed on a direct current component.

Next, the surfaces of the respective photoconductor drums 52 having a uniform surface potential are irradiated with laser beams L corresponding to the respective colors by the exposure unit 62 to form electrostatic latent images corresponding to the image information of the respective colors. As a result, the surface potential at the portion of the photoconductor drum 52 exposed to the laser beam L is removed to a predetermined level.

The electrostatic latent images formed on the surfaces of the respective photoconductor drums 52 are developed by respective corresponding developing devices 58 so that toner images of respective colors are visible on the respective photoconductor drums 52 .

Next, the toner images of the respective colors formed on the respective photoconductor drums 52 are statically primary-transferred onto the corresponding first intermediate transfer drums 68 , 70 . As a result, the Y color and M color toner images formed on the photoconductor drums 52Y, 52M are transferred to the first intermediate transfer drum 68, while the K color and C color toner images formed on the photoconductor drums 52K, 52C The toner image is transferred onto the first intermediate transfer drum 70 .

Thereafter, the toner images formed on the first intermediate transfer drums 68 , 70 are statically secondarily transferred onto the second intermediate transfer drum 72 . As a result, a toner image including a monochrome image and images of four colors Y, M, K, C superimposed is formed on the second intermediate transfer drum 72 .

Finally, the toner image formed on the second intermediate transfer drum 72 is thirdly transferred by the transfer roller 74 onto the paper passing through the paper conveyance path. After the third transfer, the toner image formed on the paper is heated and fixed by the fixing unit 32, and then the image forming process ends.

(Output image density correction control)

Although in theory, since the image recorded on the paper is developed based on the image data with a specified toner supply to the developing device 58 and a predetermined developing bias, an appropriate output image density can always be maintained, in practice On the other hand, the output image density varies depending on the ambient temperature, deterioration of each component over time, error in toner supply amount, change in developing bias voltage, etc.

In this way, in order to periodically correct the output image density, an output image density correction patch image is formed, transferred to the transfer roller 74 and detected by the density sensor 224 . The detection result is compared with a predetermined target value (actual target value) to correct the amount of light and the developing bias.

Basically, stable output image density can be obtained by this output image density correction control.

(Output image density target value correction)

However, if the output image density correction is continued for a long time, cumulative errors occur, so that an appropriate image density cannot be obtained. Thus, according to this first embodiment, every time the pixel count accumulation data reaches a predetermined value, it is determined whether the toner supply amount accumulation value maintains its specified value (within the range from the upper limit value to the lower limit value), if If it deviates from the specified value, the actual target value is corrected.

The flow of the above-described correction control of the actual target value will be described below with reference to the flowchart shown in FIG. 4 . Incidentally, the flowchart of Fig. 4 starts at the end of each task.

It is determined at step 150 whether the pixel count accumulation data exceeds a predetermined value, and in the case of a negative judgment, the process is ended. If an affirmative judgment is made at step 150 , the current time is determined as the actual target value correction timing, and the process proceeds to step 152 .

At step 152, the current (updated) toner supply amount accumulation data and pixel accumulation data are read out, and at step 154, the toner supply amounts for the previous three times (three times before, two times before, and the latest time) are read out The data is accumulated and the data is accumulated by pixels, after which the process proceeds to step 156 .

In step 156, the change (slope) is calculated based on the read-out current toner supply-amount cumulative data, the read-out current pixel cumulative data, and the previous three toner supply-quantity cumulative data, the previous three-time pixel cumulative data .

In the next step 158, the calculated change (hereinafter referred to as change calculation value) is compared with a specified value (upper limit value). If it is determined at this step 158 that the variation calculation value is larger than the upper limit value, it is determined that the output image density is higher than the desired density, and the process proceeds to step 160 . Actual target value correction data is then generated to reduce the image density, and the process proceeds to step 166 .

If it is determined at step 158 that the calculated variation value is less than or equal to the upper limit value, the process proceeds to step 162 where the calculated variation value is compared with a specified value (lower limit value).

If it is determined at step 162 that the variation calculation value is smaller than the lower limit value, it is determined that the output image density is lower than the desired density, and the process proceeds to step 164, at which actual target value correction data for raising the image density is generated, and then the process proceeds to Go to step 166.

If it is determined at step 162 that the change calculation value is greater than or equal to the lower limit value, it is determined that the output image density remains the desired density, and the process proceeds to step 168 .

At step 166 , the actual target value is corrected based on the generated actual target value correction data, and the process proceeds to step 168 . By correcting this actual target value, an optimum output image density can be obtained without any physical adjustment (for example, adjustment of developing bias voltage or adjustment of light amount).

In step 168, the accumulated toner supply amount data and the accumulated pixel data for the previous three times are updated. That is, the data three times before is deleted, the data two times ago is used as the new data three times before; the latest data is used as the data two times before, and the updated data is used as the latest data, and then the process ends.

FIG. 5 is for explaining an example of actual target value correction of the first embodiment.

When the specified amount of accumulated image dots is exceeded after the toner cartridge is replaced, the accumulated image dot amount 1 and the accumulated toner supply amount 1 at that time are stored (see (1)").

When the next specified amount of cumulative image dots is exceeded, store the latest cumulative image dot amount 1 and the latest cumulative toner supply amount 1 as cumulative image dot amount 2 and cumulative toner supply amount 2, and then store the The cumulative image dot amount and the cumulative toner supply amount of (see (2)) are taken as the cumulative image dot amount 1 and the cumulative toner supply amount 1 .

In addition, when the next specified amount of accumulated image dots is exceeded, the accumulated image dot amount 2 and the accumulated toner supply amount 2 two times before are stored as the accumulated image dot amount 3 and the accumulated toner supply amount 3 . Likewise, the latest cumulative image dot amount 1 and cumulative toner supply amount 1 are stored as cumulative image dot amount 2 and cumulative toner supply amount 2, and the cumulative image dot amount and cumulative toner supply amount at that time are stored amount (see (3)) as the accumulated image dot amount 1 and the accumulated toner supply amount 1.

Because of data of three times or more (see (1) and (3)), these three values are used to calculate an approximate expression of the slope of the accumulated image dot amount and the accumulated toner supply amount according to the least square method. The slope A based on this approximate expression is combined with the slope k1 (which is the upper limit value of the slope of the cumulative image dot amount and the cumulative toner supply amount set in advance) and the slope k2 (which is the cumulative image dot amount and the cumulative toner supply amount). the lower limit value of the agent supply amount), and if the slope A is larger than the slope k1, the target value of the output image density is corrected to be lower, and if the slope A is smaller than the slope k2, the target value of the output image density is corrected to be higher.

When the target value of the output image density is corrected to be lower, toner consumption is suppressed so that the cumulative toner supply amount relative to the cumulative image dot amount excessively increases. As a result, the toner density of the device increases. Since the device suppresses the toner supply amount to correct the toner density, the accumulated toner supply amount is suppressed.

Conversely, because if the target value is corrected to be high, toner consumption is accelerated and the cumulative toner supply amount with respect to the cumulative image dot amount excessively decreases, so the toner density of the device is lowered. To correct this, the device accelerates the supply of toner so that the cumulative toner supply amount increases.

Also, when the next specified amount of accumulated image dots is exceeded, the accumulated image dot amount 3 and the accumulated toner supply amount 3 three times before are stored as the accumulated image dot amount 4 and the accumulated toner supply amount 4 (see <1 >), store the accumulated image dot amount 2 and the accumulated toner supply amount 2 twice before as the accumulated image dot amount 3 and the accumulated toner supply amount 3 (see <2>), store the latest accumulated image dot amount 1 and cumulative toner supply amount 1 as cumulative image dot amount 2 and cumulative toner supply amount 2 (see <3>), and store the update value as cumulative image dot amount 1 and cumulative toner supply amount 1 (see <4>).

An approximate expression of the slope of the accumulated image dot amount and the accumulated toner supply amount is calculated using these four values (see <1>-<4>) according to the least square method. If, as a result of comparing the slope A of this approximate expression with the above k1 and k2, the slope A is larger than the slope k1, the target value of the output image density is corrected to be lower, while if the slope A is smaller than the slope k2, the output image density The target value of is corrected to be higher.

By updating the value with the next specified amount of accumulated image points and correcting the output image density using the four points updated in this way, the slope A is changed such that the slope A becomes smaller than the slope k1 and larger than the slope k2. As a result, image density can be controlled within a specified range.

According to the first embodiment described above, the method for correcting the density of the output image is performed by periodically forming a patch image for output image density correction and detecting the density of the patch image by the density sensor 224 to compare the detected value with a preset target value. The light amount and developing bias are corrected for output image density correction. On this premise, the change in the toner supply amount integrated value relative to the pixel integrated data is calculated, and it is determined whether the change maintains its predetermined value (within the range from the upper limit value to the lower limit value). If the change exceeds the upper limit value, the actual target value is corrected to lower the output image density, and if the change is lower than the lower limit value, the actual target value is corrected to increase the output image density. As a result, an appropriate output image density can be maintained for a long time.

(modified example)

Although the first embodiment has been described in a state where the toner supply amount accumulation data and the pixel accumulation data of the previous three times are stored, naturally, the transition period sometimes has less previous data (data of two times or less) ). In this case, although it is allowed not to perform the target value correction until the data of the first three times are collected, it is also allowed to calculate the change from the data of the first two times, for example.

Also, in the first embodiment, although the correction data for the target value is generated based on the change, only the toner supply amount can be corrected by comparing it with specified values (upper and lower limit values). Accumulated data (absolute quantity) is corrected (similar to ON/OFF control), as shown in Figure 6.

Fig. 6 shows the first embodiment, in which the axis of abscissas represents the accumulated image dot amount, and the axis of ordinates represents the accumulated toner supply amount. Two dashed lines indicate the upper limit value and the lower limit value of the cumulative toner supply amount at the cumulative image dot amount at that time. If the actual cumulative toner supply exceeds the upper limit value, it indicates that the output image density is too high, and conversely, if the actual cumulative toner supply amount is lower than the lower limit value, it indicates that the output image density is too low.

According to the first embodiment, the cumulative toner supply amount at the actual cumulative image dot amount is compared with its upper limit value and lower limit value at a predetermined timing, and if the actual cumulative toner supply amount is higher than the upper limit value, then The output image density target value is corrected in the direction of decreasing the output image density, and conversely, if the actual accumulated toner supply amount is lower than the lower limit value, the output image density target value is corrected in the direction of increasing the output image density. Correction.

Since the cumulative toner supply amount is higher than the upper limit value at the predetermined timing in FIG. 6 (see circled "1" in FIG. 6 ), correction is performed in a direction to lower the output image density target value. Next, since the cumulative toner supply amount is between the upper limit value and the lower limit value at predetermined timing (see circled "2" in FIG. 6 ), the output image density target value is not corrected. Next, since the accumulated toner supply amount is lower than the lower limit value at predetermined timing (see circled "3" in FIG. 6 ), correction is performed in a direction of increasing the output image density target value. In addition, since the cumulative toner supply amount is within the target range again at predetermined timing (see circled "4" in FIG. 6 ), the output image density target value is not corrected.

In this way, the accumulated toner supply amount is compared with the upper limit value and the lower limit value every time at predetermined timing to determine the necessity of correction of the output image density target value.

In this case, although the accuracy of the correction of the actual target value is reduced, the control system is simplified, so the conditions are optimal for simply correcting the actual target value (for example, in cheap and where no Accurate image quality of the machine type, etc.).

[example]

For example, a predetermined amount of pixels is assumed to be 1 as the accumulated image dot amount. More specifically, a value for providing five image dots on A4-sized paper at a print density of about 1% is used.

Therefore, if a toner cartridge capable of printing 8,000 sheets (printing an image on A4-sized paper at a printing density of 5%) is used, the cumulative image dot amount is 5×5×8,000=200,000 dots.

For example, if the specified cumulative image dot amount is set to 12500, the toner supply amount cumulative value is updated every time the cumulative image dot amount increases by 12500 to 12500, 25000, and 37500. Although the interval of the cumulative image dot amount is set to be constant, the interval does not always have to be constant, but may be shortened immediately after the use of the toner cartridge is started, and may be lengthened just before the end of use of the toner cartridge.

The toner cartridge discharges the toner from the toner discharge port of the toner cartridge into the developing device by driving a coil auger (in which each color is independently set) provided with a dispensing motor inside .

The toner supply amount is measured by the above-mentioned dispensing frequency. When the dispensing motor rotates for 0.5 seconds, the dispensing frequency is counted as one such that about 1800 counts are required to supply all the toner in the toner cartridge.

The distribution frequency is monitored as the cumulative toner supply amount instead of the cumulative image dot interval of 12500, and every time the distribution frequency exceeds 100 times, the cumulative image dot amount is updated.

Although the interval of the cumulative toner supply amount is set to be constant, the interval does not always have to be constant, but may be shortened, for example, immediately after the use of the toner cartridge is started, and may be lengthened just before the end of use.

According to the first example, the cumulative amount of printed sheets set in the memory is counted every time one sheet is printed. In addition, according to the first example, the accumulated image dot amount and the accumulated toner supply amount are updated every time the accumulated printed sheet amount exceeds 500, instead of the accumulated image dot interval of 12500 in Example 2.

Although the interval of the cumulative printed sheet amount is set to be constant, the interval does not always have to be constant, but may be shortened immediately after the use of the toner cartridge is started, and may be lengthened just before the use of the toner cartridge is ended.

This device has a mechanism for resetting the correction of the target value of the output image density when the toner cartridge is replaced.

In this image forming apparatus, a value of 1.3 is stored at address A on the memory as an initial value of the target value for the output image density of yellow. According to Example 4, if the target value of the output image density is lowered by 0.05 by correction based on the relationship between the cumulative image dot amount and the cumulative toner supply amount when the cumulative printed sheet volume exceeds 1500, the address B on the memory Store -0.05 as the correction value. The target value of the output image density after 1500 sheets becomes 1.25 by summing the values at address A and address B.

The value at address B on the memory is updated every 500 sheets, and if it is assumed that the correction value of address B on the memory is -0.15 when the toner in the toner cartridge is exhausted, the target value of the image density is output is 1.15.

If the toner cartridge is replaced with a new one, the image forming apparatus detects that the toner cartridge is new from information in a memory provided in the toner cartridge. If it is detected that the toner cartridge has been replaced, the image forming apparatus resets the value at address B on the memory to 0. In this way, when the toner cartridge is replaced with a new one, the target value of the output image density is returned to the initial value of 1.3.

Although the address B is set on the memory of the image forming apparatus, the address B may also be set on the memory of the toner cartridge. Since the correction value is set in conjunction with the toner cartridge, even if a partially used toner cartridge is reused, since the correction value at the last time the toner cartridge was used is recorded, it can continue to be used based on the correction value. toner cartridge.

The image density target value is corrected when the cumulative toner supply amount at a predetermined cumulative image dot amount exceeds the standard value or falls below the standard value for three consecutive times.

If the cumulative toner supply amount exceeds the preset standard value three consecutive times at predetermined timing, correction is made to lower the image density target value. Conversely, if it falls below the standard value for three consecutive times, correction is made to increase the image density target value. In any state where the standard value is not exceeded or dropped below the standard value three times in a row, for example in the case of above-below-above, no correction is made.

[Second embodiment]

A second embodiment of the second aspect of the present invention will be described below.

In the second embodiment, the same reference numerals are used to denote the same constituent parts as in the first embodiment, and descriptions of their structures are omitted.

The second embodiment is characterized by the dedicated target value correction in the image forming apparatus 10 of the first embodiment during the transition period of apparatus operation from factory shipment to image forming process for several hundred sheets. That is, this correction period is a period that does not overlap with the target value correction period of the first embodiment.

FIG. 11 is a block diagram showing the actual target value correction control implemented by the main controller 202 during the device transition period. Incidentally, although the main controller 202 executes the actual target value correction control for the regular period shown in the first embodiment, FIG. 11 omits this part. Also, similar to Fig. 3, this block diagram does not specify any hardware.

The main controller 202 is provided with a target value correction execution mode determination section 300 that determines whether the current time is a device operation transition period or a regular period based on information such as an image formation process history from the image formation process control section 206 .

If the target value correction execution mode determination section 300 determines that the current time is a regular period, normal mode control is executed (first embodiment). In this case, the device operation transition period control program and the normal period control program may be stored in advance, and selectively read and executed. Alternatively, each control system may be constituted by hardware and any control system may be activated.

The image density control condition reading section 302 is connected to the target value correction execution mode determination section 300 . If a signal indicating the transition period mode is input to this image density control condition reading section 302 from the target value correction execution mode determination section 300 , the image density control condition reading section 302 reads out the determined output image density correction execution control section 104 The image density control condition and send it to the comparing section 304.

The standard image density control condition reading section 306 is connected to the image density control condition reading section 302 . When the determined image density control condition is read out by the image density control condition reading section 302 , a read synchronization signal is synchronously input from the image density control condition reading section 302 to the standard image density control condition reading section 306 .

The standard image density control condition reading section 306 reads out humidity data from the humidity sensor 222 based on the read synchronous signal, and reads out from the humidity standard output image density control condition characteristic map 308 (see FIG. 12 ) based on the read out humidity data. The standard output image density control condition corresponding to this humidity is calculated and sent to the comparing section 304.

If the difference between the determined image density control condition and the standard output image density control condition is larger than a predetermined value (outside the range independently set on the plus side (α) and the minus side (β)), the comparison section 304 compares the difference to The information is sent to the output image density target value correction section (transition period) 310 to correct the output image density target value.

Since the output image density target value correcting section (transition period) 310 has the same function as the output image density target value correcting section 108 (see FIG. 3 ) of the first embodiment, it is possible to share the output image density target value correcting section ( transition period) 310.

The output image density target value correction section (transition period) 310 sets an output image density target value corresponding to the difference information, and stores updated correction information in the execution output image density target value memory 106 .

As a result, output image density correction by the output image density correction execution control section 104 is performed based on the updated target value.

The operation of the second embodiment will be described below with reference to the flowchart in FIG. 13 .

It is determined in step 350 whether the output of the image forming process by the apparatus is below a predetermined value and whether the pixel count accumulation value is below a predetermined value, and if a negative judgment is made, the current time is determined to be regular time, and the process ends.

If an affirmative judgment is made at step 350 , the current time is determined to be the device operation transition period, and the process proceeds to step 352 .

The determined image density control condition DTMN determined by the output image density correction execution control section 104 is read out at step 352 . More specifically, it is a developing bias corrected by feedback by detecting a patch image.

In the next step 354, the humidity data detected by the humidity sensor 222 is received, and the process proceeds to step 356, in which the data corresponding to The received humidity data corresponds to the development bias, and the process then proceeds to step 358 .

In step 358, the determined image density control condition DTMN and the standard output image density control condition STND are compared with each other. If DTMN>STND+α, since the possibility of image density enhancement is high, the process proceeds to step 360 where the output image density target value is executed in the direction of lowering the image density (lowering the developing bias voltage). renew.

On the other hand, if it is determined at step 358 that DTMN≦STND+α, the process proceeds to step 362 where the determined image density control condition DTMN and the standard output image density control condition STND are compared with each other again. If it is determined in this step 362 that DTMN<STND+β, since the possibility of image density decrease is high, the process proceeds to step 364, where the output image density target value is executed in the direction of emphasizing the image density. renew.

If it is determined at step 362 that DTMN≥STND+β, the process is terminated without updating the target value because the image density is appropriate.

According to the second embodiment, as described above, during the device operation transition period in which the relationship between the image and the toner consumption amount cannot be obtained yet, on the premise that the toner cartridge is new and the toner density is known A standard output image density condition (here, developing bias) based on an environmental condition (here, humidity) is stored, and an image density output condition (developing bias) determined based on the standard output image density condition and an image density determined by actually reading a patch image is stored. The difference between to update the target value.

As a result, the target value can converge to a stable value in a relatively short time, thereby enabling high-precision image density correction immediately after starting the regular period.

Correcting the target value every time the output image density correction is performed during the transition period of the device operation prevents the dispersion of the patch image from being easily affected when the toner charge state is unstable (especially after the device is installed), And make the image density close to the target value.

In addition, using humidity as an environmental condition makes it possible to compensate for the influence of the toner whose charge state changes according to the humidity.

Although the second embodiment automatically performs the target value correction whenever the output image density correction is performed during the device operation transition period, this may also be performed manually according to an operator's instruction from the user interface 204 . As a result, if automatic correction is insufficient, target value correction can be quickly performed according to the operator's judgment.

Furthermore, although the second embodiment automatically executes the target value correction whenever the output image density correction is executed during the transient period of device operation, if the target value is updated, the execution interval of the output image density correction may also be changed, or according to the updated Change the execution interval of output image density correction by the degree.

[Third embodiment]

A third embodiment of the present invention will be described below. This third embodiment is a combination of the first aspect and the second aspect of the present invention, wherein in a single device, as shown in FIG. affirmative judgment in 400), and when the transitional period ends and the regular period begins (affirmative judgment in step 404), regular period target value correction control is executed (step 406).

As a result, stable output image density correction is enabled in all cases from the transitional period immediately after shipment of a single image forming apparatus to the regular period, leading to improvement in image quality.

Although the toner cartridge 64 is not described in detail in the first to third embodiments, the toner cartridge 64 can be formed not only by a structure filled with developer only but also by integrating other image forming function members such as , The structure of the photoconductor drum) is applied to the present invention.

The above-described embodiments are just examples, and it should be understood that the present invention can be modified in various ways within the scope of the present invention.

In the first aspect of the present invention, the target value correction by the target value correction section may be performed every time the pixel count accumulation value stored in the pixel count value accumulation memory section exceeds a predetermined value.

Since the output image density target value can be corrected at predetermined pixel count intervals, the toner consumption can be corrected at equal intervals, so that efficient and accurate correction can be expected.

In the first aspect of the present invention, the target value correction by the target value correcting section may be performed every time the toner supply amount accumulated value stored in the toner supply amount accumulated memory section exceeds a predetermined value.

Since the output image density target value can be corrected at predetermined toner supply intervals, the correction interval can be realized by a simpler method.

In the first aspect of the present invention, it may further include a cumulative printing paper volume memory section storing a cumulative printing paper volume, wherein the execution by the object may be performed every time the cumulative printing paper volume stored in the cumulative printing paper volume memory section exceeds a predetermined value. Target value correction performed in the Value Correction section.

Since the output image density target value can be corrected at predetermined printing paper volume intervals, the correction interval can be set most easily. In addition, since the amount of printing paper when correction is to be performed is clear, the effect of correction can be easily verified.

Also, in the first aspect of the invention, the toner cartridge can be loaded on the developing device or the image forming apparatus main body, and the data corrected by the target value correcting portion can be reset by exchanging the toner cartridge.

Since the correction performed so far can be reset by exchanging the toner cartridge, optimum correction can be performed for the toner cartridge even if the development characteristics differ greatly between toner cartridges.

Also, in the first aspect of the present invention, the change may be calculated based on the pixel count accumulation value stored in the pixel count value accumulation memory section and the toner supply amount stored in the toner supply amount accumulation memory section; The change is compared with a change in the cumulative value of the toner supply amount at a preset pixel count cumulative value; and when the comparison result deviates by more than a certain value, the target value correcting section is in the direction of suppressing the deviated state Correct the target value.

Since the change (slope) of the toner supply amount integrated value with respect to the pixel count integrated value can be adjusted to a predetermined change, the output image density can be adjusted to a target value, and at the same time, the occurrence of the following problems can be suppressed, That is, the service life of the toner cartridge cannot be reached due to the high output image density. Another feature is that it is possible to easily construct a system that is highly resistant to dispersion of the accumulated value of the toner supply amount.

Also, in the first aspect of the present invention, an upper limit value and a lower limit value may be set in advance for the toner supply amount cumulative value at the pixel count cumulative value; and when the toner supply amount at the pixel count cumulative value When the supply amount integrated value is outside the upper limit value and the lower limit value, the target value correction section corrects the target value in such a direction that the toner supply amount integrated value falls within the range specified by the upper limit value and the lower limit value .

Since the output image density is corrected by comparing the toner supply amount integrated value at a predetermined pixel count integrated value with its upper limit value and lower limit value, complicated calculations and processes for calculating the change (slope) Much memory consumption becomes unnecessary. Another feature is that since correction can be performed from the first pixel point, an immediate effective system can be easily constructed.

In addition, in the first aspect of the present invention, a specified value may be set in advance for the toner supply amount integrated value at the pixel count integrated value; and when the toner supply amount integrated value at the pixel count integrated value continues The target value correcting section corrects the target value in a direction in which the accumulated value of the toner supply amount approaches the specified value when the number of times the ground deviates from the specified value exceeds a predetermined number of times.

Because the integrated value of the toner supply amount at the predetermined pixel count integrated value is compared with its standard value, and the output image density is corrected when the actual toner supply amount integrated value continuously exceeds or falls below the predetermined value a predetermined number of times, It is therefore possible to prevent correction deviation due to dispersion of the integrated value of the toner supply amount.

Also, in the first aspect of the present invention, when the detected density of the patch image deviates from the target value by more than a certain value, the target value correction by the target value correcting section may be prohibited.

In addition, in the first aspect of the present invention, a driving torque measuring portion that measures a driving torque of a toner supply portion for supplying toner to the developing device may be further included, wherein when the driving torque measured by the driving torque measuring portion When the driving torque of the toner supplying portion deviates from a preset reference torque by more than a certain value, the target value correction by the target value correcting portion may be prohibited.

Since the target density correction is not performed in the case where the measured patch density deviates from the target value by more than a certain value or the driving torque of the toner supply device deviates from its reference torque by more than a certain value, the actual toner supply rate due to In the case of a change due to an error in the device, a deviation of the toner, etc., the target density correction is not performed, thereby preventing occurrences due to performing correction to decrease the density even if the actual density is low or conversely performing increase the density even if the actual density is high. Defects caused by the correction.

In the second aspect of the present invention, the target value correction by the target value correction section may be performed every time the output image density control condition is determined by the output image density control section in the apparatus operation transition period.

Since the environmental conditions vary greatly during the transition period of device operation, it is preferable to perform the target value correction every time the output image density control condition is determined by the output image density control section.

Also, in the second aspect of the present invention, the device operation transition period may be a period in which an integrated value of image pixel amounts at the time of image formation is lower than a predetermined value.

The device operation transition period is specified as a period in which an integrated value obtained by accumulating image pixel amounts at the time of image formation is lower than the predetermined value.

Also, in the second aspect of the present invention, the device operation transition period may be a period in which the integrated value of the toner quantitatively supplied to the developing device is lower than a predetermined value.

The device operation transition period is specified as a period in which an integrated value obtained by accumulating the amount of toner quantitatively supplied to the developing device is smaller than the predetermined value.

In addition, in the second aspect of the present invention, when the target value is corrected, the operation time for determining the output image density control condition by the output image density control section can be shortened.

The existence of the target value correction means that the environment changes greatly, and with the environment change, the operation time for determining the output image density control condition by the output image density control section is shortened.

As described above, the first aspect of the present invention has an excellent effect that, especially when correcting the density of a patch image for output image density adjustment by comparison with a target value, despite the scattering of the patch image and the developer , photoconductor, intermediate transfer members, etc., can also accurately stabilize the output image density for a long time.

The second aspect of the present invention can correct the target value according to the environmental conditions especially in the device operation transition period in which the first aspect of the present invention is ineffective, thereby stabilizing the output image density.

The third aspect of the present invention enables stable correction of the target value throughout the operation of the device, thereby stabilizing the output image density from the initial period of device operation.

Claims (11)

1. An image forming apparatus having an image forming engine that forms an electrostatic latent image by uniformly charging the surface of an image carrier and irradiating a light beam to the uniformly charged image carrier in correspondence with image data , developing the electrostatic latent image with a toner by a developing device, transferring the toner image to a recording medium directly or through an intermediate transfer body, and fixing the transferred toner image to form an image , the image forming device includes: an output image density control section that forms a patch image for output image density correction, and determines an output image density control condition based on a comparison result of the density of the patch image with a preset target value; a pixel counting section capable of counting the amount of image pixels when the image is formed; a pixel count value accumulating memory section which accumulates and stores pixel count values obtained by counting by said pixel counting section; a toner supply portion capable of quantitatively supplying toner to the developing device; a toner supply amount measuring section capable of measuring an amount of toner supplied to the developing device by the toner supply section; a toner supply amount accumulation memory section that integrates and stores the toner supply amount measured by the toner supply amount measurement section; and a target value correcting section that corrects the pixel count accumulation value stored in the pixel count accumulation memory section and the toner supply amount accumulation value stored in the toner supply amount accumulation memory section. The target value of the density of the block image is corrected. 2. The image forming apparatus according to claim 1, wherein the target value correction by the target value correction section is performed every time the pixel count accumulation value stored in the pixel count value accumulation memory section exceeds a predetermined value . 3. The image forming apparatus according to claim 1, wherein said target value correcting portion is executed every time a toner supply amount accumulated value stored in said toner supply amount accumulated memory portion exceeds a predetermined value. Target value correction performed. 4. The image forming apparatus according to claim 1, further comprising a cumulative printing paper volume memory section for storing a cumulative printing paper volume, wherein whenever the cumulative printing paper volume stored in said cumulative printing paper volume memory section exceeds Target value correction by the target value correcting section is performed at a predetermined value. 5. The image forming apparatus according to claim 1, further comprising a toner cartridge loaded on the developing device or the image forming apparatus main body, wherein the toner cartridge passes through the toner cartridge by replacing the toner cartridge. The above-mentioned target value correction part resets the corrected data. 6. The image forming apparatus according to claim 1, wherein based on the pixel count accumulation value stored in the pixel count value accumulation memory section and the toner supply amount accumulation memory section stored in the toner supply amount accumulation memory section The change is calculated from the supply amount; the change is compared with the change in the cumulative value of the toner supply amount at a preset pixel count cumulative value; and when the comparison result deviates by more than a certain value, the target value correcting section The target value is corrected in a direction that suppresses the deviation from the state. 7. The image forming apparatus according to claim 1, wherein an upper limit value and a lower limit value are set in advance for the toner supply amount cumulative value at the pixel count cumulative value; and when the pixel count cumulative value When the integrated value of the toner supply amount at is outside the upper limit value and the lower limit value, the target value correcting section makes the integrated value of the toner supply amount lie between the upper limit value and the lower limit value. The target value is corrected for directions within the range specified by the value. 8. The image forming apparatus according to claim 1, wherein a specified value is set in advance for the toner supply amount cumulative value at the pixel count cumulative value; and when the toner supply amount at the pixel count cumulative value The target value correcting section corrects the target value in a direction to bring the toner supply integrated value closer to the specified value when the supply amount integrated value continuously deviates from the specified value more than a predetermined number of times. 9. The image forming apparatus according to claim 1, wherein the target value correction section is prohibited from performing target value correction when the detected density of the patch image deviates from the target value by more than a certain value. 10. The image forming apparatus according to claim 1, further comprising a driving torque measuring portion that measures a driving torque of a toner supply portion for supplying toner to said developing device, wherein when measured by the driving torque When the partially measured driving torque of the toner supply portion deviates from a preset reference torque by more than a certain value, the target value correction portion is prohibited from performing target value correction. 11. An output image density correction method, in an image forming apparatus, the method being executed at a predetermined timing during the entire operation of the apparatus to form a block image for output image density correction, and The image forming apparatus has an image forming engine that uniformly charges the surface of the image carrier by uniformly charging the surface corresponding to the image data to determine the output image density control condition. The image carrier irradiates a light beam to form an electrostatic latent image, develops the electrostatic latent image with a toner by a developing device, transfers the toner image to a recording medium directly or through an intermediate transfer body, and converts the transferred image to a recording medium. A printed toner image is fixed to form an image, the method comprising: Obtaining a difference between an environmental condition at the time of determining said output image density control condition and a standard output image density control condition in the case where the toner density is known at a preset device operation transition period, and based on the difference to said target value is corrected; and accumulating the image pixel amount at the time of image formation in periods other than the device operation transition period, accumulating the toner supply amount supplied to the developing device, and based on the integrated value of the pixel amount and the toner supply The relationship between the integrated values of the amounts corrects the target value of the density of the patch image.

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