JP3071853B2 - Toner supply control method and image forming apparatus using the method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer for visualizing a latent image formed by an electrophotographic method as a toner image. It is.

[0002]

2. Description of the Related Art In an image forming apparatus of this type, for example, an apparatus using a two-component developer, toner consumption is reduced in order to maintain a constant toner density of a developer in a developing device in order to obtain a desired image density. Accordingly, it is necessary to supply toner to the developing device. For this reason, in an image forming apparatus that forms an image based on image data, it is assumed that a proportional relationship is established between the total number of dots of the image and the toner consumption. Is known, and a toner corresponding to the toner consumption amount obtained by the calculation is supplied to the developing device (for example, Japanese Patent Application Laid-Open No. 60-256168).
JP, JP-A-62-109078, JP-A-62-109078
-116973, JP-A-1-108070). When replenishing the developing device with toner corresponding to the toner consumption, the toner is replenished from the replenishment toner storage unit to the developing device. For example, the rotational driving time of the replenishment roller is controlled in accordance with the toner consumption. .

[0003]

However, if the remaining amount of the toner for replenishment in the toner container such as the hopper decreases due to the continuation of the copying operation, the driving of the toner replenishing mechanism is the same as when the remaining amount is sufficiently large. Under the conditions, for example, the rotational driving time of the supply roller, the amount of toner supplied from the toner storage unit to the developing device (hereinafter, referred to as toner supply amount) decreases. For example, FIG. 18 shows the relationship between the remaining amount in the toner hopper and the toner supply amount by plotting the toner supply amount per 30 seconds of rotation of the supply roller on the vertical axis and the toner remaining amount in the toner hopper on the horizontal axis. It is shown. In the area A in the figure, a linear relationship is established between the toner supply amount and the rotation time of the supply roller, and a stable toner supply of 300 mg / sec is performed. In the reduced area B, this relationship is broken and the toner supply amount is rapidly reduced due to the decrease in the remaining amount of toner. Accordingly, in the case where the drive of the toner supply mechanism is controlled based on the toner supply amount per unit time in the area A even though the remaining amount of toner in the toner hopper is reduced as in the area B, However, there still remains a problem that the toner density in the developing device is reduced due to insufficient toner supply, and the image density is reduced. or,
Such a toner container itself is constituted by, for example, a toner cartridge which can be attached to and detached from the apparatus main body. When the remaining amount of toner is exhausted, an empty toner cartridge is taken out and discarded, and an image in which a new toner cartridge is mounted is mounted. In the forming apparatus, a detection result of a toner density by a toner density sensor or the like in a developing device is used in order to omit an element for detecting presence or absence of a remaining amount of toner in a toner cartridge. That is, when the toner density in the developing device is reduced to the predetermined toner density by the detection of the toner density, the toner replenishing operation is performed for a predetermined time or a predetermined number of times. If the density does not rise above the predetermined density, it is determined that the toner in the toner cartridge has run out. In the case where the presence / absence of the remaining amount of toner in the toner cartridge is detected as described above, even though the remaining amount of toner in the toner cartridge has decreased as in the above-described area B, the area A
Assuming the toner supply amount per unit time in,
When performing the toner replenishment operation and determining whether or not the final replenishment toner is present, it is determined that the replenishment toner does not remain when the replenishment toner remains, and an instruction to replace the toner cartridge is issued. However, there is still a problem that the toner cartridge with the replenishment toner remaining may be discarded. Incidentally, the above-mentioned JP-A-62
Japanese Patent Application Laid-Open No. 1-169733 discloses that when the toner concentration detected by a toner concentration detecting means disposed in a developing device falls within a predetermined range, the amount of toner consumption is calculated based on image data, and the calculated value is obtained. When the detected toner density is lower than the predetermined range, the toner is replenished for a predetermined number of times in the replenishment time when the detected toner density is lower than the predetermined range. It is described that when the toner density does not return to the predetermined range even after the number of executions, the toner absence display (toner near end display) is performed. In this case, since there is only one threshold level, when the threshold level is set to a relatively low toner density, the toner replenishment amount cannot be increased until the toner density becomes considerably low. However, when the threshold level is set to a relatively high toner concentration, there still remains a problem that the toner supply amount is increased only by slightly lowering the toner concentration, and the toner concentration becomes higher than the proper toner concentration. Was.

The present invention has been made in view of the above problems, and an object of the present invention is to appropriately control the toner supply amount even when the remaining amount of the supply toner in the toner storage unit becomes small. Accordingly, it is possible to prevent the image density from being lowered due to the shortage of the toner replenishing amount, and to configure the toner container with a container that can be attached to and detached from the apparatus main body, and replace the container based on the toner concentration detection result in the developing device. An object of the present invention is to provide a toner supply control method capable of using up the supply toner in the container even when the instruction is given, and an image forming apparatus using the method.

[0005]

In order to achieve the above object, the present invention calculates a total area of a toner adhering area on a photoreceptor using image data in an image area, and calculates a total area according to the total area. A first supply mode in which a predetermined amount of toner can be supplied to the developing device, a second supply mode in which a predetermined amount of toner can be supplied to the developing device, and a toner supply device capable of supplying a larger amount of toner to the developing device. A third supply mode, wherein the first supply mode is selected when the detected toner concentration is within a predetermined first concentration range based on the toner concentration of the developer; The second replenishment mode is selected when the toner density is within a predetermined second density range that is lower than the density range, and the toner density is within a predetermined third density range that is lower than the second density range. In this case, the third supply mode is selected.

[0006]

According to the present invention, when the toner density of the developer is within a predetermined first density range, the total area of the toner adhering area on the photoreceptor is calculated by using the image data in the image area. The first replenishment mode in which toner can be supplied to the developing device according to the total area is selected, whereby toner substantially corresponding to the toner consumption is supplied into the developing device. When the remaining amount of toner for replenishment in the toner storage unit decreases and the toner replenishment amount per replenishment operation of the toner replenishment mechanism decreases, and the toner density falls within the second density range, the toner is supplied to the developing device. A second replenishment mode capable of replenishing a fixed amount of toner is selected, whereby a sufficient amount of toner is replenished to maintain the image density even when the amount of replenishment toner in the toner storage unit is low. . Further, when the toner density decreases and falls within the third density range, a third replenishment mode capable of replenishing a larger amount of toner than the toner replenishment amount in the second replenishment mode is selected. The replenishment toner in the toner container is used up.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a digital camera as an example of an image forming apparatus will be described below. The digital copying machine includes a reading device (scanner) as document reading means and a copying device (printer) for executing a series of processes for copying read document information onto paper. As a reading device, for example, the original on the contact glass is sub-scanned by a moving optical system having a lamp for illuminating the original placed below the contact glass, and reflected on the lower surface of the original according to the density of the original image. Light is incident on a one-dimensional image sensor via a mirror and a lens. The one-dimensional image sensor detects one line in the main scanning direction on the document image, and performs two-dimensional scanning of the document by sub-scanning of the moving optical system. A device that reads an image can be used.

FIG. 1 shows a schematic configuration of a mechanical section of a copying apparatus according to the present embodiment. In FIG. 1, a charging charger 2, a writing unit (not shown), a developing unit 4, a transfer separation unit 5, a cleaning unit 6, a static eliminator 7, and the like are provided around a photosensitive drum 1. First, the surface of the photosensitive drum 1 is uniformly charged to a high potential by a corona current generated by the charging charger 2. The surface is irradiated with laser light from the writing unit, the charging potential changes according to the intensity of the light, and a potential distribution is formed according to the presence or absence of laser light irradiation. The writing unit includes a semiconductor laser (hereinafter, referred to as a writing LD) as a laser light source, and irradiates the laser light emitted from the semiconductor laser to the surface of the photosensitive drum 1 through an optical system such as a rotating multi-plane, a lens, and a mirror. The rotating polygon mirror may be one that performs main scanning on the photosensitive member by being driven to rotate at a constant speed at a high speed by an electric motor. Then, a position signal (recording / non-recording) for each pixel to be recorded by the control device is applied to the writing LD so that each pixel position is synchronized with the rotation position of the rotary polygon mirror, and each scanning position of the image is scanned. Then, on / off control of the laser light is performed according to the density of the pixel (recorded / not recorded). As a result, the potential distribution formed on the photosensitive drum 1 corresponds to the density of the document image and forms an electrostatic latent image. This electrostatic latent image is visualized by toner supplied by a developing unit 4 disposed downstream of the writing unit. The developing unit 4 includes a developing device 21 having a developing roller 20 for supplying toner onto the photoreceptor, and a toner hopper 22 containing toner to be supplied to the developing device 21. And an agitator 23 and a supply roller 24 are provided. On the other hand, the transfer paper fed from a cassette (not shown) is sent to the surface of the photosensitive drum 1 via the registration roller 9, and is separated from the surface of the photosensitive drum 1 after the transfer separation unit 5 transfers the toner image. . The transfer paper onto which the toner image has been transferred passes through a fixing device (not shown), where the toner image is fixed, and is discharged to a discharge tray (not shown). On the surface of the photosensitive drum 1 between the developing unit 4 and the transfer / separation unit 5, an optical sensor 25 for detecting the amount of reflected light from the photosensitive member surface is provided.

FIG. 2 shows a schematic configuration of an electrical unit of a digital color copying machine. In the housing of the reading device 10, a reading control circuit 20, a reading driving device 30, an image reading circuit 40
And an image processing circuit 50, and an image information storage device 60 as a storage unit for storing read document information, a copying circuit 70, a system control device 61, and a system control device in a housing of the copying device 90. An operation device 80 as operation means for performing key input is accommodated in 61. The information storage device 60 includes an image memory unit 62 and the system control device 61. The read control circuit 20, the write drive control circuit 71 included in the copy circuit 70, and the operation device 80 are connected to the system control circuit 61 by signal lines L1, L2, and L3, and perform data transmission with each other. ing.

The reading control circuit 20 receives a signal from the system control circuit 61 via L1 and receives a signal from the scanner motor 31.
, The control of the heater of the fluorescent lamp 32, the instruction to turn on the fluorescent lamp 32, the control of the filter solenoid 33 for document size detection, the control of the scanner power supply cooling fan, and the like. The image reading circuit 40 amplifies the signal from the CCD 41 for converting the reflected light from the document into an analog signal of 80 dpi into an odd number (ODD) and an even number (EVEN) (a time per pixel is very short). Therefore, a switching element 43 for combining the ODD and EVEV signals from the amplifier 42 into a serial analog signal, and a switching element 43
Signal from the image processing circuit 50 to the fluorescent lamp 3
2. Amplification degree instruction data A for correcting the fluctuation of brightness of 2.
A variable amplifier 44 for amplifying by GC, an A / D converter 45 for converting an analog signal from the variable amplifier 44 into a digital signal, and the like are provided. The image processing circuit 50 includes five gate arrays 51 to 55 and a clock generation circuit 5 for processing an image signal sent from the image reading circuit 40.
6, a ROM 57, a RAM 58, and the like. The gate array 51 is used for detecting the light amount, shading correction, timing control, command control, data editing / output, generating a CCD drive clock, etc.
Is magnification in the main scanning direction, the gate array 53 is halftone processing,
The binarization process, document size detection, gate array 54 is responsible for character / halftone separation, blanking editing, and gate array 55 is responsible for mark area detection. The image memory unit 62 includes a memory board and a memory control board. The system control circuit 61 controls the entire system and instructs reading and writing of image data. System-wide controls include system ready status monitoring,
Includes detection of transfer paper size / remaining amount, instruction to start document reading and paper feed, control of scanner copy mode and printer copy mode, etc. Are doing.
The copying circuit 70 includes a line driver circuit 72 for receiving image data from the image memory unit 62, a laser driver circuit 73 for amplifying the image data signal from the line driver circuit 72, and a semiconductor laser (LD) driven by the laser driver circuit 73. ) 74, a read drive control circuit 75, a write drive control circuit 71, a drive device 76, and the like.
The operation device 80 includes an operation panel 81 provided with a display for displaying various information and input keys, and an operation control circuit 82.

FIG. 3 shows a detailed configuration of the write drive control circuit. Reference numeral 390 includes an actuator group of the sheet feeding device (pickup solenoid, sheet feeding clutch, tray lock solenoid, lifting motor), a serial parallel receiver, and the like, and is connected to an output port of the CPU 703. The sensor group 390a connected to the input gate array 701 includes a sensor group (paper size detection sensor, paper end detection sensor, tray set detection sensor, connection detection sensor) in the paper feeding device. A conversion table 801 is connected to the video controller 800, and video data (VIDEO DATA)
Is also entered. The video controller 800 is configured as a part of the CPU 810 as shown in FIG.
The configuration is such that video data (EXTERNAL VIDEO DATA) from the outside is read from an input port of the CPU 810 and output to a conversion table 801 composed of a P-ROM. A sensor group 705 connected to the input gate array 702 includes various sensors for paper feed and conveyance, a main body door open detection sensor, an optical sensor (analog), etc. The input synchronization detection signal is also input to the input gate array 702. The actuator group 707 connected to the output gate array 706 includes various clutches for feeding and conveying, a main drive motor, a cleaning blade solenoid, a toner supply solenoid, a motor for a rotating polygon mirror, a fixing heater, a high voltage for charging, A power supply circuit, a high-voltage power supply circuit for transfer, a static elimination lamp, an optical sensor 25 (see FIG. 1), and the like are included. An LD output adjustment output of the optical sensor 25 is also output from the output gate array 706.

Next, toner supply control in this embodiment will be described. In this embodiment, the total area of the toner adhering area on the photoconductor is calculated using the image data in the image area, and the toner adhering amount per unit area of the toner adhering area on the photoconductor is detected. Then, based on the detected toner adhesion amount (hereinafter, referred to as a detected toner adhesion amount), the toner concentration of the developer is changed into a first density range, a second density range, and a third density range as shown in FIG. It is determined in which range the toner density falls within the first density range. If the toner density is within the first density range, replenishment of toner to the developing device is performed based on the toner adhesion amount per unit area and the total area. Calculate the roller drive time. If the toner density is within the second density range, the replenishing roller 24 needs to supply a sufficient amount of toner to maintain the image density even when the remaining amount of toner in the toner hopper 22 is reduced. The rotation drive time is set to a fixed value of 2 seconds. If the toner density is within the third density range, the rotational driving time of the supply roller 24 is set to a fixed value of 4 seconds in order to use up the toner in the toner hopper 22.

First, the calculation of the total area of the toner adhering region will be described. Conventionally, toner adheres to a portion (hereinafter, referred to as a dot) corresponding to black data on a photoreceptor, and by utilizing the fact that the number of black data relates to the amount of consumed toner, the toner density in a developing device It has been proposed to calculate the total number of black data in one image to obtain a toner replenishment amount based on the total number of black data in order to control (hereinafter, referred to as toner density) constant. This is based on the assumption that the amount of attached toner per dot is constant.
The amount of toner consumed for forming one image is determined from the total number of dots in the image. However, the amount of toner attached per dot differs depending on writing conditions such as the amount of light when writing one dot and the toner density. For example, in the graph of FIG. 4, the vertical axis shows the toner adhesion amount per unit area when the dots are densely packed in a unit area of 1 cm ² , and the horizontal axis shows the pulse width of the writing LD. The toner concentration is 3.2%,
In each case of 2.5% and 1.8%, the toner adhesion amount per unit area is shown. The specific multi-valued data of black data (hereinafter referred to as L
D multivalued data) and the pulse width of the write LD. As can be seen from this figure, even with one dot developed with a developer having the same toner concentration, the pulse width of the writing LD (determined by specific multi-value data of black data)
The amount of applied toner differs depending on the toner density, and even for one dot having the same writing LD pulse width, the amount of applied toner varies depending on the toner density. Further, in this example, the relationship between the LD multi-valued data and the pulse width of the writing LD is not proportional, so that the relationship between the LD multi-valued data and the toner adhesion amount is not linear. The toner adhesion amount of the data 0001 does not correspond to 1/16 of the toner adhesion amount of the LD multi-value data 1111. Therefore, in general, the toner adhesion amount is determined by the pulse width of the LD and the toner density, and can be expressed as in the following equation (1) using the function F that defines the correspondence. (Toner adhesion amount) = F [(LD multi-value data), (toner density data)] (1) The correspondence represented by this function F can be obtained, for example, as follows.

FIG. 5 shows the multi-level LD data for a toner concentration of 2.5%, which is obtained by an experiment by taking the multi-level LD data on the vertical axis and the toner adhesion amount per unit area on the horizontal axis 1. 6 is a graph showing a correspondence curve a between data and the amount of toner adhered per unit area. The horizontal axis 2 below the horizontal axis 1 is
This is for reading the value of the consumption data corresponding to the toner adhesion amount. On this horizontal axis 2, LD multi-value data 1
The scale of the point b 'on the horizontal axis 2 corresponding to the maximum value of the toner adhesion amount per unit area corresponding to 111 (the value indicated by the point b) is set to 15, for example, and the scale on the horizontal axis 2 corresponding to the toner adhesion amount 0 is set to 15. The scale of the point a 'is set to, for example, 0, and the point b'
The interval between '(15) and a' (0) is divided at equal intervals and a scale is taken. Using this vertical axis, horizontal axis 2 and the corresponding curve a,
By reading the scale on the horizontal axis 2 corresponding to the LD multi-value data, the correspondence shown in Table 1 below is shown as the correspondence between the LD multi-value data and the consumption data (multi-value data) when the toner density is 2.5%. Can be obtained. Here, the LD multi-value data 111
Although the scale of the point b ′ on the horizontal axis 2 corresponding to the maximum value of the toner adhesion amount per unit area corresponding to 1 (the value indicated by the point b) is set to 15, the present invention is not limited to this. A constant larger than 15 may be used when it is desired to detect the toner adhesion amount per unit surface more accurately than in the example, and a smaller constant may be used when the accuracy is lowered. . For other toner densities, instead of the above-mentioned corresponding curve a, a corresponding curve between the multi-valued LD data obtained experimentally for each toner concentration and the amount of toner adhering per unit area is used and corresponds to the multi-valued LD data 1111. The scale at the point b 'on the horizontal axis 2 corresponding to the maximum value of the toner adhesion amount per unit area (the value indicated by the point b) is shown below with the scale at the toner density of 2.5% (15). Is set to be the same as the ratio between the maximum value of the toner adhesion amount in the case of this toner concentration and the above-mentioned maximum value in the case of the toner concentration of 2.5%. The correspondence between data and consumption data (multi-valued data) is obtained.

[0015]

By the way, in this example, the shape of the corresponding curve between the LD multi-value data and the amount of toner adhering per unit area does not greatly differ at each toner concentration as shown in FIG. Ratio between consumption data in density (for example, when the toner density is 2.5%, 15:15:
14: 13: 11: 10: 8: 7: 6: 4:...) Can be approximated to be the same between the toner concentrations as shown in Table 2. Constants Mi, exemplified in Table 2,
Mj is the maximum value of the toner adhesion amount per unit area when the toner density is 1.8% and 3.2%, and the toner density 2.
This is the ratio with the maximum value of the toner adhesion amount per unit area in the case of 5%.

[0017]

That is, in this example, in the above equation (1),
As a special case, as shown in the following equation (2), the function MA and the function F
It can be approximated as a product of _one . (Toner adhesion amount) = MA [(toner density data)] · F ₁ [(LD multi-value data)] (2) Here, the function F ₁ is a writing L as a writing condition for one dot.
The pulse width of D is changed (for example, LD multi-level data 00
Set the pulse width to 0 to 50 ns according to 00 to 1111
c), the change in the toner adhesion amount based on the change in the potential on the photoconductor and the area of one dot. This change in potential on the photoconductor is the same as the change in the area of one dot in that the amount of toner adhering to one dot is changed.
This can be handled as a change in the toner attachment area per dot. Therefore, the consumption data can be handled as data relating to the toner adhesion area. on the other hand,
The function MA can be handled as expressing the toner adhesion amount per unit area, that is, the toner adhesion ratio.

[0019] Therefore, in this example, instead of obtaining the toner consumption in the conventional manner one image simply by calculating the total number of black data, the relationship and function MA corresponding to the function F ₁ A corresponding relationship is obtained by an experiment, and the LD multivalued data is converted into consumption data for each dot in one image by using the correspondence corresponding to the function F1, and _one of the consumption data is converted. The sum of the images of one sheet is calculated to obtain the sum of the toner adhesion areas in one image, the toner density is detected, and the toner adhesion rate is calculated from the toner density using the correspondence corresponding to the function MA, The toner consumption in one image is obtained by multiplying the sum of the toner attachment areas by the toner attachment rate.

First, a description will be given of an operation for obtaining the total sum of the toner adhering areas using the image data. FIG. 6 shows a conversion and counting circuit for converting the LD multi-level data into consumption data for this purpose. This circuit mainly includes a conversion table 8 for converting LD multi-valued data to consumption data.
10, an adder 811 for counting the consumption data to calculate the total toner adhesion area, a flip-flop 812 for positioning, a counter 813, and the like. The adder 811, the flip-flop 8 for positioning
12, the counter 813, etc.
0 (see FIG. 2). Conversion table 8
10 is the video controller 80 shown in FIG.
0 connected to the CPU 810 where
It comprises a ROM 801. Then, the multi-level LD data input to the video controller 800 (CPU 801) as external video data is output to the video controller 80.
0 (CPU 801) is output to the conversion table 810, and the consumption data from the conversion table 810 is input to the video controller 800 (CPU 801), and the counting is executed.

In FIG. 6, first, LD multi-value data is converted into consumption data from a conversion table 810, latched by a flip-flop 814 at the first stage, and then sent to an adder 811. The adder 811 calculates the sum of the input data and the previous remaining data, and outputs the result as a query to the next counter. This adder 81
In 1, performance is determined by input consumption data (multi-value data level). For example, when the consumption data is 3 to 4 values, 2 bits and 2 bits are used, when the consumption data is 5 to 8 values, 3 bits and 3 bits are used, and when the consumption data is 9 to 16 values, 4 bits are used. And 4 bits are used. Thus, the size of the adder 811 is determined according to the number of bits of the data. FIG. 8 is a timing chart showing the timing at which a carry occurs, in which the consumption data is 4-bit data (0000 to 111).
This is an example in the case of 1). The counter increments the count each time a carry is input, counts the carry, and determines total toner adhesion area data as the sum of consumption data. The counter FGAT is turned on during the writing period of the effective image area.
Counts up only when E is ON, and this is OF
Cleared when falling to F state. The output of the counter is latched by a flip-flop when FGATE falls, and is read by the CPU. The toner adhesion area data read here is represented by upper 8 bits.

As described above, it is possible to obtain the total area of the toner adhering area in consideration of the size of the toner adhering area per dot according to the LD multi-value data. In the configuration of this example, the count can be similarly performed whether the input of the conversion table is code data or binary data (0000 or 1111).

In this example, the sum of the consumption data is converted into the consumption data of the LD multi-value data 1111 and the converted upper 8 bits are read by the CPU and used as the toner adhesion area data. Here, for example, A3 size (420
× 297), the total number of dots is 1 according to the following equation (1).
110110000000101000011110B
Therefore, the upper 8 bits become 0eCH, and the total sum of the image data is 1110011010011111100111101 from the following equation (2) except for each end 2 mm.
B, and the upper 8 bits become 0e6H.
When the toner adhesion area data read into the PU is 0e6H, the LD is applied to the entire surface of A3 (excluding 2 mm from the end).
This corresponds to an image written with the multi-value data 1111. (Total number of dots) = 420 × (400 / 25.4) × 297 × (400 / 25.4) = 30935582 (dots) = 1111010000000101000011110B (1) (sum of image data) = (420−4) × (400 / 25.4) × (297-4) × (400 / 25.4) = 30228285 (dots) = 11100111010011111100111101B (2)

FIG. 9 is a flow chart of control for reading the output of the counter latched by the flip-flop by the CPU. In step 1, toner adhesion area data (LDCNT), which is the output of the counter latched by the flip-flop, is read. Since this LDCNT can read only the upper 8 bits as described above, it is determined whether or not the read LDCNT is 0. If the read LDCNT is 0, the LDCNT is stored in the register LDCNT in step 3.
After storing 1 as data, in step 4 this LDC
The NT data is stored in the register LDONCT. Conversely 0
If not, the read LDCNT is stored in the register LDONCT.

Next, detection of toner concentration for calculating the toner adhesion rate will be described. The detection of the toner density in the present embodiment does not directly detect the toner density in the developing device, but forms a predetermined electrostatic latent image (hereinafter, referred to as a reference pattern latent image) on the photosensitive member. The optical density of a visible image (hereinafter, referred to as a reference pattern toner image) obtained by developing the pattern latent image by the developing device is detected, and the toner density in the developing device is calculated from the detected optical density. Specifically, it is detected as follows. First, a reference pattern is written on the photoreceptor in the non-image area by the same laser beam as that used for writing the image area to form a reference pattern latent image. The reference pattern latent image is conveyed to the developing device by the rotation of the photoreceptor, developed, and then opposed to the optical sensor 25. The light receiving portion of the optical sensor 25 is turned on, and the non-pattern portion (photosensitive member background portion) is read by the light receiving element, and the reference pattern toner image portion is similarly read. At this time, the lower the toner density in the developing device, the smaller the amount of toner adhering to the reference pattern toner image, and the higher the toner density, the greater the amount of toner adhering to the reference pattern toner image. To detect. Here, the background portion is also detected because the influence of the eccentricity of the photosensitive drum and the toner contamination of the optical sensor 25 is canceled out by taking the ratio between the detection value of the background portion and the detection value of the reference pattern toner image portion. It is. Hereinafter, the output of the optical sensor for reading the background of the photoreceptor is referred to as output _VSG , and the output of the optical sensor for reading the toner image portion of the reference pattern is referred to as output _VSP .

Next, control when the detection output of the background portion or the reference pattern toner image portion is an abnormal value will be described. If toner, paper dust, or the like adheres to the surface of the optical sensor 25 over time, the sensor output decreases, sufficient SN characteristics cannot be obtained, and erroneous detection of the toner concentration occurs.
Abrupt fluctuations in toner density due to excessive toner replenishment, etc.
Runaway of the toner density may occur. As mentioned above,
Or using the ratio of the output V _SG and the reference pattern toner image portion of the detection output V _SP (hereinafter referred to as the output V _SP), it executes the output adjustment of the optical sensor 25, to prevent the occurrence of such a situation Although this contributes, there is a limit to this, and if the amount of toner or the like becomes large, it is impossible to cope with the problem, and the above-described problem occurs. Therefore, in this example, if the output of the optical sensor 25 is not within the range set in advance, it is determined that the output is abnormal, and the output is not used for calculating the toner density. Then, the toner density is calculated using the data set in advance. Specifically, the output V _SG
Is smaller than 2.5 or the output _VSP is 2.5 V or more, it is determined to be abnormal, and the toner density is calculated using the data set in advance.

The specific control of reading the detection output of the optical sensor 25, including the control when the detection output of the optical sensor 25 is abnormal, will be described with reference to FIG. First,
In step 1, it is determined whether or not the detection of the photoconductor background portion and the reference pattern toner image portion by the optical sensor 25 has been completed.
When the detection is completed, it is determined in Steps 2 and 3 whether or not the detection output of the optical sensor 25 is abnormal. The determination as to whether or not the detection output is abnormal is made in steps 2 and 3 based on the above criteria. If it is determined that there is an abnormality, the process proceeds to step 8, and the preset appropriate values of V _SG 4.0 volts and V _SP 0.25 volt are stored in the registers V _SG and V _SP . I do. Next, steps 4 and 5
Register DVGN in which the latest outputs V _SG and V _SP are stored
The contents of EW and DVPNEW are stored in registers DVGOLD and DVP in which outputs V _SG and V _SP related to the immediately preceding detection are stored.
After updating and storing in OLD, in steps 6 and 7, the contents of the registers V _SG and V _SP relating to the current detection are updated and stored in the registers DVGNEW and DVPNEW. This completes the reading of the outputs V _SP and V _SG .

Next, the above registers DVGNEW, DVP
The calculation of the toner density using the outputs V _SG and V _SP stored in NEW will be described. In this example, the output V _SG
There is a certain relationship as shown in the first quadrant in FIG. 11 between (V) and the ratio V _SP / V _SG between the output V _SP (V) and the toner density in the developing device. Therefore, this relationship is stored in a RAM, for example, as a data table, and after reading the outputs V _SG and V _SP from the optical sensor 25, the data table is looked up with V _SP / V _SG to determine the toner density of the developing device 21. Ask.

The second quadrant in FIG. 11 shows the corresponding characteristic between the toner density and the toner adhering amount per unit area by taking the toner adhering amount with the unit area on the horizontal axis. From the characteristics, the function MA in the above equation (2), that is, the correspondence between the toner density and the toner adhesion rate can be obtained. The correspondence between the toner density and the toner adhesion rate is stored in a data table.

Here, in this example, when an image having a large amount of toner consumption such as a solid black image is formed, toner is replenished in accordance with the amount of toner consumption as described later, so that a good image is obtained. In some cases, the amount of toner that temporarily exceeds the developer stirring capacity of the developing device 21 for performing sufficient toner charging may be supplied. If the reference pattern toner image is read by the optical sensor 25 immediately after such amount of toner is supplied (the reference latent image is developed for that), the toner is temporarily agitated due to insufficient stirring of the developer (carrier) and the toner. Due to insufficient toner charging, the amount of toner adhering to the reference latent image is smaller than when the toner charging amount is appropriate. Therefore, thinner as compared with the case where the optical density of the reference pattern toner image is developed with the appropriate toner charge amount, as shown in FIG. 12, the output V _SP of the optical sensor 25 becomes high.
In FIG. 12, the horizontal axis indicates the area ratio (｛toner adhesion area / A3 (4)
20 × 297) area｝ × 100%), and the vertical axis indicates the output V _SP at the time of reading the sensor, and the actual toner density is 1.8%, 2.0%, and 2.7%. shows the relationship between the area ratio of the image according to the copy operation sensor reading timing immediately before and the output V _SP when the sensor reading. In any of the toner density, it can be seen that the output V _SP is higher as the area ratio increases. Therefore, the sum of the consumption data of the image according to the image formation of the immediately preceding reading optical sensor timing, i.e. the sum of the toner adhesion area is equal to or larger than a predetermined value, corrects the V _SP read as shown in FIG. 13. Incidentally, the sum of the consumption data of the image according to the image formation of the immediately preceding reading optical sensor timing, i.e. not only the sum of the toner adhesion area, corrects the V _SP read using the sum of the toner adhesion area from plural previous You may do it.

FIG. 13 shows the area ratio obtained from the toner adhesion area data relating to the copy operation immediately before the sensor reading timing on the horizontal axis, and the number of correction bits of the _VSP data on the vertical axis. One bit of this correction bit number is equivalent to about 0.02 V of the output of the optical sensor 25 (5 V / 25
5). The number of correction bits is obtained in advance by an experiment. Correction of the _VSG data makes it possible to obtain an accurate toner concentration (toner concentration after a sufficient stirring operation).

The specific control of the above-described calculation of the toner density and the calculation for obtaining the toner adhesion ratio MA will be described with reference to FIG. First, the output V _SP read from the register DVPNEW in step 1 is stored in the register DV
Using the output V _SG read from GNEW, the output V _SG is converted into V _SP data when the output V _SG is 4.0 volts, and the register A
To be stored. Here, V _SP when the output V _SG is 4.0 V
The reason why the output V _SP is multiplied by the constant 204 in order to convert the data into data is that the data of the optical sensor 25 is read from the analog port of 8 bits and the upper limit of 5 V (255 × 4V ÷ 5V = 204). Next, in step 2, it is determined whether or not the value is greater than the _VSP data value of 40.
Correct to 0 (step 3). This is the V _SP data, i.e. the relationship of the size of the data table for obtaining the toner concentration from the ratio of the output V _SP and V _SG, V _SP data 4
0 or more of the things is to approximate as V _SP data 40 collectively. Next, in steps 4 and 5, it is determined whether the _VSP data is 0 or not. If it is 0, it is corrected to 1 (step 5). This is also approximated by the size relationship of the data table. Then, in Step 6 to 10, with LDCNT, to correct the V _SP data shown in Figure 13 described above. Here, the LDCNT 184 indicates that the area ratio of the image is 80%.
%, LDCNT 138 to 60%, LDCNT 69
Correspond to the same 30% respectively. Although not shown in the flowchart, it is set to 1 when the result of the subtraction processing in steps 9 to 11 is smaller than 1. next,
Step 12 using a V _SP data, V _SP data, i.e. by searching the data table corresponding to the ratio and the toner density of the output V _SP and the output V _SG is stored, reads the toner density data, this After the data is stored in the register A, the data is stored in the register DBTDEN in step 13. Next, in step 14, using the toner density data stored in the register A, a data table storing the correspondence between the toner density and the toner adhesion rate is searched, and the toner adhesion rate data is read. After storing this in register A,
In step 15, the data in the register A is stored in the register DBTN.
Store in MA.

Using the toner adhesion area and the toner adhesion ratio for one image obtained as described above, the amount of toner consumed for one image is calculated. Specifically, the product of the above-mentioned toner adhesion area data and toner adhesion ratio data is calculated to determine the amount of toner consumed per image formation.

Next, the calculation of the toner supply amount will be described. Ideally, if the driving conditions of the toner replenishment mechanism are controlled so that the toner replenishment amount matches the toner consumption amount obtained by the above calculation, the toner concentration should be kept constant. In addition to the fact that the toner supply amount calculated due to machine-to-machine variations and environmental fluctuations of the toner supply mechanism does not always match the actual amount of toner to be replenished, in this example, the target toner concentration is also reduced due to the following reasons. Deviation occurs. That is, in this example, the toner concentration of the developer in the developing device 21 is
Since the optical density is obtained by detecting the optical density of the reference pattern toner image obtained by developing the reference latent image formed thereon, toner is consumed to form the reference pattern toner image, and the cleaning device 6 , The burden of cleaning the reference pattern toner image also occurs. Therefore, as described above, the toner density is detected every ten image formations, and during the ten image formation after the detection, the toner adhesion ratio MA calculated using the detected toner density and the image formation operation are determined. The toner consumption per one image formation is calculated from the sum of the toner adhering areas obtained by the calculation. However, since the toner density also changes during the formation of 10 images after the detection of the toner density, an error occurs between the toner consumption amount and the actual toner consumption amount. Deviates from the intended toner concentration.

Therefore, in the present embodiment, in addition to the latest toner density detection result, the toner density relating to the latest toner density detection is compared with the toner density relating to the previous toner density detection to obtain the result. In consideration of the transition of the toner density, the toner replenishment amount is determined. As a result, if the actual toner density deviates from the target toner density,
Immediately converge to the target toner concentration.

That is, based on the latest toner density detection result, when the detected toner density is higher than the target toner density, the toner replenishment amount is made smaller than the toner consumption amount, and conversely, the detected toner density becomes lower than the target toner density. If the detected toner concentration is lower than the latest detected toner concentration (when the toner concentration tends to decrease), the toner replenishment amount is larger than the toner consumption amount. When the replenishment amount is larger than the toner consumption amount, and when the previous detected toner concentration is higher than the latest detected toner concentration (when the toner concentration tends to increase), the toner replenishment amount is set to be smaller than the toner consumption amount. The toner supply amount is determined from the viewpoint of reducing the amount of toner.

In order to determine the toner replenishment amount from the above viewpoint, in this example, the variable GA in the toner replenishment amount calculation is used.
IN is used. Hereinafter, the variable GAIN in this example
Will be specifically described. The variable GAIN corresponds to the ratio between the toner supply amount and the toner consumption amount. When this value is 1.0, the toner supply amount and the toner consumption amount become equal. And
When the latest detected toner density is lower than the target toner density, the variable GAIN is set to be larger than 1.0 to increase the toner density, and this increase is taken into consideration in consideration of the above-described transition of the toner density. Make a decision. Similarly, when the latest detected toner density is higher than the target toner density, this variable GAIN is made smaller than 1.0 to lower the toner density. Make decisions based on consideration.

The specific value of the variable GAIN varies depending on the characteristics of the developing device 21 and the toner replenishment method, and is obtained experimentally. Hereinafter, an example is shown. When the latest detected toner density is lower than the target toner density and the previous detected toner density is lower than the target toner density, the GAIN value is set to 1.4 to 2.3.
The latest detected toner concentration is lower than the target toner concentration,
When the previous detected toner density is higher than the target toner density, the GAIN value is 1.3 to 3.0, the latest detected toner density is higher than the target toner density, and the previous detected toner density is higher. Is lower than the target toner density, the GAIN value is 0.5 to 0.8, the latest detected toner density is higher than the target toner density, and the previous detected toner density is also lower than the target toner density. GAI when high
The value of N is set in the range of 0.6 to 1.0. Specifically, they are set as shown in Table 3 below. In addition, A in the vertical direction in the following Table 3
= 0 to 4 correspond to the latest detected toner density, and Tables 1 to 5 in the horizontal direction correspond to the previous detected toner density. A = 0 to 4 and Tables 1 to 5 correspond to the detected toner density categories as shown in the flowcharts of FIGS. 15 and 16 showing specific control. The tables 1 to 5 correspond to data tables for retrieving GAIN data from the respective sections A.

The specific control for obtaining GAIN will be described with reference to FIGS. First, in step 1, similarly to step 1 in the flowchart of FIG. 14, the output V _SP read from the register DVPNEW is
Using the output V _SG read from the register DVGNEW, the output V _SG is converted into V _SP data when the output V _SG is 4.0 volts, and stored in the register A. In step 2, this is stored in the register DBPNEW. Before the data is stored in the register DBPNEW, the correction processing of steps 6 to 11 in the flowchart of FIG. 14 described above may be performed. Next, in steps 3 and 4, similarly, the output V _SP read from the register DVPOLD is used to calculate the output V _SP when the output V _SG is 4.0 volts, using the output V _SG read from the register DVGOLD.
_The data is converted into _SP data, stored in the register A, and stored in the register DBPOLD. And steps 5-13
In first with V _SP data at the time of the previous detection read from the register DBPOLD, select whether to use any of the data table in Table 3 above. Then, step 14
With V _SP data at the time of the last detected read from the register DBPNEW at ~19 to determine the division of A in Table 3 above. Then, in step 23, the data table selected as described above is searched using the determined section A, and the searched GAIN data is stored in the register A. In step 24, this is stored in the register DBGAIN.

FIG. 17 shows the toner replenishment amount calculation using GAIN or the like obtained as described above. In FIG. 17, first, in step 1, the register DBPNEW (FIG.
It is determined whether or not the predetermined _VSP data read from the second step in FIG. 7 is equal to or higher than the above-mentioned first density range of 0.6 V. Unless the V _SP data 0.6V or higher, and sets 0 to the near-end counter in step 2, a second concentration range the V _SP data described above in Step 3 0.5
It is determined whether it is 5 V or more (and less than 0.6 volt). If the V _SP data is not 0.55 V or more (ie,
In step 4 (if the first density range described above), register D
The product of the toner adhesion ratio data read from BTNMA and the toner adhesion area data read from the register LDCNT is calculated to obtain toner consumption data, which is stored in the register DB.
ADDT, and in step 5, this register DBAD
The toner consumption data read from the DT is multiplied by the GAIN data read from the register DBGAIN to obtain toner supply amount data, and the register DBADDL / H
To be stored. As a result, the first replenishment mode is set to a toner replenishment operation time at which the toner replenishment amount is in accordance with the toner consumption amount obtained from the total area of the toner adhered area on the photoconductor and the toner adherence rate. In this example, the toner supply amount is represented by DBADD which is the toner consumption amount data per sheet.
The product is obtained by the product of T and GAIN.
May be determined by: DBADDT + (1−GAIN) × A (3) where A is a constant In the calculation of the expression (3), the difference between the toner consumption amount and the toner replenishment amount is determined in accordance with the detected toner density and the transition of the toner density. And performs an operation to approach the target toner concentration. On the other hand, the V _SP data in the above step 3 is 0.55
If it is determined that the voltage is equal to or higher than V (less than 0.6 V than in Step 1), a fixed value of 2 seconds is stored in the register DBADDL / H in Step 6. As a result, the second replenishment mode is set to a long toner replenishment operation time capable of increasing the toner concentration in the developing device irrespective of the total area of the toner adhering area on the photoconductor. In addition, instead of setting the fixed value such as 2 seconds as the replenishment operation time in the second replenishment mode, a predetermined fixed value is added to the toner replenishment operation time (steps 4 and 5) in the first replenishment mode. The set value is set as a replenishment operation time, the toner replenishment operation time in the first replenishment mode is set to a value multiplied by a predetermined value, and any one of these values is set for each size of the image area (or transfer paper). You may change it. Further, when the V _SP data in step 1 is determined to be 0.6V or more, stores 4 seconds register DBADDL / H in step 7. As a result, the third supply mode is set to a supply operation time longer than the supply operation time in the second supply mode so as not to leave the supply toner in the hopper. And step 8
Increments the near end counter at step 9
It is determined whether or not the content of the near-end counter is equal to or greater than a predetermined count value n. If the content is not n or more, the process returns to the main flow as it is. If the content is n or more, toner near-end display is performed in step 10.

Next, the toner supply operation will be described.
The toner is replenished according to the toner consumption. The setting of the replenishment toner amount is set according to the rotational driving time of the replenishment roller 24. The amount of toner consumption per image is the product of the toner consumption area and the toner adhesion rate as described above, and is specifically expressed by the following equation (4). (Toner consumption) = LDCNT × 2 ¹⁷ × MA × 1 / (400 / 2.54) ² ≒ LDCNT × MA × 655/124 (4) Here, the unit of (toner consumption) is mg, and LDCNT × 2
The unit of ¹⁷ is dot, the unit of MA is mg / cm ² , 1 / (40
0 / 2.54) ² of the unit is cm ² / dot. In addition, LD
It is What multiplied by 2 ¹⁷ to CNT, because it represents the upper 8 bits of the toner adhesion area data LDCNT as described above. On the other hand, the toner supply in this example is performed by rotating the supply roller 24 by driving the clutch. As shown in FIG. 18, in the area A where the toner supply amount per unit time is stable, the toner of 300 mg / sec is supplied. Supply is performed. FIG. 18 shows the relationship between the remaining amount in the toner hopper 22 and the toner supply amount by taking the amount of toner supply per 30 seconds on the vertical axis and the remaining amount of toner in the toner hopper 22 on the horizontal axis. Things. The toner replenishment amount in the first replenishment mode is obtained by multiplying the toner consumption amount by GAIN, and is converted into a replenishment time (rotation time of the replenishment roller 24). Become. (Supply time) = (toner consumption) × GAIN × 1/300 ≒ LDCNT × MA × 131/124 × 60 (5) The unit of the (supply time) is seconds. During this replenishment time, the clutch is turned on to replenish the toner.
It should be noted that in the above-described flowchart, constant processing (× 131, 124 × 60
Etc.) are omitted.

When the driving source for the image forming operation (the motor for driving the drum 1 and the registration roller 9) and the driving source for the developing device 4 (the motor for driving the mag roller and the supply roller 24) are provided independently. Then, at an arbitrary timing of feeding of each recording sheet, the supply electromagnetic clutch is turned on for a time corresponding to the supply amount data DBADDL and DBADDH. Thereby, the agitator 2 in the toner hopper 22
3 and the supply roller 24 is driven to supply toner into the developing device 21. When the driving sources are the same, the toner replenishing operation is performed at the time of recording or at the timing when the transfer of the toner image on the photosensitive member 1 is completed, in order to prevent the image deterioration due to the fluctuation of the load of the driving source. Preferred.

As described above, in this embodiment, the reference toner image is detected by the optical sensor every predetermined number of sheets, and the toner density TC '
Is obtained, and if necessary, this is corrected with the sum LDCNT of the toner adhesion area data relating to the immediately preceding copy to obtain the toner density TC. With this TC, the toner adhesion rate MA per unit area is calculated and stored in the register. Further, this TC is compared with the TC related to the previous detection, and a variable GAIN is calculated from the transition of the toner density and stored in the register. Then, the toner replenishment amount is calculated by multiplying the LDCNT counted for each copy by MA and GAIN read from the register, and the toner is replenished for each copy. As a result, the toner density can be converged to a target toner density, and a stable visualization capability of the developing device 4 can be obtained. When the remaining amount of toner in the toner hopper 22 decreases and the toner supply amount decreases with respect to the rotation time of the supply roller 24 and the toner concentration decreases, the supply roller rotation time is quickly switched to the supply roller rotation time capable of supplying a predetermined amount of toner. Thus, when a document or the like that consumes a small amount of toner is copied and the toner supply amount is set using MA and GAIN as described above, the toner cannot be replenished enough to enrich the thinned toner density. It is possible to prevent the toner density from remaining. If the toner density still becomes lower without increasing, the rotation time is switched to a longer supply roller rotation time, whereby the toner in the toner hopper 22 can be used up.

FIG. 19 shows the execution timing of each control and the use relationship of each calculation result in the above embodiment based on the timing of the copy operation. In the drawing, “△” indicates a sensor check timing, which is set for the first sheet after the main switch of the image forming apparatus is turned on and every ten sheets thereafter. At this timing, the pattern on the photoconductor 1 is read by the optical sensor 25, and the output V _SG and the output V _SP are obtained. “TC ′” indicates the toner density calculation, and calculates the toner density (TC) in the developing device 21 from the output ratio between the output V _SG and the output V _SP . “TC” indicates toner density correction, which checks the toner adhesion area (LDCNT) of the recording paper immediately before the sensor check timing, and a certain value or more (if the amount of adhesion is large, the stirring of the developing device 21 is insufficient. ), The toner density is corrected to a value higher than TC ′. Let TC be the corrected toner density. "M
"A" indicates the calculation of the toner adhesion rate. Since the toner adhesion amount per unit area on the photoreceptor 1 varies depending on the toner density even under the same process conditions, the adhesion rate MA is obtained from the TC value in the data table. "LDCNT" indicates the calculation of the toner adhesion area, which is the image data (multi-value data, etc.)
Is converted to a toner adhesion area using a data table,
The total toner adhesion area LDCNT per recording sheet is determined. “UT.” Indicates the calculation of the toner consumption, and the toner consumption uT. As the product of the adhesion ratio MA and the toner adhesion area LDCNT. Is calculated. “GAIN” indicates the calculation of the variable GAIN, and the detected V _SG , V _SP and the previously detected V _SG ,
Comparing V _SP, the toner concentration TC (V _SG, V _SP) of the aimed obtaining a variable GAIN for adjusting the supply amount so as to become. “ADDT” indicates the toner supply amount calculation, and the consumed toner amount uT. And the variable GAIN are used to calculate the toner supply amount. With the above flow, the toner replenishment amount is obtained for each recording sheet to execute the toner replenishment. However, the variable GAIN is changed every sensor check timing.

As described above, in this embodiment, in order to detect the toner adhesion rate, which is the toner adhesion amount per unit area on the photosensitive member 1, the toner concentration of the developer in the developing device 21 is determined by using the optical sensor 25. However, instead of this, a toner density sensor may be provided in the developing device 21. Further, the toner density is detected every predetermined number of sheets, but may be detected every time instead. Further, when the output of the optical sensor 25 is not within the predetermined range, the value of the preset data table is read out (step 5 in the flowchart of FIG. 10 and subroutine CHKV in FIG. 14), and this value is stored in the optical sensor 25. output to the corresponding data (V _SG data, V _SP data) used as a substitute data in place of calculating the toner adhesion rate (the flow chart of FIG. 18), the toner supply on the basis of the toner adhesion rate and the toner adhesion area The second replenishment amount calculating means is configured to calculate the toner replenishment rate. Alternatively, when the output of the optical sensor 25 is not within a predetermined range, the toner adhesion rate corresponding to the output of the optical sensor 25 is calculated. A value to be used as substitute data in place of the above data is set in a data table in advance, and when the output of the optical sensor 25 is not within a predetermined range, this data table is set. Read substitute data in place of data of the toner adhesion rate Le, may be calculated toner supply amount based on the the substitute data and the toner adhesion area. In the above embodiment, as described above, the above equation (2) is satisfied as a special case of the above equation (1). However, such an equation (2) is not satisfied. If it is necessary to convert the toner consumption per dot into consumption data using both the multi-valued data of the image and the toner density, a data table for retrieving the consumption data from the multi-valued data of the image is required. It may be provided for each toner concentration. The toner density data for this may be obtained by detecting the toner density every time, or when the toner density is detected at predetermined intervals as in the above embodiment, the latest toner density may be used. good. Furthermore,
In the above embodiment, since the toner adhesion area varies depending on the pulse width of the writing LD, the multi-value data of the image is converted into consumption data, and the total of the consumption data per image is the toner per image. Although the adhesion area is obtained, even when the pulse width of the writing LD is constant, if the toner adhesion amount changes due to the density of dots in the image, for example, an increase in the toner adhesion amount occurs due to an edge effect in development. Even when the toner adhesion amount changes depending on whether the distance between the dots is close to each other, the relationship between the distance between the dots and the toner adhesion amount is determined in advance, and this relationship is multiplied by the image. It is used as a conversion table from value data to consumption data, and once converted from multi-valued data of an image to consumption data, the total of the consumption data per image is one image. Request toner adhesion area or.
Also, in the above embodiment, various data tables are used. Of those, those that can be replaced by arithmetic expressions are replaced with arithmetic expressions, and instead of searching the data table, the arithmetic processing of this arithmetic expression is executed. Is also good.

[0045]

According to the first aspect of the present invention, when the toner density of the developer is within the predetermined first density range, the toner adhesion area on the photoconductor is determined using the image data in the image area. The total area is calculated, and the first replenishment mode in which the toner can be supplied to the developing device is selected according to the total area, whereby toner substantially corresponding to the toner consumption is supplied into the developing device. Then, the remaining amount of the replenishing toner in the toner storage unit decreases, and the toner replenishing amount per replenishing operation of the toner replenishing mechanism decreases,
When the toner density falls within the second density range, a second replenishment mode in which a predetermined amount of toner can be replenished to the developing device is selected, whereby the remaining amount of the replenishing toner in the toner storage unit decreases. The toner can be replenished in an amount sufficient to maintain the image density even when the image is in the state. Further, when the toner density decreases and falls within the third density range, a third replenishment mode capable of replenishing a larger amount of toner than the toner replenishment amount in the second replenishment mode is selected. The replenishment toner in the toner container can be used up.
According to the second aspect of the present invention, in the first aspect of the present invention, the toner near end is displayed when the third replenishment mode is continuously selected a predetermined number of times. It is possible to notify the user of replacement of the toner container. Further, according to the invention of claim 3, an area calculating means for calculating the total area of the toner adhering area on the photoreceptor using the image data in the image area, and an amount corresponding to the calculation result of the area calculating means First supply amount setting means for setting a toner supply mechanism drive condition for supplying toner, and toner supply for supplying a larger amount of toner than the toner supply mechanism drive condition set by the first supply amount setting means Second supply amount setting means for setting a mechanism driving condition;
Third supply amount setting means for setting a toner supply mechanism drive condition for supplying a larger amount of toner than the toner supply mechanism drive condition set by the second supply amount setting means; and detecting a toner concentration of the developer. Selecting a first replenishing amount setting unit when the toner concentration detected by the toner concentration detecting unit is within a predetermined first density range; The second replenishment amount setting means is selected when the toner density is within a predetermined second density range which is a low density, and when the toner density is within a predetermined third density range which is lower than the second density range. And a selection means for selecting the third supply amount setting means, so that a sufficient amount of toner can be supplied to maintain the image density even when the remaining amount of the supply toner in the toner storage section is reduced. To be able to do It can be made to use up the replenishment toner in the container portion to provide an image forming apparatus capable.

[Brief description of the drawings]

FIG. 1A is a schematic configuration diagram around a photoconductor of a digital copying machine according to an embodiment of the present invention, and FIG. 1B is an explanatory diagram for explaining toner supply control of the copying machine.

FIG. 2 is a block diagram showing a configuration of an electrical unit of the copying machine.

FIG. 3 is a block diagram showing a configuration of a write drive control circuit of FIG. 2;

FIG. 4 is a characteristic diagram showing a relationship between a pulse width of a writing LD and a toner adhesion amount in the copying machine.

FIG. 5 is a characteristic diagram showing a relationship between LD multi-value data and an amount of applied toner of the copying machine.

FIG. 6 is a configuration diagram of a counter circuit for calculating the toner adhesion area of the copying machine.

FIG. 7 is a circuit diagram showing a CPU including the counter circuit and peripheral circuits.

FIG. 8 is a timing chart of the counter circuit.

FIG. 9 is a flowchart of reading control of toner adhesion amount data in the copying machine.

FIG. 10 is a flowchart of reading control of an optical sensor output of the copying machine.

FIG. 11 is a characteristic diagram of the optical sensor.

[12] characteristic diagram showing the relationship between the area ratio of the image according to the image formation of the optical sensor detection immediately before and the output V _SP.

FIG. 13 is a graph showing the relationship between the number of correction bits of the output of the optical sensor and the area ratio.

FIG. 14 is a flowchart of control of optical sensor output correction and toner adhesion amount calculation of the copying machine.

FIG. 15 is a part of a flowchart of control of variable GAIN calculation of the copying machine.

FIG. 16 shows the remaining part of the control flow for calculating the variable GAIN shown in FIG. 15 of the copying machine.

FIG. 17 is a flowchart of control of calculating a toner supply amount in the copying machine.

FIG. 18 is a characteristic diagram of a toner supply mechanism of the copying machine.

FIG. 19 is a timing chart showing execution timings of various controls of the copying machine.

[Explanation of symbols]

Reference Signs List 1 photoreceptor drum, 4 developing device 6 cleaning device, 21 developing device 22 toner hopper, 23 agitator 24 supply roller, 25 optical sensor 800 video controller, 801 PR
OM (conversion table) 811 Adder 813 Counter 815 Latch circuit

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-60-69666 (JP, A) JP-A-2-262169 (JP, A) JP-A-63-228180 (JP, A) JP-A-62-1988 43674 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/08 G03G 15/00 303

Claims (3)

(57) [Claims] A first supply mode for calculating a total area of a toner adhering area on a photoreceptor using image data in an image area and supplying an amount of toner corresponding to the total area to a developing device; A second replenishment mode for replenishing the developing device with a predetermined amount of toner and a third replenishment mode for replenishing the developing device with toner larger than the predetermined amount are provided. Based on the toner concentration of the developer, The first replenishment mode is selected when the detected toner density is within a predetermined first density range, and when the toner density is within a predetermined second density range lower than the first density range. Selecting the second replenishment mode, and selecting the third replenishment mode when the toner density is within a predetermined third density range which is lower than the second density range. Control method. 2. The toner replenishment control method according to claim 1, wherein when the third replenishment mode is continuously selected a predetermined number of times, a toner near end is displayed. 3. An area calculating means for calculating a total area of a toner adhering area on a photoreceptor using image data in the image area;
First replenishing amount setting means for setting a toner replenishing mechanism driving condition for replenishing an amount of toner according to a result of the calculation by the area calculating means; and a toner replenishing mechanism driving condition set by the first replenishing amount setting means. Second supply amount setting means for setting a toner supply mechanism drive condition for supplying a larger amount of toner, and supplying a larger amount of toner than the toner supply mechanism drive condition set by the second supply amount setting means. Replenishing amount setting means for setting a driving condition of the toner replenishing mechanism for detecting the toner density of the developer, a toner density detecting means for detecting a toner density of the developer, and a toner density detected by the toner density detecting means in a predetermined first density range. When the toner density is within the predetermined range, the first replenishment amount setting unit is selected. When the toner density is within a predetermined second density range that is lower than the first density range, the second replenishment amount setting unit is selected. Selecting means for selecting the third supply amount setting means when the toner density is within a predetermined third density range which is lower than the second density range. .