JPH04296782A - Method for controlling toner replenishment and image forming device using it - Google Patents

Abstract

PURPOSE:To prevent image density from being deteriorated caused by the shortage of toner replenishment even when the residual quantity of toner for replenishment in a toner storage part is small untill the toner in the toner storage part is spent out. CONSTITUTION:The total area of a toner adhereing area on a photosensitive body is calculated by using image data in an image area and toner adhereing quantity per unit area of the toner adhereing area on the photosensitive body is detected. When the concentration of the toner is within first concentration range, a driving time for rotating a replenishing roller 24 is calculated based on the toner adhereing quantity and the total area. When the concentration of the toner is within the second concentration range, the driving time for rotating is set to 2 seconds being a fixed value in order to replenish the sufficient quantity of the toner for keeping the image density even under a state that the residual quantity of the toner in a toner hopper 2 is reduced. Besides, when the concentration of the toner is within the third concentration range, the driving time for rotating is set to 4 seconds being the fixed value in order to spend all of the toner in the hopper 22.

Description

[Detailed description of the invention]

0001

[Industrial field of application] Pertains to image forming devices such as copying machines, facsimiles, and printers that visualize latent images formed by electrophotography as toner images, and in particular, relates to toner replenishment to developing devices. It is.

0002

2. Description of the Related Art In this type of image forming apparatus, for example, one using a two-component developer, toner consumption is controlled in order to maintain a constant toner concentration of the developer in a developing device in order to obtain a desired image density. It is necessary to replenish toner to the developing device accordingly. For this reason, in an image forming apparatus that forms an image based on image data, on the premise that a proportional relationship exists between the total number of dots in an image and the amount of toner consumption, It is known to calculate the amount of toner consumed by this calculation and replenish the developing device with toner corresponding to the toner consumption amount obtained by this calculation. 1986-
116973, JP-A-1-108070). In order to replenish the developing device with toner corresponding to this amount of toner consumption, for example, the rotation drive time of the replenishment roller that replenishes the toner from the replenishment toner storage section to the developing device is controlled in accordance with the amount of toner consumption. .

0003

However, when the amount of replenishing toner in a toner storage unit such as a hopper decreases due to continued copying operations, the same toner replenishing mechanism is not driven as when the remaining amount is sufficiently large. Under certain conditions, such as the rotation drive time of the replenishment roller, the amount of toner replenished from the toner storage portion to the developing device (hereinafter referred to as toner replenishment amount) decreases. For example, in FIG. 18, the vertical axis represents the toner replenishment amount per 30 seconds of rotation of the replenishment roller, and the horizontal axis represents the remaining amount of toner in the toner hopper. This is what is shown. In region A of this figure, a linear relationship is established between the amount of toner replenishment and the rotation time of the replenishment roller, and a stable toner replenishment of 300 mg/sec is performed, but the amount of toner remaining in the toner hopper is In region B where the amount of toner is decreasing, this relationship breaks down and the amount of toner replenishment decreases rapidly due to the decrease in the amount of remaining toner. Therefore, even though the remaining amount of toner in the toner hopper is decreasing as shown in area B, area A
Based on the toner replenishment amount per unit time,
When controlling the drive of the toner replenishment mechanism, there remains the problem that the toner concentration within the developing device decreases due to insufficient toner replenishment, and as a result, the image density decreases. In addition, such a toner storage unit itself is configured with a toner cartridge that is removable from the main body of the apparatus, and when the remaining amount of toner runs out, the empty toner cartridge is removed and discarded, and a new toner cartridge is installed. In image forming apparatuses, in order to omit an element for detecting the presence or absence of a remaining amount of toner in a toner cartridge, the toner density detection result by a toner density sensor or the like in a developing device is used. That is, when the toner concentration in the developing device decreases to a predetermined toner concentration by such toner concentration detection, a toner replenishment operation is performed for a predetermined time or a predetermined number of times, and the detected toner concentration remains unchanged. If the density does not rise above a predetermined level, it is determined that the toner in the toner cartridge has run out. In such a device that detects the presence or absence of the amount of toner remaining in the toner cartridge, even though the amount of toner remaining in the toner cartridge is decreasing as shown in area B above, area A
Based on the toner replenishment amount per unit time,
When executing the above toner replenishment operation and making a final determination as to whether or not there is replenishment toner, it is determined that there is no replenishment toner remaining, and an instruction to replace the toner cartridge is issued. There was also the problem that there was a risk of discarding a toner cartridge that still contained replenishment toner after removing it. In addition, the above-mentioned Japanese Patent Application Laid-open No. 62
Publication No. 116973 discloses that when the toner density detected by a toner density detection means disposed in the developing device is within a predetermined range, the amount of toner consumption is calculated based on image data, and the amount of toner consumed is calculated based on the image data. The developer is replenished with toner corresponding to the amount of toner consumed, and when the detected toner density is lower than the predetermined range, the toner is replenished a predetermined number of times during the replenishment time assuming that the image data is completely black, and this replenishment is performed within a predetermined range. It is described that a toner out display (toner near end display) is performed when the toner concentration does not return to the predetermined range even after a number of executions. In this case, there is only one threshold level, so if the threshold level is set to a relatively low toner concentration, the toner replenishment amount cannot be increased until the toner concentration becomes considerably thin, and vice versa. In addition, when the threshold level is set to a relatively high toner concentration, there is a problem that even if the toner concentration decreases slightly, the toner replenishment amount is increased and the toner concentration becomes higher than the appropriate toner concentration. Ta.

The present invention has been made in view of the above problems, and an object of the present invention is to appropriately control the amount of toner replenishment even when the amount of replenishment toner remaining in the toner storage section is low. As a result, it is possible to prevent a decrease in image density due to insufficient toner supply, and the toner storage section is configured with a container that can be detached from the main body of the apparatus, and the container can be replaced based on the result of detecting the toner concentration in the developing device. It is an object of the present invention to provide a toner replenishment control method that can use up the replenishment toner in the container even when instructed to do so, and an image forming apparatus using the method.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention calculates the total area of the toner adhesion area on the photoreceptor using image data in the image area, and a first replenishment mode in which the developer can be replenished with a predetermined amount of toner; a second replenishment mode in which the developer can be replenished with a predetermined amount of toner; and a second replenishment mode in which the developer can be replenished with a larger amount of toner than the predetermined amount. A third replenishment mode is provided, and the first replenishment 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 second density range, and the toner density is within a third predetermined density range that is lower than the second density range. The present invention is characterized in that the third replenishment mode is selected in the case where the third replenishment mode is selected.

[0006]

[Operation] When the toner concentration of the developer is within a predetermined first concentration range, the present invention calculates the total area of the toner adhesion area on the photoreceptor using image data in the image area. A first replenishment mode that allows toner to be replenished to the developing device according to the total area is selected, and thereby toner is replenished into the developing device approximately according to the toner consumption amount. Then, when the remaining amount of toner for replenishment in the toner storage section decreases, the amount of toner replenishment per replenishment operation of the toner replenishment mechanism decreases, and the toner concentration falls within the second concentration range, the amount of replenishment toner in the developing device decreases. The second replenishment mode that can replenish a fixed amount of toner is selected, thereby replenishing a sufficient amount of toner to maintain image density even when the amount of replenishment toner remaining in the toner storage unit is decreasing. . Further, when the toner concentration decreases and falls within the third concentration range, a third replenishment mode is selected that can replenish a larger amount of toner than the toner replenishment amount in the second replenishment mode, and thereby, This is to use up the replenishment toner in the toner storage unit.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a digital camera, which is an example of an image forming apparatus, will be described below. This digital copying machine is comprised of a reading device (scanner) that is a document reading means, and a copying device (printer) that executes a series of processes for copying the 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 the image is reflected from the lower surface of the original according to the density of the original. Light is incident on a one-dimensional image sensor via a mirror and a lens, and while this one-dimensional image sensor detects one line in the main scanning direction on the original image, the two-dimensional image of the original is detected by the sub-scanning of the moving optical system. You can use something that reads images.

FIG. 1 shows a schematic configuration of the mechanical section of the copying apparatus in this embodiment. In FIG. 1, a 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 charger 2. This surface is irradiated with laser light from the writing unit,
The charged potential changes depending on the intensity of the light, and a potential distribution is formed depending on whether or not laser light is irradiated. The writing unit uses a semiconductor laser (
The laser beam emitted by the writing LD is irradiated onto the surface of the photoreceptor drum 1 through an optical system such as a rotating polygon, lenses, and mirrors, and this rotating polygon mirror is controlled at high speed by an electric motor. It is possible to use one that performs main scanning on the photoreceptor by rotating at high speed. Then, the control device applies a pixel-by-pixel position signal (recorded/not recorded) to be recorded to the writing LD so that each pixel position is synchronized with the rotational position of the rotating polygon mirror, and each scanning position of the image is Then, the laser light is controlled on/off depending on the density of that pixel (recorded/not recorded). This results in
The potential distribution formed on the photosensitive drum 1 corresponds to the density of the original image and constitutes an electrostatic latent image. This electrostatic latent image is transferred to a developing unit 4 located downstream of the writing unit.
The image is visualized by the toner supplied with the image. The developing unit 4 includes a developing device 21 equipped with a developing roller 20 that supplies toner onto a photoreceptor, and a toner hopper 22 that stores toner to be supplied to the developing device 21. An agitator 23 and a replenishment roller 24 are provided. On the other hand, the transfer paper fed out from a cassette (not shown) is fed onto the surface of the photoreceptor drum 1 via the registration rollers 9, and separated from the surface of the photoreceptor drum 1 after the toner image is transferred by the transfer separation unit 5. . When the transfer paper with the toner image transferred thereon passes through a fixing device (not shown), the toner image is fixed thereon, and the paper is ejected to a paper ejection tray (not shown). The photosensitive drum 1 is located between the developing unit 4 and the transfer separation unit 5.
An optical sensor 25 is provided on the surface to detect the amount of light reflected from the surface of the photoreceptor.

FIG. 2 shows a schematic configuration of the electrical equipment section of a digital color copying machine. Inside the housing of the reading device 10, there are a reading control circuit 20, a reading drive device 30, and an image reading circuit 40.
and an image processing circuit 50 are housed in the housing of the copying device 90, and an image information storage device 60, which is a storage means for storing read document information, a copying circuit 70, a system control device 61, and a system control device. 61 accommodates an operating device 80 which is an operating means for performing key input. This information storage device 60 consists of an image memory section 62 and the system control device 61 described above. The read control circuit 20, the write drive control circuit 71, and the operating device 80 included in the copy circuit 70 are connected to the system control circuit 61 through 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 drives the scanner motor 31.
, heater control of the fluorescent lamp 32, lighting instruction for the fluorescent lamp 32, control of the filter solenoid 33 for detecting the document size, and control of the scanner power supply cooling fan. The image reading circuit 40 has an amplifier 42 (the time per pixel is very short) that converts the light reflected from the original into an 80 dpi analog signal and divides the signal from the CCD 41 into odd numbers (ODD) and even numbers (EVEN) and amplifies the signal. switching element 43, which combines the ODD and EVEV signals from the amplifier 42 into a serial analog signal;
The analog signal from the fluorescent lamp 3 from the image processing circuit 50
Amplification degree instruction data A for correcting brightness fluctuations in step 2
It includes a variable amplifier 44 that amplifies by GC, an A/D converter 45 that converts an analog signal from the variable amplifier 44 into a digital signal, and the like. The image processing circuit 50 includes five gate arrays 51 to 55 and a clock generation circuit 5 to process image signals sent from the image reading circuit 40.
6, ROM57, RAM58, etc. Gate array 51 performs light amount detection, shading correction, timing control, command control, data editing/output, CCD drive clock generation, etc. Gate array 52
is for magnification in the main scanning direction, gate array 53 is for halftone processing,
The gate array 54 is responsible for binarization processing, document size detection, character/halftone separation and hollow editing, and the gate array 55 is responsible for mark area detection. The image memory section 62 is composed of a memory board and a memory control board. A system control circuit 61 controls the entire system and gives instructions for reading and writing image data. This system-wide control includes system readiness monitoring,
This includes detecting transfer paper size and remaining amount, instructing original reading and paper feeding start, controlling scanner copy mode and printer copy mode, etc., and grasping the remaining amount of memory when giving instructions for reading and writing image data. is being carried out. The copying circuit 70 includes a line driver circuit 72 that receives image data from the image memory section 62, a laser driver circuit 73 that amplifies 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. 390 includes a group of actuators of the paper feeding device (pickup solenoid, paper feeding clutch, tray lock solenoid, lift motor), serial parallel receiver, etc., and is connected to the 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 a conversion table 801 is connected to the video controller 800.
) is also input. This video controller 800 is shown in FIG.
As shown in the figure, it is configured as a part of the CPU 810, and receives external video data (EXTERNAL VIDEO DATA) from the input port of the CPU 810.
) is read and a conversion table 801 consisting of P-ROM is read.
The configuration is configured to output to . Input gate array 702
The sensor group 705 connected to the
analog), etc., and write LD feedback output (
Gate array 7 for inputting analog) and write synchronization detection signals
02 is input. In addition, the actuator group 707 connected to the output gate array 706 includes various clutches for paper feeding and conveyance, a main drive motor, a cleaning blade solenoid, a toner replenishment solenoid, a rotating polygon mirror motor, a fixing heater, and a high voltage for charging. It includes 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, and the LD output adjustment output of the optical sensor 25 is also output from this output gate array 706.

Next, toner replenishment control in this embodiment will be explained. In this embodiment, the total area of the toner adhesion area on the photoreceptor is calculated using image data in the image area, and the amount of toner adhesion per unit area of the toner adhesion area on the photoreceptor is detected. Then, from the detected toner adhesion amount (hereinafter referred to as the detected toner adhesion amount), the toner concentration of the developer falls within the first density range, second density range, and third density range as shown in FIG. 1(b). If the toner concentration is within the first concentration range, replenishment of toner to the developing device based on the toner adhesion amount per unit area and the total area. Calculate the rotation drive time of the roller. If the toner density is within the second density range, the replenishment roller 24 is operated to replenish a sufficient amount of toner to maintain the image density even when the remaining amount of toner in the toner hopper 22 is decreasing. The rotation drive time is set to a fixed value of 2 seconds. Further, if the toner concentration is within the third concentration range, the rotation driving time of the replenishment roller 24 is set to a fixed value of 4 seconds in order to use up the toner in the toner hopper 22.

First, calculation of the total area of the toner adhesion area will be explained. Conventionally, toner adheres to areas corresponding to black data (hereinafter referred to as dots) on the photoconductor, and the number of black data is related to the amount of toner consumption. In order to control the toner density (hereinafter referred to as toner density) at a constant level, it has been proposed to calculate the total number of black data in one image and determine the amount of toner replenishment based on this total number of black data. This is based on the premise that the amount of toner adhering per dot is constant, and the amount of toner consumed in forming one image is determined from the total number of dots in one image. However, the amount of toner adhering per dot varies depending on the writing conditions such as the amount of light and the toner density when writing one dot. For example, in the graph of FIG. 4, the vertical axis shows the toner adhesion amount per unit area, assuming that the dots are densely packed in a unit area of 1 cm2, and the horizontal axis shows the pulse width of the writing LD. , toner density is 3.2%, 2
．． The toner adhesion amount per unit area is shown for each case of 5% and 1.8%. Below the horizontal axis of the figure, specific multivalued data of black data (hereinafter referred to as LD
The figure shows the correspondence between the data (referred to as multivalued data) and the pulse width of the writing LD. As can be seen from this figure, even for one dot developed with a developer with the same toner concentration, the amount of toner adhesion differs depending on the pulse width of the writing LD (determined by the specific multi-value data of black data). Even for one dot where the pulse width of the writing LD is the same, the amount of toner adhesion differs depending on the toner concentration. Furthermore, in this example, combined with the fact that the LD multi-value data and the write LD pulse width are not in a proportional relationship,
The relationship between LD multi-value data and toner adhesion amount is not linear; for example, the toner adhesion amount for LD multi-value data 0001 is L.
This does not correspond to 1/16 of the toner adhesion amount of the D multi-value data 1111. Therefore, in general, the toner adhesion amount is determined by the LD pulse width and the toner concentration, and can be expressed as in the following equation (1) using a function F that defines the correspondence relationship. (toner adhesion amount)=F [(LD multi-value data), (toner density data)]...(1) The correspondence relationship expressed by this function F can be obtained, for example, as follows.

FIG. 5 shows the LD multivalue data at a toner concentration of 2.5%, which was determined experimentally by taking the LD multivalue data on the vertical axis and the toner adhesion amount per unit area on the horizontal axis 1. 3 is a graph showing a correspondence curve a between data and toner adhesion amount per unit area. The horizontal axis 2 below this horizontal axis 1 is
This is for reading the value of consumption data corresponding to the amount of toner adhesion. On this horizontal axis 2, LD multivalue data 1
For example, if the scale of point b' on the horizontal axis 2 corresponding to the maximum value of the toner adhesion amount per unit area (value indicated by point b) corresponding to 111 is 15, on the horizontal axis 2 corresponding to the toner adhesion amount 0, For example, set the scale of point a' to 0, and this point b
Divide the area between '(15) and a'(0) into equal intervals and take a scale. Using this vertical axis, horizontal axis 2, and the corresponding curve a,
Read the scale on the horizontal axis 2 corresponding to the LD multi-value data, and calculate the LD multi-value data and consumption data (
The correspondence shown in Table 1 below can be obtained as a correspondence with multivalued data). Here, LD multi-value data 1111
The scale of point b' on the horizontal axis 2 corresponding to the maximum value of toner adhesion amount per unit area (value indicated by point b) corresponding to 15
However, it is not limited to this, and if you want to detect the amount of toner adhering per unit surface with higher precision than in this example, you can use a constant larger than 15, and conversely, you can use a constant larger than 15. When detecting a drop, a small constant may be used. For other toner densities, instead of using the corresponding curve a above, L is calculated experimentally for each toner density.
Using the correspondence curve between the D multi-value data and the toner adhesion amount per unit area, and also the horizontal line corresponding to the maximum value of the toner adhesion amount per unit area (value indicated by point b) corresponding to the LD multi-value data 1111. The ratio of the scale of point b' on axis 2 to the scale (15) for the above toner concentration of 2.5% is:
Set the ratio to be the same as the maximum value of the toner adhesion amount for this toner concentration and the maximum value for the above toner concentration of 2.5%, and do the same with the LD multi-value data and consumption data ( (multivalued data).

[0015]

By the way, in this example, the shapes of the correspondence curves between the LD multi-value data and the toner adhesion amount per unit area do not differ greatly at each toner density, as shown in FIG. Ratio between consumption data in density (for example, in the case of toner density 2.5%, 15:15:
14:13:11:10:8:7:6:4:...) can be approximated to be the same for each toner density, as shown in Table 2. The constants Mi exemplified in this Table 2,
Mj is the maximum value of toner adhesion amount per unit area when the toner concentration is 1.8% and 3.2%, and the above toner concentration 2.
This is the ratio to the maximum amount of toner adhesion per unit area in the case of 5%.

[0017]

That is, in this example, in the above formula (1),
As a special case, the function MA and the function F as shown in equation (2) below
It can be expressed approximately as a product of 1. (toner adhesion amount) = MA [(toner density data)]
・F1 [(LD multi-value data)]


...(2) Here, the function F1 changes the pulse width of the write LD as the write condition for one dot (for example, the LD
The pulse width is changed from 0 to 50 nsec in accordance with multi-value data 0000 to 1111), and thereby the potential on the photoreceptor and the area of one dot change, and the amount of toner adhesion changes. This potential change on the photoreceptor changes the amount of toner adhesion per dot, which is the same as the change in the area of one dot, so both changes can be treated as a change in the toner adhesion area per dot. I can do it. Therefore, the above consumption data can be treated as data regarding the toner adhesion area. On the other hand, the function MA can be treated as representing the amount of toner adhesion per unit area, that is, the toner adhesion rate.

Therefore, in this example, instead of calculating the toner consumption amount for one image by simply calculating the total number of black data as in the conventional case, we calculate the correspondence corresponding to the function F1 and the function MA. Experimentally find the correspondence relationship corresponding to the function F1, convert the LD multi-value data to consumption data for each dot in one image, and convert the consumption data into consumption data for each dot in one image. The total sum in the image is calculated to find the total toner adhesion area in one image, while the toner density is detected and the toner adhesion rate is calculated from this toner density using a correspondence relationship corresponding to the function MA. The amount of toner consumed in one image is determined by multiplying the total area by the toner adhesion rate.

First, a calculation for calculating the total toner adhesion area using image data will be explained. FIG. 6 shows a counting circuit for converting LD multi-value data into consumption data for this purpose. This circuit mainly uses a conversion table 81 for converting LD multi-value data to consumption data.
It is comprised of an adder 811, a flip-flop 812 for positioning, a counter 813, etc., for counting consumption data and calculating the total toner adhesion area. This adder 811, flip-flop 812 for positioning
, counter 813, etc., are connected to the video controller 800 (
(see Figure 2). Also, conversion table 810
As mentioned above, the P-RO is connected to the CPU 810 in which the video controller 800 shown in FIG. 7 is configured.
It is composed of M801. The LD multi-value data inputted to the video controller 800 (CPU 801) as external video data is then input to the video controller 800 (CPU 801).
The consumption data from the conversion table 810 is input to the video controller 800 (CPU 801) and counted.

In FIG. 6, first, LD multi-value data is converted into consumption data using a conversion table 810, latched by a first-stage flip-flop 814, and then the data is sent to an adder 811. The adder 811 calculates the sum of the input data and the remaining data from the previous time, and outputs the result as a carry to the next stage counter. This adder 81
1, the performance is determined by input consumption data (multilevel data level). For example, if the consumption data is 3 to 4 values, use 2 bits and 2 bits, if it is 5 to 8 values, use 3 bits and 3 bits, and if the consumption data is 9 to 16 values, use 4 bits. and 4 bits are used. In this way, the size of the adder 811 is determined depending on the number of bits of data. FIG. 8 is a timing chart showing the timing when a carry is issued, and the consumption data is 4-bit data (0000 to 1111).
) is an example. The counter increments the count each time a carry is input, and by counting the carry, total toner adhesion area data is obtained as the sum of consumption data. This counter is connected to the signal FGATE which remains ON during the writing period of the effective image area.
Counts up only when the is ON, and this is OFF
Cleared when falling into state. Further, the output of the counter is latched into a flip-flop when FGATE falls, and the CPU reads this. The toner adhesion area data read here is represented by the upper 8 bits.

As described above, it is possible to obtain the total area of the toner adhesion area, taking into account the size of the toner adhesion area per dot according to the LD multi-value data. In the configuration of this example, counting can be performed in the same way whether the input to the conversion table is code data or binary data (0000 or 1111).

In this example, the total consumption data is converted into consumption data of the LD multi-value data 1111, and the upper 8 bits after conversion are read by the CPU and used as toner adhesion area data. Here, for example, A3 size (420
×297), the total number of dots is 1 from the formula (1) below.
110110000000101000011110B
Therefore, the upper 8 bits are 0eCH, and the total image data is 11100110100111111100111101 from the formula (2) below, excluding 2 mm at each end.
B, and the upper 8 bits are 0e6H, and from this, C
If the toner adhesion area data read into the PU is 0e6H, LD is applied to the entire A3 (excluding 2 mm from the edge).
This corresponds to an image written with multivalued data 1111. (Total number of dots) = 420 x (400/25.4) x 29
7×(400/25.4)
=30935582 (dots)
=11101100000001010000
11110B

…
(1) (Total image data) = (420-4) x (400
/25.4)×(297-4)
×(400/25.4)
=30228285 (dots) =11100110
10011111100111101B


...(2)

FIG. 9 shows
It is a flowchart of the reading control of the output of the counter latched by the said flip-flop by CPU. In step 1, toner adhesion area data (LDCNT), which is the output of the counter latched in the flip-flop, is read. Since this LDCNT can only read the upper 8 bits as described above, the LDCNT read in step 2
It is determined whether NT is 0 or not, and if it is 0, 1 is stored in the register LDCNT as LDCNT data in step 3, and then this LDCNT data is stored in the register LDONCT in step 4. Conversely, if it is not 0, the read LDCNT is stored in the register LDONCT.

Next, the detection of toner concentration for calculating the toner adhesion rate will be explained. The detection of toner density in this embodiment does not directly detect the toner density in the developing device, but rather forms a predetermined electrostatic latent image (hereinafter referred to as a reference pattern latent image) on the photoreceptor and uses this reference pattern as a latent image. The optical density of a developed image (hereinafter referred to as a reference pattern toner image) obtained by developing a pattern latent image with a developing device is detected, and the toner concentration 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 a non-image area using the same laser beam used for writing in the image area to form a reference pattern latent image. After this reference pattern latent image is conveyed to a developing device by rotation of the photoreceptor and developed, it is made to face the optical sensor 25. The light receiving portion of the optical sensor 25 is turned on, and the non-pattern portion (the background portion of the photoreceptor) is read by the light receiving element, and the reference pattern toner image portion is also read in the same manner. At this time, the lower the toner concentration in the developing device, the smaller the amount of toner that adheres to the reference pattern toner image, and conversely, the higher the toner concentration, the greater the amount of toner that adheres to the reference pattern toner image. To detect. Here, the background part is also detected by taking the ratio of the detected value of the background part and the detected value of the reference pattern toner image part, and detects the eccentricity of the photoreceptor drum and the detection value of the optical sensor 25.
This is to offset the effects of toner contamination. below,
Outputs the optical sensor output of reading the surface of the photoconductor VSG,
The optical sensor output for reading the reference pattern toner image portion is referred to as output VSP.

Next, a description will be given of control when the detection output of the background portion or the reference pattern toner image portion is an abnormal value. If toner, paper dust, etc. adhere to the surface of the optical sensor 25 over time, the sensor output will decrease, making it impossible to obtain sufficient SN characteristics, resulting in false detection of toner concentration.
Sudden fluctuations in toner concentration due to excessive toner supply, etc., or toner concentration that deviates significantly from the target toner concentration,
There is a risk that the toner concentration will run out of control. As mentioned above,
Output VSG and detection output VSP of reference pattern toner image area
(hereinafter referred to as output VSP) or adjusting the output of the optical sensor 25 contributes to preventing the occurrence of such a situation, but there are limits to this as well, such as the adhesion of toner, etc. If the amount becomes too large, it will not be possible to cope with the problem, and the above problem will occur. Therefore, in this example, if the output of the optical sensor 25 is not within a preset range, it is determined that there is an abnormality, and the output is not used for calculating the toner concentration, but instead , the toner density is calculated using data set in advance. Specifically, if the output VSG is smaller than 2.5 or the output VSP is 2.5V or more, it is determined that there is an abnormality and the toner density is adjusted using preset data. calculate.

Specific control of reading the detection output of the optical sensor 25, including control when the detection output of the optical sensor 25 is abnormal, will be explained with reference to FIG. First of all,
In step 1, it is determined whether the optical sensor 25 has finished detecting the photoreceptor background portion and the reference pattern toner image portion;
When the detection is completed, in steps 2 and 3, it is determined whether the detection output of the optical sensor 25 is abnormal or not. A 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 preset appropriate values of VSG 4.0 volts and VSP 0.25 volts are stored in registers VSG and VSP. Next, in steps 4 and 5, the contents of the registers DVGNEW and DVPNEW in which the latest outputs VSG and VSP are stored are changed to the registers DVGNEW and DVPNEW in which the outputs VSG and VSP related to the previous detection are stored.
After updating and storing GOLD and DVPOLD, the registers VSG and VS related to the current detection are updated in steps 6 and 7.
The contents of P are updated and stored in the registers DVGNEW and DVPNEW. This completes reading of the output VSP and VSG.

Next, the above registers DVGNEW, DVP
The calculation of toner density using the outputs VSG and VSP stored in NEW will be explained. In this example, there is a certain relationship between the ratio VSP/VSG of the output VSG (V) and the output VSP (V) and the toner concentration in the developing device as shown in the first quadrant of FIG. Therefore, this relationship is stored in RAM as a data table, for example, and after reading the outputs VSG and VSP at the optical sensor 25, VSP/V
Look up this data table in SG and select developer 2.
Find the toner density of 1.

The second quadrant of FIG. 11 shows the correspondence between the toner concentration and the toner adhesion amount per unit area, with the above-mentioned toner adhesion amount per unit area taken on the horizontal axis. From the characteristics, the function MA in equation (2), that is, the correspondence between toner concentration and toner adhesion rate can be determined. The correspondence between this toner concentration and toner adhesion rate is stored in a data table.

In this example, when an image with a large amount of toner consumption, such as a black solid image, is formed, toner is replenished according to the amount of toner consumption, as will be described later, so that a good image can be obtained. In some cases, an amount of toner temporarily exceeds the developer agitation capacity of the developing device 21 to sufficiently charge the toner. If the reference pattern toner image is read by the optical sensor 25 immediately after replenishing such an amount of toner (and the reference latent image is developed for this purpose), temporary damage may occur due to insufficient stirring of the developer (carrier) and toner. Due to insufficient toner charging, the amount of toner adhering to the reference latent image is smaller than when the toner is properly charged. For this reason, the optical density of the reference pattern toner image becomes thinner than when it is developed with an appropriate toner charge amount, and as shown in FIG. 12, the output VSP of the optical sensor 25 becomes high. In FIG. 12, the horizontal axis represents the area ratio of the image related to the copy operation immediately before the sensor reading timing ({toner adhesion area/A3 (4
20 x 297) area} x 100%), and the output VSP at the time of sensor reading is plotted on the vertical axis, and when the actual toner density is 1.8%, 2.0%, and 2.7%, It shows the relationship between the area ratio of the image related to the copy operation immediately before the sensor reading timing and the output VSP at the time of sensor reading. It can be seen that at any toner density, the output VSP increases as the area ratio increases. Therefore, if the sum of the image consumption data related to image formation immediately before the optical sensor reading timing, that is, the sum of the toner adhesion area is greater than a certain value, the read VSP is
Correct as shown. Note that the VSP read is corrected using not only the sum of image consumption data related to image formation immediately before the optical sensor reading timing, that is, the sum of toner adhesion areas, but also the sum of toner adhesion areas from a plurality of sheets before. You can also do it.

In FIG. 13, the horizontal axis represents the area ratio determined from the toner adhesion area data related to the copying operation immediately before the sensor reading timing, and the vertical axis represents the number of corrected bits of the VSP data. One bit of this correction bit number corresponds to approximately 0.02V of the optical sensor 25 output (5V/25
5). This number of correction bits is determined in advance through experiments. By correcting this VSG data, it becomes possible to obtain accurate toner concentration (toner concentration after sufficient stirring operation).

Specific control of the above calculation of toner concentration and calculation of the toner adhesion rate MA will be explained with reference to FIG. 14. First, the output VSP read from the register DVPNEW in step 1 is stored in the register D.
Using the output VSG read from VGNEW, the output V
It is converted to VSP data when SG is 4.0 volts and stored in register A. Here, in order to convert to VSP data when the output VSG is 4.0V, the reason why the output VSP is multiplied by the constant 204 is because the optical sensor 25
data is read from an 8-bit analog port with an upper limit of 5V (255 x 4V ÷ 5V = 204)
. Next, in step 2, it is determined whether the VSP data value is greater than 40, and if it is greater than this, register A is corrected to 40 (step 3). This is because of the size of the data table used to calculate the toner density from the VSP data, that is, the ratio of output VSP and VSG.
This is approximated as data 40. Next, in steps 4 and 5, it is determined whether the VSP data is 0 or not, and if it is 0, it is corrected to 1 (step 5), and if it is not 0, it is directly proceeded to the next step. This is also approximated based on the size relationship of the data table. Then, in steps 6 to 10, the VSP data shown in FIG. 13 described above is corrected using LDCNT. Here, LDCNT1
84 corresponds to an area ratio of 80%, LDCNT138 corresponds to 60%, and LDCNT69 corresponds to 30%. Although not shown in the flowchart, if the result of the subtraction processing in steps 9 to 11 is smaller than 1, it is set to 1. Next, in step 12, the VSP data, that is, the output VSP and the output VS
After searching the data table in which the correspondence between the G ratio and the toner density is stored, reading the toner density data and storing it in the register A, in step 13, the data table is stored in the register D.
Store in BTDEN. Next, in step 14, using the toner density data stored in register A, a data table storing the correspondence between toner density and the above-mentioned 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 register A is stored in register DBTNMA.

Using the toner adhesion area and toner adhesion rate for one image obtained in the above manner, the amount of toner consumed by this one image is calculated. Specifically, the product of the toner adhesion area data and the toner adhesion rate data is calculated to determine the amount of toner consumed per image formed on one sheet.

Next, the calculation of the amount of toner replenishment will be explained. Ideally, if the driving conditions of the toner replenishment mechanism were controlled so that the toner replenishment amount matched the toner consumption amount determined by the above calculation, the toner concentration would be kept constant, but in reality, as described above, In addition to the fact that the calculated toner replenishment amount does not necessarily match the actual amount of toner replenished due to machine-to-machine variations in the toner replenishment mechanism and environmental changes, in this example, the target toner concentration may vary due to the following reasons. A misalignment will occur. That is, in this example, the toner concentration of the developer in the developing device 21 is set to
Since the optical density is determined 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 This also creates a burden of cleaning the reference pattern toner image. Therefore, as described above, the toner density is detected every 10 image formations, and during the 10 image formation after the detection, the toner adhesion rate MA calculated using the detected toner density and each image forming operation are The amount of toner consumed per image formation on one sheet is calculated from the total toner adhesion area calculated in . However, since the toner density changes during the image formation on 10 sheets after this toner density detection, an error occurs between the above toner consumption amount and the actual toner consumption amount, and as a result, the toner density deviates from the target toner density.

Therefore, in this embodiment, in addition to the latest toner concentration detection result, the toner concentration according to the latest toner concentration detection is compared with the toner concentration according to the previous toner concentration detection. The amount of toner replenishment is determined by taking into consideration the change in toner concentration.As a result, if the actual toner concentration deviates from the target toner concentration,
The toner density is quickly converged to the target.

That is, from the latest toner concentration detection results, if the detected toner concentration is higher than the target toner concentration, the toner replenishment amount is made smaller than the toner consumption amount, and conversely, if the detected toner concentration is higher than the target toner concentration If the toner concentration is low, the toner replenishment amount should be made larger than the toner consumption amount, and if the previously detected toner concentration is lower than the latest detected toner concentration (the toner concentration is on a downward trend), the toner supply amount should be increased. Set the replenishment amount to be greater than the toner consumption amount, and conversely, if the previously detected toner concentration is higher than the latest detected toner concentration (when the toner concentration is on the rise), set the toner replenishment amount to be greater than the toner consumption amount. The amount of toner replenishment is determined from the viewpoint of reducing the amount of toner.

In order to determine the amount of toner replenishment from the above point of view, in this example, the variable GA for calculating the amount of toner replenishment is
IN is used. Below, the variable GAIN in this example
This will be explained in detail. The variable GAIN corresponds to the ratio between the toner supply amount and the toner consumption amount, and when this is 1.0, the toner supply amount and the toner consumption amount are equal. and,
When the latest detected toner concentration is lower than the target toner concentration, this variable GAIN is made larger than 1.0 to increase the toner concentration, and this increase is calculated by taking into account the above-mentioned toner concentration transition. Let them decide. Similarly, if the latest detected toner concentration is higher than the target toner concentration, this variable GAIN is made smaller than 1.0 to lower the toner concentration, and this decrease is applied to the above toner concentration transition. Make sure to consider it before making a decision.

The specific value of this variable GAIN varies depending on the characteristics of the developing device 21 and the toner replenishment method, and is determined experimentally. An example is shown below. When the latest detected toner concentration is lower than the target toner concentration and the previous detected toner concentration is also lower than the target toner concentration, the GAIN value is 1.4 to 2.3.
The latest detected toner concentration is lower than the target toner concentration.
In addition, when the previously detected toner concentration is higher than the target toner concentration, the value of GAIN is 1.3 to 3.0, and when the latest detected toner concentration is higher than the target toner concentration and the previously detected toner concentration is The value of GAIN is 0.5 to 0.8 when the toner concentration is lower than the target toner concentration, and the latest detected toner concentration is higher than the target toner concentration, and the previously detected toner concentration is also lower than the target toner concentration. GAI when high
The value of N is set in the range of 0.6 to 1.0. Specifically, the settings are as shown in Table 3 below. In addition, A in the vertical direction in Table 3 below
=0 to 4 correspond to the latest detected toner concentrations, and horizontal tables 1 to 5 correspond to the previously detected toner concentrations. These 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. Tables 1 to 5 among these correspond to data tables for searching GAIN data from each A category.

The specific control for determining GAIN will be explained using FIGS. 15 and 16. First, in step 1, similarly to step 1 in the flowchart of FIG. 14 described above, the output VSP read from the register DVPNEW is
Using the output VSG read from the register DVGNEW, it is converted into VSP data when the output VSG is 4.0 volts and stored in register A, and in step 2 this is stored in register DBPNEW. This register DBPNE
Before storing in W, the correction processing of steps 6 to 11 in the flowchart of FIG. 14 described above may be performed. Then,
Similarly in steps 3 and 4, the output VSP read from the register DVPOLD is converted into VSP data when the output VSG is 4.0 volts using the output VSG read from the register DVGOLD, and stored in the register A.
This is stored in register DBPOLD. Then, in steps 5 to 13, first, using the VSP data at the time of previous detection read from the register DBPOLD, which data table in Table 3 is to be used is selected. Next, in steps 14 to 19, the category A in Table 3 is determined using the latest detected VSP data read from the register DBPNEW. Then, in step 23, the data table selected as described above is searched using the determined classification A, and the searched GAIN data is stored in register A. In step 24, this is stored in the register DB.
Store in GAIN.

FIG. 17 shows the toner replenishment amount calculation using GAIN and the like determined as above. In FIG. 17, first, in step 1, it is determined whether the predetermined VSP data read from the register DBPNEW (see second step in FIG. 15) is equal to or higher than 0.6V, which is the first concentration range. If the VSP data is not 0.6V or higher, in step 2 the near-end counter is set to 0, and in step 3 the VSP data is set to 0, which is within the second concentration range described above.
．． It is determined whether the voltage is 55V or more (and less than 0.6V). If the VSP data is not higher than 0.55V (that is, if it is in the first density range described above), calculate the product of the toner adhesion rate data read from the register DBTNMA and the toner adhesion area data read from the register LDCNT in step 4. to obtain the toner consumption data and store it in the register DBADDT.In step 5, this register DB
The toner consumption data read from ADDT is multiplied by the GAIN data read from register DBGAIN to obtain toner replenishment amount data, and the data is sent to register DBADDL.
/H. As a result, as the first supply mode,
The toner replenishment operation time is set so that the toner replenishment amount corresponds to the toner consumption amount determined from the total area of the toner adhesion area on the photoreceptor and the toner adhesion rate. In this example, the toner replenishment amount is expressed as DBA, which is toner consumption data per sheet.
It is calculated by the product of DDT and GAIN, but instead of this, the following formula (
3) may be obtained. DBADDT+(1-GAIN)×A
…(3
) However, A is a constant. Also in the calculation of this equation (3), a difference is made between the toner consumption amount and the toner replenishment amount in response to the detected toner concentration and the toner concentration transition, and an operation is performed to bring the toner concentration closer to the target toner concentration. . On the other hand, in step 3, the VSP data is 0.55.
If it is determined that the voltage is equal to or higher than V (less than 0.6 V from step 1), a fixed value of 2 seconds is stored in register DBADDL/H in step 6. As a result, the second replenishment mode is set to a longer toner replenishment operation time that can increase the toner concentration in the developing device regardless of the total area of the toner adhesion area on the photoreceptor. Note that instead of setting a fixed value such as 2 seconds as the replenishment operation time in the second replenishment mode, the toner replenishment operation time (
The replenishment operation time can be set to a value obtained by adding a predetermined fixed value to steps 4 and 5), the toner replenishment operation time in the first replenishment mode can be set to a value multiplied by a predetermined value, or any of these values can be set. may be changed depending on the size of the image area (or transfer paper). Further, if it is determined in step 1 that the VSP data is 0.6V or higher, 4 seconds, which is the register DBADDL/H, is stored in step 7. As a result, the third replenishment mode is set to a replenishment operation time longer than the replenishment operation time in the second replenishment mode, so that no replenishment toner remains in the hopper. And step 8
Increment the near-end counter in step 9.
Then, it is determined whether the content of the near-end counter is greater than or equal to a predetermined count value n. If the content is not n or more, the process returns to the main flow, and if it is n or more, a toner near end display is performed in step 10.

Next, the toner replenishing operation will be explained. Toner is replenished according to this amount of toner consumption. The amount of replenishment toner is set based on the rotation driving time of the replenishment roller 24. As described above, the toner consumption amount per image is the product of the toner consumption area and the toner adhesion rate, and specifically expressed as the following equation (4). (Toner consumption) = LDCNT x 217 x MA x 1
/(400/2.54)2
≒LDCNT×MA×655/124
...(4) Here, (toner consumption)
The unit of is mg, the unit of LDCNT×217 is dot, M
The unit of A is mg/cm2, 1/(400/2.54)2
The unit of is cm2/dot. In addition, 21 to LDCNT
The reason why it is multiplied by 7 is that the toner adhesion area data LDCNT is expressed in the upper 8 bits as described above. On the other hand, toner replenishment in this example is performed by rotating the replenishment roller 24 driven by a clutch, and as shown in FIG. 18, in region A where the amount of toner replenishment per unit time is stable, 300 mg/sec of toner Replenishment will take place. FIG. 18 shows the relationship between the remaining amount in the toner hopper 22 and the toner replenishment amount, with the vertical axis representing the toner replenishment amount per 30 seconds and the horizontal axis representing the remaining amount of toner in the toner hopper 22. It is something. Then, the toner replenishment amount in the first replenishment mode is calculated by multiplying the toner consumption amount by GAIN, and when this is converted into replenishment time (rotation time of the replenishment roller 24), it is calculated as shown in equation (5) below. Become. (Replenishment time) = (toner consumption) x GAIN x 1/
300 ≒LDCNT×M
A×131/124×60…(5
) The unit of this (replenishment time) is seconds. During this replenishment time, the clutch is turned on to replenish toner. In the above-described flowchart, constant processing (×131, 124×60, etc.) for matching the above-described unit systems is omitted.

Note that if the drive source for the image forming operation (the motor that drives the drum 1 and the registration roller 9) and the drive source for the developing device 4 (the motor that drives the mag roller and the supply roller 24) are provided independently, , an electromagnetic clutch for replenishment is turned ON for a time corresponding to replenishment amount data DBADDL and DBADDH at an arbitrary timing of feeding each recording paper. As a result, the agitator 23 inside the toner hopper 22
and drives the replenishment roller 24 to replenish toner into the developing device 21. In addition, when the above drive sources are the same, it is recommended to perform toner replenishment operation at the time of recording or at the timing when the toner image on the photoreceptor 1 has finished being transferred, in order to prevent image deterioration due to load fluctuations of the drive sources. preferred.

As described above, in this embodiment, the reference toner image is detected every predetermined number of sheets by the optical sensor, and the toner concentration TC' is determined.
is calculated, and if necessary, this is corrected using the sum LDCNT of the toner adhesion area data related to the immediately preceding copy to obtain the toner concentration TC. At this TC, the toner adhesion rate MA per unit area is calculated and stored in a register. Further, this TC is compared with the TC related to the previous detection, and a variable GAIN is calculated from the change in toner density and stored in a register. Then, the amount of toner replenishment is calculated by multiplying the LDCNT counted for each copy by MA and GAIN read from the register, and toner is replenished for each copy. Thereby, it is possible to converge to the target toner concentration, and a stable developing ability of the developing device 4 can be obtained. Then, when the remaining amount of toner in the toner hopper 22 becomes low and the toner replenishment amount decreases with respect to the rotation time of the replenishment roller 24 and the toner density becomes thin, the replenishment roller rotation time is promptly changed to a time that can replenish a predetermined amount of toner. , As a result, when copying originals with low toner consumption, if the toner replenishment amount setting using MA and GAIN is maintained as described above, it will not be possible to replenish enough toner to increase the toner density that has become thinner, and the toner will become thinner. This can prevent the toner density from remaining the same. If the toner concentration does not increase even after this and becomes thinner, the replenishment roller rotation time is changed to a longer one, thereby making it possible to use up the toner in the toner hopper 22.

Incidentally, FIG. 19 shows the execution timing of each control and the usage relationship of each calculation result in the above embodiment, based on the timing of the copy operation. In the figure, "△" indicates the sensor check timing,
1st image after turning on the main switch of the image forming device and 1st image after that
Set for each 0 sheet. At this timing, the optical sensor 25
Read the pattern on the photoconductor 1, output VSG, output V
Obtain SP. "TC'" indicates toner concentration calculation, and the toner concentration (TC) in the developing device 21 is calculated from the output ratio of the output VSG and the output VSP. "TC" indicates toner concentration correction, which checks the toner adhesion area (LDCNT) of the recording paper immediately before the sensor check timing, and checks the toner adhesion area (LDCNT) of the recording paper just before the sensor check timing. ), the toner density is corrected to a value darker than TC'. Let the toner density after correction be TC. "M
A" indicates calculation of toner adhesion rate. Since the amount of toner adhesion per unit area on the photoreceptor 1 differs depending on the toner concentration even under the same process conditions, the adhesion rate MA is determined from the data table from the value of TC. "LDCNT" indicates the calculation of the toner adhesion area, and this is image data (multi-value data, etc.)
Convert to toner adhesion area using a data table,
The total toner adhesion area LDCNT per recording paper is determined. "uT." indicates the calculation of toner consumption, and the toner consumption uT. is calculated as the product of adhesion rate MA and toner adhesion area LDCNT. Calculate. "GAIN" indicates the calculation of the variable GAIN, and the detected VSG, VSP and the previously detected V
Compare SG and VSP and determine the target toner concentration TC (VSG
, VSP). Variable GA to adjust the supply amount so that
Ask for IN. "ADDT" indicates the toner supply amount calculation, and the consumed toner amount uT. The toner replenishment amount is calculated as the product of the variable GAIN and the variable GAIN. In the above-described flow, the amount of toner replenishment is determined for each recording paper, and toner replenishment is executed. However, the variable G
AIN is changed at each sensor check timing.

As described above, in this embodiment, in order to detect the toner adhesion rate, which is the amount of toner adhesion per unit area on the photoreceptor 1, the optical sensor 25 is used to determine the toner concentration of the developer in the developing device 21. However, instead of this, a toner density sensor may be provided inside the developing device 21. Further, although the toner density is detected every predetermined number of sheets, instead of this, it may be detected every time. Furthermore, when the output of the optical sensor 25 is not within a predetermined range, the value of the preset data table is read out (step 5 in the flowchart of FIG. 10 and subroutine CHKV of FIG. 14), and this value is sent to the optical sensor 25. Data corresponding to the output of (VSG
data, VSP data) to calculate the toner adhesion rate (flowchart in FIG. 18), calculate the toner replenishment amount based on this toner adhesion rate and the toner adhesion area, and thereby calculate the toner adhesion rate. The replenishment amount calculation means is configured, but instead of this, when the output of the optical sensor 25 is not within a predetermined range, a value is used as substitute data in place of the toner adhesion rate data corresponding to the output of the optical sensor 25. is set in the data table in advance, and the optical sensor 25
When the output is not within a predetermined range, substitute data for the toner adhesion rate data may be read from this data table, and the toner replenishment amount may be calculated based on this substitute data and the toner adhesion area. . In addition, in the above embodiment, as mentioned above, the above equation (2) was established as a special case of the above equation (1), but such equation (2)
) does not hold, and as a result, if it is necessary to convert the toner consumption amount per dot into consumption data using both the multi-value data of the image and the toner density, the consumption data is converted from the multi-value data of the image. It is sufficient to provide a data table for each toner density to search for. The toner density data for this purpose may be obtained by detecting the toner density every time, or if 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 differs depending on the pulse width of the writing LD, the multi-value data of the image is converted into consumption data, and the total amount of consumption data per image is calculated as follows: However, even if the pulse width of the writing LD is constant, the amount of toner adhesion changes depending on the density of dots in the image.For example, the amount of toner adhesion may increase due to edge effects during development. Even if the amount of toner adhesion changes depending on whether the distance between the dots is close enough to cause Use this as a conversion table from multi-value data to consumption data, convert the multi-value data of an image to consumption data, and calculate the toner adhesion area per image by the sum of this consumption data per image. demand. In addition, in the above embodiment, various data tables are used, but those that can be replaced with an arithmetic expression are replaced with an arithmetic expression, and instead of searching the data table, the arithmetic processing of this arithmetic expression is executed. Also good.

[0045]

According to the invention as claimed in claim 1, when the toner concentration of the developer is within a predetermined first concentration range, image data in the image area is used to determine the toner adhesion area on the photoreceptor. A first replenishment mode is selected in which the total area is calculated and toner is replenished into the developing device according to the total area, thereby replenishing the developing device with toner approximately corresponding to the toner consumption amount. Then, the remaining amount of replenishment toner in the toner storage section decreases, and the amount of toner replenishment per replenishment operation of the toner replenishment mechanism decreases.
When the toner density falls within the second density range, a second replenishment mode is selected that allows replenishing the developing device with a predetermined amount of toner, thereby reducing the amount of replenishment toner in the toner storage section. It is possible to replenish a sufficient amount of toner to maintain image density even when Further, when the toner concentration decreases and falls within the third concentration range, a third replenishment mode is selected that can replenish a larger amount of toner than the toner replenishment amount in the second replenishment mode, and thereby, It is possible to use up the replenishment toner in the toner storage section. Further, according to the invention of claim 2, in the invention of claim 1, when the third replenishment mode is selected consecutively a predetermined number of times, a toner near-end display is performed. It is possible to notify the replacement of the toner storage unit, etc. Furthermore, according to the invention of claim 3,
Area calculation means for calculating the total area of the toner adhesion area on the photoreceptor using image data in the image area, and toner replenishment mechanism driving conditions for replenishing an amount of toner according to the calculation result of the area calculation means. a first supply amount setting means for setting;
a second replenishment amount setting means for setting a toner replenishment mechanism driving condition for replenishing a larger amount of toner than the toner replenishment mechanism driving condition set by the first replenishment amount setting means; and a second replenishment amount setting means. a third replenishment amount setting means for setting a toner replenishment mechanism driving condition for replenishing a larger amount of toner than a set toner replenishment mechanism driving condition; a toner concentration detection means for detecting the toner concentration of the developer; When the toner density detected by the density detection means reaches a predetermined first value,
The first replenishment amount setting means is selected when the toner concentration is within the density range, and the second replenishment amount setting means is selected when the toner density is within a predetermined second density range that is lower than the first density range. and selecting means for selecting the third replenishment amount setting means when the toner concentration is within a predetermined third concentration range that is lower than the second concentration range. It is possible to replenish a sufficient amount of toner to maintain image density even when the remaining amount of replenishment toner is decreasing, and furthermore, it is possible to use up the replenishment toner in the toner storage section. An image forming apparatus can be provided.

[Brief explanation of drawings]

FIG. 1(a) is a schematic configuration diagram of the vicinity of a photoreceptor of a digital copying machine according to an embodiment of the present invention, and FIG. 1(b) is an explanatory diagram for explaining toner replenishment control of the copying machine.

[Fig. 2] Block diagram showing the configuration of the electrical component of the copying machine

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

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

FIG. 5 is a characteristic diagram showing the relationship between LD multi-value data and toner deposition amount 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 and peripheral circuits in which the counter circuit is configured.

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

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

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

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

FIG. 12 is a characteristic diagram showing the relationship between the image area ratio and output VSP related to image formation immediately before optical sensor detection.

FIG. 13 is a graph showing the relationship between the number of corrected bits of the output of the same 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 for calculating the variable GAIN in the copying machine.

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

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

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

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

[Explanation of symbols]

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 , 80
1 P-ROM (conversion table) 811 Adder
, 813 counter 815 latch circuit

Claims (3)

[Claims] 1. A first replenishment mode in which the total area of the toner adhesion area on the photoreceptor is calculated using image data in the image area, and an amount of toner corresponding to the total area is refilled to the developing device; A second replenishment mode that can replenish the developer with a predetermined amount of toner, and a third replenishment mode that can replenish the developer with a larger amount of toner than the predetermined amount, and 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 that is lower than the first density range. The second replenishment mode is selected when the toner concentration is within a predetermined third concentration range that is lower than the second concentration range, and the third replenishment mode is selected. Control method. 2. The toner replenishment control method according to claim 1, wherein when the third replenishment mode is selected consecutively a predetermined number of times, a toner near-end message is displayed. 3. Area calculation means for calculating the total area of the toner adhesion area on the photoreceptor using image data in the image area;
a first replenishment amount setting means for setting a toner replenishment mechanism driving condition for replenishing an amount of toner according to the calculation result of the area calculation means; and a toner replenishment mechanism driving condition set by the first replenishment amount setting means. a second replenishment amount setting means for setting a toner replenishment mechanism driving condition for replenishing a larger amount of toner than the second replenishment amount setting means; and a second replenishment amount setting means for replenishing a larger amount of toner than the toner replenishment mechanism driving condition set by the second replenishment amount setting means. a third replenishment amount setting means for setting toner replenishment mechanism drive conditions; a toner concentration detection means for detecting the toner concentration of the developer; and a first concentration range in which the toner concentration detected by the toner concentration detection means is within a predetermined first concentration range. If the toner concentration is within a predetermined second density range that is lower than the first density range, the second replenishment amount setting means is selected. and a selection means for selecting the third replenishment amount setting means when the toner density is within a predetermined third density range lower than the second density range. Device.