JP2607008B2 - Image forming device - 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 for exposing a photoreceptor to image light to form an electrostatic latent image on the photoreceptor, developing the latent image with toner and transferring the latent image to recording paper. The present invention relates to a toner supply system that supplies toner to a developing unit.

[0002]

2. Description of the Related Art In an image forming apparatus of this type, if the amount of toner in a developing section is insufficient, the density of a recorded image is reduced. Therefore, a predetermined amount of toner is supplied to the developing section for each green sheet on a predetermined sheet. Each time a predetermined amount of toner is supplied to the developing unit,
The recorded image density or the corresponding image forming processing value is detected, and toner is supplied to the developing unit according to the detection result. The toner supply device generally turns on the toner using a clutch, a solenoid, or the like. The toner is supplied to the developing unit.

[0003]

In many cases, the toner conveying means is coupled to the drive system of the photosensitive member by the biasing of the clutch or the solenoid, and the speed variation of the photosensitive member is caused by the load fluctuation when the clutch or the solenoid is biased. And the disturbance such as jitter occurs in the electrostatic latent image. Further, if toner supply is performed immediately after the start of transfer, the recording density becomes higher due to the supplied toner at the rear of the developed image, resulting in density unevenness.

An object of the present invention is to prevent recording density unevenness due to toner supply.

[0005]

An image forming apparatus according to the present invention develops a latent image formed on a latent image carrier by carrying a developer on a developer carrier facing the latent image carrier. In an image forming apparatus having a developing means, a toner replenishing means for replenishing toner to the developer carrier, and a detecting means for detecting toner density on the latent image carrier, toner is supplied at least during development. stops operating, said developing operation for each termination
First to supply a predetermined amount of toner through the toner supply means
Control means for detecting the toner density on the latent image carrier every time the developing operation is completed a plurality of times, and based on the detected value ,
Second control means for performing toner supply via the toner supply means .

[0006]

The second control means is provided for each time the developing operation is completed a plurality of times.
Latent image bearing member of the toner - based the concentration detection value of the detection Sico
Since performing auxiliary supply, toner - - come toner concentration is determined to a constant value for each of a plurality of images formed. The first control means performs a developing operation.
A predetermined amount of toner but each ends - so performing auxiliary supply, repeatedly current
The toner concentration reduction speed due to the image operation is low, and the second control
The toner supply control by the stage compensates for the shortage of the toner supply of the first control means . As a result, the toner density fluctuation width can be set to be extremely narrow and the toner density control cycle (the number of development operations ) performed by the second control means can be set long (large).

Since the first control means stops the toner supply operation at least during the development, the first and second control means stop the toner supply operation .
The toner replenishment by the control means is at a timing at least outside the development period, so that the toner density does not fluctuate during the development, and the recording density unevenness does not occur. Development during replenishment operation
Unnecessary toner on developer carrier due to vibration of developer carrier
There is no scattering and does not pollute the surroundings. In addition, the latent image
Necessary toner adhesion does not occur, and no soiling occurs on the transfer member.

[0008] Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment shown in FIG. 1 and the following will be described below. This embodiment is a copying machine, in which a predetermined amount of toner is supplied to a developing unit for each copy, and at the same time, every 10 copies. The image density is detected and the toner is replenished based on the detection result. The ratio of the density detection value of the white pattern and the density value of the black pattern for the image density detection is basically controlled, and the characteristics of the density detection system and the photoreceptor are used. The green density control is performed stably with respect to the change. In the density control based on the ratio of the detected density values, the division is omitted from the calculation of the detected density ratio, and when the detected values are digitally converted, the A / D conversion range is switched and the digital values are changed in different ranges. The recording density is controlled based on the result of comparing the converted data. The developed image density of the pattern on the photoreceptor (accurately the reciprocal thereof) Vsg and the developed image density of the black pattern on the photoreceptor (accurately the reciprocal thereof) V
If the sp ratio Vsp / Vsg is less than 4/1, the image contrast is low, so toner replenishment is necessary. If the sp ratio is 4/1 or more, the image contrast is high, so toner replenishment is unnecessary. By setting the pattern density ratio threshold (4/1) in this manner, Vsp
/ Vsg = 4/1, Vsp = 4Vsg is used as a threshold, and Vsp <4
Insufficient contrast at Vsg: toner supply required and Vsg
≧ 4 Vsg, suitable for contrast: Density control can be performed such that toner supply is not required. That is, it is possible to determine whether toner supply is necessary without performing the division process. When the density detection analog signals Vspa and Vsga are digitally converted in the range of 1: 4, the A / D converted digital data of Vspa indicates Vsp and the A / D converted digital data of Vsga indicates 4 Vsg. Only by comparing the digitally converted data of Vsga, it is possible to determine whether toner supply is necessary.

Even when performing density control based on the ratio of the density detection values of this type, it is necessary to initialize the characteristics to predetermined ones for each image forming apparatus or each density detection apparatus. This is because each of the light emitting source, the photoelectric converter, the photoconductor, and the like has different characteristics for each one. In addition, since the density detection system is generally arranged in a place where the toner is easily contaminated with toner, even if the detection value is controlled by the ratio of the detection value itself, it is usually adjusted by adjustment or cleaning when the detected value itself deviates considerably from the normal control detection value. In this embodiment, when the detected value deviates from the predetermined range, the brightness of the light source is changed to return the detected value to the predetermined range. It is preferable that the brightness is shifted by a predetermined step every time the light is shifted once, and if the shift is no longer desirable due to the characteristics and life of the light source, the shift is stopped there and a notification such as a serviceman call is issued. That is, errors corresponding to various characteristic changes within a predetermined range are absorbed by the control based on the ratio of the density detection values, and in this control, when the detection value fluctuates as the error increases,
The brightness of the light source is shifted by a predetermined step.

FIG. 1 shows a schematic configuration of an embodiment of the present invention. In this embodiment, a copying machine is used.
Image, the first mirror 2 ₁ a document of the upper (not shown), a second
Mirror 2 ₂ , in-mirror lens 3 and third mirror 2 ₃
The light is projected on the surface of the photosensitive drum 4 .
In synchronization with the counterclockwise rotation of the sensitive light drum 4, the first mirror 2 ₁ and the second mirror 2 ₂ right from the exposure scanning drive to the left at a predetermined speed ratio, the exposure end position of the document size corresponding When it reaches, return drive is performed from left to right. The surface of the photosensitive drum 4 is uniformly charged by the main charger 5,
The remaining area is discharged by the erase lamp 6 except for the area corresponding to the document size. The charged area of the charged document size corresponding electrostatic latent image of the original image corresponding by the exposure scanning Ru formed <br/>. This electrostatic latent image is developed with the developer of the developing roller 7 of the developing device. The toner image formed on the surface of the photosensitive drum 4 in this manner is transferred to recording paper by the transfer charger 8. The recording paper is sent to a fixing unit by a separation belt 9.

[0012] In this embodiment, the white pattern MRg have been added at the image projection field in the first mirror 2 ₁ a home position, and black pattern MRp is attached to the left side, the first mirror 2 ₁ exposure scanning When driven to the left, an electrostatic latent image of a white pattern MRg and a black pattern MRp is continuously formed on the surface of the photosensitive drum. A photo sensor 11 for detecting the toner density on the surface of the photosensitive drum 4 is disposed between the developing device (7) and the transfer charger 8, and a detection signal of the sensor 11 is supplied to an A / D converter 18
A / D conversion (analog-digital conversion) in the second
14 (MPU2) as control means for
Is applied to Microprocessor 14, the white pattern corresponding toner image MRg and black pattern MR p calculates the concentration ratio (toner image pattern) defines the toner supply amount from the concentration ratio, during a time corresponding to the toner supply amount solenoid driver 15 To the clutch solenoid 16 while the solenoid driver 15 receives the instruction.
Turn on electricity. When the clutch solenoid 16 is energized,
The toner cutting roller 10 is connected to the photosensitive drum drive system and rotates, and toner is supplied to the developing roller 7 from the toner storage tank.

In this embodiment, the microprocessor 14, which is the second control means, supplies the toner in accordance with the detected value from the toner image density detection, and the other first control means supplies the toner.
A certain microprocessor MPU1 performs other copy control. Note that the toner supply amount according to the recording paper size is determined in advance, and the MPU 1 supplies the copy size corresponding amount of toner for each copy. Therefore, the microprocessor 14 supplies the toner that is insufficient in the quantitative supply.

FIG. 2 shows the microprocessor 1 shown in FIG.
4 shows four electrical connections. In FIG. 2, 11 ₁ and 11 ₂
Is a light emitting Daioza and phototransistors constituting the photosensor 11, the light emitting Daioto 11 ₁ is projected on the photosensitive drum 4, the reflected light of the drum 4 is detected by the photo transistor 11 _2. Emitter voltage of the phototransistor 11 _2, directly to the input channel A ₁ of the A / D converter 18 (MB4052 manufactured by Fujitsu), also applied to the input channel A ₀ through minute圧端EX _2, EX _1. The digital data (serial) output terminal DATA OUT of the A / D converter 18 is connected to the interrupt terminal T _{1 of the} processor 14.
The control input terminals (A / D CLK to RS) are connected to the output port of the processor 14.

FIG. 3 shows the internal configuration of the A / D converter 18. The A / D converter 18 can extend the range four times by switching the input voltage range of Vcc / 2 and Vcc / 8 and expanding the range by range selection in 8-bit A / D conversion. Preliminary experimental results show the following values in the standard case. Detection level (background level) Vsg = 4.0 of the photoconductor surface toner density of the portion corresponding to the white pattern MRg
V, and the toner density detection level Vsp = 1.6 V of the photosensitive member surface corresponding to the black pattern MRg. The maximum voltage of the input channel A ₀ to A ₃ is 2.5V contrast.

From the above data, it is possible to obtain (Vcc / 2) × 4 → 0 from the background level Vsg by using range expansion.
The measurement range of 10 V is Vcc / 2 for the black level Vsp.
→ Use a measurement range of 0 to 25V. A / D converter 1
Connect the emitter of phototransistor 11 ₂ EX ₂ of 8, because it connects the EX ₁ to the input channel A _0, in the indicated A / D converting an input channel A _0, 4
Since the times of the range extension defines an input channel A ₀ for background level Vsg detection, also phototransistor 1
Since connecting a _second emitter directly to the input channel A _1, it defines an input channel A ₁ for black level Vsp detected. Therefore, the A / D conversion data of Vsg
Is in the same range as the value of the A / D conversion data of Vsg. That is, the relationship between the digital output n and the input voltage is represented by the following equation. Background level Vsg (n) = 62 + (n−1) × 39.126 mV Black level Vsp (n) = 17 + (n−1) × 9.7756 mV (Example) When background level Vsp (N) = 163, Vsg (analog) ) = 62 + 102 × 39.126 mV = 3.991 V When black level Vsg (n) = 103, Vsp (analog) = 17 + 162 × 9.7756 mV = 1.006006 V According to the confirmation, Vsp = 4Vsg, that is, 4 as described above.
When the toner replenishment control is performed with a threshold value of / 1, the contrast is maintained high. Therefore, in this embodiment, as compared with black pattern digital density data obtained by inputting the density detection signal to the input channel A _1, were obtained by inputting the density detection signal to the input channel A ₀ white pattern digital density data The necessity of toner supply is determined.

Referring again to FIG. The output port S1~S3 of the microprocessor 14 resistance R1~R3 are connected, these resistors are connected to the light emitting diode 11 _1. The resistors R1 to R3 are light emitting diodes 11
₁ determines the brightness of the microprocessor 1
4 can set the brightness of the light emitting Daioto 11 ₁ to any one of the states shown in Table 1 of the following three states of the bit to be set in the output port S1 to S3.

[0018]

[Table 1]

In Table 1, the brightness No. 7, such as a resistor connected photo sensor 11 and its 2, in the expected range variation, the light emitting diode 11 _1, a state in which passing a current upper limit value that does not unduly shorten the life,
Brightness No. 4 is a state passing a standard current to the light emitting Daioto 11 ₁ in a standard concentration detection state, brightness N
o. There sequentially current decreases to flow to the light emitting Daioto 11 ₁ as smaller stepwise than 4, brightness N
o. So they current applied to the light emitting diode 11 ₁ increases successively in steps as sequentially larger than 4, the value of the resistor R1~R3 is defined. The brightness No. 1, the brightness setting codes S1 to S3 are 000
A is, it does not flow substantially current to the light emitting diode 11 _1.

The output port PS of the microprocessor 14 as the second control means is connected to a solenoid driver 15
(Figure 1) the base of the switching transistor Tr ₂ configuring is connected to, the collector of the transistor Tr ₂ and the clutch solenoid 16 is connected, set the high level "1" (H) to the output port PS transistor Tr ₂ is turned, the toner cut roller 10 a current flows through the solenoid 16 (FIG. 1) rotates and is connected to the photoconductor drive system by. A transistor Tr ₃ is connected to the solenoid 16 in order to supply an amount of toner corresponding to the copy size for each copy.
toner is supplied by the on of r _3. This transistor Tr ₃ is turned on / off by a copy control microprocessor MPU1, which is a first control means . When at least one of the transistors Tr ₂ and Tr ₃ are turned on, that is, when the toner supply, the light emitting diode PD2 for toner supply display which is connected to one end of the solenoid 16 is turned on. The output port Pa of the microprocessor 14 includes:
The transistor Tr ₁ is connected to the base of the transistor Tr ₁ via the OR gate OR ₁ , and the light emitting diode PD ₁ for alarm is connected to the transistor Tr ₁ . If the detected value does not fall within the predetermined range even after the value is set to 7, the output of "1" is set. Due to this "1", the diode PD1 emits light continuously and the other microprocessor MPU1
Is notified that the development density cannot be controlled. Upon receiving this signal "1", the MPU 1 sets the serviceman call indicator light on the operation board to ON, and then 20 copies can be made, but when the number reaches 20, the copy operation is stopped and the protection operation is stopped. .

Brightness setting signals S1 to S of the processor 14
3 are also given to the AND gate AN1, and if they are all 1 (brightness No. 7), the output of AN1 is "1".
As a result, the flasher oscillator PG is energized to give a blinking pulse to the OR gate OR1. Therefore, the brightness setting is No. 7, the diode PD1
Flashes. This blinking means that the concentration detection has reached the upper limit, but the other processor MPU
2 is not notified of this.

To the interrupt end INT of the microprocessor 14, one pulse is applied as a toner density control instruction signal from the copy control processor MPU1 every ten copies while the power of the copying machine is turned on. To T ₀ , a drum rotation synchronization pulse that is generated for one rotation of the photosensitive drum 4 at a predetermined small angle is applied. Furthermore, the second
Input terminal PC of microprocessor 14 as control means
In addition, during exposure scanning and development, a high level “1” (this 1
Indicates that toner supply is prohibited. ) Is the first control
It is provided from a microprocessor MPU1 as a means via an OR gate OR2 (FIGS. 2 and 9 ). As described below, microprocessor 14 is a second control means
Controls the toner supply amount by counting the drum rotation synchronization pulse. This is because the output of the OR gate OR2 is "0".
This is performed only when (the toner can be supplied).

A monitor unit MON can be connected to and detached from the output port of the processor 14 via a connector 22. The monitor unit MON is connected by a serviceman during maintenance and inspection of the copying machine. The monitor unit MON includes character displays 20G1 to 20G3 for displaying the white level Vsg, character displays 20P1 to 20P3 for displaying the black level Vsp, and the density ratio V.
Character press 20R1, 2 for displaying sg / Vsp
0R2, segment decoder 21DS, digit decoder 21
DC, segment drivers DAM1 to DAM7 and digit drivers DTR1 to DTR8 are provided. When this unit MON is connected to the connector 22, Vsg, Vsp and Vsg / V
sp is displayed. In FIG. 2, a switch 19 is a toner density control instruction switch, and when this switch is momentarily closed, the toner density control is started. This switch 19 is closed during maintenance and inspection.

FIG. 4 shows an outline of (a part of) a copy control flow of the copy control microprocessor MPU1 mainly focusing on quantitative toner supply. When the state of each part of the copying machine becomes a copy enabled state, the MPU 1 sets 1 to a copy number counter (program counter) for obtaining a toner density control instruction timing, and has a print switch (SW) closed (copy instruction). . And print SW
When There is closed, to urge the Chiyajiya 5, exposure starts and begins counting drum rotation sync pulse, the white pattern MRg projected by the first mirror 2 ₁ a drum 4, reaches the sensor 11 parts At that point, the microprocessor 14
(MPU2) gives a toner density control instruction signal (start pulse) to an interruption end INT. When the content of the copy number counter is 1 to 10, the start pulse is not applied, and the erase lamp 6 is energized to eliminate the charge to the black pattern MRp. Then, the copy control is continued. When one copy is completed, the paper size data (toner supply time associated with the paper size: the number of drum rotation synchronization pulses) is set in the toner supply counter (program counter), and the transistor Tr ₃ (FIG. 2) is turned on. , then 1 decrements the toner supply counter every time the drum rotation sync pulse arrives, and turns off the transistor Tr ₃ the contents of the toner supply counter reaches zero.

Next, the copy number counter is incremented by one. When continuous copying (repeat mode) is set, copying is started again. When single copy is set, the process returns to waiting for a copy instruction input by the print SW. Each time the content of the copy number counter becomes 11, the content of the copy number counter is reset to 1, and only when the content of the copy number counter is 1, the processor MPU2 (14) is instructed to control the toner density. The toner density control is performed once every ten sheets. Further, since a predetermined amount of toner for one copy is supplied after the end of one copy (end of development), the solenoid 16 is not energized during exposure scanning and development of a latent image, and a load variation is applied to the photosensitive member drive system. No impact and no mechanical vibration. Furthermore, the recording density does not differ between the beginning and the end of the copy.

Next, the toner density control by the processor 14 (MPU 2) will be described. White and black patterns MRg, MR
The detection of the toner density of the image projected on the photosensitive drum 4 of p, the determination of the necessity of toner supply based on the detected value, and the setting of the toner supply based on the determination are performed by the MPU 1 to the interrupt input terminal INT.
In response to the application of the toner concentration control instruction pulse (start pulse), interrupt control is performed to control the supply of the set amount of toner and display 201G1 to 20G3, 20P1.
20P3, 20R1, and 20R2 are controlled in the main routine.

First, the interrupt control will be described with reference to a flowchart shown in FIG.
When the interrupt input terminal INT changes from the high level "1" to the low level "0", the output port to the connector 22 is set to "0" to turn off the display of the monitor unit MON. Then read port T ₁ A / D conversion data (8 bits) serially applied to data conversion timing pulses (A / DCLK) to the A / D converter 18, the A / D conversion data, A / D data Addition memory to register.
When this A / D conversion and data addition are repeated 16 (2 ⁴ ) times, the contents of the A / D data register are shifted to the lower 4 bits. The contents of A / D data register by the digit shift indicates the average value of the A / D conversion data of 2 ⁴ times. As described above, the toner concentration control instruction pulse (start pulse) to the INT is issued at the timing when the projected toner image of the white pattern MRg reaches the sensor 11 (11 ₁ , 11 ₂ ). the aforementioned a / D conversion data to the specified channel a ₀ indicates the white level toner density (Vsg).

The MPU 2 stores the average value of the white level toner density in the Vsg register. Next, the contents of the Vsg register are compared with the lower limit a of the predetermined range. If it is larger than a, it is compared with the upper limit b. If it is smaller than b, the detected value is within the proper range. Proceed to the detection of the boundary between and the black pattern. The lower limit value a is set to 2.6 V when Vsg is 4 V in the standard state, and the standard value is 4/4 = 4 in the conversion range.
Since it is 1 V, a = 2.6 / 4 = 0.65 V. Since the A / D conversion range is 1/4 when the upper limit value b is 5.4V, b = 5.4 / 4 = 1.35V.

The white pattern toner image density detection value is lower than the lower limit a.
If it is smaller, the brightness instruction value k currently stored in the brightness setting register is referred to, and the maximum value 7
, Since the brightness setting is already at the maximum, a development density control disable signal “1” is set to the output port Pa,
Return to the standby state (interrupt pulse wait). If it is not 7, the content k of the brightness setting register is updated to a value obtained by adding 1 to the previous value k, and the process returns to the standby state.

The white pattern toner image density detection value is equal to the upper limit value b.
If it is larger, the brightness reference value k currently stored in the brightness setting register is referred to, and the minimum value 1
, Since the brightness setting has already been minimized, a development density control disable signal “1” is set to the output port Pa, and
Return to the standby state (interrupt pulse wait). If it is not 1, the content k of the brightness setting register is updated to a value obtained by subtracting 1 from the previous value k, and the process returns to the standby state.

When the detection value Vsg is within the predetermined range ab, the reading counter is cleared to detect the boundary between the white pattern (MRg) toner image and the black pattern (MRg) toner image. A / D conversion input channel is set to A ₁ , and similarly, after waiting for the drum rotation synchronization pulse to arrive, A
/ D conversion is performed. As described above, the input channel A _1, the toner density detection voltage is applied by direct (no partial pressure), moreover, the maximum value limit 2.5V of the input analog voltage, even white pattern The toner density detection voltage (analog) is always 2.5 V or more because the lower limit a is set to 2.6 V in the previous detection value determination, and the toner density detection voltage of the black pattern is less than 2.5 V. so (because it is full-scale 2.5V, digital data indicating the 2.5V when the higher) input voltage of the input channel a ₁ is more 2.5V whether on whether white pattern or the black pattern is the I understand. Therefore, when the digital conversion data indicates 2.5 V, the MPU 2 determines again that the sensor 11 is still detecting the white pattern and returns to A
/ D conversion is performed and this is repeated.

When the digital conversion data indicates less than 2.5V, the content of the reading counter is incremented by one, and when the A / D conversion data is less than 2.5V after waiting for the arrival of the drum rotation synchronization pulse. as (the contents of the read counter becomes zero), containing toner image of the black pattern to the detection field of the sensor 11, specifies the input channel of the a / D converter 18 to a _1, the counter is cleared. Then, in order to avoid the detection of the transition region, it waits for the arrival of five drum rotation synchronization pulses.

It should be noted that, after the A / D conversion data once indicates less than 2.5 V, (m-1) times of repeated A / D conversion
If the data shows 2.5 V at least once during the conversion, the reading counter is set to 3 again, and A is repeated three times.
In A / D conversion, A /
Repeat D conversion.

When the content of the reading counter reaches 6, A
/ D conversion is carried out for, then integrating two ^four A / D converted data by performing A / D conversion every time the drum rotation synchronization pulse arrives at the A / D data register. Upon completion of the accumulation of 2 ^four conversion and data, MPU 2 is shifted 4 bits to the contents of the A / D data register lower digit direction. Thus, the contents of the A / D data register indicate the average Vsp of the input voltage detection values (Vsp). At this stage, Vsg is 1 of the average value of 16 samplings of the white level.
/ 4, and Vsp indicates an average value of 16 samplings of the black level. Here, the MPU 2 compares these densities Vsp and Vsg and has a low contrast (Vsp> Vsp).
sg) At that time, a predetermined value is set in the toner counters (registers) 1 and 2 and a toner supply flag is set.

The supply of about 1 g of toner is a time for counting 1792 pulses of the drum rotation synchronization pulse.
Assuming that the toner supply amount (predetermined amount) per time is K, the period during which the solenoid 16 is energized is K × 1792 = K × 7 × 2 ⁸
It is. Therefore MPU2 will memory K × 7 × 2 ⁸ in the toner counter 2 to share the toner counter 1 (register) the upper 8 bits of memory to share the lower 8 bits of the memory. This means that all the bits 0 are stored in the lower 8-bit toner counter 1 and the upper 8-bit toner counter 2 is stored.
Is stored by storing binary data indicating K × 7. After storing the toner supply time (the count of the drum rotation synchronization pulse) in the toner counters 1 and 2, the MPU 2 returns to the main routine (FIG. 6).

Next, the main routine of the MPU 2 will be described with reference to FIG. In the main routine, while the drum synchronizing pulse (port T ₀ ) is at L, the MPU 2 performs display energizing control for sequentially energizing each character display unit of the display MON in a time-division manner. When the drum synchronization pulse (port T ₀ ) changes from L to H, the MPU 2 increments the key counter (program counter) by one and displays one (1).
Digit display), referring to port T ₀ , repeating this operation as long as it is H, and repeating this α times. If port T ₀ is continuously H during this time, the drum rotation synchronization pulse , The key end flag 1 indicating the arrival of the synchronization pulse is set.

When the key end flag 1 is set (drum rotation synchronization pulse arrival index is set), the second control
The MPU 2 as a control means refers to the port PC, and if it is "0" (toner supply possible), refers to the toner supply flag, and if there is, sets the solenoid 16 to the energized state.
When the content of the toner counter is not zero, the control waits until the drum synchronization pulse becomes L, and controls the display energizing while waiting. When the drum synchronizing pulse becomes L, it is determined that the arrival of one pulse has been completed, the key end flag and the key counter are cleared, and the port T _{0 is} energized while pressing the display.
Wait for H to become H.

As described above, the toner counter (1, 2) is decremented by one each time the drum rotation synchronization pulse arrives, and when the content becomes zero, that is, the toner supply time is supplied to the toner counter (1, 2). Set solenoid 1
When the toner supply time elapses after turning ON the solenoid 6, the solenoid 16 is turned OFF, the toner supply flag is reset, and thereafter only display energizing control is performed.

As described above, in the above embodiment, the microprocessor MP as the first control means for performing copy control
At U1, in the toner replenishment for each copy, the toner replenishment is energized after the completion of the exposure scanning and the development, and the insufficient toner supply by the density detection is similarly performed after the exposure scanning and the development is completed. Therefore, image disturbance and density unevenness do not occur. When the development is completed before the replenished toner reaches the developing roller while being agitated, or when it is sufficient to prevent the image from being disturbed due to a load change, the toner supply may be started at the same time when the exposure scanning is completed. I just need.
In this case, for example, the OR gate OR2 is omitted and only the mirror scan signal is supplied to the microprocessor 14.

In the above embodiment, the detection voltage of the toner image density in the white pattern area is about 4 V, and the detection voltage of the toner image density in the black pattern area is about 1.7 V. Paying attention to always output digital data indicating 2.5 V when the input voltage is 2.5 V or more and the input voltage is 2.5 V or more, after detecting the toner image density in the white pattern area, the A / D converter 18 Is less than 2.5 V, and when the three subsequent detection values both show less than 2.5 V, it is determined that a black pattern has arrived at the sensor 11 and the black pattern density Since the process shifts to the detection, the pattern density detection timing setting is simplified, and only the reading timing of the white pattern as the first pattern is set.
It is not necessary to set another timing even if the copy magnification changes. Further, since the necessity of toner supply is determined based on a predetermined development density ratio Vsg / Vsp of the white pattern and the black pattern,
Relatively stable toner density control is performed with respect to changes in the characteristics of the sensor and the characteristics of the photosensitive member. For example, when the image density detection voltage of the sensor 11 is a standard value and shows a characteristic shown by a solid line in FIG. 7 and changes to a characteristic shown by a dotted line in FIG. 7 due to a change in the characteristic of the sensor 11 and / or the photoconductor surface,
The difference between the developed toner density detection voltages Vsg and Vsp of the white and black patterns changes from 3.0 V to 1.5 V, indicating a change of 50%. However, the ratio of both Vsg and Vsp is 4.0. Therefore, it can be said that the system is stable against changes in the characteristics of the toner image density sensor and the photosensitive member.

Further, when the detected value of the white pattern is a to b
Outside than the range of (2.6~2.5.4V), the brightness of the diode 11 ₁ in a direction falling within the range is changed by one step. Accordingly, due to the initial characteristics and changes in the characteristics of the photosensor 11, the initial characteristics and changes in the characteristics of the photoconductor, and the like, the detected value is initially a due to the variation in the initial values.
If it does not enter b, the diode 1 will automatically enter
Adjusts the brightness of 1 _1, the detection value due to the subsequent characteristic change and dirt of the sensor deviates from to b, to automatically change the brightness of the diode 11 ₁ to enter. Even in such a change, even when not be changed within the range of a~b the detection value is allowable biasing range of early and diode 11 ₁ is energized level adjustment of the diode 11 ₁ is stopped, the concentration control Also stop and alert the serviceman call,
After that, 20 copies can be made, but when the 20 copies are completed, copying becomes impossible. Therefore, the initial setting of the density detection system can be omitted even in the initial (new) setting of the copying machine, and even if the copying machine is started to be used, the interval of maintenance and inspection becomes extremely long, and the stable recording density control is performed during that time. In this way, the adjustment of the mechanical assembly is simplified, and the user does not need to perform maintenance and inspection of the concentration detection system for a long time after starting use. If the concentration detection system fails, an alarm is automatically issued. Even when the photoconductor and the sensor are replaced, there is no need to adjust and set the density detection system.

In the above embodiment, the A / D conversion resolution of the black pattern toner density detection voltage Vsp is four times the A / D conversion resolution of the white pattern toner density detection voltage Vsg. As is well known, minute white spots and black spots are scattered due to roughness and the like in the developed toner image, and even on the same pattern, the detection level slightly varies depending on the measurement site. The absolute value of this variation is large at Vsg and small at Vsp. Therefore, the resolution is determined for each pattern, and the input voltage level of the A / D conversion is set to the same level as described above, so that the fluctuation of one detection level does not occupy a large weight. In particular, in the case of A / D conversion, if the resolution is the same, the range including both Vsg and Vsp is wide, and the weight of Vsp is lower than Vsg unless the number of conversion bits is increased. However, the smaller the number of bits of the A / D converted data is, the better in terms of element configuration and arithmetic processing. By determining the resolution for each pattern as described above, the number of bits of the A / D conversion data can be reduced, and the necessity of toner supply based on the ratio is determined not by division but by magnitude comparison. Therefore, the arithmetic processing is simple, and the determination of whether toner supply is necessary is quick.

[0043]

As described above, according to the present invention, the second control means
The step moves the toner on the latent image carrier every time the developing operation is completed plural times.
- since the auxiliary supply, toner - - based-out toner to the detected value of the detection Sico concentration density is determined at a constant value for each of a plurality of images formed. First control means, bets <br/> Na predetermined amount developing operation for each finished - since the auxiliary supply, toner by repeated development operations - density reduction rate is low, toner according to the second control unit - supply The control compensates for the shortage of toner supply by the first control means . As a result, the toner density fluctuation width is extremely narrow and the toner density control cycle ( developing operation) performed by the second control means.
Count) long (large) may be set.

Since the first control means stops the toner supply operation at least during the development, the first and second control means stop the toner supply operation .
The toner replenishment by the control means is at a timing at least outside the development period, so that the toner density does not fluctuate during the development, and the recording density unevenness does not occur. Development during replenishment operation
Unnecessary toner on developer carrier due to vibration of developer carrier
There is no scattering and does not pollute the surroundings. In addition, the latent image
Necessary toner adhesion does not occur, and no soiling occurs on the transfer member.

[Brief description of the drawings]

FIG. 1 is a side view showing a configuration mainly related to toner density control of a copying machine according to an embodiment of the present invention.

FIG. 2 shows a microprocessor 14 and an A / D shown in FIG.
FIG. 3 is an electric circuit diagram showing a connection relation of a converter 18 and the like.

FIG. 3 is a block diagram showing an internal configuration of the A / D converter 18 shown in FIG.

FIG. 4 is a flowchart mainly showing quantitative toner supply control and toner density control instruction timing control of the copy control microprocessor MPU1 of the copying machine shown in FIG. 1;

FIG. 5 is a flowchart showing an interrupt process of a microprocessor MPU2 shown in FIG.

6 is a flowchart showing a main flow of the microprocessor MPU2 shown in FIG.

FIG. 7 is a graph showing a relationship between a density detection voltage of the photo sensor 11 shown in FIG. 1 and a toner image density.

FIG. 8 is a circuit diagram illustrating a configuration of an A / D converter unit that implements the present invention in one modification.

FIG. 9 is a block diagram schematically showing a combination of a microprocessor MPU1 for controlling the entire copy sequence and each copy element.

[Explanation of symbols]

1: contact glass plate 2 ₁ to 2 _3:
Mirror 3: In-mirror lens 4:
Photoconductor drum 5: Main charger 6:
Erase lamp 7: Developing roller 8:
Transfer Charger 9: Separating and Conveying Belt 10:
Toner cut-out roller 11: Fort sensor 1
11 ₁ : light emitting diode 11 ₂ : phototransistor 1
8: A / D converter MPU1: first microprocessor 14 (MPU2): second microprocessor

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yasushi Furuichi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-59-164572 (JP, A)

Claims (2)

(57) [Claims] A developing means for developing a latent image formed on the latent image carrier by carrying the developer on a developer carrier opposed to the latent image carrier; An image forming apparatus having a toner replenishing means for replenishing toner and a detecting means for detecting the toner density on the latent image carrier, wherein the toner replenishing operation is stopped at least during development, and each time the developing operation is completed. First control means for replenishing a predetermined amount of toner via the toner replenishing means ; detecting toner density on the latent image carrier every time the developing operation is completed a plurality of times; An image forming apparatus comprising: a second control unit that performs toner supply via the toner supply unit. 2. The toner replenishing means includes at least a toner replenishing means.
An electric coil that is electrically energized at the time of replenishment and a switching element that energizes the electric coil, wherein the first control means and the second control means respectively energize the switching element. Item 2. The image forming apparatus according to Item 1.