JP2740760B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for visualizing a latent image formed by an electrophotographic method as a toner image. 2. Description of the Related Art Conventionally, as a developing method of developing means used in this type of apparatus, there are a two-component developing method in which a polyester resin toner and iron powder are mixed, and a polyester resin toner. There is a one-component development system in which development is performed only with a single component. [0003] In the two-component developing method, the toner concentration in the developer fluctuates due to a decrease in the toner in the developer due to a developing operation or an increase in the toner due to toner replenishment. If the toner density is low, the image density on the recording material (recording paper) is low,
Fading or even image loss is caused. If the toner density is high, fogging or the like on a non-image portion occurs. In order to overcome this problem, a method of controlling the toner concentration in the developer by the following methods (1) and (2) has been proposed and implemented. (1) A method in which a predetermined amount of toner is replenished when the number of rotations of the photoconductor accompanying image formation reaches a predetermined number of rotations. (2) A method of directly detecting the toner concentration in the developer in the developing device, and replenishing a predetermined amount of toner when the detection signal falls below a predetermined level. [0006] However, the above (1)
In the method (1), the toner density becomes excessive or insufficient for the quantitative replenishment irrespective of the type (blackening ratio) of the recorded image, and the recorded image becomes too light or too dark, so that the image output is not stable. In the method (2), since the toner concentration in the developer is directly detected, the supply control is easy.
High-precision detection is difficult, and the toner is not replenished until the toner reaches a certain level or less, and is replenished only when the toner reaches a certain level or less. In this case, the toner density in the developer changes drastically, and during continuous printing of the same image, the density of the first output image and the density of the subsequently output image are different. Will be output. This means that in a multi-color (two or three or more single color) or full-color printer having a plurality of developing devices, it is difficult to reproduce a faithful color if the toner density varies. In addition, at the time of continuous printing, images having different color developing properties are generated between output recorded images. Since human color perception is particularly sensitive, it is necessary to keep each toner concentration accurately and constant. In order to compensate for these drawbacks, there has been proposed a method of counting the number of dots forming an image portion from an image signal, calculating the toner consumption, and determining the toner supply amount. In this method, the amount of toner consumed in the image area is calculated from the number of dots to determine the replenishment amount, so that the amount of toner consumption can be accurately calculated, fine-tuning control can be performed, and the toner density can be controlled. This is advantageous for maintaining stability. However, the amount of toner consumption is not only proportional to the image area, but also greatly affected by the environment around the developing device, the toner storage section and the image carrier. FIG. 9 shows the relationship between the surface potential of the image carrier (photoconductor) and the output image density in the process of recording the same image information (the same number of dots). In this figure, H indicates a high humidity environment, and N
Indicates a normal humidity environment, and L indicates a low humidity environment. The vertical axis indicates the concentration, and the horizontal axis indicates the surface potential. As can be seen from this figure, the toner density fluctuates depending on the environment around the developing device, the toner storage section and the image carrier, even if the number of dots and the surface potential of the image section are the same. That is, since the toner consumption amount consumed from the developing device has a characteristic that varies depending on the environment, even if the toner consumption amount uniquely determined from the number of dots is replenished, the toner density becomes insufficient or excessive, There have been many problems such as the inability to output an image of a desired density. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems. The number of dots forming an image portion is counted from the toner density in a developer and image information to control the amount of toner replenishment. It is another object of the present invention to provide an image forming apparatus capable of managing the toner concentration with higher accuracy and maintaining the set toner concentration stably for a long period of time. An image forming apparatus according to the present invention forms an electrostatic latent image on an image carrier in accordance with an image signal, and stores a developer containing a toner and a carrier. Means for developing the electrostatic latent image by means,
Measuring means for measuring an image signal, calculation means for calculating the toner consumption based on the measured value of the measuring means, and supply means for replenishing the amount of toner is calculated by the calculating means to the developing means, the developing means And a correcting means for correcting the calculation of the consumed toner amount by the calculating means based on the detection output of the detecting means. In the present invention, when the density in the developing means is optically detected by the detecting means, the measured value by the measuring means for measuring an image signal in accordance with the detecting means outputted from the detecting means is provided. The amount of toner replenishment based on the image signal is controlled, and the difference between the amount of toner consumption and the amount of replenishment based on the image signal is reduced to supply an appropriate amount of toner. FIG. 1 is a sectional view of a replenishing means and a developing means showing one embodiment of the present invention. Reference numeral 1 denotes a hopper serving as a replenishing means, and is filled with yellow toner Ty. Reference numeral 2 denotes a developing device serving as a developing unit. Reference numeral 3 denotes a replenishing roll, which rotates in response to driving of the pulse motor M, and replenishes the lower portion of the yellow toner Ty. Screws 4 and 5 circulate a developer D (a two-component developer in which a magnetic powder made of iron powder or the like as a carrier and a toner are mixed).
Reference numeral 6 denotes a fixedly provided magnet roller. The developer D is sucked up by its magnetic force, moves in the direction of the arrow in accordance with the rotation of the sleeve 6a, and becomes a photosensitive member serving as an image carrier at the portion A exposed from the housing 7. The body 8 is developed. Reference numeral 9 denotes a doctor blade which regulates the thickness of the developer D on the sleeve 6a. 10 is a developer concentration detection device (ATR),
Optical means (to be described later) provided at a predetermined location of the developing device 2
To detect the developer concentration. Next, the operation will be described. The developer D is conveyed from the near side in the drawing by driving the screw 4, and is conveyed from the back by the driving of the screw 5, and circulates in the developing device 2. During the conveyance by the screw 4, the developer D is sucked up by the magnetic force of the fixed magnet roller 6, moves in the direction of the arrow with the rotation of the sleeve 6 a, and transfers the toner to the photoconductor 8 at the portion A exposed from the housing 7. Supply and develop the latent image. The amount of toner consumed in the developing step is supplied from the hopper 1 to the screw 5 by the supply roller 3 and is agitated to be uniform. The supply roll 3 is driven by, for example, a pulse motor M and supplies a desired amount of developer. This drive control is performed by first and second supply control means described later. FIG. 2 shows the developing device 2 and the ATR 1 shown in FIG.
FIG. 3 is a diagram for explaining a relationship with the light source 1;
0a, light guide 10b, optical lens 10c, light guide 1
0d, a light receiving element 10e, a filter 10f, etc.
The density of the developer D is detected through a transparent window 7a provided in a part of the sleeve 6a. Light from the light source 10a passes through the light guide 10b and the transparent window 7a, and is applied to the developer D. From the developer D, reflected light corresponding to the amount of toner is scattered, and a part of the reflected light enters the light receiving element 10e via the optical lens 10c, the filter 10f, and the light guide 10d. A developer concentration detection signal is obtained from the reflected light. The filter 10f is
For example, an external transmission filter selected from the spectral reflection characteristics of each toner is used. FIG. 3 is a block diagram for explaining a control configuration of the image forming apparatus according to an embodiment of the present invention. Reference numeral 11 denotes a first replenishment control means of the present invention, which is set in advance with the output of the ATR 10. A comparator 12 for comparing the set value lower limit Smin with a set value, a comparator 13 for comparing the output of the ATR 10 with a preset set value upper limit Smax, and a comparator 1
A decoder 14 decodes the outputs of the pulse motors 2 and 13, a setting timer 15 for determining the rotation amount of the pulse motor M, and the like. The second replenishment control means 21 of the present invention calculates the toner consumption from the output of a counter 22 for measuring the printing dots of the image forming section in the image signal fv transmitted from an external device (not shown). It comprises a calculating circuit 23, a timer 24 for determining the rotation amount of the pulse motor M from the output of the calculating circuit 23, a reset circuit 25 for clearing the contents of the counter 22, and the like. Reference numeral 30 denotes an OR circuit for calculating the logical sum of the setting timer 15 and the timer 24. A toner remaining amount calculation circuit 31 constantly updates the amount of developer remaining in the hopper 1 in accordance with the operations of the first and second supply control means 11 and 21. Reference numeral 32 denotes a drive control unit, which includes a setting timer 15 and a timer 24.
The supply driving unit 33 is driven in accordance with the output of. FIG. 4 is a diagram for explaining the input / output relationship between the comparators 12 and 13 and the decoder 14 shown in FIG.
(A) to (c) show operating states. When "H", input / output occurs, and when "L", input / output is stopped. Next, the operation will be described. The comparator 12 and 13 compare the toner density detection signal output from the ATR 10 with a set value lower limit Smin and a set value upper limit Smax, and the results are input to the decoder 14, respectively. Note that the set value upper limit Smax and the set value lower limit Smin are upper and lower limits that are allowed in the process of the toner concentration in the developer so that the output image density becomes satisfactory without excess or deficiency. For example, the developer (carrier + toner) 13% by weight of yellow toner and magenta toner and 1% of cyan toner
4 ± 1% wt and black toner 12 ± 1% wt. When the toner density has the upper and lower limit values, respectively, an optimum image output can be obtained. The decoder 14 receives the input 1 from the comparator 12
Then, the output 2 for setting the timer 24 is output. The output 2 of the timer 24 is determined according to the states (a) to (c) shown in FIG. The decoder 14 receives the input 2 from the comparator 13 and outputs the output 1 for setting the setting timer 15.
Is output. The setting timer 15 is in a state (a) shown in FIG.
Output 1 is determined according to (c). For example, ATR1
When the output value of 0 is smaller than the set value lower limit Smin, the output 1
Becomes "H" level and the output 2 becomes "L" level, only the setting timer 15 operates, and the drive control unit 32 passes through the OR circuit 30 and the driving control unit 32 responds to the output of the setting timer 15 to supply.
Is driven for a predetermined time. This supply amount is 1% wt ratio
And raises the toner density to a reference set value. If the output value of the ATR 10 is within the set range, the output 1 goes to the "L" level and the output 2 goes to the "H" level, and according to the states (a) to (c) shown in FIG.
Only operable. The timer 24 counts the number of print dots forming an image portion from the image signal fv by the counter 22, and calculates the consumption by the calculation circuit 23. Based on the result, the operation time of the timer 24 is determined. You. Further, when the output value of the ATR 10 is larger than the set value upper limit Smax, as shown in the states (a) to (c) of FIG. Not executed. On the other hand, the outputs of the setting timer 15 and the setting timer 24 are input to the drive control section 32 through the OR circuit 30 and at the same time to the remaining toner amount calculating circuit 31. When the consumption is calculated by the calculation circuit 23, the count value of the counter 22 is cleared by the reset circuit 25. Thus, the image forming apparatus according to the present invention includes:
When the density in the developing means (developing device 2) is optically detected by a detecting means (corresponding to ATR 10 in this embodiment), an image signal is measured according to the detecting means output from the detecting means. Measuring means (in this embodiment, the counter 22
Is controlled in accordance with the procedure shown in the flowcharts shown in FIGS. 5 and 7 described below to reduce the difference between the toner consumption based on the image signal and the replenishment amount of the developing device 2. , To supply an appropriate amount of toner. Next, the developer supply operation of the present invention will be described with reference to FIG. FIG. 5 is a flowchart illustrating developer supply control according to an embodiment of the present invention. In addition,
(1) to (17) show each step. First, a counter value j counted by a counter (not shown) of the first supply control means 11 is initialized, that is, set to "0" (1). Next, the printer waits for a print key (not shown) to be pressed (2). When the print key is pressed, the ATR 10 directly detects the toner density (3) and outputs a toner density detection signal to the comparators 12 and 13. I do. In response, the comparators 12 and 13 set the ATR
The output of 10 is set to a preset lower limit Smin,
The value is compared with the set value upper limit Smax (4). In this comparison, AT
When the output of R10 is smaller than the set value lower limit Smin,
A timer setting value for replenishing a predetermined amount t of toner is output to the setting timer 15, and the drive control unit 32 drives the replenishment drive unit 33 to replenish toner by a predetermined amount t (5). Next, the counter value j for counting the number of replenishments by the first replenishment control means 11 is counted up (6), and the total replenishment amount A (j
× t) is calculated (7). Subsequently, the initial toner amount H in the hopper 1 is compared with the total replenishment amount A (8). If the initial toner amount H ≦ the total replenishment amount A, it is determined that there is no toner, and the display unit of the operation unit (not shown) Is displayed, and the control is terminated (9). If the initial toner amount H> the total replenishment amount A, the control is shifted to the replenishment control by the second replenishment control means 21, that is, the ATR 10 is compared in step (4). Is within the upper and lower limits of the set value, and the counter output N of the counter 22 for counting the number of print dots to form an image from the i-th image signal fv
i is read (10), and the calculation circuit 23
i (α · Ni) is calculated (11). Next, a timer set value for replenishing toner corresponding to the calculated toner consumption Ti is set in the timer 24, and the drive control unit 32
Drives the supply driving unit 33 to supply the toner consumption Ti (12). Next, the total toner amount B (ト ナ ー T
i) is obtained (13). Subsequently, the sum of the total supply amount A obtained by the first supply control means 11 obtained in step (7) and the total supply amount B obtained in step (13) is reduced from the initial toner amount H, and Toner remaining amount K (H
− (A + B)) is calculated (14). Subsequently, it is determined whether or not the remaining amount K of toner in the hopper 1 obtained in step (14) is> 0 (15). If NO, the process returns to step (9) to display a warning and wait for toner replenishment. Then Y
If ES, the process returns to step (2) and waits for a print command generated by pressing the print key. On the other hand, in the judgment of step (4), ATR1
If the output of 0 is larger than the set value upper limit Smax, the supply driving unit 33 is maintained in a stopped state, the toner supply operation is stopped (16), the printing process is continued (17), and the process proceeds to step (2). Returning, the toner concentration in the developer is reduced, the supply driving unit 33 is stopped until the output value of the ATR 10 falls within the set value range, and when the output value of the ATR 10 falls within the set value range, the second The control is shifted to the control after step (10) by the replenishment control means 21. The above operation is performed for each color toner. Next, a developing device and a replenishing device using one-component toner will be described with reference to FIG. FIG. 6 is a sectional view of a developing device and a replenishing device showing another embodiment of the present invention.
Reference numerals a, 7 and 9 denote the same components as those in FIG. 1, and Q denotes a level sensor which detects the toner filling amount in the housing 7 as a position level. The toner T moves with the rotation of the sleeve 6a whose surface on the outer periphery of the fixed magnet roller 6 is roughened, and a tribo (triboelectric charge μc / g) is obtained by frictional charging with the surface of the sleeve 6a. A part of the toner moving along with the rotation of the sleeve 6a is regulated by the doctor blade 9, and the part of the toner is coated with a predetermined thickness (μ order) to develop the latent image. On the other hand, the other toner is reversed and moves in the direction of the arrow a, circulates in the housing 7, and repeats this to obtain a tribo again to contribute to development. However, if the thickness of the toner in the housing 7 becomes extremely smaller than a certain level and new toner is replenished, the toner is insufficiently tribo-coated and if the toner is developed, image fogging or reversal development occurs. Occurs. On the other hand, if the level is extremely higher than a certain level, the toner in the upper part of the housing 7 will prevent the toner from moving in the direction of the arrow a due to its own weight, and insufficiently triboelectric toner will be developed. Therefore, it is necessary to control the toner within a predetermined level. Therefore, by attaching a level sensor Q to a part of the housing 7 and replacing the output of the level sensor Q with the output of the ATR 10, the toner can be replenished with high accuracy as described above, and Can be accurately managed. The level sensor Q may be any sensor that detects a change in inductance or a change in natural frequency. FIG. 7 is a flowchart of a developer supply control according to another embodiment of the present invention. In addition, (1)-
(17) is the same as the flow in FIG. 5, and (21), (2)
2) shows steps. In step (4), the output value of the ATR 10 is compared with the upper and lower limits of the set value, and if it is determined that the output of the ATR 10 is smaller than the lower limit of the set value Smin,
Since it can be determined that the amount of toner consumed in the previous printing process, that is, the amount of toner consumption calculated by the second replenishment control unit 21 in step (11) is smaller than the amount of toner actually consumed. After step (8), a step (21) of increasing the conversion coefficient α by β (β> 0) for calculating the toner consumption from the number of print dots is provided, and the control of the second replenishment control means 21 is performed. If the operation is shifted to the operation, a calculation result closer to the actual consumption can be obtained using the corrected conversion coefficient α. In step (4), the output value of the ATR 10 is compared with the upper and lower limits of the set value.
If it is determined that the output of the ATR 10 is larger than max, the amount of toner consumed in the previous printing process, that is, the toner consumption calculated by the second replenishment control unit 21 performed in step (11). Since it can be determined that the amount is greater than the amount of toner actually consumed, a step (22) of reducing the conversion coefficient α by γ (γ> 0) is provided after step (17), and the second supply control means 21
In this case, the calculation result closer to the actual consumption can be obtained by using the corrected conversion coefficient α. Thus, for example, due to an environmental change or the like,
Even if the result of the calculation in step (11) results in a difference from the actual consumption, and is outside the set value range, the first replenishment control means 11
To the set value, and the correction process steps (21) and (22) make it possible to bring the calculation result in step (11) as close as possible to the actual consumption amount. The replenishment operation is performed by the replenishment control means 21, and as a result, the output image density can be stably maintained. FIG. 8 is a sectional view of a color image forming apparatus to which the present invention is applied. In FIG. 8, reference numerals 1 and 8 denote the same units as in FIG. 1, and reference numerals 1y, 1m, 1c, and 1bk denote hoppers, respectively. The toner is filled with a replenishing yellow toner Ty, a magenta toner Tm, a cyan toner Tc, and a black toner Tbk. Reference numerals 6y, 6m, 6c, and 6bk denote sleeves for developing each toner on the photoreceptor 8. 41 is an optical system,
An LED driver (not shown) is provided with an LED driver (not shown) in accordance with a color-separated image signal.
The D array 41a selectively emits light, and forms a dot-shaped electrostatic latent image on the photosensitive member 8 uniformly charged by the charger 42 through the light converging lens 41b. Reference numeral 43 denotes a cleaner for collecting residual toner on the photoconductor 8 after image formation.
A transfer drum 44 includes a gripper 44a for gripping the recording paper (discharge) P, and a transfer charger 44b for transferring a toner image to the recording paper P. Reference numeral 45 denotes a paper feed cassette which stores recording paper P. Reference numeral 46 denotes a separation claw, which separates the recording paper P to which each toner has been transferred from the transfer drum 44. 47
Is a transfer belt that conveys the recording paper P to the fixing device 48. 4
Reference numeral 9 denotes a discharge tray on which the recording paper P is placed. The image forming operation conforms to a known electrophotographic method, and a description thereof will be omitted. In the above embodiment, the description has been given of the case of the image forming apparatus for forming a latent image in a dot shape in accordance with the image signal fv. However, the image signal fv may be multi-valued information including halftone. In that case, a counter corresponding to the multi-valued information may be provided, the number of print dots may be counted, the blackening rate may be obtained from the sum of these, and the toner consumption may be calculated. Further, the present invention can be easily applied to a one-component developing system using a magnetic toner. Further, it goes without saying that the exposure device for exposing the photoconductor 8 may be a semiconductor laser, a gas laser, or the like. As described above, according to the present invention, an electrostatic latent image is formed on an image carrier according to an image signal.
In an image forming apparatus that develops the electrostatic latent image by a developing unit that contains a developer containing a toner and a carrier, a measuring unit that measures an image signal, and a calculation that calculates an amount of consumed toner based on a measurement value of the measuring unit Means, a replenishing means for replenishing the developing means with the amount of toner calculated by the calculating means, a detecting means for optically detecting the toner concentration in the developing means, and the calculating means based on a detection output of the detecting means. And a correction means for correcting the calculation of the consumed toner amount according to the present invention, the deviation between the actual consumed toner amount and the calculated value can be reduced or eliminated, and the ratio of the toner and the carrier is appropriately maintained. Thus, even when the amount of toner consumed by the image signal fluctuates, an excellent effect that an image with a good density can be always formed can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a replenishing means and a developing means showing one embodiment of the present invention. FIG. 2 is a diagram illustrating a relationship between a developing device and a developer concentration detecting device illustrated in FIG. 1; FIG. 3 is a block diagram illustrating a control configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a diagram illustrating an input / output relationship between a comparator and a decoder shown in FIG. 3; FIG. 5 is a flowchart illustrating developer supply control according to an embodiment of the present invention. FIG. 6 is a sectional view of a developing device and a replenishing device according to another embodiment of the present invention. FIG. 7 is a flowchart illustrating developer supply control according to another embodiment of the present invention. FIG. 8 is a sectional view of an image forming apparatus to which the present invention is applied. FIG. 9 is a relative waveform diagram due to environmental changes in surface potential and image density. DESCRIPTION OF SYMBOLS 1 Hopper 2 Developing device 3 Supply roll 4 Screw 5 Screw 6 Magnet roller 7 Housing 8 Photoreceptor 9 Doctor blade 10 Developer concentration detecting device 11 First supply control means 21 Second supply control means

Claims (1)

(57) [Claims] Forming an electrostatic latent image on the image carrier according to the image signal,
In an image forming apparatus that develops the electrostatic latent image by a developing unit that contains a developer containing toner and a carrier, a measuring unit that measures an image signal, and a calculation that calculates an amount of consumed toner based on a measurement value of the measuring unit Means, a replenishing means for replenishing the developing means with the amount of toner calculated by the calculating means, a detecting means for optically detecting the toner concentration in the developing means, and the calculating means based on a detection output of the detecting means. And a correction unit configured to correct the calculation of the amount of toner consumed by the image forming apparatus.