JP4914243B2 - Development device - Google Patents

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a printer, a facsimile using an electrophotographic system, and a multifunction machine functionally equipped with these.

  Conventionally, a printing rate control method for supplying toner based on the dot count detection level (printing rate) of the output image to the toner in the developing device consumed in the image forming process, or toner toner in the developing device. A developing device that employs a magnetic permeability control system that replenishes toner based on a density detection level (magnetic permeability) is known.

In addition, a developing device that adjusts a toner replenishment amount by detecting an image density (patch density) formed on a photoreceptor using an image density sensor in combination with toner replenishment by a printing rate control method is known. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 06-003962

  However, in the developing device configured as described above, for example, in the case of printing rate control using dot count, when a thin line or a small dot image is output as an output image and when a solid image is output Even with the same dot count, the amount of toner to be developed is different, so the toner density of the toner becomes unstable, and toner replenishment control in milligram units is required, resulting in a complicated and expensive developing device. There was a problem.

  Further, in a developing device that adjusts the replenishment amount of toner for replenishment from the toner container by using both the detection level by the toner concentration sensor and the detection level by the dot count, if the toner concentration in the developing device is lower than the target control value When the toner concentration sensor detects that the toner replenishment amount is calculated based on the level detected by the dot counter and the toner is replenished, and the toner concentration sensor detects that the toner concentration in the developing device is higher than the target control value. In general, toner is not replenished.

  However, in the case of a developing device in which a toner conveyance path is provided between the toner container and the developing device, the replenishment toner is actually fed into the developing device via the toner conveyance path after the replenishment toner is sent from the toner container. Since it takes time for the toner density sensor to supply toner after it is replenished, there is a problem that when the high density document is continuously printed, the toner density in the developing device becomes insufficient and image unevenness occurs. It was.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a developing device capable of stabilizing toner density and image density without requiring a complicated and expensive toner supply system. And

The developing device of the present invention includes a toner container that stores replenishment toner, a developing device that supplies toner to a photoconductor, a toner conveyance path that conveys the replenishment toner from the toner container to the developing device, a toner density sensor for detecting the toner density in the developing device, and the dot counter for detecting the printing ratio of the output image, a combination of a detection level by the dot counter and the detection level by the toner density sensor And a control unit that adjusts the replenishment amount of the replenishment toner from the toner container. The control unit has a detection level of the toner density sensor lower than a threshold value and a detection level of the dot counter. If it is higher than the threshold value, the first predetermined value is added to the replenishment toner amount calculated based on the detection level based on the dot count. When the replenishment toner amount supplemented with, both the detection level of the dot counter and the toner density sensor are both detected a higher high than the threshold, calculated on the basis of the detection level by the dot counter An amount of replenishment toner obtained by subtracting a second predetermined value from the amount of replenishment toner to be supplied is characterized in that

  At this time, it is preferable that the control unit performs the above-described toner replenishment control when two or more image forming processes are continuously performed.

  The developing device of the present invention can realize stabilization of toner density and stabilization of image density without requiring a complicated and expensive toner supply system.

  Next, a developing device according to an embodiment of the present invention is applied to a printer as an image forming apparatus and will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram of a developing device according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing the relationship between the toner concentration in the developing device and the detection level of the toner concentration sensor in the developing device according to an embodiment of the present invention. FIG. 3 is a flowchart of a main control routine of a control circuit in the developing device according to the embodiment of the present invention, and FIG. 4 is a toner density in the case where control is performed by the control circuit in the developing device of the embodiment of the present invention. FIG. 5 is a comparative graph of sensor output voltage, FIG. 5 is a comparative graph of image density in the presence or absence of control by a control circuit in the developing device according to one embodiment of the present invention, and FIG. 6 is a developing device according to one embodiment of the present invention. It is a flowchart of the treatment control routine of the control circuit in FIG.

  In FIG. 1, reference numeral 1 denotes an endless belt-like intermediate transfer belt, a part of which is omitted (right side in the figure), 2 is a temporary turn of the intermediate transfer belt 1 and the intermediate transfer belt 1 is rotated (see arrows a and b in the figure). 3) a driving side or driven side pulley 3 for receiving the print data output from a personal computer (not shown), and 4 for driving the entire printer based on the print data received by the receiving unit 3. 5 is a storage unit such as a ROM that stores various control programs executed by the control circuit 4, and 6 is an image forming process control and toner replenishment control under the control of the control circuit 4. Development device.

  The control circuit 4 and the storage unit 5 constitute a microcomputer for executing the toner supply control of the present invention. In addition, the control circuit 4 temporarily stores the print data received by the receiving unit 3 and the image data included in the print data in a RAM, HDD, or the like (both not shown), and then performs image forming processing by the developing device 6. Execute.

  Although only one developing device 6 is disclosed here, for example, in the case of a full-color printer, four (yellow, magenta, cyan, black) toners are used for the rotational movement direction of the intermediate transfer belt 1. A tandem system is used. Further, the developing device 6 is disposed above the intermediate transfer belt 1 and has a toner container 7 that stores the replenishment toner of one of the above-described colors, and a drum-shaped photosensitive member disposed below the intermediate transfer belt 1. A transfer roller 9 that faces the photoconductor 8 with the intermediate transfer belt 1 interposed therebetween, a developing device 10 that supplies toner to the photoconductor 8, and a toner conveyance path that conveys replenishment toner from the toner container 7 to the developing device 10. 11. A cleaning member 12, a charge eliminator 13, a charger 14, an exposure unit 15, and a toner replenishing drive unit 16 disposed along the rotation direction upstream of the developing unit 10 in the rotation direction of the photosensitive member 8. . In addition to the various configurations described above, the developing device 6 includes a dot counter 17 for calculating a printing rate (detection level) from image data (output image) included in the print data received by the receiving unit 3, and a photoconductor. 8 is provided with an image density sensor 18 for detecting the image density (for example, patch density) of the toner image T transferred from the intermediate transfer belt 1 to the intermediate transfer belt 1, and the dot counter 17 and the image density sensor 18 are each developed. Shared for device 6.

  The toner container 7 includes an agitator 19 for stirring the supplied replenishment toner, a conveyance screw (not shown) for executing supply / stop of the replenishment toner to the toner conveyance path 11, a shutter 20, and the like. Driving systems such as the agitator 19, the conveying screw, and the shutter 20 are driven by the toner replenishing driving unit 16.

  The photoconductor 8 is made of OPC, amorphous silicon, or the like. For example, in the case of OPC, the photoconductor 8 is selected based on a balance between sensitivity and life, for example, a film thickness of 20 μm to 40 μm.

The developing device 10 is formed by a casing 21 containing toner to be supplied to the photosensitive member 8, a pair of stirring mixers 22 and 23 for stirring the toner in the casing 21, and an exposure device 15 adjacent to the photosensitive member 8. The developer carrying member 24 that forms a toner image on the photosensitive member 8 based on the electrostatic latent image thus formed, the regulating blade 25 that regulates the flow rate of the developer carried on the developer carrying member 24, and the toner transport path 11 And a toner concentration sensor 26 for detecting the toner concentration in the developing device 10 including the replenishment toner supplied via the toner.
The developer carrier 24 includes a rotatable sleeve containing a fixed magnet (both not shown), holds the toner after the flow rate is adjusted by the regulating blade 25, and faces the photoreceptor 8. The toner is developed on the photosensitive member 8 at the position, and the agitation mixers 22 and 23 are replaced with new toner.

  The replaced toner is circulated in the developing device 10 by the agitating mixers 22 and 23, and the toner concentration is detected at the position of the toner concentration sensor 26 during the circulation, and from the toner container 7 through the toner conveyance path 11 as necessary. Supply toner via

  Since the toner container 7 and the developing device 10 are arranged so that the intermediate transfer belt 1 is sandwiched between the toner transfer path 11 on the upper and lower sides, the replenishment toner between them is lateral to avoid the intermediate transfer belt 1. And spirals 27 and 28 for transporting the replenishing toner supplied from the toner container 7 to the developing device 10 when the shutter 20 is in the open state.

  The toner replenishment drive unit 16 constitutes a general drive system for replenishing replenishment toner from the toner container 7 to the developing device 10 via the toner transport path 11. For example, a drive system ( For example, a rotation drive of the agitator 19 and opening / closing of the shutter 20), a stirring mixers 22 and 23, a driving system of the developer carrier 24, driving systems of the spirals 27 and 28, and the like are provided. These drive systems do not mean synchronous drive by one drive source.

  In the above configuration, an electrostatic latent image is formed on the surface of the photoconductor 8 charged by the charger 14 by the beam emitted from the exposure device 15 based on the image data included in the print data received by the receiving unit 3. The toner is supplied to the surface of the photoconductor 8 by the developing device 10, and the electrostatic latent image is visualized as a toner image.

  In the present invention, the toner image formed on the surface of the photoconductor 8 is once transferred as a toner image T to the surface of the intermediate transfer belt 1, and an image density sensor 18 is used to detect an image density such as calibration. The concentration is detected.

  Further, the photosensitive member 8 is neutralized by the static eliminator 13 after removing the transfer residual toner or the like that has not been completely transferred to the intermediate transfer belt 1 from the toner image formed on the surface thereof by the cleaning member 12.

  On the other hand, the toner density sensor 26 outputs an output voltage signal as a magnetic permeability (detection level) of toner in the developing device 10 to the control circuit 4 during image printing (during development of toner from the developing device 10 to the photoconductor 8). Output. The control circuit 4 calculates the toner density in the developing device 10 based on the output voltage signal.

  For example, when the toner density is high, the output voltage of the toner density sensor 26 is low, and when the toner density is low, the output voltage of the toner density sensor 26 is high.

  Then, as shown in FIG. 2, when two or more image forming processes are performed, if the toner density is lower than a predetermined threshold (stored in the storage unit 5), a dot is generated based on the image data. The amount of toner replenishment corresponding to the printing rate calculated by the counter 17 is calculated, and the toner is replenished slightly more (+ α) than the toner replenishing amount corresponding to the printing rate.

  When the toner density is higher than the threshold value, toner is supplied by an amount (−β) smaller than the toner supply amount corresponding to the printing rate calculated by the dot counter 17 based on the image data.

  At this time, since the toner density is higher than the threshold value by a certain value or more, if it is necessary to quickly reduce the toner density, it is not necessary to supply the toner. When the toner density is lower than a threshold value by a certain level or more, the printing operation is stopped and the treatment operation is performed.

  Next, an example of toner supply control by the control circuit 4 will be described with reference to the flowchart of FIG.

(Step S1)
In step S1, the control circuit 4 executes an image forming process based on the image data included in the print data received by the receiving unit 3, and calculates the printing rate by the dot counter 17 based on the image data. The process proceeds to S2.

(Step S2)
In step S2, the control circuit 4 calculates the current toner density in the developing device 10 based on the output voltage (magnetic permeability) output from the toner density sensor 28, and sets a control voltage set in advance from the output voltage. It is determined whether or not a voltage difference obtained by subtracting (threshold) is larger than a treatment threshold voltage difference A (for example, 0.1 V) set to require a treatment operation, and the voltage difference is greater than the treatment threshold voltage difference A. If the difference is larger, the process proceeds to step S10 and the treatment operation routine shown in FIG. 6 is processed. If the voltage difference is smaller than the treatment threshold voltage difference A, the process proceeds to step S3.

(Step S3)
In step S3, the control circuit 4 compares the output voltage with the control voltage. If the output voltage is greater than the control voltage, the control circuit 4 proceeds to step S4, and the control voltage is greater than the output voltage. To step S5.

(Step S4)
In step S4, since the control circuit 4 does not require the treatment operation and requires toner replenishment, the toner for replenishment is slightly larger (for example, 110% to 120%) than the printing rate obtained in step S1. The amount is calculated and the process proceeds to step S7.

(Step S5)
In step S5, the control circuit 4 determines whether or not the voltage difference obtained by subtracting the output voltage from the control voltage is smaller than the no-replenishment threshold voltage difference B (for example, 0.03V) set so as to make toner replenishment unnecessary. If it is determined that the voltage difference is smaller than the non-replenishment threshold voltage difference B, the process proceeds to step S6. If the voltage difference is greater than the non-replenishment threshold voltage difference B, the toner replenishment is unnecessary and this routine is terminated. .

(Step S6)
In step S6, the control circuit 4 calculates the amount of toner for replenishment that requires toner replenishment, and the toner replenishment amount is less than the printing rate obtained in step S1 (for example, 50%), and proceeds to step S7. Transition.

(Step S7)
In step S7, the control circuit 4 replenishes the replenishment toner for the toner replenishment amount obtained in step S4 or step S6 from the toner container 7 to the developing device 10 via the toner transport path 11 and ends this routine. To do.

  FIG. 4 shows the transition of the output voltage of the toner density sensor 26 and FIG. 5 shows the transition of the image density when an original (image data) with a printing rate of 50% is continuously printed. As shown in FIGS. 4 and 5, when the toner replenishment control of the present invention is used, both the transition of the toner density sensor output voltage and the image density are compared with the case where the toner replenishment control of the present invention is not used. It turned out to be stable.

  In the treatment operation routine described above, as shown in FIG. 6, the treatment operation is executed (step S11), and the sensitivity (sensor abnormality) of the toner concentration sensor 26 is included by the output signal from the toner concentration sensor 26. When the toner concentration in the developing device 10 is monitored and the toner concentration is not increased because the toner needs to be replenished or only a small amount of toner is replenished (step S12), etc. An exchange message or the like of the toner container 7 is notified that the replenishment toner in the container 7 is empty (step S13).

  As described above, according to the developing device of the present invention, when two or more image forming processes are being performed, the toner density detected by the toner density sensor 26 is a case where the dot counter 17 has a high detection rate and a high printing rate. Is higher than the threshold value, a complicated and expensive toner replenishment system is not required by replenishing a replenishment toner amount smaller than the replenishment toner amount calculated based on the detection level by the dot counter 17. In addition, stabilization of the toner density and stabilization of the image density can be realized.

  In the above embodiment, the developing device of the present invention is applied to a tandem color printer. However, it is needless to say that the developing device can be applied to general image forming apparatuses such as a copying machine and a multifunction machine. .

It is explanatory drawing of the developing device which concerns on one Embodiment of this invention. FIG. 6 is an explanatory diagram showing a relationship between a toner density in a developing device and a detection level of a toner density sensor in a developing device according to an embodiment of the present invention. It is a flowchart of the main control routine of the control circuit in the developing device concerning one embodiment of the present invention. FIG. 6 is a comparative graph of toner density sensor output voltage when control is performed by a control circuit in the developing device according to the embodiment of the present invention. FIG. 10 is a comparative graph of image density when control is performed by a control circuit in the developing device according to the embodiment of the present invention. It is a flowchart of the treatment control routine of the control circuit in the developing device concerning one embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Intermediate transfer belt 4 ... Control circuit (control part)
DESCRIPTION OF SYMBOLS 6 ... Developing device 7 ... Toner container 8 ... Photoconductor 10 ... Developing device 11 ... Toner transport path 16 ... Toner replenishment drive unit 17 ... Dot counter 18 ... Image density sensor 26 ... Toner density sensor

Claims (2)

A toner container containing replenishing toner, a developing device for supplying toner to the photosensitive member, a toner transport path for transporting the replenishing toner from the toner container to the developing device, and a toner concentration in the developing device. a toner density sensor for detecting a dot counter for detecting the printing ratio of the output image, replenishment from the a combination of a detection level by the dot counter and the detection level by the toner density sensor toner container A developing device including a controller for adjusting a toner replenishment amount;
When the detection level of the dot counter is high and the toner density by the toner density sensor is lower than a threshold value , the control unit calculates the replenishment toner amount calculated based on the detection level by the dot counter In the case where the amount of replenishment toner added to the first predetermined value is replenished and the detection level of the dot counter is high and the toner density by the toner density sensor is higher than a threshold value, the dot count is increased. developing and wherein the replenishing amount of the replenishment toner obtained by subtracting a second predetermined value from the replenishment toner amount calculated based on the detected level by the motor. The control unit is configured to detect the dot counter when the detection level of the dot counter is high and the toner density by the toner density sensor is lower than a threshold when two or more image forming processes are performed continuously. When the replenishment toner amount calculated by adding the first predetermined value to the replenishment toner amount calculated on the basis of the detection level is supplied, and the image forming process continues two or more, the dot counter detects If the toner concentration is higher than the threshold are by and the toner concentration sensor even when the level is high, subtracting the second predetermined value from the replenishment toner amount calculated based on the detection level by the dot counter the developing device according to claim 1, characterized in that supplemented with the replenishment toner amount.

Images