JPH09197797A - Image forming device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To perform appropriate toner replenishment without excess or deficiency with respect to variations in toner replenishment performance between devices and changes in image area ratio. A developing device (4) near a photosensitive drum (1),
A toner replenishing unit 7 for replenishing the toner T is provided. The toner replenishing unit 7 is a hopper 7 that stores the toner T.
a and a toner replenishing roller 7b that rotates to replenish the toner T to the developer accommodating portion 4a. The photosensitive drum 1 is provided with a reflection type photo sensor 8 for detecting the image density. Based on the density detected by the reflective photo sensor 8, the CPU 10 controls the rotation of the toner replenishing roller 7b to control the replenishing amount of the toner T. At this time, the rotation time corresponding to the actual toner replenishment amount based on the detected density is determined based on the ratio (replenishment rate) with respect to the rotation time of the toner replenishment roller 7b that maximizes the replenishment amount of the toner T. To do. That is, the supply amount is adjusted according to the frequency of the maximum supply rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for replenishing a developer in an image forming apparatus using electrophotography without excess or deficiency.

[0002]

2. Description of the Related Art Generally, a toner and a carrier are used.
In an image forming apparatus using a component developer, when a document that consumes less toner is transferred, the toner concentration is maintained at the upper limit value for a long time, toner scattering and insufficient mixing with the carrier occur, In the case of a solid original that causes a reduction in the quality of a transferred image or consumes much toner, the toner replenishment member deteriorates because it is necessary to replenish toner frequently. Therefore, a means for controlling the toner replenishment is required so that the toner replenishment can be properly performed without excess or deficiency.

Conventionally, as a control means for supplying toner to a developing device, a reference image is formed on a photosensitive drum, and the image density of this reference image is detected by an image density detecting means such as a reflection type photosensor. Replenishment of toner based on the detection result (JP-A-3-87779, JP-A-4-4)
0482, JP-A-4-261566, JP-A6-1
No. 75500), the ratio of the image information of the original image is calculated, and the toner replenishment amount is determined accordingly (JP-A-6-102760), the toner concentration of the developer in the developer accommodating portion is changed to the toner concentration. A means for detecting toner by a detecting means and supplying toner based on the detection result (Japanese Patent Laid-Open No. 60-57).
873) is known. There is also a method of correcting the toner replenishment amount based on the integrated value of the drive time of the replenishment drive unit or the integrated value of the number of copies within the toner replenishment period, or by comparing both integrated values with a reference value.

[0004]

Among the above-mentioned conventional apparatuses, in the toner replenishment control means using the image density detecting means, the density of the developed image and the image area ratio and those of the actual original are not necessarily required. They do not coincide with each other, a special calculation means for calculating the image area ratio is required, and it is possible to cope with the fluctuation of the developed image which is different for each image of the original document. There is a problem in that it cannot be corrected for changes in the environment or the environment. Further, the means for correcting the difference between the toner replenishment amount and the consumption amount on the basis of the toner concentration detection result can correct the toner replenishment amount with time or environmental changes. When many images having a large image area ratio are used, it is impossible to stabilize the developed image by increasing the toner supply amount as necessary. For example, using 10,000 originals with 3% image area,
In the case of using 00 50% originals, the toner supply amount remains small. Therefore, it is an object of the present invention to provide an image forming apparatus that performs appropriate toner replenishment without excess or deficiency with respect to variations in toner replenishment performance among apparatuses or changes in image area ratio.

[0005]

In order to solve the above problems, in the first invention, the detection result of the image density detecting means 8 for detecting the image density of the reference image formed on the image carrier 1 or the developing device. No. 4 toner replenishing means 7 for replenishing the developer accommodating portion 4a with toner T based on the detection result of the toner concentration detecting means for detecting the toner concentration in the developer accommodating portion 4a.
In the image forming apparatus including the control unit 10 for controlling the toner T, the control unit 10 controls the toner T for a predetermined number of times of image formation.
The frequency of the number of times of image formation which is the maximum replenishment amount of the toner T is calculated, and from the plurality of divisions of the replenishment amount of the toner T for a single transfer material, which is pre-ranked according to the magnitude of the frequency, the division to which the frequency belongs The image forming apparatus is configured by controlling the toner replenishing means so that the replenishment amount is In the second invention,
The control means 10 calculates the frequency of the number of times of image formation that is the maximum amount of toner supply for a predetermined number of times of image formation, and a plurality of the amounts of toner T supply per unit time that are pre-ranked according to the magnitude of this frequency. The toner replenishing means is controlled so that the replenishment amount is set to the category to which the frequency belongs.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. Referring to FIG. 1, in this image forming apparatus, a photosensitive drum 1, a charging charger 2 for uniformly charging the photosensitive drum 1 around the photosensitive drum 1, and an optical unit for exposing the photosensitive drum 1 to form an electrostatic latent image. A system 3, a developing device 4 for visualizing an electrostatic latent image with a developer, a transfer / separation charger 5 for transferring the visible image onto a transfer paper and separating the transfer paper from the photosensitive drum 1, The cleaning device 6 removes the transfer residual toner on the drum 1. The developing device 4 is provided with a developing roller 4b at the front opening of the developer container 4a. A toner replenishing unit 7 for replenishing the toner T from above is provided in the developer accommodating portion 4a. The toner replenishing unit 7 includes a hopper 7a for storing the toner T.
And a toner replenishing roller 7b provided at the lower end opening of the hopper 7a so as to drop an appropriate amount of toner T into the developer accommodating portion 4a. The photosensitive drum 1 is provided between the transfer / separation charger 5 and the cleaning device 6.
A reflection type photo sensor (hereinafter referred to as P sensor) 8 which is an image density detecting means for detecting the above image density is provided. The P sensor 8 is connected to the CPU 10, which is a control device, via an A / D converter 9. A ROM 11 and a RAM 12 are connected to the CPU 10. CP
U10 is connected via a motor driver 14 to a drive motor 13 that rotationally drives the toner supply roller 7b so as to control the rotation of the toner supply roller 7b and supply the toner T from the hopper 7a to the developer accommodating portion 4a. ing.

In the image forming apparatus of the present embodiment, a gray visible image is formed on the photosensitive drum by the toner T, and the density of the image is detected by the P sensor 7. And
When the density of the detected visible image is lower than the predetermined reference value set in advance, the CPU 10 drives the drive motor 12 to rotate the replenishment roller 7b to replenish the toner container T with the toner T. Increase toner density. That is, the larger the difference between the reference value and the detected value of the toner density, the longer the rotation time of the toner replenishing roller 7b and the more the toner replenishing amount. This control is treated as a replenishment amount per transfer sheet. Based on the detected density, the rotation time of the toner replenishing roller 7b that maximizes the replenishment amount of the toner T to the developer accommodating portion 4a in order to maximize the concentration of the toner T due to a thin original image or the like is based on the detected concentration. The rotation time corresponding to the actual toner replenishment amount is expressed as a ratio (replenishment rate),
The toner replenishment amount is corrected based on this replenishment rate. FIG. 2 shows a correction flow for the toner replenishment amount in the image developing apparatus of this embodiment. Every time the transfer operation for one transfer sheet is completed, the transfer sheet number counter n1 is incremented (S1, S2). When the maximum supply rate is reached during this transfer operation, the maximum supply rate counter m1 is incremented (S3, S4). Then, for every 1000 sheets of transfer paper, it is judged whether or not the number of times of reaching the maximum replenishment rate exceeds 5 times (S5, S6), and if it is more than 5 times,
The step (hereinafter referred to as step) corresponding to the maximum replenishment rate pre-ranked in 5 steps is stepped up by 1 (S7). However, if it is step 5,
Do not step up any further. The number counter n1 and the maximum replenishment rate counter m1 for every 1000 transferred sheets
Is cleared and returns to the initial state (S8). Through these processes, the number of revolutions of the drive motor 12 is changed so as to change the maximum replenishment rate in five stages, and the toner replenishment amount is corrected.
Table 1 shows the maximum supply rate according to the number of steps.

[Table 1] As described above, the larger the number of steps is, the higher the replenishment rate is, so that the toner supply amount is increased.

On the other hand, in the case of the process of reducing the maximum replenishment rate, in addition to the counting of the transfer sheet number counter n1 in units of 1000, the number counter n2 is counted in units of 10,000 (S2). If the maximum number of replenishment rates for each number is 0 (S9, S10), the maximum replenishment rate is lowered by one step (S11), and the number counter n2 and the maximum replenishment rate counter m2 for each transfer number of 10,000 sheets are set.
Is cleared (S12). In this way, if the maximum number of replenishment rates is 0, that is, if there is no relatively large replenishment amount, the replenishment amount is corrected so as to decrease.

The "maximum replenishment rate" is represented by a ratio (%) corresponding to the image area rate, but is substantially the rotation time of the replenishment roller 7b. In the above embodiment,
Although the toner replenishment amount is corrected based on the concept of the maximum toner replenishment rate, other factors that determine the actual toner concentration, such as the density of the visible image and the developer accommodating portion 4 are used.
You may use the density of the toner in a.

As another embodiment, instead of the above-mentioned replenishment rate, the replenishment amount of toner can be directly treated as the rotation speed of the replenishment roller. Also, in the previous embodiment,
Although the replenishment amount per transfer sheet was used, as shown in Table 2, instead of this, the replenishment amount per unit time was ranked in five stages, and the rotation speed of the replenishment roller was changed accordingly. May be.

[Table 2]

[0011]

As described above, according to the present invention, the replenishment amount for each single transfer material or the replenishment amount per unit time or the drive time of the drive unit is corrected based on the frequency of the maximum replenishment rate. It is possible to replenish the toner in a sufficient amount even when the amount of replenishment of toner varies due to a dynamic change or environmental change, or when a user transfers a document having a large image area ratio at a low frequency.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention.

FIG. 2 is a flowchart showing a replenishment rate correction process based on the frequency of the maximum replenishment rate.

[Explanation of symbols]

 1 Photosensitive Drum 2 Charging Charger 3 Optical System 4 Developing Device 4a Developer Storage Section 4b Developing Roller 7 Toner Replenishing Unit 7a Hopper 7b Toner Replenishing Roller 8 Reflective Photo Sensor 10 CPU 13 Drive Motor T Toner

Claims (2)

[Claims] 1. Based on a detection result of an image density detecting means for detecting an image density of a reference image formed on an image carrier or a toner density detecting means for detecting a toner density in a developer accommodating portion of a developing device. In an image forming apparatus including a control unit that controls a toner replenishing unit that replenishes toner to a developer accommodating portion, the control unit controls the frequency of the number of image formations that is the maximum amount of toner replenishment with respect to a predetermined number of image formations. The toner replenishing means is controlled so that the replenishment amount is calculated from a plurality of toner replenishment amounts for a single transfer material, which are pre-ranked according to the magnitude of the frequency, and to be the replenishment amount of the segment to which the frequency belongs. An image forming apparatus characterized by the above. 2. Based on a detection result of an image density detecting means for detecting an image density of a reference image formed on an image carrier or a detection result of a toner density detecting means for detecting a toner density in a developer accommodating portion of a developing device. In an image forming apparatus including a control unit that controls a toner replenishing unit that replenishes toner to a developer accommodating portion, the control unit controls the frequency of the number of image formations that is the maximum amount of toner replenishment for a predetermined number of image formations. It is characterized in that the toner replenishing means is controlled so that the replenishment amount of the division to which the frequency belongs is calculated from a plurality of divisions of the toner replenishment amount per unit time that are calculated and ranked in advance according to the magnitude of this frequency. Image forming apparatus.