JPH0594090A - Image forming device - Google Patents

Abstract

PURPOSE:To stably and highly accurately detect image density and to stably replenish toner in an image forming device such as a copying machine or printer. CONSTITUTION:First a photosensitive body 1 is controlled so that its potential becomes nearly zero and a bias voltage of the same polarity as toner is applied to a developing sleeve 11. Consequently, the toner from the developing sleeve 11 is stuck to the photosensitive body 1 and the prescribed reference image is formed. Changed on the photosensitive body 1 attending on the formation of the reference image are accumulated in a capacitor 6 and the quantity of the accumulated charges is measured by a controller 7, thereby detecting the image density based on the quantity of the charges. The quantity of toner replenished to the main body 8 of a developing device 3 by a toner replenishment device 10 is adjusted based on the detected value.

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 such as a copying machine or a printer, and more particularly to an image forming apparatus having a function of stabilizing a toner supply amount.

[0002]

2. Description of the Related Art Generally, an image forming apparatus of this type is provided with a photoconductor, a developing device, etc., which is a toner replenishing device for replenishing toner from a hopper to a toner tank and a toner on the surface of the photoconductor. And a toner supply device for supplying toner to the developing sleeve. Then, when the photoconductor on which the electrostatic latent image is formed passes through a portion facing the developing device in the state where the bias voltage is applied, the toner from the developing sleeve is attached to the electrostatic latent image. , The electrostatic latent image is visualized. As an apparatus having a function of performing such an image forming procedure, detecting the image density of a visible image on the photoconductor, and replenishing toner based on the detected image density, for example, Japanese Patent Laid-Open No. 61-279876. The one disclosed in is known. In the apparatus disclosed in the above publication (see FIG. 5), during a normal image forming operation, the developing device is connected to a stabilized developing bias power source to form an image. On the other hand,
When image density detection (toner adhesion amount detection) is performed and toner is replenished, the developing bias power source is switched,
Toner is attached to the basic latent image formed on the surface of the photoconductor by so-called self-bias development. At this time, the developing current flows through the resistance element, but the voltage generated with the flow of the developing current is measured, and the toner adhesion amount is calculated based on this voltage value. In this case, the basic latent image is obtained by scanning the black reference pattern attached to the lower surface side of the document table with the optical system. When the toner adhesion amount is equal to or less than the reference value, a toner replenishment signal is output, and the toner is replenished to the toner tank based on the signal.

[0003]

In the toner replenishing process performed as described above, since the self-bias development is applied at the time of detecting the image density as described above, unlike the case where the developing bias power source is used, The potential difference generated during the development of the basic latent image is not stable. That is, the amount of toner adhered to the surface of the photoconductor is not stable. Further, the potential difference due to the developing bias at the time of actual image formation performed using the developing bias power source is different from the potential difference caused by the adhesion of toner at the time of image density detection. That is, there is a gap in the correspondence relationship of the toner adhesion amount. Therefore, the conventional image forming apparatus cannot detect the image density stably and highly accurately, and the toner replenishment performed based on the detection result cannot accurately stabilize the replenishment amount. Therefore, the present invention has been devised in view of the above circumstances, and utilizes the developing bias during normal image formation to stably and highly accurately detect the image density and perform stable toner supply. It is an object of the present invention to provide an image forming apparatus capable of performing the above.

[0004]

In order to achieve the above-mentioned object, the first means adopted by the present invention is the gist of the invention, in which an electrostatic latent image is formed on the surface of a photoreceptor and toner is discharged from a hopper. An image forming apparatus for applying a bias voltage to a developing device having a toner replenishing means for replenishing the electrostatic latent image to attach the toner from the developing device to the electrostatic latent image to visualize the electrostatic latent image, A potential control means for bringing the potential of the photoconductor to a substantially zero state, and a bias voltage having the same polarity as the toner to the developing device are applied to the photoconductor which is brought to a state of a substantially zero potential by the potential control means. A reference image forming means for forming a predetermined reference image by adhering toner from the developing device, a charge accumulating means for accumulating electric charges in the photoconductor due to the formation of the reference image, and an electric charge accumulating means for accumulating the charges. Amount of charge Measuring means for measuring an image forming apparatus according to the points obtained by and a toner supply speed control means for controlling the toner supply speed of the toner replenishing means based on the amount of charge measured by said measuring means. Further, the second means adopted by the present invention is, as the gist thereof, that a bias voltage is applied to a developing device provided with a toner replenishing means for replenishing toner from a hopper while forming an electrostatic latent image on the surface of a photoreceptor. In the image forming apparatus for applying the toner from the developing device to the electrostatic latent image to make the electrostatic latent image visible, the potential control means for setting the potential of the photoconductor to a substantially zero state. Then, a bias voltage having the same polarity as that of the toner is applied to the developing device, and the toner from the developing device is attached to the photoconductor that is brought to a state of substantially zero potential by the potential control means to form a predetermined reference image. Reference image forming means for forming, charge accumulating means for accumulating electric charges in the photoconductor due to formation of the reference image, measuring means for measuring the amount of electric charge accumulated in the charge accumulating means, and measurement by the measuring means. Done A toner replenishing means for controlling the toner replenishing speed of the toner replenishing means on the basis of the amount of electric charge and controlling the bias voltage for the developing device to regulate the toner supply amount from the developing device to the photoconductor. The image forming apparatus according to the above point.

[0005]

In the image forming apparatus according to the present invention, first,
The photoconductor is controlled to have a substantially zero potential, and a bias voltage having the same polarity as the toner is applied to the developing device. As a result, the toner from the developing device is attached to the photoconductor to form a predetermined reference image. The charge on the photoconductor due to the formation of the reference image is accumulated by the charge accumulating means, and the amount of charge accumulated in the charge accumulating means is measured. Then, the image density is detected based on this charge amount, and the toner replenishment speed is mainly controlled to stabilize the toner replenishment amount.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the accompanying drawings for the understanding of the present invention. The following embodiments are examples of embodying the present invention and are not of the nature to limit the technical scope of the present invention. Here, FIG. 1 is a schematic diagram of a main part of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a flow chart showing a procedure for stabilizing the toner supply amount in the image forming apparatus, and FIG.
FIG. 4 is a configuration diagram of a main part of an image forming apparatus according to another embodiment of the present invention, and FIG. 4 is a table showing a correspondence relationship between polarities of a photoconductor and a developing device at the time of image formation and image density detection in each developing method. Is. In the image forming apparatus according to this embodiment, for example, as shown in FIG. 1, a main charger 2, a developing device 3, a cleaning device 4, etc. are arranged around a photoconductor 1.
The photoconductor 1 is grounded via a ground changeover switch 5 and a capacitor 6 arranged in parallel. The capacitor 6 is connected to a control device 7 including a microcomputer, a memory, etc. via a comparison circuit 14,
In the memory, a control procedure at the time of image formation of the image forming apparatus, a control procedure at the time of stabilizing the toner replenishment amount, and the like are stored in advance. In the developing device 3, a toner hopper 9 is provided on the upper part of the main body 8, and the toner hopper 9 is rotatably driven by a motor 15 in the toner hopper 9.
A toner replenishing device 10 for replenishing toner from the toner hopper 9 into the main body 8 is provided. A motor (not shown) rotates in the main body 8, and a developing sleeve 11 that supplies toner toward the photoconductor 1 and a motor (not shown) rotate and drive the developing sleeve 1.
A toner supply roller 12 and the like for supplying toner to 1 are provided. The developing sleeve 11 and the toner supply roller 12 are connected to a bias power source 13.

When an image is formed in the image forming apparatus, for example, in the reversal development method (see FIG. 4), the main body 2 is charged with the main charger 2 when the grounding switch 5 is turned on and the grounded state is established. Are uniformly charged to the negative (-) side. Then, the uniformly charged surface of the photoconductor 1 is exposed to form an electrostatic latent image on the surface of the photoconductor 1. Subsequently, toner (charged to the negative side) from the developing sleeve 11 is attached to the electrostatic latent image to make the electrostatic latent image visible. In this case, the developing sleeve 11 is provided with the bias power source 1
At 3, a bias voltage of the same polarity is applied to the toner. Next, in the image forming apparatus, the procedure for adjusting the toner replenishment amount based on the image density so that the toner replenishment can be stably performed will be described with reference to FIG.
It will be explained based on. In the figure, S1, S2, ... Show each processing step. In S1, the copy button provided on the operation panel (not shown) is turned on, and the image density detection processing is performed at an appropriate timing during the copying operation. That is, in S2, control is performed to bring the potential of the photoconductor 1 to a substantially zero state. In detail, first, the main charger 2
And the photoconductor 1 with the bias power supply 13 turned off.
Is driven to rotate, and the entire surface of the photoconductor 1 is exposed. At this time, the ground changeover switch 5 is turned on, and the photoconductor 1 is in the grounded state. As a result, the charges of the photoconductor 1 are released to the ground side. Subsequently, the ground changeover switch 5 is turned off, and the photoconductor 1 is in a state of being electrically connected only to the capacitor 6 (S3). Then, in S4, the toner from the developing sleeve 11 is attached to the photosensitive member 1 to form a predetermined reference image. That is, the bias power source 13 applies the same bias voltage (bias having the same polarity to the toner) to the developing sleeve 11 as in the normal image forming operation for a predetermined time (for example, 0.3 seconds), Toner is adhered (developed) on the photoconductor 1 at a known area (developing sleeve width (cm) × time (sec) × photoconductor peripheral speed (cm / sec)) to form the reference image. Therefore, the area of this reference image is small, and the amount of toner supplied to it is extremely small.

Then, the charges on the photoconductor 1 due to the formation of the reference image are accumulated in the capacitor 6, and the amount of charges accumulated in the capacitor 6 is measured by the controller 7 (S5). After the measurement of the charge amount, the ground changeover switch 5 is turned on to return to a state where normal image formation can be performed (S6). Since the charge amount and the development amount by the toner are in a proportional relationship according to the toner concentration on the photoconductor 1, the comparison circuit between the charge amount in the capacitor 6 and the reference data corresponding to the preset toner development amount is provided. By comparing and determining in 14 (S7), the development amount by toner, that is, the image density is detected. When the image density is detected as described above and a decrease in the toner density due to a decrease in the amount of toner transferred to the photoconductor 1 is detected, the motor 15 is rotated for a predetermined time corresponding to the decrease in the toner density. Under control (S8), the toner is supplied from the toner hopper 9 to the main body 8. After the toner replenishment amount adjustment process is completed as described above, the normal image forming process is resumed (S9). In the image forming apparatus according to this embodiment, the image density is detected by the procedure as described above, and the toner is replenished based on the detection. That is, since the image density can be detected by utilizing the developing bias during the normal image formation, the image density can be detected more stably and more accurately than in the case of the conventional apparatus, and the toner replenishment is further performed. Can be performed stably. Further, since the reference pattern as in the case of the conventional device is unnecessary, it is possible to contribute to simplification of the configuration.

Next, an image forming apparatus according to another embodiment of the present invention, which can achieve substantially the same effects as described above, will be described with reference to FIG. The same reference numerals are used for the same elements as those of the embodiment apparatus shown in FIG. 1, and the detailed description thereof will be omitted. In the apparatus of the above-described embodiment, the motor 15 is used according to the toner density (corresponding to the measured value) on the photoconductor 1.
In contrast to the rotation control of only the motor 15, in the image forming apparatus shown in FIG. 3, the variable bias power supply device 19 is also controlled. In the control device 20, the comparison circuit 14 compares the measured value with the reference data to control the motor 15 as described above. When the measured value is lower than the reference data, the developing bias is high and the measured value is When it is higher than the reference data, the developing bias is controlled to be changed to a low value. As a result, the amount of toner supplied from the developing sleeve 11 to the photoconductor 1 is also adjusted. In this case, the toner supply roller 12 may be configured as a power source separate from the bias power source device 19. In each of the above embodiments, the case where the photoconductor 1 and the toner are both charged to the negative side in the reversal development method has been described as an example. However, the photoconductor 1 and the toner are charged to the plus (+) side. In this case, even in the case of the positive development method, the image density can be detected and the toner replenishment amount can be adjusted by the same procedure as described above. However, in the normal development method, it goes without saying that bias voltages of different polarities are applied to the toner during normal image formation (see FIG. 4).

[0010]

Since the image forming apparatus according to the present invention is configured as described above, it is possible to detect the image density by utilizing the developing bias during the normal image formation. Therefore, in the image forming apparatus, it is possible to stably and highly accurately detect the image density and to stably supply the toner, as compared with the case of the conventional apparatus.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing a procedure for stabilizing the toner supply amount in the image forming apparatus.

FIG. 3 is a configuration diagram of a main part of an image forming apparatus according to another embodiment of the present invention.

FIG. 4 is a chart showing a correspondence relationship between polarities of a photoconductor and a developing device at the time of image formation and image density detection in each developing method.

FIG. 5 is a schematic block diagram showing a main configuration of a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photosensitive member 2 ... Main charger 3 ... Developing device 5 ... Grounding switch 6 ... Capacitor 7, 20 ... Control device 8 ... Main body 9 ... Toner hopper 10 ... Toner replenishing device 11 ... Developing sleeve 12 ... Toner supply roller 13 ... Bias Power supply 14 ... Comparison circuit 15 ... Motor 19 ... Bias power supply device S1 to S9 ... Processing step

Claims (2)

[Claims] 1. A bias voltage is applied to a developing device having a toner replenishing means for replenishing toner from a hopper while forming an electrostatic latent image on the surface of a photoconductor, and the electrostatic latent image is fed from the developing device. In an image forming apparatus that visualizes the electrostatic latent image by adhering toner, a potential control unit that sets the potential of the photoconductor to a substantially zero state, and a bias voltage having the same polarity as the toner to the developing device. A reference image forming unit that forms a predetermined reference image by applying toner from the developing device to the photoconductor that has been applied and is brought to a state of substantially zero potential by the potential control unit. Charge accumulating means for accumulating charges in the photoconductor, measuring means for measuring the amount of electric charges accumulated in the charge accumulating means, and toner replenishment of the toner replenishing means based on the electric charge amount measured by the measuring means. An image forming apparatus comprising: a toner replenishment speed control means for controlling the speed. 2. A bias voltage is applied to a developing device provided with a toner replenishing means for replenishing toner from a hopper while forming an electrostatic latent image on the surface of a photoreceptor, and the electrostatic latent image is fed from the developing device. In an image forming apparatus that visualizes the electrostatic latent image by adhering toner, a potential control unit that sets the potential of the photoconductor to a substantially zero state, and a bias voltage having the same polarity as the toner to the developing device. A reference image forming unit that forms a predetermined reference image by applying toner from the developing device to the photoconductor that has been applied and is brought to a state of substantially zero potential by the potential control unit. Charge accumulating means for accumulating charges in the photoconductor, measuring means for measuring the amount of electric charges accumulated in the charge accumulating means, and toner replenishment of the toner replenishing means based on the electric charge amount measured by the measuring means. An image forming apparatus comprising: a toner amount adjusting means for controlling a speed and a bias voltage for the developing device to adjust a toner supply amount from the developing device to the photosensitive member.