JPH117198A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change voltage applied to the rollers and blade of a developing unit, in accordance with an environmental change and the density of an image, for keeping the density of the image of a copy constant by providing a power source for feeding power to each of the supplying roller, developing roller and blade and a current limiting resistor, in a state that it is connected to the power source and one of the power-fed members. SOLUTION: The developing unit 10 is provided with paths for directly applying the voltage to the developing roller 14 and blade 15 through power sources 30a and 30b. Further, paths for feeding the power to the supplying roller 13 from the power source 30 directly and through the resistor R are arranged. Then, a switching device 37 is arranged in these two power feeding paths as well. When an environmental temp. is varied and the operational environment of a device is varied as well, the detection signal of a sensor 35 is inputted to a controller 36 and the path for directly applying the applied voltage from the power source 30 is switched to the path for applying the voltage through the resistor R, in accordance with conditions set in the controller 36.

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 using an electrophotographic system, and more particularly to an image forming apparatus capable of stably supplying toner from a developing roller of a developing device to a photosensitive member. .

[0002]

2. Description of the Related Art A general electrophotographic image forming apparatus uses a drum-shaped or belt-shaped photosensitive member for carrying a toner image, and a charging device for uniformly charging the photosensitive member. An exposure device for irradiating the surface of the body with light to form an electrostatic latent image, a developing device for forming a toner image by attaching toner to the electrostatic latent image, and a toner image formed on the photoconductor. It is equipped with a transfer device for transferring to paper. In the developing device, a stirrer that feeds toner while stirring the toner inside the toner container, a supply roller, and a developing roller for supplying toner to the photoconductor are arranged. To form a thin layer of toner.

In the above-described image forming apparatus, in the case of a developing device using a one-component toner, a voltage of a predetermined value is applied to each of a supply roller, a developing roller, and a blade, so that the toner smoothly flows between the roller members. And transferred to the photoreceptor. Further, in order to attach the toner to the surface of the developing roller and expose the toner to the developing position with respect to the photoconductor, the toner is charged between the supply roller and the developing roller, and a thin layer having a certain thickness is provided by a blade. Is required to be formed.

[0004]

However, in a conventional developing device using a one-component toner, the change from the developing roller to the supply roller due to a change in environment such as temperature and humidity and a change in printing ratio such as image density. The inflow current may increase, which may cause a problem that the toner is not properly supplied to the developing roller. When such a problem occurs, the charge amount of the toner changes, and the printing density changes (increases or decreases), which may make it impossible to maintain a constant copy quality. Also, in a blade for forming a thin layer of toner in contact with the developing roller, if the current flowing from the developing roller toward the blade increases, the charge amount of the toner changes, and the print density cannot be maintained satisfactorily. There was a problem.

The present invention solves the problems of the conventional developing device as described above, and changes the voltage applied to the rollers and blades of the developing device in accordance with changes in the environment and image density. It is an object of the present invention to provide an image forming apparatus for maintaining a constant image density of a copy.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a developing roller for supplying toner to a photoreceptor, a supply roller for supplying toner to the developing roller, and a blade for forming a thin layer of toner on the surface of the developing roller. The present invention relates to a developing device provided with:
According to the first aspect of the present invention, a power supply for supplying power to each of the supply roller, the developing roller, and the blade is provided, and a current limiting resistor is connected to one of the power supply and the power-supplied member. It is characterized by the following. According to a second aspect of the present invention, in the developing device, a resistor is interposed between a supply roller for supplying toner to the developing roller and a power supply. Further, in the invention according to claim 3, in the developing device, a blade for forming a thin layer of toner on the developing roller is supplied with power from the same power supply as the developing roller via a resistor.

Therefore, in the developing device of the present invention,
By adjusting the voltage applied to the supply roller, the developing roller, or the blade, it is possible to set the difference between the voltages applied to the respective members and to perform the toner supply operation satisfactorily. Then, by stabilizing the charge amount of the toner supplied to the photoconductor, it is possible to prevent a toner supply failure or the like from occurring and to maintain a good image density of the toner image transferred to the paper. Further, in the present invention, the device for changing the voltage only adds a resistor of a predetermined value to the conventional power supply circuit, and additionally provides a detection value of a detection device such as a temperature to the control device. , Means for inputting control information based on the detected value is used,
The configuration of the device is not complicated.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The overall structure of an image forming apparatus according to the present invention will be described below with reference to FIG. The image forming apparatus 1 is configured such that a paper feed cassette 2 is attached to a lower portion of its main body to feed paper. The paper feed cassette 2 is provided with a bottom plate 2a on which paper is placed and a separation claw 2b for separating paper. Further, a pickup roller 3 is provided for feeding paper from a paper feed cassette, and a half-moon roller is used as the roller 3. Conveying roller devices 4 and 5 are disposed in a sheet conveying path for guiding the sheet fed from the sheet feeding cassette, and a fixing device 28 is provided downstream of an image transfer section by a transfer roller 26, and a discharge roller device 29 is provided. And a path for discharging the copy via the. Then, the photosensitive roller 21 is arranged by a transport roller device disposed immediately before the photosensitive member.
By applying a voltage from the transfer roller 26 while feeding the paper in time with the toner image formed on the photoconductor, the toner image formed on the photoconductor is transferred onto the paper.

In the image forming apparatus shown in this embodiment,
A side plate 7 of the apparatus main body is provided to be openable and closable in a part of the sheet conveying path from the sheet cassette 2, and when a paper jam or the like occurs in the sheet conveying path, a guide plate provided integrally with the side plate is provided. Used when performing jam clearance when opened. Also, the side plate 7
A manual feed tray 6 is provided through an opening provided in an upper portion of the paper feed tray. A manual feed roller 8 is arranged corresponding to the paper feed path, and another paper feed system for feeding paper toward the registration roller device 5 is provided. Is composed. Further, sensors S1, S2 and the like for detecting the paper are arranged in the paper transport path, and the transport of the paper in the paper transport path is controlled using the detection information of the sensors.

In the main body of the image forming apparatus, a process unit disposed above the frame is constituted by combining a developing unit 10 and a photosensitive unit 20. The two units 10 and 20 constituting the process unit are provided so that the upper lid member 9 provided at the upper part of the apparatus main body can be taken out upward with the open state via the fulcrum 9a. Further, the upper lid member 9 is provided with an image writing device 25 for writing an image on the photoconductor, and in a state where the upper lid member 9 is closed, a writing position of the image writing device with respect to the photoconductor 21 is provided. Set automatically.

The developing unit 10 provided in the process unit includes a stirrer 12 for stirring toner in a toner container 11 containing one-component toner, a developing roller 14 disposed corresponding to a photosensitive member, and Developing roller 1
A supply roller 13 for supplying the toner 4 while charging the toner, and a blade 15 for forming the toner adhered to the surface of the developing roller 14 as a thin layer are arranged. The supply roller 13 and the developing roller 14 are driven in the same direction while being pressed against each other, so that the toner is charged by friction between the two rollers so that the toner adheres to the surface of the developing roller. . The toner adhered to the surface of the developing roller 14 is formed as a thin layer having a constant thickness by pressing the blade 15, and is exposed toward a developing position with respect to the photoconductor 21.

In the photoconductor unit 20 combined with the developing unit, a photoconductor 21 and a charging roller 22 for uniformly charging the photoconductor are provided. Connected to the body frame ground and grounded. Further, the photoconductor unit 2
A seal with a brush 23 is provided at the lower part of the frame No. 0 so that the toner cloud generated inside the frame does not leak to the image transfer unit.

In the process unit constructed as described above, the supply roller 13 provided on the developing unit 10 is provided with a sponge-like conductive elastic body or a flocking body having a conductive fiber having a predetermined thickness. It can be configured as an elastic roller provided as described above. The shaft of the supply roller 13 is provided with a power supply member (not shown)
A bias voltage having a value of about 600 to -700 V, preferably about -600 V is applied. Further, the developing roller 14
Is made of a metal roller shaft made of stainless steel or the like coated with conductive rubber (silicone rubber, urethane rubber, NBR) with a predetermined thickness, and has a smooth roller surface. A bias voltage having a value of -250 V to -400 V, preferably about -300 V is applied to the developing roller 14. The blade 15 disposed on the developing roller 14 is
This is for uniformly setting a thin layer of toner formed on the surface of the device, and has a spring property made of a urethane resin sheet or a stainless steel plate member. And, for the blade 15, -300V to -700
A bias voltage in a range of V, preferably around -400 V is applied.

The center distance between the supply roller 13 and the developing roller 14 is set to be slightly smaller than the sum of the radii of the two rollers, and by rotating both rollers in the same direction (the direction of arrow X). At the contact portion between the two rollers, the roller is slid in the opposite direction while being pressed. Then, the toner is charged between the two rollers by the frictional action of the two rollers and the difference between the voltages applied to the respective rollers, and the toner adheres to the surface of the developing roller 14. Further, the toner adhered to the surface of the developing roller 14 is formed to a uniform thickness by the blade 15 and is exposed to the photoconductor, and the toner is transferred to a latent image formed on the photoconductor to form a toner image. Form.

The photoconductor unit 20 arranged in combination with the developing unit 10 is provided with a photoconductor 21 and a charging roller 22 such as a brush roller whose surface is formed by a flocked member or the like. Then, an image writing device 25 is arranged on the photoconductor 21 to write an image, and the toner image formed on the photoconductor is transferred to a sheet by the voltage of the transfer roller 17. The image writing device 25 includes an LED array head. Based on information from an image information output device, the image writing device 25
Is emitted to irradiate the photosensitive member with light. The surface of the photoconductor 21 is made of a grounded photoconductor, and is charged by −600 V to −800 V by the charging roller 22.
The potential of the part irradiated with light from the image writing device 25, that is, the potential of the black portion of the image information becomes about -80 V or less, and the potential difference between the light irradiated portion and the non-irradiated portion (the portion corresponding to the white of the image information) is reduced. As a result, an electrostatic latent image corresponding to the image information is formed.

The electrostatic latent image formed on the photoreceptor is substantially -650V adhered to the surface of the developing roller 14.
When the charged toner contacts the photosensitive member 21,
Is attracted to the light-irradiated site on the surface of the photoconductor, and a toner image is formed on the surface of the photoconductor (reversal development). At the transfer position of the toner image, the transfer roller 17 applies 50
By applying a bias voltage of 0 to 3 kV,
The toner image is transferred to the paper. The sheet on which the toner image has been transferred is sent to the fixing device 18 by rotation of the photoconductor. Further, the toner remaining on the surface of the photoreceptor after transferring the toner image to the paper is charged by the charging roller 22.
And is dispersed on the surface of the photoconductor, and is charged to the same potential as the surface of the photoconductor. Then, at a position where the photosensitive member contacts the developing roller 14, the photosensitive member is transferred to the developing roller 14 due to a potential difference between the two, and is mixed with toner newly supplied from the container portion and reused.

[0017]

In the developing unit 10 disposed in the process unit, as shown in FIG. 4, power supplies 30, 30a and 30b are disposed for the supply roller 13, the developing roller 14 and the blade 15, respectively. Then, a voltage of a predetermined value is applied from each power supply. For example, in the embodiment, the supply roller 13 has a voltage of -600 V,
A voltage of -300 V is applied to the developing roller 14 and a voltage of -400 V is applied to the blade 15. However, if the environmental conditions (e.g., temperature) of the copying machine greatly change with respect to the set value, even if a constant voltage is applied to each member, the voltage balance between the supply roller and the developing roller cannot be maintained. In some cases, the charge amount of the toner may change. Further, similar problems may occur between the developing roller and the blade, and when such problems occur, an undesired phenomenon that the toner is not sufficiently supplied to the developing roller occurs, and an image is formed. Problems such as blurring and poor printing occur, and the problem that the printing density changes remarkably occurs.

In order to prevent the above-mentioned inconvenience from occurring, for example, it was considered that a power supply circuit via a resistance member can be provided in each voltage application path for each member to which a voltage is applied. . When a large change occurs in the image density or when an environment such as temperature changes, power is supplied to an arbitrary power supply circuit via a resistor, and each of a supply roller, a developing roller, and a blade is controlled. By changing the voltage applied to the member, adjustment can be performed so that the toner supply operation can be performed normally. However, it is not advisable to provide a resistance member and a power supply switching circuit for all the voltage application circuits.

Therefore, in the present invention, in the developing unit 10 shown in FIG. 2, a path for directly applying a voltage to the developing roller 14 and the blade 15 via the power supplies 30a and 30b is provided. A path for directly supplying power from the power supply 30 and a path for supplying power via the resistor R are provided for the supply roller 13, and a switching device 37 is provided for the two power supply paths. When the environmental temperature changes and the operating environment of the device changes, the detection signal of the sensor 35 is input to the control device 36, and the voltage applied from the power supply 30 is changed according to the conditions set in the control device. The path for directly applying the voltage is switched to the path for applying the voltage via the resistor R. A resistor R arranged in the power supply circuit
For example, if a value of 1 MΩ or more is used,
Since the change in the voltage applied to the supply roller is set to a large value, it is possible to prevent a large change in the image density even when the environment changes due to a temperature change inside the apparatus.

In the example shown in FIG. 3, a constant voltage is applied to the supply roller 13 of the
The blade and the blade 15 are provided with a path for supplying power from the same power supply 30a, and a method of applying the same voltage to the two members is used. In this example, a power supply path for the blade 15 is arranged in parallel with a path provided with a resistor R and a path for directly supplying power without a resistor, and a switching device 37 for switching between the two power supply paths is provided. Deploy. In the switching device 37, information of a sensor 35 disposed inside the device is input to a control device 36, and when it is determined that an abnormality occurs in the control device, the power supply path of the switching device 37 is changed to a path through a resistor R. To reduce the voltage applied to the blade 15. When a resistor R having a value of, for example, 1 MΩ or more is used as the resistor R disposed in the power supply circuit, a value for reducing the voltage applied to the supply roller can be greatly changed. , The value of the change in the applied voltage can be set arbitrarily.
Therefore, even when a condition occurs in which the image density changes due to a temperature change inside the apparatus, it is possible to prevent the image density transferred to the paper from greatly changing.

As the sensor used for controlling the developing device of the present invention, in addition to the case of using the temperature detecting means, a sensor combining information of image density formed on the photoreceptor and two information of temperature and humidity. For example, means for inputting arbitrary information, such as obtaining the information, to the control device can be used. In addition, when information on the charging voltage of the photoreceptor is detected from the installation circuit, information on the charging voltage of the toner can be obtained at the same time. It can be obtained as information.

[0022]

Since the developing device of the present invention is constructed as described above, by adjusting the voltage applied to the supply roller, the developing roller or the blade disposed in the developing device, it is possible to control each member. Set the applied voltage difference,
The operation of supplying the toner can be favorably performed. Then, by stabilizing the charge amount of the toner supplied to the photoconductor, it is possible to prevent a toner supply failure or the like from occurring and to maintain a good image density of the toner image transferred to the paper. Further, in the present invention, the device for changing the voltage only adds a resistor of a predetermined value to the conventional power supply circuit, and additionally provides a detection value of a detection device such as a temperature to the control device. Since the means for inputting control information based on the detected value is used, the configuration of the apparatus is not complicated.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of an image forming apparatus of the present invention.

FIG. 2 is an explanatory diagram of an example in which a resistor is arranged in a power supply circuit for a supply roller of a developing device.

FIG. 3 is an explanatory diagram of an example in which a resistor is arranged in a power supply circuit for a blade of a developing device.

FIG. 4 is an explanatory diagram of a voltage applying device of a general developing device.

[Explanation of symbols]

1 image forming apparatus, 2 paper feed cassette, 3 pickup roller, 4.5 transport roller device, 9
Top cover member, 10 developing unit, 11 toner container, 12 stirrer, 13 supply roller,
Reference Signs List 14 developing roller, 15 blade, 20 photoconductor unit, 21 photoconductor, 22 charging roller, 23 brush, 25 image writing device,
26 transfer roller, 28 fixing device, 30
Power supply, 35 sensor, 36 controller, 37
Switching device.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03G 15/00 303 G03G 15/00 303

Claims (3)

[Claims] 1. A developing device comprising: a developing roller for supplying toner to a photoreceptor; a supply roller for supplying toner to the developing roller; and a blade for forming a thin layer of toner on a surface of the developing roller. An image forming apparatus, comprising: a power supply for supplying power to each of a supply roller, a developing roller, and a blade; and a current limiting resistor connected to one of the power supply and the power-supplied member. 2. In the developing device, between a supply roller for supplying toner to the developing roller and a power supply,
2. The image forming apparatus according to claim 1, wherein a resistor is interposed. 3. The developing device according to claim 1, wherein power is supplied to a blade for forming a thin layer of toner on the developing roller from the same power supply as the developing roller via a resistor. The image forming apparatus as described in the above.