JP3478298B2 - Image forming device - Google Patents

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, a laser printer, and a facsimile. More specifically, it is a method of charging by a contact type charging member, and the charging area is irradiated with light. However, the present invention relates to an image forming apparatus that controls a current flowing through a charging member.

[0002]

2. Description of the Related Art As a contact charging member (for example, a charging roller) for contacting a photosensitive member to perform a charging process, an elastic member having a certain resistance characteristic is generally used, but it is not suitable for the environment (for example, surroundings). When the temperature changes, a resistance change occurs there. Therefore, when a constant voltage is applied to this charging member to charge the photoconductor, the current of the charging member is not constant and the potential of the photoconductor changes, resulting in stable image quality. There wasn't.

Therefore, conventionally, a constant current control is performed while driving the charging roller before the image forming process, the applied voltage at that time is stored in a memory, and the constant voltage control is performed based on the voltage value stored in the memory. There is known one that executes an image forming process. The constant voltage control is executed during image formation because the uniformity of charging is better than that in the case of constant current control.

As a reference technical document related to the present invention, there is an "image forming apparatus" disclosed in Japanese Patent Laid-Open No. 4-181962. In this, the potential of the photoconductor charged by the charging member is detected by the potential detection member, and the applied voltage is changed based on the detection result.

[0005]

However, in the conventional image forming apparatus as described above,
The potential of the photoconductor charged by the charging member is detected by the potential detection member, and the applied voltage is changed based on the detection result. Therefore, it is necessary to secure an installation space for the potential detection member. However, there is a problem in that the cost of the device is increased as well as the increase in cost.

Further, in the conventional image forming apparatus, the photosensitive member is driven before the image formation is started, the charging member is subjected to constant current control, and the applied voltage at that time is stored in the memory. In order to perform image formation by performing constant voltage control based on the voltage value, the drive time for pre-rotation before image formation is required, and power supplies for constant current control and constant voltage control are also required. There was a problem in terms of economic efficiency as well as hindering rapid processing.

The present invention has been made in view of the above, and in a contact charging type image forming apparatus, the size of the apparatus can be reduced and the apparatus can be downsized without providing potential detecting means around the photoconductor. In addition to avoiding the cost increase, the pre-rotation at the time of image formation is not performed, the economic efficiency is improved, the work efficiency is improved, and the surface potential of the photoconductor is controlled to be constant to change the environmental conditions. The purpose is to stabilize the image even if it exists.

[0008]

In order to achieve the above-mentioned object, the present invention provides an image forming apparatus using a contact type charging member, and a current detecting means for detecting a current flowing through the charging member; Voltage control means for controlling the applied voltage applied to the charging member, light irradiation means for irradiating the charging area by the charging member with light, and application of voltage to the charging member to start the application of the voltage when the photoconductor is stopped. At the same time while increasing the voltage, the light irradiation means irradiates the charging area with light, and the voltage control means controls the applied voltage so that the current flowing through the charging member becomes a predetermined value, and the current detection means detects it. current value is based on the applied voltage upon reaching a predetermined value, after the current value reaches the predetermined value, ingredients and control means for executing image formation to start rotation of the photosensitive member There is provided an image forming apparatus.

Further, the light irradiating means has an irradiating position changing means so that the light can be irradiated in two directions of an erase area and a charging area on the photoconductor.

Further, the control means increases the amount of light when the light irradiation means irradiates the charging area with light, as compared with that during image formation .

Further, the control means controls a predetermined current value flowing through the charging member based on the number of image formations and / or the driving time of the photoconductor.

[0012]

[0013]

In the image forming apparatus according to the present invention, the control means applies the voltage to the charging member through the voltage control means when the photosensitive member is stopped, and at the same time, the charging area is irradiated with light by the light irradiation means, The applied voltage is controlled while being detected by the current detection means so that the current flowing through the charging member reaches a predetermined value, and the current flowing through the charging member roller reaches a predetermined value based on the applied voltage when the current reaches the predetermined value. After that, the rotation of the photoconductor is started to form an image.

Further, an existing eraser is used as the above-mentioned light irradiating means, and the eraser is rotated so as to be capable of irradiating in two directions of the erase area and the charging area.

Further, when the charged area is irradiated with light by the control means described above, the amount of light is increased as compared with that during image formation , the photoconductor fatigue in the normal state is suppressed, and stable charge removal in the charged area is performed. To do.

Further, by controlling a predetermined current value flowing through the charging member on the basis of the number of times of image formation or the driving time of the photosensitive member, the charging potential is controlled to be constant with respect to the change of the charging characteristics with the lapse of time along with the environmental conditions. To do.

[0017]

[0018]

Embodiments of the image forming apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing a schematic configuration of an image forming system in an image forming apparatus to which the present invention is applied. In the figure, 101 is a photosensitive drum that forms an electrostatic latent image, and 102 is configured to be able to contact and separate in parallel to the surface of the photosensitive drum 101. By contacting the photosensitive drum 101, the surface of the photosensitive drum 101 is A charging roller 103 for charging and an eraser 103 for irradiating the surface of the photosensitive drum 101 with light. Also, the eraser 1
03 irradiates the photosensitive drum 101 with a normal erase processing area and a charging area by the charging roller 102, so that the solenoid is turned on / off in two directions, for example.
Is configured to rotate.

Further, 104 is image light by scanning light such as slit exposure which optically reads a document (not shown) or laser light according to an image signal, and 105 contains toner and is developed based on a developing process. Developing device for processing,
Reference numeral 106 denotes a transfer / separation charger that transfers an image formed on the photoconductor drum 101 to recording paper and separates the recording paper after the transfer processing from the photoconductor drum 101, and 107 denotes the photoconductor drum 101 after the transfer processing. A cleaning unit 107a for removing the residual toner, paper dust and the like is a cleaning blade provided in the cleaning unit 107.

Next, the operation will be described. The surface of the photosensitive drum 101 is uniformly charged to a high potential by the charging roller 102 that is in contact with the photosensitive drum 101.
When the surface of the photosensitive drum 101 is irradiated with the image light 104, the electric potential of the irradiated portion is lowered. Image light 1
04 is the distribution of the amount of light according to the black / white of the image,
By the irradiation of the image light 104, a potential distribution corresponding to the recorded image, that is, an electrostatic latent image is formed on the surface of the photosensitive drum 101.

When the portion of the photosensitive drum 101 on which the electrostatic latent image is formed passes through the developing device 105, the toner adheres to the electrostatic production according to the level of the potential, and the electrostatic latent image is formed. A visible toner image is formed. The recording paper is conveyed to a portion where the toner image is formed by a registration roller (not shown) at a predetermined timing, and the recording paper is superposed on the toner image. This toner image is transferred / separated by the charger 106.
The transfer corona part of is discharged onto the recording paper by being discharged.

Then, the separation corona portion of the transfer / separation charger 106 is discharged, so that the recording paper is separated from the photosensitive drum 101. The separated recording paper is conveyed through a conveyance path, thermally fixed by a heat roller and a pressure roller having a heater of a fixing unit (not shown), and then discharged to the outside of the machine. After the transfer process is completed, residual toner and the like on the surface of the photoconductor drum 101 are removed by the cleaning blade 107a of the cleaning unit 107, and a standby state is prepared for the next image forming process.

FIG. 2 is a block diagram showing a schematic structure of a control system in the image forming apparatus according to the present invention. In the figure, 201 is a central unit for executing various controls for the entire apparatus based on a stored control program. An arithmetic processing unit (hereinafter referred to as a CPU), which is internally provided with a work memory for storing data being processed and the like. Also, 20
Reference numeral 2 is a current detection circuit for detecting the current flowing through the charging roller 102, 203 is a voltage control circuit for controlling the voltage applied to the charging roller 102 via the current detection circuit 202, 20
Reference numeral 4 is a rotary drive device that changes the irradiation direction of the eraser 103, 205 is a drive control circuit that controls the drive of the rotary drive device 204, and 206 is an applied voltage control that controls the voltage applied to the eraser 103 to control the amount of light. Circuit, 207
Is a drive time detection circuit for detecting the drive time of the photosensitive drum 101.

FIG. 3 is an explanatory view showing the operation of the image forming apparatus according to the present invention, and FIG. 4 is a current value I1 flowing into the charging roller 102 with respect to the driving time of the photosensitive drum 101.
It is a graph which shows the characteristic of.

Next, the operation will be described. First, when the apparatus main body is powered on, as shown in FIG. 3, the rotation driving device 204 is turned on, and the eraser 103 is moved from the erase area A, which is the irradiation position to the surface of the normal photosensitive drum 101, to the charging roller 102. It rotates to the charging area B by. In this state, the voltage is applied to the charging roller 102 while changing the voltage, and at the same time, the eraser 103 is caused to emit light. At this time, the current value flowing into the charging roller 102 is detected by the current detection circuit 202, and the voltage is set by the voltage control circuit 203 so that the detected current value becomes the predetermined current value I1. Remember that value. Then, based on the stored voltage value, the above-mentioned FIG.
The image forming process of the operation described in step 1 is executed.

Since the surface of the photosensitive drum 101 becomes a conductor by irradiating light, applying a voltage while irradiating light produces the same effect as, for example, a condition in which voltage is applied to an aluminum photosensitive member. As a result, a constant current flows through the photosensitive drum 101. On the contrary, if a voltage is applied to the photoconductor drum 101 in a state where no light is emitted, the surface of the photoconductor drum 101 is charged, so that no current flows.

In the above-described operation, the photosensitive drum 1 is actually driven while the photosensitive drum 101 is being driven.
If the current value required for the charging potential aiming at 01 is I2, there is a relation of I2 = I1 × α (α is 1 or less), and I2 = 40 μA for I1 = 400 μA.
It can be confirmed from the test results that it is μA.

Further, in the above-mentioned method, when the photosensitive drum 101 is charged in the charging area, accurate control cannot be performed. Therefore, when the eraser 103 is used for erasing the charge in the charging area, it is different from the normal image formation. Eraser 1
It is desirable to increase the light quantity of 03. This is because when the eraser 103 is rotated, the distance to the irradiation surface is different, and when the eraser 103 is opposed to the surface of the photoconductor drum 101, it is better to reduce the amount of light as much as possible. This reduces fatigue.

Further, the current value I2 required to charge the photoconductor drum 101 to a target potential is larger than that at the initial stage when the photoconductor drum 101 wears and the electrostatic capacity becomes large over time. Will be needed. Therefore, the value of the current value I1 is controlled based on the number of times of image formation on the photoconductor drum 101 (for example, the total number of copies or prints) and the drive time of the photoconductor drum 101 detected by the drive time detection circuit 207. As a result, the charged potential can be maintained accurately and stably.

Next, the effect of the above embodiment will be described. First, the applied voltage is corrected by the photosensitive drum 101.
Therefore, it is possible to reduce the hazard (wear, etc.) to the photoconductor drum 101, and it is possible to eliminate the noise caused by driving the photoconductor due to this process. Further, it is not necessary to perform the pre-rotation of the photoconductor drum 101 before the copying operation, so that quick office work can be realized.

Second, as a member for irradiating the charging area by the charging roller 102 with light, the conventional eraser 10 is used.
Since the design of 3 can be changed so as to be rotatable, the cost of the entire apparatus can be reduced.

Thirdly, by increasing the light amount of the eraser 103 only when the charged area is irradiated,
It is possible to reduce the sensitivity fatigue of the photoconductor drum 101 and to stably remove the charge in the charged area.

Fourthly, since the value of the current value I1 is controlled on the basis of the driving time of the photosensitive drum 101 and the image forming processing time, it is possible to maintain the charging potential constant even with environmental changes and changes with time. it can.

[0034]

As described above, according to the image forming apparatus of the present invention, the control means applies the voltage to the charging member through the voltage control means when the photosensitive member is stopped, and at the same time, the charging area is applied to the charging area. On the other hand, the applied voltage is controlled by irradiating light by the light irradiating means and detecting the current flowing through the charging member by the current detecting means so that the current flows to the predetermined value. Based on the applied voltage when the predetermined value is reached , Current value is
In order to start the rotation of the photoconductor and execute the image formation after reaching the predetermined value, in the image forming apparatus of the contact charging type, the device is provided without providing the potential detecting means around the photoconductor. In addition to promoting the miniaturization of the device, avoiding an increase in the cost of the device, further improving work efficiency while improving the economical efficiency without pre-rotation at the start of image formation, and keeping the surface potential of the photoconductor constant. It is possible to stabilize the image even when there is a change in environmental conditions by controlling to.

[0035]

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of an image forming system in an image forming apparatus to which the present invention is applied.

FIG. 2 is a block diagram showing a configuration of a control system in the image forming apparatus according to the present invention.

FIG. 3 is an explanatory diagram showing an operation of the image forming apparatus according to the present invention.

FIG. 4 is a graph showing the characteristics of the current value flowing into the charging roller with respect to the driving time of the photosensitive drum according to the present invention.

[Explanation of symbols]

Reference Signs List 101 photoconductor drum 102 charging roller 103 eraser 201 central processing unit (CPU) 202 current detection circuit 203 voltage control circuit 204 rotation drive device 205 drive control circuit 206 applied voltage control circuit 207 drive time detection circuit

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Claims (4)

(57) [Claims] 1. An image forming apparatus using a contact type charging member, a current detecting unit for detecting a current flowing through the charging member, a voltage control unit for controlling an applied voltage applied to the charging member, and the charging unit. A light irradiating means for irradiating the charged area by the member and a voltage is applied to the charging member when the photosensitive member is stopped to increase the applied voltage, and at the same time, the light irradiating means irradiates the charged area with light. The voltage control means controls the applied voltage so that the current flowing through the charging member reaches a predetermined value, and based on the applied voltage when the current value detected by the current detection means reaches a predetermined value. An image forming apparatus comprising: a control unit that starts rotation of the photoconductor and executes image formation after the current value reaches the predetermined value. 2. The image forming apparatus according to claim 1, wherein the light irradiating unit has an irradiation position changing unit so that the light irradiating unit can irradiate in two directions of an erase region and a charging region on the photoconductor. 3. The image forming apparatus according to claim 1, wherein the control unit increases the amount of light when the light irradiating unit irradiates the charging area with light, as compared with when the image is formed . 4. The control means controls a predetermined current value supplied to the charging member based on the number of image formations and / or the driving time of the photoconductor.
The image forming apparatus described.