JPH08110663A - Image forming device - Google Patents

Abstract

(57) [Summary] [Object] To provide an image forming apparatus in which the potential of an image bearing member is accurately controlled and in which image quality is improved. [Structure] When the latent image condition is adjusted, the linear velocity of the image bearing member and the output of the charging power source are changed from that at the time of image formation to measure the potential of the image bearing member, so that the potential of the image bearing member at the developing position is accurately measured. Good detection is performed, and the potential of the image carrier is controlled based on the detection result.

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 printer or a facsimile machine using an electrophotographic process. More specifically, the present invention relates to an image forming apparatus equipped with means for detecting the surface potential of an image carrier and controlling the output conditions of the image forming process based on the detected calculation result.

[0002]

2. Description of the Related Art A typical example of a conventional image forming apparatus is shown in FIG. 1, in which an image carrier is provided by a charging charger 2 and has a photoconductive layer on its surface. The photoconductor drum 1 is charged, and an electrostatic latent image is formed on the photoconductor drum 1 by the exposure device 3 including a document placing table 14 for placing a document, an exposure lamp 15 for exposing the document, and the like. Next, after the unnecessary charges are removed by the eraser 4 in the non-image area such as the inter-recording paper area and both ends of the recording paper, the toner is supplied to the electrostatic latent image by the developing device 5, and the toner is transferred onto the photosensitive drum 1. A toner image is formed at. The transfer paper 6 is charged by corona discharge by the transfer charger 6, the toner image on the photosensitive drum 1 is transferred, and the toner image is removed by discharging the transfer paper by corona discharge by the separation charger 7. Meet the photoconductor drum 1
Make it easier to separate the transfer paper that is electrostatically adsorbed on. Transfer paper 10
Is conveyed to a fixing device (not shown) and fixed by heat and pressure. The toner remaining on the photosensitive drum 1 without being transferred in the transfer process is removed by the cleaning device 8. The photosensitive drum 1 from which the toner has been removed is electrostatically initialized by being irradiated with light from the charge eliminating lamp 9, and is repeatedly used.

In such an image forming apparatus, the electrostatic characteristic of the photosensitive drum changes with the environment and the passage of time. Further, the exposure amount also changes due to deterioration of the exposure lamp, mirrors, and dirt on the lens. In order to always maintain a stable latent image that fluctuates due to such a reason, Japanese Patent Publication No. 57-19784 discloses that the surface potential of a photosensitive drum is detected and the calculation result is fed back to each process of charging and exposure. In this, a method of always obtaining a stable latent image is proposed.

A specific operation example of the latent image potential control of the photosensitive drum which has been conventionally performed will be described below. An operation for automatically determining each process condition by turning on the main body power is shown in FIG. It is executed according to the control flow as shown in FIG. Here, V _O is the image portion potential on the surface of the photosensitive drum (potential after the black pattern exposure corresponding to the image portion), _VL is the background portion potential (potential after the white pattern exposure corresponding to the background portion), V
_R is the residual potential (potential after static elimination by erase). First, the charging charger 2 under the conditions used last time.
Is applied to the surface of the photosensitive drum 1 to charge it,
After this is discharged by the eraser 4, V _R is measured by the surface potential meter 11. Then, the V _R memory - and performs calculation by this _{result, V OR (= V R +850} ), V
To set a target value of the _LR (= V _R +200). Next, the exposure device 3 exposes the surface of the charged photosensitive drum 1 with the reflected light of the reference black pattern 12 to form an image portion potential portion, which is detected by the surface electrometer 11. And
The output of the charging power source is adjusted so that V _O becomes the target value. That is, when V _O is smaller than the target value, the output of the charging power source is increased, and when V _O is larger than the target value, the output of the charging power source is reduced and V _O is measured again. Then, this is repeatedly adjusted until V _O falls within the target value ± 2%.

Next, the output of the exposure power source is adjusted so that V _L becomes the target value. That is, the surface of the charged photosensitive drum 1 is exposed to the reflected light of the reference white pattern 13 by the exposure device 3 to form the background potential, which is detected by the surface electrometer. Then, when _VL is smaller than the target value, the output of the exposure power supply is reduced, and when _VL is larger than the target value, the output of the exposure power supply is increased and _VL is measured again. Repeat this until V _L also falls within the target value ± 2%. Since V _O , V _L , and V _R affect other values when one condition is changed, the condition is converged by repeating a series of measurement and adjustment a plurality of times.

That is, this control makes the potential difference between V _O and V _L constant for the purpose of obtaining a proper image. And
V _R changes depending on the environment, changes over time, and variations in the electrostatic characteristics of the photoconductor drum, but if these conditions are the same, it cannot be changed even if the amount of erase light is increased, so V _O , V _L it is assumed that by adding a constant value to the control target value V _R.

[0007]

However, the above-mentioned image forming apparatus in the prior art has a problem that an appropriate image cannot be obtained. That is, in order to obtain an appropriate image, it is necessary to keep the potential relationship of the photosensitive drum at the developing position constant. Therefore, in the above-mentioned conventional technique, the surface potential of the photoconductor drum is detected and controlled so as to reach the target value. However, since the surface potential of the charged photoconductor drum decays with time, it should be originally at the developing position. It is necessary to measure the potential of the photosensitive drum in. However, in reality, this is not possible. Therefore, in the above-mentioned conventional technique, the surface potential detecting device is arranged at a position different from the developing position so that a potential relationship for obtaining a proper image is created at the developing position. In consideration of attenuation in advance, the control potential at the surface potential detection position is determined and controlled. However, since the attenuation of the surface potential of the photoconductor from the surface potential detection position to the development position differs depending on the electrostatic characteristics of the photoconductor drum, in the above conventional technique, the potential relationship at the development position is not constant and a proper image is obtained. I couldn't. The present invention has been made in view of the above points, and an object thereof is to provide an image forming apparatus with improved image quality.

[0008]

In order to achieve the above object, the present invention comprises an image carrier, a charging unit for charging the surface of the image carrier, and a charging power source for supplying a voltage to the charging unit. An exposing means for exposing the surface of the image carrier charged by the charging means to form a latent image, and a developing means for developing the latent image formed on the image carrier with a developer,
An image forming apparatus having a transfer means for transferring a developed image formed on the image carrier onto a transfer material, and a surface potential detecting means for detecting the potential of the surface of the image carrier, the charging means and the surface potential detecting means. When the distance on the surface of the image bearing body between the charging means and the developing device is L ₁ , and the distance on the surface of the image bearing body between the charging means and the developing device is L ₂ , the moving speed of the surface of the image bearing body and When the output value of the charging power source is set to L ₁ / L ₂ which is the condition value at the time of image formation, the potential of the surface of the image carrier is detected, and when the image formation of the charging power source is performed based on the detection result. It has a control means for controlling the output value of.

According to the present invention, the image carrier, the charging means for charging the surface of the image carrier, the charging power source for supplying a voltage to the charging means, and the image carrier charged by the charging means. Exposure means for exposing the surface to form a latent image,
An exposure power source for applying a voltage to the exposure means, a developing means for developing a latent image formed on the image carrier with a developer, and a developed image formed on the image carrier to a transfer material. In the image forming apparatus having the transfer means and the surface potential detecting means for detecting the potential of the surface of the image carrier, the distance on the surface of the image carrier between the exposing means and the surface potential detecting means is L ₃ , When the distance on the surface of the image carrier between the exposing means and the developing device is L ₄ , the moving speed of the surface of the image carrier, the output of the charging power source, and the output value of the exposure power source are The condition value L ₃ / L ₄ at the time of image formation respectively
And a control means for detecting the potential of the surface of the image carrier and controlling the output value of the exposure power source based on the detection result.

[0010]

According to the present invention, the time from the charging of the image carrier to the detection of the surface potential is approximately the time from the charging of the image carrier to the development position. By controlling the output of the charging power source so that they become equal and the detected image portion potential becomes a predetermined potential, the image portion potential of the image carrier at the developing position can be made suitable.

According to the present invention, the time from the exposure of the image carrier to the detection of its potential is the time from the exposure of the image carrier to the development position. Therefore, by controlling the output of the exposure power source so that the detected background potential becomes a predetermined potential, the background potential of the image carrier at the developing position can be made suitable.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. In this example shown in the drawings,
The same parts as those of the conventional one are referred to by the same reference numerals and the description thereof will be omitted, and mainly different parts will be described.

The image forming apparatus and the image forming process in this embodiment are the same as the conventional one shown in FIG. For the sake of explanation, in FIG. 1, the distance between the charging charger 2 on the surface of the photosensitive drum 1 and the surface electrometer 11 is L ₁ , and similarly, the charging charger 2 and the developing device 5 are provided.
Is L ₂ , the distance between the exposure position of the exposure device 3 and the surface electrometer 11 is L ₃ , and the distance between the exposure position of the exposure device 3 and the developing device 5 is L ₄ . The linear velocity of the photosensitive drum 1 during image formation is v.

Then, in this embodiment, the control of each part is performed based on the block diagram shown in FIG. That is, the photoconductor drive motor 20 is controlled by the CPU 21 and rotates at a speed different from that at the time of image formation during latent image potential control in this embodiment. During the latent image potential control, the detection value detected by the surface potential detecting device 11 is the CPU 21.
Is input to the power source 22 and calculation is performed based on the input value to control the charging power source 22 and the exposure power source 23.

In this embodiment, the latent image condition adjustment is executed according to the control flow shown in FIG. 3 when the photosensitive drum 1 is replaced. The latent image condition adjustment starts by setting the output value of the charging power source 22 that determines the action of the charging charger 2. When the charging power supply output is set, the photosensitive drum 1 rotates at the linear velocity v · L ₁ / L ₂ under the control of the CPU 21. Then, the charging power source 22 outputs a value obtained by multiplying the output value I set and stored last time by L ₁ / L ₂ . Therefore, the linear velocity of the photosensitive drum 1 is L when the image is formed.
A ₁ / L _2, min linear velocity of the photosensitive drum 1 becomes slow, the charge potential of the photosensitive drum 1 surface because the output is reduced in charging power source 22 is the same as the time of image formation.

In this embodiment, under such conditions, the output of the charging power source 22 is repeatedly adjusted until V _O falls within the target value ± 2%, as in the prior art. At this time, since the photoconductor drum 1 is rotating at a linear velocity of v · L ₁ / L ₂ , the time from when the photoconductor drum 1 is charged to when it reaches the surface potential detecting device 4 is at the time of image forming operation. It is equal to the time from when the photoconductor drum 1 is charged to when it reaches the developing device 5. Therefore, the charging potential V _O detected at this time is substantially equal to the surface potential at the developing position where development is performed during image formation. Thus, assuming that the finally determined output value of the charging power source 22 is I ′, the charging power source 22 outputs a value of I ′ · L ₂ / L ₁ at the time of image formation. It becomes approximately V _O. Therefore, according to this embodiment, the photosensitive drums 1 having different electrostatic characteristics are provided.
Even in this case, a suitable charging potential can always be obtained at the developing position.

Next, the output value of the exposure power source 23 that determines the operation of the exposure apparatus 3 is set. When the power supply for exposure is set, the photosensitive drum 1 is actuated by the CPU 21 so that the linear velocity v
・ Rotate at L ₃ / L ₄ . Then, the charging power source 22 and the exposure power source 23 respectively output the output values I and E set and stored at the previous time multiplied by L ₃ / L ₄ . At this time, in the exposure device 4, the scanner moves to the exposure position of the white pattern arranged in the optical unit and exposes it. By such an operation, the photosensitive drum 1
A ground portion potential V _L is formed on the top. Here, the linear velocity of the photoconductor drum 1 is L ₃ / L ₄ during the image forming operation, and the output of the power source 23 for exposure is reduced by the linear velocity of the photoconductor drum 1 being reduced, so that the photoconductor drum 1 is reduced. The background potential V _L of the surface is the same as that at the time of image formation.

In this embodiment, under such conditions, the output of the exposure power supply 23 is repeatedly adjusted until V _L falls within the target value ± 2%, as in the prior art. At this time, since the photoconductor drum 1 is rotating at a speed of v · L ₃ / L ₄ , the time from the exposure of the photoconductor drum 1 to the arrival at the surface potential detection device 4 is The time from when the drum 1 is exposed to when it reaches the developing device 5 is the same. Therefore, the charging potential _VL detected at this time is substantially equal to the background potential at the developing position where development is performed during image formation. Thus, assuming that the finally determined output value of the exposure power supply 23 is E ′, a value of E ′ · L ₄ / L ₃ is output from the exposure power supply 23 at the time of image formation, so that the background potential at the developing position. Is approximately V _L. Therefore, according to this embodiment, the photosensitive drums 1 having different electrostatic characteristics are provided.
Even in this case, it is possible to always obtain a suitable background potential at the developing position.

In this embodiment, the charging power supply output and the exposure power supply output are adjusted only once in the present embodiment, but they may be repeated a plurality of times as in the prior art. In this embodiment, the latent image condition adjustment is performed when the photoconductor drum 1 is replaced. However, when the photoconductor drum whose potential attenuation amount changes depending on the environment or time is used, the main body power is turned on every time. The latent image condition adjustment may be performed.

[0020]

As described above, according to the present invention, it is possible to provide an image forming apparatus capable of accurately controlling the image portion potential of the photosensitive drum at the developing position and improving the image quality.

Further, according to the present invention, it is possible to provide an image forming apparatus in which the background potential of the photosensitive drum at the developing position can be accurately controlled and the image quality is improved.

[Brief description of drawings]

FIG. 1 is a main part configuration diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing an embodiment of the present invention.

FIG. 3 is a flow chart showing an embodiment of the present invention.

FIG. 4 is a flowchart showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum 2 Charging device 3 Exposure device 5 Developing device 6 Transfer device 11 Surface potential detection device 21 CPU 22 Charging power supply 23 Exposure power supply

Claims (2)

[Claims] 1. An image carrier, charging means for charging the surface of the image carrier, charging power supply for supplying a voltage to the charging means, and exposure of the surface of the image carrier charged by the charging means. Exposing means for forming a latent image by a developing means, and developing means for developing the latent image formed on the image bearing member with a developer,
An image forming apparatus having a transfer means for transferring a developed image formed on the image carrier onto a transfer material, and a surface potential detecting means for detecting the potential of the surface of the image carrier, the charging means and the surface potential detecting means. When the distance on the surface of the image bearing body between the charging means and the developing device is L ₁ , and the distance on the surface of the image bearing body between the charging means and the developing device is L ₂ , the moving speed of the surface of the image bearing body and When the output value of the charging power source is set to L ₁ / L ₂ which is the condition value at the time of image formation, the potential of the surface of the image carrier is detected, and when the image formation of the charging power source is performed based on the detection result. An image forming apparatus having a control means for controlling the output value of the image forming apparatus. 2. An image carrier, charging means for charging the surface of the image carrier, a charging power source for supplying a voltage to the charging means, and exposure of the surface of the image carrier charged by the charging means. Exposing means for forming a latent image by applying a voltage to the exposing means, a developing means for developing the latent image formed on the image bearing member with a developer, and an exposing power source on the image bearing member. In an image forming apparatus having a transfer means for transferring the formed developed image to a transfer material and a surface potential detecting means for detecting the potential of the surface of the image carrier, an image between the exposing means and the surface potential detecting means. When the distance on the surface of the carrier is L ₃ and the distance on the surface of the image carrier between the exposing unit and the developing device is L ₄ , the moving speed of the surface of the image carrier and the output of the charging power source , And the output value of the exposure power source when the image is formed. Is set to L ₃ / L ₄ matters value detects the potential of the image bearing member surface, the image forming, characterized by comprising control means for controlling the output value of the exposure source on the basis of the detection result apparatus.