JP2003287942A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily and properly adjust a development bias voltage in a developing device that performs development by impressing the development bias voltage on which a DC voltage and an AC voltage are superposed between a toner carrier and an image carrier faced at a required interval in a development area. <P>SOLUTION: In the developing device that develops an electrostatic latent image by providing the toner carrier 11 so as to face the image carrier 1 at the required interval in the development area, impressing the development bias voltage on which the DC voltage and the AC voltage are superposed between the toner carrier and the image carrier and by supplying a toner from the toner carrier to the image carrier, it is provided with a leakage generation means 20 that generates leakage between the image carrier and the toner carrier by varying a leak detection voltage to be impressed between the image carrier and the toner carrier and a leakage detection means 30 that detects the leakage based on a current flowing between the image carrier and the toner carrier. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as a copying machine or a printer, which is opposed to an image carrier on which an electrostatic latent image is formed in a developing area with a required space. A toner carrying member is provided so that a developing bias voltage in which a DC voltage and an AC voltage are superposed is applied between the toner carrying member and the image carrying member, so that the toner carried on the toner carrying member is carried on the image carrying member. In the developing device which supplies the toner to the body and develops the electrostatic latent image, even if an error occurs in the distance between the toner carrier and the image carrier, the toner may be placed between the toner carrier and the image carrier. It is characterized in that the developing bias voltage to be applied can be easily adjusted appropriately.

[0002]

2. Description of the Related Art Conventionally, in image forming apparatuses such as copying machines and printers, various developing devices have been used to develop an electrostatic latent image formed on an image bearing member. As a device, a two-component developing system using a developer containing a carrier and a toner, and a one-component developing system using only a toner containing no carrier are known.

Further, in such a one-component developing system developing device, a contact developing system developing device is provided so that the toner carrier is brought into contact with the image carrier, and the toner carrier is provided in the developing region. Is known as a non-contact developing type developing device provided so as to face each other with a required interval.

In the case of the contact developing type developing device,
Since the toner is brought into contact with the image bearing member for development, the reproducibility of the electrostatic latent image formed on the image bearing member is excellent, but the toner is also attached to the non-image portion where the electrostatic latent image is not formed. Therefore, there is a problem that fog occurs in the formed image.

For this reason, conventionally, the adhesion of the toner to the non-image portion is suppressed by changing the moving speeds of the image carrier and the toner carrier, but in this case, the toner carrier is There is a problem that the surface of the image bearing member is easily worn by the contact with, and stable image formation cannot be performed.

On the other hand, in the case of the non-contact developing type developing device in which the toner carrying member is provided so as to face the image carrying member with a required gap, there is no problem as in the contact developing system developing device. In order to supply the toner from the toner carrier to the opposing image carrier through the required interval, the developing bias voltage in which the DC voltage and the AC voltage are superimposed is applied between the toner carrier and the image carrier. The toner held on the toner carrier is caused to fly between the toner carrier and the image carrier.

Further, in order to make the toner carrier and the image carrier face each other with a required space as described above, a spacer member is generally provided between the toner carrier and the image carrier to provide the toner carrier and the image carrier. I was trying to face the body at regular intervals.

However, even in this case,
For example, when the molding accuracy and the mounting state of the image carrier and the toner carrier vary, the spacer member is worn or deformed, and the toner carrier and the image carrier facing each other in the developing region are separated from each other. There is a problem in that the distance fluctuates, the electric field strength acting between the toner carrier and the image carrier fluctuates, and uneven density occurs in the formed image.

Therefore, conventionally, the peak-to-peak value of the AC voltage in the developing bias voltage applied between the toner carrier and the image carrier is increased so that the toner is transferred between the toner carrier and the image carrier. In order to prevent uneven density from occurring,

However, when the peak / peak value of the AC voltage in the developing bias voltage applied between the toner carrier and the image carrier is increased as described above, the surface potential of the image carrier and the peak value of the developing bias voltage are increased. There is a problem that the potential difference between the two becomes large, a leak occurs between the toner carrier and the image carrier, and noise is generated in the formed image.

Therefore, at the present time, the developing bias voltage applied between the toner carrier and the image carrier is changed to cause a leak, and the toner adhering to the image carrier due to the leak is detected by the density sensor. Based on this, the developing bias voltage is properly set.

However, the above-mentioned concentration sensor is expensive and costly, and even if a leak occurs at a position other than the position detected by this concentration sensor, it cannot be detected and the leak should not always occur. Therefore, there is a problem that the developing bias voltage cannot be properly set.

[0013]

SUMMARY OF THE INVENTION According to the present invention, a toner carrier is provided so as to face a surface of an image carrier on which an electrostatic latent image is formed with a required space in a developing area. Development in which a developing bias voltage in which a DC voltage and an AC voltage are superposed is applied to the image carrier and the toner held on the toner carrier is supplied to the image carrier to develop an electrostatic latent image. It is an object of the present invention to solve the above problems in the device.

That is, according to the present invention, in the developing device as described above, even if an error occurs in the distance between the toner carrier and the image carrier, a leak occurs between the toner carrier and the image carrier. It is an object of the present invention to make it possible to easily and appropriately adjust the developing bias voltage so as to prevent the occurrence of noise, and to stably obtain a good image without noise.

[0015]

In order to solve the above problems, in the developing device of the present invention, the developing device is opposed to the image bearing member on which the electrostatic latent image is formed in the developing region with a required space. A toner carrier is provided in the toner carrier, and a developing bias voltage in which a DC voltage and an AC voltage are superimposed is applied between the toner carrier and the image carrier to apply the toner held on the toner carrier to the image carrier. In the developing device that supplies and develops the electrostatic latent image, a leak is generated between the image carrier and the toner carrier by changing the leak detection voltage applied between the image carrier and the toner carrier. The leak generating means for causing the leak and the leak detecting means for detecting the leak based on the current flowing between the image bearing member and the toner bearing member are provided.

Here, in the developing device according to the present invention, the leak detection voltage applied between the image carrier and the toner carrier is changed by the leak generating means,
A leak is generated between the image bearing member and the toner bearing member, and based on the current flowing between the image bearing member and the toner bearing member due to this leak, the leak is detected by the leak detecting means, so an expensive concentration sensor is used. Since it is not necessary to use it, the cost is reduced, and the occurrence of the leak can be reliably detected regardless of the position where the leak occurs.

Therefore, even if an error occurs in the distance between the toner carrier and the image carrier, the developing bias voltage is set so that the leak does not occur between the toner carrier and the image carrier. It can be adjusted appropriately, and a good image without noise can be stably obtained.

When the leak is detected by the leak detecting means on the basis of the current flowing between the image bearing member and the toner bearing member as described above, the leak detecting means causes noise in a circuit other than the leak in the leak detecting means. In order to prevent the current from being detected and being judged as a leak,
The maximum potential difference ΔVmax between the leak detection voltage applied between the image bearing member and the toner bearing member by the leak generating means and the surface potential of the image bearing member is gradually increased so that the leak voltage between the image bearing member and the toner bearing member is increased. It is preferable that the leak detection unit determines that the current is a leak when the current flowing through the line continuously increases.

Further, as described above, the leak detection voltage applied between the image bearing member and the toner bearing member is changed by the leak generating means to cause a leak between the image bearing member and the toner bearing member. In this case, the surface potential of the image carrier changes due to this leak, and in order to prevent toner from being supplied from the toner carrier to the portion of the image carrier where such a leak has occurred, the leak detection voltage So that the potential difference ΔVL between the average voltage and the surface potential of the image carrier and the potential difference ΔVa between the surface potential of the image carrier before the leak and the surface potential of the image carrier after the leak satisfy the condition of ΔVL ≧ ΔVa. Is preferred.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A developing device according to an embodiment of the present invention will be specifically described below with reference to the accompanying drawings.

In the developing device of this embodiment, as shown in FIG. 1, a toner carrier 11 having a resistance layer 11b provided on the outer circumference of a metal roller 11a is provided at a required distance d from the image carrier 1 in the developing area. The toner carrier 11 and the image carrier 1 are rotated so as to face each other, and the toner t accommodated in the main body 10 of the apparatus is fed.
The toner t is supplied to the supply roller 13 which rotates in contact with the toner carrier 11 by means of 2, and the toner t is supplied from the supply roller 13 to the surface of the toner carrier 11.

The toner t thus supplied to the surface of the toner carrier 11 is regulated by the regulation member 14 and the toner t is charged, and then the toner t is image-carried by the toner carrier 11. A developing bias voltage in which a DC voltage and an AC voltage are superposed is applied from the DC power supply 15a and the AC power supply 15b between the toner carrier 11 and the image carrier 1 while being guided to the developing area facing the body 1. Then, the toner t is supplied to the portion of the electrostatic latent image formed on the image carrier 1 to perform the development.

Here, in the developing device in this embodiment, before appropriately performing the development as described above, in appropriately setting the developing bias voltage applied from the DC power supply 15a and the AC power supply 15b, the image bearing is carried out. As the leak generating means 20 for generating a leak between the body 1 and the toner carrier 11, the voltage applied between the toner carrier 11 and the image carrier 1 is changed from the DC power supply 15a and the AC power supply 15b. A voltage adjusting device 21 is provided.

Further, as a leak detecting means 30 for detecting a leak based on a current flowing between the image carrier 1 and the toner carrier 11, a current flowing between the image carrier 1 and the toner carrier 11 is detected. A current detector 31 for controlling the voltage regulator 21 is provided, and a controller 32 for controlling the voltage regulator 21 by determining the presence or absence of a leak based on the result detected by the current detector 31.

Until the controller 32 detects a leak, the controller 32 controls the voltage adjusting device 21 to apply the leak detection voltage applied between the toner carrier 11 and the image carrier 1. Image carrier 1
A leak is generated between the toner carrier 11 and the toner carrier 11.

Further, the voltage adjusting device 21 is controlled by the control device 32 based on the leak detection voltage at the time when the leak occurs in this way, and the toner carrier 11 is connected from the DC power supply 15a and the AC power supply 15b. Image carrier 1
In between, the developing bias voltage is applied so that appropriate development can be performed under the condition that no leak occurs.

When detecting a leak between the image carrier 1 and the toner carrier 11, the leak detection voltage applied between the toner carrier 11 and the image carrier 1 is a DC voltage or an AC voltage. The voltage may be superposed, or only the DC voltage may be used.

Here, in the developing device which performs the reversal development using the negatively chargeable toner t, the leak detection voltage in which the DC voltage and the AC voltage are superposed as described above is applied to the toner carrier 11 and the image. In detecting a leak between the image carrier 1 and the carrier 1, for example, as shown in FIG. 2, the surface potential Vo of the image carrier 1 is set to −550 V, and a DC voltage Vdc of −370 V is applied from the DC power supply 15 a. The peak-to-peak value Vpp of the AC voltage applied from the AC power supply 15b is changed to increase the maximum potential difference ΔVmax between the leak detection voltage and the surface potential Vo of the image carrier 1 and the toner carrier 11 and the image. When a leak is generated between the image carrier 1 and the carrier 1, when the surface potential Vi of the image carrier 1 at the leaked portion becomes −50 V, the leaked image is generated in this way. The portion of the bearing member 1 toner t is supplied, so that toner t is wasted.

Therefore, when the leak detection voltage in which the DC voltage and the AC voltage are superimposed as described above is applied and the leak between the toner carrier 11 and the image carrier 1 is detected, As shown in FIG. 3, an AC voltage having a short duty time and a small duty ratio is applied, or as shown in FIG. 4, a leak detection voltage in which a DC voltage and an AC voltage are superposed. Average voltage VL (D
In the case of an AC voltage with a duty ratio of 50%, it is the same as the DC voltage Vdc applied from the DC power supply 15a. ) And the potential difference ΔVL (= | Vo-VL |) between the surface potential Vo of the image carrier 1 in the non-leakage portion and the image of the surface potential Vo of the non-leakage image carrier 1 and the leaked portion. Potential difference ΔVa (= | V from the surface potential Vi of the carrier 1)
It is preferable that o-Vi |) satisfy the condition of ΔVL ≧ ΔVa.

Further, as shown in FIG. 5, when only the DC voltage Vdc is applied as the leak detection voltage, the toner t is prevented from being supplied to the leaked portion of the image carrier 1. To be done.

When the leak detection means 30 detects a leak based on the current flowing between the image carrier 1 and the toner carrier 11 as described above, the current is detected by noise in a circuit other than the leak. Since a current may be detected in the container 31 and the controller 32 may determine that there is a leak, as shown in FIG. 6, the voltage adjuster 21 causes the image carrier 1 and the toner carrier 11 to be leaked.
The maximum potential difference ΔVmax between the leak detection voltage applied between the image carrier 1 and the toner carrier 11 is gradually increased to detect the current flowing between the image carrier 1 and the toner carrier 11. When the value detected by the current detector 31 is continuously increasing, it is preferable that the control device 32 determines that there is a leak for the first time.

When the current detector 31 detects the current flowing between the image carrier 1 and the toner carrier 11 as described above, the current flows between the image carrier 1 and the toner carrier 11 due to a leak. Since the change in current is small, as shown in FIG. 7, the image carrier 1 and the toner carrier 11 are
The metal portions 1a and 11a are exposed at the ends of the image carrier 1 and the toner carrier 11. The metal portions 1a and 11a of the image carrier 1 and the toner carrier 11 thus exposed cause a leak, and the leak causes the image carrier 1 to move. The change in the current flowing between the toner carrier 11 and the toner carrier 11 can be increased. In this case, since the leak voltage is different between the metal portions 1a and 11a and the portions other than the metal portions 1a and 11a, the voltage at which the leak occurs in the metal portions 1a and 11a, The correlation with the voltage at which leakage occurs in portions other than the metal portions 1a and 11a is obtained, and based on this, the voltage adjusting device 21 is controlled by the control device 32, and the toner carrier 11 and the image carrier 1 are controlled. In the meantime, it is necessary to apply a developing bias voltage capable of performing appropriate development under the condition that no leak occurs.

In the developing device of this embodiment, as described above, a leak is generated between the image carrier 1 and the toner carrier 11, and the DC power supply 15a and the AC power supply 1 are used.
The operation of appropriately setting the developing bias voltage to be applied from 5b and 5b is performed not only when a new developing device is used but also sequentially when a predetermined number of sheets are developed by using this developing device, and an appropriate developing bias is always applied. Voltage is image carrier 1
Is preferably applied between the toner carrier 11 and the toner carrier 11.

[0034]

As described above in detail, in the developing device of the present invention, the developing bias voltage applied between the toner carrier and the image carrier facing each other with a required space in the developing region is appropriately adjusted. In doing so, by changing the leak detection voltage applied between the image bearing member and the toner bearing member by the leak generating means, a leak is caused between the image bearing member and the toner bearing member, and this leak causes the image bearing member. Since the leak is detected by the leak detecting means based on the current flowing between the toner carrier and the toner carrier, it is not necessary to use an expensive concentration sensor as in the conventional case to detect the leak, and the cost is reduced. In addition, no matter what position the leak occurs, the occurrence of the leak can be reliably detected.

As a result, in the developing device according to the present invention, even if an error occurs in the distance between the toner carrier and the image carrier, no leak occurs between the toner carrier and the image carrier. In this way, the developing bias voltage can be properly adjusted, and good development without noise can be stably performed.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of a developing device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a developing device according to the above-described embodiment, which is applied between the toner carrier and the image carrier in order to detect a leak between the toner carrier and the image carrier.
It is a figure showing the waveform of the leak detection voltage.

FIG. 3 is a diagram illustrating a developing device according to the above-described embodiment, which is applied between the toner carrier and the image carrier in order to detect a leak between the toner carrier and the image carrier.
It is a figure showing the waveform of the leak detection voltage.

FIG. 4 is a schematic diagram illustrating a developing device according to the above-described embodiment, which is applied between a toner carrier and an image carrier in order to detect a leak between the toner carrier and the image carrier;
It is a figure showing the waveform of the leak detection voltage.

FIG. 5 is a diagram showing a developing device according to the above embodiment, which is applied between the toner carrier and the image carrier in order to detect a leak between the toner carrier and the image carrier.
It is a figure showing the waveform of the leak detection voltage.

FIG. 6 is a diagram showing the developing device according to the above embodiment, in which the maximum potential difference ΔVmax between the leak detection voltage applied between the image bearing member and the toner bearing member and the surface potential of the image bearing member is gradually increased to cause leakage. Is generated, ΔVmax
It is the figure which showed the state which the detection value by a current detector increases continuously with increase of.

FIG. 7 is a view showing the developing device according to the above-described embodiment, in which metal portions are exposed at end portions of the image bearing member and the toner bearing member, and the metal portions of the image bearing member and the toner bearing member thus exposed are exposed. 2 is a schematic explanatory view showing a state in which a leak is generated in FIG.

[Explanation of symbols]

1 image carrier 11 toner carrier 15a direct current power supply 15b alternating current power supply 20 leak generating means 21 voltage adjusting device 30 leak detecting means 31 current detector 32 controller t toner d toner image carrier and toner carrier facing each other in the developing area Interval ΔVmax Maximum potential difference between leak detection voltage and surface potential of image carrier VL Average voltage of leak detection voltage Vo Surface potential of image carrier before leak Vi Vi Surface potential of image carrier after leak ΔVL Average of leak detection voltage Potential difference between the voltage and the surface potential of the image carrier ΔVa Potential difference between the surface potential of the image carrier before the leak and the surface potential of the image carrier after the leak

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shuichi Nakagawa             2-3-3 Azuchi-cho, Chuo-ku, Osaka             Kokusai Building Minolta Co., Ltd. F-term (reference) 2H027 DA02 DA04 DA15 DE05 DE07                       DE09 EA05 EA15 EC06 EC09                       ED01 ED09                 2H073 AA01 BA04 BA13 BA22 BA23                       CA02                 2H077 AD06 AD36 BA07 DB08 EA11                       EA16

Claims (3)

[Claims] 1. A toner carrier is provided so as to face the image carrier on which the electrostatic latent image is formed in a developing region with a required gap, and a DC voltage is applied between the toner carrier and the image carrier. In a developing device for applying a developing bias voltage superimposed with an AC voltage to supply toner held on a toner carrier to the image carrier to develop an electrostatic latent image, the above-mentioned image carrier and toner carrier Based on the leak generation means for changing the leak detection voltage applied between the image carrier and the toner carrier to generate a leak between the image carrier and the toner carrier, and the current flowing between the image carrier and the toner carrier. A developing device provided with a leak detecting means for detecting a leak. 2. The developing device according to claim 1, wherein:
When the maximum potential difference ΔVmax between the leak detection voltage and the surface potential of the image carrier is gradually increased and the current flowing between the image carrier and the toner carrier is continuously increased, the above leak occurs. A developing device characterized in that a leak is judged by a detection means. 3. The developing device according to claim 1, wherein the potential difference ΔVL between the average voltage of the leak detection voltage and the surface potential of the image carrier, and the surface potential of the image carrier before the leak. A developing device characterized in that a potential difference ΔVa from the surface potential of the image carrier after the leak satisfies a condition of ΔVL ≧ ΔVa.