JP3815356B2 - Development device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a developing device for use in an image forming apparatus such as a copying machine or a printer, in which a toner carrier is provided so as to face an image carrier on which an electrostatic latent image is formed with a predetermined distance in a development area. 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, and the toner held on the toner carrier is supplied to the image carrier to electrostatically In a developing device that develops a latent image, an appropriate developing bias voltage is applied between the toner carrier and the image carrier even when an error occurs in the interval between the toner carrier and the image carrier. It is characterized in that it can be adjusted easily.
[0002]
[Prior art]
Conventionally, in an image forming apparatus such as a copying machine or a printer, various developing devices are used to develop an electrostatic latent image formed on an image carrier. As such a developing device, a carrier is used. In addition to a two-component developing type developing device using a developer containing toner and a toner, a one-component developing type developing device using only a toner not containing a carrier is known.
[0003]
Further, in such a one-component development type developing device, a contact developing type developing device in which the toner carrier is provided in contact with the image carrier, and the required distance between the toner carrier and the image carrier in the development region. There is known a non-contact developing type developing device provided so as to face each other.
[0004]
Here, in the case of a contact developing type developing device, since development is performed by bringing toner into contact with the image carrier, the electrostatic latent image formed on the image carrier is excellent in reproducibility. There is a problem that fog is generated in an image formed by being attached to a non-image portion where no image is formed.
[0005]
For this reason, in the past, the adhesion of the toner to the non-image portion was suppressed by changing the moving speed between the image carrier and the toner carrier, but in this case, the contact with the toner carrier is not possible. As a result, the surface of the image carrier is likely to be worn, and stable image formation cannot be performed.
[0006]
On the other hand, in the case of a non-contact developing type developing device in which the toner carrier is provided so as to face the image carrier with a required interval, there is no problem as in the case of the contact developing type developing device, but the required interval In order to supply the toner from the toner carrier to the opposite image carrier through the toner, 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, and the toner carrier The toner held on the body is caused to fly between the toner carrier and the image carrier.
[0007]
Further, as described above, in order to make the toner carrier and the image carrier face each other with a predetermined interval, a spacer member is generally provided between the toner carrier and the image carrier, and the toner carrier and the image carrier are separated from each other. It was made to oppose at a fixed space | interval.
[0008]
However, even in this case, for example, the molding accuracy or mounting state of the image carrier or toner carrier may vary, the spacer member may be worn out or deformed, and the opposing areas in the development area. The distance between the toner carrier and the image carrier to be changed fluctuates, whereby the electric field strength acting between the toner carrier and the image carrier fluctuates, resulting in uneven density in the formed image. was there.
[0009]
For this reason, 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, and the toner is sufficiently transferred between the toner carrier and the image carrier. It was made to fly to suppress the occurrence of uneven density.
[0010]
However, if the peak-to-peak value of the AC voltage in the development bias voltage applied between the toner carrier and the image carrier is increased, the potential difference between the surface potential of the image carrier and the peak value of the development bias voltage is increased. There is a problem that the size of the toner is increased and a leak occurs between the toner carrier and the image carrier, and noise is generated in the formed image.
[0011]
Therefore, at present, the development bias voltage applied between the toner carrier and the image carrier is changed to generate 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 was set appropriately.
[0012]
However, the above density sensor is expensive and expensive, and even if a leak occurs at a position other than the position detected by this density sensor, it cannot be detected. There was a problem that the voltage could not be set appropriately.
[0013]
[Problems to be solved by the invention]
According to the present invention, a toner carrier is provided so as to face an image carrier on which an electrostatic latent image is formed with a predetermined distance in the development area, and a DC voltage and an alternating current are provided between the toner carrier and the image carrier. Solves the above-mentioned problems in a developing device that applies a developing bias voltage superimposed with a voltage and supplies the toner held on the toner carrier to the image carrier to develop the electrostatic latent image. It is an object to do.
[0014]
That is, according to the present invention, in the developing device as described above, even when an error occurs in the distance between the toner carrier and the image carrier, no leakage occurs between the toner carrier and the image carrier. Thus, it is an object of the present invention to make it possible to easily and appropriately adjust the developing bias voltage and to stably obtain a good image free from noise.
[0015]
[Means for Solving the Problems]
In the developing device according to the present invention, in order to solve the above-described problems, a toner carrier is provided so as to face the image carrier on which the electrostatic latent image is formed with a predetermined distance in the development area. A developing bias voltage in which a DC voltage and an AC voltage are superimposed is applied between the carrier and the image carrier, and the toner held on the toner carrier is supplied to the image carrier to develop the electrostatic latent image. In the developing device, a leak generating 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 an image carrier A leak detection means for detecting a leak based on a current flowing between the toner carrier and the toner carrier, and gradually increasing the maximum potential difference ΔVmax between the leak detection voltage and the surface potential of the image carrier to Carrying And when the current flowing between the toner carrying member is increased continuously, it was so as to determine a leak by the aforementioned leakage detection means.
[0016]
Here, in the developing device according to the present invention, the leakage detection voltage applied between the image carrier and the toner carrier is changed by the above-described leak generating means, so that the leak occurs between the image carrier and the toner carrier. Since the leak is detected by the leak detection means based on the current flowing between the image carrier and the toner carrier due to the leak, there is no need to use an expensive density sensor, and the cost is reduced. Regardless of the position where the leak occurs, the occurrence of the leak is reliably detected.
[0017]
For this reason, even when there is an error in the distance between the toner carrier and the image carrier, the development bias voltage is adjusted appropriately so that no leakage occurs between the toner carrier and the image carrier. Therefore, a good image free from noise can be obtained stably.
[0018]
In addition, when the leak detection unit detects a leak based on the current flowing between the image carrier and the toner carrier as described above, the current is detected by the leak detection unit due to noise in a circuit other than the leak. In order to suppress the determination as a leak, in the present invention, as described above, the leak detection voltage applied between the image carrier and the toner carrier by the leak generating means and the surface potential of the image carrier gradually increased up to the potential difference ΔVmax with, when the current flowing between the image bearing member and the toner carrying member is increased continuously, it was so as to determine a leak by the leak detection means.
[0019]
Further, in the case where 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 by the leak generating means as described above, This leak changes the surface potential of the image carrier, and in order to prevent toner from being supplied from the toner carrier to the portion of the image carrier where the leak has occurred, the average voltage of the leak detection voltage described above Between the surface potential of the image carrier 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 INVENTION
Hereinafter, a developing device according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings.
[0021]
In the developing device in this embodiment, as shown in FIG. 1, a toner carrier 11 having a resistance layer 11b provided on the outer periphery of a metal roller 11a is opposed to the image carrier 1 with a required distance d in the development region. The toner carrier 11 and the image carrier 1 are rotated so that the toner t accommodated in the apparatus main body 10 is rotated in contact with the toner carrier 11 by the feeding member 12. The toner t is supplied to the surface of the toner carrier 11 from the supply roller 13.
[0022]
After the toner t thus supplied to the surface of the toner carrier 11 is regulated by the regulating member 14 and the toner t is charged, the toner carrier 11 and the toner t are transferred to the image carrier 1. A developing bias voltage in which a DC voltage and an AC voltage are superimposed is applied between the toner carrier 11 and the image carrier 1 from the DC power source 15a and the AC power source 15b. Development is performed by supplying toner t to the portion of the electrostatic latent image formed on the image carrier 1.
[0023]
Here, in the developing device in this embodiment, before the development is performed as described above, the image bearing member 1 and the image carrier 1 are used to appropriately set the developing bias voltage applied from the DC power supply 15a and the AC power supply 15b. As the leak generating means 20 for generating a leak between the toner carrier 11 and the DC power source 15a and the AC power source 15b, a voltage adjustment for changing the voltage applied between the toner carrier 11 and the image carrier 1 is performed. A device 21 is provided.
[0024]
Further, as a leak detection means 30 for detecting a leak based on a current flowing between the image carrier 1 and the toner carrier 11, a current detection for detecting a current flowing between the image carrier 1 and the toner carrier 11. 31 and a control device 32 for controlling the voltage regulator 21 by determining the presence or absence of leakage based on the result detected by the current detector 31.
[0025]
The control device 32 controls the voltage adjusting device 21 until the control device 32 detects a leak, thereby changing the leak detection voltage applied between the toner carrier 11 and the image carrier 1. Leakage is generated between the image carrier 1 and the toner carrier 11.
[0026]
Further, based on the leak detection voltage at the time when the leak occurs in this way, the voltage adjusting device 21 is controlled by the control device 32, and the toner carrier 11 and the image carrier are supplied from the DC power source 15a and the AC power source 15b. A developing bias voltage that allows appropriate development under the condition that no leakage occurs is applied between the two.
[0027]
Note that when the leak between the image carrier 1 and the toner carrier 11 is detected, the leak detection voltage applied between the toner carrier 11 and the image carrier 1 is a DC voltage and an AC voltage. It may be superposed or only DC voltage.
[0028]
Here, in the developing device that performs the reversal development using the negatively chargeable toner t, as described above, the leakage detection voltage obtained by superimposing the DC voltage and the AC voltage is applied to the toner carrier 11 and the image carrier 1. 2, for example, as shown in FIG. 2, the surface potential Vo of the image carrier 1 is set to −550 V, a DC voltage Vdc of −370 V is applied from the DC power supply 15 a, and the AC power supply described above is applied. The peak-to-peak value Vpp of the AC voltage applied from 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 carrier 1 are increased. When the surface potential Vi of the image carrier 1 at the leaked portion becomes −50 V, the leaked portion of the image carrier 1 is generated. Toner t is supplied, so that toner t is wasted on.
[0029]
For this reason, when a leak detection voltage in which a DC voltage and an AC voltage are superimposed as described above is applied to detect a leak between the toner carrier 11 and the image carrier 1, FIG. As shown in FIG. 4, an average voltage of leak detection voltages in which a DC voltage and an AC voltage are superimposed as shown in FIG. A potential difference ΔVL (= | Vo−) between VL (in the case of an AC voltage with a duty ratio of 50%, the same as the DC voltage Vdc applied from the DC power supply 15a) and the surface potential Vo of the image carrier 1 in a non-leaked portion VL |) and the potential difference ΔVa (= | Vo−Vi |) between the surface potential Vo of the image carrier 1 which is not leaked and the surface potential Vi of the image carrier 1 in the leaked portion is ΔVL ≧ ΔV It is preferable that the condition is satisfied.
[0030]
Also, 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 image carrier 1 portion.
[0031]
In addition, 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 detector 31 is caused to have a noise by a circuit other than the leak. Since there is a case where the current is detected and the control device 32 determines that there is a leak, the voltage adjustment device 21 applies the current between the image carrier 1 and the toner carrier 11 as shown in FIG. The current detector 31 detects the current flowing between the image carrier 1 and the toner carrier 11 by gradually increasing the maximum potential difference ΔVmax between the leak detection voltage and the surface potential Vo of the image carrier 1. When the detected value continuously increases, it is preferable that the control device 32 first determines that there is a leak.
[0032]
Further, when the current detector 31 detects the current flowing between the image carrier 1 and the toner carrier 11 as described above, a change in the current flowing between the image carrier 1 and the toner carrier 11 due to leakage is detected. Therefore, as shown in FIG. 7, the metal portions 1a and 11a are exposed at the ends of the image carrier 1 and the toner carrier 11, respectively, and the image carrier 1 and the toner carrier thus exposed are exposed. A leak can be generated in the metal portions 1a and 11a with the body 11, and a change in current flowing between the image carrier 1 and the toner carrier 11 can be increased due to the leak. In this case, since the voltage at which leakage occurs is different between the metal portions 1a and 11a and the portions other than the metal portions 1a and 11a, the voltage at which leakage occurs in the metal portions 1a and 11a in advance, The correlation with the voltage at which leakage occurs in the 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 In the meantime, it is necessary to apply a developing bias voltage capable of appropriate development under the condition that no leakage occurs.
[0033]
In the developing device according to this embodiment, as described above, a leak is generated between the image carrier 1 and the toner carrier 11, and a developing bias voltage applied from the DC power supply 15a and the AC power supply 15b is appropriately set. The setting operation is performed not only when a new developing device is used but also when a predetermined number of developments are performed using this developing device, and an appropriate developing bias voltage is always applied to the image carrier 1 and the toner carrier 11. It is preferable to apply between the two.
[0034]
【The invention's effect】
As described above in detail, in the developing device according to the present invention, a leak occurs when appropriately adjusting the developing bias voltage applied between the toner carrier and the image carrier facing each other with a predetermined interval in the development region. The leak detection voltage applied between the image carrier and the toner carrier is changed by the means to generate a leak between the image carrier and the toner carrier, and the leak causes the image carrier and the toner carrier to Since the leak detection means detects the leak based on the current flowing between the two, there is no need to use an expensive concentration sensor as in the prior art, and the cost is reduced and Even if a leak occurs at any position, the leak is reliably detected.
[0035]
As a result, in the developing device according to the present invention, even when an error occurs in the distance between the toner carrier and the image carrier, no leakage occurs between the toner carrier and the image carrier. The development bias voltage can be appropriately adjusted, and good development without noise can be stably performed.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view of a developing device according to an embodiment of the present invention.
FIG. 2 shows a first leak detection applied between the toner carrier and the image carrier in order to detect a leak between the toner carrier and the image carrier in the developing device according to the embodiment. It is the figure which showed the waveform of the voltage.
FIG. 3 shows a second leak detection applied between the toner carrier and the image carrier in order to detect a leak between the toner carrier and the image carrier in the developing device according to the embodiment. It is the figure which showed the waveform of the voltage.
FIG. 4 shows a third leak detection applied between the toner carrier and the image carrier in order to detect a leak between the toner carrier and the image carrier in the developing device according to the embodiment. It is the figure which showed the waveform of the voltage.
FIG. 5 shows a fourth leak detection applied between the toner carrier and the image carrier in order to detect a leak between the toner carrier and the image carrier in the developing device according to the embodiment. It is the figure which showed the waveform of the voltage.
FIG. 6 shows a developing device according to the above embodiment in which the maximum potential difference ΔVmax between the leak detection voltage applied between the image carrier and the toner carrier and the surface potential of the image carrier is gradually increased to increase the leak. Is a diagram showing a state in which the detection value by the current detector continuously increases as ΔVmax increases.
FIG. 7 shows a developing device according to the above embodiment in which metal portions are exposed at the end portions of the image carrier and the toner carrier, and the exposed metal portions of the image carrier and the toner carrier. It is the schematic explanatory drawing which showed the state made to generate | occur | produce a leak.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image carrier 11 Toner carrier 15a DC power supply 15b AC power supply 20 Leak generation means 21 Voltage adjustment device 30 Leak detection means 31 Current detector 32 Control device t Toner d Between image carrier and toner carrier facing each other in development 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 Average surface potential of image carrier after leak ΔVL Average of leak detection voltage Potential difference between voltage and surface potential of image carrier ΔVa Potential difference between surface potential of image carrier before leak and surface potential of image carrier after leak

Claims (2)

A toner carrier is provided so as to face the image carrier on which the electrostatic latent image is formed with a predetermined distance in the development area, and a DC voltage and an AC voltage are superimposed between the toner carrier and the image carrier. In a developing device for applying an applied development bias voltage and supplying the toner held on the toner carrier to the image carrier to develop the electrostatic latent image, the image is provided between the image carrier and the toner carrier. Leak generation means for generating a leak between the image carrier and the toner carrier by changing a leak detection voltage to be applied, and a leak for detecting a leak based on a current flowing between the image carrier and the toner carrier Detecting means, and gradually increasing the maximum potential difference ΔVmax between the leak detection voltage and the surface potential of the image carrier, and the current flowing between the image carrier and the toner carrier continuously increases. If the above Developing apparatus characterized by determining a leak by click detection means. 2. The developing device according to claim 1, wherein a potential difference ΔVL between the average voltage of the leak detection voltage and the surface potential of the image carrier, the surface potential of the image carrier before the leak and the surface potential of the image carrier after the leak. And the potential difference ΔVa satisfy the condition of ΔVL ≧ ΔVa .

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