JP2004117756A - Developing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To constitute a developing apparatus so that a toner after a developing process can be appropriately destaticized and returned into the apparatus body through a contact member even in the case the toner is deteriorated, as for the developing apparatus where the toner held by a toner carrier after the developing process is brought into contact with the contact member and destaticized, and then, the toner is returned into the apparatus body. <P>SOLUTION: As for the developing apparatus where the electrified toner (t) is carried by the toner carrier 12 into a developing area facing an image carrier 1, a bias voltage obtained by superposing an AC voltage on a DC voltage is applied on the toner carrier from a power source 14 so as to develop a latent image formed on the image carrier, then, the toner after the developing process held by the toner carrier is brought into contact with the contact member 15 and destaticized, then, the toner is returned into the apparatus body through the contact member, the contact member is connected to the power source, and also, a rectifying element 20 for reducing the potential of the AC voltage whose polarity is opposite to that of the electrified toner is arranged between the power source and the contact member. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a developing device used to develop an electrostatic latent image formed on an image carrier in an image forming apparatus such as a copying machine or a printer, and more particularly to a developing device that uses a toner carrier to transfer charged toner to the image. The toner carrier is conveyed to a development area facing the carrier, and a bias voltage in which an AC voltage is superimposed on a DC voltage is applied from a power supply to the toner carrier to develop an electrostatic latent image formed on the image carrier. In the developing device, the toner held in the toner carrier is brought into contact with a contact member to remove electricity, and the toner is returned into the apparatus main body through the contact member. In addition to being neutralized, it is characterized in that the contact member is used to properly return the device into the apparatus main body.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, various developing devices have been used to develop an electrostatic latent image formed on an image carrier.
[0003]
As one of such developing devices, the one shown in FIG. 1 is used.
[0004]
Here, in this developing device, the toner t contained in the device main body 10 is supplied by a toner feeding member 11 to a roller-shaped toner carrier 12 provided so as to face the image carrier 1, and the toner t While the carrier 12 is being rotated and the supplied toner t is being conveyed to the developing area facing the image carrier 1, the regulating member 13 is pressed against the surface of the toner carrier 12 and developed by the toner carrier 12. The amount of the toner t to be conveyed to the area is regulated, and the toner t is frictionally charged.
[0005]
The toner t thus regulated and frictionally charged is guided by the toner carrier 12 to a development area facing the image carrier 1, and an AC voltage is superimposed on a DC voltage from the power supply 14 on the toner carrier 12. By applying a bias voltage, toner t is supplied to the portion of the electrostatic latent image formed on the image carrier 1 to perform development.
[0006]
Further, after the toner t is supplied to the portion of the electrostatic latent image formed on the image carrier 1 to perform development, the developed toner t remaining on the toner carrier 12 is transferred to the apparatus main body 10. The static electricity is removed by contacting the contact member 15 provided, and the toner t is returned into the apparatus main body 10 through the contact member 15.
[0007]
Here, in the developing device as described above, when the toner t remaining on the toner carrier 12 is brought into contact with the contact member 15 to remove the charge, generally, as shown in FIG. The same bias voltage as that of the toner carrier 12 is applied from the power source 14 or a bias voltage whose potential on the side opposite to the charging polarity of the toner t is higher than that of the toner carrier 12 is applied.
[0008]
However, as described above, the same bias voltage as that of the toner carrier 12 is applied to the contact member 15, or a bias voltage in which the potential on the side opposite to the charge polarity of the toner t is higher than that of the toner carrier 12 is applied. In this case, when the toner t gradually deteriorates and its charge amount decreases, the adhesion of the toner t to the toner carrier 12 becomes weak, and the toner t after development does not pass through the contact member 15 well. In addition, there is a problem in that a part of the toner t remains in a contact portion with the contact member 15 and gradually increases and spills out of the developing device, thereby contaminating the recording paper and the inside of the image forming apparatus.
[0009]
[Problems to be solved by the invention]
The present invention conveys a charged toner to a developing area opposed to an image carrier by a toner carrier, and applies a bias voltage in which an AC voltage is superimposed on a DC voltage from a power supply to the toner carrier by applying the bias voltage to the image carrier. A developing device that develops the electrostatic latent image formed on the toner carrier, contacts the toner held on the toner carrier after the development with a contact member to remove static electricity, and returns the toner into the apparatus main body through the contact member. It is an object of the present invention to solve the above-mentioned problem.
[0010]
In other words, according to the present invention, in the above-described developing device, even if the toner gradually deteriorates, the charge amount thereof decreases, and the adhesion of the toner to the toner carrier becomes weak, the toner after the development is in contact with the toner. It is an object of the present invention to make it possible to properly return the device to the inside of the device main body through the member and to appropriately perform the charge removal.
[0011]
[Means for Solving the Problems]
In the developing device according to the present invention, in order to solve the above-described problem, the charged toner is transported by a toner carrier to a developing area opposed to the image carrier, and the toner carrier is supplied with a DC voltage from a power supply to a DC voltage. The electrostatic latent image formed on the image carrier is developed by applying a bias voltage on which the voltage is superimposed, and the toner held on the toner carrier after the development is brought into contact with a contact member to remove the electricity. In the developing device in which the toner is returned into the apparatus main body through the member, the contact member is connected to the power supply, and an AC voltage having a polarity opposite to the polarity of the charged toner is applied between the power supply and the contact member. A rectifying element for lowering the potential is provided.
[0012]
Then, as in the developing device of the present invention, when a rectifying element is provided between the power supply and the contact member for reducing the potential of the AC voltage having a polarity opposite to the charging polarity of the toner, the power supply supplies the contact member with the rectifier. At the time when an AC voltage having a polarity opposite to the charging polarity of the toner is applied, the potential of the AC voltage acting on the contact member decreases due to the action of the rectifying element, and the potential of the AC voltage acting on the toner carrier becomes lower than the potential of the AC voltage acting on the toner carrier. And the electric field in the direction of pressing the toner against the toner carrier acts between the contact member and the toner carrier, so that the toner is pressed against the toner carrier.
[0013]
For this reason, even when the toner gradually deteriorates and the charge amount decreases, and the adhesion of the toner to the toner carrier becomes weak, if the developed toner comes into contact with this contact member, the charge polarity of the toner is reversed. At the time when the AC voltage of the polarity is applied, the toner is pressed against the toner carrier, and the developed toner is appropriately returned into the apparatus main body through the contact member by the toner carrier, and a part of the toner is developed. Is prevented from remaining in the contact portion with the contact member, and the toner remaining in the contact portion with the contact member as in the related art is suppressed, and the toner is suppressed from spilling out of the developing device.
[0014]
Further, in the developing device according to the present invention, when an AC voltage having the same polarity as the charging polarity of the toner is applied to the contact member and the toner carrier from the power supply, the contact member and the toner carrier have the same potential. When the developed toner comes into contact with the contact member, the toner is appropriately neutralized by the contact member, and the toner thus neutralized is appropriately returned into the apparatus main body as described above. Development can be performed. That is, in the case where an AC voltage having the same polarity as the charging polarity of the toner is applied, if the potential of the contact member is higher than that of the toner carrier, the toner is less likely to be discharged by contact with the contact member, and thus the charge is removed. Unused toner is used again for development, and fogging called ghost is likely to occur. On the other hand, when an AC voltage having the same polarity as the charging polarity of the toner is applied, if the potential of the contact member is lower than that of the toner carrier, the toner is pressed from the toner carrier to the contact member, and after development. It becomes difficult for the toner to pass through the contact member, and a part of the toner remains in the contact portion with the contact member and accumulates, and the toner spills out of the developing device.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a developing device according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings.
[0016]
In the developing device according to this embodiment, as shown in FIG. 2, the toner t is accommodated in the apparatus main body 10, a toner feeding member 11 is provided in the apparatus main body 10, and the toner feeding member 11 is rotated. The toner t accommodated in the apparatus main body 10 is supplied to the toner supply unit 10a separated by the partition member 16 through a supply port 16a provided in the partition member 16.
[0017]
Here, as described above, when the toner t is supplied to the toner supply unit 10a through the supply port 16a provided in the partition member 16 by the toner supply member 11, as shown in FIG. Supply ports 16a are provided on both sides of the partition member 16, and an opening / closing member 19 is attached to each of the supply ports 16a. Each opening / closing member 19 is pushed by the toner t sent by the toner feeding member 11 to supply each opening. 16, the toner t is fed to the toner supply unit 10a from the supply ports 16a on both sides.
[0018]
The toner t fed into the toner supply unit 10a from the supply ports 16a on both sides is guided to the center in the toner supply unit 10a and provided to face the image carrier 1. The toner t is supplied to the toner carrier 12 by a toner supply roll 17 that rotates while being in contact with the roller-shaped toner carrier 12.
[0019]
Here, in guiding the toner t sent from the supply ports 16a on both sides to the toner supply unit 10a to the center in the toner supply unit 10a as described above, in the developing device of this embodiment, the toner supply unit 10a A plurality of guide members 18 extending below the toner supply roll 17 from the partition member 16 are provided so as to be inclined in the opposite direction with respect to the center of the toner supply unit 10a. With the rotation of, the toner t supplied to both sides of the toner supply unit 10a is guided to the center of the toner supply unit 10a by the guide members 18 described above. Note that, instead of the guide member 18 described above, a screw member (not shown) that guides the toner t supplied to both sides to the central portion of the toner supply unit 10a may be provided.
[0020]
While the toner t supplied to the toner carrier 12 as described above is being conveyed to the developing area facing the image carrier 1 by the rotating toner carrier 12, a regulating member is provided on the surface of the toner carrier 12. 13 is pressed into contact with the toner carrier 12 to regulate the amount of toner t to be conveyed to the development area, and the toner t is frictionally charged.
[0021]
The toner t thus regulated and frictionally charged is guided by the toner carrier 12 to a development area facing the image carrier 1, and an AC voltage is superimposed on a DC voltage from the power supply 14 on the toner carrier 12. By applying a bias voltage, toner t is supplied to the portion of the electrostatic latent image formed on the image carrier 1 to perform development.
[0022]
Further, after the toner t is supplied to the portion of the electrostatic latent image formed on the image carrier 1 to perform the development, the developed toner t remaining on the toner carrier 12 is removed from the toner carrier 12. The contact member 15 connected to the same power supply 14 as the body 12 contacts the contact member 15 to remove electricity, and the toner t after development is returned into the apparatus main body 10 by the toner carrier 12 through the contact member 15.
[0023]
Here, in the developing device of this embodiment, the contact member 15 is connected to the same power source 14 as the toner carrier 12 as described above, and the DC voltage is superimposed on the contact member 15 from the power source 14. In applying the bias voltage, a zener diode 20 is provided between the power supply 14 and the contact member 15 as a rectifying element 20 for lowering the potential of an AC voltage having a polarity opposite to the charging polarity of the toner t.
[0024]
When the Zener diode 20 is provided between the power supply 14 and the contact member 15 so as to lower the potential of the AC voltage having the polarity opposite to the charging polarity of the toner t, the charging polarity of the toner t is When an alternating voltage having a polarity opposite to that of the zener diode 20 is applied, the potential of the contact member 15 becomes lower than the potential of the toner carrier 12 due to the action of the Zener diode 20, and the toner carrier 12 and the contact member 15 During this period, an electric field in the direction of sending the toner t to the toner carrier 12 acts to cause the toner t to be pressed against the toner carrier 12, while an AC voltage having a polarity opposite to the charging polarity of the toner t is applied. In this case, the toner carrier 12 and the contact member 15 have the same potential.
[0025]
Here, when the negatively charged toner t is used, a DC voltage (−V _DC ) and a pulsed AC voltage are superimposed on the toner carrier 12 and the contact member 15 from the power source 14 to bias the voltage. When applying a, as shown in FIG. 4, at the time of charging polarity opposite the polarity of the + AC voltage of the toner t is applied, by the action of the Zener diode 20, the potential V ₂ of the contact member 15 is toner It becomes lower by the zener voltage ΔV than the potential V ₁ of the carrier 12, - charged toner t comes to be pressed against the toner carrying member 12 in. On the other hand, at the point of time when the negative AC voltage having the same polarity as the charged polarity of the toner t acts, the Zener diode 20 does not act and the contact member 15 and the toner carrier 12 have the same potential.
[0026]
For this reason, even when the toner t gradually deteriorates and its charge amount decreases, and the adhesion of the toner t to the toner carrier 12 becomes weak, the toner t after development is transported by the toner carrier 12 and When the AC voltage having the opposite polarity to the toner t acts as described above, the toner t is pressed against the toner carrier 12 and has the same polarity as the charged polarity of the toner t. At the time when the AC voltage is applied, the contact member 15 and the toner carrier 12 are at the same potential, so that the toner t after development is not pressed against the contact member 15 and the toner t contacts the contact member 15. As a result, the toner t is appropriately discharged.
[0027]
As a result, the toner t after the development is appropriately returned into the apparatus main body 10 through the contact member 15 in a state where the charge is appropriately removed, and the toner t accumulates in the contact portion with the contact member 15 and spills. Is suppressed, and the toner t after development is appropriately discharged, so that good development can be stably performed.
[0028]
【Example】
Next, in the developing device as described above, the developing devices of Examples 1 to 3 in which the Zener diodes 20 having different Zener voltages ΔV are provided between the power supply 14 and the contact member 15 and the Zener diodes 20 are provided. An experiment was conducted using a developing device of a comparative example that was not used, and it was clarified that the developing devices of Examples 1 to 3 were superior to the developing device of the comparative example.
[0029]
Here, in the first embodiment, a Zener diode having a Zener voltage ΔV of 10 V, a Zener diode having a Zener voltage ΔV of 50 V in the second embodiment, and a Zener diode having a Zener voltage ΔV of 100 V in the third embodiment. Using.
[0030]
In each developing device of Examples 1 to 3 and Comparative Examples, the average particle diameter became 8.3 .mu.m - using a charging of the toner t, the DC voltage _{V DC} of -290V from the power supply 14, Applying a bias voltage in which an AC voltage composed of a rectangular wave having a peak-to-peak value Vpp of 1.8 kV and a frequency of 2 kHz is applied, the system speed is set to 160 mm / s, and one image having a black ratio of 1% is printed. Each time, printing was performed intermittently, and image defects due to toner spills and defective static elimination were examined.
[0031]
As a result, in each of the developing devices of Examples 1 to 3 and the comparative example, no image failure due to the static elimination failure occurred, but in the developing device of the comparative example, the toner spilled at the time of printing 12,000 sheets. There has occurred.
[0032]
On the other hand, in the developing device of the first embodiment, toner spill only slightly at the time of printing 14,000 sheets, and in the developing device of the second embodiment, the time of printing 20,000 sheets In the developing device of the third embodiment, no toner spill occurred even at the time of printing 20,000 sheets. The occurrence of spill was suppressed. In particular, when a Zener diode having a Zener voltage ΔV of 50 V or more was used, the problem of toner spillage hardly occurred.
[0033]
【The invention's effect】
As described in detail above, in the developing device of the present invention, the toner held on the toner carrier after development is brought into contact with the contact member to remove the charge, and when the toner is returned into the apparatus main body through the contact member, A power source for applying a bias voltage in which an AC voltage is superimposed on a DC voltage to the toner carrier is connected to the contact member, and the potential of the AC voltage having a polarity opposite to the charging polarity of the toner is reduced between the power source and the contact member. In the case where an AC voltage having the same polarity as the charging polarity of the toner is applied to the contact member and the toner carrier, the contact member and the toner carrier have the same potential, and When the toner contacts the contact member and the charge is appropriately removed, while the contact member and the toner carrier are applied with an AC voltage having a polarity opposite to the charge polarity of the toner, the toner is regulated. By the action of the element, the potential of the AC voltage applied to the contact member becomes lower than the potential of the AC voltage applied to the toner carrier, the toner is adapted to be pressed against the toner carrying member.
[0034]
As a result, in the developing device according to the present invention, even after the toner is gradually deteriorated and its charge amount is reduced, and the adhesion of the toner to the toner carrier becomes weak, the developed toner is appropriately discharged. Together with the contact member so that the toner remaining in the contact portion with the contact member is prevented from accumulating and spilling out of the developing device, and the toner after development is prevented. Was appropriately discharged, and good development could be stably performed.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view showing a conventional developing device.
FIG. 2 is a schematic explanatory view showing a developing device according to one embodiment of the present invention.
FIG. 3 is a schematic explanatory view showing a state in which the toner sent into the toner supply unit through the supply port provided in the partition member is sent in the toner supply unit in the developing device of the embodiment.
FIG. 4 is a diagram showing waveforms of voltages applied to a toner carrier and a contact member in the developing device of the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image carrier 10 Device main body 12 Toner carrier 14 Power supply 15 Contact member 20 Rectifier (Zener diode)
t toner

Claims (1)

The charged toner is conveyed by the toner carrier to the developing area facing the image carrier, and a bias voltage in which an AC voltage is superimposed on a DC voltage is applied from a power supply to the toner carrier to form the toner carrier. In the developing device, the electrostatic latent image is developed, and the toner held on the toner carrier after the development is brought into contact with a contact member to remove electricity, and the toner is returned into the apparatus main body through the contact member. A developing device, wherein the contact member is connected to a power source, and a rectifying element is provided between the power source and the contact member for reducing a potential of an AC voltage having a polarity opposite to a charging polarity of the toner.

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