JPH06332349A - Cleaning device for image forming device and method for adjusting resistance value of brush roller thereof - Google Patents

Abstract

PURPOSE:To inexpensively and surely stabilize the resistance value of the electrical conductive brush of a brush roller by providing a current supply means making a prescribed constant current flow between the brush shaft of the rotating brush roller and a toner recovery means in a fixed time before an image forming device is used. CONSTITUTION:Before the brush roller 14 is actually used, it is driven to be rotated by a motor 18 controlled by a control board 28 and a prescribed position is occupied by a switch 29. When a power source 19 supplying current controlled to be constant is turned on, the constant current is supplied to the brush 17. Then, the current is made to flow to a toner recovery roller 15 through the brush 17 and the brush 17 becomes of a high resistance. When the resistance value thereof is stabilized, the switch 29 is changed over and the power source 19 is turned off. Then, the supply of the constant current to the brush 17 is stopped. Therefore, after the image forming device is actually started to be used, a prescribed bias voltage can be impressed on the rollers 15 and 14 by the power source 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning device for an image forming apparatus and a method for adjusting a resistance value of a brush roller thereof.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine, a printer or a facsimile, a toner image is formed on a latent image carrier and the toner image is transferred to a transfer material. After that, the toner remaining on the latent image carrier is cleaned by a cleaning device.

As such a cleaning device, one having a brush roller for rubbing the surface of the latent image carrier after the toner image transfer to remove the toner remaining on the latent image carrier is known. This brush roller has a conductive brush shaft that is driven to rotate, and a brush provided on the peripheral surface thereof. Such a brush roller is rotatably driven at the time of cleaning the latent image carrier, and at the same time, a predetermined bias voltage is applied to the brush roller, and the rubbing action of the brush for rubbing the latent image carrier and the static force based on the voltage application are applied. The residual toner on the latent image carrier is removed by an electric attraction force. The toner adhering to the brush roller is electrostatically sucked and collected by the toner collecting member that is in contact with the brush.

Since this type of cleaning device produces a small amount of noise when it is operated, can be downsized, and has a high degree of freedom in the location where it is installed, it has recently begun to be used in some copying machines and printers.

By the way, as the brush of the above-mentioned brush roller, a conductive brush having a specific resistance of each brush fiber of about 10 ^{2 to} 10 ⁶ Ωcm is generally used. This is because, for example, when a brush having a high specific resistance of 10 ⁸ Ωcm or more is used, a high voltage must be applied to the brush, which requires a high voltage power source, which increases the cost of the cleaning device.

For this reason, a brush roller having a conductive brush has been conventionally used.
Another significant problem arises with such brushes. That is, when the potential difference between the brush roller and the latent image carrier becomes too large when a bias voltage is applied to the brush roller, electric discharge occurs from the brush fiber tip of the brush to the latent image carrier, which causes latent image carrier. The residual toner on the body may be charged with a polarity opposite to the predetermined polarity. If the residual toner is charged in the opposite polarity in this way, it cannot be electrostatically attracted by the brush roller, cleaning failure of the latent image carrier occurs, and the image quality of the image formed next deteriorates. To do.

Therefore, before using the image forming apparatus, for example, in a manufacturing factory of the image forming apparatus, while rotating the brush roller, the electrode is brought into contact with the tip of the brush fiber, and a high voltage is applied between the electrode and the brush shaft. Is applied for a certain period of time to increase the electric resistance value of the brush and stabilize the resistance value (see, for example, Japanese Patent Publication No. 1-55456).

However, when the above method is carried out with the cleaning device incorporated in the image forming apparatus, the brush of the brush roller remains in contact with the latent image carrier, for example, the photosensitive member, and therefore a high voltage is applied. When applied, a current may leak from the tip of the brush fiber having a low resistance value to the pinhole of the latent image carrier, damaging the carrier.

When the brush resistance is adjusted as described above during the break-in operation before the image forming apparatus is actually used, an expensive high voltage power source is used for image formation only for this adjustment. It must be mounted on the apparatus, and the cost of the image forming apparatus rises.

Further, if the specific resistance of each brush fiber of the brush before the resistance value adjustment varies, the resistance value of each brush fiber of the brush after the adjustment also varies.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cleaning device for an image forming apparatus and a method for adjusting the resistance value of its brush roller, which eliminates the above-mentioned conventional drawbacks.

[0012]

SUMMARY OF THE INVENTION To achieve the above object, the present invention rubs the surface of a latent image bearing member after toner image transfer, and the rubbing action and electrostatic attraction force the latent image bearing member. A brush roller for removing the toner remaining on the body; and a toner collecting member that comes into contact with the brush roller and electrostatically attracts and collects the toner adhering to the brush roller. In a cleaning device for an image forming apparatus, which has a conductive brush shaft that is rotationally driven and a conductive brush that is provided on the peripheral surface of the brush shaft, rotate the image forming device before actually using it. There is proposed a cleaning device provided with a current supply means for flowing a predetermined constant current for a predetermined time between the brush shaft of the brush roller and the toner collecting member.

To achieve the above object, the present invention also rubs the surface of the latent image bearing member after the toner image is transferred, and remains on the latent image bearing member due to the rubbing action and electrostatic attraction. A brush roller for removing toner, and a toner collecting member that comes into contact with the brush roller and electrostatically attracts and collects the toner adhering to the brush roller are provided. In a cleaning device of an image forming apparatus having a flexible brush shaft and a conductive brush provided on a peripheral surface of the brush shaft, a brush of a rotating brush roller before actually using the image forming device. A current supplying means for supplying a predetermined constant current between the shaft and the toner collecting member, a potential difference detecting means for detecting that the potential difference between the brush shaft and the toner collecting member exceeds a predetermined threshold value, and the detecting means. Output Therefore we propose a cleaning apparatus provided with a switching means for stopping the supply of the constant current.

Further, in order to achieve the above object, the present invention rubs the latent image carrier after the toner image is transferred, and the toner remaining on the latent image carrier is rubbed by the rubbing action and electrostatic attraction. In the method of adjusting the resistance value of the brush roller for removing the current, a method of adjusting the resistance value of the brush roller is characterized in that a constant current is applied to the conductive brush of the brush roller for a certain time while rotating the brush roller. To do.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings, and the problems of the prior art will be more concretely clarified with reference to the drawings.

FIG. 1 is a schematic view showing a laser printer which is an example of an image forming apparatus equipped with a cleaning device according to an embodiment of the present invention. First, the overall structure and operation of the laser printer will be clarified.

A reference numeral 1 in FIG. 1 is a drum-shaped photosensitive member which is an example of the constitution of the latent image carrier, and the photosensitive member 1 is rotationally driven in the clockwise direction shown by an arrow A in FIG. It
At this time, the surface of the photoconductor is charged to a predetermined polarity, which is negative in this example, by the charging charger 2, and the charged surface is image-exposed by the modulated laser beam emitted from the optical writing unit 3, whereby the photoconductor 1 is exposed. A predetermined electrostatic latent image is formed on.

The latent image is visualized as a toner image by the toner of the developing unit 4. In this example, the toner of the developing unit 4 is negatively charged with the same polarity as the charging polarity of the photoconductor 1, and the electrostatic latent image is made visible by so-called reversal development.

The toner image thus formed is transferred by the action of the transfer charger 7 onto the transfer paper 6 which is an example of the transfer material fed from the paper feeding section 5. The transfer paper 6 onto which the toner image has been transferred is separated from the photoconductor 1 by the action of the separation charger 8 and then passes through the fixing device 9, where the toner image is fixed. The transfer paper 6 that has passed through the fixing device 9 is discharged onto the paper discharge tray 10.

On the other hand, the toner remaining on the surface of the photoconductor after the transfer of the toner image is removed by the cleaning device 11, and then the surface of the photoconductor is initialized by the charge removal function of the charge removal lamp 12.

Next, details of the structure and operation of the cleaning device 11 will be clarified.

As shown in FIG. 2, the cleaning device 11 includes a casing 13 having an opening on the side facing the surface of the photosensitive member 1, and a brush roller 14 disposed inside the casing 13.
And a toner collecting roller 15. The brush roller 14 includes a conductive brush shaft 16 made of metal such as stainless steel and aluminum, and the brush shaft 16
And a brush 17 provided on the peripheral surface of the brush shaft 16
Are rotatably supported by the casing 13. The brush 17 is, for example, planted on a base cloth (not shown), and the base cloth is fixed to the peripheral surface of the brush shaft 16.

As will be described later in detail, the brush 17 is made of a conductive brush, and the individual brush fibers thereof are made of, for example, carbon-containing chemical fibers (acrylic, nylon, polyester, etc.) and have a specific resistance. Is usually set to 10 ^{2 to} 10 ⁶ Ωcm. A part of such a brush 17 projects from the opening of the casing 13 and contacts the surface of the photoconductor 1 with a certain amount of bite.

The toner collecting roller 15 is made of a metal such as stainless steel whose surface is polished, contacts the brush 17 of the brush roller 14 as shown in FIG. 2, and is rotationally driven clockwise in FIG. .

Further, the cleaning device 11 has a pre-cleaning charger 22 formed of a corona discharger provided outside the casing 13.

As described above, the toner image is transferred onto the transfer paper 6 (FIG. 1).
The surface of the photoconductor after being transferred to the sheet passes through the portion of the precleaning charger 22 by its rotation. At this time, the surface of the photoconductor and the residual toner T adhering thereto are originally discharged by the discharge of the precleaning charger. , The negative polarity in this example. The pre-cleaning charger 22 discharges by superimposing an alternating current on the negative side of the direct current, removes unevenness of the surface potential of the photoconductor 1, and adjusts the charge amount of the residual toner to a certain constant value width of the negative polarity. The value is set to an appropriate value according to the shape of the toner, its volume resistance value and its dielectric constant.

The surface portion of the photoreceptor 1 charged as described above then passes through the portion of the brush roller 14. At this time, the brush shaft 16 is rotationally driven by the motor 18,
The brush roller 14 rotates in the clockwise direction shown by the arrow B in FIG. 2, and the brush 17 rubs the surface of the photoconductor.

Moreover, the toner collecting roller 15 is attached to the brush roller 14 whose brush shaft 16 is in an electrically floating state.
A power source 19 connected via
A bias voltage is applied to 15. At this time, the relationship between the potentials of the toner collecting roller 15, the brush roller 14, and the photoconductor surface is: toner collecting roller> brush roller> photoconductor surface. In this way, the potential gradient is applied to form an electric field between the brush roller 14 and the photoconductor 1 in a direction in which the residual toner T on the photoconductor 1 is electrostatically attracted to the brush roller 14 side.

As described above, the brush roller 14 is
The surface of the photoconductor 1 after the transfer of the toner image is rubbed, and the toner T remaining on the photoconductor 1 is removed by the rubbing action and the electrostatic attraction force.

FIG. 3A is an explanatory view showing the state at this time, and the reference numeral 17a indicates the brush 17 of the brush roller 14.
1 of one of the brush fibers is shown. Here, it is assumed that the surface potential of the photosensitive member 1 charged by the pre-cleaning charger 22 (FIG. 2) is −700V, and the power source 19
Assuming that the potential of the tip end portion of the brush fiber 17a of the brush roller 14 to which the bias voltage is applied is −450 V, the residual toner T on the photoconductor 1 is negatively charged by the pre-cleaning charger 22. The brush fibers 17 a, which are relatively positive, are electrostatically drawn and captured by the brush 17.

In this example, a negative voltage is applied to the brush 17 by the power source 19, and the potential thereof is -450.
Although it becomes V, this potential is on the plus side relative to the surface potential -700V of the photoconductor 1 as described above. Therefore, in FIG. 3A, the brush fiber 17a is given a + sign. (The same applies to (b) and (c) of FIG. 3).
Of course, a voltage having a polarity opposite to the charging polarity of the toner T may be applied to the brush 17.

The toner T transferred to the brush roller 14 as described above is knocked off by the flicker member 23 which is in contact with the brush 17 with a biting amount of about 1 mm as shown in FIG. Still, the toner that is not removed from the brush roller 14 and adheres to the roller 14 is collected by the toner collecting roller 15 that rotates while contacting the brush 17 of the brush roller 14. That is, as described above, the voltage applied to the toner collecting roller 15 causes the electric field formed between the toner collecting roller 15 and the brush roller 14 to cause the toner attached to the brush roller 14 to the toner collecting roller 15. It is electrostatically attracted and transferred.

The toner transferred to the toner collecting roller 15 is scraped off from the roller 15 by the elastic blade 20 which is an example of a scraper in pressure contact with the surface of the roller 15, and the toner dropped by the flicker member 23, together with the casing 13. The toner is conveyed to the outside of the casing by the toner conveying member 21 that is provided at the bottom of the rotating member. The cleaning device 11 has a function of removing not only the residual toner on the photoconductor 1 but also paper dust and the like attached to the photoconductor.

The above-mentioned toner collecting roller 15 constitutes an example of a toner collecting member which comes into contact with the brush roller and electrostatically sucks and collects the toner attached to the brush roller.

The ratio of the linear velocities of the outer peripheral portions of the photoconductor 1 and the brush roller 14 is set to, for example, about 1: 0.6 to 1.2. The ratio of the linear velocities of the parts is also set to about 1: 0.6 to 1.2, for example.

As in the embodiment shown in FIG. 2, the toner recovery roller 15 and the brush roller 14 are driven by the common power source 19.
Instead of applying a bias voltage to each of the rollers 14 and 15, a predetermined bias voltage capable of achieving the above-described operation may be applied to each of the rollers 14 and 15 by a separate power source. Further, for the purpose of extending the life of the elastic blade 20, the surface of the toner collecting roller may be coated with a fluorine resin, for example, a resin containing carbon in Teflon, Lumiflon, or the like.

The cleaning device 11 is constructed as described above. As the brush 17 of the brush roller 14, a conductive brush having a specific resistance of 10 ^{2 to} 10 ⁶ Ωcm is used as described above.

However, as described above, assuming that the conductive brush 17 is used as it is without any adjustment, a bias voltage is applied to the brush roller 14 in the initial state when the brush roller is started to be used. At times, current easily flows from the tip of the brush fiber 17a to the photoconductor, and moreover, discharge easily occurs.

FIG. 3B is an explanatory view showing the state at this time, and the brush roller 14 to which the bias voltage is applied.
Discharge occurs from the tip of the brush fiber 17a toward the photoconductor 1 as indicated by the symbol X.
When the tip of 7a contacts the photoconductor 1, a large amount of current flows toward the photoconductor 1.

It is considered that such discharge or current flow is generated from the tip surface 17b of the brush fiber 17a. That is, the brush fibers 17a are obtained by dispersing conductive particles made of, for example, conductive carbon in the insulating resin to increase the conductivity of the fibers 17a as described above. As indicated by reference numeral C in (a) and (b) of FIG. 4, the carbon particles are arranged in a chain shape in the brush fiber, and the carbon particles are the tip surface 17 of the brush fiber 17a.
Since it is exposed to b, it is considered that discharge is generated from this exposed carbon C or a current flows to the photoconductor 1. The same applies when conductive particles other than carbon are used.

In any case, when the discharge or the excessive current flow occurs as described above, the pre-cleaning charger 2
As shown in FIG. 3B, the charge polarity of the residual toner T that has been negatively charged by 2 is inverted to the opposite positive polarity. In this case, the toner cannot be electrostatically attracted to the minus-side brush 17, and the toner remains attached to the photoconductor 1.
The toner transferred to the brush 17 is returned onto the photoconductor 1 and cleaning failure of the photoconductor occurs. As a result, the background image formed next becomes markedly stained, which inevitably results in the image quality being deteriorated.

When the discharge to the photoconductor 1 as described above occurs and an excessive current flows through the photoconductor 1, the photoconductor 1 may be damaged.

Therefore, it is conceivable to use, as the brush 17 of the brush roller 14, a brush fiber having a high resistance of, for example, 10 ⁸ Ωcm or more. In fact, if the brush roller 14 having such a high resistance brush is used, even if a bias voltage is applied to the roller 14, as shown in FIG.
The discharge from 7b does not occur, and an excessive current can be prevented from flowing to the photoconductor 1. Further, when the resistance value of the brush 17 is large, the potential difference between the brush roller and the photoconductor can be increased, and the removability of the residual toner on the photoconductor 1 can be improved.

However, when the resistance value of the brush 17 is high,
As described above, a very high voltage must be applied to the brush 17 in order to match the electric potential at the tip of the brush fiber 17a to the optimum condition with respect to the electric potential of the photoconductor 1. A high voltage power supply is required, which increases the cost of the cleaning device. When such a high-voltage power supply is not used, the brush fibers 17 as shown in FIG.
The potential of a becomes too low and the residual toner T on the photoconductor 1
There is a problem that you can not capture enough.

Therefore, a conductive brush 17 having a specific resistance of 10 ⁶ Ωcm or less is used. Before actually using the brush 17, the resistance value of the brush 17 is adjusted to reverse the charge polarity of the residual toner or to discharge the toner. It is most preferable to prevent the trouble that occurs. As such a brush resistance value adjustment method,
As described above, there is known a method of applying a high voltage to a brush before starting the use of the brush roller, for example, in a manufacturing factory of the image forming apparatus or during a break-in operation immediately after the image forming apparatus is delivered to the user. However, according to this method, as described above, current leaks into the pinhole of the photoconductor, or a high-voltage power supply is required exclusively for the purpose of this adjustment,
In addition, there is a problem that the resistance value of the brush fiber varies.

As a result of repeating various experiments in order to solve the above-mentioned problems, the present inventor does not always adjust the resistance value of the conductive brush 17 to increase the resistance value as in the conventional case. It was clarified that the application of a high voltage is not necessary and a “constant current” may be passed through the brush 17.

FIG. 5 is a schematic view of an apparatus used for the one experiment, in which reference numeral 24 is a rotatably supported conductor roller, and a drawing amount of 1 mm with respect to the roller 24 is shown. A new brush roller 14 having the same structure as that shown in FIG. 1 is rotatably supported. The new brush roller 14 is a brush roller for which the resistance value of the brush 17 has not been adjusted yet.

Here, the brush roller 14 and the conductor roller 24 are rotationally driven in the directions shown by the arrows in FIG. 5, and the brush shaft 16 of the brush roller 14 and the conductor roller 24 are rotated.
A constant current of 10 μA was applied by a power source 25 controlled to a constant current. At this time, the conductor roller 24 may be stopped without rotating.

As a new brush roller 14, a brush 17 having a specific resistance of 10 ⁶ Ωcm and a brush 1
Each of the above experiments was carried out by using No. 7 having a specific resistance of 10 ² Ωcm, and the voltage between the root part and the tip part of the brush was measured by the voltmeter 26. FIG. 6 shows the result, P
Is the result of a brush roller having a brush 17 having a specific resistance of 10 ⁶ Ωcm (hereinafter referred to as P brush roller), and Q is a brush roller having a brush 17 having a specific resistance of 10 ² Ωcm (hereinafter referred to as a Q brush roller). Say),
In either case, the voltage value at the time when the current starts to flow is low, and the voltage value rises as time passes. This indicates that the resistance value of the brush 17 is gradually increasing with the passage of time.

In the case of the P brush roller, the voltage value reached about 100 V when about 5 minutes had passed after the current started to flow, and thereafter the voltage value did not rise. Similarly, in the case of the Q brush roller, the voltage value reaches about 20V after about 5 minutes, and thereafter the voltage value does not rise. That is, in any brush roller, the resistance value gradually increases after the constant current starts to flow, and after about 5 minutes, the resistance value becomes a constant value and the resistance value does not increase any more, and this is stable. Will be transformed. From this,
It can be seen that increasing the resistance of the brush 17 depends on the value of the current flowing through it and the time.

Through a series of experiments, it became clear that the greater the specific resistance of the brush 17, the more energy is required to raise and stabilize the resistance value. As an example, for the P brush roller described above, 2
When a constant current of μA was applied, the brush 1
The resistance value of No. 7 did not rise, and the resistance value of the brush 17 could not be adjusted. This is because, in the case of the brush 17 having a relatively high specific resistance of 10 ⁶ Ωcm, it is necessary to pass a low constant current of 2 μA to increase the resistance value, and there is insufficient energy to stabilize it. Is shown.

As described above, the conductor roller 24 is brought into contact with the tip of the conductive brush 17, and while the brush roller 14 is rotated, a certain current density (total current / brush and conductor roller 24) is applied to the conductive brush 17. When a constant current exceeding the contact area) is applied for a certain period of time, the resistance value of the brush 17 rises and stabilizes, which is considered as follows.

The brush fibers of the brush 17 are the conductor rollers 24.
When a constant current flows therethrough, the electrical characteristics of the tip end surface of the brush fiber contacting the conductor roller 24 change, and it becomes difficult for the current to flow there. This is because the resin at the tip of the low-resistance brush fiber is melted by the heat energy generated by the electric current, and at that time, the carbon particles arranged in a chain in the brush fiber and exposed from the tip surface of the brush fiber (see FIG. 4 ) Is coated with a molten resin, and the resistance is increased, or the arrangement of carbon on the tip end surface of the brush fiber in contact with the conductor roller 24 is changed, which is considered to increase the resistance.

In any case, by supplying a constant current to the brush 17, a high resistance portion is formed on the tip surface 17b of the brush fiber 17a, as indicated by reference numeral 27 in FIG. 3 (a). As a result, the overall resistance value of the brush fiber 17a is increased, and this is stabilized.

The specific resistance of the brush fiber portion other than the high resistance portion 27 does not change at all or before and after the constant current flows. This is clear from the fact that when the resistance value of the brush fiber 17a from which the high resistance portion 27 is removed is measured, it is confirmed that this substantially matches the resistance value of the brush fiber 17a before adjustment.

As described above, since only the tip portion 27 of the brush fiber 17a has a high resistance, the brush roller 14 having such a brush 17 is incorporated into the cleaning device 11 as shown in FIG. When the above is used as described above, the potential of the brush fiber 17a can be quickly raised to a certain height with the start of the application of the bias voltage to the brush roller 14 without using a special high-voltage power supply. . That is, since the specific resistance of the brush fiber portion other than the high resistance portion 27 is 10 ⁶ Ωcm or less, the brush 1
Even if a particularly high voltage is not applied to 7, the high resistance portion 27
It is possible to prevent the potential of the brush fiber portion other than the above from rapidly rising, and thereby prevent the cleaning property of the brush roller 14 from being lowered. In this way, a high cleaning performance can be obtained during the image forming operation without applying a high voltage to the brush 17 unlike the case of using the brush 17 having a large specific resistance from the beginning.

Since the high resistance portion 27 is formed at the tip of the brush fiber 17a, even if a relatively high bias voltage is applied to the brush roller 14, an excessive current flows from the brush 17 toward the photosensitive member 1. Flow can be prevented or discharge can be prevented from occurring, high cleaning performance can be maintained, and a problem that damages the photoconductor can be prevented. As described above, the current flow from the brush fiber to the photoconductor or the discharge occurs on the tip surface 17b of the brush fiber (see (b) of FIG. 3). The tip surface 17b has a high resistance. Part 2
Since 7 is formed, it is possible to prevent the excessive current flow and the occurrence of discharge without hindrance.

As described above, when the specific resistance is 10 ² Ωcm or more, 1
By using the conductive brush 17 having a resistance of 0 ⁶ Ωcm or less and increasing the resistance of the tip portion of the brush fiber, a high cleaning property can be always guaranteed. Since a brush having a specific resistance of less than 10 ² Ωcm has a low ratio of insulating resin constituting the brush, even if a constant current is applied to the brush to adjust its resistance value, the molten resin covering the carbon particles There is a possibility that the specific resistance of the high resistance portion 27 formed at the tip end of the brush fiber cannot be sufficiently increased due to the small amount. For this reason, it is desirable that the specific resistance of the brush 17 is 10 ⁶ Ωcm or less and 10 ² Ωcm or more.

Here, the resistance value adjustment of the brush roller 14 may be performed on the brush roller 14 before being incorporated in the cleaning device 11 by the same device as the experimental device shown in FIG. 5, or before the adjustment. 2 is assembled in the cleaning device 11 as shown in FIG. 2, this cleaning device is assembled in the image forming apparatus, and then a constant current is applied to the brush 17 to adjust its resistance value as described above. Good. The point is to adjust the resistance value of the brush roller before starting to use, but what is important here is that in any case, when a constant current is passed through the brush 17 to adjust its resistance value, The voltage applied to 17 is low,
In the example of FIG. 6, in the case of the P brush roller, it is about 100V,
In the case of Q brush roller, it is about 20V and brush 17
The point is that the resistance value of can be increased and this can be stabilized.

As a result, the high-voltage power supply required in the conventionally proposed method for adjusting the resistance value of the brush roller of the high-voltage application method is not required, and the cost required for the adjustment can be reduced. Moreover, it is not necessary to switch the voltage.

When the brush roller 14 is incorporated in the image forming apparatus as shown in FIG. 2 and the resistance value of the brush 17 is adjusted, the brush shaft 16 will be described in detail later.
And the toner collecting roller 15 in contact with the tip of the brush 17.
Connect a power source to and to supply a constant current to the brush 17,
Since the voltage at this time is a very low value of 20 V to 100 V, which is much lower than the discharge voltage, as in the above example, almost no current flows to the photoconductor 1 in contact with the brush 17. This can prevent the problem that the current leaks to the pinhole of the photoconductor 1 and damages the photoconductor as in the conventional method.

Further, in the conventional method of adjusting the resistance value of the brush roller of the high voltage application method, if the specific resistance of each brush fiber varies, as described above, the resistance of each brush fiber of the adjusted brush is changed. The value also fluctuated, and it was difficult to keep the resistance value in the circumferential direction of the brush roller constant. The reason is as follows.

When a constant current is applied to the brush fibers for a certain period of time, the total current flowing through the brush fibers having a low specific resistance increases, and the total current flowing through the brush fibers having a high specific resistance decreases. Here, as described above, the rate of change of the resistance value of the brush fiber is substantially determined by the magnitude of the total current flowing through it, so if the values of the total current flowing through the brush fibers differ from each other, adjustment is made. The resistance value of each brush fiber afterward also differs from each other.

In the above-described method according to the present invention, since a constant current is applied to the brush 17 for a certain period of time, the total current flowing through each brush fiber is constant, so that the resistance values of the brush fibers after adjustment are substantially equalized. Therefore, the brush roller 14 having a substantially constant resistance value in the circumferential direction can be configured. As a result, high cleaning performance can be maintained at all times.

The brush fibers are coated with Teflon,
A method of increasing the overall resistance value of the fiber and adjusting this is as follows.
For example, as disclosed in Japanese Patent Application Laid-Open No. 60-170878, according to this configuration, the coating layer of the brush fiber may be scraped with time, and if the coating layer is too thick, the coating layer may be formed. Holds the charge by frictional charging,
This may lower the cleaning property, but such a problem will not occur if the resistance value of the brush is adjusted by the method according to the present invention as exemplified above.

By the way, in the cleaning device 11 shown in FIG. 2, a new brush roller is installed after the cleaning device 11 is installed in the image forming device and before the brush roller 14 is used for actual image formation. The resistance value of 14 can be adjusted, and for the purpose of adjustment, the above-mentioned power source 19 used in a normal image forming operation can be used. The details will be made clear below.

In FIG. 2, before the brush roller 14 is actually used, for example, during the running-in operation immediately after the image forming apparatus manufacturing factory or the image forming apparatus is delivered to the user, the above-described control by the control board 28 is performed. The brush roller 14 is rotationally driven by the motor 18, and the switch 2
9 occupies the position shown in FIG. 2, and the constant current is supplied to the brush 17 when the constant current controlled power supply 19 is turned on.
The current value at this time is that the specific resistance of the brush 17 is 10 ⁵ Ωcm.
~ 10 ⁶ Ωcm, about 4 ~ 10μA / 100m
It is set to a fixed value of m longitudinal width (width in the axial direction of the brush roller). At this time, the photoconductor 1 and the toner collecting roller 15 may be rotating or stopped,
The brush roller 14 is always driven to rotate. The bite amount of the brush 17 with respect to the toner collecting roller 15 is about 1 mm.

In this way, the brush shaft 16 is moved to the brush 1
A current flows through the toner recovery roller 15 through 7, the resistance of the brush 17 becomes high, the switch 29 is switched to the position when the resistance value becomes stable, and the power supply 19 is turned off to supply a constant current to the brush 17. Be stopped.

FIG. 7 is a time chart of the above-described operation. The constant current supply to the brush 17 is turned on and off by timing with the clock signal of the image forming apparatus main body, and the current supply to the brush 17 is supplied. After a certain time has elapsed from the start, the rotation of the motor 18 is stopped by the control of the control board 28, the rotation of the brush roller 14 is stopped, and the power supply 19 is turned off. At the same time, the switch 29 is switched from the position of to the position of by the control of the control board. Time t for supplying constant current to the brush 17
₀ is determined by the specific resistance of the brush 17 and the magnitude of the set current value. Further, this constant current value is set to a value equal to or larger than the current flowing from the brush 17 to the photoconductor 1 when an image forming operation is actually performed using the image forming apparatus.

After the resistance value of the brush 17 is adjusted, the switch 29 is switched to the position of. Therefore, after the image forming apparatus is actually used, the power supply 19 causes the toner collecting roller 15 and the brush to move as described above. A predetermined bias voltage can be applied to the roller 14.

In the above-described embodiment, the power supply 19 and the control board 28 cause a predetermined constant current to flow between the brush shaft of the rotating brush roller and the toner collecting member for a certain time before actually using the brush roller. It constitutes a current supply means.

Also in the cleaning device 11 shown in FIG. 8, the brush roller 14 is rotationally driven by the motor 18 before the brush roller 14 is actually used, for example, during the accustomed operation of the image forming apparatus, and the analog switch 29 is used.
Occupies the position shown in FIG. 8 and is a constant current controlled power supply 1
A constant current is supplied to the brush 17 by 9. As described above, in this example, the power supply 19 constitutes a current supply means for supplying a predetermined constant current between the brush shaft 16 of the brush roller 14 and the toner collecting roller 15. However, when this current supply is started, The resistance value of the brush 17 increases with the passage of time, and as shown in FIG. 9, the potential difference between the voltages V ₁ and V ₂ , that is, the potential difference between the brush shaft 16 and the toner collecting roller 15 (V ₁ −V _2). ) Becomes larger.

Therefore, this potential difference is output by the subtraction circuit 30 shown in FIG. 8 and is input to the comparison circuit (for example, comparator) 31 to be compared with the reference voltage (threshold value) V ₀ . When the potential difference (V ₁ -V ₂ ) exceeds a certain voltage V ₀ , the analog switch 27 is switched to the position by the output signal from the comparison circuit 31, the motor 18 is stopped, and the rotation of the brush roller 14 is stopped. stop. At this time, the resistance value of the brush 17 is increased and stabilized as in the above-described embodiment.

As described above, in the present example, the subtraction circuit 30 and the comparison circuit 31 constitute a potential difference detecting means for detecting that the potential difference between the brush shaft 16 and the toner collecting roller 15 exceeds the predetermined threshold value. Further, the analog switch 29 constitutes switching means for stopping the supply of the constant current to the brush 17 by the output of the potential difference detecting means.

In this embodiment, the potential difference (V ₁ -V ₂ ) is detected, and the time for supplying the constant current to the brush 17 is controlled by the detected value, so that the resistance value of the brush 17 is increased more accurately and Can be stabilized.

Other configurations and operations of the cleaning device 11 shown in FIG. 8 are the same as those of the embodiment shown in FIG. Figure 8
When the switch 29 shown in is switched to the position,
The brush shaft 16 of the brush roller 14 is electrically floated, and the bias voltage from the power source 19 is applied to the toner collecting roller 15 and the brush roller 14.
Therefore, the image forming operation can be performed immediately after the resistance value of the brush 17 is adjusted.

As described above, in any of the embodiments, the resistance value of the brush 17 can be constantly stabilized even if the specific resistance of the brush 17 varies and the environment changes, and the brush 17 can be used for a long period of time. High cleaning performance can be maintained.

Even when the brush roller is replaced with a new one due to deterioration of the brush roller or the like, before or after mounting the new brush roller 14 in the cleaning device,
The resistance value of the brush 17 can be adjusted in the same manner as described above.

[0079]

According to the constitutions of claims 1 to 3,
It is possible to reliably stabilize the resistance value of the brush even if there are variations in the specific resistance or environmental changes.

According to the first and second aspects of the present invention, it is possible to apply a constant current to the brush and apply a bias voltage to the brush roller after the image forming operation is started by the same power source. The cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a laser printer including a cleaning device according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional explanatory view of a cleaning device.

FIG. 3 is an explanatory diagram showing a state in which toner is adsorbed on brush fibers.

FIG. 4 is an explanatory diagram showing a state of carbon of brush fibers.

FIG. 5 is a schematic view of an experimental device.

FIG. 6 is a diagram illustrating an experimental result.

FIG. 7 is a timing chart when adjusting the brush resistance value of the cleaning device shown in FIG.

FIG. 8 is a partial cross-sectional explanatory view showing another embodiment of the cleaning device.

FIG. 9 is a diagram showing a relationship between a potential difference and time.

[Explanation of symbols]

 11 Cleaning Device 14 Brush Roller 16 Brush Shaft 17 Brush T Toner

Claims (3)

[Claims] 1. A brush roller for rubbing the surface of a latent image carrier after transferring a toner image, and removing the toner remaining on the latent image carrier by the rubbing action and the electrostatic attraction force, and the brush. And a toner collecting member that comes into contact with the roller and electrostatically attracts and collects the toner attached to the brush roller. The brush roller includes a conductive brush shaft that is driven to rotate and a brush shaft of the brush shaft. In a cleaning device of an image forming apparatus having a conductive brush provided on a peripheral surface, a predetermined distance is provided between a brush shaft of a rotating brush roller and a toner collecting member before actually using the brush roller. A cleaning device comprising a current supply means for supplying a constant current for a predetermined time. 2. A brush roller for rubbing the surface of a latent image carrier after transferring a toner image, and removing the toner remaining on the latent image carrier by the rubbing action and electrostatic attraction. And a toner collecting member that comes into contact with the roller and electrostatically attracts and collects the toner attached to the brush roller. The brush roller includes a conductive brush shaft that is driven to rotate and a brush shaft of the brush shaft. In a cleaning device of an image forming apparatus having a conductive brush provided on a peripheral surface, a predetermined distance is provided between a brush shaft of a rotating brush roller and a toner collecting member before actually using the brush roller. Current supply means for supplying a constant current, potential difference detecting means for detecting that the potential difference between the brush shaft and the toner collecting member exceeds a predetermined threshold value, and the output of the detecting means stops the supply of the constant current. Let Cleaning apparatus, characterized in that a and switch means. 3. The latent image carrier after the toner image transfer is rubbed,
In the method of adjusting the resistance value of the brush roller for removing the toner remaining on the latent image carrier by the rubbing action and the electrostatic attraction force, the conductive brush of the brush roller is rotated while the brush roller is rotated. A method for adjusting the resistance value of a brush roller, which is characterized by flowing a constant current for a certain period of time.