JP2000122388A - Image forming device - Google Patents

Image forming device

Info

Publication number
JP2000122388A
JP2000122388A JP30638098A JP30638098A JP2000122388A JP 2000122388 A JP2000122388 A JP 2000122388A JP 30638098 A JP30638098 A JP 30638098A JP 30638098 A JP30638098 A JP 30638098A JP 2000122388 A JP2000122388 A JP 2000122388A
Authority
JP
Japan
Prior art keywords
image
potential
voltage
developing
carrier
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP30638098A
Other languages
Japanese (ja)
Inventor
Makoto Nonomura
Yukihiro Ozeki
Katsuhiro Sakaizawa
Manami Sekiguchi
勝弘 境澤
行弘 大関
真 野々村
真奈実 関口
Original Assignee
Canon Inc
キヤノン株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Canon Inc, キヤノン株式会社 filed Critical Canon Inc
Priority to JP30638098A priority Critical patent/JP2000122388A/en
Publication of JP2000122388A publication Critical patent/JP2000122388A/en
Pending legal-status Critical Current

Links

Abstract

PROBLEM TO BE SOLVED: To enhance the cleaning efficiency of an image carrier due to an oscillating to be applied to a developing means, and suppress a ground fogging phenomenon, in an image forming device of simultaneously developing and cleaning system by a contact type developing.
SOLUTION: In the image formation applying simultaneous developing and cleaning system, at the time of developing, as the oscillating bias voltage for applying to the developing roller of a developing device held in contact with a photoreceptor drum, this image forming device applys the oscillating voltage alternately repeating the first peak voltage Va provided with a potential level between the back ground part potential VD of the electrostatic latent image on the photosensitive drum and the image part potential VL, and the second peak voltage Vb provided with the potential level located on the side opposite to the back ground potential VD with respect to the image part potential VL on the photoreceptor drum 1.
COPYRIGHT: (C)2000,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus of an electrophotographic type or the like, and more particularly to an image forming apparatus of a simultaneous developing and cleaning type.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a developing method for developing a latent image on a photosensitive drum, which is an image bearing member, with a toner of a one-component developer includes a developing device which carries toner of developing means. In addition to a non-contact developing method in which a developing roller as an agent carrier is developed in non-contact with a photosensitive drum, there is a contact developing method in which a developing roller is brought into contact with a photosensitive drum for development.

In recent years, in order to save energy and reduce running costs, a dedicated cleaning device is not provided on the photosensitive drum, and the transfer residual toner remaining on the photosensitive drum in the transfer process is removed by a developing roller that is in contact with the photosensitive drum. A so-called simultaneous development cleaning method based on a contact development method, which performs development while collecting, has attracted attention.

FIG. 7 shows a schematic configuration of a conventional image forming apparatus of the simultaneous cleaning and developing system. Here, as an example, a description will be given of an image forming apparatus of a reversal development system using a negatively-charged non-magnetic toner as a one-component developer.

As shown in FIG. 7, an image forming apparatus includes a photosensitive drum 101 rotating in the direction of an arrow e,
01, the surface of the photosensitive drum 101 is exposed based on image information,
An exposure device 103 for forming an electrostatic latent image, a developing device 104 for developing the formed latent image using a non-magnetic toner and visualizing it as a toner image, and an obtained toner image supplied to the photosensitive drum 101 Transfer charger 10 for transferring to transfer material P
5 and the like.

The developing device 104 has a developing roller 110 which carries a non-magnetic toner of a one-component developer accommodated therein and transports the non-magnetic toner to a developing section in contact with the photosensitive drum 101. The developing roller 110 is an elastic roller having an elastic layer formed on a conductive metal core, and rotates in the direction indicated by the arrow f in contact with the photosensitive drum 101. Around the developing roller 110, the developing roller 110 contacts the developing roller 110 and rotates in the direction of arrow g to apply and carry the toner on the developing roller 110. Regulates the toner carried on it,
A regulating blade 112 that applies a predetermined amount of triboelectric charge to the toner and forms a toner layer having a predetermined thickness, and a developing power supply 113 that applies a developing bias voltage between the developing roller 110 and the photosensitive drum 101 during development. Having.

The potential of each part and the behavior of the toner will be described with reference to FIG.

FIG. 8A shows the potential after charging on the photosensitive drum 101 and before exposure. When a print signal is input to the image forming apparatus and image formation is started, the photosensitive drum 101 rotates, and in the course of this rotation, the surface of the photosensitive drum 101 is uniformly charged by the charger 102. This charged potential is referred to as a background portion potential VD.

FIG. 8B shows the behavior of the toner in the developing section after exposure. The exposed portion of the photosensitive drum 101 has an attenuated potential and becomes an image portion of an electrostatic latent image. This potential is defined as an image portion potential (exposure portion potential) VL.

Here, the developing bias Vdc is applied to the developing roller 11.
When the voltage is applied to 0, the toner S on the developing roller 110 adheres to the image area, and the latent image is developed. The potential relationship of each part in the reversal development has | VD |> | Vdc |> | VL |.

The toner adhered to the image area by the development is transferred to the transfer material P by the transfer device 105. The transfer residual toner remaining on the photosensitive drum 101 without being transferred passes through the charger 102 and the exposure device 103 and reaches the developing device 104.

FIG. 8C shows a state of simultaneous development and cleaning. The transfer residual toner S 'existing in the unexposed portion (the background portion of the electrostatic latent image) is collected on the developing roller 110 by the potential relationship between the background portion potential VD and the developing bias Vdc. At the same time, the image portion VL is developed with the toner S, as in FIG.

By continuously performing the above operations, the image formation by the simultaneous development and cleaning method is repeated.

[0014]

However, when the image forming operation was performed by the above-mentioned conventional simultaneous cleaning with developing method, the following problems were found.

[0015] In recent years, as part of improving the quality of electrophotography,
Although the use of atomized toner has been advanced, the number and surface area of the toner per unit weight have increased due to the atomization of the toner, and excessively charged toner has come to be seen. The excessively charged toner is transferred to the photosensitive drum 10
When the image is transferred to the background portion VD, the image is adhered with a strong electrostatic reflection force. In this state, even if a developing bias Vdc consisting of only a DC voltage is applied, an electric field sufficient to pull the excessively charged toner from above the photosensitive drum 101 to the developing roller 110 is not obtained, and the photosensitive drum 101 is sufficiently cleaned. Can not do.

As a developing bias, an oscillating bias voltage obtained by superimposing DC and AC shown in FIG. 9 is also used. The oscillating bias voltage includes a peak voltage V1 for urging the toner from the developing roller 110 toward the image portion and the background portion of the latent image on the photosensitive drum 101 in a direction toward the toner. Developing roller 11
The peak voltage V2 for urging the toner in the upward direction of 0 is a repetitive vibration voltage.

As shown in FIG. 9, the peak voltage V1 is located on the opposite side of the image portion potential VL with respect to the background portion potential VD on the photosensitive drum 101, and the peak voltage V2 is
With respect to VD.

During the peak voltage V1 and the time t1, the negatively charged toner on the developing roller 110 is transferred from the developing roller 110 to the photosensitive drum 1 in the developing area in the contact development.
01 to the image part and the background part. During the peak voltage V <b> 2 and the time t <b> 2, part of the toner adhered to the image part and most of the toner adhered to the background part are pulled back from the photosensitive drum 101 to the developing roller 110.

In the present specification, the development area in the contact development is mainly a portion Z shown in FIG. 10, that is, a portion Y where the photosensitive drum 101 and the developing roller 110 are in contact.
Refers to the non-contact part after Even in the non-contact portion X between the photosensitive drum 101 and the developing roller 110 before the contact portion Y, the toner can move between the photosensitive drum 101 and the developing roller 110, and the latent image is developed. However, the toner image obtained here is disturbed by a peripheral speed difference and a contact pressure between the photosensitive drum 101 and the developing roller 110 at a contact portion Y between the photosensitive drum 101 and the developing roller 110. A normal toner image without disturbance is finally obtained by re-development of the latent image in the non-contact portion Z after the contact portion Y. Therefore, the non-contact portion Z is defined as a development region in contact development in the sense of a development region where a normal toner image is obtained.

However, even if an oscillating bias voltage is applied to return the toner present in the background of the photosensitive drum 101 from the photosensitive drum 101 to the developing roller 110 by the peak voltage V2 of the oscillating bias, the voltage V2 and the background portion When the electric field formed by the potential difference V3 of the potential VD is lower than the adhesive force of the toner existing in the background, the toner cannot be pulled back onto the developing roller 110. In other words,
A ground fogging phenomenon in which the normally charged toner adheres to the background portion occurs.

When the latent image on the photosensitive drum 101 comes out of the developing area due to rotation when the peak voltage V1 of the vibration bias is applied, the toner remains on the background portion of the drum, and A fogging phenomenon occurs.

Further, the potential difference V4 = | V1-VL | between the peak voltage V1 of the vibration bias and the exposure portion potential VL and the potential difference V3 = | V2-VD | between the peak voltage V2 of the vibration bias and the background portion potential VD start discharging. When the voltage exceeds the voltage, a leak due to electric discharge easily occurs between the photosensitive drum 101 and the developing roller 110, and the photosensitive drum 101 and the developing roller 1
Problems occur, such as damage to the photoconductor 10 and loss of control over the charging potential. Even if an electrostatic latent image is formed, it cannot be formed properly in response to an image signal, so that a desired image cannot be obtained. .

In order to prevent the ground fogging phenomenon and the discharge phenomenon, the difference between the maximum peak voltage and the minimum peak voltage (maximum value and minimum value) of the oscillation bias voltage, that is, the so-called peak-to-peak voltage Vpp is shown in FIG. Thus, the voltage was applied to the developing roller 110.

In FIG. 11, the two peak values V6 and V7 of the vibration bias voltage correspond to the image portion potential V of the photosensitive drum 101.
It is located between L and the background portion potential VD.

During the peak voltage V6 and the time t3, the negatively charged toner on the developing roller 110
Adheres to the image portion VL of the photosensitive drum 101 from the
Does not adhere to D. Even during the peak voltage V7 and the time t4, the negatively charged toner on the developing roller 110 adheres from the developing roller 110 to the image portion VL of the photosensitive drum 101 and does not adhere to the background portion VD. As described above, in the direction from the developing roller 110 to the photosensitive drum 101, the toner selectively adheres only to the image portion, and therefore, no ground fogging occurs.

However, if excessively charged toner is present in the developed image area (toner image) of the photosensitive drum 101, the toner is transferred by a strong electrostatic mirror force, so that the toner image is transferred. At the time of transfer to the material, the toner may remain on the photosensitive drum 101 without being transferred to the transfer material. When the next new electrostatic latent image is formed on the photosensitive drum 101 and development is performed without cleaning the remaining transfer residual toner, the photosensitive drum 10
Since there is no electric field for urging the toner in the direction from the image portion 1 to the developing roller 110, the transfer residual toner cannot be collected during the next development, and the history of the toner image of the previous circumference remains on the photosensitive drum. Will be lost. As a result, when a latent image having a uniform density is visualized as a toner image,
Density unevenness occurs.

Further, as described above, since the toner cannot reciprocate between the developing roller 110 and the photosensitive drum 101 in the image area, the gradation property is lower than in the case where the vibration bias voltage is applied in FIG. Inferior.

Accordingly, it is an object of the present invention to improve the cleaning efficiency of the image carrier by the vibration bias applied to the developing means and to suppress the ground fogging phenomenon in an image forming apparatus of a simultaneous cleaning type using contact development. It is an object of the present invention to provide an image forming apparatus which is enabled.

[0029]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
The image carrier and the developer carrier of the developing means are brought into contact with each other, and the developer carrying the electrostatic latent image formed on the image carrier on the developer carrier causes a developing bias to be applied to the developer carrier. In the image forming apparatus that develops under the application of the developing bias, the developing bias is a voltage that urges the developer in a direction from the developer carrier toward the image portion of the electrostatic latent image on the image carrier. A first peak voltage whose potential level is between the potential of the image portion of the electrostatic latent image on the image carrier and the potential of the background portion; And a voltage applied in a direction toward the developer carrying member, and the potential level of the voltage is the second level located on the opposite side of the potential level of the first peak voltage with respect to the potential of the image portion of the electrostatic latent image. An image forming apparatus comprising: a vibration bias voltage having a peak voltage.

Typically, the image forming apparatus of the present invention removes the residual developer adhering on the image carrier during the development.
An image forming apparatus using a simultaneous development and cleaning method, wherein the electrostatic latent image on the image carrier and the developer carrier to which a developing bias is applied is collected on the developer carrier by a potential difference.

According to the present invention, the time average voltage of the vibration bias voltage has a value between the potential of the image portion and the potential of the background portion of the electrostatic latent image on the image carrier. The first peak voltage and the second peak voltage of the oscillation bias voltage may be generated by turning on / off a DC bias power supply. Further, the DC bias power supply is grounded, and when the power supply is turned off, the second of the oscillation bias voltage
A peak voltage is generated at 0V. Further, the duty ratio of the oscillation bias voltage can be changed while keeping the frequency of the oscillation bias voltage, the potential of the first peak voltage, and the potential of the second peak voltage constant. The waveform of the oscillation bias voltage may be a rectangular wave. The image portion of the electrostatic latent image is formed as an exposed portion, and a non-magnetic toner of a one-component developer is attached to the image portion, and the image portion can be reversely developed.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a developing device according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 FIG. 1 is a schematic structural view showing an embodiment of the image forming apparatus of the present invention.

The present image forming apparatus employs a simultaneous cleaning method using a developing unit 4 and a reversal developing system in which the developing unit 4 applies negatively charged toner to an exposed portion of the photosensitive drum 1. The developing device 4 is a contact developing device that performs development by bringing a developing roller 6 carrying negatively charged toner into contact with the photosensitive drum 1.

A feature of the present invention resides in that in the simultaneous developing method using contact development, a vibration bias voltage applied as a developing bias to the developing roller 6 is devised in order to prevent a background fogging phenomenon.

In FIG. 1, the photosensitive drum 1 rotates in the direction of arrow a, and a charger 2, an exposure unit 3, a developing unit 4 and a transfer unit 5 are arranged around the photosensitive drum 1 along the rotating direction. Have been.

The developing device 4 has a developing roller 6, a coating roller 7, a regulating blade 7, an AC high-voltage power supply 1 and a DC high-voltage power supply 11, and contains a non-magnetic toner 9 as a one-component developer. The developing roller 6 is made of an elastic roller, and is arranged to be in contact with the photosensitive drum 1 and to be rotatable in the direction of arrow b. The application roller 7 contacts the developing roller 6 and is rotatably arranged in the direction of arrow c. The regulating blade 8 contacts the developing roller 6 on the upstream side of the regulating blade 8 and is grounded.

The AC high-voltage power supply 10 applies a vibration bias voltage to the developing roller 6, and the DC high-voltage power supply 11 applies an offset bias voltage to the developing roller 6.
AC high voltage power supply 10 and DC high voltage power supply 11 are connected in series,
The AC high voltage power supply 10 is connected to the developing roller 6 and the DC high voltage power supply 11 is grounded.

To form an image, the photosensitive drum 1 is pointed by an arrow a
, The charging bias is applied to the charger 2, and the surface of the photosensitive drum 1 is uniformly charged to a negative polarity by the charger 2. Next, the surface of the photosensitive drum 1 is exposed to a laser beam modulated by an image signal by an exposing device 3, and the photosensitive drum 1 is exposed.
An electrostatic latent image corresponding to the image information is written and formed on the surface of.

On the other hand, in the developing device 4, the application roller 7 rotates in the direction of arrow c, and conveys and carries the non-magnetic toner on the surface of the developing roller 6 which rotates in the direction of arrow b. The developing roller 6 transports the carried toner toward the developing area. In the course of the conveyance, when the toner passes between the developing roller 6 and the regulating blade 8 in contact with the developing roller, the toner is charged to a negative polarity by friction with the developing roller 6 and the thickness of the toner layer is regulated.

An oscillating bias voltage obtained by superimposing AC and DC is applied to the developing roller 6 by an AC high voltage power supply 10 and a DC high voltage power supply 11. Due to the oscillating electric field formed from the oscillating bias voltage and the surface potential of the photosensitive drum 1, the negatively charged toner is developed in the developing region (Z portion in FIG. 10) after the contact portion between the photosensitive drum 1 and the developing roller 6. Oscillates and reverse develops the electrostatic latent image. The toner not consumed in the development is returned into the developing device 4 by the rotation of the developing roller 6, peeled off at the contact portion by the application roller 7, and collected.

Photosensitive drum 1 formed by developing a latent image
The upper toner image is transferred to the transfer material P by applying a positive bias voltage to the transfer device 5 located on the opposite side of the photosensitive drum 1 with the transfer material P supplied to the photosensitive drum 1 interposed therebetween. You.

The vibration bias voltage will be described with reference to FIG. As the oscillation bias voltage, the first peak voltage Va and the second peak voltage Vb appear alternately. The first peak voltage Va corresponds to the charging potential VD of the background portion (unexposed portion) of the electrostatic latent image on the photosensitive drum 1 and the charging potential V of the image portion (exposed portion).
L and a potential level located between L and L. The second peak voltage Vb is the background portion potential VD with respect to the image portion potential VL.
The potential level is located on the opposite side of The first peak voltage Va lasts for time ta, the second peak voltage Vb lasts for time tb, and these two peak voltages are used as one cycle T of the vibration bias.

The first peak voltage Va is a voltage for urging the toner from the developing roller 6 toward the image portion VL on the photosensitive drum 1. Accordingly, at the time ta, the toner moves from the developing roller 6 to the image portion VL on the photosensitive drum 1 and adheres to develop the image portion VL. On the other hand, the direction of the electric field in the background portion VD on the photosensitive drum 1 acts in the opposite direction to the direction of the electric field in the image portion VL, so that the toner does not adhere to the background VD from the developing roller 6.

The second peak voltage Vb is a voltage that urges the toner from the image portion VL on the photosensitive drum 1 toward the developing roller 6. Therefore, part of the toner attached to the image portion VL on the photosensitive drum 1 at the time ta is reduced to the time t.
At b, the toner adheres to the developing roller 6.

In the background portion VD on the photosensitive drum 1,
Regardless of the time ta or tb, an electric field is always generated in the direction from the photosensitive drum 1 toward the developing roller 6 due to the toner.
No background fog in which the normally negatively charged toner adheres to the background portion does not occur.

After the toner image is formed on the photosensitive drum 1 through the above-described development process, the toner image is formed as described above.
The image is transferred to the transfer material P supplied to the photosensitive drum 1 by the transfer device 5.

By the way, on the photosensitive drum 1 after the transfer, there is a small amount of toner remaining untransferred, that is, a so-called transfer residual toner. The photosensitive drum 1 to which the transfer residual toner is adhered is uniformly charged to the negative polarity again by the exposure device 2, and after the charging, the exposure device 3 forms an electrostatic latent image based on the next new image information. Thereafter, the photosensitive drum 1 reaches the developing device 4.

Of the transfer residual toner on the photosensitive drum 1,
The background portion VD of the electrostatic latent image newly formed on the photosensitive drum 1
As described above, the transfer residual toner remaining on the photosensitive drum 1 and the developing roller 6 in the non-contact portion (X portion in FIG. 10) before the contact between the photosensitive drum 1 and the developing roller 6.
Due to the electric field acting in the direction toward, the toner is collected by the developing roller 6 and reliably removed from the photosensitive drum 1.

On the other hand, the transfer residual toner remaining on the image portion VL of the new electrostatic latent image on the photosensitive drum 1 is peeled off from the image portion VL by the vibration bias voltage, and is newly supplied from the developing roller 6. Similarly to the toner, the toner reciprocates between the photosensitive drum 1 and the developing roller 6 and adheres to the image portion VL to form a new toner image. Therefore, the residual image memory of the residual toner is erased for the new toner image.

Thereafter, the new toner image is transferred to the photosensitive drum 1
10 is once disturbed at the contact portion of the developing roller 6 (Y portion in FIG. 10), and then the developing region in the contact development, that is, the non-contact portion after the contact between the photosensitive drum 1 and the developing roller 6 (Z in FIG. 10).
) Is developed again.

The new toner image on the photosensitive drum 1 is
The image is transferred to the next transfer material P supplied to the photosensitive drum 1 by the transfer device 5. By repeating the above steps, image formation is performed by the simultaneous development and cleaning method.

As described above, in this embodiment, at the time of development, the toner is always applied in the direction from the photosensitive drum 1 to the developing roller 6 in the background portion of the electrostatic latent image on the photosensitive drum 1 by the vibration bias voltage. Since the energizing electric field is formed, the ground fogging phenomenon which has conventionally been a problem can be greatly improved. Also, at the time tb of the vibration bias voltage, the back contrast (the potential difference | Vb−VD | between Vb and VD) becomes large, so that the cleaning of the excessively charged toner which becomes a problem when the DC bias voltage Vdc as shown in FIG. 8 is applied. No failure occurs. Then, in the image portion VL on the photosensitive drum 1, the toner repeatedly develops by reciprocating between the photosensitive drum 1 and the developing roller 6, so that the gradation of the image can be sufficiently obtained.

A numerical example of this embodiment will be described.

As the photosensitive drum 1, a photoconductive drum composed of an organic photosensitive member was used. The surface of the photosensitive drum 1 was charged by the charger 2 at a charging potential of -600V. With the laser exposure of the photosensitive drum 1 by the exposure device 3,
The potential of the exposed portion was reduced to -150 V, and an electrostatic latent image was formed at an exposed portion potential of -150 V and a background portion potential VD of -600 V. During development, the vibration bias voltage applied to the developing roller 6 includes a first peak voltage Va = −550 V, a second peak voltage Vb = + 50 V, and a peak-to-peak voltage Vpp.
= 600V, time average voltage Vc = -350V, frequency 1
/ T = 1800 Hz and duty ratio = 2/1.

In the present invention, the above-mentioned duty ratio is defined as follows. The oscillation bias voltage is a function V of time t.
(T), and the function V (t) is time-integrated by one cycle time T of the oscillation cycle. The integral value is calculated as the time T of one cycle.
Is referred to as the time average voltage of the oscillation bias voltage for convenience, and is represented by Vc. That is, Vc = (∫V (t) dt) / T

The time length during which the potential of the vibration bias voltage V (t) is located on the same side as the background potential VD on the photosensitive drum 1 with respect to the potential of the time average value Vc within one cycle of the vibration, and The ratio of the time lengths located on the same side as the partial potential VL is defined as the duty ratio. That is, the duty ratio in the present embodiment is a ratio ta / tb between the time length ta of the first peak and the time length tb of the second peak.

When an image was formed by the simultaneous development and cleaning method under the above conditions, the cleaning efficiency of the photosensitive drum 1 was improved, and an image with sufficient gradation without a fogging phenomenon could be obtained.

In the above, the background potential VD of the photosensitive drum 1 is
Is -600 V and the peak-to-peak voltage Vpp of the oscillating bias voltage is 600 V. In general, no leakage occurs and a sufficient back contrast (potential difference | Vb-VD | between Vb and VD) is obtained. -9
00V <VD <-500V, 400V <Vpp <100
It is preferable to set the range to 0V.

The frequency 1 / T of the oscillation bias voltage is 1
800 Hz, but generally 500 Hz <1 / T.
A range of <10 kHz is preferred. At about 500 Hz or less, unevenness due to the oscillation cycle of the oscillation bias voltage appears in the toner image on the photosensitive drum 1 to the extent that it is visible. If the frequency is higher than about 10 kHz, a high frequency power supply is required, which is not preferable from the viewpoint of cost and miniaturization of the apparatus.

As described above, according to this embodiment, at the time of development, the charged potential V of the background portion of the electrostatic latent image on the photosensitive drum 1 is set.
A first peak voltage Va having a potential level between D and the charged potential VL of the image portion, and a second peak voltage Vb having a potential level located on the opposite side of the charged potential VD of the background portion with respect to the image portion potential VL. Since the vibration voltage that is alternately repeated is applied to the developing roller 6 of the developing device 4, the image formation is performed by the simultaneous development cleaning method, the cleaning efficiency of the photosensitive drum 1 is improved, and the gradation is eliminated without the ground fogging phenomenon. Sufficient images could be obtained.

Embodiment 2 In this embodiment, the same effect as in Embodiment 1 can be obtained by a simpler method. FIG. 3 shows the image forming apparatus of the present embodiment, and FIG. 4 shows a vibration bias voltage applied to the developing roller 6 of the developing device 4.

As shown in FIG. 4, the oscillation bias voltage V (t) is such that the first peak voltage Va is maintained for a time ta,
The second peak voltage Vb is 0 V and is maintained for a time tb. The first peak voltage Va has a potential level between the charged potential VD of the background portion of the electrostatic latent image on the photosensitive drum 1 and the charged potential VL of the image portion, and the second peak voltage Vb (0 V)
Has a potential level located on the opposite side of the charged potential VD of the background portion with respect to the image portion potential VL.

In this embodiment, an AC high voltage power supply is not provided for the developing roller 6 of the developing device 4 but a grounded DC high voltage power supply 21 is provided.
The high-voltage input power supply 21 is provided with a high-speed input switch 22, and the switch 22 switches between the DC voltage of the DC high-voltage power supply 21 and 0 V of the ground, thereby generating the vibration bias voltage.

According to this, since the dedicated AC high-voltage power supply is omitted, the image forming apparatus can be greatly simplified.
The same effect as that described above can be obtained, and the cost and size of the device can be reduced.

A numerical example relating to the second embodiment will be described.

An electrostatic latent image was formed at the exposure portion potential VL = -150 V and the background portion potential VD = -600 V, as in the first embodiment. The oscillation bias voltage is the first peak voltage Va = −
500 V, second peak voltage Vb = 0 V, peak-to-
Peak voltage Vpp = 500V, time average voltage Vc = -1
67 V, frequency 1 / T = 1800 Hz, and duty ratio = 2/1.

An image was formed by the simultaneous development and cleaning method under the above conditions. As a result, the cleaning efficiency of the photosensitive drum 1 was improved, and an image having sufficient gradation without a fogging phenomenon was obtained.

In this embodiment, one of the peak voltages is set to ground 0
V, but even if an offset voltage is applied to the developing roller by another power source, the DC high-voltage power source is turned on / off.
By switching the FF, an oscillation bias voltage as in the first embodiment can be formed.

As described above, according to the present embodiment, the high-speed input switch 22 is provided in the grounded DC high-voltage power supply 21 and the switch 22 switches the DC voltage of the DC high-voltage power supply 21 and 0 V of the ground. A first peak voltage Va having a potential level between the charged potential VD of the background portion of the electrostatic latent image on the photosensitive drum 1 and the charged potential VL of the image portion, and a charge potential VD of the background portion with respect to the image portion potential VL. The second bias voltage Vb (0 V) having the potential level located on the opposite side is generated and applied to the developing roller 6 of the developing device 4 by generating an oscillating bias voltage that is alternately repeated. By performing image formation by the cleaning method, the cleaning efficiency of the photosensitive drum 1 is improved, an image with sufficient gradation can be obtained without a background fogging phenomenon, and the image forming apparatus is greatly simplified. As a result, the cost and size of the apparatus can be reduced.

Embodiment 3 As a method of adjusting the image density, conventionally, the waveform of the vibration bias voltage is moved up and down in parallel, or the peak-to-
A method of changing the peak voltage is known. However, as the image density increases, a background fogging phenomenon becomes remarkable, and a problem such as that a leak easily occurs occurs.

In the third embodiment, the above problem was solved while adjusting the image density. FIG. 5 shows the image forming apparatus of this embodiment.
FIG. 6 shows the vibration bias voltage applied to the developing roller 6 of the developing device 4.

In this embodiment, the control device 33 for automatically changing the duty ratio of the vibration bias voltage applied to the developing roller 6 in response to a signal from a document density detection device (not shown) is provided to the vibration voltage generator. installed.

For example, when a lower image density is required, the controller 33 selects the vibration bias voltage Vlow (t) as shown in FIG. When the image density of FIG.
A vibration bias Vhigh (t) as shown in FIG. 3B is selected and applied to the developing roller 6.

In FIGS. 6A and 6B, the first peak voltage Va, the second peak voltage Vb, and the oscillation period T are the same as the oscillation bias voltages Vlow (t) and Vhigh (t), and the duty ratio tLa / tLb and tHa / tHb have different values. The first peak voltage Va has, of course, a potential level between the background portion potential VD and the image portion potential VL, and the second peak voltage Vb is located on the opposite side of the background portion potential VD with respect to the image portion potential VL. It has a potential level.

As described above, in this embodiment, the developing roller 6
Since the duty ratio of the vibration bias voltage to be applied is changed in accordance with the image density, it is possible to adjust the image density while obtaining the same effect as in the first embodiment by forming an image by the simultaneous development and cleaning method.

A numerical example of the third embodiment will be described.

An electrostatic latent image was formed with an exposure portion potential of -150 V and a background portion potential VD of -600 V, as in Example 1. The oscillation bias voltages Vlow and Vhigh are the first peak voltage Va = −550 V, the second peak voltage Vb = + 50 V,
(Peak-to-peak voltage Vpp = 600 V), frequency 1 / T = 1800 Hz. The duty ratio tLa / tLb of the vibration bias voltage Vlow in FIG. 6A is 1/1, and the duty ratio t of the vibration bias voltage Vhigh in FIG.
Ha / tHb was 2/1. Therefore, the time average value Vc of the oscillation bias voltage Vlow in FIG. 6A is -250 V, and the time average voltage Vc of the oscillation bias voltage Vhigh in FIG. 6B is -350 V.

As a result of forming an image by the simultaneous cleaning method under the above-described conditions, the cleaning efficiency of the photosensitive drum 1 is improved, an image having a sufficient gradation without a fogging phenomenon can be obtained, and the image density can be improved. Could also be adjusted.

As described above, in this embodiment, the vibration bias voltage having the duty ratio changed in accordance with the image density is applied to the developing roller 6, so that the ground fog can be improved.
The image density can be adjusted while performing the simultaneous cleaning with development.

As described above, in this embodiment, the same vibration bias voltage applied to the developing roller 6 as in the first embodiment is used while changing the duty ratio in accordance with the image density. Image formation by
The improvement of the cleaning efficiency of the photosensitive drum 1, the improvement of the background fog of the image, the improvement of the gradation, and the adjustment of the image density were able to be performed.

In each of the above embodiments, the oscillation bias voltage applied to the developing roller 6 is a rectangular wave, but other waveforms, for example, when changing from the first peak voltage Va to the second peak voltage Vb, Or the second peak voltage Vb
Even if a waveform having a gradient in the time change of the potential when changing from the first peak voltage Va to the first peak voltage Va is used, the performance of the simultaneous development cleaning method is improved and the ground fogging phenomenon is significantly improved, as in the first embodiment. Sufficient gradation was obtained.

That is, in the vibration bias voltage usable in the present invention, the potential of the first peak voltage Va is located between the background potential VD of the electrostatic latent image on the photosensitive drum 1 and the image potential VL. The potential of the second peak voltage Vb is
As long as the vibration waveform is located on the opposite side of the background potential VD with respect to the upper image potential VL, the waveform is not limited to a rectangular wave, but may be a triangular wave, a sawtooth wave, a sine wave, or the like. .

Although the description has been made by taking the reversal development method as an example, the present invention may be carried out by a positive reversal development method or a regular development method. The image can be formed by the simultaneous development and cleaning method, which has no background fog and excellent gradation.

[0085]

As described above, according to the present invention,
In contact development in which the image carrier and the developer carrier of the developing means are in contact with each other, the potential level of the developer carrier is set between the background potential of the electrostatic latent image on the image carrier and the image potential. And a second peak voltage whose potential is on the opposite side of the background portion potential VD with respect to the image portion potential on the image carrier, was applied. It is possible to improve the cleaning efficiency of the image carrier, further reduce the background fogging phenomenon, and obtain an image with sufficient gradation.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of an image forming apparatus of the present invention.

FIG. 2 is a waveform chart showing an oscillation bias voltage used in the embodiment of FIG.

FIG. 3 is a schematic configuration diagram showing another embodiment of the image forming apparatus of the present invention.

FIG. 4 is a waveform diagram showing an oscillating bias voltage used in the embodiment of FIG.

FIG. 5 is a schematic configuration diagram showing still another embodiment of the image forming apparatus of the present invention.

FIG. 6 is a waveform diagram showing an oscillation bias voltage used in the embodiment of FIG.

FIG. 7 is a schematic diagram showing a conventional image forming apparatus.

FIG. 8 is a waveform diagram showing a DC bias voltage used in the conventional simultaneous cleaning for development.

FIG. 9 is a waveform diagram showing a vibration bias voltage used in the conventional simultaneous cleaning for development.

10 is an explanatory diagram illustrating the vicinity of a contact portion between a photosensitive drum and a developing roller in contact development performed by the image forming apparatus in FIG.

FIG. 11 is a waveform diagram showing another example of the vibration bias voltage used in the conventional simultaneous cleaning of development.

[Explanation of symbols]

 1 Photosensitive drum 4 Developing device 6 Developing roller 9 Non-magnetic toner 10 AC high voltage power supply 11 DC high voltage power supply 22 Input switch 33 Control device V (t) Vibration bias voltage Va First peak voltage Vb Second peak voltage Vc Time average voltage VD Background Partial potential VL Image part potential

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukihiro Ozeki 3- 30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Katsuhiro Sakaizawa 3- 30-2 Shimomaruko 3-chome, Ota-ku, Tokyo Non-corporation F term (reference) 2H073 AA03 AA05 AA09 BA04 BA07 BA13 BA45 CA02 2H077 AA37 AC04 AD02 AD06 AD13 AD37 AE03 DB08 EA14 GA17

Claims (8)

    [Claims]
  1. An image carrier is brought into contact with a developer carrier of a developing means, and an electrostatic latent image formed on the image carrier is carried on the developer carrier by a developer. In an image forming apparatus that performs development while applying a developing bias to a carrier, the developing bias is a voltage that urges a developer in a direction from a developer carrier to an image portion of an electrostatic latent image on an image carrier. A first peak voltage whose potential level is between the potential of the image portion and the potential of the background portion of the electrostatic latent image on the image carrier; A voltage that is applied in a direction from the image portion of the latent image toward the developer carrier, and the potential level of the voltage is related to the potential of the image portion of the electrostatic latent image.
    An image forming apparatus comprising: a vibration bias voltage having a second peak voltage located on a side opposite to a potential level of a first peak voltage.
  2. 2. An image forming apparatus according to claim 1, wherein the image carrier and the developer carrier of the developing means are brought into contact with each other, and the electrostatic latent image formed on the image carrier is carried on the developer carrier. The developing is performed while a developing bias is applied to the carrier, and at the time of the developing, the remaining developer adhering to the image carrier is removed by developing the electrostatic latent image on the image carrier and the developing bias. In the image forming apparatus of the simultaneous cleaning with developing method, wherein the developer is collected on the developer carrier by a potential difference between the developer carriers, the developing bias is used to transfer the developer from the developer carrier to an electrostatic latent image on the image carrier. A first peak voltage whose potential level is between the potential of the image portion and the potential of the background portion of the electrostatic latent image on the image carrier; From the image portion of the electrostatic latent image on the image carrier to the developer carrier To a voltage which biases relates potential of the image portion potential level electrostatic latent image of the voltage,
    An image forming apparatus comprising: a vibration bias voltage having a second peak voltage located on a side opposite to a potential level of a first peak voltage.
  3. 3. The image forming apparatus according to claim 1, wherein the time average voltage of the vibration bias voltage has a value between a potential of an image portion and a potential of a background portion of the electrostatic latent image on the image carrier. .
  4. 4. The image forming apparatus according to claim 1, wherein the first peak voltage and the second peak voltage of the vibration bias voltage are generated by turning on / off a DC bias power supply.
  5. 5. The image forming apparatus according to claim 4, wherein the DC bias power supply is grounded, and the second peak voltage of the vibration bias voltage is generated at 0 V when the power supply is turned off.
  6. 6. The oscillation bias voltage according to claim 1, wherein the duty ratio of the oscillation bias voltage is changed while keeping the frequency of the oscillation bias voltage, the potential of the first peak voltage, and the potential of the second peak voltage constant. The image forming apparatus according to any one of the above items.
  7. 7. The image forming apparatus according to claim 1, wherein the waveform of the vibration bias voltage is a rectangular wave.
  8. 8. The image portion of the electrostatic latent image is formed as an exposed portion, and a non-magnetic toner of a one-component developer is adhered to the image portion to reversely develop the image portion. An image forming apparatus according to any of the above items.
JP30638098A 1998-10-12 1998-10-12 Image forming device Pending JP2000122388A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP30638098A JP2000122388A (en) 1998-10-12 1998-10-12 Image forming device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP30638098A JP2000122388A (en) 1998-10-12 1998-10-12 Image forming device

Publications (1)

Publication Number Publication Date
JP2000122388A true JP2000122388A (en) 2000-04-28

Family

ID=46516980

Family Applications (1)

Application Number Title Priority Date Filing Date
JP30638098A Pending JP2000122388A (en) 1998-10-12 1998-10-12 Image forming device

Country Status (1)

Country Link
JP (1) JP2000122388A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1154332A2 (en) * 2000-05-12 2001-11-14 Seiko Epson Corporation Developing device
US7031629B2 (en) * 2002-04-15 2006-04-18 Canon Kabushiki Kaisha Image forming apparatus which recovers toner by developing device
US7239831B2 (en) 2003-12-15 2007-07-03 Canon Kabushiki Kaisha Image forming apparatus when a maximum developing bias voltage |V| max and surface potential Vd of a charged image bearing member satisfy: |V| max≦|Vd|
JP2008185838A (en) * 2007-01-30 2008-08-14 Konica Minolta Business Technologies Inc Developing device

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1154332A2 (en) * 2000-05-12 2001-11-14 Seiko Epson Corporation Developing device
US6526238B2 (en) 2000-05-12 2003-02-25 Seiko Epson Corporation Developing device
EP1154332A3 (en) * 2000-05-12 2008-09-24 Seiko Epson Corporation Developing device
US7031629B2 (en) * 2002-04-15 2006-04-18 Canon Kabushiki Kaisha Image forming apparatus which recovers toner by developing device
US7239831B2 (en) 2003-12-15 2007-07-03 Canon Kabushiki Kaisha Image forming apparatus when a maximum developing bias voltage |V| max and surface potential Vd of a charged image bearing member satisfy: |V| max≦|Vd|
JP2008185838A (en) * 2007-01-30 2008-08-14 Konica Minolta Business Technologies Inc Developing device

Similar Documents

Publication Publication Date Title
US3893418A (en) Xerographic developing apparatus
US6950620B2 (en) Image forming apparatus with settable peak to peak voltages applied to image bearing member
JP4065496B2 (en) Image forming apparatus
US6128449A (en) Image forming apparatus and method for controlling charging and developing bias voltage
US3866574A (en) Xerographic developing apparatus
DE3706873C2 (en) Imaging device
JP5207646B2 (en) Image forming apparatus
US5768665A (en) Image forming apparatus with bias control to prevent undesirable toner deposition
JP2004117960A (en) Image forming apparatus
JP2005242281A (en) Developing device in image forming apparatus
EP0415753B1 (en) An image forming apparatus
JP4154168B2 (en) Image forming apparatus
US5835821A (en) Image forming apparatus
US7146123B2 (en) Image forming apparatus
JP4355152B2 (en) Image developing apparatus, image developing apparatus cleaning method, and image developing method
US5521683A (en) Image forming apparatus using constant voltage or constant current AC signal applied to developer bearing member, and control function in accordance with detected voltage or current of developer bearing member
JP5042676B2 (en) Image forming apparatus
JP4123750B2 (en) Image forming apparatus
EP3062159A2 (en) Image forming apparatus
JP5172182B2 (en) Image forming apparatus
US6006055A (en) Image forming apparatus
JP2003345210A (en) Image forming device
JP3250851B2 (en) Multicolor image forming device
US6505021B2 (en) Image forming apparatus having a member for barring an electrification particle form leaking
JPH08137261A (en) Cleaning method of contact electrifying means for image forming device