JPH0887220A - Image forming device - Google Patents

Abstract

PURPOSE: To execute a cleaning mode for cleaning a beltlike or rolllike member separately from an image forming mode and to effectively clean a member coming into contact with an image carrier and rotating by providing a latent image pattern forming means forming a latent image pattern for cleaning which has a large number of edges. CONSTITUTION: In the cleaning mode, a photoreceptor 10 is rotated in a state where the operations of an optical writing means 14 and a developing device 16 are stopped, to be uniformly electrified to the same polarity as that in the image forming mode by an electrifying member 12. The uniformly charged photoreceptor part, passes through a developing part by the developing device 16, but the photoreceptor part is not developed because toner is electrified to the same polarity as that of the photoreceptor 10. When its periphery passes through the slid position of the latent image pattern forming means 17, the latent image pattern for cleaning is formed. Thus, the toner on the surface of a transfer member 20 is moved/stuck to the side of the photoreceptor 10 regardless of the polarity of the charge and removed/recovered from the photoreceptor by the cleaning device 22.

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".

[0002]

2. Description of the Related Art A belt-shaped or drum-shaped image bearing member is rotated in a fixed direction to form an electrostatic latent image, which is developed with toner. The toner image obtained is transferred onto a transfer sheet to form a desired image. The obtained image forming apparatus has been widely known as an electronic copying machine or an optical printer.

In such an image forming apparatus, a corona discharger has been widely used as a charger for charging the surface of an image carrier, a transfer device for transferring a toner image, and the like.
There is a problem that ozone generated by corona discharge pollutes the environment, and a contact-type charger or a transfer device that can perform charging and transfer without ozone generation has been attracting attention.

FIG. 6A schematically shows only an essential part of an image forming apparatus using a contact type charger and a transfer device.

The photoconductive photoconductor 10 is formed in a drum shape and rotates in the direction of the arrow, and the surface thereof is uniformly contact-charged by a roll-shaped charging member 12. An image is written on the uniformly charged surface of the photoconductor by the optical writing means 14, and an electrostatic latent image corresponding to the written image is formed. Since the optical writing means 14 exposes a portion to be an image, what is formed on the photoconductor 14 is a so-called negative electrostatic latent image.

The negative electrostatic latent image is reversely developed by the developing device 16 with toner having the same polarity as that of the electrostatic latent image to form a toner image. The recording sheet S to which the toner image is transferred is guided by the guide 18 in synchronization with the movement of the toner image.
Is sent to the transfer part by the transfer member 20.
Is pressed by.

The transfer member 20 is roll-shaped and has a resistance of 10 ¹⁰ Ω.
The metal core roll is covered with a "medium resistance sponge-like rubber" of about cm, and a voltage having a polarity opposite to that of the toner is applied to the metal core roll, and the toner image on the photoconductor 10 is recorded on the recording sheet S. Transcribe.

The recording sheet S on which the toner image is transferred is
The toner image is fixed in a fixing unit (not shown) and is discharged to the outside of the apparatus. After the toner image is transferred, the toner remaining on the photoconductor 10 is cleaned by the cleaning device 22.
Removed and collected from above.

In this example, since the charging member 12 and the transfer member 20 are in direct contact with the surface of the photoconductor 10, the photoconductor 10
Toner is easily attached from the side.

For example, if toner adheres to the surface of the charging member 12, it causes "charging unevenness" in the charging of the surface of the photosensitive member. Further, when the toner adheres to the surface of the transfer member 20, the "back surface stain" of the recording sheet easily occurs.

FIG. 6B is a plan view showing the peripheral surface of the photoconductor 10 in a developed state. As the photoconductor 10 rotates, the peripheral surface moves in the direction of the arrow (to the left in the figure). To do. The rectangular area surrounded by “e, f, g, h” in the figure is an area where an electrostatic latent image is formed and is called an “image area”. In, the recording sheet overlaps with this image area.

A portion other than the image area, that is, "a, b,
The two rectangular areas surrounded by “f, e” and “c, d, h, g”, the area on the left side of the line segment ad and the area on the right side of the line segment bc are “non-image areas”. .

At the time of transferring the toner image, in the "image area",
Since the recording sheet S is interposed between the photoconductor 10 and the transfer member 20, the peripheral surface of the transfer member 20 does not directly contact the surface of the photoconductor, but in the "non-image portion", the transfer member 20 is exposed to light. The toner is transferred from the side of the photoconductor 10 in direct contact with the body 10.

The toner attached to the transfer member 20 causes the back surface of the recording sheet to be soiled at the time of the next toner image transfer.

Therefore, the toner attached to the charging member 12 and the transfer member 20 needs to be removed by cleaning.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and is a novel one capable of cleaning and removing toner adhering to a belt-shaped or roll-shaped member contacting the surface of an image carrier. An object is to provide an image forming apparatus (claims 1 to 8).

[0017]

According to another aspect of the present invention, there is provided an image forming apparatus, wherein an electrostatic latent image is formed while rotating a belt-shaped or drum-shaped image carrier in a fixed direction, and the electrostatic latent image is developed with toner. An image forming apparatus for transferring the obtained toner image onto a transfer sheet to obtain a desired image, and cleaning "a belt-shaped or roll-shaped member that contacts the surface of the image carrier and circulates and rotates". The "cleaning mode" for the above can be executed separately from the image forming mode.

The "image carrier" is belt-shaped or drum-shaped and forms an electrostatic latent image while rotating in a fixed direction. The image carrier is generally a photoconductive photoconductor, and in this case, an electrostatic latent image can be formed by uniform charging and exposure (image exposure or optical writing).

However, an image bearing member "having an insulating layer formed on a conductive substrate" is used as an image bearing member, and the surface thereof is "position-selectively" charged or discharged by a stylus electrode array or the like.
It is also possible to form an electrostatic latent image.

The "recording sheet" is a medium onto which a toner image is transferred, and is a transfer sheet, a transparent sheet for an overhead projector, or the like.

The image forming apparatus according to the present invention has a latent image pattern forming means.

The "latent image pattern forming means" is means for forming a latent image pattern for cleaning with many edge portions in the cleaning mode. The “edge portion” is a portion where the surface potential of the image carrier changes stepwise.

An image forming apparatus according to a second aspect has a latent image pattern forming means and a voltage applying means.

In the cleaning mode, the "latent image pattern forming means" have potentials of substantially V ₁ and V ₂ (│V ₁ │> │).
V ₂ |) for forming a latent image pattern for cleaning.

The "voltage applying means" is a means for applying an intermediate potential between the potentials V ₁ and V ₂ to the member to be cleaned.

In any of the image forming apparatus described in claims 1 and 2, the electrostatic latent image formed on the image carrier is "negative electrostatic latent image (image exposure of negative image, optical writing, stylus It may be formed by position-selective charging or charge removal by the electrode array), and this may be subjected to reversal development with toner (Claim 3), or the electrostatic latent image formed on the image carrier may be positively formed. It is also possible to form an electrostatic latent image, erase the non-image area, and then perform normal development with toner (claim 4).

The "latent image pattern forming means" in the image forming apparatus according to claims 1 and 2 may have the same structure or the same device, but the latent image patterns for cleaning formed by the respective means are: The inventions of claims 1 and 2 are not the same.

For example, in the image forming apparatus according to the first or second aspect, the "latent image pattern" formed by the latent image pattern forming means is a "stripe" which is orthogonal or parallel to the moving direction of the peripheral surface of the image carrier. However, in the invention according to claim 1, the stripe pattern has a pitch of 2 mm or less, preferably 1 mm or less, and edge portions are formed everywhere. It is a thing.
On the other hand, in the second aspect of the invention, the pattern pitch of the striped pattern is preferably 2 mm or more.

The striped pattern may intersect with the moving direction of the peripheral surface of the image carrier at an angle different from a right angle.

In addition to the latent image pattern for cleaning, a pattern in which shapes such as a circle, an ellipse, a rectangle and a polygon are regularly or randomly arranged can be given. In this case, if the size of the shape and the arrangement pitch are 2 mm or less, preferably 1 mm or less, the "latent image pattern for cleaning with many edges" is obtained.

The "belt-shaped or roll-shaped member" to be cleaned may be a transfer member (claim 6), a charging member or a recording sheet guide member described later (claim 7). If desired, the developing roll indicated by the reference numeral 161 and the cleaning roll indicated by the reference numeral 221 in FIG. 6 can also be targets for cleaning.

When the dedicated "latent image pattern forming means" is provided, it is preferable to provide it on the downstream side of the developing device and on the upstream side of the belt-shaped or roll-shaped member to be cleaned (claim 8).

In addition, the electrostatic latent image is formed by optical writing means (for example, a system of deflecting a laser beam, or LE
In the case of using a D array and a roof mirror lens array, etc.), "the optical writing means is a latent image pattern forming means".
It can also serve as (claim 9).

In this case, when the formed "latent image pattern" passes through the developing position, the bias voltage of the developing device is changed so that the latent image pattern is not developed by the developing device, or the developing device is retracted from the developing position. It is preferable. However, the so-called "jumping development type development device"
Then, it is not necessary to switch the state of the developing device between the image forming mode and the cleaning mode.

The peripheral speed of the belt-shaped or roll-shaped member to be cleaned may be switched between the image forming mode and the cleaning mode by the "peripheral speed switching means" (claim 10).

[0036]

When the negative electrostatic latent image is formed on the image bearing member and the reversal development is performed, the "non-image area" on the image bearing member has the same polarity as the normal toner. Toner that is charged to the non-image area is
Examples include toner that is abnormally charged to a polarity opposite to that of normal toner, and toner that has a normal polarity but has a small charge amount such that the adhesive force such as van der Waals force overcomes the electric repulsive force.

When a positive electrostatic latent image is formed on the image bearing member and the non-image area is erased and then normally developed with toner, the toner is attached to the non-image area. It is mainly the adhesive force such as the Van der Waals force that causes the adhered toner to have a normal polarity or an opposite polarity.

The charged state of the toner is also affected at the time of transfer. For this reason, the toner attached to the "belt-shaped or roll-shaped member" which contacts the photoconductor and rotates in a circulating manner. In general, although the amount is not so large, there are positive polarity and negative polarity as the charging polarity.

In developing an electrostatic latent image with toner,
Since the phenomenon called "edge effect" appears regardless of the charge polarity of the toner, the invention according to claim 1 forms a latent image pattern having many edge portions on the image carrier, and the latent image pattern causes an edge effect. The toner on the member to be cleaned is adsorbed and removed.

According to the second aspect of the present invention, the potential applied to the member to be cleaned is set between the two potentials forming the latent image pattern for cleaning. Is adsorbed and the member is cleaned.

Needless to say, the toner imaged on the image carrier in the cleaning mode is removed from the image carrier by the cleaning device for the image carrier.

[0042]

EXAMPLES Specific examples will be described below.

FIG. 1A shows an embodiment in which the invention according to claim 1 is applied to the image forming apparatus described with reference to FIG. Therefore, the same reference numerals as in FIG. 6 are used for the same equipment as in FIG.

In this embodiment, the charging member 12, the developing roller 161, the transfer member 20, and the cleaning member are the belt-shaped or roll-shaped members that rotate in contact with the photosensitive member 10, which is the "image carrier", in a circulating manner. Roll 221 of 4
A member to be cleaned, which is a kind, is a transfer member (formed by covering the outer circumference of a metal core roll with a medium resistance sponge-like rubber material) 20.

The image forming process in the image forming mode is the same as the process described with reference to FIG.

The "latent image pattern forming means" indicated by reference numeral 17 in FIG. 1 (a) has a light source and slit means. The light source is formed by finely arranging minute light emitting sources such as LDs and LEDs that can turn on / off light emission in a short time in a direction orthogonal to the drawing of FIG. The slit means is provided so as to surround the above-mentioned light source, and 0.5 m is provided in a portion near the photoconductor 10.
An extremely narrow slit of about m is opened.

Therefore, when the light emission sources in the light source are made to emit light all at once, the photosensitive member 1 can be irradiated in a narrow slit shape. As shown in FIG. 1B, a striped pattern having a width of 2 mm or less is formed on the photoconductor 10 by repeatedly turning on and off the light source at minute intervals according to the rotation speed of the photoconductor 10.
Can be exposed to.

In the cleaning mode, the photoconductor 10 is rotated while the operations of the optical writing unit 14 and the developing device 16 are stopped, and the charging member 12 causes the same polarity as in the image forming mode (for the specificity of the description, Negatively charged) to be uniformly charged. The uniformly charged photoreceptor portion is the developing device 16
However, since the toner is charged with the same polarity as the photoconductor 10, the development is not performed.

When the uniformly charged peripheral surface of the photoconductor 10 passes through the slit position of the latent image pattern forming means 17,
The light sources of the means 17 are repeatedly turned on and off at the same time, and a striped pattern having a width of 2 mm or less is exposed to form a latent image pattern for cleaning.

When this latent image pattern passes the position of the transfer member 20, the transfer member 20 is rotated by following the surface of the photosensitive member. At this time, the metal core roll may be in a "ground" or "float" state, but it is preferable to apply an appropriate bias voltage depending on the polarity distribution of the toner on the transfer roller.

FIG. 2 is an explanatory view showing a part of the "latent image pattern for cleaning with a lot of edges" formed on the photoconductor 10 as described above. Reference numeral 10A indicates a conductive base, and reference numeral 10B indicates a photoconductive layer. At the “edge portion”, the electric force lines include those that extend from the surface of the photoconductor as shown in the figure and those that draw a curve toward the surface of the photoconductor, and also the toner T (+) positively charged as shown in the figure. The negatively charged toner T (−) also adheres to the surface of the photoconductor 10.

As a result, the toner attached to the surface of the transfer member 20 is transferred to the side of the photoconductor 10 regardless of the charging polarity, and then removed and collected from the photoconductor 10 by the cleaning device 22. Thus, the surface of the transfer member 20 is cleaned.

In the latent image pattern forming means 17, if the light source is brought very close to the surface of the photoconductor and the light is emitted for every other light source, the exposure is performed in parallel with the moving direction of the surface of the photoconductor. A latent image pattern corresponding to such a striped pattern can be formed for cleaning.

When the invention according to claim 2 is implemented,
A latent image pattern for cleaning is formed in the same manner as in the cleaning mode of the above embodiment. At this time, the on / off cycle of the light source in the latent image pattern forming means 17 is lengthened to have a pitch of 2 mm or more, for example, A 5 mm pitch striped pattern is exposed.

FIG. 3 shows the potential distribution of the latent image pattern for cleaning thus formed. That is, this cleaning latent image pattern is substantially V
It is formed with two potentials of ₁ and V ₂ (| V ₁ |> | V ₂ |). In the example described, both V ₁ and V ₂ are negative.

At this time, on the metal core roll of the transfer member 20, as shown in FIG. 3, an intermediate potential between the potentials V ₁ and V ₂ :
When V ₀ is applied by “voltage applying means (which is configured to switch the power supply for transfer and the power supply for cleaning in the image forming mode)” (not shown), the positive toner on the transfer member 20 becomes The negative polarity toner is transferred to the portion of potential: V ₁ on the photoconductor 10 and is transferred to the portion of potential V ₂ respectively, and then removed and collected from the photoconductor 10 by the cleaning device 22. Thus, the surface of the transfer member 20 is cleaned.

In any of the embodiments described above, claims 3 and 4
It is also the embodiment of 5, 6, and 8.

In order to carry out the invention according to claim 4, for example, in the apparatus of FIG. 1, the optical writing means 14 is replaced with an image exposure device in a normal analog copying apparatus, and a space between the image exposure part and the developing part is provided. A well-known erase device is provided, and in the image forming mode, a positive electrostatic latent image is formed by image exposure,
After the non-image area is erased, normal development may be performed.

In the cleaning mode, after the photoreceptor 10 is uniformly charged, the latent image pattern forming means 17 forms the above-mentioned two types of latent image patterns to determine whether the edge effect or the voltage is applied to the transfer member. Cleaning may be performed by using such a method, but it is necessary to devise a method for preventing the uniformly charged surface of the photoconductor from being developed by the developing device.

For this purpose, the bias voltage in the developing device is increased to enhance the binding force of the developing roll to the toner, or the charge polarity of the photoconductor 10 is made opposite to the charge polarity in the image forming mode. Good (in this case, of course, a photosensitive member having “both chargeability” is used).

When an electrostatic latent image is formed by using the optical writing means 14 as in the device example shown in FIG. 1, a latent image pattern for cleaning can be formed by the optical writing means 14. Also in this case, the bias of the developing device is switched or the developing device is retracted from the developing unit so that the latent image pattern is not developed by the developing device.

FIG. 4 shows only a characteristic part of one embodiment of the invention as defined in claim 10.

A gear 21 for transmitting a driving force is coaxially fixed to the transfer member 20, and the driving gear 23, which is a "peripheral speed switching means", can engage with the gear 21 or release the engagement. It is like this.

In the image forming mode, the transfer member 20 is driven by the photosensitive member 10, and in the cleaning mode, the drive gear 2
3 is meshed with the gear 21 so as to have a peripheral speed different from that of the photoconductor 10. By doing so, the surface of the transfer member 20 is rubbed against the surface of the photoconductor 10, so that the cleaning effect is further improved.

The cleaning method of each of the embodiments described above can be similarly applied to the cleaning of the transfer member 12 in FIG.

A recording sheet guide member 25 as shown in FIG. 5 can be considered as a belt-shaped or roll-shaped member which comes into contact with the image carrier and rotates in a circulating manner.
The recording sheet guide member 25 includes a guide 18 and a transfer device 27.
In between, the recording sheet S fed from the guide 18 is rotated to come into contact with the photoconductor 10 and is guided to the transfer portion. It is obvious that the present invention can also be applied to cleaning such a recording sheet guide member.

Further, it can be applied to the developing roll 161 and the cleaning roll 221 as required.

[0068]

As described above, according to the present invention, a novel image forming apparatus can be provided. Since the present invention is configured as described above, it is possible to effectively clean the member that rotates in contact with the image carrier (claims 1-10).

According to the invention of claim 5, it is easy to form a latent image pattern for cleaning.

In the ninth aspect of the invention, the dedicated latent image pattern forming means is not required, and the image forming apparatus does not become complicated and large.

According to the tenth aspect of the invention, the cleaning effect is further improved.

[Brief description of drawings]

FIG. 1 is a diagram for explaining one embodiment of the present invention.

FIG. 2 is a diagram for explaining cleaning with a latent image pattern for cleaning having many edge portions in the above-described embodiment.

FIG. 3 is a diagram for explaining an embodiment of the invention according to claim 2;

FIG. 4 is a diagram for explaining an embodiment of the invention according to claim 10;

FIG. 5 is a diagram for explaining a recording sheet guide member.

FIG. 6 is a diagram for explaining a conventional technique and its problems.

[Explanation of symbols]

 10 Photoconductor (Image Carrier) 20 Transfer Member 17 Latent Image Pattern Forming Means

Claims (10)

[Claims] 1. A belt-shaped or drum-shaped image bearing member is rotated in a fixed direction to form an electrostatic latent image, which is developed with toner. The toner image obtained is transferred onto a transfer sheet to form a desired image. In the image forming apparatus to be obtained, a cleaning mode for cleaning a belt-shaped or roll-shaped member which contacts the surface of the image bearing member and circulates can be executed separately from the image forming mode. An image forming apparatus comprising: a latent image pattern forming means for forming a latent image pattern for cleaning, which has many parts. 2. A belt-shaped or drum-shaped image bearing member is rotated in a fixed direction to form an electrostatic latent image, the latent image is developed with toner, and the obtained toner image is transferred onto a transfer sheet to form a desired image. In the image forming apparatus to be obtained, a cleaning mode for cleaning a belt-shaped or roll-shaped member that contacts the surface of the image bearing member and circulates can be executed separately from the image forming mode. Two potentials: V ₁ ,
V ₂ (| V ₁ |> | V ₂ |) latent image pattern forming means for forming a latent image pattern for cleaning, and a potential intermediate between the potentials V ₁ and V _{2 to} the member to be cleaned. An image forming apparatus comprising: a voltage applying unit that applies a voltage. 3. The image forming apparatus according to claim 1 or 2, wherein the electrostatic latent image formed on the image carrier is a negative electrostatic latent image and is reverse-developed with toner. Image forming apparatus. 4. The image forming apparatus according to claim 1 or 2, wherein the electrostatic latent image formed on the image bearing member is a positive electrostatic latent image, and the non-image area is erased and then toner is used. An image forming apparatus that is normally developed. 5. The image forming apparatus according to claim 1, 2 or 3 or 4, wherein the latent image pattern for cleaning is a striped pattern orthogonal or parallel to the moving direction of the peripheral surface of the image carrier. An image forming apparatus characterized by. 6. The image forming apparatus according to claim 1, 2 or 3 or 4 or 5, wherein the belt-shaped or roll-shaped member to be cleaned is a transfer member. 7. The image forming apparatus according to claim 1, 2 or 3 or 4 or 5, wherein the belt-shaped or roll-shaped member to be cleaned is a charging member or a recording sheet guide member. Forming equipment. 8. The image forming apparatus according to claim 1, 2 or 3 or 4 or 5 or 6 or 7, wherein the latent image pattern forming means has a belt-like or roll-like shape to be cleaned downstream of the developing device. An image forming apparatus, wherein the image forming apparatus is provided on the upstream side of a member. 9. The image forming apparatus according to claim 1, 2 or 3 or 4 or 5 or 6 or 7, wherein an electrostatic latent image for image formation is formed by an optical writing unit, and the optical writing unit is the latent image. An image forming apparatus that also functions as a pattern forming unit. 10. An image forming apparatus according to claim 1, 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9, wherein a peripheral speed of a belt-shaped or roll-shaped member to be cleaned is set to an image forming mode. An image forming apparatus having a peripheral speed switching means for switching between a cleaning mode and a cleaning mode.