JPH04138484A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the making of trouble caused by the shaving of the mark of the roller of an image carrier by disposing a transfer roller pressing quantity regulating members which come into contact with an image carrier surface part out of an image carrier surface region corresponding to the developing effective width region of a developing sleeve or a developing roller. CONSTITUTION:A position where the pressing quantity regulating members of a contact type electrifying member (electrifying roller) 2, and a transfer member (transfer roller) 6, come into contact with an image carrier surface, is set in the developing effective width region of a developing device, or the electrifying effective width region of an electrifying member 2, or the cleaning effective width region of a cleaning means (cleaning blade) 8, or the image carrier surface part out of the image carrier surface region corresponding to the transfer effective width region of a transfer means 6. Thus, the making of the trouble caused by the shaving of the mark of the roller of the image carrier 1 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to image forming apparatuses such as copying machines, printers, facsimile machines, computer terminals, and word processor output machines.

More specifically, an image carrier such as an electrophotographic photoreceptor or an electrostatic recording dielectric is provided with a charging means for charging the surface of the image carrier, a developing means for developing an electrostatic latent image formed on the surface of the image carrier, and a developing means for developing an electrostatic latent image formed on the surface of the image carrier. An image is formed by an image forming process means including a transfer means for transferring the developed image on the image carrier surface to a transfer material, and a cleaning means for contacting the image carrier surface and cleaning the image carrier surface after the developed image has been transferred to the transfer material. The present invention relates to an image forming apparatus configured to perform image formation and repeatedly use an image carrier for image formation.

(Prior Art) As described above, an image forming apparatus that uses a transfer method and uses an image bearing member to repeatedly form images is generally configured as a rotating drum type or a rotating belt type as an image bearing member, and is driven to rotate or rotated. A configuration is adopted in which image formation is repeatedly performed by applying a series of image forming process means to the surface of the image carrier that is being moved by driving.

Charging means, developing means, and
Various configurations and systems are known for individual process means such as transfer means and cleaning means, but the following are generally adopted.

The charging means is a non-contact type corona charger.

Recently, contact-type charging devices, which uniformly charge the surface of an image carrier to a predetermined polarity and potential by bringing a charging member to which a voltage is applied directly into contact with the surface of the image carrier as a charged object, have been introduced, which are better than corona chargers. However, it has attracted attention and has been put into practical use because of its advantages such as lower pressure, less generation of corona discharge products such as ozone, and the ability to make the device smaller and lower in cost.

The mechanism of charging is that dielectric breakdown of the air occurs in a small gap near the contact area between the charging member and the image carrier, and this causes charge to move from the charging member to the image carrier, resulting in charging. it is conceivable that.

The charging member is an electrically conductive member, generally in the form of a rotating body (charging roller) made of conductive elastic rubber, which is pressed against the surface of the image carrier against elasticity to a predetermined pressure. are placed in contact with each other. The charging member can also be in a form other than a roller type.

In addition to the corona charger, the transfer means often employs a transfer roller that rotates in contact with the image carrier. A transfer material is introduced into the contact nip between the image carrier and the transfer roller, and the transferable image on the image carrier surface is transferred to the transfer material surface using the bias applied to the transfer roller and the pressing force of the transfer roller. .

The transfer roller is generally made of conductive elastic rubber and is placed in contact with the surface of the image carrier by pressing against the surface of the image carrier with a predetermined amount of pressure.

The cleaning means uses a cleaning blade made of an elastic material such as rubber and wipes the surface of the image carrier by bringing its edge into contact with the surface of the image carrier, which is simple in construction, low cost, and has a toner removal function. is also excellent, so
It has been widely used in practice.

(Problems to be Solved by the Invention) When a contact-type charging member (hereinafter referred to as a charging roller) or a transfer member (hereinafter referred to as a transfer roller) as described above is adopted as a charging means or a transfer means, Charging rollers and transfer rollers such as the above are brought into pressure contact with the surface of the image carrier by applying a pressing force from a pressing member near both ends, but due to manufacturing errors in the pressing members, the image on the charging roller or transfer roller may The amount of pressure applied to the carrier at the pressure contact portion (contact nip portion) tends to be different at both ends, making it difficult to obtain a uniform charging state and transfer state.

Therefore, when both ends of the charging roller or transfer roller are pressed against the image carrier surface against elasticity and are in contact with the image carrier surface with a predetermined pressing force, the charging roller or transfer roller It is effective to provide a configuration in which a pressing amount regulating member is provided that prevents an increase in the pressing amount and maintains the pressing amount of the roller against the image carrier substantially constant at each longitudinal portion. Specifically, for example, abutment rollers or the like are provided concentrically on both ends of the charging roller or transfer roller as pressure amount regulating members, and the outer diameter is smaller than the outer diameter of the roller under no load. By pressing the roller against the image carrier surface against elasticity and maintaining that state until the abutment roller abuts against the image carrier surface, the roller can be pressed against the image carrier surface regardless of variations in the pressing characteristics of the pressing member or environmental changes. The amount of pressure is made approximately constant at each longitudinal portion.

In addition, in the above-mentioned developing means, the developing sleeve is maintained at a predetermined distance 11 (for example, several hundred μm) from the surface of the image carrier, so that a radius is set at both ends of the developing sleeve by the predetermined distance above the radius of the developing sleeve. The developing device is equipped with enlarged abutting rollers (spacer rollers), and the developing device is biasedly biased until the rollers at both ends abut against the surface of the image carrier, thereby maintaining the developing sleeve and the image carrier at a predetermined distance apart. ing.

The developing means also includes a developing roller that is brought into pressure contact with the image carrier.

However, as mentioned above, there is a problem when the charging roller, transfer roller, developing sleeve, etc. are provided with abutment rollers, etc., which contact the image carrier surface and serve as regulating members for the amount of pressure and spacers, on both ends of the charging roller, transfer roller, developing sleeve, etc. As durability progresses, the portion of the surface of the image carrier that is in contact with the abutment rollers gets scratched (hereinafter referred to as roller trace scraping), and the following troubles caused by this tend to occur.

■ Roller scratches on the surface area of the image carrier corresponding to the effective development width of the developing device are caused by, for example, the amount of toner adhering to that area in the case of reversal development, and conversely in the case of regular images. The amount decreases, and in either case, it becomes impossible to obtain a uniform development state.

(2) If the surface area of the image carrier is scratched by the rollers, which corresponds to the effective charging width of the charging means, the charging current may leak from the scratched portion, resulting in a temporary charging failure.

Furthermore, since the core metal of the image carrier is grounded, if the charging current leaks, noise will be added to the signal ground of the image forming apparatus, which may cause the CPU that controls the apparatus to run out of control.

(2) When the roller marks on the surface area of the image carrier corresponding to the cleaning effective width of the cleaning means are scraped, the toner in that area is not completely removed and remains.This residual toner varies depending on the configuration of the device, but for example, , stain the surface of the transfer material, stain the inside of the device, adhere to the charging roller, transfer roller, etc., and stain the back side of the transfer material.

(2) If the roller trace scrapes on the surface area of the image carrier corresponding to the effective transfer width of the transfer means, the transfer current may leak from the scraped portion, resulting in temporary transfer failure.

Furthermore, since the core metal of the image carrier is grounded, if the transfer current leaks, noise may be introduced to the signal land of the image forming apparatus, and the CPU that controls the apparatus may run out of control.

An object of the present invention is to prevent the above-mentioned troubles caused by scraping of roller marks on an image bearing member.

(Means for Solving the Problems) The present invention adjusts the contact position of the pressure amount regulating member of a contact-type charging member or transfer member with respect to the image carrier surface, which causes roller trace scraping on the image carrier surface, of a developing device. Set on a portion of the image carrier surface that is outside the image carrier surface region corresponding to the development effective width region, the charging effective width region of the charging member, the cleaning effective width region of the cleaning means, or the transfer effective width region of the transfer means. It is.

(Function) With the above method, the image carrier surface area corresponds to the developing effective width of the developing device, the image carrier surface area corresponds to the charging effective width of the charging means, or the image carrier surface area corresponds to the cleaning effective width. Since roller marks and abrasions do not occur in the image carrier surface region or in the image carrier surface region corresponding to the effective transfer width of the transfer means, troubles such as those described in (1) to (3) above can be eliminated.

(Embodiment) FIG. 1 is a perspective view of essential parts of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view showing the arrangement of process equipment. This example is a laser beam printer or copying machine that uses a transfer electrophotographic process.

Reference numeral 1 designates a drum-type photoreceptor (hereinafter referred to as a photoreceptor drum) provided with an OPC photoreceptor layer as an image carrier, and is rotated clockwise as indicated by arrow a at a predetermined circumferential speed (process speed).

Reference numeral 2 denotes a charging roller as a charging member of the contact type charging means. The charging roller 2 of this example includes a core metal 2a, a conductive elastic rubber roller portion 2b formed concentrically around the outer periphery of the core metal by mold molding, etc., and a conductive elastic rubber roller portion 2b that is rotatably provided concentrically at both ends of the core metal 2a. Abutting roller 3 as a member for determining the amount of pressure applied to the charging roller
It consists of 3. The outer diameter of the abutting rollers 3 is set to be slightly smaller than the outer diameter of the rubber roller portion 2b of the charging roller 2 in the no-load state.

The charging roller 2 is placed substantially parallel to the photosensitive drum 1, and both ends of the core metal 1a are rotatably supported by bearing members (not shown), and both ends of the core metal 18 are pressed by pressing members such as springs (not shown). Then, the rubber roller portion 2b is brought into pressure contact with the surface of the photosensitive drum. Nl (FIG. 2) indicates the contact nip.

The charging roller 2 is pressed against the photosensitive drum 1 by a pressing member against the elasticity of the rubber roller 2b until the abutting rollers 3 at both ends abut against the photosensitive drum 1, and this state is maintained.

As a result, the amount of pressure of the charging roller 2 against the photosensitive drum 1 is made substantially constant at each longitudinal portion of the charging roller, and this state is maintained, regardless of variations in the pressing characteristics of the pressing member or environmental changes. The charging roller 2 rotates as the photosensitive drum 1 rotates.

11 is a bias application power source for the charging roller 2;
By applying a DC voltage with a predetermined polarity and voltage, or a predetermined superimposed voltage of a DC voltage and an oscillating voltage such as an alternating current, through the core metal 28, one surface of the rotating photosensitive drum is brought into contact with a predetermined polarity and potential. It is charged in a similar manner. In this embodiment, one surface of the photosensitive drum is uniformly charged to about 1,700 μm.

The surface of the rotating photosensitive drum that has been subjected to the charging process is then subjected to image forming exposure (slit exposure) of the document image by an exposure means (not shown).
By receiving image exposure such as scanning exposure of image-modulated laser light (see FIG. 2), an electrostatic latent image corresponding to the exposure image information is formed.

13 (FIG. 2) is a jumping developing type developing device. Reference numeral 4 designates a developing sleeve opposed to the photosensitive drum 1, and reference numeral 5 designates rotatable abutting rollers provided concentrically with the sleeve at both ends of the developing sleeve. The abutting rollers 5 are slightly larger than the outer diameter of the developing sleeve 4. By holding the developing device 13 in an even-odd biased state toward the photosensitive drum 1 until the rollers 5 abut against the photosensitive drum 1, the developing sleeve 4 moves from the surface of the photosensitive drum 1 to the roller 5.
- A predetermined distance α (FIG. 2, for example, several 100 μm) corresponding to the diameter difference between the sleeve 4 and the sleeve 4 is maintained.

The developing device 13 in this example is a reversal developing device and stores negatively charged toner, and a negative DC voltage and an oscillating voltage such as an alternating current are applied to the developing sleeve 4 from a power source 12.
The electrostatic latent image formed on the surface is reverse developed.

Reference numeral 6 denotes a transfer roller as a transfer member of the contact type transfer means. The transfer roller 6 of this example includes a core metal 6a, a conductive elastic rubber roller portion 6b (volume resistivity, e.g., 109 Ωcm or less) formed concentrically and integrally on the outer periphery of the core metal by molding, etc., and a core metal 6a. It consists of abutting rollers 7, 7 as transfer roller pressing amount regulating members provided concentrically and rotatably at both ends.

The outer diameter of the abutting rollers 7 is set to be slightly smaller than the outer diameter of the rubber roller portion 6b when the transfer roller 6 is under no load. The transfer roller 6 is placed substantially parallel to the photosensitive drum 1, and both ends of the core metal 6a are rotatably supported by bearing members (not shown), and both ends of the core metal 6a are pressed by pressing members such as springs (not shown). Then, the rubber roller portion 6b is brought into pressure contact with the surface of the photosensitive drum. N2 (FIG. 2) indicates the contact nip. The transfer roller 6 is pressed against the photosensitive drum 1 by a pressing member against the elasticity of the rubber roller portion 6b until the abutment rollers 7, 7 at both ends abut against the photosensitive drum surface, and this state is maintained.

As a result, the amount of pressure of the transfer roller 6 against the photosensitive drum 1 is substantially stopped at each longitudinal portion of the transfer roller, and this state is maintained, regardless of variations in the pressing characteristics of the pressing member or environmental changes.

The transfer roller 6 is rotationally driven in the forward direction of the photosensitive drum 1 by a drive system (not shown) so that the circumferential speed at the contact nip portion N2 is approximately the same as the circumferential speed of the photosensitive drum 1.

10 is a bias application power source for the transfer roller 6;
A DC bias of a predetermined polarity and potential is applied via the metal core 6a. In this embodiment, a DC bias having a polarity opposite to that of the negatively charged toner in the developing device 13 is applied.

When the leading edge of the formed image on the surface of the photosensitive drum 1 reaches the contact nip N2 (transfer part) between the photosensitive drum 1 and the transfer roller 6, the leading edge of the transfer material P also reaches and enters the contact nip N2. The transfer material P is fed from a paper feeding means (not shown) at a proper timing, and application of a bias voltage to the transfer roller 6 is started, and the developed image on the photosensitive drum 1 side is deposited on the surface of the transfer material P passing through the transfer portion N2. are transcribed in sequence.

The transfer material P that has passed through the transfer section N2 is separated from the photosensitive drum 1, is conveyed to a fixing means (not shown), undergoes image fixation, and is output as an image forming apparatus.

After the image has been transferred, the surface of the photosensitive drum 1 is cleaned by wiping off adhering contaminants such as residual toner by a cleaning plate 8 of a cleaning device 14 (FIG. 2), and is repeatedly used for image formation.

FIG. 3 shows the effective width A of the photosensitive drum, the effective cleaning width B of the cleaning blade 8, and 11! - Charging effective width C1 of the electric roller, transfer effective width D of the transfer roller 6, maximum paper passing width E, plasto effective width F of the developing sleeve 4 (development effective width)
shows the interrelationship between

The relationship is A<B<C<D<E<F. G indicates the contact width of the abutting rollers 3, 5, and 7 with respect to the photosensitive drum 1.

Abutting rollers 7 at both ends of the transfer roller 6 and charging roller 2
・By arranging 7.3.3 so as to contact the portion of the surface of the photosensitive drum outside the effective blast width F of the developing sleeve 4, no roller marks are created on the surface area of the photosensitive drum corresponding to the effective blast width F of the developing sleeve 4. No scraping occurs, and uniform developability is maintained over a long period of time.

By arranging the abutment rollers 7 at both ends of the transfer roller 6 so as to contact the photosensitive drum surface area outside the charging effective width C of the charging roller 2, no roller marks are left on the photosensitive drum surface area within the charging effective width. No scraping occurs, and during durability, temporary charging failures due to charging current leaks and control failures due to erroneous leaks are prevented.

Abutting rollers 7 at both ends of the transfer roller 6 and charging roller 2
- By arranging 7.3.3 so as to contact the portion of the photosensitive drum surface outside the cleaning effective width B of the cleaning blade 8, roller traces and scrapes occur in the photosensitive drum surface area corresponding to the cleaning effective width B. This prevents poor cleaning and toner stains on the transfer material, charging roller, and transfer roller during durability.

By arranging the abutting rollers 3 at both ends of the charging roller 2 so as to contact the portion of the photosensitive drum surface outside the effective transfer width of the transfer roller 6, the photosensitive drum surface corresponding to the area within the effective transfer width is No roller marks are produced in the area, and during durability, temporary charging failures due to transfer current leaks and control failures due to erroneous leaks are prevented.

Further, in this embodiment, as shown in FIG. 3, the transfer roller effective width is larger than the blasting effective width F (developing effective width) of the developing sleeve, and the charging roller effective width C is larger than the transfer roller effective width. The effective width B of the cleaning plate is made larger than the effective width C of the charging roller, and a charging roller (
The charging roller abutting rollers 3, 3 and the transfer rollers (transfer roller abutting rollers) 7, 7 are in contact with each other. In this way, the charging roller and transfer roller are connected to the effective developing width of the developing sleeve.
By installing the roller outside the effective width of the transfer roller, the effective width of the charging roller, and the effective width of the cleaning roller, even if the photoreceptor is scraped by the charging roller and transfer roller, the effective width of the developing sleeve, the effective width of the transfer roller, and the charging roller Uniform development, transfer, charging, and cleaning conditions can be maintained within the effective width and cleaning blade effective width, respectively.

The developing device may be a developing roller that is pressed into contact with the photosensitive drum.

(Effects of the Invention) As described above, according to the present invention, it is possible to prevent the occurrence of troubles caused by the above-mentioned scraping of the roller marks on the image bearing member, and the intended purpose is well achieved.

[Brief explanation of drawings]

FIG. 1 is a perspective view of essential parts of an embodiment of the device. FIG. 2 is a schematic cross-sectional view showing the arrangement of process equipment. Figure 3 is a diagram showing the relationship between the effective widths of each process equipment. 1 is a rotating photosensitive drum 2 as an image bearing member, and a charging roller 3 is a charging means.
A charging roller 4 is a developing sleeve 5, which is a roller that abuts the sleeve against a photosensitive drum; a roller 6, which is a transfer means; a transfer roller 7, a roller that abuts a photosensitive drum of the roller (
Transfer roller) 8 is the cleaning blade patent applicant Canon Co., Ltd.

Claims (9)

[Claims] (1) An image forming process that includes a charging device that charges the surface of the image carrier, a developing device that develops the electrostatic latent image formed on the surface of the image carrier, and a transfer device that transfers the developed image on the surface of the image carrier to a transfer material. In an image forming apparatus configured to perform image formation by a means and to repeatedly use an image carrier for image formation, the developing means is a developing sleeve or an image carrier maintained at a predetermined distance from the surface of the image carrier. It is a means for supplying toner to an image carrier from a developing roller that is brought into pressure contact with the body to develop an electrostatic latent image, and the transfer means is a transfer roller that rotates in contact with the surface of the image carrier. , When the transfer roller is pressed against the image carrier surface against elasticity and is in contact with the image carrier surface with a predetermined amount of pressure, the transfer roller contacts the image carrier surface and prevents the transfer roller from further increasing the amount of pressure, thereby changing the image on the transfer roller. A transfer roller pressure amount regulating member that maintains a predetermined amount of pressure on the carrier is brought into contact with a portion of the image carrier surface that is outside an image carrier surface region corresponding to an effective development width region of the developing sleeve or the developing roller. An image forming apparatus characterized by: (2) An image forming process that includes a charging device that charges the surface of the image carrier, a developing device that develops the electrostatic latent image formed on the surface of the image carrier, and a transfer device that transfers the developed image on the surface of the image carrier onto a transfer material. In an image forming apparatus configured to perform image formation by a means and to repeatedly use an image carrier for image formation, the charging means is a charging member that comes into contact with a surface of the image carrier to charge the surface of the image carrier; The transfer means is a transfer roller that rotates in contact with the surface of the image carrier, and the transfer roller is pressed against the surface of the image carrier against elasticity and is in contact with the surface of the image carrier with a predetermined amount of pressure. A transfer roller pressing amount regulating member that contacts the transfer roller to prevent further increase in the pressing amount and maintains the pressing amount of the transfer roller against the image carrier at a predetermined level is connected to the image corresponding to the charging effective width area of the charging member. An image forming apparatus characterized in that the image forming apparatus is arranged so as to be in contact with a surface portion of an image carrier that is outside a surface region of the image carrier. (3) A charging device that charges the surface of the image carrier, a developing device that develops the electrostatic latent image formed on the surface of the image carrier, a transfer device that transfers the developed image on the surface of the image carrier to a transfer material, and a device that charges the surface of the image carrier. In an image forming apparatus configured to perform image formation by an image forming process means including a cleaning means that contacts and cleans the surface of the image carrier after the developed image is transferred to the transfer material, and the image carrier is repeatedly subjected to image formation, The transfer means is a transfer roller that rotates in contact with the image carrier surface, and the transfer roller is pressed against the image carrier surface against elasticity and contacts the image carrier surface with a predetermined amount of pressure. A transfer roller pressing amount regulating member that prevents a further increase in the pressing amount of the transfer roller and maintains the pressing amount of the transfer roller against the image bearing member at a predetermined level is attached to the image bearing member corresponding to the cleaning effective width area of the cleaning means. An image forming apparatus characterized in that the image forming apparatus is arranged so as to be in contact with a surface portion of an image carrier that is outside a body surface area. (4) An image forming process that includes a charging device that charges the surface of the image carrier, a developing device that develops the electrostatic latent image formed on the surface of the image carrier, and a transfer device that transfers the developed image on the surface of the image carrier to a transfer material. In an image forming apparatus configured to perform image formation by a means and to repeatedly use an image carrier for image formation, the charging means is a charging member that comes into contact with a surface of the image carrier to charge the surface of the image carrier; The developing means supplies toner to the image carrier from a developing sleeve maintained at a predetermined distance from the surface of the image carrier or a developing roller brought into pressure contact with the image carrier to develop the electrostatic latent image. The charging member contacts the image carrier surface in a state in which the charging member is pressed against the image carrier surface against elasticity and contacts the image carrier surface with a predetermined amount of pressure, and prevents the charging member from further increasing the amount of pressure. A charging member pressing amount regulating member for maintaining a predetermined pressing amount of the charging member against the image carrier is applied to a portion of the image carrier surface that is outside the image carrier surface region corresponding to the effective development width region of the developing sleeve or the developing roller. An image forming apparatus characterized in that the image forming apparatus is arranged so as to be in contact with each other. (5) An image forming process that includes a charging device that charges the surface of the image carrier, a developing device that develops the electrostatic latent image formed on the surface of the image carrier, and a transfer device that transfers the developed image on the surface of the image carrier to a transfer material. In an image forming apparatus configured to perform image formation by a means and to repeatedly use an image carrier for image formation, the charging means is a charging member that comes into contact with a surface of the image carrier to charge the surface of the image carrier; When the charging member is pressed against the surface of the image carrier against elasticity and contacts the surface of the image carrier with a predetermined amount of pressure, the charging member contacts the surface of the image carrier and prevents the charging member from further increasing the amount of pressure, thereby causing the charging member to carry the image. A charging member pressing amount regulating member for maintaining a predetermined amount of pressing against the body is disposed so as to be in contact with a portion of the surface of the image carrier that is outside a surface region of the image carrier corresponding to the effective transfer width region of the transfer means. An image forming apparatus characterized by: (6) A charging device that charges the surface of the image carrier, a developing device that develops the electrostatic latent image formed on the surface of the image carrier, a transfer device that transfers the developed image on the surface of the image carrier to a transfer material, and a device that charges the surface of the image carrier. In an image forming apparatus configured to perform image formation by an image forming process means including a cleaning means that contacts and cleans the surface of the image carrier after the developed image is transferred to the transfer material, and the image carrier is repeatedly subjected to image formation, The charging means is a charging member that charges the surface of the image carrier by contacting the surface of the image carrier, and when the charging member is pressed against the surface of the image carrier against elasticity and comes into contact with the surface of the image carrier with a predetermined amount of pressure, the image is charged. A charging member pressing amount regulating member that contacts the surface of the charging member to prevent further increase in the pressing amount of the charging member to maintain a predetermined amount of pressing of the charging member against the image bearing member is provided in the cleaning effective width region of the cleaning means. An image forming apparatus characterized in that the image forming apparatus is arranged so as to be in contact with a surface portion of an image carrier that is outside a corresponding image carrier surface area. (7) Claims (2) and (4), characterized in that the charging member is a charging roller that rotates in contact with the image carrier.
Or the image forming apparatus described in (5) above. (8) Claim (3) characterized in that the image carrier surface contacting member of the cleaning means is a cleaning blade.
Or the image forming apparatus described in (6) above. (9) The image forming apparatus according to any one of claims (1) to (6), wherein the pressure amount regulating member of the transfer roller or the charging member is a roller that abuts against the surface of the image carrier.