JP3458332B2 - Image forming machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic image forming machine such as an electrostatic copying machine, a printing machine and a facsimile, and more specifically, an image bearing means which may be in the form of a rotary drum or an endless belt, and an image bearing means. To a predetermined polarity, exposing means for selectively removing the charged image bearing means to form an electrostatic latent image, and developing the electrostatic latent image on the image bearing means into a toner image. The reversal developing means, the transfer means for transferring the toner image on the image carrying means onto the image receiving member which may be plain paper, and the cleaning means for removing the toner remaining on the image carrying means after the transfer. Image forming machine.

[0002]

2. Description of the Related Art In an image forming machine of the above-mentioned form, a charging means which can be constituted by a corona discharger charges an image carrying means to a specific polarity with a predetermined effective charging width. The width of the image carrier is larger than the effective charge width, and the surface of the image carrier is not stably charged to a predetermined potential on both sides of the effective charge width, and the potential is substantially lower than the predetermined potential. It can have zero potential or opposite polarity. In the development by the reversal developing means, the toner is not attached to the portion where the charge potential remains, but the toner is attached to the charge eliminating portion where the charge potential is lost. Therefore, in the image forming machine employing the reversal developing means, the toner tends to be attached and contaminated on both sides of the effective charging width on the surface of the image carrying means. Even if the effective developing width by the developing means is substantially equal to or slightly smaller than the effective charging width, the floating toner such as toner repelled by the charging potential on the image carrying means causes an image on both sides of the effective charging width. It can be deposited on the carrier means.

On the other hand, as the transfer means in the image forming machine of the above-mentioned form, a transfer roller to which a transfer voltage is applied instead of the transfer corona discharger has been recently used, or it is rotationally driven. An endless transfer belt having a structure including an endless transfer belt and a transfer voltage applying unit for applying a transfer voltage to the back surface of the transfer belt has been proposed and put into practical use. The transfer roller or the transfer belt is brought into contact with the image carrying means through the image receiving member and directly over the entire width thereof. The transfer voltage applying means is usually composed of a voltage applying roller which is made of a conductive material and to which the transfer voltage is applied. The width of the voltage application roller is substantially the same as the width of the transfer belt. Therefore, the transfer belt is brought into contact with the image carrying means over its entire width and the transfer voltage is applied over its entire width.

When the width of the transfer roller or the transfer belt is larger than the effective charging width, the maximum image receiving member is usually slightly smaller than the effective charging width, and therefore, the image receiving member is interposed on both sides of the effective charging width. Without contact, the transfer roller or transfer belt is brought into direct contact with the image carrying means, so that the toner adhering to the image carrying means is transferred onto the transfer roller or transfer belt, whereby the surface of the transfer roller or transfer belt is transferred by the toner. It will be contaminated. When the both sides of the surface of the transfer roller or the transfer belt are contaminated with the toner, the contact state between the image carrying means and the transfer roller or the transfer belt is deteriorated, and transfer failure is generated. The surface of the image carrying means is damaged. It causes problems such as being lost. As a solution to such a problem, Japanese Patent No. 25975
Japanese Patent Laid-Open No. 40 proposes to make the width of the transfer roller (or transfer belt) smaller than the effective charging width.

[0005]

When the width of the transfer roller or the transfer belt is made smaller than the effective charging width, the toner adhering to the image carrying means on both sides of the effective charging width is transferred to the transfer roller or the transfer belt. This is prevented, but the following separate problems arise. Primarily,
When the width of the transfer roller or the transfer belt is made smaller than the effective charging width, the width of the transfer roller or the transfer belt becomes substantially the same as or smaller than the maximum image receiving member, and the transferability of the image receiving member by the transfer roller or the transfer belt deteriorates. However, the image receiving member tends to skew or jam.
Secondly, especially when the effective cleaning width of the cleaning means is substantially the same as or smaller than the effective charging width, the toner adhering to both sides of the effective charging width on the surface of the image carrying means is accumulated without being removed. Due to this, the following phenomena occur. That is, the charging means, the reversal developing means, and the cooling means respectively have components that extend outward in the width direction or are positioned outward in the width direction with respect to the effective charging width, the effective developing width, and the effective cleaning width, for example, image carrying means. A gap setting roller for setting the gap between the toner and the toner is sufficiently precise, and various sealing members for preventing the toner from scattering are provided, but they are attached to both sides of the effective charge width on the surface of the image carrier. The accumulated toner stagnates and accumulates between these constituent elements and the surface of the image carrying means, thereby impairing the interval setting function of the interval setting roller, impairing the sealing function of various sealing members, and again the image carrying means. It is not uncommon for the interval setting roller or various sealing members to be damaged. Further, it is not uncommon for the toner attached to both sides of the effective charging width on the surface of the image carrier to accidentally float and contaminate the inside or the periphery of the image forming apparatus. In particular, floating toner adheres to the bearing mechanism of the transfer roller, the bearing mechanism of the support roller for the transfer belt, the transfer voltage applying means to the transfer roller or the transfer belt, and not only contaminates them, but also inhibits these functions. Tend to do.

The present invention has been made in view of the above facts, and its main technical problem is to solve the above-mentioned various problems relating to the toner adhered to both sides of the effective charge width on the surface of the image carrier. The solution is to adopt a unique structure for the transfer means.

[0007]

DISCLOSURE OF THE INVENTION As a result of earnest research, the present inventors have constructed a transfer belt in which the transfer means is rotationally driven, and a transfer voltage applying means for applying a transfer voltage to the back surface of the transfer belt. and, a transfer voltage applying means applies a transfer voltage to the transfer belt at a predetermined effective transfer width, the surface of the transfer belt is brought into contact with and directly image carrying means through the image receiving member at a predetermined effective contact width, the effective The contact width is set to be larger than the effective developing width, the effective cleaning width and / or the effective charging width and larger than the effective transfer width, and the interval setting roller or various sealing members are set within the effective contact width. It has been found that the above-mentioned main technical problems can be achieved by arranging them.

In one aspect of the present invention, an image carrier means that is sequentially moved through a charging area, an exposure area, a developing area, a transfer area and a cleaning area, and the image carrying means is charged in the charging area. Charging means, exposing means for selectively discharging the image carrying means in the exposure area to form an electrostatic latent image on the image carrying means, and toner for the electrostatic latent image in the developing area. Reversal developing means for developing an image, transfer means for transferring the toner image on the image carrying means onto the image receiving member in the transfer area, and on the image carrying means after transfer in the cleaning area. Cleaning means for removing residual toner, and the transfer means includes a transfer belt which is rotationally driven and a transfer voltage applying means for applying a transfer voltage to the back surface of the transfer belt. In the forming machine, the reversal developing means develops the image bearing means with a predetermined effective developing width, the transfer voltage applying means applies the transfer voltage to the transfer belt with a predetermined effective transfer width, and the surface of the transfer belt has a predetermined value. An image having an effective contact width which is brought into contact with the image bearing means directly and through the image receiving member, the effective contact width being larger than the effective developing width and larger than the effective transfer width. A forming machine is provided.

In a preferred embodiment, the developing means is
A developing housing having an opening at a portion facing the image bearing means.
And the image through the opening disposed in the developer housing.
Developer applying means acting on the carrying means, and the developing housing
And a free end on the upstream side of the developer applying means.
Upstream seal part whose edge is in contact with the image bearing means
Material, both of the developing material applying means disposed in the developing housing
A pair of side shields that are brought into contact with the image bearing means on the side.
Rotatably mounted on the developing member and / or the developing housing.
Is attached to the image bearing means on both sides of the developer applying means.
A pair of gap setting rollers that are brought into contact with each other, and
Flow seal member width, between the outer ends of the pair of side seal members
Length and / or length of outer ends of the pair of spacing rollers
It Is Greater than the effective development width and greater than the effective contact width
It has a small width.

In another aspect of the present invention, an image carrier means that is sequentially moved through a charging area, an exposure area, a developing area, a transfer area, and a cleaning area, and the image carrying means is charged in the charging area. Charging means, an exposing means for selectively discharging the image carrying means in the exposure area to form an electrostatic latent image on the image carrying means, and an electrostatic latent image in the developing area. Reversal developing means for developing to a toner image, transfer means for transferring the toner image on the image carrying means onto the image receiving member in the transfer area, and on the image carrying means after transfer in the cleaning area. Cleaning means for removing the residual toner, and the transfer means includes a transfer belt that is rotationally driven and a transfer voltage application means that applies a transfer voltage to the back surface of the transfer belt. In the image forming machine, the cleaning means removes the toner remaining on the image carrying means with a predetermined effective cleaning width, and the transfer voltage applying means applies the transfer voltage to the transfer belt with a predetermined effective transfer width. The surface of the transfer belt is brought into contact with the image bearing means directly and through the image receiving member with a predetermined effective contact width, the effective contact width being larger than the effective cleaning width and larger than the effective transfer width. An image forming machine characterized by the above is provided.

In a preferred embodiment, the cleaning means has a cleaning housing having an opening at a portion facing the image carrying means, and a front end portion of the cleaning housing is pressed against the image carrying means. A cleaning blade, an upstream seal member disposed in the cleaning housing and having a free edge in contact with the image carrying means on the upstream side of the cleaning blade, and / or both sides of the cleaning blade disposed in the cleaning housing. And a pair of side seal members that are brought into contact with the image carrying means in the above, the width of the upstream seal member and / or the length between the outer ends of the pair of side seal members is larger than the effective cleaning width and the effective cleaning width is larger than the effective cleaning width. It has a width smaller than the contact width.

In still another aspect of the present invention, an image carrier means that is moved sequentially through a charging area, an exposure area, a developing area, a transfer area and a cleaning area, and the image carrying means is charged in the charging area. A charging means for biasing, an exposing means for selectively discharging the image carrying means in the exposure area to form an electrostatic latent image on the image carrying means, and an electrostatic latent image in the developing area. Developing means for developing the toner image into a toner image, a transfer means for transferring the toner image on the image carrying means onto the image receiving member in the transfer area, and an image carrying means after the transfer in the cleaning area. And a transfer belt which is driven to rotate and a transfer voltage applying section which applies a transfer voltage to the back surface of the transfer belt. In the image forming machine, the charging means is a corona discharger for charging the image bearing means with a predetermined effective charging width, and the corona discharger is rotatably mounted on the corona discharger to contact the image bearing means on both sides of the effective charging width. The transfer voltage applying means includes a pair of interval setting rollers that are in contact with each other.
The transfer voltage is applied to the transfer belt with a constant effective transfer width,
The surface of the transfer belt has a predetermined effective contact width through the image receiving member.
And directly contacting the image bearing means,
The contact width is larger than the width between the outer ends of the pair of spacing rollers.
An image forming machine which is large and is larger than the effective transfer width .

In any aspect of the present invention, the effective contact width is preferably larger than the maximum image receiving member width.
Further, the transfer means includes a belt cleaning means for removing adhered toner from the surface of the transfer belt, and the effective cleaning width of the belt cleaning means is preferably larger than the effective contact width.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of an image forming machine constructed according to the present invention will be described in more detail below with reference to the accompanying drawings.

FIG. 1 schematically illustrates the main components of a preferred embodiment of an image forming machine constructed in accordance with the present invention. The image forming machine shown in the figure has four image forming units arranged in tandem, namely a black toner image forming unit 2a, a magenta toner image forming unit 2b, a cyan toner image forming unit 2c and a yellow toner image forming unit 2d, and one transfer unit. The belt unit 4 is provided so that a color image can be formed. The transfer belt unit 4 includes a driven roller 6, a driven roller 8, a tension roller 10, and an endless transfer belt 12 wound around these (the transfer belt unit 4 further includes four voltage applying means). It also includes a voltage applying roller and a pressure roller attached to the voltage applying roller, which will be described later in detail). The driven roller 6 and the driven roller 8 are arranged at a predetermined interval in the left-right direction in FIG. The transfer belt 12 can be formed of a flexible material having conductivity such as conductive synthetic rubber. The driven roller 6 is rotationally driven in the direction indicated by the arrow 14, whereby the transfer belt 12 is rotationally driven in the direction indicated by the arrow 14. Black toner image forming unit 2a, magenta toner image forming unit 2b, cyan toner image forming unit 2c, and yellow toner image forming unit 2
d is arranged in a row so as to face the upper running portion of the transfer belt 12 in the transfer belt unit 4.

Each of the black toner image forming unit 2a, the magenta toner image forming unit 2b, the cyan toner image forming unit 2c and the yellow toner image forming unit 2d forms a toner image of a different color (hence, the respective developing processes). Except that the colors of the toners used in the means are different). Therefore,
The configuration of the black toner image forming unit 2a will be described in detail below, and the magenta toner image forming unit 2 will be described.
The detailed description of the configurations of b, the cyan toner image forming unit 2c, and the yellow toner image forming unit 2d is omitted to avoid duplication. The black toner image forming unit 2a includes a rotating drum 14 that constitutes an image bearing unit.
It has a. An electrostatic photoconductor is arranged on the outer peripheral surface of the rotary drum 14a. Rotating drum 14a
Is driven to rotate in the direction indicated by arrow 16a, and the outer peripheral surface thereof has a charging area 18a, an exposure area 20a, a developing area 22a, and a transfer area 2.
4a and the cleaning area 26a are sequentially moved. In the charging area 18a, the outer peripheral surface of the rotary drum 14a is charged to a specific polarity by the charging means 28a, and in the exposure area 20a, the outer peripheral surface of the rotary drum 14a is selectively exposed and discharged by the exposing means 30a. As a result, an electrostatic latent image is formed on the outer peripheral surface of the rotating drum 14a. In the developing area 22a, black toner is applied to the electrostatic latent image on the outer peripheral surface of the rotating drum 14a by the reversal developing means 32a, and the electrostatic latent image is developed into a black toner image. The reversal developing means 32a develops the electrostatic latent image into a toner image by a so-called reversal developing method, that is, the toner charged to the same polarity as the charging of the outer peripheral surface of the rotating drum 14a by the charging means 28a on the outer peripheral surface of the rotating drum 14a. The electrostatic latent image is developed into a toner image by selectively adhering to the area where the charge is removed. In a region of the outer peripheral surface of the rotating drum 14a where electric charges remain without being discharged, electrostatic repulsion prevents toner adhesion. In the transfer area 24, the black toner image on the outer peripheral surface of the rotary drum 14 a is transferred onto the image receiving member conveyed through the transfer area 24 by the action of the transfer means described in detail later. The image receiving member may be a plain paper sheet.
In the cleaning area 26a, the cleaning means 3
4a removes the toner remaining on the outer peripheral surface of the rotating drum 14a.

FIG. 2 shows the charging means 28a in the black toner image forming unit 2a. The charging unit 28a in the illustrated embodiment is composed of a corona discharger and has a shield case 36a extending in the axial direction of the rotary drum 14a. Shield case 36a
Is a long and narrow box-like shape having an opening on the surface facing the rotary drum 14a, that is, the lower surface, and a conductive wire 38a extending in the axial direction of the rotary drum 14a is stretched inside the shield case 36a. A grid 40a is arranged on the lower surface of the shield case 36a. A large number of slits are formed in the grid 40a in the main part excluding both ends thereof, and in the region of the width W1 where the large number of slits are formed, the outer peripheral surface of the rotating drum 14a is corona-discharged to cause the rotating drum to rotate. The outer peripheral surface of 14a is charged to a specific polarity. At both ends of the grid 40a, the grid 40a
Corona discharge is blocked by. Therefore, the charging means 28
Although "a" charges the outer peripheral surface of the rotating drum 14a in the region of the width W1. The outer peripheral surface of the rotating drum 14a is not substantially charged on both sides of the width W1. Therefore, the width W1 is nothing but the effective charging width of the charging means 28a. The charging means 28a shown in the drawing further includes a space setting roller 42a rotatably mounted on the shield case 36a on both sides of the grid 40a. The outer peripheral surface of the interval setting roller 42a is projected beyond the lower surface of the shield case 36a.
By bringing 2a into contact with the outer peripheral surface of the rotary drum 14a, the distance between the outer peripheral surface of the rotary drum 14a and the grid 40a of the charging means 28a is set to a predetermined value. The length between the widthwise outer ends of the pair of interval setting rollers 42a is W2, which is larger than the effective charging width W1.

The exposing means 30a may have a known form in which a large number of light emitting elements are arranged in the axial direction of the rotary drum 14a. The exposure unit 30a has a maximum exposure width W3.
In FIG. 8, the peripheral surface of the rotary drum 14a is selectively exposed to form a required electrostatic latent image.

Referring to FIG. 3 together with FIG. 1, the reversal developing means 32a, which may be of a known form per se, includes a developing housing 4 containing a developer (not shown).
4a is included. The developer may be a two-component developer including toner and carrier particles or a one-component developer including only toner. The rotary drum 1 is provided in the developing housing 44a.
An opening is formed in a portion facing the outer peripheral surface of 4a. A developer applying means 46a is disposed in the developing housing 44a, and the developer applying means 46a is provided in the rotary drum 14.
It has a sleeve member 48a extending in the axial direction of a.
The outer peripheral surface of the sleeve member 48a has a developing housing 44a.
Partially protruding through the opening of the. A stationary magnet (not shown) is arranged in the sleeve member 48a, and the sleeve member 48a is rotationally driven in the direction indicated by an arrow 50a. The developer is held on the outer peripheral surface of the sleeve member 48a by the magnetic attraction force of the stationary magnet,
The developer is applied to the electrostatic latent image formed on the outer peripheral surface of the rotating drum 14a. In the illustrated embodiment,
The stationary magnet is arranged in the area of the width W4, and the sleeve member 48a holds the developer on the outer peripheral surface thereof in the area of the width W4 and applies the developer to the outer peripheral surface of the rotary drum 14a. Therefore, the width W4 is the effective developing width of the reversal developing means 32a. Interval setting rollers 52a are rotatably arranged on both sides of the sleeve member 48a. The outer diameter of the interval setting roller 52a is larger than the outer diameter of the sleeve member 48a by a predetermined amount, and the outer peripheral surface of the sleeve member 48a and the outer peripheral surface of the rotary drum 14a are brought into contact with each other by bringing the interval setting roller 52a into contact with the outer peripheral surface of the rotary drum 14a. The distance from the surface is set to a predetermined value.
The length between the outer ends of the pair of interval setting rollers 52a is W5, which is larger than the effective developing width W4. In the developing housing 44a, the upstream seal member 5 is associated with the opening.
4a and a pair of side seal members 56a are provided.
The upstream seal member 54a, which can be formed of an appropriate synthetic resin film, has a strip shape that is elongated in the axial direction of the rotary drum 14a, and its free edge is the outer periphery of the rotary drum 14a on the upstream side of the developing area 22a. It is touching the surface. The pair of side sealing members 56a, which can be formed from a flexible material such as a pile sheet,
The rotary drum 14a is provided on both sides of the developer applying means 46a.
Is in contact with the outer peripheral surface of the. Upstream seal member 54
a and the pair of side seal members 56a are used for the developing housing 4
The toner contained in the developer 4a is provided to prevent the toner from scattering around. The upstream seal member 54a has a width W6 larger than the effective developing width W4. The length between the outer ends of the pair of side seal members 56a is W7, which is larger than the effective developing width W4.

Continuing the description with reference to FIG. 4 in conjunction with FIG. 1, the cleaning means 34, which may be of a form known per se.
a includes a cleaning housing 58a. An opening is formed in a portion of the cleaning housing 58a facing the outer peripheral surface of the rotary drum 14a. The cleaning blade 58 is attached to the cleaning housing 58a.
0a and the cleaning brush 62a are attached.
The cleaning blade 60a is made of a flexible material such as synthetic rubber, and the tip edge portion thereof is the rotating drum 14.
It is pressed against the outer peripheral surface of a. Cleaning brush 6
2a is rotated in a direction indicated by an arrow 63a, and a flexible brush arranged on the outer peripheral surface of the 2a acts on the outer peripheral surface of the rotary drum 14a. The cleaning brush 62a partially removes the toner remaining on the peripheral surface of the rotary drum 14a after the transfer, and applies a so-called loosening action to the residual toner. The cleaning blade 60a removes the toner subjected to the loosening action from the outer peripheral surface of the rotary drum 14a.
The cleaning blade 60a is slenderly extended over the width W8 in the axial direction of the rotary drum 14a, and the width W8 is the effective cleaning width of the cleaning means 34a. The width of the cleaning brush 62a is also substantially the same as the width W8, and both ends of the cleaning brush 62a are substantially aligned with both ends of the cleaning blade 60a. The cleaning housing 58a is also provided with an upstream seal member 64a and a pair of side seal members 66a in association with the opening. Upstream seal member 64a that can be formed from an appropriate synthetic resin film
Has a strip shape that extends in the axial direction of the rotary drum 14a, and its free end edge has a cleaning area 26.
The outer peripheral surface of the rotary drum 14a is brought into contact with the upstream side of a. A pair of side seal members 66a, which can be formed of a flexible material such as a pile sheet, are brought into contact with the outer peripheral surface of the rotary drum 14a on both sides of the cleaning blade 60a and the cleaning brush 62a. The upstream seal member 64a and the pair of side seal members 66a are provided to prevent the toner removed from the outer peripheral surface of the rotary drum 14a and contained in the cleaning housing 58a from scattering around. The upstream seal member 64a has a width W9 larger than the effective cleaning width W8. Also, the pair of side seal members 66a
The length between the outer ends of the above is also a width W10 larger than the effective cleaning width W8. Cleaning housing 58a
Further, a static eliminator 68a is disposed on the lower surface thereof. The static elimination means 68a is, for example, the rotary drum 14a.
Can be formed from a large number of light emitting elements arranged in the axial direction of the rotating drum 14a by irradiating the outer peripheral surface of the rotating drum 14a between the transfer area 24a and the cleaning area 26a.
The residual charge on the outer peripheral surface of a is eliminated. Static eliminator 68
“A” irradiates the outer peripheral surface of the rotary drum 14a with an effective charge removal width W11 that is larger than the effective cleaning width W8.

Transfer belt unit 4 constituting transfer means
Includes a support frame body 70 (a part of which is shown by a chain double-dashed line in FIG. 5) arranged at a predetermined position in a housing (not shown) of the image forming machine. 6, the driven roller 8 and the tension roller 10 are rotatably mounted on the support frame 70. The illustrated transfer belt unit 4 includes the above-mentioned four image forming units, that is, the black toner image forming unit 2a, the magenta toner image forming unit 2b, and the cyan toner image forming unit 2c.
And the transfer voltage applying means 72a, 72b, 72c and 72d arranged in association with the transfer areas 24a, 24b, 24c and 24d of the yellow toner image forming unit 2d. Further detailed description will be given with reference to FIGS. 5 and 6 showing the transfer voltage applying means 72a.
1 and 6, both ends of the common support shaft 74a extending in the direction perpendicular to the paper surface in FIGS. 1 and 6 are supported by the support frame 70 via the shaft support mechanism 76a (FIG. 6). The common support shaft 74a can be formed from a suitable conductive metal material such as steel. The support frame 70 has both side plate portions which are arranged at intervals in the left-right direction in FIG. 5, and the support short shafts 7 that project substantially horizontally on the both side plates.
8a is fixed. Each of the shaft support mechanisms 76a includes an inverted L-shaped swivel plate 80a rotatably attached to each of the support short shafts 78a, and one end of each of the swivel plates 80a rotates one end of the common support shaft 74a. It is installed freely. A tension spring 82a is arranged between the other end of the swivel plate 80a and the support frame 70, and the swivel plate 80a is elastically biased clockwise in FIG.

As clearly shown in FIG. 5, the common support shaft 7
A voltage application roller 84a that constitutes the voltage application means 72a is fixed to 4a. Further, a pair of pressing rollers 86a arranged on both sides of the voltage applying roller 84a are also fixed to the common support shaft 74a. The voltage application roller 84a is conveniently formed of a relatively flexible material having electrical conductivity, such as conductive synthetic rubber. On the other hand, it is convenient that the pressing roller 86a is made of an insulating and relatively flexible material, for example, an insulating synthetic rubber. A required transfer voltage is applied to the voltage application roller 84a via the common support shaft 74a and the swivel plate 80a. Figure 5
6 and 6, the swivel plate 80a is elastically biased clockwise in FIG. 6 by the tension spring 82a, so that the voltage application roller 84a and the pressure roller 86a are moved upward in FIG. Is biased elastically. Thus, the voltage applying roller 84a and the pressing roller 86a are elastically pressed against the outer peripheral surface of the rotating drum 14a in the black toner image forming unit 2a via the transfer belt 12. The transfer voltage applied to the voltage applying roller 84a is transmitted to the transfer belt 12. Therefore, in the transfer area 24a, in the area where the voltage applying roller 84a extends, that is, in the area of the width W12, the outer peripheral surface of the rotating drum 14a and the transfer belt 12 are transferred. A transfer voltage is applied to an image receiving member (not shown) that is conveyed through the gap between and, and a black toner image is transferred from the outer peripheral surface of the rotating drum 14a to the image receiving member in the area of the width W12. Because of this, the width W12 is the effective transfer width. Since the pressing roller 86a is insulative, the transfer belt 12 is located outside the width W12.
No effective transfer voltage is applied to. However, due to the presence of the pair of pressing rollers 86a, the transfer belt 1 is not formed in the region of the width W13 larger than the effective transfer width.
2 is pressed against the outer peripheral surface of the rotating drum 14a. Therefore, the width W13 is an effective contact width in which the transfer belt 12 is brought into direct contact with the outer peripheral surface of the rotary drum 14a in a portion where the image receiving member exists and the portion where the image receiving member does not exist via the image receiving member. As clearly shown in FIG. 5, in the illustrated embodiment, the transfer belt 12 has a width W14 that is larger than the effective contact width W13, and therefore, on both sides of the transfer belt 12, the outer peripheral surface of the rotary drum 14a is formed. There is a non-contact part that does not come into intimate contact with. In such a non-contact portion, a protrusion 88 having a width W15 is formed on the inner surface of the transfer belt 12 (the protrusion 88 will be described later). The width of the rotating drum 14a may be substantially the same as or slightly larger than the width W14 of the transfer belt 12.

In the illustrated embodiment, the voltage applying roller 84a and the pressing roller 86a are fixed to the common support shaft 74. However, as viewed in the moving direction of the transfer belt 12, the upstream side and / or the upstream side of the voltage applying roller 84a. A separate supporting shaft is rotatably mounted on the downstream side, and the pressing roller 86a is attached to the supporting shaft.
Can also be fixed. In this case, the pressing roller 8
6a can be formed to continuously extend over the effective contact width W14.

[0024] Having described a transfer voltage applying means 72a and its associated components that are disposed allowed related to the transfer zone 24a of the black toner image forming units 2a, Mazets <br/> te toner image forming unit 2b, cyan Toner image forming unit 2c and yellow toner image forming unit 2
The transfer voltage applying means 72b, 72c and 72d arranged in association with the transfer areas 24b, 24c and 24d of d and their related components are also substantially the same, and therefore detailed description thereof will be omitted. To do.

Continuing the description with reference to FIG. 7 together with FIGS. 1 and 5, the support frame 70 has a support shaft 90 extending in the left-right direction in FIG. 5 and in the direction perpendicular to the paper surface in FIG.
Is rotatably mounted, and the driven roller 6 is fixed to the support shaft 90. One end of the support shaft 90 projects beyond one side plate of the support frame 70, and an input gear (not shown) is fixed to the projecting end. The input gear is connected to a rotary drive source (not shown), which may be an electric motor, through an appropriate transmission means, and when the rotary drive source is energized, the driven roller 6 is moved to the position shown in FIG.
Is rotated in the direction indicated by arrow 14.
As clearly shown in FIG. 7, the driven roller 6 has a central main portion 94 and small diameter portions 96 arranged on both sides. The overall width W16 of the driven roller 6 is substantially the same as the overall width W14 of the transfer belt 12, and the width W17 of the small diameter portion 96 is the same.
The width W15 of the protrusion 88 formed on both sides of
Is substantially the same as The radius difference between the central main portion 94 and the small diameter portion 96 of the driven roller 6 may be substantially the same as the protruding thickness of the protruding portion 88 of the transfer belt 12. Therefore, as shown in FIG. 7, the transfer belt 12 has a central main portion 94 of the driven roller 6 in a region between the protrusions 88 on both sides thereof.
The protrusions 88 on both sides of the transfer belt 12 are positioned on the both side small diameter portions 96 of the driven roller 6. The driven roller 8 and the tension roller 10 have substantially the same structure as the driven roller 6, and the protrusions 88 formed on both sides of the transfer belt 12 are provided on both sides of the driven roller 6, the driven roller 8 and the tension roller 10. The transfer belt 12 is prevented from meandering by being located in the formed small diameter portion.

As shown in FIGS. 1 and 7, a belt cleaning means 98 is arranged below the portion where the driven roller 6 is arranged. The belt cleaning means 98 includes a cleaning case 100 and a cleaning blade 102. The cleaning blade 102, which can be formed of a flexible material such as synthetic rubber, is fixed in place, and its free edge is pressed against the surface of the transfer belt 12. The cleaning case 100 fixed at a required position may have a box shape surrounding a cleaning blade 102. As will be further described later, although toner may adhere to the surface of the transfer belt 12, the free edge of the cleaning blade 102 is pressed against the driven roller 6 via the transfer belt 12,
As a result, the toner that adheres to the surface of the transfer belt 12 is removed. The removed toner is stored in the cleaning case 100. Cleaning blade 10
2 is a width W18 that is substantially the same as the width W14 of the transfer belt 12.
The toner is removed from the surface of the transfer belt 12 over the entire width W18. Therefore, the width W18
Is the effective cleaning width of the belt cleaning means 98. On the inner surfaces of both side walls of the cleaning case 100, which extend upward beyond the lower surface of the driven roller 6, side seals that are brought into close contact with the end surface of the driven roller 6, the side surface of the transfer belt 12, and the side surface of the cleaning blade 102. The piece 104 can be disposed. The sealing piece 104 can be formed from a flexible material such as a pile sheet. If desired, upstream and downstream sealing strips, which are conveniently formed from a synthetic resin film, are brought into intimate contact with the surface of the transfer belt 12 upstream and downstream of the cleaning case 100 as seen in the direction of transfer belt 12 movement. It is also possible to provide (not shown).

Continuing the description with reference to FIG. 8, in the image forming machine constructed according to the present invention, the transfer belt 1
The effective contact width W13 of No. 2 is larger than the effective transfer width W12 defined by the extension width of the voltage applying roller 84a, and also the effective charging width W of the charging unit 18a.
It is made larger than 1. As described above, in the region outside the effective charging width W1, the peripheral surface of the rotating drum 14a may have a potential considerably lower than the predetermined potential, substantially zero potential or the opposite polarity, and thus the rotating drum 14a in that region. Toner may adhere to the peripheral surface of the. The toner attached to the peripheral surface of the rotating drum 14a outside the effective charging width W1 is transferred from the rotating drum 14a in the transfer area 24a because the effective contact width W13 of the transfer belt 12 is larger than the effective charging width W1. Transfer to the surface of the belt 12. Then, the toner transferred to the surface of the transfer belt 12 is removed from the surface of the transfer belt 12 by the action of the cleaning blade 102 of the belt cleaning unit 98. Therefore, while the toner adhering to the peripheral surface of the rotary drum 14a on both sides of the effective charging width W1 remains attached to the peripheral surface of the rotary drum 14a and is moved along with the rotation of the rotary drum 14a, the rotary drum 14a is moved. It can be effectively prevented from floating from the peripheral surface and contaminating the inside or the periphery of the image forming machine. In addition, the maximum image receiving member width W19
Is usually substantially the same as or slightly larger than the effective transfer width W12, but the effective contact width W of the transfer belt 12 is
13 and therefore the image receiving member is the transfer belt 12
With the cooperation of the rotary drum 14a and the rotary drum 14a, they can be conveyed sufficiently well between them. It may be intended to expand the effective transfer width W12 itself to substantially set the effective contact width W13 to omit the pressing roller 84a. In such a case, however, the transfer belt 12 can be operated without an image receiving member. In a region outside the maximum image receiving member width W19, which is brought into direct contact with the rotating drum 14a, a transfer voltage is applied to the transfer belt 12, which causes a relatively large amount of current to flow into the rotating drum 14a. Rotating drum 14a
May be deteriorated at an early stage. The transfer drum 12 has a rotating drum 14 over its effective contact width W12.
The toner is transferred from a, and the toner is transferred to the transfer belt 12
Since the toner may adhere to the surface of the transfer belt 12 in the width direction, the effective cleaning width W18 of the belt cleaning unit 98 is set to the above-mentioned effective cleaning width W18 of the transfer belt 12 in order to sufficiently remove the toner adhering to the surface of the transfer belt 12. It is preferably somewhat larger than the effective contact width W13, and may be substantially the same as the transfer belt width W14, for example. The effective charging width W1 of the charging means 28a may be somewhat larger than the effective transfer width W12 defined by the extending width of the voltage applying roller 84a.

Continuing the description with reference to FIG. 8, in the illustrated embodiment, the effective charging width W of the charging means 18a.
1, the maximum image receiving member width W19, the effective transfer width W12 defined by the extension width of the voltage application roller 84a, and the effective charge removal width W in the cleaning unit 34a.
11 and the effective cleaning width W8, reversal developing means 3
The effective developing width W4 of 2a and the maximum exposure width W3 of the exposing means 30a are also the effective contact width W13 of the transfer belt 12.
The width of each width is set to W13>W11>W8>W4>W19> W3.

The width W2 for the pair of gap setting rollers 42a in the charging means 18a and the width W for the pair of gap setting rollers 52a in the reversal developing means 32a.
5, upstream seal member 54a in the reversal developing means 32a
Of the width W6, the width W7 of the pair of side seal members 56a of the reversal developing means 32a, the width W9 of the upstream seal member 64a of the cleaning means 34a, and the width W10 of the pair of side seal members 66a of the cleaning means 34a. Transfer belt 12
It is preferable that the effective contact width W13 is smaller than the effective contact width W13.
When set in this way, the widths W2, W5,
In the range of W6, W7, W9, and W10, the toner attached to the outer peripheral surface of the rotating drum 14a is transferred to the transfer belt 12.
The toner does not remain on the outer peripheral surface of the rotating drum 14a. Therefore, it is possible to sufficiently prevent the toner from being accumulated between the interval setting rollers 42a and 52a and the outer peripheral surface of the rotary drum 14a and damaging the interval setting. And again, the sealing members 54a, 5
6a, 64a and 66a and the outer peripheral surface of the rotary drum 14a, the toner is accumulated and the seal members 54a, 56a and 6a.
Damage to the sealing effect of 4a and 66a can be avoided with certainty.

[0030]

In the image forming machine of the present invention, the above-mentioned various problems existing in the conventional image forming machines, which are related to the toner adhered on both sides of the effective charging width on the surface of the image carrier, are solved. .

[Brief description of drawings]

FIG. 1 is a simplified diagram showing the main components of a preferred embodiment of an image forming machine constructed in accordance with the present invention.

FIG. 2 is a simplified partial cross-sectional view showing a charging unit in the image forming machine shown in FIG.

FIG. 3 is a simplified partial cross-sectional view showing developing means in the image forming machine shown in FIG.

FIG. 4 is a simplified partial cross-sectional view showing a cleaning unit in the image forming machine shown in FIG.

5 is a simplified partial sectional view showing a transfer unit in the image forming machine shown in FIG.

FIG. 6 is a simplified diagram showing a mounting manner of a voltage applying roller and a pressing roller in the transfer unit of the image forming machine shown in FIG.

FIG. 7 is a simplified partial cross-sectional view showing belt cleaning means in the transfer means of the image forming machine shown in FIG.

FIG. 8 is a schematic diagram showing a relative relationship of various widths in the image forming machine shown in FIG.

[Explanation of symbols]

2a: Black toner image forming unit 2b: Magenta toner image forming unit 2c: Cyan toner image forming unit 2d: Yellow toner image forming unit 4: Transfer belt unit (transfer means) 12: Transfer belt 14a: rotating drum (image bearing means) 18a: charged area 20a: Development area 22a: Development area 24a: transfer area 26a: cleaning area 28a: charging means 30a: exposure means 32a: Reversal developing means 42a: Interval setting roller in charging means 52a: Interval setting roller in reversal developing means 54a: upstream seal member in reversal developing means 56a: Side seal member in reversal developing means

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI G03G 15/16 103 G03G 15/16 103 21/10 21/00 318 (56) Reference JP-A-7-56443 (JP, A, JP ) JP-A-6-186898 (JP, A) JP-A-1-277269 (JP, A) JP-A-9-274382 (JP, A) JP-A-4-138484 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03G 15/08 502 G03G 15/08 505 G03G 15/08 506 G03G 15/02 101 G03G 15/16 103 G03G 21/10

Claims (10)

(57) [Claims] 1. An image carrying means for sequentially moving through a charging area, an exposing area, a developing area, a transferring area and a cleaning area, a charging means for charging the image carrying means in the charging area, An exposing means for selectively removing the electric charge from the image carrying means in the exposure area to form an electrostatic latent image on the image carrying means; and an developing means for developing the electrostatic latent image into a toner image in the developing area. Reversal developing means, transfer means for transferring the toner image on the image carrying means onto the image receiving member in the transfer area, and removing toner remaining on the image carrying means after transfer in the cleaning area. In an image forming machine, the transfer means includes a cleaning means for rotating the transfer belt, and the transfer means includes a transfer belt that is rotationally driven and a transfer voltage applying means that applies a transfer voltage to the back surface of the transfer belt. Means develops the image bearing means with a predetermined effective developing width, the transfer voltage applying means applies the transfer voltage to the transfer belt with a predetermined effective transfer width, and the surface of the transfer belt receives the image with a predetermined effective contact width. An image forming machine which is brought into contact with the image bearing means through a member and directly, wherein the effective contact width is larger than the effective developing width and larger than the effective transfer width. 2. The developing means includes a developing housing having an opening at a portion facing the image carrying means, a developing material applying means arranged in the developing housing and acting on the image carrying means through the opening, An upstream seal member disposed in the developing housing and having a free edge in contact with the image carrying means on the upstream side of the developer applying means, the upstream seal member being larger than the effective developing width and The image forming machine according to claim 1, having a width smaller than an effective contact width. 3. The developing means includes a developing housing having an opening at a portion facing the image carrying means, a developing material applying means arranged in the developing housing and acting on the image carrying means through the opening, A pair of side seal members disposed on the developing housing and brought into contact with the image bearing unit on both sides of the developer applying unit, wherein a length between outer ends of the pair of side seal members is smaller than the effective developing width. The image forming machine according to claim 1, wherein the image forming machine is also larger and smaller than the effective contact width. 4. The developing means includes a developing housing having an opening at a portion facing the image carrying means, a developing material applying means arranged in the developing housing and acting on the image carrying means through the opening, A pair of interval setting rollers rotatably mounted on the developing housing and abutted on the image carrying means on both sides of the developing material applying means, and the length of the outer ends of the pair of interval setting rollers is the effective developing The image forming machine according to claim 1, wherein the image forming machine is larger than the width and smaller than the effective contact width. 5. An image carrying means for sequentially moving through a charging area, an exposing area, a developing area, a transferring area and a cleaning area, a charging means for charging the image carrying means in the charging area, An exposing means for selectively removing the electric charge from the image carrying means in the exposure area to form an electrostatic latent image on the image carrying means; and an developing means for developing the electrostatic latent image into a toner image in the developing area. Reversal developing means, transfer means for transferring the toner image on the image carrying means onto the image receiving member in the transfer area, and removing toner remaining on the image carrying means after transfer in the cleaning area. In the image forming machine, the transfer means includes a cleaning means for rotating the transfer belt, and the transfer means includes a transfer belt that is rotationally driven and a transfer voltage applying means that applies a transfer voltage to the back surface of the transfer belt. The cleaning means removes the toner remaining on the image carrying means with a predetermined effective cleaning width, the transfer voltage applying means applies the transfer voltage to the transfer belt with a predetermined effective transfer width, and the surface of the transfer belt has a predetermined area. Is contacted to the image bearing means directly and through the image receiving member with an effective contact width,
An image forming machine, wherein the effective contact width is larger than the effective cleaning width and larger than the effective transfer width. 6. The cleaning means includes a cleaning housing having an opening at a portion facing the image carrying means, a cleaning blade disposed in the cleaning housing and having a leading edge pressed against the image carrying means. An upstream seal member disposed in the cleaning housing and having a free edge in contact with the image carrying means at an upstream side of the cleaning blade, the upstream seal member having a size larger than the effective cleaning width and the effective cleaning width. The image forming machine according to claim 5, which has a width smaller than the contact width. 7. The cleaning means includes a cleaning housing having an opening at a portion facing the image bearing means,
A cleaning blade disposed in the cleaning housing and having a leading edge pressed against the image bearing means; and a pair of side seal members disposed in the cleaning housing and contacting the image bearing means on both sides of the cleaning blade. 7. The image forming machine according to claim 6, further comprising: a length between outer ends of the pair of side sealing members that is larger than the effective cleaning width and smaller than the effective contact width. 8. An image carrying means for sequentially moving through a charging area, an exposing area, a developing area, a transferring area and a cleaning area, a charging means for charging the image carrying means in the charging area, An exposing means for selectively removing the electric charge from the image carrying means in the exposure area to form an electrostatic latent image on the image carrying means; and an developing means for developing the electrostatic latent image into a toner image in the developing area. Reversal developing means, transfer means for transferring the toner image on the image carrying means onto the image receiving member in the transfer area, and removing toner remaining on the image carrying means after transfer in the cleaning area. In the image forming apparatus, the transfer means includes a cleaning means for rotating the transfer belt, and the transfer means includes a transfer belt that is rotationally driven and a transfer voltage applying means that applies a transfer voltage to the back surface of the transfer belt. The step is a corona discharger for charging the image bearing means with a predetermined effective charging width, and a pair of interval setting rollers rotatably mounted on the corona discharger and abutting the image bearing means on both sides of the effective charging width. Including the transfer voltage applying means
The step applies the transfer voltage to the transfer belt with a predetermined effective transfer width
The surface of the transfer belt has a predetermined effective contact width and the image receiving member
Through and directly into contact with the image bearing means,
The effective contact width is the width between the outer ends of the pair of spacing rollers.
And an effective transfer width that is larger than the effective transfer width . 9. The image forming machine according to claim 1, wherein the effective contact width is larger than the maximum image receiving member width. 10. The transfer means includes a belt cleaning means for removing adhered toner from the surface of the transfer belt, and the effective cleaning width of the belt cleaning means is larger than the effective contact width. The image forming machine according to any one of 1 to 9.