JPH0425884A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent a photosensitive drum area which exceeds the width of a transfer material from being charged electrostatically by a transfer charger to the opposite polarity by providing a shield means which is variable in shield width between the photosensitive drum and transfer charger. CONSTITUTION:A couple of shield members 43a and 43b are provided between the photosensitive drum and transfer charger 36 and supported while enabled to swing horizontally around support shafts 44, and their gears are engaged with each other to make the shield members approach and leave each other associatively. When transfer paper has maximum width, they are open to solid- line positions, but when the transfer paper is narrower, the shield width is varied as shown by imaginary lines corresponding to the transfer paper width. Therefore, the photosensitive drum area which exceeds the width of the transfer paper is prevented from being charged electrostatically by the transfer charger 36 to the opposite polarity, fogging is caused at neither side part, and the toner consumption is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image forming apparatus that forms images using an electrophotographic method, such as a copying machine, a facsimile machine, or a printer.

Conventional electrophotographic image forming apparatuses normally charge a photosensitive drum 1.01 uniformly with a charger 102 and expose it with light using an exposure means 103 to form an electrostatic latent image, as shown in FIG. The toner image is transferred to a transfer material 106 by a transfer charger 105, and the toner image on the transfer material 106 is then fixed by a fixing device. The toner remaining on the photosensitive drum 101 is cleaned by a cleaning blade 107, and the remaining charge is further removed by an erase lamp 108, and the process is repeated.

In the example shown in FIG. 8, a photosensitive drum 1.01 that is charged ten times is used, and the charger 102 applies ten charges to charge it, and the exposure means 103 exposes the image area to remove the charge, and the toner charged ten times is charged. The transfer charger 105
The toner image is transferred to the transfer material 106 by applying one charge at the transfer material 106 .

Problems to be Solved by the Invention By the way, the axial length of the photosensitive drum E1, the transfer charger 105, etc. is set to correspond to the maximum width of the transfer material on which an image can be formed. Images are often formed on a transfer material 106 whose width is narrower than that of the image, and in that case, as shown in FIG. 9, the transfer material 106 is interposed between the photosensitive drum 101 and the transfer charger 105 during transfer. A region 109 directly facing the transfer charger 105 is generated. Transfer material 106
As shown in FIG. 10(a), the charged potential of the photosensitive drum 101 drops to nearly 0 potential at the exposed portion, and during transfer, the photosensitive drum 101 is shielded by the transfer material 106, so that the photosensitive drum 101 is The potential does not drop, and after that, the charged potential of the non-exposed area is erased during erasing, and then the process of being charged again by the charger 102 is repeated. However, in the area 109 directly facing the transfer charger 105, as shown in FIG.
5, the area 109 is strongly reversely charged and is charged to the opposite polarity beyond 0 potential, and cannot be charged to a predetermined charging potential at the next charging time, and as a result, this area 109 is not exposed. However, there is a problem in that the toner is developed and so-called "fogging" occurs. In addition, as a result, there is a problem that toner consumption increases.Furthermore, there is a problem that the portion of the photosensitive drum 101 corresponding to the area 1°9 is severely degraded, and the life of the photosensitive drum 101 is shortened due to uneven deterioration. Ta.

In particular, in the case of a small and low-priced image forming apparatus, it is not possible to increase the capacity of the charging unit 102, and since the sensitivity of the photosensitive drum 101 is increased, reverse charging is likely to occur and the speed is low. This problem is serious because there is not enough time to allow the photosensitive drum 101 to rotate idly until its characteristics become stable.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus that prevents an area of an image carrier exceeding the width of a transfer material from being reversely charged by a transfer charger.

Means for Solving the Problems In order to achieve the above-mentioned problems, the present invention provides an image forming apparatus in which a toner image on an image carrier is transferred to a transfer material by a transfer charger. The present invention is characterized in that a shielding means whose shielding area can be changed in the axial direction of the image carrier is disposed between the transfer charger.

Function In the above structure of the present invention, the width of the side portion N of the transfer material is adjusted depending on the width of the transfer material.
By shielding the transfer charger from the image carrier with the shielding means in the area, it is possible to reliably prevent the image carrier from being reversely charged during transfer charging,
It is possible to prevent "fluttering" on the sides, reduce toner consumption, and prevent uneven deterioration of the image bearing member.

Embodiment A printer according to an embodiment of the present invention shown in FIGS. 1 to 7 will be described below.

FIG. 1 shows an image forming cartridge 1 used in the printer of this embodiment and its surroundings. As shown in the figure, this cartridge 1 is formed by connecting a developer casing 2 and a waste toner casing 3. Waste toner casing 3
A photosensitive drum 4 is provided at the connecting end of the drum 4 and is pivotally supported on the side wall of the waste toner casing 3 by a shaft 6.

A cleaning blade 7 is brought into pressure contact with the back of the photosensitive drum 4, and residual toner scraped off from the top of the photosensitive drum 4 is stored in the waste toner casing 3.

To accommodate this, the photosensitive drum 4 of the waste toner casing 3 is
A paddle 8 is provided near the rear bottom of the photosensitive drum 4.
The toner scraped from the toner is scraped into the waste toner casing 3. The photosensitive drum 4 has a photoconductive layer made of zinc oxide, selenium, organic photoconductive material, etc. formed on the surface of a metal base such as aluminum, and forms an electrostatic latent image by imagewise exposure.

A developing roller II for developing the electrostatic latent image on the photosensitive drum 4 with toner is provided at the connecting end of the developing device casing 2, and is pivotally supported on the side wall by a shaft I2. A sponge roller 13 is provided on the back of the developing roller 11 and is pivotally supported on the side wall of the developing device casing 2 by a shaft 14, which charges the developer and supplies it to the developing roller 11. A developer supply paddle 15 is provided inside the developer casing 2 and is pivotally supported on a side wall by a shaft 16 for agitating the developer in the developer casing 2 while supplying it to the sponge roller 13 . The shaft 16 is equipped with stirring blades 17 to prevent toner from forming into blocks.
is installed.

A wire 82 for scraping off the developer is provided on the back of the sponge roller 13. This wire 82 is stretched between the opening edges of a partition plate 95 in the developer casing 2 and is pressed against the back surface of the sponge roller 13. As a result, when the residual developer that has been supplied to the developing roller 11 on the sponge roller 13 returns to the back side of the sponge roller 13, this residual developer is scraped off from the surface of the sponge roller 13 by the wire 82. Returned to unused developer. Therefore, the residual developer that remains after being supplied to the developing roller 11 does not leave the surface of the developing roller 11 and is repeatedly supplied to the developing roller 11 as it is, or is scraped off once from the surface of the developing roller 11. This prevents the development roller 11 from being captured by the sponge roller 13 and supplied to the development roller 11 without being mixed with the unused development side. For this reason, the sponge roller 13
It is possible to prevent the stress of the residual developer that was not supplied to the developing roller 11 from affecting the developing characteristics.

The developer casing 2 and the waste toner casing 3 are connected to the shaft 2.
Positioning rollers 23 and 24 provided on the shafts 6 and 12 of both the photosensitive drum 4 and the developing roller 11 are connected to each other so as to be swingable by the shafts 6 and 1 of the photosensitive drum 4 and the developing roller 11.
They are brought into pressure contact with each other, and a predetermined gap is maintained between the photosensitive drum 4 and the developing roller 11 while absorbing manufacturing and assembly errors of each part.

A lid 3o is attached to an upwardly opened developer input port 83 of the developer casing 2, and is fixed to the developer casing 2 by an appropriate method such as adhesion, welding, or screwing. The lid 3o extends to the waste toner casing 3 and covers the waste toner casing 3, making it easy to handle the image forming cartridge 1 as an integral part. In particular, since M2O is heavier than the waste toner casing 3 and is fixed to the side of the large developer casing 2 to form the gripping portion H for integral handling, the stability of the image forming cartridge 1 during handling is improved. , it becomes even easier to handle. Note that a play is provided between the lid 30 and the waste toner casing 3 to an extent that does not prevent the necessary rocking of the waste toner casing 3 relative to the developer casing 2 due to pressure contact between the positioning rollers 23 and 24. Further, in addition to the developer input port 83, a developer supply port (not shown) is formed on the side surface of the developer casing 2, and although this cannot be opened and closed by the user, it can be opened and closed at a factory or the like. By closing with an opening/closing lid, it may be configured so that the developer can be easily replenished.

Further, a sealing plate 25 is provided at the bottom of the connecting end opening of the developer casing 2 and extends to the circumferential surface of the developing roller 11 and comes into pressure contact therewith. A seal plate 26 is provided that extends to the drum 4 and presses against it. As a result, the developer handling space of the image forming cartridge 1 formed by the developer casing 2 and the waste toner casing 3 becomes almost sealed, thereby preventing the developer from scattering to the outside. I can do it.

Note that the sealing performance can be further improved by providing the seal plates 25 and 26 in the developer casing 2 and the waste toner casing 3 in multiple stages as necessary, and pressing them against the surfaces of the developing roller 11 and the photosensitive drum 4 in multiple stages in their rotational directions. improves.

This image forming cartridge 1 is used by being attached to a printer 31 shown in FIG. 4, for example. In this printer 31, an upper frame 33 can be opened and closed vertically about a hinge shaft 34 with respect to a lower frame 32, and the image forming cartridge 1 is mounted on the upper frame 33 as shown in FIG. This attachment is performed detachably from the rear of the upper frame 33 that opens upwardly along guides (not shown) provided inside both side walls of the upper frame 33. When the upper frame 33 of the image forming cartridge 1 is closed with respect to the lower frame 32,
Transfer charger 3 provided on the lower frame 32 side
A paper passing bus 37 for printing is formed between the upper frame 33 and the upper frame 33 as shown in FIG. 4, and the paper passing path 37 is opened to facilitate troubleshooting such as jams. .

A laser scanning unit 38 is provided above the portion of the upper frame 33 where the image forming cartridge 1 is mounted. This laser scanning unit 38 deflects a laser beam 39 from a laser emission source modulated according to an image signal provided by a personal computer, image league, etc., onto the photosensitive drum 4 using an appropriate scanning means such as a polygon mirror. image exposure on the photosensitive drum 4. For this image exposure, the image forming cartridge 1 is provided with an exposure slit 51 in a part of the lid 30 that enables image exposure to the photosensitive drum 4.
Inside, an electrostatic latent image is formed by image exposure.
A charger 52 that uniformly charges the surface of the photosensitive drum 4 is provided in front of the image exposure position of the photosensitive drum 4.

Between the photosensitive drum 4 and the transfer charger 36, preferably between the paper passing bus 37 and the transfer charger 36, both ends of the photosensitive drum 4 in the axial direction are connected to the transfer charger as shown in FIGS. A pair of shielding members 43a and 43b which can be shielded from each other are provided. These shielding members 4
3a and 43b are supported so as to be horizontally swingable around a support shaft 44 disposed on one side of the transfer charger 36, and gears 45 that mesh with each other are formed on opposing portions, and the shielding portions on the transfer charger 36 are configured to swing toward and away from each other in conjunction with each other. Moreover, one shielding member 4
A drive pinion 46 that meshes with the gear 45 of 3a is provided,
It is configured to be rotatably driven by a drive motor 47. Further, a guide member 48 is provided on the drive portion of these shielding members 43a, 43b so as not to interfere with the paper passing bus 37.

The drive motor 47 is driven and controlled based on a detection signal of the size of the transfer paper on which an image is to be formed, and when the transfer paper is at its maximum width, the transfer charger 36 is opened over almost its entire length as shown by the solid line in FIG. When the width is narrow, areas on both sides of the transfer paper are shielded by shielding members 43a and 43b according to the width of the transfer paper, as shown by imaginary lines. Thus, during transfer, the photosensitive drum 4 is shielded by the shielding members 43a and 43b even in areas protruding from both sides of the transfer paper, and is shielded from the transfer charger 36 over the entire length in the axial direction. It can prevent reverse charging and will not cause "fogging" on both sides. Furthermore, as a result, the amount of toner consumed can be reduced.

Furthermore, since deterioration due to repeated charging and reverse charging of both ends of the photosensitive drum 4 does not occur, uneven deterioration is also prevented, and the life of the photosensitive drum 4 can be extended.

Note that since the transfer charger 36 is turned off between the transfer sheets, reverse charging does not occur.

However, due to recent miniaturization and weight reduction, the thickness of each member forming the image forming cartridge 1 tends to become thinner and the rigidity tends to decrease. Therefore, when handling the image forming cartridge 1 alone, an external force for gripping the image forming cartridge 1 acts on the developing device casing 2 forming the grip part H of the image forming cartridge 1, causing temporary deformation such as twisting or denting. It may also occur. At this time, the volume of the developer casing 2 momentarily decreases, and the developer may be blown out along with the internal air from the weak portion of the seal.

Therefore, in this embodiment, an opening 84 is formed in the lid 30, and the opening 84 is closed with a semipermeable membrane 85. The semipermeable membrane 85 is one that allows air to pass through but does not allow the developer to pass through. As a result, even if the developing device casing 2 is deformed as described above during handling of the image forming cartridge 1 and the volume is reduced and internal air is blown out, the semi-permeable membrane with low resistance prevents the air from blowing out. 85, and the developer tries to get onto the ejected air, the semipermeable membrane 8
5 to prevent it from spewing out to the outside. Such a structure can be applied to the waste toner casing 3 as well, if necessary.

As shown in detail in FIGS. 5 and 6, an elastic blade 41 is pressed against the developing roller 11. As shown in FIGS. As the elastic blade 41, a rubber blade made of urethane rubber, silicone rubber, or the like, or a metal blade made of spring-use phosphor bronze, spring steel, or the like is useful. The upper end of the elastic blade 41 is attached by adhesive or the like to a metal support member 42 that extends over the side wall of the developer casing 2, and the lower end is pressed against the surface of the developing roller 11.

By the way, the developing roller 11 has development breakage and damage on the longitudinal center side.
The holding area X is formed on a satin surface by sandblasting or the like so as to be advantageous for carrying the developer. Both ends of the developing roller 1, which are on both sides of the developer carrying area It is. For this reason, the developer non-carrying area Y is kept as a smooth surface to avoid carrying the developer.

As a result, the developer carrying area X of the developing roller 11 has a satin-like unevenness formed on its surface, and the convex portion rises from the surface of the fabric, so that the diameter thereof is slightly increased compared to the developer non-carrying area Y. In addition, since the developer carrying area X of the developing roller 11 carries the developer supplied from the sponge roller 13, although the developer is thinned to a predetermined layer thickness by pressure contact with the elastic blade 41, the developing roller The diameter of the developer carrying area X portion of No. 11 is further increased. Therefore, the diameter of the developer carrying area X of the developing roller 11 is somewhat different from that of the developer non-carrying area Y, and there is a gap between the developer carrying area X and the developer non-carrying area Y of the developing roller 11. Step Z (
(Fig. 6) will occur.

Therefore, if the elastic blade 41 is uniformly and continuously pressed over the entire length of the developing roller 11, it will not carry the developer, and moreover, the developer non-carrying area Y will have a small diameter.
Floating occurs between the two and causes the developer to leak forward.

In order to solve this problem, in this embodiment, a notch 86 cut from the tip is formed in the portion of the elastic blade 41 facing the boundary K between the developer carrying area X and the developer non-carrying area Y of the developing roller 11. is forming. As a result, the elastic blade 41 is divided by the notch 86 into the center side in the longitudinal direction facing the developer carrying area X and the developer non-carrying area Y of the developing roller 11, and the sections 41a and 41b on both sides thereof. Since the respective parts 41a and 41b independently press against the developer carrying area X and the developer non-carrying area Y of the developing roller 11 without being influenced by each other, there is a step Z between the respective heads X and Y. Part 4 of elastic blade 41
1b can be brought into close contact with a portion of the developer non-carrying area Y, as shown in FIG. 6, regardless of the portion 41a of the elastic blade 41 that is pushed away by the developer in the developer carrying area X. Therefore, the elastic blade 41
It is possible to eliminate the inconvenience in which the developer floats from the developing roller 11 in the developer non-carrying area Y and the developer leaks from the developer non-carrying area Y to the photosensitive drum 4 side.

Further, the portion 41b of the elastic blade 41 is attached to the support member 42.
It is held down by presser metals 57 attached to both ends of the holder, which further prevents it from lifting up. Developing roller 1
A sealing material 88 is interposed between 1 and the side wall 87.

Furthermore, in a long continuous portion of the elastic blade 41 in the longitudinal direction, pressure contact with the developing roller 11 tends to be stronger in the central portion of the continuous range than in other portions.
The layer thickness of the developer formed on the developing roller 11 tends to be non-uniform in the axial direction of the developing roller 11, which causes uneven development characteristics. Therefore, in this embodiment, in order to solve this problem,
A groove 81 as shown in FIGS. 1 and 5 is formed on the back surface of the elastic blade 41. This groove 81 is located approximately in the center of the elastic blade 4 in the width direction, and is formed in a range excluding both ends of the portion 41a between the long cuts 86 of the elastic blade 41.

This allows the long portion 41a of the elastic blade 41 to
The bending rigidity at the central portion in the longitudinal direction is weakened by the concave groove 81, the pressing force against the developing roller 11 is reduced, and the pressing force against the developing roller 11 of the entire long portion 41a of the elastic blade 41 is reduced. become even.

Furthermore, stress is concentrated in the concave groove 81 portion of the elastic blade 41, and by equalizing the stress in other portions, the pressing force against the developing roller 11 can be made uniform.

Therefore, a thin layer of developer can be formed with a uniform layer thickness over the entire developer carrying area X of the developing roller 11, and uniform development characteristics can be expected over the entire developer carrying area X of the developing roller 11.

In addition, the elastic blade 41 is made of polyethylene terephthalate (
If it is formed by punching from a sheet such as PET, the cost will be lower than when a molded product such as urethane foam is used. In this case PET
Since it is made of a strong material, it does not damage the developing roller 11 or cause chattering, and it is preferable to press the developing roller 11 at the so-called abdomen in order to avoid contact with the tip edge.

Furthermore, since the elastic blade 41 is made of an insulating material, the frictional charging between the developer and the elastic blade 41 can be increased, and the overall charging state can be sufficiently stabilized. In this sense, forming a coating layer of an insulating material on the surface of the developing roller 11 can further improve the charging characteristics. Furthermore, since the insulating coating layer can form a satin surface during resin molding without sandblasting, the cost of the boundary image roller 11 is reduced accordingly, and the developer can be transported to areas where the electric field is not diffused. At the same time, the gap between the developing roller 11 and the photosensitive drum 4 can be shortened beyond the discharge limit.
Resolution in development is improved.

As another example, an insulating elastic roller may be used instead of the elastic blade 41, in which case the developing roller 11
You can set the relative speed with G in any way you like.

This allows the charging characteristics to be adjusted in various ways, and the surface layer of the developer on the developing roller 11 can be adjusted by rotating the elastic roller in the subordinate direction relative to the developing roller 11 or in the opposite direction. This makes it possible to choose whether to actively apply the development process or to make it difficult for the image to be subjected to the development process. Such selection corresponds to various image forming conditions such as the type of developer, developer supply mechanism, photosensitive drum 4, etc.
Useful when meeting special requirements.

In addition, a speed change mechanism is provided in the drive system of the developing roller 11, and when forming an image with poor reproducibility such as a line drawing or a dot image, the rotational speed of the developing roller 11 is increased. By increasing the supply amount of the agent, the reproducibility of even line drawings and dot/throat drawings is improved.

In this embodiment, the configuration of the charger 52 is devised in response to the fact that the photosensitive drum 4 is designed to have an extremely small diameter. The photosensitive drum 4, which has an extremely small diameter, faces the charging charger 52 on a curved surface with a sharp degree of curvature, and it is difficult to perform stable charging due to the influence of higher speeds. Therefore, the charger 52 connects the mesh of the grid section 53 to the photosensitive drum 4.
It is arranged so that it gradually becomes finer from the upstream side to the downstream side in the direction of rotation (Fig. 1, Fig. 3). As a result, the charger 52 is initially a corotron-type charger without a grid or a similar charging characteristic to ensure charging performance for the rotating photosensitive drum 4, and then a scorotron-type charger with a grid is used as the charger 52. This ensures controllability of charging by exhibiting charging characteristics as described above.

This makes it possible to achieve stable charging by ensuring both charging performance and charging controllability.

Although the charger 52 is formed into one for miniaturization, two chargers, a corotron type charger and a scorotron type charger, may be installed. Further, the change in size of the mesh may be continuous or discontinuous. The charger 52 has a grid section 5 for miniaturization.
3 and a discharge stabilizing frame 54 are integrally formed from a metal plate. The corona wire 55 is installed between resin blocks 56 attached to both side walls of the developer casing 2, and the ends of the discharge stabilizing frame 54 are held by the resin blocks 56.

Note that the corona wire 55 has a wire diameter of about 80 μm, which is extremely thin, so there is a problem with elongation and cutting, which makes it troublesome to handle during installation, and maintenance such as cleaning when it becomes dirty due to use is also troublesome. Therefore, it is conceivable that a metal plate is buried in a resin base (not shown) by insert molding or the like, and a part of the buried metal plate is exposed to be used in place of the corona wire. In this case, costs can be reduced and the strength of the corona electrode portion is improved, making assembly and cleaning easier. Alternatively, a predetermined metal material may be printed in a line shape on the surface of the resin base to serve as a substitute for the corona wire. In this case as well, the same effects as the above improvements can be expected.

Further, the discharge stabilizing frame 54 can also be formed by applying metal plating to the inner surface of the resin housing. In this case, the resin housing can be integrally formed with a part of the existing member such as the lid 30, and the structure can be simplified.

When the upper frame 33 is closed on the lower frame 32, the transfer charger 36 faces the photosensitive drum 4 of the image forming cartridge 1 with a certain gap, and is connected to the paper passing bus 37.
The developed toner image formed on the photosensitive drum 4 is transferred to the transfer paper 91 from the back side of the transfer paper 91 being conveyed.
Transfer it on top.

In addition, in the case of the transfer charger 36, the same improvement as that of the charging charger 52 can be made for the corona wire.

A timing roller pair 61 is provided in front of the transfer section of the paper passing bus 37, as shown in FIG. The timing roller pair 61 temporarily stops receiving the transfer paper 91 pinked up and fed from the paper feed cassette 92 by the pickup roller 931 in a stopped state, and then feeds the transfer paper 91 at a predetermined timing. The leading edge of the photosensitive drum 4 is aligned with the toner image formed on the photosensitive drum 4 for transfer.

A pair of fixing rollers 62 is provided behind the transfer section, and heat fixes the transfer sheet fed after the transfer.

The surface of the photosensitive drum 4 after the transfer is cleaned by a cleaning blade 7 to remove residual toner.

An eraser lamp 63 is provided immediately after the transfer charger 36 of the lower frame 32, and irradiates erase light onto the surface of the photosensitive drum 4 after transfer through the transfer paper 91 that is being passed, thereby eliminating any residue on the surface of the photosensitive drum 4. Removes charge. Near this eraser lamp 63, a light receiving end 65a of an optical fiber 65 is provided.
is positioned facing the photosensitive drum 4. This optical fiber 65 is designed to guide reflected light when a toner image formed on the photosensitive drum 4 is illuminated by the laser beam processor 3 to a density sensor 64 provided at an appropriate position. As a result, the density sensor 54 can detect the density of the toner image by sharing the eraser lamp 63 for illuminating the image to be inspected. By sharing the eraser lamp 63 and using the optical fiber 65, a special space is created around the transfer section. It is possible to detect the density of a toner image without the need for a , and cost is also reduced because the eraser lamp 63 is shared.

By sending the detected density of the toner image to the control system, it is possible to determine the state of developer shortage or deterioration, and to take measures such as a warning of the usage limit due to the lifespan of the image forming cartridge I or to stop printing.

Note that if the eraser lamp 63 is installed within the discharge stabilizing frame of the transfer charger 36, further space saving can be achieved.

Furthermore, the cleaning blade 7 can be formed of a transparent resin material and used as a light guide to irradiate the surface of the photosensitive drum 4 with eraser light. According to such an erase method, the degree of freedom in selecting the installation location of the eraser lamp 63 increases. Furthermore, cleaning blade 7
Similarly to the elastic blade 41, a concave groove can be formed on the back of the blade to equalize the pressing force. In this case, the resonant frequency of the blade can be easily selected.

Furthermore, the cost can be reduced by punching out a PET sheet, and the waste toner casing 3 is provided with an unused detection mechanism 71 linked to the drive system, as shown in FIG. . This unused detection mechanism 71 is a gear 73 provided on one shaft of the drive system, for example, the rotating shaft 72 of the paddle 8 for scraping in waste toner.
The detection gear 74 is engaged. The detection gear 74 has teeth 75 only on a part of the outer periphery, and the other part of the outer periphery is a cam surface 77 having a recess 76 in a part. The waste toner casing 3 also includes a detection pin 78 facing the cam surface 77.
is held movably forward and backward, and this detection pin 78 is brought into contact with the cam surface 77 by a spring 79. When the image forming cartridge 1 is not in use, that is, when the drive system has never been operated and no developer is consumed, this abutment position is set a predetermined amount downstream from the recess 76 of the cam surface 77 in the driving direction. It's a position where I can do it.

When the image forming cartridge 1 is installed in the printer 31 and is driven and used even once, the gear 7 that is interlocked with the drive is activated.
3 rotates the detection gear 74. The concave portion 76 of the cam surface 77 faces the detection pin 78 by a small amount of rotation compared to the amount of drive for use. At this opposing position, the detection pin 78 is fitted into the recess 76 by the force of the spring 79.

The detection pin 78 protrudes outside the waste toner casing 3 when the image forming cartridge 1 is not in use, and when the image forming cartridge 1 is mounted on the upper frame 33, the switch 94 provided on the upper frame 33 is activated. It is pushed by the detection pin 78 and automatically detects that the image forming cartridge 1 is unused. This detection signal is sent to the control system of the printer 31 to start counting the number of prints using the image forming cartridge 1 and to issue a restriction or warning against use of more than a predetermined number of prints based on this count. Conversely, if the image forming cartridge 1 to be installed has already been used, the detection pin 78 is retracted toward the waste toner casing 3, so even if the image forming cartridge 1 is installed in the upper frame 33, Switch 94 cannot be pressed. Therefore, no action is taken as would be the case when the unused waste toner casing 3 is attached.

However, the usage status can also be detected at the necessary time. For example, by detecting the point in time when a predetermined number of sheets, such as 500 sheets, have been used and using this as a use start signal, it is possible to support test use of up to 500 sheets. Furthermore, it can be said that the point in time when the image forming cartridge 1 has been used for printing the maximum number of sheets for use is detected and a warning is given for further use.

Effects of the Invention According to the present invention, by shielding the transfer charger from the image carrier by the shielding means in the side region of the transfer material in accordance with the width of the transfer material, the image carrier is reversely charged by the transfer charger. It is possible to reliably prevent the occurrence of "fluffing" on the sides, reduce toner consumption, and extend the life of the image carrier by preventing uneven deterioration. be effective.

[Brief explanation of the drawing]

1 to 7 show a printer according to an embodiment of the present invention,
Figure 1 is a sectional view of an image forming cartridge used in a printer, Figure 2 is a plan view of a transfer charger and shielding means, and Figure 3 is a cross-sectional view of an image forming cartridge used in a printer.
The figure is a partially enlarged sectional view of the charger, FIG. 4 is a front view showing a schematic configuration of the printer, FIG. 5 is a perspective view showing the developing roller section, and FIG. 6 is an enlarged front view of a portion of the developing roller section. ,
FIG. 7 is a cross-sectional view of a part of the waste toner casing showing the unused detection mechanism of the image forming cartridge, FIG. 8 is a side view of the main parts showing an example of an electrophotographic image forming apparatus, and FIG. FIG. 10 is a perspective view showing the relationship between the area of the transfer charger facing the transfer material and the area not facing the transfer material, and FIG. 10 is a graph showing the change in potential after the turning portion of the photosensitive drum. Photosensitive drum transfer charger 3a 3b...shielding member.

Claims (1)

[Claims] (1) In an image forming apparatus in which a toner image on an image carrier is transferred to a transfer material using a transfer charger, the shielding area can be changed in the axial direction of the image carrier between the image carrier and the transfer charger. An image forming apparatus characterized in that a shielding means is provided.