JPH08314222A - Rotary body fall-off preventing device - Google Patents

Abstract

PURPOSE: To provide a rotary body fall-off preventing device capable of surely preventing gears supported by the end parts of shafts from falling off without using a restraining ring. CONSTITUTION: The outside plate 53 of a unit case 2 is arranged proximately outside the gears 68 and 69 supported by the shafts 63 and 64, to prevent the falling off of the gears 68 and 69 out of the shafts 63 and 64 caused by the outside plate 53.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary body supported on an axial end portion of a shaft, which is moved outward from the axial direction of the shaft from a predetermined mounting position on the shaft to the end portion of the shaft. The present invention relates to a rotating body separation preventing device including a stopper that prevents separation from the rotating body.

[0002]

2. Description of the Related Art Various types of rotating bodies such as gears, rollers, pulleys, or drums are used in various devices such as image forming apparatuses, and such rotating bodies cannot rotate relative to a shaft or can rotate relative to each other. And is rotatably driven by a drive device via its shaft or via another transmission element. When such a rotating body is supported at the axial end of the shaft, the rotating body may be moved outward from the predetermined axial position of the shaft in the axial direction of the shaft and separated from the end of the shaft. I need to stop.

For this reason, conventionally, a stopper made of a locking ring such as an E ring or a C ring is fitted on the shaft to prevent the rotating body from being displaced outward from the shaft in the axial direction of the shaft. It was However, when the rotating body separation preventing device having such a locking ring is used, the number of parts of the device in which the shaft and the rotating body are incorporated is increased by the amount of the locking ring, and the cost thereof is increased. In addition, when the rotating body is attached to or detached from the shaft, the locking ring must be attached or detached, so that the workability is inevitable.

[0004]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above-mentioned novel recognition. The object of the present invention is not to use a retaining ring as in the prior art, but to use a rotating body as an axis. Another object of the present invention is to propose a rotating body separation preventing device that can prevent the separation of the rotating body from the outside in the axial direction.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to a rotary body separation preventing device of the type described at the beginning, in which the case wall of the device in which the shaft and the rotary body are incorporated is the shaft. A rotation body detachment prevention device characterized in that the case wall is located outward of the end portion of the shaft in the axial direction of the shaft, and the case wall constitutes a stopper that prevents the rotation body from detaching. To do.

In this case, the case wall has a protrusion projecting toward the rotating body at a portion facing the rotating body, and the projecting portion is a part of a surface of the rotating body facing the protruding portion. Advantageously, its shape is set such that it abuts against and prevents the rotor from coming off the shaft.

In each of the above constructions, the shaft is supported by a unit case of an image forming unit constructed by incorporating at least one image forming element in the unit case, and the case wall is a wall portion of the unit case. It is advantageous.

Further, in the above structure, the wall portion forming the case wall is an outer plate of the unit case, and the shaft is supported by the inner plate of the unit case located inside the unit case with respect to the outer plate. It is particularly advantageous if the rotary body is located between the inner and outer plates.

Further, in the above-mentioned constitution, it is advantageous that the inner plate constitutes a developing case for accommodating a developer therein.

Further, in the above structure, at least one of the inner plate and a bearing rotatably supporting the shaft on the inner plate restricts movement of the rotating body inward in the axial direction with respect to the shaft. It is particularly advantageous to construct the means.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention can be widely applied to a rotary member separation preventing device in various kinds of devices, but the following will be referred to as an image forming device formed as a copying machine, a printer, a facsimile, or a composite machine thereof. An embodiment in which the present invention is applied to a rotating body separation preventing device used in a unit will be described. First, the overall structure and operation will be clarified.

FIG. 1 is a vertical sectional view of an image forming unit 1 mounted on an image forming apparatus main body (not shown).
FIG. 3 is an external perspective view of the image forming unit. The image forming unit 1 is detachably attached to the main body of the image forming apparatus. In this example, the image forming unit 1 is pushed in the direction shown by an arrow A in FIG. The image forming unit 1 can be taken out from the main body of the image forming apparatus by loading and setting 1 at a predetermined position in the main body of the image forming apparatus shown in FIG. 1 and pulling out the image forming unit in the direction opposite to the arrow A. . The image forming apparatus is configured as, for example, a copying machine, a printer, a facsimile or a multifunction machine thereof.

As shown in FIGS. 1 and 2, the image forming unit 1 has a unit case 2 and various image forming elements incorporated therein, which will be described later. The unit case 2 shown as an example in the drawings is A case main body 3, a case cover 4 attached to the upper part thereof, a developing case cover 5 constituting an upper wall of a developing device 10 described later, an upper wall of a toner conveying path of a toner recycling device also described later, and a developing device. An upper cover 6 forming a part of the upper wall, and the case cover 4, the developing case cover 5, and the upper cover 6 are snap-fitted to the case body 3 (so-called patching).
It is detachably locked by. The opening 102 (FIG. 2) formed in the developing case cover 5 is closed by a developer cartridge 81 (FIG. 1) not shown in FIG.

FIG. 3 is an external perspective view showing a state in which the case cover 4, the developing case cover 5, and the upper cover 6 shown in FIGS. 1 and 2 are removed from the case body 3, and FIG. 4 is the same. It is a partial cross-section top view in a state.

Inside the unit case 2, a drum-shaped photosensitive member 7 which is an example of an image bearing member on which an electrostatic latent image is formed and a charging roller 8 which is an example of a charging device are rotatably provided. Assembled, the charging roller 8 extends parallel to the photoconductor 7. In FIG. 3, a part of the charging roller 8 is shown separated from the photoconductor 7.

During the image forming operation, the photosensitive member 7 is rotationally driven in the clockwise direction in FIG. 1 by a driving device (not shown), and at this time, a discharging light from a discharging device (not shown) supported by the main body of the image forming device. L1 is the case cover 4
The light enters the inside of the unit case 2 through the opening 34 formed in, and irradiates the surface of the photoconductor 7. As a result, the surface potential of the photoconductor 7 is averaged to the reference potential of 0 to -150V, for example. On the other hand, the charging roller 8 is pressed against the surface of the photoconductor 7 and is rotated by the rotation of the photoconductor 7, while the photoconductor 7 has a surface potential of, for example, -1100.
It is uniformly charged to be around V. At this time, a predetermined voltage is applied to the charging roller 8 by a power source (not shown).

The light-modulated laser beam L2 is applied to the surface portion of the photoconductor 7 charged to a predetermined polarity as described above in the exposure section 9. The laser light L2 is emitted from an exposure optical system (not shown) supported by the main body of the image forming apparatus, and enters the unit case 2 through an opening 35 formed in the case cover 4. By such exposure,
A predetermined electrostatic latent image is formed on the photoconductor 7. For example, the surface potential of the photosensitive member portion (image portion) irradiated with the laser light L2 is 0 to -290V, and the surface potential of the photosensitive member portion (background portion) not irradiated with the laser light L2 is -1100V described above. The front and back are almost maintained. It is also possible to illuminate a document (not shown) and form a reflected light image on the photoconductor 7 to form an electrostatic latent image.

On the other hand, in the unit case 2, as shown in FIGS. 1 and 4, the developing sleeve 11 of the developing device 10 is provided.
(Not shown in FIG. 3) is rotatably supported, and this sleeve 11 is rotationally driven counterclockwise in FIG. 1 during an image forming operation. Further, a developing case 12 of the developing device 10 is constituted by a part of the case body 3 in the unit case 2 and the above-mentioned developing case cover 5 covering the upper part thereof, and a developer chamber 90 is defined therein. The developer chamber 90 in the developing case 12 contains a powdery two-component developer 101 (FIG. 1) containing toner and carrier, and the inside of the developing sleeve 11 is generally denoted by reference numeral 13.
The plurality of magnets indicated by are fixedly arranged.

By rotating the developing sleeve 11 as described above, the developer 101 in the developing case 12 is carried while being carried on the developing sleeve 11 by the magnetic force of the magnet 13, and is formed by the doctor blade 14. The amount of developer transported is regulated by the. The regulated developer is carried to the developing area between the developing sleeve 11 and the photoconductor 7, and at this time, for example, −80 in the developing sleeve 11.
Since the developing bias voltage of about 0 V is applied, the toner in the developer conveyed to the developing area is electrostatically transferred to and adheres to the image portion on the photoconductor 7, and the predetermined amount on the photoconductor 7. Toner image is formed. The electrostatic latent image formed on the photoconductor 7 is visualized as a toner image.

As described above, the developing device 10 visualizes the electrostatic latent image formed on the image carrier composed of the photoconductor 7 as a toner image by using the two-component developer 101 having toner and carrier. The developing sleeve 11 serves as an example of a developer carrying member for carrying and carrying the two-component developer 101 to be developed.

On the other hand, as shown in FIG. 1, a transfer roller 15 which is an example of a transfer device is rotatably supported by the main body of the image forming apparatus so as to face the photoconductor 7. Further, a sheet feeding device (not shown) is provided on the image forming apparatus main body side, and from this sheet feeding device, a transfer sheet 100, which is an example of a transfer material, is provided with a photoconductor 7 and a transfer roller as indicated by an arrow B in FIG. The sheet is conveyed toward the transfer section 22 between the sheet and the sheet 15. Such transfer paper 10
0 passes through the transfer portion 22 between the photoconductor 7 and the transfer roller 15 in a state where the tip of the toner image matches the tip of the toner image formed on the photoconductor 7. At this time, the transfer roller 15
Is in contact with the photoconductor 7 via the transfer paper 100, as shown in FIG.
Of the transfer roller 1 which rotates counterclockwise in
Since the transfer bias voltage is applied to 5, the toner image on the photoconductor 7 is transferred to the transfer paper 100.

The transfer paper 100 that has left the photoconductor 7 is conveyed to a fixing device (not shown) as indicated by an arrow B1 in FIG. 1, where a toner image is transferred by the action of heat and pressure. It is fused and fixed on 100. A charge eliminating needle 16 supported by the image forming apparatus main body is arranged on the downstream side of the transfer unit 22 in the transfer direction of the transfer paper 100. The static elimination needle 16 is made of a thin metal plate extending parallel to the photoconductor 7, and the portion of the static elimination needle 16 on the side facing the photoconductor 7 is formed in a sawtooth shape, and the tip of each tooth is sharpened. . A voltage is applied to the static elimination needle 16 by a power source (not shown), whereby the transfer paper 100 is neutralized and the transfer paper 100 is easily separated from the photoconductor 7.

An intermediate transfer member is used as a transfer material, and the toner image on the photoconductor is primarily transferred to the intermediate transfer member, and then the toner image is secondarily transferred to a transfer paper which is the final transfer material. You can also do it.

Residual toner adhering to the photoconductor 7 after the toner image is transferred is scraped off the surface of the photoconductor 7 by the cleaning blade 18 of the cleaning device 17 shown in FIG. In this way, the surface of the photoconductor 7 is cleaned and the next image forming operation starts again. Cleaning device 1
7 has a cleaning case 19 formed by a part of the case body 3 in the unit case 2, and the toner scraped off by the cleaning blade 18 is
The toner carrying member 20 disposed in the cleaning case 19 is discharged to the outside of the cleaning device 17 and reused in the developing device 10 as described later. The toner carrying member 20 is configured in an appropriate form such as a toner carrying screw or a toner carrying coil. The cleaning blade 18 is an example of a cleaning member that removes toner remaining on the surface of the photoconductor 7 from the surface and cleans the surface, and is fixedly held by the case body 3 as described later. ing.

As described above, the illustrated image forming apparatus is
The toner image formed on the image carrier composed of the photoconductor 7 is transferred onto the transfer paper 100 conveyed toward the image carrier to obtain a recorded image, and the main body of the image forming apparatus is configured. The detachably mounted image forming unit is one in which at least one of the image forming elements including the above-mentioned image carrier is assembled in a unit case. In the illustrated example, the photoconductor 7, the charging roller 8 and the developing unit are provided. The respective components of the apparatus 10 and the cleaning device 17 are assembled in the unit case 2 to form the image forming unit 1.

Here, in order to properly convey the transfer paper 100 toward the photoconductor 7, it is necessary to provide a guide portion for guiding the transfer paper 100. Therefore, in the image forming apparatus shown in FIG.
Upper and lower guide portions 23 and 24 for guiding 00 are provided. The lower guide portion 24 is composed of a guide member fixed to the main body of the image forming apparatus, and this guide member also serves to guide the transfer paper 100 separated from the transfer portion 22 in the direction of arrow B1.

As for the upper guide portion 23 described above,
Although it is also possible to configure the guide member fixed to the image forming apparatus main body, in this case, in addition to the lower guide member, the upper guide portion 23 is provided in the image forming apparatus main body as an independent member. Inevitably, this increases the number of parts and increases the cost.

Therefore, in the image forming apparatus of this example,
The lower part of the unit case of the image forming unit 1 attached to the main body of the image forming apparatus, that is, the lower part of the case main body 3 in the illustrated example
The upper guide portion 23 that regulates the traveling direction of the transfer sheet 100 that is conveyed is configured. The unit case 2 of the image forming unit 1 is positioned with respect to the image forming apparatus main body so that the lower part of the unit case constitutes the guide portion 23. The guide portion 23 is the lower guide portion 2
4 for guiding the transfer sheet 100 which is located above the transfer section 22 and is located upstream of the transfer section 22 with respect to the transfer sheet 100 transfer direction. Make up.

As described above, since the unit case itself constitutes the guide portion 23 for guiding the transfer paper 100, it is not necessary to provide an independent member as the upper guide portion, and the number of parts of the image forming apparatus can be reduced. , The cost reduction can be achieved.

FIG. 5 is a perspective view showing the case main body 3 of the unit case 2 constituting the image forming unit 1, which is vertically inverted from the state shown in FIG. As you can see from this figure,
The unit case 2, the bottom wall 2 of the case body 3 in this example
A part of the photoconductor 7 protrudes from the notch 25 formed in the outer side of the unit case 2. Further, the arrow B in FIG. 5 indicates the conveyance direction of the transfer paper 100 sent toward the transfer portion 22 (FIG. 1), as in the arrow B in FIG. Further, the symbol W indicates a paper passing area through which the transfer paper 100 passes, and the transfer paper 100 having the maximum width also passes through this area W.

In this example, as shown in FIGS. 1 and 5, the guide portion 23 formed by the lower part of the unit case is
The unit case 2 is formed of a plurality of guide ribs 26 protruding from the bottom wall 21 of the case body 3 and extending along the transfer direction B of the transfer paper 100.
These ribs 26 are separated from each other in a direction orthogonal to the transfer direction B of the transfer paper 100, and the transfer paper 100 is
Is provided in the sheet passing area W through which the sheet passes, and the free end edge of the rib 26 can reliably guide the transfer sheet 100 of the maximum size.

Instead of the above-mentioned guide rib 26, a flat surface of the lower part of the unit case, for example, the lower surface of the bottom wall 21 thereof, can constitute a guide part for guiding the transfer paper 100 conveyed to the transfer part 22. If the guide portion is a flat surface, the electrostatic force of the transfer paper 100 causes
The transfer paper 100 comes into close contact with the flat guide surface, and the transfer paper 1
In some cases, the transportability of 00 is deteriorated. If such a decrease in transportability occurs, the toner image transferred onto the transfer paper 100 may expand or contract, resulting in an abnormal image. Further, when the toner adheres to the guide portion formed of a flat plane, the adhered area becomes large, so that the adhered toner may re-adhere to the leading end of the transfer paper in a large amount and the transfer paper may be significantly soiled.

On the other hand, as in the example shown in FIGS. 1 and 5, the guide rib 26 constitutes the guide portion 23,
If the transfer paper 100 is configured to be guided by the free edges of the guide ribs 26, even if the transfer paper 100 comes into contact with the guide portion 23, the contact area becomes extremely small, so that the transfer paper 100 has electrostatic force. Therefore, it is possible to prevent the guide portion 23 from being in close contact with the guide portion 23 and prevent the occurrence of an abnormal image. Moreover, even if toner adheres to the guide portion 23 constituted by the free end edge of the guide rib 26, since the contact area between the guide portion 23 and the transfer paper 100 is small, a large amount of toner adheres to the transfer paper 100. Transfer paper 100
In addition, it is possible to prevent the occurrence of remarkable dirt due to the toner.

Further, as shown in FIGS. 1 and 5, the transfer is performed on the lower part of the unit case 2 other than the paper passing area W through which the transfer paper 100 passes, that is, the lower part of the case body 3 in the illustrated example. A protrusion 27 that protrudes outward (downward in FIG. 1) from the guide portion 23 of the paper 100 is provided. The protrusion 27 is provided at the lower portion of the unit case 2 that does not hinder the transfer paper 100 from being conveyed. In the example of FIGS. 1 and 5, the transfer paper 1 guided by the guide portion 23
Protrusions 27 formed integrally with the case main body 3 are provided on both outer sides of the paper passing width range of 00, and a total of four protrusions 27 are provided. The height H of the protrusions 27 protruding from the bottom wall 21 of the unit case 2 is higher than the height h of the guide ribs 26 protruding from the bottom wall 21.

Here, when the image forming unit 1 is taken out from the main body of the image forming apparatus as described above, the unit 1
Is placed on a flat surface such as a floor or a desk surface with the lower side of the unit case facing downward. At this time, since the protrusions 27 protruding outward from the guide portion 23 are provided in the lower portion of the unit case 2, these protrusions 27 come into contact with the mounting surface. That is, the guide portion 23 existing between the protrusions 27, in this example, the free end edge of the guide rib 26 does not contact the mounting surface.

According to the above construction, even if a foreign matter is present on the mounting surface, there is no risk that the foreign matter will adhere to the guide portion 23 or the guide portion 23 will be damaged by the foreign matter. Therefore, even if the image forming unit 1 is loaded again into the main body of the image forming apparatus and used as it is, foreign matter does not adhere to the transfer sheet 100, and the guide portion 23 functions to guide the transfer sheet 100 without any trouble. be able to. Further, even if foreign matter on the mounting surface adheres to the projection 27 or the projection 27 is damaged to some extent by the foreign matter, when the image forming unit 1 is set in the main body of the image forming apparatus, the projection Since 27 is located outside the paper passing area W through which the transfer paper 100 passes, there is no risk that the transfer paper 100 may be hindered from being conveyed.

In FIG. 5, the transfer sheet 100 being conveyed is shown.
Although the protrusions 27 are provided on both sides of the sheet, the protrusions 2 are formed on other portions of the lower portion of the unit case outside the paper passing area W.
7 may be provided. 6A and 6B show the outer sides of the transfer sheet to be conveyed and the portion of the unit case bottom wall 21 on the upstream side in the transfer sheet conveyance direction with respect to the sheet passing area W to the outside of the unit case from the guide portion 23 including the guide ribs 26. Protruding part 2
7 shows an example in which 7 are provided respectively.

The protrusion height H from the bottom wall 21 of the protrusion 27 shown in FIGS. 1, 5 and 6 is such that when the image forming unit 1 is placed on the mounting surface, the photosensitive member 7 and the mounting surface thereof are mounted. The size is set so that it does not touch the table.

Next, in order to understand the present invention, each device constituting the illustrated image forming apparatus and each component thereof will be described in more detail.

First, the photoconductor 7 illustrated in FIG. 1 is a laminated type OPC photoconductor, and FIG. 7 is a schematic enlarged view of the cross-sectional structure thereof. 7 has a charge generation layer (CGL) 29 having a thickness of 0.1 to 1 μm and a charge transfer layer (CTL) having a thickness of 10 to 30 μm on a conductive substrate 28. ) 30 are sequentially stacked, and the charge generation layer 29 and the charge transfer layer 30 form a photosensitive layer 31. The laser beam L2 incident on the photoconductor 7 passes through the transparent charge transfer layer 30 and is absorbed by the charge generation layer 29, and carriers are generated by the excitation energy in the charge generation layer 29. The generated carriers are injected into the charge transfer layer 30 by the force of the external field, move in the charge transfer layer 30, reach the surface of the photoconductor, and neutralize the surface charge. The charge transfer layer 30 shown in FIG. 7 is of a hole transport type and shows a state when it is negatively charged.

Next, the charging roller 8 shown in FIGS.
Is an example of a charging device that charges the image bearing member to form an electrostatic latent image on the image bearing member. The charging roller 8 includes a conductive rubber on the outer peripheral surface of a metal cored bar. Is wound around and contacts the surface of the photoconductor 7 when the photoconductor 7 is charged. The charging roller 8 has a bearing 33a, one end of which is shown in FIG.
Are rotatably supported by the respective bearings 33a,
Charging roller case 3 extending parallel to the charging roller 8
Along with the charging roller 8, the photoconductor 7
It is supported so as to be movable in a predetermined range in a direction approaching or separating from. On the surface of the charging roller case 33 facing the charging roller 8, a cleaning pad 32 which is an example of a charging roller cleaning member extending along the charging roller 8 is attached.

A first compression spring (not shown) is press-fitted between each of the bearings 33a described above and each end of the charging roller case 33 in the longitudinal direction.
3a is pressed toward the photoconductor 7 so that the charging roller 8 can be pressed against the surface of the photoconductor 7. Further, the charging roller case 33 is also formed in the case main body 3 of the unit case 2 so that each end of the case 33 in the longitudinal direction is movable in a direction of approaching or leaving a predetermined range with respect to the surface of the photoconductor 7. And each notch 36 (only one is shown in FIG. 3). Such charging roller case 33
The case cover 4 (FIGS. 1 and 2) prevents the case main body 3 from coming off. Further, a second compression spring 37 (only one of which is shown in FIG. 3) different from the above-described first compression spring is provided between the case body 3 and each longitudinal end portion of the charging roller case 33. The charging roller case 33 is pressure-loaded and is biased in the direction away from the surface of the photoconductor 7.

The case cover 4 functions as a protective cover for preventing the human body from touching the photoconductor 7, the charging roller 8 and the like. In addition, as described above, the second compression spring 37 is used. The charging roller case 33, which is biased by, also functions as a stopper that prevents the charging roller case 33 from coming off the case body 3. Accordingly, it is not necessary to provide an independent stopper member for the charging roller case 33, and the simplification of the configuration can be achieved.

On the other hand, as shown in FIG. 1, the main body of the image forming apparatus is provided with an electromagnetic clutch 39 for controlling rotation of the cam 38. The cam 38 is fixed to the rotary shaft of the electromagnetic clutch 39. Is configured to rotate 120 ° in one operation. In addition, this cam 38
One end 41a of a swing arm 41, which is swingably supported by the image forming apparatus main body via a pivot pin 40, comes into pressure contact with the action of a spring (not shown), and the other end 41b of this arm 41 is attached to the case cover 4. Charging roller case 33 through the opening 34
Is in contact with the upper surface of the The upper surface of the charging roller case 33 is in pressure contact with the other end 41b of the swing arm 41 by the pressing action of the second compression spring 37 described above.

The charging roller case 33 is also shown in FIG. 1 when the cam 38 occupies the rotational position shown in FIG. 1 and the cam surface portion indicated by the symbol a _{1 is in contact} with the one end 41a of the swing arm 41. However, at this time, the charging roller 8 is pressed against the surface of the photoconductor 7 by the pressing action of the first compression spring, and the voltage applied to the core of the charging roller 8 causes As described above, the photoconductor 7 is charged to a predetermined polarity.

As described above, since the charging roller 8 is continuously in contact with the surface of the photoconductor 7 during the charging operation for charging the photoconductor 7, the fine toner adhering to the photoconductor 7 stains the charging roller 8. Therefore, uneven charging may occur on the photoconductor 7. Therefore, in the image forming apparatus of the present embodiment, the electromagnetic clutch 39 is activated to rotate the cam 38 by 120 ° at an appropriate time other than the charging operation by the charging roller 8, and the cam surface portion indicated by reference numeral a ₂ in FIG. Comes into pressure contact with one end 41 a of the swing arm 41. As a result, the other end 41b of the swing arm 41 pressurizes and moves the charging roller case 33 in a direction approaching the surface of the photoconductor 7. At this time, the charging roller 8 is still in pressure contact with the surface of the photoconductor 7, and therefore the cleaning pad 32 is in pressure contact with the peripheral surface of the charging roller 8. At that time, the charging roller 8 rotates following the rotation of the photoconductor 7, and the cleaning pad 32 cleans the peripheral surface of the charging roller 8. In this way, it is possible to prevent the charging operation of the photoconductor 7 from being performed while the charging roller 8 is soiled by the toner, and it is possible to prevent uneven charging of the photoconductor 7.

When the operation of the image forming apparatus is stopped,
By the operation of the electromagnetic clutch 39, the surface of the cam 38 indicated by reference numeral a ₃ in FIG. 1 is brought into pressure contact with the one end 41 a of the swing arm 41. As a result, the other end 41b of the swing arm 41 is lifted above the state shown in FIG.
3 moves in a direction away from the photoconductor 7 by the action of the second compression spring 37 described above. As a result, the charging roller 8 also separates from the surface of the photoconductor 7. If the charging roller 8 is kept in contact with the photoconductor 7 for a long time while the image forming apparatus is not operating, the photoconductor 7 may be contaminated and an abnormal image may be generated. In the device,
As described above, when the operation is stopped, the charging roller 8 is separated from the photoconductor 7 to prevent the abnormal image from being generated during the image forming operation.

Although a charging device composed of a corona discharger can be used in place of the charging roller 8, if the charging roller 8 is adopted as in this example, the ozone generation amount when the corona discharger is used is 1/100. It is possible to reduce the amount to 1/1000, which eliminates the need to attach an ozone processing member to the main body of the image forming apparatus.

Next, the charging mechanism by the charging roller 8 will be described. FIG. 8 is a charging model diagram schematically showing the photoconductor 7 and the charging roller 8, and FIG. 9 shows an equivalent circuit of the charging model. Here, the voltage applied to the core metal at the center of the charging roller 8 is Va, the voltage applied to the charging roller 8 is Vr, the discharge start voltage in the gap 42 near the contact portion between the charging roller 8 and the photoconductor 7 is Vg, When the surface potential of the photoconductor 7 is Vd, these relationships are expressed as Va = Vr + Vg + Vd (1). Here, the voltage Vr applied to the charging roller 8
Vr = I · R (2), where R is the resistance value of the charging roller 8 and I is the flowing current value, and the discharge start voltage Vg in the air gap is the film thickness of the photosensitive layer 31 of the photoconductor 7 d. , The relative dielectric constant of the photosensitive layer 31 is K
If d, then Vg = 312 + 6.2 × d / Kd + √ (7737.6 × d / Kd) (3) The surface potential Vd of the photoconductor is Vd = Q / C (4) where Q is the charge supplied to the photoconductor 7 and C is the capacitance of the photoconductive layer 31. Here, the peripheral speed of the photoconductor 7 is Vp, and the charging roller 8 is
Is L and its dielectric constant is K ₀ , then Q = I / L · Vp C = (K ₀ · Kd) / d and Vd = (I · d) / (K ₀ · Kd · L · Vp) (5). Therefore, the formula (1) becomes Va = I · R + 312 + 6.2 × d / Kd + √ (7737.6 × d / Kd) + (I · d) / (K ₀ · Kd · L · Vp) (6) . The above is the charging model formula.

Next, considering the charging control method by the charging roller 8, either a constant voltage control method or a constant current control method can be adopted as this method.

The constant voltage control system is the V of the equations (1) and (6).
This is a control method that keeps a constant. In this case, it is the term Vd that is actually used as the charging potential of the photoconductor 7 in the equation (1). Therefore, changes in Vr and Vg affect Vd. Looking at each term here, the term of Vr is
The resistance value of the charging roller 8 is a variable factor. Therefore, when the resistance value of the charging roller 8 rises due to environmental changes, the Vr value rises and the Vd falls. Therefore, in order to suppress this effect, it is necessary to provide a temperature detecting means and correct Va. Further, since the charging roller resistance value remarkably rises at low temperature and humidity, it is desirable to provide a heater (not shown) or the like so that the temperature does not drop below a certain temperature.

Next, in the term of Vg, the film thickness d of the photosensitive layer 31 is affected, but a numerical value is actually substituted and d is initially set.
= 28 μm, and decreased by 4 μm over time, Kd = 3.2
When calculated as, Vg (28) = 626, Vg (24)
= 599, the difference is 27V. Since the change is to this extent, it is considered that the influence on the charging potential (normally 800 to 1000 V) is small. Since the value of the current flowing when the resistance value of the charging roller fluctuates is small, it is possible to reduce the influence on Vd by suppressing the charging roller resistance value to a low level (for example, 10 ⁷ Ω or less). .

The constant current method is a control method in which I is constant in the equation (6) and is not affected by the terms Vr and Vg. However, the influence of the change in the photosensitive layer film thickness d in the term of Vd directly affects Vd, and the initial 28 μm shown in the above example.
And, when it changes by 4 μm with time, Vd is Vd × 24 with time.
The value is / 28, and if Vd is 850V in the initial stage,
With time, it becomes 728 V and drops by 100 V or more, and the charging performance may not be guaranteed. In order to prevent this, the change in the film thickness of the photosensitive layer 31 may be detected and corrected, but in reality, such a detection mechanism is expensive and cannot be mounted. Therefore, increase the hardness of the photoconductor surface,
Currently, it is difficult to take measures except to use a photoconductor that does not wear.

For the above reasons, the charging roller 8 is used in this example.
Although it is necessary to correct the applied voltage with respect to the resistance fluctuation of the above, a constant voltage control method is adopted. Then, as a temperature detecting means of the charging roller 8, as shown in FIG.
The thermistor 43 attached to is used. The thermistor 43 detects the surface temperature of the charging roller 8 and sends a signal to a circuit for correcting the applied voltage corresponding to the change in temperature of the charging roller 8 and the change in its electric resistance. In the thermistor 43, the charging roller 8 has the photosensitive member 7
It is provided at a position where it contacts the charging roller 8 when it is separated from the surface.

Since the thermistor 43 is attached to the case cover 4 as described above, it is not necessary to separately provide a dedicated attachment member for the thermistor, and the structure of the image forming apparatus, particularly the image forming unit 1 thereof, is simplified. be able to. Further, when the charging roller 8 is separated from the photoconductor 7, that is, when the voltage is not applied to the charging roller 8, the thermistor 43 contacts the peripheral surface of the charging roller 8 and can detect the temperature of the roller 8. Therefore, there is no possibility that the thermistor 43 will be broken by the influence of the voltage applied to the charging roller 8.

Next, the developing device 10 will be described. As described above with reference to FIGS. 1, 3 and 4, the developing case 12 contains the two-component developer 101 having a carrier and a toner, for example, a small iron ball. 101 is agitated while being circulated and conveyed in the developer chamber 90 of the developing case 12 by the first and second agent agitating members 44 and 45 which will be described in detail later.
1 is supplied. As described above, the layer thickness of the developer supplied to the developing sleeve 11 is regulated by the doctor blade 14 provided around the developing sleeve 11.
A portion of the peripheral surface of the developing sleeve 11 facing the photoconductor 7 is exposed to the outside from the developing case 12.

Here, the developing sleeve 11 is made of a non-magnetic cylindrical body made of aluminum having an outer diameter of, for example, 16 to 20 mm, and its peripheral surface is formed smoothly, or in order to enhance the transportability of the developer. An unevenness such as a V groove is formed on the outer peripheral surface of the developing sleeve 11.

As shown in FIG. 4, a shaft 46 penetrates the inside of the developing sleeve 11, and the magnet 13 is fixed to the shaft 46. An end portion 46a on the front side of the shaft 46 is fixed and supported to the case body 3 of the unit case 2 as described later, and an end portion 46b on the rear side is fitted and fixed to the rear side end of the developing sleeve 11. It is fitted to the sleeve end member 47 via a bearing so as to be relatively rotatable. The shaft portion 47a of the sleeve end member 47 is rotatably supported by the case body 3 of the unit case as described later. The front end of the developing sleeve 11 is rotatably supported by the shaft 46 via a bearing. The "back side" and "front side" referred to here are based on the attachment / detachment direction of the image forming unit 1 to / from the image forming apparatus main body.

As described above, the shaft 46 is immovably supported together with the magnet 13 with respect to the unit case 2, and the shaft 4 is fixed.
A developing sleeve 11 is rotatably supported by the roller 6. Then, the sleeve end member 47 is rotationally driven via a coupling 48 attached to the sleeve end member 47 and a coupling 49 (FIG. 2) on the image forming apparatus main body side which engages with the sleeve end member 47, so that the developing sleeve 11 can be rotated. It is driven to rotate in the counterclockwise direction at 1. The bias voltage to the developing sleeve 11 is applied from the image forming apparatus main body side via the couplings 48 and 49 described above.

FIG. 10 is an explanatory view showing the relationship between the developing sleeve 11, the magnet 13 arranged inside the developing sleeve 11 so as not to rotate, and the photoconductor 7. As shown here, the individual magnets of the magnet 13, namely the first to fifth magnets 13a to 1
3e are arranged in the circumferential direction of the developing sleeve 11, are fixedly fixed to the shafts 46, and extend in the longitudinal direction of the sleeve 11. Then, these magnets 13a to 13
By e, magnetic force distributions P _{1 to} P _{6 in the} normal direction are formed in the circumferential direction of the developing sleeve 11.

The first magnet 13a substantially faces the photoconductor 7 and its magnetic force distribution has a peak above the line connecting the centers of the photoconductor 7 and the developing sleeve 11 by θ = 3 ° to 10 °. are doing. The peak magnetic flux density is 80-100
(MT millitesla). If the peak magnetic flux density is too low, the carrier of the developer cannot be held on the developing sleeve 11 and the developer scatters. On the other hand, if the size is too large, the toner developed on the photoconductor 7 is likely to have a trace of the ears in the circumferential direction, and the toner attached to the low potential portion of the photoconductor 7 is collected again in the developing sleeve 11. Sometimes. If the angle θ is too large, the developing ability will decrease.

The magnetic force distribution P ₂ by the second magnet 13b is
It has a peak magnetic flux density of 50 to 80 (mT) near the opening of the developing case 12. This magnetic force has a function of carrying the developer into the developing case 12 and also carrying the air near the lower side of the developing case 12 into the developing case 12. As a result, it is possible to prevent the toner from scattering outside the developing case 12. In order to improve the efficiency of air transportability, the shape of the developing case portion 12a corresponding to the peak magnetic flux density portion may be slightly expanded in the direction away from the developing sleeve 11.
This makes it possible to smoothly form the ears of the developer.

[0063] The third magnet 13c forms a magnetic field distribution P _3, conveys the developer to the developing case 12 by the magnetic force, in cooperation with the fourth magnet 13d, force distribution P
₄ (magnetic flux density of 10 mT or less) is formed. As a result, the developer that has been used for development is separated from the developing sleeve 11.

The magnetic force of the fourth magnet 13d serves to hold the developer supplied by the second agent stirring member 45 (FIG. 4) described later in detail in the developing sleeve 11. By reducing the magnetic flux density in the region of the doctor blade 14 and allowing the developer to pass in the state of being in close contact with the developing sleeve 11, the layer thickness of the developer can be regulated stably.

The fifth magnet 13e forms a magnetic force distribution P ₆ and carries the developer held by the magnetic force of the fourth magnet 13d to the region of the first magnet 13a, while stabilizing the developer and In order to control the air flow around the developing sleeve 11, the peak magnetic flux density of the magnetic force distribution P ₆ is set so that the inlet seal 50, which will be described later, comes into contact with the developer.

Gap between developing sleeve 11 and photoconductor 7
Is the gap G between the developing sleeve 11 and the doctor blade 14.
Determined by the relationship with d, Gp = Gd × (0.8-1.
0) and Gp-Gd = (0 to 0.15) mm.

The peripheral speed of the developing sleeve 11 is set to vs (mm / se
c), where the peripheral speed of the photoconductor 7 is vp (mm / sec), the relationship between them is as follows. vs = (1 to 2.5) × vp

As shown in FIGS. 4 and 11, the shaft portion 47a of the sleeve end member 47 projecting from the rear end portion of the developing sleeve 11 is rotatably fitted to the rear support member 57, and the shaft 46a. The front end portion 46a is fitted into the front support member 58 so as not to rotate relative to each other. These support members 57, 58
As shown in FIG. 11, is connected to the doctor blade 14 by a screw 59 that is inserted into the long holes formed in these and screwed into the doctor blade 14. Therefore, by loosening these screws 59, the doctor blade 14
Can be positionally adjusted with respect to the developing sleeve 11 in the substantially normal direction. After the adjustment, the screw 59 is tightened to fix the doctor blade 14 to the developing sleeve 11. The value obtained by moving the doctor blade 14 with respect to the developing sleeve 11 as described above and the gap between the two correspond one-to-one. Further, such adjustment work can be easily performed with the doctor blade 14 and the developing sleeve 11 removed from the developing device.

As shown in FIGS. 3 and 4, the case body 3 of the unit case 2 has a front side outer plate 51 on its front side.
And a front side inner plate 52, and a back side outer plate 53 and a back side inner plate 54 on the back side thereof. Inner plates 5 of case body 3
The lower edges of the front and rear side plates of the developing case cover 5 (FIGS. 1 and 2) are in contact with the upper edges of the reference numerals 2, 54, and the front and rear side plates and the front and rear inner plates 52, 54 of the case body 3, respectively. The front and rear side plates of the entire developing case 12 are constituted by. As described above, the developing case 12 containing the two-component developer is formed by a part of the unit case 2. As for the front and rear side plates of the developing case cover 5, only the side plates on the back side thereof are shown with reference numeral 5a in FIG.

In the photoconductor 7, the flange members 86 and 87 fixed to the respective longitudinal end portions of the photoconductor 7 have the positioning plate 5 on the front side.
A rear inner plate 52 and a rear outer plate 53 of the case main body are rotatably supported via a rear plate 5 and a rear positioning plate 56, respectively. The front support member 58 fitted to the front end portion 46a of the shaft 46 is also non-rotatably supported by the front inner plate 52 of the unit case 2 via the front positioning plate 55. Further, the shaft portion 47 a of the sleeve end member 47 is also rotatably supported by the back side outer plate 53 of the unit case 2 via the back side positioning plate 56. Back side support member 57
Is detachably fitted into the concave groove of the inner plate 54 on the back side.

As described above, the photoconductor 7 and the developing sleeve 1
1 is a positioning plate 5 whose front side and back side are common to each other.
It is supported by the unit case via 5, 56, so that the center distance between the developing sleeve 11 and the photoconductor 7 is kept constant, and the gap Gp between them is always kept constant.

Further, as shown in FIG. 11, the inlet seal cover 60 is provided on each of the support members 57 and 58 on the back side and the front side.
, And the above-mentioned inlet seal 50 is attached to the cover 60 as shown in FIGS. 1 and 10.
As shown in FIG. 1, the inlet seal cover 60 is located on the upstream side of the developing area between the developing sleeve 11 and the photoconductor 7, covers the upper portion of the developing sleeve 11, and regulates the developer on the developing sleeve. At the same time, it regulates the flow of air. The inlet seal 50 is made of, for example, a thin resin such as PET or PUR, and prevents the toner from scattering outside the developing device 10.

Further, as shown in FIG. 11, side seals 61 and 62 made of thin resin or the like are attached to the support members 57 and 58 on the back side and the front side, respectively, and these side seals 61 and 62 are developed. The sleeve 11 faces the peripheral surface of each end of the sleeve 11 in the longitudinal direction, and prevents the toner and the carrier from scattering from each end.

Next, the above-mentioned first and second stirring members 4
4, 45 are composed of shafts 63, 64 and a plurality of elliptical plates 65, 66 fixed to the shafts 63, 64, respectively. Although the oval plates are not shown in FIG. 3 for the sake of clarity, the oval plates 65 and 66 are each formed by cutting out an ellipse. Instead of an elliptical plate, use screws for each shaft 63, 64
Alternatively, the stirring members 44 and 45 may be fixed to the above.

In the first stirring member 44, each longitudinal end of the shaft 63 is rotated by bearings on the front side support wall 67 and the back side inner plate 54 in the case body 3 of the unit case 2, respectively. The second stirring member 45 is supported freely.
The longitudinal ends of the shaft 64 are rotatably supported by the front inner plate 52 and the rear inner plate 54 of the unit case 2 via bearings. Also, these stirring members 4
The drive gear 6 is provided at the rear end portions of the shafts 63 and 64 of the shafts 4 and 45.
8, 69 are non-rotatably supported with respect to their respective shafts, and a drive gear 70 is also fixed to the sleeve end member 47. These gears 70, 69, 68 mesh with each other via an intermediate gear (not shown).

Further, in the case main body 3 which constitutes the developing case 12, a partition wall 71 extending parallel to the stirring members 44 and 45 is provided upright in a region between the first and second stirring members 44 and 45. The front and back sides of the partition wall 71 are cut out to form passages 71a and 71b, respectively.

When the sleeve end member 47 is rotationally driven by the drive unit on the image forming apparatus main body side as described above, the developing sleeve 11 is rotated and the sleeve end member 47 is rotated by the drive gears 70, 69, 68. Is transmitted to the first and second stirring members 44 and 45 via the intermediate gear, and these members are rotationally driven in predetermined directions. As a result, the developer accommodated in the developer chamber 90 in the developing case 12 is conveyed while being stirred in the direction of the arrow X, and the developer is guided by the partition wall 71, and the passages 71a and 71b at both ends thereof are guided. Circulate through. As a result, the toner of the developer and the carrier are triboelectrically charged with different polarities. The developer is supplied to the developing sleeve 11, and the developer from the developing sleeve 11 is returned to the stirring member side. Since each of the elliptical plates 65 and 66 has a shape in which a part of an ellipse is cut out, the developer is agitated by hitting the edge of the cutout with the developer.

Here, when the pitch of the elliptical plates 65 and 66 of each stirring member 44 and 45 is P and the minor axis of the elliptical shape is Y, P = (1/3 to 4/5) × Y is satisfied. Is desirable. If the pitch P is smaller than this, the carrying force of the developer decreases, so the stirring member 4
The number of rotations of 4, 45 increases, and the developer is likely to deteriorate. If the pitch P is larger than the above formula, the stirring performance with respect to the developer deteriorates.

The rotation speeds of the first and second stirring members 44 and 45 are equal to each other, and the outer diameter Y and the pitch P of the elliptical plates 65 and 66 are also equal to each other. In addition, the respective elliptical plates 65, 6
It is desirable that the relationship between the peripheral speed v in the minor axis portion 6 and the peripheral speed vs of the developing sleeve 11 satisfy the following: vs = (1.1 to 1.5) × v.

If the peripheral speed v of the elliptical plates 65 and 66 is higher than that expressed by the above equation, the stress on the developer becomes large, and conversely, if the peripheral speed v is low, the developer on the developing sleeve 11 is replaced. It takes a lot of time, and uneven density occurs in the toner image formed on the photoconductor 7.

Elliptical plates 65, 66 of the stirring members 44, 45
And the partition wall 71 or the developing case wall have a gap of 0.
It is desirable to set it to 5 to 2 mm. If this gap is larger than this value, the developer cannot be conveyed reliably, and the developer that remains remains. If this gap is narrower than the above value,
The developer may be excessively strongly rubbed against the partition wall 71 or the developing case wall, and may deteriorate early.

When the gap between the elliptical plate 66 of the second stirring member 45 and the developing sleeve 11 is set to 1.5 to 3 mm, the developer can be smoothly supplied to the developing sleeve 11 and the developing sleeve 11 can be supplied. The developer can be smoothly collected from. If the gap between the two is too large, the developer is not sufficiently supplied to and collected from the developing sleeve 11. On the contrary, if it is too small, the developer is deteriorated due to stress and uneven toner supply occurs.

As shown in FIGS. 1 and 4, the developing case 12 includes a sensor for detecting the toner density of the developer 101,
In this example, a magnetic permeability measuring sensor 72 is provided. Further, the toner bottle 73 shown in FIGS. 1 and 2 is detachably attached to the main body of the image forming apparatus.

When the sensor 72 detects that the toner concentration of the developer 101 stored in the developer chamber 90 in the developing case 12 is below the reference value, the toner is supplied by the toner replenishment signal based on the detection signal. The bottle 73 is rotationally driven via its drive shaft 74, whereby the toner is supplied from the replenishment port 73a of the toner bottle 73 through the opening 6a (FIG. 2) formed in the upper wall of the upper cover 6 and the case main body 3 And is supplied to the toner replenishing section 75 (FIGS. 3 and 4) formed by.

Toner bottle 73 containing replenishment toner
Has a spiral protrusion formed on its inner wall surface, and by its rotation, the toner inside is sequentially sent from the back side to the replenishment port 73a on the front side, and is replenished to the toner replenishing section 75. At this time, a hopper (not shown) for guiding the replenishment toner is provided between the toner bottle 73 and the toner replenishment section 75, whereby the toner from the toner bottle 73 does not scatter to the toner replenishment section 75. Supplied. Toner bottle 7
An electromagnetic clutch (not shown) is provided on the drive shaft 74 that rotates 3 and when the toner replenishment signal is output, the electromagnetic clutch is turned on and the drive shaft 74 for the toner bottle is turned on.
Rotates.

As shown in FIGS. 3 and 4, a thin resin sheet having a large number of small holes is formed between the toner replenishing portion 75 and the developer chamber 90 containing the two-component developer. A shielding plate 76 is arranged, and a toner feeding member 78 made of a thin resin sheet having a base end fixed to a shaft 77 is arranged in the toner replenishing unit 75. The gear 79 fixed to the shaft 77 is The gear 80 fixed to the shaft 63 of the first stirring member 44 is meshed with the gear 80. The diameter of the small hole formed in the shielding plate 76 is, for example, about 0.5 to 1 mm. The shaft 77 is rotatably supported by the case body 3.

When the first stirring member 44 rotates as described above, the rotation is transmitted to the shaft 77 via the gears 80 and 79, the toner feeding member 78 rotates, and the tip portion thereof slides on the shield plate 76. Contact. As a result, the toner replenishing unit 75
Of the toner passes through the small holes of the shielding plate 76, and the stirring member 44
Is sent to the developer chamber 90 provided with.

As described above, since the toner from the toner bottle 73 is temporarily accumulated in the toner replenishing section 75 and is sent out to the developer chamber 90 little by little through the small holes of the shield plate 76, the toner from the toner bottle 73 is definite amount by a certain amount. Even if the developer is not discharged, the developer chamber 90 is replenished with toner in a constant amount. The toner supplied to the developer chamber 90 is stirred and mixed by the stirring members 44 and 45 with the two-component developer existing therein.

If the sensor 72 continues to detect a decrease in toner concentration even after the above-described toner replenishing operation is performed, it is assumed that the toner in the toner bottle 73 has run out, and the display unit indicates that the toner end is near. , And inform the user to that effect. If the toner bottle is not replaced despite such a display, the operation of the image forming apparatus is stopped when the image forming operation for 50 sheets of A4 size transfer paper is performed after the display. To do.

The replacement operation of the toner bottle 73 is judged by the opening / closing time of the front door (not shown) of the main body of the image forming apparatus. After the replacement of the toner bottle 73, the toner replenishing operation is performed for a certain period of time, and the detection voltage of the sensor 72 is detected. After confirming that has reached a certain value, the operation prohibition of the image forming apparatus is released.

As shown in FIG. 2, the developing case cover 5
An opening 102 is formed in the opening 102, and the developer cartridge 81 shown in FIG. 1 is mounted in the opening 102. When a new image forming unit 1 is shipped from a manufacturing factory or a store, the lower opening of the developer cartridge 81 is covered with a flexible sealing member (not shown), and toner and carrier are stored inside the cartridge 81. The two-component developer which it has is accommodated. At this time, no developer exists in the developer chamber 90.

When the image forming unit 1 is delivered to the user, by rotating a roller (not shown),
The seal member is wound around the roller to open the opening of the developer cartridge 81. As a result, the developer inside thereof falls into the developer chamber 90 inside the developing case 12.
As described above, since the developer is sealed and stored in the developer cartridge 81 until the image forming unit 1 is delivered to the user, deterioration of the developer due to moisture absorption during storage of the image forming unit 1 is prevented. It is also possible to prevent the developer from leaking from the developing device.

Next, the developing mechanism using the two-component developer, especially the basic concept of the magnetic brush development by the two-component developer centering on the force acting on the toner will be described.

Development Electric Field The development electric field formed between the photoconductor 7 and the development sleeve 11 shown in FIG. 10 is generally expressed by the following equation. E = ε (Vd−Vb) / Gp (7) E = Developing electric field (V / mm) ε: Dielectric constant of developer V
d: image portion potential of photoconductor (V) Vb: development bias voltage (V) Gp: development gap (gap between photoconductor and development sleeve) (mm) From the formula (7), the development electric field is the development bias voltage. It turns out that it is possible to control. Therefore, the image density is controlled by changing the developing bias voltage and controlling the developing electric field.

Forces Acting on Toner : a) Adhesive Force between Developer Carrier and Toner: A model diagram of the adhesive force of toner particles adhering to carrier particles C is shown in FIG. The toner particles T exchange some charges with the surface of the carrier C due to some contact and friction, have a negative charge of q, and a positive charge corresponding thereto is on the carrier side. The adhesive force Ft at the contact point between the two is the charge q
It consists of the Coulomb force due to and the short-range van der Waals force Fv, and is expressed as follows. Ft = Fv + αq ² / 4πε ₀ r ² (8) where r is the toner particle radius, ε ₀ is the dielectric constant of vacuum, and α
Is a constant (1 to 1.9) depending on the dielectric constant of the toner.

B) Model of Insulating Magnetic Brush Development In two-component development, development is carried out when the developing driving force (electrostatic force) (q.E) acting on the toner particles becomes larger than the adhesive force with the carrier. . q · E> Fv + αq ² / 4πε ₀ r ² (9) Equation (9) is easy to understand when explained with reference to FIG. 13. Here, a developing electric field such that E ₁ <E ₂ is shown, and a straight line shows each developing force. Development does not occur in the electric field of E ₁ and qE ₂ above the Ft curve is between q ₁ and q ₂ , so all toners with charges in this range are developable.

The above is a description of the developing device 10 and the structure related thereto. In a conventional image forming unit in which at least a photoconductor and a developing device are assembled, the developing device does not have a carrier. The mainstream is to use a component type developer. In this case, when the toner particles are adhered from the developing sleeve to the photoconductor, there is no medium such as a carrier of the two-component developing system, so the developing sleeve needs to be close to the photoconductor, and the distance is usually 0 to 0. It is as small as 0.3 mm. Therefore, when attempting to remove the waste toner tank and other parts by carrying out the toner recycling as will be described later, which is adopted in this embodiment, the recycled toner collected by the cleaning device once adheres to the photoconductor, Therefore, if the gap between the photoconductor and the developing roller is narrow, the foreign matter such as paper dust is caught in the gap, and an abnormal image such as white stripes is likely to occur.
Therefore, in the one-component developing method, toner recycling is not suitable. In addition, there is a one-component developing method in which toner is recycled, but in this case, the life of the image forming unit is, for example, 10K (K = 1000) in terms of the number of copies.
Short before and after the sheet.

On the other hand, in this embodiment, the developing system is the two-component developing system, so that the photosensitive member 7 and the developing sleeve 11 are
The distance between them can be 0.5 mm or more, and even if toner recycling is performed, foreign matter such as paper dust will not be caught, and the life of the image forming unit can be reduced by the number of copies.
For example, it can be stretched to 30K or more. Therefore,
Compared to the one-component development method, the cost for using the carrier is higher, but the life of the image forming unit 1 is more than doubled, so the total cost is reduced, and the replacement interval of the image forming unit 1 is extended, and the maintenance cost is also increased. Is also reduced.

Next, the transfer device will be described. The transfer roller 15 shown in FIG. 1 is formed by winding a conductive resin around a metal cored bar, and is pressed together with the bearing toward the photoconductor by a compression spring (not shown). A constant current is passed through the transfer roller 15 to transfer the toner on the photoconductor onto the transfer paper. The transfer roller 15 can also be brought into contact with and separated from the photoconductor 7 by a mechanism similar to that of the charging roller 8.

The transfer mechanism will be described with reference to FIG.
4, there is a charged toner layer dt having a volume charge density ρ on a photoconductor 7 having a photosensitive layer 31 having a thickness dm, and a transfer paper 100 having a thickness dp is located below the charged toner layer dt. The gap between the toner layer and the transfer paper is g. Furthermore, on the transfer paper 100,
It gives a charge σc of the opposite polarity to the charged toner. In this state, the force Fe (x) in the direction of the recording paper acting on the toner T having the charge amount qt at the position x from the surface of the photoconductor is expressed by the following equation. Fe (x) = qt {-σc -ρ (dt-x)} / (ε 0 · Kt) (10) where, epsilon ₀ is the vacuum dielectric constant, Kt is the relative permittivity of the toner layer. Charged toner T at a distance x from the surface of the photoconductor
Assuming that the electrostatic force Fe (x) acting on the is balanced with the mechanical adhesive force Fa, at which point the toner layer is divided and only the toner layer of thickness (dt-x) is transferred to the transfer. The transfer rate η is expressed by the following equation. η = (dt−x) / dt = ∫ ₀ ¹ −1 / (ρ · dt) {σc + (ε ₀ · Kt) Fa / qt} (11) In the formula (10), the volume charge density ρ is Is δ, the filling rate of the charged toner layer is p, and the toner specific charge is Tp, then ρ = δ · p · Tp. Further, the toner charge amount qt is qt = Tp, where m is the mass of one toner.
・ It can be expressed as m. Thus equation (10), Fe (x) = {- σc · m · Tp-δ · p · m (dt-x) Tp 2} / (ε 0 · Kt) (12) and the write is also expressed. The above is the transcription model formula.

Explaining the transfer control method, first, an equivalent circuit is shown in FIGS. 15 and 16 as a transfer model in the case where toner is present in the maximum copy width size paper. Thus, the image portion transfer current Ib is obtained. Ib = (V-Vl) / (R + Zb) (13) However, Zb = (1 / Cd + 1 / Cp + 1 / Ct) Cd = K 0 · Kd · L · Vp / d Cp = K 0 · Kp · L · Vp / dp Ct = K ₀ · Kt · L · Vp / dt V: Transfer voltage, Vl: Image surface potential, R: Transfer roller resistance value, K ₀ : Dielectric constant, Kd: Photosensitive layer relative dielectric constant, Kp:
Transfer paper relative dielectric constant, Kt: Toner layer relative dielectric constant, d: Photosensitive layer film thickness, dp: Transfer paper thickness, dt: Toner layer thickness, L: Paper passing width,
Vp: replacing the values in the photosensitive member peripheral speed (13), when the expression representing the section V-Vl, V-Vl = Ib · R + (Ib · dp) / (K 0 · Kp · L · Vp ) + (Ib · dt) / (K 0 · Kt · L · Vp) + (Ib · d) / (K 0 · Kd · L · Vp) (14) (14) from equation, the transfer control method constant current As a method,
Since the transfer charge σc acting on the transfer described in the transfer mechanism is the same as Ib / L · Vp in the term of the transfer paper of the formula (14), it is always stable by controlling so that Ib becomes constant. The transfer charge is applied, and the transfer conditions are stabilized.

On the other hand, in the case of constant voltage control, when V is constant in the equation (14), the resistance value R of the transfer roller 15 greatly changes due to the environmental change, and when the resistance value becomes large, the transfer roller part The voltage increases, the voltage value applied to the transfer paper decreases correspondingly, the transfer charge changes, and stable transfer conditions cannot be obtained. Therefore, the constant current control is advantageous for the resistance value change of the transfer roller 15.

Next, consideration will be given to the case where the area where the transfer paper exists but the toner exists is small, or the case where the transfer paper size is small and the area where the photoconductor 7 and the transfer roller 15 directly contact each other is large. 17 and 18 show the case where the transfer paper 100 is present but the toner layer is not present, and FIGS. 19 and 20 show the case where the photoconductor 7 and the transfer roller 15 are in direct contact with each other.
Here, letting each current flow be Iw and Id, Iw = (V-Vd) / (R + Zw) (15) where Zw = (1 / Cd + 1 / Cp) Id = (V-Vd) / (R + Zd) ( 16) However, Zd = (1 / Cd) Vd: surface potential of non-image portion of photoconductor. In case of constant current control, small size (A6 etc.)
When the transfer paper of No. 1 is passed, most of the applied current flows into the photoconductor 7, and as a result, Ib does not have a sufficient value, the transfer charge becomes small, and transfer failure occurs. As a means for preventing this, there is a method of once measuring the resistance value of the transfer roller and then applying a voltage suitable for this resistance value so that an appropriate transfer charge can be obtained. Explaining this, assuming that the voltage at which the current I ₁ flows during non-image formation is V ₁ , the resistance value R of the transfer roller is obtained from the relationship of I ₁ = (V ₁ −Vd) / (R + Zd) (17). That is, R = 1 / I ₁ · {V ₁ −Vd− (I ₁ · Id) / Cd} (18) where Vd is the charging potential and Cd is the capacitance of the photosensitive layer. It is a known value.

Next, when the voltage value at which Ib becomes the appropriate current value I ₂ during image formation is V ₂ , I ₂ = (V ₂ −Vl) / (R + Zb) (19) Substituting into the equation and calculating V ₂ , V ₂ = (I ₂ / I ₁ ) × (V ₁ −Vd) + I ₂ (Zb−Zd) + Vl (20), and V ₁ obtained at the time of non-image formation In contrast, (20)
By applying a constant voltage at the time of image formation with the voltage value V ₂ derived by the formula, it is possible to always transfer at an appropriate voltage V according to the resistance value R of the transfer roller.

The influence of the linear velocity will be considered. To see the relationship between the peripheral speed Vp of the photoconductor and the resistance R of the transfer roller,
3), (14), and (15) are solved for R, R = (V-Vl) / (Qb.L.Vp) -Yb / Vp (21) R = (V-Vd) / ( Qw.L.Vp) -Yw / Vp (22) R = (V-Vd) / (Qd.L.Vp) -Yd / Vp (23) where Yb / Vp = 1 / Cd + 1 / Cp + 1 / Ct Yw / Vp = 1 / Cd + 1 / Cp Yd / Vp = 1 / Cd Here, Qb, Qw, and Qd are charge amounts per unit area of the image portion, the non-image portion, and the non-sheet passing portion, respectively. That is, Qb = Ib
/ L · Vp, Qw = Iw / L · Vp, Qd = Id / L · Vp. Therefore, it is understood that when changing the peripheral speed of the photoconductor, the resistance value of the transfer roller may be changed in inverse proportion to the peripheral speed.

In the equation (16), the discharge start voltage (V
The term of g) is omitted, but this is because the formula of Vg is Vg = 31
It is represented by 2 + 6.2 × d / Kd + √ (7737.6 × d / Kd), and can be regarded as a substantially constant value determined by d: the thickness of the photosensitive layer and Kd: the relative dielectric constant of the photosensitive layer. Therefore omitted.

Next, the cleaning device 17 shown in FIG.
Will be described. The cleaning blade 18 of the cleaning device 17 is made of a flat plate-like elastic material such as polyurethane rubber, and is fixed to a metal blade holder 82 with an adhesive or a double-sided tape. The blade boulder 82
As shown in FIG. 3, the two positioning pins 83 provided on the inclined surface 84 formed on the case body 3 regulate the position in the direction parallel to the inclined surface 84, and the photoconductor 7
It is fixed to the case main body 3 with a screw 85 in a so-called counter direction that faces the rotation direction of the. This screw 85
Is in the same direction as the attachment surface of the cleaning blade 18, and the blade holder 82 is completely brought into close contact with the inclined surface 84 formed on the case body 3, and the inclined surface 84
The position of the cleaning blade 18 in the direction perpendicular to the inclined surface 84 is regulated.

As described above, the contact angle and pressure of the cleaning blade 18 with respect to the photosensitive member 7 are completely guaranteed,
Prevents problems such as poor cleaning and abnormal noise. Further, the position of the screw 85 for fixing the blade holder 82 to the case body 3 in the thrust direction can be set further outside than both ends of the photosensitive member including the flange members 86 and 87. The advantage is that only the cleaning blade can be replaced without removing the cleaning blade.

Next, the toner recycling device will be described.

Cleaning device 1 shown in FIGS. 1 and 3.
The toner scraped off from the photoconductor 7 by the cleaning blade 18 of No. 7 is conveyed to the front side in the cleaning case 19 by the toner conveying member 20, and is discharged to the outside through the pipe 88 integrally provided on the case 19. It A gear (not shown) is fixed to the rear end of the toner conveying member 20, and the gear meshes with a gear integrally formed with the flange member 87 on the rear side of the photoconductor 7.
The rotation of the photoconductor 7 is transmitted to the toner conveying member 20, and the toner conveying member 20 is rotationally driven.

As shown in FIGS. 3, 21, and 22, the toner conveying member 20 protruding outside the cleaning case 19
A roller portion 91 and a pair of pins 89 protruding from the roller portion 91 are provided at the front end of the roller portion 91, and a toner recycling belt 92 is wound around the roller portion 91. A large number of long holes 93 of equal length are formed in the belt 92 along the circumferential direction at equal pitches, and the pins 89 described above are inserted into any of the long holes 93. As shown in FIG. 3, the toner recycle belt 92 is located in the toner transport path inside the trough-shaped portion 94 formed by a part of the case body 3, and the upper portion of this toner transport path is the upper cover 6 as described above.
(See also FIG. 2).

As shown in FIGS. 3 and 22, the trough-shaped portion 94
A driven roller 95 is rotatably supported by the roller, and the toner recycling belt 92 is wound around the roller 95. When the toner conveying member 20 is rotationally driven as described above, the roller portion 91 integrated with the toner conveying member 20 is rotated, and at this time, each pin 89 causes the elongated hole 93 of the toner recycling belt 92.
The toner recycle belt 92 is driven in the direction indicated by the arrow in FIG. 22.
On the outer surface of the toner recycling belt 92, a large number of elastic fins 96 arranged in the circumferential direction of the toner recycling belt 92 are provided so as to project.
Is in sliding contact with the gutter-shaped portion 94 and the inner wall surface of the upper cover 6.

The toner discharged to the outside of the cleaning case 19 of the cleaning device 17 by the toner conveying member 20 moves unstablely in the vicinity of the transfer portion with the toner recycling belt 92, and the long hole 93 of the belt 92. And falls on the inner wall surface of the trough-shaped portion 94. Then, the elastic fins 96 of the driven toner recycling belt 92 convey the toner in the toner conveying path, and the developing device 1
It is sent to the developer chamber 90 of 0. At this time, since the elastic fins 96 are pressed against the inner wall surface of the trough-shaped portion 94, the toner is not completely left behind and conveyed toward the developing device 10, and it is possible to prevent the toner from being excessively stressed.

Further, the gutter-shaped portion 94 near the driven roller 95.
A slanting surface 94a is formed on the inner wall surface of the slanted surface by a projection. When each elastic fin 96 rubs against the slanting surface 94a, the elastic fin 96 is elastically bent and deformed, so that the slanting surface 94a.
After passing a, each elastic fin 96 vigorously returns to the natural state. Therefore, the elastic fins 96
The toner conveyed by is blown to the second stirring member 45 shown in FIG. In this way, the toner can be reliably conveyed to the developer chamber 90. The toner conveyed to the developer chamber 90 is agitated and mixed with the developer 101 present therein, and is reused.

As shown in FIG. 21, the thickness of the toner recycling belt 92 is t ₁ , and the elastic fins 96 integrated with the toner recycling belt 92 are t ₁ .
When the thickness of each is t ₂ , t ₁ <t ₂ .
As a result, the waist strength of the elastic fins 96 becomes stronger than the waist strength of the toner recycling belt 92, and the elastic fins 96 are pressed against the inner wall surface of the trough-shaped portion 94 as shown in FIG. The elastic fins 96 when transported
It does not bend and deform significantly. When the elastic fin 96 starts to contact the inclined surface 94a, the fin 96 largely bends and deforms, and when the elastic fin 96 elastically returns, the toner is vigorously ejected.

By using the toner recycling device as described above, the waste toner tank for storing the toner collected from the photoconductor 7 can be abolished, and the collected toner is collected by the developing device 1.
At 0, it can be reused efficiently.

Further, the gutter-shaped portion 94 which constitutes the toner conveying path.
Is composed of a part of the case body 3,
As in the case where the trough-shaped portion 94 and the other case body portion are separately configured, it is possible to prevent the problem that the toner leaks from the gap between them, and a sealing material such as sponge for preventing the toner leak is provided. There is no need to provide it. Further, since the gutter-shaped portion 94 and the other case body portion are integrated, the assembling property of the image forming unit 1 is improved.

By the way, as described above, the shafts 63 and 64 of the first and second stirring members 44 and 45 rotatably supported by the unit case 2 are driven to the ends on the back side. Gears 68 and 69 are fitted to the shafts 63 and 64 so as not to rotate relative to each other. These drive gears 68, 69
Is an example of a rotating body supported on the axial end portion of the shaft, and when the rotating body is supported on the shaft, the rotating body moves from a predetermined mounting position to the shaft in the axial direction of the shaft. It must be prevented from moving outwards and disengaging from the end of the shaft. Since the rotating body is slidable with respect to the shaft, the rotating body moves outward from the axial direction of the shaft from a predetermined mounting position on the shaft, and the rotating body is provided with a stopper that separates from the end of the shaft. It requires a body detachment prevention device.

Therefore, conventionally, as described above, a locking ring composed of an E-ring or a C-ring is fitted on the shaft so as to prevent the rotating body from slipping off from the shaft in the axial direction thereof. The locking ring prevented the rotor from slipping off the shaft. The locking ring was used as a stopper to prevent the rotating body from coming off. However, if the rotating body detachment prevention device including such a locking ring is adopted, the number of parts is increased by the amount of the locking ring and the cost is increased. In addition, since the locking ring must be attached to and detached from the shaft when attaching and detaching the rotating body, the workability is reduced. This applies not only to the rotating body made of gears, but also to rotating bodies such as rollers, pulleys, and drums supported at the axial end of the shaft.

Therefore, in the rotating body detachment preventing device of this embodiment, the case wall of the device in which the shaft and the rotating body are incorporated is located outward of the end of the shaft in the axial direction, and The case wall constitutes a stopper that prevents the rotating body from coming off. More specifically, as shown in FIG. 3 and FIG. 4, the back side outer plate 53 of the unit case 2 is located close to the outside of the drive gears 68 and 69 that form the rotating body. , The drive plates 68, 6 are controlled by the outer plate 53.
A stopper is configured to prevent the shaft 9 from coming off the shafts 63 and 64 in the axial direction. That is, the case body 3 of the unit case 2 has a rear inner plate 54 that rotatably supports the shafts 63 and 64, and a rear outer plate 53 that is located further outside thereof, and between the plates 53 and 54. Drive gear 6
8 and 69 are arranged and the gear 6 supported by the shafts 63 and 64
When the drive shafts 68, 69 try to move outward in the axial direction with respect to the shafts 63, 64, the movement is held by the outer plate 53 on the back side, and the drive gears 68, 69 are disengaged from the shafts 63, 64. To prevent. The upper part of the space where the gears 68 and 69 are located is covered with a part of the developing case cover 5.

As described above, a device including the shafts 63 and 64 and the drive gears 68 and 69 forming the rotating body, that is, a case wall formed of the outer plate 53 forming the unit case 2 of the image forming unit 1. However, rather than the ends of the shafts 63 and 64,
The case wall formed by the outer plate 53 is located outward of the shafts 63 and 64 in the axial direction and close to the gears 68 and 69, and constitutes a stopper that prevents the gears 68 and 69 from separating. . According to this structure, the outer plate 53 has not only its original function but also the function of a stopper for the gears 68 and 69, so that the conventionally required locking ring can be omitted. The number of parts can be reduced and the cost can be reduced.

As shown in FIG. 23 or 24, a rib-shaped or cylindrical projection 97 is formed on the surface of the back side outer plate 53 facing the drive gears 68, 69, and the projection 97 is formed. Part 9
If the end surfaces of the drive gears 68 and 69 are in contact with 7, it is possible to reduce the area in which the drive gears 68 and 69 contact the back side outer plate 53, and thus the frictional force acting between them can be reduced. Therefore, the driving torque of the gears 68 and 69 can be reduced. Moreover, the wear of the gears 68, 69 and the unit case 2 can be reduced and the service life thereof can be extended.
In this way, the outer plate 53, which is an example of the case wall, has the protrusion 97 that protrudes toward the gears 68 and 69 at the portion facing the gears 68 and 69 that is an example of the rotating body.
The protrusion 97 is provided with the gears 68, 6 facing the protrusion 97.
The gears 68, 69 are brought into contact with a part of the surface of the shaft 9,
Its shape is set so as to prevent it from coming off from No. 4. As a result, the above-described excellent effects can be achieved.

Further, in this example, the shafts 63 and 64 are supported by the unit case 2 of the image forming unit 1 constructed by incorporating at least one image forming element into the unit case 2, and the case wall is outside the unit case 2. Although it is constituted by the wall portion constituted by the plate 53, the gears 68, 6 are
Since the locking ring for preventing the detachment of 9 is unnecessary, the image forming unit 1 can be provided at low cost. Moreover, since it is not necessary to attach / detach the retaining ring when attaching / detaching the gears 68, 69, it is possible to enhance the maintainability of the image forming unit.

Further, the wall portion constituting the case wall as the stopper of the gears 68, 69 is the outer plate 5 of the unit case 2.
3, the shafts 63 and 64 are supported by bearings on the inner plate 54 located inside the unit case 2 with respect to the outer plate 53, and the gears 68 and 69 are provided between the inner plate 54 and the outer plate 53. The rotating body is located. In this way, each gear 6
Since 8 and 69 are located in the sealed space between the outer plate 53 and the inner plate 54 on the back side, it is possible to eliminate the possibility that a person may touch the gears 68 and 69 with hands, and enhance the safety. be able to. In this example, the side plate 5a (FIG. 1) on the back side of the developing case cover 5 contacts the upper edge of the inner plate 54 of the case body 3, and the upper part of the accommodation space of the gears 68 and 69 is covered by the developing case cover 5. Since the space is closed, the space can be sealed almost safely, and the safety can be more surely guaranteed.

Further, the inner plate 54 cooperates with the side plate 5a of the developing case cover 5 to form the developing case 12, the gears 68 and 69 are positioned outside the inner plate 54, and the case body 3 serves as the inner plate 54. Since the outer plate 53 has a double wall structure, the developer of the developing device 10 can be more reliably prevented from leaking to the outside of the image forming unit 1. Even if some developer leaks to the outside of the inner plate 54 and the side plate 5a (FIG. 1) on the inner side of the developing case cover 5, the outer plate 53 can prevent the developer from leaking out of the image forming unit. .

Various configurations can be adopted to prevent the drive gears 68, 69 from shifting inward in the axial direction with respect to the shafts 63, 64. For example, as shown in FIG. The inner plate 54 and the shaft 63 attached to the inner plate 54,
Bearing 154 for rotatably supporting 64 with respect to inner plate 54
At least one of them can prevent the gears 68, 69 from moving inward in the axial direction of the shafts 63, 64. Alternatively, as shown in FIG. 26, each shaft 63, 64
A step portion 163 is formed on each of the gears 6 by the step portion 163.
It may be possible to prevent the 8, 69 from shifting inward in the axial direction. Further, as shown in FIG. 27, each of the gears 63, 6 is provided by a locking ring 164 composed of an E ring or a C ring.
It may be possible to prevent the inward displacement of 4 in the axial direction.

Among the above-mentioned constitutions, the inner plate 54 and the bearing 15 which rotatably supports the shafts 63 and 64 on the inner plate 54.
If at least one of 4 constitutes a regulating means for regulating the movement of the rotating body composed of the gears 68, 69 inward in the axial direction with respect to the shafts 63, 64, it is necessary to provide a special regulating means. Therefore, the cost of the image forming unit 1 can be further reduced.

The rotating body detachment preventing device and the structure related thereto described above are not limited to the image forming device and its image forming unit, but can be widely applied to various devices. Further, the invention is not limited to the case where the rotating body is a gear, but can be applied to a case where a rotating body such as a roller, a pulley, and a drum is supported at the end of the shaft. Further, in the illustrated example, the rotating body composed of the gears 68 and 69 is supported so as not to be rotatable relative to the shafts 63 and 64, but when the rotating body is supported so as to be rotatable with respect to the shaft, With the above-described rotating body detachment prevention device and the structure related thereto, it is possible to prevent the rotating body from moving axially outward with respect to the shaft and preventing the rotating body from coming off the shaft.

By the way, the illustrated image forming apparatus and the image forming unit 1 thereof have a large number of elements, and the two-component developer 101 is accommodated in the developer chamber 90 for use.
Each of these elements deteriorates with time and finally becomes unusable. Usually, these elements are replaced with new ones when they are no longer usable or shortly before. This replacement period is the life of each element.
At that time, if each element is configured to have a completely different life, the element must be replaced each time the life of each element is reached, and the replacement work becomes very complicated. . If each of the constituent elements of the image forming apparatus is configured such that the constituent elements of the image forming apparatus have almost the same service life, the plurality of constituent elements of the service life can be collectively replaced, and the work can be simplified. .

Therefore, in this example, these are configured so that the life of the photoconductor 7 and the life of the carrier of the two-component developer 101 coincide with each other, and the photoconductor 7 and the developer 101 have reached the life. At this time, it is possible to exchange them all at once.

Further, not only the life of the photosensitive member 7 and the life of the carrier, but also the life of the charging roller 8 which constitutes the charging device and the life of the cleaning blade 18 which constitutes the cleaning member are all made equal to each other. When it becomes, these can be collectively replaced and the workability thereof can be further improved.

At this time, the image forming unit 1 is constructed by assembling the photoconductor 7, the charging roller 8, the developing sleeve 11, and the cleaning blade 18 into the unit case 2, and the two-component developer 101 is Since it is housed in the developing case 12 formed by a part of the unit case 2, the whole of the image forming unit 1 can be replaced with a new one at the end of their life. Even in this case, since each element of the image forming unit 1 has already reached the end of its life at the time of replacement, it does not impose an excessive financial burden on the user.

Here, the life of each component of the image forming unit 1 can be set as follows, for example. In addition, here, the life of each element is assumed to be when it is in a state immediately before it becomes unusable.

First, the life of the developer, more precisely, the life of the carrier is determined by stirring and circulating the developer.
It is determined by the fact that the coating layer on the surface of the carrier is peeled off with time and the triboelectric charging characteristics of the carrier are deteriorated. That is, the life of the developer 101 can be roughly determined by selecting the coating layer thickness of the carrier and the total amount of the developer 101 accommodated in the developer chamber 90 of the developing device 10.

The life of the photosensitive member 7 is mainly determined by its photosensitive layer 31.
However, it is determined by the fact that the cleaning blade 18 scrapes the film with time, the thickness of the film is reduced, and the proper charging potential cannot be obtained. That is, by selecting the film thickness of the photosensitive layer 31, the approximate life of the photoconductor 7 can be set.

The life of the cleaning blade 18 is determined by the contact pressure of the cleaning blade 18 on the photosensitive member 7 and the amount of wear of the blade edge in contact with the photosensitive member 7. In general,
If the amount of wear increases, the cleaning property for the residual toner on the photoconductor deteriorates. However, when the contact pressure of the cleaning blade 18 with respect to the photoconductor 7 is higher,
Although the amount of wear of the cleaning blade 18 increases, the cleaning property thereof increases, so that the life of the cleaning blade 18 extends. However, if the contact pressure is high, the load torque of the photoconductor 7 increases. Therefore, by selecting the contact pressure of the cleaning blade 18 with respect to the photoconductor 7, the life of the cleaning blade 18 can be roughly set.

The life of the charging roller 8 depends on the pressure with which the cleaning pad 32 (FIG. 1) for cleaning the minute toner adhering to the surface of the charging roller 8 is pressed against the charging roller 8. If the pressing pressure is large, the charging roller 8
However, the surface of the charging roller is scratched over time, resulting in image unevenness. Further, if the pressing pressure is small, the cleaning property for the charging roller 8 is deteriorated. Therefore, by selecting the pressing force of the cleaning pad 32 against the charging roller 8, the life of the charging roller 8 can be roughly set.

The above are the factors that determine the life of each element constituting the image forming unit 1. Next, the photoconductor 7 and the developer 1 will be described.
A more specific example of matching the lifetimes of the carrier No. 01 will be shown.

First, since the image forming unit 1 is started to be used, when an image is formed on S sheets of transfer paper, that is, when the number of copies reaches S sheets, the photoconductor 7 and the developer 10 are formed.
Has reached the end of its life, at which time the entire image forming unit 1 is to be replaced.

When the developer 101 is used until it becomes unusable due to its deterioration, the carrier 101 may be deteriorated in the triboelectrification property immediately after the above S sheets of images have been formed. Determine the coating layer thickness and the amount of developer. The carrier triboelectricity polarity is
It can be represented by the toner specific charge (charge amount per unit weight Q / M), and FIG. 28 shows the relationship between the toner specific charge and the number of copies. If the toner specific charge (Q / M) falls below the permissible range, background stains and image density drop occur.
Immediately before such a state, the coating layer thickness of the carrier and the amount of the developer are set so that the number of copies is S sheets.

For example, the above S sheets are 30K sheets and 40K sheets.
When the number of sheets or 50K sheets (K = 1000) is set, the life of the developer is determined by the value of the toner specific charge (Q / M) which is a substitute value of the frictional charging characteristic of the carrier as described above.
The toner specific charge is lower than this value so that this value is within the range of 10 to 40 μc / g even after passing 30 K, 40 K, or 50 K sheets, and immediately after reaching each copy number. As described above, the life of the developer can be correctly set by selecting the coating layer thickness of the carrier and the amount of the developer. Specifically, the coating layer thickness is, for example, 0.5.
It is selected from the range of μm to 1.5 μm, and the developer amount (weight) is selected from the range of 2.45N to 4.41N. If the amount of the developer 101 is small, the cost can be reduced accordingly. Therefore, when the number of copies for life is 30K, the amount of the developer is smaller than that for 50K. It is desirable to set.

Next, assuming that the photoconductor 7 is also used until it deteriorates, so that the proper charging current cannot be obtained immediately after the number of copies reaches S,
The film thickness of the photosensitive layer 31 is set. As an example, considering a case where the width of change in the charging potential of the photosensitive layer 31 due to the change in the film thickness of the photosensitive layer 31 with time is set to 20 V or less, in the formula shown in the charging mechanism of the charging roller 8 above, The film thickness of the photosensitive layer 31 may be selected so that the variation of the term of the discharge start voltage (charging start voltage) Vg affected by the film thickness of the layer 31 is 20 V or less. Since the amount of wear of the photosensitive layer after copying S sheets is known in advance, this is set to 1. If the initial film thickness of the photosensitive layer is d, its relative permittivity is Kd, the initial charging start voltage is Vgs, and the charging start voltage after copying S sheets is Vge, then Vgs = 312 + 6.2 × d / Kd + √ (7737.6 × d / Kd) Vge = 312 + 6.2 × (dl) / Kd + √ {7737.6 × (dl) / Kd} Vgs-Vge = 1.931 + 49.17 {√d-√ (Dl)} Here, assuming that l is 3 μm, Vgs−Vge = 5.79 + 49.17 {√d−√ (d−3)}, and if the change width is 20 V or less, Vgs−Vge = 5. 79 + 49.17 {√d−√ (d-3)} ≦ 20 √d−√ (d-3) ≦ 0.289. Here, if √d = D and d−3 = D ² −3, then D−√ (D ² −3) ≦ 0.289 √ (D ² −3) ≦ D−0.289, and both sides thereof are When ^{squared, D 2 -3 ≦ D 2 -0.578D} + 0.0835 from 0.578D ≦ 3.0835 ∴D ≦ 5.33 √d = D, d = D 2 ∴d = 5.33 2 = 28. 4 μm

Therefore, if the photosensitive layer 31 is abraded by 3 μm after copying S sheets, the fluctuation range can be set to 20 V or less by selecting a photosensitive layer having a film thickness of 28.4 μm.

For example, in order for the photoconductor 7 to reach the end of its life with the number of copies of 30K sheets, the potential drop due to the change in the thickness of the photosensitive layer after passing 30K sheets should be 20V or less.
Moreover, the film thickness of the photosensitive layer 31 is set so that the potential drop becomes larger than 20 V immediately after the photoconductor is used as it is. Assuming that the amount of wear of the photosensitive layer 31 after copying 30K sheets is 2 μm, the initial film thickness will be around 13 μm from the above calculation formula.

Similarly, when the life of the photoconductor 7 is reached up to 40K sheets, the wear amount of the photoconductor layer 31 is 2.5.
Since the thickness is μm, the initial film thickness may be set to around 20 μm.

Further, when the photoconductor 7 reaches the end of its life at 50K sheets, the amount of abrasion of the photosensitive layer 31 becomes 3 μm, so the initial film thickness thereof is set to around 28.4 μm.

As described above, it is possible to make the lives of the developer and the photoconductor the same, and it is possible to collectively replace the image forming unit in which the photoconductor and the developing device are integrated. As a result, the maintenance cost can be significantly reduced as compared with the case where a serviceman at a different time carries out and replaces each part.

Further, in order for the cleaning blade 18 to reach the end of its life after copying S sheets,
As can be seen from the graph of FIG. 29 showing the relationship between the contact pressure of the cleaning blade 18 on the surface of the photoconductor and the wear amount of the cleaning blade
For example, when the contact pressure of the cleaning blade 18 becomes small, the cleaning failure does not occur at the end of copying S sheets, and when the cleaning blade 18 is further used as it is, cleaning is performed immediately after copying S sheets. The contact pressure is set so that a defect occurs. The same applies when the contact pressure of the cleaning blade 18 becomes large.

When the contact pressure is set to a high value, the amount of wear of the cleaning blade 18 increases, but the number of copies that can clean the photosensitive member with the cleaning blade 18 in a good cleaning state increases, and the life of the cleaning blade 18 increases. The extension can be well understood from FIG. However, if the contact pressure is large, the load torque of the photoconductor increases as described above, and the load on the drive motor is correspondingly increased, and the capacity of the drive motor must be increased. The cost increases. Therefore, it is economical not to set the contact pressure of the cleaning blade 18 against the photoconductor 7 too high.

As described above, the life of the cleaning blade 18 can be set, and by matching the life of the cleaning blade 18 with the life of the photoconductor 7 and the developer, they can be replaced at the same time, and the maintenance cost can be further reduced. .

For example, as described above, the developer and the photoreceptor 7
When the number of copies is 30K, the contact pressure of the cleaning blade 18 against the photoconductor 7 is set to 0.1176.
When the number of copies is set to about N / cm and the life is set to 40K, the contact pressure of the cleaning blade 18 to the photoconductor 7 is set to about 0.1568 N / cm. When the number of copies to reach the end of life is 50K, the contact life of the cleaning blade 18 is set to about 0.196 N / cm so that the lives of the respective elements can be made substantially the same.

The charging roller 8 reaches the end of its life when the number of copies is S, and the roller 8 can be replaced at this time in the following manner.

30 and 31, the pressing force (pad pressure) with which the cleaning pad 32 for cleaning the fine toner adhering to the surface of the charging roller 8 contacts the surface of the charging roller 8 and the cleaning property of the pad 32. And the relationship of image unevenness due to scratches generated on the surface of the charging roller 8. The range indicated by "OK" in these figures is a range in which the cleaning property of the charging roller 8 by the cleaning pad 32 is good and image unevenness is small.

From FIG. 30 and FIG. 31, after the S sheets have been copied, the cleaning property by the cleaning pad 32 is good, there is no image unevenness, and when the charging roller 8 is continuously used as it is, the S sheets are printed. Immediately after copying, the pad pressure is selected so that the cleaning property and the image unevenness are defective. In this way, the lives of the developer 101, the photoconductor 7, the cleaning blade 18, and the charging roller 8 can all be made the same.

For example, the number S of copies until the end of its life is set to 3
When it is set to 0K, the pressure contact force (pad pressure) of the pad 32 to the charging roller 8 is set to near 5.88N, and when the life copy number S is 40K, the pad pressure is set to near 7.84N. Similarly, when the life copy number S is 50K, the pad pressure is set near 9.8N.

The pad pressure is preferably set to a low value if the cleaning property of the charging roller 8 by the pad 32 can be satisfied, and the driving load of the photoconductor 7 can be reduced by this. A small capacity can be used and the cost can be reduced.

As described above, the replacement elements assembled in the unit case 2, that is, the photoconductor 7, the developer 101, the cleaning blade 18, and the charging roller 8 are copied so that they all reach the end of their life at the same time. By selecting the material of each element and setting the characteristic value, it is possible to configure a unit that is more economical and less wasteful than ever, and when replacing the parts, you can replace one image forming unit for replacement work. It will be completed, the maintainability will be greatly improved, and the maintenance cost will be greatly reduced.

On the other hand, if it is possible to use low-cost, high-durability parts, it is also possible to change the life of each individual part.

As described above, the present invention can be widely applied to the rotating body separation preventing device in various devices other than the image forming device and the image forming device.

[0160]

According to the rotating body detachment preventing device of the first aspect, it is possible to prevent the rotating body from coming off the shaft without using the locking ring, which simplifies the structure and reduces the cost. Can be achieved.

According to the rotating body detachment preventing device of the second aspect, since only the protrusion of the case wall contacts the rotating body, the contact area between the case wall and the rotating body can be made small, and thus the contact area between them can be reduced. The frictional force acting can be reduced, and the driving torque for the rotating body can be reduced. Moreover, it is possible to reduce the wear of the rotor and the case wall, and to extend the life of the rotor.

According to the rotating body separation prevention device of the third aspect, the cost of the image forming unit in which it is incorporated can be reduced, and the maintainability thereof can be improved.

According to the rotating body detachment preventing device of the fourth aspect, since the rotating body is located between the inner plate and the outer plate, it is possible to prevent the human body from touching the rotating body and to enhance safety. be able to.

According to the rotating body detachment preventing device of the fifth aspect, it is possible to reliably prevent the developer in the developing case from leaking to the outside of the image forming unit.

According to the rotating body detachment prevention device of the sixth aspect, it is possible to regulate the movement of the rotating body inward in the axial direction of the shaft without providing a special independent regulating means.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an image forming unit mounted on an image forming apparatus main body.

FIG. 2 is a schematic external perspective view showing an image forming unit to which a developer cartridge is not mounted and a toner bottle.

FIG. 3 is a perspective view showing the image forming unit with a case cover, a developing case cover, and an upper cover removed.

FIG. 4 is a partial cross-sectional plan view of the same state as FIG.

FIG. 5 is a perspective view showing a state in which the case body is inverted.

FIG. 6 is a perspective view similar to FIG. 5, showing another example.

FIG. 7 is an enlarged schematic cross-sectional view of a photoconductor.

FIG. 8 is a schematic view of a photoconductor and a charging roller.

FIG. 9 is a diagram showing an equivalent circuit of a charging roller, a photosensitive member, and a power supply.

FIG. 10 is an explanatory cross-sectional view showing a relationship between a developing device and a photoconductor.

FIG. 11 is an exploded perspective view of a doctor blade, a developing sleeve, a support member, and an inlet seal cover.

FIG. 12 is an explanatory diagram showing a development model.

FIG. 13 is a graph showing an example of the relationship between the toner charge and the force acting on the toner.

FIG. 14 is an explanatory diagram showing a transcription model.

FIG. 15 is an explanatory diagram showing a relationship between a photoconductor and a transfer roller.

16 is a diagram showing an equivalent circuit of FIG.

FIG. 17 is an explanatory diagram showing a relationship among a photoconductor, a transfer roller, and a transfer paper.

FIG. 18 is a diagram showing an equivalent circuit of FIG. 17.

FIG. 19 is an explanatory diagram showing a relationship between a photoconductor and a transfer roller.

20 is a diagram showing an equivalent circuit of FIG. 19. FIG.

FIG. 21 is an enlarged perspective view of the toner recycling belt.

FIG. 22 is a vertical sectional view of the toner recycling belt.

FIG. 23 is a perspective view showing another example of the back side outer plate of the unit case.

FIG. 24 is a perspective view showing still another example of the back side outer plate of the unit case.

FIG. 25 is a horizontal cross-sectional view showing one structural example for preventing the drive gear from shifting inward in the axial direction of the shaft.

FIG. 26 is a horizontal cross-sectional view showing another configuration example for preventing the drive gear from shifting inward in the axial direction of the shaft.

FIG. 27 is a horizontal cross-sectional view showing still another configuration example for preventing the drive gear from shifting inward in the axial direction of the shaft.

FIG. 28 is a graph showing an example of the relationship between the number of copies and the toner specific charge.

FIG. 29 is a graph showing an example of the relationship between the number of copies and the wear amount of the cleaning blade.

FIG. 30 is a graph showing an example of the relationship between the number of copies and the cleaning property of the charging roller.

FIG. 31 is a graph showing an example of the relationship between the number of copies and image unevenness.

[Explanation of reference numerals] 1 image forming unit 2 unit case 12 developing case 53 outer plate 54 inner plate 63 shaft 64 shaft 97 protrusion 101 developer 154 bearing

Claims (6)

[Claims] 1. A rotation body supported on an axial end portion of a shaft is prevented from moving outward from an axial direction of the shaft from a predetermined mounting position with respect to the shaft and detaching from the end portion of the shaft. In the rotating body disengagement prevention device having a stopper, the case wall of the device in which the shaft and the rotating body are incorporated is located outward of the end of the shaft in the axial direction of the shaft, The rotating body detachment preventing device, wherein the case wall constitutes a stopper that prevents the rotating body from detaching. 2. The case wall has a projecting portion projecting toward the rotating body at a portion facing the rotating body, and the projecting portion is formed on a part of a rotating body surface facing the projecting portion. Abut,
So as to prevent the rotating body from separating from the shaft,
The rotating body detachment preventing device according to claim 1, wherein the shape is set. 3. The shaft is supported by a unit case of an image forming unit configured by incorporating at least one image forming element in the unit case, and the case wall is a wall portion of the unit case. The rotation body separation prevention device according to item 1. 4. The wall portion forming the case wall is an outer plate of the unit case, and the shaft is supported by the inner plate of the unit case located inside the unit case with respect to the outer plate, and the inner plate and The rotating body detachment preventing device according to claim 3, wherein the rotating body is located between the outer plate and the outer plate. 5. The rotating body detachment preventing device according to claim 4, wherein the inner plate constitutes a developing case that accommodates a developer therein. 6. The regulating means for regulating movement of a rotating body axially inward with respect to the shaft, at least one of the inner plate and a bearing rotatably supporting the shaft on the inner plate. The rotating body detachment preventing device according to claim 4 or 5, wherein.