JP2018072385A - Image formation apparatus and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of image abnormality due to developer shortage in a developer supply unit even at the time of change of the image formation speed by reducing the fluctuations in the developer quantity at the time of switching of the image formation speed without adding a new member in an image formation apparatus having a development device in which the developer supply unit and a developer stirring unit are arranged in the substantially vertical direction.SOLUTION: A development device 100 includes: a developer carrier such as a development roller 101; a developer supply unit 103 which is arranged on the lower side of the developer carrier; and a developer stirring unit 105 which is arranged on the lower side of the developer supply unit, and can execute the first mode such as the standard mode in which image formation is performed when the peripheral speed of an image carrier such as a photoreceptor 201 is at the first peripheral speed and the second mode such as the slow mode in which the image formation is performed at the second peripheral speed slower than the peripheral speed in the first mode. In the second mode, the ratio of the peripheral speed of the developer carrier to the peripheral speed of the image carrier is made to be larger than that of the first mode.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus and a process cartridge.

  A two-component developing system developing device is a device that develops and visualizes an electrostatic latent image formed on an image carrier using a two-component developer containing toner and a carrier. In this developing device, the developer in which the developing process is completed in the developing region and the toner is consumed is collected, mixed with the replenished toner, stirred, and again used for development. In order to obtain a stable toner image, the developer used in the developing device having such a configuration needs to maintain a constant toner concentration and charge amount.

  The toner density is adjusted by the amount of toner consumed in development and the amount of replenished toner, and the charge amount is given by frictional charging during mixing and stirring of the carrier and toner. The toner electrostatically attracted to the carrier adheres to an electrostatic latent image (image portion) on the image carrier under the influence of an electric field formed between the developer carrier and the image carrier in the development region. . The force received from the electric field in the developing area at this time exceeds the electrostatic force of the carrier that electrostatically attracts the toner, so that the toner leaves the carrier and flies to the image carrier side.

  In order to charge the additional replenishment toner, the developer agitating unit and the developer supplying unit for supplying the developer to the developer carrying member are provided in the developing device, and are provided by two conveying members arranged substantially in the horizontal direction. A horizontal biaxial circulation type developing device that circulates the developer between the developer stirring unit and the developer supply unit is generally used.

  In order to meet the demand for printing on thick paper and special paper, image forming apparatuses often have a plurality of image forming speeds. Immediately after the image forming speed is switched, there is a problem that the balance of the developer is lost. In particular, when the standard speed is switched to a low speed, the developer in the developer supply section is insufficient and an image defect occurs until the steady state is reached. In order to solve these problems, Patent Literature 1 relating to a technique for performing control for adding an empty stirring time for adjusting the developer balance after switching of the image forming speed and Patent Literature 2 relating to control for gradually switching the speed of the conveying member have already been disclosed. Are known.

  In recent years, there has been an increasing demand for downsizing of the image forming apparatus main body. In a full-color image forming apparatus, there is a strong need for downsizing of the developing device because a plurality of developing devices are arranged. As one of the downsizing methods, the developer agitating unit and the developer supplying unit are arranged almost vertically. (Hereinafter also referred to as a vertical circulation type developing device). The width of the developing device can be reduced by arranging the developer agitating unit and the developer supplying unit in a substantially vertical direction. For example, the intervals between the black, cyan, magenta, and yellow color units and process cartridges can be reduced. There is an advantage that can be arranged.

  However, when the developer agitating unit and the developer supplying unit are arranged in a substantially vertical direction, it is necessary to lift the developer in the antigravity direction in order to move the developer between the developer agitating unit and the developer supplying unit. . In this lifting portion (lifting region), the developer tends to stay, the developer is increased on the developer stirring portion side arranged below, the developer on the developer supply portion side arranged above is insufficient, and the image This may cause defective images such as blurring.

  In view of this, there is a case in which a developer is smoothly lifted by increasing the conveying force of the conveying member of the developer agitating unit than the conveying member of the developer supplying unit. However, when the image forming speed is lower than that in the normal mode (first mode) such as the thick paper mode or the high image quality mode (second mode), the conveyance amount reduction ratio of the conveyance members of the developer supply unit and the developer agitation unit Therefore, there is a problem that the balance of the developer is lost, the developer on the developer supply unit side is insufficient, and an image abnormality occurs.

In order to solve such a problem at the time of changing the image forming speed, a technique is known in which the conveying member is driven separately so that the rotational speed is not lowered during low speed driving (for example, see Patent Document 3).
However, this technique requires a drive source for the conveying member, which increases the cost.

Further, in order to reduce the fog on the white background that increases during the image forming mode in which the peripheral speed of the photosensitive drum is reduced, in the horizontal biaxial circulation type developing device, the peripheral speed ratio between the developing roller and the photosensitive member is set at low speed driving. The technique to raise is known (for example, refer patent document 4). Even if this technique is used, it appears that the amount of decrease in the rotational speed of the conveying member during low-speed driving can be suppressed as a result, and fluctuations in the developer bulk can be suppressed.
However, this technology does not take into account any change in the conveying capacity of the conveying member when the image forming speed is switched in the vertical circulation type developing device, and the developer bulk fluctuation at the time of low speed driving in the vertical circulation type developing device. The problem is not solved.

  In view of the above-described circumstances, the present invention provides an image forming speed without adding a new member in an image forming apparatus including a developing device in which a developer supply unit and a developer stirring unit are arranged in a substantially vertical direction. An object of the present invention is to reduce the change in the developer bulk at the time of switching, and to prevent the occurrence of image abnormality due to the lack of developer at the developer supply unit even when the image forming speed is changed.

  In order to achieve the above object, the present invention provides an image carrier that carries a latent image on its surface, and a latent image that is disposed opposite to the surface of the image carrier and is formed on the image carrier. A developer carrying member for supplying and developing the toner in the developer, a developer supply unit disposed below the developer carrying member for supplying the developer to the developer carrying member, and the developer supply An image forming apparatus comprising: a developer agitation unit disposed below the unit and having a developer agitation unit for agitating the developer and circulating the developer between the developer supply unit and the image carrier It is possible to execute a first mode in which image formation is performed at a peripheral speed of the body at a first peripheral speed and a second mode in which image formation is performed at a second peripheral speed that is slower than the peripheral speed in the first mode. In the second mode, the circumferential speed of the image carrier is higher than that in the first mode. Serial is an image forming apparatus to increase the ratio of the peripheral speed of the developer carrying member.

  According to the present invention, in the image forming apparatus including the developing device in which the developer stirring unit and the developer supplying unit are arranged substantially in the vertical direction, the developer at the time of switching the image forming speed without adding a new member. It is possible to reduce the bulk fluctuation and prevent the occurrence of image abnormality due to the shortage of developer in the developer supply unit even when the image forming speed is changed.

1 is a schematic configuration diagram of a copying machine as an image forming apparatus to which the present invention is applied. 1 is a front sectional view showing a configuration of a main part of an image forming apparatus including a process cartridge according to Embodiment 1 of the present invention. FIG. 3 is a longitudinal sectional view of the developing device constituting the process cartridge of FIG. 2 when cut in the vertical direction. FIG. 4 is a cross-sectional view of a main part when a lifting region in the developing device of FIG. 3 is viewed from the direction of arrow E.

  Hereinafter, embodiments of the present invention including examples will be described in detail with reference to the drawings. In each embodiment, components (members and components) having the same function, shape, and the like will be omitted by giving the same reference numerals after being described once unless there is a possibility of confusion.

A copier 1000 as an example of an image forming apparatus to which the present invention is applied will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of a copying machine 1000 as an example of an image forming apparatus to which the present invention is applied.
In FIG. 1, X is the width direction of the main body of the image forming apparatus, Y is the longitudinal direction (axial direction) of the photoreceptor 2 which will be described later orthogonal to the width direction X, and Z is the vertical direction orthogonal to the width direction X and the longitudinal direction Y. Each direction (vertical direction) is shown. 1 indicates the front side of the main body of the image forming apparatus, and the rear side of the paper surface of FIG. 1 indicates the rear side of the main body of the image forming apparatus.

  As shown in FIG. 1, a copying machine 1000 is a printer unit 600 that is mainly an image forming unit of a copying apparatus main body, a sheet feeding unit 700 that is a sheet feeding table on which the printer unit 600 is mounted, and a scanner attached on the printer unit 600. The scanner unit 800 is configured.

The printer unit 600 includes process cartridges 1 (Y, M, C, and K) as four process units. In addition to the process cartridge 1 (Y, M, C, K), the printer unit 600 is stretched by an exposure device 6 as exposure means and a plurality of stretching rollers, and moves in the direction of arrow D in FIG. An intermediate transfer belt 7 as an intermediate transfer member, a fixing device 12 as a fixing unit, and the like are provided.
The four process cartridges 1 (Y, M, C, K), the exposure device 6, the intermediate transfer belt 7, the secondary transfer device described later, and the like constitute an image forming device 15 that forms an image by an electrophotographic method.

  The suffixes Y, M, C, and K attached to the four process cartridges 1 indicate the specifications for forming images of each color for yellow, magenta, cyan, and black (black). ing. The four process cartridges 1 (Y, M, C, and K) have substantially the same configuration except that the colors of the toners to be used are different. Therefore, the subscripts Y, M, C, and K are omitted below. I will explain. For simplification of FIG. 1, only the process cartridge 1 </ b> Y is given a reference numeral of a constituent member.

  The exposure device 6 irradiates the surface of the photoconductor described later with a laser beam based on the image of the document read by the scanner unit 800 or image data sent from an external computer or the like connected so as to be able to transmit and receive. An electrostatic latent image is formed by writing the electrostatic latent image. The exposure device 6 uses a conventional LD writing method, and has a scanning optical system for scanning light in the longitudinal (main scanning) direction of the photosensitive member and a drive unit for driving a polygon mirror and the like.

  The process cartridge 1 includes a drum-shaped photosensitive member 2 that is an image carrier or a latent image carrier, a charging member 3 that is a charging unit, a developing device 4 that is a developing unit, and a photosensitive member cleaning device 5 that is a cleaning unit. The unit is supported integrally. Each process cartridge 1 can be attached to and detached from the copying machine main body 500 as the main body of the image forming apparatus by releasing the stopper member provided in each process cartridge 1. The four process cartridges 1 are arranged in parallel in the surface movement direction of the intermediate transfer belt 7 so that the toner images formed on the respective photoreceptors 2 are sequentially superimposed on the intermediate transfer belt 7 as will be described later. The image is transferred and a visible image is formed on the intermediate transfer belt 7.

The charging member 3 uniformly charges the surface of the photosensitive member 2. In this example, the charging member 3 is pressed against the surface of the photosensitive member 2 using a roller-shaped charging roller, and is driven to rotate by the rotation of the photosensitive member 2. To do.
The charging means is not limited to the roller-shaped charging member 3 that comes into contact with the surface of the photoreceptor 2, and a non-contact charging method such as corona charging may be used.

The developing device 4 includes a developing roller as a developer carrying member that supplies toner to the electrostatic latent image formed on the photoreceptor 2 and develops the developer, a developer supply member that supplies the developer to the developing roller, and developer agitation. It has members. Each color developing device 4 contains a two-component developer containing toner and carrier.
The photoconductor cleaning device 5 cleans the transfer residual toner remaining on the surface of the photoconductor 2 that has passed the position facing the intermediate transfer belt 7.

The operation of the process cartridge 1 will be described. At the time of image formation, a charging member to which a predetermined bias is applied by a high-voltage power source when the photoreceptor 2 corresponding to each color (hereinafter also referred to as each photoreceptor 2) rotates in a clockwise direction indicated by an arrow in the drawing. 3 uniformly charges the surface of the photoreceptor 2. The surface of each photoconductor 2 that has been subjected to the charging process is irradiated with laser light L that has been modulated and deflected in accordance with each color of the image data by the exposure device 6. An electrostatic latent image is formed.
Thus, in the four process cartridges 1, toner images for respective colors of yellow, magenta, cyan, and black are formed on the photoreceptor 2.

  As shown in FIG. 1, a primary transfer roller 8 serving as a primary transfer unit is disposed at a position facing each photoconductor 2 across the intermediate transfer belt 7. A primary transfer bias is applied to the primary transfer roller 8 by a high voltage power source, and a primary transfer electric field is formed between the primary transfer roller 8 and the photoreceptor 2. By forming a primary transfer electric field between the photosensitive member 2 and the primary transfer roller 8, the toner image formed on the surface of the photosensitive member 2 is transferred to the surface of the intermediate transfer belt 7. One of a plurality of stretching rollers that stretch the intermediate transfer belt 7 is rotationally driven by a drive motor, so that the intermediate transfer belt 7 moves in the direction of arrow D in the drawing.

A full color image is formed on the surface of the intermediate transfer belt 7 by sequentially transferring the toner images of the respective colors on the surface of the intermediate transfer belt 7 moving on the surface.
On the other hand, the transfer residual toner remaining on the surface of each photoconductor 2 that has passed the position facing the intermediate transfer belt 7 is cleaned and removed by the photoconductor cleaning device 5.

  With respect to the position where the four process cartridges 1 are opposed to the intermediate transfer belt 7, the intermediate transfer belt 7 is intermediately transferred to the secondary transfer counter roller 9 a, which is one of the stretching rollers, on the downstream side of the surface movement direction of the intermediate transfer belt 7. A secondary transfer roller 9 is disposed at a position facing the belt 7 across the belt 7. As a result, a secondary transfer nip is formed between the secondary transfer counter roller 9 a and the secondary transfer roller 9. A predetermined voltage is applied between the secondary transfer roller 9 and the secondary transfer counter roller 9a constituting the secondary transfer device to form a secondary transfer electric field.

  The full color formed on the surface of the intermediate transfer belt 7 when the transfer paper P, which is a transfer material fed from the paper supply unit 700 and conveyed in the direction of arrow S in FIG. 1, passes through the secondary transfer nip. The image is transferred to the transfer paper P. At this time, the full-color image on the intermediate transfer belt 7 is transferred to the transfer paper P by a secondary transfer electric field formed between the secondary transfer roller 9 and the secondary transfer counter roller 9a. Needless to say, an image can be formed using not only the sheet-like recording medium / transfer sheet P which is a transfer material but also an OHP film sheet.

A fixing device 12 is arranged on the downstream side in the transport direction of the transfer paper P with respect to the secondary transfer nip. The transfer paper P that has passed through the secondary transfer nip reaches the fixing device 12, the full color image transferred onto the transfer paper P is fixed by heating and pressurization in the fixing device 12, and the transfer paper P on which the image is fixed is The image is output and discharged outside the copying machine 1000.
On the other hand, the toner remaining on the surface of the intermediate transfer belt 7 without being transferred to the transfer paper P at the secondary transfer nip is collected by the transfer belt cleaning device 11.

  As shown in FIG. 1, a toner bottle 900 (Y, M, C, K) that stores toner of each color is detachably disposed above the intermediate transfer belt 7 with respect to the copying machine main body 500. The toner stored in each color toner bottle 900 is supplied to each color developing device 4 by a toner replenishing device corresponding to each color.

(Embodiment 1)
An image forming apparatus provided with a process cartridge according to the first embodiment of the present invention will be described with reference to FIG. FIG. 2 is a front sectional view showing a configuration of a main part of the image forming apparatus including the process cartridge according to the first embodiment of the present invention.
The image forming apparatus of the first embodiment is different from the image forming apparatus of FIG. 1 in place of the process cartridge 1 (1Y, 1M, 1C, 1K) of FIG. 1 and the process cartridge 50 (50Y, 50M) shown in FIG. , 50C, 50K) and the use of the exposure apparatus 300 instead of the exposure apparatus 6 is mainly different.

  As shown in FIG. 2, the process cartridge 50 according to the first embodiment includes a photosensitive member 201 as an image carrier, a developing device 100 as a developing unit, a charging device 202 as a charging unit, and a photosensitive member as a cleaning unit. And a cleaning device 203. The photosensitive member 201, the developing device 100, the charging device 202, and the photosensitive member cleaning device 203 are integrally supported by a casing-like cartridge main body 51 indicated by a two-dot chain line. The cartridge body 51 together with these devices and members is configured to be detachable from the copying machine body 500 of the copying machine 1000 of FIG. That is, the exposure apparatus 6 is removed from the copying machine 1000 in FIG. 1, and the image forming apparatus is provided with the exposure apparatus 300 for each color fixedly arranged corresponding to the position of the copying machine main body 500 to which the process cartridge 50 is mounted. For the (copier), the process cartridge 50 of the first embodiment is detachably provided.

The process cartridge 50 according to the first embodiment includes four process cartridges 1 (Y, M, C, and C) constituting the image forming device 15 of the copying machine 1000 that is the tandem intermediate transfer image forming apparatus illustrated in FIG. Similarly to K), four are arranged in the vicinity of the lower part of the intermediate transfer belt 7. Hereinafter, as shown in FIG. 3, the process cartridge 50 will be described as a representative of the four process cartridges 50Y, 50M, 50C, and 50K.
As shown in FIG. 2, the exposure apparatus 300 corresponding to one of the four process cartridges 50 (Y, M, C, K) is attached and fixed to the copying machine main body 500 side.

In the first embodiment, as shown in FIG. 2, in order to reduce the width in the width direction X of the developing device 100 and reduce the size of the image forming apparatus, the developer supply unit 103 provided in the developing case 108 and the developer The structure which arrange | positions the stirring part 105 to a substantially perpendicular direction (substantially up-down direction Z) is employ | adopted.
Further, the exposure apparatus 300 using the LED array as a light emitting element is employed to reduce the size of the exposure apparatus (writing apparatus) and the image forming apparatus.

  The charging device 202 is disposed between the photoconductor cleaning device 203 and the exposure device 300, and includes a charging roller 202a and a cleaning roller 202b. The charging roller 202a is in pressure contact with or opposed to or close to the surface of the photoconductor 201, and uniformly charges the surface of the photoconductor 201 while rotating. The cleaning roller 202b is in pressure contact with the charging roller 202a and cleans the surface of the charging roller 202a while being driven to rotate.

  The photoconductor cleaning device 203 includes a cleaning blade 203a, a seal member 203b, a removed toner conveyance member 203c, and a cleaning support member 203d that attaches and supports these members. The cleaning blade 203 a makes a counter contact with the rotation direction of the photoconductor 201 to remove and collect residual toner on the photoconductor 201. The seal member 203b is in contact with the surface of the photoreceptor 201 and prevents the removed residual toner from scattering. The removed toner conveying member 203c conveys the removed residual toner.

The exposure apparatus 300 is disposed below the photoconductor 201 shown in FIG. The exposure apparatus 300 uses, as a light emitting element, an LED array that writes a latent image by irradiating the photosensitive member 201 with light. The LED array portion of the exposure apparatus 300 is arranged close to the surface of the photoconductor 201 along the entire image area in the longitudinal direction Y of the photoconductor 201.
The exposure apparatus 300 includes a lens unit, an LED substrate to which the LED array is attached, a control substrate for driving and controlling the LED array, and the like.
The exposure apparatus 300 is not limited to this, and an organic EL (electroluminescence) or the like that can reduce the size of the exposure apparatus may be used.

  The developing device 100 is a substantially vertical (vertical) type vertical biaxial circulation type developing device in which the constituent members are provided in a specific arrangement relationship as will be described later. Arranged along the entire image area in the direction Y. The developing device 100 employs a two-component developing system that includes toner and a carrier. The developing device 100 is disposed on the downstream side in the rotation direction of the photoconductor 201 adjacent to the exposure device 300 so as to be close to and opposed to the exposure device 300.

The developing device 100 includes a developing roller 101, a developer regulating member 102, a developer supplying unit 103 having a first conveying screw 104, a developer stirring unit 105 having a second conveying screw 106, a pressure release filter 107, a developing case 108, and the like. It has.
The developing roller 101 is disposed to face the surface of the photoconductor 201 and supplies a developer in the two-component developer carried on the electrostatic latent image formed on the photoconductor 201 to develop the developer. Functions as a body.

The developing device 100 is disposed below the developing roller 101 provided in the developing case 108, and is disposed below the developer supplying unit 103 that supplies the developer to the developing roller 101, and below the developer supplying unit 103. It is divided into a developer agitation unit 105 that agitates the developer and circulates the developer (additional replenishment toner) with the developer supply unit 103. The developer supply unit 103 and the developer stirring unit 105 communicate with each other at both ends in the longitudinal direction Y of the developing device 100.
The developing roller 101 is disposed close to the surface of the photoconductor 201 along the entire image area in the longitudinal direction Y of the photoconductor 201. As an example of the developing roller 101, one having a diameter of 16 mm is used.

  The developer regulating member 102 regulates the amount of developer (developer layer thickness) carried by the developing roller 101. As an example of the developer regulating member 102, a magnetic metal round bar having an outer diameter of 5 mm is used.

  In the developer supply unit 103, a first conveying screw 104 is disposed as a developer supply member that is disposed near the lower portion of the developing roller 101 along the longitudinal direction Y of the developing roller 101 and supplies the developer to the developing roller 101. It is installed. The first transport screw 104 also has a function of collecting the developer.

The developer agitating unit 105 is disposed in the vicinity of the lower portion of the first conveyance screw 104 along the longitudinal direction Y of the first conveyance screw 104, and agitate the developer between the first conveyance screw 104 and the developer. A second conveying screw 106 is disposed as a developer agitating member to be circulated.
The first transport screw 104 and the second transport screw 106 also function as a developer transport member or a rotational transport member.

  The depressurizing filter 107 releases only the increased pressure in order to prevent the internal pressure in the developing device 100 from increasing, and also has a function of preventing leakage of the developer.

The developing case 108 rotatably supports the developing roller 101, the first conveying screw 104, and the second conveying screw 106 described above, and attaches and supports the developer regulating member 102 and the pressure release filter 107. Further, the developing case 108 accommodates the developer present in the developer supply unit 103, the developer stirring unit 105, and the like.
The developing case 108 is arranged in the longitudinal direction Y of the photoconductor 201 on the downstream side in the rotation direction of the photoconductor 201 that is close to and faces the exposure apparatus 300.

  Next, the operation of the developing device 100 will be described. In the developer supply unit 103, the developer conveyed to the vicinity of the developing roller 101 by the first conveying screw 104 rotating in the direction of the arrow in FIG. 2 is adsorbed to the developing roller 101 by magnetic force, and desired by the developer regulating member 102. Regulated by the transport amount. Thereafter, the developer regulated to a desired transport amount is transported to the development area by the developing roller 101 rotating in the direction of the arrow in FIG. Thereafter, the toner is returned as it is into the developing case 108 by the developing roller 101, separated from the developing roller 101 by the repulsive magnetic force, and returned to the developer supply unit 103 again.

  The developer returned into the developing case 108 is transferred from the developing region to the developing case 108 on the downstream side in the rotation direction of the developing roller 101 by a magnetic brush formed by the developing roller 101 formed in the developing region with the photoconductor 201. Developer is conveyed. At this time, the developer returned into the developing case 108 generates an air current sucked into the developing device 100 by the magnetic brush. This airflow can prevent scattering of toner that has not been used for development. Further, the pressure in the developing device 100 with the increased internal pressure is released by the pressure release filter 107.

With reference to FIG. 2, an image forming mode in the image forming apparatus to which the process cartridge of Embodiment 1 is mounted will be described.
The image forming apparatus to which the process cartridge 50 according to the first embodiment is mounted includes a standard mode (first mode) for forming an image on plain paper or the like depending on the type of transfer paper P that is a transfer material / recording medium to be used, and 200 g. There are at least two modes including a low-speed mode (second mode) for forming an image on thick paper or special paper of / m ² or more, and these two modes are configured to be executable.

In the image forming apparatus to which the process cartridge 50 is mounted, as shown in FIG. 2, a photoconductor driving motor that is an image carrier driving source that drives the photoconductor 201 based on a control command signal from the control unit 250. The rotation drive of 210 and the development drive motor 220, which is a development device drive source for driving the development roller 101 of the development device 100, can be controlled independently of each other.
The control unit 250 is configured by a microcomputer including a CPU, a ROM, a RAM, a timer, and the like that function as control means, for example. In the ROM, relational data for setting the peripheral speed shown in Table 1 below (hereinafter also simply referred to as peripheral speed) is stored in advance.
A standard mode signal related to the standard mode or a low speed mode signal related to the low speed mode is generated by pressing a key on the operation panel 230 provided in the image forming apparatus and selecting a paper feeding cassette on which transfer paper to be selected is loaded. And transmitted to the control unit 250.

Table 1 shows the photosensitive drum 201, the peripheral speed (peripheral speed) of the developing roller 101, and the first transport screw 104 and the second transport screw 106, which are the rotational speeds of the transport members, for each of the standard mode and the low speed mode in the first embodiment. , The peripheral speed ratio (peripheral speed ratio) between the peripheral speed of the developing roller and the peripheral speed of the photosensitive member.
As shown in Table 1, in the standard mode, the photosensitive member driving motor 210 and the developing driving motor 220 are controlled so that the photosensitive member peripheral speed is 320 mm / sec and the developing roller peripheral speed is 531 mm / sec. . The peripheral speed ratio (peripheral speed ratio) between the developing roller peripheral speed and the photosensitive member peripheral speed is set to 531/320 = 1.66. In Table 1, the peripheral speed ratio between the developing roller peripheral speed and the photosensitive member peripheral speed is simply described as developing roller / photosensitive member.

On the other hand, in the low speed mode, the photosensitive member driving motor 210 and the developing driving motor 220 are controlled so that the photosensitive member peripheral speed is 97 mm / sec and the developing roller peripheral speed is 198 mm / sec. The peripheral speed ratio (peripheral speed ratio) between the developing roller peripheral speed and the photosensitive member peripheral speed is set to 198/97 = 2.04. The reason why the peripheral speed ratio between the developing roller peripheral speed and the photosensitive member peripheral speed is set according to the standard mode and the low speed mode as shown in Table 1 will be collectively described later.
Further, when driven in the standard mode, both the rotation speeds of the first transfer screw 104 and the second transfer screw 106 are 610 rpm, and when driven in the low speed mode, both the rotation speeds of both screws are 228 rpm.

A detailed configuration and supplementary operation of the developing device 100 and a drive transmission configuration will be described with reference to FIGS. 3 and 4. FIG. 3 is a longitudinal sectional view of the developing device constituting the process cartridge of FIG. 2 cut in the vertical direction. FIG. 4 is a cross-sectional view of the main part when the lifting region 112 in the developing device of FIG. 3 is viewed from the direction of arrow E.
As shown in FIG. 3, the basic configuration of the developing device 100 is divided into a developer supply unit 103 and a developer stirring unit 105 which are separated by a partition wall provided in the developing case 108. Communication portions 111 and 112 that are open communication with each other are provided. The opening diameter of the communication portions 111 and 112 is a rectangle with a longitudinal direction Y of 25 mm and a width direction X (paper surface direction in FIG. 3) of 10 mm. Then, the developer supply unit 103 and the developer are transported by transporting the developer in the arrow direction GF indicated by a thick solid line in FIG. 3 by the first transport screw 104 and the second transport screw 106 which are also transport members or rotating transport members. The developer is circulated between the stirring unit 105.
The communication unit 111 is a lifting area 112 which is a developer delivery unit from the developer stirring unit 105 to the developer supply unit 103.

  The developer used for development on the developing roller 101 is returned again to the developer supply unit 103 by the repulsive magnetic force formed on the developing roller 101, and is conveyed to the developer stirring unit 105 through the communication unit 110. The developer returned to the developer agitation unit 105 is mixed with the toner replenished from the toner replenishing port provided in the developer agitation unit 105, and is conveyed again to the developer supply unit 103, so that the desired toner is always obtained. A developer having a concentration can be supplied to the developing roller 101. In order to perform control for supplying the developer having the optimum toner density to the developing roller 101 as described above, the developer agitation unit 105 is provided with a toner density sensor 109 for detecting the toner density.

  In a vertical biaxial circulation type developing device, also called a vertical biaxial circulation type, in a lifting area which is a developer delivery section from a developer stirring section to a developer supply section, in a direction against gravity (antigravity direction) It must be transported to lift the developer. Therefore, the developer tends to stay in the lifted area of the developer stirring unit, the developer is biased toward the developer stirring unit, and sufficient developer cannot be supplied to the developer supply unit. For this reason, a shortage of developer on the developer supply unit side, insufficient stirring of the developer, and a decrease in the volume of the developer make it impossible to supply a sufficient amount of developer to the developing roller, resulting in a decrease in the amount of developer transported to the developing roller. As a result, image defects such as blurring occur.

In order to lift the developer smoothly, the conveying force of the conveying member (second conveying screw) in the developer agitating unit is set higher than that of the conveying member (first conveying screw) in the developer supplying unit. Even if there is resistance due to gravity at the part, the developer can be smoothly circulated without staying and a sufficient amount of developer can be supplied to the developing roller.
To lift the developer, the developer is flipped up by the rotation of the blades of the conveying member, and the developer accumulated in the lifting portion is lifted upward by receiving pressure in the conveying direction from the conveying member. However, when the low-speed mode (second mode) is entered, the developer jumps less by the conveying member. Therefore, in order to lift the developer smoothly, the peripheral speed of the standard mode (first mode) is used for the developer. Even stronger pressure must be applied, and in the low speed mode, the developer balance fluctuates and becomes unstable.

  In other words, the developer balance described above fluctuates and becomes unstable immediately after the start of driving rotation in the developing device, from the second conveying screw of the developer stirring unit to the first conveying screw of the developer supplying unit. It can be said that there is a time lag (time delay) between the lifting of the developer at the portion and the supply of the lifted developer from the first conveying screw of the developer supply portion to the developing roller. In particular, a significant time lag occurs immediately after the image forming speed is switched from high speed to low speed.

Therefore, in the first embodiment of the present invention, in addition to the control shown in Table 1, the first transport screw 104 as a developer supply member that is also a rotary transport member and the second as a developer stirring member that is also a rotary transport member. By making the conveying screw 106 have the following characteristics, the efficiency of developer delivery is improved, and the developer can be easily supplied to the developer supply unit 103 side.
As shown in FIG. 4, the first conveying screw 104 on the developer supply unit 103 side rotates by having a screw blade 104b as a blade helically attached around a screw shaft 104a as a shaft. The developer is conveyed.
The first conveying screw 104 has a screw outer diameter 104c, which is the outer diameter of the screw blade 104b, of φ13 mm, an axial diameter of the screw shaft 104a in the lifting region 112 of φ6 mm, and a screw shaft 104aa, which is the other part, of φ8 mm. The shape of the screw blades 104b is three windings with a lead length of 45 mm, and the blade pitch is 15 mm.

As shown in FIG. 4, the second conveying screw 106 on the developer stirring unit 105 side rotates by having a screw blade 106b as a blade spirally attached around a screw shaft 106a as a shaft. The developer is conveyed.
The second conveying screw 106 has a screw outer diameter 106c, which is the outer diameter of the screw blade 106b, of 15 mm, and a screw shaft 104a has a diameter of 6 mm. The shape of the screw blade 106b is a double winding with a lead length of 25 mm, and the blade pitch is 12.5 mm.
The lengths in the longitudinal direction Y of the first transport screw 104 and the second transport screw 106 are both 290 mm.

Here, the length of the blade (screw blade) = screw outer diameter−shaft diameter is defined. Length of blades (screw blades) of the first conveying screw 104 in the lifting region 112 = 13−6 (lifting region 112) = 7 mm. Further, the length of the blades (screw blades) of the first conveying screw 104 other than the lifting area 112 is 13−8 = 5 mm.
The length of the blades (screw blades) of the second conveying screw 106 = 15−6 = 9 mm.
Accordingly, the length (5 mm, 7 mm) of the blade (screw blade) of the first transport screw 104 is set to be smaller than the length (9 mm) of the blade (screw blade) of the second transport screw 106.

  As shown in FIG. 3, the developing roller 101 is rotatable because both ends of the shaft of the developing roller 101 are rotatably supported via bearings provided in the developing unit. A developing roller gear 117 is fixed to one end portion of the shaft of the developing roller 101 (the left end portion in FIG. 3, corresponding to the back side when the process cartridge 50 in FIG. 2 is mounted and set in the image forming apparatus main body). . In the vicinity of the developing roller gear 117, an input gear 116 that receives driving force from the main body of the image forming apparatus is rotatably supported at the left end portion of the developing case 108 via an input gear shaft. A first transport screw gear 118 is fixed to one end (left end in FIG. 3) of the screw shaft of the first transport screw 104. The input gear 116 meshes with the developing roller gear 117 and meshes with the first transport screw gear 118.

  The input gear 116 that receives the driving force from the main body of the image forming apparatus transmits the driving force of a developing driving motor 220 (see FIG. 2) as a developing device driving source disposed on the main body side of the image forming apparatus. A driving gear as a driving force transmitting member is selectively meshed.

In the drawing of the developing case 108, an idler gear 120 is rotatably supported via an idler gear shaft. A first transport screw gear II 119 that meshes with the idler gear 120 is fixed to the other end portion (right end portion in FIG. 3) of the screw shaft of the first transport screw 104. A second transport screw gear 121 that meshes with the idler gear 120 is fixed to the other end (right end in FIG. 3) of the screw shaft of the second transport screw 106.
The input gear 116, the developing roller gear 117, the first conveying screw gear 118, the first conveying screw gear II 119, and the idler gear 120 and the second conveying screw gear 121 are examples of a driving force transmission member that transmits a driving force.

  The driving force of the rotary conveying member is transmitted to the first conveying screw gear 118 simultaneously with the developing roller gear 117 via the input gear 116 that receives the driving force from the main body of the image forming apparatus. Further, the second conveying screw 106 is rotated by being transmitted to the second conveying screw gear 121 via the first conveying screw gear II 119 and the idler gear 120. By configuring the gear train shown in FIG. 3, the rotation directions of the first transport screw 104 and the second transport screw 106 coincide with each other as shown by the arrow direction A as shown in FIG. 4.

  In this way, the developer lifted by the second transport screw 106 is quickly taken into the developer supply unit 103 by the first transport screw 104. Therefore, the delivery of the developer in the lifting area 112 that is the lifting portion becomes smooth, and the retention of the developer can be reduced. The driving force from the input gear 116 at the start of driving is transmitted in the order of the first conveying screw 104 and then the second conveying screw 106. Therefore, the first conveyance screw 104 starts driving slightly faster than the second conveyance screw 106. Therefore, the developer pressure in the upper part of the lifting area 112 is relaxed immediately after the start of driving, so that a rapid increase in developer pressure at the lifting portion can be suppressed immediately after driving, and the fixing and aggregation of the developer can be prevented.

Although the explanation will be mixed, the reason why the peripheral speed ratio between the peripheral speed of the developing roller and the peripheral speed of the photosensitive member is set according to the standard mode and the low speed mode as shown in Table 1 will be supplemented.
For the reasons described above, the change in the developer volume that occurs when the image forming speed is switched occurs as long as the rotation speeds of the first conveying screw and the second conveying screw that are conveying members do not change with respect to the change in the image forming speed. do not do. However, for this purpose, as described in the background art, it is necessary to provide a separate drive source for the conveying member, which is an obstacle in terms of cost.

  Therefore, in the first embodiment of the present invention, the reduction in the rotational speed of the first transport screw 104 and the second transport screw 106 is reduced by changing the peripheral speed ratio between the photosensitive member and the developing roller in the low speed mode and the standard mode. That is, during low-speed driving, the peripheral speed ratio of the developing roller to the photosensitive member is increased within an appropriate range, and the change in the rotation speed on the drive input side of the developing device is reduced with respect to the change in the image forming speed. The decrease in the rotational speed of the screw 104 and the second conveying screw 106 is reduced. As a result, even in the low speed mode, it is possible to suppress the developer stagnation in the lifting part to the developer supply part and to suppress the developer bulk fluctuation. Thereby, even when the image forming speed is changed, it is possible to prevent the occurrence of image abnormality due to the shortage of developer in the developer supply unit.

  In other words, in the image forming apparatus including the developing device in which the developer supplying unit and the developer agitating unit are arranged in the substantially vertical direction, the developer is supplied to the developer lifting unit in the developing device. It can be said that the following configuration is provided for smooth lifting. That is, the developer carrying force of the developer agitating member below the developer supply member on the upper side is increased, and the developer carrying body and the image carrier are in the second mode in which the image forming speed is slower than in the first mode. The image forming apparatus includes a developing device that suppresses fluctuations in the developer bulk in the developer supply unit by changing a peripheral speed ratio of the body, a process cartridge including the developing device, a developing device, or a process cartridge.

  As described above, according to the first embodiment, in the image forming apparatus including the vertical biaxial circulation type developing device, the developer bulk fluctuation at the time of switching the image forming speed is reduced without adding a new member. Even when the image forming speed is changed, it is possible to prevent the occurrence of image abnormality due to the lack of developer in the developer supply unit.

As described above, it can be said that the following first to seventh aspects are substantially described in the first embodiment.
The first aspect is an image carrier that carries a latent image on the surface of the photoconductor 201 and the like, and a development that is arranged opposite to the surface of the image carrier and carried on the latent image formed on the image carrier. A developer carrier such as a developing roller 101 for supplying and developing the toner in the developer; a developer supply such as a developer supply unit 103 disposed below the developer carrier and supplying the developer to the developer carrier; And a developing device 100 having a developer stirring unit such as a developer stirring unit 105 that is disposed below the developer supply unit and circulates the developer between the developer supply unit by stirring the developer. And a developing device, wherein a peripheral speed of the image carrier is a first mode in which image formation is performed at a first peripheral speed, and a second speed is lower than the peripheral speed of the first mode. And a second mode in which image formation is performed at a peripheral speed. In, than the first mode, increasing the ratio of the peripheral speed of the developer carrying member to the circumferential speed of the image bearing member.

  According to the first aspect, in the image forming apparatus provided with the vertical circulation type developing device, the developer bulk change at the time of switching the image forming speed is reduced without adding a new member, and the image forming speed is changed. Even at times, it is possible to prevent the occurrence of image abnormality due to the lack of developer in the developer supply unit.

In a second aspect, in the first aspect, the developing device such as the developing device 100 includes a blade such as a screw blade 104b that is disposed in the developer supply unit and supplies the developer to the developer carrier. A developer supply member such as a rotatable first conveying screw 104 and a screw blade 106b which is disposed in the developer agitating unit and agitates the developer to circulate the developer between the developer supply unit and the like. A developer agitating member such as a rotatable second conveying screw 106 provided with a blade, and the length of the blade of the developer supplying member is made smaller than the length of the blade of the developer agitating member.
According to the second aspect, the conveying force of the developer agitating member of the developer agitating unit is likely to be larger than the conveying force of the developer supplying member of the developer supplying unit, and the developer enters the developer supplying unit. Since the volume tends to be small, the developer bulk at the developer supply unit is increased, and it becomes easy to supply an appropriate amount of developer to the developer carrier.

According to a third aspect, in the second aspect, the development device such as the development device 100 is a development device such as a development drive motor 220 for rotationally driving the developer carrier, the developer supply member, and the developer stirring member. A driving input unit such as an input gear 116 to which a rotational driving force from a driving source for transmission is transmitted, and a rotational driving force from the driving input unit is applied to the developer carrier, the developer supply member, and the developer stirring member, respectively. A driving force transmission member such as a transmission gear is disposed, and the rotation direction of the developer supply member such as the first conveyance screw 104 and the developer stirring member such as the second conveyance screw 106 are the same direction; The drive force transmission member to the developer supply member transmits the rotational drive force from the drive input unit faster than the drive force transmission member to the developer stirring member.
According to the third aspect, it is possible to further smoothly deliver the developer in the developer lifting portion from the developer stirring portion to the developer supply portion, and to prevent the developer from staying in the developer stirring portion. Can do. Further, it is possible to suppress a rapid increase in the developer pressure of the lifting portion at the start of driving.

  In a fourth aspect, the driving force transmitting member is a gear in the third aspect, and the gear to the developer supply member has a rotational driving force from the drive input unit faster than the gear to the developer agitating member. It is a gear train structure to be transmitted.

  In a fifth aspect, in any one of the first to fourth aspects, the peripheral speed of the developer carrier such as the developing roller 101 is set to be larger than the peripheral speed of the image carrier such as the photoconductor 201.

A sixth aspect is any one of the first to fifth aspects, wherein the sixth aspect is disposed along the longitudinal direction of the image carrier and facing the surface of the image carrier, and forms a latent image on the image carrier. A light-emitting element that includes an exposure apparatus such as the exposure apparatus 300 and is used in the exposure apparatus is an LED array that irradiates light onto an image carrier and writes a latent image.
According to the sixth aspect, it is possible to reduce the size of the image forming apparatus.

The seventh aspect is detachable from the main body of the image forming apparatus such as the copying machine main body 500, an image carrier such as the photosensitive member 201, a charging means such as the charging device 202, and a developing means such as the developing device 100. And at least the developing means selected from cleaning means such as the photoconductor cleaning device 203, the developing means is the developing apparatus according to any one of claims 1 to 6, and The image carrier according to any one of Items 1 to 6 and the developing device according to any one of Items 1 to 6 constitute a process cartridge such as a process cartridge 50. According to this aspect, operability such as replacement of consumable parts is improved.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments, and the present invention described in the claims is not specifically limited by the above description. Various modifications and changes are possible within the scope of the above. For example, the technical matters described in the above embodiments and examples may be appropriately combined.

  For example, the image forming apparatus and the image forming apparatus include four process cartridges 50 that are applied to the copying machine 1000 of FIG. 1 and four exposure apparatuses 300 arranged corresponding to the respective process cartridges 50. It is not limited to what is comprised. That is, an image forming apparatus or an image forming apparatus each including a single image carrier and developing device and a single exposure device may be used. Further, it may be an image forming apparatus or an image forming apparatus provided with a single process cartridge and a single exposure device.

Alternatively, the photoconductor 201, the charging device 202, and the photoconductor cleaning device 203 may be integrated to form a photoconductor unit that can be attached to and detached from the cartridge body 51.
The developing device 100 and the photosensitive unit can be attached to and detached from the cartridge body 51 while being attached to the copying machine body 500 as the process cartridge 50 and detached from the copying machine body 500 as the process cartridge 50. . That is, the unitized developing device 100 and the photosensitive unit can be individually detached from the copying machine main body 500, and can be individually replaced when an image defect occurs due to deterioration over time.

  Further, the image forming apparatus and the image forming apparatus to which the present invention is applied are not limited to the tandem type intermediate transfer system as shown in FIG. 1, and the tandem type direct transfer system image forming apparatus using a conveyance belt for conveying a sheet. An image forming apparatus may be used.

  The effects appropriately described in the embodiments of the present invention are merely a list of the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. It is not a thing.

50 Process Cartridge 90 Image Making Device 100 Developing Device 101 Developing Roller (Example of Developer Carrier)
103 Developer Supply Unit 104 First Conveying Screw (Example of Developer Supply Member)
104a Screw shaft 104b Screw blade 104c Screw outer diameter 105 Developer stirring unit 106 Second transport screw (an example of developer stirring member)
106a Screw shaft 106b Screw blade 106c Screw outer diameter 108 Developing case (developing container)
116 Input gear (an example of a drive input unit)
117 Development roller gear (an example of a driving force transmission member)
118 1st conveying screw gear (an example of a driving force transmission member)
119 First conveying screw gear II (an example of a driving force transmission member)
120 idler gear (an example of a driving force transmission member)
121 2nd conveying screw gear (an example of a driving force transmission member)
201 photoconductor (an example of an image carrier)
202 Charging device (charging means)
203 Photoconductor cleaning device (cleaning)
210 Photoconductor driving motor (drive source for driving image carrier)
220 Development drive motor (drive source for developing device drive)
300 Exposure apparatus (exposure means)
500 Copying machine main body (image forming device / image forming device main body)
X Image forming device body width direction Y Longitudinal direction Z Vertical direction, vertical direction

JP 2014-026157 A JP 2012-128143 A Japanese Patent Laying-Open No. 2015-125157 JP 2006-171245 A

Claims (7)

An image carrier carrying a latent image on the surface;
A developer carrier that is arranged to face the surface of the image carrier and supplies toner in the developer carried on the latent image formed on the image carrier, and develops the developer carrier. A developer supply unit disposed below and supplying a developer to the developer carrying member, and a developer supply unit disposed below the developer supply unit and stirring the developer to the developer supply unit A developing device having a developer stirring section for circulating the
An image forming apparatus comprising:
A first mode in which image formation is performed at a peripheral speed of the image carrier at a first peripheral speed, and a second mode in which image formation is performed at a second peripheral speed that is lower than the peripheral speed in the first mode. Each is executable
In the second mode, the ratio of the peripheral speed of the developer carrier to the peripheral speed of the image carrier is larger than that of the first mode. The image forming apparatus according to claim 1.
The developing device is disposed in the developer supply section, and is disposed in the developer agitating section, which is provided with a rotatable developer supply member having blades for supplying the developer to the developer carrier, and is developed. A rotatable developer stirring member provided with blades for stirring the developer and circulating the developer between the developer supply unit,
An image forming apparatus, wherein a length of the blade of the developer supply member is smaller than a length of the blade of the developer stirring member. The image forming apparatus according to claim 2.
The developing device has a drive input unit to which a rotational driving force is transmitted from a developing device drive source for rotationally driving the developer carrier, the developer supply member, and the developer agitating member,
A driving force transmission member that transmits a rotational driving force from the drive input unit is disposed on the developer carrier, the developer supply member, and the developer stirring member,
The rotation direction of the developer supplying member and the developer agitating member is the same direction, and the driving force transmitting member to the developer supplying member is more than the driving force transmitting member to the developer agitating member. In the image forming apparatus, the rotational driving force from the drive input unit is transmitted quickly. The image forming apparatus according to claim 3.
The driving force transmission member is a gear, and the gear to the developer supply member transmits a rotational driving force from the drive input unit earlier than the gear to the developer stirring member. An image forming apparatus. The image forming apparatus according to any one of claims 1 to 4,
2. An image forming apparatus according to claim 1, wherein a peripheral speed of the developer carrier is set to be larger than a peripheral speed of the image carrier. The image forming apparatus according to any one of claims 1 to 5,
An exposure device is provided along the longitudinal direction of the image carrier and opposite to the surface of the image carrier, and forms a latent image on the image carrier.
The light-emitting element used in the exposure apparatus is an LED array that writes a latent image by irradiating the image carrier with light. In a process cartridge that is detachably attached to the main body of the image forming apparatus and integrally includes an image carrier and at least the developing unit selected from a charging unit, a developing unit, and a cleaning unit.
The developing unit is the developing device according to any one of claims 1 to 6,
The image carrier according to any one of claims 1 to 6 and the developing device according to any one of claims 1 to 6 constitute the process cartridge. To process cartridge.

Images