JP2001209248A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably regulate the thickness of a toner layer over a long term while preventing a filming caused by the sticking of toner. SOLUTION: One end of an elastic doctor blade 16 is attached to a freely rotatable polygonal pillar supporting body 15, and an other end thereof is protruded toward the upstream side in a rotating direction. The protruded end of the blade 16 abuts on a developing roller 5 so as to regulate the thickness of the layer of toner 3 carried by the roller 5. When the time decided in accordance with the service term of one blade 16 comes, a new blade 16 abuts on the roller 5 by rotationally moving the supporting body 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an image forming apparatus such as a copying machine, a printer, a facsimile, and an electrostatic recording apparatus using an electrophotographic system, and an electrostatic latent image formed on a latent image carrier. The present invention relates to a developing device for developing a toner by attaching a fine powder toner to the toner.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, a photoreceptor (latent image carrier) is charged and exposed to form an electrostatic latent image on the photoreceptor. Certain toner is attached to the electrostatic latent image on the photoreceptor to visualize the image. The visualized toner image is electrostatically transferred to a transfer sheet, and then the toner image is heated and fixed on the transfer sheet by a fixing device to form a copy or a printed image.

As a developer for an image forming apparatus, a one-component developer composed of only a toner and a two-component developer composed of a toner and a carrier are known. Generally, in a developing method using a two-component developer, a toner and a carrier are stirred in a developing tank to charge the toner, and a developing roller (developer carrying member) is used in a state where the toner is attached to the surface of the carrier. As a result, the sheet is conveyed to a developing area at a position where the photosensitive member and the developing roller are opposed to each other. For this reason, a sufficient conveyance amount can be obtained, and a high-density image can be obtained.

However, in the case of the two-component developer, it is necessary to maintain the mixing ratio of the toner and the carrier constant in order to maintain the development density constant, and there is a problem that the configuration of the entire developing device becomes complicated.

[0005] On the other hand, a developing device using a one-component developer is easy to handle. That is, as a one-component developer (hereinafter, abbreviated as toner), a non-magnetic one-component developer is known, and a non-magnetic one-component developing device using the non-magnetic toner adsorbs the toner onto a developing roller. Since there is no need for a magnet roller to provide magnetic force to hold
The configuration is simple.

In a non-magnetic one-component developing device, a toner layer having a predetermined thickness is formed by a layer thickness regulating member disposed opposite to a developing roller, and the toner is brought into contact with the layer thickness regulating member by contacting the toner. Tribocharges. The developing roller on which the charged toner layer is formed comes into contact with the photoconductor and visualizes the electrostatic latent image formed on the photoconductor.

As a layer thickness regulating member in this developing system, a thin metal plate, rubber, or a member obtained by laminating them is generally used. A toner layer is formed on the developing roller.

However, the following problems have been pointed out in the non-magnetic one-component developing device having such advantages. In other words, in this method, the layer thickness regulating member and the developing roller are always in pressure contact at one point (one point in the circumferential direction of the developing roller). A phenomenon (filming) in which the toner softens and adheres to the contact portion of the layer thickness regulating member that comes into contact with the developing roller or a position in the vicinity thereof due to a combination of environmental factors such as pressure or the temperature inside the apparatus. Easier to do. Initially, this adhered substance is a slight one with a thin film on the surface, and at a level that does not cause any particular problem on the image, but grows as the use is repeated, and eventually adversely affects the image. Exert. That is, the adhered substance deteriorates the chargeability of the toner by the layer thickness regulating member, closes the toner inflow opening between the developing roller, and mechanical irregularities on the contact surface with the developing roller. As a result, the overall or local decrease in toner layer thickness or local slip-through (increase in layer thickness) is caused, and a uniform toner layer cannot be formed. As a result, there is a problem that the density is reduced on the image, and defects such as white streaks are generated in a solid image portion (solid image portion) of the recorded image.

In order to cope with such a problem, for example, Japanese Patent Application Laid-Open No. 60-233679 discloses a method in which a layer-thickness regulating member is formed in a roller shape, and is constantly rotated, so that a toner regulating member and a developing roller are formed. A configuration is disclosed in which the contact between the developing roller and the toner layer is always prevented at one point, and the thickness of the toner layer on the developing roller is regulated.

However, in the above configuration, the toner is likely to be caught in the contact position between the layer thickness regulating member and the developing roller. Therefore, the contact pressure to the developing roller tends to be uneven, and it is difficult to uniformly regulate the layer thickness. In the case of a one-component developer, since almost all of the toner layer on the developing roller moves to the electrostatic latent image, the thickness of the toner layer directly affects the image density, and a change in the layer thickness is not preferable. Further, there is a problem that the toner layer on the developing roller becomes thick. When the thickness of the toner layer is increased, the amount of toner that does not come into contact with the regulating member and is not charged increases. In order to avoid this, it is sufficient to increase the pressure for pressing the layer thickness regulating member against the developing roller. However, doing so increases the load on the toner, so that the time until the sticking occurs is shortened, and the developing roller Since the load on the bearing also increases, the driving torque also increases. Therefore,
In non-magnetic one-component development, it is preferable to form the toner layer by minimizing the contact pressure of the layer thickness regulating member with the developing roller, but a uniform layer thickness cannot be obtained.

In Japanese Patent Application Laid-Open No. 5-127509, a regulating blade for regulating the layer thickness of the toner supplied onto the developing roller is provided so as to uniformly contact the developing roller. In order to prevent the toner from sticking to the developing roller, a configuration is disclosed in which the regulating blade is moved to change the contact position of the regulating blade with the developing roller.

However, in the above configuration, since the contact pressure changes with a change in the distance from the fixed end of the regulating blade to the contact position with the developing roller, the layer thickness of the toner layer formed on the developing roller changes. Resulting in. In addition, the layer thickness regulating member is reciprocated or vibrated for the purpose of removing the adhered toner. However, when the developing roller and the layer thickness regulating member rub against each other, scratches or the like are likely to occur, which may adversely affect the image quality. There is.

To solve the above-mentioned problem, Japanese Patent Application Laid-Open No. 10-83118 discloses a toner regulating member having a step formed on the surface of a cylindrical roll, and rotating it to the next step when necessary. By controlling the rotation angle and the distance from the contact position between the toner regulating member and the developing roller to the step edge, the amount of toner on the developing roller is controlled, and the toner filming on the developing roller and the toner regulating member is performed. And attempts to extend the life of the developing device are disclosed.

[0014]

In the toner regulating member provided with the step, the distance from the center of rotation to the outer peripheral portion of the step changes in the circumferential direction, and the contact position between the toner regulating member and the developing roller is changed. The thickness of the toner layer on the developing roller is controlled by varying the distance from to the step edge. Therefore, the cross-sectional shape of the toner regulating member becomes a special shape, and the deviation of the rotation axis affects the layer thickness of the toner, thereby deteriorating the image quality. Further, depending on the contact position of the toner regulating member, the contact pressure is weak, and the toner is easily caught between the toner regulating member and the developing roller. Therefore, in order to control the contact pressure to be constant, it is necessary to accurately position the rotation center of the toner regulating member, and a complicated structure and accuracy are required.

SUMMARY OF THE INVENTION In view of the above, the present invention prevents the filming of the toner on the developing roller and the layer thickness regulating member with a simple configuration to extend the life, and reduces the thickness of the toner layer on the developing roller. It is an object to provide a developing device that can be stably controlled.

[0016]

Means for Solving the Problems According to the present invention, a layer thickness regulating member for regulating the layer thickness of a developer layer formed on the surface of the developing roller in contact with the developing roller has one end on the surface of the developing roller. And a plurality of elastic pieces having the other end attached to a support member, and the elastic pieces contacting the developing roller are switched. Then, the support of the layer thickness regulating member is rotated or horizontally moved by the switching means.

According to this, the layer thickness regulating member is provided with a plurality of elastic pieces each acting independently as a layer thickness regulating member, and the elastic piece to be used, that is, the elastic piece in contact with the developing roller is provided. The switching means can switch the elastic pieces so as to sequentially contact the developing roller. Therefore, by switching to a new elastic piece, filming due to toner sticking to the elastic piece can be prevented, and the life of the layer thickness regulating member can be extended.

Incidentally, the elastic piece is formed in a thin plate shape, so that the developer does not get caught in the pressure contact portion unlike the roller-shaped layer thickness regulating member. Therefore, a developer layer having a uniform and stable thickness can be formed on the developing roller with a simple structure without designing a complicated shape in consideration of the involvement of the developer. In addition, since the elastic piece itself has elasticity like a leaf spring, even if a slight displacement occurs due to the movement of the support, the elastic force of the elastic piece absorbs this displacement, and the developing roller It does not affect the thickness of the developer layer formed thereon.

The timing for switching the plurality of elastic pieces may be such that the elastic pieces are automatically switched for each service life of each elastic piece, and each elastic piece itself may be formed of a relatively inexpensive material. The structure can be simplified, the material selection range of the layer thickness regulating member can be increased, and the cost can be reduced. Here, in order to switch the elastic pieces, the number of image forming operations or the number of rotations of the developing roller may be measured, and the switching means may be driven when the number reaches the number determined by the service life of the elastic pieces. In addition, in the case where the switching of the elastic pieces is performed manually, the number of times of switching the elastic pieces is measured, and information such as the number of times of the switching and the remaining number of times that the switching can be performed is displayed and notified by voice or the like.
Whether or not there is an unused elastic piece can be easily grasped, and the workability of switching is improved.

At this time, if the life of the developing device and the total period of the life of each elastic piece are set to be the same, stable developing performance can be exhibited even if the developing device is used for a long time. Parts and materials can be used effectively.

Further, by using a conductive material for the support and the elastic piece of the layer thickness regulating member, the charging of the developer can be promoted, the charging can be stabilized, and the deterioration of image quality such as fogging can be prevented. In particular, if a bias voltage having the same polarity as the developer charging polarity and greater than the developing bias voltage is applied to the layer thickness regulating member, the charge is injected into the developer from the layer thickness regulating member to uniformly charge the developer. And excellent charging efficiency. Thus, a developing device suitable for using a non-magnetic one-component developer can be obtained.

[0022]

FIG. 1 shows a developing device provided in an image forming apparatus according to an embodiment of the present invention. A developing device 2 is provided so as to face a photoconductor 1 which is an example of a latent image carrier. In the developing device 2, a toner 3, which is a non-magnetic one-component developer, is contained in a developing tank 4. Inside the developing tank 4, a developing roller 5 as a developer carrier and a developing roller 5
Toner supply roller 6 for supplying toner 3 to the developing tank 4
Transport rollers 7 and 8 for transporting the toner 3 supplied to the developing roller 5 to the developing roller 5 while agitating the toner 3 are provided rotatably, and a layer of a toner layer formed on the surface thereof in contact with the developing roller 5 A layer thickness regulating member 9 for regulating the thickness is provided.

The photoreceptor 1 is in the form of a drum having a diameter of 65 mm, and is rotationally driven by a motor in the direction of arrow A, and its peripheral speed is 190 mm / s. In addition, the conductive base, which is the base of the photoconductor 1, is grounded, and the surface of the photoconductor 1 is charged to a surface potential of −550 V by a bias power supply.

The developing roller 5 has a volume resistivity of 10 ⁶ Ωcm to which a conductive agent such as carbon black is added.
A conductive elastic roller made of conductive urethane rubber having a IS-A hardness of 60 to 70 degrees and having a diameter of 34 mm has a surface roughness R
z = 3 to 6 μm (according to JIS B-0601). The developing roller 5 is rotatably supported by the developing tank 4 via a stainless steel rotating shaft 10 having a diameter of 18 mm, and is rotationally driven by a motor at a peripheral speed of 285 mm / s in the direction of arrow Y. And is in contact with the photoreceptor 1 at a contact depth of 0.1 to 0.3 mm via a toner layer in a state where a part of the photoreceptor is exposed. The developing roller 5 has a developing bias power supply 11 via a rotating shaft 10.
, A developing bias voltage of -450 V is applied.
Although the developing roller 5 is an example of a developer carrier, a belt-shaped developer carrier may be used instead of the roller.

The toner supply roller 6 has a volume resistivity of about 10
⁵ Ωcm, cell density 80-140 cells / inch, Asuka F
This is a conductive elastic foam roller having a diameter of 20 mm and made of conductive urethane foam having a hardness of 60 degrees to an Asker C hardness of 30 degrees. The developing roller 4 is rotatably supported by a developing tank 4 via a stainless steel rotary shaft 12 having a diameter of 8 mm.
Is rotated by a motor at a peripheral speed of 170 mm / s in the direction of arrow C while contacting with a contact depth of 0.5 to 1 mm to perform toner stirring and toner removal from the developing roller 5 after development. Further, a toner supply bias voltage of −550 V is applied to the toner supply roller 6 from the toner supply bias power supply 13 via the rotation shaft 12.

The toner 3 in the developing tank 4 is conveyed by the conveying rollers 7
8, the toner is transported to the toner supply roller 6 while being stirred,
Next, the toner is supplied to the developing roller 5 by the toner supply roller 6. At the time of this supply, the toner 3 is frictionally charged to a predetermined positive or negative polarity (here, frictionally charged to a negative polarity), adheres electrostatically to the peripheral surface of the developing roller 5, and is carried by the developing roller 5.

The toner 3 thus carried on the peripheral surface of the developing roller 5 forms a toner layer, is conveyed by the rotation of the developing roller 5, is leveled by the layer thickness regulating member 9, and the layer thickness is regulated. You. Next, the toner 3 is conveyed to a developing area Z where the photoconductor 1 and the developing roller 5 face each other,
Here, the electrostatic latent image formed on the photoreceptor 1 is electrostatically moved to visualize the electrostatic latent image. Thereafter, the visible image formed on the photoreceptor 1 is transferred to a transfer sheet (not shown), is fixed on the transfer sheet by a fixing device, and is discharged out of the device.

On the other hand, the toner 3 which has not passed through the development zone Z without being used for development is conveyed while being carried on the development roller 5, and is removed from the peripheral surface by the toner supply roller 6. In the drawing, reference numeral 14 denotes a lower seal made of a mylar film or the like, which prevents leakage of the toner 3 from the developing tank 4.

Here, the layer thickness regulating member 9 has a plurality of doctor blades 16 mounted on a rotatable support 15 at predetermined intervals, and one layer is provided at a position upstream of the developing region Z in the rotation direction. The doctor blade 16 is arranged so as to contact the developing roller 5.

The support 15 is formed by molding a conductive material into a polygonal prism, preferably a regular polygonal prism, and its rotating shaft 17 is rotatably supported by the developing tank 4. Is driven to rotate. Here, the doctor blade 16 attached to each of the six surfaces of the support 15 which is a regular hexagonal prism is an elongated thin plate-like elastic piece having the same shape, for example, a stainless steel thin plate having a thickness of 0.1 to 0.2 mm. Is the same as the length of the developing roller 5 in the axial direction,
The length is at least larger than the image forming width. The other end of the doctor blade 16 is fixed to the support 15 by screwing, bonding, or the like, and one end protrudes toward the upstream side in the rotational direction along each surface, and has a cantilever beam structure having a free end. You. Therefore, doctor blade 1
Reference numeral 6 denotes a state where the abdomen near one end has a linear pressure 10
５０50 gf / cm (98 to 490 mN / cm). Further, a blade bias voltage of −550 V is applied to the doctor blade 16 from the blade bias power supply 18 via the support 15.

As a result, the doctor blade 16 extending toward the upstream side in the rotation direction of the developing roller 5
Excess toner 3 among the transported toner 3 is scraped off, the thickness of the toner layer is regulated, and a toner layer having a constant thickness is formed. Therefore, the non-magnetic one-component toner 3, which is preliminarily negatively charged by the toner supply roller 6 and supplied to the surface of the developing roller 5, has a toner adhesion amount of 0.6 to 1.
0 mg / cm ² , toner charge amount -10 to -15 μC / g
And subjected to contact reversal development.

When the layer thickness regulating member 9 is an insulator, electric charges generated by friction with the toner 3 are accumulated without escape, so that the potential of the layer thickness regulating member 9 partially increases, Although the charging state of the toner 3 becomes unstable and fogging or the like easily occurs in the image quality, the potential of the layer thickness regulating member 9 is immediately uniformed and stabilized by forming the layer thickness regulating member 9 with a conductive material. Therefore, the charging of the toner 3 can be promoted, and the charging of the toner 3 can be stabilized. Although bias voltages having different voltage values are applied to the layer thickness regulating member 9 and the developing roller 5, respectively, by applying a bias voltage having an absolute value larger than that of the developing roller 5 to the layer thickness regulating member 9, Electric charge can be injected from the layer thickness regulating member 9 into the toner 3 to uniformly charge the toner 3. The charging efficiency is better than relying only on triboelectric charging in which the toner 3 on the developing roller 5 is strongly rubbed and charged by the layer thickness regulating member 9.

Here, one doctor blade 16 is in contact with the developing roller 5, but the supporting member 1 is so arranged that the contacting doctor blade 16 can be sequentially switched.
5 is rotated by a certain angle, here, 60 degrees. That is, as illustrated in FIG. 2, the control unit 21 controls the driving of the switching unit 20 including a motor that rotates the support 15. The control unit 21 is a control center of the image forming apparatus including a CPU and the like, and controls operations of the developing device 2 and the photoconductor 1, the image forming process unit, the sheet conveying unit, and other components. .

The controller 21 controls the doctor blade 16 which contacts the developing roller 5 every time the count reaches a predetermined number based on the count value of a counter 22 which counts the number of image forming operations by the image forming process unit. The driving of the switching means 20 is controlled so as to switch to the next one. The number of rotations of the developing roller 5 may be counted instead of the number of image forming operations.

Thus, each time the image formation is performed by the development, the number of operations is counted each time. When the number of operations is reached, the switching means 20 is driven and the support 15 is moved Rotated by degrees. Then, the doctor blade 16 is automatically switched to the next doctor blade 16 before toner sticks to the doctor blade 16, so that the doctor blade 16 in a healthy state is always used, and the layer thickness regulating member 9 is used for a long time. Also, a stable developing ability without white streaks can be obtained.

Here, the number of image forming operations, which is the timing for switching the doctor blade 16, is determined by the time until toner sticking to the doctor blade 16, but this time depends on the pressing force of the doctor blade 16, the toner 3, depending on the softening point, glass transition point and its fluidity. Therefore, in the present embodiment, 50
Switching is performed every 00 times. In setting the switching period, it is natural that the switching period is set to be shorter than the time until toner sticking occurs on the doctor blade 16. However, the life period of the developing device 2 and the life period of all the doctor blades 16 are totaled. Are desirably set to be substantially the same. In this way, the doctor blade 1
6 is prevented beforehand, and a streak or the like is hardly generated in the developed solid image, and the image quality can be improved. Moreover, by setting the life of the doctor blade 16 and the life of the developing device 2 to be substantially the same,
Parts and members can be used effectively, and rational design can be performed.

Further, since the doctor blade 16 to be used is automatically switched, the switching can be performed without bothering the user or the serviceman. In particular, in the one-component developing method using the non-magnetic toner 3, in view of the durability and stability of the toner 3 and the developing device 2, a cartridge type developing device that completely replaces the developing device 2 itself when replenishing the toner is used. 2 is mainly used, the toner 3 in the cartridge is formed by adopting such a configuration.
Even if you use it for a long time until the life of the cartridge comes,
A stable developing ability can be obtained without causing a deterioration in image quality due to the adhesion of the toner to the layer thickness regulating member 9, and the reliability of the machine can be improved.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that many modifications and changes can be made to the above-described embodiment within the scope of the present invention. In the above embodiment, the developing device uses a non-magnetic one-component developer, but the present invention is also applicable to a developing device using a two-component developer or a magnetic one-component developer. In addition to the automatic switching of the doctor blade, a configuration in which the doctor blade can be switched by, for example, manually driving a motor by a user or a serviceman may be employed. For this purpose, if the configuration is such that the number of switching of the doctor blade is counted and the information of the number of switching or the number of times that the switching is possible is notified, the developing device is used to check whether there is an unused doctor blade. This eliminates the need for the operation of pulling out the machine from the machine and checking it with the eyes, making it possible to replace the doctor blade at an appropriate time, improve the workability, and easily predict the replacement time of the developing device, which is useful.

Further, as shown in FIG.
Alternatively, a plurality of doctor blades 16 may be attached to the belt-shaped support 15 at regular intervals, and the support 15 may be wound around the driving pulley 23 and the driven pulley 24. The switching is performed so that the doctor blade 16 contacts the developing roller 5.
Alternatively, as shown in FIG.
A plurality of holes 25 having a narrow opening may be formed at regular intervals so that the doctor blade 16 does not come out, and the bent other end of the doctor blade 16 may be inserted into the holes 25.

[0040]

As is apparent from the above description, according to the present invention, since a plurality of elastic pieces are used as layer thickness regulating members which can be switched so as to contact the developing roller one by one, filming of the developer can be prevented. It is possible to switch to a new elastic piece before the generation, and the layer thickness of the developer layer can be stably controlled, so that the performance of the layer thickness regulating member can be maintained for a long period of time. Moreover, since the elastic piece has a simple structure of a thin plate, the elastic piece can always be brought into contact with the developing roller with a constant contact pressure, and uniform and stable layer thickness regulation can be performed. Therefore, a highly reliable developing device can be obtained, and an image forming apparatus capable of performing high-quality recording stably for a long period of time can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a developing device according to an embodiment of the present invention.

FIG. 2 is a control block diagram of a developing device.

FIG. 3 is a view showing a layer thickness regulating member of another embodiment.

FIG. 4 is a diagram showing a layer thickness regulating member according to another embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor 2 developing device 3 toner 4 developing tank 5 developing roller 6 toner supply roller 9 layer thickness regulating member 15 support 16 doctor blade 20 switching means 21 control unit 22 counter

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Eiichi Kido 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Hiroaki Yoshida 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Incorporated (72) Inventor Masahiro Sakai 22-22 Nagaikecho, Abeno-ku, Osaka, Osaka Sharp Corporation (72) Inventor Minao Masuda 22-22 Nagaikecho, Abeno-ku, Osaka, Osaka Sharp Corporation F-term (reference) 2H073 AA03 BA02 BA11 BA12 BA13 CA02 2H077 AC04 AD13 AD17 AD32 AD35 EA14 EA15 FA01 FA13 FA22 FA27 GA17

Claims (7)

[Claims] 1. A developer carrying member for carrying and transporting a developer on a surface thereof, and a layer thickness regulating member for contacting the developer carrying member and regulating a layer thickness of a developer layer formed on the surface. With
The layer thickness regulating member has a plurality of elastic pieces, one end of which is in contact with the surface of the developer carrying member, and moves the layer thickness regulating member so as to switch the elastic piece in contact with the developer carrying member. A developing device comprising switching means. 2. The layer thickness regulating member, wherein the other end of a thin plate-like elastic piece is fixed to each surface on the outer periphery of a rotatable polygonal support, and the support is rotated by a predetermined angle by switching means. The developing device according to claim 1, wherein the developing is performed. 3. The control device according to claim 1, further comprising: a control unit that measures the number of image forming operations and drives the switching unit when the number of operations reaches a number of operations determined by the life of the elastic piece. Developing device. 4. The developing device according to claim 3, wherein a life period of the developing device is set to be equal to a total period of the life periods of the elastic pieces. 5. The developing device according to claim 3, further comprising a notifying unit that counts the number of times of switching of the elastic pieces and notifies information based on the number. 6. The developing device according to claim 1, wherein a conductive material is used for the layer thickness regulating member. 7. The developing device according to claim 6, wherein a bias voltage having the same polarity as the charge polarity of the developer and higher than the developing bias voltage is applied to the layer thickness regulating member.