JP5836597B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine and a laser beam printer, and a developing device used therefor.

  As a conventional developing device, as shown in FIG. 11, there is a vertical stirring type developing device 4 in which a developing chamber 4h and a stirring chamber 4i are arranged vertically to reduce the size of the device. However, in the vertical stirring type developing device 4, in both the developing chamber 4h and the stirring chamber 4i, the distribution of the toner amount (developer amount) in the developing device 4 tends to deviate from the main scanning direction. Specifically, the toner amount decreases from the upstream (6) portion in the transport direction of the developing chamber 4h to the central portion (1) and the downstream (2) portion, and from the upstream (3) portion in the transport direction of the stirring chamber 4i. The toner amount increases from the central portion (4) to the downstream side (5).

  If the amount of toner in the developing chamber is deviated, toner (developer) supply unevenness to the developing sleeve 4b, that is, toner coat unevenness on the developing sleeve may occur, and image density unevenness may occur. .

  Further, in the stirring chamber 4i, if toner is excessively accumulated at the downstream end ((5) portion in FIG. 11) of the stirring chamber, carrier deterioration such as toner being stressed and toner resin sticking to the carrier surface is promoted, and the transfer portion The toner may overflow to the opening of the developing sleeve 4b without passing through the developing chamber 4h.

  As a method for solving the above-described problem, in Patent Document 1, the toner conveyance amount of the first and second conveyance screws 4e and 4f is made sufficiently larger than the supply amount to the developing sleeve, so It is small.

  However, when the toner conveying amount is increased by increasing the rotation speed of the conveying screws 4e and 4f, there is a risk that the rotating torque of the conveying screws 4e and 4f increases, the stress on the toner increases, and the toner scatters. For this reason, the toner conveyance amount cannot be increased to a certain extent. Further, when the toner conveyance amount is increased by improving the pitch and shape of the conveyance screws 4e and 4f, the toner conveyance amount cannot be increased so much and the deviation of the toner cannot be sufficiently prevented.

  Further, in Patent Document 2, a barrier is provided so as to block the bottom of the developing chamber immediately before the transfer portion provided at the downstream end of the developing chamber so that toner is accumulated near the downstream end. As a result, the amount of toner conveyed from the developing chamber to the stirring chamber through the transfer unit is regulated to a certain amount or less, and the deviation of the toner amount distribution in the developing chamber is reduced.

  However, toner stays and reverses in the vicinity of the barrier, and density unevenness may occur in the vicinity of the barrier portion. In order to prevent this, the barrier must be separated from the image forming area, but the size of the developing device 4 needs to be increased in the main scanning direction, and the developing device becomes large.

  Further, in Patent Document 3, a toner agent surface detecting unit that detects the position of the toner agent surface in the developing chamber is provided, and the deviation of the toner amount distribution in the developing chamber is corrected based on the detection result. However, this method complicates and enlarges the developing device, and requires a control time for keeping the toner agent surface in a constant state.

JP-A-5-333691 JP 2002-6599 JP 2003-186293 A

  Accordingly, the present invention provides a vertical stirring type developing device that reduces the deviation of the toner without increasing the complexity and size of the developing device, and sufficiently prevents density unevenness and toner overflow from the opening of the developer carrier. It is an object to provide a developing device and an image forming apparatus that can be suppressed.

In order to solve the above-described problems, a developing device according to the present invention includes a developing container that contains a developer, a developing chamber, and a developer that is carried in the developing chamber and that is transported to a developing area facing the image carrier. A developer carrying member, a stirring chamber disposed below the developing chamber and collecting the developer after passing through the developing region from the developer carrying member, and between the developing chamber and the stirring chamber. A developing member that circulates the developer, and that develops the electrostatic latent image formed on the image carrier with the developer, in which the toner conveyed by the conveying member collides A low repulsion member is provided on the wall surface of the developing container in the vicinity of the transfer portion for transferring the developer from the stirring chamber to the agitating chamber. The low repulsion member is an environment of 70 ° C. in a compressed state of 50% in accordance with JIS K 6401. Leave under for 22 hours, then release the compressed state Change in thickness after 30 minutes elapsed Te is characterized in that it is a member of more than 3.0%.

  According to the present invention, by providing a low resilience member on the wall surface of the developing container that comes into contact with the toner, in the vertical stirring type developing device, the deviation of the toner can be reduced without making the device complicated and large. Further, density unevenness and toner overflow from the developer carrier opening can be sufficiently suppressed.

1 is a configuration diagram of an image forming apparatus according to a first embodiment. 1 is a configuration diagram of an image forming apparatus according to a first embodiment. FIG. 5A is a model diagram illustrating an example of toner circulation when the agent pressure in the developing chamber is low in the vertical stirring type developing device according to the first embodiment. (B) In the vertical stirring type developing device according to the first embodiment, it is a model diagram showing an example of toner circulation when the agent pressure in the developing chamber is high. (A) It is a schematic diagram which shows the measuring method of the toner agent pressure which the wall surface of the toner delivery part of the developing chamber which concerns on 1st Embodiment receives. FIG. 6B is a relationship diagram illustrating a relationship between a toner agent surface height in the vicinity of the toner delivery portion of the developing chamber according to the first embodiment and a toner agent pressure received by a wall surface of the toner delivery portion. It is a related figure which shows the relationship between the deflection rate of the low resilience member of 1st Embodiment, and a pressure. (A) It is a model figure which shows the circulation of the toner in the conventional vertical stirring type developing device. (B) It is a related figure which shows the density nonuniformity of the main scanning direction of the past and 1st Embodiment. (A) It is a figure which shows the other shape of the low resilience member which concerns on 1st Embodiment. (B) It is a figure which shows the other shape of the low resilience member which concerns on 1st Embodiment. (A) In the vertical stirring type developing device according to the second embodiment, it is a model diagram showing an example of toner circulation when the agent pressure in the developing chamber is low. (B) In the vertical stirring type developing device according to the second embodiment, it is a model diagram showing an example of toner circulation when the agent pressure in the developing chamber is high. (A) It is a model figure which shows an example of the shape of the low resilience member arrange | positioned in the toner delivery part of the stirring chamber which concerns on 2nd Embodiment. (B) It is a model figure which shows an example of the shape of the low resilience member arrange | positioned in the toner delivery part of the stirring chamber which concerns on 2nd Embodiment. (A) In the vertical stirring type developing device according to the third embodiment, a model diagram illustrating an example of toner circulation when the agent pressure in the developing chamber is low. (B) In the vertical stirring type developing device according to the third embodiment, it is a model diagram showing an example of toner circulation when the agent pressure in the developing chamber is high. FIG. 10 is a model diagram showing toner circulation in a conventional vertical stirring type developing device.

[First embodiment]
A developing device and an image forming apparatus according to a first embodiment of the invention will be described with reference to the drawings. FIG. 2 is a configuration diagram of the image forming apparatus according to the present embodiment. As shown in FIG. 2, in the image forming apparatus 100 of the present embodiment, a photosensitive drum (image carrier) 1 charged by a charging roller 2 is irradiated with laser light L according to image information by an exposure device 3, An electrostatic latent image is formed. The electrostatic latent image formed on the photosensitive drum 1 is developed as a toner image by the developing device 4, and is primarily transferred to the intermediate transfer belt 5b at the nip portion with the primary transfer roller 5a.

  The toner image is formed at each of the yellow, magenta, cyan, and black stations (Y-st, M-st, C-st, K-st) and is superimposed on the intermediate transfer belt 5b. The transfer residual toner remaining on the photosensitive drum 1 after the primary transfer is cleaned by the cleaning device 6.

  On the other hand, the sheets P stacked on the sheet cassette 9 are conveyed to the nip portion between the intermediate transfer belt 5b and the secondary transfer roller 5f, and the toner image is secondarily transferred. The sheet P onto which the toner image has been secondarily transferred is heated and pressed by the fixing device 8 to fix the toner image, and is discharged out of the image forming apparatus main body. The transfer residual toner remaining on the intermediate transfer belt 5b after the secondary transfer is cleaned by the cleaning device 7.

(Developing device 4)
FIG. 1 is a configuration diagram of a vertical stirring type developing device 4 according to this embodiment. FIG. 3 is a model diagram showing toner circulation in the vertical stirring type developing device 4 according to this embodiment. As shown in FIG. 3, the vertical stirring type developing device 4 of the present embodiment is obtained by providing a low resilience member A to the conventional vertical stirring type developing device 4 shown in FIG.

  As shown in FIGS. 1 and 3, the developing device 4 includes a developing container 4a, a developing sleeve (developer carrier) 4b, a magnet roller 4c, a developer coating blade 4d, first and second conveying screws (first And a second conveying member) 4e, 4f, and a partition wall 4g. The toner (developer) accommodated in the developing chamber 4h of the developing container 4a is attracted and held (supported) on the outer peripheral surface of the developing sleeve 4b by the magnetic force of the magnet roller 4c in the developing sleeve 4b. The developer sleeve 4b is rotated and conveyed along with the rotation of the developing sleeve 4b, and is layered into a predetermined thin layer by the developer coating blade 4d, and corresponds to the electrostatic latent image on the surface of the photosensitive drum 1 in the developing area facing the photosensitive drum 1. Then, it selectively adheres to become a toner image. The toner after passing through the development area is collected in the stirring chamber 4i.

  The partition 4g divides the developing container 4a into an upper developing chamber 4h and a lower stirring chamber 4i. At both ends of the partition wall 4g, a delivery unit 4j that transports toner from the developing chamber 4h to the stirring chamber 4i and a delivery unit 4k that transports toner from the stirring chamber 4i to the developing chamber 4h are provided.

  The low resilience member A is provided on the wall surface 4l on the downstream side in the transport direction where the toner transported by the transport screw 4e collides. The low resilience member A is provided from the ceiling of the developing container 4a to the transfer portion 4j perpendicular to the toner conveyance direction.

  Here, the low resilience member is compliant with JISK6401 and is allowed to stand in an environment of 70 ° C. for 22 hours in a compressed state of 50%, after which the thickness change after 30 minutes has elapsed after releasing the compressed state. Has material properties that are 0% or less. Such material characteristics can be realized by using a foamed body having a uniform cell structure made of high-density microcapsules. In this embodiment, the low-rebound member A made of low-rebound urethane foam is used.

  The surface of the low resilience member A is coated with a fluorine-based resin and subjected to a low friction treatment. This reduces the friction between the surface of the low-repulsive member A and the toner, prevents the low-repulsive member A from obstructing the flow of toner in the developing device 4, and prevents the toner on the surface of the low-repulsive member A. This is to prevent adhesion.

(Effect of low resilience member A)
In the conventional vertical stirring type developing device 4 shown in FIG. 11, since the transfer section 4j is large, the amount of toner (developer amount) transferred from the developing chamber 4h to the stirring chamber 4i also increases. As a result, the toner agent surface becomes lower on the downstream side in the transport direction of the transport screw 4e.

  Therefore, in the present embodiment, as shown in FIG. 3A, the low repulsion member A is disposed so as to regulate the size of the delivery portion 4j. That is, the amount of toner delivered from the developing chamber 4h to the stirring chamber 4i is limited by the low-repulsive member A, and the toner agent surface is suppressed from being lowered on the downstream side in the conveying direction of the conveying screw 4e in the developing chamber 4h. .

  However, if only this effect is obtained, the size of the transfer section 4j may be simply reduced. However, when the size of the transfer portion 4j is reduced, the toner amount in the developing chamber 4h may be larger than that in the stirring chamber 4i due to a change in toner fluidity.

  Here, as an example of the change in the fluidity of the toner, as the toner is used, for example, the adhesion state of the external additive on the toner surface changes or the toner resin adheres to the carrier surface. There is a decrease in fluidity with changes in powder properties. Further, when the use environment of the developing device 4 is a high humidity environment, there is a decrease in fluidity due to liquid crosslinking between powders due to moisture in the atmosphere.

  When the toner in the developing chamber 4h becomes too much and the toner in the stirring chamber 4i decreases, that is, when the toner cannot be sufficiently circulated in the developing device 4, the replenished toner is uniformly mixed and stirred in the toner. This is a cause of image density unevenness.

  In contrast to this phenomenon, since the low repulsion member A is used in this embodiment, when the toner amount in the developing chamber 4h increases, the toner pressure on the low repulsion member A increases, and FIG. As shown in (b), the low resilience member A is compressed. As a result, the size of the transfer section 4j is increased and the amount of toner transferred to the stirring chamber 4i is increased, so that the toner amount in the developing chamber 4h is maintained at an optimum amount without increasing.

  That is, when the amount of toner in the developing chamber is small (when the toner pressure applied to the low-repulsive member A is low), the low-repulsive member A serves as a regulating member, and the size of the transfer portion 4j. Keep small. Thereby, the amount of toner delivered to the stirring chamber 4i is small, and it is possible to accumulate toner in the developing chamber and maintain the toner agent surface uniform in the main scanning direction.

  On the other hand, when the toner amount in the developing chamber 4h increases (when the toner pressure of the toner received by the low-repulsive member A increases), the low-repulsive member A is compressed and the size of the delivery portion 4j is increased. And the amount of toner delivered to the stirring chamber 4i also increases, so that it is possible to prevent an excessive increase in toner in the developing chamber.

  FIG. 4A is a schematic diagram showing a method for measuring the toner pressure in the vicinity of the toner delivery portion 4j from the developing chamber 4h to the stirring chamber 4i. As shown in FIG. 4A, a pressure sensor 10 is provided in the transfer section 4j to measure the toner pressure.

  As the pressure sensor 10, an optical fiber ultra-small sensor manufactured by Fizeau, Technology, Inc. was used. The pressure sensor 10 employs a method of measuring the amount of deflection of the silicon diaphragm. The sensor surface is 0.5 mm × 0.5 mm, the measurement range is 0 to 34 kPa, and the measurement accuracy is 1%.

  FIG. 4B is a diagram showing the relationship between the height of the toner agent surface in the vicinity of the transfer portion and the pressure measured according to FIG. As shown in FIG. 4B, when the toner agent surface is low, almost no agent pressure is applied. On the other hand, when the toner agent surface is 2.0 mm or more, the agent pressure applied suddenly increases. In this embodiment, the height of the toner agent surface of the developing chamber 4h for maintaining the density uniformity in the main scanning direction is about 1.1 mm or more (75% or more of the screw diameter).

  FIG. 5 shows the relationship between the compression rate and pressure of the low resilience member A. From FIG. 4B and FIG. 5, for example, when the toner agent surface height in the developing chamber 4h is 2.0 mm, the pressure applied to the low repulsive member A is 3.0 kPa, and the low repulsive member is 40 % Shrinkage.

  Even if an elastic member is used instead of the low repulsive member A, the same effect can be expected. However, in the case of an elastic member, a repulsive force is applied to the toner, so that carrier deterioration due to adhesion of toner resin to the carrier surface, There is a risk of promoting toner deterioration such as embedding external additives on the toner surface. Since the low repulsion member has a characteristic of maintaining a deformed shape for a certain period of time, the repulsion force applied to the toner is small, and the low repulsion member is more preferable than the elastic member.

  FIG. 6 is a diagram showing the relationship of density uniformity (reflection density) with respect to the main scanning direction of the developing chamber 4h. As shown in FIG. 6, in the conventional developing device 4, the density is greatly reduced because the toner agent surface is lowered on the downstream side of the developing chamber. On the other hand, in the developing device 4 of the present embodiment, since the toner agent surface of the developing chamber 4h is uniform, the density uniformity is maintained on the downstream side of the developing chamber without lowering the density.

  FIG. 7 is a view showing another shape of the low resilience member A. FIG. In the shape of FIG. 7 (a), a base material A1 having a triangular cross section formed by a resin mold is provided on the wall surface 41, and a low resilience member A2 having a triangular cross section is attached to the base material A1, and the low resilience shown in FIG. The shape is the same as that of the sex member A. The shape of FIG. 7 (b) is shown in FIG. 3, in which the base A1 is recessed in a circular arc shape, and a low-rebound member A2 having a 1/4 circle cross section is attached to the recessed portion. The shape is the same as that of the low resilience member A.

  By adopting such a shape, the amount of change on the lower side in the vertical direction of the low-repulsive member A2 increases when the toner is transferred from the developing chamber 4h to the stirring chamber 4i. For this reason, it becomes possible to deliver the toner stably.

  According to the above configuration, toner deviation in the main scanning direction in the developing chamber of the developing device 4 can be reduced without increasing the complexity and size of the apparatus, and density unevenness in the main scanning direction caused by toner deviation is caused. And can stably output high-quality images over a long period of time.

[Second Embodiment]
Next, a second embodiment of the developing device and the image forming apparatus according to the present invention will be described with reference to the drawings. The same parts as those in the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted.

  FIG. 8 is a model diagram showing an example of toner circulation in the vertical stirring type developing device 4 according to this embodiment. As shown in FIG. 8, the developing device 4 of the present embodiment is obtained by providing the developing device 4 of the first embodiment with a low resilience member B.

  As described above, in the stirring chamber 4i, a certain amount of toner pressure is required at the downstream end of the stirring chamber (portion (5) in FIG. 11) for toner delivery. However, if the toner is excessively stored, the toner may overflow into the opening of the developing sleeve 4b.

  Therefore, in the present embodiment, as shown in FIG. 8A, the low resilience member B is disposed on the downstream side in the transport direction of the stirring chamber 4i where the toner transported by the transport screw 4f collides with the transfer portion 4k. And provided on the wall surface 4m on the upstream side in the developer conveyance direction of the developing chamber 4h. The low resilience member B is provided from the bottom surface to the ceiling of the developing container 4a perpendicular to the toner conveyance direction.

  In this way, by providing the low resilience member B and reducing the size of the transfer portion 4k from the stirring chamber 4i to the developing chamber 4h, the toner is transferred from the stirring chamber 4i to the developing chamber 4h even if the toner pressure is low. It can be delivered.

  On the other hand, when the toner amount in the agitating chamber 4i increases (when the toner pressure applied to the low-repulsive member B increases), the low-repulsive member B is compressed. As a result, the size of the transfer portion 4k is increased, and the amount of toner transferred to the developing chamber 4h is also increased, so that it is possible to suppress an excessive increase in toner on the downstream side of the stirring chamber.

  FIG. 9 is a view showing another shape of the low resilience member B. FIG. In the shape of FIG. 9 (a), a base material B1 having a triangular cross section formed of a resin mold is provided on the wall surface 4m, and a low resilience member B2 having a triangular cross section is attached to the base material B1, thereby reducing the low resilience shown in FIG. The shape is the same as that of the sex member B. The shape of FIG. 9B is shown in FIG. 8 in which the base material B1 is recessed in a circular arc shape, and a low-repulsive member B2 having a ¼ circle cross section is attached to the recessed portion. The shape is the same as that of the low resilience member B.

  By taking such a shape, when the toner is transferred from the stirring chamber 4i to the developing chamber 4h, the amount of change on the upper side in the vertical direction of the low resilience member B2 becomes large. For this reason, it becomes possible to deliver the toner stably.

  With the above configuration, in addition to the effects of the first embodiment, it is possible to prevent the toner from being excessively stressed at the downstream portion in the transport direction of the stirring chamber 4i of the developing device 4. As a result, it is possible to promote toner deterioration caused by stress on the toner and to prevent toner overflow from the opening of the developing sleeve 4b, and to stably output a high-quality image over a long period of time.

[Third embodiment]
Next, a third embodiment of the developing device and the image forming apparatus according to the present invention will be described with reference to the drawings. The same parts as those in the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted. FIG. 11 is a model diagram showing an example of toner circulation in the vertical stirring type developing device 4 according to this embodiment. As shown in FIG. 11, the developing device 4 of the present embodiment is obtained by providing a low repulsive member C to the developing device 4 of the first embodiment.

  As described above, in the stirring chamber 4i, a certain amount of toner pressure is required at the downstream end of the stirring chamber (portion (5) in FIG. 11) for toner delivery. However, if the toner is excessively stored, the toner may overflow into the opening of the developing sleeve 4b.

  Therefore, in this embodiment, as shown in FIG. 10A, the low repulsion member C is provided over the entire bottom surface of the stirring chamber 4i. As a result, as shown in FIG. 10 (b), when the toner pressure increases toward the downstream side in the transport direction of the stirring chamber 4i, the low-rebound member C on the bottom surface of the stirring chamber 4i is compressed and contracted. To increase. As a result, it is possible to prevent the toner from being excessively stressed in the downstream portion of the agitating chamber 4i in the transport direction, and to promote toner deterioration caused by the stress on the toner, and toner overflow from the opening of the developing sleeve 4b. Suppresses and can stably output high-quality images over a long period of time.

A, B, C ... Low repulsive member P ... Sheet 1 ... Photosensitive drum (image carrier)
4 ... developing device 4a ... developing container 4b ... developing sleeve (developer carrier)
4c: Magnet roller 4e, 4f: Conveying screw (conveying member)
4g ... partition wall 4h ... developing chamber 4i ... stirring chamber 4j, 4k ... transfer section 4l, 4m ... wall surface 5a ... primary transfer roller 5b ... intermediate transfer belt 10 ... pressure sensor 100 ... image forming apparatus

Claims (6)

A developer container containing a developer;
A development chamber,
A developer carrying member that carries the developer in the developing chamber and conveys the developer to a developing region facing the image carrier;
A stirring chamber that is disposed below the developing chamber and collects the developer after passing through the developing region from the developer carrier;
A conveying member that circulates the developer between the developing chamber and the stirring chamber,
In the developing device for developing the electrostatic latent image formed on the image carrier with a developer,
A low repulsion member is provided on the wall surface of the developing container in the vicinity of the transfer section for transferring the developer from the developing chamber to the stirring chamber, where the toner conveyed by the conveying member collides ;
According to JIS K 6401, the low resilience member is allowed to stand in an environment of 70 ° C. for 22 hours in a compressed state of 50%, and after that, after 30 minutes have passed after releasing the compressed state, the thickness change is 3.0. % Developing member. The low resilience member is provided on a wall surface of the developing container in the vicinity of a transfer portion for transferring the developer from the stirring chamber to the developing chamber where the toner conveyed by the conveying member collides. The developing device according to claim 1 . The thickness of the low resilience member, developing device according to claim 1 or 2, characterized in that thicker with the conveying direction of the developer.   The developing device according to claim 1, wherein the low resilience member is provided on a bottom surface of the stirring chamber. The surface of the low resilience member is a developing device according to any one of claims 1 to 4, characterized in that it is a low friction treatment. An image carrier for carrying an electrostatic latent image;
The developing device according to any one of claims 1 to 5 , wherein the electrostatic latent image formed on the image carrier is developed with a developer;
An image forming apparatus comprising:

Images