JP3812670B2 - Development device - Google Patents

Description

  The present invention relates to a developing device that forms a visible image by selectively attaching colored fine particles (toner) to a latent image, for example, a developing device applied to an electrophotographic image forming apparatus. More specifically, the present invention relates to a developing device having a developer carrying member and a supply member that supplies the developer (toner) including the used developer (toner) to the developer carrying member.

  A developing device having a supply member that supplies toner to the developer carrying member is known (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3).

  In such a developing apparatus, it has been proposed to use a foam as a supply member.

This foam is classified into an open-cell foam and a closed-cell foam according to the form of the bubbles. Such a classification method is well known (see, for example, Non-Patent Document 1).
Japanese Patent Laid-Open No. 61-42672. JP-A-62-257185. JP-A-2-191974. Plastic foam handbook (published by Nikkan Kogyo Shimbun, editor: Makino and Atsushi Kosaka, first published on February 28, 1973).

  When an open-cell foam is used as the supply member, toner enters the foam bubbles, causing the foam to become clogged, causing problems such as a decrease in the toner conveying force of the supply member and an increase in the hardness of the supply member. Will occur.

  Such a problem does not occur when a closed cell foam is used as the supply member. However, closed-cell foams are generally hard, and on the other hand, supply members have been conventionally required to have a low hardness of about 10-40 ° Asker C hardness. When the body is actually used for a long period of time, the partition wall between the bubbles is broken by mechanical stress repeatedly applied to the supply member, and the same problem as that of the open cell foam occurs. In addition, the closed cell foam is difficult to manufacture, the material is limited, and the closed cell foam is more expensive than the open cell foam and is not suitable for practical use.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to prevent the above-described problems while simplifying a supply member that supplies toner to the developer carrier. An object of the present invention is to provide a developing device that can be used.

  Further, when the developing device reuses used toner, for example, when the toner attached to the latent image carrier is collected and cleaned by the cleaning device, and further, the collected toner is transferred to the developing device and reused. Alternatively, when the developing device also functions as a cleaning device and development and recovery cleaning are performed simultaneously or separately, a large amount of foreign matter is mixed in the developing device.

  This is a particular problem when the developing device reuses used toner.

  When the developing device reuses used toner, the foreign matter mixed in the developing device is dust, dust, or a part of the recording medium (for example, paper is used as the recording medium). In the case, the filler or paper powder), or a part of the latent image carrier (debris on the surface of the latent image carrier due to friction with a cleaning device or the like). Among them, paper dust is a problem.

  The paper dust is typically in the form of short fibers having a diameter of about 10 μm to 40 μm and a length of about 0.1 mm to 3 mm. However, there is a large amount of paper dust generated from the cut surface of paper.

  This paper dust depends on the quality of the paper (for example, whether it is high-quality paper made from virgin pulp or recycled paper made from old paper), but paper equivalent to 30000 sheets of A4 size paper About 0.1 to 0.3 g or more of paper dust is mixed in the developing device (this has been confirmed by experiments by the present inventor).

  The paper dust mixed in the developing device enters the foam of the supply member, and the foam is clogged, causing problems such as a decrease in the toner conveying force of the supply member and an increase in the hardness of the supply member. Since paper powder is extremely poor in fluidity compared to toner, it is difficult for the powder to be discharged from the inside of the foam. Therefore, when the used toner is reused by the developing device, it is very early compared to the case where the toner is not reused. Problems occur.

  Further, when the developing device reuses the used toner, it is necessary to cope with the deteriorated toner because the toner is repeatedly used. By repeatedly using the toner, the external additive applied to the toner in order to improve the fluidity of the toner falls off from the surface of the toner or is embedded in the toner, thereby reducing the fluidity of the toner, Alternatively, there is a problem in that the toner is destroyed by a mechanical force (by a developing device, a cleaning device, or the like), and the fluidity is reduced as the diameter is further reduced.

  Such deteriorated toner also causes the same problem as paper dust.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to prevent the above-described problems while simplifying a supply member that supplies toner to the developer carrier. An object of the present invention is to provide a developing device that can be used.

  In particular, the purpose of the supply member is due to clogging of the foam caused by paper dust or the like mixed in the developing device entering the inside of the foam of the supply member when the used toner is reused. It is an object of the present invention to provide a developing device capable of preventing problems such as a decrease in toner conveying force and an increase in hardness of a supply member.

  The developing device of the present invention solves the above-described problems, and is a developing device having a developer carrying member and a supply member that supplies the developer to the developer carrying member, and recycles the used developer. In the developing device to be used, the supply member is an open cell foam having an average cell diameter of 0.5 mm or more, an open cell ratio of 70% or more, and an Asker F hardness of 85 °, and hydrophobic silica is externally added to the developer. A developer comprising a non-magnetic one-component toner having a volume average particle diameter of 10 μm and a toner obtained by stirring the non-magnetic one-component toner is used.

  In the developing device of the present invention, the gap between the outline of the supply member and the bottom wall surface of the developing device is 0.1 mm or more.

  Furthermore, the developing device of the present invention is characterized in that hydrophobic silica is impregnated inside the bubbles of the open-cell foam.

(Function)
According to the first aspect of the present invention, a developer comprising a non-magnetic one-component toner having a volume average particle diameter of 10 μm externally added with hydrophobic silica and a toner obtained by stirring the non-magnetic one-component toner is used. The supply member for supplying toner to the carrier is composed of an open cell foam having an average cell diameter of 0.5 mm or more, an open cell ratio of 70% or more, and an Asker F hardness of 85 °, and the foam surface is opened. By making the diameter of the hole sufficiently large so as not to impair the fluidity of the toner, the toner entering from the open hole on the surface of the foam is easily discharged again from the open hole into which the toner has entered.

  In addition, since the supply member is an open-cell foam, even if the toner enters the inside, the open hole on the surface of the foam communicates with the open hole on the other surface. To be discharged.

  Further, by making the supply member an open cell foam having an open cell ratio of 70% or more, even if the toner entering from the open holes on the surface of the foam enters the inside of the foam, a plurality of open holes on the surface of the foam are formed. Because of the mutual communication, the toner is easily discharged from the inside of the foam.

  Furthermore, the supply member has an Asker F hardness of 85 °, and the foam (supply member) is made of a material that is more easily deformable than before, so that the foam can be easily deformed, thereby entering the inside of the foam. The toner is forcibly and promptly discharged by deformation of the foam.

  In this way, the diameter of the open holes on the surface of the foam (supply member) is made sufficiently large, and the plurality of open holes on the surface of the foam are in communication with each other, and the foam is easily deformed. Thus, in the developing device that reuses the used toner, the foreign matter such as the toner and paper dust that has entered the inside of the foam is smoothly and forcibly discharged from the foam.

  According to the second aspect of the present invention, the gap between the outline of the supply member and the bottom wall surface of the developing device is 0.1 mm or more, and the gap between the supply member and the bottom wall surface of the developing device facing the supply member is By making it sufficiently large so as not to impair the fluidity, the discharge of the toner that has entered the foam (supply member) is not hindered and is smoothly discharged.

  According to the third aspect of the present invention, by impregnating the inside of the cell of the open cell foam with hydrophobic silica, fluidity can be re-applied to the used deteriorated toner. This is more effective for smoothly discharging the toner that has entered the inside of the foam.

(effect)
As described above, according to the developing device of the present invention, a developer comprising a nonmagnetic one-component toner having a volume average particle diameter of 10 μm externally added with hydrophobic silica and a toner obtained by stirring the nonmagnetic one-component toner is used. In addition, the supply member for supplying the toner to the developer carrying member is composed of an open cell foam having an average cell diameter of 0.5 mm or more, an open cell ratio of 70% or more, and an Asker F hardness of 85 °. Since the diameter of the open hole on the surface of the foam is sufficiently large so as not to impair the fluidity of the toner, the toner entering from the open hole on the surface of the foam is easily discharged again from the open hole into which the toner has entered.

  Further, according to the developing device of the present invention, an open cell foam having an open cell ratio of 70% or more is used as a supply member for supplying the developer to the developer carrying member, so that even if the toner enters the inside, the foam is generated. Since the plurality of open holes on the body surface communicate with each other in the form of a network, it is easily discharged from the inside of the foam.

  Further, according to the developing device of the present invention, by using an open cell foam having an Asker F hardness of 85 ° as a supply member for supplying the developer to the developer carrying member, the foam can be more easily formed than before. By deforming, the toner that has entered the inside of the foam is forcibly and promptly discharged.

According to the developing device of the present invention, the gap between the outline of the supply member that supplies the developer to the developer carrying member and the bottom wall surface of the development device is 0.1 mm or more, so that the supply member and its supply Since the gap between the bottom wall surface of the developing device facing the member is sufficiently large so as not to impair the fluidity of the toner, the discharge of the toner that has entered the inside of the foam is not hindered, and from the supply roller to the developing roller The toner is smoothly supplied from a place other than the supply portion (the contact portion between the developing roller and the supply roller and the vicinity thereof) where the toner is supplied.

That is, according to the developing device of the present invention, foreign matters such as toner and paper dust enter the inside of the foam, clogging occurs, the hardness of the foam increases, and consequently, it is necessary to drive the developing device. Torque increases and image jitter does not occur.
Further, it is possible to prevent the image from being fogged when the low-charged or reverse-charged toner that has entered the foam is supplied to the developing roller. Further, it is possible to prevent toner filming due to generation of toner agglomerates or the like, or white streaks of an image due to foreign matters such as paper dust, and black spots on a non-image portion.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.
FIG. 1 shows a process unit in which a developing device and other components are integrated so as to be applied to an electrophotographic image forming apparatus, and shows an embodiment of the developing device of the present invention.

  In FIG. 1, reference numeral 1 denotes a case body that accommodates a set of electrophotographic process units.

  The case body 1 is provided with a photosensitive drum 2 as an electrostatic latent image carrier at the center of the case body 1.

  Further, on one side of the case main body 1, a developing device 5 including a developing roller 3 as a developer carrying member and a supply roller 4 as a supplying member for supplying toner to the developer carrying member is partitioned by a partition wall 7. Is done. Reference numeral 8 in the figure denotes a doctor blade which is a regulating member for regulating the toner supplied from the supply roller 4 to the developing roller 3 into a thin layer.

  Further, a cleaning device 10 having a cleaning blade 9 for collecting and removing toner from the electrostatic latent image carrier is defined on the other side of the case body 1.

  In FIG. 1, reference numeral 13 denotes a charging roller which is a charging member for charging the electrostatic latent image carrier. The charging roller 13 is disposed in a chamber 14 defined by the partition wall 7 and the cleaning blade 9.

  Further, the case body 1 located on the lower side in the rotational direction of the photosensitive drum 2 has a slit 15 for guiding a light beam scanned by an image exposure unit (not shown), for example, a light beam scanning unit, to the surface of the photosensitive drum 2. It is formed along the longitudinal direction of the photosensitive drum 2.

  In FIG. 1, reference numeral 20 denotes a toner conveying belt that circulates and conveys toner while stirring the toner from the cleaning device 10 to the developing device 5 and from the developing device 5 to the cleaning device 10. The toner conveying belt 20 is formed by an endless coil spring, and is driven by a gear-type driving pulley 23 disposed at one corner of the case body 1 to circulate around the inner peripheral portion of the case body 1. 10 and the developing device 5 are configured to pass through from one end to the other end in the longitudinal direction thereof to transfer the toner.

  The toner conveying belt 20 is configured such that one passes through an upward belt guide groove 12 provided below the cleaning device 10 and the other passes through a downward belt guide groove 6 provided above the developing device 5. The toner in the developing device 5 is sent to the cleaning device 10, where new toner and untransferred toner collected and removed from the photosensitive drum 2 by the cleaning blade 9 are stirred and mixed to develop the developing device 5. Configured to be sent back to.

In FIG. 1, reference numeral 25 denotes a toner hopper for supplying new toner into the developing device 5. The toner hopper 25 is disposed at an arbitrary position in the toner circulation path except for the developing device 5 and the cleaning device 10.

The toner hopper 25 in this embodiment is mounted on a driving pulley 23 disposed at the inlet portion of the developing device 5, and an agitator 28 provided in the toner hopper 25 is coupled to the driving pulley 23 and simultaneously driven. Is configured to do. Reference numeral 29 in the figure denotes a scraper that rotates together with the agitator 28 to scrape toner on the hopper bottom surface 26 into the hopper 25.

In FIG. 1, a symbol d indicates a gap between the supply roller 4 and the bottom wall surface of the developing device 5. In the present invention, the bottom wall surface of the developing device 5 is a generic term for a portion of the inner wall surface of the developing device 5 that faces the outer peripheral surface of the supply roller 4.

  Now, the developing device 5 will be described in more detail.

  The developing roller 3 has a configuration in which an elastic layer is formed on the outer periphery of the metal shaft. As the elastic layer, a known rubber, elastomer, resin or foam thereof can be used, and a known conductive agent or the like is added as necessary.

In this embodiment, a developing roller having an Asker C hardness of 50 ° and a volume resistivity of about 10 ⁶ Ω · cm using polyester-polyurethane with carbon black added as a conductive agent as an elastic layer is used. The developing roller 3 is in pressure contact with the photosensitive drum 2 with a load of 60 g / cm.

The supply roller 4 has a configuration in which an elastic layer made of open cell foam is formed on the outer periphery of the metal shaft. A known rubber, elastomer, or resin foam can be used as the elastic layer, and a known conductive agent or the like is added as necessary.

  Examples of the rubber or resin include natural rubber, styrene / butadiene rubber, isoprene rubber, butadiene rubber, nitrile rubber, chloroprene rubber, silicone rubber, ethylene / propylene rubber, fluorine rubber, acrylic rubber, epichlorohydrin rubber, styrene resin, vinyl chloride. Polyurethane, phenolic resin, urea resin, epoxy resin, polyethylene, methacrylic resin, etc. can be applied.

In this embodiment, a supply roller having a volume resistivity of about 10 ⁴ Ω · cm using an open-cell foam of polyurethane with carbon black added as a conductive agent as an elastic layer is used. Further, the supply roller 4 is disposed so as to contact the developing roller 3. The contact width between the supply roller 4 and the developing roller 3 is preferably 0.5 to 5 mm.

The doctor blade 8 is made of an elastic plate material. As the elastic plate material, known rubber, elastomer, resin, and metal can be used.

  In this embodiment, a thin plate made of stainless steel (SUS304) having a thickness of 100 μm is used as the elastic plate member. The doctor blade 8 is in pressure contact with the developing roller 3 with a load of 40 g / cm.

Hereinafter, the present invention will be further described using specific experimental examples.

(Experimental example 1)
This experimental example focuses on the problem that the toner enters the foam of the supply roller and clogs the toner, thereby increasing the hardness of the supply roller and, as a result, increasing the torque for driving the developing device. It was done.

In this experimental example, as the supply roller 4, a roller in which a foam having an open cell ratio of 80% and an Asker F hardness of 85 ° was coated on the outer peripheral surface of the shaft so as to have a layer thickness of 3 mm was used. Moreover, the average cell diameter of the foam was made into four types, 0.1 mm, 0.5 mm, 1 mm, and 2 mm. In addition, although the open cell rate of a foam is performed by a well-known method, the value measured by the air pycnometer method (ASTM D2856) is shown in a present Example.

  Further, in this experimental example, the developing roller 3 and the supply roller 4 are arranged so as to contact each other with a nip width of 2 mm.

The gap d between the supply roller 4 and the bottom wall surface of the developing device 5 was 0.1 mm.

  Further, as a developer, 0.5 wt% of hydrophobic silica is externally added and a non-magnetic one-component toner (toner A) having a volume average particle diameter of 7 μm, or a volume average particle diameter of which hydrophobic silica is externally added in the same manner. A 10 μm non-magnetic one-component toner (toner B) was used.

The compression rate of toner A is 34%, and the compression rate of toner B is 27%. The compression rate indicates the fluidity of the toner and is defined by the following formula.

In this experimental example, the torque required to drive the developing device was measured when image formation was started and when image formation was performed continuously and a predetermined time had elapsed. In addition to the above measurement, the presence or absence of image jitter (image disturbance due to uneven driving of the image forming apparatus) was evaluated.

In this experimental example, the torque at the start of image formation was 0.9 to 1.2 kg · cm, hardly depending on the difference in the average cell diameter of the foam and the compression rate of the toner.

  If toner is clogged in the supply roller during continuous image formation, the hardness of the supply roller increases, and as a result, the torque of the developing device increases. The increase in torque appears as image jitter.

  In this experimental example, when the increase in the torque of the developing device exceeds 20% at the start of image formation, a slight jitter starts to occur in the image (but there is no problem in practical use), and further exceeds 50%. In such a case, clear jitter occurred in the image, making it unsuitable for practical use. However, when 8 hours have passed since the image formation started, even if the supply roller is clogged with toner, the clogging is almost in a steady state, and the hardness of the supply roller is further increased. The increase in torque also remained almost constant.

The results of this experimental example are shown in Table 1. Table 1 shows the torque required to drive the developing device when image formation is started and when image formation is continuously performed for 8 hours, and the presence or absence of image jitter when image formation is continuously performed for 8 hours Is evaluated.

In Table 1, x indicates that the image has obvious jitter and is unsuitable for practical use, ○ indicates that the image has slight jitter, but is acceptable for practical use, and ◎ indicates that the image has almost no jitter Indicates something that is not allowed

As is apparent from the above table, by using an open cell foam having an average cell diameter of 0.5 mm or more, more preferably 1 mm or more as the supply roller, a good supply roller with almost no toner clogging can be obtained. Can do. The average cell diameter of the foam of the supply roller is preferably 50 times or more, more preferably 100 times or more the volume average particle diameter of the toner.

(Experimental example 2)
This experimental example relates to a supply roller made of a foam having a larger average cell diameter than that of experimental example 1.

In the present experimental example, a supply roller 4 having the same configuration as that of Experimental example 1 was used except that a foam having an average cell diameter of 3 mm was coated so as to have a layer thickness of 6 mm.

  Further, the developing roller 3 and the supply roller 4 were arranged so as to contact each other with a nip width of 4 mm.

The results of this experimental example are shown in Table 2. Table 2 shows the torque required to drive the developing device when image formation is started and when image formation is continuously performed for 8 hours, and the presence or absence of image jitter when image formation is continuously performed for 8 hours Is evaluated. The legend is the same as in Table 1.

(Experimental example 3)
This experimental example is conducted paying attention to the deterioration of the toner when the image forming apparatus is driven for a long period of time, and further the deterioration of the image due to the deterioration of the toner.

Examples of toner deterioration include:
-Lowering of toner fluidity due to external additives such as hydrophobic silica added to the toner being gradually embedded in the toner due to mechanical stress applied to the toner,
・ Increase in small-diameter toner due to toner crushing, or the amount of toner charge during development is proportional to the particle diameter of the toner. Accumulation of small particle size toners, and lower fluidity due to these small particle size toners,
-Generation of agglomerates due to aggregation of toners with reduced fluidity,
These cause deterioration of the image.

  Small toner particles tend to have an excessively large charge amount and have a strong mirror image force on the latent image carrier, so that they are observed as non-image areas (so-called image fogging) in images. Is done. In addition, the toner having a small particle diameter is easily scattered and is scattered from the opening of the developing device and causes internal contamination of the image forming apparatus.

Further, when the fluidity of the toner is lowered, the toner is insufficiently frictionally charged in the developing device, and a toner having a polarity opposite to a desired charging polarity is generated. This reverse polarity toner is still observed as image fog.

  In addition, the toner with reduced fluidity and the aggregates thereof cannot smoothly pass through the contact portion between the developing roller and the doctor blade, so that the charging is insufficient and the image is fogged. In addition, the agglomerates may be fused (so-called filming) to the surface of the developing roller or doctor blade due to the mechanical force and frictional heat at the contact portion between the developing roller and the doctor blade, or the agglomerates may become extremely extreme. If it is too large, the contact portion will be clogged as it is. As a result, a toner layer is not formed on the developing roller at the contact portion where filming or the like has occurred, and an image corresponding thereto is observed as a white streak (image omission).

  As a result of intensive studies, the present inventors have found that when a foam is used as a supply roller that supplies toner to the developing roller, the toner that has entered the foam of the supply roller may cause image fogging or image white streaks. I noticed that it would cause

  That is, the toner that has entered the foam of the supply roller for a while has no contact with the other, so that the amount of charge is considerably reduced or charged in the opposite polarity. In the supply unit (the contact portion between the development roller and the supply roller) where the toner is supplied from the supply roller to the developing roller, the toner is held inside the supply roller together with the toner held on the surface of the supply roller (sufficiently charged and fresh). Since the toner is supplied to the developing roller together, the image is fogged. In this case, the fog is observed as an increase in the reflection optical density of the non-image portion when the non-image portion becomes dark overall and becomes noticeable.

  Further, when the fluidity of the toner decreases, the toner that has entered the foam of the supply roller becomes difficult to be discharged to the outside of the foam, and is gradually pressurized by the toner that has entered the bubbles later, Agglomerates are generated. Since this agglomerate is supplied to the developing roller together with the toner held on the surface of the supply roller, image fogging similarly occurs. In this case, the fog is observed as a black spot (having a diameter of approximately 200 to 500 μm or less) on the non-image portion, and is a local image defect. Concentration is hardly affected. However, it is clearly observed visually, and if it is noticeable, it gives the user an unpleasant feeling and becomes a practical problem. Furthermore, this agglomerate causes filming, and consequently white streaks in the image.

  The present experimental example has been made in view of such problems, and the supply of toner from the supply roller to the developing roller without clogging the toner that has entered the foam of the supply roller. This is an attempt to solve the above-mentioned problem by discharging the toner that has entered the foam of the supply roller outside of the section.

In this experimental example, as the supply roller 4, a roller in which a foam having an Asker F hardness of 85 ° was coated on the outer peripheral surface of the shaft so as to have a layer thickness of 3 mm was used. In addition, the open cell ratio of the foam was 5 types of 60%, 70%, 80%, 90%, and 95%, and the average cell diameter was 2 types of 0.5 mm and 2 mm.

  Further, as a developer, 100 parts by weight of a non-magnetic one-component toner (toner B) having a volume average particle diameter of 10 μm, to which 0.5 wt% of hydrophobic silica is externally added, and a toner obtained by stirring toner B in a ball mill for 1 hour ( A mixture (toner C) in which 20 parts by weight of hydrophobic silica was forcibly embedded in the toner surface or a part of the toner was crushed and the toner was forcibly deteriorated was used. This toner C corresponds to the state of toner in the developing device when the image forming apparatus is driven for 100 hours or more.

The conditions other than the above are the same as in Experimental Example 1.

In this experimental example, image formation was continuously performed for 30 hours by the developing device having the above-described configuration, and the presence or absence of image fogging and white streaks was evaluated.

The results of this experimental example are shown in Table 3.

In Table 3, x indicates a clear image defect, which is inappropriate for practical use (a white streak is visible in the image regardless of the size, or the image fog is optical reflection density) In which the number of black spots in the non-image area due to toner agglomerates exceeds 20 per image area equivalent to A4 size paper)
Δ indicates a defect in the image, but there is no practical problem (it does not correspond to evaluation ×, but the black spot of the non-image portion is 6 to 20 per image area equivalent to A4 size paper. ),
○: Some image defects are recognized, but there is no problem in practical use (non-image part has 5 or less black spots),
The symbol も の indicates that no image defect is observed (the image cannot have white streaks, fog, or black spots visible).

As is apparent from the above table, as the supply roller, an open cell foam having an open cell ratio of 70% or more, more preferably 90% or more is used, so that even if deteriorated toner is used, the image is not affected. A good supply roller can be obtained.

  In the supply roller of this experimental example, there is almost no clogging of toner by using an open cell foam having a sufficiently large average cell diameter.

  Furthermore, in the supply roller of this experimental example, by making the continuous bubble rate sufficiently high, a plurality of bubbles communicate with each other, and a flow path between the bubbles is formed in a network shape, so that the supply roller The toner that has entered from the opening on the surface can be discharged from another opening through which the bubbles communicate. That is, in the supply unit where the developing roller and the supply roller are in contact with each other and toner is supplied to the development roller, only the toner held on the surface of the supply roller is supplied to the development roller, but has entered the foam of the supply roller The toner is not supplied to the developing roller, and is smoothly discharged from the opening other than the contact portion of the supply roller while being further pushed by the pressure of the contact portion between the developing roller and the supply roller and the deformation of the supply roller due to the pressure. Therefore, the occurrence of toner agglomerates is prevented, and low-charged or reverse-charged toner is prevented from being supplied to the developing roller.

As described above, the supply roller of this experimental example is particularly effective when the toner once developed on the latent image carrier is easily collected by the developing device and used again, such as an image forming apparatus that is reused. is there.

Further, it is more effective to impregnate the inside of the bubbles of the foam of the supply roller with hydrophobic silica or the like for imparting fluidity to the deteriorated toner again.

In this experimental example, the pressure for discharging the toner that has entered the foam of the supply roller was due to the pressure at the contact portion between the developing roller and the supply roller. A pressure member for deforming the roller may be provided separately.

(Experimental example 4)
This experimental example is a supply roller composed of an open cell foam in which an average cell diameter is sufficiently large, a plurality of bubbles communicate with each other, and a flow path between the bubbles is formed in a network shape. Part of the toner that has entered the foam is discharged to the bottom wall surface of the developing device, but in order to smoothly discharge the toner, the gap between the outline of the supply roller and the bottom wall surface of the developing device is removed. It shows that it is necessary to make it the optimal size.

  In other words, if the outline of the supply roller is in contact with the bottom wall surface of the developing device, or the gap between the two is extremely narrow, the toner that should be discharged from the inside of the foam to the bottom wall surface of the developing device However, it is not discharged at all from the inside of the foam or only a very small amount is discharged.

  If the toner is not smoothly discharged from the inside of the foam, problems such as an increase in the hardness of the supply roller and the generation of toner agglomerates inside the foam occur.

In this experimental example, as the supply roller 4, a roller in which a foam having an Asker F hardness of 85 ° was coated on the outer peripheral surface of the shaft so as to have a layer thickness of 3 mm was used. Furthermore, the open cell ratio of the foam was 70% and 90%, and the average cell diameter was 0.5 mm and 2 mm.

The gap d between the supply roller 4 and the bottom wall surface of the developing device 5 was set to four types of 0 mm, 0.1 mm, 0.3 mm, and 1 mm.

Further, toner C was used as a developer.

  The conditions other than the above are the same as in Experimental Example 1.

First, in this experimental example, the torque required to drive the developing device was measured at the start of image formation and when image formation was continuously performed for 8 hours. In addition to the above measurement, the presence or absence of jitter in the image was evaluated.

Table 4 shows the results of this experimental example. Table 4 shows the torque required to drive the developing device when image formation is started and when image formation is continuously performed for 8 hours, and the presence or absence of image jitter when image formation is continuously performed for 8 hours. Is evaluated. The legend is the same as in Table 1.

As apparent from the above table, a supply roller composed of an open cell foam having an average cell diameter of 0.5 mm or more and an open cell ratio of 70% or more is used, and the outline of the supply roller and the bottom of the developing device are used. By setting the gap d to the wall surface to be 0.1 mm or more, more preferably 0.3 mm or more, the toner that has entered the foam can be smoothly discharged to the bottom wall surface side of the developing device.

However, it is desirable that the gap between the outline of the supply roller and the bottom wall surface of the developing device does not exceed 3 mm.

  This is because, when the gap between the outline of the supply roller and the bottom wall surface of the developing device exceeds 3 mm, a high-duty image (for example, a so-called black solid image) is continuously displayed immediately after toner is supplied to the developing device for the first time. This is because the amount of toner supplied from the supply roller to the developing roller is insufficient when the toner is formed, and the image density after the image area corresponding to one or two rotations of the developing roller is lowered.

  In this experimental example, toner is supplied from the supply roller to the development roller at the contact portion between the development roller and the supply roller. This supply operation is performed by mechanically rubbing the toner on the surface of the supply roller against the development roller. Caused by

  However, when the gap between the outline of the supply roller and the bottom wall surface of the developing device exceeds 3 mm, the toner on the surface of the supply roller constituted by the open cell foam is foamed immediately after the toner is supplied to the developing device for the first time. Since the toner enters the inside of the body and is easily discharged to the bottom wall surface side of the developing device, the mechanical force does not act effectively on the toner on the surface of the supply roller at the contact portion between the development roller and the supply roller. Most of the toner moves toward the inside of the supply roller and hardly moves to the developing roller. As a result, insufficient supply of toner to the developing roller occurs.

  Therefore, it is preferable that the gap between the outline of the supply roller and the bottom wall surface of the developing device does not exceed 3 mm. However, this is not the case when a sufficient electric field is applied between the developing roller and the supply roller so that toner is supplied from the supply roller to the development roller.

  In the present experimental example, the rotation direction of the supply roller was set to the direction indicated by the arrow in FIG. Thus, when the toner in the gap between the outline of the supply roller and the bottom wall surface of the developing device moves along the rotation direction of the supply roller, the direction of the opening of the developing device (the portion facing the latent image carrier) However, the toner that has entered the inside of the foam and easily discharged to the bottom wall surface of the developing device falls or scatters from the opening of the developing device. Can be avoided.

(Experimental example 5)
This experimental example is a supply roller composed of an open cell foam in which an average cell diameter is sufficiently large, a plurality of bubbles communicate with each other, and a flow path between the bubbles is formed in a network shape. This indicates that the hardness of the supply roller needs to be optimized in order to smoothly discharge the toner that has entered the foam.

  Here, the Asker F hardness indicating the hardness of the foam used in this experimental example will be described.

The Asker hardness is a hardness measured by a rubber / plastic hardness meter (coil spring type) manufactured and sold by Kobunshi Keiki Co., Ltd. The mold of the hardness meter is appropriately selected according to the hardness of the rubber or plastic to be measured. For example, when the object to be measured is hard, an Asker A type hardness meter is used, and the Asker A hardness is 100 ° to 0 °. When the object to be measured is soft, an Asker C type hardness meter is used. The Asker C hardness is 100 ° to 0 °. The Asker F hardness is a hardness measured by an Asker F hardness meter that measures softer than the Asker C hardness, and cannot be indicated by the Asker C hardness (Asker C hardness 0 ° or less).

In this experimental example, as the supply roller 4, a roller in which an open cell foam was coated on the outer peripheral surface of the shaft so as to have a layer thickness of 3 mm was used. Furthermore, the Asker F hardness of the foam is 6 types of 50 °, 70 °, 80 °, 90 ° and Asker C hardness 15 °, the open cell ratio is 2 types of 70% and 90%, and the average cell diameter is Two types of 0.5 mm and 2 mm were used.

Further, toner C was used as a developer.

  The conditions other than the above are the same as in Experimental Example 1.

In this experimental example, image formation was continuously performed for 30 hours by the developing device having the above-described configuration, and the presence or absence of image fogging and white streaks was evaluated.

The results of this experimental example are shown in Tables 5 and 6. Table 5 shows the results of using a foam having an Asker F hardness of 50 ° to 90 ° as the supply roller, and Table 6 shows the results of using a foam having an Asker C hardness of 15 ° as the supply roller. The legend is the same as in Table 3.

As is clear from the above table, the average cell diameter is sufficiently large, the open cell ratio is sufficiently high, a plurality of bubbles communicate with each other, and a flow path through the bubbles is formed in a network. In the supply roller constituted by the bubble foam, the hardness of the open cell foam is set to 90 ° or less, more preferably 80 ° or less, so that the toner entering from the opening of the surface of the supply roller can be Can be smoothly discharged from other openings communicating with each other. That is, by configuring the supply roller with an open-cell foam having an Asker F hardness of 90 ° or less, the pressure at the contact portion between the developing roller and the supply roller, and the supply roller easily and greatly deformed by the pressure, the foam inside the foam. Since the toner that has entered the toner is forced and smoothly discharged from the opening other than the contact portion of the supply roller while being further pushed into the supply roller, toner agglomeration is prevented, and low charge or reverse The charged toner is prevented from being supplied to the developing roller.

(Experimental example 6)
In this experimental example, a developing device that reuses used toner (more specifically, an image forming device that collects the developer once developed on the latent image carrier and collects it again and reuses it) is developed. This is done by paying attention to the deterioration of the image when paper dust is mixed with the toner collected in the apparatus.

  If paper dust is not discharged smoothly from the inside of the foam, foaming is caused by an increase in the hardness of the supply roller, which causes image jitter and clogs the paper dust inside the foam. Problems such as generation of toner agglomerates due to hindered smooth discharge of toner from inside the body occur.

  Also, paper dust is caught because it cannot smoothly pass through the contact portion between the developing roller and the doctor blade, and the toner film forms on the surface of the developer roller or blade starting from the place where the paper dust is caught. If the paper dust is extremely large, the contact portion will be clogged as it is. As a result, a toner layer is not formed on the developing roller, and an image corresponding thereto is observed as a white stripe.

  The present experimental example has been made in view of such problems, and the toner does not clog the paper powder that has entered the foam of the supply roller, and the toner is supplied from the supply roller to the developing roller. The present invention has been made to solve the above problem by smoothly and forcibly discharging the toner that has entered the foam of the supply roller at a place other than the supply section to be supplied.

In this experimental example, as the supply roller 4, a roller in which a foam having an Asker F hardness of 80 ° was coated on the outer peripheral surface of the shaft so as to have a layer thickness of 3 mm was used. Furthermore, the open cell ratio of the foam was 70% and 90%, and the average cell diameter was 0.5 mm and 2 mm.

  Further, as a developer, 100 parts by weight of a non-magnetic one-component toner (toner B) having a volume average particle diameter of 10 μm, to which 0.5 wt% of hydrophobic silica is externally added, and 1 part by weight of paper powder collected from fine paper are mixed. (Toner D) was used.

The conditions other than the above are the same as in Experimental Example 1.

First, in this experimental example, the torque required to drive the developing device was measured at the start of image formation and when image formation was continuously performed for 8 hours. In addition to the above measurement, the presence or absence of jitter in the image was evaluated.

Table 7 shows the results of this experimental example. Table 7 shows the torque required to drive the developing device when image formation is started and when image formation is continuously performed for 8 hours, and the presence or absence of image jitter when image formation is continuously performed for 8 hours Is evaluated. The legend is the same as in Table 1.

Further, in this experimental example, image formation was continuously performed for 30 hours by the developing device having the above-described configuration, and the presence or absence of white streaks in the image was evaluated. However, no white streak in the image due to the paper powder clogging at the contact portion between the developing roller and the doctor blade was observed.

Therefore, as apparent from the above, as the supply roller, an open cell foam having an open cell ratio of 70% or more, more preferably 90% or more, or an average cell diameter of 0.5 mm or more, more preferably 2 mm. By using the above open-cell foam, it is possible to obtain a good supply roller that does not affect the image even when paper dust is mixed into the developing device.

As described above, the supply roller of this experimental example is likely to be mixed with foreign matters such as paper dust in the developing device such as an image forming device in which the toner once developed on the latent image carrier is recovered and reused in the developing device. It is especially effective in cases.

Although the embodiments have been described above, the present invention relates to a developing device having a developer carrying member and a supply member for supplying the developer to the developer carrying member, and in particular, the developer once developed on the latent image carrier is developed again. This is effective when deteriorated toner is likely to be generated as in an image forming apparatus that is collected and reused in the apparatus, or when foreign substances such as paper dust are likely to be mixed into the developing apparatus.

  Needless to say, the present invention can also be applied when a two-component developer or a one-component magnetic developer is used as the developer. However, in the one-component nonmagnetic developer, a supply member for forcibly applying the developer to the developer carrying body at the same time as peeling off the developer remaining on the developer carrying body after development is necessary. Further, the developer carrier side of the developer on the surface of the supply member such as electrostatic force by the carrier of the two-component developer or magnetic force from the developer carrier to the one-component magnetic developer (without pushing into the supply member) Therefore, the present invention is particularly effective for a one-component nonmagnetic developer.

  Further, as other members of the image forming apparatus other than the developing device, for example, means for charging the latent image carrier, and means for transferring a visible image by the developer on the latent image carrier to a recording medium (paper or the like). Alternatively, it is also effective when a foam is used as a cleaning means for removing the developer on the latent image carrier. This is because these members often come into contact with the toner, and when these members are made of foam, the toner enters the foam, causing clogging, and the hardness of the foam. This is because the toner increases or causes toner agglomerates.

  The image forming apparatus of the present invention can be applied not only to a printer but also to a copying machine, a facsimile, a display, and the like.

  The developing device of the present invention includes a developer carrying member and a supply member that supplies the developer (toner) including the developer (toner) used to the developer carrying member, and the developer (toner) is applied to the latent image. Can be suitably used in, for example, an image forming apparatus using an electrophotographic method or the like.

FIG. 2 is an exploded perspective view of the developing device of the present invention and an image forming apparatus in which the developing device is integrated. The cross-sectional schematic of an apparatus same as the above.

Explanation of symbols

2 Photosensitive drum 3 Developing roller 4 Supply roller 5 Developing device 8 Doctor blade 20 Toner transport belt 25 Toner hopper

Claims (3)

In a developing device having a developer carrying member and a supply member for supplying the developer to the developer carrying member and reusing the used developer,
The supply member is an average cell diameter 0.5mm or more, the open cell ratio of 70% or more, Ri open cell foam der an Asker F hardness 85 °,
Development characterized in that a developer comprising a non-magnetic one-component toner having a volume average particle diameter of 10 μm and externally added hydrophobic silica and a toner obtained by stirring the non-magnetic one-component toner is used as the developer. apparatus. A developing device according to claim 1, wherein the gap between the bottom wall surface of the outline and the developing device of the supply member, characterized in that at 0.1mm or more. The developing device according to claim 1, wherein hydrophobic silica is impregnated inside the bubbles of the open-cell foam.

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