JP2004029843A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device capable of preventing problems such as deterioration of a force for transporting the toner in the feeding member and increase in the hardness of the feeding member, while these problems are due to clogging of a foamed body caused by paper dust and the like mixing in the developing device and entering the foamed body of the feeding member, in the case where used toner is recycled. <P>SOLUTION: The developing device is provided with a developer carrier and the feeding member for supplying a developer to this carrier, and is designed to recycle the used developer. Because the feeding member is a foamed body and because foams having a cell diameter of 80 μm or below is not more than 1% of the total foams on the surface of the feeding member, the toner is smoothly discharged from inside the feeding member. As a result, the foamed body is prevented from being clogged, thereby eliminating the problems concerning the feeding member such as the lowering of the toner transporting force and the increase in the hardness. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a developing device for forming 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 device. More specifically, the present invention relates to a developing device having a developer carrier and a supply member for supplying a developer (toner) to the developer carrier.

現 像 Developing devices having a supply member for supplying toner to a developer carrier are known (for example, see Patent Document 1, Patent Document 2, and Patent Document 3).

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

The foams are classified into open-cell foams and closed-cell foams according to the form of the cells. Such a classification method is well known (for example, see Non-Patent Document 1).
JP-A-61-42672. JP-A-62-257185. JP-A-2-191974. Plastic Form Handbook (published by Nikkan Kogyo Shimbun, editor: Makihiro and Atsushi Kosakada, first edition published on February 28, 1973).

When the open-cell foam is used as the supply member, the toner enters the inside of the foam, causing clogging of the foam, 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. appear.

問題 When closed cell foam is used as the supply member, such a problem does not occur. However, closed-cell foams are generally hard, and in order to have a low hardness suitable as a supply member, the material is limited, production is difficult, and it is expensive compared to open-cell foams. It is.

Further, when a foam is used as the supply member, regardless of whether the foam is an open-cell foam or a closed-cell foam, the toner captured by the bubbles on the surface of the supply member is not discharged from inside the bubbles. Then, there is a problem that the toner taken in the air bubbles gradually forms an aggregate due to mechanical stress repeatedly applied to the supply member.

(4) While the aggregate is held in the foam for a long period of time, the charge amount is lower than that of the normal toner, or the aggregate is charged to the opposite polarity. Therefore, the aggregate separated from the surface of the supply member adheres to the non-image portion of the latent image carrier (so-called image fog) via the developer carrier. This is observed as a black spot (having a diameter of approximately 200-500 μm or less) in the non-image area.

Further, since the aggregates cannot smoothly pass through the contact portion between the developer carrier and the regulating member for regulating the amount of toner transported on the developer carrier, the mechanical Due to the force and frictional heat, the toner is fused (so-called filming) to the surface of the developer carrying member or the regulating member, or when the aggregate is extremely large, the contact portion is directly clogged. As a result, at the contact portion where filming or the like has occurred, no toner layer is formed on the developer carrying member, and an image corresponding to the toner layer is observed as a white streak (image omission).

Further, when a foam is used as the supply member, the toner conveying function of the supply member is performed by an open hole on the surface of the foam. The open hole on the body surface is substantially crushed, and the toner conveying function of the supply member is reduced. When the toner conveying function of the supply member is reduced, a sufficient amount of toner is not supplied to the developer carrier, and there is a problem that the density of the image is reduced (blurred).

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

Further, when the developing device reuses the 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 performs development and recovery cleaning at the same time or separately, a large amount of foreign matter is mixed into the developing device.

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

When the used toner is reused by the developing device, foreign matter mixed into the developing device may be dust, dust, or part of the recording medium (for example, paper used as the recording medium). In such a case, the filler or paper dust) or a part of the latent image carrier (fragment on the surface of the latent image carrier due to friction with a cleaning device or the like). Above all, paper dust is a problem.

Paper powder is typically a short fiber having a diameter of about 10 μm to 40 μm and a length of about 0.1 mm to 3 mm. However, there are rarely larger paper powders generated from the cut surface of the paper.

This paper dust depends on the quality of the paper (for example, whether it is high quality paper mainly made of only virgin pulp or recycled paper made of waste paper, etc.), but it is equivalent to 30,000 A4 size papers. About 0.1 to 0.3 g or more of paper dust from the paper enters the developing device (this has been confirmed by experiments by the present inventors).

The paper dust mixed into the developing device enters the inside of the foam of the supply member and causes clogging of the foam. As a result, problems such as a decrease in the toner conveying force of the supply member and an increase in the hardness of the supply member occur. Paper powder has extremely poor fluidity compared to toner and is hard to be discharged from the inside of the foam. Therefore, when a developing device reuses used toner, it becomes very early when compared with a case where it is not reused. Problems arise.

Further, the paper dust is caught because it cannot smoothly pass through the contact portion between the developing roller and the doctor blade, and the toner is filmed on the surface of the developing roller or the blade starting from the place where the paper dust is caught. If the paper dust is excessively large or the paper dust is extremely large, the contact portion is directly clogged. As a result, no toner layer is formed on the developing roller, and the corresponding image is observed as a white stripe.

(4) When the developing device reuses the used toner, the toner is used repeatedly, so it is necessary to deal with the deteriorated toner. By repeatedly using the toner, the external additive applied to the toner to improve the fluidity of the toner is dropped off from the surface of the toner or conversely embedded in the toner. Alternatively, there is a problem that the toner is broken by a mechanical force (by a developing device or a cleaning device or the like), so that the diameter is reduced, and the fluidity is reduced as the diameter is reduced.

(4) Such a deteriorated toner causes the same problem as paper dust.

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

Particularly, when the used toner is reused, the purpose of the supply member is to cause clogging of the foam caused by paper powder or the like mixed in the developing device entering the inside of the foam of the supply member. Another object of the present invention is 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-mentioned problems, and is a developing device having a developer carrier and a supply member for supplying the developer to the developer carrier, and reusing used developer. In the developing device used, the supply member is a foam, and among the bubbles on the surface of the supply member, bubbles having a cell diameter of 80 μm or less are 1% or less of the total number.

Further, the developing device of the present invention is characterized in that the supply member is a foam having an Asker F hardness of 90 ° or less and an open cell ratio of 40% or less.
Further, the developing device according to the present invention is characterized in that the developing device includes a member that contacts the supply member and deforms the supply member.

Further, in the developing device of the present invention, the member that deforms the supply member is the developer carrier that rubs against the supply member or a pressure member that applies pressure to the supply member.
Furthermore, the developing device of the present invention is characterized in that hydrophobic silica is impregnated inside the bubbles of the foam.

(Action)
According to the first aspect of the present invention, in the developing device for recycling used toner, the supply member is formed of a foam, and the cell diameter of the bubbles on the surface of the supply member (foam) is 80 μm. By setting the following bubbles to 1% or less of the total number, foreign substances (aggregates due to paper dust or deteriorated toner) from the outside of the developing device can be easily clogged in the open holes on the foam surface. Is discharged.

That is, regardless of the cross-sectional shape (when cut in the depth direction) of the open hole on the foam surface, the diameter of the open hole on the foam surface is sufficiently increased so that the used hole can be used. In a developing device that reuses toner, paper dust can be particularly smoothly discharged from a foam.

By the way, although the cross-sectional shape of the open hole on the foam surface varies, it can be roughly classified into a bowl shape and a pot shape.

FIG. 5 shows a schematic cross-sectional view of an open hole on the surface of the foam.

FIG. 5A shows an example in which the cross section of the open hole is bowl-shaped. The bowl shape means that the bubbles (parallel to the open surface) are closer to the bottom of the open hole than the diameter d ₀ of the open surface of the open hole (surface exposed on the surface of the supply member) of the foam surface. The shape is such that the diameter d _{1 (} in the plane) becomes progressively smaller.

FIG. 5B shows an example in which the cross-sectional shape of the open hole is a pot shape. The pot, than the diameter d ₀ of the open surface of the open pores of the foam surface, toward the bottom of the open hole, the diameter d ₁ of the bubble is gradually larger shape.

In the present invention, the cell diameter of the bubbles on the surface of the supply member is the diameter d ₀ of the open surface of the bubbles.

By the way, as for the open holes on the surface of the foam, those having a bowl-shaped cross section and a pot-shaped cross section are mixed.

気 泡 In bubbles having a pot-shaped cross-section, paper powder that has entered the inside of the bubbles is complicatedly bent or entangled, and particularly easily clogged.

Therefore, by making the cell diameter of the open pores on the foam surface sufficiently larger than the paper powder and setting the number of cells having a small cell diameter to a certain ratio or less, regardless of the cross-sectional shape of the open pores on the foam surface, In a developing device that reuses used toner, foreign matter such as paper powder that has entered the foam can be smoothly discharged from the foam.

According to the second aspect of the present invention, the supply member for supplying the toner to the developer carrier is made of an open-cell foam having an Asker F hardness of 90 ° or less and an open-cell ratio of 40% or less. The foreign substances such as toner and paper powder conveyed through the open holes are easily discharged without further entering the inside of the foam.

That is, the upstream of the supply unit (contact portion between the developer carrier and the supply member) where the toner is supplied from the supply member to the developer carrier near the rotation direction of the supply member (the moving direction of the surface of the supply member). In the above, the supply member is easily deformed by contact with the developer carrier, and the direction of the deformation of the supply member is a direction of squeezing out the toner from the inside of the supply member. The toner does not enter the foam.

FIG. 4 is a schematic view of a contact portion between the supply member and the developer carrier. FIG. 4 shows an example in which the supply member and the developer carrier move in opposite directions at the contact portion, but the same applies to the case where the developer member rotates in the same direction. However, when rotating in the same direction, it is preferable that the surface speed of the supply member is higher than the surface speed of the developer carrier.

In the supply section, the toner is supplied to the developer carrier while the supply member rubs against the developer carrier. Here, a part of the toner conveyed by the supply member is a part of the developer carrier. And remains on the supply member. Further part of the toner remaining on the supply member tends to be pushed into the supply member by the contact pressure with the developer carrier in the supply section. However, the supply member is already deformed on the upstream side of the supply unit, and in the supply unit, the open hole on the surface of the supply member is substantially crushed. Hardly penetrates.

Further, by making the supply member a foam having an open cell ratio equal to or less than a predetermined value, even if the toner enters the inside of the supply member, the toner is not pushed into a deep portion of the supply member. Therefore, as described above, when the supply member passes through the supply unit and returns to the supply unit again, the supply member deforms in a direction to squeeze the toner from the inside of the supply member, thereby causing the inside of the foam to be removed. From the toner is easily discharged.
It is more preferable to use a closed-cell foam as the supply member.

(effect)
As described above, according to the developing device of the present invention, by using an open-cell foam having an Asker F hardness of 90 ° or less and an open-cell rate of 40% or less as a supply member for supplying a toner to a developer carrier, By easily deforming the foam, it is possible to forcibly and promptly discharge the toner that has entered through the open hole on the surface of the foam again from the open hole into which the toner has entered.

Further, according to the developing device of the present invention, even in a case where the used toner is reused and paper dust or deteriorated toner is mixed in the developing device, the bubbles on the surface of the supply member are removed. By setting the bubbles having a cell diameter of 80 μm or less to 1% or less of the total number, clogging of the supply member, white streaks of an image, and black spots on a non-image portion due to agglomeration of paper dust or toner are prevented. be able to.

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.

に お い て In FIG. 1, reference numeral 1 denotes a case main body that accommodates a set of electrophotographic process units.

ケ ー ス The case body 1 has a photosensitive drum 2 as an electrostatic latent image carrier in the center of the inside thereof.

On one side of the case main body 1, a developing device 5 having 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 7 to form a partition. 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 to a thinner layer.

{Circle around (2)} On the other side of the case body 1, a cleaning device 10 having a cleaning blade 9 for collecting and removing toner from the electrostatic latent image carrier is formed.

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

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

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

The toner transport 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 the new toner and the untransferred toner collected and removed from the photosensitive drum 2 by the cleaning blade 9 are stirred and mixed. It is configured to send back to.

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

The toner hopper 25 in this embodiment is mounted on a drive pulley 23 provided at the entrance of the developing device 5, and an agitator 28 provided inside the toner hopper 25 is coupled to the drive pulley 23 to be driven simultaneously. It is configured to Reference numeral 29 in the figure denotes a scraper that rotates together with the agitator 28 and scrapes the toner on the hopper bottom surface 26 into the hopper 25.

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 a metal shaft. As the elastic layer, known rubbers, elastomers, resins or their foams can be used, and if necessary, known conductive agents and the like are added.

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

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

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, and vinyl chloride. It is possible to apply polyurethane, phenol resin, urea resin, epoxy resin, polyethylene, methacryl resin and the like.

In this embodiment, a supply roller having a volume resistivity of about 10 ⁴ Ω · cm and using an elastic layer made of polyurethane foam to which carbon black is added as a conductive agent is used. The density of the foam used for the supply roller 4 varies depending on the expansion ratio of the foam, the average cell diameter, and the like, but is preferably 100 to 400 kg / m ³ .

(4) The supply roller 4 is disposed so as to be in contact with the developing roller 3. Note that 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. Known rubber, elastomer, resin, and metal can be used as the elastic plate material.

In this embodiment, a thin plate made of stainless steel (SUS304) having a thickness of 100 μm is used as the elastic plate material. The doctor blade 8 is in pressure contact with the developing roller 3 at 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 the toner is clogged, 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, a roller in which a foam having an average cell diameter of 200 μm was coated on the outer peripheral surface of the shaft so as to have a layer thickness of 3 mm was used as the supply roller 4. In addition, as a foam, the cell diameter distribution of the bubbles is within ± 100 μm with the average cell diameter as a center value. The number of bubbles is 98% or more of the total number, and the cell diameter distribution is within ± 30 μm with the average cell diameter as a center value. The number of bubbles having a cell diameter of 60% or more and a cell diameter of 80 μm or less was 1% or less of the total number. The average cell diameter and cell diameter distribution were measured from an image obtained by observing the surface of the foam (supply roller) with an optical microscope at a magnification of 30 to 50 times.

Further, in this experimental example, four types of foams of the supply roller 4 having an open cell ratio of 40% and 20% and an Asker F hardness of 90 ° and 60 ° were used. Further, as a comparative example, an experiment was performed using a foam having an open cell ratio of 60% and an Asker F hardness of 60 ° and a foam having an open cell ratio of 20% and an Asker C hardness of 15 °.

Here, the open cell ratio of the foam used in the present experimental example will be described.

連 続 The open cell rate of the foam is measured by a known method. In this example, the open cell rate is indicated by a value (water absorption rate) measured by a water absorption test method (ASTM D 1056). A foam having an open cell ratio of 5% or less is classified as a closed cell foam, and a foam having an open cell ratio exceeding 5% is classified as an open cell foam.

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

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

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

In this experimental example, a non-magnetic one-component toner (toner A) having a volume average particle diameter of 7 μm and externally added 0.5 wt% of hydrophobic silica was used as a developer. The compression ratio of the toner A is 34%.

When toner is clogged in the supply roller while image formation is continuously performed, the hardness of the supply roller increases, and as a result, the torque of the developing device increases. The increase in the torque appears as image jitter (image disturbance due to driving unevenness of the image forming apparatus).

ト ル ク In this experimental example, the torque at the start of image formation was 0.9 to 1.2 kg · cm almost without depending on the difference in the average cell diameter of the foam and the compression ratio of the toner. Further, in the present experimental example, eight hours after the start of the image formation, 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 higher than that. , And the increase in the torque of the developing device also settled out almost uniformly.

Table 1 shows the results of this experimental example. Table 1 shows the evaluation of the presence or absence of jitter in the image when image formation was continuously performed for 8 hours.

In Table 1, x indicates that the image had obvious jitter and was unsuitable for practical use, ○ indicates that slight jitter was recognized in the image, but did not interfere with practical use, and ◎ indicates that the image had almost no jitter. Those not observed are indicated (-indicates a combination for which no experiment was performed).

As is clear from the above table, by using a foam having an open cell ratio of 40% or less and an Asker F hardness of 90 ° or less as the supply roller, a good supply roller with almost no toner clogging can be obtained.

In addition, by using a foam having a Asker F hardness of 90 ° or less as the supply roller, wear of the developing roller in contact with the supply roller and deterioration of the toner due to mechanical force at the contact portion between the supply roller and the developing roller can be reduced. Can be reduced.

(Experimental example 2)
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 again into the developing device and reuses it) This is performed by paying attention to the deterioration of an image when paper dust is mixed with the toner collected in the apparatus.

In this experimental example, a roller in which a foam having an open cell ratio of 40% and an average cell diameter of 180 μm was coated on the outer peripheral surface of the shaft so as to have a layer thickness of 3 mm was used as the supply roller 4.

In this experimental example, as the foam of the supply roller 4, among the bubbles on the surface of the supply member having an Asker F hardness of 90 ° and 60 °, bubbles having a cell diameter of 80 μm or less account for 1% of the total number, 0.5%. % Were used. Further, as a comparative experiment example, an experiment was performed using a foam having an open cell ratio of 40%, an Asker F hardness of 60 °, and a cell having a cell diameter of 80 μm or less of 10% of the total number of bubbles among the bubbles on the surface of the supply member. .

Further, as a developer, 100 parts by weight of toner A and a toner obtained by stirring toner A for 1 hour in a ball mill (hydrophobic silica was forcibly embedded in the toner surface, or a part of the toner was crushed, (Toner D) was used in which 20 parts by weight of a deteriorated toner) and 1 part by weight of paper powder collected from high-quality paper were mixed.

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

First, in this experimental example, the presence or absence of jitter in an image when image formation was continuously performed for 8 hours was evaluated.

Table 2 shows the results of this experimental example. The legend is the same as in Table 1.

Further, in the present experimental example, image formation was continuously performed for 30 hours using the developing device having the above configuration, and the presence or absence of fog and white streaks of the image was evaluated.

Table 3 shows the results of this experimental example.

In Table 3, x indicates that a clear image defect was recognized and the image was unsuitable for practical use (white streaks were visible in the image regardless of the size, or the fog of the image was the optical reflection density. Exceeds 0.1, or 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 that an image defect is recognized, but there is no problem in practical use (Evaluation × does not apply, but black spots in non-image areas are 6 or more and 20 or less per image area equivalent to A4 size paper). ),
○: Some image defects are recognized, but there is no problem in practical use (the number of black spots in the non-image area is 5 or less),
◎ indicates that no image defect was observed (white streaks, fog, and black spots of the image were not visible).

As is clear from the above table, as the supply roller, by using a foam of 1% or less, more preferably 0.5% or less of the total number of cells having a cell diameter of 80 μm or less among the bubbles on the surface thereof, Even when paper dust or deteriorated toner is mixed in the developing device, a good supply roller which does not affect the image can be obtained.

As described above, in the supply roller of the present experimental example, foreign matter such as paper dust easily enters the developing device such as an image forming device in which the toner once developed on the latent image carrier is collected and reused in the developing device. This is particularly effective in cases.

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

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

(Experimental example 3)
This experimental example is an example in which a foam having a smaller open cell ratio than that of Experimental Example 2 is used as a supply member.

In this experimental example, a roller in which a foam having an open cell ratio of 4%, an average cell diameter of 180 μm, and an Asker F hardness of 60 ° was coated on the outer peripheral surface of the shaft to a layer thickness of 3 mm was used as the supply roller 4.

In this experimental example, as the foam of the supply roller 4, four types of bubbles having a cell diameter of 80 μm or less, 1% and 0.5% of the total number of the bubbles on the surface of the supply member were used. Further, as a comparative experiment example, an experiment was performed using 10% of foams having a cell diameter of 80 μm or less among bubbles on the surface of the supply member.

The conditions other than those described above are the same as in Experimental Example 2.

First, in this experimental example, the presence or absence of jitter in an image when image formation was continuously performed for 8 hours was evaluated.

Table 4 shows the results of this experimental example. The legend is the same as in Table 1.

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

Table 5 shows the results of this experimental example. The legend is the same as in Table 3.

As is clear from the above table, as the supply roller, by using a foam of 1% or less, more preferably 0.5% or less of the total number of cells having a cell diameter of 80 μm or less among the bubbles on the surface thereof, Even when paper dust or deteriorated toner is mixed in the developing device, a good supply roller which does not affect the image can be obtained.

As described above, in the supply roller of the present experimental example, foreign matter such as paper dust easily enters the developing device such as an image forming device in which the toner once developed on the latent image carrier is collected and reused in the developing device. This is particularly effective in cases.

In Experiment 3, a relatively soft foam could be used as a supply member by using a polyurethane-based material. However, a foam such as polyethylene or polystyrene was hard, and as it was, a supply member was used. Is not suitable.

For a foam made of such a hard material, it is effective to use means for mechanically reducing the hardness of the foam, as shown in FIG. For example, as shown in FIG. 4 (a), a slit (cut) is formed from one side to the other, or as shown in FIG. 4 (b), a part of the foam is cut (like a lotus root). It is effective to form a through hole) or to perform a large number of needle punches so as to break the wall between bubbles. However, when the slits and the cutting portion reach the surface of the foam (toner conveying surface), the toner enters therefrom, and the supply member is clogged. Therefore, it is important that the slits and the cut portions are not exposed at places other than the non-contact surface with the toner, such as the side surfaces of the supply member.

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

The present invention is, of course, applicable to a case where a two-component developer or a one-component magnetic developer is used as the developer. However, in the case of the one-component non-magnetic developer, a supply member for forcibly applying the developer to the developer carrier at the same time as peeling off the developer remaining on the developer carrier after the development is required. Further, the developer on the surface of the supply member such as the electrostatic force of the carrier of the two-component developer or the magnetic force from the developer carrier to the one-component magnetic developer is sucked toward the developer carrier without pushing the developer into the supply member. The present invention is particularly effective for a one-component non-magnetic developer since there is no means for performing the above-mentioned operation in a one-component non-magnetic developer.

Further, as other members of the image forming apparatus other than the developing device, for example, a unit for charging a latent image carrier, a unit for transferring a visible image by a developer on the latent image carrier to a recording medium (paper or the like) Alternatively, the present invention is also effective when a foam is used as cleaning means for removing the developer on the latent image carrier. Because these members have many chances to come into contact with the toner, when these members are made of a foam, the toner enters the inside of the foam, causing clogging and the hardness of the foam. Is increased or an aggregate of toner is generated.

The image forming apparatus of the present invention is applicable 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 carrier and a supply member that supplies the developer (toner) including the used developer (toner) to the developer carrier, and the developer (toner) is applied to the latent image. Can be suitably applied to an image forming apparatus that forms a visible image by selectively adhering, for example, an electrophotographic method.

FIG. 1 is an exploded perspective view of a developing device of the present invention and an image forming apparatus in which the developing device is integrated. FIG. FIG. 3 is a schematic cross-sectional view of a contact portion between a supply member and a developer carrying member in the developing device of the present invention. FIG. 2 is a schematic cross-sectional view showing one embodiment of a supply member used in the developing device of the present invention. FIG. 3 is a schematic cross-sectional view of bubbles on the surface of a foam.

Explanation of reference numerals

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

Claims (5)

A developing device having a developer carrier and a supply member for supplying the developer to the developer carrier, and a developing device that reuses used developer,
The developing device, wherein the supply member is a foam, and among the bubbles on the surface of the supply member, bubbles having a cell diameter of 80 μm or less are 1% or less of the total number. The developing device according to claim 1, wherein the supply member is a foam having an Asker F hardness of 90 ° or less and an open cell ratio of 40% or less. The developing device according to claim 1, further comprising a member that contacts the supply member and deforms the supply member. 4. The developing device according to claim 3, wherein the member that deforms the supply member is the developer carrier that rubs against the supply member or a pressure member that applies pressure to the supply member. 5. The developing device according to claim 1, wherein hydrophobic silica is impregnated inside the cells of the foam.

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