JPH08190262A - Developing device - Google Patents

Abstract

PURPOSE: To prevent increase in the torque to drive a developing device caused by intrusion of a toner into a foamed body and to prevent fog and white stripes in an image by constituting a toner supply member of a continuous foamed body having specified ASKER F-type hardness and a specified continuous foam rate. CONSTITUTION: A supply roller 4 to supply a toner to a developer carrying body consists of a continuous foamed body having <=90 ASKER F-type hardness and <40% continuous foam rate. By this method, a toner carried by the open holes on the surface of the foamed body is prevented from entering further inside but is easily discharged from the body. Namely, near the upstream side for the rotation direction of the supply roller 4 (moving direction of the surface of the supply roller 4) of the supply part where the toner is supplied from the supply roller 4 to the developer carrying body (the contact area between the developer carrying body and the supply roller 4), the roller can be easily deformed by contact with the developer carrying body. The direction of deformation of the supply roller is along the direction to squeeze the toner from inside of the roller 4. Thereby, the toner carried in the open holes of the foamed body surface is prevented from entering inside of the foamed body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for forming a visible image by selectively adhering colored fine particles (toner) to a latent image, for example, a developing device applied to an electrophotographic image forming apparatus. Regarding For more information,
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.

[0002]

2. Description of the Related Art A developing device having a supply member for supplying a toner to a developer carrying member is known, and is disclosed in, for example, JP-A-61-61.
-42672, JP-A-62-257185, JP-A-2-191974 and the like.

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

[0004]

Foams are classified into open-cell foams and closed-cell foams depending on the form of cells. Such a classification method is well known, and is described in, for example, a plastic foam handbook (published by Nikkan Kogyo Shimbun, editor: Makihiro / Atsushi Kosakada, first edition issued February 28, 1973). .

When an open-cell foam is used as the supply member, toner enters the inside of the foam and the foam is clogged, which reduces the toner conveying force of the supply member and increases the hardness of the supply member. Problem occurs.

It is said that such a problem does not occur when the closed cell foam is used as the supply member. But,
The closed-cell foam is generally hard, and in order to have a low hardness suitable as a supply member, the material is limited, it is difficult to manufacture, and it is expensive as compared with the open-cell foam. .

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 taken in by the bubbles on the surface of the supply member is inside the bubble. If it is not discharged from the supply member, there is a problem that the toner taken in the air bubbles gradually forms an aggregate due to the mechanical stress repeatedly applied to the supply member.

[0008] The agglomerates have a lower charge amount than normal toner or are charged to the opposite polarity while being held inside the foam for a long time. for that reason,
The aggregates separated from the surface of the supply member adhere to the non-image portion of the latent image carrier (so-called image fogging) via the developer carrier. This is observed as black dots in the non-image areas (having a diameter of approximately 200-500 μm or less).

Further, since the aggregated mass cannot smoothly pass through the contact portion between the developer carrying member and the regulating member for regulating the toner carrying amount on the developer carrying member, the contact portion thereof. When the toner is fused (so-called filming) on the surface of the developer carrying member or the regulating member due to the mechanical force and frictional heat in the case, or the aggregate is extremely large, the toner is directly stuck in the contact portion. I will end up.
As a result, the toner layer is not formed on the developer bearing member at the contact portion where filming or the like occurs, and the image corresponding thereto is observed as white streaks (image loss).

Further, when the foam is used as the supply member, the toner carrying function of the supply member is carried by the open hole on the surface of the foam, but the toner taken in the bubbles on the surface of the supply member is not discharged from the inside of the bubbles. Then, the open pores on the surface of the foam are substantially crushed, and the toner transport function of the supply member deteriorates. If the toner transport function of the supply member deteriorates, a sufficient amount of toner cannot be supplied to the developer carrying member, which causes a problem that the density of the image decreases (dullness).

The present invention has been made in view of the above problems, and an object thereof is to prevent the above problems while simplifying the supply member for supplying the toner to the developer carrying member. It is to provide a developing device capable of performing.

In the case where the developing device reuses the used toner, for example, the toner attached to the latent image carrier is collected and cleaned by a cleaning device, and the collected toner is transferred to the developing device for reuse. In the case where the developing device also functions as a cleaning device and the developing device and the collecting and cleaning process are performed simultaneously or separately, a large amount of foreign matter is mixed into the developing device.

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

When the developing device reuses the used toner, foreign matter mixed in the developing device is dust or dust adhering to the recording medium or a part of the recording medium (for example, paper as the recording medium). When it is used, it is a filler or paper powder), or a part of the latent image carrier (fragments on the surface of the latent image carrier due to friction with a cleaning device). Above all,
Paper dust is a problem.

Paper dust typically has a diameter of about 10 μm.
It is a short fiber having a length of 40 μm and a length of about 0.1 mm to 3 mm. However, for paper dust generated from the cut surface of paper,
Larger ones rarely exist.

This paper powder depends on the quality of the paper (for example, is it a high-quality paper mainly made of virgin pulp or a recycled paper made from waste paper, etc.)? About 0.1 to 0.3 g or more of paper dust is mixed into the developing device from a sheet of paper (this is
It has been confirmed by experiments by the present inventor).

The paper powder mixed in the developing device enters the inside of the foam of the supply member and causes the foam to be clogged. 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 less likely to be discharged from the inside of the foam, so when the developing device reuses used toner, it is extremely early compared with the case where it is not reused. The problem occurs.

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 place where the paper dust is caught is the starting point.
When the toner is filmed on the surface of the developing roller or the blade, or when the paper powder is extremely large, the contact portion is directly clogged. As a result, the toner layer is not formed on the developing roller, and the image corresponding thereto is observed as white stripes.

Further, when the developing device reuses the used toner, since the toner is repeatedly used, it is necessary to deal with the deteriorated toner. By repeatedly using the toner, the external additive imparted 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 on the contrary, whereby the fluidity of the toner is lowered, Alternatively, there is a problem that the toner is destroyed by a mechanical force (by a developing device, a cleaning device, or the like), so that the toner has a smaller diameter, and further, the fluidity is reduced as the diameter becomes smaller.

Such deteriorated toner causes the same problem as paper dust.

The present invention has been made in view of such conventional problems, and an object thereof is to prevent the above-mentioned problems while simplifying the supply member for supplying the toner to the developer carrying member. It is to provide a developing device capable of performing. In particular, it is an object of the invention to provide a developing device capable of preventing the above-mentioned problems even when reusing used toner.

[0022]

SUMMARY OF THE INVENTION The developing device of the present invention is to solve the above-mentioned problems. The supply member for supplying the toner to the developer carrying member has an Asker F hardness of 90 ° or less and an open cell ratio. It is characterized by being 40% or less of an open cell foam.

The developing device of the present invention is a developing device for reusing used toner, wherein the supply member for supplying the toner to the developer carrying member is a foam, and the surface of the supply member. Among the bubbles, the number of bubbles having a cell diameter of 80 μm or less is 1% or less of the total number.

Further, in the developing device of the present invention, the supply member has an Asker F hardness of 90 ° or less and an open cell ratio of 4
It is characterized by being 0% or less of foam.

[0025]

According to the invention of claim 1, the supply member for supplying the toner to the developer carrying member is an open cell foam having an Asker F hardness of 90 ° or less and an open cell ratio of 40% or less, The toner conveyed by the open holes on the surface of the foam is easily discharged without further entering the inside of the foam.

That is, as viewed from the rotation direction of the supply member (the moving direction of the surface of the supply member) 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. In the vicinity of the upstream side, the supply member is easily deformed by contact with the developer carrier, and the direction of the deformation of the supply member is the direction of squeezing out the toner from the inside of the supply member, thereby opening the foam surface. The toner carried by the holes does not enter the inside of the foam.

FIG. 4 shows a schematic view of the contact portion between the supply member and the developer carrying member. FIG. 4 shows an example in which the supply member and the developer carrying member move in opposite directions at their contact portions, but the same applies when rotating in the same direction. However, when rotating in the same direction, the surface speed of the supply member is preferably higher than the surface speed of the developer carrying member.

In the supply unit, the supply member is rubbed against the developer carrying member to supply the toner to the developer carrying member. Here, a part of the toner conveyed by the supply member is developed. It does not transfer to the agent carrier and remains on the supply member. Further, a part of the toner remaining on the supply member tends to be pushed into the supply member due to the contact pressure with the developer carrying member in the supply unit. However, the supply member
Since the toner has already been deformed on the upstream side of the supply unit and the open holes on the surface of the supply member are substantially crushed in the supply unit, the toner remaining on the supply member hardly enters the inside of the supply member. Absent.

Further, by making the supply member a foam having an open cell ratio of not more than a predetermined value, even if the toner enters the inside of the supply member, the toner will not be pushed deep into the supply member. Absent. 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 the direction of squeezing out the toner from the inside of the supply member, so that the toner is removed from the inside of the foam. Are easily discharged.

According to the second aspect of the present invention, in the developing device for reusing used toner, the supply member is made of foam, and the cells of the bubbles on the surface of the supply member (foam) are By setting bubbles with a diameter of 80 μm or less to 1% or less of the total number, foreign matter (paper dust, agglomerates due to deteriorated toner, etc.) from outside the developing device can be prevented from clogging the open pores on the foam surface. , Easily discharged.

That is, no matter what the cross-sectional shape (when cut in the depth direction) of the open holes on the surface of the foam is to make the diameter of the open holes on the surface of the foam sufficiently large, In a developing device that reuses used toner, especially paper dust can be smoothly discharged from the foam.

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

FIG. 5 shows a schematic sectional view of open pores on the surface of the foam.

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

Further, FIG. 5B shows an example in which the cross-sectional shape of the open hole is a pot shape. The pot shape is a shape in which the diameter d _{1 of} the bubbles gradually becomes larger toward the bottom of the open hole than the diameter d ₀ of the open surface of the open hole on the foam surface.

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.

The open pores on the surface of the foam are mixed in bowl shape and pot shape in cross section.

In the case of a bubble having a pot-shaped cross section, the paper powder that has entered the bubble is complicatedly bent or entangled, and is particularly likely to be clogged.

Then, the cell diameter of the open pores on the foam surface is made sufficiently larger than that of the paper powder, and the number of bubbles having a small cell diameter is set to a certain ratio or less, whereby the cross-sectional shape of the open pores on the foam surface is made. Regardless, in a developing device that reuses used toner, foreign matter such as paper dust that has entered the inside of the foam can be smoothly discharged from the foam.

Further, according to the third aspect of the present invention, the foreign matter such as toner and paper dust conveyed through the open holes on the surface of the foam is easily discharged without further entering the inside of the foam. . It is more preferable to use a closed cell foam as the supply member.

The present invention will be described in detail below with reference to examples.

[0042]

1 is 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. Is.

In FIG. 1, reference numeral 1 is a case body for accommodating 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 inside thereof.

Further, 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 provided with a partition wall 7. Is divided into sections. Note that reference numeral 8 in FIG.
Is a doctor blade that is a regulating member for regulating the toner supplied from the supply roller 4 to the developing roller 3 to a thinner layer.

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

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

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

Further, in FIG. 1, reference numeral 20 is a toner carrying belt for circulating and carrying 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 carrying belt 20 is formed by an endless coil spring, and is driven by a gear type driving pulley 23 arranged at one corner of the case body 1,
The cleaning device 10 and the developing device 5 are configured to pierce the cleaning device 10 and the developing device 5 from one end to the other end in the longitudinal direction of the case body 1 while circulating the inner peripheral portion of the case body 1 to transfer the toner.

One of the toner conveying belts 20 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. Configured to send the toner in the developing device 5 to the cleaning device 10,
Here, the new toner and the untransferred toner collected and removed from the photosensitive drum 2 by the cleaning blade 9 are agitated and mixed and sent back to the developing device 5.

Further, in FIG. 1, reference numeral 25 is a toner hopper for supplying new toner into the developing device 5. The toner hopper 25 is arranged at any position in the toner circulation path except the developing device 5 and the cleaning device 10.

Toner hopper 25 in this embodiment
Is a drive pulley 23 disposed at the entrance of the developing device 5.
The agitator 28 provided inside the toner hopper 25 is connected to the drive pulley 23 and driven simultaneously. Incidentally, reference numeral 2 in the drawing
Reference numeral 9 denotes a scraper that rotates together with the agitator 28 to scrape the toner on the bottom surface 26 of the hopper into the inside of the hopper 25.

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

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

In this example, polyester-polyurethane containing carbon black as a conductive agent was used as the elastic layer, the Asker C hardness was 50 °, and the volume resistivity was about 10.
⁶ Ω · cm developing roller 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 structure in which an elastic layer made of open-cell foam is formed on the outer circumference of a metal shaft. As the elastic layer, a known foam of rubber, elastomer, or resin can be used, and a known conductive agent or the like is added if 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, fluororubber,
It is possible to apply acrylic rubber, epichlorohydrin rubber, styrene resin, vinyl chloride, 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 a polyurethane foam containing carbon black as a conductive agent as an elastic layer is used. The density of the foam used for the supply roller 4 varies depending on the foaming ratio of the foam, the average cell diameter, etc.
It is preferably 100 to 400 kg / m ³ .

The supply roller 4 is arranged 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, or 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 material. The doctor blade 8 is pressed against the developing roller 3 with a load of 40 g / cm.

The present invention will be further described below with reference to specific experimental examples.

(Experimental Example 1) In this experimental example, the toner enters the foam of the supply roller and the toner is clogged, so that the hardness of the supply roller increases, and as a result, the torque for driving the developing device is increased. This was done focusing on the problem that

In this experimental example, as the supply roller 4, a roller having a shaft outer peripheral surface coated with a foam having an average cell diameter of 200 μm so that the layer thickness is 3 mm was used. still,
As the foam, the cell diameter distribution of the cells is within the range of ± 100 μm with the average cell diameter as the central value, the number of cells is 98% or more of the total number, and the average cell diameter with the central value is ± 30 μm.
In the range of m, 60% or more of the total number and the number of bubbles having a cell diameter of 80 μm or less were 1% or less of the total number. Further, the average cell diameter and the 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, the supply roller 4
As the foams, the following four types were used: open cell ratio 40%, 20%, Asker F hardness 90 °, 60 °. Further, as a comparative experiment example, the open cell ratio is 60%, the Asker F hardness is 60.
The experiment was conducted using a foam having a degree of 20 °, an open cell rate of 20%, and a foam having an Asker C hardness of 15 degrees.

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

The open cell ratio of the foam is measured by a well-known method, but in this embodiment, the water absorption test method (ASTM) is used.
It is shown by the value (water absorption) measured according to D 1056). A foam having an open cell rate of 5% or less is classified as a closed cell foam, and a foam having an open cell rate of more than 5% is classified as an open cell foam.

Next, the Asker F hardness, which is 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 type of hardness tester is appropriately selected according to the hardness of the rubber or plastic to be measured. For example, if the object to be measured is hard, an Asker A hardness meter is used, and the Asker A hardness is 100 ° to 0 °. If the object to be measured is soft, the Asker C hardness meter is used. Asker C
The hardness is shown as 100 ° to 0 °. The Asker F hardness is a hardness measured by an Asker F hardness meter, which is softer than the Asker C hardness, and cannot be shown by the Asker C hardness (Asker C hardness 0 ° or less).

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

Further, in this experimental example, a non-magnetic one-component toner (toner A) having a volume average particle diameter of 7 μm to which 0.5 wt% of hydrophobic silica was externally added was used as a developer.
The compression rate of Toner A is 34%.

If the supply roller becomes clogged with toner 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 the torque appears as image jitter (image disturbance due to drive unevenness of the image forming apparatus).

In the present experimental example, the torque at the start of image formation was 0.9 to 1.2 kg.cm, which hardly depended on the difference in the average cell diameter of the foam or the compressibility of the toner. In addition, in this experimental example, even if the toner clogging the supply roller 8 hours after the start of image formation, 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 were almost constant.

The results of this experimental example are shown in Table 1. Table 1 evaluates the presence or absence of image jitter when image formation is continuously performed for 8 hours.

In Table 1, x indicates clear jitter in the image, which is unsuitable for practical use, ○ indicates slight jitter in the image, which is acceptable for practical use, and ⊚ indicates that the image does not exist. It shows that the jitter was hardly observed (-indicates a combination for which no experiment was performed).

[0076]

[Table 1]

As is clear from the above table, by using a foam having an open cell rate 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. You can

Further, by using a foamed body having an Asker F hardness of 90 ° or less as the supply roller, the toner due to the abrasion of the developing roller in contact with the supply roller and the mechanical force at the contact portion between the supply roller and the development roller are used. Can be reduced.

(Experimental Example 2) In this experimental example, a developing device for reusing used toner (more specifically, the developer once developed on the latent image bearing member is recovered by the developing device and reused). Image forming apparatus), the deterioration of the image when paper powder is mixed with the toner collected in the developing device is focused on.

In the present experimental example, as the supply roller 4, a roller having a foamed body having an open cell rate of 40% and an average cell diameter of 180 μm coated on the outer peripheral surface of the shaft to have a layer thickness of 3 mm was used.

Further, in this experimental example, the supply roller 4
As the foams, four kinds of bubbles having Asker F hardness of 90 ° and 60 ° and 1% and 0.5% of the total number of bubbles having a cell diameter of 80 μm or less among the bubbles on the surface of the supply member were used. Further, as a comparative experiment example, the open cell rate is 40%, the Asker F hardness is 6
An experiment was conducted using a foam body in which the number of bubbles having a cell diameter of 80 μm or less was 10% of the total number of bubbles on the surface of the supply member at 0 °.

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

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

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

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

[0086]

[Table 2]

Further, in this experimental example, image formation was continuously carried out for 30 hours by the developing device having the above-mentioned constitution, and the presence or absence of image fogging and white lines was evaluated.

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

In Table 3, x indicates a clear image defect and is not suitable for practical use (white streaks are visually recognized in the image regardless of size, or image fogging is optical. The reflective density exceeds 0.1, or the number of black spots in the non-image area due to the agglomeration of toner exceeds 20 per image area equivalent to A4 size paper). The top is safe (evaluation ×
However, the number of black dots in the non-image area is 6 or more and 20 or less per image area corresponding to A4 size paper. ), ○
The image has some image defects, but there is no problem in practical use (there are no more than 5 black spots in the non-image area), and ◎ has no image defects (white streaks, fog in the image,
Black dots are not visible).

[0090]

[Table 3]

As is clear from the above table, as the supply roller, of the bubbles on the surface, 1% or less, more preferably 0.5% or less of the total number of bubbles having a cell diameter of 80 μm or less is used. This makes it possible to obtain a good supply roller that does not affect the image even when paper powder or deteriorated toner is mixed in the developing device.

As described above, the supply roller of the present experimental example has a developing device such as an image forming device that collects the toner once developed on the latent image bearing member in the developing device and reuses the toner. It is especially effective when it is easily mixed.

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

Further, in the present experimental example, the pressure for discharging the toner that has entered the foam of the supply roller depends on the pressure at the contact portion between the developing roller and the supply roller. In addition, a pressure member for deforming the supply roller may be separately provided.

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

In the present experimental example, as the supply roller 4, a roller having a foamed body having an open cell ratio of 4%, an average cell diameter of 180 μm and an Asker F hardness of 60 ° is coated on the outer peripheral surface of the shaft to a layer thickness of 3 mm. I was there.

Further, in this experimental example, the supply roller 4
As the foam, the four types of bubbles having a cell diameter of 80 μm or less, 1% and 0.5% of the total number of bubbles on the surface of the supply member, were used. Further, as a comparative experimental example, among the bubbles on the surface of the supply member, the number of bubbles having a cell diameter of 80 μm or less is 1
Experiments were conducted with 0% foam.

Conditions other than the above are the same as in Experimental Example 2.

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

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

[0101]

[Table 4]

Further, in this experimental example, image formation was continuously carried out for 30 hours by the developing device having the above-mentioned constitution, and the presence or absence of image fogging and white lines was evaluated.

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

[0104]

[Table 5]

As is clear from the above table, as the supply roller, of the bubbles on the surface, 1% or less, more preferably 0.5% or less of the total number of bubbles having a cell diameter of 80 μm or less is used. This makes it possible to obtain a good supply roller that does not affect the image even when paper powder or deteriorated toner is mixed in the developing device.

As described above, the supply roller of the present experimental example has a developing device such as an image forming device that collects the toner once developed on the latent image carrier into the developing device and reuses the toner. It is especially effective when it is easily mixed.

In Experiment 3, a relatively soft foam could be used as the supply member by using a polyurethane-based material, but a foam such as polyethylene or polystyrene is hard, and as it is, Not suitable as a supply member.

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

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

Needless to say, the present invention can be applied to the 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 peeling off the developer remaining on the developer carrying member after development and forcingly applying the developer to the developer carrying member is required. Further, the developer on the surface of the supply member such as the electrostatic force by the carrier of the two-component developer or the magnetic force from the developer carrier to the one-component magnetic developer is not pushed into the supply member, but is sucked to the developer carrier side. The present invention is particularly effective for the one-component non-magnetic developer because the means for doing so does not exist in the one-component non-magnetic developer.

As other members of the image forming apparatus other than the developing device, for example, a means for charging the latent image carrier, a visible image by the developer on the latent image carrier is recorded on a recording medium (paper or the like). It is also effective when a foam is used as a transfer means or a cleaning means for removing the developer on the latent image carrier. Because these members often come into contact with the toner, when these members are made of foam, the toner enters the inside of the foam,
This is because clogging occurs, the hardness of the foam increases, and agglomerates of toner are generated.

The image forming apparatus of the present invention can be applied not only to printers but also to copying machines, facsimiles, displays and the like.

[0113]

As described above, according to the developing device of the present invention, as the supply member for supplying the toner to the developer carrying member, the Asker F hardness is 90 ° or less and the open cell foaming rate is 40% or less. By using the body, the foam can be easily deformed, and the toner that has entered through the open holes on the surface of the foam can be forcibly and promptly discharged again through the open holes where the toner has entered. .

Further, according to the developing device of the present invention, even if the used toner is reused and the paper powder or the deteriorated toner is mixed in the developing device, the air bubbles on the surface of the supply member are generated. Out of which 1% of all bubbles with a cell diameter of 80 μm or less
By the following, it is possible to prevent clogging of the supply member, white streaks on the image, and black spots on the non-image area due to paper powder, aggregates of toner, and the like.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a developing device of the present invention and an image forming apparatus integrally incorporating the developing device.

FIG. 2 is a schematic cross-sectional view of the same device.

FIG. 3 is a schematic cross-sectional view of a contact portion between a supply member and a developer carrier in the developing device of the present invention.

FIG. 4 is a schematic sectional view showing an embodiment of a supply member used in the developing device of the present invention.

FIG. 5 is a schematic cross-sectional view of bubbles on the surface of a foam.

[Explanation of symbols]

 2 photoconductor drum 3 developing roller 4 supply roller 5 developing device 8 doctor blade 20 toner transport belt 25 toner hopper

Claims (3)

[Claims] 1. A developing device having a developer carrier and a supply member for supplying the developer to the developer carrier, wherein the supply member has an Asker F hardness of 90 ° or less and an open cell ratio of 40% or less. A developing device, which is a foam. 2. A developing device having a developer carrier and a supply member for supplying the developer to the developer carrier, wherein the supply member is a foam. And the number of bubbles having a cell diameter of 80 μm or less is 1% or less of the total number of bubbles on the surface of the supply member. 3. The Asker F hardness of 90 °
The developing device according to claim 2, which is a foam having an open cell ratio of 40% or less.