JPH11119547A - Developing device, process cartridge and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the developing device which maintains an amount of electrified charge of toner uniformly and highly in the direction of the length of a developing sleeve and is not influenced by an environmental change. SOLUTION: In an opening opposite a photoreceptor drum 1 the developing sleeve 5 is provided sidewise, and its both ends are provided with end seal members 19. On the developing sleeve 5 on the upstream side of the developing part, a toner electrification roller 20 is disposed. On the upstream side of it and in the counter direction an elastic blade 7 is disposed, and on the further upstream side of it an elastic roller 6 is disposed. To the nonmagnetic toner on the developing sleeve, a bias whose voltage is higher than that used at the start of discharging and whose polarity is the same as that of the toner is applied by means of the toner electrification roller 20 from a power source 18 shared with the developing sleeve 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine and an electrophotographic printer, a developing device provided in the image forming apparatus, and at least the developing device detachably mounted on the image forming apparatus. And a process cartridge containing the same.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, an electrostatic latent image formed on an image carrier is visualized as a toner image by a developing device.

As one of such developing devices, various dry one-component developing devices have been proposed and put into practical use. However, it is difficult for any developing device to form a thin layer of toner, which is a one-component developer, on a developer carrier.

However, at present, there is a demand for improvements in image resolution, sharpness, and the like, and development of a method and an apparatus for forming a thin layer of toner is indispensable, and several measures have been proposed. ing.

For example, as disclosed in JP-A-54-43038, an elastic blade as a regulating member made of a material such as metal or rubber is brought into contact with a developing sleeve as a developer carrying member, By restricting the toner by passing it between the contact portions of the elastic blade and the developing sleeve, a thin layer of the toner is formed on the developing sleeve, and sufficient tribo is applied to the toner by friction at the contact portions. It is to be provided.

In this case, when the non-magnetic toner is regulated by the elastic blade, a toner supply member for supplying the toner onto the developing sleeve is separately required. This is because in the case of magnetic toner, toner can be supplied onto the developing sleeve by the magnetic force of the magnet in the developing sleeve, but in the case of non-magnetic toner, toner cannot be supplied.

Therefore, a developing device 50 as shown in FIG.
Was proposed. In this conventional developing device 50, a polyurethane foam that comes into contact with the developing sleeve 52 at a position upstream of the elastic blade 51 in the rotation direction of the developing sleeve 52 in a developing container 54 containing a non-magnetic toner 53 as a one-component developer, An elastic roller 55 using a foam made of a sponge or the like or a fur brush is provided.
Has been supplied.

The toner 53 supplied onto the developing sleeve 52 is sent to the contact portion between the elastic blade 51 and the developing sleeve 52 with the rotation of the developing sleeve 52 to be thinned, and the photosensitive member as an image carrier is formed. 1 for developing the electrostatic latent image. Then, the toner 53 remaining without being consumed in the development on the developing sleeve 52 is peeled off by the elastic roller 55, and new toner 53 is supplied to the developing sleeve 52 by the elastic roller 55 as described above, and the above-described operation is repeated. . At this time, when a metal material is used as the developing sleeve 52, a thin metal plate as the elastic blade 51 is not preferable in terms of abrasion of the developing sleeve.
In order to obtain a good toner thin layer, it is necessary to use a rubber material such as urethane or silicon.

By adopting such a constitution, a thin layer of non-magnetic toner can be formed on the developing sleeve. FIG. 16 is a view of the developing device 50 of FIG. 15 viewed from the direction of the photoconductor 1. For convenience of explanation, the developing sleeve 52 is not shown, and the developing sleeve 5 of the elastic blade 51 is not shown.
The abutment nip for No. 2 is shaded.

[0010] As shown in FIG.
Wool felt in the gap between both ends of the
An end seal member 57 made of a fiber material such as a Teflon pile or a material such as polyurethane foam or sponge rubber is provided to prevent leakage of toner from between the longitudinal ends of the developing container 54 and the developing sleeve 52. As shown in FIG.
And between the end seal member 57 (i.e., by pressing the elastic blade 51 in the direction from the back side of the contact portion of the elastic blade 51 with the developing sleeve 52) by the end seal member 57. To prevent leaks.

However, in this conventional configuration, in order to ensure the sealing performance, the end sealing member 57 is pressed at a pressure equal to or higher than a predetermined value.
Must be pressed against the developing sleeve 52, and the elastic blade 51 sandwiched between the developing sleeve 52 and the end seal member 57 is provided on the peripheral surface of the developing sleeve 52 from the nip portion of the developing sleeve 52 at both ends to the front end. It is deformed along the way.

As a result, the inside of the elastic blade 51 at both ends in the longitudinal direction tends to rise, and the developer layer formed on the developing sleeve 52 in this portion becomes excessively large as compared with other portions, and therefore the toner 53 As a result, the charging becomes uneven in the longitudinal direction of the developing sleeve 52, and when a voltage is applied as a developing bias to the developing sleeve 52 during the developing operation, the toner 53 is applied to the photosensitive member 1 from both ends of the developing sleeve 52. There is a problem that the image is transferred as fog and that image density unevenness occurs due to uneven charge amount of toner on the developing sleeve 52.

Therefore, in order to cope with the above problem, an oblique cut is provided at both ends of the elastic blade. As shown in FIG. 17, the distance from the most downstream point in the developing sleeve rotation direction of the nip portion of the elastic blade 58 in contact with the developing sleeve 52 to the tip of the elastic blade 58 is set to the side end portion in the vicinity of both ends in the longitudinal direction of the elastic blade 58. , And at least the tip at the end on the elastic blade 58 side is formed in the contact nip.
For this reason, the inside of the elastic blade 58 at both ends in the longitudinal direction tends to rise, and the developing sleeve 52 at this portion also tends to rise.
Even if the developer layer formed thereon is excessively large as compared with the other portions, the developing sleeve 52 and the elastic blade 58 are formed because the contact nip is small and the edge comes into contact with the edge.
A thin layer of non-magnetic toner can be satisfactorily formed on the developing sleeve 52 while preventing toner leakage at both ends, so that an electrostatic latent image on the photoreceptor 1 as an image carrier can be favorably developed. Became possible.

[0014]

However, when the developing operation is repeated many times using the above-mentioned conventional developing device, the charge amount of the toner fluctuates with the fluctuation of the operating environment. In particular, the repetition of the developing operation in a high-temperature and high-humidity environment greatly reduces the charge amount of the toner, and the toner is transferred to the photoconductor as fog during the development, and the toner is scattered.

Accordingly, an object of the present invention is to provide a developing device which maintains the charge amount of a developer uniform and high in the longitudinal direction of the developer carrier and is not affected by environmental fluctuations, an image forming apparatus provided with the developing device, Another object of the present invention is to provide a process cartridge having at least the developing device and detachable from the image forming apparatus.

[0016]

The above object is achieved by a developing device, a process cartridge and an image forming apparatus according to the present invention. In summary, the present invention relates to a developing device having a developer container for storing a developer and a developer carrier extending and rotating at an opening of the developer container, wherein the developer carrier on the upstream side of the developing unit is provided. A developing device comprising: a pressing elastic member provided on a body; and a bias having a polarity equal to or higher than a discharge start voltage and being applied to the developer on the developer carrier by the pressing elastic member. is there.

According to another aspect of the present invention, at least a developing device having a developing container for storing a developer and a developer carrier extending at an opening of the developing container and rotating is integrally formed to form an image. In the process cartridge detachably mounted on the apparatus main body, the developing device includes a pressing elastic member provided on the developer carrier on the upstream side of a developing unit, and the developer on the developer carrier is provided by the pressing elastic member. A bias that is equal to or higher than the discharge starting voltage and has the same polarity as the developer.

According to still another aspect of the present invention, there is provided an image carrier on which a latent image is formed, a developer container accommodating at least the developer, and a developer carrier extending at the opening of the developer container and rotating. And a developing device having a developing unit, wherein the developing device is provided with a pressing elastic member on the developer carrying member on the upstream side of a developing unit, and the developer on the developer carrying member is provided by the pressing elastic member. A bias having a voltage equal to or higher than a discharge starting voltage and having the same polarity as that of the developer is provided.

In each of the above-mentioned present inventions, it is preferable that the image forming apparatus has a regulating member which comes close to or in contact with the developer carrying member via a developer. It is preferable that the regulating member is located on the upstream side of the pressing elastic member in the rotation direction of the developer carrier. It is preferable that the regulating member has a rotatable elastic roller provided in contact with an abutting portion of the developer carrier with respect to the developer carrier. It is preferable that the pressing elastic member has a roller shape. It is preferable that the press-contact elastic member is driven or has the same peripheral speed as the developer carrier. It is preferable that the pressure-contact elastic member is disposed on both the developer carrying portion and the developer non-bearing portion on the developer carrying member.

The developer is preferably a non-magnetic one-component developer. According to another aspect, it is preferable that the developer is a negatively chargeable magnetic one-component developer, and the developer carrier has a sleeve and a magnetic field generating means fixed inside the sleeve. The developer has a shape factor SF-1 of 10
0 to 180, and the shape factor SF-2 is 100 to 140
It is preferred that

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a developing device, a process cartridge and an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 Embodiment 1 of the present invention will be described below with reference to FIGS.

In the image forming apparatus of this embodiment shown in FIG. 1, a photosensitive drum 1 as an image carrier rotates in a direction of an arrow A, and is uniformly charged by a charging device 2 for charging the photosensitive drum 1. Then, an electrostatic latent image is formed on the surface of the photosensitive drum 1 by the laser beam 3 serving as an exposure unit for writing the electrostatic latent image.

This electrostatic latent image is developed by a developing device 4 which is disposed close to the photosensitive drum 1 and is detachable from the image forming apparatus main body as a process cartridge.
Visualize as a toner image. In this embodiment, so-called reversal development for forming a toner image on an exposed portion is performed.

The visualized toner image on the photosensitive drum 1 is transferred to the recording medium paper 13 by the transfer roller 9, and the transfer residual toner remaining on the photosensitive drum 1 without being transferred is scraped off by the cleaning blade 10. The photosensitive drum 1 stored and cleaned in the waste toner container 11 repeats the above operation to form an image.

On the other hand, the paper 13 onto which the toner image has been transferred is subjected to a fixing process by the fixing device 12, discharged outside the device, and the printing operation is completed.

The developing device 4 of this embodiment will be further described with reference to FIG.

Referring to FIG. 2, a developing device 4 includes a developing container 14 containing a non-magnetic toner 8 as a one-component developer and an opening extending in the longitudinal direction of the developing container 14 and facing the photosensitive drum 1. A developing sleeve 5 is provided as a developer carrier, and the electrostatic latent image on the photosensitive drum 1 is developed and visualized.

The developing sleeve 5 is provided laterally with the substantially right half circumferential surface shown in the drawing protruding into the developing container 14 at the opening, and the substantially left half circumferential surface exposed outside the developing container 14. The surface exposed to the outside of the developing container 14 faces the photosensitive drum 1 located on the left side of the developing device 4 in FIG.

The developing sleeve 5 is driven to rotate in the direction of arrow B. The surface of the developing sleeve 5 increases the probability of rubbing with the toner 8,
In addition, the toner 8 has appropriate irregularities for excellent conveyance of the toner 8. The developing sleeve 5 of this embodiment has a diameter of 16 m.
glass beads (# 6)
00), the surface roughness Rz of which is about 3 μm, and the gap with the photosensitive drum 1 is 3 mm.
And the peripheral speed of the photosensitive drum 1 is 50 μm.
It is rotated at a peripheral speed of 80 mm / s, which is slightly faster than mm / s.

In order to prevent the toner from leaking from both ends of the developing sleeve 5, end sealing members 19 are provided at the openings of the developing container to seal both ends of the developing sleeve 5.

A rubber material such as urethane or silicon or a SUS having spring elasticity is provided above the developing sleeve 5.
Alternatively, using a phosphor bronze metal sheet as a base,
The elastic blade 7 as a regulating member made of a rubber material adhered to the contact surface side of the
And is provided so that the vicinity of the tip on the free end side abuts on the outer peripheral surface of the developing sleeve 5 by surface contact. It is a so-called counter direction located upstream in the rotation direction.

The elastic blade 7 of this embodiment has a thickness of 1.0
mm plate-shaped urethane rubber is adhered to the blade supporting metal plate 15. The contact pressure against the developing sleeve 5 is 23 to 35 g / cm (the linear pressure is measured by using a thin metal plate having a known friction coefficient. Three sheets were inserted into the abutting portion, and one in the center was converted from the value obtained by pulling out with a spring only.)

The elastic roller 6 is in contact with the contact portion of the elastic blade 7 with the surface of the developing sleeve 5 on the upstream side in the rotation direction of the developing sleeve 5 and is rotatably supported.
As this structure, a foamed skeleton sponge structure or a fur brush structure in which fibers such as rayon and nylon are planted on a cored bar are used in terms of supplying the toner 8 to the developing sleeve 5 and removing undeveloped toner. Preferably, in the present embodiment, an elastic roller 6 having a diameter of 12 mm in which a polyurethane foam is provided on a cored bar 6a is used. The contact width of the elastic roller 6 with the developing sleeve 5 is 1 to 8 m.
m is effective, and it is preferable to provide a relative speed to the developing sleeve 5 at the contact portion thereof. In this embodiment, the contact width is set to 3 mm, and the developing operation is performed as the peripheral speed of the elastic roller 6. Occasionally, it was driven to rotate at a predetermined timing by driving means (not shown) so as to be 50 mm / s (the relative speed with respect to the developing sleeve 5 was 130 mm / s).

FIG. 3 is a view of the developing device 4 of FIG. 2 viewed from the direction of the photoconductor 1, and the developing sleeve 5 is not shown for convenience of explanation.

The elastic blade 7 is, as shown in FIG.
The distance from the contact nip with the developing sleeve 5 to the tip of the elastic blade 7 indicated by the hatched portion in the drawing is configured to be continuously shortened from the normal developing region to both ends of the elastic blade 7. The tip positions of the elastic blades 7 at both ends are configured to be within the contact nip. That is, the thickness of the toner layer formed on the developing sleeve 5 is affected by the distance from the point of the contact nip on the upstream side in the rotation direction of the developing sleeve 5 to the tip, and the longer this distance is, the more the toner layer is formed on the developing sleeve 5. It is conventionally known that the toner layer becomes thinner as the toner layer becomes thicker and shorter,
In this embodiment, compared to this distance in the normal development area, the distance is shortened by the area in contact with the peripheral surface of the developing sleeve corresponding to the non-contact portion in the longitudinal direction of the elastic roller 6, so that the toner in this area is reduced. Is increasing its regulatory power.

The toner 8 is a non-magnetic one-component developer,
As described above, when the transfer residual toner remaining on the photosensitive drum 1 without being transferred is excellent in lubricity when cleaning the same with a cleaning means such as a blade or a fur brush, the wear of the photosensitive drum 1 is reduced. A toner having advantages such as a small amount, that is, a toner having a spherical shape and a smooth surface is used. Specifically, the toner volume resistance value is 10 ¹⁴ Ω, and the measurement conditions are a measurement electrode plate area of 0.238 cm ² , a diameter of 6 mm, and a pressure of 1: 1.
Using a 500 g weight, a pressure of 980 / cm ² (96.1
kPa), powder layer thickness during measurement: 0.5 to 1.0 mm, 40
0V DC voltage applied micro ammeter (YHP4140pA
The amount of current is measured with a METER / DC VOLTAGE SOURCE, and a volume resistance value (specific resistance) is calculated from the resistance value.

As a shape factor, SF-1 is 100 to 18
0 and SF-2 of 100 to 140 is used. These SF-1 and SF-2 are Hitachi FE-
Using a SEM (S-800), a toner image was randomly
The sample is sampled, the upper part of the image is introduced into an image analyzer (Luzex3) manufactured by Nicole via an interface, analyzed, and the value obtained by the following equation is defined.

SF-1 = (MXLNG) ² / AREA × π / 4 × 10
0 SF-2 = (PERI) ² / AREA × π / 4 × 100 (AREA: toner projected area, MXLNG: absolute maximum length, PERI: peripheral length) The shape factor SF-1 of the toner indicates a spherical degree, and
As the value increases from 0, the shape gradually changes from a spherical shape to an irregular shape. SF-2 indicates the degree of unevenness. As the value increases from 100, the unevenness of the toner surface becomes more remarkable.

As for the method of producing the toner, if the shape factor falls within the range of the above-mentioned shape factor, in addition to the production method by the so-called pulverization method, JP-A-36-102231 and JP-A-59-5
No. 3856, a method of directly producing a toner using a suspension polymerization method, and a method of dispersion polymerization in which a toner is directly produced by using an aqueous organic solvent in which a polymer obtained is soluble and insoluble in a monomer. It can be produced by a method or an emulsion polymerization method typified by a soap-free polymerization method of directly polymerizing in the presence of a water-soluble polar polymerization initiator to form a toner.

In this embodiment, the shape factor S of the toner
F-1 is 100 to 180, SF-2 is 100 to 140
The suspension polymerization method under normal pressure or under pressure can be easily controlled, and a fine particle toner having a sharp flow distribution and a particle size of 4 to 8 μm can be obtained relatively easily. Styrene and n- Butyl acrylate, a salicylic acid metal compound as a charge control agent, a saturated polyester as a polar resin, and a colorant were added, and the weight average particle size was 7 μm.
m of colored suspended particles were produced.

Then, 1.5 wt.
%, The toner 8 having excellent transferability as described above and having a small amount of abrasion during cleaning of the photosensitive drum 1 was produced.

In the developing device 4 as described above, during the developing operation, as shown in FIG. 2 again, the toner 8 in the developing container 14 is fed in the direction of the elastic roller 6 with the rotation of the stirring member 16 in the direction of arrow C. Can be

Next, the toner 8 is carried to the vicinity of the developing sleeve 5 by the rotation of the elastic roller 6 in the direction of arrow D. The toner 8 carried on the elastic roller 6 is
At a contact portion between the developing sleeve 5 and the elastic roller 6, the toner is rubbed with the developing sleeve 5, thereby receiving a triboelectric charge and attaching to the developing sleeve 5.

Thereafter, as the developing sleeve 5 rotates in the direction of arrow B, the toner 8 is sent under pressure of the elastic blade 7, receives an appropriate tribo (amount of triboelectric charge), and becomes thin on the developing sleeve 5. A layer is formed. In the present embodiment, a good charge amount of −60 to −20 μC / g and a good toner coat amount of 0.4 to 1.0 mg / cm
^{2. The} thickness of the toner layer is set to be 10 to 20 μm.

However, if the toner 8 is repeatedly developed in a high-temperature, high-humidity environment, the charge amount of the toner 8 decreases.

Therefore, in this embodiment, in order to prevent the charge amount of the toner 8 from decreasing, the toner charging roller 20 as a pressure contact elastic member is pressed against the entire developer layer formed on the developing sleeve 5 and discharged. It was electrified.
The toner charging roller 20 is a rubber roller made of NBR,
It is attached to the pressing member 21. The contact load of the toner charging roller 20 against the developing sleeve 5 by the pressing member 21 was set to 100 to 200 gF. By the contact of the toner charging roller 20, the developer layer on the developing sleeve 5 is finely filled and uniformly coated. The longitudinal positional relationship between the elastic blade 7 and the toner charging roller 20 is preferably such that the toner charging roller 20 can cover the entire area of the developing sleeve 5 in contact with the elastic blade 7 as shown in FIG. preferable.

In this embodiment, after the toner 8 is regulated by the elastic blade 7, the toner 8 is regulated by the toner charging roller 20.
However, the toner charging roller 20 may also serve as the elastic blade 7.

The longitudinal positional relationship of the toner charging roller 20 on the developing sleeve 5 is such that the toner charging roller 20 is in contact with both the non-toner coated portion and the toner coated portion on the developing sleeve 5 as shown in FIG. This is because the toner charging roller 20 slips due to the high fluidity of the toner when the toner coating roller 20 is in contact only with the toner coat portion, and cannot be stably driven. Therefore, it is necessary to contact the non-toner coat portion. It is.

The driving of the toner charging roller 20 is required to be driven or at the same peripheral speed between the toner charging roller 20 and the developing sleeve 5. This causes the toner to transfer to the photosensitive member 1 as fog during development, and causes scattering or leakage of the toner.

The bias of the toner charging roller 20 branches an AC voltage (development AC voltage) obtained by superimposing a DC applied between the developing sleeve 5 and the photosensitive drum 1 by the power source 18 (see FIG. 2). Are applied by an equivalent circuit as shown in FIG.

The developing sleeve 5 and the toner charging roller 2
The waveform of the bias of 0 is as shown in FIG. 6, and the capacitor C in FIG. 5 is designed so that a potential difference between the developing sleeve 5 and the toner charging roller 20 occurs when the toner pullback bias is applied.
1. The capacity of C2 is adjusted. As described above, the toner 8 on the developing sleeve 5 receives the charge from the toner charging roller 20. Discharge is used as a method for applying charges.

In this embodiment, the bias applied to the developing sleeve 5 is a direct current voltage: Vdc = -300 V
C: A rectangular wave with Vpp = 2200 V and f = 2200 Hz superimposed. The bias applied to the toner charging roller 20 is Vdc = −900 V AC: square wave Vpp =
1000 V, f = 2200 Hz are superimposed.
There is no phase difference between the bias applied to the developing sleeve 5 and the bias applied to the toner charging roller 20.

Here, a method for applying a charge by the toner charging roller 20 will be described below.

As shown in FIG. 7, the toner charging roller 20
Is 10 ⁶ Ω, the toner surface potential behaves as shown by the solid line. Toner surface potential is applied voltage 0V
Also has a surface potential of -20V. This is because the elastic blade 7 was subjected to triboelectric charging. Excluding the surface potential due to the triboelectric charging, the discharge start voltage with the toner rises from -600 V at an inclination of 1 as shown by the dotted line in FIG. 7, and exhibits the same behavior as the DC discharge charging on the photoconductor.

The discharge start voltage of the toner charging roller 20 and the toner 8 is determined by the intersection of the following equations (1) and (2). That is, Vb = 312 + 6.2g (1) Vg = g (Va−Vc) / {(Lt / Kt) + g} (2) In the above equation, g: gap distance Vb: g> 8 μm Approximate expression of Paschen's law at the time of Vg: Air gap voltage on toner charging roller and toner layer surface Va: Voltage applied to toner charging roller Vb: Toner layer surface potential Lt: Toner layer thickness Kt: Toner layer relative permittivity

Since the toner 8 used in this embodiment has an excellent particle size distribution and a spherical shape, the ratio of toner to air in the toner layer is constant, and Kt (toner layer relative dielectric constant) in the formula (2) Rate) is stable, and charge is provided by stable discharge.

As another method for imparting charge to the toner, there is injection charging. In this case, the voltage applied to the toner charging roller and the toner surface potential behave as shown in FIG. FIG.
The middle and solid lines (thick) show the most ideal injection charging behavior.
It rises at an inclination of 1 from an applied voltage of 0V. The slope does not exceed 1 in the injection charging. The solid line (thin) and the dotted line show the behavior when the injection charging property is lowered.

From the above results, it is considered that the method of applying electric charge in this embodiment uses discharge.

Note that the above experimental results show that the toner charging roller 2
0 is the case where the entire area of the length 0 is in contact with the toner coat portion,
Actually, since both the toner-coated portion and the non-toner-coated portion are in contact with each other, if the resistance of the toner charging roller 20 is 10 ⁶ Ω, a current flows from the non-toner-coated portion and the toner The voltage does not satisfy the firing voltage. Then, the resistance range in which the toner can be discharged was examined. As a result, as shown in Table 1 below, 10 ⁷ Ω
In the following case, the voltage between the toner charging roller 20 capable of discharging toner and the toner coat portion cannot be obtained, and when the voltage is 10 ¹² Ω or more, the bias of the toner charging roller 20 is obtained from the developing bias in the configuration as in this embodiment. The firing voltage is too high and is not suitable. Therefore, the range of the resistance of the toner charging roller 20 is 10 ⁸ to 10 ¹¹ Ω. However, when the toner charging roller 20 has a dielectric layer on the non-toner coated portion where the toner charging roller 20 contacts, or when the resistance of the entire developing sleeve is high, the lower limit value of the appropriate range of the resistance of the toner charging roller 20 may be increased. Needless to say.

[0061]

[Table 1]

The method for measuring the resistance is as follows. That is, as shown in FIG. 9, the aluminum roller 22 having a diameter of 16 mm and the toner charging roller 20 are brought into contact with each other with a contact load of 170 gF, and the aluminum roller 22 having a diameter of 16 mm is rotated at 2 rps.
Rotate with. Next, V1 = 4 is applied to the toner charging roller 20.
A DC voltage of 00V is applied. A resistance of 10 MΩ is arranged on the ground side, the voltage V2 across the two ends is measured, the current is calculated, and the resistance of the toner charging roller 20 is calculated.

The discharge starting voltage between the toner charging roller 20 and the toner having a reduced charge amount in the toner 8 on the developing sleeve 5 is 1200 V or more. Therefore, the potential difference between the developing sleeve 5 and the toner charging roller 20 when the toner pull-back bias is applied is 1200 V or more, and the charge amount of the toner 8 after discharging is in a low-temperature and low-humidity environment (an environment where the charge amount of the toner is the highest). The capacitances of the capacitors C1 and C2 in FIG. 5 are adjusted so as to have the same charge amount.
Therefore, in the present embodiment, as shown in FIG. 10, the voltage applied to the toner charging roller is set to 1500 V at which there is no difference in the amount of toner charge between environment and durability. Note that under the above conditions, the toner charging roller 20 is kept under a low temperature and low humidity environment.
Even if a voltage is applied, the surface potential of the toner layer is high, so that the discharge starting voltage is not satisfied and no discharge is performed. Therefore,
Under both high-temperature, high-humidity, and low-temperature, low-humidity environments, the charge amount of the toner 8 becomes substantially equal.

After being charged by the toner charging roller 20, the thin toner layer formed on the developing sleeve 5 is uniformly conveyed to a developing section which is a portion facing the photosensitive drum 1.

In this developing section, the thin toner layer formed on the developing sleeve 5 is, as shown in FIG.
8, an AC voltage (developing AC bias) in which a direct current applied between both the developing sleeve 5 and the photosensitive drum 1 is superimposed.
Thus, the electrostatic latent image on the photosensitive drum 1 is developed as a toner image.

Undeveloped toner that has not been consumed in the developing section is transferred to the developing sleeve 5 as the developing sleeve 5 rotates.
Collected from the bottom of A seal member 17 made of a flexible sheet is provided at the collection portion to allow the undeveloped toner to pass into the developing container 14 and to allow the developing container 1
4 prevents the toner 8 inside the developing sleeve 4 from leaking from the lower part of the developing sleeve 5.

The collected undeveloped toner on the developing sleeve 5 is peeled off from the surface of the developing sleeve 5 at the contact portion between the elastic roller 6 and the developing sleeve 5. Most of the peeled toner is conveyed with the rotation of the elastic roller 6 and mixed with the toner 8 in the developing container 14.
The charge of the toner 8 is dispersed. At the same time elastic roller 6
With the rotation of, new toner is supplied onto the developing sleeve 5, and the above operation is repeated.

By providing the toner charging roller 20 as described above, the toner 8
After the passage, the charge is applied by the toner charging roller 20, and the charge amount of the toner 8 can be kept high. Therefore, in the longitudinal direction of the developing sleeve, it is possible to provide a developing device which maintains the charge amount of the toner uniform and high and is not affected by environmental fluctuations, and stably and favorably forms a thin toner layer on the developing sleeve. Becomes

In this embodiment, a case has been described in which the present invention is applied to a process cartridge comprising a developing device detachably mountable on the image forming apparatus main body. However, the present invention is fixed in the image forming apparatus main body and supplies only toner. The present invention may be applied to a developing device having such a configuration. Further, the present invention is applied to a process cartridge including at least the developing device and optionally forming all or some of the photosensitive drum, the cleaning blade, the waste toner container, and the charging device, and detachably attached to the image forming apparatus main body. May be.

Embodiment 2 Hereinafter, Embodiment 2 of the present invention will be described with reference to FIGS. As shown in FIG. 11, the developing device 24 of this embodiment omits the elastic blade 7 as the regulating member in the first embodiment, and attaches and detaches the same to the image forming apparatus main body shown in FIG. This is a flexible process cartridge.

In the developing device 24, during the developing operation, the toner 28 in the developing container 214 is sent toward the elastic roller 26 with the rotation of the stirring member 216 in the direction of arrow C.

Next, the toner 28 is carried to the vicinity of the developing sleeve 25 by the rotation of the elastic roller 26 in the direction of arrow D. The toner 28 carried on the elastic roller 26 is slightly frictionally charged by being rubbed with the developing sleeve 25 at a contact portion between the developing sleeve 25 and the elastic roller 26, and the toner 28 is thinned on the developing sleeve 25. A layer is formed. In this embodiment, a good toner coating amount is 0.4 to 1.0 mg / cm ² , and a toner layer thickness is 10 to 10 mg / cm ² .
It is set so that 20 μm and a charge amount of −20 to −10 μC / g can be obtained.

Thereafter, with the rotation of the developing sleeve 25 in the direction of arrow B, the toner charging roller 220 and the developing sleeve 2 are rotated.
6 is transferred to the contact portion.

In order to maintain the charge amount of the toner 28 uniform and high, the toner charging roller 220 is brought into contact with the entire area of the developer layer formed on the developing sleeve 25 and is charged by discharging.

The toner charging roller 220 and the developing sleeve 2
5, the voltage between the toners 28 is 15 as shown in FIG.
When the voltage is set to 00 V, there is no difference in the amount of charged toner in the environment and durability. Therefore, when the toner pull-back bias is applied, the developing sleeve 25 and the toner charging roller 220
The capacitances of the capacitors C1 and C2 in FIG. 5 are adjusted so that the potential difference becomes 1500 V. Thereafter, the thin toner layer formed on the developing sleeve 25 is uniformly conveyed to a developing unit which is a portion facing the photosensitive drum 1.

By providing the toner charging roller 220 as described above, after the toner 28 passes through the elastic roller 2,
The charge is applied by the toner charging roller 220, and the charge amount of the toner 28 can be kept high. Therefore, in the longitudinal direction of the developing sleeve, it is possible to provide a developing device that maintains the charge amount of the toner uniform and high and is not affected by environmental fluctuations, and can stably and satisfactorily form a thin toner layer on the developing sleeve. It becomes possible.

In this embodiment, the case where the present invention is applied to a process cartridge including a developing device which is detachable from the image forming apparatus main body has been described. The present invention may be applied to a developing device configured to replenish only the developer. Further, the present invention is applied to a process cartridge including at least the developing device and optionally forming all or some of the photosensitive drum, the cleaning blade, the waste toner container, and the charging device, and detachably attached to the image forming apparatus main body. May be.

Embodiment 3 Hereinafter, Embodiment 3 of the present invention will be described with reference to FIGS. In this embodiment, a magnetic one-component developer is used in the first embodiment, and a developing device 34 will be described with reference to FIG.

The developing device 34 of this embodiment is provided at a developing container 314 containing a magnetic toner 38 as a one-component developer and at an opening extending in the longitudinal direction in the developing container 314 so as to face the photosensitive drum 1. Developing sleeve 35 is provided, and the electrostatic latent image on the photosensitive drum 1 is developed and visualized.

Similar to the above embodiment, the developing sleeve 35 has a substantially right half circumferential surface shown in the drawing protruding into the developing container 314 at the opening, and a left substantially half circumferential surface exposed to the outside of the developing container 314 to be laterally provided. Have been. The surface exposed outside the developing container 314 is
It faces the photosensitive drum 1 located at the left side of the developing device 34 in FIG.

The developing sleeve 35 is driven to rotate in the direction of arrow B, and has four magnetic poles N1, N2, S1, S2 inside.
Is attached. The elastic blade 3 is provided on the peripheral surface of the developing sleeve 35.
7 and the toner charging roller 320 are brought into contact with each other in the same manner as in the first embodiment. Further, end sealing members 319 are provided at both ends in the longitudinal direction of the developing sleeve 35 as in the first embodiment.

In FIG. 1, the photosensitive drum 1 is uniformly charged to a charging potential Vd = −600 V by the charging device 2. Next, it is exposed by the laser 3 according to the image signal,
The potential of the exposed portion becomes the image portion potential V1 = -100 V, and an electrostatic latent image is formed in which the exposed portion is an image portion to which toner adheres. The electrostatic latent image formed on the photosensitive drum 1 is shown in FIG.
3 is developed by the developing device 34 shown in FIG.

The toner 38 of this embodiment is different from the non-magnetic one-component toners of the first and second embodiments in that a negatively charged magnetic one-component toner is used. 100 parts by weight of a styrene copolymer as a binder resin, 100 parts by weight of magnetic particles, 2 parts of a negative charge control agent,
Three parts of the wax are melt-kneaded with a heated twin-screw extruder, and the cooled kneaded material is roughly pulverized with a hammer mill, classified, and then sphered by a hybridization method.
A classified powder having an average particle size of 5.0 μm is obtained. Subsequently, 1.0 part by weight of hydrophobic silica fine powder was added to the classified product having an average particle size of 5.0 μm to obtain a developer. Toner 38 of this embodiment
Has a weight-average particle diameter in the range of 3.5 to 7.0 μm, and has the same resistance and shape as those in Example 1.

After the toner 38 in the developing container 314 is sent to the vicinity of the developing sleeve 35 by the stirring member 316, the developing sleeve 3 is driven by the magnetic field generated by the magnet roll 322.
5 and is conveyed with the rotation of the developing sleeve 35. Thereafter, the toner is conveyed to the developing area under the application of a tribo at the contact portion with the elastic blade 37 and the regulation of the layer thickness. The toner coat amount on the sleeve is 0.8 to 2.0 mg / cm ² ,
The toner layer thickness is 10 to 20 μm, and the toner charge amount is −
5-10 C / g is applied.

The developing sleeve 35 is a non-magnetic aluminum sleeve having a diameter of 16.0 mm, the surface of which is coated with a resin layer containing conductive particles.
m sleeve. Develop sleeve 35 to drum 1
It rotates at a peripheral speed of 00 to 140%.

A magnet roll 322 is fixedly arranged in the developing sleeve 35. One magnetic pole S1 of the magnet roll 322 is disposed so as to face the photoconductor 1, and the magnetic pole S1
The peak value of the magnetic flux density in the radial direction on the surface of
50-950G. A fog toner is formed in the developing area, and the fog toner is pulled back in the sleeve direction.

An alternating voltage obtained by superimposing a direct current and an alternating current is applied to the developing sleeve 35 from a power source 318 to form a developing electric field between the photosensitive member 1 and the electrostatic latent image is developed in accordance with the electric field. A DC voltage: Vdc = −5 is applied to the developing sleeve 35.
AC to 00V: square wave Vpp = 1600V, f = 180
A developing bias 318 superimposed with 0 Hz is applied. The developing sleeve 35 and the photoconductor 1 are opposed to each other with a gap of 300 μm at the closest position, and reversal development is performed.

However, when the toner 38 is repeatedly developed in a high-temperature and high-humidity environment, the charge amount of the toner 38 decreases.

In order to prevent the charge amount of the toner 38 from decreasing, the toner charging roller 320 contacts the entire area of the developer layer formed on the developing sleeve 35 and is charged by discharging.

Toner charging roller 320 and developing sleeve 3
5, the voltage between the toners 38 on the
When the voltage is set to 500 V, there is no difference in toner charge amount between environment and durability. Therefore, when the toner pull-back bias is applied, the developing sleeve 35 and the toner charging roller 32
The capacitances of the capacitors C1 and C2 in FIG. 5 are adjusted so that the potential difference of 0 becomes 1500 V.

Thereafter, the thin toner layer formed on the developing sleeve 35 is uniformly conveyed to a developing section which is a section facing the photosensitive drum 1.

By providing the toner charging roller 320 as described above, after the toner 38 has passed through the elastic blade 37, charge is applied by the toner charging roller 320, so that the charge amount of the toner 38 can be maintained high. Therefore, in the longitudinal direction of the developing sleeve, it is possible to provide a developing device that maintains the charge amount of the toner uniform and high and is not affected by environmental fluctuations, and can stably and satisfactorily form a thin toner layer on the developing sleeve. It becomes possible.

In this embodiment, the case where the present invention is applied to a process cartridge comprising a developing device detachable from the image forming apparatus main body has been described. However, the present invention is fixed in the image forming apparatus main body and only toner is supplied. The developing device can be applied to a process cartridge which is integrally formed with the developing device, the photosensitive drum, the cleaning blade, the waste toner container, and the charging device, and is detachable from the image forming apparatus main body. May be applied.

[0094]

As is apparent from the above description, according to the present invention, a bias having a voltage equal to or higher than the discharge starting voltage and having the same polarity as the developer is applied to the developer on the developer carrier by the press-contact elastic member. By doing so, in the longitudinal direction of the developer carrying member, a developing device that maintains the charge amount of the toner uniform and high and is not affected by environmental fluctuations, and an image forming apparatus including the developing device and capable of obtaining a good image , And at least the developing device, which can be detachably attached to the image forming apparatus, to provide a process cartridge excellent in handling.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus using a developing device according to a first embodiment.

FIG. 2 is a schematic configuration diagram of a developing device according to a first exemplary embodiment.

FIG. 3 is a view of the developing device of the first embodiment viewed from a photoconductor direction, with a developing sleeve not shown.

FIG. 4 is a diagram illustrating a developing sleeve when the developing device of the first embodiment is viewed from a photoconductor direction.

FIG. 5 is an equivalent circuit in the developing device according to the first exemplary embodiment.

FIG. 6 is a bias waveform diagram according to the first embodiment.

FIG. 7 is a graph showing toner discharge characteristics of a 10 ⁶ Ω roller.

FIG. 8 is a graph showing toner charging characteristics in the case of injection charging.

FIG. 9 is a schematic diagram for explaining a roller resistance measuring method.

FIG. 10 is a graph showing the relationship between the toner charging roller of Example 1 and the toner charge amount on the developing sleeve.

FIG. 11 is a schematic configuration diagram illustrating a developing device according to a second embodiment.

FIG. 12 is a graph showing a relationship between a toner charging roller of Example 2 and a charge amount of toner on a developing sleeve.

FIG. 13 is a schematic configuration diagram illustrating a developing device according to a third embodiment.

FIG. 14 is a graph showing the relationship between the toner charging roller of Example 3 and the amount of charge on the developing sleeve.

FIG. 15 is a schematic configuration diagram showing a conventional non-magnetic one-component developing device.

FIG. 16 is a view of the developing device of FIG. 15 as viewed from a photoconductor direction.

FIG. 17 is a view showing another example of the conventional developing device as viewed from the photoconductor direction.

[Explanation of symbols]

Reference Signs List 1 photosensitive drum (image carrier) 2 charging device 4, 24, 34 developing device 5, 25, 35 developing sleeve (developer carrier) 6, 26 elastic roller 7, 37 elastic blade (regulating member) 8, 28, 38 Toner (developer) 14, 214, 314 Developing container 20 Toner charging roller (pressing elastic member)

Claims (30)

[Claims] 1. A developing device comprising: a developer container for storing a developer; and a developer carrier extending and rotating at an opening of the developer container, wherein the developer carrier is provided on the developer carrier upstream of a developing unit. A developing device comprising: a press-contact elastic member, wherein the press-contact elastic member applies a bias having a voltage equal to or higher than a discharge starting voltage and having the same polarity as the developer to the developer on the developer carrier. 2. The developing device according to claim 1, further comprising a regulating member that comes into contact with or contacts the developer carrying member via a developer. 3. The developing device according to claim 2, wherein said regulating member is located upstream of said pressing elastic member in a direction of rotation of said developer carrier. 4. A rotatable elastic roller provided in contact with an abutting portion of the regulating member with the developer carrying member on an upstream side in a rotational direction of the developer carrying member. The developing device according to claim 2. 5. The developing device according to claim 1, wherein the pressing elastic member has a roller shape. 6. The apparatus according to claim 1, wherein the pressure contact elastic member is driven or has the same peripheral speed as the developer carrier.
6. The developing device according to any one of items 1 to 5. 7. The image forming apparatus according to claim 1, wherein the pressure contact elastic member is disposed on both a developer carrying portion and a developer non-bearing portion on the developer carrying member. The developing device as described in the above. 8. The developing device according to claim 1, wherein the developer is a non-magnetic one-component developer. 9. The developer according to claim 1, wherein the developer is a negatively chargeable magnetic one-component developer, and the developer carrier has a sleeve and a magnetic field generating means fixed inside the sleeve. The developing device according to any one of the above items. 10. The developer has a shape factor SF-1 of 100 to 180, and a shape factor SF-2 of 100 to 1
The developing device according to claim 8, wherein the number is 40. 11. An image forming apparatus main body, wherein at least a developing device having a developer container for storing a developer and a developer carrier extending to an opening of the developer container and rotating is integrally mounted on the image forming apparatus main body. In the process cartridge, the developing device is provided with a pressing elastic member on the developer carrier on the upstream side of a developing section, and the pressing elastic member causes the developer on the developer carrier to have a discharge start voltage or more and A process cartridge to which a bias having the same polarity as that of the developer is applied. 12. The process cartridge according to claim 11, further comprising a regulating member that comes into contact with or contacts the developer carrying member via a developer. 13. The process cartridge according to claim 12, wherein said regulating member is located upstream of said pressing elastic member in the direction of rotation of said developer carrier. 14. A rotatable elastic roller provided so as to abut on a portion of the regulating member that abuts the developer carrier on the upstream side in the rotation direction of the developer carrier. The process cartridge according to claim 12. 15. The process cartridge according to claim 11, wherein the pressing elastic member has a roller shape. 16. The process cartridge according to claim 11, wherein the pressing elastic member is driven or has the same peripheral speed as the developer carrier. 17. The image forming apparatus according to claim 11, wherein the press-contact elastic member is disposed on both a developer carrying portion and a developer non-bearing portion on the developer carrying member. The process cartridge as described. 18. The process cartridge according to claim 11, wherein said developer is a non-magnetic one-component developer. 19. The developer according to claim 11, wherein the developer is a negatively chargeable magnetic one-component developer, and the developer carrier has a sleeve and a magnetic field generating means fixed inside the sleeve. The process cartridge according to any one of the above items. 20. The developer has a shape factor SF-1 of 100 to 180 and a shape factor SF-2 of 100 to 1.
The process cartridge according to claim 18, wherein the number of the cartridges is 40. 21. An image having an image carrier on which a latent image is formed, and a developing device having at least a developing container for housing a developer and a rotating developer carrier extending to an opening of the developing container. In the forming apparatus, the developing device is provided with a press-contact elastic member on the developer carrier on the upstream side of a developing unit, and the press-contact elastic member causes the developer on the developer carrier to have a discharge start voltage or higher and An image forming apparatus, wherein a bias having the same polarity as that of a developer is applied. 22. The image forming apparatus according to claim 21, further comprising a regulating member that approaches or abuts on the developer carrying member via a developer. 23. The image forming apparatus according to claim 22, wherein the regulating member is located on the upstream side in the rotation direction of the developer carrier that is elastically pressed. 24. The image forming apparatus according to claim 20, further comprising a rotatable elastic roller provided so as to abut on a portion of said regulating member abutting on said developer carrier at a position upstream of said developer carrier in the rotational direction. The image forming apparatus according to claim 22. 25. The image forming apparatus according to claim 21, wherein the pressing elastic member has a roller shape. 26. The image forming apparatus according to claim 21, wherein the pressing elastic member is driven or has the same peripheral speed as the developer carrier. 27. The image forming apparatus according to claim 21, wherein the press-contact elastic member is arranged on both a developer carrying portion and a developer non-bearing portion on the developer carrying member. The image forming apparatus as described in the above. 28. The image forming apparatus according to claim 21, wherein said developer is a non-magnetic one-component developer. 29. The developer according to claim 21, wherein said developer is a negatively chargeable magnetic one-component developer, and said developer carrier has a sleeve and magnetic field generating means fixed inside said sleeve. The image forming apparatus according to any one of the above items. 30. The developer has a shape factor SF-1 of 100 to 180, and a shape factor SF-2 of 100 to 1
30. The image forming apparatus according to claim 28, wherein the number is 40.