JPH06110331A - Developing device - Google Patents

Abstract

PURPOSE:To accurately detect the accumulated amount of developer in a developer housing chamber and to keep developer amount stored in the developer housing chamber nearly a specified one so that an image may be formed well even though a developing device is miniaturized. CONSTITUTION:As to the developing device provided with the developing housing chamber 6 storing the developer, a developer carrier 2 carrying the developer from the developer housing chamber 6 to a developing area A faced to an electrostatic latent image holding body 1, and a developer carrying means 9 carrying the developer from a developer storing box 11 to which the developer is supplied from an external part to the developer housing chamber 6; a first and a second electrodes 5 and 7 are disposed on the developer housing chamber 6 in a state where the developer stored in the chamber is interposed, on the other hand, a developer amount detecting means 8 impressing an A/C voltage between the electrodes 5 and 7, and detecting current value flowing between the electrodes 5 and 7 is disposed, and a supply controlling means 10 drives the developer carrying means 9 based on the detecting signal from the developer amount detecting means 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in, for example, an electrophotographic copying machine or a laser printer, and more particularly, to a developer storage box provided outside the housing of the developing device to accommodate the developer in the housing. The present invention relates to an improvement of a developing device of a type in which a developer is appropriately supplied to a chamber.

[0002]

2. Description of the Related Art In recent years, copying machines and printers such as color copying machines and plus one-color copying machines capable of forming images of a large number of colors have become widespread. It is necessary to dispose a large number of developing devices around the electrostatic latent image carrier, and downsizing of the developing device is an important issue. Therefore, the size of the developer accommodating chamber provided in the housing of the developing device is minimized, and the developer is supplied from the developer storage box provided outside the housing to the developer accommodating chamber as needed. Has been used a lot.

In such a mechanism, the developer transport means for transporting the developer from the developer storage box to the developer accommodating chamber is
The drive must be controlled so that the amount of developer deposited in the developer storage chamber is always substantially constant. This is because the developer in the developer accommodating chamber gradually decreases unless the supply amount of the developer by the developer conveying means is smaller than the consumption amount of the developer for image formation. Causes a partial decrease in density and image defects. Further, if the developer supply amount by the developer conveying means is larger than the consumption amount of the developer, the developer in the developer accommodating chamber gradually increases, so that the developer clumps in the developer accommodating chamber, The developer is clogged in the transport passage leading from the storage box to the developer storage chamber.

In order to control the drive of the developer conveying means, it is necessary to accurately detect the amount of the developer accumulated in the developer accommodating chamber, which means is disclosed in JP-A-61-109082. It is disclosed in Japanese Patent Laid-Open No. 61-77070. The former Japanese Patent Laid-Open No. 61-109082 discloses a device for detecting the drive current of a motor for driving the developer carrier and detecting the amount of the developer accumulated in the developer accommodating chamber from this current value. .
The latter recording device disclosed in Japanese Patent Laid-Open No. 61-77070 includes means for accumulating the black level period of the image signal,
The consumption status of the developer is monitored from the accumulated value.

[0005]

However, the devices disclosed in these publications have the following problems. The detection device disclosed in Japanese Patent Laid-Open No. 61-109082 detects the amount of the developer in the developer accommodating chamber by the rotational load of the motor that drives the developer carrier. There is contact with a seal member for preventing the dissipation of the developer, and in this case, most of the rotational load of the motor is due to the contact friction. Therefore, it is not possible to separately detect the fluctuation of the rotational load due to the decrease in the amount of accumulated developer and the fluctuation of the rotational load due to other factors, and it is impossible to accurately detect the accumulated amount of the developer.

Further, in the recording apparatus disclosed in Japanese Patent Laid-Open No. 61-77070, the developer consumption is monitored only from the value obtained by integrating the black level period of the image signal. Since it is not possible to detect the variation in the amount of developer consumed due to the variation in the latent image potential on the image carrier, the error between the actual amount of developer consumed and the detected amount of developer consumed must be large.

A detection sensor using a piezoelectric element is generally used as another device for detecting the amount of accumulated developer in the developer accommodating chamber. However, when the developer accommodating chamber is downsized, the developer is detected. Since the contact pressure between the developer and the detection sensor becomes small, the amount of developer deposited cannot be accurately detected.

The present invention has been made in view of the above problems, and an object of the present invention is to accurately determine the amount of developer accumulated in the developer accommodating chamber even when the developing device is downsized. It is an object of the present invention to provide a developing device capable of performing excellent image formation by maintaining the amount of the developer stored in the developer accommodating chamber at a substantially constant amount.

[0009]

In order to achieve the above object, the developing device of the present invention has a developer accommodating chamber for accommodating the developer, and the electrostatic latent image holding member facing from the developer accommodating chamber. In a developing device provided with a developer carrier for carrying out the developer to the developing area, and a developer carrying means for carrying the developer from the developer storage box to which the developer is replenished from the outside to the developer containing chamber, In the developer accommodating chamber, the first and second electrodes are arranged so as to sandwich the developer stored in the chamber, while applying an AC voltage between these electrodes and flowing between the electrodes. A developer amount detecting means for detecting the current value is provided, and the supply control means drives the developer conveying means based on a detection signal of the developer amount detecting means. is there.

In such a technical means, as the first and second electrodes, the deposition level of the developer in the developer accommodating chamber depends on the amount of the developer consumed and the surface of the first and second electrodes. These electrodes may be arranged in any shape or at any position as long as they can be displaced along the direction. However, in view of the object of the invention to reduce the size of the developing device, the first electrode serves as a transport and supply member that rotates in the developer accommodating chamber to adhere the developer to the developer carrier, while the second electrode It is preferable that the fixed electrode is fixed to the wall surface of the developer accommodating chamber with a predetermined gap maintained between the conveying and supplying member.

When the first electrode is used as the carrying / supplying member, it is preferable that the carrying / supplying member is a conductive sleeve having a plurality of openings formed on its peripheral surface. With this configuration of the transport supply member, the developer also enters the hollow portion of the transport supply member, which improves the fluidity of the developer in the developer storage chamber and prevents the developer from being unevenly accumulated. can do. Therefore, the amount of the developer accumulated in the developer accommodating chamber can always be detected accurately.

Further, although the application of the AC voltage and the detection of the current value by the developer amount detecting means may be performed during the developing operation, a motor for driving the developer carrier and a developing bias voltage are generated during the developing operation. There is a lot of electrical noise from the high-voltage power supply, etc., and the amount of developer in the developer accommodating chamber is unstable, so it is not possible to accurately detect the current value corresponding to the actual amount of accumulated developer. Therefore, it is preferable that the application of the AC voltage by the developer amount detecting means is performed when the developing operation is stopped.

The AC voltage applied between the first and second electrodes is 0.1 V or more so that the detected current value is not affected by electrical noise generated from other power sources. Is desirable. On the other hand, avoid changing the charge amount of the developer due to the electric field created by the AC voltage between the electrodes,
Further, in order to prevent current from leaking from the housing or the like, the AC voltage is preferably 50 V or less, and its frequency is preferably 100 Hz to 100 kHz.

[0014]

According to such technical means, when the amount of the developer accumulated in the developer accommodating chamber decreases due to the consumption of the developer, the first electrode and the second electrode are sandwiched. The amount of developer is also reduced. Generally, the dielectric constant of the developer is larger than that of air, so that when the amount of the developer sandwiched between the first and second electrodes decreases, the capacitance between these electrodes decreases. That is, the first and second electrodes function like capacitors, and when a constant AC voltage is applied between these electrodes, the current flowing between the electrodes becomes smaller as the capacitance decreases. Therefore, when the value of the current flowing between the first and second electrodes falls below a predetermined specified value,
The supply control means determines that the amount of the developer accumulated in the developer accommodating chamber has fallen below a specified value, and drives the developer conveying means. As a result, the developer is supplied from the developer storage box to the developer storage chamber.

On the other hand, when a sufficient amount of the developer is introduced from the developer storage box into the developer accommodating chamber and the amount of the developer sandwiched between the first and second electrodes is increased, the space between these electrodes is increased. The capacitance increases and the current flowing between the two electrodes increases. Therefore, when the current value exceeds the prescribed value, the supply control means determines that the amount of the developer accumulated in the developer accommodating chamber exceeds the prescribed value, and stops the developer conveying means, or Decrease the agent delivery force. As a result, the supply of the developer from the developer storage box to the developer storage chamber is stopped or reduced.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The developing device of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows a first embodiment of a developing device to which the present invention is applied, and is arranged adjacent to an electrostatic latent image holder 1 which rotates in the direction of arrow B in the drawing.

Reference numeral 2 is a developer carrying member for carrying the developer from the developer accommodating chamber 6 provided in the housing 4 to the developing area A facing the electrostatic latent image holding member 1. The developer carrying member is provided on the peripheral surface. Attach and rotate in the direction of arrow C in the figure. The developer carrier 2 has a peripheral surface coated with a semiconductive layer such as phenol resin and has a diameter of about 5 to 40 m.
It is a round bar or hollow pipe made of aluminum or stainless steel of m.
The finish is Ra = 0.1 to 1.0 μm (preferably Ra = 0.2 to 0.4 μm). Mechanical polishing such as sud blasting, liquid honing, or emery polishing is used as the circumferential surface polishing method, and chemical polishing can be used in addition to mechanical polishing. When the material is aluminum, a semiconductive layer may be provided on the peripheral surface by anodizing treatment without coating with a phenol resin or the like. When the peripheral surface has a semiconductive layer, the volume resistivity in the thickness direction of the surface layer of the developer carrying member 2 is about 10 ⁵ to 10 ¹² Ωcm.

The developer carrying member 2 is usually set to rotate at 100 to 300 rpm and has a thickness of about 100 to 400 μm (preferably 150 μm).
It is opposed to the electrostatic latent image holder 1 while maintaining a gap of up to 300 μm). A DC bias AC voltage is applied between the developer carrier 2 and the electrostatic latent image carrier 1 by the developing bias power source 13, the AC component of which is 1000 to 4000 Vpp (peak-to-peak voltage), and the frequency is About 1-5kHz (preferably 2.5-4kHz),
The DC component is -50 to -400V. Further, the voltage of the AC component is preferably set so that the value obtained by dividing the peak voltage by the gap between the developer carrier 2 and the electrostatic latent image carrier 1 is in the range of 4 to 7 V / μm.

Further, reference numeral 3 is a developer regulating member for forming the developer adhering to the developer carrier 2 into a thin layer having a predetermined thickness, and the tip of a stainless steel leaf spring having a thickness of about 0.03 to 0.3 mm. It is made by vulcanizing and adhering a soft elastic body such as silicon rubber or EPDM rubber having a width of about 10 mm, a thickness of about 1 mm and a rubber hardness of 50 °. The developer regulating member 3 is attached to the holder 2
It is fixed to the housing 4 by 0 and the soft elastic body is about 20
It is in contact with the developer carrier 2 with a contact pressure of about 200 g / cm.
As a result, the developer attached to the surface of the developer carrier 2 is thinned to a thickness of about 5 to 30 μm, and a charge of about 2 to 20 μC / g is imparted by triboelectrification.

Further, reference numeral 5 in the drawing is a conveying and supplying member for supplying the developer stored in the developer accommodating chamber 6 to the developer carrying member 2, and has a diameter of about 10 to 20 mm and a wall thickness of about 1 to 4 mm. A plurality of elliptical or oval openings 5a are formed on the circumferential surface of the aluminum or stainless steel sleeve. The conveyance supply member 5 is arranged to face the developer carrying member 2 while maintaining a gap of about 0.5 to 2.0 mm, and rotates at a peripheral speed about 1 to 5 times that of the developer carrying member 2. A DC bias voltage of about 200 to 1000 V is applied between the carrier supply member 5 and the developer carrier 2 by the developer supply bias power source 14, and the developer is transferred to the carrier supply member 5 side by this potential difference. Is sucked from the developer carrier 2 side.

A fixed electrode 7 is arranged on the wall surface of the developer accommodating chamber 6 while maintaining a gap of about 0.2 to 5 mm with the transport supply member 5. The fixed electrode 7 is disposed on the side wall of the developer accommodating chamber 6 so that when the amount of the developer accumulated in the developer accommodating chamber 6 changes, the deposition surface moves along the surface direction of the fixed electrode. It has become. Further, a developer amount detection circuit 8 having an AC power source is connected between the electrode 7 and the conveyance supply member 5, and while applying an AC voltage between the fixed electrode 7 and the conveyance supply member 5. The current value flowing between the members 5 and 7 is detected, and the detection signal is output to the controller 10.

On the other hand, outside the housing 4, a developer storage box 11 to which the developer is appropriately replenished by a user such as a copying machine or a mechanic is disposed, and the internal space of the developer storage box 11 is a transport passage. 21 is connected to the developer storage chamber 6. The transport passage 21 has a screw-shaped transport member.
9 is provided, and when the conveying motor 9 is rotated by the dispense motor 12, the developer is replenished from the developer storage box 11 to the developer accommodating chamber 6.

The dispense motor 12 is a controller
Driven by control signals from 10. Controller 10
Checks whether or not the current value between the fixed electrode 7 and the transport supply member 5 is smaller than a preset current value, based on the detection signal fetched from the developer amount detection circuit 8.
When it is determined that it is small, the dispense motor 12 is driven for a certain period.

Reference numeral 15 in the drawing is a thin plate-like elastic member having a thickness of about 50 to 500 μm provided in contact with the surface of the feeding / supplying member 5, and the developer is fixed to the peripheral surface of the feeding / feeding member 5. Prevent. Further, reference numeral 16 is a seal member for preventing the dissipation of the developer, and a bias voltage is applied by a power supply 17.

The developer used in this example is a non-magnetic one-component type developer, and is used in various thermoplastic resins such as styrene resin, acrylic resin or polyester resin, and pigments such as carbon and metal-containing azo dyes are contained in the thermoplastic resin. Disperse the polarity control agent,
The size is adjusted to 5 to 20 μm by pulverization and classification, and a charge control agent is externally added. As the charge control agent, fine particles of hydrophobized silica, alumina, titanium or the like having a size of 0.1 μm or less are used, and hydrophobic silica is most preferable.

In the developing device configured as described above, the developer stored in the developer accommodating chamber 6 is transported and supplied by the feeding member 5.
Is introduced into the conveyance supply member 5 through the opening 5a of
The developer carrier 2 is dispersed in the axial direction of the developer carrier 2 while being stirred by the rotation of the transport supply member 5. Further, an electric field is generated between the carrier supply member 5 and the developer carrying member 2 by the bias voltage applied from the developer supply bias power source 14, and the carrier supply member
The developer in the inside of 5 and the vicinity of the feeding member is the developer carrier 2
Is sucked into.

The developer adhering to the surface of the developer carrier 2 is thinned and charged by the developer regulating member 3 and faces the electrostatic latent image carrier 1 by the rotation of the developer carrier 2. It is transported to the development area A. In this developing area A, an oscillating electric field is generated between the developer carrier 2 and the electrostatic latent image carrier 1 due to the DC superimposed AC voltage applied to the developer carrier 2, and the developer is attracted to this electric field. The developer carrier 2
From the side to the electrostatic latent image holding member 1 side, and finally adheres to the electrostatic latent image formed on the electrostatic latent image holding member 1 to develop it.

By repeating such a developing operation, the developer in the developer accommodating chamber 6 is consumed, and the deposition surface of the developer in the developer accommodating chamber 6 gradually decreases. That is,
As shown in FIG. 2 (a) → FIG. 2 (b), the deposition surface of the developer 18 existing between the fixed electrode 7 and the transport supply member 5 also decreases with time. Therefore, when the developer is consumed, the fixed electrode 7
The electrostatic capacitance of the pseudo capacitor formed by the transfer and supply member 5 gradually decreases, and the fixed electrode 7 and the transfer and supply member 5
The value of the current flowing between both members 5 and 7 also decreases when an AC voltage is applied between them. Figure 3 shows voltage 10Vrms, frequency 10kHz
When a sinusoidal AC voltage of is applied between the fixed electrode 7 and the transport supply member 5, the relationship between the current value flowing between these members 5 and 7 and the weight of the developer in the developer accommodating chamber 6 is shown. It is a graph shown. From this graph, it can be seen that the current value decreases in proportion to the decrease in the weight of the developer.

The developer amount detection circuit 8 applies an AC voltage between the fixed electrode 7 and the transport supply member 5 every time a series of developing operations is completed, and detects the value of the current flowing between both members 5, 7. To do.
Then, the detection signal is input to the controller 10. If the controller 10 determines that the detected current value is smaller than the preset threshold value, the dispense motor 12
The control signal is output to. As a result, the driving of the dispense motor 12 is started, and the transport member 9 moves the developer storage box 1
The developer is carried into the developer storage chamber 6 from 1.

On the other hand, when a sufficient amount of the developer is carried into the developer accommodating chamber 6, as shown in FIG. 2 (b) → FIG. 2 (a), the fixed electrode
Since the deposition surface of the developer 18 existing between the carrier supply member 5 and the carrier 7 rises, the capacitance of the pseudo capacitor formed by the fixed electrode 7 and the carrier supply member 5 gradually increases. That is, when an AC voltage is applied between the fixed electrode 7 and the transport supply member 5, the value of the current flowing between both members 5, 7 also increases. Therefore, the controller 10 stops the discharge motor when the current value detected by the developer amount detecting circuit 8 exceeds a specified value, and stops the carrying of the developer into the developer accommodating chamber.

As described above, in the developing device of this embodiment, the actual amount of the developer stored in the developer accommodating chamber 6 is electrically detected, and the developer is stored in the developer storage box 11 according to the detection result. Since the loading of the developer into the developer storage chamber 6 is controlled, the amount of the developer in the developer storage chamber 6 is always maintained substantially constant.

It should be noted that when the current value detected by the developer amount detection circuit 8 exceeds the specified value, it is not always necessary to stop the dispense motor 12, and the rotation speed of the dispense motor 12 is reduced to convey the sheet. It may be configured to reduce the developer transport amount per hour by the member 9.
It is also possible to set the prescribed value stepwise and to gradually reduce the developer conveying amount per time by the conveying member based on the comparison between the detected current value and each prescribed value.

In order to confirm the temporal stability of the technical effects of the present invention, a long-term print test was conducted under the following conditions using a copying machine equipped with the developing device of this embodiment. Electrostatic latent image carrier Negatively charged organic photoreceptor Process speed 160 mm / sec Developer carrier 24 mm diameter, rotation speed 180 rpm Phenolic resin coating (volume resistance 10 ⁶ Ωcm) Developer supply member diameter 19 mm, rotation speed 600 rpm Stainless steel development Agent control member Leaf spring made of SUS303, thickness 0.12 mm soft elastic EPDM rubber, thickness 1 mm Contact pressure with developer carrier is about 120 gf / cm Gap between electrostatic latent image carrier and developer carrier is about 200 μm Potential on electrostatic latent image carrier Latent image area -100V Background area -350V Development bias potential DC component -200V AC component 2400Vpp, Frequency 4kHz Bias power supply for developer 600V DC Developer Non-magnetic one component color developer (polyester system)

As a result, the amount of the developer in the developer accommodating chamber 6 is kept substantially constant even after the copying operation is performed on about 60,000 sheets, and the technical effect of the present invention is stable over time. Was confirmed.

[0035]

As described above, according to the developing device of the present invention, the developing device disposed in the developer accommodating chamber according to the change in the amount of the developer stored in the developer accommodating chamber. Since the value of the current flowing between the first and second electrodes changes, the amount of the developer in the developer accommodating material can be accurately detected by detecting this current value. Further, since the supply control means controls the drive of the developer transport means for transporting the developer from the developer storage box to the developer storage chamber based on the detected current value, the developer in the developer storage chamber is always used. Can be kept constant.

[Brief description of drawings]

FIG. 1 is a schematic view showing a first embodiment of a developing device of the invention.

FIG. 2 is a diagram showing the displacement of the developer between the conveyance supply member and the fixed electrode according to the first embodiment.

FIG. 3 is a graph showing the relationship between the weight of the developer in the developer accommodating chamber and the value of the current flowing through the fixed electrode.

[Explanation of symbols]

1 ... Electrostatic latent image carrier, 2 ... Developer carrier, 5 ... Transport supply member, 6 ... Developer storage chamber, 7 ... Fixed electrode, 8 ... Developer amount detection circuit, 9 ... Transport member, 10 ... Controller (Supply control means), 11 ... Developer storage box

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mikio Yamamoto 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd.

Claims (4)

[Claims] 1. A developer accommodating chamber for storing the developer, a developer carrier for discharging the developer from the developer accommodating chamber to a developing area facing the electrostatic latent image carrier, and a developer from the outside. In a developing device equipped with a developer transport means for transporting a developer from a developer storage box to be replenished to the developer accommodating chamber, the developer stored in the chamber is sandwiched in the developer accommodating chamber. While arranging the first and second electrodes,
A developer amount detecting means for applying an AC voltage between the electrodes and detecting a current value flowing between the electrodes is provided, and the supply control means is operated based on a detection signal of the developer amount detecting means. A developing device, characterized in that a developer conveying means is driven. 2. The first electrode is a carrying and supplying member which rotates in a developer accommodating chamber to adhere the developer in the developing chamber to a developer carrying member, and the second electrode is a predetermined part of the carrying and supplying member. 2. The developing device according to claim 1, wherein the developing device is a fixed electrode disposed on the wall surface of the developer accommodating chamber with a gap therebetween. 3. The developing device according to claim 2, wherein the feeding / supplying member is a conductive sleeve having a plurality of openings on its peripheral surface. 4. The application of the AC voltage by the developer amount detecting means is performed when the developing operation is stopped.
2 or the developing device according to claim 3.