JP2008129242A - Developing device and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To more accurately detect a quantity of developer remaining in a developing device by removing the developer stuck to a remaining developer quantity detection means in the developing device, without causing a density decrease resulting from excessive supply (packing) to a developing darkroom with developer, and coarsened powder. <P>SOLUTION: A stirring and conveying member is composed of a flexible elastic member. When deflection of the stirring and conveying member which is disposed in a developer storage chamber and bent by a bending means for bending the stirring and conveying member, is released, the stirring and conveying member and the remaining developer quantity detecting means are made to collide with each other, thereby, developer stuck to or accumulated on the remaining developer quantity detecting means in the developing device is removed while a density decrease, resulting from excessive supply (packing) of the developing chamber with developer and coarsened powder is prevented. This prevents void and ensures more accurate detection of the quantity of remaining developer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing device that converts a latent image formed and supported on a latent image carrier into a visible image using a developer (toner), and a process cartridge including the developing device.

Conventionally, in an image forming apparatus employing an electrophotographic image forming process, a latent image carrier and process means for subjecting the latent image carrier to process processing such as charging and developing are integrally formed into a cartridge, and the cartridge A process cartridge system is widely used that can be detachably attached to the main body of the image forming apparatus. According to these process cartridge systems, the maintenance of the latent image carrier and each process means can be performed by the user himself / herself without depending on the service person, so that the operability is remarkably improved.

In addition, an electrophotographic image forming apparatus such as an electrophotographic copying machine or a laser beam printer forms a latent image by irradiating an electrophotographic photosensitive member as a latent image carrier with light corresponding to image information. An image is formed on the recording medium by supplying a developer (toner) to the image by using a developing means to visualize the image, and further transferring the image from the photoreceptor to the recording medium. Developer is stored in the developing means, and the developer is consumed by forming an image.

The image forming apparatus includes a developer amount detecting device that detects when the developer is consumed and notifies the user, that is, a developer remaining amount detecting device. The apparatus makes it possible to know from time to time how much developer that can be used for image formation remains in the developing device.

In particular, not only notifying the user that the developer has run out, but also detecting the amount of developer in sequence and notifying the user further improves the convenience for the user. In such an image forming apparatus, the amount of developer remaining when not used is calculated and notified to the user one after another, or the amount of developer has decreased so that image formation of a predetermined quality cannot be performed. In some cases, a “no developer” display is displayed to warn the user that the remaining developer is low before an image failure occurs.

As a means for detecting the developer amount, a metal rod serving as an electrode is provided at a location facing the developer carrying member or at a plurality of other locations, and the capacitance between the metal rod and the developer carrying member is provided. However, there is a technique that utilizes the fact that the amount varies depending on the amount of developer used as an insulating toner.

That is, if the space between the metal rod and the developer carrying member is filled with the developer, the capacitance between the metal rod and the developer carrier increases, and as the developer decreases, the ratio of air to the space between the two increases. The capacitance becomes smaller. Accordingly, if the relationship between the electrostatic capacity between the sheet metal and the developer carrying member and the remaining amount of the developer is obtained in advance, the remaining amount of the developer can be detected by measuring the electrostatic capacity.

However, in the case of the developer remaining amount detecting means as described above, if the developer is fed toward the electrode metal rod by stirring, the developer tends to adhere to or accumulate on the metal rod, and the measured electrostatic capacity is measured. An error may occur in the capacity, and as a result, there may be a case where the value of the remaining amount of developer detected by the remaining developer detecting means does not match the remaining developer amount actually remaining in the developing device.

For example, when the developer adheres to or accumulates on the electrode metal rod, a situation occurs in which the developer remains around the electrode metal rod but the developer is not supplied to the developer carrier. A state in which the entire area of the image cannot be visualized due to a small amount of developer on the developer carrying member and an image defect occurs (hereinafter, white void) may occur before the warning is issued.

In particular, in a high-temperature and high-humidity environment, moisture is adsorbed on the surface of the metal rod, which is an electrode, and the developer itself also adsorbs moisture. A problem that a blank image is generated before the image is generated easily occurs.

In order to solve the above problems, a method has been proposed in which an electrode is disposed within the rotation radius of the developer stirring member, and the developer accumulated on the electrode is removed by bringing the developer stirring member into contact with the electrode.

JP 2003-162139 A

However, in order to remove the developer deposited on the electrode, it is necessary to bring the developer stirring member into contact with the electrode many times or for a long time. When this is performed, the developer feed amount (conveyance) by the developer stirring member is required. As a result, the developer may be excessively supplied (packing) to the developing chamber, and the density may be reduced due to coarsening of the developer.

Therefore, an object of the present invention is to prevent excessive developer supply (packing) to the developing chamber and density thinning due to coarsening, to remove the developer attached to the developer remaining amount detecting means in the developing device, It is an object of the present invention to provide a developing device or a process cartridge including the developing device that can detect the remaining amount of developer in the developing device more accurately.

  A developing device according to the present invention is a developing device for developing an electrostatic latent image formed on a latent image carrier used in an image forming apparatus main body with a developer, and develops the latent image forming region on the latent image carrier. A developer chamber in which a rotatable developer carrying member for conveying and transferring the developer is disposed, a developer accommodating chamber for accommodating the developer adjacent to the developing chamber, and a developer in the developer accommodating chamber are conveyed to the developing chamber. And a stirrer / conveying member for detecting the remaining amount of developer in the main body of the developing device based on a change in electrostatic capacity between the rotatable agitating / conveying member and the developer carrier. The member is composed of an elastic member having flexibility, and when the bending of the agitating / conveying member bent by the bending means provided in the developer storage chamber for deflecting the agitating / conveying member is released, The developer remaining amount detection means To.

  According to the present invention having such a configuration, the developer adheres to or accumulates on the developer remaining amount detecting means in the developing device while preventing excessive developer supply (packing) to the developing chamber and density thinning due to coarsening. The developer can be removed, the occurrence of white spots can be prevented, and the developer remaining amount can be detected more accurately.

Further, the bending means may be a developer accommodating chamber that overlaps the stirring and conveying member side from the rotation radius of the stirring and conveying member.

Further, the amount of developer transported to the developing chamber by the stirring transport member may be 30 to 50 g / min.

Furthermore, the developing device may be included in a process cartridge that is detachable from the image forming apparatus.

According to the present invention, the developer adhered or deposited on the developer remaining amount detecting means in the developing device can be effectively removed by a simple method, and the accurate developer remaining amount can always be grasped. .

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of a printer as an example of an image forming apparatus including a process cartridge including a developing device of the present invention.

The image forming apparatus includes a rotatable photosensitive drum 1, a charging roller 2 serving as a charging unit around the photosensitive drum 1, an exposure device 3, a developing device 4, a transfer roller (transfer charger) 5, an electrostatic separation charging device (separation charging). 6) and a cleaning device 7 are disposed, and a fixing device 8 is disposed downstream of the electrostatic separation and charging device 7 in the conveyance direction of the transfer material P.

The photosensitive drum 1 is an organic photosensitive drum in the present embodiment, and is rotationally driven at a predetermined peripheral speed (process speed) in the arrow R1 direction. The charging roller 2 is connected to a charging bias power source 2a in which AC / DC is superimposed, and the surface of the photosensitive drum 1 is uniformly charged by a discharge product due to a corona discharge phenomenon generated in a minute gap between the charging roller 2 and the photosensitive drum 1. To do. The exposure device 3 performs image exposure L corresponding to the image information on the surface of the photosensitive drum 1 charged by the charging roller 2. The exposure apparatus 3 includes a laser driver 20, a laser diode 21, a polygon mirror 22, and a reflection mirror 23, and (intensity) modulation corresponding to the time-series electric digital image signal of image information input to the laser driver 20. The laser beam thus output is output from the laser diode 21, and image exposure L is performed on the photoconductive layer on the surface of the photosensitive drum 1 via the polygon mirror 22 and the reflection mirror 23, and an electrostatic latent image corresponding to the input image information is generated. It is formed.

The developing device 4 includes a developing sleeve 4a. The developing device 4 coats the toner stored in the developing device 4 on the developing sleeve 4a, and attaches the toner to the electrostatic latent image formed on the photosensitive drum 1 at the developing position. Thus, the toner image is visualized.

A recording material P (hereinafter referred to as a transfer material) P is stacked and stored in a paper feed cassette 40 located below the image forming apparatus, and a paper feed roller 41 is driven based on a paper feed start signal. The transfer material P in the paper feed cassette is fed one by one, is transported by the transport roller 42 and the registration roller 43, passes through the paper path 44, and is a transfer site that is a contact nip portion between the photosensitive drum 1 and the transfer roller 5. It is introduced into T at a predetermined timing. That is, the transfer of the transfer material P is controlled by the registration rollers so that the timing at which the leading edge of the toner image on the photosensitive drum 1 reaches the transfer site T and the timing at which the leading edge of the transfer material P reaches the transfer site T are synchronized. Is done.

The transfer material P introduced into the transfer site T is nipped and conveyed to the transfer site T. At that time, a predetermined transfer bias is applied to the transfer roller 5 from the high-voltage power supply 11. A transfer bias having a polarity opposite to that of the toner is applied to the transfer roller 5, whereby the toner image on the surface of the photosensitive drum 1 is electrostatically copied onto the surface of the transfer material P at the transfer portion T. An ammeter (not shown) detects a transfer current flowing through the photosensitive drum 1 via the transfer roller 5 and the transfer material P.

The transfer roller 5 as a contact transfer member is composed of an elastic layer 5a of an ion conductive sponge rubber (NBR rubber) and a cored bar 5b. The resistance value is measured in an N / N environment (23 ° C., 50% RH) and 2 kv applied. , 9.0E + 07 (9 × 10 7) rollers were used. Further, ATVC control was used as the transfer roller voltage control.

The transfer material P that has received the transfer of the toner image at the transfer portion T is separated and conveyed from the photosensitive drum 1, and is conveyed and introduced into the fixing device 8 through the paper path 45. Is discharged out of the machine by the paper discharge roller.

On the other hand, the transfer residual toner remaining on the surface of the photosensitive drum 1 after the toner image transfer is removed by the cleaning device 7.

In this embodiment, a negatively chargeable magnetic one-component toner is used as a toner that is a magnetic developer. The toner was prepared by adding 100 parts by weight of a styrene / n-butyl acrylate copolymer as a binder resin, 80 parts by weight of magnetic particles, 2 parts of a negative charge control agent of a monoazo iron complex, and 3 parts of a low molecular weight polypropylene as a wax at 140 ° C. Melt-kneaded with a heated twin-screw extruder, the cooled kneaded product is coarsely pulverized with a hammer mill, the coarsely pulverized product is finely pulverized with a jet mill, and the resulting finely pulverized product is air-classified and weight averaged. A classified powder having a diameter of 5.0 μm was obtained. Then, 1.0 part by weight of hydrophobic silica fine powder was mixed with a classified product having an average diameter of 5.0 μm with a Henschel mixer to obtain a developer.

The melt index (MI), which is an index of fixability of the developer, is 20 g / 10 min. Here, the melt index (MI) is measured using an apparatus described in JIS K7210 (an apparatus used for a thermoplastic flow test method), and the conditions at that time are [Condition] Measurement temperature: 125 ° C. , Load: 5kg, Sample filling amount: 5-10g
As measured by the manual cutting method. At this time, the measured value was converted into a 10-minute value.

The average particle size of the toner was measured using a Coulter Multisizer II type (manufactured by Coulter), and the weight-based weight average particle size D4 (μm) was determined from the toner volume distribution. In addition, as the toner of the developing device of the present embodiment, a toner having a MI of 3 to 30 g / 10 min and a weight average particle size of 3.0 to 7.2 μm can be used.

The developing sleeve 4a disposed facing the photosensitive drum 1 has, for example, a surface roughness Ra = 1.0 μm in which the surface of a nonmagnetic aluminum sleeve of φ16.0 is coated with a resin layer containing conductive particles. A sleeve is used, and the toner can be conveyed in the direction of the photosensitive drum 1 by rotating in a direction opposite to the clockwise direction. The developing sleeve 4a and the photosensitive drum 1 are opposed to each other with a gap of 300 μm at the closest position. Further, a magnet roller (not shown) fixedly arranged in the developing sleeve 4a can form magnetic fields at least at four positions of the N1, P2, N2, and S1 poles of the developing sleeve 4a. ing.

The developing blade 10 that is in contact with the developing sleeve 4a and regulates the amount of developer is formed of, for example, silicone rubber having a rubber hardness of JISA of 40 °, and the end of the developing blade 10 is a surface at a predetermined position of the developing sleeve 4a. The toner layer having a uniform thickness can be formed on the surface on the downstream side in the rotation direction of the developing sleeve from the position of the developing blade 10. At this time, the contact force P [P: contact load (gf) per unit length (1 cm) in the longitudinal direction of the developing sleeve] with which the developing blade 10 is in contact with the developing sleeve 4a was about 30 gf / cm. Further, the contact width (nip) between the developing sleeve 4a and the developing blade 10 is 1.0 mm, and the distance from the most upstream position to the free end of the developing blade with respect to the rotation direction of the developing sleeve at the contact portion is 2.0 mm. did. Under such conditions, the developer amount (toner coat amount) W on the developing sleeve 4a was about 1.30 (mg / cm @ 2).

FIG. 2 is a cross-sectional view of the developing device of this embodiment.

The developing device 4 is broadly divided into a developing chamber 4A in which a developing sleeve 4a is accommodated, a toner container chamber 4C in which a toner container 4D is accommodated, and a developer accommodating chamber 4B in which the developing chamber 4A and the toner container chamber 4C are connected. It is done. A replaceable toner container 4D is mounted in the toner container chamber 4C. When the toner in the developing device runs out, images can be continuously formed by replacing the toner container and supplying the toner. In the toner container 4D, a stirring unit 33 for conveying the toner is provided. As the agitating unit 33 rotates, the toner T in the toner container 4D is conveyed to the developer storage chamber 4B. In the developer storage chamber 4B, an agitating and conveying member 30 for conveying the toner T conveyed from the toner container 4D to the developing chamber 4A is disposed. As the stirring and conveying member 30 rotates, the toner T is supplied to the developing chamber 4A while being stirred. In the developing chamber 4A, a developing sleeve 4a that is a developer carrying member, a developing stirring bar 34 that supplies toner T to the developing sleeve 4a, and an electrode metal bar 100 (hereinafter referred to as an antenna bar) that is a developer remaining amount detecting means are provided in the developing device 4. It is arrange | positioned over the inner longitudinal direction.

As shown in FIG. 3, the stirring and conveying member 30 has a shaft 32 and a sheet 32 having a thickness of about 100 μm made of a material such as PET or PPS. A ladder-shaped hole 32B is formed in the sheet 32 in order to optimize the toner conveyance amount. The toner conveyance amount can be adjusted by changing the size of the hole 32B and the area of the free end side tongue portion 32A of the sheet 32. It is possible to adjust. As shown in FIG. 2, the sheet 32 penetrates (overlaps) the container rather than the storage chamber bottom 4E of the developer storage chamber 4B, and the storage chamber bottom 4E of the developer storage chamber 4B serves as the stirring and conveying member 30. It also functions as a flexible member. The stirring / conveying member 30 rotates while being bent, and when it exceeds the opening 35, the bending force formed by the deflection formed when the stirring / conveying member 30 is in contact with the storage chamber bottom 4E is released. The toner deposited on the antenna rod 100 can be scraped off.

The antenna rod 100 may be basically any material that can flow current, but in this embodiment, SUS that is resistant to rust is used as the material. For example, as shown in FIG. 1, an AC bias of about 2 KHz and a DC bias of about −400 V, which are normal development biases, are applied to the developing sleeve 4 a and the antenna rod 100. Then, an alternating current flows between the developing sleeve 4a and the antenna rod 100, a current value is measured by a current measuring device (not shown), and the capacitance is measured from this current value. By arranging this antenna rod 100 in the developing device 4 and observing a change in capacitance between the antenna rod 100 and the developing sleeve 4a as the toner T in the developing device 4 decreases, The remaining amount of toner T in the developing device 4 can be determined.

FIG. 4 shows a circuit configuration for detecting the toner amount in the developing device. As for the toner amount, when a predetermined AC bias is output from the developing bias circuit 104 as the developing bias applying means, the applied bias is applied to the reference capacitor 105 and the developing sleeve 4a, respectively. As a result, a voltage V1 (reference voltage) is generated at both ends of the reference capacitor 105, and a voltage V2 (antenna voltage) in which the toner amount is regarded as the electrostatic capacity C is induced between the developing sleeve 4a and the antenna rod 100. .

The detection circuit 109 generates a difference voltage V3 from the voltage difference between the input reference voltage V1 and the antenna voltage V2, and outputs the difference voltage V3 to the AD conversion unit 110. The AD conversion unit 110 outputs the result of digital conversion of the analog voltage V3 to the main body control unit 112. The main body control unit 112 recognizes the toner amount in the developing device 4 from the voltage value converted into the digital value.

As described above, in this embodiment, the image forming apparatus main body converts the electrostatic capacitance value detected by the toner remaining amount detection unit 101 into a voltage and outputs the voltage as shown in FIG. The relationship between the capacitance and the voltage varies depending on the circuit of the image forming apparatus, and the relationship between the capacitance and the voltage may be the same decreasing function or an increasing function.

In the developing device that detects the remaining amount of toner by means as described above, in the embodiment (1) of the present invention, as shown in FIG. 6, a PPS sheet having a thickness of 100 μm is placed on the buffer agitation bar 3 in the developing device 4. Was used, and the amount of penetration into the toner chamber was set to 3.0 mm, and the amount of overlap with the antenna rod was set to 1.0 mm. In the embodiment (2) of the present invention, as shown in FIG. 6, the thickness of the sheet is 75 μm. As a comparative example (1), the PPS sheet was set to have a thickness of 190 μm, and as the comparative example (2), a PPS sheet was set to have a thickness of 50 μm. The toner container 4D is filled with 500 g of toner, and an endurance test is performed until white spots occur in a high-temperature and high-humidity environment (32 ° C., 80%). The detected value from the toner remaining amount detection unit 101: difference voltage (antenna voltage− The transition of the reference voltage is shown in FIG.

The comparative example (2) has a configuration in which the PPS sheet is in contact with the antenna rod 100, but is not thick enough to remove the toner deposited on the antenna rod 100, and white spots occur near the differential voltage of 0V. Yes. Further, Comparative Example (1) has a configuration in which the thickness of the PPS sheet is increased, but the toner removing ability in the vicinity of the antenna rod 100 is strong, and the detected differential voltage value itself becomes low, so that sufficient latitude is taken. Is difficult. FIG. 8 shows the measured toner transport amount and toner particle size. The toner transport amount is determined by setting a toner container filled with 500 g of toner in the developing device and transporting it to the developing chamber in one minute. The toner particle size is obtained by measuring the toner particle size on the developing sleeve when white spots occur. According to this, the comparative example (1) having a strong toner conveyance amount has a large toner particle size. The large conveyance amount means that the stirring force is strong. Therefore, it is presumed that the frictional electrification of the toner is promoted due to excessive mechanical stirring, and the small particle size toner that tends to have a higher charge is developed. When the toner particle size is increased, the density becomes low due to toner charging failure and the image quality is deteriorated.

On the other hand, in the configuration used in the embodiments (1) and (2), the toner conveyance amount in FIG. 8 is 30 to 50 g / min, and the increase in particle size is suppressed to 1 μm or less. Further, from the difference voltage transition result of FIG. 7, no whiteout occurs before the detection difference voltage of 0V, and the voltage difference between the difference voltage when the toner is stable and the difference voltage when the toner is white is 0.6 to 0.7V. Is also secured. When the remaining amount of toner decreases, the agitating / conveying member conveys the toner while bending the bottom of the container, hits the antenna rod 100 in a form that is bounced beyond the DT opening and knocks. Since the toner adhering to the antenna rod 100 is effectively removed, the toner deposited on the antenna rod 100 can be effectively removed with a small toner conveyance amount configuration.

The toner deposited on the antenna rod 100 cannot be removed unless it comes into contact with a certain amount of force, but simply increasing the stirring force of the stirring / transporting member 30 increases the amount of toner transport, which causes packing in the developing chamber. In addition, it is necessary to satisfy both the toner conveyance amount and the contact force to the antenna rod 100. In the present embodiment, PPS having elasticity is used for the toner stirring sheet material, the toner conveying force is set to 30 to 50 g / min, and the toner deposited on the antenna rod 100 using the sheet bending force. By adopting a stirring configuration that removes the toner, it is possible to achieve both prevention of erroneous detection of toner remaining amount detection and prevention of developing chamber packing.

When the configuration of the present embodiment is used, the remaining amount of toner is detected because the stirring sheet is bent by the weight of the toner and does not collide even if it contacts the antenna rod 100 when the toner is sufficiently left in the first half of the life. No variation in voltage or noise occurs, and when the amount of toner decreases, the stirring sheet is bent and collided with the antenna rod using the force that is repelled, and the adhered or accumulated toner is scraped off. It has a feature that it can accurately detect the remaining amount of toner.

In this embodiment, the toner container bottom and the bending member are combined. However, a bending member may be separately provided at a position immediately before contacting the antenna rod 100.

The preferred embodiments of the present invention have been described above, but various modifications and changes other than those mentioned above can be made. For example, the image forming apparatus including the developing device of the present invention or the process cartridge including the developing device has been described by taking a printer as an example.

1 is a diagram illustrating a schematic configuration of a printer as an example of an image forming apparatus including a developing device of the present invention. It is a schematic block diagram of the developing device shown in FIG. FIG. 3 is a configuration diagram of a toner stirring rod according to an exemplary embodiment of the present invention. FIG. 3 is a circuit configuration diagram for detecting the amount of toner in the developing device according to the embodiment of the present invention. 4 is a relationship between a remaining toner amount and a detection voltage according to an embodiment of the present invention. 5 is a configuration table of an embodiment according to the present invention and a comparative example. 6 is a relationship between a remaining toner amount and a detection voltage in the embodiment according to the present invention and a comparative example. 6 is a toner conveyance amount and particle size result table of an embodiment according to the present invention and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging roller 3 Exposure apparatus 4 Developing apparatus 4a Developing sleeve (developing roller)
4A Developing chamber 4B Developer container chamber 4C Toner container chamber 4D Toner container 4E Developer container chamber bottom 5 Transfer roller 23 Controller 26 Main body remaining amount detection detector 30 Toner stirring rod 31 Toner stirring rod shaft 32 Toner stirring sheet member 35 D -T opening 100 antenna rod 104 development bias power supply 105 reference capacitor 109 detection circuit 110 AD converter T toner

Claims (4)

In a developing device for developing an electrostatic latent image formed on a latent image carrier used in an image forming apparatus main body with a developer,
A developing chamber in which a rotatable developer carrying member that conveys and transfers the developer to a latent image forming region in the latent image carrying member is disposed; a developer containing chamber that contains the developer adjacent to the developing chamber; Detects the remaining amount of developer in the developing device main body based on a change in electrostatic capacity between a rotatable agitating and conveying member for conveying the developer in the developer accommodating chamber to the developing chamber and the developer carrier. A developer remaining amount detecting means for
The agitating / conveying member is composed of an elastic member having flexibility, and when the bending of the agitating / conveying member bent by the bending means for deflecting the agitating / conveying member provided in the developer accommodating chamber is released. The developing device, wherein the agitating / conveying member and the developer remaining amount detecting means collide with each other. The developing device according to claim 1, wherein the bending unit is the developer storage chamber that overlaps the stirring and conveying member side with respect to the rotation radius of the stirring and conveying member. 3. The developing device according to claim 1, wherein an amount of the developer conveyed to the developing chamber by the stirring and conveying member is 30 to 50 g / min. In a process cartridge detachable from an image forming apparatus,
A process cartridge comprising at least the developing device according to claim 1.

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