JP2001209240A - Developing device, process cartridge and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device, a processing cartridge and an image forming device realizing a developer surface capable of coping with both of a requirement for improving stirring ability and a requirement for improving toner concentration detecting accuracy with a simple constitution and having excellent quality. SOLUTION: In a 2nd screw 6 being a carrying member provided to freely rotate in a stirring chamber 10b, the pitch P1 of a blade in the vicinity of a replenishing port 11 being the replenishing part of a replenishing mechanism 12 is set to be larger than the pitch P2 of the blade in the vicinity of a measuring part by an inductance sensor 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device, a process cartridge, and an image forming apparatus using a two-component developer composed of a toner and a carrier.

[0002]

2. Description of the Related Art Conventionally, in a developing device provided in an image forming apparatus adopting an electrophotographic system such as a copying machine or a page printer, a two-component developing device has been used because of its excellent chargeability to toner. Is widely used.

Hereinafter, with reference to FIGS. 3, 5, and 6,
The two-component developing device will be described. Here, FIG. 3 is a schematic cross-sectional view (showing a state in contact with the photoconductor) of the developing device (a cross-sectional view perpendicular to the axis), and FIG. 5 is a schematic cross-sectional view of the developing device according to the related art (the axis). 6 is a schematic cross-sectional view (a cross-sectional view parallel to an axis and viewed from a side) of a developing device according to the related art.

The developing device generally carries a developer container 10, a developer transport member provided inside the developer container 10, and a developer transported by the developer transport member, and transports the developer further downstream. And a developing sleeve 2 as a developer carrying member for supplying toner to the latent image formed on the photoreceptor to develop the latent image.

[0005] The developing sleeve 2 is a hollow metal sleeve and has therein a magnet roller 3 serving as a magnetic field generating means.
And carries the developer by a magnetic attraction force.

The developer container 10 has two chambers, a developing chamber 10a and a stirring chamber 10b, both substantially parallel to the developing sleeve 2 with an inner wall 7 serving as a partition therebetween.
Each of these chambers is provided with a transport member for transporting the developer.

[0007] These transport members have a structure in which spiral blades are attached to a rotating shaft, are rotatably provided in each chamber, and have a mechanism for transporting the developer along the spiral by the rotation thereof. .

Here, for convenience of explanation, the conveying member in the developing chamber 10a is referred to as a first screw 105, and the conveying member in the stirring chamber 10b is referred to as a second screw 106. The first screw 105 and the second screw 106 are configured to convey the developer in opposite directions.

As shown in FIGS. 5 and 6, the developing chamber 10a and the stirring chamber 10b are not completely separated from each other by the inner wall 7.
There is provided a communication portion for communicating between the a and the stirring chamber 10b.

With the above configuration, when the first screw 105 and the second screw 106 rotate, the developing chamber 1
The developer circulates from 0a to the stirring chamber 10b via one communication part and from the stirring chamber 10b to the developing chamber 10a via the other communication part without interruption.

During the circulation, charging occurs due to friction between the toner constituting the developer and the carrier particles, and the toner is charged to a polarity for developing the latent image formed on the surface of the photoreceptor. Then, it is carried on the developing sleeve 2 in a charged state.

Here, an inductance sensor 9 as a measuring means for measuring the toner concentration in the developer is installed in the upstream part of the stirring chamber 10b.

That is, since only the toner in the developer is consumed by the developing operation, it is necessary to keep the toner concentration constant. Therefore, it is necessary to measure the toner concentration in the developer. Provided.

Since the two-component developer is composed of a non-magnetic toner and a magnetic carrier,
Since the magnetic permeability of the developer is determined by the amount of the carrier occupying a certain volume, the ratio between the toner and the carrier (toner concentration) can be measured by measuring the magnetic permeability of the developer with the inductance sensor 9.

A toner replenishing port 11 as a replenishing portion is provided slightly downstream of the inductance sensor 9. When toner is used during image formation and the toner concentration in the developer decreases, the developer is replenished. The amount of decrease in toner density is measured when passing through the inductance sensor 9, and an appropriate amount of toner is supplied into the developer container through the supply port 11 by the toner supply mechanism 12, and the toner concentration in the developer is always kept constant. It is a mechanism that is.

Here, a new developing device is provided with an initial developer adjusted to a predetermined toner concentration in advance.

Thus, when a new developing device is set in the image forming apparatus, the stirring member rotates for a certain period of time, so that the developer reaches the developing chamber and the stirring chamber evenly, and the developer circulates in a steady state. When the inductance sensor 9
To measure the toner density.

The value measured at this time is stored in a storage device (for example, a writable EP-ROM) mounted on the developing device, and the toner concentration inherent in the developing device is set as a standard value.

At the time of normal toner density control, by comparing the difference between the measured value and the standard value, it is possible to know how much the current toner density is different from the initial developer. The amount can be calculated.

Here, when designing a two-component developing apparatus,
Basically, the surface of the developer in the developer container (hereinafter, referred to as a developer surface) is substantially horizontal in the developing chamber and the stirring chamber.

If the developer surface in the developing chamber is inclined obliquely in the longitudinal direction, the amount of the developer supplied to the developing sleeve becomes uneven in the longitudinal direction, and a difference occurs in the longitudinal concentration. Further, when the agent surface of the stirring chamber is inclined, the charging performance due to stirring is reduced.

Further, the developing chamber is provided from the viewpoint of stable supply of the developer to the developing sleeve, and the agitating chamber is provided with the developer surface in each developing chamber being kept substantially horizontal from the viewpoint of improving the agitating property of the developer. Is adjusted to be slightly higher and the level of the agent in the stirring chamber is slightly lower.

[0023]

However, in the case of the above-described prior art, the partial requirements of the stirring chamber cannot always be satisfied.

As mentioned in the above description of the prior art,
It is preferable that the level of the agent in the stirring chamber is lower, and it is basically better that the level is lower than the top of the second screw 106.

The reason for this is that the stirring chamber has a purpose of stirring the replenished toner and developer. If the level of the developer becomes higher than the uppermost part of the second screw 106, the developer located at a higher position than the screw is stirred. Because it is hard to be worshiped.

In particular, if toner is supplied when the developer surface immediately below the supply port 11 is at a position higher than the uppermost portion of the second screw 106, the toner having a lower specific gravity than the developer may remain on the developer surface. There is.

In this case, the replenished toner does not easily mix with the developer, and almost uncharged toner is supplied to the developing sleeve side, which may cause a problem such as fogging or density defect.

On the other hand, if the developer surface is lower than the uppermost portion of the second screw 106, the toner is semi-forcibly taken into the developer with the rotation of the screw even if the toner is supplied, and the toner is sufficiently removed. No problems such as fogging and poor density occur due to stirring.

FIG. 6 shows a case where the agent surface is lower than the uppermost portion of the second screw 106 as described above.

As described above, while there is a demand for lowering the agent surface for the purpose of improving the stirring property, it is preferable that the agent surface near the inductance sensor 9 is higher.

The reason is that the inductance sensor 9 is originally provided to measure the ratio of the toner to the carrier (toner concentration) by measuring the magnetic permeability of the developer. In addition to the change, the change also occurs when the amount of developer near the sensor increases or decreases.

Therefore, it is preferable that the fluctuation of the developer amount near the sensor be as small as possible. Here, if the level of the developer in the stirring chamber is lowered too much, when the amount of the developer changes due to the toner concentration or the charge amount of the developer, the measured value is greatly affected, and the detection accuracy is reduced. There is a possibility that it will.

As described above, there is a contradiction between the desire to lower the agent surface for improving the stirring property and the requirement to increase the agent surface for improving the detection accuracy of the toner concentration. However, in the case of the above-mentioned prior art, these requests could not be answered.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and has as its object the purpose of improving the agitation performance and improving the toner density detection accuracy with a simple configuration. It is another object of the present invention to provide a developing device, a process cartridge, and an image forming apparatus which are excellent in quality and realize an agent surface capable of coping with the problem.

[0035]

According to the present invention, in order to achieve the above object, the present invention is provided so as to be rotatable in a stirring chamber,
A stirring chamber conveying member having spiral blades for conveying the developer including the toner and the carrier while stirring the toner in the rotation axis direction; a replenishing mechanism for replenishing the toner into the stirring chamber; and a toner in the developer. And a sensor for measuring the density of the developer, wherein the pitch of the blades of the conveying member in the stirring chamber near the replenishing unit by the replenishing mechanism is wider than the pitch of the blades near the measuring unit by the sensor. Features.

Accordingly, the flow rate of the developer conveyed near the replenishing section by the replenishing mechanism becomes faster, and the flow rate of the developer conveyed decreases near the measuring section by the sensor. In the vicinity of the measurement section, the level of the agent is high.

A developing chamber provided with the agitating chamber separated from the partition, a developing chamber transport member rotatably provided in the developing chamber and transporting the developer in the direction of the rotation axis, and both ends of the partition; And a communication portion that communicates with the developing chamber and the stirring chamber, and a communication member that is provided adjacent to the developing chamber and that is rotated by the conveying member and the conveying member in the developing chamber. And a developer carrier to which a developer circulating between the stirring chamber and the developing chamber is supplied.

It is preferable that the replenishing mechanism replenishes the toner by an amount based on a result measured by the sensor.

The sensor may measure the toner concentration in the developer by measuring the magnetic permeability of the circulating developer.

Further, in the process cartridge of the present invention, the process cartridge is detachably mounted on the image forming apparatus.
It has the developing device described above.

In the image forming apparatus of the present invention,
An image formed on a sheet is transferred by transferring an image developed by the developing device onto a sheet to be conveyed.

[0042]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the dimensions of the components described in this embodiment,
The materials, shapes, relative arrangements, and the like are not intended to limit the scope of the present invention only to them unless otherwise specified.

(First Embodiment) A developing device and an image forming apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a schematic cross-sectional view (cross-sectional view parallel to an axis and viewed from a side) of a developing device according to a first embodiment of the present invention, and FIG. 2 is a first embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of an image forming apparatus according to the first embodiment, and FIG. 3 is a schematic cross-sectional view (a cross-sectional view perpendicular to an axis) of a developing device (showing a state in contact with a photoconductor).

For the sake of convenience, the same components in the drawings referred to in the above description of the prior art will be described with the same reference numerals. Although FIG. 3 is referred to in the description of the related art, basic components other than the transport member are the same, and thus are referred to in the description of the present embodiment.

The description of the components described in the description of the related art, which are the same as those of the present embodiment, will be omitted as appropriate.

As shown in FIG. 2, the image forming apparatus has, as its main components, a photosensitive drum 1 serving as a latent image carrier, a charging device 20 for uniformly charging the surface of the photosensitive drum 1, and An exposure device 21 for irradiating light on the surface of the photosensitive drum 1 to form a latent image, a developing device 22 for visualizing the latent image formed on the surface of the photosensitive drum 1 with toner, Toner supply mechanism 12 for replenishment, and transfer device 25 for transferring the visualized toner image onto a transfer material
And a fixing device 26 for fixing the toner image transferred on the transfer material, and a cleaning device 23 for removing transfer residual toner remaining on the surface of the photosensitive drum 1.

As shown in FIGS. 1 and 3, the developing device 22 has a developer container 10, and the inside thereof is partitioned into a developing chamber 10 a and a stirring chamber 10 b by an inner wall 7.

A first screw 5 is provided in the developing chamber 10a as a conveying member in the developing chamber, and a second screw 6 is provided in the stirring chamber 10b as a conveying member in the stirring chamber.

These transport members have a structure in which spiral blades are mounted on a rotating shaft, are rotatably provided in each chamber, and have a mechanism for transporting the developer along the spiral by the rotation thereof. The first screw 5 and the second screw 6 are configured to convey the developer in opposite directions.

A developer in which the toner particles and the magnetic carrier particles are mixed is contained in the developing chamber 10a and the stirring chamber 10b. A toner replenishing mechanism 12 is provided above the stirring chamber 10b. And replenishment toner (non-magnetic toner) is stored therein.

A supply port 11 as a supply section is provided on the outer wall surface of the developer container, and an amount of toner corresponding to the toner consumed in the development is dropped from the toner supply mechanism 12 into the stirring chamber. Is done.

The toner replenishment mechanism is a known technique, and a description thereof will be omitted.

As the toner, a known toner obtained by adding a colorant, a charge control material, and the like to a binder resin can be used. In the present embodiment, a toner having a volume average particle diameter of 5 to 15 μm is used.

On the other hand, as the magnetic carrier, besides magnetic particles such as ferrite, magnetic particles coated with an extremely thin resin are preferably used, and the average particle diameter is preferably 5 to 70 μm. .

An opening is provided at a portion of the developer container 10 which is in close proximity to the photosensitive drum 1, and a developing sleeve 2 serving as a non-magnetic developer carrier such as aluminum or non-magnetic stainless steel is provided in the opening. Is provided.

The developing sleeve 2 contains a magnet roller 3 therein, and carries the developer by a magnetic attraction force, and rotates the developer in the direction of the arrow to transfer the developer in which the toner and the carrier are mixed. And carried.

Then, the thin developer layer formed on the surface of the developing sleeve 2 regulated by the developer layer thickness regulating blade 4 is applied to the photosensitive drum 1 which rotates in the direction of the arrow in FIG. The toner comes into contact as a brush, and only the toner adheres to the electrostatic latent image formed on the surface of the photosensitive drum 1 to be developed.

In FIG. 2, reference numeral 17 denotes a storage device provided in the developing device. In this embodiment, a readable / writable EP-ROM is used. The storage device 17 is electrically connected to the engine controller 27 by, for example, setting the developing device cartridge in the image forming device main body, so that the information of the cartridge can be read and written from the image forming device side.

In the present embodiment, the initial developer concentration (standard value) stored when the developing device is initially installed is stored.

In the toner supply, an appropriate amount of toner is replenished at any time in response to a replenishment toner request from the engine controller 27.

In this embodiment, the diameter of the developing sleeve 2 of the developing device is φ16 mm, and the number of revolutions is 3.5 rps. The diameter of the first screw 5 is 15 mm, the length is 380 mm, the number of revolutions is 5.0 rps, the pitch of the blades is 18 mm, the diameter of the second screw 6 is 15 mm, the length is 380 mm, and the number of revolutions is 5.5 rps. And

In the embodiment of the present invention,
In the second screw 6 which is a transport member rotatably provided in the stirring chamber 10b, the pitch P1 of the blade near the supply port 11 which is the supply section of the supply mechanism 12 is set to the value of the blade P near the measurement section by the inductance sensor 9. The feature is that the pitch is larger than the pitch P2.

That is, the blade pitch P1 near the supply port 11 is set to be larger than the other normal pitch P0, and the blade pitch P2 near the measurement section is set.
Is set smaller than other normal pitches P0 (P1>P0> P2).

In the present embodiment, as an example, the normal pitch P0 of the entire region in the longitudinal direction is basically 15 m.
m, 40 m near the measuring part of the inductance sensor 9
The pitch P2 in the region of m was 10 mm, and the pitch P1 in the region from 15 mm upstream of the supply port 11 to 35 mm downstream of the supply port 11 was 20 mm.

As described above, by making the pitch of the blades of the screw partially different in the longitudinal region, the flow rate of a certain amount of the developer conveyed by the screw is partially different. Fluctuate accordingly.

That is, since the agent surface becomes higher at a location where the flow velocity is slow and becomes lower at a location where it is fast, in the configuration of the present embodiment, the agent surface near the inductance sensor 9 having a narrow screw pitch rises, The agent level near the supply port 11 having a wide screw pitch fell.

As described above, with the simple configuration in which the pitch of the blades is made different, there is a demand for lowering the agent surface for improving the stirring performance and a higher agent surface for improving the detection accuracy (measurement accuracy). It is now possible to answer both of these requests.

With the above configuration, a high-density image and a low-density image were printed under the condition that toner was supplied, and the fluctuation of the developer surface in the stirring chamber was observed. Even if the amount of the sample slightly fluctuated, the agent level near the inductance sensor was always kept high, and a relatively stable detection result (measurement result) could be obtained.

Further, since the developer surface near the replenishing port is relatively low, there is no problem that the replenished toner floats on the developer surface without mixing with the developer. It was taken into the developer with the rotation of the screw, and sufficient stirring properties could be obtained.

Incidentally, regarding the dimensions, the diameter of the screw,
It depends on the rotation speed, the opening length of the developing chamber and the stirring chamber, the pitch of the screw blades, and the like. You need to be careful.

Regarding the setting of the screw pitch near the inductance sensor 9,
In consideration of the effective measurement range described above, it is desirable to predict and set a little stagnation a little downstream from the measurement unit of the sensor.

If the pitch is too narrow, the movement speed of the agent becomes too low and the detection (measurement) reaction becomes slow. Therefore, it is necessary to keep the reaction at an appropriate level.

Regarding the setting of the screw pitch in the vicinity of the supply port 11, if the screw pitch is too wide, the flow rate of the agent becomes too high.
The balance of the exchange with the first screw 5 is lost,
Conversely, the reduction in the stirring time deteriorates the toner's electric resistance. Therefore, it is only necessary to lower the agent surface near the replenishing port 11 to the extent that the agent surface works advantageously during toner replenishment.

In order to improve the agitation of the second screw 6, for example, a rib or the like may be provided on the screw shaft. Since the feature of the present invention is that the screw pitch differs in the longitudinal region, other configurations are not particularly limited.

By partially varying the screw pitch of the stirring chamber in consideration of the above conditions, it is possible to create an ideal state of the developer surface in the developing device with a cheap and simple configuration, and even in view of durability. Stable circulation of the developer can be realized.

(Second Embodiment) FIG. 4 shows a second embodiment. In the present embodiment, a configuration in which various members including the developing device are formed into a cartridge is shown.

The basic configuration and functions other than the cartridge configuration are the same as those of the first embodiment, and a description thereof will be omitted.

FIG. 4 is a schematic sectional view of a process cartridge according to a second embodiment of the present invention.

In the present embodiment, the developing device 22 described in the first embodiment is replaced with the photosensitive drum 1 and the photosensitive drum 1.
The cleaning device 23 is configured integrally with the charging device 20 as a process unit acting on the image forming apparatus, and is detachable from the image forming apparatus main body as a process cartridge.

As shown in FIG. 4, the process cartridge includes the photosensitive drum 1, a charging device 20, a developing device 22, and a cleaning device 23. The configuration and functions of the developing device 22 and the like are the same as those described in the first embodiment, and a description thereof will not be repeated.

As described above, by making the cartridge, in addition to obtaining the effects described in the first embodiment, it is possible to easily replace these components.

Accordingly, the maintainability of the image forming apparatus is significantly improved. Further, by replacing the cartridge, important components of the electrophotography are replaced with new ones, so that a high-quality image can always be maintained.

[0084]

As described above, according to the present invention, with a simple structure in which the pitch of the blades is changed appropriately, the agent level can be lowered near the replenishing section and raised near the measuring section. Therefore, it is possible to meet both the demand for improving the stirring property and the demand for improving the accuracy of detecting the toner density, and thus the quality is excellent.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a developing device according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a schematic sectional view of a developing device.

FIG. 4 is a schematic sectional view of a process cartridge according to a second embodiment of the present invention.

FIG. 5 is a schematic sectional view of a developing device according to a conventional technique.

FIG. 6 is a schematic sectional view of a developing device according to a conventional technique.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 2 developing sleeve 3 magnet roller 4 developer layer thickness regulating blade 5 first screw 6 second screw 7 inner wall 9 inductance sensor 10 developer container 10a developing chamber 10b stirring chamber 11 supply port 12 replenishing mechanism 17 storage device 20 charging Apparatus 21 Exposure apparatus 22 Developing apparatus

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masahide Kinoshita 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H077 AB02 AB18 AC02 BA08 BA09 DA10 DA35 DA54

Claims (6)

[Claims] 1. A stir chamber transport member having spiral blades, which is rotatably provided in a stirring chamber and transports a developer comprising a toner and a carrier while stirring in a rotation axis direction. A developing device comprising: a replenishing mechanism for replenishing toner; and a sensor for measuring the concentration of toner in the developer, wherein the sensor detects a pitch of blades of the conveying member in the stirring chamber near a replenishing unit by the replenishing mechanism. A developing device which is wider than the pitch of the blades in the vicinity of the measuring section. A developing chamber provided between the stirring chamber and the partition; a transport member rotatably provided in the developing chamber and transporting the developer in a rotation axis direction; and the partition. And a communication portion provided at both ends of the developing device and communicating with the developing chamber and the stirring chamber; and a communication member provided adjacent to the developing chamber and rotating by the stirring chamber conveying member and the developing chamber conveying member. 2. The developing device according to claim 1, further comprising: a developer carrier to which a developer that circulates through the stirring chamber and the developing chamber via the developer carrier is supplied. 3. The developing device according to claim 1, wherein said replenishing mechanism replenishes toner by an amount based on a result measured by said sensor. 4. The developing device according to claim 1, wherein the sensor measures the toner density in the developer by measuring the magnetic permeability of the circulating developer. 5. A process cartridge which is detachably mounted on an image forming apparatus and has the developing device according to claim 1. 6. An image formed on a sheet by transferring an image developed by the developing device according to claim 1 onto a conveyed sheet. Image forming apparatus.