JP2003255705A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent locking of a screw and fusing of toner to a screw end resulting from speed-up. <P>SOLUTION: A sleeve and a screw are driven separately, and an image duty and an amount of consumed toner are detected to control an amount of rotation of the screw. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine and a laser beam printer which use an electrophotographic system or an electrostatic recording system in which a developer is attached to a latent image formed on a photosensitive drum to form a visible image. The present invention relates to the image forming apparatus, and particularly to the developing apparatus.

[0002]

2. Description of the Related Art A two-component developing method using a mixture of a non-magnetic toner and a magnetic carrier as a developer is more advantageous than other methods in terms of image stability and developing unit durability. It is used in many full-color image forming apparatuses.

In FIG. 4, a developing device 101 is a developing container 102 for accommodating a two-component developer consisting of a non-magnetic toner and a magnetic carrier, and a developer carrying and conveying means rotatably arranged at its opening. It has a developing sleeve 103.

The developing sleeve 103 is made of a non-magnetic material, rotates in the direction of the arrow in the drawing during the developing operation, and has a magnet 105 as a magnetic field generating means fixed therein. The developing sleeve 103 containing the magnet 105 carries and conveys the two-component developer whose layer thickness is regulated in the developing area,
A developer is supplied to the photosensitive drum 128 in a developing area facing the photosensitive drum 128 to develop the electrostatic latent image formed on the photosensitive member.

The two-component developer after the electrostatic latent image on the photosensitive drum 128 is developed in the developing area and the toner is consumed is rotated from the developing area by the rotation of the developing sleeve 103.
It is transported into 01. Here, the magnet 105 is provided with adjacent magnetic poles having the same pole, and a region (repulsive magnetic field region) having a magnetic flux density of approximately 0 gauss is provided between the magnetic poles, and the two-component developer has the developing sleeve 10 in this repulsive magnetic field region.
3 is peeled off, and is accommodated in the developing container 102.

After that, the two-component developer that has consumed the toner is
The two-component developer in the developing container 102 is mixed and stirred, and again provided for development.

In the developing container 102, a rotatable first stirring member 104A for stirring the two-component developer housed in each of two compartments (developing chamber 102A and stirring chamber 102B) separated by a partition 106. The second agitating member 104B is arranged, and is rotated by receiving drive from the developing sleeve 103, and mixes and agitates the two-component developer in the developing container 102, and further circulates it in the developing container 102.

The toner consumed by the development of the electrostatic latent image is appropriately replenished from the toner cartridge 109 as the toner replenishing screw 110 rotates. The replenished toner is triboelectrically charged with the carrier by being mixed and stirred with the two-component developer in the developing container 102, and provided for development with a predetermined charge.

The mixing and stirring of the two-component developer will be explained. Regarding the transportation and the mixing and stirring of the two-component developer, in addition to the method shown in this conventional example, a transporting member whose feed direction is reversed is arranged coaxially. It is known that a two-component developer is circulated on the center side and the outer side of the shaft by rotating the shaft, and two stirring members are arranged vertically as in the conventional example.

When resin powder such as toner that easily softens enters the bearing portion of such a stirring member, agglomerates are generated by rubbing and fusion of the bearing portion is caused. Therefore, in the developing device 102 as in the conventional example, various measures have been taken to prevent the toner from entering the bearing portion.

As a first example of the stirring member bearing method, a magnetic material is formed near the end of the shaft of the stirring member, and a ring-shaped magnet is arranged so as to surround the circumference of the stirring member. There is a method in which the shaft is supported by a bearing or the like at the outer portion of the shaft while preventing the leakage. This method is suitable for an image forming apparatus that requires high productivity because there are few friction points between members.

As a second example of the stirring member bearing method, the shaft of the stirring member is made of metal, the surface of which is mirror-finished, and then the bearing is formed of a resin member having a high slip property so as to be in close contact with the mirror surface. There is. Since this method is less expensive than the first method, it is suitable for a low-price image forming apparatus.

[0013]

In recent years, the market for full-color image forming apparatuses has greatly expanded, and therefore high productivity and high durability are required regardless of the price range.
In order to meet this demand, the operating speed of the entire image forming apparatus tends to be higher, and of course, the developing device 101
Driving speed is no exception.

However, when the driving speed of the developing device 101 becomes high, the rotational speed of the stirring member which is driven by the developing sleeve 103 and rotates also increases. Therefore, with the configuration of the second example of the stirring member bearing method described above, the frictional heat between the shaft and the bearing portion is increased, and toner fusion is likely to occur, resulting in an image defect due to the toner fusion mass. Or
There is a possibility of causing trouble such as locking of the developing device 101. In addition, even if the friction points between the members are small as in the first example of the stirring member bearing method, the temperature of the bearing rises, and the temperature rises at the contact portion between the magnetic carrier and the stirring member shaft. Is likely to occur and cause similar problems.

In order to prevent such a problem, it is conceivable to reduce the rotational speed of the stirring member to reduce the shaft diameter of the stirring member to decrease the linear velocity. However, with this method, when the print ratio of the image to be formed is high, the supply of toner to the developing sleeve 103 cannot be kept up, and there is a risk of insufficient image density. In the other method, the strength of the shaft is impaired and vibration is generated, which may cause a malfunction.

Therefore, an object of the present invention is to suppress the temperature rise of the bearing portion due to the rotation of the agitating member, and to cause the problems such as the toner fusion and the image defect due to the toner fusion lump and the locking of the developing device. It is to achieve speeding up of a full-color image forming apparatus.

[0017]

The above object can be achieved by an image forming apparatus according to the present invention as described below.

The first image forming apparatus according to the present invention is an electrophotographic image forming apparatus provided with a two-component developing device using a non-magnetic toner and a magnetic carrier. 2 consisting of non-magnetic toner and magnetic carrier
A developing container for accommodating the component developer; a developer carrier rotatably installed in the developing container for carrying the two-component developer in the developing container and transporting it to the latent image carrier; A developer stirring member rotatably installed in the developing container for stirring the two-component developer in the developing container, wherein the developer carrying member and the developer stirring member are independent of each other. It is configured so that it can be driven at the timing of
The driving frequency of the developer stirring member is determined by a single parameter or a plurality of parameters reflecting the toner amount consumed by image formation, and the rotation driving amount of the developer stirring member is increased according to the increase in the toner amount consumed. The image forming apparatus is characterized in that it is driven so as to increase.

With the above structure, the temperature rise of the bearing portion due to the rotation of the stirring member can be suppressed, and the object of the present invention can be achieved.

The single or plural parameters reflecting the amount of toner consumed by image formation are as follows (1)
Or (6) can be considered.

(1) Printing amount or printing ratio of a document or image information input to the image forming apparatus (2) Exposure amount (3) of exposing means for exposing the latent image carrier of the image forming apparatus ) After the exposing means exposes the latent image carrier,
Result of potential measurement on the surface of the latent image carrier (4) Result of toner concentration detection in the two-component developer housed in the two-component developing device (5) Result of the two-component developing device on the latent image carrier Result of toner amount detection on the reference toner image formed by developing the formed reference latent image (6) Replenishment means for replenishing toner consumed by the two-component developing device in image formation The amount of toner replenished is the second, and the second of the image forming apparatus according to the present invention is a non-magnetic toner.
An electrophotographic image forming apparatus including a two-component developing device using a magnetic carrier and a two-component developing device, the two-component developing device containing a two-component developer including the non-magnetic toner and a magnetic carrier. And a developer carrier rotatably installed in the developing container for carrying the two-component developer in the developing container and transporting it to the latent image carrier, and the two components in the developing container. A developer stirring member rotatably installed in the developing container for stirring the developer is provided, and the developer carrying member and the developer stirring member can be driven at independent timings. The image forming apparatus is provided with a toner replenishing unit for replenishing the toner consumed by the two-component developing device in image formation, and the toner replenishing unit is driven. Source An image forming apparatus wherein the the same as the driving source of the toner replenishing means.

With the above structure, the object of the present invention can be achieved in a simpler and cheaper form than the first embodiment of the present invention.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) In the following,
A first embodiment of an image forming apparatus according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an outline of a full-color image forming apparatus of the present invention. The Y, M, C, and K stations have substantially the same configuration and form yellow (Y), magenta (M), cyan (C), and black (K) images in a full-color image, respectively. In the following description, for example, if there is the developing device 1, the developing device 1Y, the developing device 1M, the developing device 1C, and the developing device 1K in the Y, M, C, and K stations will be commonly referred to.

First, the operation of the entire image forming apparatus will be described with reference to FIG.

The photosensitive drum 28, which is a latent image carrier, is rotatably provided. The photosensitive drum 28 is uniformly charged by a primary charger 21, and an information signal is converted into an information signal by a light emitting element 22 such as a laser. Exposure is performed with light modulated accordingly to form an electrostatic latent image. The electrostatic latent image is visualized as a toner image by the developing device 1. Next, the visible image is transferred by the transfer charger 23 onto the transfer paper 24 conveyed by the transfer paper conveying sheet 27, and further, the fixing device 25.
To fix and obtain a permanent image. In addition, the photosensitive drum 2
The transfer residual toner on 8 is removed by the cleaning device 26. Further, the toner consumed in the image formation is replenished from the toner cartridge 9 to the developing device 1 as the replenishment screw 10 is driven to rotate.

Next, the operation of the developing device 1 will be described with reference to FIG. 2, which illustrates the Y, M, C, and K stations of FIG. 1 in detail.

In FIG. 2, the developing device 1 arranged to face the photosensitive drum 28, which is an image bearing member, includes a developing container 2, a developing sleeve 3 as a developer carrying means, and a stirring screw 4 as a developer stirring means. (4A, 4B). The developing container 2 is divided into two spaces by a partition wall 6, and each of them is composed of a non-magnetic toner and a magnetic carrier.
A component developer is contained. The space on the side of the developing sleeve 3 is called the developing chamber (2A), and the other space is called the stirring chamber (2B).

The developing device 1 has an opening in a developing area facing the photosensitive drum 28, and the developing sleeve 3 is rotatably arranged so as to be partially exposed in the opening. The developing sleeve 3 is made of a non-magnetic material and rotates in the direction of the arrow in FIG. 2 during the developing operation. Inside the developing sleeve 3, a magnet 5 as a magnetic field generating means is fixed. The developing sleeve 3 containing the magnet 5 is provided in the developing container 2.
The component developers are held in layers and carried to the developing area, and the two-component developer is supplied to the developing area facing the photosensitive drum 28 to develop the electrostatic latent image formed on the photosensitive drum 28.

Next, a characteristic part of the present invention will be described.

In the developing device 1 of this embodiment, the developing sleeve 3 and the stirring screw 4 are separate driving sources, that is, a developing sleeve driving mechanism 11 and a stirring screw driving mechanism 12, respectively.
Driven from.

The drive control of the developing sleeve drive mechanism 11 and the stirring screw drive mechanism 12 is performed by an engine controller (not shown) for controlling various operations of the image forming apparatus.

Basically, the developing sleeve 3 is provided with a latent image corresponding to an image portion while passing a portion opposed to the developing sleeve 3 (in the case of the present embodiment, 1000 m in A4 paper size transverse feed).
sec), it is controlled by the engine controller so as to be rotationally driven at a constant speed.

On the other hand, the stirring screw 4 can be driven by changing the rotation time T according to an instruction from the engine controller, and the rotation speed is constant at 500 rpm in this embodiment. The rotation speed is sufficient to stir an amount of toner that can be replenished from the toner cartridge 9 when a black solid image having an image ratio of 100% is taken and convey the toner to the developing chamber 2A.

The rotation time T of the stirring screw 4 is determined as follows. The image forming apparatus is equipped with the image information signal processing means (not shown) shown in FIG. This image information signal processing means forms an image at 600 dpi.
For each pixel (about 3.5 x 10 ⁷ pixels for A4 paper size), each density level (0 for white background, 2 for maximum density)
The pixel amount integrating means 14 for calculating the integrated pixel number P by integrating 256 steps (55). For A4 paper size, P is 8.9 x 1 at maximum (at maximum front density)
It can take the value of 0 ⁹ (pixel level). The integrated pixel number P calculated by the pixel amount integrating means 14 is transmitted to the engine controller by the image information signal processing means. In the engine controller, T corresponding to the value of P is calculated by the table 1 shown in FIG. Table 1
Is T = 500 (mse when P = 0 (pixel level)
c), P = 8.9 × 10 ⁹ (pixel level) and T = 10
It is set to be 00 (msec), and it is linear during that period.

The image with the highest copy frequency in the color market is mainly composed of characters, and the image ratio is about 5 to 10%, that is, P = 0.445 × 10 ⁹ to
The range is 0.89 × 10 ⁹ . That is, the stirring screw 4 of this embodiment uses 525 to 550 per A4 image.
It is rotated for (msec). Here, the rotation speed of the stirring screw 4 is 500 rpm, which is 10 rpm as described above.
If the image is driven for 00 msec, the amount of stirring and conveyance is sufficient for the toner consumption when the image ratio is 100%, so that the drive time is sufficient for the replenishment amount when the image ratio is about 5 to 10%.

In this way, by reducing the rotation time of the stirring screw 4 when the printing ratio is high, which is frequently used, it is possible to suppress the temperature rise of the bearing portion due to the rotation of the stirring member. Can be achieved.

In this embodiment, the integrated pixel number P calculated by the pixel amount integrating means 14 in order to detect the toner consumption amount.
However, it is of course possible to use a print ratio divided by the maximum value of the total number of pixels. In addition, the consumed toner amount can be detected from the integrated value of the light emission time and the light emission amount of the laser 22, the detection result of the surface potential of the photosensitive drum 28, and the effect of the present invention can be obtained as in the present embodiment. You can

Further, the toner density sensor provided in the developing device 1 and the reflectance of the reference toner image obtained by developing the reference latent image are reflected on the photosensitive drum 28, the transfer sheet conveying sheet 27, or on the transfer sheet or in the middle. The consumed toner amount can also be detected by the signal of the reference toner image reflection amount sensor detected on the transfer body. Here, the detection results of the toner concentration sensor and the reference toner image reflection amount sensor are the replenishment screw 10
Since it is usually used also for the drive control of, the rotation time of the stirring screw 4 may be controlled by the value used for the drive control.

Further, in the present embodiment, the rotation time of the stirring screw 4 is controlled based on the toner consumption amount detection result. However, this also makes the rotation time constant and increases or decreases the rotation speed, or the rotation time and rotation. Various forms are conceivable, such as controlling the speed together and controlling the rotation angle by detecting it.

Furthermore, in any case, the conversion table from the toner consumption amount to the rotation amount is not limited to that shown in FIG. 3, and a non-linear one or a step-like one may be used, or a set numerical value. The effect of the present invention can be obtained if the image ratio is small when the image ratio is low and large when the image ratio is high.

(Second Embodiment) Next, an image forming apparatus according to a second embodiment of the present invention will be described.

In the image forming apparatus of this embodiment, the drive of the supply screw 10 at each station is directly connected to the drive of each stirring screw 4. As described in the first embodiment, since the replenishment screw 10 is driven to supplement the toner consumed by the image formation, if the driving amount and the stirring screw 4 are connected by a gear or the like, the replenishment screw 10 of the present invention can be driven. The effect can be obtained with a simple and inexpensive structure.

However, in the case of the configuration of the present embodiment, the two-component developer separated from the developing sleeve 3 such as on the stirring chamber 2B side is not conveyed to the toner concentration sensor position until it is conveyed by the stirring conveyance of the stirring screw 4. It cannot be configured to reach. Therefore, it is preferable to replenish the toner by detecting the toner density near the developing sleeve 3 or by detecting the reflected light amount of the reference toner image.

[0045]

As described above, in the image forming apparatus according to the present invention, the developer carrier of the two-component developing device and the developer stirring member can be driven at independent timings. The driving frequency of the developer stirring member is a single parameter or a plurality of parameters that reflect the toner amount consumed by image formation, and the rotational driving amount of the developer stirring member increases as the toner amount consumed increases. The image forming apparatus is characterized in that the image forming apparatus is driven so as to be changed.

With the above structure, the temperature rise of the bearing portion due to the rotation of the stirring member can be suppressed, and the object of the present invention can be achieved.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating in detail the developing device 1 of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 illustrates an image forming apparatus according to a first embodiment of the present invention,
The figure explaining the relational expression of P and T.

FIG. 4 is a diagram illustrating a conventional example.

[Explanation of symbols]

1. Development device 2. Developer container 2A. Development room 2B. Stirring room 3. Development sleeve 4. Stirring screw (4A, 4B) 5. magnet 6. Partition 9. Toner cartridge 10. Toner supply screw 13. Engine controller 14. Image information signal processing means

Continued front page    F-term (reference) 2H027 DA10 DA21 DA45 DD07 DE02                       DE07 DE10 EA06 EB04 ED01                       ED10 EE02 EE03 EE07 FA05                       FA28 FB15                 2H077 AB02 AB22 AC02 AD06 BA02                       DA03 DA10 DA12 DA24 DA42                       DA47 DA63 DB01 EA03 GA13

Claims (3)

[Claims] 1. An electrophotographic image forming apparatus comprising a two-component developing device using a non-magnetic toner and a magnetic carrier, wherein the two-component developing device comprises the non-magnetic toner and a magnetic carrier. A developing container containing a two-component developer, and a developer carrier rotatably installed in the developing container for carrying the two-component developer in the developing container and transporting it to the latent image carrier. For stirring the two-component developer in the developing container,
A developer stirring member rotatably installed in the developing container, wherein the developer carrying member and the developer stirring member are configured to be driven at independent timings; The drive frequency is driven by a single parameter or a plurality of parameters that reflect the amount of toner consumed by image formation so that the rotational drive amount of the developer stirring member increases or decreases according to the increase or decrease in the amount of toner consumed. An image forming apparatus characterized by the above. 2. A single or a plurality of parameters reflecting the amount of toner consumed by image formation, including at least one of the following parameters (1) to (6): 1. The image forming apparatus of 1. (1) Printing amount or printing ratio of a document or image information input to the image forming apparatus (2) Exposure amount of exposure means for exposing the latent image carrier of the image forming apparatus (3) Exposure After the means exposes the latent image carrier,
Result of potential measurement on the surface of the latent image carrier (4) Result of toner concentration detection in the two-component developer housed in the two-component developing device (5) Result of the two-component developing device on the latent image carrier Result of toner amount detection of the reference toner image formed by developing the formed reference latent image (6) A toner replenishing means for replenishing the toner consumed by the two-component developing device in image formation Toner supply amount 3. An electrophotographic image forming apparatus comprising a two-component developing device using a non-magnetic toner and a magnetic carrier, wherein the two-component developing device comprises the non-magnetic toner and a magnetic carrier. A developing container containing a two-component developer, and a developer carrier rotatably installed in the developing container for carrying the two-component developer in the developing container and transporting it to the latent image carrier. For stirring the two-component developer in the developing container,
A developer agitating member rotatably installed in the developing container; the developer carrying member and the developer agitating member are configured to be driven at independent timings; , A toner replenishing means for replenishing the toner consumed by the two-component developing device during image formation, and a drive toner replenishing amount of the toner replenishing means, a drive source of the developer stirring member is a toner replenishing means of the toner replenishing means. An image forming apparatus, which is the same as a driving source.