JPH03140982A - Developing device - Google Patents

Abstract

PURPOSE:To always stir developer at an optimum speed even though the revolving speed of a magnet sleeve is varied in accordance with an original image by providing a driving device which variably rotates the magnet sleeve and a stirring member which is rotated at a constant speed regardless of the revolving speed of the magnet sleeve. CONSTITUTION:The magnet sleeve 42 is drive by a driving transmission means 46 provided with a developing device driving pulley 46a, a main driving belt 46b, a developing device driving gear 46c and a sleeve driving gear 46d and a driving device 48 consisting of a 1st motor 47. The revolving speed of the 1st motor 47 is made variable so as to drive the magnet sleeve 42 at a different revolving speed. On the other hand, a mixer 43 is always driven at the constant speed by a 2nd motor 50 through a mixer driving gear 49 and a motor gear 50a. Thus, by adjusting the revolving speed of the magnet sleeve 42 in accordance with the original image, the excellent image quality is obtained and the appropriate stirring is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a developing device for developing an image carrier using a magnetic brush in an image forming apparatus or the like.

(Prior art) In image forming devices such as electrophotographic devices and printers,
Conventionally, a so-called magnetic brush type developing device is used to develop an electrostatic latent image on a photoreceptor, which is an image carrier, in which a magnetic brush formed by the rotation of a magnetic sleeve around a magnet roller is brought into sliding contact with the electrostatic latent image. is frequently used. In addition, in recent years, with the diversification of information, documents with many characters or solid areas have strong contrast and high image density, making it difficult to clearly reproduce characters without blurring. On the other hand, for originals with many halftones such as photographic images, it is necessary to have high gradation density reproducibility, good resolution, even reproduction of halftones, and clear images without blurring of fine lines. is required.

However, in conventional magnetic brush type developing devices, the number of rotations of the magnetic sleeve is constant, so devices suitable for documents with many characters have poor halftone reproducibility. However, in the case of an apparatus suitable for photographic images, it was not possible to simultaneously satisfy the above-mentioned contradictory requirements, such as blurring of characters and solid areas.

For this reason, devices have also been developed that attempt to improve both image quality by varying the number of rotations of the magnetic sleeve depending on the original image.

However, in such devices, the stirring member is normally driven from the drive shaft of the magnetic sleeve, and when trying to vary the rotational speed of the magnetic sleeve,
The rotational speed of the stirring member has also been varied. For this reason, as the rotation speed increases, the load applied to the stirring member in particular increases, requiring high strength in both its structure and material, and also requiring an increase in the power of the driving power source. On the other hand, the ability to stir the developer in the developer container is significantly different between low-speed rotation and high-speed rotation. In addition, the developer generally has a characteristic that even if the stirring ability of the stirring member is large or small, a sufficient charge cannot be obtained, and the amount of charge is reduced. From this fact, if the stirring ability of the developer by the stirring member in the developer container is significantly different, such as when rotating at low speed and rotating at high speed, the developer cannot be uniformly charged and transported within the developer container, and the developer is This has the problem of being biased or hardened, which has a significant negative effect on image quality.

(Problems to be Solved by the Invention) Conventionally, as the rotation speed of the magnetic sleeve is changed depending on the document image, the rotation speed of the stirring member is also changed. Therefore, when rotating at high speed, the load on the stirring member increases, the strength of the stirring member itself is required, a larger drive power source is required to drive it, and furthermore, the stirring speed becomes uneven. Due to insufficient charging and non-uniform charging, there is a problem in that the developer becomes uneven or hardens, which has a significant negative effect on image quality.

Therefore, the present invention was made based on the above circumstances, and
Despite fluctuations in the rotational speed of the magnetic sleeve, the developer is uniformly stirred and charged without increasing the load on the stirring member, thereby extending the life of the stirring member and increasing the drive power. Furthermore, it is an object of the present invention to provide a highly reliable developing device that can charge the developer uniformly, improve the image quality, and improve image quality.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides a developer container provided at a development position of an image carrier, and a developer container supported by the developer container so as to face the image carrier. a magnetic field generating member, a magnetic sleeve that is rotatably provided around the magnetic field generating member and supports developer like a magnetic brush, a drive device that variably rotates the magnetic sleeve, and a magnetic sleeve that rotates at a constant speed regardless of the number of rotations of the magnetic sleeve. A rotating stirring member is provided.

(Function) According to the above-described means, the stirring member is always rotated at a constant speed even though the rotational speed of the magnetic sleeve is varied depending on the original image. To withstand overload without increasing the load,
There is no need to provide the stirring member with high strength or increase the driving power source. Further, since the developer is always stirred at an optimum speed, sufficient and uniform charging can be obtained, good development can be performed, and reliability of the apparatus can be improved by improving image quality.

(Example) An example of the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 is a schematic explanatory diagram of the inside of a copying machine main body 9, which is an image forming apparatus.

On the top surface of the copying machine main body 9, there is an operation panel including a document table 10 made of transparent glass, an input switch llb including a selection button lla for selecting the rotation speed of a magnetic sleeve 42, which will be described later, a copy button lid, and a display device 11c. A panel 11 is provided. A paper feeding means 12 is provided on the right side of the copying machine main body 9, and a paper ejection means 13 is provided on the left side. Further, inside the copying machine main body 9, there is an image forming means 14 for forming an image corresponding to the image information of the original on the original placing table 1O, and a sheet fed from the paper feeding means 12 through the image forming means 14. It has a conveyor belt IB for conveying it to the ejection means 18. Image forming means 14
has a photosensitive drum 17 rotatably supported within the main body 9 of the copying machine. Around this photosensitive drum 17,
Along the rotational direction, the charging device 18, the exposure section 20 of the exposure device 21 that irradiates the document (not shown) on the document table 9 and guides the reflected light 20a to the photoreceptor drum 17, the developing device 22, Transfer device 23, peeling device 24, cleaning device 26,
Static eliminators 29 are sequentially arranged. Further, the image forming means 14 includes a fixing device 27. Cooling fans 28 are provided on seven sides of the fixing device 27 to forcibly exhaust the warm air inside the housing IO and to introduce cooled air from outside.

The paper feeding means 12 includes upper and lower paper feeding cassettes 30a and 30b.
, and each -L side has paper 1. First and second pickup rollers 31 for taking out P2P. a, 81b are provided. Furthermore, 33.34 transfers the paper P to the transfer device 2.
3 is a guide plate that guides the photoreceptor drum 17 to the 3 side.
This is an aligning roller that aligns the leading edge of the paper P and sends it out in synchronization with the toner image above.

The ejection means 13 includes a pair of ejection rollers 37 for ejecting the paper P transported by the transport belt 16 to the outside of the copying machine main body 9, and a paper ejection tray 38 for receiving the ejected paper P.

Further, the developing device 22 includes, in its developing container 40, a magnet roller 41 which is a magnetic field generating member, and a magnet sleeve 42 which is rotatably provided around the magnet roller 41 and holds a magnetic brush 42a. Further, 43 is the developer container 4
a mixer that is a stirring member that stirs the developer 44 in 0;
44 is a leveler, and 45 is a scraper. The magnetic sleeve 42 is connected to the developer drive pulley 46a.
1 main drive belt 46b1 developer drive gear 4
It is driven by a drive device 48 consisting of a drive transmission means 4B having a 6C1 sleeve drive gear 4Bd and a first motor 47.

This first motor 47 moves the magnetic sleeve 42 three times.
00 [r, p, ml high speed rotation and 250 [r, p,
The rotation speed is made variable so that the low speed rotation of IIl is driven at different rotation speeds. On the other hand, the mixer 43 is always driven at 250 [r, p, ml] by the second motor 50 via the mixer drive gear 49 and the motor gear 50a.

Furthermore, FIG. 3 is a block diagram showing a control system of the copying machine main body 9, and 51 is a control device that controls the entire copying machine main body 9. As shown in FIG. On the input side of the control device 51, each input switch 11b1 such as a selection button lla on the operation panel 11 is provided.
Other switches/sensors necessary for image forming operations 52
is connected. Further, the output side of the control device is connected to a display device 11C on the operation panel 11, a paper feeding means 12, an image forming means 14 including a paper ejection means 13, a first motor 47, a second motor 50, etc. .

Next, I will talk about the effect. When the power source (not shown) is turned on, the control device 50 automatically selects a high-speed rotation mode suitable for documents with many characters and solid areas in the copying apparatus main body 9, and rotates the magnetic sleeve 42 at 300[rpm]. , p
, ml, and this fact is displayed on the display device lie. Therefore, if the original to be copied is a text original, input other copy conditions such as the number of copies and paper size on the operation panel 11 without operating the selection button lla, and then press the copy button lla.
Turn on the ID and start copying. As a result, as the photoreceptor drum 17 rotates, the steps of charging, exposure, development, transfer, and peeling are sequentially performed, and the paper P with the toner image is
is discharged to a paper discharge tray 38 via the fixing device 27, while the photosensitive drum 17 passes through the cleaning device 26 and is made ready for the next copy. However, at this time, in the developing device 22, the magnetic sleeve 42 is rotated by the first motor 47 at a high speed of 300 r, p, ml. Therefore, a high-density magnetic brush 42a is formed around the magnetic sleeve 42, and the electrostatic latent image on the photosensitive drum 17 is developed with high contrast to form a clear toner image. Become. On the other hand, the mixer 43 is rotated by the second motor 50 at a constant speed of 250 [r, I), +n]. Then, such copying operations are repeated to obtain the required number of copies. Then a new manuscript
In the case of a photo original containing halftones or a copy original, the operator inputs other copy conditions from the operation panel 11, turns on the selection button lla, and uses the control device 50 to turn the copying apparatus main body 9 into a half-tone image. Switch to a low speed rotation mode suitable for originals with many tones, and set the magnetic sleeve 42 to rotate at a low speed of 250 [r, p, ■]. As a result, the display device lie displays the fact that the rotation speed is low, and then the copy button lid is turned on to start copying. As a result, while copying, the mixer 43 is rotated by the second motor 50 at a constant speed of 250 [r, p side] similar to the high speed rotation mode, but the magnetic sleeve 42 is rotated by the first motor 50. 47, 25ocr, p.

I], and a magnetic brush 42a having a lower density than when rotating at a high speed is formed around it. Therefore, the electrostatic latent image on the photoreceptor drum 17 has good gradation reproducibility and fine line resolution, and in the case of photo originals, halftones are developed evenly and clearly, and further copies are made from the copy original. However, there is no smudging or blurring of characters.

In this way, even if copying is repeated while changing the number of rotations of the magnetic sleeve 42, the mixer 43 is always rotated at a constant speed by the second motor 50, so the developer 44 is kept in the developer container 40. is constantly stirred at an optimum speed, and is evenly and sufficiently charged within the developing container 40 without solidifying or becoming uneven.

With this configuration, by switching the rotational speed of the magnetic sleeve 42, it is possible to obtain a clear copy without blurring, even if the document has many characters or solid areas. For futon originals, gradation is evenly reproduced, clear copies can be obtained, and image quality can be significantly improved depending on the original. Moreover, since the rotation of the mixer 43 is kept constant regardless of the variation in the rotation speed of the magnetic sleeve 42, the load applied to the mixer 43 does not increase during high-speed rotation as in the conventional case.
There is no need to increase the power supply or strengthen the mixer to extend its life. In addition, since the developer 44 is always stirred stably at the optimum speed, it does not become uneven or solidify, and can obtain a uniform and sufficient electrical charge.
As a result, good image quality can be obtained.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be modified in various ways. For example, the rotation speed of the magnetic sleeve can be set arbitrarily depending on the required image quality2. The reference mode may be low speed rotation, and the mode may be switched to high speed rotation mode when necessary. Further, the optimum rotational speed of the stirring member is also arbitrary depending on the characteristics of the developer. Furthermore, the rotational speed of the magnetic sleeve may be varied not by varying the rotational speed of the motor, but by providing a plurality of gears with different gear ratios and selecting a predetermined gear.

[Effects of the Invention] As detailed above, according to the present invention, by adjusting the rotation speed of the magnetic sleeve according to the original image, even character originals that require high contrast and clarity can be processed.
In addition, gradation reproducibility is good, and good image quality can be obtained for both photo originals and copy originals that require high resolution. In addition, since the stirring member is always rotated at a constant speed regardless of fluctuations in the rotation speed of the magnetic sleeve, the life of the stirring member may be shortened due to the increased load during high-speed rotation, and the driving power supply There is no need for an increase in . Furthermore, because the stirring ability changes drastically between low-speed rotation and high-speed rotation, it is impossible to perform proper stirring, and there is no possibility of uneven toner distribution due to poor charging or toner solidification in the developer container. Sufficient and uniform charging can be obtained, and good images can be obtained.

[Brief explanation of the drawing]

1 to 4 show one embodiment of the present invention, FIG. 1 is a schematic explanatory diagram of the copying machine main body, FIG. 2 is a schematic perspective view of the copying machine main body, and FIG. 3 is a schematic illustration of the copying machine main body. A schematic block diagram of the control system; Figure 4 is a sectional view, and Figure 5 is a schematic side view from the rear side. 9... Copying machine body, lla... selection button, 17... photosensitive drum, 22... developing device, 42... magnetic sleeve, 43... mixer 47... first motor , 50... second motor.

Claims (1)

[Claims] A developer container provided at the development position of the image carrier, a magnetic field generating member supported by the developer container so as to face the image carrier, and a magnetic field generating member rotatably provided around the magnetic field generating member to distribute the developer in the form of a magnetic brush. a cylindrical magnetic sleeve supported by the magnetic sleeve, a driving device for variably rotating the magnetic sleeve, a stirring means provided in the developer container for stirring the developer, and a second driving means for driving the stirring means at a constant speed. A developing device characterized by comprising: