JPH01251048A - Image forming device - Google Patents

Abstract

PURPOSE:To surely correct the difference of developer supply ability between plural developing devices in simple constitution by differentiating the surface shapes of developing sleeves in developing devices so as to make almost equal developer supply amount possessed by each developing device. CONSTITUTION:The title device is provided with plural developing devices D1 and D2 arranged facing a photosensitive body 1. The developing sleeves D12 and D22 are formed on the surface shapes each of which has different developer holding power so that the developing sleeves D12 and D22 provided on developing devices D1 and D2, respectively, have almost equal developer supply ability. Thus, the difference of the developer supply ability between plural developing devices D1 and D2 can surely be corrected in simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an image forming apparatus, and particularly relates to an image forming apparatus comprising a plurality of developing devices arranged opposite to a photoreceptor on which an electrostatic latent image is formed. .

(Prior Art) In recent years, various image forming apparatuses such as color copying machines include those in which a plurality of developing devices are installed in parallel with respect to a photoreceptor,
2. Description of the Related Art Various image forming apparatuses having a plurality of developing devices in one main body have been developed and put into practical use, such as one in which a plurality of replaceable developing devices are selectively installed and used. For example, in a full-color copying machine, four or three developing devices are installed in parallel facing one photoreceptor drum, and within each developing device, colors such as black, cyan, magenta, and yellow are mutually printed. Different developers are accommodated respectively.

In addition, twin color copying machines are equipped with a developing device that stores color developers in addition to a developing device that stores black developer. It is possible to exchange one at will.

Each of the plurality of developing devices used in such an image forming apparatus has a different capacity depending on the frequency of use. Generally, there are more black images than color images, so the black developing device is set to have the largest capacity, and the color developing device is set to be smaller than the black developing device.

However, if the sizes of the developing devices are made to be different from each other as described above, there is a problem in that there will be a difference in developer supply ability between the developing devices.

In other words, in a small-sized developing device, the developing sleeve that holds the developer and transports it to the developing area is also downsized, and as a result, the size, characteristics, and shape of the magnet installed in the developing sleeve are restricted. As a result, the developer holding capacity, that is, the developer transporting capacity is reduced. Therefore, a state of excessive toner concentration occurs in a small-sized developing device, which may lead to problems such as background stains or toner scattering. Further, the developer conveying ability may vary depending on the position where each developing device is placed, resulting in similar problems.

(Objective) Therefore, an object of the present invention is to provide an image forming apparatus that can reliably correct the difference in developer supply capacity between a plurality of developing devices with a simple configuration.

(Structure) In order to achieve the above object, the present invention includes a plurality of developing devices disposed opposite to a photoconductor, each of which has a plurality of developing devices that convey a developer while holding it on its surface. In an image forming apparatus provided with a developing sleeve that supplies toner to the electrostatic latent image formed on the photoreceptor, each of the developing sleeves provided in each of the developing devices has approximately the same amount of developer. Each developing sleeve is formed with a surface shape having a different developer holding power so as to have a sufficient supply capacity.

In an image forming apparatus having such a configuration, the surface shape of the developing sleeve provided in each developing device has a different developer holding power, that is, a different developer conveying ability, depending on the capacity and arrangement position of the developing device. As a result, the amount of toner supplied from each developing device is approximately the same.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 shows an example of a twin color copying machine to which the present invention is applied. Around the photoreceptor drum 1, there is a charging charger 2 that uniformly charges the surface of the photoreceptor drum 1 along the rotational direction of the photoreceptor drum 1, and a predetermined optical image is placed on the charged surface of the photoreceptor drum 1. an exposure optical system 3 that irradiates and exposes to form an electrostatic latent image, an eraser 4 that eliminates static electricity from non-image areas, a first developing device D1 and a second developing device D2 that develop and visualize the electrostatic latent image, and a developing device. A transfer charger 5 transfers the toner visible image obtained by the above onto the recording paper.
, a separation charger 6 for separating the transferred recording paper from the photoreceptor drum 1, and a cleaning device 7- for removing toner remaining on the surface of the photoreceptor drum after transfer.
′ ゛-Hibiki ■-11≠m, etc. are arranged. Further, in the transfer section where the transfer charger 5 is disposed, there is disposed a conveyor belt 9 that feeds and sends out the recording paper to the transfer section.

The first developing device D1 is a color developing device that uses color toner, and the second developing device 1D2 is a black developing device that uses black toner. , a larger capacity than the color developing device D1, which is used less frequently. These first developing devices D1
Developing sleeves DI2 and D22, which hold the developer and transport the developer to a developing area formed in a portion facing the photoreceptor drum 1, are provided in the developing casings 11 and D2i of the second developing device D2. are respectively provided, and the developing casing [) 11 and D
The developer stored in 21 is transferred to the developing sleeve [) 12
and [) 22, respectively, stirring roller D
13. D14 and D23. D24 is provided in each developing casing D11 and D21, respectively.

At the rear end portions of the developing casings [)11 and D21, there are cartridges D15 and D2 for storing new toner.
5 are arranged in series.

Further, each of the developing sleeves D12 and D22 has a surface shape shown in FIGS. 1(a) and 1(b). That is, in the developing sleeve DI2, the first
As shown in Figure (a), a plurality of grooves [ ) 12a having a double-shaped cross section are provided on the outer periphery of a cylindrical body having an outer diameter of 25φ. Each of the grooves [ ) 12a has a groove depth of 0.2 #I in the radial direction, a groove width angle of 6° in the circumferential direction, and the grooves [ ) 12a are formed adjacent to each other at a pitch of 12°. has been done. In addition, in the convex part formed between each of these groove parts [ ) 12a, 5 in the circumferential direction
The width angle is 6°, so the groove D
The concave portion in which I2a is formed and the convex portion are alternately arranged at equal intervals. Also, the groove D1
The groove depth of 2a is 0.2 m, and carrier particles (particle size 75~
100 μm>, which corresponds to the thickness of 2 to 3 layers, and the groove width angle of 6° is
10 to 30 of carrier particle diameter (75 to 100 μTrL)
The size is set based on the size equivalent to twice (1.0 to 1.5 mg+).

On the other hand, in the developing sleeve D22, as shown in FIG. 1(b), a plurality of grooves D22a having a V-shaped cross section are provided on the outer circumference of a cylindrical body having an outer diameter of 30φ. Each groove D
Each of the grooves 22a has a groove depth of 0.2 mm in the radial direction and is formed at a pitch of 7.2 degrees. Note that the groove depth of the groove portion D22a is 0.2 mm, similar to the developing sleeve [) 12, and the groove depth of the groove portion D22a is 0.2 mm.
The dimensions are set based on the thickness of three layers.

FIG. 2 shows the developer supply amount (vertical axis) with respect to the doctor blade developing sleeve interval (horizontal axis) when the above-mentioned developing sleeves D12 and D22 are used in such an embodiment. In this figure, the line ■ indicates the second developing device D2
In addition, the diagram ◎' shows the developer supply amount characteristics of the developing sleeve D12 in the first developing device D1. As can be seen from these figures, the developer supplying capacity of the developing sleeve D22 and the developer supplying capacity of the developing sleeve D12 are approximately the same. In addition, in this figure, the line ■' represents the surface shape of the developing sleeve D22 in the second developing device D2.
It shows the developer supply amount characteristics when the surface shape of the developing sleeve D12 in the first developing device D1 is taken as the surface shape. In this case, it can be seen that the developer supplying capacity of the developing sleeve D22 becomes too large. Furthermore, the diagram O is the first
The developer supply amount characteristics are shown when the surface shape of the developing sleeve D12 in the developing device D1 is set to the surface shape of the developing sleeve D22 in the second developing device D2.

It can be seen that in this case, the developer supplying ability of the developing sleeve D12 is significantly reduced.

In this way, each developing device D1. Each developing sleeve D12 provided in D2. By making each surface shape of D22 different from each other, each developing sleeve [)12. The developer holding power, that is, the developer transporting ability in [) 22 is adjusted, and as a result, the amount of toner supplied from each developing device [) 1 and [) 2 is made to be the same. ing. In other words, the developer holding capacity of each developing sleeve D12゜022 is determined by the cross-sectional area, groove width, groove depth, etc. of the grooves formed on the respective surfaces, and by increasing these, the developing sleeve D12゜022 can develop. It is possible to increase the developer holding capacity, that is, the developer transporting capacity.

The developing sleeve with the increased developer holding capacity can be replaced with a compact one whose developer carrying capacity is originally reduced due to restrictions on the size, characteristics, or shape of the magnet installed inside the developing sleeve. By applying the present invention to a developing device, the developer supplying capacity of a small developing device as in the above embodiment can be made comparable to that of a large-sized developing device.

In addition, in order to increase the developer conveyance capacity of the developing sleeve, it is possible to increase the distance between the doctor blade and the developing sleeve as shown in FIG. Manufacturing errors are likely to occur in the distance between the two, and therefore it is not preferable to strictly regulate the distance to adjust the amount of developer supplied.

(Effects) As described above, the image forming apparatus according to the present invention is capable of making the developer supply m of each of the plurality of developing devices almost the same regardless of the day or the arrangement position of each of the plurality of developing devices. Since the surface shapes of the developing sleeves in each developing device are made to be different from each other, differences in developer supply capacity between multiple developing devices can be reliably corrected with a simple configuration, and stabilization of the developing action is achieved. Problems such as background stains and toner scattering can be effectively avoided.

[Brief explanation of the drawing]

1(a) and 1(b) are partially enlarged cross-sectional views showing the surface shape of a developing sleeve in an embodiment of the present invention, FIG. 2 is a diagram showing the developer supply capacity of each developing sleeve, and FIG. FIG. 3 is a schematic side view showing a twin color copying machine as an example of an image forming apparatus to which the present invention is applied. 1... Photosensitive drum, DI, D2... Developing device,
DI2, 'D22...Developing sleeve, [)12a,
D22a--Groove. C≧

Claims (1)

[Claims] It is equipped with a plurality of developing devices disposed opposite to the photoreceptor, and each of the developing devices contains a developer that is conveyed while holding the developer on the surface thereof, and transfers it to the electrostatic latent image formed on the photoreceptor. In an image forming apparatus that is provided with a developing sleeve that supplies toner, each of the developing sleeves provided in each of the developing devices has different developer retention powers so that they each have approximately the same developer supply capacity. An image forming apparatus characterized in that each developing sleeve is formed in a surface shape having a surface shape.