JPS5967563A - Developer density detector - Google Patents

Abstract

PURPOSE:To seal an optical system completely from a developer and external dust for prevention against contamination, and to perform invariably stable developer density detection with high reliability, by supporting a developer container wherein a two-component developer of a carrier and toner is stored rotatably in a fixed housing, and arranging a developer detecting means in the space between the developer container and fixed housing. CONSTITUTION:A magnet roll 32 is fixed in the main frame 31 of a developing device 3 which has an opening in the surface facing a photoreceptor 2, and a nonmagnetic sleeve 33 which rotates as shown by an arrow alpha is provided outside the magnet roll. The developer 34 scooped up by this developing sleeve rubs against the photoreceptor surface in a brush shape after its layer thickness is adjusted by a doctor blade 33, visualizing a latent image on the photoreceptor surface. A shoot 41 has one end abutting on the developing sleeve 33 in a tangential direction and guides the residual developer removed from on the developing sleeve into a developer density detector 6. The optical system consisting of a light source 66 and a photodetecting element 67 is sealed completely by housings 63 and 64, so it is never stained with the developer, external dust, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device that visualizes a latent image formed on an image bearing surface by an image forming device such as an electrophotographic device, an electrostatic recording device, a magnetic recording device, etc. (for example, colored resin powder).

In this type of developing device, the mixing ratio of carrier and toner (developer concentration) is an extremely important factor in terms of the developing effect. That is, an electrostatic latent image is formed on a photoreceptor 2 by charging exposure 1, this is developed by a developing device 3, a toner image is transferred to paper 4, and this is fixed by a heat source 5 to obtain a copy. In Figure 1), the developer attached to the magnet rubs against the electrostatic latent image, and the latent image is developed with toner. As a result, the toner from the developer is gradually consumed and the ratio of toner to carrier decreases, that is, the concentration of the developer decreases and the density of the developed image gradually decreases. Therefore, toner is replenished as appropriate, but in that case, if more than the appropriate amount of toner is replenished, the density of the image becomes too dark and fog occurs.

Therefore, in order to continuously obtain images with desirable tones, it is necessary to maintain the concentration and level of the developer at appropriate levels.

Conventionally, as described in Japanese Patent Publication No. 38-17245, a method for automatically controlling the concentration of developer is to use different colors of carrier and toner, and adjust the mixed developer of carrier and I/toner according to toner consumption. Some devices optically detect the density of the developer by utilizing changes in the mixed color density, and control a toner replenishment mechanism to the developer according to the detected density to keep the developer density constant.

Also, as seen in Japanese Patent Publication No. 16199/1984, etc., a standard image on a photosensitive plate is developed, the developed density is optically detected by reflection or transmission, and correction is performed according to the density change.
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However, the former cannot detect the density if the carrier and toner have similar tones, and the latter requires a device to form an electrostatic latent image with a standard density on the photoreceptor, resulting in a complex configuration and a light source. The optical system, such as the photodetector and photodetector, will be exposed to toner stains. Many other methods have been proposed in which a reference electrode is provided in the developing device and the amount of toner adhering to the reference electrode is optically detected. It was necessary to add complex equipment for this purpose.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a developer concentration detection device capable of solving the problems of the conventional device described above and detecting developer concentration while stirring and mixing carrier and toner.

Embodiments of the apparatus of the present invention will be described below with reference to the drawings. FIG. 2 shows an example in which the developer concentration detecting device 6 of the present invention is provided inside the developing device 3. As shown in FIG. The developing device 3 includes a magnet roller 32 in a device main body 31 having an opening 30 on the surface facing the photoreceptor 2.
is fixed, and a non-magnetic developing sleeve 33 that rotates in the direction of arrow α is provided outside the magnet roller. The developer 34 drawn up by the developing sleeve has its layer thickness adjusted by a doctor blade 35, and then rubs against the surface of the photoreceptor like a brush to visualize the latent image on the surface of the photoreceptor. After development, the developer remaining on the developing sleeve 33 falls onto a screw roller 36 provided at the bottom of the apparatus main body 31, and a portion of the developer is sent to one end of the developing sleeve by the screw roller. A screw roller 38 is arranged parallel to the screw roller 36 with a partition wall 37 in between. The direction of the screw of this screw roller 38 is opposite to the direction of the screw of the screw roller 36, and when both rollers 36, 38 are rotationally driven in the same direction as indicated by the arrow by a rotational drive source (not shown), the screw roller 36. If the developer 34 is transferred from the front side to the back side of the paper surface, the developer is transferred from the back side to the front side of the paper surface depending on the screw roller 38. The transferred developer passes through openings 39 and 40 formed in the partition wall 37 at both ends of the screw rollers 36 and 38, respectively, and is transferred between the two screw rollers. Therefore, the developer concentration detection device 6 described later
The toner appropriately replenished onto the screw roller 38 from a toner hopper (not shown) in response to a detection signal is well stirred and mixed with the developer 34 circulating through the screw rollers 36-38 and the openings 39 and 4o.

One end of the shoe 1 41 contacts the developing sleeve 33 in a tangential direction, and guides the residual developer removed from the developing sleeve into the developer concentration detecting device 6 .

The developer concentration detection device 6 has an inlet 60 for receiving the developer from the chute 41 and an outlet 61, and a developer container 64 rotatably supported by a housing 63 via bearings 62a and 62b. Transparent developer concentration detection portions 65a formed oppositely on both sides of this developer C container
- Consists of a light source 66 and a light receiving element 67 provided in a housing 63 with 65b in between, and the housing 63 is provided in the apparatus main body 31 so that the rotating shaft portion 64a of the developer container 64 is substantially horizontal, and the rotating shaft portion 64a of the developer container 64 is In this configuration, the portion 64a is connected to a rotational drive source 42 disposed in the device main body 31.

In the above configuration, when the developer container 64 is rotationally driven, the developer carried in from the chute 41 moves in the axial direction inside the developer container 64 while being stirred, and falls into the apparatus main body 31 from the discharge port 61. do. Then, the toner according to the concentration of the agitating and moving developer is detected at the concentration detection portions 65a and 65.
The light receiving element 6 adheres to the inner surface of b and changes depending on the amount of adhesion.
The developer concentration can be detected by the output change of 7.

Here, the optical system consisting of the light source 66 and the light receiving element 67 is completely sealed by the housing 63, the bearings 62a and 62b provided in the housing, and the developer container 64, so that the developer, external dust, etc. not be contaminated by

In addition, the inner surfaces of the developer concentration detection sections 65a and 65b may be made conductive and grounded through the developer container 64, or between the developer container 64 and the concentration detection sections 65a and 65b, or between the concentration detection section 65a and the concentration detection section 65b. A bias voltage may be applied to stabilize toner adhesion.

As shown in FIG. 3, the developer container 64 in the example shown in FIG.
5a and 65b are formed. Figure 4 shows numbers 2 and 3.
A standard cell 43 with a reference transmission density is provided in a part between the circular density detection parts 65a and 65b in the figure, and the density determined by this standard cell 43 and the actual developer density due to the toner attached to the density detection parts 65a and 65b are alternately determined. This is used to detect and compare temperature and
Changes in the characteristics of the light source 66 and the light receiving element 67 based on the atmosphere such as humidity can be corrected.

In FIG. 5, a transparent window 44 is provided on a part of the circumferential surface of a developer container 64, and a reflective plate 45 is provided inside the container so as to face the window. The developer concentration is detected by changing the amount of light reflected to the light receiving element 67 depending on the amount of toner attached to the surface of the reflecting plate 45.

In this case, by using the amount of light reflected from the developer container itself without the transparent window 44 as the reference reflection density, changes in the characteristics of the light source 66 and the light receiving element 67 can be corrected in the same manner as described above.

FIG. 6 shows another embodiment of the apparatus of the present invention, in which two developing side temperature detecting devices 8 of the present invention are provided outside the developing device 3. The developing device 3 is integrally provided with a case portion 48 that bears long and short three-piece screw rollers 46 and 47 that protrudes from the end surface of the device main body 31 in the axial direction. A case portion 48b that bears the short screw roller 47 is provided with an inlet 49 for receiving the developer to be transported to the device 3, and a discharge port 50 for the developer sent out from the developing device 3 by the screw roller, and a replenishment toner container 51. A receiving port 54 is provided to receive the toner 53 that has fallen under its own weight from the end of the screw roller 52 inside.

The developer concentration detection device 8 includes a bearing 8 in a fixed housing 8o.
1a and 81b rotatably support the developer container 82, and a rotary drive source 83 is connected to a rotating shaft portion 82a penetrating one end wall of the fixed housing 80, and The case portion 48 is inserted into the developer container 82 through the opening 84. Two circumferential grooves 85 and 86 are formed on the outer periphery of the developer container 82.
Transparent windows 87 are provided oppositely on both sides of the U-shaped cross section between 86 and 86.
A-87b is provided, and a light source 88 and a light receiving element 89 are provided in the circumferential groove so as to sandwich this U-shaped portion. Also,
A plurality of developer stirring blades 9o are provided on the inner surface of the developer container 82.
is provided.

Since this example has the above-described configuration, when the developer container 82 is rotationally driven by the rotational drive source 83, the developer 34 inside
rotates around the case part 48 while being stirred by the stirring blade 9o, and a part of it is passed from the loading port 49 to the screw roller 4.
6 and is fed to the developing device 3 by the screw roller.

On the other hand, l·ner corresponding to the developer concentration is displayed through the transparent window 87a.
- The developer concentration is detected by the change in the output of the light receiving element 89, which changes depending on the amount of toner attached to the inner surface of the toner 87b. Based on this detection signal, the screw roller 52 in the replenishment toner container 51 is operated by a drive source (not shown),
The replenishment toner 53 is dropped onto the screw roller 47, mixed with the developer discharged from the developing device 3 by the screw roller, and fed in the direction of the arrow to be carried into the developer container 82 through the discharge port 5o. It is something to do.

As described above in detail, the apparatus of the present invention includes a developer container rotatably provided in the outer casing, and a developer container located in the space between the container and the outer casing, facing the developer concentration detection section of the developer container. An optical system for detecting developer concentration consisting of a light source and a light-receiving element is installed.
This optical system is completely sealed from the developer and external dust, so it is not contaminated and can always perform stable and reliable developer concentration detection. Further, by comparing the base i concentration and the detected concentration to detect the actual developer concentration, changes in the characteristics of the light source, light receiving element, etc. can be corrected, and the concentration can be detected with high accuracy. Furthermore, since the developer container is constantly rotated, the carrier and toner are well stirred and mixed, and a high quality developed image without density unevenness or capri can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an electrophotographic apparatus, FIG. 2 is a cross-sectional view of a developing device equipped with a developer concentration detection device of the present invention, FIG. 3 is a front view of a developer container, and FIGS. 4 and 5. 6 is a vertical sectional view showing a modified example of the developer container, and FIG. 6 is a vertical sectional view showing a modified example of the developer concentration detection device of the present invention. 3 is a developing device, 6 and 8 are developer concentration detection devices, 6408
2 is a developer container, 66 and 88 are light sources, and 67 and 89 are light receiving elements.

Claims (1)

[Claims] (1) A developer container containing a two-component developer consisting of carrier and toner is rotatably supported within a fixed body, and the developer is A developer concentration detection device characterized in that a concentration detection means is disposed in a space between the developer container and the fixed housing.