JPH0486777A - Developing device - Google Patents

Abstract

PURPOSE:To properly maintain the toner concentration of developer and to stably obtain an image with high image quality by bringing a replacement blade into contact with the surface of a carrying path near a toner concentration detection means at the part of a developer carrying means which is opposed to the toner concentration detection means, scraping the developer and periodically replacing it. CONSTITUTION:The replacement blade 61 is fixed to a shaft 142a almost on the diameter of a carrying roller 142. Besides, it is disposed on both sides of a toner concentration sensor 51 in the direction of the shaft 142a. Then, the tip of the blade 61 is slided along the carrying path 141a of the developer by the rotation of the shaft 142a. The developer 145 on the detection surface of the sensor 51 is periodically replaced by the rotation of the blade 61. However, since the tip of the blade 61 is not brought into contact with the detection surface of the sensor 51, the developer 145 on the surface of the sensor and the periphery thereof is replaced by sliding and the blade 61 on the peripheral carrying path 141a. Thus, the toner concentration of the developer is always properly maintained and the image with high image quality is stably obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a developing device provided in, for example, an electrophotographic image forming apparatus.

(Prior Art) For example, an electrophotographic image forming apparatus is provided with a developing device for visualizing an electrostatic latent image formed on a photoreceptor. This developing device is classified into a two-component type and a one-component type. In the former, toner is attached to carrier particles and transported to the outer periphery of a developing roller, forming a developer layer and brought into contact with the surface of a photoreceptor drum, and is developed by the Coulomb force of the electrostatic latent image formed on the photoreceptor drum. The toner is separated from the carrier particles and attached to the latent image area. In the latter method, a developer layer is formed on the outer periphery of the developing roller using toner alone, and the toner is similarly attached to the latent image area.

In any of the above cases, it is necessary to keep the toner concentration in the developer layer constant, and the former two-component developing device uses a toner concentration sensor, which is an optical toner concentration detection means.

FIG. 7 shows an example of the configuration of the two-component developing device 14. Inside the casing 141 is a pair of conveyance rollers 1 whose axial direction is parallel to the axial direction of the photoreceptor drum 13 and which is a developer conveyance means.
42, 14B and a developing roller 144 are provided.

Further, the conveying rollers 142, 143 and the developing roller 144 are rotationally driven in the directions indicated by arrows A, B, and C by drive systems (not shown), respectively. Then, the developer 145 filled in the casing 141 is conveyed to the developing roller 144 side by the rotation of the conveying rollers 142 and 143.
A developer layer 145a is formed on the outer periphery of 44. This developer layer 145a comes into contact with the surface of the photoreceptor drum 13, and the above-described development is performed. Note that reference numeral 146 is a spike control blade for making the thickness of the developer layer 145a formed on the outer periphery of the developing roller 144 uniform.

On the other hand, a toner concentration sensor 51 is provided on the lower surface of the casing 14 so as to face the conveyance roller 142, and detects the toner concentration while conveying the developer 145 along the conveyance path 141a. A toner supply device (not shown) is controlled in response to changes in the output of the sensor 51 to keep the toner concentration constant. Therefore, a means is required to replace the same developer so that it does not accumulate on the detection surface of the sensor 51.

This developer exchange means has conventionally been constructed as shown in FIGS. 8 and 9. FIG. 8 shows the shaft 1 of the conveying roller 142.
42a is a sectional view taken in a direction perpendicular to 42a, and FIG. 9 is a sectional view taken in a parallel direction. In the figure, the shaft 142a
The conveying blades 142b are attached radially in an inclined manner, and the conveying blades 142b are attached to the portion facing the sensor 51.
A pair of exchanging blades 52 as developer exchanging means are attached in the diametrical direction instead of the developer exchanging means 2b. Then, as the conveyance roller 142 rotates, the tip of the replacement blade 52 periodically scrapes off the developer 145 on the sensor 51 directly and replaces the developer 145.

(Problem to be Solved by the Invention) However, according to the above conventional developer replacement means, the tip of the replacement blade 52 comes into contact with the detection surface of the sensor 51, which scrapes the detection surface and shortens the life of the sensor 51. ,
Furthermore, there is a problem in that the sensor output changes due to damage to the detection surface, making it impossible to accurately detect toner concentration.

Furthermore, since the tip of the replacement blade 52 periodically contacts the detection surface of the sensor 51, noise is generated each time it contacts the sensor output waveform, as shown in FIG. As a result, it becomes difficult to control the toner density, and there is also the problem that defective images and over-toner stains occur inside the apparatus.

The present invention has been made in view of the above points, and an object of the present invention is to provide a developing device that can always maintain an appropriate toner concentration in a developer and can stably obtain high-quality images. shall be.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a developing device in which a developer conveying means and a toner concentration detecting means are provided in a developer conveying path. The toner concentration detecting means is characterized in that, in the portion facing the toner concentration detecting means, a developer exchanging means is provided for contacting the conveying path surface near the toner concentration detecting means, stripping off the developer, and periodically replacing the developer. .

(Function) According to the above configuration, the developer on the detection surface of the toner concentration detection means is not directly scraped off by the developer replacement means, but is removed onto the sensor surface by scraping off the periphery other than the detection surface. The developer also moves and can be replaced smoothly. Therefore, since the developer replacement means does not come into contact with the detection surface of the toner concentration detection means, this detection surface is not damaged and the toner concentration of the developer can be accurately detected.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

1 and 2 are vertical sectional views in two orthogonal directions showing a developer exchange means according to an embodiment of the present invention, and FIG. 3 shows the overall configuration of an image forming apparatus to which this embodiment is applied. The explanatory drawing and FIG. 4 are also external perspective views.

The image forming apparatus shown in FIG. 3 and FIG.
A document cover 3 whose one end is rotatably supported on the top surface and covers the top surface of the document table 2; and upper and lower paper feed cassettes which are removably loaded vertically on one side of the main body 1 and protrude from the negative side. 4
．． 5, and a tray 6 protruding from the paper discharge end of the other side of the main body 1.

Inside the main body 1, there are an exposure lamp 7 and mirrors 8, 9, 10 that move back and forth in the direction of arrow a along the lower surface of the document table 2.
a photoreceptor drum 13 that forms an image of the light reflected by the exposure scanning of the optical system through a variable magnification lens block 11 and a mirror 12; and an electrostatic latent image formed on the surface of the photoreceptor drum 13. A developing device 14 that attaches toner to make a visible image, and copy paper P stored in a cassette 4 or pouch in synchronization with the rotation of the photosensitive drum 13 as shown by arrow C.
is sent to the transfer charger 20 and the peeling charger 21 through the delivery roller mechanism 15 or 16 and the guide path 17 or 18, and the registration roller pair 22 and the transfer charger 20 are brought into close contact with the surface of the photoreceptor drum 13. a conveyor belt 23 that transfers the toner image through the transfer belt 23 and conveys the copy paper P separated from the drum 13 by a force-stripping charger 21;
A fixing roller pair 24 that is provided at the end of the conveyor belt 23 and fixes the toner image onto the copy paper P, and a fixing roller pair 2
4, the copy paper P is discharged onto the tray 6 through the pair of rollers 25.

Further, a charger 2 for removing electricity is provided for removing electricity from the drum 13 after transfer along the rotational direction from one circumferential edge of the photoreceptor drum 13.
6. The surface of the drum 13 after static electricity removal (1J-toner 27 for removing the toner that has adhered to the surface), the static elimination lamp 28 for erasing the afterimage on the drum 13, and the surface of the photoreceptor drum 13 are charged and exposed. time (t when an electrostatic latent image is formed)
Second charger 29 force (located.

Furthermore, inside the main body 1, there is a cooling fan 30 for preventing temperature rise, and a plurality of micro-swivels for detecting the size of the skein and throat, which are located at the insertion tip of the skein and throat 4.5. 1 skein/soto size detector 31
．． 32 etc. are provided and 0 is provided.

The general structure of the developing device 14 is almost the same as that of the conventional device f11 shown in FIG.

FIGS. 1 and 2 show the structure of a replacement blade 61, which is a developer replacement means that is a feature of this embodiment.

In the figures, parts that are the same or equivalent to those of the conventional example shown in FIGS. 8 and 9 are denoted by the same reference numerals, and explanations thereof will be omitted as appropriate. The replacement blade 61 is attached to the conveyor roller 14 on the shaft 142a.
The replacement blade 6 is fixed on both sides in the direction of the axis 142a of the toner concentration sensor 51, which is a toner concentration detection means.
The rotation of the shaft 142a around the tip C of the developer transport path 1
It comes into sliding contact along 41a and becomes LM.

Next, the operation of this embodiment will be explained. When the shaft 142a rotates in the direction indicated by the arrow, the developer 145 in the casing 141 is conveyed by the conveying blade 142b from the conveying roller 142 force 1 to the conveying roller 143 side as shown in FIG.

Similarly, the developer 145C is conveyed from the conveyance roller 143 to the developing roller 144, and as described above, the developer 145C is conveyed to the developing roller 144.
The toner is attracted to the electrostatic latent image on the photoreceptor drum 13, and the latent image portion is visualized and developed.

At this time, the sensor 51 detects the toner concentration in the developer 145.
45 is periodically replaced by rotation of the replacement blade 61. Here, the tip of the replacement blade 61 does not contact the detection surface of the sensor 51, but slides on the conveyance path 141a around the sensor surface and the developer 1 around the sensor surface.
45 will be replaced. As a result, as shown in Fig. 5, the output waveform of the sensor 51 becomes noise-free, and as is clear from the paper passing test results shown in Fig. 6, the toner density and image density are 30,000 copies made. is almost constant, and stable high quality images can be obtained.

According to this embodiment, the replacement blade 61 that replaces the developer 145 on the detection surface of the toner concentration sensor 51 does not directly contact the detection surface, thereby preventing damage to the detection surface and extending the life of the sensor 51. be able to. Also sensor 5
1 output is accurate, and the toner concentration of the developer can always be maintained at an appropriate level. As a result, high-quality images can be stably obtained, and furthermore, it is possible to prevent the occurrence of contamination in the apparatus due to overtoner of the developer.

〔Effect of the invention〕

As explained above, according to the present invention, since there is no direct contact with the detection surface of the developer replacement means or the toner concentration detection means,
It is possible to prevent damage to the detection surface and extend its life. Furthermore, the toner concentration detected by the toner concentration detection means is accurate, the toner concentration of the developer can always be maintained at an appropriate level, and high-quality images can be stably obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view taken in a direction perpendicular to the axial direction, showing a developer exchange means provided in a developer conveyance means according to an embodiment of the present invention; FIG. 2 is a sectional view parallel to the axial direction; 3 is an explanatory diagram showing the overall configuration of an image forming apparatus to which this embodiment is applied, FIG. 4 is an external perspective view, and FIG. 5 is a diagram showing the output waveform of the toner density detection means according to this embodiment. 6th
The figure also shows a diagram showing changes in toner density and image density,
FIG. 7 is a longitudinal sectional view showing the configuration of the developing device, FIG. 8 is a sectional view taken in a direction perpendicular to the axial direction and shows a conventional developer exchange means, and FIG. 9 is a sectional view parallel to the axial direction. FIG. 10 is a diagram showing the output waveform of the toner concentration detection means shown in FIGS. 8 and 9. FIG. 51... Toner concentration detection means (toner concentration sensor) 6
1...Developer exchange means (exchange blade) 141a...
・Developer conveyance path 142, 143...Developer conveyance means (conveyance roller) 1
45...Developer

Claims (1)

[Claims] In a developing device in which a developer conveying means and a toner concentration detecting means are provided in a developer conveying path, a portion of the developer conveying means facing the toner concentration detecting means comes into contact with a surface of the conveying path near the toner concentration detecting means. and remove the developer.
A developing device comprising a developer replacing means for periodically replacing the developer.