JPH041347B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a developing device applied to a copying machine.

<Prior art and its disadvantages> In the developing method that has been commonly used in the past, as shown in FIG. 3, the photosensitive drum 1 is rotated clockwise, and the rotating sleeve 2 of the developing roller is also rotated clockwise. This is a method of developing while controlling the thickness of the developer on the sleeve with a doctor 5. This developing method is called reverse development due to the relative relationship in the rotational direction with the photoreceptor drum. In response to this reverse development, recently, as a response to higher image quality in copying, a method has been used in which the sleeve is rotated counterclockwise to reduce the relative speed between the drum and the sleeve, as shown in Figure 4. It's coming. This is called normal rotation development as opposed to the above-mentioned reverse development.

Incidentally, a developer concentration detection sensor (hereinafter simply referred to as a sensor) 6 is attached to the developer tank in order to control the concentration of the developer 4. In the case of reverse development shown in Fig. 3, the sensor 6 is installed above the sleeve in order to maintain a stable flow of developer on the sensor detection surface and for structural reasons of the developer tank. Since the concentration of the developer is detected, this method is not preferable as a developer concentration control method.

Therefore, if the developer concentration before development is detected and forward development is to be performed, the arrangement will be as shown in FIG. The excess developer scraped off becomes clogged between the sensor detection section 7 and the doctor 5. As a result, the clogged developer obstructs the flow of new developer, resulting in poor conveyance, and also makes it impossible to accurately detect the concentration, leading to a decrease in development performance.

<Object of the Invention> In view of the above-mentioned conventional drawbacks, an object of the present invention is to provide a developing device that can improve developer conveyance in normal rotation development and stably detect developer concentration. do.

<Structure of the Invention> The present invention provides a developing device in which a detection sensor is arranged to control the concentration of the developer. It is placed above the developing roller in order to scrape off part of the developer so that the amount is constant, and has an opposing surface that faces the developing roller at a constant distance in front of the doctor. The tip is opposed near the doctor so that some of the developer scraped off by the blade flows to the back surface opposite to the facing surface, and the developer flowing on the back surface at the end opposite to the tip is directed to the stirring roller. A regulating plate is provided facing the stirring roller so as to be guided, and the developer concentration detecting sensor is placed on the regulating plate so that the detection surface of the developer concentration detecting sensor is located on the opposite surface side of the regulating plate facing the developing roller. It is characterized by the arrangement of sensors.

<Embodiment> FIGS. 1 and 2 are structural diagrams of main parts of a developing device according to an embodiment of the present invention, and a view taken in the direction of arrow A. In the figures, the same parts as in FIGS. 3 and 4 are designated by the same reference numerals.

A developing roller 9 and a stirring roller 3 are provided within the developing tank 8 . The developing roller 9 consists of a group of fixed magnets (not shown) arranged along the circumference and a non-magnetic rotating sleeve surrounding the group of fixed magnets. 12 is a toner container, and the toner 11 supplied from this container is attracted by the magnetic attraction force of the developing roller 9 and is attracted to the rotating sleeve. A doctor 5 is disposed above the developing roller 9. Toner is regulated by Doctor 5 as the rotating sleeve rotates.
It is held and adsorbed to a constant thickness on the rotating sleeve. The rotating sleeve rotates in the opposite direction to the photoreceptor drum 1 to perform normal rotation development.

The difference between this embodiment and the developing device shown in FIG. 4 is that a regulating plate 10 is provided near the doctor 5;
In addition, the detection surface of the developer concentration detection sensor 6 is connected to the regulation plate 1.
This is because the developing roller 9 is disposed on the opposite surface facing the developing roller 9 of No. 0.

The regulating plate 10 serves both as a developer flow plate and a sensor fixing plate, and this and the doctor 5 are made of a non-magnetic material. As shown in FIG. 2, the regulating plate 10 together with the doctor 5 has opposing surfaces that are disposed opposite to each other along the rotating surface of the rotating sleeve of the developing roller 9, and has a portion (excess) that has been scraped off by the doctor 5. ) in order to guide the developer to the back surface opposite to the opposing surface, the tip is brought close to the tip of the doctor 5, and the end opposite to the tip guides the developer flowing on the back surface of the regulation plate to the stirring roller 3. The developer tank 8 is extended toward the stirring roller 3 side, and both end portions are fixed between the side walls 13 and 14 of the developer tank 8 . The regulating plate 10 is inclined toward the stirring roller 3 side, and the interval between the regulating plate 10 and the rotating sleeve is slightly wider than the interval between the doctor 5 and the rotating sleeve. The developer concentration detection sensor 6 is composed of a magnetic permeability sensor, and its detection portion 7 has a cylindrical shape, and concentration detection is mainly performed at the flat portion at the tip. The detection part 7 protrudes toward the rotary sleeve from a hole bored at the narrowest distance between the regulating plate 10 and the rotary sleeve. The periphery of the protruding portion of the detection section 7 is sealed and fixed to the regulation plate 10.

In the above configuration, the new developer stirred by the stirring roller 3 is adsorbed by the rotating sleeve and conveyed to the lower part of the doctor 5 while being compressed. The excess developer scraped off by the doctor 5 is removed from the regulating plate 10 without flowing back to the surface of the regulating plate 10 facing the developing roller 9 at the distal end of the regulating plate 10, which is closely opposed to the distal end of the doctor 5. The developer is guided to the back surface of the developer, and is pushed out by its own weight and the excess developer scraped off by the doctor 5 on the back surface, and falls to the stirring roller 3 side.
The excess developer that falls onto the stirring roller 3 and is collected is stirred together with new developer, and the same operation is repeated. As mentioned above, the regulating plate 10 is
Since the developer acts as a sink plate to flow the excess developer scraped off to the stirring roller 3 side, the developer is not guided between the regulating plate 10 and the developing roller 9 around the doctor 5, and is removed at the position of the doctor 5. To improve developer transportability without causing accumulation or clogging of developer.

Detection of developer concentration is performed by measuring inductance changes using a magnetic permeability sensor, which is mainly measured at the tip surface of the detection section 7. In this case, since the developer around the detection part 7 is regulated by the regulation plate 10,
It contacts the detection part 7 with a constant pressure. Therefore, the contact pressure of the developer against the detection part 7 is always constant,
Accurate and stable density detection can be performed, thereby improving development performance.

<Effects of the Invention> According to the developing device of the present invention, the developer scraped off by the doctor is allowed to flow to the back surface of the regulation plate, and the developer scraped off flows between the regulation plate and the development plate without being disturbed by the developer. It is possible to constantly detect the concentration of new developer flowing between the developing roller, and even if the amount of developer absorbed by the developing roller changes, detection can always be performed under a constant contact pressure, making it more accurate. By detecting the concentration, it is possible to control the concentration of the developer within a standard, thereby improving the development performance.

In addition, the sensor only needs to be attached to the regulation plate, and there is no need for any separate means for attachment, and the configuration is also very simple in that the excess developer conveyed by the developing roller is returned to the agitation roller by the regulation plate. It's easy.

[Brief explanation of drawings]

1 and 2 are structural diagrams of main parts of a developing device according to an embodiment of the present invention, a view in the direction of arrow A, and FIGS. 3 and 4.
Each figure is a structural diagram of a main part of a conventional developing device. 1... Photosensitive drum, 3... Stirring roller, 5...
...Doctor, 6...Developer detection sensor, 7...
Detection section (of the developer detection sensor 6), 9...Developing roller, 10...Regulation plate.

Claims (1)

[Scope of Claims] 1. A developing roller facing the photosensitive member, a stirring roller, a doctor facing the developing roller, and a developer concentration detection sensor are disposed in a developing tank, and the developing roller is connected to the photosensitive member. In a developing device that rotates in a direction opposite to the photoreceptor and controls the developer concentration based on the detected concentration of the developer concentration detection sensor, the doctor is conveyed by a developing roller to the photoreceptor. It is placed above the developing roller in order to scrape off part of the developer before it is rubbed against the body so that the amount of the developer is constant. The blade has facing surfaces facing apart from each other, and has a tip facing near the doctor so that a portion of the developer scraped off by the doctor flows to a back surface opposite to the facing surface, and an end opposite to the tip. A regulating plate is provided facing the stirring roller so that the developer flowing on the rear surface is guided to the stirring roller, and a detection surface of the developer concentration detection sensor faces the developing roller of the regulating plate. A developing device characterized in that the developer concentration detection sensor is disposed on a regulating plate so as to be located on an opposing surface side.