JPH0619316A - Developing device - Google Patents

Abstract

PURPOSE:To improve the detecting accuracy of toner concentration in a developing device in which the toner detecting-surface of a toner concentration detecting means for detecting the toner concentration in developer is disposed upward or in a state where it faces upward in a developer carrying path. CONSTITUTION:In the developing device 1 in which the toner detecting surface 12a of the toner concentration detecting means 12 for detecting the toner concentration in the developer 9 is disposed upward or in a state where it faces upward in the developer carrying path, the toner concentration detecting surface 12a forms an inclined surface, and a unit lower case 8 positioned below a developing roller 2, a paddle roller 3, and a mixing roller 4 is formed to be curved so that it may projects horizontary or downward except a partial inclined surface 8a adjacent to the surface 12a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to detection of toner concentration in a developing device using a dry two-component developer.

[0002]

2. Description of the Related Art A developing device is described in Japanese Utility Model Laid-Open No. 62-293267 or Japanese Patent Application Laid-Open No. 1-251065.

In the developing device disclosed in Japanese Utility Model Laid-Open No. 62-293267, a toner density sensor is arranged at a portion corresponding to a position between a developing roller and a paddle roller on the bottom of the developing unit, and the toner density sensor is provided on the sensor surface. By allowing the developer to always flow uniformly, the change in toner concentration is accurately detected to maintain the toner concentration of the developer at a predetermined level.

Further, in the developing device described in Japanese Patent Application Laid-Open No. 1-251065, the gap between the mixing roller and the detection surface of the toner concentration detecting member and the gap between the inner wall of the developing layer supporting the toner concentration detecting member are respectively formed. 0.2mm to 1.0m
It is set (specified) from m, 0.3 mm to 2.5 mm to improve the detection accuracy and responsiveness of the toner concentration in the developer.

[0005]

In the developing device having such a structure, the position of the toner concentration detecting sensor is devised, or the toner is made to flow constantly on the detecting surface of the sensor. However, image forming apparatuses such as copying machines are becoming more compact year by year, and along with this, around the developing unit, especially on the side of the photosensitive drum, the gap between the developing roller and the paddle roller is narrowed due to the reduction in diameter of the drum. Therefore, it may be difficult to attach a toner concentration sensor or the like during this period as in the conventional case. That is,
Accurate detection of the toner concentration by the toner concentration sensor or the like must be restricted by the layout in the device, and how to accurately detect the toner concentration without being restricted by the layout in the device. This is an issue in this field.

[0006]

Therefore, in the present invention, the toner concentration detecting surface in the dry type two-component developer housed in the developing unit case is mounted in the developer conveying path in an upward or upward direction. In the developing device, the toner concentration detecting surface forms an inclined surface, and the developing unit case below the member that rotates in the vicinity of the toner concentration detecting surface as a means for transporting the developer is the toner concentration detecting surface. A part of the member that is curved so as to project horizontally or downward except for a part of the inclined surface adjacent to the surface and that rotates so as to stir and convey the developer with respect to the toner concentration detection surface is The toner density detection surface is periodically approached or contacted from other parts. Further, a permanent magnet is periodically arranged at the tip of the rotating member so as to face the toner concentration detecting surface, or the toner concentration detecting surface is replenished with a paddle roller arranged at the bottom of the developing device. Between the lower mixing roller and the mixing roller, the mixing roller was disposed directly on the mixing roller or at a position near the mixing roller.

[0007]

According to the first aspect of the invention, the toner concentration detecting surface forms an inclined surface and is located below a member that rotates in the vicinity of the toner concentration detecting surface as a means for conveying the developer. Is curved so as to project horizontally or downward except for a part of the inclined surface adjacent to the toner concentration detection surface, the developer near the toner concentration detection surface smoothly flows.

According to the second and third aspects of the present invention, the rotating member that stirs and conveys the developer onto the toner concentration detecting surface is provided with the elastic member that periodically approaches or contacts the toner concentration detecting surface. Therefore, the elastic member is rotated with the rotation of the rotating member, and the developer around the toner concentration sensor is convected. Further, even if the elastic member comes into contact with the toner concentration detection surface, it is not a rigid body, so that there is no possibility of excessive contact pressure or damage to the detection surface.

In the inventions of claims 4 and 5, since the permanent magnet is disposed on the rotating member that stirs and conveys the developer with respect to the toner concentration detection surface, the magnetic substance in the component of the developer is the permanent magnet. The developer is attracted to form a developer brush, and the developer near the toner concentration detection surface is convected. Further, since the peeling member is arranged in the vicinity of the rotating member having the permanent magnet, the developer magnetically fluxed by the rotating member is scraped off.

According to the sixth aspect of the present invention, since the toner concentration detecting surface is disposed between the paddle roller and the mixing roller located below the toner replenishment, it is disposed directly below the mixing roller or at a portion corresponding to the roller, and therefore, it is new. It is possible to detect the latest toner concentration information in the improved developer by mixing the developer supplied to the developer and the old developer.

[0011]

EXAMPLES Examples of the present invention will be described below in order. Figure 1
In the developing device 1 indicated by reference numeral 1, the developing roller 2,
A drive unit (not shown) includes a developing unit including the paddle roller 3 and the mixing roller 4, and a toner replenishing unit including a toner hopper 6 having a toner replenishing roller 5 disposed above the mixing roller 4. It is arranged in the vicinity of the photoconductor 7 which is rotationally driven by.

The mixing roller 3 and the paddle roller 4 are disposed in the vicinity of the lower case 8 of the developing unit and at a constant interval from the lower case 8, and the two-component developing system including the magnetic carrier contained in the unit is developed. The agent 9 is conveyed to the developing roller 2. The developing roller 2 is configured to magnetically adsorb and hold the developer 9 that is agitated and mixed by the mixing roller 4, and is pumped up and conveyed by the paddle roller 3, and is disposed in the vicinity of the photoconductor 7. It is driven to rotate counterclockwise in the figure.

The toner replenishing roller 5 is rotated by a detection signal generated by a toner density detecting means, which will be described later, and supplies the toner T in the toner hopper 6 into the developing unit. In the lower case 8, a portion near the mixing roller 4 is substantially horizontal, a portion located between the mixing roller 4 and the paddle roller 3 is inclined, and a portion near the developing roller 2 and the paddle roller 3 is curved downward. Has been formed. In the developing unit, a doctor plate 10 for regulating the layer thickness of the magnetic brush carried by the developing roller 2 is arranged at a position where an arbitrary position on the peripheral surface of the developing roller 2 reaches before facing the photoconductor 7. It is installed, doctor plate 1
In the vicinity of 0, a separator 11 whose one end in the extension direction is located on the mixing roller 4 side is arranged.

On the other hand, in the vicinity of the inclined portion 8a of the lower case 8 located between the paddle roller 3 and the mixing roller 4, a toner concentration detecting sensor 12 (hereinafter referred to as "toner sensor 12") is provided as toner concentration detecting means. It is arranged. The toner sensor 12 electrically detects the toner concentration contained in the developer inside the unit, and as shown in FIG. 2, the toner concentration detection surface 12a is formed in an inclined shape.
(Hereinafter, referred to as “detection surface 12a”) is provided so as to protrude toward the inside of the lower case 8. That is, the toner sensor 12 is attached to the lower case 8 so that the detection surface 12a is immersed in the developer 9 housed inside the unit, and the flow of the developer 9 is smoothed on the detection surface 12a. It is configured.

The characteristics of the toner sensor 12 will be described below. As the toner sensor 12, a type in which the sensor output (voltage) is lower as the toner concentration is higher, as shown in FIG. 3, is used. Further, since the bulk density of the developer 9 increases slightly when the developer 9 is stationary than when it is moving, even if the developer 9 has the same toner concentration as a whole, the toner density is increased while the developer 9 is stationary. It will detect it in the dark side.
That is, as shown by the broken line in FIG. 2, the sensor output tends to be output higher than the sensor output that can be placed at the actual toner concentration.

Toner sensor 12 having such characteristics
FIG. 4 shows a measurement of the difference in the sensor output depending on whether the flow of the developer 9 is good or bad using. FIG. 4A shows that the flow of the developer 9 is good, that is, the detection surface 12 according to the embodiment.
4A shows the output difference of the sensor output from the inclined toner sensor 12 when the developing device 1 is in operation and when it is inactive. FIG. 4B shows the output of the toner sensor in which the developer 9 does not flow well. 2 shows the output difference between the sensor output of the developing device 1 and the developing device 1 when it is not operating.

According to FIG. 4, if the flow of the developer 9 is not good, the developing device 1 is left for a long time, for example, the sensor output (V) immediately after the equipment which has not been used for a day and immediately left for a short time. There is a large difference in the sensor output (V) from when the device stands for a certain period of time after operation, and there is a long time until the output stabilizes. However, if the flow of the developer 9 is good, the sensor output immediately after the device starts up. It can be seen that the difference between (V) and the sensor output (V) when a certain period of time elapses after the operation of the device is small and the output is stable from a fast time.

Having the time until the difference between the sensor outputs is large and stable means that the toner concentration detected even when the device is operated and the copying is started is longer than the actual toner concentration is detected. To do. In other words, the toner T is supplied from the toner hopper 6 and the developer 9 is excessively supplied.
Although the toner concentration in the inside becomes high, as in this embodiment, the detection surface 12a of the toner sensor 12 is formed in an inclined shape to smooth the flow of the developer 9 in the vicinity of the detection surface 12a. The sensor output can be stabilized from the time, and the accurate toner concentration can be detected from the copy operation immediately after the start-up. Further, since the toner density is stabilized early, the copy image can be stabilized and unnecessary toner supply can be prevented. In the embodiments described below, the same reference numerals are given to those having the same functions as those of the first embodiment, and the description thereof will be omitted.

FIG. 5 shows a second embodiment. In FIG.
The toner sensor 12 is disposed on the horizontal portion 8b of the lower case 8 located below the mixing roller 4, and the detection surface 12 thereof is provided.
a is projected into the developing unit. This detection surface 12
Different from the first embodiment, a is horizontal as shown in FIG. 6, and the protrusion amount G is set in the range of 0.5 ± 0.5 mm. That is, it is arranged so as to sink into the developer 9.

A blade 13 formed of an elastic member is provided on the peripheral surface 4a of the mixing roller 4 in a protruding manner, and the protrusion amount g of the blade 13 is within the range of 1 to 2 mm from the peripheral surface 4a. In addition, the blade 13 is provided so as to rotate on an orbit such that the tip of the blade 13 slightly contacts the detection surface 12a.

As described above, since the blade 13 is provided so as to project on the peripheral surface 4a of the mixing roller 4 and the tip of the blade 13 is brought into contact with the detection surface 12a, the developer 9 in the vicinity of the toner sensor 12 is mixed. Each time the roller 4 rotates, it is periodically swept away by the blade 13, the flow of the developer 9 is improved, and the sensor output from the toner sensor 12 can be stabilized. Further, since the blade 13 is formed of an elastic member, an excessive contact pressure is not required even if the blade 13 is brought into contact with the detection surface 12a, and the durability of the detection surface 12a is improved.

FIG. 7 shows a third embodiment. The third embodiment is
A permanent magnet 14 is provided in the mixing roller 4 instead of the blade 13 of the second embodiment. The permanent magnet 14 is attached to the inner surface of the mixing roller 4 on the side of the peripheral surface 4 a, and the permanent magnet 14 causes the magnetic toner contained in the developer 9 to form a part of the peripheral surface 4 a of the mixing roller 4. The magnetic force is magnetically attracted to the portion to form the developer brush B.
A scraper 15 is provided on the downstream side of the rotation direction of the mixing roller 4 and near the peripheral surface 4a.
Is arranged so as to come into contact with, and scrapes off the toner agent magnetically attracted to the peripheral surface 4a. The toner sensor 12 is arranged immediately below the mixing roller 4 so that the detection surface 12a thereof contacts the developer brush B formed on the peripheral surface 4a.

With this structure, the developer brush B periodically passes the detection surface 12a by the rotation of the mixing roller 4, so that the toner density of the developer brush B is detected every time the mixing roller 4 rotates. The toner density of the developer 9 can be detected. Further, since the magnetically adsorbed toner agent is scraped off by the scraper 15 every one rotation, the toner agent adsorbed on the mixing roller 4 can be always updated, and the latest toner information, that is, the toner in the actual developer, can be obtained. The concentration can be detected.

[0024]

According to the present invention, the flow of the developer in the vicinity of the toner density detecting surface of the toner density detecting means in the developing device using the dry two-component type developer provided with the toner density detecting means. Therefore, the developer can be prevented from staying, the flow of the developer can be stabilized in a short time, and the toner concentration can be accurately detected.

Further, since the rotating member that comes into contact with the toner concentration detecting surface is formed of an elastic member, it is possible to prevent an excessive contact pressure and reduce the risk of impairing the durability of the toner concentration detecting means. Furthermore, since it is possible to always provide a new developer to the toner concentration detection surface, the latest toner information can be obtained and the toner concentration detection accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a developing device in which a first embodiment of the present invention is implemented.

FIG. 2 is an enlarged view showing a main part of the first embodiment.

FIG. 3 is an output characteristic diagram of a toner density detecting unit used in the present invention.

FIG. 4A is a graph showing the displacement of the sensor output depending on the operating state of the device when the flow of the developer is good, and FIG. 4B is the displacement of the sensor output depending on the operating state of the device when the flow of the developer is poor. It is a graph which shows.

FIG. 5 is a schematic configuration diagram of a developing device in which a second embodiment of the present invention is implemented.

FIG. 6 is an enlarged view of an arrangement portion of a toner concentration detecting means, which is a main part of the second embodiment.

FIG. 7 is a configuration diagram of a third embodiment of the present invention.

[Explanation of symbols]

 1 Developing Device 3 Paddle Roller 4 Mixing Roller 5 Toner Replenishing Roller 6 Toner Hopper 8 Developing Unit Case 9 Dry Two-Component Developer 12 Toner Density Detecting Means 12a Toner Density Detecting Surface 13 Blade 14 Permanent Magnet 15 Developer Stripping Member (Scraper) T toner

Claims (6)

[Claims] 1. A dry type 2 housed in a developing unit case.
In a developing device in which a toner detection surface of a toner concentration detection means for detecting the toner concentration in a component type developer is attached in a state in which it is directed upward or upward in a developer transport path, the toner concentration detection surface forms an inclined surface. In addition, the developing unit case below the member that rotates in the vicinity of the toner concentration detecting surface as a means for conveying the developer is horizontal or downward except for a part of the inclined surface adjacent to the toner concentration detecting surface. A developing device, which is curved so as to protrude to the outside. 2. A developing device in which a toner detecting surface of a toner concentration detecting means for detecting toner concentration in a dry two-component developer is attached in a state in which the toner detecting surface is directed upward or upward in a developer conveying path. The bottom of the developing unit adjacent to the detection surface is curved so as to project horizontally or downward, and a part of the member that rotates so as to stir and convey the developer with respect to the toner concentration detection surface is in the axial direction. A developing device characterized in that the toner concentration detecting surface is periodically approached or contacted from another portion. 3. The developing device according to claim 2, wherein a portion of the rotating member that is close to or in contact with the toner concentration detecting surface is an elastic member. 4. A dry type 2 housed in a developing unit case.
In a developing device in which a toner detection surface of a toner concentration detecting means for detecting the toner concentration in a component type developer is attached in a state in which it is upward or upward in a developer conveying path, the developing unit adjacent to the toner concentration detection The bottom of the member is curved so as to project horizontally or downward, and the tip of the member that rotates so as to stir and convey the developer facing the toner concentration detection surface periodically faces the toner concentration detection surface. A developing device, which is a permanent magnet. 5. A developing device according to claim 4, further comprising a peeling member facing a rotating member to which a permanent magnet is attached, for peeling the developer magnetically attracted by the permanent magnet. . 6. Development in which a toner detection surface of a toner concentration detection means for detecting the toner concentration in a dry two-component type developer housed in a developing device is attached in a state in which the toner detection surface is directed upward or upward in a developer transport path. In the apparatus, the toner concentration detection surface is arranged between the paddle roller arranged at the bottom of the developing device and the mixing roller located below the toner replenishment, and immediately below the mixing roller or at a portion corresponding to the roller. A developing device characterized by being installed.