JP3255175B2 - Toner presence detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner detecting device used in a developing device of an image forming apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, toner in a developing device is consumed in forming an image.
It is necessary to always detect the presence or absence of toner in the developing device by a toner presence / absence detection device.

As a typical example of the toner presence / absence detecting device, for example, two electrode rods are provided in a developing device, and a change in capacitance between these electrode rods is detected to detect toner in the developing device. Some detect the presence or absence. That is,
In this toner presence / absence detection device, if sufficient toner exists between the electrode rods, since the dielectric constant of the toner is larger than that of air, the capacitance between the electrode rods increases. Since the capacitance between the electrode rods decreases, the presence or absence of toner in the developing device can be detected by this.

[0004]

However, in the toner presence / absence detection device using the above electrode rod, the capacitance between the electrode rods is, for example, 5 when the toner is sufficiently present.
In the absence of PF and toner, it is about 3 PF. This change in capacitance is large, but its absolute value is small. Therefore, a large error in the detection value is caused by the influence of stray capacitance from the electrode rod to the detection circuit. There was a problem that would occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a toner presence / absence detection device capable of detecting a presence / absence of toner in a toner storage section with high accuracy while suppressing a detection error. To provide.

[0006]

To achieve the above object, according to an aspect of the present invention, in the toner presence detection device for detecting the presence or absence of the toner in the toner accommodating portion for accommodating the toner, the planar having a plurality of irregularities 1st electrode part and 2nd electrode
Parts so that these uneven shapes are combined with each other
An electrode pattern disposed in parallel with a predetermined gap , wherein the electrode pattern is disposed in the toner container so as to be rubbed by a toner stirring member for stirring the toner in the toner container. A detection circuit that receives an output value output from the electrode pattern, the output value corresponding to the capacitance between the first electrode unit and the second electrode unit. Presence / absence is detected based on a change in capacitance between the first electrode unit and the second electrode unit.

[0007]

According to the present invention, a plane constituting an electrode pattern is provided.
The first electrode portion of the Jo and the second electrode portion, these irregularities
Are provided with a predetermined gap so that
Arranged in rows. Therefore, the facing length between these electrode portions can be increased, and the output value corresponding to the capacitance can be increased. Therefore, an effect is obtained that the presence or absence of the toner in the toner storage unit can be detected with high accuracy while suppressing the detection error to a small value.

[0008]

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

First, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows a cross section of a developing device 2 disposed on one side of a photosensitive drum 1 which is an image carrier in an image forming apparatus. The developing device 2 visualizes the electrostatic latent image formed on the photosensitive drum 1 as a toner image, and is a developing unit that is close to the photosensitive drum 1 side and supplies toner to the photosensitive drum 1. 20, provided on one side of the developing unit 20;
The developing unit 20 includes a developer accommodating unit 21 serving as a toner accommodating unit for supplying toner to the developing unit 20.

The developing unit 20 rotates while adhering toner to the outer peripheral surface thereof, moves the toner to the photosensitive drum 1 side, and flies the toner to the photosensitive drum 1 by applying a developing bias. A developing sleeve 22 as a developer carrier, and an application roller 23 that rotates while being in contact with the developing sleeve 22 and apply the toner in the developing unit 20 to the developing sleeve 22 are provided.

Further, a stirring blade 24 which rotates around a support shaft 24a and stirs and conveys the internal toner toward the developing unit 20 is disposed at the center of the developer accommodating unit 21.
The stirring blade 24 can be deformed to some extent, and rotates while abutting on the upper and lower surfaces of the developer accommodating portion 21 to agitate and convey substantially the entire amount of toner in the developer accommodating portion 21. It is a configuration that can be done.

When an image forming operation is started on the photosensitive drum 1 or the like of the image forming apparatus, the developer accommodating portion 21
The stirring blade 24 in the inside rotates to supply the toner inside to the developing unit 20, and the developing sleeve 2 of the developing unit 20
2 and the application roller 23 also rotate.

The application roller 23 applies the toner in the developing unit 20 to the developing sleeve 22. The developing sleeve 22 on which the toner is applied is a toner whose thickness is regulated to a thin layer by a blade (not shown) or the like. It is moved to the photosensitive drum 1 side. A developing bias voltage is applied to the developing sleeve 22 at the timing when the electrostatic latent image formed on the photosensitive drum 1 moves to the developing sleeve 22 side of the developing device 2, and the toner on the developing sleeve 22 is removed. Photosensitive drum 1
Side to visualize the electrostatic latent image as a toner image.

The toner image on the photosensitive drum 1 is transferred onto a transfer sheet via a transfer charger (not shown). The transfer sheet is further sent to a fixing unit, and the toner image is transferred to a permanent image. It is established as.

By the way, as the image forming operation progresses, the toner in the developer accommodating section 21 is consumed, and finally the toner in the developer accommodating section 21 is exhausted. Therefore, the developing device 2 is provided with a toner presence / absence detection device that detects the presence / absence of toner and notifies the worker of the presence / absence.

The above-mentioned toner presence / absence detection device detects the presence / absence of toner by a change in capacitance between electrodes.
The electrode plate 30 having an electrode serving as the detection unit is provided in the developing device 2.
The other detection circuits (comparison / determination circuits, etc.) are provided outside the developing device 2 on the side of the image forming apparatus main body.

The electrode plate 30 is attached to the lower surface 21a of the developer accommodating portion 21 below the stirring blade 24, and the toner above the electrode plate 30 is sufficiently stirred by the stirring blade 24. For this reason, as shown in FIG.
If the toner T is sufficiently present in 1, the toner T is also sufficiently present on the electrode plate 30, and the electrode plate 30 is rubbed by the stirring blade 24 via the toner T.

If there is no toner T in the developer accommodating section 21, there is no toner T on the electrode plate 30 as shown in FIG. 3, and the electrode plate 30 is directly rubbed by the stirring blade 24. Becomes

Therefore, the presence or absence of the toner in the developer accommodating portion 21 can be detected by the presence or absence of the toner T on the electrode plate 30. That is, the presence / absence of the toner on the electrode plate 30 indicates the presence / absence of the toner in the developer accommodating portion 21.
0 is set in the movable range of the stirring blade 24 as a toner stirring member.

Here, as shown in FIG. 2, a pair of plane electrodes 31, 32 formed by the same manufacturing method as the wiring pattern on the printed board has a predetermined gap on the outer surface of the electrode plate 30. It is arranged in parallel so as to have. Since the pair of planar electrodes 31 and 32 are formed of a large number of concave and convex shapes combined with each other as a plurality of bent portions, the facing length between the electrodes 31 and 32 is long, and the capacitance between the electrodes 31 and 32 is large. It is much larger than a rod or the like.

When sufficient toner T exists in the developer accommodating portion 21 of the developing device 2 and sufficient toner T exists on the electrode plate 30 as shown in FIG. 30
Since the space between the upper plane electrodes 31 and 32 is also filled with sufficient toner, the plane electrodes 31 and 32 output a large toner output value (capacitance value) to the detection circuit of the toner presence / absence detection device.

On the other hand, when there is almost no toner T in the developer accommodating portion 21 and there is almost no toner T on the electrode plate 30 as shown in FIG. There is not enough toner, and the planar electrodes 31 and 32
Since the dielectric constant of air is smaller than that of the toner T, an output value without toner that is sufficiently smaller than the output value with toner is output to the detection circuit. In this case, the detection circuit detects that the toner T is insufficient in the developing device 2 and notifies the worker that the toner T is insufficient in the developing device 2 via a warning lamp or the like.

As described above, since the presence or absence of the toner T in the developing device 2 is detected via the electrodes 31 and 32 having a large capacitance between the electrodes 31 and 32 that are long facing each other. Regardless of the presence or absence of T, the absolute value of this detection signal is large, and the signal value is not affected by the stray capacitance between the electrodes 31, 32 and the detection circuit.

Accordingly, the detection error of the toner presence / absence detection device is reduced, and the detection accuracy is improved. The electrodes 31,
Even though the facing length between the electrodes 32 is long, the electrodes 31 and 32 are flat electrodes, so that they do not take up an installation space, and therefore there is no inconvenience that the developing device 2 becomes large.

Further, since the electrodes 31 and 32 can be manufactured by the same method as the wiring pattern on the printed board, even if the shape is complicated and the facing length between the electrodes is sufficiently long,
There is a merit that manufacturing is easy.

Here, as shown in FIG. 5, it is also possible to obtain parallel electrodes 31 and 32 having a complicated shape in which the distance between each other is large. Such electrodes 31, 32 are obtained by forming a copper pattern on a normal printed circuit board by etching, and are manufactured by the same method as a so-called printed circuit board wiring pattern manufacturing method. Even with a simple pattern, the manufacturing cost is the same as that of a simple pattern.

Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 6, components having the same functions as those according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the present embodiment, the electrodes 31, 32, which are the detecting portions of the toner presence / absence detecting device for detecting the presence / absence of toner in the developer accommodating portion 21 of the developing device 2, are connected to the electrode plate 30 as in the first embodiment. Instead of being mounted on the top, it was directly mounted on the lower surface 21a of the developer accommodating portion 21 below the stirring blade 24.

That is, a pair of electrodes 31 and 32 made of aluminum foil are adhered to the lower surface 21 a of the developer accommodating portion 21, or a pair of electrodes 3 are attached to the lower surface 21 a of the developer accommodating portion 21.
1 and 32 are formed by printing or spraying a conductive paint. In this case, the electrodes 31, 32 have a large number of uneven shapes combined with each other as a plurality of bent portions, like the electrodes 31, 32 of the first embodiment.
It is assumed that the facing length between the two is sufficiently long.

Thus, in the toner presence / absence detecting device according to the present embodiment, similarly to the first embodiment, the presence / absence of the toner can be detected with high accuracy. Since the electrode plate 30 as in the embodiment is not required, the cost can be reduced accordingly, and the volume in the developer accommodating portion 21 can be increased by the absence of the electrode plate 30. can get.

In the above-described first and second embodiments, the toner presence / absence detection device for the developing device 2 has been described. However, the present invention is not limited to this, and any device in an image forming apparatus having a toner storage unit may be used. It goes without saying that the toner presence / absence detection device according to the present invention is applicable.

[0033]

As is clear from the above description, according to the present invention, according to the present invention, the plane constituting the electrode pattern is formed.
The first electrode portion of the Jo and the second electrode portion, these irregularities
Are provided with a predetermined gap so that
Arranged in rows. Therefore, the facing length between these electrode portions can be increased, and the output value corresponding to the capacitance can be increased. Therefore, an effect is obtained that the presence or absence of the toner in the toner storage unit can be detected with high accuracy while suppressing the detection error to a small value.

[Brief description of the drawings]

FIG. 1 is a sectional view of a developing device and the like according to a first embodiment of the present invention.

FIG. 2 is a perspective view of an electrode plate used in the developing device.

FIG. 3 is a cross-sectional view of the electrode plate when there is no toner on the electrode plate.

FIG. 4 is a sectional view of the electrode plate when toner is present on the electrode plate.

FIG. 5 is a view showing another electrode pattern on the electrode plate.

FIG. 6 is a sectional view of a developing device and the like according to a second embodiment of the present invention.

[Explanation of symbols]

 21 developer storage section (toner storage section) 24 stirring blade (toner stirring member) 31, 32 electrode (electrode section) T toner

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-1444582 (JP, A) JP-A-57-84317 (JP, A) JP-A-52-123242 (JP, A) JP-A-2- 251874 (JP, A) JP-A-3-200989 (JP, A)

Claims (3)

(57) [Claims] An apparatus for detecting the presence or absence of toner in a toner storage section for storing toner, comprising: a first planar electrode portion having a plurality of concave and convex shapes ;
The electrode part is formed by combining these uneven shapes.
As described above, an electrode pattern disposed in parallel with a predetermined gap provided therein, the electrode pattern being disposed in the toner storage portion so as to be rubbed by a toner stirring member for stirring the toner in the toner storage portion. A detection circuit to which an output value output from the electrode pattern according to the capacitance between the first electrode unit and the second electrode unit is input; A toner presence / absence detecting device, wherein presence / absence of the toner is detected based on a change in capacitance between the first electrode portion and the second electrode portion. 2. The toner presence / absence detection device according to claim 1, wherein the detection circuit is provided outside the toner storage unit and on a side of the image forming apparatus main body. 3. The toner presence / absence detecting device according to claim 1, wherein the first electrode portion and the second electrode portion are obtained by forming a pattern on a printed board by etching.