JP2000214674A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device provided with a high sensitivity and high resolution residual toner quantity detection sensor or a toner density detection sensor. SOLUTION: This developing device is provided with a container body 3 of a developer replenishing device and a developing roll 7 that is inside this container body consisting of a non magnetic sleeve 4 and a magnetic shaft 5 where a multiple number of magnetic poles are alternately magnetized and installed to face a photoreceptor drum 1, developer 2 that consists of a component able to be adhered to the outer surface of the non magnetic sleeve 4 and the residual quantity detection sensor or the density detection sensor 9 of the developer that detects magnetic field emitted from the developing roll 7 (the magnet shaft 5) by magnetic impedance element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device such as an electronic copying machine, in which a sensor for detecting a remaining amount of a one-component toner or a density of a two-component toner and a developing roll are incorporated in a container body. The present invention relates to a developing device, and more particularly to an improvement in a remaining amount detection sensor or a density detection sensor that detects the remaining amount or concentration of a developer with high sensitivity.

[0002]

2. Description of the Related Art In an electrostatic recording apparatus (so-called dry copying apparatus) such as an electronic copying machine or an electrostatic printer, an electrostatic latent image is developed on the surface of a photosensitive drum using a magnetic developer by a magnetic brush method or the like. Then, it is thermally or pressure-fixed to obtain a final image. Here, in order to keep the density of the image constant, it is necessary to replenish only the toner consumed by copying. Therefore, when the one-component toner is used, the remaining amount of the toner must be monitored. When the two-component toner is used, the mixing ratio between the magnetic carrier and the toner powder must be monitored with high accuracy. As a detection sensor therefor, a toner level sensor and a toner density sensor are known.

Hereinafter, a developing device having a toner density sensor and a density detecting mechanism will be described by taking a two-component developing machine as an example. FIG. 4 is a schematic view of a main part showing an example of a two-component developing machine. Two-component developer 2 consisting of magnetic carrier and toner 10
Is housed in the container body 3 of the developer supply device,
A cylindrical developing roll 7 is provided inside the container body 3 so as to face the photosensitive drum 1 rotating in the direction of the arrow shown in the figure. The developing roller 7 includes a non-magnetic sleeve 4 and a magnet shaft 5 having a plurality of magnetic poles provided therein. An impeller 9 for causing the toner 10 to frictionally charge the toner 10 is rotatably installed inside the container main body 3, and the thickness of the developer 2 charged and adhered to the non-magnetic sleeve 4 is provided on the photosensitive drum side. A doctor blade 13 for adjusting the height is provided. On the other hand, a toner tank 12 containing the toner concentration sensor 6 and the toner 10 is provided above the toner tank, and a toner supply roll 11 is rotatably provided below the toner tank 12. The doctor blade 13
The positional relationship between the toner density sensor 6 and the toner density sensor 6 may be upside down. Rather, the toner density sensor is often provided to face the lowest developer accumulation portion of the container body 3.

The structure of the two-component developing machine is substantially as described above. When the non-magnetic sleeve 4 is rotated in the direction indicated by arrow B, the developer 2 adsorbed on the non-magnetic sleeve 4 is removed from the doctor gap d. The sheet is transported toward the developing gap D. In the vicinity of the developing gap D, the surface of the photosensitive drum 1 is rubbed with the magnetic brush formed by the developer 2 to develop the electrostatic latent image formed on the drum.
When the developer 2 that has passed through the development gap D reaches the same-polarity opposing portion, it is scraped off from the non-magnetic sleeve 4 by a repelling magnetic field and is collected in the developer tank of the container body 3. The recovered developer 2 is stirred and mixed by the impeller 9 together with the toner 10 discharged from the toner tank 12 by the rotation of the toner supply roll 11, and then is adsorbed on the non-magnetic sleeve 4 again to be used for development. Will be. Here, when the developer 2 reaches the vicinity of the S pole after passing through the developing gap D, the toner density of the developer is detected by the toner density sensor 6 in contact with the developer layer, and the external density is determined in accordance with the detected toner density. A signal is output, and the toner supply roll 11 is rotated by a driving unit (not shown) to control the toner concentration to be constant.

As a conventional toner density sensor, for example, a differential transformer type sensor is known. In the example shown in FIG. 4, the detection coil L2 is arranged close to the developer side, an output coil L3 for outputting a differential voltage is placed thereon, and a differential transformer between the output coil L2 and the detection coil L2 is further placed thereon. Are arranged. When the developer passes over the detection coil L2, the magnetic permeability μ changes due to the magnetic substance in the developer, and the differential output of the output coil L3 also changes according to the change in the magnetic permeability. It detects the density or the remaining amount of toner (see, for example, JP-A-4-72229). Thus, this toner concentration sensor is mounted on the wall of the container body 3. However, it has been limited to detect the alternating magnetic flux generated from the detection surface of the detection coil within a range of 2 to 3 mm from the detection surface. That is, this means local detection of magnetic permeability, and is not suitable for detecting a change in magnetic permeability of the entire developer. In addition, the output is often influenced by the mounting location of the sensor for local detection, so that the mounting position is restricted.

[0006]

In view of the above, in order to maintain a high quality image in a developing device, it is necessary to know the toner concentration in the entire developer container as much as possible. Was desired. Also,
In the case of the remaining amount sensor that detects from the outside of the developer container, it is difficult to detect a change in the magnetic flux of the developer if the wall of the container is thick. For example, if the wall thickness is 2 mm or more, the conventional toner remaining amount There is a problem that the detection sensor cannot detect the magnetic flux.

Accordingly, the present invention has solved the above-mentioned problems of the prior art, and is capable of sufficiently detecting a change in magnetic flux even if a sensor for detecting the concentration of developer in a wider range is mounted or mounted outside the container. An object of the present invention is to provide a developing device provided with a sensitive remaining amount detection sensor.

[0008]

According to the present invention, there is provided a container body of a developer replenishing apparatus, a developing roll in the container body having a plurality of magnetic poles therein, and refillably housed in the container body. A developing device, and a sensor for detecting the remaining amount of the developer or a sensor for detecting the concentration of the developer, wherein the magnetic field emitted from the developing roll is detected by a magnetic impedance element.

The above-described magneto-impedance element (hereinafter, referred to as
It is called an MI element. The impedance effect of ()) means that when a high-frequency current in the MHz band is applied to a magnetic material, the impedance of the magnetic material changes due to an external magnetic field. It is a phenomenon that does. The resolution of the magnetic flux detection of the MI element is high, for example, several hundred times higher than that of the MR element. That is, here, the developing roll (magnet shaft) is used as a magnetic field generating source,
The magnetic sensor is formed of a magnetic element having a high magnetic permeability. When the magnetic sensor detects a change in magnetic flux generated from the developing roll (magnet shaft) when the two move relative to each other, the magnetic permeability of the magnetic sensor changes, so that a skin effect of a high-frequency current appears and a change in magnetic impedance. Occurs. In other words, if a change in the magnetic field of the developing roll is detected using an ultra-high sensitivity sensor of the MI element, and a change in the impedance is converted into an electric signal to obtain an output, the remaining amount of the developer can be detected with high accuracy. It can be a sensor or a concentration detection sensor. With such an MI element sensor, the mounting position of the sensor does not need to be in contact with the developer, and sufficient detection accuracy and high resolution can be obtained even if the sensor is located far away from the container (for example, several hundred mm). Can be done.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic explanatory view showing an example of the developing device according to the present invention. FIG. 2 is an explanatory view showing one embodiment of the magnetic element. FIG. 3 is a characteristic diagram showing magnetic impedance characteristics. Since the developing device of the present invention can use the conventional technology other than the remaining amount detection sensor or the density detection sensor, the description of those portions will be omitted because it is the same as the description of FIG. 4 described above. Note that the following embodiments also take a density sensor as an example.

In FIG. 1, a plurality of magnetic poles (usually 4 to 8 poles) are alternately magnetized on the outer periphery of a magnet shaft 5 in a developing roll 7. It is provided rotatably. The non-magnetic sleeve 4 is not always necessary, and the number of magnetic poles can be set as appropriate. It can also be used for a cartridge type developing device. Now, in FIG.
Reference numeral 1 denotes a first magnetic element, and reference numeral 92 denotes a second magnetic element provided to be shifted from the first magnetic element by a half pitch of a magnetizing pitch of a developing roll (magnet shaft).
The first and second magnetic elements together constitute a toner density sensor.

FIG. 2 shows the first and second magnetic elements, which are MI elements used in this embodiment. In the present embodiment, a high permeability magnetic film (hereinafter, referred to as a magnetic film) 80 is formed in a zigzag pattern on a non-magnetic substrate 84 (hereinafter, referred to as a substrate). In this embodiment, the substrate 84 is made of a non-magnetic material such as calcium titanate (Ti-Ca-based ceramic) oxide glass, titania (TiO2), alumina (Al2O3) or the like, which is a rectangular flat plate. On the other hand, the magnetic film 80 is made of Fe—Co—
B type amorphous film, Fe-Ta-C type, Fe-T
It is composed of a high magnetic permeability metal magnetic film such as an a-Nb based microcrystalline film or the like, and is formed in a single layer or a plurality of layers. Here, a magnetic thin film is taken as an example, but the MI element of the present invention is not limited to this. For example, a Co—Fe—Si—B
An MI element using a system amorphous wire can also be used.

The magnetic film 80 includes a plurality of magnetic detectors 81 arranged on a plurality of straight lines, and a plurality of straight lines connected in a direction perpendicular to the magnetic detectors 81 so as to sequentially turn the ends of the magnetic detectors. It is formed in a zigzag pattern composed of the upper magnetic coupling portion 82. It is also possible to adopt a configuration in which at least two magnetic detection output portions and one magnetic coupling portion are provided without being folded. Further, the magnetic detecting portion 8 of the magnetic film
Terminals 83 and 83 'are provided continuously at both ends of the device 1. The terminals 83 and 83 ′ are formed as conductive films of Cu, Au, or the like, or formed by extending both ends of the magnetic film 80.

The substrate 84 of the first magnetic element and the second
The substrate 84 of the magnetic element is mounted on a container or another member so as to be opposed to the developing roll 7 in parallel. Here, in the present invention, as shown in FIG. 1, it may be arranged at a further rear portion as long as it is opposed to the container without being particularly attached to the container. As described above, the magnetic detection is performed by the first magnetic element, the other second magnetic element is used as the comparison element, and the differential output is obtained from both. During operation of the toner concentration sensor, terminals 83 provided at both ends of the magnetic film 80 of each magnetic element,
A high-frequency current is applied from 83 ', and the magnetic flux generated from the magnetic field of the developing roll 7 (the same applies to the magnet shaft 5 and below) is detected by a magnetic detecting section, so that the terminals 83, 8 at both ends are detected.
Since the impedance between 3 'changes, this change is converted into an electric signal to obtain a differential output.

Therefore, the magnetic flux generated from the individual magnetized areas formed on the developing roll 7 is detected by each of the magnetic detecting portions 81 of the magnetic film, and the magnetic flux changes are detected one after another by the relative movement with respect to the developing roll 7. At this time, since the magnetic permeability of the magnetic film changes according to the toner concentration of the developer, a skin effect of a high-frequency current appears, and a magnetic impedance effect occurs.
Here, the magnetic flux flows in the forward and reverse directions between the adjacent detection units, but the magneto-impedance effect has a target characteristic with respect to the direction of the external magnetic field as shown in FIG. Instead, the overall impedance of the magnetic film 80 can be obtained as the sum of the impedances of the respective magnetic detection units.

In the present invention, the density of the magnetic sensor composed of the MI element can be detected only by installing one magnetic element formed on the first magnetic element 91, for example. It is desirable to provide a magnetic element as a comparison element, and to displace the magnetic element by a half pitch of a magnetized medium, for example, a magnetized pitch of a developing roll (magnet shaft). As a result, when a high-frequency current is applied from both ends of the magnetic films of the first magnetic element 91 and the second magnetic element 92, the magnetic film pattern of the first magnetic element and the magnetic film pattern of the second magnetic element are applied. The magnetic flux of the developing roll is detected by the respective magnetic detectors provided in the above, and the output of the impedance change due to this is input to the differential amplifier via the detection circuit, and the difference between the two is obtained to obtain the output. Therefore, since the magnetic film of the first magnetic element and the magnetic film of the second magnetic element are displaced from each other by ２ magnetization pitch, the impedance generated between the two magnetic films is replaced with the output waveform. 180 degrees out of phase with each other, causing a mutual noise shift in the mutual signal.
Furthermore, since the difference between the two signals is obtained, the noise component is cancelled, and only the target impedance change can be extracted in the form of a sine wave. Therefore, the noise of the external magnetic field can be canceled out and ignored, and the developing device can be used.

As described above, the toner density sensor 9 (the magnetic element 91 and the magnetic element 92) using the MI element of the present invention.
According to this method, an extremely high sensitivity can be obtained, so that the degree of freedom in design is improved without being restricted by a position where the image forming apparatus is directly attached to the developer container 3 as in the related art. According to the confirmation test, it was confirmed that even when the distance G between the developer container 3 and the toner density sensor 9 was about 100 mm, a change in the magnetic flux of the developing roll 7 was detected.

[0018]

According to the present invention, a change in the entire developer can be detected, so that the sensitivity does not decrease depending on the mounting position of the sensor and the like. And a developing device having a high degree of freedom in design can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a developing device according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing one embodiment of a magnetic element.

FIG. 3 is a characteristic diagram showing a magnetic impedance characteristic.

FIG. 4 is a cross-sectional view illustrating an example of a conventional developing device.

[Explanation of symbols]

1: photosensitive drum, 2: two-component developer, 3: container body,
4: Non-magnetic sleeve 5: Magnet shaft, 6: Toner density sensor, 7:
Developing roll, 8: magnetic sensor, 9: toner density sensor,
91: first magnetic element, 92: second magnetic element, 80:
Magnetic film, 81: magnetic detection unit, 82: comparison detection unit, 83,
83 ': terminal, 84: non-magnetic substrate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G053 AA29 AB06 AB26 BA05 CA02 CA17 DB02 2H031 AC19 BA04 BC03 DA01 2H077 AD06 AD13 AD18 AD31 AE05 DA10 DA15 DA43 DA52 EA03 3J103 AA02 GA02 GA03 GA52 GA57

Claims (3)

[Claims] 1. A container body of a developer replenishing device, a developing roll in the container body having a plurality of magnetic poles therein, a developer housed in the container body so as to be refillable, and the developing roll A developer remaining amount detection sensor or a concentration detection sensor configured to detect a magnetic field generated by the magnetic impedance element. 2. The magnetic impedance element according to claim 1, wherein the magnetic impedance element is a magnetic sensor including a first magnetic element and a second magnetic element formed on a non-magnetic substrate. The magnetic detection is performed by the second
2. The developing device according to claim 1, wherein the differential operation is performed using the magnetic element as a comparison element. 3. The developing device according to claim 1, wherein the first magnetic element and the second magnetic element are electrically connected to each other by being shifted by a half pitch with respect to a magnetization pitch of the developing roll. A sensor is movably opposed to each other, a high-frequency current is applied from both ends of the first magnetic element and the second magnetic element, and the first magnetic element and the second magnetic element are caused by magnetic flux from the developing roll. 3. The developing device according to claim 2, wherein a difference between impedances generated between both ends of the developing device is converted into an electric signal to obtain an output.