JPS60147775A - Developing device - Google Patents

Abstract

PURPOSE:To improve detecting accuracy sharply by arranging a toner density detecting member oppositely to a scraper member and inclining the detecting surface of the toner density detecting member from the upper surface of the scraper surface by a slight angle. CONSTITUTION:When the detecting surface of the toner density detecting member 8 is inclined from the upper surface of the scraper 15 by a slight angle theta, a developer is properly pressed on the detecting surface when the developer passes through the upper surface of the scraper. The developer 2 is properly pressed and contacted with the detecting surface under comparatively thick state, i.e. the density of the developer 2 is detected under almost constant state, so that the variation width of an output signal can be narrowed and highly accurate detection can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a developing device for converting an image, an electrostatic image formed on the surface or surface of a carrier, by a magnetic brush method.

[Prior art] In image forming devices such as electrophotographic devices and electrostatic recording devices, an electrostatic latent image is formed on the surface of an image carrier (selenium photoreceptor, zinc oxide photoreceptor, organic photoconductor, dielectric material, etc.). and developing the electrostatic latent image with a magnetic brush using a magnetic developer,
The image is then fixed, or the developed image is transferred onto a transfer sheet such as plain paper and then fixed to obtain the final image.

As the magnetic developer used in the magnetic brush method, a two-component developer which is a mixture of a ferromagnetic carrier and toner particles is often used. This magnetic carrier is made of iron powder, ferrite powder, nickel powder, etc., or their surfaces are coated with an organic polymer, and the toner particles are made of resin in which additives such as color pigments and dyes are dispersed. ,
The materials of the carrier particles and toner particles are selected so that they are triboelectrically charged to opposite polarities when mixed together.

When an electrostatic latent image is developed using the above-mentioned two-component developer, the toner particles are evaporated by the development, so that when the development is repeated, the toner concentration in the developer decreases. If development is performed while the toner density remains low, the image density will decrease.

Therefore, when using a two-component developer, toner in the developer? In order to maintain IIU at a predetermined level (approximately 3 to 10%), a means for detecting toner concentration is installed, and the developing device is configured to replenish toner according to the signal from the detection member. It is true. Toner deepness detection methods often utilize the fact that the toner concentration in the developer changes and the magnetic permeability of the developer changes. For example, a Hall element is installed in the magnetic field of a permanent magnet member, and (Refer to Japanese Unexamined Patent Publication No. 117047/1983).

Although Hall elements have high detection accuracy, they are susceptible to temperature changes and have reliability problems. Therefore, usually the developer forms part of the magnetic circuit of the detection coil, and the toner concentration is often detected as a change in the inductance of the detection coil. (For example, JP-A-53-49
(Refer to No. 437 and No. 54-159233) Furthermore, in a developing device using a two-component developer, it is necessary to mix the developer after development with newly replenished toner. A scraper member is often provided close to the non-magnetic sleeve in order to scrape off the material from the non-magnetic sleeve (for example, Japanese Utility Model Publication No. 55-50685, Japanese Utility Model Publication No. 55-50685)
3-34921).

By the way, by detecting the change in the inductance of the detection coil,
When detecting the toner concentration, the magnetic carrier is magnetically saturated by the magnetic field of the permanent magnet, so changes in inductance due to the temperature characteristics of the magnet and differences in the degree of saturation due to changes over time appear as detection errors. Since the size of the detection coil is limited due to the installation space, problems arise such as detection errors due to non-uniform mixing of the developer. Therefore, conventionally, toner concentration has been generally detected by taking out a portion of the developer as a sample and performing it at a position where it is not exposed to the magnetic field of a permanent magnet (for example, JP-A-53-126944@, JP-A-54-761). accompanied by defects.

Therefore, in order to dispose the detection coil along the developer flow without providing a sampling mechanism, the detection surface of the toner concentration detection member is provided opposite to and parallel to the upper surface of the above-mentioned scraper member. It is. However, in this case, the contact between the detection surface and the developer becomes unstable, and the density of the developer inevitably fluctuates, so the reliability of the detected depth is low. Ta.

[Objective J] An object of the present invention is to solve the above-mentioned problems of the prior art and provide a developing device capable of detecting toner concentration with high reliability.
Is Rukoto.

[Summary] The developing device of the present invention includes a nonmagnetic sleeve that holds a developer containing a magnetic carrier and toner particles, and a plurality of !C fixed and arranged inside the nonmagnetic sleeve. In the developing device, the developing device includes a permanent magnet member having an l pole, a scraper member provided close to the non-magnetic sleeve, and a toner concentration detection member provided opposite to the scraper member. It is characterized in that the detection surface of the toner concentration detection member is inclined by a small angle with respect to the upper surface.

[Example] The details of the present invention will be explained below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the developing device of the present invention, FIG. 2 is a diagram showing the □ circuit configuration of the toner concentration detection member shown in FIG. 1, and FIG. 3 is an output waveform of the circuit shown in FIG. 2. This is shown in Figure 1.

□ First, in FIG. 1, developer 2 consisting of magnetic carrier and toner is used to form a developed image I! A cylindrical non-magnetic sleeve 4 is rotatably arranged inside the image tank 3 facing the photosensitive drum 1 which rotates in the direction of arrow Z in the figure. A permanent magnet member 7 having a permanent magnet 5 having a plurality of magnetic poles (four in the figure) fixed to a shaft 6 is fixedly disposed within the non-magnetic sleeve 4. N of the magnetic poles
1 pole is a developing magnetic pole located opposite the developing gap D"k:' □, S1 pole assembly 37 is a scraping magnetic pole, and N2 and S2 poles are conveying magnetic poles. The rotation direction of the non-magnetic sleeve 4. A scraper member 15 is installed behind the pole 81 when viewed from above.A pair of screws 9 and 9' are rotatably installed on the opposite side of the non-magnetic sleeve 4 from the photoreceptor drum 1. A toner tank 10 for storing toner 2a is formed above the toner tank 10. At the upper opening of the toner tank 10, a toner supply roll 13 formed by fixing a porous elastic layer 12 around a shaft 11 is provided. The IA image tank 3 is also provided with a doctor member 14 that regulates the thickness of the developer on the non-magnetic sleeve 4.The toner concentration detection member 8 is attached to the scraper member 14. Member 15
is installed opposite.

The operation of the above-mentioned developing device will be explained as follows.

First, when the non-magnetic sleeve 4 is rotated in the direction of the arrow X shown in the figure, the developer 2 adsorbed onto the sleeve is conveyed from the doctor gap d toward the development gap D. Near the developing gear D, a magnetic brush formed by the developer 2 rubs the surface of the photoreceptor drum 1 to develop an electrostatic latent image (not shown) formed on the drum. After passing through the developing gap D, the developer 3 is scraped off from the non-magnetic sleeve 2 by the scraper member 15 and collected into the developer 13.

Next, the collected developer 3 is stirred and mixed with the toner 2a discharged from the toner tank 10 by the rotation of the toner supply roll 13 by the screener 1-9.9', and then absorbed onto the non-magnetic sleeve 4 again. and then subjected to development.

Further, as the developer 2 passes over the scraper member after passing through the development gap D, the toner concentration in the developer is detected by the toner degree detection member 8 that comes into contact with the developer layer there, and the detected toner concentration is Accordingly, an external signal is output to control the rotation of the toner supply roll 13 by a drive means (not shown).

Next, various structures are known as the toner concentration detection member 8 that utilizes changes in the inductance of a detection coil, and for example, a structure shown in FIG. 2 has been proposed.

In the figure, the 1-shaped magnetic core 16a has a primary coil L+
a and the secondary coil L2a, and the primary coil L+b and the secondary coil L2b are wound around the magnetic core 16b as shown in [175], thereby forming two transformers. -Next coil Lea and L+b
is connected to the output terminal (not shown) of the oscillator 17, the secondary coils L'2a and L2b are connected to the signal input terminal (not shown) of the phase comparator 18, and the secondary coils L'2a and L2b are connected to the signal input terminal (not shown) of the phase comparator 18. Comparison signal detection coils LR+ and LR2 are wound on the next side, and these are connected to the comparison signal type horn terminal of the phase comparator 18. An output terminal (not shown) of the phase comparator 18 is connected to an input terminal (not shown) of a potential comparator 190 where it is compared with a reference voltage corresponding to a predetermined toner concentration;
A signal is output according to the potential difference. Then, the potential comparator 19 connects the load (drive source such as a motor 2) via the drive circuit 20.
Connected to 1.

According to the above circuit configuration, the output from the transmitter is applied to the secondary coils L2a and 1b, and the output (,i@) corresponding to the degree of coupling of each magnetic circuit is applied to the secondary coils L2a and 1b. Induced by L2b.

Here, when the degrees of coupling of both magnetic circuits are equal, the outputs of the secondary coils L2a and L2b are in opposite phases, so they cancel each other out, and the operating output thereof becomes O. Therefore, when the degrees of coupling between the two magnetic circuits are different, the output of one of the secondary coils L2b becomes larger and an operating output is generated according to the difference in the coupling degrees, so the operating outputs are compared in phase. vessel 19
The reference voltage is adjusted so that the phase detection output corresponding to the relevant phase becomes 0 (see Figure 3 (a)), and the toner concentration changes and the developer When the magnetic permeability fluctuates, the phase detection horn corresponding to the change in magnetic permeability is output (see Figure 3 (b)).
do it.

As a sensitivity adjustment mechanism for this toner-8i degree detection member, a screw core made of a magnetic material such as soft ferrite may be used, and this may be provided on the reference magnetic circuit side.

As described above, according to this toner concentration detection member, 2
Since the detection unit detects toner concentration by comparing the output signals of two magnetic circuits, it is virtually unaffected by changes in environmental conditions such as temperature and humidity, making it possible to detect extremely reliable toner concentration. Become.

When the toner concentration is detected using changes in the inductance of the detection coil as described above, if the fluctuation range (noise) of the output signal is human, the toner concentration cannot be detected with high accuracy. Therefore, it is generally necessary to keep this fluctuation range as small as possible. However, in the conventional developing device, the detection surface of the toner concentration detection member is installed parallel to the scraper, which causes the above-mentioned problems.

As a result of studies conducted by the present inventor, it has been found that the detection accuracy can be improved by tilting the detection surface slightly -C with respect to the upper surface of the scraper.

In detail, if the detection surface is tilted at a small angle with respect to the top surface of the scraper, when the developer passes over the top surface of the scraper, the developer is moderately compressed by the detection surface and the developer is Because the developer comes into close contact with the detection surface, detection is performed with the density of the developer almost constant, which allows for a narrow range of variation in the output signal, making highly accurate detection possible. A range of 2° to 10° is appropriate for the specific inclination angle (shown e'c in Figure 1).This is because when there is no 2° swirl, the developer density unevenness (pressure)] Fluctuations in detection accuracy exceed 40%; on the other hand, when the angle exceeds 10°, the flow of developer is obstructed, and it is easily affected by developer density, resulting in fluctuations in output reliability. The optimum range of the inclination angle is 36 to 8 degrees.

[Specifics] In FIG. 1, the photosensitive drum 1 is a 3e drum (outer diameter 120InIIlφ, circumferential speed 150Il1m/se).
c, ) as the non-magnetic sleeve 4 with an outer diameter of 3211 n1
A Ba-ferrite magnet of 11φ was used. Also permanent magnet 5
In this case, the N1 pole is 800G1N2, and the sl and s2 poles are all 7650G (all values on the sleeve).
,'two.

The magnetic pole opening angles θ2, θ3 and θ4 are 90' and 120', respectively.
and 60°. However, the angle θ1 between the line connecting the N pole and the center O of the permanent magnet portion H and the horizontal line a was 10°. As the developer, iron powder Kyrelia (EFV manufactured by Nippon Iron Powder Co., Ltd.) having a particle size of 100 to 200 μm and toner particles having a particle size of 5 to 20 μm were used.

A covey test was conducted on 10,000 consecutive sheets by rotating the toner at il and il, and setting the reference value of the toner concentration in the developer to 5%.

Here, as the detection member C, the one shown in Fig. 2 is used, the median value of the output signal is set to 2.5V, and the target variation Ill is set to 1V.
Change the inclination angle by setting as below! The output signal during IC was measured. The measurement results are as shown in Figure 4. From FIG. 4, it can be seen that when the angle of inclination is in the range of 2° to -8°, the fluctuation range of the output voltage is within 1 V, and the detection accuracy of the toner concentration can be increased.

[Effect J As described above, according to the present invention, the toner concentration in the developer can be detected accurately and stably.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the developing device of the present invention, FIG. 2 is a diagram showing the circuit configuration of the toner detection section, and FIG. 3 is a diagram showing the output waveform of the circuit in FIG. 1. FIG. 4 is a diagram showing the relationship between the tilt angle and the output voltage. 1: Photosensitive drum, 2: Developer, 4: Non-magnetic sleeve,
7: Permanent magnet member, 8: Toner concentration detection member, 15: Scraper part 1 Figure 2 eb Figure 3

Claims (1)

[Scope of Claims] 1. A non-magnetic sleeve that holds a developer containing a magnetic carrier and toner particles, a permanent magnet member provided within the non-magnetic sleeve and having a plurality of magnetic poles on its surface, and a permanent magnet member that holds the developer. The present invention includes a developer tank, a scraper section provided close to the non-magnetic sleeve, a shrine, and a toner concentration detection member provided opposite the scraper member.
1. A developing device characterized in that the detection surface of the detection member is inclined by a small angle with respect to the upper surface of the scraper member. 2. The developing device according to claim 1, wherein the inclination angle is set in a range of 2'' to 10 degrees.