JP2576688B2 - One-component developing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-component developing apparatus used for an electrophotographic copying machine, a laser printer, and the like, and more particularly, to an improvement in a waveform of a developing bias voltage applied to the apparatus. About.

2. Description of the Related Art Conventionally, as a one-component developing device of this type, for example, as shown in FIG.
And a developer roll 2 (hereinafter referred to as a development roll) in which a magnet roll 22 having a plurality of magnetic poles is fixedly disposed in a rotatable cylindrical sleeve 21 and magnetic toner 10 is attracted onto the sleeve 21 by a magnetic force. And a developer regulating member 3 for reducing the thickness of the magnetic toner 10 brought into pressure contact with the developing roll 2 to the developing area to a predetermined layer thickness.

In the one-component developing apparatus thus configured, the magnetic toner 10 accommodated in the hopper 1 is first carried on the rotating sleeve 21, and then the developer located in the middle of the transport path of the magnetic toner 10 After being thinned by the regulating member 3 so that the amount of toner adhering to the sleeve 21 is 0.5 to 2.0 mg / cm ² , the toner is conveyed to a developing area facing the electrostatic latent image carrier 4. The conveyed magnetic toner 10 has a predetermined charge due to rubbing with the developing roll 2 in the hopper 1 and rubbing with the developer regulating member 3 on the sleeve 21. The sleeve 21 includes an AC high-voltage power supply 5 and a DC power supply 6 that output a sinusoidal AC voltage as a developing bias power supply.
Is connected, and the toner 10 charged by the electric field formed between the electrostatic latent image carrier 4 and the developing roll 2 is caused to fly toward the electrostatic latent image carrier 4 to form an electrostatic latent image 7. The mechanism is such that a corresponding toner image 8 is formed.

By the way, when a DC superimposed AC voltage having a sine waveform as shown in FIG. 11 is applied as a developing bias voltage,
In the one-component developing device using the magnetic toner as described above,
Since the magnetic force of the magnet roll included in the developing roll acts on the developing area, the so-called toner chain in which the toner flying from the developing roll to the electrostatic latent image carrier continues in a chain along the line of magnetic force on the carrier. Is easy to occur.

When the toner image is transferred to the recording sheet, the toner chain appears as a so-called “tailing” in which a number of stripes are generated at the end of the toner image as shown in FIG. 9A, for example. , And appears as a so-called "blurring" as shown in FIG. 9B, and there is a problem that an image defect is not generated in the transferred image.

In order to solve such a problem, the present inventors have proposed a one-component developing device in which the time waveform of the developing bias voltage has a saw blade shape as shown in FIG.
2-210422).

According to this proposal, formation of a toner chain during development can be effectively suppressed, and image defects such as “tailing” and “blurring” described above can be prevented.

[Problems to be Solved by the Invention] However, the following problems newly arise according to the proposals of the present inventors.

That is, since the developing bias voltage was changed from the sinusoidal waveform shown in FIG. 11 to the sawtooth shape shown in FIG. 10, the effective value of the development expressed by the shaded area in FIGS. 11 and 10 decreased. As a result, the amount of toner necessary for reproducing the image density could not be made to fly toward the electrostatic latent image carrier due to the decrease in the energy applied to the toner on the developing roll. For this reason, in the one-component developing device proposed above,
A decrease in density was observed in the recorded image, and the density of the original image could not be reproduced sufficiently.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and aims at "tailing" and "blurring".
It is an object of the present invention to provide a one-component developing apparatus which does not cause image defects such as the above and can obtain a sufficient image density.

Means for Solving the Problems In order to achieve the above object, a one-component developing apparatus of the present invention includes a developer carrier facing an electrostatic latent image carrier while maintaining a predetermined gap, A developer supply unit for supplying the developer to the carrier; and a developer regulating member for pressing the developer carrier to make the developer thinner, and an AC voltage applied to the developer carrier. Assuming a one-component developing device in which the thinned developer is caused to fly onto the electrostatic latent image carrier and develops the electrostatic latent image on the electrostatic latent image carrier, the AC voltage is set in the development promoting direction. satisfy the relationship of T _R ≧ T _F a rise or fall time of the voltage T _F, when the fall or rise time of the voltage to the developing suppression direction is T _R to, and, the
Waveform of the AC voltage in the T _R is characterized in that has a convexly curved projecting the development accelerator direction.

In such technical means, in order to fully enjoy the effects of the present invention described above, it is necessary that the toner conveyed to the developing area is sufficiently charged. Therefore, in the present invention, the toner amount regulating member is brought into pressure contact with the outer peripheral surface of the rotating developing roll to increase the charge amount of the developer. In the following, a description will be given of a development in a case where the charge amount is insufficient in a comparative example described later.

[Operation] According to the above technical means, as shown in FIG. 2, the waveform of the developing bias voltage has a saw-toothed waveform, and the formation of the toner chain in the developing area is effectively prevented. The area of the hatched area is larger than the conventional developing bias voltage shown in FIG. 10, and the effective value of development is improved.

Hereinafter, a one-component developing apparatus of the present invention will be described in detail with reference to the accompanying drawings.

◎ First Embodiment In this embodiment, the present invention is applied to a one-component developing device using a positively charged magnetic toner as a developer, and the external configuration is the same as that of the conventional one-component developing device shown in FIG. Are identical. That is, the developing roller 2 includes a developing roller 2 opposed to the electrostatic latent image carrier 4 and a developer regulating member 3 whose leading end is disposed to be in pressure contact with the developing roller 2. It is arranged in a hopper 1 for housing. The developing roll 2 is connected to an AC high-voltage power supply 5 and a DC power supply 6 for applying a developing bias voltage.

The developing roll 2 is magnetized with a plurality of magnetic poles (N, S,...) Having different polarities and magnetic forces, and is rotated around a magnet roll 22 fixedly supported by a casing (not shown). The magnetic toner 10 is attracted, conveyed, and released from the sleeve 21 in accordance with the magnetic pattern of the magnet roll 22 in accordance with the rotation of the sleeve 21. still,
In this embodiment, the sleeve 21 has a resistance value of 4.2 × 10
Of ¹⁰ Omega · cm phenol resin and molded into a cylindrical wall thickness 1.0 mm, was used anti conductive sleeve polished longitudinally so as to be R _Z = 4.3 [mu] m in ten point average roughness of the surface JIS .

The hopper 1 is disposed so as to cover the side from below the developing roll 2, and the stored magnetic toner 10 is deposited on the back side of the developing roll 2, and is placed on the surface of the sleeve 21 after passing through the developing area. On the other hand, the magnetic toner 10 can be continuously supplied. In this embodiment, the hopper 1
As the magnetic toner 10 housed therein, a toner containing 50% by weight of magnetic powder is used.

On the other hand, the developer regulating member 3 is provided with a soft elastic member 32 made of silicon rubber having a rubber hardness of 50 ° and a thickness of 1 mm at the tip of a spring plate member 31 made of a non-magnetic stainless steel (SUS3043 / 4H material) having a thickness of 0.1 mm. Is formed by flow bonding. The restricting member 3 has a free end facing the rotation direction of the sleeve 21 and the soft elastic member 32
Is supported by the holder 9 so as to contact with a linear pressure of 100 g / cm. Incidentally, as a result of actual measurement, the amount of the magnetic toner 10 thinned by the regulating member 3 adhered to the sleeve 21 was 10 mg / cm ² .

What is characteristic in this embodiment is the waveform of the developing bias voltage applied to the sleeve 21 by the AC high-voltage power supply 5 and the DC power supply 6. This DC superimposed AC voltage is
It has a waveform as shown in FIG. 2, and has a frequency f = 2.4 k
Hz, peak-to-peak voltage VPP = 2 kV, DC component 200
V, convex rise time T _F of the voltage to development acceleration direction is set to 1/6 with respect to period T, and, the waveform of the voltage fall time of T _R in the development inhibition direction protrudes to the developing accelerator direction It has a shape curve.

In order to confirm the performance of the one-component developing apparatus of the present embodiment configured as described above, the present inventors conducted an experiment in which the apparatus was arranged in a copying machine and a copy was taken. The electrostatic latent image carrier 4 used in the experiment is a photoconductive drum having a surface made of a negatively charged organic photoreceptor, and its outer peripheral surface is charged to a predetermined potential (for example, -600 V) by a charger (not shown). ), The potential of the background portion is reduced to a predetermined potential (for example, -200 V) by exposure to form an electrostatic latent image 7. Then, the developing device was disposed in the copying machine such that the gap between the electrostatic latent image carrier 4 and the sleeve 21 of the developing roll 2 was 230 μm.

When a copy was taken under the above conditions, a very clear image without "tailing" or "blurring" was obtained. Regarding the image density, a sawtooth waveform developing bias voltage shown in Fig. 10 was applied. An extremely good image density was obtained as compared with the case of the above.

In this regard, the length of the toner chain formed on the electrostatic latent image carrier 4 is set to a sinusoidal waveform of the developing bias voltage (the eleventh bias voltage).
(See the figure), it was found that the toner chain formed in this embodiment was extremely short.

Next, to confirm the improvement of the image density, the inventors of the present application
With respect to both the conventional developing bias voltage shown in FIG. 10 and the developing bias voltage of this embodiment, the image density of the original was changed, and the change in the image density of the copy was observed. FIG. 3 shows the present embodiment by a solid line and the conventional technique by a broken line. As is clear from the results, the present embodiment has an improved image density as compared with the prior art.

◎ Second Embodiment This embodiment shows an example in which the present invention is applied to a one-component developing apparatus using a negatively charged magnetic toner as a developer. The external configuration is the same as that of the first embodiment shown in FIG. It is exactly the same as the developing device.

However, since development is performed with negatively charged toner, the waveform of the development bias voltage applied to the sleeve of the development roll is
As shown in FIG. 4, the polarity of the AC component is reversed from that of the first embodiment. That is, the developing bias voltage of the present embodiment has a frequency f = 2.4 kHz and a peak-to-peak voltage.
V _PP = 2 kV, the DC component is -200 V, and the time at which the voltage falls in the development promoting direction is _TF , which is 1/6 of the cycle T.
And the time T _{R at} which the voltage rises in the development suppression direction
Is a convex curve protruding in the development promoting direction.

The electrostatic latent image carrier 4 in which the developing device is disposed with a predetermined gap is an organic photosensitive drum of a negative charging system as in the first embodiment. In forming
After the surface of the carrier 4 was uniformly charged, the latent image was formed by lowering the potential of the image area by exposure. At this time, the potential of the image portion is, for example, 150 V, and the potential of the background portion is -450 V.

When a copy was actually collected with the above device,
As in the first embodiment, a clear recorded image without "tailing" was obtained, and the image density was also good.

Comparative Example Next, in order to confirm the effectiveness of the toner amount regulating member of the present invention, the magnetic toner 10 was removed by using the developing device shown in FIG. An experiment was conducted to observe the formation of a toner chain when the present invention was applied to a developing device having a thin layer.

The configuration of the apparatus is exactly the same as that of the first embodiment except that the developer regulating member 3 in the first embodiment is replaced by the trimmer bar 11. Therefore, members performing the same function are denoted by the same reference numerals in FIG. 5 and description thereof is omitted.

In the experiment, when the developing bias voltage having the waveform shown in FIG. 2 is applied to the sleeve 21 of the developing roll 2 and the _TF / T is changed, the length of the toner chain attached to the electrostatic latent image carrier 4 Was observed. FIG. 6 shows the results. According to this result, it was found that the effect of the present invention was weak in the developing device of the comparative example.

This development can be explained by the difference in the charge distribution of the toner. 7 and 8 show the charge distribution of the toner in the comparative example and the charge distribution of the toner in the present invention, respectively. According to this, the average charge amount of the toner of Comparative Example using the trimmer bar is as low as 0.71 μC / g and contains 28% by weight of poorly charged toner, whereas the toner of the present invention using the developer regulating member is used. The toner has an average charge of 10.48
μC / g, poorly charged toner contains only 4% by weight. That is, in the first and second embodiments, the developer regulating member is in pressure contact with the developing roll to make the toner thinner, so that the toner has a high ability to impart electric charge. However, in the comparative example using the trimmer bar, the toner is charged. Relies solely on rubbing with the sleeve, so that the toner is not sufficiently charged.
When the charge of the toner is low, the force received from the electric field is naturally small. Therefore, it is considered that the effect of the voltage waveform according to the present invention hardly appears in the comparative example. From the above,
It has been confirmed that the present invention is extremely effective for a developing device provided with a developer regulating member that makes a thin layer of the developer by pressing against the developing roll.

In each of the above embodiments, a semiconductive sleeve was used as the sleeve 21 of the developing roll 2, but a conductive material such as a metal may be used, or the surface of the sleeve may be coated with an oxide, ceramic, resin, or the like. A sleeve can be used.

Further, the direction in which the developer regulating member 3 is disposed does not need to be opposed to the rotation direction of the developing roll 2, and may be in the forward direction with respect to the rotation direction.

[Effects of the Invention] As described above, according to the one-component developing apparatus of the present invention, the formation of a toner chain that occurs during the development of an electrostatic latent image is suppressed, so that “tailing”, “blurring”, etc. In addition to being able to form a high-quality recorded image free from defects, the effective value of development is improved, so that it is possible to obtain a good recorded image having an improved image density as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a first embodiment of a one-component developing apparatus of the present invention, FIG. 2 is a graph showing a waveform of a developing bias voltage according to the first embodiment, and FIG. FIG. 4 is a graph showing the experimental results of the image density, FIG. 4 is a graph showing the waveform of the developing bias voltage of the second embodiment of the present invention, FIG. 5 is a schematic diagram showing a one-component developing device of the comparative example, and FIG. FIGS. 7 and 8 are graphs showing the experimental results of the comparative example, FIGS. 7 and 8 are graphs showing the toner charge distribution of the comparative example or the present invention, respectively, and FIGS. 9 (A) and (B) are generated in a conventional developing device. Figures showing “tailing” or “blurring” of recorded images, FIGS. 10 and
FIG. 11 is a diagram showing a waveform of a conventional developing bias voltage. [Explanation of Signs] 2: Developing roll (developer carrier) 3: Developer regulating member 4: Electrostatic latent image carrier 5: AC high voltage power supply 6: DC power supply 7: Electrostatic latent image 8: Toner image 10: Toner (developer)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigeru Inaba 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd. Inside

Claims (1)

(57) [Claims] A developer carrying member which faces the electrostatic latent image carrier with a predetermined gap; developer supply means for supplying a developer to the developer carrier; A developer regulating member for making the developer thinner, and causing the thinned developer to fly to the electrostatic latent image carrier by an AC voltage applied to the developer carrier, In the one-component developing device that develops an electrostatic latent image on a latent image carrier, the AC voltage has a rising or falling time T _{F of} a voltage in a development promoting direction, a falling or falling time of a voltage in a development suppression direction. one component satisfies the relationship T _R ≧ T _F the rise time when the T _R, and, the waveform of the AC voltage in the T _R, characterized in that has a convexly curved projecting the development accelerator direction Developing device.