JP2002244414A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device that can highly accurately detect the quantity of remaining developer while preventing the developer from scattering or sticking to an image non-printing area. SOLUTION: The image forming device has a photoreceptor drum (image carrier) 1 which holds an electrostatic latent image thereon, a developing device 2 which includes inside a developing roller 2-1 being in contact with the photoreceptor drum 1 and develops the electrostatic latent image with toner (developer) on the developing roller 2-1, a development bias power source which applies a DC bias to the developing device 2, and a remaining developer quantitative detection means which detects, as electrostatic capacity, a quantity of toner remaining in the developing device 2. In the image forming device, the development bias power source is periodically turned on and off when the quantity of remaining developer is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic process such as an electrophotographic copying machine, a laser beam printer, an LED printer, and a facsimile machine, and more particularly to an image forming apparatus having a process cartridge. It is.

[0002]

2. Description of the Related Art In general, a known image forming apparatus using an electrophotographic recording system includes a photoreceptor driven in rotation, a primary charger for uniformly charging the surface of the photoreceptor, and an exposing surface of the photoreceptor. Exposure means for forming an electrostatic latent image corresponding to an image signal on a photoconductor, developing means for developing the electrostatic latent image with toner to form a visible image, and recording the developed visible image on a recording sheet. The image forming apparatus includes a transfer unit for transferring the image on the recording medium, a fixing unit for fixing a visible image on a recording sheet, and the like.

In this case, as a developing means, a developing roller performs development by contacting with a photoreceptor (hereinafter, this is referred to as a contact developing system) and a developing roller performs development without contacting the photoreceptor. (Hereinafter, referred to as a non-contact developing system) are known, and contact developing systems include Japanese Patent Application Laid-Open Nos. 62-223771 and 1-23956.
Japanese Patent Laid-Open Publication No. HEI 6 (1994) -104, which discloses a type in which a developing roller is elastically brought into contact with the surface of a photoreceptor, as disclosed in
As a developing roller disclosed in JP-A-247478, there is a developing roller in which a thin resin roller is provided on the surface of a roller made of an elastic body.

The principle of development in these developing means is as follows.
Regardless of whether it is a contact development method or a non-contact development method, it is based on the relationship (developing contrast) between the potential of the light and dark portions due to the electrostatic latent image formed on the photoconductor and the bias voltage of the developing roller. A predetermined amount of toner is transferred to and adhered to the electrostatic latent image formed on the photoreceptor to form a visible image corresponding to the electrostatic latent image on the photoreceptor. There is a difference.

In general, the developing bias for non-contact development includes:
Since it is necessary to sufficiently cause the toner to fly from the developing roller to the photoconductor, a developing bias in which an AC bias for assisting toner flying is superimposed on a DC bias for determining a developing contrast is used. On the other hand, in contact development, since there is no need to actively fly the toner, most of them simply apply a DC bias according to the development contrast. Of course, a developing bias in which an AC bias is superimposed may be used for contact development. However, in addition to increasing the cost of a bias power source, when a so-called non-magnetic one-component toner containing no magnetic material is used, the AC bias is superimposed. This causes so-called AC scattering in which toner having a small charge amount flowing between the developing roller and the photoconductor is scattered.
Not generalized.

FIG. 7 is a schematic sectional view of a conventional image forming apparatus using a contact developing system as a developing means.

In FIG. 7, 1 is a drum-shaped photosensitive member (photosensitive drum), 2 is a developing device, 2-1 is a developing roller, and 2-2.
Is a toner supply roller, 2-3 is a developing blade, 3 is a transfer device, 4 is a toner cleaning means, 5 is a primary charger,
Reference numeral 6 denotes an exposure device, 7 denotes a toner cleaning unit, and 10 denotes a toner.

Here, the operation of the conventional image forming apparatus having the above configuration will be described.

First, the overall operation will be described. First, the surface of the photosensitive drum 1 rotating in the direction of the arrow shown in the figure is uniformly charged by the primary charger 5, and then the image signal is applied to the surface by the exposure device 6. Is formed. Subsequently, the electrostatic latent image is developed by transferring the toner 10 on the developing roller 2-1 to the photosensitive drum 1 by a developing bias, and a visible image corresponding to the electrostatic latent image is formed on the surface of the photosensitive drum 1. Is done.

Next, the visible image formed on the surface of the photosensitive drum 1 is transferred onto the recording paper 8 by the transfer device 3,
The transferred visible image is fixed on the recording paper 8 and then discharged together with the recording paper 8 as a recording image.

The surface of the photosensitive drum 1 that has passed through the transfer device 3 is cleaned with toner through a toner cleaning means 4, and the above steps are repeated.

The developing bias includes a bright portion potential V
When reversal development is performed on an electrostatic latent image having L of −100 V and a dark part potential Vd of −800 V using a negative toner having a negative charging polarity on the toner 10, approximately −400 V to 50 V
A 0 V DC bias is used.

As described above, when the contact developing method is used as the developing method, an AC bias power supply circuit is not required as a developing bias, and therefore, there is an advantage that a less expensive apparatus can be provided than an apparatus using the non-contact developing method. There is.
In particular, in a color image forming apparatus which has been actively developed in recent years, the merit of the contact developing method is great when using a color toner containing no magnetic material, and it is used in many apparatuses.

[0014]

However, in the contact developing method which does not require the use of an AC bias power supply for the developing bias, there is an advantage that the cost of the high-voltage power supply can be greatly reduced. Problems arise.

In general, in a developing device using an AC bias as a developing bias, an electrode (antenna) is provided in a developing device, and a voltage induced by the AC bias is measured on this electrode, so that the remaining amount of toner in the developing device is measured. In many cases, a so-called antenna type remaining toner amount detection (hereinafter, referred to as an antenna remaining detection) for determining the remaining amount is used. This antenna residual test
It is also known that since the remaining amount of toner between the developing roller and the electrode can be continuously grasped and the detection circuit is inexpensive, the cost performance is higher than other types of toner remaining amount detection.

However, in the contact developing method using no AC bias as the developing bias, the same detection method cannot be adopted. Therefore, an optical sensor including a light emitting element and a light receiving element is used to determine whether toner is present in the developing unit. Optical remaining amount detection method that makes use of the fact that light is blocked by
At present, in the case of a laser beam printer, the amount of consumed toner is estimated by a so-called video counting method or the like that counts a light emission signal of a laser.

However, in the optical remaining amount detection method, only the presence / absence of toner can be determined, and only a binary determination as to whether or not the amount is below a certain remaining amount can be made. It is difficult to predict the number of printable sheets by monitoring the consumption.

Further, since the toner amount is not directly measured in the video counting method, when the toner consumption rate for the video data fluctuates due to the use environment or a printed image (for example, a difference between a solid image and a line image), the toner remaining amount is not changed. It may not be possible to accurately determine the amount.

Furthermore, in recent years, a technology has been developed that allows a large amount of transfer material to be loaded on an image forming apparatus and that prints at a high speed, and these devices are used by being shared by a plurality of users via a computer network. Under the present circumstances, it is becoming an important usability to be able to accurately determine whether or not the remaining amount of toner can be printed for the number of sheets to be printed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a purpose thereof is to prevent the scattering of the developer and the adhesion of the developer to a non-printing portion, and to detect the remaining amount of the developer with high accuracy. It is an object of the present invention to provide an image forming apparatus capable of performing the above.

[0021]

In order to achieve the above object, the present invention provides an image bearing member for carrying an electrostatic latent image, and a developing roller for contacting the image bearing member. A developing device that develops an electrostatic latent image with a developer, a developing bias power supply that applies a DC bias to the developing device, and a developer remaining amount detecting unit that detects the remaining amount of the developing device as an electrostatic capacity The developing bias power supply is periodically turned on / off when the remaining amount of the developer is detected.
It is characterized by performing FF.

Further, according to the present invention, there is provided an image bearing member for carrying an electrostatic latent image, and a developing roller in contact with the image bearing member, wherein the electrostatic latent image is developed with a developer on the developing roller. Developing device, a developing bias power supply for applying a DC bias to the developing device, a developer remaining amount detecting means for detecting the remaining amount of the developing device as an electrostatic capacity, and a developing roller and an image carrier. In the image forming apparatus provided with a means for changing the capacitance, the developing bias power supply is periodically turned on / off when the remaining amount of the developer is detected, and the developing roller and the image carrier are changed by the means for changing the capacitance. It is characterized in that the electrostatic capacitance between them is variable.

[0023]

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

<First Embodiment> FIG. 1 is a schematic sectional view of an image forming apparatus according to the present invention.

In the image forming apparatus according to the present embodiment, the photosensitive drum 1, the developing device 2, the primary charger 5 and the cleaning device 4 are integrated to constitute a developing cartridge. It is removably mounted on the apparatus main body. In this embodiment, the developing cartridge system is adopted, but this system is not always required.

The developing device 2 includes a developing roller 2-1, a developing blade 2-3, a toner supply roller 2-2, and a stirrer in a developing container containing a non-magnetic toner (one-component toner) 10 as a one-component toner. Blade 2-4, remaining amount detection electrode 2-5
And the like. Further, the developing device 2 includes
As shown in (1), the developing roller 2-1 and the photosensitive drum 1 are configured to be able to contact and separate by a contact and separation mechanism including a driving cam 9 and a pressure spring 2-6.

The above-mentioned contact / separation mechanism uses the center of the first stage gear 2-7 for transmitting the drive to the developing roller 2-1 and the stirring blade 2-4 as a rotation center, and connects the developing roller 2-1 and the stirring blade 2-4. It is configured to be able to swing while being driven.

The remaining amount detecting electrode 2-5 for detecting the remaining amount of the toner 10 includes a toner supply roller 2-2, a developing blade 2-
3 and a developing roller 2-1. The developing roller 3 is disposed in a state of being stretched in a horizontal direction inside a developing section constituted by the developing roller 3 and the developing roller 2-1.

In this embodiment, the developing bias power source is D
A means for generating an alternating electric field between the developing roller 2-1 and the electrode 2-5 only when the remaining amount of toner is detected by using a C bias power supply and turning it on / off is used. Therefore, unlike the conventional non-contact developing method in which the remaining amount of toner is detected by using the AC bias power supply as the developing bias, it cannot be performed when developing the electrostatic latent image on the photosensitive drum 1. Furthermore,
When an AC bias is applied to the non-magnetic one-component toner on the developing roller 2-1 in a state where sufficient development can be performed even with a DC bias, the toner flies also in the vicinity of a nip formed between the developing roller 2-1 and the photosensitive drum 1. Since there is a possibility that the inside of the apparatus may be significantly contaminated, when the detection is performed, the developing device 2
Apart.

FIG. 3 shows a printing sequence of the image forming apparatus according to the present invention.

In FIG. 3, the detection of the remaining amount of toner is performed between printings (so-called paper intervals) for each printing of each image. The rotation cycle of the stirring blade 2-4 of the developing device 2 is shorter than the time during which printing is not performed due to the paper interval, and at least the rotation of the stirring blade 2-4 is performed at least one rotation when the remaining amount of toner is detected.

The toner remaining amount detecting circuit 50 used in the present embodiment is the same as a conventional toner remaining amount detecting circuit configuration using an AC bias as a developing bias power supply, which will be described with reference to FIG. I do.

The toner remaining amount detection circuit 50 connects the electrode 2-4 with the capacitance detection circuit 52 as a means for measuring the capacitance between the electrode 2-4 and the developing roller 2-1. ,
The capacitance between the electrode 2-4 and the developing roller 2-1 is measured by detecting the signal generated when the developing bias supplied to the developing roller 2-1 alternates with the electrode 2-4. .

Further, the toner remaining amount detection circuit 50 is connected with a reference capacitance circuit 53 as a means for setting a capacitance as a reference for comparison, and a developing bias power supply to measure the reference capacitance. By detecting a developing bias through a reference capacitance circuit 53 by a capacitance detection circuit 51 as a means for performing the measurement, a reference capacitance for measuring an unknown capacitance is obtained. The output of the capacitance detection circuit 52 and the capacitance detection circuit 5 of the reference capacitance
The output of No. 1 is compared by a comparing circuit 55 as a comparing means, the difference is detected, and the remaining amount of the toner 10 is determined to enable highly accurate remaining amount detection.

During the separation of the developing device 2, the photosensitive drum has the advantage of preventing toner scattering and the characteristic that it cannot follow high-speed switching as an electrical characteristic of a DC bias power supply used as a developing bias power supply for contact development. There is also a purpose of assisting by reducing the capacitance formed between the developing roller 1 and the developing roller 2-1.

FIG. 5 shows a high-voltage output at the time of ON / OFF when the developing roller 2-1 is in contact with the photosensitive drum 1 and when it is separated.

The toner remaining amount detecting circuit 50 detects the remaining amount of toner.
Can be detected in the same manner even if the waveform of the applied bias differs to some extent, but as shown in FIG. 5, the circuit 50 cannot follow ON / OFF, and if Vp- _pp becomes small, the toner remaining The detection level detected by the amount detection circuit 50 becomes low, and more accurate detection cannot be performed.

In this embodiment, since the output value of the DC bias may be different from that at the time of development if the toner does not fly, the output level is, for example, −500 V during the development.
However, the voltage may be set to -1000 V when detecting the remaining amount of toner.
Of course, it is desirable that the surface of the photosensitive drum 1 is maintained at the dark potential Vd by which the toner is less likely to fly by the primary charger 5, but it is obvious that this potential may be varied.

Further, an electrostatic latent image for each color is sequentially developed on a single photoreceptor 1 by a plurality of developing devices in each color developing device, and each developed color image is multi-transferred to an intermediate transfer member or a transfer material. When a contact developing method is used in a color image forming apparatus, the developing roller 2-1 and the photosensitive drum 1 must be separated from each other, and the developing device can be driven independently other than during development. In addition, if an independent developing bias power source is used, it is possible to detect the remaining amount of toner according to the present invention during development of another color.

In this embodiment, the remaining amount detecting electrode 15
Is provided in the developing device 2, but as disclosed in Japanese Patent Application No. 11-148909.
Or the image forming apparatus described in Japanese Patent Application No. 11-148915 may be arranged outside the developing device.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG.

FIG. 6 is a schematic sectional view of the image forming apparatus according to the present embodiment.

In the image forming apparatus according to the present embodiment, a switch 11 for cutting off the circuit is provided on an electric circuit for grounding the photosensitive drum 1, and this switch 11 controls the operation of the apparatus main body. ON by the control circuit 12
/ OFF. For this reason, in the present embodiment, by switching the switch 11, the photosensitive drum 1 can be switched between an electrically grounded state and a floating state. When the photosensitive drum 1 is in a floating state, even if the DC bias power supply is turned ON / OFF while the developing roller 2-1 is in contact with the photosensitive drum 1, the photosensitive drum 1 is changed according to the alternating electric field. 1 does not fly the toner 10.

Therefore, in the present embodiment, there is no need to move the developing device 2 as in the first embodiment, and similar effects can be obtained with a cheaper configuration.

[0045]

As is apparent from the above description, according to the present invention, an image carrier for carrying an electrostatic latent image and a developing roller in contact with the image carrier are included and the A developing device for developing an electrostatic latent image with a developer, and a DC
In an image forming apparatus comprising: a developing bias power supply for applying a bias; and a developer remaining amount detecting unit for detecting a remaining amount of the developer of the developing device as an electrostatic capacity, when the remaining amount of the developing agent is detected, the developing bias power supply is used. Since the ON / OFF operation is performed periodically, the effect of preventing the scattering of the developer and the adhesion of the developer to the non-printing portion can be obtained, and the remaining amount of the developer can be detected with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an image forming apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a sectional view of a contact / separation mechanism of the image forming apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a diagram showing a print sequence of the image forming apparatus according to Embodiment 1 of the present invention.

FIG. 4 is a configuration diagram of a toner remaining amount detection circuit.

FIG. 5 is a diagram illustrating a difference in a developing bias waveform due to contact and separation of a developing roller.

FIG. 6 is a schematic sectional view of an image forming apparatus according to Embodiment 2 of the present invention.

FIG. 7 is a schematic sectional view of a conventional image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image carrier) 2 Developing device 2-1 Developing roller 10 Toner (developer) 11 Switch 50 Toner remaining amount detection circuit (developer remaining amount detecting means) 51, 52 Capacitance detection circuit 53 Reference electrostatic Capacitance circuit 55 Comparison circuit

Continued on the front page F-term (reference) 2H027 DA02 DA04 DD02 DE04 DE07 DE09 EA05 EA15 EA18 EB06 EC06 ED01 ED09 EE01 EE05 ZA01 2H030 AD17 BB22 BB33 BB34 BB71 2H073 AA10 BA02 BA09 BA13 BA21 BA22 AD41 BA04 AD07 DA59 DA86 DB08 DB14 EA15 GA12

Claims (5)

[Claims] An image carrier for carrying an electrostatic latent image, a developing device including a developing roller in contact with the image carrier, and developing the electrostatic latent image with a developer on the developing roller; An image forming apparatus comprising: a developing bias power supply for applying a DC bias to the developing device; and a developer remaining amount detecting unit for detecting a remaining amount of the developer of the developing device as an electrostatic capacity. An image forming apparatus, wherein the developing bias power supply is turned on / off periodically. 2. An image carrier for carrying an electrostatic latent image, a developing device including a developing roller in contact with the image carrier, and developing the electrostatic latent image with a developer on the developing roller. A developing bias power supply for applying a DC bias to the developing device, a developer remaining amount detecting means for detecting a remaining amount of the developer of the developing device as an electrostatic capacity, and an electrostatic capacity between the developing roller and the image carrier. In the image forming apparatus provided with a variable means, when the remaining amount of the developer is detected, the developing bias power supply is periodically turned on / off, and the electrostatic capacity between the developing roller and the image carrier is changed by the variable capacity means. An image forming apparatus having a variable capacity. 3. The image forming apparatus according to claim 2, wherein the means for varying the capacitance between the developing roller and the image carrier comprises a switch for turning on / off the ground of the image carrier. 4. The image forming apparatus according to claim 2, wherein the means for varying the electrostatic capacity between the developing roller and the image carrier is constituted by a contact / separation mechanism for bringing the developing roller and the image carrier into contact with each other. . 5. The image forming apparatus according to claim 1, further comprising a plurality of developing devices, wherein the developing device detects the remaining amount of the developer exclusively in a certain developing device. .