JPS62105173A - Image forming device - Google Patents

Abstract

PURPOSE:To stabilize the quality of an image even when a toner has been consumed in large quantities, by halting an operation and replenishing the toner, in case when the toner quantity has become lower than the second prescribed value, and restarting an image forming operation, in case when the toner quantity has been restored to the first prescribed value. CONSTITUTION:Turning-on and-off of a toner replenishing signal S1 are repeated, and a toner mixing ratio of a developer is controlled so as to be converged to a proper level Tc. When an image formation is executed continuously, even if a toner is replenished, a toner mixing ratio of the developer is lowered. When the mixing ratio becomes lower than a level Ta, and an output voltage of a magnetic sensor becomes higher than a prescribed value Va, a toner empty signal S3 is outputted, continuous copying is halted temporarily, and the toner is replenished. When said mixing ratio becomes higher than the proper level Tc, the output voltage of the magnetic sensor 47 becomes lower than a prescribed value Vc, the toner replenishing signal S1 is turned off, the replenishment of the toner is stopped and the continuous copying which has been halted until that time is restarted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image forming apparatus such as an electronic copying machine, and more particularly to control of replenishment of developer to a developing device.

[Technical background of the invention and its problems] Conventionally, as a control means for toner replenishment in an image forming apparatus that performs development using a two-component developer, a sensor detects the toner mixture ratio in the developing device, and the toner mixture ratio is determined to be a specified value. If it is lower, toner is supplied from the toner hopper to the developing device.

However, with this method, if a large amount of toner is replenished at once, the toner mixing ratio will become uneven within the developing device.
Only a small amount of toner can be replenished.

Therefore, when copying that consumes a large amount of toner is performed continuously, toner cannot be replenished in time, resulting in a decrease in toner mixing ratio, resulting in a problem of deterioration of image quality and adhesion of developer to paper.

[Object of the Invention] The present invention has been made based on the above circumstances, and an object of the present invention is to provide an image forming apparatus with stable image quality even when a large amount of toner is consumed.

[Summary of the Invention] In order to achieve the above object, the present invention includes a developing device for developing an electrostatic m-image in an image forming apparatus, and a developing device provided in the developing device to detect the amount of toner in the developing device. a toner amount detecting means for outputting a signal corresponding to the toner amount detecting means; a toner replenishing means for replenishing toner to the developing device; and a toner amount detecting means for replenishing toner to the developing device; When the amount of toner is lower than a first predetermined value set by caulking, the toner replenishing means is operated, and when the amount of toner falls below a second predetermined value which is set to a value lower than the first predetermined value, the toner replenishing means is operated. When the developing operation is interrupted and the toner amount recovers to the first specified value, or after a predetermined period of time or after replenishing a predetermined amount of toner, the developing unit performs the developing operation. The system is equipped with a control means for controlling the system to restart.

According to the present invention, a first specified value when the amount of toner in the developing device is in an optimal state and a second specified value at a lower level are set in advance, and continuous image formation is performed. If the toner amount falls below the second specified value during operation, the operation is interrupted and toner is replenished, and when the toner amount recovers to the first specified value, or after a predetermined time has elapsed, or after the predetermined amount is After toner is replenished, the image forming operation can be restarted when the toner is restored to the second specified value.

Examples of the invention] Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 5 is a sectional view of one embodiment of the present invention.

That is, this image forming apparatus includes a main body 1 and a main body 1.
The document feeder 3 is provided so as to be openable and closable so as to cover the document table 2 on the upper surface of the document feeder 3. A paper feed cassette 4.5.6 is located on the right side of the main body 1, and a paper output tray 7 is located on the left side.
are installed respectively. The top paper feed cassette 40 cassette cover of the cassettes serves as a manual paper feed tray 8 for manually feeding paper as appropriate.

Further, a photosensitive drum 9 is disposed approximately at the center of the main body 1 . Around this photosensitive drum 9, a charging device 10, an exposure optical system 11, a two-color color developing device 12,
Transfer charger 13, peeling charger 14, cleaning device 15,
, an electrostatic lamp 16, etc. are arranged in this order.

Furthermore, a paper feed cassette 4.5.6 is provided at the bottom of the main body 1.
A paper feed roller 17 and a separation roller 1 for preventing double sheet taking.
8 or manually fed from the manual paper feed tray 8, the paper is transferred to the paper output tray 7 via the image transfer section 19 between the photosensitive drum 9 and the transfer charger 13. A paper conveyance path 20 is formed that leads to. and,
An aligning roller 21 is disposed on the upstream side of the image transfer section 19 of the paper conveyance path 20, and a heat roller 22 and a paper discharge roller 23 as a fixing device are disposed on the downstream side.

The developing device 12 is divided into a first developing device 121 and a second developing device 122, and the first developing device 121 uses a red (or yellow, blue, green, etc.) developer that is rarely used. , the second developing device 122 uses black developer, which is frequently used. Note that the above developer is a non-component developer consisting of toner and carrier. By selectively driving the first developing device 121 and the second developing device 122, color development of black or one other color (for example, red) is performed.

Roughly, the exposure optical system 11 includes an exposure lamp 24 that moves back and forth along the lower surface of the document table 2 in the direction of the arrow shown in the drawing, and irradiates light onto the document, and a first mirror that reflects light reflected from the document in a predetermined direction. 25, a second mirror 27 and a second mirror 27 that move in the same direction at half the speed in synchronization with the exposure lamp 24 and the first mirror 25 and reflect the reflected light from the first mirror 25 toward the lens unit 26 side. 3 mirror 28, and a fixed fourth mirror 29 and fifth mirror 30 that reflect the reflected light that has passed through the lens unit 26 in a predetermined direction.
It is comprised of a fixed sixth mirror 31 that reflects the reflected light from the fifth mirror 30 toward the photosensitive drum 9 side.

Next, the image forming operation of this image forming apparatus will be explained.

First, the exposure lamp 24 and the first mirror 25 are
The upper original is optically scanned and an image is formed on the rotating photoreceptor drum 9, and an electrostatic latent corresponding to the image of the original is formed on the photoreceptor drum 9, which is uniformly charged by the charging device 10. form an image.

The electrostatic latent image thus formed is opposed to the developing device 12, where it is developed into a developer image and sent to the image transfer section 19, where it is placed on the paper fed by the aligning roller 21. The image is transferred.

After the paper to which this developer image has been transferred is separated from the photosensitive drum 9 by the separation charger 14, the paper is transferred to the paper transport path 20.
The sheet is guided through the heat roller 22, where the transferred image is fixed, and then discharged to the paper discharge tray 7 by the paper discharge roller 23.

On the other hand, the photosensitive drum 9 after the developer image has been transferred onto the paper
By facing the cleaning device 15, the remaining developer (toner) is cleaned from the surface of the copying machine 15, and afterimages are roughly erased by the static eliminating lamp 16, in preparation for the next copying operation.

FIG. 4 shows, for example, the second developing device 122 in detail, and is equipped with a magnetic sensor for detecting the toner mixing ratio. That is, this developing device includes a developer conveying means A that conveys the developer from the toner hopper to the photosensitive drum, a toner amount detecting means B, and a developer rectifying means C that adjusts the flow of the developer near the toner m detecting means. , a developer conveying means A, a developer rectifying means C1, and a casing D housing a part of the toner amount detecting means B.

The developer conveying means A includes a magnetic roller (developing roller) 41 that conveys the developer to a developing area, that is, a contact area with the photosensitive drum 9 by forming a magnetic brush for the developer on its surface; A toner conveying device 44 consisting of a toner conveying pipe 42 and a toner conveying shaft 43 rotating within the toner conveying tube 42, and a first developer that preliminarily stirs the toner conveyed by the toner conveying device 44 with a developer. It is composed of a stirring body 45 and a second developer stirring body 46 that stirs the developer.

Further, the toner amount detection means B is constituted by a magnetic sensor 47 attached to the casing D with the detection head 47a exposed inside the developing device.

Further, the developing device rectifying means C includes a doctor 48 that regulates the thickness of the magnetic brush on the magnetic roller 41, and a doctor 48 that regulates the thickness of the magnetic brush on the magnetic roller 41.
The developer rectifying member 49 receives the developer scraped off by the magnetic sensor 8 and creates a stable flow of the developer toward the detection head 47a of the magnetic sensor 47.

FIG. 1 schematically shows a control system of an image forming apparatus according to the present invention.

That is, this control system includes a magnetic sensor 47 whose detection head is exposed inside the developing device, a voltage comparator 50 that compares the voltage output from the magnetic sensor with a predetermined specified value, and a signal from the voltage comparator 50. The microprocessor 52 controls the toner replenishment controller 51.

Furthermore, the magnetic sensor 47 comes into contact with the developer in the developing device,
A detection head 47a that detects the magnetic permeability of the developer, an amplifier 47b that amplifies the minute output signal from this detection head 47a, an oscillator 47c that drives the detection head 47a and outputs a reference phase signal, and It consists of a phase comparator 47d that compares the phase difference between the output reference phase signal and the detection signal amplified by the amplifier 47b, and a low-pass filter 47e that rectifies the waveform of the signal output from the phase comparator 47d. ing.

The characteristics of the output voltage of the magnetic sensor 47 with respect to the developer/toner mixture ratio are as shown in FIG. 2, and as the toner mixture ratio increases, the output voltage of the magnetic sensor 47 decreases. Here, the output voltage of the magnetic sensor 47 for the optimum toner mixing ratio Tc for obtaining a good quality image is Vc, the toner mixing ratio when the toner in the toner hopper is exhausted and no toner is conveyed into the developing device at all. The output voltage of the magnetic sensor 47 with respect to Ta is Va.

These Va and VC are set as comparison voltages of the voltage comparator 50 and compared with the output voltage of the magnetic sensor 47. Then, the output voltage of the magnetic sensor 47 is the specified value VC.
When the voltage becomes higher than , the supply signal S from the voltage comparator 50
S+ is output.

Furthermore, when the output voltage of the magnetic sensor 47 becomes higher than the specified value Va, the voltage comparator 50 sends a toner empty signal @
S3 is output.

FIG. 3 shows changes in the toner replenishment signal @S1 and toner empty signal @S3 due to image forming operations and fluctuations in the output voltage of the magnetic sensor 47 when image formation is actually performed.

First, when image formation is performed, the toner mixing ratio of the developer decreases, and the output voltage of the magnetic sensor 47 increases. At point A, the toner mixture ratio of the developer is at an appropriate level T.
When the output voltage of the magnetic sensor 47 becomes higher than VC, the toner replenishment signal S1 is output, the toner replenishment motor 51 is turned on, and, for example, the developing device 122 is replenished with toner. In this way, feedback is performed so that the toner mixture ratio of the developer returns to the appropriate level TC.

Conversely, when the toner mixing ratio of the developer becomes higher than the appropriate level C and the output voltage of the magnetic sensor 47 becomes lower than the specified value Vc, the toner replenishment signal $1 is turned off and toner replenishment is stopped.

In this way, when there is toner in the toner hopper and the toner is being replenished normally, the toner replenishment signal S1
is repeatedly turned ON and OFF, and the toner mixture ratio of the developer is controlled so as to converge to the appropriate level Tc.

However, if you continuously perform image formation that consumes more toner than the amount of toner replenished from the toner hopper, even though toner is being replenished,
The toner mixing ratio of the developer decreases. At this time, the output voltage of the magnetic sensor 47 gradually increases. Then, at point 0, when the toner mixing ratio of the developer falls below the level Ta and the output voltage of the magnetic sensor becomes higher than the specified value Va, a toner empty signal S3 is output, continuous copying is temporarily interrupted, and the photoconductor Only the drum 9 and the developing device 122 are driven, and toner is replenished while the developer is stirred and rectified.

By doing this, the toner mixing ratio of the developer increases, and the output voltage of the magnetic sensor 47 decreases. When the toner mixing ratio of the developer becomes higher than the appropriate level Tc, the output voltage of the magnetic sensor 47 becomes lower than the specified value VC, the toner replenishment signal S1 is turned off, and toner replenishment is stopped and interrupted. Continuous copying is resumed.

Here, the specified value (a) is defined by the output voltage of the magnetic sensor 47 at the lowest toner mixing ratio Ta at which the developer does not adhere to the paper due to a decrease in the toner mixing ratio of the developer.

As explained above, according to this embodiment, the amount of toner replenishment ink can be reduced, which not only increases the degree of freedom in the shape and structure of the toner hopper and the stirring body of the developing device, but also reduces the size of the developing device itself. be able to. Further, there is no unevenness in the toner mixing ratio of the developer in the developing device, improving image quality, and also preventing the developer from adhering to the paper due to a decrease in the toner mixing ratio.

In the above embodiment, the copying operation is restarted after the toner mixture ratio in the developing device has recovered to the appropriate level Tc, but after a certain period of time, or after a certain amount of toner is replenished, the toner mixing ratio is at the lowest level Ta. If the above conditions are met, it is possible to restart the copy operation. In this way, the copy interruption time can be shortened compared to the above embodiment.

[Effects of the Invention] As explained above, according to the present invention, the developing operation is interrupted and the amount of toner in the developing device is controlled to be optimal.
Stable images can be formed even when a large amount of toner is consumed, and the developing device and toner supply means are simplified.
Can be made smaller.

[Brief explanation of drawings]

FIG. 1 is a block diagram schematically showing a control system according to an embodiment of the present invention, FIG. 2 is a characteristic diagram of the output voltage with respect to the toner mixing ratio of the magnetic sensor of the embodiment, and FIG. 3 is a diagram of the output voltage characteristics of the magnetic sensor of the embodiment. A timing chart diagram for explaining the image forming operation, FIG. 4 is a longitudinal sectional view of the developing device of the same embodiment, and FIG. 5 is a longitudinal sectional view of the same embodiment. 12...Developing device 47...Magnetic sensor 50...Voltage comparator 51...Toner replenishment motor 52...
...Microprocessor applicant Toshiba Corporation Patent attorney Satoshi Suyama - Figure 1 Figure 2

Claims (1)

[Claims] (1) A developing device that develops an electrostatic latent image, a toner amount detection means provided in the developing device that detects the amount of toner in the developing device, and outputs a signal corresponding to the toner amount, and a toner replenishing means for replenishing toner, and a toner replenishing means for operating the toner replenishing means when the amount of toner detected by the toner amount detecting means during the developing operation of the developing device falls below a first specified value set in advance; , when the amount of toner falls below a second specified value set to a value lower than the first specified value, the developing operation of the developing device is interrupted, and when the amount of toner recovers to the first specified value or a predetermined value. An image forming apparatus characterized by comprising: a control means for controlling the developing device to restart the developing operation when the second specified value is exceeded after a lapse of time or after replenishing a predetermined amount of toner. .