JPH06138765A - Image forming device - Google Patents

Abstract

PURPOSE:To detect an accurate service life and to stabilize image quality according to a degree of developer fatigue by judging the degree of developer fatigue based on a detection value found by a torque detecting means. CONSTITUTION:Torque in the rotation of a stirring roller 16 is measured. Since the fluidity of developer becomes wrong in accordance with the developer fatigue, the load applied on the stirring roller 16 becomes heavy, so that the torque increases. Here, an electrifier output, exposure, a development bias, pretransfer destaticization and a transfer unit output are controlled for a photosensitive drum 1 by utilizing a change of the torque of the stirring roller 16 with a degree of developer fatigue, thereby making image density constant. Additionally, a control part is provided with a microcomputer. It has a judging function which is to judge from the torque value of the stirring roller 16 the degree of developer fatigue and a function which is to judge the end of the service life of the developer when the torque value exceeds a reference level and to stop the execution of an image process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of an image forming process based on the degree of fatigue of a developer in an image forming apparatus such as a two-component developing type copying machine or printer.

[0002]

2. Description of the Related Art Conventionally, in a copying machine using a two-component developer, as the number of copies increases, the fatigue of the developer lowers the image density (ID) value as shown in FIG. . Therefore, in order to prevent the image density from being lowered due to the fatigue of the developer, the developer is replaced, but the replacement time of the developer (developer life) is determined by a copy number counter.

The basis of determining the life of the developer is to carry out a life test of the developer under various conditions (changing the copy mode, the environmental condition, the developer rod, etc.) and predict the life of the developer based on the obtained results. And decided the life.

When the number of copies reaches the life of the developer thus determined, the developer is considered to be fatigued and is replaced.

[0005]

However, in the life of the developer, all the factors (copy mode, environmental condition, develod) that determine the life of the developer have various errors. Considering this, the life of the developer is determined with a margin.

Further, since the life is determined from the result obtained in the life test, it is easy to make a difference from the life of the developer actually used. That is, it is difficult to obtain the actual life of the developer because the direct property of the developer actually used is not measured. Further, the image quality may not be adversely affected before the life of the developer reaches its end due to early fatigue of the developer.

In view of the above, the present invention can detect the accurate life without being disturbed by various disturbance factors (environmental characteristics, copy mode, Develod, etc.) by directly reading the life of the developer, and developing An object of the present invention is to provide an image forming apparatus capable of stabilizing the image quality depending on the degree of fatigue of the agent.

[0008]

An object of the present invention is to provide an image forming apparatus which uses a two-component developer and executes a series of image forming processes of charging, exposing, developing and transferring on a photosensitive drum 1. 3, torque detecting means 30 for detecting the rotation torque of the stirring roller 15 for stirring the developer in the developing tank 4, and judging means for judging the degree of fatigue of the developer based on the detection value from the torque detecting means 30. An image quality stabilizing means is provided for controlling the charger output, the exposure amount, the developing bias, the pre-transfer charge elimination, and the transfer device output for the photoconductor drum 1 in accordance with the degree of fatigue of the developer to keep the image density constant. It has been done.

When the fatigue level exceeds the reference level, it is judged that the developer has reached the end of life, and the execution of the image forming process is stopped.

[0010]

In the above means for solving the problem, the torque when the stirring roller 16 is rotated is measured. Since the fluidity of the developer deteriorates with the fatigue of the developer, the load on the stirring roller 16 increases and the torque increases.

Here, utilizing the fact that the torque of the stirring roller 16 changes in accordance with the degree of fatigue of the developer,
For the photoconductor drum 1, by controlling the charger output, the exposure amount, the developing bias, the pre-transfer charge elimination, and the transfer device output,
Keep image density constant. As a result, the image quality is always stable.

When the torque value reaches the reference level corresponding to the image density corresponding to the life of the developer, it is determined that the life of the developer has come and the machine is stopped.

[0013]

【Example】

(First Embodiment) In the copying machine of the present embodiment, as shown in FIG. 1, a charger 2, a blank lamp 3, a developing tank 4 are provided around a rotatable photosensitive drum 1 for executing an image forming process. , Pre-transfer static eliminator 5, pre-transfer static eliminator 6, transfer device 7, peeling static eliminator 8, pre-cleaning static eliminator 9, cleaner unit 10, static eliminator 11, PFL (PreF
attitude Lamp) / CFL (Cycle Fa)
A title lamp) 12 is arranged.

Then, between the blank lamp 3 and the developing tank 4, the reflected light of the original image by the light source 13 is exposed on the photosensitive drum 1.

Further, an infrared sensor 14 as an image density detector for detecting the amount of toner adhering to the photosensitive drum 1 is arranged between the peeling static eliminator 8 and the pre-cleaning static eliminator 9.

In the developing tank 4, as shown in FIG. 2, the magnet roller 15 and the stirring roller 1 are arranged from the side closer to the photosensitive drum 1.
6. An agitator 17 is rotatably arranged. A toner hopper 18 is mounted above the agitator 17 of the developing tank 4.

The toner hopper 18 is provided in the toner box 1
9 and a toner transport unit 20. The toner box 19 has an agitator 21 and a toner supply screw 22 installed therein, and the toner carrying unit 20 has toner carrying screws 23 and 24 and a toner replenishing roller 25.
Is decorated. In the figure, 26 is a doctor, 27
Is a toner concentration sensor.

The magnet roller 15, the stirring roller 16 and the agitator 17 of the developing tank 4 are rotationally driven in synchronization with each other by a motor.

The developer is composed of a carrier in which ferrite is coated with silicon resin, and a toner made of styrene-acrylic resin. Since the developer deteriorates in fluidity with fatigue as it is used, the stirring roller 1 is used.
The torque applied to 6 increases. That is, as shown in FIG. 3, when the number of copies increases and the fatigue of the developer increases, the torque applied to the stirring roller 16 increases. That is, the degree of fatigue of the developer can be known from the amount of change in the rotation torque applied to the stirring roller 16.

Therefore, as a developer fatigue measuring device, a torque detecting means 3 for detecting the rotating torque of the stirring roller 16 is used.
0 and a control unit 31 that evaluates the life of the developer by determining the degree of fatigue of the developer based on the detection value from the torque detection unit 30.

The torque detecting means 30, as shown in FIGS.
The roller shaft 16a of the stirring roller 16 is directly driven to rotate D
By reading the current value of the C motor 32, the stirring roller 1
The torque T concerning 6 and the amount of change ΔT of the torque are read.

The control unit 31 is equipped with a microcomputer and has a judgment function for judging the degree of fatigue of the developer from the torque value of the stirring roller 16 and judges that the developer has reached the end of its life when the torque value exceeds the reference level. And a stop function for stopping the execution of the image forming process, that is, for stopping the machine.

In the above structure, the toner from the toner box 19 in the toner hopper 18 passes through the toner supply screw 22 and the toner conveying screws 23 and 24,
The toner supply roller 25 quantitatively feeds the toner into the developing tank 4. Then, in the developing tank 4, the fed toner and the carrier such as iron powder are agitated and mixed by the agitating roller 16, adsorbed to the magnet roller 15 and supplied to the photosensitive drum 1. .

When the agitating roller 16 is rotated, the current value of the motor 32 is detected and calculated to obtain a torque measurement result.

Here, when the developer is used for a long period of time, the spent toner adhering to the toner on the carrier increases and the charge amount decreases, or the carrier coating agent comes off. As shown in FIGS. 6 and 7, as the number of copies increases, the amount of spent toner increases and the residual rate of the coating agent on the carrier decreases. Then, the image density decreases as shown in FIG. 8 depending on the degree of fatigue of the developer. Thus, it can be seen that the change in the torque value of the stirring roller 16 changes according to the degree of fatigue of the developer.

At this time, since the developer has poor fluidity, the load applied to the stirring roller 16 increases and the torque increases. When this torque value reaches the reference level corresponding to the image density corresponding to the life of the developer, it is determined that the life of the developer has expired, and the machine is stopped. In addition,
This reference level is preset to a different level depending on the machine.

Therefore, the actual life of the developer can be known from the fluctuation of the torque of the stirring roller 16 without being affected by various disturbance factors. Then, the image quality can be stabilized by stopping the machine according to the degree of fatigue of the developer. Moreover, it becomes possible to predict the life of the developer from the current torque of the stirring roller 16.

(Second Embodiment) In the present embodiment, the fact that the degree of fatigue of the developer can be judged from the fluctuation of the torque of the stirring roller 16 allows the control unit 31 to control the photosensitive drum 1 according to the degree of fatigue. An image quality stabilizing function is added to control the output of the charger and keep the image density constant.

That is, as shown in FIG. 9, since the image density decreases according to the degree of fatigue of the developer, the grid voltage of the scorotron charger as the charger 2 is agitated so that the image density becomes constant. It is controlled so as to increase in accordance with the increase in the torque of the roller 16.

As a result, the surface potential of the photosensitive drum 1 rises, so that even if the triboelectric charge of the toner increases due to the fatigue of the developer, the potential difference between the photosensitive drum 1 and the toner does not decrease, and A decrease in the amount of toner adhered to the drum 1 does not occur, and a decrease in image density can be prevented. Therefore, the image quality can be always stabilized and the life of the developer can be extended.

(Third Embodiment) In this embodiment, the image density is made constant by controlling the exposure amount to the photosensitive drum 1 according to the degree of fatigue.

That is, since the image density decreases according to the degree of fatigue of the developer, the output voltage to the light source 13 should be increased according to the increase in the torque of the stirring roller 16 so that the image density becomes constant. To control.

As a result, the potential difference between the bright portion and the dark portion of the photosensitive drum 1 becomes large, the amount of toner adhering to the photosensitive drum 1 does not decrease, and the image density can be prevented from decreasing.
Therefore, the image quality can be always stabilized and the life of the developer can be extended.

(Fourth Embodiment) In the present embodiment, the image density is made constant by controlling the developing bias for the photosensitive drum 1 according to the degree of fatigue.

That is, since the image density decreases according to the degree of fatigue of the developer, the bias voltage to the magnet roller 15 is decreased according to the increase of the torque of the stirring roller 16 so that the image density becomes constant. To control.

As a result, the charged toner is easily attracted to the magnet roller 15, and the photosensitive drum 1
A decrease in the image density can be prevented without a decrease in the amount of toner adhered to the toner. Therefore, the image quality can be always stabilized and the life of the developer can be extended.

(Fifth Embodiment) In this embodiment, the output of the transfer device to the photosensitive drum 1 is controlled according to the degree of fatigue to keep the image density constant.

That is, since the image density decreases according to the degree of fatigue of the developer, the voltage applied to the transfer device 7 is increased according to the increase in the torque of the stirring roller 16 so that the image density becomes constant. To control.

As a result, when a voltage higher than the surface potential of the photosensitive drum 1 is applied to the transfer paper, the toner is easily adsorbed from the photosensitive drum 1 to the paper,
It is possible to prevent a decrease in image density. Therefore, the image quality can be always stabilized and the life of the developer can be extended.

(Sixth Embodiment) In this embodiment, the image density of the pre-transfer charge eliminator on the photosensitive drum 1 is controlled in accordance with the degree of fatigue to keep the image density constant.

That is, since the image density decreases according to the degree of fatigue of the developer, the voltage applied to the pre-transfer charge eliminator 5 is changed according to the increase in the torque of the stirring roller 16 so that the image density becomes constant. Control to increase.

As a result, the coupling force between the photosensitive drum 1 and the toner becomes weak, the toner is easily adsorbed from the photosensitive drum 1 to the paper, and the image density can be prevented from lowering.
Therefore, the image quality can be always stabilized and the life of the developer can be extended.

Similarly, the output voltage to the pre-transfer charge eliminating lamp 6 may be increased.

The present invention is not limited to the above embodiment, and it goes without saying that many modifications and changes can be made to the above embodiment within the scope of the present invention.

In the case of a copying machine, a copy lamp is used as a light source, and if an LED or a laser beam is used, it can be applied to a facsimile or a laser printer in addition to the copying machine.

At least one of the output of the charging device, the output of the light source for exposure, the exposure amount, the developing bias voltage, the output of the transfer device, the static eliminator for pre-transfer neutralization, and the static eliminator lamp according to the fatigue level of the developer. Of course, or it is of course possible to control a plurality of these.

[0047]

As is apparent from the above description, according to the present invention, the fatigue degree of the developer is read from the rotation torque of the stirring roller for stirring the developer, and the factor that determines the life of the developer is controlled. Without this, it is possible to directly evaluate the developer life. Therefore, the life of the developer can be predicted from the fluctuation of the torque of the stirring roller.

Then, according to the degree of fatigue of the developer judged from the rotation torque of the agitating roller, the charger output, the exposure amount, the developing bias, the pre-transfer charge elimination are applied to the photosensitive drum.
Since the outputs of the transfer devices are controlled respectively, the image density can be kept constant, the image quality can be always stabilized, and the life of the developer can be extended.

Further, by stopping the machine depending on the fatigue of the developer, the image formation using the deteriorated developer is not performed and the image quality can be stabilized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an image forming process unit of a copying machine showing an embodiment of the present invention.

FIG. 2 is a sectional view of the developing tank.

FIG. 3 is a diagram showing a change in rotation torque of a stirring roller due to fatigue of a developer.

FIG. 4 is a plan view of a stirring roller.

FIG. 5 is a configuration diagram of a torque detection unit of a stirring roller.

FIG. 6 is a diagram showing changes in the amount of spent toner due to the use of a developer.

FIG. 7 is a diagram showing changes in the carrier peeling rate due to the use of a developer.

FIG. 8 is a diagram showing a relationship between image density and torque of a stirring roller.

FIG. 9 is a diagram showing a change in image density with respect to fatigue of a developer when the image forming process is controlled.

FIG. 10 is a diagram showing a change in image density due to developer fatigue.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum 2 Charging device 4 Developing tank 5 Pre-transfer static eliminator 6 Pre-transfer static erasing lamp 7 Transfer device 13 Light source 15 Magnet roller 16 Stirring roller 30 Torque detecting means 31 Control unit 32 DC motor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication location G03G 15/02 102 15/04 120 9122-2H 15/06 101 15/16

Claims (2)

[Claims] 1. An agitator for agitating a developer in a developing tank in an image forming apparatus which uses a two-component developer to execute a series of image forming processes of charging, exposing, developing and transferring on a photosensitive drum. Torque detection means for detecting the rotation torque of the roller, judgment means for judging the degree of fatigue of the developer based on the detection value from the torque detection means, charger output to the photoconductor drum according to the degree of fatigue, exposure amount, An image forming apparatus, comprising: an image quality stabilizing unit that controls at least one of a developing bias, pre-transfer charge removal, and a transfer device output to keep an image density constant. 2. The image forming apparatus according to claim 1, wherein the image forming process is stopped when the degree of fatigue of the developer judged by the judging means exceeds a reference level. .