JPH05127533A - Toner concentration controller - Google Patents

Abstract

PURPOSE:To provide a toner concentration controller capable or more stably maintaining toner concentration. CONSTITUTION:As to the toner concentration controller for detecting the toner concentration by a toner sensor 346, etc., and for replenishing the toner when the toner concentration lies at a level between a toner replenishing level and a toner empty level, the controller is provided with a storing means such as a memory 2, etc., for storing a switching level which is set between the toner replenishing level and the toner empty level, and a switching control means constituted of a switching means constituted of a driving control means 5, etc., for switching the toner replenishing velocity and a discriminating means 4, etc., for switching the toner replenishing velocity so that it may be set at a low velocity in the case that the toner concentration lies equal to or below the toner replenishing level, and so that it may be set at a high velocity in the case that the toner concentration lies equal to or below a switching level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner density control device for detecting a toner density in a developing unit of an image forming apparatus and supplying toner when the toner density is between a toner supply level and a toner empty level.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer for developing an electrostatic latent image formed on a photosensitive drum with a toner, the toner density in the developing unit is set to the toner density in order to keep the toner density properly. When the supply level is lower than the supply level, the toner is supplied from the toner hopper into the developing device. That is, in the image forming apparatus, the toner density is detected as a voltage by the toner sensor, and when the detected voltage of the toner sensor exceeds the voltage V1 corresponding to the toner replenishment level as shown by the solid line A1 in FIG. The motor for driving is driven, and when the voltage becomes V1 or less, the motor is stopped so that the toner density is stabilized at the toner replenishment level.

By the way, in the above-mentioned image forming apparatus, for example, when a large number of originals having many black portions are continuously copied, the toner supply amount cannot follow the toner consumption amount, and as shown by the one-dot chain line B1 in FIG. The toner concentration is large and fluctuates, and it becomes difficult to maintain the toner concentration stably. Further, since the toner in the developing device is consumed in a large amount in a short time and is replenished in a large amount, toner scattering easily occurs.

Further, in an image forming apparatus capable of image processing such as a digital copying machine, black and white may be reversed and continuous output may be performed. In such a case, the toner consumption amount becomes too large as compared with the toner replenishment amount. As indicated by the two-dot chain line C1, the toner replenishment cannot be made in time and the toner concentration continues to decrease. Therefore, the toner empty is erroneously displayed beyond the voltage V3 corresponding to the toner empty level even though the toner remains in the toner hopper.

On the other hand, as shown in Japanese Patent Application Laid-Open No. 58-178381, when the toner density is lowered and a toner request signal requesting toner supply is issued, toner supply is started,
When the toner request signal continues to be output for a predetermined time or more, the toner replenishment speed is increased, and when the toner request signal is output for a predetermined time or more while the toner replenishment speed is increased, the toner empty is displayed and the toner concentration is displayed. It has been proposed to prevent the decrease and surely detect the toner empty.

Further, as shown in Japanese Patent Application Laid-Open No. 60-209763, when a black and white inverted image is continuously output, the bias voltage applied to the toner is adjusted to change the toner density. Those that maintain are proposed.

[0007]

However, in the toner concentration control device disclosed in Japanese Patent Laid-Open No. 58-178381, the toner replenishment speed is increased regardless of the toner concentration, so that the toner concentration may fluctuate greatly. Therefore, it is difficult to maintain a stable toner concentration.

Further, in the toner concentration control device disclosed in Japanese Patent Laid-Open No. 60-209763, the toner concentration can be maintained, but the toner concentration becomes low as a whole.

An object of the present invention is to solve the above problems and to provide a toner concentration control device capable of maintaining the toner concentration more stably.

[0010]

In order to achieve the above object, the present invention provides a toner density control apparatus for detecting toner density and supplying toner when the toner density is between the toner supply level and the toner empty level. , A storage unit for storing a switching level set between the toner replenishment level and the toner empty level, a switching unit for switching the toner replenishment speed, and a low speed when the toner density is equal to or lower than the toner replenishment level. A switching control means for switching the toner replenishment speed to a high speed when the switching level is below the switching level is provided.

[0011]

According to the toner density control device having the above structure, the switching level is set and stored between the toner replenishment level and the toner empty level. The toner replenishment speed is switched so that the toner is replenished at a low speed when the detected toner concentration is below the toner replenishment level, and is replenished at a high speed when the detected toner concentration is below the switching level.

[0012]

FIG. 2 is a schematic configuration diagram showing an example of an image forming apparatus (copier). The copy machine has a document holder 2 on top of it.
0 and contact glass 21 with an optical system L inside
And image forming means P. The document retainer 20 is
The document placed on the contact glass 21 is pressed.

The optical system L includes a document irradiation lamp 22 such as a halogen lamp, a first moving frame 25 having a reflecting plate 23 and a mirror 24, a second moving frame 28 having mirrors 26 and 27, and a lens 29. And a mirror 30. Then, when the copying operation is started, the first moving frame body 25 starts scanning and the document irradiation lamp 22
Lights up and the document on the contact glass 21 is illuminated. The reflected light from the document is reflected by the mirror 24 and the mirror 2.
After being guided to the lens 29 via 6, 27, the mirror 30
Then, the following photosensitive drum 31 is exposed.

The image forming means P includes a photosensitive drum 31,
It comprises a charging device 32, a blank lamp 33, a developing device 34, a transfer device 35, a separating device 36, a cleaning device 37 and the like. Then, the surface of the photoconductor drum 31 is uniformly charged by the charging device 32, the unnecessary area of the charge is removed by the blank lamp 33, and then the surface of the photoconductor drum 31 is exposed by the reflected light from the original document, whereby the electrostatic latent image is generated. An image is formed. The electrostatic latent image is developed with toner by the developing device 34, the toner image is transferred onto a transfer sheet by the transfer device 35, and then the photosensitive drum 31 is transferred by the separating device 36.
Separated from. On the other hand, the toner remaining on the photosensitive drum 31 is removed by the cleaning device 37.

In addition, from the upstream side of the transfer paper feeding direction,
Paper feed cassettes 38 and 39, paper feed rollers 40 and 41, conveyance roller pairs 42 and 43, and registration roller pair 44 are arranged. Then, the transfer papers in the paper feed cassettes 38 and 39 are taken out by the paper feed rollers 40 and 41, conveyed to the registration roller pair 44 by the conveyance roller pairs 42 and 43, and then the registration roller pair 44 moves the optical system L of the optical system L. The image is fed to the photosensitive drum 31 in synchronization with the scanning.

A conveyor belt 45, a fixing device 46, a discharge roller pair 47, etc. are arranged downstream of the transfer sheet after the transfer. Then, the transfer paper after the transfer is the conveyor belt 4
5 is conveyed to the fixing device 46 and is fixed by the fixing device 46.
Is discharged to.

Next, the structure of the developing device 34 will be described with reference to FIG. The developing device 34 includes a toner hopper 340, a supply roller 341, a developing housing 342,
The stirring roller 343, 344, the developing roller 345, the toner sensor 346, and the like. The toner hopper 340 stores the toner. The replenishing roller 341 replenishes the toner from the toner hopper 340 into the developing housing 342. Further, the replenishing roller 341 is configured to replenish toner at a predetermined speed by being driven by the drive motor 1 described later.

The stirring rollers 343 and 344 stir and mix the developer consisting of the toner and carrier in the developing housing 342, and frictionally charge the toner. The developing roller 345 supplies toner to the photosensitive drum 31 to develop the electrostatic latent image formed on the photosensitive drum 31 with toner.

The toner sensor 346 is used in the developing housing 3.
It is arranged at an appropriate position of 42 and outputs a detection voltage (hereinafter referred to as a sensor voltage) according to the toner concentration in the developing housing 342. The sensor voltage of the toner sensor 346 decreases as the toner concentration increases,
On the contrary, the toner density increases as the toner density decreases.

Next, an embodiment of the control system for controlling the toner density will be described with reference to the block diagram of FIG. This control system includes a memory 2, a control unit 3, and the like. The memory 2 has a voltage V1 corresponding to the toner concentration at the toner replenishment level requiring toner replenishment, a voltage V2 (> V1) corresponding to the toner concentration at the replenishment speed switching level for switching the toner replenishment speed, and an extremely low toner concentration. It stores preset voltage data such as the voltage V3 (> V2) corresponding to the toner density at the toner empty level causing a defect, the processing program of the control unit 3, and the like.

The control unit 3 is composed of a CPU and the like, and has a discrimination means 4
And drive control means 5 and the like. The determination unit 4 compares the sensor voltage V from the toner sensor 346 with the voltages V1, V2, V3 stored in the memory 2. When the sensor voltage V exceeds the voltage V1, the discriminating means 4 outputs a first control signal to the drive control means 5 to replenish the toner at a low speed, and the sensor voltage V becomes the voltage V2. When the value exceeds the limit, it has a toner replenishment speed switching control function of outputting a second control signal to the drive control means 5 in order to replenish toner at a high speed. further,
The determination means 4 outputs a stop signal to the drive control means 5 to stop the drive motor 1 when the sensor voltage V is equal to or lower than the voltage V1. Also, the discrimination means 4
When the sensor voltage V exceeds the voltage V3, a display signal is output to the display unit 6 to perform an empty display, and a stop signal is output to the drive control means 5.

The drive control means 5 is the first one from the discrimination means 4.
The drive motor 1 is controlled to be intermittently driven by, for example, driving for 1 second and stopped for 2 seconds by receiving the control signal of 1), and the drive motor 1 is continuously driven by receiving the second control signal from the determining unit 4. It has a function of switching the toner replenishment speed. Further, the drive control means 5 controls the drive motor 1 to stop by receiving the stop signal from the determination means 4.

Next, the toner density control operation of the developing device 34 will be described with reference to the flowchart of FIG. 4 and the timing chart of FIG. In addition, in FIG.
A solid line A shows a case where a normal document is continuously copied, a one-dot chain line B shows a case where a document with a lot of black portions is continuously copied, and a two-dot chain line C shows a document with a lot of black portions such as a black-and-white inverted document. The figure shows the case of continuous copying.

First, the toner sensor 346 detects the sensor voltage V (step S1), and the sensor voltage V is input to the discrimination means 4 and compared with the voltage V1 (step S2). If the sensor voltage V is equal to or lower than the voltage V1 (YES in step S2), it is not necessary to replenish the toner, and the drive motor 1 is stopped (step S3).

On the other hand, when the sensor voltage V exceeds the voltage V1 in step S2 (N in step S2)
O), the sensor voltage V is compared with the voltage V2 (step S4). The sensor voltage V is the voltage V
If it is 2 or less (YES in step S4), the drive motor 1 is intermittently driven (step S5), and toner is replenished from the toner hopper 340 into the developing housing 342 at a low speed. Therefore, the toner is consumed in relatively small amounts with continuous copying, and as shown by the solid line A in FIG. 5, when the sensor voltage V exceeds the voltage V1, the toner is slowly transferred until the sensor voltage V becomes equal to or lower than the voltage V1. Will be replenished. This allows
Fluctuations in toner density are smaller than when toner is replenished at high speed.

On the other hand, when the sensor voltage V exceeds the voltage V2 in step S4 (N in step S4)
O), the sensor voltage V and the voltage V3 are compared (step S6). If the sensor voltage V is equal to or lower than the voltage V3 in step S6 (YES in step S6).
S), the drive motor 1 is continuously driven (step S
8). That is, when an original with many black portions is continuously copied, the toner supply amount does not catch up with the toner consumption amount in the intermittent drive of the drive motor 1, and as shown by the one-dot chain line B or two-dot chain line C in FIG. The voltage V gradually rises. Therefore, the drive motor 1 is switched to the continuous drive to increase the toner replenishment speed. After that, when the sensor voltage V becomes equal to or lower than the voltage V2 due to the high speed toner supply, the drive motor 1 is switched to the intermittent drive again. That is,
The intermittent drive and the continuous drive of the drive motor 1 are repeated to maintain the toner density corresponding to the voltage V2.

On the other hand, when the toner in the toner hopper 340 is exhausted, the toner density in the developing housing 342 becomes extremely low. When the sensor voltage V reaches the voltage V3 (NO in step S6), as shown in the latter half of the solid line A in FIG. 5, empty display is performed (step S7).

In this way, when the toner consumption is small as in the case of continuously copying a normal original, the drive motor 1
Since the toner is replenished at a low speed by the intermittent driving, the fluctuation of the toner density can be reduced. Also,
If the toner supply amount cannot keep up with the toner consumption amount as in the case of continuously copying an original with many black portions, the intermittent drive and continuous drive of the drive motor 1 are repeated with the toner concentration slightly reduced. The toner supply amount easily catches up with the toner consumption amount. Therefore, the toner density is stable, and the difference in toner density between the first and last sheets of continuous copying can be reduced.

Further, even when an original having a lot of black portions such as a black-and-white inverted original is continuously copied, the chain double-dashed line C in FIG.
As shown in (3), the toner density fluctuates but does not continue to decrease, and the toner empty level is not reached and an erroneous display of empty is not performed despite the toner remaining in the toner hopper.

In the above description, the toner replenishment speed is switched by intermittently driving or continuously driving the drive motor 1, but the invention is not limited to this. For example, the rotation speed of the drive motor 1 is switched. Alternatively, the toner replenishment speed may be switched.

Further, the image forming apparatus is not limited to the copying machine shown in FIG. 2 described above, and the present invention can be applied to a digital copying machine or printer capable of image processing such as black and white reversal of a document. can do.

[0032]

According to the present invention, toner is replenished at a low speed when the toner concentration is determined to be below the toner replenishment level, and is replenished at a high speed when it is determined to be below the switching level. Even when the image is replenished with toner and the image with many black portions is continuously output, the fluctuation of the toner concentration is reduced, the toner concentration is maintained stable, and a stable image can be continuously output. Further, excessive supply of toner is prevented, and toner scattering can be reduced. Further, even when a document having a lot of black portions is continuously output, the toner density does not continue to decrease, the false display of the empty is prevented, and the reliability of the empty display is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a toner density control device according to the present invention.

FIG. 2 is a schematic configuration diagram illustrating an example of an image forming apparatus.

FIG. 3 is a configuration diagram of a developing device.

FIG. 4 is a flowchart showing a toner density control operation according to the present invention.

FIG. 5 is a timing chart showing a toner density control operation according to the present invention.

FIG. 6 is a timing chart showing a conventional toner density control operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drive motor 2 Memory 3 Control part 4 Discrimination means 5 Drive control means 6 Display part 31 Photosensitive drum 34 Developing device 340 Toner hopper 341 Replenishing roller 342 Developing housing 345 Developing roller 346 Toner sensor

Claims (1)

[Claims] 1. A toner density control device for detecting toner density and supplying toner when the toner density is between the toner replenishment level and the toner empty level, and is set between the toner replenishment level and the toner empty level. The storage means for storing the switching level, the switching means for switching the toner replenishment speed, and the toner replenishment speed to the low speed when the toner density is below the toner replenishment level and the high speed when the toner concentration is below the switching level. A toner density control device comprising a switching control means for switching.