JPH0695255B2 - Automatic image density controller for copiers - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a weak current caused by toner transfer from a developing roll to a photoconductor during development, and replenishes an amount of toner according to the detected current. The present invention relates to an automatic image density control device of a copying machine for controlling the image.

2. Description of the Related Art In a conventional electronic copying machine, an electrostatic latent image formed on a surface of a photoconductor in an exposure process is developed into a toner image in a developing process, and the toner image is transferred to a sheet in a transferring process. Further, in the developing step, the surface of the photoconductor is developed by the developing roll to which the developing bias is applied, but when the toner is transferred from the developing roll to the photoconductor during development, a weak current is generated in the developing bias applying circuit. This weak current is proportional to the amount of toner transferred from the developing roll to the photosensitive member, that is, the amount of toner consumed during development.Therefore, this current value is detected and toner corresponding to this current value is newly supplied to the developing device. For example, the toner density of the developer in the developing device is always constant, and thus a copy image having a stable density can be obtained.

Also, "Automatic image density control method for copying machine" utilizing the above method has already been disclosed in Japanese Patent Application Nos. 59-274175 and 59-274176.
Nos. 59-274177 and 59-274178 of the present application.

Problems to be Solved by the Invention However, in any of the applications, "automatic image density control method for copiers"
In the above application, no specific control device is disclosed.

In addition, since the conventional automatic image density control device does not have a toner supply rate adjustment mode, it is difficult to finely adjust the toner supply rate in each copying machine, and when the automatic image density control mode is used, the toner supply control mode can be used. There was also a problem that disappeared.

The present invention has been made for the purpose of improving the above problems.

Means and Actions for Solving the Problems In order to achieve the above object, the present invention provides the developing bias applying circuit with a current flowing from the developing bias applying circuit to the developing roll according to the amount of toner consumed during development. In the copying machine which supplies the developing device 4 with an amount of toner commensurate with the toner consumed at the time of development by controlling the rotation time of the toner supply motor according to the current value detected by the current detecting means. The toner supply rate adjustment mode in which the toner supply rate that differs for each copying machine is adjusted by the adjusting means, and the toner consumption amount is calculated from the current value detected by the current detecting means, and the toner corresponding to the toner consumption amount is obtained in the developing device. The automatic image density adjustment mode that controls the toner supply motor to be supplied to the toner supply motor and the toner supply motor is rotated by pressing the toner increase switch. A toner supply control mode for supplying toner to the developing device, the toner supply rate adjustment mode, and a selection unit for selecting the automatic image density adjustment mode and the toner supply control mode.
By selecting the toner supply rate adjustment mode by the selection means, the toner supply rate can be adjusted in a short time.

By selecting the automatic image density control mode, the amount of toner consumed at the time of development is replenished, so the image density can be kept constant, and by selecting the toner supply control mode, the density adjustment can be made arbitrarily. You can do it.

Embodiment An embodiment of the present invention will be described in detail with reference to the drawings. In the figure, 1 is a photoconductor of a copying machine, 2 is a charger for charging the surface of the photoconductor 1, and 3 is an electrostatic latent image formed on the surface of the photoconductor 1 by guiding an original image to the surface of the photoconductor 1. An optical system such as a self-locking lens is shown. The electrostatic latent image formed on the surface of the photoconductor 1 in the exposure step is developed into a toner image by the developing device 4 and then transferred to the paper 6 fed by a paper feeding device (not shown) at the transfer device 5 portion. Then, the toner image on the sheet 6 is fixed on the surface of the sheet 6 by being conveyed to a fixing device (not shown) by the conveying unit 7. Further, the untransferred toner remaining on the surface of the photoconductor 1 without being transferred onto the paper 6 is removed by the cleaning device 8.

On the other hand, the developing device 4 is provided with a developing roll 10 in the housing 4a in the vicinity of the photoconductor 1. Developing roll 10 above
2 is a structure in which a sleeve 10b which is rotated in the arrow direction by a drive system (not shown) is provided around a magnet roll 10a having magnetic poles as shown in FIG.
Thus, the developing bias power source 12 is applied, and the developer in the housing 4a is adsorbed in a brush shape on the surface of the sleeve 10b by the magnetic action of the magnet roll 10a. The developer adsorbed on the surface of the sleeve 10b is trimming bar 1
Trimming is performed by 3 so that the height of the spikes becomes constant, and then reaches the photoconductor 1 to develop the electrostatic latent image formed on the surface of the photoconductor 1. When the toner is transferred to 1, a weak current flows in the developing bias circuit 11 as follows.

That is, as shown in FIG. 2, there is usually a gap of about 1.0 to 1.5 mm between the photoconductor 1 and the developing roll 10. During development, this gap is a carrier having a sufficient insulating property and friction charging between the carrier and the carrier. Is filled with the toner having a sufficient insulating property that is electrostatically adsorbed to the carrier. At this time, the toner having a certain charge by frictional charging and the carrier are electrically balanced, but the photoconductor 1 on which the electrostatic latent image is formed is formed.
The toner in the developer is transferred to the side of the photoconductor 1 by an amount corresponding to the amount of electric charge of the electrostatic latent image when the toner comes into contact with the surface. As a result, the charge on the developing roll 10 disappears by the amount of the electric charge of the toner particles, and a weak current flows to the developing roll 10 to replenish it.

This weak current is proportional to the amount of toner transferred from the developing roll 10 to the photoconductor 1 during development, that is, the amount of toner consumed by development, and is detected by the current detector 14 provided in the developing bias applying circuit 11. Then, it is taken into the control device 15 composed of a micro computer. Controller 15
As shown in Fig. 3, two switches SW1 and SW2 are externally attached to the switch, and one of the following three modes can be selected by the combination of ON and OFF of these switches SW1 and SW2. I'm running.

That is, as shown in Table-1, when the switch SW1 is turned on and the switch SW2 is turned off, the inside of the control device 15 is in the toner supply rate adjustment mode so that the toner supply rate can be adjusted for each copying machine. The toner supply rate can be adjusted by rotating a variable resistor (not shown) provided separately in the controller 15. Also, switch SW1 is turned off, switch S
When W2 is turned on, the automatic image density control mode is set, and the toner consumed during development is supplied to the developing device 4 as follows.

As described above, a current proportional to the amount of toner consumed at the time of development is detected by the current detector 14 provided in the developing bias applying circuit 11 and taken into the controller 15, but the controller 15 does not. The toner consumption amount is calculated according to the entered current value and is output to the toner supply motor 16 as a control signal. A toner supply auger 17 is connected to the toner supply motor 16, and the toner bottle is rotated as the toner supply motor 16 rotates.
By supplying the toner in 18 to the developing device 4, the amount of toner commensurate with the toner consumed at the time of development is increased.
Is replenished, so that a copy image having a constant density can always be obtained.

The above is the automatic image density control mode.

On the other hand, when both the switches SW1 and SW2 are turned off, the toner supply control mode is set and the automatic image density control mode is released. This toner supply control mode is used when the toner density is artificially changed. When the toner increase switch (not shown) is pressed in this mode, the toner supply motor
16 is rotated so that toner is supplied to the developing device 4, and a copy image having a desired density can be obtained.

The selection of the mode by the combination of ON and OFF of the switches SW1 and SW2 is not necessarily limited to the combination shown in Table 1 above.

In the above embodiment, the switch externally attached to the controller 15
The mode is selected by SW1 and SW2.
As shown in the figure, a switch SW is provided on a part of the operation panel 20 provided on the main body of the copying machine (not shown), and the switch SW is turned on / off to automatically control the image density control mode and toner supply. The control mode may be selected, and the mode can be selected without opening the rear panel of the main body of the copying machine, which has the effect of improving operability.

As described in detail above, according to the present invention, the toner amount consumed during development is detected by the current detecting means provided in the developing bias applying circuit, and the rotation time of the toner supply motor is determined according to this current value. In the copying machine in which the amount of toner commensurate with the toner consumed at the time of development is supplied to the developing device by controlling, the toner supply rate adjustment mode, the automatic image density control mode, and the toner supply control mode are provided. Since these modes can be selected by the switch operation, the toner supply rate can be easily adjusted for each copying machine by selecting the toner supply rate adjustment mode. Also, by selecting the automatic image density control mode, the developing device is automatically replenished with an amount of toner commensurate with the toner consumed at the time of development, so that a copy image with a constant density is always obtained and the toner supply control is performed. It is also possible to arbitrarily adjust the image density by selecting the mode.

Further, in the past, it took a long time to adjust the toner supply rate, which is different for each copying machine, and the work efficiency was poor, but according to the present invention, by selecting the toner supply rate adjustment mode, the toner supply rate can be adjusted in a short time. In addition to the adjustment, the toner supply mode cannot be used in the conventional automatic image density control mode. However, such a problem can be solved.

Moreover, since all the reference supply rates can be changed to positive values by the toner supply rate adjustment mode, the automatic image density control mode and the toner supply control mode can always be efficiently operated.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, FIG. 1 is an overall configuration diagram, FIG. 2 is an explanatory diagram of a developing device and a control system, FIG. 3 is a block diagram of the device of the present invention, and FIG. It is explanatory drawing which shows an Example. 4 is a developing device, 11 is a developing bias applying circuit, 15 is a control circuit, and 16 is a toner supply motor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Otani 2274 Hongo, Ebina City, Kanagawa Fuji Zero Tux Co., Ltd. Ebina Business Office (56) References JP-A-60-10275 (JP, A) JP-A-58- 172655 (JP, A) JP 59-104677 (JP, A) JP 57-130068 (JP, A) JP 59-7978 (JP, A) Actual development 55-105441 (JP, U)

Claims (1)

[Claims] 1. A current detecting means provided in the developing bias applying circuit 11 detects a current flowing from the developing bias applying circuit 11 to the developing roll 10 in accordance with the amount of toner consumed at the time of development. Depending on the toner supply motor 16
In the copying machine that supplies the developing device 4 with an amount of toner commensurate with the toner consumed at the time of development by controlling the rotation time of, the toner supply rate adjustment for adjusting the toner supply rate different for each copying machine by the adjusting means. Toner consumption is detected from the mode and the current value detected by the current detection means,
An automatic image density adjustment mode in which the toner supply motor 16 is controlled so that toner corresponding to the toner consumption amount is supplied to the developing device, and a toner supply motor is rotated by pressing the toner increase switch to supply toner to the developing device 4. An automatic image density control apparatus for a copying machine, comprising: a toner supply control mode for controlling the toner supply rate; a toner supply rate adjustment mode; and a selection unit for selecting the automatic image density adjustment mode and the toner supply control mode.