JPS62106481A - Print density control system - Google Patents

Abstract

PURPOSE:To obtain an economical developing device where the use efficiency of a printer is not degraded, by determining properly two counter values to make it unnecessary that the printer is stopped immediately by detection of toner empty state. CONSTITUTION:If a toner concentration sensor 8 detects that the quantity of a toner is smaller than a prescribed value and sends a voltage higher than a reference voltage, a comparing circuit 14 sends '1' to report toner replenishment, and contents of a counter 15 are counted up. When contents of the counter 15 reach a prescribed value, '1' is sent to switch a switch 11, and a bias voltage is changed to stick better the toner to a recording medium 1. Counting-up of a counter 16 is started simultaneously; and when contents of this counter reach a prescribed value, signal '1' indicating the stop of printing is sent. Since a prescribed print density is kept during printing of a certain quantity of papers after the indication of toner replenishment is issued, toner replenishment is prepared and the toner is replenished during this period.

Description

[Detailed Description of the Invention] [Summary] When a decrease in the amount of toner is detected by the toner density sensor in a developing unit of a printing device that does not include a toner empty (toner end) detection sensor, the bias voltage is changed to increase the printing density. Printing is continued by preventing the drop in toner, and during this time preparations and toner replenishment are performed.

[Field of Application of Industry-12] The present invention relates to a printing device using an electrophotographic method, and in particular, when a toner is attached to a latent image formed on a recording medium and developed, a bias voltage of Ij is applied to the toner. The present invention relates to a print density control method that maintains the print density of a certain amount of paper to 1.1 even after toner empty detection.

In printing devices that use electrophotography, a latent image is formed using light or the like on a uniformly charged recording medium, toner is attached to this latent image and developed, and the developed toner is transferred to paper. Desired characters, figures, etc. are printed.

Incidentally, these printing apparatuses perform toner empty detection in order to have the toner replenished when the toner is used up. To detect empty toner, the toner hopper is provided with a dedicated mechanical or electrical detection function, but historically, the developing device is also provided with a sensor for detecting the amount of toner.

Generally, the mechanical or electrical toner empty detection function is expensive, and it is desirable to be able to use a toner concentration sensor instead, but it is necessary that no inconvenience occurs if only a 1-toner depth sensor is used.

[Conventional technology]

FIG. 4 is a diagram illustrating an example of a conventional developing device.

The recording medium 1 usually has a drum shape and rotates in the direction shown by the arrow. The recording medium 1 is uniformly charged by a charger, and a latent image is formed using, for example, a laser beam.

Toner 4 for developing this latent image is stored in a toner hopper 2, and a toner empty detection sensor 3 detects whether the toner is empty.

This toner 4 is delivered by a toner supply roller 5 when the toner depth decreases according to an instruction from a toner concentration sensor 8, and is mixed with a developer 6 by a mixing roller 7. This developer 6 is attracted to the magnetic roller 10 and the blade 9
It is squeezed into a thin film and contacts the recording medium 1. Therefore, the toner 4 accompanying the developer 6 adheres to the latent image formed on the recording medium 1.

[Problem that the invention seeks to solve]

As mentioned above (conventionally, the toner empty detection sensor 3 is installed in addition to the toner empty detection sensor 8), which makes the developing device expensive, but when installing the toner empty detection sensor 3, consider the position. For example, even after the toner empty is detected, printing at a constant density is possible for a while, and during that time, 1q of toner is refilled.
This makes it possible to efficiently operate the printing device.

However, if the 1st toner empty detection sensor 3 is omitted for the purpose of an economical developing device, and the 1st to 3rd depth sensor 8 also serves to detect toner empty, if printing continues even after the 1st empty state is detected. , because the amount of toner decreases.
As the printing density decreases, the carrier in the developer comes into contact with the recording medium and is electrostatically attracted, causing the carrier to flow out. Therefore, it is necessary to immediately stop printing when toner empty is detected, and preparations for toner replenishment cannot be made in time, resulting in a problem that usage efficiency of the printing apparatus is reduced.

In view of these problems, the present invention maintains the printing density constant by changing the bias voltage applied to the toner, making it possible to continue printing for a while even after the toner empty is detected. During this time, it is possible to prepare and replenish toner.

[Means for solving problems]

FIG. 1 is a block diagram of a circuit showing one embodiment of the present invention.

1 is a recording medium, 2 is a toner hopper, 4 is toner, 6 is a developer, 7 is a mixing roller, 8 is a toner density sensor, 9 is a blade, and 10 is a magnet roller.

11 is a switch for changing the bias voltage applied to the magnet roller 10; 12 and 13 are bias power supplies; 14 is a comparator circuit for comparing the output voltage of the toner density sensor 8 with a reference voltage; and 15 is a switch when the output of the comparator circuit 14 is "1". A counter that counts up when it reaches "0" and cents when it reaches "0".
16 is a counter that counts up when the output of the counter 15 becomes "1" and resets when it becomes "'O";17;
is the power supply that sends out the reference voltage.

When the toner level sensor 8 detects that the level of j. ”I
” is sent to notify toner replenishment, the counter 15 is made to count and amplify.

When the counter 15 reaches a predetermined value, it sends out "1", switches the switch I+, changes the bias voltage,
To improve the adhesion of toner onto a recording medium.

At the same time, the counter 16 starts counting up, and when it reaches a predetermined value, it sends out a signal "']" instructing to stop printing.

[Effect]

With the above configuration, after an instruction to replenish toner is issued, printing on a certain type of paper can maintain a predetermined print density, so it is possible to prepare and replenish toner during this time. Become.

〔Example〕

FIG. 2 is a diagram for explaining an example of the developing bias, and FIG. 3 is a diagram for explaining the operation of the toner density sensor.

In FIG. 1, the recording medium 1 is uniformly charged with <600V, for example, as shown in FIG. 2a. The charge on the area exposed to light decreases to 50V, forming a latent image. The magnet roller 10 is connected to the bias power supply 1 via the switch 11.
3, a voltage of 200V is applied, and the toner 4 accompanying the carrier 6 is repelled from the charged area of 600V due to this voltage difference, and is attracted to and adheres to the latent image of 50V.

The toner concentration sensor 8 detects the amount of toner 4 from the developer 6 mixed by the mixing roller flow, and detects the amount of toner 4 from the developer 6 mixed by the mixing roller flow, for example, as shown in FIG. It sends out a control voltage in the range of OV. In other words, with 2.5V as the reference voltage, if a higher voltage is sent out, it indicates that the amount of toner 4 is insufficient, and if a lower voltage is sent out, it indicates that the amount of toner 4 is large. show.

The comparator circuit 14 compares the reference voltage sent by the power supply 17 and the voltage sent by the toner concentration sensor 8, and when the voltage reaches the reference voltage plate - at the point indicated by ■, it sends out "1" and outputs "1" through terminal B. Instructs to replenish toner 4, counter 15 reads 1
~Start up.

When the output voltage of the toner concentration sensor 8 becomes lower than the reference voltage at the point indicated by ■, the comparator circuit 1
4 sends "0", sends a toner supply stop instruction via terminal B, and resets the counter I5.

When the toner 4 in the toner hopper 2 runs out and the toner wetness sensor 8 reaches the voltage 1 (or higher) at the point indicated by [phase], and even if the comparator circuit 14 sends out 1'', there is no replenishment of the toner 4, the toner The voltage sent by the concentration sensor 8 increases.

Therefore, the comparator circuit 14 continues to send out "1°",
When the counter 15 reaches a predetermined value, it sends "1" to the counter 16, switch 11, and terminal. The counter 16 starts the count amplifier, and the switch 11 turns on the magneso! - Supply the voltage of the bias power supplies 12 and 13 to the roller 10 to <300V as shown in FIG. Also terminal A
The "1" sent out during this period becomes a toner empty signal requesting toner replenishment.

By setting the bias voltage to 300V, toner 4
The suction force for adhering to the latent image increases, and the toner 4 whose mixing ratio in the developer G is decreased increases, so that the printing density does not decrease.

When the counter 1G counts up to a predetermined value, it sends "1" to the terminal C, instructing the printing device to stop. Toner 4 is replenished by the toner empty signal from terminal A.
When the voltage sent by the toner concentration sensor 8 becomes lower than the reference voltage, the comparator circuit 14 sends out "0", so the counters 15 and 16 are reset.

In this embodiment, the bias voltage is switched once, but by changing the bias voltage finely, the range of change in printing density can be reduced.

〔Effect of the invention〕

As explained above, by appropriately determining the values of the counters 15 and 16, the present invention eliminates the need to immediately stop the printing device upon detection of toner empty, and provides an economical solution that does not reduce the usage efficiency of the printing device. It is possible to provide a standard developing device.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a circuit showing an embodiment of the present invention, FIG. 2 is a diagram explaining an example of a developing bias, FIG. 3 is a diagram explaining the operation of a toner density sensor, and FIG. FIG. 3 is a diagram illustrating an example of a developing device. In the figure, 1 is a recording medium, 2 is a toner filter, 3 is a toner empty detection sensor, 4 is a toner, 5 is a toner supply roller, 6 is a developer, 7 is a mixing roller, 8 is a toner density sensor, 9 is a blade, 10 is a magnet roller, 11 is a switch, 12.13 is a bias power supply, 14 is a comparison circuit, 15.16 is a counter, and 17 is a power supply. On the left side of the town ＼゛Iasu's first distortion' story ε 兇 ro υ υ 2■ The door is dark 7 The power of the Teja River f lower and the 5 liters of the moon b 榔 0 GI 3
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Claims (1)

[Claims] In a developing device that attaches toner (4) to a latent image formed on a recording medium (1) of a printing device using an electrophotographic method and develops it, a bias voltage applied to the toner (4). a switching means (11) for switching, a comparison means (14) for comparing the output of the toner concentration sensor (8) with a reference voltage, and a first counting means (15) for counting the comparison result of the comparison means.
), and a second counting means (16) that counts based on the counting result of the first counting means (15), and the toner concentration sensor (8) detects when the amount of toner (4) is lower than a specified value. When it is detected that the comparison means (14)
) activates the first counting means (15) and instructs to replenish the toner (4), and when the amount of toner (4) does not increase, the first counting means (15) continues counting. let me,
When the predetermined value is reached, the switching means (11) is switched to change the bias voltage applied to the toner (4), and the second counting means (16) is notified that the toner (4) is finished. ), and when the second counting means (16) reaches a predetermined value, an instruction is given to stop the printing apparatus.