JPS635750B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic developer concentration adjustment device in a wet electrophotographic apparatus.

A wet electrophotographic device develops an electrostatic latent image formed on a drum-shaped or belt-shaped photoreceptor using a developer containing colored fine particles (toner) in an insulating dispersion (developer). However, in order to obtain stable and high-quality copy images, it is necessary to always keep the dispersion ratio of developer and toner constant.

An example of a device that has been conventionally adopted to keep this dispersion ratio constant is explained with reference to FIG. For example, the concentration of the developer is detected by an optical toner concentration detector 14 consisting of a light source and a light receiving element, and this detection signal activates the toner supply solenoid 12 via the solenoid dedicated circuit 4 to supply the toner to the developer tank 5. It supplies toner. Note that the reference numeral 6 in the figure is a photosensitive drum;
11 is the main motor, 13 is the pump motor,
7 indicates a toner container.

However, if the electrophotographic device has not been used for a long period of time, the toner may have settled in the developer, and the developer may not have the proper dispersion ratio when the main switch is turned on. The toner is sent to the detection unit 3, and the conventional device described above detects the concentration in such a state and operates the toner supply solenoid 12, easily causing an oversupply of toner.

In order to solve the drawbacks of the conventional apparatus, the present invention detects the concentration of the developer that has reached a steady state and determines toner supply based on this, thereby eliminating the adverse effects caused by excessive supply of toner and reducing the amount of toner used. It is intended to reduce

Hereinafter, the details of the present invention will be explained based on the drawings.

FIG. 3 is a block diagram showing one embodiment of the present invention, in which 15 is a main switch, and 16 is a time period from the stop of operation of the device (more precisely, the pump motor for circulating the developer) to the start of the next operation. This is a memory that stores the voltage corresponding to the EV, and as shown in Figure 2, it holds the voltage of the EV while the device is operating, and stores the voltage that approaches 0 (dotted chain line) when the device enters a stopped state. It's becoming like that. Reference numeral 17 denotes a delay means for delaying the toner supply operation by a time corresponding to the time from when the pump motor 13 for circulating the developer stops operating until it starts the next operation. Toner supply solenoid 1 after a period of time inversely proportional to the memorized voltage value has elapsed.
This is a timer that outputs a signal to activate the memory 16.Explaining it in Fig. 2, at restart point A, the time from the stop of the device to the time of restart is short, and the memory 16
The operating time of the timer 17, which is determined by the output voltage E'V, is as short as t', but if the restart time is longer from the stop of the device to the restart, as in case B, the output of the memory 16 will be The voltage drops to E′V, and conversely, the operating time of timer 17 that is determined from now on is
It is preferable that the operating time of the timer 17 remains constant after a certain period of time C has elapsed since the device stopped. Returning to FIG. 3 again, 14 indicates the toner. concentration detection means,
That is, the toner concentration detector generates a low-level output when the developer has a predetermined concentration or less, and a high-level output when the developer has a predetermined concentration or more, and uses an optical detection mechanism as explained in FIG. 1. 18 is a control circuit that controls the main motor 11 for driving the photosensitive drum; 19 is a control circuit that controls the toner supply solenoid 12 as toner supply means;
22 is an OR circuit (hereinafter abbreviated as OR circuit), one input terminal of which is connected to the output terminal of the timer 17, and the other input terminal connected to the output terminal of the timer 17 when the copy switch 20 is turned on.
The output side of this OR circuit 22 is connected to the input circuit of the main motor control circuit 18, and the output is high. When the output reaches the low level, the main motor control circuit 18 operates, and when the output reaches the low level, it turns OFF. 23 is a logical NOR circuit (hereinafter abbreviated as NOR circuit), one input terminal is connected to the output terminal of the timer 17, the other input terminal is connected to the output terminal of the toner concentration detector 14, and the output terminal is connected to the output terminal of the toner concentration detector 14. is connected to the input end of the solenoid control circuit 19, and when the output is high level, this control circuit 19 is activated, and when it is low level, it is turned off. Incidentally, a pump motor 13 serving as a developer circulation means is connected to a main switch 15.

Next, this action will be explained using the time chart shown in FIG.

First, at point a, turn on the main switch 15.
When turned ON, the time corresponding to the stop time up to that point is set by the output voltage from the memory 16, and the timer 17 becomes high level. On the other hand, since the output of the input line 21 is at a low level when the copy switch 20 is OFF, the output of the OR circuit 22 is at a high level, and the main motor 11 shown in FIG. 4 starts rotating. Next, the detector 14 begins to detect the concentration of the developer, but as shown in FIG. The output becomes low level and the solenoid 12 does not operate. The pump motor 13 starts continuous operation,
The developer begins to be supplied to the developing tray 2 via the detection unit 3.

Next, at point b, the time corresponding to the voltage stored in the memory 16 has elapsed and the timer 17 becomes low level. Therefore, since the inputs to the OR circuit 22 are both at low level, the output of this circuit also becomes low level, and the operation of the main motor 11 is stopped. On the other hand, the developer sent to the detection section has already reached a steady state at this point.
As shown in FIG. 4, when the concentration is below a predetermined concentration, the output of the detector 14 shows a low level;
Since the inputs to the NOR circuit 23 are both at low level, the output of this circuit 23 becomes high level, operating the solenoid 12 and supplying toner to the developer tank (FIG. 4).

Note that when the developer has a predetermined concentration, the output of the detector 14 becomes high level, and the NOR circuit 2
There is no output for solenoid 3, and of course solenoid 1
2 becomes inactive and no toner is supplied.

The operation of the solenoid 12, that is, the toner supply when the developer concentration does not reach a predetermined value at time b has already been described. As time passes, when the developer concentration reaches a predetermined value at point c, the solenoid 12 becomes inactive due to an operation similar to the above-mentioned additional writing operation, and all of the automatic toner supply is performed. The operation ends.

Therefore, when the copy switch 20 is operated at time d, the high level output of the input line 21 and the low level output of the timer 17 are input to the OR circuit 22, so the output of this circuit 22 becomes high level. Then, the main motor 11 is activated, the photosensitive drum begins to rotate, and development work begins.

In the embodiment described above, the memory 16 and the timer 17 are used as means for delaying the start of toner supply by a time proportional to the stop time of the electrophotographic apparatus, and these are counted from the stop time and are used for the next time. It is also possible to replace it with a counter that continues counting until the point in time when the counter operates, and a timer that remains ON for a time proportional to the count value of this counter. Furthermore, JP-A-50-74429
It is also possible to use the circuit disclosed in the above publication, that is, the circuit that adjusts the length of the cleaning time before the start of copying depending on the length of the stop time of the electrophotographic apparatus, in combination with this apparatus.

As described above, according to the present invention, the transmission prevention means prevents the detection signal of the toner concentration detection means from being transmitted to the toner supply means, so that the time from the stop of operation of the developer circulation means to the start of the next operation is controlled. Since the toner that is settling while the electrophotographic device is stopped can be returned to a steady state over a period of time commensurate with the stop period, the toner that is settling can be returned to a steady state. It becomes possible to supply toner according to the concentration of the developer, and the supply amount can be made extremely accurate. This not only ensures that the developer concentration is kept constant and obtains high-quality images, but also reduces the toner supply amount by providing an appropriate toner supply, making it an excellent automatic developer concentration adjustment device. It is something.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of a conventional developer concentration automatic adjustment device, FIG. 2 is a voltage diagram stored in a memory used in an embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. FIG. 4 is a block diagram showing the timing. 11... Main motor, 12... Toner supply solenoid, 13... Pump motor, 14...
...Toner concentration detector, 16...Memory, 17...
...Timer, 20...Copy switch, 22...
OR circuit, 23...NOR circuit.

Claims (1)

[Claims] 1. A toner supply means that operates according to the output signal of the toner concentration detection means, and a time corresponding to the time that is activated at the start of the operation of the developer circulation means and until the circulation means starts operation.The output of the toner concentration detection means An automatic developer concentration adjustment device comprising means for preventing transmission of a signal to a toner supply means.