JPS6356544B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a dry electrophotographic copying method, and more particularly to an improvement in a dry electrophotographic copying method using a two-component developer of toner and a magnetic carrier.

In this type of dry electrophotographic copying method, toner is consumed and its density decreases during repeated copying operations, so it is necessary to control the toner density using a toner density maintenance device.

This toner concentration maintenance device measures the toner concentration with a built-in toner sensor, and when the concentration falls below a specified value, a toner replenisher replenishes the toner into the developing tank, and uniformizes the toner concentration through stirring and circulation. However, these tasks take a considerable amount of time. In particular, in order to reduce uneven developer density, it is not possible to replenish a large amount of toner at once, so it is necessary to replenish small amounts multiple times.As a result, the toner sensor detects a shortage and toner replenishment is turned on and off. This is done through frequent repetition.

Here, in the conventional device, the operation of the toner concentration maintenance device, that is, the concentration detection by the toner sensor, toner replenishment, stirring, and circulation, is performed as shown in 1 and 2 in Fig. 1, taking into consideration the wear and life of each part of the machine. This is performed only during copy operation (from print on to the end of copying), and during standby before and after that (from main switch on to print on, and from copy end to main switch off or next print switch on) Because the machine was set not to be used during this period, the machine went into standby mode before the toner was replenished sufficiently.
As a result, toner density may not be controlled accurately. Furthermore, it may be necessary to provide a separate detection mechanism to detect the toner end.

The present invention has been made in consideration of the above points, and
In a dry electrophotographic copying method using a two-component developer of toner and a magnetic carrier, toner density control is performed even after copying is completed, and toner end is displayed when toner shortage or density unevenness occurs. The purpose is to

The invention will now be explained with reference to the illustrated embodiments.

FIG. 2 shows a developing section of a dry type electrophotographic copying machine to which the method for maintaining toner density according to the present invention is applied.

In the figure, a toner concentration maintenance device is housed in a developing tank 1, and is stirred by a stirring screw (not shown) to maintain the toner concentration of a developer 4 circulating along the surfaces of a magnetic roll 2 and a scraping plate 3. Toner sensor 5 provided on the bottom surface of drop plate 3
Detect with. When the toner concentration is insufficient, a toner replenishing machine (not shown) that operates according to the output of the toner sensor 5 supplies the toner tank 6.
The toner inside is replenished into the developing tank 1. In the figure,
7 is a photosensitive drum, and 8 is a doctor blade.

The toner supply machine has a rotary pitting lever (not shown) that throws toner, and when a drive signal is applied and the rotary pitting lever is connected to a drive source (not shown), it rotates and fills the toner tank. Scoop up the toner in 6 and throw it into developer tank 1.

The drive signal is generated in response to a toner concentration detection signal from the toner sensor 5, and when the density is insufficient, the drive signal is applied, and when the density reaches a specified value, the drive signal is stopped.

As explained with reference to FIG. 1, the detection output of the toner sensor does not always produce an insufficient density signal even in an insufficient density state, but an insufficient density signal appears intermittently. The reason for this is that when the toner concentration is insufficient, the toner replenishment device replenishes the toner by throwing the toner near the toner sensor using the pitching lever, so the moment the toner is replenished, the toner concentration near the toner sensor immediately reaches the specified value. Thereafter, the insufficient density signal does not occur until the magnetic roll 2 rotates and the developer without toner replenishment circulates to the scraping plate 3. This time is shown in FIG.

When this time t1 elapses and an insufficient density signal is generated, a drive signal is generated, and the toner replenishing machine performs toner replenishment. This operation continues as long as insufficient density is detected when time t1 has elapsed since the previous toner replenishment. The fact that the insufficient density signal does not occur even after time t1 means that the toner density has reached the specified value.

In conventional devices, the toner concentration maintenance device operates only during copying operations, but in the present invention, it operates not only during copying operations but also during standby until the toner concentration reaches a specified value. That is, toner replenishment is performed at predetermined time intervals until the toner concentration reaches a specified value based on the output obtained by constantly detecting the toner concentration by the toner sensor.

However, as shown in FIG. 1, if the toner replenishment continues at t1, which is shorter than the specified time t1', even after the end of the copying operation, the toner sensor and toner replenishment unit continue to operate. make it work. Then, the elapsed time t2 after replenishment
When t2≧t1', it is determined that the developer has reached a specified concentration, and the operation of the toner sensor is stopped. This specified time t1' is longer than the time t1 until the magnetic roll 2 rotates and the developer without toner is circulated to the scraping plate 3, and is not too long compared to t1. selected for the value.

Such an operation can be realized by the circuit configuration shown in FIG. That is, the output of the toner sensor is led to a toner density detection circuit 11, where it is converted into an appropriate output signal, which is then sent to a set density comparison circuit 12, where it is compared with a reference value.

Based on this comparison output, an operation signal is generated from the toner replenishment operation command circuit 13. In this case, by passing this operation signal through the replenishment interval detection circuit 14, the replenishment interval, that is, the time interval between one toner replenishment operation and the next same operation, is detected, and this is the specified time t.
When the value becomes equal to or greater than 1', the operation of the toner sensor is stopped.

In the present invention, as shown in FIGS. 4 and 5, the time t4 for detecting shortage by the toner sensor is
When the reference time t3', which is set longer than the normal toner replenishment time, that is, the sum of the time t3 for rotating the pitching lever and the specified time t1, is exceeded, it is determined that the toner has run out. Based on this determination result, a toner end display is performed.

After the toner end is displayed, if the toner sensor is on standby, the operation of the toner sensor is immediately stopped as shown in Figure 1, 4, and if the copying operation is in progress as shown in Figure 5, the operation of the toner sensor is stopped and the toner sensor is stopped until the toner sensor is finished. Stop sensor operation.

The operation of the toner sensor in the standby state here means the measurement of toner concentration by the toner sensor, the circulation of developer, and the operation of the toner replenishment section, and the photosensitive drum etc. may be activated or not. good.

As described above, the present invention detects the toner concentration of the developer and replenishes the toner even after copying is completed, so unlike conventional devices, the operation stops before the toner concentration has fully recovered. do not have. Furthermore, although toner replenishment is performed continuously until the specified concentration is reached by constantly detecting the toner concentration, the replenishment operation itself is performed at predetermined time intervals, so it is said to have the same effect as the intermittent replenishment method, that is, it does not cause density unevenness. It also has effects.

Further, since the toner end is displayed when it is detected that the toner shortage state continues for a predetermined period of time or more, toner can be replenished accurately.

[Brief explanation of the drawing]

FIG. 1 is a timing chart for explaining the toner density maintenance operation in the dry electrophotographic copying method of the conventional method and the present invention, and FIG. FIG. 3 is a diagram showing an example of a circuit configuration for implementing the method of the present invention. 1...Developing tank, 2...Magnetic roll, 3...
Scraping plate, 4...developer, 5...toner sensor, 6...toner tank.

Claims (1)

[Scope of Claims] 1. A dry type device equipped with a toner concentration maintenance device that detects the toner concentration of the developer circulating in the developing tank with a toner sensor and replenishes toner from the toner tank into the developing tank based on this detection signal. In an electrophotographic copying method, if the toner concentration is insufficient at the end of copying, the toner concentration maintenance device continues to operate, and after the toner concentration reaches a specified value, it enters a standby state. A dry electrophotographic copying method characterized by: 2. In a dry electrophotographic copying method comprising a toner concentration maintenance device that detects the toner concentration of the developer circulating in the developer tank with a toner sensor and replenishes toner from the toner tank into the developer tank based on this detection signal, A dry electrophotographic copying method characterized in that a toner end display is issued when toner shortage continues for a certain period of time or more.