JPS62102263A - Concentration detector for developer - Google Patents

Abstract

PURPOSE:To detect efficiently the concentration of a developer by forming a sensor for detecting the transmissivity of a developer carried by a sleeve and arranging a baffle plate on the lower part of the sensor to stabilize the quantity of the developer flowing into the sensor. CONSTITUTION:The developer carried by the sleeve 14 passes a developing area opposed to a photosensitive body 11 and then passes the sensor 21 to detect the transmissivity of the developer in accordance with the toner density. When the transmissivity is larger than that of a reference toner density value, toner is fed from a toner feeder into a developing tank 13. The developed developer on the sleeve 14 is carried to the sensor 21 by a carrying blade. Since the baffle plate 25 is arranged near the sensor 21, partial flow of the developer is suppressed and the stay of the developer can be generated in the sensor 21. Then, a new developer 17 is carried by the carrying blade. Consequently, the quantity of the developer 17 flowing into the sensor 21 is held at a fixed value. Thus, the stable concentration of toner can be detected.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a developing device for visualizing an electrostatic latent image formed on a recording medium, and particularly to a developing device for visualizing an electrostatic latent image formed on a recording medium. Regarding equipment.

<Prior art> Electrophotographic copying machines, electrostatic recording devices, laser beam printers, etc. form electrostatic latent images on recording media according to image information, and are equipped with developing devices to visualize this latent image. ing. That is, the developing device creates a visible image by selectively attaching toner to the electrostatic latent image. In this case, the developing device uses, for example, a two-component developer consisting of the above-mentioned toner and carrier.

When visualizing an electrostatic latent image using the two-component developer, if the concentration of the two components, that is, the mixing ratio of carrier and toner is not appropriate, the image density will be low and difficult to see. Or it may be too dark, causing problems such as an increase in capri. Therefore, until a certain period of time, a manual toner supply amount adjustment device was attached to the supply device that supplied toner into the developing device, and the user was able to adjust this device when he noticed a change in the copy density. However, even if the amount of toner supplied is adjusted, the mixing ratio within the developing device does not change rapidly, resulting in a problem with responsiveness.

Moreover, it was therefore difficult to adjust the concentration to an appropriate level. Furthermore, it is extremely troublesome for the user to perform various adjustment operations.

In order to overcome the above drawbacks, various automatic development density control methods have been proposed and implemented. Among these, there are those that detect and control the magnetic permeability that changes depending on the mixing ratio of carrier and toner, or those that detect and control the color that changes depending on the mixing ratio of carrier and toner that are colored in different colors. There are some that perform control by using a fixed amount of carrier, and others that control by capturing changes in the amount of toner with respect to a fixed amount of carrier as changes in volume.

Among these methods, the method of controlling the change in the amount of toner as a change in volume is often used because the reference value can be easily detected. This method controls the toner concentration, taking into account that once the developer is sufficiently stirred and put into the developer tank by an agitation roller, its height will be approximately constant if the concentration is constant. .

Now, when the toner in the developer is consumed by copying, the volume decreases by that amount and the surface position of the developer lowers.

When the developer surface position falls below the reference position in this way, the developer loses contact with a detection element such as a ceramic vibrator installed at the reference position, and the vibrator starts to vibrate. A detection signal is sent to a control circuit.

Based on this signal, a drive motor (not shown) that drives a toner supply roller of the toner supply device is energized by the control circuit, and toner supply is started. Thereafter, when the volume of the developer increases again and reaches the reference position, the vibration of the vibrator stops, and the supply of toner also stops. Thereafter, by repeating these nine times, the concentration of the developer is automatically controlled.

It is clear that this method assumes that the carrier and toner are sufficiently stirred and that the amount of carrier is always constant. That is, regarding the former,
This is due to the fact that the volume of the mixture of carrier and toner decreases to a certain extent as it is stirred, and for the latter, as the carrier volume increases or decreases, the amount of toner increases or decreases in the opposite direction. This is due to the inability to maintain the standard concentration.

However, it cannot be said that the replacement developer during maintenance is sufficiently agitated and the volume change converges, and the carrier also adheres to the photoreceptor during development, albeit in a small amount, and this repeats over and over again. Since a considerable amount of carrier is lost during printing, the above method has the problem that capri occurs as the number of copies increases.

On the other hand, if the magnetic permeability, which changes depending on the mixing ratio of carrier and toner, is detected and controlled, there is an advantage that the mixing ratio of toner can be kept constant even if the carrier decreases. An example of this is shown in FIG. The developing roller 1 is placed inside a cylindrical sleeve 2 made of a non-magnetic material. A magnet 3 having a plurality of poles with a main pole is provided, and the main pole of the magnet 3 is fixed so as to be located in a developing area facing a photoreceptor 4, and the sleeve 2 is rotated in the direction of the arrow. As a result, the developer 5 adhering to the sleeve 2 is conveyed to the development area, and by facing the N1 pole, stands up like a brush and rubs against the surface of the photoreceptor 4, and the toner is conveyed to the area. in,
The amount of adhesion to the sleeve 2 is regulated by a doctor 6 to a constant amount.

In the structure as described above, the sensor 7 for detecting the toner concentration is disposed particularly at a position facing the N2 pole after the development is completed. That is, as the sleeve 2 rotates, the developer 5 after development faces the N2 pole, stands up like a brush, and flows so as to come into sliding contact with the detection surface of the sensor 7.

Thereby, the magnetic permeability of the developer 5 is detected and the drive of the toner supply roller 9 of the toner supply device 8 is controlled to maintain a constant toner concentration. In this case, developer 5
Even if the amount of carrier decreases, the toner concentration can always be controlled to be constant because the magnetic permeability that changes depending on the mixed state of the toner is detected regardless of changes in the volume of the developer.

However, since the developer 5 whose adhesion amount is regulated by the doctor 6 flows on the surface of the sensor 7, the area where the developer 5 contacts the sensor 7 changes depending on the change in the amount regulated by the doctor 6. There has been a big change. This will result in an erroneous detection as a change in magnetic permeability ([j) by the sensor.

Therefore, as shown in the figure, a developer 5 is placed downstream of the sensor 7.
A baffle board that regulates the flow of water! 0 is set. This baffle plate 10 restricts the conveyance of a portion of the developer 5 passing through the sensor 7 portion, and a pool of developer 5 is formed in the sensor 7 portion. Thereby, the magnetic permeability can be detected satisfactorily by the sensor 7.

The problem here is the distance between the baffle plate 10 and the sleeve 2, which needs to be set within 0.5 m. In other words, if the interval is large, a pool of developer 5 cannot be formed and accurate toner concentration detection cannot be performed. For this reason, it is necessary to set the interval within 0.5 cabinets. However, if the above-mentioned interval becomes too narrow, there is a risk of contacting the sleeve 10 and damaging the sleeve itself.
Also, when assembling the developing device, the baffle plate 10 and the sleeve 1 are
Adjusting the interval with 0 will be very troublesome.

<Purpose> The present invention detects the concentration of developer as magnetic permeability, and an object of the present invention is to improve the flow of developer to a sensor that detects magnetic permeability and to enable accurate detection.

<Embodiment> FIG. 1 is a sectional view of a developing device portion equipped with a developer concentration detecting device according to the present invention. This detects a change in toner concentration as a change in magnetic permeability, and toner replenishment is performed by comparing the magnetic permeability at a reference toner concentration with the magnetic permeability when the toner concentration decreases. In the figure, I1 is a drum-shaped photoreceptor, and I2 is a developing device that develops an electrostatic latent image formed on the photoreceptor. Developing device I2
In the developing tank I3, a developing roller 16 is provided which is composed of a cylindrical non-magnetic sleeve 14 and a magnet 15 having an odd number of poles provided inside the sleeve. The sleeve I4 is rotated clockwise in the figure, and the magnet 15 is fixed so that the N1 pole (main pole) in particular faces the developing position of the photoreceptor 11. Therefore, the developer 17 in the developer tank 13 is attracted onto the sleeve 14 by the magnetic force of the magnet 15, and this developer 17 is transported to the development position facing the photoreceptor 11 as the sleeve +4 rotates. Afterwards, it is returned to the developer tank 13 and the stirring roller! Stir at 8. The developer 17 adsorbed on the sleeve I4 is transported to a position facing the photoreceptor 11, and the adhesion amount is regulated by the doctor 19 to a constant value. They are fixed to the developing tank 13 with screws or the like so as to be separated from each other.

A toner replenishing device (not shown) for replenishing toner into the tank is attached to the opening 20 of the developer tank 13 above the stirring roller 18. The toner supplied by the toner supply device is mixed with the developer in the tank 13 by an agitating roller 18, sufficiently agitated, and sent to the developing roller 16.

As described above, in order to replenish the developer tank 13 with toner from the toner replenishing device, the sensor 2I for detecting the toner concentration of the developer 17 is disposed at an appropriate location. This sensor 21 is for detecting the magnetic permeability of the developer, and as shown in the figure, the sensor 21 is arranged so that its detection surface 2Ll is separated from the sleeve 14 of the developing roller 16 by a considerable distance.
3 is placed at the appropriate location. A conveyance blade 22 is rotatably provided between the detection surface 21-1 of this sensor 21 and the sleeve 14 to convey the developer 17 etc. on the sleeve +4 to the detection surface 21-1. 1 has a structure in which wing plates 24 bent in a dogleg shape are attached to a rotationally driven roller portion 23 in order to effectively convey the developer 17 at equal intervals. This conveyor blade 22 is a sleeve! 4 and the stirring roller 18.

A baffle plate 25 for regulating the flow of the developer is provided downstream of the sensor 21 in the direction in which the developer 17 is conveyed. This baffle plate 25 has one end fixed to the developer tank 13, and suppresses the conveyance of a portion of the developer 17 flowing so as to come into contact with the detection surface 21-1 of the sensor 21. In particular, the baffle plate 25 is provided only in the part facing the sensor 21, and the part where this baffle plate 25 is not provided is
The developer is conveyed as is to the stirring roller 18.

With the configuration shown in FIG. 1, the developer conveyed by the sleeve 14 passes through the development area facing the photoreceptor 1 and then passes through the sensor 21, which determines the toner concentration of the developer. Magnetic permeability is detected.

If the detected magnetic permeability is greater than that of the reference toner concentration, the toner is removed from the toner replenishing device and developing tank 13.
Here, the action of the developer 17 passing through the iris of the sensor 2 is that the developer 17 on the sleeve 14 after development is transported to the sensor 2 by the transport blade 22. At this time, since a baffle plate 25 is provided behind the sensor 21, the flow of part of the developer 7 corresponding to the sensor 2I is suppressed. Therefore, the developer 17 is placed in the sensor 21 section.
New developer is transferred to the conveying blade 22 so that a reservoir is formed. The developer 17 flowing through the sensor 21 is
The amount of developer flowing through the sensor 21 portion is maintained at a constant amount by the conveying blades 22. At this time, sensor 2
A developer reservoir is formed on the entrance side of the sensor 21, and the sensor 21 is surrounded so as to be filled with the developer. Therefore,
Unstable factors for detecting toner concentration are eliminated, stable concentration detection becomes possible, and it is not affected by external magnetic fields and the like.

As described above, since the conveying blades 22 are provided to convey the developer to the sensor 21 as in the present invention, the baffle plate 2
The interval adjustment in step 5 can be ignored, and the assembly of the developing device can be simplified. Further, the conveying blade 22 not only conveys the developer 17 but also has a stirring ability, and since the agitated developer 17 is conveyed, the concentration of the agitated developer can be detected. . Therefore, the sensor 21 can stably detect the toner concentration.

FIG. 2 shows that toner is replenished based on the toner concentration detection output of the sensor 21 according to the present invention as described above, and
3 is a block diagram illustrating an example of control for keeping the developer concentration within 3 constant at all times. FIG. As shown in the figure, the sensor 21 includes a coil Ll that applies a reference signal to the ferrite core 30;
A coil L2 for detecting the magnetic permeability of the developer 17 and a coil L3 for standard adjustment are wound around the coil L2, in particular, the coil L2 side faces the developer 17 to be detected, and the developer 17 and the ferrite core 30 are connected to each other. constitutes a closed magnetic circuit.

Further, on the side of the coil L3, a screw-shaped standard adjustment core 3 is provided which forms another closed magnetic path with the ferrite core 30, and the core 31 adjusts the magnetic flux passing through the coil L3. The coil L2 and the coil L3 are wound in opposite directions and have one end commonly connected. And coil L3
The other end of the coil L2 is grounded, and the other end of the coil L2 is connected to the phase detector 32.
is connected to one terminal of the

An oscillator 33 that outputs a reference signal is connected to the coil L1, and is supplied with the reference signal. Oscillator 3
The inverted signal of the reference signal No. 3 is supplied to the other terminal of the phase detector 32. The phase detector 32 outputs a square wave (pulse) signal according to the phase difference between the two signals, and this output signal is supplied to the smoothing circuit 34. In other words, developer 1
If the toner concentration in 7 decreases, the magnetic permeability increases, and the voltage induced in coil L2 increases proportionally and the phase shifts.0 And coil L3 hardly changes.
By supplying a composite signal of the induced voltage of 2 and the voltage of the coil L2 to the position detector 32, the phase relationship with the reference signal is compared, and the pulse width of the output signal is increased.

Therefore, since the pulse width is wide in the smoothing circuit 34, it is supplied as a high voltage to the next voltage comparator 35. Therefore,
The voltage comparator 35 outputs a signal (“H”). Accordingly, the output unit 36 drives the toner replenishing device to replenish toner.

However, if the toner concentration is at a constant level, the output of the voltage comparator 35 becomes ("L"), and the toner replenishing device is not driven. In other words, the output from the smoothing circuit 34 when the developer 17 with the standard toner concentration is stored in the developer tank 13 is
The reference adjustment core 31 of the sensor 21 is adjusted so that the voltage is lower than (or equal to) the reference voltage of the voltage comparator 35. Therefore, if the toner concentration decreases, the reference voltage of the comparator 35 becomes higher. A signal (pulse width) is output from the phase detector 32, and toner replenishment is controlled until the reference toner concentration is reached.

According to the embodiment of the present invention, as a means for conveying the developer 17 to the sensor 21 section, a conveying blade 22 is used as shown in FIG.
is illustrated, but the developer 1 is not limited to the one having such a configuration.
7 to the sensor 21 section, the object of the present invention can be fully achieved.

Effects> According to the developer concentration detection device according to the present invention, a conveyance means is provided for conveying the developer conveyed by the sleeve X to a sensor for detecting the magnetic permeability of the developer. By providing a baffle plate downstream of the sensor, the amount of developer flowing through the sensor is stabilized, and the detection of developer concentration is stabilized. Further, the position of the baffle plate is not subject to any restrictions, and it does not pose an obstacle when assembling the developing device.

[Brief explanation of drawings]

FIG. 1 is a lock diagram of an apparatus for detecting developer concentration according to the present invention, and FIG. 3 is a sectional view of a developing apparatus showing an example of conventional developer concentration detection. 12: Developing device 13: Developing tank I4 sleeve 15
: Magnet 16: Developing roller 17: Developer 21: Sensor 22: Conveying blade 23: Roller section 24: Vane plate agent Patent attorney Aihiko Fukushi (and 2 others) Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. In a developer concentration detection device comprising a sensor that detects magnetic permeability of the developer in order to detect the concentration of the developer in the developer tank, a conveying means for conveying the developer to the detection surface of the sensor; A developer concentration detecting device comprising: a baffle plate disposed on a non-flowing side of the sensor section to suppress the developer flowing through the sensor section when being transported by the transport means.