JPH0451065A - Image forming device with residual developer detector - Google Patents

Abstract

PURPOSE:To surely detect the consumption of a developer even if it is locally consumed by arranging two detecting conductors while opposing to a developer carrier. CONSTITUTION:The detecting conductors 3a and 3b are arranged while opposing to a developing sleeve 1, and a change in the quantity of toner 4 is detected as a voltage. The detected direct current voltages VDC1 and VDC2 are supplied to corresponding comparatiors 9a and 9b, respectively, and compared with constant direct current voltages VS1 and Vs2 from reference voltage sources 8a and 8b. When the toner 4 is unequally consumed, the output from the comparators 9a and 9b is inverted, a toner bias display circuit 11 is operated through an OR circuit 10, and the bias of the toner is informed outside. Thus, even if the developer 4 is unequally consumed, the fact can be surely detected.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. The present invention relates to an image forming apparatus such as a copying machine or a printer. The present invention relates to an image forming apparatus equipped with a developer remaining amount detection device that detects the remaining amount of developer using changes.

For example, in a developing device used in an electrophotographic image forming apparatus, a developing sleeve that carries and conveys a thin layer of developer and an electrostatic latent image carrier are connected in a developing area. A bias voltage having an AC component (DC voltage superimposed on AC voltage) is applied between the developing sleeve and the electrostatic latent image carrier, which are arranged facing each other, and an alternating electric field is formed in the developing area by this bias voltage. Therefore, the so-called jumping development method, in which developer (toner) is caused to move back and forth between the two, is widely used. As a method for detecting developer exhaustion in such a developing device, a rod-shaped or plate-shaped conductor facing the developing sleeve is provided in the developer container, and a bias voltage applied to the developing sleeve causes the developer to run out. A detection method using induced voltage generated in a conductor is conventionally known.

This detects a change in capacitance between the developing sleeve and the conductor due to a change in the amount of developer present between the two as a voltage, and compares it with a reference voltage.

FIG. 6 is a circuit diagram showing a typical example of a conventional developer exhaustion detection device using the above-mentioned principle, and shows a case where the device is used in combination with a developing device 20 of an electrophotographic image forming apparatus. In this example, the developing device 20 is configured to perform development using a well-known jumping development method using a one-component magnetic toner 4, and a toner container 21 containing the toner 4 is supplied with a predetermined AC bias voltage from an AC bias source 2. It consists of a developing sleeve 1 to which a DC voltage (usually a DC voltage superimposed on an AC voltage) is applied, and a detection conductor 15 that is stretched horizontally opposite to the developing sleeve 1 and detects and warns when the toner is running out. ing. The toner 4 adheres to the developing sleeve 1 and jumps from the developing sleeve 1 due to a predetermined AC bias voltage applied to the developing sleeve 1 from the AC bias source 2, and is transferred to the electrostatic latent image carrier, in this example, the photoreceptor drum 22. The electrostatic latent image formed thereon is developed.

The detection conductor 15 and the developing sleeve 1 each correspond to the electrode plates of a capacitor, and the toner shortage (toner remaining amount) is detected based on the fact that the capacitance between them changes depending on the amount of toner existing between them. This is a warning. The voltage output generated on the detection conductor 15 is connected to the rectifier circuit 6 and the capacitor -
It is converted into a DC voltage V++c through the voltage conversion circuit 7,
A change in capacitance, that is, a change in toner amount, is detected as a voltage. ■This detected DC voltage. , are supplied to one input of the comparison circuit 9. A constant reference DC voltage V is supplied from a reference voltage source (reference voltage generation circuit) 8 to the other input of the comparison circuit 9, and the two voltages are compared in the comparison circuit 9. Here, for example, the reference DC voltage V supplied from the reference voltage source 8 to the comparator circuit 9 is the DC voltage V supplied to the comparator circuit 9 when almost no toner 4 is left between the detection conductor 15 and the developing sleeve l. If it is set to a value equal to the voltage VDC, when the remaining amount of toner decreases and there is almost no toner between the detection conductor 15 and the developing sleeve 1, the reference DC voltage V becomes the DC voltage VI from the conversion circuit 7. ,
Since the value becomes larger than c, the output from the comparator circuit 9 is inverted, and the toner out display circuit 16 is activated to notify the outside that the toner is out.

However, the toner 4 in the developing device is not necessarily consumed uniformly. For example, if printing is repeatedly performed only at a position offset with respect to the conveying direction of the paper to be printed, as shown in FIG. , the toner 4 decreases only on one side (the left side in the figure). If printing continues in this state, the amount of remaining toner has not decreased enough to notify that the toner has run out, so in the conventional developer running out detection device configured as described above, the DC output from the capacitance-voltage conversion circuit 7 There is a drawback that the voltage V0° has not decreased to a level at which toner exhaustion is detected, and therefore, even though the toner exhaustion is not notified to the outside, white spots and the like occur in the image.

Therefore, an object of the present invention is to detect when the developer is consumed unevenly and to notify the outside that the developer is running out, and to prevent the occurrence of white spots on the image before notifying the outside that the developer is running out. An object of the present invention is to provide an image forming apparatus equipped with a developer remaining amount detection device that prevents the occurrence of defects.

The above-mentioned object is achieved by an image forming apparatus according to the present invention. To summarize, the present invention provides a detection conductor facing a developer carrier in a developing device, and applies an AC bias voltage to the developer carrier to generate a detection signal and a reference signal obtained from the detection conductor. In the image forming apparatus, the image forming apparatus includes a developer remaining amount detection device that detects the remaining amount of developer in the developing device by comparing the amount of developer remaining in the developing device. a sensing conductor, a first comparing means for comparing a sensing signal obtained from the first sensing conductor with a first reference signal, and a sensing signal obtained from the second sensing conductor as a second reference signal. The present invention is characterized by comprising a developer remaining amount detection device including a second comparison means for comparison and a means for indicating the developer remaining amount according to the comparison result of the first and second comparison means. It is an image forming apparatus.

In one preferred embodiment of the present invention, signal adjustment means are provided on the input sides of the first and second comparison means, respectively.

K Presentation 3 Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a circuit configuration diagram showing a remaining developer amount detection device of a first embodiment of an image forming apparatus according to the present invention, and FIG. 2 shows an enlarged view of the developer remaining amount detection device of this embodiment. used in combination with a developing device 20 of an electrophotographic image forming apparatus,
Further, the developing device 20 is configured to perform development using the one-component magnetic toner 4 by a well-known jumping development method.

In this embodiment, the first
and second two sensing conductors 3a and 3b are respectively arranged parallel to the developing sleeve 1 and in a line, and each sensing conductor 3a, 3b is connected to the corresponding first and second rectifier circuits 6a and 6b, respectively. When an AC bias (usually a DC voltage superimposed on an AC voltage) is applied to the developing sleeve 1 from an AC bias source 2, the voltage output generated in each detection conductor is connected to these rectifier circuits 6a, 6b and these rectifiers. The first and second capacitance-voltage conversion circuits 7a and 7b are connected in series with the circuit, respectively.
are converted into DC voltages Voc+ and Voet, respectively, and a change in the capacitance between the detection conductors 3a, 3b forming a capacitor and the developing sleeve 1, that is, a change in the amount of toner, is detected as a voltage.

As usual, each detected DC voltage V oc+ and V
oci are the corresponding first and second comparison circuits 9a and 9b
are respectively supplied to one input of the . These comparison circuits 9
The other inputs of a and 9b are supplied with first and second constant DC voltages Vll and V from reference voltage sources 8a and 8b, respectively.
□ is supplied, the pressures of both types are compared in these comparison circuits 9a and 9b, and the comparison results are input to an OR circuit 10 and an AND circuit 12, respectively. The output from the OR circuit 10 is supplied to a toner offset display circuit 11, and the output from the AND circuit 12 is supplied to a toner out display circuit 13.
It is configured to be able to display both toner imbalance (local toner outage) and toner outage.

Here, for example, from the reference voltage source 7, each comparison circuit 9a and 9
The first and second reference DC voltages Vll and V input to the converter circuits 7a and 7b are applied to the converter circuits 7a and 7b when almost no toner 4 is present between the detection conductors 3a and 3b and the developing sleeve 1.
to each comparison circuit 9a.

DC output voltages Voe+ and V input to 9b. If you set them to be equal to e2, for example, the second
As shown in the figure, when the toner is consumed unevenly, there is sufficient toner 4 between the first sensing conductor 3a and the developing sleeve 1, but there is no toner between the second sensing conductor 3b and the developing sleeve 1. 4 (therefore, the voltage output generated on the second sensing conductor 3b becomes small, and the DC output voltage v oat from the second capacitance-voltage conversion circuit 6b becomes the second reference DC voltage. As a result, the output from the first comparator circuit 9a is still not inverted, but the output from the second comparator circuit 9b is inverted.
The toner deviation display circuit 11 is activated through the OR circuit 10, and the deviation of the toner is notified to the outside. That is, the fact that the toner is locally running out (toner shortage) is notified to the outside. Similarly, even if the toner on the first detection conductor 3a side is consumed unevenly, the toner unevenness display circuit 1
1 is activated, and the deviation of the toner is notified to the outside.

On the other hand, the toner 4 is consumed almost equally, and both detection conductors 3a
, 3b and the developing sleeve 1, the outputs of both the first and second comparison circuits 9a and 9b are inverted, so an output signal is generated from the AND circuit 12 and the toner out indication circuit is activated. 13 is activated to notify the outside that the toner is out (toner shortage).

(Thus, according to this embodiment, even if the toner is consumed unevenly, or even if the toner is unevenly distributed for some reason, this can be detected before white spots etc. occur in the image.) However, since it is possible to notify the outside of a local toner shortage, for example, if the developer is a cartridge type,
As shown in FIG. 1, if the user can remove the developing device from the main body of the image forming apparatus along the guide 23 that detachably supports the developing device, the toner deviation display circuit 11 When a user is notified that the toner is running out, the user can remove the developing device from the main body of the device and shake it to equalize the remaining amount of toner on each detection conductor. When the developing device is installed in the developing device, a local toner-out alarm is not generated, and the developing device can be used again without replenishing toner or replacing the cartridge. Therefore, it is possible to eliminate the drawback that white spots on the image occur before the toner exhaustion level 5 is notified. Further, according to this embodiment, there is an advantage that the toner can be used to the end. This also applies to devices in which the developing device and photoreceptor, or if necessary, process equipment such as a charger and cleaner are installed in the same housing so that they can be attached to and removed from the main body of the image forming apparatus. .

FIG. 3 is a circuit diagram showing a remaining developer amount detection device of a second embodiment of an image forming apparatus according to the present invention. The developing device 20 is used in combination with a developing device 20, and the cartridge type developing device 20 is configured to perform development using the one-component magnetic toner 4 by a well-known jumping developing method.

In the above embodiment, the detection circuit was constructed assuming that the distances between the two detection conductors 3a, 3b and the developing sleeve 1 were constant and equal;
It may also happen that the distances between the two sensing conductors 3a, 3b and the developing sleeve 1 are not equal. If the distances of both sensing conductors to the developing sleeve 1 are not equal, the magnitudes of the DC voltages V, V, and c* detected through both sensing conductors will be different, so in reality, the distance between both sensing conductors and Even if toner remains uniformly between the developing sleeves, a problem arises in that one of the detection voltages, which has a lower voltage value, notifies the outside that the toner is running out.

This embodiment focuses on the above point, and the first and second reference voltage sources (reference voltage generation circuits) 14a and 14b are configured to allow voltage adjustment, and the developing sleeve 1 and each detection conductor 3
When a and 3b are in the same state, that is, both sensing conductors 3
DC voltage V detected when toner 4 is uniformly present between a, 3b and the developing sleeve 1. C3 and V
The potential difference between Del and Del is measured, and an offset voltage corresponding to the potential difference is applied to one of the reference voltage sources.

As shown in FIGS. 3 and 4, due to mechanical installation errors, the distance between the second sensing conductor 3b and the developing sleeve 1 is larger than the distance between the first sensing conductor 3a and the developing sleeve 1. In this case, the DC voltage V detected through each sensing conductor 3a, 3b. The relationship between 0 and the amount of toner is shown in FIG. As is clear from the figure, the DC voltage V Del detected by the first sensing conductor 3a is larger than the DC voltage Voc* detected by the second sensing conductor 3b at any given same amount of toner (g). Therefore, the DC voltage at the position where the amount of toner is detected to be out of toner is also VDC.
I is more Vwa. , is greater than . Therefore, in this embodiment, the first and second reference voltage sources 14a and 14b, which generate the reference DC voltage (2) for determining toner out (toner shortage) and Vex, are configured so that the voltages can be adjusted. , DC voltage V detected when toner 4 is uniformly interposed between both detection conductors 3a, 3b and developing sleeve 1. el and ■. The amount corresponding to the potential difference between c2,
V II or v by adjusting either side reference voltage source
By applying an offset voltage to (2), the outputs of the first and second comparison circuits 9a and 9b are inverted almost simultaneously based on the detected DC voltage V DCIVocz at the position of the toner amount at which toner exhaustion is detected. Note that the other configurations of this embodiment are the same as those of the first embodiment shown in FIG. 1, so corresponding elements and members are designated by the same reference numerals and their explanations will be omitted.

With this configuration, as in the first embodiment, even if the toner is consumed unevenly, or even if the toner is unevenly distributed for some reason, the image can be processed before white spots or the like occur. Not only can this be detected and externally notified of local toner exhaustion, but the mechanical attachment of the detection conductor can also absorb errors, which is achieved by the first embodiment. In addition to the above effects, there is also the advantage that the installation of the detection conductor becomes easier and the detection accuracy is improved.

In the above embodiment, the reference voltage source has a configuration in which the voltage can be adjusted, but the reference voltage is a common constant DC voltage, and the detected DC voltage Voc+ input to the comparison circuits Q 9 a and 9 b
, Vwa. , may be configured so that they can be adjusted respectively. Further, in the above embodiment, the sensing conductor disposed parallel to and facing the developing sleeve, which is a developer carrier, is a rod-shaped body, but the shape, size, installation position, etc. of the sensing conductor can be changed as desired. Furthermore, although the present invention has been described as being applied to an electrophotographic image forming apparatus configured to perform development by a well-known jumping development method using a one-component magnetic developer, the present invention is limited to a one-component developer. The present invention can be similarly applied to developing devices that use other developers including two-component developers. Furthermore, the developing method is not limited to the jumping developing method, and is equally applicable to image forming apparatuses of various configurations that use various developing methods. Of course, the present invention can also be applied to image forming apparatuses using electrostatic recording methods and the like.

As explained above, in the image forming apparatus according to the present invention, the two detection conductors are arranged to face the developer carrier, so that even if the developer is locally consumed, it can be detected reliably. Therefore, it is possible to prevent defects such as white spots on images from occurring before the developer is notified that the developer is running out. In addition, if the developer is configured to be removable from the main body of the device, the developer deviation display allows the user to correct deviations due to local consumption of developer, etc. It can be used up to

In addition, by symmetrically arranging the two sensing conductors,
Since the terminals can be pulled out symmetrically from each detection conductor, detection can be performed under the same conditions, and stable detection results can always be obtained. Furthermore, by making the reference voltage or the detection DC voltage adjustable, the mechanical attachment of the detection conductor has many advantages, such as being able to correct errors.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram showing a developer remaining amount detection device of a first embodiment of an image forming apparatus according to the present invention. FIG. 2 is a top view showing essential parts of the developing device used in the image forming apparatus of FIG. 1. FIG. 3 is a circuit configuration diagram showing a developer remaining amount detection device of a 20th embodiment of an image forming apparatus according to the present invention. FIG. 4 is a top view showing the main parts of the developing device used in the image forming apparatus of FIG. 3. FIG. FIG. 5 is a diagram showing the relationship between the amount of toner and the detected DC voltage that may occur in the configuration of the image forming apparatus according to the present invention. FIG. 6 is a circuit diagram showing a typical example of a developer exhaustion detection device for a conventional image forming apparatus. 1: Developing sleeve 2: AC bias sources 3a, 3b: Detection conductor 4: Toner 6a, 6b: Rectifier circuits 7a, 7b = Capacitance-voltage conversion circuits 8a, 8b, 14a, 14b: Reference voltage sources 9a, 9b =
Comparison circuit 10: OR circuit 11: Toner offset display circuit 12: AND circuit 13: Toner out display circuit 20: Developing unit indicator Figure 5

Claims (1)

[Claims] 1) A detection conductor is provided facing a developer carrier in a developing device, and a detection signal and a reference signal obtained from the detection conductor by applying an AC bias voltage to the developer carrier. In the image forming apparatus, the image forming apparatus includes a developer remaining amount detection device that detects the remaining amount of developer in the developing device by comparing the amount of developer remaining in the developing device. a sensing conductor and a sensing signal obtained from the first sensing conductor.
a first comparison means for comparing the detection signal obtained from the second detection conductor with a second reference signal; and a second comparison means for comparing the detection signal obtained from the second detection conductor with a second reference signal; An image forming apparatus comprising: a developer remaining amount detection device having a means for indicating the developer remaining amount according to a comparison result. 2) The image forming apparatus according to claim 1, wherein the first and second comparing means each include a signal adjusting means on their input sides.