JPH03225382A - Residual toner detector - Google Patents

Abstract

PURPOSE:To accurately detect residual toner with high precision by providing plural antennas whose height is changed with respect to a developing sleeve and which is oppositely arranged and detecting the residual toner through a change in the electrostatic capacity of the antenna. CONSTITUTION:First and second antennas 2 and 3 acting as the other electrodes are arranged to face oppositely the developing sleeve 1 in such a manner that their height are changed, and the electrostatic capacity is given between the sleeve 1 and antennas 2 and 3. A reference signal 12 supplied to an input terminal 16 passes through a HPF composed of the electrostatic capacity and respective resistors R1 and R2, and is supplied to first and second AND circuits 7 and 8 via first and second zero-cross comparators 4 and 5. The changes in the electrostatic capacities of the antennas 2 and 3 are converted into phases with an output signal modulated by a positional difference from a signal 12, so that the output of the circuits 7 and 8 detect the residual toner. Thus, the residual toner is consecutively and almost linearly detected over a wide area.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. The present invention relates to a toner remaining amount detecting device that detects the remaining amount of toner in a toner container using capacitance between a developing sleeve and a plurality of antennas facing the developing sleeve. .

2. Description of the Related Art Devices for detecting the amount of toner remaining in a toner container used in a printing device are conventionally known, and the remaining amount is generally detected by detecting changes in impedance, particularly reactance. Conventionally known methods for detecting and processing changes in actance include a method using an AC bridge, a method that constructs a series/parallel resonant circuit and extracts it as a change in the magnitude of voltage or current. There is a method of configuring an oscillation circuit as part of an oscillation element, treating the change in reactance as a change in reactance of the oscillation circuit, and extracting it as a change in the oscillation frequency or a change in the level of the oscillation output.

First, when detecting changes in reactance using the AC bridge method described above, even when using a Maxwell bridge circuit, which is relatively suitable for detecting changes in inductance, for example, This Maxwell
As long as the bridge circuit is an AC bridge, the deviation output (deviation voltage) of the bridge circuit will not become zero unless the magnitude and phase of the voltage on the opposite side completely match each other. The AC bridge circuit normally used as a detection circuit detects only the magnitude of the voltage of the deviation output, so even if the Q of the detection coil is increased, the deviation output does not become completely zero, so this deviation output must be amplified. Even if we try to increase the detection sensitivity by doing so, there are limits.

Next, in the method of configuring a resonant circuit described above, when considering a series resonant circuit, for example, the current that flows changes greatly due to the resonance between the inductance and capacitance, but due to the unimodal characteristic, the current flows around the resonance point as a boundary. Since the direction of flow is reversed, there is a drawback that it is not possible to utilize the large variation near the resonance point.

Furthermore, in the above-mentioned method of extracting changes in the oscillation frequency and the level of the oscillation output, the oscillation circuit is configured to function as an active circuit, so the oscillation frequency changes depending on changes in the surrounding environment such as temperature and humidity. The problem is that it is unstable and lacks reliability because the level of the oscillation output changes.

Therefore, an object of the present invention is to detect the remaining amount of toner as a change in capacitance in a substantially linear relationship over a wide range, and to convert this change in capacitance into a change in phase. It is an object of the present invention to provide a toner remaining amount detection device that eliminates various technical drawbacks and improves detection sensitivity and accuracy.

The above object is achieved by the toner remaining amount detection device according to the present invention. In summary, the present invention provides a plurality of antennas arranged opposite to each other at different heights with respect to a developing sleeve of a toner container used in a printing device, and a plurality of antennas that are arranged opposite to each other at different heights with respect to a developing sleeve of a toner container used in a printing device, and that each of the antennas means for detecting a change in capacitance as a change in phase; and a phase difference detection means for detecting the change in phase as a phase difference from a reference signal. The present invention is a toner remaining amount detecting device that can detect the remaining amount of toner over a wide range with high accuracy by switching the electrostatic capacitance of each antenna.

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

FIG. 1 is a circuit diagram showing an embodiment of a remaining toner amount detection device according to the present invention. A first electrode that faces the developing sleeve 1 that acts as one electrode and acts as the other electrode.
The second two antennas 2 and 3 are arranged at different heights, and a capacitance is provided between the developing sleeve 1 and these antennas 2 and 3, respectively. Developing sleeve 1 and antenna 2.
The positional relationship between the two antennas 2 and 3 is as shown in FIG. They are arranged in the axial direction (horizontal direction) of the developing sleeve 1 at different heights. In the illustrated example, the first
antenna 2 is located higher than the second antenna 3,
When the toner 14 filled in the toner container 13 decreases, the capacitance between the first antenna 2 and the developing sleeve 1 is first affected (changed). In other words, the detection range of the remaining amount of toner is
．． It is divided into 3 sections, and the height is changed to enable almost linear detection over a wide range of remaining amount. The toner container 13 acts as a cartridge and is provided with a photosensitive drum 15 as usual. FIG. 2(B) is a perspective view of the developing sleeve 1, the antennas 2 and 3, and the photosensitive drum 15, in which two antennas 2.3 in the form of wires are placed at a predetermined interval in the axial direction of the developing sleeve 1. This is to illustrate that they are arranged in parallel.

The first antenna 2 is connected to one input of a first zero-cross comparator 4 via a first resistance circuit R1, and the second antenna 3 is connected to one input of a first zero-cross comparator 4 via a second resistance circuit R2. It is connected to one input of the zero cross comparator 5.

On the other hand, a reference signal 12 is supplied to the developing sleeve 1 via an input terminal 16. Although this reference signal 12 is a pulse signal in this embodiment, it is not limited to a pulse signal. The reference signal 12 is also supplied to one of the third zero-cross comparators 6 via the reference capacitor 11 and the third resistance circuit R3 in series. 1st, 2nd
and the other human power of the third zero-cross comparator 4.5 and 6 is grounded as usual, and the output of the first zero-cross comparator 4 is connected to one input of the first AND circuit 7, and the second The output of the zero cross comparator 5 is connected to one input of the second AND circuit 8, and the output of the third zero cross comparator 6 is connected to both the first and second AND circuits.
It is connected to the other input of circuits 7 and 8, respectively.

The output of the first AND circuit 7 is sent to the first low-pass filter 9.
The output of the second AND circuit 8 is connected to the second output terminal 18 via the second low-pass filter 10.

Next, the operation of the toner remaining amount detection device according to the present invention having the above configuration will be explained.

The capacitance between the developing sleeve 1 and the antenna 2.3 changes depending on the remaining amount of toner. -Changes in boat fishing show the trends shown in Figure 3. In Figure 3, the horizontal axis represents the remaining amount of toner in duram (g), and the vertical axis represents the developing sleeve 1 and antenna 2.
．． 3 is expressed in picofarads (pF). As long as the remaining amount of toner is at a certain level higher than the first higher antenna 2, the capacitance of both antennas does not change and remains constant, but as the remaining amount of toner decreases further, The capacitance of antenna 2 of antenna 1 is affected and decreases as the toner decreases, as shown by curve a. The remaining amount of toner further decreases and approaches the second antenna 3 (and the capacitance of this second antenna 3 is also affected and decreases as the toner decreases, as shown by the curve). As is clear from the figure, the decrease in the amount of remaining toner and the decrease in capacitance are almost linear over a considerable range, and if the outputs of both antennas 2 and 3 are switched within a certain range, the remaining amount of toner can be reduced over a wide range. The amount can be detected linearly.

Reference signal (pulse signal) 12 supplied to input terminal 16
pass through high-pass filters constituted by the capacitance between the developing sleeve 1 and the antenna 2.3 and the respective resistance circuits R1 and R2, and are input to the first and second zero-cross comparators 4 and 5. is supplied to The outputs of these zero-cross comparators 4 and 5 are supplied to one input of the first and second AND circuits 7 and 8, respectively, as described above. The other input of these AND circuits 7 and 8 is the output of a third zero-cross comparator 6, and this third zero-cross comparator 6 has a high-pass filter configured by a reference capacitor 11 and a third resistor circuit R3. A reference signal 12 that has passed through is supplied. Therefore, the outputs of the AND circuits 7 and 8 are output signals pulse width modulated by the phase difference from the reference signal 12,
This means that the change in capacitance of antenna 2.3 is converted into a change in phase. Pulse width modulated AND circuit 7.8
The output signal is converted to a DC level by a low-pass filter 9.10 and then output to an output terminal 17.18. (As shown in FIG. 3, if the remaining toner amount range for the first antenna 2 is assigned as can be detected almost linearly.The resistance value of the above-mentioned high-pass filter must be determined in consideration of the reference signal frequency so that the pole (cutoff frequency) of this filter is near the reference signal frequency. For example, if the reference signal 12 is 2 KHz (pulse repetition frequency) and the capacitance varies in the range of 5 to 10 pF as shown in FIG. 3, the resistance value may be selected to be approximately IOMΩ.

As described above, in this embodiment, the two antennas 2.3 are arranged opposite to the developing sleeve 1 at different heights to provide electrostatic capacitance between them and the developing sleeve 1, thereby reducing the amount of remaining toner. It is detected as a change in capacitance, and a reference signal is passed through each high-pass filter containing these capacitances and a high-pass filter containing a reference capacitor, and the two are compared. Since the change in is detected as a phase difference from the reference signal,
Problems such as poor detection sensitivity, unavailability of large curve changes, and lack of stability, as in the conventional technology described above, do not occur. Since it can be switched and used, the detection range of the remaining amount of toner is considerably widened, and since the linearity is good, stable and highly accurate detection of the remaining amount of toner is possible.

FIG. 4 is a circuit configuration diagram showing a second embodiment of the present invention. Since this embodiment is substantially the same as the embodiment shown in FIG. 1 except that the high-pass filter is made of two stages, the same reference numerals will be given to the same components as in FIG. 1, and the explanation thereof will be omitted. do. That is, the capacitance and resistance of each antenna 2.3
constitute a first high-pass filter, respectively, and
After that, capacitors 22 and 23 and resistor circuits R1 and R2
A second high-pass filter configured by a capacitor 24 and a resistor circuit R3 is connected to the first high-pass filter configured by a reference capacitor 11 and a resistor 21. A second high-pass filter is connected to the second high-pass filter.

When the high-pass filter is arranged in two stages in this way, the amount of change in the phase difference with respect to the change in capacitance between the developing sleeve 1 and each antenna 2.3, that is, the change in the output of the low-pass filter 9.10, is reduced. Since the number is doubled, there is an advantage that the accuracy can be further improved.

It should be noted that the above-mentioned embodiments are merely illustrative examples of implementing the present invention, and the circuit configuration, the elements used, etc. can be variously changed as necessary. Further, although two antennas are used, the number may be increased as necessary. Of course, the toner container is not limited to a cartridge type toner container.

As described above, the toner remaining amount detection device according to the present invention divides the remaining toner amount detection range between a plurality of antennas, uses only the portion with good linearity, and uses the Since the remaining amount of toner is detected as a change in capacitance, it is possible to detect the remaining amount of toner with good linearity over a wide range, thus increasing detection sensitivity and stability.
A remarkable effect is that the remaining amount of toner can be detected accurately and with high precision.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a remaining toner amount detection device according to the present invention. FIG. 2(A) is a schematic side view of a cartridge type toner container to which the present invention is applied. FIG. 2(B) is a schematic perspective view showing the arrangement relationship of a developing sleeve, an antenna, and a photosensitive drum within a cartridge-type toner container. FIG. 3 is a characteristic curve diagram showing the relationship between the remaining amount of toner and the antenna capacitance. FIG. 4 is a circuit diagram showing a second embodiment of the remaining toner amount detection device according to the present invention. l: Developing sleeve 2.3: Antenna 4.5.6: Zero cross comparator 7.8: AND circuit 9.10: Low pass filter 11: Reference capacitor 12: Reference signal 12 Figure 2 Figure 3 Figure 4 figure

Claims (1)

[Claims] 1) A plurality of antennas arranged opposite to each other at different heights with respect to a developing sleeve of a toner container used in a printing device;
means for detecting a change in the capacitance of each of the antennas due to a decrease in the amount of toner remaining in the toner container as a change in phase; and a phase difference detection means for detecting the change in phase as a phase difference from a reference signal. The remaining amount of toner, characterized in that the remaining amount of toner can be detected over a wide range with high accuracy by switching the remaining toner amount detection range between each of the antennas and changing the capacitance of each of the antennas. Detection device.