JPH09262990A - Residual amount detection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively provide a residual amt. detection apparatus preventing the effect of electrolysis or the like on a liquid even if an electrode is utilized. SOLUTION: A residual amt. detection apparatus is constituted so that voltage is applied across a pair of the electrodes 1, 2 arranged in a tank and electric resistance receiving the effect of the liquid present between the electrodes 1, 2 to change is detected to detect the residual amt. of the liquid in the tank. In this case, at a time of non-detection, reference voltage of predetermined potential is applied across both electrodes 1, 2 and, at a time of detection, the potential of one of a pair of the electrodes 1, 2 is alternately changed across reference voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a remaining amount detecting device for detecting the remaining amount of liquid in a container by means of electrodes.
In particular, the present invention relates to a remaining amount detection device in consideration of prevention of electrolysis and characteristic deterioration that may occur in a liquid to be detected.

[0002]

2. Description of the Related Art For example, conventionally, a remaining amount detecting device for detecting the remaining amount of ink is provided in an ink tank fixed to a main body of an ink jet printer. In order to detect the remaining amount of the ink, a reed switch detects a float with a built-in magnet that moves according to the change of the ink surface, or an optical sensor is used for confirmation. However, in such a detection device, complicated components are required, the device itself is liable to malfunction, and the ink adhering to the wall surface of the container does not allow light to pass through as desired, and accurate detection cannot be performed. There was an inconvenience.

Therefore, in order to eliminate such inconvenience, a detection device in which two electrodes are arranged in a height difference in the ink tank is adopted. Since the electrical resistance changes depending on the presence or absence of ink interposed between the two electrodes, the amount of ink is detected by measuring the change in resistance.

[0004]

However, the remaining amount detecting device for detecting the electrode by providing the electrode in the ink tank as described above has an advantage that accurate detection is possible with a simple structure, but the ink is not the ink. Due to the direct current flowing through it, electrolysis was caused and the characteristics of the ink such as the composition of the ink were changed. Therefore, the ink whose characteristics have deteriorated affects the ejection at the time of printing, which is not preferable. Therefore, in order to prevent such characteristic deterioration of ink such as electrolysis, an AC signal is applied between the electrodes in the ink tank.

However, although problems such as electrolysis were avoided by applying an AC signal between the electrodes,
A negative power source is required to generate the AC signal, which causes a new problem that the detection device itself becomes expensive. This is considered to be a more important problem as the number of objects to be detected increases, such as in a color inkjet printer.

Further, at present, there is a reality that a logic circuit is mainly used for a control circuit and a negative power source is hardly used.

[0007] Therefore, in order to solve the above problems, the present invention uses an electrode, and an object thereof is to provide at low cost a remaining amount detecting device which prevents the influence of electrolysis or the like on a liquid. To do.

[0008]

The remaining amount detecting device of the present invention applies a voltage between a pair of electrodes arranged in a tank, and changes an electric resistance which changes under the influence of a liquid existing between the electrodes. A remaining amount detection device for detecting the remaining amount of liquid in a tank by detecting, when a non-detection, a reference voltage of a predetermined potential is applied to both electrodes, and at the time of detection, the potential of one of the pair of electrodes is An alternating voltage supply means for alternatingly changing the reference voltage is provided, and the alternating voltage supply means has a push-pull circuit.

Further, it is preferable that the average value of the voltage change at the time of the detection is approximately the reference voltage as in the remaining amount detecting device according to the second aspect of the present invention.

The remaining amount detecting device according to claim 3 of the present invention is
A voltage is applied between the pair of first and second electrodes arranged in the tank, and the electric resistance that changes under the influence of the liquid existing between the electrodes is detected to detect the remaining amount of the liquid in the tank. The alternating voltage supply means is connected to apply a direct current signal of a square wave, a sine wave or a triangular wave to the first electrode, the alternating voltage supply means being controlled by the push-pull circuit to be in an energized state or a non-energized state. And a second voltage supply means connected to the second electrode for applying an offset voltage to a predetermined output circuit connected to the first electrode. , The first voltage supply means is de-energized to apply a reference voltage having a predetermined potential to both electrodes, and when the detection is performed, the first voltage is supplied to the first electrode.
The direct current signal is applied to the first electrode by energizing the voltage supply means, and the potential between the two electrodes alternates with the reference voltage as a boundary.

Further, in the remaining amount detecting device according to claim 4 of the present invention, the maximum voltage applied to the first electrode by the first voltage supply means is the same as the maximum voltage applied to the second electrode by the second voltage supply means. A voltage that is twice the applied voltage is preferable.

Further, as in the remaining amount detecting device according to claim 5 of the present invention, the first voltage supply means is composed of a two-stage Zener diode, and supplies the measurement voltage to the first electrode. It is preferable that the voltage supply means is composed of a single stage Zener diode and supplies a reference voltage to the second electrode.

In the remaining amount detecting device having such a configuration, it is preferable that the output circuit is a comparator to which a comparison voltage is applied, as in the remaining amount detecting device according to claim 6 of the present invention. .

Further, it is preferable that the pair of electrodes are arranged with a height difference, as in the remaining amount detecting device according to claim 7 of the present invention.

The remaining amount detecting device of the present invention is an electric device that changes voltage under the influence of a liquid existing between a pair of electrodes arranged in a tank with a height difference provided between them. The remaining amount of liquid in the tank is detected by detecting the resistance, but even if a DC signal that would affect electrolysis of the liquid is input, the reference voltage of a predetermined potential is applied to both electrodes when not detected. The current flow between the electrodes is stopped by applying a voltage, and at the time of detection, the potential of one of the electrodes is changed by alternating it with the reference voltage as a boundary so that it acts as if an alternating current flows between the two electrodes. Therefore, a negative power source for generating an AC signal is not required, and an inexpensive remaining amount detecting device having a simple structure can be provided. Further, in the remaining amount detecting device of the present invention, the push-pull circuit controls the potential of one of the electrodes so that the detection or non-detection timing in the present device is created.

Further, in the remaining amount detecting device of the present invention, if the average value of the voltage change at the time of the detection is substantially the reference voltage, the influence of the current becomes smaller.

In the remaining amount detecting device of the present invention, a voltage is applied between a pair of a first electrode and a second electrode arranged in a tank, and an electric resistance that changes under the influence of a liquid existing between the electrodes is changed. By detecting, the remaining amount of liquid in the tank is detected. At this time, a DC signal of a square wave is applied from the first voltage supply means connected to the first electrode, but the first supply means is in a non-energized state when not detected, and the second voltage connected to the second electrode. Due to the offset voltage by the voltage supply means, a reference voltage of a predetermined potential is applied to both electrodes. On the other hand, at the time of detection, the first supply means is energized, a DC signal is applied to the first electrode, and the potential between both electrodes alternates with the reference voltage as a boundary. Acts to flow. Therefore, the influence of electrolysis or the like that occurs in the liquid is prevented.

Further, the remaining amount detecting device of the present invention is the above first
If the maximum voltage applied to the first electrode by the voltage supply means is twice the voltage applied to the second electrode by the second voltage supply means, the average value of the voltage change at the time of detection is:
The voltage becomes almost the reference voltage, and the influence of the current is smaller. Further, the first voltage supply means has a two-stage Zener diode and supplies the measurement voltage to the first electrode, and the second voltage supply means is composed of a one-stage Zener diode and the reference voltage is supplied to the second electrode. If it supplies, the alternating voltage supply means which has the said effect can be achieved with a simple structure.

Further, in the remaining amount detecting device of the present invention, the signal which has received the amount of resistance change which changes depending on the presence or absence of the liquid in the tank is input to the comparator circuit which is an output circuit, and a predetermined detection signal is output. .

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the remaining amount detecting apparatus of the present invention having the above-mentioned structure will be described with reference to the drawings. FIG. 1 is a schematic cross section showing an ink tank containing ink to be inspected, and FIG. 2 is a circuit configuration diagram showing a remaining amount detecting device of the present embodiment.

As shown in FIG. 1, the ink tank 3 includes
A pair of the first electrode 1 and the second electrode 2 are fixedly provided with a height difference. A circuit as shown in FIG. 2 is formed on the electrodes 1 and 2 fixed to the ink tank 3 in this way.

First, the current limiting resistor 10, the Zener diode A11, and the Zener diode B12 are connected between the power supply voltage and the ground to form a first reference voltage supply means and a second reference voltage supply means.

The output terminal of the push-pull circuit 4 is connected to the first electrode 1 through the detection resistor 5. The emitter side of the PNP transistor 4a of the push-pull circuit 4 has the current limiting resistor 10 and the Zener diode A11.
And a first reference voltage is supplied. On the other hand, the NPN transistor 4 of the push-pull circuit 4
The emitter side of b is grounded. The push-pull circuit 4, the detection resistor 5, and a signal transmission circuit (not shown) for inputting the DC square wave to the input terminals t1 and t2 of the push-pull circuit 4 constitute a first voltage supply means.

The positive side input terminal of the comparator 7 is connected to the first electrode 1. A comparison voltage 8 is applied to the negative side input terminal of the comparator 7, and an output port 9 for outputting a pulse signal indicating the result of the ink remaining amount in the ink tank 3 is connected to the output terminal.

On the other hand, the second electrode 2 of the ink tank 3 has a Zener diode A11 and a Zener diode B12.
And the voltage of the second electrode 2 is the second
It is the reference voltage. That is, the second reference voltage supply means also serves as the second voltage supply means.

In the remaining amount detecting device having such a structure,
The remaining amount of ink in the ink tank 3 is detected as follows. Here, FIGS. 3A to 3E are time charts showing potentials (signals) at respective points of the circuit forming the remaining amount detecting device.

FIG. 3A shows the PN of the push-pull circuit 4.
The input signal Vx is a DC square wave input to the input terminal t1 that controls the P-transistor, and has an H level of 5
The V and L levels indicate 0V. FIG. 3 (B)
An input signal V which is a DC square wave input to an input terminal t2 which controls the NPN transistor of the push-pull circuit 4.
y, and like the input terminal t1, the H level indicates 5V and the L level indicates 0V.

The L-level pulse width of the input signal Vx to the input terminal t1 of the push-pull circuit 4 and the H-level pulse width of the input signal Vy to the input terminal t2 are the same, so that they continuously change without overlapping. Entered in. That is, the PNP transistor 4a and the NPN transistor 4b of the push-pull circuit 4 are not turned on at the same time, and the ON time is the same and are continuously controlled.

Both the input signal Vx and the input signal Vy are L
When a level signal is input and when both the input signal Vx and the input signal Vy are H level signals (PNP
When either the transistor 4a or the NPN transistor 4b is "ON", the input signal Vx is at the H level and the input signal Vy is at the L level (PNP).
Both the transistor 4a and the NPN transistor 4b are "OFF", which is unmeasured.

FIG. 3C shows the output voltage Va of the push-pull circuit 4.

By the way, when both the input signal Vx and the input signal Vy are L level signals to the output of the push-pull circuit 4 (only the PNP transistor 4a is "O").
N ”), the emitter potential of the PNP transistor 4a is output, and when both the input signal Vx and the input signal Vy are H level signals (only the NPN transistor 4b is“ O ”).
The emitter potential of the NPN transistor 4b is output to (N "). Further, when a signal in which the input signal Vx is at the H level and the input signal Vy is at the L level is input (the PNP transistor 4a and the NPN transistor 4b are both “OF”).
F]) is in a disconnected state where the output terminal is not connected to the internal circuit. Therefore, when the input signal Vx and the input signal Vy are both L level signals, the first reference voltage is output, and when the input signal Vx and the input signal Vy are both H level signals, the ground voltage is output. Is output.

Therefore, when the input signal Vx is at the H level and the input signal Vy is at the L level, the push-pull circuit 4 is cut off as described above. No current flows and the zener voltage Vz (which is the reference voltage) is substantially equal to the level of the second reference voltage. Then, the input signal Vx and the input signal Vy
When an L-level signal is input to both, the output voltage of the push-pull circuit 4 changes, and the potential of the output voltage Va changes from the reference voltage to the first reference voltage (2Vz). When both the input signal Vx and the input signal Vy are H level signals, the output voltage of the push-pull circuit 4 changes, and the potential of the output voltage Va changes from the first reference voltage to the ground voltage (0V).
Changes to When the input signal signal Vx is at the H level and the input signal Vy is at the L level, the push-pull circuit 4 is cut off again, so that no current flows and the level of the second reference voltage is almost equal to the ground voltage to the Zener voltage Vz
Changes to

On the other hand, FIG. 3D shows the detection resistor 5 and the first resistor.
6 shows the input voltage Vb to the positive terminal of the comparator 7, which shows the voltage level between the electrodes 1. This too
When the output of the push-pull circuit 4 is released, no current flows and the zener voltage Vz is substantially equal to the level of the second reference voltage. Either the PNP transistor 4a or the NPN transistor 4b of the push-pull circuit 4 is When turned on, the same change as the output voltage Va is received.

Therefore, the output voltage Va and the input voltage V
Regarding b, let us look at M1 time when the ink is filled between the first electrode 1 and the second electrode 2 in the ink tank 3. There, when both the input signal Vx and the input signal Vy are L level signals, the potential on the first electrode 1 side increases, so that both the output portion voltage Va and the input portion voltage Vb are at high levels (first 2 based on the reference voltage).

On the other hand, the input signal Vx and the input signal V
When both y-level signals are input, the first electrode 1
Since the potential on the side becomes low, the output voltage Va and the input voltage Vb both become low levels (based on the second reference voltage).

Therefore, when the output voltage Va becomes a low level, a current flows from the second electrode 2 side connected to the second reference voltage set to the Zener voltage Vz to the first electrode 1 side, and the output voltage Va increases. On the contrary, when the level becomes high, a current flows from the first electrode 1 to the second electrode 2, and an alternating current flows substantially between the electrodes 1 and 2 at the time of detection.

By the way, M2 in FIG. 3 shows a case where the ink is not filled between the first electrode 1 and the second electrode 2 in the ink tank 3. In this case, the resistance between the electrodes 1 and 2 changes depending on whether ink is present or absent, so that the voltage division ratio with the detection resistor 5 is increased. Therefore, the output portion voltage Va changes in the same manner, but the input portion voltage Vb greatly changes up and down as shown in the figure.

Therefore, the output voltage Vo from the comparator 7 shown in FIG. 3 (E) is output at the H level by comparing the change amount of the input portion voltage Vb at M2 with the comparison voltage 8.

According to the remaining amount detecting apparatus of this embodiment, the push-pull circuit 4 is connected to the first electrode 1 while the second reference voltage is connected to the second electrode 2 to obtain the Zener voltage. By applying the voltage of Vz, the characteristic deterioration of the ink does not occur. That is, the output voltage Va
As can be seen from the above, since the voltage fluctuates up and down with respect to the Zener voltage Vz at the time of detection, there is no potential difference between the electrodes 1 and 2 when there is no detection and no current flows, but an AC current substantially flows during detection. As a result, it is possible to prevent the deterioration of the characteristics of the ink, etc., even though the DC signal is input and detected. Therefore, it is possible to provide an inexpensive remaining amount detecting device without requiring negative charges for generating an AC signal.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention.

For example, it is not necessary to output signals at the intervals shown in the above-mentioned embodiments, and it is possible to change it according to the situation. In particular, in order to avoid the influence of the current on the electrolysis of the ink, it is desirable that the electric powers of the currents flowing through both electrodes at the time of detection are equal, and therefore it is necessary for the adjustment.

Further, in the embodiment, the detection of the remaining amount of ink has been described, but the liquid to be detected is not limited to the ink and corresponds to all the things that may cause inconvenience such as electrolysis.

[0043]

Therefore, according to the present invention, when a voltage is applied between a pair of electrodes and the electric resistance that changes depending on the presence or absence of the liquid existing between the electrodes is detected, the remaining amount of the liquid in the tank is detected. At the time of non-detection, a reference voltage of a predetermined potential is applied to both electrodes, and at the time of detection, the potential of one of the pair of electrodes is alternately changed with the reference voltage as a boundary. It has become possible to inexpensively provide a remaining amount detecting device that prevents the influence of the above.

In the remaining amount detecting device of the present invention, the first voltage supply means for applying a DC signal of a square wave, a sine wave or a triangular wave to one of the pair of electrodes arranged in the tank, and the other electrode. Since the second voltage supply means for applying the offset voltage is connected to the device, the influence of the electrolysis on the liquid is prevented, and the device itself is inexpensive.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an ink tank in which a remaining amount detecting device according to the present invention is used.

FIG. 2 is a circuit configuration diagram showing a first embodiment of a remaining amount detecting device according to the present invention.

FIG. 3 is a time chart diagram showing potentials (signals) at respective points of the circuit which constitutes the remaining amount detecting device of the first embodiment.

[Explanation of symbols]

 1 1st electrode 2 2nd electrode 3 Ink tank 4 Push-pull circuit 4a PNP transistor 4b NPN transistor 5 Detecting resistor 7 Comparator 8 Comparison voltage 9 Output port 10 Current limiting resistor 11 Zener diode A 12 Zener diode B

Claims (7)

[Claims] 1. A remaining amount of a liquid in a tank is detected by applying a voltage between a pair of electrodes arranged in the tank and detecting an electric resistance that changes under the influence of a liquid existing between the electrodes. An alternating voltage for applying a reference voltage having a predetermined potential to the both electrodes when not detected, and changing the potential of one of the pair of electrodes by alternating the reference voltage with the reference voltage as a boundary. A remaining amount detecting device including a supply unit, wherein the alternating voltage supplying unit includes a push-pull circuit. 2. The remaining amount detecting device according to claim 1, wherein an average value of voltage changes at the time of detection is substantially the reference voltage. 3. A voltage is applied between a pair of a first electrode and a second electrode arranged in the tank, and an electric resistance that changes under the influence of a liquid existing between the electrodes is detected to detect the internal resistance of the tank. A remaining amount detecting device for detecting the remaining amount of liquid, wherein the alternating voltage supply means is controlled to be in a conducting state or a non-conducting state by the push-pull circuit, and a square wave, a sine wave or a triangular wave is applied to the first electrode. First voltage supply means connected to apply a certain DC signal and second voltage supply means connected to the second electrode to apply an offset voltage to a predetermined output circuit connected to the first electrode. And, when not detected, by applying a reference voltage of a predetermined potential to the both electrodes by deactivating the first voltage supply means,
At the time of detection, the direct current signal is applied to the first electrode by energizing the first voltage supply means, and the potential between the electrodes changes alternately with the reference voltage as a boundary. The remaining amount detecting device according to claim 1. 4. The remaining amount detecting device according to claim 3, wherein the maximum value of the voltage applied to the first electrode by the first voltage supply means is such that the second voltage supply means applies a voltage to the second electrode. A remaining amount detecting device characterized in that the applied voltage is twice the applied voltage. 5. The remaining amount detecting device according to claim 4, wherein the first voltage supply means is composed of a two-stage Zener diode, and supplies the measurement voltage to the first electrode, and the second voltage supply means. A remaining amount detecting device comprising a one-stage Zener diode and supplying a reference voltage to the second electrode. 6. The remaining amount detecting device according to claim 3, wherein the output circuit is a comparator to which a comparison voltage is applied. 7. The remaining amount detecting device according to claim 1, wherein the pair of electrodes are arranged with a height difference.