JPH01197776A - Toner detecting circuit - Google Patents

Abstract

PURPOSE:To prevent erroneous use of an electrophotographic printer in a state where the toner is not proper by providing a toner detecting section in the development device constituting the printer and causing the section to inform that no toner is detected and the toner quantity becomes less than a prescribed quantity. CONSTITUTION:The height of the toner contained in a development device 22 provided in a laser printer is detected with a toner sensor 24 and the output voltage of the sensor 24 is supplied to an informing unit 26. The unit 26 makes the output voltage smoother by means of a smoothing circuit 30 provided in the unit 26 and the voltage thus obtained is inputted to comparators 32 and 34. When the output voltage of the circuit 30 is lower than a 1st reference voltage, it is judged by the comparator 32 that the sensor 24 and informing unit 26 are disconnected with each other. When the output voltage of the circuit 30 is higher than 2nd reference voltage, on the other hand, the comparator 34 judges that the toner is insufficient. In any case, an LED 58 is turned on and printing operations of this printer are inhibited. Therefore, not only the insufficient quantity of toner, but also faulty connection, disconnection of a connecting line, un-mounting of development device, etc., can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a toner detection circuit for detecting a shortage of toner used in the printing operation of an electrophotographic printing apparatus such as a laser printer or a dry copier.

[Prior Art] In a typical laser printer, toner is stored in a removable developing device. This developing device is usually installed inside the laser printer, and is taken out from the laser printer when toner is to be replenished. Conventionally, the following toner detection circuit is known. This toner detection circuit includes a toner sensor fixed to the developer, a notification unit installed at any location within the laser printer, and a set of first and second connectors.

The first connector is fixed to the laser printer cabinet and connected to the notification unit. A second connector is fixed to the developer and connected to the toner sensor. The second connector is mechanically coupled to the first connector when the developing device is installed in the printer, and electrically connects the toner sensor and the notification unit.

The toner sensor generates a voltage signal when toner is used for printing and is no longer in the developer. This voltage signal is supplied from the toner sensor to the notification unit via the first and second connectors. In response to this voltage signal, the notification unit turns on a light emitting diode to notify of toner shortage.

[Problems to be Solved by the Invention] The conventional toner detection circuit has the following drawbacks. For example, consider a case where the connection between the first and second connectors is not complete when the developer is installed in a laser printer.

In this case, even if the toner sensor generates a voltage signal, this voltage signal may not be supplied to the notification unit.

If this is the case, the light emitting diode will not light up even if the toner in the developer runs out while the laser printer is in use because the notification unit cannot respond to this voltage signal. Further, the light emitting diode will not light up in the same way if you forget to attach the developing device or if the wiring cable between the toner sensor and the notification unit is disconnected. Therefore, when a conventional toner detection circuit is used, there is a risk that the laser printer may perform a printing operation without toner.

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner detection circuit that can prevent erroneous use of an electrophotographic printing device when toner is in short supply.

Means for Solving Problem E] According to the present invention, the toner is fixed to a developing device installed in an electrophotographic printing apparatus, and detects that a predetermined amount or more of toner is contained in the developing device, and calculates the average level. a toner detection unit that generates a predetermined voltage signal higher than OV as an output signal; a notification unit that notifies an abnormality when the predetermined voltage signal is not input; and when the developer is installed in an electrophotographic printing apparatus. The toner detection section and the notification means are connected to each other, and the output signal of the toner detection section is sent to the notification means.

and connection means for supplying toner.

[Function] According to the present invention, even if the toner sensor and the notification means are electrically separated due to, for example, a poor connection of the connector, a disconnection of the cable, or a forgetting to attach the developing device, the toner detection circuit can be reliably operated. Since the abnormality is notified to the user, it is possible to prevent the electrophotographic printing device from accidentally performing a printing operation.

[Embodiment] Hereinafter, a toner detection circuit according to an embodiment of the present invention will be described with reference to the drawings. FIG. 2 schematically shows the internal structure of a laser printer in which this toner detection circuit is incorporated. This laser printer has a conventionally known charging drum unit 12, charging charger 14, transfer charger 16, transfer roller 18, heat fixing roller 20, developing device 22, etc. in a cabinet 10. This laser printer further has a door 12 at the top of the cabinet 10, and the door 1
2 can be opened and closed using the rotating shaft 31 as a fulcrum. The developing device 22 is installed inside the cabinet 10 while containing toner, and is taken out of the can and vignette 10 when toner is to be replenished.

The toner detection circuit includes a toner sensor 2 as shown in FIG.
4, notification unit 26, and negative set of 3-terminal connector 2
8A and 28B. The toner sensor 26 is a sensor using a ceramic vibrator, and is fixed to the developing device 22 at a position slightly higher than the bottom portion 22A, as shown in FIG.
A by a cable 30. Notification unit 26
is installed at any location of the laser printer and connected to a connector 28B fixed to the cabinet 10. Second
In the figure, the 3-terminal PWR of connectors 28A and 28B,
Both GND and SNR are arranged in the depth direction of the drawing. Connectors 28A and 28B are mechanically coupled when developer 22 is installed inside cabinet 10, and electrically connect toner sensor 24 and notification unit 26. Terminal PWR of connectors 28A and 28B.

GND is used to supply the power supply voltage VCC (for example, 5V) to the toner sensor 24, and the terminal SNR%GND is used to supply the output positive signal of the toner sensor 24 to the notification unit 26. The toner sensor 24 performs a toner detection operation under the power supply voltage vCC, and during this time continuously generates a square wave voltage as an output signal. This square wave voltage is set to different amplitudes depending on the presence or absence of toner.

That is, the toner sensor 24 detects toner when the toner is at a height higher than the position of the toner sensor 24 in the developing device 22, and generates a square wave voltage that periodically changes from one of level A and level B to the other. do. Furthermore, if the toner is at a lower height than the position of the toner sensor 24 in the developing device 22, the toner is not detected by the toner sensor 24. In this case, toner sensor 24 generates a square wave voltage that changes periodically from one of Level A and Level C to the other.

In other words, when the remaining amount of toner becomes less than a predetermined value determined by the height of the toner sensor 24, the lower level of the square wave voltage increases from level B to level C.

The notification unit 26 includes, for example, a smoothing circuit 30 composed of a capacitor, a resistor, and a diode. and a first and second comparator 32.3 each constituted by, for example, an operational amplifier.
It has 4. The output signal of the toner sensor 24, ie, the above-mentioned square wave voltage, is smoothed by a smoothing circuit 30 and supplied to comparators 32 and 34. The output voltage of the smoothing circuit 30 is set to approximately o, tav when toner is detected, and is set to approximately 0.2 V when toner is not detected.

The output voltage of the smoothing circuit 30 is compared with a first reference voltage by a comparator 32, and compared with a second reference voltage by a comparator 34. The first and second reference voltages are generated by voltage divider circuits 36, 38 each having two resistors connected in series between the power supply terminal vCC and the ground terminal GND, and the first reference voltage is less than 0.13V. The second reference voltage is set to a predetermined level slightly lower than 0.2V.

Here, each predetermined level of the first and second reference voltages is determined by the comparators 32 and 34 due to slight fluctuations in the output voltage of the smoothing circuit.
Consideration has been taken to prevent the output state from becoming unstable. The comparators 32 and 34 generate a high level output voltage when the output voltage of the smoothing circuit 3G exceeds the first reference voltage and the second reference voltage, respectively, and otherwise output a low level, for example, Ov. Generates voltage. The output voltage of the comparator 32 is supplied to one input terminal of a two-power NOR gate 52 via a Schmitt inverter 50 . The output voltage of comparator 34 is supplied to the other input terminal of NOR gate 52 via Schmitt inverter 54 and inverter 56. A light emitting diode 58 is connected to the output terminal of this NOR gate 52 as shown in FIG. The output voltages of the comparators 32 and 34 are also supplied to the printer control circuit 60. This printer control circuit 60 is provided to control the operation of each of the above-mentioned mechanical sections in accordance with a print command from, for example, an operation panel 62, and checks the output voltages of the comparators 32 and 34 before starting printing. Laser printer control circuit 60 invalidates the print command when the output voltage of comparator 32 is low level and when the output voltage of comparator 34 is high level, and performs corresponding predetermined processing.

Next, the operation of the toner detection circuit of this embodiment will be explained. First, consider a case where the developing device 22 is not installed in the laser printer, or a case where the connector 28A on the developing device 22 side and the connector 28B on the notification unit 26 side are not completely connected.

In this case, the toner sensor 24 and the notification unit 26 are electrically separated. Therefore, the output voltage of the toner sensor 24 is not supplied to the notification unit 26, and the input voltage of the notification unit 26 is set to Ov as shown at 2 in FIG. When this input voltage of Ov is supplied through the smoothing circuit 30 to a comparator 32, the comparator 32 compares this voltage with a first reference voltage, thereby producing a low level output voltage. This output voltage is supplied to the NOR gate 52 via the Schmitt inverter 50, and the output terminal of the NOR gate 52 is set to ground potential. As a result, the light emitting diode 58 lights up.

Next, consider the case where the developer 22 is installed in a laser printer and the toner is present within the developer 22 to a height indicated by Y in FIG. In this case, the toner sensor 24 and the notification unit 2
6 are electrically connected to each other via a connector 28A12gB, and the notification unit 26 receives the output voltage of the toner sensor 24 as shown by Y in FIG. When this output voltage is smoothed by the smoothing circuit 30, a voltage of about 0.13V is transferred from the smoothing circuit 30 to the comparator 32, 34, as shown by Y in FIG.
and these comparators 32. ．． 34 to first and second reference voltages, respectively. As a result, a high level output voltage is generated from comparator 32 and a low level output voltage is generated from comparator 34. At this time, the output terminal of the NOR gate 52 is set to a potential at the vCC level. Therefore, the light emitting diode 58 does not light up.

When the toner drops from the height shown by Y in FIG. 4 to the height shown by 2 in the developing device 22 installed in the laser printer, the notification unit 26 detects the toner sensor 24 as shown by Z in FIG. The receiver takes the output voltage of. This output voltage is smoothed by a smoothing circuit 30 and supplied from the smoothing circuit 30 to a comparator 34, where it is compared with a second reference voltage. As a result, a high level output voltage is generated from comparator 32.

At this time, a high level output voltage is generated from the comparator 34. At this time, the output terminal of the NOR gate 52 is set to the ground potential, and the light emitting diode 58 is turned on.

In the toner detection circuit of this embodiment, the square wave voltage is set to the first amplitude when toner is detected, and is set to the second amplitude when toner is not detected, to the toner sensor 2.
4 is generated and supplied to the notification unit 26. The input voltage of the notification unit 26 is smoothed by a smoothing circuit 30 and supplied to comparators 32 and 34. This comparator 32 detects that the toner sensor 24 is not connected to the notification unit 26 when the output voltage of the smoothing circuit 30 is lower than the first reference voltage. On the other hand, the comparator 34 detects a toner shortage when the output voltage of the smoothing circuit 30 is higher than the second reference voltage. The light emitting diode 58 lights up in each of the above cases. That is, according to this embodiment, in addition to the toner shortage, there is also the problem of forgetting to install the developing device and the toner sensor 24 and the notification unit 2.
6 can be easily detected by lighting the light emitting diode 58. Further, when using this toner detection path, there is no need to increase the number of signal lines for supplying the output signal of the toner sensor 24 to the notification unit 26. Furthermore, the output voltages of comparators 32, 34 can be used independently in printer control circuit 62.

[Effects of the Invention] According to the present invention, when the toner sensor 24 and the notification unit 26 are electrically separated due to poor connection of the connector, disconnection of the cable, forgetting to attach the developing device, etc.
Since the toner detection circuit reliably reports an abnormality, it is possible to prevent an electrophotographic printing apparatus such as a laser printer from erroneously performing a printing operation.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the circuit structure of a toner detection circuit according to an embodiment of the present invention, FIG. 2 is a diagram schematically showing the internal structure of a laser printer in which this toner detection circuit is incorporated, and FIG. 5 to 5 are diagrams for explaining the operation of the toner detection circuit of this embodiment. FIG. 3 shows the input voltage of the notification unit, and FIG. 4 shows the change in the height of the toner. 5 shows the output voltage of the smoothing circuit shown in FIG. 2. 22...Developer, 24...Toner sensor, 26...
・Notification unit, 28A, 28B... connector, 30
...Smoothing circuit, 32.34...Comparator, 36.38
... Voltage divider circuit, 58... Light emitting diode. Applicant's agent Patent attorney Takehiko Suzue W&3 Figure 5

Claims (3)

[Claims] (1) A signal that is fixed to a developing device installed in an electrophotographic printing device and outputs a predetermined voltage signal whose average level is higher than 0 V upon detecting that a predetermined amount or more of toner is contained in the developing device. a toner detecting section that generates an abnormality when the predetermined voltage signal is not input; and a toner detecting section that generates an abnormality when the predetermined voltage signal is not input; and connecting means for connecting the toner detecting section to supply the output signal of the toner detecting section to the notifying means. (2) The toner detection section is arranged at a predetermined height position from the bottom of the developing device, and when it detects that there is toner, it is set to a first average level higher than 0V, while there is no toner. 2. The toner detection circuit according to claim 1, further comprising a toner sensor that generates, as the output signal, a square wave voltage signal that is set to a second average level higher than the first average level when detecting the first average level. (3) The notification means includes a smoothing circuit to which the output voltage signal of the toner sensor is supplied via the connection means, and a signal obtained when the square wave voltage signal of the first average level is smoothed by the smoothing circuit. lower than the first predetermined voltage and 0V
generates a second reference voltage that is lower than a second predetermined voltage that is obtained when the smoothing circuit smoothes a first reference voltage higher than the first reference voltage and a square wave voltage signal of the second average level that is higher than the first predetermined voltage; a reference voltage generating section that detects that the output voltage of the smoothing circuit is lower than the first reference voltage and generates an output signal indicating that the toner detecting section and the notification means are electrically separated. 3. The toner according to claim 2, further comprising a comparison means and a second comparison means for detecting that the output voltage of the smoothing circuit is higher than the second reference voltage and generating an output signal indicating a shortage of toner. detection circuit.