JP2007101597A - Offset adjustment circuit and toner residual quantity detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an offset adjustment circuit capable of automatically adjusting an offset voltage, and a toner residual quantity detector. <P>SOLUTION: A switch 50 is closed, and the offset voltage appearing in an output of an operational amplifier 41 is converted to a digital offset signal by an A/D converter 42 and is stored in a memory 43. When a toner residual quantity detecting operation is performed, the switch 50 is opened, and a light emitting diode 21 is lit, and light transmitted through toner is received by a photo transistor 22, and a light reception output signal is amplified by an operational amplifier 41, and the light reception output signal is compared with a threshold resulting from correcting the offset voltage stored in the memory 43 by a peculiar value, by a comparator 46, and a light reception signal exceeding the offset voltage, out of an amplified component of the light reception output signal is outputted to a CPU 47 as a toner residual quantity detection signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an offset adjustment circuit and a toner remaining amount detection circuit using the offset adjustment circuit. For example, the present invention relates to an offset adjustment circuit that adjusts an offset voltage generated in the output of an operational amplifier and a toner remaining amount detection device that detects the remaining amount of toner using the offset adjustment circuit. .

  FIG. 6 is a schematic configuration diagram of a printer described in Japanese Patent Laid-Open No. 10-1981149 (Patent Document 1). In FIG. 6, the photosensitive drum 1 is uniformly charged by the charging charger 2 while being driven to rotate in the direction of arrow A, and then scanned and exposed based on image information by the laser optical device 3, and the surface of the photosensitive drum 1. An electrostatic latent image is formed. Here, the image information to be exposed is monochromatic image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. The electrostatic latent image formed on the photosensitive drum 1 is developed with yellow, magenta, cyan, and black toners as predetermined developers by the rotary developing device 4, whereby each color is developed on the photosensitive drum 1. An image is formed.

  Each color image formed on the photosensitive drum 1 is primary for each single color of yellow, magenta, cyan, and black on an intermediate transfer belt 5 that rotates in the direction of arrow B in the figure in synchronization with the photosensitive drum 1. The images are sequentially superimposed and transferred by the transfer charger 6. The yellow, magenta, cyan, and black images superimposed on the intermediate transfer belt 5 are transferred from the double-sided copying / automatic sheet feeding cassette 7 or the manual sheet feeding tray 7a through the sheet feeding rollers 8, 8a and the registration roller 9. Are transferred onto the transfer paper 10 by the secondary transfer charger 11. After the transfer, the transfer paper 10 is fixed with a toner image by a fixing device 12 and discharged as a full color print.

  The toner on the photoconductive drum 1 that has not been transferred onto the intermediate transfer belt 5 is removed from the photoconductive drum 1 by the photoconductor cleaner 13, and the toner on the intermediate transfer belt 5 that has not been transferred onto the transfer paper 10. The toner is removed from the intermediate transfer belt 5 by the intermediate transfer belt cleaner 14.

  In the rotary developing device 4 shown in FIG. 6, it is necessary to detect the remaining amounts of yellow, magenta, cyan and black toners. As a method for this, the light from the light emitting diode is transmitted to the toner in the developing machine, There is a method of detecting the remaining amount by receiving light and converting it into an electric signal. The transmitted light becomes the intensity of light depending on the remaining amount of toner, which is converted as the intensity of an electric signal, and the remaining amount of toner is detected by detecting the intensity.

  In the conventional monochromatic image forming apparatus, since the toner is one color, the remaining amount of toner can be sufficiently detected even if the received light signal transmitted through the toner is amplified by an operational amplifier having a relatively small amplification factor. However, in a full-color image forming apparatus, it is necessary to detect the remaining amounts of four different colors of toner, and the light transmittance of the toner differs for each color. Further, even if the color is easy to transmit, it is necessary to make a difference between the presence and absence of toner, so the amount of light emission is suppressed. Therefore, the detection accuracy is increased by reducing the light emission amount of the light emitting diode and setting the amplification factor of the operational amplifier high.

  However, since the offset voltage exists in the operational amplifier, the offset voltage appears as an error for a weak signal, and the detection accuracy is deteriorated. For example, if the amplification factor of the operational amplifier is 100 times, the output voltage of the operational amplifier is amplified to 3.3 V even if the input voltage is 0.033 V and the offset voltage is only 9 mV, but the offset voltage of 900 mV is included. Therefore, an error of 30% is included.

In order to correct such an offset voltage, Japanese Patent Laid-Open No. 2-76406 (Patent Document 2) describes an offset correction device. This offset correction device has a comparator to which an offset voltage is applied on the output side of the operational amplifier, connects a light emitting diode on the output side of the comparator, and adjusts the variable resistance connected to the operational amplifier while observing the lighting state of the light emitting diode. Correct the offset voltage.
JP-A-10-1981149 (paragraph number 0023, FIG. 1) JP-A-2-76406 (2nd page, 4th column to 6th column, FIG. 1)

  In the offset correction apparatus described in Patent Document 2, it is necessary to set an optimum offset correction value for each toner, and there is a problem that it takes time and effort.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an offset adjustment circuit capable of automatically adjusting an offset voltage and a toner remaining amount detection device using the same.

  The present invention is an offset adjustment circuit for adjusting an offset voltage of an operational amplifier, and a storage means for storing an offset voltage output from the operational amplifier when no signal is input to the operational amplifier, and a signal input to the operational amplifier. A comparator that reads out the offset voltage stored in the storage means, compares the offset voltage with the voltage amplified by the operational amplifier, and outputs a signal from which the offset voltage has been removed.

  Preferably, the storage unit further stores a predetermined eigenvalue, and the comparison unit reads the eigenvalue when reading the offset voltage from the storage unit, corrects the offset voltage based on the eigenvalue, and corrects the offset voltage and the operational amplifier. Is compared with the input voltage amplified in step (b).

  Preferably, the storage unit further stores a predetermined eigenvalue, and the comparison unit reads the eigenvalue together when reading the offset voltage from the storage unit, corrects the eigenvalue based on the offset voltage, and the corrected offset voltage The input voltage amplified by the operational amplifier is compared.

  In one embodiment, the switch includes a switch for setting the input terminal of the operational amplifier to the ground level, and the storage unit stores an offset voltage output from the operational amplifier when the input terminal of the operational amplifier is set to the ground level by the switch.

  Another embodiment includes a light receiving element that outputs a light reception signal to the operational amplifier and a light emitting element that outputs a light emission signal to the light receiving element, and the storage means outputs from the operational amplifier when the light emitting element stops emitting light. The offset voltage to be stored is stored.

  Another aspect of the present invention includes a toner chamber that is divided into a plurality of portions in the circumferential direction and encloses toners of different colors, and has a plurality of developing units that develop images with the toners of the respective colors by rotating. In the type developing device, a remaining toner amount detecting device for detecting the remaining amount of each toner, provided at a predetermined position with respect to the rotary developing device, and when any one of the developing machines rotates and is in a predetermined position In addition, a toner remaining amount detection sensor including a light emitting element for irradiating light to the toner chamber of the developing machine, and a light receiving element for receiving light transmitted through the toner in the toner chamber, and a light receiving output from the light receiving element are amplified. An operational amplifier that outputs a toner remaining amount detection signal indicating the remaining amount of toner, and a storage unit that stores a voltage output from the operational amplifier as an offset voltage when no signal is input to the operational amplifier; When the output is input to the p-amp, the offset voltage stored in the storage means is read, the offset voltage is compared with the voltage amplified by the operational amplifier, and the toner remaining amount detection signal from which the offset voltage has been removed is obtained. Comparing means for outputting.

  Another aspect of the present invention includes a toner chamber that includes a toner chamber that is divided into a plurality of portions in the circumferential direction and in which different color toners are sealed, and that has a developing device that rotates to develop an image with each color toner. A toner remaining amount detecting device for detecting a remaining amount of each toner, provided at a predetermined position with respect to the rotary developing device, and when any of the developing machines is rotated to a predetermined position, A toner remaining amount detection sensor including a light emitting element that irradiates light to the toner chamber of the developing machine, and a light receiving element that receives light transmitted through the toner in the toner chamber, and a light reception output from the light receiving element is amplified to An operational amplifier that outputs a toner remaining amount detection signal that indicates the remaining amount, a storage unit that stores an eigenvalue, and when a light reception output is input to the operational amplifier, reads an eigenvalue stored in the storage unit, It compares the voltage amplified by the amp, and a comparison means for outputting a toner remaining amount detection signal.

  Preferably, each developing device includes a first optical unit that guides the light from the light emitting element to the toner chamber and irradiates the toner, and a second optical unit that guides the light irradiated to the toner and transmitted through the toner to the light receiving element. Including.

  The present invention stores the voltage output from the operational amplifier as an offset voltage when no signal is input to the operational amplifier, and reads the stored offset voltage when the signal is input to the operational amplifier. Since the output signal from which the offset voltage is removed is derived by comparing the voltage and the voltage amplified by the operational amplifier, the offset voltage can be automatically adjusted.

  In addition, the offset voltage stored when detecting the remaining amount of toner in each developing machine is used as a common threshold value, and the output of the operational amplifier is compared by the comparison means, so that the remaining toner amount detected for each developing machine is detected. There is no variation in the signal.

  FIG. 1 is an external perspective view showing a rotary developing device provided with a toner remaining amount detecting device using an offset adjustment circuit according to an embodiment of the present invention. FIG. 2 is a toner remaining amount included in the toner remaining amount detecting device. FIG. 3 is an external perspective view showing a configuration of a detection sensor, and FIGS. 3 and 4 are diagrams showing an arrangement relationship between a rotary developing device and a toner remaining amount detection sensor.

  The rotary developing device 30 shown in FIG. 1 is provided in an image forming apparatus such as a printer or a copying machine, is formed in a cylindrical shape, and rotates in the circumferential direction, as described in FIG. Further, the electrostatic latent image formed on the photosensitive drum is developed with yellow, magenta, cyan, and black toners as predetermined developers, respectively, thereby forming each color image on the photosensitive drum. For this purpose, the rotary developing device 30 includes four developing machines 31 divided into four in the circumferential direction. The four developing machines 31 individually contain yellow, magenta, cyan, and black toners. In order to detect the remaining amount of yellow, magenta, cyan, and black toners enclosed in each developing device 31, the toner remaining amount detection sensor 20 faces the end face of the rotary developing device 30 and has a certain interval. And provided at a predetermined position.

  As shown in FIG. 2, the toner remaining amount detection sensor 20 is configured by attaching a light emitting diode 21 as a light emitting element, a phototransistor 22 as a light receiving element, and a connector 23 to a substrate 24. The light emitting diode 21 and the phototransistor 22 are provided so that their optical axes are parallel to each other at a predetermined interval.

  Each developing machine 31 includes optical systems 25 and 26 as first and second optical means, prisms 27 and 28 so as to face the light emitting diode 21 and the phototransistor 22 as shown in FIG. Is provided. One end side of the optical system 25 is used as an incident surface and faces the light emitting diode 21 so that the optical axes thereof coincide with each other, and a prism 27 is provided on the other end side. One end side of the optical system 26 is used as an exit surface and faces the phototransistor 22 so that the optical axes thereof coincide with each other, and a prism 28 is provided on the other end side. A stirring rotor 35 having stirring blades 36 and 36 for stirring the toner is provided between the prisms 27 and 28.

  As shown in FIG. 3, rectangular holes 33 and 34 are formed in the side wall 32 of the developing machine 31, and the optical systems 25 and 26 shown in FIG. 2 are inserted into the holes 33 and 34, respectively. The end face of one end of the end is exposed to the side wall 32. The prisms 27 and 28 are exposed to the toner chamber 37 in the developing machine 31. A toner remaining amount detection sensor 20 is arranged to face one end of the optical systems 25 and 26 exposed from the side wall 32 of the developing device 31.

  The toner remaining amount detection sensor 20 is rotated when the rotary developing device 30 rotates and faces the side wall 32 of each developing device 31, and the light emitting diode 21 and the phototransistor 22 face the optical systems 25 and 26. In addition, the remaining toner amount of the corresponding developing device 31 is detected. As a result, the remaining amount of toner in the four developing devices 31 is sequentially detected by one remaining toner amount detecting sensor 20 each time each developing device 31 rotates without providing the remaining toner amount detecting sensor in each developing device 31. Can be detected.

  The light emitting diode 21 of the toner remaining amount detection sensor 20 and the phototransistor 22 are connected to an offset adjustment circuit 40 shown in FIG. The toner remaining amount detecting sensor 20 and the offset adjusting circuit 40 constitute a toner remaining amount detecting device. When detecting the remaining amount of toner, the stirring rotor 35 maintains a state rotated 90 degrees from the state shown in FIG. 2 so that the light is not blocked by the stirring blades 36.

  FIG. 5 is a circuit diagram showing an offset adjustment circuit in one embodiment of the present invention. In FIG. 5, the output of the phototransistor 22 shown in FIGS. 2 and 3 is given to the normal rotation input terminal (+) of the operational amplifier 41 as a toner remaining amount detection signal. A switch 50 is provided between the normal input terminal of the operational amplifier 41 and the ground. By closing the switch 50, the normal rotation input terminal of the operational amplifier 41 can be set to the ground level, and the offset voltage appearing at the output can be detected.

  The operational amplifier 41 amplifies the toner remaining amount detection signal. A resistor R1 is connected between the inverting input terminal (−) of the operational amplifier 41 and the ground, and a negative feedback resistor R2 is connected between the inverting input terminal and the output terminal. The output signal of the operational amplifier 41 is given to the comparison input terminal of the A / D converter 42 and the comparator 46 as the comparison means via the resistor R3.

  The A / D converter 42 converts the offset voltage appearing in the output signal of the operational amplifier 41 into a digital signal when the switch 50 is closed, and supplies the digital signal to the memory 43. The memory 43 stores the offset voltage. The memory 43 stores eigenvalues that are different for each color in advance. This eigenvalue is a value for correction because the input level of each color is not necessarily the same.

  At the time of development in each developing machine, the offset voltage and the unique value corresponding to each color are read from the memory 43 and given to the threshold correction circuit 44. The threshold correction circuit 44 subtracts the unique value from the offset voltage. It is corrected and converted into a threshold voltage. This threshold voltage is converted into an analog signal by the D / A converter 45 and applied to the reference input terminal of the comparator 46 as a threshold signal.

  The comparator 46 compares the threshold signal with the amplified toner remaining amount detection signal output from the operational amplifier 41, and outputs a signal component exceeding the threshold signal as a toner remaining amount detection signal. The CPU 47 outputs a drive signal for driving the light emitting diode 21 and gives it to the base of the transistor 48. The collector of the transistor 48 is connected to the cathode of the light emitting diode 21 via a resistor R4, and the DC voltage + V is supplied to the anode. The emitter of transistor 48 is grounded.

  Next, the operation of the offset adjustment circuit according to the embodiment of the present invention will be described. First, the switch 50 is closed to adjust the offset voltage. By closing the switch 50, the normal input terminal of the operational amplifier 41 becomes the ground level, and only the offset voltage appears at the output of the operational amplifier 41. This offset voltage is converted into a digital offset voltage by the A / D converter 42. The offset voltage converted into the digital signal is stored in the memory 43.

  In the toner remaining amount detection operation for each color, with the switch 50 open, the CPU 47 outputs a drive signal to turn on the transistor 48 and turn on the light emitting diode 21. The light emitted from the light emitting diode 21 is incident on the incident surface on one end side of one optical system 25, is reflected by the prism 27, transmits the toner existing between the prisms 27 and 28, and passes through the other prism. 28, and enters the phototransistor 22 through the optical system 26. The light reception output signal of the phototransistor 22 is given to the normal input terminal of the operational amplifier 41.

  The operational amplifier 41 amplifies the received light output signal and gives it to the comparator 46 as a comparison input. The output of the operational amplifier 41 shows not only the amplified component of the received light output signal but also the offset voltage. The CPU 47 designates the address of the memory 43 and reads the inherent value corresponding to the offset voltage of the operational amplifier 41 stored in advance. This eigenvalue may be detected by detecting the developing machine of the color to be detected by a sensor (not shown) and reading the associated eigenvalue from the memory 43 based on the detection signal. The read offset voltage and eigenvalue are given to the threshold correction circuit 44, the offset voltage is corrected based on the eigenvalue, the threshold voltage is output, and converted to an analog signal by the D / A converter 45. A reference input is provided to the comparator 46.

  The comparator 46 compares the amplified component of the received light output signal as a comparison input with the threshold voltage, and outputs only the component exceeding the offset voltage among the amplified components of the received light output signal to the CPU 47 as the received light signal. As a result, the amplified component of the received light output signal from which the offset component has been removed is given to the CPU 47.

  As described above, the output voltage of the operational amplifier 41 when no input signal is supplied to the operational amplifier 41 is stored in advance in the memory 43 together with the eigenvalues corresponding to the respective colors, and the memory together with the eigenvalues corresponding to the respective colors during the remaining toner amount detecting operation. By outputting the amplified component of the received light output signal using the threshold voltage read from 43, corrected with the eigenvalue and converted into an analog signal as a threshold, it is possible to obtain a received light output signal that is not affected by the offset voltage. The CPU 47 can detect the remaining amount of toner based on the received light output signal.

  In addition, the toner remaining amount detection sensor 20 and the offset adjustment circuit 44 are commonly used to detect the remaining amount of toner in each developing device 31, and the memory 43 receives the received light output as each remaining toner amount detection signal. Since the offset voltage stored in is corrected by the eigenvalue and compared by the comparator 46, there is no variation in the toner remaining amount detection for each of the developing machines 31.

  Without providing the switch 50, the drive of the light emitting diode 21 by the CPU 47 is stopped so that the output signal from the phototransistor 22 is not given to the normal input terminal of the operational amplifier 41, and the offset voltage is adjusted. May be.

  In the above embodiment, the offset voltage when the input signal of the operational amplifier 41 is not given is converted into a digital signal and stored in the memory 43, and when the input signal is given to the operational amplifier 41, the offset voltage is stored in the memory 43. The offset voltage thus corrected is corrected with an eigenvalue, converted into an analog signal, and given to the comparator 46 as a threshold voltage. However, the present invention is not limited to this, and the offset voltage when the input signal of the operational amplifier 41 is not given is stored as an analog value, and when the input signal is given to the operational amplifier 41, the analog value is stored in the comparator 46. You may make it give.

  Furthermore, in the above-described embodiment, the offset voltage is corrected with the eigenvalue, but the value corrected by removing the offset voltage from the eigenvalue may be used as the threshold voltage, or simply the offset voltage is used as the threshold voltage. Also good.

  In the above embodiment, the eigenvalue is stored as the correction value. However, the invention is not limited to this, and the eigenvalue is stored as a reference value for each color, and this is compared with the output signal of the operational amplifier 41 by the comparator 46. Good. In this case, this eigenvalue may be corrected with an offset voltage.

  Further, in the above description, the present invention is applied to the case where the offset voltage of the operational amplifier 41 for detecting the remaining amount of toner in an image forming apparatus such as a printer or a copying machine is adjusted. In the case where an operational amplifier is used in this embodiment, the present invention may be applied to one that adjusts an offset voltage.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to the thing of embodiment shown in figure. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

1 is an external perspective view showing a rotary developing device provided with a toner remaining amount detecting device according to an embodiment of the present invention. 3 is an external perspective view of a toner remaining amount sensor included in the toner remaining amount detecting device. FIG. FIG. 3 is an external perspective view showing an arrangement state of a developing machine and a toner detection sensor. FIG. 3 is an external perspective view showing an arrangement state of a developing machine and a toner detection sensor. It is a circuit diagram which shows the offset adjustment circuit in one Embodiment of this invention. It is a schematic block diagram of the conventional printer.

Explanation of symbols

  20 toner remaining amount detection sensor, 21 light emitting diode, 22 phototransistor, 25, 26 optical system, 27, 28 prism, 30 rotary developing device, 31 developing machine, 32 side wall, 37 toner chamber, 41 operational amplifier, 42 A / D Converter, 43 Memory, 44 Threshold correction circuit, 45 D / A converter, 46 Comparator, 47 CPU, 48 transistor, 50 switch.

Claims (8)

An offset adjustment circuit for adjusting an offset voltage of an operational amplifier,
Storage means for storing an offset voltage output from the operational amplifier when no signal is input to the operational amplifier;
When a signal is input to the operational amplifier, the offset voltage stored in the storage means is read, the offset voltage is compared with the input voltage amplified by the operational amplifier, and the offset voltage is removed. And an offset adjustment circuit. The storage means further stores a predetermined eigenvalue,
The comparison unit reads the eigenvalue together when reading the offset voltage from the storage unit, corrects the offset voltage based on the eigenvalue, and corrects the offset voltage and the input voltage amplified by the operational amplifier. The offset adjustment circuit according to claim 1, wherein The storage means further stores a predetermined eigenvalue,
The comparison unit reads the eigenvalue when reading the offset voltage from the storage unit, corrects the eigenvalue based on the offset voltage, and corrects the corrected offset voltage and the input voltage amplified by the operational amplifier. The offset adjustment circuit according to claim 1, wherein A switch for setting the input terminal of the operational amplifier to a ground level;
4. The offset adjustment according to claim 1, wherein the storage unit stores a voltage output from the operational amplifier when the input terminal of the operational amplifier is set to a ground level by the switch as an offset voltage. 5. circuit. A light receiving element that outputs a light reception signal to the operational amplifier;
A light emitting element that outputs a light emission signal to the light receiving element,
5. The offset adjustment circuit according to claim 1, wherein the storage unit stores a voltage output from the operational amplifier when the light emitting element stops emitting light as an offset voltage. 6. In a rotary type developing device including a toner chamber that is divided into a plurality of circumferentially divided toners and in which different color toners are sealed, and that develops an image with each color toner by rotating, the remaining amount of each toner A toner remaining amount detecting device for detecting
A light emitting element that is provided at a predetermined position with respect to the rotary developing device and that irradiates light to a toner chamber of the developing machine when any one of the developing machines rotates and is at the predetermined position; A toner remaining amount detection sensor including a light receiving element that receives light transmitted through the toner;
An operational amplifier that amplifies a light reception output from the light receiving element and outputs a toner remaining amount detection signal indicating the remaining amount of toner;
Storage means for storing an offset voltage output from the operational amplifier when no signal is input to the operational amplifier;
When the received light output is input to the operational amplifier, the offset voltage stored in the storage means is read, and the offset voltage is compared with the voltage amplified by the operational amplifier, and the offset voltage is removed. Comparing means for outputting a toner remaining amount detection signal. In a rotary type developing device including a toner chamber that is divided into a plurality of circumferentially divided toners and in which different color toners are sealed, and that develops an image with each color toner by rotating, the remaining amount of each toner A toner remaining amount detecting device for detecting
A light emitting element that is provided at a predetermined position with respect to the rotary developing device and that irradiates light to a toner chamber of the developing machine when any one of the developing machines rotates and is at the predetermined position; A toner remaining amount detection sensor including a light receiving element that receives light transmitted through the toner;
An operational amplifier that amplifies a light reception output from the light receiving element and outputs a toner remaining amount detection signal indicating the remaining amount of toner;
Storage means for storing eigenvalues;
When the light reception output is input to the operational amplifier, the eigenvalue stored in the storage means is read, the eigenvalue is compared with the voltage amplified by the operational amplifier, and a toner remaining amount detection signal is output. A toner remaining amount detection circuit comprising: a comparison unit;   Each of the developing machines guides light from the light emitting element to the toner chamber and irradiates the toner, and first light means that irradiates the toner and transmits the toner to the light receiving element. The toner remaining amount detection device according to claim 6, comprising two optical means.

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