JP2017076096A - Toner amount detection device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable compensation of variation in inductance value of a coil.SOLUTION: A toner amount detection device detects the amount of a magnetic toner stored in a developing part included in an image forming apparatus. The toner amount detection device comprises: an oscillation circuit that generates a source electric signal with a certain frequency; a resonance circuit that includes a coil that is arranged to have inductance vary according to the amount of the magnetic toner and a variable capacitor, includes a capacitor circuit that can adjust the capacitance according to the potential to be applied to the variable capacitor, and resonates with the source electric signal to generate a resonance signal; a phase comparison part that detects a phase difference between the source electric signal and the resonance signal and generates a phase difference signal according to the detected phase difference; an integration circuit part that integrates the phase difference signal and generates an output signal; and a control part that adjusts the capacitance so that the frequency of the source electric signal and the frequency of the resonance signal match with each other.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a toner amount detecting device used in an image forming apparatus, and more particularly to a toner amount detecting device used in an image forming apparatus using magnetic toner.

  An image forming apparatus using magnetic toner (for example, a printer, a multifunction printer, or a multifunction peripheral) includes a toner amount detection device that detects the amount of powder toner in a developing device. In general, the toner amount detection device has an oscillation circuit that oscillates a clock having a constant frequency and a resonance circuit that resonates with the frequency, and compares two phases of the original oscillation frequency and the resonated frequency. The amount of toner is detected by using the phase difference, and in the resonance circuit, the coil inductance and the capacitor capacity are set in accordance with the oscillating source frequency, but the inductance value of the coil varies depending on the variation of the coil component itself. With respect to such problems, Patent Document 1 discloses that the sweep oscillation circuit operates reliably. It has proposed a sweeping oscillation circuit to test the easy.

JP 2012-123202 A

  However, when the inductance value of the coil fluctuates due to variations in the coil components and the resonance circuit does not fall within the preset specification range, there is a sufficient method for bringing the resonance circuit within the specification range. It was not examined.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a technique for compensating for fluctuations in the inductance value of a coil.

  The toner amount detection device of the present invention detects the amount of magnetic toner stored in the developing unit of the image forming apparatus. The toner amount detection device includes an oscillation circuit that generates a source electric signal having a constant frequency, a coil that is arranged so that an inductance varies according to the amount of the magnetic toner, and a varicap. A capacitor circuit configured to be capable of adjusting an electrostatic capacity according to a potential applied to the resonance circuit, a resonance circuit that resonates with the source electric signal to generate a resonance signal, and the source electric signal and the resonance A phase comparator that detects a phase difference of the signal and generates a phase difference signal according to the detected phase difference; an integration circuit that integrates the phase difference signal to generate an output signal; and the source electrical signal And a controller that adjusts the capacitance so that the frequency of the resonance signal matches the frequency of the resonance signal.

  In the toner amount detection device, the control unit compares the frequency of the source electrical signal with the frequency of the resonance signal based on a preset condition, and compares the frequency of the source electrical signal with the frequency of the resonance signal. When the frequency is different, the capacitance may be adjusted so that the frequency of the source electrical signal matches the frequency of the resonance signal.

  The image forming apparatus of the present invention includes the above-described toner amount detection device.

  According to the present invention, fluctuations in the inductance value of the coil can be compensated.

3 is a block diagram illustrating a functional configuration of a toner amount detection device according to the first exemplary embodiment of the present invention. FIG. 3 is a circuit diagram of a toner amount detection device according to the first embodiment. 6 is a graph showing output characteristics of a toner amount detection device according to a comparative example and the first embodiment. 6 is a flowchart illustrating an adjustment procedure of the toner amount detection device according to the first embodiment. 6 is a block diagram illustrating a functional configuration of a toner amount detection device according to a second embodiment of the present invention. FIG. 6 is a circuit diagram of a toner amount detection device according to a second embodiment. 9 is a flowchart illustrating processing contents of a toner amount detection device according to a second embodiment.

Hereinafter, modes for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in the following order with reference to the drawings.
A. First embodiment:
B. Second embodiment:
C. Variations:

A. First embodiment:
FIG. 1 is a block diagram showing a functional configuration of a toner amount detection apparatus 1 according to the first embodiment of the present invention. The toner amount detection device 1 detects the amount of magnetic toner stored in the developing unit of the image forming apparatus. The toner amount detection device 1 includes a source oscillation circuit unit 10, a resonance circuit unit 20, a phase comparison unit 30, an integration circuit unit 40, an amplification unit 50, a frequency adjustment circuit 60, and a control unit 90. Yes. The source oscillation circuit unit 10 oscillates a source rectangular wave Ps having a preset frequency and amplitude. The resonant circuit unit 20 generates a resonant rectangular wave Pr having a phase difference Pd with respect to the source rectangular wave Ps. The phase difference Pd changes according to the amount of the magnetic toner MT, and details thereof will be described later.

  The phase comparison unit 30 outputs a phase difference pulse Pc as a logical exclusive sum of the true and false values of the source rectangular wave Ps and the resonant rectangular wave Pr (here, a value in which the high potential is true and the low potential is false). . Specifically, the phase difference pulse Pc becomes true (high potential) when only one of the source rectangular wave Ps and the resonance rectangular wave Pr is true (when the true and false are different from each other), and the source rectangular wave It is false (low potential) when both Ps and the resonant rectangular wave Pr are true or false (when true and false coincide with each other). The source rectangular wave Ps is also called a source electric signal. The phase difference pulse Pc is also called a phase difference signal. The resonance rectangular wave Pr is also called a resonance signal.

  The integration circuit unit 40 integrates (integrates) the high-potential time of the phase difference pulse Pc into a detectable signal. The amplifying unit 50 converts the voltage level to a voltage level suitable for subsequent processing in toner amount detection. The frequency adjustment circuit 60 adjusts the characteristics of the resonance circuit unit 20.

  The control unit 90 includes main storage means such as RAM and ROM, and control means such as MPU (Micro Processing Unit) and CPU (Central Processing Unit). The control unit 90 also has controller functions related to various I / O, USB (Universal Serial Bus), bus, and other hardware interfaces, and controls the entire toner amount detection apparatus 1. The control unit 90 is a storage device including a hard disk drive or flash memory which is a non-temporary recording medium, and includes a storage unit (not shown) that stores a control program for processing executed by the control unit 90 and data. Yes.

  FIG. 2 is a circuit diagram of the toner amount detection device 1 according to the first embodiment. FIG. 2 particularly illustrates in detail the circuit configurations of the resonance circuit unit 20 and the frequency adjustment circuit 60. The resonance circuit unit 20 includes an inverter V, two capacitors C1 and C2, and two coils L1 and L2 that are magnetically coupled. The two coils L1 and L2 are arranged so that the magnetic permeability in the vicinity thereof changes and the inductance changes according to the amount of the magnetic toner MT.

  The inverter V inverts (shifts 180 degrees) the phase of the source rectangular wave Ps. The two capacitors C1 and C2 advance the phase of the voltage by 90 degrees so as to have opposite phases. The inverter V inverts the phase of the source rectangular wave Ps (shifts by 180 degrees), so that the phase change caused by the two capacitors C1 and C2 can be canceled.

  The coil L1 constitutes an inverter V, a capacitor C1, and a first resonance circuit (LC circuit). In the first resonance circuit, the source oscillation circuit unit 10 is connected to the input of the inverter V, the output of the inverter V is connected to one electrode of the capacitor C1, and the other electrode of the capacitor C1 is connected to one electrode of the coil L1. The other electrode of the coil L1 is grounded. That is, the inverter V, the capacitor C1, and the coil L1 constitute a series circuit.

  The coil L2 is magnetically coupled to the coil L1, and the capacitor C2 and the frequency adjustment circuit 60 constitute a second resonance circuit (LC circuit). One electrode of the coil L2 is grounded, and the other electrode of the coil L2 is connected to one electrode of the capacitor C2 and one electrode of the frequency adjustment circuit 60. The other electrode of the capacitor C2 is connected to the input of the phase comparison unit 30. The other electrode of the frequency adjustment circuit 60 is grounded. The coil L2 constitutes an LC circuit with a combined capacitance corresponding to the sum of the capacitance of the frequency adjustment circuit 60 and the capacitance of the capacitor C2. The parallel circuit of the capacitance of the frequency adjustment circuit 60 and the capacitor C2 is also referred to as a capacitor circuit.

  The frequency adjustment circuit 60 includes a varicap 61, a first capacitor 62, and a second capacitor 63. One electrode of the varicap 61 and one electrode of the first capacitor 62 are both grounded. The other electrode of the varicap 61 and the other electrode of the first capacitor 62 are both connected to one electrode of the second capacitor 63. The other electrode of the second capacitor 63 is connected to the coil L2 together with the capacitor C2. That is, the varicap 61 is connected in parallel with the first capacitor 62. A parallel circuit composed of the varicap 61 and the first capacitor 62 constitutes a series circuit with the second capacitor 63.

  An output terminal of the control unit 90 is connected to a connection point J between the varicap 61 and the second capacitor 63. The capacitance of the varicap 61 varies depending on the control voltage applied to the connection point J by the control unit 90. Specifically, the capacitance of the varicap 61 is inversely proportional to the square root of the control voltage. Thus, the frequency adjustment circuit 60 has a variable capacitance that can be operated by the control voltage from the control unit 90. Thereby, the characteristics of the second resonance circuit (LC circuit) can be adjusted by the control unit 90.

  The two coils L1 and L2 generate a phase difference Pd between the source rectangular wave Ps and the resonant rectangular wave Pr in accordance with the amount of magnetic toner MT disposed in the vicinity. The phase difference Pd is integrated by the integration circuit unit 40, and further amplified by the amplification unit 50 to a voltage level suitable for subsequent processing in toner amount detection. In this way, the toner amount detection device 1 outputs a voltage that varies according to the phase difference Pd (output voltage). The output voltage is also called an output signal.

  FIG. 3 is a graph showing output characteristics of the toner amount detection apparatus 1 according to the comparative example and the first embodiment. FIG. 3A is a graph showing the output characteristics when the reference value voltage is not adjusted in the comparative example. FIG. 3B is a graph showing output characteristics when the reference voltage is adjusted in the first embodiment. The horizontal axis represents the capacitance Cv of the varicap 61, and the vertical axis represents the output voltage of the toner amount detection device 1. In the present embodiment, by changing the capacitance of the varicap 61, any point on the horizontal axis can be used in the characteristic curves of the curve CH and the curve CL.

  A curve CH indicates characteristics when the product of the inductance L of the coil L2 and the capacitance C of the capacitor C2 is excessive due to individual variation. A curve CL indicates characteristics when the product of the inductance L of the coil L2 and the capacitance C of the capacitor C2 is too small due to individual variation.

  In FIG. 3A, attention is focused on a region R1 of the curve CH. In the region R1, it can be seen that the adjustment sensitivity S1 (inclination of the tangent S1) is excessively large in the vicinity of the reference voltage Vref for adjustment. That is, adjustment is difficult because the output voltage changes excessively in the vicinity of the reference voltage Vref due to a slight change in the capacitance Cv in the vicinity of the capacitance Cv1 of the varicap 61.

  In FIG. 3A, attention is focused on a region R2 of the curve CL. In the region R2, the output voltage cannot reach the reference voltage Vref by adjusting the capacitance Cv of the varicap 61. That is, the curve CL means that the reference voltage Vref cannot be adjusted.

  In FIG. 3B, attention is paid to a region R1A of the curve CH. In the region R1A, since the reference voltage VrefA for adjustment is set higher than the reference voltage Vref, it can be seen that the adjustment sensitivity S1A (the slope of the tangent S1A) is appropriate in the vicinity of the reference voltage VrefA. That is, since the output voltage appropriately changes in the vicinity of the reference voltage VrefA due to the change in the capacitance Cv of the varicap 61, adjustment is easy.

  In FIG. 3B, attention is paid to a region R2B of the curve CL. In the region R2B, since the reference voltage VrefB for adjustment is set lower than the reference voltage Vref, the output voltage can reach the reference voltage VrefB by adjusting the capacitance Cv of the varicap 61. That is, the curve CL means that the reference voltage VrefB can be adjusted. It can also be seen that the adjustment sensitivity S1B (inclination of the tangent S1A) is appropriate in the vicinity of the reference voltage VrefB. That is, since the output voltage changes appropriately in the vicinity of the reference voltage VrefB due to the change in the capacitance Cv of the varicap 61, the adjustment is easy.

  FIG. 4 is a flowchart showing an adjustment procedure of the toner amount detection apparatus 1 according to the first embodiment. In step S11, the output voltage of the toner amount detection device 1 is maximized. The maximum output voltage of the toner amount detection device 1 is obtained by setting the electrostatic capacity Cv of the varicap 61 to the minimum (control voltage = 0 V) or by searching by sweeping. In step S12, the maximum output voltage is acquired. In step S13, a predetermined coefficient (for example, 80%) of the maximum output voltage is multiplied. The predetermined coefficient can be set in advance according to the shape of the output characteristic graph shown in FIG. In step S14, absolute value correction is performed. The absolute value correction is performed based on a voltage obtained by multiplying a predetermined coefficient.

  Thus, in the first embodiment, any point of the output characteristics of the toner amount detection device 1 can be used by changing the capacitance Cv of the varicap 61 and setting the reference voltage. This absorbs individual variations in the inductance of the two coils L1 and L2, and reduces the burden of the adjustment work by effectively using the portion having a slope that facilitates the adjustment work. It is also possible to improve the yield by reducing defects due to individual variations in inductance.

B. Second embodiment:
FIG. 5 is a block diagram showing a functional configuration of the toner amount detection device 1a according to the second embodiment of the present invention. FIG. 6 is a circuit diagram of the toner amount detection device 1a according to the second embodiment. The toner amount detection device 1a according to the second embodiment is different from the toner amount detection device 1 according to the first embodiment in that it includes a changeover switch 70, and is common in other configurations. The changeover switch 70 can switch the output destination of the resonant rectangular wave Pr to either the phase comparison unit 30 or the control unit 90.

  FIG. 7 is a flowchart showing the processing contents of the toner amount detection apparatus 1a according to the second embodiment. In step S21, the image forming apparatus including the toner amount detection device 1a is turned on. In step S <b> 22, the control unit 90 operates the changeover switch 70 to connect the resonance circuit unit 20 to the control unit 90. Thereby, the control unit 90 is in a state where the resonance rectangular wave Pr and the source rectangular wave Ps of the resonance circuit unit 20 can be input.

  In step S23, the control unit 90 measures the resonance frequency (f) that is the frequency of the resonance rectangular wave Pr. The resonance frequency (f) can be measured, for example, by counting the number of pulses within a preset time. The source oscillation frequency (F) that is the frequency of the source rectangular wave Ps is also measured in the same manner.

  In step S24, the control unit 90 compares the source oscillation frequency (F) that is the frequency of the source rectangular wave Ps with the resonance frequency (f) that is the frequency of the resonant rectangular wave Pr. If the source oscillation frequency (F) does not match the resonance frequency (f), the process proceeds to step S25. Here, “matching” does not necessarily mean that matching is strictly necessary, but means that it is within a presumed error (tolerance) range.

  In step S25, the control unit 90 adjusts the electrostatic capacitance Cv of the varicap 61, and returns the process to step S23. By repeating this process, the resonance frequency (f) and the source oscillation frequency (F) can be matched. When the resonance frequency (f) matches the source oscillation frequency (F), the process proceeds to step S26.

  In step S <b> 26, the control unit 90 operates the changeover switch 70 to connect the resonance circuit unit 20 to the phase comparison unit 30. Thereby, the toner amount detection device 1a can output the output voltage corresponding to the toner amount and measure the toner amount as in the first embodiment. In step S27, the control unit 90 returns the process to step S23 when detecting a certain environmental change (for example, temperature change) and based on the change over time. Thus, step S23 returns the process to step S23 based on the preset condition.

  As described above, in the second embodiment, the resonance frequency (f) that is the frequency of the resonance rectangular wave Pr can be automatically matched with the source oscillation frequency (F) that is the frequency of the source rectangular wave Ps. It is possible to further improve the accuracy of toner amount detection by eliminating variations in the characteristics of components and circuits than when adjusting the voltage. Furthermore, since the resonance frequency (f) can be controlled by adjusting the electrostatic capacity Cv of the varicap 61 by the control unit 90 that can be configured by the CPU, it can be realized with a simple configuration.

  The present invention can be implemented not only in the above embodiments but also in the following modifications.

C. Variations:
Modification 1: In each of the above-described embodiments, the first and second examples are configured independently, but may be combined. The first and second embodiments can be configured independently or in combination.

  Modification 2: In each of the above embodiments, the amount of magnetic toner is detected using the analog voltage value amplified by the amplification unit 50. For example, without using the amplification unit 50, the magnetic toner is obtained only by digital processing. May be detected.

  Modification 3: In each of the above embodiments, a rectangular wave is used as the electrical signal, but other waveforms such as a sine wave may be used. However, if a rectangular wave is used, there is an advantage that phase difference detection and the like can be easily implemented.

DESCRIPTION OF SYMBOLS 1, 1a Toner amount detection apparatus 10 Source oscillation circuit part 20 Resonance circuit part 30 Phase comparison part 40 Integration circuit part 50 Amplification part 60 Frequency adjustment circuit 61 Varicap 62 First capacitor 63 Second capacitor 70 Changeover switch 90 Control part

Claims (3)

A toner amount detection device for detecting the amount of magnetic toner stored in a developing unit of an image forming apparatus,
An oscillation circuit for generating a source electric signal having a constant frequency;
A capacitor having a coil and a varicap arranged so that the inductance varies according to the amount of the magnetic toner, and a capacitance that can be adjusted according to the potential applied to the varicap. A resonant circuit that resonates with the source electrical signal to generate a resonant signal;
Detecting a phase difference between the source electric signal and the resonance signal, and generating a phase difference signal according to the detected phase difference;
An integrating circuit unit that integrates the phase difference signal to generate an output signal used for the detection;
A controller that adjusts the capacitance so that the frequency of the source electrical signal and the frequency of the resonance signal match;
A toner amount detection device comprising: The toner amount detection device according to claim 1,
The control unit compares the frequency of the source electrical signal and the frequency of the resonance signal based on a preset condition, and when the frequency of the source electrical signal and the frequency of the resonance signal are different, A toner amount detection device that adjusts the electrostatic capacitance so that the frequency of the source electrical signal and the frequency of the resonance signal match. An image forming apparatus,
An image forming apparatus comprising the toner amount detection device according to claim 1.