JP2018105759A - Permeability sensor and method for detecting permeability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a permeability sensor which can detect a change in the permeability of a detection object more precisely even by a simpler structure, and a method for detecting a permeability using the permeability sensor.SOLUTION: The permeability sensor includes: a first coil L1 and a second coil L2; a first oscillation circuit including the first coil 1 for oscillation; a second oscillation circuit including the second coil 2 for oscillation; a reception unit for receiving a reference time signal showing a time from an exterior device; a measurement unit U1 for measuring the respective oscillatory frequencies of the first and second oscillation circuits on the basis of the reference time signal; a calculation unit U1 for calculating the difference between the oscillatory frequencies measured by the measurement unit U1; and a conversion unit U1 for converting the difference calculated by the calculation unit U1 into a differential permeability.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a magnetic permeability sensor for detecting the magnetic permeability of an object to be detected, and a magnetic permeability detection method using the magnetic permeability sensor.

  An electrophotographic copying machine or printer includes a toner sensor that magnetically detects the toner concentration or remaining amount in a developing unit used to develop an electrostatic image formed on a photoreceptor. Yes.

  For example, Patent Literature 1 includes a first coil and a second coil, a first oscillation circuit that oscillates including the first coil 1, and a second coil 2 at different distances from the object to be detected. A second oscillation circuit that oscillates, measures an oscillation frequency in each of the first oscillation circuit and the second oscillation circuit, calculates a difference between the measured oscillation frequencies, and converts the difference into a magnetic permeability, A magnetic permeability sensor that magnetically detects concentration or remaining amount is disclosed.

Japanese Patent Laying-Open No. 2015-99144

  In the conventional magnetic permeability sensor as described above, the oscillation frequency in each of the first oscillation circuit and the second oscillation circuit is measured at regular time intervals based on the clock signal of the oscillator built in the microcomputer used. The

  In order to avoid a so-called EMI (radiated noise) problem, the clock is generally subjected to spread spectrum that intentionally changes the frequency randomly. Further, the clock signal has a low frequency fluctuation (jitter) and the frequency is slightly changed. Therefore, the conventional magnetic permeability sensor has a problem that even if the oscillation frequency is measured using the built-in clock, accurate measurement cannot be performed and an error occurs.

  There is also a method that uses an external oscillator (oscillator) and uses this clock signal as a reference. However, the oscillator is expensive, which increases the manufacturing cost of the product and complicates the structure of the product. is there.

  Further, in the conventional magnetic permeability sensor, in order to adjust the detection sensitivity, it is necessary to physically change the distance from the object to be detected. However, the magnetic permeability sensor and the mounting member to which the magnetic permeability sensor is attached are individually mounted. Due to the difference, it was not easy.

  The present invention has been made in view of such circumstances, and the object of the present invention is to detect the change in the magnetic permeability of the detected object with higher accuracy at a lower cost and easily adjust the detection sensitivity. Another object of the present invention is to provide a magnetic permeability sensor that can be used, and a magnetic permeability detection method using the magnetic permeability sensor.

  A magnetic permeability sensor according to the present invention includes a first oscillation circuit that oscillates including a first coil that receives magnetism from the object to be detected, and a magnetic field sensor that detects the magnetic permeability of the object to be detected; A second oscillation circuit that oscillates including a second coil that receives magnetism; a receiver that receives a reference time signal representing time from an external device; and oscillation frequencies of the first oscillation circuit and the second oscillation circuit, respectively. A measurement unit that measures based on a reference time signal, a calculation unit that calculates a difference between oscillation frequencies measured by the measurement unit, and a conversion unit that converts the difference calculated by the calculation unit into permeability. It is characterized by.

In the present invention, the oscillation frequency of the first oscillation circuit including the first coil disposed in the vicinity of the detected object is different from the distance to the detected object in the vicinity of the detected object from the first coil. The measurement unit measures the oscillation frequency of the second oscillation circuit including the arranged second coil. At this time, the measurement unit performs measurement based on the reference time signal received from the external device by the reception unit. A receiving unit that receives a reference signal from an external device is provided, and can receive a reference signal from the outside. The calculation unit calculates a difference between both oscillation frequencies measured by the measurement unit, and the conversion unit converts the difference calculated by the calculation unit into a magnetic permeability. As the magnetic permeability of the object to be detected increases, the inductance of the coil increases and the oscillation frequency of the oscillation circuit including the coil decreases. Here, in the coil closer to the object to be detected, the amount of change in inductance corresponding to the change in magnetic permeability increases, so the fluctuation of the oscillation frequency in the oscillation circuit also increases. Therefore, the magnetic permeability can be detected from the difference between the oscillation frequencies of the respective oscillation circuits using two coils arranged with different distances from the object to be detected. At this time, a planar coil such as a coil formed by patterning printing on the substrate can be used as the two coils, and the configuration is downsized.
In the case of a coil having a small inductance such as a planar coil, the oscillation frequency is high. As a result, since the computer clock is lower than the oscillation frequency, in the case of frequency measurement, the measurement time for obtaining the same resolution can be shortened, and the measurement time can be made constant. In addition, a series of processes for measuring the oscillation frequency, calculating the difference between the oscillation frequencies, and converting the difference to the magnetic permeability can be performed by software using a microcomputer, etc., and the number of parts can be reduced. The detection accuracy is high.

  The magnetic permeability sensor according to the present invention is characterized in that the measurement unit alternately measures an oscillation frequency in the first oscillation circuit and an oscillation frequency in the second oscillation circuit.

  In the present invention, the measurement unit alternately performs measurement of the oscillation frequency in the first oscillation circuit and measurement of the oscillation frequency in the second oscillation circuit while switching based on the reference time signal from the external device. . Therefore, when the oscillation frequency of one oscillation circuit is measured, the other oscillation circuit is not oscillating. Therefore, the measurement value of the oscillation frequency of one oscillation circuit is not affected by the oscillation of the other oscillation circuit. Therefore, accurate oscillation frequencies in both oscillation circuits can be measured, and the permeability detection accuracy is high.

  In the magnetic permeability sensor according to the present invention, the reference time signal is a clock signal of the external device.

In the present invention, the reference time signal from the external device having the object to be detected is a clock signal of the external device, and the measuring unit is configured to output the first oscillation circuit and the second oscillation signal based on the clock signal of the external device. Measures the oscillation frequency in the oscillation circuit.
By using the external clock signal as a reference time signal, it is possible to know an accurate magnetic permeability.

  In the magnetic permeability sensor according to the present invention, the reference time signal is a signal obtained by multiplying the clock signal of the external device.

In the present invention, the reference time signal from the external device having the object to be detected is a signal obtained by multiplying the clock signal of the external device, and the measurement unit is configured to generate the first oscillation circuit based on the multiplied clock signal. And the oscillation frequency in the second oscillation circuit is measured.
The sensitivity of the magnetic permeability sensor can be adjusted by multiplying the clock signal.

The magnetic permeability sensor according to the present invention is characterized in that the reference time signal is a control signal representing a measurement period of an oscillation frequency by the measurement unit based on a clock signal of the external device.

In the present invention, the reference time signal from the external device having the object to be detected is a control signal indicating the measurement period of the oscillation frequency based on the clock signal of the external device, and the measurement unit is configured to control the control signal. Based on the above, the oscillation frequency in the first oscillation circuit and the second oscillation circuit is measured.
A highly accurate measurement can be performed based on the external clock signal.

  The magnetic permeability sensor according to the present invention includes a processing unit that performs a multiplication process on the reference time signal received by the receiving unit.

In the present invention, the processing unit includes, for example, a PLL (Phase Locked Loop) circuit, and multiplies the reference time signal received by the receiving unit.
The sensitivity of the magnetic permeability sensor can be adjusted by multiplying the clock signal.

  The magnetic permeability sensor according to the present invention is characterized in that the magnetic permeability detection sensitivity is adjustable.

  In the present invention, for example, since the reference time signal received by the receiving unit can be multiplied by the processing unit, the frequency (interval) of measurement of the oscillation frequency by the measuring unit can be changed, and the magnetic permeability The detection sensitivity can be adjusted.

  The magnetic permeability detection method according to the present invention is a magnetic permeability detection method in which a magnetic permeability sensor detects the magnetic permeability of an object to be detected, and the first coil and the second coil are placed at different distances from the object to be detected. An oscillation frequency of an oscillation circuit that oscillates including the first coil and oscillates including the second coil is received based on the reference time signal. The oscillation frequency of the oscillation circuit is measured, the difference between the oscillation frequencies measured by the measurement unit is calculated, and the calculated difference is converted into magnetic permeability.

  According to the present invention, it is possible to detect a change in the magnetic permeability of an object to be detected with higher accuracy at a lower cost and easily adjust the detection sensitivity.

It is a perspective view which shows the structure of the magnetic permeability sensor which concerns on this Embodiment. It is sectional drawing which shows the structure of the magnetic permeability sensor which concerns on this Embodiment. It is sectional drawing which shows the example of attachment to the developing unit of the magnetic permeability sensor which concerns on this Embodiment. It is a functional block diagram which shows the function structure of the magnetic permeability sensor which concerns on this Embodiment. It is a circuit diagram which shows the example of 1 structure of the magnetic permeability sensor which concerns on this Embodiment. It is a timing chart for demonstrating operation | movement of the magnetic permeability sensor which concerns on this Embodiment. It is a flowchart for demonstrating operation | movement of the magnetic permeability sensor which concerns on this Embodiment. It is a perspective view which shows the structure of the coil in a 1st modification. It is sectional drawing which shows the structure of the magnetic permeability sensor in a 2nd modification. It is sectional drawing which shows the structure of the magnetic permeability sensor in a 3rd modification. It is sectional drawing which shows the structure of the magnetic permeability sensor in a 4th modification. It is sectional drawing which shows the structure of the magnetic permeability sensor in a 5th modification. It is a top view which shows the structure of the shield member suitable for the magnetic permeability sensor of this Embodiment.

  Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof. 1 and 2 are a perspective view and a cross-sectional view showing a configuration of a magnetic permeability sensor 20 according to the present embodiment.

  1 and 2, reference numeral 10 denotes a flat rectangular substrate. A first coil 1 is formed on one surface (the lower surface in the drawing) of one end portion in the longitudinal direction of the substrate 10 (see FIG. 2). A second coil 2 is formed on the other surface (upper surface in the drawing) of the one end of the substrate 10 so as to be coaxial with the first coil 1. The first coil 1 and the second coil 2 are formed, for example, by printing a copper foil pattern on the substrate 10.

  A connector 3 is mounted on the upper surface of the other end portion in the longitudinal direction of the substrate 10 such that a part thereof protrudes from the end of the other end portion in the longitudinal direction. On the upper surface of the central portion of the substrate 10, an electronic chip 4 including a microcomputer for performing various processes described later is mounted. Further, a circuit component 5 is mounted in the vicinity of the electronic chip 4. The circuit component 5 includes a capacitor for forming an oscillation circuit with the first coil 1 or the second coil 2. The magnetic permeability sensor 20 is configured as described above.

  FIG. 3 is a cross-sectional view showing an example of attachment of the magnetic permeability sensor 20 according to the present embodiment to the developing unit. In FIG. 3, reference numeral 30 denotes a partition partitioning the inside and outside of the developing unit of the copying machine, for example. A recess 31 is formed outside the partition wall 30, and the magnetic permeability sensor 20 is attached to the developing unit in a state of being housed in the case 21 so as to be fitted into the recess 31. In addition, the connector 3 has a leading end extracted from the case 21 to the outside.

  At this time, the magnetic permeability sensor 20 is attached to the partition wall 30 of the developing unit so that the lower surface of the substrate 10 shown in FIGS. 1 and 2 faces the partition wall 30. Therefore, the first coil 1 is disposed closer to the developing unit than the second coil 2, in other words, closer to the developer (detected object) in the developing unit. The recess 31 to which the magnetic permeability sensor 20 is attached is sealed with a seal 32.

  FIG. 4 is a functional block diagram showing a functional configuration of the magnetic permeability sensor 20 according to the present embodiment. In FIG. 4, the same or similar parts as those in FIGS. 1 and 2 are denoted by the same reference numerals.

  The first coil 1 and a part of the circuit component 5 constitute a first oscillation circuit 6, and the second coil 2 and a part of the circuit component 5 constitute a second oscillation circuit 7. That is, in the magnetic permeability sensor 20 according to the present embodiment, in the first oscillation circuit 6 and the second oscillation circuit 7, the other constituent members except the first coil 1 and the second coil 2 are common. Therefore, the number of parts can be reduced. Furthermore, the oscillation frequency measured by each of the first oscillation circuit 6 and the second oscillation circuit 7 is not affected by the characteristic variation due to different constituent members, and an accurate value is measured. Therefore, the magnetic permeability detection accuracy is high.

  The electronic chip 4 includes a measurement unit 41 that measures the oscillation frequency in each of the first oscillation circuit 6 and the second oscillation circuit 7, a calculation unit 42 that calculates a difference between the oscillation frequencies measured by the measurement unit 41, and a calculation unit. It has functionally the conversion part 43 which converts the difference calculated in 42 into magnetic permeability.

  Furthermore, the circuit component 5 includes, for example, a processing unit 50 having a PLL circuit, and the processing unit 50 multiplies a reference time signal representing time received by a fifth terminal (receiving unit) described later. Can be done. Based on the reference time signal multiplied by the processing unit 50 in this way, the measurement unit 41 measures the oscillation frequency.

  FIG. 5 is a circuit diagram showing a configuration example of the magnetic permeability sensor 20 according to the present embodiment. In FIG. 5, a coil L1 and a coil L2 correspond to the first coil 1 and the second coil 2 described above, respectively. The microcomputer U1 corresponds to the electronic chip 4 described above.

  One end of the coil L1 is connected to the sixth terminal of the microcomputer U1, and one end of the coil L2 is connected to the third terminal of the microcomputer U1. The other end of the coil L1 and the other end of the coil L2 are connected to the base of the transistor Q1 via the capacitor C1. A resistor R2 is provided between the base and collector of the transistor Q1, and a capacitor C2 is provided between the base and emitter of the transistor Q1. The collector of the transistor Q1 is connected to the second terminal of the microcomputer U1 and is grounded through the resistor R3.

  The first terminal of the microcomputer U1 is connected to the input terminal for the power supply voltage Vdd. The input terminal of the power supply voltage Vdd is connected to the emitter of the transistor Q1 through the resistor R1. One end of a capacitor C3 is connected between the resistor R1 and the emitter of the transistor Q1, and the other end of the capacitor C3 is grounded. One end of a capacitor C6 is connected between the input terminal of the power supply voltage Vdd and the first terminal, and the other end of the capacitor C6 is grounded. A grounding terminal is connected to the eighth terminal of the microcomputer U1.

  An output terminal that outputs a detection voltage Vout corresponding to the magnetic permeability is connected to the seventh terminal of the microcomputer U1 via a resistor R4. One end of a capacitor C7 is connected between the output terminal and the resistor R4, and the other end of the capacitor C7 is grounded. The fourth terminal of the microcomputer U1 is connected to an input terminal for inputting a control voltage Vcont for performing offset control via a resistor R6. One end of a capacitor C5 is connected between the fourth terminal of the microcomputer U1 and the resistor R6, and the other end of the capacitor C5 is grounded.

  Furthermore, the clock signal output terminal 101 of the copying machine (external device) is connected to the fifth terminal of the microcomputer U1 through the resistor R5. One end of a capacitor C4 is connected between the fifth terminal and the resistor R5, and the other end of the capacitor C4 is grounded. The copying machine has the developing unit described above.

  A device such as a copying machine incorporates a high-accuracy oscillator that generates a clock signal, and various digital processes are performed based on the clock signal. In general, spread spectrum or the like is applied to a clock signal generated by an oscillator included in the microcomputer U1 as a measure against so-called EMI.

  In the magnetic permeability sensor 20 according to the present embodiment, a clock signal (hereinafter also referred to as a reference time signal) generated by an oscillator of a copying machine as an example and not subjected to spread spectrum or the like (hereinafter also referred to as a reference time signal) is used for the microcomputer U1. The fifth terminal is configured to be able to receive. Based on the received reference time signal (the fifth terminal is assigned to the clock signal receiving terminal (receiving unit)), the measuring unit 41 measures the oscillation frequency. Further, when the fifth terminal of the microcomputer U1 receives the reference time signal from the copying machine, the processing unit 50 performs a process of multiplying the frequency of the received reference time signal, and based on the multiplied reference time signal. Thus, the measurement unit 41 may be configured to measure the oscillation frequency. That is, the reference time signal may be a signal obtained by multiplying the clock signal of the copying machine. Note that such multiplication processing may be performed by the magnetic permeability sensor 20 as described above, or may be performed by a copying machine.

  The coil L1, the two capacitors C2 and C3, and the transistor Q1 constitute the first oscillation circuit 6 (Colpitts oscillation circuit), and the coil L2, the two capacitors C2 and C3, and the transistor Q1 described above. A second oscillation circuit 7 (Colpitts oscillation circuit) is configured. Then, by the switching operation of the microcomputer U1 (the switching operation is performed at the third terminal and the sixth terminal of the microcomputer U1), the first oscillation circuit 6 and the second oscillation circuit 7 oscillate alternately at predetermined time intervals. It is like that.

  Next, the operation of the magnetic permeability sensor 20 according to the present embodiment will be described. FIG. 6 is a timing chart for explaining the operation of the magnetic permeability sensor 20 according to the present embodiment.

  The first oscillating circuit 6 and the second oscillating circuit 7 are alternately oscillated for a predetermined time, and the measuring unit 41 measures the oscillation frequency in each oscillation using the reference time signal from the copying machine. The predetermined time is 2 ms, for example. Specifically, a control signal representing the start timing and end timing (see arrows in FIG. 6) of the measurement by the measurement unit 41 is generated using the reference time signal, and the measurement unit 41 performs the first operation according to the control signal. The oscillation frequency in the oscillation circuit 6 and the second oscillation circuit 7 is measured.

  At this time, as shown in FIG. 6, in the period in which the first oscillation circuit 6 is oscillated and the oscillation frequency is measured, the second oscillation circuit 7 is not oscillated, and the second oscillation circuit 7 is oscillated and the oscillation is performed. The first oscillation circuit 6 is not oscillated during the frequency measurement period. Therefore, since the oscillation frequency is measured without being influenced by oscillation, the measured value is highly accurate.

  When the measurement of the oscillation frequency for each predetermined time (for example, 2 ms) is finished, the oscillation frequency measured in the first oscillation circuit 6 (derived from the first coil 1) and the oscillation frequency in the second oscillation circuit 7 (in the second coil 2) The difference from the measured oscillation frequency is calculated by the calculation unit 42. And the conversion part 43 converts the calculated difference into a magnetic permeability, and calculates | requires the variation | change_quantity of a magnetic permeability. In this way, the magnetic permeability sensor (toner sensor) 20 attached to the developing unit detects the toner concentration.

  Further, in the period in which the first oscillation circuit 6 is oscillated and the oscillation frequency is measured, the difference between the previous measurement values (for example, A ′ and B ′) of the first oscillation circuit 6 and the second oscillation circuit 7 is calculated as follows: The calculation unit 42 calculates the difference, and the conversion unit 43 converts the calculated difference into the magnetic permeability to obtain the change amount of the magnetic permeability. Therefore, the change amount of the magnetic permeability is measured at the timing of starting the measurement of the oscillation frequency of each oscillation circuit. Updates are made sequentially.

  FIG. 7 is a flowchart for explaining the operation of the magnetic permeability sensor 20 according to the present embodiment. In the following, for convenience of explanation, a case where the clock signal of the copying machine 100 is used will be described as an example.

  First, the copying machine 100 transmits a clock signal generated by its own oscillator to the magnetic permeability sensor 20 (step S101), and the magnetic permeability sensor 20 receives the clock signal.

  Generally, since such a clock signal often has a high frequency, the processing unit 50 performs a multiplication process on the received clock signal (step S201). However, the magnetic permeability sensor 20 according to the present embodiment is not limited to this, and may receive a clock signal that has already been multiplied by the copying machine 100. In this case, the multiplication process by the processing unit 50 may be omitted.

  Furthermore, in the magnetic permeability sensor 20 according to the present embodiment, the detection sensitivity of the magnetic permeability can be adjusted by receiving a clock signal having a different frequency or by changing an integral multiple of the multiplication processing by the processing unit 50. It is.

  Next, the measurement unit 41 uses the multiplied clock signal as a reference time signal, and based on this, oscillates the first oscillation circuit 6 and the second oscillation circuit 7 alternately for a predetermined time and measures the oscillation frequency (step) S202).

  Further, the calculation unit 42 calculates a difference between the oscillation frequency measured by the first oscillation circuit 6 and the oscillation frequency measured by the second oscillation circuit 7 (step S203).

  Further, the conversion unit 43 converts the difference calculated by the calculation unit 42 into magnetic permeability (that is, voltage output) (step S204). Thereby, the toner density in the developing unit of the copying machine 100 can be detected.

  Thereafter, the detection result by the magnetic permeability sensor 20 is transmitted to, for example, the copying machine 100 (step S205) and output via a display unit (not shown) of the copying machine 100 (step S102).

  The magnetic permeability sensor 20 according to the present embodiment is not limited to the above description. For example, a determination unit (not shown) that determines whether the frequency of the clock signal received from the copier 100 is equal to or higher than a predetermined threshold is provided, and only when the determination unit determines that the frequency is higher than the predetermined threshold. You may comprise so that such a multiplication process may be performed.

  In this embodiment, there are the following advantages. Depending on the type of toner used, the toner density control range may change. In this case, for example, by using an unused terminal of the microcomputer U1 and controlling the voltage level of the unused terminal from the outside, the toner density control range is adjusted to an appropriate range for the toner to be used. Offset function can be given.

  In recent years, depending on the electrophotographic method, the particle size of the toner itself tends to be small in order to obtain high image quality. Further, the amount of unnecessary toner is reduced as much as possible to reduce the cost and weight, and as a result, the change in magnetic permeability that can be detected tends to be small. In order to accurately detect the reduced permeability change, it is necessary to increase the detection sensitivity by performing amplification or the like on the small permeability change. However, in this case, the change in the magnetic permeability is not linear, and the magnetic permeability cannot be measured accurately. According to the present embodiment, by using a method using software such as linear correction, it becomes possible to improve the deteriorated linearity and to accurately grasp the change in magnetic permeability.

  Note that although FIG. 5 shows a microcomputer having eight terminals as an example, it is not limited to this configuration. If necessary, it is possible to use a microcomputer with a different number of terminals and transmit information such as permeability change to the upper control side by means of serial communication etc. and receive control signals from the upper side. is there.

  Hereinafter, the principle that the magnetic permeability can be detected (the toner density can be detected) by the above-described procedure will be described.

  When the magnetic permeability of the object to be detected increases, the inductance of the coil arranged in the vicinity of the object to be detected increases according to the fluctuation of the magnetic permeability. As a result, the oscillation frequency of the oscillation circuit including the coil decreases. Here, when two coils are arranged at different distances from the object to be detected, the inductance of each coil increases, and the oscillation frequency of any oscillation circuit decreases. However, the coil closer to the object to be detected is more affected by the change in permeability than the coil farther away, so in the above case, the amount of increase in inductance is large and the amount of decrease in oscillation frequency is also large. Become. Therefore, a difference corresponding to the degree of change in the magnetic permeability occurs in the oscillation frequency in the two oscillation circuits including the two coils. Thus, since there is a correlation between the difference between both oscillation frequencies and the magnetic permeability, in this embodiment, the magnetic permeability of the object to be detected is detected based on the difference between the oscillation frequencies of both oscillation circuits. It is possible.

  In the magnetic permeability sensor 20 in the above-described embodiment, the first coil 1 corresponds to a coil closer to the detected object, and the second coil 2 corresponds to a coil farther from the detected object.

  The developer in the developing unit is a mixture of toner and magnetic material (iron powder). At the time of copying, the toner adheres to the paper and the magnetic material hardly adheres. Therefore, as the copying process proceeds, the amount of toner decreases but the amount of magnetic material hardly changes, so the magnetic permeability of the developer increases. Therefore, there is an inversely proportional correlation between the magnetic permeability in the developing unit and the toner density (remaining amount). In the present embodiment, since the magnetic permeability of the detection object (developer) can be detected as described above, the toner concentration can be detected based on the detected magnetic permeability of the developer in the developing unit.

  In the above-described embodiment, two oscillations driven based on the reference time signal based on the change in inductance of two coils (first coil 1 and second coil 2) arranged on the substrate 10 on the same axis. The difference between the oscillation frequencies in the circuit (the first oscillation circuit 6 and the second oscillation circuit 7) is detected, and the difference (amount of change in oscillation frequency) is calculated by the microcomputer U1 to detect the change in permeability. Yes. Here, the two coils are alternately connected to the oscillation circuit, and based on the reference time signal, the oscillation frequency is alternately measured by the microcomputer U1 over a predetermined time, and the difference is calculated to obtain the magnetic permeability. Changes are detected.

  In the present embodiment, since the first coil 1 and the second coil 2 are coaxially arranged on the upper and lower surfaces of the substrate 10, the area necessary for the coil arrangement can be reduced and the horizontal compactness can be achieved. . In addition, since the coil is formed by printing the conductor pattern on the substrate 10, it is possible to reduce the height in the height direction (the thickness direction of the substrate 10). Furthermore, since various processes are performed using a microcomputer, the number of components can be reduced and the area for mounting circuit components can be reduced. From the above, the magnetic sensor can be greatly downsized.

  Since the measurement of the oscillation frequency in the two oscillation circuits is alternately performed, the measurement of the oscillation circuit including one coil is not affected by the magnetic flux generated in the other coil (inductance change in the other coil). Therefore, an accurate oscillation frequency can be measured, and as a result, the magnetic permeability can be detected with high accuracy.

  In this embodiment, since the transistors and capacitors constituting the two oscillation circuits are shared, and the coils are arranged in the oscillation circuits, the number of parts can be reduced and the cost can be reduced. In addition, since the number of components is small, variations in component characteristics can be reduced, and it is difficult to be affected by disturbances such as temperature changes and noise, and accurate measurement is possible.

  Since various processes are performed by software using a microcomputer, the number of circuit parts as hardware can be reduced and the influence of variations in characteristics of circuit parts is reduced. In addition, since it is processed by software, it is less affected by the environment (temperature, humidity, etc.). Therefore, the accuracy of the detected magnetic permeability can be increased.

  Further, even when the set toner density is different, it can be easily dealt with only by changing the contents of the software. Therefore, since management for each set value with different toner density is not required, mass production is facilitated, and cost can be reduced.

  In the magnetic permeability sensor 20 according to the present embodiment, by changing the reference time signal, the measurement time for measuring the control signal, that is, the oscillation frequency can be changed, so that the detection sensitivity can be easily adjusted. More specifically, the clock signal of the copying machine 100 may be appropriately processed (for example, multiplied), or the clock signal received from the copying machine 100 may be multiplied by the permeability sensor 20.

  In the above description, the case where the reference time signal is the clock signal of the copying machine 100 has been described. However, the present embodiment is not limited to this. For example, the reference time signal may be a control signal representing the start and / or end of measurement of the oscillation frequency by the measuring unit 41 based on the clock signal of the copying machine 100. That is, a control signal used for measuring the oscillation frequency by the measuring unit 41 may be generated by the magnetic permeability sensor 20 or the copying machine 100 based on the clock signal of the copying machine 100.

  By the way, in the above-described embodiment, the magnetic permeability sensor 20 is attached to the developing unit of the copying machine 100 while being housed in the case 21. However, in this embodiment, there is no possibility that the developer leaks. 21 is not necessarily provided. In such a case, notches are formed in a plurality of locations on the substrate 10, and the magnetic permeability sensor 20 is attached to the developing unit by hooking the notches of the developing unit into the notches, or the substrate 10 and the partition walls are attached by double-sided tape. 30 may be attached to attach the magnetic permeability sensor 20 to the developing unit.

  In the above-described embodiment, the first coil 1 and the second coil 2 are formed coaxially by printing conductor patterns on the upper surface and the lower surface of the substrate 10, respectively. The forming method 2 is not limited to this, and may be another method. Hereinafter, these other methods will be described as modified examples.

(First modification)
FIG. 8 is a perspective view showing the configuration of the coil in the first modification. 8, the same or similar members as those in FIGS. 1 and 2 are denoted by the same reference numerals. In FIG. 8, the upper and lower surfaces of the substrate 10 are shown opposite to those in FIG. In the first modification, the first coil 1 and the second coil 2 are formed concentrically on the upper surface of the substrate 10 in FIG. 8 by, for example, pattern printing of copper foil. The coil is not formed on the lower surface of the substrate 10 in FIG. 8, and the electronic chip 4, the circuit component 5, and the connector 3 similar to those in the above-described embodiment are mounted.

(Second modification)
FIG. 9 is a cross-sectional view showing the configuration of the magnetic permeability sensor in the second modification. 9, the same or similar members as those in FIGS. 1 and 2 are denoted by the same reference numerals. In the second modification, the first coil 1 and the second coil 2 are formed on the lower surface of the substrate 10 on the same axis with an insulating layer interposed therebetween, for example, by pattern printing of copper foil. Further, no coil is formed on the upper surface of the substrate 10, and the electronic chip 4, the circuit component 5, and the connector 3 similar to those of the above-described embodiment are mounted. The first coil 1 and the second coil 2 are formed immediately below the mounting position of the electronic chip 4 and the circuit component 5. Therefore, further downsizing of the configuration of the magnetic permeability sensor can be achieved. Unlike the configuration shown in FIG. 9, the concentric first coil 1 and second coil 2 described in the first modification are formed immediately below the mounting positions of the electronic chip 4 and the circuit component 5. You may do it.

(Third Modification)
FIG. 10 is a cross-sectional view showing the configuration of the magnetic permeability sensor in the third modification. 10, the same or similar members as those in FIGS. 1 and 2 are denoted by the same reference numerals. In the third modification, a first coil 1 is formed by mounting a separate air core coil on the lower surface of one end portion of the substrate 10, and is coaxial with the first coil 1 on the upper surface of one end portion of the substrate 10. The second coil 2 is formed by mounting a separate air core coil. In the remaining area on the upper surface of the substrate 10, the electronic chip 4, the circuit component 5, and the connector 3 similar to those in the above-described embodiment are mounted.

(Fourth modification)
FIG. 11 is a cross-sectional view showing the configuration of the magnetic permeability sensor in the fourth modification. In FIG. 11, the same or similar members as those in FIGS. 1 and 2 are denoted by the same reference numerals. In the fourth modification, the first coil 1 and the second coil 2 are formed by stacking and mounting two air core coils of different parts on the upper surface of one end of the substrate 10. In the remaining area on the upper surface of the substrate 10, the electronic chip 4, the circuit component 5, and the connector 3 similar to those in the above-described embodiment are mounted. In addition, unlike the structure shown in FIG. 11, you may make it form the 1st coil 1 and the 2nd coil 2 which make the laminated structure of the above two air-core coils in the lower surface of the board | substrate 10. FIG.

(5th modification)
FIG. 12 is a cross-sectional view showing the configuration of the magnetic permeability sensor in the fifth modification. 12, the same or similar members as those in FIGS. 1 and 2 are denoted by the same reference numerals. In the fifth modification, a plurality of chip coils are mounted on the lower surface of one end portion of the substrate 10 to form the first coil 1, and the upper surface of one end portion of the substrate 10 is aligned with the first coil 1. A plurality of chip coils are mounted to form the second coil 2. In the remaining area on the upper surface of the substrate 10, the electronic chip 4, the circuit component 5, and the connector 3 similar to those in the above-described embodiment are mounted.

  In the present embodiment, the first coil and the second coil may be covered with an electrostatic shield. The coil described in this embodiment uses an air-core coil, and if there is a coil having a close dielectric constant, the measured value may vary due to a change in capacitance. In such a case, the influence from the outside can be suppressed by covering the coil with a shield member made of copper or the like. However, in the case of the magnetic permeability sensor of the present embodiment, it is considered that an eddy current is generated in the shield member due to a change in magnetic permeability, that is, a change in magnetic field lines, and this eddy current causes a measurement error in the magnetic permeability sensor. It is done. Therefore, it is necessary to provide a shield member that takes measures against eddy currents into consideration.

  13A to 13C are plan views showing a configuration of a shield member suitable for the magnetic permeability sensor of the present embodiment. In the example shown in FIG. 13A, a copper shield member 61 having a shape in which a plurality of comb teeth are extended in the same direction is provided above the coil 60 formed on the substrate 10. The shield member 61 is grounded. In the example shown in FIG. 13B, a copper shield member 62 having a shape in which a plurality of comb teeth are alternately extended in the opposite direction is provided above the coil 60 formed on the substrate 10. The shield member 62 is grounded. By providing the shield member having such a configuration, eddy current can be reduced.

  FIG. 13C shows an annular shield member. A shield member 63 having a C-shape with a part of the copper ring missing is provided on the outer peripheral side of the coil 60 formed on the substrate 10. The shield member 63 is grounded. By providing the shield member 63, eddy current can be reduced. In the example of FIG. 13C, since the shield member 63 is provided on the same plane as the coil 60, the permeability sensor can be thinned.

  The shield member as described above may be provided on both sides of the substrate 10 or may be provided only on the surface opposite to the development unit. Further, as described above, the shield member is preferably grounded. However, the effect can be obtained even if it is not grounded.

  The disclosed embodiments should be considered as illustrative in all points and not restrictive. The scope of the present embodiment is shown not by the above description but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

DESCRIPTION OF SYMBOLS 1 1st coil 2 2nd coil 3 Connector 4 Electronic chip 5 Circuit component 6 1st oscillation circuit 7 2nd oscillation circuit 10 Board | substrate 20 Magnetic permeability sensor 41 Measurement part 42 Calculation part 43 Conversion part 50 Processing part 100 Copier

Claims (8)

In a magnetic permeability sensor for detecting the magnetic permeability of an object to be detected,
A first oscillation circuit that oscillates including a first coil that receives magnetism from the object to be detected;
A second oscillation circuit that oscillates including a second coil that receives magnetism from the object to be detected;
A receiving unit for receiving a reference time signal representing time from an external device;
A measurement unit that measures an oscillation frequency in each of the first oscillation circuit and the second oscillation circuit based on the reference time signal;
A calculation unit for calculating a difference between oscillation frequencies measured by the measurement unit;
A magnetic permeability sensor comprising: a conversion unit that converts the difference calculated by the calculation unit into magnetic permeability.   2. The magnetic permeability sensor according to claim 1, wherein the measurement unit alternately measures an oscillation frequency in the first oscillation circuit and an oscillation frequency in the second oscillation circuit.   The magnetic permeability sensor according to claim 1, wherein the reference time signal is a clock signal of the external device.   The magnetic permeability sensor according to claim 1, wherein the reference time signal is a signal obtained by multiplying a clock signal of the external device.   3. The magnetic permeability sensor according to claim 1, wherein the reference time signal is a control signal representing a measurement period of an oscillation frequency by the measurement unit based on a clock signal of the external device.   The magnetic permeability sensor according to claim 3, further comprising a processing unit that performs a multiplication process on the reference time signal received by the receiving unit.   The magnetic permeability sensor according to claim 6, wherein the magnetic permeability detection sensitivity is adjustable. In a magnetic permeability detection method for detecting the magnetic permeability of an object to be detected by a magnetic permeability sensor,
Disposing the first coil and the second coil at different distances from the object to be detected;
A reference time signal representing time is received from an external device,
Based on the reference time signal, the oscillation frequency of the oscillation circuit that oscillates including the first coil and the oscillation frequency of the oscillation circuit that oscillates including the second coil are respectively measured.
Calculate the difference of the oscillation frequency measured by the measurement unit,
A magnetic permeability detection method, wherein the calculated difference is converted into a magnetic permeability.

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