JP2017111051A - Permeability sensor and permeability detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a permeability sensor capable of accurately detecting a change of permeability of a detection object even with a small and simple configuration, and provide a permeability detection method using the permeability sensor.SOLUTION: The permeability sensor includes: a first coil 1 formed of a plurality of layers whose operations can be changed validly or in-validly; a second coil 2 formed of a plurality of layers whose operations can be changed validly or in-validly; a first oscillation circuit 6 that includes the first coil 1 and oscillates; a second oscillation circuit 7 that includes the second coil 2 and oscillates; a measurement unit 41 for measuring the oscillation frequency of each of the first oscillation circuit 6 and the second oscillation circuit 7; a calculation unit 42 for calculating the difference between the oscillation frequencies measured by the measurement unit 41; and a conversion unit 43 for converting the difference calculated by the calculation unit 42 into permeability.SELECTED DRAWING: Figure 4

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 a toner concentration or remaining amount in a developing unit used to develop an electrostatic image formed on a photoreceptor. . An example of such a toner sensor is disclosed in Patent Document 1. The sensor disclosed in Patent Document 1 uses four coils and detects toner density by a differential transformer method.

  Patent Document 2 discloses a first oscillation circuit that generates a phase shift in an oscillation wave corresponding to an inductance change in the first detection coil, and a phase shift in an oscillation wave that corresponds to an inductance change in the second detection coil. There is disclosed a technique that includes a second oscillation circuit, obtains a difference between the phase shifts of the two, and detects a metal state.

JP 2001-165910 A JP 2009-31257 A

  The toner sensor of Patent Document 1 adopts a differential transformer system, and when the drive coil and the differential coil are located in the vicinity, the influence of the toner affects both. It is difficult to completely eliminate the influence on the coil. Further, when an oscillation circuit is configured including a flat coil, there is little change in the degree of coupling of inductance when a magnetic body approaches, and it is difficult to operate such a flat coil with an analog circuit.

In Patent Document 2, the oscillation wave from the first oscillation circuit and the second oscillation circuit is measured, the time when the measured value reaches a predetermined value is measured, and the phase of the accumulated oscillation wave is measured based on the measured time. Since the deviation is detected, there is a problem that the detection process is complicated.
In Patent Document 2, since a coil wound around a high permeability material is used and the oscillation frequency is low, the time for obtaining the same resolution can be shortened. Therefore, a method of detecting a phase shift is advantageous. It is disadvantageous when using.
Patent Document 2 is a technique for magnetically detecting the torque of the rotating shaft, and its application to a sensor for detecting the toner concentration is neither disclosed nor suggested.

  In a sensor that detects magnetic permeability using two coils, the two coils are spaced apart in the horizontal direction in order to prevent the other coil from being affected by the magnetic flux generated in one coil. The configuration is common. Specifically, one coil is placed near the object to be detected (magnetic material) to be easily affected by the change in permeability, and the other coil is arranged away from the object to be detected (magnetic material). Make it less susceptible to changes in permeability. According to the arrangement of the plurality of coils extending in the horizontal direction, there is a problem that the sensor cannot be reduced in size.

  Further, the magnetic permeability is detected according to the change in the inductance of the plurality of coils, but many circuit components are used for this detection. There is a problem in that circuit components have variations in characteristics and the circuit components are easily affected by the detection environment, so that high-precision detection cannot be achieved.

  The present invention has been made in view of such circumstances, and uses a magnetic permeability sensor and a magnetic permeability sensor that can detect a change in the magnetic permeability of an object to be detected with high accuracy even with a small and simple configuration. An object of the present invention is to provide a magnetic permeability detection method.

  The magnetic permeability sensor according to the present invention is a magnetic permeability sensor for detecting the magnetic permeability of an object to be detected. The magnetic field sensor comprises a plurality of layers capable of effectively or invalidally changing the operation of each layer, and receives a magnetism from the object to be detected. A first oscillation circuit that oscillates including a second coil that oscillates including a second coil that receives magnetism from the object to be detected; Measurement means for measuring the oscillation frequency in each of the first oscillation circuit and the second oscillation circuit, calculation means for calculating the difference between the oscillation frequencies measured by the measurement means, and the difference calculated by the calculation means as the permeability Conversion means for converting. Here, “being magnetized” means being magnetically coupled to an object to be detected.

In the magnetic permeability sensor of the present invention, the oscillation frequency of the first oscillation circuit including the first coil disposed in the vicinity of the detected object, and the first coil in the vicinity of the detected object is the distance to the detected object. The measurement means measures the oscillation frequency of the second oscillation circuit including the second coil arranged differently. The calculating means calculates the difference between the two oscillation frequencies measured by the measuring means, and the converting means converts the difference calculated by the calculating means into 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 flat 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 flat coil, the oscillation frequency is high. As a result, since the clock of the computer is lower than the transmission 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.
Furthermore, the first coil and the second coil are composed of a plurality of layers, and the interval between the first coil and the second coil can be changed by changing the operation of each layer effectively or invalidally. Sensitivity can be changed.

  The magnetic permeability sensor according to the present invention is characterized in that the first coil and the second coil have a terminal to which a short-circuit wire for invalidating the operation of each layer can be connected.

  In the present invention, since the first coil and the second coil have terminals that can be connected to a short-circuit wire that disables the operation of each layer, the operation of each layer is effective after the first coil and the second coil are formed. Or it can be set to invalid.

  The magnetic permeability sensor according to the present invention is characterized in that each of the first coil and the second coil is a two-layer coil.

  In the present invention, the first coil and the second coil have a total of four layers, and the sensitivity can be switched in three stages by changing the number of layers for which the operation is effective from 2 to 4.

  The magnetic permeability sensor according to the present invention is characterized in that the measuring means is configured to alternately measure the oscillation frequency in the first oscillation circuit and the oscillation frequency in the second oscillation circuit.

  In the magnetic permeability sensor of the present invention, the measurement of the oscillation frequency in the first oscillation circuit and the measurement of the oscillation frequency in the second oscillation circuit are alternately performed while switching. 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.

  The magnetic permeability sensor according to the present invention is characterized in that the first coil and the second coil are arranged coaxially.

  In the magnetic permeability sensor of the present invention, the first coil and the second coil are arranged coaxially. Therefore, the area required for arranging the coils is small, and the magnetic permeability sensor can be miniaturized.

  In the magnetic permeability sensor according to the present invention, the constituent members of the first oscillation circuit and the second oscillation circuit are common except for the first coil and the second coil.

  In the magnetic permeability sensor of the present invention, in the first oscillation circuit and the second oscillation circuit, the other components except the first coil and the second coil are common. Therefore, the oscillation frequency measured by each of the first oscillation circuit and the second oscillation circuit is not affected by variations in characteristics due to different components other than the coil, and an accurate value is measured. Therefore, the magnetic permeability detection accuracy is high.

  The magnetic permeability detection method according to the present invention is a magnetic permeability detection method for detecting the magnetic permeability of an object to be detected. The first coil composed of a plurality of layers that can change the operation of each layer effectively or invalidally and the operation of each layer are enabled or disabled. A second coil composed of a plurality of layers that can be changed ineffectively is arranged at different distances from the detected object, and an oscillation frequency of an oscillation circuit that oscillates including the first coil, and the second coil The oscillation frequency of the oscillation circuit including the oscillation circuit is measured, a difference between the measured oscillation frequencies is calculated, and the calculated difference is converted into a magnetic permeability.

  In the present invention, the magnetic permeability of an object to be detected can be detected with high accuracy even with a small and simple configuration.

It is a perspective view which shows the structure of the magnetic permeability sensor of this invention. It is sectional drawing which shows the structure of the magnetic permeability sensor of this invention. It is sectional drawing which shows the example of attachment to the developing unit of the magnetic permeability sensor of this invention. It is a block diagram which shows the function structure of the magnetic permeability sensor of this invention. It is a circuit diagram which shows one structural example of the magnetic permeability sensor of this invention. It is a timing chart for demonstrating operation | movement of the magnetic permeability sensor of this invention. It is sectional drawing which shows the example of attachment to the developing unit of the magnetic permeability sensor of a prior art example. 6 is a graph showing toner density detection sensitivity characteristics in an example of the present invention and a conventional example. It is a graph which shows the control voltage characteristic for performing offset control in an example of the present invention and a conventional example. 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 perspective view which shows the other structure of the magnetic permeability sensor of this invention. It is sectional drawing which shows the other structure of the magnetic permeability sensor of this invention. It is description which shows the structure of the coil in the other structure of this invention. It is sectional drawing which shows the operation | movement pattern of a 1st coil and a 2nd coil. It is a table | surface which shows the relationship between the operation pattern of a coil, and a jumper wire. 5 is a graph showing the relationship between the detected magnetic permeability and the sensor output in the magnetic permeability sensor 20. It is a top view which shows the structure of the shield member suitable for the magnetic permeability sensor of this invention. It is a disassembled perspective view which shows the sensor part of the magnetic permeability sensor by the other structure of this invention. It is explanatory drawing which shows the assembly method of a sensor part. It is sectional drawing which shows the attachment state of a sensor part.

Embodiment 1
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 the configuration of the magnetic permeability sensor of the present invention.

  1 and 2, reference numeral 10 denotes a flat rectangular substrate. A first coil 1 is formed on one surface (lower surface) of one end of the substrate 10 (see FIG. 2). A second coil 2 is formed on the other surface (upper surface) of 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 of the substrate 10 with a part protruding from the other end. On the upper surface of the central portion of the substrate 10, an electronic chip 4 composed of 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 of the present invention is configured as described above.

  FIG. 3 is a cross-sectional view showing an example of attaching the magnetic permeability sensor 20 of the present invention to the developing unit. In FIG. 3, reference numeral 30 denotes a partition wall that partitions the inside and outside of the developing unit. A recess 31 is formed in the partition wall 30, and the magnetic permeability sensor 20 is attached to the developing unit while being housed in the case 21 so as to be fitted into the recess 31. The tip of the connector 3 protrudes from the case 21.

  At this time, the magnetic permeability sensor 20 is attached to the partition wall 30 of the developing unit so that the lower surface side of the substrate 10 shown in FIGS. Therefore, the first coil 1 is disposed closer to the developing unit than the second coil 2, in other words, closer to the developer 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 block diagram showing a functional configuration of the magnetic permeability sensor 20 of the present invention. 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. In the magnetic permeability sensor 20 of the present invention, 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 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.

  FIG. 5 is a circuit diagram showing a configuration example of the magnetic permeability sensor 20 of the present invention. In FIG. 5, the coil L1 and the 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. An input terminal for inputting a control voltage Vcont for performing offset control is connected to the fifth terminal of the microcomputer U1 via a resistor R6. One end of a capacitor C4 is connected between the fifth terminal of the microcomputer U1 and the resistor R6, and the other end of the capacitor C4 is grounded.

  The coil L1, the two capacitors C2 and C3, and the transistor Q1 constitute the first oscillation circuit 6 (Colpitts oscillation circuit). 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 of the present invention will be described. FIG. 6 is a timing chart for explaining the operation of the magnetic permeability sensor 20 of the present invention.

  The first oscillating circuit 6 and the second oscillating circuit 7 are alternately oscillated for a predetermined time, and the oscillation frequency in each oscillation is measured by the measuring unit 41. The predetermined time is 2 ms, for example. 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. A 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.

  The present invention has 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 change in the reduced permeability, it is necessary to increase the measurement sensitivity by a method such as amplification in order to increase the change in the small permeability. In this case, the change in the magnetic permeability is not linear, and the magnetic permeability cannot be measured accurately. According to the present invention, by using a method using software such as linear correction, it becomes possible to improve the deteriorated linearity, and it is possible 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 the present invention, the magnetic permeability of the object to be detected can be detected based on the difference between the oscillation frequencies of both oscillation circuits. 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. In the present invention, since the magnetic permeability of the detection target (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 embodiment described above, the change in inductance of the two coils (the first coil 1 and the second coil 2) coaxially arranged on the substrate 10 is measured with the accuracy of the oscillator built in the microcomputer (electronic chip 4). Is detected as a difference in oscillation frequency between two oscillation circuits (first oscillation circuit 6 and second oscillation circuit 7) driven by a simple clock signal, and the difference (amount of change in oscillation frequency) is processed by a microcomputer. The change in permeability is detected. Here, the two coils are alternately connected to the oscillation circuit, the oscillation frequency is measured alternately by a microcomputer for a predetermined time, and the difference is calculated to detect the change in the magnetic permeability.

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 arrangement of the coils can be reduced, and the narrowing in the horizontal direction can be achieved. . Further, since the coil is formed by printing the conductor pattern on the substrate 10, the height in the height direction can be reduced. 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.
In the present invention, the term “coaxial” is not limited to simply indicating the positional coaxiality of the coils (the central axes coincide), but may be electrically equivalent to the coaxiality.
In other words, even if the position of the central axis is deviated, it can be regarded as coaxial if the effect of the present invention is obtained as in the case of coaxial.

  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 parts is small, variations in part characteristics can be reduced, and further accurate measurement is possible without being affected by disturbances such as temperature changes and noise.

  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.

  Next, a comparison of characteristics (toner density detection) between the example of the present invention and the conventional example will be described. The magnetic permeability sensor (toner sensor) of the present invention example has the configuration shown in FIGS. 1 and 2 described above, and is attached to the developing unit as shown in FIG. 3 described above.

  FIG. 7 is a cross-sectional view showing an example of attaching a conventional magnetic permeability sensor to a developing unit. In FIG. 7, the same or similar parts as those in FIG.

  A differential transformer 51 is provided on the upper surface side of one end of the substrate 10. The differential transformer 51 includes a drive coil to which an alternating oscillation signal is applied, and a differential coil (reference coil and detection coil) coupled to the drive coil. A hole 33 is formed in the partition wall 30 at a position facing the differential transformer 51, and a part (detection coil side) of the differential transformer 51 protrudes from the hole 33, and the detection coil serves as a developer in the developing unit. It comes to touch directly. A connector 3 is formed on the lower surface of the other end portion of the substrate 10 with a part protruding from the other end, and various circuit components 5 are mounted on the lower surface of the central portion of the substrate 10. The magnetic permeability sensor having such a configuration is attached to the recess 31 of the partition wall 30 while being accommodated in the case 21.

  In the conventional magnetic permeability sensor, since the differential transformer 51 protrudes, there is a disadvantage that the shape of the case 21 is complicated, and the configuration is larger than that of the present invention example. Moreover, since the hole 33 is formed in the partition wall 30, the developer may leak.

  FIG. 8 is a graph showing detection sensitivity characteristics of toner density in the present invention example and the conventional example. In FIG. 8, the horizontal axis represents the toner concentration, and the vertical axis represents the output voltage as a result of magnetic permeability detection. Further, (a) and (b) in FIG. 8 show the characteristics of the present invention example and the conventional example, respectively.

  When the present invention example and the conventional example are compared, in the present invention example, the portion where the output voltage fluctuates linearly with respect to the change in the toner density is wider than the conventional example. Therefore, it can be seen that the detection accuracy of the example of the present invention is superior to the detection accuracy of the conventional example.

  FIG. 9 is a graph showing control voltage characteristics for performing offset control in the present invention example and the conventional example. In FIG. 9, the horizontal axis represents the control voltage to be applied, and the vertical axis represents the output voltage. Also, (a) and (b) in FIG. 9 show the characteristics of the inventive example and the conventional example, respectively.

  When the present invention example is compared with the conventional example, the output voltage varies only linearly with respect to the change in the control voltage in the conventional example, whereas in the present invention example, the change in the control voltage occurs. On the other hand, the output voltage varies linearly throughout. Therefore, it can be seen that the accuracy of the offset control in the example of the present invention is superior to the accuracy of the conventional example.

  By the way, in the above-described embodiment, the magnetic permeability sensor 20 is attached to the developing unit in a state of being accommodated in the case 21. However, in the present invention, since there is no possibility that the developer leaks, the case 21 is not necessarily provided. good. 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. 10 is a perspective view showing the configuration of the coil in the first modification. 10, the same or similar members as those in FIGS. 1 and 2 are denoted by the same reference numerals. In FIG. 10, the upper and lower surfaces of the substrate 10 are illustrated opposite to FIG. 1. In the first modification, the first coil 1 and the second coil 2 are formed concentrically on the lower surface of the substrate 10 by, for example, pattern printing of copper foil. A coil is not 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 in the above-described embodiment are mounted.

(Second modification)
FIG. 11 is a cross-sectional view showing the configuration of the magnetic permeability sensor in the second 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 second modification, the first coil 1 and the second coil 2 are formed on the lower surface of the substrate 10 in a coaxial manner 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. 11, the concentric first coil 1 and second coil 2 as 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. 12 is a cross-sectional view showing the configuration of the magnetic permeability sensor in the third modification. 12, 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. 13 is a cross-sectional view showing the configuration of the magnetic permeability sensor in the fourth modification. 13, 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. Note that, unlike the configuration shown in FIG. 13, the first coil 1 and the second coil 2 that form the stacked configuration of the two air-core coils as described above may be formed on the lower surface of the substrate 10.

(5th modification)
FIG. 14 is a cross-sectional view showing the configuration of the magnetic permeability sensor in the fifth modification. 14, 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 coaxial 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.

Embodiment 2
In the magnetic permeability sensor 20 described above, the first coil 1 and the second coil 2 are premised on single-layer coils, but one or both coils may be multilayer coils. FIG. 15 is a perspective view showing another configuration of the magnetic permeability sensor of the present invention. FIG. 16 is a cross-sectional view showing another configuration of the magnetic permeability sensor of the present invention. 15 and 16, the same or similar members as those in FIGS. 1 and 2 are denoted by the same reference numerals. As shown in FIG. 16, the substrate 10 is a four-layer printed circuit board. That is, the substrate 10 includes four wiring layers and three insulator layers 11, 12, and 13. In the second embodiment, the first coil 1 and the second coil 2 are multilayer coils composed of a plurality of layers. The first coil 1 has a two-layer structure of a first subcoil 1a and a second subcoil 1b. Similarly, the second coil 2 has a two-layer structure of a first subcoil 2a and a second subcoil 2b. The first subcoil 1a and the second subcoil 1b of the first coil 1 are connected in series. Similarly, the first subcoil 2a and the second subcoil 2b of the second coil 2 are connected in series. Each subcoil of the first coil 1 and the second coil 2 is formed of a printed wiring pattern. That is, each subcoil of the first coil 1 and the second coil 2 is formed on each wiring layer of the substrate 10. In FIG. 16, if each wiring layer of the substrate 10 is a first layer, a second layer, a third layer, and a fourth layer in order from the top, the first subcoil 2a of the second coil 2 is formed in the first layer. Yes. The second subcoil 2b of the second coil 2 is formed in the second layer. The first subcoil 1a of the first coil 1 is formed on the third layer. The second subcoil 1b of the first coil 1 is formed on the fourth layer. Each of these subcoils is formed, for example, by printing a copper foil pattern on the substrate 10. The outer shapes of the subcoils of the first coil 1 and the second coil 2 are rectangular. Not only that, but the outer shape of each sub-coil may be elliptical as in the first embodiment.

  17A-B are explanations showing the structure of a coil in another configuration of the present invention. FIG. 17A is an explanatory diagram illustrating a connection relationship between coils and through holes provided in each layer. FIG. 17B is an explanatory diagram representing FIG. 17A with a circuit diagram. The arrows with A, B, and C shown in FIGS. 17A and 17B indicate the input / output ends of the first coil 1 and the second coil 2. The two input / output ends of the first coil 1 are A and C, and the two input / output ends of the second coil 2 are B and C. One of the input / output terminals of the first coil 1 and the second coil 2 is common (C).

  H11, h12,..., H61 shown in FIG. 17A are lands of respective layers that are electrically connected to the respective through holes. For example, h11 and h12 are conductive. Also in FIG. 17B, a land code is attached to indicate the correspondence with the land of FIG. 17A. 17A and 17B show two jumper lines J1 and J2. The jumper line J1 connects the land h11 and the land h31. Accordingly, since the land h12 and the land h32 are conducted, both ends (land h12 and land h32) of the second subcoil 2b of the second coil 2 are short-circuited by the jumper wire J1, as shown in FIG. 17B. The operation of the two subcoil 2b becomes invalid. Similarly, the jumper line connects the lands h21 and h51, whereby the land h23 and the land h53 are short-circuited. As a result, the operation of the first subcoil 1a of the first coil 1 becomes invalid.

  18A to 18D are cross-sectional views showing operation patterns of the first coil 1 and the second coil 2. Among the sub-coils, those with hatches indicate that the operation is set to be valid, and those without hatches indicate that the operation is set to be invalid. In FIG. 18B, the first sub-coil 2a of the second coil 2 is set to be effective, and the second sub-coil 2b is set to be invalid. For the first coil 1, the first subcoil 1a and the second subcoil 1b are set to be effective. FIG. 18D is the setting shown in FIG. 17, and the operation of the first subcoil 1 a of the first coil 1 and the second subcoil 2 b of the second coil 2 is set to be invalid by two jumper wires.

  FIG. 19 is a list showing the relationship between the coil operation pattern and jumper wires. In FIG. 19, a pattern row indicates an operation pattern. The operation patterns A, B, C, and D correspond to FIGS. 18A, 18B, 18C, and 18D, respectively. One jumper line and two jumper lines indicate the setting of the jumper lines. The operation pattern D corresponds to the setting shown in FIG. In the operation pattern D, the jumper line 1 indicates that the land h11 and the land h31 are connected. The jumper line 2 indicates that the land h21 and the land h51 are connected.

  Next, the relationship between the coil operation pattern and the sensitivity of the magnetic permeability sensor 20 will be described. As described above, in the magnetic permeability sensor 20, the first coil 1 and the second coil 2 are arranged so that the distance from the object to be detected is different. This is because the coil closer to the object to be detected uses the property that it is more affected by the change in magnetic permeability than the coil farther away. Then, the temporal changes in the magnetic permeability obtained from the first coil 1 and the second coil 2 are compared, and the change in the magnetic permeability of the object to be detected is detected based on the magnitude of the two changes. Thereby, high accuracy is ensured as compared with the case where the magnetic permeability can be detected with a single coil. For this reason, the detection sensitivity of the magnetic permeability sensor 20 increases as the difference in distance between the first coil 1 and the second coil 2 from the object to be detected increases and decreases as the distance decreases.

  From the above, in the operation pattern shown in FIG. 18, the operation pattern D (FIG. 18D) in which the distance between the first coil 1 and the second coil 2 is the largest has the highest sensitivity. In addition, the operation pattern A in which the distance between the first coil 1 and the second coil 2 is the smallest has the lowest sensitivity. In addition, the sensitivity of the operation pattern B and the operation pattern C that are in the above intermediate state is also intermediate. Note that the distance between the first coil 1 and the second coil 2 is a distance in the vertical direction of FIG. 18 and is a distance between the centers of the two coils. That is, when the operation of the two subcoils is enabled, the middle of the two subcoils is one end of the distance measurement point.

  FIG. 20 is a graph showing the relationship between the detected magnetic permeability and the sensor output in the magnetic permeability sensor 20. The horizontal axis of the graph shown in FIG. 20 is magnetic permeability, and the unit is H / m. The vertical axis represents the sensor output voltage, and the unit is V. The 2nd, 3rd, and 4th layers in the legend indicate the number of subcoils for which the operation is enabled. The fourth layer shows the operation pattern A, the third layer shows the operation patterns B and C, and the second layer shows the operation pattern D. The sensitivity of the magnetic permeability sensor 20 is represented by the slope of the graph. The steeper slope, that is, the greater the absolute value of the slope, the higher the sensitivity. The graph shown in FIG. 20 is based on the above description, and the absolute value of the inclination of the second layer (operation pattern D) is the largest, and the absolute value of the inclination of the four layers (operation pattern A) is the smallest. The absolute values of the inclinations of the three layers (operation patterns B and C) are intermediate.

  Embodiment 2 has the following effects. By switching the validity / invalidity of the operation of the subcoils constituting the first coil 1 and the second coil 2, the sensitivity of the magnetic permeability sensor can be switched.

  Further, since the first coil 1 is composed of the two subcoils 1a and 1b, when the two subcoils 1a and 1b are used, the amount of inductance of the first coil 1 is increased. Will improve. The same applies to the second coil 2.

  By forming the subcoil constituting the first coil 1 and the second coil 2 with a printed wiring pattern, it can be formed simultaneously with the circuit pattern constituting the substrate 10. Thereby, it is not necessary to prepare the coil as a separate body and attach it to the substrate, and the number of assembly steps can be reduced. At the same time, the thickness of the coil itself can be made substantially zero. That is, by forming the first coil 1 and the second coil 2, the thickness of the substrate 10 does not increase. In addition, since the outer shapes of the first coil 1 and the second coil 2 are rectangular, it is possible to effectively utilize the coil installation area on the flat rectangular substrate 10. In addition, although the 1st coil 1 and the 2nd coil 2 were each made into two layers, it is good not only that but the 1st coil 1 and the 2nd coil 2 may be made into three or more layers. The number of layers of the first coil 1 and the second coil 2 may not be the same. For example, the first coil 1 may have three layers and the second coil 2 may have two layers. The first coil 1 may be a single layer and the second coil 2 may be three layers.

  In the present invention, the first coil and the second coil may be covered with an electrostatic shield. The coil described in the present invention uses an air-core coil. If there is a coil having a dielectric constant close to the coil, 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 invention, 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 may cause a measurement error in the magnetic permeability sensor. Therefore, it is necessary to provide a shield member that takes measures against eddy currents into consideration.

  21A to 21C are plan views showing a configuration of a shield member suitable for the magnetic permeability sensor of the present invention. In the example shown in FIG. 21A, 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. 21B, 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. 21C 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. 21C, since the shield member 63 is provided on the same plane as the coil 60, the magnetic permeability sensor can be made thinner. The shielding effect is small.

  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.

  21A to 21C illustrate a case where a shield member is provided in the magnetic permeability sensor 20 of the first embodiment. In the second embodiment, a shield member may be provided similarly.

Embodiment 3
The substrate 10 constituting the magnetic permeability sensor 20 in the first and second embodiments is a glass composite substrate, a glass epoxy substrate, or the like. Therefore, the magnetic permeability sensor 20 can be mounted only on a flat surface. In the third embodiment, a coil serving as a sensor unit is formed of a flexible printed circuit board (FPC). Thereby, the sensor part of the magnetic permeability sensor can be attached to the curved surface. Specifically, it can be fixed to the curved portion of the developer tank.

  FIG. 22 is an exploded perspective view showing a sensor unit 200 of a magnetic permeability sensor according to another configuration of the present invention. The sensor unit 200 of the magnetic permeability sensor includes a first coil 201, a base body 202, and a second coil 203. The first coil 201 and the second coil 203 are configured as an FPC. The base body 202 is disposed between the first coil 201 and the second coil 203. The base body 202 plays a role of arranging the first coil 201 and the second coil 203 so that the distance from the object to be detected is different. The base 202 is formed of an elastic material such as nylon or polyester. Further, the base body 202 may be formed of a hard material if a material that can be molded along the mounting surface of the sensor unit 200 at the time of molding is used. For example, the base body 202 may be formed of hard plastic. The thickness of the base body 202 is, for example, 0.5 to 1.0 mm.

  FIGS. 23A and 23B are explanatory diagrams illustrating a method for assembling the sensor unit 200. FIG. FIG. 23A shows a case where the base body 202 is formed of an elastic material. In this case, the 1st coil 201 and the 2nd coil 203 are affixed on both surfaces of the base | substrate 202 with a double-sided tape or an adhesive agent, respectively. The assembled sensor unit 200 is deformed and attached along the curved surface of the developer tank.

  FIG. 23B shows a case where the base body 202 is formed of a hard material. In this case, the first coil 201 and the second coil 203 are attached to both surfaces of the base 202 with a double-sided tape or an adhesive while being deformed along the curved surface of the base 202. The assembled sensor unit 200 is attached to the curved surface of the developer tank. Since the curvature of the curved surface of the substrate 202 is a value along the curved surface of the developer tank, which is the mounting surface, it can be mounted without being deformed as it is. The sensor unit 200 is attached with a double-sided tape, an adhesive, or the like regardless of the material of the base body 202. However, the present invention is not limited to this, and other attachment methods may be adopted as long as attachment is possible so that there is no gap between the sensor unit 200 and the attachment surface.

  FIG. 24 is a cross-sectional view showing a mounting state of the sensor unit 200. The sensor unit 200 is attached to the curved attachment surface of the developer tank case 81. The sensor unit 200 can be mounted along the mounting surface. In the sensor unit 200, the wiring 210 to the first coil 201 and the second coil 203 is also composed of FPC. The circuit portions 220 such as the first oscillation circuit 6 and the second oscillation circuit 7 are formed on a glass / epoxy substrate or the like. The circuit part 220 is provided on a part of the case 81 of the developer tank with a flat attachment surface, and is attached to the attachment surface.

  In the developer tank shown in FIG. 24, the developer is stirred by the stirring blade 821 provided in the stirring paddle 82 provided in the vicinity of the magnetic roller 83, and the magnetic permeability is measured. Therefore, as shown in FIG. 24, it is desirable that the sensor unit 200 is mounted so as to face the stirring blade 821 and be as uniform as possible with a distance from the stirring blade 821 as small as possible.

  Embodiment 3 has the following effects. Since the first coil 201 and the second coil 203 constituting the sensor unit 200 of the magnetic permeability sensor are formed by FPC, it can be attached to the mounting surface which is a curved surface without a gap. Thereby, the measurement error of the magnetic permeability sensor can be reduced. By reducing the measurement error, the developer concentration in the developer tank can be measured more accurately.

  In the third embodiment, the first coil 1 and the second coil 2 are single-layer coils, but may have the same configuration as that of the second embodiment. That is, each of the subcoils constituting the first coil 1 and the second coil 2 is formed by FPC. A multilayer coil can be formed by providing and laminating a substrate between the formed subcoils.

  The disclosed embodiments should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 1st coil 1a 1st subcoil 1b 2nd subcoil 2 2nd coil 2a 1st subcoil 2b 2nd subcoil 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 Unit 42 calculation unit 43 conversion unit 200 sensor unit 201 first coil 202 base 203 second coil

Claims (7)

In a magnetic permeability sensor for detecting the magnetic permeability of an object to be detected,
A first oscillating circuit that oscillates including a first coil that receives magnetism from the object to be detected, and includes a plurality of layers that can change the operation of each layer to be effective or invalid;
A second oscillation circuit comprising a plurality of layers capable of changing the operation of each layer to be effective or invalid, and oscillating including a second coil that receives magnetism from the detected object;
Measuring means for measuring an oscillation frequency in each of the first oscillation circuit and the second oscillation circuit;
Calculating means for calculating a difference between oscillation frequencies measured by the measuring means;
A magnetic permeability sensor comprising: conversion means for converting the difference calculated by the calculation means into magnetic permeability.   The magnetic permeability sensor according to claim 1, wherein the first coil and the second coil have a terminal to which a short-circuit wire for invalidating the operation of each layer can be connected.   The magnetic permeability sensor according to claim 1, wherein each of the first coil and the second coil is a two-layer coil.   The said measurement means is comprised so that the oscillation frequency in the said 1st oscillation circuit and the oscillation frequency in the said 2nd oscillation circuit may be measured alternately, The any one of Claim 1 to 3 characterized by the above-mentioned. The magnetic permeability sensor described in 1.   5. The magnetic permeability sensor according to claim 1, wherein the first coil and the second coil are arranged coaxially. 6.   6. The magnetic permeability sensor according to claim 1, wherein components of the first oscillation circuit and the second oscillation circuit are common except for the first coil and the second coil. . In the magnetic permeability detection method for detecting the magnetic permeability of the object to be detected,
A first coil composed of a plurality of layers capable of changing the operation of each layer effectively or invalidally and a second coil composed of a plurality of layers capable of changing the operation of each layer validly or invalidally with different distances from the detected object. Place and
Measure 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, respectively.
Calculate the difference between the measured oscillation frequencies,
A magnetic permeability detection method, wherein the calculated difference is converted into a magnetic permeability.

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