JP2020101412A - Permeability sensor - Google Patents

Abstract

To provide a permeability sensor which detects changes in permeability of an object to be detected with high accuracy, despite its simple constitution, by restricting an influence of temperature fluctuation.SOLUTION: The permeability sensor comprises: a first coil and a second coil; a first oscillation circuit including the first coil and oscillating; a second oscillation circuit including the second coil and oscillating; a measurement part measuring the number of oscillation pulses in each of the first oscillation circuit and the second oscillation circuit; an adjustment part adjusting a measurement time of the number of oscillation pulses in the first oscillation circuit measured by the measurement part, and a measurement time of the number of oscillation pulses in the second oscillation circuit measured by the measurement part; a calculation part calculating a difference between the numbers of oscillation pulses measured by the measurement part; and a conversion part converting the difference calculated by the calculation part to permeability. The permeability sensor has: a first board including the first oscillation circuit excluding the first coil, the second oscillation circuit excluding the second coil, the measurement part, the adjustment part, the calculation part, the conversion part, and the first coil and the second coil; and a second board having on its front and rear surfaces the first coil and the second coil. The first board and the second board are arranged on different planes.SELECTED DRAWING: Figure 2

Description

The present invention relates to a magnetic permeability sensor that detects magnetic permeability of an object to be detected.

An electrophotographic copying machine or printer is equipped with a toner sensor for magnetically detecting the density or the remaining amount of toner in a developing unit used for developing an electrostatic image formed on a photoconductor. .. An example of such a toner sensor is disclosed in Japanese Unexamined Patent Application Publication No. 2004-242242. The sensor disclosed in Patent Document 1 uses four coils and detects the toner density by a differential transformer method.

Further, in Patent Document 2, a first oscillation circuit that causes a phase shift in an oscillating wave according to an inductance change of a first detection coil, and a phase shift in an oscillating wave according to an inductance change of a second detection coil. A technique is disclosed that includes a second oscillation circuit and detects the state of metal by obtaining the difference between the phase shifts of the two.

JP 2001-165910 A JP, 2009-31257, A Japanese Patent No. 3900442

The toner sensor of Patent Document 1 employs 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, so that the toner is separated from the drive coil and the differential coil. It is difficult to completely eliminate the effect on the coil. Further, when the oscillation circuit is configured to include the flat coil, there is little change in the coupling degree of the inductance when the magnetic body approaches, and it is difficult to operate such a flat coil in an analog circuit.

Patent Document 3 discloses a technique that has a drive coil and a differential coil wound around a bobbin, uses the coils as a reference coil and a detection coil, and detects the toner concentration from the differential output between the detection coil and the reference coil. Has been done. Also in the toner sensor of Patent Document 3, as in Patent Document 1, since the influence of the toner affects both coils, it is difficult to completely eliminate the influence of the toner on the drive coil and the differential coil. Further, the magnetic flux generated in one coil may affect the other coil. Further, when the coil is formed by winding the wire around the bobbin, there is a risk that the number of steps is increased when the coil is mass-produced and the cost is increased.

The technique described in Patent Document 1 or Patent Document 3 is designed to detect the magnetic permeability according to changes in the inductance of a plurality of coils, but a large number of circuit components are used for this detection. There is a problem in that highly accurate detection cannot be achieved because the circuit components have characteristic variations and are easily affected by the detection environment such as temperature.

In Patent Document 2, since a coil wound around a high magnetic permeability material is used and the oscillation frequency is low, the time for obtaining the same resolution can be shortened. Therefore, the method of detecting the phase shift is advantageous, but the flat coil Is advantageous. However, in Patent Document 2, the oscillating waves from the first oscillating circuit and the second oscillating circuit are measured, the time when the measured value reaches a predetermined value is measured, and the accumulated oscillating wave is accumulated based on the measured time. Since the phase shift is detected, there is a problem that the detection process is complicated. Further, Patent Document 2 is a technique for magnetically detecting the torque of the rotating shaft, and is not disclosed or suggested to be applied to a sensor for detecting the toner concentration.

In a sensor that detects magnetic permeability using two coils, the two coils are arranged in a horizontal direction in order to prevent the other coil from being affected by the magnetic flux generated in one coil. The configuration is general. Specifically, one coil is placed near the object to be detected (magnetic material) to make it more susceptible to changes in magnetic permeability, and the other coil is placed away from the object to be detected (magnetic material). Makes it less susceptible to changes in permeability. According to such arrangement of the plurality of coils in the horizontal direction, there is a problem that the sensor cannot be downsized.

The present invention has been made in view of such circumstances, and even with a small and simple structure, it is possible to suppress the influence of temperature fluctuations and detect the change in the magnetic permeability of the object to be detected with high accuracy. The purpose is to provide.

A magnetic permeability sensor according to the present invention is a magnetic permeability sensor for detecting magnetic permeability of an object to be detected, comprising: a first oscillating 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, a measurement unit that measures the number of oscillation pulses in each of the first oscillation circuit and the second oscillation circuit, and oscillation in the first oscillation circuit by the measurement unit. An adjustment unit that adjusts at least one of a pulse number measurement time and an oscillation pulse number measurement time in the second oscillation circuit by the measurement unit, and a calculation unit that calculates a difference between the oscillation pulses measured by the measurement unit. And a conversion unit that converts the difference calculated by the calculation unit into magnetic permeability, the first oscillation circuit excluding the first coil, the second oscillation circuit excluding the second coil, the measurement unit, and the adjustment unit. Section, the calculation section and the conversion section, and a second substrate having the first coil and the second coil on its front and back surfaces, and the first substrate and the second substrate are on different planes. It is arranged in. Here, "to receive magnetism" means to be magnetically coupled to the object to be detected.

In the present invention, the number of oscillation pulses means the number of pulses oscillated in each oscillation circuit within a predetermined measurement time at each oscillation frequency. Therefore, if the measurement times are the same, the difference in the number of oscillation pulses can be regarded as the same as the difference in the oscillation frequency.

In the magnetic permeability sensor of the present invention, the number of oscillation pulses of the second oscillating circuit including the second coil arranged near the object to be detected and the second coil near the object to be detected are The number of oscillation pulses of the first oscillation circuit including the first coil arranged at different distances is measured by the measurement unit. The calculation unit calculates the difference between the two oscillation pulse numbers measured by the measurement unit, and the conversion unit converts the difference calculated by the calculation unit into magnetic permeability. When the magnetic permeability of the object to be detected increases, the inductance of the coil increases, and the number of oscillation pulses of the oscillation circuit including the coil decreases. Here, since the amount of change in the inductance of the coil closer to the object to be detected increases according to the change in magnetic permeability, the number of oscillation pulses in the oscillation circuit also increases. Therefore, the magnetic permeability can be detected from the difference in the number of oscillation pulses by the respective oscillation circuits by using the two coils arranged at different distances from the object to be detected.

Here, at least one of the first measurement time when the number of oscillation pulses of the first oscillation circuit is measured and the second measurement time when the number of oscillation pulses of the second oscillation circuit is measured is adjusted by the adjustment unit. Specifically, when the distance from the object to be detected is shorter in the second coil than in the first coil, the inductance of the second coil is larger than the inductance of the first coil, and the number of oscillation pulses of the second oscillation circuit is increased. Since the number of oscillation pulses is smaller than that of the first oscillation circuit, the second measurement time is adjusted to be relatively longer than the first measurement time and the number of oscillation pulses is adjusted to be the same. By performing such adjustment, the influence of temperature fluctuation during actual detection is reduced.

At this time, flat coils such as coils formed by patterning printing on the substrate can be used as the two coils. Compared to the case where a coil is formed by winding a wire around a non-magnetic bobbin or the like, it is possible to reduce the cost when a large number of coil parts are produced. In the case of a coil having a small inductance such as a flat coil, the oscillation frequency is high (the number of pulses within a fixed time is large). As a result, the clock frequency of the computer within a fixed time is smaller than the number of oscillation pulses, so that the measurement time for obtaining the same resolution can be shortened when measuring the number of oscillation pulses. In addition, the series of processes of measuring the number of oscillation pulses, calculating the difference in the number of oscillation pulses, and returning the difference to the magnetic permeability can be performed by software using a microcomputer, etc., and the number of parts can be reduced. Is less likely to be affected and the detection accuracy is improved.

In the magnetic permeability sensor according to the present invention, the measuring unit is configured to alternately measure the number of oscillation pulses in the first oscillation circuit and the number of oscillation pulses in the second oscillation circuit. To do.

In the magnetic permeability sensor of the present invention, the measurement of the number of oscillation pulses in the first oscillation circuit and the measurement of the number of oscillation pulses in the second oscillation circuit are alternately performed while switching. Therefore, since the other oscillation circuit does not oscillate when the number of oscillation pulses in one oscillation circuit is measured, the measured value of the number of oscillation pulses in one oscillation circuit is not affected by the oscillation in the other oscillation circuit. Therefore, the number of oscillation pulses can be accurately measured in both oscillation circuits, and the magnetic permeability detection accuracy is improved.

In the magnetic permeability sensor according to the present invention, the first coil and the second coil are coaxially arranged.

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

In the magnetic permeability sensor according to the present invention, 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, the first oscillator circuit and the second oscillator circuit have the same components other than the first coil and the second coil. Therefore, the number of oscillation pulses measured by each of the first oscillation circuit and the second oscillation circuit is not affected by the characteristic variation due to different constituent members other than the coil, and an accurate value is measured. Therefore, the accuracy of detecting the magnetic permeability is increased.

The magnetic permeability sensor according to the present invention acquires a storage unit that stores an initial measurement time for each of a plurality of sensitivities and a selection signal that selects one from the plurality of sensitivities, and supports the sensitivities selected by the acquired selection signals. A first measurement time for measuring the number of oscillation pulses of the first oscillation circuit, and a second measurement for measuring the number of oscillation pulses of the second oscillation circuit. An initial setting unit for setting a measurement time, and the calculation unit obtains the number of oscillation pulses obtained by the measurement unit measuring the first oscillation circuit at the first measurement time, and the second measurement. It is characterized in that the measuring unit calculates the difference in the number of oscillation pulses obtained by measuring the second oscillation circuit with respect to time.

The magnetic permeability sensor of the present invention can adjust the sensitivity by a selection signal. It is possible to support multiple sensitivities without changing the hardware configuration.

In the magnetic permeability sensor according to the present invention, the adjustment unit adjusts at least one of the first measurement time set by the initial setting unit and the second measurement time, and the measurement unit is the adjustment unit. The number of oscillation pulses is measured during the first measurement time and the second measurement time based on the adjustment result.

In the magnetic permeability sensor of the present invention, at least one of the first measurement time when the number of oscillation pulses of the first oscillation circuit is measured and the second measurement time when the number of oscillation pulses of the second oscillation circuit is measured is adjusted by the adjusting unit. Adjust according to. Specifically, when the distance from the object to be detected is shorter in the first coil than in the second coil, the inductance of the first coil is larger than the inductance of the second coil, and the number of oscillation pulses of the first oscillation circuit is Since the number of oscillation pulses is smaller than the number of oscillation pulses of the second oscillation circuit, the first measurement time is adjusted to be relatively longer than the second measurement time and the number of oscillation pulses is adjusted to be the same. By performing such adjustment, the influence of temperature fluctuation during actual detection is reduced.

At this time, flat coils such as coils formed by patterning printing on the substrate can be used as the two coils. Compared to the case where a coil is formed by winding a wire around a non-magnetic bobbin or the like, it is possible to reduce the cost when a large number of coil parts are produced. In the case of a coil having a small inductance such as a flat coil, the oscillation frequency is high (the number of pulses within a fixed time is large). As a result, the clock frequency of the computer within a fixed time is smaller than the number of oscillation pulses, so that the measurement time for obtaining the same resolution can be shortened when measuring the number of oscillation pulses. In addition, the series of processes of measuring the number of oscillating pulses, calculating the difference in the number of oscillating pulses, and converting the difference into magnetic permeability can be performed by software using a microcomputer, etc., and the number of parts can be reduced. Is less likely to be affected and the detection accuracy is improved.

In the magnetic permeability sensor according to the present invention, the adjusting unit adjusts the second measurement time.

In the present invention, it is possible to operate with the first oscillation circuit as a reference.

A magnetic permeability sensor according to the present invention is a magnetic permeability sensor for detecting magnetic permeability of an object to be detected, comprising: a first oscillating 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, a measurement unit that measures the number of oscillation pulses in each of the first oscillation circuit and the second oscillation circuit, and oscillation in the first oscillation circuit by the measurement unit. A first adjustment unit that adjusts the measurement time so that the number of pulses becomes a predetermined value, a measurement time of the oscillation pulse number in the first oscillation circuit that is adjusted by the first adjustment unit, and an oscillation in the second oscillation circuit. A second adjustment unit that adjusts at least one of the pulse number measurement times based on each oscillation pulse number measured under a predetermined environment, and measurement after adjustment by the first adjustment unit and the second adjustment unit. A first calculation unit that includes a calculation unit that calculates a difference in the number of oscillation pulses measured by the measurement unit and a conversion unit that converts the difference calculated by the calculation unit into magnetic permeability in terms of time; An oscillation circuit, a second oscillation circuit excluding the second coil, a first substrate including the measurement unit, the adjustment unit, the calculation unit, and the conversion unit, and the first coil and the second coil on the front and back surfaces thereof. A second substrate is provided, and the first substrate and the second substrate are arranged on different planes.

In the present invention, the magnetic permeability can be detected by using the two coils (the first coil and the second coil) based on the difference between the numbers of oscillation pulses generated by the respective oscillation circuits.

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

According to the present invention, the area required for arranging the coils can be small, and the magnetic permeability sensor can be downsized.

The magnetic permeability sensor according to the present invention is characterized in that constituent members of the first oscillation circuit and the second oscillation circuit are common except for the first coil and the second coil.

According to the present invention, the number of oscillation pulses measured by each of the first oscillation circuit and the second oscillation circuit is not affected by the characteristic variation due to different constituent members other than the coil, and an accurate value is measured. Therefore, the accuracy of detecting the magnetic permeability is increased.

The magnetic permeability sensor according to the present invention is characterized by adjusting the measurement time of the number of oscillation pulses in the second oscillation circuit.

In the present invention, it is possible to operate with the first oscillation circuit as a reference.

In the magnetic permeability sensor according to the present invention, the calculating unit may adjust the measurement time by the first adjusting unit and the second adjusting unit, and then, in a predetermined environment, the measuring unit may adjust the first adjusting unit and the second adjusting unit. The difference in the number of oscillation pulses measured in the measurement time after adjustment by the second adjusting unit is calculated, and the calculated difference is used to determine the number of oscillation pulses in the first oscillation circuit and the number of oscillation pulses in the second oscillation circuit. It is characterized in that it further comprises a third adjusting unit for adjusting at least one of them.

In the present invention, the difference between the oscillation pulse numbers measured in the measurement time after the adjustment by the first adjusting unit and the second adjusting unit is calculated, and the calculated difference is the oscillation pulse number in the first oscillation circuit, and Since at least one of the number of oscillation pulses in the second oscillation circuit is adjusted, it is possible to make the difference in magnetic permeability 0 in a predetermined environment which should be the center of measurement.

In the magnetic permeability sensor according to the present invention, the third adjusting unit adjusts the number of oscillation pulses in the second oscillating circuit.

In the present invention, it is possible to operate with the first oscillation circuit as a reference.

The magnetic permeability sensor according to the present invention is characterized in that it is realized by using a reference magnetic plate under a predetermined environment.

In the present invention, by using the reference magnetic plate, it is possible to set a predetermined magnetic permeability at the center of the measurement range.

The magnetic permeability sensor according to the present invention acquires a storage unit that stores an initial measurement time for each of a plurality of sensitivities and a selection signal that selects one from the plurality of sensitivities, and supports the sensitivities selected by the acquired selection signals. A first measurement time for measuring the number of oscillation pulses of the first oscillation circuit, and a second measurement for measuring the number of oscillation pulses of the second oscillation circuit. An initial setting unit for setting a measurement time, and the calculation unit obtains the number of oscillation pulses obtained by the measurement unit measuring the first oscillation circuit at the first measurement time, and the second measurement. It is characterized in that the measuring unit calculates the difference in the number of oscillation pulses obtained by measuring the second oscillation circuit with respect to time.

In the magnetic permeability sensor of the present invention, the sensitivity can be adjusted by the selection signal.

In the magnetic permeability sensor according to the present invention, the measuring unit is configured to alternately measure the number of oscillation pulses in the first oscillation circuit and the number of oscillation pulses in the second oscillation circuit. And

In the present invention, since the other oscillation circuit does not oscillate when measuring the number of oscillation pulses in one oscillation circuit, the measured value of the number of oscillation pulses in one oscillation circuit is Not affected. Therefore, the number of oscillation pulses can be accurately measured in both oscillation circuits, and the magnetic permeability detection accuracy is improved.

According to the present invention, it is possible to detect the magnetic permeability of an object to be detected with high accuracy by suppressing the influence of temperature fluctuations even with a small and simple structure.

It is a perspective view which shows the example of a magnetic permeability sensor. It is an exploded perspective view showing an example of composition of a magnetic permeability sensor. It is a perspective view showing an example of composition of an assembled coil. It is a top view which shows the formation example of a coil. It is a partial cross-sectional view of a configuration example of a magnetic permeability sensor. FIG. 4 is a cross-sectional view showing an example of attachment of a magnetic permeability sensor to a developing unit. It is a block diagram which shows the functional structure of a magnetic permeability sensor. It is a circuit diagram which shows one structural example of a magnetic permeability sensor. 6 is a timing chart for explaining the operation of the magnetic permeability sensor. It is a flow chart which shows the example of a processing procedure of measurement time adjustment processing. It is a flow chart which shows the example of a processing procedure of initial amendment processing. It is a flow chart which shows the example of a processing procedure of amendment processing. It is a flow chart which shows the example of a processing procedure of forced correction processing. 7 is a flowchart illustrating an example of a procedure of a forced correction process after the magnetic permeability correction process is performed. 6 is a graph showing toner density detection sensitivity characteristics of the present invention example and the conventional example. 7 is a graph showing control voltage characteristics for performing offset control in the example of the present invention and the conventional example. It is a block diagram showing other examples of functional composition of a magnetic permeability sensor. 6 is a graph showing an example of the relationship between the detected toner density and the output voltage for each mode. It is a chart figure which shows a sensitivity selection method. It is a fragmentary sectional view of the example of composition of a magnetic permeability sensor. It is a fragmentary sectional view of the example of composition of a magnetic permeability sensor. It is a fragmentary sectional view of the example of composition of a magnetic permeability sensor.

(Embodiment 1)
Hereinafter, a specific description will be given based on the drawings illustrating the embodiments. FIG. 1 is a perspective view showing an example of a magnetic permeability sensor. FIG. 2 is an exploded perspective view showing a configuration example of the magnetic permeability sensor.

The magnetic permeability sensor 10 has a rectangular parallelepiped shape. The magnetic permeability sensor 10 includes a cover 11, a case 12, and a connector 15. The magnetic permeability sensor 10 is provided with positioning holes 16 and 123. The cover 11 has a box shape with one surface opened. The cover 11 includes a through hole 111 and a through hole 112. The cover 11 is made of resin.

The case 12 has a box shape with one surface opened. The case 12 is longer than the cover 11 in the longitudinal direction. The case 12 includes a housing 121, a through hole 122, a positioning hole 123, and a plurality of recesses 124. The housing 121 has a cylindrical shape. The accommodating portion 121 projects substantially vertically from the wide surface of the case 12. An annular portion 1221 is provided on the circumferential portion of the through hole 122. The recess 124 has a rectangular shape. A control board 13 (first board) to which the assembled coil 14 is fixed is housed inside the case 12.

The control board 13 has a rectangular shape. On the upper surface of the central portion of the control board 13, an electronic chip 4 including a microcomputer that performs various processes described later is mounted. Further, a circuit component 5 is mounted near the electronic chip 4. The circuit component 5 includes a capacitor and the like for forming an oscillation circuit. The control board 13 has a through hole 131. A connector 15 is arranged at one end of the control board 13 in the longitudinal direction. The connector 15 has one end of a pin fixed to the control board 13 by, for example, soldering. An assembly coil 14 is arranged at the other end of the control board 13. The assembled coil 14 is electrically connected to the control board 13 via three lead wires 17.

FIG. 3 is a perspective view showing a configuration example of the assembled coil. FIG. 4 is a plan view showing an example of forming a coil. The assembled coil 14 includes a substrate 141 (second substrate), a pedestal 142, and three terminals 143. The substrate 141 has a disc shape, and the substrate 141 is a printed circuit board (PCB: Printed Circuit Board). Coils are formed on the front and back surfaces of the substrate 141. The first coil 1 is formed on one surface of the substrate 141, and the second coil 2 is formed on the other surface by patterning printing. The board 141 is provided with a through hole for conducting the winding start 11 of the first coil 1 and the winding start 21 of the second coil 2. The substrate 141 is provided with lands that are electrically connected to the winding end 12 of the first coil 1 and the winding end 22 of the second coil 2.

A pedestal 142 is placed on the surface on which the first coil 1 is formed. The pedestal 142 has a rectangular shape. The pedestal 142 is formed of an insulating material such as resin. Three terminals 143 are provided on a side portion in the longitudinal direction of the pedestal 142 at predetermined intervals so that a part of the terminal 143 projects from the pedestal 142. The terminal 143 is connected to the coil by soldering, for example. Of the terminals 143, the terminal 143 at the center of the pedestal in the longitudinal direction is connected to the land at the center of the substrate 141. The land is a land of a through hole that conducts the winding start 11 of the first coil 1 and the winding start 21 of the second coil 2. A terminal 143 at one longitudinal end of the pedestal is connected to a land that is electrically connected to the winding end 12 of the first coil 1. The terminal 143 at the other end in the longitudinal direction of the pedestal is connected to the land that is electrically connected to the winding end 22 of the second coil 2. The connection between each terminal 143 and the corresponding land is performed by, for example, soldering. The three terminals 143 are connected to the three lead wires 17 extending from the control board 13, respectively. The connection between the terminal 143 and the lead wire 17 is performed, for example, by soldering.

FIG. 5 is a partial cross-sectional view of a configuration example of the magnetic permeability sensor. FIG. 5 is a cross section taken along a cross sectional line parallel to the longitudinal direction. The pedestal 142 is used to mount the lead wire 17 and the terminal 143 on the substrate 141, and the terminal 143 and the lead wire 17 penetrate through the pedestal 142 (dotted line portion). In other words, the pedestal 142 is formed so as to hold the lead wire 17 and the terminal 143. As the lead wire 17, for example, a copper single wire bent is used. In the example shown in FIG. 5, the lead wire 17 whose one end is connected to the control board 13 is bent after penetrating the pedestal 142. The other end of the lead wire 17 is connected to the terminal 143 mounted on the upper surface of the coil.

The magnetic permeability sensor 10 configured as described above is assembled as follows, for example. The pedestal 142, the terminal 143, and the lead wire 17 whose one end is connected to the terminal are prepared as an integrated component. A substrate 141 on which the first coil 1 and the second coil 2 are formed, a control substrate 13 on which an electronic chip 4, a circuit component 5 and a connector 15 are mounted, a case 12 and a cover 11 are prepared. The terminals of the one-piece component are soldered to the lands of the board 141. The assembled coil 14 to which the lead wires 17 are connected is completed. The assembled coil 14 is fixed to the housing portion 121 of the case 12. The control board 13 is placed in a case, and the other end of the lead wire 17 is soldered to the control board 13. The cover 11 is attached to the case 12. Inside the cover 11, there is provided a protrusion (not shown) corresponding to the recess 124. The cover 11 is fixed to the case 12 by fitting the concave portion 124 of the case 12 and the convex portion of the cover 11 together. The magnetic permeability sensor 10 is assembled with the above configuration.

FIG. 6 is a sectional view showing an example of attachment of the magnetic permeability sensor to the developing unit. In FIG. 6, reference numeral 30 is a partition wall that partitions the inside and outside of the developing unit. A recess 31 is formed in the partition 30, and the magnetic permeability sensor 10 is attached to the developing unit while being housed in the case 12 so as to be fitted into the recess 31.
A hole 33 is formed in the partition wall 30 at a position facing the housing portion 121, and a part of the housing portion 121 projects from the hole 33.
The tip of the connector 15 projects from the cover 11.

At this time, the magnetic permeability sensor 10 is attached to the partition wall 30 of the developing unit so that the lower surface side of the magnetic permeability sensor 10 shown in FIGS. Therefore, the second coil 2 is arranged at a position closer to the inside of the developing unit than the first coil 1, in other words, a position closer to the developer in the developing unit. The recess 31 to which the magnetic permeability sensor 10 is attached is sealed with a seal 32.

FIG. 7 is a block diagram showing a functional configuration of the magnetic permeability sensor 10 of the present invention. 7, parts that are the same as or similar to those in FIGS. 1 to 5 are given the same reference numerals.

The first coil 1 and a part of the circuit component 5 form a first oscillation circuit 6, and the second coil 2 and a part of the circuit component 5 form a second oscillation circuit 7. In the magnetic permeability sensor 10 of the present invention, the first oscillator circuit 6 and the second oscillator circuit 7 share the other constituent members except the first coil 1 and the second coil 2. Therefore, the number of oscillation pulses 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 accuracy of detecting the magnetic permeability is increased.

Also, the electronic chip 4 measures the oscillation pulse number in each of the first oscillation circuit 6 and the second oscillation circuit 7, and the measurement time of the oscillation pulse number in the first oscillation circuit 6 in the measurement unit 41 ( An adjustment unit (first adjustment unit, second adjustment unit, third adjustment unit) 42 for adjusting at least one of the oscillation pulse number measurement time (second measurement time) in the second oscillation circuit 7; It functionally has a calculation unit 43 that calculates the difference in the number of oscillation pulses measured by the measurement unit 41, and a conversion unit 44 that converts the difference calculated by the calculation unit 43 into magnetic permeability.

Here, the first adjustment unit adjusts the measurement time so that the number of oscillation pulses in the first oscillation circuit becomes a predetermined value. The second adjustment unit determines at least one of the measurement time of the oscillation pulse number in the first oscillation circuit and the measurement time of the oscillation pulse number in the second oscillation circuit based on each oscillation pulse number measured under a predetermined environment. adjust. After adjusting the measurement time by the first adjusting unit and the second adjusting unit, the third adjusting unit measures the difference in the number of oscillated pulses after adjustment under a predetermined environment, and then oscillates in the first oscillating circuit from the difference. At least one of the number of pulses and the number of oscillation pulses in the second oscillator circuit is adjusted.

FIG. 8 is a circuit diagram showing a configuration example of the magnetic permeability sensor 10 of the present invention. In FIG. 8, the coil L1 and the coil L2 correspond to the above-mentioned first coil 1 and second coil 2, 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 also grounded via the resistor R3.

The input terminal of the power supply voltage Vdd is connected to the first terminal of the microcomputer U1. The input terminal of the power supply voltage Vdd is connected to the emitter of the transistor Q1 via 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 terminal for grounding is connected to the eighth terminal of the microcomputer U1.

An output terminal for outputting the detection voltage Vout corresponding to the magnetic permeability is connected to the seventh terminal of the microcomputer U1 via the 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 above-described first oscillation circuit 6 (Colpitts oscillation circuit), and the coil L2, the two capacitors C2 and C3, and the transistor Q1 are described above. The second oscillation circuit 7 (Colpitts oscillation circuit) is configured. Then, the first oscillation circuit 6 and the second oscillation circuit 7 are adjusted by the adjustment unit 42 by the switching operation of the microcomputer U1 (the switching operation is performed by the third terminal and the sixth terminal of the microcomputer U1). It is designed to oscillate alternately for each measurement time.

Next, the operation of the magnetic permeability sensor 10 of the present invention will be described. FIG. 9 is a timing chart for explaining the operation of the magnetic permeability sensor 10 of the present invention.

The process of oscillating the first oscillation circuit 6 and measuring the number of oscillation pulses by the measuring unit 41 over the first measurement time adjusted by the adjusting unit 42, and the second adjustment by the adjusting unit 42. The process of oscillating the second oscillation circuit 7 and measuring the number of oscillation pulses by the measuring unit 41 is alternately performed over the measurement time. At this time, as shown in FIG. 9, during the period in which the first oscillation circuit 6 is oscillated and the number of oscillation pulses thereof is measured, the second oscillation circuit 7 is not oscillated and the second oscillation circuit 7 is oscillated to The first oscillation circuit 6 is not oscillated during the period in which the number of oscillation pulses is measured. Therefore, since the number of oscillation pulses is measured without being affected by each other's oscillations, the measurement value is highly accurate.

When the measurement of the number of oscillation pulses for each predetermined time (first measurement time and second measurement time) is completed, the measured number of oscillation pulses (from the first coil 1) in the first oscillation circuit 6 and the second oscillation The difference from the measured oscillation pulse number (from the second coil 2) in the circuit 7 is calculated by the calculation unit 43. Then, the conversion unit 44 converts the calculated difference into magnetic permeability to obtain the amount of change in magnetic permeability. Specifically, the median value of the desired magnetic permeability detection range is set to 0, and the amount of change from the median value is obtained based on the amount of the calculated difference compared with the difference corresponding to this median value. A magnetic permeability sensor (toner sensor) 10 attached to the developing unit detects the toner density.

In the period in which the first oscillation circuit 6 is oscillated and the number of oscillation pulses thereof is measured, the difference between the measured values (for example, A′ and B′) of the first oscillation circuit 6 and the second oscillation circuit 7 before that is calculated. The calculation unit 43 calculates the difference, and the conversion unit 44 converts the calculated difference into the magnetic permeability to obtain the amount of change in the magnetic permeability. Therefore, the change in magnetic permeability occurs at the timing of starting the measurement of the number of oscillation pulses in each oscillation circuit. The quantity is updated sequentially.

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

When the magnetic permeability of the object to be detected becomes large, the inductance of the coil arranged near the object to be detected increases in accordance with the change in the magnetic permeability. As a result, the number of oscillation pulses of the oscillation circuit including the coil is reduced. Here, when two coils are arranged at different distances from the object to be detected, the inductance of each coil increases and the number of oscillation pulses of each oscillation circuit decreases. However, since the coil closer to the object to be detected is more affected by the change in magnetic permeability than the coil farther away, in the above case, the amount of increase in inductance increases and the amount of decrease in the number of oscillation pulses also increases. growing. Therefore, the number of oscillating pulses in the two oscillating circuits including the two coils respectively will be different depending on the degree of change in magnetic permeability. As described above, since there is a correlation between the difference between the two oscillation pulses and the magnetic permeability, the present invention detects the magnetic permeability of the object to be detected based on the difference between the oscillation pulse numbers of the two oscillation circuits. It is possible.

In the magnetic permeability sensor 10 in the above-described embodiment, the first coil 1 corresponds to the coil farther from the object to be detected, and the second coil 2 corresponds to the coil closer to the object to be detected. In the present invention, the coil closer to the object to be detected is the detection coil, and the coil farther from the object is the reference coil.

The developer in the developing unit is a mixture of toner and magnetic material (iron powder). At the time of copying, the toner is attached to the paper and the magnetic substance is hardly attached. Therefore, as the copying process progresses, the amount of toner decreases but the amount of magnetic material hardly changes, so that 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 concentration. In the present invention, since the magnetic permeability of the object to be detected (developer) can be detected as described above, the toner density can be detected based on the detected magnetic permeability of the developer in the developing unit.

Here, the adjustment process of at least one of the first measurement time and the second measurement time in the adjustment unit 42 will be described.

Since the first coil 1 far from the object to be detected and the second coil 2 close to the object to be used have different operating environments, the detection characteristics of the magnetic permeability sensor are easily affected by temperature fluctuations. Further, since the first coil 1 and the second coil 2 are formed on the substrate 141 by patterning printing as described above, there is a difference in the characteristics of the first coil 1 and the second coil 2 due to the difference in the printing condition. It can occur.

In order to solve such a problem, the magnetic permeability sensor 10 of the present invention adjusts at least one of the first measurement time and the second measurement time. This adjustment process is performed before the actual magnetic permeability detection process is performed, such as when the magnetic permeability sensor 10 is shipped or when a copying machine having the magnetic permeability sensor 10 is used for copying. In the situation of the median value in the desired detection range, these measurement times are adjusted so that there is no difference in the number of pulses in one measurement period in the first coil 1 and the second coil 2. Since it is troublesome to prepare the toner to create the situation of the median of the detection range, a metal having the same magnetic permeability (the above median) is used. The environmental temperature at this time is normal temperature.

The second coil 2 arranged at a position close to the developer is greatly affected by the magnetic material (developer) and has a large inductance. On the other hand, the first coil 1 arranged at a position far from the developer is hardly affected by the magnetic material (developer) and the inductance does not become so large. Since the oscillation frequency is substantially inversely proportional to the inductance, the number of oscillation pulses of the second oscillation circuit 7 is smaller than the number of oscillation pulses of the first oscillation circuit 6. Therefore, the second measurement time is adjusted to be relatively longer than the first measurement time by the amount of compensating the difference due to the magnitude of the influence of the magnetic material (developer). Specifically, the measurement time is adjusted so that the number of oscillation pulses of the first oscillation circuit 6 and the number of oscillation pulses of the second oscillation circuit 7 are the same.

When the second measurement time is adjusted to be relatively longer than the first measurement time, the second measurement time is not changed and the first measurement time is shortened. The first measurement time is not changed. Either adjustment for lengthening the second measurement time or adjustment for shortening the first measurement time and lengthening the second measurement time may be performed.

For the adjustment of the measurement time, first, the respective measurement times are set to be the same, the number of oscillation pulses is measured by the first oscillation circuit 6 and the number of oscillation pulses is measured by the second oscillation circuit 7, and then the difference is calculated. Measure and adjust either measurement time so that the difference disappears. In this case, the number of oscillation pulses may not be the same even if the measurement time is adjusted once. In that case, the adjustment is performed as follows. Specifically, the number of oscillation pulses by the first oscillation circuit 6 and the number of oscillation pulses by the second oscillation circuit 7 are measured again with the adjusted measurement time, the difference in the number of oscillation pulses is calculated, and the difference is eliminated. Adjust the measurement time for either one. Finally, the state in which the difference between the number of oscillation pulses by the first oscillation circuit 6 and the number of oscillation pulses by the second oscillation circuit 7 is the smallest is set as the initial value (set as the center value of the detection range), and the actual measurement is performed. May go. This correction corresponds to step 2 (correction processing) described later.

The entire measurement time adjustment described above will be described using a flowchart. FIG. 10 is a flowchart showing a processing procedure example of the measurement time adjustment processing. The measurement time adjustment process is a process performed mainly by the adjustment unit 42 of the electronic chip 4. The adjustment unit 42 performs an initial correction process (step S1). The initial correction process is a process mainly intended to correct an error in the clock of the electronic chip 4. The adjustment unit 42 performs a correction process (step S2). The correction process is a process whose purpose is to make the difference in the number of measured pulses between the first oscillation circuit 6 and the second oscillation circuit 7 to be the minimum value (including 0) in an environment that is assumed to be the central value of the measurement range. .. The adjustment unit 42 performs a forced correction process (step S3). The forcible correction process is a process for forcibly reducing the difference in the number of measured pulses between the first oscillation circuit 6 and the second oscillation circuit 7 to 0 in an environment where the central value of the measurement range is assumed. The forced correction process is a process for forcibly setting the minimum value of the difference obtained in the correction process to 0, and is a process including the meaning of confirming that the difference has become the minimum value in the correction process. The adjustment unit 42 ends the measurement time adjustment process.
Then, the magnetic permeability is repeatedly measured by the procedure shown in FIG. 10 (step S4).

FIG. 11 is a flowchart showing a processing procedure example of the initial correction processing. The coil forming the first oscillation circuit 6 is a reference coil, the coil forming the second oscillation circuit 7 is a detection coil, the first oscillation circuit 6 is a reference oscillation circuit, and the second oscillation circuit 7 is a detection oscillation circuit. The adjustment unit 42 causes the measurement unit 41 to measure the number of oscillation pulses of the first oscillation circuit 6 in the initial measurement time (t0) (step S11). The adjusting unit 42 calculates the difference between the number of pulses measured by the calculating unit 43 and the predetermined value (step S12). Based on the predetermined value, the measurement time of the first oscillation circuit 6 is corrected so that the number of oscillation pulses of the first oscillation circuit 6 becomes the predetermined value (step S13). The adjusting unit 42 ends the initial correction process and returns the process to the calling source. The corrected measurement time is, for example, t0+α. The initial correction is completed in step S13. After step S13, the measurement unit 41 measures the number of oscillation pulses of the first oscillation circuit 6 at the measurement time t0+α, and performs a process of confirming whether or not the measured number of oscillation pulses reaches a predetermined value. The number of oscillation pulses of the first oscillation circuit 6 is measured at the measurement time t0+α (step S14). The adjustment unit 42 determines whether the number of oscillation pulses has reached a predetermined value (step S15). When the adjusting unit 42 determines that the number of oscillation pulses is not the predetermined value (NO in step S15), the process returns to step S12. When the adjusting unit 42 determines that the number of oscillation pulses is the predetermined value (YES in step S15), the process ends and returns to the calling source. If the number of oscillating pulses does not reach the predetermined value or α does not converge, the value that minimizes the difference between the number of oscillating pulses and the predetermined value is set to α. In addition, in order to simplify the processing, the processing of steps S14 and S15 may be omitted.

For example, the first oscillation circuit 6 is designed to oscillate at 10 MHz. Then, it is assumed that the number of oscillation pulses is measured 30,000 times. In this case, the initial measurement time t0 is 3 ms. The measurement unit 41 measures the number of oscillation pulses of the first oscillation circuit 6 for 3 ms. When the number of measured oscillation pulses is less than 30,000, the measurement time is lengthened by the number of pulses that is less than that. That is, α is a positive value. When the number of measured oscillation pulses exceeds 30,000, the measurement time is shortened by the number of pulses that exceeds the number. That is, α is a negative value. When the number of oscillation pulses measured is 30,000, α is set to 0. The operation of the adjusting unit 42 in the initial correction process is an example of the operation as the above-described first adjusting unit.

FIG. 12 is a flowchart showing a processing procedure example of the correction processing. The correction process is performed in an environment where the center of the measurement range and the magnetic permeability are measured. For example, a magnetic plate (reference magnetic plate) that creates such an environment is used. The adjustment unit 42 measures the number of oscillation pulses of the first oscillation circuit 6 by the measurement unit 41 at the measurement time t0+α obtained in the initial correction process (step S21). The adjusting unit 42 stores the measured oscillation pulse number of the first oscillation circuit 6 (step S22). The adjusting unit 42 measures the number of oscillation pulses of the second oscillation circuit 7 by the measuring unit 41 at the measurement time t0+α obtained in the initial correction process (step S23). The adjustment unit 42 calculates the difference between the number of oscillation pulses of the second oscillation circuit 7 measured by the calculation unit 43 and the stored number of oscillation pulses of the first oscillation circuit 6 (step S24). The adjusting unit 42 ends the correction process and returns the process to the calling source. The measurement time of the second oscillation circuit 7 is corrected so that the difference becomes 0 (step S25). The adjusting unit 42 sets the corrected measurement time to, for example, t0+α+β. When the number of pulses of the second oscillation circuit 7 is smaller than the number of oscillation pulses of the first oscillation circuit 6, β is set to a positive value. When the pulse number of the second oscillation circuit 7 is larger than the oscillation pulse number of the first oscillation circuit 6, β is set to a negative value. When the number of pulses of the second oscillation circuit 7 is equal to the number of oscillation pulses of the first oscillation circuit 6, β is set to 0. After step S25, the number of oscillation pulses of the first oscillation circuit 6 is measured at the measurement time t0+α, the number of pulses of the second oscillation circuit 7 is measured at the measurement time t0+α+β, and it is confirmed whether the two pulse numbers are equal. You may go. If they are not equal, β is set again. When β does not converge, the difference between the number of oscillation pulses and the predetermined value is set to the smallest value. Specifically, after step S25, the adjusting unit 42 determines whether the measured oscillation pulse number of the first oscillation circuit 6 and the measured oscillation pulse number of the second oscillation circuit 7 match. When the adjustment unit 42 determines that the numbers of both pulses match, the correction process ends. When the adjusting unit 42 determines that the numbers of both pulses do not match, the process returns to S21 and repeats Step S21 and the subsequent steps. The measurement time at this time is t0+α in the first oscillation circuit 6 (step S21), and t0+α+β in the second oscillation circuit 7 (step S25). In the same manner, the time of the second oscillation circuit 7 is corrected and the number of oscillation pulses is corrected to be the same. Further, instead of correcting the measurement time of the second oscillation circuit 7, the measurement time of the first oscillation circuit 6 may be corrected. The operation of the adjusting unit 42 in the correction process is an example of the operation as the above-described second adjusting unit.

FIG. 13 is a flowchart showing a processing procedure example of the forced correction processing. The forcible correction process is a process for finally confirming the difference in the number of oscillation pulses in the measurement time set in the correction process and forcibly setting the difference to zero. Like the correction process, the forced correction process is performed in an environment in which the magnetic permeability, which is the center of the measurement range, is measured using the reference magnetic plate. The adjusting unit 42 measures the number of oscillation pulses of the first oscillation circuit 6 by the measuring unit 41 at t0+α (step S31). The adjustment unit 42 stores the measured oscillation pulse number of the first oscillation circuit 6 (step S32). The adjusting unit 42 measures the number of oscillation pulses of the second oscillation circuit 7 by the measuring unit 41 at t0+α+β (step S33). The adjusting unit 42 stores the measured number of oscillation pulses of the second oscillation circuit 7 (step S34). The adjustment unit 42 calculates the difference between the number of oscillation pulses of the first oscillation circuit 6 and the number of oscillation pulses of the second oscillation circuit 7 by the calculation unit 43 (step S35). After that, the difference is forcibly set to 0. By this processing, the value measured by the reference magnetic plate is set as the median value of magnetic permeability (step S36). This step shows S52 to S57 described later. The operation of the adjusting unit 42 in the forced correction process is an example of the operation as the above-described third adjusting unit.

A series of steps in the magnetic permeability correction processing (after correction and forcible correction) will be described using a flowchart. FIG. 14 is a flowchart showing an example of the procedure of the forced correction process after the magnetic permeability correction process. The adjustment unit 42 sets the measurement time of the first oscillation circuit 6 (first measurement time t1) to t0+α. The adjusting unit 42 sets the measurement time of the second oscillation circuit 7 (second measurement time t2) to t0+α+β (step S51). The measurement unit 41 measures the number of oscillation pulses of the first oscillation circuit 6 at the first measurement time t1 (step S52). The measuring unit 41 stores the measured number of oscillation pulses of the first oscillation circuit 6 (step S53). The measurement unit 41 measures the number of oscillation pulses of the second oscillation circuit 7 at the second measurement time t2 (step S54). The measuring unit 41 stores the measured number of oscillation pulses of the second oscillation circuit 7 (step S55). The adjustment unit 42 corrects the number of oscillation pulses of the first oscillation circuit 6 or the number of oscillation pulses of the second oscillation circuit 7 with the difference (forced difference) obtained by the forced correction process. In the forced correction process, when the number of oscillation pulses of the first oscillation circuit 6 is larger than the number of oscillation pulses of the second oscillation circuit 7, the forced difference is added to the value of the number of oscillation pulses of the second oscillation circuit 7. When the oscillation pulse number of the first oscillation circuit 6 is smaller than the oscillation pulse number of the second oscillation circuit 7, a forced difference is subtracted from the value of the oscillation pulse number of the second oscillation circuit 7 (the difference is forcibly set to 0). This completes the correction (steps S56 and S57). By this processing, the measured value on the reference magnetic plate is set as the median value of magnetic permeability.

By performing the adjustment as described above, it is possible to suppress the fluctuation of the detection output due to the temperature fluctuation. Further, as a result, compensation for the difference in the characteristics of the first coil 1 and the second coil 2 at the time of formation as described above can be performed. Therefore, in the magnetic permeability sensor 10 of the present invention, the magnetic permeability of the developer can be detected with high accuracy while suppressing the influence of temperature fluctuations, and an accurate toner concentration can be obtained.

Note that the initial correction in step S1 and the forced correction in step S3 are not essential, and may be appropriately combined depending on the required specifications.

When performing the correction and the forced correction after performing the initial correction, the measurement time of the reference coil (the first coil 1 in this specification) is kept constant, and the measurement time of the detection coil (the second coil 2 in this specification) is set. It is desirable to adjust

The present invention has the following advantages. The control range of the toner density may change depending on the type of toner used. In this case, for example, the unused terminal of the microcomputer U1 is used to externally control the voltage level of the unused terminal, whereby the control range of the toner density is adjusted to be an appropriate range for the toner used. Offset function can be provided.

Further, in recent years, the particle size of the toner itself tends to be small in order to obtain high image quality depending on the electrophotographic method. In addition, the amount of unnecessary toner is reduced as much as possible to reduce cost and weight, and as a result, change in detectable magnetic permeability tends to be small. In order to accurately detect the decreased change in permeability, it is necessary to increase the measurement sensitivity by a method such as amplification in order to increase the small change in permeability. In this case, the change in the magnetic permeability loses linearity, and the magnetic permeability may not be accurately measured. According to the present invention, by using a method using software such as linear correction, it is possible to improve the deteriorated linearity, and it is possible to accurately grasp the change in magnetic permeability.

Although a microcomputer having eight terminals is shown in FIG. 8 as an example, the present invention is not limited to this configuration. If necessary, a microcomputer with a different number of terminals can be used to transmit information such as changes in magnetic permeability to the upper control side by means such as serial communication, and to receive control signals from the upper side. is there.

In the above-described embodiment, the change in the inductance of the two coils (the first coil 1 and the second coil 2) arranged coaxially is determined by the accurate clock signal of the oscillator built in the microcomputer (electronic chip 4). Detected as a difference in the number of oscillation pulses in the two oscillation circuits (first oscillation circuit 6 and second oscillation circuit 7) driven by, and the difference (change amount of the oscillation pulse number) is processed by a microcomputer. Changes in permeability are detected. Here, each of the two coils is alternately connected to the oscillation circuit, and the number of oscillation pulses is alternately measured by the microcomputer for a predetermined time, and the difference is calculated to detect the change in magnetic permeability. ing.

In the present embodiment, the first coil 1 and the second coil 2 are formed by patterning printing on the substrate. Compared with the conventional case where a coil is formed by winding a wire around a non-magnetic bobbin or the like, the cost can be suppressed when a large number of coil parts are produced. In the present embodiment, since the first coil 1 and the second coil 2 are coaxially arranged, the area required for coil arrangement can be reduced. Further, since various processes are performed by using the microcomputer, the number of parts can be reduced and the area for mounting the circuit parts can be reduced. From the above, the magnetic permeability sensor can be significantly downsized.

Since the number of oscillation pulses is measured alternately in the two oscillation circuits, the measurement of the oscillation circuit including one coil is affected by the magnetic flux generated in the other coil (inductance change in the other coil). Since it does not exist, the number of oscillation pulses can be accurately measured, and as a result, the magnetic permeability can be detected with high accuracy.

In the present embodiment, the transistors and capacitors forming the two oscillation circuits are shared, and the coils are arranged in each oscillation circuit. Therefore, the number of parts can be reduced and the cost can be reduced. Further, since the number of parts is small, it is possible to reduce variations in parts characteristics, and further, it is difficult to be affected by disturbances such as temperature change and noise, and accurate measurement is possible.

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

Further, even when the toner density to be set is different, it can be easily dealt with by only changing the contents of the software. Therefore, since it is not necessary to manage each set value of different toner density, mass production is facilitated and cost reduction can be achieved.

FIG. 15 is a graph showing toner density detection sensitivity characteristics in the present invention example and the conventional example. In FIG. 15, the horizontal axis represents the toner concentration, and the vertical axis represents the output voltage as the magnetic permeability detection result. Further, (a) and (b) in FIG. 15 show the characteristics of the present invention example and the conventional example, respectively.

When the example of the present invention and the example of the related art are compared, in the example of the present invention, the portion where the output voltage changes linearly with respect to the change of the toner density is wider than that of the example of the related art. 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. 16 is a graph showing control voltage characteristics for performing offset control in the example of the present invention and the conventional example. In FIG. 16, the horizontal axis represents the applied control voltage and the vertical axis represents the output voltage. Further, (a) and (b) in FIG. 16 respectively show the characteristics of the present invention example and the conventional example.

When the present invention example and the conventional example are compared, in the conventional example, the output voltage changes linearly only partially with respect to the change in the control voltage, whereas in the present invention example, the output voltage changes linearly. On the other hand, the output voltage varies linearly throughout. Therefore, it is understood that the accuracy of the offset control in the example of the present invention is superior to the accuracy of the conventional example.

(Embodiment 2)
The magnetic permeability sensor 10 of the present embodiment enables setting of sensitivity. The magnetic permeability sensor 10 of the present embodiment has the same configuration as that of the first embodiment except for a part. In the following description, the points different from the first embodiment will be mainly described.

FIG. 17 is a block diagram showing another example of the functional configuration of the magnetic permeability sensor. The difference from the first embodiment is the functional configuration of the electronic chip 4. The electronic chip 4 functionally has the measuring unit 41, the adjusting unit 42, the calculating unit 43, and the converting unit 44, as in the first embodiment. In addition, the electronic chip 4 in the present embodiment functionally has a storage unit 45 and an initial setting unit 46. The functions of the measuring unit 41 to the converting unit 44 are the same as those in the first embodiment. The storage unit 45 stores the initial value of the number of oscillation pulses according to the sensitivity. The initial setting unit 46 selects a sensitivity based on a selection signal input from the outside, reads an initial value corresponding to the selected sensitivity from the storage unit 45, and sets it as an initial value of the oscillation pulse number measurement time (initial measurement time). Set.

In the present embodiment, the output terminal for outputting the control voltage Vref for selecting the sensitivity is connected to the fifth terminal of the microcomputer U1 shown in FIG. 8 via the resistor R6. The control voltage Vref is input to the fifth terminal to set the sensitivity.

In this embodiment, three operation modes (hereinafter, simply referred to as modes) are prepared, and different sensitivities are associated with the respective modes. Select the mode before starting measurement. The three modes are called high sensitivity mode, medium sensitivity mode, and low sensitivity mode in order of increasing sensitivity. Hereinafter, the high sensitivity mode is simply referred to as high sensitivity, the medium sensitivity mode is simply referred to as medium sensitivity, and the low sensitivity mode is simply referred to as low sensitivity.

FIG. 18 is a graph showing an example of the relationship between the detected toner density and the output voltage for each mode. In FIG. 18, the horizontal axis represents the toner concentration, and the unit is weight% (wt %). The vertical axis represents the output voltage, and the unit is volt (V). A graph 71 shows an example of a high sensitivity graph. A graph 72 shows an example of a medium sensitivity graph. The graph 73 shows an example of a low sensitivity graph. In each mode, the output voltage is 2.5 V at the center value of the detection range. The sensitivity can be set because the amount of change in the output voltage with respect to the detected concentration is determined by determining the concentrations at which the output voltage is 2 V and 3 V before and after the median value, respectively. In order to increase the amount of change in the output voltage with respect to the change in detected concentration, the time for measuring the number of oscillation pulses is lengthened.

In the sensitivity settings shown in FIG. 18, the median values in the high-sensitivity mode, the medium-sensitivity mode, and the low-sensitivity mode are different, but the present invention is not limited thereto. The medians may be the same in all modes. The medians may be matched in any two modes. Furthermore, the detection ranges may or may not overlap between the plurality of modes.

In setting the sensitivity, a magnetic plate (reference magnetic plate) having a magnetic permeability corresponding to the toner concentration is prepared. Explaining using the values shown in FIG. 18, a total of three magnetic plates each having a magnetic permeability corresponding to the density Hb, the density Hc, and the density Ht are prepared for setting the high sensitivity. For medium sensitivity, a magnetic plate having magnetic permeability corresponding to the concentrations Mb, Mc, and Mt is prepared. For low sensitivity, a magnetic plate having magnetic permeability corresponding to the concentrations Lb, Lc, and Lt is prepared. A total of nine prepared magnetic plates are measured by the magnetic permeability sensor 10 to determine the measurement time. The determined measurement time for each sensitivity is stored in the electronic chip 4.

Next, a method of selecting sensitivity during operation will be described. The sensitivity is selected using Vref (selection signal) input to the fifth terminal of the microcomputer U1 from an external device. FIG. 19 is a chart showing the sensitivity selection method. From the top of FIG. 19, the case where low sensitivity is selected, the case where medium sensitivity is selected, and the case where high sensitivity is selected are shown. FIG. 19 shows the waveform of Vref. The vertical axis represents the voltage applied to Vref. The horizontal axis indicates the elapsed time. When Vref is set to the H level (5V) for 1 second, the microcomputer U1 shifts to the initial setting mode. In the next 1 second, the sensitivity is designated by the voltage Vref. If Vref is kept at 0V, it operates with low sensitivity. If Vref is kept at 2.5V, it operates at medium sensitivity. If Vref is kept in an open state (high impedance), it may operate with medium sensitivity. If Vref is kept at 5V, it operates with high sensitivity. In the example shown in FIG. 19, the median value is set within 1 second after the sensitivity is selected. The voltage input to Vref becomes the output voltage at the median of the detection range. Although the sensitivity is set to three levels, the sensitivity is not limited to this. There may be four or more steps by increasing the value of Vref for designating the sensitivity. Further, the sensitivity may be specified not by one terminal of the microcomputer U1 but by two or more terminals.

The adjustment process of at least one of the first measurement time and the second measurement time in the adjustment unit 42 is the same as that in the first embodiment. The entire measurement time adjustment is the same as that of the first embodiment shown in FIG. 10 except for the following points. In the present embodiment, the electronic chip 4 first sets the sensitivity. The initial setting unit 46 determines the corresponding sensitivity from the value of the control voltage Vref, and reads the initial measurement time for the determined sensitivity from the storage unit 45. The electronic chip 4 executes step S1 and subsequent steps shown in FIG.

The processing procedure of the initial correction processing is the same as the procedure of the first embodiment shown in FIG. The processing procedure of the correction processing is the same as the procedure of the second embodiment shown in FIG. However, in the present embodiment, the correction process is performed in an environment in which the center of the detection range and the magnetic permeability are measured. That is, a magnetic plate (reference magnetic plate) according to the sensitivity is used. The processing procedure of the forced correction processing is the same as the procedure of the first embodiment shown in FIG. A series of steps in the magnetic permeability correction processing (after correction and forcible correction) are the same as those in the first embodiment shown in FIG.

The present embodiment has the following effects in addition to the effects of the first embodiment. Multiple sensitivities were prepared in advance so that they could be selected during operation. Therefore, even if the control range of the toner density changes depending on the type of toner used, it is possible to deal with the problem by changing the sensitivity. Note that the sensitivity is set to three, but the sensitivity is not limited to this. The number may be two or four or more.

(Modification 1)
Hereinafter, modified examples of the assembled coil 14 will be described. FIG. 20 is a partial cross-sectional view of a configuration example of the magnetic permeability sensor. The cross section line is the same as in FIG. In the magnetic permeability sensor 10 shown in FIG. 20, the terminal 143 is L-shaped in a side view. The terminal 143 includes a base portion 1431 and a vertical portion 1432. A part of the base portion 1431 and the vertical portion 1432 is embedded in the pedestal 142. The base portion 1431 has a rectangular parallelepiped shape. The surface of the base portion 1431 parallel to the surface of the substrate 141 is connected to the land of the substrate 141 by soldering. On the upper surface of the vertical portion 1432, one end of the lead wire 17 is connected by soldering. As the lead wire 17, a wire having low rigidity such as a twisted wire is used. If the rigidity of the lead wire 17 is low, the assembled coil 14 may rattle in the housing portion 121. Therefore, an annular protrusion 1211 is formed on the inner surface of the housing 121 of the case 12. The substrate 141 is fixed inside the accommodation portion 121 by the protrusion 1211.

(Modification 2)
FIG. 21 is a partial cross-sectional view of a configuration example of the magnetic permeability sensor. The cross section line is the same as in FIG. In the form shown in FIG. 21, the terminal 143 is arranged below the pedestal 142. The lead wire 17 penetrates the pedestal 142 and is connected to the upper surface of the terminal 143. The lower surface of the terminal 143 and the land of the substrate 141 are soldered by reflow soldering.

In this modified example, the terminals 143 are soldered to the substrate 141 by reflow soldering, so that the number of manual steps during assembly can be reduced and the manufacturing cost can be suppressed. Since the terminal 143 and the land of the substrate 141 are connected by reflow soldering, the quality of soldering is improved and the yield is improved as compared with manual soldering.

(Modification 3)
FIG. 22 is a partial cross-sectional view of a configuration example of the magnetic permeability sensor. The cross section line is the same as in FIG. In the form shown in FIG. 22, the pedestal 142 and the terminal 143 are omitted. The control board 113 and the board 141 are connected only by the lead wire 17. One end of the lead wire 17 is soldered to the land of the board 141. The other end of the lead wire 17 is soldered to a land or the like of the control board 13. The lead wire 17 is composed of a stranded wire having low rigidity so that it can be easily soldered.

In the modified example, by omitting the pedestal 142 and the terminal 143, it is possible to reduce the component cost. Further, since the number of parts is reduced, management work such as procurement of parts and securing of inventory is reduced.

It should be understood that the disclosed embodiments are illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

10 Permeability Sensor 11 Cover 12 Case 121 Housing 1211 Protrusion 13 Control Board 14 Assembly Coil 141 Substrate 142 Pedestal 143 Terminal 15 Connector 1 First Coil 2 Second Coil 4 Electronic Chip 41 Measuring Section 42 Adjusting Section 43 Calculating Section 44 Converting Section 45 storage unit 46 initial setting unit 5 circuit components 6 first oscillation circuit 7 second oscillation circuit

Claims (16)

In a magnetic permeability sensor that detects 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;
A second oscillating circuit that oscillates including a second coil that receives magnetism from the object to be detected;
A measuring unit for measuring the number of oscillation pulses in each of the first oscillation circuit and the second oscillation circuit;
An adjustment unit that adjusts at least one of a measurement time of the number of oscillation pulses in the first oscillation circuit by the measurement unit and a measurement time of the number of oscillation pulses in the second oscillation circuit by the measurement unit;
A calculation unit that calculates a difference in the number of oscillation pulses measured by the measurement unit,
A conversion unit that converts the difference calculated by the calculation unit into magnetic permeability,
A first oscillator circuit excluding the first coil, a second oscillator circuit excluding the second coil, a first substrate including the measuring unit, the adjusting unit, the calculating unit, and the converting unit, the first coil, and the first substrate. A magnetic permeability sensor comprising: a second substrate having two coils on its front and back surfaces, wherein the first substrate and the second substrate are arranged on different planes. The magnetic permeability according to claim 1, wherein the measuring unit is configured to alternately measure the number of oscillation pulses in the first oscillation circuit and the number of oscillation pulses in the second oscillation circuit. Sensor. The magnetic permeability sensor according to claim 1 or 2, wherein the first coil and the second coil are coaxially arranged. The magnetic permeability sensor according to claim 1, wherein constituent members of the first oscillation circuit and the second oscillation circuit are common except for the first coil and the second coil. .. A storage unit that stores the initial measurement time for each of the plurality of sensitivities,
A selection signal for selecting one from a plurality of sensitivities is acquired, an initial measurement time corresponding to the sensitivity selected by the acquired selection signal is read from the storage unit, and the read initial measurement time is stored in the first oscillation circuit. A first measurement time for measuring the number of oscillation pulses, and an initial setting unit for setting a second measurement time for measuring the number of oscillation pulses of the second oscillation circuit,
The calculation unit includes the number of oscillation pulses obtained by the measurement unit measuring the first oscillation circuit during the first measurement time, and the second measurement time when the measurement unit includes the second oscillation circuit. The magnetic permeability sensor according to any one of claims 1 to 4, wherein the difference in the number of oscillation pulses obtained by performing the measurement is calculated. The adjustment unit adjusts at least one of the first measurement time set by the initialization unit and the second measurement time,
The transparent unit according to claim 5, wherein the measuring unit measures the number of oscillation pulses at the first measurement time and the second measurement time based on the adjustment result of the adjusting unit. Magnetic susceptibility sensor. The magnetic permeability sensor according to claim 6, wherein the adjustment unit adjusts the second measurement time. In a magnetic permeability sensor that detects 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;
A second oscillating circuit that oscillates including a second coil that receives magnetism from the object to be detected;
A measuring unit for measuring the number of oscillation pulses in each of the first oscillation circuit and the second oscillation circuit;
A first adjustment unit that adjusts the measurement time so that the number of oscillation pulses in the first oscillation circuit by the measurement unit becomes a predetermined value;
At least one of the measurement time of the oscillation pulse number in the first oscillation circuit adjusted by the first adjustment unit and the measurement time of the oscillation pulse number in the second oscillation circuit is measured under a predetermined environment. A second adjusting unit for adjusting based on the number of oscillation pulses,
A calculation unit that calculates a difference in the number of oscillation pulses measured by the measurement unit in the measurement time after the adjustment by the first adjustment unit and the second adjustment unit;
A conversion unit that converts the difference calculated by the calculation unit into magnetic permeability,
A first substrate including a first oscillator circuit excluding the first coil, a second oscillator circuit excluding the second coil, the measuring unit, the first adjusting unit, the second adjusting unit, the calculating unit, and the converting unit. And a second substrate having the first coil and the second coil on the front and back surfaces thereof, and the first substrate and the second substrate are arranged on different planes. The magnetic permeability sensor according to claim 8, wherein the first coil and the second coil are coaxially arranged. The magnetic permeability sensor according to claim 8 or 9, wherein constituent members of the first oscillating circuit and the second oscillating circuit are common except for the first coil and the second coil. The magnetic permeability sensor according to any one of claims 8 to 10, wherein the second adjustment unit adjusts a measurement time of the number of oscillation pulses in the second oscillation circuit. The calculation unit adjusts the measurement time by the first adjustment unit and the second adjustment unit, and then performs adjustment by the first adjustment unit and the second adjustment unit in the measurement unit under a predetermined environment. Calculate the difference in the number of oscillation pulses measured in the measurement time,
The third adjustment unit that adjusts at least one of the number of oscillation pulses in the first oscillation circuit and the number of oscillation pulses in the second oscillation circuit according to the difference calculated by the calculation unit. The magnetic permeability sensor according to any one of claims 8 to 11. The magnetic permeability sensor according to claim 12, wherein the third adjusting unit adjusts the number of oscillation pulses in the second oscillating circuit. The magnetic permeability sensor according to any one of claims 8 to 13, which is realized by using a reference magnetic plate under the predetermined environment. A storage unit that stores the initial measurement time for each of the plurality of sensitivities,
A selection signal for selecting one from a plurality of sensitivities is acquired, an initial measurement time corresponding to the sensitivity selected by the acquired selection signal is read from the storage unit, and the read initial measurement time is stored in the first oscillation circuit. A first measurement time for measuring the number of oscillation pulses, and an initial setting unit for setting a second measurement time for measuring the number of oscillation pulses of the second oscillation circuit,
The calculation unit includes the number of oscillation pulses obtained by the measurement unit measuring the first oscillation circuit during the first measurement time, and the second measurement time when the measurement unit includes the second oscillation circuit. The magnetic permeability sensor according to any one of claims 8 to 14, wherein the difference in the number of oscillating pulses obtained by performing the measurement is calculated. 16. The measuring unit according to claim 8, wherein the measuring unit is configured to alternately measure the number of oscillation pulses in the first oscillation circuit and the number of oscillation pulses in the second oscillation circuit. The magnetic permeability sensor according to any one of claims.

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