JP2579413Y2 - Magnetic sensing device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic detecting device for magnetically detecting the presence, quantity, concentration or distance of a magnetic substance or a conductor, and more particularly, to an electrophotographic development including a magnetic carrier and an insulating toner. The present invention relates to a magnetic detection device suitable as a toner concentration detection device for an agent.

[0002]

2. Description of the Related Art An electrophotographic developer is used for development of electrophotography or electrostatic recording. However, when the mixing ratio of toner to a magnetic carrier is reduced, the density of a developed image is reduced. When the ratio is high, the density of the image becomes too high and fogging increases. Therefore, in order to continuously obtain an image having an appropriate color tone, it is necessary to detect the toner density in the developer and maintain the density at an appropriate constant level. As a means therefor, various detection devices have been conventionally proposed. For example, as disclosed in Japanese Patent Application Laid-Open No. Sho 59-10814, a differential transformer is used, its drive coil is driven by an AC drive source, and a detection coil coupled to the drive coil is provided. 2. Description of the Related Art A differential transformer type magnetic detecting device for detecting a density from a differential output of a reference coil is known.

Another conventional example is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 2-26.
As disclosed in JP-A-202, a pair of oscillating circuits are formed using a pair of oscillating coils, and one of the pair of oscillating coils is brought close to the toner, and the oscillation output of the pair of oscillating circuits is adjusted to the toner concentration. 2. Description of the Related Art There is known a phase difference type magnetic detecting device which generates a corresponding phase difference and detects toner density from the phase difference.

[0004]

However, the conventional differential transformer type magnetic detector and the phase difference type magnetic detector have the following problems. (A) The differential transformer type magnetic detection device requires at least three coils of a drive coil and a detection coil to be differentially connected to the differential transformer of the detection portion, so that the structure becomes complicated, the size becomes large, and the mounting is performed. Subject to the above restrictions. (B) Since the phase difference type magnetic detection device has a structure in which a pair of oscillation coils are integrated, the structure of the detection portion becomes large, as in the case of the differential transformer type, and is subject to mounting restrictions. (C) Since the phase difference type magnetic detection device detects the toner concentration from the phase difference between the oscillation frequencies of the two oscillation circuits,
It is assumed that the oscillation frequencies of the two oscillation circuits are the same. However, since a pair of oscillation coils are integrated and mutual interference occurs between the oscillation coils, it is not easy to adjust the oscillation frequencies of the two oscillation circuits to match. (D) The phase difference type magnetic sensing device is expensive because the exclusive OR gate for detecting the phase mismatch is an essential component.

It is an object of the present invention to solve the above-mentioned problems and to provide a small, thin, and inexpensive magnetic detecting device which is easy to adjust and assemble.

[0006]

Means for Solving the Problems] To solve the problems described above, the magnetic sensing device according to the present invention, the organic and the reference signal generating circuit, and a detection signal generating circuit, and a signal processing circuit, and a circuit board . The reference signal generation circuit is a circuit that outputs a reference signal having a constant frequency. The detection signal generation circuit has a detection coil and an oscillation circuit. The detection coil changes its inductance when electromagnetically coupled to the object to be detected, and the oscillation circuit changes the oscillation frequency in response to the change in the inductance and outputs the oscillation frequency as a detection signal . The signal processing circuit is a circuit that receives the reference signal and the detection signal as input signals, and outputs an electric signal including a frequency signal of a difference between the frequency of the reference signal and the frequency of the detection signal . The circuit board,
The reference signal generation circuit, the detection signal generation circuit, and the signal processing circuit are supported . The detection coil is mounted on a surface of the circuit board. Further, the reference signal
The generation circuit has a reference oscillation circuit and a reference coil.
The reference oscillation circuit determines an inductance value of the reference coil.
And outputs the reference signal corresponding to
It is mounted on the surface of the circuit board. The detection coil and
And the reference coil so that the coil winding axes intersect each other.
Are located in

[0007]

The detection signal generation circuit has a detection coil and an oscillation circuit. When the detection coil is electromagnetically coupled to the object to be detected, the inductance changes, and the oscillation circuit oscillates in response to the change in the inductance. Since the frequency changes and the oscillation frequency is output as a detection signal, the detection signal has a different frequency depending on the presence of the object, the concentration of the magnetic material in the object, the proximity distance to the object, and the like. Is obtained. For this reason, the detection part requires only one detection coil, and the detection part can be downsized.

The signal processing circuit receives the reference signal and the detection signal as input signals and outputs an electric signal including a frequency signal having a difference between the frequency of the reference signal and the frequency of the detection signal. A change in the electromagnetic coupling between the detection signal and the detection object is detected as an electric signal including a frequency signal of a difference between the frequency of the reference signal and the frequency of the detection signal. Therefore, it is not necessary to make the frequency of the reference signal generation circuit and the frequency of the detection signal generation circuit the same. In addition, since the reference signal generation circuit and the detection signal generation circuit can be separated from each other, the oscillation frequencies of both can be easily adjusted. Further, as compared with the case of using a sum frequency signal, the frequency is lowered and the frequency band used is narrowed, so that the circuit configuration is simplified and the detection sensitivity is improved. Further, since the exclusive OR gate need not be used, the cost is reduced.

The circuit board supports a reference signal generation circuit, a detection signal generation circuit, and a signal processing circuit. Since the detection coil is mounted on the surface of the circuit board, the entire circuit can be assembled on the circuit board. It is easy to assemble and small and thin.

[0010]

FIG. 1 is a block diagram showing a circuit configuration of a magnetic detecting device according to the present invention. In the figure, 1 is a reference signal generation circuit, 2 is a detection signal generation circuit, and 3 is a signal processing circuit.

The reference signal generating circuit 1 has a constant frequency f1
Is output. The reference signal generation circuit 1
It is sufficient that a reference signal having a constant frequency f1 can be generated, and a coil can be constituted by an oscillation circuit which is not an essential component.

The detection signal generation circuit 2 includes a detection coil 21
And an oscillation circuit 22. The detection coil 21
Inductance L when electromagnetically coupled to the object 20
21 changes. The oscillation circuit 22 has an inductance L21.
The oscillation frequency f2 changes according to the change of the oscillation frequency f
2 is output as the detection signal 221. The detection target 20 is
It can be made of a magnetic material such as iron or a conductive material such as copper. If the detection target 20 is a magnetic material, the inductance L21 of the detection coil 21 is changed due to a change in the magnetic circuit.
Changes, and if the conductive material is used, the inductance L21 of the detection coil 21 changes due to the eddy current. Therefore, the detection signal 221 of the variable frequency f2 based on the existence of the detection target 20, the concentration of the magnetic material in the detection target 20, the proximity distance to the detection target 20, and the like is obtained. For this reason, only one detection coil 21 is required for the detection part, and the detection part is reduced in size.

The signal processing circuit 3 receives the reference signal 121 and the detection signal 221 as input signals, and includes an electric signal including a frequency signal | f1-f2 | of a difference between the frequency f1 of the reference signal 121 and the frequency f2 of the detection signal 221. 31 is output. Therefore, the change in the electromagnetic coupling between the detection coil 21 and the detection target 20 is a frequency signal | f1-f that is the difference between the frequency f1 of the reference signal 121 and the frequency f2 of the detection signal 221.
2 | is detected as an electric signal 31 containing 2 |. For this reason,
It is not necessary to make the frequency of the reference signal generation circuit 1 and the frequency of the detection signal generation circuit 2 the same frequency, and it is not necessary to detect the phase difference. Further, as compared with the case of using the sum frequency signal | f1 + f2 |, the frequency is reduced and the frequency band used is narrowed, so that the circuit configuration is simplified and the detection sensitivity is improved. Further, since the exclusive OR gate need not be used, the cost is reduced. The electric signal 31 may be a frequency signal itself or a signal converted into another signal form such as a voltage signal.

Further, it is not necessary to integrate a pair of oscillating coils as in the conventional phase difference type magnetic detecting device and to make the frequency f1 of the reference signal 121 and the frequency f2 of the detection signal 221 the same. The oscillation frequencies of the reference signal generation circuit 1 and the detection signal generation circuit 2 can be easily adjusted.

FIG. 2 is a partial sectional view showing an example of an assembling structure of the magnetic sensing device according to the present invention having the circuit configuration shown in FIG. 5 is a circuit board. The circuit board 5 supports the reference signal generation circuit 1, the detection signal generation circuit 2, and the signal processing circuit 3. The circuit board 5 is formed of a conventionally known glass-epoxy board or aluminum board. The circuit pattern forming technique using these substrate materials is well known, and has a conductor pattern (not shown) formed according to the known technique, and the circuits 1 to 3 are mounted on this conductor pattern. Also, the detection coil 21
It is mounted on the surface of the circuit board 5. With the above-described structure, the entire structure can be assembled on the circuit board 5, which facilitates the assembly and reduces the size and thickness.

The detection coil 21 shown in FIG.
0, the coil 211 is buried inside, and the terminal of the coil 211 is led out of the insulating exterior body 210,
It is mounted on the surface of the circuit board 5. 3 to 6 show partial cross-sectional views of a coil device that can be used as the detection coil 21. 3 to 6, the coil 21
1 is wound around a core 212 made of ferrite or the like,
It has a structure covered with an insulating sheath 210 made of a suitable insulating resin. 213 and 214 are lead terminals for leading terminals of the coil 211.

FIG. 3 shows an example of a chip type coil in which the axis of the coil 211 is parallel to the mounting surface, and FIG. 4 shows an example of a chip type coil in which the axis of the coil 211 is vertical to the mounting surface. An example is shown. FIG.
FIG. 6 shows a type of coil in which one axis is parallel to the mounting surface, the lead terminals 213 and 214 are extended out of the insulating sheath 210 and the lead terminals 213 and 214 are inserted into the circuit board. Indicate that the axis of the coil 211 is perpendicular to the mounting surface and the lead terminals 213 and 214
To the outside of the insulating sheath 210, and the lead terminal 2
13 shows a coil of a type in which the coils 13 and 214 are inserted into a circuit board. Although not shown, a structure without the insulating sheath 210 may be used.

FIG. 7 is a block diagram showing another configuration of the magnetic detection device according to the present invention. In the figure, the same reference numerals as those in FIG. 1 indicate the same components. Reference numeral 4 denotes an F / V conversion circuit. The signal processing circuit 3 has an F / V conversion circuit 4, and the F / V conversion circuit 4 outputs a difference frequency signal | f1-f2 |
Is converted into a voltage signal and an electric signal 31 is output. Therefore, the change in the electromagnetic coupling between the detection coil 21 and the detection target 20 is converted into a voltage signal corresponding to the frequency signal | f1−f2 | of the difference between the frequency f1 of the reference signal 121 and the frequency f2 of the detection signal 221. Is output. Therefore, compared with the case where the sum frequency signal | f1 + f2 |
The frequency band used by the conversion circuit 4 is narrowed, and the voltage signal per unit frequency can be increased, so that the detection sensitivity increases.

The reference signal generating circuit 1 includes a reference coil 11
And a reference oscillation circuit 12. The reference coil 11 and the reference oscillation circuit 12 have the same circuit configuration as that of the detection signal generation circuit 2. For this reason, even when the inductances L11 and L21 change due to temperature or the like and the oscillation frequencies f1 and f2 change, the frequency change | f1-f2 of the electric signal 31 also occurs.
Are canceled and a stable output is obtained.

The signal processing circuit 3 includes a multiplication circuit 32 and a filter circuit 33. The multiplication circuit 32 multiplies the reference signal 121 and the detection signal 221 to output a multiplication signal. The multiplied signal includes a frequency signal (f1 + f) of the sum of the frequency f1 of the reference signal 121 and the frequency f2 of the detection signal 221.
2) or the difference frequency signal | f1-f2 |
The filter circuit 33 receives the multiplied signal and passes a frequency signal | f1−f2 | which is a difference between the frequency f1 of the reference signal 121 and the frequency f2 of the detection signal 221 included in the multiplied signal. Specifically, the difference frequency signal is passed by a low-pass filter that passes a frequency signal in a frequency band lower than the frequency f1 of the reference signal 121. Therefore, the reference signal 12
Thus, an electric signal 31 is obtained which is a frequency signal | f1−f2 | which is a difference between the frequency f1 of 1 and the frequency f2 of the detection signal 221.

The reference coil 11 can have the structure shown in FIGS. Further, regarding the relative combination structure of the detection coil 21 and the reference coil 11, various modes can be considered. Examples thereof are shown in FIGS.

First, in the embodiment shown in FIG.
Are mounted on one surface of the circuit board 5, and the reference coil 11 is mounted on the other surface of the circuit board 5. The detection coil 21 and the reference coil 11 are arranged such that the axes of the coils 211 and 111 are parallel to the surface of the circuit board 5.

In FIG. 9, the detection coil 21 and the reference coil 11 are arranged such that the axes of the coils 211 and 111 are perpendicular to the surface of the circuit board 5.

In FIG. 10, the detection coil 21 and the reference coil 11 are arranged at geometrically distant positions as arranged at opposite ends of the circuit board 5, and the magnetic coupling between the two coils 11-21 is established. This shows an example of avoidance.

In FIG. 11, the detection coil 21 and the reference coil 11 are arranged such that the axes of the coils 211 and 111 are perpendicular to the surface of the circuit board 5.

In FIG. 12, the detection coil 21 and the reference coil 11 are arranged such that the axes of the coils 211 and 111 intersect each other. Thereby, mutual linkage of the magnetic flux of the detection coil 21 and the reference coil 11 is avoided, and a stable detection operation can be secured.

FIG. 13 shows that the axis of the coil 211 of the detection coil 21 is parallel to the surface of the circuit board 5 and the axis of the coil 111 of the reference coil 11 in avoiding mutual linkage of the magnetic flux of the detection coil 21 and the reference coil 11. An example is shown in which the axis is arranged to be perpendicular to the surface of the circuit board 5.

FIG. 14 shows a coil 211 of the detection coil 21.
2 shows an example in which the axis of the reference coil 11 is arranged to be perpendicular to the surface of the circuit board 5 and the axis of the coil 111 of the reference coil 11 is parallel to the surface of the circuit board 5.

FIG. 15 is a partial cross-sectional view showing another example of an assembling structure of the magnetic detection device according to the present invention having the circuit configuration shown in FIG. 7, FIG. 16 is a plan view of FIG. 15, and FIG. 15 is a bottom view of FIG. In this embodiment, the detection coil 21
And each of the reference coils 11 is surrounded by the conductor patterns 215 and 115,
15 and 115 are connected to each other by a through-hole conductor 216. In the case of this structure, the detection coil 21
And the ambient temperature of the reference coil 11
5, 115 and the through-hole conductor 216 are transmitted to each other, and the temperature conditions of the two 21 and 11 are similar.
Detection errors due to temperature can be canceled.

In FIG. 18, the reference coil 11 has a magnetic shield member 117. Thereby, the influence of the external magnetic field is cut off by the magnetic shield member 117, and a reference signal having a constant frequency can be obtained.

In FIG. 19, not only the reference coil 11 and the detection coil 21 having the magnetic shield member 117 but also the reference signal generation circuit 1, the detection signal generation circuit 2 and the signal processing circuit 3 are on the same surface of the circuit board 5. Shows an example of implementation. In the case of this embodiment, since the mounting is performed on one side, the mounting operation on the circuit board 5 is facilitated.

Although the illustration of the combination of the detection coil 21 and the reference coil 11 is omitted, it goes without saying that the examples of combinations shown in FIGS.

FIG. 20 is a specific circuit diagram of the magnetic detection device according to the present invention, and FIG. 21 is a waveform diagram for explaining the operation of each circuit. 20, the same reference numerals as those in FIGS. 1 and 7 indicate the same components. In FIG.
(A) is a waveform diagram of the reference signal 121, (b) is a detection signal 2
21, (c) is an output waveform diagram of the multiplication circuit 32 forming the signal processing circuit 3, (d) is an output waveform diagram of the filter circuit 33 forming the signal processing circuit 3, (e) is a signal processing circuit. 3, an output waveform diagram of the waveform shaping circuit 34 constituting
(F) is an output waveform diagram of the differentiating circuit 42 constituting the F / V conversion circuit 4, (g) is an output waveform diagram of the time element circuit 43 constituting the F / V conversion circuit 4, and (h) is an F / V diagram. FIG. 9 is an output waveform diagram of the conversion circuit 4.

Although there are various uses of the magnetic detecting device, a case where the magnetic detecting device is used as a toner concentration detecting device will be described as an example.

The reference signal generating circuit 1 includes a reference coil 11
And a reference oscillation circuit 12. Reference coil 11
Is provided to cancel a change in the electric signal 31 due to a change in the frequency f2 due to a temperature effect or the like of the detection coil 21. It is preferable that conditions such as the number of turns be the same as those of the detection coil 21. The reference coil 11 does not need to be provided close to the developer. The oscillation circuit 12 has capacitors 13, 14, a resistor 15, and a NAND gate 16,
Together with the reference coil 11, a well-known Colpitts oscillation circuit is formed. Input terminal 161 of NAND gate 16
When a signal of logic "1" (power supply voltage VDD) is input to the CPU, oscillation starts. The oscillation frequency f1 depends on the inductance L11 of the detection coil 11 and the capacitor 1
It is determined by the capacitances C13 and C14 of the capacitors 3 and 14. As a result, a reference signal 121 having a constant frequency f1 is output to the signal processing circuit 3 as shown in FIG.

The detection signal generation circuit 2 includes a detection coil 21
And an oscillation circuit 22. The oscillation circuit 22 includes capacitors 23 and 24, a resistor 25, and a NAND gate 26.
And constitutes a well-known Colpitts oscillation circuit together with the detection coil 21. When a signal of logic "1" (power supply voltage VDD) is input to the input terminal 261 of the NAND gate 26, oscillation starts. The oscillation frequency f2 is obtained from the inductance L21 of the detection coil 21 and the capacitances C23 and C24 of the capacitors 23 and 24. Although not shown, the detection coil 21 is provided at an appropriate position such as the side wall of the developer container so as to come into contact with the developer, and the inductance L21 changes depending on the concentration of the magnetic carrier contained in the developer. ing. That is, when the toner concentration decreases and the magnetic carrier concentration increases, the inductance L21 of the detection coil 21 increases, and the oscillation frequency f2 of the Colpitts oscillation circuit decreases. Conversely, when the toner concentration increases and the magnetic carrier concentration decreases, the inductance L21 of the detection coil 21 decreases.
Becomes smaller, and the oscillation frequency f2 of the Colpitts oscillation circuit becomes higher. As a result, the toner density is converted into a detection signal 221 of the variable frequency f2, and a detection signal 221 as shown in FIG. Usually, the frequency f2 is higher than the frequency f1.

The signal processing circuit 3 includes a multiplication circuit 32 and a low
It has a pass filter circuit 33 and a waveform shaping circuit 34. The multiplication circuit 32 is constituted by a NAND gate 321. The NAND gate 321 performs NAND logic of the reference signal 121 and the detection signal 221. Therefore, the output of the NAND gate 321 includes a frequency signal (f1 + f2) of the sum of the frequency f1 of the reference signal 121 and the frequency f2 of the detection signal 221 or a frequency signal | f1-f2 | An output waveform as shown in (c) is obtained.

The low-pass filter circuit 33 includes a resistor 331
And a capacitor 332. The low-pass filter circuit 33 calculates the frequency f1 of the reference signal 121 and the detection signal 2
The frequency signal (f1 + f2) of the sum of the frequency f2 of the reference signal 121 and the detection signal 22 is cut off.
And outputs a frequency signal | f1−f2 | FIG. 21D shows the output waveform.

The waveform shaping circuit 34 includes a capacitor 341 and
It includes a resistor 342 and a NAND gate 343, converts the output of the low-pass filter circuit 33 into a square wave of the same frequency, and forms a square of | f1-f2 | as shown in FIG. The waves are supplied to the F / V conversion circuit 4. Specifically, the output of the low-pass filter circuit 33 is connected to the NAND gate.
Input to one input terminal of the NAND gate 343.
The conversion is performed using 43 threshold levels.

The F / V conversion circuit 4 has a differentiating circuit 42, a time elemental circuit 43, and an integrating circuit 44. Differentiating circuit 42 includes a capacitor 421 and a resistor 422, and |
A square wave having a frequency of f1-f2 | is differentiated. The output of the differentiating circuit 42 is as shown in FIG. Time element circuit 4
Numeral 3 includes a NAND gate 431. NAND gate
431, a logic "1" is given to one of the input terminals,
A signal obtained by differentiating the square wave is applied to the other of the input terminals, and a time element t for charging or discharging per unit frequency is generated as shown in FIG. In the present embodiment, the discharge time t is the discharge time t in relation to the integration circuit 44 at the subsequent stage. The integrating circuit 44 includes a resistor 441 and a capacitor 442.
And The integration circuit 44 uses the charging voltage of the capacitor 442 as the voltage signal 31. Capacitor 442
Performs the charging / discharging with the time | f1−f2 | · t as the discharging time and the time (1− | f1−f2 | · t) as the charging time within the unit time. For this reason, when the toner concentration decreases, the frequency f2 of the detection signal 221 decreases, and the discharge time decreases, so that the voltage signal 31 increases. Conversely, when the toner concentration increases, the frequency f2 of the detection signal 221 increases and the discharge time increases, so that the voltage signal 31 decreases. FIG. 21H shows the voltage signal 31.

As a result, it is possible to use only an inexpensive NAND gate without using an exclusive OR gate.

Although not shown, the detection coil 21 and the reference coil 11 are attached to the circuit board by the structure shown in FIGS. 2, 8 to 19 or a combination thereof. In the above embodiment, for the purpose of concrete description, a magnetic detection device for detecting toner concentration has been described as an example. However, the present invention is not limited to this, and is widely used for magnetic substance detection such as presence, quantity, concentration or distance of a magnetic substance. It can be used not only for magnetic materials but also for conductor detection. In the case of conductor detection, the inductance of the detection coil changes with the eddy current of the conductor, and this is used.

[0043]

[Effects of the present invention] As described above, according to the present invention, the following effects can be obtained. (A) The detection signal generation circuit has a detection coil and an oscillation circuit. The inductance of the detection coil changes when the detection coil is electromagnetically coupled to the object, and the oscillation circuit generates an oscillation frequency corresponding to the change of the inductance. Is changed and the oscillation frequency is output as a detection signal, so that the detection portion requires only one detection coil, and a magnetic detection device capable of reducing the size of the detection portion can be provided. (B) The signal processing circuit receives the reference signal and the detection signal as input signals and outputs an electric signal including a frequency signal having a difference between the frequency of the reference signal and the frequency of the detection signal. There is no need to make the frequency of the generation circuit and the detection signal generation circuit the same frequency, and the reference signal generation circuit and the detection signal generation circuit can be separated from each other. Therefore, it is possible to provide an inexpensive magnetic detector in which the oscillation frequencies of both can be easily adjusted. (C) Since the signal processing circuit outputs an electric signal including a frequency signal of a difference between the frequency of the reference signal and the frequency of the detection signal, the circuit configuration is simple and the magnetic detection has high detection sensitivity. Equipment can be provided. (D) The circuit board supports the reference signal generation circuit, the detection signal generation circuit, and the signal processing circuit. Since the detection coil is mounted on the surface of the circuit board, the entire circuit board can be assembled on the circuit board. It is easy to assemble, small,
A thin magnetic detecting device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a magnetic detection device according to the present invention.

FIG. 2 is a partial sectional view showing an example of an assembling structure of the magnetic sensing device according to the present invention having the circuit configuration shown in FIG. 1;

FIG. 3 is a partial cross-sectional view showing a specific example of a detection coil used in the magnetic detection device according to the present invention.

FIG. 4 is a partial sectional view showing another specific example of the detection coil used in the magnetic detection device according to the present invention.

FIG. 5 is a partial cross-sectional view showing another specific example of the detection coil used in the magnetic detection device according to the present invention.

FIG. 6 is a partial sectional view showing another specific example of the detection coil used in the magnetic detection device according to the present invention.

FIG. 7 is a block diagram showing another configuration of the magnetic detection device according to the present invention.

8 is a partial cross-sectional view showing an example of an assembly structure of the magnetic detection device according to the present invention having the circuit configuration shown in FIG. 7;

FIG. 9 is a partial cross-sectional view showing an example of an assembling structure of the magnetic sensing device according to the present invention having the circuit configuration shown in FIG. 7;

FIG. 10 is a partial cross-sectional view showing another example of an assembling structure of the magnetic detection device according to the present invention having the circuit configuration shown in FIG. 7;

11 is a partial cross-sectional view showing another example of an assembling structure of the magnetic sensing device according to the present invention having the circuit configuration shown in FIG. 7;

FIG. 12 is a partial cross-sectional view showing another example of an assembling structure of the magnetic sensing device according to the present invention having the circuit configuration shown in FIG. 7;

FIG. 13 is a partial cross-sectional view showing still another example of an assembling structure of the magnetic detection device according to the present invention having the circuit configuration shown in FIG. 7;

FIG. 14 is a partial cross-sectional view showing another example of an assembling structure of the magnetic detection device according to the present invention having the circuit configuration shown in FIG. 7;

FIG. 15 is a partial cross-sectional view showing still another example of an assembling structure of the magnetic detection device according to the present invention having the circuit configuration shown in FIG. 7;

FIG. 16 is a plan view of FIG.

FIG. 17 is a bottom view of FIG.

FIG. 18 is a partial cross-sectional view showing another example of an assembling structure of the magnetic detection device according to the present invention having the circuit configuration shown in FIG. 7;

FIG. 19 is a partial sectional view showing still another example of an assembling structure of the magnetic sensing device according to the present invention having the circuit configuration shown in FIG. 7;

FIG. 20 is a specific circuit diagram of the magnetic detection device according to the present invention.

FIG. 21 is a waveform diagram illustrating the operation of each section of the circuit.

[Description of Signs] 1 Reference signal generation circuit 121 Reference signal 2 Detection signal generation circuit 21 Detection coil 210 Insulating armor 211 Coil 22 Oscillation circuit 221 Detection signal 3 Signal processing circuit 5 Circuit board

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-182502 (JP, A) JP-A-2-266260 (JP, A) JP-A-62-245152 (JP, A) JP-A 61-182 160052 (JP, A) JP-A-51-43175 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 27/72-27/90

Claims (8)

(57) [Scope of request for utility model registration] 1. A reference signal generation circuit and a detection signal generation circuit
Magnetic detection device having a signal processing circuit and a circuit board
The reference signal generation circuit outputs a reference signal having a constant frequency.
The detection signal generation circuit includes a detection coil and an oscillation circuit.
And the detection coil is electromagnetically coupled to the object to be detected.
When the inductance changes, the oscillation circuit
The oscillation frequency changes in response to the change in
A circuit for outputting a frequency as a detection signal, wherein the signal processing circuit converts the reference signal and the detection signal
As an input signal, the frequency of the reference signal and the detection signal
A circuit that outputs an electrical signal that includes a frequency signal with a difference from the frequency
A circuit, wherein the circuit board includes the reference signal generation circuit, the detection signal.
The detection coil supports a generation circuit and the signal processing circuit, and the detection coil is mounted on a surface of the circuit board.
AndFurther, the reference signal generation circuit includes a reference oscillation circuit and a reference oscillation circuit.
And a reference oscillation circuit for the reference coil.
Outputting the reference signal corresponding to the inductance value,
The reference coil is mounted on the surface of the circuit board,  The detection coil and the reference coil have coil winding axes that are
A magnetic sensing device arranged to intersect. 2. The detecting coil is provided on one surface of the circuit board.
The magnetic sensing device according to claim 1 , wherein the reference coil is mounted on another surface of the circuit board . 3. The detection coil and the reference coil,
The magnetic sensing device according to claim 1 , wherein the magnetic sensing device is mounted on the same surface of the circuit board. 4. The coil of said detection coil and said reference coil .
Each is surrounded by a conductor pattern,
The said conductor patterns are mutually connected.
Or the magnetic detection device according to any one of the above items 3 . 5. The reference coil has a magnetic shield.
A magnetic sensing device according to claim 1, 2 , 3, or 4. 6.The detection coil;The reference coil isInsulation
A coil is buried inside the exterior body, and the end of the coil is
The battery according to claim 1, wherein the battery is led out of the insulating sheath.
A magnetic sensing device according to any one of 2, 3, 4 and 5.
Place. 7. The signal processing circuit includes an F / V conversion circuit.
The F / V conversion circuit converts the difference frequency signal to a voltage
7. The magnetic detection device according to claim 1 , wherein the magnetic detection device is a circuit that converts the electric signal into a signal and outputs the electric signal . 8. A signal processing circuit comprising: a multiplication circuit;
A multiplier circuit, wherein the multiplying circuit includes the reference signal and the
Multiplying by a detection signal to output a multiplied signal;
A circuit includes the multiplied signal as an input signal and is included in the multiplied signal.
Between the frequency of the reference signal and the frequency of the detection signal.
A circuit for passing a difference frequency signal .
The magnetic sensing device according to any one of 3, 4, 5, 6, and 7.