JPS5841321A - Detecting device of magnetic body - Google Patents

Abstract

PURPOSE:To make the detection of the quantity of magnetic powder extremely accurate, by changing the inductance of an oscillating coil, performing the first detection based on the presence or absence of the oscillation in an oscillating circuit, and performing the second detection based on the change in the oscillating frequency. CONSTITUTION:When the quantity of the magnetic powder P in a container 1 is higher than Z level, a compressing force due to the volume and density of the powder P is applied to a piezoelectric vibrator 3, the impedance of the vibrator 3 is changed, the oscillating conditions at a preset frequency f1 or f2 is not satisfied, and the transistor oscillating circuit is not oscillated. When the quantity of the powder P becomes lower than Y level, the circuit 20 is oscillated at a resonant frequency based on the vibrator 3 and a supporting body. In this case, since the powder P is closely located to a detecting winding 5 of the oscillating coil T, the oscillation occurs at the lower frequency f1 and the detected signal is outputted to an output terminal 31 of a BPF FL1. When the powder P becomes lower than X level, the circuit 20 is oscillated at the higher frequency f2, and the detected signal is outputted to an output terminal 32 of a BPF FL2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic substance detection device that detects the amount of magnetic powder, magnetic liquid, magnetic particles, etc. using a piezoelectric vibrator.

Conventionally, devices for detecting objects such as powders and liquids include a piezoelectric vibrator placed at the bottom of a container containing the object to be detected, such as powder or liquid, and when the object comes into contact with the piezoelectric vibrator, the object is detected. Some objects are detected by utilizing a change in the oscillation state of the piezoelectric vibrator when a pressing force due to its bulk and density is applied to the piezoelectric vibrator. However, this method can only detect whether or not the object to be detected is in contact with the piezoelectric vibrator.

Therefore, in the case where powder, liquid, etc. have magnetism, the present invention utilizes this magnetism to change the inductance of the oscillation coil, so that the inductance of the oscillation coil using the piezoelectric vibrator is changed depending on whether or not the oscillation circuit using the piezoelectric vibrator oscillates. The present invention provides a magnetic body detection device capable of performing one stage of magnetic body detection and second stage of magnetic body detection by changing the oscillation frequency.

Embodiments of the magnetic body detection device according to the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the mounting structure of the piezoelectric vibrator and the detection winding of the oscillation coil in an embodiment of the magnetic body detection device of the present invention. In this figure, a cylindrical protruding support body 2 is integrally formed at the bottom of a container 1 for storing magnetic powder P, etc.
The peripheral portion of the piezoelectric vibrator 30 is supported and fixed at the tip end surface of the support body 2. Further, a detection winding recess 4 is formed in the side surface of the container 1 further below the mounting position of the piezoelectric vibrator 3, and a detection winding 5 of the oscillation coil is disposed within this detection winding recess 4.

As shown in FIGS. 2 and 3, the piezoelectric vibrator 3 has a piezoelectric ceramic 11 attached on a diaphragm 10 made of a thin plate of non-magnetic metal such as copper or aluminum, and an electrode 12 on the piezoelectric ceramic 11.
A and 12B are formed. Here, each diaphragm 10H functions as a common electrode facing the poles 12A and 12B, and the diaphragm 10 and each electrode 12A
, 12BK are lead wires 13A to 13 for electrical connection.
0 is connected. In use, three such piezoelectric vibrators come into contact with the contents in the container 1 at the diaphragm 100 portion, and the piezoelectric ceramic 11 and the electrode 12A.

The diaphragm 12B is made so as not to come into direct contact with the contents, and the diaphragm 10 is usually set to have a thickness of about 30 to 500 μm.

As shown in FIG. 4, the oscillation coil T used in the oscillation circuit that drives the piezoelectric vibrator 3 has a second winding N and a second winding N! and the detection winding 5 connected in series with the secondary winding Iil, and the capacitor 01 is connected to the series connection of the secondary winding N1 and the detection winding 5 to form a parallel resonant circuit. It is configured.

On the other hand, the electrical configuration of the magnetic substance detection device is shown in FIG. In this figure, the transistor oscillation circuit 20 has the piezoelectric vibrator 3 inserted into a feedback circuit, and has an oscillation coil T provided on the collector side of the transistor Qt.
A base bias is applied to the base of the transistor Q1 by a resistor R1+R1, and a base bias is applied to the base of the transistor Q1.
There is a variable resistor VR between the emitter and ground for gain adjustment.
is inserted. The primary winding Nl of the oscillation filter T, the detection winding 5, and the capacitor O1 constitute a parallel resonant circuit, and the DC voltage supplied to the power supply terminal 21 via this parallel resonant circuit is applied to the collector of the transistor Ql. be done.

Secondary winding N of oscillation coil T.

One end is grounded, and the other end is connected to one electrode of the piezoelectric vibrator 3 (electrode 12A in FIG. 3). The other electrode of the piezoelectric vibrator 3 (electrode 12B in FIG. 3) is connected to the pace of the transistor Q1.

What is important about the transistor oscillation circuit 20 is that the piezoelectric vibrator 3 is not driven at its own fundamental resonant frequency, but the piezoelectric vibrator 3 and the support resonate at a frequency that exceeds this fundamental resonant frequency. This means that the piezoelectric vibrator 3 is driven at at least one of the frequencies. The reason for this is that if the automatic oscillation circuit is configured to oscillate at the fundamental resonant frequency unique to the piezoelectric vibrator, there are many factors such as the mounting position of the piezoelectric vibrator, the tightening pressure, and the distortion of the support that supports the piezoelectric vibrator. This is because the oscillation can easily stop due to various factors, making the operation extremely unstable, making it difficult to set the detection sensitivity, and making it easy for variations to occur.

Figure 6 shows the fundamental resonance frequency f when a piezoelectric vibrator 3 with a diameter of 20 m is used, and the resonance frequencies f+ and fs when the piezoelectric vibrator 3 is mounted on a support.
, fs... and the thickness vibration frequency f of the piezoelectric vibrator 3. As can be seen from this figure, if the fundamental resonance frequency f1 is about 2 + 500 Hz, the thickness vibration frequency f? is considerably higher than that, around 4MH2, and the resonance frequency f due to both the piezoelectric vibrator 3 and the support body is
1. f*, fs...ke f, and f? It will be located in the frequency range between . For example, ft t f snow + f
s... takes a value of about several tens of KHz to several hundred KHz. Therefore, the primary resonance frequency of the oscillation coil T when the magnetic powder P in the container 1 is below the level X in FIG. is above the X level and below the Y level, if the primary side resonance frequency of the oscillation coil T is set to fl, the amount of magnetic powder P can be detected as a change in the oscillation frequency of the transistor oscillation circuit 20. I understand.

Now, the output of the transistor oscillation circuit 20 in FIG. 5 is connected to the collector of the transistor Qs by the capacitor C! and a bandpass filter FLI.

0 added to FJ Here, the bandpass filter FLI passes signals near the frequency fl and outputs them to the output terminal 31, and is a bandpass filter! The L signal is for passing a signal near the frequency f2 and outputting it to the output terminal 32. Note that the power supply line 22 connected to the power supply terminal 21 is grounded through a capacitor Os.

In the configuration of the above embodiment, if the amount of magnetic powder P in the container 1 is sufficiently large and is equal to or higher than the level 2 shown in FIG. In addition, the impedance of the vibrator 3 changes, and the oscillation condition at the preset frequency f1 or f is not satisfied,
The transistor oscillation circuit 20 does not oscillate. Therefore, no signal is output to either of the output terminals 31 and 32. Next, when the amount of magnetic powder P in the container 1 decreases and becomes below level Y, the piezoelectric vibrator 3 oscillates as a transistor at the resonance frequency of the piezoelectric vibrator 3 and the support without being affected by the powder P. Circuit 20 oscillates. However, in this case, since the magnetic powder P is close to the detection winding 5 of the oscillation filter T, it oscillates at the lower resonance frequency f1, and therefore a detection signal is output to the output terminal 31 of the bandpass filter FLI. This detection signal makes it possible to identify that the amount of magnetic powder P is below the Y level and above the X level. Furthermore, when the magnetic powder P in the container 1 becomes extremely small and becomes below level X,
Since the magnetic powder P does not come close to the detection winding 1g15,
The transistor oscillation circuit 20 oscillates at the higher resonant frequency fw, and the bandpass filter PL.

A detection signal is output to the output terminal 32 of. This detection signal makes it possible to identify that the magnetic powder P is below the X level.

According to the configuration of the embodiment as described above, the following effects can be achieved.

(1) A part of the oscillation coil in the transistor oscillation circuit 20 is set as a detection winding [5] so as to be close to the magnetic powder P. In addition to the step-by-step detection operation, a second-step detection operation can be performed based on the presence or absence of the magnetic powder P approaching the detection winding @5.

Therefore, the amount of magnetic powder P can be detected more accurately.

(2) The oscillation circuit 20 of the transistor oscillation circuit 20 is oscillated by using a higher resonance frequency of the piezoelectric vibrator 3 and its support without using the fundamental resonance frequency of the piezoelectric vibrator 30. Therefore, fluctuations in the operation due to external factors such as the mounting position of the piezoelectric vibrator 3, the tightening pressure, and strain on the support side are extremely small.

Therefore, it is possible to reduce variations in detection sensitivity and improve reliability.

In addition, the bandpass filter FL! A four-pass filter may be used instead of the bandpass filter PL, and a bypass filter may be used instead of the bandpass filter PL.

As described above, according to the present invention, the inductance of the oscillation coil is changed using the magnetism of powder, liquid, etc., and the first stage is determined by the presence or absence of oscillation of the oscillation circuit using the piezoelectric vibrator. In addition to detecting a magnetic body, it is possible to obtain a magnetic body detection device capable of performing second-stage magnetic body detection based on a change in oscillation frequency caused by the change in inductance.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the arrangement of the piezoelectric vibrator and the detection winding of the oscillation coil in the magnetic substance detection device of the present invention, Fig. 2 is a front view of the piezoelectric vibrator used in the embodiment, and Fig. 3 is the bottom view of the piezoelectric vibrator. Figure 4 is a circuit diagram showing the oscillation coil used in the example, Figure 5 is a circuit diagram showing the electrical configuration of the example, and Figure 6 is the resonance frequency of the piezoelectric vibrator and support and the piezoelectric vibrator. FIG. 3 is an explanatory diagram showing a relationship with a unique fundamental resonance frequency. 1... Container, 2... Support, 3... Piezoelectric vibrator,
4...Four parts for the detection winding, 5...Detection winding i1! , 10
...Diaphragm, 11...Piezoelectric ceramic, 20...
Transistor oscillation circuit, 21... power supply terminal, 31.3
2... Output terminal, 01 to 0. ...Capacitor, F
Ll, 'IPLg...bandpass filter, P...magnetic powder, Q4...transistor, T...oscillation coil. Patent Applicant Tokyo Denki Kagaku Kogyo Co., Ltd. Eroica Coordination Co., Ltd. Agent Patent Attorney Takashi Murai Figure 1 Figure 3

Claims (1)

[Claims] (1) A piezoelectric vibrator is attached to a support so that it can come into contact with a magnetic material, and at least one of the resonance frequencies of the piezoelectric vibrator and the support exists in a frequency range exceeding the fundamental resonance frequency of the piezoelectric vibrator itself. In one step, the piezoelectric vibrator is driven by an oscillation circuit, and at least a part of an oscillation coil of the oscillation circuit is arranged so as to be close to the magnetic body, and the magnetic body is detected in the first stage based on the presence or absence of oscillation of the oscillation circuit. A magnetic body detection device characterized in that a second stage of magnetic body detection is performed by changing the oscillation frequency of the oscillation circuit.