JPH0719932A - Powder level detecting device - Google Patents

Abstract

PURPOSE:To provide a powder levle detecting device for detecting the level of the powder with a piezoelectric vibrator equipped with comb electrodes. CONSTITUTION:Comb electrodes 8a, 8b are formed in the surface of a piezoelectric vibrator 7, and a vibrating circuit 9 is connected to these comb electrodes 8a, 8b through a frequency detecting circuit 10, and a display circuit 11 is connected to the frequency detecting circuit 10. In a powder level detecting device with this structure, when the oscillating output is applied to the comb electrodes 8a, 8b from the oscillating circuit 9, the piezoelectric vibrator 7 generates the flexural vibration, and this flexural vibration changes the frequency of the signal, which is applied to the comb electrodes 8a, 8b, by the powder, which abuts on the piezoelectric vibrator 7. Consequently, the level of the powder can be detected by detecting this frequency change with the frequency detecting circuit 10 and displaying it with the display circuit 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder level detecting device for detecting the level of powder by means of a piezoelectric vibrator having comb-shaped electrodes formed on one surface.

[0002]

2. Description of the Related Art Conventionally, as a level detecting device of this type,
As shown in FIG. 4, the piezoelectric ceramics 4 is adhered to the metal plate 3 attached to the opening 2 of the case 1, the circuit board 5 is attached to the case 1, and the detection circuit 6 is attached to the circuit board 5. Mounted devices have been proposed.

Further, as shown in FIG. 5, the piezoelectric ceramic 4 is provided with a main electrode 4a in the center, a feedback electrode is provided around the main electrode 4a, and an oscillation signal is inputted to the main electrode 4a. A signal is detected by the feedback electrode, and the level of the powder is detected from the change in the gain of the detected signal.

[0004]

By the way, since the level detecting device detects the amount of powder by turning the oscillation output on and off, the powder may cover the metal plate 3 or the powder may detect the metal plate 3. The presence or absence of powder is detected depending on whether it has dropped from the position,
There is a drawback that the amount of powder cannot be detected linearly.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a strip-shaped piezoelectric vibrator having comb-shaped electrodes formed on one surface thereof is mounted on a container, and the piezoelectric vibrator is attached to the piezoelectric vibrator according to a contact state between the piezoelectric vibrator and powder. A frequency detection circuit for detecting a frequency change of an input signal is connected to the comb-shaped electrode.

[0006]

According to the present invention, when the output from the oscillation circuit is input to the comb-shaped electrode of the piezoelectric vibrator, when the piezoelectric vibrator is in the air, it vibrates at a predetermined frequency. When touched, the frequency of the signal from the oscillation circuit changes.

The level of the powder can be detected by detecting the change in the frequency with the frequency detecting circuit.

[0008]

1 is a block diagram of a powder level detecting device according to an embodiment of the present invention, in which a strip-shaped piezoelectric vibrator 7 and a comb-shaped electrode 8 are provided.
a and 8b are formed, an oscillator circuit 9 is connected to the comb-shaped electrodes 8a and 8b via a frequency detection circuit 10, and a display circuit 11 is connected to the frequency detection circuit 10.

The piezoelectric vibrator 7 is mounted in a container in which powder is detected, and the comb-shaped electrode 8 of the piezoelectric vibrator 7 from the oscillation circuit 9 is installed.
When an oscillation signal is input to a and 8b, the comb-shaped electrodes 8a and 8b of the piezoelectric vibrator 7 vibrate.

Due to this surface vibration, the piezoelectric vibrator 7 vibrates at a predetermined frequency in the air, but when the powder comes into contact with the piezoelectric vibrator 7, the frequency becomes low. Display circuit 1 detected by
Display as 1.

FIG. 2 is a graph showing the values displayed on the display circuit 11 when the frequency change of the piezoelectric vibrator 7 is detected by the frequency detection circuit 10. The piezoelectric vibrator 7 having a length of 70 mm is shown in FIG.
Is not in contact with the powder at all, the detected frequency is 3.67 MHz, but when contacted up to 20 mm,
The detected frequency is 3.663MHz,
When the piezoelectric vibrator 7 is covered with powder up to 40 mm, the detected frequency is 3.633 MHz, and when the piezoelectric vibrator 7 is completely covered with powder, the frequency is 3.53 M.
It becomes H, and the detected frequency changes as shown in FIG.

In this embodiment, the level of the powder can be accurately detected by detecting the frequency change of the piezoelectric vibrator 7 in this way.

FIG. 3 is a block diagram of a powder level detecting device according to another embodiment of the present invention, in which a piezoelectric vibrator 7 having comb-shaped electrodes is vertically mounted in a container 13 containing powder 12. Further, the feedback oscillation circuit 14 is connected to the piezoelectric vibrator 7,
Further, the output of the feedback oscillation circuit 14 is connected to the frequency counter 15, the output of the frequency counter 15 is input to the arithmetic unit 16, and the output of the arithmetic unit 16 is the display circuit 1.
It is input to 1.

In this embodiment thus constructed, the output of the feedback oscillation circuit 14 is the comb-shaped electrodes 8a, 8 of the piezoelectric vibrator 7.
The frequency counter 15 counts changes in the frequency of the signals input to the comb electrodes 8a and 8b as well as to b.

When the number of pulses counted by the frequency counter 15 is input to the arithmetic unit 16, the arithmetic unit 16 counts the reference frequency and the powder 12 counts when the frequency is changed. The position of the frequency is calculated and displayed on the display circuit 11.

In this way, in this embodiment, the level of the powder 12 contained in the container 13 can be detected by detecting the frequency of the signal input to the comb electrodes 8a and 8b of the piezoelectric vibrator 7. it can.

[0017]

As described above, in the powder level detecting device of the present invention, when the oscillation output is input to the comb-shaped electrode formed on the piezoelectric vibrator, the piezoelectric vibrator vibrates, and a predetermined resonance occurs in the air. Although it vibrates at the frequency, when the powder comes into contact with the piezoelectric vibrator, this vibration is affected, and the frequency input to the comb-shaped electrode changes depending on the level of the powder. There is an advantage that the body level can be detected and the configuration is simple.

[Brief description of drawings]

FIG. 1 is a block diagram of a powder level detecting device according to an embodiment of the present invention.

FIG. 2 is a graph showing values detected by the device of FIG.

FIG. 3 is a block diagram of a powder level detecting device according to another embodiment of the present invention.

FIG. 4 is a side sectional view of a conventional powder level detecting device.

5 is a view of the detection unit of the apparatus of FIG. 4 viewed from the inside of the apparatus.

[Explanation of symbols]

 7 Piezoelectric vibrator 8a, 8b Comb-shaped electrode 9 Oscillation circuit 10 Frequency detection circuit 11 Display circuit 12 Powder 13 Container 14 Feedback oscillation circuit 15 Frequency counter 16 Arithmetic device

Claims (2)

[Claims] 1. A strip-shaped piezoelectric vibrator having comb-shaped electrodes formed on one surface thereof is mounted in a container, and a frequency change of a signal input to the piezoelectric vibrator is detected by a contact state between the piezoelectric vibrator and powder. A powder level detecting device characterized in that a frequency detecting circuit is connected to the comb-shaped electrode. 2. The frequency detection circuit calculates a feedback oscillation circuit connected to the piezoelectric vibrator, a frequency counter that counts the frequency of a signal from the feedback oscillation circuit, and the number of pulses counted by the frequency counter. A computing device,
2. The powder level detecting device according to claim 1, further comprising a display circuit for displaying an output signal calculated by the calculating device.