JPS5947246B2 - Powder level detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a level detection device for powder and granular material, and more particularly to a forced excitation type powder and granule level detection device suitable for detecting the level of adhesive powder of ultrafine particles.

A self-excited oscillation circuit is constructed using a vibrating body such as a tuning fork or a vibrating piece, and the powder is brought into contact with the vibrating body, the vibration is attenuated or stopped, and the level of the powder is detected using the signal. The device is well known. A self-oscillating powder level detection device using a conventional vibrating body such as a tuning fork or a vibrating piece is used to detect the level of powder, especially ultrafine powder (such as toner in a copying machine). In this case, ultrafine particles have strong cohesive force and adhesion, so even if the powder adheres to the vibrating body and the level of the powder falls below the vibrating body, the vibrating body remains restrained. Therefore, self-oscillation becomes impossible. Therefore, there is a major drawback in that it is impossible to detect the level of powder or granular material. SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the conventional devices as described above, and to provide a powder level detection device that can operate reliably even when applied to powder particles with strong cohesive force and adhesive force.

The present invention is such that a vibrating body such as a nine-tuned fork or a vibrating piece is forcibly vibrated at its natural frequency to prevent or remove powder and granules from adhering to the vibrating body for detecting the level of powder and granules.

The present invention will be explained below with reference to an embodiment shown in FIG.

In the figure, a rectangular section 1 that utilizes the lateral vibration of a bar is supported around the lateral vibration node by a thin supporting membrane plate 2 so that the vibration is not restricted. Electrostrictive vibrating elements 3a and 3b are bonded near the vibration nodes on both sides of the vibrating bar 1. The oscillation circuit 4 is C
, R are connected to the electrostrictive vibrating element 3a through a DC current or disconnection circuit, and the other electrostrictive vibrating element 3b is connected to the input side of the amplifier 5 through a DC current or disconnection circuit of C and R as described above. connected to. A signal processing circuit 6 is connected to the output side of the amplifier 5. The reason why we added DC and disconnection to C and R is that if DC voltages of different polarities are left applied to the electrostrictive vibrating elements 3a and 3b, the decrease in polarization will stop significantly even at a considerably low voltage. This is because it will be put away.

Therefore, when DC voltages of different polarities are not applied to the electrostrictive vibrating elements 3a and 3b, there is no need for DC current flow or disconnection of C and R. In addition, when there is a sufficient electrical signal generated by the electrostrictive vibrating element 3b, the amplifier 5 is removed and the signal processing circuit 6 is directly
can be connected to. In the above configuration, the output voltage of the oscillation circuit 4, which generates an arbitrary voltage in the range of several volts to less than the withstand voltage of the electrostrictive vibrating element at a frequency approximately equal to the natural frequency of the vibrating bar 1, is applied to the electrostrictive vibrating element 3a. Then, the electrostrictive vibration element 3a
produces distortion and the vibrating bar 1 is forced to vibrate at its natural frequency, so the electrostrictive vibrating element 3b produces distortion and generates an electrical signal.

After the electrical signal is amplified by an amplifier 5, it is converted into an arbitrary signal by a signal processing circuit 6. Now, when a powder or the like comes into contact with the vibrating bar 1 and restrains it, the vibration of the vibrating bar 1 is attenuated or stopped.

When the powder, etc. that restrained the vibrating bar 1 is removed, the vibrating bar begins to vibrate separately. Therefore, the electric signal generated by the electrostrictive vibrating element 3b, that is, the output voltage of the amplifier 5, is as shown in FIG. Therefore, it is possible to detect the level of something that restrains the vibration of the vibrating bar 1, such as a powder or granule.Furthermore, according to the present invention, since the vibrating bar 1 is forcibly vibrated, sound piece 1
Since the powder or granules that have adhered to the surface are easily shaken off and no longer adhere, the level of the powder or granules can be detected reliably. FIG. 3 shows another embodiment of the present invention, which differs from FIG. 1 in that a frequency sweep circuit 1 is used instead of the oscillation circuit 4 in FIG.

Frequency sweep circuit T is Astable multipipulator 8
generates a rectangular wave, integrates the waveform in the integrator circuit 9, converts it into a nearly triangular wave, and uses the voltage of that waveform as the bias voltage of the next astable multiviprator 10 to obtain a frequency-swept output. . The appropriate output voltage range is from about several volts to less than the withstand voltage of the electrostrictive vibrating element 3a. Note that the design is such that the natural frequency of the vibrating bar 1 is always included within the frequency range to be swept. Furthermore, the frequency sweep circuit T is not limited to the above configuration. If the vibrating bar 1 is forced to vibrate using the output voltage of the frequency diagram sweep circuit T.
Even if the natural frequency changes due to variations in the natural frequency during manufacture of the vibrating bar 1 or due to ambient conditions such as eccentricity, there is an effect that there is always a frequency that matches the natural frequency. The operation is the same as the embodiment described in FIG. Although the present invention has been described above in a powder level detection device using a vibrating element and an electrostrictive vibrating element, the present invention can also be applied to a tuning fork vibrating body, an electromagnetic vibrating element, etc. .

According to the above explanation, since the present invention employs a separately excited oscillation method in which the powder or granular material level detection vibrator is forced to vibrate, it will vibrate even if the powder or granular material is attached to the level detection vibrator. The powder and granules are shaken off, and it also has the effect of preventing adhesion.

Therefore, whenever the powder level falls below the level detection vibrator, separately excited oscillation is started and level detection can be performed reliably, which is extremely effective in practical use.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a vibrating bar type powder level detection device showing an embodiment of the present invention, FIG. 2 is an output waveform explaining the operation of the device configured in FIG. 1, and FIG. FIG. 2 is a configuration diagram of a vibrating piece type powder repell detection device showing an embodiment of the present invention. 1...Sound piece. 2... Thin support membrane plate, 3a, 3b... Electrostrictive vibration element, 4...
...Oscillation circuit, 5 ...Amplifier, 6 ...
...Signal processing circuit, T ...Frequency sweep circuit,
8, 10...Astable multivibrator, 9...Integrator circuit.

Claims (1)

[Scope of Claims] 1. Supporting the vibration nodes of a vibrating body having a natural frequency, such as a rod or plate shape, and attaching two electro-mechanical conversion elements to the vibrating body, and attaching one of the electro-mechanical conversion elements to the vibrating body. , powder grains that apply a voltage of approximately the same frequency as the natural frequency of the vibrating body to cause distortion, and restrain the vibrating body depending on the magnitude of the electric signal generated in the other electro-mechanical conversion element. A powder or granular material level detection device characterized in that it detects the level of a granular material. 2. A powder level detection device according to claim 1, characterized in that the frequency applied to the electro-mechanical conversion element is swept.