JPS5825214B2 - Powder level detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powder or granule level detection device, and particularly relates to a powder or granule level detection device, in which the powder or granule is applied to a vibrating element, and the presence or absence of a restraining force on the free vibration of the vibrating element is determined by the presence or absence of a restraining force on the free vibration of the vibrating element. The present invention relates to a powder level detection device for detecting the level of granular material.

A device has been proposed that detects the level of the powder by bringing a powder or granule into contact with a vibrating piece such as a tuning fork or a vibrating piece, restraining it, stopping or attenuating its vibration, and converting the behavior into an electrical signal. ing.

In such a level detection device, if the powder or granules are ultrafine particles such as toner from a copying machine, such powder or granules have strong cohesive force and adhesion, so the powder or granules will adhere to the vibrating element and cause Even if the particle level was lower than the installation position of the vibrating piece, the restraining force of the vibrating piece was not sufficiently weakened, and level detection was sometimes impossible.

SUMMARY OF THE INVENTION An object of the present invention is to propose a powder level detection device that can operate reliably even for powder particles with strong cohesive force and adhesive force.

The present invention provides a vibrating piece provided so as to be exposed in a powder container at a level detection position, an electro-mechanical conversion element attached to the vibrating piece, and a vibrating piece housed in the powder container. and an electric circuit that detects the level of the powder or granule in the powder or granule container based on an electrical signal obtained from the electro-mechanical conversion element due to the free vibration of the vibrating piece due to exposure from the powder or granule. In the body level detection device, a forced excitation means that intermittently applies a strong forced excitation force including a resonance frequency of the vibrating element to the vibrating element, and in connection with intermittent forced excitation of the vibrating element by the excitation means; By providing a means for stopping the electric circuit from detecting the level based on the electrical signal obtained from the electro-mechanical conversion element while the vibrating element is in operation and a forced excitation force is applied to the vibrating element, the vibrating element is forced to move. The vibrating element is strongly vibrated to reliably remove the powder particles attached to the vibrating piece, and the detection device is prevented from performing level detection operation due to the electrical signal from the electro-mechanical conversion element generated with this forced excitation. , is characterized by eliminating level detection malfunctions.

The following description will be made based on the embodiments shown in the drawings.

In FIG. 1, reference numeral 1 denotes a vibrating piece (vibrating piece) with a rectangular cross section that utilizes the transverse vibration of a rod, and is supported by a thin membrane plate 2 around the nodes of transverse vibration so that the vibration is not restricted.

Electrostrictive vibrators 3, 3' are placed near the vibrating parts on both sides of the vibrating bar 1.
Glue.

The electrode of the electrostrictive vibrator 3 is connected to the input side of the amplifier 4, and the electrode of the electrostrictive vibrator 3' is connected to the output side of the amplifier 4, respectively.
1 and C2 through a DC cutoff circuit consisting of resistors R1 and R2, and form a positive feedback loop through the vibrating bar 1.

This is because the DC cutoff circuit has bias voltages of the same polarity at the input and output terminals of the amplifier 4 of the - power supply, and the polarities of the two electrostrictive oscillators 3 and 3' have different polarities of positive and negative as shown in the figure. be.

That is, if a DC voltage of opposite polarity is applied to the electrostrictive vibrators 3, 3', even if the voltage is quite low, the polarization decreases significantly and a phenomenon occurs in which the positive feedback oscillation of the vibrating bar is attenuated and stopped.

An oscillation circuit 5 for forcibly exciting the vibrating bar 1 is connected to an electrode of the electrostrictive vibrator 3 via a relay 6.

A relay 7 is also connected between the output of the amplifier 4 and the signal processing circuit 9.

Relay 6.7 is controlled by relay drive circuit 8, and relay 6.7 is controlled by relay drive circuit 8.
When relay 7 is closed, relay 7 is open, and when relay 6 is open, relay 7 is open.
It operates synchronously and periodically so that the gates are closed.

In the above configuration, the vibrating bar 1 vibrates self-excited in a free state, and the vibration is converted into an electric signal by the electrostrictive vibrator 3 and amplified by the amplifier 4.

The amplified signal is applied to the other electrostrictive vibrator 3', causing distortion in the electrostrictive vibrator 3', and this distortion acts to promote the vibration of the vibrating bar 1 (positive feedback loop).

Finally, the vibration comes to be sustained at the natural frequency of sound bar 1.

However, when powder or the like comes into contact with the vibrating bar 1 and restraining the vibrating bar 1, the positive feedback loop is broken and the vibration is attenuated or stopped.

When the powder, etc. that was restraining sound piece 1 is removed, sound piece 1
begins self-excited oscillation again.

The vibration output of the amplifier 4 is converted by the signal processing circuit 9 into an electrical output of a magnitude corresponding to the magnitude (or presence or absence) of self-excited vibration.

In this way, the sound piece 1 is
It is possible to know whether there is powder or granular material around (installation level).

By the way, as previously explained, if particles or the like adhere to the vibrating bar 1, self-excited vibration will not occur even if the particle is below the installation level of the vibrating bar 1.

However, according to the present invention, such problems can be prevented in the following manner.

The relay drive circuit 8 periodically outputs a relay drive voltage 1 as shown in FIG. 2a.

This relay drive voltage v1 is applied to the coil of the relay 6.7, and its contacts are opened and closed as shown in FIG. 2c.

Relay 6 is closed and relay 7 is open.

At this time, the output of the oscillation circuit 5 (the frequency is the same as the resonant frequency of the vibrating bar 1) is applied to the electrostrictive vibrator 3', and the vibrating bar 1 is forcibly excited.

At this time, even if the electrostrictive vibrator 3 outputs an output, this output will not be given to the signal processing circuit 9 because the relay 7 is open.

The particles attached to the vibrating bar 1 are shaken off by the vibration of the vibrating bar 1 due to this forced excitation.

Next, when relay 6 opens and relay 7 closes, vibrating bar 1 becomes self-excited due to the positive feedback loop, so the vibration of vibrating bar 1 depends on whether or not there is powder at the installation level of vibrating bar 1. A signal corresponding to the presence or absence of vibration is output from the signal processing circuit 9.

Note that similar effects can be obtained by applying the output of the oscillation circuit 5 to the electrostrictive vibrator 3.

FIG. 3 shows another embodiment, which has improved safety compared to the embodiment described in FIG.

Elements with the same reference numerals as in FIG. 1 are equivalent elements, so detailed explanations will be omitted.

10 is a variable (sweep) frequency oscillation circuit, which includes a first astable multi-by-break 11, an integrating circuit 12, and a second
It is composed of an astable multi-vibration router 13.

The first astable multi-by-break 11 generates a rectangular wave of about 1 second, and this output is converted into a triangle (with DC bias) centered at a predetermined level by the integrator circuit 12. It is applied to the bias circuit of the multi-by-break 13.

The second astable multivib break 13 is designed to oscillate at the same frequency as the resonant frequency of the vibrating bar 1 when biased with a DC bias voltage at a predetermined level, and therefore has a triangular wave bias voltage as described above. By applying this, the oscillation frequency of the second astable multi-bi flake 13 is vertically fluctuated (swept) around the resonant frequency of the vibrating bar 1.

Therefore, even if there are some fluctuations in electrical and mechanical constants due to changes in the temperature and humidity of the atmosphere, the vibrating bar 1 is forcibly excited at a frequency that includes the resonance frequency, and the shaking-off effect is stabilized.

FIG. 4 shows a vertical sectional view of a vibrating bar mechanism used as such a level detection device.

In the figure, a thin membrane plate 2 is silver-brazed around the transverse vibration node of a rectangular cross-section vibrating bar 1.

Then, electrostrictive vibrators 3 and 3' are bonded to both sides of the vibrating bar 1.

Hard insulating ring backings 14 and 15 are applied to both sides of the periphery of this membrane plate 2, and tightened and fixed to the main body 16 with cap nuts 17.

However, the gasket 15 may be omitted depending on the case.

The flexible thin wire 18 from each electrostrictive vibrator 3, 3' is soldered to each lead wire fixing conductive wire 19.

A similar flexible ground wire is led out from the brazing section between the vibrating bar 1 and the membrane plate 2.

(Not shown) Such a vibrating bar mechanism is attached to the powder container by the flange 16A of the main body 16.

In this case, sound bar 1 is located at the level at which the powder or granule is desired to be detected, and when the powder is above this level, sound bar 1 is restrained by the powder, and when it has fallen below this level, sound bar 1 is be released.

As described above, according to the present invention, the vibrating piece that comes into contact with the powder particles is intermittently strongly excited with a forced excitation force that includes the resonant frequency of this vibrating piece, so that the powder particles attached to the vibrating piece are Reliable level detection can be performed by shaking the body down, and since the level detection operation is paused during forced excitation, there is no problem with level detection due to forced excitation, and in the end, the cohesive force Therefore, it is possible to obtain a powder level detection device that operates reliably even for powder particles with strong adhesion.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIGS. 1 and 3 are electrical connection diagrams, FIG. 2 is a relay operation waveform diagram, and FIG. 4 is a vertical sectional side view of the vibrating bar mechanism. 1... Sound piece, 2... Membrane plate, 3, 3'.
...Electrostrictive vibrator, 4...Amplifier, 5...
...Oscillation circuit, 6,7...Relay, 8...
... Relay drive circuit, 9 ... Signal processing circuit, 10 ... Variable frequency oscillation circuit.

Claims (1)

[Claims] 1. A vibrating piece provided so as to be exposed inside the powder container at a level detection position, an electro-mechanical conversion element attached to the vibrating piece, and a vibrating piece installed in the powder container. an electric circuit that detects the level of the powder or granular material in the powder or granular material container based on an electrical signal obtained from the electro-mechanical conversion element due to the free vibration of the vibrating piece due to exposure from the contained powder or granular material; a forced excitation means that intermittently applies a strong forced excitation force including a resonance frequency of the vibrating element to the vibrating element; A powder or granular material characterized in that a means is provided for stopping the electric circuit from detecting the level based on the electric signal obtained from the electro-mechanical conversion element while the forced excitation force is applied to the vibrating piece. Level detection device. 2. The powder level detection device according to claim 1, wherein the excitation frequency of the forced excitation force to the vibrating element is swept in a frequency range that includes the resonance frequency of the vibrating element.