JP4564764B2 - Level detector - Google Patents

Description

  The present invention relates to a level detection device that detects a filling level in a container storing fine powder such as wheat flour with a vibrating rod.

  The level detection device vibrates the vibration rod with a natural frequency and a constant amplitude as shown in FIG. 7A, and the vibration frequency generated when the upper surface of the fine powder filled in the container contacts the vibration rod. In addition, the amount of decrease in amplitude is detected, and it is detected that the fine powder has been filled up to the position of the vibrating rod installed in the container (see, for example, Patent Document 1).

By the way, fine powder such as wheat flour easily adheres to the vibrating rod, and when the vibrating rod detects the fine powder, that is, when the vibrating rod is buried in the fine powder, the fine powder may adhere to the vibrating rod. Further, when the fine powder is pulled out from the container, the fine powder may remain deposited on the upper part of the vibration rod. If fine powder adheres or accumulates on the vibrating rod when the container is full, the vibration rod shifts or restrains the amplitude, so it returns to the full detection state where the vibrating rod vibrates. And a full signal indicating that the container is full is output, resulting in a detection error of the filling level. For this reason, conventionally, for example, the cross-sectional shape of the vibration rod has been processed so that the head is substantially triangular, so that the fine powder is less likely to adhere or accumulate.
Japanese Patent Application No. 9-53973

  On the other hand, when the level detection device is downsized, it is necessary to reduce the size while giving the strength to the vibration rod, so that the vibration sustainability is lowered. This is because the magnitude of strength and the ease of vibration have the opposite properties. Further, it can be said that the smaller the ratio of the weight of the adhered or deposited fine powder to the weight of the vibrating rod, the more susceptible to the adhered or deposited fine powder. When the amount of adhesion or deposition on the vibrating rod increases when the container is full, the vibration of the vibrating rod decreases as shown in FIG. 7B, and the vibration frequency also shifts. Since it is more likely to occur, it is not possible to return to the full detection state where the vibrating rod is oscillating, and a full signal is output and a detection error of the filling level occurs. On the other hand, when the cross-sectional shape of the vibrating rod is processed into a special shape so as to make it difficult for the fine powder to adhere or accumulate as in the prior art, the processing steps of the vibrating rod increase and the cost increases.

  The present invention has been made in view of the above-described conventional problems, and automatically removes fine powder adhering to or accumulating on the vibrating rod without processing the vibrating rod into a special shape. It is an object of the present invention to provide a level detection device that can restore vibration of a vibrating rod to a state where detection is possible, and suppress detection errors of a filling level.

In order to achieve the above object, a level detection device according to one configuration of the present invention includes a vibrating rod that protrudes into a container that stores a supplied fine powder, and vibrates the vibrating rod at a constant frequency and a constant amplitude. A rod drive unit, a filling level detection unit for detecting a predetermined filling level of the fine powder by detecting changes in vibration frequency and amplitude of the vibrating rod, and removing or fixing the fine powder adhering to or depositing on the vibrating rod A vibration unit that intermittently increases the amplitude of the vibrating rod so that the vibration unit intermittently outputs a vibration signal, and the vibration signal is input. And an amplification degree switching circuit for increasing the amplification degree of the rod driving unit, and when the filling level detection unit detects the predetermined filling level, a filling level detection signal is sent to the vibration unit. Is configured to force the vibration portion, when the fill level detection signal is input, it is configured to intermittently increase the amplification degree of the rod drive unit.
According to the above configuration, since the amplitude of the vibrating rod is intermittently increased, the fine powder adhering to or depositing on the vibrating rod is automatically peeled off, and the detection error of the filling level due to adhesion or deposition can be suppressed. In addition, with a simple structure, the amplification degree of the rod drive unit can be intermittently increased, and the amplitude can be increased by driving the vibrating rod with a large drive signal. In addition, the vibration rod is driven by a large drive signal and the amplitude is increased only while a predetermined filling level (full) is detected, so that useless driving operation is eliminated and power saving is achieved. Long life can be achieved.

In addition, a level detection device according to another configuration of the present invention includes a vibrating rod that protrudes into a container that stores the supplied fine powder, a rod driving unit that vibrates the vibrating rod at a constant frequency and a constant amplitude, A filling level detector for detecting a predetermined filling level of the fine powder by detecting a change in vibration frequency and amplitude of the vibrating rod, and so as to remove or prevent sticking of the fine powder adhered or deposited on the vibrating rod, A vibration unit that intermittently increases the amplitude of the vibration rod, and the vibration unit generates an vibration signal, a timer circuit that intermittently outputs the generated vibration signal, and vibration wherein the vibration signal detected from the rod and an operational amplifier for adding or multiplying the excitation signal is configured to enter the operational amplified signal to the rod drive unit, the filling Les Le detecting unit, when detecting the predetermined filling level, it is configured to fill level detection signals to output to the vibrating unit, when the vibrating section, wherein the fill level detection signal is input, The rod drive unit is configured to increase the amplification degree intermittently.
According to the above configuration, since the amplitude of the vibrating rod is intermittently increased, the fine powder adhering to or depositing on the vibrating rod is automatically peeled off, and the detection error of the filling level due to adhesion or deposition can be suppressed. In addition, with a simple structure, the input signal of the rod drive unit can be increased intermittently, and the vibration rod can be driven with a large drive signal to increase its amplitude. In addition, the vibration rod is driven by a large drive signal and the amplitude is increased only while a predetermined filling level (full) is detected, so that useless driving operation is eliminated and power saving is achieved. Long life can be achieved.

  Hereinafter, a first embodiment of a level detection apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a block circuit diagram of a level detection device. A vibrating piece 1 made of a metal plate on a plane has a base end portion 1a and a portion 1b serving as a vibration node in a cylindrical casing 2, and a pair of upper and lower supports. It is supported by 3a and 3b. A weight 4 is fixed to the vibration piece 1 at an intermediate portion between the supports 3a and 3b, and a vibration piezoelectric element 5a and a vibration detection piezoelectric element 5b are provided on both surfaces between the weight 4 and the support 3a. Is attached to constitute the vibrating rod 6. The piezoelectric elements 5a and 5b may be attached side by side or attached to the outside (base end 1a side) of the support 3a. The piezoelectric element 5a to which the drive signal is applied from the variable amplification drive amplifier 11 vibrates the vibrating rod 6. Unnecessary components are removed from the voltage signal generated in the vibration detecting piezoelectric element 5b by the vibration of the vibrating rod 6 by the band filter 12, and an AC voltage signal proportional to the amplitude at the vibration frequency of the vibrating rod 6 is amplified by the amplifier 13. Is input. The signal vo amplified by the amplifier 13 is input to the variable amplification drive amplifier 11, and the amplified drive signal vd is applied to the exciting piezoelectric element 5a, so that the vibration of the vibrating rod 6 is maintained. The variable amplification degree driving amplifier 11, the rod driving unit 10, the piezoelectric elements 5a and 5b, the band filter 12 and the amplifier 13 constitute a rod driving unit 10 which is a positive feedback transmission circuit.

  The amplified signal vo is input to the filling level detector 20. The filling level detection unit 20 outputs a filling level detection (full) signal m when the change amount of the frequency and amplitude of the input signal vo becomes a preset value, that is, when the decrease amount of the frequency and amplitude becomes the set value. . The full signal m is transmitted to a control device (not shown), and is used as a signal for stopping the supply of fine powder to the container, or operating a lamp or alarm buzzer (not shown).

  As shown in FIG. 2A, the timer circuit 31 of the vibration unit 30 switches the amplification signal S of FIG. 1 intermittently, that is, for a predetermined time interval. This is output to the circuit 32, and the timing for increasing the amplitude of the vibrating rod 6 is determined. At this timing, the amplification degree increasing signal Au is output from the amplification degree switching circuit 32 to the variable amplification degree driving amplifier 11 of the rod driving unit 10, and the amplification degree of the variable amplification degree driving amplifier 11 is switched so as to increase. Along with this, the drive signal vd output also increases. As a result, the amplitude of the vibrating rod 6 increases from the normal amplitude Ao to Al as shown in FIG. 2B, and the fine powder adhering to or depositing on the vibrating rod 6 peels off and falls off. Is removed or its sticking is prevented. Therefore, the vibration of the vibrating rod 1 can be returned to a state in which the fullness of the container can be detected, and the detection error of the filling level due to the fine powder adhering or depositing on the detecting vibrating rod 1 can be suppressed.

  FIG. 3 is a block circuit diagram showing a second embodiment of the level detection apparatus according to the present invention. The same components as those in FIG. In FIG. 3, the excitation unit 30 includes a timer circuit 31 including an oscillation circuit 33 and an operational amplifier (adder) 34. The timer circuit 31 of the vibration unit 30 generates an increase signal vb (FIG. 4B) generated by the oscillation circuit 33 and increasing the vibration signal S (FIG. 4A). As shown in FIG. 8, the intermittent increase signal vb1 is output to the operational amplifier 34 intermittently, that is, for a predetermined time interval, and the timing for increasing the amplitude of the vibrating rod 6 is determined. is doing. At this timing, in the operational amplifier 34, the intermittent increase signal vb1 is arithmetically amplified (added) to the voltage signal vo (FIG. 4D) input from the amplifier 13, and the operational amplification shown in FIG. The drive signal vob (vo + vb1) is output to the drive amplifier 14. The drive amplifier 14 amplifies the input drive signal vob to drive the vibrating rod 6, and intermittently increases the amplitude of the vibrating rod 6 as shown in FIG. The operational amplifier 34 adds the intermittent increase signal vb1 to the voltage signal vo. However, the voltage signal vo may be multiplied by the intermittent increase signal vb1. Also in the second embodiment, the fine powder adhering to or accumulating on the vibrating rod 6 can be removed similarly to the first embodiment, and the same effect can be obtained.

  FIG. 5 is a block circuit diagram showing a third embodiment of the level detection apparatus according to the present invention. The same or corresponding parts as those in FIG. In FIG. 5, the filling level detection unit 21 outputs a filling level detection (full) signal m to the timer circuit 31 of the vibration unit 30 when the filled fine powder reaches a level at which the fine powder comes into contact with the vibrating rod 6. To do. The timer circuit 31 outputs the excitation signal S to the amplification degree switching circuit 32 from when the full signal m is input until the full signal indicating that the container is full is output. The vibration rod 6 is driven in the same manner as in the first embodiment.

  According to the third embodiment, as in each of the above-described embodiments, in addition to removing fine powder adhered or deposited on the vibration rod 6, the vibration operation is performed only when the full signal m is output. Thus, it is possible to realize power saving during operation of the level detection device and a longer life by shortening the operation time of the excessive vibration of the vibration rod 6.

  FIG. 6 is a block circuit diagram showing a fourth embodiment of the level detection apparatus according to the present invention. The same or corresponding parts as those in FIG. In FIG. 6, the filling level detection unit 21 vibrates a filling level detection (full) signal m when the filled fine powder reaches a level at which the fine powder comes into contact with the vibrating rod 6, as in the third embodiment. Also output to the timer circuit 31 of the unit 30. The timer circuit 31 outputs the drive signal vob shown in FIG. 4 (E) to the drive amplifier 14 from when the full signal m is input until the full signal is output. Hereinafter, the same as in the second embodiment. To drive the vibrating rod 6.

  Also in the fourth embodiment, the fine powder adhering to or accumulating on the vibrating rod 6 can be removed as in the third embodiment, and in addition, the vibration operation is performed only when the full signal m is output. Therefore, it is possible to realize power saving during operation of the level detection device and a longer life by shortening the operation time of excessive vibration of the vibrating rod.

1 is a block circuit diagram of a level detection apparatus according to a first embodiment of the present invention. It is a signal waveform diagram of the same embodiment. It is a block circuit diagram of the level detection apparatus which concerns on 2nd Embodiment of this invention. It is a signal waveform diagram of the same embodiment. It is a block circuit diagram of the level detection apparatus which concerns on 3rd Embodiment of this invention. It is a block circuit diagram of the level detection apparatus which concerns on 4th Embodiment of this invention. (A) is a figure which shows a vibration waveform when fine powder etc. have not adhered to a vibration rod, (B) is a figure which shows a vibration waveform when fine powder etc. adhere to a vibration rod.

Explanation of symbols

6: Vibrating rod 10: Rod drive unit 11: Variable amplification drive amplifier 14: Drive amplifier 20, 21: Filling level detection unit 30: Excitation unit 31: Timer circuit 32: Amplification switching circuit 33: Oscillation circuit 34: Calculation Amplifier (adder)

Claims (2)

A vibrating rod protruding into a container for storing the fine powder fed;
A rod driving unit that vibrates the vibrating rod at a constant frequency and a constant amplitude;
A filling level detector for detecting a predetermined filling level of the fine powder by detecting changes in vibration frequency and amplitude of the vibrating rod;
A vibration unit that intermittently increases the amplitude of the vibration rod so as to remove or prevent the fine powder adhered or deposited on the vibration rod ;
The excitation unit includes a timer circuit that intermittently outputs an excitation signal, and an amplification degree switching circuit that increases the amplification degree of the rod drive unit while the excitation signal is input.
When the filling level detection unit detects the predetermined filling level, the filling level detection unit is configured to output a filling level detection signal to the excitation unit, and the excitation unit receives the filling level detection signal. And a level detecting device configured to intermittently increase the amplification degree of the rod driving unit . A vibrating rod protruding into a container for storing the fine powder fed;
A rod driving unit that vibrates the vibrating rod at a constant frequency and a constant amplitude;
A filling level detector for detecting a predetermined filling level of the fine powder by detecting changes in vibration frequency and amplitude of the vibrating rod;
A vibration unit that intermittently increases the amplitude of the vibration rod so as to remove or prevent the fine powder adhered or deposited on the vibration rod;
An oscillation circuit for generating an excitation signal, a timer circuit for intermittently outputting the generated excitation signal, and an operational amplifier for adding or multiplying the excitation signal to a vibration signal detected from a vibration rod And is configured to input the operation amplified signal to the rod driving unit,
When the filling level detection unit detects the predetermined filling level, the filling level detection unit is configured to output a filling level detection signal to the excitation unit, and the excitation unit receives the filling level detection signal. And a level detecting device configured to intermittently increase the amplification degree of the rod driving unit .

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