JPS63212843A - Method for vibrating vibration piece of viscometer - Google Patents

Abstract

PURPOSE:To keep the drive power to a vibration source constant regardless of any change in impedance accompanied by the change of circumferential environment, by measuring the current and voltage applied to the vibration source and controlling both of them so as to make the driving power of the vibration source constant. CONSTITUTION:An ammeter A is connected to a vibration source 21 in series with respect to a power amplifier 36 and a voltmeter V is connected in parallel to the series circuit of the ammeter A of the vibration source 21. The indication values (i), (v) of the ammeter A and voltmeter V are read by the operation part of a measuring apparatus main body. A control signal is outputted to the power amplifier 36 from an operational control part through an oscillator in order to regulate a current and/or voltage so as to make the driving power P applied to the vibration source 21 given by formula I (wherein Za is the internal impedance of the ammeter) constant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of vibrating a vibrating element of a viscometer mainly used for measuring the viscosity of a high-temperature melt such as powder for continuous casting.

[Prior art]

A vibrating one-sided type viscometer applies vibration at a predetermined frequency to the vibrating piece directly or indirectly using an excitation source powered by an electromagnet or a drive coil, and measures the viscosity of the vibrating piece in the air and at that time. The structure is such that the amplitude within the object is detected and the viscosity is measured based on the relationship between the viscosity and the amplitude determined in advance.

By the way, in order to improve the accuracy of viscosity measurement, it is necessary to maintain the vibration energy applied to the vibrating piece by the excitation source constant during the measurement period, and for this reason, it is usually done by constant control of the voltage or current applied to the excitation source. We are trying to achieve this.

4th. Fig. 5 is a schematic diagram showing conventional excitation source drive systems, and the drive system shown in Fig. 4 is a constant current control type, and the drive system shown in Fig. 5 is a constant voltage control type. be.

The constant current control type drive system shown in Fig. 4 is a power amplifier 36.
An ammeter A is connected in series with the excitation source 21, and the current is controlled to be constant and applied to the excitation on the assumption that the impedance Z of the excitation source 21 is always constant. The driving power P (=t''Z) is controlled to be constant.

Furthermore, the constant voltage control type drive system shown in FIG. Basically, the voltage is controlled to be constant so that the driving power P (=V''/Z) applied to the excitation source 21 is constant.

[Problem that the invention seeks to solve]

However, in both of these configurations, it is assumed that the impedance Z of the excitation source 21 is constant, but the iron core, coil, etc. that constitute the excitation source 21 are subject to environmental conditions 9 such as temperature, temperature, etc.
It is known that impedance changes due to changes in humidity, and if only the current or voltage is controlled at a constant level, the driving power at the excitation source will change, and accordingly, the vibration amplitude value that should be applied from the excitation source to the vibrating piece will change. There was a limit to the improvement of viscosity measurement accuracy.

Figure 6 is a graph showing the relationship between excitation source temperature and vibration, with excitation source temperature ('C) plotted on the horizontal axis and excitation source amplitude (μm) on the vertical axis. be.

As is clear from this graph, a change in temperature of about 1°C changes the amplitude value by about 10 μm (about 2.9χ), which is about 15% in terms of viscosity, which is an extremely large error factor. .

The method of the present invention was made in view of the above circumstances, and
The purpose of this is a viscometer that can apply the driving power to the vibration source to a predetermined vibration energy to the vibrating piece, regardless of impedance changes due to changes in the surrounding environment at the vibration source. The purpose of the present invention is to provide a method for exciting a vibrating element.

[Means for solving problems]

In the method of the present invention, a vibrating bar excitation method for a viscometer equipped with an excitation source that excites a vibrating bar by electrical means includes:
The current and voltage to be applied to the excitation source are measured, and the current and/or voltage are controlled so that the driving power of the excitation source is constant.

[Effect]

Thereby, the method of the present invention can maintain the driving power for the excitation source constant regardless of impedance changes due to changes in the surrounding environment.

〔Example〕

The method of the present invention will be specifically explained below based on the drawings. 1st
The figure is a schematic diagram of a viscometer to which the method of the present invention is applied, where 1 is a heating furnace and 2 is a viscosity measuring device.

3 indicates the main body of the measuring device.

The heating furnace 1 is composed of an electric furnace or the like, and has an opening 1a at the center of the upper wall, and has a crucible 11 for storing the object to be measured and a heater 1 for heating and melting the object to be measured for viscosity.
2 is disposed, and a feeder 13 for supplying the material to be measured for viscosity to the crucible 11 is installed at the upper outside of the furnace. The material is put into the crucible 11 through the guide hole 1b, and heated and melted to a predetermined temperature by the heater 12.

The heater 12 is controlled by a furnace controller 14 that operates based on a control signal from the arithmetic control section 31 of the measuring device main body 3, and the results are transmitted to the furnace temperature detection probe 15a and the temperature detection probe 15b of the object to be measured for viscosity. Detected temperature using multi-thermometer 32. Furnace controller 1 through arithmetic control section 31
This will be fed back to 4th. Further, the amount of the material to be measured for viscosity taken out from the supply device 13 is also adjusted by the arithmetic control section 31 through the sequencer 33 of the measuring device main body 3.

The viscosity measuring device 2 has a shaft 22 whose upper end is connected to an excitation source 21 constituted by a cone-shaped speaker, etc., hangs down through a heat shield plate 23, and a vibrating piece 24 is provided at the lower end of the shaft 22. A displacement meter 25 for detecting the amplitude of the vibrating piece 24 faces near the upper end, and the position where the vibrating piece 24 is pulled up to the outside of the heating furnace l as shown in the drawing by means of lifting means (not shown). The vibrating piece 24 is moved up and down through the opening 1a to a position where it is immersed in the object to be measured for viscosity inside the crucible 11.

The heat shield plate 23 is equipped with a water cooling jacket, and the heating furnace 1
The viscosity measuring device 2 is designed to cut off heat from the viscosity measuring device 2, thereby reducing the influence of heat on the viscosity measuring device 2.

Further, the displacement meter 25 is configured to detect the amplitude of the vibrating piece 24 through the shaft 22, and the detection signal is taken into the calculation control section 31 through the controller 26 and the multimeter 34 of the measuring device main body 3.

The vibration source 21 is configured to vibrate the diaphragm using an electric means such as an electromagnet or a drive coil, and transmit the vibration to the vibrating piece 24 through the shaft 22.
The amplitude is set by manually inputting a control signal from the arithmetic control section 31 of the measuring device main body 3 to the oscillator 35 and power amplifier 36. The resonance frequency of the vibration system is mainly used as the frequency, and the amplitude at that time is also used as the amplitude.

FIG. 2 is a schematic diagram showing the drive system of the vibration source 21,
An ammeter A is connected in series with the excitation source 21 to the power amplifier 36.
and a voltmeter V is connected in parallel with the series circuit of the excitation source 21 and the ammeter A, and the indicated values i of the ammeter A and the voltmeter ■.

(2) is read by the calculation control unit, and the calculation control unit outputs power through the oscillator 35 in order to adjust the current and/or voltage so that the driving power P given to the excitation source 21 given by the following equation (1) is constant. A control signal is output to the amplifier 36.

P=vi−i”Za −(1) However, Za:
The internal impedance 16 of the ammeter is a standard viscosity liquid, and the vibrating piece 24 is immersed in it before starting viscosity measurement.
temperature at that time.

It is used to detect the amplitude and define the characteristics of the viscosity measuring device 2 itself.

The arithmetic control unit 31 of the measuring device main body 3 reads the vibration amplitude Ea in the air of the vibrating piece 24, which is the source of the resonance frequency detected by the displacement meter 25, and the vibration amplitude E in the object to be measured for viscosity, and calculates the following. The viscosity η of the viscosity measurement object is calculated according to equation (2).

However, ρ: Density of the object to be measured for viscosity RH: Resistance outline of mechanical impedance specific to the viscometer a: Resonance frequency in air f: Resonance frequency in the object to be measured for viscosity S: Area of both sides of the vibrating piece R4'/πfaS'' in equation (2) is an apparatus constant, and if this is K, and it is 8, then equation (2) can be rewritten as equation (3).

ρη = 80 (3) Resonance frequency fa in air and vibration amplitude Ea in air are the frequencies at which vibrations of different frequencies are given to the vibrating piece in the air before the start of measurement, and the amplitude is maximum. is the resonance frequency fa, and the amplitude at that time is H
It is defined as a.

In addition, for n, before starting the measurement, the vibrating piece is immersed in two or more types of standard viscosity liquids, and the vibrating piece is vibrated at different frequencies, and the frequency at which the amplitude is maximum is f.

The amplitude at that time is defined as E, and the density of the standard viscosity liquid is ρ.
, is determined in advance based on viscosity, etc.

The temperature and viscosity of the object to be measured for viscosity determined by the arithmetic control section 31 are displayed and recorded on a CRT or printer each time.

The results of the viscosity measurement test using the method of the present invention as described above are shown in FIG.

The graph in FIG. 3 shows the temperature ('C) of the vibration source on the horizontal axis and the amplitude of the vibration source on the vertical axis.

As is clear from this graph, when the method of the present invention is used, the amplitude change is within 0.5 μm (approximately 0.5%) when the excitation source temperature changes by around 50°C, and the viscosity The converted error is approximately 0.7%, and it can be seen that the measurement accuracy is significantly improved compared to the conventional method shown in FIG.

〔effect〕

As described above, in the method of the present invention, the current and/or voltage is controlled to keep the driving power constant for the vibration source of the vibrating element, so it is possible to The present invention has excellent effects, such as being able to maintain a constant excitation source driving power without being affected, and significantly improving viscosity measurement accuracy.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a viscometer to which the method of the present invention is applied, Fig. 2 is a schematic diagram showing the drive system of the excitation source shown in Fig. 1, and Fig. 3 is the relationship between the amplitude of the excitation source and temperature. 4.5 is a schematic diagram showing a conventional excitation source drive system, and FIG. 6 is a graph showing the relationship between the amplitude of the excitation source and its temperature when using the conventional method. 1... Heating furnace 2... Viscosity measuring device 3... Measuring device body 11... Crucible 12... Heater 13.
...Supplier 14...Furnace controller 15a, 1
5b...Temperature detection probe 16...Standard viscosity liquid
21... Vibration source 22... Shaft 24... Vibration piece 25... Displacement meter 31... Arithmetic control unit Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney
Noboru Kono Calculation temperature ('C) Fig. 3 Excitation source temperature (1) Fig. 4

Claims (1)

[Claims] 1. In a method of excitation of a vibrating element of a viscometer equipped with an excitation source that is vibrated by electrical means, the current and voltage to be applied to the excitation source are measured, and the driving power of the excitation source is kept constant. A method for exciting a vibrating element of a viscometer, characterized in that the current and/or voltage is controlled in such a manner as to