JPH0625728B2 - Zero deviation correction method for rotary viscometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention corrects the deviation of the zero point of the measured data of a rotary viscometer with a digital display that uses a converter that converts a viscous torque measurement value into an electric signal. According to the method.

[Prior Art] (a) The viscometer according to the present invention is used in petroleum / oil industry, paints,
Processes and quality control processes that are carried out in the ink industry, synthetic chemical industries such as synthetic resins and synthetic fibers, food industry, pharmaceutical industry, and almost all industrial fields that handle liquids such as detergents and cosmetics. In many cases, a rotary viscometer is often used for measuring the viscosity of a liquid, which is performed by sampling a sample liquid, because of its easy handling, wide measuring range, high reliability of measured values, and the like. In particular, a rotary viscometer having a signal converter for converting the viscosity measurement result into an electric signal is used.

(B) The operating principle of the rotary viscometer is shown in FIG. 2, and the vertical cross-sectional view of the one incorporating a signal converter is shown in FIG.

The method of correcting the zero point of the measured value in this kind of viscometer will be described below.

In FIG. 2, (1) is a motor with a speed change mechanism, (2)
Is a rotary drive shaft, (3) is a scale plate, (4) is a spring, (5)
Is the rotor shaft, (6) is the sample liquid, (7) is the rotor, (8)
Is a guideline. Sample liquid (6) by rotation of motor (1)
From the amount of angular displacement between the rotor shaft (5) and the drive shaft (2) when the viscous torque generated in the rotor (7) due to the viscosity of the rotor balances with the elastic force of the spring (4), that is, on the scale plate (3). The viscosity of the sample solution can be obtained from the finger pointer as being proportional to the finger pointer. In a rotary viscometer based on this principle,
As shown in FIG. 3, the relative angular displacement between the drive shaft (2) and the rotor shaft (5) is converted into an electric signal by using a signal converter such as a built-in rotary encoder or rotary differential transformer. In the figure, (1a) is an output shaft of a transmission motor, (2a) is a shaft coupling, (4) is a spiral spring, and (5a).
Is a pin, (5b) is an extended axis, (12) is an arm, (1
3) is a signal converter, (14) is a pivot, (15) is a jewelry bearing, and (15a) is a U-shaped member. The drive shaft (2) drives the rotor shaft (5) via the arm (12) and the spiral spring (4), and the upper end of the rotor shaft (5) is a pin (5a).
Is supported on the lower end of the drive shaft (2) by means of a pivot (14), and the drive shaft (2) supports the arm (1
It is supported by a jewel bearing (15) which is swiveled via 2).

FIG. 4 shows an overall view of a viscosity measuring device when the rotary viscometer with a built-in converter is used. In the figure, (21)
Is the main body of the viscometer. When the rotary encoder is used as a converter, the angular displacement is pulse counted by the pulse counter (22) (incremental encoder) or converted by the decoder (22) (absolute encoder). When the rotary differential transformer is used as the converter, its output is converted by the A / D converter (24) and displayed as a digital value on the display (23).
, Or print it on a printer.
(25) is a rotation speed setting device.

(C) The rotary viscometer detects the angular displacement of the rotor shaft when the torsional torque of the spiral spring is balanced against the viscous resistance torque generated by the rotation of the rotor (7) in the sample liquid (6). Since the viscosity of the sample liquid is obtained by the above, the friction torque between the pivot (14) and the gem bearing (15) becomes background noise against the condition of torque balance, which deteriorates the measurement accuracy.

(D) Experimental data are shown in FIGS. 5 and 6. In Fig. 5, the rotation speed of the viscometer is set so that the viscous torque of the Newtonian fluid swings to about 70% of the full-scale torque of the spiral spring (nominal value of the torque measured by the viscometer), and a timer is used. 2 is a recording example in which an analog signal output from a signal converter when repeating rotation for 2 minutes and stopping for 1 minute is recorded by a chart recorder.

FIG. 6 is a detailed explanatory diagram of an analog signal for one cycle in which rotation and stop of FIGS. 6 and 5 are repeated.

In FIG. 6, when the viscometer starts rotating at time t ₁ , the motor rapidly starts to rotate, the spiral spring is wound up by the motor and is biased in the rotational direction, and the rotor (7) starts rotating in the liquid. The angular displacement of the drive shaft (2) and the rotor shaft (5) is a record of the sharp rise indicated by (121). Next, after overshooting (122), the signal level converges to the signal level (123) corresponding to the angular displacement of the torque balance, and then stabilizes. Next, when the motor is stopped at time t _2, the flow returns to zero level (126) after the under-shoot indicated by the analog recording sharply falling (125) as indicated by (124). Due to the friction between this winding, the pivot and the jewel bearing, zero
The level shifts e as shown in the figure.

FIG. 5 is a record when the operation of FIG. 6 is repeated using a timer, and an overshoot (122) and an undershoot (124) are recorded for each repetition. The reproducibility of the signal level (123), which is obviously rotated and measured, is good, but the zero level when stopped
The level (126) is randomly distributed within the range of dispersion and the reproducibility is not good. This means that the zero level that is the standard of the viscometer's finger is not determined, and the index of the viscometer is not clear.

The cause of the zero level (126) variation is that when the viscometer stops, the restoring torque of the spiral spring is weak due to friction between the pivot and the gem bearing. Because it can stop at random positions.

On the other hand, the stable signal level (123) during rotation is due to the fact that the friction torque between the jewel bearings at the pivot is in a dynamic friction state due to the minute vibration associated with the rotation of the viscometer, and therefore has an effect on the torque balance. Is extremely small.

From the above, the currently practiced method of eliminating the zero-level variation is to remove the rotor (7) from the viscometer body to significantly reduce the load applied to the pivot and to reduce the viscometer to a low level of about 6 rpm. Idling at a rotational speed to create a dynamic friction state between the pivot and the jewel bearing, thus digitally storing the signal level as a zero level when the rotor shaft (5) rotates in a no-load state with only shaft weight. In actual viscosity measurement, a zero level correction method of measuring with reference to this zero level was performed.

[Problems to be Solved by the Invention] The above-described method of correcting the zero level in the no-load idle state is effective in eliminating the zero return instability when the viscometer is stopped due to static friction between the pivot and the jewel bearing. However, when the roque is removed from the main body of the viscometer and it spins, the friction torque decreases and the return torque of the spiral spring returns to true zero. Appears.

That is, Japanese Patent Application No. 1-179479 “Rotary viscometer with digital display” and Japanese Patent Application No. 1-17
As described in 9480 "Rotary viscometer with vibration damping device", this is fluctuation due to relative misalignment between the drive shaft of the viscometer and the rotor shaft.

That is, in FIG. 7, (0 ₁ ) is the center of rotation of the rotor shaft, (0 ₂ ) is the center of rotation of the drive shaft, (4) is the spiral spring,
(E) is the fixed end of the outer winding end of the spiral spring. The rotor shaft center (0 ₁ ) and the drive shaft center (0 ₂ ) are eccentric, and (ε)
It is supposed to be off. The outer fixed end (E) of the spiral spring revolves on a rotation locus (CT ₁ ) centered on (0 ₂ ). This means that the rotor shaft center (0 ₁ ) is relatively fixed and the outer fixed end (E) of the spiral spring is fixed to the rotor shaft center (0 ₁ ).
₁ ) and the center of the drive shaft (0 ₂ ) are equivalent to moving on a circle (CT ₂ ) whose radius is the amount of misalignment in synchronization with the rotation of the drive shaft. Superimpose Will be subject to rocking. That is, when the rotor is removed and the viscometer idles, the friction torque decreases and the torque of the spiral spring becomes zero.However, due to the above-mentioned swing of the rotor shaft due to misalignment of the drive shaft and the rotor shaft, The rotor shaft produces a relative variable angular displacement represented by the equation (1) with respect to the shaft, and transmits a variable signal via a signal converter.

An example of this fluctuation signal using the dimensions of the components actually used is as follows.

In FIG. 7, a differential transformer is used as the R ₀ = 15 mm signal converter, and the rotation angle range with good linearity is 0.
If it is set to -60 °, 60 ° becomes the full span of the viscometer transmission output, and if the fluctuation signal is allowed to be ± 0.2% of the full span, the following equation is established from the equation (1), That is, the allowable misalignment amount is 0.032 mm, which requires extremely strict accuracy.

FIG. 8 shows an example of zero level fluctuations caused by misalignment. It is a sinusoidal variation whose amplitude is determined by (ε) and (R ₀ ).

Conventionally, the fluctuation was ignored and the viscometer was idly rotated at a low speed with no load, and a reading timing signal was generated at an appropriate time after the overshoot to read the zero point at that time. , The accuracy of the measured values due to the above fluctuations,
There was a risk of degrading reproducibility.

Therefore, the present invention provides a zero deviation correction method for a rotary viscometer with a converter, which eliminates the above-mentioned defects of the zero displacement correction method for a conventional rotary viscometer and enables stable and accurate viscosity measurement. The purpose is to do.

[Means for Solving the Problems] In order to achieve the above object, in the method for correcting zero deviation of a rotary viscometer of the present invention, a motor with a transmission, a drive shaft having a spiral spring and a rotor are provided. One rotation of the signal converter that converts the angular displacement between the suspended rotor shafts into an electric signal and the output shaft of the motor or the drive shaft that is rotationally driven by engaging with the output shaft is evenly divided (2n). Rotation angle detecting means for producing a trigger signal for sampling the output of the signal converter for each rotation angle, 2n stacks for stacking and storing the sampled signal converter output data, and an average value by integrating the data in the stack In a rotary viscometer that has a computing unit for calculating, a zero register for temporarily storing the obtained average value, and a timing circuit for generating a read tine mig signal, the rotor is removed from the rotor shaft. The output from the signal converter is sampled by the trigger signal from the rotation angle detection means and A / D converted and sent to the stack for storage, and the average value of these data is calculated by the arithmetic unit. This is a zero deviation correction method in which the average value is obtained and read and stored in a zero register according to a timing signal, and this value is used as a correction amount for zero deviation as a reference amount for the subsequent viscosity measurement.

[Operation] Since the rotor is removed, the load applied to the pivot and jewel bearings is almost zero, and because of the low speed rotation, there is a dynamic friction state, and the error due to friction is almost eliminated. Furthermore, the core of the drive shaft and the rotor shaft is eliminated. The sinusoidal zero variation due to the shift is completely eliminated.

EXAMPLES The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a schematic diagram of a first embodiment of a rotary viscometer for carrying out the method of the present invention. The pulse motor is driven by the time-series pulse signal, and this pulse is processed by the rotation angle detecting means to produce a sampling trigger signal. (21) is the viscometer body, (32) is the pulse motor of the drive source, (3
3) is a rotary differential transformer as a built-in signal converter. (25) is a rotation speed setting device, which is a rotation speed required to change the static friction between the pivot and the jewel bearing into dynamic friction,
For example, a drive pulse having a pulse rate corresponding to 6 rpm is transmitted from the pulse generator (35) to generate a pulse pulse.
Rotate the motor at low speed. (30) is a clock.

On the other hand, the drive pulse is counted by the counter (36), and when the counter reaches a preset count value, the signal of the rotary differential transformer (33) is A / D converted and a sampling / timing signal is transmitted to be reset and counted again. To start. If the number of pulses required for one rotation of the pulse motor is N and the count of the counter is N / 2n, the output of the rotary differential transformer can be sampled at every angle that exactly divides one rotation of the rotor into 2n. (24) is an A / D converter. The sampled output of the rotary differential transformer is input to the stack (38-1), and at the same time, before that, each address (38-1), (38-2) of the stack is ...
.. (38-2), (38-3), ... (38-)
2n) at the same time, the last address (38-2
The data contained in n) are discarded. In this way, the differential transformer output data at each rotational position that divides one revolution of the rotor into 2n equal parts is held in the stack, and the oldest data is discarded each time new sampled data is entered.

On the other hand, the clock pulse from the clock (30) is integrated and counted by the timer (41), and there is a time delay from the start of rotation of the viscometer until the output of the rotary differential transformer goes through transient fluctuation and becomes sufficiently stable. When the read command signal is transmitted, each data in the stack (38) is averaged by the average value calculator (39), and the average value is stored in the zero register (40).

As shown in FIG. 8, these average value data include 2n pieces of data corresponding to one period (in the figure, the case is divided into 8 equal parts), so that the sinusoidal fluctuation component is completely removed and the level is zero-shifted. Is the most accurate zero level.

FIG. 9 shows a second embodiment for carrying out the method of the present invention. In this embodiment, as the rotation angle detecting means, a disk (51) having slits provided at every angle that equally divides the entire circumference into 2n is attached to the motor output shaft, and the slit is detected by sandwiching the outer edge of the disk. And a detector (52) for generating the sampling trigger signal. The other structure is the same as that of the first embodiment.

[Advantages of the Invention] In the conventional viscosity measurement using the rotary viscometer, the correction method of the present invention completely eliminates the sinusoidal fluctuation caused by the misalignment between the drive shaft and the rotor shaft, which occurs at the zero level which is the reference of the viscosity measurement. Since it can be removed, the following effects can be obtained.

Improvement of accuracy and reproducibility of viscosity measurement value Zero level does not fluctuate and is stable, so workers do not feel uneasy.

Automation of zero level measurement is possible. The present invention can be easily added to the function of the prior application of the present inventor, Japanese Patent Application No. 1-179479 "Rotary viscometer with digital display".

The product quality as a viscometer can be improved.

Conventionally, there were no definitive countermeasures for the pivot material, tip radius, and processing method to reduce the pivot friction, which was a problem in this type of rotary viscometer. Since the zero level sinusoidal variation in kinetic rather than static friction has been eliminated, the low friction requirements for pivot and jewel bearings can be greatly relaxed.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a first embodiment of a rotary viscometer for carrying out the method of the present invention, FIG. 2 is an operation principle diagram of the rotary viscometer, and FIG. 3 is a rotary viscometer incorporating a signal converter. FIG. 4 is a vertical cross-sectional view of the viscometer main body, FIG. 4 is a schematic diagram of a viscosity measuring device including the rotary viscometer main body shown in FIG. 3, and FIG. 5 is a viscometer that rotates for about 2 minutes and stops for about 1 minute. Chart record recording of the analog output signal from the signal converter when repeating the above, Fig. 6 is a detailed enlarged view of one rotation / stop cycle in Fig. 5, and Fig. 7 is the core of the drive shaft and rotor shaft. FIG. 8 is a diagram for explaining a sinusoidal fluctuation of the converter output due to deviation, FIG. 8 is a graph showing an example of zero level fluctuation caused by misalignment of the drive shaft and the rotor shaft, and FIG. 9 is a method for implementing the method of the present invention. It is a second embodiment of the body of the rotary viscometer. (2) …… Drive shaft, (5) …… Rotor shaft, (13) ……
Signal converter, (51) ... disk, (52) ... detector,
(30) …… Clock, (31) …… Viscometer body, (3
2) …… Motor with transmission, (33) …… Rotary differential transformer, (25) …… Rotary speed setting device, (35) …… Pulse generator, (36) …… Counter, (24) …… A
/ D converter, (38) ... stack, (39) ... average value calculator, (40) ... zero register, (41) ...
Timer.

Claims (1)

[Claims] 1. A transmission motor, a drive shaft for driving a rotor shaft connecting a rotor by the motor via a spiral spring, and a signal for converting relative angular displacement between the rotor shaft and the drive shaft into an electric signal. The converters (13) and (33) and a rotation angle detection means (36) for generating a trigger signal for sampling the output signal of the signal converter for each rotation angle that equally divides one rotation of the drive shaft into an even number (2n). ), (51), (52)
An A / D converter for digitizing the output signal of the sampled converter, 2n stacks for stacking these digital signals, and an average value calculation for accumulating the data in the stack to obtain an average value. And a timer,
In a rotary viscometer having a zero register, the rotor is removed from the rotor shaft, the rotor shaft is rotated at a low speed in an unloaded state, and a sampling trigger signal is generated by the rotation angle detecting means to output an output signal from the converter. Is sampled at the same time, A / D converted and stored in 2n stacks, an average value is created from the stored signal by an average value calculator, and a zero
A zero deviation correction method for a rotary viscometer, which is stored in a register and is used as a reference value for subsequent viscosity measurement to perform zero deviation correction.