JPH0344535A - Rotary viscometer with digital display - Google Patents

Abstract

PURPOSE:To stabilize the display of a signal and to make the measurement correct by sampling an output signal of a signal converter every rotating angle equally dividing the rotation of a driving shaft to an even number, and displaying the average value of the data of the even number corresponding to the rotating period. CONSTITUTION:When a pulse motor 32 is rotated at constant speeds, an electric signal proportional to the viscosity torque of a sample solution is sent out from a rotary differential transformer 33. A counter 36 counts this electric signal. Supposing that the counting number of the counter 36 is N/2n, the detecting data of the viscosity is A/D converted and sampled by 37 for every angles correctly dividing one rotation of a rotor into 2n. The sampling data is stored in a stack 38. The data within the stack 38 is integrated to obtain the average value by an average value arithmetic unit 39. The average value is output to a display device 41. Accordingly, in this structure, the sine variation which is inevitably superimposed with the measuring value can be completely removed. thereby making it possible to stabilize the display of the signal and to read the correct measuring value.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention applies resistance torque generated by the viscosity of the sample liquid to a cylindrical or cone-shaped rotor that is brought into contact with the sample liquid and driven to rotate. The present invention relates to a rotational viscometer with a digital display that measures the viscosity of a sample liquid by converting it into an electrical signal from the angular displacement of a spiral spring or the strain of a leaf spring interposed therebetween.

[Prior art] Conventionally, this type of viscometer uses a method in which the resistance torque generated by the viscosity of the sample liquid is balanced by a spiral spring, and the viscosity is measured from the amount of angular displacement when the rotor shaft is angularly displaced relative to the drive shaft. The prior art will be explained below with reference to the viscometer of .

In this type of viscometer, the principle of operation (constant shear rate method) is as shown in Figure 2. ), connect the rotor shaft (5) to the lower end (2°) of the drive shaft (2) via the spring (4), and measure the viscosity at the lower end of the rotor shaft (5). A rotor (7) is attached which is immersed in the sample liquid (6).

On the other hand, a pointer (8) extending above the scale plate (3) is attached to the rotor shaft (5), and the scale indicates the relative angular displacement between the drive shaft (2) and the rotor shaft (5). It can be read by the position of the pointer (8) on the plate (3).

With this configuration, as the rotor (7) rotates, the torque generated in the rotor (7) due to the viscosity of the sample liquid is balanced by the elastic force of the spiral spring (4).
5) is angularly displaced with respect to the drive shaft (2), the viscosity of the sample liquid (6) can be measured from the amount of angular displacement. That is, if the screw spring constant of the spiral spring (4), the dimensions of the rotor (7), and its rotation speed are determined, the index of the pointer (8) on the scale plate [3] will be the same as that of the sample liquid (6). The viscosity of the sample liquid can be determined by the index of the pointer (8).

Although Figure 2 shows the measurement principle when a single cylinder is used as the rotor, the measurement principle when the rotor is a combination of a cone and plate, the so-called cone-plate method, is as shown in Figure 3. In Fig. 3, a cone (7°) is attached to the rotor shaft (5) instead of the rotor (7), and a sample liquid (10) is filled between it and the stationary plate (9). Other members are shown with the same reference numerals corresponding to those in FIG. 2.

Moreover, FIG. 4 is an enlarged view of the cone (7°) and the vicinity of the plate (9).

There are various viscometer products based on this measurement principle, and recently, the relative angular displacement between the drive shaft (2) and the rotor shaft (5) can be measured using a scale plate (3) and a pointer (8). ), but there are also products on the market that can convert this displacement angle into an electrical signal using a signal converter built into the mechanism and transmit it.

A rotary encoder or a rotary differential transformer is used for this purpose.

Figure 5 shows one of the viscometers equipped with such a signal converter.
In the structural diagram showing an example, (1) is a motor with a speed change mechanism, (2)
) is the rotational drive shaft, which is connected to the motor output shaft (la) and the shaft coupling (2).
a) to engage and rotate. (5) is the rotor shaft, and a spiral spring (4) is attached to the top of the shaft.
), the center of the spring is fixed to the rotor shaft (5), and the outer winding end of the spring is fixed to the arm (12) extending downward from the drive shaft (2). Therefore, the rotation of the drive shaft (2) causes the arm (1
2) rotates around the rotor axis (5), so the rotor axis (
5) means that rotation is transmitted via the spiral spring (4), and if there is a load torque on the rotor shaft, the rotation will be transmitted between the drive shaft (2) and the rotor shaft (5) in proportion to the magnitude of the load torque. will result in a relative angular displacement. This angular displacement amount is converted into an electrical signal by a signal converter (13) interposed between the lower end of the drive shaft (2) and the upper end of the rotor shaft (5), and is transmitted. Note that the bottle (5) fitted on the upper end of the rotor shaft (5)
a) is inserted into a hole (not shown) provided in the center of the lower end surface of the drive shaft (2), so that the upper end of the rotor shaft (5) is prevented from steadying, and the lower part of the rotor shaft (5) is The pivot (14) attached to the square-shaped member (15b) and the jewel bearing (
15). A cone (7°) is attached to the lower end of the shaft (5b) extending below the U-shaped member. (9) is a stationary plate.

For example, when a viscometer with a built-in signal converter with such a structure is used as a converter, as shown in Fig. 6, the converter output is converted to a pulse counter (22) (incremental encoder ), by pulse counting the angular displacement, or by converting it with the decoder (22) (in the case of an absolute encoder), or by converting the angular displacement when using a rotary differential transformer as a converter. The output of the device is converted by the A/D converter (24) and displayed as a digital value on the display (24).
3) The configuration and function of this type of viscometer has been to employ an appropriate display and recording method, such as displaying the information on the screen or printing it on a printer. In addition, in Figure 6 (
21) is the viscometer body, (25) is the rotation speed setting device, (26
) indicates a circulating constant temperature water bath to maintain a constant temperature of the sample solution attached to the viscometer.

[Problems to be Solved by the Invention] However, in a rotational viscometer, whether the rotor is a single cylinder, double cylinder, or cone plate, due to actual machining and assembly errors, the rotor may be different from the drive shaft (2). The amount of angular displacement between the rotor shafts (5) fluctuates unstablely, and for this reason, if the digital value displayed on the display (23) in Fig. 6 is a 3-digit display, the minimum The displayed values of the digits may vary widely, making it difficult for the operator to read them. One or two typical causes of this will be listed below, and the situation in which the unstable fluctuations occur will be explained below.

Since the angular displacement detection method has been described so far, the following explanation will also be given using the angular displacement detection method as an example. The causes of unstable fluctuations can be roughly divided into two types: those caused by deviation of the rotor from the ideal state, and those caused by relative misalignment between the drive shaft and rotor shaft within the viscometer mechanism.

An example of a cone-plate type rotor is shown below.

FIG. 8 shows a case in which the cone is rotating in an ideal state in which the axis of rotation is perpendicular to the plate j.

First, in the case of Fig. 8, the gap G around the rotor is approximated by G = rα since the angle α is relatively small, and the linear velocity of the loaf surface is v = r ω.Therefore, the speed γ is γ = v / G: rω/rα = ω/α If η is the viscosity coefficient of the liquid, the generated torque T is expressed as 3α. From this equation, it can be seen that in an ideal state, there are no temporal fluctuation factors.

Next, FIG. 9 assumes that the plate is tilted at an angle δ8 from the ideal state shown in FIG. 8, and the cone axis swings around at an angle δ2 with respect to the rotation axis. Let us consider the rotor generated torque when the ideal state shown in FIG. 8 deviates from the ideal as shown in FIG. However, δ2 is a small angle compared to α.

The gap G (θ, t) around the rotor is given by azimuth θ, time t, and rotational angular velocity ω of the rotor, then G (θ, t) = ra
−rδ, cosθ−rδzcos(θ−ωt) Shear rate γ(θ, t) is γ (θ, 1)= r ω (α−δl CO3 θ−δ, C08 (θ−ωtN α −δ neck COS θ one δ2 C08 (θ-ωt) The sliding resistance torque T (1) is - δz Co5 (θ-ωt) - δ, C05 (θ-ωt).

(δ , +62 O8 ωt) O8 θ dθ - δz sin ωt ln θ Here, if we set δ 1+62 COS ωt=a δz sin ωt=b, the denominator of the equation in the integral sign is a-(acos θ+bsin θ)=α -ψ7 Bow ears 7 cos (θ-β) Here, β=jan-' and the condition of α〉〉ψ57th edition is established, so α - 7 skillF cos (θ-β) 3 terms in parentheses Since the following description is minute, it will be omitted. The first term in the parentheses is the same as the viscous torque in the ideal state, and the second term can be regarded as an increasing component generated when the second term deviates from the ideal state. If the increasing component is To, δl'+261 δ, COS ωt+δ! ``CO5'' ωt 1ηωR3 (δl'+62'') + 2δ1δx CO8 (AJ t, that is, in the state shown in Figure 9, the increasing component consists of a fixed component due to the inclination angles δ1 and δ2, and a variable component, both of which are seen to be minute amounts, It can be seen that the fluctuation component is a sine fluctuation with one rotation as one period.

Next, FIG. 1O shows the occurrence of fluctuations caused by misalignment between the drive shaft and rotor shaft in the viscometer mechanism. In the figure (O3
) is the rotation center of the rotor shaft, (0°) is the rotation center of the drive shaft, (4) is the spiral spring, and (E) is the outer fixed end of the spiral spring (4). Rotor shaft center (01) and drive shaft center (0,
) is off-centered, the outer fixed end (E) of the spiral spring (4) will have a rotational trajectory (CTI) centered at (0□).
It will rotate above. Relatively speaking, this means that the rotor shaft center (OI) is fixed and the spiral spring outer fixed end (E) is misaligned between the rotor shaft center (0,) and the drive shaft center (0□).
A circle (CT) whose radius is ε).

) is equivalent to moving the upper part in synchronization with the rotation of the drive shaft, and the rotor shaft is subjected to the oscillation of φ=(ε/Ro) sin ωt superimposed on the constant rotation of the drive shaft.

As described above, the rotor shaft receives a viscous torque with a fluctuation component as the rotor rotates, and a driving force with a swing component from the drive shaft side.

On the other hand, as shown in Figures 2, 3, and 5, the rotor shaft has a structure in which the mass including the rotor is suspended by a spring, and there is a damping effect due to the sample liquid in contact with the rotor. This forms a resonant vibration system in the rotational direction. Therefore, the fluctuating load torque and fluctuating driving force generated in synchronization with the rotation of the rotor described above become forcing forces, and the conditions for viscosity measurement,
In cases where it is necessary to select a rotor rotation speed close to the resonant frequency, resonance may generate quite significant vibrations, and sinusoidal fluctuations may appear in the measured signal as shown in Figure 7. .

The present invention eliminates the drawbacks of the conventional rotational viscometer described above,
An object of the present invention is to provide a rotational viscometer with a digital display that has a stabilized signal display that enables stable and accurate viscosity measurement.

[Means for Solving the Problems] In order to achieve the above object, the viscometer of the present invention includes a motor with a transmission, a signal converter that converts torque generated by sample liquid viscosity into an electric signal, and the above-mentioned a rotation angle detection means for generating a trigger signal for sampling viscosity measurement data at every rotation angle that divides one rotation of the output shaft of the motor or a drive shaft engaged with the output shaft into an even number of 20; 20 stacks that store measured data in stacks, a calculator that integrates the data in the stacks and calculates the average value, a register that temporarily stores the obtained average value, and a display that displays the average value in the register. The viscometer is configured to output and display the average value of data sampled at each rotation angle that divides one rotation of the viscometer into 20 equal parts.

[Function] In the rotational viscometer of the present invention having the above configuration, when the motor is rotated at a constant speed, viscous torque of the sample liquid is generated in the rotor as the rotor rotates, and an electric signal proportional to this viscous torque is transmitted. . As explained in detail above, this electrical signal contains a regular sinusoidal fluctuation component whose period is one rotation of the rotor. By performing A/D conversion and sampling, that is, sampling the data at each point that divides one cycle of rotor rotation into 20 equal parts, storing it in 20 stacks, and outputting the average value, the sinusoidal fluctuation component is removed. New data is added to the stack every time the drive shaft rotates, so the average value is always equal to 1 drive shaft rotation.
The moving average of the interval corresponding to the period is displayed and output, and therefore the indication is stabilized.

[Example] Hereinafter, preferred embodiments of the present invention will be explained in detail based on the drawings.

FIG. 1 is a diagram showing the main components of the first embodiment of the viscometer of the present invention. In this embodiment, a pulse motor is driven by a time-series pulse signal, and this pulse is processed to generate a sampling trigger signal. It has angle detection means. (31) indicates the viscometer main body, which includes a pulse motor (32) as a driving source and a rotary differential transformer (33) as a signal converter for converting a displacement angle into an electric signal. Rotation speed setting device (34)
When you set the rotation speed of the viscometer, the setting signal will cause
The pulse generator (35) divides the clock pulses from the clock (30) and transmits drive pulses at a pulse rate necessary to rotate the pulse motor at a specified speed, thereby rotating the pulse motor. On the other hand, the drive pulses are counted by a counter (36), and when the counter (36) reaches a predetermined count value, it sends out a sampling timing signal to sample the signal of the rotary differential transformer (33) and resets it. counting starts again. By setting the count value of the counter to N/2n, viscosity measurement data is sampled at every angle that accurately divides one rotation of the rotor into 20 equal parts. (37)
is a converter that A/D converts the analog signal of the rotary differential transformer. The viscosity measurement data sampled in this way is input to the stack (38-1), and at the same time, it is input to each address (38-1), (38-1) of the stack.
2),... Each measurement data contained in (38-2n) is (38-2), (38-3),... (38
-2n) all at once, and then shift to the last address (38-
The measurement data contained in 2n) is discarded. In this way, measurement data at each rotation angle that divides one rotation of the rotor into 2n equal parts is held in the stack, and the oldest data is discarded every time newly sampled data is input. Each data in the stack is black 7ri (30)
The average value is calculated by the average value calculator (39) at regular intervals from then on, and the calculated average value is written by refreshing the old data stored in the register (40). The data in this register (40) can be displayed on the display (41) every time it is refreshed, or can be output to a printer and recorded if necessary.

As shown in Fig. 7, the average value data obtained in this way is obtained by constantly averaging 20 pieces of data corresponding to one period, and creating a new one.
The oldest data 1 every time data is sampled
Since the average value is discarded, the interval in which the average value is taken is displayed and recorded as a so-called moving average value that moves every rotational phase of π/n, so that the sinusoidal fluctuation component can be completely removed.

Further, FIG. 11 shows a rotation angle detection means for generating a trigger signal for sampling in a second embodiment of the viscometer of the present invention.
In this embodiment, a disk (17) with slits provided at every angle dividing the entire circumference into 2n equal parts is attached to the motor output shaft, and the slits at each angle dividing the circumference into 20 equal parts are detected by sandwiching the outer edge of the disk. A detector (18) is provided to generate the desired sampling trigger signal. The other configurations are the same as in the first embodiment.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and may be applied to a drive source that uses a constant velocity motor such as a synchronous motor that uses a gear transmission as a transmission mechanism, and that is connected to the output shaft of this motor or to the output shaft of this motor. It is also possible to obtain a sampling trigger signal by optically, magnetically, or mechanically detecting the rotation angle divided into 2n equal parts using a slit or magnetic mark on a disk attached to the drive shaft. In this case, use phase-locked loop frequency modulation (PLL control) instead of a pulse motor, such as a DC servo motor.
Using a rotation control system stabilized with time-series pulse signals, the pulse signal can be processed to obtain a sampling trigger signal, or the time required for one rotation (T) can be calculated backwards from the drive shaft rotation speed setting. Time to divide into 20 equal parts (T・/
It is also possible to easily transmit a sampling trigger signal every 2n) using a built-in timer.

In addition, for viscous torque signal converters, there are not only angular displacement detection methods such as rotary differential transformers and encoders, but also stress detection methods such as piezo effect, 6n strain, and strain gauges. , single cylinder system, double cylinder system, etc., the present invention can be implemented without changing the gist of the invention.

[Effects of the Invention] As is clear from the above description, according to the present invention, it is possible to completely eliminate the sinusoidal fluctuation component that inevitably appears superimposed on the measured value depending on the rotational conditions in a conventional rotational viscometer. so you can read accurate measurements,
The following effects can be obtained.

■Make data easier to read for workers who operate the viscometer.

■Since the measured values do not vary, it does not cause anxiety to the worker.

■Easy to operate even by inexperienced users of viscometers.

■The cost of the viscometer product can be reduced because it is not necessary to increase rotor accuracy or the accuracy of each part of the viscometer.

■The quality of the product as a viscometer can be improved.■Even for viscous liquids whose characteristics are such that the viscosity of the sample liquid changes over time during viscosity measurement, all measurement data is replaced with one rotation of the rotor. No loss of response.

[Brief explanation of drawings]

Fig. 1: Overall configuration diagram of the first embodiment of the rotational viscometer of the present invention Fig. 2: Diagram of the operating principle of a conventional rotational viscometer having a cylindrical rotor Fig. 3: Conventional Figure 4 is a diagram of the operating principle of a rotary viscometer with a cone-plate rotor. Figure 5 is an enlarged view of the cone-plate section.
Figure 6 is a vertical cross-sectional view of the main body of a rotary viscometer with a built-in conventional signal converter. Figure 7 is an overall configuration diagram of a conventional rotary viscometer.
・・Output measurement value from the signal converter Fig. 8 ・・Cone・
Figure 9 is an enlarged view of the ideal state of the plate. Figure 10 is an enlarged view of the cone plate in a state deviated from the ideal state. Figure 11 is an operation diagram when the rotor shaft and drive shaft are eccentric. A vertical cross-sectional view of the main body of the second embodiment of the rotational viscometer of the present invention (30) is the clock, (31) is the viscometer main body, (32)
is a pulse motor, (33) is a rotating differential transformer, (34
) is the rotation speed setting device, (35) is the pulse generator, (3
6) is a counter, (37) is an A/D converter, (38) is a stack, (39) is an average value calculator, (40) is a register, and (41) is a display.

Claims (1)

[Claims] A rotational viscometer with a digital display includes a rotation angle detection means for generating a sampling timing signal at each rotation angle that divides one rotation of a drive shaft that drives the rotor at a constant speed into even numbers, and rotation of the rotor. It has a built-in signal converter that converts the viscous resistance torque that occurs due to It is characterized by having means for creating a moving average value of an even number of data corresponding to one cycle of one rotation, and by displaying and outputting the moving average value as a viscosity measurement result, the measurement signal display is stabilized. Rotational viscometer with digital display.