JPH0257261B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to an improvement of a spring-type hardness meter for measuring the hardness of an elastic body such as rubber, and in particular, to an improvement of a spring-type hardness meter for measuring the hardness of an elastic body such as rubber. This invention relates to a digital hardness meter that can automatically read hardness and display the measured value digitally.

[Conventional example]

Conventional spring-type rubber hardness meters described in JIS K6301 Section 5.2, SRIS 0101 Section 4.2, and ASTM D2240 press an indenter against the sample to be measured, and the indenter moves up and down due to the reaction force of the material to be measured. An analog system was used in which directional movement was converted into rotation by a rack and pinion mechanism, and the scale on the gauge board was read from the movement of the indicator needle on the analog gauge board.

Furthermore, recently, Japanese Patent Publication No. 55-20191 and Japanese Patent Application Laid-open No. 56-153235 have proposed a digital rubber hardness meter that uses a differential transformer to convert the amount of vertical movement of an indentation needle into an electrical signal. It has been reported in JP-A-57-184949 and JP-A-58-
Publication No. 9044 describes a method of converting into electrical signals using a variable resistor, Japanese Patent Application Laid-open No. 72032/1983 describes a method of converting into electrical signals using a rotary encoder, and Publication of Utility Model Application Publication No. 59-20146 describes a method of converting into electrical signals using a variable resistor. Methods of converting signals into electrical signals using scales have been reported, but all of these methods have problems and are still in use today, but they have not yet been put into practical use. It is.

Incidentally, there are already tens of thousands of rubber hardness testers on sale in Japan, but most of them are analog systems using a rack and pinion mechanism. The characteristics of this method are that it is small, easy to carry, and inexpensive. However, on the other hand, there are problems with poor measurement accuracy and measurement results that change over time, making it impossible to record accurately by visual measurement. Ta.

This is because the vertical movement of the indenter is converted into rotational movement, and since it is small, it is not possible to obtain a sufficient amount of rotation, and the conversion part tends to rattle, causing problems in measurement accuracy. It was unavoidable.

Therefore, with the rotary encoder method, which uses this conversion method to convert vertical movement into rotational movement, problems arise in measurement accuracy in this conversion part, and it is difficult to understand how computers and other devices can be used to analyze it afterwards. However, this does not mean that the hardness of the sample being measured has been accurately measured, and the conventional problems have not been solved.

On the other hand, the method of digital conversion using a variable resistor involves contacting the resistor with the amount of vertical movement of the push needle and converting the amount of change into an electrical signal.
This method not only cannot accurately detect the small amount of vertical movement of the indenter due to the friction caused by contact, but also the detected electrical resistance is an analog value, and it cannot be converted into a digital meter without converting it from analog to digital. As a result, the hardness meter has a large number of components, which poses a major problem: not only is the measurement accuracy poor, but the hardness meter is large and expensive.

In addition, although the differential transformer method has already been put into practical use, it requires analog/digital conversion of the electrical quantity, and like the variable resistor method, it has the problem that the hardness meter itself is large and expensive. There is. These large hardness testers cannot be powered by batteries from the point where they require power, so they cannot be carried anywhere, and they also have other problems such as being susceptible to power fluctuations and electrical noise. have.

In addition, a linear scale as shown in the above-mentioned Japanese Utility Model Publication No. 59-20146 has been proposed, but in a device using this linear scale, the movement of the slit is controlled by an optical sensor using a single slit plate. However, since the system was designed to be read, there is a problem in that the reading accuracy is poor.

For example, JIS K6301 section 5.2, SRIS 0101 4.2
In the spring-type hardness tester described in Section 1 and ASTM D2240, the push needle protrudes 2.54 mm from the hardness tester, and the hardness becomes 100 when the pressure moves 2.54 mm.
In other words, with hardness 1, it is necessary to detect the movement of the indenter by 0.0254 mm, and in order to accurately detect such minute displacement from the movement of a single slit plate, a lens is required to magnify and detect the displacement. The hardness tester itself becomes large and expensive because it requires a device using a micrometer or a minute light-receiving element. Furthermore, if a magnifying device is not used, only about 10 units of hardness can be read, resulting in poor accuracy.

[Purpose of the invention]

Therefore, the purpose of the present invention is to solve the various problems of the conventional digital hardness meter and to obtain highly accurate hardness measurements by directly detecting the amount of vertical movement of the indenter using a linear encoder. Moreover, it is an object of the present invention to provide a completely novel and excellent digital hardness meter that is small and portable, and which can obtain the dispersion degree of a sample at a low cost.

[Structure of the invention]

The digital hardness meter of the present invention that achieves the above object is a hardness meter that measures the hardness of a flexible material using an elastic member, and is provided with a linear encoder that detects the amount of movement of the indenter. The encoder includes a movable slit plate that is interlocked with the indenter, a fixed slit plate that is attached to a position opposite to the movable slit plate and has slits that are slightly inclined with respect to the slits of the movable slit plate, and a position that is opposite to the movable slit plate with these two interposed therebetween. The device is composed of a light-emitting element and a light-receiving element provided in the light-emitting element, and the light-receiving element converts changes in moiré fringes caused by the movement of a movable slit plate in front of the light-emitting element into an electrical signal and detects the change. Further, the linear encoder is connected to a control circuit capable of converting the electrical signal into pulses and digitally displaying the amount of movement of the pusher needle.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 are a front view and a side view of an embodiment of the digital hardness meter of the present invention. The hardness meter main body 1 has a display operation section 3 having a digital hardness display 2 on the front side, and a linear encoder 4 is attached behind it. A spindle 5 is attached so as to pass vertically through this linear encoder 4. The spindle 5 moves up and down, and its upper end is in contact with the lower end of the load spring 6. The upper end of the load spring 6 comes into contact with an adjustment screw 7 screwed into the hardness meter body 1, and by adjusting the strength of the load spring 6 with the adjustment screw 7, the strength of the load spring 6 is adjusted to JIS K6301.
Standards, Section 4.2 of SRIS 0101 and ASTM D2240 standards. (Although a coil spring is used in FIG. 2, a leaf spring can also be used.) Also, a pusher needle 8 is attached to the lower end of the spindle 5.
This is also attached with dimensions suitable for each of the above-mentioned standards, and its tip protrudes from the lower surface of the pressure leg 9 fixed to the hardness meter main body 1, that is, the pressure surface 10.

In the above structure, the hardness meter body 1 is connected to the pressure surface 10.
When pressed against the sample surface to be measured, the pusher needle 8 and spindle 5 are displaced upward with respect to the pressurizing surface 10 according to the reaction force of the sample, that is, the hardness of the sample due to the action of the load spring 6. By reading this amount of movement, the hardness of the sample can be measured by converting the relationship between this amount of movement and hardness. The linear encoder 4 has a built-in mechanism and circuit for extracting the amount of movement as a digital signal.
This digital signal is processed by a circuit built into the display operation section 3 and displayed on the hardness display 2 as a spring type hardness value described in each of the above regulations.

3 and 4 are structural diagrams of a linear encoder used in a digital hardness meter, and FIG. 5 is a detailed diagram of a slit plate used in the linear encoder.

The linear encoder 4 includes a movable slit plate 11 that is fixed to a spindle 5 and moves linearly in the axial direction of the spindle 5, a fixed slit plate 12 that is fixed to the main body of the linear encoder 4, and a movable slit plate 1.
1 and two sets of light emitting elements 13, 13' placed before and after the fixed slit plate 12, and light receiving elements 14, 14',
It is composed of a voltage comparator 15. The slit plates 11 and 12 are transparent plates with thin opaque lines printed at regular intervals.
1 and 12 are attached so that the printed lines have a slight inclination angle with respect to each other, resulting in moire fringes (shaded stripes) as shown in FIG. When the slit plate 11 moves, the moire fringes move left and right. Then, the change in brightness due to the movement of the shading of the moiré fringes is converted into an electrical signal of an approximate sine wave 25 by the light receiving elements 14, 14' and extracted, and then further shaped into a rectangular wave 26 by the voltage comparator 15.

Both of the slit plates 11 and 12 may be inclined in opposite directions with respect to the horizontal line, or one of them may be made horizontal and the other may be inclined with respect to the horizontal line.

For example, if the movable slit plate 11 has horizontal slits and the fixed slit plate 12 is tilted with respect to the movable slit plate 11, the slight inclination of the fixed slit 12 will change the pitch of the slit by d, for example. If the angle is α, the distance S between moire fringes is given by S≒d/α, so if the size of the light receiving element is 4 mmφ, the distance S between moire fringes must be 4 mm or more, or two in one element. stripes are detected. Therefore, when reading hardness to the nearest 0.05, the interval d between the slit lines is 0.005 mm,
Inclination angle α = d/s = 0.005/5 = 0.001 rad (radian...1 rad = 57 degrees), and similarly when reading down to 1 unit of hardness, 0.1/5 = 0.02 rad.
Although these numbers depend on the dimensions of the element, the inclination angle of the fixed slit is usually selected in the range of 0.001 to 0.02 rad according to the measurement accuracy.

When reading the hardness value in units of 0.05 degrees, the spacing between the slit lines needs to be 0.00125 mm x 4 = 0.005 mm (when using the quadruple pulse described later). By counting the number, the amount of movement of the spindle 5 can be measured. In addition, in order to recognize the moving direction of the spindle 5, the set consisting of elements 13 and 14 and the set consisting of elements 13' and 14' are positioned at a certain distance apart, and one Either the line of one of the slit plates sandwiched between the elements of the other set is shifted from the line of the previous same slit plate between the other elements, or the two sets of elements are shifted in the direction of movement of the moiré fringes. Just do it.
Due to this deviation, from the pair of elements 13 and 14, the A phase,
The direction of movement can be determined by outputting B-phase signals whose phases differ by 90 degrees from each other from the pair of elements 13' and 14'.

FIG. 6 is a waveform chart showing the manufacturing procedure of a circuit for determining the moving direction of the spindle 5. The linear encoder 4 outputs two signals (phase A and phase B) whose phases are shifted by 90 degrees. FIG. 6 shows waveforms when the spindle 5 is raised and lowered.

Next, a differentiating circuit is used to generate an A-phase rising timing pulse At and an A-phase falling timing pulse shown in FIG. FIG. 6 shows the logical product At×B of the timing pulse At and the B phase, and the logical product×B of the timing pulse and the B phase. When both signals of this logical product are inputted to an RS flip-flop, the output becomes as shown in FIG. 6, so that the direction of upward and downward movement of the spindle 5 can be determined.

Further, by taking the logical sum of the logical product and the logical product, the counting pulse shown in FIG. 6 can be obtained.

Furthermore, using the inversion of the B phase, At,
If you combine it with , you will get twice as many pulses. Further, by combining this double pulse, the rising and falling pulses of the B phase, and the double pulse obtained by inverting the A phase and the A phase, a quadruple pulse can be obtained.

FIG. 7 is a circuit diagram of the embodiment shown in FIG. As shown in FIG. 7, the displacement signal output from the linear encoder 4 is displayed on the hardness display 2 through the direction discrimination circuit 16, reversible counter 17, time control circuit 18, and display control circuit 19 in the display operation section 3. Ru. The direction discrimination circuit 16 inputs the two signals of A phase and B phase from the linear encoder 4, and generates a number of pulses proportional to the displacement of the spindle 5, that is, the amount of movement, along with a discrimination signal for raising or lowering the spindle 5. It is output and sent to the next reversible counter 17. The reversible counter 17 counts the number of pulses and outputs the amount of movement of the spindle 5 in the form of a binary number, for example, and increases or decreases the count output signal depending on the direction discrimination signal. The time control circuit 18 is operated by a stress relaxation phenomenon that is normally observed in hardness measurement of a sample to be measured. In contrast to the phenomenon where the value is almost stable,
It has a peak hold circuit that holds the maximum value, and a circuit that determines which period of time the value is to be the hardness value of the sample to be measured, and for example, indicates the maximum value,
Alternatively, after the set time has elapsed, the display on the hardness indicator 2 maintains the value at that time. In this case, by inputting a set time in advance using the time signal setter 20, after the maximum value of hardness is obtained, the hardness value after the set time has elapsed can be held and displayed.

The display control circuit 19 converts the hardness data signal (for example, a binary data signal) from the time control circuit 18 into a form that can be displayed on the display, and includes a decoder and a multiplexer.

The hardness indicator 2 is, for example, a 7-segment light emitting diode (LED) (or liquid crystal [LCD]) with 3 to 4 digits.
Consists of a numeric display. This display is used selectively as an input signal display for the time signal setting device 20 described above, and also as an input signal display for the pass/fail criterion setting device 22 described later.

In addition to this, the display operation section 3 includes a pass/fail determination circuit 21 that determines whether or not the set hardness value is within a preset allowable range. This is done by comparing the measured hardness value with a reference hardness value input in advance into the pass/fail criterion setting device 22,
The result is output to the pass/fail judgment display 23. In this case, an upper limit, a lower limit, and an upper and lower limit can be set for the reference hardness value depending on the purpose. As an example of the pass/fail judgment display 23,
It is also possible to use means such as providing LEDs that individually light up when the measurement result exceeds the upper or lower limit of the allowable range.

Furthermore, the display operation section 3 can be provided with a function of sending the measurement results to an external data processing device (for example, a printer, a microcomputer, etc.). In this case, it is preferable to provide versatility by, for example, converting the measurement results into binary coded decimal numbers (BED) using the signal converter 24, if necessary.

Note that the time control circuit 18 and subsequent parts in FIG. 7 can be constructed by hardware as shown in the figure, but they can also be constructed by software using a microcomputer.

The display operation section 3 may be separated from the hardness meter of the present invention and held as an external function in combination with an external data processing device. In that case, there is an advantage that the hardness value can be obtained simultaneously with the external data processing results. Furthermore, if the display operation section 3 is separated from the main body, all functions except the linear encoder 4 shown in FIG. 7 will be retained as external functions.

If the digital hardness meter of the present invention as described above is used to directly detect the amount of vertical movement of the indenter using a linear encoder, there will be no mechanism to convert the vertical movement into rotational movement, and this will prevent backlash and friction of each part. Since the influence of

In particular, when glass is used for the slit of a linear encoder and the scale is created by vapor-depositing chromium on the glass, it is possible to optically detect displacements up to about 1 μm, making it possible to detect displacements with extremely low error and high precision. It becomes possible.

If you use such a high-precision linear encoder and a load spring and use a means to keep the measurement conditions (for example, pushing force on the sample, temperature, etc.) constant,
Conventionally, the minimum unit of hardness value was ±1, which was read from an analog value, but now it is possible to accurately obtain a hardness value of ±0.05 as a digital value, increasing accuracy by up to 20 times. Of course, depending on the purpose, it is easy to lower the accuracy to ±0.1 (as in the embodiment shown in FIG. 1).

〔Effect of the invention〕

As described above, in the digital hardness meter of the present invention,
By measuring the hardness of a sample with high precision that cannot be obtained with conventional hardness testers, the applications of hardness testers are expanded. It becomes possible to examine the dispersion state of the compounded ingredients.

In addition, by directly detecting the movement amount of the pusher needle from the movement of the moiré fringes, it is possible to detect it more reliably.
Moreover, the amount of movement of the indenter can be detected with high precision without being affected by the thickness of the line on the linear scale.

Further, since the pulse signal from the linear encoder can be counted as a digital value as it is, there is no need for electrical conversion means such as an A/D converter, and furthermore, the above-mentioned mechanical conversion means is not required. The main body of the meter is small and light, making it easy to carry, and since it is battery operated, there is no need to worry about abnormalities in measurement results caused by electrical noise, solving the problems of conventional digital hardness meters. There are also big effects.

Furthermore, JIS K6301 and ASTM D2240 state that the pushing load at the time of measurement is 1 kgf for JIS A type and durometer type A, respectively, and the self weight of the digital hardness meter of the present invention is also 1 kg. If adjusted in this manner, the advantages of accuracy can be obtained, such as eliminating individual errors in measurement values. In addition, the digital method of the present invention has functions such as peak-holding the hardness measurement results obtained as electrical signals, displaying the hardness value after a certain period of time, and determining pass/fail in comparison with the standard hardness value. When using a hardness meter in a factory, etc., it is effectively used as it is easy to read because of its digital value.

[Brief explanation of the drawing]

FIG. 1 is a front view of an embodiment of the digital hardness meter of the present invention, FIG. 2 is a partially cutaway side view of the digital hardness meter of FIG. 1, and FIG. 3 is a front view of an embodiment of the digital hardness meter of the present invention. FIG. 4 is a cross-sectional view of the linear encoder shown in FIG. 4, and FIG. 5 is a portion of moire fringes caused by the slit plate used in the linear encoder of the digital hardness meter of the present invention. An enlarged view, FIG. 6 is an operating waveform diagram of the direction determining circuit used in the digital hardness meter of the present invention, and FIG. 7 is a block diagram showing the configuration of the digital hardness meter of the present invention. 1... Hardness meter body, 2... Display, 3... Operation unit, 4... Linear encoder, 5... Spindle, 6... Load spring, 7... Adjustment screw, 8
... Pressure needle, 9 ... Pressure leg, 10 ... Pressure surface, 11
...Movable slit plate, 12...Fixed slit plate,
13, 13'... Light emitting element, 14, 14'... Light receiving element, 15... Voltage comparator, 16... Direction discrimination circuit, 17... Reversible counter, 18... Time control circuit, 19... Display device Control circuit, 20... Time signal setter, 21... Pass/fail judgment circuit, 22... Pass/fail judgment standard setter, 23... Pass/fail judgment display.

Claims (1)

[Claims] 1. A hardness meter that measures the hardness of a flexible material using an elastic member is provided with a linear encoder that detects the amount of movement of the indenter, and this linear encoder includes a movable slit plate that is interlocked with the indenter; The fixed slit plate is attached at a position opposite to the fixed slit plate and has a slit slightly inclined with respect to the slit of the movable slit plate, and a light emitting element and a light receiving element are disposed at positions facing each other with the movable slit plate interposed therebetween. , a change in moiré fringes caused by the movement of the movable slit plate in front of the light emitting element is converted into an electric signal by a light receiving element so that it can be detected; and the linear encoder is configured to convert the electric signal into a pulse. A digital hardness meter, characterized in that it is connected to a control circuit that can digitally display the amount of movement of the indenter.