JPH0257260B2 - - 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]

The conventional spring-type rubber hardness tester described in JIS K6301 Section 5.2 presses an indenter against a sample to be measured, and uses a rack and pinion mechanism to move the indenter in the vertical direction due to the reaction force of the sample to be measured. An analog method was used in which the rotation amount was converted 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 reports a method of converting into an electrical signal using a variable resistor, and Japanese Patent Application Laid-Open No. 1972-72032 reports a method of converting into an electrical signal using a rotary encoder, but both of these methods have problems. Although it is currently being used with some problems, it has not yet been put into practical use.

As another prior art, the invention disclosed in Japanese Patent Application Laid-open No. 51-84684 proposes that a guard ring is installed around the indentation needle to solve the problem that conventional hardness meters produce errors when measuring curved objects. The ring is pressed against the surface to be measured with an elastic body separate from the indenter, so that it can be used even on curved surfaces, and the displacement of the indenter is converted into electrical changes. However, the means for converting the displacement of the indenter into an electrical quantity disclosed in the publication uses a photoconductive element to detect changes in the amount of light passing through photoresistive pieces of different thickness. Therefore, since the displacement of the indenter is converted into an electrical analog quantity, there is a problem in that the detection accuracy cannot be improved.

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 requires converting vertical movement into rotational movement using this conversion method, problems occur in measurement accuracy in this conversion part, and it is difficult to understand how to use computers etc. 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, the hardness meter itself has the problem of being large and expensive. It is. These large hardness testers cannot be powered on by batteries since they require electricity.
They cannot be carried anywhere, and they also have other problems such as being susceptible to power fluctuations and electrical noise.

By the way, as a length measuring device that directly detects length as a digital quantity, there is a digital gauge described in Japanese Utility Model Application Publication No. 52-155056. As a specific means of the prior art, the publication states that a transparent slit plate with a lattice is attached to the movable axis for measuring the length, and in parallel to the slit plate, windows with the same lattice width are each set to 1/4. A method is described in which fixed slit plates are arranged at four locations with the phase shifted by width, and the movement of the slits is converted into a pulse signal and digitally displayed using a photoelectric converter that detects the light transmitted through the window. has been done.

However, the prior art disclosed in the above-mentioned publication uses a slit plate with four rows of windows whose phases are shifted by 1/4 of the grating width. It is extremely difficult to obtain precisely carved slits for the grid of columns;
The problem is that it is expensive.

For example, the spring type hardness meter specified in JIS K6301 specifies that a needle movement of 2.54 mm is 100 degrees of hardness. Therefore, in order to accurately measure hardness to the order of at least 0.1 degree using a measuring means that conforms to the standard, it is necessary to have a hardness accuracy of ±0.05 degrees or less, that is, a reading accuracy of approximately ±1.3 μ or less. The above-mentioned publication does not suggest any means for achieving such high accuracy.

Furthermore, the length measuring device in the publication merely discloses a means for measuring length, and does not mention at all what quantity should be measured and displayed when measuring the hardness of rubber, etc. .

[Purpose of the invention]

The purpose of the present invention is to solve the various problems of the conventional digital hardness meter, and to detect slight changes in hardness with high accuracy by directly detecting the vertical movement of the indenter using a linear encoder. It can be detected, and it can also be made small and portable.
Our objective is to provide a completely new and excellent digital hardness meter that satisfies the JIS K 6301 standard.

[Structure of the invention]

To achieve the above object, the digital hardness meter of the present invention has a structure including a movable slit plate that is elastically biased and moves in conjunction with a presser needle that presses against a flexible material; A light-emitting element and a light-receiving element are arranged at two positions sandwiching the two slit plates, respectively, at positions where pulse signals outputted from the respective light-receiving elements cause a phase shift with respect to each other. The encoder outputs the second signal when the indenter enters the material.
The rising and falling timings of one of the two pulses are determined, and the moving direction of the indenter is determined from the logical value obtained by ANDing the timing and the other pulse signal. A control circuit is provided with a reversible counting means for counting the number of penetration pulses of the indenter, and a display means for holding the maximum penetration value of the indenter and the penetration value of the indenter after a predetermined time and displaying it as a digital hardness value. It is characterized by

The moving direction of the pusher needle may be determined as follows by selecting the pulse whose timing is to be determined. In other words, if the pulse for determining the rise and fall timing is a pulse on the side with an advanced phase, when the push needle enters, a count pulse will be obtained at the fall timing, and when the push needle returns, a count pulse will be obtained at the rise timing. can get. If the pulse for determining the timing is a pulse on the side with a delayed phase, a count pulse will be obtained at the rising timing when the indenter enters, and a counting pulse will be obtained at the falling timing when reversing.

The encoder having the above configuration can detect the movement of the slit plate with high precision using the two slit plates, and with even higher precision when interference fringes are used. In addition, the configuration in which the rise and fall timings are determined from one of the pulse signals and the logical product with the other pulse signal is determined can determine the intrusion amount of the indenter by determining the moving direction of the indenter.

Therefore, it is possible to accurately detect the behavior of the indenter when the indenter having the above structure is applied to a flexible material such as a rubber elastic body. The hardness of materials can be measured.

〔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.
It has become compliant with the standards. (Although a coil spring is used in FIG. 2, a plate spring can also be used.) Also, a pusher needle 8 is attached to the lower end of the spindle 5.
However, this is also attached with dimensions suitable for the JIS K6301 standard, and its tip protrudes from the lower surface of the pressurizing leg 9 fixed to the hardness meter main body 1, that is, the pressurizing 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 the hardness display 2 displays JIS K6301 No. 5.2.
It is displayed as the spring type stiffness value listed in the section.

3 and 4 are structural diagrams of a linear encoder used in a digital hardness meter. The linear encoder 4 consists of a movable slit plate 11 fixed to the spindle 5 and moving linearly in the axial direction of the spindle 5, a fixed slit plate 12 fixed to the main body of the linear encoder 4, and a movable slit plate 11 and the fixed slit plate 12. Two sets of light emitting elements 1 placed in front and behind
3 and 13', light receiving elements 14 and 14', and a voltage comparator 15. slit plate 11,
Reference numeral 12 is a transparent plate with thin opaque lines printed at regular intervals, and depending on the upper and lower positions of the spindle 5, the lines on the movable slit plate 11 and the fixed slit plate 12 may overlap or not overlap at all. It's becoming like that. The light receiving elements 14 and 1 detect changes in brightness and darkness depending on the degree of overlap between the lines.
4' converts it into an electrical signal of an approximate sine wave 25 and extracts it, and then converts it into a rectangular wave 2 by a voltage comparator 15.
Shape the waveform to 6.

When reading the hardness value in units of 0.05 degrees, the spacing between the lines of the slits needs to be 0.00125 mm x 4 = 0.005 mm, and by counting the number of square waves, the amount of movement of the spindle 5 can be calculated. 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 The line of one of the slit plates sandwiched between the elements of the other set is offset from the line of the same slit plate in front of the other element. Due to this deviation, from the pair of elements 13 and 14, the A phase, element 13',
The moving direction can be determined by outputting B-phase signals whose phases are different from each other by 90 degrees from the group 14'.

FIG. 5 is a waveform diagram showing the operating 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. 5 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. 5 shows the logical product of the timing pulse At and the B phase×B, and the logical product of the timing pulse and the B phase×B. If both signals of this logical product are inputted to an RS flip-flop, the output will be as shown in FIG. 5, so that the direction of rise and fall 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. 5 can be extracted.

Furthermore, using the inversion of the B phase, At in Fig. 5 2,
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. 6 is a circuit diagram of the embodiment shown in FIG. 1. As shown in FIG. 6, the displacement signal output from the linear encoder 4 is displayed on the hardness display 2 after passing 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, a multiplexer, and the like.

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, the display operation section 3 includes a pass/fail determination circuit 21 that determines whether the measured hardness value is within a preset tolerance range. This is done by comparing the measured hardness value with a reference hardness value that has been input into the pass/fail judgment standard setter 22 in advance.
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 (BCD) using the signal converter 24, if necessary.

Note that the time control circuit 18 and subsequent parts in FIG. 6 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 other than the linear encoder 4 shown in FIG. 6 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 made 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 read from an analog value of ±1 degree, but now it is possible to accurately obtain a hardness value of ±0.05 degree 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 degree (as in the embodiment shown in FIG. 1).

〔Effect of the invention〕

As explained above, the digital hardness meter of the present invention consists of a movable slit plate that is elastically biased and moves in conjunction with a pusher needle that presses against a flexible material, and a fixed slit plate that is placed opposite the movable slit plate. and has
The indenter is inserted into the material from an encoder placed at two positions sandwiching the two slit plates, with a light emitting element and a light receiving element, respectively, at positions where the pulse signals output from the respective light receiving elements are out of phase with each other. Determine the rise and fall timing of one of the two pulses output at the time of intrusion, and move the pusher needle based on the logical value obtained by ANDing the timing and the other pulse signal. Reversible counting means for determining the direction and counting the number of intrusion pulses of the indenter; and display means for holding the maximum intrusion value of the indenter and the intrusion value of the indenter after a predetermined time and displaying it as a digital hardness value. Since the configuration includes the control circuit, the following effects can be obtained.

a By providing two movable and fixed slit plates, it is possible to utilize interference fringes, so for example, if the spacing between the slit lines is 0.005 mm, the hardness value can be read in units of 0.05 degrees. This makes it possible to improve reading accuracy by 20 times compared to conventional methods.

b. Since the amount of change in the indentation needle that changes moment by moment, the maximum value and the value after a specified elapsed time can be read and held with high accuracy, it is possible to reduce variations in measured values.

c This digital hardness meter can be made small and portable, and it also makes it possible to find correlations between hardness measurements and various other properties of the material, which is much easier to do than with conventional hardness meters. It has now become possible to expand the range of uses that would otherwise have been possible. In other words, the return value (relaxation amount) from the maximum displacement amount of the indenter is:
For example, when the material to be measured is vulcanized rubber, detecting variations in the vulcanized state, detecting the dispersion state of mixed materials by hardness, and estimating the amount of heat generated when rubber is used dynamically such as in tires. It can be useful for things such as.

Therefore, 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, since the pulse signal from the linear encoder can be counted directly as a digital value, there is no need for electrical conversion means such as an A/D converter, and furthermore, since the above-mentioned mechanical conversion means is not used, the hardness meter of the present invention The main body 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. It's also effective.

In addition, JIS K6301 states that the pushing load at the time of measurement is 1Kg.
If the digital hardness meter of the present invention is adjusted so that its own weight is 1 kg, the advantage 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. 4 is a cross-sectional view of the linear encoder shown in FIG. 4, FIG. 5 is an operation waveform diagram of the direction discrimination circuit used in the digital hardness meter of the present invention, and FIG. 6 is a longitudinal sectional view showing the internal configuration. FIG. 1 is a block diagram showing the configuration of a 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. It has a movable slit plate that is elastically biased and moves in conjunction with a presser needle that presses against a flexible material, and a fixed slit plate that is disposed opposite to the movable slit plate,
The indenter is inserted into the material from an encoder placed at two positions sandwiching the two slit plates, with a light emitting element and a light receiving element, respectively, at positions where the pulse signals output from the respective light receiving elements are out of phase with each other. Determine the rise and fall timing of one of the two pulses output at the time of intrusion, and move the pusher needle from the logical value obtained by ANDing the timing and the other pulse signal. Reversible counting means for determining the direction and counting the number of intrusion pulses of the indenter; and display means for holding the maximum intrusion value of the indenter and the intrusion value of the indenter after a predetermined time and displaying it as a digital hardness value. A digital hardness meter equipped with a control circuit.