JPS5857683B2 - Method and device for detecting changes in cross-sectional shape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for detecting a change in cross-sectional shape of a long extruded product such as a rubber or resin hose by extracting a change in the external shape, that is, a change in the cross-sectional shape, as a change in the cross-sectional area. Regarding the device.

When inspecting the external shape of long objects such as rubber or resin hoses,
Light is emitted from a projector onto the surface of the test object, and changes in the reflected light are detected to detect abnormalities in the external shape of the test object, or contacts placed in contact with the surface of the test object. The external shape of the test object was inspected by detecting the child's movement using a differential transformer, potentiometer, etc.

However, with the former testing method, false detections may occur due to the shaking of the test object, water adhering to the surface of the test object, and the need to place multiple detectors around the test object. In addition, the latter inspection method involves testing by bringing the contactor into contact with the test object, which may cause vibrations, vibrations, etc. of the test object.
This method has the drawback of causing false detection due to displacement or deformation of the object to be tested.

This invention focuses on the above points, and accurately detects changes in the external shape of a long object, that is, changes in the cross-sectional shape, without being affected by rocking, vibration, displacement, or surface condition of the long object. It is an object of the present invention to provide a method and device for detecting a change in cross-sectional shape, in which a detection unit and a detection signal processing circuit can be easily configured.

In order to achieve this objective, the present invention disposes a plurality of annular electrodes at predetermined intervals along the inner surface of a cylindrical body. The change in electrical resistance that occurs between the annular electrodes as it is inserted into the cylindrical body and passed through is extracted as the amount of voltage change, and changes in the cross-sectional shape of the specimen are detected based on the voltage fluctuations between the annular electrodes. It is composed of

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a schematic diagram of the detector and shows its configuration.

Reference numeral 1 denotes a cylindrical body having a shape into which a test object 2 can be inserted and passed, and is made of an insulating material.

The test object 2 is a long object with a constant cross section, such as a rubber or resin hose, and at least its surface is an electrical insulator.

Four annular electrodes 3, 4, 5, and 6 are inserted inside the cylinder 1 at regular intervals, and the surface of each electrode is exposed on the surface of the cylinder 1.

The cylinder body 1 is
is immersed in a conductive liquid.

Therefore, when the test object 2 is inserted into the cylinder 1, a resistance R1 is formed between the annular electrodes 3 and 4 due to the cylindrical conductive liquid interposed between the annular electrodes 3 and 4. Similarly, a resistance R2 is formed between the annular electrodes 4 and 5, and a resistance R3 is formed between the annular electrodes 5 and 6, and these resistance values change depending on the thickness of the object 2, that is, the cross-sectional area. If there is,
It changes according to a change in the cross-sectional area, that is, a change in volume, of the conductive liquid interposed between the test object 2 and each electrode.

Each of the annular electrodes 3, 4, 5,
6 is connected to a stabilized DC power source 7 as shown in FIG. 1, and its equivalent circuit is connected to a resistor R as shown in FIG.
2 and a resistor R3 are connected in series, a resistor R1 is connected in parallel with these, and a DC power supply 7 is connected to both ends of the resistor R1.

As shown in FIG. 3, in order to detect changes in the resistance values of resistors R2 and R3 as changes in voltage, resistors R4 and R5 are connected in parallel to resistors R2 and R3 to form a bridge circuit. It is configured so that a bridge voltage is applied by a DC power supply 7, and the change in the resistance value of resistors R2 and R3 is caused by the resistance R2.
The voltage at the midpoint between R4 and R3 and the midpoint between resistors R4 and R5 is extracted and detected as an output.

The output of such a bridge circuit is input to a differential amplifier 8, and the output of the differential amplifier 8 is connected to be input to a discrimination circuit 9.

Note that errors due to fluctuations in the resistance of the conductive liquid on the outer periphery of the cylinder 1 can be avoided by short-circuiting the annular electrodes 3 and 6, ignoring the resistance between them, and connecting the annular electrodes 3 and 6 to the negative electrode of the DC current. This problem is solved by setting the potential of the lever to zero and also by common grounding with the signal processing circuit.

Further, such common grounding can also prevent noise applied to the output line from the electrode of the detector from being mixed in due to various forms such as human contact with the conductive liquid or a container of the conductive liquid.

Next, a method for detecting a change in the cross-sectional shape of the test object 2 using the detector and its signal processing device shown in FIGS. 1 and 3 will be described.

First, when the test object 2 is passed inside the cylinder 1, if the external shape of the test object 2, that is, the cut shape is constant, the cylinder 1
Since the volume of the conductive liquid interposed between each of the annular electrodes 3, 4, 5, and 6 is constant, its resistances R1, R2, and R3 do not change.

Therefore, the output voltage of the bridge circuit is constant.

Now, when the part where the protrusion 10 is formed on the outer periphery of the test object 2 is inserted into the cylindrical body 1 and enters between the annular electrodes 3 and 4, the protrusion 10 causes the volume of the conductive liquid between them. decreases and the value of resistor R1 increases.

However, the output of the bridge circuit does not change due to the increase fto of the resistor R1.

On the other hand, the protrusion 10 advances and enters between the annular electrodes 4 and 5,
If the resistance R2 increases during this time, the output voltage of the bridge circuit will increase.

decreases, and the protrusion 10 further advances to form the annular electrodes 5 and 6.
When the resistance R3 increases by 7JD, the output voltage of the bridge circuit increases.

increases (Figure 4). This output voltage ■.

The change △■ appears largely as a change from peak to peak as shown in the voltage waveform diagram A in FIG. The amount of change in voltage is compared with a predetermined set value, and if the amount of voltage change is greater than or equal to the set value, it operates to output a protrusion detection signal.

In this way, in order to compare the difference in change in the two resistances R2 and R3, the volume resistivity of the conductive liquid may be changed slowly economically.

Note that if the test object 2 has a recess, the resistors R2 and R3
decreases during this passage, so the output voltage of the bridge circuit ■.

, changes from an increasing peak to a decreasing peak, contrary to the case of FIG. 4, and the detection signal of the concave portion can also be extracted in the same manner as above.

FIG. 5 shows another embodiment of the invention, in which the cylindrical body 1
Five annular electrodes lL12,13°14.15 in 0,
The spacing between the annular electrodes 11 and 12 is equal to that between the annular electrodes 12 and 13, and the spacing between the annular electrodes 13 and 14 is the same as that between the annular electrodes 14.
and 15 so that the distance between them is equal.

The conductive liquid filled inside the cylinder 10 is a liquid that is controlled to always have a constant volume resistivity.

In this detector, two systems of detection circuits are used with the annular electrode 13 as a common electrode, and the spacing between the electrodes of the two detection circuits is different, so the size of the recess or protrusion of the test object is wide. When detection cannot be performed with narrowly spaced electrodes, the electrode spacing can be determined according to the size of the protrusion or the like to be detected, and the detection signal can be obtained from a plurality of detection circuits.

In addition, in the detection method of the present invention, the change in the cross-sectional area of the object to be measured is determined by the volume of the conductive liquid (
Since the detection is based on the resistance value), detection errors due to shaking or vibration of the test object are minimal.

Further, fine bubbles contained in the conductive liquid may adhere to the annular electrode and cause noise during detection, but this noise can be eliminated by mixing a surfactant into the conductive liquid.

Furthermore, since the conductive liquid is ionized when DC current is applied, which may affect the detection results, it is recommended to keep the voltage of the DC power supply 7 as low as possible and allow the conductive liquid inside the cylinder 1 to flow. The tobacco problem can be solved.

In the embodiments shown in FIGS. 1 to 5, if the cross-sectional area of the object to be examined changes gradually over a long section, that is, over two or more electrode intervals, for example, In FIG. 3, since the resistors R2 and R3 change in the same way, the change in the output voltage of the bridge circuit is small and cannot be detected.

The embodiment shown in FIGS. 6 to 9 improves this point, and the detector is intercepted as shown in FIGS. 6 and 7.

As shown in FIG. 6, four annular electrodes 16 are installed inside the cylinder 1.
, 17, 18.degree. 19 are arranged such that the spacing between the annular electrodes 16 and 17 and the spacing between the annular electrodes 18 and 19 are equal.

The annular electrodes 16 and 19 are short-circuited and connected to the negative electrode of the DC power source 7, and the annular electrode 17 is connected to the annular electrode 1 through a resistor R9.
8 is connected to the positive electrode of the DC power supply 7 via a resistor 10.

Here, the annular electrodes 16 and 1 are immersed in a conductive liquid.
Assuming that the resistance between the electrodes 17 and 18 is a resistance R6, the resistance between the annular electrodes 17 and 18 is a resistance R7, and the resistance between the annular electrodes 18 and 19 is R8, the detector circuit is as shown in FIG. It is taken out as an output and input to the arithmetic circuit 20, and this output is connected to the discrimination circuit 9 so as to be manually inputted.

In this detection circuit, the resistance values of the resistors R9 and R10 are made equal, and the intervals between the annular electrodes 16 and 17 and the annular electrodes 18 and 19 are arranged equally, so the values of the resistors R6 and R8 can be regarded as equal. .

Therefore, in the circuit shown in FIG. 7, the potentials applied to both ends of the resistor R7 are equal and the potential difference between them is zero, so the resistance value of the resistor R7 is considered to be infinite, and the series circuit of resistors R9 and R6 and the resistor R10 The series circuit of R8 and R8 can be treated separately.

For this reason, the voltage division value of the series circuit of resistors RIO and R8 can be extracted as a change in the resistance value of resistor R8, that is, a change in the cross-sectional area of test object 2, without being affected by resistor R7. .

In this way, by changing the resistance value of one resistor R8,
For detection, the conductive liquid must always have a constant volume resistivity.

Next, a method of detecting a change in the cross-sectional shape of a test object using the detector shown in FIG. 6 will be described.

When a test object 2 whose cross-sectional area gradually changes is inserted into a cylinder 1 immersed in a conductive liquid and allowed to pass through it,
The resistance values of resistors R6 and R8 in FIG. 7 increase as the cross-sectional area of the test object 2 increases fyo, and decrease as the cross-sectional area decreases, as shown in graph 21 of FIG. 9.

Therefore, the voltage VO3 applied to the resistor R8, which is a divided voltage value of the voltage applied by the DC power supply 7, changes in the same phase as the resistance value of the resistor R8, as shown in the voltage waveform 22 of FIG.

This output voltage (2o3) is input to the calculation circuit 20, and the cross-sectional area of the object to be inspected is calculated as follows.

That is, if the current of the resistor R8 is ■ and the resistance is R, the output voltage is VO32RI where ρ is the volume resistivity of the conductive liquid, l is the distance between the annular electrodes 18 and 19, and So is the cylindrical body. The cross-sectional area of the inner hole 1 and Sl are the cross-sectional areas of the test object 2.

ρ7I Therefore, the cross-sectional area can be expressed as 5l-8o-7.

In addition, in FIG. 7, resistors R9 and R10 are replaced by resistors R6,
If the resistance value is considerably larger than R8, the current flowing through the series circuit of resistors R9 and R6 or resistors R10 and R8 will be equal to the resistor R.
6. It can be considered to be constant without being affected by changes in R8.

And So. ρ and l are constants.

Once, in the arithmetic circuit 20, the constant S.

, ρ. A voltage signal (■) corresponding to the cross-sectional area S1 of the test object 2 is obtained by setting constants for l and I and using VO3 as a manual input.

4 is reciprocated and output as shown in voltage waveform 23 in FIG.

This signal voltage V. 4 is input to the discrimination circuit 9, and the test object 2
Compare the voltage signal o4 as cross-sectional area data with preset upper and lower limit values, and output the high output signal 24 when VO4 is high, and output the low output signal 25 when it is low, and calculate the detected value. If the cross-sectional area data of the object to be inspected falls within the set value, an output signal 26 is obtained.

The above detection method is based on the fact that the electric field formed between the annular electrodes is a uniform electric field, but the diameter of the object to be tested is significantly smaller than the diameter of the cylinder, and the conductive liquid is If the portion increases too much, an error will occur between the detected value and the actual cross-sectional area of the object.

In other words, if the thickness of the cylindrical conductive liquid increases beyond a certain value, it can no longer be considered an equal electric field.
As shown in FIG. 8, the detected output voltage is ■ in the area below the cross-sectional area Ss of the object to be tested.

The value of 3 is detected to be slightly higher than the voltage Vs calculated from the actual cross-sectional area.

Therefore, the area where the conductive liquid between the electrodes can be approximated to have a uniform electric field is 1 of the accurate cross-sectional area with no error for the shaded area in Fig. [pause] can be carried out.

As described above, according to the method and apparatus for detecting changes in cross-sectional shape according to the present invention, a plurality of annular electrodes are arranged at predetermined intervals along the inner surface of a cylinder, and the inside of the cylinder is conductive. While the test object is inserted into the cylindrical body filled with liquid and passed through, the change in electrical resistance that occurs between the annular electrodes is extracted as the amount of voltage change, and based on the voltage variation between the annular electrodes. Since the configuration is configured to detect changes in the cross-sectional shape of the test object, changes in the external shape of a long object, that is, changes in the cross-sectional shape, can be detected without being affected by swings, vibrations, changes, etc. of the test object. In addition, changes in the cross-sectional shape of the test object can be detected without any problem even if water or the like adheres to the surface of the test object.Also, since there is no contact with the test object, the detector and the test object can be easily detected. This has the advantage that the detector is not damaged due to contact, and the structure of the detector is simple.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, in which Fig. 1 is a schematic explanatory diagram of a detection section, Fig. 2 is an equivalent circuit of the detector in Fig. 1, Fig. 3 is a detection circuit including a block diagram, and Fig. 4 is a Resistance value and output voltage in the detection circuit shown in Figure 3 ■. 5 is a schematic explanatory diagram of the detecting section showing another embodiment, FIG. 6 is a schematic explanatory diagram of the detecting section showing yet another embodiment, and FIG. 7 is a schematic explanatory diagram of the detecting section showing another embodiment. The detection circuit including the block diagram, Figure 8 shows the output voltage of the detector with respect to the volume of the specimen.
. The graph of No. 3 and FIG. 9 shows changes in the resistance values of resistors R6 and R8 and the output voltage V. 3. . 7 is a graph showing a voltage waveform of VO4 and a determination output signal waveform of a determination circuit. 1... Cylindrical body, 2... Test object, 3 to 6
, 11 to 15, 16 to 19... annular electrodes,
R1 to R10...Resistor, 8...Differential amplifier, 9...Discrimination circuit, 20...Arithmetic circuit.

Claims (1)

[Claims] 1. A plurality of annular electrodes are arranged at predetermined intervals along the inner surface of a cylindrical body, and a test object is placed inside the cylindrical body with a conductive liquid filled inside the cylindrical body. The change in electrical resistance that occurs between the annular electrodes while being inserted into the interior and passing through is extracted as a voltage change amount, and the change in the cross-sectional shape of the test object is detected based on the voltage variation between the annular electrodes. Featured method for detecting changes in cross-sectional shape. 2. A detector in which a plurality of annular electrodes are arranged at predetermined intervals along the inner surface of a cylindrical body, a conductive liquid is filled inside the cylindrical body, and a test object is passed through the inside of the cylindrical body. a bridge circuit formed using the electric resistance of , and other fixed resistances, and a signal obtained by extracting a change in the resistance value between the annular electrode as a change in the output voltage of the bridge circuit, and inputting it via a differential amplifier, A cross-sectional shape change detection device that detects a change in cross-sectional shape from a discrimination circuit that determines whether the object to be inspected is good or bad by comparison with a set value. 3. A detector in which a plurality of annular electrodes are arranged at predetermined intervals along the inner surface of a cylindrical body, a conductive liquid is filled inside the cylindrical body, and a test object passes through the inside of the cylindrical body. There is an arithmetic circuit that detects changes in electrical resistance as changes in voltage, uses this voltage as input to calculate the cross-sectional area of the test object, and calculates the cross-sectional area of the test object by manually inputting the output of the arithmetic circuit and comparing it with a set value. A cross-sectional shape change detection device that is separated from a discrimination circuit that determines whether the