Liquid adhesion detecting device

Abstract

A liquid adhesion detecting device according to the present disclosure is a device for detecting adhesion of a water-insoluble liquid that contains a sulfur component. The liquid adhesion detecting device comprises: a first resistor and a second resistor that are connected in series in order to divide a power supply voltage; and a determining unit that, on the basis of fluctuations in the value of the divided voltage divided by the first resistor and the second resistor, determines adhesion of a water-insoluble liquid containing a sulfur component to at least one of the first resistor and the second resistor. Each of the first resistor and the second resistor includes a component that combines with the sulfur component.

Description

Liquid adhesion detection device

[0001] The present disclosure relates to a liquid attachment detection device.

[0002] When using industrial machinery such as robots and machine tools, detecting liquids that may cause malfunctions is an important technology. For example, one known liquid detection technology is to monitor changes in the resistance value of a resistor and detect raindrops adhering to the resistor based on the fluctuations in the resistance value (see, for example, Patent Document 1). However, water is not the only liquid used in industrial machinery; for example, cutting machines use non-water-soluble cutting fluids.

[0003] Japanese Patent Application Publication No. 186746 / 1986

[0004] It is desirable to provide a technique for detecting non-aqueous liquids containing sulfur components, such as cutting fluids.

[0005] The liquid adhesion detection device according to the present disclosure comprises first and second resistors connected in series to divide a power supply voltage, the first and second resistors containing a component that combines with a sulfur component, and a determination unit that determines adhesion of a liquid containing a sulfur component to at least one of the first and second resistors based on fluctuations in the value of the divided voltage obtained by dividing the voltage by the first and second resistors.

[0006] FIG. 1 is a diagram showing an example of the circuit configuration of a liquid adhesion detection device according to this embodiment. FIG. 2 is a first supplementary diagram for supplementing the explanation of the determination process performed by the liquid adhesion detection device. FIG. 3 is a second supplementary diagram for supplementing the explanation of the determination process performed by the liquid adhesion detection device. FIG. 4 is a diagram showing an example of the circuit configuration of a liquid adhesion detection device according to a first modified example of this embodiment. FIG. 5 is a diagram showing an example of the circuit configuration of a liquid adhesion detection device according to a second modified example of this embodiment. FIG. 6 is a diagram showing an example of the circuit configuration of a liquid adhesion detection device according to a third modified example of this embodiment.

[0007] The liquid adhesion detection device according to this embodiment will be described with reference to the drawings. In the following description, components having substantially the same functions and configurations are designated by the same reference numerals, and redundant description will be given only when necessary.

[0008] FIG. 1 is a circuit diagram of a liquid adhesion detection device according to this embodiment. As shown in FIG. 1, the liquid adhesion detection device 1 includes a power supply 10, first and second resistors 11 and 12 for dividing the voltage of the power supply 10, and a determination unit 20 for determining whether a liquid is attached to at least one of the first and second resistors 11 and 12 based on fluctuations in the value of the divided voltage obtained by dividing the voltage between the first and second resistors 11 and 12. The term "liquid" is intended to encompass both water (a water-soluble liquid) and non-water-soluble liquids such as cutting fluids containing sulfur components. Typically, the determination unit 20 includes an AD converter 18 and a control circuit 19. The first and second resistors 11 and 12 are connected in series to the power supply 10. An input terminal of an analog-to-digital converter (hereinafter referred to as "AD converter") 18 is connected to a voltage division point (node) between the first resistor 11 and the second resistor 12, and an input terminal of the control circuit 19 is connected to an output terminal of the AD converter 18. The AD converter 18 converts the voltage value of the voltage at the voltage division point (divided voltage) into a digital signal. For example, the divided voltage corresponds to the voltage across the second resistor 12. The control circuit 19 determines whether liquid has adhered to at least one of the first resistor 11 and the second resistor 12 based on fluctuations in the voltage value of the divided voltage converted into a digital signal. The determination process by the determination unit 20 (control circuit 19) will be described in detail below. The liquid adhesion detection device 1 may also include a notification unit that notifies the user of liquid adhesion upon determining that liquid adhesion has occurred. For example, the control circuit 19 may be connected to a speaker that notifies the user of liquid adhesion by sound, a display device that notifies the user of liquid adhesion by visual display, or a light. Of course, the liquid adhesion detection device 1 may also include a communication unit and be configured to transmit a signal indicating liquid adhesion to an external device via a local area network or the Internet. The sound generated when the detected liquid is water may be different from the sound generated when the detected liquid is a sulfur-containing liquid. Similarly, the display mode of the display device when the detected liquid is water may be different from the display mode when the detected liquid is a liquid containing a sulfur component.

[0009] One feature of the liquid adhesion detection device 1 according to this embodiment is that the internal electrodes of the first resistor 11 and the second resistor 12 contain at least a component that combines with sulfur components so that the first resistor 11 and the second resistor 12 function as detection elements for detecting water-insoluble liquids such as cutting fluids containing sulfur components. In other words, the first resistor 11 and the second resistor 12 are configured as resistors that undergo sulfuration and open circuit when exposed to water-insoluble liquids such as cutting fluids containing sulfur components.

[0010] Materials containing at least a component that combines with sulfur include both materials consisting solely of components that combine with sulfur, such as silver or copper, and materials in which a material consisting solely of a component that combines with sulfur is mixed with a component that does not combine with sulfur. Here, the former is described. Examples of the latter include silver alloys and copper alloys. Typically, the internal electrodes of the first resistor 11 and the second resistor 12 are configured as silver or copper electrodes. Preferably, the internal electrodes are configured as silver electrodes to avoid oxidation. When a liquid containing sulfur adheres to a resistor having silver internal electrodes, sulfurization of the internal electrodes progresses. As sulfurization of the internal electrodes progresses, the resistance value of the resistor gradually increases. Furthermore, as sulfurization of the internal electrodes progresses, the internal electrodes (resistors) eventually break. The liquid adhesion detection device 1 according to this embodiment can detect the adhesion of a liquid containing sulfur before the first and second resistors 11 and 12 break. Sulfuration is a phenomenon in which, for example, silver components contained in the internal electrode combine with sulfur components contained in the liquid, causing the internal electrode to change into silver sulfide, which has low conductivity (high specific resistance). In this embodiment, adhesion of a liquid containing sulfur components to the resistor is detected by utilizing the fact that the resistance value increases when the liquid containing sulfur components adheres to the resistor. The second resistor 12 may have the same resistance value as the first resistor 11, or may have a resistance value different from that of the first resistor 11.

[0011] 2 and 3, the determination process by the determination unit 20 will be described. The determination unit 20 determines whether a liquid containing sulfur components has adhered to at least one of the first and second resistors 11 and 12 based on fluctuations in the voltage value of the divided voltage.

[0012] As shown in Figure 2, when a liquid containing a sulfur component adheres to the first resistor 11, the resistance value of the first resistor 11 increases as sulfurization of the internal electrode progresses. As the resistance value of the first resistor 11 increases, the voltage value of the divided voltage decreases from the initial value V0. As sulfurization of the internal electrode progresses further, the internal electrode breaks down, and the divided voltage becomes zero. The determination unit 20 determines that a liquid containing a sulfur component has adhered to the first resistor 11 when the voltage value of the divided voltage reaches or falls below a predetermined first threshold value Vth1.

[0013] 3, when a liquid containing a sulfur component adheres to the second resistor 12, the resistance value of the second resistor 12 increases as sulfurization of the internal electrode progresses. As the resistance value of the second resistor 12 increases, the voltage value of the divided voltage increases from the initial value V0. As sulfurization of the internal electrode progresses further, the internal electrode breaks, and the divided voltage becomes zero. The determination unit 20 determines that a liquid containing a sulfur component has adhered to the second resistor 12 when the voltage value of the divided voltage reaches or exceeds a predetermined second threshold value Vth2.

[0014] It is desirable to use resistors with low resistance values, such as several tens of MΩ, for the first and second resistors 11 and 12, in order to increase the rate of increase in resistance relative to the initial resistance value as sulfurization of the internal electrodes progresses. This allows for a larger change per unit time in the ratio of the resistance value of the first resistor 11 to the resistance value of the second resistor 12, for example, when a liquid containing a sulfur component adheres to the first resistor 11 and the resistance value of the first resistor 11 increases. This increases the rate of decrease per unit time in the voltage value of the divided voltage, thereby shortening the time until the voltage value of the divided voltage falls below the first threshold. This allows for early detection of the adhesion of a liquid containing a sulfur component.

[0015] Using the same principle, the determination unit 20 can determine, based on fluctuations in the voltage value of the divided voltage, whether water or a water-soluble liquid has adhered to at least one of the first and second resistors 11 and 12. In this embodiment, adhesion of water to a resistor means that water has crossed the resistor body, causing a short circuit between the internal electrodes, resulting in a decrease in the resistance value.

[0016] When water adheres to the first resistor 11, the resistance value of the first resistor 11 decreases. The decrease in the resistance value of the first resistor 11 increases the voltage value of the divided voltage. The determination unit 20 determines that water is adhering to the first resistor 11 when the voltage value of the divided voltage exceeds a preset third threshold value.

[0017] When water adheres to the second resistor 12, the resistance value of the second resistor 12 decreases. The voltage value of the divided voltage decreases due to the decrease in the resistance value of the second resistor 12. The determination unit 20 determines that water is adhering to the second resistor 12 when the voltage value of the divided voltage becomes less than a fourth threshold value set in advance.

[0018] In order to increase the extent of the decrease in resistance when water adheres to the first and second resistors 11 and 12, it is desirable to use resistors having a large resistance value, such as several tens of MΩ, as the first and second resistors 11 and 12. This increases the extent of the increase in the voltage value of the divided voltage when water adheres to at least one of the first and second resistors 11 and 12, thereby improving the accuracy of detecting water adhesion to the resistors.

[0019] The determination unit 20 compares the voltage value of the divided voltage with the first to fourth threshold values, thereby determining whether liquid has adhered to at least one of the first resistor 11 and the second resistor 12, and further determining whether the adhered liquid is water (a water-soluble liquid) or a liquid containing a sulfur component. However, when the threshold values ​​are close to each other, it may not be possible to make these determinations with high accuracy by threshold processing alone.

[0020] Therefore, the judgment unit 20 can determine, based on the change over time in the voltage value of the divided voltage, whether liquid has adhered to at least one of the first resistor 11 and the second resistor 12, and further whether the adhered liquid is water or a liquid containing sulfur components.

[0021] For example, when water adheres to a resistor, the resistance value of the resistor decreases from a first resistance value to a second resistance value and remains at the second resistance value. During the decrease from the first resistance value to the second resistance value, the resistance value of the resistor does not decrease gradually over time, but changes from the first resistance value to the second resistance value instantaneously.

[0022] On the other hand, when a liquid containing sulfur components adheres to a resistor, the resistance value of the resistor gradually increases from the initial resistance value as sulfurization of the internal electrodes progresses. Eventually, the internal electrodes break. Thus, the time change in the resistance value of a resistor with water attached thereto differs from the time change in the resistance value of a resistor with a liquid containing sulfur components attached thereto. Therefore, based on the time change in the voltage value of the divided voltage, such as the amount of change in the resistance value per unit time of the voltage value of the divided voltage, the rate of change in the resistance value per unit time, and the elapsed time until the voltage value of the divided voltage reaches a threshold value, it is possible to determine whether liquid has adhered to at least one of the first resistor 11 and the second resistor 12 and whether the attached liquid is water or a liquid containing sulfur components.

[0023] The liquid adhesion detection device 1 according to this embodiment can detect not only the adhesion of water but also the adhesion of water-insoluble liquids such as cutting fluid containing sulfur components. Furthermore, there is no need to prepare a dedicated resistor for detecting the adhesion of water-insoluble liquids such as cutting fluid containing sulfur components. Instead, a resistor with an internal electrode made of silver, which is not normally used in environments where water-insoluble liquids such as cutting fluid containing sulfur components may adhere, can be used as the detection element for detecting the adhesion of water-insoluble liquids such as cutting fluid containing sulfur components. This makes it possible to realize the liquid adhesion detection device 1 according to this embodiment at relatively low cost and with high accuracy.

[0024] Furthermore, because there are two resistors functioning as detection elements, the first resistor 11 and the second resistor 12, it is possible to detect adhesion of a water-insoluble liquid, such as cutting fluid containing sulfur components, at two locations, and the number of detection locations can be increased compared to when there is only one detection element. As will be described in the modified example below, the liquid adhesion detection device 1 can be said to be highly scalable because the number of detection locations can be easily increased by adding more resistors.

[0025] Furthermore, the liquid adhesion detection device 1 according to this embodiment can determine whether liquid has adhered and whether the adhered liquid is water or a liquid containing sulfur components, and therefore can be used in environments where both water and liquid containing sulfur components may adhere, making it more versatile than devices that can detect only water or only liquids containing sulfur components.

[0026] The configuration of the determination unit 20 is not limited to this embodiment. For example, the determination unit 20 may be configured with a comparator that compares the divided voltage with a reference voltage and outputs the comparison result as a voltage signal, and a control circuit that determines whether a liquid containing a sulfur component has adhered to the surface of the liquid based on the voltage signal output from the comparator.

[0027] In the liquid attachment detection device 1 according to this embodiment, if a liquid containing sulfur components attaches to both the internal electrodes of the first resistor 11 and the second resistor 12 at approximately the same time, and sulfurization progresses at approximately the same rate, the resistance values ​​of the first resistor 11 and the second resistor 12 may increase approximately equivalently. In such a case, it is expected that the divided voltage value will no longer fluctuate. In this situation, the determination unit 20 may not be able to detect the attachment of a liquid containing sulfur components.

[0028] To avoid such a situation, rather than both the internal electrodes of the first resistor 11 and the second resistor 12 containing a component that combines with sulfur components, one of the internal electrodes of the first resistor 11 and the second resistor 12 may contain a component that combines with sulfur components, while the other internal electrode of the first resistor 11 and the second resistor 12 does not contain a component that combines with sulfur components. Typically, the other internal electrode is configured as a gold electrode, which is made of a material that does not contain a component that combines with sulfur components. Note that this is intended to mean that one of the first resistor 11 and the second resistor 12 is a resistor that generates sulfuration, and the other is a resistor that does not generate sulfuration. However, as long as the resistor does not generate sulfuration, the configuration is not limited to a resistor with gold internal electrodes. For example, a resistor that uses silver internal electrodes and is coated to prevent sulfuration may be used as a resistor that does not generate sulfuration.

[0029] In this case, even if a liquid containing a sulfur component adheres to the internal electrodes of both the first resistor 11 and the second resistor 12 at approximately the same time, sulfuration will progress in one of the internal electrodes of the first resistor 11 and the second resistor 12, but will not occur in the other internal electrode. Therefore, the divided voltage will fluctuate, making it possible to detect adhesion of a liquid containing a sulfur component to one of the first resistor 11 and the second resistor 12. Note that, in order to detect adhesion of the liquid to either the first or second resistor 11, 12, two systems may be provided: one system in which the first resistor 11 is configured with silver electrodes and the second resistor 12 is configured with gold electrodes, and the other system in which the first resistor 11 is configured with gold electrodes and the second resistor 12 is configured with silver electrodes.

[0030] The form of the substance containing sulfur components is not limited to liquid, and may be a solid containing sulfur components or a gas containing sulfur components, as long as it can cause sulfurization of the first resistor 11 and the second resistor 12. In other words, the liquid attachment detection device 1 according to this embodiment can be used as a device for detecting attachment of a solid containing sulfur components to a resistor, or a device for detecting exposure of a resistor to a gas containing sulfur components.

[0031] The number of resistors connected in series to the power supply 10 is not limited to two. FIG. 4 shows the circuit configuration of a liquid adhesion detection device according to a first modification of this embodiment. As shown in FIG. 4, the liquid adhesion detection device 2 according to the first modification has a third resistor 13, which contains a component that combines with sulfur, connected in series between the power supply 10 and the first resistor 11 of the liquid adhesion detection device 1 according to this embodiment. The liquid adhesion detection device 2 according to the first modification configured in this manner can increase the number of resistors functioning as detection elements for detecting liquid compared to the liquid adhesion detection device 1 according to this embodiment, thereby increasing the number of liquid detection locations compared to this embodiment. Meanwhile, the more resistors functioning as detection elements for detecting liquid, the smaller the fluctuation in the resistance value of the second resistor due to liquid adhesion to the resistors. Therefore, from the perspective of detection accuracy, the liquid adhesion detection device 1 according to this embodiment is advantageous over the liquid adhesion detection device 2 according to the first modification because it has fewer resistors and can increase the fluctuation in the voltage value of the divided voltage due to liquid adhesion to the resistors. It is desirable that at least the first resistor 11 and the third resistor 13 have different resistance values. This makes it possible to identify the resistor to which the liquid has adhered, in other words, to identify the location to which the liquid has adhered, and to estimate the location into which the liquid has entered, based on the fluctuation in the voltage value of the divided voltage.

[0032] The circuit configuration is not limited to this embodiment. For example, another resistor may be connected in parallel to at least one of the first resistor and the second resistor. Fig. 5 shows the circuit configuration of a liquid adhesion detection device according to a second modified example of this embodiment. Fig. 6 shows the circuit configuration of a liquid adhesion detection device according to a third modified example of this embodiment.

[0033] As shown in Figure 5, the liquid adhesion detection device 3 of the second modified example has a fourth resistor 14 and a fifth resistor 15 connected in parallel to the second resistor 12 of the liquid adhesion detection device 1 of this embodiment.

[0034] As shown in Figure 6, the liquid adhesion detection device 4 of the third modified example has a sixth resistor 16 and a seventh resistor 17 connected in parallel to the first resistor 11 of the liquid adhesion detection device 1 of this embodiment.

[0035] The liquid adhesion detection devices 3 and 4 according to the second and third modifications configured in this manner can increase the number of liquid detection locations compared to the liquid adhesion detection device 1 according to the present embodiment, for the same reasons as the liquid adhesion detection device 2 according to the first modification. In the second modification, it is desirable that at least the second resistor 12, the fourth resistor 14, and the fifth resistor 15 have different resistance values. In the third modification, it is desirable that at least the first resistor 11, the sixth resistor 16, and the seventh resistor 17 have different resistance values. This makes it possible to identify the resistor to which liquid has adhered, or in other words, to identify the location to which liquid has adhered, and estimate the location where the liquid has entered, based on fluctuations in the voltage value across the second resistor 12.

[0036] In the liquid adhesion detection device 1 according to the present embodiment and the liquid adhesion detection device 2 according to the first modification, if any resistor breaks, the divided voltage input to the determination unit 20 becomes zero, and therefore adhesion of a liquid containing a sulfur component is detected before the resistor breaks. On the other hand, in the liquid adhesion detection devices 3 and 4 according to the second and third modifications, the divided voltage does not become zero even if a resistor connected in parallel breaks due to sulfuration, and therefore adhesion of a liquid containing a sulfur component can continue to be monitored.

[0037] The following supplementary notes are further disclosed regarding this embodiment and its modifications. (Supplementary Note 1) The liquid attachment detection device 1 includes first and second resistors 11 and 12 connected in series to divide the power supply voltage and containing a component that combines with sulfur components, and a determination unit 20 that determines whether a liquid containing sulfur components has attached to at least one of the first and second resistors 11 and 12 based on fluctuations in the value of the divided voltage obtained by dividing the voltage by the first and second resistors 11 and 12. (Supplementary Note 2) In the liquid attachment detection device 1 described in Supplementary Note 1, the first and second resistors 11 and 12 contain a silver component that combines with sulfur components. (Supplementary Note 3) The liquid attachment detection device described in Supplementary Note 1 or Supplementary Note 2 further includes a third resistor 13 connected in series with the first resistor 11 and the second resistor 12 and containing a component that combines with sulfur components. (Supplementary Note 4) In the liquid adhesion detection device 1 described in Supplementary Note 3, the determination unit 20 determines adhesion of a liquid containing a sulfur component to at least one of the first, second, and third resistors 11, 12, and 13 based on fluctuations in the voltage across the second resistor 12, and the third resistor 13 has a resistance value different from that of the first resistor 11. (Supplementary Note 5) The liquid adhesion detection device 1 described in Supplementary Note 1 or Supplementary Note 2 further comprises a resistor 14 that is connected in parallel to at least one of the first resistor 11 and the second resistor 12 and contains a component that combines with the sulfur component. (Supplementary Note 6) In the liquid adhesion detection device 1 described in Supplementary Note 5, the resistor 14 is connected in parallel to the second resistor 12 and has a resistance value different from that of the second resistor 12. (Supplementary Note 7) The liquid adhesion detection device 1 includes first and second resistors 11, 12 connected in series to divide the power supply voltage, and a determination unit 20 that determines adhesion of a liquid containing a sulfur component to at least one of the first and second resistors based on fluctuations in the value of the divided voltage obtained by dividing the voltage by the first and second resistors 11, 12. One of the first and second resistors 11, 12 contains a component that combines with the sulfur component, and the other of the first and second resistors 11, 12 does not contain a component that combines with the sulfur component. (Supplementary Note 8) In the liquid adhesion detection device 1 described in Supplementary Note 7, one of the first and second resistors 11, 12 is configured as a silver electrode, and the other of the first and second resistors 11, 12 is configured as a gold electrode.

[0038] Although the embodiments of the present disclosure have been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the invention or the concept and spirit of the present invention derived from the content of the claims and their equivalents. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments.

[0039] REFERENCE SIGNS LIST 1...liquid adhesion detection device, 10...power supply, 11, 12...resistors, 18...AD converter, 19...control circuit, 20...determination unit

Claims

1. A liquid adhesion detection device comprising: first and second resistors connected in series to divide a power supply voltage, the first and second resistors containing a component that combines with sulfur components; and a determination unit that determines adhesion of a liquid containing sulfur components to at least one of the first and second resistors based on fluctuations in the value of the divided voltage obtained by dividing the voltage by the first and second resistors.

2. The liquid attachment detection device according to claim 1, wherein the first and second resistors contain a silver component as a component that combines with the sulfur component.

3. The liquid attachment detection device according to claim 1 or 2, further comprising a third resistor connected in series with the first resistor and the second resistor, the third resistor including a component that combines with the sulfur component.

4. The liquid adhesion detection device according to claim 3, wherein the determination unit determines adhesion of the liquid containing sulfur components to at least one of the first resistor, the second resistor, and the third resistor based on fluctuations in the voltage across the second resistor, and the third resistor has a resistance value different from that of the first resistor.

5. The liquid attachment detection device according to claim 1 or 2, further comprising a third resistor connected in parallel to at least one of the first resistor and the second resistor, the third resistor including a component that combines with the sulfur component.

6. The liquid attachment detection device according to claim 5, wherein the third resistor is connected in parallel to the second resistor and has a resistance value different from that of the second resistor.

7. A liquid adhesion detection device comprising: first and second resistors connected in series to divide a power supply voltage; and a determination unit that determines adhesion of a liquid containing a sulfur component to at least one of the first and second resistors based on fluctuations in the value of the divided voltage obtained by dividing the voltage by the first and second resistors, wherein one of the first and second resistors contains a component that combines with the sulfur component, and the other of the first and second resistors does not contain a component that combines with the sulfur component.

8. The liquid attachment detection device according to claim 7, wherein one of the first and second resistors is configured as a silver electrode, and the other of the first and second resistors is configured as a gold electrode.

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