JP2003215150A - Conductive liquid, and liquid acceleration sensor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive liquid usable even for a liquid acceleration sensor of a long life, reduced in a size, easily attachable, and of which the output changes continuously, and a liquid acceleration sensor with the liquid sealed therein. <P>SOLUTION: The liquid used in the present invention is a liquid constituted of a solution in which lithium nitrate or potassium iodide is dissolved as a conductive agent in a mixture solution comprising a 1-4C lower alcohol and an alkyl propionate of which the carbon number in an alkyl group is 4 or less, having 500 MΩcm or less of specific resistance at 20°C, and having 0.1 mPa*s-100 mPa*s of viscosity at 20°C. The liquid is sealed in a container to manufacture the acceleration sensor. The mixture solution is preferably constituted of ethyl propionate and methyl alcohol. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a conductive liquid for a liquid acceleration sensor and a liquid acceleration sensor using the same.

[0002]

2. Description of the Related Art In recent years, liquid acceleration sensors have been drawing attention because they have a long service life, can be miniaturized, and can be easily mounted. In this liquid acceleration sensor, a pair of electrodes are usually provided inside a closed container, and a conductive liquid and an inert gas are enclosed. When the airtight container is in a normal posture and is in a stationary state, the pair of electrodes is partially immersed in the conductive liquid, a constant current flows between the electrodes, and the electric resistance value between the electrodes is also in a constant state. Has become. On the other hand, when the airtight container vibrates, the vibration separates the conductive liquid from the electrode and interrupts the electric path. On the other hand, when the airtight container is in a normal posture and is in a stationary state, at least one of the electrodes does not come into contact with the conductive liquid, and the conductive liquid and the electrode come into contact with each other due to vibration, so that a current flows between the electrodes. Flowing. In this way, since the energization state between the pair of electrodes changes, a sensor having a mechanism for detecting vibration is established. Further, mercury has been conventionally used as the conductive liquid.

[0003]

In recent years, there has been a demand for a sensor that changes its output value stepwise or continuously according to the magnitude of acceleration. However, in the case of the above-described liquid acceleration sensor using mercury, since the specific resistance value of mercury is low, the change in the specific resistance value due to the change in the contact area with the electrode is very small, and it is difficult to detect the change. Therefore, substantially only the so-called on or off state can be detected, and the acceleration and the inclination angle cannot be continuously detected.

The present invention has a long life, can be miniaturized,
It is another object of the present invention to provide a conductive liquid that is easy to mount and can be used as a liquid acceleration sensor that continuously changes output, and a liquid acceleration sensor that contains the liquid.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that lower alcohols having 4 or less carbon atoms and alkyl propionate having 4 or less carbon atoms in an alkyl group. A solution prepared by dissolving a specific conductive agent in a mixed liquid of ester has conductivity that can be used for a liquid acceleration sensor, has little corrosiveness to electrodes, and has little fluctuation in viscosity due to temperature change, Furthermore, it was found that the rate of change in resistance value due to temperature change was small. The present invention has been completed based on such findings.

That is, according to the present invention, (1) Lithium nitrate or potassium iodide is dissolved as a conductive agent in a mixed solution of a lower alcohol having 4 or less carbon atoms and an alkyl propionate having an alkyl group having 4 or less carbon atoms. And the specific resistance value at 20 ° C is 500 MΩc.
m or less and the viscosity at 20 ° C. is 0.1 mPa · s
Is a conductive liquid for a liquid acceleration sensor, characterized by being in the range of ˜100 mPa · s, and (2) a reference electrode and a detection electrode are provided inside an airtight container, and the conductive liquid and the conductive liquid are also provided. A gas that does not substantially change the liquid is enclosed in the airtight container, the reference electrode does not substantially change the contact area with the conductive liquid in the range of use, and the reference electrode and the Between the detection electrode and the conductive liquid can be energized, when the airtight container is in a normal posture, in a stationary state,
When the contact area of the detection electrode with the conductive liquid does not change, and when the airtight container vibrates, the contact area of the detection electrode with the conductive liquid changes temporarily, in which case In the liquid acceleration sensor in which the electric resistance value between the reference electrode and the detection electrode changes, the conductive liquid includes a lower alcohol having a carbon number of 4 or less and an alkyl propionate alkyl ester having a carbon number of 4 or less. Which is a solution obtained by dissolving lithium nitrate or potassium iodide as a conductive agent in the mixed solution of, and has a specific resistance value at 20 ° C. of 500 MΩcm or less and a viscosity at 20 ° C. of 0.1 mPa · s to 100 mPa · s. It is in the range of.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The conductive liquid of the present invention comprises a conductive agent and a solvent.

As the conductive agent used in the present invention, lithium nitrate or potassium iodide is used. Lithium nitrate and potassium iodide dissociate well in various solvents, and since the atomic weights of lithium and potassium are small, even if added in a small amount, a conductive liquid, that is, a liquid with a low specific resistance value can be obtained, and toxicity is low. Less and less corrosive to electrodes.

As the solvent used in the present invention, an alkyl propionate having an alkyl group having 4 or less carbon atoms and a lower alcohol having 4 or less carbon atoms are used. Examples of the alkyl group of the propionic acid alkyl ester include a methyl group, an ethyl group, a propyl group and a butyl group. Examples of alcohols include methanol, ethanol, propanol and butanol. Among them, a combination of methyl propionate or ethyl propionate and methanol is preferable.

Methyl propionate or a mixed solution of ethyl propionate and methanol has little change in viscosity due to temperature change, and has a small rate of change in specific resistance value due to temperature change. Further, methanol is mixed with methyl propionate or ethyl propionate at an arbitrary ratio, and further lithium nitrate or potassium iodide is stably dissolved.

These solvents are safer and easier to handle than mercury that has been used conventionally, and the work when the liquid acceleration sensor is damaged or discarded is very simple. .

As described above, the conductive liquid of the present invention contains a conductive agent and a solvent as essential components, and, if necessary, has a specific resistance value and a viscosity within the above range. It is also possible to mix three components. For example, a resin for adjusting the viscosity, a dye for coloring the conductive liquid, various metal salts for adjusting the specific resistance value of the conductive liquid, organic salts, acidic salts, basic salts, salts such as complex salts , Antifungal agents, light stabilizers and the like. However, these third components must be selected so that they can be dissolved or stably dispersed in a solvent so that the conductive liquid can be maintained in a stable state.

The conductive liquid of the present invention has a specific resistance value at 20 ° C. of 500 MΩcm or less, preferably 50 MΩc.
m or less and the viscosity at 20 ° C. is 0.1 mPa ·
s-100 mPas, preferably 0.1 mPas-
It is in the range of 10 mPa · s. If the specific resistance value is larger than the above range, it is not preferable because a current is difficult to flow between the electrodes in a normal power source using a battery of several volts.
If the lower limit of the specific resistance value is too low, it becomes difficult to detect the continuous change of the resistance value of the sensor by the detection circuit or the like.
It is suitable from the experiment that the lower limit value is 40 Ωcm or more. Therefore, in order to use it as a sensor for detecting the continuous change of the resistance value, the specific resistance value of the conductive liquid is 4
It is preferably 0 Ωcm to 50 MΩcm.

Further, if the viscosity is lower than the above range, the sensitivity of the liquid acceleration sensor is too good, and malfunction easily occurs. Conversely, if the viscosity is higher than the range, the sensitivity becomes poor.

In order to obtain a conductive liquid having such characteristic values, lithium nitrate or potassium iodide is mixed in the solvent in an amount of 0.000001 to 10% by weight, preferably 0.00002 to 2% by weight. Is appropriate. In addition, the mixing ratio on a weight basis of the alkyl propionate forming the solvent and the alcohol is (100: 0.1
~ 10,000), preferably (100: 0.5-700)
0) is suitable. Note that when the amount of alcohol is small, the solubility of lithium nitrate and potassium iodide decreases, and the stability tends to deteriorate.

Next, a typical example of a liquid acceleration sensor using the conductive liquid of the present invention will be specifically described with reference to FIGS. 1 and 2.

FIG. 1 is a vertical sectional view of a liquid acceleration sensor of the present invention, and FIG. 2 is a perspective view for explaining the structure of electrodes in this sensor. The acceleration sensor 1 has a substantially cylindrical metal container 2 and a metal plate 3 which are closed at one end, and an airtight container is formed by fixing the metal plate 3 to the opening of the metal container 2 by welding or the like. To be done. A conductive liquid 4 is enclosed in this airtight container. In this example, since the metal container 2 has a cylindrical shape, the contact area with the conductive liquid does not substantially change within the use inclination range, and therefore the metal container 2 itself is used as the reference electrode.

As shown in FIG. 2, electrodes 5A to 5D are arranged on the metal plate 3 at equal intervals.
A to 5D are fixed in a plurality of through holes 3A formed in a metal plate in an airtight and electrically insulated state by an electrically insulating filler 6 such as glass. Each of these electrodes 5A to 5D
Is a detection electrode whose contact area with the conductive liquid changes as the inclination angle of the liquid surface of the conductive liquid 4 changes.

A conductive liquid 4 enclosed in an airtight container
Is such that each of the detection electrodes is immersed by about half.

When the liquid acceleration sensor 1 is in the normal posture, the liquid level of the conductive liquid 4 is almost the same as that of each of the electrodes 5A to 5D as shown by 4A in FIG. Are in contact. At this time, the resistance value between each of the electrodes 5A to 5D, which is one of the electrodes, and the metal container 2, which is the other electrode, is set as a reference value.

On the other hand, when the liquid acceleration sensor 1 receives an acceleration, the liquid surface tilts as shown by 4B. Therefore, the contact area between each electrode arranged in the acceleration direction and the conductive liquid 4 changes, and the electric resistance value between the electrode and the metal container changes.

In the above example, the case where the resistance value between the reference electrode and the detection electrode continuously changes according to the inclination of the liquid surface of the conductive liquid has been described. However, for example, either at rest or at vibration. The sensor may be energized and the sensor may be turned on and off. This example will be described with reference to FIG.

The acceleration sensor 11 is an airtight container composed of a substantially cylindrical metal container 12 having one end closed and a metal plate 13, and the conductive liquid 4 is enclosed in the airtight container. Same, but when used, metal plate 13
The operation is different from that of the above-described example because one electrode is normally set so as not to come into contact with the conductive liquid with the above.
That is, the metal plate 13 has the electrode 15 on which the electrically insulating filler 16
Although the metal container 12 serving as the reference electrode is constantly in contact with the conductive liquid 4, the detection electrode 15 is fixed to the conductive liquid 4 in a normal posture when stationary. Do not touch. When the liquid acceleration sensor 11 is given an acceleration or the liquid acceleration sensor 11 tilts, the liquid surface tilts to contact the electrodes and form an electric path.

In this example, the electrode 15 is provided at the center of the metal plate 13, but at this position the liquid surface hardly changes, so there is a possibility that the liquid surface change due to acceleration or vibration cannot be detected as it is. . So electrode 1
A disk-shaped electrode plate 15A is fixed in a conductive state to the tip of the inside of the container 5 by welding or the like. The magnitude of the detectable acceleration is determined by the diameter of the electrode plate 15A, the inner diameter of the metal container 12, the amount of the conductive liquid 4, and the like. In addition,
For example, instead of this electrode plate, a plurality of electrodes may be arranged on the circumference as in the above example.

With such an acceleration sensor, it is possible to always energize between the reference electrode and the detection electrode, to detect a change in electric resistance value due to vibration, or to energize the sensor either at rest or during vibration. By turning ON / OFF the power, it can be effectively used for various sensors. For example, (a) extinguish the fire when the oil fan heater receives vibration such as an earthquake, (b) an alarm sounds when the crane is tilted over a certain amount, and (c) the liquid level changes at the liquid interface. Then, it can be used for applications such as stopping the supply of liquid or gas, and (2) turning off the power when vibration is detected in various electrical products, and also for a level or the like for obtaining an inclination angle.

[0027]

EXAMPLES Examples of the present invention will be described in detail below.

[Examples 1 to 4] and [Comparative Examples 1 and 2] The components shown in Table 1 below were mixed by stirring to prepare a conductive liquid. The numerical values in Table 1 are "parts by weight" unless otherwise specified. The specific resistance value, the rate of change of the specific resistance value and the viscosity of each of the obtained conductive liquids are as shown in the lower part of Table 1.

[0029]

[Table 1] Note 1) Desktop PH / conductivity meter MPC227 (METTLER.
The specific resistance value at 20 ° C. was measured by Toledo Corporation. Note 2) Conductive liquid at 70 ℃, AC1.5V (1kH
An energization test was performed for 3000 hours under the condition of z), and the rate of change in the specific resistance value before and after the test was calculated. Note 3) Ostwald viscometer 70 ℃, 20 ℃, -20 ℃
The viscosity at was measured.

From the results shown in Table 1, the electroconductive liquids of Examples 1 to 4 have sufficient electroconductivity, the rate of change of the specific resistance value is small with respect to the temperature change, and the change with respect to the temperature change. It can be seen that there is little change in viscosity and can be effectively used as a conductive liquid for a liquid acceleration sensor. On the other hand, Comparative Example 1 in which zinc bromide was added as the conductivity had a large change rate of the specific resistance value at the time of the electric current test, and Comparative Example 2 in which the alkyl propionate was not added had a large change in viscosity with temperature change. The liquid acceleration sensor was unsuitable from the viewpoint of reliability.

[0031]

As described above, the conductive liquid of the present invention has the characteristics required for a liquid acceleration sensor, is less corrosive to electrodes, and has a small change in specific resistance value due to temperature change. Furthermore, handling during manufacturing is easy.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a basic structure of a liquid acceleration sensor of the present invention.

FIG. 2 is a perspective view for explaining a configuration of electrodes in the liquid acceleration sensor of FIG.

FIG. 3 is a vertical cross-sectional view showing another structure of the liquid acceleration sensor of the present invention.

[Explanation of symbols]

1, 11: Liquid acceleration sensor 2, 12: Metal container 3,13: Metal plate 4: Conductive liquid 5A, 5B, 5C, 5D, 15: Electrode 15A: Electrode plate 6,16: Electric insulating filler

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yuji Yamazaki             1920-1 Osawara, Otawara, Tochigi Prefecture (72) Inventor Hiroyuki Tanabe             8-15 Asahi-cho, Nishinasuno-cho, Nasu-gun, Tochigi Prefecture (72) Inventor Mitsuhiro Urano             4-30 Hoshocho, Minami-ku, Nagoya-shi, Aichi             Ikukata Manufacturing Co., Ltd. (72) Inventor Hiroshi Murata             4-30 Hoshocho, Minami-ku, Nagoya-shi, Aichi             Ikukata Manufacturing Co., Ltd. (72) Inventor Takashi Toda             4-30 Hoshocho, Minami-ku, Nagoya-shi, Aichi             Ikukata Manufacturing Co., Ltd. (72) Inventor Eisaku Yokota             4-30 Hoshocho, Minami-ku, Nagoya-shi, Aichi             Ikukata Manufacturing Co., Ltd.

Claims (4)

[Claims] 1. A solution obtained by dissolving lithium nitrate or potassium iodide as a conductive agent in a mixed solution of a lower alcohol having 4 or less carbon atoms and an alkyl propionate having 4 or less carbon atoms of an alkyl group, and A conductive liquid for a liquid acceleration sensor, which has a specific resistance value at 20 ° C. of 500 MΩcm or less and a viscosity at 20 ° C. in a range of 0.1 mPa · s to 100 mPa · s. 2. The specific resistance value is 40 Ωcm to 50 MΩc
The conductive liquid for a liquid acceleration sensor according to claim 1, which is in a range of m. 3. A reference electrode and a detection electrode are provided inside the airtight container, and a conductive liquid and a gas that does not substantially change the quality of the conductive liquid are enclosed inside the airtight container.
The reference electrode does not substantially change the contact area with the conductive liquid in the range of use, and the reference electrode and the detection electrode are made conductive by the conductive liquid, When the airtight container is in a normal posture and is in a stationary state, the contact area of the detection electrode with the conductive liquid does not change, and when the airtight container vibrates, the conductivity of the detection electrode is changed. In the liquid acceleration sensor in which the contact area with the ionic liquid temporarily changes, and at that time the electric resistance value between the reference electrode and the detection electrode changes, the conductive liquid has a carbon number of 4 or less. A mixture of a lower alcohol and an alkyl propionate whose alkyl group has 4 or less carbon atoms, in which lithium nitrate or potassium iodide is dissolved as a conductive agent, and the temperature is 20 ° C.
Has a specific resistance value of 500 MΩcm or less at 20 ° C.
A liquid acceleration sensor having a viscosity in the range of 0.1 mPa · s to 100 mPa · s. 4. The specific resistance value is 40 Ωcm to 50 MΩc.
The liquid acceleration sensor according to claim 3, wherein the liquid acceleration sensor has a range of m.