JPS62177411A - Tilt sensor - Google Patents

Abstract

PURPOSE:To obtain a sensor which easily reads a tilt angle and as a result, is simple in a circuit design of a signal process and moreover, has good sensitivity by winding a coil round an annular container wherein a magnetic fluid is enclosed in a part of its annular hollow part. CONSTITUTION:The magnetic fluid 2 is filled up by about 50% of the volume of the annular hollow part in the circular annular container 1 and the coil 31 is wound round the container. In this case, the coil 31 is wound on one side of the right side and the left side with respect to a reference line S of tilt angle measurement and the number of windings is made about 100-1,000 turns. Further, in order to improve detecting accuracy, two coils can be wound symmetrically as the coils 31 and 32 as necessary. Accordingly, the coils 31 and 32 are wound round the annular container 1 in the part of which the fluid 2 is enclosed and the tilt angle is measured by the variation of inductance. In this way, the variation of the inductance and the tilt angle is made the linear relation in a wide range and as a result, the sensor which processes a read signal easily and is also simple in its circuit design and moreover, has good sensitivity is obtained.

Description

[Detailed description of the invention] Background of the invention Technical field The present invention relates to a tilt sensor.

Prior Art and Its Problems Due to its characteristics, magnetic fluids are expected to have a variety of applications.

One of them is a tilt sensor. Conventional tilt sensors are made by filling a hollow rod-shaped container with an amount of magnetic fluid equivalent to approximately half of the container's volume. The coils are wound on the left and right sides so that they are symmetrical. Then, set it at the point where you want to measure the inclination angle, apply an alternating current in conjunction with the above method, and measure the inductance that changes as the left and right volumes of the magnetic fluid increase or decrease according to the inclination. It is something to be measured. The magnetic fluid in this case uses an oxide magnetic material (magnetite).

However, in such a conventional tilt sensor, the range in which the relationship between the tilt angle and the amount of change in inductance is linear is narrow, making it difficult to read the tilt angle, and the sensitivity is insufficient.

OBJECTS OF THE INVENTION It is an object of the present invention to provide an inclination sensor in which the inclination angle can be easily read, the signal processing circuit design is simple, and the sensitivity is good.

■Disclosure of invention Such objects are achieved by the invention described below.

That is, the present invention is a tilt sensor characterized in that a coil is wound around a ring-shaped container in which a part of the ring-shaped hollow part is filled with magnetic fluid, and the tilt angle is measured based on the amount of change in inductance.

■Specific structure of the invention The specific configuration of the present invention will be explained in detail below.

The tilt sensor of the present invention has a coil wound around a ring-shaped container partially filled with magnetic fluid.

The shape of the ring-shaped container is not particularly limited as long as it has a ring-shaped hollow part, but it is preferably symmetrical about a certain center line, and it is particularly preferable that it has a ring shape such as a circular cross section. .

For example, in the case of a ring with a circular cross section, the inner diameter of the cross section of the ring-shaped hollow part is about 2 to 101!1ff1, and the outer and inner diameters of the ring are 10 to 100 mm and 5 to 80 cm, respectively.
It is preferable that the value is about IIl111.

Also, the material of this ring-shaped container may be any non-magnetic material.
, A text, metals such as Cu, various glasses, plastics,
Examples include rubber.

The amount of magnetic fluid sealed in this annular container is not particularly limited as long as it is a part of the annular hollow part, and the position of the fluid can be changed according to the inclination of the magnetic fluid. About 20 to 80% of the volume of the hollow part, especially about 5
Approximately 0% is preferable.

A preferred example of 7g of the present invention is shown in FIG. 1, for example.

That is, a circular annular container 1 is filled with magnetic fluid 2 to an extent of about 50% of the volume of the annular hollow portion, and a coil is wound around this. In this case, the coil 31 is the reference for measuring the tilt angle! ! It is wound on one side of the right side and the left side with respect to aS, and the number of turns is about 100 to too many turns each.

The winding portion of the coil 31 can be changed in various ways.

An alternating current is applied to such a device and the inductance of the magnetic fluid is measured.

In this case, the alternating current has a current of 0.1 to 10 mA and a frequency of about IKHz to 100 MHz.

This inductance then changes with the tilt angle. In other words, the volume of the magnetic fluid increases or decreases depending on the slope.
The inductance changes accordingly.

Therefore, the tilt angle is detected by detecting this inductance.

Detection of inductance and calculation and display of inclination angle may be performed by known means.

For example, as shown in FIG. 3, signal processing may be performed as follows: oscillator time limiter time differentiation circuit - monostable circuit -> integration circuit - square conversion circuit (logarithm, reciprocal) - display circuit.

In the example shown in Figure 1, the coil is wound on one side and the inclination angle is calculated from the inductance of the coil, but in order to further improve detection accuracy, the coil may be wound as shown in Figure 2. may be wound symmetrically into two coils 31 and 32. In this case, since the inclination angle is calculated based on the difference in inductance between both coils, detection sensitivity can be further improved.

Also, as shown in Figure 1, the measurement range of the inclination angle is ±90° when the coil is only on one side, but when two coils are installed symmetrically as shown in Figure 2, it is ±180°. As a result, the range of detection angles is also expanded.

The magnetic fluid used in the present invention may be one obtained by treating fine particles of conventional oxide magnetic material (magnetite, Fe304) with a surfactant and dispersing it in colloidal form in oil, water, etc.; Metal fine particles are dispersed in a suitable medium using various surfactants (Japanese Patent Application No. 59-159930, No. 59-187) filed by the applicant.
No. 164, No. 59-194321, No. 59-1943
No. 22, No. 59-194985), etc. may be used.

Among these, those using fine metal particles are preferred because of their high saturation magnetization.

Cobalt or iron metal particles are used as the metal particles.

The particle size is 70 to 120 particles in the case of cobalt metal particles, and 10 to 100 particles in the case of iron metal particles.

This is because it is impossible to disperse ferromagnetic fine particles in a liquid, and it is necessary to overcome their magnetic cohesive force.

The magnetic fluid usually preferably contains an antioxidant in order to prevent oxidation of the metal particles.

The antioxidant used may be a general oil-soluble one, but
Particularly suitable is tocopherol.

As tocopherol, DL-α-tocopherol represented by the following formula [1] is particularly preferable.

[II magnetization, β-tocopherol, γ-tocopherol, δ
-tocopherol, d-α-tocopherol can also be used.

The amount of antioxidant added is 0.5 to 0.5 to
It is 3% by weight.

This is not effective if Q is less than 5gL, and 3% by weight.
This is because if it exceeds this, there will be an adverse effect on the magnetic properties.

Various media can be used for such magnetic fluid depending on the purpose.

Examples of the medium used include a hydrocarbon medium which is a low boiling point solvent, and a dicarboxylic acid diester medium or a fatty acid saturated hydrocarbon medium which is a high boiling point solvent.

The hydrocarbon used as the medium preferably has 7 to 22 carbon atoms, and paraffin to olefin types such as kerosene, and aromatic types such as toluene and xylene can be used.

The hydrocarbon medium is contained in an amount of 50 to 250% by weight based on the metal fine particles.

The dicarboxylic acid diester has 6 to 10 carbon atoms.
Diesters of aliphatic saturated dicarboxylic acids and aliphatic saturated alcohols having from 3 to 10 carbon atoms are preferred, which are
It is represented by the following formula [II].

[II] ROOC(CH2)n C0OR In the above formula [II], n=4 to 8.

As the aliphatic saturated dicarboxylic acid, adipic acid with n=4, 7gelaic acid with n=7 or sebacic acid with n=8 are preferred.

R is an aliphatic saturated hydrocarbon group having 3 to 3 carbon atoms;
Preferably, there are 8 octyl groups in 10.4'\.

For example, one or more of the following are suitable.

;) Dioctyl adipate i+ ) Dioctyl sebacate i'i) Di(2-ethylhexyl) azelaate dicarboxylic acid diester medium is 100%
Contains ~800% by weight.

Instead of or in addition to the diester medium, one or more aliphatic saturated hydrocarbon media can be used as a solvent.

In this case, carbon atoms fi19-30,') are preferred.

Listed below are compounds suitable for ().

i) Bristane ((C)l) C)1(C13)3CM(CH3)(
CH3)30H(C)13)(OH3)3CH(CH3
)2) ii) Squalane ((C:)l ) C)I(C)l ) C)1(CH
3)(CH2)3C:)l(C)! 3) CH2CH2)
2) α-olefin oligomer (n is 1 to 4, especially 1 or 2.R is 2 to 1 carbon atoms)
2, especially an alkyl group of the order of 6 1 e.g. 5yncelan
e30, manufactured by Nikko Chemicals ■) One of these aliphatic saturated hydrocarbon media or the second or more type contains a total of 50 to 300π15% of the metal fine particles together with the diester system added as necessary. It will be done.

In addition to or instead of a high boiling point solvent such as a dicarboxylic acid diester type or a fatty acid saturated hydrocarbon type, a low boiling point solvent, especially a hydrocarbon type, can be used as this medium.

The hydrocarbon used as the medium has 7 to 2 carbon atoms as described above.
2 is preferable, and paraffin or olefin type 1
For example, kerosene, aromatic systems such as toluene, xylene, etc. can be used.

Note that the klN of these media is 50
Contains ~300% by weight.

Further, in order to disperse metal fine particles in a medium, various surfactants are used depending on the medium.

It is preferable to use a fatty acid ester nonionic surfactant or a phospholipid lecithin as the hydrocarbon medium as a low boiling point solvent.

The nonionic surfactant is preferably one or more of polyglycerin or sorbitan fatty acid ester.

The fatty acid ester of polyglycerin is represented by the following formula % Formula % [ ] In the above formula [IV], R is a saturated or unsaturated fatty acid acyl group or hydrogen.

Further, n is a positive integer. In addition, when R is an acyl group, the plurality of R's may be different depending on the case, but are usually the same.

In the fatty acid ester of polyglycerin, the degree of polymerization of polyglycerin is preferably 2 to 10, that is, n=0 to 8, more preferably n; 4 to 8.

Moreover, these are preferably partial esters of fatty acids. In this case, the esterification rate is approximately 25 to 85%.

As a fatty acid ester of sorbitan, l.

It may be a mono- or sesqui (mixture of mono and di) fatty acid resins such as 5-sorbitan and 1,4-sorbitan.

However, among these, 1,5-sorbitan or 1,4-sorbitan fatty acid mono- or esters represented by [Vl and [V1] are preferred.

[Vl Crystal [■ Cory] In the above formula [V] or [■], R is a saturated or unsaturated fatty acid-based acyl group.

These fatty acid esters are preferably esters of fatty acids having 10 to 18, especially 18 carbon atoms, ie stearic acid, instearic acid or oleic acid.

Note that commercially available esters may be used as the above esters.

By adding fine metal particles to obtain these surfactants, it is possible to prevent to a considerable extent the solidification of the magnetic fluid that occurs when fine metal particles are used at a high concentration to obtain high saturation magnetization.

Specific examples of the surfactants used are listed below.

1) Polyglycerin fatty acid ester i) Decaglyceryl pentaolate ii) Decaglyceryl pentastearate Seedling) Decaglyceryl pentaisostearate lma) Decaglyceryl hebutastearate V) Decaglyceryl hebutaisostearate 1, mal) Deca Glyceryl hebutaoleate mai+) Decaglyceryl decoin stearate ma)
Decaglyceryl decastearate ix) Decaglyceryl decaolate Hexaglycerylpenstearate! My) Hexaglyceryl pentaolate z
vii) Hexaglyceryl pentastearate 2) Sorbitan unsaturated fatty acid ester 1) 1,5-sorbitan monooleate 1i) 1,4-sorbitan monooleate ■) 1,4-sorbitan monostearate iv) 1,4-sorbitan monooleate Isostearate v) 1,4-sorbitan monooleate (i) 1,4-sorbitan sesquiisostearate In this case, two or more of these surfactants may be used.

These surfactants to be added have a 6%
It is 0% by weight or less, particularly about 25 to 60% by weight.

If it is less than 25% by weight, it is not effective, and if it exceeds 60% by weight, agglomeration and sedimentation of metal fine particles will occur during the cooling stage after the reaction.

In addition to or in place of these, lecithin, a phospholipid used as a surfactant, is obtained from soybeans and is a natural product.

Or it may be a refined version of this,
It is represented by the following formula [■].

[■] Lecithin (phosphatidylcholine) above formula [■]
In, R1 and R2 are saturated or unsaturated fatty acids. That is, palmitic acid, stearic acid, oleic acid, linoleic acid, lylunic acid, etc., having 15 or more carbon atoms.
18.

Note that R and R2 may be different or the same.

The amount of such surfactant added is 250% by weight or less, especially 60 to 250% by weight based on the metal fine particles. ! ! The amount is about %.

Note that commercially available lecithin may be used.

These are particularly effective when used with low boiling point solvents.

For low-volatile solvents, especially dicarboxylic acid diester media, one or more types of surfactants such as nonionic surfactants or oil-soluble anionic surfactants are preferred in the case of C/S metal fine particles.

As the nonionic surfactant, fatty acid esters of polyglycerin represented by the above formula [■] are preferred, and oleic esters are particularly preferred.

Further, as the nonionic surfactant, an alkyl ether of polyethylene gelcol represented by the following formula [■] is suitable.

[VII[] R-0-(CH2CH20) n H In the above formula [VII[], R is an unsaturated alkyl group. Moreover, n is 1-3.

These are commercially available as mixtures with different n.
The following are preferred.

1) Dioxyethylelyl ether ii) Neugen ET69 (polyethylene glycol oleyl ether, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., 2.3 moles of ethylene glycol mixed in with oleyl alcohol) (containing 3.8 moles of ethylene glycol) The oil-soluble anionic surfactant is preferably a sulfosuccinate ester, which is represented by the following formula % formula % [] In the above formula [IX], R is an aliphatic saturated hydrocarbon group. 2-ethylhexyl group having 8 carbon atoms is preferred. Further, Y is an alkali metal such as Na or hydrogen or hydrogen.

These surfactants to be added are
It is about 20% by weight.

It is not effective if it is less than 5% by weight, and if it exceeds 20% by weight,
It will become pasty and will not disperse.

Furthermore, in the case of iron metal fine particles, lecithin, which is the aforementioned phospholipid, may be used as a surfactant.

The amount of surfactant added is 100% by weight based on the metal fine particles.
Below, it is about 50 to 100% by weight.

If it is less than 50% by weight, it is not effective, and if it exceeds 100% by weight, it becomes pasty and cannot be dispersed.

For aliphatic saturated hydrocarbon media, which are low-volatility solvents, the above-mentioned nonionic surfactants (polyglycerin fatty acid esters, alkyl ethers of polyethylene glycol) or oil-soluble anionic surfactants can be used as surfactants. A sulfosuccinic acid ester may be used.

The amount of the surfactant added is 20% by weight or less, particularly about 5 to 20% by weight, based on the metal fine particles.

It is not effective if it is less than 5% by weight, and if it exceeds 20% by weight,
It becomes a paste and does not disperse.

In the case of cobalt, CO2 (Co
)8. In the case of iron, Fe(Co)5 may be used.

In addition, the thermal decomposition temperature is 140 to 160°C in the case of cobalt.
In the case of iron, the temperature is 140-180°C, and the thermal decomposition time is about 2 to 4 hours in the case of cobalt. The temperature and time may be changed as appropriate depending on the metal concentration.

When using a low-volatile solvent, a dispersion composition of fine particles in a low-boiling solvent is first prepared, a polar solvent or an insoluble solvent is added to this, the fine particles are agglomerated, and this is dispersed in a low-boiling solvent containing a surfactant. It may be redispersed in a volatile solvent.

Such magnetic fluid must be kept in a predetermined container. The inside of the container is preferably replaced with an inert gas such as argon or nitrogen.

■Specific effects of the invention According to the present invention, a coil is wound around a ring-shaped container partially filled with magnetic fluid, and the inclination angle is measured based on the amount of change in inductance. has a linear relationship over a wide range, and as a result, a tilt sensor with easy processing of read signals, very simple circuit design, and good sensitivity can be obtained.

Since the magnetic fluid is made of cobalt or iron metal fine particles dispersed in a hydrocarbon medium using various surfactants, the slope of the above straight line becomes large.
Sensitivity is further improved.

(2) Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown and the present invention will be explained in more detail.

Example First, I will explain how to make magnetic fluid. Ru.

A solution of 12 g of decaglyceryl hebutaolate and 2 g of the antioxidant DL-α-tocopherol dissolved in 30 g of kerosene medium was placed in a three-necked flask equipped with a condenser, a thermometer, and a stirring device. To this was added 120 g of octacarbonyl dicobalt CQ2 (Co)11.

This mixed solution was gradually heated with a mantle heater while stirring, and cobalt carbonyl was thermally decomposed while refluxing.

At this time, CO decomposed from the upper part of the cooler is generated. This generation of CO was confirmed by passing it through a PdCl2 solution (acetone:water=1:l). That is,
This is because the orange PdCl2 solution changes to black due to the introduction of CO.

After the generation of CO ended, stirring was continued for about 30 minutes, and then the mixture was cooled. This resulted in a black solution. This black solution was centrifuged at 6000 rpm for 1 hour. However, at this time, there was almost no separatist conflict.

Next, as shown in Fig. 1, the magnetic fluid produced as described above was placed in a circular annular container (material: Teflon; inner diameter of the cross section of the hollow part: 3 mm; outer and inner diameters of the annular body: 50 mm,
40 mm) in an amount equivalent to 50% of its volume. Then, a 500-turn winding was applied to one side of the base ζ wire S, an alternating current (IKHz, 0, 5 mA) was applied, and the relationship between the inclination angle and the amount of change in inductance was investigated.

The results are shown in Figure 4.

Further, as in the prior art, the above magnetic fluid was sealed in a rod-shaped container (made of Pyrex; inner diameter: 8+ om; length: 40 m+a) in an amount corresponding to 50% of the volume of the container. Then, a 300-turn winding was applied to one of the right and left sides of the thing, and an alternating current (1KHz, 5A) was applied.
The relationship between the angle of inclination and the amount of change in inductance was investigated.

The results are shown in Figure 5.

From the above results, the effects of the present invention are clear.

[Brief explanation of drawings]

1 and 2 are schematic diagrams of the tilt sensor of the present invention, respectively. FIG. 3 is a block diagram when the inclination sensor of the present invention shown in FIG. 1 is used. FIG. 4 is a graph showing the relationship between inclination angle and inductance when the inclination sensor of the present invention shown in FIG. 1 is used. FIG. 5 is a graph showing the relationship between tilt angle and inductance when a conventional tilt sensor is used. Explanation of symbols 1...Annular container, 2...Magnetic fluid, 31.32...Coil FIG, 2 Threat angle/degree

Claims (1)

[Claims] (1) A tilt sensor characterized in that a coil is wound around a ring-shaped container in which a part of the ring-shaped hollow part is filled with magnetic fluid, and the tilt angle is measured based on the amount of change in inductance.