JP2000275088A - Oil level-detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and durable oil level-detecting device with accurate resolution by changing the relative position between a magnetic response member and a detection part according to the up and down movement of a float member, and by outputting a signal. SOLUTION: When a float 2 for detecting oil level is moved up and down according to the displacement of oil level, a permanent magnet 5 reciprocates in an X direction by the amount of the displacement of the oil level via an arm 3 and a displacement element 4. On the other hand, a detection part 6 has a magnetic body core 7 being wound by primary and secondary coil winding, and is arranged near a position opposite to the magnet 5 while sandwiching the body of a tank 7. Then, when the magnet 5 approaches the magnetic body core 7, the place is magnetically saturated, and induction output is changed, thus obtaining an induction output signal corresponding to the position of the float 2 from the secondary coil winding, and detecting the height of an oil level based on the output. As a result, the height can be detected without any contact, thus eliminating sliding abrasion, and also manufacturing the detection device extremely easily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a magnetic coupling between a primary coil and a secondary coil.
The present invention relates to a liquid level detection device that detects a position of a liquid level of a liquid filled in a fuel tank or the like.

[0002]

2. Description of the Related Art A liquid level detecting device detects a liquid level of a liquid (for example, gasoline or oil) filled in a casing such as a fuel tank. Conventionally known liquid level detection devices include, for example, a liquid level detection float that moves up and down in accordance with the rise and fall of the liquid level in a casing forming a fuel tank. The height of the liquid surface of the liquid can be detected from the sliding resistance value of the sliding variable resistor that changes according to the movement.

[0003]

By the way, in the above-mentioned conventional liquid level detecting device, the sliding element which slides the change of the sliding resistance value of the sliding variable resistor (that is, the liquid level) is used. This is based on a mechanical method of detecting at a contact position of a (slide brush), that is, a contact method. Therefore, mechanical wear and corrosion on the slider and its sliding surface due to repetitive sliding operation cannot be avoided, and the durability is poor, and it has been used for several years to measure the liquid level. There is a problem that an error occurs. Further, in order to perform precise measurement with the sliding variable resistor, the structure of the mechanism of the sliding variable resistor must be complicated and precise. However, there is a problem that the apparatus becomes large and the cost becomes high.

The present invention has been made in view of the above points, has a small and simple structure, can detect a liquid level with high precision resolution, and has no danger of sliding wear. It is an object of the present invention to provide a non-contact type liquid level detecting device which is rich in properties. It is another object of the present invention to provide a liquid level detecting device having a simple structure that makes manufacturing extremely easy.

[0005]

According to the present invention, there is provided a liquid level detecting apparatus comprising: a float member which is vertically displaced in accordance with a rise and fall of a liquid level of a liquid;
A magnetic response member and a detection unit are disposed so that one is relatively displaced relative to the other, and the detection unit is disposed so as to surround the magnetic response member, Primary and secondary windings magnetically coupled over a predetermined range along the direction of the relative displacement;
A change in magnetic coupling occurs at the position of the magnetic response member, and the relative position between the magnetic response member and the detection unit changes in accordance with the rise and fall of the float member. The magnetic coupling between the winding and each secondary winding changes according to the position of the magnetic responsive member, and the position of the liquid surface is detected by obtaining an output signal corresponding thereto from the secondary winding. Is what you do.

In a preferred embodiment of the present invention, the magnetic response member includes a magnet, and the detecting section includes a magnetic core extending over a predetermined range along a direction of relative displacement of the magnet. 1 through the body core
The secondary and secondary windings are magnetically coupled so that magnetic saturation occurs at a predetermined location of the magnetic core that strongly receives the magnetic flux from the magnet, and the magnet is coupled to the magnet in accordance with the rise and fall of the float member. The relative position of the detection unit changes, and the predetermined location where magnetic saturation occurs in the magnetic material core is displaced accordingly, and the primary and secondary windings between the primary and secondary windings are displaced in accordance with the displacement of the magnetic saturation location. In some cases, the position of the liquid surface is detected by changing the magnetic coupling and obtaining an output signal corresponding to the change from the secondary winding.

[0007] In the detecting portion arranged close to the magnet, a predetermined portion of the magnetic core strongly receives the magnetic flux from the magnet which is relatively displaced in conjunction with the float member, and the magnetic saturation at that portion. Is configured to occur. At the place where the magnetic core is in a magnetically saturated state, it is as if the magnetic core does not exist at that place, and the degree of magnetic coupling between the primary and secondary windings is significantly reduced. Accordingly, an output signal corresponding to such a decrease in the degree of magnetic coupling is obtained from the secondary winding, and the position of the float member, that is, the liquid level can be detected. That is, the primary and secondary positions of the magnetic core extending over a predetermined range along the direction of relative displacement of the magnet are detected so as to detect which position is in a magnetic saturation state.
By properly arranging the next winding, it is possible to continuously detect the position of the magnet over the predetermined range. It should be noted that the arrangement of the primary and secondary windings may be appropriately determined by a known arrangement of the inductive position detecting device.

For example, if the primary winding is excited by a single-phase AC signal in the detecting section and a plurality of secondary windings are arranged at different positions with respect to the displacement direction of the magnet, a resolver type A position detection output signal can be obtained. That is, the magnetic coupling between the primary winding and each of the secondary windings is changed according to the position of the float member by displacing the magnetically saturated portion of the magnetic core in accordance with the relative displacement. Can be induced in each of the secondary windings with different amplitude function characteristics according to the displacement of the arrangement of each of the secondary windings. As is known in resolvers, each secondary winding can be arranged to produce a sine and cosine phase output, which is then detected as an inductive output AC signal that is amplitude modulated according to the position. A first output AC signal (for example, sinθsinωt) having a sine function amplitude function and a second output AC signal (for example, cosθs) having a cosine function amplitude function with respect to a target position (for example, indicated by θ)
inωt).
In that case, since a phase detection circuit for a resolver or a device similar thereto is known, the first output AC signal and the second output AC signal are input to the phase detection circuit to indicate the linear position. It can be configured to detect the phase value θ of the sine function and the cosine function.

As the magnet, it is preferable to use a permanent magnet because it is the simplest. However, the use of an electromagnet instead of the permanent magnet is also included in the scope of the present invention.
The number of magnets provided may be one or more.

In another embodiment of the present invention, the magnetic responsive member is configured to include at least one of a magnetic material and a conductor. Similarly to the above-described configuration, for example, in the detection unit, the primary winding is excited by a one-phase AC signal in the detection unit, and the plurality of coils are arranged at different positions with respect to the direction of the relative displacement of the magnetic response member. In this case, a resolver type position detection output signal can be obtained. That is, for example, when a magnetic material such as iron is used as the magnetic response member, the magnetic coupling between the primary winding and each secondary winding increases and changes according to the relative displacement of the magnetic material according to the position of the magnetic material. Thereby, the induced output AC signal amplitude-modulated according to the position is induced in each secondary winding with a different amplitude function characteristic according to the displacement of each secondary winding. be able to. Therefore, the apparatus further includes a phase detection circuit that inputs the first output AC signal and the second output AC signal to a phase detection circuit and detects a phase value θ of the sine function and the cosine function indicating the linear position. The detection target position can be absolutely detected. As such a phase detection circuit, an RD (resolver-digital) converter conventionally known as a resolver phase detection circuit can be used, or a phase detection circuit of another system can be used. The fact that such a resolver type phase detection circuit can be used means that an error occurs in the electrical phase shift in the secondary output signal due to a change in the impedance of the primary and secondary windings due to a temperature change or the like. This is advantageous because the disadvantage described above can be eliminated. Note that such a phase detection circuit is not limited to a digital circuit, and may be configured by an analog circuit. A non-magnetic (good conductor) such as copper may be used as the magnetic response member. In this case, the magnetic coupling between the primary winding and the secondary winding decreases and changes at that location due to eddy current loss. By doing so, detection can be performed in the same manner as described above.

Further, the liquid level detecting device according to the present invention comprises a float member which is displaced up and down in accordance with the rise and fall of the liquid level of the liquid; A magnetic response member and a detection unit disposed so as to be relatively displaced, wherein the detection unit is a plurality of coils excited by an in-phase AC signal, and sequentially along the direction of the relative displacement. Including those that are arranged,
The relative position of the magnetic response member and the coil changes according to the rise and fall of the float member, and the inductance of each coil changes according to the relative position. During the displacement from one end to the other end of the coil, the voltage between both ends of the coil gradually increases or decreases. Further, by taking out the voltage of each of the coils and adding and / or subtracting them, An analog arithmetic circuit that generates a plurality of AC output signals each showing an amplitude according to a predetermined periodic function characteristic according to the detection target position, wherein the periodic function characteristic that defines the amplitude of each of the plurality of AC output signals is A plurality of AC output signals generated by inputting a plurality of AC output signals generated by a periodic function having the same characteristic that differs by a predetermined phase, and a correlation between amplitude values of the AC output signals. An amplitude-to-phase conversion unit that detects a specific phase value in the predetermined periodic function that defines the amplitude value, and generates position detection data based on the detected phase value. It is characterized by being used as According to this, only the primary winding needs to be provided, and the secondary winding is not required.
Since the above-described detection can be performed even if the next winding is omitted, the device can be simply configured. That is, it is possible to provide a liquid level detection device having a small and simple structure.

As is apparent from the above, according to the present invention, it is possible to configure a non-contact type liquid level detecting device which does not require the magnetic responsive member to come into contact with the detecting portion.
Therefore, it is possible to provide a highly durable liquid level detection device that does not have to worry about sliding wear. Further, it is possible to provide a liquid level detection device having a small and simple structure and capable of performing precise measurement over a wide range. Further, it is possible to provide a liquid level detecting device having a simple structure that makes the manufacture extremely easy.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an overall schematic sectional view schematically showing one embodiment of a liquid level detecting device according to the present invention. FIG. 2 is a partially enlarged view in which the detection unit of the liquid level detection device shown in FIG. 1 is particularly enlarged and shown in detail. Note that FIG.
For convenience of illustration, the detection unit 6 is illustrated as if it is a straight line, but in actuality, the detection unit 6 has an arcuate shape as schematically shown in FIG. Are located in In the fuel tank 1, a liquid level detecting float 2 (hereinafter simply referred to as a float) formed of an object or substance (for example, a hollow body or urethane) having sufficient buoyancy on the liquid level is provided. The liquid is mounted so as to float above the liquid surface and move up and down in conjunction with the displacement of the liquid surface. The float 2 has an arm 3
And a displacer 4 is fixedly connected to the arm 3 (or via a gear or the like) at the tip of the arm 3 opposite to the float 2 so as to share the fulcrum Z with the arm 3. ing. A permanent magnet 5 is fixedly arranged at a predetermined position of the displacement element 4. Therefore, when the float 2 moves up and down with the displacement of the liquid level, the arm 3 and the displacement element 4
, The permanent magnet 5 is reciprocated in the direction of the arrow X by the displacement of the liquid level. On the other hand, a detection unit 6 is provided outside the tank 1 along the direction of the reciprocation of the magnet 5 (the direction of the arrow X). The detecting unit 6 includes the magnet 5
, A primary winding PW and secondary windings S1 to S4 that are magnetically coupled via the magnetic core 7 over a predetermined range along the reciprocating direction (the direction of the arrow X). , And is disposed close to the position facing the magnet 5 with the tank 1 body interposed therebetween. For example, the detection unit 6 is housed in an appropriate non-magnetic casing, and is fixedly disposed at a predetermined position on the outer periphery of the tank 1 also made of the non-magnetic casing. The magnetic material core 7 is made of a magnetic material such as silicon steel having a large relative permeability and a small coercive force, and may have an elongated columnar shape or an elongated shape formed by laminating silicon steel plates. An appropriate shape such as a rectangular parallelepiped shape may be used. The primary winding PW and the secondary windings S1 to S1
S4 is wound in a predetermined arrangement. Although the diameter of each winding in the detection unit 6 is large and the magnetic core 7 is drawn thick for the sake of illustration, actually, these can be considerably thinned. It is considerably thinner (thinner) compared to the like.

The four secondary windings S1 to S4 are arranged at different positions in the displacement direction. For example,
Assuming that the coil length of one secondary winding (S1 to S4) is P / 4, the total length of the four secondary windings S1 to S4 is P. The primary winding PW is provided so as to cover the entirety of the secondary windings S1 to S4. As long as the magnet 5 is not close, the primary windings PW and 2
The degree of magnetic coupling between the secondary windings S1 to S4 is large, and a large level of inductive output is obtained from the secondary windings S1 to S4. However, when the magnet 5 approaches any part of the long magnetic material core 7 according to the position of the float 2 at that time, the part strongly receives the magnetic flux emitted from the magnet 5, It becomes a magnetic saturation state. In other words, the performance, size, and the like of the magnet 5 are determined so that the magnet 5 is partially magnetically saturated at the position of the magnetic core 7 close to the magnet 5, and an appropriate induction The coil length, the number of turns, and the like of each of the windings PW, S1 to S4 are set so as to obtain a change in output.

At the magnetic core 7 in the magnetically saturated state, the electromagnetic induction performance between the primary and secondary windings is equivalent to the empty state in which the magnetic core 7 does not exist. The degree of magnetic coupling between the secondary windings decreases. Therefore, according to the proximity of the magnet 5, that is, according to the position of the float 2,
An inductive output signal will be obtained from each of the secondary windings S1 to S4. Basically, the secondary winding S1
Based on the output of S4, the position of the float 2, that is, the height of the liquid level can be detected. Secondary winding S
There may be various configurations for specifically obtaining the liquid level detection data based on the outputs of 1 to S4. Most simply, the output level of each of the secondary windings S1 to S4 is simply compared, and the position where one of the lowest level secondary windings (one of S1 to S4) is located is displayed. There is a method of detecting as a liquid level. However, in this case, the range of P is 4
There is a disadvantage that detection can be performed only at the divided resolution. As a modification of such an idea, the number of secondary windings may be only one, or may be four or more or less than four.
It turns out that. An empty state where there is no liquid in the tank 1 (that is, a state in which the liquid level is minimum) or a full state in which the tank 1 is sufficiently filled with liquid (that is, a state in which the liquid level is maximum). When only one of them is detected, such an embodiment is also possible. That is, in the present invention, the number of secondary windings is not limited to four, and may be one or an arbitrary plural number. Alternatively, it is also possible to provide only two secondary windings in a differential connection, and obtain an analog voltage corresponding to a continuous movement position of the float 2 like a differential transformer.

However, the embodiment shown in FIG. 2 is most suitable and advantageous for a position detection process according to the resolver principle described below. FIG. 3 is a diagram illustrating a connection state of the primary winding PW and the secondary windings S1 to S4 employed for performing the position detection process according to the resolver principle. The primary winding PW is excited by a one-phase AC signal (for convenience, denoted by sinωt). Secondary windings S1 and S3 arranged alternately are differentially connected to form a first output AC signal A.
Is generated. Secondary winding S arranged every other one of the other
2 and S4 are also differentially connected to produce a second output AC signal B. This means that the movement of the magnetically saturated portion of the magnetic core 7 in accordance with the displacement of the magnet 5 in the range P is generally represented by an angle of 0 ° ≦ θ ≦ 360 °, and the secondary winding S1 Can be represented by sin θ, the function of the induced output in the next secondary winding S2 can be represented by cos θ, and the next secondary winding S
3 can be represented by -sinθ, and the function of the induced output in the next secondary winding S4 is -c.
It can be represented by osθ. In other words,
It is designed so that such a relationship can be obtained. Considering that the magnetic coupling change due to the magnetic saturation occurring in the magnetic core 7 is in one direction, strictly speaking, the function of the induction output in one secondary winding (for example, S1) is 0.
Although it does not rotate in the entire range of degrees ≦ θ ≦ 360 degrees, this is possible by differentially connecting two secondary windings that are arranged every other.

Therefore, the first output AC signal A obtained from the differential connection of one of the secondary windings S1 and S3 generally has an amplitude function sin θ of a sine function in accordance with the displacement of the magnet 5 in the range P. That is, A = sin θ sin ωt, and the other secondary winding S2
The second output AC signal B obtained from the differential connection of S4 has an amplitude function cos θ of a cosine function, that is, co
sθsinωt. Thus, according to the arrangement and the winding configuration as shown in FIGS. 2 and 3, two output AC signals (in-phase AC and having a two-phase amplitude function) similar to those obtained in a conventionally known resolver. It can be understood that the sine output and the cosine output can be obtained in the liquid level detection device. Therefore,
Two-phase output AC signals (A = sinθ · sinωt and B = cosθ · si) obtained by the liquid level detection device of the present invention.
nωt) can be used or processed in the same manner as the output of a conventionally known resolver. For example, using a suitable digital or analog phase detection circuit 22, the sine function sin in the two-phase output AC signals A and B is used.
θ and the phase value θ of the cosine function cos θ can be measured by digital or analog. Thereby, the height of the continuous liquid level can be detected with high resolution.

In the configuration shown in FIG. 2, the relationship between the primary winding and the secondary winding may be reversed as shown in FIG. 4 so as to constitute a known phase shift type position detector. . That is, the four windings S1 to S4 are primary windings and the winding P
W is a secondary winding. In this case, one differentially connected pair of primary windings S1 and S3 is connected to, for example, a sine-phase AC signal s.
The pair of primary windings S2 and S4, which are excited by inωt, and are differentially connected to each other, for example, a cosine-phase AC signal cos
Excited by ωt. Then, the primary windings S1, S
From the above, the induction output on the secondary side due to 3 is, for example, sin θ ·
sinωt, and the primary winding S
2, the induction output on the secondary side by S4 is, for example, co
sθ · cosωt. Therefore, these combined outputs obtained on the secondary winding PW are signals containing an electrical phase shift θ corresponding to the liquid level (for example,
n (ωt + θ)). This output signal sin
The known phase measurement circuit 9 may detect the electrical phase shift θ at (ωt + θ) in a digital or analog manner. Also in this case, the continuous liquid level can be detected with high resolution.

In the liquid level detecting device according to the above-described embodiment, the permanent magnet 5 may be arranged directly on the float 2 as shown in FIG. However, in this case, it is necessary to install the partition 8 inside the tank 1 so that the magnet 5 is always close to the detection unit 6. Further, as shown in FIG. 6, the detection unit 6 may be housed inside the tank 1 together with the float 2 on which the permanent magnets 5 are arranged. However, also in this case, it is needless to say that the magnet 5 must always be brought close to the detection unit 6. Therefore, in the embodiment shown in FIG. 6, the float 2 on which the permanent magnets 5 are installed is configured to have the same shape as the shape of the detection unit 6 (a cross-sectional shape in a direction orthogonal to the figure), and the magnet 5 is always detected. It is made to approach the part 6. For example, when the detection unit 6 has a cylindrical shape, the float 2 is formed in a donut shape, and the detection unit 6 is passed through the hole at the center of the float. In this case, the magnet 2 does not separate from the detection unit 6 and is always in a close proximity. In this case, the magnet 5 is best installed on the surface of the float 2 opposite to the detection unit 6 in the center, but the output AC signal is output from the secondary windings S1 to S4 with the displacement of the magnet 5. You can install it anywhere you can.

FIG. 7 is a conceptual diagram conceptually showing a liquid level detecting apparatus according to another embodiment of the present invention. FIG. 7 shows another embodiment of the liquid level detecting device, in which an inner wall surface 61 has a non-magnetic property and an outer wall surface 62 is made of a material having a non-magnetic or magnetic property. The detection unit 6 is formed in a cylindrical body having an appropriate shape as described above, and an inner wall surface 61 and an outer wall surface 62 are integrally connected at an upper surface and a lower surface. This inside 61 and outside 6
The primary winding PW and the secondary windings S1 to S4 are wound in a predetermined sealed space surrounded by the second wall. The secondary windings S1 to S4 have a larger diameter than the primary winding PW, and are wound around the primary winding PW. In FIG. 7, as in FIG.
Four primary windings S1 to S4 and a primary winding PW are provided at predetermined positions so as to cover the entire secondary windings S1 to S4. The float 2 has a large relative permeability and a small coercive force. The thin plate or thin wire made of a magnetic material such as silicon steel is encapsulated with an object or substance having sufficient buoyancy to a liquid. It may have a columnar shape or an appropriate shape such as an elongated rectangular parallelepiped formed by laminating silicon steel plates. However, as described later, the float 2 must have a shape and a size that allow the float 2 to freely move up and down along the inner wall surface 61. That is, the diameter of the float 2 must be smaller than at least the diameter of the inner wall surface 61.

The float 2 is disposed close to the inner wall surface 61 of the cylindrical body, and moves linearly and reciprocally along the inner wall surface 61 in conjunction with a change in the liquid level in the tank 1. Can be displaced. Further, the primary winding PW and the secondary windings S1 to S4 are fixedly wound in a predetermined arrangement around the path along which the float 2 is displaced.
Thus, the float 2 including the magnetic material is displaced linearly relative to the detection unit 6 in conjunction with the change in the liquid level.

Even with such a configuration, the secondary windings S1 to S4 can be excited by exciting the primary winding PW with a one-phase AC signal in the same manner as in the other embodiments described above.
Output a position detection output signal, whereby the height of the liquid level can be detected. That is, by relatively changing the position of the magnetic material having a large relative magnetic permeability, the magnetic coupling between the primary winding PW and the secondary windings S1 to S4 is changed according to the liquid level. Then, an induced output AC signal whose amplitude is modulated in accordance with the liquid level is induced in each of the secondary windings S1 to S4. Therefore, the liquid level can be detected in this embodiment also through the phase detection circuit 22 as in the above-described embodiment. Of course, also in this embodiment, not only the above-described resolver-type position detection,
It goes without saying that phase shift type position detection can be performed. In the above-described embodiment, the detection unit 6 is configured in a liquid so that the detection unit 6 faces the magnetic body because of the arrangement of the magnetic body on the float 2. Are configured separately and moved in conjunction with each other, the detection unit 6 need not be configured in the liquid.

In each of the above-described embodiments, the primary winding PW is on the inside and the secondary windings S1 to S4 are on the outside to constitute the detecting unit. Conversely, the primary winding PW is on the outside. Even if the detection unit 6 is configured with the secondary windings S1 to S4 inside, there is no difference in that the above-described position detection can be performed.

FIG. 8 is a conceptual diagram conceptually showing another embodiment of the liquid level detecting device. As in the embodiment shown in FIG. 1, a liquid level detecting float 2 (hereinafter, referred to as a hollow body or urethane) formed of an object or substance having sufficient buoyancy on the liquid level (for example, a hollow body or urethane) is provided inside the fuel tank 1. , Simply referred to as a float) is mounted so as to float on the liquid surface of the liquid in the tank 1 and move up and down in conjunction with the displacement of the liquid surface. An arm 3 is connected to the float 2, and the tip of the arm 3 opposite to the float 2 shares a fulcrum Z with the arm 3 so as to be fixed to the arm 3 (or via a gear or the like). ) Displacer 4 is connected. A magnetic response member 11 is fixedly disposed on the displacement element 4. When the float 2 moves up and down with the displacement of the liquid level, the liquid level is displaced via the arm 3 and the displacement element 4. It reciprocates in the direction of the arrow Y in a somewhat arcuate manner. In this embodiment, when the liquid level rises, the magnetic response member 11 moves rightward (displacement).
On the contrary, when the liquid level drops, the magnetic response member 1
1 moves leftward (displaces). Then, the detecting unit 6 detects the displacement of the magnetic response member 11.

FIG. 9 shows a detecting section for obtaining an amplitude change in a full range of electrical angles from 0 to 360 degrees in two AC output signals each having an amplitude indicating sine and cosine function characteristics. 6 shows an example. FIG.
(A) shows an example of the physical arrangement relationship between the coil unit 10 and the magnetic response member 11 in the detection unit 6 of the liquid level detection device according to this embodiment by an external appearance schematic diagram, and FIG. A schematic sectional view in the axial direction, and FIG.
It is a figure which shows an example of an electric circuit of 0. As mentioned above,
The detection unit 6 in the liquid level detection device shown in FIG. 9 detects the liquid level at the linear position of the magnetic response member 11. For example, the coil unit 10 is relatively fixed, and the magnetic response member 11 It relatively linearly displaces according to the displacement of the liquid surface (that is, according to the displacement of the float 2). Coil section 10
Are six coils L having the same properties such as the number of turns and the coil length.
α, LA, LB, LC, LD, Lβ
1 are sequentially arranged along a displacement direction (arrow Y direction: see FIG. 8). The magnetic response member 11 is made of a magnetic material such as a bar-shaped iron, for example, and enters the coil space of the coil unit 10. As an example, when the magnetic response member 11 advances rightward in FIG. 8 (that is, when the liquid level rises), the tip 11a of the magnetic response member 11 first enters the coil Lα, and then the coil LA. , LB, LC, and LD in this order, and finally into the coil Lβ. A two-dot chain line 11 ′ indicates the magnetic response member 11 that has penetrated to the last coil Lβ.

The four middle coils LA, LB, LC, L
The range corresponding to D is the effective detection range. Assuming that the length of one coil is K, a length 4K that is four times the length is the effective detection range. The coils Lα and Lβ provided one by one before and after the effective detection range are auxiliary coils. Auxiliary coils Lα, L
β is provided so that the cosine function characteristic can be obtained faithfully, and can be omitted when the accuracy is not so much pursued.

As shown in FIG. 9C, each coil Lα,
LA, LB, LC, LD, and Lβ are excited by a predetermined one-phase AC signal (tentatively indicated by sinωt) generated from AC power supply 12 at a constant voltage or a constant current. If the voltage between both ends of each coil Lα, LA, LB, LC, LD, Lβ is indicated by Vα, VA, VB, VC, VD, Vβ, respectively,
These voltages Vα, VA, VB, VC, VD, V
Terminals 13 to 19 are provided for extracting β. As can be easily understood, each coil Lα, LA, L
B, LC, LD, and Lβ need not be separate coils that are physically separated, but only terminals 13 to 19 need to be provided at positions that divide the total length of a series of coils into six equal parts. That is, the coil portion between the terminals 13 and 14 is the coil Lα, the coil portion between the terminals 14 and 15 is the coil LA, the coil portion between the terminals 15 and 16 is the coil LB, and the terminals 16 and 1
The coil between the terminals 7 and 18 is the coil LC, the coil between the terminals 17 and 18 is the coil LD, and the coil between the terminals 18 and 19 is the coil Lβ. Output voltage Vα, V of each coil
A, VB, VC, VD, and Vβ
And 21 are input in a predetermined combination and added or subtracted in accordance with a predetermined arithmetic expression, so that each of the analog arithmetic circuits 20 and 21 has two amplitudes indicating sine and cosine function characteristics corresponding to the detection target position. An AC output signal (that is, two AC output signals having amplitude function characteristics shifted by 90 degrees from each other) is generated. For example, the output signal of the analog operation circuit 20 is represented by sinθsinωt, and the output signal of the analog operation circuit 21 is represented by cosθsi
Indicated by nωt. The analog operation circuits 20 and 21 are configured to include operational amplifiers OP1 and OP2 and resistance circuit groups RS1 and RS2. 8 and 9, for convenience of illustration, the coil unit 10 and the magnetic response member 11 of the detection unit 6 are illustrated as if they are straight straight lines. However, the magnetic response member 11 is actually Since the circular motion is performed, it is needless to say that the circular shape is formed in accordance with the circular motion.

With the above configuration, the self-inductance of the coil increases as the degree of the magnetic response member 11 approaching or entering each coil increases, and the end of the member is displaced from one end of one coil to the other end. The voltage between both ends of the coil gradually increases. A plurality of coils Lα, LA, LB,
Since the LC, LD, and Lβ are sequentially arranged along the direction of displacement of the detection target, the position of the magnetic response member with respect to these coils is relatively displaced in accordance with the displacement of the detection target. ), The voltages Vα, VA, VB, VC, VD, and Vβ between both ends of each coil gradually change. In FIG. 10A, in a section where the output voltage of a certain coil is inclined, the end of the magnetic response member 11 is displaced from one end of the coil to the other end. Typically, the magnetic response member 1
A gradual change curve of the voltage between both ends of one coil which is generated while one end is displaced from one end of the coil to the other end can be compared to a function value change in a range of 90 degrees in a sine or cosine function. it can. Therefore, by adding and / or subtracting the output voltages Vα, VA, VB, VC, VD, and Vβ of each coil in an appropriate combination, each has an amplitude indicating a sine and cosine function characteristic according to the position to be detected. Two AC output signals sin
θsinωt and cosθsinωt can be generated.

That is, in the analog operation circuit 20, the output voltages VA, VB, V of the coils LA, LB, LC, LD are output.
By calculating C and VD as in the following equation (1), FIG.
An AC output signal showing an amplitude curve of a sine function characteristic as shown in FIG. 0 (B) can be obtained, which can be equivalently represented by “sin θ sin ωt”. (VA−VB) + (VD−VC) Equation (1)

In the analog arithmetic circuit 21, the output voltages Vα, Vα of the coils Lα, LA, LB, LC, LD, Lβ
By calculating VA, VB, VC, VD, and Vβ as in the following equation (2), an AC output signal showing an amplitude curve of a cosine function characteristic as shown in FIG. 10B can be obtained. Although the amplitude curve of the cosine function characteristic shown in FIG. 10B is actually a minus cosine function characteristic, that is, “−cos θ sin ωt”, the cosine function characteristic is shifted by 90 degrees from the sine function characteristic. It is equivalent to characteristics. Therefore, this is called an AC output signal having a cosine function characteristic, and hereinafter, equivalently, "cos
θsinωt ”. (VA−Vα) + (VB−VC) + (Vβ−VD) Expression (2) Instead of the operation of the expression (2), the operation of the following expression (2 ′) may be performed. (VA−Vα) + (VB−VC) −VD Equation (2 ′)

The AC output signal “−cos θ sin ωt” having the negative cosine function characteristic obtained by equation (2) is electrically phase-inverted by 180 degrees, so that c is actually obtained.
A signal represented by osθsinωt may be generated and used as an AC output signal having a cosine function characteristic. However, in the subsequent phase detection circuit (amplitude / phase conversion circuit) 22, for example, the AC output signal having the cosine function characteristic is converted into “−cos θs
inωt ”, the AC output signal“ −cos θ ”having a negative cosine function characteristic is used.
sin ωt ”. Equation (2)
By performing the operation of the following equation (2 ") instead of the operation of
Actually, the AC output signal “cosθsi
nωt ”can be generated. (Vα−VA) + (VC−VB) + (VD−Vβ) Equation (2 ″)

The phase angle θ in the sine and cosine functions, which is the amplitude component of each AC output signal, corresponds to the position to be detected, and the phase angle θ in the range of 90 degrees corresponds to the length K of one coil. Yes, it is. Accordingly, the effective detection range having a length of 4K corresponds to the range of 0 to 360 degrees of the phase angle θ. Therefore, by detecting the phase angle θ, the detection target position in the range of the length of 4K can be absolutely detected.

Here, the compensation of the temperature characteristic will be described. The impedance of each coil changes according to the temperature.
The output voltages Vα, VA, VB, VC, VD, and Vβ also fluctuate. For example, each voltage increases or decreases in one direction as shown by a broken line with respect to a solid line curve in FIG. However, AC output signals sinθsinωt and c of the sine and cosine function characteristics obtained by adding and subtracting these are
In the case of os θ sin ωt, as shown by a broken line with respect to a solid line curve in FIG. If this is shown using the amplitude coefficient A, Asi
n.theta.sin.omega.t and Acos.theta.sin.omega.t, and the amplitude coefficient A changes according to the ambient temperature, and this change appears in the two AC output signals in the same manner. As is clear from this, the amplitude coefficient A indicating the temperature characteristic does not affect the phase angle θ in the respective sine and cosine functions. Therefore, in this embodiment, the temperature characteristics are automatically compensated, and accurate position detection can be expected.

The phase components θ of the amplitude functions sin θ and cos θ in the sine and cosine function AC output signals sin θ sin ωt and cos θ sin ωt are measured by a phase detection circuit (or amplitude phase conversion means) 22 so that the position to be detected is absolute. Can be detected. The phase detection circuit 22 may be configured using, for example, a technique disclosed in Japanese Patent Application Laid-Open No. 9-126809 filed by the present applicant. Alternatively, an R-D converter used for processing a known resolver output may be used as the phase detection circuit 22.

As shown in FIG. 10B, an AC output signal sin θ sinω having sine and cosine function characteristics
t and cos θ sinωt are represented by the angle θ
Assuming that the correspondence between the and the detection target position x has linearity, it does not show true sine and cosine function characteristics. However, in the phase detection circuit 22, the AC output signals sin θ sinωt and cos θ sinωt
Are subjected to phase detection processing as having sine and cosine function amplitude characteristics, respectively. As a result, the detected phase angle θ does not show linearity with respect to the detection target position x. However, in position detection,
The non-linearity between the detection output data (the detected phase angle θ) and the actual detection target position is not a very important problem. In other words, it suffices if the position can be detected with a predetermined reproducibility. If necessary, the output data of the phase detection circuit 22 is subjected to data conversion using an appropriate data conversion table so that accurate linearity is obtained between the detected output data and the actual detection target position. Can be easily performed. Therefore, the AC output signal sinθsi having the amplitude characteristics of the sine and cosine functions referred to in the present invention.
The values of nωt and cosθsinωt do not have to indicate true sine and cosine function characteristics, but may actually be a triangular wave shape as shown in FIG. What is necessary is just to show such a tendency. That is, any periodic function similar to a trigonometric function such as a sine may be used. Note that FIG.
In the example of (B), changing the viewpoint, the scale on the horizontal axis is assumed to be θ and the scale is formed of a required non-linear scale. If the scale on the horizontal axis is assumed to be x, the scale is apparent. Even if it looks like an upper triangular wave, it can be said that θ is a sine function or a cosine function.

The change range of the phase component θ of the amplitude functions sin θ and cos θ in the AC output signals sin θ sinωt and cos θ sinωt having the sine and cosine function characteristics is limited to the change in the full range from 0 degrees to 360 degrees as in the above embodiment. Instead, the change may be in a narrower limited angle range. In that case, the configuration of the coil can be simplified. The effective detection range may be narrow when the purpose is to detect a minute displacement, and in such a case, the detectable phase range may be an appropriate range of less than 360 degrees. In addition, there are various cases where the detectable phase range may be an appropriate range of less than 360 degrees depending on the purpose of detection, and the present invention can be appropriately applied to such a case.
Hereinafter, these modifications will be described.

FIG. 11 shows an embodiment capable of producing a phase change in the range from 0 degrees to 180 degrees. In this case, the coil unit 10 includes two coils LA and LB corresponding to the effective detection range and auxiliary coils Lα and Lβ provided one before and after the other. In the analog operation circuit 23, the voltages Vα, VA, V
B and Vβ are input, and an AC output signal sinθsinωt showing an amplitude curve of a sine function characteristic is generated by, for example, calculating as in the following equation (3), and cosine by calculating as in the following equation (4). An AC output signal cosθsinωt indicating an amplitude curve of a function characteristic is generated. VA-VB: Equation (3) (VA-Vα) + (VB-Vβ): Equation (4)

As can be easily understood by referring also to FIG. 10 described above, the calculation of the equation (3) allows 0 ° to 180 °.
An AC output signal sinθsinωt indicating an amplitude curve of a sine function characteristic in a range of degrees can be generated. In addition, according to the calculation of Expression (4), -90 degrees to 0 degrees
AC output signal cosθs showing the amplitude curve of the cosine function characteristic in the range of 90 degrees to 180 degrees to 270 degrees
inωt can be generated. As described above, the auxiliary coil Lβ can be omitted. In this case, by detecting the phase angle component θ of the amplitude function, the two coils L
The position to be detected in the range corresponding to the coil length 2K of A and LB can be absolutely detected. The arithmetic expression is not limited to the above, and can be set as appropriate. That is, the arithmetic expression can be appropriately changed depending on in which angle range a phase change having a width of 180 degrees is caused. For example, to generate an effective phase change corresponding to an angle range from 180 degrees to 360 degrees, “(Vα−
VA) + (Vβ−VB) ”, an AC output signal sinθsinωt having a sine function characteristic is generated, and“ V
An AC output signal cos θ sinωt having a cosine function characteristic can be generated by the arithmetic expression of “B-VA”.

FIG. 12 shows an embodiment capable of producing a phase change in the range from 0 degrees to 90 degrees. In this case, the coil unit 10 includes one coil LA corresponding to the effective detection range and one auxiliary coil L provided before and after the coil LA.
α, Lβ. Analog operation circuit 24
The AC output signal sinθs representing the amplitude curve of the sine function characteristic is input by inputting the voltages Vα, VA, and Vβ between the terminals of each coil and calculating the voltage as, for example, the following equation (5).
inωt is generated and calculated as in the following equation (6) to obtain an AC output signal c indicating an amplitude curve of a cosine function characteristic.
osθ sinωt is generated. VA-Vβ ... Equation (5) VA-Vα ... Equation (6)

As can be easily understood from the above with reference to FIG. 10 as well, the amplitude of the sine function characteristic in the range of 0 to 90 to 180 degrees is obtained by the calculation of the equation (5). An AC output signal sinθsinωt indicating a curve can be generated. In addition, by the calculation of Expression (6),
AC output signal cos θsin representing the amplitude curve of the cosine function characteristic in the range of −90 degrees to 0 degrees to 90 degrees
ωt can be generated. Therefore, a range of 0 to 90 degrees can be secured as the effective detection range. Also in this case, the arithmetic expression is not limited to the above expression, and can be set as appropriate.
That is, the arithmetic expression can be appropriately changed depending on the angle range in which the phase change having a width of 90 degrees is caused.

FIG. 13 is a side view and a sectional view showing another example of the configuration of the coil section 10 and the magnetic response member 11. In this case, the mutual arrangement interval of the coils Lα, LA to LD, Lβ is K as in the example of FIG. 9, but the length of each coil is shorter. That is, each adjacent coil Lα, L
A to LD and Lβ do not need to be close as shown in FIG. 9 and may be separated as appropriate. The tip 11a of the magnetic response member 11 has a pointed, tapered shape. For example, a tip portion having a length of about K is tapered. Thereby, the inductance change of the coil accompanying the movement of the tip 11a of the magnetic response member 11 can be made to have a smooth gradually increasing (or gradually decreasing) change characteristic. Of course, even when the coils Lα, LA to LD, Lβ are closely arranged as shown in FIG. 9, the tip 11 a of the magnetic response member 11 may be appropriately tapered.

In each of the above embodiments, the magnetic responsive member 11 is not limited to a magnetic material, but may be a non-magnetic good conductor such as copper or aluminum. In that case,
As the magnetic response member 11 approaches, the voltage between the coil terminals gradually decreases due to the eddy current loss. Further, a hybrid type combining a magnetic material and a conductor may be used.
In this case, for example, as shown in FIG.
Non-magnetic good conductor 1 having a tapered shape
It is preferable to arrange the magnetic body 11c so as to compensate for the decrease of 1b.

As another embodiment, the magnetic response member 11 may include a permanent magnet, and each coil of the coil unit 10 may include an iron core. FIG. 15 shows an example of the permanent magnet 1 functioning as the magnetic response member 11.
1M has, for example, a hollow ring shape, and the coil portion 10 enters into this ring space. An iron core 31 is inserted into the axial space of each of the coils Lα, LA to LD, Lβ of the coil unit 10.
The coil is excited so that is in a magnetically saturated state. When the permanent magnet 11M approaches any one of the coils, the iron core 31 corresponding to the vicinity thereof is partially supersaturated, and the voltage between terminals of the coil decreases. Permanent magnet 11M
The length of the permanent magnet 11M has at least a length corresponding to the coil length K so that the voltage between both ends of the coil gradually decreases while the coil moves from one end to the other end of one coil. Thus, when the permanent magnet 11M is used as the magnetic response member 11, the magnetic response member 11, that is, when the permanent magnet 11M is one, similarly to the case where the nonmagnetic good conductor 11b is used.
During the displacement from one end of the coil to the other, a gradual change in the voltage across the coil can be caused.
However, in the example of FIG. 15, when the permanent magnet 11 </ b> M passes a certain coil, the state returns to the saturated state again.
The output amplitude level change of the desired sine and cosine function characteristics may be obtained by appropriately performing the subsequent analog operation. Alternatively, the supersaturated state may be maintained by continuously arranging a plurality of permanent magnets 11M as the magnetic response member 11. Permanent magnet 11M
Is not limited to a ring shape, but may be a rod shape or other shapes. In that case, the magnetic response member 11 composed of the permanent magnet 11M passes in the vicinity thereof in parallel with the axial direction and has an arrangement configuration.

Further, in each of the above embodiments, two output AC signals s having amplitude characteristics of sine and cosine functions are provided.
An example of generating inθsinωt and cosθsinωt (in other words, an example of generating a resolver-type two-phase output) has been described. However, the present invention is not limited to this, and three or more output AC signals having three or more trigonometric amplitude characteristics indicating a predetermined phase shift are provided. (For example, sin θ · sin ωt, sin (θ−120
°) · sinωt and sin (θ-240 °) · sin
ωt) may be output. The number of coils LA to LD to be arranged may be four or more. In each of the above embodiments, the coil portion 10 is fixed. On the contrary, the magnet 5 or the magnetic responsive member 11 is fixed, and the coil portion 10 can be moved in accordance with the rising and lowering of the float 2. 5 or the magnetic responsive member 11.

[0045]

As described above, according to the present invention, the height of the liquid surface can be detected by the non-contact detection method. A surface detection device can be provided. In addition, it is possible to provide a liquid level detecting device having a small and simple structure and capable of detecting a liquid level continuously over a wide range. Further, it is possible to provide a liquid level detecting device having a simple structure that makes the manufacture extremely easy.

[Brief description of the drawings]

FIG. 1 is a schematic front view showing an overall schematic configuration according to an embodiment of a liquid level detecting device according to the present invention.

FIG. 2 is an enlarged partial cross-sectional view showing a part of the liquid level detection device shown in FIG. 1;

FIG. 3 is a diagram showing a connection example of primary and secondary windings of a detection unit in FIG. 1;

FIG. 4 is a diagram showing another example of connection of primary and secondary windings of the detection unit in FIG. 1;

FIG. 5 is a sectional view showing another embodiment of the liquid level detecting device according to the present invention.

FIG. 6 is a sectional view showing another embodiment of the liquid level detecting device according to the present invention.

FIG. 7 is a sectional view showing another embodiment of the liquid level detecting device according to the present invention.

FIG. 8 is a conceptual diagram showing another embodiment of the liquid level detecting device according to the present invention.

9A and 9B show an embodiment of the liquid level detecting device shown in FIG. 8, wherein FIG. 9A is a schematic view, FIG. 9B is a sectional view in the coil axis direction, and FIG. Electrical circuit diagram.

FIG. 10 is a diagram illustrating a detection operation of the liquid level detection device in FIG. 9;

FIG. 11 shows another embodiment of the liquid level detecting device of FIG.
The electric circuit diagram relevant to a coil part.

FIG. 12 is an electric circuit diagram related to a coil unit, showing still another embodiment of the liquid level detecting device of FIG. 9;

FIG. 13 is a schematic cross-sectional view showing still another modification of the coil arrangement and the modification of the tip shape of the magnetic response member in each embodiment relating to FIG. 9;

FIG. 14 is a plan view schematically showing an example in which a magnetic response member is hybridly configured by a magnetic body and a conductor in each embodiment related to FIG. 9;

FIG. 15 is a perspective view schematically showing an example in which a permanent magnet is included as a magnetic response member in each embodiment related to FIG. 9;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Float 3 Arm 4 Displacer 5 Permanent magnet 6 Detector 61 Detector inner wall 62 Detector outer wall 7 Magnetic core 8 Tank inner partition 9 Phase measurement circuit 10 Coil unit 11 Magnetic response member 11a Tip 11b Conductor 11M Permanent magnet 12 AC power supply 20, 21, 23, 24, 25, 26, 28 Analog operation circuit 22 Phase detection circuit 30, 31 Iron core PW, S1 to S4 Primary winding and secondary winding Lα, LA, LB, LC, LD, Lβ coil

Claims (6)

[Claims] 1. A float member which is displaced up and down in accordance with a rise and fall of a liquid level of a liquid, and which is close to one another so as to be displaced relatively to the other in conjunction with the up and down movement of the float member. A magnetic response member and a detection unit disposed, wherein the detection unit is disposed so as to surround the magnetic response member, and is magnetically coupled over a predetermined range along a direction of relative displacement of the magnetic response member. A primary winding and a secondary winding, wherein a change occurs in magnetic coupling at the position of the magnetic response member. As the relative position changes, the magnetic coupling between the primary winding and each of the secondary windings changes according to the position of the magnetic response member, and an output signal corresponding thereto is obtained from the secondary winding. Liquid level detection A liquid level detection device characterized by performing a discharge. 2. The method according to claim 1, wherein the primary winding is excited by a one-phase AC signal, and includes a plurality of the secondary windings arranged at different positions with respect to the relative displacement direction, wherein the magnetic response member is displaced. As a result, the magnetic coupling between the primary winding and each secondary winding is changed in accordance with the position of the magnetic response member, whereby the inductive output AC signal whose amplitude is modulated in accordance with the position is converted into each secondary winding. The liquid level detecting device according to claim 1, wherein the liquid level position is detected by being induced in each of the secondary windings with different amplitude function characteristics according to the displacement of the winding arrangement. 3. A first output AC signal having a sine function amplitude function and a cosine function amplitude as the inductive output AC signal amplitude-modulated in accordance with the linear position output from each of the secondary windings. A second output AC signal having a function, a first output AC signal and a second output AC signal being input, and a phase for detecting phase values of the sine function and the cosine function indicating the linear position. 3. The liquid level detection device according to claim 1, further comprising a detection circuit. 4. The magnetic response member includes a magnet, and the detection unit includes a magnetic core extending over a predetermined range along a direction of relative displacement of the magnet, and the detection unit includes the magnetic core via the magnetic core. The secondary and secondary windings are magnetically coupled, and magnetic saturation occurs at a predetermined location of the magnetic core that strongly receives the magnetic flux from the magnet. The relative position of the detection unit changes, and the predetermined location where magnetic saturation occurs in the magnetic material core is displaced accordingly, and the primary and secondary windings between the primary and secondary windings are displaced in accordance with the displacement of the magnetic saturation location. 4. The liquid level detecting device according to claim 1, wherein the position of the liquid level is detected by changing the magnetic coupling and obtaining an output signal corresponding thereto from the secondary winding. 5. The liquid level detecting device according to claim 1, wherein the magnetic response member includes at least one of a magnetic material and a conductor. 6. A float member which is displaced up and down in accordance with the rise and fall of the liquid level of the liquid, and is arranged so that one is displaced relatively to the other in conjunction with the up and down movement of the float member. A magnetic response member and a detection unit, wherein the detection unit includes a plurality of coils excited by an in-phase AC signal, the coils being sequentially arranged along the direction of the relative displacement, The relative position of the magnetic response member and the coil changes according to the rise and fall of the float member, and the inductance of each coil changes according to the relative position. The voltage between both ends of the coil gradually increases or decreases during the displacement from one end to the other end of the coil. Further, the voltages of the respective coils are taken out and added and / or subtracted. An analog arithmetic circuit for generating a plurality of AC output signals each representing an amplitude according to a predetermined periodic function characteristic according to the detection target position, wherein the periodic function characteristic defining the amplitude of each of the plurality of AC output signals Is a periodic function having the same characteristic that differs by a predetermined phase, and the predetermined periodic function that inputs the plurality of generated AC output signals and defines the amplitude value from the correlation between the amplitude values in the AC output signal. Detecting a particular phase value at
A liquid level detection device, comprising: an amplitude / phase conversion unit that generates position detection data based on a detected phase value, wherein the position detection data is used as liquid level position data.