JP2001194213A - Level sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a level sensor whose detecting accuracy is high and whose structure is simple and compact. SOLUTION: In the level sensor 1 by this invention, a magnetic body 2 equipped with a float is moved by following a change in the level of the surface of a liquid. A detection coil part 3 is arranged and installed along the movement stroke region of the magnetic body 2 equipped with the float, and a change in a magnetic field due to the movement of the magnetic body 2 equipped with the float is detected by the detection coil part 3. As a result, the level of the surface of the liquid can be detected according to the change, in the magnetic field, which is detected by the detection coil part 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level sensor for detecting a change in the liquid level of a liquid contained in a container or the like, and more particularly to a liquid level sensor having a high detection accuracy and a simple compact structure. .

[0002]

2. Description of the Related Art Conventionally, as a liquid level sensor of this type, for example, a float type liquid level measuring device disclosed in Japanese Patent Publication No. 6-29754 is known. As shown in FIG. 9, the float type liquid level measuring device vertically arranges a float guide pipe 102 having a closed bottom in a tank 101 storing liquid, and an outer peripheral portion of the float guide pipe 102 includes: A float 103 that can be moved up and down while being guided by a float guide pipe 102 is provided.

As shown in FIG. 10, a cored coil 105 is provided in a float guide pipe 102, and an air-core coil 108 which is concentric with the float guide pipe 102 is provided in a float 103.

[0004] An AC current is supplied from an AC power supply 106 to a cored coil 105 provided in the float guide pipe 102. Thus, an alternating magnetic field is generated in the longitudinal direction of the float guide pipe 102.

The alternating magnetic field induces an AC voltage in the air-core coil 108 in the float 103 arranged concentrically outside the float guide pipe 102, and an AC current flows in the DC power supply circuit 109. This AC current is converted into a DC current by an AC / DC conversion circuit or the like, and the energy storage circuit 1
11 and the control circuit 110.

In the amplifier 112, the control circuit 1
The DC signal supplied from the energy storage circuit 111 is amplified by the control signal from the controller 10, and the vibrator 113 is driven.

Next, vibration is propagated to the outer peripheral wall 102c of the float guide pipe 102 via the contact 107 by the vibration energy of the vibrator 113, and the vibration wave generates a sound wave by resonance inside the float guide pipe 102. It is measured by the measurement circuit 116 via the sound wave detector 114 and the amplifier 115.

For this reason, when the height position of the float 103 changes according to the liquid level of the liquid in the tank 101,
The measurement corresponding to this change can be performed by the measurement circuit 116, and the liquid level of the liquid in the tank 101 can be detected.

[0009]

However, in the case of this type of conventional liquid level sensor described above,
There were the following problems.

(1) Since the number of components in the detection portion provided in the float 103 is large and the overall structure is complicated, it is difficult to reduce the manufacturing cost.

(2) Since the float 103 is provided on the outer periphery of the float guide pipe 102 so as to be able to move up and down while being guided by the float guide pipe 102, the outside diameter of the float portion is increased, and the liquid in the tank is increased. The occupied space of the surface level sensor becomes large.

In view of the above circumstances, it is an object of the present invention to provide a simple and compact liquid level sensor with high detection accuracy.

[0013]

In order to achieve the above object, the invention of claim 1 is directed to a magnetic body with a float which is moved following a change in the liquid level, A detection coil portion disposed along the movement stroke area and detecting a change in a magnetic field accompanying the movement of the float-attached magnetic body, and detecting a liquid level according to the change in the magnetic field detected by the detection coil portion. It is characterized by doing.

According to the first aspect of the present invention, the magnetic body with the float is moved following the change in the liquid level. Also,
A detection coil section is provided along the movement range of the magnetic member with a float, and detects a change in a magnetic field accompanying the movement of the magnetic member with a float by the detection coil portion. Therefore, the liquid level can be detected according to the change in the magnetic field detected by the detection coil unit.

[0015] In the invention according to claim 2, the detection coil portion is arranged so that the magnetic body with the float is movable so as to follow the liquid level, and along the moving range of the magnetic body with the float. It is characterized in that the guide pipes to be provided are integrally provided.

According to the second aspect of the present invention, the detection coil portion is arranged so that the magnetic member with the float is movable so as to follow the liquid level, and is arranged along the movement range of the magnetic member with the float. Since the provided guide pipe is provided integrally, the outer diameter of the float portion is inevitably reduced. For this reason, for example, when the liquid level sensor is inserted into the tank and the liquid level of the liquid in the tank is detected, the space occupied by the liquid level sensor can be minimized.

According to a third aspect of the present invention, the detection coil section includes a primary coil connected to an AC power supply, and a secondary coil connected to a detection circuit, wherein the secondary coil has a moving stroke of the magnetic member with the float. It is characterized in that a measure is taken to reduce the winding density from sparse to dense from the low level corresponding part side of the liquid surface to the high level corresponding part side along the area.

According to the third aspect of the present invention, there is provided a primary coil connected to an AC power supply, and a secondary coil connected to a detection circuit. Along the way, a measure is taken to gradually change the winding density from sparse to dense from the low level corresponding part side of the gasoline liquid level to the high level corresponding part side.

In this configuration, when a current flows through the primary coil from the AC power supply, an AC current according to the generated magnetic field flows through the secondary coil due to the induced electromotive force generated in the primary coil.

Further, when the liquid level is initially at a height position near the low-level corresponding part side, and then changed to a height position near the high-level corresponding part side, the magnetic material with the float is moved to the liquid level. It moves following the change of.

For this reason, the AC voltage generated in the secondary coil changes when the magnitude of the magnetic field intensity changes at the height position of the magnetic body with the float. The detection circuit that receives the output signal of the secondary coil indicating this change, for example, rectifies and converts it to a DC signal, amplifies and outputs it to the control system of the liquid feeding system, and drives the voltmeter of the control system. Can be.

When the liquid level is detected by such a series of operations, the secondary coil has a high level corresponding to the low level corresponding to the low level of the liquid surface along the moving range of the magnetic body with the float. Since a measure is taken to gradually change the winding density from sparse to dense toward the site, it is possible to set the linearity of the detection signal to linear. For this reason, the setting which can detect a liquid level accurately can be taken easily.

According to a fourth aspect of the present invention, the detection coil section includes a primary coil connected to an AC power supply and a plurality of secondary coils connected to a detection circuit.
From among a plurality of secondary coils, two coils whose generated voltage increases according to the position of the magnetic body with the float are selected, and the difference between the actually measured voltage values of the two coils is compared with the difference between the set voltage values. The operation is performed.

According to the fourth aspect of the present invention, the detection coil section includes a primary coil connected to an AC power supply and a plurality of secondary coils connected to the detection circuit. From the secondary coils, two coils whose generated voltage is increased according to the position of the magnetic body with the float are selected, and an operation of comparing the difference between the actually measured voltage values of these two coils with the difference between the set voltage values is performed. .

In this configuration, when a current flows through the primary coil by the AC power supply, an AC current corresponding to the generated magnetic field flows through each of the plurality of secondary coils due to the induced electromotive force generated in the primary coil.

Further, when the liquid level is initially at a height near the low-level corresponding part and then changed to a height near the high-level corresponding part, the magnetic material with the float is moved to the liquid level. It moves following the change of.

For this reason, the AC voltage generated in each of the plurality of secondary coils changes as the magnitude of the magnetic field intensity changes at the height position of the magnetic member with the float. The output signal of each of the plurality of secondary coils indicating this change is input to the detection circuit.

The detection circuit selects two coils having a high voltage value from the received output signals of the plurality of secondary coils, and determines the difference between the actually measured voltage values of the two coils as the set voltage value. An operation for comparing with the difference is performed, and a DC signal obtained as a result of the operation is output to, for example, a control system of a liquid feeding system, and a voltmeter of the control system can be driven.

When the liquid level is detected by such a series of operations, the detection circuit detects two of the plurality of secondary coils whose voltage is increased in accordance with the position of the magnetic member with the float. Since the function configuration is such that a coil is selected and the difference between the actually measured voltage values of the two coils is compared with the difference between the set voltage values, the linearity of the detection signal can be set linearly. For this reason, the setting which can detect a liquid level accurately can be taken easily.

According to a fifth aspect of the present invention, the detection coil section includes an coil that forms an oscillation circuit and is connected to the detection circuit, and the coil is provided along a moving stroke area of the magnetic member with the float. It is characterized in that a measure for reducing the winding density from sparse to dense from the side of the liquid surface corresponding to the low level to the side corresponding to the high level is provided.

According to the fifth aspect of the present invention, the detection coil section includes an coil that forms an oscillation circuit and is connected to the detection circuit, and the coil includes a moving stroke area of the magnetic material with the float. A measure is taken to increase the winding density from sparse to dense from the low level corresponding part side of the liquid surface to the high level corresponding part side along.

In this configuration, the inductance of the coil forming the oscillation circuit changes according to the position of the magnetic body with the float, and the oscillation frequency of the coil changes.

In the detection circuit receiving the change in the frequency, the change in the frequency is detected as a change in voltage through, for example, a frequency / voltage converter, and the obtained detection signal is output to, for example, a control system of a liquid feeding system. , The voltmeter of the control system can be driven.

When the liquid level is detected by such a series of operations, as described above, the coil is provided along the movement range of the magnetic body 2 with a float from the portion corresponding to the low level of the liquid surface. Since a measure is taken to gradually change the winding density from sparse to dense toward the high level corresponding site side, the linearity of the detection signal can be set linearly. For this reason, the setting which can detect a liquid level accurately can be taken easily.

[0035]

FIG. 1 is an exploded view showing an example of the configuration of a liquid level sensor according to the present invention (the configuration of the first and second aspects of the present invention). 1 is a perspective view, FIG. 2 is a state explanatory view showing a use state of the liquid level sensor of FIG. 1, and FIG. 3 is a configuration diagram showing a first embodiment of the liquid level sensor of FIG. 4, FIG. 4 is a characteristic diagram thereof, FIG. 5 is a configuration diagram showing a second embodiment (a configuration of the invention according to claim 4) of the liquid level sensor of FIG. 1, FIG. 6 is a characteristic diagram thereof, and FIG. FIG. 8 is a configuration diagram showing a third embodiment (a configuration of the invention according to claim 5) of the liquid level sensor, and FIG. 8 is a characteristic diagram thereof.

As shown in FIG. 1, a liquid level sensor 1 according to the present invention comprises a magnetic body 2 with a float, a detection coil 3
, A detection circuit 4 and a connector 5.

The magnetic member 2 with a float has a structure in which a core member 7 as a magnetic member is assembled to a float member 6, and is moved following a change in the level of the liquid surface.

The detection coil unit 3 is provided so that the magnetic member 2 with a float can be moved so as to follow the liquid level, and a detection coil, which will be described later, is provided along the movement range of the magnetic member 2 with a float. The guide pipe 8 is provided integrally (the configuration of claim 2).

In this case, the outer diameter of the float portion is inevitably reduced. For this reason, for example, when the liquid level sensor 1 is inserted and arranged in the tank and the liquid level of the liquid in the tank is detected, the space occupied by the liquid level sensor 1 can be minimized. Note that the detection coil unit 3 is
As long as it is disposed along the movement range of the magnetic body 2 with a float and can detect a change in the magnetic field accompanying the movement of the magnetic body 2 with a float, the configuration can be made without using the guide pipe 8. It is also possible to do this (the configuration of claim 1).

The detection circuit 4 receives a signal indicating a change in the magnetic field detected by the detection coil unit 3, detects the liquid level in accordance with the change in the magnetic field detected by the detection coil unit 3, and outputs the detection data. The signal is output to a control system (not shown) of the liquid supply system via the connector 5.

The liquid level sensor 1 according to the present invention having these components is disposed in a container 9 as shown in FIG. 2, for example, and detects the liquid level S of the liquid 10 which is increased or decreased in the container 9. Used to

In the case of this arrangement example, the float-attached magnetic body 2 moves following the change in the liquid level S, and the change in the magnetic field accompanying this movement is detected by the detection coil section 3, which is detected. A signal indicating a change in the magnetic field is input to the detection circuit 4.
As a result, the detection circuit 4 detects the liquid level according to the change in the magnetic field detected by the detection coil unit 3, and outputs the detection data to a control system (not shown) of the liquid supply system via the connector 5, for example. be able to.

The liquid level sensor shown in FIG. 1 can employ the first to third embodiments described below.

<First Embodiment> A first embodiment (Claim 3)
In the configuration of the present invention), the detection coil unit 3 and the detection circuit 4 are configured as shown in FIGS.

That is, in the first embodiment, the detection coil unit 3 has the primary coil 11 and the secondary coil 12 arranged inside the guide pipe 8 so as to face each other. Oscillation circuit 13 connected to primary coil 11
And a receiving circuit 14 connected to the secondary coil 12.

The winding density of the secondary coil 12 gradually decreases from the low level corresponding portion SL to the high level corresponding portion SH on the gasoline liquid level along the movement range of the float-attached magnetic body 2. The procedure to shift from to dense is taken.

In this configuration, when a current flows through the primary coil 11 at the output of the oscillation circuit 13, an alternating current according to the generated magnetic field flows through the secondary coil 12 due to the induced electromotive force generated in the primary coil 11.

Also, inside the guide pipe 8, the liquid level S of the gasoline is initially at a height near the SL side, for example, as shown in FIG.
As shown in (b), when gradually changing to the height position near the SH side, the magnetic body with float 2 moves following the change of the liquid level S.

For this reason, the AC voltage generated in the secondary coil 12 changes when the magnitude of the magnetic field intensity changes at the height position of the magnetic body 2 with the float. The output signal of the secondary coil 12 indicating this change is input to the receiving circuit 14.

In the receiving circuit 14, the received secondary coil 12
After rectifying and converting the output signal of FIG.
For example, the output is supplied to a control system (not shown) of the liquid supply system via the connector 5 to drive a voltmeter of the control system.

As described above, according to the first embodiment, when detecting the liquid level, as described above, the secondary coil 12 is provided with the gasoline liquid level along the moving stroke area of the magnetic member 2 with the float. Since the winding density is gradually changed from sparse to dense from the low-level corresponding portion SL to the high-level corresponding portion SH, the linearity of the detection signal can be set linearly. . For this reason, the setting which can detect the liquid level S with high accuracy can be easily adopted.

According to the experimental results of the present inventors, when the magnitude of the AC voltage applied to the primary coil is fixed and the secondary coil is wound while the winding pitch is changed from sparse to dense, FIG. As shown in (1), the voltage value output from the secondary coil has a linear characteristic with respect to the liquid level. In this case, almost no electric circuit is required, and the meter can be swung only with mechanical parts.

<Second Embodiment> A second embodiment (claim 4)
In the configuration of the present invention), the detection coil section 3 and the detection circuit 4 are configured as shown in FIGS.

That is, in the second embodiment, the detection coil unit 3 includes a primary coil 15 and a plurality of secondary coils 16a to 16e arranged inside the guide pipe 8 so as to face each other. The detection circuit 4 includes an oscillation circuit 17 connected to the primary coil 15 and a plurality of secondary coils 16a to 16
e and a receiving circuit 18 connected to the e.

Then, the receiving circuit 18 selects two coils of which the generated voltage becomes higher according to the position of the float-attached magnetic body 2 from the plurality of secondary coils 16a to 16e,
A functional configuration is provided for performing a calculation for comparing the difference between the actually measured voltage values of the two coils with the difference between the set voltage values.

In this configuration, when a current flows through the primary coil 15 at the output of the oscillation circuit 17, each of the plurality of secondary coils 16a to 16e responds to the magnetic field generated by the induced electromotive force generated in the primary coil 15. AC current flows.

Further, inside the guide pipe 8, the liquid level S of the gasoline initially becomes, for example, as shown in FIG.
When it is at a height position near the L side and thereafter is changed to a height position near the SH side as shown in FIG. 4B, the magnetic body with float 2 moves following the change in the liquid level S thereof. I do.

For this reason, a plurality of secondary coils 16a-1
The AC voltage generated in each of the magnetic fields 6e changes as the magnitude of the magnetic field intensity changes at the height position of the magnetic body 2 with a float. A plurality of secondary coils 16a-1 showing this change
Each output signal of 6e is input to the receiving circuit 18.

The receiving circuit 18 selects two coils having a high voltage value from the received output signals of the plurality of secondary coils 16a to 16e, and calculates the difference between the actually measured voltage values of the two coils. An operation for comparing with the difference between the set voltage values is performed, and a DC signal obtained as a result of the operation is output to a control system (not shown) of the liquid supply system via the connector 5 in FIG. The voltmeter can be driven.

When the liquid level is detected by such a series of operations, as described above, the receiving circuit 18 operates according to the position of the magnetic member 2 with a float among the plurality of secondary coils 16a to 16e. Function that selects the two coils that generate a higher voltage and compares the difference between the measured voltage values of these two coils with the difference between the set voltage values, so that the linearity of the detection signal is set linearly. It is possible to For this reason, the setting which can detect the liquid level S with high accuracy can be easily adopted. According to the experimental results of the present inventors, a substantially linear characteristic as shown in FIG. 6 is obtained.

<Third Embodiment> A third embodiment (Claim 5)
In the configuration of the present invention), the detection coil section 3 and the detection circuit 4 are configured as shown in FIGS. 7 (a) and 7 (b).

That is, in the third embodiment, the detection coil section 3 forms an oscillation circuit and includes a coil 19 connected to the detection circuit 4. The coil 19 includes the magnetic member 2 with the float. A measure is taken to reduce the winding density from sparse to dense from the low level corresponding part SL side to the high level corresponding part SH side of the liquid surface along the movement stroke area.

In this configuration, the inductance of the coil 19 changes according to the position of the magnetic member 2 with the float, and the oscillation frequency changes as f = 1 / 2πLC. In the detection circuit 4 receiving the change in the frequency, the change in the frequency is detected as a change in voltage through, for example, a frequency / voltage converter, and the obtained detection signal is transmitted through the connector 5 in FIG. It can output to the control system of the transmission system and drive the voltmeter of the control system.

As described above, according to the third embodiment, when detecting the liquid level, as described above, the coil 19
Along the movement range of the magnetic body 2 with the float, the high level corresponding portion S from the low level corresponding portion SL side of the gasoline liquid surface
Since a measure is taken to gradually change the winding density from sparse to dense toward the H side, the linearity of the detection signal can be set linearly. For this reason, the setting which can detect the liquid level S with high accuracy can be easily adopted. According to the experimental results of the present inventors, the characteristics shown in FIG. 8 are obtained.

[0065]

As described above, according to the first aspect of the present invention, the magnetic body with the float is moved following the change in the liquid level, and the change in the magnetic field accompanying the movement of the magnetic body with the float is detected. Since the detection is performed by the coil unit, the liquid level can be accurately detected according to the change in the magnetic field detected by the detection coil unit.

According to the second aspect of the present invention, the detection coil portion is arranged so that the magnetic member with the float can be inserted so as to be movable following the liquid level, and is arranged along the movement range of the magnetic member with the float. Since the guide pipe is provided integrally, the outer diameter of the float portion is inevitably reduced, for example, a liquid level sensor is inserted and arranged in the tank,
When detecting the liquid level of the liquid in the tank, the space occupied by the liquid level sensor can be minimized.

According to the third aspect of the present invention, the secondary coil has a winding density along the movement range of the float-attached magnetic body from the low level corresponding portion of the liquid surface to the high level corresponding portion. Since the process of gradually shifting from sparse to dense is performed, the linearity of the detection signal can be set linearly. For this reason, the setting which can detect a liquid level accurately can be taken easily.

According to the fourth aspect of the present invention, two coils whose generated voltage increases according to the position of the magnetic member with the float are selected from the plurality of secondary coils, and the measured voltage values of these two coils are selected. Of the detection signal is compared with the difference of the set voltage value, so that the linearity of the detection signal can be set linearly. For this reason, the setting which can detect a liquid level accurately can be taken easily.

According to the fifth aspect of the present invention, the winding density of the coil gradually decreases from the low level corresponding portion side to the high level corresponding portion side of the liquid surface along the movement range of the float-attached magnetic body. Since the process of shifting from to 密 is performed, the linearity of the detection signal can be set linearly.
For this reason, the setting which can detect a liquid level accurately can be taken easily.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing the configuration of an embodiment of a liquid level sensor according to the present invention.

FIG. 2 is a state explanatory view showing a use state of the liquid level sensor of FIG. 1;

FIG. 3 is a configuration diagram showing a first embodiment of the liquid level sensor of FIG. 1;

FIG. 4 is a characteristic diagram of the first embodiment of the liquid level sensor shown in FIG. 3;

FIG. 5 is a configuration diagram showing a second embodiment of the liquid level sensor of FIG. 1;

FIG. 6 is a characteristic diagram of a second embodiment of the liquid level sensor shown in FIG.

FIG. 7 is a configuration diagram showing a third embodiment of the liquid level sensor of FIG. 1;

8 is a characteristic diagram of a third embodiment of the liquid level sensor shown in FIG.

FIG. 9 is a state explanatory view showing a use state of an example of a conventional liquid level sensor.

FIG. 10 is a configuration explanatory view showing an example of a conventional liquid level sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid-level sensor 2 Magnetic body with a float 3 Detection coil part 4 Detection circuit 5 Connector 5 6 Float material 7 Core material 8 Guide pipe 9 Container 10 Liquid 11 Primary coil 12 Secondary coil 13 Oscillation circuit 14 Receiving circuit 15 Primary coil 16a ~ 16e Secondary coil 17 Oscillation circuit 18 Receiving circuit 19 Coil

Claims (5)

[Claims] 1. A magnetic body with a float that moves following a change in the level of a liquid surface, and is disposed along a movement range of the magnetic body with a float,
A detection coil unit for detecting a change in the magnetic field accompanying the movement of the float-attached magnetic body, and a liquid level detected in accordance with the change in the magnetic field detected by the detection coil unit. Sensor. 2. The liquid level sensor according to claim 1, wherein the detection coil section is arranged so that the float-attached magnetic body is movably inserted to follow the liquid level, and the float-attached magnetic body is provided. A liquid level sensor, wherein a guide pipe disposed along a moving stroke area of the above is integrally provided. 3. The liquid level sensor according to claim 1, wherein the detection coil unit includes a primary coil connected to an AC power supply, and a secondary coil connected to a detection circuit. The secondary coil was subjected to a treatment to reduce the winding density from low to high from the low level corresponding part side to the high level corresponding part side of the liquid surface along the movement range of the float-attached magnetic body. Liquid level sensor characterized by the above-mentioned. 4. The liquid level sensor according to claim 1, wherein the detection coil unit includes a primary coil connected to an AC power supply and a plurality of secondary coils connected to a detection circuit. In the detection circuit, from among a plurality of secondary coils, two coils whose generated voltage is increased according to the position of the magnetic member with a float are selected, and a difference between each measured voltage value of the two coils is selected. The liquid level sensor performs an operation of comparing the set value with a difference between the set voltage values. 5. The liquid level sensor according to claim 1, wherein the detection coil unit includes an coil that forms an oscillation circuit and is connected to the detection circuit. Is a liquid characterized in that a winding density is reduced from sparse to dense from a low level corresponding portion side to a high level corresponding portion side of the liquid surface along a movement stroke area of the float-attached magnetic body. Surface level sensor.