JPH035865Y2 - - Google Patents

Description

[Detailed explanation of the invention] Purpose of the invention (industrial application field) This invention is for storing gasoline, oil, petroleum, water, and other various liquids in tanks and other containers installed in automobiles, industrial machinery, etc. Pertaining to liquid level meters for detecting and displaying levels,
Specifically, the invention relates to a core used in a coil in a liquid level detection section.

(Prior art) Conventional liquid level meters include a float arm type that operates a potentiometer using a float arm, a linear potentiometer type, an induction type that uses changes in the inductance of a coil, and many other types. It has been known. Among these, the induction type is particularly superior in that it is not affected by friction and has high measurement accuracy.

Some of the inventors of the present invention first movably provided a conductive ring with a float around the outer circumference of the coil, and converted changes in the inductance of the coil due to the movement of the conductive ring into voltage changes to drive an indicator. He has devised a type of inductive liquid level meter. In this liquid level meter, it is desirable to provide a core inside the coil in order to increase the change in inductance of the coil and increase the detection sensitivity of the liquid level.

Further, it is effective to form the core from a magnetic material having electrical insulation properties in order to release the winding component of the core itself and cause the inductance change of the coil to be caused only by the movement of the conductor ring. A typical core formed in this manner is a ferrite core.

(Problem to be solved by the invention) However, if the core is made of a magnetic material that has electrical insulation properties, stray capacitance that occurs in the coil due to its electrical insulation properties becomes a problem, and this stray capacitance that distorts the coil voltage becomes a problem. In order to cancel out the capacitance, it is necessary to provide a separate means.Since powder is press-molded, as typified by ferrite cores, a mold corresponding to the length of the core is required.
Long cores have problems with formability and strength, so
There were problems such as bending and breaking due to impact.

In order to solve these problems, it is extremely effective to laminate a plurality of conductive magnetic materials to form a core. However, since this core has a rectangular cross section, there is a problem in that if the coil is wound directly around the core, it will be difficult to wind because of the angular edges.

One way to solve this problem of difficulty in winding is to wrap a cylindrical bobbin around the core and wind the wire around it, but that would waste the space between the winding wire and the core. The problem remains.

Structure of the invention (Means for solving the problems) In order to solve the above problems, the liquid level meter of this invention uses a plurality of linear conductive magnetic materials that are electrically insulated in the cross-sectional direction of the coil. However, a method was adopted in which a core was formed all together and the core was provided inside the winding of the coil.

(Function) Since a plurality of linear magnetic materials are collectively formed to form a core, the cross-sectional outer peripheral shape of the core approaches a circular shape. Therefore, since the winding wire can be provided in a substantially spiral shape around the outer periphery of the core, the winding wire is not only easily wound without irregularities, but also is not subjected to excessive stress due to bending. In addition, since there is almost no wasted space between the winding wire and the core, the coil can be made thinner, making it easier to insert into a container of liquid to be measured, which is convenient for increasing inductance, and There is no need to increase the number.

Further, since the plurality of linear conductive magnetic materials are electrically insulated in the cross-sectional direction of the coil, only an extremely small overcurrent flows in each magnetic material in the cross-sectional direction of the core. Therefore, overcurrent loss in the core is negligibly small. Furthermore, in the equivalent circuit of the coil, the winding component of the core itself is almost completely released, so that changes in the inductance of the coil are hardly affected by the winding component.

Further, since the magnetic material has conductivity, the stray capacitance generated in the winding of the coil becomes extremely small. Therefore, distortion of the coil voltage due to this stray capacitance hardly occurs, and there is no need to separately provide means for canceling the stray capacitance.

Furthermore, the core can be easily manufactured by simply gathering the magnetic materials without using a mold.
Even when manufacturing cores of various lengths, there is no need to prepare molds corresponding to the lengths. Further, a long core can be easily manufactured, and there is no problem in its strength.

(Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings for a liquid level meter that is attached to a fuel tank of an automobile and displays the remaining amount of fuel such as gasoline or diesel oil.

First, the outline of the entire configuration will be explained according to FIG. 4. In this embodiment, a detection unit is constructed in which a float having a built-in conductor ring is movably provided around the outer periphery of a coil having a rod-shaped core. A is connected to the same coil, and its inductance change is expressed as voltage change,
Conversion circuit B that converts into current changes, etc., and conversion circuit B
It consists of an output correction circuit C for matching the output voltage of the indicator to the characteristics of the indicator, and an indicator D for the liquid level. Therefore, each of these parts A to D will be explained in detail in order.

[Detection part A]

The detection part A will be explained with reference to FIGS. 1 to 6. Reference numeral 1 denotes a fuel tank of an automobile that stores fuel 2 such as gasoline or diesel oil, and only the top plate 3 and bottom plate 4 are shown. Reference numeral 5 denotes a mounting hole for the detection section A provided in the upper plate 3.

Reference numeral 6 denotes a housing of the detection part A that is attached to the upper plate 3 of the tank 1 with screws 7, and a through hole 8 is provided in the center thereof. Reference numeral 9 denotes a storage recess provided in the upper part of the housing 6, and a cover 10 is attached to the upper surface thereof. 11 is a rubber gasket interposed between the housing 6 and the tank 1.

12 is a rod-shaped coil that is attached to the through hole 8 at the upper end and extends vertically downward to just above the bottom plate 4, and has a core, a winding, and a sleeve as described below.

Reference numeral 13 denotes a core that is attached to the through hole 8 by a core holder 13a made of a non-magnetic material and extends directly above the bottom plate 4. As shown in FIGS. The magnetic materials 13b (more than 200 pieces) are electrically insulated and grouped together in the cross-sectional direction of the coil 12, so that the cross-sectional outer circumferential shape approaches a circle with an outer diameter of 10 mm, and the length is approximately
It is formed to 160mm.

The magnetic material 13b used in this example has a wire diameter of approximately 0.5
The magnetic members 13b are made of mild steel having a diameter of 1 mm, and electrical insulation is provided between the magnetic members 13b by applying an electrically insulating varnish to the surface thereof.

Reference numeral 13c is a thin cylindrical bobbin made of synthetic resin that is placed around the core 13. Since the cross-sectional outer peripheral shape of the core 13 is close to a circle, there is no wasted space between the bobbin 13c and the core 13. It has become almost non-existent.

14 is a winding wire of the coil 12 wound around the outer periphery of the bobbin 13c, and is wound in the following manner. In other words, as shown in FIG.
14a is formed, and the distance from the bottom of core 13 is 10~
A flat wound portion 14b wound uniformly and in one direction is formed in a range of 140 mm, and a close wound portion 1 with many turns is formed in a range of 10 to 20 mm from the upper end of the core 13.
4c is formed, approximately 10mm at the top end of the core 13.
An unwound portion 14d is formed in the portion.

Note that the winding wire 14 is formed on a cylindrical bobbin 13c.
Since it is wound in a spiral shape, it is not only easy to wind without any angularity, but also avoids excessive stress due to bending.

15 is loosely fitted around the outer periphery of the winding 14, and is inserted into the through hole 8.
This sleeve is made of synthetic resin (non-magnetic material) and is fitted to protect the winding 14 and guide the vertical movement of the float, which will be described below. A synthetic resin (non-magnetic) cap 16 is fitted onto the lower end of the sleeve 15 and prevents the fuel 2 from entering the sleeve 15.

A float 17 is loosely fitted around the outer circumference of the coil 12 so as to be able to move up and down, and is formed into a donut shape from rubber or synthetic resin foam (non-magnetic material), and its specific gravity is smaller than the specific gravity of the fuel 2. . Therefore, the float 17 floats on the fuel 2 and is moved up and down as the liquid level of the fuel 2 changes. Reference numeral 18 denotes a conductive ring attached to the inner circumference of the float 17, and is made of a polymeric material having low specific gravity (close to the specific gravity of fuel 2) and conductivity, such as synthetic resin filled with carbon. . The lower end of the conductor ring 18 is locked to the cap 16 to prevent it from falling.

Reference numeral 19 denotes a board mounted in the storage recess 9 of the housing 6, into which a conversion circuit B and an output correction circuit C, which will be described later, are incorporated.

An equivalent circuit of the coil 12 is shown in FIG. Since the magnetic materials 13b assembled together are electrically insulated, most of the winding component Sc of the core 13 itself is released.

Furthermore, since the conductor ring 18 has conductivity, its winding component Sr is short-circuited. Sm is a winding component of the winding 14, and Cm is a stray capacitance of the winding 14, but since the magnetic material 13b has conductivity, the stray capacitance Cm is extremely small. Cx is the capacitance between the conductor ring 18 and the coil 12, and is constant regardless of the movement of the conductor ring 18.

Next, a method for manufacturing the core 13 and effects on refinement will be explained.

For the magnetic body 13b of the core 13, a commercially available bare mild steel wire with a wire diameter of about 0.5 mm is used. First, varnish is applied to the surface of the magnetic material 13b while continuously feeding it into the varnish in a predetermined container. Next, this mild steel wire is cut into a plurality of magnetic materials 13b at intervals of approximately 160 mm, and these are assembled. Furthermore, it is preferable in terms of handling that these magnetic materials 13b be impregnated with varnish and bonded to each other.

Therefore, in this embodiment, the core 13 can be easily manufactured without using a mold, which is essential for manufacturing ferrite cores and the like. In particular, when manufacturing cores 13 of various lengths, it is not necessary to prepare molds according to the lengths, so production costs can be significantly reduced. Moreover, even if the core 13 is long, it can be easily manufactured.
There is no problem with its strength.

Further, the winding wire 14 is formed on a cylindrical bobbin 13c.
Since it is wound in a spiral shape, it is not only easy to wind without angularity, but also because it is not bent, excessive stress is not applied. In addition, as described above, the bobbin 13c
Since there is almost no wasted space between the winding 14 and the core 13, and the bobbin 13c itself is thin, there is almost no wasted space between the winding 14 and the core 13. Therefore, the entire coil 12 can be made thinner, and the tank 1 of the fuel 2 to be measured can be made thinner.
This is convenient for increasing inductance, and there is no need to increase the number of turns of the winding 14.

Next, the operational effects of the detection section A configured as described above will be explained.

When the magnetic circuit of the coil 12 is in an open state, a magnetic flux distribution occurs when a voltage is applied.
Here, if there is a conductive ring 18, the same ring 1
Electromagnetic induction occurs in 8, but since it is a conductor, overcurrent loss occurs. Therefore, the inductance seen from the winding 14 is reduced. That is, the manner in which the inductance decreases changes depending on the magnetic flux distribution of the coil 12. Incidentally, the conductor ring 18 moves on the outer circumference of the coil 12 as the float 17 moves up and down due to changes in the liquid level, but the magnetic flux density perpendicular to the conductor ring 18 varies depending on the position of the coil 12. , the overcurrent loss is also different. Therefore, the inductance changes as the conductor ring 18 moves.

Here, the displacement of the float 17 from the lower end of the coil 12 is defined as X, and when the fuel 2 becomes empty, the float 17
When is at the lowest position, X=O, and when fuel 2 is filled and the float 17 is at the highest position, X=F.

Assuming that all the windings 14 are uniform flat-wound parts, the coil will be vertically symmetrical, and the magnetic flux density perpendicular to the conductor ring 18 will be maximum at the center of the coil 12, so the inductance will be It becomes minimum when it is close to /2. Therefore, linearity of inductance over the entire displacement cannot be maintained.

However, in this embodiment, the densely wound portion 14c is provided continuously above the flat wound portion 14b to make the magnetic flux distribution asymmetrical, so that the magnetic flux density perpendicular to the conductor ring 18 is reduced near the upper end of the coil 12. become maximum.
Therefore, the position of the conductor ring 18 where the inductance is minimum rises to near the top of the coil 12, and the inductance constantly decreases as the float 17 moves upward. In addition, the unwound portion 14a,
14d, the magnetic flux distribution changes and
The increase in inductance near =F is suppressed.

From the above, the inductance of the coil 12 changes linearly with the displacement X of the float 17.

In addition, the coil 12 is connected between each linear magnetic material 13b.
Since the core 13 is electrically insulated in the cross-sectional direction, only an extremely small overcurrent flows in each magnetic material 13b in the cross-sectional direction of the core 13. Therefore, the overcurrent loss in the core 13 is negligibly small.

In addition, in the equivalent circuit of the coil 12, the winding component Sc of the core itself is almost released, so
The change in inductance of the coil 12 is the winding component.
Almost unaffected by Sc. Therefore, since the inductance is changed only by the conductor ring 18, the detection sensitivity is increased.

Further, since the magnetic material 13b has conductivity, the stray capacitance Cm generated in the winding 14 of the coil 12 becomes extremely small. Therefore, distortion in the coil voltage due to this stray capacitance Cm hardly occurs, so there is no need to separately provide means for canceling the stray capacitance Cm.

Furthermore, since the conductor ring 18 is formed of a material with a low specific gravity, it is lightweight and floats with low buoyancy. Therefore, the float 17 can be formed small.

Therefore, the detection part A can be easily attached to the fuel tank 1, and the range of movement within the tank 1 is also small.
Further, since the detection part A is electrically non-contact, the float 17 can move up and down smoothly without being affected by friction. Therefore, there is no small malfunction or decrease in accuracy, and the rocking of the float 17 does not lead to failure.

Furthermore, since there are no surface irregularities on the coil 12, dust in the liquid is difficult to adhere to, and malfunctions of the float 17 are significantly reduced. Furthermore, since the float 17 moves linearly around the outer periphery of the coil 12, there is little loss in accuracy due to horizontal fluctuations in the liquid level.

[Conversion circuit B]

Next, a conversion circuit B that is connected to the detection section A and converts a change in the inductance of the coil 12 into a voltage change, a current change, etc. will be described. The configuration of the circuit B is not limited to a specific one, and for example, the following circuit can be adopted.

A rectangular wave pulse of several KHZ to several tens of KHZ is applied to the LR series circuit consisting of the coil 12 and a resistor, and the resulting transient response is used to perform L-V conversion.

At this time, the stray capacitance of the winding 14 of the coil 12
If Cm is large, a resonant circuit is formed and distortion occurs in the coil voltage waveform generated in the LR series circuit. However, in the detection section A of this embodiment, since the magnetic material 13b has conductivity as described above, the stray capacitance Cm of the winding 14 is extremely small and the above-mentioned distortion hardly occurs.

The coil 12 is incorporated into an oscillation circuit, and changes in the oscillation frequency due to this inductance are detected.

Detection is made from the phase difference in the LR series circuit made up of the coil 12 and the resistor. This is a method in which the oscillation waveform is a sine wave and the phase delay of the current in the LR series circuit is detected.

[Output correction circuit C and indicator D]

The indicator D may be of any type, whether analog or digital, as long as it can indicate the liquid level. However, the power supply of the car
It is preferable to have one that can maintain the current instruction even if it is turned off. This is because the opportunity to know the remaining amount of fuel increases, and it is therefore possible to prevent a situation where the vehicle runs out of fuel during driving due to neglecting to refuel. One example is a hold type meter in which the pointer swings to a position where the electromagnetic force generated in the driving electromagnetic coil and the electromagnetic force generated in the braking electromagnetic coil are balanced.

Further, the output correction circuit C is provided to match the output voltage, output current, etc. of the conversion circuit B to the characteristics of the indicator D, and is designed as appropriate depending on the types of the conversion circuit B and the indicator D. It is something. Therefore, due to the nature of the conversion circuit B and indicator D, they can be omitted if unnecessary.

Note that this invention is not limited to the configuration of the embodiment described above, and may be embodied as follows, for example.

(1) The material of the magnetic material 13b constituting the core 13 is not limited to the above-mentioned mild steel, but any magnetic material that is linear and has conductivity may be used. For example, silicon steel plate, permalloy, amorphous alloy, etc. can be mentioned.

In particular, the use of magnetic materials with high magnetic permeability is
This is preferable because the inductance of No. 2 can be increased. However, magnetic materials with high magnetic permeability are generally not commercially available as linear bodies, and even if they are commercially available, they are expensive. Therefore, in the above embodiment, easily available mild steel was used.

(2) The dimensions of the core 13 are not limited to the above embodiments,
It can be arbitrarily determined depending on the measurement target. Also, the wire diameter of the magnetic material 13b is not limited, but considering prevention of overcurrent, ease of manufacture, etc., it is 0.3 to 1 mm.
The degree is common. Furthermore, it is also possible to use a magnetic material 13b whose cross-sectional shape is other than circular (for example, square).

(3) In the above embodiment, the core 13 was formed by combining 200 or more pieces of the magnetic material 13b.
The number of b is the desired inductance, the magnetic material 13
It can also be arbitrarily changed depending on the wire diameter of b.

(4) Instead of the synthetic resin bobbin 13c, as shown in Figure 7, a plate-shaped magnetic material is wound once in a roll, and the ends of the magnetic material are A rolled core 13d may be provided with gaps formed between portions.
Since the rolled core 13d works together with the magnetic material 13b as the core 13 of the coil 12, the inductance is increased and the space efficiency of the coil is further improved.

(5) The bobbin 13c or the rolled core 13d may be omitted, and the winding 14 may be directly wound around the core 13 made of the magnetic material 13b. Also in this case, since the cross-sectional outer peripheral shape of the core 13 approaches a circular shape, the winding wire 14 can be easily wound without excessive stress.

(6) In addition to the liquid level meter in an automobile fuel tank, it can also be embodied as a liquid level meter in various containers such as an oil tank, a water storage tank, a petroleum tank, and an electrolyte tank.

Effects of the invention As detailed above, this invention allows the coil to be made thinner, making it easier to insert into the container of the liquid to be measured, which is also convenient for increasing inductance, and reducing overcurrent loss in the core. , the stray capacitance generated in the coil windings is also extremely small.
The core is easy to manufacture, long cores can be formed easily and inexpensively, and there are no problems with the strength.

[Brief explanation of the drawing]

Figures 1 to 6 show an embodiment of this invention in a liquid level meter in an automobile fuel tank.
Fig. 1 is a sectional view of the coil, Fig. 2 is a sectional view of the entire detection section, Fig. 3 is a perspective view showing a part of the core, and Fig. 4 is a sectional view of the coil.
5 is a front view of the same coil, FIG. 6 is a circuit diagram showing a magnetic equivalent circuit of the same coil, and FIG. 7 is a sectional view of another example of the core. Coil...12, Core...13, Magnetic material...1
3b, winding wire...14.

Claims (1)

[Scope of utility model registration request] In a liquid level meter that detects the liquid level using changes in coil inductance, a plurality of linear conductive magnetic materials 13b are electrically insulated in the cross-sectional direction of the coil 12 and assembled into a core 13.
and the core 13 is connected to the winding 14 of the coil 12.
A liquid level meter characterized by being installed inside the.