JP6019317B2 - Float type liquid level detector - Google Patents

Description

  The present invention relates to a liquid level detecting device, and more specifically, a float type liquid level detecting device that detects a change in liquid level from a change in position of the magnet float using a magnet float having magnetism. About.

  Conventionally, as a mechanism for detecting the liquid level, a float that detects a change in the liquid level by detecting a change in the position of the float using a float that floats on the liquid level. The device is known.

FIG. 6 is a schematic configuration diagram illustrating an example of a conventional liquid level detection device.
As shown in FIG. 6, the conventional liquid level detecting device 100 includes a substantially cylindrical stem 102, a magnetic float 104 having magnetism, and a magnetic sensitive element 106 that is turned on when the magnetic float 104 comes close. And a lead wire 108 for taking out a signal from the magnetic sensitive element 106.

  The magnetic float 104 is formed in a ring shape having a through-hole in the center, and the stem 102 is inserted into the through-hole, and is arranged in a state that can move up and down along the stem 102. Further, the magnetic float 104 is formed to have a specific gravity smaller than that of a liquid for detecting the liquid level (hereinafter referred to as “detected liquid”).

  The liquid level detecting device 100 configured as described above is attached to a container in which a liquid to be detected is stored in a substantially vertical shape. Since the magnetic float 104 floats on the liquid level of the liquid to be detected, the liquid level changes in this state, for example, when the liquid level reaches a predetermined position by increasing or decreasing, The magnetic sensitive element 106 is turned ON, and an ON signal is output via the lead wire 108.

  Accordingly, it is possible to detect that the liquid level of the liquid to be detected has changed, for example, the liquid level has risen or lowered to reach a predetermined position.

  As the magnetic float 104 used in the float type liquid level detection device, for example, a so-called foamed plastic float obtained by integrally molding a sintered magnet and a plastic foam, a sintered magnet and a nitrile rubber (NBR), etc. A so-called foamed NBR float obtained by integrally molding a rubber foam, or a so-called metal float in which a sintered magnet is incorporated in a hollow metal is used.

  However, in the foamed plastic float, the foamed part is open-celled, so if the skin layer, which is a thin plastic layer where foaming of the outer surface of the float is not progressing, is damaged, or if moisture vapor permeates in hot water, Liquid accumulates in the float, and the position of the float relative to the liquid surface changes due to a change in the weight of the float itself. In some cases, the float may sink into the liquid.

  On the other hand, in the foamed NBR float, since the foamed portion is a closed cell, the liquid does not enter the float even when the outer surface of the float is damaged. However, the foamed NBR swells with hot water of 60 ° C. or higher, so that the weight of the float itself may change or the integrated sintered magnet may fall off the float.

  In addition, the reliability of welded parts is not sufficient for metal floats. For example, liquids may enter the floats and the floats may sink into the liquid. It is necessary to use a float that is suitable for the environmental conditions.

  For this reason, a magnetic float formed by mixing a magnetic powder with a synthetic resin having chemical resistance has been proposed (Patent Document 1). There are two types of magnet floats: synthetic resin foamed and non-foamed ones. However, synthetic resin foamed has the same problem as the above-mentioned foamed plastic float, and foams synthetic resin. It is preferable to use a magnetic float that is not allowed to occur.

  However, since the specific gravity of the synthetic resin is usually about 0.95 to 2.0, and the specific gravity of the magnetic powder is about 3 to 9, the specific gravity of the magnet float which is a mixed molded body of these is the synthetic resin. Depending on the mixing ratio of the magnetic powder, it becomes 1 or more.

  When the specific gravity of the magnet float becomes 1 or more, the liquid level of water having a specific gravity of 1 or oil having a specific gravity of about 0.8 is detected using the float. It ’s not enough to sink in the liquid.

  In order to solve the problem in the case of using such a magnet float, a method of giving an additional buoyancy to the magnet float using a magnet arranged so as to form a repulsive magnetic field with respect to the magnetic pole of the magnet float has been proposed. (Patent Documents 2 and 3).

Japanese Utility Model Publication No. 55-161224 JP 2010-122070 A Japanese Utility Model Publication No. 61-47536

  However, since the magnetic force of the magnet is inversely proportional to the square of the distance, in such a float type liquid level detection device, if the gap between the magnet float and the magnet becomes large, sufficient additional buoyancy is not given to the magnet float. The magnet float may sink in the liquid to be detected.

  In addition, when such a float type liquid level detection device is used in a device such as a transportation device that generates a liquid surface ripple due to vibration, the float moves up and down due to the influence of the ripple.

  For this reason, the chattering phenomenon in which the magnetic sensitive element incorporated in the liquid level detection device repeats ON-OFF occurs, and there is a problem that the liquid level cannot be accurately detected.

  In addition, in order to reduce the influence of the undulation of the liquid level, there is a method of covering the float with a cylinder slightly larger than the float outline of the liquid level detection device, but the structure of the liquid level detection device is complicated and manufactured. Costs will also increase.

  In view of such a current situation, the present invention provides sufficient additional buoyancy to the magnet float in the entire movable range of the magnet float even when the specific gravity of the magnet float is larger than the specific gravity of the liquid to be detected. An object of the present invention is to provide a float type liquid level detecting device in which the magnet float does not sink into the liquid to be detected.

  Furthermore, in the present invention, even if the liquid level of the liquid to be detected is increased and the position of the magnet float is increased, the magnet float is stabilized by the attractive force generated on the upper surface side of the magnet float, and the influence of the ripple of the liquid surface is caused. It is an object of the present invention to provide a liquid level detecting device that is difficult to be affected and can accurately detect a change in liquid level.

The present invention was invented in order to solve the above-described problems in the prior art, and the liquid level detection device of the present invention has a magnet float having a magnet arranged substantially vertically. A float type liquid level detecting device that is intubated to move up and down along the outer periphery and detects a change in the liquid level of the liquid to be detected from a change in the position of the magnet float,
Repulsion means for generating a repulsive force on the lower surface side of the magnet float;
Suction means for generating a suction force on the upper surface side of the magnet float;
It is characterized by providing.

The attraction means is preferably an attraction magnet that forms an attraction magnetic field with respect to the magnetic pole of the magnet float.
Further, it is preferable that the suction means is fixed at a predetermined position of the stem by a fixing means, and a gap is formed between the suction means and the magnet float by the fixing means.

  In the float type liquid level detecting device of the present invention, the combined force F, which is the sum of the repulsive force of the repelling means and the attractive force of the attracting means, is expressed by the following formula (1) in the movable range of the magnet float And, at the upper end position of the magnet float, the combined force F ′, which is the sum of the repulsive force of the repulsive means and the attractive force of the attracting means, preferably satisfies the following formula (2).

F> A−C × G Formula (1)
F ′ <A Formula (2)
However,
F is the combined force (g weight) of the repulsive force of the repelling means and the attractive force of the attracting means when the magnet float is in the movable range,
F ′ is the combined force (g weight) of the repulsive force of the repulsive means and the attractive force of the attracting means when the magnet float is at the upper end position,
A is the weight of the magnetic float (g),
C is the volume of the magnetic float (cm ³ ),
G is the density of the liquid to be detected (g weight / cm ³ ),
And

The repulsion means may be a repulsion magnet that forms a repulsion magnetic field with respect to the magnetic pole of the magnet float.
The repulsion means may be a compression spring attached to the lower surface of the magnet float.

  According to the present invention, since the repelling means for generating the repulsive force on the lower surface side of the magnet float and the suction means for generating the attractive force on the upper surface side of the magnet float are provided, the specific gravity is higher than that of the liquid to be detected. Large magnet floats can be used.

  For this reason, for example, when immersed in a liquid to be detected, such as foamed plastic or foam rubber, it is not necessary to use a material that causes the liquid to be detected to enter or swell into the magnet float, and there is no risk of quality deterioration. It can be a magnet float.

  Also, when the magnet float reaches the vicinity of the upper end position of the movable range as the liquid level rises, the magnet float is attracted by the suction means, so that it is less susceptible to the influence of the liquid level ripple. Can do.

  Further, when a magnet is used as the suction means and the repulsion means, metal magnetic powder that may be mixed in the liquid to be detected can be adsorbed by the magnet and removed from the liquid to be detected. Thereby, the lifetime of the apparatus which attached the liquid level detection apparatus can be achieved.

  Furthermore, when a compression spring is used as the repelling means, it is less expensive than a magnet, and therefore the manufacturing cost of the liquid level detecting device can be reduced.

FIG. 1 is a cross-sectional view of an example of the liquid level detecting device of the present invention. FIG. 2 is a schematic configuration diagram showing another example of the shape of the magnet float 14, FIG. 2A is a plan view of the magnet float 14, and FIG. 2B is a central sectional view of the magnet float 14. is there. FIG. 3A is a schematic cross-sectional view showing an example in which a repulsion means is attached to the magnet float 14, and FIG. 3B is a schematic view showing an example of a compression spring. FIG. 4 shows a combination of the gap between the lower surface of the magnet float 14 and the upper surface of the repelling magnet 20, the repulsive force of the repelling magnet 20, and the attractive force of the attracting magnet 22 in the embodiment of the liquid level detecting device of the present invention. It is a graph of Table 1 showing the relationship with force. FIG. 5 shows the gap between the lower surface of the magnet float 14 and the upper surface of the repelling magnet 20, the repulsive force of the repelling magnet 20, and the attractive force of the attracting magnet 22 in another embodiment of the liquid level detecting device of the present invention. Table 2 which shows the relationship with the synthetic | combination power of is graphed. FIG. 6 is a cross-sectional view of an example of a conventional liquid level detection device.

Hereinafter, embodiments (examples) of the present invention will be described in more detail with reference to the drawings.
FIG. 1 is a cross-sectional view of an example of the liquid level detecting device of the present invention.
As shown in FIG. 1, the liquid level detecting device 10 of this embodiment includes a substantially cylindrical stem 12, a magnet float 14 having magnetism, and a magnetic sensitivity in which a switch is turned on when the magnet float 14 comes close. The element 16, a lead wire 18 for taking out a signal from the magnetic sensing element 16, a repulsion magnet 20 that generates a repulsive force on the lower surface side of the magnet float 14, and an attraction that generates an attractive force on the upper surface side of the magnet float 14 And a magnet 22 for use.

  The stem 12 is integrally formed with a threaded portion 12b at the upper end portion of the flange portion 12a. The stem 12 is substantially vertical to a container (not shown) in which the liquid to be detected is stored via, for example, a packing and a nut (not shown). It is attached to the shape.

  Moreover, as the magnetic sensitive element 16, a reed switch etc. can be used, for example, The magnetic sensitive element 16 and the lead wire 18 are electrically connected, for example by methods, such as soldering.

  The magnetic sensitive element 16 is disposed at a predetermined position in the stem 12, and the lead wire 18 includes, for example, an insulating means 32 such as a bushing, and a molding material 34 such as an epoxy resin for the purpose of forming a waterproof and drip-proof structure. It is fixed by.

  One end portion of the lead wire 18 is led out of the stem 12 and connected to a control circuit (not shown). As will be described later, when the ON signal from the magnetic sensing element 16 is detected by the control circuit, it is detected that the liquid level of the liquid to be detected has changed.

  In addition, the magnet float 14 is not particularly limited, and a known magnet float can be used. However, liquid does not enter the float and has excellent chemical resistance. From the viewpoint of cost performance and magnetic characteristics, an appropriate amount of strontium ferrite powder is preferably mixed with a plastic resin material, such as ferrite magnets such as strontium ferrite and rare earth magnets, and injection molded into a ring shape. The magnet float 14 is preferably magnetized so as to have an N pole and an S pole in the thickness direction of the magnet float 14.

In the present embodiment, in FIG. 1, the magnet float 14 is magnetized so that the upper surface side is the S pole and the lower surface side is the N pole.
In the present embodiment, the repulsion magnet 20 acts as a repulsion means for generating a repulsive force on the lower surface side of the magnet float 14 and forms a repulsive magnetic field with respect to the magnetic poles of the magnet float 14. The upper surface side of 20 is an N pole, and the lower surface side is an S pole so that the stem 12 is fixed so as not to drop off by a method such as press-fitting, adhesion, or welding.

  In this embodiment, the attracting magnet 22 acts as an attracting means for generating an attracting force on the upper surface side of the magnet float 14 and forms an attracting magnetic field with respect to the magnetic pole of the magnet float 14. The upper surface side of 22 is an S pole and the lower surface side is an N pole so that it is attached to a predetermined position of the stem 12 by, for example, a fixing means 24 made of a nonmagnetic material such as an E ring, C ring, or snap ring. It has been.

  The repulsion magnet 20 and the attraction magnet 22 are not particularly limited. For example, a plastic magnet, a rubber magnet, a sintered magnet, a rare earth magnet, and the like can be used. The shape of the attracting magnet 22 is not particularly limited.

The fixing means 24 has a purpose of forming a gap between the magnet float 14 and the suction magnet 22 in addition to the purpose of fixing the suction magnet 22 at a predetermined position.
When the magnet float 14 comes into close contact with the attracting magnet 22 as the liquid level rises, if the liquid to be detected intervenes on this contact surface, an adhesive force is generated due to the surface tension of the liquid to be detected, and the liquid level decreases. Accordingly, the lowering operation of the magnet float 14 is delayed.

  In order to prevent this phenomenon, by attaching the fixing means 24, a gap is formed between the magnet float 14 and the suction magnet 22, and adhesion between the magnet float 14 and the suction magnet 22 is prevented. The movement when descending can be made smooth.

  In this embodiment, the range from the upper surface of the repulsion magnet 20 to the lower surface of the fixing means 24 is a movable range in which the magnet float 14 can move up and down, and the lower surface of the magnet float 14 is on the upper surface of the repulsion magnet 20. The closest position is the “lower end position” of the magnet float 14, and the uppermost position of the magnet float 14 is the “upper end position” of the magnet float 14 where the upper surface is closest to the lower surface of the fixing means 24.

  As shown in Table 1 and FIG. 4 described later, when the fluctuation of the resultant force of the repulsive magnet 20 and the attractive force of the attracting magnet 22 is large, the resultant force fluctuation range is small. A movable range of the magnet float 14 can also be limited by using a stopper (not shown) or the like so that the magnet float 14 moves up and down.

  In the present embodiment, the magnetic sensitive element 16 is disposed in the vicinity of the upper end position of the magnet float 14, and when the magnet float 14 reaches the vicinity of the upper end position as the liquid level rises, the lead wire 18 is connected. An ON signal is output through the terminal.

  In the liquid level detecting device 100 configured as described above, a repulsive force is generated on the lower surface side of the magnet float 14 and an attractive force is generated on the upper surface side of the magnet float 14.

  For this reason, even if the liquid level rises and the gap between the magnet float 14 and the repulsion magnet 20 increases and the repulsive magnetic force of the repulsion magnet 20 decreases, the gap between the magnet float 14 and the attracting magnet 22. , The attractive magnetic force of the attractive magnet 22 is increased, and the additional buoyancy to the magnet float 14 is sufficiently provided.

  As described above, in order to sufficiently give the additional buoyancy to the magnet float 14, the shape and magnetic force of the magnet float 14, the repulsion magnet 20, and the attraction magnet 22 are set so as to satisfy the condition represented by the following formula (1). Is preferably selected as appropriate.

F> A−C × G Formula (1)
However,
F is the combined force (g weight) of the repulsive force of the repulsive magnet 20 and the attractive force of the attracting magnet 22 when the magnet float 14 is in the movable range;
A is the weight (g weight) of the magnet float 14;
C is the volume (cm ³ ) of the magnet float 14;
G is the density of the liquid to be detected (g weight / cm ³ ),
And

  Further, in order to move the magnet float 14 up and down in accordance with the change in the liquid level of the liquid to be detected, the magnet float 14, the repulsion magnet 20, and the attraction for satisfying the condition expressed by the following formula (2) It is preferable to select the shape and magnetic force of the magnet 22 as appropriate.

F ′ <A Formula (2)
However,
F is a combined force (g weight) of the repulsive force of the repulsive magnet 20 and the attractive force of the attracting magnet 22 when the magnet float 14 is at the upper end position;
A is the weight (g weight) of the magnet float 14;
And

  The combined force that satisfies the expressions (1) and (2) is a necessary buoyancy for floating the magnet float 14 on the liquid to be detected. By selecting in this way, the magnet float 14 can be floated on the liquid level of the liquid to be detected, and the magnet float 14 moves up and down the movable range in the stem 12 as the liquid level of the liquid to be detected changes. Will do.

When the combined force F of the repulsive force of the repulsive magnet 20 and the attractive force of the attracting magnet 22 when the magnet float 14 is at the lower end position is larger than the weight A of the magnet float 14, the magnetic float 14 is repelled. It will not be in close contact with the magnet 20 for use, but will float at a position where the combined force F and weight A are balanced.
Therefore, the movable range of the magnet float 14 is such that the magnet floats at a position where the combined force F and the weight A are balanced from the upper surface of the repulsion magnet 20 rather than from the upper surface of the repulsion magnet 20 to the lower end of the fixing means 24. Since the distance from the lower surface of the float 14 is shortened, the liquid level detection range becomes narrow, which is not preferable.
Therefore, it is preferable that the synthetic force F satisfies the following formula (3).

A>F> A-C × G Formula (3)
However, F, A, C and G are the same as described above.

By extending the entire length of the stem 12, the liquid level detection range can be widened, but the design tends to be complicated and the manufacturing cost tends to increase.
By selecting the magnetic force of the magnet float 14, the repulsion magnet 20, and the attracting magnet 22 so as to satisfy the expression (3), the magnet float 14 can accurately move up and down as the liquid level of the liquid to be detected changes. In addition, the movable range of the magnet float 14 can be maximized.

  When the liquid level detecting device 10 configured in this way is used, for example, to detect the liquid level of lubricating oil such as transportation equipment and generators, the lubricating oil is contained in the lubricating oil as the usage time of the equipment elapses. May contain magnetic metal powder.

  In this case, there is a problem that affects the life of the device, and therefore it is usually necessary to replace the filter or the lubricating oil. However, the magnetic metal powder is a repulsion magnet of the liquid level detecting device 10. 20 and the attracting magnet 22.

  Thus, since the magnetic metal powder in the liquid to be detected such as lubricating oil can be removed by the repulsion magnet 20 and the suction magnet 22 of the liquid level detection device 10, the liquid level detection device 10 is attached. Longer service life is expected.

  In addition, since magnetic metal powder adheres to the magnet float 14 very little, magnetic metal powder mixes between the magnet float 14 and the stem 12, and the movement of the magnet float 14 is not hindered. .

  FIG. 2 is a schematic configuration diagram showing another example of the shape of the magnet float 14, FIG. 2A is a plan view of the magnet float 14, and FIG. 2B is a central sectional view of the magnet float 14. is there.

  As shown in FIG. 2, the magnet float 14 includes a cylindrical ring-shaped float body 26 formed of a synthetic resin, preferably a plastic resin having chemical resistance, and rubber magnets or the like on the upper and lower surfaces of the float body. A thin plate magnet 28 having a thin ring shape is attached.

  In FIG. 2, reference numeral 26 a denotes a thin plate magnet mounting rib for fixing by a method such as heat welding in a state of being inserted into a fixing hole 28 a provided in the thin plate magnet 28. The thin-plate magnet mounting rib 26a also has an effect of forming a gap for preventing the magnet float 14 from repelling the magnet 20 and the attracting magnet 22 from coming into close contact with each other.

  In the embodiments so far, the attracting magnet is used as the attracting means and the repelling magnet is used as the repelling means. However, the present invention is not limited to this. For example, a compression spring is used as the repelling means as shown below. You can also.

3A is a central sectional view of an example in which the compression spring 30 is attached to the magnet float 14, and FIG. 3B is a compression spring attached to the lower surface side of the magnet float 14. FIG.
As shown in FIG. 3A, when a compression spring is used as the repulsion means, a compression spring 30 is attached to the lower surface side of the magnet float 14.

  For example, the compression spring 30 is formed by punching a spring plate material such as a stainless steel plate or phosphor bronze having a thickness of about 0.03 mm to 0.10 mm with a mold, forming a conical shape with a load, and performing a heat treatment to obtain a spring. Is.

  The maximum load of the compression spring 30 manufactured in this way can be as small as several grams, can generate a repulsive force on the lower surface side of the magnet float 14, and can be used in place of the repulsive magnet 20. Can do.

  The material of the compression spring 30 is not particularly limited, and for example, a plastic resin material or a rubber material may be used.

  As mentioned above, although one Example of this invention was described, this invention is not limited to this, For example, the opposing relationship of the magnetic pole of the magnet float 14, the repulsion magnet 20, and the attraction magnet 22 is shown in this Example. It can also be attached to be opposite to each other.

  In this embodiment, the ON level signal is output via the lead wire 18 when the liquid level increases and the magnet float 14 reaches the vicinity of the upper end position. By arranging it near the lower end position of the magnet float 14, an ON signal is output via the lead wire 18 when the liquid level drops and the magnet float 14 reaches near the lower end position. Various modifications can be made without departing from the object of the present invention.

[Example 1]
The relationship between the gap between the lower surface of the magnet float 14 and the upper surface of the repulsion magnet 20 and the resultant force of the repulsion force of the repulsion magnet 20 and the attraction force of the suction magnet 22 in the embodiment of the liquid level detection apparatus of the present invention. The properties are shown in Table 1.

  The magnet float 14 used in Example 1 is obtained by mixing a polypropylene resin with a magnetic powder of strontium ferrite and injection-molding it into a ring shape, and magnetizing it so that it has N and S poles in the thickness direction. .

The magnet float 14 has an outer diameter: 18.5 mm, an inner diameter: 6.5 mm, a thickness: 8 mm, a weight: 1.952 g weight, a volume: 1.593 cm ³ , a specific gravity: 1.225, and a magnetic force: 12.7 mT. .

  Therefore, the buoyancy necessary for the magnet float 14 to float on the liquid to be detected is, for example, 1.952-1.593 × 1.0 = 0.359 (g weight) if the water has a specific gravity of 1. If the oil has a specific gravity of 0.8, it is 1.952-1.593 × 0.8 = 0.678 (g weight).

  Table 1 shows that a magnet float 14 is placed on an electronic balance, and a repulsion magnet (corresponding to the repulsion magnet 20) and a suction magnet (corresponding to the suction magnet 22) are parallel and coaxial with the magnet float 14, respectively. And the change in weight when the gap between the magnet float 14 and the repulsion magnet or the attraction magnet is changed by 0.5 mm is measured.

  In FIG. 1, the position of the gap 0.0 mm represents the case where the lower surface of the magnet float 14 is close to the upper surface of the repulsion magnet 20, that is, the lower end position. The position of the gap 0.5 mm is In FIG. 1, the lower surface of the magnet float 14 is located at a position 0.5 mm away from the upper surface of the repulsion magnet 20. Further, in Table 1, the maximum value of the gap represents the case where the upper surface of the magnet float 14 is in a position close to the lower surface of the fixing means 24, that is, the upper end position.

  FIG. 4 is a graph of the measurement results in Table 1, and the value of the resultant force satisfies the above-described formula (3).

  By selecting the magnetic force of the repulsion magnet (repulsion magnet 20) and the attraction magnet (attraction magnet 22) in this way, when the magnet float 14 reaches the vicinity of the upper end position, the magnet float 14 becomes the attraction magnet (attraction). Since the magnet 22) receives a strong attractive force, it is not easily affected by the undulation of the liquid surface.

[Example 2]
In another embodiment of the liquid level detecting device of the present invention, the gap between the lower surface of the magnet float 14 and the upper surface of the repulsive magnet 20, the combined force of the repulsive force of the repelling magnet 20 and the attractive force of the attracting magnet 22, Table 2 shows the relationship.

  The magnet float 14 used in the second embodiment is formed by the same material and method as in the first embodiment. On the other hand, the outer diameters of the repulsion magnet 20 and the attraction magnet 22 are about half the outer diameter of the magnet float 14 and the magnetic force of the attraction magnet is increased (30.00 mT).

  Thus, in the second embodiment, the volume of the magnet float is the same, the outer diameter is increased, the thickness is decreased, the outer diameters of the repulsion magnet 20 and the attracting magnet are decreased as much as possible, and the magnetic force is increased. By doing so, the magnetic force of the magnet float 14, the repulsion magnet 20, and the attracting magnet 22 acts on each other efficiently, so that the change in the combined force can be reduced.

  As the liquid level detecting device as in the second embodiment, the minimum value of the combined force in the entire movable range of the magnet float 14 is 80% or more of the maximum value of the combined force in the entire movable range of the magnet float 14. An apparatus that is 90% or more is more preferable.

  FIG. 5 is a graph of the measurement results in Table 2. As shown in FIG. 5, the change in the combined force in the entire movable range of the magnet float 14 is less than that in FIG. 4. That is, the floating level of the magnet float 14 in the liquid to be detected hardly changes in the entire movable range of the magnet float 14, and the liquid level can be detected more accurately.

  Thus, it is shown that the liquid level detection device having different characteristics can be obtained by selecting the shape and magnetic force of the repulsion magnet (repulsion magnet 20) and the attraction magnet (attraction magnet 22). It can be used properly depending on the application.

DESCRIPTION OF SYMBOLS 10 Liquid level detection apparatus 12 Stem 12a Flange part 12b Screw part 14 Magnet float 16 Magnetosensitive element 18 Lead wire 20 Repulsion magnet 22 Attraction magnet 24 Fixing means 26 Float main body 26a Thin plate magnet mounting rib 28 Thin plate magnet 28a Fixing hole 30 Compression spring 32 Insulating means 34 Mold material 100 Liquid level detecting device 102 Stem 104 Magnetic float 106 Magnetic sensitive element 108 Lead wire

Claims (6)

A magnet float having a magnetic, intubated to move up and down along the outer periphery of the stem that is disposed substantially vertically, from the change of the position of the magnet float, float type for detecting a change in liquid level of the detected liquid A liquid level detection device,
Repulsion means for generating a repulsive force on the lower surface side of the magnet float;
Suction means for generating a suction force on the upper surface side of the magnet float;
A float type liquid level detecting device comprising:   The float type liquid level detecting device according to claim 1, wherein the attraction means is an attraction magnet that forms an attraction magnetic field with respect to the magnetic pole of the magnet float.   2. The suction means is fixed to a predetermined position of the stem by a fixing means, and a gap is formed between the suction means and the magnet float by the fixing means. Or the float type liquid level detection apparatus of 2. In the movable range of the magnet float, the combined force F, which is the sum of the repulsive force of the repulsive means and the attractive force of the attracting means, satisfies the following formula (1), and at the upper end position of the magnet float, and repulsive force of the repulsive means, float according to any one of claims 1 to 3, which is the sum of the attractive force resultant force F 'is characterized by satisfying the following formula (2) of said suction means Liquid level detection device.
F> A−C × G Formula (1)
F ′ <A Formula (2)
However,
F is the combined force (g weight) of the repulsive force of the repelling means and the attractive force of the attracting means when the magnet float is in the movable range,
F ′ is the combined force (g weight) of the repulsive force of the repulsive means and the attractive force of the attracting means when the magnet float is at the upper end position,
A is the weight of the magnetic float (g),
C is the volume of the magnetic float (cm ³ ),
G is the density of the liquid to be detected (g weight / cm ³ ),
And It said repulsion means, wherein the pole of the magnet float, float type liquid level detection device according to any one of 4 claims 1, characterized in that the repelling magnet to form a repulsive magnetic field. The repulsion means, float-type liquid level detection device according to claim 1, wherein in any one of the four that is a compression spring mounted to the lower surface of the magnet float.

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