JP3905707B2 - Liquid level sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid level sensor, and more particularly, to a non-contact type liquid level sensor using a magnetoelectric conversion element.
[0002]
[Prior art]
This type of liquid level sensor is used, for example, as a level sensor for monitoring the amount of fuel in an automobile. In this type of liquid level sensor, an annular magnet connected to a float linked to the liquid level, and a magnetic force generated by the magnet according to the liquid level is converted into an electric signal by a magnetoelectric transducer such as a Hall element. The liquid level is detected by conversion.
[0003]
However, in the conventional liquid level sensor, the Hall element is disposed in the gap of the core as a magnetic flux collecting member having a shape obtained by dividing the cylinder into two layers in the annular magnet. That is, it is difficult to reduce the thickness of the portion due to the thickness of the core and the annular magnet. In addition, the above-described one set of cores is required, and the structure is complicated, the number of parts is increased, and the cost is increased.
[0004]
These problems will be described with reference to FIGS. FIG. 6 is a structural explanatory view showing an outline of a conventional liquid level sensor. FIG. 7 is a perspective view schematically showing a detection unit of the liquid level sensor of FIG. FIG. 8 is a graph showing the relationship between the magnet rotation angle, the magnetic flux density, and the Hall voltage by the liquid level sensor of FIG.
[0005]
As shown in FIG. 6, the conventional liquid level sensor is fixed to a part of the inner wall of the container in order to detect the liquid level of the liquid LQ in the container TNK. The float 101 is connected to the magnet holder 103 via a rod-shaped arm 102. The float 101 is formed of a member having buoyancy with respect to the liquid LQ for measuring the liquid level, and has a cylindrical shape. One end of the arm 102 passes through the center of the float 101 and is coupled to the float 101.
[0006]
An annular magnet 104 is attached to the inner side surface of the magnet holder 103 using an adhesive or the like, and an arm holding portion for holding the other end of the arm 102 is provided on the outer side surface. The magnet holder 103 is pivotally attached to a rotary shaft 111 formed integrally with the frame 105 via a rotary shaft 106 fixed by a bush 112. With such a structure, the magnet 104 rotates around the rotation shaft 106 in conjunction with the float 101 that moves according to the liquid level. The magnet 104 is an annular permanent magnet with two poles on one side.
[0007]
Further, a pair of cores 110 (core 110A, core 110B) having a shape obtained by dividing the cylinder into two are arranged on the inner wall of the frame 105 at a position facing the magnet 104, and in the gap between the pair of cores 110, The Hall element 108 is fixed to the frame 105 through the wiring board 107 in the positional relationship as shown in FIG. An electric signal based on the magnetic flux density detected by the Hall element 108 is supplied to the outside via the terminal 109. The inside of the frame 105 is filled with a molding agent 113.
[0008]
The Hall element 108, the core, and the magnet 104 constitute a magnetic flux density detector as shown in FIG. 7, and the magnet 104 that rotates in the direction indicated by the arrow in the drawing according to the liquid level fluctuation. The magnetic flux density that fluctuates with this rotation is detected by the Hall element 108 via the core 110A and the core 110B. As shown in FIG. 8, the relationship between the rotation angle of the magnet 104, the magnetic flux density, and the Hall voltage both changes linearly with respect to the rotation angle (range from −90 degrees to +90 degrees). Using this characteristic, the liquid level is measured.
[0009]
[Problems to be solved by the invention]
By the way, the conventional liquid level sensor described above has a structure in which the core 110 is arranged in layers on the annular magnet 104 as shown in FIG. That is, the thickness a + b, which is the sum of the thickness a (holder height) generated by the magnet 104 and the magnet holder 103 and the thickness b (frame height) of the frame 105 that houses the core, is the conventional thickness a + b. At a minimum, the liquid level sensor was required. Due to the thickness a + b, it is difficult to reduce the thickness of the conventional liquid level sensor. Further, the one set of cores 110A and 110B is also required, the structure is complicated, the number of parts is increased, and the cost is increased.
[0010]
Therefore, in view of the present situation described above, an object of the present invention is to provide a liquid level sensor in which the detection unit is improved and thinned to achieve downsizing and cost reduction of the entire apparatus.
[0011]
[Means for Solving the Problems]
The liquid level sensor according to claim 1, which has been made to solve the above problems, includes a float 1 that floats on the liquid level and moves according to the liquid level, as shown in FIGS. The arm 2 with one end locked, the magnet holder 3 locked with the other end of the arm 2, the frame 5 on which the magnet holder 3 is rotatably mounted, and the magnet holder 3 are held and accommodated. A cylindrical magnet 4 magnetized with two poles, and a magneto-electric conversion attached to the frame 5 so as to be disposed in the same plane as the magnet 4 and directly opposite to the inner wall of the magnet at the center of the magnet The magnetoelectric conversion element 8 has an element 8 and changes according to the rotation angle of the magnet 4 that rotates together with the magnet holder 3 as the float 1 moves. That a Teisu Ru liquid level sensor measuring the liquid level on the basis of the electrical signal, the magnet holder 3 is pivoted to the frame 5 so as to rotate the center of the annular magnet 4 as a virtual axis of rotation It is possible to be mounted.
[0012]
According to invention of Claim 1, the float 1 moves according to the fluctuation | variation of a liquid level. Since the magnet holder 3 rotatably attached to the frame is rotated via the arm 2 in accordance with the movement of the float 1, the cylindrical magnet 4 held and accommodated in the magnet holder 3 is also associated therewith. Rotate. And a magnetoelectric conversion element detects the magnetic flux density according to the rotation angle of the magnet 4 which rotates according to the movement of the said float 1, and converts this into an electric signal, thereby liquid level based on this electric signal. Level is measured. The magnetoelectric conversion element of the liquid level sensor that measures the liquid level by such an operation is arranged on the frame so as to be arranged on the same plane as the magnet 4 and in the central part of the magnet 4 so as to directly face the inner wall of the magnet. Since it is attached, the liquid level sensor can be thinned. Further, since a pair of cores or the like as a magnetic collecting member is not required as in the prior art, the number of parts is reduced and the cost can be reduced. Further, since there is no fear of displacement between the magnetoelectric conversion element and the magnetism collecting member, the measurement accuracy is improved. Further, since the magnet holder 3 is mounted on the frame so as to be rotatable about the virtual rotation axis, the rotation axis 106 in the prior art shown in FIG. 6 is not necessary.
Furthermore, since the magnet 4 has an annular shape, the manufacture is easy, and the movement when rotating according to the movement of the float 1 is stabilized. Therefore, according to the first aspect of the invention, the cost can be further reduced and the measurement accuracy can be improved. Further, according to the first aspect of the present invention, since the magnetoelectric conversion element is disposed at the center of the annular magnet 4, the magnetic flux density that changes according to the rotation of the magnet 4 can be detected most effectively. Can do. Therefore, according to the invention of claim 1, the measurement accuracy can be further improved.
[0017]
The liquid level sensor according to claim 2, which has been made to solve the above-mentioned problem, is the liquid level sensor according to claim 1 , as shown in FIGS. 1, 2, 3, and 5. The liquid level is measured by detecting the magnetic flux density in a range where the magnetic flux density of the magnet 4 that rotates with the movement of the float 1 correspondingly increases monotonously by the magnetoelectric transducer. Features.
[0018]
According to the second aspect of the invention, the magnetoelectric transducer detects the magnetic flux density in the range where the magnetic flux density of the magnet 4 that rotates with the movement of the float 1 corresponding to the liquid level increases monotonously. Thus, since the liquid level is measured, the processing until the liquid level is finally calculated from the detected magnetic flux density becomes easy.
[0019]
The liquid level sensor according to claim 3, which has been made to solve the above-mentioned problems, is a liquid level sensor according to claim 1, wherein the magnetoelectric transducer is a Hall element as shown in FIGS. 1 to 3. 8 is a feature.
[0020]
According to the third aspect of the present invention, since the magnetoelectric conversion element is the Hall element 8, it is widely spread and easily available, and the shortening of the manufacturing time can be promoted. Therefore, according to the invention of claim 3 , further cost reduction can be achieved.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, an embodiment of a liquid level sensor according to the present invention will be described with reference to FIGS. FIG. 1 is an explanatory view showing the outline of one embodiment of the liquid level sensor of the present invention. FIG. 2 is a plan view showing an overview of an embodiment of the liquid level sensor of the present invention. FIG. 3 is a perspective view schematically showing a detection unit of the liquid level sensor of FIG.
[0022]
As shown in FIG. 1, this liquid level sensor is fixed to a part of the inner wall of the container TNK so as to waterproof the internal electric circuit in order to detect the liquid level of the liquid LQ in the container TNK. ing. The float 1 is connected to the magnet holder 3 via the arm 2. The float 1 is formed of a member having buoyancy with respect to the liquid LQ for measuring the liquid level, and has a cylindrical shape. The arm 2 is made of a long and narrow bar-like metal such as stainless steel. One end of the arm 2 passes through the center of the float 1 and is coupled to the float 1.
[0023]
The magnet holder 3 has an accommodating portion for accommodating the annular magnet 4 on the inner side, and an arm holding portion for retaining the other end (float arm 21) of the arm 2 having, for example, a T shape on the outer side. 31. The magnet holder 3 is made of a non-magnetic material, and the outer shape of the magnet holder 3 is such that the arm holding portion 31 is provided at the outer central portion of the cylindrical shape that is slightly larger than the outer shape of the magnet 4 accommodated therein. Yes. The arm 2 coupled to the float 1 is also connected to the magnet holder 3 via the arm holding portion 31.
[0024]
As shown in FIG. 2, the magnet holder 3 is held by three flange-preventing flanges 61, 62, 63 of the frame 5 arranged every 120 degrees as shown in FIG. The frame 5 is rotatably mounted. The removal prevention flange 63 is detachable from the frame 5. When the magnet holder 3 is assembled into the frame 5, the removal prevention flange 63 is positioned after the magnet holder 3 is positioned at a predetermined position of the frame 5. Installed. Further, the drop prevention flanges 61 and 62 may be formed integrally with the frame 5 or may be detachable from the frame 5 in the same manner as the drop prevention flange 63. 2 represents the rotation angle of the magnet 4 accommodated in the magnet holder 3 that rotates according to the liquid level.
[0025]
The accommodating portion of the magnet 4 of the magnet holder 3 described above has a cylindrical inner diameter in accordance with the outer shape of the annular magnet 4. The magnet 4 is fixed to the housing part using an adhesive or the like. With such a structure, the magnet 4 rotates about the rotation axis in conjunction with the float 1 that moves according to the liquid level. The magnet 4 is an annular permanent magnet with two poles. Thus, since the magnet 4 has an annular shape, it is easy to manufacture, and the movement when rotating according to the movement of the float 1 is stabilized, and the measurement accuracy is improved.
[0026]
A magnetoelectric conversion element is mounted on the wiring board 7 and fixedly arranged at the center of the annular magnet 4. This magnetoelectric conversion element detects the magnetic flux density by the magnet 4 that rotates according to the liquid level, converts it into an electrical signal, and outputs it. For example, a known Hall element 8 is used. The Hall element 8 and the magnet 4 constitute a magnetic flux density detection part in the present liquid level sensor, and the Hall element 8 is fixed to the center of the annular magnet 4 as shown in FIG. Is arranged. Since the magnet 4 rotates in the direction indicated by the arrow in the drawing according to the liquid level as described above, the magnetic flux density with respect to the Hall element 8 that fluctuates with this rotation is used for the liquid level measurement. The
[0027]
Thus, since the Hall element 8 is disposed at the center of the annular magnet 4, the magnetic flux density that changes according to the rotation of the magnet 4 can be detected most effectively. Therefore, the measurement accuracy can be further improved. In addition, since the Hall element 8 is widely spread and easily available, the manufacturing time can be shortened. Therefore, it helps to reduce costs.
[0028]
The wiring board 7 on which the Hall element 8 is mounted is fixed to the frame 5 constituting the outer shape of the casing of the liquid level sensor by screws or the like (not shown). A terminal 9 for outputting an electric signal corresponding to a liquid level converted from the magnetic flux density and related electric circuit components necessary for the surface level measurement is also mounted. A cover 10 is covered on the back side of the frame 5.
[0029]
In the configuration as described above, the float 1 moves according to the fluctuation of the liquid level. As the float 1 moves, the magnet holder 3 rotates via the arm 2, and accordingly, the magnet 4 held and accommodated in the magnet holder 3 also rotates. And a magnetoelectric conversion element detects the magnetic flux density by the magnet 4 which rotates according to the movement of the said float 1, and converts this into an electrical signal, The liquid level is measured based on this electrical signal It will be.
[0030]
Since the Hall element 8 of the main liquid level sensor that measures the liquid level by performing such an operation is disposed on the same plane as the magnet 4 and in the center of the magnet 4, the Hall element 8 of the main liquid level sensor is thin. Can be realized. That is, as can be seen by comparing FIG. 1 and FIG. 6, the liquid level sensor of the present embodiment of FIG. 1 has substantially no thickness a portion in the conventional liquid level sensor of FIG. Thinner. In addition, since a pair of cores or the like as a magnetic collecting member is not required as in the conventional device, the number of parts is reduced and the cost can be reduced. Further, since there is no fear of positional deviation between the Hall element 8 and the core, the measurement accuracy is improved.
[0031]
Next, the principle of liquid level detection by the liquid level sensor will be described with reference to FIGS. 4 (A) to 4 (C) are explanatory views showing the detection principle of the magnetic flux density that fluctuates according to the liquid level by the liquid level sensor. FIG. 5 is a graph showing the relationship between the magnet rotation angle and the Hall voltage.
[0032]
As shown in FIG. 4A, magnetic field lines as shown by arrows are generated from the north pole to the south pole of the annular magnet 4. As shown in FIGS. 4B and 5, the Hall element 8 has a positional relationship such that the detected magnetic flux density becomes 0 (T) when the magnet (magnet) rotation angle θ is 0 degrees. The magnet 4 is disposed almost at the center. With this arrangement, the detected magnetic flux density monotonously increases as the magnet 4 rotates at the magnet rotation angle θ as shown in FIG. 5 when the angle θ is between 0 and 90 degrees. It turns out that it decreases monotonically between 90 degrees and 180 degrees. The Hall voltage also shows similar characteristics.
[0033]
By utilizing such characteristics, the position of the float 1 corresponding to the rotation angle θ of the magnet 4 can be specified, so that the liquid level can also be measured. For example, in this embodiment, as shown in FIGS. 4B and 5, the magnetic flux density is substantially 0 (T) when the rotation angle θ is 0 degrees, and at this time, the liquid level is at the lowest level. The float 1 is initially set so that the range in which the angle θ increases monotonously between 0 ° and 90 ° corresponds to the lowest to highest liquid level.
[0034]
Thus, since the magnetic flux density is detected when the angle θ is between 0 ° and 90 ° and the liquid level is measured, the liquid level is finally calculated from the detected magnetic flux density. Is easy to process. The measurement range may be assigned when the angle θ is between 90 degrees and 180 degrees.
[0035]
As described above, according to the present embodiment, a liquid level sensor can be obtained in which the magnetic flux density detector is improved and thinned to achieve downsizing and cost reduction of the entire apparatus.
[0036]
【The invention's effect】
As described above, according to the first aspect of the present invention, the magnet holder is rotatably attached to the frame, and the magnetoelectric conversion element is flush with the magnet 4 and on the inner wall of the magnet at the center of the magnet 4. Since they are arranged directly opposite to each other, the structure of the magnetoelectric conversion part is simple and the liquid level sensor can be made thin. Furthermore, as described above, the arrangement of the magnetoelectric conversion element eliminates the need for a pair of cores as a magnetic collecting member as in the prior art, thereby reducing the number of parts and reducing the cost. . Furthermore, since the magnetic collecting member becomes unnecessary and there is no fear of positional deviation between the magnetoelectric conversion element and the magnetic collecting member, the measurement accuracy is improved. Furthermore, according to the first aspect of the present invention, the magnet holder is rotatably mounted on the frame so as to rotate about the center of the annular magnet as a virtual rotation axis. As a result, the complicated structure of rotating as the liquid level sensor becomes unnecessary, and the liquid level sensor can be reduced in cost and size. Further, according to the first aspect of the invention, the magnet 4 is annular, the magnetoelectric conversion element, because it is located in the center of the annular magnet 4 varies according to the rotation of the magnet 4 Since the magnetic flux density can be detected most effectively, the liquid level sensor can be easily manufactured, and the movement when rotating according to the movement of the float 1 is stabilized. Therefore, according to the first aspect of the present invention, it is possible to further reduce the cost and improve the measurement accuracy of the liquid level sensor.
[0039]
According to the second aspect of the invention, the magnetoelectric transducer detects the magnetic flux density in the range where the magnetic flux density of the magnet 4 that rotates with the movement of the float 1 corresponding to the liquid level increases monotonously. Thus, since the liquid level is measured, the processing until the liquid level is finally calculated from the detected magnetic flux density becomes easy.
[0040]
According to the third aspect of the present invention, since the magnetoelectric conversion element is the Hall element 8, it is widely spread and easily available, and the shortening of the manufacturing time can be promoted. Therefore, according to the invention of claim 3, further cost reduction can be achieved.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an outline of an embodiment of a liquid level sensor according to the present invention.
FIG. 2 is a plan view showing an overview of an embodiment of the liquid level sensor of the present invention.
3 is a perspective view schematically showing a detection unit of the liquid level sensor in FIG. 1; FIG.
FIGS. 4A to 4C are explanatory views showing the principle of detection of the magnetic flux density that fluctuates according to the liquid level by the liquid level sensor.
FIG. 5 is a graph showing a relationship between a magnet rotation angle and a Hall voltage.
FIG. 6 is a structural explanatory diagram showing an outline of a conventional liquid level sensor.
7 is a perspective view schematically showing a detection unit of the liquid level sensor in FIG. 6. FIG.
8 is a graph showing a relationship between a magnet rotation angle, a magnetic flux density, and a Hall voltage by the liquid level sensor of FIG.
[Explanation of symbols]
1 Float 2 Arm 3 Magnet holder 4 Magnet 5 Frame 7 Wiring board 8 Hall element 9 Terminal 10 Cover 21 Float arms 61-63 Flange prevention flange

Claims (3)

A float that floats on the liquid level and moves according to the liquid level;
An arm whose one end is locked to the float;
A magnet holder locked to the other end of the arm;
A frame on which the magnet holder is rotatably mounted;
A two-pole magnetized cylindrical magnet held and accommodated in the magnet holder;
A magnetoelectric conversion element attached to the frame so as to be arranged in the same plane as the magnet and directly opposed to the inner wall of the magnet at the center of the magnet;
Have
It changes according to the rotation angle of the magnet which rotates together with the magnet holder in accordance with the movement of the float, in Teisu Ru liquid level sensor measuring the liquid level on the basis of the electric signal which the magnetoelectric converting element and outputs There,
The liquid level sensor , wherein the magnet holder is rotatably mounted on the frame so as to rotate about the center of the annular magnet as a virtual rotation axis . The liquid level is measured by detecting, with the magnetoelectric transducer, the magnetic flux density in a range where the magnetic flux density of the magnet that rotates with the movement of the float according to the liquid level increases monotonously. The liquid level sensor according to claim 1 , wherein: Liquid level sensor according to claim 1 or 2, wherein the magnetoelectric converting element is characterized by a Hall element.

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