JP2002206959A - Liquid level sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid level sensor achieving miniaturization of an entire device and cost reduction. SOLUTION: A magnet holder 3 rotates via an arm 2 as a float 1 moves according to the level of liquid, and a magnet 4 held in the magnet holder 3 also rotates accordingly. A Hall element 8 detects the density of magnetic flux produced by the magnet 4 rotated according to the movement of the float 1, and converts it into an electric signal whereby the level of the liquid is measured based on the electric signal. In this liquid level sensor which measures the level of the liquid through such action, the Hall element 8 is positioned on the same plane as the magnet 4 and at the center of the magnet 4, whereby the liquid level sensor can be made thinner.

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, and more particularly, to a non-contact type liquid level sensor using a magnetoelectric conversion element.

[0002]

2. Description of the Related Art This type of liquid level sensor is, for example,
It is used as a level sensor for monitoring the fuel level of 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 corresponding to the liquid level generated by the magnet are converted into an electric signal by a magnetoelectric conversion element such as a Hall element. By performing the conversion, the liquid level is detected.

However, in the conventional liquid level sensor,
The Hall element is disposed in a gap of a core as a magnetic flux collecting member having a shape obtained by dividing a cylinder into two layers in a layer shape on the annular magnet. That is, it is difficult to reduce the thickness of this portion due to the thickness of the core and the annular magnet added. Further, the above-mentioned one set of cores is also 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. 6 to 8. 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.

As shown in FIG. 6, the conventional liquid level sensor is fixed to a part of the inner wall of the container to detect the liquid level of the liquid LQ in the container TNK. And
The float 101 is connected to a magnet holder 103 via a bar-shaped arm 102. Float 101
Is formed of a member having a buoyancy with respect to the liquid LQ for measuring the liquid level, and has a cylindrical shape. One end of the arm 102 is connected to the float 101 through the center of the float 101.

An annular magnet 104 is attached to the inner side of the magnet holder 103 using an adhesive or the like, and an outer side is provided with an arm holding portion for holding the other end of the arm 102. Magnet holder 103
Is rotatably mounted on a rotating shaft 111 formed integrally with the frame 105 via a rotating shaft 106 fixed by a bush 112. With such a structure, the magnet 104 moves the float 10 that moves according to the liquid level.
1 and rotates about the rotation shaft 106. Note that the magnet 104 is a ring-shaped permanent magnet having two poles on one side.

Further, a pair of cores 110 (cores 110A and 110B) each having a shape obtained by dividing a cylinder into two are arranged on the inner wall of the frame 105 at a position facing the magnet 104. In the gap, the Hall element 108 has a positional relationship as shown in FIG.
And is fixed to the frame 105 via. An electric signal based on the magnetic flux density detected by the Hall element 108 is supplied to the outside via the terminal 109. Note that the molding agent 113 is provided inside the frame 105.
Is filled.

The Hall element 108, the core and the magnet 104 constitute a magnetic flux density detecting section as shown in FIG. 7, and rotate in the direction shown by the arrow in the figure according to the liquid level fluctuation. The magnetic flux density of the magnet 104 fluctuating with the 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, the magnetic flux density, and the Hall voltage of the magnet 104 changes linearly with respect to the rotation angle (a range from -90 degrees to +90 degrees). The liquid level is measured using this characteristic.

[0009]

By the way, in the above-mentioned conventional liquid level sensor, as shown in FIG. 6, the core 110 is arranged in a layer on the annular magnet 104. As shown in FIG. That is, the thickness a (holder height) generated by the magnet 104 and the magnet holder 103, and the thickness b of the frame 105 containing the core.
(A frame height) plus the thickness a + b is required at least in the conventional liquid level sensor. Because of the thickness a + b, it was difficult to reduce the thickness of the conventional liquid level sensor. Further, the set of cores 110A,
110B was also required, the structure was complicated, the number of parts was increased, and the cost was high.

In view of the above-mentioned situation, it is an object of the present invention to provide a liquid level sensor in which the above-described detection unit is improved and thinned, and the entire apparatus is reduced in size and cost is reduced.

[0011]

According to a first aspect of the present invention, there is provided a liquid level sensor, comprising:
As shown in FIG. 3, a float 1 formed of a member having a buoyancy with respect to a liquid LQ whose liquid level is to be measured, a cylindrical magnet 4 magnetized with two poles, and a magnet 4
A magnet holder 3 for rotatably holding and housing
The arm 2 connecting the float 1 and the magnet holder 3 is arranged on the same plane as the magnet 4 and at the center of the magnet 4, and with the movement of the float 1 according to the liquid level, A magneto-electric conversion element that detects a magnetic flux density of the magnet 4 that rotates together with the magnet holder 3 and converts the magnetic flux density into an electric signal;
The liquid level is measured based on the electric signal.

According to the first aspect of the present invention, the float 1 moves according to the fluctuation of the liquid level. This float 1
The magnet holder 3 is rotated via the arm 2 in accordance with the movement of the arm, so that the cylindrical magnet 4 held and accommodated in the magnet holder 3 is also rotated. Then, the magnetoelectric conversion element detects the magnetic flux density of the magnet 4 that rotates according to the movement of the float 1 and converts the magnetic flux density into an electric signal, whereby the liquid level is measured based on the electric signal. . Since the magnetoelectric conversion element of the present liquid level sensor that measures the liquid level by performing such an operation is disposed on the same plane as the magnet 4 and at the center of the magnet 4, the thin liquid level sensor of the present liquid level sensor is provided. Becomes possible. Further, since a pair of cores or the like as a magnetic flux collecting member as in the related art becomes unnecessary, the number of parts is reduced,
The cost can be reduced. Further, since there is no need to worry about a displacement between the magnetoelectric conversion element and the magnetic flux collecting member, the measurement accuracy is improved.

According to a second aspect of the present invention, there is provided a liquid level sensor according to the first aspect, wherein the magnet is formed in a circular shape. It is characterized by being annular.

According to the second aspect of the present invention, since the magnet 4 is annular, manufacture is easy, and the float 1
The movement at the time of turning according to the movement of is stabilized. Therefore, according to the second aspect of the present invention, the cost can be further reduced and the measurement accuracy can be further improved.

According to a third aspect of the present invention, there is provided a liquid level sensor according to the second aspect, wherein the magnetoelectric conversion element includes: It is characterized in that it is arranged at the center of the annular magnet 4.

According to the third 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 in accordance with the rotation of the magnet 4 can be most effectively reduced. Can be detected. Therefore, according to the third aspect of the invention, the measurement accuracy can be further improved.

According to a fourth aspect of the present invention, there is provided a liquid level sensor according to the third aspect, wherein the liquid level sensor comprises:
By detecting the magnetic flux density in a range where the magnetic flux density of the magnet 4 that rotates according to the movement of the float 1 according to the liquid level monotonically increases by the magnetoelectric conversion element, the liquid level is detected. Is measured.

According to the fourth aspect of the present invention, 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 according to the liquid level monotonically increases is determined by the magnetoelectric conversion element. Since the liquid level is measured by the detection, the processing until the final calculation of the liquid level from the detected magnetic flux density becomes easy.

According to a fifth aspect of the present invention, there is provided a liquid level sensor according to the fourth aspect, wherein the magnetoelectric conversion element has a hole. Element 8 is characterized.

According to the fifth aspect of the present invention, since the magnetoelectric conversion element is the Hall element 8, the magnetoelectric conversion element is widely used, easily available, and can reduce the manufacturing time. Therefore,
According to the invention of claim 5, the cost can be further reduced.

[0021]

Embodiments of the present invention will be described below 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 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 one embodiment of the liquid level sensor of the present invention. FIG.
FIG. 4 is a perspective view schematically showing a detection unit of the liquid level sensor of FIG.

As shown in FIG. 1, the present liquid level sensor detects the liquid level of the liquid LQ in the container TNK, so that a part of the inner wall of the container TNK waterproofs the internal electric circuit. Is fixed. And float 1
Is connected to the magnet holder 3 via the arm 2. The float 1 is formed of a member having a buoyancy with respect to the liquid LQ for measuring the liquid level, and has a cylindrical shape. The arm 2 is formed of an elongated rod-shaped metal such as stainless steel. One end of the arm 2 is connected to the float 1 through the center of the float 1.

The magnet holder 3 has an accommodating portion for accommodating the annular magnet 4 on the inside, and holds the other end (float arm 21) of the arm 2 in a T-shape on the outside. It has an arm holding part 31. The magnet holder 3 is formed of a non-magnetic material, and its outer shape is such that the arm holding portion 31 is provided at the outer central portion of a cylindrical shape slightly larger than the outer shape of the magnet 4 housed therein. I have. The arm 2 connected to the float 1 via the arm holding portion 31
Is also connected to the magnet holder 3.

As shown in FIG. 2, the magnet holder 3 holds an imaginary rotating shaft formed by these three retaining flanges 61, 62, 63 of the frame 5 arranged at every 120 degrees while holding them. It is mounted on the frame 5 so as to be rotatable about the center. The detachment prevention flange 63 is detachable from the frame 5. When the magnet holder 3 is incorporated into the frame 5, the detachment prevention flange 63 is positioned after the magnet holder 3 is positioned at a predetermined position on the frame 5. Be attached. The detachment prevention flanges 61 and 62 are connected to the frame 5.
And may be detachable from the frame 5 as in the case of the detachment prevention flange 63. Θ shown in FIG.
Is a magnet holder 3 that rotates according to the liquid level.
Is the rotation angle of the magnet 4 housed in the magnet.

The accommodating portion of the magnet 4 of the magnet holder 3 has a cylindrical inner diameter corresponding to the outer shape of the annular magnet 4. And the magnet 4
It is fixed to this housing portion using an adhesive or the like. With such a structure, the magnet 4 rotates around the rotation axis in conjunction with the float 1 that moves according to the liquid level. The magnet 4 is a ring-shaped permanent magnet with two poles. As described above, since the magnet 4 is annular, it is easy to manufacture, and the movement when the float 1 rotates in accordance with the movement of the float 1 is stabilized, and the measurement accuracy is improved.

At the center of the annular magnet 4, a magnetoelectric conversion element is mounted on the wiring board 7 and fixedly arranged. This magnetoelectric conversion element detects the magnetic flux density by the magnet 4 that rotates according to the liquid level,
This is converted into an electric signal and output. For example, a known Hall element 8 is used. The Hall element 8 and the magnet 4 are used in the present liquid level sensor.
A magnetic flux density detection unit is configured, and as shown in FIG.
The Hall element 8 is fixedly arranged at the center of the annular magnet 4. Since the magnet 4 rotates in the direction indicated by the arrow in the figure 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 liquid level measurement. You.

Since the Hall element 8 is disposed at the center of the annular magnet 4 as described above,
The most effective detection of the magnetic flux density that changes according to the rotation of. Therefore, the measurement accuracy can be further improved. In addition, since the Hall element 8 is widely spread and easily available, the reduction of the manufacturing time can be promoted. Therefore, it helps to reduce costs.

The wiring board 7 on which the above-mentioned Hall element 8 is mounted is fixed to a frame 5 constituting the outer shape of the housing of the present liquid level sensor by screws or the like (not shown). Also, a terminal 9 for outputting related electric circuit components necessary for the liquid level measurement and an electric signal corresponding to the liquid level converted from the magnetic flux density to the outside is mounted. A cover 10 is provided on the back side of the frame 5.

In the above-described configuration, the float 1 moves according to a change in the liquid level. In response to the movement of the float 1, the magnet holder 3
Rotates, so that the magnet holder 3
The magnet 4 held and accommodated also rotates. Then, the magnetoelectric conversion element detects the magnetic flux density of the magnet 4 that rotates according to the movement of the float 1 and converts the magnetic flux density into an electric signal, whereby the liquid level is measured based on the electric signal. Will be.

The Hall element 8 of the present liquid level sensor for measuring the liquid level by performing the above operation is provided by the magnet 4
And the liquid level sensor is arranged at the center of the magnet 4, so that the liquid level sensor can be made thinner. That is, as can be seen by comparing FIGS. 1 and 6, FIG.
In the liquid level sensor of the present embodiment, the portion of the conventional liquid level sensor shown in FIG. Further, since a pair of cores and the like as a magnetic flux collecting member as in the conventional device is not required, the number of parts is reduced, and the cost can be reduced. Furthermore, since there is no need to worry about a displacement between the Hall element 8 and the core, the measurement accuracy is improved.

Next, the principle of liquid level detection by the present liquid level sensor will be described with reference to FIGS. FIGS. 4A to 4C are explanatory views showing the principle of detecting the magnetic flux density that varies according to the liquid level by the present liquid level sensor. FIG. 5 is a graph showing the relationship between the magnet rotation angle and the Hall voltage.

As shown in FIG. 4A, lines of magnetic force are generated from the north pole to the south pole of the annular magnet 4 as indicated by arrows. 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 degree. It is arranged substantially at the center of the magnet 4. With this arrangement, the detected magnetic flux density is changed as the magnet 4 rotates at the magnet rotation angle θ.
As shown in FIG. 5, it can be seen that the angle monotonically increases when the angle θ is between 0 degree and 90 degrees, and monotonically decreases when the angle θ is between 90 degrees and 180 degrees. Further, the Hall voltage shows similar characteristics.

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 the present embodiment, as shown in FIGS. 4B and 5, when the rotation angle θ is 0 degree, the magnetic flux density is almost 0 (T).
And at this time, the float 1 is initially set so that the liquid level is at the lowest level, and the range in which the angle θ monotonically increases between 0 degree and 90 degrees is defined as the lowest level of the liquid level. Try to meet from top to top.

As described above, since the liquid level is measured by detecting the magnetic flux density when the angle θ is between 0 ° and 90 °, the liquid level is finally determined from the detected magnetic flux density. Processing until calculation is facilitated. In addition,
The measurement range may be allocated when the angle θ is between 90 degrees and 180 degrees.

As described above, according to the present embodiment, it is possible to obtain a liquid level sensor in which the magnetic flux density detecting section is improved and thinned, and the entire apparatus is reduced in size and cost is reduced.

[0036]

As described above, according to the first aspect of the present invention, since the magnetoelectric conversion element is arranged on the same plane as the magnet 4 and at the center of the magnet 4,
The liquid level sensor can be made thinner. Further, as described above, by arranging the magnetoelectric conversion elements, a pair of cores or the like as a magnetic flux collecting member as in the related art is not required, so that the number of parts is reduced and cost can be reduced. . Further, since there is no need to worry about a displacement between the magnetoelectric conversion element and the magnetic flux collecting member, the measurement accuracy is improved.

According to the second aspect of the present invention, since the magnet 4 is annular, it is easy to manufacture and the float 1
The movement at the time of turning according to the movement of is stabilized. Therefore, according to the second aspect of the present invention, the cost can be further reduced and the measurement accuracy can be further improved.

According to the third aspect of the present invention, since the magnetoelectric conversion element is arranged at the center of the annular magnet 4, the magnetic flux density that changes according to the rotation of the magnet 4 can be most effectively reduced. Can be detected. Therefore, according to the third aspect of the invention, the measurement accuracy can be further improved.

According to the fourth aspect of the present invention, 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 according to the liquid level monotonically increases is determined by the magnetoelectric conversion element. Since the liquid level is measured by the detection, the processing until the final calculation of the liquid level from the detected magnetic flux density becomes easy.

According to the fifth aspect of the present invention, since the magnetoelectric conversion element is the Hall element 8, the magnetoelectric conversion element is widely used, easily available, and can reduce the manufacturing time. Therefore,
According to the invention of claim 5, the cost can be further reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an outline of an embodiment of a liquid level sensor of the present invention.

FIG. 2 is a plan view showing an overview of an embodiment of a liquid level sensor according to the present invention.

FIG. 3 is a perspective view schematically showing a detection unit of the liquid level sensor of FIG. 1;

FIGS. 4A to 4C are explanatory views showing the principle of detecting a magnetic flux density that fluctuates according to the liquid level by the present 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 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. 6;

8 is a diagram showing a magnet rotation angle by the liquid level sensor of FIG. 6,
4 is a graph showing a relationship between a magnetic flux density and a Hall voltage.

[Explanation of symbols]

 DESCRIPTION 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 arm 61-63 Flanging prevention flange

Claims (5)

[Claims] 1. A float formed of a member having a buoyancy with respect to a liquid for measuring a liquid level, a cylindrical magnet magnetized with two poles, and a magnet for rotatably holding and housing the magnet. A holder, an arm connecting the float and the magnet holder, and a magnet arranged along the same plane as the magnet and at the center of the magnet, with the movement of the float according to the liquid level. And a magnetic-electric conversion element that detects a magnetic flux density of the magnet that rotates together with the magnet and converts the detected magnetic flux into an electric signal, and measures the liquid level based on the electric signal. 2. The liquid level sensor according to claim 1, wherein the magnet has an annular shape. 3. The liquid level sensor according to claim 2, wherein the magnetoelectric conversion element is arranged at a center of the annular magnet. 4. The liquid level sensor according to claim 3, wherein the magnetic flux density in a range in which the magnetic flux density of the magnet that rotates with the movement of the float according to the liquid level monotonically increases is: A liquid level sensor, wherein the liquid level is measured by detecting with the magnetoelectric conversion element. 5. The liquid level sensor according to claim 4, wherein the magnetoelectric conversion element is a Hall element.