JP2002107205A - Sensor for liquid level - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems that since the basic constitution of a conventional contact type moving part can not be used as it is, it takes a long time to build a reliable product, and the specified accuracy can not be obtained without coincidence of the rotation center of a float arm 21 with the center position of a magnet. SOLUTION: This sensor for a liquid level is equipped with the float arm fitted with a float displacing up and down according to the vertical motion of a liquid level and rotating on the rotating shaft according to the vertical motion of the float; a magnet fit to the vicinity of the rotation center of the float arm so that a magnetic field is generated in the direction crossing to the float arm; a liquid level detecting means arranged facing the magnet and detecting the liquid level according to the variation of the magnetic field strength varying according to the rotation of the magnet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid level detecting device,
In particular, the liquid level sensor is mounted in a gasoline tank of an automobile and detects a liquid level in the tank.

[0002]

2. Description of the Related Art Conventional liquid level sensors of this type include:
17 to 20 shown in Japanese Utility Model Publication No. 2-34584. That is, the bracket 2 attached to the back side of the lid 1 closing the opening of the fuel tank.
, A synthetic resin housing 3 is fixed,
A bearing 4 is provided integrally with the housing 3, and a bent end 6 at the base end of the float arm 5 is inserted into a bearing hole 4 ′ of the bearing 4. The housing 3 is integrally provided with a pair of columns 7, 7 extending in the same direction as the bearing hole 4 ', and the ends of the columns 7, 7 extend from the end face of the bearing 4 to the bearing hole 4'. The engagement claws 8 are provided at predetermined intervals in the axial direction.

After the bent end 6 of the float arm 5 is inserted into the through hole 10 provided in the resin rotary piece 9, the float arm 5 is fixed to the rotary piece 9 by the stopper claw 11. I have. Further, the bent end 6 of the float arm 5 penetrates through the bearing hole 4 ′ of the bearing 4, and the base end of the rotating piece 9 is fitted between the bearing 4 and the engagement claw 8 to fit the housing 3 On the other hand, the rotating piece 9 is rotatably held.

In FIG. 19, a resistance plate 14 fixed to the housing 3 by two pairs of fixed claws 13 on the left and right sides.
A resistor pattern 16 and a conductor pattern 17 connected to the pattern 16 are baked on a ceramic substrate 15, and the contact 18 is slid on the resistor pattern 16. That is, as the float 19 rises in liquid level, the float arm 5 generates clockwise turning power, and the liquid level is detected by sliding the contact 18 on the resistance pattern 16. is there.

However, in recent years, the contact 18
Instead of a sensor which detects the liquid level by sliding on the resistance pattern 16, a non-contact type liquid level sensor having no contact, for example, as disclosed in JP-A-8-94413, has been developed. I am trying to do.

This is, as shown in FIGS. 21 and 22,
For example, a rotary shaft 22 integrally formed on the rear end of a float arm 21 having a front end connected to a float 20 floating on a liquid surface such as water or gasoline and rotatably supported, and a rotatably supported rotary shaft 22. Resin housing 23 and the rotating shaft 2
A magnet 24 embedded coaxially with the back end of the float arm 21 with one side exposed at the rear end thereof, and a magnetoresistive element 25 coaxially opposed to the rotating shaft 22 of the magnet 24. The float arm 21 rotates in response to the float 20 that is displaced upward or downward in accordance with the displacement of the liquid level, and the magnet 2
The amount (magnetic field intensity) of the magnetic flux emitted from the magnetic flux line 4 passing through the magnetoresistive element 25 changes, and the liquid level is detected.

[0007]

As described above, when a liquid level sensor is constructed by using the magnet 24 and the magnetoresistive element 25, for example, it is necessary to form the magnet 24 in a disk shape. Since the shape of the shaft 22 is greatly different, the basic configuration of the conventional contact type movable portion cannot be used as it is, and much time is required to produce a reliable product.

In this case, since a predetermined accuracy cannot be obtained unless the center of rotation of the float arm 21 and the center position of the magnet 24 are made to coincide with each other, a high mounting accuracy is required. There were problems such as taking time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to obtain a liquid level sensor which does not require high mounting accuracy of a magnet while maintaining the conventional basic shape of a movable portion. And

[0010]

According to the present invention, there is provided a float arm mounted with a float which is vertically displaced in accordance with a vertical movement of a liquid surface, and which rotates about a rotation axis in accordance with the vertical movement of the float; A magnet mounted near the center of rotation of the float arm so as to generate a magnetic field in a direction intersecting with the float arm, and a change in magnetic field intensity which is arranged opposite to the magnet and changes with the rotation of the magnet. And a liquid level detecting means for detecting the liquid level.

The magnet can be accurately detected by disposing the magnet so as to move in a plane parallel to the axis of rotation of the float arm, facing the liquid level detecting means.

Further, by arranging the float arm between the N pole and the S pole of the magnet, a practical liquid level can be detected even if the float arm is a magnetic material. In this case, if the float arm is attached so as to match the magnetic neutral point formed between the magnetic poles of the magnet, even if the float arm is made of a magnetic material, the effect can be completely eliminated.

Further, as a material of the float arm, an extremely inexpensive and proven iron lot rod (magnetic rod) which has been conventionally used as a float arm material can be used, so that an increase in cost can be prevented.

[0014]

Next, an embodiment according to the present invention will be described. Embodiment 1 FIG. This will be described with reference to FIGS. That is, reference numeral 30 denotes a lid for closing the opening of the fuel tank A (not shown), and a bracket 31 is provided on the back side of the lid 30 so as to hang down from the lid 30. A housing 32 made of synthetic resin is screwed to the front end side of the bracket 31 by screws 33. The housing 32 is provided with a bearing hole 34 ′ constituting a bearing 34.
Nine rotating shafts 39b are rotatably inserted.

That is, the resin rotating piece 39 is integrally formed with a holding portion 39a and a rotating shaft portion 39b projecting perpendicularly from an end of the holding portion 39b. Is provided with a plurality of claws 39d for holding,
By the holding claw 39d, the magnetic float arm 35 with the float 42 attached to the tip is rotated by the rotating piece 3.
9 and the bent end 35a of the base end of the float arm 35 is fitted into a through hole 40 formed so that the center axis coincides with the rotation axis of the rotation shaft 39b.

At the center of the holding portion 39a of the resin rotary piece 39, a pair of wings 3 is provided in which a rectangular magnet 41 is embedded so as to be orthogonal to the longitudinal direction of the holding portion 39a.
9c is provided, and the embedment position of the rectangular magnet 41 straddles a pair of wings 39c, and is magnetized such that one tip is an N pole and the other tip is an S pole. I have. Since the float arm 35 is attached so as to coincide with a magnetic neutral point (a point that is neither an N pole nor an S pole) formed in the center of the rectangular magnet 41 in the longitudinal direction, the float arm Even if the material of 35 is a magnetic material, there is no magnetic influence.

Reference numeral 42 denotes a circuit board on which a Hall element 43 for detecting the intensity of a magnetic field formed by the magnet 41 is mounted and housed in the housing 32. That is, the Hall element 43 includes a point E (empty point) indicating the lowest liquid level and a point F (full point) indicating the highest liquid level when the float arm 35 moves up and down the liquid level in the tank A. ) (Indicated by the symbol θ in FIG. 2), the output voltage (according to the characteristic curve Z) is changed as shown in FIG. It should be noted that the characteristic Z is affected by the ambient temperature and rises as shown by a characteristic curve X when the ambient temperature is lowered, and the slope becomes smaller as shown by a characteristic curve Y when the ambient temperature is increased. O is not affected by its ambient temperature and becomes a neutral point.

Reference numeral 45 stands upright so as to face the periphery of the bearing hole 34 'formed in the housing 32.
A pair of columns 37 extending in the same direction as the bearing hole 34 '.
An engaging claw 45a is formed integrally with the housing 32, and is provided at a tip end of each of the pair of columns 45 with an engaging claw 45a protruding in a direction facing each other. The float arm 35 is prevented from detaching from the housing 32 by engaging with the end face of the rotating shaft portion 39b which forms the base flat surface of 39.

With this configuration, when the magnet 41 is located at the position corresponding to the point E (empty point), the positional relationship between the Hall element 43 and the magnet 41 is as shown in FIG. In FIG. 2, when the position coincides with the position of the Hall element 43,
When the liquid level in the tank A changes between the point E indicating the lowest liquid level and the point F indicating the highest liquid level, the Hall element 43 From Figure 6
An output voltage is obtained as shown in FIG.

As shown in FIG. 8, the rectangular magnet 41 passes through a magnetic neutral point (middle position between the north pole and south pole) formed at the center in the longitudinal direction of the magnet 41, and When the float arm 35 having magnetism such as iron is attached in a direction perpendicular to the longitudinal direction of the magnet 41 as described above, the float arm 35 attracts the magnets 41 with the attraction force F1, F2 from the N pole and the attraction force from the S pole. Force F
3, F4 becomes the same, that is, a state in which it is not magnetically affected. If this is paradoxically seen, magnet 4
No. 1 is not affected by the float arm 35 even if there is a float arm 35 having a magnetic material in the vicinity. Further, even if the magnetization amount varies during mass production of the magnet 41, the magnetic neutral points of the magnet 41 are all generated at the same neutral position, so that the float arm 35 can be reliably positioned at the center position. Magnetic influence by the float arm 35 can be prevented.

Next, a circuit for processing an electric signal output from the Hall element 43 will be described with reference to FIG.
That is, the output signal from the Hall element 43 is supplied to the correction circuit 48 via the differential amplifier 47,
Then, the display 50 is driven by correcting the temperature based on a temperature signal from a thermistor 49 that is arranged near the Hall element 43 and detects the temperature of the Hall element 43. In addition,
Reference numeral 51 denotes a battery.

Embodiment 2 FIG. In the first embodiment, the magnet 41 is configured to be embedded in the pair of wings 39d. However, in this embodiment, as shown in FIGS. The entire 39d may be made of a magnet, that is, a so-called plastic magnet. Alternatively, the rotating piece 39 may be formed of a resin containing magnetic powder, and thereafter, only the pair of wing portions 39d may be partially magnetized to be magnetized. Thereby, the number of parts can be reduced.

Embodiment 3 FIG. In the first embodiment, the magnet 41 is configured as a rectangular parallelepiped in which all surfaces are flat. However, as shown in FIGS. 11 and 12, the magnetically neutral position described above, that is, the center of the magnet 41 in the longitudinal direction is used. A single groove 41a is provided at the position so as to cross the magnet 41, and the float arm 35 is disposed in the groove 41a, so that the thickness T in a state where the magnet 41 is assembled to the float arm 35 is provided. Can be reduced.

Embodiment 4 In the first and third embodiments, one rectangular magnet 41 is configured to be embedded in the pair of wings 39c. However, the magnet 41 is divided as shown by reference numerals 41a and 41b in FIGS. Then, one may be provided for each of the pair of wing portions 39c. Thus, the weight of the magnet 41 in a state where the magnet 41 is incorporated in the yoke 39 can be reduced.

Embodiment 5 FIG. In the fifth embodiment shown in FIGS. 15 and 16, when the float arm 35 is located at the position corresponding to the point E, the Hall element 43 is located at the position where the magnetic neutral point O of the magnet 41 coincides. It is set as follows. As a result, only the characteristic on the right side of the neutral point is used in FIG. 6A, and the characteristic on the left side is not used. Accordingly, the characteristic curve at this time is shown in FIG.
As shown in (B), indicating that the fuel level is low, the "E" point of the fuel gauge, which is very important in using the vehicle, is fixed at a fixed point irrespective of the ambient temperature. It can be.

[0026]

As described above, since there is no need to make the center of rotation of the float arm coincide with the position of the magnet, the degree of freedom in layout is increased. The mechanical sliding part that has been used can be used as it is, the reliability of the mechanical sliding part can be secured, and development can be performed in a short time. Use of a magnetic material for the float arm does not affect the detection accuracy,
It is possible to use an iron arm material that has been used, and it is not necessary to use an expensive non-magnetic material such as stainless steel, thereby suppressing an increase in cost.

[Brief description of the drawings]

FIG. 1 is an overall configuration explanatory diagram for describing Embodiment 1 of the present invention.

FIG. 2 is an enlarged explanatory view of a main part in FIG. 1;

FIG. 3 is a sectional view taken along the line AA in FIG. 2;

FIG. 4 is an explanatory diagram illustrating a state in which a magnet 41 is embedded in a rotating piece 39 in FIG.

FIG. 5 is an explanatory cross-sectional view along AA in FIG. 4;

6A is an output characteristic diagram of the Hall element 42 when the float arm 35 is rotated from the point E to the point F in FIGS. 1 and 2, and FIGS. In FIG. 2, the float element 35 is connected to the Hall element 42 by “E”.
FIG. 9 is a characteristic diagram when the magnet 43 is arranged at a position that coincides with the magnetic neutral point of the magnet 43 when located at a point. FIG. 4 is a diagram showing that the position of the neutral point does not change even when the amount of magnetization of the magnet 41 varies.

FIG. 7 is a circuit block diagram illustrating a signal processing circuit for an output signal from a Hall element 43.

FIG. 8 is an explanatory diagram for explaining a magnetic neutral point.

FIG. 9 is an explanatory diagram for describing Embodiment 2;

FIG. 10 is a cross-sectional view taken along the line AA in FIG.

FIG. 11 is an explanatory diagram for describing Embodiment 3;

FIG. 12 is a sectional view taken along the line AA in FIG. 11;

FIG. 13 is an explanatory diagram for describing Embodiment 3;

FIG. 14 is an explanatory sectional view taken along the line AA in FIG. 13;

FIG. 15 is an explanatory view of the overall configuration of a conventional contact type device.

FIG. 16 is an explanatory sectional view showing a contact structure in FIG. 15;

FIG. 17 is an explanatory plan view showing a contact structure in FIG. 15;

FIG. 18 is an explanatory cross-sectional view for explaining the substrate mounting structure in FIG. 15;

FIG. 19 is an explanatory view of the entire structure of a conventional contactless type.

20 is an explanatory sectional view of FIG. 19;

FIG. 21 is a diagram illustrating a use state of a conventional liquid level sensor.

FIG. 22 is a longitudinal sectional view of a conventional liquid level sensor.

[Explanation of symbols]

 1,30 Lid 2,31 Bracket 3,23,32 Housing 4,34 Bearing 4 ', 34' Bearing hole 5,21,35 Float arm 6 Folded end 7,45 Support 8,45a Engagement claw 9,39 Resin Rotating piece 10 Through hole 11 Stopping claw 13 Fixed claw 14 Resistor plate 15 Ceramic substrate 16 Resistance pattern 17 Conductor pattern 18 Contact 19, 20, 42 Float 22 Rotation axis 24, 41, 41a, 41b Magnet 25 Magnetic resistance element 39a Holder 39b Rotating shaft 39c Wing 42 Circuit board 43 Hall element 41a Groove

Claims (5)

[Claims] A float that is vertically displaced in accordance with the vertical movement of the liquid surface, is mounted on the float arm, and rotates about an axis of rotation in accordance with the vertical movement of the float; and a vicinity of the rotation center of the float arm. A magnet mounted so as to generate a magnetic field in a direction intersecting with the float arm, and the liquid level being changed in accordance with a change in the magnetic field intensity which is arranged to face the magnet and changes with the rotation of the magnet. A liquid level sensor comprising: 2. The liquid according to claim 1, wherein the magnet is arranged so as to move in a plane parallel to the plane of rotation of the float arm, facing the liquid level detecting means. Surface level sensor. 3. The liquid level sensor according to claim 2, wherein said float arm is positioned between magnetic poles of said magnet. 4. The liquid level sensor according to claim 3, wherein said float arm is attached so as to coincide with a magnetic neutral point formed between magnetic poles of said magnet. 5. The liquid level sensor according to claim 4, wherein said float arm is formed of a magnetic material.