JP5995654B2 - Float type liquid level sensor - Google Patents

Description

  The present invention relates to a float type liquid level sensor.

  As an example of a float type liquid level sensor, a float to which a permanent magnet is fixed, a guide member that loosely fits the float and guides the raising and lowering of the float, and a magnetic sensor disposed above and below the guide member There is a type in which the liquid level is detected by a magnetic sensor detecting the magnetic flux density of a permanent magnet that moves up and down with the float.

  2A and 2B show a configuration example of a conventional float type liquid level sensor, where FIG. 2A is a longitudinal sectional view and FIG. 2B is a transverse sectional view. The liquid level detection device 1 is installed in an engine oil tank of an automobile and detects the level of engine oil. The liquid level detecting device 1 has a float 3 that moves up and down following a liquid level (engine oil level) F. The float 3 is made of foamed NBR (nitrile rubber), foamed PA66 (polyamide) or the like, and has a substantially cylindrical shape with an outer diameter of about 25 mm, an inner diameter of about 12 mm, and a vertical length (height) of about 15 mm. Above the inner peripheral surface 3n of the float 3, a concave groove 3h is formed that is recessed over the entire circumference of the inner peripheral surface 3n.

  The substantially ring-shaped permanent magnet 5 is fitted and fixed in the concave groove 3h so that the inner peripheral surface 3n of the float 3 and the inner peripheral surface 5n of the permanent magnet 5 are substantially flush with each other. Yes. The permanent magnet 5 is made of a rare earth magnet (neodymium magnet), and has an outer diameter of about 18 mm, an inner diameter of about 12 mm, and a vertical length (height) of about 10 mm. Further, the magnetic force is about 150 mT, the inner peripheral surface 5n side is uniformly magnetized to the N pole, and the outer peripheral surface 5g side is uniformly magnetized to the S pole. Therefore, magnetic lines of force as shown by broken lines and arrows in FIG. 2 are generated around the permanent magnet 5.

  Further, the liquid level detection device 1 includes a guide member 11 that guides the lifting and lowering of the float 3. The guide member 11 extends in the vertical direction, and has a substantially cylindrical stem portion 13 having a diameter of about 8 mm and a vertical length (height) of about 30 mm that is loosely inserted into the hole of the float 3. The stem portion 13 is made of a material such as PA66 (polyamide). Further, a substantially disc-shaped upper disc 15 and a lower disc 17 having a diameter of about 20 mm larger than the inner diameter of the float 3 and smaller than the outer diameter are fixed to the upper end and the lower end of the stem portion 13. Accordingly, the float 3 can freely move in the vertical direction along the stem portion 13, while the upper end disc portion 15 and the lower end disc portion 17 prevent the stem 3 (guide member 11) from being detached.

  A substantially rectangular plate-like substrate 19 having a horizontal length of about 7 mm, a vertical length of 28 mm, and a thickness of about 1 mm is inserted and fixed in the stem portion 13 of the guide member 11. Two Hall elements (first Hall element 21 and second Hall element 23), which are magnetic sensors, are fixed to one surface of the substrate 19 so as to be separated from each other in the vertical direction. The first Hall element 21 and the second Hall element 23 are spaced apart by about 8 mm, and the first Hall element 21 is fixed upward and the second Hall element 23 is fixed downward. These first and second Hall elements 21 and 23 have similar characteristics. That is, when a driving voltage is applied to the first and second Hall elements 21 and 23, a magnetic flux density that changes in accordance with the ascending / descending position of the permanent magnet 5 disposed on the float 3 following the liquid surface is detected, and the magnetic flux An electric signal corresponding to the density, more specifically, a voltage corresponding substantially linearly to the magnetic flux density is output. This output voltage is proportional to the drive voltage.

JP 2002-277308 A

  However, in the conventional liquid level detection device described above, when the permanent magnet inside the float is extremely close to the magnetic sensor, especially when measuring the low liquid level of the tank contents, the magnetic force detected by the magnetic sensor is detected. The direction is reversed, and accurate liquid level measurement is not possible. Further, since the float is loosely fitted to the guide member, the vertical position of the permanent magnet may change due to rattling of the float, and an error may occur in the detection output of the magnetic sensor.

  Therefore, an object of the present invention is to provide a float type liquid level sensor that can measure the liquid level with higher accuracy than in the past.

According to the first aspect of the present invention for solving the above-described problem, a float (32) to which a permanent magnet (31) is fixed, and the float (32) in which the float (32) is loosely fitted to follow the liquid level. ) And a magnetic sensor (34, 35) disposed above and below the guide member (33), wherein the float ( 32) has a predetermined inner diameter, outer diameter, and height, a disk part (321) that contacts the liquid surface, and an inner diameter and the disk of the same size communicating with the inner diameter of the disk part (321) has a smaller outer diameter than the section (321), through the disc portion (321) cylindrical portion integrally formed on the (322), Ri convex float der consisting the disc portion (321) A through hole (32 in the hole (321a) and the cylindrical portion (322); and the guide member (33) is passed through a), said permanent magnet (31), characterized in that fixed to the upper surface and outer periphery of the disk portion of the convex float (321) .

According to a second aspect of the present invention for solving the above-described problem, in the float type liquid level sensor according to the first aspect, the cylindrical portion (322) is located above the disc portion (321). Features.

  Note that the reference numerals in parentheses in the description of the means for solving the above-described problems correspond to the reference numerals of the constituent elements in the description of the mode for carrying out the invention below. It is not intended to limit the interpretation of the claims.

According to the first aspect of the present invention, since there is a protruding portion (cylindrical portion) of the convex float, the inclination (rattle) of the float with respect to the guide member can be suppressed as compared with the conventional one, and the liquid level is highly accurate Can be measured. Moreover, the upper limit of the measurable area | region of a liquid level can be set by adjusting the length of the protruding part (cylindrical part) of a convex float.
Further, since the permanent magnet is fixed near the upper surface and the outer periphery of the disk portion of the convex float, the distance between the magnetic sensor and the permanent magnet can be secured, and a low liquid level can be measured with high accuracy.

It is a longitudinal cross-sectional view which shows the structural example of one Embodiment of the float type liquid level sensor which concerns on this invention. The structural example of the conventional float type liquid level sensor is shown, (A) is a longitudinal cross-sectional view, (B) is a cross-sectional view.

  FIG. 1 is a longitudinal sectional view showing a configuration example of an embodiment of a float type liquid level sensor according to the present invention. The float type liquid level sensor 30 of the present invention includes a float 32 to which a permanent magnet 31 is fixed, a guide member 33 in which the float 32 is loosely fitted and guides the ascent and descent of the float 32 following the liquid level, and a guide member 33. Magnetic sensors 34 and 35 disposed on the upper and lower sides of the magnetic sensor. The float type liquid level sensor 30 is arranged in a tank 40 containing a liquid whose liquid level is to be measured so that the magnetic sensor 34 is above and the magnetic sensor 35 is below.

  The float 32 is a convex float that includes a disc portion 321 and a cylindrical portion 322 integrally formed on the disc portion 321 and has a convex cross-sectional shape. The disc portion 321 has a through-hole 321a formed in the center and has a predetermined inner diameter, outer diameter, and height, and its lower part is immersed in the liquid. The cylindrical portion 322 has a through-hole 322a having an inner diameter that is the same as the inner diameter of the through-hole 321a of the disc portion 321 and has an outer diameter smaller than the disc portion 321 and a height higher than the disc portion 321. Have

  The permanent magnet 31 is an annular magnet, and is fixed to the upper surface of the float disk portion 321 and in the vicinity of the outer periphery.

  The guide member 33 is a resin-made cylindrical member, for example, and has an outer diameter to which the float 32 is loosely fitted. A circuit board 36 is built in the guide member 33 from its upper end to its lower end. Magnetic sensors 34 and 35 are mounted near the upper and lower ends of the circuit board 36, respectively.

  When the float type liquid level sensor of the present invention having the above-described configuration is used, the permanent magnet 31 moves up and down together with the float 32 following the liquid level. The magnetic sensors 34 and 35 detect a magnetic flux density that changes in accordance with the raising and lowering of the permanent magnet 31, and output a detection voltage corresponding to the magnetic flux density. The detection voltages from the magnetic sensors 34 and 35 are input to a detection circuit (not shown), converted into a voltage corresponding to the liquid level, and output to the outside. For example, the liquid level is applied to a meter or the like installed in the interior of an automobile. Is displayed.

  According to the float type liquid level sensor of the present invention described above, the fluctuation of the liquid level at a lower liquid level can be detected by the convex float. Even at a liquid level below the thickness of the float disc, the float can be floated on the liquid level by adjusting the draft rate by increasing the float volume relative to the weight of the permanent magnet and float. Can be measured. Since the permanent magnet is fixed near the upper surface and the outer circumference of the disk part of the float, the distance between the lower magnetic sensor and the permanent magnet can be secured even at a low liquid level, and in the same way as above, Even at the surface level, the distance between the upper magnetic sensor and the permanent magnet can be secured, and it is prevented that the direction of the magnetic force detected by the magnetic sensor is reversed because the permanent magnet is too close to the magnetic sensor as in the conventional configuration. Therefore, the liquid level can be measured with high accuracy. In addition, since there is a protruding part (cylindrical part) of the convex float, the inclination (rattle) of the convex float with respect to the guide member caused by fluctuations in the liquid level and raising and lowering of the float is suppressed compared to the float of the conventional structure. The liquid level can be measured with higher accuracy. Furthermore, by adjusting the length of the protruding part (cylindrical part) of the convex float (for example, it is adjusted to 20% of the height inside the tank in FIG. 1), the measurable region of the liquid level can be measured. An upper limit can be set.

  As described above, one embodiment of the present invention has been described. However, the present invention is not limited to this, and various modifications and applications are possible.

  For example, in the above-described embodiment, the permanent magnet 31 is an annular magnet, but is not limited to an annular shape, and may have another shape.

  Further, according to the present invention, the inclination (with backlash) of the refloat 32 is suppressed by adding the cylindrical portion 322 of the convex float. The relationship between the distance between the magnet 31 and the central axis of the guide member 33 and the overall height of the convex float (the total height of the height of the disk portion 321 and the height of the cylindrical portion 322) The detection error when the upper and lower inner peripheries of the float 32 are in contact with the upper and lower outer peripheries of the guide member 33 while tilting to the maximum may be set so as to fall within an allowable error range for measuring the liquid level.

  The float 32 may be made of a foamed resin material such as foamed nitrile rubber, and a permanent magnet may be embedded therein.

DESCRIPTION OF SYMBOLS 30 Float type liquid level sensor 31 Permanent magnet 32 Float 321 Disc part 321a Through hole 322 Cylindrical part 322a Through hole 33 Guide member 34 Magnetic sensor 35 Magnetic sensor 36 Circuit board 40 Tank

Claims (2)

A float type having a float to which a permanent magnet is fixed, a guide member for loosely fitting the float and guiding the raising and lowering of the float following the liquid level, and a magnetic sensor disposed above and below the guide member A liquid level sensor,
The float has a predetermined inner diameter, outer diameter, and height, a disk portion that contacts the liquid surface, an inner diameter of the same dimension that communicates with the inner diameter of the disk portion, and an outer diameter that is smaller than the disk portion. a, a cylindrical portion integrally formed on the disc portion, Ri convex float der consisting
The guide member is passed through the through hole of the disk part and the through hole of the cylindrical part,
The float type liquid level sensor , wherein the permanent magnet is fixed to the upper surface of the convex float and the vicinity of the outer periphery . In the float type liquid level sensor according to claim 1,
The float type liquid level sensor, wherein the cylindrical part is located above the disk part .

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