JP2006029804A - Liquid level detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress erroneous detection consequent upon a change in posture or vibration of a float as to a liquid level detector for detecting the level of a liquid in a container. <P>SOLUTION: This liquid level detector is provided with a load detection means 3 fixed at an under part in a fuel tank 2, the float 5 for receiving buoyancy acting on fuel 4, and an elastic body 14 as a biasing means for downwardly biasing the float 5 to press it against the detection means 3. A force, obtained by subtracting the buoyancy from a downward biasing force caused to act on the float 5 by the elastic body 14, is adapted to act on the detection means 3 as a downward force. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid level detection device.

  Conventionally, various liquid level detection devices have been proposed. Patent Document 1 discloses a liquid level detection device as an example.

  The liquid level detection device of the above publication is a device that detects the liquid level in the container, and the upper end of the float that receives buoyancy from the liquid is fixed to the lower surface of the frame member that is horizontally mounted on the upper part of the container. The liquid level is detected by distortion of the frame member due to the buoyancy of the float. That is, when the liquid level is high, the buoyancy with respect to the float increases and the distortion of the frame member increases, and when the liquid level is low, the buoyancy with respect to the float decreases and the distortion of the frame member decreases.

In this liquid level detection device, the float extends long downward from the attachment to the frame member toward the bottom of the container, and its lower end is a free end.
JP 2000-46626 A

  However, in the liquid level detection device, the float is fixed in a so-called cantilever state so as to hang down from the frame member. For this reason, under a situation where acceleration or vibration acts on the container, the posture change or vibration of the float increases due to inertia or transmitted vibration, and the frame member may be distorted by the posture change or vibration, which may cause false detection. . Such erroneous detection is likely to occur particularly when the float is exposed from the liquid, that is, when the remaining amount of liquid in the container is small.

  The present invention has been made in view of the above circumstances, and an object thereof is to improve detection accuracy in a liquid level detection device.

  In order to achieve the above object, according to the first aspect of the present invention, in the liquid level detection device, a load detection means fixed to a lower portion in the container, a float for receiving buoyancy from the liquid in the container, and the float facing downward. A force obtained by subtracting the buoyancy from the downward biasing force acting on the float by the biasing means and acting on the load detecting means. The purpose.

  According to a second aspect of the present invention, in the first aspect of the present invention, a restricting means for restricting the lateral movement of the float is provided.

  According to the first aspect of the present invention, since the urging means for pressing the float to the load detecting means side is provided, the urging force can suppress the posture change and vibration of the float, and improve the liquid level detection accuracy. be able to.

  According to the invention of claim 2, since the restricting means for restricting the lateral movement of the float is provided, the lateral movement of the float can be suppressed and the liquid level can be detected more reliably.

  (First Embodiment) An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, a liquid level detection device mounted on a fuel tank of an automobile equipped with an internal combustion engine is exemplified.

  FIG. 1 is a side view showing a liquid level detection device according to the present embodiment mounted on a fuel tank, and FIG. 2 is a plan view (top view) of a float provided in the liquid level detection device.

  The liquid level detection device 1 according to the present embodiment includes a load detection means 3 fixed to a lower portion in the fuel tank 2 and a float 5 that receives buoyancy from the fuel 4 in the fuel tank 2.

  In the liquid level detection device 1, the load detection means 3 is fixed to the surface (upper surface) of the plate-like base member 15 that is in contact with the bottom surface 2 d of the fuel tank 2. The load detection means 3 includes, for example, a strain sensor, a piezoelectric element, and the like, and outputs an electrical signal (detection signal) corresponding to the downward pressing force applied to the upper surface 3a.

  The upper side and the side of the load detection means 3 (that is, the inside of the fuel tank 2) are covered with a bottomed cylindrical cover body 10 with a space therebetween, and the float 5 is disposed above the cover body 10. Yes. A plurality of (four in this example) arm portions 5b extending downward from the lower end of the main body portion 5a are provided at the lower portion of the float 5, while these arm portions 5b are loosely inserted into the upper wall 10a of the cover body 10. A through hole 10b is provided. Note that the lower end of the float 5 (that is, the lower end of the arm portion 5b) is not fixed to the upper surface 3a of the load detecting means 3, but is simply brought into contact with it by being biased downward by an elastic body 14 described later. It is.

  The main body 5a of the float 5 is formed in a substantially cylindrical shape that is long in the vertical direction. The buoyancy of the float 5 is appropriately adjusted depending on the outer shape, material, internal cavity, encapsulating substance, etc. of the main body 5a. The height of the float 5 is 90% or more of the distance between the inner surface of the upper wall 2a of the fuel tank 2 and the bottom surface 2d, and the liquid level in the fuel tank 2 can be detected from an empty state to a full state. Is preferable.

  A through hole 5c penetrating vertically is provided in a substantially central portion (axial center portion) of the main body portion 5a of the float 5, and a guide bar 11 is provided so as to penetrate the through hole 5c vertically. . The lower end portion of the guide bar 11 is inserted into a bottomed hole 10 c provided in the approximate center of the upper wall 10 a of the cover body 10, while the upper end portion thereof is a lid body 8 provided at the upper portion in the fuel tank 2. The cylinder body 12 is in contact with the inner surface of the cylinder body 12 and is guided by the inner cylinder portion of the cylinder body 12 so as to be movable up and down. An elastic body (for example, a spring or the like) 13 is inserted into the inner cylinder portion of the cylinder body 12 and urges the guide bar 11 downward. The elastic body 13 urges the guide bar 11 downward (that is, the cover body 10 side) and urges the cylinder body 12 upward (that is, the upper wall 2a side of the fuel tank 2). The cylinder body 12 has a function of extending vertically in the fuel tank 2 and erection at this position. That is, the guide bar 11 remains in this position even when the distance between the inner surface and the bottom surface 2d of the upper wall 2a of the fuel tank 2 fluctuates due to fluctuations in the remaining amount of the fuel 4 or fluctuations in the internal pressure of the fuel tank 2. Can do.

  In addition, the liquid level detection device 1 according to the present embodiment is an elastic body (for example, a spring or the like) that urges the float 5 in a direction of pressing the float 5 against the back surface of the lid 8 toward the load detection means 3 (ie, downward). 14 is provided.

  In this liquid level detection device 1, the elastic body 14 is mounted (exterior) around the peripheral wall of the cylinder body 12, the upper end of which is in contact with the lower surface of the base portion of the cylinder body 12, and the lower end thereof is the float 5. It is in contact with the upper surface of the (main body portion 5a). The elastic body 14 moves the float 5 downward even when the distance between the inner surface and the bottom surface 2d of the upper wall 2a of the fuel tank 2 is fluctuated due to fluctuations in the remaining amount of the fuel 4 or fluctuations in the internal pressure of the fuel tank 2. The float 5 is abutted against the upper surface 3 a of the load detecting means 3.

  A downward force obtained by reducing the upward buoyancy received by the float 5 from the fuel 4 from the downward urging force of the elastic body 14 as the urging means acts on the upper surface 3 a of the load detection means 3.

  In addition, the liquid level detection device 1 according to the present embodiment includes a regulation unit that regulates the movement of the float 5 in the lateral direction.

  In the liquid level detection device 1, the lateral movement of the main body 5 a of the float 5 is restricted by the guide bar 11 described above, and the arm portion of the float 5 is formed by the through hole 10 b formed in the upper wall 10 a of the cover body 10. The horizontal movement of 5b and the rotation around the central axis are restricted.

  In the present embodiment, the lid 8 is sandwiched between the upper wall 2a of the fuel tank 2 and the lock ring 7 fixed to the upper wall 2a with bolts 6 or the like. An annular packing 9 is mounted between the lower surface of the lid 8 and the upper surface of the upper wall 2a, and the airtightness and liquid tightness of this part are ensured.

  Further, the fuel tank 2 is formed with an inner peripheral flange portion 2b having a constant width that is stepped down from the upper wall 2a to the inner side (lower side) of the fuel tank 2 and opens as an inner peripheral edge of the inner peripheral flange portion 2b. Part 2c is formed.

  According to the liquid level detection device 1 according to the present embodiment, the higher the liquid level and the greater the remaining amount of the fuel 4, the more the bottom wall 2e of the fuel tank 2 bends due to its weight, and the upper wall 2a and the bottom wall 2e. Therefore, the lower urging force Fs acting on the float 5 from the elastic body 14 becomes smaller as the liquid level becomes higher. On the other hand, the upward buoyancy Ff acting on the float 5 increases as the liquid level increases. Therefore, in the present embodiment, the downward load F (= Fs−Ff) detected by the load detection unit 3 decreases as the liquid level increases.

  As described above, since the liquid level detection device 1 according to the present embodiment includes the elastic body 14 as an urging unit that presses the float 5 toward the load detection unit 3, the posture change of the float 5 is caused by the urging force. And vibration can be suppressed, and the liquid level detection accuracy can be improved.

  In the present embodiment, the lower end of the float 5 is not fixed to the upper surface 3a of the load detecting means 3, but is simply brought into contact. If the upper end of the float 5 is fixed to the upper surface 3a of the load detecting means 3, a bending moment is generated when a lateral inertia force acts on the float 5, and the bending moment is input to the load detecting means 3 as a pressing force. However, according to the present embodiment, in such a case, the float 5 can escape in the horizontal direction (however, within a restricted range). Can be suppressed.

  In addition, since the liquid level detection device 1 according to the present embodiment is provided with the restriction means for restricting the movement of the float 5 in the lateral direction, the float 5 can be brought into contact with the load detection means 3 more reliably and more reliably. The liquid level can be detected.

  In this embodiment, the elastic body 13 is provided as means for urging the guide bar 11 as one of the regulating means toward the bottom wall 2e of the fuel tank 2 with respect to the upper wall 2a of the fuel tank 2. Even if the distance between the upper wall 2a and the bottom wall 2e of the fuel tank 2 fluctuates, the guide bar 11 does not slide in the lateral direction but remains in the initial installation position, and the load 5 is detected in a proper posture. 3 can be brought into contact.

  (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a side view showing the liquid level detection device according to the present embodiment attached to the fuel tank. The liquid level detection device 1A according to the present embodiment includes the same components as the liquid level detection device 1 according to the first embodiment. Therefore, the same components are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this embodiment, a plate-like pressing force transmission portion 5d joined to the lower end of the arm portion 5b is provided at the lower end portion of the float 5A, and the load detecting means 3 has a downward force from the pressing force transmission portion 5d. Is entered. By doing so, the places where the float 5A abuts against the load detecting means 3 can be combined into one place, and detection can be performed more reliably than in the case of inputting from a plurality of places.

  In the present embodiment, as a means for urging the float 5A toward the load detection means 3, an elastic body 14A that urges the lower part of the float 5A downward is provided. Specifically, an elastic body (for example, a spring or the like) 14A is provided between the upper wall 10a of the cover body 10 and the pressing force transmission portion 5d. Also with the elastic body 14A having such a configuration, the same effects as those of the first embodiment can be obtained.

  The present invention can be embodied in another embodiment as follows. In other embodiments described below, the same operations and effects as in the above embodiments can be obtained.

  (1) In the above-described embodiment, the guide bar 11 is urged downward by the elastic body 13 in contact with the upper end thereof. Instead, the bottom of the fuel tank 2 is supported by the elastic body in contact with the lower end of the guide bar 11. The wall 2e may be urged upward.

  (2) In the above embodiment, the floats 5 and 5A are configured such that the buoyancy Ff changes linearly according to the liquid level. However, the outer shape of the float 5, the contents, or the positions of the internal cavities By adjusting the above, etc., the buoyancy Ff may change in a curve or nonlinearly according to the liquid level.

  (3) Further, the buoyancy of the floats 5 and 5A may be set so as to balance the weight of the floats 5 and 5A in a state where the fuel 4 is almost filled in the fuel tank 2.

  (4) Furthermore, the present invention can be similarly applied to containers other than automobile fuel tanks.

  Further, technical ideas other than the claims that can be grasped from the above embodiment will be described together with the effects thereof.

  (A) In the liquid level detection device according to claims 1 and 2, the guide bar is inserted between the upper wall and the bottom wall of the fuel tank by inserting the regulating means into a through hole provided in the float. Is preferable.

  In this way, the restriction means can be realized with a simple configuration.

  (B) In the liquid level detection device according to claim 1, 2 or (b), there is provided second urging means for urging the guide bar toward the upper wall or the bottom wall of the fuel tank. Is preferred.

  In this way, even if the gap between the top and bottom walls of the fuel tank changes, the guide bar stays at the original installation position without sliding laterally, and the float is used as a load detection means in an appropriate posture. It can be made to contact.

1 is a side view (partial cross-sectional view) showing a liquid level detection device according to a first embodiment of the present invention. The top view (figure seen from the lower part) of the float provided in the liquid level detection apparatus concerning embodiment of this invention. The side view (partial cross section figure) which shows the liquid level detection apparatus concerning 2nd Embodiment of this invention.

Explanation of symbols

1,1A Liquid level detector 2 Fuel tank (container)
3 Load detection means 4 Fuel 5, 5A Float 10b Through hole (regulation means)
11 Guide bar (regulation means)
14, 14A Elastic body (biasing means)

Claims (2)

A load detecting means fixed to the lower part of the container;
A float that receives buoyancy from the liquid in the container;
Urging means for urging the float downward and pressing it against the load detecting means;
With
A liquid level detection apparatus characterized in that a force obtained by subtracting buoyancy from a downward urging force acting on the float by the urging means acts on the load detection means. The liquid level detection apparatus according to claim 1, further comprising a regulation unit that regulates lateral movement of the float.

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