JP4957493B2 - Liquid level detector - Google Patents

Description

  The present invention relates to a liquid level detection device that is mounted in a container and detects the liquid level of the liquid in the container.

As a conventional liquid level detection device of this type, for example, a resistance element and a wiper type contact assembly are accommodated in a sealed chamber, one end is rotatably supported by a housing outside the chamber, and a float is attached to the other end. A magnetic coupling is composed of a second magnet fixed to the wiper-type contact and a first magnet fixed to the lever, and the rotational movement of the lever is transmitted to the wiper-type contact to move the wiper-type contact to the lever. The liquid level is detected on the basis of the resistance value between the resistance element and the wiper-type contact by moving the resistance element on the resistance element (see Patent Document 1).
JP 2004-3a3486 A

  In the conventional liquid level detection device described above, in order to obtain good electrical continuity between the wiper type contact and the resistance element, a predetermined contact pressure is generated between the wiper type contact and the resistance element. This contact pressure acts in a direction perpendicular to the resistance element surface. Further, when the wiper-type contact assembly rotates in conjunction with the rotation of the lever due to liquid level fluctuation, the wiper-type contact moves while sliding on the resistance element, that is, slides. When the wiper-type contact slides on the resistance element in the state where the contact pressure is applied, a force is applied to the wiper-type contact in a direction parallel to the surface of the resistance element and in a direction opposite to the sliding direction. Works. That is, a frictional force acts. The magnitude of this frictional force is the product of the sliding friction coefficient between the resistance element and the wiper-type contact and the contact pressure described above. In order to move the wiper-type contact with high responsiveness to the liquid level movement, the force for rotating the wiper-type contact assembly, that is, the transmission force by the magnetic joint composed of the first magnet and the second magnet is increased. There is a need to. The magnitude of the transmission force by the magnetic coupling is increased by the magnetic force acting between the first magnet and the second magnet as the magnetic force increases. As means for increasing the magnetic force acting between the first magnet and the second magnet, the first magnet and the second magnet are enlarged, or the first magnet and the second magnet are magnets having a higher magnetic flux density, that is, It may be formed from a magnet with a larger maximum energy product. In the former case, the physique of the liquid level detection device is enlarged, and there is a possibility that the physique and shape of the container in which the liquid level detection device is mounted are limited. In the latter case, such a material generally contains a rare earth element and is expensive, resulting in an increase in the cost of the liquid level detection device.

  The present invention has been made in view of such problems, and an object thereof is to provide a liquid level detection device capable of reducing the size and cost by reducing the frictional force acting between the resistance element and the contact point. It is.

  The present invention employs the following technical means to achieve the above object.

According to a first aspect of the present invention, there is provided a liquid level detecting device including a housing having a hermetically sealed chamber, an arm rotatably held around one end of the housing, and a liquid fixed to the other end of the arm. A float that floats in the chamber, and in the chamber, an arm member that is supported by the housing so as to be rotatable in a plane parallel to the rotation surface of the arm, and a resistance element that is arranged in parallel to the rotation surface of the arm member; A contact member supported by the arm member so as to be capable of contact conduction with the resistance element, and a first magnet fixed to the arm member, and a first conductor conducting to one end of the resistance element and a second conductor conducting to the contact member When the arm member is pulled out of the chamber and the arm member rotates, the resistance value between the first conductor and the second conductor changes, and the arm includes a magnetic member that generates a magnetic force that attracts the first magnet. In response to fluctuations in When the arm rotates due to the change in the float position, the rotational movement of this arm is transmitted to the arm member by the action of magnetic force, the arm member rotates following the rotation of the arm, and the liquid level is detected based on the resistance value. The contact level member is rotatably held by the arm member about the arm member as a rotation axis and is in rolling contact with the resistance element. The resistance element is an arm member in the axial direction of the rotation axis of the arm member. And a magnetic member .

In the above configuration, the contact member is in rolling contact with the resistance element. When an object moves in contact with a flat surface, the friction coefficient acting between the two is greatly different between when the moving state is a sliding state and when the moving state is a rolling state. It is much smaller than the coefficient of friction. Therefore, according to the liquid level detection device of the first aspect of the present invention, the contact pressure between the contact member and the resistance element is the same as that of the conventional liquid level detection device, that is, good electrical conductivity is obtained. In this state, the frictional force acting on the contact member when the contact member moves on the resistance element can be remarkably reduced as compared with the conventional liquid level detection device. That is, the force required to rotate the arm member with high responsiveness to fluctuations in the liquid level can be made smaller than in the case of the conventional liquid level detection device. That is, the magnetic force acting between the first magnet fixed to the arm member and the magnetic member provided in the arm can be made smaller than in the case of the conventional liquid level detection device. For example, the size of the first magnet can be reduced, or the first magnet can be formed from a magnet having a lower magnetic flux density, that is, an inexpensive magnet having a smaller maximum energy product. Thereby, the liquid level detection apparatus which can be reduced in size and cost can be provided.
Furthermore, in the above-described configuration, the direction of the magnetic force acting between the first magnet and the arm coincides with the direction of pressing the contact member against the resistance element. As a result, when the liquid level detection device vibrates, even if a force in a direction away from the resistance element acts on the contact member, the magnetic force acts in a direction to press the contact member against the resistance element. The electrical continuity between the member and the resistance element can be maintained satisfactorily.

  The liquid level detection apparatus according to claim 2 of the present invention is characterized in that the magnetic member is a second magnet.

  According to the above configuration, the magnetic member can be reduced in size while making the magnitude of the magnetic force acting between the arm member and the arm equal.

  According to a third aspect of the present invention, in the liquid level detection device, the magnetic member is a part of an arm formed of a magnetic metal.

  In the above-described configuration, a part of the arm made of magnetic metal functions as a magnetic member that is one of the components that generate magnetic force. Thereby, since it is not necessary to provide a magnetic member as another component, the structure of a liquid level detection apparatus can be simplified.

  Hereinafter, a case where the liquid level detection device according to the embodiment of the present invention is applied to a fuel level gauge 1 that is mounted in a fuel tank of an automobile and detects the level of fuel will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same component in each figure.

  As shown in FIG. 1, the fuel level gauge 1 is disposed and fixed in the fuel tank 18, for example, in the fuel tank 18, and the fuel 17 is sent to the outside of the fuel tank 18, for example, an engine (not shown). It is fixed to a fuel pump module 19 for delivery. FIG. 1 shows a state in which the liquid level 17a in the fuel tank 18 is at the lowest position, that is, the empty position. Further, the highest position of the liquid surface 17a in the fuel tank 18, that is, the full tank position is indicated by a two-dotted line in FIG.

  As shown in FIG. 1, the fuel level gauge 1 includes a housing 2 and an arm 3 having one end rotatably supported by the housing 2 and a float 4 floating on the fuel 17 fixed to the other end. Further, as shown in FIG. 2, the resistance element 5, the arm member 6 rotatably supported by the housing 2, and the resistance element 5 are in conductive contact with each other in a chamber C hermetically formed in the housing 2. And a contact member 7 held by the arm member 6. Then, the rotational movement of the arm 3 due to the vertical movement of the float 4 synchronized with the fluctuation of the liquid level 17a is transmitted to the rotational movement of the arm member 6 to change the contact position between the resistance element 5 and the contact member 7, and the resistance element 5 and The resistance value between the contact members 7 is changed, and the level of the liquid level 17a is detected as a change in the resistance value between the resistance element 5 and the contact member 7.

  Below, the structure of the fuel level gauge 1 is demonstrated.

  The housing 2 is formed, for example, in a substantially box shape having one end opened from a resin material. A cover 14 is fixed to the open end of the housing 2 as shown in FIG. A chamber C is formed as a space surrounded by the cover 14 and the inner wall of the housing 2. When the cover 14 is fixed to the housing 2, the chamber C is hermetically sealed. That is, the fuel 17 does not flow into the chamber C from the outside of the housing 2.

  As shown in FIG. 2, the housing 2 is formed with a boss portion 2a. The boss portion 2 a is formed perpendicular to the bottom surface 2 c corresponding to the bottom portion of the box-shaped housing 2. As shown in FIG. 2, a through hole 2b is formed in the boss 2a coaxially with the boss 2a. The through hole 2b is rotatably fitted with a shaft portion 3a which is one end of an arm 3 which will be described later. Thereby, the arm 3 is rotatably held by the housing 2. As shown in FIG. 2, a stopper 15 is fixed to the tip of the shaft portion 3a of the arm 3 to prevent the shaft portion 3a from coming off the boss portion 2a.

  The arm 3 is made of a magnetic material, for example, a carbon steel wire that is a magnetic metal. As shown in FIG. 2, a float 4 is attached to an end portion of the arm 3 opposite to the shaft portion 3 a. As shown in FIG. 2, a stopper 16 is fixed to the tip of the arm 3 to prevent the float 4 from coming off the arm 3. In the arm 3, a portion connecting the shaft portion 3a and the float attachment portion 3b to which the float 4 is attached is a connecting portion 3c.

  The float 4 is made of, for example, a resin material, and has an apparent specific gravity so as to be surely floated on the liquid level 17 a of the fuel when attached to the arm 3. When the float 4 moves up and down according to the change in the position of the liquid level 17a, this movement is transmitted to the arm 3, and the arm 3 rotates about its shaft portion 3a as a rotation axis. During the rotation of the arm 3, the rotation surface of the connecting portion 3 c of the arm 3 is a plane parallel to the bottom surface 2 c of the housing 2, and is a direction orthogonal to the paper surface in FIG. 2.

  As shown in FIG. 2, a resistance element 5 is attached in the chamber C of the housing 2, that is, in the bottom surface 2 c of the housing 2. The resistance element 5 is formed by forming, on an insulating substrate, for example, a ceramic substrate, a resistance film 5a made of a high-resistance metal film such as a carbon film or nichrome in a substantially fan shape as shown in FIG. The resistance film 5 a is formed in a sector shape with the boss 2 a of the housing 2 as the center (essential). As shown in FIG. 3, a plurality of electrode portions 5b are formed in a comb-teeth shape on the tip side of the fan-shaped resistance film 5a, that is, on the side opposite to the main part of the fan. The electrode portion 5 b is formed in a radial shape centered on the boss portion 2 a of the housing 2.

  In the chamber C of the housing 2, the arm member 6 rotates in a plane parallel to the rotation surface of the connecting portion 3 c of the arm 3, in other words, in a plane parallel to the bottom surface 2 c of the housing 2. Thus, it is supported by the housing 2. That is, the through-hole 6a provided in the arm member 6 is rotatably fitted to the boss 2a as shown in FIG. A contact member 7 is attached to the arm member 6. The contact member 7 is formed on a disk having a through hole 7a in the center from a conductive material such as a copper-based metal. As shown in FIG. 4, the contact member 7 is held by the arm member 6 so that the through-hole 7 a can be fitted to the arm member 6 and can be rotated about the arm member 6. As shown in FIG. 3, the contact member 7 is held at a position in contact with the electrode portion 5 b of the resistance element 5. When the arm member 6 rotates about the boss 2a of the housing 2, the contact member 7 rotates about the arm member 6 and rotates on the electrode portion 5b while being in contact with the electrode portion 5b. As shown in FIG. 2, the coil spring 13 is disposed coaxially with the boss portion 2 a between the arm member 6 and the cover 14 in the boss portion 2 a. The coil spring 13 is mounted in a compressed state, and the arm member 6 is pressed leftward in FIG. 2 by its elastic deformation force. Due to the elastic deformation force of the coil spring 13, the contact member 7 is pressed against the electrode portion 5 b of the resistance element 5, and a contact pressure is generated between the contact member 7 and the electrode portion 5 b of the resistance element 5. Due to this contact pressure, good electrical continuity between the contact member 7 and the electrode portion 5b of the resistance element 5 is obtained. The inside of the chamber C is hermetically sealed and shut off from the outside. That is, the fuel 17 does not flow into the chamber C from the outside of the housing 2. As a result, the resistance element 5 and the contact member 7 are corroded by the fuel 17, or foreign matter mixed in the fuel 17 is interposed between the resistance element 5, the contact member 7, and the contact portion. It is possible to prevent the occurrence of trouble such as poor electrical continuity between the two.

  As shown in FIG. 3, a terminal 9 and a terminal 10 are fixed to the housing 2. The housing 2 and the terminal 9 and the terminal 10 are fixed in close contact with each other, and there are no gaps between the outer peripheral surfaces of the terminal 9 and the terminal 10 and the housing 2. The terminal 9 and the terminal 10 are formed in a rod shape from a conductive material, for example, a copper-based metal. As shown in FIG. 3, the terminal 9 is connected to the resistance film 5a via a lead wire 11, and the terminal 10 is connected to the arm member 6 via a lead wire 12 as shown in FIG. The lead wire 12 is formed of a flexible stranded wire or the like and does not hinder smooth rotation of the arm member 6. The fuel level gauge 1 is connected to an external electric circuit via the terminal 9 and the terminal 10. The terminal 9 and the lead wire 11 are first conductive wires that connect the resistance element 5 to the outside of the housing 2, and the terminal 10 and the lead wire 12 are second conductive wires that connect the arm member 6 to the outside of the housing 2.

  A magnet 8 that is a first magnet is fixed to the end of the arm member 6 opposite to the through hole 6a. The magnet 8 is arranged so as to be close to the bottom surface 2c of the housing 2 as long as it does not contact the bottom surface 2c. The magnetic flux from the magnet 8 flows through the connecting portion 3c of the arm 3 which is a magnetic body across the bottom surface 2c of the housing 2, and a magnetic circuit is formed by the magnet 8 and the connecting portion 3c of the arm 3. As a result, a force is generated between the magnet 8 and the connecting portion 3 c of the arm 3 to attract them.

  Next, the liquid level 17a level detection operation of the fuel 17 in the fuel level gauge 1 according to one embodiment of the present invention will be described.

  When the float 4 moves up and down according to the change in the position of the liquid level 17a, this movement is transmitted to the arm 3, and the arm 3 rotates about its shaft portion 3a as a rotation axis. The rotational movement of the arm 3 is transmitted to the arm member 6 by the magnetic force generated between the magnet 8 and the connecting portion 3 c of the arm 3, and the arm member 6 rotates in synchronization with the rotation of the arm 3. . When the arm member 6 rotates, the contact member 7 moves while rolling on the electrode portion 5b of the resistance element 5 by rotating about the arm member 6 as a rotation axis. At this time, the electrical continuity between the contact member 7 and the electrode portion 5b of the resistance element 5 is well maintained without interruption. Thus, when the float 4 moves up and down according to the fluctuation of the liquid level 17a position, the contact position between the contact member 7 and the electrode portion 5b of the resistance element 5 changes, and the resistance value between the terminal 9 and the terminal 10 is changed. Change. Accordingly, the liquid level 14 a of the fuel 17 in the fuel tank 18 is detected based on the resistance value between the terminal 9 and the terminal 10.

  As described above, in the fuel level gauge 1 according to the embodiment of the present invention, the contact member 7 for electrically connecting the arm member 6 to the electrode portion 5b of the resistance element 5 is formed on the disk having the through hole 7a. The through hole 7a is fitted to the arm member 6 and is held by the arm member 6 so that the arm member 6 can be rotated about the rotation axis. Thereby, when the arm member 6 rotates according to the change in the position of the liquid surface 17a, the frictional force acting on the contact portion between the contact member 7 and the resistance element 5, that is, the rotational movement of the arm member 6 is prevented. Compared with the case of the conventional liquid level detection apparatus, the force to perform can be made remarkably small. Therefore, the force required to rotate the arm member 6 with high responsiveness to fluctuations in the liquid level 17a can be made smaller than in the case of the conventional liquid level detection device. That is, the magnetic force acting between the magnet 8 fixed to the arm member 6 and the connecting portion 3c of the arm 3 can be made smaller than in the case of the conventional liquid level detection device. For example, the size of the magnet 8 can be reduced, or the magnet 8 can be formed from a magnet having a smaller magnetic flux density than that of a conventional liquid level detection device, that is, an inexpensive magnet having a smaller maximum energy product.

  Moreover, in the conventional liquid level detection apparatus, the magnet was attached to both the arm and the arm member in the chamber. That is, two magnets are used. However, in the fuel level gauge 1 according to the embodiment of the present invention, the magnet 8 is attached only to the arm member 6 in the chamber C, that is, one magnet is provided. The connecting portion 3c, which is a portion, is a magnetic member that generates a magnetic force attracting the magnet 8. Thereby, the number of parts constituting the fuel level gauge 1 can be reduced and the cost can be reduced.

  As described above, a fuel level gauge that can be reduced in size and reduced in cost can be realized.

  In the fuel level gauge 1 according to the embodiment of the present invention described above, a magnetic member that is provided on the arm 3 and generates a magnetic force that attracts the magnet 8 is used as a connecting portion 3c that is a part of the arm 3. However, the arm 3 may be provided with a magnet, that is, a second magnet may be provided.

  Further, in the embodiment of the present invention described above, the case where the liquid level detecting device is applied to the fuel level gauge 1 for an automobile has been described as an example. However, the use thereof needs to be limited to the fuel level gauge 1 for an automobile. There is no. You may apply for the detection of the liquid level in containers, such as other liquids mounted in a motor vehicle, for example, brake fluid, engine cooling water. Furthermore, the present invention is not limited to automobiles, and may be applied for detecting a liquid level in a liquid container provided in various consumer devices.

It is a front view of fuel level gauge 1 by one embodiment of the present invention. It is the II-II sectional view taken on the line in FIG. It is the III-III sectional view taken on the line in FIG. It is a schematic diagram explaining the magnetization state and magnetic flux distribution of the magnet 6 in the fuel level gauge 1 by one Embodiment of this invention.

Explanation of symbols

1 Fuel level gauge (Liquid level detector)
2 Housing 2a Boss part 2b Through hole 2c Bottom face 3 Arm 3a Shaft part 3b Float attachment part 3c Connecting part (magnetic member, part of arm)
4 Float 5 Resistance element 5a Resistance film 5b Electrode part 6 Arm member 7 Contact member 7a Through hole 8 Magnet (first magnet)
9 Terminal (first conductor)
10 Terminal (second conductor)
11 Lead wire (first conductor)
12 Lead wire (second conductor)
13 Coil Spring 14 Cover 15 Stopper 16 Stopper 17 Fuel (Liquid)
17a Liquid level 18 Fuel tank 19 Pump module C chamber

Claims (3)

A housing having a hermetically sealed chamber;
An arm rotatably held around one end of the housing;
A float floating in a liquid fixed to the other end of the arm,
In the chamber, an arm member supported by the housing so as to be rotatable in a plane parallel to the rotation surface of the arm, a resistance element disposed in parallel to the rotation surface of the arm member, and the resistance element A contact member supported by the arm member so that contact conduction is possible, and a first magnet fixed to the arm member;
A first conductive wire conducting to one end of the resistance element and a second conducting wire conducting to the contact member are drawn out of the chamber, and when the arm member rotates, a resistance value between the first conductive wire and the second conductive wire changes. And
The arm includes a magnetic member that generates a magnetic force attracting the first magnet,
When the arm rotates due to the change in the float position in response to the change in the liquid level, the rotational movement of the arm is transmitted to the arm member by the action of the magnetic force, and the arm member is moved to the arm. Rotate following the rotation,
A liquid level detection device for detecting the liquid level based on the resistance value,
The contact member is held by the arm member so as to be rotatable about the arm member as a rotation axis, and is in rolling contact with the resistance element,
The liquid level detecting device according to claim 1, wherein the resistance element is disposed between the arm member and the magnetic member in an axial direction of a rotation axis of the arm member .   The liquid level detection device according to claim 1, wherein the magnetic member is a second magnet.   The liquid level detection device according to claim 1, wherein the magnetic member is a part of the arm formed of a magnetic metal.

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