JP2009109371A - Liquid level detecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid level detecting apparatus whose size and cost can be reduced by reducing frictional forces at the bearing portions of an arm member. <P>SOLUTION: By arranging a shaft B being the rotary shaft of the arm member 6 and a shaft A being the rotary shaft of an arm 3 in parallel with each other while separating them by a predetermined distance D in their radial direction, the shaft portion 6b of the arm member 6, and its bearing portion 2d and bearing portion 14a can be arranged at positions separate from a boss portion 2a being a bearing for the arm 3, and the magnitude of frictional forces between the shaft portion 6b and both bearing portions 2d, 14a can be reduced by thinning the thickness of the shaft portion 6b to a necessary minimum. Moreover, by arranging the shaft B being the rotary shaft of the arm member 6, in other words, the shaft portion 6b of the arm member 6, inside a sector range F being the rotation range of the arm 3 and on the more resistance element 5 side than the shaft A, the length of the arm member 6, i.e., the length of an arm portion 6a can be shortened, and consequently the weight of the arm member 6 can be reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

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 above-described conventional liquid level detection device, the wiper-type contact assembly is disposed coaxially with the rotation axis of the lever, with its rotation axis coinciding with the rotation axis of the lever. Specifically, the outer periphery of the boss portion of the housing holding the lever rotatably and the through hole of the wiper contact assembly are rotatably fitted to form a bearing structure for the wiper contact assembly. Yes. For this reason, the circumferential length at the fitting portion between the wiper-type contact assembly and the housing is increased, and the contact area at the fitting portion between the two is increased. As a result, the frictional force generated in the bearing portion when the wiper-type contact assembly rotates by transmitting the rotation of the lever is increased.

  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 the above problems, and an object of the present invention is to provide a liquid level detection device capable of reducing the size and cost by reducing the frictional force generated in the bearing portion of the wiper type contact assembly. That 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 to the resistance element, and a first magnet fixed on the outer side of the rotation from the contact member of the arm member, and a first conductor and a contact member that are conducted to one end of the resistance element When the second conductor conducting to the outside 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 attracting the first magnet, Liquid liquid When the arm rotates due to the change in the float position in response to the level change, the rotational movement of this arm is transmitted to the arm member by the action of the magnetic force, and the arm member rotates following the rotation of the arm. A liquid level detection device for detecting a liquid level, wherein a first rotation axis that is a rotation axis of an arm and a second rotation axis that is a rotation axis of an arm member are parallel to each other and separated from each other by a predetermined distance in the radial direction. It is characterized by being arranged.

  According to the above-described configuration, the bearing structure portion in which the housing rotatably supports the arm member is disposed away from the bearing structure portion in which the housing rotatably supports the arm in the radial direction of the shaft. That is, the shape of the bearing structure portion in which the housing rotatably supports the arm member can be designed without being restricted by the bearing structure portion in which the housing rotatably supports the arm. Thus, the bearing structure in which the housing rotatably supports the arm member can be determined so that the frictional force generated when the arm member rotates is as small as possible. Therefore, the force required to rotate the arm member with high responsiveness to the fluctuation of 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.

  The liquid level detection device according to claim 2 of the present invention is characterized in that the second rotating shaft is disposed inside the substantially sector-shaped range that is the rotating range of the arm and closer to the resistance element than the first rotating shaft. .

  According to the above-described configuration, the length of the arm member, that is, the length from the second rotation shaft, which is the rotation shaft of the arm member, to the distal end portion on the resistance element side, The first rotating shaft that is the rotating shaft of the arm and the second rotating shaft that is the rotating shaft of the arm member can be shortened compared to the configuration in which the rotating shaft is coaxially arranged. As a result, the weight of the arm member can be reduced, and the rotational torque of the magnet can be increased relative to the friction torque of the contact, so that the force required to rotate the arm member can be made smaller than in the case of the conventional liquid level detection device. .

  The liquid level detection device according to claim 3 of the present invention is characterized in that the contact 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.

  According to 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.

  The liquid level detection apparatus according to claim 4 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.

  The liquid level detection apparatus according to claim 5 of the present invention is characterized in that 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.

  The liquid level detection apparatus according to claim 6 of the present invention is characterized in that the resistance element is disposed between the first magnet and the magnetic member in the axial direction of the rotation axis of the arm member.

  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.

  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. As a result, the arm 3 is rotatably held by the housing 2 and rotates about the axis A, which is the first rotation axis, as the rotation axis, as shown in FIG. 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 3 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 shaft portion 6 b of the arm member 6 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 5b is formed radially with the shaft portion 6b as the center.

  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.

  As shown in FIG. 2, the arm member 6 includes an arm portion 6a and a shaft portion 6b fixed so as to be orthogonal to the arm portion 6a. That is, the arm member 6 is formed in a letter shape. As shown in FIG. 2, both end portions of the shaft portion 6b are formed in a conical shape coaxial with the shaft portion 6b. One end portion of the shaft portion 6b is fitted into a bearing portion 2d formed on the bottom surface 2c of the housing 2, and the other end portion of the shaft portion 6b is fitted into a bearing portion 14a formed on the cover 14. . As a result, the arm member 6 is rotatably supported in the chamber C, and as shown in FIG. 2, the arm member 6 rotates about the axis B serving as the second rotation axis. Both end portions of the shaft portion 6b and the bearing portions 2d and 14a are in a substantially point contact state, and the rotational resistance of the shaft 6a is extremely small. As shown in FIG. 2, the axis B, which is the rotation axis of the arm member 6, is parallel to the axis A, which is the rotation axis of the arm 3, and is separated by a predetermined distance D in the radial direction (vertical direction in FIG. 2). Are arranged. Further, as shown in FIG. 1, the axis B is disposed inside the sector range F that is the rotation range of the arm 3 and closer to the resistance element 5 than the axis A. The predetermined distance D is determined so that the arm member 6 can smoothly rotate without interfering with the boss portion 2a of the housing 2 in a state where the arm member 6 is mounted in the chamber C. Thus, the shaft portion 6b of the arm member 6 and the bearing portion 2d and the bearing portion 14a that are the bearings of the shaft portion 6b are disposed at positions away from the boss portion 2a that is the bearing of the arm 3, thereby By reducing the thickness of the portion 6b to the minimum necessary level, the magnitude of the frictional force between the shaft portion 6b and both the bearing portions 2d and 14a can be reduced.

  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 around the boss 2a of the housing 2, the contact member 7 rotates about the arm 6b of the arm 6 and rotates on the electrode 5b while being in contact with the electrode 5b. .

  In this way, 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, and the arm member 6 is fitted with the through hole 7a. Is held by the arm member 6 so that it 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. The force to do can be reduced. Further, the inside of the chamber C is hermetically sealed and is 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. The occurrence of troubles such as poor electrical continuity between the two can be prevented.

  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, which is a first magnet, is fixed to the end portion of the arm member 6 opposite to the shaft portion 6 b and outside the contact member 7. 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.

  In the fuel level gauge 1 according to the embodiment of the present invention described above, the axis B that is the rotation axis of the arm member 6 is parallel to the axis A that is the rotation axis of the arm 3 and is predetermined in the radial direction thereof. By arranging the distance D apart, the shaft portion 6b of the arm member 6 and the bearing portion 2d and the bearing portion 14a which are bearings of the shaft portion 6b are separated from the boss portion 2a which is the bearing of the arm 3. The thickness of the shaft portion 6b can be reduced to the necessary minimum, and the magnitude of the frictional force between the shaft portion 6b and the two bearing portions 2d and 14a can be reduced.

  Furthermore, the axis B, which is the rotation axis of the arm member 6, in other words, the shaft portion 6 b of the arm member 6 is disposed inside the sector range F, which is the rotation range of the arm 3, and closer to the resistance element 5 than the axis A Thus, the length of the arm member 6, that is, the length of the arm portion 6b can be shortened, so that the weight of the arm member 6 can be reduced.

  Thus, reducing the magnitude of the frictional force of the bearing portion of the arm member 6 and simultaneously reducing the weight of the arm member 6, and the distance from the shaft portion 6 b to the magnet 8 with respect to the distance from the shaft portion 6 b to the contact member 7. By increasing the ratio, the force required to rotate the arm member 6 with high responsiveness to the fluctuation of 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. 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 the IV-IV sectional view taken on the line in FIG.

Explanation of symbols

1 Fuel level gauge (Liquid level detector)
2 Housing 2a Boss part 2b Through hole 2c Bottom face 2d Bearing part 3 Arm 3a Shaft part 3b Float attachment part 3c Connection part (magnetic member, part of arm)
4 Float 5 Resistance element 5a Resistance film 5b Electrode part 6 Arm member 6a Arm part 6b Shaft part 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 14a Bearing 15 Stopper 16 Stopper 17 Fuel (Liquid)
17a Liquid level 18 Fuel tank 19 Pump module A shaft (first rotating shaft)
B axis (second rotation axis)
C Chamber D Predetermined distance F Fan range (rotation range)

Claims (6)

A housing having a hermetically sealed chamber;
An arm held rotatably about the 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 parallel to the rotation surface of the arm member, and the resistance element A contact member that is supported by the arm member so as to be capable of contact conduction; and a first magnet that is fixed to the outer side of the arm member and is rotated outward from the contact member;
A resistance value between the first conductor and the second conductor changes when the first conductor conducting to one end of the resistance element and the second conductor conducting to the contact member are drawn out of the chamber and the arm member rotates. And
The arm includes a magnetic member that generates a magnetic force attracting the first magnet,
When the arm rotates due to a change in the float position in response to a change in the liquid level of the liquid, 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 liquid level detection characterized in that the first rotation axis that is the rotation axis of the arm and the second rotation axis that is the rotation axis of the arm member are arranged in parallel to each other and at a predetermined distance in the radial direction. apparatus.   2. The liquid level detection device according to claim 1, wherein the second rotation shaft is disposed inside a substantially sector-shaped range that is a rotation range of the arm and closer to the resistance element than the first rotation shaft.   3. The liquid according to claim 1, wherein the contact 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. 4. Surface detection device.   The liquid level detection device according to any one of claims 1 to 3, wherein the magnetic member is a second magnet.   The liquid level detection device according to any one of claims 1 to 3, wherein the magnetic member is a part of the arm formed of a magnetic metal.   The said resistance element is arrange | positioned between the said 1st magnet and the said magnetic member in the axial direction of the rotating shaft of the said arm member, The Claim 1 thru | or 5 characterized by the above-mentioned. Liquid level detection device.

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