JP2004020538A - Liquid level sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid level sensor reduced in the number of parts and miniaturized without lowering the degree of detection. <P>SOLUTION: In this liquid level sensor 1, a first bearing part 2a and a second bearing part 2b are formed with a space at a frame 2, and an upper holding part 4a and a lower holding part 4b are formed with a space at an arm holder 4. The lower holding part 4b of the arm holder 4 is insert-fitted between the first bearing part 2a and second bearing part 2b of the frame 2 in the state of allowing the upper face of the lower holding part to abut on the lower face of the second bearing part 2b, and the first bearing part 2a is insert-fitted between the upper holding part 4a and lower holding part 4b of the arm holder 4. A rotating shaft part 3a of a front arm 3 is insert-fitted into the upper holding part 4a, the first bearing part 2a, the lower holding part 4b and the second bearing part 2b. The frame 2 and the arm holder 4 are formed of different resin materials, and either one of the resin materials has excellent sliding property. <P>COPYRIGHT: (C)2004,JPO

Description

【００２８】
上記表１からも明らかなように、本実施例のものは、摺動トルクが低減し、またきしみ音が低減している。
【００２９】
【発明の効果】
上記説明したように本発明の請求項１記載の液面レベルセンサによれば、アームホルダーの第１軸受部と第２軸受部との間にフレームの第１軸受部が挟み込まれ、フレームの第１軸受部と第２軸受部との間にアームホルダーの第２軸受部が挟み込まれているので、フロートアームの回動安定性が増し、スムーズな回動が可能になって測定精度が向上する。
また、第１従来例と比較して、抜け落ち防止のためのブッシュやワッシャが不要になり、部品点数の削減、組立工数の削減、軽量化に伴う低コスト化が可能になる。
特に、回動支点となる第１軸受部の下面部と下側保持部の上面部とが摺動可能に当接されるので、フロートアームの回動の妨げになる接触抵抗が小さくなる。すなわち、本発明の液面レベルセンサでは、第２従来例よりも接触抵抗の発生する箇所が回転軸に近くなるので、梃子の原理により回転トルクがより大きくなる。したがって、スムーズな回動が可能になり、第２従来例よりも測定精度が向上する。
【００３０】
また、フレームの第１軸受部と第２軸受部との間にアームホルダーの下側保持部を、該下側保持部の上面を第１軸受部の下面に当接させて、金属ワッシャを省いているが、フレームとアームホルダーを異なる材質によって形成するとともに、いずれか一方を摺動性に優れた材質にすることによって、摩擦抵抗の低減が図れる。したがって、ワッシャ廃止により部品点数の削減が図れ、部品費および加工費を削減できるばかりでなく、コンパクト化も図ることができる。
【００３１】
また、本発明の請求項２記載の液面レベルセンサによれば、フレームまたはアームホルダーのいずれか一方の材料を従来から採用されている汎用ＰＯＭ樹脂とし、他方の材料を快摺動性ＰＯＭまたはＰＰＳ樹脂としている。快摺動性ＰＯＭまたはＰＰＳ樹脂は、収縮率が汎用ＰＯＭよりも小さいため接圧変化が小さく、安定した検出制度を確保できる。
【００３２】
以上の結果、高い測定精度を維持しながらも、部品点数削減および小型化を達成した液面レベルセンサを得ることができる。
【図面の簡単な説明】
【図１】本発明に係る液面レベルセンサを概念的に示した斜視図である。
【図２】図１における要部拡大縦断面図である。
【図３】第１従来例および第２従来例の液面レベルセンサに共通する平面図である。
【図４】図４（Ａ）は第１従来例の液面レベルセンサの要部拡大断面図であり、図４　（Ｂ）は第２従来例の液面レベルセンサの要部拡大断面図である。
【符号の説明】
１　　　　液面レベルセンサ
２　　　　樹脂製のフレーム
２ａ　　　第１軸受部
２ｃ　　　第１軸受部回転軸穴
２ｂ　　　第２軸受部
２ｄ　　　第２軸受部回転軸穴
３　　　　金属性のフロートアーム
３ａ　　　回転軸部
３ｂ　　　回動部
３ｃ　　　先端部
４　　　　樹脂製のアームホルダー
４ａ　　　上側保持部
４ｂ　　　下側保持部
４ｃ　　　アーム保持部
５　　　　コンタクト片
５ａ　　　接点
６　　　　フロート
７　　　　配線基板
７ａ　　　抵抗体
８　　　　出力端子
９ａ，９ｂ　ストッパ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid level sensor having a float arm that rotates according to a liquid level, and more particularly to a liquid level sensor that is attached to a fuel tank of a vehicle that uses a liquid such as gasoline or light oil as a fuel to detect the remaining amount of fuel. The present invention relates to a contact-type liquid level sensor suitable for the present invention.
[0002]
[Prior art]
Conventionally, this type of liquid level sensor has a structure shown in FIGS. Here, two types of liquid level sensors are illustrated as conventional examples. FIG. 3 is a plan view common to the first conventional example and the second conventional example. FIG. 4A is an enlarged cross-sectional view of a main part of a liquid level sensor as a first conventional example, and FIG. 4B is an enlarged cross-sectional view of a main part of a liquid level sensor as a second conventional example.
[0003]
First, a liquid level sensor according to a first conventional example will be described with reference to FIGS. 3 and 4A. This liquid level sensor 91A has a circuit mounted with a resin frame 92, a metal float arm 93, a resin arm holder 94, a contact 95, a float 96 having a buoyancy for a liquid to be measured, and a resistor 97a. It is configured to include the substrate 97.
[0004]
One end of the float arm 93, that is, the rotating shaft 93a is inserted into a mounting hole 94a provided in the arm holder 94, and the intermediate portion 93b of the float arm 93 is formed by a claw 94b formed on the arm holder 94. While being clamped and fixed, it is rotatably inserted into a mounting hole 92 a provided in the frame 92.
A bush 99 is press-fitted at the tip of the rotating shaft 93a with a washer 99a interposed therebetween. As described above, the arm holder 94 is attached to the frame 92 so as to be rotatable about the rotation shaft 93a.
Further, a float 96 is attached to the other end of the float arm 93, that is, a tip 93c.
[0005]
The contact piece 95 fixed to the above-mentioned arm holder 94 has elasticity, and a contact point 95 a provided at a tip portion is urged by elasticity to contact a resistor 97 a attached to the frame 92. Note that the coil spring 98 is provided to obtain conduction between the contact 95a of the contact piece 95 and an output terminal (not shown) provided on the frame 92 side.
[0006]
The liquid level sensor 91A is attached to a container (not shown) for storing liquid, and when the float 96 moves up and down due to fluctuations in the liquid level, the float arm 93 rotates around the mounting hole 92a within a predetermined angle range. Move. Due to this rotation, the contact 95a of the contact piece 95 slides on the resistor 97a, and a sensor circuit (not shown) moves between one end of the resistor 97a and the output terminal (not shown), that is, the contact 95a of the contact 95. Changes the resistance value. By detecting this resistance change, a level signal indicating the liquid level fluctuation amount can be extracted. In the drawing, X1 indicates a bearing length which is one of the measures of stability when the float arm 93 rotates.
[0007]
As shown in FIGS. 3 and 4B, the liquid level sensor 91B of the second conventional example has a resin frame 92 and a metal float, similarly to the liquid level sensor 91A of the first conventional example. An arm 93, an arm holder 94 made of resin, a contact piece 95, a float 96 having a buoyancy with respect to a liquid to be measured, and a circuit board 97 on which a resistor 97 a is mounted. However, in the liquid level sensor 91B, the arm holder 94 is provided with a drop-off prevention piece 94c, so that the washer 99a and the bush 99 of the liquid level sensor 91A of the first conventional example are unnecessary.
As shown in FIG. 4 (B), the falling-off prevention piece 94c has a shape like a bent and extended side surface of the arm holder 94. The falling-off prevention piece 94c is in contact with the float arm 93 over the rotation stroke so as to sandwich the arc-shaped end portion 92b of the frame 92. Thus, the arm holder 94 integrated with the float arm 93 is attached to the frame 92 so as to be able to rotate without falling off.
The liquid level sensor 91 of the second conventional example can perform the same operation as that of the liquid level sensor 91A of the first conventional example, and can output a level signal indicating the liquid level fluctuation amount. Further, in the drawing, X2 indicates a bearing length which is one measure of stability when the float arm 93 rotates.
[0008]
[Problems to be solved by the invention]
However, the first and second conventional examples have the following problems.
That is, according to the first conventional example, a bearing length X1 that is equal to or longer than a predetermined length is required in order to maintain detection accuracy equal to or higher than a predetermined value. In addition to the bearing length X1, the washer 99a and the bush 99 are required. Thickness B is added, and miniaturization becomes difficult.
Further, according to the second conventional example, the size can be reduced as compared with the first conventional example. However, since the contact friction between the falling-off preventing piece 94c and the frame 92 is newly generated at the time of rotation, the float is required. The smooth rotation of the arm 93 is hindered. In particular, since the drop-off prevention piece 94c generates contact resistance at a position far away from the rotation axis, that is, near the circumference of the rotating circle, smooth rotation of the float arm 93 is further hindered, and downsizing is achieved. Pursuing it will reduce the detection accuracy.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid level sensor capable of reducing the number of components and reducing the size without lowering the detection accuracy, in view of the above-described situation.
[0010]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a liquid level sensor comprising a rotating shaft portion and a rotating portion which is bent substantially at right angles to the rotating shaft portion and rotates about the rotating shaft portion. A rod-shaped float arm, a float attached to a tip of a rotating part of the float arm, having a buoyancy for the liquid to be measured, and detecting a liquid level of the liquid to be measured based on the rotation of the float arm. Frame, on which an electric circuit board is mounted, a first bearing portion formed as a part of the frame near an end of the frame, and the rotary shaft portion provided on the first bearing portion are inserted. A U-shaped cross section including a first bearing portion rotating shaft hole and an upper holding portion and a lower holding portion formed so as to be substantially parallel to each other with a portion having the first bearing portion rotating shaft hole from above and below. Arm holder, A holder rotating shaft hole provided in the arm holder, wherein the rotating shaft portion is inserted, and formed on the upper surface of the upper holding portion, wherein the rotating portion is press-fittable from above, and the press-fitted rotating portion is formed. The first bearing portion is sandwiched between the upper holding portion and the lower holding portion, and the rotating shaft portion is inserted into the first bearing portion rotating shaft hole and the holder rotating shaft hole from above. A liquid level sensor in which the rotating portion is held by the arm holding portion, and a lower surface portion of the first bearing portion and an upper surface portion of the lower holding portion are slidably contacted with each other;
The frame and the arm holder are formed of different resin materials, and one of the resin materials is excellent in slidability.
[0011]
That is, the liquid level sensor forms the first bearing portion and the second bearing portion at intervals on the frame, and forms the upper holding portion and the lower holding portion at intervals on the arm holder. A lower holding portion of the arm holder is inserted and fitted between the first bearing portion and the second bearing portion with an upper surface of the lower holding portion abutting against a lower surface of the second bearing portion. The first bearing portion is inserted between the upper holding portion and the lower holding portion, and the rotating shaft portion of the float arm is inserted into the upper holding portion, the first bearing portion, the lower holding portion, and the second bearing portion. The frame and the arm holder are formed of different resin materials, and one of the resin materials is excellent in slidability.
[0012]
The liquid level sensor is configured such that a lower holding portion of an arm holder is provided between a first bearing portion and a second bearing portion of a frame, and an upper surface of the lower holding portion abuts on a lower surface of the first bearing portion. It is inserted.
If the frame and the arm holder are formed of the same resin, the frictional force increases, the sliding torque increases, and the detection accuracy decreases.
In such a case, a metal washer is interposed between the lower surface of the first bearing portion of the frame and the upper surface of the lower holding portion of the arm holder to reduce frictional resistance. According to the liquid level sensor of the present invention, the frame and the arm holder are formed of different resin materials, and one of the resin materials has excellent slidability, so that frictional resistance is reduced and a metal washer is provided. Is unnecessary.
[0013]
In the liquid level sensor according to the second aspect of the present invention, the frame and the arm holder are made of a commonly used general-purpose polyacetal resin (general-purpose POM resin), and the arm holder is made of a slidable material. It is preferable to use a POM or polyphenylene sulfide resin (PPS resin) having excellent free sliding property.
When the frame and the arm holder are formed of different resin materials, it is possible to reduce frictional resistance and wear of the sliding portions thereof. In particular, in the case of the free slidable POM resin and the PPS resin, the shrinkage ratio is smaller than that of the general-purpose POM, and dimensional change hardly occurs under the use conditions.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a liquid level sensor according to the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view conceptually showing a liquid level sensor according to the present invention, and FIG. 2 is a sectional view of a main part thereof.
[0015]
As shown in FIGS. 1 and 2, the liquid level sensor 1 of the present embodiment includes a frame 2 made of general-purpose polyacetal resin (general-purpose POM resin), a float arm 3 made of metal, and a slidable polyacetal resin (free sliding). It comprises an arm holder 4 made of a dynamic POM resin), a contact piece 5, a float 6 having buoyancy with respect to a liquid to be measured, and a wiring board 7.
[0016]
The frame 2 is provided with an electric circuit for detecting the liquid level based on the rotation of the float arm 3 in response to the liquid level fluctuation of the liquid to be measured as indicated by an arrow in FIG. The body 7a, the output terminal 8 and the like are mounted. The upper surface is open and has a predetermined thickness.
The rotatable angle of the float arm 3 is defined by stoppers 9a and 9b having a predetermined height in consideration of the structure of the float arm 3 at a part of the upper and lower edges on the side where the frame 2 is open. . That is, the point at which the float arm 3 contacts the stopper 9a corresponds to the highest liquid level, and the point at which the float arm 3 contacts the stopper 9b corresponds to the lowest liquid level.
[0017]
As shown in FIG. 2, a first bearing portion 2 a is formed near the right end of the frame 2 as a part of the frame 2. The first bearing 2a is provided with a first bearing rotation shaft hole 2c into which the rotation shaft 3a of the float arm 3 is inserted.
Below the first bearing 2a, a second bearing 2b is formed as a part of the frame 2 while maintaining a predetermined distance substantially parallel to the first bearing 2a. The second bearing portion 2b is also provided with a second bearing portion rotating shaft hole 2d which is provided so as to face the first bearing portion rotating shaft hole 2c and into which the rotating shaft portion 3a is rotatably inserted. I have. A space between the first bearing 2a and the second bearing 2b is configured to be attachable so that a lower holding portion 4b of the arm holder 4, which will be described later, meshes with the first bearing 2a.
[0018]
The float arm 3 is a single metal rod, and includes a rotating shaft 3a serving as a fulcrum of rotation and a rotating portion 3b which is bent substantially at right angles to the rotating shaft 3a and rotates about the rotating shaft 3a. Consists of A rectangular parallelepiped float 6 made of a material having a buoyancy with respect to the liquid to be measured is attached to the tip of the rotating portion 3b of the float arm 3. The tip of the rotating portion 3b is fixed by penetrating the center of both ends of the float 6.
[0019]
The arm holder 4 holds the float arm 3 and engages with the frame 2 to rotate the held float arm 3 around the rotation shaft 3a. The arm holder 4 has a U-shaped cross section including an upper holding portion 4a and a lower holding portion 4b formed so as to be substantially parallel to each other with the first bearing portion 2a of the frame 2 sandwiched from above and below. I have.
The upper holding portion 4a and the lower holding portion 4b are provided with an upper holding portion rotation shaft hole 4d and a lower holding portion rotation shaft hole 4e so as to face each other. The rotating shaft portion 3a of the float arm 3 is rotatably inserted into the upper holding portion rotating shaft hole 4d and the lower holding portion rotating shaft hole 4e.
[0020]
On the upper surface of the upper holding portion 4a, the turning portion 3b of the float arm 3 can be press-fitted from above, and the claw-shaped arm holding portion 4c having an open upper side for holding the press-fit turning portion 3b. Is formed.
The contact piece 5 fixed to the arm holder 4 has elasticity, and a contact 5a provided at the tip thereof is urged by the elasticity to the resistor 7a of the circuit board 7 attached to the frame 2 to make contact. are doing. These are used at the time of liquid level detection based on the rotation of the float arm 3.
[0021]
The second bearing portion rotation shaft hole 2d extends from the lower surface of the second bearing portion 2b to the lower surface in a cylindrical shape. The extended portion x corresponds to the thickness of the bush of the first conventional example, as can be seen by comparing FIGS. 2 and 4A. In the first conventional example, since the bush rotates together with the float arm 3, this does not become the bearing length, but in the present embodiment, the extended portion x becomes a part of the bearing length.
That is, according to the present embodiment, the bearing length is extended by x to become X3, so that the stability of the rotation of the float arm 3 is further improved. In other words, when manufacturing the liquid level sensor of the first conventional example and the present embodiment having the same bearing length, the present invention is more compact.
[0022]
The upper holding portion rotation shaft hole 4d has a chamfered inner peripheral edge, and gradually decreases in diameter from the upper surface portion of the upper holding portion 4a to the lower portion. Are formed so as to be substantially equivalent to the rotating shaft 3a. Therefore, the rotation shaft portion 3a of the float arm 3 is easily inserted into the rotation shaft hole 4d, and the assembling time is reduced.
[0023]
At the time of assembly, the rotating shaft portion 3a of the float arm 3 is connected to the upper holding portion rotating shaft hole 4d, the first bearing rotating shaft hole 2c, the lower holding portion rotating shaft hole 4e, and the second bearing rotating shaft hole 2d. It is inserted from the top in order. Then, the rotating part 3b of the float arm 3 is pressed into and held by the arm holding part 4c. At this time, the lower surface of the first bearing portion 2a is in contact with the upper surface of the lower holding portion 4b.
That is, the float arm 3 comes off from the frame 2 due to the insertion of the rotating shaft portion 3a into each shaft hole, the holding of the rotating portion 3b by the arm holding portion 4c, and the contact between the first bearing portion 2a and the lower holding portion 4b. Not to be.
[0024]
The liquid level sensor 1 having such a structure is attached to a container (not shown) for storing a liquid to be measured such as gasoline. When the float 6 moves up and down due to a change in the liquid level, the float arm 3 rotates around the rotation shaft 3a within the above-defined predetermined angle range.
Due to this rotation, the contact 5a of the contact piece 5 slides on the resistor 7a, and the resistance value between one end of the resistor 7a and the output terminal 8, that is, the contact 5a of the contact piece 5 in the detection circuit. Change. By detecting this resistance change, a level signal indicating the liquid level fluctuation can be taken out from the output terminal 8.
[0025]
In the liquid level sensor 1 having such a structure, the frame 2 is made of a general-purpose polyacetal resin (general-purpose POM resin) which has been conventionally used, and the arm holder 4 is made of a free-sliding POM or polyphenylene having excellent slidability. It is a sulfide resin (PPS resin). It has been confirmed that when such dissimilar materials are used, the sliding torque can be reduced and the squealing noise can also be reduced.
[0026]
〔Example〕
The frame 2 is made of POM resin (Duracon M90-44), the arm holder 4 is made of free slidable POM (Duracon TW-51), gasoline is applied to the sliding part, and the shaft is slid several times. After that, the sliding torque and the squeaking noise of the shaft were confirmed.
The result is the same structure as that of the present invention, in which the frame 2 and the arm holder 4 are formed of a conventionally employed POM resin (Comparative Example 1), and the liquid of the conventional structure shown in FIG. Table 1 shows a conventional level sensor (comparative example 2) in which a frame 2 and an arm holder 4 are formed of POM resin and a washer is interposed between them.
[0027]
[Table 1]

[0028]
As is clear from Table 1 above, in this embodiment, the sliding torque is reduced and the squeaking noise is also reduced.
[0029]
【The invention's effect】
As described above, according to the liquid level sensor of the first aspect of the present invention, the first bearing portion of the frame is sandwiched between the first bearing portion and the second bearing portion of the arm holder, and the Since the second bearing portion of the arm holder is sandwiched between the first bearing portion and the second bearing portion, the rotation stability of the float arm is increased, smooth rotation is possible, and measurement accuracy is improved. .
Further, compared with the first conventional example, a bush and a washer for preventing falling off are not required, so that the number of parts can be reduced, the number of assembling steps can be reduced, and the cost can be reduced due to the weight reduction.
In particular, since the lower surface of the first bearing portion serving as a pivot point and the upper surface of the lower holding portion are slidably contacted with each other, contact resistance that hinders rotation of the float arm is reduced. That is, in the liquid level sensor according to the present invention, since the location where the contact resistance occurs is closer to the rotation axis than in the second conventional example, the rotation torque is further increased by the principle of leverage. Therefore, smooth rotation is possible, and measurement accuracy is improved as compared with the second conventional example.
[0030]
Further, the lower holding portion of the arm holder is provided between the first bearing portion and the second bearing portion of the frame, and the upper surface of the lower holding portion is brought into contact with the lower surface of the first bearing portion, so that the metal washer is omitted. However, the frictional resistance can be reduced by forming the frame and the arm holder from different materials and using one of the materials having excellent slidability. Therefore, the number of parts can be reduced by eliminating the washer, so that not only the cost for parts and processing can be reduced, but also the size can be reduced.
[0031]
Further, according to the liquid level sensor according to the second aspect of the present invention, one of the material of the frame and the arm holder is a conventionally used general-purpose POM resin, and the other material is a free slidable POM or It is PPS resin. The free-sliding POM or PPS resin has a smaller change in contact pressure since the shrinkage is smaller than that of the general-purpose POM, so that a stable detection accuracy can be secured.
[0032]
As a result, it is possible to obtain a liquid level sensor that achieves a reduction in the number of parts and a reduction in size while maintaining high measurement accuracy.
[Brief description of the drawings]
FIG. 1 is a perspective view conceptually showing a liquid level sensor according to the present invention.
FIG. 2 is an enlarged vertical sectional view of a main part in FIG.
FIG. 3 is a plan view common to the liquid level sensors of the first conventional example and the second conventional example.
FIG. 4A is an enlarged cross-sectional view of a main part of a liquid level sensor according to a first conventional example, and FIG. 4B is an enlarged cross-sectional view of a main part of a liquid level sensor according to a second conventional example. is there.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Liquid level sensor 2 Resin frame 2a 1st bearing part 2c 1st bearing part rotating shaft hole 2b 2nd bearing part 2d 2nd bearing part rotating shaft hole 3 Metallic float arm 3a Rotating shaft part 3b Rotating part 3c Tip part 4 Resin arm holder 4a Upper holding part 4b Lower holding part 4c Arm holding part 5 Contact piece 5a Contact 6 Float 7 Wiring board 7a Resistor 8 Output terminal 9a, 9b Stopper

Claims (2)

A single rod-shaped float arm formed by a rotating shaft portion and a rotating portion bent substantially at right angles to the rotating shaft portion and rotating about the rotating shaft portion; and a tip of a rotating portion of the float arm A float mounted on the unit, having a buoyancy with respect to the liquid to be measured, and a frame on which an electric circuit board for detecting a liquid level of the liquid to be measured based on the rotation of the float arm is mounted; A first bearing formed near the end as a part of the frame, a first bearing rotary shaft hole provided in the first bearing and into which the rotary shaft is inserted, and the first bearing An arm holder having a U-shaped cross section including an upper holding portion and a lower holding portion formed so as to be substantially parallel to each other with a portion having a rotation shaft hole from above and below, the rotation shaft being provided on the arm holder; Department A holder rotating shaft hole to be inserted, is formed on the upper surface of the upper retaining portion is capable pressed the rotator is from above, comprises an arm holder for holding the rotating portion which is press-fitted,
The first bearing portion is sandwiched between the upper holding portion and the lower holding portion, the rotating shaft portion is inserted into the first bearing portion rotating shaft hole and the holder rotating shaft hole from above, and the rotating portion is configured to hold the arm. A liquid level sensor, wherein the lower surface of the first bearing portion and the upper surface of the lower holding portion are slidably in contact with each other,
A liquid level sensor, wherein the frame and the arm holder are formed of different resin materials, and one of the resin materials has excellent slidability. 2. The liquid level sensor according to claim 1, wherein one of the frame and the arm holder is made of a free slidable polyacetal resin or a polyphenylene sulfide resin.

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