JP2003004506A - Liquid level sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid level sensor which achieves reduction in number of part items and miniaturized without decreasing the precision in detection. SOLUTION: The device is assembled so as to have a frame 2 whose cross-section is U-shaped and an arm holder 4 engage with each other, so that the stability of the turn of a float arm 3 is increased and enables its smooth turn, thereby increasing the measurement precision. Moreover, bushes and washers to prevent slip-off become unnecessary, which brings about a reduction in the number of part items, a reduction man-hours in assembly, and a reduction in the cost by making the device lightweight. Moreover, the under side part and the upper side part of a lower side support part 4b of a frame bearing part 2a which forms a fulcrum are contacted in a slidable way, so that the contact resistance that obstructs the turn of the float arm 3 is decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level sensor equipped with a float arm that rotates in accordance with the liquid level, and more particularly to a liquid level sensor mounted on a fuel tank of a vehicle that uses a liquid such as gasoline or light oil as a fuel. , A liquid level sensor suitable for detecting the remaining amount of fuel.

[0002]

2. Description of the Related Art Conventionally, a liquid level sensor of this type has a structure shown in FIGS. Here, two types of liquid level sensors are illustrated as conventional examples. FIG. 4 is a plan view common to the first conventional example and the second conventional example. FIG. 5A is an enlarged cross-sectional view of a main part of a liquid level sensor as a first conventional example, and FIG.
It is a principal part expanded sectional view of the liquid level sensor as a prior art example.

First, referring to FIG. 4 and FIG.
A conventional liquid level sensor will be described. The liquid level sensor 91A includes a resin frame 92, a metal float arm 93, a resin arm holder 94,
It includes a contact 95, a float 96 having a buoyancy with respect to the liquid to be measured, and a resistor 97.

One end of the float arm 93, that is, the rotary shaft portion 93a is attached to the mounting portion 94a of the arm holder 94.
The intermediate portion 93b of the float arm 93, which is inserted into the mounting hole 94a1 provided in, is clamped and fixed by the claw portion 94b formed by extending from the mounting portion 94a, and is also provided in the mounting portion 92a of the frame 92. It is rotatably inserted into the mounting hole 92a1. Further, a bush 99 is press-fitted at the tip of the rotary shaft portion 93a with a washer 99a interposed therebetween. In this way, the arm holder 94 is attached to the frame 92 so as to be rotatable around the rotation shaft portion 93a. Further, a float 96 is attached to the other end of the float arm 93, that is, the tip 93c.

The above-mentioned contact 95 fixed to the arm holder 94 has elasticity, and the contact 95a provided at the tip end thereof is elastically biased to contact the resistor 97 attached to the frame 2. There is. The coil spring 98 is provided to obtain electrical continuity between the contact 95a of the contact 95 and an output terminal (not shown) provided on the frame 92 side.

The liquid level sensor 91A is attached to a container (not shown) for storing the liquid, and when the float 96 moves up and down due to fluctuations in the liquid level, the float arm 93 moves around the mounting hole 92a1 in a predetermined angle range. Rotate inside.
By this rotation, the contact 95 slides on the resistor 97, and one end of the resistor 97 and a non-illustrated output terminal, that is, the contact 9 of the contact 95 in the sensor circuit (not shown).
When the resistance value between 5a and 5a changes, this can be detected and a level signal indicating the liquid level fluctuation amount can be taken out. In the figure, X indicates a bearing length which is one of the indexes of stability when the float arm 93 rotates.

Further, a liquid level sensor 91 of the second conventional example.
As shown in FIGS. 4 and 5B, B is a resin-made frame 2, similar to the liquid level sensor 91A of the first conventional example.
It is configured to include a float arm 3 made of metal, a holder 4 made of resin, a contact piece 5, a float 6 having buoyancy with respect to the liquid to be measured, and a resistor 7. However, in the liquid level sensor 91B, the arm holder 94 is provided with the fall-preventing piece 94c, so that the washer 99a and the bush 99 of the liquid level sensor 91A of the first embodiment are unnecessary. As shown in FIG. 5B, the drop-out prevention piece 94c has a shape in which the side surface of the arm holder 94 is extended and bent. The fall prevention piece 94c comes into contact with the arcuate end 92b of the frame 92 over the rotation stroke of the float arm 93 so that the arm holder 94 integrated with the float arm 93 falls off the frame 92. It is attached so that it can be rotated without doing. The liquid level sensor 91B of the second conventional example can also perform the same operation as the liquid level sensor 91A of the first conventional example to extract the level signal indicating the liquid level variation amount.

[0008]

However, the above-mentioned first and second conventional examples have the following problems. That is, according to the above-mentioned first conventional example, in order to maintain the detection accuracy above a certain level, the bearing length X above a predetermined length is required.
In addition to the bearing length X, the washer 99a and the thickness B of the bush 99 are added, and miniaturization becomes difficult.
Further, there is a limitation on the mounting place by the washer 99a and the bush 99. Further, according to the second conventional example, the size can be reduced as compared with the first conventional example, but since contact friction is newly generated between the cap 94c and the frame 92 at the time of rotation, the float. The smooth rotation of the arm 93 is hindered. In particular, the drop-out prevention piece 94c causes contact resistance at a position largely separated from the rotation axis, that is, in the vicinity of the circumference of the rotation circle, so that the smooth rotation of the float arm 93 is further hindered. That is,
According to the second conventional example, the detection accuracy is lowered due to the pursuit of miniaturization.

Therefore, in view of the above-mentioned present situation, it is an object of the present invention to provide a liquid level sensor which achieves a reduction in the number of parts and a reduction in size without lowering the detection accuracy.

[0010]

A liquid level sensor according to a first aspect of the present invention, which has been made to solve the above-mentioned problems, has a rotating shaft portion 3a (13a) and this rotating shaft, as shown in FIGS. A rod-shaped float arm 3 (13) formed by a rotating portion 3b (13b) that is bent substantially at right angles to the portion 3a (13a) and that rotates about the rotating shaft portion 3a (13a). , A float 6 (16) attached to the tip of the rotating part 3b (13b) of the float arm 3 (13) and having buoyancy with respect to the liquid to be measured, and the float arm 3 (13). A frame 2 (12) on which an electric circuit for detecting the liquid surface level of the liquid to be measured is mounted based on the frame 2 (12) and a part of the frame 2 (12) formed near the end of the frame 2 (12). Frame bearing portion 2a (1 And a), the frame bearing part 2a
The rotating shaft portion 3a (13a) provided on (12a)
The frame shaft hole 2a1 (12a1) into which is inserted, and the upper holding portion 4a (14a) and the lower side which are formed so as to be substantially parallel to each other with the portion having the frame shaft hole 2a1 (12a1) sandwiched from above and below. An arm holder 4 (14) having a U-shaped cross section including a holding portion 4b (14b), and the rotary shaft portion 3a provided on the arm holder 4 (14).
Holder shaft holes 4a1 and 4b1 into which (13a) is inserted
(14b1) and the rotating portion 3b (13b) formed on the upper surface of the upper holding portion 4a (14a) can be press-fitted from the upper side, and the rotating portion 3b (13b) is press-fitted.
And an arm holding portion 4b (14b) for holding the frame bearing portion 2a (12a).
(14a) and the lower holding portion 4b (14b), the rotary shaft portion 3a (13a) is inserted into the frame shaft hole 2a1 (12).
a1) and the holder shaft holes 4a1, 4b1 (14b1) are inserted from above, the rotating portion 3b (13b) is held by the arm holding portion 4b (14b), and the lower surface of the frame bearing portion 2a (12a). And the upper surface of the lower holding portion 4b (14b) are slidably abutted.

According to the first aspect of the invention, the arm holders 4 (14) are arranged substantially parallel to each other with the portion of the frame 2 (12) having the frame shaft holes 2a1 (12a1) interposed therebetween from above and below. The formed upper holding portion 4a (14
It has a U-shaped cross section including a) and the lower holding portion 4b (14b). And this arm holder 4 having a U-shaped cross section
The frame bearing portion 2a (12a) of the frame 2 (12) is attached so as to be sandwiched by (14). Further, the rotating shaft portion 3a (13) of the float arm 3 (13)
a) is inserted into each shaft hole from above, and the rotating portion 3b (13)
b) is held by the arm holding portion 4b (14b), and the lower surface portion of the frame bearing portion 2a (12a) and the upper surface portion of the lower holding portion 4b (14b) slidably abut. With such a structure, a bush and a washer for preventing the falling-off are unnecessary. Further, since the lower surface portion of the frame bearing portion 2a (12a) that serves as a fulcrum of rotation and the upper surface portion of the lower holding portion 4b (14b) are slidably abutted, the rotation of the float arm 3 (13) is prevented. The contact resistance that hinders movement is reduced. That is, according to the present invention, since the location where the contact resistance is generated is close to the rotating shaft,
The lever principle enables smooth rotation even if the rotation torque is small.

A liquid level sensor according to a second aspect of the present invention, which has been made in order to solve the above-mentioned problems, as shown in FIG. 1, in the liquid level sensor according to the first aspect, below the frame bearing portion 2a, A frame lower portion bearing portion 2b formed as a part of the frame 2 and a frame lower portion bearing portion 2b are arranged so as to face the frame shaft hole 2a1 while maintaining a predetermined distance substantially in parallel with the frame bearing portion 2a. And a lower frame shaft hole 2b1 into which the rotary shaft portion 3a is rotatably inserted. The rotary shaft portion 3a includes the holder shaft hole 4a1 and the frame shaft hole 2a.
1, holder lower shaft hole 4b1 and frame lower shaft hole 2b
1 is inserted from above in this order.

According to the second aspect of the present invention, below the frame bearing portion 2a, a lower frame bearing portion 2b is formed as a part of the frame 2 while maintaining a predetermined distance substantially parallel to the frame bearing portion 2a. Is included. That is, the frame 2 also has a U-shaped cross section like the arm holder 4. In this way, since the frame 2 and the arm holder 4 having a U-shaped cross section are assembled so as to be engaged with each other, the stability of the rotation of the float arm 3 is increased.

A liquid level sensor according to a third aspect of the present invention, which is made in order to solve the above-mentioned problems, as shown in FIG. 1, in the liquid level sensor according to the second aspect, the frame lower shaft hole 2b1 has the above-mentioned structure. It is characterized in that it extends downward in a tubular shape from the lower surface of the frame lower bearing portion 2b.

According to the third aspect of the invention, the frame lower shaft hole 2b1 formed in the frame lower bearing portion 2b.
Extends downward in a cylindrical shape from the lower surface of the frame lower bearing portion 2b. This extended portion is shown in FIG.
As can be seen by comparing with (A), this corresponds to the thickness of the bush of the first conventional example. 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 invention, this extended portion becomes a part of the bearing length. That is, according to the present invention, the bearing length is extended and the stability of the rotation of the float arm 3 is improved.

A liquid level sensor according to a fourth aspect of the present invention, which has been made in order to solve the above-mentioned problems, as shown in FIG. 2, is the liquid level sensor according to the first, second or third aspect, wherein the frame bearing portion 2a is provided. The lower holding portion 4b and the lower holding portion 4b are both made of resin, and the metal washer 20 having a hollow hole 20a into which the rotary shaft portion 3a can be inserted is provided between the frame bearing portion 2a and the lower holding portion 4b. It is characterized by being installed.

According to the fourth aspect of the present invention, both the frame bearing portion 2a and the lower holding portion 4b are made of resin, and the metal washer 20 is interposed between them. As a result, smooth rotation of the float arm 3 due to sliding friction between resins is impeded, and the occurrence of hysteresis characteristics is greatly reduced.

A liquid level sensor according to a fifth aspect of the present invention, which has been made to solve the above-mentioned problems, as shown in FIGS. 1 and 2, in the liquid level sensor according to the fourth aspect, the holder shaft hole 4a1 is The diameter of the upper holding portion 4a is gradually reduced from the upper surface of the upper holding portion 4a, and the lower surface of the upper holding portion 4a has a diameter substantially equal to that of the rotating shaft portion 3a. .

According to the fifth aspect of the invention, the diameter of the holder shaft hole 4a1 gradually becomes smaller as it goes downward from the upper surface of the upper holding portion 4a. It becomes easy to insert into 4a1.

A liquid level sensor according to a sixth aspect of the present invention, which has been made in order to solve the above-mentioned problems, as shown in FIG. 3, in the liquid level sensor according to the first aspect, a lower surface portion of the frame bearing portion 12a is provided. Is a cylindrical convex cylindrical portion 12a3 extending downward so as to surround the frame shaft hole 12a1.
And a cylindrical concave cylindrical portion 14b2 having a shape corresponding to the convex cylindrical portion 12a3 and extending upward from around the holder shaft hole 14b1 is formed on the upper surface of the lower holding portion 14b, The convex cylindrical portion 12a3 and the concave cylindrical portion 14b2 are rotatably fitted.

According to the sixth aspect of the invention, since the convex cylindrical portion 12a3 and the concave cylindrical portion 14b2 are rotatably fitted, the stability of the rotation of the float arm 3 is increased. Further, it is possible to eliminate a protrusion such as a bush from the outer surface.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment of the liquid level sensor of the present invention will be described with reference to FIG. Figure 1
(A) And (B) is the top view and the principal section expanded sectional view showing a 1st embodiment of a liquid level sensor of the present invention, respectively.

As shown in FIGS. 1A and 1B, the first
The liquid level sensor 1 according to the embodiment includes a resin frame 2, a metal float arm 3, a resin arm holder 4, a contact piece 5, a float 6 having a buoyancy force against a liquid to be measured, and a resistor 7. Composed of and.

The frame 2 is an electric circuit for detecting the liquid surface level based on the rotation of the float arm 3 according to the liquid surface level fluctuation of the liquid to be measured as shown by the arrow in the figure, for example, A resistor 7 and an output terminal 8 which will be described later are mounted. As shown in FIG. 1 (A), the outer shape has a shape close to a trapezoid when viewed from above, and as shown in FIG. 1 (B), the top surface is open and has a predetermined thickness. There is.
Stoppers 9a and 9b having a predetermined height in consideration of the structure of the float arm 3 are formed on a part of upper and lower edges of the frame 2 on the open side. This stopper 9a
And 9b define the rotatable angle of the float arm 3. That is, basically, the float arm 3
The point in contact with the stopper 9a corresponds to the highest level of the liquid surface, and the point in contact with the stopper 9b corresponds to the lowest level of the liquid surface.

As shown in FIG. 1A, the vicinity of the right end portion of the frame 2 is a part of the frame 2 and the frame bearing portion 2 is formed.
a is formed. The frame bearing portion 2a is provided with a frame shaft hole 2a1 into which the rotary shaft portion 3a of the float arm 3 is inserted. Further, below the frame bearing portion 2a, a frame lower bearing portion 2b is formed as a part of the frame 2 while maintaining a predetermined distance substantially in parallel with the frame bearing portion 2a. This frame lower bearing 2
Also in b, a frame lower shaft hole 2b1 which is provided so as to face the frame shaft hole 2a1 and into which the rotary shaft portion 3a is rotatably inserted is provided. A space between the frame bearing portion 2a and the frame lower bearing portion 2 has a shape that can be attached so that a lower holding portion 4b of an arm holder 4, which will be described later, engages with each other.

The float arm 3 is in the shape of a single metal rod, and is a fulcrum of rotation. The rotary shaft portion 3a is bent, and is bent at a substantially right angle to the rotary shaft portion 3a to rotate about the rotary shaft portion 3a. It is composed of a rotating portion 3b. A cylindrical float 6 made of a material having 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 bottom surfaces of the float 6.

The arm holder 4 holds the float arm 3 and engages with the frame 2 to rotate the held float arm 3 with the rotating shaft portion 3a as a fulcrum. The arm holder 4 has a U-shaped cross-section including an upper holding portion 4a and a lower holding portion 4b which are formed so as to be substantially parallel to each other with the frame shaft hole 2a1 of the frame 2 sandwiched from above and below. is doing. A holder shaft hole 4a1 and a holder lower shaft hole 4b are provided so as to face the upper holding portion 4a and the lower holding portion 4b, respectively.
1 (in claim 1, the holder shaft hole 4a1 and the holder lower shaft hole 4b1 are both described as a holder shaft hole). In the holder shaft hole 4a1 and the holder lower shaft hole 4b1, the rotary shaft portion 3 of the float arm 3 is inserted.
a is rotatably inserted.

Further, the rotating portion 3b of the float arm 3 can be press-fitted into the upper surface of the upper holding portion 4a from above.
An arm holding part 4b having a claw shape with an open upper side for holding the press-fitted rotating part 3b is formed. Further, the contact piece 5 fixed to the arm holder 4 has elasticity,
The contact point 5a provided at the tip end thereof is elastically urged into contact with the resistor 7 attached to the frame 2. These are based on the rotation of the float arm 3,
Used when detecting the liquid level.

The lower frame shaft hole 2b1 extends downward from the lower surface of the lower frame bearing portion 2b in a cylindrical shape. This extended portion X1 is shown in FIG. 1 (B) and FIG.
As can be seen by comparing with (A), it corresponds to the thickness B of the bush of the first conventional example. 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, this extended portion X1.
Is part of the bearing length. That is, according to the present embodiment, the bearing length extends by X1 and the stability of the rotation of the float arm 3 is further improved. On the contrary, when manufacturing the liquid level sensor of the first conventional example and the present embodiment having the same bearing length,
The invention is smaller.

Further, the diameter of the holder shaft hole 4a1 gradually decreases from the upper surface of the upper holding portion 4a as it goes downward, and the diameter of the lower surface of the upper holding portion 4a is substantially the same as that of the rotating shaft portion 3a. have. Therefore, the float arm 3 can be easily inserted into the shaft hole 4a1, and the assembly time can be shortened.

At the time of assembly, the rotary shaft portion 3a of the float arm 3 is inserted into the holder shaft hole 4a1, the frame shaft hole 2a1, the holder lower shaft hole 4b1 and the frame lower shaft hole 2b1 in this order from above. It And
The rotating portion 3b of the float arm 3 is press-fitted and held in the arm holding portion 4b. At this time, the lower surface portion of the frame bearing portion 2a and the upper surface portion of the lower holding portion 4b are in pressure contact with each other. That is, the rotation shaft portion 3a is inserted into each shaft hole, the rotation portion 3b is held by the arm holding portion 4b, and the frame bearing portion 2 is held.
The float arm 3 is prevented from falling off the frame 2 by the contact between the a and the lower holding portion 4b.

The liquid level sensor 1 having such a structure is
It is attached to a container (not shown) that stores a liquid to be measured such as gasoline. Then, when the float 6 moves up and down due to the fluctuation of the liquid level, the float arm 3 moves to the rotating shaft portion 3a.
Is used as a fulcrum to rotate within the regulated predetermined angle range as described above. By this rotation, the contact piece 5 slides on the resistor 7, and a detection circuit (not shown) causes a gap between one end of the resistor 7 and the output terminal (not shown), that is, the contact 5a of the contact piece 5. When the resistance value changes, this can be detected and a level signal indicating the amount of liquid level fluctuation can be taken out from the output terminal 8.

As described above, according to the first embodiment, the frame bearing portion 2a of the frame 2 is mounted so as to be sandwiched between the arm holders 4 having a U-shaped cross section. Also,
Like the arm holder 4, the frame 2 also has a U-shaped cross section. Since the frame 2 and the arm holder 4 having a U-shaped cross section are assembled so as to be engaged with each other, the stability of the rotation of the float arm 3 is increased, the smooth rotation is possible, and the measurement accuracy is improved. Further, as compared with the first conventional example, a bush and a washer for preventing slipping out 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. Particularly, since the lower surface portion of the frame bearing portion 2a, which serves as a fulcrum of rotation, and the upper surface portion of the lower holding portion 4b slidably abut, the second bearing shown in FIG.
As is clear from comparison with the conventional example, the float arm 3
The contact resistance that hinders the rotation of is reduced. That is,
In the present embodiment, since the location where the contact resistance is generated is closer to the rotating shaft than the second conventional example, the principle of leverage makes the rotation smooth even if the rotating torque is small. Therefore, smooth rotation is possible, and the measurement accuracy is improved as compared with the second conventional example. As a result of the above, according to the first embodiment, it is possible to obtain a liquid level sensor that achieves reduction in the number of parts and miniaturization while maintaining high measurement accuracy.

Next, a second embodiment of the liquid level sensor of the present invention will be described with reference to FIG. FIGS. 2A and 2B are a plan view and an enlarged cross-sectional view of an essential part showing a second embodiment of the liquid level sensor of the present invention, respectively.

Basically, in the liquid level sensor of the second embodiment, in order to reduce the sliding resistance of the liquid level sensor 1 of the first embodiment shown in FIG. 1, the frame bearing of the frame 2 is used. The lower surface of the portion 2a and the arm holder 4
A metal washer 20 is provided between the lower holding portion 4b and the upper surface portion.

As shown in FIGS. 2A and 2B, this washer 20 is a substantially trapezoidal metal plate having a predetermined thickness. A hollow hole 20a into which the rotary shaft portion 3a of the float arm 3 can be inserted is provided in the center of the washer 20.
Is provided. This washer 20 is shown in FIG.
2 is inserted under the frame shaft hole 2a1 shown in FIG.
As shown in (B), it is mounted between the lower surface portion of the frame bearing portion 2a of the frame 2 and the upper surface portion of the lower holding portion 4b of the arm holder 4. Hollow hole 20 of washer 20
The rotary shaft portion 3a of the float arm 3 is inserted through a. In FIG. 2, parts having the same structures as those in FIG. 1 are designated by the same reference numerals, and duplicate description will be omitted. Since the operation is the same, duplicate description will be omitted.

As described above, according to the second embodiment, both the frame bearing portion 2a and the lower holding portion 4b are made of resin,
A metal washer 20 is interposed between them. As a result, smooth rotation of the float arm 3 due to sliding friction between resins is impeded, and the occurrence of hysteresis characteristics is greatly reduced. Therefore, according to this embodiment, the stability of the rotation of the float arm 3 is further improved. Also,
The wear of the sliding surfaces of the frame bearing portion 2a and the lower holding portion 4b is also reduced, and the product life is extended. Of course, it is needless to say that the same effect as that of the first embodiment can be obtained.

Further, a third embodiment of the liquid level sensor of the present invention will be described with reference to FIG. 3 (A) and 3 (B) are a plan view and an enlarged cross-sectional view of an essential part showing a third embodiment of the liquid level sensor of the present invention, respectively. Figure 3
FIG. 3C is an enlarged sectional view of an essential part showing a state where the frame and the arm holder in FIG. 3B are separated. This third
The liquid level sensor 10 of the embodiment has the same basic idea as that of the first embodiment of FIG. 1 described above, but the shapes of the frame and the arm holder are slightly different. This Figure 3
The liquid level sensor 10 according to the third embodiment indicated by corresponds to the invention of claim 6.

As shown in FIGS. 3A and 3B, the third
The liquid level sensor 10 according to the embodiment includes a resin frame 12, a metal float arm 13, a resin arm holder 14, and a float 16 having buoyancy with respect to the liquid to be measured.

In FIGS. 3 (A) and 3 (B), the frame 12 detects the liquid level based on the rotation of the float arm 13 according to the fluctuation of the liquid level of the liquid to be measured as shown by the arrow. An electric circuit for doing so, for example, a hall element 15c described later is mounted. When viewed from above, the outer shape has a shape close to a rectangle, as shown in FIG. The frame 12 is formed with an electronic device housing portion 12b that is open to the upper side. The electronic device housing 12b includes a Hall element 15c as a magnetoelectric conversion element that detects a magnetic force from a ring-shaped magnet 15a described later and converts the magnetic force into an electric signal, and a wiring board 15d on which the Hall element 15c and the like are mounted. It is housed. This wiring board 15d
An output terminal 15e for guiding the electric signal output from the hall element 15c to the outside is connected to the. The electronic device accommodating portion 12b is filled with a molding material (not shown). As will be described later, this electric signal corresponds to the rotatable angle of the float arm 3, that is, the liquid level. Further, a core 15f as a magnetism collecting member is also attached to the frame 12 in the Hall element 15c.

As shown in FIG. 3B, a frame bearing portion 12a is formed as a part of the frame 12 near the right end of the frame 12. The bearing portion 12a is provided with a frame shaft hole 12a1 into which the rotary shaft portion 13a of the float arm 13 is inserted. This frame shaft hole 1
The diameter of 2a1 is gradually reduced as it goes downward from the opening, so that the diameter of 2a1 becomes substantially the same as that of the rotating shaft portion 3a. Around the frame shaft hole 12a1 whose diameter is gradually reduced, the cylindrical convex cylindrical portion 12 is formed.
It is a2. A cylindrical convex cylindrical portion 12a3 is formed so as to surround the frame shaft hole 12a1 and extend downward.

The float arm 13 is in the shape of a single metal rod, and has a rotating shaft portion 13a serving as a fulcrum of rotation, and the rotating shaft portion 1 which is bent substantially at right angles to the rotating shaft portion 13a.
It comprises a rotating portion 13b which rotates about 3a. A cylindrical float 16 made of a material having buoyancy with respect to the liquid to be measured is attached to the tip of the rotating portion 13b of the float arm 13. The tip of the rotating portion 13b is fixed by penetrating the center of both bottom surfaces of the float 16.

The arm holder 14 holds the float arm 13 and meshes with the frame 12 to hold the float arm 13 in the rotating shaft portion 13a.
Rotate around as a fulcrum. This arm holder 14
The frame 12 has a U-shaped cross section including an upper holding portion 14a and a lower holding portion 14b which are formed so as to be substantially parallel to each other with the portion having the frame shaft hole 12a1 interposed therebetween from above and below. The upper holding portion 14a has a convex cylindrical portion 12a.
It is bent so as to bypass the part with 2 (Fig. 3
(See (A)). In the lower holding portion 14b, the holder shaft hole 1
4b1 is provided. Further, a cylindrical concave cylindrical portion 14b2 having an inner wall surface corresponding to the shape of the convex cylindrical portion 12a3 so as to extend upward from around the shaft hole 14b1.
Are formed. A ring-shaped magnet 15a is attached to the outer wall of the concave cylindrical portion 14b2. The convex cylindrical portion 12a3 is also rotatably fitted in the concave cylindrical portion 14b2. Further, the rotating portion 13b of the float arm 13 can be press-fitted into the upper surface of the upper holding portion 14a of the arm holder 14 from the upper side, and the upper side holding the pressed-in rotating portion 13b has a claw shape with an open upper side. The arm holding portion 14c is formed.

The frame 12 and the arm holder 1
4 is molded separately as a component as shown in FIG. Then, in the direction indicated by the arrow, the arm holder 14
Are assembled by sandwiching the frame 12.
Further, the convex cylindrical portion 12a3 is replaced by the concave cylindrical portion 14
The rotation shaft portion 13 of the float arm 13 is fitted to the b2.
a is inserted into the shaft hole 14b1 from above. And
The rotating portion 13b of the float arm 13 is an arm holding portion 14
It is pressed into c and held. At this time, the convex cylindrical portion 12a
3 and the concave cylindrical portion 14b2 are rotatably in contact with each other.
With such a structure, the float arm 13 does not fall off the frame 12.

The liquid level sensor 10 having such a structure
Is a container for storing the liquid to be measured such as gasoline (not shown)
Attached to. Then, when the float 16 moves up and down due to the fluctuation of the liquid level, the float arm 13 rotates within the predetermined angle range with the rotating shaft portion 13a as a fulcrum.
This rotation changes the magnetic force from the magnet 15a detected by the hall element 15c, and an electric signal indicating the liquid surface level based on this change can be taken out from the output terminal 8.

As described above, according to the third embodiment, in particular, since the convex cylindrical portion 12a3 and the concave cylindrical portion 14b2 are rotatably fitted, the rotational stability of the float arm 3 is increased, Smooth rotation is possible and measurement accuracy is improved. Further, since it is possible to eliminate a protrusion such as a bush from the outer surface, there is also an effect that restrictions on the mounting place are lessened.

As described above, according to the first to third embodiments, it is possible to obtain the liquid level sensor which achieves the reduction of the number of parts and the miniaturization while maintaining the high measurement accuracy. Become.

[0048]

As described above, according to the first aspect of the present invention, as compared with the first conventional example, a bush and a washer for preventing slipping out are not required, and the number of parts is reduced and the number of assembling steps is reduced. It is possible to reduce the cost and to reduce the cost by reducing the weight. Further, the frame bearing portion 2a (1
Since the lower surface portion of 2a) and the upper surface portion of the lower holding portion 4b (14b) slidably contact each other, as is apparent from the comparison with the second conventional example of FIG. Arm 3 (1
The contact resistance that hinders the rotation of 3) becomes small. That is, in the present invention, since the portion where the contact resistance is generated is closer to the rotating shaft than the second conventional example, the lever principle enables smooth rotation even if the rotating torque is small. This smooth rotation improves the measurement accuracy as compared with the second conventional example. As a result of the above, according to the present invention, it is possible to obtain a liquid level sensor in which the number of parts is reduced and the size is reduced while maintaining high measurement accuracy.

According to the invention described in claim 2, the frame 2
Like the arm holder 4, it also has a U-shaped cross section.
In this way, since the frame 2 and the arm holder 4 having a U-shaped cross section are assembled so as to be engaged with each other, the stability of the rotation of the float arm 3 is increased, and a smoother rotation is made possible for measurement. Accuracy is improved.

According to the third aspect of the invention, the frame lower shaft hole 2b1 formed in the frame lower bearing portion 2b.
Extends downward in a cylindrical shape from the lower surface of the frame lower bearing portion 2b. This extended portion is shown in FIG.
As can be seen by comparing with (A), this corresponds to the thickness of the bush of the first conventional example. 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 invention, this extended portion becomes a part of the bearing length. That is, according to the present invention, the bearing length is extended, and the stability of the rotation of the float arm 3 is further improved.
On the contrary, in the case of manufacturing the first conventional example and the liquid level sensor of the present invention having the same bearing length, the present invention becomes smaller in size.

According to the fourth aspect of the invention, both the frame bearing portion 2a and the lower holding portion 4b are made of resin, and the metal washer 20 is interposed between them. As a result, smooth rotation of the float arm 3 due to sliding friction between resins is impeded, and the occurrence of hysteresis characteristics is greatly reduced. Therefore, according to the present invention, the stability of the rotation of the float arm 3 is further improved. Further, the wear of the sliding surfaces of the frame bearing portion 2a and the lower holding portion 4b is reduced, and the product life is extended.

According to the fifth aspect of the present invention, the diameter of the holder shaft hole 4a1 gradually becomes smaller as it goes downward from the upper surface of the upper holding portion 4a. 4a1 can be easily inserted and assembly time can be shortened.

According to the invention described in claim 6, the convex cylindrical portion 12a3 of the frame bearing portion 12a and the lower holding portion 14b.
Since it is rotatably fitted with the concave cylindrical portion 14b2 of
The stability of the rotation of the float arm 3 is increased, smooth rotation is possible, and the measurement accuracy is improved. Further, since it is possible to eliminate a protrusion such as a bush from the outer surface, there are less restrictions on the mounting place.

[Brief description of drawings]

1A and 1B are a plan view and an enlarged cross-sectional view of a main part showing a first embodiment of a liquid level sensor of the present invention, respectively.

2 (A) and 2 (B) are respectively a plan view and an enlarged sectional view of an essential part showing a second embodiment of the liquid level sensor of the present invention.

3 (A) and 3 (B) are respectively a plan view and an enlarged sectional view of an essential part showing a third embodiment of the liquid level sensor of the present invention. FIG. 3C is an enlarged cross-sectional view of an essential part showing a state where the frame and the arm holder in FIG. 3B are separated.

FIG. 4 is a plan view common to a first conventional example and a second conventional example.

FIG. 5 (A) is an enlarged sectional view of an essential part of a liquid level sensor of a first conventional example, and FIG. 5 (B) is an enlarged sectional view of an essential part of a liquid level sensor of a second conventional example. is there.

[Explanation of symbols]

1, 10 Liquid level sensor 2, 12 frames 3,13 float arm 4,14 Arm holder 5 contact pieces 6, 16 float 7 resistor 8 output terminals 9a, 9b stopper

Claims (6)

[Claims] 1. A rod-shaped float arm formed by a rotary shaft part and a rotary part that is bent substantially at right angles to the rotary shaft part and rotates about the rotary shaft part, and the float arm. It is attached to the tip of the rotating part of
A float having buoyancy with respect to the liquid to be measured, a frame on which an electric circuit for detecting the liquid level of the liquid to be measured based on the rotation of the float arm is mounted, and the frame near the end of the frame. A frame bearing part formed as a part of the frame bearing part, a frame shaft hole provided in the frame bearing part into which the rotating shaft part is inserted, and a portion having the frame shaft hole from above and below and substantially parallel to each other. And an upper holder and a lower holder each having a U-shaped cross section, a holder shaft hole into which the rotating shaft is inserted, the holder being provided in the arm holder, and the upper holder. The rotation part formed on the upper surface part of the part is press-fittable from the upper side, and includes an arm holding part that holds the press-fitted rotation part, wherein the frame bearing part is the upper holding part. And the lower holding portion, the rotary shaft portion is inserted from above into the frame shaft hole and the holder shaft hole, the rotating portion is held by the arm holding portion, and the lower surface portion of the frame bearing portion and the A liquid level sensor, wherein an upper surface portion of a lower holding portion is slidably abutted. 2. The liquid level sensor according to claim 1, wherein a lower portion of the frame formed as a part of the frame below the frame bearing portion and maintaining a predetermined distance substantially in parallel with the frame bearing portion. The rotating shaft part further includes a bearing part and a frame lower shaft hole in which the rotating shaft part is rotatably inserted in the frame lower bearing part so as to face the frame shaft hole. A liquid level sensor, which is inserted through the holder shaft hole, the frame shaft hole, the holder lower shaft hole, and the frame lower shaft hole in this order from above. 3. The liquid level sensor according to claim 2, wherein the frame lower shaft hole extends cylindrically downward from a lower surface portion of the frame lower bearing portion. 4. The liquid level sensor according to claim 1, 2 or 3, wherein both the frame bearing portion and the lower holding portion are made of resin, and are provided between the frame bearing portion and the lower holding portion. Is a metal level washer having a hollow hole into which the rotary shaft portion can be inserted, and a liquid level sensor. 5. The liquid level sensor according to claim 4, wherein the holder shaft hole has a diameter that gradually becomes smaller as it goes downward from an upper surface of the upper holding portion, and a lower surface of the upper holding portion has a smaller diameter. In, the liquid level sensor has a diameter substantially equal to that of the rotating shaft portion. 6. The liquid level sensor according to claim 1, wherein a cylindrical convex cylindrical portion extending downward is formed on a lower surface portion of the frame bearing portion so as to surround the frame shaft hole. On the upper surface of the side holding part, a cylindrical concave cylindrical part extending upward from around the holder shaft hole is formed in a shape corresponding to the convex cylindrical part, and the convex cylindrical part and the concave cylindrical part. A liquid level sensor, in which is rotatably fitted.