JP5230284B2 - Liquid level detector - Google Patents

Description

  The present invention relates to a liquid level detecting device, and more specifically, the level of a liquid level of a fuel tank of an automobile which uses an electrolyte (alcohol) itself such as ethanol, methanol, etc. or gasoline containing the electrolyte as fuel. The present invention relates to a liquid level detecting device capable of detecting the thickness.

  Conventionally, as a liquid level detection device for detecting the liquid level of a fuel tank of an automobile, a sliding arm is slid on a resistance plate by a float that moves up and down according to the liquid level, and the liquid level is changed to a potential difference. There is known a liquid level sensor that detects the liquid level by converting (see, for example, Patent Document 1 and Patent Document 2). As shown in FIG. 9, a liquid level sensor 1 described in Patent Document 1 includes a frame 2, a float arm 3, an arm holder 4, a contact piece 5, a float 6, a resistor plate 7, and an output terminal. 8A and 8B.

  The other end of a float arm 3 having a float 6 disposed at one end is rotatably supported by a bearing portion provided integrally with the frame 2. A contact piece 4 is fixed to the arm holder 5 held by the float arm 3, and a contact provided at the tip of the contact piece 4 comes into contact with the resistance plate 7 as the float arm 3 rotates. Rotate while. Thereby, the liquid level is converted into a potential difference between the output terminals 8A and 8B and output. Patent Document 1 does not particularly describe details such as materials of the output terminals 8A and 8B and an output harness for connecting the output terminals 8A and 8B to an external circuit or the like.

  The liquid level detection device described in Patent Document 2 has a detection mechanism similar to that of the liquid level sensor 1 of Patent Document 1, and includes a terminal that connects one end of the resistor and an external circuit and a connector terminal plate. The terminal is made of phosphor bronze or beryllium copper. One end of the terminal is in contact with one end of the resistor by spring elasticity, and the other end is caulked with a conductive wire to be electrically connected.

Japanese Patent No. 3898913 Japanese Patent Laid-Open No. 9-5145

  By the way, the liquid level detection device may be used in an automobile fuel tank that uses an electrolyte (alcohol) itself such as ethanol, methanol, or the like or gasoline containing the electrolyte as fuel. When the output terminals 8A and 8B, the connection terminals connected to the output terminals 8A and 8B, and the like are immersed in the fuel, electrolysis occurs due to a potential difference between the terminals 8A and 8B.

  Commonly used connection terminals are made of copper or copper alloy, and tin-plated ones are often used, and the positive output terminal copper or copper alloy melts by electrolysis and the negative output These metal ions are deposited on the terminals. Also, copper and copper alloys are melted out from the lead wires, contacts and fuel system part. Furthermore, when the float arm 11 is plated, the plated metal (generally zinc or zinc alloy) also melts out. In addition, metals contained in the constituent members such as magnesium and sodium are also dissolved. The deposited metal ions become metal oxides (insulators), increasing the contact resistance and greatly affecting the detection accuracy at the liquid level. As described above, there is a problem that the detection accuracy of the automobile liquid level detection device using ethanol or ethanol mixed gasoline as fuel is lowered.

  The present invention has been made in view of the above-described circumstances, and its purpose is to prevent the influence of electrolysis when immersed in an electrolyte solution, and to provide a vehicle using ethanol or ethanol mixed gasoline as fuel. An object of the present invention is to provide a liquid level detecting device capable of accurately detecting the liquid level.

In order to achieve the above-described object, the liquid level detecting device according to the present invention is characterized by the following (1) to ( 4 ).
(1) A liquid level detecting device for detecting a liquid level of a liquid containing an electrolytic solution,
A first sliding part, a second sliding part, a positive electrode electrically connected to the first sliding part, a negative electrode electrically connected to the second sliding part, A resistance plate having a conductive pattern formed on the substrate, and
A float that moves up and down according to the displacement of the liquid level to be measured;
A float arm having one end attached to the float and having the other end pivotably supported to rotate as the float moves up and down;
A sliding arm that slides on the resistance plate in conjunction with rotation of the float arm according to the liquid level;
A positive electrode connection terminal connected to the positive electrode;
A negative electrode connection terminal connected to the negative electrode;
With
The potential difference between the plus side electrode and the minus side electrode generated according to the position of the first sliding portion and the second sliding portion that the sliding arm contacts is the plus electrode connecting terminal and the minus electrode. It is output to the external circuit via the connection terminal,
The positive electrode connection terminal has a pair of contact pieces that sandwich the resistance plate with a spring elastic force, and one of the pair of contact pieces is in contact with the plus side electrode of the resistance plate,
The negative electrode connection terminal has a pair of contact pieces that sandwich the resistance plate with a spring elastic force, and one of the pair of contact pieces is in contact with the negative side electrode of the resistance plate,
Of the positive electrode connecting terminal and the negative electrode connecting terminal, only the contact surface of the contact piece that contacts the negative electrode of the negative electrode connecting terminal is coated with a metal having a higher redox potential than chromium. .
(2) A liquid level detecting device having the configuration of (1) above,
The metal is at least one of gold or gold alloy, silver or silver alloy, platinum or platinum alloy.
(3) The liquid level detecting device according to (2) above,
The metal is gold or a gold alloy.
(4) The liquid level detection device according to any one of (1) to (3) above,
The negative electrode connection terminal is covered with a plating layer made of at least one of tin or tin alloy, nickel or nickel alloy, chromium or chromium alloy, and the metal is applied to the contact surface of the contact piece. Be covered with .

  According to the present invention, it is possible to prevent metal ions from being deposited on the negative electrode connection terminal due to electrolysis when immersed in an electrolytic solution, and to accurately adjust the liquid level of an automobile using ethanol or ethanol mixed gasoline as fuel. It can be detected well.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.

  1 is a cross-sectional view showing the configuration of the liquid level detecting device of the present invention, FIG. 2 is a plan view of a resistance plate in FIG. 1, FIG. 3 is a cross-sectional view taken along arrow III-III in FIG. FIG. 5 is a side view of the connection terminal, FIG. 6 is a plan view of the connection terminal, FIG. 7 is a side view showing a state in which the connection terminal of the output harness is connected to the electrode of the resistor plate, and FIG. It is an enlarged view which shows the connection state of a connection terminal and the negative | minus side electrode of a resistance board.

  As shown in FIG. 1, the liquid level detection device 100 of the present embodiment is mounted on an automobile to detect the height of the liquid level FS of the fuel F in the fuel tank, and should be measured. A float 10 that moves up and down in accordance with the displacement of the liquid level, a float arm 11, a resistance plate 12, a sliding arm 13, and an output harness 14 are provided. More specifically, the float 10 that floats on the liquid level FS of the fuel F in the fuel tank is supported at the tip of the float arm 11. In FIG. 1, the base end side of the float arm 11 bent in a direction perpendicular to the paper surface is rotatably supported by a bearing portion (not shown) provided on the frame 15. The frame 15 is provided with a resistance plate 12 and a sliding arm 13 that slides on the resistance plate 12 in conjunction with the rotation of the float arm 11.

  As shown in FIG. 2, the resistance plate 12 is provided with a conductive pattern 20 made of silver-palladium that has excellent conductivity, resistance to deterioration, and corrosion resistance. The conductive pattern 20 includes an arc-shaped first sliding portion 21, an arc-shaped second sliding portion 22, a plus-side electrode 27A, and a minus-side electrode 27B formed on the insulating substrate 12A.

  The first sliding portion 21 includes a plurality of first conductive segments 23 arranged at intervals in the sliding direction of the sliding arm 13. Resistors 24 are formed on the plurality of first conductive segments 23 so as to extend in a direction intersecting the longitudinal direction of each first conductive segment 23. The resistor 24 is a resistance layer made of ruthenium oxide, which has excellent resistance to sulfidation compared to silver palladium and is less susceptible to deterioration or corrosion due to electrolysis even when exposed to an electrolytic solution such as ethanol or methanol. Adjacent first conductive segments 23 are connected to each other via a resistor 24.

  The second sliding portion 22 includes a plurality of second conductive segments 25. These second conductive segments 25 are arranged so as to draw an arc at intervals in the sliding direction of the sliding arm 13. The second conductive segments 25 adjacent to each other are electrically short-circuited by an arc-shaped conductive connecting portion 26.

  On one end side of the first sliding portion 21, a plus-side electrode 27 </ b> A that is a part of the conductive pattern 20 made of silver palladium or the like and a first conductive path 28 are provided. The first conductive path 28 electrically connects the first sliding portion 21 and the plus side electrode 27A. Further, on one end side of the second sliding portion 22, a negative electrode 27 </ b> B and a second conductive path 29 that are part of the conductive pattern 20 made of silver palladium are provided. The second conductive path 29 electrically connects the second sliding portion 22 and the negative electrode 27B.

  The sliding arm 13 is composed of a conductive member, and includes a first contact portion 30 that slides on the first sliding portion 21 and a second contact portion 31 that slides on the second sliding portion 22. Have The first contact portion 30 of the sliding arm 13 comes into contact with the corresponding first conductive segment 23, and the second contact portion 31 comes into contact with the corresponding second conductive segment 25, whereby the first contact portion 30 passes through the sliding arm 13. The sliding part 21 and the second sliding part 22 are electrically connected.

  As shown in FIG. 3, a protector 32 that covers the first conductive path 28 is formed on the first conductive path 28. The protector 32 is superior in sulfidation resistance to the same material as the resistor 24, that is, silver palladium, and is less susceptible to degradation or corrosion due to electrolysis even when exposed to an electrolyte such as ethanol or methanol (in other words, In this case, the resistance layer is made of ruthenium oxide, which is less likely to undergo electrolysis. Therefore, the protector 32 can prevent the first conductive path 28 from being electrolyzed.

  The circuit pattern of the resistor plate 12 is formed on the insulating substrate 12A by means of screen printing or the like by the first sliding portion 21, the first conductive path 28, the plus side electrode 27A, the second sliding portion 22, and the second conductive portion. After the passage 29 and the negative electrode 27B are formed, the resistor 24 and the protective body 32 are further formed by means such as screen printing.

  As shown in FIG. 4, the output harness 14 is for outputting a potential difference generated between the plus side electrode 27A and the minus side electrode 27B to an external circuit (not shown) via the conductive wire 41. It has a positive electrode connection terminal 42A connected to the electrode 27A and a negative electrode connection terminal 42B connected to the negative electrode 27B.

  As shown in FIGS. 5 and 6, the positive electrode connection terminal 42 </ b> A and the negative electrode connection terminal 42 </ b> B have substantially the same shape except for the presence or absence of a coating layer 50 described later. The positive electrode connection terminal 42A and the negative electrode connection terminal 42B are a contact member 43 that electrically connects the positive electrode 27A and the negative electrode 27B and the conductive wire 41, and a positive electrode connection terminal 42A and a negative electrode connection terminal 42B. And a locking member 44 for locking the frame to the frame 15.

  The contact member 43 is formed by, for example, pressing a thin plate of copper or a copper alloy (for example, phosphor bronze or beryllium copper), which is a conductor, and is opposed to the main body 43a formed in a substantially rectangular shape in cross section. A pair of contact pieces 43b and 43c extend forward from the two sides. The contact pieces 43b and 43c are formed in an arc shape so that the tips approach each other as they approach the tip and come into contact with each other after contact. With such a shape, spring elastic force is applied to the contact pieces 43b and 43c, and in the connected state with the resistance plate 12 shown in FIG. 8, the electrodes 27A and 27B are strongly pressed when the resistance plate 12 is sandwiched. Conductivity can be ensured. Further, caulking portions 43d and 43e having a substantially U-shaped cross section that are caulked to the core wire and the covering portion of the conductive wire 41 by caulking are provided behind the main body portion 43a. The plurality of contact members 43 having such a shape are manufactured in a state of being connected to the belt-like carrier 45 at a predetermined interval. And it cut | disconnects from the carrier 45 with the cutting line CL, and uses it. Note that a cut surface 43 f is formed on the contact member 43 by being separated from the carrier 45.

  The locking member 44 is formed, for example, by a stainless steel thin plate into a substantially square-shaped cross section having an inner dimension slightly larger than the outer dimension of the main body 43a of the contact member 43. The locking member 44 is provided with a pair of engaging portions 44a with rear end portions of both side surfaces cut and raised outward. The locking member 44 is externally fitted and fixed to the main body 43a of the contact member 43 to constitute connection terminals 42A and 42B.

  In the present invention, at least the portion of the negative electrode connection terminal 42B that contacts the negative electrode 27B of the resistor plate 12, specifically, the contact surface of the contact piece 43b with the negative electrode 27B, has a higher redox potential than chromium. It coat | covers with the coating layer 50 which consists of a metal which has (refer FIG. 8). Among metals having a higher redox potential than chromium, iron (−0.447V), cobalt (−0.28V), nickel (−0.257V), tin (−0.138V) in consideration of the environment. ), Copper (+0.342 V), silver (+0.800 V), platinum (+1.118 V), gold (+1.498 V) and the like can be suitably used. Also, an alloy of these metals may be used.

  Further, the contact member 43 is preferably entirely covered with a plating layer made of tin or a tin alloy, nickel or a nickel alloy, chromium or a chromium alloy in order to prevent corrosion. Formed on. However, in this case, there is a possibility that these plating metals are eluted in a portion where the coating layer 50 is not formed. Therefore, the metal forming the covering layer 50 is more preferably silver, platinum, or gold having a higher redox potential than tin, nickel, or chromium. Moreover, a silver alloy, a platinum alloy, and a gold alloy may be used.

  Furthermore, in the connection state of the contact pieces 43b and 43c and the negative electrode 27B of the resistor plate 28, the covering layer 50 strongly presses the upper surface of the negative electrode 27B by the spring elastic force. Fine irregularities are formed on the surface of the minus side electrode 27, and in order to improve conduction, it is necessary that the metal forming the coating layer 50 enter the fine irregularities on the surface of the minus side electrode 27. For this purpose, the metal forming the coating layer 50 is preferably soft, and gold or a gold alloy is particularly preferable among the metals listed above.

  Silver or a silver alloy may react with sulfur in gasoline to produce silver sulfide, which may cause corrosion. In addition, since platinum cannot be formed by plating, there are manufacturing restrictions. Also from such a point, gold or a gold alloy is preferable.

  The negative electrode connection terminal 42B can be manufactured by the following processing methods.

  In the first processing method, first, a phosphor bronze strip-shaped thin plate is plated with tin, nickel, or chrome on the entire surface as necessary, and then at least a portion that becomes the contact piece 43b is made of gold or a coating layer 50. After the gold alloy is plated, the contact member 43 is formed by pressing. Then, a stainless locking member 44 is externally fitted and fixed to the main body 43 a of the contact member 43.

  In the second processing method, a thin sheet of phosphor bronze is pressed to form a shape in which a plurality of contact members 43 are continuously connected to the carrier 45, and then tin, nickel, Chrome plating is performed, and gold or gold alloy plating is then applied as a coating layer 50 to at least the portion that becomes the contact piece 43b. And it cuts off from the carrier 45 with the cutting line CL.

  In the third processing method, a phosphor bronze strip-shaped thin plate is pressed to form a plurality of contact members 43 connected to the carrier 45 and separated from the carrier 45 by a cutting line CL. On the other hand, if necessary, the entire surface of the groove is plated with tin, nickel, or chromium, and then, at least the contact piece 43b is plated with gold or a gold alloy as the coating layer 50.

  As shown in FIGS. 1 and 7, the positive electrode connection terminal 42 </ b> A and the negative electrode connection terminal 42 </ b> B are inserted into a terminal accommodating portion 46 that is a square hole formed in the frame 15, and between the pair of contact pieces 43 b and 43 c. The resistance plate 12 is sandwiched. Accordingly, the pair of contact pieces 43b and 43c are brought into electrical contact with the plus side electrode 27A and the minus side electrode 27B by a spring force. At this time, the pair of engaging portions 44a formed in the locking member 44 engages with the rear wall surface of the locking hole 47 provided in the frame 15, and the positive electrode connecting terminal 42A and the negative electrode connecting terminal 42B. The disconnection from the frame 15 is prevented, and the connection with the resistor plate 12 (the positive electrode 27A and the negative electrode 27B) is secured.

  As described above, since a potential difference is generated between the plus side electrode 27A and the minus side electrode 27B (in other words, between the plus electrode connecting terminal 42A and the minus electrode connecting terminal 42B) at the time of detecting the liquid level, it is configured by electrolysis. The metal of the member elutes and deposits on the negative electrode connection terminal 42B, and further becomes a metal oxide, which lowers the detection accuracy. However, since the negative electrode connection terminal 42B of the present invention is formed with the coating layer 50 made of a metal having a higher redox potential than chromium, it is possible to prevent metal deposition due to electrolysis and to prevent increase in contact resistance. Thus, the liquid level of the fuel F such as ethanol or ethanol mixed gasoline can be accurately measured.

  In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably. In addition, the material, shape, dimension, numerical value, form, number, arrangement location, and the like of each component in the above-described embodiment are arbitrary and are not limited as long as the present invention can be achieved.

  For example, the positive electrode connection terminal 42A and the negative electrode connection terminal 42B are not limited to the above configuration as long as the resistor plate 12 can be sandwiched by elasticity, and are described in, for example, Japanese Patent Laid-Open No. 9-5145. It can also be used as a terminal.

  In the above embodiment, the positive electrode connection terminal 42A and the negative electrode connection terminal 42B have been described as being connected to the external circuit via the output harness 14 connected to the resistor plate 12. However, the positive electrode connection terminal 42A and the negative pole connection terminal 42B may be directly connected to an external circuit.

  Note that the above-described protective body 32 may not be formed.

It is sectional drawing which shows the structure of the liquid level detection apparatus of this invention. It is a top view of the resistance board in FIG. It is the III-III arrow sectional drawing in FIG. It is a top view of an output harness. It is a side view of a connection terminal. It is a top view of a connection terminal. It is a side view which shows the state in which the connection terminal of an output harness is connected to the electrode of a resistance board. It is an enlarged view which shows the connection state of a minus pole connection terminal and the minus side electrode of a resistance plate. It is sectional drawing which shows the structure of the conventional liquid level detection apparatus.

Explanation of symbols

10: Float 11: Float arm 12: Resistance plate 12A: Substrate 13: Sliding arm 14: Output harness 15: Frame 20: Conductive pattern 21: First sliding portion 22: Second sliding portion 27A: Positive side electrode 27B : Negative electrode 28: first conductive path 32: protector 42A: positive electrode connection terminal 42B: negative electrode connection terminal 43: contact member 43f: cut surface 44: locking member 44a: engagement portion 50: coating layer 100: Liquid level detector FS: Liquid level

Claims (4)

A liquid level detecting device for detecting a liquid level of a liquid containing an electrolytic solution,
A first sliding part, a second sliding part, a positive electrode electrically connected to the first sliding part, a negative electrode electrically connected to the second sliding part, A resistance plate having a conductive pattern formed on the substrate, and
A float that moves up and down according to the displacement of the liquid level to be measured;
A float arm having one end attached to the float and having the other end pivotably supported to rotate as the float moves up and down;
A sliding arm that slides on the resistance plate in conjunction with rotation of the float arm according to the liquid level;
A positive electrode connection terminal connected to the positive electrode;
A negative electrode connection terminal connected to the negative electrode;
With
The potential difference between the plus side electrode and the minus side electrode generated according to the position of the first sliding portion and the second sliding portion that the sliding arm contacts is the plus electrode connecting terminal and the minus electrode. It is output to the external circuit via the connection terminal,
The positive electrode connection terminal has a pair of contact pieces that sandwich the resistance plate with a spring elastic force, and one of the pair of contact pieces is in contact with the plus side electrode of the resistance plate,
The negative electrode connection terminal has a pair of contact pieces that sandwich the resistance plate with a spring elastic force, and one of the pair of contact pieces is in contact with the negative side electrode of the resistance plate,
Of the positive electrode connection terminal and the negative electrode connection terminal, only the contact surface of the contact piece that contacts the negative electrode of the negative electrode connection terminal is coated with a metal having a higher redox potential than chromium. A liquid level detecting device characterized by the above.   2. The liquid level detecting device according to claim 1, wherein the metal is at least one of gold or gold alloy, silver or silver alloy, platinum or platinum alloy.   The liquid level detector according to claim 2, wherein the metal is gold or a gold alloy. The negative electrode connection terminal is covered with a plating layer made of at least one of tin or tin alloy, nickel or nickel alloy, chromium or chromium alloy, and the metal is applied to the contact surface of the contact piece. The liquid level detection device according to claim 1, wherein the liquid level detection device is covered with a liquid level detection device.

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