JP5880879B2 - Liquid level detector - Google Patents

Description

  The present invention relates to a liquid level detection device for detecting the height of a liquid level.

  Conventionally, as disclosed in Patent Document 1, a liquid level detection apparatus including a float arm that holds a float that floats on a liquid level, an arm holder that holds the float arm, and a frame that rotatably supports the arm holder. Are known. In the liquid level detection device of Patent Document 1, a ceramic substrate having a resistor is fixed to a frame, and a conductive plate is fixed to an arm holder. In the above configuration, when the plate slides on the surface of the resistor due to the rotation of the float arm, the electric resistance value of the resistor changes. By measuring the electrical resistance value, the liquid level can be detected.

  Now, in the float of the liquid level detection device as disclosed in Patent Document 1, charges are accumulated by friction with the liquid. When this electric charge is discharged from the conductive float arm to the resistor, the detection accuracy of the liquid level detection device is lowered. Therefore, in Patent Document 1, the arm holder is formed of a conductive resin material. With the above configuration, electrical continuity between the float arm and the plate is ensured. Therefore, the charge generated in the float can be released to the resistor.

Japanese Patent No. 3941735

  However, the conductive resin forming the arm holder of Patent Document 1 is imparted with conductivity by adding carbon or the like. Due to the addition of carbon or the like, the conductive resin material is likely to be inferior in resistance to a liquid such as a fuel as compared with a standard resin material having no conductivity. For this reason, if the arm holder is formed of a conductive resin, the reliability of the liquid level detection device is hardly sufficient.

  The present invention has been made in view of the above problems, and an object thereof is to provide a liquid level detection device having high reliability.

In order to achieve the above object, the invention according to claim 1 is a liquid level detecting device for detecting the liquid level of a liquid, and is a conductive float arm for holding a float (60) floating on the liquid level. (50), a rotating body (30) that is formed of a resin material and holds the float arm, a support body (20) that rotatably supports the rotating body, and is fixed to the rotating body. A conductive conductive member (45) that is displaced; and a variable resistance section (40a) that is fixed to the support and changes the electrical resistance value according to the rotation angle of the rotating body by sliding the conductive member. The support body has a support portion (26) that rotatably supports the rotating body, and the rotating body has a sliding surface (32) that is supported by the support portion and slides relative to the support portion. and the rotating body, is conducting a float arm and the conductive member That the conductive coating (39) is characterized by Tei Rukoto formed to avoid the sliding surface.

  In the present invention, electrical continuity between the float arm and the conductive member is ensured by the conductive coating formed on the rotating body. Therefore, the electric charge generated in the float can be released to the variable resistance portion through the float arm, the conductive film, and the conductive member. And if the above-mentioned conduction is ensured by a conductive film, the resin material which forms a rotating body does not need to have conductivity. Therefore, a resin material having high resistance to the liquid can be employed as the material for the rotating body. Therefore, the liquid level detection device can acquire high reliability.

  Note that the reference numbers in the parentheses are merely examples of correspondence with specific configurations in the embodiments described later in order to facilitate understanding of the present invention, and limit the scope of the present invention. It is not intended.

It is a front view of the liquid level detection apparatus by one Embodiment of this invention. It is a side view of the liquid level detection apparatus seen from the direction of arrow II of FIG. It is a top view of an insulator. It is a side view of an insulator. It is a perspective view of an insulator.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, a liquid level detection device 100 according to an embodiment of the present invention is installed in a fuel tank 90 that stores fuel as a liquid. The liquid level detection device 100 detects the height of the liquid level of the fuel stored in the fuel tank 90 while being held by the fuel pump module 93 or the like. The detection result detected by the liquid level detection device 100 is output from the connector 96 toward a combination meter (not shown), and is displayed to the driver by the combination meter.

  The liquid level detection device 100 includes a float 60, a float arm 50, an insulator 30, a housing 20, a circuit board 40, and a sliding plate 45.

  The float 60 is made of a material having a specific gravity smaller than that of a fuel such as foamed ebonite. The float 60 can float on the liquid surface of the fuel. The float 60 is held by a float arm.

  The float arm 50 is formed of a round bar-shaped core made of a conductive metal material such as stainless steel. The float arm 50 is formed with a float holding portion 53 and a rotating shaft 51. The float holding part 53 is formed by bending one end side of the float arm 50. The rotating shaft 51 is formed by bending the other end side of the float arm 50 by about 90 degrees in a direction along the rotating axis of the insulator 30. The float arm 50 holds the float 60 by the float holding part 53 and is rotatably supported by the housing 20 by the rotating shaft 51. The float arm 50 configured as described above converts the vertical movement of the float 60 into the rotational motion of the insulator 30.

  The insulator 30 is made of a resin material such as polyacetal (POM) resin. The insulator 30 is supported by the housing 20 so as to be relatively rotatable. A float arm 50 is attached to the insulator 30. The insulator 30 rotates relative to the housing 20 integrally with the float arm 50. In the following description, one of the both surfaces of the insulator 30 formed in a plate shape that faces the circuit board 40 is referred to as a back surface, and the other located on the opposite side of the back surface is referred to as a front surface.

  The housing 20 shown in FIGS. 1 and 2 is formed of a resin material such as POM resin. The housing 20 is attached to the fuel pump module 93 and is fixed to the fuel tank 90 via the fuel pump module 93. A circuit board 40 and a plus terminal 71 and a minus terminal 74 connected to the circuit board 40 are attached to the housing 20. The housing 20 is formed in a container shape having a bottom wall and a side wall, and forms a board accommodating portion 28 that accommodates the circuit board 40. In addition, the housing 20 is formed with terminal mounting portions 23 and 27, a cylindrical portion 26, and a substrate housing portion 28.

  The terminal attachment portions 23 and 27 are formed on the side wall of the housing 20. A positive terminal 71 is fitted in the hole provided in the terminal mounting portion 23. A minus terminal 74 is fitted in the hole provided in the terminal mounting portion 27. The cylindrical portion 26 is formed in a cylindrical shape that penetrates the bottom wall of the housing 20. The cylindrical portion 26 rotatably supports a bearing surface 32 (see FIG. 5), which will be described later, of the insulator 30 by a cylindrical outer peripheral wall. In addition, the cylindrical portion 26 rotatably supports the rotating shaft 51 of the float arm 50 by a cylindrical surface-shaped inner peripheral wall.

  The circuit board 40 shown in FIG. 1 is held by the housing 20 while being housed in the board housing portion 28. A pair of resistor patterns 43 and 44 are formed on the circuit board 40 as a detection circuit 40a. Each of the resistor patterns 43 and 44 is formed on a surface of the circuit board 40 that is positioned on the insulator 30 side. Each of the resistor patterns 43 and 44 is formed in an arc shape around the rotation axis of the insulator 30. One resistor pattern 43 is formed by arranging a plurality of resistors having a predetermined electric resistance value. The resistor pattern 43 is an electrode pattern serving as a positive electrode, and is electrically connected to the positive terminal 71. The other resistor pattern 44 is an electrode pattern that becomes a negative pole, and is electrically connected to the negative terminal 74. As a result, a ground potential is applied to the resistor pattern 44 via the connector 96.

  The sliding plate 45 is a plate-like member made of a metal material. The sliding plate 45 has conductivity. As shown in FIGS. 1 and 5, the sliding plate 45 is formed in a U shape as a whole. The sliding plate 45 has a base end portion 48, a flexible portion 47, and a sliding contact 46. The base end portion 48 is attached to the back surface of the insulator 30. Thereby, the sliding plate 45 rotates integrally with the insulator 30. A pair of the flexible portions 47 extends from the base end portion 48. Each flexible portion 47 can bend in the thickness direction of the sliding plate 45. The sliding contact 46 is provided at each distal end portion in the extending direction of each flexible portion 47. Each sliding contact 46 is pressed toward the resistor patterns 43 and 44 by the elasticity of the sliding plate 45.

  The detection circuit 40a and the sliding plate 45 of FIG. 1 described so far form a variable resistor 41 in cooperation. The electric resistance value in the detection circuit 40 a changes according to the rotation angle of the insulator 30. More specifically, when the insulator 30 rotates, the sliding plate 45 fixed to the insulator 30 brings the sliding contacts 46 (see FIGS. 4 and 5) into contact with the resistor patterns 43 and 44, respectively. It is displaced relative to the circuit board 40. Thereby, each sliding contact 46 slides on each resistor pattern 43,44. When the sliding contacts 46 are closest to the terminals 71 and 74, the electric resistance value of the detection circuit 40a is the smallest. When the sliding contacts 46 are moved away from the terminals 71 and 74 by the rotation of the insulator 30 from this state, the electrical resistance of the detection circuit 40a gradually increases. Based on the above principle, the rotation angle of the insulator 30 can be detected by the variable resistor 41. The combination meter connected to the detection circuit 40a can acquire the potential difference between the terminals 71 and 74 according to the electric resistance value of the detection circuit 40a as detection information of the liquid level.

  Next, the detailed configuration of the above-described insulator 30 will be further described with reference to FIGS.

  The insulator 30 is formed with a plate mounting portion 37, a fitting portion 36, an arm insertion hole 33, an arm locking claw 31, and an arm stopper 34.

  The plate attachment portion 37 is provided on the back surface of the insulator 30. The plate attachment portion 37 is formed at a position away from the arm insertion hole 33 in the insulator 30. A base end portion 48 is fixed to the plate attaching portion 37 by heat caulking or the like. With such a configuration, the plate mounting portion 37 holds the sliding plate 45.

  The fitting portion 36 is externally fitted to a cylindrical portion 26 (see FIG. 2) provided in the housing 20. The inner peripheral wall of the fitting portion 36 forms the bearing surface 32 described above. The bearing surface 32 is formed in a cylindrical surface shape. The bearing surface 32 slides with respect to the outer peripheral wall of the cylindrical portion 26 by the rotation of the insulator 30.

  The arm insertion hole 33 is a cylindrical hole that penetrates the insulator 30 in the plate thickness direction. The arm insertion hole 33 is positioned coaxially with the bearing surface 32 and the cylindrical portion 26 (see FIG. 2). A rotation shaft 51 is inserted into the arm insertion hole 33 and the cylindrical portion 26. The inner peripheral wall of the arm insertion hole 33 fitted to the rotating shaft 51 is in close contact with the outer peripheral wall of the rotating shaft 51.

  Two arm locking claws 31 are provided on the front surface of the insulator 30. These arm locking claws 31 are arranged along the radial direction of the arm insertion hole 33. The arm locking claw 31 extends from the front surface and is curved in an arc shape. With such a shape, the end in the extending direction of the arm locking claw 31 is opposed to the front surface of the insulator 30. A gap formed between the tip of the arm locking claw 31 and the front surface of the insulator 30 is made smaller than the diameter of the float arm 50.

  The arm stopper 34 is formed so as to protrude from the front surface of the insulator 30. The arm stopper 34 can be displaced from the front surface side to the back surface side in the plate thickness direction of the insulator 30. The arm stopper 34 is positioned with respect to the arm locking claw 31 in each of the circumferential direction and the radial direction of the arm insertion hole 33.

  A float arm 50 is assembled to the insulator 30 as shown in FIG. The steps will be described in order. First, the rotating shaft 51 is inserted into the arm insertion hole 33. Thereby, the arm stopper 34 is urged | biased by the float arm 50, and is pushed in to the back surface side. Then, with the rotation shaft 51 being inserted into the arm insertion hole 33, the float arm 50 is rotated relative to the insulator 30 so that the arm 50 has a gap formed by each arm locking claw 31. And is fitted into each arm locking claw 31. As described above, the contact surface 35 formed on the inner peripheral wall of the arm locking claw 31 is in a state of being in press contact with the float arm 50 due to the elasticity of the locking claw 31. Further, the arm stopper 34 released from the urging force is displaced to the front surface side, thereby preventing the float arm 50 from being detached from the arm locking claw 31.

  Furthermore, a metal film 39 is formed on the insulator 30. The metal film 39 is a conductive film formed of a metal material. The metal film 39 is formed by metal plating applied to the insulator 30. Hereinafter, the plating process for plating the insulator 30 will be described in order.

  First, minute holes are formed on the outer surface of the resin material forming the insulator 30 by a process such as etching. Thus, a catalyst film is formed on the insulator 30 whose outer surface is roughened by a catalyst material having a strong reducing power, specifically, palladium-tin. Then, by removing tin from the catalyst coating, palladium is activated and the outer surface of the insulator 30 is made conductive. Electroplating is performed on the insulator 30 described above. Specifically, copper is first plated to form a base. Next, nickel is plated. Finally, the hardness of the metal film 39 is ensured by plating with chromium. By the above plating process, the metal film 39 covering the entire outer surface of the insulator 30 is formed.

  The metal film 39 formed in this way covers each contact surface 35 that presses the float arm 50. In addition, the metal coating 39 covers the inner wall surface of the arm insertion hole 33 that fits into the rotating shaft 51. Therefore, conduction between the metal film 39 and the float arm 50 is reliably formed. In addition, the metal coating 39 covers the plate attachment portion 37 that holds the base end portion 48. Therefore, conduction between the metal film 39 and the sliding plate 45 is also reliably formed. Thus, the metal coating 39 can make the float arm 50 and the sliding plate 45 conductive.

  In the present embodiment described so far, electrical conduction between the float arm 50 and the sliding plate 45 is ensured by the metal film 39. As a result, a static electricity path from the fuel to the negative resistor pattern 44 is formed. Therefore, the electric charge generated in the float 60 due to the friction with the fuel moves to the resistor pattern 44 through the float arm 50, the metal film 39, and the sliding plate 45, and can be released from the negative terminal 74 to the outside.

  In addition, as long as such conduction is ensured by the metal film 39, the resin material forming the insulator 30 may not have conductivity. Therefore, a standard resin material that has been proven to have high resistance to fuel, specifically, POM that does not contain carbon or has a low carbon content can be adopted as a material for the insulator 30. Become. Therefore, the liquid level detection apparatus 100 can acquire high reliability.

  In addition, as in this embodiment, the metal film 39 formed of a metal material such as nickel and chromium is very easy to conduct electricity. Therefore, continuity from the float arm 50 to the sliding plate 45 can be reliably ensured. Therefore, the charge generated in the float 60 can be surely released from the resistor pattern 44 to the minus terminal 74.

  Moreover, in this embodiment, the contact surface 35 which is pressing especially the float arm 50 among the arm latching claws 31 is covered with at least the metal film 39. Therefore, the metal coating 39 can maintain the state in which it is in reliable contact with the float arm 50 by the pressing force of the arm locking claw 31. Therefore, the conduction from the float arm 50 to the sliding plate 45 can be more reliable.

  Further, if the entire outer surface of the insulator 30 is covered with the metal film 39 as in the present embodiment, the insulator 30 is protected by the metal film 39 and is not easily exposed to fuel. Therefore, the resin material forming the insulator 30 can maintain mechanical properties over a long period of time. Therefore, the liquid level detection apparatus 100 can obtain higher reliability.

  In the present embodiment, the housing 20 corresponds to the “support” described in the claims, the cylindrical portion 26 corresponds to the “support” described in the claims, and the insulator 30 corresponds to the claims. It corresponds to the “rotary body” described in the range. Further, the arm locking claw 31 corresponds to the “locking claw” recited in the claims, the bearing surface 32 corresponds to the “sliding surface” recited in the claims, and the contact surface 35 claims. This corresponds to the “region where the float arm is pressed” described in the above item. The metal film 39 corresponds to the “conductive film” recited in the claims, the detection circuit 40a corresponds to the “variable resistance portion” recited in the claims, and the sliding plate 45 claims. It corresponds to the “conductive member” described in the range.

(Other embodiments)
As mentioned above, although one embodiment by the present invention was described, the present invention is not interpreted limited to the above-mentioned embodiment, and is applied to various embodiments and combinations within the range which does not deviate from the gist of the present invention. be able to.

  In the first modification of the above embodiment, the metal film is formed avoiding the bearing surface 32. The bearing surface 32 slides with respect to the cylindrical portion 26 as described above. Therefore, the metal film formed on the bearing surface 32 is easily peeled off. The peeled metal film may cause damage to the cylindrical portion 26 and the like. Therefore, in the first modification, the above-described concern can be solved by forming the metal film while avoiding the bearing surface 32. Therefore, the reliability of the liquid level detection device according to the modified example 1 becomes even more reliable.

  Further, as in Modification 1 above, the metal film may not cover the entire outer surface of the insulator. If the metal film covers at least the contact surface 35 or the arm insertion hole 33 that contacts the float arm 50 and the plate mounting portion 37 that contacts the sliding plate 45, and these components 50 and 45 are electrically connected. The formation range may be changed as appropriate.

  Insulator 30 of the above-mentioned embodiment will be immersed in various liquids concerning formation of a coat in a plating process after molding. Therefore, it is desirable that the branch-like surplus portion inevitably formed by a mold gate and liner at the time of molding is separated from the insulator 30 after the plating step. By holding the insulator 30 in such a surplus portion or the like, the process of immersing the insulator 30 in the liquid can be easily performed. Moreover, in the said embodiment, the resin material which forms the insulator which was POM resin may be changed suitably, if mechanical properties, such as intensity | strength, are ensured.

  In the above embodiment, the metal film 39 is formed by overlapping a plurality of types of metal plating. However, the configuration of the metal film is not limited to that of the above embodiment, and may be changed as appropriate. For example, chrome plating may be applied to the base by copper plating by omitting nickel plating in the above embodiment. Further, the metal film may be a single layer. Further, the type of metal used for plating may be changed as appropriate.

  Furthermore, the “conductive film” described in the claims is not limited to that formed by metal plating. For example, the “conductive film” may be formed by applying a coating containing a metal to the outer surface of the insulator 30. Furthermore, the “conductive film” may not contain a metal material. For example, the conductive film may be formed of a resin material containing carbon.

  In the above-described embodiment, in the liquid level detection device that detects the height of the liquid level based on the change in the electrical resistance value of the detection circuit 40a, the insulator 30 that functions as the “rotating body” has the “conductive film”. Was formed. However, in the liquid level detection device that detects the height of the liquid level based on the change in magnetic flux density acting on the Hall IC, a “conductive film” is formed in a configuration that functions as a “rotating body”. May be. The “conductive film” having such a configuration is desirably conducted to a minus terminal or the like that transmits the output of the Hall IC.

  The present invention has been described based on an example in which the present invention is applied to a vehicle level detecting device for detecting the remaining amount of fuel. However, the application target of the present invention is not limited to such a liquid level detection device, but is a liquid level detection device in a container of other liquids mounted on the vehicle, such as brake fluid, engine cooling water, and engine oil. May be. Furthermore, the present invention is applicable not only to vehicles but also to liquid level detection devices provided in liquid containers provided in various consumer devices and various transport machines.

20 Housing (support), 26 Tube (support), 30 Insulator (rotating body), 31 Arm locking claw (locking claw), 32 Bearing surface (sliding surface), 35 Contact surface (area), 39 Metal film (film), 40a detection circuit (variable resistance part), 45 sliding plate (conductive member), 50 float arm, 60 float, 100 liquid level detection device

Claims (3)

A liquid level detection device for detecting the liquid level of a liquid,
A conductive float arm (50) holding a float (60) floating on the liquid surface;
A rotating body (30) formed of a resin material and holding the float arm;
A support (20) for rotatably supporting the rotating body;
A conductive member (45) fixed to the rotating body and displaced by rotation of the rotating body;
A variable resistance portion (40a) fixed to the support and changing an electric resistance value according to a rotation angle of the rotating body by sliding the conductive member;
The support has a support portion (26) for rotatably supporting the rotating body,
The rotating body is supported by the support portion and has a sliding surface (32) that slides relative to the support portion,
Wherein the rotating body, a liquid level detecting device conductive coating for conducting the one conductive member and the float arm (39), characterized in Tei Rukoto is formed to avoid the sliding surface.   The liquid level detection device according to claim 1, wherein the coating is formed of a metal material. The rotating body has a locking claw (31) for locking the float arm,
The liquid level detection device according to claim 1 or 2, wherein the coating covers at least a region (35) for pressing the float arm in the locking claw .

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