Liquid level detection device

Abstract

To provide a liquid level detector capable of improving tensile strength of lead wires.SOLUTION: A liquid level detector 2 comprises: a device body 10a including a detection unit 60 for detecting a displacement amount for deriving a liquid level; at least three lead wires 30a having one end connected to the device body 10a so as to communicate with at least the detection unit 60, and arranged in parallel with each other; and a connector 37 that connects the other end of each lead wire 30a. The lengths of first lead wires 31a, 33a located at ends in a parallel direction, of the at least three lead wires 30a, are longer than the length of a second lead wire 32a located so as to be sandwiched between the other two lead wires.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present invention relates to a liquid level detection device.

Background Art

[0002] Conventionally, there has been a liquid level detection device that detects the liquid level of a liquid based on the displacement of an arm following the vertical movement of a float floating in the liquid. Patent Document 1 discloses a technique related to a liquid level detection device that is attached inside a fuel tank mounted on a vehicle such as an automobile and can detect the liquid level of the fuel stored in the fuel tank. In this liquid level detection device, three lead wires are drawn out from the device body. The other end of each lead wire is generally connected to one connector. And the length of each lead wire is generally the same.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, when installing a liquid level detection device in a fuel tank, an operator tries to connect a connector while holding the connector in a narrow space area to a receiving connector that is the mating target. Therefore, if the lengths of the respective lead wires are the same as in the liquid level detection device disclosed in Patent Document 1, depending on the internal structure of the fuel tank, the three lead wires may be pulled in a tilted direction, and as a result, a tensile load may concentrate on a certain lead wire. At this time, if the tensile load exceeds the tensile strength of the lead wire, there is also a possibility of disconnection.

[0005] The present invention has been made in view of the problems of such conventional technologies. And an object of the present invention is to provide a liquid level detection device that improves the tensile strength of lead wires.

Means for Solving the Problems

[0006] A liquid level detection device according to an aspect of the present invention includes a device body including a detection unit that detects a displacement amount for deriving a liquid level of a liquid, at least one end of which is connected to the device body so as to communicate with at least the detection unit, and at least three lead wires arranged in parallel with each other, and a connector that connects the other ends of the respective lead wires. Among the at least three lead wires, the length of the first lead wire located at the end in the parallel direction is longer than the length of the second lead wire positioned so as to be sandwiched between the two other lead wires.

Brief Description of the Drawings

[0007]

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Mode for Carrying Out the Invention

[0008] Hereinafter, the liquid level detection device according to each embodiment will be described in detail with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for convenience of explanation and may be different from the actual ratios. Also, in each embodiment, components having the same configuration are denoted by the same reference numerals and are in corresponding relationships.

[0009] (First Embodiment) FIG. 1 is a perspective view of the liquid level detection device 1 according to the first embodiment. FIG. 2 is an exploded perspective view of the main part of the liquid level detection device 1. FIG. 3 is a cross-sectional view of the main part of the liquid level detection device 1 cut along a plane extending in the vertical direction while including the central axis of the shaft portion 21. Hereinafter, "up and down" in the liquid level detection device 1 refers to above or below in the vertical direction.

[0010] The liquid level detection device 1 detects the liquid level (liquid surface position) of the liquid based on the displacement of the arm 51 following the up and down movement of the float 50 floating in the liquid. Hereinafter, as an example, the liquid level detection device 1 is mounted in a fuel tank of a vehicle such as an automobile and detects the liquid level of the fuel stored inside the fuel tank. The liquid level detection device 1 includes a device main body 10, a lead wire 30, a connector 37, a holder 40, a float 50, and an arm 51.

[0011] The device main body 10 is the main body part of the liquid level detection device 1. The device main body 10 includes a frame 11, a lead frame 12, and a holding member 13. Hereinafter, "front and rear" in the device main body 10 refers to the front or rear in the horizontal direction. At this time, the side where the holder 40 is supported in the device main body 10 is the front side, and the side where the lead frame 12 and the like are insert-molded is the rear side.

[0012] The frame 11 is, for example, a resin structure and rotatably supports the holder 40. The frame 11 has a rotation recess 20, a shaft portion 21, a locking groove 22, a pair of insertion holes 23, a guide ridge 24, a first stopper surface 25a, and a second stopper surface 25b.

[0013] The rotation recess 20 is provided in a circular shape in plan view on the front side of the frame 11 and rotatably houses a part of the holder 40. The shaft portion 21 is coaxially provided at the center of the rotation recess 20 and is the rotation reference of the holder 40, and engages with a shaft recess 42 formed in the holder 40.

[0014] The locking groove 22 is provided over the circumferential direction in the inner peripheral portion of the rotation recess 20 and rotatably locks the flange portion 43 of the holder 40. The pair of insertion holes 23 are provided at positions facing each other in the horizontal direction at the edge of the rotation recess 20 and communicate with the locking groove 22 respectively. The guide ridge 24 is provided at the bottom of the rotation recess 20 so as to surround the shaft portion 21 and guides the rotation of the holder 40.

[0015] The first stopper surface 25a and the second stopper surface 25b are a pair of first stoppers that contact the arm 51 to restrict the swinging of the arm 51, thereby restricting the rotation of the holder 40. The pair of first stoppers is provided on the front side of the frame 11 and below the center of the rotation recess 20, spaced apart from each other, and facing each other along the outer periphery of the rotation recess 20. When the holder 40 rotates, the arm 51 contacts one of the pair of first stoppers on the tip side rather than the position facing the shaft portion 21. Thereby, the rotation range of the holder 40 is restricted to the angular range θ. The first stopper surface 25a contacts the arm 51 at the maximum detection position of the liquid level among the liquid levels that the liquid level detection device 1 can detect. That is, the first stopper surface 25a is at the position where the arm 51 contacts when the remaining fuel volume in the fuel tank is near full. The second stopper surface 25b contacts the arm 51 at the minimum detection position of the liquid level among the liquid levels that the liquid level detection device 1 can detect. That is, the second stopper surface 25b is at the position where the arm 51 contacts when the remaining fuel volume in the fuel tank is near empty.

[0016] Further, the frame 11 may have a rotation groove 26, a first auxiliary stopper surface 27a, and a second auxiliary stopper surface 27b. The rotation groove 26 is provided at the upper edge of the rotation recess 20 between the two insertion holes 23, and serves as the trajectory of the locking end 51a of the arm 51 when the holder 40 rotates.

[0017] The first auxiliary stopper surface 27a and the second auxiliary stopper surface 27b are a pair of second stoppers that contact the locking end 51a of the arm 51 to restrict the swinging of the arm 51, thereby restricting the rotation of the holder 40. The pair of second stoppers are provided at both ends of the rotation groove 26, are spaced apart from each other, and face each other along the edge of the rotation recess 20. Therefore, when the holder 40 rotates, the arm 51 contacts one of the pair of second stoppers at the locking end 51a on the proximal end side with respect to the position facing the shaft portion 21. Here, the rotation range of the holder 40 restricted by the pair of second stoppers may be set to a larger rotation angle than the angle range θ restricted by the pair of first stoppers. The first auxiliary stopper surface 27a is located at a position where the locking end 51a of the arm 51 contacts when the remaining fuel volume in the fuel tank is near full. The second auxiliary stopper surface 27b is located at a position where the locking end 51a of the arm 51 contacts when the remaining fuel volume in the fuel tank is near empty. When an overload is applied to the arm 51, the arm 51 bends by contacting one of the pair of first stoppers with a large load, and the locking end 51a of the arm 51 also abuts against one of the pair of second stoppers. Thereby, the overload acting on the arm 51 can be made to act on and dispersed to not only the first stopper but also the second stopper.

[0018] Furthermore, the frame 11 has an insert molding portion 28 and a lead wire arrangement portion 29. The insert molding portion 28 is a region where a part of the lead frame 12, a part of the hall element 60, the conductive portion 70, etc. are insert molded into the frame 11. The lead wire arrangement portion 29 exposes a part of the lead frame 12 that connects the lead wires 30 to the outside of the frame 11, and arranges the tip portions of the lead wires 30 that are connected to the lead frame 12.

[0019] The lead frame 12 is a conductor part partially insert-molded into the frame 11. The lead frame 12 includes a plurality of terminals which are independent plate bodies respectively, according to the type of the lead wires 30 based on the detection method of the detection part, etc. In the present embodiment, the lead frame 12 includes an input terminal 34, a ground (GND) terminal 35, and an output terminal 36. To the input terminal 34, the ground terminal 35, and the output terminal 36, lead wires 62 extending from the Hall element 60 are electrically connected according to their respective functions.

[0020] The holding member 13 is assembled to the lead wire arrangement part 29 provided on the frame 11 and holds the lead wires 30. For example, the holding member 13 may have a groove 13a for each lead wire 30 according to the diameter of the lead wire 30. The holding member 13 can make it difficult for the lead wires 30 to come off from the lead frame 12 by sandwiching the groove 13a with the lead wire arrangement part 29 in a state where the lead wires 30 are engaged with the groove 13a.

[0021] The apparatus main body 10 further includes a Hall element 60 as a detection part for detecting the rotation angle of the holder 40 and lead wires 62.

[0022] The Hall element 60 is embedded in the shaft part 21 of the frame 11 and is a magnetic detection element that generates a Hall voltage proportional to the magnetic flux density passing through the Hall element 60 when a magnetic field is applied from the outside in a state where a voltage is applied. On the other hand, inside the holder 40, a magnet 65 described later is installed. When the holder 40 rotates due to a change in the liquid level, the magnet 65 also rotates and displaces, and the intersection angle between the magnetic flux of the Hall element 60 and the magnet 65 changes, and accordingly, the Hall voltage changes. That is, based on the measured Hall voltage, the rotation angle of the holder 40 can be detected, and as a result, the liquid level of the fuel can be detected. The lead wires 62 extend from the Hall element 60 as described above and are electrically connected to the respective terminals included in the lead frame 12.

[0023] Also, part of the Hall element 60, lead 62, and lead frame 12 may be attached inside the frame 11 by insert molding multiple times. For example, by the first-stage insert molding, the Hall element 60 and lead 62 may be attached to the frame 11 together with the resin body 63. Thereafter, by the second-stage insert molding, the lead frame 12 may be attached to the frame 11. The resin body 63 has an inner shaft 63a coaxially embedded inside the shaft portion 21 of the frame 11. The inner shaft 63a has the Hall element 60 installed further inside thereof. The Hall element 60 and lead 62 may be pre-embedded inside the resin body 63 using the resin member 64. Although not shown, the resin member 64 may include other electronic components related to the operation of the Hall element 60 and the like.

[0024] Furthermore, the apparatus main body 10 includes a conductive portion 70 at least partially embedded in the frame 11. The conductive portion 70 will be described in detail again below.

[0025] A plurality of lead wires 30 are provided based on the detection method of the detection unit and the like, and electrically connect between the liquid level detection device 1 and an external device such as a measuring instrument. In the present embodiment, the lead wires 30 include an input wire 31 related to power supply, a ground (GND) wire 32, and an output wire 33 related to signals, which are independent of each other. One end of the input wire 31 is connected to the input terminal 34 in the lead wire arrangement portion 29. One end of the ground wire 32 is connected to the ground terminal 35 in the lead wire arrangement portion 29. One end of the output wire 33 is connected to the output terminal 36 in the lead wire arrangement portion 29.

[0026] The connector 37 connects the other ends of the input wire 31, ground wire 32, and output wire 33 in a non-contact manner with each other and is connected to the receiving-side connector that is electrically continuous with the external device.

[0027] The holder 40 is a member made of, for example, resin, holds the proximal end side of the arm 51, and converts the displacement of the arm 51 following the vertical movement of the float 50 accompanying the change in the liquid level of the fuel into rotational motion. Hereinafter, "front and rear" in the holder 40 refers to the front or rear in the horizontal direction. At this time, the side that holds the arm 51 is the front side, and the side that is supported by the apparatus main body 10 in the holder 40 is the rear side. The holder 40 has a holder main body 41 and an arm holding portion 46.

[0028] The holder main body 41 is a cylindrical member having a shaft recess 42, a pair of flange portions 43, and a guide recess 44.

[0029] The shaft recess 42 is provided on the rear surface side of the holder main body 41 and coaxially with the central axis of the shaft portion 21, and engages with the shaft portion 21 in a rotationally slidable manner with the shaft portion 21 provided on the frame 11 as a rotation axis. In this embodiment, the central axis of the shaft recess 42 is referred to as the "rotation axis" separately from the central axis of the shaft portion 21. The pair of flange portions 43 are each provided so as to project radially outward from the rear edge portion of the holder main body 41. Further, the pair of flange portions 43 project in opposite directions along the extending direction of the arm 51 when the arm 51 is held by the arm holding portion 46. The guide recess 44 is provided on the rear surface side of the holder main body 41 and on the outer peripheral side of the magnet 65 installed in the holder main body 41, and houses the guide protrusion 24 provided on the frame 11.

[0030] When assembling the holder 40 to the frame 11, the operator fits the holder 40 into the rotation recess 20 with a pair of flange portions 43 aligned with the positions of a pair of insertion holes 23 in the frame 11. When the flange portions 43 pass through the insertion holes 23, the shaft portion 21 of the frame 11 is inserted into the shaft recess 42 of the holder 40. Also, the guide protrusion 24 of the frame 11 fits into the guide recess 44 of the holder 40. Next, when the operator rotates the holder 40 fitted into the rotation recess 20 so that the locking hole 47 described later is positioned upward, the flange portion 43 enters the locking groove 22 of the frame 11, and the holder 40 cannot come out of the rotation recess 20. In a state where the holder 40 holds the arm 51, the rotation range of the holder 40 is restricted by a first stopper or the like, so the holder 40 is also prevented from coming out of the rotation recess 20 due to the movement of the flange portion 43 to the position of the insertion hole 23.

[0031] The arm holding portion 46 holds the arm 51 such that the extending direction of the arm 51 is orthogonal to the rotation axis of the holder 40. The arm holding portion 46 has a locking hole 47. The locking hole 47 is provided in a part of the peripheral edge of the holder body 41 so as to penetrate in the front-rear direction of the holder 40, and locks the locking end 51a at the proximal end side of the arm 51.

[0032] Also, the holder 40 includes an annular magnet 65. The magnet 65 is installed inside the holder body 41 so as to be disposed on the inner peripheral side of the shaft recess 4, and is a displacement member used for detecting the rotation angle of the holder 40 by the Hall element 60. In this case, the Hall element 60 is positioned on the inner diameter side of the magnet 65 that rotates and displaces as the holder 40 rotates.

[0033] The float 50 is floated on a liquid fuel. That is, the float 50 moves up and down as the liquid level of the fuel in the fuel tank changes.

[0034] The arm 51 is a rod-shaped member that connects the holder 40 and the float 50. The arm 51 supports the float 50 on the tip side. On the other hand, the arm 51 is held by the arm holding portion 46 of the holder 40 at the base end side of the arm 51, which is opposite to the tip side. Note that the arm 51 may have one or a plurality of bent portions. The end portion on the base end side of the arm 51 is a locking end 51a that is bent at a right angle. The locking end 51a is inserted into the locking hole 47 in a state where the arm holding portion 46 holds the arm 51. The locking end 51a inserted into the locking hole 47 is disposed in the rotation groove 26 provided in the frame 11.

[0035] Next, the conductive portion 70 will be described in detail. FIG. 4 is a perspective view of a main part of the liquid level detection device 1 when the apparatus main body 10 and the holder 40 are viewed obliquely downward from the front. In FIG. 4, a state where the arm 51 is in contact with the second stopper surface 25b of the frame 11 is illustrated. FIG. 5 is a perspective view showing the conductive portion 70 illustrating the arm 51 at the intermediate detection position of the liquid level, excluding the frame 11 from the apparatus main body 10. FIG. 6 is a perspective view corresponding to FIG. 5 and showing the conductive portion 70 illustrating the arm 51 at the minimum detection position of the liquid level. In FIGS. 5 and 6, the arm 51 is drawn with a two-dot chain line while assuming that it is held by the holder 40.

[0036] The conductive portion 70 is a conductive member having an extension portion 71, a first end portion 72, and a second end portion 73. The extension portion 71 is the main body of the conductive portion 70. The first end portion 72 is one end portion of the extension portion 71 and is connected to the ground terminal 35 included in the lead frame 12. The second end portion 73 is the other end portion of the extension portion 71 and is positioned to be contactable with the arm 51. In the conductive portion 70, all of the extension portion 71, the first end portion 72, and the second end portion 73 are formed of, for example, a metal plate material.

[0037] Here, the hall element 60 and the lead frame 12 can be attached inside the frame 11 by insert molding multiple times. Therefore, the conductive part 70 may also be attached inside the frame 11 by insert molding. In this case, the first end 72 may be pre-joined to the ground terminal 35 by welding or the like before insert molding.

[0038] In the present embodiment, there are two conductive parts 70 having symmetrical shapes with respect to each other. As shown in FIG. 4, the second end 73 of one conductive part 70 is exposed from the first stopper surface 25a of the pair of first stoppers toward the orbit of the arm 51. Further, as shown in FIG. 4, the second end 73 of the other conductive part 70 is exposed from the second stopper surface 25b of the pair of first stoppers toward the orbit of the arm 51. Each extension part 71 is embedded inside the frame 11 so as to extend from the first end 72 to the second end 73 along a path that does not interfere with other components and is not exposed to the outside of the frame 11. That is, the shape of the extension part 71 is determined based on the internal structure or shape of the frame 11.

[0039] In such a conductive part 70, first, as shown in FIG. 5, when the liquid level of the fuel is at the intermediate detection position, the arm 51 does not contact either the second end 73 exposed from the first stopper surface 25a or the second end 73 exposed from the second stopper surface 25b. Here, the intermediate detection position of the liquid level refers to a position that is approximately the middle liquid level among the liquid levels that the liquid level detection device 1 can detect. The intermediate liquid level corresponds to, for example, the liquid level indicated when the remaining capacity of the fuel in the fuel tank is approximately half of the full tank. Note that as long as the detection position of the liquid level is not only at the intermediate detection position but also at the maximum detection position or the minimum detection position, the arm 51 will not contact either second end 73.

[0040] On the one hand, as shown in FIG. 6, when the liquid level of the fuel is at the minimum detection position, the arm 51 contacts the second end portion 73 exposed from the second stopper surface 25b. Similarly, although not shown, when the liquid level of the fuel is at the maximum detection position, the arm 51 contacts the second end portion 73 exposed from the first stopper surface 25a.

[0041] Next, the operation of the liquid level detection device 1 will be described.

[0042] First, in the liquid level detection device 1, as a basic operation, following the up and down movement of the float 50 accompanying the change in the liquid level of the fuel, the arm 51 swings, and the holder 40 to which the arm 51 is connected rotates with respect to the device main body 10. The hall element 60 in the device main body 10 detects the change in the magnetic flux of the magnet 65 in the holder 40, and the detection result is transmitted to a measurement unit or the like as an external device through the output line 33. For example, the measurement unit measures the liquid level based on the output signal transmitted from the liquid level detection device 1, and issues a warning such as fuel exhaustion in the fuel tank as necessary.

[0043] Here, when the liquid level detection device 1 is installed in the fuel tank of an automobile, due to the vibration during the running of the automobile, the fuel may swing, or static electricity may be generated when resin components slide against each other, and the arm 51 may become charged. In contrast, when the remaining fuel capacity is full or empty, or even when the remaining fuel capacity is neither full nor empty and the swing width of the arm 51 becomes large due to large vibrations during running, the arm 51 contacts either one of the pair of first stoppers. That is, the arm 51 contacts the second end portion 73 of the conductive portion 70 exposed from the first stopper surface 25a or the second stopper surface 25b. Since the conductive portion 70 is connected to the ground terminal 35 via the first end portion 72, the static electricity remaining on the arm 51 is discharged to the ground wire 32 through the conductive portion 70 as it contacts the second end portion 73 of the arm 51.

[0044] Next, the effects of the liquid level detection device 1 will be described.

[0045] The liquid level detection device 1 includes a float 50 that floats on the liquid, an arm 51 that supports the float 50 on the tip side, and a holder 40 that holds the base end side of the arm 51 and converts the displacement of the arm 51 following the up and down movement of the float 50 due to the change in the liquid level of the liquid into a rotational movement. The liquid level detection device 1 includes a frame 11 having a shaft portion 21 serving as a rotation reference of the holder 40, a detection portion provided on the frame 11 for detecting the rotation angle of the holder 40, and a ground terminal 35 connected to the detection portion. Further, the liquid level detection device 1 has a first end portion 72 connected to the ground terminal 35 and a second end portion 73 positioned to be in contact with the arm 51, and includes a conductive portion 70 at least partially embedded in the frame 11.

[0046] Here, in the above example, the detection portion corresponds to the Hall element 60. However, the detection method employed in the liquid level detection device 1 is not limited to the method using the Hall element 60, and other detection methods may be employed as long as they can detect the rotation angle of the holder 40.

[0047] Also, in the liquid level detection device 1, the frame 11 may have a pair of first stoppers that contact the tip side rather than the position facing the shaft portion 21 in the arm 51 to regulate the rotation range of the holder 40. In this case, the second end portion 73 may be exposed toward the orbit of the arm 51 from each of the first stopper surface 25a and the second stopper surface 25b that constitute the pair of first stoppers.

[0048] According to the liquid level detection device 1, the conductive portion 70 has a first end portion 72 connected to the ground terminal 35 and a second end portion 73 positioned to be in contact with the arm 51. Therefore, even if the arm 51 is charged, when the arm 51 contacts the second end portion 73, the static electricity remaining in the arm can be discharged to the ground wire 32 through the conductive portion 70. Accordingly, it is possible to suppress in advance the generation of sparks around the liquid level detection device 1 caused by the arm 51 being charged and, as a result, static electricity flowing from the arm 51 to a place with a lower potential.

[0049] Further, according to the liquid level detection device 1, at least a part of the conductive portion 70 is embedded in the frame 11. Therefore, even if the liquid level detection device 1 is provided with the conductive portion 70, there is no significant difference in appearance compared to the case where the conductive portion 70 is not provided. Thus, for example, when an operator installs the liquid level detection device 1 in a fuel tank, the workability is not reduced due to the enlargement or complication of the liquid level detection device 1.

[0050] Furthermore, according to the configuration in which the second end portion 73 of the conductive portion 70 is exposed from the first stopper surface 25a or the like toward the orbit of the arm 51, the above-described effects can be realized with a simple structure. Also, regarding the outer shape of the liquid level detection device 1, the position or structure of the first stopper surface 25a or the like in the frame 11 is equivalent to that of an existing liquid level detection device. Therefore, even when the conductive portion 70 is newly provided in the frame 11, it is not necessary to significantly change the outer shape of the frame 11 from the existing one. Further, since the second end portion 73 is provided in accordance with the first stopper surface 25a or the like, the conductive portion 70 does not hinder the swinging of the arm 51. Therefore, the presence of the conductive portion 70 does not affect the detection result of the liquid level detection device 1.

[0051] As described above, according to the present embodiment, it is possible to provide the liquid level detection device 1 having a compact outer shape and suppressing the generation of sparks around it.

[0052] Also, in the liquid level detection device 1, the conductive portion 70 may be a conductive plate material.

[0053] According to this liquid level detection device 1, the conductive portion 70 can be easily formed in terms of ease of processing and the like. Also, when the conductive portion 70 is embedded in the frame 11 by insert molding, it is easy to maintain the conductive portion 70 in a desired shape in advance, which can also be advantageous in terms of improving the efficiency of the work during insert molding.

[0054] In addition, in the liquid level detection device 1, the frame 11 may have a pair of first stoppers that contact the tip side of the arm 51 at a position closer to the tip than the position facing the shaft portion 21 of the arm 51 to restrict the rotation range of the holder 40. Further, the frame 11 may have a pair of second stoppers that contact the base end side of the arm 51 at a position closer to the base end than the position facing the shaft portion 21 of the arm 51 to restrict the rotation range of the holder 40. The rotation range restricted by the pair of second stoppers is larger than the rotation range restricted by the pair of first stoppers. In this case, the second end portion 77 may be exposed from each of the first auxiliary stopper surface 27a and the second auxiliary stopper surface 27b that constitute the pair of second stoppers toward the trajectory of the arm 51.

[0055] In the above description, the case where the second end portion 73 of the conductive portion 70 is installed in accordance with the first stopper surface 25a and the second stopper surface 25b, which are a pair of first stoppers, is exemplified. On the other hand, as described above, the liquid level detection device 1 has, in addition to the pair of first stoppers, a pair of second stoppers including a first auxiliary stopper surface 27a and a second auxiliary stopper surface 27b that the locking end 51a of the arm 51 can contact. Therefore, instead of the first stopper surface 25a and the second stopper surface 25b, it may be possible to install the second end portion of the conductive portion in accordance with the first auxiliary stopper surface 27a and the second auxiliary stopper surface 27b.

[0056] FIG. 7 corresponds to FIG. 5 and is a perspective view showing the conductive portions 74 and 80 as two other examples of the conductive portion that the liquid level detection device 1 may employ. In order to distinguish between the conductive portion 74 and the conductive portion 80, the conductive portion 80 is drawn with a two-dot chain line. Further, since the configurations other than the conductive portions 74 and 80 are the same as the configurations illustrated in FIG. 5, the description thereof is omitted.

[0057] The conductive part 74 is a conductive member having an extending part 75, a first end part 76, and a second end part 77, similar to the above-mentioned conductive part 70. However, the second end part 77 is exposed from each of the first auxiliary stopper surface 27a and the second auxiliary stopper surface 27b toward the orbit of the locking end 51a of the arm 51. Also, depending on the exposed position of the second end part 77, for example, the extending part 75 may be shorter than the extending part 71 of the conductive part 70. Since the locking end 51a contacts the first auxiliary stopper surface 27a or the second auxiliary stopper surface 27b when an overload is applied to the arm 51, the contact frequency is lower than the case where the second end part 73 of the conductive part 70 contacts either of the pair of first stoppers. However, since the opportunity for the locking end 51a to contact either of the second end parts 77 provided on the pair of second stoppers is ensured, the liquid level detection device 1 can have a compact outer shape and suppress the generation of sparks around, which is the same point.

[0058] On the other hand, the conductive part 80 is a substitute for the above-described conductive part 70 or conductive part 74, and is a conductive structure having an extending part 81, a first end part 82, and a second end part. The extending part 81 is, for example, a wiring made of metal. Here, the point that one end part of the extending part 81 connected to the ground terminal 35 is the first end part 82 is the same as that of the conductive part 70. In contrast, the second end part in the conductive part 80 is not the other end part itself of the extending part 81, but a part of the block body 84 to which the other end part 83 of the extending part 81 is connected. The block body 84 is a conductive member.

[0059] Also in this case, there are two conductive parts 80 having symmetrical shapes with respect to each other. A part of the block body 84 included in one conductive part 80 may be exposed from the first stopper surface 25a of the pair of first stoppers toward the orbit of the arm 51. Also, a part of the block body 84 included in the other conductive part 80 may be exposed from the second stopper surface 25b of the pair of first stoppers toward the orbit of the arm 51. Furthermore, the point that a part of the block body 84 may be exposed from the first auxiliary stopper surface 27a and the second auxiliary stopper surface 27b constituting the pair of second stoppers is the same as that of the conductive part 74.

[0060] As described above, in the liquid level detection device 1, the conductive part 80 may be a combination of a member having conductivity including a second end part and a wiring.

[0061] According to this liquid level detection device 1, even if the conductive part 70 is not necessarily formed of a plate material, a liquid level detection device 1 with a compact outer shape that suppresses the generation of sparks around can be simply configured.

[0062] FIG. 8 corresponds to FIG. 3 and is a schematic cross-sectional view showing two other examples of the conductive part, namely the conductive part 85 and the conductive part 85a, that can be adopted by the liquid level detection device 1. Note that since the configurations other than the conductive part 85 and the conductive part 85a are the same as the example configuration in FIG. 3, the description thereof is omitted.

[0063] The conductive part 85 is a replacement for the conductive part 70 described above and is a conductive structure having an extending part 86, a first end part, and a second end part. The extending part 86 may be a metal plate material or a metal wiring. Note that in FIG. 8, the extending part 86 and the first end part are schematically shown using broken lines. The path inside the frame 11 where the extending part 86 can be located can be set in various ways under the condition that, for example, it does not interfere with other components and does not expose outside the frame 11.

[0064] And the second end part of the conductive part 85 may be a protruding part 87 that protrudes from the frame 11 toward the orbit of the arm 51 so as to contact the arm 51 at the intermediate detection position of the liquid level. In this case, the protruding part 87 may be installed on the arm facing part 11c as a plane that is exposed toward the orbit of the arm 51 between the first stopper surface 25a and the second stopper surface 25b.

[0065] On the other hand, the conductive part 85a is a replacement for the conductive part 85 described above and is a conductive structure having an extending part 86a, a first end part, and a second end part. The extending part 86a is equivalent to the extending part 86 of the conductive part 85.

[0066] And the second end portion at the conductive portion 85a may be a protruding portion 87a that protrudes from the frame 11 toward the orbit of the arm 51 so as to contact the arm 51 at the intermediate detection position of the liquid level. In this case, the protruding portion 87a may be installed in the rotation groove 26 that is exposed toward the orbit of the locking end 51a on the proximal end side of the arm 51 between the first auxiliary stopper surface 27a and the second auxiliary stopper surface 27b.

[0067] According to this liquid level detection device 1, even if the conductive portion 70 or the like is not necessarily installed on the first stopper or the second stopper, the liquid level detection device 1 with a compact outer shape that suppresses the generation of sparks around can be simply configured. Further, since the protruding portion 87 or the like as the second end portion is provided so as to contact the arm 51 at the intermediate detection position of the liquid level, the contact frequency is higher than the case where it is provided on the first stopper or the like corresponding to the maximum detection position or the minimum detection position of the liquid level. Therefore, there is an advantage that it is easier to suppress the generation of sparks around the liquid level detection device 1.

[0068] (Second Embodiment) FIG. 9 is a perspective view of the liquid level detection device 2 according to the second embodiment. FIG. 10 is a plan view of the liquid level detection device 2 excluding a part of the float 50 and the arm 51. Hereinafter, "up and down" in the liquid level detection device 2 refers to above or below in the vertical direction.

[0069] The liquid level detection device 2 detects the liquid level (liquid surface position) of the liquid based on the displacement of the arm 51 following the up and down movement of the float 50 floating in the liquid. Hereinafter, as an example, the liquid level detection device 2 is attached to a fuel tank mounted on a vehicle such as an automobile, and detects the liquid level of the fuel stored inside the fuel tank. The liquid level detection device 2 includes a device body 10a, a lead wire 30a, a connector 37, a holder 40, a float 50, and an arm 51.

[0070] The device main body 10a is the main body part of the liquid level detection device 2. The device main body 10a includes a frame 11a, a lead frame 12, a holding member 13, and a Hall element 60. Hereinafter, "front and rear" in the device main body 10a refers to the front or rear in the horizontal direction. At this time, the side where the holder 40 is supported in the device main body 10a is the front side, and the side where the lead frame 12 and the like are insert-molded is the rear side.

[0071] The frame 11a is, for example, a resin structure that rotatably supports the holder 40. The frame 11a has a lead wire arrangement portion 29 at the upper part. The lead wire arrangement portion 29 exposes a part of the lead frame 12 that connects the lead wire 30a to the outside of the frame 11a and arranges the tip portion of the lead wire 30a connected to the lead frame 12.

[0072] The lead frame 12 is a conductor part with a part insert-molded in the frame 11a. The lead frame 12 includes at least three terminals that are independent plate bodies according to the type of the lead wire 30a based on the detection method of the detection part and the like. In the present embodiment, the lead frame 12 includes an input terminal 34, a ground (GND) terminal 35, and an output terminal 36. The input terminal 34, the ground terminal 35, and the output terminal 36 are electrically connected to the Hall element 60 as the detection part according to their respective functions. That is, one end of the lead wire 30a is connected to the device main body 10a so as to communicate with the Hall element 60.

[0073] The holding member 13 is assembled to the lead wire arrangement portion 29 provided on the frame 11a and holds the lead wire 30a. For example, the holding member 13 may have a groove 13a for each lead wire 30a according to the diameter of the lead wire 30a. The holding member 13 can make it difficult for the lead wire 30a to come off the lead frame 12 by sandwiching the groove 13a with the lead wire arrangement portion 29 in a state where the lead wire 30a is engaged with the groove 13a.

[0074] The Hall element 60 is a magnetic detection element that detects the rotation angle of the holder 40, and is an example of a detection unit that detects a displacement amount for deriving the liquid level of fuel.

[0075] At least three lead wires 30a are provided based on the detection method of the detection unit and the like, and electrically connect between the liquid level detection device 2 and an external device such as a measuring instrument. In the present embodiment, the lead wire 30a includes an input wire 31a related to power supply, a ground (GND) wire 32a, and an output wire 33a related to a signal, which are independent of each other. One end of the input wire 31a is connected to the input terminal 34 in the lead wire arrangement portion 29. One end of the ground wire 32a is connected to the ground terminal 35 in the lead wire arrangement portion 29. One end of the output wire 33a is connected to the output terminal 36 in the lead wire arrangement portion 29.

[0076] Here, in the present embodiment, the lengths of at least three lead wires 30a are not the same as shown in FIG. 10. This point will be described in detail again below.

[0077] The connector 37 connects the other ends of the input wire 31a, the ground wire 32a, and the output wire 33a in a non-contact manner with each other, and is connected to the receiving-side connector that is electrically continuous with the external device.

[0078] The holder 40 is a member made of, for example, resin, holds the base end side of the arm 51, and converts the displacement of the arm 51 following the vertical movement of the float 50 accompanying the change in the liquid level of the fuel into a rotational movement. The rotation range of the holder 40 is restricted to an angular range θ by a stopper such as the first stopper surface 25a provided on the frame 11. The holder 40 includes an annular magnet inside. The magnet is a displacement member used for detecting the rotation angle of the holder 40 by the Hall element 60 provided on the frame 11a. The float 50 is floated on the liquid fuel. That is, the float 50 moves up and down as the liquid level of the fuel in the fuel tank changes. The arm 51 is a rod-shaped member that connects the holder 40 and the float 50. The arm 51 supports the float 50 at the tip side.

[0079] Next, the length of the lead wire 30a will be described in detail. In the present embodiment, there are three lead wires 30a, namely an input wire 31a, a ground wire 32a, and an output wire 33a. Here, the arrangement relationship of the three lead wires 30a is defined by the three grooves 13a provided in the holding member 13. The input wire 31a, the ground wire 32a, and the output wire 33a are arranged in parallel with each other and at equal intervals in a direction perpendicular to both the vertical direction and the front-rear direction with respect to the apparatus main body 10a, taking this direction as the parallel direction.

[0080] Also, among the three lead wires 30a, the length of the first lead wire located at the end in the parallel direction is longer than the length of the second lead wire located so as to be sandwiched between the other two lead wires. In the present embodiment, both the input wire 31a and the output wire 33a correspond to the first lead wire. On the other hand, the ground wire 32a located so as to be sandwiched between the input wire 31a and the output wire 33a corresponds to the second lead wire. Therefore, as shown in FIG. 10, when the connector 37 is separated upward from the apparatus main body 10a, the ground wire 32a is in a state of being stretched with a length L, and the input wire 31a and the output wire 33a are in a slack state respectively.

[0081] FIG. 11 is a conceptual diagram for explaining the setting of the length of the lead wire 30a corresponding to FIG. 10. In FIG. 11, a state is illustrated in which the output wire 33a, which is the first lead wire, is tilted toward the ground wire 32a while the ground wire 32a, which is the second lead wire, is kept stretched.

[0082] Here, the length of the second lead wire, that is, the ground wire 32a, is defined as L. The width between the first lead wire, that is, the output wire 33a, located at one end in the parallel direction and the ground wire 32a located adjacent to the output wire 33a is defined as W. Also, the inclination angle with respect to the parallel direction when the output wire 33a is tilted toward the ground wire 32a is defined as θ A . In this case, the length of the output wire 33a is longer than the length L of the ground wire 32a by the extended length L represented by Wcosθ A and is represented by (L + Wcosθ E ). At this time, the inclination angle θ A ) Ais set so that 25° < θ A <is in the range of 65°. Alternatively, the inclination angle θ A may be set to 45°.

[0083] Here, although the length of the output line 33a, which is one of the first lead wires, has been described, the length of the input line 31a, which is the other first lead wire, can be set in the same way.

[0084] Next, the operation of the liquid level detection device 2 will be described.

[0085] FIG. 12 is a conceptual diagram for explaining the tensile load applied to the lead wire 30a corresponding to FIG. 10. In FIG. 12, the receiving connector 100, which is the mating target of the connector 37 when the liquid level detection device 2 is attached in the fuel tank, is illustrated by a two-dot chain line.

[0086] For example, when an operator attaches the liquid level detection device 2 into the fuel tank, as shown in FIG. 12, assume a case where the operator connects the connector 37 to the receiving connector 100 that is diagonally above the position of the device main body 10a while holding the connector 37. In particular, it is assumed that the receiving connector 100 is provided at a position closer to the input line 31a side along the parallel direction of the lead wire 30a than directly above the device main body 10a.

[0087] First, as a comparative example, assuming that the lengths of all the lead wires 30a are the same, when an operator tries to connect the connector 37 to the receiving connector 100, the input line 31a on the side closer to the receiving connector 100 is likely to slack. However, the output line 33a on the side farther from the receiving connector 100 is likely to be pulled toward the receiving connector 100 provided on the opposite side in the parallel direction. Therefore, there is a possibility that the tensile load F applied to the entire three lead wires 30a will concentrate on the output line 33a at one end in the parallel direction of the lead wire 30a.

[0088] In contrast, in the present embodiment, the length of the output line 33a at one end in the parallel direction of the lead wire 30a is set in advance to be longer than the length of the ground line 32a disposed adjacent to the output line 33a. Therefore, even if the output line 33a on the side farther from the receiving connector 100 is pulled toward the receiving connector 100, as shown in FIG. 12, the degree of pulling is approximated by the output line 33a and the ground line 32a. Accordingly, the tensile load F applied to the entire three lead wires 30a is distributed between the output line 33a and the ground line 32a.

[0089] As an example, it is assumed that the tensile strength of each lead wire 30a is 70 N. In the case of the above comparative example, since the tensile load F is applied to only one output line 33a approximately, the tensile strength of the entire lead wire 30a is also about 70 N. On the other hand, in the case of the present embodiment, since the tensile load F is distributed between the two output line 33a and the ground line 32a, the tensile strength of the entire lead wire 30a is about 140 N, which is approximately twice as much.

[0090] Here, the case where the receiving connector 100 is provided at a position closer to the input line 31a side along the parallel direction of the lead wire 30a than directly above the apparatus main body 10a has been illustrated. In contrast, in the present embodiment, the length of the input line 31a on the opposite side of the output line 33a along the parallel direction is also set to be longer than the length of the ground line 32a. Therefore, even when the receiving connector 100 is provided at a position closer to the output line 33a side along the parallel direction of the lead wire 30a than directly above the apparatus main body 10a, the tensile strength of the entire lead wire 30a is improved in the same manner.

[0091] Further, the liquid level detection device 2 is attached to the inner wall of the fuel tank such that the rear surface side of the apparatus main body 10a faces the inner wall surface of the fuel tank. At this time, the operator connects the connector 37 to the receiving connector 100 while allowing the lead wire 30a to crawl on the inner wall of the fuel tank. Therefore, when the liquid level detection device 2 is attached, since the lead wire 30a basically moves along the parallel direction in many cases, the length setting of the lead wire 30a as described above can be effective.

[0092] Next, the effects of the liquid level detection device 2 will be described.

[0093] The liquid level detection device 2 includes a device body 10a including a detection unit that detects a displacement amount for deriving the liquid level of the liquid. Further, the liquid level detection device 2 includes at least three lead wires 30a having one end connected to the device body 10a so as to communicate with at least the detection unit and arranged in parallel with each other, and a connector 37 that connects the other ends of the respective lead wires 30a. Among the at least three lead wires 30a, the length of the first lead wire located at the end in the parallel direction is longer than the length of the second lead wire located so as to be sandwiched between the other two lead wires.

[0094] Here, in the above example, the detection unit corresponds to the Hall element 60. However, the detection method adopted by the liquid level detection device 2 is not limited to the method using the Hall element 60, and other detection methods may be adopted as long as the rotation angle of the holder 40 can be detected. Further, in the above example, the first lead wire corresponds to the input wire 31a and the output wire 33a, and the second lead wire corresponds to the ground wire 32a.

[0095] In the liquid level detection device 2, among the at least three lead wires 30a, the length of the first lead wire located at the end in the parallel direction is set to be longer than the length of the second lead wire located so as to be sandwiched between the other two lead wires. Therefore, according to the liquid level detection device 2, even if the lead wire 30a is pulled obliquely upward, it is difficult to concentrate the tensile load on the first lead wire located at the end in the parallel direction. Accordingly, the tensile load F applied to the entire at least three lead wires 30a can be dispersed to a plurality of lead wires 30a including the first lead wire, and as a result, the tensile strength of the entire lead wire 30a can be improved.

[0096] As described above, according to the present embodiment, it is possible to provide the liquid level detection device 2 that improves the tensile strength of the lead wire 30a.

[0097] In the above description, the case where there are three lead wires 30a has been exemplified. However, depending on conditions such as differences in the detection method of the detection unit and the addition of electronic components that perform other functions, there may be four or more lead wires 30a. For example, when there are four lead wires 30a, there will be two adjacent second lead wires.

[0098] Also, in the liquid level detection device 2, let the length of the second lead wire be L, and let the width between the first lead wire located at one end in the parallel direction and the second lead wire located adjacent to the first lead wire be W. Also, let the inclination angle with respect to the parallel direction when the first lead wire is inclined toward the second lead wire be θ. A Then, the length of the first lead wire is represented by (L + Wcosθ A ), and the inclination angle may be in the range of 25° < θ A < 65°.

[0099] According to this liquid level detection device 2, in view of the installation position of the receiving connector 100 with respect to the mounting position of the device main body 10a in the internal structure of a general fuel tank mounted on a vehicle such as an automobile, the above effects can be achieved.

[0100] Also, in the liquid level detection device 2, the inclination angle may be 45°.

[0101] According to this liquid level detection device 2, in view of the installation position of the receiving connector 100 with respect to the mounting position of the device main body 10a in the internal structure of a general fuel tank mounted on a vehicle such as an automobile, the above effects can be more reliably achieved.

[0102] (Third Embodiment) FIG. 13 is a perspective view of a liquid level detection device 3 according to the third embodiment. FIG. 14 is a cross-sectional view of a main part of the liquid level detection device 3 cut along a plane extending in the vertical direction while including the central axis AX of the shaft portion 21. Hereinafter, "up and down" in the liquid level detection device 3 refers to above or below in the vertical direction.

[0103] The liquid level detection device 3 detects the liquid level (liquid surface position) of the liquid based on the displacement of the arm 51 following the up and down movement of the float 50 floating in the liquid. Hereinafter, as an example, the liquid level detection device 3 is mounted in a fuel tank mounted on a vehicle such as an automobile, and detects the liquid level of the fuel stored inside the fuel tank. The liquid level detection device 3 includes a device main body 10b, a lead wire 30, a connector 37, a holder 40, a float 50, and an arm 51.

[0104] The device main body 10b is the main body part of the liquid level detection device 3. The device main body 10b includes a frame 11b, a lead frame 12, and a holding member 13. Hereinafter, "front and rear" in the device main body 10b refers to the front or rear in the horizontal direction. At this time, the side where the holder 40 is supported in the device main body 10b is the front side, and the side where the lead frame 12 and the like are insert-molded is the rear side.

[0105] The frame 11b is, for example, a resin structure, and rotatably supports the holder 40. The frame 11b has a rotation recess 20, a shaft portion 21, a locking groove 22, a pair of insertion holes 23, a guide ridge 24, a first stopper surface 25a, a second stopper surface 25b, and an arm facing portion 11c.

[0106] The rotation recess 20 is provided in a circular shape in plan view on the front side of the frame 11b, and rotatably accommodates a part of the holder 40. The shaft portion 21 is provided coaxially with the center of the rotation recess 20, and is the rotation reference of the holder 40, and engages with the shaft recess 42 formed in the holder 40.

[0107] The locking groove 22 is provided over the circumferential direction in the inner peripheral portion of the rotation recess 20, and rotatably locks the flange portion 43 of the holder 40. The locking groove 22 has two side walls 22a facing each other in the direction along the central axis AX of the shaft portion 21. The pair of insertion holes 23 are provided at positions facing each other in the horizontal direction at the edge of the rotation recess 20, and communicate with the locking groove 22 respectively. The guide ridge 24 is provided at the bottom of the rotation recess 20 so as to surround the shaft portion 21, and guides the rotation of the holder 40.

[0108] The first stopper surface 25a and the second stopper surface 25b are a pair of stoppers that regulate the rotation of the holder 40 by contacting the arm 51 and restricting the swinging of the arm 51. The pair of stoppers is provided on the front side of the frame 11b and below the center of the rotation recess 20, and are spaced apart from each other and face each other along the outer periphery of the rotation recess 20. When the holder 40 rotates, the arm 51 contacts one of the pair of stoppers on the tip side of the shaft portion 21. Thereby, the rotation range of the holder 40 is restricted to the angular range θ. The first stopper surface 25a contacts the arm 51 at the maximum detection position of the liquid level among the liquid levels that the liquid level detection device 3 can detect. That is, the first stopper surface 25a is at a position where the arm 51 contacts when the remaining fuel volume in the fuel tank is near full. The second stopper surface 25b contacts the arm 51 at the minimum detection position of the liquid level among the liquid levels that the liquid level detection device 3 can detect. That is, the second stopper surface 25b is at a position where the arm 51 contacts when the remaining fuel volume in the fuel tank is near empty.

[0109] The arm facing portion 11c is a part of the outer peripheral surface of the frame 11b provided at a position facing the orbit of the arm 51. Here, the orbit of the arm 51 refers to the region where the arm 51 can be located when the arm 51 moves with the angular range θ, which is the rotation range of the holder 40 as shown in FIG. 13, as the movement range. Also, the position facing the orbit of the arm 51 refers to a position that can face the orbit of the arm 51 in the direction along the central axis AX of the shaft portion 21. In the present embodiment, the arm facing portion 11c corresponds to a plane that is perpendicular to the central axis AX of the shaft portion 21 and is exposed toward the orbit of the arm 51 between the first stopper surface 25a and the second stopper surface 25b. The first interval G1 and the like regarding the arm facing portion 11c will be described in detail again below.

[0110] Furthermore, the frame 11b has an insert molding portion 28 and a lead wire arrangement portion 29. The insert molding portion 28 is an area where a part of the lead frame 12, a part of the Hall element 60, etc. are insert molded into the frame 11b. The lead wire arrangement portion 29 exposes a part of the lead frame 12 that connects the lead wires 30 to the outside of the frame 11b, and arranges the tip portions of the lead wires 30 that are connected to the lead frame 12.

[0111] The lead frame 12 is a conductor portion, a part of which is insert molded into the frame 11b. The lead frame 12 includes a plurality of terminals that are independent plate bodies according to the type of the lead wires 30 based on the detection method of the detection portion, etc. In the present embodiment, the lead frame 12 includes an input terminal, a ground (GND) terminal 35, and an output terminal. To the input terminal, the ground terminal 35, and the output terminal, leads 62 extending from the Hall element 60 are electrically connected according to their respective functions. Note that in FIGS. 13 and 14, the input terminal and the output terminal are not shown.

[0112] The holding member 13 is assembled to the lead wire arrangement portion 29 provided on the frame 11b and holds the lead wires 30. For example, the holding member 13 may have a groove 13a for each lead wire 30 according to the diameter of the lead wire 30. The holding member 13 can make it difficult for the lead wires 30 to come off the lead frame 12 by sandwiching the groove 13a with the lead wire arrangement portion 29 in a state where the lead wires 30 are engaged with the groove 13a.

[0113] Also, the apparatus main body 10b includes a Hall element 60 as a detection portion for detecting the rotation angle of the holder 40 and leads 62.

[0114] The Hall element 60 is embedded in the shaft portion 21 of the frame 11b and is a magnetic detection element that generates a Hall voltage proportional to the magnetic flux density passing through the Hall element 60 when a magnetic field is applied from the outside while a voltage is applied. On the other hand, a magnet 65, which will be described later, is installed inside the holder 40. When the holder 40 rotates due to a change in the liquid level, the magnet 65 also rotates and displaces, and the intersection angle between the magnetic flux of the Hall element 60 and the magnet 65 changes, and accordingly, the Hall voltage changes. That is, based on the measured Hall voltage, the rotation angle of the holder 40 can be detected, and as a result, the liquid level of the fuel can be detected. As described above, the lead 62 extends from the Hall element 60 and is electrically connected to each terminal included in the lead frame 12.

[0115] Also, a part of the Hall element 60, the lead 62, and the lead frame 12 may be attached inside the frame 11b by multiple insert moldings. For example, by the first-stage insert molding, the Hall element 60 and the lead 62 may be attached to the frame 11b together with the resin body 63. Thereafter, by the second-stage insert molding, the lead frame 12 may be attached to the frame 11b. The resin body 63 has an inner shaft 63a that is coaxially embedded inside the shaft portion 21 of the frame 11b. The Hall element 60 is installed further inside the inner shaft 63a. The Hall element 60 and the lead 62 may be pre-embedded inside the resin body 63 using a resin member 64. Although not shown, the resin member 64 may include other electronic components and the like related to the operation of the Hall element 60.

[0116] A plurality of lead wires 30 are provided based on the detection method and the like of the detection unit, and electrically connect between the liquid level detection device 3 and an external device such as a measuring instrument. In the present embodiment, the lead wire 30 includes an input wire 31 related to power supply, a ground (GND) wire 32, and an output wire 33 related to a signal, which are independent of each other. One end of the input wire 31 is connected to the input terminal in the lead wire arrangement portion 29. One end of the ground wire 32 is connected to the ground terminal 35 in the lead wire arrangement portion 29. One end of the output wire 33 is connected to the output terminal in the lead wire arrangement portion 29.

[0117] The connector 37 connects the other ends of the input line 31, the ground line 32, and the output line 33 to each other in a non-contact manner and is connected to the receiving-side connector that is electrically continuous with an external device.

[0118] The holder 40 is a member made of, for example, resin, holds the base end side of the arm 51, and converts the displacement of the arm 51 following the up and down movement of the float 50 accompanying the change in the liquid level of the fuel into a rotational movement. Hereinafter, "front and rear" in the holder 40 refers to the front or rear in the horizontal direction. At this time, the side that holds the arm 51 is the front side, and the side that is supported by the apparatus main body 10b in the holder 40 is the rear side. The holder 40 has a holder main body 41 and an arm holding portion 46.

[0119] The holder main body 41 is a cylindrical member having a shaft recess 42, a pair of flange portions 43, and a guide recess 44.

[0120] The shaft recess 42 is provided on the rear surface side of the holder main body 41 and coaxially with the central axis AX of the shaft portion 21, and engages with the shaft portion 21 in a rotationally slidable manner with the shaft portion 21 provided on the frame 11b as a rotation axis. In the present embodiment, the central axis of the shaft recess 42 is referred to as the "rotation axis" separately from the central axis AX of the shaft portion 21. The pair of flange portions 43 are each provided so as to project radially outward from the rear edge portion of the holder main body 41. Further, the pair of flange portions 43 project in opposite directions along the extending direction of the arm 51 when the arm 51 is held by the arm holding portion 46. The guide recess 44 is provided on the rear surface side of the holder main body 41 and on the outer peripheral side of the magnet 65 installed in the holder main body 41, and houses the guide protrusion 24 provided on the frame 11b.

[0121] When assembling the holder 40 to the frame 11b, the operator fits the holder 40 into the rotation recess 20 with a pair of flange portions 43 aligned with the positions of a pair of insertion holes 23 in the frame 11b. When the flange portions 43 pass through the insertion holes 23, the shaft portion 21 of the frame 11b is inserted into the shaft recess 42 of the holder 40. Further, the guide protrusion 24 of the frame 11b enters the guide recess 44 of the holder 40. Next, when the operator rotates the holder 40 fitted in the rotation recess 20 so that the locking hole 47 described later is disposed upward, the flange portion 43 enters the locking groove 22 of the frame 11b, and the holder 40 does not come out of the rotation recess 20. Incidentally, in a state where the holder 40 holds the arm 51, the rotation range of the holder 40 is restricted by the first stopper surface 25a or the like, so that the holder 40 is also prevented from coming out of the rotation recess 20 due to the movement of the flange portion 43 to the position of the insertion hole 23.

[0122] The arm holding portion 46 holds the arm 51 such that the extending direction of the arm 51 is orthogonal to the rotation axis of the holder 40. The arm holding portion 46 has a locking hole 47. The locking hole 47 is provided in a part of the peripheral edge of the holder body 41 so as to penetrate in the front-rear direction of the holder 40, and locks the locking end 51a on the proximal end side of the arm 51.

[0123] Further, the holder 40 includes an annular magnet 65. The magnet 65 is installed inside the holder body 41 so as to be disposed on the inner peripheral side of the shaft recess 42, and is a displacement member used for detecting the rotation angle of the holder 40 by the Hall element 60. In this case, the Hall element 60 is positioned on the inner diameter side of the magnet 65 that rotates and displaces as the holder 40 rotates.

[0124] The float 50 is floated on a liquid fuel. That is, the float 50 moves up and down as the liquid level of the fuel in the fuel tank changes.

[0125] The arm 51 is a rod-shaped member that connects the holder 40 and the float 50. The arm 51 supports the float 50 on the tip side. On the other hand, the arm 51 is held by the arm holding portion 46 of the holder 40 on the base end side of the arm 51, which is opposite to the tip side. Note that the arm 51 may have one or more bent portions. The end portion on the base end side of the arm 51 is a locking end 51a that is bent at a right angle. The locking end 51a is inserted into the locking hole 47 in a state where the arm holding portion 46 holds the arm 51.

[0126] Next, the arm facing portion 11c provided on the frame 11b will be described in detail. Normally, the extending direction of the arm 51 is approximately perpendicular to the central axis AX of the shaft portion 21. At this time, a gap (clearance) having a first interval G1 is formed in the direction along the central axis AX of the shaft portion 21 between the arm facing portion 11c and the orbit of the arm 51. That is, normally, the arm 51 does not contact the arm facing portion 11c. Here, "normally" means a time when no unintended external force is applied to the arm 51 other than the vertical movement of the float 50.

[0127] On the other hand, normally, the flange portion 43 of the holder 40 is approximately parallel to the side wall 22a of the locking groove 22 provided in the frame 11b. At this time, a gap (clearance) having a second interval G2 is formed in the direction along the central axis AX of the shaft portion 21 between the side wall 22a of the locking groove 22 and the flange portion 43. The size of this gap is set in consideration of dimensional variations during manufacturing, temperature changes during use, or aging deterioration in advance. As an example, when the liquid level detection device 3 is installed in a fuel tank of a general automobile, the gap represented by the second interval G2 in this embodiment is about 0.3 mm.

[0128] FIG. 15 is an enlarged cross-sectional view of the main part of FIG. 14 for explaining the relationship between the first interval G1 and the second interval G2. In this embodiment, the first interval G1 regarding the gap between the frame 11b and the arm 51 is smaller than the second interval G2 regarding the gap between the frame 11b and the holder 40.

[0129] Here, as a first assumption, assume a case where the arm 51 is tilted by an external force F in a direction coming from the outside toward the front side of the liquid level detection device 3. A In this case, if the distance from the central axis AX of the shaft portion 21 to the first contact point P1 where the arm facing portion 11c contacts when the arm 51 is tilted is L1, the first maximum angle θ1 when the arm 51 is tilted by the external force F A satisfies the relationship of tanθ1 = G1 / L1.

[0130] On the other hand, when the arm 51 is tilted by the external force F A the holder 40 holding the arm 51 also tilts. That is, the flange portion 43 which is a part of the holder 40 also tilts with respect to the side wall 22a of the locking groove 22. Here, as a second assumption, assume a case where the first interval G1 is set relatively large and the arm facing portion 11c does not contact even when the arm 51 is tilted by the external force F A In this case, one flange portion 43 contacts the one side wall 22a of the locking groove 22 at the second contact point P2, and the holder 40 tilts with the second contact point P2 as a base point, so that the other flange portion 43 contacts the other side wall 22a of the locking groove 22. And if the distance from the outermost end of one flange portion 43 to the outermost end of the other flange portion 43 is L2, the second maximum angle θ2 of the holder 40, that is, the flange portion 43, satisfies the relationship of tanθ2 = G2 / L2.

[0131] Considering the above first and second assumptions, as the relationship between the first interval G1 and the second interval G2 in the present embodiment, the first maximum angle θ1 is smaller than the second maximum angle θ2. For example, when the liquid level detection device 3 is installed in a fuel tank of a general automobile, the second maximum angle θ2 is about 1.5°.

[0132] Next, the operation of the liquid level detection device 3 will be described.

[0133] First, in the liquid level detection device 3, as a basic operation, as the float 50 moves up and down following the change in the liquid level of the fuel, the arm 51 swings, and the holder 40 to which the arm 51 is connected rotates with respect to the device main body 10b. The hall element 60 in the device main body 10b detects the change in the magnetic flux of the magnet 65 in the holder 40, and the detection result is transmitted to a measurement unit or the like as an external device through the output line 33. For example, the measurement unit measures the liquid level based on the output signal transmitted from the liquid level detection device 3, and issues a warning such as fuel exhaustion in the fuel tank if necessary.

[0134] On the other hand, when the liquid level detection device 3 is in use, an unintended external force F, such as that exemplified in the explanation of the relationship between the first interval G1 and the second interval G2, may be applied to the arm 51. A When the arm 51 is tilted under the action of the external force F, the holder 40 holding the arm 51 also tilts. Here, since the hall element 60 is provided in the shaft portion 21 of the frame 11b and the magnet 65 is provided in the holder 40, when the holder 40 tilts with respect to the shaft portion 21 serving as the rotation reference of the holder 40, the arrangement relationship between the hall element 60 and the magnet 65 changes. Therefore, when the tilt of the holder 40 increases, the magnetic flux density applied to the hall element 60 may change more than in the normal state, resulting in an output error. A For example, in the engagement structure between the frame 11b and the holder 40, the holder 40 is held by the frame 11b by the engagement of a pair of flange portions 43 provided on the holder 40 with the locking groove 22 provided on the frame 11b. Therefore, as a comparative example, when the first interval G1 is set relatively large as exemplified in the second assumption above, the arm 51 is subjected to the external force F.

[0135] For example, in the engagement structure between the frame 11b and the holder 40, the holder 40 is held by the frame 11b by the engagement of a pair of flange portions 43 provided on the holder 40 with the locking groove 22 provided on the frame 11b. Therefore, as a comparative example, when the first interval G1 is set relatively large as exemplified in the second assumption above, the arm 51 is subjected to the external force F. AEven if it is tilted under the influence, it does not contact the arm facing portion 11c. As a result, the holder 40 will tilt such that one flange portion 43 contacts one side wall 22a of the locking groove 22 at the second contact point P2 and the other flange portion 43 contacts the other side wall 22a of the locking groove 22. As the output error caused by the tilted posture of the holder 40, it can be considered that the output error that can occur is maximized when the holder 40 is in such a tilted posture.

[0136] On the other hand, in the present embodiment, the position of the arm facing portion 11c is set such that a first interval G1 regarding the gap between the frame 11b and the arm 51 is smaller than a second interval G2 regarding the gap between the frame 11b and the holder 40. Therefore, when the arm 51 is tilted under the influence of an external force F A it contacts the arm facing portion 11c before the tilted posture of the holder 40 reaches the tilted posture where the output error that can occur is maximized. That is, the holder 40 that holds the arm 51 is less likely to tilt to the posture where the output error that can occur is maximized, so the output error caused by the tilted posture of the holder 40 can be suppressed as much as possible.

[0137] Next, the effects of the liquid level detection device 3 will be described.

[0138] The liquid level detection device 3 includes a float 50 that floats on the liquid, an arm 51 that supports the float 50 on the tip side, and a holder 40 that holds the base end side of the arm 51 and converts the displacement of the arm 51 following the up and down movement of the float 50 due to the change in the liquid level of the liquid into a rotational movement. The liquid level detection device 3 includes a frame 11b having a shaft portion 21 that is a rotation reference of the holder 40. Further, the liquid level detection device 3 includes a magnetic detection element provided on the shaft portion 21 for detecting the rotation angle of the holder 40, and a magnet 65 provided on the holder 40 for applying a magnetic field to the magnetic detection element. The holder 40 has a shaft recess 42 that rotatably slidably engages with the shaft portion 21, and an arm holding portion 46 that holds the arm 51 such that the extending direction is orthogonal to the direction along the central axis of the shaft recess 42. Further, the holder 40 has a pair of flange portions 43 that project in opposite directions along the extending direction of the arm 51 at the arm holding portion 46. The frame 11b has two side walls 22a facing each other in the direction along the central axis of the shaft portion 21 and has a locking groove 22 for rotatably locking the flange portion 43, and an arm facing portion 11c provided at a position facing the trajectory of the arm 51. A first interval G1 between the arm facing portion 11c and the trajectory of the arm 51 is smaller than a second interval G2 between the side wall 22a of the locking groove 22 and the flange portion 43.

[0139] Here, in the above example, the magnetic detection element corresponds to the Hall element 60.

[0140] According to this liquid level detection device 3, the first interval G1 between the arm facing portion 11c and the trajectory of the arm 51 is set smaller than the second interval G2 between the side wall 22a of the locking groove 22 and the flange portion 43. Therefore, as described above, even if the arm 51 is tilted by receiving an external force F A before reaching the tilting posture where the possible output error becomes maximum due to the engagement relationship between the frame 11b and the holder 40, it contacts the arm facing portion 11c. Therefore, the holder 40 that holds the arm 51 is less likely to tilt to the posture where the possible output error becomes maximum, so that the output error caused by the tilting posture of the holder 40 can be suppressed.

[0141] As described above, according to the present embodiment, it is possible to provide the liquid level detection device 3 that suppresses the output error.

[0142] Further, in the liquid level detection device 3, the first interval is G1, and the distance from the central axis AX of the shaft portion 21 to the first contact point P1 where the arm facing portion 11c contacts when the arm 51 is tilted is L1. At this time, it is assumed that the first maximum angle θ1 when the arm 51 is tilted by receiving the external force F A satisfies the relationship of tanθ1 = G1 / L1. Also, the second interval is G2, and the distance from the outermost end of one flange portion 43 to the outermost end of the other flange portion 43 is L2. At this time, it is assumed that the second maximum angle θ2 when one flange portion 43 contacts one side wall 22a of the locking groove 22 and the other flange portion 43 contacts the other side wall 22a of the locking groove 22 satisfies the relationship of tanθ2 = G2 / L2. In this case, the first maximum angle θ1 may be smaller than the second maximum angle θ2.

[0143] According to this liquid level detection device 3, the first interval G1 and the second interval G2 can be derived from the relationship between the first maximum angle θ1 and the second maximum angle θ2 in consideration of the dimensions of each part of the frame 11b and the holder 40. Therefore, the above-described effect of suppressing the output error caused by the tilting posture of the holder 40 can be more reliably achieved.

[0144] As described above, although each embodiment has been described, the embodiments are not limited to these, and various modifications are possible within the scope of the gist of the embodiments.

Explanation of Reference Numerals

[0145] 2 Liquid level detection device 10a Device main body 30a Lead wire 31a Input wire 32a Ground wire 33a Output wire 37 Connector 60 Hall element

Claims

1. An apparatus main body including a detection unit that detects a displacement amount for deriving a liquid level of a liquid, at least three lead wires having one end connected to the apparatus main body so as to communicate with at least the detection unit and arranged in parallel with each other, and a connector that connects the other ends of the respective lead wires, Among at least three of the lead wires, a length of a first lead wire positioned at an end in a parallel direction is longer than a length of a second lead wire positioned so as to be sandwiched between the two other lead wires. A liquid level detection device.

2. Let the length of the second lead wire be L, and let the width between the first lead wire positioned at one end in the parallel direction and the second lead wire positioned adjacent to the first lead wire be W. Let θ be the inclination angle with respect to the parallel direction when the first lead wire is inclined toward the second lead wire. Ａ Then, The length of the first lead wire is (L + Wcosθ Ａ ) and is represented by The inclination angle satisfies 25° < θ Ａ < 65°, and the liquid level detection device according to claim 1.

3. The liquid level detection device according to claim 2, wherein the inclination angle is 45°.

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