JP2009128195A - Liquid level detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a non-contact type liquid level detector which is made compact, while suppressing deformation of a magnetic shielding member. <P>SOLUTION: In the liquid level detector 1, a hollow space part 4B to be disposed on a portion of a second spindle part 4a2 formed on a body frame 4, which is made of a synthetic resin material and pivots about a rotatable holder 5, is made recessed from the other lateral side of the body frame 4; a detecting element 9 is disposed in the space part 4B, which detects a magnetic change caused by the rotation of a ring-shaped magnet 8, rotating along with a moving float; a circuit board 10 is arranged along the other lateral side of the body frame 4; and the magnetic shielding member 13, which is smaller than the contour of the body frame 4 and arranged so as to surround the magnet 8, the detecting element 9 and the circuit board 10, is fixed to and held by the body frame 4 from the other lateral side of the body frame 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid level detection device for detecting the amount of various liquids stored in a storage tank, and particularly to an improved structure of a non-contact type liquid level detection device.

  Conventionally, as a liquid level detection device for detecting the liquid level (liquid level) in a fuel tank of a vehicle such as a vehicle, a float arm is attached to a float that moves up and down according to the remaining amount of fuel. It is known to detect the position of the float (fuel level) by converting it into an electrical resistance value by sliding on a fixed contact connected to the resistor with a sliding contact that is linked to the movement of .

  By the way, the liquid level detection device described above involves electrical contact between the sliding contact and the fixed contact, and therefore cannot be used when the fuel is a conductive liquid.

Therefore, as a liquid level detection system that replaces the contact type liquid level detection apparatus, a magnetic sensor such as a magnetoresistive element is used as a detection element that detects a change in magnetism as the magnet rotates following the movement of the float. There has been proposed a non-contact type liquid level detection device (see, for example, Patent Document 1).
JP-A-8-94413

  In a liquid level detection device according to Patent Document 1 or the like, a detection element (magnetic sensor) that detects a change in magnetism with a predetermined interval in the thickness direction on the magnet side as the magnet rotates following the movement of the float. ) Is installed on the main body frame side of the liquid level detection device, there is a problem that it becomes bulky due to the total thickness of the unit of the liquid level detection device. In order to accommodate a liquid level detection device, a fuel pump, or the like installed in a fuel tank of a vehicle or the like, downsizing the liquid level detection device is an important issue.

  Further, when the fuel pump or other electric parts are disposed close to the liquid level detecting device, the liquid level detecting device is provided by the influence of magnetism by the motor and electric parts of the fuel pump. The magnetic field between the magnet and the detection element (magnetic sensor) is disturbed, which causes a change in the output of the detection element, which may appear as an output error as a result. For this purpose, the magnet and the detection element are covered with a magnetic shield member. However, at the time of manufacturing or assembling the liquid level detection device, the liquid level detection device may be brought into contact with other parts to deform the magnetic seed member, and the deformation of the magnetic shield member may cause a problem in the magnetic circuit. It was.

  Therefore, the present invention has been made paying attention to the above-mentioned problems, and aims to suppress deformation of the magnetic shield member while realizing miniaturization of the non-contact type liquid level detection device. .

  In the present invention, as described in claim 1, a main body frame made of a synthetic resin material, a support shaft provided on one side of the main body frame, and a support rotatably supported by the support shaft. A holder, a float arm that is attached to the holder and has a float that follows the displacement of the liquid level, a ring-shaped magnet that is disposed on the holder and rotates in accordance with the operation of the float, and the magnet And a circuit board electrically connected to the detection element, and a current-carrying terminal electrically drawn out from the circuit board to the outside. In the liquid level detection device, a space portion including a hollow recess is formed in a part of the support shaft portion provided on the body frame that pivotally supports the holder from the other side surface side of the body frame. Part And the circuit board is disposed along the other side surface of the main body frame, surrounds the magnet, the detection element, and the circuit board, and is smaller than the outer shape of the main body frame. The magnetic shield member is fixedly held on the main body frame from the other side surface of the main body frame.

  According to a second aspect of the present invention, in the liquid level detection device according to the first aspect, the main body frame includes a protective wall that prevents the magnetic shield member from contacting another member. is there.

  The liquid level detection device according to claim 1 of the present invention is a space formed by a hollow recess from the other side surface of the main body frame in a part of the support shaft portion provided on the main body frame that pivotally supports the holder. Forming a portion, disposing the detection element in the space, disposing the circuit board along the other side surface of the body frame, surrounding the magnet, the detection element, and the circuit board, The magnetic shield member that is smaller than the outer shape of the main body frame is fixedly held on the main body frame from the other side of the main body frame, thereby reducing the size of the non-contact type liquid level detection device and deforming the magnetic shield member. Can be suppressed.

  The liquid level detection device according to claim 2 of the present invention is the liquid level detection device according to claim 1, wherein the main body frame includes a protective wall for preventing contact between the magnetic shield member and another member. Thus, contact from other members can be reliably prevented.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. The liquid level detection apparatus 1 according to the present invention detects the position of the liquid level 3A, which is the amount of the liquid 3 stored in the tank 2. The liquid level detection device 1 includes a liquid level detection main body 1A attached to the tank 2 side, a main body frame 4 of a liquid level meter unit made of a synthetic resin assembled to the liquid level detection main body 1A, and the main body frame 4 A holder 5 made of a synthetic resin material that is rotatably supported on the side, a float arm 7 that is attached to the holder 5 and includes a float 6 that operates to follow the displacement of the liquid level 3A, and the holder 5. A magnet 8 that rotates together with the holder 5 in accordance with the operation of the float 6, and a detection element 9 that detects and outputs a change in magnetism along with the rotation of the magnet 8, for example, using a magnetically sensitive element composed of a Hall element; A circuit board 10 that holds the detection element 9 and is electrically connected to the detection element 9, and a signal detected by the detection element 9 from the circuit board 10 is liquid level detected. And energizing terminal 11 for output of the device 1 to the outside, and a magnetic shield member 13.

  Further, on one side surface of the main body frame 4, a support shaft portion 4 </ b> A that rotatably supports the holder 5 is provided. In this embodiment, the support shaft portion 4A is provided with a first support shaft portion 4a1 having a small diameter and a second support shaft portion 4a2 having a large diameter coaxially with the first support shaft portion 4a1. ing. A hollow space 4B that is recessed from the other side surface of the main body frame 4 is formed in a part of the support shaft 4A, and a magnetically sensitive element (detection element) 9 including a Hall element is formed in the space 4B. Is arranged. Further, an annular (ring-shaped) magnet 8 that is supported by the holder 5 and is magnetized in two poles is arranged opposite to the outer peripheral portion of the support shaft portion 4A. The magnet 8 is integrally and coaxially formed by means such as insert molding simultaneously with the molding of the holder 5. Further, the detection element 9 is not limited to this embodiment, and any means that magnetically detects the rotation of the magnet 8 may be used. For example, a detection element such as an MR element may be used.

  The circuit board 10 is made of a hard board such as glass epoxy resin, and leads extending from the detection elements 9 are fixed by soldering, and electronic components (not shown) are mounted on the circuit board 10. The energization terminal 11 drawn out from the circuit board 10 is provided to output a signal detected by the detection element 9 to the outside of the liquid level detection device 1, and the energization terminal 11 is on the main body frame 4 side. The end of the energizing terminal 11 and the circuit board 10 are fixed by soldering. A hollow space 4B and a housing recess 4C formed on the other side surface of the main body frame 4 by covering the detection element 9, the circuit board 10, or a part of the energizing terminal 11 with a filler 12 for the purpose of protection. It is configured to maintain a watertight state so that dust and liquid 3 do not enter the housing space portion. The main body frame 4 is provided with a mounting recess 4D for disposing the magnetic shield member 13 on the other side surface, and the magnetic shield member 13 is fitted with the mounting recess 4D at its open end. The boss body 4F provided around the mounting recess 4D of the main body frame 4 is welded to be fixed to the mounting recess 4D. Further, the main body frame 4 includes a protective wall 4E for preventing contact between the magnetic shield member 13 and other members outside the mounting recess 4D. The other member is a jig for mounting the liquid level detection device 1 or a floor in an assembly process when the liquid level detection device 1 is dropped at the time of mounting.

  The magnetic shield member 13 is made of, for example, an iron-nickel material, is smaller than the outer shape of the main body frame 4, and is fixedly held on the other side of the main body frame 4. As shown in FIG. 4, the protective wall 4 </ b> E that protects the magnetic shield member 13 is formed without a break so as to surround the magnetic shield member 13. Further, as shown in FIG. 5, the lower end of the protective wall 4E is formed so as to extend to the lower side in FIG. 5 at a position substantially equal to or more than the bottom surface of the magnetic shield member 13. With this configuration, the magnetic shield member 13 can be seen from the back side of the liquid level detection device 1 as shown in FIG. 4 and also as shown in FIG. Even when viewed from the side, it is smaller than the outer shape of the main body frame 4 and is protected by the main body frame 4.

  In the present embodiment, the protective wall 4E is formed without breaks, but may be divided as long as the magnetic shield member 13 can be protected.

  The magnetic shield member 13 surrounds the magnet 8, the detection element 9, and the circuit board 10, and is formed in a cup shape so as to cover the bottom portion and the outer peripheral surface side of the magnet 8. By arranging the O-ring 14 between the side and the main body frame 4 side, a watertight state can be maintained so that dust and liquid 3 do not enter, and the internal electrical components can be protected.

  In the present embodiment, the float 6 is made of a metal material that is not easily corroded, such as stainless steel, and moves as the liquid level 3A fluctuates. In addition, the material of the float 6 is not limited to this embodiment, You may form with a synthetic resin etc.

  The float arm 7 is made of a non-magnetic metal, holds the float 6 at one end, and is inserted and supported by the arm insertion support portion 5A provided at the holder 5 at the other end. Are held by an arm locking portion 5B provided on the holder 5 that supports the shaft portion of the float arm 7.

  Further, in the central portion of the holder 5, a first radial receiving portion 5 </ b> C supported on the outer peripheral surface of the first support shaft portion 4 a 1 provided on the main body frame 4 and a second radial portion provided on the main body frame 4. A second radial receiving portion 5D supported on the outer peripheral surface of the support shaft portion 4a2, and a thrust receiving portion 5E that abuts against the tip end portion of the first support shaft portion 4a1 and restricts the movement of the holder 5 in the thrust direction. And are provided.

  A frame cover 15 is disposed above the holder 5 that is rotatably supported by the support shaft portion 4A of the main body frame 4, and the holder 5 is held by the frame cover 15 in a retaining state. . At this time, the frame cover 15 may be provided as a bearing portion that pivotally supports the upper portion of the holder 5. Although not shown, the first support of the main body frame 4 is used instead of the frame cover 15. You may form so that the latching member which retains the holder 5 may be integrally provided in the front-end | tip (upper end part) of the axial part 4a1.

  Next, the detection of the liquid level 3A of the liquid level detection apparatus 1 of the present embodiment will be described.

  The float 6 moves up and down with the displacement of the liquid level 3A in the tank 2, and the float 6 moves to the outer peripheral surface of the first support shaft portion 4a1 provided on the support shaft portion 4A of the main body frame 4 together with the float arm 7. The first radial receiving portion 5C of the holder 5 to be supported, the second radial receiving portion 5D of the holder 5 supported on the outer peripheral surface of the second support shaft portion 4a2, and the tip of the first support shaft portion 4a1. The holder 5 in which the radial direction and the thrust direction are well supported by the thrust receiving portion 5E that restricts the abutting movement of the holder 5 in the thrust direction at the portion is rotated. The magnet 8 is also rotated by the rotation of the holder 5, the magnetic flux density of the magnet 8 facing the detection element 9 is changed, the change of the magnetic flux density is detected by the detection element 9, and the energization terminal 11 is detected from the circuit board 10. Based on this output signal, an electric signal indicating the liquid level is output to an external device (indicating instrument) (not shown), and the amount of liquid in the tank 2 is detected.

  As described above, in the liquid level detection device 1 of the present invention, the detection element 9 is disposed on a part of the support shaft portion 4A provided on the main body frame 4 of the liquid level gauge unit made of synthetic resin. In addition to the function of the support member that rotatably supports the holder 5 by arranging the annular magnet 8 on the outer peripheral portion of the support shaft portion 4A, the storage portion (in the embodiment) Can also be used as a hollow space 4B), which enables downsizing and allows the detection element 9 to be installed on the same plane as the magnet 8 provided on the holder 5. The thickness dimension of the frame 4 can be suppressed, and a thin and small liquid level detection device 1 can be provided.

  In addition, since the magnet 8 disposed on the outer peripheral portion of the support shaft portion 4A is formed in a ring shape, the magnet 8 can be disposed concentrically with the support shaft portion 4A via the holder 5. A stable indicating characteristic can be realized by the detection element 9 that detects a change in magnetism with the rotation of the ring-shaped magnet 8. The holder 5 is formed of a synthetic resin material, and the holder 5 is molded. Sometimes the magnet 8 is integrally formed. Alternatively, the member including the holder 5 and the magnet 8 on the movable part side can be easily and integrally formed by press-fitting and holding the holder 5, so that the component on the movable part side is small and highly accurate. Can be provided.

  Further, the magnetic shield member 13 is formed in a cup shape, and the magnet 8, the detection element 9, and the circuit board 10 are covered with the magnetic shield member 13, so that the magnetism from the outside of the liquid level detection device 1 is provided. Can be blocked by the magnetic shield member 13, and the magnetic field between the magnet 8 and the detection element 9 is not adversely affected, so that a highly reliable and highly accurate detection output can be obtained. In addition, the bottom surface and the outer peripheral surface of the magnet 8 are covered with the magnetic shield member 13, and an O-ring 14 is disposed between the inner surface side of the magnetic shield member 13 and the main body frame 4 side. It is possible to protect the electrical components.

  Further, by making the magnetic shield 13 smaller than the outer shape of the main body frame 4, the deformation of the magnetic seed member 13 that occurs when the liquid level detection device 1 is dropped or brought into contact with other components at the time of attachment is prevented. Since it can be prevented, the magnetic circuit constituted by the magnetic shield member 13 is prevented from being hindered, so that the yield as the liquid level detection device 2 can be improved and the liquid level detection accuracy can be improved.

  The main body frame 4 includes a protective wall 4E that prevents the magnetic shield member 13 from coming into contact with other members, and can reliably prevent contact from other members.

  With the main body frame 4 made of a synthetic resin material as a reference, the float 6, the float arm 7, and the holder 5 that supports the main body frame 4 can be rotatably set on one side of the main body frame 4. Since the electrical routing components including the detection element 9 and the circuit board 10 can be easily set on the other side surface, the assembling work can be performed satisfactorily. Further, the holder 5 that is rotatably supported by the support shaft portion 4A is supported by the first support shaft portion 4a1 having a small diameter and the second support shaft portion 4a2 having a large diameter. ) Can be reduced, sliding friction can be reduced, smooth rotation drive can be achieved, and rattling at the pivotal support location can also be suppressed.

  In the embodiment described above, the type in which only the liquid level gauge unit is attached and fixed to the liquid level detection main body 1A has been described as an example. However, in addition to the main body frame of the liquid level gauge unit, the fuel pump unit is liquid-liquid. The present invention can also be applied to the surface detection main body 1 </ b> A portion and a fixing type.

It is a whole outline front view showing a 1st embodiment of a liquid level detection device of the present invention. It is the side view which represented the liquid level gauge unit part of FIG. 1 in the cross section. It is a front view of the liquid level indicator unit part of FIG. It is a rear view of the liquid level indicator unit part of FIG. It is sectional drawing which showed the AA line location of the liquid level meter unit part of FIG. FIG. 6 is an exploded cross-sectional view of the level gauge unit portion of FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid level detection apparatus 3A Liquid level 4 Main body frame 4A Support shaft part 4B Space part 4E Protection wall 5 Holder 6 Float 7 Float arm 8 Magnet 9 Detection element 10 Circuit board 11 Current supply terminal 13 Magnetic shield member

Claims (2)

A main body frame made of a synthetic resin material, a support shaft provided on one side of the main body frame, a holder rotatably supported by the support shaft, and a liquid level attached to the holder. A float arm having a float that operates following displacement, a ring-shaped magnet that is disposed in the holder and rotates in accordance with the operation of the float, and a detection element that detects a change in magnetism as the magnet rotates And a circuit board electrically connected to the detection element, and a current-carrying terminal electrically drawn out from the circuit board to the outside, wherein the holder is pivotally supported. Forming a space part formed of a hollow indentation from the other side of the body frame in a part of the support shaft part provided in the body frame, and disposing the detection element in the space part, Is disposed along the other side surface of the main body frame, surrounds the magnet, the detection element, and the circuit board, and a magnetic shield member smaller than the outer shape of the main body frame is provided from the other side surface side of the main body frame. A liquid level detecting device characterized by being fixedly held on a main body frame. The liquid level detection device according to claim 1, wherein the main body frame includes a protective wall that prevents contact between the magnetic shield member and another member.

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