System for detecting remaining amount of liquid in tank

A liquid remaining-amount detecting system includes a displacement transmitting part for transmitting displacement of a float to a rotation-angle sensor and including a bracket mounted to the bottom of a tank, an arm having a base end mounted to the bracket and a front end mounted to the float, and a link mechanism for coupling the rotation-angle sensor and the base end of the arm. The link mechanism serves to cancel displacement of the float resulting from vertical displacement of the bottom of the tank.

BACKGROUND OF THE INVENTION

The present invention relates to a system for detecting the remaining amount of liquid in a tank, which is suitably used, for example, in detecting the remaining amount of fuel accumulated in an automotive fuel tank.

Typically, as disclosed in JP-U 64-38534, the fuel tank mounted on the vehicle is provided with a float-type level detecting system, for example, to detect the remaining amount of fuel accumulated in the tank. The float-type level detecting system comprises essentially a float arranged vertically movably with the level of fuel accumulated in the fuel tank, a sensor part fixedly arranged in the tank and for sensing a fuel level position in accordance with displacement of the float, and a displacement transmitting part comprising an arm for transmitting displacement of the float to the sensor part.

When fuel in the fuel tank increases or decreases, the float moves vertically with the fuel level, which is transmitted to the sensor part where the fuel remaining amount in the tank is detected in accordance with a fuel level position.

However, the typical level detecting system is constructed to detect the fuel remaining amount through the sensor part fixedly mounted to the top face of the fuel tank, to which displacement of the float moving vertically with the level of fuel in the fuel tank is directly transmitted through the arm. Such construction causes the following problem.

In recent passenger cars and the like, there is a tendency to make fuel tanks from a light flexible material such as synthetic resin so as to achieve a weight reduction in the whole car. The fuel tanks made from a light flexible material can be deformed with variations in weight of fuel accumulated therein, tank pressure, and ambient temperature, and with vibrations, impact, and the like occurring during vehicle cruising.

When the fuel tank is deformed, the level of fuel in the fuel tank is displaced vertically accordingly. Then, the above level detecting system detects and outputs the fuel remaining amount including this level displacement as variations in the fuel remaining amount, which is different from the actual fuel remaining amount, leading to impossibility of stable detection of the correct fuel remaining amount.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a system for detecting the remaining amount of liquid in a tank, which allows continuous and stable detection of the remaining amount of liquid in the tank, and thus enhancement in the reliability of the system.

The present invention provides generally a system for detecting a remaining amount of liquid in a tank, which comprises: a float which produces a displacement with a level of liquid; a sensor part mounted to the tank at a position above a bottom thereof, the sensor part sensing the remaining amount of liquid in accordance with the displacement of the float; and a displacement transmitting part which transmits the displacement of the float to the sensor part, the displacement transmitting part comprising a support member mounted to the bottom of the tank, an arm having a base end mounted to the support member and a front end mounted to the float, and a link mechanism which couples the sensor part and the base end of the arm.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings wherein like reference numerals designate like parts throughout the views, a description is made about a system for detecting the remaining amount of liquid in a tank embodying the present invention.

Referring toFIGS. 1-3, there is shown first embodiment of the present invention. A fuel tank1to be mounted on the vehicle comprises a main body2made from a light flexible material such as synthetic resin, and a cover plate3as will be described later. Fuel tank1comprises a mounting flange, not shown, provided to a top face2C, an upper portion of a side face2B, or the like of tank main body2as will be described later, through the use of which fuel tank1is fixed to a frame and the like of the vehicle.

As shown inFIG. 1, tank main body2comprises a bottom face2A, side face2B extending upward to surround bottom face2A, top face2C integrally formed with the upper end of side face2B to conceal side face2B from above, an opening2D formed roughly in the center of top face2C, and the like. Together with a fuel pump, not shown, a fuel remaining-amount detecting system11as will be described later is inserted into tank main body through opening2D.

Cover plate3, which constitutes fuel tank1together with tank main body2, is made from substantially the same resin material as that of tank main body2. Cover plate3serves to close opening2D of tank main body2from above. A rotation-angle sensor13as will be described later is fixed on the underside of cover plate3facing the inside of tank main body2.

Fuel remaining-amount detecting system11, which forms a system for detecting the remaining amount of liquid in the embodiment, serves to detect the remaining amount of a fuel F accumulated in fuel tank1. System11comprises a float12as will be described later, rotation-angle sensor13, a displacement transmitting part14, and the like.

Float12is mounted at the front end of an arm18as will be described later, and moves vertically with the level of fuel F accumulated in fuel tank1.

Rotation-angle sensor or sensor part13is fixedly arranged in fuel tank1above bottom face2A, and serves to sense the angle of rotation electrically, magnetically, or optically. As shown inFIGS. 1 and 2, rotation-angle sensor13comprises essentially a base plate13A fixed on the underside of cover plate3, a rotation shaft13B rotatably mounted to base plate13A, a resistor13C circularly formed about rotation shaft13B, and a conductive slider13D fixed to a second lever21as will be described later to make slide contact with resistor13C.

Displacement of float12is transmitted through second lever21and the like to slider13D, which moves on resistor13C in a sliding way, obtaining a change in a value of resistance of resistor13C in accordance with displacement of float12. Rotation-angle sensor13senses a level position or remaining amount of fuel F in accordance with a value of resistance of resistor13C.

Displacement transmitting part14serves to transmit displacement of float12to rotation-angle sensor13, and comprises a bracket15as will be described later, arm18, a link mechanism19, and the like.

Bracket or support member15is arranged on bottom face2A of tank main body2, and comprises a stationary portion or stationary support portion16fixedly mounted to bottom face2A and a movable portion or movable support portion17movably mounted to stationary portion16.

Stationary bracket portion16is shaped like a rectangular plate, and is arranged to extend upward from bottom face2A of tank main body2. A slot16A is formed in the upper end of stationary bracket portion16to extend horizontally in parallel to bottom face2A. On the other hand, movable bracket portion17is shaped like a rectangular plate smaller than that of stationary bracket portion16, and has a lower end having two guide pins17A protruding therefrom. Movable bracket portion17is slidably engaged in slot16A of stationary bracket portion16, and can move horizontally while being guided therein. A pin17B is arranged in the center of movable bracket portion17to protrude in the direction opposite to stationary bracket portion16.

Arm18has a base end18A rotatably supported by pin17B of movable bracket portion17, and a front end or free end18B mounted to float12. A first lever20as will be described later is integrated with base end18A of arm18.

Link mechanism19is arranged between rotation-angle sensor13and base end18A of arm18, and include a parallel link comprising first lever20, a second lever21, a first rod22, a second rod23, and the like as will be described later. Link mechanism19serves to transmit displacement of float12which moves with the level of fuel F to rotation-angle sensor13through arm18.

First lever20is integrated with base end18A of arm18, and forms a given angle with arm18. First lever20rotates, together with arm18, about pin17B of movable bracket portion17. A pin20A is protrusively arranged at the front end of first lever20.

Second lever21is fixedly mounted to rotation shaft13B of rotation-angle sensor13, and has substantially the same length as that of first lever20. As shown inFIG. 2, slider13D is fixed to second lever21in a portion facing resistor13C of rotation-angle sensor13. A pin21A is protrusively arranged at the front end of second lever21.

First rod22is arranged between rotation shaft13B of rotation-angle sensor13and pin17B of movable bracket portion17, and has one end rotatably mounted to rotation shaft13and another end rotatably mounted to pin17B.

Second rod23is arranged between first lever20and second lever21, and has substantially the same length as that of first lever22. Second lever23has one end rotatably mounted to pin20A of first lever20and another end rotatably mounted to pin21A of second lever21.

When the level of fuel F accumulated in fuel tank1is displaced from a position shown by solid line inFIG. 1to a position shown by solid line inFIG. 3to cause displacement of float12with the fuel level. Then, arm18rotates in the direction of an arrow A about pin17B of movable bracket portion17. First lever20causes rotation together with arm18, which is transmitted to second lever21through second rod23. Second lever21rotates in the direction of an arrow B about rotation shaft13B. With this, slider13D fixed to second lever21moves on resistor13C of rotation-angle sensor13in a sliding way.

Next, operation of fuel remaining-amount detecting system11is described. Using a fuel pump, not shown, fuel F accumulated in fuel tank1is discharged to the outside of fuel tank1for supply to an automotive engine, for example. Fuel F in fuel tank1reduces gradually in accordance with consumption in the engine, having the level lowering accordingly.

When filling fuel tank1with fuel F at a service station and the like, not shown, fuel F is gradually accumulated in fuel tank1by this filling amount, having the level increasing upward.

When the level of fuel F accumulated in fuel tank1is displaced from the position shown by solid line inFIG. 1to the position shown by solid line inFIG. 3due to consumption of fuel F, float12moves downward with the fuel level. Displacement of float12causes arm18and first lever20integrated with base end18A of arm18to rotate in the direction of arrow A about pin17B of movable bracket portion17.

Since link mechanism19includes a parallel link, second lever21coupled to first lever20through second rod23rotates in the direction of arrow B by the same angle of rotation as that of first lever20about rotation shaft13B of rotation-angle sensor13. With this, slider13D fixed to second lever21moves on resistor13C of rotation-angle sensor13in a sliding way.

Thus, rotation-angle sensor13can sense a level position of fuel F in accordance with a value of resistance of resistor13C, from which the remaining amount of fuel F accumulated in fuel tank1can be determined.

When the level of fuel F is located at a position shown by solid line inFIG. 3, and that tank main body2is deformed due to pressure variations in fuel tank1or the like to cause downward displacement of bottom face2A by a distance C, a level position of fuel F accumulated in fuel tank1is also displaced downward with displacement of bottom face2A as shown by two-dot chain line in FIG.3.

A description is made about an example where displacement of the level of fuel F is equal to distance C. Then, stationary bracket16and movable bracket17move downward with displacement of bottom face2A. However, since guide pins17A of movable bracket portion17are slidably engaged in slot16A of stationary bracket portion16, and pin17B of movable bracket portion17is coupled to rotation shaft13B of rotation-angle sensor13through first rod22, movable bracket portion17rotates about rotation shaft13B, and moves horizontally with respect to stationary bracket portion16while being guided in slot16A. With this, referring toFIG. 3, first lever20, first rod22, and second rod23which constitute link mechanism19are displaced from a position shown by solid line to a position shown by two-dot chain line.

Since link mechanism19includes a parallel link, second lever21constituting link mechanism19holds the position shown by solid line inFIG. 3, i.e. position before displacement of bottom face2A, regardless of displacement of first lever20, first rod22, and second rod23. Thus, slider13D fixed to second lever21does not move on resistor13C of rotation-angle sensor13, allowing a resistance of resistor13to be held at a given value.

With this, when the level of fuel F is displaced with deformation of fuel tank1, displacement part of float12due to deformation of fuel tank1can be canceled by link mechanism19, preventing erroneous transmission of displacement of float12to rotation-angle sensor13.

Thus, in the first embodiment, bracket15is arranged on bottom face2A of fuel tank1, and base end18A of arm18having float12at front end18B is rotatably mounted to pin17B of movable bracket portion17which constitutes bracket15. And base end18A of arm18and rotation-angle sensor13are coupled by link mechanism19.

With this, even if fuel tank1is deformed, displacement part of float12due to deformation thereof can be canceled by link mechanism19and the like, allowing stable detection of the correct remaining amount of fuel F in fuel tank1with influence of deformation of fuel tank1eliminated. Therefore, the detection accuracy of the remaining amount of fuel F can be increased, resulting in enhanced reliability of fuel remaining-amount detecting system11.

If displacement of bottom face2A due to deformation of fuel tank1(distance C inFIG. 3, for example) does not correspond to that of the level of fuel F (distance C) in a 1:1 ratio, the length or the like of levers20,21is adjusted in accordance with a ratio produced at each fuel tank1to appropriately set operation of link mechanism19. With this, erroneous transmission of displacement of float12to rotation-angle sensor13can be prevented in the same way as described above. Moreover, even if displacement detected at bottom face2A of tank main body2does not linearly correspond to that of the level of fuel F produced accordingly, setting of an appropriate approximate value allows achievement of accurate following of the apparatus.

Referring toFIGS. 4 and 5, there is shown second embodiment of the present invention which is substantially the same as the first embodiment except that a sensor casing hermetically isolated from fuel is arranged in the fuel tank to accommodate therein a sensor part.

Specifically, a fuel remaining-amount detecting system31is arranged in fuel tank1, and has roughly the same structure as that of fuel remaining-amount detecting system11in the first embodiment, comprising float12, displacement transmitting part14, a sensor casing32, a rotation-angle sensor33as will be described later, and the like.

Sensor casing32is arranged in fuel tank1and fixed on the under face of cover plate3. As shown inFIG. 5, sensor casing32is formed as a box hermetically isolated from fuel F in fuel tank1to accommodate therein rotation-angle sensor33. A bottomed concave cylindrical portion32A is formed in the side face of sensor casing32to protrude inward of sensor casing32.

Rotation-angle sensor or sensor part33is disposed in sensor casing32, and comprises a rotation shaft33A to which displacement of float12is transmitted through a shaft35, a magnet coupling36as will be described later, and the like. Rotation-angle sensor33serves to electrically or magnetically sense, for example, the angle of rotation of rotation shaft33A through the use of a detection element, not shown, in accordance with which a level position of fuel F, i.e. the remaining amount of fuel F in fuel tank1is determined.

A shaft support plate34is fixed on the underside of cover plate3to face concave cylindrical portion32A of sensor casing32. An axially middle portion of shaft35is rotatably supported at the lower end of shaft support plate34. Shaft35has one end to which second lever21constituting link mechanism19is fixed and first rod22is mounted rotatably, and another end extending into concave cylindrical portion32A of sensor casing32.

Magnet coupling or non-contact coupling36is arranged between rotation shaft33A of rotation-angle sensor33and another end of shaft35, and comprises a female portion37fixed to rotation shaft33A of rotation-angle sensor33and a male portion38fixed to another end of shaft35. Magnet coupling36serves to transmit rotation of shaft35to rotation shaft33A of rotation-angle sensor33in a non-contact way with concave cylindrical portion32A of sensor casing32held between female and male coupling portions37,38.

Female coupling portion37comprises a magnet mounting cylinder37A formed like a lidded cylinder to surround concave cylindrical portion32A of sensor casing32and fixed to rotation shaft33A, and an outer magnet37B having S and N poles circumferentially alternately disposed on the inner peripheral surface of magnet mounting cylinder37A. On the other hand, male coupling portion38comprises a magnet mounting cylinder38A located at the inner periphery of concave cylindrical portion32A of sensor casing32and engaged on another end of shaft35, and an inner magnet38B having S and N poles circumferentially alternately disposed on the outer peripheral surface of magnet mounting cylinder38A.

With magnet coupling36, outer magnet37B of female coupling portion37and inner magnet38B of male magnet38are attracted to each other across concave cylindrical portion32A of sensor casing32, obtaining rotation of female coupling portion37together with male coupling portion38. With this, displacement of float12can be transmitted to rotation shaft33A of rotation-angle sensor33hermetically accommodated in sensor casing32through arm18, link mechanism19, shaft35, magnet coupling36, and the like.

Operation of fuel remaining-amount detecting system31is fundamentally the same as that of fuel remaining-amount detecting system11described in the first embodiment.

In the second embodiment, rotation-angle sensor3for sensing the remaining amount of fuel F in fuel tank1is disposed in sensor casing32hermetically isolated from fuel F in fuel tank1. And rotation shaft33A of rotation-angle sensor3and second lever21of link mechanism19are coupled through non-contact coupling36.

Thus, even if the level of fuel F accumulated in fuel tank1waves greatly during vehicle cruising or the like, sensor casing32can surely prevent fuel F from adhering to rotation-angle sensor33. With this, corrosion of rotation-angle sensor33due to adhesion of fuel F can be restraint, allowing rotation-angle sensor33to carry out accurate detection of the remaining amount of fuel F over the long term.

Having described the present invention in connection with the illustrative embodiments, it is noted that the present invention is not limited thereto, and various change and modifications can be made without departing from the scope of the present invention.

By way of example, in the first embodiment, rotation-angle sensor33is fixed to top face2C of fuel tank1through cover plate3. Optionally, referring toFIG. 6, rotation-angle sensor13may be fixed to side face2B of fuel tank1. In this variation, there is arranged a sensor support plate41fixed to side face2B of fuel tank1, through which rotation-angle sensor13is fixed to side face2B.

Further, in the second embodiment, sensor casing32is disposed in fuel tank1. Optionally, the sensor casing may be arranged outside fuel tank1wherein rotation-angle sensor13disposed in the sensor casing and link mechanism19are coupled through non-contact coupling36.

Still further, in the second embodiment, magnet coupling36is adopted to transmit rotation of shaft35to rotation shaft33A of rotation-angle sensor33. Alternatively, other means such as Hall element may be applied to that end.

Furthermore, in the illustrative embodiments, first rod22constituting link mechanism19is connected to rotation shaft13B of rotation-angle sensor13and pin17B of movable bracket portion17. Alternatively, first rod22may be connected to a pin provided to any member other than rotation shaft13B and a pin provided to any member other than movable bracket portion17.

Further, in the illustrative embodiments, movable bracket portion17is movably mounted to stationary bracket portion16. Optionally, movable bracket portion17may be mounted to other member arranged in fuel tank1, the inner surface of tank main body2, or the like.

Still further, in the illustrative embodiments, rotatably mounted to base plate13A of rotation-angle sensor13is rotation shaft13B, to which second lever21constituting link mechanism19is fixed. Optionally, there may be arranged a shaft fixedly mounted to base plate13A, to which second lever21is mounted rotatably.

Still further, in the illustrative embodiments, pin17B is protrusively provided to movable bracket portion17so as to rotatably support base end18A of arm18. Alternatively, a separate and distinct pin from movable bracket portion17may be adopted to couple movable bracket portion17and base end18A of arm18. The same can be applied to pin20A of first lever20and pin21A of second lever21.

Furthermore, in the illustrative embodiments, the present invention is applied to the system for detecting the remaining amount of fuel F accumulated in fuel tank1. Optionally, the present invention can be applied to systems for detecting the remaining amount of liquid accumulated in a tank, such as working fluid, chemical agent, or the like. The entire contents of Japanese Patent Application P2003-001324 filed Jan. 7, 2003 are incorporated hereby by reference.