JP2001091341A - Liquid level detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid level detector which can linearly detect the level of even a conductive liquid, which can be miniaturized and which is favorable in terms of cost. SOLUTION: A plurality of opening and shutting means which are arranged at prescribed intervals in the up-and-down direction of a cylindrical member and which are turned on and off by a magnetic force are provided. Resistances which are connected in series with the opening and shutting means and whose resistance values are changed sequentially from the opening and shutting means on one side toward the opening and shutting means on the other side are provided, A float which is fitted to and mounted on the outer circumferential part of the cylindrical member so as to be up and down movable is provided. When the float is moved up and down according to the level of a liquid and when the prescribed opening and shutting means out of the plurality of opening and shutting means is turned on, the level of the liquid can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level detector mounted on a fuel tank of, for example, a water heater or a motorcycle to detect a liquid level in the tank.

[0002]

2. Description of the Related Art Conventionally, as this type of liquid level detector, for example, the one shown in FIG. 5 is known. This liquid level detector 5
Reference numeral 1 denotes a structure in which a resistor 51a is attached to a ceramic substrate, and a contact 51b connected to a float lever 52a of a float 52 slides on the resistor 51a to change its resistance value. . The liquid level detector 51 has one end grounded, the other end connected to one end of a coil 53a of an analog meter 53, and the other end connected to a battery 56 via a voltage regulator 54 and a switch 55. To form a detection circuit 57.

According to the detection circuit 57, the switch 55
Is turned on, the battery voltage is supplied to the detection circuit 57, and the voltage is supplied from the voltage regulator 54 to the series circuit of the analog meter 53 and the liquid level detector 51 in accordance with the resistance value of the liquid level detector 51, that is, the position of the float 52. Current flows, and the analog meter 5
The third pointer 53b indicates a predetermined liquid level.

[0004]

However, in this liquid level detector 51, a resistor 51a and a contact 51b are provided.
For example, when the liquid level of the conductive liquid is detected, when the liquid level detector 51 itself is immersed in the liquid, the liquid intervenes between the resistor 51a and the contact 51b. Even if the liquid level detector 51 is arranged outside the tank, the liquid is likely to adhere to the resistor 51a and the like, and an accurate resistance value cannot be obtained. Had the problem of being unsuitable.

Further, since the float 52 and the contact 51b are connected by a relatively long float lever 52a, the liquid level detector 51 including the float 52 becomes large,
In addition, the expensive voltage regulator 5
However, there is also a problem that the use of No. 4 is disadvantageous in terms of cost.

Further, the characteristic of the detection circuit 57 using the liquid level detector 51 generally shows that the resistance value R and the current value I change in a curve according to the liquid level L as shown in FIG. Therefore, there is a problem that the liquid level cannot be detected linearly. Therefore, in order to solve this problem, the resistance of the liquid level detector 51 is set so that the curve is made closer to linear. It is also conceivable to change the resistance value distribution of 51a. However, in this case, the resistor 5
There is a problem in that the fabrication of 1a is complicated, the liquid level detector 51 itself becomes costly, and it is difficult to obtain a long-term stable contact state of the contact 51b with the resistor 51a.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the invention described in claim 1 is to enable the liquid level of a conductive liquid to be detected linearly and to reduce the size of the liquid. An object of the present invention is to provide a liquid level detector which can be made more cost-effective. The object of the invention described in claim 2 is:
In addition to the object of the first aspect of the present invention, it is another object of the present invention to provide a liquid level detector which can reduce the cost and can detect the liquid level stably for a long time.

[0008]

In order to achieve the above object, the invention according to claim 1 of the present invention comprises a plurality of opening / closing means arranged at predetermined intervals in a vertical direction of a cylindrical member and turned on / off by a magnetic force. A resistance that is connected in series to the opening / closing means and whose resistance value sequentially changes from one opening / closing means side to the other opening / closing means side, and is fitted to the outer peripheral portion of the tubular member so as to be vertically movable. And a float having a magnet for turning on / off the opening / closing means, and the float is moved up and down according to the liquid level, and a predetermined opening / closing means of the plurality of opening / closing means is turned on. The liquid level is detected based on the resistance.

With this configuration, for example, the cylindrical member and the float arranged in the liquid move up and down on the outer peripheral portion of the cylindrical member according to the liquid level, and the magnetic force of the magnet of the float As a result, among the plurality of opening / closing means, the opening / closing means corresponding to the position of the float is turned on. When the opening / closing means is turned on, a current corresponding to the resistance value of the resistor connected to the opening / closing means flows through the detection circuit, and this current value is indicated to, for example, a meter, thereby detecting the liquid level.

[0010] Since the liquid level is detected by a non-contact method of turning on and off the opening and closing means by magnetic force, the liquid level detector can be used in a conductive liquid and the resistance value of each resistor can be reduced. Since they are set in order, the liquid level is detected linearly. In addition, since the float moves up and down on the outer peripheral surface of the cylindrical member, the liquid level detector itself can be reduced in size, and an expensive voltage regulator or the like is not required. Is formed at a low cost.

The invention according to claim 2 is characterized in that the opening / closing means and the resistor are mounted on a substrate, and the substrate is housed and arranged in a substantially sealed state in a tubular member. With such a configuration, for example, a reed switch and a resistor as opening / closing means can be mounted on a single substrate, and the substrate can be assembled simply by housing and disposing the substrate in a tubular member. Since the cost can be reduced and the substrate is stored and arranged in a substantially sealed state in the tubular member, the substrate is not affected by the liquid, and the liquid level can be stably detected over a long period of time.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. 1 to 4 show an embodiment of a liquid level detector according to the present invention. FIG. 1 is a perspective view showing a part of the liquid level detector, FIG. 2 is a cross sectional view thereof, and FIG. FIG. 4 is a circuit diagram showing an example of the detected circuit, and FIG. 4 is a characteristic diagram thereof.

In FIG. 1 and FIG. 2, the liquid level detector 1 is
It has a cylindrical member 2 having a bottom and a cylindrical shape having a predetermined length. A printed circuit board 3 is housed and arranged inside the cylindrical member 2. Is fitted so as to be able to move up and down. The tubular member 2 is
For example, it is formed of a stainless material or the like which is resistant to corrosion and the like and has excellent liquid resistance.

The length of the printed circuit board 3 housed and arranged in the tubular member 2 is set to be substantially the same as the length of the tubular member 2 and a plurality of printed circuit boards 3 are provided on the surface side at predetermined intervals w1 in the vertical direction. (Four in the figure) reed switches 6a to 6d are fixed by soldering, and on the back side thereof, resistors 7a to 7d (resistors 7b to 7d) corresponding to the respective reed switches 6a to 6d are provided.
d is FIG. 3) is fixed by soldering.

The reed switches 6a to 6d are relatively small and have the same specifications. The resistances of the resistors 7a to 7d are sequentially increased at predetermined intervals from the upper side of the tubular member 2 (for example, the resistors 7a to 7d). When the resistance values of 7d are R1 to R4, R1 = 20 KΩ, R2 = 40 KΩ, R3 = 60 K
Ω, R4 = 80 KΩ). Although a double-sided board is used as the printed board 3 in this example, when a single-sided board is used, the reed switches 6a to 6d and the resistors 7a to 7d are soldered and fixed to the front side.

The printed circuit board 3 on which the reed switches 6a to 6d and the resistors 7a to 7d are mounted uses, for example, guides 8 provided on both sides of the cylindrical member 2 in the diameter direction as shown in FIG. By being inserted from the upper end opening, it is stably housed in the tubular member 2. Also, the reed switches 6a to 6
As described later, d is soldered and fixed, for example, in a state of floating above the printed circuit board 3 so as to be as close as possible to the inner surface of the tubular member 2 in order to more easily receive the magnetic force of the float 4.

Further, as shown in FIG. 1, a terminal plate 9 is provided on the lid 5 for closing the opening at the upper end of the cylindrical member 2.
The printed circuit board 3 is connected to the two terminals 9a and 9b of the terminal plate 9.
Are electrically connected. The lid 5 is removably disposed together with the terminal plate 9 at the opening at the upper end of the tubular member 2. The printed circuit board 3 is molded as required with, for example, resin so that the reed switch 6 a
To 6d and resistances 7a to 7d are improved.

The float 4 is formed in a ring shape by, for example, a lightweight resin or the like, and has a ring-shaped magnet 10 embedded therein. This float 4 has a width w
Are formed corresponding to the interval w1 of the reed switches 6a to 6d, so that the plurality of reed switches 6a to 6d are not turned on at the same time, and one of the reed switches 6a to 6d is set to be turned on. ing. In this example, the magnet 10 is formed in a ring shape. However, for example, when a magnet 10a having a shape indicated by a two-dot chain line in FIG. 2 is used, the magnet 10a is connected to each of the reed switches 6a to 6d.
In order to oppose d, a guide 11 composed of a ridge, a groove, or the like may be provided on the outer peripheral surface of the tubular member 2 and the inner peripheral surface of the float 4.

This liquid level detector 1 is, as shown in FIG.
The terminal 9a of the terminal plate 9 is connected to the battery 13 via the switch 12, the terminal 9b is connected to one end of the coil 14a of the analog meter 14, and the capacitor 15 is connected to the other end of the coil 14a of the analog meter 14. As a result, the detection circuit 16 is formed. When the liquid level is low and the float 4 is located at the lowest position, the reed switch 6d is turned on (the reed switches 6a to 6c are turned off), and a small current corresponding to the resistance 7d is detected. It flows to the circuit 16, and the pointer 14b of the analog meter 14 indicates that the liquid level is the lowest.

Further, the float 4 rises as the liquid level rises, and the reed switches to be turned on are changed from 6d to 6c.
6b, and the reed switch 6a is turned on (the reed switches 6b to 6d are turned off) when the liquid level reaches the highest level. When the reed switch 6a is turned on, a large current corresponding to the resistance 7a flows to the detection circuit 16, and the pointer 14b of the analog meter 14 indicates that the liquid level is the highest.

That is, a plurality of reed switches 6a are moved up and down following the rise and fall of the liquid level of the float 4.
To 6d are turned on, a current corresponding to the resistance values of the resistors 7a to 7d connected to the turned on reed switches 6a to 6d flows to the detection circuit 16, and the analog meter 14
Indicates the liquid level. Therefore, as shown in FIG. 4, each of the liquid level L1 to L4 and the resistance value R1 to R4
A substantially linear characteristic is obtained in between, and the liquid level is detected linearly.

As described above, in the liquid level detector 1 of the above embodiment, a plurality of reed switches 6 are provided inside the tubular member 2.
A magnet 10 that houses and arranges a printed circuit board 3 having a series circuit of a to 6d and resistors 7a to 7d and that turns on and off reed switches 6a to 6d on the outer periphery of the tubular member 2
Is mounted so as to be able to move up and down, so that any one of the reed switches 6a to 6d is turned on according to the up and down movement of the float 4 following the liquid level, and the liquid level is detected. can do. As a result, the liquid level can be detected by the non-contact method, and the troubles associated with the conventional contact method can be eliminated. For example, even if the liquid level is a conductive liquid, the liquid level detector 1 is immersed in the liquid. Surfaces can be detected.

Further, a plurality of reed switches 6a to 6d and resistors 7a to 7d are arranged along the rising and falling directions of the liquid level, and the resistance values of the resistors 7a to 7d are sequentially changed at regular intervals as going upward from below. Since the liquid level is set to be small, the liquid level can be detected almost linearly.For example, when applied to the detection of the liquid level in a fuel tank of a water heater or a fuel tank of a motorcycle, the liquid level in the tank can be detected. A large effect can be expected, such as high accuracy and quick detection of

Further, since the printed circuit board 3 on which the reed switches 6a to 6d and the resistors 7a to 7d as electronic parts are mounted and housed in the tubular member 2 in a substantially sealed state, the printed circuit board 3 It is possible to prevent direct contact and adhesion of the liquid, and to perform stable liquid level detection for a long period of time.

Further, the ring-shaped float 4 is connected to the cylindrical member 4.
The liquid level detector 1 itself can be formed small (compact) because it has a structure in which the float lever or the like having a long length is unnecessary as in the related art. Also, the parts to be used may be relatively inexpensive reed switches 6a to 6b and resistors 7a to 7d, etc., so that the cost of parts can be reduced and the printed circuit board 3 that has been assembled is guided inside the tubular member 2. 8, the liquid level detector 1 itself can be reduced in cost.

Further, by removing the lid 5 of the tubular member 2, the printed board 3 can be taken out of the tubular member 2, so that maintenance work such as repair or replacement of the printed board 3 can be easily performed. In addition, by preparing a plurality of types of printed circuit boards 3 in which the number and resistance of the reed switches 6a to 6d and the resistors 7a to 7d are appropriately set in advance, the shape and size of the liquid to be detected and the tank can be adjusted. The liquid level detector 1 having various characteristics can be easily obtained.

In the above embodiment, the cylindrical member 2
Has been described as having a cylindrical shape. However, the present invention is not limited to this, and may be formed in a rectangular tube shape, or may have reed switches 6a to 6d and resistors 7a to 7d.
The number d, the position of the terminal plate 9 and the number of terminals, the circuit configuration of the detection circuit 16, the type of the opening / closing means, and the like are also examples, and can be variously changed without departing from the gist of each invention according to the present invention. Needless to say.

[0028]

As described above in detail, according to the first aspect of the present invention, the opening / closing means and the resistor are housed and arranged in the cylindrical member, and the opening / closing means is vertically fitted on the outer peripheral portion of the cylindrical member. Because it is turned on and off by the magnetic force of the mounted float, the liquid level can be detected in a non-contact manner, it can be used even in a conductive liquid, and by setting the resistance value of each resistor in order, The liquid level can be detected linearly. In addition, since the float moves up and down on the outer peripheral surface of the cylindrical member, the liquid level detector can be downsized,
Expensive electronic components are not required, and the configuration of the liquid level detector itself and the detection circuit using the same can be simplified and formed at low cost.

According to the second aspect of the present invention, in addition to the effects of the first aspect, for example, a reed switch and a resistor as opening / closing means are mounted on one substrate, and this substrate is formed into a cylindrical shape. Since the liquid level detector itself can be assembled simply by being housed and arranged in the member, the cost of the liquid level detector itself can be reduced, and the substrate is housed and arranged in a substantially sealed state in the tubular member, so that it is not affected by the liquid. In addition, there is an effect that stable liquid level detection can be performed over a long period of time.

[Brief description of the drawings]

FIG. 1 is a partially broken perspective view showing one embodiment of a liquid level detector according to the present invention.

FIG. 2 is a cross-sectional view of the same.

FIG. 3 is a circuit diagram showing an example of a detection circuit using the liquid level detector.

FIG. 4 is a characteristic diagram showing the relationship between the liquid level and the resistance value.

FIG. 5 is a circuit diagram of a detection circuit using a conventional liquid level detector.

FIG. 6 is a characteristic diagram of the same.

[Explanation of symbols]

 1 ... Liquid level detector 2 ... Cylindrical member 3 ... Printed circuit board 4 ... Float 6a to 6d Reed switch 7a to 7d Resistor 8 Guide 9 Terminal plate 10, 10a Magnet 12. Switch 13 Battery 13 Analog meter Capacitor 16 Detection circuit

Claims (2)

[Claims] 1. A plurality of opening / closing means which are arranged at predetermined intervals in a vertical direction of a cylindrical member and are turned on / off by a magnetic force, respectively connected in series to the opening / closing means, and from one opening / closing means side to the other opening / closing means side. And a float having a magnet that is vertically fitted to an outer peripheral portion of the cylindrical member and that turns on and off the opening / closing means, wherein the float has a liquid level. The liquid level detector is characterized in that the liquid level is detected based on a resistance connected to the opened and closed opening means when the predetermined opening and closing means is turned on by moving up and down according to . 2. The liquid level detector according to claim 1, wherein said opening / closing means and said resistor are mounted on a substrate, and said substrate is housed and arranged in a substantially sealed state in a tubular member.