JP2001311653A - Liquid level sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid level sensor capable of easily and surely obtaining a prescribed detection output even if multiple point actions of reed switch mixedly exist for different liquid levels. SOLUTION: One end of a first reed switch RSWn is connected to a grounded first resistor R. A plurality of resistors R1 to Rn which each are connected in series, power source voltage is impressed from a power source voltage terminal Vin to one end, and the other ends of reed switches RSWn are connected to the other ends are provided. Also, a plurality of reed switches RSW1 to RSWn-1 each of which keeps one end connected to the connection point of each of a plurality of resistors R1 to Rn are provided. To each of other ends of reed switches RSW1 to RSWn-1 and RSWn, a detection terminal OUT is connected. The magnet 1 installed in the float slides according to the liquid level and switch-controls the corresponding reed switch.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level sensor for detecting a liquid level of a liquid in a tank.
The present invention relates to a liquid level sensor for detecting a liquid level by opening and closing a plurality of reed switches arranged in accordance with the liquid level with a magnet built in a float.

[0002]

2. Description of the Related Art A liquid level sensor of this kind is, for example,
It is used as a level sensor for monitoring the amount of liquid such as gasoline and engine oil of automobiles. A conventional liquid level sensor has a ring-shaped float with a built-in magnet. A plurality of reed switches arranged in accordance with the amount of liquid are built in a float guide shaft penetrating the center of the ring-shaped float.
Since a plurality of reed switches must be arranged on an elongated cylindrical shaft in accordance with the amount of liquid, they are vertically arranged in tandem. The liquid level is detected by opening and closing a corresponding reed switch by a magnet built in a float that slides up and down according to the liquid amount.

[0003] However, in the conventional case, various problems occur in the configuration of the reed switches and the detection circuits arranged vertically and vertically. Hereinafter, using FIGS.
A conventional circuit and its problems will be described.

FIG. 6 is a circuit diagram of a conventional liquid level sensor. 7 (A) and 7 (B) are operating position characteristic diagrams of a conventional liquid level sensor. FIGS. 8A and 8B are equivalent circuits in the case of one-point operation and two-point operation in the conventional example of FIG. 6, respectively.

As shown in the conventional circuit diagram of FIG. 6, a plurality of reed switches RSW1, 2,..., RSWn-1 and RSWn are arranged in cascade in parallel with the sliding direction of the magnet 1. These reed switches RSW1, RSW
,..., RSWn−1 and one end of RSWn are connected together and connected to the detection terminal OUT. On the other hand, the other ends of the reed switches RSW1, 2,..., RSWn-1 and RSWn are respectively connected in series and the terminal V is connected to one end.
, Rn−1, Rn, and R are connected to a connection point to which a power supply voltage from “in” is supplied. Note that the series resistances R1, R2,.
The other ends of the power supply voltage terminals Vin of Rn-1, Rn and R are grounded. Such a circuit is built in the float guide shaft. It is assumed that the reed switches RSW1 to RSWn are in an open state when there is no influence of the magnetic force of the magnet 1.

The ring-shaped float has a built-in rectangular magnet 1 which slides according to the liquid level. The sliding direction is the direction of the arrow shown in FIG.
This rectangular magnet 1 has a pair of N and S poles, and the axis connecting the N and S poles of the magnet 1 is substantially orthogonal to each reed switch, and the S pole faces each reed switch when sliding. And housed in a float.

The operating position characteristics of the magnet thus installed will be described with reference to FIG. FIG. 7 (A)
In the operating position characteristic diagram of FIG. 7, the arrow direction corresponds to the arrow direction shown in FIG. That is, it indicates the float sliding direction. And the axis connecting the N pole and the S pole is the reed switch RS
The S pole is orthogonal to Wn and faces the reed switch.
In the figure, the portion described as “ON” is a region where the magnet 1 operates to switch and hold the reed switch RSWn, and the portion described as “HOLD” is “OF”.
This is a hold area that can be switched to the “ON” area side and held when it deviates from the portion described as “F”. That is, as can be seen from the operation position characteristic diagram, there are two “ON” regions having a dead zone at the center.

[0008] Having such an operation position characteristic diagram,
The magnet operates one reed switch or two reed switches in response to a change in the liquid level. That is, the magnet operates one reed switch or two reed switches according to the liquid level by the two “ON” areas and the dead zone area therebetween. FIGS. 8A and 8B show equivalent circuits of the conventional circuit shown in FIG. 6 when such one-point operation and two-point operation are performed.

It is assumed that only the reed switch RSW1 is closed during the one-point operation shown in FIG. FIG.
It is assumed that both the reed switches RSW1 and RSW2 are closed during the two-point operation shown in FIG. FIG.
In the one-point operation shown in (A), at the detection terminal OUT, the power supply voltage Vin is equal to the resistance R1 and the series resistance R2 + R3 +
.., A voltage divided by + Rn + R is detected. On the other hand, during the two-point operation shown in FIG. 8B, a voltage obtained by dividing the power supply voltage Vin by the resistor R1 and the series resistors R3 + R3 +... + Rn + R is output from the detection terminal OUT as a detection output.

[0010]

However, in some cases, the liquid level may fluctuate up and down drastically due to vibrations and the like. A problem arises in that complicated processing is required to obtain the output. In addition, depending on the arrangement of the magnet and the reed switch, there is an example in which more multipoint operation is used, but if the reed switch to be switched and controlled is not always constant despite the same liquid level, the same problem as described above occurs. Occurs.

The operating position characteristics having two "ON" regions as shown in FIG. 7A and a dead zone region therebetween are shown in FIG.
There is also an idea to improve the operation position characteristics having only one “ON” region as shown in FIG. FIG. 7 (B)
, The magnet 1 is installed so that the N pole and the S pole are parallel to the reed switch RSWn, and the magnet 1 is connected to the reed switch RSWn as shown in the direction of the arrow in the drawing.
Slides in parallel. "ON", "OFF" and "HOL"
The meaning of "D" is the same as that described with reference to FIG. The positional relationship between the magnet 1 and the reed switch RSWn as shown in FIG.
It is assumed that the present invention is applied to the circuit of FIG. 6 instead of (A).

However, since the reed switches RSWn are vertically arranged in tandem, a high detection resolution cannot be obtained. If each reed switch RSWn is arranged close to the vertical direction in order to obtain a high detection resolution,
As described with reference to FIG. 7A, one-point operation and two-point operation are mixed. Furthermore, a multi-point operation may be used by a predetermined arrangement of the magnet and the reed switch. In this case, the reed switch to be switched and controlled is not always constant irrespective of the same liquid level. If they are mixed, complicated processing is required to obtain a predetermined detection output as long as the circuit of FIG. 6 is employed.

In view of the above situation, the present invention provides a liquid level sensor capable of easily and reliably obtaining a predetermined detection output even when different reed switch multipoint operations are mixed at a corresponding detection liquid level. It is another object of the present invention to provide a liquid level sensor capable of providing a high liquid level detection resolution.

[0014]

According to a first aspect of the present invention, there is provided a liquid level sensor comprising: a first resistor R having one end grounded; Are connected in series with each other, a power supply voltage is applied to one end, and a plurality of resistors R1 to Rn connected to the other end of the first reed switch RSWn are connected to the first reed switch RSWn. 1 reed switch RSWn
And a plurality of reed switches RSW1 to RSWn-1 having one ends connected to respective connection points of the plurality of resistors R1 to Rn, and the plurality of reed switches RSW1 to RSWn. -1 and first
A detection terminal OUT connected to each other end of the reed switch RSWn, and the plurality of reed switches RSW1 to RSW
A magnet 1 for switching the n-1 and the first reed switch RSWn from an open state to a closed state by a magnetic force, and a float 2 that accommodates the magnet 1 and is guided by a shaft and slides according to a liquid level. Features.

According to the first aspect of the invention, one end of the first reed switch RSWn is connected to the grounded first resistor R. A plurality of resistors R are connected in series, one end is supplied with a power supply voltage from a power supply voltage terminal Vin, and the other end is connected to the other end of the reed switch RSWn.
1 to Rn. Further, one end has a plurality of resistors R1 to R
n has a plurality of reed switches RSW1 to RSWn-1 connected to respective connection points. Further, a detection terminal OUT is connected to each other end of each of the reed switches RSW1 to RSWn-1 and RSWn. The magnet 1 incorporated in the float is guided by the shaft and slides according to the liquid level, and controls switching of the corresponding reed switch from the open state to the closed state. In the first aspect of the present invention, the reed switch may be configured not only to switch from the open state to the closed state as described above, but also to be configured to switch from the closed state to the open state. Good.

In order to solve the above-mentioned problem, a liquid level sensor according to a second aspect of the present invention provides a liquid level sensor according to the second aspect, as shown in FIGS. To RSWn-1 and the first reed switch RSWn are arranged in a row in accordance with the liquid level. The magnet 1 has a pair of N and S poles, and an axis connecting the N and S poles is arranged in the row. The plurality of reed switches RSW1 to RSWn-1 and the first reed switch RSWn are housed in the float 2 so as to be substantially parallel to the provided reed switches RSW1 to RSWn-1.

According to the second aspect of the present invention, the plurality of reed switches RSW1 to RSWn-1 and the first reed switches RSWn are arranged in a row in accordance with the liquid level. In order to control these reed switches to be closed according to the liquid level, the magnet 1 is housed in the float 2 such that the axis connecting the N and S poles is substantially parallel to each reed switch during sliding. Have been.

According to a third aspect of the present invention, there is provided a liquid level sensor according to the third aspect, wherein the plurality of reed switches RSW1 to RSWn- are provided. The first and first reed switches RSWn are arranged in tandem according to the liquid level,
The magnet 1 has a pair of N and S poles.
And the axis connecting the S pole is substantially orthogonal to the plurality of reed switches RSW1 to RSWn-1 and the first reed switch RSWn arranged in tandem, and either the N pole or the S pole is
The plurality of reed switches RSW1 to RSWn-1 are accommodated in the float 2 so as to face each other.

According to the third aspect of the present invention, the plurality of reed switches RSW1 to RSWn-1 and the first reed switches RSWn are arranged in tandem according to the liquid level. In order to control these reed switches to be closed according to the liquid level, the magnet 1 has an axis connecting the N and S poles substantially orthogonal to each reed switch, and either the N pole or the S pole is It is accommodated in the float 2 so as to face each reed switch during operation.

According to a fourth aspect of the present invention, there is provided a liquid level sensor according to the first aspect, wherein the liquid level sensor comprises:
The plurality of reed switches RSW1 to RSWn-1 and the first reed switch RSWn are arranged in tandem according to the liquid level, and the magnet 1 has a pair of N and S poles. The plurality of reed switches RSW1 to RSWn-1 and the first
It is housed in the float 2 so as to be substantially parallel to the reed switch RSWn.

According to the fourth aspect of the present invention, the plurality of reed switches RSW1 to RSWn-1 and the first reed switches RSWn are arranged in tandem according to the liquid level. In order to control these reed switches to be closed according to the liquid level, the magnet 1 is accommodated in the float 2 such that the axis connecting the N and S poles is substantially parallel to each reed switch when sliding. ing.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. First, the overall configuration of the liquid level sensor of the present invention will be described with reference to FIG. FIG. 5 is an overall configuration diagram of the liquid level sensor according to the present invention.

As shown in the overall configuration diagram of FIG. 5, the float 2 having the magnet 1 built in the end is
Are guided vertically by a shaft 3 passing through a guide hole provided in a central portion of the sliding member. Both ends of the shaft 3 are joined to two bottom surfaces of the level sensor frame 4. These two bottom surfaces are connected to reed switches RSW1 and RSW1
Both ends of the distribution board 5 on which SW2,..., RSWn are mounted are also joined. These reed switches RSW1 to RSW1
RSWn is mounted on a vertically long rectangular power distribution plate 5 so as to correspond to the liquid level in the horizontal direction. The power distribution plate 5 is also hermetically sealed by a vertically long reed switch case or the like, but the reed switch case is omitted here for the sake of simplicity. In this configuration, a plurality of reed switches are not mounted in an elongated shaft as in the related art, and a rectangular power distribution plate 5 is provided independently of the shaft 3. Can be mounted in parallel in the lateral direction so as to correspond to the liquid level.

The liquid level sensor having such a structure detects the liquid level of a liquid such as gasoline 7 in the tank 6. That is, the magnet 1 built in the float 2 slides up and down according to the liquid level, and the reed switch corresponding to the liquid level is controlled to open and close by the magnetic force of the magnet 1, so that a predetermined liquid level is obtained. A surface level is detected. The detection output is supplied to a fuel meter unit and the like disposed on a display panel of the vehicle via a lead wire (not shown). The gasoline 7 in the tank 6 is supplied to a vehicle engine (not shown).

Next, a first embodiment of the liquid level sensor of the present invention will be described with reference to FIG. FIG. 1 is a circuit diagram showing a first embodiment of a liquid level sensor according to the present invention.

In the embodiment shown in FIG. 1, one end of a reed switch RSWn (corresponding to a first reed switch in the claims) is connected to a grounded resistor R (corresponding to a first resistor R in the claims). . In this embodiment, a plurality of resistors R1 to Rn are connected in series, one end of which is supplied with a power supply voltage from a power supply voltage terminal Vin, and the other end of which is connected to the other end of the reed switch RSWn. Furthermore, it also has a plurality of reed switches RSW1 to RSWn-1 whose one ends are connected to respective connection points of the plurality of resistors R1 to Rn. Furthermore, each of the reed switches RSW1 to RSW
A detection terminal OUT is connected to each other end of n-1 and RSWn. Each of these reed switches RSW1-RSW
n-1 and RSWn are arranged in rows according to the liquid level. Each of the reed switches RSW1 to RSWn-1 and RSWn has no influence by the magnetic force of the magnet 1,
Assume that it is in the open state.

The float 2 has a square magnet 1.
Is housed. The float 2 is guided by the shaft and slides according to the liquid level, and closes the reed switches RSW1 to RSWn by the magnetic force of the magnet 1 housed therein. The sliding direction is the direction of the arrow shown in FIG. This rectangular magnet 1 has a pair of N and S poles, and the axis connecting the N and S poles is connected to each reed switch RS.
It is installed on the float so as to be substantially parallel to W1 to RSWn.

The operating position characteristics of the magnet thus installed will be described with reference to FIG. FIG. 2 is an operating position characteristic diagram of the embodiment of FIG. 2, the arrow direction corresponds to the arrow direction shown in FIG. That is, it indicates the float (or magnet) sliding direction. The magnet 1 slides in a direction substantially parallel to the reed switches RSWn in which the axes connecting the N and S poles are arranged in a row. In the figure, the portion described as "ON" is a region where the magnet 1 operates to switch and hold the reed switch RSWn, and the portion described as "HOLD" is shifted from the portion described as "OFF". If the
This is a hold area that can be switched to the “N” area side and held. That is, as can be seen from this operating position characteristic diagram,
There is only one "ON" region with a peak in the center.

Having such an operating position characteristic diagram,
The magnet can basically operate only one reed switch with respect to the fluctuation of the liquid level. That is, one "ON" region allows the magnet to operate only one reed switch in accordance with the liquid level. And to further increase the detection resolution,
Each of the reed switches RSWn can be arranged closer to each other so as to be closer to each other. When the magnets 1 are arranged closer to each other and arranged in a row, the magnets 1 may mix one-point operation and two-point operation, mix two-point operation and three-point operation, or perform three-point operation and four-point operation for a plurality of reed switches RSWn. Point operations may be mixed.

However, according to the embodiment of FIG.
These problems can be solved. This is shown in FIGS.
This will be described with reference to the circuit diagram shown in FIG. 3 (A) to 3 (D) are equivalent circuits in the case of operating at one to four points in the embodiment of FIG. 1, respectively. FIG.
(E) is a figure which shows the example at the time of employ | adopting a four-point operation system.

It is assumed that only the reed switch RSW1 is closed during the one-point operation shown in FIG. FIG.
It is assumed that both the reed switches RSW1 and RSW2 are closed during the two-point operation shown in FIG. FIG.
At the time of the three-point operation shown in FIG.
Assume that both RSWs 3 are closed. FIG. 3 (D)
In the four-point operation shown in FIG.
Assume that both 4 are closed.

In the one-point operation shown in FIG.
At the detection terminal OUT, a voltage obtained by dividing the power supply voltage Vin by the resistors R1 and R is detected. FIG.
In the two-point operation shown in (B), the resistance value of the resistor R2 is ignored, and a voltage obtained by dividing the power supply voltage Vin by the resistor R1 and the series resistor R is output as a detection output at the detection terminal OUT. . The same applies to the case of one-point operation and the case of two-point operation by other continuously arranged reed switches.

Further, in the three-point and four-point operation shown in FIGS. 3C and 3D, the resistance values other than the resistance R1 closest to the power supply voltage Vin are ignored, and the resistance R and the power supply voltage Vin are ignored. Is output as a detection output. That is, FIG. 3 (C) and FIG.
In the three-point and four-point operation shown in (D), their equivalent circuits are the same as in FIG. The same can be considered for a multi-point operation with four or more points. Also, depending on the liquid level, the reed switches RSW2 and RSW3
Is closed (two-point operation) or reed switch RSW
2, RSW3 and RSW4 may be closed (three-point operation), but this case can be considered in the same way.

As described above, when the circuit configuration shown in FIG. 1 is adopted, when the one-point operation and the two-point operation are mixed, the two-point operation and the three-point operation are mixed, or the three-point operation and the four-point operation are performed. This is also effective when there is a mixture of multi-point operations, and when there are more different multi-point operations. That is, even when different multipoint operations are mixed, the voltage divided by the resistor R and the series resistance between the power supply voltage Vin and the closed control reed switch closest to the power supply voltage Vin is always output as the detection output. become. As a result, each reed switch can be arranged closer to each other, and level detection with higher resolution can be performed.

The circuit configuration shown in FIG. 1 is effective even when any one of the reed switches does not function. This will be described with reference to FIG. In the example shown in FIG. 3 (E), the liquid level is detected by positively utilizing the four-point operation by arranging the magnet and the reed switch in a predetermined relationship. According to this example, even if different multipoint operations are mixed as described above, a stable liquid level is obtained based on the reed switch (RSW1 in this example) closest to the power supply voltage Vin that is closed and controlled according to the liquid level. Level is detected. Further, it is assumed that any or all of the reed switches RSW2, RSW3, and RSW4 do not function for some reason. However, also in this case, the reed switch RSW closest to the power supply voltage Vin
1, a stable liquid level is detected. next,
It is assumed that only the reed switch RSW1 does not function. In this case, since level detection is performed based on the reed switch RSW2, only one level error occurs. According to the circuit configuration shown in FIG. 1, high-resolution level detection can be performed. Therefore, even in such a case, an almost realistic level detection value can be obtained, which is not a serious problem.
In order to detect the liquid level with a high resolution, in practice, two-point operation or three-point operation is often actively employed.
The embodiment described above is very effective. Usually, there is almost no probability that a plurality of reed switches fail or stop functioning at the same time, and employing the circuit configuration shown in FIG. 1 has a large merit in practice.

As described above, according to the first embodiment, for example, in the case of two-point operation, two consecutive reed switches R
SW1 and RSW2 (the reed switch RSW1 closer to the power supply voltage terminal Vin and the reed switch RSW farther away
2) at the same time, the state shown in FIG.
3B, the resistance R2 connected to the reed switch RSW2 is connected to the detection terminal OU.
It has no effect on the detection output from T. FIG.
As shown in FIG. 3C and FIG. 3D, even when a plurality of reed switches are closed at the same time, the resistance value connected to a switch other than the reed switch closer to the power supply voltage terminal Vin has no effect. Reed switch R closer to voltage terminal Vin
Only the series resistance between SWn-1 and the power supply voltage terminal Vin is substantially connected to the detection terminal OUT and the first resistance R. Therefore, even when the reed switch performs one-point operation, two-point operation, or a mixture of different multipoint operations, a predetermined detection output can be easily and stably obtained from the detection output from the detection terminal OUT. it can.

According to the first embodiment, each of the reed switches RSW1 to RSWn is arranged in a row in accordance with the liquid level. Then, in order to control these reed switches to a closed state according to the liquid level, a magnet 1 is used.
Are accommodated in the float 2 such that the axis connecting the N and S poles is substantially parallel to each reed switch during sliding. Since each reed switch is arranged in a row, more reed switches can be arranged corresponding to the liquid level, and high detection resolution can be obtained. And, even if the reed switches are too close to each other and the one-point operation and the two-point operation coexist,
A predetermined detection output can be easily and stably obtained. The first embodiment corresponds to the first and second aspects of the present invention.

Further, a second embodiment of the liquid level sensor according to the present invention will be described with reference to FIG. FIG. 4 is a circuit diagram showing a second embodiment of the liquid level sensor according to the present invention.

In the embodiment shown in FIG. 4, the axis connecting the N and S poles of the magnet 1 is substantially orthogonal to each reed switch, and the S pole is This is an improvement of the type housed in the float so as to face each reed switch. The basic circuit configuration is based on the first embodiment shown in FIG.

That is, as shown in FIG. 4, one end of a reed switch RSWn is connected to a grounded resistor R. In the second embodiment, each is connected in series,
The power supply voltage from the power supply voltage terminal Vin is applied to one end, and the other end has a plurality of resistors R1 to Rn to which the other end of the reed switch RSWn is connected. Furthermore, it also has a plurality of reed switches RSW1 to RSWn-1 whose one ends are connected to respective connection points of the plurality of resistors R1 to Rn. Further, a detection terminal OUT is connected to each other end of each of the reed switches RSW1 to RSWn-1 and RSWn. These reed switches RSW1 to RSWn-1 and RSWn are arranged in tandem according to the liquid level.
Each reed switch RSW1-RSWn-1 and RSWn
Is assumed to be in the open state when there is no influence of the magnetic force of the magnet 1.

The float 2 has a square magnet 1.
Is housed. The float 2 is guided by the shaft and slides according to the liquid level, and closes the reed switches RSW1 to RSWn by the magnetic force of the magnet 1 housed therein. The sliding direction is the direction of the arrow shown in FIG. The square magnet 1 is accommodated in the float such that the axis connecting the N and S poles is substantially orthogonal to each reed switch, and the S pole faces each reed switch when sliding.

The magnet thus installed has the same operating position characteristics as shown in FIG. However, the equivalent circuits at the time of one-point operation and two-point operation of the reed switch in the embodiment of FIG. 4 are shown in FIGS. 3A and 3B for the same reason as described in the embodiment of FIG. It is the same as shown in FIG.

Accordingly, the second embodiment is of a type in which a reed switch is tandemly arranged in a ring type float as described in the conventional example and a shaft passing through the center of the float as a float sliding guide. Effective for sensors. This embodiment solves the problem of the mixed one-point operation and two-point operation of the conventional example of this type in terms of the circuit for the same reason as described in the first embodiment. , The effect of miniaturization of the device can be fully obtained. It should be noted that the second embodiment shown in FIG.
Invention.

Further, in the third embodiment, the circuit configuration is the same as that of FIG. 4 and the magnets are arranged as shown in FIG. 7B. That is, in the third embodiment, the plurality of reed switches RSW1 to RSWn-1 and the first reed switches RSWn are arranged in tandem according to the liquid level. In order to control these reed switches to be closed according to the liquid level, the magnet 1 is accommodated in the float 2 such that the axis connecting the N and S poles is substantially parallel to each reed switch when sliding. ing.

Therefore, the third embodiment is of a type in which a reed switch is tandemly arranged in a ring type float as described in the conventional example and a shaft passing through the center of the float as a float sliding guide. Enabled for sensors. That is, in this embodiment, the problem of mixed one-point operation and two-point operation or mixed multi-point operation more than that is solved in a circuit for the same reason as described in the first embodiment. The switches can be arranged close to each other in the sliding direction, and the detection resolution can be made higher than in the second embodiment. Of course, since the reed switch can be incorporated in the shaft, the effect of reducing the size of the device can be enjoyed. The third embodiment corresponds to the first and fourth aspects of the present invention.

According to the above-described embodiment, the reed switch is controlled to switch from the open state to the closed state as described above. However, the circuit is controlled so that the reed switch is changed from the closed state to the open state. You may comprise.

[0047]

As described above, according to the first aspect of the present invention, in the case of two-point operation, for example, two consecutive reed switches RSW1 and RSW2 (power supply voltage terminal Vi)
n and the farther reed switch RSW2) are simultaneously closed.
As shown in the equivalent circuits of FIGS. 3A and 3B, the resistor R2 connected to the reed switch RSW2
Has no effect on the detection output from the detection terminal OUT. Further, as shown in FIGS. 3C and 3D, even if a plurality of reed switches are simultaneously closed, the resistance value connected to a switch other than the reed switch closer to the power supply voltage terminal Vin is not affected. Instead, only the series resistance between the reed switch RSWn-1 closer to the power supply voltage terminal Vin and the power supply voltage terminal Vin is substantially connected to the detection terminal OUT and the first resistance R. Therefore, even when the reed switch performs one-point operation, two-point operation, or a mixture of different multipoint operations, a predetermined detection output can be easily and stably obtained from the detection output from the detection terminal OUT. it can. In addition, when the reed switch other than the reed switch closest to the power supply voltage Vin does not function for some reason, if the corresponding reed switch closest to the power supply voltage Vin at the corresponding liquid level is normal, the accurate liquid level is not changed. Is detected.

According to the second aspect of the invention, the plurality of reed switches RSW1 to RSWn-1 and the first reed switches RSWn are arranged in a row in accordance with the liquid level. In order to control these reed switches to be closed according to the liquid level, the magnet 1 is housed in the float 2 such that the axis connecting the N and S poles is substantially parallel to each reed switch during sliding. Have been.

As described above, since the reed switches are arranged in a row, more reed switches can be arranged corresponding to the liquid level, and in addition to the effects of the first aspect, An effect that a high detection resolution can be obtained is obtained.

According to the third aspect of the present invention, the plurality of reed switches RSW1 to RSWn-1 and the first reed switches RSWn are arranged in tandem according to the liquid level. In order to control these reed switches to be closed according to the liquid level, the magnet 1 has an axis connecting the N and S poles substantially orthogonal to each reed switch, and either the N pole or the S pole is It is accommodated in the float 2 so as to face each reed switch during operation.

As described above, by arranging the reed switches in tandem, the reed switches are incorporated in the ring type float and the shaft penetrating the center of the float as a float sliding guide as described in the conventional example. The present invention is effective for a type of level sensor.
The present invention solves the problem of the mixed one-point operation and two-point operation of this type in terms of a circuit as described in the first aspect of the present invention. Therefore, it is possible to reduce the size of the device by incorporating a reed switch in the shaft. The effect can be fully obtained.

According to the fourth aspect of the present invention, the plurality of reed switches RSW1 to RSWn-1 and the first reed switches RSWn are arranged in tandem according to the liquid level. In order to control these reed switches to be closed according to the liquid level, the magnet 1 is accommodated in the float 2 such that the axis connecting the N and S poles is substantially parallel to each reed switch when sliding. ing.

Therefore, the invention according to claim 4 is a level of the type in which the reed switches are arranged in tandem in a ring type float as described in the conventional example and a shaft passing through the center of the float as a float sliding guide. Enabled for sensors. That is, in the present invention, since the problem of the mixed one-point operation and the two-point operation is solved in terms of a circuit as described in the first aspect of the present invention, it is possible to arrange the reed switches close to each other in the sliding direction. Thus, the detection resolution can be made higher than that of the second aspect of the present invention. Of course, since the reed switch can be incorporated in the shaft, the effect of reducing the size of the device can be enjoyed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a liquid level sensor according to the present invention.

FIG. 2 is an operating position characteristic diagram of the embodiment of FIG.

FIGS. 3 (A) to 3 (D) are equivalent circuits in the case of operating at one to four points in the embodiment of FIG. 1, respectively. FIG. 3E is a diagram showing an example of a case where the four-point operation method is adopted.

FIG. 4 is a circuit diagram showing a liquid level sensor according to a second embodiment of the present invention.

FIG. 5 is an overall configuration diagram of a liquid level sensor according to the present invention.

FIG. 6 is a circuit diagram of a conventional liquid level sensor.

7 (A) and 7 (B) are operating position characteristic diagrams of a conventional liquid level sensor. FIG.

8 (A) and 8 (B) are equivalent circuit diagrams in the case of one-point operation and two-point operation in the conventional example of FIG. 6, respectively.

[Explanation of symbols]

 1 Magnet R1 to Rn, R Resistance RSW1 to RSWn Reed switch Vin Power supply voltage terminal OUT Detection terminal

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kenichi Tanaka 1-7-1 Yokoi, Shimada-shi, Shizuoka Yazaki Keiki Co., Ltd. (72) Inventor Masaki Hirota 1-7-1, Yokoi, Shimada-shi, Shizuoka (72) Inventor Masahiro Kasai 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Yuichi Ono 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Invention Person Katsuaki Kawabata 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Masahiro Takamatsu 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 2F013 AA05 BC02 BG01

Claims (4)

[Claims] A first resistor having one end grounded and a first reed switch having one end connected to the resistor, each of which is connected in series, and one end of which is supplied with a power supply voltage;
The other end is provided with a plurality of resistors to which the other end of the first reed switch is connected, together with the first reed switch, in accordance with a change in the liquid level to be measured, and one end is connected to each of the plurality of resistors. A plurality of reed switches connected to each other; a detection terminal connected to each of the other ends of the plurality of reed switches and the first reed switch; and a state in which the plurality of reed switches and the first reed switch are opened to closed by magnetic force. A liquid level sensor, comprising: a magnet accommodating the magnet; and a float that is guided by a shaft and slides according to the liquid level. 2. The liquid level sensor according to claim 1, wherein the plurality of reed switches and the first reed switch are arranged in a row in accordance with the liquid level, and the magnet has a pair of N and S poles. A liquid level sensor, wherein the axis connecting the north and south poles is accommodated in a float such that the axis is substantially parallel to the plurality of reed switches and the first reed switch arranged in a row. . 3. The liquid level sensor according to claim 1, wherein the plurality of reed switches and the first reed switch are arranged in tandem according to the liquid level, and the magnet has a pair of N and S poles. An axis connecting the N and S poles is substantially orthogonal to the plurality of reed switches and the first reed switch arranged in tandem, and either the N pole or the S pole faces the plurality of reed switches. A liquid level sensor, wherein the liquid level sensor is accommodated in a float. 4. The liquid level sensor according to claim 1, wherein the plurality of reed switches and the first reed switch are arranged in tandem according to the liquid level, and the magnet has a pair of N and S poles. And a liquid level sensor, wherein the axis connecting the north and south poles is accommodated in the float such that the axis is substantially parallel to the plurality of reed switches and the first reed switch arranged in tandem. .