KR20050063693A - Liquid surface level sensor - Google Patents

Abstract

It is to provide a liquid level sensor that can accurately measure liquid level.

The liquid level sensor comprises three sensor parts 2, 3, 4 and a measuring circuit 6, and the sensor part 2 and the sensor part 3 are connected to the first surface 1a of the container 1. It is arranged at a predetermined distance. The sensor part 4 is arrange | positioned at the 2nd surface 1b of the container 1, and is separated from the sensor part 2 and the sensor part 3 by the predetermined distance, respectively. The inclination angle of the container 1 can be calculated from the information of the liquid level level measured by each sensor part 2, 3, and 4.

Description

Liquid level sensor {LIQUID SURFACE LEVEL SENSOR}

The present invention relates to a liquid level sensor for measuring liquid level.

Some containers containing a liquid include a liquid level sensor for measuring the liquid level. As a liquid level sensor, the float sensor, the sensor using an ultrasonic wave, a capacitive sensor, etc. are known, for example.

Here, when the container is small, for example, 20 mm in height and 20 mm in diameter, the float sensor must have a small float, so the buoyancy of the float itself becomes too small. For this reason, there exists a problem that a position detection element which cooperates with a float, such as a variable resistor, an optical element, a magnetic element, cannot fully be supported. Moreover, in a small container, since the volume is small, the absolute value of the liquid level becomes small, for example, high measurement precision of about plus or minus 0.5 mm in a height direction is calculated | required. When a sensor using ultrasonic waves is applied to a small container having such specificity, the distance for transmitting / receiving ultrasonic waves cannot be sufficiently secured, so the measurement accuracy is low, and the liquid level cannot be measured with high accuracy.

On the other hand, the capacitive sensor can be made smaller than the float type sensor, and the liquid level can be measured with higher accuracy than the sensor using ultrasonic waves.

The capacitive sensor has a configuration in which a pair of measuring electrodes, part of which is immersed in a liquid, is disposed along the vertical direction of the container. Here, since the dielectric constant in the liquid is larger than the dielectric constant in the air, the electrostatic capacitance of the portion of the pair of measuring electrodes that is immersed in the liquid is large. Therefore, the higher the liquid level is, the larger the capacitance becomes. Therefore, the liquid level can be measured by giving an AC signal to one set of measuring electrodes and measuring the capacitance. Here, in the conventional liquid level sensor, the inclination of a container can be measured using a some electrode. As a specific structure, the board | substrate is provided with the board | substrate which consists of a square cylinder with a cross section, and the three measuring electrode and one correction electrode were formed in each surface of this board | substrate. And when there is a difference in the signal output from each measuring electrode, the inclination angle of the container is calculated from this difference (for example, refer to Japanese Patent No. 3128930). As a method of processing signals from a plurality of measuring electrodes, a method of sequentially selecting signals using a multiplexer is known (see, for example, Japanese Unexamined Patent Publication No. Hei 6-34423).

However, when the measuring electrodes were formed on each surface of one substrate, the distance between the electrodes was close, so the difference in capacitance due to the inclination of the container was small, and measurement errors were likely to occur. In addition, since a plurality of measuring electrodes are in close proximity, electrostatic coupling occurs between the measuring electrodes, and a long cylindrical substrate is difficult to miniaturize, and thus it is difficult to accurately arrange the electrodes on each side thereof.

In addition, when the multiplexer is used for signal processing, signals output from a plurality of measuring electrodes cannot be detected simultaneously. For this reason, when the inclination angle of a container changes frequently, a liquid level cannot be detected correctly.

This invention is made | formed in view of the said situation, The objective is to provide the liquid level sensor which can measure a liquid level level precisely.

MEANS TO SOLVE THE PROBLEM This invention employ | adopted the following means in order to solve the said subject.

The liquid level sensor of this invention is equipped with the some electrode arrange | positioned in a container, and the sensor part which detects the liquid level in the said container based on the change of the electrical property between the said electrodes, The 1st surface parallel to the height direction of the said container It is characterized by juxtaposition along the plurality.

Since this liquid level sensor arrange | positioned two or more sensor parts along the surface of a container, the distance between sensor parts can be enlarged. For this reason, since the electrode which measures an electrical characteristic in one sensor part and the electrode which measures an electrical characteristic in another sensor part fall, the electrostatic coupling between electrodes is prevented. In addition, the amount of change in the electrical characteristics when the container is tilted becomes large.

In the liquid level sensor, it is preferable to form a shield between the juxtaposed sensor portions.

Since the liquid level sensor is arranged between the sensor part and the sensor part which are juxtaposed, the electrostatic coupling between the electrodes belonging to the other sensor parts is reliably prevented.

In the said liquid level sensor, it is preferable that the said some sensor part is integrally formed with the insulating film.

Since this liquid level sensor is integrally formed with the insulating film, manufacture becomes easy. Moreover, it can be fixed to a container easily. In addition, it is easy to keep the distance between each sensor part constant.

In the said liquid level sensor, it is preferable to arrange | position at least 1 sensor part in the 2nd surface orthogonal to the said 1st surface of the said container.

Since this liquid level sensor is divided into two surfaces orthogonal to a some sensor part, measurement of a liquid level and the inclination measurement of the two axial directions of a container are attained.

In the liquid level sensor, a plurality of the sensor units disposed on each of the first and second surfaces are integrally formed by an insulating film, and the insulating film is along the first and second surfaces. It is preferable to bend to.

Since this liquid level sensor is integrally formed with the insulating film, manufacture becomes easy. Moreover, it can be fixed to a container easily. In addition, it is easy to keep the distance between each sensor part constant.

Moreover, the liquid level sensor of this invention is equipped with the some electrode arrange | positioned at a container, and has at least 2 sensor parts which detect the liquid level in the said container based on the change of the electrical property between the said electrodes, The said sensor part is the said container It is characterized in that it is disposed along each of the two axes perpendicular to the height direction of.

Since this liquid level sensor has arrange | positioned several sensor part along each of two axis lines, the distance between sensor parts can be enlarged. Moreover, the measurement of the liquid level and the inclination measurement of the two axial directions of a container are attained. In particular, the amount of change in electrical characteristics when the container is tilted becomes large.

In addition, the liquid level sensor of the present invention includes a plurality of electrodes disposed in the container and has three sensor parts for detecting the liquid level in the container based on a change in electrical characteristics between the electrodes, and the sensor part having the height of the container. It is characterized by arrange | positioning so that triangular arrangement may be seen from the cross section orthogonal to a direction.

Since the liquid level sensor has a triangular arrangement when the sensor section is seen in cross section, the distance between the sensor sections can be increased. In addition, the inclination angle of the container can be measured with high accuracy. In particular, the inclination angle can be measured even when the container has a complicated shape or a circular cross section.

(The best mode for carrying out the invention)

Best Mode for Carrying Out the Invention A detailed description will be given with reference to the drawings.

As shown in FIG. 1, the liquid level sensor in 1st Embodiment is electrically connected to the three sensor parts 2, 3, 4 and each sensor part 2, 3, 4 arrange | positioned in the container 1. As shown in FIG. It has the measuring circuit 6 connected.

Three sensor parts 2, 3, 4 are attached to the inner wall of the container 1 substantially parallel to the axis C1 in the height direction of the container. The sensor part 2 and the sensor part 3 are arrange | positioned at predetermined distance to the 1st surface 1a along the axis C2 which is substantially orthogonal to the axis C1. In more detail, the sensor part 2 is arrange | positioned at the one edge part of the 1st surface 1a, and the sensor part 3 is arrange | positioned at the other edge part of the 1st surface 1a. The sensor part 4 is arrange | positioned at the 2nd surface 1b along the axis C3 orthogonal to each of the axis C1 and the axis C2. The sensor part 4 is arrange | positioned at the side edge part opposite to the side edge part which contact | connects the 1st surface 1a in the 2nd surface 1b. This sensor part 4 is formed in the sensor part 2 and the sensor part 3 in the position which set predetermined distance, respectively. In other words, each sensor part 2, 3, 4 is triangularly arranged when seen from the cross section orthogonal to the axis C1.

Next, the structure of each sensor part 2, 3, 4 is demonstrated. In addition, since the structure of each sensor part 2, 3, 4 is the same, only the sensor part 2 is demonstrated as an example below.

As shown in FIG. 2 and FIG. 3, the sensor part 2 is an elongate film shape, one base end 2a side of the longitudinal direction is connected to the measuring circuit 6, and the front end 2b of the container 1 is carried out. It is fixed to be located near the bottom. Moreover, the width | variety of the sensor part 2 becomes wider while it goes toward the front-end | tip 2b from the base end 2a. It is preferable that the tip is immersed in the liquid in this widening portion 21.

This sensor part 2 has laminated | stacked the cover film 7, the 1st insulating film 8, the 2nd insulating film 9, and the cover film 10 in this order. Each film 7, 8, 9, 10 is made of an insulating member having a low water supply rate such as polyethylene terephthalate (PET), polyester, nylon, liquid crystal polymer, or the like.

On the cover film 7 which contacts one outermost layer, the shield layer 11 which has a width about 1/2 of the cover film 7 is formed in the sheet form. The first insulating film 8 is in close contact with the cover film 7 with the cover film 7 interposed between the shield layers 11. Each of the first insulating films 8 includes a linear measuring electrode 12, a driving electrode (measurement signal supply electrode; 13), a first shield electrode 14, a reference electrode 15, and a second The shield electrodes 16 are spaced apart from each other along the longitudinal direction of the first insulating film 8 and arranged substantially in parallel. The second insulating film 9 is in close contact with the first insulating film 8 so as to sandwich the electrodes 12, 13, 14, 15, and 16 with the first insulating film 8. On this second insulating film 9, a shield layer 17 having a width of about 1/2 of the second insulating film 9 is formed in a sheet form. The cover film 10 is in close contact with the second insulating film 9 together with the second insulating film 9 with the shield layer 17 therebetween.

2, the base end 2a side of the sensor part 2 becomes shorter than the cover film 7 and the 1st insulating film 8 of the 2nd insulating film 9 and the cover film 10 as shown in FIG. Each electrode 12, 13, 14, 15, 16 is exposed to a predetermined length on the base end 2a side corresponding to the upper portion of the sensor unit 2.

As shown in FIG.2 and FIG.3, the drive electrode 13 is formed from the base end to the vicinity of the front end on the surface 18 of the 1st insulating film 8 by predetermined | prescribed line width and thickness. The upper end of the drive electrode 13 is connected to the measurement circuit 6 (see Fig. 1) at the base end 2a side of the sensor portion 2, and a predetermined drive AC signal is input. The lower end (tip) 13a of the drive electrode 13 is located above the front end 8a of the first insulating film 8 by a predetermined distance r1.

The measuring electrode 12 is formed on the surface 18 at a predetermined distance from the drive electrode 13. The line width and thickness of the measuring electrode 12 are the same as the driving electrode 13. The upper end of the measuring electrode 12 is connected to the measuring circuit 6 at the base end 2a side of the sensor portion 2. The lower end (tip) 12a of the measuring electrode 12 is located above the tip end 8a of the first insulating film 8 by a predetermined distance r1.

The measuring electrode 12 and the drive electrode 13 form a capacitor. The capacitance is determined by the surface area of the measuring electrode 12 and the driving electrode 13, the distance between the electrodes, and the dielectric constant. The permittivity is large enough that the liquid permittivity is relative to the permittivity of air. Therefore, the capacitance between the measuring electrode 12 and the driving electrode 13 is approximately proportional to the surface area immersed in the liquid surface, that is, the length from the lower end of the measuring electrode 12 and the driving electrode 13 to the liquid level described later. do.

Further, the first shield electrode 14 is formed at a position substantially symmetrical with respect to the drive electrode 13 with respect to the drive electrode 13 on the surface 18. That is, the distance from the drive electrode 13 to the measurement electrode 12 and the distance from the drive electrode 13 to the first shield electrode 14 are approximately equal. The upper end of the first shield electrode 14 is grounded. The lower end (tip) 14a of the first shield electrode 14 is located above the tip end 8a of the first insulating film 8 by a predetermined distance r2. Moreover, the distance r2 is larger than the distance r1.

The reference electrode 15 is disposed at a position further separated from the drive electrode 13 on the surface 18. The width and thickness of the reference electrode 15 are the same as the drive electrode 13. The upper end of the reference electrode 15 is connected to the measurement circuit 6 at the base end 2a side of the sensor portion 2. The lower end (tip) 15a of the reference electrode 15 is located above the front end 8a of the first insulating film 8 by a predetermined distance r1.

The second shield electrode 16 is disposed on the surface 18 with the first shield electrode 14 interposed therebetween with the reference electrode 15 interposed therebetween. That is, the distance from the reference electrode 15 to the second shield electrode 16 is approximately equal to the distance from the reference electrode 15 to the first shield electrode 14. The upper end of the second shield electrode 16 is connected to ground. The lower end (tip) 16a of the second shield electrode 16 is located above the tip end 8a of the first insulating film 8 by a predetermined distance r2.

In addition, the shield layer 11 is formed at a position overlapping each of the shield electrodes 14 and 16 and the shield layer 17. Specifically, the width of the shield layer 11 is approximately equal to the value obtained by adding the widths of the shield electrodes 14 and 16 to the distance between the electrodes of the shield electrodes 14 and 16. In addition, the lower end (front end) of the shield layer 11 is located above the front ends of the first insulating film 8 and the second insulating film 9 by a predetermined distance r2 similarly to the respective shield electrodes 14 and 16. Located in Here, the shield layer 11 is made of a conductive material. And it is electrically connected with the 2nd shield electrode 16 via the conductive through-hole part 20 formed in the 1st insulating film 8. As shown in FIG. In addition, the conductive through hole portion 20 is formed by plating a conductive material on the through hole formed in the first insulating film 8, for example.

The shield layer 17 is made of a conductive material and has the same shape as the shield layer 11. Moreover, the shield layer 17 is formed in the surface 19 on the opposite side to the surface in which the 2nd insulating film 9 is in close contact with the surface 18 of the 1st insulating film 8. Lower ends (tips) of the shield layer 17 are located at the same positions as the shield electrodes 14 and 16 and the shield layer 11. In addition, the shield layer 17 is electrically connected to the first shield electrode 14 through the conductive through hole portion 23 formed in the second insulating film 9.

The shield layer 11 and the shield layer 17 are positioned between the reference electrode 15 and each shield electrode 14, 16 by the first insulating film 8 and the second insulating film 9. It is formed in. Therefore, the pair of shield electrodes 14, 16 and the pair of shield layers 11, 17 are arranged to surround the reference electrode 15, and are also electrically connected. Since each shield electrode 14, 16 is connected to the ground as described above, the pair of shield electrodes 14, 16 and the pair of shield layers 11, 17 are electrically connected to the reference electrode 15. It becomes a shield.

The portion protruding from the shield near the lower end 15a of the reference electrode 15 becomes the reference measuring portion 25, and the shielded portion becomes the signal conducting portion 26. The reference measuring section 25 forms a driving electrode 13 and a capacitor. The capacitance is determined by the surface area of the reference measuring unit 25 and the drive electrode 13, the distance between the electrodes, and the dielectric constant. The length of the reference measuring unit 25 is the length obtained by subtracting the predetermined distance r1 from the predetermined distance r2, and the value of the capacitance (dielectric constant) at this time is a reference value when measuring the liquid level. The signal conducting section 26 is connected to the measuring circuit 6 at its upper end, and serves to input a predetermined signal generated by the reference measuring section 25 to the measuring circuit 6.

In addition, each of the electrodes 12, 13, 14, 15, and 16 and the shield layers 11, 17 partially etch the conductive material in each of the films 7, 8, 9 to which a conductive material of a predetermined thickness is adhered. It is formed. Moreover, in the width | variety expansion part 21 of the sensor part 2, the arrangement | positioning space | interval of each electrode 12, 13, 14, 15, 16 also becomes long centering on the 1st shield electrode 14. As shown in FIG.

As shown in FIG. 1, the measuring circuit 6 includes a first measuring circuit 27 connected to the sensor unit 2, a second measuring circuit 28 connected to the sensor unit 3, and a sensor unit ( And a third measuring circuit 29 connected to 4). In addition, since each measuring circuit 27, 28, 29 has the same circuit structure, only the structure of the 1st measuring circuit 27 is demonstrated below.

As shown in FIG. 4, the 1st measuring circuit 27 has the oscillation circuit 31 which produces | generates a rectangular AC signal, for example. This oscillation circuit 31 comprises a series circuit consisting of three inverters 32, 33, 34, a resistor 35 connected to an input terminal and an output terminal of the series circuit, an input terminal and an inverter 33 of the inverter 32. It has the capacitor | condenser 36 connected to the output terminal of. The output terminal of the series circuit is connected to the drive electrode 13 of the sensor unit 2.

The first measuring circuit 27 has a resistor 37 and an analog switch 38 having one end connected to the measuring electrode 12. In addition, the first measuring circuit 27 has a resistor 39 and an analog switch 40 having one end connected to the reference electrode 15. Each other end of the resistors 37 and 39 is connected to ground. Each analog switch 38, 40 is connected to a low pass filter 41. In addition, the control terminal of each analog switch 38, 40 is connected to the oscillation circuit 31, and a switch is switched ON or OFF according to the output waveform of the oscillation circuit 31. Moreover, as shown in FIG.

The low pass filter 41 has a capacitor 42 and a resistor 43, one end of which is connected to the analog switch 38, and the other end of the resistor 43 has a capacitor 44, a resistor 45, and a capacitor ( 46) is connected. In addition, the low pass filter 41 has a capacitor 47 and a resistor 48 having one end connected to the analog switch 40, and the other end of the resistor 48 has a capacitor 49, a resistor 50, The capacitor 46 is connected. The output of the low pass filter 41 is connected to the differential amplifier circuit 51. Moreover, the other end of the capacitor | condenser 42 and the capacitor | condenser 47, the capacitor | condenser 44 and the capacitor | condenser 49, the resistor 45, and the resistor 50 is grounded. The capacitor | condenser 46 is interposed in the other end of the resistor 43 and the resistor 48, respectively.

The differential amplifier circuit 51 mainly consists of three operational amplifiers 52, 53, and 54. The output of the measuring electrode 12 side of the low pass filter 41 is connected to the non-inverting input terminal of the operational amplifier 52. The output terminal and the inverting input terminal of the operational amplifier 52 are connected with the resistor 55 interposed therebetween, and a negative feedback loop is formed. The output terminal of the operational amplifier 52 is connected to the inverting input terminal of the operational amplifier 54 with the resistor 56 interposed therebetween. The inverting input terminal of the operational amplifier 52 is connected to the inverting input terminal of the operational amplifier 53 with the resistor 57 and the variable resistor 58 interposed therebetween.

The output of the reference electrode 15 side of the low pass filter 41 is connected to the non-inverting input terminal of the operational amplifier 53. A resistor 59 is interposed between the output terminal and the inverting input terminal of the operational amplifier 53. The output terminal of the operational amplifier 53 is connected to each of the resistor 60 and the resistor 61. The other end of the resistor 60 is connected to ground, and the resistor 61 is connected to the non-inverting input terminal of the operational amplifier 54.

One end of the resistor 62 is connected to the output terminal of the operational amplifier 54. This resistor 62 is connected to another control circuit, where a signal corresponding to the distance (liquid level) from the reference position h0 to the liquid level is output. In addition, the resistor 63 and the capacitor 64 are connected in parallel between the other end of the resistor 62 and the inverting input terminal of the operational amplifier 54.

Next, the operation of this liquid level sensor will be described. Moreover, the container 1 shall be filled with the liquid to the height (reference position h0) equal to the distance r2 at least as shown in FIG.

As shown in Fig. 4, the oscillation circuit 31 of the first measurement circuit 27 generates an AC signal for driving. This AC signal is input to the drive electrode 13, and propagates to the measurement electrode 12, the reference measurement portion 25 of the reference electrode 15, and the shield using air and liquid as a medium. The signal propagates to the measuring electrode 12 with a capacitance based on the dielectric constant of the liquid, i.e., a reception signal according to the liquid level. This received signal is input to the analog switch 38 of the first measuring circuit 27. Further, the reference measuring section 25 (see Fig. 2) generates a received signal corresponding to the electrostatic capacitance based on the dielectric constant of the liquid by the propagation of the signal. This received signal is input to the analog switch 40 of the first measuring circuit 27. In addition, since the shield is grounded, no reception signal is generated.

Since each of the analog switches 38 and 40 switches the interruption of the switch in accordance with the drive exchange of the oscillation circuit 31, the reception voltage of the measurement electrode 12 and the reception voltage of the reference electrode 15 are synchronized. Detected. Each received voltage synchronously detected by the respective analog switches 38 and 40 is inputted to the low pass filter 41 to remove excess AC components, and DC components are extracted. Further, after being input to the differential amplifier circuit 51 and amplified, a signal proportional to the difference obtained by subtracting the reception voltage of the reference electrode 15 serving as the reference value from the reception voltage of the measurement electrode 12 is output.

Here, the dielectric constant between the measurement electrode 12 and the portion immersed in the liquid of the drive electrode 13 and the dielectric constant between the measurement electrode 12 and the reference measuring portion 25 of the reference electrode 15 are the same. Value. Therefore, when the amount of liquid in the container 1 increases and the liquid level rises beyond the reference position h0, the capacitance between the drive electrode 13 and the measuring electrode 12 increases approximately in proportion to the liquid level. On the other hand, the reference electrode 15 is a reference portion because portions beyond the reference position h0 are sealed to each shield electrode 14, 16 and each shield layer 11, 17 as shown in FIG. It does not change from the capacitance corresponding to the position h0. As described above, the sensor output is proportional to the difference between the signal based on the capacitance on the measurement electrode 12 side and the signal based on the capacitance on the reference electrode 15 side. Therefore, as the liquid level rises, it increases in proportion to this. Likewise, the sensor output decreases proportionally as the liquid level drops. In this way, the sensor output of the sensor unit 2 becomes a signal approximately in proportion to the liquid level based on the received voltage of the reference measuring unit 25. Therefore, the absolute value of the liquid level can be known from the magnitude of the signal.

In the same way, the liquid level at each attachment position is detected also in the sensor part 3 and the sensor part 4 based on an AC signal.

Here, as shown in FIG. 1, when the container 1 is in a horizontal state, the sensor output corresponding to each sensor part 2, 3, 4 will become substantially the same value. On the contrary, when the container 1 is in a tilted position, different sensor outputs are obtained for each of the sensor sections 2, 3, 4. In this case, the inclination angle of the container 1 can be calculated by making a predetermined calculation based on each sensor output, that is, the value of each liquid level and the position of each sensor part 2, 3, 4. Specifically, the inclination around a specific axis can be detected from the sensor outputs of two sensor parts selected from three sensor parts 2, 3, and 4. For example, the inclination angle around the axis C3 can be detected from the sensor part 2 and the sensor part 3. From the sensor part 2 and the sensor part 4, the inclination angle around the axis line C2 can be detected. And from the sensor part 3 and the sensor part 4, the inclination angle of the circumference | surroundings which connects the sensor part 3 and the sensor part 4 can be detected. And the three-dimensional inclination can be detected from the sensor output of three sensor parts 2, 3, and 4. The inclination angle in these cases can be calculated by the following formula (1).

Is the angle of inclination of the liquid level with respect to the horizontal direction, and Δh is the difference of the liquid level. The difference in the liquid level can be obtained from the value of the liquid level at the sensor output of two sensor units arbitrarily selected from the three sensor units 2, 3, and 4. For example, it is obtained by subtracting the value of the liquid level by the sensor output of the sensor unit 3 from the value of the liquid level by the sensor output of the sensor unit 2. De is the distance between the measuring electrodes, and corresponds to, for example, a straight line distance from the measuring electrode 12 of the sensor unit 2 to the measuring electrode 12 of the sensor unit 3. In addition, the value set in advance for each container 1 is used for the distance between each measuring electrode 12. As shown in FIG. In addition, the distance between the sensor part 2, the sensor part 4, and the measurement electrodes 12 of the sensor part 3 and the sensor part 4 is also set in advance for each container 1.

According to this embodiment, the some sensor part 2, 3, 4 is divided | segmented into the axis line C2 and the axis line C3, and each container part 2, 3, 4 has a sufficient distance between containers, Since it adhered to the inner surface of (1), the electrostatic coupling between each electrode 12, 13, 15 of the other sensor part 2, 3, 4 can be suppressed. Therefore, the liquid level can be measured with high accuracy. In addition, since part of the reference electrode 15 is electronically sealed, the accuracy of the liquid level detected by each sensor unit 2, 3, 4 can also be improved.

And the inclination angle of the container 1 can be detected by performing predetermined calculation based on the position of the some sensor part 2, 3, 4, and each sensor output. Here, since the three sensor parts 2, 3, 4 are arrange | positioned separately and arrange | positioned with sufficient distance, the inclination angle can be measured with high precision.

Since the unsealed portion, that is, the reference measuring portion 25 is disposed near the bottom of the container 1 at the lower end of the reference electrode 15, the capacitance used as a reference can be easily measured. Therefore, the liquid level can be measured with high accuracy even with a small amount of liquid. Here, the liquid level is determined as the distance from the reference position h0. Since the reference position h0 is a known value when the attachment position to the vessel 1 of the liquid level sensor is determined, the vessel 1 The absolute value from the bottom of the surface to the surface can be simply obtained.

In addition, since the measurement electrode 12 and the reference electrode 15 share the drive electrode 13 and measure the liquid level with three electrodes, the liquid level sensor can be miniaturized. Moreover, since each electrode 12, 13, 15 was covered with the some film 7, 8, 9, 10 with a small water absorption, contact with each electrode 12, 13, 15 and a liquid can be prevented.

Application examples of this liquid level sensor include a container for storing fuel or a waste liquid in a fuel cell developed as a power source of a portable terminal device such as a PDA (electronic notebook), a computer, a cellular phone, or a vehicle driving source. It can be applied to detect the storage amount (remaining amount) of the container. Since the reference capacitance measured by the reference electrode 15 can be measured with high accuracy, it is possible to reliably detect the liquid level even when a liquid having a different dielectric constant, such as pure methanol, a mixture of formic acid, and formaldehyde, is placed in the container. Can be. The liquid level sensor may be applied to a liquid such as water stored in a container such as a washing machine, a dishwasher, an electric pot, and a bathtub.

Next, 2nd Embodiment is described with reference to drawings. In addition, the same code | symbol is attached | subjected to the component same as 1st Embodiment. In addition, redundant description is abbreviate | omitted.

This embodiment is characterized in that the plurality of sensor portions are formed integrally with an insulating film.

As shown in FIG. 5, the insulating film 70 is attached to the plane 1a along the axis C2 of the container 1. On this insulating film 70, two sensor parts 2 and 3 are formed in parallel with the axis C1. The liquid level sensor in this embodiment is comprised including the two sensor parts 2 and 3 on the insulating film 70, the sensor part 4, and the measuring circuit 6 (refer FIG. 1).

The width of the insulating film 70 is approximately equal to the length in the direction of the axis C2 of the first surface 1a, and the height is approximately equal to the height in the direction of the axis C1 of each sensor part 2, 3. The sensor portion 2 is brought into close contact with one edge portion of the insulating film 70 in the width direction. In addition, the sensor portion 3 is brought into close contact with the other edge portion in the width direction of the insulating film 70. In addition, the insulating film 70 is made of the same material as each of the films 7, 8, 9 and 10. And the sensor part 4 has the structure similar to FIG.

In addition, the sensor part 4 has the same structure as the sensor part 2 shown in FIG.

Since two sensor parts 2 and 3 are integrally formed by the insulating film 70, this liquid level sensor is easy to fix each sensor part 2 and 3 to the container 1. As shown in FIG. And since the two sensor parts 2 and 3 are connected by the insulating film 70, the position of each sensor part 2 and 3 does not shift | deviate well, and a measurement precision can be improved.

In addition, you may use the insulating film 70 instead of the cover film 7 of each of the sensor part 2 and the sensor part 3. That is, the shield layer 11 (refer FIG. 3) is formed in each edge part of the width direction of the insulating film 70, and this shield layer 11 is used as the conductive through-hole part 20 on the 1st insulating film 8 Is connected to the second shield electrode 16.

And the insulating film 70 is made into two layers structure, and instead of the cover film 7 and the 1st insulating film 8 of each of the sensor part 2 and the sensor part 3, it uses two insulating films 70, You may also In this case, the insulating film 70 which arrange | positioned each electrode 12, 13, 14, 15, 16 on the insulating film 70 in which the shield layer 11 was formed is closely contacted. The shield layer 11 and each of the electrodes 12, 13, 14, 15, and 16 are formed on both edge portions in the width direction of the two insulating films 70, respectively. And the 2nd insulating film 9 and the cover film 10 (both FIG. 3) are laminated | stacked on it.

In the same manner, the cover film 7, the first insulating film 8, and the second insulating film 9 of the sensor unit 2 and the sensor unit 3 may be replaced with three insulating films 70. And all the films 7, 8, 9, and 10 of the sensor part 2 and the sensor part 3 may be replaced by four insulating films 70. As shown in FIG. As described above, when each of the films 9 and 10 is replaced with the insulating film 70, the axis line is exposed so that a part of each of the electrodes 12, 13, 14, 15, and 16 is exposed to connect with the measuring circuit 6. The height in the (C1) direction is adjusted.

In this case, manufacture of the liquid level sensor becomes easy. Here, each of the electrodes 12, 13, 14, 15, 16 and the shield layers 11, 17 can use the above-described conventional etching technique, so that the manufacturing cost can be lowered. In particular, in the case where the film on which the measuring electrode 13 or the like is arranged is used as the insulating film 70, the electrodes 12, 13, 14, 15, and 16 are formed on the large-area film. Surface precision can be improved.

Moreover, as shown in FIG. 6, you may integrally form all the three sensor parts 2, 3, 4 arrange | positioned in parallel with the axis line C1 by the insulating film 72. As shown in FIG. The insulating film 72 in this case is substantially the same width as the length of the 1st surface 1a and the 2nd surface 1b total. Moreover, about 90 degrees are bent at the connection part of the 1st surface 1a and the 2nd surface 1b so that along each surface 1a, 1b. For this reason, the insulating film 72 has a L-shape in plan view. And the sensor part 4 is formed in one edge part of the insulating film 72, and the sensor part 3 is formed in the other edge part. In addition, the sensor part 2 is formed in the vicinity of the bent part 73 of the insulating film 72. The insulating film 72 is made of the same material as the insulating film 70. Each sensor part 2, 3, 4 is formed on the insulating film 72, or is comprised using the insulating film 72 for at least 1 piece of film.

In such a liquid level sensor, the same effects as described above are obtained for the three sensor units 2, 3, 4.

Next, a third embodiment will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the component same as each said embodiment. In addition, redundant description is abbreviate | omitted.

This embodiment is characterized in that an electronic shield is formed between the plurality of sensor units.

As shown in FIG. 7, the liquid level sensor includes three sensor parts 2, 3, 4 and a measurement circuit 6 (see FIG. 1) arranged in parallel with the axis C1. The sensor portion 3 is formed integrally with the insulating film 81. And the shield electrode 82 which becomes a shield part is formed in the substantially intermediate position from the insulating film 81 to the sensor part 2 to the sensor part 3. And the shield part 83 is formed along the plane 1b in the substantially intermediate position from the sensor part 2 to the sensor part 4.

The insulating film 81 is the same shape as the insulating film 70 shown in FIG. 5, and is formed with the same material. The insulating film 81 is attached to the 1st surface 1a along the axis C2. In addition, although the sensor part 2 and the sensor part 3 are formed in parallel on both edge parts of the insulating film 81 width direction, as mentioned above, the several film which comprises each sensor part 2 and 3 ( At least one of 7, 8, 9, 10 (see Fig. 3) may be used as the insulating film 81.

The shield electrode 82 is arranged in parallel with the height direction of the container 1, and the length of the height direction is the same length as the other electrodes 12, 13, and 15. As shown in FIG. The shield electrode 82 is formed by partially etching the conductive material from the insulating film 81 to which a conductive material of a predetermined thickness is bonded. Moreover, it is preferable to cover the shield electrode 82 with a film so that the shield electrode 82 does not directly contact a liquid. For example, when the insulating film 81 has a two-layer structure, the insulating film 81 is laminated so that the shield electrode 82 is interposed therebetween.

In addition, the shield part 83 is the structure which covered the conductive shield electrode 84 with the insulating film 85, and the insulating film 85 is in close contact with the 2nd surface 1b. The shield electrode 84 is made of the same material as the shield electrode 82 and has the same shape. The insulating film 85 is made of the same material as the insulating film 81.

This liquid level sensor is used with the shield electrode 82 and the shield electrode 84 grounded. For this reason, during the measurement of the liquid level, the signals propagated from the drive electrode 13 of the sensor unit 2 toward the sensor unit 3 and the sensor unit 4 are respectively shielded electrodes 82 and shields. It is blocked by the electrode 84. For this reason, electrostatic coupling between the sensor part 2 and the sensor part 3 or the sensor part 4 is prevented. Similarly, the signal from the sensor portion 3 does not propagate to the sensor portion 2 because the shield electrode 82 is present. The signal from the sensor portion 4 does not propagate to the sensor portion 2 because the shield electrode 84 is present. In addition, since the distance between the sensor part 3 and the sensor part 4 is far enough, the electrostatic coupling between them does not occur.

Therefore, in this liquid level sensor, signals from the other sensor units 2, 3, and 4 cannot be received by the measuring electrode 12 or the reference electrode 15, so that the measurement accuracy of the liquid level is improved. Moreover, the measurement precision of the inclination angle of the container 1 calculated based on the liquid level and the arrangement | positioning of each sensor part 2, 3, 4 can also be improved.

Here, when the sensor part 2 and the sensor part 3 are arrange | positioned independently as shown in FIG. 1, the seal of the same structure as the shield part 83 between the sensor part 2 and the sensor part 3 is shown. By arranging the electrode portion and grounding the electrode, electrostatic coupling between the sensor portions 2 and 3 can be prevented.

In addition, when the three sensor parts 2, 3, 4 are integrally formed with the insulating film 72 (refer FIG. 6), the shield electrode 84 is formed on the sensor film 4 on the insulating film 72. Moreover, as shown in FIG. By arranging in the middle from the arrangement position of the to the bent portion 73 to ground connection, the electrostatic coupling between the sensor portion 2 and the sensor portion 4 can be prevented.

Moreover, this invention is not limited to the above-mentioned embodiment, It can apply widely.

For example, the measurement circuit may be provided with a current detection circuit and a voltage detection circuit so as to detect the liquid level by measuring impedance, which is a higher concept of capacitance, by using an impedance proportional to an electrode area immersed in a liquid.

In addition, each measuring circuit 27, 28, 29 may be configured to input an AC signal of a different frequency to each of the sensor units 2, 3, 4 to each drive electrode 13. Since the crosstalk in each sensor part 2, 3, 4 and the measurement circuit 6 is prevented, the measurement precision improves.

In addition, in each embodiment, the number of sensor parts may be four or more. The sensor part after 4th may be arrange | positioned at the 1st surface 1a, and may be arrange | positioned at the 2nd surface 1b. Moreover, you may arrange | position to the other surface of the container 1. And four or more sensor parts may be integrally formed with the insulating film, and the same shield part as the shield electrode 82 or the shield part 83 may be arrange | positioned between each sensor part.

Incidentally, the shape of the container 1 is not limited to the rectangle, and may have a circumferential shape, a polygonal shape, or irregularities on the inner surface. Even in such a case, the liquid level or the inclination angle can be measured with high accuracy by dividing three or more sensor parts into two axes orthogonal to the height direction of the container 1 or by arranging them triangularly when viewed in cross section.

In addition, each of the films 7, 8, 9, and 10 may use a material having no absorbency or a material having almost no absorbency only in each cover film 7, 10, which is the outermost layer, and may also be glass coated on the outer surface of the film. You may prevent absorption by further covering with another waterproofing material.

In addition, each sensor part 2, 3, 4 may be a structure which does not have a shield. In this case, it is preferable to narrow the width of the signal conducting portion 26 with respect to the reference measuring portion 25 of the reference electrode 15.

In the measuring circuit 6, an abnormal circuit 100 (see FIG. 4) may be interposed between the analog switches 38 and 40 and the oscillation circuit 31 to shift the phase of the signal by 90 °. Since the signal intensity of the received voltage whose phase is shifted by 90 ° with respect to the driving waveform can be processed in a large phase portion, higher sensitivity can be achieved.

According to this invention, since the sensor part provided with the electrode which measures the change of a liquid level is arrange | positioned at a predetermined distance on the 1st surface of a container, electrostatic coupling with another sensor part electrode can be prevented. Therefore, the liquid level and the inclination angle of the container can be measured with high accuracy. And if a shield is formed between the sensor parts provided with an electrode, since the electrostatic coupling between other sensor parts can be effectively prevented, measurement accuracy will improve. In addition, when a plurality of sensor units are integrally formed, manufacturing and handling become easy.

BRIEF DESCRIPTION OF THE DRAWINGS The whole block diagram of the liquid level sensor in embodiment of this invention.

2 is a diagram showing a sensor unit of a liquid level sensor.

3 is an exploded perspective view of a sensor unit of the liquid level sensor.

4 is a diagram illustrating a part of a configuration of a measurement circuit.

5 is a configuration diagram of a liquid level sensor in an embodiment of the present invention.

6 is a configuration diagram of a liquid level sensor in an embodiment of the present invention.

7 is a configuration diagram of a liquid level sensor in an embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings *

1: container 1a: first side

1b: 2nd surface 2, 3, 4: sensor part

7, 10: cover film (insulation film) 11, 17: shield layer (sealed)

12 measuring electrode 13 driving electrode

15: reference electrode 70, 72, 81: insulating film

82: shield electrode (sealed portion) 83: sealed portion

C1, C2, C3: Axis h0: Reference position

Claims (7)

And a plurality of sensor units including a plurality of electrodes disposed in the container and detecting a liquid level in the container based on a change in electrical characteristics between the electrodes, arranged in parallel along a first surface parallel to the height direction of the container. Liquid level sensor. The method of claim 1, A liquid level sensor, characterized in that a shield portion is formed between the sensor portions arranged in parallel. The method of claim 1, A plurality of said sensor part is integrally formed with the insulating film, The liquid level sensor characterized by the above-mentioned. The method of claim 1, At least one sensor part is arrange | positioned at the 2nd surface orthogonal to the said 1st surface of the said container, The liquid level sensor characterized by the above-mentioned. The method of claim 4, wherein A plurality of the sensor portion disposed on each of the first surface and the second surface is integrally formed by an insulating film, the insulating film is bent along the first surface and the second surface. Liquid level sensor. At least two sensor parts including a plurality of electrodes disposed in the container and detecting the liquid level in the container based on a change in electrical characteristics between the electrodes, and two sensor parts orthogonal to the height direction of the container. A liquid level sensor, arranged along each axis. It is provided with three electrodes arranged in a container, and provided with three sensor parts which detect the liquid level level in the said container based on the change of the electrical property between the said electrodes, The said sensor part was seen from the cross section orthogonal to the height direction of the said container. Liquid level sensor, characterized in that arranged in a triangular arrangement when.