JP2010203871A - Sensor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor device which detects the liquid level and the liquid quality of a measuring object liquid with high accuracy without providing a complicated arithmetic device. <P>SOLUTION: This sensor device includes a first detecting electrode 22 which is always located in the measuring object liquid, a second detecting electrode 23 which measures capacitance between electrodes without being affected by a dielectric constant that the measuring object liquid has, a third detecting electrode 24 which measures the liquid level of the measuring object liquid, and a fourth detecting electrode 25 which is always located outside the measuring object liquid. In the device, a first canceling electrode 32 is disposed along a leader 27 of the first detecting electrode 22 and a second canceling electrode 40 is disposed between a leader 28 of the second detecting electrode and a leader 35 of the third detecting electrode 24, while a third canceling electrode 42 is disposed along a leader 36 of the fourth detecting electrode 25. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sensor device that detects the level of liquid stored in a container, and more particularly to a sensor device that detects the level and quality of engine oil and fuel in automobiles, construction machines, and the like.

  As sensor devices for detecting the level of engine oil or fuel for automobiles, construction machines, etc., those shown in FIGS. 6 and 7 are known (see Patent Document 1). FIG. 6 is a front view of a detection unit of a conventional sensor device. In FIG. 6, reference numeral 1 denotes a rectangular substrate extending vertically, and a first detection of a comb-like shape is provided at the lower end of the substrate 1. The electrode 2 is provided with a comb-shaped second detection electrode 3 at a substantially central portion. The first detection electrode 2 is composed of a plurality of linear electrodes 4 arranged at predetermined intervals in the vertical direction, and these are alternately arranged on lead lines 5 and 6 extending vertically along both side edges of the substrate 1. It is connected to the. The second detection electrode 3 includes a plurality of linear electrodes 7 arranged so as to extend from the upper end portion to the lower end portion at a predetermined interval on the left and right sides, and the upper ends of these linear electrodes 7 are leads. The lines 8 and 9 are alternately connected.

  At the time of liquid level measurement, the detection unit is immersed in the liquid to be measured. At this time, the first detection electrode 2 is always arranged to be immersed in the liquid to be measured. On the other hand, the second detection electrode 3 intersects the liquid surface to be measured, and the portion immersed in the liquid increases or decreases as the liquid level rises and falls.

  FIG. 7 shows a detection circuit diagram using the above-described detection unit, and includes an oscillation circuit 10 and a processing circuit 17. The oscillation circuit 10 includes inverters 11, 12, and 13 and a resistor 14, and the first and second detection electrodes 2 and 2 in the detection unit are connected between the inverters 12 and 13 via analog switches 15 and 16, respectively. 3 is connected. The processing circuit 17 having a microcomputer first closes the analog switch 15 and calculates and stores the dielectric constant of the liquid to be measured from the oscillation frequency determined by the resistor 14 and the capacitance of the first detection electrode 2. . Subsequently, the processing circuit 17 closes the other analog switch 16 in place of the one analog switch 15, and the oscillation frequency determined by the resistor 14 and the capacitance of the second detection electrode 3 and the dielectric constant of the liquid to be measured. The liquid level is calculated from the above, and the accurate liquid level can be known even when the dielectric constant of the liquid to be measured fluctuates.

As prior art document information relating to the invention of this application, for example, Patent Document 1 is known.
JP-A-63-79016

  However, in the conventional sensor device described above, the dielectric constant of the liquid to be measured is calculated from the oscillation frequency of the oscillation circuit 10 that is always determined by the capacitance between the first detection electrodes 2 immersed in the liquid to be measured. After storing, the oscillation frequency of the oscillation circuit 10 determined by the capacitance between the second detection electrodes 3 that intersects with the liquid surface to be measured and is increased or decreased as the liquid level rises or lowers. Since the liquid level of the liquid to be measured is calculated from the dielectric constant of the liquid to be measured, there is a problem that the calculation device becomes complicated and large.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a sensor device that can detect the liquid level and liquid quality of a liquid to be measured with high accuracy without providing a complicated arithmetic device. To do.

  In order to achieve the above object, the present invention has the following configuration.

  According to the first aspect of the present invention, the influence of the first detection electrode that is always in the liquid to be measured from the lower side to the upper side and the dielectric constant of the liquid to be measured is applied to the detection unit that is erected in the vertical direction. A second detection electrode that measures the capacitance between the electrodes without receiving, a third detection electrode that measures the liquid level of the liquid to be measured, and a fourth detection electrode that is always outside the liquid to be measured are provided. The third detection electrode is charged for a time proportional to the length of the portion immersed in the liquid to be measured, and the third detection electrode is proportional to the length of the portion outside the liquid to be measured. A circuit that repeats the operation of discharging the charged charge for a period of time, and further includes a common lead line for the first detection electrode and the second detection electrode, and a third detection electrode and a fourth detection electrode. Provide a pulse generation circuit to input pulses to the common lead line. Both the first cancel electrode, the first detection electrode, and the second detection electrode extend along a lead line of the first detection electrode that extends along a common lead line of the first detection electrode and the second detection electrode. The second cancel electrode extends along the common lead line of the third detection electrode and the fourth detection electrode along the lead line of the second detection electrode extending along the common lead line of the second detection electrode. A third cancel electrode extends along a lead line of the third detection electrode, and a third cancel electrode extends along a lead line of the fourth detection electrode extending along a common lead line of the third detection electrode and the fourth detection electrode. A fourth cancel electrode is disposed, and a signal obtained by inverting the pulse is input to the first cancel electrode, the second cancel electrode, the third cancel electrode, and the fourth cancel electrode. 1 detection power , The charge accumulated between the first detection electrode and the common extraction line of the second detection electrode, the extraction line of the second detection electrode, the first detection electrode and the second detection electrode Charge accumulated between the common lead lines of the detection electrodes, and the charge line accumulated between the lead lines of the third detection electrode and the common lead lines of the third detection electrode and the fourth detection electrode. The charge and the charge accumulated between the lead line of the fourth detection electrode and the common lead line of the third detection electrode and the fourth detection electrode are canceled, respectively. Therefore, the capacitance generated between the lead lines of each detection electrode can be canceled, so that a voltage that is accurately proportional to the liquid level and liquid quality can be output without providing a complicated arithmetic unit. This makes it easy to provide highly accurate sensors It has the effect of being able to.

  As described above, the sensor device according to the present invention is affected by the first detection electrode in the liquid to be measured and the dielectric constant of the liquid to be measured from the lower side to the upper side on the detection unit standing in the vertical direction. Without providing a second detection electrode for measuring the capacitance between the electrodes, a third detection electrode for measuring the liquid level of the liquid to be measured, and a fourth detection electrode that is always outside the liquid to be measured; Charging is performed for a time proportional to the length of the portion where the third detection electrode is immersed in the liquid to be measured, and the time is proportional to the length of the portion where the third detection electrode is outside the liquid to be measured. A circuit that repeats the operation of discharging the charged electric charge, and a common lead line for the first detection electrode and the second detection electrode, and a common line for the third detection electrode and the fourth detection electrode. A pulse generation circuit is provided to input pulses to the leader line. And a first cancel electrode extending along a lead line of the first detection electrode extending along a common lead line of the first detection electrode and the second detection electrode, and the first detection electrode and the second detection electrode extending along the lead line of the first detection electrode. The second cancel electrode extends along the common lead line of the third detection electrode and the fourth detection electrode along the lead line of the second detection electrode extending along the common lead line of the second detection electrode. A third cancel electrode extends along a lead line of the third detection electrode, and a third cancel electrode extends along a lead line of the fourth detection electrode extending along a common lead line of the third detection electrode and the fourth detection electrode. A fourth cancel electrode is disposed, and a signal obtained by inverting the pulse is input to the first cancel electrode, the second cancel electrode, the third cancel electrode, and the fourth cancel electrode. 1 detection The charge accumulated between the lead wire of the pole and the common lead wire of the first detection electrode and the second detection electrode, the lead wire of the second detection electrode, the first detection electrode and the first detection electrode The charge accumulated between the common lead lines of the two detection electrodes, the charge accumulated between the lead lines of the third detection electrode and the common lead lines of the third detection electrode and the fourth detection electrode. And the charges accumulated between the lead lines of the fourth detection electrode and the common lead lines of the third detection electrode and the fourth detection electrode are respectively canceled. Capacitance generated between the lead wires of the detection electrode can be canceled, so that a voltage that is accurately proportional to the liquid level and liquid quality can be output without providing a complicated arithmetic unit. It is possible to easily provide a sensor with high accuracy. The effect is achieved.

  Hereinafter, a sensor device according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a front view of a detection unit of a sensor device according to an embodiment of the present invention. In FIG. 1, reference numeral 21 denotes a detection unit made of a rectangular polyimide film or the like extending vertically. A pair of first detection electrodes 22 made of comb-shaped carbon or the like is provided at the lower end of the first electrode. In addition, a pair of second detection electrodes 23 made of comb-shaped carbon or the like is provided on the upper portion of the first detection electrode 22, and the upper portion of the second detection electrode 23 is similarly comb-shaped. A pair of third detection electrodes 24 made of carbon or the like is provided, and a pair of fourth detection electrodes 25 made of comb-like carbon or the like is provided on the third detection electrode 24. The first and second detection electrodes 22, 23 are connected to terminals 29, 30, 31 by a common lead line 26 and respective lead lines 27, 28. Reference numeral 32 denotes a first cancel electrode which is connected to the terminal 33 and is disposed along the lead line 27 of the first detection electrode 22, and the first cancel electrode 32 is the upper end portion of the first detection electrode 22. It is provided over. The third and fourth detection electrodes 24, 25 are connected to terminals 37, 38, 39 by a common lead line 34 and lead lines 35, 36, respectively. Reference numeral 40 denotes a second cancel electrode which is connected to the terminal 41 and is arranged between the lead line 28 of the second detection electrode 23 and the lead line 35 of the third detection electrode 24. The second cancel electrode Is provided across the upper end of the second detection electrode 23 and the lower end of the third detection electrode 24. Reference numeral 42 denotes a third cancel electrode which is connected to the terminal 43 and is disposed along the lead line 36 of the fourth detection electrode 25. The third cancel electrode 42 is a lower end portion of the fourth detection electrode 25. It is provided over.

  FIG. 2 is a cross-sectional view taken along line AA of the second detection electrode 23 in FIG. 1. As shown in FIG. 2, the second detection electrode 23 insulates the entire opposing electrode 44. In this configuration, the lines of electric force generated between the opposing electrodes 44 do not pass through the liquid to be measured. The capacitance between the opposing electrodes 44 measured by the two detection electrodes 23 is not affected by the dielectric constant of the liquid to be measured.

  As the insulator 45, it is desirable to select a liquid to be measured, a solid material impregnated with the liquid to be measured, or a substance having substantially the same dielectric constant temperature characteristics as the liquid to be measured. Thereby, the influence of the temperature change in liquid quality measurement can be removed.

  FIG. 3 shows a detection circuit diagram of the sensor device according to one embodiment of the present invention. In FIG. 3, the pulse from the pulse generation circuit 51 is input to the terminals 29 and 37 of the detection unit 21. In addition, signals obtained by inverting the pulses are input to the terminals 33, 41, and 43 of the detection unit 21 via level adjusters 52, 53, and 54, respectively. In this detection circuit, a signal branched from the input of the NOR gate in the final stage of the pulse generation circuit 51 is input to the terminals 33, 41, 43 of the detection unit 21.

  When a pulse from the pulse generation circuit 51 is input to the terminals 29 and 37 of the detection unit 21, the electric charge accumulated in the capacitance of the first detection electrode 22 is between the terminals 29 and 30 of the detection unit 21. In addition, there is a charge accumulated in the capacitance between the common lead line 26 and the lead line 27 of the first detection electrode 22, and the second detection electrode is between the terminals 29 and 31 of the detection unit 21. There are electric charges accumulated in the electrostatic capacity 23 and electric charges accumulated in the electrostatic capacity between the common lead line 26 and the lead line 28 of the second detection electrode 23. Similarly, between the terminals 37 and 38 of the detection unit 21, the electric charge accumulated in the electrostatic capacitance by the third detection electrode 24 and the space between the common lead line 34 and the lead line 35 of the third detection electrode 24. The charge accumulated in the capacitance of the fourth detection electrode 25, the common lead line 34, and the first charge are provided between the terminals 37 and 39 of the detection unit 21. There is an electric charge accumulated in the capacitance between the lead lines 36 of the four detection electrodes 25.

  In the sensor device according to the embodiment of the present invention, the first cancel electrode 32 is connected to the lead line 28 of the second detection electrode 23 along the lead line 27 of the first detection electrode 22. A second cancel electrode 40 is disposed between the lead line 35 of the third detection electrode 24 and a third cancel electrode 42 is disposed along the lead line 36 of the fourth detection electrode 25. By inputting a signal obtained by inverting the pulse from the pulse generation circuit 51 to the cancel electrode 32, the second cancel electrode 40, and the third cancel electrode 42 through the level adjusters 52, 53, and 54, respectively, Charges accumulated between the lead line 27 of the first detection electrode 22, the common lead line 26 of the first detection electrode 22 and the second detection electrode 23, and the second detection voltage 23, the charge accumulated between the first detection electrode 22 and the common detection line 26 of the second detection electrode 23, and the extraction line 35 of the third detection electrode 24; Charge accumulated between the third detection electrode 24 and the common lead line 34 of the fourth detection electrode 25, the lead line 36 of the fourth detection electrode 25, the third detection electrode 24, The charge accumulated between the four lead electrodes 34 of the four detection electrodes 25 is canceled.

  As a result, the capacitance measured between the terminals 29 and 30, between the terminals 29 and 31, between the terminals 37 and 38, and between the terminals 37 and 39 is at the comb-shaped detection electrodes 22, 23, 24, and 25, respectively. It is only the capacitance to be measured.

  Reference numeral 55 denotes a first differential amplifier. A node voltage between the terminal 30 of the detection unit 21 and one end of the first resistor 56 is input to one terminal of the first differential amplifier 55. Similarly, one terminal of each of the second differential amplifier 57, the third differential amplifier 58, and the fourth differential amplifier 60 is connected to the terminal 31 of the detection unit 21 and one end of the second resistor 58. , The node voltage between the terminal 38 of the detection unit 21 and one end of the third resistor 59, and the node voltage between the terminal 39 and the fourth resistor 61 of the detection unit 21 are input to the + terminal. Is inputted with a threshold value from a threshold value generating means (not shown). In the embodiment of the present invention, this threshold is set to 1/4 of the power supply voltage. The other ends of the first, second, third, and fourth resistors 56, 58, 59, and 61 are connected to the first, second, third, and fourth differential amplifiers 55, 57, 58, and 60, respectively. Connect to the output side. Further, a diode and a resistor are connected in series between the input and output of each differential amplifier.

  As a result, the first detection electrode 22, the second detection electrode 23, the third detection electrode 24, and the fourth detection electrode 25 are connected to the first resistor 56, the first differential amplifier 55, and the second resistor, respectively. 58, the second differential amplifier 57, the third resistor 59, the third differential amplifier 58, the fourth resistor 61, and the fourth differential amplifier 60. At this time, a time constant determined by the interelectrode capacitance of the first detection electrode 22 and the first resistor 56 in a state where the first, third, and fourth detection electrodes 22, 24, and 25 are all outside the liquid to be measured. The time constant determined by the interelectrode capacitance of the third detection electrode 24 and the third resistor 59 and the time constant determined by the interelectrode capacitance of the fourth detection electrode 25 and the fourth resistor 61 are substantially equal. To be equal. The time constant determined by the second detection electrode 23 and the second resistor 58 in a state where both the first detection electrode 22 and the second detection electrode 23 are immersed in the liquid to be measured is the first detection value. The time constant determined by the interelectrode capacitance of the electrode 22 and the first resistor 56 is made smaller.

  Next, the output potential of the first differential amplifier 55 is compared with a threshold value from a threshold value generating means (not shown) in the first comparison means 62. Similarly, the output potential of the second differential amplifier 57, the output potential of the third differential amplifier 58, and the output potential of the fourth differential amplifier 60 are respectively compared with the second comparing means 63 comprising a comparator. The third comparing means 64 and the fourth comparing means 65 compare with the threshold value from the threshold value generating means (not shown). In the embodiment of the present invention, this threshold is set to ½ of the power supply voltage.

  Next, the output signals of the first, third and fourth comparing means 62, 64 and 65 are input to a logic circuit 66 comprising a logic element and a flip-flop. A first analog switch 67 and a second analog switch 68 that are controlled to open and close by an output signal of the logic circuit 66 are provided between the first potential 69 and the second potential 70 at the subsequent stage of the logic circuit 66. It has been. Reference numeral 71 denotes a fifth resistor having one end connected to the midpoint of the first analog switch 67 and the second analog switch 68 and the other end connected to the output terminal 72. Reference numeral 73 denotes a capacitor having one end connected to the first potential 69 and the other end connected between the fifth resistor 71 and the output terminal 72.

  The output signals of the first and second comparing means 62 and 63 are input to a logic circuit 74 composed of logic elements and flip-flops. A first analog switch 67 and a second analog switch 76 that are controlled to open and close by an output signal of the logic circuit 74 are provided between the first potential 69 and the second potential 70 at the subsequent stage of the logic circuit 74. It has been. Reference numeral 77 denotes a sixth resistor having one end connected to the midpoint of the first analog switch 75 and the second analog switch 76 and the other end connected to the output terminal 78. Reference numeral 79 denotes a capacitor having one end connected to the first potential 69 and the other end connected between the sixth resistor 77 and the output terminal 78.

  The terminals of the detection unit 21 are connected to the pulse generation circuit 51, the resistors 56, 58, 59, 61 and the like with minimum dimensions so as not to generate stray capacitance.

  The circuit operation of the sensor device according to one embodiment of the present invention will be described with reference to FIG. 4 (a), (b), (c), (d), (e), (f), (g), (h), (i), (j), (k), (l), and (m) are voltage waveforms at various parts of the sensor device. Is shown. 1 is immersed in a liquid to be measured such as engine oil in an oil pan (not shown). At this time, the first detection electrode 22 and the second detection electrode 23 are always immersed in the liquid to be measured, and the fourth detection electrode 25 is always disposed outside the liquid to be measured. The third detection electrode 24 intersects with the liquid surface to be measured, and the portion immersed in the liquid increases or decreases as the liquid level rises and falls.

In the sensor device according to the embodiment of the present invention, in the initial state (t ₀ ) before the power is turned on, electric charges are present between the first, second, third, and fourth detection electrodes 22, 23, 24, 25. Since it does not exist, the node potential between the first resistor 56 and the first detection electrode 22, the node potential between the second resistor 58 and the second detection electrode 23, the third resistor 59 and the third detection electrode 24. And the node potentials of the fourth resistor 61 and the fourth detection electrode 25 are all at the first potential 69 (V ₁ ).

When the power is turned on (t ₀ ), a pulse from the pulse generation circuit 51 is input to the terminals 29 and 37 of the detection unit 21 as shown in FIG. This pulse is differentiated by a differentiation circuit comprising the fourth resistor 61, the interelectrode capacitance of the fourth detection electrode 25 and the fourth differential amplifier 60, and the output potential of the fourth differential amplifier 60 is shown in FIG. As shown in FIG. 5B, the fourth resistor 61 and the interelectrode capacitance of the fourth detection electrode 25 are determined from the _first potential 69 (V ₁ ) toward the second potential 70 (V ₂ ). It rises exponentially with a time constant. Further, the output potential of the differentiation circuit composed of the third resistor 59, the interelectrode capacitance of the third detection electrode 24, and the third differential amplifier 58 is the first potential 69 as shown in FIG. From (V ₁ ) toward the second potential 70 (V ₂ ), it rises exponentially with a time constant determined by the third resistor 59 and the interelectrode capacitance of the third detection electrode 24. At this time, since a part of the third detection electrode 24 is in the liquid to be measured, the time constant determined by the third resistance 59 and the capacitance of the third detection electrode 24 is the fourth resistance. It becomes larger than the time constant determined by 61 and the fourth detection electrode 25. Similarly to this, the output potential of the differential circuit composed of the first resistor 56, the interelectrode capacitance of the first detection electrode 22, and the first differential amplifier 55 is the first as shown in FIG. 1 exponentially increases from a potential 69 (V ₁ ) toward a _second potential 70 (V ₂ ) with a time constant determined by the capacitance between the first resistor 56 and the first detection electrode 22. To do. At this time, since the first detection electrode 22 is always immersed in the liquid to be measured, the time constant determined by the first resistor 56 and the capacitance of the first detection electrode 22 is the third constant. It becomes larger than the time constant determined by the resistor 59 and the third detection electrode 24. Further, the output potential of the differential circuit composed of the second resistor 58, the interelectrode capacitance of the second detection electrode 23, and the second differential amplifier 57 is the first potential 69 (see FIG. 4E). From V ₁ ) to the second potential 70 (V ₂ ), it rises exponentially with a time constant determined by the second resistor 58 and the interelectrode capacitance of the second detection electrode 23. At this time, the time constant determined by the second detection electrode 23 and the second resistor 58 in a state where both the first detection electrode 22 and the second detection electrode 23 are immersed in the liquid to be measured as described above. Is smaller than the time constant determined by the interelectrode capacitance of the first detection electrode 22 and the first resistor 56.

When the output potential of the fourth differential amplifier 60 reaches a threshold voltage _Vth determined by a threshold generation means (not shown), the output of the fourth comparison means 65 comprising a comparator is shown in FIG. Thus, a transition from high to low is made (t ₁ ). Similarly, when the output potential of the third differential amplifier 58 reaches a threshold voltage _Vth determined by a threshold generation means (not shown), the output of the third comparison means 64 comprising a comparator is as shown in FIG. As shown in (g), the transition is made from high to low (t ₂ ). When the output potential of the second differential amplifier 57 reaches a threshold voltage _Vth determined by a threshold generation means (not shown), the output of the second comparison means 63 comprising a comparator is as shown in FIG. Transition from high to low as shown in (t ₃ ). Further, when the output potential of the first differential amplifier 55 reaches a threshold voltage _Vth determined by a threshold generation means (not shown), the output of the first comparison means 62 comprising a comparator is shown in FIG. Since the pulse generation from the pulse generation circuit 51 stops at the same time as transitioning from high to low as shown in FIG. 3, the first differential amplifier 55, the second differential amplifier 57, the third differential amplifier 58, The output voltage of the fourth differential amplifier 60 rises to the second potential (V ₁ ) (t ₄ ).

After that, the diodes connected between the input and output of the first differential amplifier 55, the second differential amplifier 57, the third differential amplifier 58, and the fourth differential amplifier 60 are turned on. When the output voltage of the dynamic amplifier drops rapidly and reaches the threshold potential applied to the + input of each differential amplifier, the output of each differential amplifier returns to the _first potential 69 (V ₁ ). At the same time, the outputs of the first, second, third and fourth comparing means 62, 63, 64 and 65 are changed from low to high as shown in FIGS. 4 (i), (h), (g) and (f), respectively. As shown in FIG. 4A, a pulse is generated from the pulse generation circuit 51 and input to the terminals 30 and 38 of the detection unit 21 (t ₅ ).

Thereafter, the output potentials of the first differential amplifier 55, the second differential amplifier 57, the third differential amplifier 58, and the fourth differential amplifier 60 are again the first potential 69 (t ₁ ). Toward the second potential 70 (t ₂ ), as shown in FIGS. 4D, 4E, 4C, and 4B, respectively, between the first resistor 56 and the first detection electrode 22 Capacitance, capacitance between the second resistor 58 and the second detection electrode 23, capacitance between the third resistor 59 and the third detection electrode 24, the fourth resistor 61 and the fourth detection electrode It rises exponentially with a time constant determined by the interelectrode capacitance of 25, and thereafter the same operation as in the interval from t ₀ to t ₅ is repeated.

  The output signals of the first, third, and fourth comparison means 62, 64, and 65 are input to a logic circuit 66 composed of logic elements and flip-flops. 4), a pulse signal having a pulse width from the falling edge of the pulse shown in FIG. 4 (f) to the falling edge of the pulse shown in FIG. 4 (g) is supplied to the second analog switch 68. As shown in (k), a pulse signal having a pulse width from the falling edge of the pulse shown in FIG. 4 (g) to the falling edge of the pulse shown in FIG. 4 (h) is output.

In this case, the first analog switch 67 is “closed” when the signal input to the first analog switch 67 is high, and “open” when the signal is low. The second analog switch 68 is “closed” when the signal input to the second analog switch 68 is high, and “open” when the signal is low. As a result, the first analog switch 67 is “closed” and the second analog switch 68 is “open” at times t _{1 to} t ₂ and t _{6 to} t ₇ in FIG. The capacitor 73 is charged from 70 through the fifth resistor 71. Then, during the times t _{2 to} t ₄ and t _{7 to} t ₉ in FIG. 4, the first analog switch 67 is “open” and the second analog switch 68 is “closed”. The charged charges are discharged to the _first potential 69 (V ₁ ) through the fifth resistor 71.

In addition, since the first analog switch 67 and the second analog switch 68 are both “open” at times t _{0 to} t ₁ and t _{4 to} t ₅ in FIG. Is preserved. In this way, the first analog switch 67 and the second analog switch are for a time determined by the length of the portion where the third detection electrode 24 is immersed in the liquid to be measured and the length of the portion outside the liquid to be measured. The liquid level of the liquid to be measured can be output as an analog voltage to the output terminal 72 by alternately opening and closing 68 and charging / discharging the capacitor 73.

FIG. 5 shows the case where the resistance R of the fifth resistor 71 is 500 kΩ, the capacitance C of the capacitor 73 is 100 pF, the charging time Tc is 1 μsec, and the discharging time Td is 4 μsec, that is, the ratio of Tc to Td. That is, when the ratio of the length of the portion of the third detection electrode 24 immersed in the liquid to be measured and the length of the portion outside the liquid to be measured is 1: 4, the analog output to both ends of the capacitor 73. This is a simulation of the voltage V ₀ .

As can be seen from FIG. 5, after about 500 μsec, an output voltage V ₀ in which a ripple having an amplitude of approximately ± 0.04 [V] is superimposed on a DC component of 1 [V] is obtained. Since this ripple is removed by the low-pass filter, a DC voltage representing the liquid level of the liquid to be measured is output to the output terminal 72 after a predetermined time has elapsed since the power was turned on.

  Further, the output signals of the first and second comparing means 62 and 63 are inputted to a logic circuit 74 composed of logic elements and flip-flops, and the first analog switch 75 has a signal as shown in FIG. A pulse signal having a pulse width from the falling edge of the pulse shown in FIG. 4 (i) to the falling edge of the pulse shown in FIG. 4 (h) is shown in FIG. 4 (m). Thus, a pulse signal having a pulse width from the rising edge of the pulse shown in FIG. 4 (h) to the falling edge of the pulse shown in FIG. 4 (i) is output.

In this case, the analog switch is “closed” when the signal input to each analog switch is high, and “open” when the signal is low. As a result, the first analog switch 75 is “closed” and the second analog switch 76 is “open” at times t _{3 to} t ₄ and t _{8 to} t ₉ in FIG. The capacitor 79 is charged through the sixth resistor 77 from 70. Then, during the times t _{0 to} t ₃ and t _{5 to} t ₈ in FIG. 4, the first analog switch 75 is “open” and the second analog switch 76 is “closed”. The charged charges are discharged to the _first potential 69 (V ₁ ) through the sixth resistor 77.

  In this way, the capacitance measured by the first detection electrode 22 that is always immersed in the liquid to be measured and is affected by the dielectric constant of the liquid to be measured, and the dielectric constant of the liquid to be measured The capacitor 79 is charged for a time proportional to the difference from the capacitance measured by the second detection electrode 23 that is not affected, and the capacitance measured by the first detection electrode 22. The voltage proportional to the liquid quality of the liquid to be measured can be output to the first output terminal 78 by repeating the operation of discharging the electric charge charged in the capacitor 79 for a time proportional to.

  Next, the role of the cancel electrode provided in the sensor device in one embodiment of the present invention will be further described.

  In the detection unit of the sensor device according to the embodiment of the present invention shown in FIG. 1, when the first cancel electrode 32 is not disposed, the position (crossing the third detection electrode 24 on the liquid surface of the liquid to be measured ( As the liquid level changes, and the position where the common lead line 28 and the lead line 27 of the first detection electrode 22 intersect on the liquid surface of the liquid to be measured also changes, the common lead line 28 and the first detection are detected. The capacitance generated between the lead wire 27 of the electrode 22 changes. As a result, the fall of the pulse shown in FIG. 4 (h) changes, and an error occurs in the output voltage value representing the liquid level.

  Further, when the second cancel electrode 40 is not disposed, the position (liquid level) intersecting the third detection electrode 24 on the liquid level of the liquid to be measured changes, and the common extraction on the liquid level of the liquid to be measured is performed. Since the position at which the line 26 and the lead line 28 of the second detection electrode 23 intersect also changes, the capacitance generated between the common lead line 26 and the lead line 28 of the second detection electrode 23 changes. To do. As a result, the trailing edge of the pulse shown in FIG. 4 (j) changes, and the reference for measuring the liquid quality varies, and an error occurs in the output voltage value representing the liquid quality. At the same time, the position (liquid level) intersecting the third detection electrode 24 on the liquid surface of the liquid to be measured changes, and the common lead line 34 and the third detection electrode 24 on the liquid surface of the liquid to be measured are drawn. Since the position where the line 35 intersects also changes, the capacitance generated between the common lead line 34 and the lead line 35 of the third detection electrode 24 changes. As a result, the fall of the pulse shown in FIG. 4 (j) and the fall of the pulse shown in FIG. 4 (g) change, and an error occurs in the output voltage value representing the liquid level.

  Similarly, when the third cancel electrode 42 is not disposed, the position (liquid level) intersecting the third detection electrode 24 on the liquid level of the liquid to be measured changes, and the liquid level of the liquid to be measured. Since the position where the common lead line 34 and the lead line 36 of the fourth detection electrode 25 cross each other also changes, the electrostatic force generated between the common lead line 34 and the lead line 36 of the fourth detection electrode 25 is changed. The capacity changes. As a result, the trailing edge of the pulse shown in FIG. 4 (f) changes, and an error occurs in the output voltage value representing the liquid level.

  On the other hand, in the sensor device according to the embodiment of the present invention, the first cancel electrode 32 is connected to the lead line 28 of the second detection electrode 23 along the lead line 27 of the first detection electrode 22. The third cancel electrode 40 is disposed between the third detection electrode 24 and the lead line 35 of the third detection electrode 24, and the third cancel electrode 42 is disposed along the lead line 36 of the fourth detection electrode 25. , 53, 54 to input a signal obtained by inverting the pulse from the pulse generation circuit 51, thereby canceling the electric charge accumulated between the lead lines of the detection electrodes and the common lead line. The capacitance measured between the terminals 29 and 30, between the terminals 29 and 31, between the terminals 37 and 38, and between the terminals 37 and 39 is measured with the comb-shaped detection electrodes 22, 23, 24, and 25, respectively. Capacitance Those that you are only. As a result, the capacitance of the liquid to be measured detected by each detection electrode is not affected by the liquid level of the liquid to be measured, and as a result, an output voltage value that accurately represents the liquid level and liquid quality can be obtained. .

  As is clear from the above description, the sensor device according to the embodiment of the present invention can output a voltage that is accurately proportional to the liquid level and the liquid quality without providing a complicated arithmetic device, so that it is highly accurate. This sensor can be easily provided.

  The sensor device according to the present invention can output a voltage that is accurately proportional to the liquid level and the liquid quality without providing a complicated arithmetic unit, and thus can provide a highly accurate sensor easily. It has an effect, and is particularly useful as a sensor device for detecting the level of engine oil or fuel in automobiles, construction machines and the like.

The front view of the detection part of the sensor apparatus in one embodiment of this invention Sectional drawing in the AA line of the 2nd detection electrode in FIG. Detection circuit diagram of the sensor device (A)-(m) Waveform diagram for demonstrating circuit operation | movement of the sensor apparatus The time variation of the output voltage V ₀ when the ratio of the length of the portion of the second detection electrode immersed in the liquid to be measured and the length of the portion outside the liquid to be measured in the sensor device is 1: 4 is shown. Characteristics chart Front view of detection unit of conventional sensor device Detection circuit diagram of the sensor device

21 detection unit 22 first detection electrode 23 second detection electrode 24 third detection electrode 25 fourth detection electrode 26, 34 common lead line 27, 28, 35, 36 lead line 32 first cancel electrode 40 first 2 cancel electrode 42 3rd cancel electrode

Claims (1)

The first detection electrode in the liquid to be measured is always measured from the lower part to the upper part on the detection unit standing in the vertical direction, and the capacitance between the electrodes is measured without being affected by the dielectric constant of the liquid to be measured. A second detection electrode, a third detection electrode for measuring the liquid level of the liquid to be measured, and a fourth detection electrode that is always outside the liquid to be measured are provided, and the third detection electrode is in the liquid to be measured. Charging for a time proportional to the length of the portion immersed in the electrode, and discharging the charged charge for a time proportional to the length of the third detection electrode outside the liquid to be measured. Generating a pulse for inputting a pulse to a common lead line for the first detection electrode and the second detection electrode and a common lead line for the third detection electrode and the fourth detection electrode, respectively. A circuit, and a first detection electrode and a first detection electrode; A first cancel electrode extends along a common lead line of the first detection electrode and a second detection electrode along a lead line of the first detection electrode extending along a common lead line of the first detection electrode. A second cancel electrode extends along a lead line of the second detection electrode and a lead line of the third detection electrode extends along a common lead line of the third detection electrode and the fourth detection electrode. A third cancel electrode is disposed along a lead line of the fourth detection electrode extending along a common lead line of the third detection electrode and the fourth detection electrode, respectively. By inputting a signal obtained by inverting the pulse to the first cancel electrode, the second cancel electrode, the third cancel electrode, and the fourth cancel electrode, the lead line of the first detection electrode, and the first cancel electrode, 1 detection power Between the lead wire of the second detection electrode and the common lead wire of the second detection electrode and the charge accumulated between the lead wire of the second detection electrode and the common lead wire of the second detection electrode The accumulated charge, the charge accumulated between the third detection electrode lead line and the third detection electrode common lead line and the fourth detection electrode lead line, and the fourth detection electrode lead A sensor device that cancels the electric charge accumulated between the line and the common lead line of the third detection electrode and the fourth detection electrode, respectively.

Images