JPS6039510A - Liquid level detecting element - Google Patents

Abstract

PURPOSE:To detect a liquid level with good responsiveness in a wide range of temp. to be used by covering a heater, a temp. measuring element and a prescribed part of a conductor passage with a ceramic convering layer adhered closely to an electrical insulator ceramic. CONSTITUTION:The heater 7, the conductor passage 3, a power source voltage terminal 4, a signal voltage terminal 5 and an earthing terminal 6 are printed on an alumina green sheet 13 by a screen printing method. After said sheet is dried at 80 deg.C for 10min, an alumina paste layer 15 is screen printed to leave pier holes 14, 14' and dried. Said layer is again subjected to screen printing and drying. Next, electrodes 2-2''' are printed, and said holes are filled with conductor paste. After the drying, said sheet is calcined at 1,400 deg.C in hydrogen atmosphere, a thermister thin film 17 as temp. measuring element and said film 17' as temp. compensating element are formed by sputtering on a calcination body 16. An almina paste layer 15' as the ceramic covering layer is printed, calcined again at 1,400 deg.C in hydrogen atmosphere to obtain a liquid level detecting element.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid level detection element that has good responsiveness in detecting the liquid level of a conductive or insulating liquid over a wide operating temperature range and has a long life.

Conventionally, liquid level detection elements that detect the liquid level by utilizing the temperature difference caused by the difference in heat dissipation coefficients in liquid and gas have been widely known. There is an IT system that detects changes in electrical resistance due to the difference in heat radiation coefficients between air and liquid by directly contacting the liquid. However, conventional elements that directly contact the thermistor with liquid may cause corrosion of the thermistor,
The change over time due to impurity adhesion, abrasion, etc. is large, and it cannot be used to detect the level of conductive liquid.

The present invention was made to solve these drawbacks, and its purpose is to detect the level of liquid with good responsiveness and stability over a long period of time, regardless of whether it is conductive or insulating, over a wide range of operating temperatures. That is.

A second object of the present invention is to perform continuous or stepwise liquid level detection on lljl stools.

That is, the first aspect of the present invention comprises an electrically insulating ceramic body, a heater provided in close contact with the electrically insulating ceramic body, a temperature measuring element provided adjacent to the heater G, and the heater. A conductive path connected to the temperature measuring element, and a ceramic coating layer that covers a predetermined portion of the conductive path, the heater, and the temperature measuring element and is in close contact with at least a portion of the electrically insulating gelatinous body. A second invention is a liquid level detection element comprising: an electrically insulating ceramic body; at least one pair of a temperature measuring element and a temperature compensating element having mutually similar temperature characteristics; and a liquid level detecting element connected to each of the elements. A liquid m1 detection element comprising a conductor path and a ceramic coating layer that covers at least the entirety of the temperature measuring element and a portion of the conductor path and is in close contact with at least a portion of the electrically insulating ceramic body. be.

The details of the invention will be explained below.

First, the first invention is based on the principle of detecting the liquid level by outputting the temperature difference that occurs in a temperature measuring element heated by a heater as a voltage or current difference due to the difference in heat radiation coefficients between liquid and gas. It is something.

Therefore, in the present invention, an electrically insulating ceramic body,
It is preferable that each constituent material of the liquid level detection element, such as the ceramic coating layer, has thermal shock resistance, and the heater and temperature measurement element should be in close contact as much as possible to the extent that electrical insulation is guaranteed. preferable. That is, the temperature measuring element may be provided on the electrically insulating ceramic body on which the heater is provided, close to the heater, or may be provided on the heater with an electrically insulating material interposed therebetween. Further, since the heater provided in the electrically insulating ceramic body heats the temperature measuring element, it is preferable that the electrically insulating ceramic body is made of a material with good thermal conductivity and has a structure with low thermal resistance. The heater may be provided in close contact with the surface of the electrically insulating ceramic body, or may be provided within the electrically insulating ceramic body.

The ceramic coating layer that covers the temperature measurement element, the heater, and a predetermined portion of the conductor path electrically insulates the temperature measurement element and the detection liquid from either conductive or insulating detection liquid, and Constructed from corrosion-resistant material. Further, it is preferable that this ceramic coating layer has excellent thermal conductivity and low thermal resistance like the electrically insulating ceramic body described above. The ceramic coating layer is provided to prevent the temperature measuring element and the heater from coming into contact with the detection liquid, and therefore needs to be sealed to at least a portion of the electrically insulating ceramic body. In order to achieve low thermal resistance and miniaturization, a two-layer ceramic coating layer should be used to tightly bond the temperature measuring element and heater provided on the electrically insulating ceramic body to a part of the conductor path connected to them. It is preferable to coat with As the temperature sensing element, a temperature sensing element such as a thermistor or a semiconductor may be used, and one formed by a printing method, sputtering vapor deposition, etc. or an individual component may be used. In addition, in order to detect each level of the liquid level in stages, a plurality of temperature measuring elements are used. In this case, it is preferable to provide a plurality of temperature measuring elements in a straight line. It is preferable that the liquid level detecting element is provided at a distance of 5 mm or more from the tip of the liquid level detection element, that is, the end of the electrically insulating ceramic body covered with the ceramic coating layer on the side of the liquid surface to be detected. The reason for this is that when the tip of the liquid level detection element is exposed to air from the liquid level,
This is because if a droplet remains at the tip of the liquid level detection element, it will interfere with the temperature rise of the temperature measurement element and cause a delay in response time.

In addition, in order to prevent detection liquid droplets from remaining on the detection element surface or to prevent impurities in the detection liquid from adhering to the detection element surface, a glaze may be applied to the surface of the liquid level detection element of the present invention. Glass, plastic, etc. may be coated.

In order to apply the liquid level detection element of the present invention to liquids in a wide temperature range, it is preferable to provide the humidity compensation element on the electrically insulating ceramic body or ceramic coating layer in a portion not affected by the heat of the heater. Note that the temperature characteristics of this temperature compensating element regarding resistance, potential difference, electromotive force, etc. are preferably similar to the temperature characteristics of the temperature measuring element.

Next, the second invention of the present invention will be explained. The difference from the first invention is that the function of the heater of the first invention is achieved by self-heating of the temperature measuring element. , the other configurations and objects are almost the same as the first invention, so details will be omitted.

Embodiments of the present invention will be described using FIGS. 1 to 18.

As shown in Fig. 1 (Ca), electrodes 2, 2', conductor path 8, power supply voltage terminal 4, signal voltage Terminals 5 and ground terminals 6 were printed, dried, and then fired at 850°C in the atmosphere. Similarly, the heater 7 was printed using a ruthenium oxide resistor paste, dried, and then fired at 850° C. in the atmosphere. Next, a thermistor chip 8 as a temperature measuring element is soldered with silver to the electrodes 2, 2/, and a B layer is placed on the alumina porcelain plate 1' as a ceramic layer M.
aO-PbO-Sin, -ZrO2 glass powder, acrylic resin powder and terpineol at 20-1:10
Apply the paste mixed in a weight ratio of 10 at 80°C.
After drying for a few minutes, the layers were stacked and fired at 850°C in the atmosphere. In this liquid level detection element, the end face of the thermistor chip is provided at a distance of Qmtqg from the tip of the detection element.

An electrical connection method between the heater of the liquid level detection element and the temperature measurement element is shown in FIG. 1(b). The resistance of the heater 7 shown in FIG. 1 (bl) was 80Ω, the resistance of the thermistor 11 was 810Ω at 25°C, and the thermistor constant was 4500.

The electrically insulating ceramic body of the present invention is shown in FIG.
It is not limited to the alumina porcelain plate, but electrically insulating ceramic materials with high thermal conductivity such as zirconia, silicon nitride, silica, mullite, beryllia, cordierite, crystallized glass, and lath are preferable. A fired body or green sheet of a ceramic material can be used, and furthermore, an electrically insulating ceramic material screen-printed on the fired body or green sheet, or a method using a vapor deposition method, a sputtering method, an ion-blating method, or A thin film of electrically insulating ceramic material formed by CVD or the like can be used.

The heater material of the present invention is not limited to the yttrium oxide shown in FIG.
Metals or whole family compounds such as polides, rare earth borides, nichrome, and tungsten carbide are preferred; for example, these metals or compounds are made into a paste,
Alternatively, a thick film forming method in which a mixture of powders of these metals or compounds and powders of the electrically insulating ceramic material is made into a paste and screen printed, or a vacuum evaporation method, an ion plating method, or a sputtering method, C
The heater of the present invention is formed by a thin film forming method such as a VD method. The capacity of the heater is preferably 10 mW to IOW.

In addition to the 11th m(a+) thermistor chip, the temperature measuring element of the present invention may include, for example, In, Co, Ni,
Oxides of transition metals such as Fe or SiOr Ti0B
A thermistor made of a sintered body such as BaTi0.
or (Ba, Sr) Tie, or (Ba
+pb) Positive temperature coefficient thermistor made of a sintered body such as T108 or O made of a sintered body of vanadium oxide
Temperature-sensitive semiconductors with large temperature resistance changes such as TR, or S
Intrinsic semiconductors used without adding large amounts of impurities such as i, Ge, GaAS, lCd5, ZnO, etc., or junction elements such as diodes or transistors using semiconductors such as Si, GaAs, or copper-constantan, iron-constantan, chromel -Alumel, chromel-constantan, etc. thermocouples are preferred.

These temperature measuring element materials can be made into chips or pastes and formed by a screen printing method, a vacuum evaporation method, a sputtering method, an ion plating method, a CVD method, or the like.

In addition to the silver-plated radium shown in FIG.
Preferably, it is formed by screen printing a paste of nickel or the like, or by vacuum deposition, sputtering, ion plating, or CVD.

The ceramic coating layer of the present invention is shown in Fig. 1 (in addition to Kawa's alumina porcelain plate), a ceramic plate coated with paste glass on the contact surface with the electrically insulating ceramic body, or a ceramic plate coated with a screened ceramic material. Preferred are printed films, ceramic green sheets thereof, or ceramic thin films formed by vapor deposition, ion plating, sputtering, or CVD.The thickness of the ceramic coating layer is 1 μ to 1 m. preferable.

In addition, in the present invention, the electrical connection method between the heater and the temperature measuring element may be the one-terminal common method or the two-voltage terminal method as shown in Section 1, the parallel method shown in FIG. A completely independent wiring method as shown in FIG. 4 or a method of dividing the voltage of the semiconductor element using a heater as shown in FIG. 4 is preferable and can be selected and used.

Apply voltage 12V1 using the liquid level detection element of Fig. 1 fal.
Figure 5(a) shows the measurement circuit when water surface was detected at 25°C with a voltage dividing resistor of 100KQ, and Figure 5(b) shows the response results. .7v and the gas detection voltage is set to 8.7■, the results in Figure 5+b) show that the temperature sensing element is in the gas and the output voltage is constant at 0.8v, but the temperature sensing element is in the liquid. The time it takes for the output voltage to immediately rise and reach 8.7 cm corresponds to the liquid detection response time.

Next, when the temperature measuring element is in the liquid and the output voltage is saturated at 6.6V, when the temperature measuring element is introduced into the gas, the output voltage immediately decreases to 3.7V. Corresponds to detection response time. Therefore, the response time for liquid detection is approximately 0.7 seconds and the response time for gas detection is approximately 5 seconds, providing excellent responsiveness.In particular, the response time for gas detection is extremely short compared to conventional liquid level detection elements, making it suitable for temperature measurement elements. The feature of the present invention in which the heater is connected instantaneously has been clarified.

Furthermore, since the detection element is required to have thermal shock resistance in order to perform detection with an extremely short response time, the results shown in Figure 5 (bl) indicate that the liquid level detection element of the present invention has excellent thermal shock resistance. Something also became clear.

Further, in the liquid level detection element of the present invention, a temperature compensation element having temperature characteristics similar to that of the temperature measurement element is provided in close proximity to the electrically bonded ceramic body and at a position substantially unaffected by the heater. An example in which liquid level detection was performed with good responsiveness over a wide operating temperature range will be described next. That is, the 6th E2
4, a resistor made of 50% by weight of tungsten powder, 20% by weight of alumina powder, 3.5% by weight of ethyl cellulose, and 26.5% by weight of tetralin was fabricated by screen printing on an 800 micron thick alumina green sheet 18. The heater 7 was made of body paste, and 67.5% by weight of tungsten powder, 7.5% by weight of mixed powder consisting of alumina:silica:calcia with a heavy forging ratio of 45:a:2, 3.5% by weight of ethyl cellulose, and 21% by weight of tetralin.
The conductor tracks 3, the supply voltage terminals 4, the signal voltage terminals 5 and the ground terminals 6 are printed with a conductor paste consisting of 5% by weight. 8
After drying for 10 minutes at 0°C, the alumina paste layer 15 was screen printed leaving the pier holes 14, 14', dried, screen printed again and dried to give a 20 micron thick layer.

Next, the electrodes 2, 2', 2',
2'' was printed, and the peer holes were filled with conductor paste. After drying, the fired body 16 was fired in a hydrogen atmosphere at 1400°C to obtain a fired body 16 as an electrically insulating ceramic body. A thermistor # film 17 made of SiC as a temperature element and a thermistor thin frame 17' made of SiO as a temperature compensation element are formed by sputtering, and an alumina paste layer 15' having the same composition as the alumina paste layer 15 is formed as a ceramic coating layer. 20 microns and baked again at 14oC in a hydrogen atmosphere to obtain a liquid level detection element.However, as shown in Fig. 6, the thermistor thin film 17 was placed 5111 #I away from the tip of the liquid level detection element. The measurement circuit used to detect the water surface with an applied voltage of 12V using this liquid level detection element is shown in Fig. 1al, and the response results at 25°C are shown in Fig. 7fb). The solid line shows the response results at 100″C in Figure 7 I′.
Indicated by the dashed line in b). The resistance of the thermistor of the temperature measuring element shown in Figure 7 (ta) is 470 KQ at 25°C, the thermistor constant is 8000, and the resistance of the thermistor of the temperature compensation element is 100Ω at 25°C, the thermistor constant is 8000.
It was K. As shown in FIG. 7(b), the liquid detection voltage is set to 4. OV.

Gas detection voltage 4. If Ov, the liquid detection response time when the temperature sensor comes into contact with liquid from gas is 25°C.
When the output voltage is saturated, the gas detection response time is approximately 0.4 seconds at 25℃, and approximately 0.1 seconds at 100℃. It will be 0.6 seconds,
It had excellent responsiveness and was able to detect the same detection voltage even under conditions where the temperature was significantly different. Further, no deterioration was observed even after the tip of this detection element was immersed in water at 120'C for 1000 hours.

Note that the material for the temperature compensation element of the present invention can be the same as that of the temperature measuring element, and the heater and temperature measuring element of the present invention may both have the same total weight as shown in No. 11yJ, for example. A structure in which either the heater and the temperature measuring element are placed side by side on the surface of the electrically insulating ceramic body, or as shown in FIG. Further, the present invention may be preferably used by taking the following? The electrical connection method of the 1I11 element and the temperature compensation element is a series connection as shown in FIG. 8, a parallel connection as shown in FIG. 9, or a 10. As shown in the figure, these can be made part of a bridge circuit, or the
As shown in Figure 1, two independent wiring methods can be selected and used.
Figure 2 (a), (shown in bl).

That is, on an alumina-silica ceramic green sheet 2° serving as an electrically insulating ceramic body, a heater 7 is formed using a ruthenium oxide resistor paste using a screen printing method, and an electrode 2, a conductor path 8, and a terminal 4 are formed using a silver palladium conductor paste. , 5.6 was printed. Next, after drying at 80"C, manganese-cobalt-nickel based thermistor pastes 21 and 21' were printed. After drying, ceramic green sheets 20 and 20' were laminated by thermocompression bonding, and then wrapped around a metal rod. A cylindrical green sheet laminate 22 was prepared and fired at 900° C. in the atmosphere.As described above, the liquid level detection element of the present invention preferably has a plate-like, rod-like, or tubular shape.

Further, in the liquid level detection element of the present invention, by arranging the plurality of temperature measuring elements adjacent to the heater substantially in a straight line, it is possible to detect the liquid level in stages, and it can be used more preferably. A specific example thereof is shown in FIG. 18 Ca). 1st
Figure 3 (Figure 18 Ca) shows how to electrically connect multiple temperature measuring elements in the al liquid level detection element, and Figure 18 ('b) shows how to electrically connect multiple temperature measuring elements. In addition to the series connection as shown, there is a method of taking out any element terminal of the series connection as shown in Fig. 14, or a method of taking out all multiple terminals by making one end of all the elements common as shown in Fig. 15, or these methods. A combination etc. can be used.

Further, FIG. 16 shows a specific example in which the temperature measuring element is set to a predetermined length so that the liquid level can be detected continuously according to the change in the liquid level. That is, the liquid level detection element of the present invention shown in FIG. 16 includes the thermistor thin film 17 made of SiC shown in FIG.
17', a thermistor paste 21 of a predetermined length
, 21' was screen printed, and after drying, 850
℃, and the fired body 16 and the alumina porcelain plate 1 were sealed with glass in the same manner as in the embodiment shown in FIG.

Further, FIG. 17 shows a specific example in which a self-heating type temperature measuring element is used without placing a heater adjacent to the temperature measuring element.

That is, the electrode 2, the conductor path 8, and the terminals 4, 5.6 are printed with silver-palladium conductor paste by the liquid level detection and clean printing method of the present invention shown in FIG. 17, and after drying, manganese-cobalt-nickel series thermistor paste 21,
21', and further printed N24 (the paste of the crystallized glass with a thickness of 80 μm after drying), and after drying, 85 μm in the atmosphere.
It was fired at 0'C.

Next, the effect of the distance between the tip of the liquid level detection element and the jl temperature element on the response will be explained. That is, Fig. 1 1ω
Using the liquid level detection element shown in Figure 1, which has a 1° l construction and in which only v+va from the tip of the detection element to the thermistor chip has been changed from 2 bars to 6 bars, the measurement circuit shown in Figure 1 υ is used. Applied voltage 12v1 voltage divided by resistance 100Ω at 25°C
Figure 18 shows the results of responsiveness when water surface detection was performed. Based on this result, when the liquid detection voltage is set to L7V and the gas detection voltage is set to 3.7■, the liquid detection response time is approximately 0.
．． 7 seconds, and the gas detection response time is approximately 3 seconds, which is a significant improvement over the device shown in Figure 1) in terms of gas detection response time. An electrically insulating ceramic body is used, a heater, a temperature measuring element provided adjacent to the heater, and a predetermined portion of a conductor path connected to these are covered with a ceramic coating layer, and the electrically insulating ceramic body is coated with a ceramic coating layer. By closely adhering the liquid to the ceramic coating layer, liquid level detection can be performed with good responsiveness over a wide operating temperature range, regardless of whether the liquid to be detected is conductive or insulating. It is useful for detecting the liquid level of coolant in various devices, the water level of washing machines, etc., and the present invention is an industrially extremely advantageous liquid level detection element.

[Brief explanation of drawings]

Figure 1 (al is an explanatory diagram showing the developed structure of one specific side of the liquid level detection element of the present invention, Figure 1 I'b), Figures 2 to 4
The figures are explanatory diagrams showing the electrical connection between the heater and the temperature measuring element of the present invention, respectively, and Figures 5(a) and 5fbl are the measurement circuit and liquid level of one embodiment of the liquid level detection element of the present invention. An explanatory diagram showing the response measurement results in detection, FIG. 6 is an explanatory diagram showing the expanded structure of the liquid level detection element of the present invention on the body side,
Fig. 7('b) is an explanatory diagram showing the measurement circuit of one embodiment of the liquid level detection element of the present invention and the response measurement results in liquid level detection, and Figs. Explanatory diagram showing the electrical connection method between the temperature measuring element and the temperature compensating element, No. 12
FIG. 12(a) is an explanatory diagram showing the developed structure of the liquid level detecting element of the present invention on the one-body side, and FIG. 12('b) is an explanatory diagram showing the cross section of another concrete side of the liquid level detecting element of the present invention. , Figure 13(a)
18(b), 14, and 15 are explanatory diagrams showing the developed structure of the liquid level detecting element of the present invention on the side of another detector, and FIG. 18(b), FIG. 14, and FIG. FIGS. 16 and 17 are explanatory diagrams showing the expanded structure of the liquid level detection element of the present invention on the one side, respectively. It is an explanatory view showing a response measurement result in surface detection. 1.1'...Alumina porcelain plate, 2, 2', 2',
2"...Electrode, 8...Conductor path, 4...Power supply voltage terminal, 5, 5', 5', 5"...Signal voltage terminal,
6... Ground terminal, 7, 7'... Heater 1.8, 8
'...Thermistor chip, 9. ...DC! source, 1'0
, 10'... voltage dividing resistor, 11, 11', 11', 1
11... Temperature measuring element, 12.12'... Reference terminal, 1
8...Alumina green sheet, 14.14'...
- Pier hole, 15, 15'... Alumina paste layer, 16... Sintered body, 17.17'... Thermistor thin film, 18... Temperature compensation element, 19... Voltage dividing terminal, 20. 20'... Alumina/silica ceramic green sea), 21.21'... Manganese/cobalt/nickel based thermistor paste, 22... Green sheet laminate, 28... Crystallized glass plate, 24...・Crystallized glass paste layer. Patent Applicant: Nippon Insulators Co., Ltd. Figure 1 (bo) (a) Figure 6-114' Figure 7 (b) aq Maggen Figure 8 Figure 1O Figure 11 Figure 12 (b) (b) Figure 17 Figure 18 Time (e) Procedural amendment August 28, 1980, case description 1982 Patent Application No. 1471i6B 5゜6゜7゜1, page 2 of the specification, lines 15 to 15 In line 16, "liquid level in a wide operating temperature range" is changed to "the liquid level detection element that detects the liquid level, and more importantly, in a wide operating temperature range."
I am corrected. 2. In the first line of page 12, "Semiconductor elements with heaters" should be
I am corrected by saying, ``Tunyuan tun pressure with a heater.''

Claims (1)

[Scope of Claims] L An electrically insulating ceramic body, a heater provided in close contact with the electrically insulating ceramic body, a temperature measuring element provided in instantaneous contact with the heater, and the heater and the temperature measuring element. and a ceramic coating layer that covers a predetermined portion of the conductor path, the heater, and the temperature measuring element and is in close contact with at least a portion of the electrically insulating ceramic body. Characteristic Liquid Level Detection Element-2 The liquid level detection element according to claim 1, wherein a humidity compensation element having temperature characteristics similar to the temperature measurement element is provided at a position not affected by the heater. . & The liquid level detection element according to claim 1 or 2, wherein a plurality of temperature measurement elements are arranged in a straight line. 4. An electrically insulating ceramic body, at least one pair of a temperature measuring element and a temperature compensation element having mutually similar temperature characteristics, a conductor path connected to each of the elements, and at least the entirety of the temperature measuring element and the conductor. 1. A liquid level detection element comprising: a ceramic covering m/1 which covers a portion of the channel and is in close contact with at least a portion of the electrically insulating ceramic body. 6. The liquid level detection element according to claim vJJ, paragraph 4, in which a plurality of temperature measurement elements are arranged in a straight line. a The distance between the tip of the liquid level detection element and the temperature measurement element is 5 rn
+... The liquid level detection element according to claim 1, 2, or 4, which is above.