JPS58501393A - Liquid level and temperature sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Liquid level and temperature sensor Technical field The present invention relates to fluid level sensors, and more particularly to electronic liquid level and humidity sensors. is related to.

Engines and drive systems may be operated with insufficient cooling, lubrication, or transmission fluids. If it is created, it may be damaged. Therefore, various fluids in engines and automobiles The tank is equipped with a liquid level sensor to detect low liquid level and communicate this status to the driver. That is convenient. In addition, the liquid level sensor is used as a fully automatic safety device. It is even more important to stop the engine from continuing to operate when the liquid level drops to a dangerous level. This is a good thing.

A typical existing safety sensor of this type is the U.S. Patent No. 2,700,153 to Huckabee Are listed. This sensor is a warning device with an engine stop function and is applied to radiators.

A pair of electrical contacts are installed at different liquid level positions in the radiator, initially at - Alerts you if a predetermined amount of coolant is lost and if further cooling occurs. When coolant leaks, the second contact completely cuts off power to the engine's starting coil and shuts off the engine. stop the engine.

Other types of liquid level sensors use thermistors. f-mister releases heat from gas When the thermistor is in contact with the body, it is less active than when the thermistor is in contact with a liquid heat sink. - It is well known that there is little heat transfer from the mister. This means that such a liquid level This is the basic concept of the detector, for example, as published by Waywood (Wa. iwood) in U.S. Patent No. 3,955,416, issued to . This device uses a resistor as a heat source adjacent to a thermistor. sir The mister is thermally coupled to the liquid to be detected, and as the liquid level rises, the thermistor The apparent heat capacity of the tank is increasing. Measuring the resistance value of the thermistor The liquid level is measured by Unfortunately, the Weyland sensor is It is also sensitive to splashing water and measures the swaying liquid level, so there are restrictions on the environment in which it can be used. Similarly, it cannot be applied to places with large vibrations, such as cars and engines.

A liquid level sensor can measure both the temperature of the liquid and detect when the liquid contacts the sensor tip. It would be beneficial to develop something that can. Also, if this sensor is robust and reliable, It would be even more beneficial if it were as simple as possible. Moshi liquid and Uses metal contacts for contact, does not require a precisely controlled heat source It would be even more beneficial if a sensor could be developed.

The present invention is intended to overcome one or more of the problems mentioned above.

Disclosure of invention A sensor according to the invention comprises first and second spatially spaced current resistive elements. These elements have temperature-dependent impedance. of these elements A device is provided for heating one side. Furthermore, the impedance difference between the two elements A signal generating device associated with the system is provided.

A sensor that can indicate when the liquid in the liquid container has fallen below a certain level, is necessary. The newly developed sensor consists of a pair of sensors that are in thermal contact with the liquid in the container. - one of these thermistors is heated. When the liquid level is above the sensor As it decreases downward, the apparent heat capacity of the thermistor being heated decreases.

Magnify the temperature difference between two thermistors. The increase in temperature difference is due to the difference in resistance value in the sensor. It is measured as. The sensor is designed so that the difference in resistance exceeds a preselected value. and output accordingly.

To aid in understanding the invention, reference is made to the accompanying drawings.

FIG. 1 is a schematic diagram of one embodiment of the present invention, which is installed in a liquid container. indicates; FIG. 2 is a detailed 11 diagram of an electronic circuit suitable for use in the present invention.

The attached drawings are not intended to limit the scope of the invention and are for illustrative purposes only. It is understood that it is a thing.

In the accompanying figures, a liquid level and temperature sensor embodying the principles of the invention is designated by the reference numeral 10. It is shown in The following detailed description of the liquid level and temperature sensor 10 is currently unknown. It will be understood that the present invention relates to the best described embodiment. Liquid level and temperature sensor Many other embodiments of the ten are possible without departing from the scope of the claims. This will be obvious to engineers skilled in this technical field.

The sensor 10 has a storage container 12, which has an outer periphery 13 and a protrusion 14. Ru. These protrusions 14 create hollow portions or gaps 16. This gap 16 may be obtained by physically removing the material of the protrusion 14, and may be a relatively highly insulating part. It is preferably fully assembled with the threaded portion 20 opened in the wall 22 of the container 24. It is made to fit together. The storage container 12 is made of a relatively inert and strong insulating material. It is preferably made of a material that can withstand the range of temperatures to which it is expected to be exposed. It is further preferred that the material from which the storage container 12 is made has a low heat capacity. It is.

The current resistance elements, such as the first and second thermistors 26 and 28, each have two protrusions. 14. These thermistors 26 and 28 are almost identical It is suitably selected to have voltage-temperature characteristics of .

Each thermistor 26, 28 has an input 30, 30' and an output 32, 32'. do. Inputs 30 and 30' supply input voltage to each thermistor 26 and 28. 34. This voltage supply means 34 includes a conductor 35 which is The thermistor inputs 30 and 30' are fully connected to the stabilized DC power supply 36. each A resistor 37 is inserted into each conductor 35. These resistors 37 are preferably sized. are combined.

A controllable heat source 38 is positioned in thermal proximity to the second thermistor 28 . system A controllable heat source 38 is also preferably located in thermal proximity to the outer periphery 13 of the sensor 10. ing. The controllable heat source 38 preferably includes a heating resistor 39 and a power source. Ru. The resistance value of the heating resistor 39 is also the same as the resistance value of the thermistor 26.28. It is kept small throughout the operating temperature range. As a result, from the heating resistor 39 The heat emitted from the thermistor 26 and 28 is also sufficiently large. Become. Thermistor 26.28 raises its own temperature by more than 92-3 degrees above the ambient temperature. It is preferable that it does not generate enough heat.

Apparatus 40 monitors the impedance of first and second impedance elements 26 and 28. and compare their impedances to find the amount that is within a predetermined range. This is a device that outputs all the signals according to the impedance difference between the thermistors and thermistors. It is electrically connected to the input 30° 30' of the terminal 26.28. This device 40 is A voltage comparator 42 is suitably included. In the submitted embodiment, voltage comparator 42 is These voltage input terminals have an output terminal 43 and output according to the voltage input of the comparator 42. The force is the voltage at the inputs 30, 30' of the thermistor 26, 28, and these Provides an output when the potential difference exceeds a preselected amount. This output is e.g. It is used to control the switch 44 which is a resistor.

Output terminal 43 of voltage comparator 42 is preferably connected to control terminal 46 of switch 44. This switch 44 also has an input terminal and an output terminal 48.50. Input power When the pressure deviation exceeds a preselected amount or set point, an output signal from comparator 42 is generated. The number can be used to drive all alarm devices, fuel cutoff devices of automobiles, etc. This is disposing the switch 44 between the alarm device or the fuel cutoff device and its power supply circuit; This can be achieved by The voltage difference between the preselected operating points is determined by the voltage difference between the sensor 10 The small difference that occurs in the output voltage of the thermistor 26 and 28 when the thermistor is immersed in liquid It must be large enough so that liquid is removed from the sensor 10. The output voltage of the comparator should be so large that it cannot exceed that value within 2-3 seconds. Nor.

The output from the first thermistor 26 is also connected to a device 41 which connects the first thermistor 2 The temperature of 6 [? it's shown.

The method of converting a known thermistor resistance value into a total temperature display is in this technology and field. well known. Since the first thermistor 26 is not heated, it indicates the correct liquid temperature. vinegar.

industrial applicability The method of use to which the present invention is best suited is to detect when the liquid level has fallen below a certain point. This is a case where it is necessary to

This cell is particularly well suited for detecting a drop in the radiator coolant level.

Liquid level sensors can also be used to detect liquids in lubrication systems, control systems, hydraulic systems, transmission systems, fuel tanks, etc. Can be used to detect temperature and low liquid level. What is important is that the liquid level and temperature sensor Performance is not significantly affected by liquid temperature or relatively rapid changes in liquid temperature. This is a point. Therefore, the liquid level and temperature sensors are rarely or never changed. It can be used for various purposes.

Normally, fluid surrounds sensor 10 when the present invention is used. The liquid is usually Having a relatively high thermal conductivity coefficient, most of the heat generated by the heating resistor 39 is Emit into liquid. Therefore, when the sensor 10 is immersed in liquid, two thermistors Ta 26 and 28 have approximately the same temperature IE. The characteristics of these thermistors are combined Since both terminals receive almost the same input voltage, the potential difference at their input terminals is The difference will be small and almost constant. This constant difference is of course caused by the second thermistor. This also depends on the fact that the tank 28 is being heated. This constant difference is almost constant even when the liquid temperature changes. It will be a certain value.

Therefore, when the probe portion of the sensor 10 is immersed in liquid, the voltage comparator 42 becomes large. Since the voltage mismatch condition will not be detected at all, the output will turn on the switch. It will be quiet. Not only the bias point of the comparator 42 but also the point where the aforementioned sensor is in contact with the liquid It is selected because of the constant capping that occurs between the thermistor outputs when the

As will be understood by those skilled in this field of technology, thermistor resistors A comparison of is obtained through the use of a voltage divider. As already mentioned, each thermistor 26.28 connects a known power source 36 to a resistor 37 and one thermistor corresponding to each phase. grounded through a series connected circuit. That is, each thermistor 26, 28 is combined with resistor 37. These resistors 37 are preferably matched. The voltage is divided between each thermistor 26° set 8 and the corresponding resistor 37. When the thermistors 26 and 28 are at the same temperature, the voltages that appear are approximately equal. There is. In this example, the comparison voltage is taken from thermistor inputs 30, 30'. However, resistor 37 is placed between thermistors 26 and 28 and the ground wire. If so, the voltage comparison is made to the thermistor output voltage. degree In either case, by using a voltage divider in this way, the phases of thermistors 26 and 28 can be adjusted. Comparison of resistance values can now be performed using the comparator 42.

When no liquid surrounds the sensor 10, the heat generated from the second resistor 39 is relatively low. It emanates slowly. As a result, the temperature of the second thermistor 28 is lower than that of the first thermistor 26. The temperature rises considerably compared to that of the previous year. Therefore, the resistance value of these thermistors 26 and 28 is As a result, the voltages at input terminals 30 and 30' are also significantly different. It's coming. This voltage difference is small at first, and when the liquid is no longer in contact with the sensor 10, It increases over time from this point. After a certain period of time, this voltage difference becomes relatively Stable at large values. The bias value of the voltage comparator is determined after the liquid is separated from the sensor 10. The voltage difference is selected to be smaller than the voltage difference reached after a short period of time, preferably 1 to 10 seconds. Ru. Voltage comparator 42 detects this condition and drives switch 44 accordingly. Outputs all signals. This switch 44 is placed in the alarm circuit or the vehicle stop circuit. There is. This signal is used to drive a warning system or vehicle stop device.

As shown in FIG. 1, sensor 10 is preferably mounted vertically. As a result, / The hook projections 14 of the hooks leave the liquid surface almost at the same time.

The liquid level and temperature sensor 10 may be modified in many ways without departing from the scope of the claimed invention. It should be noted that other structures of are possible. Other features and objects of the invention , the advantages and usage, etc. can be understood from the accompanying drawings, written content, and the scope of the attached claims. .

Submission of translation of written amendment (Special Article 1r Ugly Article 184-7, Paragraph 1) April 26, 1982 8 Commissioner of the Patent Office 1. Indication of patent application I’OT/US811011552 Title of invention Liquid level and temperature sensor 3. Patent applicant 4. Agent Address: Shin-Otemachi Building 33, 2-2-1 Otemachi, Chiyoda-ku, Tokyo 100 1 5. Date of submission of amendment: December 1981; Scope of claims t) a liquid level sensor (10) comprising: first and second thermistors (26°28) separated from each other; heating one of the first and second resistive elements (26, 28) in a continuously controlled manner; the heater (38) and the resistance of the first and second thermistors (26, 28). Continuously monitors the resistance difference between the two and detects it if it is within a predetermined range. and a device (40) for controllingly generating an output signal accordingly.

2) In the liquid level sensor (10) according to claim 1, the monitoring and signal The generator (40) generates a resistance difference between the first and second thermistors (26, 28). A liquid level sensor that outputs a signal when the liquid level exceeds a predetermined value.

3) Delete 4) In the liquid level sensor (10) according to claim 1, a controllable heater is provided. (38) is a liquid level sensor including a resistor.

5) In the liquid level sensor (10) according to claim 1, the thermistor ( 26, 28) are each connected between the ground wire and one power supply (36), and the two The thermistors (26, 28) are parallel to each other, and the thermistors (26, 28) are parallel to each other. , 28) each have a resistor (37)' connected in series with each other, and the monitoring and the signal generator (40) includes a voltage ratio converter (42) having two inputs. , one of the inputs is connected to the first thermistor (26) and its corresponding resistor (37). ), and the other input is connected to the second thermistor (28) and the second thermistor (28). A liquid level sensor connected to a connection part with a resistor (37) corresponding to the liquid level sensor.

6) In the liquid level sensor (10) according to claim 1, further comprising: and a container (12)'r containing a second thermistor (26°28), said container (12) creates a gap between the first and second thermistors (26, 28) liquid level sensor.

7) In the liquid level sensor (10) according to claim 1, the monitoring and signal The generator (40) has a voltage comparator (42) at one output (43)'. electrically connected to the comparison output (43) section and controlled by the output. and a switch (44) that is open and closed. and the switch (44) switches from one of the open and closed states to the open and closed states. In the other state of closure, the voltage comparator (42) generates a predetermined A liquid level sensor adapted to change its state depending on an output signal of magnitude. sa.

8) In the liquid level sensor (10) according to claim 1, the controllable A heater (38) is disposed close to the second thermistor (28) and is connected to the sensor. (10) further includes the input and output of the first and second thermistors (Z, 6*28). receiving a signal from one of the first and second thermistors (26, 28); Liquid level contained in a device (41) that outputs a signal that changes directly in response to a single resistance change sensor.

9) In the liquid level sensor (10) according to claim 8, the thermistor ( 26, 28) are each connected between the ground wire and one power supply (36), and the two The thermistors (26, 28) are in a row with each other, and the thermistors (26, 28) are in a row with each other. 28) each has a resistor (37)k connected in series thereto.

Country @ Survey Japanese beef

Claims (1)

[Claims] 10 Liquid level sensor (10) current resistance elements (26, 28) having a -dance; the first and second resistance elements ( 26, 28); means (38) for heating under full control; The impedance of the resistive elements (26 and 28 is monitored and the difference in impedance between them is detected) When the difference reaches a predetermined range, all output signals are generated in a controlled manner. A liquid level sensor comprising means (40) for 2) In the liquid level sensor (10) according to claim 1, the monitoring and signal The generating means (40) generates an impedance of the front first and second resistance elements (26, 28). A liquid level sensor that outputs a signal accordingly when the difference in water exceeds a predetermined value. sa. 3) In the liquid level sensor (10) according to claim 1, the first and second A liquid level sensor in which the resistance elements (26, 28) are thermistors. 4) In the liquid level sensor (10) according to claim 1, a controllable heater is provided. (38) is a liquid level sensor containing a resistor. 5) In the liquid level sensor (10) according to claim 1, the current resistance element (26, 28) are each connected between the ground wire and one power source (36), and two The two current resistance elements (26, 28) are parallel to each other, and the current resistance elements (26, 28) each have a resistor (37) connected in series with the The monitoring and signal generation means (40) include a voltage comparator (42) with two inputs. One of the inputs is connected to the first current resistance element (26) and the corresponding resistor (26). 37), and the other input is connected to the second current resistance element (26). and the corresponding resistor (37). 6) In the liquid level sensor (10) according to claim 1, further comprising: and a second resistance element (26°28); A liquid level sensor which creates a gap (16) v between the first and second resistance elements (26, 28) Nsa. 7) In the liquid level station (10) according to claim 1, the monitoring and signal The generator (40) comprises a voltage comparator (42) having one output (43) and said electrically connected at the comparator output (43) and controlled by said output. and a switch (44) that is open and closed. and the switch (44) switches from one of the open and closed states to the open and closed states. The voltage comparator (42) generates a predetermined signal in the other state of closed and closed. A liquid level sensor adapted to change its state in response to an output signal of a given magnitude. Nsa. 8) Range of a request In the liquid level sensor (1o) according to item 1, the controllable A heating element (38) is arranged close to the second resistance element (28) and is arranged close to the second resistance element (28). 10) further includes one of the input and output of the first and second resistance elements (26°28). receiving a signal from one of the first and second resistive elements (26, 28); means (41) for outputting a signal that changes directly in response to a change in impedance; position sensor. 9) In the liquid level sensor (1o) according to claim 8, the current resistance element (26, 28) are each connected between the ground wire and one power source (36), and two The two current resistance elements (26, 28) are parallel to each other, and the resistance elements (26, 28) are parallel to each other. , 28) each having a resistor (37)'t- connected in series with each other. Nsa. 10) A liquid level sensor (10) comprising: Storage container (12) and: first and second electrical resistance elements (26, 28) housed in the storage container (12); ), the resistance values of the first and second resistance elements (26, 28) are temperature dependent. , said first and second having inputs (30, 30') and outputs (32, 32'). electrical resistance elements (26, 28); A heater that heats the first and second resistance elements (26, 28) while controlling the blade metal. (38) and; one power source (36); Two sets of resistors (37) are connected in series with each of the resistive elements (26, 28). The combinations of resistors and resistance elements (37, 26) and (37, 28) are connected in parallel with each other. Moreover, each of them was connected between the power supply (36) and the ground wire. a resistor (37); and a resistor (37); Compare the voltage at the connection point with the resistor (37) and set it within a predetermined range. means for outputting a predetermined output signal in response to the difference between said voltages within the (40) A liquid level sensor comprising: 11) In the liquid level sensor (1o) according to claim 10, further comprising: and a second state, said switch (44) having said comparison state. and the output (43) of the signal generating means (40), said predetermined When it receives all output signals, it switches from one of the states to the other. Liquid level sensor adapted to. JDt■