JPH03199971A - Sensor for detecting clogging of filter - Google Patents

Abstract

PURPOSE:To make it possible to detect the contaminated degree of a filter safely with a compact and inexpensive device by detecting the strength of the air stream passing the filter based on the temperature change in a thin-film- resistor temperature sensor for a heater which is formed on a board. CONSTITUTION:A thin-film-resistor temperature sensor 14 for a heater, a thin- film-resistor temperature sensor 16 for measuring the temperature of fluid and a detecting circuit 18 for connecting the sensors are formed on a board 12 by printing and the like, and a filter-clogging detecting sensor 10 is constituted. When the sensor 14 is conducted and heated to about 50 deg.C, air which has passed through a dust collecting filter comes into contact with the sensor 10, and the heat in the sensor 14 is removed. Since the resistance value of the sensor 14 is changed, an operation amplifier 26 in the circuit 18 outputs the signal corre sponding to the change in resistance value. Thus, the strength of the air stream after the passing of the filer is measured, and the contamination degree and the clogging state in the dust collecting filter can be found. Furthermore, the sensor 16 is used for correcting the measuring error of a wind speed caused by the difference in air temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a filter clogging detection sensor, and particularly to a filter clogging detection sensor used for detecting the degree of contamination of a dust collection filter of an air conditioner. Regarding sensors.

(Prior Art) Dust collection filters are used in devices that breathe in air, such as near conditioners.

Such dust collection filters become dirty and clogged with dust in the air, resulting in a decline in their functionality. Therefore, it is necessary to inform the user when to clean the filter.

Some systems have been adopted in which a timer or the like is used to notify the user when it is time to clean the filter by using a lamp or the like after a certain period of time has elapsed since the filter was removed.

(Problems to be Solved by the Invention) However, in such a system, it is not possible to take measures according to the usage environment, such as the amount of dust in the air. In order to instruct the appropriate time to clean the filter according to the usage environment, a sensor that detects filter clogging is required. As such a sensor, for example, a method of detecting changes in airflow due to clogging using a thermal type wind speed sensor or the like can be considered. However, conventional hot-wire type wind speed sensors reach high temperatures, which poses a risk of fire. Additionally, there is a risk of explosion if there is flammable gas. Furthermore, conventional hot wire type wind speed sensors are large and expensive.

Thus, no sensor has appeared that can be installed safely and at low cost in a narrow space.

Therefore, the main object of the present invention is to provide a filter clogging detection sensor that can be installed safely and at low cost in a narrow space and can detect the degree of dirt on a filter.

(Means for Solving the Problems) The present invention includes a substrate, a thin film resistance temperature sensor for a heater formed on the substrate, a thin film resistance temperature sensor for measuring fluid temperature formed on the substrate or another substrate, The detection circuit includes a detection circuit formed on a substrate or a separate substrate to which a thin film resistance temperature sensor for a heater and a thin film resistance temperature sensor for measuring fluid temperature are connected, and detects the strength of the airflow downstream of the dust collection filter. This is a filter clogging detection sensor for this purpose.

(Function) A thin film resistance temperature sensor for a heater is made to generate heat to about 50° C. by passing an electric current through it. When the thin film resistance temperature sensor for the heater generates heat and its temperature changes due to the airflow,
Its resistance value changes. This change in resistance value is detected by a detection circuit, thereby detecting the strength of the airflow passing through the filter. At this time, the temperature of the air is measured by a thin film resistance temperature sensor for measuring fluid temperature, and measurement errors due to the temperature of the air are corrected.

(Effects of the Invention) According to the present invention, the strength of the airflow passing through the filter is detected. Therefore, by detecting that the strength of the airflow has decreased, it is possible to know how dirty or clogged the filter is.

Therefore, it is possible to take measures according to the usage environment, such as the amount of dust in the air, and to clean the filter at an appropriate time.

Furthermore, since a thin film type is used as the resistance temperature sensor for the heater, it only needs to be heated to about 50° C., and there is no risk of fire or explosion.

In addition, thin film type temperature sensors can be formed by printing on b (IJ) and are cheaper than hot wire type temperature sensors.Furthermore, they can be smaller than hot wire type temperature sensors. Therefore, a wind speed sensor using a thin film type temperature sensor can be installed in a narrow place, and is useful as a filter clogging detection sensor for near conditioners and the like.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

(Embodiment) FIG. 1 is a plan view showing an embodiment of the present invention. This filter clogging detection sensor IO includes a substrate 12. On the substrate 12, a heater thin film resistance temperature sensor 14 and a fluid temperature measurement thin film resistance temperature sensor 6 are formed by, for example, printing.

Further, a detection circuit 18 is formed on the substrate 12 by, for example, printing. As this detection circuit 18, for example, a constant temperature circuit as shown in FIG. 2 is formed. This detection circuit 18 includes a bridge circuit 20. The bridge circuit 20 includes a heater thin film resistance temperature sensor 14. Thin film resistance temperature sensor for fluid temperature measurement 16. It is formed by a resistor 22 and a resistor 24. The output of this bridge circuit 20 is
It is input to the operational amplifier 26. The output terminal of operational amplifier 26 is connected to the base of transistor 28.

Further, the collector of the transistor 28 is connected to the power supply vCc, and the output from the emitter of the transistor 28 is fed back to the bridge circuit 20.

It is also conceivable that the thin film resistance temperature sensor 14 for the heater, the thin film resistance temperature sensor 16 for fluid temperature measurement, and the detection circuit 18 be formed on separate substrates and integrated by bonding or the like.

This filter clogging detection sensor lO is, for example, a third
As shown in the figure, it is installed after the dust collection filter 32 of the near conditioner 30. At this time, a current is passed through the heater thin film resistance temperature sensor 14, and the heater thin film resistance temperature sensor 14 is heated to about 50°C. The air that has passed through the dust collection filter 32 is sent to the filter clogging detection sensor 1.
Touch 0. At this time, the heat of the heater thin film resistance temperature sensor 14 is removed. As a result, the resistance value of the thin film resistance temperature sensor 14 for the heater changes, and a signal corresponding to the change in the resistance value of the thin film resistance temperature sensor 14 for the heater is output from the output side of the operational amplifier 26.

In this way, the strength of the airflow after passing through the dust filter 32 is measured. Note that the temperature of the air is measured by the thin film resistance temperature sensor 16 for measuring fluid temperature, and errors in measurement of wind speed due to differences in air temperature are corrected.

When the temperature of the heater thin film resistance temperature sensor 14 falls, the transistor 28 is turned on by the output of the operational amplifier 26, which works to prevent the temperature of the heater thin film resistance temperature sensor 14 from changing.

In this filter clogging detection sensor 10, thin film type sensors are used as the two temperature sensors 14 and 16, so they are smaller and have a faster response speed than hot wire type sensors. Furthermore, since the two temperature sensors 14 and 16 and the detection circuit 18 are formed close to each other on one substrate 12, they are less susceptible to noise and the like. Further, the heater thin film resistance temperature sensor 14 only needs to be heated to about 50° C., and does not need to be heated to a high temperature unlike wire-wound type, thermistor type, transistor type, etc. Therefore, there is less fear of a fire occurring.

Based on these facts, this filter clogging detection sensor 1
By using 0, it can be easily attached to a near conditioner, etc., and safe and reliable wind speed measurement is possible. Therefore, by measuring the strength of the airflow that has passed through the dust collection filter 32, the clogged state of the filter can be accurately detected, and the filter can be cleaned in accordance with the usage environment.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention. FIG. 2 is a circuit diagram showing a detection circuit of the filter clogging detection sensor shown in FIG. 1. FIG. 3 is an illustrative view showing a state in which the filter clogging detection sensor shown in FIG. 1 is attached to a near conditioner. In the figure, 10 is a filter clogging detection sensor, 12
14 is a thin film resistance temperature sensor for a heater, 16 is a thin film resistance temperature sensor for measuring fluid temperature, and 18 is a detection circuit.

Claims (1)

[Scope of Claims] A substrate, a thin film resistance temperature sensor for a heater formed on the substrate, a thin film resistance temperature sensor for measuring fluid temperature formed on the substrate or another substrate, and a thin film resistance temperature sensor formed on the substrate or another substrate. and includes a detection circuit connected to the heater thin film resistance temperature sensor and the fluid temperature measurement thin film resistance temperature sensor, and a filter eye for detecting the strength of the airflow downstream of the dust collection filter. Clogging detection sensor.