JP4804150B2 - Thermal conductivity type gas sensor - Google Patents

Description

  The present invention relates to a thermal conductivity gas sensor that detects a gas concentration based on a difference in thermal conductivity, and more particularly to a thermal conductivity gas sensor that includes a temperature compensation element.

  As shown in FIG. 5, the gas sensor that detects the component and concentration of the gas based on the apparent thermal conductivity minimizes the error due to the temperature change of the gas. A substrate D, such as a circuit board, is placed as close as possible to the tensioned gas sensor A and a temperature compensating element C configured to be housed in a sealing cap B and insulated from the test gas. The resistance difference between the two heater wires R and R is detected by being fixed to.

  However, when the temperature of the environment changes at a constant speed from a reference temperature, for example, 20 ° C., the temperature compensating element B having the hermetic cap is less affected by the temperature of the environment. An error signal is generated as indicated by the dotted line 5.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a heat conduction type gas sensor capable of preventing the influence of the temperature of the environment or the temperature of the test gas as much as possible. Is to provide.

  In order to achieve such a problem, in the present invention, the first element formed by extending the heater wire on the two stays penetrating the base and the two stays penetrating the relay base are provided. A second element configured by extending a heater wire; and a cap that accommodates the first and second elements in a vertical relationship and is fixed to the base. The relay stand is divided into two areas for accommodating the elements, and only one of the areas is communicated to the outside through a through hole formed in the cap.

Since the two elements that make up the temperature compensation element and the detection element are both housed in the cap, they can follow the external temperature change in the same form as much as possible to prevent the generation of pseudo signals accompanying the temperature change. can do.
Moreover, since it can comprise by arrange | positioning two elements in an up-down relationship and mounting | wearing with one cap, simplification of a sealing structure and simplification of an assembly operation can be achieved.

  FIGS. 1A, 1B, 2A, and 2B show an embodiment of the present invention. The heater wire 11 constituting the temperature compensating element 10 is provided with a base 12. The two stays 13, 13 that pass through are stretched.

  On the other hand, the heater wire 21 constituting the gas detection element 20 has the same structure as the heater wire 11 of the temperature compensation element 10 and is stretched on two stays 23 penetrating the relay stand 22, and then is used for temperature compensation. A stay 23 is inserted into the base 12 and arranged in layers so as to be orthogonal to the heater wire 11 of the element and located on the far side of the base 12 with respect to the heater wire 11. Preferably, the relay table 22 is supported by the tip of the stay 13 of the temperature compensating element 10.

  The cap 30 has a gas inlet 31 at the tip thereof and is attached to the base 12 in order to bring the test gas into contact with the heater wire 21 of the detection element 20. Packing 40 is attached to the outer periphery of the relay stand 22, and a compensation chamber 50 including a sealed space is formed between the relay stand 22 and the base 12, and a required standard gas is sealed in the compensation chamber 50. Yes. Reference numeral 14 in the drawing denotes a through hole for inserting the stay 23.

  In this embodiment, when the heater wire 11 of the temperature compensation element 10 and the heater wire 21 of the detection element 20 are bridge-connected or differentially connected, the same test gas as the compensation chamber 50 flows into the detection chamber 51. In this state, since both heater wires 11 and 21 are maintained at the same temperature, a zero signal is output.

  On the other hand, when a test gas containing a component different from the standard gas flows from the gas inlet 31 into the detection chamber 51, the heat dissipation degree of the heater wire 21 changes according to the thermal conductivity of the gas, and both heater wires are changed. A difference occurs in the resistance between them, and a signal is output.

  On the other hand, when the temperature of the test gas fluctuates, the heater wire 11 of the temperature compensation element 10 is also affected by the same thermal effect as the heater wire 21 of the detection element 20 via the standard gas in the compensation chamber 50. The influence of the temperature change of gas can be prevented as much as possible.

  That is, in the present invention, since the compensation chamber 50 in which the heater wire 11 of the temperature compensating element is accommodated is in contact with the test gas via the single cap 30, the temperature of the environment is substantially equal. Follow.

FIG. 3 shows the output characteristics when the temperature of the test gas is changed from 0 ° C. to 40 ° C. at a constant rate in 200 minutes. In the present invention, both the detection element and the temperature compensation element are accommodated in a single cap. Therefore, as shown by the solid line in FIG. 5, the temperature of each heater becomes the same, and no pseudo signal is generated.
On the other hand, in the conventional device shown by the dotted line in FIG. 5, since only the temperature compensating element is accommodated in the cap, a temperature difference is generated between the detecting element and a pseudo signal is generated in response to the temperature change. It was seen.

  In the above-described embodiment, the test gas inlet 31 is formed at the top of the cap. However, as shown in FIG. 4, the gas is taken into the body of the cap 30 in the region in which the lower heater wire 11 is accommodated. It is obvious that the same effect can be obtained even if the opening 31 'is formed and the upper heater wire 21 is used as a temperature compensating element and the lower heater wire 11 is used as a detecting element. In the present specification, the terms “upper”, “lower”, or “upper / lower” are used, but this is a term including the fact that they are positioned in the same posture on the same line for explanation corresponding to the drawings. .

FIGS. 1A and 1B are sectional views showing an embodiment of the present invention. Figures (a) and (b) are exploded views of the gas sensor. It is a diagram which shows the output at the time of the temperature change of this invention and the conventional heat conduction type gas sensor. It is sectional drawing which shows the other Example of this invention. It is a figure which shows an example of the conventional heat conduction type gas sensor.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Temperature compensation element 11 Heater wire 12 Base 13 Stay 20 Gas detection element 21 Heater wire 22 Relay stand 23 Stay 30 Cap 31, 31 'Gas intake port 40 Packing 50 Compensation chamber 51 Detection chamber

Claims (2)

A first element configured by extending a heater wire between two stays penetrating the base, and a second element configured by extending a heater wire between two stays penetrating the relay base And a cap that accommodates the first and second elements in a vertical relationship and is fixed to the base,
The heat-conducting gas sensor, wherein the cap is divided into two regions for accommodating the elements by the relay stand, and only one of the regions is communicated to the outside through a through hole formed in the cap.   The heat conduction type gas sensor according to claim 1, wherein a packing is loaded between an outer periphery of the relay stand and an inner surface of the cap.

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