JP3343882B2 - Alcohol removal filter for contact combustion type sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a filter for removing alcohol from a gas to be measured of a catalytic combustion sensor.

[0002]

2. Description of the Related Art A contact combustion type sensor detects a combustible gas in air and is widely used as a gas leak alarm. However, when a low-boiling fuel gas such as methane or ethane is used as a gas leak detector, the conventional sensor is sensitive to alcohols in the atmosphere. For example, alcohols for cleaning or wiping are used. In addition, there has been a problem that alcohol vapor generated by heating liquor during cooking or the like is detected and falsely reported.

[0003] According to Japanese Patent Publication No. 57-22544, a phenolic activated carbon fiber (activated carbon fiber, fibrous activated carbon) containing a sensor α is knitted, woven, and felt as shown in FIGS. , And a cylindrical filter β having a bottom made of paper.
Japanese Patent No. 27864 has proposed a technique of improving the gas desorption property by forming an annular filter β ′ as shown in FIG. 4C and partially projecting the sensor portion α ′. In addition, Japanese Patent Application Laid-Open No.
As shown in FIG. 5A, a technique of setting a housing β ″ having a gas-permeable adsorbent γ in which a granular activated carbon and a particulate fluororesin are integrally formed by heat molding in a sensor α ″ (see FIG. 5B) Has been proposed. Reference numeral δ denotes a gas inspection flow hole, which facilitates inspection of this sensor.

[0004] However, the effects of these filters according to the prior art are easily lost due to impact such as dropping. That is, if the setting of these filters to the detecting element portion is incomplete due to a shift or disconnection caused by an inadvertent impact at the time of transportation, transportation or mounting after manufacturing, the effect is lost. Particularly, in the case of a contact combustion type gas sensor composed of a detection element and a comparison element which are considered to be highly reliable because stable detection results are obtained over a long temperature range over a wide temperature range, the detection element and the comparison element are inserted into these detection elements. If any one of the filters becomes displaced or dislocated, the thermal balance between these elements will be lost, resulting in a detection error or a detection error, which may cause a problem such as not being detected despite the presence of the gas to be detected. When the housing described in Japanese Patent Application Laid-Open No. 7-19778 is used, the gas check and flow hole δ provided in the housing β ″ of the sensor is used.
In addition to restricting the mounting attitude of the sensor itself so as not to impair the function of, if the inspection gas is excessively exposed, the inspection gas adsorbed by the adsorbent γ is gradually desorbed and detected by the sensor, There is also a drawback in that the alarm is continued for a long time after the completion of the inspection to give anxiety to the surrounding people. In this manner, the housing using the filter-dedicated case increases the size of the entire sensor, increases the cost, and increases the number of assembly steps.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned disadvantages of the prior art, that is, it is inexpensive and easy to inspect.
It is an object of the present invention to provide an alcohol removal filter for a contact combustion type sensor, which is capable of accurately measuring the gas concentration of a target gas, in which a measurement error hardly occurs, and which can be made compact.

[0006]

According to the present invention, the alcohol removal filter for the catalytic combustion type sensor according to the first aspect of the present invention , after elongation of at least 1.3 times without being destroyed, originally.
An alcohol removal filter for a contact-combustion sensor, which is made of a flexible and highly stretchable material having elasticity returning to the shape of the above, and which is held at the air collecting hole position of the sensor element portion by the elasticity and covers the air collecting hole. , And simultaneously cover both the gas sampling hole of the detection element and the gas sampling hole of the comparison element.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The alcohol removal filter for a catalytic combustion type sensor according to the present invention must be made of a material that is flexible and highly stretchable. That is, by having this property, the elasticity of the sensor element allows the sensor element portion to be held at the position of the air sampling hole and cover the air sampling hole to ensure the effect of removing the influence of alcohols. When the alcohol removal filter for the catalytic combustion type sensor of the present invention is made of urethane foam having an adsorptive property, it can be easily inserted into the sensor element portion,
In addition, it is preferable because occurrence of a shift and a shift is extremely reduced. That is, in addition to holding by elasticity due to the elasticity, the synergistic effect of the difficulty of the urethane material to be displaced further ensures the effect of the present invention.

[0008] Here, for example, felts, cloths, papers and the like made mainly of activated carbon fibers (also called activated carbon fibers or fibrous activated carbon) may have some elasticity in some cases. However, these are 900-1300
It is fired at an ultra-high temperature of ℃, and its properties are extremely brittle, similar to carbon fibers, and it cannot be included in the category of the flexible and stretchable material referred to in the present invention. I can't get it. In the present invention, sufficient elasticity means at least about 1.3 times, preferably 1.5 times without breaking.
The elasticity is such that it returns to its original shape after double, more preferably double, elongation. Further, when the urethane foam having adsorptivity is a urethane foam holding powdered activated carbon, it is possible to completely exclude the influence of alcohols.

Here, the powdered activated carbon may be, in addition to ordinary powdered activated carbon, one obtained by milling activated carbon fibers into a substantially powdered form. These have a remarkably high adsorption rate as compared with granular activated carbon, crushed carbon, and the like, so that a sufficient effect can be obtained even with a relatively thin layer. Such an effect is crushed charcoal,
It cannot be obtained with granular or granulated coal. The urethane foam used in the present invention has a cell size of 15 cells / 2.54 mm or more.
0 / 2.54 mm or less. In other words, the alcohol removal effect is insufficient with a large bubble size of 15 or less per 2.54 mm. on the other hand,
If it is smaller than 30 pieces per 2.54 mm, the permeability to inspection gas (generally butane gas) is inferior.
It takes time to perform the inspection, and it is easy to cause a problem that the alarm continues to be issued for a long time after the inspection. Furthermore, these bubbles need to be continuous. That is, if they are not continuous, the target gas cannot reach the detection element or becomes difficult, which is not practical. A urethane foam having such open cells is available from Bridgestone Corporation.

The loading of the powdered activated carbon on the urethane foam can be easily carried out, for example, by supporting an adhesive or tacky adhesive on the urethane foam and then contacting the powdered activated carbon. With this support, the manufacturing cost can be very low. The loading amount of these powdered activated carbons is 0.025 g or more per 0.05 ml of bulk volume of urethane foam.
It is desirable that 5 g or less be carried. That is, if the loading amount is less than 0.025 g per 1 ml of bulk volume, a sufficient effect is not obtained, and if the layer height is increased in order to increase the contact time with the gas in order to enhance the effect, it is generally required for inspection. There are disadvantages that the responsiveness to butane gas used as an inspection gas is low, or that an alarm is continuously issued for a long time after the inspection is completed. On the other hand, even if the carried amount is 0.55 g or less per 1 ml of bulk volume, the responsiveness to butane gas at the time of inspection is low, or the alarm continues to be notified for a long time after the inspection is completed.

In the case of a sensor having two sensor elements, that is, a detection element and a comparison element, it is desirable that the sensor simultaneously covers both the air sampling hole of the detection element and the air sampling hole of the comparison element. That is, by covering both with one filter, the correspondence to both alcohols can be made completely the same, and the distance between them can be easily shortened, so that the entire sensor unit can be easily miniaturized. In addition, checking of the sensor element and the like can be easily performed because the filter can be easily removed.

FIG. 1A shows an example of an alcohol removal filter for a catalytic combustion sensor according to the present invention. This device has a length of 33 mm, a width of 16 mm, a thickness of 7.5 mm, and an element setting hole 1 which is a mechanism for setting an element having an inner diameter of 8.5 mm.
a. This has open cells, in which powdered activated carbon is supported.

The filter 1 is set on an element as shown in FIG. At this time, the diameters of both the detecting element 2 and the comparative element are larger than the above-mentioned element setting hole 1a by 10.7.
mm. However, since the alcohol removal filter 1 for a contact combustion type sensor is made of urethane foam having high elasticity, it is easy to set, and after setting, it comes off.
There is no shift. That is, in the present invention, it is preferable that the setting mechanism for the sensor element is considerably smaller than the object to be set. The difference in size and the flexible and stretchable configuration of the present invention ensure that the alcohol removal filter for the catalytic combustion type sensor of the present invention is detached even after it is set. Reference numerals 2a and 3a denote air holes of these elements, the width of which is 5.
5 mm. FIG. 1 shows a state in which the alcohol removal filter 1 for a catalytic combustion sensor is set in an element.
It is shown in (c). Since the thickness of the filter 1 is sufficiently larger than the width of the gas sampling hole, all the gas reaching the gas sampling hole of the element is sufficiently in contact with the activated carbon supported in the open cells of the filter 1 to remove alcohols. Becomes

[0014]

EXAMPLE Two kinds of alcohol removal filters for a catalytic combustion sensor having the shape shown in FIG. 1A were produced. One is an alcohol removal filter a for a catalytic combustion sensor according to the present invention, which has air bubbles (open cells) of 30 pieces / 2.54 mm in size and powdered activated carbon (benzene adsorption amount:
48% by weight (based on JIS K1474)) 1m bulk volume
It is carried so as to be 0.035 g per liter. On the other hand, as a comparative example, Kuraray Chemical's activated carbon fiber (F
(T-15, specific surface area: 1500 m ² / g) This is an alcohol removal filter b for a catalytic combustion sensor made of felt. This is less elastic than the alcohol removal filter a for the catalytic combustion type sensor.

Each of these filters was inserted into a sensor, exposed to air containing 5000 ppm of ethyl alcohol, and the output value at that time was examined for a change with time. FIG. 2 shows the results together with the results of the sensor without a filter.
Shown in From FIG. 2, it can be seen that the performance of the alcohol removal filter a for the catalytic combustion sensor according to the present invention has the same alcohol removal effect as using the filter b according to the prior art. Further, a drop impact test of 100 G was repeated for each of the sensors in which the filters a and b were set, and the amount of filter displacement at that time was examined. These results are shown in FIG. From FIG. 3, it can be seen that the alcohol removal filter a for the catalytic combustion sensor according to the present invention can completely prevent the occurrence of the displacement generated in the filter b. The filter a can be easily attached and detached by the operator's hand, and does not impair workability when attachment or detachment is necessary.

[0016]

The alcohol removal filter for the catalytic combustion sensor according to the present invention does not require a housing, and is therefore inexpensive.
It is compact, easy to inspect even after the sensor is inserted, hardly causes measurement errors, and can accurately measure the gas concentration of the target gas.

[Brief description of the drawings]

FIG. 1 is a view showing an alcohol removal filter for a catalytic combustion sensor according to the present invention. (A) It is the figure seen from the upper surface. (B) It is the figure which showed the insertion method to a sensor element. (C) It is a figure showing the situation where it was inserted in the sensor element.

FIG. 2 is a view showing an alcohol removing effect of an alcohol removing filter for a catalytic combustion sensor according to the present invention.

FIG. 3 is a diagram showing the reliability of the insertion of the alcohol removal filter for a catalytic combustion sensor according to the present invention.

FIG. 4 is a diagram showing a conventional technique. (A) It is a figure which shows the sensor which has a bottomed cylindrical filter which consists of activated carbon fiber. (B) It is a figure showing a situation when a bottomed cylindrical filter is inserted in a sensor part. (C) It is a figure which shows the sensor which has the filter which consists of an annular hard material in the sensor part air intake hole part.

FIG. 5 shows a sensor according to the prior art having a housing cover with a disc-shaped filter molded from granular activated carbon and plastic. (A) It is a figure which shows the setting method of a housing cover. (B) It is a figure showing the situation after setting.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 The alcohol removal filter which concerns on this invention 1a Element set hole 2 Detecting element 2a Air sampling hole 3 Comparative element 3a Air sampling hole

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 27/00-27/49

Claims (3)

(57) [Claims] 1. Elongation of at least 1.3 times without breaking
After that, it is made of a flexible and highly elastic material having elasticity that returns to the original shape, and the elasticity of the contact combustion type sensor that is held at the air sampling hole position of the sensor element portion and covers the air sampling hole.
A filter for removing alcohol for
An alcohol removal filter for a catalytic combustion sensor, wherein the filter simultaneously covers both pores and a sampling hole of a comparison element . 2. The alcohol removal filter for a catalytic combustion type sensor according to claim 1, wherein the alcohol removal filter for a catalytic combustion type sensor is made of urethane foam having adsorptivity. 3. The alcohol removal filter for a catalytic combustion sensor according to claim 2, wherein the urethane foam having adsorbability is a urethane foam holding powdered activated carbon.